WO2013094610A1 - Silicone rubber composition, molded article and electric wire - Google Patents

Abstract

This silicone rubber composition comprises: 0.1 to 15 parts by mass of a copper oxide (I) with respect to 100 parts by mass of a polysiloxane, which has a plurality of polymerizable unsaturated bonds in one molecule; and a cross-linking agent.

Description

Silicone rubber composition, molded product and electric wire

The present invention relates to a silicone rubber composition having excellent long-term heat resistance, a molded product obtained using the silicone rubber composition, and an electric wire using the molded product.
This application claims priority based on Japanese Patent Application No. 2011-279747 for which it applied to Japan on December 21, 2011, and uses the content here.

Silicone rubber is known as a useful material that has high heat resistance, cold resistance and flexibility, and has a low environmental impact. Utilizing these characteristics, silicone rubber is widely used as a molded product from household goods to industrial products. Yes. Usually, polysiloxane is blended with fillers, additives, reinforcing agents, etc. depending on the purpose, and the compounded composition is commercially available for general use, and it is crosslinked with organic peroxide or metal catalyst. A silicone rubber molded article is produced by adding an agent, kneading, and crosslinking by heating. However, since the composition compounded as described above is used, it is not easy for the user to obtain a silicone rubber whose characteristics are finely adjusted by the user.

Silicone rubber is excellent in heat resistance. For example, there is a silicone rubber having instantaneous heat resistance that can withstand use at 250 ° C. for a short time of 1 to 50 hours. However, for example, it is usually used at 180 ° C. or lower for a long period exceeding 200 hours. At higher temperatures, materials such as fluororubber and fluororesin that are further excellent in heat resistance are used. However, in recent years, in consideration of the environment, a material having no long-term heat resistance has been demanded. As such materials, engineering plastics and super engineering plastics are known. However, since these materials are inferior in flexibility, their use is limited, for example, not suitable for use as a coating material for electric wires. There was a problem. Therefore, it is desired to further improve the heat resistance of the silicone rubber, and a silicone rubber obtained by using a silicone rubber composition containing cerium oxide is disclosed (see Patent Document 1).

Japanese Patent Laid-Open No. 2002-179917

However, cerium is a metal element belonging to rare earths, and cerium oxide has poor versatility as a raw material, and there is a problem that it is not easy to produce silicone rubber having long-term heat resistance.

The present invention has been made in view of the above circumstances, and can be produced without the use of special raw materials, and a silicone rubber molded product having long-term heat resistance, and a silicone rubber composition suitable for production of the molded product. The issue is to provide.

In order to solve the above problems, the silicone rubber composition of the first aspect of the present invention is 0.1 to 15 parts by mass with respect to 100 parts by mass of polysiloxane having a plurality of polymerizable unsaturated bonds in one molecule. Copper (I) oxide and a crosslinking agent.
By using the silicone rubber composition, a molded product of silicone rubber having long-term heat resistance can be produced without using a special raw material.

The silicone rubber composition according to the first aspect of the present invention preferably contains 0.1 to 10 parts by mass of the copper (I) oxide with respect to 100 parts by mass of the polysiloxane.
When the content of copper (I) oxide in the silicone rubber composition is in the above-mentioned range (0.1 to 10 parts by mass), the molded product of the silicone rubber is impaired in the characteristic and long-term heat resistance of the silicone rubber. And excellent mechanical properties.

The molded article of the second aspect of the present invention is obtained by crosslinking and molding the silicone rubber composition of the first aspect.
The molded article has long-term heat resistance in addition to the characteristics unique to silicone rubber.

Moreover, the electric wire of the 3rd aspect of this invention is equipped with the molded article of the said 2nd aspect as a coating layer.
By providing the coating layer, the electric wire has a high protective effect and exhibits a stable function over a long period of time.

According to the present invention, there can be provided a molded product of silicone rubber that can be produced without using a special raw material and has long-term heat resistance, and a silicone rubber composition suitable for producing the molded product.

<Silicone rubber>
The silicone rubber composition according to the present invention comprises 0.1 to 15 parts by mass of copper (I) oxide (Cu ₂ O) with respect to 100 parts by mass of polysiloxane having a plurality of polymerizable unsaturated bonds in one molecule. ) And a crosslinking agent. When the silicone rubber composition contains a predetermined amount of copper (I) oxide, a molded product having long-term heat resistance can be produced without impairing mechanical properties, as will be described later. Further, a molded product can be manufactured without using special raw materials such as rare earths and other difficult raw materials or expensive raw materials.

The polysiloxane constitutes the main skeleton of the silicone rubber and has a plurality of polymerizable unsaturated bonds in one molecule in order to be cured by a crosslinking reaction, and (A) is bonded to a silicon atom in the polysiloxane. The group other than the group having a polymerizable unsaturated bond may be either an organic group or a hydrogen atom. Known polysiloxanes can be used as appropriate.
The number of the polymerizable unsaturated bonds in the polysiloxane may be two or more, may be two, or may be three or more.

The polysiloxane preferably has an unsaturated bond between carbon atoms as the polymerizable unsaturated bond, preferably has a double bond, and preferably has an alkenyl group.
Examples of the alkenyl group include ethenyl group (vinyl group), 2-propenyl group (allyl group), and 1-propenyl group. The plurality of alkenyl groups in the polysiloxane may all be the same, all may be different, or only a part may be different.
The alkenyl group is preferably bonded to a silicon atom constituting the main skeleton of polysiloxane.

Examples of the organic group other than the alkenyl group constituting the polysiloxane include an alkyl group and an aryl group which may have a substituent.

The alkyl group may be linear, branched or cyclic, but preferably has 1 to 10 carbon atoms.
Preferred examples of the linear or branched alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, and n-pentyl. Group, isopentyl group, neopentyl group, tert-pentyl group, 1-methylbutyl group, n-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group N-heptyl group, 2-methylhexyl group, 3-methylhexyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3-dimethylpentyl group, Such as 3-ethylpentyl group, 2,2,3-trimethylbutyl group, n-octyl group, isooctyl group, nonyl group, decyl group, etc. 0 groups can be exemplified.
The cyclic alkyl group may be monocyclic or polycyclic. Preferably, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclodecyl group, norbornyl group, isobornyl group, 1-adamantyl group, 2-adamantyl group, tricyclodecyl group Examples thereof include groups having 3 to 10 carbon atoms.

The aryl group may be monocyclic or polycyclic. Preferably, a phenyl group, o-tolyl group (2-methylphenyl group), m-tolyl group (3-methylphenyl group), p-tolyl group (4-methylphenyl group), 1-naphthyl group, 2-naphthyl group Examples thereof include groups having 6 to 15 carbon atoms such as groups.

The alkyl group and aryl group may have a substituent. Here, “the alkyl group (aryl group) has a substituent” means that one or more hydrogen atoms constituting the alkyl group (aryl group) are substituted with a group other than a hydrogen atom, or an alkyl group It means that one or more carbon atoms constituting (aryl group) are substituted with a group other than carbon atoms. And both the hydrogen atom and the carbon atom may be substituted with a substituent.
The alkyl group and aryl group having a substituent preferably include the substituent in the above-mentioned range (an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 15 carbon atoms).

Examples of the substituent for substituting the hydrogen atom of the alkyl group and aryl group include an alkyl group, an alkyloxycarbonyl group, an alkylcarbonyloxy group, an alkoxy group, an alkylcarbonyl group, an alkenyl group, an alkenyloxy group, an aryl group, and an alkylaryl group. And an arylalkyl group, an aryloxy group, an arylalkyloxy group, an alkylaryloxy group, a hydroxyl group (—OH), a cyano group (—CN), and a halogen atom.

Examples of the alkyl group that substitutes a hydrogen atom include the same groups as the alkyl group in the organic group.
Examples of the alkyloxycarbonyl group that substitutes a hydrogen atom include monovalent groups in which an alkyl group in the organic group is bonded to an oxycarbonyl group.
Examples of the alkylcarbonyloxy group that substitutes a hydrogen atom include a monovalent group in which an alkyl group in the organic group is bonded to a carbonyloxy group.
Examples of the alkoxy group for substituting a hydrogen atom include a monovalent group in which an alkyl group in the organic group is bonded to an oxygen atom.
Examples of the alkylcarbonyl group replacing a hydrogen atom include a monovalent group in which an alkyl group in the organic group is bonded to a carbonyl group.

The alkenyl group for substituting a hydrogen atom is an alkyl group in the organic group, a group in which one single bond (C—C) between carbon atoms is replaced with a double bond (C═C), and polymerization. Examples thereof include groups that do not correspond to the alkenyl group having a polymerizable unsaturated bond. The position of the double bond between carbon atoms in the alkenyl group substituting for a hydrogen atom is not particularly limited.
Examples of the alkenyloxy group that substitutes a hydrogen atom include monovalent groups in which the alkenyl group as a substituent is bonded to an oxygen atom.

Examples of the aryl group that substitutes a hydrogen atom include the same groups as the aryl group in the organic group.
Examples of the alkylaryl group for substituting a hydrogen atom include groups in which one hydrogen atom bonded to the carbon atom constituting the aromatic ring of the aryl group in the organic group is substituted with the alkyl group in the organic group it can.
Examples of the arylalkyl group that substitutes a hydrogen atom include a group in which one hydrogen atom of an alkyl group in the organic group is substituted with an aryl group in the organic group.
Examples of the aryloxy group replacing a hydrogen atom include a monovalent group in which the aryl group in the organic group is bonded to an oxygen atom.
Examples of the arylalkyloxy group for substituting a hydrogen atom include a monovalent group in which an aryl group and an oxygen atom in the organic group are bonded to an alkylene group obtained by removing one hydrogen atom from the alkyl group in the organic group.
As the alkylaryloxy group for substituting a hydrogen atom, an arylene group obtained by removing one hydrogen atom bonded to a carbon atom constituting an aromatic ring from an aryl group in the organic group, and an alkyl group in the organic group And a monovalent group in which an oxygen atom is bonded.

Examples of the halogen atom that replaces the hydrogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The number of substituents replacing the hydrogen atom is not particularly limited, and may be one or plural. Moreover, all the hydrogen atoms may be substituted with a substituent.
Moreover, the position of the hydrogen atom substituted with a substituent is not particularly limited.

Examples of the substituent for substituting the carbon atom of the alkyl group and aryl group include a carbonyl group (—C (═O) —), an ester bond (—C (═O) —O—), an amide bond (—NH—C). (= O)-), a hetero atom can be exemplified.
Examples of the hetero atom that substitutes a carbon atom include an oxygen atom, a nitrogen atom, a sulfur atom, and a boron atom.
The number of substituents replacing the carbon atom is not particularly limited, and may be one or more.
Further, the position of the carbon atom substituted with the substituent is not particularly limited.

As the polysiloxane, a commercially available product may be used, or a polysiloxane synthesized according to a known method may be used.
Polysiloxane may be used individually by 1 type, and may use 2 or more types together. When using 2 or more types together, the combination and ratio may be appropriately selected according to the purpose.

In the silicone rubber composition, the polysiloxane content is preferably 84 to 99.5% by mass, more preferably 85.5 to 99% by mass, and further preferably 88 to 99% by mass. preferable. When it is at least the lower limit (84% by mass), the molded product has more remarkable characteristics specific to silicone rubber, and when it is at most the upper limit (99.5% by mass), the molded product has long-term heat resistance. It can be easily obtained.

Copper (I) oxide imparts long-term heat resistance to the silicone rubber composition. Copper oxide may be produced by a known method, or commercially available copper oxide may be used.
The reason why copper (I) oxide can provide long-term heat resistance is not clear, but it is presumed that the deterioration caused by radicals is suppressed by erasing radicals generated by heating.

In the silicone rubber composition, the content of copper oxide (I) with respect to 100 parts by mass of polysiloxane is 0.1 to 15 parts by mass, preferably 0.1 to 10 parts by mass. By being above the lower limit (0.1 part by mass), the molded product has sufficient long-term heat resistance, and by being below the upper limit (15 parts by mass), the molded product has characteristics specific to silicone rubber. Is more prominently obtained. Particularly, when the content of copper oxide (I) is 10 parts by mass or less, the mechanical properties of the molded product are further improved.

As the crosslinking agent, a known crosslinking agent that cures polysiloxane can be used.
Examples of the crosslinking agent include organic peroxides such as dialkyl peroxides, diacyl peroxides, peroxyketals, and peroxyesters; and metal catalysts such as platinum. From the viewpoint that decomposition products are less likely to remain in the molded article, the cross-linking agent is preferably a metal catalyst, and more preferably a platinum catalyst. In the case of using an organic peroxide, for example, by heating at a temperature of 160 ° C. or higher at the time of manufacturing a molded product to be described later, a decomposition product of the organic peroxide can be easily removed as a gas.

Examples of the dialkyl peroxide include dicumyl peroxide, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, 1,3-bis (tert-butylperoxyisopropyl) benzene, and tert-butyl. Examples thereof include cumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis (tert-butylperoxy) -3-hexyne and the like.
Examples of the diacyl peroxide include dibenzoyl peroxide, di (2-methylbenzoyl) peroxide, di (3-methylbenzoyl) peroxide, di (4-methylbenzoyl) peroxide, and the like.
Examples of the peroxyketal include n-butyl 4,4-di (tert-butylperoxy) valerate, 1,1-di (tert-butylperoxy) cyclohexane, 1,1-di (tert-hexylperoxy). A cyclohexane etc. can be illustrated.
Examples of the peroxyester include 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, tert-hexylperoxybenzoate, tert-butylperoxy-3-methylbenzoate, and tert-butylperoxybenzoate Can be illustrated.

The crosslinking agent may be used alone or in combination of two or more. When using 2 or more types together, the combination and ratio may be appropriately selected according to the purpose. However, it is usually sufficient to use a kind of crosslinking agent.

In the silicone rubber composition, the content of the crosslinking agent with respect to 100 parts by mass of the polysiloxane is preferably 0.5 to 3 parts by mass, and more preferably 1 to 2 parts by mass. By being the lower limit (0.5 part by mass) or more, the cross-linking reaction of (A) polysiloxane proceeds more sufficiently, and by being the upper limit (3 parts by mass) or less, the molded product has better characteristics. Is obtained.

The silicone rubber composition may further contain other components in addition to polysiloxane, copper (I) oxide and a crosslinking agent within a range not impeding the effects of the present invention. By including other components, the desired characteristics can be imparted to the molded product.

As other components constituting the silicone rubber composition, known components can be used as appropriate, and examples thereof include fillers, additives, reinforcing agents, pigments, anti-aging agents, etc. Preferred materials include silica, carbon black, oxidation titanium (TiO ₂₎ or the like can be exemplified.
Other components may be used alone or in combination of two or more. When using 2 or more types together, the combination and ratio may be appropriately selected according to the purpose.

The silicone rubber composition preferably has a content of other components of less than 10% by mass. That is, the silicone rubber composition preferably has a total content of polysiloxane, copper (I) oxide and crosslinking agent of 90% by mass or more. By doing in this way, the molded article excellent in long-term heat resistance is obtained.
It is preferable to adjust the content of other components in the silicone rubber composition as appropriate according to the type of the component. For example, silica is less than 10% by mass, carbon black is less than 0.5% by mass, and titanium oxide is 5% by mass. It is preferable that it is less than.

A silicone rubber composition can be manufactured by mix | blending polysiloxane, copper (I) oxide, a crosslinking agent, and another component as needed.
At the time of blending each component, it is preferable to add the above-described components and sufficiently mix them with various apparatuses and methods. And each component may be mixed, adding these sequentially, and may be mixed after adding all the components.
The mixing method of each component is not particularly limited. For example, a known method of mixing for a predetermined time at normal temperature or under heating conditions using a stirring blade, a ball mill, a roll mill, an ultrasonic disperser, a kneader, or the like. Apply.
Moreover, when kneading this immediately after manufacture of a silicone rubber composition and manufacturing a molded article by heat-molding, you may knead | mix kneading also as manufacture of a silicone rubber composition.

<Molded product>
The molded product according to the present invention is obtained by crosslinking and molding the silicone rubber composition. This molded product can be produced in the same manner as a conventional silicone rubber molded product except that the silicone rubber composition is used.

Crosslinking and molding may be performed separately, or crosslinking and molding may be performed in parallel.
The crosslinking reaction may be carried out by a known method. For example, a method of heating and crosslinking by reacting at 150 to 180 ° C. for 5 to 20 minutes can be exemplified.

By using the silicone rubber composition, the molded article has long-term heat resistance without impairing mechanical properties in addition to the characteristics unique to silicone rubber such as heat resistance (instant heat resistance), cold resistance and flexibility. . Here, “having long-term heat resistance” means that a change in physical properties of the molded product is suppressed at 200 ° C. or more for 200 hours or more and endures use.
Moreover, the said molded article can be manufactured without using a special raw material so that it may be clear from the description so far.

The mechanical properties of the molded product can be evaluated based on the strength and elongation values before heating. Molded products with inferior mechanical properties are not suitable for practical use. And the molded product after a heating can evaluate long-term heat resistance by the value of intensity | strength (residual strength) and elongation (residual elongation) similarly. Here, the strength and elongation of the molded product before and after heating can be measured in accordance with, for example, JIS K 6251, but the measurement method is not limited thereto. If the sample can be obtained from the molded product, the strength and elongation may be measured using this sample. For example, a sheet-like molded product having a thickness of about 1 to 2 mm is manufactured using the same silicone rubber composition used for manufacturing the product, and a sample is obtained from the sheet-like molded product and measured. Good.

The molded product preferably has mechanical properties such that the strength is 9.0 MPa or more and the elongation is 350% or more. Moreover, it is preferable that the residual strength has a long-term heat resistance of 4.5 MPa or more and the residual elongation is 200% or more.

The molded article is suitable for mounting on various household goods or industrial articles or for the purpose of covering or protecting the members used therein. Since the molded product has long-term heat resistance, a product or member to which the molded product is attached can obtain a high protection action and can exhibit a stable function over a long period of time.

The shape of the molded product is not particularly limited, and can be arbitrarily selected according to the purpose, such as a sheet shape or a cylindrical shape. For example, a cylindrical molded product is suitable as a coating layer included in various cables, and an electric wire can be exemplified as the preferable cable. For example, since the mechanical properties of the molded product can be improved by adjusting the content of copper (I) oxide in the silicone rubber composition, the molded product is particularly suitable as a coating layer for electric wires.

The thickness of the molded product can be arbitrarily set according to the purpose. For example, the thickness of the sheet-like molded product is preferably 3.0 mm or less. Further, when the tubular molded product has a structure in which the sheet-shaped molded product is rounded into a hollow shape, the thickness of the sheet is preferably 3.0 mm or less.

The molding method may be a known method such as an injection molding method, an extrusion molding method, or a mold molding method, and may be appropriately selected according to the purpose.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples.

[Examples 1 to 7, Comparative Examples 1 to 10]
<Manufacture of silicone rubber composition and molded product>
Add a polysiloxane, a metal oxide other than copper oxide (I) or copper oxide (I) (hereinafter abbreviated as “metal oxide”), and a crosslinking agent so as to have the composition shown in Table 1. These were mixed by a two-roll mill at room temperature (23 ° C.) to obtain a silicone rubber composition.
Next, using this silicone rubber composition, a sheet having a thickness of 1 mm was produced as a molded article by a heating press at 160 ° C. for 10 minutes using a press.

In addition, each component in Table 1 is shown below.
Polysiloxane: TSE2425U (manufactured by Momentive)
Copper (I) oxide: Showa Chemical Co., Ltd. Crosslinker: TC-12 (Momentive, Di (3-methylbenzoyl) peroxide)
Metal oxide: Zinc oxide (manufactured by Wako Pure Chemical Industries), magnesium oxide (manufactured by Kyowa Chemical Industry), tin oxide (manufactured by Wako Pure Chemical Industries)

<Evaluation of molded products>
About the obtained molded product, a test piece punched into a dumbbell shape according to JIS K 6251 was prepared, and its strength (MPa) and elongation (%) were measured. The strength and elongation were measured according to JIS K6521.
Next, after heating the test piece in an oven at 225 ° C. for 10 days, the strength (MPa) and the elongation (%) were measured by the same method as described above to obtain the residual strength (MPa) and the residual elongation (%), respectively. .
From these measured values, the mechanical properties and long-term heat resistance of the molded products were evaluated according to the following evaluation criteria. The results are shown in Table 1.
Mechanical properties: About the test piece before heating by the oven, the test piece obtained with the result of the strength of 9.0 MPa or more and the elongation of 350% or more was determined to be acceptable (the test piece indicated by the symbol “◯” in Table 1). And the test piece from which the result other than that was obtained was determined to be rejected (the test piece indicated by the symbol “x” in Table 1).
Long-term heat resistance: About the test piece after heating in the oven, the test piece obtained with the result that the residual strength was 4.5 MPa or more and the residual elongation was 200% or more passed (the test piece indicated by the symbol “◯” in Table 1). The test piece from which the other results were obtained was judged as rejected (the test piece indicated by the symbol “x” in Table 1).

As is apparent from the above results, the silicone rubber compositions containing 0.1 to 15 parts by mass of copper (I) oxide were used for the molded articles of Examples 1 to 7 with respect to 100 parts by mass of polysiloxane. Thus, the strength and elongation values before and after heating were large, and both mechanical properties and long-term heat resistance were excellent.
In contrast, the molded products of Comparative Examples 1 to 10 were inferior in at least one of mechanical properties and long-term heat resistance. Specifically, Comparative Example 1 using a silicone rubber composition containing neither copper oxide (I) nor metal oxide, containing 20 parts by mass of copper (I) oxide with respect to 100 parts by mass of polysiloxane. Comparative Example 2 using a silicone rubber composition, and the molded products of Comparative Examples 3-7 and 9-10 using a silicone rubber composition containing other metal oxides instead of copper (I) oxide It was inferior in heat resistance. And the molded product of Comparative Examples 6 and 8 was also inferior in mechanical properties. Although the long-term heat resistance of Comparative Example 8 has not been confirmed directly, it is clear from the results of Comparative Example 7 that the long-term heat resistance is similarly inferior.
Thus, it was confirmed that the long-term heat resistance of the molded article obtained from the silicone rubber composition is greatly changed by the content of copper (I) oxide and the type of metal oxide to be blended.

The present invention can be used as a molded product used for various purposes such as covering and protection in various daily goods or industrial goods.

Claims (4)

1. Silicone rubber characterized by containing 0.1 to 15 parts by mass of copper (I) oxide and a crosslinking agent with respect to 100 parts by mass of polysiloxane having a plurality of polymerizable unsaturated bonds in one molecule Composition.
2. The silicone rubber composition according to claim 1, wherein the copper oxide (I) is contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the polysiloxane.
3. A molded article obtained by crosslinking and molding the silicone rubber composition according to claim 1 or 2.
4. An electric wire comprising the molded product according to claim 3 as a coating layer.