JPH09208747A - Rubber composition and heat-resistant coating material for electric wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber material having excellent heat-resistance, resistant to hardening and deterioration even by exposing to a high temperature atmosphere over a long time and useful especially as a wire-coating material. SOLUTION: This rubber composition is produced by compounding an organic peroxide to a rubber component composed of (1) 40-90wt.% (based on the total rubber component) of a nitrile-containing highly saturated copolymer rubber having an iodine value of <=120 and (2) 10-60wt.% (based on the total rubber component) of a polyacrylate polymer rubber essentially free from carbon-carbon unsaturated bond and derived from 90-100wt.% of ethyl acrylate and 0-10wt.% of a copolymerizable monomer. A wire-coating material is produced by using the rubber composition.

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 good heat resistance and an electric wire coating material formed from such a rubber composition. More specifically, it relates to a nitrile group-containing highly saturated copolymer rubber. TECHNICAL FIELD The present invention relates to a rubber composition containing a blend with a polyacrylic acid ester-based polymer rubber as a rubber component and having good heat resistance and being resistant to heat aging, and an electric wire coating material comprising a crosslinked product of such a rubber composition. .

[0002]

2. Description of the Related Art An electric wire coating material is exposed to a severe temperature environment for a long period of time due to heat generated when electricity is applied. Therefore, the electric wire coating material is cracked due to heat aging, and sometimes insulation failure or insulation breakdown occurs. Furthermore, it may be heated from the outside depending on the use environment. Many rubbers such as natural rubber and styrene-butadiene copolymer rubber (SBR) are used as the electric wire coating material, and as the electric wire coating material which is particularly required to have heat resistance, fluororubber and ethylene-propylene-diene copolymer are used. Polymer rubber (EPDM) and silicone rubber are used. However, fluororubber is very expensive, and EPDM has a relatively low heat resistance temperature.
Silicon rubber has a relatively high heat resistance (150-
However, it has a drawback that it is inferior in strength characteristics.

Further, unsaturated nitrile-conjugated diene copolymer rubber hydride (HNBR) and acrylic rubber (AR)
Blends with are known to have good heat resistance. For example, in Japanese Patent Laid-Open No. 2-3438, HNBR
Describes a rubber composition obtained by blending an organic peroxide and a bismaleimide compound in a blend of acrylic rubber with acrylic rubber, and this rubber composition is excellent in heat resistance, abrasion resistance, flex fatigue resistance and oil resistance. It is said that. The acrylic rubber contained in this rubber composition has a crosslinkable monomer unit having a carbon-carbon unsaturated bond as a crosslinkable component, and this rubber composition has a long temperature at a temperature of about 150 ° C., for example. It is difficult to use as an electric wire covering material that requires heat resistance because it hardens and deteriorates when exposed for a period of time.

[0004]

The object of the present invention is to provide a heat-resistant rubber material which has good heat resistance and which maintains good rubber characteristics without being cured and deteriorated even when exposed to high temperatures for a long period of time. To provide a rubber composition capable of giving Another object of the present invention is to provide a heat-resistant electric wire coating material made of a rubber material that does not harden and deteriorate even when exposed to a high temperature for a long time.

[0005]

According to the present invention, (1)
40-90% by weight (based on the total amount of rubber components) of a nitrile group-containing highly saturated copolymer rubber having an iodine value of 120 or less,
(2) Polyacrylate ester-based polymer rubbers 10 to 60 obtained from 90 to 100% by weight of ethyl acrylate and 0 to 10% by weight of a copolymerizable monomer, and containing substantially no carbon-carbon unsaturated bond. Provided is a rubber composition obtained by blending a rubber component consisting of wt% (based on the total amount of rubber components) with an organic peroxide.

Further, according to the present invention, there is provided a heat resistant electric wire coating material comprising a crosslinked product of the above rubber composition.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The heat resistant rubber composition of the present invention contains a nitrile group-containing highly saturated copolymer rubber and a polyacrylic acid ester polymer rubber as its basic rubber components. (Nitrile Group-Containing Highly Saturated Copolymer Rubber) The nitrile group-containing highly saturated copolymer rubber used in the present invention is an unsaturated nitrile-conjugated diene copolymer or an unsaturated nitrile-conjugated diene-copolymerizable monomer. Which is obtained by hydrogenating the conjugated diene portion of the copolymer of the body, generally good heat resistance,
Has ozone resistance. This copolymer has a Mooney viscosity of 15 to 200, preferably 30 to 100 and an iodine value of 1.
It is 20 or less, preferably 80 or less, more preferably 15 or less. When the Mooney viscosity is less than 15, only a coating material having low strength can be obtained, which is not preferable. If it exceeds 200, the viscosity increases, and extrusion molding becomes difficult. If the iodine value is too high, the heat resistance of the rubber composition will be poor.

The content of the bound unsaturated nitrile unit in the unsaturated nitrile-conjugated diene copolymer is 10 to 50% by weight, preferably 15 to 40% by weight. Specific examples of unsaturated nitriles include acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile. Specific examples of the conjugated diene include 1,3-butadiene, 2,3-dimethylbutadiene, isoprene and 1,3
-Pentadiene and the like.

If desired, in addition to the unsaturated nitrile and the conjugated diene, to the extent that the objects of the present invention are not impaired,
Further, unsaturated carboxylic acid ester or other copolymerizable monomer may be copolymerized. Generally, the amount of unsaturated carboxylic acid ester and other monomers is usually 50% by weight or less, more preferably 40% by weight or less.

Specific examples of the unsaturated carboxylic acid ester which is optionally copolymerized are methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate and isononyl acrylate. , N-hexyl acrylate, 2-methyl-pentyl acrylate, n-octyl acrylate, 2-
Acrylates and methacrylates having an alkyl group having about 1 to 18 carbon atoms such as ethylhexyl acrylate, n-dodecyl acrylate, methyl methacrylate, and ethyl methacrylate;

Acrylates having an alkoxyalkyl group having about 2 to 12 carbon atoms such as methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate, ethoxypropyl acrylate, methoxyethoxy acrylate and ethoxybutoxy acrylate; α- and β An acrylate having a cyanoalkyl group having about 2 to 12 carbon atoms such as cyanoethyl acrylate, α-, β- and γ-cyanopropyl acrylate, cyanobutyl acrylate, cyanohexyl acrylate, and cyanooctyl acrylate;

Acrylates having hydroxyalkyl groups such as 2-hydroxyethyl acrylate and hydroxypropyl acrylate; monoethyl maleate, dimethyl maleate, dimethyl fumarate, diethyl fumarate, di-n-butyl fumarate, di-2 fumarate. -Ethylhexyl, dimethyl itaconate, diethyl itaconate,
Unsaturated dicarboxylic acid mono- and dialkyl esters such as di-n-butyl itaconate and di-2-ethylhexyl itaconate;

Further, dimethylaminomethyl acrylate, diethylaminoethyl acrylate, 3- (diethylamino) -2-hydroxypropyl acrylate,
Amino group-containing unsaturated carboxylic acid ester-based monomer such as 2,3-bis (difluoroamino) propyl acrylate;

Trifluoroethyl acrylate, tetrafluoropropyl acrylate, pentafluoropropyl acrylate, heptal orobutyl acrylate, octafluoropentyl acrylate, nonafluoropentyl acrylate, undecafluorohexyl acrylate, pentadecafluorooctyl acrylate, heptadecafluorononyl Fluoroalkyl groups such as acrylate, heptadecafluorodecyl acrylate, nonadecafluorodecyl acrylate, trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, octafluoropentyl methacrylate, dodecafluoroheptyl methacrylate, pentadecafluorooctyl acrylate, hexadecafluorononyl methacrylate Have Acrylate and methacrylate;

Fluorine-substituted benzyl acrylates and methacrylates such as fluorobenzyl acrylate, fluorobenzyl methacrylate and difluorobenzyl methacrylate can be mentioned.

The unsaturated nitrile of the above unsaturated nitrile-conjugated diene copolymer is preferably acrylonitrile, and the conjugated diene is preferably butadiene.
The unsaturated carboxylic acid ester used as desired generally includes unsaturated dicarboxylic acid dialkyl esters.

As the copolymerizable monomer other than unsaturated carboxylic acid ester, vinyl monomers such as styrene, α-methylstyrene and vinylpyridine; vinyl norbornene, dicyclopentadiene, 1,4- Non-conjugated diene monomers such as hexadiene; fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether, fluoropropyl vinyl ether, trifluoromethyl vinyl ether, trifluoroethyl vinyl ether, perfluoropropyl vinyl ether, perfluorohexyl vinyl ether, o- or p-tri Fluorine-containing vinyl monomers such as fluoromethylstyrene, vinyl pentafluorobenzoate, difluoroethylene and tetrafluoroethylene; unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid Itaconic acid, fumaric acid, unsaturated dicarboxylic acids or anhydrides such as maleic acid; Furthermore, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, epoxy (meth) acrylate, and urethane (meth) acrylate.

The method for hydrogenating the unsaturated nitrile-conjugated diene copolymer is not particularly limited, and it can be hydrogenated according to a conventional method. Examples of the catalyst used in the hydrogenation include palladium / silica and palladium complex (JP-A-3-252405). Furthermore, JP-A-62-125858, JP-A-62-42937, JP-A-1-45402, JP-A-1-45403, JP-A-1-45404, and JP-A-1-45404.
It is also possible to use rhodium or ruthenium compounds such as those described in US Pat.

The nitrile group-containing highly saturated copolymer rubber used in the present invention can also be obtained by directly hydrogenating a latex of an unsaturated nitrile-conjugated diene copolymer.

As a method for directly hydrogenating, a method using a palladium-based catalyst (for example, JP-A-2-17830) is used.
5) and a method using a rhodium-based catalyst (for example, JP-A-59-115303 and JP-A-56-133219).
No. 3,898,208), and a method using a ruthenium-based catalyst (for example, JP-A-6-184).
No. 223 and JP-A-6-192323), but the invention is not limited thereto. As a specific example, when a palladium-based catalyst is used, for example, an organic solvent that dissolves or swells a nitrile group-containing unsaturated copolymer is used as described in JP-A-2-178305. The method of adding in latex is adopted. According to this method, the nitrile group-containing unsaturated copolymer in the copolymer latex swells with an organic solvent, and the hydrogenation catalyst can be easily accessible to the double bond in the copolymer, so that the aqueous solution The hydrogenation reaction can be efficiently performed while maintaining the emulsion state.

Specific examples of the palladium compound include palladium salts of carboxylic acids such as formic acid, acetic acid, propionic acid, lauric acid, succinic acid, stearic acid, oleic acid, phthalic acid and benzoic acid; palladium chloride, dichloro (cycloocta). Diene) palladium, dichloro (norbornadiene) palladium, dichloro (benzonitrile)
Palladium, dichlorobis (triphenylphosphine)
Chlorides of palladium such as palladium, ammonium tetrachloropalladium (II) and hexachloropalladium (IV); palladium bromide; palladium iodide; palladium sulfate dihydrate; potassium tetracyanopalladium (II) Examples thereof include inorganic compounds such as trihydrate; and complex salts, but are not limited thereto. Among them, palladium salts of carboxylic acids, dichloro (norbornadiene) palladium, ammonium hexachloropalladate and the like are particularly preferable.

(Polyacrylic Ester Copolymer Rubber) The polyacrylic ester rubber used in the present invention comprises 90 to 100% by weight of ethyl acrylate and 0 to 10% by weight of a copolymerizable monomer. Is a structural unit and is substantially composed of a polymer containing no carbon-carbon unsaturated bond. It is important that this polymer rubber is a homopolymer of ethyl acrylate or a copolymer containing an ethyl acrylate unit as a main component. Instead of ethyl acrylate, other alkyl acrylates, alkoxy acrylates and other monomers are used. A rubber composition having high heat resistance cannot be obtained with a copolymer used in a large amount.

In the case of a copolymer of ethyl acrylate, a monomer copolymerized with ethyl acrylate is obtained in order to obtain a copolymer having high heat resistance and hardly causing deterioration by curing even if it is held for a long period of time. Is a monomer having substantially no carbon-carbon double bond (excluding the benzene ring) other than the carbon-carbon double bond involved in the copolymerization with ethyl acrylate, and Also, the amount of the monomer must be 10% by weight or less based on the weight of the copolymer. The amount of comonomer is preferably 5% by weight or less.

As the copolymerizable monomer, styrene,
Vinyl-based monomers such as α-methylstyrene and vinylpyridine; fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether, fluoropropyl vinyl ether, trifluoromethyl vinyl ether, trifluoroethyl vinyl ether, perfluoropropyl vinyl ether and perfluorohexyl vinyl ether, o-
Alternatively, fluorine-containing vinyl monomers such as p-trifluoromethylstyrene, vinyl pentafluorobenzoate, difluoroethylene, and tetrafluoroethylene; unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; itaconic acid, fumaric acid, and maleic acid. Unsaturated dicarboxylic acid or anhydride such as acid; alkyl acrylate having an alkyl group having 8 or less carbon atoms such as methyl acrylate or propyl acrylate; alkoxy alkylate having an alkoxy group having 8 or less carbon atoms such as methoxymethyl acrylate; Polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, epoxy (meth) acrylate, urethane (meth)
Acrylate and the like.

Further, it is also possible to copolymerize a monomer which is usually used as a crosslinkable monomer of a polyacrylic acid ester type polymer rubber. However, as such a monomer, a monomer that does not substantially have a carbon-carbon double bond other than the carbon-carbon double bond involved in the copolymerization with ethyl acrylate (excluding the benzene ring) is used. Use a quantity. Examples of usable monomers include 2-chloroethyl vinyl ether, vinyl chloroacetate, allyl chloroacetate, vinylbenzyl chloride, 2-chloroethyl vinyl ether, chloromethyl vinyl ketone, 5-chloromethyl-2-norbornene and the like containing active chlorine. Unsaturated monomers, inactive chlorine-containing unsaturated monomers such as 2-chloroethyl vinyl ether, epoxy group-containing unsaturated monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, vinyl glycidyl ether, and the like. . In addition, a carboxyl group-containing unsaturated monomer can also be used. Among these monomers, the active base-containing unsaturated monomer is preferable. Generally, an unsaturated compound having a carbon-carbon double bond in addition to the carbon-carbon double bond involved in copolymerization with an acrylate as a component for crosslinking acrylic rubber (eg, butadiene, 2-butenyl acrylate, tetrahydrobenzyl). (Acrylate, allyl acrylate, triallyl isocyanurate, divinylbenzene, etc.) have also been used, but such an unsaturated compound having a carbon-carbon unsaturated bond promotes curing type deterioration, and therefore the heat resistant rubber composition of the present invention. It cannot be used for things.

The polyacrylic acid ester-based copolymer rubber preferably has a Mooney viscosity ML ₄ of 10 to 90. If the viscosity is too low, the strength of the coating material will decrease, and if the viscosity is too high, the extrusion moldability will decrease.

(Organic Peroxide-Based Crosslinking Agent) The organic peroxide-based crosslinking agent used in the present invention is not particularly limited as long as it is one used in ordinary peroxide vulcanization of rubber. Specific examples thereof include dicumyl peroxide and 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) hexyne, α, α′-bis (t-butylperoxy-m-isopropyl) benzene and the like can be mentioned. Of these, di-t-butyl peroxide is preferable. These organic peroxides are a total of 10 nitrile group-containing highly saturated copolymer rubbers and polyacrylic ester polymer rubbers.
0.5 to 30 parts by weight relative to 0 parts by weight, preferably 1 to 2
Used in the range of 0 parts by weight.

Further, a crosslinking aid can be used.
The cross-linking aid usually includes unsaturated compounds used as a cross-linking aid in organic peroxide vulcanization. Examples thereof include ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, N, N'-
Examples thereof include m-phenylene dimaleimide and triallyl isocyanurate. Of these, triallyl isocyanurate is preferable from the viewpoint of vulcanization properties. The addition amount of these is in the range of 0.1 to 15 parts by weight with respect to 100 parts by weight of the copolymer rubber.

In addition, the heat-resistant rubber composition of the present invention may contain, if necessary, other conventional compounding agents used in the rubber field, such as reinforcing agents (carbon black, silica, talc, etc.) and fillers. (Calcium carbonate, clay, etc.),
Processing aids, process oils, antioxidants, antiozonants, vulcanization aids, coloring aids and the like can be added.
The method for producing the heat-resistant rubber composition of the present invention is not particularly limited, but usually, a mixer such as an extruder, a roll, or a Banbury mixer, a nitrile group-containing highly saturated copolymer rubber, a polyacrylic acid ester-based copolymer The rubber composition is produced by kneading and mixing the united rubber and the organic peroxide and other compounding agents. When used as a wire coating material, in accordance with a conventional method, using an extruder directly connected to the vulcanizer,
A method in which a rubber composition is extruded from an extruder to coat an electric wire and is heat-crosslinked is adopted.

[0030]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The parts and% in the examples, comparative examples and reference examples are based on weight unless otherwise specified. The characteristics of the rubber composition and the raw material components were measured as follows. (1) Physical properties of vulcanized sheet According to JIS K6301, an uncrosslinked rubber composition prepared according to the formulation of Table 1 was crosslinked under conditions of 170 ° C. for 20 minutes to obtain a sheet having a thickness of 2 mm and a No. 3 dumbbell. Punching using it to make a test piece, tensile strength (unit:
kgf / cm ² ), 100% tensile stress (unit: kgf /
cm ² ), 300% tensile stress (unit: kgf / cm ² ) and elongation (unit:%) were measured. The hardness was measured using a JIS spring type A hardness tester.

(2) Air heat aging test The test piece was tested at 150 ° C. for 168 hours, 504 hours and 10 hours.
After being left for 08 hours, the elongation (%) was measured according to JIS-K6301 and the rate of change (%) with respect to the elongation (%) before being left under heat aging conditions was determined. A negative rate of change indicates a decrease in growth.

(3) Mooney viscosity ML _{1 + 4} Measured at 100 ° C. according to JIS-K6383. (4) Vulcanizability According to SRIS 3102, scorch time (t'10 and t'at 170 ° C. using a curast meter).
90) (unit: min) and maximum torque (Vmax) (unit: kgf · cm) were measured.

Examples 1 to 3 and Comparative Examples 1 to 3 A nitrile group-containing highly saturated copolymer rubber and a polyacrylic acid ester copolymer rubber shown below were used, and various compounding agents shown in Table 1 were added to the rubber. The ingredients were blended and kneaded at 50 ° C. to prepare a vulcanizable rubber composition, and the vulcanizability, Mooney viscosity, vulcanization physical properties and elongation change rate after standing under heat aging conditions were measured. Table 1 shows the measurement results. (A) HNBR: hydride of acrylonitrile-butadiene copolymer, content of bound acrylonitrile 36%, intrinsic viscosity 4, Mooney viscosity 65, iodine value 4

(B-1) AR1: ethyl acrylate (98%)-vinyl chloroacetate (2%) copolymer rubber, Mooney viscosity 50 (B-2) AR2: ethyl acrylate (95%)-acrylonitrile (2%) ) -Allyl glycidyl ether (3%) copolymer rubber, Mooney viscosity 55 (B-3) AR3: ethyl acrylate (20%)-butyl acrylate (78%)-vinylbenzyl chloride (2%) copolymer rubber, Mooney viscosity 50 (B-4) AR4: ethyl acrylate (98%)-ethylidene norbornene (2%) copolymer rubber, Mooney viscosity 53

[0035]

[Table 1]

Note: * 1 Carplex 1120: Silica * 2 Greg G-8 205: Fatty acid metal salt (lubricant) * 3 Naugard # 445: Substituted diphenylamine * 4 Nocrac MBZ: 2-mercaptobenzimidazole zinc salt * 5 Vul- Cup 40KE: α, α′-bis (t
-Butyl peroxyisopropyl) benzene 40% product

[0036]

[Effects of the Invention] The main component is ethyl acrylate unit,
If desired, a polyacrylic acid ester-based polymer rubber containing a monomer unit having substantially no carbon-carbon unsaturated bond and a nitrile group-containing highly saturated copolymer rubber are used as a basic rubber component, and an organic peroxide is added. The contained rubber composition of the present invention has good heat resistance, and maintains good properties as a rubber without being cured and deteriorated even when exposed to high temperature for a long period of time.
When a monomer unit having a carbon-carbon double bond is used (Comparative Example 2) or when a polyacrylate polymer rubber having an alkyl acrylate unit other than an ethyl acrylate unit as a main component is used In (Comparative Example 1), heat aging is remarkable.

Therefore, the rubber composition of the present invention can be used in electric wire coating materials; automobile parts such as heat-resistant seals, gaskets and oil hoses; and OA equipment parts such as IC substrate cushion materials. It is useful as a wire coating material that is exposed to high temperatures for a long period of time.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION A rubber composition of the present invention, namely, (1) 40 to 90% by weight (based on the total amount of rubber components) of a nitrile group-containing highly saturated copolymer rubber having an iodine value of 120 or less; 2) Ethyl acrylate units 90-10
10 to 60% by weight of a polyacrylate polymer rubber having 0% by weight and 0 to 10% by weight of a crosslinkable monomer unit which does not substantially contain a carbon-carbon unsaturated bond as a constitutional unit.
The preferred embodiments of the rubber composition in which the organic peroxide is mixed with the rubber component (based on the total amount of the rubber component) are summarized as follows.

(1) The nitrile group-containing highly saturated copolymer rubber has a Mooney viscosity of 15 to 200, more preferably 30 to
100. (2) The iodine value of the nitrile group-containing highly saturated copolymer rubber is 80 or less, more preferably 15 or less. (3) The content of the bound unsaturated nitrile unit in the nitrile group-containing highly saturated copolymer rubber is 10 to 50% by weight, more preferably 15 to 40% by weight.

(4) The nitrile group-containing highly saturated copolymer rubber is a hydride of an unsaturated nitrile-conjugated diene copolymer or a copolymer of an unsaturated nitrile-conjugated diene-copolymerizable other monomer. It is a hydride. (5) The nitrile group-containing highly saturated copolymer rubber is obtained by hydrogenating the conjugated diene portion of the butadiene-acrylonitrile copolymer.

(6) The polyacrylic acid ester-based polymer rubber contains ethyl acrylate units of 95 to 100% by weight and copolymerizable monomer units of 0 to 5% by weight as constitutional units. (7) polyacrylate ester polymer rubber has a Mooney viscosity ML ₄ 10 to 90. (8) The amount of the organic peroxide is 0.5 to 30 parts by weight, more preferably 1 to 20 parts by weight based on 100 parts by weight of the total of the nitrile group-containing highly saturated copolymer rubber and the polyacrylic acid ester-based polymer rubber. Parts by weight.

Claims (2)

[Claims] 1. A nitrile group-containing highly saturated copolymer rubber having an iodine value of 120 or less (40 to 90% by weight (based on the total amount of rubber components)) and (2) ethyl acrylate (90 to 90%).
10 to 60% by weight of a polyacrylic acid ester-based polymer rubber substantially free from carbon-carbon unsaturated bond, obtained from 100% by weight and 0 to 10% by weight of a copolymerizable monomer
(Based on the total amount of rubber components) A rubber composition comprising a rubber component and an organic peroxide. 2. A heat resistant electric wire coating material obtained from the rubber composition according to claim 1.