JPS58101032A - Method of molding epoxy resin - Google Patents

Abstract

PURPOSE:To effect molding in a quick molding cycle without producing any sink or crack even for a large-sized molded item, by melting, kneading and plasticizing an epoxy resin composition at high temperature, casting the composition in a mold having a low temperature, and removing the molded item before it is cured so that it is postcured. CONSTITUTION:An epoxy resin composition having a melting temperature of 50-350 deg.C is kneaded and plasticized at temperature higher than its melting point, and then the composition is cast and molded in a mold having a temperature, preferably 20 deg.C lower or more lower than the melting point of said composition. Before curing of the molded item is completed, it is removed from the mold, and the postcuring is effected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present application relates to a novel method for molding epoxy resins. In conventional molding methods, the epoxy resin compound composition is heated at a low temperature within the range that allows cross-contamination to prevent the curing reaction from proceeding during kneading and plasticization, and the mold temperature during casting is kept as high as possible to ensure curing. Methods have generally been adopted to shorten the molding cycle by speeding up the molding cycle.

For example, in the case of injection molding of epoxy resin, the temperature of the kneading and plasticizing cylinder is usually maintained at around 110°C to prevent rapid progress of the curing reaction, while the mold temperature is maintained at 1 so'c or higher. After casting, a method of rapidly curing is used.

However, in such a method, even if the mold temperature is set as high as possible, it generally takes about 5 to 10 minutes to complete the curing reaction of the molded product within the mold.
During this time, the molded product must be kept tightly sealed in the mold.
Therefore, the next molding is performed after demolding, and one molding cycle takes 5 to 10 minutes or more.

Conventionally, attempts have been made to remove the epoxy resin compound from the mold before the curing reaction is completed in order to shorten the molding cycle, but if the mold is removed before the curing reaction is completed, the curing reaction of the epoxy resin may be an exothermic reaction. As a result, shrinkage and warping occur after demolding, making it impossible to put it to practical use as a side sole, especially in large molded products.

Therefore, epoxy resin has excellent functionality.
It could only be used for small molded products of less than 0.002 or for applications where the required performance could only be met by epoxy resin, even though the cost was high.

The inventors of the present application have conducted extensive research on a method to provide molding cycleability comparable to thermoplastic resins while taking advantage of the excellent heat resistance, corrosion resistance, and electrical properties of epoxy resins, and have adopted the method described below. It has succeeded in achieving its purpose.

That is, the heat-plasticized epoxy resin blended composition is heated to a temperature higher than the melting point of the blended composition to mix and disperse the blended components, and then adjusted to a temperature lower than the melting point of the epoxy resin blended composition. The mold is molded while being rapidly cooled by transferring it into a mold, and the mold is removed in a short cycle of about 3 to 60 seconds, which is similar to the thermoplastic resin molding cycle, and the mold is used for the next molding. This is what I intend to use.

In addition, for the molded product, the post-curing reaction may be completed at room temperature or in a heated state, or by means such as radiation, ultraviolet rays, or electron beam irradiation.For the molded product during the post-curing reaction, Phenomena such as warping, shrinkage, or cracking, which were observed in the conventional method, were not observed.

By using the molding method of the present application, it is possible to mold medium to large molded products with a weight of 300 to 10,009, which was previously difficult, without sink marks or cracks, and of course high cycle molding can be performed without problems even in the case of small products. I was able to do that.

This is because if the curing reaction of epoxy resin progresses rapidly in a conventional high-temperature mold, internal stress tends to remain in the molded product. This is thought to be due to the effect of reducing residual internal stress by making the reaction proceed slowly.

The epoxy resins used in this application include bisphenol-type epoxy resins, which are usually called epoxy resins;
Novolac type epoxy resin, halogenated epoxy resin,
In addition to hydrogenated epoxy resins, alicyclic epoxy resins, and hydantoin epoxy resins, silicone epoxy resins, epoxy furan resins, epoxy ester resins, phenoxy resins, epoxy urethane resins, and liquid rubbers whose terminal groups are modified with epoxy It is also possible to use resins that are cured with modified epoxy resins or phenolic epoxy resins such as polyvinyl phenol.

Compounding agents for these epoxy resins include known reinforcing agents, curing agents, fillers, plasticizers,
Examples include diluents, flame retardants, photopolymerization initiators, and pigments.

Of course, other known thermoplastic or thermosetting resins that are compatible with the above epoxy resin can also be blended.

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

Reinforcer,! :L'-r includes fibrous reinforcing agents such as inorganic fibers such as glass fiber, carbon fiber, and asbestos, and organic fibers such as aramid fiber, nylon, and polyester, as well as fibrous reinforcing agents such as aluminum oxide, silicon carbide, and graphite. Whiskers can also be used.

Other compounding agents include glass flakes, glass powder,
mica, carbon black, talc, clay, silica,
Fillers and pigments such as calcium carbonate, aluminum hydroxide, titanium white, or plasticizers such as dioctyl phthalate and tricresyl phosphate, reactive or non-reactive diluents such as butyl glycidyl ether, xylene, Flame retardants such as antimony dioxide and chlorinated paraffin, photopolymerization initiators such as isopropyl benzoin ether, and the like are appropriately selected and used.

The present invention is applicable to all known molding methods such as injection molding, transfer molding, extrusion molding, blow molding, and normal pressure injection. It is.

The present invention targets an epoxy resin composition with a melting point of 50 to 350°C;
If the temperature is less than .degree. C., even if the resin composition is cooled to around room temperature, it will be difficult to demold the resin composition until the curing reaction is completed, and the object of the present application will not be achieved. On the other hand, if the melting point is 350°C or higher, the energy consumption in the kneading and plasticizing step is large and approaches the decomposition temperature of the polymer itself, and the curing reaction becomes extremely rapid, impeding molding workability. Considering this point, even if the epoxy resin compound composition has a preferable melting point range, in the case of a high melting point compound composition, the curing reaction rate will be slow under the set plasticizing crosstalk conditions. It is desirable to select the curing agent and catalyst system shown below.

In order to achieve the object of the present invention, it is necessary to maintain the mold temperature below the melting point of the epoxy resin compound composition, but preferably at a temperature lower than the melting point by -4°C or more. is appropriate.

Even if the melting point of the epoxy resin itself is 350°C or higher, it is sufficient that the melting point of the composition obtained by kneading plasticizers and other compounding agents is 350°C or lower. Its own melting point is less than 50 ° C,
If the melting point of the composition kneaded with fillers and reinforcing materials is 50°C or higher, the object of the present application can be achieved.

The melting point of the epoxy resin blended composition defined in the present invention was determined using a heat medium type melting point meter manufactured by Yanagimoto Seisakusho Co., Ltd.
Raise the temperature by 1°C per minute, and
It is expressed as the temperature at which more than half of the volume of a small piece of the blended composition of 3 m9 is melted. Matanari,
The completion of the curing reaction for the 4-shaped product was determined when the surface of the molded product was wetted with acetone solvent and no stickiness was felt on the fingers.

Mitsui Petrochemical Ushihana epoxy resin R3o4 (melting point 80℃
) 100 parts by weight, 8 parts by weight of phthalic anhydride and 2 parts by weight of silicic anhydride.
50 parts by weight were added, heated and mixed at 180'C, cooled once to room temperature (20°C), and then ground into pellets.

The melting point of this pellet-like pulverized product was 100°C.

Weigh out 100 f of this pulverized material and preheat it to 180°C.
Using a commercially available transfer molding machine set to the following conditions: 1 pressure 50 kg/cd 1 mold temperature 60''c, a flat plate-shaped molded product with a thickness of 10 cm was molded.The molded product was demolded after 50 seconds.
After heating at 100°C for several days, the temperature was raised to 150°C and post-curing was performed for 2 hours. This product was not sticky at all when wetted with acetone, so the curing reaction was judged to be complete. The molded product had a good appearance with no warpage or sink marks observed.

What should be noted in this example is that almost no protrusion of the mold beyond the parting line of the mold was observed.

Comparative Example Transfer molding was carried out in the same manner as in Example 1, only the mold temperature was changed to 160°C. When an attempt was made to remove the mold 10 minutes after molding, there was no deformation due to incomplete curing. It was difficult to demold the mold. It became possible to demold the mold after one hour had passed at the mold temperature of 16o''C.Furthermore, the molded product had a thin barrier formed around the entire circumference at the parting line of the mold.

Example 2 Epoxy resin Epicoat +009 (melting point 114°C) made by Oil Shell Epoxy ■ crushed into 150 meshes (melting point 114°C) ioo
5 parts by weight of hexahydrophthalic acid and 250 parts by weight of silicic anhydride powder were mixed in powder form, and 10 parts by weight of Epicoat 1004 (melting point 80°C) powder manufactured by Yuka Shell Epoxy ■ was added. After mixing at °C, the mixture was cooled to room temperature (21 °C) and ground into pellets.

Using a commercially available injection molding machine for thermoplastic resin, the pulverized pellets were heated at 220°C near the gate of the cylinder and at 220°C in the center.
A flat plate-shaped molded body was molded under the following conditions: 10°C, hopper part 200°C, mold temperature 60°C, and injection pressure 1ooOKg/cd. The molded body was demolded after 60 seconds and post-cured at 170°C for 1 hour.

The average thickness of the molded product is 151w, the length is 1501R1, the width is 200m, and the weight is 7202mm.There are no defects such as sink marks or warping, and when a large molded product like this example is injection molded, There was also very little formation of flakes from the parting line of the mold.

In addition, the pellet-like composition fed into the injection molding machine is mixed at a low temperature such as 120°C to prevent the progress of the curing reaction before molding, so the composition is not completely melted and mixed. When measuring the melting point of the product, it was first heated to 250°C to form a molten mixture state, and after cooling to room temperature, the melting point was measured, and the result was that the melting point was 200°C.

Example 3 Average molecular weight i o, o crushed to 150 mesh.

O1 Bisphenol A type epoxy resin 1 with melting point 165℃
00 parts by weight, glass fiber (chopped strand) 4
0 parts by weight, 3 parts by weight of tetrahydrophthalic acid, and 7 parts by weight of diaminodiphenylmethane α are mixed in powder or fibrous form, and then Epicoat 10 made from Yuka Shell Epoxy ■ is mixed.
Add 50 parts by weight of powder of 09 (melting point 114"C),
Mixed and pelletized at 0°C. The melting point of the resulting blended composition was 205°C. This composition was heated in a commercially available injection molding machine for thermoplastic resin at 250°C in the vicinity of the cylinder gate, 230°C in the center, and 210°C in the hopper.
Injection pressure 1.000 Kl/ct/i, mold temperature 80
Injected into a mold with a total of 4 cavities, including 2 dalbells (JI No. 81 type, thickness 2 IIm) for tensile strength testing at ℃, and 2 flat plates with a width of 251g, a length of 150g, and a thickness of 2mm. Molded. The amount of injection per shot was 60f.

In this example as well, the occurrence of flaking from the parting line portion of the mold was hardly observed.

The molded product was molded for 60 seconds and kept at 150°C for 3 hours, 20
Post-curing was performed for 2 hours at 0°C for a total of 5 hours. Table 1 shows the results of measuring the physical properties of this molded article.

Table 1 As shown in each example, the present invention is made by kneading and plasticizing the epoxy resin blended composition at a temperature higher than the melting point, and molding it in a mold at a temperature lower than the melting point of the composition.
Possibly because the fluidity of the epoxy resin compounded composition injected into the mold is moderately constrained, under all conditions, there is little occurrence of gouges, and therefore it is difficult to use for resin molding for semiconductor encapsulation. In addition, there is no need to spend more effort and expense on improving mold accuracy than necessary to prevent the occurrence of paris.
In addition, since the holding time of the molded object in the mold can be shortened to less than 1 minute, the number of molds per 111 molds per expensive injection mold is more than 5 times that of conventional methods, which is a dramatic improvement of about 6 times. This is a useful invention with extremely high industrial value.

patent applicant Toyo Rubber Industries Co., Ltd.

Claims (1)

[Claims] An epoxy resin blended composition with a melting point of 50 to 350°C is kneaded and plasticized at a temperature higher than its melting point, and then cast and molded at a mold temperature lower than the melting point of the epoxy resin blended composition. A method for molding an epoxy resin, which comprises demolding the epoxy resin molding before the curing reaction is completed and post-curing the epoxy resin molding.