JPH0632931A - Thermosetting foam material - Google Patents

Abstract

PURPOSE:To provide a foamed material having a room-temperature stability of 3 weeks or longer, can foam and cure sufficiently near 80 deg.C and is excellent in adhesion. CONSTITUTION:This foamed thermosetting material comprises 100 pts.wt. epoxy resin, 1-30 pts.wt. thermoplastic resin soluble in the epoxy resin, 10-50 pts.wt. thermally decomposable latent curing agent which can be activated near 80 deg.C and 5-80 pts.wt. heat-expansible microcapsules the shell walls of which comprise a vinylidene chloride polymer and which contain a low-boiling hydrocarbon and start to expand at 80 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting foam material which foams and cures at a relatively low temperature and has excellent storage stability at room temperature.

[0002]

2. Description of the Related Art Foams are used in various applications such as automobile related materials, electronic materials, civil engineering and construction, and sports applications as a lightweight auxiliary material or heat insulating material. It is also used as an auxiliary material for internal pressure molding, in which a mold is formed together with the prepreg and a pressure is applied from the inside so that the prepreg is properly aligned with the mold when cured.

The performance required as a foamed material for such applications is that the adhesiveness with the prepreg after curing is good, and foaming is performed under the same conditions as the molding conditions of the prepreg so that sufficient internal pressure is applied, After that, maintaining the shape of the prepreg until it hardens. Particularly, in recent years, a prepreg that cures at a low temperature has been developed, and it has been desired to develop a foam material for internal pressure molding which can be applied to such a prepreg.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a foamed material which has a stability at room temperature of 3 weeks or more and is sufficiently foamed and cured at a temperature of about 80 ° C. and which is excellent in adhesiveness. is there.

[0005]

Means for Solving the Problems That is, the present invention provides (A) epoxy resin: 100 parts by weight (B) thermoplastic resin soluble in epoxy resin: 1 to 3
0 parts by weight (C) Heat-curable latent curing agent activated at around 80 ° C .: 10 to 50 parts by weight (D) At 80 ° C. containing a vinylidene chloride copolymer as a shell wall and a low boiling point hydrocarbon TECHNICAL FIELD The present invention relates to an epoxy-based foamed material which comprises thermally expandable microcapsules which start to expand: 5 to 80 parts by weight, which foams and cures at 80 ° C. and has excellent storage stability at room temperature.

The foamed material according to the present invention is sufficiently foam-cured at 80 ° C. for 1 hour and has sufficient storage stability such that the life at 25 ° C. is 3 weeks or more.

The epoxy resin of component (A) used in the present invention is not particularly limited, and bisphenol A is used.
Type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, or glycidyl amine type epoxy resin. Among these, it is preferable to use a bisphenol A type epoxy resin that is well balanced in terms of handleability, CFRP characteristics to be obtained, and economy. Also, of course, in order to have various properties, it is possible to mix and use several kinds of epoxy resins, or use a product obtained by reacting the epoxy resin with an amine compound or an acid anhydride within a range not gelling. Is also a more preferred embodiment of the present invention.

The thermoplastic resin which is soluble in the epoxy as the component (B) plays a role of controlling the handling property in the present invention. In other words, it does not affect the curing characteristics so much,
By adjusting the viscosity of the epoxy resin composition, it is possible to suppress the flow and to impart appropriate tackiness and drape property when formed into a sheet. However, the addition amount is preferably 1 to 30 parts. When 30 parts or more of such an additive is added, the reactivity is lowered, and when it is cured at a low temperature, the curing becomes insufficient and it is very difficult to obtain a molded article having mechanical strength and the like. If the amount is small, the expected viscosity adjusting effect cannot be obtained.

The thermoplastic resin soluble in epoxy as the component (B) is, for example, polyvinyl butyral, polyvinyl formal, polyether sulfone, polysulfone, polyarylate, etc., but is not limited thereto. Among these, polyvinyl butyral, polyvinyl formal, and polyether sulfone are highly effective and particularly preferable.

Examples of the thermosetting latent curing agent which is activated at about 80 ° C. of the component (C) include amine adduct type curing agents (commercially available from Ajinomoto Co. under the trademark "Amicure") and microcapsule type curing agents. (Commercially available from Asahi Kasei Kogyo Co., Ltd. under the trademark "Novacure"), etc., and even when these curing agents are mixed with an epoxy resin, they are relatively stable at room temperature to 50 ° C and hardly react, but are active at around 80 ° C. It is a so-called heat-curable latent curing agent in which the reaction starts when the reaction starts.
The addition amount of these latent curing agents is suitably 10 to 50 parts, and if less than 10 parts, insufficient curing will result.
Addition of more than 0 parts is not preferable because the physical properties are extremely lowered and the stability at room temperature is lowered. These latent curing agents may be used alone, or these latent curing agents and urea compounds, cyano compounds, dihydrazide compounds,
A curing agent such as an acid anhydride may be used in combination. When used in combination with other curing agents, the reactivity at low temperatures decreases, but the storage stability at room temperature to around 50 ° C improves, so
It is advisable to mix them appropriately according to the purpose.

As the component (D) used in the present invention, there is Matsumoto Microsphere F-30 manufactured by Matsumoto Yushi-Seiyaku Co., Ltd., which contains a low boiling point hydrocarbon having a vinylidene chloride copolymer as a shell wall. The heat-expandable microcapsules start to expand at 80 ° C. The addition amount of the component (D) is preferably from 5 to 80 parts, and when it is less than 5 parts, the foaming effect is hardly obtained, and when it is 80 parts or more, the workability of uniform mixing is deteriorated and the curing of the matrix is difficult. It may also adversely affect the properties or the strength of the foam after molding. The expansion ratio of the present foam material can be basically controlled by the addition amount of this component (D).

In the method for preparing the foamed material of the present invention, since the component (C) is activated at a relatively low temperature to start a reaction and the component (D) also starts to expand at a low temperature, it is preferable to mix them all at once. Absent. The thermoplastic resin of component (B) is generally difficult to dissolve in the epoxy resin of component (A) and must be dissolved at high temperature, for a long time with stirring, or by adding a solvent. It is considered that there is a decrease or the influence of the solvent on the components (C) and (D). Therefore,
First, it is preferable that the component (B) is uniformly dissolved in the component (A). At that time, when heated, it is sufficiently cooled before adding the components (C) and (D), and when a solvent is added, the solvent is completely removed. Then, after that, (C) and (D) are added at around room temperature and uniformly mixed.

The use of the foamed material according to the present invention is not particularly limited, and it can be used anywhere as long as it can take advantage of the characteristic of the present invention that foams and cures at a low temperature.
It is particularly preferably used as an auxiliary material for internal pressure molding of a low temperature curable prepreg.

[0014]

The present invention will be described in more detail with reference to the following examples.

Abbreviations of compounds in Examples and test methods are as follows.

Ep828: Bisphenol A type epoxy resin (oiled shell) PVF: Polyvinyl formal Denka formal #
200 (Denka) PN-23: Amine adduct type latent hardener Amicure (Ajinomoto) HX-3721: Microcapsule type latent hardener Novacure (Asahi Kasei) F-30: Thermally expandable microcapsules (Matsumoto Yushi-Seiyaku Co., Ltd.) Example 1> Component (B) PVF (10 parts by weight) was dissolved in component (A) Ep828 (100 parts by weight) at 160 ° C. for 3 hours, cooled to room temperature, and then at room temperature PN- of component (C).
23 (25 parts by weight) and component (D) F-30 (50 parts by weight) were added and mixed homogeneously to obtain the foamed material of the present invention. The foamed material thus obtained was molded under the conditions shown in Table 1 and the expansion ratio was examined. Further, the same examination was carried out for the foamed material after 30 ° C. × 3 weeks. The results are shown together in Table 1.

<Example 2> A foam material was prepared in the same manner as in Example 1 except that the amount of F-30 as the component (D) was changed as shown in Table 2, and all were molded at 80 ° C for 1 hour. The expansion ratio was examined. The results are shown together in Table 2.

<Comparative Example 1> A foam material was prepared in the same manner as in Example 1 except that the amount of F-30 as the component (D) was changed as shown in Table 2, and all were molded at 80 ° C for 1 hour. The expansion ratio was examined. The results are shown together in Table 2. F-30 hardly foamed at 3 parts by weight, and the foamed article after molding was very brittle at 85 parts by weight.

Example 3 Component (C) PN-23 (2)
The expansion ratio was examined in the same manner as in Example 1 except that 5 parts by weight) was changed to HX-3721 (29 parts by weight). The results are shown in Table 3.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

The resin composition of the present invention is sufficiently foamed and cured at 80 ° C. and has a life of 3 weeks or more at room temperature.
It can be fully used as an auxiliary material for internal pressure molding of 80 ° C curing type prepreg.

Claims (2)

[Claims] 1. (A) Epoxy resin: 100 parts by weight (B) Thermoplastic resin soluble in epoxy resin: 1 to 3
0 parts by weight (C) 10 to 50 parts by weight of a heat-curable latent curing agent that is activated near 80 ° C. (D) Expanding at 80 ° C. containing a vinylidene chloride copolymer as a shell wall and a low boiling point hydrocarbon Thermally expandable microcapsules: 5 to 80 parts by weight of thermosetting foam material. 2. The thermosetting foam material according to claim 1, wherein the thermoplastic resin as the component (B) is polyvinyl formal.