JP2007031476A - Epoxy resin composition for molding material, molded and cured product thereof, and method for producing the molded and cured product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin composition for a molding material, capable of expressing excellent mechanical characteristics and heat resistance of a cured product obtained by an epoxy resin/acid anhydride curing agent system and capable of being cured at a low temperature, to provide a molded and cured product thereof, and to provide a method for producing the molded and cured product. <P>SOLUTION: This epoxy resin composition for the molding material contains an epoxy resin (A), an acid anhydride-based curing agent (B), and a curing accelerator (C), wherein the curing accelerator (C) comprises 1,2-dimethylimidazole. The method for producing the molded and cured product comprises casting the epoxy resin composition for molding, and then heating and curing the composition at 70-100°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a low-temperature curable epoxy resin composition for molding materials that can exhibit excellent mechanical properties and heat resistance of a cured product obtained in an epoxy resin / anhydride curing agent system, a molded cured product thereof, And a method for producing the molded cured product thereof.

  Conventionally, a molded cured product obtained by curing an epoxy resin with an acid anhydride curing agent has a higher heat distortion temperature than a cured product obtained by using an amine as a curing agent, resulting in electrical characteristics, mechanical characteristics, etc. Are also widely used as artificial marble, electrical and electronic insulating materials, etc. However, in order to obtain a cured product having excellent mechanical properties and heat resistance, it is necessary to heat at a high temperature exceeding 100 ° C. for a long time, and energy saving by low temperature curing is required. The low temperature curing system is also a technology that is expected to be able to use an inexpensive FRP resin mold.

  In addition, large molded products are hardened with amines that currently have problems in workability such as pot life and rash due to lack of a curing furnace that can be heated at high temperatures for a long time. However, if an acid anhydride curing system that can be cured at low temperature is completed, there is a strong demand for development of low temperature curing because the problem of workability can be solved.

  In response to these requirements, for example, it has been proposed that the curing temperature can be reduced to 100 ° C. or less by using a quaternary ammonium salt as a curing accelerator in an epoxy resin / anhydride curing agent system ( For example, see Patent Document 1.) However, some of the quaternary ammonium salts are commercially available in the form of an aqueous solution. Due to the influence of moisture and the influence of moisture due to moisture absorption in the solid state, the mechanical properties of the cured product may be reduced, and voids in the cured product may be reduced. Therefore, further improvement is required.

JP 2002-167424 A (page 3)

  In view of the above circumstances, the present invention is an epoxy resin for molding materials that can be cured at low temperature and can exhibit excellent mechanical properties and heat resistance of a cured product obtained with an epoxy resin / anhydride curing agent system. It is providing the composition, its shaping | molding hardened | cured material, and the manufacturing method of the shaping | molding hardened | cured material.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a molded cured product having excellent mechanical strength and heat resistance even when the curing temperature is low by using 1,2-dimethylimidazole as a curing accelerator. As a result, the present invention was completed.

  That is, the present invention is an epoxy resin composition for a molding material containing an epoxy resin, an acid anhydride curing agent and a curing accelerator, wherein the curing accelerator is 1,2-dimethylimidazole. The present invention provides an epoxy resin composition for a molding material and a molded cured product thereof.

  Furthermore, the present invention is a molding cured product characterized by heat-curing an epoxy resin composition for molding material containing an epoxy resin, an acid anhydride curing agent and 1,2-dimethylimidazole at 70 to 100 ° C. This manufacturing method is also provided.

  By using the epoxy resin composition for molding materials of the present invention, a molded cured product having excellent mechanical strength and heat resistance under low temperature curing conditions can be provided even in an epoxy resin / acid anhydride curing agent system. Further, the present invention can be applied to a large molded product, and is effective in reducing the total cost.

  The epoxy resin (A) used in the present invention is not particularly limited as its structure, and various types can be used, but it is a liquid epoxy resin at room temperature from the viewpoint of excellent workability as a molding material. Preferably, for example, bisphenol type liquid epoxy resin such as bisphenol A type liquid epoxy resin, bisphenol F type liquid epoxy resin, alicyclic epoxy resin such as hydrogenated bisphenol A type liquid epoxy resin, tertiary butyl catechol and epihalohydrin And divalent phenol type epoxy resins such as epoxy resins derived from the above, and so-called reactive diluents such as monoepoxy compounds and alcohol ether type epoxy resins can be used alone or as a mixture of two or more types You may do it. Among these, it is preferable to contain a bisphenol-type liquid epoxy resin, particularly preferably a bisphenol A-type liquid epoxy resin, from the viewpoint of excellent mechanical properties and heat resistance of the resulting cured product.

  In addition, when various solid epoxy resins are used as the epoxy resin (A), the above-described reactive diluent, liquid epoxy resin, etc. are used in combination, and the mixture is heated and mixed to liquefy, or an acid anhydride described later. It is preferable to improve workability by mixing with a product curing agent and liquefying.

  The acid anhydride curing agent (B) used in the present invention is not particularly limited, and examples thereof include phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride. Examples thereof include acid, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, and the like. These may be used alone or in admixture of two or more.

  The blending ratio of the acid anhydride curing agent (B) is 0.8 to 1.2 with respect to 1 equivalent of epoxy group of the epoxy resin (A) from the viewpoint of excellent heat resistance of the cured product, particularly hot water resistance. Equivalent, preferably in the range of 0.95 to 1.05 equivalent.

  As the curing accelerator (C) used in the present invention, it is essential to use 1,2-dimethylimidazole in that a cured product that exhibits mechanical strength and heat resistance under low temperature curing conditions is obtained. It is also possible to use other imidazoles or the like in combination as long as the effects of the above are not impaired.

  The blending amount of the curing accelerator (C) is not particularly limited, but generally, the greater the blending amount of the curing accelerator, the more likely to cause resin burns and cracks in the resulting cured product. For the reason that the pot life of the epoxy resin composition for molding materials is shortened, etc., it is usually used for 100 parts by weight of the total of the epoxy resin (A) and the acid anhydride curing agent (B). A hardening accelerator (C) is mix | blended in 0.4-1.5 weight part, Preferably it mix | blends in 0.5-1.0 weight part.

  The epoxy resin composition for molding material of the present invention is not limited at all except that the epoxy resin (A), the acid anhydride curing agent (B), and the curing accelerator (C) are used. As long as the effects of the present invention are not impaired, various additives such as a filler, an ultraviolet absorber, an antioxidant, a release agent, and a defoaming agent may be used in combination.

  The method for obtaining the epoxy resin composition for molding material of the present invention is not particularly limited. After the epoxy resin (A) and the acid anhydride curing agent (B) are uniformly mixed, a curing accelerator (C ) And other additives, etc., and stirring until uniform, a curing accelerator (C) or other additive is added to one of the epoxy resin (A) and the acid anhydride curing agent (B) in advance. After mixing, there may be mentioned a method of adding a predetermined amount of other components and mixing until uniform. Moreover, as a method of eliminating the bubbles generated with uniform stirring, for example, a method of allowing the bubbles to return gradually after being left for a certain period of time under reduced pressure can be mentioned.

  The molding hardened | cured material of this invention can be easily obtained by heat-hardening the epoxy resin composition for molding materials obtained above, As the temperature, it is 70-100 degreeC normally, 80-100 The curing time is preferably 3 to 8 hours, and preferably 3 to 5 hours. The curing method is not particularly limited, and the epoxy resin for molding material according to the present invention is uniformly stirred and mixed in various materials, for example, a mold made in advance with a resin such as tempered glass, metal or FRP. There is a so-called casting curing method in which the composition is injected. The mold used at this time does not need to use an expensive mold because the epoxy resin composition for molding materials of the present invention can be cured at a low temperature, and can be used with a mold made of an inexpensive material. Therefore, the total cost can be reduced.

  EXAMPLES The present invention will be described in detail below by examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, “parts” and “%” are based on weight.

Example 1
Bisphenol A type liquid epoxy resin EPICLON 850 (Dainippon Ink Chemical Co., Ltd., epoxy equivalent 188 g / eq) 100 g, bisphenol F type liquid epoxy resin EPICLON 830 (Dainippon Ink Chemical Co., Ltd., epoxy equivalent 170 g / eq) 28 g, reactive diluent EPICLON 726 (Dainippon Ink Chemical Co., Ltd., epoxy equivalent 154 g / eq) 25 g, methyltetrahydrophthalic anhydride EPICLON B-570 (Dainippon Ink Chemical Co., Ltd.) as an acid anhydride curing agent , Acid anhydride equivalent 166 g / eq) 143 g and 1,2-dimethylimidazole 1.5 g were mixed in a 1 liter polycup (diameter 12 cm, height 14 cm) and mixed with a spatula for 1 minute 30 seconds to form a molding material Epoxy resin composition 1 for use It was.

  Next, the polycup containing the epoxy resin composition 1 obtained above was placed in a desiccator having an internal volume of about 15 liters at 25 ° C., and vacuum defoaming was performed using a vacuum pump.

  Next, a cured product was prepared using a glass plate (300 mm × 300 mm) subjected to a release treatment with a silicone release agent SH-7020 (manufactured by Dow Corning Toray Silicone Co., Ltd.) as a mold. First, an epoxy resin composition 1 obtained by vacuum defoaming treatment as described above was cast using a glass die having a glass rod 3 mm sandwiched between two glass plates as a mold. This was left in a dryer controlled at 85 ° C. for 5 hours, and the molded product was taken out and slowly cooled in a room temperature atmosphere to obtain a cured product for measuring physical properties having a thickness of about 3 mm.

Comparative Example 1
In Example 1, the epoxy resin composition 2 was blended in the same manner as in Example 1 except that dimethylbenzylamine was used instead of 1,2-dimethylimidazole, and the thickness was about 3 mm under the same curing temperature conditions as in Example 1. A cured product for measuring the physical properties of was obtained.

Comparative Example 2
A cured product for measuring physical properties having a thickness of about 3 mm as in Comparative Example 1 except that the epoxy resin composition 2 of Comparative Example 1 was used and the curing temperature was 120 ° C. for 2 hours and post-curing was performed at 150 ° C. for 3 hours. Got.

Comparative Example 3
In Example 1, the epoxy resin composition 3 was blended in the same manner as in Example 1 except that 2-ethyl-4-imidazole (2E4MZ) was used instead of 1,2-dimethylimidazole. A cured product for measuring physical properties having a thickness of about 3 mm was obtained under the same curing temperature conditions.

Comparative Example 4
In Example 1, an epoxy resin composition 4 was blended in the same manner as in Example 1 except that a tetramethylammonium chloride 50% (TMAC-50) aqueous solution was used instead of 1,2-dimethylimidazole. A cured product for measuring physical properties having a thickness of about 3 mm was obtained under the same curing temperature conditions.

  Using the obtained cured product, the measurement of the heat distortion temperature, the tensile test, and the bending test were performed as follows. The results are shown in Table 1.

Measurement method of heat distortion temperature The cured product having a thickness of about 3 mm obtained above was cut into a size of 12.5 mm × 125 mm, and according to JIS K 7207, a desktop HDT tester CU-6422P manufactured by Toyo Seiki Co., Ltd. -Measured using TS1.

Method of bending test The molded cured product having a thickness of about 3 mm obtained above was cut into a size of 25 mm x 75 mm, measured according to JIS K 6911 using an AUTOGRAPH AG-I manufactured by Shimadzu Corporation, Bending strength and flexural modulus were determined.

Tensile test method After the molded cured product having a thickness of about 3 mm obtained above was cut into a size of 180 mm × 20 mm, a test piece mold was prepared by a tensile test piece preparation machine (manufactured by Tohken Precision Industry Co., Ltd.). According to JIS K 6911, the tensile strength and the elongation were determined by using A & D Tensilon (RTC1350A).

Footnotes in Table 1:
1,2-DMZ: 1,2-dimethylimidazole DMBA: dimethylbenzylamine 2E4MZ: 2-ethyl-4-methylimidazole TMAC-50: tetramethylammonium chloride

Claims (6)

An epoxy resin composition for a molding material containing an epoxy resin (A), an acid anhydride curing agent (B), and a curing accelerator (C), wherein the curing accelerator (C) is 1,2-dimethylimidazole An epoxy resin composition for a molding material, characterized in that The molding material of Claim 1 which uses 0.4-1.5 weight part of hardening accelerators (C) with respect to a total of 100 weight part of the said epoxy resin (A) and an acid anhydride type hardening | curing agent (B). Epoxy resin composition. The epoxy resin composition for molding materials according to claim 1 or 2, wherein the epoxy resin (A) contains a bisphenol type liquid epoxy resin. A molded and cured product obtained by heat-molding and curing the epoxy resin composition for molding materials according to any one of claims 1 to 3. Molded cured product characterized by heat-curing an epoxy resin composition for a molding material containing an epoxy resin (A), an acid anhydride curing agent (B), and 1,2-dimethylimidazole at 70 to 100 ° C. Manufacturing method. The method for producing a molded cured product according to claim 5, wherein the molded cured product is injected into a mold and cured by heating.