JPH0367143B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a 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 adhesion between the composite and the resin to increase the interlaminar shear strength of the resulting composite. 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 Ebikoat 828 and Epicoat 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 during 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, greatly improves the handling properties of carbon fibers by suppressing the occurrence of fuzz and thread breakage, and also improves the adhesion between carbon fibers and matrix resin. The present invention provides a sizing agent for carbon fibers that imparts excellent interlaminar shear strength to the resulting composite. <Means for Solving the Problems> As a result of intensive research from the above viewpoint, the present inventors discovered that a specific polyalkylene ether epoxy compound is correct and suitable, and have completed the present invention. Ivy. That is, the present invention relates to a sizing agent for carbon fibers characterized by containing a polyalkylene ether epoxy compound represented by the following general formula (). General formula ();

[Formula] [However, Z is a residue of mono- to trivalent alcohol or phenol. R is selected from alkylene groups having 2 to 4 carbon atoms, singly or as a mixture, and in the case of a mixture, the part between the l's is a block or random bond. Y is

[Formula] Can be used alone or in combination with OH. In the case of a mixture, the part enclosed by m is a block or random bond. The part enclosed by n is the part enclosed by l and m
The enclosed parts are blocks or random connections. X is H or

[Formula] l is an integer from 0 to 40, m is an integer from 1 to 5, and n is an integer from 1 to 3 determined by the valence of Z. ] Regarding Z in the above general formula (), examples of monohydric alcohols include ethanol, propanol, butanol, octanol, dodecanol, etc., and examples of dihydric alcohols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, and triethylene glycol. , polyethylene glycol, polytetramethylene glycol, polypropylene glycol, etc. Further, trivalent alcohols include glycerin, trimethylolethane, trimethylolpropane, etc.
Regarding Z, monovalent phenols include phenol, phenylphenol, octylphenol, nonylphenol, styrenated phenol, benzylated phenol, cumylphenol, cresol, etc., and divalent phenols include bisphenol A. , bisphenol F, bisphenol S, hydroquinone, resorcinol, and trivalent phenols such as pyrogallol. Among these, bisphenols, therefore Z is preferably a bisphenol residue. 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. Further, in the general formula (), l is an integer of 5 to 10, and R is an ethylene group/propylene group + butylene group ≧4/1 (molar ratio)
It is even more preferable. In this case, the polyalkylene ether epoxy compound represented by the general formula () exhibits solubility or self-emulsifying property in water, and the interlaminar shear strength of the resulting composite is further improved. This is because the effect becomes even more pronounced. In addition to the polyalkylene ether epoxy compound represented by the above general formula (), the sizing agent according to the present invention may optionally contain conventional sizing agents, smoothing agents, surfactants, etc. to achieve the effects of the present invention. It can be contained within a range that does not cause any damage. To illustrate these, examples of the sizing agent include bisphenol A diglycidyl ether type, noporak type glycidyl ether type, or N,N,N',
There are epoxy compounds such as N'-tetraglycidyldiaminodiphenylmethane, smoothing agents include fatty acid esters such as stearyl laurate, lauryl stearate, and oleyl oleate, and surfactants include polyoxyethylene ( Non-ionic surfactants such as 6 mol) nonyl phenyl ether or polyoxyethylene (30 mol) tristyrenated phenyl ether. In either case, the sizing agent according to the present invention usually contains 10% by weight or more, preferably 50% by weight or more of the polyalkylene ether epoxy compound represented by the general formula (). <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 applied, the sizing agent is used as is or in the form of an aqueous solution or emulsion with a small amount of emulsifier, usually 25% by weight calculated as the active ingredient.
Hereinafter, it is preferably adjusted to 0.5 to 5% by weight. The amount of the sizing agent attached to the carbon fiber is usually 0.2 to 6% by weight, preferably 0.3 to 6% by weight in terms of the active ingredient.
It is 2% by weight. <Effects of the Invention> As explained above, the present invention has the following effects in summary. (1) Can be made into a homogeneous and stable aqueous solution or aqueous emulsion as is or with a small amount of emulsifier;
Since it can be applied to carbon fiber in this state, 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, for the polyalkylene ether epoxy compound represented by the general formula (), the following A-1
~A-9 was synthesized. A-1; (X ¹ ) (AY ¹ ) (E) ₅ (Z ¹ ) (E) ₅ (AY ¹ )
(X ¹ ) [However, X ¹ is

[Formula] A is

[Formula] Y ¹ is

[However, ^Y2 is -OH and P is an oxypropylene group. These are the same below. random〕

A-3; (Z ² ) (E) ₄ (AY ¹ ) ₃ (X ₁ ) [However, Z ² is

[Formula] Random] A-4; (Z ³ ) [(E) ₄ (AY ² ) (X ¹ )] ₃ [However, Z ³ is

[However, Z ⁴ is -OCH ₂ CH ₂ O-. random〕

A-6; (X ¹ ) (AY ¹ ) ₂ (P) ₆ (E) ₂ (Z ⁵ ) (E) ₂
(P)
₆ (AY ¹ ) ₂ (X ¹ ) [However, Z ⁵ is a bisphenol S residue. Random] A-7; (Z ⁶ ) (E) ₄ (AY ¹ ) ₂ (X ¹ ) [However, Z ⁶ is C ₁₂ H ₂₅ O-. Random] A-8; (X ¹ ) (AY ¹ ) ₂ (P) (E) ₆ (Z ¹ ) (E) ₆ (
P)
(AY ¹ ) ₂ (X ¹ ) [However, block] A-9; (X ¹ ) (AY ¹ ) ₃ (E) ₇ (Z ⁵ ) (E) ₇ (AY ¹ ) ₃
(X ¹ ) [However, block] Synthesis methods for A-1 and A-2 are listed below. The synthesis of A-3 to A-9 was carried out according to the synthesis of A-1 and A-2. 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. In this flask, 334 g (0.5 mol) of polyoxyethylene ether with a molecular weight of 668, obtained by addition polymerization of 10 mol of ethylene oxide using bisphenol A as a starting material, and 6.7 g of potassium hydroxide.
(2.0% by weight) was added thereto, and 74 g (1.0 mol) of glycidol was added dropwise at 150 to 160° C. over a period of 3 hours. After the dropwise addition was completed, the mixture was stirred at the same temperature for 1 hour, and the potassium hydroxide was neutralized with orthophosphoric acid. Furthermore, add 2.0g (0.5% by weight) of boron trifluoride etherate and heat at 60-80℃.
Then, 407 g (4.4 mol) of epichlorohydrin was added dropwise. Subsequently, stir at 90-100℃ for 2 hours, and then stir at 80-100℃.
At 100° C., a 40% aqueous solution containing 247 g (4.4 mol) of potassium hydroxide was gradually added, and stirring was continued at that temperature for 3 hours. After dehydration under reduced pressure, by-produced salts were removed to obtain product (A-1). Synthesis method of A-2: A 1.5 autoclave was used. In this autoclave, 228 g (1.0 mol) of bisphenol A and 250 g of xylene were added as a solvent.
ml and 7.0 g of potassium hydroxide as a catalyst.
A mixture of 352 g (8 mol) of ethylene oxide, 348 g (6 mol) of propylene oxide, and 444 g (6 mol) of glycidol was introduced under pressure at 110 to 120°C and 3 to 5 kg/cm ² over 6 hours to react. Ta. After the injection, the mixture was stirred for 2 hours at 125° C. and 5 kg/cm ² . The reaction product was taken out, the catalyst was separated using an adsorbent, and the solvent was removed to obtain 1360 g of polyalkylene glycol ether. Add 6.8 g (0.5% by weight) of boron trifluoride etherate to this product, and add epichlorohydrin at 60-80°C.
204 g (2.2 mol) was added dropwise. After completion of dripping, 90~
The mixture was stirred at 100°C for 2 hours, a 40% aqueous solution containing 124 g (2.2 mol) of potassium hydroxide was added at 80-100°C, and stirring was continued at the same temperature for 3 hours. After vacuum dehydration,
The by-produced salt was removed to obtain a product (A-2). Next, using the thus synthesized A-1 to A-9, etc., the sizing agents listed in Table 1 (Examples 1 to 9,
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 (7μ/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 1.0% by weight. and dried in an oven at 120°C for 5 minutes. ●Composite molding: 100 g of Epicote 828 (manufactured by Ciel, bisphenol A diglycidyl ether monomer) + 5 g of porontrifluoride 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%. ●Fuzz 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 per 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
A fiber-to-fiber abrasion test was performed by reciprocating 500 times at a speed of 20 mm and 100 times/min. Both were evaluated using the following 5-level criteria. A = Almost no fuzz 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. ●Comprehensive evaluation of fuzz and thread breakage: A comprehensive evaluation of fuzz and thread breakage was made using the following two-level criteria. Good = If the results of the above TM formula and rubbing formula are both A or B. Bad = If the results of the above TM formula and rubbing formula are C, D, or E. Interlaminar shear strength test: As above The molded composite 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. 〇 = No separation △ = Creamy separated substance floated × = Precipitation occurred

【table】

【table】

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

Claims (1)

[Scope of Claims] 1. A sizing agent for carbon fibers, characterized by containing a polyalkylene ether epoxy compound represented by the following general formula (). General formula ();
[Formula] [However, Z is a residue of mono- to trivalent alcohol or phenol. R is selected from alkylene groups having 2 to 4 carbon atoms, singly or as a mixture, and in the case of a mixture, the part between the l's is a block or random bond. Y is [Formula] alone or a mixture of this and OH, and in the case of a mixture, the part enclosed by m is a block or random bond. The part enclosed by n is the part enclosed by l and m
The enclosed parts are blocks or random connections. X is H or [Formula] l is an integer from 0 to 40, m is an integer from 1 to 5, and n is an integer from 1 to 3 determined by the valence of Z. 2. The sizing agent for carbon fibers according to claim 1, wherein Z in the general formula () is a bisphenol residue. 3 In the general formula (), l is an integer of 5 to 10, and R is an ethylene group/propylene group + butylene group ≧4/1
(molar ratio) The sizing agent for carbon fibers according to claim 2.