JPH0433892B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is a method for producing precursor fibers for producing carbon fibers, and is particularly suitable for producing carbon fibers with excellent quality and physical properties, as well as markedly improving process passability during the production of carbon fibers. The present invention relates to a method for producing a precursor fiber for carbon fiber production (hereinafter referred to as a precursor). (Prior art) Carbon fiber is made of acrylic precursor,
Rayon-based, pitch-based, or polyvinyl alcohol-based fibers are converted into oxidized fibers by heating and baking in air at 200 to 400°C or in an oxidizing atmosphere such as nitrogen oxide (flame-retardant process), and then treated with nitrogen, argon, helium, etc. It is obtained through a method of carbonization by further heating at a high temperature of 300 to 2000℃ in an inert atmosphere (carbonization process), and due to its excellent physical properties, it is widely used in many applications, especially as a reinforcing fiber suitable for composite materials. has been done. However, in the above-mentioned industrial manufacturing method of carbon fibers, there is a problem in that single fibers are fused together in the flameproofing step of converting the precursor into oxidized fibers and in the subsequent carbonization step. If this fusion occurs between single fibers, it will not be possible to bake them uniformly, causing fuzz and thread breakage, which will not only be a major cause of hindering process passability, but also carbon fibers with excellent quality and physical properties. It becomes impossible to manufacture. Therefore, in order to prevent such fusion between single fibers, many methods of improving the oil agent to be applied have been disclosed. For example, a method of applying a specific oil, especially a silicone oil
No. 52-24136, Special Publication No. 51-12739, Japanese Patent Publication No. 1983-
No. 99011, JP-A-58-214517, JP-A-52-
148227 publications), further improved heat resistance,
Alternatively, a method of applying an oil with specified heat resistance (for example, Japanese Patent Publication No. 58-5287, Japanese Patent Application Laid-open No. 60-146076,
JP-A-59-66518, JP-A-58-120819, JP-A-55-103313), and so on. However, even if the above-mentioned means are used alone or in various combinations, they cannot sufficiently prevent fusion between single fibers, and are insufficient as means for preventing fusion. On the other hand, it is possible to prevent fusion by lowering the temperature of the atmosphere during the firing process, but in this case, the processing speed must also be slowed down, resulting in a decrease in production efficiency. Therefore, it cannot be used as an industrial means of production. (Problems to be Solved by the Invention) An object of the present invention is to prevent the fusion of single fibers that occurs during the firing process, thereby making it possible to obtain carbon fibers of high quality and excellent physical properties. An object of the present invention is to provide a method for producing precursor fibers for producing carbon fibers. (Means for Solving the Problems) The above object of the present invention is to have a viscosity of 1000 at 25°C.
~15,000 centistokes, an epoxy-modified silicone oil with 0.05~10% by weight of alicyclic epoxy groups added, and a viscosity of ~250~ at 25°C.
10,000 centistokes, and is characterized in that an amino-modified silicone oil having an amino group modification amount of 0.05 to 10% by weight is attached to the fiber in an amount of 0.01 to 5% by weight. This can be achieved by a manufacturing method. A feature of the silicone oil applied in the present invention is that it contains not only an epoxy-modified silicone oil and an amino-modified silicone oil, but also two. Furthermore, the epoxy-modified silicone oil agent is characterized in that the epoxy group serving as the modifying group is an alicyclic epoxy group. Examples of the alicyclic epoxy group as a modifying group in the epoxy-modified silicone oil applied in the present invention include a 1,2-epoxy-cyclohexyl group (the following structural formula) and a 1,2-epoxy-cyclohexyl group (the following structural formula).
A typical example is a cyclopentyl group (the following structural formula). Examples of the silicone oil agent to which the alicyclic epoxy group of the above structural formula () is added include those having the following structural units. (Here, n ₁ is a positive integer of 1 to 5, n ₂ is 0 or 1. R ₁ to _{R 9} are hydrogen atoms, or /
and an alkyl group. ) Here, the basic skeleton of the silicone oil of the present invention is:
It has a siloxane bond, -SiO-,
The silicon atom or the group bonded to Si (for example, R in the above structural formula) may be a hydrogen atom or/and an alkyl group having 1 to 3 carbon atoms, a phenyl group, or an alkoxy group thereof. Among these, dimethylsiloxane is particularly preferred as the basic skeleton. Up to now, it has been proposed to apply a silicone-based oil in order to prevent fusion between single filaments during the firing process of carbon fibers. Regarding epoxy-modified silicone oils, for example, Japanese Patent Publication No. 18334/1983, Japanese Patent Application Laid-Open No. 181322/1982,
Publication No. 181323 discloses a method in which a glycidyl-type epoxy group (not an alicyclic epoxy group) modified product is applied alone or in a mixture with other modified silicone-based oils. However, although these methods have the effect of preventing fusion between single yarns during the firing process, the effect is not sufficient, and the quality of the products is improved by preventing fusion between single yarns, which is the objective of the present invention. This was insufficient to produce carbon fibers with excellent quality. When the epoxy-modified silicone oil of the present invention having the above structure is applied, the fusion between single fibers is reduced compared to the previously disclosed glycidyl-type epoxy group-modified oil. The present inventors have already found that the prevention effect becomes greater, and the reason for this is that the affinity for the fiber substrate increases due to the presence of alicyclic groups, and as a result, the coating of the oil agent becomes uniform. This is thought to be due to the fact that it is strongly formed. Furthermore, it has been found that fusion between single fibers can be more effectively prevented by applying an amino-modified silicone-based oil in combination with the epoxy-modified silicone-based oil, which is one of the components applied in the present invention. This heading led to the present invention. The reason why the method of the present invention more effectively prevents fusion between single fibers is not clear, but as mentioned above, the coating of the epoxy-modified silicone oil having a specific structure coats the fiber matrix. The epoxy groups in this epoxy-modified silicone oil react with the amino groups in the amino-modified silicone oil, resulting in a resin-forming reaction, and a stronger oil film is formed on the fiber surface. It is assumed that The oil film thus formed has excellent heat resistance and is thought to be able to effectively prevent fusion between single yarns during the firing stage. Examples of the amino-modified silicone oil used in the present invention include those having the following structural units. (Here, n ₃ is an integer of 1 to 10, n ₄ is an integer of 1 to 10, n ₅ is an integer of 0 to 5, R ₁₀ to R ₁₂ are hydrogen atoms,
or/and an alkyl group. ) Here, the basic skeleton of the amino-modified silicone oil of the present invention has a siloxane bond, -SiO-, similar to the above-mentioned epoxy-modified silicone oil, and this silicon atom, a group bonded to Si (e.g. Examples of R') in the above structural formula include a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a phenyl group, and an alkoxy group thereof. Among these, dimethylsiloxane is particularly preferred as the basic skeleton. A method of combining an epoxy-modified silicone oil and an amino-modified silicone oil is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 181322/1983, but as already mentioned, it is difficult to combine glycidyl-type epoxy groups. Therefore, a modified epoxy-modified silicone oil agent was applied, and it was not possible to sufficiently prevent fusion between single filaments. Also,
The above-mentioned Japanese Patent Application Laid-Open No. 181323/1983 discloses a silicone oil having an epoxy group and an amino group in the same molecule, but this method also sufficiently prevents fusion between single filaments. It was something I couldn't do. In the epoxy-modified silicone oil used in the present invention, the amount of modification of the alicyclic epoxy group is 0.05 to 10% by weight in terms of the weight of the epoxy group CH ₂ CH ₂ O.
and preferably 0.1 to 5% by weight. 0.05
If the amount is less than % by weight, the effect of the alicyclic epoxy group will not be exhibited, and fusion between single fibers cannot be effectively prevented. On the other hand, if the amount of modification exceeds 10% by weight, the heat resistance of the oil component itself decreases, and fusion between single fibers cannot be effectively prevented. The viscosity of the epoxy-modified silicone oil of the present invention is
1000 to 15000 centistokes (abbreviated as cs), preferably 2000 to 12000 cs, measured at 25°C.
If it is less than 1000 cs, the heat resistance will be low and it will not be possible to prevent fusion between single yarns. When it exceeds 15000cs,
It becomes difficult to disperse it in water or to find a solvent with excellent solubility, making it impossible to uniformly apply it to the surface of the yarn. In the amino-modified silicone oil agent used in the present invention, the amino group that is the modifying group is of the monoamine type (when n ₅ = 0), as shown by the structural formula ().
However, it may also be a polyamine type (in the case of n ₅ ≠0), as long as it has an amino group that can react with an epoxy group. The amount of modification of the amino group is 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the amount of terminal amino groups converted to _NH2 . If the amount is less than 0.05% by weight, even if it is applied together with an epoxy-modified silicone oil agent, sufficient heat resistance will not be exhibited and fusion between single yarns will not be effectively prevented.
On the other hand, if the amount of amino group modification exceeds 10% by weight, the heat resistance of the oil agent itself decreases, and fusion between single fibers cannot be prevented. In addition, the viscosity of the above amino-modified silicone oil is 250 to 10,000 cs, preferably 500 cs.
~8000cs. If it is less than 250cs, the heat resistance will not be sufficient, and if it exceeds 10,000cs, it will be difficult to disperse it in water, or it will be difficult to find a solvent with excellent solubility, and it will be difficult to apply it uniformly to the fiber. It becomes difficult. In the present invention, the siloxane skeleton of an alicyclic epoxy group or an amino group that is a modified group, that is,
The mode of bonding to -SiO- is that they are adjacent to each other
It may be continuously bonded to the Si part in a block shape (for example, the bonded state shown in A below), or it may be bonded to the adjacent Si part (for example, the bonded state shown in B below). or a combination of these combinations. The point is that the amount of the above alicyclic epoxy group added is 0.05~
It is sufficient that the content is 10% by weight and the addition amount of amino groups is 0.05 to 10% by weight. (E represents an alicyclic epoxy group or a modified group containing an amino group.) As described above, heat resistance is an important characteristic of the oil agent of the present invention, and the viscosity within the above range, It is preferable to use a material having a modified amount and a heat resistance residual rate (r) of 20% or more, more preferably 30% or more. Here, the heat resistance residual rate r shall be defined below. In other words, the residual rate when heat treated in air at 240°C for 60 minutes is r ₁ (%),
Furthermore, when the residual rate when heat-treated for 30 seconds in nitrogen at 450° C. is defined as r ₂ (%), r=r ₁ ×r ₂ /100 (%). The flame-retardant process of converting the precursor into oxidized fiber in the firing process is an oxidation treatment process of the yarn at a high temperature of 200 to 400℃.If the heat resistance of the oil agent present on the surface of the yarn is poor, the yarn The oil component applied to the surface is decomposed and volatilized in this step, making it impossible to prevent yarns from fusing. In the carbonization step under an inert atmosphere that follows the flameproofing step, for example, when acrylic fibers are fired, in the first half of the carbonization step, a network structure is formed between the naphthyridine rings formed in the flameproofing step, and the carbonization It is said that in the latter half of the process, a higher-order structure of this network structure is formed and grows. The present inventors have discovered that in the first half of this carbonization process, single fibers are still likely to fuse together, and that fusion no longer occurs for the first time in the second half. As described above, the ability of the oil component to prevent the single fibers from adhering is an essential property not only in the flameproofing process but also in the first half of the carbonization process. In order to increase the affinity of the precursor for the substrate, an epoxy-modified silicone oil having an alicyclic epoxy group is used as the first component, and an amino-modified silicone oil that can react with this is used as the first component. A feature of the present invention is that the second component forms a uniform and strong film on the surface of the fibers to avoid fusing of single fibers during firing, and this feature is more effectively exerted. In order to achieve this, it is preferable to have the above heat resistance. These oil components can be used by being emulsified and dispersed in water by using a suitable emulsifier, or can be applied as a solution dissolved in a suitable solvent such as water or an organic solvent. The epoxy-modified silicone oil and the amino-modified silicone oil may be applied at the same time or separately, but considering the affinity of the epoxy-modified silicone oil to the fiber substrate, it is recommended that they be applied at the same time. Alternatively, it is preferable to apply the epoxy-modified silicone-based oil first and then apply the amino-modified silicone-based oil. Epoxy-modified silicone oil and amino-modified silicone oil are 5 to 95% by weight versus 95 to 5% by weight,
Preferably it is applied in a ratio ranging from 10 to 90% by weight to 90 to 10% by weight. The amount of these oil components to be applied to the yarn is preferably 0.01 to 5% by weight, preferably 0.1 to 3% by weight, based on the amount of yarn, including both components. If the amount applied is less than 0.01% by weight, the purpose of the present invention cannot be achieved, while if it exceeds 5% by weight, problems such as increased stickiness due to oil components during firing and deposition of volatile matter during the process occur. This is not preferable because it reduces productivity. Precursors to which the oil component of the present invention can be applied include acrylic, rayon, pitch, and polyvinyl silicone precursors, but are not particularly limited. It is possible to prevent the fusion of single fibers that occurs during the process, but it is particularly effective when applied to acrylic fibers that are prone to fusion. Examples applicable to acrylic fibers are described below. The acrylic fiber preferably used in the present invention contains acrylonitrile (hereinafter referred to as AN) as a main component, preferably 94% by weight or more, particularly preferably 97% by weight or more of AN, and preferably 6% by weight or more of AN.
% by weight or less, particularly preferably 3% by weight or less
A copolymer of AN and a vinyl group-containing compound (hereinafter referred to as a vinyl monomer) that is copolymerizable with AN and promotes a flame-retardant reaction is used. Examples of vinyl monomers that promote flame resistance include acrylic acid, methacrylic acid,
Examples include itaconic acid, alkali metal salts and ammonium salts thereof, α(1-hydroxylethyl)acrylonitrile, and acrylic acid hydroxyl ester. In addition to these vinyl monomers that have the ability to promote flame resistance, lower alkyl esters of acrylic acid and methacrylic acid, allylsulfonic acid, methallyl A third component such as sulfonic acid, styrene sulfonic acid and their alkali metal salts, vinyl acetate or vinyl chloride may be copolymerized within a range where the total amount of copolymerized components is 6% by weight or less, preferably 3% by weight or less. good. AN-based copolymers are polymerized using known emulsion suspension, bulk, and solution polymerization methods, and when producing acrylic fibers from these polymers, dimethylformamide, dimethyl sulfoxide, and nitric acid are used. , a polymer solution such as a Rodan soda aqueous solution is used as a spinning stock solution, and a conventional wet spinning method or a dry spinning method is used.
It can be spun into fibers by wet spinning or dry spinning. In particular, when a dry-wet spinning method is used, fusion between single fibers is more likely to occur, so the effects of the present invention are more pronounced. The oil agent of the present invention may be applied during the yarn spinning process, or after yarn spinning, during the firing process, but
In order to uniformly apply it to the precursor, it is preferable to apply it during the spinning process. Particularly in the case of acrylic fibers, it is preferable to apply it to the yarn in a water-swollen state before drying and densification. Application methods include soaking the yarn in an oil dispersion or solution and then adjusting the amount of adhesion to a predetermined level by spraying with a nip roller or compressed air, or bringing it into contact with a roller moistened with an oil agent. Alternatively, it can also be applied in the form of a mist using an air atomization method. In addition, in the present invention, it is preferable to use an antistatic agent in combination in order to avoid the occurrence of unraveling of single yarns, winding around rollers, fuzz, etc., which greatly affect process passability in the spinning and firing stages. Examples of these antistatic agents include sulfonates such as alkylbenzene sulfonates, phosphoric acid esters such as alkyl phosphates and polyoxyethylene alkyl phosphates, and polyoxyethylene alkyl ethers and alkyl esters. nonionic surfactants, such as
Alternatively, cationic surfactants may be used.
Furthermore, as these antistatic agents, it is preferable to use compounds with excellent heat resistance from the viewpoint of stability in the firing process, such as silicon-based compounds modified with alkylene oxide or surface active compounds containing fluorine atoms. Agents, etc. can be mentioned. (Effect of the invention) By applying the precursor fiber for carbon fiber production obtained by the method of the present invention, fusion between fibers that occurs in the flameproofing process and carbonization process due to the effect of the specific oil component can be largely avoided, making it possible to produce carbon fibers with excellent process passability, high quality, and high performance. The present invention will be explained in more detail with reference to Examples below. In addition, in the text and examples, the performance (strength, elastic modulus) of carbon fiber is the physical property of a strand impregnated with epoxy resin measured according to JIS R-7601, and is calculated from the average of n = 10 measurements. This is the obtained value. The amount of the oil component attached was determined by extraction from the fibers after application of the oil agent but before drying and densification. Further, the heat resistance residual rate r based on the above definition was measured by the following procedure. (1) Pretreatment of oil agent Before starting the above-mentioned heat treatment operation necessary for measuring the heat resistance residual rate, prepare 1 g of oil agent into a mold with a diameter of approximately 60 mm and a height of approximately
Collected in a 20mm aluminum container and placed in an oven.
Dry at 105℃ for 5 hours. (2) Measurement using a differential thermal analyzer (TGA)
Collect 15 to 20 mg into a cylindrical aluminum container (pan) with a height of 5 mm and place it on a differential thermal analyzer (TGA).
Determine the heat resistance residual rate. Measurement conditions, etc. are described in (3) to (6) below. (3) Under the following heating conditions, raise the temperature to 240°C under a stream of air, and then calculate the residual rate from the amount of oil remaining when processing at 240°C for 60 minutes. The residual rate at this time is defined as r ₁ (%). Air flow rate: 30 l/min Temperature increase rate: °C/min (4) After completing the heat treatment at 240 °C for 60 minutes in (3), the heating atmosphere was changed from air to nitrogen while maintaining the temperature at 240 °C. Hold for 5 minutes. Nitrogen flow rate: 30 l/min (5) The temperature is raised from 240°C to 450°C under the following heating conditions, held at 450°C for 30 seconds, and the residual rate r ₂ (%) is determined. Nitrogen flow rate: 30 l/min Temperature rising rate: 10 °C/min (6) The heating residual rate r ₁ in air and the heating residual rate in nitrogen determined in (3) and (5) above From r ₂ , the heat resistance residual rate r of the oil agent is determined from r=r ₁ ×r ₂ (%). Example 1 A dimethyl sulfoxide (DMSO) solution of a copolymer of 99.3% AN and 0.7% itaconic acid was used as a spinning stock solution. The concentration of the copolymer in this stock solution was 20% by weight, and the intrinsic viscosity of the copolymer was 1.80. This spinning dope was once discharged into the air using a nozzle with a diameter of 0.15 mm and 3000 holes, passed through a space of approximately 3 mm, and then introduced into a 35% DMSO aqueous solution and solidified. This coagulated yarn was desolvated in a water washing tank, and then stretched four times in hot water to obtain water-swollen acrylic fibers (hereinafter referred to as bath-drawn yarn). A dimethylsiloxane-based epoxy-modified silicone oil agent containing a basic skeleton unit with an epoxy group bonded to the bath-drawn yarn represented by the following structural formulas (1, the present invention) and (2, outside the present invention); Structural formula (3)
Mix equal amounts of a dimethylsiloxane-based amino-modified silicone oil containing a basic skeleton with an amino group bonded to it, and mix it in water with a nonionic surfactant mainly consisting of an ethylene oxide adduct of nonylphenol. It was dispersed and emulsified and applied. The viscosity of the oil components applied here at 25℃ is 4500 to 5000cs for all epoxy-modified silicone oils.
The amino-modified silicone oil is 1000~
It was 1200cs. The amount applied to the fibers was set within the range of 1±0.2% by weight by adjusting the concentration of the oil bath. The yarn obtained in this way after applying the oil agent,
Drying and densification treatment was performed using a heated roller at 130°C. The yarn after drying and densification was further drawn three times in saturated steam at 3 kg/mm ² -G. The precursor fiber thus obtained had a single yarn denier of 0.5 de, a total denier of 2400 De, a strength of 6.5 to 7.0 g/d, and an elongation of 10.5 to 11.2%. This precursor fiber is flame-resistant treated in a flame-proofing furnace with a temperature gradient of 250 to 280°C (processing time = 25 minutes).
Then, it was converted into carbon fiber by firing in a carbonization furnace with a temperature gradient of 300 to 1300°C under a nitrogen atmosphere. The strand strength of the carbon fibers thus obtained is shown in Table 1 along with the amount of modification of the applied oil.

[Table] Items with marks added.
**Example 2 outside the present invention has the same basic skeleton as the structural formula (1) of Example-1, the amount of epoxy modification by alicyclic epoxy group is 1.5% by weight, and The viscosity of is 7000cs
An epoxy-modified silicone oil agent and an example-
It has the same basic skeleton as the structural formula (3) of 1, the amount of modification by amino group is 1.0% by weight, and 25
An amino-modified silicone oil having a viscosity of 1200 cs at °C was mixed and applied in equal amounts. Carbon fibers were obtained in the same manner as in Example 1, except that the amount of the oil component applied to the yarn was changed. Table 2 shows the applied amount and the strand strength of the carbon fiber.

[Table] Example 3 In Example-2, equal amounts of oil components having different viscosities at 25°C and different amounts of modification by epoxy groups and amino groups were applied. Carbon fibers were obtained by applying it to bath-drawn yarn in the same manner as in Example-1. Table 3 shows the viscosity, amount of modification, and heat resistance r, as well as the strand strength of the carbon fibers.

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【table】

Claims (1)

[Claims] 1. An epoxy-modified silicone oil having a viscosity of 1,000 to 15,000 centistokes at 25°C and to which 0.05 to 10% by weight of alicyclic epoxy groups are added, and a viscosity of 250 to 10,000 centistokes at 25°C, 1. A method for producing a precursor fiber for carbon fiber production, which comprises depositing an amino-modified silicone oil having an amino group modification amount of 0.05 to 10% by weight based on the weight of the fiber.