JPS5914592B2 - Carbon fiber finishing agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a finish for 20 carbon fibers that has the function of facilitating handling of the carbon fibers and improving the composite properties thereof.

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 surfaces25. A conventional method has been to improve the adhesion or affinity between carbon fibers and resin, and then finish the surface with a bisphenol A diglycidyl ether type epoxy resin or a finishing agent containing it as a main component. 30 In this case, the surface oxidation treatment of carbon fibers is only effective for the single purpose of improving the physical properties of the composite, and the surface finishing is effective for improving the handling properties, respectively. I can't hope for a long time.

35- 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 are naturally certain degrees of oxidation. .

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,
e-RlaminarShearStrengthl (hereinafter abbreviated as 1LSS) has not yet reached the performance level required for practical use, and improvements are needed, for example, in the application field of carbon fiber reinforced composite materials where reliability is important. is currently strongly desired. On the other hand, conventional finishing agents for carbon fibers, which are bisphenol A diglycidyl ether type epoxy resins or auxiliary ingredients such as lubricants and softeners added thereto, impart a certain degree of cohesiveness to carbon fibers and are difficult to handle. However, this level of cohesiveness is extremely insufficient when carbon fibers are particularly required to have a binding force, such as when manufacturing carbon fiber fabrics. Further improvement is desired.

Furthermore, the finishing agents for carbon fibers conventionally used do not have the function of improving composite physical properties including ILSS, as described above. In response to this situation, the present inventors have conducted extensive research into a carbon fiber finishing agent that can further actively improve the composite properties of surface-oxidized carbon fibers and facilitate their handling. They discovered a finishing agent for carbon fibers that has these two functions at the same time, and completed the present invention.

That is, the present invention relates to a carbon fiber finishing agent characterized by containing a vinyl-based addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component and a novolac type epoxy resin.

When the finishing agent for carbon fibers according to the present invention is used, the physical properties of carbon fiber composites (
In particular, it is possible to further improve ILSS) by 10 to 25%, and at the same time, it is possible to impart strong cohesiveness to carbon fibers and greatly improve their handling properties.

Furthermore, by using the finishing agent for carbon fibers according to the present invention, it becomes possible to impart appropriate flexibility to carbon fibers. In the finishing agent for carbon fibers according to the present invention, the vinyl-based addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component includes glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether,
α-ethyl glycidyl acrylate, crotonyl glycidyl ether, glycidyl crotonate, glycidyl isocrotonate, monoalkyl itaconate monoglycidyl ester, diglycidyl itaconate, monoalkyl monoglycidyl fumarate ester, diglycidyl fumarate ester, maleic acid Polymerizing one or more oxirane ring-containing ethylenically unsaturated compounds selected from monoalkyl monoglycidyl esters, maleic acid diglycidyl esters, etc., alone or together with other ethylenically unsaturated compounds. A vinyl addition polymer obtained by

These vinyl addition polymers include one or two selected from the aforementioned oxirane ring-containing ethylenically unsaturated compounds.
One or more monomers alone or alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate , alkyl methacrylates such as lauryl methacrylate, styrene, α-
Styrene derivatives such as methylstyrene and vinyltoluene, fatty acid vinyl esters such as vinyl acetate and vinyl propionate, unsaturated hydrocarbons such as butadiene and isoprene, halogenated unsaturated hydrocarbons such as vinyl chloride and chloroprene, acrylonitrile, and methacrylic. Unsaturated nitrile compounds such as nitrile, acrylic acid, methacrylic acid? , itaconic acid, crotonic acid, maleic acid, fumaric acid,
Vinyl acetic acid, α-ethyl acrylic acid, angelic acid; monoethyl ester, monoethyl ester, monobutyl ester of itaconic acid, maleic acid, or fumaric acid; unsaturated fatty acids such as maleic anhydride, itaconic anhydride, etc.
-Hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 2-chloro-3-hydroxypropyl methacrylate, phosphoric acid mono(hydroxypropyl methacrylate) ester, atarylamide, metatarylamide, N-methylolacrylamide, N- Solution polymerization, emulsion polymerization, or suspension polymerization by a conventional method with one or more monomers selected from ethylenically unsaturated compounds such as methoxymethylacrylamide and N-butoxymethylacrylamide. Manufactured by.

The vinyl addition polymer containing at least one oxirane ring-containing monomer unit thus obtained has a glass transition temperature in the range of -10 to 70°C and a solubility parameter of 8.8. (Cal/Cc) ★ or more, the copolymerization rate of the oxirane ring-containing monomer unit is 2 mol % or more, and the intrinsic viscosity at 25°C is, for example, 0.04. d1/9
The above polymers are particularly effective in achieving the desired effects of the present invention.

On the other hand, the novolak type epoxy resin that can be used in the finishing agent for carbon fibers according to the present invention has the general formula ~ (wherein R, Rl, and R2 represent -H or -CH3).

In addition, the polyglycidyl ether of phenol formaldehyde novolak shown in the following chemical formula (1) obtained by the reaction of a novolak type phenolic resin and epichlorohydrin (n is an integer from 1 to 8), and the chemical formula () Typical examples include polyglycidyl ether of cresol formaldehyde novolak shown in .

Further, in the above general formula, an intermediate product in which some of the 12 groups remain as unreacted monoCH groups can also be used as a component of the finishing agent for carbon fibers according to the present invention.

In the finishing agent for carbon fibers according to the present invention, the vinyl addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component imparts strong cohesiveness to the carbon fibers and improves their handling properties. At the same time, the oxirane ring present in the molecule functions to have the effect of improving the physical properties of the carbon fiber composite.

In addition, the combination of the vinyl addition polymer containing the oxirane ring-containing monomer unit as its constituent component and the novolac type epoxy resin, which is the other active ingredient, takes advantage of the polyfunctionality of the latter. It has a synergistic effect of improving the composite physical properties of carbon fibers and at the same time imparting appropriate flexibility to the carbon fibers.

Therefore, extremely high composite physical properties and strong cohesiveness can only be achieved by using a combination of a vinyl addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component and a novolak type epoxy resin. , and appropriate flexibility can be simultaneously imparted to the carbon fiber.

In the carbon fiber finishing agent according to the present invention, at least one
There is no particular restriction on the blending ratio of the vinyl addition polymer containing the oxirane ring-containing monomer unit as a constituent component and the novolak type epoxy resin, but it is important to consider the ease of handling the carbon fiber and the physical properties of the composite. Taking this into consideration, it is practically preferable that the ratio be within the range of 80:20 to 20:80.

However, the optimum mixing ratio of the two varies depending on the priority of the objective effect of sizing, the copolymer composition and molecular weight of the vinyl addition polymer, and therefore, when implementing the present invention, it is necessary to It is important to design the formulation accordingly. For example, in cases where carbon fiber cohesiveness is particularly required, it is extremely effective to increase the blending ratio of the vinyl addition polymer. The carbon fiber finish according to the present invention is typically used as a solution or emulsion.

In this case, the solvent may be a ketone, alcohol, ester, ether, aromatic hydrocarbon, or a mixture thereof, depending on the chemical composition of each component. Furthermore, as the dispersion medium for the emulsion, water or a mixture of water and a water-soluble organic solvent is preferable, and in this case, an anionic surfactant, a nonionic surfactant, or a mixture thereof is usually used as an emulsion stabilizer. used as. The finishing agent for carbon fibers according to the present invention includes, in addition to a vinyl-based addition polymer and a novolak-type epoxy resin containing at least one oxirane ring-containing monomer unit as a constituent component, a diluent, as desired. Auxiliary ingredients such as lubricants, softeners, film-forming aids, etc. may also be included.

In the finishing agent for carbon fibers according to the present invention, diluents that can be contained as desired include n-butyl glycidyl ether, phenyl glycidyl ether, etc.
An example of this can be given.

Furthermore, examples of lubricants that can be included as desired include stearic acid, stearic acid alkyl esters, anionic or nonionic surfactants, and silicon compounds.

However, the use of a lubricant may reduce the interfacial adhesion between the carbon fiber and the resin matrix, so when using a lubricant, it is necessary to carefully select the chemical structure and determine the amount added. On the other hand, in the finishing agent for carbon fibers according to the present invention, examples of softening agents that can be contained as desired include nonionic or anionic surfactants, polyethylene glycol, polypropylene glycol, etc. I can give it to you.

Film-forming aids that can be included as desired include plasticizers such as dibutyl phthalate and dioctyl phthalate, high-boiling organic solvents, and water. When these auxiliary components are contained, the content of these auxiliary components based on the total weight of the vinyl addition polymer containing at least one oxirane ring-containing monomer unit, the novolak type epoxy resin, and these auxiliary components is: 40
It is preferable not to exceed %.

The sizing of carbon fibers using the carbon fiber finishing agent of the present invention is usually carried out by immersing the carbon fibers in a solution or emulsion of the finishing agent and then drying to remove the solvent or dispersion medium. It is done.

The active ingredient concentration of the finishing solution or emulsion is 20
% or less, and is particularly preferably within the range of 0.5 to 5%. Furthermore, when sizing carbon fibers using the finishing agent of the present invention, the amount of the effective ingredients of the finishing agent deposited on the carbon fibers is within the range of 0.2 to 6%, and these ingredients are coated on the surface of the carbon fibers. In order to ensure uniform adhesion, it is preferable to control the concentration of the active ingredient in the sizing bath, the temperature of the sizing bath, the dipping time or dipping speed, the tension of the carbon fiber during dipping, the squeezing conditions after impregnation, the drying conditions, etc.
After impregnating, the carbon fibers passed through the squeezing roller are dried using an infrared lamp, hot air, etc. at a temperature depending on the type of solvent or dispersion medium in the surface finishing agent for a predetermined period of time to remove volatile components. When sizing carbon fibers using the finishes of the present invention, a first component, such as a novolak-type epoxy resin, is first applied to the carbon fibers in the manner described above, and then a second component, such as at least one It can also be carried out by a two-step process in which a vinyl addition polymer containing an oxyla 7-ring-containing monomer unit is attached to carbon fibers.

Carbon fibers to which the carbon fiber finishing 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. Ingredients: pine, textiles,
You can give things like braided things.

Furthermore, the carbon fiber finishing agent of the present invention can be applied regardless of the type of carbonaceous or graphite fiber or single crystal starting material (precursor). Carbonaceous or graphite fibers or single crystals whose surfaces have been surface activated by surface oxidation treatment or other mechanical methods are particularly preferred as targets for application of the finishing agent of the present invention. Examples of the present invention will be described below.

Example 1 Carbon fiber (high strength yarn, tensile strength 300 kg/m", tensile modulus 23 t/M) obtained by finally firing polyacrylonitrile fiber to 1300
d) tow (consisting of 6,000 single yarns with a diameter of approximately 8μ)
was oxidized with an aqueous sulfuric acid solution of potassium dichromate, and then a novolac type epoxy resin 109 with an epoxy equivalent of 175 obtained by reacting a novolac type phenolic resin and epichlorohydrin in the presence of an alkali using a bopin sizer and a solution It was prepared by dissolving 10 g of methyl methacrylate/butyl acrylate/glycidyl methacrylate terpolymer with a copolymerization ratio of 37:32:41 (molar ratio) obtained by a method in acetone 9809. The fibers were sized with a finish solution.

For sizing, the carbon fibers are passed continuously through a bath filled with a finishing agent solution at a speed of 6 m/min. After squeezing it out, it was dried at 75°C for 1 minute. The amount of active ingredients in the finishing agent attached to the carbon fibers was 2.2% based on the carbon fibers. The carbon fiber thus obtained was highly flexible.
Next, the binding force of the obtained carbon fibers was measured using a TM binding force tester.

The ranking of conjugation power was performed according to the following criteria. Note that the binding force test was conducted at a load of 2009. A: Only singular fuzz is generated. B: Multiple fluffs are generated.

C: Fuzz occurs in clusters.

D: Fluff occurs all over the surface.

The results obtained are shown in Table 1.

Next, 40 parts of epoxy resin "Epicote 8828" manufactured by Ciel Corporation and epoxy resin "ECN1235" manufactured by Ciba-Geigi Co., Ltd. (polyglycidyl ether of orthocresol formaldehyde novolac) were added to the carbon fibers obtained here.
40 parts of boron trifluoride monoethylamine, and 16 parts of acetone were continuously impregnated using a drum winder complete impregnation device.

The carbon fiber tow impregnated with a resin solution is wound around a drum wrapped with silicone-treated release paper, aligned parallel to each other, and then the solvent contained in the resin is evaporated, and then 130% resin is applied. A prepreg was prepared by heat treatment at C for 15 minutes.

The prepreg obtained in this way was cut into a length of 280 mm.
After cutting into a size of 1 width 30 m 71 L, stacking 11 sheets and placing them in a mold, they were inserted between the hot plates of a hydraulic press heated to 130°C, and under the pressure of 7 kg/(-Fil). The mixture was heated at 130°C for 30 minutes and then at 170°C for 1 hour.

Then, the molded product was placed in an oven at 170℃ for 2 hours.
Time to do that post cure. The resulting composite contained 56% by volume of carbon fiber, and its L
The SS was measured according to the method of ASTM D-2344 and was found to be 9.10k9/Md.

Example 2 Instead of the finishing agent solution in Example 1, a novolak type epoxy resin 159 with an epoxy equivalent of 172 obtained by reacting a novolak type phenolic resin and epichlorohydrin in the presence of an alkali and a novolak type epoxy resin 159 obtained by a solution polymerization method were used. Except that a finishing agent solution prepared by dissolving methyl methacrylate/butyl acrylate/glycidyl methacrylate terpolymer 59 with a copolymerization ratio of 37:22:41 (molar ratio) in acetone 9809 was used. The carbon fibers were sized in the same manner as in Example 1, and the physical properties of the obtained carbon fibers and composite were measured.

The amount of active ingredients in the finishing agent adhered to the carbon fibers obtained here was 2.4% based on the carbon fibers.

The carbon fiber thus obtained was extremely flexible, and its binding strength was as shown in Table 2.
In addition, the composite made from the carbon fibers obtained here contains 58% by volume of carbon fibers, and its L
SS was 9.031<g/1d.

Example 3 Instead of the finishing agent solution in Example 1, an epoxy resin [EPNll38'' (polyfunctional epoxy novolac resin) 109 manufactured by Ciba-Geigi Co., Ltd. and a copolymerization ratio of 33:24 obtained by a solution polymerization method were used. :43 (molar ratio)
Styrene/butyl acrylate/glycidyl methacrylate terpolymer 109 of acetone 980f! The carbon fibers were sized in the same manner as in Example 1 except that a finishing solution prepared by dissolving the carbon fibers was used, and the physical properties of the obtained carbon fibers and composite were measured.

The amount of active ingredients in the finishing agent adhered to the carbon fibers obtained here was 2.0% based on the carbon fibers.

The carbon fiber thus obtained was highly flexible, and its binding strength was as shown in Table 3. In addition, the composite made from the carbon fibers obtained here has 5
It contains 8% carbon fiber by volume, and its LSS is 8.
971<f! /Md. Example 4 Instead of the finishing agent solution in Example 1, an epoxy resin "ECN1235" (polyglycidyl ether of orthocresol formaldehyde novolac) manufactured by Ciba Geigi Co., Ltd. 109 and a copolymerization ratio of 37 obtained by a solution polymerization method were used. :22:
41 (mole 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 finishing solution prepared by dissolving 09 in acetone 9809 was used, and the physical properties of the obtained carbon fibers and composite were measured.

The amount of active ingredients in the finishing agent adhered to the carbon fibers obtained here was 2.1% based on the carbon fibers.

The carbon fiber thus obtained was highly flexible, and its binding strength was as shown in Table 4. In addition, the composite made from the carbon fiber obtained here was 59
It contains % carbon fiber by volume, and its ILSS is 9.
It was 20 kg/Md.

Comparative Example 1 Instead of the finishing agent solution in Example 1, epoxy resin "Epicoat 8828" 8f! made by Ciel Corporation was used! Carbon fibers were sized in the same manner as in Example 1, except that a finishing solution prepared by dissolving the same company's epoxy resin "Epicoat 81001J129 in methyl ethyl ketone 980f!" was used. and measured the physical properties of the composite.

The amount of active ingredients in the finishing agent adhered to the carbon fibers obtained here was 2.1% based on the carbon fibers.

Further, the binding strength of the obtained carbon fibers was as shown in Table 5. In addition, the composite made from the carbon fibers obtained here contains 60% by volume of carbon fibers,
Its ILSS was 7.45 kg/M77l.

Claims (1)

[Scope of Claims] 1. A carbon fiber finishing agent characterized by containing a vinyl-based addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component and a novolak-type epoxy resin. 2. The vinyl-based addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component is glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, α-ethyl glycidyl acrylate, crotonyl glycidyl ether, glycidyl croto nate, glycidyl isocrotonate, itaconate monoglycidyl ester, itaconate diglycidyl ester,
At least one oxirane ring-containing ethylenically unsaturated compound selected from the group consisting of monoalkyl monoglycidyl fumarate, diglycidyl fumarate, monoalkyl monoglycidyl maleate, and diglycidyl maleate, alone or in combination with other The finishing agent for carbon fibers according to claim 1, which is a vinyl addition polymer obtained by polymerizing with an ethylenically unsaturated compound. 3 Novolac type epoxy resin has the following chemical formula (I)
The carbon fiber finishing agent according to claim 1, which is a compound represented by (II) or (II). (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (n in chemical formula (I) is an integer from 1 to 8)