JPH10168232A - Rubber composition and molding made therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition which can give moldings highly resistant to aliphatic hydrocarbon fuels such as gasoline and can give smoothly demoldable vulcanized members by mixing a hydrogenated acrylonitrile/ butadiene rubber, a peroxide-type vulcanizing agent and a silicone oil. SOLUTION: The silicone oil used may be any one of methylsilicone, dimethylsilicone, methylphenylsilicone and a modified silicone oil. It is added in an amount of desirably 0.2 to below 2.0 pts.wt. per 100 pts.wt. hydrogenated acrylonitrile/butadiene rubber. Rubber moldings obtained by vulcanizing the composition are particularly useful as rubber molded components used in storage tanks for aliphatic hydrocarbon fuels such as gasoline or lubricating oils or in transportation pipe systems. A vibration-proof rubber molding for a fuel tank has a rubber hardness of 45-60Hs. Which is attained by adjusting the amounts of vulcanizing agents and additives.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having excellent fuel resistance and mold release properties, and a molded product using the same. The molded article made of the rubber composition of the present invention is particularly useful as a rubber mold part used for a storage tank or a pipeline system for transferring an aliphatic hydrocarbon fuel such as gasoline and a lubricating oil.

[0002]

2. Description of the Related Art Rubber mold parts used in gasoline tanks have low solubility and swellability in gasoline and sour gasoline (oxidized gasoline), and do not deteriorate in properties such as strength for a long time. That is, gasoline resistance and sour gasoline resistance are required. Further, it is necessary that the components such as the copper plate commutator of the pump motor and the components of the piping connected to the tank not be contaminated or blocked. For this reason, for such applications, acrylonitrile-butadiene rubber (NBR) having a small swelling due to aliphatic hydrocarbons and alcohols, particularly hydrogenated NBR (HN) having excellent heat resistance and good sour gasoline resistance
A molded product obtained by subjecting (BR) to peroxide vulcanization (crosslinking) is suitably used. Also, when vibration isolation is required,
H-NBR with good vibration insulation and low hardness is used.

[0003] However, H-NBR tends to adhere to the surface of a mold during vulcanization molding, and it is more difficult to remove the mold after vulcanization than other materials. This tendency becomes more pronounced as the number of times the mold is used for vulcanization, and in the worst case chipping of the rubber molded article occurs when the mold is removed from the mold. In particular, such defects are likely to occur in rubber products having low hardness.

[0004] In order to address these problems, conventionally,
(1) Use a mold with increased releasability by coating the surface with Teflon or a composite Teflon obtained by mixing Teflon with a metal component, or (2) Apply a mold to the inner surface prior to use For example, a method of spraying or applying a silicone or fluorine release agent is employed. However, in the method (1), it is necessary to clean the mold surface in advance and bake after coating (about 350 to 400 ° C. for about 1 hour). Must be created and used interchangeably. Further, there is a problem in durability of the coating layer, and a permanent effect cannot be expected. In the method (2), it is necessary to perform coating or the like every one or several times of vulcanization, and a post-application baking treatment is required to enhance the durability. For this reason, productivity is poor, leading to deterioration of the working environment.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a rubber composition which has high durability against aliphatic hydrocarbon fuels such as gasoline and which can release a member from a mold smoothly after vulcanization. It is an object to provide a product and a rubber molded product using the same.

[0006]

Means for Solving the Problems The inventors of the present invention have been studying to solve the above problems, and have added silicone oil, which has been conventionally used as an external release agent, to the H-NBR component itself before vulcanization. By doing so, it is possible to obtain a composition that is excellent in fuel resistance and lubricating oil resistance, has excellent mold release properties after vulcanization, and has no adverse effect such as clogging in the fuel transfer pipeline. And completed the present invention.

That is, the present invention provides the following rubber composition and molded article. (1) A rubber composition having excellent fuel resistance and releasability, comprising hydrogenated acrylonitrile-butadiene rubber (H-NBR), a peroxide-based vulcanizing agent and silicone oil. (2) The content of silicone oil is H-NBR10
2. The rubber composition according to the above 1, wherein the amount is 0.2 parts by weight or more and less than 2.0 parts by weight based on 0 parts by weight. (3) The silicone oil described in 1 or 2 above, wherein the silicone oil is methyl silicone (methyl polysiloxane), dimethyl silicone (dimethyl polysiloxane), methyl phenyl silicone (methyl phenyl polysiloxane), modified polysiloxane, or a mixture of two or more thereof. 3. The rubber composition according to item 1. (4) A rubber molded product obtained by molding and vulcanizing the rubber composition according to any of the above items 1 to 3. (5) The rubber molded product for a member inside a fuel tank according to (4). (6) The anti-vibration rubber molded product for a fuel tank according to the item 4, wherein the rubber hardness is 45 to 60 Hs (JIS-A).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

I. Rubber Composition The rubber composition of the present invention basically comprises a rubber base component, silicone oil, a peroxide-based vulcanizing agent, and other additives. Hereinafter, each component will be described in detail. (1) Rubber Base Component In the present invention, H-NBR having excellent fuel resistance, lubricating oil resistance and heat resistance is used as a base component of the composition. H-
NBR is obtained by subjecting acrylonitrile-butadiene rubber (NBR) obtained by polymerizing butadiene and acrylonitrile (AN) to a hydrogenation treatment. H-N
The content of AN in BR can be in various ranges, but preferably H-NBR containing 33 to 50% by weight, more preferably 40 to 45% by weight of AN is used. When the AN content is less than 33% by weight, there is a problem that the dimensional change becomes large due to swelling of the fuel oil, and when it exceeds 50% by weight, there is a problem that the rubber hardness at a low temperature becomes high and the vibration insulation becomes poor. The hydrogenation rate is usually about 90 to 100% of the total double bonds.

The rubber base component may be added with polyvinyl chloride (PVC) or the like to improve sour gasoline resistance. These rubber components can be used up to about 30 parts by weight or less based on 100 parts by weight of H-NBR, though depending on the type of the components. If it exceeds 30 parts by weight, problems such as deterioration of compression set will occur.

(2) Silicone Oil In the present invention, by adding and mixing silicone oil to the above-mentioned H-NBR rubber base, in addition to oil resistance and heat resistance, the releasability after vulcanization is improved. Conventionally, silicone oil has been used as an external release agent at the time of vulcanization, but there is no example of adding this as an internal release agent to H-NBR rubber. In addition, as shown in a comparative example described below, even if a higher fatty acid-based wax or the like, which is also used as an external mold release agent, is added to the H-NBR rubber, an effect similar to that of silicone oil is not obtained. Problems such as clogging of the flow path occur.

As the silicone oil, straight silicone oil, that is, any of methyl silicone (methyl polysiloxane), dimethyl silicone (dimethyl polysiloxane), methyl phenyl silicone (methyl phenyl polysiloxane), and modified silicone oil can be used. it can. The modified silicone oil includes a compound in which a part of the methyl group of the straight silicone oil is substituted with lower alkyl, aralkyl, fluorinated alkyl, or the like. A compound modified by reacting with an amino group, epoxy, alcohol, mercapto, alkyl carboxylate, or the like may be used. These compounds may be used alone or in combination of two or more. Straight or modified silicone oils are preferably 20-100,
Use a material having a viscosity of 000 cst (25 ° C.). 20cs
If it is less than t, the flash point is low, and there is a risk that a fire may occur when mixing. If it exceeds 100,000 cst, the workability at the time of weighing will deteriorate. Although the amount of the silicone oil depends on the use of the rubber molded product, it is preferably 0.2 parts by weight or more and less than 2.0 parts by weight, more preferably 100 parts by weight of the H-NBR rubber.
Use 0.5 to 1.5 parts by weight. If the amount is less than 0.2 parts by weight, the effect of improving the releasability is not exhibited. If the amount is more than 2.0 parts by weight, there may be a problem in fusing the molded article.

(3) Peroxide vulcanizing agent In the present invention, an organic peroxide vulcanizing agent is added and mixed in addition to the above-mentioned components. When sulfur is used as a vulcanizing agent, unreacted sulfur or free sulfur reacts with the copper plate commutator of the fuel supply pump motor in the gasoline tank and deposits on the commutator as copper sulfide. Will not be supplied. It also leads to clogging of the fuel passage. Therefore, by using an organic peroxide-based vulcanization, the degree of hydrogenation of the H-NBR rubber can be adjusted over a wide range, and problems such as clogging of the fuel flow path due to the vulcanizing agent can be avoided. Can be As the organic peroxide-based vulcanizing agent, those usually used can be used. For example, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, benzoyl peroxide,
2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-
2,5-di (t-butylperoxy) hexane, 1,3
-Di (t-butylperoxyisopropyl) benzene and the like are useful. The amount of the organic peroxide vulcanizing agent is usually 0.5 to 5 parts by weight based on 100 parts by weight of the H-NBR rubber.

In order to improve the compression set, a crosslinking aid (coagent) is used together with an organic peroxide-based vulcanizing agent.
Can also be used. Examples of the crosslinking aid include tetrahydrofurfuryl methacrylate, ethylene dimethacrylate, 1,3-butylene methacrylate, 1,4-
Methylene dimethacrylate, 1,6-hexanediol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,
6-hexanediol diacrylate, 2,2′-bis (4-methacryloxydiethoxyphenyl) propane,
2,2'-bis (4-acryloxydiethoxyphenyl) propane, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, 3-chloro-2-
Hydroxypropyl methacrylate, oligoester acrylate, aluminum (meth) acrylate, zinc (meth) acrylate, magnesium (meth) acrylate, calcium (meth) acrylate, triallyl isocyanurate, triallyl cyanurate, triallyl trimellitate, diallyl phthalate , Diallylchlorendate, divinylbenzene, 2-vinylpyridine,
N, N'-methylenebisacrylamide, p-quinonedioxime, p, p'-dibenzoylquinonedioxime,
Examples thereof include 1,2-polybutadiene. The amount of the crosslinking aid is usually 1 to 100 parts by weight of the H-NBR rubber.
To 10 parts by weight.

(4) Additives In addition to the above-mentioned essential components, the vibration-isolating rubber composition of the present invention includes reinforcing materials, plasticizers, anti-aging agents, fillers and the like which have been conventionally used as additives for rubber. Can be blended.
Reinforcing materials used to enhance the mechanical properties (tensile strength, hardness, tear strength, abrasion, etc.) of the vulcanizate include carbon black, silica and the like. As the filler, in addition to the above-mentioned reinforcing material, calcium carbonate, clay, talc and the like can be mentioned, and these can be used alone or in combination with a plurality of reinforcing agents. Although the compounding amount cannot be specified unconditionally, it is generally 5 to 1 with respect to 100 parts by weight of the rubber component.
It is about 00 parts by weight. Examples of the plasticizer for improving the fluidity of the raw material include diethyl phthalate, dibutyl phthalate, dioctyl phthalate, dioctyl adipate, dibutyl carbitol adipate, dioctyl sebacate, dibutyl sebacate, tricresyl phosphate, chlorinated paraffin, Liquid NBR is used, and is used up to about 30 parts by weight based on 100 parts by weight of the rubber component.

Examples of the anti-aging agent (anti-deterioration agent) include quinoline, phenol and imidazole. Although this is not always necessary because it is extracted into gasoline, it can be added in an amount of about 0.5 to 2 parts by weight based on 100 parts by weight of the rubber component. In addition to the above-mentioned additives, other conventionally known additives may be used as long as they do not adversely affect the fuel.

II. Rubber molded article The above rubber composition is obtained by uniformly mixing the masticated rubber component and other additives, kneading at a temperature not higher than the vulcanization temperature, and then filling and vulcanizing in a vulcanization mold. . The vulcanization temperature and vulcanization time may be set as appropriate. Usually 150-1
90 ° C., about 5 to 30 minutes. If the temperature is too high, the degree of crosslinking between the surface and the inside of the vulcanizate tends to be non-uniform, and if the temperature is too low, vulcanization does not proceed sufficiently. Further, secondary vulcanization using an oven or a steam pipe may be performed. The rubber molded product of the present invention thus obtained is particularly used as a rubber molded product in a region likely to come into contact with a tank or a flow path of an aliphatic hydrocarbon fuel such as gasoline or light oil or a lubricating oil or a fuel or the like. Useful. Examples of such components include pulsation absorbing sheets, in-tank motor support rubber, and the like. Motor support rubber for a fuel tank or the like is required to have particularly high vibration damping properties. In such a case, the rubber hardness is set to 45 to 60 Hs (JIS-A). If it is less than 45 Hs, sufficient strength cannot be obtained. If it exceeds 60 Hs, the anti-vibration properties will be reduced. Adjustment of rubber hardness in molded products
The adjustment is performed by adjusting the vulcanizing agent and additives in the raw rubber composition, or by adjusting the vulcanizing temperature and the vulcanizing time.

[0017]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. In the following examples, the following rubber composition raw materials and test methods were used. [Rubber composition raw material] (1) Rubber component (H-NBR) Zetpol 1020 manufactured by Nippon Zeon Co., Ltd. (AN content: 44%) (2) Silicone oil dimethyl silicone (TSF4 manufactured by Toshiba Silicone Co., Ltd.)
51 (50,000 cst)) (3) Vulcanizing agent dicumyl peroxide (4) carbon black Medium reinforcing carbon black (SRF: Semi Reinforcing Furnace). (5) Filler Calcium carbonate (Shiraishi Kogyo Co., Ltd. Shirayuka CC) (6) Anti-aging agent Quinoline anti-aging agent (Nonflex RD manufactured by Seiko Chemical Co., Ltd.) (7) Plasticizer dibutyl carbitol adipate

[Test Methods] Various test methods and their evaluation criteria are as follows. Rubber hardness is JISK63
01 type A spring hardness (JIS-A). (A) Release from the mold Unvulcanized rubber was placed on a 60 mm x 25 mm x 2 mm flat metal plate (material: JIS SS41) which had been degreased in advance, and vulcanized.
A test piece as shown in Fig. 1 is prepared (Fig. 1 (a)). Immediately after vulcanization, the rubber (1) is oriented at 90 ° to the metal fitting (2) (FIG. 1).
(b) in the direction of the arrow), and measure the force required to peel the rubber from the bracket. Evaluation criteria: ○: 0.5kgf / 25mm or less △: 0.5 to 1.0kgf / 25mm ×: 1.0kgf / 25mm or more

(B) Fusing property of the weld portion: 100 mm in a vulcanizing mold of 100 mm × 100 mm × 2 mm
Two pieces of unvulcanized rubber measuring 50 mm x 2.2 mm to 2.5 mm are placed side by side, and a pressure of 100 kgf / cm ² is applied at 170 ° C for 20 minutes. Thereafter, the fused portion is observed. If there is no trace of mating between the rubber pieces, it is determined to be good (）). If there is a trace of mating and the rubber pieces are separated from each other at the mating surface, it is poor (×).
Is determined. (C) Clogging property in fuel 40 ml of commercial gasoline was put into a glass flask, 20 g of a 2 mm × 2 mm × 2 mm piece of vulcanized rubber was thrown into the glass flask, sealed and kept at 40 ° C. for 100 hours. The vulcanized rubber pieces were taken out, and the presence of a precipitate in the remaining gasoline was observed to evaluate the clogging property. The case where the sediment is 0.05 ml or less is judged as “no clogging” (○), and the case where the sediment is 0.05 ml or more is judged as “clogged” (×). A similar test was performed using light oil instead of gasoline.

Examples 1 to 4 and Comparative Examples 1 to 4 Each of the above components was added to a base formulation shown in Table 1 and a silicone oil (Example) or a wax (Comparative Examples 1 to 4) shown in Table 2.
A composition was prepared by blending 3) or adding nothing (Comparative Example 4). The obtained composition was press-vulcanized at 170 ° C. for 20 minutes to conduct various tests.

[0021]

Table 1 Formulation example of rubber composition H-NBR 100 parts by weight Vulcanizing agent 2 parts by weight Carbon black 20 parts by weight Calcium carbonate 40 parts by weight Plasticizer 20 parts by weight Antioxidant 1 part by weight

[0022]

[Table 2]

As can be seen from the above results, according to the rubber composition of the present invention, the releasability from the mold is good, and even if the rubber composition is brought into contact with a fuel such as gasoline for a long period of time, the flow path of the rubber composition is not affected. It is possible to obtain a molded article which does not cause an obstacle such as clogging. In particular, when used within the preferred range, the weldability of the weld portion is good. On the other hand, even if a general wax-based external release agent is added to the rubber composition, the effect of improving the releasability is small, and even a small amount of the compound may cause clogging of the fuel flow path. It is considered that the sediment in the fuel due to the wax-based release agent is formed by depositing a small amount of the release agent dissolved in the fuel.
Silicone oil has high solubility in fuel,
Elution from rubber into fuel does not produce such harmful precipitates. After the test, remove the sample from the fuel,
The presence or absence of the swelling was observed, but no deterioration of the characteristics such as swelling of the fuel and reduction of the strength was observed in any of Examples and Comparative Examples.

[0024]

According to the rubber composition of the present invention, release from the mold after vulcanization can be performed without performing a complicated process such as special processing on the mold or application of a release agent for each vulcanization treatment. The moldability can be greatly improved. For this reason, the workability of the vulcanization step is the same as that of a normal rubber material, and the conventional H-NBR
Compared with the rubber vulcanizing step, the number of steps can be reduced and the working environment can be reduced, and even a rubber having a high vibration proof and low hardness does not cause a defect at the time of demolding. Further, since silicone oil which is relatively easy to mix with rubber is used, no special operation is required in the rubber kneading step. Furthermore, the molded article of the composition of the present invention does not generate an inappropriate sediment which causes clogging of a flow path even when used in a fuel such as gasoline or a lubricating oil. High usefulness.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a test method for measuring releasability from a mold.

[Explanation of symbols]

 1 rubber 2 metal fittings

Claims (6)

[Claims] 1. A rubber composition having excellent fuel resistance and releasability, comprising a hydrogenated acrylonitrile-butadiene rubber (H-NBR), a peroxide-based vulcanizing agent and silicone oil. 2. The silicone oil content is H-NB.
The rubber composition according to claim 1, wherein the amount is 0.2 or more and less than 2.0 parts by weight based on 100 parts by weight of R. 3. The silicone oil is methyl silicone (methyl polysiloxane), dimethyl silicone (dimethyl polysiloxane), methyl phenyl silicone (methyl phenyl polysiloxane), modified polysiloxane, or a mixture of two or more thereof. 3. The rubber composition according to 1 or 2. 4. A rubber molded product obtained by molding and vulcanizing the rubber composition according to claim 1. 5. A rubber molded product for an internal member of a fuel tank according to claim 4. 6. A rubber hardness of 45-60 Hs (JIS-JIS).
The vibration-proof rubber molded product for a fuel tank according to claim 4, which is A).