JPH0255549B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an acrylonitrile-based fiber for obtaining flame-resistant fibers that are suitable for obtaining high-strength carbon fibers and that do not stick to each other, and a method for producing the acrylonitrile-based fibers. Previously, acrylonitrile fibers were exposed to 200 ~
Flame-resistant fibers are made by flame-retardant treatment under tension at 300℃.
Alternatively, it is known to further carbonize this flame-resistant fiber under tension in an inert gas atmosphere at 500° C. or higher to obtain carbon fiber. Flame-resistant fibers are used as flame-retardant and heat-insulating materials or packing materials, but further improvement in quality and performance is desired. The carbon fiber obtained as described above has excellent specific strength and specific elasticity, so it is used in sports and leisure products, automobiles, high-speed drives, and even in the aviation and space fields, and demand is expanding. ing. However, as demand expands, the conventional tensile strength of 300 to 350 Kg/ ^mm2 is unsatisfactory for some applications, and there is a growing demand for carbon fibers with even higher strength. Ta. In view of the above circumstances, the inventors of the present invention conducted studies to obtain the desired fibers, and found that the quality performance of conventional flame-resistant fibers was insufficient, and that the tensile strength of carbon fibers remained at the above-mentioned values. However, it was discovered that this is caused by adhesion between the single fibers during the flame-retardant treatment process, and as a result of conducting research on measures to prevent this adhesion, the present invention was achieved. An object of the present invention is to provide an acrylonitrile fiber for producing flame-resistant fibers or carbon fibers in which single fibers do not stick together, and a method for producing the same. The present invention is as follows. general formula (In the formula, R ₁ is an aliphatic hydrocarbon group having 11 to 17 carbon atoms, R ₂ and R ₃ are hydrogen atoms, lower alkyl groups, hydroxyethyl groups, hydroxyisopropyl groups,
X represents an anion of an organic acid. However, if R ₂ or R ₃ is a hydroxyisopropyl group,
X represents a chlorine atom. ) Acrylonitrile fibers for producing flame-resistant fibers or for producing carbon fibers, to which at least one fatty acid ester ammonium salt shown is attached. [Claim 1] General formula [A] at any stage from after solvent removal to completion of fiber production in the production process of acrylonitrile fibers or after completion of the production process. (In the formula, R ₁ is an aliphatic hydrocarbon group having 11 to 17 carbon atoms, R ₂ and R ₃ are hydrogen atoms, lower alkyl groups, hydroxyethyl groups, hydroxyisopropyl groups,
X represents an anion of an organic acid. However, if R ₂ or R ₃ is a hydroxyisopropyl group,
X represents a chlorine atom. ) Acrylonitrile-based for flame-resistant fiber production or carbon fiber production, which is characterized in that it is subjected to adhesion treatment with an aqueous solution or aqueous dispersion containing at least one fatty acid ester ammonium salt represented by (a) and then heat-treated. Fiber manufacturing method. [Claim 5] By subjecting the acrylonitrile fiber according to the present invention to flame-retardant treatment, a flame-resistant fiber without adhesion between single fibers can be obtained. By subsequently carbonizing such flame-resistant fibers, high-strength carbon fibers can be obtained. The flame-resistant fiber itself has improved quality, and therefore has improved spinnability. The acrylonitrile fiber according to the present invention is particularly suitable for producing high-strength carbon fibers, and is obtained from a polymer consisting of 95 mol% or more of acrylonitrile and 5 mol% or less of a vinyl monomer that can be copolymerized with acrylonitrile. Preferably. Vinyl monomers, which are copolymerization components, are those normally used in the production of acrylonitrile fibers, and include neutral monomers such as methyl acrylate, ethyl acrylate, and vinyl acetate, as well as acrylic acid and methacrylate. Examples include monomers containing acidic groups such as acids, itaconic acid or salts thereof, sodium allylsulfonate and sodium methacrylsulfonate, and monomers containing basic groups such as vinylpyridine and vinylimidazole. The above-mentioned acrylonitrile fiber can be produced by a conventionally known method. That is, for example, acrylonitrile or a vinyl monomer copolymerizable with acrylonitrile is used as a raw material in a solvent for polyacrylonitrile (for example, dimethylformamide, concentrated zinc chloride aqueous solution, dimethyl sulfoxide, dimethylacetamide, etc.). A polymerization reaction is carried out using a catalyst (e.g. benzoyl peroxide, hydrogen peroxide, sodium persulfate, etc.). The thus obtained solution of an acrylonitrile polymer having a normal molecular weight of 40,000 to 100,000 is extruded into a dilute solution of a solvent through a pore, and after removing the solvent, it is subjected to drying, stretching, relaxation, etc. The resulting product usually consists of a fiber bundle of 500 to 100,000 single fibers of 0.1 to 3.0 denier. In the present invention, the ammonium salt attached to the acrylonitrile fiber is a fatty acid ester ammonium salt represented by the general formula [A]. In the formula, R ₁ is an aliphatic hydrocarbon group having 11 to 17 carbon atoms,
In particular, the linear saturated aliphatic hydrocarbon groups, R ₂ and R ₃ ,
Represents a hydrogen atom, a lower alkyl group (alkyl group having 1 to 3 carbon atoms such as a methyl group or an ethyl group), a hydroxyethyl group, or a hydroxyisopropyl group,
represents an anion of an organic acid, such as an acetate ion, a lactate ion, or a phosphoryldioxyethanol ion. However, when R ₂ or R ₃ is a hydroxyisopropyl group, X represents a chlorine atom. One or more ammonium salts included in these general formulas may be used, or they may be used in combination with other surfactants. When used in combination with other surfactants, the ratio is preferably 50% by weight or less. As the compound represented by the above general formula [A],
For example: The method for producing these ammonium salts is carried out based on the following reaction. (In the formula, R ₁ R ₂ R ₃ and The reaction is carried out for ~15 hours, and in the second stage reaction, the reaction is carried out at 150-200°C for 5-15 hours. The ammonium salt used in the present invention is a sterically large compound containing one or more hydroxyl groups in the N atom, and is therefore characterized by extremely excellent solubility and dispersibility in water. However, it has a characteristic that it has a weak ability to penetrate into the fibers and adheres to the fiber surfaces uniformly. Furthermore, it has the unique property of reacting to larger molecules and chemically reacting with the surface layer of acrylonitrile fibers at the initial stage of flame resistance. For this reason, it functions to suppress shrinkage and disturbance of molecular orientation caused by thermal movement of molecules on the fiber surface. Generally, in the production of acrylonitrile fibers, treatments such as stretching, drying, and relaxation are performed after the solvent is removed during spinning. In the present invention, the ammonium salt adhesion treatment is performed at any stage from after solvent removal in the acrylonitrile fiber manufacturing process until the fiber manufacturing is completed, or at any stage after the fiber manufacturing is completed. That is,
In at least one treatment step as described above, or
It is carried out between one processing step and the next processing step. For ammonium salt adhesion treatment,
A solution in which one or more predetermined ammonium salts are dissolved or dispersed in water is applied to the fibers. The deposition process is usually carried out by spraying the liquid onto the fibers or by immersing the fiber bundles in a bath of the liquid. In order to sufficiently penetrate the ammonium salt between the single fibers of the fiber bundle, the bath temperature is preferably
Soak for 1 to 5 minutes at 20 to 70°C. If the temperature is higher than 70°C, the salt tends to aggregate in water, resulting in uneven adhesion and increased permeability into the interior of the fiber, resulting in a decrease in the strength of the resulting carbon fiber. On the other hand, if the temperature is lower than 20℃, dissolution and dispersion in water is difficult, and the dispersed particles are too large.
This is not preferable because it causes adhesion spots and agglutination. The concentration of the liquid used is usually 1 to 20 g/. The pH condition of the ammonium salt-containing liquid affects the product performance, and in order to obtain higher quality flame-resistant fibers and carbon fibers, the pH condition is preferably 4 or less. If the pH is higher than 4, the salt tends to aggregate, which tends to increase adhesion, which is not preferable. The pH may be any value as long as it is 4 or less, but it is usually 1 or more, preferably 2 to 3.5. In addition, PH adjustment is preferably done by
This is carried out with an acid or caustic soda having the same type of anion as X in the salt. The amount of adhesion is 0.01 to fiber weight
0.5% is good. If the adhesion amount is less than 0.01%, a sufficient anti-sticking effect cannot be obtained, and if it exceeds 0.5%, carbides are likely to be formed on the fiber surface during carbonization treatment, and the strength of the carbon fiber will decrease accordingly. When the amount of adhesion is 0.3% or less, the ammonium salt permeates into the fibers to a small extent, which is particularly suitable for producing high-strength carbon fibers. After applying the liquid containing ammonium salt, drying is performed. Drying is carried out with care so as not to reduce the strength of carbon fibers. For example, if the fiber is in a gel state, the temperature is gradually increased between 70 and 140°C. If the fiber is not gel-like, it is usually dried at 100 to 150°C. The amount of ammonium salt attached is measured by extracting the attached fibers with a mixture of equal amounts of alcohol and benzene for 3 hours using a Soxhlet extractor. When the ammonium salt-attached acrylonitrile fiber of the present invention is heated to 200 to 300°C, the ammonium salt reacts to become a water-insoluble compound, and a change is observed that is considered to be a reaction with the acrylonitrile fiber. It is thought that this can prevent sticking. The ammonium salt can be changed as described above by heat-treating the acrylonitrile fiber to which the ammonium salt has been attached for at least 0.7 minutes at 200 to 300° C. before the flame-retardant treatment. The preferred heating temperature for this heat treatment is 230℃
However, if the temperature is higher than 200℃, the heating rate should be 10℃/sec or less, usually 1 to 5℃/sec.
By doing so, a greater effect can be obtained in terms of preventing sticking, and the fiber becomes suitable for obtaining high-strength carbon fiber. In this way, at a heating rate of 10℃/sec or less,
Allylonitrile fibers heat-treated at 300℃,
Once rolled up, it may be subjected to a flame-retardant treatment step, or this heat treatment step may be performed continuously with the flame-retardant step. The ammonium salt-attached acrylonitrile fibers are subjected to flame-retardant treatment after or without heat treatment as described above. The flameproofing treatment is performed by a conventionally known method. That is, in an oxidizing atmosphere, e.g.
0.1 at a temperature of 200-300℃, preferably 250-300℃
Flame retardant treatment for ~15 hours. In order to obtain high-strength carbon fibers, it is preferable to carry out the process under a tension of 200 mg/denier or less, and in order to obtain even higher-strength carbon fibers, it is preferable to carry out the process under a tension of 10 to 100 mg/denier. Flame-retardant treatment is applied when the specific gravity of the fiber is 1.30 to 1.45.
It is preferable to carry out the treatment until the amount reaches g/cm ³ . The flame-resistant fiber thus obtained has extremely little agglutination and is suitable for carbonizing it to produce high-strength carbon fiber. The carbonization treatment of flame-resistant fibers is carried out at 1000 to 1500°C in an inert atmosphere such as nitrogen, argon, or helium. At this time, in order to obtain high-strength carbon fibers, it is preferable to carry out the process under a tension of 10 to 100 mg/denier. The carbon fiber obtained from the acrylonitrile fiber of the present invention as described above has extremely high strength. The present invention will be specifically described below with reference to Examples. In the examples, "%" and "part" are based on weight unless otherwise contrary to the nature of the matter. Example 1 100 parts of a monomer mixture consisting of 98% acrylonitrile, 0.5 mol% acrylic acid, and 1.5 mol% methyl acrylate and 1 part ammonium persulfate were dissolved in 1000 parts of a 60% zinc chloride aqueous solution, and the mixture was heated at 55°C. After polymerization for 4 hours, the molecular weight determined by the Stausinger formula
An acrylonitrile polymer solution having a viscosity of 55,000 and a viscosity of 98 poise was obtained. This material was extruded into a 25% zinc chloride aqueous solution through a nozzle having a diameter of 0.05 mm and 10,000 holes, and was stretched three times while removing zinc chloride by washing with water. Separately, a mixture of stearic acid and equimolar triethanolamine was heated at 165°C for 10 hours, and then
Compound (1) of the general formula [A] obtained by reacting the obtained compound with equimolar amounts of lactic acid and dihydroxyethyl phosphoric acid at 90°C, and PH3.3 containing the same (2). A 4 g/water dispersion of each was prepared. Using each of the above two types, the fibers after being stretched 3 times were immersed at 60°C for 0.2 minutes, and then dried at 120°C. Next, the fibers were continuously stretched 4.5 times in saturated steam at 125° C. to obtain ammonium salt-attached acrylonitrile fibers. All of these fibers had a tensile strength of 5.4 to 5.6 g/d, a tensile elongation of 11 to 12%, and a fineness of 1.1 denier. The amount of ammonium salt attached to this product was measured and was 0.025.
It was %. The acrylonitrile fiber thus obtained was placed in air at 255°C under a tension of 50 mg/d for 40 minutes.
Next, flame-retardant treatment was performed at 280℃ for 20 minutes under a tension of 40mg/d (the temperature increase rate from 200℃ to 255℃ was
30℃/sec. ) All flame-resistant fibers have a tensile strength of 3.0 to 3.3 g/
d, tensile elongation 13-14%, specific gravity 1.4 g/cc,
No agglutination was observed in the single fibers when observed using an electron microscope. This flame-resistant fiber was heated at 1300℃ in a nitrogen stream at 50mg/
Carbonization was carried out for 40 seconds under a tension of d. The properties of the obtained carbon fibers are shown in Table 1, and as with the flame-resistant fibers, no adhesion was observed.

[Table] Comparative example 1 Polyoxyethylene instead of ammonium salt
PH3.3, 50 containing 4g/15mol addition siloxane
The same treatment as in Example 1 was carried out using an aqueous dispersion at .degree. The physical properties and adhesion properties of the obtained acrylonitrile fiber and flame-resistant fiber were the same as in Example 1. The resulting carbon fiber has a tensile strength of 345
Kg/mm ² and tensile modulus of 24.2 t/mm ² , which was inferior in tensile strength to the case where the ammonium salt of the present invention was used. Although no adhesion was observed in the obtained carbon fibers, the presence of silicon was observed within the fibers, which is thought to be the cause of the low tensile strength. Example 2 In the same manner as in Example 1, an acrylonitrile polymer solution was spun, and stretched 3 times while washing with water and dechlorinating zinc. Separately, add stearic acid and equimolar amounts of hydroxyisopropyldiethanolamine.
The reaction was carried out at 180°C for 15 hours, and the reaction product was further reacted with equimolar amount of 36% hydrochloric acid at 90°C. The obtained compound (4) of the general formula [A] was adjusted to pH 3.5 with hydrochloric acid.
The same treatment as in Example 1 was carried out using the above-mentioned material. The obtained acrylonitrile fiber had a single fiber denier of 1.0, a tensile strength of 5.2 g/d, a tensile elongation of 12%,
The amount of ammonium salt deposited was 0.022%. This material was subjected to flameproofing treatment and carbonization treatment in the same manner as in Example 1 to obtain carbon fibers. This carbon fiber had a tensile strength of 410 Kg/mm ² and a tensile modulus of 24.4 t/mm ² . Example 3 In Example 1, the amount of the compound (1) stearate ammonium salt of general formula [A] was determined.
Acrylonitrile fibers were obtained in the same manner as in Example 1, except that the bath concentrations were adjusted to 0.015% and 0.038%. The tensile strength of the carbon fibers obtained from these is 405Kg/
mm ² , 360Kg/mm ² , and the tensile modulus is
It was 24.3t/ ^mm2 . Example 4 PH of aqueous dispersion of compound (1) stearic acid ester ammonium salt of general formula [A] in Example 1
Acrylonitrile fibers and carbon fibers were obtained in the same manner as in Example 1, except that the liquids obtained by adjusting the fibers to 3.0 and 4.8 were used for deposition. The tensile strength of the obtained carbon fibers is
407Kg/mm ² and 360Kg/mm ² , and the tensile modulus was 24.4t/mm ² in both cases. Comparative Example 2 The following formula does not belong to the ammonium salt of the present invention n=1, n=5, n= in the ammonium salt of
Using three types of No. 20, flameproofing treatment was performed in the same manner as in Example 1, and then carbonization treatment was performed. The tensile strengths of the obtained carbon fibers were as follows, and all showed low values. When n=1 330Kg/mm ² n=5 〃 320 〃 n=20 〃 308 〃 Example 5 97 mol% of acrylonitrile, 2.5 mol% of methyl acrylate, sodium methallylsulfonate in 1000 parts of 60% zinc chloride aqueous solution 95 parts of a monomer mixture consisting of 0.5 mol% and 0.85 parts of ammonium persulfate were polymerized at 50°C for 5 hours to obtain a molecular weight of 75,000 and a viscosity of 100 poise (45
℃) was obtained. This material was extruded into a 28% zinc chloride aqueous solution through a nozzle with a diameter of 0.06 mm and 48,000 holes, and was stretched 2.5 times while removing zinc chloride by washing with water.
7 g/water dispersion of compound (2) of the compound (2) of general formula [A] at 45°C for 0.2 minutes, at 105°C for 10 minutes, at 120°C.
and dried for 15 minutes. Then, continuously further in saturated steam at 115℃
It was stretched 5.5 times and then shrunk by 4% in saturated steam at 120° C. for 30 seconds to obtain an acrylonitrile fiber having a single fiber denier of 1.5, a tensile strength of 5 g/d, and a tensile elongation of 15%. This fiber was made flameproof using a flameproofing furnace having a multistage roller group as shown in FIG. In FIG. 1, 1 is a flame-resistant furnace, 2 is a roller, 3 is an acrylonitrile fiber, and 4 is a flame-resistant fiber.
The flameproofing treatment was carried out at 250°C for 2 hours so that the total shrinkage rate was 10% (the temperature increase rate from 200°C to 250°C was 10°C/sec). The obtained flame-resistant fiber had a specific gravity of 1.42 g/cc, a tensile strength of 3.1 g/d, and a tensile elongation of 15%, and no adhesion between single fibers was observed. When this flame-resistant fiber was made into a sliver using a turbo stapler and then spun into yarn using a ring spinning machine, the yarn could be spun without any problems such as yarn breakage or fluffing. Further, the tensile strength of the carbon fiber obtained by carbonizing the thus obtained flame-resistant fiber under the same conditions as in Example 1 was 432 Kg/mm ² , which was very excellent. Comparative Example 3 Same as Example 5 except that decyltrimethylammonium chloride, which does not belong to the ammonium salts of the present invention, is used instead of the stearate ammonium salt of compound (2) of general formula [A] used in Example 5. It was made into an acrylonitrile fiber. This material was subjected to flameproofing treatment, and then Example 1
Carbonization treatment was carried out under the same conditions. The tensile strength of the obtained carbon fiber was 320 Kg/mm ² , which was very inferior to the carbon fiber obtained in Example 5. Example 6 Acrylonitrile fibers with ammonium salt attached were produced in the same manner as in Example 5, and three
7℃/from 200℃ to 250℃ while giving % shrinkage.
The temperature was raised at sec and treated at 250°C for 1 minute to cause a thermal change in the ammonium salt. This fiber was a non-adhesive fiber with no fluff, a single fiber denier of 1.55, a tensile strength of 5 g/d, and a tensile elongation of 18%. When this fiber was flame-retardant treated in the same manner as in Example 5 and then carbonized in the same manner as in Example 1, it had an extremely high tensile strength of 440 Kg/ ^mm2 , and as a result of observation with an electron microscope. Carbon fibers without sticking were obtained. Example 7 The acrylonitrile fiber to which the ammonium salt of Example 5 was attached was further continuously subjected to heat treatment under the conditions shown in Table 2 below before flame-retardant treatment to obtain an acrylonitrile fiber. Using this material as a starting material, it was made flameproof in a flameproofing furnace as shown in Figure 1 in the same manner as in Example 1, and then heated at 1400°C for 30 minutes in a nitrogen stream.
The carbon fiber was carbonized for 1 minute under a tension of mg/d. Table 2 shows the results of measuring the tensile strength of this carbon fiber.

[Table] Shows the total time to raise the temperature to the maximum temperature and the holding time at the maximum temperature.
As is clear from the results in Table 2, when the acrylonitrile fiber to which the ammonium salt compound of the present invention is attached is once heated at a special heating rate and heat treated for a certain period of time to make it flame resistant, even higher strength can be obtained. Carbon fibers are obtained, which is even more advantageous.

[Brief explanation of the drawing]

FIG. 1 shows an example of an apparatus for flame-proofing acrylonitrile fibers. 1: Flame-resistant furnace, 2: Roller, 3: Acrylonitrile fiber, 4: Flame-resistant fiber.

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ is an aliphatic hydrocarbon group having 11 to 17 carbon atoms, R ₂ and R ₃ are hydrogen atoms, lower alkyl groups, hydroxyethyl groups, hydroxyisopropyl groups,
X represents an anion of an organic acid. However, if R ₂ or R ₃ is a hydroxyisopropyl group,
X represents a chlorine atom. ) Acrylonitrile fibers for producing flame-resistant fibers or for producing carbon fibers, to which at least one fatty acid ester ammonium salt shown is attached. 2 Acrylonitrile fiber is acrylonitrile
The fiber according to claim 1, which is obtained from a polymer comprising 95 mol% or more of acrylonitrile and 5 mol% or less of a vinyl monomer copolymerizable with acrylonitrile. 3 The compound represented by the general formula [A] is The fiber according to claim 1. 4 The amount of ammonium salt attached to the fiber weight
The fiber of claim 1 which is 0.01-0.5%. 5 General formula [A] at any stage from after solvent removal to completion of fiber production in the production process of acrylonitrile fibers, or after completion of the production process. (In the formula, R ₁ is an aliphatic hydrocarbon group having 11 to 17 carbon atoms, R ₂ and R ₃ are hydrogen atoms, lower alkyl groups, hydroxyethyl groups, hydroxyisopropyl groups,
X represents an anion of an organic acid. However, if R ₂ or R ₃ is a hydroxyisopropyl group,
X represents a chlorine atom. ) Acrylonitrile-based for flame-resistant fiber production or carbon fiber production, which is characterized in that it is subjected to adhesion treatment with an aqueous solution or aqueous dispersion containing at least one fatty acid ester ammonium salt represented by (a) and then heat-treated. Fiber manufacturing method. 6 The ammonium salt adhesion treatment is carried out on the PH containing the salt.
The manufacturing method according to claim 5, characterized in that the manufacturing method is carried out using an aqueous solution or an aqueous dispersion of 4 or less. 7. The manufacturing method according to claim 6, wherein the PH is 2 to 3.5. 8. The manufacturing method according to claim 5, wherein the temperature for adhering the aqueous solution or dispersion of ammonium salt is 20°C or more and 70°C or less. 9. The manufacturing method according to claim 5, characterized in that after the ammonium salt has been deposited, heat treatment is further carried out at 200 to 300°C until the ammonium salt becomes insoluble in water. 10. The manufacturing method according to claim 9, wherein the heat treatment is performed at 230 to 300°C. 11 After the temperature reaches 200℃ during heat treatment,
11. The manufacturing method according to claim 10, wherein the heating is performed at a temperature increase rate of 1 to 10° C./sec.