阅读说明：本技术 橡胶组合物 (Rubber composition ) 是由 古贺敦 于 2019-03-14 设计创作，主要内容包括：本发明提供一种橡胶组合物,所述橡胶组合物中每100重量份的乙烯·丁烯·5-亚乙基-2-降冰片烯三元共聚物配合有0.1重量份～2.5重量份的流动温度为50℃～100℃的润滑剂。该橡胶组合物通过配合特定的润滑剂,获得了如下效果,即,防止未硫化橡胶坯料彼此的粘附,改善橡胶坯料准备工序和密封部件等交联成型品的硫化成型工序中的生产率,并且不损害该交联成型品的低温性。该橡胶组合物可有效地用作在-39℃以下的低温环境下特别需要高压气体密封功能的密封构件的交联成型材料。(The present invention provides a rubber composition comprising 0.1 to 2.5 parts by weight of a lubricant having a flow temperature of 50 to 100 ℃ per 100 parts by weight of an ethylene-butene-5-ethylidene-2-norbornene terpolymer. The rubber composition is compounded with a specific lubricant, thereby preventing adhesion of unvulcanized rubber materials to each other, improving productivity in a rubber material preparation step and a vulcanization molding step of a crosslinked molded article such as a seal member, and obtaining the effect of not impairing low temperature properties of the crosslinked molded article. The rubber composition is useful as a crosslinked molding material for a sealing member which particularly requires a high-pressure gas sealing function in a low-temperature environment of-39 ℃ or lower.)

1. A rubber composition characterized by containing, as a main component,

0.1 to 2.5 parts by weight of a lubricant having a flow temperature of 50 to 100 ℃ is compounded per 100 parts by weight of the ethylene-butene-5-ethylidene-2-norbornene terpolymer.

2. The rubber composition according to claim 1, wherein a lubricant having a flow temperature of 60 ℃ to 95 ℃ is used.

3. The rubber composition according to claim 1 or 2, wherein the lubricant is a fatty acid-based lubricant.

4. The rubber composition according to claim 3, wherein the fatty acid-based lubricant is a fatty acid metal salt-based, fatty acid amide-based or fatty acid ester-based lubricant.

5. The rubber composition according to claim 1 or 2, wherein the lubricant is a silicone-based lubricant.

6. The peroxide-crosslinkable rubber composition according to claim 1, wherein 0.5 to 10 parts by weight of an organic peroxide is further compounded.

7. A crosslinked molded article characterized by comprising,

the crosslinked molded article is obtained by crosslinking and molding the crosslinkable rubber composition according to claim 6.

8. The crosslinked molded article according to claim 7,

the crosslinked molded article has a TR70 value of-39 ℃ or less, which is defined in JIS K6261 of ISO 2921.

Technical Field

The present invention relates to a rubber composition. More specifically, the present invention relates to an ethylene/butene/5-ethylidene-2-norbornene terpolymer rubber composition.

Background

Ethylene-propylene-diene copolymer rubber (EPDM) that exhibits sealing properties at both high and low temperatures has no unsaturated bond in the main chain, and therefore, rubber strength and low temperature properties are in a conflicting relationship with an increase in ethylene content. Therefore, the EPDM composition has difficulty in achieving sealability at low temperatures exceeding a certain temperature limit.

In order to obtain a rubber molded article which can maintain the same level of hardness as a rubber molded article using a conventional EPDM, and is excellent in particularly low-temperature rubber characteristics, the present applicant has previously proposed a rubber composition comprising an ethylene/butene/ethylidene norbornene terpolymer [ EBENB ], carbon black, a hardness modifier and a crosslinking agent (patent document 1).

This rubber composition can give a rubber molded article having a hardness at a level equivalent to that of a rubber molded article using conventional EPDM, and particularly excellent in low-temperature rubber characteristics, but EBENB has a problem of extremely poor productivity in a rubber blank preparation step and a vulcanization molding step of a crosslinked molded article such as a seal member because the adhesiveness of a polymer copolymer of EBENB is extremely high and particularly unvulcanized rubber blanks adhere to each other.

Disclosure of Invention

Technical problem to be solved by the invention

An EBENB rubber composition which can improve the productivity in the rubber billet preparation step and the vulcanization molding step of a crosslinked molded article such as a seal member, which is caused by adhesion of unvulcanized rubber billets to each other, without impairing the low temperature characteristics of the crosslinked molded article.

Means for solving the problems

The above object of the present invention is achieved by a rubber composition comprising 0.1 to 2.5 parts by weight of a lubricant having a flow temperature of 50 to 100 ℃ per 100 parts by weight of an ethylene-butene-5-ethylidene-2-norbornene (5-ethylidene-2-norbomene) terpolymer.

ADVANTAGEOUS EFFECTS OF INVENTION

The rubber composition of the present invention can obtain the following effects by blending a specific lubricant: the production efficiency in the rubber material preparation step and the vulcanization molding step of a crosslinked molded article such as a seal member is improved without impairing the low temperature properties of the crosslinked molded article.

The rubber composition is useful as a crosslinked molding material for a sealing member which particularly requires a high-pressure gas sealing function in a low-temperature environment of-39 ℃ or lower.

Detailed Description

In the rubber composition, the characteristics of the rubber material such as EBENB or EPDM greatly affect the material cost and the production efficiency of the entire rubber composition. Since EBENB has better cold resistance than EPDM, a rubber composition having desired low-temperature rubber characteristics can be realized in a smaller amount than EPDM, and the material cost of the entire rubber composition can be reduced.

Furthermore, EBENB has better flexibility than EPDM, and therefore has excellent processability such as kneading property, dispersibility, and moldability, and the production efficiency is greatly improved, and therefore, the cost of the production process can be reduced.

According to the rubber composition of the present invention using EBENB as described above, the production cost of the rubber molded product can be reduced from the viewpoint of the material cost and the production efficiency as compared with the conventional rubber composition using EPDM.

As EBENB, any EBENB obtained by copolymerizing ethylene and butene with a small amount (about 0.1 to 20 wt%, preferably about 3 to 15 wt%) of 5-ethylidene-2-norbornene can be used, and a commercially available product, for example, metalocene EBT, which is a chemical product of mitsui, can be used as it is.

The iodine value of EBENB is preferably from about 3g/100g to 20g/100g, more preferably from about 5g/100g to 18g/100 g. By setting the molecular weight in the above range, the rubber molded article can be prevented from aging due to excellent heat aging resistance and weather resistance, and a stable molecular state can be maintained even in a low-temperature environment, thereby improving low-temperature sealing properties.

Mooney viscosity ML of EBENB₁₊₄The temperature (100 ℃) is preferably about 10 to 45, and more preferably about 15 to 35. If the Mooney viscosity is too low, the compression set becomes large and the tensile strength becomes small in some cases. On the other hand, if the Mooney viscosity is too high, the physical properties are improved, but the processability may be poor. Note that the Mooney viscosity ML is₁₊₄(100 ℃) can be calculated in accordance with the provisions of JIS K6300-1: 2013.

The content of the ethylene component in EBENB is preferably about 60 to 80 wt%, and more preferably about 65 to 75 wt%. By setting the glass transition temperature Tg of EBENB to the above range, the cold resistance is improved.

In the EBENB, a lubricant having a flow temperature (in accordance with JIS K5601-2-2 corresponding to ISO 4625) of about 50 to 100 ℃, preferably about 60 to 95 ℃ is blended in an amount of 0.1 to 2.5 parts by weight, preferably 0.5 to 2.2 parts by weight, per 100 parts by weight of EBENB. Here, the flow temperature of the lubricant means the lowest temperature at which the flow state can be maintained.

When the flow temperature is lower than the above range, adhesion of the unvulcanized rubber materials to each other may occur, while when the flow temperature is higher than the above range, adhesion to a kneader during kneading cannot be prevented.

When the compounding ratio is less than the above range, adhesion between unvulcanized rubber materials cannot be prevented, and when the compounding ratio is more than the above range, low-temperature sealability is impaired.

As the lubricant having a flow temperature of about 50 to 100 ℃, preferably about 60 to 95 ℃, a fatty acid metal salt-based, fatty acid amide-based, fatty acid ester-based lubricant, silicone-based lubricant or the like can be used.

As the fatty acid metal salt-based lubricant, zinc salts of higher saturated or unsaturated fatty acids having 12 or more carbon atoms such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and the like can be used.

As the fatty acid amide-based lubricant, monoamides, substituted monoamides, bisamides, methylolamides, and the like of the above-mentioned higher fatty acids can be used.

As the fatty acid ester-based lubricant, a lower alkyl ester having 5 or less carbon atoms such as methyl ester, ethyl ester, butyl ester and the like of the above higher fatty acid can be used.

Further, as the silicone-based lubricant, a compound having a siloxane bond in the main chain, a mixture thereof with an inorganic carrier, or the like can be used.

As the crosslinking agent, it is preferable to mainly use an organic peroxide. Examples of the organic peroxide include: t-butyl peroxide, dicumyl peroxide, 2, 5-dimethyl-2, 5-di-t-butylperoxyhexane, 2, 5-dimethyl-2, 5-di-t-butylperoxy-3-hexyne, t-butylcumyl peroxide, 1, 3-di-t-butylperoxyisopropyl benzene, 2, 5-dimethyl-2, 5-di (benzoyl peroxide) hexane, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, n-butyl-4, 4-di-t-butylperoxyvalerate, and the like.

The amount of the crosslinking agent blended is preferably about 0.5 to 10 parts by weight, more preferably about 1 to 5 parts by weight, based on 100 parts by weight of EBENB. By setting the amount to the above range, foaming at the time of vulcanization can be prevented and molding failure can be prevented, and a rubber composition having sufficient physical properties can be easily obtained because the crosslinking density becomes good.

In addition, a master batch containing an organic peroxide as described above, such as DCP30ZP03K (dicumyl peroxide 30 wt%, Zetpol 2010L 30 wt%, SRF carbon black 40 wt%) and the like, which are a product of Zeon, japan, can also be used. The master batch is preferable in that the kneading property and dispersibility in the preparation of the rubber composition can be improved.

Further, a crosslinking accelerator may be contained as necessary. As the crosslinking accelerator, triallyl isocyanurate, triallyl cyanate, liquid polybutadiene, N' -m-phenylene bismaleimide, trimethylolpropane trimethacrylate, or the like can be used. By adding a proper amount of a crosslinking accelerator, the crosslinking efficiency can be improved, and the heat resistance and mechanical properties can be improved, so that the stability as a sealing member can be improved.

In addition to the above-mentioned components, a compounding agent generally used in the rubber industry, such as a filler, an acid acceptor, and an antioxidant, may be appropriately added to the rubber composition as a rubber compounding agent, if necessary. The amount of the rubber compounding agent is preferably about 300 parts by weight or less with respect to 100 parts by weight of EBENB.

Examples of the filler include: inorganic fillers such as carbon black, silica, silicate, calcium carbonate, magnesium carbonate, clay, talc, bentonite, sericite, mica, hydrated alumina, and barium sulfate; resin fillers such as polyethylene, polypropylene, polystyrene, coumarone-indene resin, melamine resin, and phenol resin.

When carbon black is used, the DBP oil absorption is preferably 100ml/100g or more, and when silica is used, it is preferable to use a silane coupling agent together.

The rubber composition can be prepared by kneading various materials using a kneader such as a single-screw extruder, a twin-screw extruder, a roll, a banbury mixer, a kneader, or a high-shear mixer.

The crosslinking of the rubber composition can be carried out by press-vulcanizing the rubber composition at a temperature of usually about 150 to 230 ℃ for about 0.5 to 30 minutes using an injection molding machine, a compression molding machine or the like. After the primary vulcanization as described above, secondary vulcanization may be performed as necessary in order to ensure vulcanization to the inside of the vulcanizate. The secondary vulcanization may be carried out by heating in an oven usually at about 150 to 250 ℃ for about 0.5 to 24 hours.

The rubber molded article obtained by vulcanization molding of the rubber composition of the present invention has excellent low-temperature rubber characteristics particularly at-50 ℃ and can be used in a low-temperature environment (for example, about-40 ℃ to-60 ℃), and is suitably used as a rubber molded article. The value of TR70 measured by a low-temperature elastic recovery test specified in JIS K6261:2006 corresponding to ISO 2921 is preferably-39 ℃ or lower for such a rubber molded article.

Further, the rubber molded article of the present invention preferably has an appropriate hardness, and for example, if the rubber molded article is an O-ring, the type a durometer hardness (durometer hardness) specified in JIS K6253-1:2012 is preferably 65 to 95.

Examples of such a rubber molded article include: sealing members for sealing low-temperature high-pressure gas, insulators, vibration insulators, sound insulators, and the like. Among them, the sealing member is suitable for use in a low-temperature environment and has excellent low-temperature sealing properties, and particularly suitable for use in a high-pressure gas (e.g., high-pressure hydrogen) apparatus.

The shape of the rubber molded article of the present invention is not particularly limited, and various shapes can be formed according to the use. Examples of the shape of the sealing member include an O-ring, a gasket, and a sheet.