Background technology
High-performance polyacrylonitrile-based carbon fiber, have excellent properties such as high specific strength, high ratio modulus, high temperature resistant, corrosion-resistant, endurance, creep resistant, conduction, heat transfer and thermal coefficient of expansion be little, be that advanced weaponries such as develop nuclear weapons, strategic missile, satellite, aerospace craft are equipped topmost critical material, simultaneously at civil areas such as airline carriers of passengers, civil construction, sports goodss wide application being arranged also, is a kind of extremely important dual-use material.The preparation process more complicated of high-performance polyacrylonitrile-based carbon fiber relates to technologies such as the pre-oxidation of spinning, precursor of synthetic, the precursor of copolymer and carbonization.The polyacrylonitrile fibril of high-quality is the basis of preparation high-performance polyacrylonitrile-based carbon fiber.Usually, can adopt wet method or dry-wet spinning technology to prepare polyacrylonitrile fibril.On technology, the wet spinning technology is directly to enter the coagulating bath of being made up of solvent and non-solvent after spinning solution is extruded from spinneret orifice to be shaped, and double diffusion promptly takes place, be separated, and forms nascent strand; The dry-wet spinning technology then is that spinning solution is extruded the back earlier by an air layer from spinneret orifice, and then enters the coagulating bath shaping.Because the existence of air layer, the dry-wet spinning technology can be spun full-bodied spinning solution, and can realize high speed spinning, high strength, high orientation are easy to get, smooth surface, the precursor that hole is few, diameter is little, core-skin difference is little is a kind of spining technology preferably for preparing the high-performance polyacrylonitrile precursor.
The existence of skin-core structure difference in the precursor is totally unfavorable for follow-up pre-oxidation, carbonization, is difficult to obtain thus high performance carbon fiber.Thereby, have only the preparation even structure, core-skin difference is minimum or do not have the high strength precursor of core-skin difference, could obtain follow-up high-performance carbon fibre.With the wet spinning technology type seemingly, when adopting the dry-wet spinning technology, the final structure of fiber depends on the forming process of strand in coagulating bath to a great extent.Double diffusion can take place in the spinning solution thread in coagulating bath, promptly solvent is diffused in the coagulating bath by the spinning solution thread; Simultaneously, the non-solvent in the coagulating bath diffuses into spinning solution thread inside.The component of polymer, solvent, non-solvent changes gradually in the thread, finally is separated, and forms the as-spun fibre of gel structure.The solidification forming process of thread in coagulating bath determined the microstructure of spun filament and finished fiber, also determined the performance of finished fiber thus.The double diffusion process of spinning solution thread in coagulating bath is slow more, and solidification forming relaxes more, just helps obtaining the high-performance fiber of even structure densification more.Reduce the solidification liquid temperature, improve the concentration (hereinafter to be referred as coagulating bath concentration) of coagulating bath solvent, all can make the mitigation that becomes of double diffusion process.Thereby, can expect to adopt the coagulating bath of low temperature, high solvent concentration (hereinafter to be referred as high concentration) to carry out solidification forming, obtain the high-performance precursor.
Common polyacrylonitrile fibril spinning technique, the general non-solvent component that adopts water as coagulating bath, water is stronger to the precipitation ability of polyacrylonitrile, thereby, except that adopting the low temperature curing condition, also should adopt the very coagulating bath of high concentration, just can make the solidification forming of spinning solution thread enough slow, thereby avoid the formation of skin-core structure in the as-spun fibre.But, adopt the coagulating bath of high concentration, the content of solvent in the as-spun fibre of acquisition is increased greatly.And the process of follow-up employing method for washing flush away residual solvent also is a double diffusion process.Higher solvent in the as-spun fibre, the strength ratio that makes as-spun fibre on the one hand a little less than, be easy to wreck; On the other hand, with the double diffusion process aggravation that makes in the washing processing.Thereby, adopt the coagulating bath of high concentration, in follow-up washing was handled, the even gel structure of as-spun fibre very easily was damaged, and forms the skin-core structure defective once more.For avoiding occurring this phenomenon, just must reduce the solvent in the coagulated yarn that enters rinsing bowl, promptly need to adopt the solidifying process of more multistage number.This just need transform existing device for spinning.
Common polyacrylonitrile fibril spinning technique generally adopts hot water predraft and the boiling water master secondary water-bath draft process that stretches, total stretching ratio be 4-7 doubly, be difficult to carry out the stretching of bigger multiplying power.Simultaneously, for high molecular, full-bodied spinning solution, total stretching ratio that can reach is lower, and it is height-oriented to be difficult to make big molecule to take place, and is unfavorable for the raising of precursor performance.Chinese patent CN1167838C has reported the drawing-off multiplying power that adopts multistage hot water drafting method to improve strand.But adopt this kind method, need transform existing device for spinning.
Summary of the invention
Technical problem to be solved by this invention provides a kind of preparation method of polyacrylonitrile base carbon fiber precursors, the drawing-off multiplying power of strand when this method effectively improves spinning, and can produce at the enterprising professional etiquette mould of existing device for spinning, preparation gained precursor even structure, fiber number is little, intensity is high.
The preparation method of a kind of polyacrylonitrile base carbon fiber precursors of the present invention may further comprise the steps:
(1) preparation polyacrylonitrile/organic solvent spinning solution;
(2) with after the deaeration of above-mentioned spinning solution process, filtration, the metering, extrude the back by spinning head and form the spinning solution thread,, enter the coagulating bath solidification forming by air layer;
(3) above-mentioned coagulated yarn is carried out air stretching, washing, predraft, main stretching, compacting by drying, steam stretching, obtain polyacrylonitrile base carbon fiber precursors.
Described step (1) polyacrylonitrile/organic solvent spinning solution is made up of two parts:
(a) polyacrylonitrile of 10%-30% (mass percent below is abbreviated as wt%);
The water-containing organic solvent solution of (b) organic solvent of 70wt%~90wt%, or 70wt%~90wt%, wherein water accounts for the 0.01wt%~8wt% of solution quality;
Described step (1) polyacrylonitrile is selected from the terpolymer by the preparation of first, second and the 3rd monomer, or by the bipolymer of first and second monomers preparation, or by the bipolymer of the first and the 3rd monomer preparation, viscosity average molecular weigh is 7.0 * 10
4~1.0 * 10
6
Described copolymer, the mass percent of its second monomer be the mass percent of the 0~10%, the 3rd monomer be 0~5%, second and the mass percent of the 3rd monomer can not be 0 simultaneously, remaining is first monomer.Said mass percent is a benchmark with the polymer monomers total mass number.
Described first monomer is an acrylonitrile, and second monomer is selected from a kind of in methyl acrylate, methyl methacrylate, acrylamide, acrylic acid or the vinylacetate; The 3rd monomer is an itaconic acid.
Described step (1) organic solvent is dimethyl sulfoxide (DMSO) (DMSO), N, one or more in dinethylformamide (DMF), the N,N-dimethylacetamide (DMAc);
Described step (1) additive is propyl alcohol, isopropyl alcohol, ethylene glycol, 1,2-propylene glycol, 1, one or more in ammediol, the glycerol;
The temperature of described spinning solution is 60~100 ℃;
The height of described air layer is 0.5~10cm;
Described step (2) coagulating bath is made up of organic solvent and rudimentary saturated fatty alcohol, and temperature is-40~15 ℃, and wherein, the mass percent of organic solvent is 0~60% (gross mass with coagulating bath is a benchmark), is preferably between 10~40%.Described rudimentary saturated fatty alcohol is that carbon number is one or more in 1-3-unit's alcohol, dihydroxylic alcohols or the trihydroxylic alcohol, is preferably monohydric alcohol.
The medium that described step (3) air stretches is that temperature is that 5~35 ℃, relative humidity are 40~90% air;
Described step (3) washing is meant the spray washing, and temperature is 40~80 ℃;
The medium of described step (3) predraft is that temperature is 40~80 ℃ a water;
Described (3) main medium that stretches is that temperature is 85~99 ℃ a water;
Described step (3) compacting by drying is meant hot-air dry, and temperature is 110~140 ℃;
The used drawing-off medium of described step (3) steam stretching is a kind of in heated dry air, superheated vapour or the saturated vapor, and temperature is 120~180 ℃.
Principle of the present invention:
(1) in the middle of coagulating tank and rinsing bowl, increases the air stretch processing of coagulated yarn.
Utilize the plasticization of solvent in the coagulated yarn, realize the high drafting of strand, make strand generation refinement, and can improve the orientation of macromolecular chain to a certain extent, thus the preparation precursor that fiber number is little, intensity is higher;
(2) adopt rudimentary saturated fatty alcohol to replace the non-solvent component of water as coagulating bath.
With respect to water, rudimentary saturated fatty alcohol to the coagulation ability of polyacrylonitrile a little less than.Adopt rudimentary saturated fatty alcohol to replace the non-solvent component of water as coagulating bath, under identical coagulating bath concentration and temperature conditions, can further slow down the double diffusion process of dynamic analysis of spinning in coagulating bath, thereby, adopt rudimentary saturated fatty alcohol non-solvent, only need to adopt the coagulating bath concentration of low concentration, just can realize the slow shaping optimization of dynamic analysis of spinning in coagulating bath, obtain the high-performance precursor of even structure.
Beneficial effect
(1) increases the air drawing process, can realize the more powerful drawing-off of strand under the same conditions, can prepare little, the high orientation of fiber number, high-intensity precursor;
(2) adopt rudimentary saturated fatty alcohol to replace the non-solvent component of water, only need to adopt the coagulating bath of low concentration, just can realize the slow shaping optimization of dynamic analysis of spinning in coagulating bath, the high-performance precursor of preparation even structure as coagulating bath;
(3) fibre forming is even, and the former silk size that makes is little, intensity height, even structure;
(4) need not increase solidification equipment, can carry out large-scale production at existing industrialization device for spinning, and can reduce the use amount and the treating capacity of organic solvent.
The specific embodiment
Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiment only to be used to the present invention is described and be not used in and limit the scope of the invention.Should be understood that in addition those skilled in the art can make various changes or modifications the present invention after the content of having read the present invention's instruction, these equivalent form of values fall within the application's appended claims institute restricted portion equally.
Embodiment 1
Raw material: polyacrylonitrile, viscosity average molecular weigh are 7.2 * 10
4, be terpolymer, wherein the mass percent of acrylonitrile is that the mass percent of 95.6%, the second monomer methyl acrylate is that the mass percent of 3.4%, the three monomer itaconic acid is 1.0%.Organic solvent is DMSO, and additive is a water.
In the DMSO/ aqueous mixtures of moisture 5% (accounting for the percentage of DMSO and water gross mass), the polyacrylonitrile powder that adds 20% (based on the percetage by weight of each material summation), 25 ℃ of following swellings 2 hours, 65 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 65 ℃ of following deaerations, filtration, after the measuring pump metering, extruded by spinnerets, through the air layer of 1cm, the DMSO concentration that enters 10 ℃ is solidification forming during 40% DMSO/ alcohol solidification is bathed.Coagulated yarn enters in 25 ℃, the air of humidity 60% and stretches, and carries out 40 ℃ washing then and handles.Washing silk enters the hot bath of 65 ℃ and 90 ℃ successively and carries out stretch processing, and total draw ratio (comprising air stretching, predraft and main stretching) is 15 times.Drawn yarn is after 115 ℃ hot-air dry densification, and drawing-off is 1.8 times in 130 ℃ of saturated vapors, and obtaining filament number is 1.01dtex, and intensity is 7.3cN/dtex, and elongation at break is 9.6% polyacrylonitrile fibril.
Embodiment 2 (reference examples 1, water is as non-solvent component)
Raw material: polyacrylonitrile, viscosity average molecular weigh are 7.2 * 10
4, be terpolymer, wherein the mass percent of acrylonitrile is that the mass percent of 95.6%, the second monomer methyl acrylate is that the mass percent of 3.4%, the three monomer itaconic acid is 1.0%.Organic solvent is DMSO, and additive is a water.
In the DMSO/ aqueous mixtures of moisture 5% (accounting for the percentage of DMSO and water gross mass), the polyacrylonitrile powder that adds 20% (based on the percetage by weight of each material summation), 25 ℃ of following swellings 2 hours, 65 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 65 ℃ of following deaerations, filtration, after the measuring pump metering, extruded by spinnerets, through the air layer of 1cm, the DMSO concentration that enters 10 ℃ is solidification forming in 40% the DMSO/ water coagulating bath.Coagulated yarn enters in 25 ℃, the air of humidity 60% and stretches, and carries out 40 ℃ washing then and handles.Washing silk enters the hot bath of 65 ℃ and 90 ℃ successively and carries out stretch processing, 9.0 times of total draw ratios.Drawn yarn is after 115 ℃ hot-air dry densification, and drawing-off is 1.8 times in 130 ℃ of saturated vapors, and obtaining filament number is 1.68dtex, and intensity is 6.2cN/dtex, and elongation at break is 10.3% polyacrylonitrile fibril.
Embodiment 3 (reference examples 2, water is as non-solvent component)
Raw material: polyacrylonitrile, viscosity average molecular weigh are 7.2 * 10
4, be terpolymer, wherein the mass percent of acrylonitrile is that the mass percent of 95.6%, the second monomer methyl acrylate is that the mass percent of 3.4%, the three monomer itaconic acid is 1.0%.Organic solvent is DMSO, and additive is a water.
In the DMSO/ aqueous mixtures of moisture 5% (accounting for the percentage of DMSO and water gross mass), the polyacrylonitrile powder that adds 20% (based on the percetage by weight of each material summation), 25 ℃ of following swellings 2 hours, 65 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 65 ℃ of following deaerations, filtration, after the measuring pump metering, extruded by spinnerets, through the air layer of 1cm, the DMSO concentration that enters 10 ℃ is solidification forming in 70% the DMSO/ water coagulating bath.Coagulated yarn enters in 25 ℃, the air of humidity 60% and stretches, and carries out 40 ℃ washing then and handles.Washing silk enters the hot bath of 65 ℃ and 90 ℃ successively and carries out stretch processing, 10.5 times of total draw ratios.Drawn yarn is after 115 ℃ hot-air dry densification, and drawing-off is 1.8 times in 130 ℃ of saturated vapors, and obtaining filament number is 1.44dtex, and intensity is 6.0cN/dtex, and elongation at break is 9.8% polyacrylonitrile fibril.
Embodiment 4
Raw material: polyacrylonitrile, viscosity average molecular weigh are 1.0 * 10
5, be terpolymer, wherein the mass percent of acrylonitrile is that the mass percent of 96%, the second monomer methyl acrylate is that the mass percent of 3%, the three monomer itaconic acid is 1.0%.Organic solvent is DMSO.
The polyacrylonitrile powder of adding 18% in the DMSO solvent, 25 ℃ of following swellings 2 hours, 70 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 70 ℃ of following deaerations, filtration, after the measuring pump metering, extrude by spinnerets, through the air layer of 3cm, the DMSO concentration that enters 5 ℃ is solidification forming in 20% the DMSO/ methyl alcohol coagulating bath.Coagulated yarn enters in 20 ℃, the air of humidity 60% and stretches, and carries out 50 ℃ washing then and handles.Washing silk enters the hot bath of 70 ℃ and 99 ℃ successively and carries out stretch processing, 8.1 times of total draw ratios.Drawn yarn after 120 ℃ hot-air dry densification, in 160 ℃ of heated dry airs, 2.0 times of drawing-offs, obtaining filament number is 1.44dtex, intensity is 7.8cN/dtex, elongation at break is 9.3% polyacrylonitrile fibril.
Embodiment 5
Raw material: polyacrylonitrile, viscosity average molecular weigh are 1.5 * 10
5, be bipolymer, wherein the mass percent of acrylonitrile is that the mass percent of 97%, the second monomer methyl acrylate is 3%.Organic solvent is DMF.
The polyacrylonitrile powder that in the DMF solvent, adds 18% (based on the mass percent of each material summation), 25 ℃ of following swellings 2 hours, 75 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 75 ℃ of following deaerations, filtration, after the measuring pump metering, extrude by spinnerets, through the air layer of 1cm, the DMF concentration that enters 5 ℃ is solidification forming in 10% the DMF/ isopropyl alcohol coagulating bath.Coagulated yarn enters in 20 ℃, the air of humidity 65% and stretches, and carries out 50 ℃ washing then and handles.Washing silk enters the hot bath of 70 ℃ and 95 ℃ successively and carries out stretch processing, 6 times of total draw ratios.Drawn yarn is after 125 ℃ hot-air dry densification, and drawing-off is 3.3 times in 140 ℃ of saturated vapors, and obtaining filament number is 1.36dtex, and intensity is 7.6cN/dtex, and elongation at break is 9.6% polyacrylonitrile fibril.
Embodiment 6
Raw material: polyacrylonitrile, viscosity average molecular weigh are 1.0 * 10
5, be terpolymer, wherein the mass percent of acrylonitrile is that the mass percent of 96%, the second monomer methyl acrylate is that the mass percent of 3%, the three monomer itaconic acid is 1.0%.Organic solvent is DMAc.
The polyacrylonitrile powder that in the DMAc solvent, adds 18% (based on the mass percent of each material summation), 25 ℃ of following swellings 2 hours, 70 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 70 ℃ of following deaerations, filtration, after the measuring pump metering, extrude by spinnerets, through the air layer of 5cm, the DMAc concentration that enters 10 ℃ is solidification forming in 10% the DMAc/ ethylene glycol coagulating bath.Coagulated yarn enters in 20 ℃, the air of humidity 65% and stretches, and carries out 60 ℃ washing then and handles.Washing silk enters the hot bath of 65 ℃ and 95 ℃ successively and carries out stretch processing, 6 times of total draw ratios.Drawn yarn is after 120 ℃ hot-air dry densification, and drawing-off is 3.5 times in 180 ℃ of superheated vapours, and obtaining filament number is 1.17dtex, and intensity is 7.9cN/dtex, and elongation at break is 8.9% polyacrylonitrile fibril.
Embodiment 7
Raw material: polyacrylonitrile, viscosity average molecular weigh are 1.0 * 10
5, be terpolymer, wherein the mass percent of acrylonitrile is that the mass percent of 96%, the second monomer methyl acrylate is that the mass percent of 3%, the three monomer itaconic acid is 1.0%.Organic solvent is DMSO.
The polyacrylonitrile powder that in the DMSO solvent, adds 18% (based on the mass percent of each material summation), 25 ℃ of following swellings 2 hours, 70 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 70 ℃ of following deaerations, filtration, after the measuring pump metering, extrude by spinnerets, through the air layer of 1cm, the DMSO concentration that enters 10 ℃ is solidification forming in 15% the DMSO/ propylene glycol coagulating bath.Coagulated yarn enters in 20 ℃, the air of humidity 65% and stretches, and carries out 60 ℃ washing then and handles.Washing silk enters the hot bath of 65 ℃ and 85 ℃ successively and carries out stretch processing, 7.5 times of total draw ratios.Drawn yarn is after 130 ℃ hot-air dry densification, and drawing-off is 2.8 times in 180 ℃ of superheated vapours, and obtaining filament number is 1.18dtex, and intensity is 7.7cN/dtex, and elongation at break is 9.8% polyacrylonitrile fibril.
Embodiment 8
Raw material: polyacrylonitrile, viscosity average molecular weigh are 8.2 * 10
4, be bipolymer, wherein the mass percent of acrylonitrile is that the mass percent of 97%, the three monomer itaconic acid is 3.0%.Organic solvent is DMSO.
The polyacrylonitrile powder that in the DMSO solvent, adds 22% (based on the mass percent of each material summation), 25 ℃ of following swellings 2 hours, 70 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 70 ℃ of following deaerations, filtration, after the measuring pump metering, extrude by spinnerets, through the air layer of 1cm, the DMSO concentration that enters 10 ℃ is solidification forming during 20% DMSO/ alcohol solidification is bathed.Coagulated yarn enters in 20 ℃, the air of humidity 65% and stretches, and carries out 60 ℃ washing then and handles.Washing silk enters the hot bath of 65 ℃ and 85 ℃ successively and carries out stretch processing, 9 times of total draw ratios.Drawn yarn is after 130 ℃ hot-air dry densification, and drawing-off is 2.5 times in 140 ℃ of saturated vapors, and obtaining filament number is 1.10dtex, and intensity is 7.5cN/dtex, and elongation at break is 9.5% polyacrylonitrile fibril.
Embodiment 9
Raw material: polyacrylonitrile, viscosity average molecular weigh are 1.0 * 10
5, be terpolymer, wherein the mass percent of acrylonitrile is that the mass percent of 96%, the second monomer methyl acrylate is that the mass percent of 3%, the three monomer itaconic acid is 1.0%.Organic solvent is DMSO, and additive is an ethylene glycol.
The polyacrylonitrile powder that in the DMSO/ ethylene glycol mixture that contains ethylene glycol 2% (accounting for the percentage of DMSO and ethylene glycol gross mass), adds 18% (based on the mass percent of each material summation), 25 ℃ of following swellings 2 hours, 70 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 70 ℃ of following deaerations, filtration, after the measuring pump metering, extrude by spinnerets, through the air layer of 5cm, the DMSO concentration that enters 10 ℃ is solidification forming in 10% the DMSO/ ethylene glycol coagulating bath.Coagulated yarn enters in 20 ℃, the air of humidity 65% and stretches, and carries out 60 ℃ washing then and handles.Washing silk enters the hot bath of 65 ℃ and 95 ℃ successively and carries out stretch processing, 6 times of total draw ratios.Drawn yarn is after 120 ℃ hot-air dry densification, and drawing-off is 3.5 times in 180 ℃ of superheated vapours, and obtaining filament number is 1.17dtex, and intensity is 7.8cN/dtex, and elongation at break is 9.3% polyacrylonitrile fibril.
Embodiment 10
Raw material: polyacrylonitrile, viscosity average molecular weigh are 7.2 * 10
4, be terpolymer, wherein the mass percent of acrylonitrile is that the mass percent of 95.6%, the second monomer methyl acrylate is that the mass percent of 3.4%, the three monomer itaconic acid is 1.0%.Organic solvent is DMAc, and additive is an isopropyl alcohol.
In the DMSO/ isopropanol mixture that contains isopropyl alcohol 5% (accounting for the percentage of DMSO and isopropyl alcohol gross mass), the polyacrylonitrile powder that adds 20% (based on the percetage by weight of each material summation), 25 ℃ of following swellings 2 hours, 65 ℃ of dissolvings 5 hours, be mixed with spinning solution, in 65 ℃ of following deaerations, filtration, after the measuring pump metering, extruded by spinnerets, through the air layer of 1cm, the DMSO concentration that enters 10 ℃ is solidification forming during 40% DMSO/ alcohol solidification is bathed.Coagulated yarn enters in 25 ℃, the air of humidity 60% and stretches, and carries out 40 ℃ washing then and handles.Washing silk enters the hot bath of 65 ℃ and 90 ℃ successively and carries out stretch processing, and total draw ratio is 15 times.Drawn yarn is after 115 ℃ hot-air dry densification, and drawing-off is 1.8 times in 130 ℃ of saturated vapors, and obtaining filament number is 1.03dtex, and intensity is 7.3cN/dtex, and elongation at break is 9.7% polyacrylonitrile fibril.