JPS5914591B2 - Finishing agent for carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a finishing agent for carbon fibers that has the function of facilitating the handling of carbon fibers and improving the physical properties of composites thereof.

15 A method for making carbon fibers easier to handle and improving their composite properties is to oxidize carbon fibers in the gas phase or liquid phase and introduce functional groups such as carboxyl groups and phenolic hydroxyl groups onto the surface. , after improving the adhesion or affinity between carbon fiber and resin,
Conventionally, a method of finishing the surface with a bisphenol A diglycidyl ether type epoxy resin or a soil filler containing it as a main component has been carried out.

In this case, the surface oxidation treatment of carbon fiber 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. Improvement in physical properties cannot be expected at all.

On the other hand, the surface oxidation treatment of carbon fibers must be carried out within a range of negligible weight loss of about 30% and within a range that does not impair 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 (Nter-1aMinerShearStrength), which is one of the most important characteristics of carbon fiber reinforced composite materials, is not necessarily at a practically satisfactory level.
h, hereafter abbreviated as 1LSS), it has not yet reached the performance level required for practical use. The current situation is that it is strongly desired.

On the other hand, conventionally used carbon fiber fillers are made by adding bisphenol A diglycidyl ether type epoxy resin or auxiliary ingredients such as lubricants and softening agents to it.
Although it has the effect of imparting a certain degree of cohesiveness to carbon fibers and making it easier to handle, this level of cohesiveness requires a particular cohesive force from the carbon fibers, for example, when manufacturing carbon fiber fabrics. In some cases, it is extremely insufficient, and more soil is desired. Furthermore, as mentioned above, the finishing agent for carbon fibers that has been conventionally used is ILSS
It does not have the function of improving the physical properties of the composite, such as In response to this situation, the present inventors
As a result of extensive research into carbon fiber finishing agents that can further improve the composite physical properties of surface-oxidized carbon fibers and make them easier to handle, we have developed a carbon fiber finishing agent that has these two functions at the same time. This finding led to the completion of the present invention.

That is, the present invention relates to a vinyl addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component and a polyglycidyl ether of a trihydric or higher aliphatic polyhydric alcohol having three or more glycidyl ether groups. The present invention relates to a soil filler for carbon fibers characterized by containing the following.

By using the finishing agent for carbon fibers of the present invention, it is possible to further improve the composite physical properties (especially ILSS) of carbon fibers that have been improved by surface oxidation treatment by 10 to 25%, and at the same time, it is possible to improve the composite properties of carbon fibers by 10 to 25%. Gives strong focusing,
It is possible to greatly improve its handling properties. Furthermore, by using the finishing agent for carbon fibers of the present invention, it becomes possible to impart appropriate flexibility to carbon fibers. In the soil agent for carbon fibers of the present invention, the vinyl 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,
One or two selected from monoalkyl monoglycidyl itaconate, siglycidyl itaconate, monoalkyl monoglycidyl fumarate, diglycidyl fumarate, monoalkyl monoglycidyl maleate, diglycidyl maleate, etc. A vinyl addition polymer obtained by polymerizing one or more oxirane ring-containing ethylenically unsaturated compounds, either alone or together with other ethylenically unsaturated compounds.

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, lauryl methacrylate Alkyl methacrylates such as styrene, α-methylstyrene, styrene derivatives such as vinyltoluene, fatty acid vinyl esters such as vinyl acetate and vinyl propionate, unsaturated hydrocarbons such as butadiene and isoprene, halogenated vinyl chloride, chloroprene, etc. Unsaturated hydrocarbons, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, acrylic acid, methacrylic acid, itaconic acid,
Crotonic acid, maleic acid, fumaric acid, vinyl acetic acid, alpha-ethyl acrylic acid, angelic acid; monomethyl ester, monoethyl ester, monobutyl ester of itaconic acid, maleic acid, or fumaric acid; maleic anhydride, itaconic anhydride, etc. unsaturated fatty acids, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 2-chloro-3-hydroxypropyl methacrylate, phosphoric acid mono(hydroxypropyl methacrylate) ester, acrylamide, methacrylamide, N-
Solution polymerization by a conventional method with one or more monomers selected from ethylenically unsaturated compounds such as methylol acrylamide, N-methoxymethyl acrylamide, N-butoxymethyl acrylamide, etc.
Manufactured by emulsion polymerization or suspension polymerization.

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 in a methyl ethyl ketone solution.
The above-mentioned polymers are particularly effective in achieving the desired effects of the present invention.

On the other hand, examples of polyglycidyl ethers of trivalent or higher aliphatic polyhydric alcohols having three or more glycidyl ether groups that can be used in the finishing agent for carbon fibers of the present invention include (1) propane such as glycerin; Triglycidyl ether of triol, butanetriol, pentanetriol, hexanetriol (2) Triglycidyl ether or tetraglycidyl ether of pentanetetrol, hexanetetrol such as erythritol, threitol, pentaerythritol (3) Triglycidyl ether of adonitol, arabitol, xylitol Glycidyl ether, tetraglycidyl ether, or pentaglycidyl ether (4) allodulcitol, talitol,
Examples include triglycidyl ether, tetraglycidyl ether, pentaglycidyl ether, or hexaglycidyl ether of sorbitol, mannitol, and galactitol. These polyglycidyl ethers are produced from the corresponding polyhydric alcohol and epichlorohydrin by commonly used methods.

In the soil filler for carbon fibers of the present invention, the vinyl-based 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 improve the physical properties of the carbon fiber composite.

In addition, the polyglycidyl ether, which is the other active ingredient, has the effect of greatly improving the composite physical properties of carbon fibers by taking advantage of its polyfunctionality, and at the same time imparting appropriate flexibility to carbon fibers. have.

Therefore, extremely high composite physical properties and strong cohesiveness can only be obtained by using a vinyl addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component in combination with the above-mentioned polyglycidyl ether. , and appropriate flexibility can be simultaneously imparted to the carbon fiber.

In the carbon fiber finishing agent of the present invention, there is no particular restriction on the blending ratio of the vinyl addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component and the polyglycidyl ether; Considering the ease of handling the fibers and the physical properties of the composite, a ratio of 80:20 to 20:80 is practically preferable.

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 soil filler for carbon fibers of the present invention is usually 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 soil agent for carbon fibers of the present invention contains, in addition to a vinyl addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component and the polyglycidyl ether,
If desired, auxiliary ingredients such as diluents, lubricants, softeners, film-forming aids, etc. can also be included.

In the finishing agent for carbon fibers of the present invention, examples of diluents that can be included as desired include n-butyl glycidyl ether, phenyl glycidyl niter, and the like.

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 of the present invention, examples of softening agents that can be contained as desired include nonionic or anionic surfactants, polyethylene glycol, polypropylene glycol, etc.
An example of this can be given.

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 polyglycidyl ether, and these auxiliary components is , 40
It is preferable not to exceed %.

The sizing of carbon fibers using the finishing agent for carbon fibers 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 impregnation, 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 finishing agent for a predetermined period of time to remove volatile components. When sizing carbon fibers using the soil filler of the present invention, the first component, for example, the polyglycidyl ether, is first attached to the carbon fibers by the method described above,
It can also be carried out in a two-step process in which a second component, for example a vinyl addition polymer containing at least one oxirane ring-containing monomer unit, is then deposited on the carbon fibers. Carbon fibers to which the finishing agent for carbon fibers 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.

Furthermore, the soil filler for carbon fibers 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 methods are particularly preferred as targets for application to the finishing agent of the present invention. Examples of the present invention will be described below.

Example 1 Polyacrylonitrile fibers were finally heated to 1300°C.
Carbon fiber obtained by firing to
tow (consisting of 6,000 single yarns with a diameter of about 8P),
After oxidation treatment with a sulfuric acid aqueous solution of potassium dichromate,
Glycerin triglycidyl ether 159 and 5 g of methyl methacrylate/butyl acrylate/glycidyl methacrylate terpolymer with a copolymerization ratio of 37:22:41 (mole ratio) obtained by a solution polymerization method were added using a Bopin sizer. , methyl ethyl ketone 9809.

For sizing, the above-mentioned carbon fibers are passed continuously through a bath filled with a finishing agent solution at a speed of 6 m/min. This was done by squeezing it out and drying it at 75°C for 1 minute.

The amount of active ingredient in the finishing agent attached to the carbon fiber was 2.3% based on the carbon fiber. The carbon fiber thus obtained was extremely flexible. 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 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, to the carbon fiber obtained here, 40 parts of epoxy resin "Epicoat 828" manufactured by Ciel Corporation, 40 parts of epoxy resin "ECN1235" (polyglycidyl ether of orthocresol formaldehyde novolac) manufactured by Ciba-Geigi Co., Ltd., 4 parts of boron trifluoride monoethylamine,
and 16 parts of acetone was continuously impregnated using a drum winder complete impregnation device.

A carbon fiber tow impregnated with a resin solution is wound around a drum wrapped with silicone-treated release paper, aligned parallel to each other, then the solvent contained in the resin is evaporated, and the temperature is further heated at 130°C. By heat treatment for 15 minutes at
Created prepreg.

The prepreg obtained in this way was cut into a length of 280 mm.
After cutting into pieces with a width of 30 mm, 11 sheets were stacked and placed in a mold, the sheets were inserted between the hot plates of a hydraulic press heated to 130°C, and under a pressure of 7 Kp/d, 130 ℃
The mixture was further heated at 170°C for 1 hour.

Then, the obtained molded product was placed in an oven at 170℃ for 2 hours.
Time to do that post cure. The resulting composite contained 56% carbon fiber by volume, and its L
The SS was measured according to the method of ASTM D-2344 and was found to be 9.07 Kf/Mm2.

Example 2 Instead of the finishing agent solution in Example 1, glycerin triglycidyl ether 109 and methyl methacrylate/butyl acrylate/butyl acrylate/butyl acrylate with a copolymerization ratio of 37:22:41 (molar ratio) obtained by a solution polymerization method were used. Carbon fibers were sized in the same manner as in Example 1, except that a finishing agent solution prepared by dissolving glycidyl methacrylate terpolymer 109 in methyl ethyl ketone 980f1 was used. The physical properties of the composite were also 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 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 I
LSS was 8.90K'/Ni2.

Example 3 Instead of the finishing agent solution in Example 1, glycerin triglycidyl ether 59 and methyl methacrylate/butyl acrylate/butyl acrylate/butyl acrylate with a copolymerization ratio of 37:22:41 (molar ratio) obtained by a solution polymerization method were used. Carbon fibers were sized in the same manner as in Example 1, except that a soil filler solution prepared by dissolving glycidyl methacrylate terpolymer 159 in methyl ethyl ketone 9809 was used. The physical properties of the fibers and composites 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 relatively flexible, and its binding strength was as shown in Table 3. Furthermore, the composite made from the carbon fibers obtained here contained 55% by volume of carbon fibers, and its LSS was 9.00 Kf/Mm2.

Example 4 Instead of the finishing agent solution in Example 1, triglycidyl ether 109 of 1,1,2-trihydroxymethylpropane was used, and the copolymerization ratio was 37:22:41 (obtained by solution polymerization method). molar ratio) of methyl methacrylate/
Carbon fibers were sized in the same manner as in Example 1, except that a finishing solution prepared by dissolving butyl acrylate/glycidyl methacrylate terpolymer 109 in methyl ethyl ketone 9809 was used. The physical properties of the carbon fibers and composites were measured.

The amount of active ingredients in the finishing agent adhered to the carbon fibers obtained here was 2.3% based on the carbon fibers.

The carbon fiber thus obtained was extremely flexible, and its binding strength was as shown in Table 4.
In addition, the composite made from the carbon fibers obtained here contains 55% by volume of carbon fibers, and its IL
SS was 9.16 K'/ml.

Example 5 Instead of the soil agent solution in Example 1, tetraglycidyl ether of pentanyrythritol 109 and a copolymerization ratio of 33:2 obtained by a solution polymerization method were used.
4:43 (molar ratio) methyl methacrylate/butyl acrylate/glycidyl methacrylate terpolymer 1
Carbon fibers were sized in the same manner as in Example 1, except that a finishing agent solution prepared by dissolving 09 in methyl ethyl ketone 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 2.2% based on the carbon fibers. The carbon fiber thus obtained was highly flexible, and its binding strength was as shown in Table 5. In addition, the composite made from the carbon fibers obtained here contains 58% by volume of carbon fibers, and its LSS is 9.27Kf/M.
It was m2.

Example 6 Instead of the finishing agent solution in Example 1, tetraglycidyl ether of pentaerythritol 109 and a copolymerization ratio of 33:24 obtained by solution polymerization method were used.
: 43 (molar ratio) of styrene/butyl acrylate/glycidyl methacrylate terpolymer 109 in methyl ethyl ketone 9809. The carbon fibers were sized and the physical properties of the resulting carbon fibers and composites were measured.

The amount of active ingredients in the surface finishing agent adhered to the carbon fibers obtained here was 2.2% based on the carbon fibers.

The carbon fiber thus obtained was highly flexible, and its binding strength was as shown in Table 6. In addition, the composite made from the carbon fibers obtained here has 5
It contained 89% carbon fiber by volume, and its ILSS was 9.12 K'/ml.

Comparative Example 1 Instead of the finishing agent solution in Example 1, a finish prepared by dissolving epoxy resin "Epicoat 828" 89 manufactured by Ciel and epoxy resin "Epicoat 81001" 129 manufactured by Ciel in methyl ethyl ketone 9809. Carbon fibers were sized in the same manner as in Example 1 except that the agent solution was used, and the physical properties of the obtained carbon fibers and composite were measured.

The amount of active ingredients in the surface finishing agent attached 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 7. In addition, the composite made from the carbon fibers obtained here contains 60% by volume of carbon fibers,
Its 1 LSS was 7.45 K'/ml.

Claims (1)

[Scope of Claims] 1. A vinyl addition polymer containing at least one oxirane ring-containing monomer unit as a constituent component and a trihydric or higher aliphatic polyhydric alcohol having three or more glycidyl ether groups. A carbon fiber finishing agent characterized by containing polyglycidyl ether. 2. The vinyl-based addition polymer containing at least one oxirane ring-containing monomer unit as its constituent component is glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, α-ethyl glycidyl acrylate,
Crotonyl glycidyl ether, glycidyl crotonate, glycidyl isocrotonate, monoalkyl monoglycidyl itaconate, diglycidyl itaconate, monoalkyl monoglycidyl fumarate, diglycidyl fumarate, monoalkyl monoglycidyl maleate, A vinyl-based addition polymer obtained by polymerizing at least one oxirane ring-containing ethylenically unsaturated compound selected from the group of maleic acid diglycidyl esters alone or together with other ethylenically unsaturated compounds. A finishing agent for carbon fibers according to claim 1. 3. The finishing agent for carbon fibers according to claim 1, wherein the polyglycidyl ether of trivalent or higher aliphatic polyhydric alcohol having three or more glycidyl ether groups is triglycidyl ether of glycerin.