DE1769820A1 - Process for the production of threads or fibers based on acrylonitrile polymers - Google Patents

Description

Badische Anilin- & Soda-Fabrik AG 17R9820

Our reference: O.Z. 25 684 Möb / km

Ludwigshafen am Rhein, July 8th, 1968

Process for the production of threads or fibers based on Acrylonitrile polymers

The invention relates to a method for producing threads or fibers based on acrylonitrile-styrene copolymers

in dimethylformamide. ™

It is known that acrylonitrile can be polymerized with styrene in dimethylformamide using catalysts to form filamentary polymers and that these polymers can be spun into filaments. Apart from the fact that the ₃ previous polymerization did not satisfy in every respect, the filaments prepared from these polymers showed disadvantages, in particular not satisfy the mechanical properties of the filaments from the known acrylonitrile-styrene polymers. Λ

The present invention relates to a process for the production of threads or fibers by spinning acrylonitrile-styrene copolymer solutions, through continuous polymerization of styrene and at least 85% by weight of acrylonitrile and optionally other conventional monomer-containing monomer mixtures in dimethylformamide with initiators in a reaction zone, with as much from the reaction zone in the steady state

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Reaction mixture is discharged were as fresh mixture is fed, prepared starting acrylonitrile-styrene copolymer solutions spinning, the strength by incorporating 30 to 50 £ monomer, from 1 to 6 Gev.% Styrene, based on total monomers, containing, in the reaction zone , Polymerizing at 45 to 70 ° C and terminating the polymerization in a conventional manner were obtained in the discharged part of the reaction mixture.

In addition to acrylonitrile, which is contained in the monomer mixture in amounts of at least 85% by weight, it is expedient to use 1 to 6, in particular 2 to 4 % by weight, based on the monomer mixture, of styrene. Since styrene is polymerized faster than acrylonitrile, the amount of styrene unit- * * .m aerylnitrile-styrene copolymer is then about 3 to 12, in particular 4 to 8 % by weight, depending on the reaction conditions.

Examples of monomers which may be used in addition to acrylonitrile and styrene are: olefinic *, ß-unsaturated monocarboxylic acids, such as acrylic, methacrylic or crotonic acid or their esters with monohydroxy! compounds with 1 to 18 carbon atoms, such as methyl acrylate, butyl acrylate, Methacrylic acid methyl ester or acrylic acid 2- ^ a t hy I-hexyl ester, also vinyl compounds such as vinyl chloride and vinyl acetate or vinyl carbazole. To improve the colorability of the polymers, copolymerizable compounds with acidic or basic groups can be used as additional monomers, in particular in amounts of 0.5 to 2 wt. For example: Styrene sulfonic acid, allyl sulfonic acid, vinyl sulfonic acid, 3-sulfopro-

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BATH ORIGINAL

pyl methacrylate, 2-sulfoethyl methacrylate, vinyl phosphonic acid or Salts of the acids mentioned, also vinylpyridine, N-vinylimidazole, 2-diethylaminoethyl acrylate or 2-trimethylaminoethyl methacrylate sulfate.

The customary polymerization initiators can be used in customary Quantities are used. It is particularly advantageous to use initiators, which decompose into radicals at the reaction temperature runs with a small half-life compared to the average residence time of the reaction mixture. Initiators with half-lives at the reaction temperature of 0.5-5 hours, in particular 1-3, are expedient Hours, used, for example cyclohexylsulfonylacetyl peroxide, dicyclohexyl peroxydicarbonate, diisopropyl peroxydicarbonate, tert-butyl pivalate, ammonium persulfate or azo-di-cyclooctyl nitrile. The initiators can be used alone or in mixtures. They can be included in the Reaction zone are introduced, but it is expedient to bring them separately, dissolved in a small amount of dimethylformamide, a. The course of the polymerization can easily be controlled by adding the initiators separately.

The preparation of the acrylic-styrene copolymer solutions used according to the invention takes place in apparatus customary for continuous polymerizations. Mixing well is advantageous of the polymerization approach. It is particularly easy to use a stirred tank with the stationary on the underside State so much reaction mixture discharged,

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how fresh mixture is supplied from above. It is expedient to polymerize 30 to 50 strength, preferably 35 to 45 strength, monomer solutions in dimethylformamide. The reaction temperature is suitably H5 - 70 ⁰ C, advantageously 55 - 65 ⁰ C. The liberated heat of reaction is removed by evaporative cooling, where appropriate at reduced pressure. The pressure above the reaction mixture is then expediently 50-300 Torr, preferably 75-200 Torr. If evaporative cooling is used, a procedure is preferred in which the coolant temperature in the evaporative cooler is controlled as a function of the temperature in the reaction mixture.

The polymerization is terminated in the discharged part of the reaction mixture by customary methods, for example by Addition of polymerization inhibitors or by rapidly distilling off the residual monomers under reduced pressure. Through this the formation of low molecular weight products and thus a lowering of the average molecular weight of the acrylonitrile-styrene copolymer avoided. The unreacted acrylonitrile can be used again for the polymerization.

It is generally polymerized up to conversions between 35 and 70 %, preferably between 40 and 60 %, with residence times of 8 to 16 hours. A maximum conversion is deliberately not aimed for in the polymerization process. This makes it possible to limit the unfavorable effect of chain transfer even at an elevated reaction temperature, that is to say that acrylonitrile copolymers are also used at an elevated reaction temperature

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the fiber production sufficiently high molecular weights can be obtained. Due to the increased reaction temperature, the residence time the reaction mixture can be reduced in the apparatus. So it happens that the space-time yield (amount of polymer per Volume of reaction mixture and time) is very favorable for the type of polymer present despite the relatively low conversion. By the relatively short residence time of the reaction mixture in the heated reaction zone also results in less discoloration of the polymer a, which is clearly shown in the whiteness of the fibers produced from the polymers. The higher reaction temperature and the not too high conversions bring as a further advantage a lower viscosity of the reaction mixture, i.e. a better stirrability and better heat dissipation, with it

The acrylonitrile-styrene copolymer solutions produced continuously as described are discontinuous or continuous, optionally also after continuous concentration or thinning, spun into threads or fibers. Avoiding intermediate storage of the solutions leads to further im Whiteness improved threads or fibers.

The spinning takes place in the usual for acrylonitrile polymer Way by precipitation or dry spinning. It was surprising that those used according to the invention were also used in dry spinning Copolymer solutions threads or fibers with excellent degrees of whiteness can be obtained. Generally in dry spinning from dimethylformamide solutions, threads with less good color values are obtained than with precipitation spinning.

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SAD ORIGINAL

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The threads or fibers produced according to the invention surprisingly show very good mechanical properties not previously obtained with threads made of acrylonitrile-styrene copolymers could become. In connection with the excellent degree of whiteness, this results in properties for threads or fibers, which bring a valuable addition to the synthetic fiber range.

The parts and percentages given in the example are weight units ™ units.

example

37.0 parts of acrylonitrile, 1.0 part of styrene and 0.4 part of sodium 3-sulfopropyl methacrylate, 61.6 parts of dimethylformamide and 0.05 part of tert-butyl perpivalate (0.75%) are continuously introduced into a stirred tank. A corresponding amount of the contents of the boiler is continuously withdrawn. The reaction temperature is 60 ^° C. The contents of the stirred tank are exchanged once within 13 hours. After reaching the steady state, the boiler discharge contains 19 % polymer with a K value of 88 (determined in 0.5-year solution in dimethylformamide according to the formula by Fikentscher, Cellulosechemie 1J3 (1932), 58), corresponding to a conversion of 50 % and a space-time yield of 13.10 ~ ^ (kg of polymer per liter of reaction mixture and hour). The boiler discharge is freed of residual monomers in an evaporator ^{at 50 °} C. at approx. 10 torr and concentrated to a polymer content of 29% by distilling off dimethylformamide. the

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BATH ORIGINAL

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The color of the spinning solution is determined by measuring the transmission of light of wavelength 430 μ on a solution diluted to 10% polymer content with dimethylformamide. At 1 cm layer thickness, the transmittance is 95% · From 29-55igen solution by dry spinning at 280 ⁰ C filaments manufactured have the following properties:

Breaking kilometers, dry 28.1

relative loop strength 56 %

Parbsaturation value 11.6

Degree of raw whiteness (remission) 64 %.

Comparative example

A mixture of 28.9 parts of acrylonitrile, 0.78 part of styrene, 0.30 part of 3-sulfopropyl methacrylate sodium, 70 parts of dimethylformamide and 0.08 part of tert-butyl perpivalate (75 Jfig) are heated for 20 hours at a temperature of 50 ⁰ C stirred. The polymer content of the reaction mixture is then 21.3 %. The reaction mixture is very cloudy. A 29 ~ strength polymer solution is prepared by distilling off residual monomers and dimethylformamide at 50 ° C. and 100 torr. A sample diluted to 10 % polymer content shows a transmission of 85 % for light with a wavelength of 430 m with a layer thickness of 1 cm. Filaments produced from the 29-jig solution by dry spinning at 280 ° C have the following properties:

Breaking kilometers, dry 15.4

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Relative loop strength 56 %, color saturation value 8.7

Degree of raw whiteness (remission) 62 %.

The poorer mechanical properties of these threads compared those produced by the process according to the invention are when comparing the dry measured tearing kilometers clearly visible.

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Claims (1)

- 9 - 0'.Z. 25 684 ' Claim Process for the production of threads or fibers by spinning acrylonitrile-styrene copolymer solutions, which are obtained by continuous polymerization of styrene and at least 85 wt. JS Acrylonitrile and optionally other conventional monomer-containing monomer mixtures in dimethylformamide with initiators in a reaction zone, whereby as much reaction mixture is discharged from the reaction zone in the steady state as fresh mixture is fed, characterized in that acrylonitrile-styrene copolymer solutions are spun that by introducing 30- to 50-% iger monomer solutions, the 1 to 6 wt.? » Styrene, based on total monomers, were obtained in the reaction zone, polymerizing at 45 to 70 ° C. and terminating the polymerization in the conventional manner in the discharged part of the reaction mixture. Badische Anilin- 4 Soda-Pabrik AG 1 0 9 8 A 1/1 7 7 B