JPS627945B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a super heat-aging resistant rubber belt obtained by vulcanizing an ethylene-propylene copolymer rubber composition. Vulcanized products obtained from ethylene/propylene copolymer rubber, such as ethylene/propylene/polyene copolymer rubber, have excellent heat resistance, ozone resistance, chemical resistance, and electrical insulation properties due to the structure of the rubber.
Because of its flexibility, belts used for power transmission and conveyors for transporting high-temperature materials are manufactured from ethylene-propylene-polyene copolymer rubber. The present invention relates to this type of rubber belt. Recently, from the viewpoint of resource saving, there has been a desire for a rubber belt that has a long service life and does not require much maintenance and inspection during use, that is, a belt that has better heat aging resistance. The inventors of the present invention have conducted intensive research to meet these demands, and have found that a composition that satisfies the conditions described below has significantly better heat aging resistance than conventionally known ethylene/propylene copolymer rubber compositions and is suitable for use as a rubber belt. discovered that it gives a vulcanizate. That is, the present invention relates to providing a rubber composition for belts that is extremely heat-resistant and aging resistant, satisfying the following conditions (a) to (g). (a) Molar ratio of ethylene and propylene (ethylene/
Blending ethylene/propylene/polyene copolymer rubber A with a ratio of about 50/50 to about 95/5 (propylene). (b) Molar ratio of ethylene and propylene (ethylene/
Blending an ethylene/propylene copolymer rubber B that does not contain a polyene component with a ratio of about 50/50 to about 95/5 (propylene). (c) The blending ratio of copolymer rubber A and copolymer rubber B is approximately 55/45 to approximately 90/10 in terms of weight ratio (A/B). (d) Organic peroxide is used as a vulcanizing agent, and it is blended in an amount of about 0.003 parts by mole or more per 100 parts by weight of the rubber component (A+B). (e) Approximately 0.003 mole part or more of the vulcanization aid should be blended with respect to 100 parts by weight of the rubber component (A+B). (f) Approximately 0.5 parts by weight or more of an antioxidant should be added to 100 parts by weight of the rubber component (A+B). (g) The amount of processing aid added to the rubber component (A+B)
The amount should be approximately 20 parts by weight or less per 100 parts by weight. The vulcanizate made from the ethylene/propylene copolymer rubber composition of the present invention exhibits amazing heat aging resistance, substantially retaining its initial physical properties even after being exposed to an air atmosphere at 120°C for 20 days. A heat aging resistant belt is obtained and can be used for a long period of time. Such effects of the present invention are achieved as a combined effect by satisfying all of the requirements (a) to (g) above. Among the requirements (a) to (g), some individual requirements or a combination of two or three of these requirements are already known, but there is no known composition that satisfies all requirements, and of course rubber belts The use of the compositions of the invention for manufacturing purposes is completely unknown. For example, in Japanese Patent Publication No. 46-32359, ethylene
100 parts by weight of propylene terpolymer (abbreviated as EPT), 20 to 130 parts by weight of ethylene propylene rubber (abbreviated as EPR), 10 to 100 parts by weight of tackifier
A self-fusing insulating composition consisting of 200 parts by weight and 0.2 to 20 parts by weight of a crosslinking agent is proposed, and the general description includes adding an antiaging agent and using an organic peroxide in addition to sulfuric acid. , No anti-aging agent is added in the formulations specifically disclosed in the examples,
In addition, sulfur is used as a vulcanizing agent, and in the present invention, tackifiers and softeners included as processing aids are added in an amount of 20 parts by weight per 100 parts by weight of the total amount of EPT and ERP.
% by weight or more, and the vulcanizate obtained from such a combination is significantly inferior in heat aging resistance compared to the vulcanizate from the composition of the present invention. Mata Tokuko Showa 47-
Publication No. 8369 discloses that ethylene/α-olefin copolymer containing EPR is added to 1 to 100 parts by weight of EPT for the purpose of improving the processability of compounded rubber in an unvulcanized state.
A rubber composition containing 0.5 to 30 parts by weight of an alkylphenol formaldehyde resin, a modified product thereof, rosin or an ester thereof is proposed, but the specifically used vulcanizing agent is a sulfur-based vulcanizing agent. There is no mention of using an antioxidant as a vulcanizing agent. In the specification of JP-A-48-745, EPT100
High molecular weight isobutylene and/or
A self-adhesive semiconductor tape manufactured by blending 50 to 150 parts by weight of EPR and a vulcanizing agent is proposed.
When using EPT and ERP in combination, we consciously avoided the use of organic peroxides, and there was no mention of the use of antioxidants. The total amount of hydrocarbon process oil used is EPT and
Exceeding 20 parts by weight per 100 parts by weight of the total amount of EPR. Furthermore, in US Patent No. 3,725,335, EPT100
Polyisobutylene and/or parts by weight
EPR50-150 parts by weight, adhesive 10-80, inorganic filler
A self-bonding insulating composition comprising 50 to 200 parts by weight of a vulcanizing agent capable of vulcanizing only EPT is proposed.
When combining ERP and EPT, the use of organic peroxides is excluded, and there is no mention of the use of antioxidants. Also, in the specification of JP-A-48-50299,
EPT, polyethylene 10 to 100 parts by weight of EPR
A self-bonding insulating tape obtained by adding 60 parts by weight of compounded rubber containing 60 parts by weight of polyisobutylene and 5 to 40 parts by weight of polyisobutylene and no filler was proposed, and in an example, an organic peroxide was used as an anti-aging agent and a cross-linking agent. Examples are disclosed in which EPT and EPR are used in combination, but no examples are disclosed in which EPT and EPR are used together. It is used in large quantities at 40 parts by weight per 100 parts by weight of EPR. Some of these known examples touch upon heat aging resistance, but according to additional tests conducted by the present inventors, the heat aging resistance is far from that of the vulcanizing agent from the composition of the present invention. Therefore, from these known examples, it is impossible to predict the remarkable effects of the present invention by satisfying all of the requirements (a) to (g) of the present invention. The objects and advantages of the present invention will be better understood by describing the present invention in detail below. Copolymer rubber A (requirement (a)) used in the present invention has a molar ratio of ethylene units to propylene units (ethylene/propylene) of about 50/50 to about 95/5,
Preferably from about 55/45 to about 85/15 ethylene.
It is a propylene copolymer rubber. Molar ratio is approximately 95/5
If it exceeds 50/50, the rubber properties of the belt will be poor.
If it is less than that, the belt will have poor strength and heat aging resistance. It is essential that the copolymer rubber A contains a polyene component, and the content thereof is about 4 to about 50, preferably about 4 to 40, more preferably about 4 to about 30 in terms of iodine value. Specifically, the polyene component includes 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene,
Chain nonconjugated dienes such as 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2- Cyclic non-conjugated dienes such as norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5- norbornene, 2-ethylidene-3
-isopropylidene-5-norbornene, 2-brobenyl-2, 2-norbornadiene, 1, 3,
Typical examples include trienes such as 7-octatriene and 1,4,9-decatriene. Suitable polyenes are cyclic nonconjugated dienes and 1,4-hexadiene, especially dicyclopentadiene or 5-ethylidene-2-norbornene. Copolymer rubber B of the present invention does not contain a polyene component. Such rubber can be obtained, for example, by copolymerizing ethylene and propylene under a Ziegler catalyst. However, a small amount of double bonds may exist in the molecular chain due to a disproportionation reaction, etc., but such copolymer rubber usually has an iodine value of about 2 or less and is suitable as copolymer rubber B of the present invention. Can be used for The Mooney viscosity (ML ₁₊₄ , 100°C) of copolymer rubber A and copolymer rubber B used in the present invention is usually about
10 to about 200, preferably about 15 to about 150, more preferably about 20 to about 100. If the Mooney viscosity exceeds about 200, there is a drawback that roll processability during the preparation of compounded rubber decreases, and if it is less than about 10, the strength of the belt decreases. The blending ratio of copolymer rubber A and copolymer rubber B, which is an essential requirement (c) of the present invention, has a specific ratio (A/B) of approximately 55/
45 to about 90/10, preferably about 60/40
or about 80/20. Even if the blending ratio exceeds about 95/5 and a large amount of copolymer rubber A is blended, it will still be about 55/5.
Even if less than 45 and a large amount of copolymer rubber B is blended, a belt with excellent heat aging resistance cannot be obtained. In the present invention, an organic peroxide is used as a vulcanizing agent (requirement (d)). Sulfur, organic sulfur compounds, organic peroxides, etc. are usually used as rubber vulcanizing agents, but when other vulcanizing agents are used instead of organic peroxides, the heat aging resistance of the belt of the present invention is poor. The organic peroxide used in the present invention includes:
Tertiary butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide,
Alkyl hydroperoxides such as 2,5-dimethyl-2,5-dihydroperoxyhexane, 2,5-dimethyl-2,5-dihydroperoxyhexine-3; di-tert-butyl peroxide;
Di-tertiary amyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, 1,4-
(or 1,3-)ditert-butylperoxyisopropylbenzene, 2,2-ditert-butylperoxybutane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl -2,5-di(tert-butylperoxy)hexyne-3, n-butyl-4,4-di-tert-butyl valerate, 1,1-di-tert-butylperoxycyclohexane, di-tert-butylperoxy-3・３・
Dialkyl peroxides such as 5-trimethylcyclohexane, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane; diacetyl peroxide, dipropionyl peroxide, dioctanoyl peroxide,
3,5,5-trimethylhexanoyl peroxide, didecanoyl peroxide, dilauroyl peroxide, stearoyl peroxide, dibenzoyl peroxide, di-p-chlorobenzoyl peroxide, di-2,4-dichlorobenzoyl peroxide, succinic acid peroxide, etc. Diacyl peroxides; tert-butyl peroxyacetate, tert-butyl peroxyisobutyrate, tert-butyl peroxybivalate, tert-butyl peroxymaleitoxacide, tert-butyl peroxyneodecanoate, tert-butyl peroxybenzoate, diacyl peroxides; Tertiary butyl peroxyphthalate, Tertiary butyl peroxylaurate, 2.
Examples include peroxy esters such as 5-dimethyl-2,5-di(benzoylperoxy)hexane and tert-butylperoxyisopropyl carbonate; ketone peroxides such as dicyclohexanone peroxide; and mixtures thereof. Among them, the temperature that gives a half-life of 1 minute is
The use of organic peroxides in the range 130°C to 200°C is preferred, especially n-butyl-4,4-ditert-butylvalerate, dicumyl peroxide, 2.
5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy) ) Hexyne-3, ditert-butyl peroxide, 1.1
Organic peroxides such as -di-tert-butylperoxy-3,3,5-trimethylcyclohexane and tert-butyl hydroperoxide are preferably used. In the present invention, such organic peroxide is used in an amount of about 0.003 mole part or more, usually about 0.003 to about
0.02 mole part is used, preferably about 0.005 to about 0.015 mole part. If it is less than about 0.003 mole part, not only the strength will decrease but also the heat aging resistance will be inferior.
When used in an amount of about 0.02 mole part or more, heat aging resistance may decrease. In the present invention, a vulcanization aid is blended together with an organic peroxide as a vulcanizing agent (requirement (e)). The combined use of a vulcanization aid not only increases the mechanical strength of the belt but also improves its heat aging resistance. Examples of vulcanization aids include quinonedioxime compounds such as p-quinonedioxime and p.p'-dibenzoylquinonedioxime; p-dinitrosobenzene, N-methyl-
dinitroso compounds such as N.4-dinitrosomethylaniline; m-dinitonibenzine, 2.
Nitro compounds such as 4-dinitrotoluene; Allyl compounds such as triallyl cyanurate, diallyl phthalate, diallyl itaconate, tetraallyloxyethane; trimethylolprapane trimethacrylate, ethylene dimethacrylate, ethylene glycol dimethacrylate, ethylene glycol dimethacrylate,
Methacrylic compounds such as polyethylene glycol dimethacrylate; other examples include N.N'-phenylene bismaleimide, divinylbenzene, and divinyltoluene;
Among them, p-quinone dioxime, p・p′-dibenzoylquinone dioxime, triallyl cyanurate, polyethylene glycol dimethacrylate,
It is preferable to use . Such a vulcanization aid is used in an amount of about 0.003 mol part or more, usually about 0.003 mol part to about 0.02 mol part, preferably about 0.005 to about 0.015 mol part, based on 100 parts by weight of the total amount of copolymer rubber A and copolymer rubber B. use part. If the amount is less than about 0.003 mole part, the strength and heat resistance will be poor, and if it is more than about 0.02 mole part, it will be wasteful or, in some cases, will result in poor heat aging resistance. It is also recommended that the vulcanization aid be used in an amount of about equimolar or less to the organic peroxide. Incidentally, since a small amount of sulfur may sometimes increase the mechanical strength of the vulcanizate, a small amount of sulfur may be added as long as it does not impede the effects of the present invention. Generally, the amount should be about 1/2 mole or less per mole of organic peroxide. In the present invention, an antioxidant is blended (requirement (f)).
As antioxidants, styrenated phenol, 2.
6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-
Tert-butyl-p-ethylphenol, 2, 4, 6
-tri-tert-butylphenol, butylhydroxyanisole, 1-hydroxy-3-methyl-4
-isopropylbenzene, mono-tert-butyl-p-
Cresol, mono-tert-butyl-m-cresol,
2,4-dimethyl-6-tert-butylphenol,
Butylated bisphenol A, 2,2'-methylene-
Bis(4-ethyl-6-tert-butylphenol), 4,4′-butylidene-bis(3-methyl-
6-tert-butylphenol), 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis(4-ethyl-6
-tert-butylphenol), 4,4'-methyl-bis(2,6-di-tert-butylphenol), 2.
2'-methylene-bis(4-methyl-6-tert nonylphenol), 4,4'-butylidene-bis(3
-methyl-6-tert-butylphenol), 2.
2'-isobutylidene-bis(4,6-dimethylphenol), 4,4'-thio-bis(3-methyl-
6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-butylbenzyl) sulfide, 4,4'-thio-bis(2-methyl-6
-tert-butylphenol), 2,2'-thio-bis(4-methyl-6-tert-butylphenol), 4.
4'-thio-bis(6-tert-butyl-3-methylphenol), 2,2-thio[diethyl-bis3
(3,5-di-tert-butyl-4-hydroxyphenol)propionate, bis-[3,3-bis(4'-hydroxy-3'-tert-butylphenol)-
butyric acid] glycol ester, bis[2-(2-hydroxy-5-methyl-3-tert-butyl-benzyl)-4-methyl-6-tert-butylphenyl] terephthalate, 1,3,5-tris(3', 5'-di-tert-butyl-4'-hydroxybenzyl) isocyanurate, N・N'-hexamethylene-bis(3,5-di-tert-butyl-4-hydroxy-hydrocinamide), n-octadecyl- 3
-(4'-Hydroxy-3',5'-di-tert-butylphenol)propionate, tetrakis[methylene-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, 1,1 '-bis(4-hydroxyphenyl)cyclohexane,
2,6-mono(α-methylbenzyl)phenol, di(α-methylbenzyl)phenol, tri(α-methylbenzyl)phenol, bis(2′-
Hydroxy-3'-tert-butyl-5'-methylbenzyl)4-methyl-phenol, 2,5-di-tert-amylhydroquinone, 2,6-di-tert-butyl-α-dimethylamino-p-cresol , 2.5
-di-tert-butylhydroquinone, 3,5-di-
Phenolic antioxidants such as diethyl ester of tert-butyl-4-hydroxybenzyl phosphate, catechol, hydroquinone, etc.; 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, 2-mercaptobenzimidazole; Benzimidazole antioxidants such as the zinc salt of mercaptomethylbenzimidazole; aliphatic thioether antioxidants such as dimyristylthiodipropionate, dilaurylthiodipropionate, distearylthiodipropinate, ditridecylthiodipropionate Agents; Metal salts of dithiocarbamic acids such as zinc or nickel salts of dibutyldithiocarbamic acid, zinc salts of diethyldithiocarbamic acid, zinc salts of ethyl-phenyl-dithiocarbamic acid, zinc salts of dimethyldithiocarbamic acid, zinc salts of diamyldithiocarbamic acid, etc. Antioxidant; 2.
Quinoline antioxidants such as 2,4-trimethyl-1,2-dihydroquinoline or its polymer, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; other phenothiazine;
4-benzoyloxy-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidine) sebacate, N-
Examples include (3'-hydroxybutylidene)-1-naphthylamine. Among these antioxidants, polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, 2,6-di-tert-butyl-4
Methylphenol, N-(3'-hydroxybutylidene)-naphthylamine, 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, nickel salt of dibutyldithiocarbamic acid, mono(α-methylbenzyl)phenol, di(α -methylbenzyl)phenol, tri(α-methylbenzyl)phenol and mixtures thereof are preferred. In the present invention, the antioxidant as described above is added to about 100 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.
0.5 parts by weight or more, but usually about 0.5 to about 4 parts by weight
Parts by weight are used, preferably from about 1 to about 3 parts by weight. If the amount used is less than about 0.5 parts by weight, the heat aging resistance will be poor, and if it is used in excess of about 4 parts by weight, it will be wasteful. In the present invention, no processing aid is blended at all, or even if it is blended, about 100 parts by weight of the rubber component (A+B)
Stay below 20 parts by weight, preferably below about 15 parts by weight. If more than about 20 parts by weight is added, the heat aging resistance of the vulcanizate will be significantly reduced. Processing aids are referred to as softeners, tackifiers, plasticizers, etc., and are used to improve processability. Specifically, for example, process oil, lubricating oil, paraffin, liquid paraffin, petroleum softeners such as petrolatum; other atactic polypropylene,
Examples include synthetic polymeric substances such as liquid polybutene. However, it is preferred to use paraffinic process oils, liquid paraffin, and liquid polybutene. In the present invention, in addition to the above-mentioned requirements (a) to (g), an inorganic filler can be added as an optional component. Usually, the amount of inorganic filler blended is about 200 parts by weight or less based on 100 parts by weight of the total amount of copolymer rubber A and copolymer rubber B, preferably about 10 to about 200 parts by weight, particularly about 30 to about 180 parts by weight. Parts by weight are recommended. By adding an inorganic filler, the surface hardness and tensile strength of the vulcanizate can be increased and favorable results can be obtained.
If more than 200 parts by weight is used, the belt will lose its flexibility and other rubbery properties. Examples of inorganic fillers that can be used include finely divided silicic acid, calcium carbonate, talc, clay, and carbon black. Further, in the present invention, a molding aid can be added as another optional component. Examples of molding aids include higher fatty acids, salts thereof, and esters thereof, such as ricinoleic acid, stearic acid, palmitic acid, lauric acid, barium stearate, calcium stearate, zinc stearate, and esters of the above-mentioned acids. These are usually rubber components (A
+B) Up to about 10 parts by weight, preferably about 1 to about 5 parts by weight per 100 parts by weight. It is also recommended that the proportion of copolymer rubber A and copolymer rubber B in the composition of the present invention is about 25% by weight or more, preferably about 35% by weight or more. As the process for manufacturing a belt from the composition of the present invention, any known process for manufacturing a belt from a conventional rubber composition using ethylene-propylene-polyene copolymer rubber can be appropriately selected. For example, after kneading copolymer rubber A, copolymer rubber B, inorganic fillers, and processing aids as necessary at 90℃ to 150℃ for 4 to 10 minutes using a mixer such as a Banbury mixer, oven rolls, etc. using rolls with a roll temperature of 40 to 80
An antioxidant, an organic peroxide, a vulcanization aid, etc. are further mixed at a temperature of °C to prepare a sheet-like or ribbon-like compounded rubber. The belt can be obtained by molding this compounded rubber into a belt shape using a roll, calendar extruder, etc., and heating the molded product to 130 to 220°C. There are many belts in which synthetic fiber cloth, natural fiber cloth, steel cord, etc. are laminated as reinforcing materials, and such belts can be easily manufactured from the composition of the present invention. Examples will be specifically described below. Copolymer rubber used in Examples and Comparative Examples Copolymer Rubber A used in Examples and Comparative Examples
(A ₁ , A ₂ , A ₃ ) and copolymer rubber B (B ₁ , B ₂ ) are shown in Table 1. In each case, copolymer rubber A used ethylidene norbornene as the diolefin.

[Table] Note that in the following examples, belts with specific shapes are not manufactured for convenience in order to make the gist of the present invention easier to understand. It will be obvious to those skilled in the art that the obtained product is obtained. Examples 1 to 3, Comparative Examples 1 to 4 Copolymer rubber A ₁ and copolymer rubber B ₁ in Table 1 were used in the proportions listed in Table 3, and compounded rubber was prepared according to the recipe in Table 2. After the preparation, a vulcanizate was obtained. Namely, copolymer rubber A ₁ , copolymer rubber B ₁ , zinc white, stearic acid, Mistron paper talc, Sheet S
and iodoplast P according to the combination table in Table 2,
After kneading for 6 minutes using a 4.3 Banbury mixer (OOC type, manufactured by Kobe Steel, Ltd.), antioxidants, vulcanizing agents and vulcanization aids were added, and the roll temperature was 40 using an 8 x 20 inch oven roll. After kneading for 15 minutes at ℃, a sheet of compounded rubber with a thickness of 5 mm was separated, and this sheet was heated at 160℃ using a heat press.
Processed under pressure 150Kg/ ^cm2 for 30 minutes, 12cm x 14cm
A sheet-like vulcanizate with a size of 2 mm was obtained. From this vulcanizate, a No. 3 dumbbell according to JIS K 6301 is punched out.
Tensile speed 500 by method according to JIS K 6301
mm/min, stress at break at break at 25°C TB ₁
(Kg/cm ² ) and elongation at break EB ₁ (%) were measured. Furthermore, according to JIS K 6301, the hardness of the vulcanizate is HS ₁ (JIS
A) was measured. These values are shown in Table 3 as initial physical properties. Next, the above-mentioned No. 3 dumbbell was tested using Toyo Seiki's "TEST TUBE AGING TESTER".
After exposing each dumbbell to an air atmosphere for 7 days at 160℃ and 20 days at 120℃, the stress at break TB ₂ (Kg/cm ² ) and elongation at break EB ₂ were determined in the same manner as above.
(%), hardness HS ₂ was measured. △TB, △EB, △HS
was calculated using the following formula and used as a measure of heat resistance. △TB (%) = TB ₂ - TB ₁ / TB ₁ × 100, △EB (%) = EB ₂ - EB ₁ EB ₁ × 100 △HS = HS ₂ - HS ₁

【table】

【table】

[Table] Examples 4 to 6 Copolymer rubber A and copolymer rubber B in Example 2
The same operations as in Example 2 were performed except that each copolymer rubber listed in Table 4 was used. The results are shown in Table 4.

[Table] Examples 7 to 13, Comparative Examples 5 and 6 In Example 2, the type and amount of antioxidant, the type and amount of vulcanizing agent, and the type and amount of vulcanization aid are listed in Table 5. The same operations were performed except for the following changes. The results are shown in Table 5. In addition, Comparative Example 5 is an example in which the amount of the antioxidant is blended is small, and Comparative Example 6 is an example in which the blended amount of the vulcanization aid is small. Comparative Example 7 An experiment was conducted in which a large amount of processing aid was added. That is, in Example 7, 30 parts by weight of paraline process oil (trade name: Diana White Process WP75; Idemitsu Kosan) was further blended. Incidentally, in order to adjust the change in the physical properties of the vulcanizate due to the addition of the oil, the blending amount of Sheest H was set to 70 parts by weight. Other operations were the same as in Example 7. The results are shown in Table 5.

【table】

【table】

[Table] Comparative Example 8 The same operations as in Example 2 were performed except that sulfur was used instead of organic peroxide as the vulcanizing agent in Example 2 and a compounded rubber was prepared according to the formulation table in Table 6. The results were obtained. Initial physical properties TB=180Kg/cm ² EB=340% HS=69 Heat aging test (160℃, 7 days) △TB=-68% △EB=-72% △HS=+19

【table】

[Table] From the above Examples and Comparative Examples, it is clear that a belt with excellent heat aging resistance can be obtained from the composition of the present invention that satisfies requirements (a) to (g).

Claims (1)

[Scope of Claims] 1. A rubber composition for belts with super heat aging resistance that satisfies the following conditions (a) to (g). (a) Molar ratio of ethylene and propylene (ethylene/
Blending ethylene/propylene/polyene copolymer rubber A with a ratio of about 50/50 to about 95/5 (propylene). (b) Molar ratio of ethylene and propylene (ethylene/
Blending an ethylene/propylene copolymer rubber B that does not contain a polyene component with a ratio of about 50/50 to about 95/5 (propylene). (c) The blending ratio of copolymer rubber A and copolymer rubber B is approximately 55/45 to approximately 90/10 in terms of weight ratio (A/B). (d) Organic peroxide is used as a vulcanizing agent, and it is blended in an amount of about 0.003 parts by mole or more per 100 parts by weight of the rubber component (A+B). (e) Approximately 0.003 mole part or more of the vulcanization aid should be blended with respect to 100 parts by weight of the rubber component (A+B). (f) Add at least 0.5 parts by weight of an antioxidant to 100 parts by weight of the rubber component (A+B). (g) The amount of processing aid added to the rubber component (A+B)
The amount should be 20 parts by weight or less per 100 parts by weight.