JPS6015431A - Solid-phase curing of solid epoxy resin molding - Google Patents

Abstract

PURPOSE:To obtain a molding of excellent strength advantageously without producing an internal stress, etc., by releasing a solid crosslinkable epoxy resin molding from a mold before the progress of crosslinking and completing its curing in a solid state while keeping the temperature of the atmosphere within a specified range. CONSTITUTION:A crosslinkable epoxy resin composition is molded in a mold by injection, extrusion, or the like, and the solidified resin molding of which the crosslinking reaction is not substantially advanced and which has a glass transition point (hereinafter, abbreviated as Tg) of 40-200 deg.C is released from the mold. The heat curing of the molding is carried out at an ambient temperature not higher than the Tg of the molding +20 deg.C, and the curing reaction is completed by raising the ambient temperature in accordance with the Tg of the molding which increases with the progress of the curing while the temperature is kept within the range not exceeding the Tg of the molding +20 deg.C. In this way, it becomes possible to perform mold release within a short time and to effect curing without deformation, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid phase curing method for a solidified epoxy resin molded product.

Conventionally, as a method of curing epoxy resins, a method of crosslinking and curing at a temperature equal to or higher than the melting point of the resin has generally been adopted. That is, in order to shape it into a certain mold, it needs to be in a molten state, and in order to crosslink and harden it as quickly as possible, it is customary to cure it at a high temperature, that is, in a molten state. =1. It is also known that when the crosslinking reaction has progressed to a certain extent and it no longer shows a molten state, it is cured in a solid state by 1 tll after-cure.

However, in this type of curing method, (1) the material is cured at a temperature above the melting point (liquid phase), so in the case of casting, transfer molding, injection molding, etc., the mold is removed until crosslinking progresses and it becomes a solid state; I can't. Usually, it takes a long time to remove the mold, ranging from 10 minutes to 24 hours, and the efficiency of mold utilization is extremely low. (2) From this point of view, there is a method of rapidly curing at a high temperature, but in this case, the curing reaction becomes uneven, leaving internal distortion in the molded product, and the cured product becomes brittle. .

An object of the present invention is to provide an industrially advantageous method for curing epoxy resin molded articles that can be demolded in an extremely short time.

However, it is an object of the present invention to provide a method for curing epoxy resin molded products that can produce molded products with excellent strength through a uniform curing reaction without causing internal distortion.

A further object of the present invention is to provide a method for curing an epoxy resin molded product which has very low curing shrinkage.

In the present invention, after demolding a solidified molded product of a cross-linkable epoxy resin with a glass transition temperature (T7) of 40 to 200°C, heat curing is performed at an ambient temperature not exceeding 20°C from T1 of the molded product. , T of the molded material increases with the progress of curing.
Corresponding to 2, the ambient temperature was set to 20
It relates to a solid-phase curing method for a solidified epoxy resin molded product, which uses a planting device to complete the curing reaction by raising the temperature while maintaining the temperature within a range not exceeding °C.

The solidified molded product of the epoxy resin mentioned here is one in which the crosslinking reaction has not substantially progressed, and the so-called after-cure temperature of a normal molded product (T which this molded product ultimately reaches)
? It is completely different from the conventional after-cure 1) 11 cured molded product, as it completely deforms and shrinks when exposed to - air (the temperature after +jiJ is generally used). 5. As an indication that the crosslinking reaction of the solidified molded product has not substantially progressed, stickiness is observed when the surface of the molded product is soaked with acetone at room temperature and rubbed with a fingertip. Conventional after cure 11J
In the cured molded product, most of the crosslinking reaction has proceeded, and this level of acetone does not cause it to become sticky.

Since the present invention cures in the same phase state, there is no need to maintain the shape in the mold, and the mold usage efficiency is extremely high, and the curing reaction can be performed uniformly at a slightly fixed atmospheric temperature. The physical properties of the cured product are excellent, and especially the cure shrinkage is much smaller than that of conventional methods, which is an unexpected advantage.

Epoxy resins used in the present invention include, for example, bisphenol type epoxy resins, novolak type epoxy resins, halogenated epoxy resins, hydrogenated epoxy resins, alicyclic epoxy resins, and hydan I/yne type epoxy resins. Silicone epoxy resin, epoxy furan resin, epoxy ester resin, phenoxy resin, epoxy urethane resin, modified epoxy resin in which the end group of liquid rubber is modified with epoxy, or phenol such as polyvinyl phenol cured with epoxy resin. Other types of resins can also be used.

Examples of compounds used as compounding agents for these epoxy resins include known reinforcing agents, curing agents, fillers, plasticizers, diluents, flame retardants, photopolymerization initiators, and other additives. Of course, it is also possible to blend other known thermoplastic or thermosetting resins that are compatible with the epoxy resin.

Specifically, as the curing agent, in addition to amines, acid anhydrides, imidazoles, organic peroxides, etc., alcohols, isocyanates, etc. can also be used depending on the polymer structure. .

As reinforcing agents, in addition to fibrous reinforcing agents such as inorganic fibers such as glass fiber, carbon fiber, asbestos snow, aramid fiber, nylon, polyester, etc., whiskers such as aluminum oxide, silicon carbide, and graphite are used. can also be used.

Other additives include fillers and pigments such as phantom 1, glass flakes, glass powder, mica, carbon black, curcum, clay, silica, calcium carbonate, aluminum hydroxide, titanium white, or dioctyl phthalate and tricresyl phosphate. Plasticizers such as esters, reactive or non-reactive diluents such as butyl glycidyl ether, xylene, flame retardants such as antimony trioxide and chlorinated paraffins, photoinitiators such as isopropyl benzoin ether, etc., as appropriate. When used selectively, it can be used.

In the present invention, the above-mentioned epoxy resin compounded composition is molded by an appropriate method to obtain a crosslinkable and hardenable solidified molded product having a Tf of 40 to 200°C. As a specific method for obtaining a solidified molded product having Tf as described above, for example: (1) The Tf of the epoxy resin itself used is about 35 to +
Select one in the 95°C range. This is because when a reinforcing agent or filler is mixed with an epoxy resin, Tf generally tends to increase.

(2) The Tf of the epoxy resin itself used is 195°C
When using the above, 9200 “You may adjust it to below C.

(3) If it is necessary to use an epoxy resin with a Ty of less than 35°C, use another epoxy resin with a high Tf or other thermosetting resin, or increase the T1. The temperature of the TV may be adjusted within the range of 40 to 200°C by increasing the amount of reinforcing agent or filler, such as a fibrous reinforcing agent.

In the present invention, by setting Tf in the above range of 40 to 200°C, it is possible to increase the atmospheric temperature during curing and shorten the curing time in the solid phase, and the curing reaction progresses too much during short kneading. This can be prevented and the permissible range of molding temperature can be widened.

In the present invention, after demolding a solidified molded product having the above-mentioned T2, the T of the molded product is removed from the mold. Heat curing is performed at an ambient temperature not exceeding 20°C from i', and the atmospheric temperature is increased by 20°C from the Tf of the molded material, corresponding to the Tf of the molded material, which increases with the progress of curing.
The curing reaction is completed by increasing the temperature while maintaining the temperature within a range not exceeding 0°C. The method of raising the ambient temperature is to
It may be raised continuously following the rise of i', or it may be raised in stages. The preferred ambient temperature is a temperature range that is approximately 15°C lower than Tf or Tf of the molded product, and its upper limit is 20°C higher than Tf. However, it is generally difficult to control the temperature within this range at all times, and depending on the situation, it may be possible to temporarily deviate from this range.

In a preferred embodiment of the invention, the molding no longer melts or deforms after the Tf of the molding has increased by at least 60% of the difference between Tii' and its initial TV that can be reached upon completion of its curing. Therefore, the ambient temperature can be set to a range higher than Tf by 20° C., thereby further promoting the crosslinking reaction in a solid state accompanied by dimensional changes.

In the present invention, in order to effectively carry out the above-mentioned solid phase curing method, the initial 1) y rise rate of the solidified molded product is approximately 0.01.
A range of 10° C./min is desirable.

What is the initial T of the solidified molded product here? The rate of rise is the T7 rise rate at time 0 of the assimilated molded product when the solidified molded product is exposed to the same ambient temperature as that of the solidified molded product '1'7 which has not been substantially subjected to thermal history.

Specifically, the initial Tgo of the solidified molded product is measured in advance, and the solidified molded product is exposed to the same ambient temperature as this 1' finger.
1) In the range of the initial T2 rise rate described in IJ, the crosslinking reaction progresses quickly and curing is completed within a relatively short time. This is convenient because the resulting molded product does not suffer from internal distortion, shrinkage, or warping. On the other hand, the atmospheric temperature is adjusted to about 0.2 to 5 times the initial T1 increase rate of the solidified molded product.
This can be easily achieved by increasing the speed preferably in the range of about 0.005 to 2 times.

In the present invention, various known molding methods can be used as the molding method, such as a casting method, an injection molding method, a transfer molding method, an extrusion molding method, a blow molding method, an ordinary pressure injection method, etc. . In addition to heating gas (for example, air), the heat source for homophase curing of the present invention may include:
Examples include liquids (for example, heat carriers such as high-boiling oil), powders (for example, sand), and the like. Further, electron beam irradiation, microwave irradiation, etc. can also be used.

A detailed explanation will be given below with reference to examples. Note that parts simply indicate parts by weight. Note that T1 hereinafter was measured using a differential scanning calorimeter manufactured by Rigaku Denki Co., Ltd.

Example 1 Epoxy resin [precondensate, number average molecular weight (Mn) 52
00, epoxy equivalent (EE) 1400:) 100 parts, silica (350 mesh) 50 parts 0' EFa monoethylamine complex salt 07 parts were mixed and pelletized, and the mixture was injection molded at a mold temperature of 65°C to form a molded product. When T2 was measured, it was 71°C. Since the initial T7 rise rate at an ambient temperature of 71°C was 0.21°C/min, this molded product was heated by 0.5°C10 from 65°C to 150°C.
When raised linearly at a speed of , it was possible to harden without deformation. T2 after curing was 144°C.

Comparative Example 1 When the ambient temperature of the molded product molded in Example 1 was raised linearly from 65°C to 150°C at a rate of 15°C/min, significant deformation occurred in less than 15 minutes after the start of the rise. As can be seen, the shape of the molded product after heating to 150°C was quite different from the original.

Example 2 Epoxy resin (precondensate, Mn 8000. EEl
ooo) 100 parts, 30 parts of glass fiber (chopped strand C8-0:3), and 5.4 parts of diaminodiphenylmethane were mixed and pelletized at a mold temperature of 75.
Transfer molding was performed at °C, and the T2 of the molded product was measured to be 82 °C.

When this molded product was placed in a thermostat adjusted to an ambient temperature of 80°C and heated for 2 hours, the T2 of the molded product was 98.
There was a woman named °C. Here, the temperature of the thermostat was set to 95°C, and when heated for 1 hour, the T7 of the molded product was 110°C. Here, the temperature of the thermostat was further set to 110°C, and when heated for 05 hours, the T2 of the molded product was 130°C.
It became.

The highest T1 of the same compound as this molded product is 154”c
(Curing conditions were 150°C x 3 hours, 180°C x 3 hours), and the T1 of the above molded product reached 67% of the highest T1, so even if heated to a temperature exceeding 20°C from T It was determined that it had deformed and was old, so it was heated in IQO'C for 1 hour. The T1 of the final fishing force molded product was 153°C, and there was no deformation during curing. Further, although the shrinkage rate of the normally cured product was 0.8 to 1.0%, according to this curing method, the shrinkage rate was % YJ 0.2 or less.

Example 3 Epoxy resin (precondensate, Mn4500, EEllo
o) 100 parts, 50 parts of silica (350 mesh), and 49 parts of diaminodiphenylmethane were mixed, and the resulting pellets were injection molded at a mold temperature (50°C), and the Tf of the molded product was
When I was measured, it was 68°C.

When this molded product was cured under the heating conditions shown in Table 1, it reached the final T2 of 148°C without deformation. The highest T1 reached was 150°C.

Table 1 Example 4 The same molded product as in Example 3 was deformed when the ambient temperature was started at 70°C and was linearly raised at a rate of 16°C/min until it reached 160°C. I was able to harden it without any problems. (above) Patent applicant: Toyo Rubber Industries Co., Ltd. Agent: Patent attorney Iwao Yamamura 249-

Claims (2)

[Claims] (1) After demolding a solidified molded product of a cross-linkable epoxy resin with a glass transition temperature (T7) of 40 to 200°C, the molded material is heat-cured at an ambient temperature that does not exceed 20°C. The T of the molded product increases with the progress of curing.
7, the ambient temperature is changed from T1 to 20 of the molded product.
1. A solid phase curing method for a solidified epoxy resin molded product, characterized in that the curing reaction is completed by raising the temperature while maintaining the temperature within a range not exceeding °C. (2) T1 of the molded article is at least 60% of the difference between the TJ that can be reached upon completion of curing and its initial T1;
The method according to claim 1, wherein after the temperature rises above, the ambient temperature is set to a range exceeding 20°C above Tt for curing.