MELT SPINNABLE COPOLYMERS FROM POLYACRYLONITRILE, METHOD FOR PRODUCING FIBERS OR FIBER PRECURSORS BY MEANS OF MELT SPINNING, AND FIBERS PRODUCED ACCORDINGLY

Abstract

The invention relates to melt spinnable copolymers of polyacrylonitrile (PAN) which are producible by means of copolymerisation of acrylonitrile with an alkoxyalkylacrylate. As additional comonomers alkylacrylates and vinyl esters may be considered. Likewise, the invention relates to a method for the production of fibres or fibre precursors, in particular carbon fibre precursors, by means of melt spinning, in which the mentioned copolymer is used. Furthermore, the invention relates to fibres produced in this way, in particular carbon fibres.

Claims

1-16. (canceled)

17. A melt spinnable copolymer of polyacrylonitrile (PAN), which is produced by copolymerisation of 95 to 80% by mol of acrylonitrile with at least one comonomer selected from a) 5 to 20% by mol of at least one alkoxyalkylacrylate of general formula I ##STR00007## with R=C.sub.nH.sub.2n+1 and n=1-8 and m=1-8, b) 0 to 10% by mol of at least one alkylacrylate of general formula II ##STR00008## with R=C.sub.nH.sub.2n+1 and n=1-18, c) 0 to 10% by mol of at least one vinyl ester of general formula III ##STR00009## with R=C.sub.nH.sub.2n+1 and n=1-18, the copolymer having a weight-average molar mass (Mw) in the range of 10,000 to 150,000 g/mol.

18. The copolymer according to claim 17, wherein the copolymer is spinnable at a temperature range from 160 to 240° C.

19. The copolymer according to claim 17, wherein the copolymer has a melt viscosity which is constant or decreasing with increasing temperature up to 240° C.

20. The copolymer according to claim 17, wherein the copolymerisation is effected by precipitation polymerisation in an aqueous medium, emulsion polymerisation in an aqueous medium and/or polymerisation in a solvent.

21. The copolymer according to claim 20, wherein the solvent is selected from the group consisting of dimethylsulphoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene carbonate, propylene carbonate, aqueous sodium rhodanide solution and mixtures thereof.

22. The copolymer according to claim 17, wherein 8 to 12% by mol of the comonomer is present in a).

23. The copolymer according to claim 17, wherein 1 to 5% by mol of the comonomer is present in b).

24. The copolymer according to claim 17, wherein 1 to 5% by mol of the comonomer is present in c).

25. The copolymer according to claim 17, wherein the copolymer has a weight-average molar mass (Mw) in the range from 15,000 to 80,000 g/mol.

26. A method for the production of fibres or fibre precursors by melt spinning, in which i. a copolymerisation of 95 to 80% by mol of acrylonitrile with at least one comonomer selected from a) 5 to 20% by mol of at least one alkoxyalkylacrylate of general formula I ##STR00010## with R=C.sub.nH.sub.2n+1 and n=1-8 and m=1-8, b) 0 to 10% by mol of at least one alkylacrylate of general formula II ##STR00011## with R=C.sub.nH.sub.2n+1 and n=1-18, c) 0 to 10% by mol of at least one vinyl ester of general formula III ##STR00012## with R=C.sub.nH.sub.2n+1 and n=1-18, is carried out in the presence of at least one initiator, and ii. the copolymer is spun from an extruder with at least one nozzle, suitable for spinning, at the extruder outlet, to form mono- or multifilaments.

27. The method according to claim 26, wherein, directly before or during extrusion in b), at least one softening agent is added, which is selected from the group consisting of water, nitroalkanes, alkylalcohols, ionic liquids, glycols, dimethyl sulphoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene carbonate, propylene carbonate, aqueous sodium rhodanide solution, and mixtures thereof.

28. The method according to claim 26, wherein the fibres are carbon fibres, and the method further includes: iii. stabilisation of the filaments by a temperature treatment at a temperature from 200 to 350° C. and iv. carbonisation of the filaments at a temperature from 800 to 1,200° C.

29. The method according to claim 28, wherein stabilisation of the filaments is effected at a temperature from 180 to 320° C.

30. The method according to claim 26, wherein the initiator is selected from the group consisting of azo compounds, peroxides, hydroperoxides, alkylperoxides, peroxodicarbonates, peroxyesters, dialkylperoxides, persulphates, perphosphates, redox initiators, and mixtures thereof.

31. A fibre produced by spinning the copolymer according to claim 17.

32. The fibre according to claim 31, wherein the fibre is a carbon fibre.

Description

EXAMPLES

[0056] In the examples, the following devices were used:

[0057] Mini-Haake: this concerns a mini-2-screw extruder “HAAKE Minilab”, Thermo Electron Corporation, Germany. At the melt outlet opening, a 1-hole-nozzle with a hole diameter of 500 μm was fitted. The metering was effected by hand. The emerging monofilament was drawn-off with a winding head (max. 400 m/min) and wound onto a bobbin.

[0058] Test unit Multi-Filament-Spinning (Spinning tester): the construction includes a 2-screw extruder (L/D=30) with 4 temperature zones. The metering was effected gravimetrically under nitrogen atmosphere, the feed was temperature-controlled to max. 40° C. At the end of the extruder, the spinning packet with melt filter (100 μm) and also nozzle plate (42-hole nozzle, hole diameter 400 μm, L/D=4) was mounted. A galette duo which could draw-off at a speed of up to 100 m/min served as draw-off element. The final winding of the filament yarn was produced by a cross-wound cone winder.

Comparative Example 1

[0059] Precipitation polymerisation to form copolymer with 10% by mol of methylacrylate and spinning on Mini-Haake.

[0060] In a jacketed reactor with reflux cooling and anchor agitator, 340 g water, 0.39 g ascorbic acid and 0.2 g mercaptoethanol were introduced under nitrogen purging. A mixture of 6.1 g methylacrylate and 33.9 g acrylonitrile is added. This is heated to 30° C. internal reactor temperature, 200 μl of a 1% solution of iron(II)sulphate heptahydrate is added and subsequently a solution of 0.45 ammonium persulphate in 10 g water is added. After 1.5 h, the reaction is terminated, the reactor contents are filtered, washed with water and ethanol and dried in a vacuum.

[0061] The resulting polymer has a relative viscosity of 2.0. The composition corresponded, with 9.7% by mol of methylacrylate and 90.3% by mol of acrylonitrile, almost to the feed values.

[0062] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 1.

[0063] An increase in the complex viscosity at temperatures above 220° C. can be noted.

[0064] The polymer was spun to form a monofilament in the Mini-Haake at 230° C. with a maximum draw-off speed of 40 m/min. Higher draw-off speeds could not be achieved. A spinning process which was stable over a fairly long time was not possible.

Comparative Example 2

[0065] Solution polymerisation to form copolymer with 10% by mol of methylacrylate and spinning on Mini-Haake

[0066] In a 250 ml round flask with reflux cooler and nitrogen inflow, 72 g N-methylpyrrolidone are introduced under magnetic agitation. A mixture of 7.4 g methylacrylate and 40.6 g acrylonitrile are added and heated with an oil bath to 60° C. A solution of 180 mg V-65 (2,2′azobis(2,4-dimethylvaleronitrile), Co. Wako) in 2 ml acetone is added after reaching the temperature. The reaction time is 6 h. The reaction mixture is precipitated in 500 ml ethanol, the polymer is filtered off, washed with ethanol and dried in a vacuum.

[0067] The resulting polymer has a relative viscosity of 1.5. The molar mass Mw was determined at 29,000 g/mol with a PDI of 1.5. The composition corresponded, with 9.3% by mol of methylacrylate and 90.7% by mol of acrylonitrile, almost to the feed values.

[0068] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 2.

[0069] An increase in the complex viscosity at temperatures above 230° C. can be noted.

[0070] The polymer was spun to form a monofilament in the Mini-Haake at 220° C. with a maximum draw-off speed of 200 m/min. A spinning process which is stable over a fairly long time was not possible.

Example 1

[0071] Precipitation polymerisation to form copolymer with 10% methoxyethylacrylate (m=2; n=1) and spinning on Mini-Haake

[0072] In a jacketed reactor with reflux cooling and anchor agitator, 340 g water, 0.39 g ascorbic acid and 1.0 g mercaptoethanol are introduced under nitrogen purging. A mixture of 8.6 g methoxyethylacrylate and 31.4 g acrylonitrile is added. It is heated to 30° C. internal reactor temperature, 200 μl of a 1% solution of iron(II)sulphate heptahydrate is added and subsequently a solution of 0.45 g ammonium persulphate in 10 g water is added. After 1.5 h, the reaction is terminated, the reactor contents are filtered, washed with water and ethanol and dried in a vacuum.

[0073] The resulting polymer has a relative viscosity of 1.4. The molar mass Mw was determined at 22,000 g/mol with a PDI of 2.3. The composition corresponded, with 10.2% by mol of methoxyethylacrylate and 89.8% by mol of acrylonitrile, almost to the feed values.

[0074] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 3.

[0075] No increase again in the complex viscosity up to temperatures of at least 255° C. can be noted.

[0076] The polymer was spun to form a monofilament in the Mini-Haake at 180° C. with a maximum draw-off speed of 200 m/min. The titre of the fibre was 2.8 tex, the strength 16.4 cN/tex, the breaking elongation 16.4%.

Example 2

[0077] Solution polymerisation to form copolymer with 10% methoxyethylacrylate and spinning on Mini-Haake

[0078] In a 250 ml round flask with reflux cooler and nitrogen inflow, 80 g dimethylsulphoxide was introduced under magnetic agitation. A mixture of 4.3 g methoxyethylacrylate, 15.7 g acrylonitrile and 500 mg mercaptoethanol is added and heated with an oil bath to 60° C. A solution of 250 mg V-65 (2,2′azobis (2,4-dimethylvaleronitrile), Co. Wako) in 1 mol acetone is added after reaching the temperature. The reaction time is 6 h. The reaction mixture is precipitated in 500 ml ethanol, the polymer is filtered off, washed with ethanol and dried in a vacuum.

[0079] The resulting polymer has a relative viscosity of 1.4. The composition corresponded, with 9.7% mol of methoxyethylacrylate and 90.3% by mol of acrylonitrile, almost to the feed values.

[0080] The polymer was spun to form a monofilament in the Mini-Haake at 180° C. with a maximum draw-off speed of 400 m/min. The titre of the fibre was 1.0 tex, the strength 11.5 cN/tex, the breaking elongation 19.0%.

Example 3

[0081] Solution polymerisation to form copolymer with 10% methoxyethylacrylate and spinning on Mini-Haake

[0082] In a 100 ml round flask with reflux cooler and nitrogen inflow, 36 g N-methyl-2-pyrrolidone (NMP) are introduced under magnetic agitation. A mixture of 5.15 g methoxyethylacrylate, 18.85 g acrylonitrile is added and heated with an oil bath to 60° C. A solution of 98 mg V-65 (2,2′azobis(2,4-dimethylvaleronitrile), Co. Wako) in 0.5 ml acetone is added after reaching the temperature. The reaction time is 6 h. The reaction mixture is precipitated in 500 ml water, the polymer filtered off, washed with ethanol and dried in a vacuum.

[0083] The resulting polymer has a relative viscosity of 1.6. The molar mass Mw was determined at 44,000 g/mol with a PDI of 1.4. The composition corresponded, with 9.6% by mol of methoxyethylacrylate and 90.4% by mol of acrylonitrile, almost to the feed values.

[0084] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 4.

[0085] No increase again in the complex viscosity up to temperatures of at least 250° C. can be noted.

[0086] The polymer was spun to form a monofilament in the Mini-Haake at 180° C. with a maximum draw-off speed of 118 m/min. The titre of the fibre was 4.3 tex, the strength 18.3 cN/tex, the breaking elongation 16.5%.

Example 4

[0087] Solution polymerisation to form copolymer with 10% butoxyethylacrylate (m=2, n=4) and spinning on Mini-Haake

[0088] In a 100 ml round flask with reflux cooler and nitrogen inflow, 36 g N-methyl-2-pyrrolidone (NMP) are introduced under magnetic agitation. A mixture of 6.4 g butoxyethylacrylate and 17.6 g acrylonitrile is added and heated with an oil bath to 60° C. A solution of 92 mg V-65 (2,2′azobis(2,4-dimethylvaleronitrile), Co. Wako) in 0.5 ml acetone is added after reaching the temperature. The reaction time is 6 h. The reaction mixture is precipitated in 500 ml water, the polymer is filtered off, washed with ethanol and dried in a vacuum.

[0089] The resulting polymer has a relative viscosity of 1.6. The composition corresponded, with 9.7% by mol of butoxyethylacrylate and 90.3% by mol of acrylonitrile, almost to the feed values.

[0090] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 5.

[0091] No increase again in the complex viscosity up to temperatures of at least 250° C. can be noted.

[0092] The polymer was spun to form a monofilament in the Mini-Haake at 200° C. with a maximum draw-off speed of 98 m/min. The titre of the fibre was 8 tex, the strength 9.5 cN/tex, the breaking elongation 14.2%.

Example 5

[0093] Solution polymerisation to form copolymer with 7.5% methoxyethylacrylate and spinning on Mini-Haake

[0094] In a 1.8 1 stainless steel reactor, 222.0 g N-methyl-2-pyrrolidone (NMP), 123.4 g acrylonitrile and 24.6 g 2-methoxyethylacrylate are introduced and made inert with nitrogen by means of an inflow pipe for 15 min. The closed reactor is thereupon heated to 55° C. and a solution of 615 mg V-40 (1,1′-azobis(cyclohexanecarbonitrile), Co. Wako) in 8 ml NMP is injected by means of a syringe via an inlet. The reaction mixture is then agitated for 6 h at 90° C.

[0095] The mixture is received in 2 1 NMP after the reaction and precipitated in 5 times the quantity of water. After filtration of the polymer, this is washed with water and ethanol and dried at 60° C. in a vacuum.

[0096] The resulting polymer has a relative viscosity of 1.4. The molar mass Mw was determined at 38,000 g/mol with a PDI of 1.2. The composition corresponded, with 7.1% by mol of methylacrylate and 92.9% by mol of acrylonitrile, almost to the feed values.

[0097] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 6.

[0098] No increase again in the complex viscosity up to temperatures of at least 250° C. can be noted.

[0099] The polymer was spun to form a monofilament in the Mini-Haake at 200° C. with a maximum draw-off speed of 98 m/min. The titre of the fibre was 7.3 tex, the strength 7.7 cN/tex, the breaking elongation 16.8%.

Example 6

[0100] Solution polymerisation to form copolymer with 10% methoxyethylacrylate and spinning on spinning tester

[0101] In a 7.5 1 stainless steel reactor, 3,000 g N-methyl-2-pyrrolidone (NMP), 1,630 g acrylonitrile and 449 g 2-methoxyethylacrylate are introduced and made inert with nitrogen by means of an inflow pipe for 15 min. The closed reactor is thereupon heated to 55° C. and a solution of 8.8 g V-40 (1,1′-azobis(cyclohexanecarbonitrile), Co. Wako) in 100 ml NMP is injected by means of a syringe via an inlet. The reaction mixture is then agitated for 6 h at 90° C.

[0102] The mixture is precipitated in 5 times the quantity of water after the reaction. After filtration of the polymer, this is washed with water and ethanol and dried at 60° C. in a vacuum.

[0103] The resulting polymer has a relative viscosity of 1.3. The composition corresponded, with 9.7% by mol of methylacrylate and 90.3% by mol of acrylonitrile, almost to the feed values.

[0104] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 7.

[0105] No increase again in the complex viscosity up to temperatures of at least 250° C. can be noted.

[0106] The polymer was spun in the spinning tester under the following conditions: temperature zones in the extruder 110° C./ 160° C./ 180° C./ 180° C.; spinning nozzle temperature 180° C.; maximum draw-off speed of 100 m/min. The titre of the individual fibre was 0.82 tex, the strength 16.3 cN/tex, the breaking elongation 17.6%.

[0107] At a draw-off speed of 40 m/min, an individual fibre titre of 2.1 tex was obtained, the strength was 10.1 cN/tex, the breaking elongation 53.6%. This fibre was stretched again in 80° C. hot water. The thereby obtained individual fibre titre was 0.80 tex, the strength 22.4 cN/tex, the breaking elongation 19.0%.

Example 7

[0108] Solution polymerisation to form copolymer with 10% methoxyethylacrylate and spinning on spinning tester

[0109] In a 1.8 1 steel reactor, 499.5 g N-methyl-2-pyrrolidone (NMP), 166.5 g DMSO, 348.8 g acrylonitrile and 95.1 g 2-methoxyethylacrylate are introduced and made inert with nitrogen by means of an inflow pipe for 15 min. The closed reactor is thereupon heated to 55° C. and a solution of 1.79 g V-40 (1,1′-azobis(cyclohexanecarbonitrile), Co. Wako) in 25 ml NMP is injected by means of a syringe via an inlet. The reaction mixture is then agitated for 6 h at 90° C.

[0110] The mixture is received in 2 1 NMP after the reaction and precipitated in 5 times the quantity of water. After filtration of the polymer, this is washed with water and ethanol and dried at 60° C. in a vacuum.

[0111] The resulting polymer has a relative viscosity of 1.6. The composition corresponded, with 10.1% by mol of methylacrylate and 89.9% by mol of acrylonitrile, almost to the feed values.

[0112] The polymer was spun in the spinning tester under the following conditions: temperature zones in the extruder 110° C./ 160° C./ 185° C./200° C.; spinning nozzle temperature 200° C.; maximum draw-off speed of 30 m/min. The titre of the individual fibre was 0.92 tex, the strength 20.3 cN/tex, the breaking elongation 20.9%.

Example 8

[0113] Solution polymerisation to form copolymer with 9% methoxyethylacrylate and 1% dodecylacrylate and also spinning on Mini-Haake

[0114] In a 1 1 steel reactor, 222.0 g N-methyl-2-pyrrolidone (NMP), 114.2 g acrylonitrile and 28.0 g 2-methoxyethylacrylate and 5.75 g dodecylacrylate are introduced and made inert with nitrogen by means of an inflow pipe for 15 min. The closed reactor is thereupon heated to 55° C. and a solution of 583 mg V-40 (1,1′-azobis(cyclohexanecarbonitrile), Co. Wako) in 8 ml NMP is injected by means of a syringe via an inlet. The reaction mixture is then agitated for 6 h at 90° C.

[0115] The mixture is received in 1 1 NMP after the reaction and precipitated in 5 times the quantity of water. After filtration of the polymer, this is washed with water and ethanol and dried at 60° C. in a vacuum.

[0116] The resulting polymer has a relative viscosity of 1.4. The composition corresponded, with 8.8% by mol of methoxyethylacrylate, 1.0% dodecylacrylate and 90.2% by mol of acrylonitrile, almost to the feed values.

[0117] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 9.

[0118] No increase in the complex viscosity at temperatures above 230° C. can be noted.

[0119] The polymer was spun to form a monofilament in the Mini-Haake at 200° C. with a maximum draw-off speed of 400 m/min. The titre of the fibre was 3.8 tex, the strength 7.5 cN/tex, the breaking elongation 107.5%.

Example 9

[0120] Solution polymerisation to form copolymer with 8% methoxyethylacrylate and 2% dodecylacrylate and also spinning on Mini-Haake In a 1 1 steel reactor, 222.0 g N-methyl-2-pyrrolidone (NMP), 112.2 g acrylonitrile and 24.5 g 2-methoxyethylacrylate and 11.3 g dodecylacrylate are introduced and made inert with nitrogen by means of an inflow pipe for 15 min. The closed reactor is thereupon heated to 55° C. and a solution of 575 mg V-40 (1,1′-azobis(cyclohexanecarbonitrile), Co. Wako) in 8 ml

[0121] NMP is injected by means of a syringe via an inlet. The reaction mixture is then agitated for 6 h at 90° C.

[0122] The mixture is received in 1 1 NMP after the reaction and precipitated in 5 times the quantity of water. After filtration of the polymer, this is washed with water and ethanol and dried at 60° C. in a vacuum.

[0123] The resulting polymer has a relative viscosity of 1.4. The composition corresponded, with 7.9% by mol of methoxyethylacrylate, 1.9% dodecylacrylate and 90.2% by mol of acrylonitrile, almost to the feed values.

[0124] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 9.

[0125] No increase in the complex viscosity at temperatures above 230° C. can be noted.

[0126] The polymer was spun to form a monofilament in the Mini-Haake at 200° C. with a maximum draw-off speed of 400 m/min. The titre of the fibre was 2.5 tex, the strength 9.1 cN/tex, the breaking elongation 76.2%.

Example 10

[0127] Solution polymerisation to form copolymer with 7% methoxyethylacrylate and 3% dodecylacrylate and also spinning on Mini-Haake

[0128] In a 1 1 steel reactor, 222.0 g N-methyl-2-pyrrolidone (NMP), 110.3 g acrylonitrile and 21.0 g 2-methoxyethylacrylate and 16.6 g dodecylacrylate are introduced and made inert with nitrogen by means of an inflow pipe for 15 min. The closed reactor is thereupon heated to 55° C. and a solution of 565 mg V-40 (1,1′-azobis(cyclohexanecarbonitrile), Co. Wako) in 8 ml NMP is injected by means of a syringe via an inlet. The reaction mixture is then agitated for 6 h at 90° C.

[0129] The mixture is received in 1 1 NMP after the reaction and precipitated in 5 times the quantity of water. After filtration of the polymer, this is washed with water and ethanol and dried at 60° C. in a vacuum.

[0130] The resulting polymer has a relative viscosity of 1.4. The composition corresponded, with 6.8% by mol of methoxyethylacrylate, 3.0% dodecylacrylate and 90.2% by mol of acrylonitrile, almost to the feed values.

[0131] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 10.

[0132] No increase in the complex viscosity at temperatures above 230° C. can be noted.

[0133] The polymer was spun to form a monofilament in the Mini-Haake at 200° C. with a maximum draw-off speed of 400 m/min. The titre of the fibre was 2.3 tex, the strength 10.7 cN/tex, the breaking elongation 29.7%.

Example 11

[0134] Solution polymerisation to form copolymer with 5% methoxyethylacrylate and 5% methylacrylate and also spinning on Mini-Haake

[0135] In a 100 ml round flask with reflux cooler and nitrogen inflow, 36 g N-methylpyrrolidone are introduced under magnetic agitation. A mixture of 1.8 g methylacrylate, 2.7 g methoxyethylacrylate and 19.6 g acrylonitrile is added and heated with an oil bath to 60° C. A solution of 90 mg V-65 (2,2′azobis(2,4-dimethylvaleronitrile), Co. Wako) in 1 ml acetone is added after reaching the temperature. The reaction time is 6 h. The reaction mixture is precipitated in water, the polymer is filtered off, washed with ethanol and dried in a vacuum.

[0136] The resulting polymer has a relative viscosity of 1.5. The molar mass Mw was determined at 47,000 g/mol with a PDI of 1.1. The composition corresponded, with 5.3% by mol of methoxyethylacrylate, 4.5% by mol of methylacrylate and 90.2% by mol of acrylonitrile, almost to the feed values.

[0137] The rheological measurement in oscillation mode (temperature sweep) is illustrated in FIG. 11.

[0138] No increase in the complex viscosity at temperatures above 230° C. can be noted.

[0139] The polymer was spun to form a monofilament in the Mini-Haake at 190° C. with a maximum draw-off speed of 98 m/min. The titre of the fibre was 2.4 tex, the strength 15.0 cN/tex, the breaking elongation 13.8%.