FR2521176A1 - Antistatic, moisture absorbent, (non)woven fabrics - including fibres of polyacrylic acid or poly:hydroxyethyl methacrylate! - Google Patents

Abstract

A textile fabric (I) resistant to accumulation of static charge comprises at least one wt.% of interlocked hydrophilic fibres (II) which can absorb up to about 50 wt.% on (I) of moisture without loss of mechanical strength and other textile properties. (II) have a rockwell hardness 50-60 and consist of a linear hygroscopic homopolymer of alpha, beta-ethylenically unsatd. carboxylic acids, alpha, beta-ethylenically unsatd. sulphonic acids, hydroxyalkyl esters of glycidyl esters of these acids, the polymers having a mol. wt. 100000-500000, a s.pt. 210-245 deg.C, a Tg above 115 deg.C and being cross-linked at a cross-linking density in range of one chemical cross-link bond per 40-100 repeat units of the polymer. (I) is light wt., abrasion resistant, antistatic and can absorb large amounts of moisture without degradation of tensile strength and other fibre properties. It may be (nonwoven or knitted, and can be used to prepare articles of apparel which contact human body, esp. ladies undergarments, including underwear, stockings, panty hose and the like.

Description

ANTISTATIC KNITTED FABRIC, RESISTANT
ABRASION AND COMFORTABLE
The subject of the present invention is filaments, the threads produced using these filaments and the textile articles obtained from said filaments and threads.

 According to the present invention, woven, nonwoven or knitted textiles have a weight of less than 22 grams per square meter, a tensile modulus of at least 30 grams per denier, a tensile strength of at least 3 grams per denier. and an elongation at break of at least 30% combined with a temperature Tg greater than 125 "C, an absorbability of humidity of 30 to 50% and an electrical conductivity greater than 10-9 ohms cm-1 The invention also relates to processes for producing said filaments. An important field of application and of great commercial interest for fine and / or transparent fabrics based on all types of fibers, that is to say - to say silk, polyamide, polyesters, is that of women's underwear, stockings, tights and other items of clothing of the same type.

 In fact, the very particular demand for such textiles has resulted in very large industrial development. Over the years, significant improvements have been made to this field of transparent or fine knitted articles, in particular monofilaments down to 7 denier. multi-lobed filament sections, composite filaments and nonwovens.

 In spite of all these exhaustive efforts, it is obvious that all the textile articles of this type currently in existence still have numerous drawbacks. It is well known that they are moist and uncomfortable, that they stick to the skin and have a tendency to generate static charges. It has been shown that these drawbacks are mainly due to the low moisture absorption capacity of the fibers constituting such textured articles, which has led to a number of attempts to improve existing techniques.

 One can assess the necessity and the benefits that would result from the solution bypassing this disadvantage in the fact that many of the major global fiber-producing forms offer various solutions to these problems.

 DuPont de Nemours has developed the grafting of acrylic and methacrylic acids on polyamide filaments, by photo-activation of the surface of the filaments.

Bayer, in Germany, offers acrylic fibers known in the trade under the brand name "Dunova" which has a possible moisture absorption rate of 15X thanks to a set of fine capillaries created during the threading of the filaments.

In Japan, Toray has developed filaments of modified polyester for female underwear, capable of absorbing increased humidity up to about 15X by partial sulfonation of the aromatic units of the macromolecule.

Another way is to add a more highly absorbent fiber in the manufacture of textile articles, as shown in the following table. Resumption of humidity of some fibers (according to Man-Made
Fibers, RW MONCRIEF, 6th edition 75 P324):
Fiber Moisture uptake -in%
- wool ...................... 16
- polyamide ................... 4.0
- polyester 0.4
- acrylic ................... 0.9
- cotton ....................... 8.5
- viscose ..................... 12.0
- cellulose acetate ... ... 6.5
Extensive studies have requested that in order to achieve satisfactory conditions with regard to comfort and antistatic properties, it is necessary to add an appreciable amount, that is to say from 15 to 30; from a hydrophilic fiber with a moisture uptake of approximately 8%, to a hydrophobic fiber with a low moisture absorption of the order of 2%. The relatively impertinent addition of a hydrophilic component frequently leads to undesirable consequences, for example on the modulus, the tensile strength, the flexibility, the elasticity, the sliding properties, etc.

 The applicants have found that all the necessary mechanical, thermal, electrical and physiological characteristics can be very satisfactorily achieved, if a small amount, that is to say from 2 to 10%, of a particular fiber is added. high absorbency greater than 35X.

 The numerous tests carried out with all known fibers having led to insufficient results, it became necessary to move towards a special fiber.

 The use of a fibrous component with a high moisture content at free, greater than 35X by weight, obviously leads to the problem that in the fully swollen state, the fiber should not be too tight. It is well known that cotton and other natural cellulosic fibers such as hemp, flax and ramie have a relatively high equilibrium moisture content (up to 15%), but do not lose tensile strength. wet condition. On the other hand, all viscose rayon with an average moisture content between 10 and 12% loses up to 70% of their tensile strength in the wet state. The reason for this incompatibility is found in the fact that the molecular weight of natural celluloses is more than ten times that of rayon and that the degree of crystallinity of natural fibers is very high (up to 95%).

 To produce a synthetic fiber with 40% moisture uptake, it is necessary to use materials whose molecular weight is around 500,000 and more. As it is not possible to achieve very high degrees of crystallinity due to the irregular conformation of the highly hygroscopic chains, the solution proposed by the applicants substitutes for crystallinity, crosslinks or other forms of lateral grafting or bypass grafting ( cross-linking).

 It is well known in rubber technology that suitably charged and treated amorphous elastomers have the same mechanical strength as their crystallizable counterparts. Thus, the essential problem of producing such products is to prepare fine, highly hygroscopic filaments made of high molecular weight polymers and then crosslinked to the desired degree.

 It is known in the prior art to prepare cross-linked hygroscopic gels in the form of articles of various shapes such as fibers, leaves, buttons, etc. and, by immersion in a saline solution, to bring them to a very swollen state in which they will remain as long as moisture remains. To prepare fine filaments, it is necessary to use a completely different route, that is to say to prepare an adequate concentrated solution of a linear polymer with high molecular weight not crosslinked, to spin it into very fine filaments and crosslinking when the product is in the desired fibrous form.

 there are many linear hygroscopic polymers having a molecular weight of more than 150,000, for example of the order of 500,000, such as polymers of acrylic acid, methacrylic acid or other acrylics, vinyl polymers, olefinic chains having acid groups attached to it such as HCOO or HSO3. There are also highly hygroscopic amides of these acids and polyacrylamide is a well known example of which the molecular weight can go up to several millions. Linear, high molecular weight, vinyl, acrylic and olefinic macromolecules are also known which have hydroxyl or amine groups and therefore have a high ability to absorb moisture. Polyhydroxyethylmethacrylate is particularly representative of this type of polymers. it is also known that polyethers and polyamides are highly hygroscopic and some of them, such as polyoxyethylene, have been able to be obtained with molecular weights of the order of several millions.

 The applicants have found that it is advantageously possible to spin filaments as long as the polymer is not crosslinked, which allows an easy laminar flow in the die.

 According to a preferred embodiment of the invention, the filaments are prepared from polymer in solution. Once the filamentary characteristics have been reached, the fibers are crosslinked under tension, dried and rewound.

It has also been found that, depending on the molecular weight of the polymer, concentrations of 10 to 30% are suitable for carrying out the invention, and more particularly from 15 to 25%. In order to coagulate the solution, it is particularly desirable to carry it out in aqueous saline solution and to remove water from the filaments by the osmotic action of
Salt. In this way, the polymer solution is converted into a non-crosslinked gel which could be reversibly reconverted into solution. The gelatinous filaments in which the individual macromolecules only hold together due to Van der Waal forces or hydrogen bonds, can be oriented by stretching to any desired degree.

 Once this state has been obtained, the filaments are transferred to a second bath which contains a crosslinking agent and they are crosslinked there by the action of chemical covalent bonds.

 According to preferred embodiments of the invention, all of the polymer solutions for spinning are aqueous. The finely powdered polymer is put into the necessary quantity of distilled water and the whole is gently stirred until complete dissolution. Depending on the molecular weight of the polymer, the concentrations of the spinning solutions are between 5 to 35%, and preferably between 15 and 25%. In order to obtain a smooth smooth spinning, the absolute viscosities measured at 20 "C of the solutions must be from 20 to 2,000 poises. With viscosities of this order, spinning speeds of the order of 70 to 190 m / min.

The solution must be carefully degassed beforehand and filtered.

The removal of air is easily done under vacuum when the solution passes into a flat and large container such as a disc. The filtration is preferably carried out on candle filters of the type of those used for viscose rayon. In the present case, it is particularly advantageous that the spinning solutions are approximately neutral (from 6.5 to 7.2), unlike the strongly alkaline solutions of the viscose rayon process. To do this, preferably woven fabrics of cotton or rayon are used. After filtration, the solution which has a viscosity comprised, preferably between 100 and 300, is pumped to the dies. Gear pumps are particularly suitable because they do not allow air to enter the solution. As an experiment, dies with 40 to 72 80 micron holes were used. it is also advantageous to provide pre-holes having approximately half the length of the channels of the die.

 It was also possible to prepare cut fibers with heads with 4,000 holes and with, moreover, the same characteristics of shape and dimensions as above.

 The spinning bath is maintained at a temperature of 25 to 450C and consists of a neutral or acidic saline solution. it has been found that ammonium chloride at a concentration of the order of 15 to 20% and sodium sulfate at 15 to 20% give satisfactory results.

 As is known, with regard to viscose rayon spinning, the cross section of the filaments is affected by the chemical characteristics and the concentration of the bath. In order to arrive at the desired section, it has proved advantageous to add to the spinning bath on the order of 5 to 10% of sulfuric acid.

 When the extruded filaments enter the bath they are dehydrated by osmotic pressure and transformed into a stretchable gel. They pass first on a first roller and 2.5 meters downstream on a second whose peripheral speed is 2.5 times that of the first. I1 results in a stretching of the individual macromolecules, which parallelizes them, stretches them and to a certain extent makes them slide one on the other since at this phase there is no chemical crosslinking bond, transverse bonds or other forms of crosslinking. It has been found that an effective way of achieving these transverse connections is the passage through a second aqueous bath containing, at least, a water-soluble crosslinking agent which is absorbed by the getified filament during the passage through this second bath. cite as bifunctional agents creating these transverse bonds between neighboring macromolecules, dicarboxylic acids or anhydrides, glycols or diamines or other bifunctional reagents. The reaction takes place in this second bath either thermally at a temperature of the order of 40 to 50 "C, or under the influence of a catalyst. After leaving the second bath, at a speed of 90 to 140 meters per minute, the filaments are dried by any conventional means and rewound.

 It has also been found that the crosslinking phase can be carried out without chemical agents but simply by exposure of said filaments, either to the action of ionizing radiation, or to that of fast electrons. In this case, a second bath is unnecessary, the filaments being exposed at the time of their winding.

 To better understand the technical characteristics and advantages of the present invention, two examples of embodiments will be described, it being understood that these are not limiting as to their mode of implementation and to the applications that can be made of them. to do.

EXAMPLE I
A solution of acrylic acid polymer with a molecular weight of 260,000 is prepared in distilled water at a concentration of 18.5% by weight of polymer at 400C. It is degassed under vacuum for 24 hours then brought by a gear pump through a candle filter to a spinning head whose die has 40 holes of 80 microns in diameter.

This solution is extruded in a 40 ° C bath containing 6% ammonium chloride, 11% magnesium sulfate and 1.2% sulfuric acid. The gelled filaments which form immediately on contact with the bath pass through it. over a distance of 5.5 meters by going back and forth on glass rollers, at a speed of 68 meters per minute.

At the end of this coagulation phase, the filaments pass into a second aqueous bath containing 2.5% ethylene diamine and 12% ammonium chloride. Under the action of methylenediamine which gradually penetrates into the gelled filaments, transverse covalent bonds occur between individual neighboring molecules of acrylic acid polymer and strands of highly swollen filaments insoluble in water are obtained. . The length of the crosslinking bath is 5.5 meters and the filaments go back and forth on glass rollers at a speed of 82 meters per minute.

 After this treatment, the strands of filaments are washed for three minutes in a third bath of distilled water. They are then returned and dried with hot air. The set of filaments corresponds to approximately 160 deniers, ie 4 deniers to the filament; after drying with hot air, they have a tensile strength of 2.5 g / denier and an elongation at break of 30X.

These filaments are capable of absorbing up to 45% by weight of water without losing their consistency and their mechanical characteristics under traction.

EXAMPLE 2
An aqueous solution is prepared at 25 ° C. by dissolving 22.5% of hydroxyethyl thacrylate in dry powder with a molecular weight of 185,000.

The solution is degassed under vacuum at 400C for 24 hours, then brought by a gear pump to a spinning head, the 72-hole die of 80 microns in diameter. It is extruded in an aqueous bath containing 2.5% sodium sulfate, 5% magnesium sulfate and 2.5% sulfuric acid at a speed of 18 meters per minute.

Upon entering the bath, the filaments coagulate in the form of a gel which is stretched at a rate of 1.25 and which is maintained in the bath over a length of 3.6 meters, making them go back and forth on glass rolls. The coagulated filaments are then brought into another bath at 60 ° C. containing 8% magnesium sulphate and 5% oxalic acid. The filaments travel there 5.5 meters at a speed of 3.6 meters per minute.

 Under the action of oxalic acid, a certain number of transverse bonds are created, the filaments being then crosslinked and becoming insoluble in aqueous solvents.

 After washing, the filaments are dried and have 3.5 denier for each filament, a tensile strength of 2.8 grams per denier and an elongation at break of 28%.

 The yarns produced using these filaments are capable of absorbing up to 38% of moisture without appreciably losing their textile characteristics.

 Using the filaments and wicks which have just been described, it is possible to manufacture textiles and articles, woven or not and knitted, of remarkable mechanical and physical properties mentioned in the preamble and whose lightness and moisture absorption are exceptional. They are particularly antistatic and comfortable and are remarkably resistant to abrasion.

 Of course, the invention is not limited to the embodiments described and shown and it is capable of numerous variants accessible to those skilled in the art, without departing from the spirit of the invention. 'invention.

Claims (16)

 1.- A method of manufacturing filaments from polymers, characterized by the fact that the filaments are subjected, after extrusion, to a phase of creation of transverse bonds between macromolecules, the starting macromolecules having an atomic weight greater than 150,000.  2.- Method according to claim 1, characterized in that the polymer in solution is extruded, the filaments passing through a coagulation phase, then through said phase of creation of transverse bonds.  3.- Method according to one of claims 1 or 2, characterized in that the phase of creation of the transverse connections is carried out in a bath containing at least one crosslinking agent.  4.- Method according to one of claims 1 to 3, characterized in that the phase of creation of the transverse connections is carried out under ionizing radiation.  5.- Method according to one of claims 1 to 4, characterized in that the phase of creation of the transverse connections is carried out under the action of fast electrons.  6.- Method according to one of claims 1 to 5, characterized in that the phase of creation of the transverse connections is carried out after stretching.  7.- Method according to one of claims 1 to 6, characterized in that which polymer is based on acrylic acid.  8.- Method according to one of claims 1 to 7, characterized in that the polymer is based on hydroxyethylmethacrylate.  9.- Method according to one of claims 7 or 8, characterized in that a crosslinking agent is ethylene diamine.  10.- Method according to one of claims 7 to 9, characterized in that a crosslinking agent is oxalic acid.  11.- Filaments characterized by the fact that they are obtained by the process according to one of claims 1 to 10.  12.- Filaments according to claim 11, characterized in that they have a tensile modulus of at least 30 g / denier, a tensile strength of at least 3 g / denier, an elongation at break at least 30%, a temperature Tg greater than 125 "C, a moisture uptake of 30 to 50% and an electrical conductivity greater than 10-9Qcm-1.  13.- Yarns characterized in that they are obtained using the filaments according to one of claims 11 or 12.  14.- Fabrics characterized by the fact that they are made from the products according to one of claims 11 to 13.  15.- fabrics according to claim 14, characterized in that they have a weight per square meter less than 22 grams.  16.- Textile articles characterized by the fact that they are manufactured using the products according to one of claims 11 to 15