DE2607659A1 - HYDROPHILIC FIBERS AND FABRICS MADE FROM SYNTHETIC POLYMERS - Google Patents

Description

Hydrophilic fibers and threads made from synthetic polymers

The invention relates to hydrophilic synthetic fibers and threads Polymers and a process for their preparation.

For a number of purposes, such as bed linen or underwear, it is desirable to use textiles made from man-made fibers to have available which in their behavior towards moisture properties similar to natural fibers like cotton. There has therefore been no lack of attempts to find the unsatisfactory properties in this regard to improve man-made fibers.

For example, natural fibers of high hydrophilicity were mixed with synthetic fibers. It is also known to mix with a second example polyacrylonitrile acrylonitrile polymer, the yo -. Containing 8o wt% of a Polyäthylenoxidmethacrylats, and the mixtures to be spun (DT-PS 16 45 552). Such aerated fibers, which contain ethoxylated acrylic acid derivatives with chemically bound polyethylene oxide, have been known for a long time because of their antistatic effect, but without having a particularly high moisture absorption.

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Attempts have also been made to improve the hydrophilicity by copolymerizing certain monomers. According to the Japanese For this purpose, patent application 2782/70 polymerizes monomers with a hydrophilic group, e.g. acrylic acid derivatives and then hydrolyzed.

In DT-OS 2o 61 215 a specially substituted Acrylamide proposed as a comonomer.

Attempts have also been made to improve the hydrophilicity by crosslinking. DT-AS 23 03 893 describes sulfuric acid hydrolysis of wet-spun swollen acrylic fibers, which are the N-methylol compound of an unsaturated amide included in polymerized form.

Pipes are also improved through networking Moisture absorption obtained according to US Pat. No. 3,733,386 by treating the fibers with aldehyde compounds and acids.

From DT-PS 2 124 473 void-containing pasers are known, which, after treatment with an agent which improves the hydrophilicity, are said to have cotton-like hydrophilic properties. Without treatment with the hydrophilic agent, however, the fibers are hydrophilic in spite of the voids present unsatisfactory and the fibers can only be used to a limited extent for certain purposes, since they fray easily and hair.

In spite of the large number and the diversity of the struck However, it has not yet been possible to produce synthetic fibers with a hydrophilicity which also only approximately achieved the good properties of cotton, these properties purely due to the Structure of the Pasern and / or the nature of the to their

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Polymerisates used in the production process, i.e. without the addition of or treatment with agents which improve the hydrophilicity or even cause it in the first place is necessary. Cotton has a moisture absorption of about 7 # at 65 $ 6 relative humidity and 21 ° C and a Water retention capacity of approx. 4-5 #.

The object of the present invention was therefore to provide such fibers and to provide threads and a process for their production that are relevant to their moisture absorption and their water retention capacity compared to the previously known synthetic fibers are improved.

It has now been found, surprisingly, that this desired improvement is achieved if a solid substance which has certain properties is added to the solvent for the polymer in a dry spinning process.

The invention therefore provides a process for the produc- tion of hydrophilic threads or fibers from thread-forming synthetic polymers by a dry spinning process, which is characterized in that the spinning solvent is 5-50 wt. #, Based on solvent and polymer solids, a substance that is solid under normal conditions adds to that

a) has a higher melting or sublimation point than the spinning solvent used,

b) is well miscible with the spinning solvent and with a washing liquid,

c) a nonsolvent for the polymer to be spun represents

and washes this substance out of the freshly spun threads.

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According to this process, porous threads and fibers, some with a core-jacket structure, can be obtained which have a moisture absorption of at least 2 # (at 65 % relative humidity and 21 ° C.) and a water retention capacity of generally more than 2o #.

The polymers used to produce the threads and fibers are preferably acrylonitrile polymers, of which those are preferred which consist of at least 50% by weight of acrylonitrile units.

When using acrylonitrile polymers, the hydrophilicity of the fibers can be further increased by the fact that one uses copolymers, which contain comonomers with hydrophilic amino sulfo, hydroxyl, N-methylol or carboxyl groups. Particularly suitable compounds are, for example, acrylic acid, methacrylic acid, methallylsulfonic acid, acrylamides and the N-methylol compounds of an unsaturated acid amide, such as, for example, N-methylolacrylamide and N-methylol methacrylamide. Mixtures of polymers can also be used.

The solvents known for dry spinning can be used as spinning solvents, e.g. dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, but preferably dimethylformamide.

The solid substance to be added to the spinning solvent under normal conditions must meet the following conditions: their melting or sublimation point must be higher, preferably by 50 ° C. or more than the boiling point of the solvent; it must with both the solvent and with Water or any other liquid that can be used as a washing liquid

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Ability to wash out the freshly spun threads, such as alcohol, be miscible, preferably miscible in all proportions, and in a practical sense it must be a nonsolvent for the polymer used be, i.e. that the polymer is only very slightly under normal conditions as well as under the spinning conditions dissolves in this substance to a small extent.

Such substances which are solid under normal conditions are, for example, monohydric or polyhydric alcohols, esters or ketones, e.g. 1,6-hexanediol, p-hydroxybenzoic acid methyl ester, inorganic or organic acids and salts such as isophthalic acid, pyromellitic acid, zinc chloride and magnesium chloride.

Of course, in addition to a single solid substance, mixtures of pesticides can also be used.

It is only important that the substances used are readily soluble in water or, if necessary, another washing liquid are so that they can be restored in the course of post-treatment of the Pasern can be removed.

It is also advantageous to use substances which are not azeotropic with the spinning solvent used Form mixtures so that they can be used as in the case of DMF-pyromellitic acid can be recovered almost completely through fractional distillation and crystallization

These substances are added to the spinning solvent in amounts of 5–5o, preferably 1o–20% by weight , based on the solvent and pesticide. The upper limit of admixable substance is determined in practice by the spinnability of the polymer solution.

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The higher the weight proportion of added substance to the spinning solvent, the greater the porosity in the fiber core and the higher the hydrophilicity of threads that are made from such dope mixtures.

In order to achieve thorough mixing of the spinning solution, it is advisable to mix the spinning solvent first e.g. dimethylformamide, with the additional substance and only then add the well-mixed solution with the polymer powder, since when directly added to polyacrylonitrile solutions in dimethylformamide, precipitates are often observed.

In order to obtain fibers of the highest possible hydrophilicity by the process according to the invention, the spinning treatment is selected in such a way that as little as possible of the added substance evaporates or is entrained by the evaporating spinning solvent. The lowest possible spinning shaft temperatures, which is just barely above the boiling point of the spinning solvent to be evaporated, short spinning shafts and high spinning take-ups and thus short residence times in the spinning shaft have proven to be extremely advantageous.

The spinning shaft temperature should, for these reasons a maximum of 8o ° C, preferably 5 - 3o ^o C, higher than the boiling point of the spinning solvent used.

This measure has the significant remains (usually 9o%) of the added substance in sliver or in the threads.

It is only washed out in the course of post-treatment removed with water or another liquid.

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The hydrophilicity of the fibers produced in this way can be determined can also be influenced by the type and manner of follow-up treatment.

For example, acrylic fibers are made from a DMF-1,6-hexanediol mixture after the spinning process according to the invention drawn in steam or water and only then washed, dried and finished post-treated, the original compact surface of the fibers or threads is also diffused out 1.6-hexanediol highly microporous, which makes acrylic fibers with receives particularly high hydrophilicity.

The spinning of ACN polymers of DMF Pyromellitsäuremischungen with 21 wt.% PolyacrylnitriIfeststoffkonzentration and 1o, 5 wt.% Pyromellitsäureanteil the spun yarns could by appropriate treatment following the outlined procedure acrylic fibers with more than 9o% water retention capacity and are prepared with 2.5% moisture absorption .

However, if the core-sheath fibers are washed first and then stretched, the compact sheath structure is retained, because the added substance is washed out before stretching and the cavities that arise as a result the stretching process can be closed again.

Acrylic fibers with a porous core and a dense core are obtained Outer surface and correspondingly lower hydrophilicity (see. Example 2).

The washing process with water or other liquids can be carried out at temperatures up to the boiling point. The dwell time should be at least 10 seconds in order to wash out the added substance thoroughly.

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In the washing process, it has also proven to be useful, the slivers or threads only under weak To maintain tension or with low shrinkage approval, to maximize the removal of the added substance.

However, you can also use substances such as isophthalic acid, which are difficult or difficult in water are insoluble but can be washed out well with another liquid such as methanol.

This process has the advantage that the wash water is distilled directly to recover the spinning solvent can without the added substance being produced. The added substance can then be in a further separate Extract the washing process almost completely and can be used again in the spinning process after work-up.

The further aftertreatment of the slivers or threads can be carried out according to the aftertreatment steps customary in technology: Preparing - curling - drying - cutting can be carried out, with the drying conditions of the Fiber exert a further influence on the hydrophilicity.

Possible mild drying conditions of maximum I6O ° C, preferably 11o - Ho ⁰ C and short residence times of no more than 2-3 minutes in the dryer result in fibers having very high hydrophilicity.

As already indicated, the threads and fibers according to the invention often have a core-sheath structure. In this core-shell structure, the core is microporous, with the average pore diameter not exceeding 1 / U amounts to. In general it is between 0.5 and 1 / u.

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The area of the core in a cross-section through the Paser is generally about 7o % of the total cross-sectional area.

The jacket can be compact or also microporous, depending on the choice of post-treatment conditions.

While the cross-sectional shape of common dry-spun threads and fibers is the well-known dumbbell or bone shape, the threads and fibers according to the invention predominantly have other cross-sectional shapes.

There are mostly trilobal, round or bean-shaped ones Structures partly next to each other. Which cross-sectional shape predominates depends on the selected spinning conditions as well as the amount of the substance added to the spinning solvent, the latter measure being the stronger Exerts influence.

In addition to the hydrophilicity described, the threads and fibers according to the invention show good fiber properties, such as high tear strength, elongation at break and good dyeability.

Another very great advantage of the fibers according to the invention with regard to wearing comfort results from their core-sheath structure. While natural fibers, such as cotton, feel wet through and through when they absorb a lot of water, this is not the case with the fibers according to the invention. It is assumed that this is due to the fact that the absorbed water diffuses into the microporous core. As a result , the fibers do not feel wet on the outside , which is associated with a dry, comfortable feeling.

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Even if mainly acrylic fibers and their production are described in the foregoing, this is the present case Invention not limited to this. Linear, aromatic polyamides such as the Polyamide made from m-phenylenediamine and isophthalyl chloride or those that may still have heterocyclic ring systems, such as polybenzimidazoles, oxazoles, thiazoles, etc. and which can be produced by a dry spinning process are, use according to the invention.

Other suitable compounds are polymers with melting points above 300 ° C, which are generally no longer from the Melt are spinnable and are produced by a solution spinning process, e.g. by dry spinning.

The water retention capacity of pasers is an important one clothing-physical measurand. A high water retention capacity means that textiles worn close to the skin contribute Increased perspiration can keep the skin relatively dry and thus improve comfort.

Determination of the water retention capacity (WR):

The water retention capacity is based on the DIN regulation 53814 (see Melliand Textile Reports 4 1973, Page 35o).

The fiber samples are immersed in water containing 0.1 wetting agent for 2 hours. Then the pasers are 10 minutes centrifuged with an acceleration of 1o ooom / sec and the amount of water that is retained in and between the pasers is determined gravimetrically. For determination of the dry weight, the fibers are dried to constant moisture content at 1o5 ° C. The water retention

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like (V / R) in percent by weight is:

nifi - m. WR = - 5 £ _ χ ioo

^m tr

m- = weight of the moist fiber material m. = weight of the dry fiber material

Determination of the moisture absorption capacity (FA);

The moisture absorption of the fiber based on dry weight is determined gravimetrically. For this purpose, the samples are exposed for hours to a climate of 21 ° C and 65 % relative humidity.

To determine the dry weight, the samples are gel at 1o5 ° C until the weight is constant would take (FA) in percent by weight:

1o5 ° C dried to constant weight. The moisture

m _f - m,

^FA = 1 - χ 100

^m tr

^m f = moisture content by weight of the fiber at 21 ° C. and 65 % rel. Humidity

^m tr ^{= dry} weight of the fiber.

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The figures show:

Fig. 1: Light microscopic cross-sectional image of pasers according to Example 1
(5oo magnification)

Fig. 2: Light microscopic cross-sectional image of pasers according to Example 3
(500x magnification).

The following examples serve to explain the invention in more detail. Parts and percentages relate if not otherwise noted, on weight.

example 1

13 * 5 kg of DMP are mixed with 2.47 kg of 1,6-hexanediol in a kettle while stirring. 4.73 kg of an acrylonitrile copolymer of 93 * 6 % acrylonitrile, 5.7 % methyl acrylate and 0.7 % sodium methallylsulfonate are then metered in with stirring, stirred for 1 hour at 80 ° C., filtered and the finished spinning solution is placed in a spinning shaft according to procedures , which are known in the art, are dry-spun from a 180-hole nozzle.

The shaft temperature is 160 ° C. The viscosity of the spinning solution, which has a solids concentration of 23 % and a hexanediol content of 12 wt. #, Based on DMP + polyacrylonitrile powder, is 65 falling ball seconds. For viscosity determination using the falling ball method, compare: K. Jost Rheologica Aota Volume 1, No. 2-3 (1958), page 303. The spun material with a titer of I600 dtex is collected on bobbins and doffed into a ribbon

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Total titre 96 ¹ OOO dtex, increased.

The fiber tow is then stretched 1: 3 * 6 times in boiling water, washed in boiling water under low tension for 3 minutes and provided with an antistatic finish. Then it is dried in a sieve drum dryer with approval of 20 % shrinkage at a maximum of 130 ° C. and cut into fibers with a stack length of 60 mm.

The individual fibers with a final denier of 3.3 dtex have a moisture absorption capacity of 3 * 2 % and a water retention capacity of 29 %.
Tear strength = 2.3 p / dtex; Elongation at break 37 #.

As the light microscope image of the cross-sections in Figure 1 shows, magnified 500 times, the fibers have a pronounced core-sheath structure with bean-shaped to trilobal cross-sectional shapes.

The proportion of residual solvent in the fiber is less than 0.2% by weight . The fibers can be colored with a blue dye of the formula

color deeply and thoroughly. The absorbance is 1.23 for 100 mg fiber per 100 ml dimethylformamide (57om / U, 1cm cuvette).

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Example 2

An acrylonitrile polymer with a chemical composition similar to that described in Example 1 was dissolved in a DMF-1,6-hexanediol mixture, filtered and spun under the same conditions. The spun material was collected on bobbins and dtex plied 96 ¹ OOO to a band having a total.

The material was then washed in boiling water under low tension for 3 minutes, then 1: 3.6 times stretched, provided with an antistatic preparation and finished as described in example 1

The fibers with a single titer of 3 * 3 dtex have a moisture absorption of 1.7 %. The water retention capacity is 9. k% » The fibers again have a pronounced core-sheath structure with a bean-shaped to trilobal cross-section.

In contrast to the fibers according to Example 1, the outer surface is more compact and practically not interspersed with cavities. This explains the relatively lower hydrophilicity of the fibers compared to Example 1. As a result of the modified Post-treatment processes are carried out by the stretching process after the washing process, by removing the hexanediol Cavities created during washing are partially closed again.

Example 3

5.6 kg of dimethylformamide are mixed with 2.8 kg of isophthalic acid In mixed in a kettle with stirring * Then 5.6 kg of an acrylonitrile copolymer of chemical composition analogous to that in Example 1 is metered in with stirring, Stirred for 1 hour at 80 ° C, filtered and

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the finished spinning solution as described in Example 1 is spun.

The viscosity of the spinning solution, which, based on DMF and PAN-solid, having a # Peststoffkonzentration of 22 wt. And a Isophthalsauregehalt of 11 wt.%, Is 68 falling ball seconds.

The spun material with a titer of 160 dtex became a fiber tow folded, in boiling water 1: 3> 6-fold stretched, in Washed boiling water under low tension for 3 minutes and then for 1 minute with ethanol from 65 - 70 ° C treated. The isophthalic acid is removed almost quantitatively. Then with antistatic Preparation provided and aftertreated as described in Example 1.

The individual fibers with a final denier of 3 * 3 dtex have a moisture absorption capacity of 2.8% and a water retention capacity of 160 %. As the light microscope image of the cross-sections in Figure 2 shows, magnified 500 times, the fibers have oval to trilobal cross-sectional shapes without deeper notches and are porous through and through.

Example 4

13.4 kg of dimethylformamide are mixed with 2.05 kg of pyromellitic acid in a kettle with stirring. Subsequently, 4.1 kg of an acrylonitrile copolymer isates of analogous chemical composition such as metered in Example 1, with stirring, stirred at 8o ° C for 1 hour, filtered, and the spinning solution spun as described in Example. 1

The viscosity of the spinning solution, which has a solids content of

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21 wt. ^ With a pyrornellitic acid content of 1o, 5 wt. #, based on DMF and PAN solids, is 69 Falling ball seconds.

The spun material with the denier ΐβοο dtex became a cable again folded and post-treated as shown in Example 1.

The individual fibers with a final denier of 3 * 2 dtex have a moisture absorption capacity of 2.6 % and a water retention capacity of 97 #.

The fibers have a bean-shaped to oval cross-section.

Example 5

10.7 kg of dimethylformamide are mixed with 2.0 kg of ρ-hydroxybenzoic acid ester mixed in a kettle with stirring. Then 4. O kg of an acrylonitrile copolymer with the chemical composition of Example 1 metered in with stirring.

The mixture is then stirred for 1 hour at 80 ° C., filtered and the finished spinning solution is spun, as indicated in Example 1, and the spun material is then aftertreated. The ester content, based on the DMF-PAN mixtures, is 12% by weight ,

The viscosity of the spinning solution having a solids content of 24 wt.%, Was 61 falling ball seconds.

The individual fibers with a final denier of 3.3 dtex have a moisture absorption of 2.7 % and a water retention capacity of 42 %,

The fibers have an oval to bean-shaped, highly porous cross-sectional shape.

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Example 6

9 * 3 kg of dimethylformamide are mixed with 1.7 kg of zinc chloride in a kettle with stirring. Then 4. O kg of an acrylonitrile copolymer according to Example 1 are metered in with stirring. After one hour stirring at 8o ° C the filtered solution containing 12 wt.% Of zinc chloride, based on DMF and PAN solid, has, as described in Example 1, dry spun and cured.

The viscosity of the spinning solution was 70 falling ball seconds.

The fibers with the final titer ^, J> dtex have an oval to bean-shaped cross-sectional shape.

The moisture absorption is 2.9 % and the water retention capacity is 28 %.

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Claims (1)

Claims 1.) Process for the production of hydrophilic threads or Pipes made from thread-forming synthetic polymers according to a dry spinning process, characterized in that the spinning solvent 5 - 50 wt. #, based on the solvent and pesticide, one under normal conditions solid substance adds to the a) has a higher melting or sublimation point than the spinning solvent used, b) is well miscible with the spinning solvent and with a washing liquid, c) a non-solvent for the polymer to be spun represents and washes this substance out of the freshly spun threads. 2.) Process according to claim 1, characterized in that the polymer is an acrylonitrile polymer. 5.) The method according to claim 2, characterized in that the acrylonitrile polymer consists of at least 5o Qew. # Of acrylonitrile units. 4.) Dry -spun threads or fibers made of thread-forming synthetic polymers with porous structures with a moisture absorption of at least 2 % at 65 % relative humidity and 21 ° C and a water retention capacity of at least 2o %. Le A 17 o2o - 18 - 7 09835/0297