JPH049810B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a prepreg impregnated with an epoxy resin composition that has a high curing speed at low temperatures and excellent storage stability. Conventionally, epoxy resins have often been used for prepregs such as carbon fibers, glass fibers, and aromatic polyamide fibers. Important properties required of this epoxy resin include a high curing speed, low temperature curing capability, and long shelf life. Dicyandiamide is used as a curing agent for epoxy resins, but in this case the prepreg has a long shelf life. This curing agent dicyandiamide is combined with a curing accelerator, such as 3-(3,4-dichlorophenyl)-
It has been proposed to use it in combination with 1,1-dimethylurea (Japanese Patent Publication No. 55-16056), and when this combination of curing agent system is applied to, for example, novolak type epoxy resin, the curing agent system can be used in combination with 120-135℃, 60- The resin completely cured in 90 minutes, and some results were obtained. Recently, in order to improve productivity, there has been a demand for further lowering the curing temperature and further increasing the curing speed of epoxy resins in general. When the above-mentioned curing agent system is applied to an epoxy resin, the improvement in curing speed cannot sufficiently satisfy this requirement. In view of the current situation, the present inventors conducted intensive studies to develop a prepreg impregnated with an epoxy resin composition that satisfies the above requirements and has excellent storage stability. It was discovered that a prepreg suitable for the purpose could be obtained by adding polyamide, and the present invention was achieved. The present invention is as follows. 100 parts by weight of epoxy resin and 1 part of dicyandiamide
A prepreg impregnated with an epoxy resin composition containing ~10 parts by weight and 1 to 10 parts by weight of a liquid or semisolid polyamide having an amino group at the end represented by the following structural formula. H-[HN-(CH ₂ CH ₂ NH-) _n CH ₂ CH ₂ NHCO-R-CO-
] _o −NH− (CH ₂ CH ₂ NH−) _n CH ₂ CH ₂ NH ₂ Both m and n are integers of 1 or more (m and n vary depending on the quality and grade of the compound.) The epoxy resin composition in the present invention comprises dicyandiamide and 3-(3,4-dichlorophenyl)-
Compared to the conventional curing agent system containing only 1,1-dimethylurea, the curing reaction can be carried out at a temperature approximately 20 to 30°C lower, and the curing time can be shortened if the temperature remains unchanged. I can do it. Moreover, the present composition is storage stable and has a storage period of 45 days or more at 20°C. The above effects can be obtained in common with epoxy resins, novolac type epoxy resins, glycidylamine type epoxy resins, etc. Here, the liquid or semi-solid polyamide having an amino group at the terminal is obtained by reacting a so-called dimer acid obtained by dimerizing an unsaturated fatty acid with a polyamine and is represented by the above structural formula. It is a reactive thermoplastic resin. This polyamide liquid has a viscosity of approximately 300~
It is 70000cps. This polyamide is sold, for example, under the trademark Tomide (manufactured by Fuji Kasei Kogyo Co., Ltd.) or Versamide (manufactured by Daiichi General Co., Ltd.). Solid polyamides have poor compatibility with epoxy resins and are not suitable. Moreover, those having no amino group at the terminal are not suitable because they do not react with the epoxy resin, have a poor effect of accelerating the curing reaction, and significantly deteriorate the physical properties of the cured product. The epoxy resin component in the resin composition is
There are no particular restrictions on the type, and bisphenol A
These include type epoxy resins, novolak type epoxy resins, glycidylamine type epoxy resins, etc., and preferably bisphenol A type epoxy resins. The content ratio of the components of the epoxy resin composition in the present invention is within the following range. That is, 1 to 10, preferably 2 to 6 parts by weight of dicyandiamide per 100 parts by weight of epoxy resin;
1 to 10, preferably 2 to 6 parts by weight of polyamide having amino groups. If the amount of dicyandiamide is less than 1 part by weight, the curing reaction will be slow, and if it exceeds 10 parts by weight, the composite properties will deteriorate, which is undesirable. Furthermore, if the polyamide having an amino group is less than 1 part by weight, the effect on low-temperature curability or curing rate is small, and if it exceeds 10 parts by weight, the heat resistance of the cured product decreases, which is not preferable. The epoxy resin composition in the present invention can contain other components as necessary. Urea compounds such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea, chlorophenyl-1,1-dimethylurea, etc., or imidazole compounds such as 2-phenyl-4-methyl as curing accelerators. −
It is more effective to add 5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and the like. These compounds are added in an amount of 1 to 10 parts by weight, preferably 3 to 7 parts by weight, per 100 parts by weight of the epoxy resin. The prepreg of the present invention is obtained by impregnating a fiber material with such an epoxy resin composition, and examples of the fiber material in this case include carbon fiber, glass fiber, and aromatic polyamide fiber. It can be made into a prepreg by a normal method. The prepreg of the present invention has a high curing speed at low temperatures and excellent storage stability. Next, the present invention will be explained with reference to examples. At the same time, production examples and comparative production examples are shown. In each example, parts represent parts by weight. Production Example 1 An epoxy resin composition having the following composition was prepared. Epicote 828 (manufactured by Ciel Chemical Co., Ltd.) [Bisphenol A type epoxy resin] 100 parts dicyandiamide 4 parts 3-(3,4-dichlorophenyl)-1,1-dimethylurea 5 parts Tomide 215× (manufactured by Fuji Kasei Kogyo Co., Ltd.) ) [Polyamide having an amino group] 4 parts The storage period of this composition was 45 days at 20°C. The gel time of this product was as shown in Table 1. Comparative Production Example 1 The same composition as in Production Example 1 was prepared except that Tomide was not added, and the curability was examined. The results were as shown in Table 1.

[Table] Production Example 2 An epoxy resin composition having the following composition was prepared. EPN1138 (manufactured by Ciba Geigy) [Phenol novolak type epoxy resin] 100 parts dicyandiamide 4 parts 3-(3,4-dichlorophenyl)-1,1-dimethylurea 5 parts Tomide 215× (manufactured by Fuji Chemical Industries, Ltd.) ) [Polyamide having an amino group] 4 parts The storage period of this composition was 40 days or more at 20°C, and the gel time was as shown in Table 2. Comparative Production Example 2 The same composition as in Production Example 2 was prepared, except that Tomide was not added, and the curability was examined. The results were as shown in Table 2.

[Table] Example 1 The resin composition obtained in Production Example 1 was dissolved in an acetone-methyl cellosolve mixed solvent to make a 50% solution. This solution was impregnated with carbon fibers (CF) while being continuously wound around a drum, and then dried at 80° C. for 1 hour to obtain a unidirectional prepreg. This was laminated and hot press molded under curing conditions of 7 kg/cm ² at 130° C. for 90 minutes to obtain a molded plate. The interlaminar shear strength (ILSS) of this molded plate was 8.0 Kg/mm ² . On the other hand, for comparison, a CF unidirectional prepreg was made using the composition obtained in Comparative Production Example 1. This was laminated and hot press molded under curing conditions of 7 kg/cm ² at 130° C. for 90 minutes to obtain a molded plate. This molded plate
ILSS was 7.1Kg/ ^mm2 . This molded plate is heated to 150℃.
When cured for 1 hour, ILSS is 8.2Kg/
It became mm ² . Example 2 The resin composition obtained in Production Example 2 was dissolved in an acetone-methyl cellosolve mixed solvent to form a 50% solution. A unidirectional prepreg was produced under the same conditions as in Example 1 while impregnating aromatic polyamide fiber Kevlar 49 (manufactured by DuPont) in this solution. This was laminated and hot press molded under curing conditions of 7 kg/cm ³ at 110° C. for 90 minutes to obtain a molded plate. The ILSS of this molded plate was 7.0 Kg/mm ² . On the other hand, for comparison, a unidirectional Kevlar prepreg was made using the composition obtained in Comparative Production Example 2.
This was hot press molded at 110° C. for 90 minutes under curing conditions of 7 kg/cm ² to obtain a molded plate. This molded plate
ILSS was 5.9Kg/ ^mm2 . This molded plate is heated to 150℃.
When cured for 1 hour, ILSS is 7.2Kg/
It became mm ² .

Claims (1)

[Scope of Claims] 1 100 parts by weight of an epoxy resin, 1 to 10 parts by weight of dicyandiamide, and 1 to 10 parts by weight of a liquid or semisolid polyamide having an amino group at the end represented by the following structural formula.
A prepreg impregnated with an epoxy resin composition containing parts by weight. H-[HN-(CH ₂ CH ₂ NH-) _n CH ₂ CH ₂ NHCO-R-CO-
] _o −NH− (CH ₂ CH ₂ NH−) _n CH ₂ CH ₂ NH ₂ Both m and n are integers of 1 or more. 2 Claim 1 in which the epoxy resin composition contains a urea compound or an imidazole compound
prepreg.