DD215591A1 - PROCESS FOR PREPARING POLYACRYLNITRILE FILAMENTS - Google Patents

Abstract

The invention relates to a process for the production of polyacrylonitrile filaments, which are used as starting materials for voroxidized and thermostabilized acrylic fibers or carbon fibers. Target u. The object of the invention is to develop a method by which high-strength filaments of conventional acrylonitrile polymers can be produced in an energy-efficient manner without much additional expenditure on apparatus. By simultaneous drying, post-stretching and stabilization in a process step, this task is solved. The resulting filaments are suitable as starting materials for pre-oxidized acrylic fibers or carbon fibers.

Description

Title of the invention

Process for the preparation of polyacrylonitrile filaments

Field of application of the invention

The invention relates to a process for the production of polyacrylonitrile filaments, which are distinguished by high strengths and are used as starting materials for vinyl-stabilized acrylic fibers and / or carbon fibers. , '...

Characteristic of the known technical solutions

It is known to produce from acrylonitrile polymers by dry or ITa spinning filaments used as starting materials for thermally stabilized acrylic fibers or carbon fibers. The mechanical properties of these fibers, e.g. the strength and modulus of elasticity depend i.a. from the degree of orientation of the structural elements constituting these fibers, with a correlation to the degree of orientation that the structural elements have in the starting polyacrylonitrile filaments. \

The degree of orientation of these filaments, in turn, is primarily a function of the stretching tuft, so that ultimately the height of the filament stretch determines the IT level of the mechanical properties of the carbon fibers. ^: The stretchability of the polyacrylonitrile filaments depends on several factors, z.3. from the composition of the polymer, the quality of the solution, the spinning delay, the degree of polymerization (DD-PS 100 980, DD-PS 135 509, DD-PS 151 079) and of the stretching temperature and the

Stretching medium in itself ..

DE-OS 2 1p6 884 describes a process in which the wet-drawn threads are dried under the admission of free shrinkage in heated gas and then subjected to a dry heat drawn by 40 % . The monofilament strength of 42 cU / tex achieved in this case is unsuitable for the production of high-quality carbon fibers. In principle similar Yerfahrensschritte are also in DE-PS 2,836,075, US-PS 3,135,812, ÜS-PS 3 097 053 vorge- beat. ·. / '.

¹ in the DE-OS 3,027,844 high strength and high modulus filaments are claimed which ITaßrecken after the technological sequence, and Hei3viialzentrocknung Kontaktnachreckung .to be prepared at least 15%, at a total stretch ratio of more than 900%.

In contrast, in DE-OS 2,851,273 the threads are stretched after 2Iaßreckung in a vapor zone at temperatures vsn 110 to 140 G under the action of saturated steam and pressure and then dried. Sine steam stretching before 'drying also describes the DD-PS 151 079.

In EP-PS 61 117, the spun threads before or, after the washing haßgereckt, dried under tension, dry-heated at 140-200 ⁰ O and finally dry-heat-set at 180-25O ⁰ G under tension. Here, special, not conventional for conventional fiber spinning '' acrylonitrile "is used. Other variants of the combinations llachrecken / drying bzia. Dry / I taching are described in JP-PS 7 222 664, 7 245 618, 7 328 986 and 7 447 622.

The different variants of the hot air or Dampfnachreckens before oder'nach'der drying to. Production of filaments with high strengths have the disadvantage that energy-consuming process stages and an additional high

Apparative effort is necessary to obtain the required degree of stretching and strength ₄ . The process steps used can also lead to microdefects on the filament surfaces which result in yarn breaks and liquid during later processing. '

Aim of the invention

The object of the invention is to produce rolyacrylonitrile filaments with improved strengths in an energy-conscious and economically advantageous manner from conventional polymers

 The process should be technically simple.

Explanation of the invention of the invention;

The invention is based on the object of demonstrating possibilities of producing filaments with high strengths from acrylonitrile polymers having the lowest possible process stages. , ·

The filaments should have no filament breaks in the cable and be suitable for further processing on thermostabilized acrylic fibers or carbon fibers. , ,

According to the invention this is achieved in that wet-spun rolyacrylonitrile filaments wet-set, washed and. optionally again wet-set and subsequently dried for 20 to 300 s at temperatures of 130 to 280 C in heated gas or on rotating moldings simultaneously and be readjusted and stabilized by 25 to 55 % .

The total elongation of the filaments with final fiber finenesses of 0.5 to 5 dtex is 1000 to 1600 %.

- 4 -

The simultaneous drying, post-stretching and stabilization can be used as the last process step in the production of high-strength polyacrylonitrile filaments for technical inserts ¹ , ie reinforcing materials or sewing threads. .

For further processing to preoxygenated bz? J. thermally stabilized acrylic or carbonase, the simultaneous drying, quenching and stabilizing can be advantageously integrated into the first pre-oxidation stage so that conventional quenching and drying of the starting materials is completely eliminated. The process according to the invention makes it possible, with reduced expenditure on energy and equipment, to produce filaments with excellent mechanical properties. The equipment is similar to those used to make conventional fibers for textile use. , ',

The resulting yarns can be wound in a known manner, cut into staple fibers or e.g. as a reinforcing material lcarz cut or else be supplied directly to further 'Vorosiydationsprozessen. , -

Embodiment . ?,

Example T.

A 23.2% solution of an acrylonitrile polymer consisting of 93.4% by weight of acrylonitrile, 5.3 % of oleic acid of 1'-ester and 1.3% of laxate of toluenesulfonate in dimethylformamide was replaced by a 3000 hole nozzle 50 LIasse-% dimethylformamide and water containing coagulation bath ^ stretched in a ö ^e to a Filamentverband spun and the same in a concentration Reckbad at 100 ⁰ C to 900%.

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After washing out the solvent, the filaments were in a Mehm "alzenv? Erk dried at roll surface temperature of 195 ⁰ C, at the same time afterstretched in z" v? Ei staged. 36% and stabilized. The drawn a total of 1224% filaments were at the terminal the drying stretch wound in a known manner.

The filaments are characterized by the following mechanical properties:

Filament fineness: 0.202 tes:

Tear resistance:,. 68.8 clT / tex hot stretch: 10.6 %

Knot strength: 11.2 cll / tex

Schingen strength: 6.8 clJ / tex

Initial module: 2025 · cll / tex

Example 2

The solution-of an acrylonitrile copolymer in Example 1 was passed through a 3,000 hole die in a 50% by weight of dimethylformamide and water containing coagulation bath su stretched a Filamentverband spun and then in a Reckbad at 100 ⁰ C to 900%. Hach leaching of the solvent \ iurde the wet cable in a Vorosydation3ofen introduced afterstretched in the first temperature zone, at 245 ⁰ C in air in a step 1.3, is simultaneously dried and stabilized. The cable was held for a further 35 minutes at a temperature of 245 ⁰ C and then treated at 27O ⁰ C in the air stream under aaochhen tension, which prevents both further elongation and a shrinkage, over a period of 120 min itie it.

The resulting thermally stabilized filaments are flexible, do not burn on contact with flames and are characterized by the following properties:

Filament Thickness: Tear Resistance Height Expansion: Initial Modulus: Moisture Absorption:

ΙΟΙ value: Density:.

0.135 tex 22 cH / tex 11.5 % cH / tez 12.5% (at 81 % rel.

Humidity) 58 1.41 g / cm ³

Claims (3)

Invention san apruch. 1. "Process for the preparation of rolyacrylonitrile filaments for further processing into thermally stabilized acrylic fibers and / or carbon fibers having filament finenesses: from 0.5 to 5 dtes by hauling polymers of acrylonitrile, stretching, washing and, if appropriate, re-stretching the filaments, characterized in that the filaments for 20 to 300 s at temperatures of 130 to 2SO ⁰ C in heated gas or on rotating moldings simultaneously dried, nachgereckt 25-55 % and - Are stabilized and the total elongation of the filaments is 1000 to 1600 % . . , .. - 2. The method according to item 1, characterized in that the badgereckte gelled cable in the first stage of a Voroxydationsofens at temperatures of 180 to 280 ⁰ C in a gas atmosphere at the same time dried, re-stretched, stabilized and in other temperature levels in oxidizing atmosphere to thermally stable fibers vie it is treated. 3 · Method according to item 2, characterized in that the Uachreckung can take place in one or more stages. ,