KR100766166B1 - High Temperature Vulcanizing Silicone Rubber Composition Having Excellent Physical Property - Google Patents

Abstract

 The present invention relates to a thermosetting silicone rubber composition having excellent mechanical properties in terms of resilience, tensile strength, and tear strength, and having excellent heat resistance to maintain rubber properties even at high temperature, and more particularly, to have a specific functional group. The present invention relates to a thermosetting silicone rubber composition having excellent mechanical properties by mixing silicone raw rubber with a specific silica as a reinforcing filler, an organosilane coupling agent, a processing aid, a releasing agent, and an organic peroxide as a mechanical reinforcing medium.

Resilience, Tear Strength, Thermosetting Silicone Rubber, Silicone Raw Rubber

Description

High Temperature Vulcanizing Silicone Rubber Composition Having Excellent Physical Property}

 The present invention relates to a thermosetting silicone rubber composition having excellent mechanical properties in terms of resilience, tensile strength, and tear strength, and having excellent heat resistance to maintain rubber properties even at high temperature, and more particularly, to have a specific functional group. The present invention relates to a thermosetting silicone rubber composition having excellent mechanical properties by mixing silicone raw rubber with a specific silica as a reinforcing filler, an organosilane coupling agent, a processing aid, a releasing agent, and an organic peroxide as a mechanical reinforcing medium.

Silicone rubber has excellent properties in various aspects such as releasability, water repellency, cold resistance, heat resistance, weather resistance, and chemical stability, and shows excellent effects compared to other materials. However, general silicone rubber does not exhibit sufficient performance in parts such as keypads or silicone rubber rolls that require special properties in resilience and mechanical properties, and loses its rubber properties when subjected to repeated high-temperature heat. In other words, they are permanently deformed and fail to function.

Conventionally, as disclosed in U.S. Patent No. 4,360,388 and the like, an attempt has been made to improve the problem of silicone rubber by using manganese, nickel, copper, zirconium, cerium, tungsten, iron oxide, and the like. When excessively used, there is a problem that the mechanical properties of the silicone rubber is lowered, and there is a limit to the use due to the problem of being colored rather than transparent in color.

An object of the present invention is to solve the problems of the conventional silicone rubber composition as described above, by applying a reinforcing filler, mechanical properties reinforcing media, processing aids, mold release agents, and organic peroxide to the silicone raw rubber having a specific functional group Without being limited to this, it is to provide a thermosetting silicone rubber composition having excellent mechanical properties such as excellent rebound elasticity, tensile strength and tear strength and excellent heat resistance capable of maintaining rubber properties even at high temperatures.

The silicone rubber composition according to the present invention comprises raw silicone rubber having a specific functional group (or 'silicon polymer'), a reinforcing filler, a mechanical reinforcing medium, a processing aid, a releasing agent, and an organic peroxide. It is done.

Hereinafter, each component contained in the silicone rubber composition of the present invention will be described in detail.

(1) silicone raw rubber

The raw silicone rubber used as the raw material rubber in the silicone rubber composition of the present invention has vinyl groups at both ends, and has at least one group selected from the group consisting of aliphatic saturated hydrocarbon groups, aliphatic unsaturated hydrocarbon groups and aromatic unsaturated hydrocarbon groups at the side chains. As a linear organopolysiloxane, it has a repeating unit represented by following formula (1).

[Formula 1]

R _a SiO _{(4-a) / 2}

In Formula 1, R is an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms, an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms, or an aromatic unsaturated hydrocarbon group having 6 to 30 carbon atoms, and a is a positive number of 1.90 to 2.05, preferably , R is a methyl group or a vinyl group or a phenyl group.

The silicone raw rubber has a number average molecular weight of 400,000 to 700,000, has a viscosity of 10,000,000 centipoise or more at 25 ° C., and is preferably a linear organopolysiloxane polymerized with 2,000 to 10,000 siloxane units.

In the silicone raw rubber, it is particularly preferable that the side chain has at least one group of methyl group, vinyl group and phenyl group, and the total vinyl group content in the silicone raw rubber is preferably 0.01-10 mol%, and 0.05-1 mol. It is more preferable that it is%. If using a vinyl group of 0.01 mol% or less does not cause sufficient curing, the rubber is soft, when using a vinyl group of 10 mol% or more too hard curing density is formed to cause a decrease in mechanical properties.

The silicone raw rubber may be used as one kind or a mixture of two or more kinds. In the case of the silicone raw rubber mixture, for example, silicone raw rubbers having different vinyl groups may be mixed, and in particular, the vinyl group content may be 0.01 to 0.15 mol. It is preferable to use a mixture of silicone raw rubber (%) and silicone raw rubber having a vinyl group content of 0.16 to 10 mol%, and more preferably, silicone raw rubber having a vinyl group content of 0.03 to 0.15 mol% and a vinyl group content of 0.16 to 8.5 It is preferable to use a mixture of silicone raw rubber in mol%, and the mixing ratio is not particularly limited, but it is preferable to use the silicone raw rubber having the vinyl content in a mixing ratio of 9: 1 to 1: 9.

The use of the raw silicone rubber having a different total vinyl group content as the mixing ratio is for improving mechanical properties such as tear strength of the silicone rubber composition, which is a state in which the crystal structure of the crosslinking point generated during curing is unevenly distributed. This is because it is important that there is no regular rule in the direction of destruction generated when a destructive force is applied from the outside. In addition, by adjusting the hardness, tensile strength, tear strength and elongation, etc. of the silicone rubber, the silicone rubber is intended to have physical properties suitable for each application.

If both ends of the raw silicone rubber do not have a vinyl group, there is a problem that the important resilience characteristics of the mobile phone keypad and the silicone rubber roll are inferior. However, in the present invention, an aliphatic saturated hydrocarbon group such as a methyl group in the side chain must have a vinyl group at both ends. By using a silicone raw rubber having at least one group of an aromatic unsaturated hydrocarbon group such as a vinyl group and an aromatic unsaturated hydrocarbon group such as a phenyl group, it is possible to provide a silicone rubber composition having excellent resilience as well as mechanical properties.

(2) reinforcing filler

As the reinforcing filler used in the silicone rubber composition of the present invention, silica is preferable, and amorphous synthetic silica is particularly preferable. The silica used in the present invention preferably has a particle size of 7 to 16 nanometers and a minimum specific surface area (BET value) of 100 to 300 m ² / g, but the particle size and minimum specific surface area are outside the above ranges. The mechanical properties will be significantly reduced.

It is preferable to use a mixture of wet silica and dry silica as the silica, because it plays an important role in the good heat resistance and excellent mechanical properties that significantly affect the rubber properties at high temperatures. More specifically, the silica is preferably in the use ratio of wet silica and dry silica is 9: 1 to 3: 7, more preferably 9: 1 to 5: 5, when the use ratio is out of the above range The effect of improving mechanical properties and heat resistance is insignificant, and the effects of rebound elasticity and heat resistance are inferior.

In the present invention, the content of the silica is preferably 10 to 100 parts by weight, more preferably 40 to 70 parts by weight with respect to 100 parts by weight of the silicone raw rubber, but less than 10 parts by weight to expect the reinforcement of mechanical properties If it is difficult and exceeds 100 parts by weight, the silica loading problem is difficult, the silica dispersion is difficult and the high modulus causes the overall mechanical properties to decrease.

(3) Mechanical property reinforcing media

As the mechanical property reinforcing medium used in the silicone rubber composition of the present invention, as the organosilane coupling agent represented by the following formula (2), an organosilane having one or more alkoxy groups, vinyl groups or ester groups at the same time is preferable.

[Formula 2]

(R'O) _a SiR '' _b R _(4-ab)

In Formula 2, R and R 'is an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms, R''is a vinyl group or ester group-containing organic material, a is an integer of 1 to 3 and b is an integer of 1 to 3 . In the organosilane coupling agent, the R '' group forms crosslinks upon curing with the silicone raw rubber, and the alkoxy group (R'O), which is another part of the silane, interacts with the silica having a hydroxy group, thereby the silicone raw rubber and the silica It improves the bonding force between and has excellent mechanical properties including tensile strength.

Preferable examples of the organosilane coupling agent include vinyltriethoxysilane, vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, butenyltrimethoxysilane, butenyltriethoxysilane, and vinyl methyldiene. Methoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyldimethylethoxysilane, vinyldiethylmethoxysilane, vinyldienylethoxysilane, and the like.

In the present invention, the content of the mechanical property reinforcing medium is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the silicone raw rubber. It is difficult to see the improvement, and when it exceeds 10 parts by weight, a large crosslinking point is formed, and the mechanical properties and rubber texture are degraded due to the high modulus and hardness of the rubber.

(4) Processing aid

The processing aid used in the silicone rubber composition of the present invention is used for the purpose of increasing the shelf life by increasing the dispersibility of silica, which is a reinforcing filler, to maintain uniform mechanical properties, to suppress the occurrence of rough hardening. The processing aid is a low viscosity silicone polymer having a methyl group or a phenyl group at the side chain, and having a hydroxyl group, an alkoxy group or an amino group at both ends thereof, and preferably having a viscosity of 100 centipoise or less at 25 ° C. Hydroxyl group dimethylsilicone, sock end alkoxy group dimethylsilicone, sock end amino group dimethylsilicone and the like.

[Formula 3]

R- (SiM ₂ ) _n -R

Processing aids may be represented by the formula (3), wherein R is a hydroxy group, an alkoxy group, or an amino group, M is a methyl group or a phenyl group, n is between 5 ~ 100, the viscosity at 25 ℃ 100 centipoise It is as follows.

These processing aids have a hydroxyl group, an alkoxy group, or an amino group at both ends to form hydrogen bonds with silica, thereby suppressing the rough cracking phenomenon in the processing process caused by the direct bonding of silica to the silicone raw rubber.

In the present invention, the content of the processing aid is preferably 0.1 to 15 parts by weight, more preferably 0.1 to 10 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the silicone raw rubber. Dispersion is difficult, and if more than 15 parts by weight, the roll roll workability is difficult due to the stickiness of the composition.

  (5) release agent

In the silicone rubber composition of the present invention, the release agent may be a metal salt of an organic fatty acid, and the metal is preferably magnesium, calcium, zinc, or the like. Representative release agents include calcium stearate, magnesium stearate and zinc stearate.

In the present invention, the content of the release agent is preferably 0.001 to 1 parts by weight, more preferably 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the silicone raw rubber, but less than 0.001 parts by weight does not have a releasable effect, 1 weight If the portion is exceeded, ink printing is difficult on the surface of the molded rubber sheet, and the mold is easily contaminated.

  (6) organic peroxide

The organic peroxide used in the silicone rubber composition of the present invention is capable of generating radicals by pyrolysis so as to form a crosslink by performing a radical reaction on the vinyl group of the silicone raw rubber, and an alkyl and acyl system may be used. Specific examples thereof include, for example, 2,5-dimethyl-2,5-t-butylhexaneperoxide (45% paste purity, mixed with silica and oil), 2,4-dichlorobenzoylperoxide (50 % Paste purity, mixed with silica and oil), and benzoyl peroxide (50% paste purity, mixed with silica and oil) and the like, and these may be used alone or in combination of two or more thereof.

In the present invention, the content of the organic peroxide is preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the silicone raw rubber, but less than 0.5 parts by weight may cause an unvulcanized problem, and if it exceeds 3 parts by weight of mechanical properties Degradation and post-curing operations (removal of organic peroxides decomposed and remaining) take time.

In addition to the above components, the silicone rubber composition of the present invention may further include conventional additives as necessary within the scope of not impairing the object of the present invention.

The present invention can be understood in more detail by the following examples and comparative examples, the following examples are only for illustrating the present invention, and are not intended to limit the protection scope of the present invention.

Example  1 to 3

The silicone rubber composition of Example was prepared by the following method.

As shown in Table 1, reinforcing fillers, organosilane coupling agents, processing aids, and release agents were added to the raw silicone silicone rubber having a specific functional group in a kneader (hermannrinden, LK III2) 1 to 5 times. After homogeneously dispersing at a temperature of 80 ° C., heat kneading was carried out at 160 ° C. to 180 ° C. for 2 hours to increase the dispersion effect of silica, and then cooling kneading was performed at 80 ° C. or less for 1 hour to prepare a silicone rubber composition.

Comparative example  1 ~ 4

According to the composition shown in Table 1 below, reinforcing filler, organic silane coupling agent, processing aid, and release agent were added to silicone raw rubber as an additive in a kneader (Hermann Linden, LK III2) 1-5 times at a temperature of 80 ° C. After homogeneous dispersion, heat kneading was carried out at 160 ° C. to 180 ° C. for 2 hours to increase the dispersion effect of silica, and then cooling kneading was performed at 80 ° C. or less for 1 hour to prepare a silicone rubber composition.

After fully plasticizing each of the uncured silicone rubber compositions prepared in Examples and Comparative Examples in a two roll mill, 0.5 parts by weight of organic peroxide (2,5-dimethyl-2) based on 100 parts by weight of the uncured silicone rubber composition , 5-t-butylhexaneperoxide (45%) was added to disperse sufficiently. Thereafter, the preform subjected to the defoaming process was pressurized at 170 ° C. for 10 minutes under a pressure of 100 kgf / cm ² in a molding molding to make a 2 mm thick sheet, followed by 200 ° C. in a hot air circulating oven for 4-6 hours. By vulcanization, decomposed organic peroxides were removed to prevent the phenomenon of vulcanization degeneration.

TABLE 1

1) Silicone raw rubber with sock end methyl group and side chain methyl vinyl (Average content of vinyl group 0.2 mol%)

2) Silicone raw rubber whose sock end is vinyl group and the side chain is methylvinyl (vinyl group average content 0.2 mol%, except that vinyl group average content is 0.18 mol%)

3) CP-102 of Tokuyama Corporation

4) Nipsil LP from Nippon Corporation

5) 3-methacryloxypropyltrimethoxysilane

6) Shin-Etsu RFL

7) Calcium Stearate

With respect to the sheet made of the silicone rubber compositions of Examples and Comparative Examples prepared as described above, the mechanical properties were measured according to the KS M6518 standard, and the results are shown in Table 2 below.

TABLE 2

Note)-Plasticity: According to the Williams plasticity measurement method

   -Heat resistance change: Calculate the change rate before and after aging by measuring the mechanical properties (hardness, tensile strength, elongation) after aging at 250 ℃ for 72 hours

As can be seen from the results in Table 2, when comparing Comparative Examples 1 to 4 and Examples 1 to 3, the silicone rubber compositions of Examples 1 to 3 have tensile strength and tear strength compared to Comparative Examples 1 to 4 It was found that the mechanical properties such as elongation and rebound elasticity are excellent. In addition, as a result of measuring the change in hardness, tensile strength and elongation after exposure to high temperature, the change in hardness was small, and the decrease in tensile strength and elongation was small, indicating that the heat resistance was significantly improved.

As can be seen from the above, according to the present invention, by using a specific reinforcing filler and a mechanical reinforcing medium in the silicone raw rubber having a specific functional group, excellent resilience, tensile strength, and phosphorus without being limited in color It is possible to provide a silicone rubber composition having mechanical properties such as thermal strength and excellent heat resistance capable of maintaining rubber properties even at high temperatures.

Claims (3)

It has a repeating unit of the formula (1), the number average molecular weight is 400,000 ~ 700,000, the viscosity at 25 ℃ more than 10,000,000 centipoise, silicon having a vinyl group at both ends of the total vinyl group content of 0.01 to 10 mol% in raw rubber 10 to 100 parts by weight of mixed silica of wet silica and dry silica, 0.1 to 10 parts by weight of organic silane coupling agent, 0.1 to 15 parts by weight of processing aid, 0.001 to 1 part by weight of release agent, and 100 parts by weight of raw rubber A thermosetting silicone rubber composition comprising 0.5 to 3 parts by weight of an organic peroxide: [Formula 1] R _a SiO _{(4-a) / 2} In Formula 1, R is an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms, an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms or an aromatic unsaturated hydrocarbon group having 6 to 30 carbon atoms, and a is a positive number of 1.90 to 2.05. According to claim 1, wherein the silicone raw rubber is a silicone raw rubber containing 0.01 to 0.15 mol% of the vinyl group in the silicone raw rubber and silicone raw rubber containing 0.16 to 10 mol% of the vinyl group in the silicone raw rubber in a weight ratio of 9: 1 to 1: 9 Thermosetting silicone rubber composition characterized in that the mixture. The thermosetting silicone rubber composition according to claim 1, wherein the mixed silica is a mixture of wet silica and dry silica in a weight ratio of 9: 1 to 3: 7.