JPH056582B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to an epoxy resin composition for casting, and more specifically, an epoxy resin composition for casting that exhibits excellent crack resistance, strength, and low shrinkage of the cured product as well as good fluidity. Regarding. [Technical background of the invention and its problems] Today, epoxy resin compositions are attracting attention for their low shrinkage during casting and good strength of the cured product, and are widely used as cast or molded products. , low viscosity epoxy resin compositions are required to facilitate casting operations. It has been known that when a fibrous filler is added to a molding material or a casting material, it is possible to improve the low shrinkage, crack resistance, strength, etc. of the resulting cured product. In general, these properties improve in proportion to the amount of fiber blended, but on the contrary, the viscosity of the composition increases significantly, and especially in casting materials, the fluidity becomes extremely low, making it impossible to inject into molds. becomes. For this reason, the amount of fiber blended is extremely limited, and no effect can be expected from the addition. Therefore, in the field of plastics, we are researching and developing resins that have both the strength of materials and the low viscosity of compositions.
As a result of the development, the following proposals have been made. In the field of thermoplastic resins, resins are known in which fibers are blended with fibers having a shorter fiber length than the normally used chopped strands in order to improve the feeding characteristics during molding. However, this feeding characteristic refers to the so-called feedability from the hopper during injection molding, and is completely different from the concept of fluidity of the casting material. Also, in JP-A-58-168619,
``Cut glass fibers have the effect of improving the flowability of high-viscosity rubbery polymers during heat curing, giving good results in sealing performance and workability, and also preventing air bubbles from forming at the adhesive interface. It is disclosed that it functions effectively to prevent defects that cause peeling of the paint film.However, according to experiments conducted by the present inventors, it has been found that cutting glass fibers alone into epoxy resin It was found that the viscosity of the composition increased significantly in proportion to the amount of the fibers added.In other words, the fluidity improvement effect described in the publication was not due only to the cut glass fibers. However, the effect of the combination on improving fluidity is weak, and even though the cut glass fibers have a very short fiber length, Since it is a fiber, even a small amount of it will cause a considerable increase in viscosity, so the above composition cannot be expected to be used as an ordinary casting material. There has been a strong desire for an epoxy resin composition for casting that contains a large amount of fiber and has a low viscosity while improving properties. The object of the present invention is to provide an epoxy resin for casting that does not cause an increase in viscosity even when the resin is used, and can provide a cured product with excellent crack resistance, strength, and low shrinkage. [Summary of the Invention] The present invention In view of the above circumstances, they conducted extensive research and found that when cut fibers with a specific shape and powder with a specific particle size distribution are used in addition to epoxy resin, the viscosity of the composition dramatically increases. The inventors have discovered that the viscosity decreases, and have completed the present invention.That is, the present invention utilizes a new phenomenon in which the viscosity decreases when two fillers that cause an increase in viscosity are used together. We have succeeded in developing an epoxy resin composition for casting that simultaneously satisfies strength, crack resistance, low shrinkage, and workability, making it possible to use fibers in conventional casting materials. The epoxy resin composition for casting of the present invention having such characteristics includes: (a) an epoxy resin and a curing agent; (b) cut fibers having a diameter of 3 to 20 μm and a length of 3 to 1500 μm; (c) At least 90% by weight of particles with a particle size of 10 μm or less, and a particle size of 10 μm or less
Inorganic powder having a particle size distribution of 50% by weight or more of particles of 5 μm or less; (d) 90% by weight or more of particle size of 50 μm or less;
Consists of inorganic powder particles with a particle size distribution of more than 10% by weight of particles exceeding 10 μm, and the total amount of components (b) to (d) is 40 parts by volume ≦ b + c + d ≦ based on 100 parts by volume of component (a) 225 parts by volume, and 10 parts by volume ≦ d ≦ 75 parts by volume (however, 40 parts by volume)
Parts by volume≦b+c+d≦150 parts by volume (excluding cases where the total of (c) and (d) contains particles of 10 μm or more in proportion by weight or less). The present invention will be explained in more detail below. The epoxy resin used in the present invention may be any epoxy resin that is generally known as an epoxy resin. Specific examples of this resin include:
Bisphenol A diglycidyl ether and its dimer, trimer, epoxy resin obtained from novolac type phenolic resin and epichlorohydrin, epoxy resin obtained from polyhydric alcohol or polyalkylene oxide and epichlorohydrin, containing cyclohexene oxide group Examples include epoxy resins. The curing agent used in the present invention may be any known curing agent for epoxy resins. Specific examples of this curing agent include phthalic anhydride, hexahydrophthalic anhydride,
Acid anhydrides such as tetrahydrophthalic anhydride, methyl-hexahydrophthalic anhydride, methyl-tetrahydrophthalic anhydride, methyl-nadic anhydride, dodecenylsuccinic anhydride, pyromellitic anhydride; triethylenetetramine, metaphenylenediamine, tris( Examples include amines such as dimethylaminomethyl)phenol; dicyandiamide; boron trifluoride-amine complex; imidazole; and one type or a mixture of two or more types selected from the group consisting of these can be used. The curing agent is usually blended in a weight ratio of 8 to 120% by weight based on the epoxy resin. The cut fibers (b) used in the present invention usually have a diameter of 3 to 20 μm, preferably 9 to 13 μm,
The length is usually 3-1500 μm, preferably 10-1500 μm.
It is a fiber with a distribution of 1000 μm. When the diameter and length of the fibers are outside the above ranges, no viscosity reduction phenomenon is observed. The cut fibers of the present invention may be of any type as long as they are used to improve the mechanical strength of resins, such as milled fibers (trade name, manufactured by Asahi Fiberglass Co., Ltd.), Examples include Micro Glass Surf Estland (trade name, manufactured by Nippon Sheet Glass Co., Ltd.), Glass Cut Fiber (trade name, manufactured by Fuji Fiber Glass Co., Ltd.), alumina fiber, boron fiber, silicon carbide fiber, metal whisker, carbon fiber, and the like. In the present invention, inorganic powders having two different particle size distributions are used. One is the particle size
Particle c has a viscosity distribution (integrated distribution) in which 90% by weight or more is 10 μm or less and 50% by weight or more is 5 μm or less in particle size. The other is powder d, which has a particle size distribution (integrated distribution) in which 90% by weight or more of particles with a particle size of 50 μm or less and 50% by weight or more of particles with a particle size of more than 10 μm. If powder particles having different particle size distributions as described above are not used, the viscosity lowering effect will be weak even when used in combination with fibers. Such inorganic powder may be any known inorganic powder, such as silica, alumina, talc, calcium carbonate, clay, aluminum hydroxide, barium sulfate, titanium dioxide, etc. . In the present invention, the blending amount of components b to d is 40 parts by volume ≦ b based on 100 parts by volume of the total amount of resin and curing agent.
+c+d≦225 capacity parts and 10 capacity parts≦d≦75 capacity parts. If (b+c+d) is less than 40 parts by volume, the viscosity of the composition will be too low and the filler will settle, making it unsuitable as a casting material. On the other hand, if (b+c+d) exceeds 225 parts by volume, the viscosity is high and casting becomes extremely difficult. Also, the d component is
If it is less than 10 parts by volume, the effect of reducing the viscosity by adding this component is weak, and if it exceeds 75 parts by volume, the viscosity becomes too high and at the same time properties such as crack resistance deteriorate, which is not suitable. The blending ratio of components b to d is ideal from the viewpoint of workability, since the viscosity is lowest approximately at the center of the isoviscosity diagram (Fig. 1), as shown in the reference example. However, in general, in addition to the viscosity of the composition, the strength, crack resistance, shrinkage rate, cost, etc. should be taken into consideration when determining the composition. The epoxy resin composition for casting of the present invention may further contain silica, alumina, talc, etc. having particle sizes used in general epoxy resin compositions for casting, if necessary, within a range that does not impair the effects of the present invention. Fillers such as calcium carbonate, clay, and titanium dioxide (filler here means those whose particle size is larger than component d), organic and inorganic colorants, surface treatment agents such as silane coupling agents, Additives such as imidazole-based, tertiary amine-based, metal complex-based curing accelerators, and the like may be added. The method for producing the epoxy resin composition for casting of the present invention is not particularly limited as long as it is a method normally applied to the production method of resin compositions. As a specific example of this method, a predetermined amount of the raw materials that are the components of the present invention are put into a mixer such as a universal mixer, and the mixture is mixed and stirred. Next, in order to mold, the obtained composition is thoroughly mixed and degassed, and then poured into a mold.
For example, it may be cured by standing at 130°C for 3 hours and then at 150°C for 15 hours. [Effects of the Invention] As in the present invention, when cut fibers having a specific shape and two types of inorganic powder particles having a specific particle size distribution are used, the viscosity of the composition is dramatically reduced. A large amount of quality filler can be blended. Therefore, it is possible to significantly improve properties such as crack resistance, strength, and low shrinkage of the cured product without impairing casting workability. The industrial value is extremely large. [Examples of the Invention] Examples 1 to 3 and Comparative Examples 1 to 7 Epoxy resins include bisphenol A type diglycidyl ether epoxy resin with an epoxy equivalent of 400 (trade name Araldite CT-200, manufactured by Ciba Geigy), and an epoxy equivalent of 184. ~194 bisphenol A type diglycidyl ether epoxy resin (trade name Epicote 828, manufactured by Shell Chemical Co., Ltd.) or alicyclic epoxy resin with an epoxy equivalent of 156 (trade name Araldite CY175, manufactured by Ciba Geigy); anhydrous phthalate as a curing agent Acid or NH2200 (trade name, manufactured by Hitachi Chemical Co., Ltd.); N,N-dimethylbenzylamine (DMBA) as a curing accelerator: Glass fiber b with a diameter of 13 μm and an average length of 50 to 60 μm as a cut fiber
(manufactured by Nippon Sheet Glass Co., Ltd.); average particle size of approximately 1 μmc (99% by weight of particles with a particle size of 5 μm or less) and approximately 12 μmd (60% by weight of particles with a particle size exceeding 10 μm) shown in Figure 2 as inorganic powder. Two types of silica powders (manufactured by Ryumori Co., Ltd.) were blended in the composition ratios shown in the table to prepare epoxy resin compositions for casting of the present invention in Examples 1 to 3. Next, after sufficient mixing and degassing,
A test piece was prepared by heating at 130°C for 3 hours and then at 150°C for 15 hours to harden. On the other hand, as Comparative Examples 1 to 6, glass fiber and 2
Test pieces were prepared in the same manner as in the example except that each type of silica was used alone or in the absence of any one of them. Further, as Comparative Example 7, a resin composition was prepared by blending 240 parts by volume of filler with 100 parts by volume of resin and curing agent, but the resin composition could not be cast due to its high viscosity. The fluidity, crack resistance, tensile strength, shrinkage rate, and coefficient of linear expansion of the test pieces prepared by the above method were measured. The obtained results are also listed in the table.

【table】

[Table] (1) Visual measurement ◎Excellent ○Good △Poor ×Pooring impossible
(2) Orifant washing method (Industrial materials vol 29, N
o.5, p59, 1981)
(3) Reference example according to JIS K 6911 Using the same resin and fillers (b) to (d) as in Example 1, the viscosity was measured when the three types of fillers were changed in various proportions. Based on the results, an isoviscosity diagram for the ternary system was drawn. Note that no curing agent was added to avoid an increase in viscosity during measurement. The viscosity was measured by heating the resin composition to 140°C and using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd.).
I asked for it. As is clear from FIG. 1, the viscosity of the composition is lowest in a region approximately in the center of the diagram, and the viscosity increases as one moves away from this region. Therefore, from the viewpoint of workability, it is found that it is preferable to use the central region where the viscosity is lowest.

[Brief explanation of the drawing]

FIG. 1 depicts isoviscosity lines when cut fibers b and silicas e and d are each blended in a range of 0 to 140 parts by volume with respect to 100 parts by volume of resin. In the figure, the numbers in the figures represent viscosity (poise). FIG. 2 shows the particle size distribution of two types of silica powders e and d used in the examples of the present invention.

Claims (1)

[Scope of Claims] 1 (a) Epoxy resin and curing agent; (b) Cut fibers having a distribution of 3 to 20 μm in diameter and 3 to 1500 μm in length; (c) 90% by weight or more of particles with a particle size of 10 μm or less , and particle size
Inorganic powder having a particle size distribution of 50% by weight or more of particles of 5 μm or less; (d) 90% by weight or more of particle size of 50 μm or less;
An inorganic powder having a particle size distribution of more than 50% by weight of particles exceeding 10 μm; and the total amount of components (b) to (d) is 40 parts by volume ≦ b + c + d per 100 parts by volume of component (a). ≦225 capacity parts, and 10 capacity parts≦d≦75 capacity parts (however, 40 capacity parts
An epoxy resin composition for casting, characterized in that parts by volume ≦ b + c + d ≦ 150 parts by volume (excluding cases where particles of 10 μm or more in the total of (c) and (d) account for 10% by weight or less).