JPH01108248A - Modified rubber composition - Google Patents

Abstract

PURPOSE:To obtain a modified rubber composition excellent in strength, thermal aging resistance, etc., by mixing a specified modified ethylene/alpha-olefin copolymer rubber with a polyorganosiloxane and a silica filler at a specified weight ratio. CONSTITUTION:A modified rubber composition is prepared by using a modified ethylene/alpha-olefin copolymer rubber (A) obtained by graft-copolymerizing an unsaturated carboxylic acid (anhydride or ester) (A), e.g., maleic anhydridemodified ethylene/propylene copolymer rubber, 0.5-30pts.wt. polyorganosiloxane (B) of an average composition of the formula (wherein R<1> is a monovalent hydrocarbon group, R<2> is vinyl, a is 1-2.5, b is 0.01-1.2, and a+b=1.8-3) and 10-100pts.wt. silica filler (C) as essential components. This rubber composition can be suitably used for the production of tubes, belts, packings, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rubber composition that is crosslinked by heating and provides excellent mechanical properties, heat aging resistance, and electrical properties.

(Prior art and its problems) Ethylene/α-olefin copolymer rubber is used as a rubber with excellent chemical resistance and electrical insulation properties, such as automobile parts, electrical parts,
Awarded for general industrial parts, etc. However, recently there have been cases where even higher strength and higher heat aging resistance are required for automobile parts, electrical parts, etc.

For this reason, for example, to improve heat aging resistance, attempts have been made to add anti-aging agents to this type of rubber, as seen in the synthetic rubber processing technology encyclopedia "Ethylene Propylene Rubber", but the improvement effect has not been found. not enough.

Therefore, an object of the present invention is to provide a vulcanizable rubber composition that exhibits the excellent chemical resistance and electrical insulation properties of ethylene/α-olefin copolymer rubber, has high strength, and has extremely excellent heat aging resistance. is a technical issue.

(Means to Solve the Problems) The present invention provides graft-modified ethylene/α-olefin copolymer rubber (A) and the following formulas (I), (R')-(R2
)b 'S i OL---b)/2...... (
I) In the formula, R' is a -valent hydrocarbon group, R2 is a vinyl group, a is a number from 1 to 2.5, and b is a number from o, oi to 1.2, and a+b is 1
．． Polyorganosiloxane CB) and silica filler (CB) having an average composition in the range of 8 to 3.
A structural feature is that it is used in combination with C).

(Function) The heat-resistant rubber composition of the present invention contains graft-modified ethylene α
- By blending the above-mentioned polyorganosiloxane (B) and silica-based filler (C) with the olefin copolymer rubber (A), it has excellent mechanical properties such as strength, as well as significantly superior properties. Shows heat aging resistance.

That is, as is clear from the examples described below, the composition of the present invention has a retention rate of about 60% in a test at 180°C for 96 hours.
This is an astonishing value. The superiority of the composition of the present invention can be understood from the fact that a conventional heat resistance test is conducted at a temperature of 140° C., and if it shows a value of 60% or more, it can be said to be a heat-resistant formulation.

In the present invention, the reason why the heat aging resistance is significantly improved is not yet clear, but the interfacial properties between the filler and the ethylene/α-olefin copolymer rubber are significantly improved by the specific polyorganosiloxane. This seems to be due to the fact that

(Preferred embodiments of the invention) (A) Modified ethylene/α-olefin copolymer rubber The modified ethylene/α-olefin copolymer rubber used in the present invention is selected from unsaturated carboxylic acids, their anhydrides, and their esters. One or more of the above compounds are used as graft copolymerization monomers, and are graft copolymerized to ethylene and α-olefin copolymer rubber.

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

Specifically, α-olefins having 3 to 10 carbon atoms include propylene, 1-butene, 1-hexene, 4-methyl-1
Examples include -pentene, 3-methyl-1-pentene, 1-octene, and 1-decene.

Furthermore, this ethylene/α-olefin copolymer rubber contains 1
More than one type of polyene component may be contained.

Specifically, the polyene component includes 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-hebutadiene, 7-methyl-1,6- linear nonconjugated dienes such as octadiene,
Cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene,
Cyclic non-conjugated dienes such as 6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-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 resulting copolymer has an iodine value of at most 30, preferably 20 or less.

The unsaturated carboxylic acid, its anhydride, and its ester to be graft copolymerized with the above-mentioned ethylene/α-olefin copolymer comb are not limited thereto, but the following may be used, for example.

Unsaturated carboxylic acids; 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, etc.

Unsaturated carboxylic acid anhydride; maleic anhydride, itaconic anhydride, citraconic anhydride,
Tetrahydrophthalic anhydride, bicyclo(2,2,1)hept-2-ene-5,6-dicarboxylic anhydride, and the like. Among these, maleic anhydride is preferred.

Unsaturated carboxylic acid esters: methyl acrylate, methyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate,
Dimethyl itaconate, diethyl citraconate, dimethyl tetrahydrophthalate anhydride, dimethyl bicyclo(2,2,1)hept-2-ene-5,6-dicarboxylate, and the like. Among these, methyl acrylate and ethyl acrylate are preferred.

The graft comonomer such as the unsaturated carboxylic acid mentioned above is
Each may be used alone or in combination of two or more types, but in any case, 0.1 to 10! It is preferable to carry out the graft copolymerization in an amount of i parts, particularly in a range of 0.2 to 5 parts by weight.

When the amount of grafting is less than the above range, the desired heat aging resistance tends not to be obtained, and when it is more than the above range, the resulting rubber composition is unsatisfactory in processability and cold resistance. It tends to become something.

Graft copolymerization is obtained by reacting the aforementioned ethylene/α-olefin copolymer rubber with an unsaturated carboxylic acid or the like in the presence of a radical initiator.

The reaction can be carried out in a solution or in a molten state. When carrying out the process in the molten state, it is most efficient to carry out the process continuously in an extruder.

The radical initiator used in the grafting reaction has a decomposition temperature of 150 to 270°C so that the half-life is 1 minute.
Those within this range are preferably used.

Specifically, organic peroxides, organic bersesters such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(peroxybenzoate) hexyne-3,1 ,4-bis(ta
rt-butylperoxyisopropyl)benzene, lauroylperoxide, tert-butylberacetate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3,2,5-dimethyl-2,5-
di(tart-butylperoxy)hexane, tert
-butylberbenzoate, tert-butylberphenylacetate, tert-butylberisobutyrate, tert-butylber-5ec-octoate, t
Mention may be made of ert-butylberbivalate, cumylberbivalate and tert-butylberdiethyl acetate.

The above-mentioned graft-modified ethylene/α-olefin copolymer rubber has a Mooney viscosity (MLI+4 (100°C)) of 5 to 180, especially from the viewpoint of mechanical properties and processability.
In particular, those in the range of 20 to 120 are preferably used.

(B) Polyorganosiloxane The polyorganosiloxane used in the present invention has the following average composition formula, (I), (R')a (R2)
b S 10 (a-a-b)/z...
In formula (I), R' is a -valent hydrocarbon group, R2 is a vinyl group, a is a number from 1 to 2.5, and b is a number from 0.01 to 1.2. , and a+b is 1
．． 8 to 3 are used, and those in which the group R1 is a methyl group or a phenyl group are particularly preferably used.

In addition, the number average molecular weight (Mn
) is generally to2 to 106, preferably 103 to 1
05, most preferably in the range 5X10' to 5X10'.

When the degree of polymerization is higher than the above range, it is not sufficiently compatible with the graft-modified ethylene/α-olefin copolymer rubber, resulting in a decrease in strength, and when it is lower than the above range, the desired heat aging resistance is not achieved. There is a tendency not to be able to do so.

As the silica filler, all known rubber compounding agents can be used, such as dry silica, wet silica, synthetic silicate white carbon, talc, clay, etc. used.

The rubber composition in the present invention comprises graft-modified ethylene.
0.5 to 3 parts by weight of a specific polyorganosiloxane (B) is added to 100 parts by weight of α-olefin copolymer rubber (A).
0! is blended in an amount of 1 part, preferably 1 to 25 parts by weight, more preferably 1.5 to 20 parts by weight.

If the amount of polyorganosiloxane (B) is too small than the above range, the desired heat aging resistance cannot be obtained, and if the amount is too large, not only the desired strength cannot be obtained but also it is extremely expensive, making it impractical.

The silica filler (C) is graft modified ethylene・α-
10 to 100 parts by weight of the olefin copolymer rubber (A) alone or as a mixture, preferably 1
It is blended in a proportion of 5 to 801 parts by weight, more preferably 20 to 6011 parts by weight.

If the amount of the silica filler is less than the above range, or if it is too much, the desired strength cannot be obtained and it is not practical.

Masakurami The rubber composition of the present invention may contain compounding agents known per se, such as rubber reinforcing agents, softeners, vulcanizing agents, vulcanization aids, etc., depending on the intended use of the vulcanizate. can do.

In this case, the total amount of the components (A) to (C) in the composition is generally 60% by weight, although it varies depending on the use etc.
In particular, it is preferable that the content be 80% by weight or more.

Rubber reinforcing agents that can be used include SRF, GPF, and F.
Carbon blacks such as EF, HAF, 15AF%SAF%FT, and MT are exemplified.

These reinforcing agents for rubber can be selected as appropriate depending on the usage, etc., but the total amount of the components (^) to (C) described above is 100%.
The amount per part by weight is preferably 50 parts by weight or less, particularly 30 parts by weight or less.

The softeners that can be used in the present invention are those normally used for rubber, but examples include process oils, lubricating oils, synthetic lubricating oils, paraffin, liquid paraffin, petroleum asphalt, petroleum softeners such as vaseline, and petroleum softeners such as coal. Coal tar-based softeners such as tar and coal tar pitch; fatty oil-based 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 , palmitic acid, barium stearate, calcium stearate, zinc laurate, and other fatty acids and fatty acid salts; petroleum resins, atactic polypropylene, coumaron indene resins, polyester resins, and other synthetic polymers, or dioctyl adipate, dioctyl phthalate, etc. Examples include ester plasticizers, microcrystalline waxes, and sub(factices).

The blending amount of these softeners can be selected as appropriate depending on the use, etc., but the total amount of the components (A) to (C) described above
O! Part by weight: 50 parts by weight or less, especially 30! It is preferable that the value is less than or equal to 0.

A vulcanizate from the composition of the present invention is produced by preparing an unvulcanized rubber compound by the method described below, and then molding the compound rubber into an intended shape, in the same way as when vulcanizing rubber. Manufactured by vulcanization. As a vulcanization method, there are a method of heating using a vulcanizing agent and a method of irradiating with an electron beam.

When using a vulcanizing agent, an organic peroxide is recommended as the vulcanizing agent. Examples of organic peroxides include dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane. dimethyl-2,5-di(tert-butylperoxy)hexyne-3,
di-tert-butyl peroxide, di-tert-butyl peroxide
Examples include 3,3,5-)-limethylcyclohexane and tert-butyl hydroperoxide, among which dicumyl peroxide, di-tert-butyl peroxide, and di-tert-butyl peroxy-3,3,5-trimethylcyclohexane are preferred. used. Organic peroxides include modified ethylene and
3X10-4 to 5X10-' mole parts, preferably 1
x10'''3 to 3xto-2 molar parts are used.

When using an organic peroxide as a vulcanizing agent, it is preferable to use a vulcanizing aid in combination. Examples of vulcanization aids include sulfur, quinone dioxime types such as p-quinone dioxime, methacrylate types such as polyethylene glycol dimethacrylate, allyl types such as diallyl phthalate and triallyl cyanurate, other maleimide types, and divinylbenzene. be done. Such a vulcanization aid is the organic peroxide used.
From 1 to 2 moles per mole, preferably about 2 moles are used.

When the vulcanization method does not use a vulcanizing agent and uses an electron beam, the molded unvulcanized compounded rubber described below is charged with 0.1 to 10 MeV (megaelectron volt), preferably 0.3 to 2. The absorption line for electrons with energy of 0 MeV is 0.5 to 35 Mrad (megarad),
It is preferable to irradiate at 0.5 to 10 Mrad. At this time, a vulcanization aid may be used in combination with the organic peroxide as the vulcanizing agent, and the amount thereof is 100% of the modified ethylene/α-olefin copolymer rubber (A).
It is blended in molar parts of txto-' to lXl0-', preferably lXl0-' to 3X10-2 molar parts, based on parts by weight. Furthermore, colorants, anti-aging agents, dispersants, and flame retardants can be added to the composition of the present invention, if necessary.

M-Kiku Wataru Niko 1 Unvulcanized compounded rubber is prepared by the following method. That is, using a mixer such as a Banbury mixer, the modified ethylene/α-olefin copolymer rubber (A), polyorganosiloxane (B), silica filler (C), and if necessary, a rubber reinforcing agent are mixed at 80 to 170°C. 3 to 1 at a temperature of
After kneading for 0 minutes, using rolls such as oven rolls, add a vulcanizing agent and, if necessary, a vulcanization accelerator or vulcanization aid, and mix at a roll temperature of 40 to 80°C for 5 to 30 minutes. After kneading, the mixture is separated to prepare a ribbon-like or sheet-like compounded rubber.

The compounded rubber thus prepared is molded into the intended shape using an extruder, calendar roll, or press,
A vulcanized product can be obtained at the same time as the 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 using a conventional method. This vulcanization step may be carried out using a mold or without a mold. If 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, a compounded rubber containing no vulcanizing agent is used.

Further, as a heating method in the vulcanized layer, a heating layer such as hot air, glass beads fluidized bed, U) IF (ultra-high frequency electromagnetic wave), steam, etc. can be used.

(Effects of the Invention) As shown in the examples below, the rubber composition of the present invention has excellent strength and heat aging resistance, and is suitable for use in electric wire coatings, tubes, belts, rubber rolls, gaskets, packings, rubber hoses, etc. Preferably used.

The excellent effects of the present invention will be explained with the following example.

(Example) The following were used as the Fugo-U-modified ethylene/α-olefin copolymer rubber (A), polyorganosiloxane (B), and silica filler (C), and according to the following recipe. A rubber composition was prepared.

・Modified ethylene/α-olefin copolymer rubber (A) α-
Olefin: Propylene ethylene/Propylene-80/20 (molar ratio) Mooney viscosity M Ll+4 (100'e): 20
Maleic anhydride content: 0.5wt% ・Polyorganosiloxane (B) (C)12) r, a (CH2-C)I) o,
2si.

Mn: 5.1xlO' - Silica filler (C) Dry silica: Specific surface area 200 m27g Formula modified ethylene/α-olefin copolymer rubber 100.
0 parts by weight Polyorganosiloxane 3.0 parts by weight Silica filler 30.0, +
7 Stearic acid 2.0 Zinc white 5.0 Organic peroxide 1
) 5, 0//sulfur
0.2〃Anti-aging agent MB”
2. ON Anti-Aging Agent 200”
1, Q) 1: Manufactured by Ohmukai Shinkosha 3) 2.6-tert-butyl-4-methylphenol: Manufactured by Ohmukai Shinkosha Kneading at 60°C to 70°C using an 8-inch oven roll
I went there for 20 minutes. Next, the mixture was press-vulcanized at 170° C. for 10 minutes to prepare a vulcanized rubber sheet with a thickness of 21 mm, which was used for measurement. All measurements were conducted in accordance with the method of JIS K 6301, and the following items were measured.

Normal state properties Tensile strength (TB), elongation (EB), heat aging resistance [Heat aging conditions: 180°C - 96 hours] Tensile strength retention rate AR (TB), elongation retention rate AR (EB) The results are , shown in Table 1 below.

5 m (Jl-1 The process was carried out in exactly the same manner as in Example 1 except that the following modified ethylene/α-olefin copolymer rubber was used in Example 1).

α-olefin: propylenebornene) Mooney viscosity M Ll-4 (100°C): 60
Maleic anhydride content: 0.5wt%! (+1-
Example 1 was carried out in exactly the same manner as in Example 1, except that the following modified ethylene/α-olefin copolymer rubber was used.

α-olefin = 1-butene Mooney viscosity MLl, 4 (100°C) = 15 Maleic anhydride content: LOwt% FUJI fi4 The same procedure as in Example 1 was carried out except that the formulation was changed as follows. Ta.

Modified ethylene/α-olefin copolymer rubber 100
．． 0 parts by weight polyorganosiloxane 20.
0 Silica-based filler 30. On stearic acid 2. O Zinc white
5.0〃Organic peroxide H5,Q)1 Sulfur 0.2〃Anti-aging agent MB” 2.Ott Anti-aging agent Zo
o" 1.0)) In Example 1, the average compositional formula of polyorganosiloxane is (CH3) 1
．． 9 (CH2=CH). , , S10Mn 4.5
The same procedure as in Example 1 was carried out except that X 10' was used.

The average compositional formula of polyorganosiloxane in Example 1 is
(CHs) 1. S (C)12 = (:H)
The same procedure as in Example 1 was conducted except that 5510Mn6.1 x 10' was used.

In Example 1, the Mn of the polyorganosiloxane was 8.0X1
The procedure was carried out in exactly the same manner as in Example 1 except that the value was set to 0'.

衷五O++ a The same procedure as in Example 1 was carried out except that the following silica-based filler was used in Example 1.

Example 1 was carried out in exactly the same manner as in Example 1, except that the following silica filler was used and the formulation was as follows.

Firing Ray: Product name Satinton NOI (Enge
manufactured by lhard Minerals & Chea, Inc.)
Modified ethylene/α-olefin copolymer rubber 100
．． 0 1i parts polyorganosiloxane 3.
0 firing ray 60. On stearic acid 2.0 Zinc white
5.0 Organic peroxide 11
5.0)) Sulfur
0.2 Anti-aging agent yi B x+
2-0 "Anti-aging agent 200" 1
．． Q Salt Mosquito ■-1 The same procedure as in Example 1 was conducted except that polyorganosiloxane was not used in Example 1.

■Mouse■-U Example 1 was carried out in exactly the same manner as in Example 1, except that the following polyorganosiloxanes were used.

Polydimethylsiloxane Mn: 4.8 xlO' 11 The same procedure as in Example 1 was repeated except that the following modified ethylene/α-olefin copolymer rubber was used.

α-olefin = 1-butene Mooney viscosity ML Ia (100°C): 30 Ethyl acrylate content: 2. Owt% Comparative Example 3 The same procedure as in Example 9 was carried out except that the formulation was changed as follows.

Compounding formula Modified ethylene/α-olefin copolymer rubber xao,
o Part by weight Polyorganosiloxane 3.0 Baked Ray 5.0 Stearic Acid 2.0 Zinc White
5.0 Organic peroxide
5.0 Sulfur 0. z〃
Anti-aging agent MB 2. On anti-aging agent 200 t, o it Comparative Example 4 Example 9 except that the formulation was as follows.
The line was similar to that.

Blending recipe Modified ethylene/α-olefin copolymer rubber 100.
0 parts by weight Polyorganosiloxane 3.0 Baked Ray 110,00/
/Stearic acid 2.0 Synthetic lubricating oil 60.0 //Zinc white
5.0 Organic peroxide
5.0 Sulfur
0.2〃Anti-aging agent MB 2.0
1) Anti-aging agent 200 1.0 11Product name Lucant HC-600: manufactured by Mitsui Petrochemical Co., Ltd. Salt Yu ■ - Interchange In Example 9, instead of the modified ethylene/α-olefin copolymer rubber, ethylene/α- before modification was used. The same procedure as in Example 9 was carried out except that olefin copolymer rubber was used.

Claims (6)

[Claims] (1) (A) 100 parts by weight of a modified ethylene/α-olefin copolymer rubber obtained by graft copolymerizing one or more compounds selected from unsaturated carboxylic acids, their acid anhydrides, and their esters; (B) The following general formula (R^1)_a(R^2)_bSiO_(_4_-_a
____b_)_/_2...(I) In the formula, R^1 is a monovalent hydrocarbon group, R^2 is a vinyl group, a is a number from 1 to 2.5, and b is , 0.01 to 1.2, and a+b is in the range of 1.8 to 3, 0.5 to 30 parts by weight of a polyorganosiloxane having an average composition represented by: and (C) silica A modified rubber composition comprising 10 to 100 parts by weight of a filler as an essential component. (2) The intrinsic viscosity of the ethylene/α-olefin copolymer rubber before graft modification was measured in decalin at 135°C.
η] is in the range of 0.5 to 4.0 dl/g. (3) Claim 1, wherein the composition of the ethylene/α-olefin copolymer rubber (A) before graft modification is ethylene/α-olefin in a molar ratio of 50/50 to 95/5.
The rubber composition described in . (4) The rubber composition according to claim 1, wherein the graft-modified ethylene/α-olefin copolymer rubber (A) contains a nonconjugated polyene having an iodine value of at most 30. (5) The rubber composition according to claim 1, wherein in the general formula (I) showing the composition of the polyorganosiloxane (B), the group R^1 is a methyl group or a phenyl group. (6) Number average molecular weight of polyorganosiloxane (B) (
The rubber composition according to claim 1, wherein M_n) is in the range of 100 to 10^6.