Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/18—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of unsaturated nitriles, e.g. polyacrylonitrile, polyvinylidene cyanide

Definitions

• the present invention relates to high-strength polyacrylonitrile fibers (hereinafter referred to as PAN fibers) of high modulus, and to a particularly adapted process for their production and their use, in particular as reinforcing materials or for the production of filters or friction linings.
• PAN fibers polyacrylonitrile fibers
• PAN fibers of high strength are known per se.
• Dobrecov et al. in soviet. Contributions to fiber research and textile technology, 9 , pp. 407-411 (1972) described PAN fibers of high strength and high modulus, which are derived from PAN types of high molecular weight; Examples of this are molecular weights of 3 * 106.
• EP-A-165,372 and -255,109 fibers of strengths with more than 8.83 cN / dtex and processes for their production are known, in which PAN types of high molecular weight are also used.
• PAN types of high molecular weight are also used.
• EP-A-255,109 PAN types with a molecular weight of more than 500,000 (weight average) are used, while according to EP-A-165,372 PAN types with an intrinsic viscosity of more than 2.5 are used, which has a molecular weight of more than 210,000 (weight average) corresponds.
• PAN types of unusually high molecular weight are used without exception.
• Usual molecular weight values for PAN fibers range approximately from 80,000 to 180,000 (cf. the statements by Falkai et al. In “Synthesefaser”, p. 200, Verlag Chemie (1981) or by Masson et al. In “ Fiber Producer”, June 1984, pp. 34-37).
• PAN fibers of high strength have also become known which have been produced with PAN types of the usual molecular weight.
• GB-A-1,193,170 describes PAN fibers which have strengths of up to 17.5 g / denier. The elongation at break of the fibers described is, however, at more than 15% too high for many applications.
• PAN fibers of high modulus which have also been produced with PAN types of the usual molecular weight are. Fibers with strengths of up to 81 cN / tex or with initial moduli of up to 1989 cN / tex are described. PAN fibers which have strengths of more than 80 cN / tex and at the same time initial moduli of more than 1800 cN / tex are not described in this document.
• PAN fibers are in demand as reinforcement materials due to their high resistance in aggressive environments, for example in strongly alkaline environments, or against radiation. High strengths and high initial moduli with low elongation at break are particularly in demand for technical applications. There is a need for PAN fibers with such a property profile, in particular for PAN fibers that can be obtained by high productivity processes.
• the present invention relates to fibers containing polyacrylonitrile homopolymer or copolymer with a weight average molecular weight of less than 210,000 as a fiber-forming substance, the fibers having strengths of more than 80 cN / tex, initial moduli, based on 100% elongation, of more than 1800 cN / tex and have elongations at break of less than 10%.
• the precipitation or solution polymers prepared by the customary processes can be used as polymer raw materials. Depending on the requirements for the areas of application, both homo- and copolymers of acrylonitrile can be used. The purity of the monmer used should be as high as possible.
• Suitable comonomers are all unsaturated compounds copolymerizable with acrylonitrile, preferably unsaturated carboxylic acids, such as acrylic acid, methacrylic acid or itaconic acid; unsaturated sulfonic acids, such as allyl, methallyl or styrene sulfonic acid; unsaturated carboxamides, such as acrylamide or methacrylamide; Esters of unsaturated carboxylic acids, such as the methyl, ethyl, propyl or butyl esters of acrylic or methacrylic acid or polyfunctional hydroxyethyl or aminoethyl esters or their derivatives of acrylic or methacrylic acid; Esters of carboxylic acids with unsaturated alcohols or ethers based on unsaturated alcohols, such as vinyl esters and ethers, for example vinyl acetate, vinyl stearate, vinyl butyrate, vinyl bromoacetate, vinyl dichloroacetate or vinyl trichloroacetate; uns
• the polymers used preferably have a content of at least 90% by weight, in particular at least 99% by weight, of acrylonitrile units.
• Polyacrylonitrile homopolymers or copolymers whose molecular weight (weight average) is 175,000 to 210,000 are used in particular.
• the strengths of the fibers according to the invention are preferably 89 to 100 cN / tex.
• the initial moduli, based on 100% elongation, of the fibers according to the invention are preferably 1850 to 2150 cN / tex, very particularly preferably 1900 to 2150 cN / tex.
• the elongations at break of the fibers according to the invention are preferably 7 to 9%.
• fibers as defined above, which have knot strengths of more than 15 cN / tex, in particular from 17 to 20 cN / tex.
• the titers of the fibers according to the invention are usually in the range of textile titers, for example in the range of less than or equal to 3.5 dtex. Fibers with a titre of 1.5 to 2.5 dtex are preferred.
• Any organic aprotic solvent or a mixture of such solvents can be used as the spinning solvent.
• solvents are dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC) and in particular dimethylformamide (DMF).
• polymers which have a weight average molecular weight of less than or equal to 500,000, preferably 74,000 to 500,000. Polymers are particularly preferably used whose weight average molecular weight is 75,000 to 400,000, in particular 175,000 to 250,000.
• the spinning mass concentration is at least 15%, preferably 17 to 22%, in particular 18 to 22%.
• dope concentrations of less than 15% problems with the nozzle run usually occur; i.e. irregularities occur at the nozzles during spinning and, as a result, sticking can occur.
• productivity of the aftertreatment line decreases directly with the decrease in the spinning mass concentration.
• the spinning mass is usually filtered before spinning. This removes gel particles and any impurities that may be present. Filtration is of great importance in the method according to the invention, since this measure can considerably reduce the error rate during spinning and aftertreatment. Spinning defects can subsequently lead to windings on the drawing rollers during contact and wet drawing of the fiber.
• the filtration can be carried out with the known devices, for example with filter presses, in which the spinning mass is pressed through several compact fabric layers.
• a measure of the filter effect is the so-called continuity; this represents an upper limit for those particle diameters that still pass through the filter.
• filters with a continuity of 5 to 15 ⁇ m are preferably used. This means that particles with a diameter of less than 5 to 15 microns can still pass through the filter. If the filtration of the spinning mass is not correct, i.e. in the case of spinning solutions with DMF as solvent with a coarser filter than 15 ⁇ m, later production disruptions are to be expected.
• the filtration temperature is preferably between 80 and 90 ° C.
• the speed at which the threads emerge from the spinneret must be selected so that the fibers practically do not bend when immersed in the liquid and maintain their previous direction of movement. This is ensured if the spinning solution has a spray speed of at least 5 m / min, preferably 5 to 7 m / min.
• the correct choice of the nozzle hole diameter significantly influences the clean and perfect entry of the threads into the coagulation bath.
• the required high spray speeds of the method according to the invention are difficult to achieve, in particular when choosing large nozzle hole diameters. In these cases, problems with spinning and spilling of the spinneret can be expected. If such problems occur, it is advisable in individual cases to reduce the nozzle diameter.
• the behavior of the thread when pressed into the liquid of the coagulation bath can be influenced by the choice of the thickness of the thread.
• the threads must be pressed into the coagulation bath under such conditions that the fibers do not bend when immersed in the liquid and lose their previous direction of speed. This can also be influenced by the choice of the diameter of the nozzle holes.
• the nozzle hole diameters are less than 120 ⁇ m; nozzle hole diameters of 60 to 120 ⁇ m are preferred.
• the spinning can be carried out according to the wet spinning method or dry nozzle wet spinning method known per se.
• the spinneret can be immersed in the coagulation bath or the spinneret is mounted at a predetermined distance from the surface of the coagulation bath, which causes the spinning to take place through an air gap.
• the distance between the spinneret and the coagulation bath surface can be varied over a wide range, preferably the distance is less than 10 millimeters, in particular 1 to 10 mm.
• the coagulation bath is usually an aqueous mixture containing an organic aprotic solvent - for example a solution, dispersion or suspension of this organic aprotic solvent in water.
• the organic aprotic solvent in the coagulation bath is preferably the spinning solvent selected in each case.
• the concentration of the organic aprotic solvent should be chosen in such a way that there is sufficiently rapid and complete coagulation. When working with relatively highly concentrated spinning solutions, it must be ensured that the concentration of the organic aprotic solvent in the coagulation bath is not or will not be too high. Will the concentration of the organic aprotic solvent in the coagulation bath chosen high, so the fibers can be glued to the take-off godet, since complete coagulation of the fibers is not guaranteed.
• concentrations of the organic aprotic solvent of less than 75% by weight, based on the solution in the coagulation bath, are used. 60 to 75% by weight are preferred.
• the fiber is post-treated; this can be done on a known aftertreatment system.
• PAN fibers can be obtained by the spinning according to the invention, which can be drawn very high.
• the spun threads are post-treated by performing one or more stretching operations, the degree of stretching between devices for drawing off the spun threads from the coagulation bath and the exit of the post-treatment section being at least 1:12, preferably 1:14 to 1:18.
• the fiber can, for example, be washed one or more times after leaving the coagulation bath, an additional coagulation being able to take place in these steps.
• the fiber is usually wet-drawn and / or softened during at least one washing step. After washing, drying is usually carried out.
• the fibers are then post-drawn in a further drawing step; this can be done by stretching in a hot air bath and / or by contact stretching, for example using heated godets.
• the fibers are then drawn off, preferably under tension. Furthermore, it is possible and preferred to fix the drawn fibers after the post-drawing.
• the fibers can then be fed to a cutting device or the fibers are further processed as filaments, for example wound up.
• the PAN fibers according to the invention can be used for a wide variety of applications. These fibers are typically used for technical purposes. Examples of this are the use as reinforcing material for the production of composite materials, for example for the production of fiber-reinforced thermoplastic or thermosetting plastics or in particular for the production of fiber-reinforced hydraulically setting materials, for example in concrete.
• the PAN fibers according to the invention can be used for the production of nonwovens which e.g. can be used as a filter or as geotextiles.
• Another preferred area of application of the PAN fibers according to the invention is the production of friction linings, in particular brake linings.
• a PAN polymer with a molecular weight of 200,000 (Example 1a) and a PAN polymer with a molecular weight of 550,000 (Example 1b) are dispersed in cold DMF and dissolved at 80-90 ° C. in a dissolver.
• the concentration of the solution is chosen so that a ball fall time of 700 ⁇ 50 sec results.
• the ball fall time is measured by the method of K. Jost (Rheologica Acta, Vol. 1, page 303) at 60 ° C.
• the following table shows the production conditions and the properties of the spinning solution: Dwell time (min) Bullet fall time Spinning mass conc. (%) Example 1a 30th 690 19th Example 1b 60 685 12th
• Example 1a The dope according to example 1a was filtered once through a 10 ⁇ filter (example 2a) and once through a 25 ⁇ m filter (example 2b). The spinning masses were then fed to a 100 hole / 120 ⁇ m nozzle.
• the following table shows the dependence of the nozzle pressure on the dwell time of the dope after filtration: Time (min) Example 2a Nozzle pressure (bar) Example 2b Nozzle pressure (bar) 1 7.0 7.0 10th 7.0 8.2 60 7.0 10.1 120 7.1 12.2 180 7.0 spun
• Example 1a A PAN polymer with a molecular weight of 200,000 was dissolved as described in Example 1a with a concentration of 16, 18 and 22% in DMF, filtered through a 10 ⁇ m filter and a 100 hole / 120 ⁇ nozzle fed.
• the precipitation bath concentration was 70% DMF in water, the precipitation bath temperature 0 ° C.
• a spinning mass was produced as described in Example 3b.
• the spinning mass temperature was varied between 85 - 120 ° C.
• the results are shown in the following table: example Spinning mass temp. ° C
• Nozzle run 4a 85 bad - run not possible 4b 90 bad - run not possible 4c 95 bad - run with interruptions 4d 100 bad - runs about 30 min.
• 4e 105 Nozzle is running - individual interruptions 4f 110 good nozzle run 4g 120 very good - nozzle run very good
• Example 4g The spinning mass from Example 4g was taken and pressed through nozzles of different diameters. The results are shown in the following table: example jet Nozzle run 5a 100/60 ⁇ m satisfactory 5b 100/80 ⁇ m Good 5c 100/120 ⁇ m Good 5d 100/150 ⁇ m bad
• Example 5c The dope was prepared as in Example 5c and the spray speed varied. The results are shown in the following table: example Spraying speed (m / min) Nozzle run 6a 3rd not possible 6b 5 good nozzle run 6c 7 good nozzle run
• Example 6b A spinning mass and spinning arrangement was prepared as described in Example 6b and the precipitation bath concentration was varied. The results are shown in the following table: example Precipitation bath concentration (%) Gluing 7a 90 very much 7b 80 much 7c 70 non-sticky 7d 60 non-sticky
• Example 7c The fiber from Example 7c was drawn off with a take-off godet and wet-drawn, washed, finished, dried, contact-drawn and removed under tension on a classic aftertreatment line. The total draw was 1:12 (example 8a) or 1:10 (example 8b). The results are shown in the following table: The fiber values are as follows: Measurement 8a 8b Titer (dtex) 2.0 2.0 Strength (cN / tex) 90 80 Knot strength (cN / tex) 20th 14 Strain (%) 8th 10th Module (cN / tex) 2000 1400

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• General Chemical & Material Sciences (AREA)
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• Textile Engineering (AREA)
• Artificial Filaments (AREA)
• Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)

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Citations (6)

• 1994
  • 1994-09-05 EP EP94113886A patent/EP0645479A1/fr not_active Withdrawn
  • 1994-09-22 JP JP6228254A patent/JPH07150410A/ja active Pending
  • 1994-09-22 HU HU9402723A patent/HU213322B/hu not_active IP Right Cessation
  • 1994-09-22 RU RU94034355/04A patent/RU94034355A/ru unknown
  • 1994-09-22 IL IL11101994A patent/IL111019A0/xx unknown
  • 1994-09-23 CA CA002132816A patent/CA2132816A1/fr not_active Abandoned
  • 1994-09-23 BR BR9403829A patent/BR9403829A/pt not_active Application Discontinuation

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