JPH0236603B2 - AKURIRONITORIRUKEIJUGOTAIYOEKINOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for preparing a spinning stock solution of an acrylonitrile polymer, and in particular, the acrylonitrile polymer polymerized by aqueous suspension polymerization is dissolved in an organic solvent without drying, and the stock solution is prepared by dissolving the acrylonitrile polymer polymerized by aqueous suspension polymerization in an organic solvent without drying. Production of an acrylonitrile polymer solution that has excellent characteristics as a spinning stock solution with a water content of 1 to 10% by weight, which has good stability and spinnability, and can easily produce threads without defects such as voids. It is about the method. [Prior art] As a method for producing acrylonitrile polymers for fiber production, an aqueous precipitation polymerization method is used in an aqueous medium using a water-soluble catalyst such as a redox initiator made of persulfate/acidic sulfite as a polymerization catalyst. is generally known, and the polymer obtained by this method is
Dimethylformamide, dimethylacetamide, ethylene carbonate or γ as a polymerization solvent
- It is possible to obtain a polymer having a relatively high molecular weight compared to a polymer obtained by so-called solution polymerization using butyrolactone or the like. [Problems to be Solved by the Invention] However, the polymer particles separated from the polymerization system after polymerization in an aqueous medium contain water in an amount of 200 to 300% by weight based on the weight of the polymer. Even if compression dehydration is performed, the dehydration rate is not high enough to dissolve the acrylonitrile polymer in dimethyl sulfoxide, dimethyl acetamide, dimethyl formamide, etc., which are good solvents, and even if it is heated to a high temperature and dissolved, it will not reach the spinning temperature. If it is lowered, the stock solution will gel and the spinning stability will become very poor. In addition, especially when an inorganic redox initiator is used, inorganic salts as catalyst residues remain, causing nozzle clogging during spinning and worsening stability. As described above, washing and drying steps are essential steps in normal aqueous suspension polymerization, and it is virtually impossible to immediately turn the polymer obtained by aqueous suspension polymerization into a spinning dope using an organic solvent. It has been. In particular, since drying is usually carried out in the air at a temperature of 50 to 100°C, there is a possibility that dust may enter the air or that the quality of the polymer may change due to heating. The development of a new process that eliminates this problem is eagerly awaited. [Means for Solving the Problems] Therefore, the present inventors conducted various studies in order to solve the above-mentioned problems, and found that the organic solvent used as the solvent for polyacrylonitrile and water were mixed in a specific ratio. A mixture of polymerizable unsaturated monomers containing acrylonitrile as a main component is polymerized using the mixed solvent used in the above as a polymerization solvent, and the water content in the acrylonitrile-based polymer obtained by subsequent separation from the polymerization system is equal to that of a normal aqueous suspension. Therefore, the solubility of acrylonitrile-based polymers in solvents is good even without forced heating or drying, and even without special dehydration methods. It is now possible to make an acrylonitrile polymer stock solution with a water content of 10% by weight or less, allowing polymerization,
The inventors discovered the possibility of a continuous spinning process that omitted the dryer, and completed the present invention. The gist of the present invention is to provide a polymerizable unsaturated monomer mixture of 10 to 70% by weight consisting of at least 70% by weight of acrylonitrile and 30% by weight or less of other copolymerizable polymerizable unsaturated monomers. 15 to 60 parts by weight of an organic solvent to be used as a solvent for polyacrylonitrile, and 15 to 60 parts by weight of water. Polymerization is initiated using a radical polymerization initiator, and if necessary, polymer precipitation is observed in the polymerization system. After that time, 1 to 10 parts by weight of water and the organic solvent, either alone or in combination, are added to 1 part by weight of the charged polymerizable unsaturated monomer mixture, and polymerization is carried out to obtain an acrylonitrile polymer. is separated from the polymerization system, and the content of the polymerization medium used in the polymerization is reduced to 100% by weight or less by solvent replacement with an organic solvent as necessary.The resulting product is dissolved in a polyacrylonitrile solvent to obtain a polymer concentration of 10 to 10%. The present invention provides a method for obtaining an acrylonitrile polymer solution for spinning having a water content of 25% by weight and a water content of 1 to 10% by weight. The acrylonitrile polymer used in the present invention contains 70% by weight or more of acrylonitrile and 30% by weight or less of other copolymerizable unsaturated monomers. Fibers, films, etc. made from polymers containing 70% or more acrylonitrile by weight: 70% by weight
It has advantages such as superior weather resistance, whiteness, and heat resistance compared to those with less than Examples of polymerizable unsaturated monomers that can be copolymerized with acrylonitrile include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, and their salts, methyl acrylate, ethyl acrylate, butyl acrylate, and octyl acrylate. , acrylic esters such as methoxyethyl acrylate, phenyl acrylate, and cyclohexyl acrylate,
Methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, methoxyethyl methacrylate, phenyl methacrylate,
Methacrylic acid esters such as cyclohexyl methacrylate, alkyl vinyl ketones, vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl sulfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid, etc. Vinyl sulfonic acids and their salts, vinyl halides or vinylidene halides such as vinyl chloride, vinylidene chloride, vinyl bromide, basic vinyl compounds such as vinylpyridine, vinylimidazole, dimethylaminoethyl methacrylate, acrolein, methacrylate, etc. Unsaturated monomers such as lonitrile and α-chloroacrylonitrile can be mentioned. As the organic solvent used in carrying out the present invention, any common solvent for polyacrylonitrile can be used, and examples thereof include dimethylformamide, dimethylacetamide, dimethylsulfoxide, and γ-butyrolactone. As mentioned above, the amount used is 15% in the mixed composition during polymerization.
It is used in a range of ~65% by weight. If it is less than 15% by weight, there will be no advantage compared to normal aqueous precipitation polymerization, and the water content in the polymer after separation from the polymerization system will be particularly high, so it is impossible to use a spinning dope containing less than 10% by weight of water. However, if the amount exceeds 65% by weight, the organic solvent used acts as a chain transfer agent, lowering the molecular weight of the polymer and causing a decrease in the performance of the fiber obtained by spinning, especially strength and elastic modulus, which is not preferable. As the polymerization initiator, common radical initiators such as 2,2'-azobisisobutyronitrile, 2,
Azo compounds such as 2'-azobis-(2,4-dimethylvaleronitrile), organic acid peroxides such as aliphatic diacyl peroxides, or peroxy esters, or persulfates, and these with reducing agents. Although combinations of redox initiators can be used, it is preferable to use organic initiators such as azo compounds or organic peroxides from the viewpoint of omitting washing and drying steps, which is the purpose of the present invention. The amount used is 0.0005 to 0.05 parts by weight, preferably 0.0005 to 0.05 parts by weight of the charged polymerizable unsaturated monomer, from the viewpoint of polymerization stability and molecular weight of the resulting polymer.
Use 0.001 to 0.02 parts by weight. When polymerization of the above charge composition is started, polymer precipitation occurs as the polymerization progresses, the viscosity of the polymerization system increases, and a state in which stirring of the system is usually impossible occurs, resulting in a high polymerization rate. I won't be able to do that. In the present invention, after the polymer precipitation is observed in the polymerization system, the charged polymerizable unsaturated monomer mixture 1
By adding 1 to 10 parts by weight of a polymerization medium selected from water and/or the above-mentioned organic solvent based on the weight part, a high polymerization rate can be achieved with sufficient stirring without deteriorating the polymerization behavior of the polymerization system. Polymerization can be carried out. The reduced viscosity (measured as a 0.5% dimethylformamide solution at 25°C) of the acrylonitrile polymer obtained by the above polymerization is 2.0 or more, especially
A major feature of this method is that it can produce polymers with a wide range of molecular weights of 2.5 or higher, and also with high molecular weights. Furthermore, fibers obtained by spinning high molecular weight acrylonitrile polymers are 7g/d or more, especially 10g/d or more.
It can have a strength of more than g/d and a high modulus of elasticity. Polymerization methods for obtaining this high molecular weight polymer include a one-tank batch polymerization method in which a mixture of a certain composition is charged into a flask and a solvent is added after polymer precipitation, or a one-tank batch polymerization method in which a mixture of a certain composition is continuously poured into a flask. Any two-stage or more multi-stage continuous polymerization method can be employed, in which the polymer is supplied to the first tank, polymerization is started, and the polymerization medium is added in the second tank or thereafter. The polymer obtained by the above polymerization method is separated from the polymerization system and dissolved to obtain an acrylonitrile polymer solution having a polymer content of 10 to 30% by weight and a water content of 1 to 10% by weight. In the present invention, since the polymerization medium in the polymerization system is a mixed solvent of organic solvent and water, the solvent content after evaporation and compression dehydration is relatively high at 150% by weight or less, preferably 100% by weight or less. Also, the solubility in organic solvents is good, and a polymer solution having a desired polymer concentration and water content can be easily prepared. On the other hand, in ordinary aqueous suspension polymerization, even if the solvent content after compression dehydration is the same as in the present invention, the solubility in organic solvents is poor and the desired polymer solution cannot be obtained. Furthermore, even if solvent replacement is performed, it is necessary to repeat dispersion in a solvent and compression dehydration several times or more, which is very disadvantageous from an economic standpoint or from the perspective of establishing a continuous process. In this way, in the present invention, 1 to 10
Since it contains water in the range of % by weight, the solution viscosity is lower than that of a system that does not contain water, and the viscosity changes less over time, which is very advantageous in terms of industrial production. If the water content is less than 1% by weight, the effect of reducing and stabilizing the solution viscosity will be low, and if it exceeds 10% by weight, it will undesirably cause gelation of the solution. In addition, the polymer concentration in the solution is preferably in the range of 10 to 30% by weight; if it is less than 10% by weight, spinning stability will be lacking and productivity will be poor;
Exceeding this is not preferable as the solution viscosity increases. The acrylonitrile polymer solution obtained by the above method can be spun by any of the usual dry spinning methods, dry-wet spinning methods, and wet spinning methods. In this way, the present invention enables continuous polymerization and spinning without the two steps of washing and drying, and creates a system with very few impurities that eliminates dust contamination and the generation of solvent-insoluble polymers. Can be done. Furthermore, when a high molecular weight polymer with a reduced viscosity of 2.5 or more is used, the fibers obtained by spinning can have high strength and high elastic modulus with few defects. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 The preparation composition shown in Table 1 was charged into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and the mixture was replaced with nitrogen.
The mixture was heated to initiate polymerization. After the start of polymerization, when the system became cloudy, the additional solvent shown in Table 1 was added, and the
Heating was continued for several hours to complete polymerization. The resulting polymer slurry is centrifugally dehydrated and compressed to remove the remaining solvent.
It was made into a 100% by weight polymer wet powder. Dimethylformamide (DMF) was added to this wet powder to prepare a polymer solution with a desired polymer concentration. If you want to further lower the water content, add enough DMF to the above wet powder so that the polymer does not dissolve, disperse the polymer, and then
Compression dehydration was performed, and DMF was added again to this to obtain a desired polymer concentration, and the mixture was heated and dissolved to obtain a polymer solution. Comparative Example 1 A redox initiator using potassium persulfate as an oxidizing agent and sodium sulfite as a reducing agent.
A polymerization slurry obtained by an aqueous precipitation polymerization method using sulfuric acid as a pH adjuster was compressed and dehydrated in the same manner as in Example 1, and an attempt was made to obtain a polymer solution, but it was not possible to reduce the water content to 10% or less. Since it was difficult to dissolve, the solvent was replaced with dimethylformamide, and then dimethylformamide was further added to prepare a spinning stock solution. Table 1 shows the results of Example 1 and Comparative Example. All procedures were carried out in accordance with Table 1 except that the polymerization scale was set to 50, and the solution stability when the obtained polymer solution was left at a constant temperature was determined in Experiment No. 2, the polymerization solution for the precursor, and the moisture content of 0% as a control.
The same thing is shown in FIG.

【table】

[Table] Example 2 The polymer solutions obtained in Example 1 and Comparative Example 1 were wet-spun according to a conventional method to obtain precursors (numbers ~) with a fineness of 1.3 d. This precursor was flame-resistant treated in air at 230-270°C in an oxidizing atmosphere, and then carbonized by applying a heating gradient of 600-1250°C under a _N2 stream. The resulting carbon fiber performance is shown in Table 2.

[Table] Measurement of metal content...by ordinary atomic absorption method As shown in Tables 1 and 2, in the present invention, a spinning dope with good stability was obtained without washing or drying, and from this a spinning stock solution was obtained which was then spun and fired. Carbon fiber has become a high-performance material. In comparison, Comparative Example 1 has a high moisture content and poor solubility in dimethylformamide, and even if it has a composition that can be dissolved, a large amount of impurities will remain in the resulting fiber, causing a decline in the performance of the precursor and, ultimately, of the carbon fiber. Invitation,
It can be seen that it is impossible to omit the washing and drying steps. Example 3 Polymerization was carried out using a two-tank continuous polymerization apparatus by continuously supplying the polymer according to the conditions shown in Table 3.

【table】

[Table] ・Total residence time: 7 hours The polymerization slurry overflowing from the second tank was taken into another 50 glass-lined tank and heated to 60°C under a reduced pressure of 250 mmHg to remove residual monomers, and a portion of this was taken and washed. , the dry polymer has a polymerization rate of 63
%, and the reduced viscosity was 4.3. The composition of the wet powder after demonomerization was polymer/DMF/water = 100/84/16, to which 300 parts of dimethylformamide was added and dissolved by heating, resulting in a polymer concentration of 20% and a moisture content of 3.2%.
A polymer solution was obtained. Example 4 The carbon fiber obtained by spinning and firing the polymer solution obtained in Example 3 according to a conventional method has a strength of 498
Kg/mm ² and elastic modulus 25.9 ton/mm ² . The amount of remaining metal in the precursor is below the limit of quantification,
It can be seen that polymerization and spinning can be carried out continuously without washing or drying.

[Brief explanation of drawings]

FIG. 1 shows the stability of the stock solution of the polymer obtained according to the present invention in terms of retention time and the corresponding change in viscosity.

Claims (1)

[Scope of Claims] 1. 10 to 70 parts by weight of a polymerizable unsaturated monomer mixture comprising at least 70% by weight of acrylonitrile and 30% by weight or less of a polymerizable unsaturated monomer copolymerizable with other acrylonitrile. , 15 to 60 parts by weight of an organic solvent as a solvent for polyacrylonitrile and 15 parts by weight of water.
Polymerization of a charging composition consisting of ~60 parts by weight is initiated using a radical polymerization initiator, and after the point at which the polymer is precipitated in the polymerization system, a polymerization medium selected from an organic solvent, water, or a mixture thereof is charged. 1 to 10 parts by weight are added to 1 part by weight of the polymerizable unsaturated monomer mixture, and a high molecular weight acrylonitrile polymer with a reduced viscosity of 2 or more obtained by polymerization is separated from the polymerization system, and the solvent content is 150% by weight. Dissolve the following acrylonitrile polymer in a solvent with a water content of 1 to 10.
1. A method for producing an acrylonitrile polymer solution, the method comprising: producing an acrylonitrile polymer solution of % by weight. 2. The manufacturing method according to claim 1, wherein the radical polymerization initiator is an azo compound or a peroxide. 3. A patent claim characterized in that after separating a high molecular weight acrylonitrile polymer with a reduced viscosity of 2 or more from a polymerization system, solvent replacement is performed to dissolve the acrylonitrile polymer with a solvent content of 150% by weight or less in a solvent. The manufacturing method according to scope 1.