JPS5911710B2 - carbon fiber sizing agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a sizing agent for carbon fibers.

More specifically, the present invention relates to a carbon fiber sizing agent that facilitates the handling of carbon fibers and improves the physical properties of the composite.

10 Carbon fiber has the characteristics of being lightweight, high strength, and high modulus, so in recent years, along with the decline in its price, it has gained an important industrial position as a reinforcing material for composite materials. It came to be occupied.

One way to make carbon fibers easier to handle and improve their composite properties is to oxidize carbon fibers in the gas or liquid phase and introduce functional groups such as carboxyl groups and phenolic hydroxyl groups onto their surfaces. After improving the interfacial adhesion between carbon fiber and resin, sizing is carried out using bisphenol A diglycidyl ether type epoxy resin or a sizing agent whose main component is bisphenol A diglycidyl ether type epoxy resin.
This has been done for a long time. In this case, surface oxidation treatment of carbon fibers is only effective for the single purpose of improving the physical properties of the composite, and sizing is effective for improving the handling properties, respectively, and sizing is unlikely to improve the physical properties of the composite. I can't hope.

On the other hand, the surface oxidation treatment of carbon fibers must be carried out within the range of negligible weight loss and within the range of not impairing the strength of the fiber itself, and there is a natural limit to the extent.

By performing this surface oxidation treatment, the adhesion between the carbon fiber and the resin is improved, and as a result, the physical properties of the composite are certainly improved.

However, the improvement effect is not necessarily at a practically satisfactory level, and in particular, the interlaminar shear strength (Int), which is one of the most important properties of carbon fiber reinforced composite materials,
er1aMinarShearStrength (hereinafter abbreviated as 1LSS)), it has not yet reached the performance level required for practical use. For example, in the application field of carbon fiber reinforced composite materials where reliability is important, improvements are needed. The current situation is that it is strongly desired. On the other hand, the conventionally used sizing agents for carbon fibers, which are bisphenol A diglycidyl ether type epoxy resins or auxiliary ingredients such as binding agents and softening agents added thereto, impart a certain degree of cohesiveness to carbon fibers. It has the effect of making it easier to handle, but with this level of convergence,
For example, when carbon fibers are particularly required to have binding strength, such as when weaving carbon fiber fabrics, this is extremely insufficient, and further improvement is desired.

Furthermore, as mentioned above, conventionally used sizing agents for carbon fibers do not have the function of improving the physical properties of composites such as 1LSS. As a result of intensive research into a carbon fiber sizing agent that can further actively improve the physical properties of oxidized carbon fiber composites and facilitate its handling, we have discovered a carbon fiber sizing agent that has these two functions at the same time. , completed this invention. That is, this invention is based on the general formula (wherein, X is -CH2-G-CH2, Y is -H or Jk4
-=or -CH2-CH-CH2・R1 and R2 are-
The present invention relates to a carbon fiber sizing agent characterized by containing an alicyclic polyfunctional epoxy compound represented by H or \/ represents -CH3, n and m represent 0 or 1, respectively.

As is well known, the performance of composite materials largely depends on the adhesion between reinforcing fibers and the matrix, and in order to produce composite materials with excellent performance, it is essential to first improve the interfacial adhesion between the two. This is a requirement.

On the other hand, epoxy resins, unsaturated polyesters, polyimides, etc. are usually used as the resin matrix of carbon fiber reinforced composite materials, and the sizing agent for carbon fibers is used not only for the composite but also for the intermediate layer at the interface between these resins and carbon fibers. This results in the formation of The interfacial intermediate layer formed from the sizing agent according to the present invention has an extremely high concentration of oxirane rings, and when carbon fibers coated with the sizing agent are impregnated with a resin matrix, the interfacial intermediate layer of the curing agent from the matrix phase is formed. It is thought that as it diffuses into the carbon fibers, it reacts effectively with the functional groups introduced onto the carbon fiber surfaces, resulting in the formation of strong bonds with the carbon fibers. Further, the interfacial intermediate layer formed from the sizing agent according to the present invention is considered to form an interdiffusion layer with the resin matrix phase and to form a strong bond by taking advantage of its polyfunctionality. When the carbon fiber sizing agent according to the present invention is used, the physical properties of carbon fiber composites (especially 1LSS), which have been improved by surface oxidation treatment, can be further improved by 1LSS.
It becomes possible to improve the carbon fiber by 0 to 30%, and at the same time, it becomes possible to improve the cohesiveness of carbon fiber and improve its handling property.

The alicyclic polyfunctional epoxy compounds used in this invention include N,N,N',N'-tetraglycidyldiaminocyclohexane, N,N,N2-triglycidyldiaminocyclohexane, N,N,NζNf-tetraglycidyl Diamino(methyl)cyclohexane, N,N,N'-triglycidyldiamino(methyl)cyclohexane, N,
N,N',N'-tetraglycidyldiamino(dimethyl)cyclohexane, N,N,N'-triglycidyldiamino(dimethyl)cyclohexane, N,N-diglycidylamino(Nf,Nl-diglycidylaminomethyl)cyclohexane, N-glycidylamino (N5,N'-diglycidylaminomethyl)cyclohexane, N,N-diglycidylamino (N'-glycidylaminomethyl)cyclohexane, N,N-diglycidylaminomethyl (N
f,N'-diglycidylaminomethyl)cyclohexane, N,N-diglycidylaminomethyl (N'-glycidylaminomethyl)cyclohexane, and the like can be used.

These alicyclic polyfunctional epoxy compounds are produced from the corresponding diamine and epichlorohydrin in the presence of an alkali catalyst by a commonly used method.

Hereinafter, the alicyclic polyfunctional epoxy compounds will be collectively referred to as simply alicyclic polyfunctional epoxy compounds.

Suitable solvents for these alicyclic polyfunctional epoxy compounds are alcohols, ketones, esters, or mixed solvents thereof, particularly methyl alcohol, ethyl alcohol, acetone, methyl ethyl ketone, ethyl acetate, or mixed solvents thereof. preferable.

These alicyclic polyfunctional epoxy compounds can be used as a solution in the above solvent or as an emulsion dispersed in water using an anionic surfactant, a nonionic surfactant, or a mixture thereof as an emulsifier. can also be used.

The moon in a solution or emulsion? There is no particular restriction on the concentration of the polyfunctional epoxy compound of the formula, but 20
% or less, and particularly preferably within the range of 0.5 to 5%.

In addition to the alicyclic polyfunctional epoxy compound, the sizing agent of the present invention may optionally contain a sizing agent L softening agent,
It can also contain one or more compounds selected from a sizing agent and a film-forming aid. As agents, stearic acid, stearic acid alkyl ester,
Examples include nonionic surfactants, anionic surfactants, and silicon compounds.

However, if a silicon compound is used in a large amount, the affinity between the carbon fiber and the resin will decrease, so the amount to be blended must be determined carefully. The content of these agents is
30% of the total weight of active ingredients contained in the sizing agent
It is preferable that it is below. As a sizing agent, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate,
Alkyl methacrylates such as lauryl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, alkyl acrylates such as lauryl acrylate, styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinyl acetate, vinyl propionate fatty acid vinyl esters such as, unsaturated hydrocarbons such as butadiene and isobrene, halogenated unsaturated hydrocarbons such as vinyl chloride and chloroprene, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid,
Vinyl acetic acid, alpha-ethyl acrylic acid, angelic acid: monomethyl, monoethyl ester, monobutyl ester of itaconic, maleic, or fumaric acid:
Unsaturated carboxylic acids such as maleic anhydride and itaconic anhydride, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 2-chloro 3-hydroxypropyl methacrylate, phosphoric acid mono(hydroxypropyl methacrylate) ester, acrylamide , methacrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-ptoxymethylacrylamide glycidyl acrylate, glycidyl methacrylate, and other ethylenic feedstock former arsenic compounds. For the vinyl addition polymer obtained by polymerizing a bisphenol A diglycidyl ether type polymer, a polymer relatively compatible with the alicyclic polyfunctional epoxy compound can be used. Epoxy resin, novolak type epoxy resin, polyether or polyester modified flexible epoxy resin, polyimide resin, etc. can be used.

When carbon fibers are particularly required to have cohesiveness, it is extremely effective to add these components to the alicyclic polyfunctional epoxy compound. The content of these sizing agents is preferably 90% or less of the total weight of the active ingredients contained in the lengthening agent. Film forming aids include plasticizers such as dibutyl phthalate and dioctyl phthalate;
Examples include high boiling point organic solvents and water.

The content of these film-forming aids is preferably 30% or less of the total weight of the active ingredients contained in the sizing agent. The alicyclic polyfunctional epoxy compound containing at least 10% of the total weight of its active ingredients (alicyclic polyfunctional epoxy compound, sizing agent, binding agent, softening agent, film forming aid) It is preferable that
It is particularly preferable that the content is 30% or more, and if the content of the alicyclic polyfunctional epoxy compound is less than 10%, the advantages based on its polyfunctionality may not be fully utilized.

The sizing of carbon fibers with the sizing agent according to the present invention is usually carried out by immersing the carbon fibers in the sizing agent (solution or emulsion) and then drying.
This is done by removing the solvent or dispersion medium.

The concentration of the active ingredient in the sizing agent is preferably 25Cf6 or less, particularly preferably in the range of 0.5 to 5%. Furthermore, when sizing carbon fibers using the sizing agent of the present invention, the concentration of the active ingredient in the carbon fiber is Adhesion amount is 0.2~
The concentration of the active ingredient in the sizing bath, the temperature of the sizing bath, the impregnation time or impregnation rate, so that these ingredients are within the range of 6% and uniformly adhere to the carbon fiber surface.
It is preferable to control the tension of the carbon fiber during impregnation, the squeezing conditions after impregnation, the drying conditions, etc. After being impregnated, the carbon fibers passed through the wringer roller are dried using an infrared lamp, hot air, or the like at a temperature depending on the type of solvent or dispersion medium for a predetermined period of time to remove volatile components. When sizing carbon fibers using the carbon fiber sizing agent according to the present invention, the first component, for example, the alicyclic polyfunctional epoxy compound, is attached to the carbon fibers by the method described above, and then the It can also be carried out in a two-step process in which a second component, for example an acrylic resin, is attached to the carbon fibers.

Carbon fibers to which the carbon fiber sizing agent according to the present invention is applied include carbon fibers, graphite fibers, carbonaceous or graphite fibers or single crystals such as graphite whiskers, and carbon fibers or single crystals mainly composed of these fibers or single crystals. Examples include pine, woven fabrics, and braided materials.

Further, the carbon fiber sizing agent according to the present invention can be applied regardless of the starting material (precursor) of carbonaceous or graphite fibers or single crystals. Carbonaceous or graphite fibers or single crystals whose surfaces have been surface-activated by surface oxidation treatment or other methods are particularly preferred as targets for application of the sizing agent of the present invention. Examples of the present invention will be described below. Example 1 Carbon fiber (high strength yarn,
Tensile strength 300kg/ml, tensile modulus 23t/7I7
11) Tow (consisting of 6000 single yarns with a diameter of approximately 8μ)
was oxidized with an aqueous sulfuric acid solution of potassium dichromate, and then 20 g of 1-(N,N-diglycidylaminomethyl)-3-(Nf,N'-diglycidylaminomethyl)cyclohexane was added using a Bopinsizer. The carbon fibers were sized with a sizing agent prepared by dissolving in 980 g of methyl ethyl ketone.The sizing was carried out by passing the carbon fibers continuously through the sizing agent bath at a speed of 67 nm/min, and then removing the sizing agent. Allow it to fully penetrate between the threads,
After squeezing out the excess sizing agent with a squeezing roller, the sample was dried at 70° C. for 1 minute.

The weight of the active ingredient of the sizing agent attached to the carbon fibers was 2.0% based on the weight of the carbon fibers. Next, 43 parts of "Epicoat 828" (trade name of epoxy resin manufactured by Ciel Corporation) and "ECNl235" were added to the carbon fiber thus obtained.
(Product name of epoxy resin manufactured by Civer-Geigy Co., Ltd.; the component is polyglycidyl ether of orthocresol formaldehyde novolac), a resin composition consisting of 43 parts of boron trifluoride monoethylamine, and 10 parts of acetone, Impregnated.

Then, the carbon fiber tow impregnated with the resin solution is wound around a drum wrapped with silicone-treated release paper, aligned parallel to each other, and the solvent contained in the resin is evaporated. A prepreg was prepared by heat treatment at ℃ for 10 minutes. The Bripreg thus obtained was cut into pieces with a length of 280 m and a width of 307 wn, and 11 sheets were laminated and placed in a mold.
Insert it between the hot plates of a hydraulic press that is heated to 0℃, and
The mixture was heated at 130° C. for 30 minutes and then at 170° C. for 1 hour under a pressure of kg/Cfi. The obtained molded article was placed in an oven and post-cured at 170° C. for 2 hours. The resulting composite contained 56% by volume of carbon fiber, and its 1LSS was fused to As-ND-2.
As a result of measurement according to the method of 344, 9.42 kg/C
It was IL.

Example 2 In place of the sizing agent v in Example 1, 11 (N, N
-diglycidylaminomethyl)-3-(Nf,N'-diglycidylaminomethyl)cyclohexane 109 and solution polymerization method, the copolymerization ratio was 37:22:
41 (molar ratio) of methyl methacrylate/butyl acrylate/glycidyl methacrylate terpolymer 1
Carbon fibers were sized in the same manner as in Example 1, except that a sizing agent prepared by dissolving No. 09 in 980 g of methyl ethyl ketone was used.

The amount of active ingredient in the sizing agent attached to the carbon fiber was 2.2% based on the carbon fiber. Next, the binding force of the obtained carbon fibers was measured using a TM type binding force tester.

The ranking of conjugation power was performed according to the following criteria. Note that the binding force test was conducted under a load of 200 g. Rank A: Only singular fuzz is generated. Rank B:
Multiple fluffs occur.

Rank C: Fuzz occurs in clusters.

Rank D: Fluff occurs all over the surface.

The results obtained are shown in Table 1.

Next, a composite was prepared from the carbon fibers obtained here in the same manner as in Example 1, and its rostability was measured.

The resulting composite contained 59% carbon fiber by volume and its 1LSS was 9.35k9/Mit. Example 3 Instead of the sizing agent in Example 1, 1-(N,N
-diglycidylaminomethyl)-3-(Nf,N2-diglycidylaminomethyl)cyclohexane 149,
Carbon fibers were sized in the same manner as in Example 1, except that a sizing agent prepared by dissolving Epicoat 1001 (trade name of epoxy resin manufactured by Ciel Corporation) 69 in methyl ethyl ketone 9809 was used. The composite physical properties of the obtained carbon fibers were measured.

The amount of active ingredient in the sizing agent adhered to the carbon fiber thus obtained was 2.1% based on the carbon fiber.

In addition, the composite made from the carbon fibers obtained here contains 57% by volume of carbon fibers, and 1L of it contains 57% by volume of carbon fibers.
SS is 8.97k9/c! It was i.

Example 4 Instead of the sizing agent in Example 1, l-(N,N
-diglycidyl aluminum methyl)-3-(N'-glycidylaminomethyl)cyclohexane 209 in methyl ethyl ketone 9809. The fibers were sized and the composite properties of the resulting carbon fibers were measured.

The amount of active ingredient in the sizing agent adhered to the carbon fiber thus obtained was 2.0 Cf1) relative to the carbon fiber.

In addition, the composite made from the carbon fibers obtained here contained 57% by volume of carbon fibers, and 1L of the composite contained 57% by volume of carbon fibers.
SS was 9.11 kg/i.

Comparative Example 1 Instead of the sizing agent used in Example 1, a 1:1 mixture 209 of "Epicote 828" (trade name of epoxy resin manufactured by Ciel) and "Epicote 1001" (same as above) was dissolved in 980 g of methyl ethyl ketone. Carbon fibers were sized in the same manner as in Example 1, except that the sizing agent prepared by the method was used, and the composite physical properties of the obtained carbon fibers were measured.

The amount of active ingredient in the sizing agent adhered to the carbon fiber thus obtained was 2.4% based on the carbon fiber.

In addition, the composite made from the carbon fibers obtained here contained 58% by volume of carbon fibers and was 1LS.
S was 7.53 kg/i.

Claims (1)

[Claims] 1 General formula▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, ▼、R_1
and R_2 is -H or -CH_3, n and m are 0
A sizing agent for carbon fibers, characterized in that it contains an alicyclic polyfunctional epoxy compound represented by: