JPH054464B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a sizing agent for carbon fibers. 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, as a sizing agent for carbon fibers, the following ones using aromatic glycidyl ethers and aromatic glycidyl amines have been proposed. 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, when carbon fibers are required to have cohesive strength and especially flexibility when weaving carbon fibers, this performance is extremely insufficient, and the effect of suppressing the occurrence of fuzz and thread breakage during weaving is low. Since this type of sizing agent requires the use of an organic solvent such as methylene chloride or dichloroethane, there is a problem in that it is highly toxic and flammable. 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 has a higher content of epoxy groups than the conventional sizing agent using bisphenol A diglycidyl ether as described above, so the adhesion between the carbon fiber and the matrix resin is better. The interlaminar shear strength of the composite is improved. However, the problem is that the epoxy group tends to change over time, and carbon fibers treated with this sizing agent lose their flexibility and become hard over time, leading to increased fuzz and thread breakage during weaving of the carbon fibers. There is. On the other hand, there is an example in which glycidyl ether or glycidyl ester consisting of an abiethyl group is used as a coupling agent between carbon fibers and matrix resin (Japanese Patent Application Laid-Open No. 144468/1983). This improves the adhesion between the carbon fiber and the unsaturated matrix resin. When this coupling agent is used, compared to the conventional sizing agent using bisphenol A diglycidyl ether mentioned above,
The adhesion between the carbon fibers and the unsaturated matrix resin is improved, and the interlaminar shear strength of the resulting composite is improved. However, since this coupling agent contains only one oxirane ring in its molecule, when it is used in a composite using an epoxy resin as a matrix resin, an intermediate layer formed at the interface between the carbon fiber and the matrix resin The oxirane ring concentration is low, so when carbon fibers coated with this coupling agent are impregnated with matrix resin, the curing agent diffuses from the matrix resin into the coupling agent layer and reacts with the oxirane rings. This is insufficient to form a strong bond, and as a result, the resulting composite still has a problem in that the interlaminar shear strength does not reach a sufficient level. In summary, conventionally proposed sizing agents for carbon fibers provide flexibility to carbon fibers, improve the abrasion resistance of carbon fibers, and suppress the occurrence of fuzz and thread breakage during weaving of carbon fibers. There is no such thing that can fully demonstrate the effect and also exhibit the effect of improving the interlaminar shear strength of the composite obtained by improving the adhesion between carbon fiber and matrix resin, and it depends on the organic solvent used. The reality is that they are toxic and even flammable. <Problems to be Solved by the Invention> The present invention solves the conventional problems as described above, and provides carbon fibers with sufficient cohesion and abrasion resistance, thereby suppressing the occurrence of fuzz and thread breakage. It is essential to greatly improve the handling properties of the carbon fibers, to improve the adhesion between the carbon fibers and the matrix resin, and to impart excellent interlaminar shear strength to the resulting composite, and to use an organic solvent. The object of the present invention is to provide a sizing agent for carbon fibers that can eliminate the danger of toxicity and flammability. <Means for Solving the Problems> As a result of intensive research from the above viewpoint, the present inventors discovered that a specific abiethylamine derivative epoxy compound with a high oxirane ring concentration is correct and suitable, and has developed the present invention. It has come to completion. That is, the present invention relates to a sizing agent for carbon fibers characterized by containing an abiethylamine derivative epoxy compound represented by the following general formula (). General formula (): [However, X, Y are

【formula】

One or more selected from [Formula] may be the same or different at the same time, and if they are different, they may be combined randomly or in a block manner. Here, n is 0 or 1 to 6
an integer, R is hydrogen or a methyl group, R' is hydrogen or

[Formula]. ] The sizing agent according to the present invention has the general formula () in that it does not require the use of an organic solvent.
It is preferable to use an aqueous system containing an abiethylamine derivative epoxy compound represented by the following formula. Containing the abiethylamine derivative epoxy compound in an aqueous system means that the sizing agent is used in a system in which water is the continuous phase. The affinity for water of the abiethylamine derivative represented by the general formula () differs depending on the contents of R, R', and n with respect to X and Y in the general formula (). or exhibit emulsifying properties in the presence of an appropriate emulsifier, for example,
R and R' are methyl groups or

An appropriate emulsifier is required when the formula is [Formula] or when R and R' are both hydrogen and n is smaller than 3. Of course,
Even when the abiethylamine derivative epoxy compound exhibits self-emulsifying properties, there is no problem in using an appropriate emulsifier. In any case, the emulsifiers used in the present invention include polyoxyethylene abiethyl ether, polyoxyethylene hydroabiethyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene benzylated phenyl ether, polyoxyethylene Surfactants such as nonyl phenyl ether are preferred. Regarding X and Y in the general formula (), when both R and R' are hydrogen and n is larger than 6, the abiethylamine derivative epoxy compound has better affinity for water, but adhesion to the matrix resin This is undesirable because it lowers the properties and the interlaminar shear strength of the resulting composite. In general, the interlaminar shear strength of the resulting composite is good when n is close to 3 with respect to X and Y in the general formula (). In addition to the abiethylamine derivative epoxy compound represented by the general formula (), the sizing agent according to the present invention may contain conventional sizing agents, smoothing agents, surfactants, etc., as necessary, to impair the effects of the present invention. It can be contained within a certain range. Examples of sizing agents include epoxy compounds such as bisphenol A diglycidyl ether type, novolak type glycidyl ether type, or N,N,N',N'-tetraglycidyldiaminophenylmethane, and smoothing agents. Examples include fatty acid esters such as stearyl laurate, lauryl stearate, and oleyl oleate, and surfactants include polyoxyethylene (6 mol) nonyl phenyl ether or polyoxyethylene (30 mol) tristyrenated fluoride. There are nonionic surfactants such as enyl 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 abiethylamine derivative epoxy compound represented by the general formula (). The abiethylamine derivative epoxy compound represented by the general formula () consists of a first step of reacting the raw material abiethylamine with glycidol, ethylene oxide and/or propylene oxide without a catalyst;
Next, the reaction product is reacted with epihalohydrin in the presence of an acidic catalyst such as a boron trifluoride ether complex to obtain a halohydrin ether. The third step of producing glycidyl ether by internal ring-closing reaction can be synthesized through the above steps. At this time, by increasing the molar ratio of epihalohydrin to glycidol used in the second step, it is possible to introduce more oxirane rings into the hydroxyl groups of the reaction product in the first step. Epichlorohydrin is industrially more advantageous than phosphorus. <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 dip method, spray method or roller method, and after impregnating the carbon fiber with the sizing agent solution, it is dried using an infrared lamp or hot air. When applied, the sizing agent is made into an aqueous solution or emulsion, or an organic solvent solution, and is usually adjusted to 10% by weight or less, preferably 0.5 to 3% by weight, in terms of the active ingredient.
The amount of the sizing agent attached to the carbon fiber is usually 0.2 to 5% 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) Since carbon fibers can be endowed with excellent cohesive strength and abrasion resistance, the occurrence of fuzz and thread breakage during weaving of the carbon fibers is suppressed, and its handling properties are greatly improved. (2) Coupled with the effect of (1) 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. (3) It does not require the use of organic solvents, can be used in a homogeneous and stable aqueous system, and has no danger of toxicity or flammability. EXAMPLES Hereinafter, the structure and effects of the present invention will be made clearer with reference to Examples, but the present invention is not limited to these Examples. <Example> First, A-1 to A-7 were synthesized using the abiethylamine derivative epoxy compounds represented by the general formula () at molar ratios with the synthesis raw materials listed in Table 1.

[Table] The synthesis methods of A-1 and A-2 are listed below.
The synthesis of A-3 to A-7 was carried out in the same manner as 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. Add abiethylamine (Amine D manufactured by Hercules) into this under a nitrogen stream.
142.5 g (0.5 mol) was added thereto, and 296 g (4 mol) of glycidol was added dropwise over 2 hours while maintaining the temperature at 110 to 130°C. After the dropwise addition was completed, the reaction was continued for 60 minutes to complete. Next, 2.2 g (0.5% by weight) of boron trifluoride etherate was added as a catalyst,
At 60-80°C, 111 g (1.2 mol) of epichlorohydrin was added dropwise. After this, it was stirred for 2 hours at 90-100℃, and at 80-100℃, 64g of potassium hydroxide was added.
A 40% aqueous solution containing (1.2 mol) was added and stirring was continued for 3 hours. After the vacuum treatment, the by-produced salt was removed to obtain product A-1. ●Synthesis method of A-2: Charge 285 g (1 mol) of abiethylamine (previously mentioned) into a 1.5 autoclave, and at 3 to 5 Kg/cm ² at 120 to 140°C.
Glycidol 148g (2 moles) and ethylene oxide
352 g (8 mol) of the mixture was reacted for 3 hours and then aged for 1 hour at the same temperature. This reaction product contains 3.9 g of boron trifluoride etherate.
(0.5% by weight) was added thereto, and then 832 g (9 mol) of epichlorohydrin was added dropwise over 2 hours at 60 to 80°C. After the addition was completed, the mixture was stirred at 90 to 100°C for 2 hours, and at 80 to 100°, a 40% aqueous solution containing 225 g (4 moles) of potassium hydroxide was added, and stirring was continued for 3 hours. After depressurization treatment, remove the by-product salt,
Product A-2 was obtained. Next, using the thus synthesized A-1 to A-7, etc., the sizing agents listed in Table 2 (Examples 1 to 1) were used.
7. Comparative Examples 1 to 4) 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 3. ●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: Add 100 g of Epicote 828 (manufactured by Ciel, bisphenol A diglycidyl 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 rate of 150 times per minute to perform a fiber-to-metal abrasion test. Separately, using a rubbing tester (manufactured by Toyo Seiki Co., Ltd.), an internal angle of 35 degrees, one burn, and a rubbing length of 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). ●Emulsion stability test: A 10% by weight emulsion of the active ingredient of an aqueous emulsion type sizing agent was prepared and left at 20°C for 7 days. And the following 3
Evaluation was made on a graded basis. 〇 = No separation △ = Creamy separated material floated × = Precipitate formed

【table】

【table】

【table】

[Table] Things. From the results in Table 3, it is clear that books such as those mentioned above
The effects of the invention are obvious.

Claims (1)

[Scope of Claims] 1. A sizing agent for carbon fibers, characterized by containing an abiethylamine derivative epoxy compound represented by the following general formula (). General formula (): [However, X and Y are one or more selected from [Formula] [Formula], and may be the same or different at the same time, and if they are different, a random combination or a block combination may be used. Here, n is 0 or 1 to 6
R is hydrogen or a methyl group, R' is hydrogen or [Formula]. 2. The sizing agent for carbon fibers according to claim 1, which contains an aqueous abiethylamine derivative epoxy compound represented by the general formula ().