JPH0676526B2 - Vulcanizable rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition which is cured by heating and has excellent mechanical properties, heat aging resistance and electrical properties.

(Prior Art) Ethylene / α-olefin copolymer rubber has mechanical properties,
As a rubber with excellent electrical insulation properties, it is widely used for automobile parts, electric parts, general industrial parts, etc. Recently, however, there have been cases where even higher heat aging resistance is required for automobile parts and electric parts.

For this reason, addition of an antioxidant has been attempted in this type of rubber as seen in "Ethylene-Propylene Rubber", which is a synthetic rubber processing technology complete book, but its improving effect is not sufficient.

(Problems to be Solved by the Invention) That is, the object of the present invention is to provide an ethylene / α-olefin copolymer rubber without impairing its mechanical properties and electrical insulation properties.
It is to significantly improve the heat aging resistance.

(Means for Solving the Problems) According to the present invention, (A) a modified ethylene resin obtained by graft copolymerizing one or more compounds selected from unsaturated carboxylic acids, their acid anhydrides and their esters. A vulcanized rubber composition comprising as essential components an α-olefin copolymer rubber (B) a silane coupling agent, or a titanium coupling agent or a mixture thereof (C) an inorganic filler mainly composed of silica, wherein A silane coupling agent, a titanium coupling agent, or a mixture thereof is compounded at a ratio of 1 to 20 parts by weight to 100 parts by weight of the ethylene / α-olefin copolymer rubber (A), and the filler (C) is added. A vulcanizable rubber composition is provided, which is blended in a ratio of 10 to 150 parts by weight.

(Function) Conventionally, it is known that the strength is improved by adding a silane coupling agent or a titanium coupling agent to an ethylene / α-olefin copolymer rubber composition,
The effect is not always sufficient.

Thus, according to the present invention, an acid-modified ethylene / α-olefin copolymer rubber is used in combination with a silane coupling agent and / or a titanium coupling agent, and further, an inorganic filler mainly containing a specific amount of silica. Not only the strength of the copolymer rubber composition is remarkably improved, but also the heat aging resistance is remarkably improved by the combination and blending.

That is, as is apparent from the examples described below, the composition of the present invention shows a surprising value of about 70% or more in strength retention in a test at 180 ° C. for 96 hours. Normal heat resistance test is 14
The superiority of the composition of the present invention can be understood from the fact that it can be said that it is a heat-resistant formulation when it is carried out at a temperature of 0 ° C. and shows a value of 70% or more.

In the present invention, the reason why the heat aging resistance is remarkably improved is not yet clear, but as a result of the acid-modified group such as maleic acid binding to the coupling agent, the interfacial properties of the copolymer rubber composition are obtained. Is considered to be due to the remarkable improvement.

(Embodiment of the invention) Modified ethylene / α-olefin copolymer rubber The modified ethylene / α-olefin copolymer rubber used in the present invention is one kind selected from unsaturated carboxylic acids, their anhydrides and their esters. The above compound is used as a graft copolymerization monomer and is graft-copolymerized on an ethylene / α-olefin copolymer rubber.

The ethylene / α-olefin copolymer rubber to be graft-copolymerized is composed of ethylene and an α-olefin having a C number of 3 to 10, and has an ethylene content of 50 to 95 mol%, preferably 60 to 92 mol. It is in the range of%.

The α-olefin having a C number of 3 to 10 is specifically propylene, 1-butene, 1-hexene, 4-methyl-1-
Pentene, 3-methyl-1-pentene, 1-octene,
1-decene etc. can be illustrated.

Further, a polyene component may be copolymerized with the ethylene / α-olefin copolymer rubber.

Specifically as the polyene component, 1,4-hexadiene,
1,6-octadiene, 2-methyl-1,5-hexadiene,
Chain non-conjugated dienes such as 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-
Norbornene, 5-methylene-2-norbornene, 5-
Cyclic non-conjugated dienes such as isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5
Typical examples are trienes such as -norbornene, 2-propenyl-2,2-norbornadiene, 1,3,7-octatriene and 1,4,9-decatriene.
Suitable polyenes are cyclic non-conjugated dienes and 1,4-hexadiene, especially dicyclopentadiene or 5-ethylidene-2-norbornene.

These polyene components are copolymerized so that the iodine value is at most 30, preferably 20 or less.

The unsaturated carboxylic acid, the anhydride thereof and the ester thereof to be graft-copolymerized with the ethylene / α-olefin copolymer rubber are not limited to these but, for example, the following compounds are used.

Unsaturated carboxylic acid; acrylic acid, methacrylic acid, maleic acid, fumaric acid,
Itaconic acid, citraconic acid, tetrahydrophthalic acid, bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acid and the like.

Unsaturated carboxylic acid anhydrides; maleic anhydride, itaconic anhydride, citraconic anhydride,
Tetrahydrophthalic anhydride, bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acid anhydride and the like. Of these, maleic anhydride is preferred.

Unsaturated carboxylic acid ester; methyl acrylate, methyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate,
Dimethyl itaconate, diethyl citraconic acid, dimethyl tetrahydrophthalic anhydride, dimethyl bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylate and the like. Among these, methyl acrylate and ethyl acrylate are preferable.

Graft copolymerization monomers such as the unsaturated carboxylic acid,
Each is used alone or in combination of two or more, and in each case, 0.1 to 10 parts by weight, particularly 0. 0, based on 100 parts by weight of the above-mentioned ethylene / α-olefin copolymer rubber.
Graft copolymerization is preferred in the range of 2 to 5 parts by weight.

When the graft amount is less than the upper limit range, the desired heat aging resistance tends not to be obtained, and when it is more than the above range, the rubber composition obtained is unsatisfactory in processability and cold resistance. Tends to be

The graft copolymerization can be obtained by reacting the above-mentioned ethylene / α-olefin copolymer rubber with an unsaturated carboxylic acid or the like in the presence of a radical initiator.

The reaction may be carried out as a solution or may be carried out in a molten state. When it is carried out in the molten state, it is most efficient to carry out it continuously in the extruder.

As the radical initiator used in the graft reaction, one having a decomposition temperature in the range of 150 to 270 ° C. so that the half-life is 1 minute is preferably used.

Specifically, organic peroxides, organic peresters such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (peroxybenzoate) hexyne-3, 1,4-bis (tert-butylperoxyisopropyl) benzene, lauroyl peroxide, tert-butylperacetate, 2,5-dimethyl-2,5
-Di (tert-butylperoxy) hexyne-3,2,5-
Dimethyl-2,5-di (tert-butylperoxy) hexane, tert-butylperbenzoate, tert-butylperphenylacetate, tert-butylperisobutyrate, tert-butylper-sec-octoate, tert-butylpervivarate , -Cumyl perbivalate and te
Examples include rt-butyl perdiethyl acetate.

In the present invention, the modified ethylene / α-olefin copolymer rubber obtained as described above is used as an essential compounding component, and among them, the Mooney viscosity [ML _{1 + 4} (100 ° C)] is used.
Is preferably used in the range of 5 to 180, especially 20 to 120. When the Mooney viscosity is lower than the above range, the rubber composition obtained becomes unsatisfactory in mechanical properties, and when it is higher than the above range, the processability tends to be impaired.

Silane Coupling Agent, Titanium Coupling Agent As the silane coupling agent and titanium coupling agent used in the present invention, known silane coupling agents and titanium coupling agents can be used.

A silane coupling agent is generally a compound represented by the formula XSi (OR) ₃ , where X is a functional group (amino group, vinyl group, epoxy group, mercapto group, chloro group, etc.) that reacts with organic matter, and OR is hydrolyzable. Group (a methoxy group, an ethoxy group, etc.) is shown.

The molecular weight of these silane coupling agents is generally 80 to 800 and the specific gravity is in the range of 0.80 to 1.35.

Suitable silane coupling agents include vinyltrimethoxysilane, γ-chloropropyltrimethoxysilane,
Examples thereof include vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane.

Titanium coupling agent is generally in _{^{(R 1 O) M -TiO-}} X-R 2 -Y) compounds represented by _N, RO- represents an alkoxy group,
O-X-R ² -Y) shows a substituted carboxyl group, etc. substituted phosphite group.

The molecular weight of these tichan coupling agents is generally 200 to 3000 and the specific gravity is in the range of 0.85 to 1.20.

Examples of suitable titanium coupling agents include isopropyl triisostearoyl titanate, isopropyl isostearoyl dimethacryl titanate, and isopropyl tri (diisooctyl phosphate) titanate.

Filler In the present invention, a filler is used as an essential component in the modified ethylene / α-olefin copolymer rubber and the silane coupling agent or the titanium coupling agent described above in order to improve mechanical properties.

As the filler, an inorganic filler containing silica (SiO ₂ ) as a main component (hereinafter sometimes simply referred to as “silica”) is used from the viewpoint of the effect of improving the characteristics described above.

Examples of these silica fillers include dry white carbon, wet white carbon, clay, and talc.

Rubber composition The rubber composition of the present invention contains 1 to 20 parts by weight of a silane coupling agent, a titanium coupling agent, or a mixture thereof (B) per 100 parts by weight of the modified ethylene / α-olefin copolymer rubber (A). Parts by weight, preferably 3 to 10
It is compounded in a ratio of 10 parts by weight and the filler (C) is 10 to 150
Part by weight It is preferably mixed in a proportion of 20 to 100 parts by weight.

When the compounding amount of the silane coupling agent, the titanium coupling agent or the mixture (B) thereof is less than the above range, the desired strength and heat aging resistance cannot be obtained. Rises and becomes unusable for practical use. If the amount of the filler (C) used is outside the above range, the mechanical properties will be impaired.

The rubber composition of the present invention may be compounded with a compounding agent known per se, such as a rubber reinforcing agent, a softening agent, a vulcanizing agent, a vulcanization aid, etc., depending on the intended use of the vulcanized product. You can

In this case, the total amount of the components (A) to (C) occupying in the composition is generally 60% by weight or more, and particularly preferably 80% by weight or more, though it varies depending on the application.

Examples of rubber reinforcing agents that can be used are SRF, GPF, FEF and HA.
Examples include carbon blacks such as F, ISAF, SAF, FT and MT.

These rubber reinforcing agents can be appropriately selected according to their applications and the like, but should be 50 parts by weight or less, particularly 30 parts by weight or less per 100 parts by weight of the total amount of the above-mentioned components (A) to (C). Is preferred.

As the softening agent which can be used in the present invention, the softening agent usually used for rubber is sufficient, but for example, petroleum softening agents such as process oil, lubricating oil, synthetic lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petrolatum, coal. Coal tar type softeners such as tar and coal tar pitch, fatty oil type softeners such as castor oil, linseed oil, rapeseed oil and coconut oil, tall oil; sub; waxes such as beeswax, carnauba wax and lanolin; ricinoleic acid , Fatty acids and fatty acid salts such as palmitic acid, barium stearate, calcium stearate, zinc laurate; synthetic polymer substances such as petroleum resin, atactic polypropylene, coumarone indene resin, polyester resin, or dioctyl adipate, dioctyl phthalate Ester Plasticizer Other Micro Lister phosphorus wax, and the like sub (factice).

The blending amount of these softening agents can be appropriately selected according to the application etc., but the total amount of the above-mentioned components (A) to (C) is 100
It is preferably 50 parts by weight or less, and particularly preferably 30 parts by weight or less per part by weight.

The vulcanized product from the composition of the present invention was prepared by once preparing an unvulcanized compounded rubber by the method described below, and then molding the compounded rubber into an intended shape in the same manner as when vulcanizing a general rubber. It is produced by post-vulcanization. As a vulcanizing method, there are a method of using a vulcanizing agent for heating and a method of irradiating with an electron beam.

Examples of the vulcanizing agent used when using the vulcanizing agent include sulfur compounds and organic peroxides. Examples of the sulfur-based compound include sulfur, sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, and selenium dimethyldithiocarbamate. Among them, sulfur is preferably used. Sulfur compounds are based on 100 parts by weight of modified ethylene / α-olefin copolymer rubber (A).
It is used in a proportion of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight. As the organic peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (tertiary butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5- Dimethyl-2,5-di (tertiary butylperoxy) hexyne-3, ditertiary butylperoxide, ditertiary butylperoxy-3,3,5-trimethylcyclohexane, tert-butyl hydroperoxide can be exemplified, but among them, Dicumyl peroxide, ditertiary butyl peroxide, ditertiary butylperoxy-3,3,5-trimethylcyclohexane are preferably used. Organic peroxide is modified ethylene / α-olefin copolymer rubber (A)
3 × 10 ⁻⁴ to 5 × 10 ⁻² mol parts, preferably 1 × 10 ⁻³ to 3 × 10 ⁻² mol parts are used per 100 parts by weight.

When a sulfur compound is used as a vulcanizing agent, it is desirable to use a vulcanization accelerator together. As the vulcanization accelerator, N-cyclohexyl-2-benzothiazole-sulfenamide, N
-Oxydiethylene-2-benzothiazole-sulfenamide, N, N-diisopropyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole, 2- (2,4-dinitrophenyl) mercaptobenzothiazole, 2- (2, 6-diethyl-4-morpholinothio) benzothiazole, dibenzothiazyl-disulfide, and other thiazoles; diphenylguanidine, triphenylguanidine, diorthotolylguanidine, orthotriyl by guanide, diphenylguanidine, phthalate, and other guanidines; acetaldehyde -Aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, aldehyde amine such as acetaldehyde ammonia or aldehyde-ammonia system; 2-mercaptoimidazole Imidazoline and the like;
Thiouria series such as thiocarbanilide, diethyl thiourea, dibutyl thiourea, trimethyl thiourea, and diorsotolyl thiourea; tetramethyl thiuram monosulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrabutyl thiuram disulfide, bentamethylene thiuram tetratra sulfide. Such as thiurams; zinc dimethyldithiocarbamate, zinc diethylthiocarbamate, zinc di-n-butyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, selenium dimethyldithiocarbamate, diethyldithiocarbamate. Dithiolates such as tellurium acid; Santates such as zinc dibutylxanthate Others, such as zinc oxide can be mentioned. These vulcanization accelerators are used in a proportion of 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the modified ethylene / α-olefin copolymer rubber (A).

When an organic peroxide is used as a vulcanizing agent, it is preferable to use a vulcanization auxiliary together. Examples of vulcanization aids include sulfur, quinone dioximes such as p-quinone dioxime, methacrylates such as polyethylene glycol dimethacrylate, allyls such as diallyl phthalate and triallyl cyanurate, maleimides, and divinylbenzene. To be done. Such a vulcanization aid is an organic peroxide used.
It is used in an amount of 1/2 to 2 mol, preferably about equimolar to the mol.

When using an electron beam without using a vulcanizing agent as a vulcanizing method, 0.1 to 1 is added to a molded unvulcanized compounded rubber described below.
The absorption line of an electron having an energy of 0 MeV (megaelectron volt), preferably 0.3 to 2.0 MeV, is 0.5 to 35 Mrad (megarad), preferably 0.5 to 10 Mrad.
Irradiate so that The time may be used vulcanizing agent used in combination with an organic peroxide as a vulcanizing agent of the, the amount modified ethylene · alpha-olefin copolymer rubber (A) 1 × 10 to 100 parts by weight of ^{- 4} to 1 × 10 ^-1
1 part by mole, preferably 1 × 10 ⁻³ to 3 × 10 ⁻² parts by mole. Further, a colorant, an antioxidant, a dispersant, and a flame retardant can be added to the composition of the present invention, if necessary.

The unvulcanized compounded rubber is prepared by the following method. That is, a modified ethylene / α-olefin copolymer rubber (A), a silane coupling agent, or a titanium coupling agent, or a mixture thereof (B), a white filler (C), and a rubber if necessary, with a mixer such as a Banbury mixer. After kneading the reinforcing agent and softening agent for 3 to 10 minutes at a temperature of 80 to 170 ° C., use rolls such as oven rolls,
A vulcanizing agent and, if necessary, a vulcanization accelerator or vulcanization aid are additionally mixed and kneaded at a roll temperature of 40 to 80 ° C. for 5 to 30 minutes and then dispensed to prepare a ribbon-shaped or sheet-shaped compounded rubber. To do.

The compounded rubber thus prepared is molded into an intended shape by an extruder, calender roll, or press,
Simultaneously with molding or by introducing the molded product into a vulcanization tank and heating it at a temperature of 150 to 270 ° C. for 1 to 30 minutes, or by irradiating it with an electron beam by the above-mentioned method, a vulcanized product can be obtained. This vulcanization step may be performed using a mold or may be performed without using a mold. When a mold is not used, the molding and vulcanization steps are usually carried out continuously.

Of course, when vulcanization is performed by electron beam irradiation, compounded rubber containing no vulcanizing agent is used.

As a heating method for the vulcanized layer, a heated layer such as hot air, a fluidized bed of glass beads, UHF (ultra-high frequency electromagnetic wave) or steam can be used.

(Effects of the Invention) The rubber composition of the present invention thus produced is excellent in mechanical properties, electrical insulation, and heat aging resistance, as shown in Examples described later, and is a wire covering, tube, belt, rubber roll, It is preferably used for gaskets, packings, rubber hoses, etc.

The excellent effect of the present invention will be described in the following example.

(Example) Example 1 Maleic anhydride-modified ethylene / propylene copolymer rubber [ethylene / propylene = 80/20 (molar ratio), maleic anhydride content 0.5 wt% Mooney viscosity [ML _{1 + 4} (100 ° C)] 2
0, vinyltrimethoxysilane, and silica [trade name Aerosil 130, manufactured by Nippon Aerosil Co., Ltd.] were mixed according to the following formulation and used for the test.

Kneading is carried out using an 8-inch oven roll at 60 ° C to 70 ° C for 20
I went for a minute.

Next, the mixture was press-vulcanized at 160 ° C. for 30 minutes to prepare a vulcanized rubber sheet having a thickness of 2 mm and used for measurement. All measurements are JIS
The following items were measured according to the method of K6301.

Normal physical properties Tensile strength (T _B ), Elongation (E _B ), Spring hardness (H _S ) Heat aging resistance (aging condition: 180 ° C-96 hours in air oven) Tensile strength retention rate (A _R (T _B )) And elongation retention (A _R (E _B )) results are shown in Table 1 below.

Example 2 Instead of the maleic anhydride modified ethylene / propylene copolymer rubber in Example 1, a maleic anhydride modified ethylene / propylene / 5-vinyl-2-norbornene copolymer comb [ethylene / propylene = 65/35 (molar ratio) was used. , 5-vinyl-
The same procedure as in Example 1 was carried out except that the 2-norbornene content was 2, the iodine value was 2, the maleic anhydride content was 1.0 wt%, and the Mooney viscosity ML _{1 + 4} (100 ° C.) 40] was used.

Example 3 Instead of the maleic anhydride-modified ethylene / propylene copolymer rubber in Example 1, maleic anhydride-modified ethylene / propylene / 5-ethylidene-2-norbornene copolymer rubber [ethylene / propylene = 65/35 (molar ratio)] , 5-ethylidene-2-norbornene content is 5, iodine value is 5, maleic anhydride content is 1.5wt%, Mooney viscosity ML _{1 + 4} (100 ℃) 5
[0] was performed in exactly the same manner as in Example 1.

The results are shown in Table 1 below.

Example 4 Example 4 was carried out in exactly the same way as Example 1 except that the compounding recipe was as follows.

Example 5 Example 1 was repeated except that the compounding recipe was changed as follows.
And went exactly the same way.

Example 6 Example 6 was carried out in exactly the same way as in Example 1 except that the formulation was as follows.

Example 7 The same procedure as in Example 1 was carried out except that the compounding recipe in Example 1 was changed as follows.

Comparative Example 1 In Example 2, maleic anhydride-modified ethylene / propylene /
Instead of 5-vinyl-2-norbornene copolymer rubber,
The same procedure as in Example 2 was carried out except that the ethylene / propylene / 5-vinyl-2-norbornene copolymer rubber before modification was used.

Comparative Example 2 The same procedure as in Example 2 was carried out except that no vinyltrimethoxysilane was added in Example 2.

Comparative Example 3 The procedure of Example 2 was repeated, except that silica was not added in Example 2.

Comparative Example 4 The procedure of Example 2 was repeated, except that 160 parts by weight of silica and 60 parts by weight of synthetic lubricating oil were blended.

Example 8 Example 2 was repeated except that 80 parts by weight of talc (Takehara Chemical Co., Ltd., trade name Hytron A) was blended in place of silica in Example 2.
And went exactly the same way.

Example 9 Instead of the maleic anhydride-modified ethylene / propylene copolymer rubber in Example 1, ethyl acrylate-modified ethylene / propylene copolymer rubber [ethylene / propylene = 80/20
(Mole ratio), Ethyl acrylate content 3.0 wt%, Mooney viscosity ML _{1 + 4} (100 ° C.) 30] The procedure was exactly the same as in Example 1.

Example 10 The procedure of Example 2 was repeated except that 100 parts by weight of silica and 40 parts by weight of a synthetic lubricating oil were blended.

Example 11 In Example 1, maleic anhydride-modified ethylene / 1-butene
5-ethylidene-2-norbornene copolymer rubber [ethylene / 1-butene = 90/10 (molar ratio), 5-ethylidene-2
-Norbornene content was 10 as iodine value, maleic anhydride content was 0.5 wt% and Mooney viscosity ML _{1 + 4} (100 ° C) 25 was used exactly as in Example 1.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C08K 3:36 5:54 5:10)

Claims (1)

[Claims] 1. A modified ethylene / .alpha.-olefin copolymer rubber obtained by graft-copolymerizing (A) an unsaturated carboxylic acid, an acid anhydride thereof and one or more compounds selected from an ester thereof (B) a silane cup. A vulcanized rubber composition comprising a ring-forming agent, a titanium coupling agent or a mixture thereof (C) an inorganic filler mainly composed of silica, the modified ethylene / α-olefin copolymer rubber (A). A silane coupling agent, a titanium coupling agent, or a mixture thereof is added in an amount of 1 to 20 parts by weight, and the filler (C) is added in an amount of 10 to 150 parts by weight, based on 100 parts by weight. A vulcanizable rubber composition characterized by being present.