JPH0253850A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To provide an epoxy resin composition compounded with a large amount of metal powder, having high fluidity and small cure shrinkage, giving a cured article having excellent thermal conductivity and suitable as a resin mold, jig, etc. CONSTITUTION:The objective composition is produced by compounding (A) a low-viscosity epoxy resin containing an alicyclic epoxy resin and having a viscosity of <=5,000cps (preferably <=3,000cps) with (B) a liquid acid anhydride- type hardener (e.g., alicyclic dibasic acid anhydride), (C) a cure accelerator (e.g., 2-ethyl-4-methylimidazole) and (D) >=100 pts.wt., preferably 150-300 pts.wt. (based on 100 pts.wt. of A+B) of metal powder (e.g., aluminum powder) containing >=50wt.% of fine powder having particle diameter of <=44mum. The composition is poured into a molding frame containing fixed master pattern and subjected to primary curing at <=80 deg.C, the master pattern is removed and the composition is heated at a high temperature to effect the secondary curing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an epoxy resin composition containing metal powder, and more specifically, to a low-viscosity epoxy resin containing a large amount of metal powder such as fine aluminum powder. The present invention relates to a resin composition that is blended with.

The resin composition of the present invention provides a cured product with a low curing shrinkage rate (and high thermal conductivity), so it is useful as resin molds, jigs, and other molded products.

(Prior Art) A resin composition made by blending an epoxy resin with a metal powder such as an aluminum powder is known as a raw material for a resin mold.

For example, in Japanese Patent Publication No. 50-38606, a resin material made by mixing 40-60% by weight of aluminum powder of 200-500 mesh and 10-20% by weight of a hardening agent with 100% by weight of epoxy resin is disclosed. A resin model for special promotion is described, which is characterized by being formed in the shape of . However, in this resin type, the upper limit of the amount of aluminum powder blended is at most 6 by weight per 100 parts of epoxy resin.
0, the curing shrinkage rate of the resin mold is large, making it impossible to faithfully transfer the original mold. Furthermore, since the thermal conductivity is low, the mold is likely to be distorted, and in order to prevent this, the temperature must be gradually raised during curing, resulting in problems such as poor operability.

Furthermore, JP-A No. 60-137623 describes a method for manufacturing a resin mold for injection molding made of epoxy resin, and includes a relatively large amount of metal powder such as aluminum powder or iron powder as a filler. However, it is also disclosed that the curing shrinkage rate and thermal conductivity of the resin mold can be improved. This resin type uses an amine curing agent as the curing agent and bisphenol A type epoxy resin as the epoxy resin, and the viscosity of the system is high, so the aluminum powder filled in it is comparatively It had to have a large target particle size. However, resin molds obtained using fillers with such large particle sizes not only have poor casting surface finish, but also have the disadvantage of forming a precipitate layer because the fillers are not uniformly dispersed. was there.

On the other hand, although resin molds are advantageous in terms of ease of manufacture and cost compared to metal molds, there is a concern that accidents such as chipping or breakage of the mold itself may occur during repeated use. When a conventionally known epoxy resin composition as described above is used to repair such a defective part, shrinkage occurs during curing, resulting in gaps in the repaired part, making it impossible to completely repair the defect.

In recent years, resin molds using epoxy resin have been developed as simple molds, but they have good physical properties such as thermal conductivity and curing shrinkage rate, and the finished surface of the resulting resin mold. A resin mold with good repairability and repairability has not yet been obtained.

(Problems to be Solved by the Invention) The purpose of the present invention is to overcome the problems of the prior art, and to maintain good fluidity even when a large amount of fine metal powder such as fine aluminum powder is blended. The object of the present invention is to provide an epoxy resin composition that can be suitably used for casting, has a small curing shrinkage rate, and provides a cured molded product with excellent thermal conductivity.

Furthermore, the purpose of the present invention is to blend a large amount of metal powder such as fine aluminum powder into the epoxy resin.
The purpose of the present invention is to provide a cured molded product such as a resin mold that has a good casting surface finish and a good surface finish when machined or polished.

Another object of the invention is to provide a repairable resin mold.

As a result of intensive research to overcome the above-mentioned problems of the prior art, the present inventors have developed a low-viscosity epoxy resin containing an alicyclic epoxy resin and having a viscosity (at 25°C) of 5000 centipoise or less. and in combination with a liquid acid anhydride curing agent and a curing accelerator,
It was discovered that an epoxy resin composition containing a large amount of fine metal powder such as fine aluminum powder can achieve the above object, and based on this knowledge, the present invention was completed.

(Means for Solving the Problems) According to the present invention, (A) a low-viscosity epoxy resin containing an alicyclic epoxy resin and having a viscosity (25°C) of 5000 centipoise or less; (B) a liquid An acid anhydride curing agent, (C) a curing accelerator, and (D) a metal powder containing 50% by weight or more of fine powder with a particle size of 44 μm or less, based on a total of 100 parts by weight of (A) and (B).
An epoxy resin composition containing 100 parts by weight or more is provided.

Further, according to the present invention, there are provided a cured epoxy resin product and a resin mold obtained by curing the epoxy resin composition.

Furthermore, according to the present invention, the epoxy resin composition
A method for manufacturing a resin mold, which is characterized by injecting a mold into a fixed mold, primary curing at 80'C or higher, removing the mold, then rapidly raising the temperature, and performing secondary curing at high temperature. is provided.

Hereinafter, the constituent elements of the present invention will be explained in detail.

(Epoxy resin) The low-viscosity epoxy resin used in the present invention contains an alicyclic boxy resin and has a viscosity (25°C) of 500
0 centivoise (cps) or less, preferably 3000c
ps or less.

Examples of the alicyclic epoxy resin include compounds having the following structures.

Cycloaliphatic epoxy adipate 3.4 Epoxycyclohexylmethyl carboxylate Vinyl cyclohexene dioxide 3.4 Epoxy-6-methylcyclohexyl methyl carboxylate Cycloaliphatic epoxy resin can be used alone, but
Aromatic epoxy resins such as bisphenol A and bisphenol F can be mixed with the alicyclic epoxy resin, thereby lowering the curing temperature and shortening the curing time. The blending ratio of aromatic epoxy resin is 70% by weight based on the total amount of alicyclic epoxy resin.
Below, it is particularly preferable that the amount is 20 to 60% by weight. As the proportion of the aromatic epoxy resin increases, the fluidity of the resin composition and the heat resistance of the cured product gradually decrease.

(Liquid acid anhydride curing agent) In the present invention, a liquid acid anhydride curing agent is used as the curing agent. Liquid acid anhydride curing agents are generally heated at 25°C.
Since the viscosity of the curing agent is 500 cps or less and the amount used is larger than that of the commonly used amine curing agent, it is possible to incorporate a large amount of fine metal powder.

The liquid acid anhydride curing agent used in the present invention may be any one commonly used as an epoxy resin curing agent, and examples thereof include alicyclic dibasic acid anhydride and long-chain alkenylsuccinic anhydride. be done.

Specific examples of alicyclic dibasic acid anhydrides include methyl-
A mixture of structural isomers of Δ4-tetrahydrophthalic anhydride,
Stereoisomeric mixtures of methyl-Δ4-tetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, 3,6-nindomethylenemethyltetrahydrophthalic anhydride, etc. Among them, methyl-Δ4-tetrahydrophthalic anhydride is preferred in terms of storage stability. Stereoisomeric mixtures of phthalic acid are most preferred.

Furthermore, even solid dibasic acid anhydrides such as tetrahydrophthalic anhydride and hexahydrophthalic anhydride,
If the eutectic mixture is liquid, it is within the scope of the present invention. Furthermore, specific examples of long-chain alkenylsuccinic anhydrides include dodecenylsuccinic anhydride, octenylsuccinic anhydride, and the like.

Among them, alicyclic dibasic acid anhydrides with a ps of 100 cps or less are preferred.

The amount of the liquid acid anhydride curing agent may be within the commonly used range (for example, it is preferable to use it so that the equivalent ratio with the epoxy resin is 6/10 to 12/10). .

Therefore, for 100 parts by weight of low viscosity epoxy resin,
It is preferable to use it in a range of 90 to 120 parts by weight.

(Curing accelerator) Examples of the curing accelerator used in the present invention include 2-
Ethyl 4-methylimidazole, 1-cyanoethyl 4-
Imidazole and its derivatives such as methylimidazole and l-benzyl-2-ethylimidazole, tertiary amines such as trisdimethylaminomethylphenol, 2,4.6-)lis(dimethylamino)phenol, dimethylcyclohexylamine, trifluorocarbon Examples include boron monoethylamine. Among these, 2.4.6-1-lis(dimethylamino)phenol and dimethylcyclohexylamine are preferred because they have low viscosity and are easy to handle.

By using a curing accelerator, low temperature curing and shortening of curing time are possible. The amount of curing accelerator used is 80
It is selected within a range that can be cured at a temperature of 0.degree.

(Metal powder) The metal powder used in the present invention includes aluminum powder,
There are various metal powders such as copper powder, but among them, aluminum powder has good thermal conductivity, low coefficient of thermal expansion (good wettability with epoxy resin), and good finish on the casting surface. Furthermore, it is prized for its low specific gravity, which allows the cured product to be made lighter.

The metal powder used in the present invention contains 50% by weight or more, preferably 70% by weight or more of fine powder with a particle size of 44 μm or less. Among these, those containing 10% by weight or more, preferably 20% by weight or more of fine powder with a particle size of 20 um or less are particularly preferred. If the metal powder is only a fine powder, the viscosity of the composition may increase and blending may become difficult. Therefore, the remaining metal powder may have a particle size exceeding 44 μm, but preferably 200 μm. Below, it is more preferably 150 μm or less.

By being a fine powder, even if a large amount of metal powder is blended, it is uniformly dispersed in the resin composition, suppresses the formation of a precipitate layer during molding, alleviates internal strain, and improves the appearance of the casting surface. Good surface finish, machining, and polishing.

The mixing ratio of the metal powder needs to be at least equal in weight to the total amount of the low-viscosity epoxy resin and the liquid acid anhydride curing agent. The upper limit of the blending ratio of metal powder is 75% of the total composition.
It can be blended up to about % by weight. Therefore, the mixing ratio of the metal powder is 100 parts by weight or more, preferably 150 to 300 parts by weight, based on a total of 100 parts by weight of the low-viscosity epoxy resin and the liquid acid anhydride curing agent.

Due to such a large proportion of metal powder,
The curing shrinkage rate is lower, and when a resin mold is used, the original mold can be faithfully transferred, improving the precision of the mold. In addition, the thermal conductivity of the cured product is high ((), causing distortion (((
, has good shape retention.By increasing the thermal conductivity,
After primary curing at a low temperature, it is also possible to quickly raise the temperature to a high temperature and perform secondary curing. Furthermore, during primary curing at low temperatures, thermal contraction occurs, and during secondary curing at high temperatures, thermal expansion occurs, and the ratio of expansion is greater than contraction, so resin molds It becomes possible to repair the missing part.

(Epoxy resin composition) The viscosity (25°C) of the epoxy resin composition is 100,000 cps.
It is preferably 50,000 cps or less, and has good fluidity even though a large amount of metal powder is blended.

As described above, since the epoxy resin composition of the present invention has good fluidity, it is suitable as a casting resin composition that is directly inverted from a master mold.

(Curing Method) The method of curing is not particularly limited, and may be carried out by a commonly used method, that is, first, primary curing is performed at a low temperature, and then secondary curing is performed at a high temperature. Specifically, it is primarily cured by heating at 50 to 80°C for 5 to 10 hours, and then secondarily cured by heating at 130 to 180°C for 2 to 6 hours. (Cured product) The cured product of the present invention usually has the following characteristics.

Heat deformation temperature: 130℃ or higher Thermal conductivity: 1.7X10-”caβ/cm・se
C.° C. or higher Heat shrinkage rate: 0.2% or less, preferably 0.15% or less (resin mold manufacturing method) As the master mold, any commonly used mold can be used.

Since primary curing is possible at 80"C or lower, molds made of rubber or plastic, for example, can also be used, and the variety of molds has expanded.

However, since the master mold made of ABS resin or methacrylic resin may be attacked by the epoxy resin composition, it is necessary to apply a barrier coating before use.

The method for manufacturing a resin mold using the epoxy resin composition of the present invention involves casting the resin composition into a mold with a fixed mold, first curing it at 80°C or less, and then demolding the mold. Then, the temperature is rapidly raised to perform secondary curing.

Specifically, after primary curing by heating at 50 to 80°C for 5 to 10 hours, the master mold is demolded, and then heated at 130 to 180°C.
Heat for 2 to 6 hours for secondary curing.

Since the cured product of the present invention has high thermal conductivity, it can be first cured at a low temperature and then quickly heated to a high temperature to be secondarily cured. In the conventional method, the thermal conductivity is poor and distortion occurs when the temperature rises rapidly, so when raising the temperature to the secondary curing temperature, for example,
The temperature had to be raised in steps of 80°C for 2 hours, 100°C for 2 hours, 120°C for 2 hours, 140°C for 2 hours, and 180°C for 2 hours, which took several hours. However,
In the present invention, it is possible to raise the temperature quickly, and the temperature increase rate is usually 3 to 60 minutes, but in some cases it is also possible to raise the temperature all at once.

The resin mold thus obtained has a heat deformation temperature of 130° C. or higher, and therefore can be used as a mold for molding at high temperatures.

(Repair of Resin Mold) The shrinkage rate of the cured product of the composition of the present invention varies depending on the stage of curing. In other words, heat shrinkage occurs during the -second curing,
Thermal expansion occurs during secondary curing. Since the rate of expansion is larger than that of contraction, when used to repair chipped parts of resin molds, this difference in contraction rate can be used to
By additionally casting the resin composition into the chipped portion, a repair mold can be obtained that is in close contact with the portion that is not to be repaired.

(Applications) The epoxy resin composition of the present invention can be used as a mold material for injection molding molds of thermoplastic resins, urethane resins, epoxy resins,
Can be used in vacuum or low-pressure casting molds, reaction injection molding molds, and foaming molds for thermosetting resins such as unsaturated polyester resins, as well as vacuum molding molds, blow molds, press molds, and jigs. can. Moreover, other molded products can also be used.

(Left below) Examples The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Note that parts and percentages are based on weight unless otherwise specified.

Example 1 A curing accelerator was added to a mixture of liquid (I) and liquid (U) prepared in the proportions shown in Table 1 and mixed to obtain an epoxy resin composition.

Measuring the viscosity (cps) of this composition at 25°C,
It is shown in Table 1.

Next, the above-mentioned epoxy resin composition was cast at room temperature into a mold in which a steel mold with a polished surface (average surface roughness: 0.05 μm) was fixed, and after vacuum degassing, it was heated under predetermined curing conditions. ,
It was cured to obtain a cured product. However, the temperature increase rate from secondary curing to secondary curing was 3° C./min on average.

The physical properties of the obtained cured product are shown in Table 1.

Note that *1 to *9 in Table 1 are as follows.

: Alicyclic epoxy resin, 3,4-epoxycyclohexylmethylcarboxylate (manufactured by Daicel Chemical Industries, Ltd., trade name: ROXIDE 2021A, epoxy equivalent: 136) *2: Bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., product name: ROXIDE 2021A, epoxy equivalent: 136) Name Epicote 828 Epoxy equivalent weight 18
6) *3 Nialuminum fine powder (manufactured by Toyo Aluminum Co., Ltd., product name A C1003, A C2500, A C5005
These three types were mixed and prepared so that the particle size distribution was 44-150 μm 10% by weight, 20-44 μm 50% by weight, and 1-20 μm 40% by weight. ) *4: Liquid acid anhydride curing agent (manufactured by Nippon Zeon Co., Ltd., trade name Finhard 200) However, in experiment number 1-4, an amine curing agent (manufactured by Hysol Japan Co., Ltd., HD3688) was used.

*5: Curing accelerator (manufactured by Shin Nippon Rika Co., Ltd., trade name Wandamin DMCA) *6: Heat distortion temperature (HDT) Measuring method JIS K-6911 *7: Curing shrinkage rate (%) Measuring method Compliant with JIS K-6911 However, only the normal pressure casting and impression surfaces were measured. The shrinkage rate of the secondary cured product indicates the value of the finally obtained cured product. (-) means expansion.

*8: Thermoelectric coefficient (can/cm-sec/'c) measurement method: Dyeing method (acetone/benzene method) *9: Method of measuring cast surface condition: According to JIS BO601, Surfcom 700B manufactured by Tokyo Seimitsu ■ Co., Ltd. 10
The average surface roughness was measured at a magnification of 10,000 times.

(Leaving space below) Example 2 Except for the formulation of experiment number 1-3 of Example 1, which was prepared to contain the three types of aluminum powder used in Example 1 in the respective proportions shown in Table 2. An epoxy resin composition and a cured product were obtained in the same manner as in 1, and their physical properties were measured. The results are shown in Table 2.

(Hereinafter, blank space) Example 3 A hole with a diameter of 5 mm and a depth of 10 mm was made in the resin mold shape part to form a defective part. The epoxy resin composition of Experiment No. 1-3 of Example 1 was cast into the defective part of the resin mold, heated at 60°C for 8 hours to perform secondary curing, and then heated at a temperature increase rate of 3°C/min. The temperature was raised at 150° C. for 5 hours to perform secondary curing.

Next, when the repaired area was polished, the cast resin composition adhered perfectly to the repaired area of the resin mold, and the defective area was completely repaired.

(Left below) (Effects of the Invention) The epoxy resin composition of the present invention has a low viscosity, is easy to cast, can be cured at low temperatures, and can also be used as a mold in rubber or thermoplastic resin. The resulting resin mold has a good casting surface finish, a good surface finish after machining and polishing, and a resin mold with good physical properties such as heat resistance, curing shrinkage rate, and thermal conductivity. Moreover, the resin composition of the present invention can be molded into various molded products.

Claims (4)

[Claims] (1) (A) Viscosity containing cycloaliphatic epoxy resin (25
℃) is 5000 centipoise or less, (B) a liquid acid anhydride curing agent, (C) a curing accelerator, and (D) a metal powder containing 50% by weight or more of fine powder with a particle size of 44 μm or less. For a total of 100 parts by weight of (A) and (B),
An epoxy resin composition containing 100 parts by weight or more. (2) A cured epoxy resin product obtained by curing the epoxy resin composition according to claim 1. (3) Claim 2, wherein the cured epoxy resin is a resin type.
Cured epoxy resin as described. (4) The epoxy resin composition according to claim 1 is injected into a mold in which a master mold is fixed, and after primary curing at 80°C or lower, the master mold is removed, and then the temperature is rapidly raised, and then the mold is heated at a high temperature. A method for manufacturing resin molds characterized by subsequent curing.