JPS63105174A - 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 used in producing 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 fields such as sports goods, automobiles, aircraft, and building materials. Applications to these various fields are mainly based on carbon fibers, epoxy resins,
It is made in the form of a composite material whose matrix resin is a thermosetting resin such as an unsaturated polyester resin, a phenol resin, or a diallyl phthalate resin, or a thermoplastic resin such as polyamide, polyolefin, polyacetal, polycarbonate, or linear polyester.

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, in the conventional method of applying an epoxy-based sizing agent to carbon fibers, the compatibility between carbon fibers and unsaturated polyester or vinyl ester is poor, and the shear strength between the matrix resin and carbon fibers, which is an indicator of adhesion, is poor. (ILSS) was low, and there was a drawback that it could not be put into practical use.

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 discovered that an unsaturated polyester compound having a reactive double bond is a sizing agent with good adhesion to carbon fibers, and that they have produced a carbon fiber composite material using an unsaturated polyester or vinyl ester as a matrix resin. In this book, we found that very good results can be obtained when the sizing agent is crosslinked with the matrix resin to exhibit a coupling effect, and that the more uniform the molecular weight of the sizing agent, the better the product performance will be without variations. invention has been achieved.

Accordingly, a first object of the present invention is to provide a sizing agent for carbon fibers having a uniform molecular weight that has been subjected to compositing 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 that in the sizing agent for carbon fibers containing an unsaturated ester compound as a main component, the unsaturated ester compound is a type of unsaturated monocarboxylic acid. This was achieved using a sizing agent for carbon fibers, which is an ester compound with one type of diol and is characterized by comprising at least one type of compound selected from compounds having unsaturated bonds at both ends.

The method for synthesizing the sizing agent of the present invention is such that the final product is
There is no particular limitation as long as the reaction product is the same as the reaction product of unsaturated monocarboxylic acid and diols. For example, transesterification may be used, but usually, the reaction product of the above unsaturated monocarboxylic acid and diols may be used. Conditions can be appropriately selected from known reaction conditions for esterification reactions by combining them as appropriate. In this case, it is natural that the ratio of unsaturated monocarboxylic acid/diol must be 2 or more in order to contain unsaturated carboxylic acids at both ends. The reaction may be carried out in a solvent-free system or in a solvent system. In the latter case, it is necessary to remove the solvent after the reaction is completed to obtain the sizing agent of the present invention.

The unsaturated monocarboxylic acid used in the present invention can be arbitrarily selected from one or more compounds having a reactive double bond that reacts with diols to form an ester bond. Examples of such unsaturated monocarboxylic acids or unsaturated monocarboxylic esters include acrylic acid, methacrylic acid, vinyl acetic acid, allyl acetic acid, methyl acrylate, and methyl methacrylate.

On the other hand, examples of diols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, bisphenol A, bisphenol F, bisphenol S, and alkylene oxide adducts of these bisphenol compounds. Here, alkylene oxide means ethylene oxide, propylene oxide, etc.

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, and by increasing the molecular weight of the sizing agent, it can improve the cohesiveness of carbon fiber yarns. It is also possible to improve the spreadability and flexibility by increasing the molecular weight of the sizing agent and reducing the molecular weight of the sizing agent. (Function) The -C-〇- group contained in the sizing agent of the present invention has high affinity with functional groups such as 1-COOH and 10H present on the surface of carbon fibers, while the The bond can form a strong bond by crosslinking with the double bond in the unsaturated polyester resin or vinyl ester resin that is the matrix.

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.

Further, the sizing agent is preferably a water-emulsion type solution from the viewpoint of cost and working environment.

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 resistance 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 formed by 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, -direction CFRP (carbon fiber matrix resin composite) with a carbon fiber content of 60% by volume is produced, and the size is 2 mm thick x 6 mm.
A test piece of width x 14 mm in length was provided with fulcrums so that the distance between the fulcrums was 10 mm, and the cross was moved at a speed of 1 m.
This is to measure ILSS in m/min.

(Effects of the Invention) The sizing agent of the present invention not only facilitates the handling of carbon fiber yarn after sizing, but also has good compatibility with unsaturated polyesters and vinyl esters, and is capable of bonding with unsaturated polyesters and vinyl esters through crosslinking reactions. Therefore, it can be strongly bonded to these resins, and a high-performance composite material can be easily formed. Furthermore, since the curing speed of unsaturated polyesters and vinyl esters is much faster than that of epoxy resins, 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. This makes it possible to shorten the composite molding cycle. The present invention is also extremely advantageous since it also aims to reduce 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゜In a reactor equipped with a stirrer, a thermometer, an N2 gas introduction tube, and a dehydration tube, 404 g (1 mol) of an adduct of bisphenol with 2 mol of ethylene oxide added on both sides and 206.4 g of methacrylic acid. (2.4 mol), 1.0 g of hydroquinone as a polymerization inhibitor and P- as a catalyst)
0.042 mol of luenesulfonic acid was charged, and the mixture was reacted at 100°C to 110°C for about 2 hours in a N2 gas stream.

After the reaction was completed, the catalyst in the product was neutralized with an alkali, and the by-produced salt was removed by washing with water, followed by dehydration under reduced pressure at 100°C to 110°C and filtration to obtain sizing agent 1. 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.

The obtained sizing agent is dissolved in methyl ethyl ketone,
It was possible to make a sizing agent coating liquid.

Sentry Q = 11 C Hibe” 10: n O: 0
0 engineering 11 hitobe]
... Synthesis Example 2゜Into the same reactor as in Synthesis Example 1, 520 g (1 mol) of an adduct obtained by adding 1 mol of propylene oxide and 2 mol of ethylene oxide to both sides of bisphenol A, and 172.8 g (2 mol) of acrylic acid were added. , 4 mol), 1.0 g of hydroquinone as a polymerization inhibitor and P- as a catalyst.
) 0.042 mol of luenesulfonic acid was added, and the mixture was reacted at 100°C to 110°C for about 2 hours in a N2 gas stream.

After the reaction was completed, the catalyst was neutralized with alkali, washed away with water, and heated for 10 minutes.
Sizing agent 2 was obtained by dehydrating under reduced pressure at 0°C to 110°C and then filtering. 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 following structural formula.

This sizing agent was also dissolved in methyl ethyl ketone, and a sizing agent coating solution could be easily prepared.

D 110
・・・ ・・
C and 11 Synthesis Example 3゜Into the same reactor as in Synthesis Example 1, 1132 g (1 mol) of an adduct obtained by adding 10 mol of ethylene oxide to both sides of bisphenol A, and 206.4 mol of methacrylic acid.
g (2.4 mol), 1.0 g of hydroquinone as polymerization inhibitor and 0 of P-)luenesulfonic acid as catalyst.
．． 042 mol was added and heated to 100°C to 11 mol in a N2 gas stream.
The reaction was carried out at 0°C for about 2 hours.

After the reaction is complete, neutralize and remove the catalyst, and heat to 100°C to 110°C.
Sizing agent 3 was obtained by dehydration under reduced pressure and filtration. The obtained sizing agent was gradually added to hot water at 70° C. to 80° C. while stirring, and could be used as a water-emulsion with a predetermined concentration. 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 following structural formula.

Example 1 Experimental details Using the carbon fibers shown below, CF-1, CF-2, CF-3, the sizing agent of the present invention manufactured in Synthesis Examples 1 to 3, and the epoxy sizing agent for comparison. , UPICAR 3140 (registered trademark of unsaturated polyester resin manufactured by Japan UPICAN), POLYSET-2167 (registered trademark of Hitachi Chemical @ wrongdoing saturated polyester resin), and NEOBALL-
A composite material with 8250H (Japanese U-Pica M [registered trademark of vinyl ester resin)] was produced. As a comparative epoxy sizing agent, a bisphenol A epoxy sizing agent (Epicoat 828 manufactured by Yuka Shell Jun Co., Ltd.) was used according to a conventional method.

1) Production of CF-1 Petroleum pitch was subjected to a thermal polycondensation reaction to obtain a softened carbonaceous pitch at 235°C having optical anisotropy of about 55%. This pitch was separated using a cylindrical centrifugal separator at 370°C.
A pitch with 98% optical anisotropy was isolated.

The pitch obtained in this way is spun, made infusible, and then fired at approximately 1,500°C to obtain high-strength carbon fibers. The surface was oxidized by electrolytic oxidation to produce carbon fiber CF-1.

2) Production of CF-2 High modulus carbon fiber CF-2 was produced in the same manner as CF-1 except that the firing was performed at 2.200°C.

3) Manufacture of CF-3 PAN-based high-strength carbon fiber (T-300■) with zero cracks
was desized using methyl ethyl ketone in an ultrasonic cleaner for two days and nights to produce carbon fiber CF-3.

4) Manufacture of composite materials Manufacture of composite materials is as follows: 100 parts of IJ Sox resin, 2 parts of penduyl peroxide (Kadonox B-CH50, manufactured by Kayaku Nouri@) and peroxy dicarbonate. (Kayaku Nouri ■ Agriculture Parriki Dox 16
(2) 0.6 part was used as a hardening agent and impregnated into carbon fibers. After setting in a mold and pressing at 80℃ for 1 hour, heat curing in an oven at 150℃ for 1 hour to obtain a carbon fiber content of 6.
A unidirectionally reinforced carbon fiber composite material (CFRP) of 0% by volume was obtained.

2mm thickness x 6mm width x 14mm from the obtained composite material
A long test piece was cut out, and ILSS (kg/mm2) was measured using the test piece by the short beam method at a distance between fulcrums of 10 mm and a crosshead speed of 1 mm/min.

Example 1 When CF-1 was used as the carbon fiber and Nippon U-Pica 3140■ (manufactured by Sun) was used as the matrix, the results were as follows.

Table 1 Sizing agent Solvent Concentration Adhesion amount ILSS (
Weight%) (Weight%) (Kg/mm2) Comparative example Unsized □ ---7,0 Invention ■ MEK
3.0 2.0 8.4 This invention ■
Water 2.5 1.7 8.6 Comparative Example Epoxy MEK 3.0 2.0 7.5 The results in Table 1 show that the sizing agent of the present invention This proves that it is extremely effective for

Example 2 The case where CF-1 was used as the carbon fiber and Polyset-2167■ manufactured by Hitachi Chemical Co., Ltd. was used as the matrix was as follows.

Table 2 Ising agent Solvent Concentration Adhesion (i IL
SS (weight χ) (weight%) (Kg/mn+ 2) Comparative example Unsized □ --□ 6.8 Present invention
■ Gate EK 3.0 2.0 8.2
This invention ■ Liver K 3.0 1.9
8.1 Present invention ■ Water 2.5 1.
7 8.3 Comparative example Epoxy MEK 3.0
2.0 7.4 The results in Table 2 also demonstrate, as in Example 1, that the sizing agent of the present invention is extremely effective in compounding high-strength pitch-based carbon fibers and unsaturated polyester matrix. It is something.

Example 3 The case where CF-1 was used as the carbon fiber and Nippon U-Pica 11 Neoball-8250H■ was used as the matrix was as follows.

Table 3 Sizing agent Solvent Concentration Amount ILSS (
Weight %) (Weight %) (Kg/mm 2 ) Comparative example Unsized □ --'7.8 Invention ■ MEK
3.0 2.0 9.0 This invention ■
MEK 3.0 1.9 9.2 Invention ■ Water 2.5 1.7 9.
3 Comparative Examples Epoxy MEK 3.0 2.0
8.2 The results in Table 3 show that the sizing agent of the present invention
This proves that this method is extremely effective in compositing high-strength pitch-based carbon fiber and vinyl ester matrix.

Example 4 When CF-2 was used as the carbon $1 fiber and Yuvica-3140 was used as the matrix, the results were as follows.

Table 4 Sizing agent Solvent Concentration Adhesion (] ILS
S (weight%) (weight%) (Kg/mm2) Comparative example Unsized □ --6,2 Invention ■? IEX 3.0 1.9
7.8 Present invention ■ Gate E 3.0
1.8 7.9 Present invention ■ Water 2.
5 1.6 7.8 Comparative example Epoxy MEK
3.0 1.8 7.0 The results in Table 4 are:
This proves that the sizing agent of the present invention is extremely effective in compositing PAN-based carbon fibers with unsaturated polyesters.

Example 5 The case where CF-2 was used as the carbon fiber and Hitachi Chemical (I'll, Polyset-2167■) was used as the matrix was as follows.

Table 5 Sizing agent Solvent Concentration Adhesion amount ILSS (
Weight%) (Weight%) (Kg/mm2) Comparative example Unsized □ --6,0 Invention ■ Water 2.5 1.6
7.5 Comparative example Epoxy gate EX 3゜0 1
．． 8 6.8 Example 6゜The following was the case where CF-2 was used as the carbon fiber and Neoball-8250H■ was used as the matrix.

Table 6 Sizing agent Solvent Concentration Adhesion ILSS
(Weight%) (Weight%) (Kg/nun 2) Comparative example Unsized □ --7,0 Invention ■ ME 3.0 1.9
8.5 Invention ■ Gate EK 3.0
1.8 8.4 Present invention ■ Water 2.5
1.6 B. 4 Comparative Example Epoxy Gate EK
3.0 1.8 7.9 The results in Table 6 are:
This proves that the sizing agent of the present invention is also effective in forming a composite of a PAN-based carbon fiber nyl ester matrix.

Example 7 When CF-3 was used as the carbon fiber and U-Pica-3140■ manufactured by Nippon U-Pica@ was used as the matrix, the results were as follows.

Table 7 Sizing agent Solvent Concentration Adhesion amount ILSS (
Weight%) (fli amount%) (Kg/mm2) Comparative example Unsized □ □ -7,1 Invention ■
MEK 3.0 2.1 13.6 Comparative example Epoxy Gate EK 3.0 1.9 7
．． 5 Example 8 When using carbon fiber λ (CF-3 as t and Neopol-8250H@ as the matrix), there were no cracks.

Table 8

Claims (1)

[Claims] 1) A sizing agent for carbon fibers containing an unsaturated ester compound as a main component, wherein the unsaturated ester compound is an ester compound of an unsaturated monocarboxylic acid and a diol, and the unsaturated ester compound is an ester compound of an unsaturated monocarboxylic acid and a diol. A sizing agent for carbon fibers, comprising at least one kind selected from compounds having unsaturated bonds. 2) The carbon according to claim 1, which contains at least one unsaturated monocarboxylic acid moiety selected from acrylic acid, methacrylic acid, vinyl acetic acid, and allyl acetic acid as the unsaturated monocarboxylic acid moiety. Sizing agent for textiles. 3) Diols are bisphenol A and bisphenol F
, bisphenol S, and alkylene oxide adducts thereof.