DE1494648B1 - Process for the production of threads with a high modulus of elasticity from a polymer mixture containing polyvinyl alcohol - Google Patents

Description

It is already known that threads made of polyvinyl alcohol (hereinafter abbreviated to PVA) have a higher Have elastic modulus than other organic filaments, and also that filaments produced by wet spinning in an ordinary precipitation bath in the form of a solution of an inorganic salt and hot stretched, a maximum stretching ratio of about 1000% and a low modulus of elasticity of only 10 g / den, while threads produced in the dry spinning process have a maximum Have stretch ratios from 1100 to 1200%, with the elastic modulus near the maximum Reached a stretching ratio of 200 g / den. Furthermore, the fact is well known that in the semi-melt process PVA filaments obtained by dissolving PVA in a solvent, for example Ethylene glycol, in high concentration at high temperature, to create single crystals from PVA and hot stretching have been recovered by 1300% and which are highly crystalline, a very high one a modulus of elasticity of 350gden and therefore point.

However, such PVA threads with a fairly high modulus of elasticity are inferior to glass fibers a modulus of elasticity of 350 g / den and therefore not as satisfactory as glass fibers or Can be used to reinforce plastics.

From British patent specification 779 815 it is also known a mixture of polyvinyl alcohol and a linear polymer having a reactive hydrogen atom on the amide nitrogen to extrude aqueous solution into an aqueous precipitation bath. The aim here is colorability and to improve the hot water resistance of the filaments obtained. In this known method are however, the polymers are water-soluble in the spinning solution, and the filaments obtained are with respect to does not improve the modulus of elasticity.

The main object of the invention, on the other hand, is to create PVA threads with a high modulus of elasticity, which, like glass fibers, can be used industrially to reinforce plastics.

According to the invention, the mixed spinning of PVA with elastic polymer for the purpose of Improving the properties of PVA threads has been carefully studied, starting from of a process for the production of threads with a high modulus of elasticity from a polyvinyl alcohol containing polymer mixture. The object set for the invention can surprisingly thereby be solved by proceeding in such a process that one uses a mixture of polyvinyl alcohol and 0.1 to 50 percent by weight, based on the mixture, of an elastic polymer im Spun wet, dry or semi-melt process and the threads obtained are stretched by more than 50%.

Threads, which consist only of PVA have, namely, at a stretching temperature of 23O ⁰ C only a maximum draw ratio of 1000%, while mixed-spun yarns according to the invention at a relatively low stretching temperature of 175 ° C with 1,800% about twice as large maximum drawing ratio exhibit. At a stretching ^{temperature of 220 °} C, the stretching ratio can be increased by more than twice that of the threads consisting only of PVA. Even at a comparatively low draw temperature, the draw ratio of filaments made by blended spinning of PVA with elastic polymer is about twice as large as the draw ratio of filaments composed of PVA alone at high temperatures, and the draw ratio of mixed spun PVA filaments at high temperatures is more than twice as large as that of filaments consisting solely of PVA. As described above, by blended spinning of PVA with elastic polymer, it is possible to significantly increase the draw ratio. By increasing the stretching ratio, the modulus of elasticity can be increased to 400 to 600 g / denier, while that of threads consisting only of PVA is only 80 g / denier. In this way, threads with the highest modulus of elasticity found in organic threads can be created. Surprisingly, by adding an elastic polymer, which on its own results in a thread with an extremely low modulus of elasticity of about 0.05 g / denier and high extensibility of about 200 to 1000%, with PVA threads with lower extensibility (less than 5%) and higher modulus of elasticity (400 g / den) than threads made from PVA alone. M.

The inventive stretching of the mixed ™ spun threads can under different conditions, for example in a gaseous medium, such as air, or in a heating medium. To achieve a high modulus of elasticity a stretch ratio of more than 50%, preferably more than 500%, is required.

Elastic polymers to be used according to the invention are copolymers of elastomeric polyurethane which contain segments with a melting point below 80 ° C., block polymers of polytetramethylene glycol and polyethylene terephthalate (polymer which is obtained by copolycondensing the two polymers and subsequent dehydration of the polymer obtained, a polymer being obtained with longer chain than that of both polymeric starting materials forms in which the PoIytetramethylenglykol block components forms), butadiene as copolymers of ethylene terephthalate and Äthylensebacat or N-Methoxymethylpolyhexamethylenadipat, as copolymers of ethylene and vinyl acetate, natural _Λ and synthetic gums, such as natural rubber, poly \ and acrylonitrile-butadiene rubber.

A particularly good effect is obtained when polyurethane elastomers include polytetramethylene glycol having a below 8O ⁰ C melting point, may be used having a molecular weight of 200 to 7000, polyisocyanates and chain extenders such as diamines, diols and water, polyglycol such as polybutylene adipate. Completely saponified products with a degree of polymerization of 500 to 3000 or products which still have a small residue of ester groups can be used as PVA. These elastic polymers and the PVA are dissolved in an organic solvent such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, ethylene glycol, glycerine, phenol, m-cresol, nitrobenzene and dichlorobenzene. A mixed solvent of any of the above organic solvents with some water can also be used. Other mixed solvents of two or more of the organic solvents mentioned can also be used with good results. As already mentioned, the threads are produced using the wet, dry or semi-melt process.

In wet spinning, a precipitation bath, which contains alcohols such as methanol, ethanol and butanol, or a Aqueous medium made by mixing water with inorganic precipitating salts (such as zinc chloride) is, or a mixture of the above-mentioned precipitation baths with the solvent of the spinning solution, such as dimethyl sulfoxide or dimethylformamide, etc., preferably a mixture with alcohol such as methanol, is used.

The amount of the elastic polymer to be added is 0.1 to 50%, preferably 1 to 30% · Wenn much more than 50% elastic polymer is added, will have the opposite effect achieved, d. that is, filaments with low Young's modulus and high draw ratio result even if the threads are stretched.

The invention is to be explained in detail with the aid of the following examples.

example 1

Polytetramethylene glycol with a molecular weight of 1500 and hydroxyl end groups was made reacted with ρ, ρ'-diphenylmethane diisocyanate in a molar ratio of 1.0: 1.5 for 3 hours at 85 ° C, whereby a prepolymer with isocyanate end groups

composition

PVA 80 / elastomer
Polyurethane 20 ..

PVA 80 / elastomer
Polyurethane 20 ..

PVAlOO

Stretching temperature

(C)

175

220 230 was created. This was dissolved in dimethyl sulfoxide and, to extend the chain, ρ, ρ'-methylenedianiline previously dissolved in dimethyl sulfoxide was added in a molar ratio of 1: 6. A 15% strength dimethyl sulfoxide solution was obtained, which was mixed with a 13% strength PVA solution (degree of polymerization 1700) in dimethyl sulfoxide in a molar ratio of PVA to polyurethane elastomer of 80:20. The mixed spinning solution obtained was spun into a methanol bath through a spinning head having 100 holes each 0.08 mm in diameter by the wet method. The threads formed were taken up at a speed of 10 m / min. PVA threads with 20% polyurethane elastomer were obtained. These were hot-stretched in the air bath of 175 and 220 ⁰ C, whereby the results shown in the following table were obtained:

For comparison purposes, the table contains the results obtained with threads after a customary dry spinning process from a 30% aqueous PVA solution (degree of polymerisation 1700) and drawing were produced, were achieved.

Maximum

Stretch ratio

1830

2160 1200

Stretching
(%>
1750
2000
1100 Titer
(the) strength
(g'den) Extensibility
<"/»)
4.8
4.3
10.2 25.7
22.3
46.0 7.46
6.28
8.50

Young module (g / den)

600

407 135

45

By admixing 20% of polyurethane elastomer, the fibers at comparatively low temperature such as 175 ° C to be stretched, can thus the maximum extensibility at an elevated temperature of 220 ⁰ C to 2160% increase. These threads have a significantly improved Young's modulus.

Example 2

A 10% solution (mixed solvent of 50% dimethylformamide and 50% dimethyl sulfoxide) of PVA with a degree of polymerization of 1700 was mixed with a 10% solution of ethylene vinyl acetate copolymer in dimethylformamide in a molar ratio of 90:10. The resulting mixed solution was spun through a spinning head with 100 holes, each 0.08 mm in diameter, into a precipitation bath containing 10% dimethylformamide in methanol. The resulting threads were taken up at a speed of 10 m / min and ^{stretched by 1300% at 200 °} C., after which they had a maximum stretching ratio of 1400% and a Young's modulus of 300 g / denier.

Claims (1)

Claim: Process for the production of filaments with a high modulus of elasticity from a polyvinyl alcohol containing Polymer mixture, characterized in that a mixture of polyvinyl alcohol and 0.1 to 50 percent by weight, based on the mixture of an elastic polymer in the wet, dry or semi-melt process spun and the threads obtained are drawn by more than 50%.