JPH048542B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an aqueous sizing agent for carbon fibers, and more particularly to a sizing agent that facilitates handling of carbon fibers and improves the physical properties of the composite. Carbon fiber is attracting attention as a reinforcing material for composites because it is lightweight, has high strength, and has high modulus. However, since carbon fibers originally have low elongation and are brittle fibers, fluff and thread breakage easily occur due to mechanical friction. These fluffs and yarn breakage significantly reduce the handling properties of the carbon fibers and also reduce the physical properties of the composite. Therefore, a sizing agent is added to the carbon fibers, and the sizing agent bundles the carbon fibers, gives flexibility to the carbon fibers, improves the abrasion resistance of the carbon fibers, and also improves the abrasion resistance of the carbon fibers. Efforts have been made to improve the essentially insufficient fitability between the composites and the composites and to improve the interlaminar shear strength of the resulting composites. The present invention relates to such a sizing agent. <Prior art and its problems> Conventionally, the following sizing agents for carbon fibers have been proposed using aromatic glycidyl ethers and aromatic glycidyl amines. First, there is a sizing agent that uses bisphenol A diglycidyl ether (Japanese Patent Publication No. 57-
15229). This uses a compound similar to that of the matrix resin in order to improve the adhesion between the carbon fiber and the matrix resin. Sizing agents of this type certainly improve the adhesion. However, since it uses organic solvents such as methylene chloride and dichloroethane,
There is a problem that the danger of toxicity and flammability is high, and that the effect of suppressing the occurrence of fuzz and thread breakage during weaving of carbon fibers is low. In addition, a sizing agent that uses bisphenol A type epoxy resin (a mixture of Epicote 828 and Epicote 1001 in a specific ratio, both manufactured by Ciel) as an aqueous emulsion using a polyoxyethylene nonionic surfactant as an emulsifier. There is (Japanese Patent Application Laid-Open No. 57-171767). In this case, since no organic solvent is used, there is no danger of toxicity or flammability. However, even if the type and amount of emulsifier used is specified, there is a problem that it is difficult to satisfy both the suppression of fuzz and thread breakage during weaving of carbon fibers and the interlayer shear strength of the resulting composite. There is also a sizing agent using N,N,N',N'-tetraglycidylphenylenediamine (Japanese Patent Publication No. 59-9664). This improves the adhesion between the carbon fiber and the matrix resin. This type of sizing agent provides better adhesion between carbon fibers and matrix resin than the conventional sizing agent that uses bisphenol A diglycidyl ether, and improves the interlaminar shear strength of the resulting composite. . However, since the epoxy group contains a tertiary amino group, the epoxy group changes over time, and as a result, the carbon fiber treated with the sizing agent loses its flexibility over time and becomes hard. There is a problem that fuzz and thread breakage increase during weaving. In summary, the conventionally proposed sizing agents for carbon fibers are those that are free of toxicity or flammability, or those that improve the adhesion between carbon fibers and matrix resin to improve the interlaminar shear strength of the resulting composite. However, there is no one that fully exhibits both of these effects and at the same time sufficiently exhibits the effect of suppressing the occurrence of fuzz and thread breakage in the weaving of carbon fibers. <Problems to be Solved by the Invention> The present invention solves the conventional problems as described above, eliminates the necessity of using organic solvents, eliminates the danger of toxicity and flammability, and It provides carbon fibers with sufficient binding strength and abrasion resistance, suppresses the occurrence of fuzz and thread breakage, greatly improves the handling properties of carbon fibers, and also improves the adhesion between carbon fibers and matrix resin. The present invention provides an aqueous sizing agent for carbon fibers that imparts excellent interlaminar shear strength to the resulting composite. <Means for Solving the Problems> However, as a result of intensive research from the above viewpoint, the present inventors have determined that an aqueous sizing agent for carbon fibers containing a specific bisphenol type polyalkylene ether epoxy compound as a main component is correct. The present inventors have found that this is suitable and have completed the present invention. That is, the present invention is characterized by containing 50 to 100% by weight of a bisphenol type polyalkylene ether epoxy compound represented by the following general formula () or () and 0 to 50% by weight of a nonionic surfactant. This invention relates to an aqueous sizing agent for carbon fibers. General formula (): General formula (): [However, R is an alkylene group having 2 to 4 carbon atoms {which may be used alone or in combination, and in the case of a mixture, it may be either a block bond or a random bond}. Y is

【formula】

[Formula] or -CH ₂ -. n is an integer from 5 to 30. X is a residue selected from the following () or () {in these residues, -O- is bonded to the terminal glycidyl group of the general formula ()}. ()

[Formula] (Z ₁ and Z ₂ are CH ₃ − or

【formula】) ()

[Formula] or

[Formula] (Z ₃ is R′O − or

[Formula], where R' is an alkyl group, alkenyl group, or substituted phenyl group having 1 to 18 carbon atoms)] In the above general formula () or (), n is 5
An integer of ~20 is preferred. This is because it has an excellent effect of suppressing the occurrence of fuzz and yarn breakage, and an effect of improving the interlayer shear strength of the resulting composite. In addition, in the general formula () or (), n is 5
is an integer of ~20, and R is ethylene group / propylene group + butylene group ≧ 8/2 (molar ratio),
More preferred. In this case, the bisphenol type polyalkylene ether epoxy compound represented by the general formula () or () comes to exhibit self-emulsifying properties in water, and the interlayer shear strength of the resulting composite is further improved, etc. This is because the effects of the present invention will be more pronounced. In addition to the bisphenol type polyalkylene ether epoxy compound represented by the general formula () or (), the sizing agent according to the present invention optionally contains a nonionic surfactant in an amount of 50% by weight or less. It can contain. Examples of such nonionic surfactants include polyoxyethylene (6 mol) nonyl phenyl ether, polyoxyethylene (30 mol) tristyrenated phenyl ether, and the like. In either case, the sizing agent according to the present invention contains 50% by weight or more, preferably 90% by weight or more of the bisphenol type polyalkylene ether epoxy compound represented by the general formula () or (). <Effects, etc.> The sizing agent according to the present invention is applied to various carbon fibers (including graphite fibers) such as PAN-based, pitch-based, or rayon-based, and exhibits the desired effects. The specific application method may be any conventional method such as a dip method, a spray method, or a roller method, and after impregnating the carbon fiber with the sizing agent, it is dried with hot air, an infrared lamp, or the like. When applying, use a sizing agent,
An aqueous emulsion is prepared as it is or with a small amount of a nonionic surfactant, and the amount is usually adjusted to 25% by weight or less, preferably 0.5 to 5% by weight in terms of active ingredients.
The amount of the sizing agent attached to the carbon fiber is usually 0.2 to 6% by weight, preferably 0.3% by weight in terms of the active ingredient.
~2% by weight. <Effects of the Invention> As explained above, the present invention has the following effects in summary. (1) It can be made into a homogeneous and stable aqueous emulsion as it is or with a small amount of nonionic surfactant, and can be applied to carbon fibers in this state, so there is no danger of toxicity or flammability. (2) Since carbon fibers can be endowed with excellent cohesion and abrasion resistance, the occurrence of fuzz and yarn breakage during weaving of the carbon fibers is suppressed, and its handling properties are greatly improved. (3) Coupled with the effects of (1) and (2) above, the adhesion between the carbon fiber and the matrix resin is also good, so the interlaminar shear strength of the resulting composite is also improved. <Example> First, the following A-1 to A-7 were synthesized with respect to the bisphenol type polyalkylene ether epoxy compounds represented by the general formula () or (). ●A-1: In the general formula (), R is an ethylene group, Y is

[Formula] n is 10. ●A-2: In the general formula (), R is an ethylene group, Y is

[Formula] n is 15, X is ●A-3: In the general formula (), R is an ethylene group, Y is

[Formula] n is 20, X is ●A-4: In the general formula (), R is a propylene group/ethylene group, Y is

[Formula] n is 20. However, random bonding with propylene group/ethylene group = 30/70 (mole ratio). ●A-5: In the general formula (), R is a propylene group/ethylene group, Y is

[Formula] n is 15. However, random bonding with propylene group/ethylene group = 30/70 (mole ratio). ●A-6: In the general formula (), R is a propylene group/ethylene group, Y is -CH ₂ -, n is 20, X
but

[Formula] However, random bonding with propylene group/ethylene group = 70/30 (mole ratio). ●A-7: Same as A-6. However, propylene group/
Random bonding with ethylene groups = 10/90 (mole ratio). Synthesis methods for A-1 to A-3 are listed below. The synthesis of A-4 to A-7 was carried out according to the synthesis of A-1 to A-3. ●Synthesis method of A-1: A 1-volume four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer was used. To this flask were added 500 g (0.5 mol) of polyalkylene ether with a molecular weight of 1000, obtained by addition-polymerizing ethylene oxide using bisphenol A as a starting material, and 6.0 g (0.1% by weight) of tetraethylene ammonium chloride, and then heated at 60 to 80°C. Epichlorohydrin 92.5g
(1.0 mol) was added dropwise. 90-100 after completion of dripping
After stirring for 2 hours at 80-100°C, 56.1 g (1.0 mol) of potassium hydroxide was added, and stirring was continued at that temperature for 3 hours. Then, the by-produced salt was removed to obtain product (A-1). ●Synthesis method of A-2: Add 129 g (1.0 mol) of dimethyldichlorosilane and 79.1 g (1.0 mol) of pyridine to the same flask as in the case of A-1.
Further, 500 g (0.5 mol) of polyalkylene ether having a molecular weight of 1000, which was obtained by addition polymerizing ethylene oxide using bisphenol A as a starting material, was added dropwise at 40° C. or below, and the mixture was stirred for 2 hours after the addition was completed. Next, 79.1 g (1.0 mol) of pyridine and 74 g (1.0 mol) of glycidol were added dropwise at 40° C. or below, and after the dropwise addition was completed, the mixture was stirred at room temperature for 2 hours. Then, the by-produced salt was removed to obtain a product (A-2). ●Synthesis method of A-3: Add 133.3 g (1.0 mol) of phosphorus oxychloride and 79.1 g (1.0 mol) of pyridine to the same flask as in the case of A-1, and then add ethylene oxide using bisphenol A as a starting material. 500 g (0.5 mol) of polyalkylene ether with a molecular weight of 1000 obtained by addition polymerization was added dropwise at 40° C. or lower, and the mixture was stirred for 2 hours after the addition was completed. Next, 158.2g (2.0mol) of pyridine and 148g of glycidol.
(2.0 mol) was added dropwise below 40℃, and the following A-2
Product (A-3) was obtained in the same manner as in the case of . Next, using the thus synthesized A-1 to A-7, etc., the sizing agents listed in Table 1 (Examples 1 to 7,
Comparative Examples 1 to 3) were prepared. In each case, carbon fibers were treated and composites were molded and tested and evaluated as follows. The results are shown in Table 2. ●Sizing treatment of carbon fiber: Commercially available PAN-based carbon fiber (8μ/3000 filament) is desized with an organic solvent, and impregnated with each sizing agent using the dip method so that the amount of active ingredient attached is 0.7% by weight. After drying, heat in the oven at 150℃
Heat treated for 30 minutes. ●Composite molding: Add 100 g of Epicote 828 (manufactured by Ciel, bisphenol A dicrycidyl ether monomer) + 5 g of boron trifluoride monomethylamine + methyl ethyl ketone to the carbon fiber sized as described above.
It was impregnated with 25g of resin liquid and semi-cured at 120°C to create a unidirectional prepreg. This prepreg was laminated in a mold and pressurized at 170°C for 1 hour to form a composite with Vf (volume % of carbon fiber in the composite) = 60%. - Fluff and yarn breakage test: Carbon fibers sized as described above were tested using a TM type conjugation force tester (manufactured by Daiei Kagaku Seiki Co., Ltd.) at a load of 50 g/
3000 filament, θ=150 degrees, rubbing length 30 mm,
A chrome-plated metal comb was reciprocated 500 times at a speed of 150 times/minute to perform a fiber-to-metal abrasion test. Separately, using a rubbing tester (manufactured by Toyo Seiki Co., Ltd.), the inner angle was 35 degrees, the twist was made once, and the rubbing length was 20.
mm, reciprocate 500 times at a speed of 100 times/min,
A fiber-to-fiber abrasion test was conducted. Both were evaluated using the following 5-level criteria. A = Almost no fluff is generated. B=Only singular fuzz is generated. C=Fuzz occurs in clusters. D=Fuzzing occurs frequently and some parts are cut off. E=3000 filament breaks. ●Interlaminar shear strength test: The composite molded as described above was measured according to ASTM D-2344 (ILSS). ●Emulsification stability test: 10 active ingredients of each sizing agent
A weight percent emulsion was prepared and left at 20°C for 7 days. Then, evaluation was made using the following three-level criteria. ○ = No separation △ = Creamy separated material floated × = Precipitate formed

【table】

【table】

【table】

[Table] Things.
From the results in Table 2, the effects of the present invention as described above are clear.

Claims (1)

[Claims] 1. Contains 50 to 100% by weight of a bisphenol type polyalkylene ether epoxy compound represented by the following general formula () or () and 0 to 50% by weight of a nonionic surfactant. Characteristic water-based sizing agent for carbon fiber. General formula (): General formula (): [However, R is an alkylene group having 2 to 4 carbon atoms {which may be used alone or as a mixture, and in the case of a mixture, it may be either a block bond or a random bond}. Y is [Formula] [Formula] or -CH ₂ -. n is an integer from 5 to 30. X is a residue selected from the following () or () {in these residues, -O- is bonded to the terminal glycidyl group of the general formula ()}. () [Formula] (Z ₁ and Z ₂ are CH ₃ − or [Formula]) () [Formula] or [Formula] (Z ₃ is R′O − or [Formula], where R′ is the number of carbon atoms 1 to 18, alkyl group, alkenyl group, or substituted phenyl group)] 2 In the general formula () or (), n is 5 to
The aqueous sizing agent for carbon fibers according to claim 1, which is an integer of 20. 3. The aqueous sizing agent for carbon fibers according to claim 2, wherein in the general formula () or (), R is ethylene group/propylene group+butylene group≧8/2 (molar ratio).