JPH0812797A - Weatherstrip for automobile - Google Patents

Abstract

PURPOSE:To obtain a weatherstrip for automobiles whose base material is a silicone rubber sponge excellent in compression set and cold resistance, low in specific gravity, properly high in hardness, high in compression load, rich in resiliency, good in sealability, excellent in surface smoothness, and beautiful in appearance. CONSTITUTION:A base material of a weatherstrip for automobiles is obtained by molding a silicone rubber sponge composition that is produced by mixing (A) a thermosetting millable-type silicone rubber composition the major components of which are (a) a polyorganosiloxane base polymer, (b) a reinforcing silica filler, and (c) a curing agent with (B) 0.1 to 20 pts.wt. thermally expandable microcapsules that will be expanded at a temperature of 80 to 200 deg.C (per 100 pts.wt. (a)) and (C) 0.5 to 10 pts.wt. organic expanding agent (for 100 pts.wt. (a)).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile weatherstrip, and more specifically, it has excellent compression set and cold resistance, and has a low specific gravity. The present invention relates to a weather strip for automobiles based on a silicone rubber sponge, which has a very high appearance, a high compression load, a high elasticity, a good sealing property, an excellent surface smoothness, and a beautiful appearance.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION AND ITS PROBLEMS Conventionally, as weather strips for automobiles, those whose base material is made of EPDM sponge have been used. However, the above-mentioned conventional weather strip for automobiles using EPDM sponge as a base material has already reached the limit as a material for the recent demand for improvement in long-term performance in the automobile industry, particularly improvement in compression set and cold resistance. The development of alternative products is required. Further, as the weight of automobiles has been reduced, it has been increasingly desired to reduce the weight of weather strips for automobiles. It has been well known that silicone rubber sponges are superior in compression set, cold resistance and weather resistance to EPDM sponges. Furthermore, this silicone rubber sponge is azobisisobutyronitrile. (AI
It is also known that an organic foaming agent such as BN), azodicarbonamide (ADCA), and dinitrosopentamethylenetetramine (DPT) is mixed with a curing agent, and the mixture is heated to foam and cure the mixture. Generally, in order to increase the expansion ratio of this silicone rubber sponge and obtain a silicone rubber sponge having a low specific gravity, it is necessary to increase the amount of the organic foaming agent and increase the amount of decomposition gas generated for foaming. Used. However, in such a method, the decomposition gas generated by the organic foaming agent is captured by the curing of the silicone rubber sponge. Therefore, as the amount of generated gas increases, the generated gas leaks from the sponge surface, and the generated gas is captured. The rate gradually decreases, and the expansion ratio is limited. Further, the weather strip for automobiles using the silicone rubber sponge as a base material obtained by such a method has a low hardness, a low compressive load, and lacks elasticity, so that the sealing property is significantly deteriorated. In addition, since a large amount of decomposition generated gas of the organic foaming agent leaks from the surface of the sponge, the surface smoothness of the skin layer is poor, and at the same time, a large amount of decomposition generated gas destroys the cells of the silicone rubber sponge, resulting in uniform fine cells. A weather strip for automobiles, which has a drawback that a structure cannot be obtained and has a low specific gravity silicone rubber sponge as a base material, has not been put into practical use so far.

[0003]

DISCLOSURE OF THE INVENTION Problems to be solved by the present invention are that the above conventional weather strips for automobiles lack the compression set and cold resistance, and that the automobile has a low specific gravity using a silicone rubber sponge as a base material. The weather strip has low hardness, low compressive load, and lack of elasticity, so the sealing property is significantly deteriorated, and a large amount of gas generated by decomposition of the organic foaming agent leaks from the sponge surface, resulting in smooth surface of the skin layer. At the same time, since a large amount of decomposition generated gas destroys the cells of the silicone rubber sponge, a uniform fine cell structure cannot be obtained, and the present invention provides a weather strip for automobiles in which such problems are solved. The purpose is to provide.

[0004]

The present inventors have conducted intensive studies to achieve the above-mentioned object, and as a result, have found that an organic foaming agent and a specific heat-expandable microcapsule are each added in a specific amount to a thermosetting millable silicone rubber composition. It is effective to use a silicone rubber sponge obtained by molding the compounded composition as a base material for an automobile weatherstrip, that is, an automobile weatherstrip using such a silicone rubber sponge as a base material has a compression set. , Excellent in cold resistance, low specific gravity, moderately high hardness, high compression load,
The inventors have found that they have excellent elasticity, good sealing properties, excellent surface smoothness, and beautiful appearance, and have completed the present invention. That is, the present invention is a weather strip for automobiles using a silicone rubber sponge as a base material, wherein the base material is (a) a polyorganosiloxane base polymer, (a ')
Mainly composed of reinforcing silica filler and (b) curing agent (A)
The thermosetting millable type silicone rubber composition, (B) 80 ~
Thermally expandable microcapsules that expand at a temperature of 200 ° C 0.1
~ 20 parts by weight (vs. (a) 100 parts by weight) and (C) organic blowing agent 0.5
A weather strip for an automobile, characterized in that it is obtained by molding a silicone rubber sponge composition containing 10 to 10 parts by weight (100 parts by weight of (a)).

First, the silicone rubber sponge composition of the present invention will be described. The silicone rubber sponge composition used in the present invention is characterized in that a thermosetting millable type silicone rubber composition (A) is blended with the above specific heat-expandable microcapsules (B) and an organic foaming agent (C). The thermosetting millable silicone rubber composition (A) used here is (a) a polyorganosiloxane base polymer, (a ') a reinforcing silica filler, (b) a curing agent, and if necessary, Various additives are blended and uniformly dispersed. (a ') Reinforcing silica filler is a substance necessary for improving the processability, mechanical strength, etc. of silicone rubber, and the commonly used precipitated silica, fumed silica, etc. Is. The amount of the (a ') reinforcing silica filler is (a) a polyorganosiloxane base polymer.
The range of 1 to 100 parts by weight is generally used with respect to 100 parts by weight, but is not particularly limited thereto. Among various components used in such a silicone rubber composition,
The (a) polyorganosiloxane base polymer and (b) curing agent are appropriately selected according to the reaction mechanism for obtaining the rubber-like elastic body. The reaction mechanism is (1)
Cross-linking methods using organic peroxide vulcanizing agents, (2) addition reaction methods, etc. are known.
It is well known that a preferable combination of the component and the component (b), that is, the curing catalyst or the crosslinking agent is determined. That is, when applying the crosslinking method of (1) above,
As the base polymer of the component (a), a polydiorganosiloxane in which at least two of the organic groups bonded to silicon atoms in one molecule are vinyl groups is usually used. As the curing agent of the component (b), an organic peroxide vulcanizing agent such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide is used, and hot air vulcanization is performed. When carried out, diacyl organic peroxides such as benzoyl peroxide and 2,4-dichlorobenzoyl peroxide are generally used. In addition, these organic peroxide vulcanizing agents are used as one kind or as a mixture of two or more kinds. The blending amount of the organic peroxide which is the curing agent of the component (b) is preferably in the range of 0.05 to 15 parts by weight with respect to 100 parts by weight of the silicone base of the component (a). If the amount of the organic peroxide is less than 0.05, the vulcanization is not performed sufficiently, and if the amount exceeds 15 parts by weight, not only there is no particular effect, but also the physical properties of the obtained silicone rubber are adversely affected. Because there is something to give. Above (2)
As the base polymer of the component (a) when the addition reaction of (1) is applied, the same base polymer as in the above (1) is used. Further, as the curing agent of the component (b), a platinum catalyst such as chloroplatinic acid, a platinum olefin complex, a platinum vinyl siloxane complex, platinum black, a platinum triphenylphosphine complex, etc. is used as a curing catalyst. As the agent, a polyorganosiloxane having an average number of hydrogen atoms bonded to silicon atoms of at least 2 in a molecule is used. In the curing agent as the component (b), the amount of the curing catalyst is preferably such that the amount of platinum element is in the range of 1 to 1000 ppm with respect to the base polymer as the component (a). If the compounding amount of the curing catalyst is less than 1 ppm as the amount of platinum element, the curing does not proceed sufficiently, and if it exceeds 1000 ppm, no particular improvement in the curing rate can be expected. In addition, the amount of the crosslinking agent is (a)
The amount of hydrogen atoms bonded to silicon atoms in the cross-linking agent is preferably 0.5 to 4.0, more preferably 1.0 to 3.0, per 1 alkenyl group in the component. If the number of hydrogen atoms is less than 0.5,
Curing of the composition does not proceed sufficiently, the hardness after curing becomes low, and when the number of hydrogen atoms exceeds 4.0, the physical properties and heat resistance of the composition after curing deteriorate. The organic groups other than the alkenyl group in the polyorganosiloxane as the base polymer of the component (a) used in the above various reaction mechanisms are monovalent substituted or unsubstituted hydrocarbon groups, such as a methyl group and an ethyl group. Alkyl groups such as propyl, butyl, hexyl, and dodecyl groups, aryl groups such as phenyl groups, unsubstituted hydrocarbon groups such as aralkyl groups such as β-phenylpropyl group, and chloromethyl groups. Substituted hydrocarbon groups such as a 3,3,3-trifluoropropyl group are exemplified. In addition, a methyl group is generally used because of its ease of synthesis. Further, the average degree of polymerization of the polyorganosiloxane as the base polymer of the component (a) is 3000 to 30,000, and if the degree of polymerization is less than 3000, the mechanical strength of the silicone rubber sponge is lowered and the degree of polymerization is
If it exceeds 30,000, it becomes difficult to mix the filler and the workability is deteriorated. The polymer is preferably substantially linear, but may be partially branched as long as it can be used.

The heat-expandable microcapsule which is the component (B) and expands at a temperature of 80 to 200 ° C. is a characteristic component for imparting the effect of the present invention. Here, the heat-expandable microcapsules that expand at a temperature of 80 to 200 ° C. must have an average particle size of 1 to 50 μm. If the average particle size is less than 1 μm, the dispersion in the rubber will be insufficient, and if it exceeds 50 μm, the silicone will be silicone. The strength of the rubber sponge is greatly reduced. The expansion ratio is preferably 10 to 100 times, and if it is less than 10 times, a sufficient expansion ratio cannot be obtained, and if it exceeds 100 times, it becomes difficult to obtain uniform fine cells. Examples of such heat-expandable microcapsules include vinylidene chloride / acrylonitrile copolymer as an outer shell and isobutane (for example, Expancel manufactured by Expancel Co., Matsumoto Yushi Pharmaceutical Co., Ltd. Matsumoto Microsphere). Is commercially available and can be easily obtained. The blending amount of component (B) is
(a) Component polyorganosiloxane base polymer 100
It is selected in the range of 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on parts by weight. If the content of component (B) is less than 0.1 parts by weight, a sufficient expansion ratio cannot be obtained, and if it exceeds 20 parts by weight, the sponge hardness becomes extremely high and the rubber elasticity is insufficient. The molded product is likely to be damaged, and the mechanical strength is greatly reduced. Since the heat-expandable microcapsules that expand the component (B) described above at a temperature of 80 to 200 ° C. expand due to heat, a large amount of decomposition gas generated when highly foamed using an organic foaming agent is generated. Since it does not occur, the amount of gas trapped by the curing of the rubber is reduced, so that the decomposition generated gas is less likely to leak from the sponge surface, the surface smoothness of the skin layer is excellent, and the base material for weather strips for automobiles As a result, it is possible to easily obtain a silicone rubber sponge extremely suitable as In addition, the heat-expandable microcapsules of component (B), which expand at a temperature of 80 to 200 ° C, have a vinylidene chloride-acrylonitrile copolymer, etc., which has a high hardness at room temperature, as an outer shell. By increasing the compressive load of the silicone rubber sponge, an elastic silicone rubber sponge can be obtained. Incidentally, the expansion temperature is less than 80 ℃ in the heat-expandable microcapsules, compression set becomes worse,
If the temperature exceeds 200 ° C, the productivity will deteriorate.

The organic foaming agent as the component (C) may be any one as long as it is used as a foaming agent for ordinary silicone rubber sponges. These include azo compounds such as azobisisobutyronitrile and azodicarbonamide, dinitrosopentamethylenetetramine, N, N
Examples include nitroso compounds such as -dimethyl-N, N-dinitrosoterephthalamide. The blending amount of component (C) is (a)
It is selected in the range of 0.5 to 10 parts by weight based on 100 parts by weight of the polyorganosiloxane base polymer as a component. (C)
If the component is less than 0.5 parts by weight, sufficient decomposition gas is not generated for sponge formation, and if it exceeds 10 parts by weight, a large amount of decomposition gas is generated and the decomposition gas leaks from the sponge surface. The surface smoothness of the skin layer is significantly deteriorated.

The silicone rubber sponge composition used in the present invention may contain, in addition to the above components, a semi-reinforcing or non-reinforcing filler as long as the effect of the present invention is not impaired. Examples of the semi-reinforcing or non-reinforcing filler include pulverized silica, diatomaceous earth, metal carbonate, clay, talc, mica, titanium oxide and the like. Further, heat resistant additives, flame retardants, antioxidants, processing aids, etc., which have been conventionally used, can be added to the silicone rubber composition. Further, it is also possible to mix carbon, ferrite powder, etc., and form by high frequency dielectric heating.

[0009]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In addition, the part in an Example represents a weight part. Example 1 To 100 parts of a thermosetting millable silicone rubber compound (YE3465U made by Toshiba Silicone), 4 parts of azobisisobutyronitrile was used as an organic foaming agent, the outer shell was vinylidene chloride / acrylonitrile copolymer, and isobutane was added. 2 parts of heat-expandable microcapsules (Expansel 461DU manufactured by Expancel Co., Ltd.) having an expansion temperature of 110 to 150 ° C., an average particle size of 5 to 30 μm and an expansion ratio of about 60 times, as a curing catalyst. 0.5 part of platinum complex of chloroplatinic acid and tetramethylvinyldisiloxane (15 ppm based on the total weight of platinum), dimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer with both ends trimethylsiloxy groups as a crosslinking agent Atom content 0.8%) 1.0 part, triallyl isocyanate as a curing inhibitor 1.0 part was blended and mixed with a two-roll mill until uniform. Next, the silicone rubber compound was molded by hot air vulcanization to obtain a weather strip for automobiles having a silicone rubber sponge as a base material (FIG. 1). In the figure, 10 is a base portion, 20 is a hollow seal portion,
30 is a lip portion, and H is a height with respect to the reference plane B. The obtained weather strip for automobiles has a uniform fine cell structure and a specific gravity of 0.20. The surface roughness of this weather strip was measured using a Tokyo Seimitsu surface roughness measuring instrument Surfcon 570A.
It was 10.1μm when measured by the method (10-point average method),
It had a very pleasing appearance. Next, the height H of the hollow seal portion 20 was compressed 30% with respect to the reference surface B, and the compression set was measured under the condition of 70 ° C. × 194 hours, and it was 24%. Further, the change in hardness (Asker C) when taken out immediately after the end of the cold resistance test under the condition of -40 ° C x 24 hours was +2. Further, this weather strip for automobiles was cut into a length of 100 mm, and the compressive load was measured when the height H of the hollow seal portion 20 was compressed by 40% with respect to the reference surface B at a speed of 20 mm / min. , 1.2 kgf / 100 mm, which was rich in elasticity and had a good sealing property.

Example 2 100 parts of thermosetting millable silicone rubber compound (TE3465U made by Toshiba Silicone) was added with 4 parts of azobisisobutyronitrile as an organic foaming agent, and the outer shell was vinylidene chloride / acrylonitrile copolymer. , Encapsulating isobutane, having an expansion temperature of 110 to 150 ° C., an average particle size of 5 to 30 μm, and an expansion ratio of about 60 times thermally expandable microcapsules (Expansel 461DU manufactured by Expancel Co., Ltd.) 2 And 0.6 part of benzoyl peroxide and 0.8 part of dicumyl peroxide as a curing agent were mixed and mixed with a two-roll mill until uniform. Next, in the same manner as in Example 1, a weather strip for automobiles having a silicone rubber sponge of substantially the same shape as a base material was obtained and tested. The obtained automotive weather strip has a uniform fine cell structure and a specific gravity of 0.18. This surface roughness was measured by the ISO method (ten-point average method) using a Tokyo Seimitsu surface roughness measuring instrument Surfcon 570A. ), It was 9.4 μm, which was a very preferable appearance. Next, the height H of the hollow seal portion 20 with respect to the reference plane B is set to
When the compression set was measured at 70 ° C for 194 hours with 30% compression, it was 25%. Further, the change in hardness (Asker C) when taken out immediately after the end of the cold resistance test under the condition of -40 ° C x 24 hours was +2. Further, this weather strip for automobiles was cut into a length of 100 mm, and the compressive load was measured when the height H of the hollow seal portion 20 was compressed by 40% with respect to the reference surface B at a speed of 20 mm / min. , 1.1 kgf / 100 mm, which was rich in elasticity and had good sealing property.

Comparative Example 1 Organic foaming agent azobisisobutyronitrile (Made by Toshiba Silicone M
E800) was mixed in the same manner as in Example 2, except that a weather strip for automobiles having a silicone rubber sponge of substantially the same shape as a base material was obtained and tested.
The obtained weather strip for automobiles had a cell structure which was not uniformly fine and had a specific gravity of 0.33. This surface roughness was measured by using Tokyo Seimitsu surface roughness measuring instrument Surfcon 570A.
When measured by the SO method (10-point average method), it was 25.4 μm, and the surface was prominently uneven. Next, the height H of the hollow seal portion 20 was compressed by 30% with respect to the reference plane B, and the compression set was measured under the condition of 70 ° C. × 194 hours, and it was 20%. Further, the change in hardness (Asker C) when taken out immediately after the end of the cold resistance test under the condition of −40 ° C. × 24 hours was ± 0. Further, this weather strip for automobiles was cut into a length of 100 mm, and the compressive load was measured when the height H of the hollow seal portion 20 was compressed by 40% with respect to the reference surface B at a speed of 20 mm / min. , 0.1 kgf / 100 mm, no elasticity, and incomplete sealability.

Comparative Example 2 Organic foaming agent azobisisobutyronitrile (Made by Toshiba Silicone M was used without adding heat-expandable microcapsules.
E800) was blended in the same manner as in Comparative Example 1 except that a weather strip for automobiles having a silicone rubber sponge of substantially the same shape as a base material was obtained and tested.
The obtained weather strip for automobiles had a cell structure that was not uniformly fine and had a specific gravity of 0.30, and this surface roughness was measured using a surface roughness measuring instrument Surfcon 570A manufactured by Tokyo Seimitsu Co., Ltd.
When measured by the SO method (10-point average method), it was 25.4 μm, and the surface was prominently uneven. Next, the height H of the hollow seal portion 20 was compressed 30% with respect to the reference plane B, and the compression set was measured under the condition of 70 ° C. × 194 hours, and it was 19%. Further, the change in hardness (Asker C) when taken out immediately after the end of the cold resistance test under the condition of −40 ° C. × 24 hours was ± 0. Further, this weather strip for automobiles was cut into a length of 100 mm, and the compressive load was measured when the height H of the hollow seal portion 20 was compressed by 40% with respect to the reference surface B at a speed of 20 mm / min. , 0.1 kgf / 100 mm, no elasticity, and incomplete sealability.

Comparative Example 3 Next, an EPDM composition shown in Table 1 was used to obtain a weather strip for automobiles based on the current EPDM having a similar shape to that of Example 1, and the same test was performed. The obtained automobile weather strip had a cell structure that was not uniformly fine and had a specific gravity of 0.55, and this surface roughness was measured by the ISO method (ten-point average method) using a Tokyo Seimitsu surface roughness measuring instrument Surfcon 570A. It was 13.8 μm, and the surface was good. Next, the height H of the hollow seal portion 20 was compressed 30% with respect to the reference surface B, and the compression set was measured under the condition of 70 ° C. × 194 hours, and it was 35%. Also,
The change in hardness (Asker C) when taken out immediately after the end of the cold resistance test under the condition of -40 ° C x 24 hours was +10. In addition, this weather strip for automobiles
When it was cut into a length of 0 mm and the height H of the hollow seal portion 20 was compressed by 40% with respect to the reference surface B at a speed of 20 mm / min, the compression load was measured and found to be 0.8 kgf / 100 mm. The sealing property was good.

[0014]

[Table 1]

[0015]

The automotive weather strip of the present invention comprises a thermosetting millable type silicone rubber composition (A),
Specific heat-expandable microcapsules (B) and organic blowing agents (C)
Since the silicone rubber sponge formed by molding the silicone rubber sponge composition is used as a base material, it has excellent compression set, cold resistance, low specific gravity, and low hardness and high hardness for automobile weather strips. , High compressive load, rich elasticity, good sealing property, excellent surface smoothness, and beautiful appearance.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a weather strip for an automobile obtained in an example.

[Explanation of symbols]

 10 Base 20 Hollow seal 30 Lip

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Takahashi 6-23-1, Roppongi, Minato-ku, Tokyo Toshiba Silicone Co., Ltd.

Claims (1)

[Claims] 1. A weather strip for an automobile, comprising a silicone rubber sponge as a base material, wherein the base material mainly comprises (a) a polyorganosiloxane base polymer, (a ') a reinforcing silica filler and (b) a curing agent. (A) thermosetting millable silicone rubber composition as a component, (B) heat-expandable microcapsules that expand at a temperature of 80 to 200 ° C. 0.1 to 20 parts by weight (vs. (a) 100 parts by weight) and ( C) A weatherstrip for automobiles, which is obtained by molding a silicone rubber sponge composition containing 0.5 to 10 parts by weight of an organic foaming agent (100 parts by weight of (a)).