JPH0432109B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an epoxy resin composition containing composite fine particles made of a flexible polymer and a cured epoxy resin. [Prior Art] Epoxy resins are used in a wide range of industrial fields as paints, adhesives, and molding agents because of their excellent mechanical, thermal, electrical, and adhesive properties. On the other hand, hard and brittle, hardened
When used as an adhesive, peel strength is particularly low due to the generation of internal stress due to cooling, and in the case of molded products, problems such as cracks are likely to occur. In order to solve these problems, various studies have been carried out in the past. The most common method is known as rubber blend modification. Specifically, liquid rubber with a molecular weight of about 3000, especially liquid butadiene-acrylonitrile copolymer (CTBN) with carboxyl groups at the terminal or pendant.
is often used. Furthermore, JP-A No. 62-22850 discloses that fine polymer particles are prepared by coating the surface of a polymer having a glass transition temperature of room temperature or lower with a polymer having a glass transition temperature of room temperature or higher by an emulsion polymerization method. A method has been proposed in which the powder is collected as a powder and then blended into an epoxy resin to reduce the internal stress of the cured epoxy resin. [Problems to be Solved by the Invention] However, carboxyl group-containing liquid rubbers have low compatibility with epoxy resins, especially epoxy resins with large molecular weights, and furthermore, when cured, the particle size of the rubber component particles forming the dispersed layer may be reduced. Since it is difficult to control, there is a problem that it is difficult to always obtain a uniformly cured resin. Furthermore, in the technique of JP-A-62-22850, since an acrylic polymer component having a relatively high glass transition temperature is present between the epoxy resin of the matrix and the acrylic polymer having a glass transition temperature below room temperature, There is a problem that the reinforcing effect of the particles is low, and in some cases, they dissolve into the epoxy resin layer and deteriorate the properties of the epoxy resin matrix. Furthermore, there was a problem in that the work was complicated due to repeated polymerization. The present invention aims to solve these problems by reducing internal stress, improving peel adhesive strength, and further increasing shear adhesive strength and impact adhesive strength without impairing the excellent properties inherent in epoxy resins. The purpose is to provide improved epoxy resin compositions. [Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration. "An epoxy resin composition characterized by substantially dispersing the following particles A in an epoxy resin. Particle A: consists of an interior and a surface layer covering it, and the surface layer is the following (a). , spherical fine particles with an average particle diameter of 100 μm or less whose interior is a phase-separated mixture of the following (a) and (b). (a): Epoxy compound having at least two epoxy groups in one molecule and epoxy curing (b): A polymer having a glass transition temperature of 20°C or less. The epoxy compound in the cured epoxy resin (a) of the present invention has at least two epoxy groups in the molecule. Epoxy resins are widely used, specifically:
Glycidyls such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac epoxy resin, cresol novolac epoxy resin, triglycidyl ether triphenylmethane, tetraglycidyl ether tetraphenyl ethane, etc. Ether type epoxy resin, glycidyl ester type epoxy resin such as hexahydrophthalic acid glycidyl ester, dimer acid glycidyl ester,
Examples include, but are not limited to, glycidylamine type epoxy resins and alicyclic epoxy resins such as triglycidyl-P-aminophenol, tetraglycidylaminodiphenylmethane, tetraglycidyl metaxylene diamine, and triglycidyl isocyanurate. It's not something you can do. Furthermore, as the epoxy curing agent used as the curing agent for the epoxy resin, those that are sparingly soluble in water are preferably used, and specifically, polyamide amines, alicyclic polyamines, aromatic polyamines, polyphenols, Examples include triamines, imidazoles, and acid anhydrides. The amount of these epoxy curing agents is preferably in the range of 0.8 to 1.2 equivalents per equivalent of epoxy group in the epoxy compound, and in the case of catalytic curing agents, it is approximately 20 parts by weight or less per 100 parts by weight of the epoxy compound. It is better to use The combination of the epoxy resin and the epoxy curing agent in the particles A is not particularly limited, but it is preferable to use the same combination as in the epoxy resin composition in which the particles A are dispersed. In the present invention, "substantially dispersing the particles A in the epoxy resin" means that each particle is independently dispersed in the epoxy resin serving as a matrix without agglomeration of the particles A. . The inside of the particle (A) of the present invention consists of a phase-separated mixture of (a) and (b), but the glass transition temperature of (b) is
The number average molecular weight of the polymer at 20° C. or lower is preferably 5,000 or more, more preferably 10,000 or more. In addition, in order to form a phase-separated structure within the particles, the solubility parameter of the epoxy compound was set to δE,
When the solubility parameter of a polymer having a glass transition temperature of 20° C. or less is δR, |δE−δR| is preferably 0.6 or more, and more preferably 1.0 or more. Examples of polymers satisfying such characteristics include isoprene rubber, butadiene rubber, butyl rubber, nitrile rubber, styrene-butadiene rubber, epichlorohydrin rubber, acrylic rubber, and hydrogenated products or derivatives thereof. Among these polymers, polymers into which at least one functional group selected from carboxyl groups, acid anhydride groups, epoxy groups (including glycidyl groups), amino groups, and hydroxyl groups have been introduced are compatible during curing of the epoxy compound. It is possible to partially react with the epoxy compound at the phase separation interface, or to make the curing behavior the same, improving the adhesion at the phase separation interface, that is, ultimately improving the properties of the epoxy resin composition in which the particles are dispersed. This is particularly preferred because it can improve the performance. In the present invention, the polymer may be a homopolymer or a copolymer, or two or more types of polymers may be used in combination. In the present invention, the composition ratio of the polymer (b) having a glass transition temperature of 20° C. or less in the spherical fine particles is preferably 90 wt % or less. If it exceeds 90 wt%, the surface of the fine particles cannot be sufficiently covered with the cured epoxy resin, which may cause blocking during handling. Next, a method for producing spherical fine particles of the present invention will be explained. In the present invention, it is preferable that (a) the epoxy compound, the epoxy curing agent, and (b) the copolymer having a glass transition temperature of 20° C. or less temporarily form a transparent compatible solution. If a compatible solution cannot be formed, a difference in composition ratio will occur between the fine particles obtained by the production method described below, and for example, fine particles containing only the polymer (b) may be produced, which is not preferable.
A heating melt kneading method is used to make the epoxy compound (a) and the epoxy curing agent, which are liquid or solid at room temperature, and the polymer (b) compatible, but the epoxy compound and the epoxy curing agent are mixed during heating. As the curing reaction progresses, it may become difficult to form spherical particles. Considering the above points, in the present invention, by dissolving each component using a common solvent,
A method of temporarily forming a compatible solution is preferably used. A method for forming the thus formed compatible solution into spherical fine particles includes a method in which the compatible solution is suspended or dispersed in a liquid mainly consisting of water. Typical methods will be listed below, but the present invention is not particularly limited to these methods. A method of cutting the compatible solution into droplets by continuously discharging the compatible solution from a nozzle that vibrates in the air or in the liquid, and collecting the droplets in the liquid. A method in which the compatible solution is ejected in pulses from a nozzle in the air or in the liquid, and then collected in the liquid. A method of emulsifying the compatible solution using an emulsifier. Among the above methods, the method from the viewpoint of productivity is preferably used in the present invention. The organic solvent suitable for the above-mentioned spherical microparticle formation method is preferably one that is substantially sparingly soluble in water and has a boiling point of less than 100°C. Specifically, hydrocarbons such as benzene and cycloxane, dichloromethane,
Examples include halogenated hydrocarbons such as chloroform, carbon tetrachloride, dichloroethane, trichloroethane, and trichloroethylene, esters such as ethyl acetate, and ketones such as methyl ethyl ketone, and two or more types may be used as a mixture. Furthermore, in order to further improve the solubility of each component, it is also possible to use an appropriate amount of an organic solvent that is miscible with water. In the above-mentioned spherical microparticle formation method, the operation can be carried out without problems if 60% by weight or more of the organic solvent used is insoluble in water. Next, the organic solvent in the compatible solution droplets in the suspension is volatilized and removed by heating and/or reduced pressure. By removing the organic solvent, a phase-separated structure between the epoxy compound and the polymer (b) may be formed in the particles. Finally, heat curing treatment is performed under normal pressure or pressure to cause the epoxy compound in the particles to react with the epoxy curing agent, followed by removing water by filtration or centrifugation, washing, and drying. Obtain spherical fine particles. The heat curing treatment temperature is preferably 60°C or higher. During this heat curing treatment, a phase-separated structure of the epoxy compound and the (b) polymer is finally formed. The spherical fine particles obtained by the method of the present invention are
As a result of transmission electron microscopy, the surface layer has a structure consisting of a hardened epoxy resin coating layer, and the inside has a glass transition temperature of 20℃.
It was observed that the following polymers formed a phase-separated structure with a continuous layer. In addition, the phase-separated state exhibits various structures such as a sea-island structure and a lotus root-like structure depending on the characteristics of the polymer (c) used, but in the present invention, a phase-separated structure is not formed. For example, the desired characteristics can be exhibited. The reason why such a structure was formed is not clear, but it is thought to have been formed during the process of dispersion in a dispersion medium mainly composed of water, desolvation in the suspension state, and subsequent hardening treatment. , is a highly preferred structure for achieving the present invention. The average particle diameter of the fine particles obtained as described above is preferably 100 μm or less, preferably 70 μm or less, and more preferably 30 μm or less. If the average particle diameter exceeds 100 μm, it is not preferable because the handling property during kneading with the epoxy resin as a matrix deteriorates or the physical properties of the composition are impaired due to failure of fine dispersion. Further, other components such as pigments, dyes, antioxidants, heat resistant agents, lubricants, antistatic agents, plasticizers, and other polymers can be added to the spherical fine particles of the present invention. Furthermore, it is also possible to use an inorganic filler such as titanium oxide, talc, or silica supported on the surface of the spherical fine particles of the present invention. The epoxy resin for the matrix of the epoxy resin composition of the present invention comprising the above-mentioned spherical fine particles as a dispersed phase is a conventionally known epoxy resin, that is,
Compounds having at least two epoxy groups in one molecule can be used. Furthermore, conventionally known compounds can be used as the curing agent. Furthermore, it is also possible to use a curing accelerator together with the curing agent. For details on these compounds, see, for example, "New Epoxy Resins" edited by Hiroshi Kakiuchi (Shokodo)
is explained in detail. In the present invention, in order to obtain the desired epoxy resin composition by blending the spherical fine particles with the epoxy resin, a three-roll machine, an extruder, a melt kneader, a ball mill, etc. are used to thoroughly mix the fine particles with the epoxy resin. Just mix. At this time, if necessary,
Additives such as curing agents, fillers, antioxidants, lubricants, and antistatic agents may be added. In the epoxy resin composition obtained as described above, the spherical fine particles are uniformly dispersed without agglomeration. In the epoxy resin composition of the present invention, particles (A)
The amount added is such that the glass transition temperature in the fine particles is 20℃ for 100 parts by weight of the epoxy resin in the matrix.
The following polymers may be used in an amount of 3 to 100 parts by weight, preferably 5 to 50 parts by weight. If it is less than 3 parts by weight, a sufficient modifying effect cannot be obtained, and if it exceeds 100 parts by weight, it becomes difficult to obtain the properties required of an epoxy resin, such as heat resistance, electrical properties, and adhesiveness. [Example] Examples of the present invention are listed below, but the present invention is not limited thereto. Synthesis Example 1 16 parts by weight of bisphenol A type epoxy resin (trade name "Epicote 828", manufactured by Yuka Ciel Epoxy Co., Ltd.), 4 parts by weight of diaminodiphenylmethane, and butyl acrylate-ethyl acrylate-acrylonitrile-acrylic acid copolymer. 300 parts by weight of ethyl acetate was added to 80 parts by weight of the combined product (number average molecular weight: 100,000, glass transition temperature: -10°C) and mixed to obtain a homogeneous solution. While stirring the solution at a rotational speed of 900 rpm at 30°C, 8% polyvinyl alcohol (trade name "Gohsenol GL-05" manufactured by Nippon Gosei Kagaku Co., Ltd.) was added.
300 parts by weight of the aqueous solution was continuously added over 10 minutes to obtain a final oil-in-water emulsion from the initial water-in-oil emulsion. While stirring the emulsion at 200 rpm, the temperature was raised to 50° C. under reduced pressure to volatilize and remove ethyl acetate.
Further, the emulsion was placed in an autoclave equipped with a stirrer, and heated at 90°C for 2 hours while gently stirring.
Subsequently, heat curing treatment was performed at 150℃ for 2 hours, and after cooling to room temperature, it was taken out from the container, filtered and dehydrated, thoroughly washed with warm water, and dried to reduce the average particle size.
Spherical fine particles of 3.1 μm were obtained. Figure 1 shows a transmission electron micrograph showing the particle structure of the obtained spherical fine particles (40,000x magnification).
The sample was stained with osmic acid,
The dark areas are cured epoxy resins, and the light areas are polymers with glass transition temperatures below 20°C. It can be seen that the epoxy resin and acrylic rubber form a phase-separated structure, and the surface layer is covered with the epoxy resin layer. Synthesis Example 2 In Synthesis Example 1, butyl acrylate-ethyl acrylate-acrylonitrile-glycidyl methacrylate copolymer (number average molecular weight: 80,000, glass transition temperature: - All operations were performed in the same manner as in Synthesis Example 1 except that the temperature was 15°C), and the average particle size was 2.9 μm.
spherical fine particles were obtained. FIG. 2 shows a transmission electron micrograph showing the particle structure of the obtained spherical fine particles (magnification: 40,000 times). Examples 1 to 4 According to Table 1, the spherical fine particles obtained in Synthesis Examples 1 and 2 were mixed with bisphenol A type epoxy resin (trade name "Epicote 828", oil-based shell epoxy
Co., Ltd.) to prepare a cured product. Curing was carried out at 80°C for 2 hours, then at 150°C for 2 hours, and finally at 180°C for 2 hours. Comparative Examples 1 and 2 According to Table 1, terminal carboxylated butadiene-acrylonitrile copolymer (trade name "Hiker") with no rubber component added and a liquid rubber
A cured modified epoxy resin (CTBN1300 x 8, manufactured by Gutduritsu) was prepared. Curing was carried out under the same conditions as in the examples. Comparative Examples 3 and 4 In Example 3, in place of the fine particles obtained in Synthesis Example 2, polymer particles of polybutyl acrylate (average particle size 0.6μ) prepared by emulsion polymerization were used.
m) (Comparative Example 3), or the cured product was prepared in the same manner as in Example 3, except that polymer particles (Comparative Example 4) whose surfaces were coated with approximately the same amount of polymethyl methacrylate by emulsion polymerization were used. Created. Evaluation of properties For Examples 1 to 4 and Comparative Examples 1 to 4 prepared above, the adhesive strength (T-peel adhesive strength, tensile shear adhesive strength, impact adhesive strength) was determined according to JIS K6854,
Measured according to JIS K6850 and JIS K6855. The measurement results are shown in Tables 2 and 3, and it was found that the epoxy resin composition of the present invention had excellent adhesive strength.

【table】

【table】

[Table] [Effects of the Invention] The epoxy resin composition of the present invention has good handling properties and excellent adhesive strength.

[Brief explanation of drawings]

FIG. 1 is a photograph showing the particle structure of spherical fine particles obtained in Synthesis Example 1 of the present invention. FIG. 2 is a photograph showing the particle structure of spherical fine particles obtained in Synthesis Example 2 of the present invention.

Claims (1)

[Scope of Claims] 1. An epoxy resin composition comprising particles A below substantially dispersed in an epoxy resin. Particle A: A spherical particle with an average particle diameter of 100 μm or less, consisting of an interior and a surface layer covering it, where the surface layer is the following (a) and the inside is a phase-separated mixture of the following (a) and (b). Fine particles. (A): A cured epoxy resin consisting of an epoxy compound having at least two epoxy groups in one molecule and an epoxy curing agent. (b): Polymer with a glass transition temperature of 20°C or less.