RU2774688C2 - Method for production of micro-fibrous non-woven synthetic suede-like material - Google Patents

Abstract

FIELD: textile industry.

SUBSTANCE: group of inventions relates to the production of non-woven materials. For the production of micro-fibrous non-woven material, two-component fiber of the “island-in-the-sea” type is obtained, in which a sea component is polymer, which is removed in hot water or in an aqueous alkaline solution. Felt is made by punching two-component fiber of the “island-in-the-sea” type with a needle. The specified felt is hot impregnated with an aqueous solution of polyvinyl alcohol (hereinafter – PVA) having a saponification degree of at least 94%, possibly with the addition of water-soluble organic or inorganic salt. The sea component is removed from felt impregnated with PVA, obtained at the stage c) by contact of felt with an aqueous basic solution of alkali or alkaline earth metal hydroxide, thus obtaining an intermediate micro-fibrous product. The intermediate micro-fibrous product is washed with neutral water containing water-soluble organic or inorganic salt, or acidic water, or neutral water, if the aqueous solution of polyvinyl alcohol (PVA) of the stage c) is supplemented with water-soluble organic or inorganic salt. The intermediate micro-fibrous product is cold impregnated with polyurethane (hereinafter – PU) dispersed in water containing additives for viscosity control and possible water-soluble substances. Polyurethane (PU) is fixed on the intermediate micro-fibrous product by coagulating a dispersion of polyurethane and subsequent drying. PVA, salt, additives are removed. Material obtained in such a way is subjected to cutting, grinding on one or both sides, and staining.

EFFECT: micro-fibrous non-woven material is obtained, which allows the use of water instead of organic solvents, but unlike already known aqueous processes, obtained non-woven material has excellent wear resistance and touch characteristics, improved stain resistance and has no defects caused by excessive adhesion between micro-fiber and polyurethane, such as, for example, noise and low elasticity, rigidity and cardboard-like touch and crack resistance after rolling.

10 cl, 11 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to a method for producing a microfiber nonwoven synthetic suede fabric which does not require the use of organic solvents and which produces a soft finished product that is resilient to the touch, with excellent yellowing resistance, high durability, and product-like appearance. obtained using a modern method using a solvent.

BACKGROUND OF THE INVENTION

From the prior art methods are known for obtaining microfiber non-woven suede-like fabrics obtained from the so-called "island-in-the-sea" fibers. According to this technology, a two-component fiber is obtained, consisting of an "island" component completely surrounded by another "marine" component. Said fiber is obtained by feeding two polymeric components into a spinneret and processed by known methods (see, for example, US 3,692,423, US 3,899,292, US 3,331,368). Typically, the fiber thus obtained is then used to make felt by needle punching, which is subjected to various stages of impregnation in aqueous solutions and an organic solvent to fix and/or remove the various components. To make suede-effect nonwovens, needle-punched felts are typically first impregnated with an aqueous solution of polyvinyl alcohol (PVA) followed by dissolution of the "marine" component, for example, in trichlorethylene. The intermediate microfiber product obtained is again impregnated with a solution of polyurethane (PU) in an organic solvent (such as, for example, DMF). Finally, after one or more wash treatments, the PVA is removed and the article thus obtained is subjected to a final treatment which includes a "peeling" step followed by sanding and staining, respectively.

From the prior art methods for producing non-woven material, in which both stages of impregnation are carried out in PU, both in aqueous and organic solvents (see, for example, EP1353006).

Methods for the manufacture of nonwoven fabric are also known which involve forming an island-in-the-sea fiber followed by impregnation in PVA and PU without the use of organic solvents (see EP1243691 and EP2780501). Although the use of water instead of the commonly used organic solvents (such as DMF and trichlorethylene, for example) represents a significant advantage both financially and environmentally, and although it is possible to obtain a finished product that is capable of maintaining the desired characteristics in touch and resistance However, there remains a need to provide a method that can produce a non-woven fabric with excellent yellowing resistance, high strength, i.e. soft, elastic, good to the touch, which has an appearance that is the same as that of products obtained with a modern solvent process, and obtained by processes with low environmental impact or which are environmentally compatible and have low production costs.

In addition, the method known from EP1243691 involves the use of certain substances that are potentially harmful to health, such as, for example, boric acid. In addition, the process variability associated with the partial solubility of PVA in complex with boric acid under the conditions of dissolution of the "marine" component can be an aspect that can lead to a decrease in the efficiency of the process as a whole.

EP 2780501 further discloses a process that overcomes the disadvantage of using boric acid to modulate PVA's water solubility, but the disclosed process produces a product that is stiff and cardboard-like to the touch due to the excessive adhesion between polyurethane and microfibers that occurs after the application of polyurethane, dispersed in water, and subsequent coagulation using the disclosed technologies.

This is primarily due to the delaminating operation after dyeing, which makes the nonwoven material stiff and rough on the cut side due to the inability to remove the polyurethane on the cut side before the dyeing process. The surface appearance of the finished product is, moreover, not comparable to the appearance of products that can be obtained with a modern solvent process, due to the fact that the microfiber is excessively glued by polyurethane, also on the surface, causing certain surface fibers to look like microfibers.

Applicant has now developed a process for producing a microfiber nonwoven fabric that allows the use of water instead of organic solvents, but unlike already known aqueous processes, the resulting nonwoven fabric has excellent wear resistance and feel, improved stain resistance, and is free from defects, caused by excessive adhesion between microfibre and polyurethane, such as, for example, noisiness and low resilience, hard and cardboard-like feel, and crack resistance after rolling. In addition, the resulting product is elastic, and also has high strength and resistance to yellowing; the appearance of the surface is, moreover, identical to that of the product obtained by the modern solvent process.

The essence of the invention

In a first aspect, the present invention relates to a process for producing a microfiber nonwoven fabric, comprising the steps of:

a) an island-in-the-sea bicomponent fiber is produced in which the marine component is a polymer that is removed in hot water or in an aqueous alkaline solution;

b) a felt is produced by punching a two-component fiber of the island-in-the-sea type with a needle;

c) carrying out hot impregnation of the said felt with an aqueous solution of polyvinyl alcohol (PVA) having a degree of saponification of at least 94%, optionally with the addition of a water-soluble organic or inorganic salt;

d) removing the marine component from the PVA-impregnated batt obtained in step c) by contacting the batt with an aqueous alkali or alkaline earth metal hydroxide basic solution, thereby obtaining an intermediate microfiber product;

e) washing the intermediate microfiber product obtained in step d) with neutral water containing a water-soluble organic or inorganic salt, or with acidic water, or with neutral water if the aqueous solution of polyvinyl alcohol (PVA) used in step c) is supplemented with a water-soluble organic or inorganic salt;

f) carrying out cold impregnation of the microfiber intermediate product indicated in step e) with polyurethane (PU) dispersed in water containing additives for adjusting the viscosity and possible water-soluble substances;

g) fixing the PU on the microfiber intermediate by coagulating the PU dispersion and then drying;

h) remove the PVA added in step c), the salt, optionally added in step c) and/or e), and the additives added in step f);

i) subjecting the resulting material to cutting, grinding on one or both sides and staining.

The dyed nonwoven fabric thus obtained already has excellent tactile and drape characteristics, but the increase in physical mechanical resistance allows the nonwoven fabric to, if necessary, be subjected to subsequent dry softening treatments or low temperature water treatments, adding, if necessary, silicone agents to making the product soft (step l).

The nonwoven web made in accordance with the present method may be further sanded on the side in contact with the blade (step m)) if this treatment was necessary to increase or modify the contact surface in order to be able to subject the woven web to a post-treatment such as, for example, gluing to fabric substrates, dispensing resins and flame retardant coating and/or to further reduce the thickness of the dyed nonwoven web or also to further soften the finished material.

In a further aspect, the invention relates to a microfiber nonwoven synthetic suede fabric made (or made) by the present process.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the invention will be illustrated below with reference to the accompanying figures, in which:

- in Fig. 1 shows a section of an intermediate microfiber product impregnated with a polyurethane preparation, dispersed in water and subsequently subjected to PVA removal (step h)); the polyurethane formulation contains a water-soluble polymer which is capable of modifying the adhesion of the polyurethane to the microfiber after removal in step h) together with the PVA used in step c).

- in Fig. 2A shows the surface of an intermediate microfiber product impregnated with a polyurethane preparation, dispersed in water and subsequently stripped of PVA (step h)).

- in Fig. 2B shows the surface of an intermediate microfiber product impregnated with a polyurethane preparation, dispersed in water and subsequently stripped of PVA (step h)); the surface in Fig. 2B is different from the surface in FIG. 2A in that, near the two outer surfaces, the presence of the salts added to the intermediate product in step e) (before impregnation with polyurethane) made it possible to obtain such an amount of polyurethane that is present on the surface to be limited, thus facilitating the separation of microfibers during grinding and staining with a significant improvement in the appearance of the surface of the product.

- in Fig. 3 shows an intermediate microfiber product impregnated with a preparation of polyurethane dispersed in water and devoid of PVA (step h)), which differs from the previous ones in that an additive capable of swelling during drying was added during preparation, producing an artificial expansion that reduces the density of the polyurethane matrix . In this case, the particles first swell and then explode to create porosity within the polyurethane matrix.

- in Fig. 4A shows an intermediate microfiber product impregnated with a preparation of polyurethane dispersed in water and devoid of PVA (step h)), which differs from the previous ones in that an additive capable of generating gaseous decomposition products during the coagulation/drying step (step g)) was used.

- in Fig. 4B shows an intermediate microfiber product impregnated with a preparation of polyurethane dispersed in water and subjected to coagulation in an aqueous formic acid solution and subsequent drying (step g)) followed by a PVA removal step (step h)). Of note is the porous structure that is formed during the coagulation process in water containing formic acid and the limited adhesion between polyurethane and microfiber, which ensures greater softness and elasticity in the final product.

- in Fig. 5A shows an intermediate microfiber product impregnated with a polyurethane preparation dispersed in water and directly coagulated/dryed (step g)).

- in Fig. 5B shows an intermediate microfiber product impregnated with a preparation of polyurethane dispersed in water, pre-treated with IR lamps before the coagulation/drying process (step g)). After removal of intermediates from PVA (step h)) a higher concentration of polyurethane is observed in the center of intermediate 5B relative to the intermediate of FIG. 5A; this leaves the surface freer with an overall improvement in the appearance of the final product.

- Fig. 6 contains Table 1 showing the impregnation weights according to Example 1 and subsequent treatments.

- in Fig. 7 shows Table 2, which contains evaluations of prototypes obtained in accordance with the present invention, in comparison with prototypes made in accordance with patent EP1323859 (solvent process, prototype A) and disclosed examples 2.2 (prototype B) and 1.1b (prototype C). ) in patent EP2780501.

- in Fig. 8 shows the Martindale scale used to evaluate the appearance of a microporous product after an abrasion test using a Martindale abrasion tester.

DETAILED DESCRIPTION OF THE INVENTION

In the method of the present invention, the preparation of the batt according to step b) takes place by needle-piercing the island-in-the-sea bicomponent fiber obtained in step a). The latter can be prepared according to prior art techniques which involve feeding two pure polymers or two mixtures of polymers with additives into a spinneret such that one of the two polymer components (the "sea") completely surrounds the other component consisting of different polymer filaments, which form various "islands".

The island component can be selected from: modified polyesters, cationic polyesters, nylon or other types of polyamides, polyethylene (PE), polypropylene (PP), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyhydroxyalkanoates (PHA), polyethylene furanoate (PEF) , polylactic acid (PLA) and polyethylene terephthalate (PET), the latter being particularly preferred. The aforementioned polymers may be obtained from renewable sources of raw materials (which completely or partially replace current fossil raw materials), or the polymers themselves may be obtained by fermentation processes or using microorganisms. Examples of polymers belonging to the first case are PTT, PEF, PET and PLA, PE. Examples of polymers belonging to the second case are PHA.

An example of a marine component is a spinnable polymer, preferably selected from: polyvinyl alcohol (PVA), polystyrene copolymers containing PVA (co-PVA-PS), styrene copolymers containing maleic anhydride or other organic monomers in the chain (co-PS), copolyesters containing PVA (co-PVA-PES), copolyolefins such as polyethylene or polypropylene containing PVA (respectively co-PVA-PE, co-PVA-PP), copolyesters containing a mixture of terephthalic acid + isophthalic acid + 5-sulfoisophthalic acids (HWS); and copolyesters containing both terephthalic acid and 5-sulfoisophthalic acid or its sodium salt (co-PES, which may also be abbreviated to TLAS), the latter being particularly preferred.

Both marine and island components can be used in admixture with added components selected from: pigments for the island component and incompatible polymers for the marine component. Incompatible polymers (i.e., immiscible with the marine component) form a heterogeneous system that, on a microscopic level, has zones scattered in a matrix consisting of a second polymer in which only one of the polymers is present; typically, these systems are brittle and, if used to form a marine component, they facilitate sheath rupture during the stretching, crimping, and intermediate felt production steps.

As pigments to be incorporated into the island component, mention may be made of UV stabilizers and carbon black, with carbon black being particularly preferred as it makes it possible to reduce the amount of dyes used in dyeing to produce colored materials in the grey/black and dark color ranges in order to obtain very high lightfastness, thus saving on the cost of the dyeing process. The UV stabilizing properties of carbon are actually known to, when combined with a reduction in the amount of dye used in the formulation, to reduce color deterioration after UV exposure and reduce the cost of producing the colored material by saving on the amount of dyes to be used. If it is not possible to use carbon black (production of very light colors), the use of UV stabilizers can still increase the light fastness of tinted materials. Dyes, especially if they are selected from materials with high light fastness, usually have a big impact on the final cost of the product.

PVA added to co-PES and polyethylene glycols (PEG) added to co-PS can be mentioned as polymers incompatible with the marine component.

In one particularly preferred embodiment, the felt of step b) is produced by needle punching a bicomponent fiber formed by PET and co-PES (possibly added with pigments in the island component and/or incompatible polymers in the marine component) cut into short fibers of about 51 mm.

The ratio between the island component and the marine component of the bicomponent fiber is such that the two components can be rotated quickly and efficiently by the spinneret. Said island/sea ratio is preferably in the range of 20:80 to 80:20, more preferably in the range of 50:50 to 80:20. Island/sea ratios below 50:50 increase the amount of marine component to be removed with a subsequent increase in product cost and lead to a clear loss of physical and mechanical properties of the treated bicomponent fiber (the marine component is weaker), except for finished products with poor appearance due to low fiber density on surfaces. Island/sea ratios above 80:20 make the spinning process difficult because the low amount of sea component does not allow good separation of the microfibers within the bicomponent fiber.

Prior to the needle-punching process, the bicomponent fiber is usually treated according to methods known in the art, which include the addition of lubricating oils during the stretching step to improve the axial orientation of the macromolecules and thereby the physico-mechanical properties, in addition to reducing the titer thus obtained fibers, this feature is especially in demand for the production of high-quality products. In a preferred embodiment of the invention, the fiber before drawing has a titer of 5.5 to 19 dtex, preferably 7.5 to 15 dtex. Stretching is further carried out in ratios that typically range from 2-5, preferably from 2.1-3.9. At the end of the stretch, the fiber is then cut to obtain a short fiber having a length of 45 to 55 mm. After step b) a felt is obtained having a thickness preferably between 2 and 4 mm and an apparent density between 0.1 and 0.5 g/cm ³ , more preferably between 0.15 and 0.25 g/cm ³ . Advantageously, these density and thickness values are optimal for obtaining a nonwoven end product having good hand, softness, elasticity, appearance and mechanical resistance to process conditions. During the preparation of the felt, it is especially important that there is no defect arising from cracks (cracks produced by rolling) on the side s obtained by cutting the product in step i) in order to expose short fibers in the initial stages of the needle punching process to transverse needle penetration. on both sides of the batt being formed to avoid over-orienting the fibers in the preferred direction.

Thus, the batt obtained after step b) is impregnated with a hot aqueous PVA solution, which has the property of becoming less soluble under conditions of removal of the marine component, once drying and high temperature processing has become possible.

The hot impregnation of the felt with the PVA solution takes place at a temperature of at least 50° C., preferably 60 to 99° C., in order to also ensure the dimensional stability of the intermediate product due to the release of stresses accumulated during the spinning, stretching and felting process. Dimensional stabilization usually also results in an increase in density, with a subsequent improvement in the aesthetic characteristics of the resulting final product.

In one embodiment of the process according to the invention, a water-soluble organic or inorganic salt is added to the aqueous PVA solution prior to impregnation (step c)), preferably in a salt/PVA weight ratio of 0.1% to 20%, preferably 5 to 12% by weight. %. Preferred salts are alkali metal salts such as, for example, NaCl and KCl.

Alternatively, a solution containing a water-soluble organic or inorganic salt can be used in the subsequent step (step e)) to wash the intermediate PVA-impregnated microfiber product.

Pure PVA or PVA to which the salt used in step c) has been added is characterized by having a solubility in water or aqueous solutions that is significantly lower than the solubility of the marine component of the bicomponent fiber under dissolution conditions.

For this purpose, the present method involves the use of PVA with a high degree of saponification, ie at least 94%, even more preferably above 97%. This degree of saponification allows the PVA to be treated in such a way as to achieve insolubility in an aqueous medium to withstand a subsequent treatment to remove the marine component (step d)) without endangering its dissolution in water in step h) of the process, as described below. Advantageously, the use of PVA with the indicated degree of saponification allows step c) to be carried out without the use of any cross-linking agent, as, on the other hand, provided in the prior art, such as, for example, boric acid or vanadium or zirconium compounds, which are potentially harmful to health .

The solubility of PVA can be modulated not only by highly saponifying PVA and salt addition, but also by heat treatment (also known as heat curing) at high temperature or irradiation carried out at the end of step c) of impregnating PVA and subsequent drying. In particular, the PVA-impregnated felt is treated after drying at a temperature of at least 100°C, preferably in the range of about 140°C to about 250°C, for example using air jet ovens or infrared radiation, for a time , which can vary from less than a minute to about 15 minutes, typically depending on the temperature used, the degree of dissolution stability required, the degree of saponification, and the salt content that may have been added to the PVA.

In this way, it is possible to stably attach PVA to the batt, allowing the subsequent marine component removal step to be carried out without significantly changing the content and distribution of PVA in the material.

In this context, step d) of removing the "marine" component occurs by contacting the PVA-impregnated felt obtained in the previous step c) with an aqueous basic solution of an alkali or alkaline earth metal hydroxide, preferably NaOH or KOH. Said contact takes place preferably by immersing (washing) the PVA-impregnated felt in a selected aqueous base solution and followed by repeated rinsing with neutral water, which may or may not contain organic or inorganic brine or acidic water to neutralize the solution and form salt "in situ" (step e)) in order to ensure the removal of possible alkaline solution residues that could cause partial hydrolysis of the microfiber during the drying step and/or deposits near the surface of the microfiber and within the PVA the salt concentration that is used to influence the subsequent step of impregnating with polyurethane. Of the salts that can be used and obtained by naturalization in the washing step, alkali metals such as, for example, NaCl and KCl are particularly effective.

Alternatively, an organic or inorganic brine solution may already be present in the PVA as it is added in step c) of the process, so after the aqueous base solution step to remove the marine component, a neutral aqueous solution wash of the felt containing PVA and salt is performed.

The pH of the stock solution used to remove the marine component is preferably 10 to 14. In one embodiment, the concentration of the stock solution is 0.1 to 48%, preferably 5 to 12%. Low concentrations of the stock solution slow down the dissolution process; on the other hand, excessively high concentrations reduce the removal selectivity between the marine component and the microfiber and furthermore cause precipitation of the marine component removal products in the main extraction solution.

The removal of the "marine" component according to step d) occurs at a temperature and for a time chosen to optimize the selective dissolution of this component, dissolving the minimum possible amount of applied PVA, while avoiding degradation of the microfiber of the "island" component. In order to obtain more efficient removal and shorter times, the temperature of the stock solution is preferably at least 40°C, more preferably at least 60°C, even more preferably 60°C to 80°C. It is known from the literature that the presence of positive metal ions such as Na ⁺ or K ⁺ and anions such as SO ₄ ^2- prevent the loss of PVA upon removal of the marine component (an effect known as "salting out"). This allows the base solution to be used at temperatures above 60°C without significant loss of PVA during the removal of the marine component. Excessively high temperatures, however, make it difficult to control the marine component removal process and reduce the removal selectivity between the marine component and the microfiber.

When co-PES is used as a marine component, the content of 5-sulfoisophthalic acid (SIPA) within the polymer significantly affects the solubility of the polymer in the alkaline solution used to remove it. In particular, a SIPA content of less than 8% by weight requires, for the same time, contact with an alkaline solution, co-PES dissolution conditions that are more radical, such as, for example, a higher concentration of sodium hydroxide and/or a higher temperature in the process. But changing these parameters adversely affects the selectivity between the removal of the marine component and the degradation of the polymer constituting the islands, and in addition, precipitation phenomena of products removing the marine component can be caused in the main extraction solution (related to the concentration of the sodium hydroxide solution in the solution). On the other hand, the content of SIPA above 12% makes the marine component less crystalline with the possible loss of part of the polymer during the production process and adversely affects the physical and mechanical characteristics of the resulting bicomponent fiber. The content of SIPA present in co-PES should therefore preferably be 8 to 12%, more preferably 9 to 11%.

In addition, the amount of SIPA must be balanced to allow the use of sodium or potassium hydroxide concentrations below about 12%, the limit at which phthalic oligomers resulting from the hydrolysis process precipitate.

The heat treatment or irradiation step after drying the PVA at high temperature cannot be performed (if minimal PVA losses are assumed) to avoid excessive overheating of the bicomponent fiber: high temperatures actually increase the crystallinity of the fiber due to the reorganization of the crystalline domains of the microfiber and their marine component. The advantages of low heat are greater softness for the microfiber and hence the resulting finished product, and greater ease of dissolution for the marine component.

Due to the fact that the crystallinity of the marine component does not increase, the dissolution temperature of the base solution can then be lowered to values ranging from 35 to 50° C., which also improves hydrolysis selectivity.

The microfiber intermediate obtained by removing the marine component can be washed with cold water or moderately hot water (step e)). Cold water at temperatures below 40°C prevents even partial removal of PVA, which occurs when removing the remaining stock solution; on the other hand, the use of moderately hot water at a temperature of 40 to 80°C makes it possible to further increase the density of the intermediate microfiber product, which is now devoid of a marine component, thus providing particularly high densities and materials produced with an even richer appearance, although, with on the other hand, losses can be caused by PVA.

A preferred embodiment of the invention consists in using a salt cleaning solution containing alkali or alkaline earth metal salts (step e)) which, in addition to preventing the loss of PVA in water, leaves a layer of salt on the intermediate product, which can then affect the adhesion and stability of the polyurethane used in the subsequent impregnation step f), especially near the surface of the material, in order to obtain, after dyeing, an appearance that is particularly rich and similar to that of the modern solvent process. Thus, these salts can be added both to the cleaning solution and obtained by neutralization of residual sodium or potassium hydroxide with dilute solutions of strong or weak acids, creating a buffer system in the latter case.

The water temperature below 60°C allows you to limit the loss of PVA to values below 10% of the original content, or to values close to zero, if the PVA is sufficiently fixed in the previous stage of heat treatment.

The presence of the salt near the surface makes it possible to change the distribution of the polyurethane used in the subsequent step f), in particular by limiting its amount near the surface of the intermediate.

The microfiber intermediate product, devoid of the "marine" component and with the possible presence of salts around the microfiber and in the PVA, is then subjected to step f) of the PU impregnation.

As is known, PU is a polymer having a polymer chain formed only by urethane bonds (i.e. -NH-(CO)-O-) or a mixture or urethane and urea bonds (i.e. -NH-(CO)- NH-) and is obtained by reaction between a polyol or a mixture of polyols and a diisocyanate. To facilitate the dispersion of the polymer in water, it may be useful to add ionomers (molecules containing ionic groups which, like polyols, bind to the isocyanate) to the chain. In the present invention, PU is preferably prepared by reacting an aliphatic or aromatic diisocyanate with polyols having an average molecular weight of 500 to 5000 Da, even more preferably selected from: polyether, polyester, polycarbonate, and polyester-polycarbonate. Polyols can also be used, which are derived from fatty acid dimerization or olefin polymerization processes that allow the introduction of highly hydrophobic functional groups into the chain to increase the resistance of the polyurethane to hydrolysis processes and increase the total content of raw materials from renewable sources present in the colored material ( processes for the production of simple olefins by fermentation and subsequent unsaturation processes are already known). It is also possible to include polydimethylsiloxanes in the reaction to obtain hybrid PU in order to improve mechanical properties and resistance to hydrolysis. It is possible to add small amounts of trifunctional monomers to the polyurethane or aminosilane type chains during the synthesis process to increase the resistance of the polymer to hydrolysis when it is applied and crosslinked.

The aforementioned raw materials can be produced by manufacturing processes that use first generation renewable sources (from food), second generation renewable resources (agricultural or industrial waste), or third generation renewable resources (direct synthesis from CO ₂ ).

The PU may be present in an aqueous medium, for example in emulsions or aqueous dispersions. It is also possible to use two-component polyurethanes, reactive systems characterized by the separation of part of the reactants, which, after they are mixed before use, begin to react in place or react as soon as they are activated thermally or by the addition of catalysts and obtain the finished polymer directly inside the intermediate microfiber product, into which they were applied. These systems, which usually do not contain solvent, in any case give good impregnation results because, until the end of the reaction, their viscosity is low enough not to interfere with its diffusion within the intermediate microfiber product.

As an alternative to polyurethanes, mixtures of polyurethanes with other elastomeric polymers can be used, such as, for example, silicone polymers, polyisoprenes, polybutadienes and their copolymers, or styrene-butadienes and polymers of natural origin (such as, for example, natural rubber latex as such or prevulcanized latex).

Preferably the concentration of the impregnation solution is 8 to 40%, more preferably 15 to 30%. Concentrations above 30% can hamper the impregnation step and limit the polyurethane content of the finished product, while concentrations below 8% can cause poor stability of the PU dispersion over time and significantly change the structure of the cured polyurethane and the type of adhesion between the polyurethane and the microfiber to the point that the resistance colorable intermediate is reduced.

The impregnation of the PU according to step f) usually takes place by dipping and dosing with pinch rollers or by prior art methods (eg pressure waves). Preferably, the microfiber intermediate is impregnated with PU by dipping and dosing with pinch rollers.

Impregnation of PU in an aqueous medium can suitably be carried out using a so-called self-emulsifying polyurethane polymer (which contains only an ionomer in the chain) and/or by adding suitable external emulsifiers such as, for example, both ionic and non-ionic surfactants. Preferably, emulsifiers are used at concentrations of 0.5 to 10% based on PU.

In order to obtain the required mechanical properties and solvent resistance, the impregnation in step e) can take place in the presence of a crosslinker, which can preferably be activated during the drying step of the PU at a temperature of from about 60°C to 200°C, preferably from about 70°C. C to about 160°C, crosslinking time is typically less than 5 minutes at the indicated temperatures and is usually completed within the next 24 hours.

Said crosslinking agent is preferably used in amounts ranging from 0.5 to 10% and may be selected from: melamines, aziridines, epoxides, zirconium compounds, carbodiimides, isocyanate derivatives or preferably a blocked isocyanate or polyisocyanate with a low deblocking temperature (temperature , in which some particularly stable groups are released from the molecule, thus regenerating the isocyanide group, which can react again with the polyurethane chains present). Carbodiimides and blocked isocyanates are particularly preferred as they provide greater process control and longer stability times for the resulting dispersions.

The impregnation of the PU takes place in the presence of viscosity adjusting additives, which are thickeners that increase the viscosity of the dispersion, thus controlling the thickness migration of the polyurethane during the drying step. Dispersions with viscosities below 200 mPa·s at 20° C. cause significant migration of the polyurethane to the surface, with a subsequent change in the thickness distribution of the polymer; this leads to an excessive presence of polyurethane on the surface and the appearance of defects such as specks and breaks in the pile (too much polyurethane on the surface makes the sanding process difficult due to excessive fixation of the microfibers that are in contact with the abrasive paper, and facilitates fatigue failure due to tension, a phenomenon also known as "pile cutting") or irregularity (certain microfibers or groups of microfibers on a polyurethane-wrapped surface resist the mechanical action of the abrasive paper during the sanding process and produce localized fibers that are larger and longer, as in Figure 2A). Viscous dispersions with a viscosity of more than 8000 mPa·s at 20° C. inhibit the migration of polyurethane during the polymer curing step g) by determining the formation of a polyurethane residue which remains at the center of the impregnated intermediate. This accumulation of polyurethane on the inner surface, which occurs after the delamination step (side s), can result in a nonwoven material that is too stiff and cardboard-like if the polymer layer is too compact. Thus, the dyed intermediate is particularly hard if, after dyeing the fabricated material, an additional grinding step is not performed to remove some of the polyurethane found on the s side (side formed after delamination); however, this results in a higher cost of material being produced due to the greater number of processes. Extremely viscous Newtonian dispersions (viscosities above 10,000 mPa·s at 20° C.) further hamper the impregnation process by preventing the polymer from penetrating the entire thickness of the microfiber intermediate.

Therefore, viscosity control is a key parameter in order to obtain a material with a suitable polyurethane thickness distribution and thus a soft, non-cardboard feel and uniform appearance.

The so-called polyurethane associative thickeners (HEUR) are particularly effective viscosity adjusting additives, they create associative structures of polyurethane thickeners that migrate with difficulty during the drying or coagulation process and give, once set, less compact polymer aggregates.

Alternatively, additives can also be used that increase the viscosity of the dispersant (water), making it difficult for the polyurethane to migrate through the microfiber substrate during the drying or coagulation process. Acrylic acid derivatives (such as for example polyacrylates or urethane/acrylic resins), additives such as synthetic polymers such as PVA, compounds derived from natural polymers such as carboxymethyl cellulose (CMC), and certain complex sugars such as, for example, xanthan, belong to this category. Associative thickeners and acrylic thickeners added alone or in admixture are particularly preferred.

It is also advantageously possible to use polyurethane emulsions or dispersions in water with a higher viscosity (i.e., a viscosity above the prescribed limits) if non-Newtonian thickeners are chosen. Said non-Newtonian thickeners actually have the property of temporarily reducing the viscosity of the polyurethane emulsion or aqueous dispersion during the impregnation step performed by the pressure rollers. Said temporary loss of viscosity is due to the high stress present in the pinch rollers. At the end of the impregnation and associated stress, the viscosity of the polyurethane emulsion or aqueous dispersion increases again, effectively preventing the polyurethane from migrating to the surface.

The polyurethane can also be pigmented with carbon black or other pigments to give the finished product a color that limits the perception of the polyurethane after coloring.

Another unexpected aspect which makes the invention particularly interesting is the presence of salts on the fiber and in the PVA of the intermediate to be impregnated with polyurethane. When the polyurethane approaches the zones of the intermediate, which are particularly rich in salts, the aqueous dispersion containing the polyurethane is destabilized and the polymer cannot effectively adhere to the microfiber.

In addition, in areas rich in PVA (near the surface of the material), an even more noticeable effect is observed, which is reflected in the almost complete absence of polyurethane, which allows the effective release of microfibers during the grinding stage and, after dyeing, a product with a particularly rich and uniform appearance, which makes the nonwoven web thus obtained very similar to that obtained in the modern solvent process (comparison between figures 2A and 2B). The lower adhesion between the fiber and the polyurethane is also reflected in the increase in the softness of the dyed product towards materials produced in the solvent-free process, which do not have the salts present in the polyurethane or in the intermediate product to be treated with the polyurethane impregnation. However, if the adhesion is excessively low, the resulting product will not survive the final dyeing step when the material is subjected to a combination of pressure, temperature and mechanical stress (a typical polyester fiber dyeing technique).

In salt-treated intermediates, the lower adhesion of the polyurethane, together with the formation of a more porous PUD structure due to the loss of salt in the washing step h) after fixing the polyurethane, makes the intermediate product more porous and at the same time more elastic, leading to the production of non-woven fabrics characterized by richer appearance, softer to the touch and with a clear improvement in resilience and abrasion resistance.

In addition, the impregnation of PU can take place in the presence of additional additives such as, for example, surfactants, destabilizing agents, salts of other alkali metals or alkaline earth metal salts, generators of acids which release protons when heated, such as, for example, diethylene glycol acetate. or diethylene glycol formate, water-repellent agents, plasticizing agents, wetting agents and dispersing agents, silicone compounds and nanoparticles, nanofibers and nanotubes which are dispersed in water, preferably in an amount of 0 to 15%, more preferably 0 to 8% with respect to PU . One example of an alkaline earth metal salt is CaCl ₂ and is used to accelerate the destabilization of a polyurethane dispersion with increasing temperature (in the case of polyurethanes that are thermally coagulated).

In addition to the additives mentioned, water-soluble substances can be added to the polyurethane, such as, for example, PVA or a polymer similar to the marine microfiber component, but characterized by good hot water solubility (for example, hot water-soluble polymers and some co-PES), which after cold impregnation of the intermediate microfiber product according to step f) of the method which is the object of the present invention, are removed in step h) of hot removal and thus form artificial porosity, which improves the hand and softness of the product.

Another type of additive that can be added to polyurethane to create porosity in its structure are expandable microspheres, such as Akzo Nobel's products known as Expancel®: these are hollow particulate polymer particles that contain a low boiling liquid inside. In the stage of drying and fixing the polyurethane, which follows the stage of impregnation f), due to the expansion of the contained liquid, these particles swell, creating zones with a low content of polyurethane. If heating is continued until these hollow particles explode, microporosity is created, which is related to the size of the hollow particles, the type of liquids they contain, and the concentration of these particles in the PU dispersion.

A similar effect can also be obtained by adding to the water-dispersed polyurethane preparation for use in the impregnation step f), a water-soluble substance such as an unstable salt (for example, NH ₄ HCO ₃ or (NH ₄ )2CO ₃ ), which, when decomposed with by heating already at a temperature of 60-70°C, produces large amounts of gas, which can generate artificial porosity in the structure of the dried polyurethane, thus contributing to the production of softer non-woven fabrics.

Another type of polymer that can be added to PU to increase the porosity and softness of the final nonwoven fabric are polymers that are partially miscible with PU, which allow the generation of heterogeneous structures capable of making the PU less compact and therefore softer. One example is mixtures of polyurethane and silicone polymers.

After impregnation step f) the intermediate microfiber product is subjected to PU fixing step g). Fixation can take place by: hot air coagulation, hot water coagulation, aqueous electrolyte coagulation, RF coagulation, microwave coagulation, ultrasonic coagulation, infrared (infrared) coagulation or steam coagulation. Preferably, air coagulation takes place, and thus thermal fixation of the PU or coagulation in aqueous solutions containing salts (such as, for example, alkali and alkaline earth metal salts) or acids which destabilize the dispersion (such as organic acids, such as formic acid) is achieved. , acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid or inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid).

In the case of hot air coagulation, the material obtained after step f) is brought into contact with air at a temperature of from about 50°C to about 200°C, preferably from about 50°C to 160°C, in order to better control the migration of the polyurethane at heating; the duration of heating may, for example, vary depending on the type of polyurethane used, because in the case of using polyurethanes that coagulate thermally, it is possible to limit the heating of the impregnated intermediate product, avoiding complete drying and thus saving on the amount of energy required to evaporate the water present. Preferably, the PU is coagulated on the microfiber intermediate in an oven, preferably a pin oven, with a temperature increase of between 50°C and 160°C. Said temperature gradient prevents the water from evaporating so rapidly that it also transports the solid portion of the dispersion to the surface before it has received sufficient heat to decompose any surfactants present that stabilize the PU.

The hot air coagulation disclosed here advantageously results in a finished product which has excellent stability and durability. In addition, when coagulated with hot air, polyurethane tends to become transparent, making possible stains less noticeable.

In the case of coagulation in an aqueous solution containing dissolved electrolytes (salts and acids), polyurethane can be coagulated at a low temperature (that is, at a temperature not exceeding 70°C) with significant energy savings.

In this case, the impregnated intermediate obtained after step f) is brought into contact, preferably by immersion, with water at a temperature of from about 20°C to 90°C, preferably from about 40°C to 80°C, containing a certain amount of a destabilizing agent (electrolyte) of the PU dispersion, which makes it possible to lower the temperature at which the PU begins to coagulate (also referred to as "cloud point").

One example of a destabilizing agent are calcium and magnesium halides and sulfates, preferably CaCl ₂ and MgSO ₄ . The selected agent can be used in amounts ranging from 0.01 to 5 wt.%, more preferably from 0.1 to 1%. Hot water coagulation is particularly suitable when an improved softness of the final product is desired.

Another example of a destabilizing agent are acids added to the coagulation solution, which cause protonation of the anionic groups present in the polyurethane chain (introduced during synthesis by adding ionomers along with polyols and isocyanate). Such acids may be selected, for example, from organic acids such as formic, acetic, oxalic, maleic acid or inorganic acids such as hydrochloric, sulfuric, phosphoric acid.

Furthermore, in a preferred embodiment of the invention, in order to minimize polyurethane migration during the coagulation process and/or minimize the loss of polyurethane in the coagulation tank, a thickener is also added to the formulation containing PU, which can increase the viscosity of the formulation. Preferably the thickener is of the associative type, ie able to bind to the PU present in the aqueous dispersion already in the form of micelles and thus create more complex dispersion structures in which the micelles aggregate together. The operation of these association systems is well known to those skilled in the art. Another type of particularly effective thickeners are polyacrylate thickeners, which not only increase the viscosity of the formulation, but also modify the structure of the polyurethane coagulated to form irregular and partially porous surfaces. Mixtures of these two types of thickeners are also particularly effective to act simultaneously on both dispersion stages (water and polyurethane).

In the case of hot air coagulation, association type polyurethane thickeners are preferred, since acrylic types generally stiffen the polyurethane to which they are added.

The intermediate product after coagulation of the polyurethane and before finishing may be crosslinked by the polyurethane due to the activation of the crosslinkers present in the impregnating composition. The crosslinking treatment generally consists of heating the material at a sufficiently high temperature to start the crosslinking process and/or release the blocked isocyanates possibly added to the impregnating composition (step f)) and bind together the polyurethane molecules, thus increasing its resistance to the subsequent staining process (step i)).

The crosslinking process can also be activated or maintained by ultraviolet rays if the crosslinker or other additives can absorb ultraviolet radiation, initiating the process.

The fixing process in step g) may be preceded by radiation with infrared lamps or radio frequencies or microwaves to quickly preheat the polyurethane dispersion, which facilitates its fixing in the inner layers, away from the surface. Of these pre-treatments, the infrared lamp stage is particularly preferred since this type of radiation acts from the surface on the entire mass of polyurethane to control the movement through the thickness. The influence of the use of IR lamps on the impregnation and coagulation process is comparable to the result obtained by adding salts before impregnating the polyurethane (step e)).

The choice of an appropriate wavelength of IR radiation makes it possible to modulate the coagulation effect of the polyurethane, acting predominantly on the surface or acting on the entire mass of the dispersion.

After that, the intermediate product containing PVA and polyurethane is treated with hot water at a temperature of from 80 to 99°C to remove PVA and other additives that may have been added earlier (step h)).

At the end of the impregnation and coagulation of the PU and the removal of the PVA as described above, the resulting material is subjected to finishing step i) to obtain the nonwoven suede fabric of the invention. In particular, the material is subjected to peeling (cutting), grinding and dyeing operations, which are preferably carried out in an open order.

The thus obtained colored intermediate containing ionic chain polyurethane (ionomers) can also be subjected to a second cycle of dyeing with specific dyes, such as, for example, cationic, anionic, sulfur-based, vat or reactive dyes, thus also obtaining dyeing of the polyurethane elastomer matrix.

Polyester microfiber is usually dyed, as described in the literature and known to those skilled in the art, by placing the product in a pressure bath at 120°C to 130°C in an acidic medium, the pH of which is adjusted by adding buffer solutions such as, for example, acetic acid/sodium acetate, using dyes belonging to the family of dispersed dyes, and dispersing and leveling agents, to mention the main additives present.

Using the method disclosed in the present invention, it is also possible to carry out the dyeing process using higher pH values (neutral or alkaline media) without affecting the physical/mechanical and aesthetic properties of the final product; some polyurethane formulations also make it possible to improve the disclosed features when coloring occurs in a basic medium. For this reason, the staining step is preferably carried out in a basic medium with a pH of 8 to 11 (measured at ambient temperature) obtained by adding sodium salts of weak acids at a suitable concentration (such as, for example, acetic acid, citric or carbonic acid) or with suitable buffer systems for better process control (such as, for example, buffers based on amino acids).

If required, for the manufacture of particularly soft materials, it is possible that the dyeing process should be followed by an additional sanding step on the side (side s) opposite to the already sanded side, in order to remove some of the polyurethane from the invisible side of the product, followed by lightening, softening and reducing the thickness of the finished product. products. Alternatively, if it is undesirable to change the appearance and characteristics of the final material by acting on the sides, the resulting product can be subjected to a softening treatment, which, using suitable machines, exposes the resulting product to mechanical stresses inside the softening chamber, using forced ventilation with bayonet technology to change the air intake, directed at the product during processing; these machines determine the further softening of the material without compromising the coloring characteristics (colour fastness), aesthetic characteristics (surface appearance) or physical-mechanical characteristics obtained with this manufacturing process. In addition, when required, a softening treatment can be carried out, for example, by providing an impregnation step with additives or softeners, such as, for example, silicones, which are able to achieve a plasticizing effect with respect to polyurethane, in order to modulate adhesion between polyurethane and microfiber, or simply change the surface sensation of the product (sliding action of the hand on the surface of the product).

The material produced in accordance with the method described can then be subjected to additional post-processing steps, such as, for example, gluing with fabric supports, distribution of resins and fire protection, application of resistant or hidden foam, embossing, inkjet printing, electric welding and laser cuts, with one side or the other, in addition to additional cutting operations, to further reduce the thickness of the dyed product. For a product made in accordance with the present invention, the softening treatment can also be carried out after the post-treatment steps that follow dyeing, without adversely affecting the performance of the product in terms of physical-mechanical properties and appearance.

In an additional aspect, finally, the invention relates to a non-woven synthetic suede fabric obtained (or obtained) using the present method. Advantageously, the non-woven web obtainable by the present method exhibits significant yellowing resistance, good strength and high durability, so that it is particularly suitable for dyeing with light colored dyes such as white for example. In addition, thanks to the finishing steps carried out as described above, the method of the invention makes it possible to obtain a final non-woven fabric which can have a thickness that is also less than 0.7 mm, yet is capable of providing interesting physical/mechanical characteristics without the aid of a structural fabric, which makes the process very versatile and applicable in various practical purposes.

Furthermore, due to the use of polyurethanes with ionic groups in the chain, the nonwoven fabric that can be obtained using the present method can also be dyed in a polyurethane elastomeric matrix. The addition of salts to the intermediate microfiber article prior to impregnation with water-dispersed polyurethane, similar to the aqueous coagulation process or pre-treatment performed with IR lamps, after the polyurethane impregnation step and before subsequent drying in the hot air coagulation process, minimizes the content of polyurethane associated with microfibers close to the surface, and better control of adhesion throughout the thickness of the material, which makes it possible to produce a particularly soft non-woven fabric with an appearance that is identical in every way to the product obtained with a modern solvent process and which has a high resistance to abrasion.

Pre-treatment with IR lamps also gives the final product greater abrasion resistance, also with low polyurethane content.

The energy required for drying can be provided entirely by infrared, radio frequencies or microwaves, or combinations thereof, just as the activation of the crosslinker can occur with infrared, preferably in the case of thin intermediate products.

The final softening processes described also make it possible to obtain a product comparable to the base materials produced today by modern solvent processes.

The invention will now be disclosed by means of the following experimental part, which, however, is not intended to limit its scope.

EXAMPLES 0. PVA REINFORCED FELT

In the family of examples 0, an intermediate product is obtained, which is designated as "D nth", where n is a consecutive number formed by microfiber and PVA. Sometimes salts may be present.

Example 0.1

The short fibers are made from an island-in-sea bicomponent fiber in which the island component is made from PET and the marine component is made from co-PES. The ratio of the island component to the marine component in the fiber is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-sea fiber.

Features of short fibers:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to obtain a felt with a density of 0.212 g/cm ³ and a specific gravity of 599 g/m ² .

The felt is spaced for 5 minutes in a 85°C solution containing 11.6% PVA with a high saponification value (98%), dried in a first oven and then processed in a second oven at 190°C for 3 minutes, sufficient time for the PVA to heat cure, indicated by the amber coloration of the PVA itself.

The subsequent step of removing the marine component from the fiber consists of two steps, followed by convective drying: an alkaline treatment with caustic soda at 8 wt.% and at 65°C and a cold wash in water sufficient to return the pH values to values below 8. Strengthened by this Thus, the element contains PVA, which is 28 wt.% and is designated as "intermediate D1".

Example 0.2

The fine fibers are made from an island-in-the-sea bicomponent fiber in which the island component is made from Bio-PET and the marine component is made from Bio-coPES.

Bio-PET was obtained by polycondensation of terephthalic acid and ethylene glycol, which are obtained from raw materials obtained as a result of fermentation processes and subsequent transformations. This polymer has a 100% renewable material percentage (>95% in ¹⁴ C units measured according to ASTM-D6866-08).

Bio-coPES was obtained by polycondensation of 5-sulfoisophthalic acid and terephthalic acid synthesized from fossil raw materials with ethylene glycol obtained by fermentation. This polymer contains 35% renewable material (equal to 20% in terms of ¹⁴ C, measured according to ASTM-D6866-08).

The ratio of the island component to the marine component in the fiber is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-sea fiber.

Features of short fibers:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to obtain a felt with a density of 0.202 g/cm ³ and a specific gravity of 603 g/m ² .

The felt is sized by passing for 5 minutes in a 85°C solution containing 11.6% PVA with a high saponification value (98%) and dried in a first oven and then processed in a second oven at 190°C for 3 minutes, sufficient time for the PVA to heat cure, indicated by the amber coloration of the PVA itself.

The subsequent step of removing the marine component from the fiber consists of two steps, followed by convective drying: an alkaline treatment with caustic soda at 8 wt.% and at 65°C and a cold wash in water sufficient to return the pH values to values below 8. Strengthened by this Thus, the element contains 27 wt.% PVA and is designated as "intermediate D2".

Example 0.3

Intermediate D1 was immersed in a 1% NaCl solution, squeezed out with a pair of brine dosing rollers, and then dried again in a convection oven. The piece thus treated contains 23 wt.% PVA, 14 wt.% NaCl and is designated as "intermediate D3".

Example 0.4

The short fibers are made from an island-in-sea bicomponent fiber in which the island component is made of PET and the marine component is made of co-PES.

In the extrusion step, a masterbatch containing 30% by weight carbon black (CB) in the PET matrix is added to the PET, the carbon black is thus dispersed at 1% by weight in the PET fibers.

The ratio of the island component to the marine component in the fiber is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-sea fiber.

Features of short fibers:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to obtain a felt with a density of 0.197 g/cm ³ and a specific gravity of 596 g/m ² .

The felt is sized by passing for 5 minutes in a 85°C solution containing 11.6% PVA with a high saponification value (98%) and dried in a first oven and then processed in a second oven at 190°C for 3 minutes.

The subsequent step of removing the marine component from the fiber consists of two steps, followed by convective drying: an alkaline treatment with caustic soda at 8 wt.% and at 65°C and a cold wash in water sufficient to return the pH values to values below 8. Strengthened by this Thus, the element contains 28 wt.% PVA and is designated as "intermediate D4".

Example 0.5

The short fibers are made from an island-in-sea bicomponent fiber in which the island component is made of PET and the marine component is made of co-PES. The ratio of the island component to the marine component in the fiber is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-sea fiber.

Features of short fibers:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to obtain a felt with a density of 0.202 g/cm ³ and a specific gravity of 603 g/m ² .

The felt is subjected to a three-dimensional withdrawal for 5 minutes in a 85° C. solution containing 11.6% PVA with a high saponification value (98%) and dried in an oven.

The subsequent step of removing the marine component from the fiber consists of two steps, followed by convective drying: an alkaline treatment with caustic soda at 8% by weight and at 45°C and a cold wash in water sufficient to return the pH to below 8. the element contains 24 wt.% PVA and is designated as "intermediate D5".

Example 0.6

The short fibers are made from an island-in-sea bicomponent fiber in which the island component is made of PET and the marine component is made of co-PES. The ratio of the island component to the marine component in the fiber is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-sea fiber.

Herd Features:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to obtain a felt with a density of 0.202 g/cm ³ and a specific gravity of 603 g/m ² .

The felt is spaced by passing for 5 minutes in a 85°C solution containing 11.6% PVA with a high saponification value (98%), it is dried in an oven and immediately after that it is exposed to IR radiation for 1 minute, modulating the intensity of the IR lamps so that the surface temperature of the intermediate product is maintained at 200°C. Under these conditions, the darkening of the intermediate is much lower than with the same intermediate in Example 0.1, as it is barely perceptible.

The subsequent step of removing the marine component from the fiber consists of two steps, followed by convective drying: an alkaline treatment with caustic soda at 8 wt% at 65°C and a cold wash in water sufficient to return the pH values to values below 8. Enhanced in this way the element contains 28 wt.% PVA and is designated as "intermediate D6".

Example 0.7

The short fibers are made from an island-in-sea bicomponent fiber in which the island component is made from bio-PET and the marine component is made from a fossil-based copolymer.

Bio-PET was obtained by polycondensation of terephthalic acid of fossil origin with ethylene glycol obtained by fermentation. This polymer has a 30% renewable material percentage ( ²⁰ % in 14C units measured according to ASTM-D6866-08).

The ratio of the island component to the marine component in the fiber is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-sea fiber.

Herd Features:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to obtain a felt with a density of 0.222 g/cm ³ and a specific gravity of 624 g/m ² .

The felt is subjected to a three-dimensional withdrawal for 5 minutes in a 85° C. solution containing 11.6% PVA with a high saponification value (98%) and dried in an oven.

The subsequent step of removing the marine component from the fiber consists of two steps, followed by convective drying: alkaline treatment with caustic soda at 8 wt.% at 45°C and cold washing in saline 1.0% NaCl.

The thus treated piece contains 23 wt.% PVA, 8 wt.% NaCl and is designated as "intermediate D7".

Example 0.8

The short fibers are made from an island-in-sea bicomponent fiber in which the island component is made of PET and the marine component is made of co-PES.

At the extrusion stage, a master batch containing carbon black (CB) in an amount of 30 wt.% in the PET matrix is added to the PET; the carbon black is thus dispersed at 1% by weight in the PET fibers.

The ratio of the island component to the marine component in the fiber is 57:43. The fiber cross section shows 16 PET microfibers in a round shape and of equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-sea fiber.

Features of short fibers:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to obtain a felt with a density of 0.189 g/cm ³ and a specific gravity of 592 g/m ² .

The felt is subjected to a three-dimensional withdrawal for 5 minutes in a 85° C. solution containing 11.6% PVA with a high saponification value (98%) and dried in an oven.

The subsequent step of removing the marine component from the fiber consists of two steps, followed by convective drying: alkaline treatment with caustic soda at 8 wt.% at 45°C and cold washing in an acidic pH solution buffered with acetic buffer.

The piece thus treated contains 23% by weight PVA, 12% sodium acetate and is designated "intermediate D8".

Example 0.9

The short fibers are made from an island-in-sea bicomponent fiber in which the island component is made from PET and the marine component from bio-co-PES.

Bio-co-PES was made by polycondensation of 5-sulfoisophthalic acid and terephthalic acid synthesized from fossil raw materials with ethylene glycol obtained by fermentation. This polymer contains 35% renewable material (equivalent to 20% in terms of ¹⁴ C measured according to standard ASTM-D6866-08).

The ratio of the island component to the marine fiber component is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-the-sea fiber.

Features of short fibers:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to make a felt with a density of 0.200 g/cm ³ and a specific gravity of 600 g/m ² .

The felt is subjected to spatial removal for 5 minutes in a 85°C solution containing 11.6% PVA with a high saponification value (98%), dried in an oven and exposed directly thereafter to IR radiation for 1 minute, modulating the IR intensity lamps so that the surface temperature of the intermediate product is maintained at 190°C. Under these conditions, the browning of the intermediate is significantly lower than that of the same intermediate in Example 0.1, which can hardly be perceived.

The subsequent step of removing the marine component from the fiber consists of two steps followed by convective drying: an alkaline treatment of caustic soda at 8% by weight at 65°C and a cold wash in water sufficient to return the pH to values below 8. Thus, enhanced the piece contains 28 wt.% PVA and is defined as "intermediate D9".

Example 0.10

The short fibers are made from an island-in-the-sea bicomponent fiber in which the island component is made from Bio-PET and the marine component is made from fossil co-PES.

Bio-PET was made by polycondensing fossil-based terephthalic acid with fermented ethylene glycol. In this polymer, the percentage of material from renewable sources is 30% (20% in terms of content ¹⁴ C, measured in accordance with standard ASTM-D6866-08).

The ratio of the island component to the marine fiber component is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-the-sea fiber.

Features of short fibers:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to make a felt with a density of 0.198 g/cm ³ and a specific gravity of 609 g/m ² .

The felt is spaced for 5 minutes in a 85°C solution containing 11.6% PVA with a high saponification value (98%), dried in the first oven and immediately afterwards subjected to IR radiation for 1 minute, modulating the intensity of the IR lamps so that the surface temperature of the intermediate product is maintained at 200°C. Under these conditions, the browning of the intermediate is significantly lower than that of the same intermediate in Example 0.1, which can hardly be perceived.

The subsequent step of removing the marine component from the fiber consists of two steps followed by convective drying: an alkaline treatment with caustic soda at 8% w/h at 45°C and a cold wash with water sufficient to return the pH to values below 8. Thus, enhanced the piece contains 23 wt.% PVA and is defined as "intermediate D10".

Example 0.11

The short fibers are made from an island-in-the-sea bicomponent fiber in which the island component is made from Bio-PET and the marine component is made from fossil co-PES.

Bio-PET was made by polycondensing fossil-based terephthalic acid with fermented ethylene glycol. This polymer contains 30% renewable material (20% in 14C units measured according to standard ASTM- ^D6866-08 ).

The ratio of the island component to the marine fiber component is 57:43. The fiber cross section shows 16 PET microfibers of round shape and equal diameter. Short fibers are obtained by subsequent stretching, crimping and cutting of a continuous island-in-the-sea fiber.

Herd Features:

denier 4.3 dtex.

length 51 mm

curl about 4/cm

stretch ratio 2.5:1

The short fibers thus defined are mechanically punched with a needle to make a felt with a density of 0.202 g/cm ³ and a specific gravity of 611 g/m ² .

The felt is subjected to a spatial withdrawal for 5 minutes in a 85°C solution containing 11.6% PVA with a high saponification value (98%) and dried in a first oven and then processed in a second oven at a temperature of 190°C for 3 minutes, which is sufficient time for the heat cure of the PVA, indicated by the amber color of the PVA itself.

The subsequent step of removing the marine component from the fiber consists of two steps followed by convective drying: alkaline treatment with caustic soda at 8 wt.% at 65°C and cold water washing sufficient to return the pH to values below 8. Thus, the reinforced piece contains 28 wt.% PVA and is defined as "intermediate D11".

EXAMPLES 1. IMPREGNATION

The intermediate products made in Examples 0 were impregnated with an aqueous dispersion containing emulsions of polyurethane and other additives such as crosslinking agent, thickener, salts and various fillers, each in a weight ratio as shown in Table 1.

In particular, the products used for aqueous dispersion are:

Polyurethane 1: Aliphatic PUD, anionic, polyester/polycarbonate base. Water content 39%.

Polyurethane 2: Type 1 BIO-PUD (aliphatic PUD, anionic, polycarbon/polycarbonate base) whose polycarbonate fraction contains 22% renewable sources (in units of ¹⁴ C, measured in accordance with standard ASTM-D6866-08). Water content 41%.

Polyurethane 3: Aliphatic PUD, anionic property, polyester base. Water content 40%.

Polyurethane 4: Aliphatic Bio-PUD, anionic, polyester base with 45% carbon from renewable sources (in units of ¹⁴ C measured in accordance with standard ASTM-D6866-08). Water content 56%.

Polyurethane 5: Aliphatic PUD, anionic property, polycarbonate base. Water content 40%.

Crosslinking agent 1: blocked aliphatic polyisocyanate dispersed in water, with a deblocking temperature of 120° C. and 55% water content.

Crosslinking agent 2: multifunctional polycarbodimide dispersed in water with a water content of 61%.

Thickener 1: Polyurethane type associative thickener, the active ingredient of which is equal to 20% of its weight (33% solids).

Thickener 2: carboxymethyl cellulose type polymeric thickener in powder form.

Thickener 3: Xanthan gum rheology modifier in powder form.

Thickener 4: acrylic thickener with its active ingredient at 10% by weight.

Filler 1: a polyvinyl alcohol solution with a viscosity of <100 cPs at 20°C with low shear stresses.

Filler 2: co-PES water solution.

Filler 3: ammonium bicarbonate solution.

Filler 4: hydrophilic emulsions of modified polysiloxane, self-emulsifying.

In the course of impregnation with the chosen formulation, the wet intermediate is dried and then taken up to 150° C. using the techniques disclosed in Table 1.

Each part is then subjected to hot water washing and drying, thus generating the nth intermediate, identified as "intermediate IE n", where "n" is the number given in Table 1. The waste liquid generated from the washing step, contains PVA which can be recycled for recovery.

Example 1.01

An aqueous dispersion is prepared containing a 3:1 mixture of pure type 2 and 3 polyurethanes, type 1 crosslinker and type 1 thickener to achieve a viscosity of 600 mPa.s at 20°C under application conditions.

The previously defined intermediate D1 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove residual water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water (devoid of alkaline earth salts) at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 33% polyurethane and is identified as "Intermediate IE 1", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.02

An aqueous dispersion is prepared containing a 3:1 mixture of type 1 and 3 polyurethanes, type 1 crosslinker and type 1 filler to achieve a viscosity of 450 mPa.s at 20° C. under application conditions.

The previously defined intermediate D1 is impregnated by immersion in this dispersion, which is twice its weight, subjected to infrared pretreatment steps ranging from 2 to 10 microns, and then subjected to heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles. substances and activation of the crosslinking agent.

The article is then washed at atmospheric pressure to remove PVA with softened water at a temperature close to the boiling point with a PVA dispersing agent as described in the prior art, and then dried again.

The intermediate product, which contains 32% polyurethane and is identified as "intermediate IE 2", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.03

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker, type 3 thickener and type 1 filler to achieve a viscosity of 662 mPa.s at 20° C. under application conditions.

The previously defined intermediate D1 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove residual water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 25% polyurethane and is identified as "Intermediate IE 3", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.04

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker and type 1 thickener to achieve a viscosity of 560 mPa.s at 20° C. under application conditions.

The previously defined intermediate D1 is impregnated by immersion in this dispersion, which is twice its weight, subjected to infrared pretreatment steps ranging from 2 to 10 microns, and then subjected to heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles. substances and activation of the crosslinking agent.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 25% polyurethane and is identified as "Intermediate IE 4", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.05

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker, type 1 thickener and type 2 filler to achieve a viscosity of 560 mPa.s at 20°C under application conditions.

The previously defined intermediate D1 is impregnated by dipping into this dispersion of twice its weight, subjected to a predetermined stage with infrared radiation ranging from 2 to 10 microns, followed by heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles. and activation of the crosslinker.

The article is then washed under atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 33% polyurethane and is identified as "intermediate IE 5", is subjected to subsequent mechanical delamination and grinding before being subjected to the acid coloring process in accordance with the prior art.

Example 1.06

An aqueous dispersion containing type 1 polyurethane, type 1 crosslinker and type 1 thickener is prepared to achieve a viscosity of 560 mPa.s at 20° C. under application conditions.

The previously defined intermediate D1 is impregnated by dipping into this dispersion twice its weight, pre-treated with radio frequency until half of the water is removed (50 seconds in a parallel field oven applying a voltage of 0, 5 kV), followed by heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate, which contains 34% polyurethane and is identified as "Intermediate IE 6", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid staining process in accordance with the previous art.

Example 1.07

An aqueous dispersion is prepared containing type 2 polyurethane, type 2 crosslinker and type 1 thickener to achieve a viscosity of 499 mPa.s at 20° C. under application conditions.

The previously defined intermediate D1 is immersed in this dispersion, which is twice its weight, and immediately treated in a convection oven to fix the suspended particles, remove water and volatiles, and activate the cross link.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 28% polyurethane and is identified as "intermediate IE 7", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid coloring process in accordance with the prior art.

Example 1.08

An aqueous dispersion is prepared containing a 3:1 mixture of pure type 1 and 3 polyurethanes, type 1 crosslinker and type 2 thickener to achieve 790 mPa.s at 20° C. under application conditions.

The previously defined intermediate D1 is immersed in this dispersion, which is twice its weight, and immediately treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 32% polyurethane and is identified as "intermediate IE 8", is subjected to subsequent mechanical delamination and grinding before being subjected to the acid staining process in accordance with the prior art.

Example 1.09

An aqueous dispersion containing type 2 polyurethane, type 1 crosslinker and type 1 thickener is prepared to achieve 560 mPa.s at 20° C. under application conditions.

The previously defined intermediate D2 is impregnated by dipping into this dispersion twice its weight, subjected to a predetermined infrared stage ranging from 2 to 10 microns, followed by heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles, and activation of the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate, which contains 33% polyurethane and is identified as "intermediate IE 9", is subjected to subsequent mechanical peeling and sanding, and then subjected to a coloring process at pH 9.4 with the addition of sodium acetate.

Example 1.10

An aqueous dispersion is prepared containing type 2 polyurethane, type 1 crosslinker and type 1 thickener to achieve a viscosity of 560 mPa.s at 20° C. under application conditions.

The previously defined intermediate D2 is immersed in this dispersion, which is twice its weight, and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 32% polyurethane and is identified as "intermediate IE 10", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.11

An aqueous dispersion is prepared containing a 3:1 mixture of pure type 2 and 3 polyurethanes, type 1 crosslinker and type 1 thickener to achieve a viscosity of 600 mPa.s at 20° C. under application conditions.

The previously defined intermediate D3 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 32% polyurethane and is identified as "Intermediate IE 11", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.12

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker and type 1 thickener to achieve a viscosity of 560 mPa.s at 20° C. under application conditions.

The previously defined intermediate D4 is immersed in this dispersion, which is twice its weight, and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 32% polyurethane and is identified as "Intermediate IE 12", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.13

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker, type 1 thickener and type 3 filler to achieve a viscosity of 555 mPa.s at 20° C. under application conditions.

The previously defined intermediate D4 is impregnated by immersion in this dispersion, which is twice its weight, and immediately heat treated first in a convection oven at low temperature (60°C to 75°C during oven time) to thermally split the ammonium salt, and then at a higher temperature to fix suspended particles, remove water and volatiles, and activate the crosslinking agent.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 34% polyurethane and is identified as "intermediate IE 13", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

The addition of additive type 3 results in a polyurethane structure which is not completely homogeneous and which leaves the microfibers partially loose, as can be seen in the SEM image of FIG. 4A.

Example 1.14

An aqueous dispersion is prepared containing a 4:1 mixture of type 1 and 3 polyurethanes, type 1 crosslinker and type 1 filler to achieve a viscosity of 450 mPa.s at 20° C. under application conditions.

The previously defined intermediate D5 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove PVA with softened water at a temperature close to the boiling point with a PVA dispersing agent as described in the prior art, and then dried again.

The intermediate product, which contains 32% polyurethane and is identified as "intermediate IE 14", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.15

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker and type 1 thickener to achieve a viscosity of 560 mPa.s at 20° C. under application conditions.

The previously defined intermediate D5 is impregnated by dipping into this dispersion twice its weight, subjected to infrared pre-treatment steps ranging from 2 to 10 microns, and then subjected to heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles. substances and activation of the crosslinking agent.

The piece is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 34% polyurethane and is identified as "intermediate IE 15", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.16

An aqueous dispersion is prepared containing type 4 polyurethane, type 2 crosslinker and type 1 thickener to achieve a viscosity of 775 mPa.s at 20° C. under application conditions.

The previously defined intermediate D5 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 30% polyurethane and is identified as "Intermediate IE 16", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.17

An aqueous dispersion is prepared containing a 4:1 mixture of type 1 and 3 polyurethanes, type 1 crosslinker and type 1 filler to achieve a viscosity of 450 mPa.s at 20° C. under application conditions.

The previously defined intermediate D6 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove PVA with softened water at a temperature close to the boiling point with a PVA dispersing agent as described in the prior art, and then dried again.

The intermediate, which contains 33% polyurethane and is identified as "intermediate IE 17", is subjected to subsequent delamination and sanding, and then subjected to a coloring process at pH 9.4 by adding sodium acetate.

Example 1.18

An aqueous dispersion is prepared containing type 3 polyurethane, type 1 crosslinker, type 1 thickener and type 4 filler to achieve a viscosity of 354 mPa.s at 20° C. under application conditions.

The previously defined intermediate D6 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 29% polyurethane and is identified as "intermediate IE 18", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.19

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker and type 1 thickener to achieve 560 mPa.s at 20° C. under application conditions.

The previously defined Intermediate D7 is immersed in this dispersion, which is twice the weight, and immediately treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 35% polyurethane and is identified as "intermediate IE 19", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.20

An aqueous dispersion is prepared containing a 4:1 mixture of type 1 and 3 polyurethanes, type 1 crosslinker and type 1 filler to achieve 450 mPa.s at 20° C. under application conditions.

The previously defined intermediate D8 is impregnated by dipping into this dispersion twice its weight, subjected to infrared pre-treatment steps ranging from 2 to 10 microns, followed by heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles. substances and activation of the cross-linking agent.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point using a PVA dispersing agent as described in the prior art, and then dried again.

The intermediate product, which contains 33% polyurethane and is identified as "intermediate IE 20", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.21

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker and type 1 thickener to achieve 560 mPa.s at 20° C. under application conditions.

The previously defined intermediate D9 is impregnated by dipping into this dispersion twice its weight, subjected to infrared pre-treatment steps ranging from 2 to 10 microns, followed by heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles. substances and activation of the cross-linking agent.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 33% polyurethane and is identified as "intermediate IE 21", is subjected to subsequent mechanical delamination and grinding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.22

An aqueous dispersion is prepared containing a 4:1 mixture of type 1 and 3 polyurethanes, type 1 crosslinker and type 1 filler to achieve 450 mPa.s at 20° C. under application conditions.

The previously defined intermediate D9 is impregnated by dipping into this dispersion twice its weight, subjected to infrared pre-treatment steps ranging from 2 to 10 microns, followed by heat treatment in a convection oven to fix suspended particles, remove residual water and volatiles. substances and activation of the cross-linking agent.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point using a PVA dispersing agent as described in the prior art, and then dried again.

The intermediate, which contains 33% polyurethane and is identified as "intermediate IE 22", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.23

An aqueous dispersion is prepared containing a 4:1 mixture of type 1 and 3 polyurethanes, type 1 crosslinker and type 1 filler to achieve 450 mPa.s at 20°C under application conditions.

The previously defined intermediate D9 is immersed in this dispersion, which is twice its weight, and immediately heat treated in a convection oven to fix suspended particles, remove residual water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove PVA with softened water at a temperature close to the boiling point with a PVA dispersing agent as described in the prior art, and then dried again.

The intermediate product, which contains 32% polyurethane and is identified as "Intermediate IE 23", is subjected to subsequent mechanical peeling and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.24

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker, type 1 thickener and type 4 filler to achieve a viscosity of 555 mPa.s at 20° C. under application conditions.

The previously defined intermediate D10 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with water devoid of alkaline earth salts at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 33% polyurethane and is identified as "intermediate IE 24", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.25

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker and type 1 thickener to achieve a viscosity of 485 mPa.s at 20° C. under application conditions.

The previously defined intermediate D1 is immersed in this dispersion, which is twice its weight, and immediately heat treated in a convection oven to fix suspended particles, remove water and volatiles, and activate the crosslinker.

Then, the article piece is washed at atmospheric pressure to remove the PVA with water devoid of alkaline earth salts at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 35% polyurethane and is identified as "intermediate IE 25", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.26

An aqueous dispersion is prepared containing type 1 polyurethane, type 1 crosslinker and type 1 thickener to achieve a viscosity of 601 mPa.s at 20°C under application conditions.

The previously defined intermediate D11 is immersed in this dispersion twice its weight and immediately heat treated in a convection oven to fix suspended particles, remove residual water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with water devoid of alkaline earth salts at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 33% polyurethane and is identified as "intermediate IE 26", is subjected to subsequent mechanical delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.27

"Intermediate IE 25" is made as described in Example 1.25 and subjected to the same mechanical processes.

In contrast, coloring occurs at pH 9.4 by adding sodium acetate.

The intermediate contains 35% polyurethane and is designated "intermediate IE 27".

Example 1.28

An aqueous dispersion is prepared containing type 5 polyurethane, type 1 crosslinker and type 1 thickener to achieve a viscosity of 654 mPa.s at 20°C under application conditions.

The previously determined intermediate D1 is impregnated by immersion in this dispersion, which is twice its weight, immersed in a coagulating solution consisting of an aqueous solution of 5% acetic acid at 50°C for 10 minutes, and then subjected to heat treatment in a convection oven to in order to fix the particles of coagulated polyurethane, remove residual water and volatile substances and activate the crosslinking agent.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate, which contains 33% polyurethane and is identified as "Intermediate IE 28", is subjected to subsequent mechanical peeling and sanding before being subjected to the prior art acid staining process.

Example 1.29

An aqueous dispersion is prepared containing type 2 polyurethane and a 1:1 mixture of type 1 and type 4 thickeners to achieve a viscosity of 3433 mPa.s at 3.58 s ^-1 at 20°C.

The previously defined intermediate D4 is impregnated by immersion in this dispersion, which is twice its weight, immersed in a coagulation solution consisting of an aqueous solution of 0.25% formic acid in hot water at a temperature of 60°C for 15 minutes, followed by heat treatment in a convection oven to fix the coagulated polyurethane particles, remove residual water and volatiles, and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate, which contains 33% polyurethane and is identified as "intermediate IE 29", is subjected to subsequent delamination and sanding before being subjected to the acid dyeing process in accordance with the prior art.

Example 1.30

An aqueous dispersion is prepared containing type 4 polyurethane, type 1 crosslinker and a 1:4 mixture of type 1 and type 4 thickeners to achieve a viscosity of 768 mPa.s at 3.58 s ^-1 at 20°C.

The previously defined intermediate D1 is impregnated by immersion in this dispersion, which is twice its weight, immersed in a coagulation solution consisting of an aqueous solution of 0.5% formic acid in hot water at a temperature of 60°C for 7 minutes, and then followed by heat treatment in a convection oven in order to fix the coagulated polyurethane particles, remove residual water and volatiles and activate the crosslinker.

The article is then washed at atmospheric pressure to remove the PVA with softened water at a temperature close to the boiling point, and then dried again.

The intermediate product, which contains 29% polyurethane and is identified as "intermediate IE 30", is subjected to subsequent mechanical delamination and grinding before being subjected to the acid dyeing process in accordance with the prior art.

The rendered intermediates after dyeing in an industrial jet having an acid pH according to the prior art for polyester-based fibers or a basic pH by adding sodium salts of weak acids were then characterized for appearance, feel, abrasion resistance and their durability. Sensory assessments by touch, by sight and by touch are carried out to compare reference products obtained by the solvent process. An assessment is made by hand about the parameters of softness and gluing (restoration of elasticity and elasticity); pile uniformity and surface feel are valued to judge appearance.

All sensory ratings are expressed as numerical values from 1 to 5, where 1 is the minimum, 5 is the maximum, and 3 is still an acceptable value.

Abrasion resistance is evaluated by measuring weight loss and/or changes in appearance. In particular, the following are assessed:

- pilling (formation of a surface layer of fluff which then tangles and forms the actual balls of fibre; the phenomenon is primarily noticeable in clothing made from natural fibers such as wool), by visual comparison with 5 reference materials, after the material has been subjected to abrasion test with a Martindale abrasion tester (EN ISO 12947) for 2000 cycles, 5000 cycles, 10000 cycles and 20000 cycles, at a pressure of 12 kPa, there is a shearing phenomenon associated with the loss of fluff from the surface during the abrasion test with a Martindale abrasion tester (EN ISO 12947) for 2000 cycles, 5000 cycles, 10000 cycles and 20000 cycles at 12 kPa; the evaluation is qualitative and is based on the evaluation of the part of the abraded surface devoid of fiber. A score of 5 is given when the lint-free surface is less than 10% of the abraded surface, 4 corresponds to a lint-free surface accounting for 10% to 20% of the total surface, 3 is given when the lint-free surface is 20% to 30 %, 2 when it is from 30 to 40%, 1 when the lint-free surface exceeds 40% of the surface subjected to abrasion.

These phenomena are generally affected by the adhesion between the polyurethane and the fiber: at high adhesion, there is no pilling phenomenon, but pile shearing phenomena may occur, due to the fact that if the fiber cannot move properly during the abrasion test, it may fail. delamination; on the other hand, when the polyurethane is poorly bonded to the fiber, pilling may occur, while the fluff shearing phenomenon is generally absent.

"Durability" is defined as the resistance of a dyed material to abrasion over time, including after prolonged and repeated exposure to light and highly hydrolysing media. Aging tests used to measure "durability":

1. Aging under the action of ultraviolet rays, carried out on Xenotest BETA equipment under the following conditions: relative humidity 20±10%; black panel temperature 100±3°C; radiation power 60 W/m ² ; holding time 190 h (standard PV1303).

2. Hydrolysis resistance (shortly known as "Jungle Test") was carried out using an ambient chamber under the following conditions: relative humidity 90 + 3%; temperature 75±1°C; exposure time 5-7-10 weeks.

Durability after aging tests is always evaluated in terms of changes in appearance. In particular, the following are assessed:

- pelletizing by visual comparison with 5 standard samples after the material has been subjected to an abrasion test with a Martindale abrasion tester (EN ISO 12947) for 20,000 cycles at a pressure of 12 kPa.

- the presence of the phenomenon of cutting the pile.

The rating scales are those that were previously disclosed.

Prototypes made in accordance with the previously illustrated examples, after they were painted in an industrial jet, were evaluated with the results summarized in table 2; in the same table, an evaluation of the prototypes made according to EP1323859 (solvent process Prototype A) and examples 2.2 (Prototype B) and 1.1b (Prototype C) disclosed in EP2780501 are shown as a comparison.

The scores in Table 2 show how the application of IR technology to the pre-treatment of polyurethane and changing the solubility of PVA entails an improvement in both physical-mechanical and aesthetic properties; moreover, the increased rigidity at the same polyurethane content in an intermediate product treated with this technology is solved by lowering the required percentage of polyurethane, with significant advantages in terms of appearance, production costs and the associated environmental impact.

The use of a filler such as PVA results in improved softness and tactility, but at the expense of resilience and surface appearance, which is worse. The gap can be partially filled by the use of IR technology.

In addition, the addition of monovalent salts prior to impregnation with polyurethane (in PVA or in the intermediate product obtained in step e) of the process) makes it possible to simulate the distribution of PUD in the product, which has a positive effect on the physical-mechanical properties and appearance, at the expense of softness for the same PUD content. In some polyurethane formulations, the dye pH (acidic or basic) can affect the appearance and physical-mechanical properties of the joint.

The use of a coagulation process in an aqueous solution of salts or acids makes it possible to obtain a porous polyurethane structure, which, in addition to imparting a product softness to the touch and an appearance that is similar to products obtained using a solvent method, also allows to obtain a porous polyurethane structure similar to the structure that can be obtained using the method using a solvent (see Fig. 4B).

The combination of the new technologies disclosed above makes it possible to target the final properties of the compound to the desired analytical and sensory characteristics.

In particular, as can be seen from the data shown in FIG. 6, in Table 1, prototypes made using the method according to the present invention (IE01-IE30) were compared with prototypes B and C made using a similar method disclosed in patent EP2780501; those. a process that does not require the use of organic solvents but does not include a washing step (step e)) of the microfiber intermediate. It can be noted that for the prototypes of the present invention, the hand sensory scores, softness and appearance are clearly superior to the results obtained for prototypes B and C, approaching or even comparing the results obtained on the reference prototype A, obtained by the modern method using the solvent disclosed in the patent EP1323859.

Of the 30 prototypes made by the method of the present invention, 83% (i.e. 25 prototypes) show a better appearance (sensory score of 4 or 5 out of a maximum of 5) than prototypes B and C (sensory score of 2 and 3 respectively) approaching or even comparing the desired appearance (5 out of 5) that can be achieved with the solvent method.

The feel and softness scores of prototypes IE01-IE30 were also better than those of B and C. e. 16 prototypes) feel better (sensory score score of 4 or 5 out of a maximum of 5) than prototypes B and C (sensory score score of 3), approaching or even matching, also in this case, softness and softness in solvent method (sensory score 5 out of 5).

In light of the comparative experiments disclosed above, it is clear that with the process according to the present invention it is possible to obtain a finished product that is achievable with low environmental impact processes or that is environmentally compatible, while at the same time being able to retain the properties feel, softness, elasticity and appearance, which are typical of products obtained by a modern process using an organic solvent.

Claims (19)

1. A method for producing a microfiber nonwoven material, which includes the steps at which: a) an island-in-the-sea bicomponent fiber is produced in which the marine component is a polymer that is removed in hot water or in an aqueous alkaline solution; b) a felt is made by punching a bicomponent fiber with an island-in-the-sea type with a needle; c) performing hot impregnation of the said felt with an aqueous solution of polyvinyl alcohol (PVA) having a degree of saponification of at least 94%, optionally with the addition of a water-soluble organic or inorganic salt; d) removing the marine component from the PVA-impregnated batt obtained in step c) by contacting the batt with an aqueous alkali or alkaline earth metal hydroxide basic solution, thereby obtaining an intermediate microfiber product; e) washing the intermediate microfibrous product obtained in step d) with neutral water containing a water-soluble organic or inorganic salt, or with acidic water, or with neutral water if the aqueous solution of polyvinyl alcohol (PVA) of step c) is supplemented with a water-soluble organic or inorganic salt; f) performing a cold impregnation of the intermediate microfiber product obtained in step e) with polyurethane (PU) dispersed in water containing additives for adjusting the viscosity and possible water-soluble substances; g) fixing the polyurethane (PU) on the intermediate microfiber product by coagulation of the polyurethane dispersion and subsequent drying; h) remove the PVA added in step c), the salt, optionally added in step c) and/or e), and the additives added in step f); i) subjecting the material thus obtained to cutting, grinding on one or both sides and dyeing. 2. Process according to claim 1, wherein the water-soluble organic and inorganic salt optionally present in step c) has a weight ratio of salt to PVA in the range of 0.1 to 20% by weight, preferably 5 to 12% by weight . 3. The method according to claim 1 or 2, wherein the water-soluble organic or inorganic salt solution of step c) or e) is a NaCl or KCl solution. 4. Method according to any one of claims 1 to 3, wherein after step c) the PVA-impregnated felt is subjected to drying and then thermal or radiation treatment at a temperature of at least 100°C, preferably in the range of 140 to 250°C . 5. The method according to any one of claims 1 to 4, wherein in step d) one aqueous basic solution of alkali or alkaline earth metal hydroxide is a solution of NaOH or KOH. 6. The method according to any one of claims 1 to 4, wherein the concentration of the alkali or alkaline earth metal hydroxide is in the range of 0.1 to 48%, preferably in the range of 5 to 12%. 7. Process according to any of claims 1 to 6, wherein the viscosity of the polyurethane (PU) dispersion in water in step f) is in the range of 200 to 800 mPa.s at 20°C. 8. The method according to any one of claims 1 to 7, in which the fixing of the polyurethane (PU) in step g) is carried out by hot air coagulation, hot water coagulation, coagulation in an aqueous solution of acidic electrolytes, radio frequency coagulation, microwave coagulation, ultrasonic coagulation, coagulation infrared (IR) radiation or steam coagulation. 9. The method according to any one of claims 1 to 7, wherein the curing in step g) is preceded by irradiation with infrared lamps or radio frequencies or microwaves in order to rapidly heat the polyurethane dispersion, thereby facilitating the curing process in the inner layers away from the surface. 10. Synthetic suede-like microfiber nonwoven material, which is obtained by the method according to any one of claims 1 to 9.

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