JPS63105178A - Sizing agent for carbon fiber - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a sizing agent for carbon fibers.

More specifically, the present invention relates to a sizing agent for carbon fibers suitable for manufacturing carbon fiber composite materials.

(Conventional technology) Conventionally, in automobiles, aircraft, and other various industrial fields,
There has been a demand for the development of high-performance materials with properties such as light weight, high strength, and high modulus of elasticity. In recent years, the excellent material performance of carbon fiber, which was developed in response to these demands, has been recognized, and its range of applications is rapidly expanding, mainly in sports goods, building materials, etc. Applications to these various fields are mainly applied to carbon fibers and thermosetting resins such as epoxy resins, unsaturated polyester resins, phenolic resins, and diallyl phthalate resins, as well as thermosetting resins such as polyamides, polyolefins, polyacetals, polycarbonates, and linear polyesters. It is made in the form of a composite material using plastic resin or the like as a matrix resin.

In this case, it is known that a sizing agent is used to improve the handling of carbon fiber threads in the manufacturing process of composite materials, but in addition, the adhesion between carbon fibers and matrix resin is It is also known that the selection of the sizing agent is important from this point of view.

That is, in general, the adhesion of carbon fibers treated with a surface treatment agent to a matrix resin changes depending on the surface treatment agent used. Therefore, for example, when using an epoxy resin as a composite matrix, it is necessary to use an epoxy-based sizing agent selected for the purpose of improving adhesion with the epoxy resin on the carbon fiber to be composited with it. There is.

(Problem to be solved by the invention) However, as the molding cycle of composites is required to be shortened and molding costs are required to be reduced, recently, unsaturated polyester (UP) and vinyl, which have a short curing time, are being used. Compositeization with ester resin (VE) has become important. In this case, carbon Ii! ! In the conventional method in which an epoxy-based sizing agent is applied to the I-fiber, the compatibility between the carbon fiber and the unsaturated polyester or vinyl ester is <1, and the interglabellar shear strength (ILSS) between the matrix resin and the carbon fiber, which is an index of adhesion, is ) was low, making it impractical.

Japanese Patent Publication No. 59-43298 discloses a sizing agent that has improved this drawback, but still has insufficient ILSS.

Generally, the sizing agent is dissolved in a solvent or dispersed as an emulsion, applied to the fibers by a suitable means such as dipping, and then dried. At this time, the solvent and dispersion medium evaporate, and then the sizing agent itself melts to form a thin film covering the surface of the fibers, thereby improving the cohesiveness of the fibers. Therefore, it is preferable that the adhesion of the sizing agent to the fibers is sufficiently good, and at the same time, the adhesion to the matrix resin is strong.

The present inventors have found that when unsaturated polyester or vinyl ester is used as a matrix resin, an unsaturated polyester compound having a reactive double bond crosslinks with the matrix resin and exhibits a coupling effect, which is extremely favorable. The present invention was achieved by discovering that the more uniform the molecular weight of the sizing agent, the less variation in product performance and the better the product performance.

Accordingly, the first object of the present invention is to provide a sizing agent for carbon fibers having uniform molecular weights that has been subjected to a composite process with an unsaturated polyester and a vinyl ester.

A second object of the present invention is to provide a composite material of carbon fiber and unsaturated polyester or vinyl ester that has good adhesive properties.

A third object of the present invention is to provide a method for shortening the molding cycle of a composite material using carbon fibers.

(Means for Solving the Problems) The above-mentioned aspects of the present invention are directed to an unsaturated ether having an unsaturated bond at both ends, which is synthesized from a glycidyl ester of an unsaturated monocarboxylic acid and a diol; This was achieved using a carbon fiber sizing agent whose main component is an unsaturated ester compound synthesized from glycidyl ester and dicarboxylic acid and having unsaturated bonds at both ends.

The glycidyl ester of unsaturated monocarboxylic acid used in the present invention is one or more compounds having a reactive double bond that reacts with diols or dicarboxylic acids to form an ether bond or an ester bond. can be selected arbitrarily.

Examples of such glycidyl esters include glycidyl esters of acrylic acid, methacrylic acid, vinyl acetic acid, and allyl acetic acid.

These glycidyl esters can be produced by known methods.

The dicarboxylic acid used in the present invention can be arbitrarily selected from compounds that react with the epoxy ring of the glycidyl ester to form an ester bond. Examples of such dicarboxylic acids include orthophthalic acid,
Mention may be made of unsaturated dicarboxylic acids such as isophthalic acid, terephthalic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and allylmalonic acid.

On the other hand, diols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, bisphenol A
and its alkylene oxide adducts, bisphenol F and its alkylene oxide adducts, bisphenol S and its alkylene oxide adducts, and the like.

Here, alkylene oxide means ethylene oxide, propylene oxide, etc.

The sizing agent of the present invention can be easily produced by reacting at least one compound selected from the above dicarboxylic acids and diols with a glycidyl compound by a known method. The reaction may be carried out in a solvent-free system or in a solvent system. In the latter case, the sizing agent of the present invention can be obtained by removing the solvent after the reaction is completed.

By selecting the diols used, the sizing agent of the present invention can be made into a self-emulsifying type that is dispersed in water. It is also possible to improve the opening property and flexibility by improving the properties and reducing the molecular weight of the sizing agent.

(Function) The 10H group and -C-0- bond contained in the sizing agent of the present invention are the 10H group and -C-0- bond contained in the sizing agent of the present invention.
On the other hand, the double bonds in the sizing agent can crosslink with the double bonds in the matrix unsaturated polyester resin or vinyl ester resin to form strong bonds. .

Therefore, since the sizing agent of the present invention has a coupling effect of bonding to both the carbon fiber surface and the matrix resin, it is possible to firmly bond the carbon fiber and the matrix resin.

The carbon fibers used in the present invention can be appropriately selected from known carbon fibers, and may be so-called polyacrylonitrile fibers or pitch fibers.

When coating the surface of these carbon fibers with a sizing agent, the sizing agent of the present invention is dissolved in a suitable solvent such as methyl ethyl ketone or dispersed in the form of a water emulsion, and then sprayed or dipped. Known methods such as coating can be appropriately employed. In this case, the surface of the carbon fiber is preferably oxidized in advance by a method such as electrolytic oxidation so that the sizing agent easily adheres to the surface of the carbon fiber.

In addition, water-emulsion type sizing agents are used from the viewpoint of cost and working environment. & is preferable.

In the present invention, a smoothing agent such as aliphatic alcohol esters (eg, oleyl oleate, etc.) can be appropriately added to these coating solutions in order to improve the abrasion properties of the fibers after sizing.

The sizing agent of the present invention has good adhesion to the matrix resin and can easily form a strong composite material. Specific examples of matrix resins used in this case include thermosetting resins such as epoxy resins, unsaturated polyester resins, vinyl ester resins, phenol resins, diallyl phthalate resins, polyamides, polyolefins, polyacetals, polycarbonates, linear Examples include thermoplastic resins such as polyester,
Among these, unsaturated polyester resins and vinyl ester resins having an unsaturated bond capable of crosslinking with the double bond of the sizing agent are particularly preferred.

Conditions for curing the matrix resin when forming a composite material can be appropriately selected from known conditions.

The adhesive strength of the composite material thus obtained can be evaluated by glabella shear strength (ILSS) measurement (short beam method). In this specific method, for example, a unidirectional CFRP (carbon fiber matrix resin composite) with a carbon fiber content of 60% by volume is produced, and the thickness is 2 mm x 13 m.
The distance between fulcrums is lQm for a test piece of rn width x 14mm length.
Set up a fulcrum so that the crosshead speed is 1 m.
ILSS is measured in m/min.

(Effects of the Invention) The sizing agent of the present invention not only makes it easy to handle carbon fiber after sizing, but also has good compatibility with unsaturated polyesters and vinyl esters (and does not bond with unsaturated polyesters or vinyl esters). It is possible to form a strong bond with these resins and easily form a high-performance composite material.In addition, the curing speed of unsaturated polyester and vinyl ester is faster than that of epoxy resin. Since it is extremely quick, the present invention allows unsaturated polyesters and vinyl esters to be used in place of epoxy resins that have been mainly used in the past, thereby shortening the molding cycle for composites. The present invention is extremely advantageous, since it also reduces the cost of the composite.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Synthesis Example 1 404 g of a 4-mole adduct of bisphenol A (usually 2 moles of ethylene oxide) was added to a 1β flask.
(1 mol), boronic trifluoride Nieteller 1. (addition reaction accelerator) L, 2rrw2, and 2.0 g of hydroquinone ethyl ether (polymerization inhibitor) were heated at 40°C.
While stirring at ~50°C, glycidyl methacrylate 2
84 g (2 mol) was added dropwise over 30 minutes, and after further stirring at 50° C. for 1 hour, the catalyst was neutralized with an aqueous KOH solution, dehydrated under reduced pressure, and filtered to obtain sizing agent 1. The obtained sizing agent was analyzed by chromatography, infrared absorption spectrum, NMR spectrum, etc. As a result, the main component was +! of the following formula. It was recognized that C1ν has a structure.

Crab = 1 Synthesis Example 2゜Instead of 404g of 4 mole adduct used in Synthesis Example 1,
Same as Synthesis Example 1, except that 376 g (1 mol) of a 4-mole adduct of bisphenol F (2 mol of ethylene oxide each) was used, and 256 g (2 mol) of glycidyl acrylate was used instead of 284 g of glycidyl methacrylate. Sizing agent 2 was obtained in exactly the same manner.

As a result of analysis of the obtained sizing agent by chromatography, infrared absorption spectrum, NMR spectrum, etc., it was confirmed that the main component had the structure of the following formula.

Synthesis Example 3゜426g of 4-mol adduct (1
Sizing agent 3 was obtained in the same manner as in Synthesis Example 1, except that 284 g (2 mol) of glycidyl vinyl acetate and 284 g (2 mol) of glycidyl vinyl acetate were used. As a result of analysis of the obtained sizing agent by chromatography, infrared absorption spectrum, NMR spectrum, etc., it was confirmed that the main component had the structure of the following formula.

1:1: N 0 Synthesis Example 4゜668 g of a 10 mole adduct in which 5 moles of ethylene oxide were added to both sides of bisphenol A as a reactant (
Sizing agent 4 was obtained in the same manner as in Synthesis Example 1, except that 312 g (2 moles) of glycidyl allyl acetate and glycidyl allyl acetate were used. This sizing agent could be used in the form of a water-emulsion. As a result of analysis of the obtained sizing agent by chromatography, infrared absorption spectrum, NMR spectrum, etc., it was confirmed that the main component had the structure of the following formula.

1 Synthesis Example 5゜To a reactor equipped with a stirring device, thermometer, N2 gas inlet tube, reagent injection tube, and exhaust port, 1.000 mj of toluene as a solvent was added.
! , 228 g (1 mol) of bisphenol A, 1.2 mJ of boron trifluoride etherate, and 2.0 g of hydroquinone monoethyl ether and heated to 100°C to 110°C.
284g of glycidyl methacrylate (284g
mol) was added dropwise over 30 minutes, stirred for an additional hour, and then cooled.
After neutralizing the catalyst with a KOH aqueous solution and washing with pure water, the solvent was removed using a rotary evaporator to obtain sizing agent 5. As a result of analysis of the obtained sizing agent by chromatography, infrared absorption spectrum, NMR spectrum, etc., it was confirmed that the main component had the structure of the following formula.

n 11 = Human H 0 = c) -0 Synthesis Example 6゜Into a reactor similar to that used in Synthesis Example 5, 1,000 ml of pyridine as a solvent, 166 g (1 mol) of terephthalic acid, 3
Boron fluoride etherate 1.2m7! , 2.0g of hydroquinone monoethyl ether was added, and the temperature was heated to 100℃~1
Glycidyl methacrylate 2 while stirring at 15℃
84 g (2 mol) was added dropwise over 30 minutes, stirred for an additional hour, cooled, neutralized the catalyst with an aqueous KOH solution, and washed with water.
, the solvent was removed using a rotary evaporator, and the sizing agent 6 was removed.As a result of analyzing the obtained sizing agent by chromatography, infrared absorption spectrum, NMR spectrum, etc., the main component was black having the structure of the following formula. was confirmed.

I 1 1 1 0=OOo-C 1=11 C-E Σ by = pm! Synthesis Example 7 Sizing agent 7 was prepared in exactly the same manner as in Synthesis Example 6 except that 166 g (1 mol) of isophthalic acid was used as the dicarboxylic acid.
I got it. As a result of analysis of the obtained sizing agent by chromatography, infrared absorption spectrum, NMR spectrum, etc., it was confirmed that the main component had the structure of the following formula.

Sizing agent 7゜Synthesis example 8゜111! 116 g (1 mol) of maleic acid in a flask of
Boron trifluoride 1.2mi! , 20 g of hydroquinone monoethyl ether was charged, and while stirring at 40°C to 50°C, 256 g (2 moles) of glycidyl acrylate was added to 3
After dropping for 0 minutes, the mixture was further stirred for 1 hour. After the reaction was completed, the solvent was neutralized with a KOH aqueous solution, followed by vacuum brine and filtration to obtain sizing agent 8. As a result of analyzing the obtained sizing agent by chromatography, infrared absorption spectrum, NMR spectrum, etc., the main component was fi i of the following formula.
? It was confirmed that it has.

C；En→TsuCHi-0=? - Example Experiment Details Using the carbon fibers shown below, CF-1, CF-2, the sizing agent of the present invention manufactured in Examples 1 to 8, and the epoxy sizing agent for comparison, U-Pica-3140
(Japan U-Pica ■Registered trademark of unsaturated polyester resin)
, Polycent-2167 (registered trademark of unsaturated polyester resin manufactured by Hitachi Chemical), and Neoball-8250H (
We manufacture a composite material with vinyl ester resin (registered trademark of Japan U-Pica) and improve the glabella adhesive strength (hereinafter abbreviated as ILSS).
was measured. As a comparative epoxy sizing agent,
A bisphenol A-based epoxy sizing agent (manufactured by Yuka Shell ■, Epicoat 828) was used according to a conventional method.

1) Production of CF-1 A petroleum pinch was subjected to a thermal polycondensation reaction to obtain a softened carbonaceous pitch having an optical anisotropy of about 55% and a temperature of 235°C. This pitch was separated in a cylindrical centrifuge at 370°C to isolate a pitch with 98% optical anisotropy.

The pinch thus obtained is spun, made infusible, and then fired at about 1,500°C to obtain high-strength carbon fiber.
Then, in order to make the surface suitable for sizing treatment,
The surface of the fiber was oxidized by electrolytic oxidation to produce carbon fiber CF-1.

2) Manufacture of CF-2 The PAN-based high-strength carbon fiber (T-300) from Toshitoshichi was desized in an ultrasonic cleaner for two days and nights using methyl ethyl ketone to produce carbon fiber CF-2. Created.

3) Manufacture of composite material To manufacture the composite material, 2 parts of benzoyl peroxide (Kayaku Nouri Q Kikusai Cadonox B-CH50) and peroxy.
Carbon fibers were impregnated with 0.6 part of dicarbonate (Kayaku Nouri A1 Fissure Bar Power Dosox 16) as a hardening agent. After setting it in a mold and pressing it at 80℃ for 1 hour,
A unidirectionally reinforced carbon fiber composite material (CF
RP) was obtained.

4) ILSS measurement 2mm thickness x 5mm width x 14mm from the obtained composite material
Cut out a length test piece and use the test piece to calculate the fulcrum-to-support ratio!
ILSS (kg/mm2) was measured by short beam method at 10 mm and crosshead speed l m m 7 min.

Example 1 CF-1 was used as the carbon fiber, and unsaturated polyester resin manufactured by Hitachi Chemical (Polyset-2167) was used as the matrix.
) was used as follows.

Table 1 Sizing agent Solvent Concentration Adhesion amount ILSS (
Weight %) (Weight χ) (Kg/mm 2 ) Comparative example
Unsized □ --7,1 Invention ■ ? 'lEK 3.0 2.
0 8.2 Invention ■ Gate EK 3.0
1.9 8.1 Present invention ■ ME/K
3.0 2.0 8.3 Present invention ■
Stand EX 3.0 1.9 8.2 Comparative example Epoxy MEK 3.0 1.9
7.5 The results in Table 1 demonstrate that the sizing agent of the present invention is extremely effective in forming a composite of high-strength pitch-based carbon fiber and unsaturated polyester matrix.

Example 2 CF-1 was used as the carbon fiber, and vinyl ester resin manufactured by Japan U-Pica G1 (Neoball-8250H) was used as the matrix.
■) The results were as follows.

Table 2 Sizing agent Solvent Concentration Adhesion amount ILSS (
(Weight %) (Weight %) (Kg/Fight 2) Comparative example Unsized − --7,5 Invention ■ MEK 3.0 2.0
9.0 Invention ■ Gate EK 3.0
2.0 9.2 Invention ■ Gate EK
3.0 1.8 8.7 Comparative example Epoxy M
EK 3.0 1.9 7.9 The results in Table 2 demonstrate that the sizing agent of the present invention is extremely effective in compounding high-strength pitch carbon fiber and vinyl ester matrix.

Example 3 In the case where CF-2 was used as the carbon fiber and Polycera-2167 was used as the matrix, the results were as follows.

Table 3 Sizing agent Solvent Concentration Amount ILSS (
Weight ■χ) (Weight %) (Kg/mm 2 ) Comparative example Unsized □ --7,2 Invention ■ MEK 3.0 1.9
8.3 Invention ■ and EK 3.0
1.8 8.1 Present invention ■ MEK
3.0 1.8 8.1 Comparative example Epoxy M
EK 3.0 1.9 7.4 The results in Table 3 demonstrate that the sizing agent of the present invention is effective in compounding PAN-based carbon fibers and unsaturated polyester matrix.

Example 4 The case where CF-2 was used as the carbon fiber and Neoball-8250H■ was used as the matrix was as follows.

Table 4 Sizing agent Solvent Concentration Adhesion amount ILSS (
Weight %) (heavy crystalline 6) (Kg/+nm2) Comparative example Unsized ---□ -□ 7.6 Present invention ■ RoEK 3.0 1.9
9.1 Present invention ■ Gate EK 3.0 1
．． 8 8.9 Present invention ■ MEK 3.
0 1.9 9.0 Invention ■ Water
2.5 1.7 9.1 Present invention ■
MEK 3.0 1.8 8.9 Invention
■ To ME 3.0 1.8 9.1
This invention ■ MEK 3.0 1.8
8.8 Present invention ■ MEK 3.0
1.7 8.9 Comparative example Epoxy gate EK
3.0 1.9 8.0 The results in Table 4 are PAN
This proves that the sizing agent of the present invention is also effective for composites of carbon fibers and vinyl ester matrices.

Claims (1)

[Scope of Claims] 1) An unsaturated ether having unsaturated bonds at both ends synthesized from a glycidyl ester of an unsaturated monocarboxylic acid and a diol, and/or an unsaturated ether synthesized from the glycidyl ester of an unsaturated monocarboxylic acid and a dicarboxylic acid. A sizing agent for carbon fibers whose main component is an unsaturated ester compound with an unsaturated bond at the end. 2) The sizing agent for carbon fibers according to claim 1, wherein the glycidyl ester of unsaturated monocarboxylic acid is at least one selected from glycidyl esters of acrylic acid, methacrylic acid, vinyl acetic acid, and allyl acetic acid. . 3) Diol is bisphenol A, bisphenol F
, bisphenol S, and alkylene oxide adducts thereof. 4) The dicarboxylic acid is orthophthalic acid, isophthalic acid,
The sizing agent for carbon fibers according to claim 1, which is at least one selected from terephthalic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.