JPS6244011B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an epoxy resin composition that is fast curing and has good composite physical properties. More specifically, the present invention relates to an epoxy resin composition for reinforcing carbon fibers that cures within 30 minutes at 130°C, has storage stability at 20°C for 1.5 months or more, and has good composite physical properties. Carbon fiber reinforced plastics (hereinafter abbreviated as CFRP) are widely used in so-called premium sports equipment such as golf club shafts and fishing rods, but many of these CFRPs have a cylindrical shape, which reduces productivity and workability. From the perspective of environmental protection, dry lamination using prepreg has become mainstream. For this reason, the demands on prepregs have become stricter in recent years, and in particular the demands on prepregs used for forming thin tubular objects such as fishing rods have become stricter. In other words, carbon fiber has good adhesion to epoxy resin, so epoxy resin is used as a matrix.
Because CFRP produces composites with high specific strength and specific modulus, epoxy resins are commonly used in premium sporting goods applications. However, while epoxy resins have good performance, they have the disadvantage of long curing times. Therefore, there is a strong demand for shortening the curing time without impairing the storage stability or mechanical properties of the prepreg. Therefore, the present inventors conducted extensive research into improving the curability of epoxy resin compositions for prepregs, and as a result, they arrived at the present invention. That is, the present invention comprises at least: A: 100 parts by weight of a novolak type epoxy resin; B: 50 to 120 parts by weight of a bisphenol type A epoxy resin.
Part by weight, C One or more epoxy groups in the molecule and an average of 0.1
an epoxy compound having at least 3 hydroxyl groups;
A fluid urethane obtained by reacting polyether or polyester with a terminal isocyanate group-containing polyurethane polymer obtained from polyisocyanate and having an NCO group content of 1 to 10% at an OH group/NCO group ratio of greater than 1. The present invention relates to an epoxy resin composition for reinforcing carbon fibers, which contains 10 to 40 parts by weight of a modified epoxy resin, 1 to 10 parts by weight of D dicyandiamide, and 1 to 10 parts by weight of a curing accelerator. By adopting such a configuration, the present invention was able to produce a prepreg that can be cured in a short time and has excellent storage stability. The novolak type epoxy resin used in the present invention has the general formula: (However, R is -H or -CH ₃ ) It is a polyfunctional epoxy resin, and commercially available products include Ep-152 and Ep-154 manufactured by Yuka Ciel Epoxy Co., Ltd., and Sumitomo Chemical Co., Ltd. ) Various grades such as ESCN-220 series can be used. Such novolak type epoxy resins have good reactivity with dicyandiamide and are suitable for use with suitable curing accelerators, such as various imidazole compounds, general formulas, (However, in the formula, X ₁ and X ₂ are OCH ₃ , NO ₂ , Cl, H
When used in combination with a urea compound represented by be. Therefore, bisphenol A type epoxy resins are generally added to premium sporting goods applications such as fishing rods. In the present invention, in order to improve the flexibility of the novolak type epoxy resin, it is preferred to add 50 to 120 parts by weight of bisphenol A type epoxy resin to 100 parts by weight of the novolak type epoxy resin. Bisphenol A
If the amount of mold epoxy resin added is less than 50 parts by weight, no effect on improving flexibility will be observed, and if it is more than 120 parts by weight, heat resistance will decrease, which is not preferable. As described above, the epoxy resin composition for prepreg used in conventional premium sporting goods etc. is composed of novolak type epoxy resin and bisphenol A.
Usually, dicyandiamide as a curing agent and a curing accelerator are added to a type epoxy resin, but such resin compositions require curing conditions of at least 1 hour at 120 to 130°C, which is difficult to use in practice. teeth
It is common to cure at 130°C for 2 hours or more. Therefore, the present inventors conducted extensive research on methods for accelerating the curing of such epoxy resin compositions, and as a result, they arrived at the present invention. In other words, by adding a urethane-modified epoxy resin to a mixture of novolak type epoxy resin and bisphenol A type epoxy resin, it is possible to cure the prepreg without impairing its storage stability even in the case of curing accelerators such as dicyandiamide and urea compounds. They succeeded in significantly improving the curability of epoxy resin compositions. That is, one or more epoxy groups in the molecule and an average
An epoxy compound having 0.1 or more hydroxyl groups and a terminal isocyanate group-containing polyurethane polymer with an NCO group content of 1 to 10% obtained from polyether or polyester and polyisocyanate, with an OH group/NCO group ratio of 1 or more. Fluid urethane-modified epoxy resin obtained by reacting in a large proportion, such as Adeka urethane-modified epoxy resin EPU-6, EPU-10 manufactured by Asahi Denka Kogyo Co., Ltd., per 100 parts by weight of novolak type epoxy resin.
By adding 10 to 40 parts by weight, they succeeded in significantly shortening the curing time, which conventionally required more than 2 hours, to less than 30 minutes. Furthermore, if the amount of the urethane-modified epoxy resin according to the present invention added is too small, the curability will not be improved, while if the amount added is too large, the water resistance will deteriorate. A range of 50% is preferred. Next, in carrying out the present invention, it is necessary to adjust the viscosity of the resin composition for prepreg in order to adjust the important tactile properties of the prepreg. It may be prepolymerized with an aromatic amine such as diaminodiphenylmethane (DDM) or diaminodiphenyl sulfone (DDS), or a thermoplastic polymer or rubbery substance may be added. Further, in carrying out the present invention, reinforcing fibers other than carbon fibers such as glass fibers and organic fibers may be included in addition to carbon fibers. Furthermore, the carbon fibers used in the present invention may be any type of carbon fiber such as rayon, polyacrylonitrile, or pitch carbon fibers, and the form of the fibers may be long fibers aligned in one direction, woven fabrics, knitted fabrics, etc. It's okay to be. Hereinafter, the content of the present invention will be explained in more detail with reference to Examples. Example 50 parts by weight of Ep154 manufactured by Yuka Ciel Epoxy Co., Ltd.
40 parts by weight of Ep828 and 10 parts of EPU-6 manufactured by Asahi Denka Kogyo Co., Ltd.
After putting the parts by weight into a heating kneader and stirring thoroughly,
4 parts by weight of 4,4'-diaminodiphenylmethane was added and prepolymerized at 130°C for 5 hours. To the obtained resin mixture, 4 parts by weight of dicyandiamide and 5 parts by weight of 3,4 dichlorophenyl-1,1 dimethylurea were added and thoroughly stirred and mixed to obtain a resin composition for prepreg. Next, carbon fiber "Torayka" T-300 made by firing and surface treating acrylonitrile fibers is aligned in one direction, and the resin composition is heated and melted to impregnate it into unidirectional carbon fibers. Got prepreg.
The obtained prepreg had moderate adhesiveness, and although it was left in a room at 20°C for 1.5 months, no significant change in adhesiveness was observed, and the storage stability was good. The prepreg obtained was cut into 30cm lengths, laminated so that the fibers were in the same direction, wrapped in Tetron taffeta, inserted between two Tetron films, and placed in a press heated to 130℃. It was then put under pressure to 7Kg/cm ² and hardened. Three types of cured plates with curing times of 10 minutes, 30 minutes, and 60 minutes were created and their physical properties were measured, as shown in Table 1.
It was found that curing was sufficiently completed within a curing time of 10 minutes.

[Table] Comparative Example 50 parts by weight of Ep154 manufactured by Yuka Ciel Epoxy Resin Co., Ltd. and 50 parts by weight of Ep828 were thoroughly stirred in a heating kneader, and 4,4'-diaminodiphenylmethane 4.
Parts by weight were added and prepolymerized at 130°C for 5 hours.
The same as in Example except that 4 parts by weight of dicyandiamide and 5 parts by weight of 3,4 dichlorophenyl-1,1-dimethylurea were added to the obtained resin mixture and thoroughly stirred and mixed to obtain a resin composition for prepreg. A prepreg was prepared using the method described above, and the resulting prepreg was molded using a heated press at 130°C. curing time
Change the curing time and Tg of the cured board by changing from 15 minutes to 150 minutes.
As shown in Table 2, it was found that a curing time of at least 60 minutes was required.

【table】

Claims (1)

[Scope of Claims] 1 At least: A: 100 parts by weight of novolac type epoxy resin; B: 50 to 120 parts by weight of bisphenol A type epoxy resin.
Part by weight, C One or more epoxy groups in the molecule and an average of 0.1
an epoxy compound having at least 3 hydroxyl groups;
A fluid urethane obtained by reacting polyether or polyester with a terminal isocyanate group-containing polyurethane polymer obtained from polyisocyanate and having an NCO group content of 1 to 10% at an OH group/NCO group ratio of greater than 1. An epoxy resin composition for reinforcing carbon fibers, comprising 10 to 40 parts by weight of a modified epoxy resin, 1 to 10 parts by weight of D dicyandiamide, and 1 to 10 parts by weight of a curing accelerator.