JPS6218671B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for sizing carbon fibers. Carbon fiber has attracted attention in recent years because of its high specific strength and specific modulus, and is being used in sports equipment and aircraft parts. Generally, carbon fiber is used by thermosetting a thermosetting resin as a matrix to obtain a molded product, but in order to take full advantage of the mechanical performance of carbon fiber, the adhesion between the matrix resin and carbon fiber must exceed a certain level. It is necessary. As a method for evaluating adhesive strength, interlaminar shear strength is measured. Epoxy resin is usually used as a matrix for carbon fibers, and an interlaminar shear strength of 7 kg/mm ² or more can be easily achieved. However, when a radical polymerization type matrix resin is used, its adhesive strength is poor, and as in the inventions disclosed in Japanese Patent Publication No. 52-29345 and Japanese Patent Publication No. 52-5064, the interlaminar shear strength is 6 to 7 Kg/ ^mm2. In reality, it was only a matter of time and could not be put to practical use. The present inventors paid attention to the fact that radical polymerization matrix resins have fast curing properties, and as a result of intensive studies on methods for improving the adhesiveness between this matrix resin and carbon fibers, they arrived at the present invention. According to the carbon fiber sizing method of the present invention, it is possible to easily obtain a composite material having an interlaminar shear strength exceeding 8 Kg/mm ² , which was extremely difficult when conventional radical polymerization matrix resins were used. As the vinyl ester resin composition used in the present invention, any unsaturated ester resin having one or more free hydroxyl groups in the molecule can be used, including glycerin, diglycerin,
A reaction product of a polyol having three or more hydroxyl groups such as trimethylolpropane or pentaerythritol and an unsaturated basic acid, a reaction product of a polycarboxylic acid and glycidyl methacrylate or glycidyl acrylate, or a molecule with an epoxy group. An epoxy compound containing at least one epoxy compound and an unsaturated basic acid, or a partially or mostly saturated basic acid, a saturated polybasic acid, an anhydrous saturated polybasic acid, an unsaturated polybasic acid , substituted with one or more selected from anhydrous unsaturated polybasic acids, are reacted by heating in the presence of a reaction catalyst and a polymerization inhibitor, especially when the constant K of the following formula is 2.
K=WPE _R /WPE _O・W ₁ /W ₁ +W ₂ WPE _O : Epoxy equivalent of raw material epoxy compound (g/eq) WPE _R : After reaction Epoxy equivalent weight of the composition (g/
eq) W ₁ : Weight of raw material epoxy compound (g) W ₂ : Weight of components other than epoxy compound used in reaction (g) Within a range not exceeding 50% by weight, α, β-amino acids such as maleic anhydride and fumaric acid are added. One or more mixtures of unsaturated alkyd resins, which are polyester condensation products of saturated dicarboxylic acids and saturated dicarboxylic acids and glycols, and one or more β polymers such as diallyl phthalate and diallyl isophthalate. There is no problem in using a mixture of mixtures and the like. The epoxy compound used in this reaction refers to all known epoxy resins,
For example, polyglycidyl ethers of diphenylolalkanes such as diphenylolpropane, diphenyloethane, and diphenylomethane, polyglycidyl ethers of polyhydric phenols such as novolak or resol, p-aminophenol, m- Epoxy resins produced by epoxidation of polyglycidyl ethers of polyvalent amines such as aminophenol and 4,4′-diaminodiphenylmethane, alicyclic compounds such as cyclohexacene, cyclopentadiene, and dicyclopentadiene,
It refers to methyl esters of 3.4-epoxy-6-methyl-cyclohexanecarboxylic acids, poly(epoxyalkyl)ethers of aliphatic polyepoxy compounds such as ethylene glycol and glycerin, and glycidyl esters of aromatic and aliphatic carboxylic acids. These may be used singly or in combination of two or more. Examples of unsaturated basic acids include methacrylic acid, acrylic acid, crotonic acid, etc., and examples of unsaturated polybasic acids or acid anhydrides thereof include maleic anhydride, fumaric acid, itaconic acid, etc. Saturated basic acids, polybasic acids, and anhydrous saturated polybasic acids include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, adipic acid, hettic acid, p-tertiarybutylbenzoic acid, etc. . As a catalyst for these reactions, ordinary esterification catalysts can be used, but more preferably lithium halides, sulfonic acids, metal hydroxides,
One or more types of metal halides, phosphonic acids, organic acids, etc. are used in an amount of 0.001 to 15 phr based on the esterification reaction product. Examples of polymerization inhibitors include quinones such as monovalent or polyvalent phenols, such as hydroquinone, methoxyhydroquinone, and parabenzoquinone.
species or two or more species to the esterification reaction product
Use in the range of 0.001 to 0.25 phr. The molar ratio of the reaction between the epoxy group of the epoxy compound and the base of the unsaturated basic acid is preferably 1:0.5 to 1.1. These reactions are usually carried out without solvent at 100
Although the reaction is carried out at a temperature of 200°C to 200°C, it is also effective to dilute the epoxy groups and unsaturated groups with a non-reactive solvent to stop the reaction and cool the reaction. When the reaction molar ratio between the epoxy group of the epoxy compound and the base of the unsaturated basic acid is less than 1:0.5, the vinyl ester resin becomes soft, and when it exceeds 1:1.1, the vinyl ester resin becomes brittle, and in either case, the composite material This is not preferable because it lowers the interlaminar shear strength. To apply the vinyl ester resin composition to the surface of carbon fibers, use a solvent that dissolves the composition and does not react with unsaturated groups, such as acetone, methyl ethyl ketone,
Solid content 0.05-5 in methylene chloride, chloroform, etc.
After passing through and impregnating the carbon fibers in this solution, the temperature is below 150℃, more preferably at 100℃.
The solvent may be distilled off as follows. This process involves only solvent distillation and can be carried out at low temperatures, so there is only slight variation in the epoxy equivalent of the sizing agent, and the process can be carried out in an extremely short time. Since the vinyl ester resin composition used in the present invention contains a polymerization inhibitor, it is also characterized by the excellent stability of the stiffness of the sizing yarn over time as described above. The appropriate application amount of the sizing agent of the present invention is 0.05
-5% by weight, more preferably 0.2-4% by weight. If it is less than 0.05% by weight, the yarn will become too fluffy and is not substantially effective, and if it exceeds 5% by weight, the adhesive strength between the matrix resin and the carbon fibers of the composite obtained therefrom will be low, which is not appropriate. The carbon fibers used in the present invention are polyacrylonitrile, cellulose, pitch, etc.
Either a so-called high-strength yarn or a high-elasticity yarn fired at a temperature close to 0.degree. C. may be used, but one whose surface has been oxidized is particularly preferable. Carbon fibers treated according to the present invention exhibit excellent adhesion between fibers and resins, especially when used as a reinforcing material for radical polymerization resins such as unsaturated polyester resins, vinyl ester resins, and diaryl phthalate resins. A good composite material can be obtained. Production example 1 78 parts of 3.4-epoxy-6-methylcyclohexynone methyl-3.4-epoxy-6-methylcyclohexanecarboxylate (epoxy equivalent: 156), 32.4 parts of acrylic acid, 0.05 parts of hydroquinone
1 part and 0.2 parts of lithium chloride were added thereto, and the mixture was heated and reacted at 100°C to obtain a vinyl ester resin composition (1) having a constant K of 6.7. Production Example 2 38 parts of 1-epoxyethyl-3.4-epoxycyclohexane (epoxy equivalent: 76) and 36 parts of acrylic acid
part, hydroquinone 0.05 part, lithium chloride
Add 0.1 part, heat the reaction at 100℃, and adjust the constant K to 10.
A vinyl ester resin composition (2) was obtained. Production Example 3 39 parts of methacrylic acid, 0.7 parts of lithium chloride, and 0.05 parts of hydroquinone were added to 95 parts of Epicote 828 (Ciel Chemical registered trademark, epoxy equivalent: 190),
A heating reaction was carried out at 100° C. to obtain a vinyl ester resin composition (3) with a constant K of 5. Production Example 4 A vinyl ester resin composition (4) was obtained in the same manner as Production Example 1 except that no hydroquinone was added. Production Example 5 A vinyl ester resin composition (5) was obtained in the same manner as Production Example 2 except that no hydroquinone was added. Production Example 6 A vinyl ester resin composition (6) was obtained in the same manner as Production Example 3 except that no hydroquinone was added. Example 1 The vinyl ester resin composition (1) obtained in Production Example 1 was dissolved in acetone at a solid content of 0.7% by weight, and carbon fiber Pyrofil AS (Mitsubishi Rayon registered trademark) was uniformly impregnated with this, and then heated at 90°C. The solvent was distilled off by passing through a hot air oven for 1 minute to obtain a 0.6% by weight sized carbon fiber. Add 25 parts of diallyl phthalate monomer, 3 parts of tertiary butyl perbenzoate, and 103 parts of methyl ethyl ketone to 75 parts of diallyl phthalate β polymer (softening point 80°C, iodine value 60) to make a lacquer, and impregnate it into the carbon fiber obtained above. While doing so, it was wound onto a drum wrapped with silicone-coated release paper. The resin content was adjusted to 40% by weight by sandwiching the impregnated carbon fiber between two glass rods and controlling the gap between them. The carbon fibers wound on the release paper were cut open and taken out from the drum, and dried in a hot air dryer at 90°C for 10 minutes to produce prepreg. The obtained prepreg was laminated in one direction and molded with a matted metal die so that the fiber volume content was 60%. Curing conditions are pressure 7Kg.
G/cm ² , 150°C, and 30 minutes. The interlaminar shear strength (ILSS) of the resulting composite was determined according to ASTM-D-
2344, it was 9.2Kg/mm ² . In addition, when using fibers that are not subjected to the above treatment
It was 6.5Kg/ ^mm2 . Example 2 A composite was prepared in the same manner as in Example 1 using the vinyl ester resin composition (2) obtained in Production Example 2. The ILSS of the resulting composite was 9.5 Kg/mm ² . Example 3 A composite was prepared in the same manner as in Example 1 using the vinyl ester resin composition (3) obtained in Production Example 3. The ILSS of the resulting composite was 9.1 Kg/mm ² . Example 4 Using the size-treated carbon fiber obtained in Example 1, 75 mol of maleic anhydride and 108 mol of propylene glycol were added.
Esterified for 3.5 hours at 140-230 °C with a composition of mol, then 25 mol of isophthalic acid and hydroquinone
Diaryl phthalate monomer 25 phr was added to an unsaturated alkyd resin with an acid value of 23.5 and a softening point of 78 to 80 °C obtained by esterification at 140 to 230 °C for 3 hours with the addition of 0.02 phr.
The lacquer was adjusted by adding 3 phr of tertiary butyl perbenzoate and 128 phr of methyl ethyl ketone. This was used to impregnate the size-treated carbon fiber obtained in Example 1 to prepare a prepreg and a composite in the same manner as in Example 1. The ILSS of the resulting composite was 9.2 Kg/mm ² . Example 5 The vinyl ester resin composition (3) obtained in Production Example 3 was diluted with 20 phr of styrene on the carbon fiber obtained in Example 1, and tertiary butyl perbenzoate was added to the carbon fiber obtained in Example 1.
The carbon fibers were impregnated with 2 phr, placed in a mold with the fibers aligned, and cured at 120°C for 5 minutes without leakage to produce a composite with a carbon fiber volume content of 50%. The ILSS of the resulting composite is
It was 9.0Kg/ ^mm2 . Example 6 In Examples 1, 2, and 3, Production Examples 4, 5, and 6
Size-treated carbon fibers were obtained in the same manner except that resin compositions (4), (5), and (6) obtained in (2) were used. The gelling behavior of these sizing agents upon standing at 30°C was determined by the presence or absence of turbidity when carbon fibers were immersed in acetone.
The results are shown in Table 1. From this result, it is clear that there is a difference in the method of adjusting the sizing agent.

[Table] ×: Cloudy

Claims (1)

[Scope of Claims] 1. A method for sizing carbon fibers, which comprises attaching a vinyl ester resin having at least one free hydroxyl group in its molecule in an amount of 0.05 to 5% by weight to carbon fibers. 2. A patent claim characterized in that the vinyl ester resin is made by reacting an epoxy compound with an unsaturated basic acid such that the molar ratio of epoxy groups to acid groups is 1:0.5 to 1.1. A method for sizing carbon fibers according to Scope 1. 3 The composition after the reaction of an epoxy compound and an unsaturated basic acid as a vinyl ester resin has the following constant K.
3. The method for sizing carbon fibers according to claim 2, characterized in that carbon fibers are sized using carbon fibers in which the carbon fiber is 2 or more. K=WPE _R /WPE _O・W ₁ /W ₁ +W ₂ WPE _O : Epoxy equivalent of the raw material epoxy compound (g/eq) _WPER : Epoxy equivalent of the composition after reaction (g/eq)
eq) W ₁ : Weight of raw material epoxy compound (g) W ₂ : Weight of components other than epoxy compound used in reaction (g)