KR100727826B1 - Silicone rubber compounds for liquid injection molding - Google Patents

Abstract

The present invention relates to an injection molding silicone rubber composition having excellent tensile properties and chemical resistance.

To this end, the present invention provides a silicone rubber composition for injection molding comprising polydimethylsiloxane and polymethylhydrosiloxane, platinum as a crosslinking agent, silica and mica as reinforcing agents.

In addition, with respect to 100 parts by weight of the silicone rubber composed of the polydimethylsiloxane and polymethylhydrosiloxane in a ratio of 1: 1, the content of the platinum is 0.1 parts by weight or less, silica and mica to 30 to 80 parts by weight It is characterized by using in combination.

Reinforcement, Silicone Rubber, Liquid, Silica, Mica

Description

Silicone rubber compounds for liquid injection molding}

The present invention relates to a silicone rubber, and more particularly, to a silicone rubber composition for injection molding having excellent tensile properties and chemical resistance.

In general, silicone rubber is a material having a wide range of applications because of excellent heat resistance, weather resistance, and electrical properties.

However, silicone rubber without a reinforcing agent has a low tensile strength of about 0.1 to 0.2 Mpa, so that the use of the reinforcing agent is essential to have physical properties required for actual products.

 In addition, the use of various non-reinforcing fillers is becoming common in order to lower the price of silicone rubber, which is expensive compared to other general rubber materials.

The shape of the filler or reinforcing agent has a great influence on the physical properties of the added material, in particular, it is known that the reinforcing agent on the fiber improves the tensile strength and the plate reinforcing agent improves the hardness.

As a reinforcing filler used in silicone rubber, amorphous silica having high purity, excellent heat resistance and reinforcing effect is used.

It is also known that the reinforcing effect of silica depends on the particle size of silica, the structure of silica and the degree of surface interaction between the silica surface and the silicone rubber backbone.

In general, the surface area, pH, and moisture content of silica used as an additive have a great influence on the properties of the silicone rubber, and silanol groups of 2.0 to 4.5 / mm 2 exist on the silica surface.

On the other hand, liquid silicone rubber is classified into a condensation type liquid silicone rubber and an addition type liquid silicone rubber according to the crosslinking method.

Since the condensed liquid silicone rubber is cured at room temperature, it is called RTV (Room Temperature Vulcanizing), and it is also called room temperature vulcanized liquid silicone.

In addition, when left in the air during use, the crosslinking reaction proceeds by moisture, thereby obtaining a rubber elastic body, generally used as an elastic adhesive and a coating agent.

In addition, the condensable two-component liquid silicone rubber is mainly supplied to the two components of the main body and the curing agent, and is mixed just before use so that curing proceeds by its own moisture and moisture in the air.

It is generally used for knitting, potting, molding, and the like, but is also used as an elastic adhesive by providing adhesiveness.

Additive liquid silicone rubber is a product by cross-linking by hydroseal reaction and is classified into one-component type and multi-component type.

Of these, the one-component type is extremely slow in the reaction rate near room temperature.

Since the reaction rate can be controlled by heating and reaction inhibitor, it is used in various fields for industrial use.

In addition, although the liquid silicone rubber for addition is inherently non-adhesive, there is a tendency to improve the adhesion form by the development of a primer or an adhesion improving agent.

In addition, the addition type liquid silicone rubber uses a method of crosslinking the siloxane chains by addition reaction of the polysiloxane containing a vinyl group and the polysiloxane having a Si—H bond. At this time, a platinum compound is used as a catalyst, and by-products do not occur in the curing reaction.

In addition, the additive liquid silicone rubber does not require moisture, but rather excessive moisture only adversely affects foaming.

The curing rate is temperature-dependent and the temperature is increased and the curing time is short.

In addition, the curing rate can be changed by changing the type or amount of platinum catalyst or by using a retardant.

Among the liquid silicone rubber for addition, there is a low-temperature vulcanization type in which curing proceeds by slight heating, and is called LTV (Low Temperature Vulcanizing), and the curing temperature is 100 to 200 ° C.

Among the additional liquid silicone rubbers, silicone rubbers manufactured to enable injection molding are referred to as silicone rubbers for liquid injection molding (LIM).

The silicone rubber for LIM has a viscosity controlled to enable injection molding, unlike general silicone molded rubber products manufactured through compression molding. Through this, it is possible to continuously produce the product, it is possible to automate, the cost reduction effect is large, the amount of waste rubber generated in the molding process is small, it has an environmentally friendly advantage.

In particular, when the silicone rubber product by injection molding is integrally formed with the present product such as a gasket, packing, etc., it can be expected to improve the compressibility with the main body, airtightness and the like.

Silicone rubber compositions used for gaskets, O-rings, packings, and the like used in various mechanical parts and the like have different required characteristics depending on the conditions of use of the parts.

Thus, as described above, the liquid silicone rubber alone is difficult to obtain physical properties that meet various requirements.

The present invention has been made in order to solve the problems described above, by using a mica having a plate-like form in combination with silica which is widely used as a reinforcing agent of liquid silicone rubber, injection having excellent tensile properties and chemical resistance It is an object to provide a silicone rubber composition for molding.

In order to achieve the above object, according to an aspect of the present invention, there is provided a silicone rubber composition for injection molding comprising polydimethylsiloxane and polymethylhydrosiloxane, platinum as a crosslinking agent, silica and mica as a reinforcing agent.

In addition, the content of the platinum to 0.1 parts by weight or less, based on 100 parts by weight of the silicone rubber composed of the polydimethylsiloxane and polymethylhydrosiloxane in a ratio of 1: 1, and 30 to 80 weight of silica and mica It is characterized by using in combination with negative.

In addition, the platinum is characterized in that the platinum carbonyl complex.

Another preferred embodiment is characterized by comprising polydimethylsiloxane and polymethylhydrosiloxane, platinum as a crosslinking agent, silica as a reinforcing agent and mica without surface treatment.

In addition, 10 to 40 parts by weight of silica and 1 to 20 parts by weight of the untreated mica are used in combination with 100 parts by weight of the silicone rubber including the polydimethylsiloxane and the polymethylhydrosiloxane in a ratio of 1: 1. It is characterized by one.

Another preferred embodiment is characterized by comprising polydimethylsiloxane and polymethylhydrosiloxane, platinum as a crosslinking agent, and mica surface treated with silica and silane coupling agents as reinforcing agents.

In addition, with respect to 100 parts by weight of the silicone rubber consisting of the polydimethylsiloxane and polymethylhydrosiloxane in a ratio of 1: 1, 10 to 40 parts by weight of silica as the reinforcing agent and mica 1 to 20 surface-treated with the silane coupling agent It is characterized by using a weight part together.

In addition, the silane coupling agent is characterized in that the glycidoxy propyl trimethoxy silane.

Hereinafter, preferred embodiments of the present invention will be described in detail.

Injection silicone rubber composition according to a preferred embodiment of the present invention, in order to improve the physical properties such as solvent resistance, tensile strength and elongation of the liquid silicone rubber capable of injection molding, two types of different types of particles in the liquid silicone rubber It is characterized by using a reinforcing agent. In particular, an appropriate amount of spherical silica and plate-shaped mica are used in combination.

In other words, platinum was used as a crosslinking agent mainly based on poly (dimethylsiloxane, PDMS) composed of vinyl groups and poly (methylhydrosiloxane, PMHS) which provides a crosslinking point. Use mica.

In more detail, the content of the organic platinum compound, which is a crosslinking agent, is used in an amount of 0.1 or less parts by weight based on 100 parts by weight of PDMS and PMHS in a ratio of 1: 1, and silica and mica are 30 to 80 as a reinforcing agent. It is used in combination with parts by weight.

Here, the organic platinum compound is a platinum carbonyl composite having a platinum content of 2 to 4%, preferably 0.05 to 0.1 parts by weight.

In addition, although silica and mica are used together, it is preferable to use together mica 1-20 weight part in the range of 10-40 weight part of silica.

This liquid silicone rubber composition has excellent chemical resistance and physical properties compared to using silica alone.

Hereinafter, specific examples (Examples 1 to 8) are described in detail in comparison with the comparative examples in a preferred embodiment of the present invention, but the present invention is not limited by the following examples.

Table 1 shows the compound silicone rubber compositions used in Comparative Examples and Examples, and physical properties thereof.

Comparative Example 1

The viscosity measured at 25 ° C. was 1,000 cSt, and the PDMS having a vinyl group content of 0.18 to 0.26% and PMHS having a viscosity of 15 to 40 cSt at 25 ° C. consisted of equal amounts of platinum. 0.1 parts by weight of 4% organic platinum compound (platinum carbonyl complex) is added.

The mixture is mixed using an ultrasonic generator and then heated for 5 minutes in a mold heated to 150 ° C.

Then, the cross-linked silicone rubber to take the dumbbell type No. 3 tensile test, and then measure the tensile strength and elongation at a speed of 300mm per minute using a universal testing machine.

In order to measure the solvent resistance of the crosslinked silicone rubber, a sample of 0.2 × 0.5 × 2 cm size was immersed in THF (TetraHydroFuran) at room temperature for 3 days, and then the volume change was measured.

Comparative Example 2

40 parts by weight of silica was added to the composition having the same composition ratio of PMDS, PMHS, and platinum catalyst as in Comparative Example 1 to prepare a specimen, and a silica having a BET surface area of 150 m 2 / g was used.

As shown in the results of Table 2, it can be seen that the tensile strength was improved by adding silica, the elongation was slightly decreased, and the solvent resistance was greatly improved.

<Example 1-4>

Example 1-4 is a case where 2, 5, 10, and 15 weight part of mica which is not surface-treated is used together with a silica reinforcement with respect to 100 weight part of silicone rubbers, respectively.

Here, mica uses an average particle size of 45 µm.

As shown in Table 2, the tensile strength decreases with increasing use of mica, and then increases again in Example 4 in which mica is used in combination with 15 parts by weight.

However, the elongation rate tends to increase gradually as the content of the mica increases, particularly in the case of Example 3 in which 10 parts by weight of mica is used.

In addition, it can be seen that the resistance to the solvent gradually decreases with increasing content of the reinforcing agent.

From the above results, the tensile strength is slightly reduced by using silica and mica together, but it can be expected to improve the elongation rate and the resistance to the solvent.

<Example 5-8>

In Example 5-8, 2, 5, 10, and 15 parts by weight of mica, surface-treated with a silane coupling agent, were used in combination with a silica reinforcing agent, respectively, based on 100 parts by weight of the silicone rubber.

Glycidoxy propyl trimethoxy silane is used as the silane coupling agent, and 1 part by weight of the silane coupling agent is dispersed and dissolved in 100 parts by weight of a solution containing 9: 1 of methanol and water. 10 parts by weight of mica is stirred and dispersed. The surface treated mica is precipitated and dried.

Hereinafter, the preparation and the test method of the specimen are the same as in Comparative Example 1.

As shown in Table 2, when the silane-coupled mica is used, the tensile strength and the elongation rate increase and the volume change rate decreases when compared with Examples 1-4 where the mica is not surface treated. have.

As shown in the above embodiment, it can be seen that by using mica in combination with liquid silicone rubber using only silica, it is possible to improve tensile strength and elongation and to improve solvent resistance.

Table 1. Comparative Example and Example Formulation Table

Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 PDMS 50 50 50 50 50 50 50 50 50 50 PMHS 50 50 50 50 50 50 50 50 50 50 Organic platinum compounds 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Silica - 40 40 40 40 40 40 40 40 40 Mica * - - 2 5 10 15 - - - Mica ** - - - - - - 2 5 10 15

Here, Mica * represents mica which has not been surface treated, and Mica ** represents mica that has been surface treated with a silane coupling agent.

Table 2. Physical Properties According to Comparative Examples and Examples

Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Tensile Strength (MPa) 10.00 14.00 12.74 10.08 7.98 11.06 13.44 12.74 10.50 14.84 Elongation (%) 460 438 433 448 551 508 521 473 565 499 Volume expansion rate 6.43 4.86 5.54 4.42 3.74 3.64 3.88 3.94 3.21 2.92

In the above description, the present invention is not limited to the above-described embodiments, and the present invention may be modified or avoided by a person having ordinary skill in the art without departing from the scope of the technical idea of the present invention. Will be in the range of.

As described above, in the present invention, by using silica and mica together, physical properties such as tensile strength and elongation can be improved as compared to liquid silicone rubber using only silica alone.

In addition, such silicone rubber compositions can be used in gaskets, o-rings and packing materials.

Claims (8)

Polydimethylsiloxane and polymethylhydrosiloxane, platinum as a crosslinking agent, silica and mica as a reinforcing agent, To 100 parts by weight of the silicone rubber comprising the polydimethylsiloxane and polymethylhydrosiloxane in a ratio of 1: 1, the content of platinum is 0.1 parts by weight or less, and silica and mica are used in combination of 30 to 80 parts by weight. Silicone rubber composition for injection molding, characterized in that the composition. Polydimethylsiloxane and polymethylhydrosiloxane, platinum as a crosslinking agent, silica as a reinforcing agent and mica without surface treatment, 10 to 40 parts by weight of silica and 1 to 20 parts by weight of the untreated mica are used as the reinforcing agent with respect to 100 parts by weight of the silicone rubber having the polydimethylsiloxane and the polymethylhydrosiloxane in a ratio of 1: 1. Silicone rubber composition for injection molding, characterized in that. A mica surface-treated with polydimethylsiloxane and polymethylhydrosiloxane, platinum as a crosslinking agent, silica as a reinforcing agent, and a silane coupling agent, 10 to 40 parts by weight of silica as the reinforcing agent and 1 to 20 parts by weight of mica surface-treated with the silane coupling agent, based on 100 parts by weight of the silicone rubber including the polydimethylsiloxane and the polymethylhydrosiloxane in a ratio of 1: 1. Silicone rubber composition for injection molding, used in combination. The method according to any one of claims 1 to 3, The platinum is injection molding silicone rubber composition, characterized in that the platinum carbonyl composite. The method of claim 3, The silane coupling agent is a silicone rubber composition for injection molding, characterized in that the glycidoxy propyl trimethoxy silane. delete delete delete