JPH0459820A - Injection-moldable epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition useful for members of automobile, etc., having small curing shrinkage, excellent dimensional stability and surface smoothness, comprising a specific epoxy compound, expandable microcapsule and a curing agent for epoxy resin. CONSTITUTION:The objective composition comprising (A) an epoxy compound composed of (i) >=65wt.% low-viscosity epoxy resin liquid at normal temperature and (ii) <=35wt.% reactive diluent containing 1-3 epoxy groups in one molecule, (B) expandable microcapsule and (C) a curing agent for epoxy resin wherein the content of the component C is 1-30 pts.wt. based on 100 pts.wt. component A. Preferably the component A is composed of only the component (i) and the composition is further mixed with (D) 5-50 pts.wt. based on 100 pts.wt. component A of a filler.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an injection moldable epoxy resin composition applied to a reactive injection molding method.

A molded article that is a cured product of the resin composition of the present invention is useful as an automobile member or the like.

<Conventional technology> Resin molding using the reactive injection molding method can be molded at lower pressure than SMC (sheet molding compound), so it requires less investment in molds and press equipment, and will be useful as a future molding method. It is. Another advantage is that a strong molded product can be obtained by performing reactive injection molding with a reinforcing material such as glass fiber installed in the mold in advance. However, when a resin is molded together with a reinforcing material such as glass fiber, the reinforcing material bulges out on the surface due to curing shrinkage of the resin, which impairs the surface smoothness of the injection molded product.

Conventionally, the following method has been used as a compounding technique for suppressing curing shrinkage of such resins.

The first method is to add fillers and thermoplastic resins to the resin composition. Shigashi, fillers,
Increase the viscosity of the resin composition and also close to its limit 3
Even when blending 0 to 40% by weight, the effect of suppressing shrinkage is still insufficient, and there is also the drawback of increasing the density of the molded product. On the other hand, thermoplastic resins have the drawback of significantly lowering the strength and heat resistance of molded products.

As another method, a method has been proposed in which a decomposable foaming agent is blended into the resin composition and the expansion force is used to reduce curing shrinkage.

However, the decomposition gas reaches the surface of the molded product, creating pinholes, and this type of foaming agent has a weak expansion force (not sufficient to suppress shrinkage).

<Problems to be Solved by the Invention> As described above, as a resin composition used for molding a resin by a reactive injection molding method, a composition with small curing shrinkage is not known.

The present invention has been made in view of the above facts, and is a low-viscosity resin composition that contains microcapsules that expand when heated, so that curing shrinkage is small. The purpose of the present invention is to provide an epoxy resin composition that can be injection molded and has excellent dimensional stability and surface smoothness.

<Means for Solving the Problems> The present invention uses a 65% by weight epoxy resin that is liquid at room temperature and has a low viscosity.
An epoxy compound consisting of the above and 35% by weight or less of a reactive diluent having 1 to 3 epoxy groups in one molecule, an expandable microcapsule, and a curing agent for epoxy resin, the expandable microcapsule content being provides an injection moldable epoxy resin composition, characterized in that the amount is 1 to 30 parts by weight based on 100 parts by weight of the epoxy compound.

The epoxy compound preferably consists only of an epoxy resin that is liquid at room temperature and has a low viscosity.

Moreover, it is preferable that the epoxy resin composition further contains 5 to 50 parts by weight of a filler based on 100 parts by weight of the epoxy compound.

Furthermore, the expandable microcapsules have an outer shell made of vinylidene chloride-acrylonitrile copolymer or methyl acrylate-acrylonitrile copolymer,
It is preferable that the particles contain a low boiling point compound therein, and/or that the average particle size when unexpanded is 100 μm or less.

The present invention will be explained in detail below.

The epoxy compound used in the present invention is an epoxy resin that is liquid at room temperature and has a low viscosity, or a mixture of the epoxy resin and a reactive diluent having 1 to 3 epoxy groups in one molecule. Note that the epoxy resin refers to an epoxy compound that has two or more epoxy groups in the molecule and is usually called an epoxy resin.

Epoxy resins that are liquid at room temperature and have low viscosity include bisphenol A epoxy resin, bisphenol F epoxy resin,
Among various epoxy resins such as glycidyl ether-based epoxy resins such as bisphenol AD type epoxy resins, alicyclic epoxy resins, glycidyl ester-based epoxy resins, glycidylamine-based epoxy resins, and heterocyclic epoxy resins, the properties at room temperature are liquid. Yes, its viscosity is 25
It refers to an epoxy resin with a low viscosity of approximately 15,000 cps or less at °C.

- A reactive diluent having 1 to 3 epoxy groups in its molecule is generally used in combination with a high-viscosity liquid epoxy resin to lower the viscosity of the resin composition, and also has an epoxy group in its molecule. Therefore, it is a compound that also contributes to curing.

- Reactive diluents having one epoxy group in the molecule include n-butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether,
Styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, P, 5ec-butylphenyl glycidyl ether, glycidyl methacrylate, vinylcyclohexene monoepoxide 1, α-pinene oxide, tertiary carboxylic acid glycidyl ester, etc. Reactive diluents with epoxy groups include hexanediol, diglycidyl ether, (poly)
Ethylene glycol diglycidyl ether, (poly)propylene glycol diglycidyl ether, butanediol diglycidyl ether, vinylcyclohexene dioxide, neobentyl glycol diglycidyl ether, diglycidyl aniline, etc. - Contains three epoxy groups in the molecule Examples of the reactive diluent include trimethylolpropane triglycidyl ether and glycerin triglycidyl ether.

In the present invention, 65% by weight or more of the epoxy compound is an epoxy resin that is liquid at room temperature and has a low viscosity. If the epoxy resin accounts for less than 65% by weight of the epoxy compound, the viscosity of the resin composition may become too low or the properties of the cured resin may deteriorate due to a decrease in crosslinking density, which is undesirable. . In particular, when a monoepoxy compound is used as a reactive diluent, the epoxy resin, which is liquid at room temperature and has a low viscosity, should preferably account for 75% by weight or more, taking into account the reduction in crosslinking density.

Further, if there is no risk of the viscosity of the resin composition becoming too high, it is preferable to use only an epoxy resin that is liquid at room temperature and has a low viscosity as the epoxy compound.

In addition, the epoxy resin is liquid at room temperature and has a low viscosity.
As the reactive diluent having three boxy groups, one type of compound may be used or two or more types of compounds may be used in combination.

The expandable microcapsules used in the present invention are hollow spherical particles having an outer shell made of a synthetic resin material, and expand upon heating.

Examples of the synthetic resin material for the outer shell include vinylidene chloride-acrylonitrile copolymer, methyl acrylate-acrylonitrile copolymer, methyl methacrylate-acrylonitrile copolymer, etc., but from the viewpoint of the softening temperature and expandability of the outer shell, , when the molding temperature is 100°C or lower, vinylidene chloride-acrylonitrile copolymer, ) O0-16
At 0°C, methyl acrylate-acrylonitrile copolymer is preferred.

Further, it is preferable that the average particle diameter when unexpanded is 100 μm or less, since this allows uniform dispersion in the epoxy compound.

Furthermore, expandable microcapsules contain certain gasifying substances inside them, and therefore expand when heated.

The gasification substance is selected depending on the curing temperature of the resin, but low-boiling compounds, especially lower hydrocarbons such as isobutane, are preferred.

The expandable microcapsule content of the resin composition of the present invention is 1 to 30 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the epoxy compound. The expandable microcapsule expands during resin curing and suppresses curing shrinkage of the resin, so 1 part by weight or more is required, while 30 parts by weight or less is sufficient from the viewpoint of curing shrinkage suppressing effect and injection moldability.

The curing agent for epoxy resin used in the present invention is a compound that reacts with the epoxy group of an epoxy compound by heating and crosslinks the epoxy compound.

Many types of curing agents for epoxy resins are known, but aliphatic polyamines include diethylenetriamine, triethylenetetramine, isophoronediamine, m-xylenediamine, etc., and aromatic polyamines include metaphenylenediamine, diaminodiphenylmethane, As acid anhydrides such as diaminodiphenylsulfone, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride can be used, and as promoters for these, 2-methylimidazole, 2-methylimidazole, etc. of imidazoles can be used.
-Ethyl-4-methylimidazole is useful. Further, as the latent curing agent, a boron trifluoride-amine complex can be used.

The content of the curing agent for epoxy resin in the resin composition of the present invention varies depending on the type of curing agent used, and cannot be generally determined. An appropriate amount determined for each hardening agent may be used.

The essential components of the resin composition of the present invention are as described above, but the resin composition also includes a filler, a reinforcing material, an antifoaming agent, a wetting agent, a pinhole preventive agent, and an internal mold release agent. etc. may be included.

Fillers are used to improve the smoothness, bending strength, and bending modulus of molded products that are cured products of the resin composition of the present invention, and specifically fillers include calcium carbonate, clay, talc, barium sulfate, and silica. Examples include powder, alumina powder, and the like.
The filler is - for boat fishing, the epoxy compound 1
5 to 50 parts by weight, preferably 20 to 00 parts by weight
40 parts by weight is used. The amount is 5 parts by weight or more from the viewpoint of improving the smoothness, bending strength, and flexural modulus of the molded product, and 50 parts by weight or less from the viewpoint of viscosity and thixotropy.

The reinforcing material is used to improve the strength of a molded product that is a cured product of the resin composition of the present invention, and specifically, reinforcing materials include glass fiber,
Inorganic fibers such as carbon fiber, polyamide, polyester,
Examples include organic fibers such as vinylon. Furthermore, these reinforcing materials can be used in either woven or nonwoven form.

These reinforcing materials are usually attached to the mold, but the proportion of their use is determined from the viewpoint of improving the strength of the molded product.
The amount is 10 to 50 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the epoxy compound.

Commercially available products can be used as the antifoaming agent, wetting agent, anti-pinhole agent, and internal mold release agent.

The resin composition of the present invention is manufactured as a two-component type, and includes a base liquid prepared by mixing components other than the curing agent, and
Store it with only the hardening agent or with a hardening agent liquid prepared by adding a compound that does not react with the hardening agent.
At the time of use, the base agent liquid and hardening agent liquid are mixed in a predetermined ratio.

The resin composition of the present invention is prepared, put into an injection molding machine, and gold is injected into it.

The mold is held at 130 to 160°C for about 2 to 7 minutes to harden the resin.

Remove the molded product from the mold.

<Example> EXAMPLES The present invention will be specifically explained below with reference to Examples.

(Example) The following main agent liquid and curing agent liquid were prepared, and each of them was injected into a mixing head type injection machine (
Transfer to a container (manufactured by Venus Corporation, EPO2 type) and heat to 40℃.
, was injected into the mold at an injection pressure of 10 kg/cm''.

The mold used was a plated mold with internal dimensions of 200 x 200 x 3 mm, and a preform mat (reinforced fiber) was installed in advance so that the content of the mat was 30% by weight relative to the cured molded product. The mold was clamped at a pressure of 20 kg/am", and cured for 5 minutes after injection at the temperature shown in Table 1. The molded product was taken out and the physical properties of the obtained molded product were measured by the following method. It is shown in Table 1.

Separately, the viscosity of the mixture of the main agent liquid and the curing agent liquid was measured by the method described below, and the results are shown in Table 1.

[Preparation of base liquid] Base liquids A-1 to A-9 were prepared in the following manner.

The viscosity of the epoxy compound in the text is a value measured using a cone viscometer (Model EHD, manufactured by Tokyo Keiki Co., Ltd.) at 25° C. and a rotation speed of 20 rpm.

(A-1) Bisphenol A type epoxy resin (viscosity 13
,000 cps, epoxy equivalent weight 189), 80 parts by weight of 1,6-hexanesiol diglycidyl ether (viscosity 18 cps, epoxy equivalent weight 150) as a reactive diluent.
) 20 parts by weight of microcapsules having an outer shell made of methyl acrylate-acrylonitrile copolymer, encapsulating isobutane, and having an average particle size of 15 am when unexpanded, and further additives including an antifoaming agent and pinholes. Inhibitor 0 each
．． 5 parts by weight were weighed and mixed.

(A-2) Prepared in the same manner as A-1 except that the microcapsules were used in an amount of 10 parts by weight.

(A-3) Except for using 15 parts by weight of macrocapsules,
It was prepared in the same manner as A-1.

(A-4) It was prepared in the same manner as A-1 except that the microcapsules were used in an amount of 25 parts by weight.

(A-5) A product was prepared in the same manner as in A-2, except that 50 parts by weight of calcium carbonate (average particle size: 3 μm) was further blended.

(A-6) In the formulation of A-5, the microcapsules have outer shells made of vinylidene chloride-acrylonitrile copolymer (
It was prepared in the same manner except that the amount was changed to 8 parts by weight of particles having an average particle size of 15 μm).

(A-7) A product was prepared in the same manner as A-1 except that the microcapsules were removed.

(A-8) A product was prepared in the same manner as A-5 except that the microcapsules were removed.

(A-9) Bisphenol F type epoxy resin (viscosity 3,
200 cps, epoxy equivalent 175) 100 parts by weight, outer shell made of methyl acrylate-acrylonitrile copolymer, encapsulating isobutane, average particle size when unexpanded is 15μ
8 parts by weight of microballoons, 15 parts by weight of calcium carbonate, and 0.5 parts by weight each of an antifoaming agent and a pinhole preventive agent as additives were weighed and mixed well.

[Preparation of hardening agent liquid] Curing agent liquids B-1 to B-4 were prepared in the following manner.

The viscosity of the curing agent in the text was measured using a cone viscometer (Model EHD, manufactured by Tokyo Keiki Co., Ltd.) at 25°C and at a rotational speed of 20.
This is a value measured in rpm.

(B-1) Only modified alicyclic polyamine (viscosity 30 cps, active hydrogen equivalent 42) (B-2) Only aliphatic polyamine (triethylenetetraamine, viscosity 20 cps, active hydrogen equivalent 24) (B-3) BFs Only amine complex (#1171 manufactured by Anchor Chemical Co., viscosity 8600 cps) (B-4) 20 parts by weight of calcium carbonate was dispersed in 24 parts by weight of modified alicyclic polyamine (viscosity 30 cps, active hydrogen equivalent 42).

[Method for measuring physical properties of molded products] ■Bending strength and bending modulus strength testing machine (manufactured by Toyo Baldwin Co., Ltd., tJTM-57)
The test was carried out in accordance with JIS 6911 using a mold).

■Smoothness surface roughness/shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom 20
2C type).

[Method for measuring viscosity of resin composition] Using a cone viscometer (Model EHD, manufactured by Tokyo Keiki Co., Ltd.),
Measurement was carried out at 0° C. and at a rotational speed of 2 Orpm.

As shown in Table 1, all of the resin compositions of Examples were:
The viscosity was such that injection molding was possible.

Furthermore, the smoothness of the molded article was definitely improved by the addition of expandable microcapsules. This becomes clear when comparing Example 1 and Comparative Example 1, or Example 5 and Comparative Example 2.

In addition, the expandable microcapsule content is 10 parts by weight or more based on 100 parts by weight of the epoxy compound (Examples 2 to 4)
The smoothness of the molded product is further improved, and calcium carbonate as a filler is also used (Example 5.6)
A molded article with particularly excellent smoothness can be obtained.

The flexural strength and flexural modulus, which are one of the general physical properties of molded products, decrease slightly with the addition of expandable microcapsules, but they are within an acceptable range, and they are recovered by the combination of calcium carbonate. .

<Effects of the Invention> According to the present invention, the resin composition has a viscosity that allows injection molding, and since it contains microcapsules that expand upon heating, curing shrinkage is small, and therefore, the molded product obtained after curing is Provided is an injection moldable epoxy resin composition that has excellent dimensional stability and surface smoothness.

Therefore, epoxy resin molded products of better quality than before can be manufactured efficiently at low cost.

Claims (5)

[Claims] (1) An epoxy compound, an expandable microcapsule, and an epoxy resin consisting of 65% by weight or more of a low-viscosity epoxy resin that is liquid at room temperature and 35% by weight or less of a reactive diluent having 1 to 3 epoxy groups in one molecule. Contains a curing agent for
An injection moldable epoxy resin composition, wherein the expandable microcapsule content is 1 to 30 parts by weight based on 100 parts by weight of the epoxy compound. (2) The injection moldable epoxy resin composition according to claim 1, wherein the epoxy compound consists only of an epoxy resin that is liquid at room temperature and has a low viscosity. (3) Claim 1 or 2 further comprising 5 to 50 parts by weight of a filler based on 100 parts by weight of the epoxy compound.
The injection moldable epoxy resin composition described in . (4) The expandable microcapsule has an outer shell made of vinylidene chloride-acrylonitrile copolymer or methyl acrylate-acrylonitrile copolymer, and encapsulates a low-boiling point compound therein. ~
3. The injection moldable epoxy resin composition according to any one of 3. (5) The injection moldable epoxy resin composition according to any one of claims 1 to 4, wherein the expandable microcapsules have an average particle diameter of 100 μm or less when unexpanded.