JPH0116929B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing carbon fiber tow that can produce a thin prepreg with high tow strength and good tow spreadability. [Conventional technology] Acrylic fiber tow is heated to 200~300% under an oxidizing atmosphere.
Flameproofed at ℃ and then under inert gas atmosphere
It is already known that carbon fibers with excellent performance can be obtained by carbonization treatment at a temperature of 1000°C or higher. However, the flame-retardant reaction carried out on acrylic fiber tow in an oxidizing atmosphere such as air is an exothermic reaction. Phenomena such as fusion and coalescence occur, and the resulting carbon fiber tow cannot have high strength, and the tow's spreadability is also insufficient, making it difficult to use it as carbon fiber for producing prepregs with excellent performance. I can't. Furthermore, if the degree of fusion or adhesion that occurs in the tow becomes severe, a large amount of fuzz will occur or breakage will occur in the tow during the subsequent heat treatment process, making it virtually impossible to bake the tow. Furthermore, carbon fiber tow with a lot of fluff has a disadvantage in that it lacks the ability to spread during the prepreg manufacturing process. The development of carbon fiber manufacturing methods that do not have these drawbacks has been considered for some time, and for example,
No. 117724 discloses a method in which an acrylic fiber tow to which a silicone oil such as methyl silicone or dimethyl silicone is attached is used as a precursor. According to this method, phenomena such as fusion and adhesion between single fibers in the process of flameproofing the precursor can be significantly improved, but since the silicone oil used here is highly hydrophobic, Static electricity is likely to be generated in the fibers during the handling process of the precursor, which causes the fibers to wrap around the rollers and guides in the flameproofing furnace, resulting in single yarn breakage and fuzz. Furthermore, Japanese Patent Publication No. 52-24136 discloses a method for producing carbon fibers without the above-mentioned difficulties, in which aminosiloxane is attached as an oil to an acrylonitrile fiber precursor and then fired. According to this method, JP-A-49-117724
Although it is possible to produce much superior carbon fiber compared to the method shown in the publication, it is extremely difficult to produce acrylic fiber tow without spots of oil due to the characteristics of this oil. In order to produce carbon fibers free of coalescence and fusion from fiber precursors, it is desired to develop a further improved method, and a method for this purpose has been proposed in Japanese Patent Laid-Open No. 56-49022. This method involves immersing acrylonitrile fiber tow in an oil bath in which an oil mixture of aminosiloxane and polyol compounds such as glycerin is dispersed in water. This is a method in which aminosiloxane is uniformly attached to acrylonitrile fiber tow by spraying it onto the fiber tow. Although this method is effective for the purpose of uniformly adhering aminosiloxane to acrylonitrile fiber tow, the acrylonitrile fibers used as precursors for carbon fiber production are highly oriented; Because the single fiber fineness is extremely thin, less than 1.5 denier, it is extremely vulnerable to impacts from the lateral direction to the fiber axis, and is considerably damaged by the jet water jet blown from the nozzle. This poses the problem of causing fuzz and thread breakage. [Problems to be Solved by the Invention] The above-mentioned method is a method for uniformly applying an amino silicone oil to an acrylonitrile fiber tow having 500 or more filaments without damaging it. Because a certain amount of the adhesive is forcibly deposited in one bath, the above-mentioned problems occur. Since aminosilicon oils are hydrophobic substances, it is extremely difficult to finely disperse them in water, so if a precursor is treated with oil using a high concentration oil bath, spots of oil will appear. On the other hand, when a large amount of polyol emulsifier is used in order to finely disperse aminosilicon in water, these polyols turn into tar during the process of making the precursor flame resistant, and this tar causes fusion during the process of making the precursor flame resistant. This is the cause of coalescence and coalescence. [Means for Solving the Problems] Therefore, the present inventors proposed that two oil baths be used to uniformly adhere the amino silicon oil to the acrylonitrile leg fiber tow having 500 or more filaments.
The inventors have discovered that the above-mentioned problems can be solved by using a multi-stage oil bath treatment method, and have completed the present invention. The gist of the present invention is that the number of filaments
An aminosiloxane oil agent represented by the general formula (1) below is applied to 500 or more acrylonitrile fiber tows.
0.1 to 5 oil per weight of dry fiber with more than 3 oil baths
% by weight of an acrylonitrile fiber precursor, which is made flame resistant, and then carbonized. The acrylonitrile fiber tow used in carrying out the present invention has a polymerized amount of acrylonitrile.
It is made from 80% by weight or more of an acrylonitrile polymer by a wet spinning method, a dry-wet spinning method, a dry spinning method, a melt spinning method, or the like. Other comonomers that can be copolymerized with acrylonitrile include vinyl carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, and vinyl monomers such as methyl acrylate, ethyl acrylate, methyl methacrylate, acrylamide, and methacrylamide. As the polymerization method for the acrylonitrile polymer, an aqueous suspension polymerization method, an emulsion polymerization method, a solution polymerization method, etc. can be used. As the aminosiloxane used in carrying out the present invention, those represented by the following general formula (1) can be used. (In the formula, R ₁ , R ₂ , R ₄ are H, -CH ₃ , -C ₂ H ₅ or -
C ₆ H ₅ or these alkoxy groups R ₃ is H, -CH ₃ , -C ₂ H ₅ , -C ₆ H ₅ , (-C ₂ H ₄ O) - _x
H or (-C ₃ H ₆ O) - _y H (x, y are integers from 0 to 10) R ₅ , R ₆ are (-CH ₂ ) - _z (z is an integer from 1 to 10) R ₇ , R ₈
is H or a _C1 to _C5 alkyl group n is an integer of 0 to 3, x is an integer of 0 or 1 or more, y is an integer of 1 or more, and x+y is 10 to 1000. ) The aminosilicon oils mentioned above can be emulsified as they are if they have an alkylene glycol structure in their molecular structure, but other aminosilicon oils can be emulsified as is, such as glycerin or polyalkylene glycols having an alkylene group with 3 or less carbon atoms, such as ethylene. Glycol, propylene glycol, butylene glycol, polyethylene glycol, polypropylene glycol, ethylene oxide nonyl phenyl ether, higher alcohol adducts of ethylene oxide or propylene oxide, etc. can be used. The amount of these emulsifiers used in combination with the aminosilicon compound is preferably 0.4 or less, particularly 0.3 or less. A precursor made using an oil containing a large amount of emulsifier is not preferable because it generates a large amount of tar during the flame-retardant process. The amount of amino silicone oil attached to acrylonitrile fiber is 0.1 to 5% by weight based on the weight of dry fiber.
Acrylonitrile fibers with less than 0.1% by weight of aminosilicon oil will not be able to prevent fusion and sticking phenomena in the flame-retardant process, while 5% by weight of aminosilicon oil
Even if a larger amount is deposited, the effect obtained will not increase much. As mentioned above, when aminosilicon oil is applied to acrylonitrile fibers in a single bath, the oil adheres unevenly, making it difficult to produce acrylonitrile fibers that can produce carbon fibers with good performance. In the present invention, the amino silicone oil is 0.01
Two oil baths containing ~10% by weight are arranged in series, and the first
The fibers may be subjected to a deposition treatment in a bath so that the amount of aminosilicone oil deposited is 0.05 to 3% by weight, and then subjected to a second bath treatment to obtain acrylonitrile fibers having an amount of deposited aminosiloxane of 0.1 to 5% by weight. Since the aminosiloxane is extremely uniformly adhered to the aminosiloxane-adhered acrylonitrile fiber tow produced by such a method, fusion and sticking phenomena are prevented during the flame-retardant and carbonization processes. Carbon fiber tow with excellent performance can be made. Furthermore, when applying the oil to the acrylic fiber tow, there is no need to use a method such as forcibly spraying the oil onto the acrylonitrile fiber tow using a nozzle installed in an oil bath, so the acrylonitrile fiber is not damaged in this process. Since the carbon fiber tow is free from fuzz and thread breakage, it is possible to obtain a carbon fiber tow without fuzz or thread breakage. The acrylonitrile fiber tow coated with the aminosilicon oil produced as described above is subjected to flameproofing treatment in air at a temperature of 200 to 400°C, and then, if necessary, at a temperature of 300 to 800°C in an inert gas atmosphere. The carbon fiber tow of the present invention can be obtained by performing a pre-carbonization treatment and then carbonizing it at a temperature of 1000° C. or higher. The carbon fibers obtained by the present invention are free from fluff and thread breakage, and do not cause entanglement of fibers in the tow due to shrinkage or elongation of the fibers during the flame-retardant process. It has extremely good spreadability and good resin impregnation properties when making prepregs, making it possible to make thin prepregs with excellent performance. [Example] The present invention will be explained in more detail with reference to Examples below. Example 1 95 parts of acrylonitrile, 4 parts of methyl acrylate
1 part of methacrylic acid and 21 parts of acrylonitrile polymer were dissolved in 79 parts of dimethylacetamide and heated at 50°C.
It was made into a spinning stock solution of 500 poise. Using a spinneret with 12,000 pores and a pore diameter of 0.070 mm, this spinning stock solution was spun in dimethylacetamide 70% and at a temperature of 30%.
The coagulated yarn was spun into an aqueous coagulation bath at 98°C.
It was stretched 8.5 times while washing in a hot water bath. This drawn yarn is coated with aminosiloxane emulsion (compound [A]) so that the amount of aminosiloxane deposited is 0.3% by weight, and then dried by passing it over a cylinder roller heated to a surface temperature of 135°C. did. Next, this dried yarn was introduced into a second stage treatment bath using an aminosiloxane emulsion having the same composition as before, and the amount of the aminosiloxane oil deposited was 0.5% by weight.
I adjusted it so that it adhered and rolled it up using a cheese rolling machine. The precursor fiber thus obtained was fired into carbon fiber by a conventional method. i.e. line speed 60
Flameproofing treatment was performed for 40 minutes in a flameproofing furnace with a hot air atmosphere with a temperature gradient in the range of 225 to 260℃ at m/hr.
Next, the material was treated in a pre-carbonization furnace with a temperature gradient ranging from 320 to 700°C and a carbonization furnace at 1200°C for 3 minutes each in a nitrogen gas atmosphere, and fired into carbon fibers. The physical properties of the obtained carbon fibers were as shown in Table 1. In the table, Comparative Example 1 uses a normal spinning process oil that does not contain aminosiloxane as the first stage oil.
Comparative Example 2 is the same as Example 1, except that a normal spinning process oil that does not contain aminosiloxane is used as the first stage oil, and an aminosiloxane-based oil is used as the second stage oil. This is a carbon fiber obtained from a precursor fiber prepared by spinning in the same manner.

[Table] In Comparative Example 1, thread breakage occurred frequently during the flameproofing treatment due to the fusion phenomenon, and the passing through the firing process was extremely poor. Prepreg (PP) using these carbon fibers
was created. The results are shown in Table 2.

[Table] It was confirmed that the present invention provides carbon fibers with high performance and excellent suitability for producing prepregs. Example 2 Table 2 shows the amount of aminosiloxane deposited in the first-stage oil agent and second-stage oil agent, which also have the same composition as Example 1, on the drawn yarn with the same composition and spinning conditions as Example 1.
A precursor modified as shown in Example 1 was obtained, and the carbon fiber was fired under the same conditions as in Example 1. The physical properties of the carbon fiber and its suitability for producing a prepreg were evaluated. These results were as shown in Table 3.

[Table] From Table 3, it can be seen that it is effective to apply the aminosiloxane oil in two stages and in an appropriate amount.

Claims (1)

[Claims] 1. An acrylonitrile water-swellable fiber tow having 500 or more filaments prepared by spinning and drawing an acrylonitrile polymer is treated with an aminosiloxane oil represented by the general formula (1), and then dried and densified. Formula (1)
Production of a carbon fiber tow characterized by treating an acrylonitrile fiber precursor with an aminosiloxane oil shown in the formula to make the acrylonitrile fiber precursor adhering to the oil at 0.1 to 5% by weight based on the dry fiber weight, and carbonizing it. Law. (In the formula, R ₁ , R ₂ , R ₄ are H, -CH ₃ , -C ₂ H ₅ or -
C ₆ H ₅ or these alkoxy groups R ₃ is H, -CH ₃ , -C ₂ H ₅ , -C ₆ H ₅ , (-C ₂ H ₄ O) - _x
H or (-C ₃ H ₆ O) - _y H (x, y are integers from 0 to 10) R ₅ , R ₆ are (-CH ₂ ) - _z (z is an integer from 1 to 10) R ₇ , R ₈
is H or a _C1 to _C5 alkyl group n is an integer of 0 to 3, x is an integer of 0 or 1 or more, y is an integer of 1 or more, and x+y is 10 to 1000. )