JPH115875A - Shock-absorbing gel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a shock-absorbing gel material restrained from dust adherence to the surface through reducing surface tack and electrification so as to maintain its high attenuation performance. SOLUTION: This shock-absorbing gel material is obtained by incorporating a polymer composition comprising at least one kind of rubber and a styrene- vinylisoprene-styrene copolymer <=30 wt.% in styrene content with a flexibilizer for the above copolymer, an antistatic agent and a peroxide as crosslinking agent followed by crosslinking reaction of the resulting blend.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock-absorbing gel material, and more particularly, to a shock-absorbing gel material having a high damping property which reduces the surface tackiness, prevents static electricity, and prevents dust from adhering.

[0002]

2. Description of the Related Art Rubber, asphalt and the like have been well known as a shock absorbing / damping material for a long time. Although many of these have been used, their shock absorbing performance, that is, the tan δ value which is a measure of the damping performance is 0.1 to 0.3, which is not necessarily large. It has been done. Among them, a polynorbornene resin containing a large amount of oil is known. This plasticizes polynorbornene by containing oil, brings the glass transition point close to room temperature, and sets the tan δ value to 1 to 2 to dramatically improve the damping performance. On the other hand, silicone gels containing silicone as a main component are promising because of their stable temperature and frequency characteristics.

[0003]

However, a shock absorbing material containing a large amount of oil in a polynorbornene resin has a tan δ peak temperature near room temperature, and therefore has a large damping performance near room temperature. Is narrow,
The drawback is that the damping performance is highly dependent on temperature and frequency and is expensive. The silicone gel also has problems such as a tan δ value of 0.2 to 0.8 and a low damping performance as compared with polynorbornene, too low elastic modulus, and high cost.

A conventional shock absorber using a styrene-vinylisoprene-styrene copolymer contains a high-molecular-weight oil in order to change the temperature range in which the hardness becomes lower or the damping becomes higher. The surface became tacky, and a large amount of oil contained therein migrated to the surface over time to amplify the tackiness. This not only makes it easier for dirt to adhere to the surface of the shock absorber, but also makes it harder to separate once the dirt adheres to it. There is a demand for a shock-absorbing gel material that does not have a crack. In addition, there is a problem that various properties such as oil resistance, weather resistance, and heat resistance are insufficient, and a shock absorbing gel material that satisfies these properties and has a high damping property is required.

[0005] Furthermore, in the operation of forming the shock absorbing material into a sheet by a roll, static electricity is generated inside the sheet, and dust adheres to the surface.

The present invention has been made to solve the above problems, and provides a shock-absorbing gel material having high damping performance in which adhesion and charging of the surface are reduced to prevent dust from adhering to the surface.

[0007]

According to the first aspect of the present invention, at least one kind of rubber and a styrene content of 30% are used.
The following styrene / vinyl isoprene / styrene copolymer polymer was added to a styrene / vinyl isoprene / styrene copolymer softener, antistatic agent, and peroxide crosslinking agent, and the resulting blend was obtained. Crosslinked shock absorbing gel material.

[0008] The invention according to claim 2 of the present application is an impact-absorbing gel material comprising a softener for rubber and a softener for styrene / vinylisoprene / styrene copolymer as a softener.

According to the invention of claim 3 of the present application, the at least one kind of rubber is a shock absorbing gel material made of nitrile rubber.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The impact-absorbing gel material of the present invention comprises a softener and a sticky styrene / vinylisoprene / styrene copolymer having a styrene content of 30% or less surrounded by at least one kind of rubber. The styrene / vinyl isoprene / styrene copolymer incorporates a softening agent and shifts the peak temperature of tan δ to a lower temperature side, so that the tan δ max (1 to
(100 Hz) ≧ 0.4.

In the impact-absorbing gel material of the present invention, at least one kind of rubber is used. The rubber contains a softener and surrounds the tacky styrene-vinylisoprene-styrene copolymer to render it non-tacky. Specific examples include nitrile rubber, hydrogenated nitrile rubber, ethylene-propylene-diene rubber, chloroprene rubber, chlorosulfonated polyethylene, acrylic rubber, ethylene-propylene-diene rubber, and natural rubber.

When surrounded by nitrile rubber, oil resistance is improved, and when surrounded by hydrogenated nitrile rubber, a shock absorbing gel material is obtained which has improved heat resistance and weather resistance in addition to oil resistance. Furthermore, aging resistance, weather resistance, and ozone resistance can be improved by enclosing with ethylene / propylene / diene rubber, chloroprene rubber, chlorosulfonated polyethylene, etc., and heat resistance and oil resistance can be improved by enclosing with acrylic rubber. It becomes an adhesive shock absorbing gel material.

The styrene / vinyl isoprene / styrene copolymer used in the present invention comprises a triblock copolymer in which polystyrene and vinyl-polyisoprene are combined, and the styrene content is 30% or less. .
This copolymer has a tan δ peak temperature around 35 ° C., and has a high damping performance near this temperature. However, since the high damping temperature region is narrow, the temperature and frequency dependence of the damping performance is low. Is big. If the styrene content exceeds 30%, the rigidity of the copolymer increases and it becomes difficult to obtain a low-hardness gel material.

As the above-mentioned styrene / vinyl isoprene / styrene copolymer, those in which the vinyl isoprene phase is hydrogenated can also be used. In this case, the hydrogenation rate is 80% or more.

The addition amount of the styrene / vinyl isoprene / styrene copolymer is 30 to 70 parts by weight based on 100 parts by weight of the total of at least one kind of rubber and the styrene / vinyl isoprene / styrene copolymer. , Less than 30 parts by weight, the maximum value of tan δ measured within a frequency of 1 to 100 Hz is less than 0.4, and the damping performance is low. On the other hand, if the amount exceeds 70 parts by weight, the relative amount of the styrene / vinyl isoprene / styrene copolymer in the blend increases, so that the rigidity increases and it becomes difficult to obtain a low-hardness gel material.

As the softener of the present invention, a softener for styrene / vinyl isoprene / styrene copolymer is used. This softener is incorporated into the styrene / vinyl isoprene / styrene copolymer to improve the damping performance.
The peak temperature of nδ is shifted to the lower temperature side. Examples of the softening agent include liquid rubber such as liquid polybutene and polyisoprene, or paraffin oil (SP value = 7.9) whose SP value is close to the SP value (8.2) of styrene / vinyl isoprene / styrene copolymer. , Naphthenic oil (SP value = 8.
2) and aroma oil (SP value = 8.7). The amount of the softener is not particularly limited.

As the softening agent for rubber, oils, plasticizers and the like having an SP value close to the SP value of the selected rubber are selected. For example, in the case of nitrile rubber, since the SP value is around 9.8, the ether ester plasticizer (S
P value = 8.9-9.2), DOP (SP value = 9.0),
A material having a value close to the SP value of rubber, such as DBP (SP value = 9.41), is selected. The amount of the softener is not particularly limited.

The antistatic agent is used as a kneading agent, and there are four types of surfactants, such as anionic, cationic, nonionic and amphoteric. Specifically, pentaalkyltripolyphosphate , Hexaalkyltetrapolyphosphate, alkylallylsulfonic acid,
Anions such as adipic acid, glutamic acid and sulfonic acid of oligostyrene, amines such as N-cyclohexylamine / butyrate, cyclohexylamine / ricinoleate, cyclohexylamine / borate, ethylene oxide adduct of ethylenediamine, propylene of ethylenediamine Oxidized amines Cationic, such as ethylene oxide adducts, fatty acid amides, ethylene oxide adducts, nonionics of amides such as dialkylamides, alanine-type metal salts, imidazoline-type metal salts, carboxylic acid-type metal salts, etc. It consists of both sexes.

The amount of the antistatic agent to be added is at least one kind of rubber and a polymer 100 composed of a styrene / vinyl isoprene / styrene copolymer having a styrene content of 30% or less.
If the amount is less than 2 parts by weight, the gel material has no antistatic effect. If the amount is more than 15 parts by weight, the gel material softens and has a predetermined hardness. I can not get it.

In the present invention, a peroxide is added as a cross-linking agent in addition to the above-mentioned additives, and a gel material having a chemically cross-linked structure can be used at a high temperature. As the peroxide, for example, di-t-
Butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, 2.5-dimethyl-2.
1. 5-di (t-butyl peroxide) -hexane;
5-dimethyl-2.5-di (t-butylperoxy)-
Hexane-3,1,3-bis- (t-butylperoxy-isopropyl) benzene, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane,
1,1-di-t-butylperoxycyclohexane,
N-butyl 4,4-di-t-oxyparerelate, 2,
2-di-t-butylperoxybutane is exemplified. Other crosslinking agents include azide-type crosslinking agents, phenol-type crosslinking agents, aldehyde-amine reaction products, sulfur, and maleic imides.

The impact-absorbing gel material of the present invention is not limited to a solid but may be a foam having an expansion ratio of 1.2 to 4. In this case, examples of the foaming agent include inorganic compounds such as sodium bicarbonate and ammonium carbonate, nitroso compounds such as dinitrosopentamethylenetetramine, azo compounds such as azodicarbonamide, azo-isobutyro-dinitrile, and other urea-based foaming aids. Agents can also be used.
The amount of the blowing agent added is styrene, vinyl isoprene,
It is 3 to 10 parts by weight based on 100 parts by weight of the styrene copolymer.

Further, in the present invention, the properties of the gel material can be improved by mixing additives selected from a filler, a light stabilizer and a thermal oxidation inhibitor. Examples of the filler include calcium carbonate, silica, clay, talc and the like, polyacrylonitrile, thermally expanded microcapsules such as vinylidene chloride and the like, and the above-mentioned capsules are foamed, and calcium carbonate, a hollow microsphere filler coated with a powder of talc or the like. Can be used.

Examples of the light stabilizer include 2-hydroxy-4-methoxybenzophenone, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4 , Di-tert-butylphenyl-3 ', 5'-di-tert-butyl-4'-hydroxybenzoate, nickel dibutyl-dithiocarbamate and the like. The light stabilizer is added in an amount of 0.2 to 5 parts by weight based on 100 parts by weight of the styrene / vinyl isoprene / styrene copolymer.

As the thermal oxidation inhibitor, for example,
6-di-tert-butyl-4-methylphenol, styrenated phenol, mixed N, N'-diallyl-paraphenylenediamine, dilauryl-3,3'-
Thiodipropylate, distearyl-3,3'-thiodipropylate, trinolylphenylphosphate, N
-Phenyl-N'-isopropyl-P-phenylenediamine and the like are used. The added amount of this thermal antioxidant is
Styrene / vinyl isoprene / styrene copolymer 100
It is 0.2 to 5 parts by weight based on parts by weight.

[0025]

Next, the present invention will be described in more detail with reference to specific examples. Examples 1 to 3 and Comparative Examples 1 to 2 Compounds were prepared using a kneader. First, a styrene / vinyl isoprene / styrene copolymer shown in Table 1, a kind of rubber (NBR), an antistatic agent, a filler, a softener, and the like are charged and thoroughly mixed until the rubber temperature reaches 120 ° C. Was added with peroxide and a crosslinking assistant to obtain a blend. The composition thus obtained was rolled to a thickness of about 2 mm on two rolls maintained at a roll temperature of 90 to 120 ° C. to obtain a sheet. This was cross-linked in a predetermined shape at 180 ° C. for 15 minutes to obtain a sheet having a thickness of 2 mm.

10 m width from the crosslinked and molded sheet
A rectangular sample having a length of 25 mm, a length of 25 mm, and a thickness of 2 mm was prepared. The damping performance of this sample was measured using a rheograph solid (manufactured by Toyo Seiki Co., Ltd.), and a sinusoidal dynamic strain of ± 0.05% or less was applied to the sample, and the frequency characteristics of 1 to 100 Hz were measured. Tanδm is the maximum value of the loss coefficient tanδ.
ax. The hardness was measured using a JIS-A type hardness meter. Adhesion was measured by pressing two samples having a width of 10 mm and a length of 50 mm, and measuring the 90 ° peeling force with a spring meter. When the peeling force was less than 50 g / cm, the adhesiveness was judged as acceptable (合格), and when the peeling force exceeded 50 g / cm, it was judged as unacceptable (x). The sheet resistance value is measured with a surface resistance meter (MCP
-TESTER). Oil resistance test is JIS K
According to 6301, the sample was immersed in JIS No. 3 oil at 40 ° C., and the volume change rate was measured. Table 1 also shows these measurement results.

[0027]

[Table 1]

According to the results, when the nitrile rubber and the antistatic agent are added, the tackiness is reduced, the oil resistance is improved, and sufficient damping characteristics can be obtained. In the temperature characteristics of the loss coefficient, the shock absorbing gel material of Example 3
There are two peak values of the loss coefficient, the styrene / vinyl isoprene / styrene copolymer is surrounded by nitrile rubber, and the state becomes sea (nitrile rubber) and island (styrene / vinyl isoprene / styrene copolymer). It indicates that

[0029]

As described above, in the present invention, the styrene / vinyl isoprene / styrene copolymer having a styrene content of 30% or less is dispersed in a state of being surrounded by at least one kind of rubber, whereby the surface tackiness is reduced. In addition, the styrene / vinyl isoprene / styrene copolymer incorporates a softener, which exhibits excellent damping performance, and because it contains an antistatic agent, has good electrical conductivity and prevents dust from adhering to the sheet surface Thus, it is possible to provide a shock-absorbing gel material having high damping performance.

Claims (3)

[Claims] 1. A polymer comprising at least one rubber and a styrene / vinyl isoprene / styrene copolymer having a styrene content of 30% or less, a softener, an antistatic agent for the styrene / vinyl isoprene / styrene copolymer, and A shock-absorbing gel material comprising a crosslinking agent obtained by adding a peroxide crosslinking agent and crosslinking the resulting composition. 2. The impact-absorbing gel material according to claim 1, wherein a softener for rubber and a softener for styrene / vinyl isoprene / styrene copolymer are used in combination as the softener. 3. The impact-absorbing gel material according to claim 1, wherein the at least one rubber is a nitrile rubber.