JPS59232146A - Silicone resin composition for transfer molding - Google Patents

Abstract

PURPOSE:To obtain a silicone resin for transfer molding, which has excellent workability and is harmless to the human body, by adding a filler and zinc benzoate to a silicone resin. CONSTITUTION:50-500pts.wt. filler and 0.5-10pts.wt. zinc benzoate are kneaded with 100pts.wt. silicone resin. If desired, additives such as pigment or partint agent may be added. Examples of the pigments are iron oxide, carbon black and titanium dioxide. Examples of the parting agents are zinc stearate and calcium stearate. Examples of the fillers are dry-process silica, wet-process silica and calcium silicate. When the quantity of zinc benzoate is less than 0.5-pts.wt., no satisfactory catalytic effect can be obtd., while, when it exceeds 10pts.wt., a problem in flow characteristics required for transfer molding is caused, so that the quantity ranging from 0.5 to 10pts.wt. is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a silicone resin composition for pressure-feed molding, and particularly to a silicone resin composition for pressure-feed molding that is considered to be harmless from a sanitary standpoint.

It is well known that silicone resin compositions for pressure molding are made by adding fillers and catalysts to silicone resin. 80-1 in advance
It is necessary to heat the silicone resin to 00°C to melt it, then add the filler and the solvent and mix them uniformly. However, when heated in the presence of a curing catalyst, the resin gradually begins to harden, and there is a risk that the resin will eventually become a molding material with poor flow characteristics. However, when this pressure molding resin is put into a mold for compression molding, transfer molding, or injection molding, it melts and gels in the mold heated to 150 to 200 degrees Celsius. It must flow into every corner of the mold, and it must also undergo a gelation reaction as quickly as possible to form a cured product with the necessary properties as a molded product. There is.

Therefore, it is necessary to select a silicone resin and a curing catalyst that make up this silicone resin for pressure-feed molding, and a curing catalyst that exhibits excellent curing properties without sacrificing flow properties. Although the use of lead, lead compounds such as lead carbonate, or heavy metal compounds such as cadmium is effective and has been put into practical use, since these types of heavy metal compounds are hazardous to hygiene, C. Although it has been proposed to use various amines, certain epixy compounds, heteropolyacids, organic carboxylic acid salts, etc., none of these gives satisfactory results as a pressure molding composition.

The present invention relates to a silicone resin composition for pressure-feed molding which solves these disadvantages, and which contains 50 to 500 parts by weight of filler and 0.5 to 10 parts by weight of zinc benzoate to 100 parts by weight of silicone resin. It is characterized by:

To explain this, the inventors have developed this pressure-feed molding)
As a result of various studies focusing on the detoxification of silicone resin for use in commercial use, we found a compound C= consisting of silicone resin and filler.
They discovered that by adding zinc benzoate, it was possible to obtain a silicone resin for pressure molding that was harmless to the human body. However, it is easy to obtain a cured molded product by molding at this temperature, but since it exhibits almost no catalytic effect at 50 to 100°C, this pressure molding composition is suitable for its production. It has excellent workability such as prior kneading in the process, and it is possible to easily obtain a composition with good characteristics.
Furthermore, the present invention was completed after confirming that there is no need to worry about the toxicity of this composition.

The silicone resin as the main ingredient constituting the composition of the present invention is known, and is 06H,5i03,2°(0
,H5)2Sin, 0H3SiOp, (OH3)
2Sin.

Examples include chitin resin, methylphenylsiloxane resin, etc., but it is preferable that the resin be methylphenylsiloxane resin and contain at least 0.1% by weight of hydroxyl groups bonded to disilicon atoms in the molecule. .

In addition, the filler compounded in this silicone resin may be a known filler, and includes dry silica such as fumed silica, wet silica, quartz powder, calcium silicate, zirconium silicate, magnesium silicate, lithium silicate, Examples include silicates such as aluminum acid, glass, diatomaceous earth, etc., which are similar to silicone resin 10 described above.
It may be added in an amount of 50 to 500 parts by weight relative to 0 parts by weight.

In the composition of the present invention, zinc benzoate is added as a curing catalyst to a silicone compound consisting of a silicone resin and a filler, and the amount of zinc benzoate added is 0.5 parts by weight or less per 100 parts by weight of silicone resin. If it is, the catalytic effect will be weak, and if it exceeds 10 parts by weight, C2 problem will occur, such as the flow characteristics required for pressure molding.
This is 0.5 to 10 parts per 100 parts of silicone resin.
It is preferable to use parts by weight.

In addition to the above-mentioned components, the composition of the present invention may also contain appropriate pigments and release agents, such as iron oxide, carbon black, titanium dioxide, etc.
Examples of the mold release agent include zinc stearate and calcium stearate.

The composition of the present invention can be obtained by mixing the above-mentioned components, which may be mixed simultaneously or sequentially. This may be carried out using an extruder, a pressure kneader, or the like.

Since the composition of the present invention uses zinc benzoate as a curing catalyst as described above, this composition does not harden at all during mixing, and its spiral flow value during pressure feeding to a mold is approximately 30. With the above-mentioned good properties, it flows easily to the nooks and crannies of the mold, and it is fast after heat treatment (
1 cures, so it is considered useful for pressure molding.
For example, 1, O, diode, rectifier, thyristor,
It is suitable for various electronic and electrical fields that require heat resistance and high electrical properties, such as resistive elements and coils, and is completely non-toxic, making it ideal for various kitchen appliance parts.

Two examples of the present invention are given below, in which parts are parts by weight and viscosity is a value measured at 25°C.

Example 1゜ It has 0.25% amount of hydroxyl groups bonded to silicon atoms.

200 parts of quartz powder, 5 parts of black pigment, and 2 parts of zinc stearate were dry mixed with 100 parts of methylphenylsilochitin resin [methyl group/phenyl group = 1 (molar ratio)] whose viscosity was 9oS in a 50% toluene solution. After that, the mixture was kneaded for 4 minutes using two rolls, one at about 100°C and the other at 50°C, and then various catalysts as shown in Table 1 were added and kneaded for 4 minutes to obtain the composition. made things.

Next, these compositions 20. P to 42 9/,! (6
00psi) into the mold, 175℃, 56KP/
When molded with crI, the spiral flow values at that time were as listed in Table 1, and the test results were as shown below.

In addition, since the AXD of this example does not use lead-based compounds as a catalyst, conventional products that use lead-based compounds contain several thousand ppm of substances harmful to the human body such as lead and cadmium. All of them contained almost no of these harmful substances, but among these a to d, only a gave satisfactory results as a silicone resin for pressure-feed molding, as shown below.

Table 1 Sample a: Satisfactory results were obtained as a pressure-feed molding resin.

Sample b: curing at high temperatures (150 to 200°C) was extremely severe twice, and could not be put to practical use.

Sample 0: Satisfactory results were obtained as a pressure molding resin, but the cured product had an acetic acid odor and was not suitable for practical use.

Sample d: Curing at high temperatures was extremely slow and could not be put to practical use.

Example 2゜Methylphenylsiloxane resin 10 used in Example 1
0 parts, 200 parts of quartz powder, 50 parts of short glass fibers, 5 parts of black pigment, and 2 parts of zinc stearate are dry-mixed, and then mixed with two rolls (a combination of rolls at about 100°C and rolls at 50°C). The mixture was kneaded for 4 minutes, and then 2.5 parts of zinc benzoate was added thereto and kneaded for about 4 minutes to prepare a composition.

Next, this composition was pressure molded in the same manner as in the previous example, and the physical properties of the resulting molded product were measured, and the results shown in Table 2 below were obtained.

Table 2 Patent applicant: Shin-Etsu Chemical Co., Ltd. 11-

Claims (1)

[Claims] 1. 50-50 parts by weight of filler in 100 parts by weight of silicone resin
0 parts by weight and 0.5 to 10 parts by weight of zinc benzoate.