IT9020573A1 - NON-WOVEN FABRIC, OF SYNTHETIC MICROFIBERS, WITH IMPROVED AGING RESISTANCE - Google Patents

Description

Description

The present invention relates to a non-woven fabric based on microfibers of synthetic thermoplastic material, with improved characteristics of stability to aging and the process for its preparation.

It is known in the art to produce synthetic microfiber non-woven fabrics by means of a process which essentially comprises the preparation of a needled felt of polyethylene terephthalate or polyamide-6 or 6.6 microfibers and the application thereto of a polyurethane elastomer to form a microfiber composite sheet, which is subjected to grinding and dyeing treatments. The polyurethane elastomer used for this purpose is the product of the reaction between a diamine-type chain extender and a prepolymer with two isocyanate end groups, the latter being in turn obtained from an organic diisocyanate and a diol, or mixture of diols. . For such a known technique, reference is made in particular to the description of U.S. patents. 3-531-368 and U.S. 3-889.292. The diamines used as chain extenders in the preparation of the polyurethane elastomer, according to the known technique, are of the aromatic or aliphatic or cycloaliphatic type. The starting diisocyanates can be aromatic, aliphatic or cycloaliphatic.

It has now been found that by using in the chain extension step, besides the conventional diamine also a small amount of a dipiperidyl compound of general formula;

in which the same or different from each other, they are H or alkyls containing up to 6 carbon atoms, preferably they are methyl and n is between 1 and 20, preferably it is 6 or 8, elastomeric polyurethanes are obtained, particularly suitable as components in the manufacture of non-woven fabrics according to the invention. The advantage achieved with the use of the polyurethanes according to the invention consists in the high resistance of the final manufactured article obtained to aging caused in particular by the action of atmospheric agents, this resistance remaining at optimal values even after repeated dry cleaning of the manufactured article.

It is known that compounds of the general formula (I) are used as stabilizers by incorporating them in small quantities by mechanical mixing in polymeric materials. The articles obtained from polymeric materials with these additives, however, have the drawback that if they are subjected to frequent "dry" washing with usual organic solvents, the stabilizer in question is progressively extracted from the solvent, thus greatly decreasing the resistance to aging of the article itself. .

The amount of compound of formula (I) to be used to obtain an adequate stabilizing effect is generally comprised between 0.1% and 5% by weight with respect to the total weight of the polyurethane obtained, preferably between 0.25% and 2.5%.

As said above, the present invention relates to a process for the preparation of a synthetic microfiber non-woven fabric which comprises the application of an elastomeric polyurethane to a non-woven microfibre fabric of polyethylene terephthalate, or polyamide-6 or 6,6, in which said elastomeric polyurethane is the product of the reaction between a diamine-type chain extender and an isocyanate-terminated prepolymer obtained from an organic diisocyanate and a mixture of a polyether diol and a polyester diol. The diamine-type chain extender can be selected from the compounds of formula:

each independently represent H or a

alkyl group, linear or branched containing from 1 to 4 carbon atoms, and X represent a hydrogen or halogen atom.

Preferably in formula (II) they each independently represent H or the methyl, ethyl or isopropyl groups and X represents the hydrogen or chlorine atom.

Specific examples of such diamines are:

- 4,4'-methylene bis (aniline);

- 4,4'-methylene bis (2-methyl-6-isopropyl-aniline);

- 4,4'-methylene bis (2,6-diisopropyl-aniline);

- 4,4'-methylene bis (2,6-diethyl ~ 3-chloro-aniline).

Other diamines suitable as chain extenders in the process of the present invention are those of the formula:

where Χ έ Η ο are H or alkyl at 1-4 C.

The non-woven fabric of polyethylene terephthalate, or polyamide-6 or 6,6 microfibers, useful for the purposes of the present invention, can be conveniently obtained in the following way. First a staple fiber is prepared consisting of polyethylene-terephthalate or polyamide-6 or 6.6 microfibres, with denier from 0.01 to 0.40 denier, and preferably of the order of 0.08-0.15 denier, in a polystyrene matrix or a styrene copolymer. More specifically, said staple fiber has the following characteristics: denier from 1.4 to 10 denier, and preferably from 3.4 to 3.8 denier; length from 40 to 60 mm, and preferably of the order of 49-51 mm /; curls from 4 to 15 per cm; stretching ratio from 2/1 to 5/1. Furthermore, the staple fiber can contain 50-80 parts by weight of polyethylene-terephthalate or polyamide-6 or 6.6, 20-50 parts by weight of polystyrene matrix and possibly about 3 parts by weight of polyethylene glycol, the latter being incorporated in the polystyrene matrix. A raw felt is prepared by means of this staple fiber, which is subjected to needle punching to form a needled felt conveniently having a density of the order of 0.15-0.35 g / cc. The needle-punched felt is then immersed in an aqueous solution of polyvinyl alcohol, for example a solution at 20% by weight and, after drying, it is immersed in a chlorinated hydrocarbon such as trichlorethylene or perchlorethylene until the polystyrene matrix is dissolved. The resulting product is subjected to drying and constitutes the non-woven fabric of polyethylene terephthalate or polyamide-6 or 6.6 microfibres, to which the elastomeric polyurethane is applied.

Suitable diisocyanates for the preparation of polyurethanes to be used in the present invention are those known in the art and normally used in the preparation of synthetic microfibrose non-woven fabrics. Of all the diphenylmethane-4,4'-diisocyanate is preferred. Other useful diisocyanates are hexamethylene diisocyanate and toluene diisocyanate.

The polyester diols suitable for the purpose have an average molecular weight of from about 800 to about 4,000 and are conveniently selected from polyethylene diol adipate, polybutylene diol adipate, polyhexamethylene diol adipate and polycaprolactone diol.

Preferably, polycaprolactone diol with a molecular weight of the order of 1,900-2,100 is used. The polyether diols suitable for the purpose have an average molecular weight, from about 800 to about 4,000 and are conveniently selected from polyethylene oxide diol, polypropylene oxide diol and polytetramethylene oxide diol. Polytetramethylene oxide diol with a molecular weight of the order of 1,900-2,100 is preferably used. In the mixture of diols the weight ratio between polyether diol and polyester diol can generally vary from 1/9 to 9/1 with preferred values from 1/4 to 4/1 and with optimal values of the order of 3/1. intermediate prepolymer, 1 mol of organic diisocyanate and 0.5 moles of the mixture of diols are conveniently made to interact, operating with a reaction time of 2-5 hours, at a temperature of 50-90 ° C, in the absence of solvent or diluent.

According to the present invention, the polymer is reacted with a diamine of formula II and / or III in admixture with a smaller quantity of dipiperidyl compound of formula I.

The reaction is preferably carried out in an organic solvent and preferably in N, N'-dimethyl formamide or in Ν, Ν'-dimethyl acetamide, using an overall amount of equimolecular, or approximately equimolecular, amine compound with respect to the diols used to form the prepolymer , and operating at a temperature from about 30 ° to about 80 ° C.

Conveniently, the solution of the diamine in an organic solvent is gradually added to the solution of the prepolymer in the same organic solvent. The reaction can be carried out in the presence of an aliphatic monoaramine, especially N, N'-n-dibutylamine having a "chain terminator" function, in quantities of the order of 20-100 moles for every 100 moles of the diamine.

According to the process of the present invention, the non-woven fabric of polyethylene terephthalate or polyamide-6 or 6,6 microfibers is impregnated by immersion in the polyurethane elastomer solution, the impregnation is squeezed by passing through a pair of rollers and proceeds then with coagulation in water, for example at 20-50 ° C. A sheet impregnated with coagulated polyurethane is thus obtained which is treated in hot water (for example at about 80 ° c), to extract the residual solvent and polyvinyl alcohol, then it is dried, cut into strips with a thickness of the order of 0 , 8-1.5 mm, and the strips are sanded to raise the hair. The crude synthetic microfiber non-woven fabric thus obtained is subjected to a dyeing treatment, dried and subjected to a final finishing.

The experimental examples which follow are reported purely for illustrative purposes of the present invention.

EXAMPLE 1 for comparison

In a first stage (prepolymerization) diphenylmethane 4,4'-diisocyanate is reacted with a mixture of diols formed by 3 parts by weight of polytetramethyleneoxy-diol having an average molecular weight of 2020 and one part by weight of polycaprolactondiol having an average molecular weight of 1996.

The quantity of diisocyanate referred to the diol is equal to 2 moles per mol. The reaction time is about 3 hours and the temperature is maintained at 65 ° 0. An amount equal to 0.5 moles of the prepolymer thus prepared is dissolved in Ν, Ν'-dimethylformamide (DMFA) to obtain a solution of 25% by weight of prepolymer.

A solution of 0.41 moles of 4,4'-methylene-bis (aniline) and 0.18 moles of di-n-butyl-amine in DMFA is prepared, in such quantities as to have a solution at 25% by weight. This solution is added to the prepolymer solution prepared as above, gradually over a time of 30 minutes, at a temperature of 40 ° C. The polyurethane elastomer solution is then diluted with DMFA to obtain a 13% by weight solution.

The solution thus obtained is then added with 0.086 moles {= approx. 41 g) of bis {2.2 ', 6.6' - tetramethyl - 4 piperidyl) - sebacate. ca. 3% weight.

A non-woven fabric prepared according to the known operating technique described above, is impregnated with the polyurethane elastomer solution prepared as above and then immersed for 1 hour in a water bath at 40 ° C, then in a bath at 80 ° C to eliminate residual solvent and polyvinyl alcohol. After drying, a composite sheet is obtained which is subjected to grinding to lift the pile. In this way, a microfiber type non-woven fabric having a thickness of 0.8 mm is obtained.

The following characteristics were measured on specimens of this product both before and after dry cleaning of the specimens (3 dry cleanings according to the AATCC-85 standard).

a) Lightfastness according to the AATCC method 16 A 1964

b) Solidity to nitrogen oxides determined according to the AATCC method 2319.

The results are shown in Table 1.

Furthermore, after dry cleaning (3 washes according to the AATCC-85 standard) and before and after artificial aging, the following characteristics are measured:

- Breaking strength (transversal toughness) measured according to ASTM 1682-64 and expressed in Kg / cm

- Burst resistance measured according to the UNI 5421-69 standard and expressed in Kg.

- Resistance to abrasion measured according to the ASTM D 1175-64T standard and expressed in cycles to break-out of the specimen.

The results are shown in Table 2.

EXAMPLE 2 for comparison

We operate as in example 1 with the only difference that 4, 4 '-methylen-bis (2 methyl-6 isopropyl-aniline) is used as the chain extender instead of 4, 4' -methylene-bis (aniline) , in equal molar quantity.

EXAMPLE 3 for comparison

In the first phase (prepolymerization), 4, 4 '-methylen-bis (cyclohexylisocyanate) in a quantity of 1 mole is reacted for 3 hours at 90 ° C, with 0.5 moles of diol consisting of a mixture of 3 parts by weight of polytetraraethyleneoxy-diol and 1 part by weight of polycaprolactondiol.

The prepolymer dissolved in DMFA is reacted with 0.3075 mol of 4.4 '-methylen-bis (2 methyl-cyclohexylamine) and with 0.1025 mol of 3-aminoethyl-3.5.5-trimethyl-cyclohexylamine and 0.18 mol di'Ν, Ν'- of n-dibutylamine. The dipiperidyl stabilizing component is not used.

EXAMPLE 4

One operates as in example 1 with the difference that the diisocyanate prepolymer is reacted, in the "chain extension" step, with 0.392 moles of 4.4 '-methylen-bis (aniline), with 0.018 moles of bis stabilizer ( 2,2, 6,6 - 4-piperidyl tetrameters) - sebacate and with 0.18 moles of Ν, Ν'-n-Dibutylamine as the chain terminator. 1.

Operating in this way, the stabilizer is inserted into the polyurethane polymer chain.

EXAMPLE 5

One operates as in example 4 by replacing the 4,4 '-methylen-bis (aniline) with the same molar quantity of 4,4' -methylen-bis (2 methyl-6 isopropyl-aniline).

EXAMPLE 6

The prepolymer is prepared as in example 3

In the chain extension phase, 0.294 moles of 4.4 'methylene-bis (2 methyl-cyclohexylamine) and 0.098 moles of 3 aminomethyl - 3.5.5 -trimethyl-cyclohexylamine and 0.18 moles of N', N-n-dibutylamine are used with 0.018 moles of bis (2,2, 6,6-tetramethyl (-4 piperidyl) -sebacate stabilizer.

EXAMPLE 7

The prepolymer is prepared as in example 1. In the "chain extension" step, 0.403 moles of 4,4'-methylene bis (2 methyl-6 isopropyl-aniline) and 0.007 moles of the stabilizer bis (2.2, 6, 6-tetramethyl - 4 piperidyl) sebacate and 0.18 moles of Ν, Ν '- of n-dibutylamine.

EXAMPLE 8

The prepolymer is prepared as in example 1.

In the "chain extension" phase, 0.3747 moles of 4,4'-methylene-bis (2 methyl-6 isopropyl-aniline) and 0.0353 moles of stabilizer bis (2,2, 6,6 -tetramethyl - 4 - piperidyl) -sebacate and 0.18 moles of N, N'-di n-dibutylamine.

EXAMPLE 9

The prepolymer is prepared as in Example 1.

In the "chain extension" phase, 0.3395 moles of 4,4 '-methylene-bis (2 methyl-6 isopropyl-aniline) and 0.0705 moles of bis stabilizer (2,2, 6,6 - tetramethyl -4 - are used piperidyl) -sebacate and 0.18 moles of Ν, Ν'- n-dibutylamine as the chain terminator.

TABLE 1

Claims (2)

CLAIMS 1) Product in sheet form, of the non-woven fabric type, based on microfibres of thermoplastic synthetic material and an elastomeric polyurethane, acting as a binder, obtained by reaction between a diamine-type chain extender and a prepolymer with isocyanate termination , obtained from an organic diisocyanate and a mixture of a polyether diol and a polyester diol, said polyurethane being characterized by the presence in the polymer chain of units deriving from the use, as a chain extender, together with conventional diamine, of a compound of formula: where equal or different from each other, they are H or alkyls at 1-4 C and n is between 1 and 20, said compound being used in an amount corresponding to 0.1% and up to 5% by weight with respect to the final polyurethane obtained. 2) Process for the preparation of the non-woven fabric according to claim 1, which substantially comprises the needling of the microfibre felt and the subsequent treatment with an elastomeric polyurethane solution of the needled felt, characterized in that an elastomeric polyurethane obtained by reaction between a diamine-type chain extender and a prepolymer with isocyanate end groups, obtained from an organic diisocyanate and a mixture of a polyether diol and a polyester diol, said chain extender being constituted not only by conventional diamine compounds but also by a compound formula: where the same or different from each other, they are H or alkyls at 1-4 C, n is between 1 and 20, the amount of the compound of formula (I) being between 0.1% and 5% by weight with respect to the final polyurethane.