JP6182963B2 - Laminate, vulcanized rubber product, conveyor belt, and method for producing vulcanized rubber product - Google Patents

Description

  The present invention relates to a laminate, a vulcanized rubber product, a conveyor belt, and a method for producing a vulcanized rubber product.

  Heat-resistant conveyor belts with heat-resistant properties include, for example, the transportation of sintered products at sintering plants, coke plants, cement plants, and chemical plants, return mineralization, coke, cement clinker, quicklime, special chemicals, and various high-temperature powdery substances. It has a wide range of uses such as transportation.

  EPDM (ethylene-propylene-diene monomer terpolymer) excellent in weather resistance, ozone resistance, and chemical resistance in addition to heat resistance may be used as the cover rubber of such a heat-resistant conveyor belt. Although known, since EPDM is more expensive than diene rubber, cost reduction can be achieved by using a laminate structure in combination with cheap diene rubber.

  EPDM is a non-diene-based nonpolar rubber, and has poor compatibility with polar diene-based rubbers, making it difficult to use by direct bonding. In Patent Document 1, a NBR modified product having a specific functional group in a polymer chain, EPDM, and a hydrogenated conjugated diene copolymer are blended in a specific range to obtain a vulcanized adhesive property with EPDM. Techniques for improving the performance are described.

JP-A-8-127682

  However, in the method of Patent Document 1, in order to improve the vulcanization adhesiveness with EPDM, it is necessary that the diene rubber layer also contains EPDM, which does not sufficiently satisfy the above cost reduction request. .

  Therefore, the advent of a laminated material with improved adhesion between EPDM and diene rubber while satisfying the above cost reduction demand is eagerly desired.

  In view of the above problems, an object of the present invention is to provide a laminate of EPDM and a diene rubber that can improve the adhesion between the EPDM and the diene rubber and can meet the demand for cost reduction. .

  Another object of the present invention is to provide a heat-resistant belt, particularly a conveyor belt, using such a laminate of EPDM and diene rubber.

The present invention includes the following (1) to (5).
(1) For 100 parts by mass of EPDM rubber,
3 to 6 parts by mass of resorcinol;
EPDM rubber composition layer containing 2 to 4.5 parts by mass of hexamethylenetetramine,
For 100 parts by mass of diene rubber,
3 to 6 parts by mass of resorcinol;
2 parts by mass or more and 4.5 parts by mass or less of hexamethylenetetramine;
A laminate obtained by laminating two layers of a diene rubber composition layer containing 1 part by mass or more and 20 parts by mass or less of silica.

(2) The diene rubber is
40 to 60 parts by weight of natural rubber,
60 parts by mass or less and 40 parts by mass or more of SBR (styrene-butadiene rubber);
The laminate as described in (1) above, which is formed by:

(3) A vulcanized rubber product obtained by vulcanizing the laminate according to (1) or (2).

(4) A conveyor belt comprising the vulcanized rubber product according to (3) above.

(5) EPDM rubber composition layer containing from 3 parts by weight to 6 parts by weight of resorcinol and from 2 parts by weight to 4.5 parts by weight of hexamethylenetetramine with respect to 100 parts by weight of EPDM rubber, and a diene type Diene containing from 3 parts by weight to 6 parts by weight of resorcinol, from 2 parts by weight to 4.5 parts by weight of hexamethylenetetramine, and from 1 part by weight to 20 parts by weight of silica based on 100 parts by weight of rubber A lamination process of obtaining a laminate by laminating two layers of a rubber-based rubber composition layer;
And a vulcanizing step for vulcanizing the laminate.

  According to the present invention, EPDM rubber and diene rubber can exhibit the characteristics of EPDM rubber such as heat resistance, weather resistance, ozone resistance, and chemical resistance, and can meet the demand for cost reduction. And a laminated body can be provided.

  The present invention can also provide a heat resistant belt, particularly a conveyor belt, using such a laminate of EPDM rubber and diene rubber.

FIG. 1 is a schematic diagram illustrating an example of a layer structure of a laminate according to the present embodiment.

  The present invention will be described in detail below. The present invention is not limited by the following modes for carrying out the invention (hereinafter referred to as embodiments). In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be appropriately combined.

[Laminate]
FIG. 1 is a schematic view showing an example of a layer structure of a laminate according to this embodiment. As shown in FIG. 1, the laminate 1 has a structure in which an EPDM rubber composition layer 2 and a diene rubber composition layer 3 are laminated.

[EPDM rubber composition layer]
The EPDM rubber composition layer 2 contains at least EPDM rubber, resorcinol, and hexamethylenetetramine. The mixing ratio of each component in the composition is preferably 3 parts by mass or more and 6 parts by mass or less of resorcinol and 2 parts by mass or more and 4.5 parts by mass or less of hexamethylenetetramine with respect to 100 parts by mass of the EPDM rubber. The present inventors have confirmed that the adhesion between the vulcanized EPDM rubber layer and the diene rubber layer is improved at a blending ratio in this range. Hereinafter, each component constituting the composition will be described.

<EPDM rubber>
Although it does not specifically limit as EPDM rubber, It is preferable that ethylene content is 40 to 60 mass%. Moreover, it is preferable that the Mooney viscosity measured with a 100 degreeC sample is 30-70. Examples of the diene component constituting the EPDM rubber include, but are not limited to, DCPD (dicyclopentadiene), ENB (5-ethylidene-2-norbornene), VNB (vinylidene norbornene), and the like. The content of the diene component is preferably 1% by mass or more and 8% by mass or less.

<Resorcinol>
Resorcinol has a function of accelerating the curing reaction of the rubber composition by functioning as a methylene acceptor in the rubber composition. The amount of resorcinol added is preferably 3 parts by mass or more and 6 parts by mass or less with respect to 100 parts by mass of the EPDM rubber.

<Hexamethylenetetramine>
Hexamethylenetetramine has a function of accelerating the curing reaction of the rubber composition by functioning as a methylene donor in the rubber composition. The amount of hexamethylenetetramine added is preferably 2 parts by mass or more and 4.5 parts by mass or less with respect to 100 parts by mass of the EPDM rubber.

  Resorcinol and hexamethylenetetramine are blended in a combination within the above range to improve the adhesion between the vulcanized diene rubber layer and the EPDM rubber layer.

<Other additives>
The EPDM rubber composition layer 2 may contain other additives depending on the use of the laminate 1. Other additives include, for example, fillers, plasticizers, softeners, anti-aging agents, organic activators, antioxidants, antistatic agents, flame retardants, vulcanizing agents, vulcanization accelerators, vulcanization delays. Agents and adhesion aids.

  Examples of the filler include carbon black, silica (white carbon), clay, talc, iron oxide, zinc oxide (ZnO), titanium oxide, barium oxide, magnesium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, barium sulfate, Examples include mica and diatomaceous earth.

  As the carbon black, carbon having a small particle size such as HAF grade, ISAF grade, SAF grade, etc. is preferable because the rubber product obtained by vulcanizing the obtained rubber composition of the present invention has good wear resistance. .

  The silica is not particularly limited, and examples thereof include crystalline silica, precipitated silica, amorphous silica (for example, high-temperature treated silica), fumed silica, calcined silica, precipitated silica, pulverized silica, and fused silica. In particular, silica is known to produce carbon gel (bound rubber) like carbon black, and can be suitably used as necessary.

  Examples of the clay include wax stone clay, kaolin clay, and calcined clay. These may be used alone or in combination of two or more.

  Examples of the plasticizer include dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate (DOA), isodecyl succinate, diethylene glycol dibenzoate, pentaerythritol ester, butyl oleate, methyl acetylricinoleate, tricresyl phosphate , Trioctyl phosphate, trimellitic acid ester, propylene glycol adipate polyester, butylene glycol adipate polyester, naphthene oil, and the like.

  Specific examples of the softening agent include aroma oils, naphthenic oils, paraffinic oils, petroleum resins, vegetable oils, liquid rubbers, and the like. You may use together.

  Examples of the antioxidant include N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine (6PPD), N, N′-dinaphthyl-p-phenylenediamine (DNPD), and N-isopropyl. -N'-phenyl-p-phenylenediamine (IPPD), styrenated phenol (SP), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD) and the like.

  Specific examples of the organic activator include stearic acid, oleic acid, lauric acid, and zinc stearate.

  Examples of the antioxidant include butylhydroxytoluene (BHT) and butylhydroxyanisole (BHA).

  Examples of the antistatic agent include quaternary ammonium salts; hydrophilic compounds such as polyglycols and ethylene oxide derivatives.

  Examples of the flame retardant include chloroalkyl phosphate, dimethyl / methylphosphonate, bromine / phosphorus compound, ammonium polyphosphate, neopentyl bromide-polyether, and brominated polyether. Examples of the non-halogen flame retardant include aluminum hydroxide, magnesium hydroxide, tricresyl phosphate, and diphenyl cresyl phosphate.

  Examples of the vulcanizing agent include vulcanizing agents such as sulfur-based, organic peroxide-based, metal oxide-based, phenol resin, and quinone dioxime.

  Examples of sulfur-based vulcanizing agents include organic sulfur-containing compounds such as sulfur, tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), dipentamethylene thiuram disulfide (DPTT), dimorpholine disulfide, and alkylphenol disulfide. A compound can be mentioned.

  Examples of sulfur include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, and insoluble sulfur.

  Examples of the organic peroxide vulcanizing agent include dicumyl peroxide, benzoyl peroxide, t-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-di ( t-butylperoxy) hexane, 2,5-dimethylhexane-2,5-di (peroxylbenzoate).

  Examples of other vulcanizing agents include resins such as zinc white, magnesium oxide, risurge, phenol resin, p-quinonedioxime, p-dibenzoylquinonedioxime, poly-p-dinitrosobenzene, and methylenedianiline. Can be mentioned.

  Examples of the vulcanization accelerator include thiazole-based, thyrium-based, and dithiocarbamate-based vulcanization accelerators.

  Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), zinc salt of 2-mercaptobenzothiazole (ZnMBT), and cyclohexylamine salt of 2-mercaptobenzothiazole (CMBT). Etc.

  Examples of the thyrium-based vulcanization accelerator include tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), dipentamethylenethiuram tetrasulfide ( DPTT), tetrabenzylthiuram disulfide and the like.

  Dithiocarbamate vulcanization accelerators include zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldiocarbamate (ZnEDC), zinc dibutyldithiocarbamate (ZnBDC), zinc N-ethyl-N-phenyldithiocarbamate (ZnEPDC), di Examples thereof include zinc benzyldithiocarbamate, tellurium diethyldithiocarbamate (TeEDC), copper dimethyldithiocarbamate (CuMDC), ferric dimethyldithiocarbamate (FeMDC), sodium dimethyldithiocarbamate, and sodium diethyldithiocarbamate (NaEDC).

  Examples of the vulcanization retarder include organic acids such as phthalic anhydride, benzoic acid, salicylic acid, acetylsalicylic acid; N-nitrosodiphenylamine, N-nitrosophenyl-β-naphthylamine, N-nitroso-trimethyl-dihydroquinoline. Nitroso compounds such as polymers; halides such as trichloromelanin; 2-mercaptobenzimidazole, N- (cyclohexylthio) phthalimide (PVI), and the like.

  As the adhesion assistant, triazine thiol compounds (for example, 2,4,6-trimercapto-1,3,5-triazine, 6-butylamino-2,4-dimercapto-1,3,5-triazine), Examples thereof include resorcin, cresol, resorcin-formalin latex, monomethylol melamine, monomethylol urea, and ethylene maleimide.

  Each of the various additives described above may be used alone or in combination of two or more. Various additives can be used in combination depending on the application.

[Diene rubber composition layer]
The diene rubber composition layer 3 contains at least diene rubber, resorcinol, hexamethylenetetramine, and silica. The compounding ratio of each component in the composition is 3 parts by mass to 6 parts by mass of resorcinol, 2 parts by mass to 4.5 parts by mass of hexamethylenetetramine, and 1 part by mass of silica with respect to 100 parts by mass of the diene rubber. The amount is preferably 20 parts by mass or less. It has been confirmed by the present inventors that the adhesion between the vulcanized diene rubber layer and the EPDM rubber layer is improved at a blending ratio in this range. Hereinafter, each component constituting the composition will be described.

<Diene rubber>
Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and chloroprene rubber. (CR) etc. can be mentioned. These rubber components can be used alone or in combination of two or more.

  Among these rubbers, natural rubber and styrene-butadiene copolymer rubber are particularly preferable. The diene rubber includes 40 to 60 parts by mass of natural rubber and 60 to 40 parts by mass of styrene. It is preferably formed with a butadiene copolymer rubber. In the combination within this range, the adhesiveness with the EPDM rubber composition layer 2 is particularly improved.

(Natural rubber)
The natural rubber is a polymer having a structure in which cis-1,4-polyisoprene is bonded to the head and tail, and a commonly used natural rubber can be used.

(Styrene-butadiene copolymer rubber)
The styrene-butadiene copolymer rubber may be emulsion polymerization or solution polymerization. Although it does not specifically limit as styrene-butadiene copolymer rubber, It is preferable that a styrene content is 20 to 35 mass%. Moreover, it is preferable that the Mooney viscosity measured with a 100 degreeC sample is 30-60.

<Resorcinol>
Resorcinol has a function of accelerating the curing reaction of the rubber composition by functioning as a methylene acceptor in the rubber composition. The amount of resorcinol added is preferably 3 to 6 parts by mass with respect to 100 parts by mass of the diene rubber.

<Hexamethylenetetramine>
Hexamethylenetetramine has a function of accelerating the curing reaction of the rubber composition by functioning as a methylene donor in the rubber composition. The amount of hexamethylenetetramine added is preferably 2 parts by mass or more and 4.5 parts by mass or less with respect to 100 parts by mass of the diene rubber.

  Resorcinol and hexamethylenetetramine are blended in a combination within the above range to improve the adhesion between the vulcanized diene rubber layer and the EPDM rubber layer.

<Silica>
Silica is a kind of inorganic filler added to the rubber composition. Examples of the silica include, but are not limited to, crystalline silica, precipitated silica, amorphous silica (for example, high-temperature treated silica), fumed silica, calcined silica, precipitated silica, pulverized silica, and fused silica. it can.

  The addition amount of silica is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the diene rubber. In the addition amount within this range, the adhesion between the vulcanized EPDM rubber layer and the diene rubber layer 3 is improved by blending into the diene rubber composition layer together with resorcinol and hexamethylenetetramine.

<Other additives>
The diene rubber composition may be blended with other additives depending on the use of the laminate 1. Other additives include, for example, fillers, plasticizers, softeners, anti-aging agents, organic activators, antioxidants, antistatic agents, flame retardants, vulcanizing agents, vulcanization accelerators, vulcanization delays. Agents and adhesion aids.

  The same additives as those used in the EPDM rubber composition can be used as the above-mentioned various additives. However, as for the vulcanization accelerator, in addition to those mentioned in the EPDM rubber composition, sulfenamide-based and thiourea-based vulcanization accelerators can be used. Agents can be used.

  Examples of the sulfenamide vulcanization accelerator include N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N- (tert-butyl) -2-benzothiazole sulfenamide (BBS), N-oxydiethylene- Examples include 2-benzothiazolylsulfenamide.

  Examples of thiourea vulcanization accelerators include 2-imidazoline-2-thiol (EU), N, N′-diethylthiourea (DEU), N, N′-dibutylthiourea (DBTU), trimethylthiourea (TMU), and the like. Can be mentioned.

[Vulcanized rubber products]
By vulcanizing the laminate 1 illustrated in FIG. 1, the EPDM rubber composition layer 2 becomes an EPDM rubber layer, the diene rubber composition layer 3 becomes a diene rubber layer, and both rubber layers are crosslinked and bonded. A rubber laminate, that is, a vulcanized rubber product is obtained. The vulcanization method will be described later.

[Conveyor belt]
The conveyor belt has at least a part of a rubber laminate obtained by vulcanization of the laminate 1, that is, a vulcanized rubber product.

[Method of manufacturing vulcanized rubber products]
<Lamination process>
The vulcanized rubber product is prepared by, for example, a method in which the EPDM rubber composition layer 2 and the diene rubber composition layer 3 having the above composition are formed by kneading and extrusion, and then bonded together, or in one continuous production line. The other composition layer can be produced by directly extruding the composition layer from the extruder on the composition layer thus formed.

  For the kneading of the raw materials, a usual method using a roll, a kneader, a Banbury mixer or the like can be adopted. The kneaded raw material can be formed into, for example, a sheet by a normal method using a roll or the like.

<Vulcanization process>
The laminate 1 of the EPDM rubber composition layer 2 and the diene rubber composition layer 3 is vulcanized by an ordinary vulcanization method so that the interfaces of both layers are bonded.

  The vulcanization is carried out by heating in the presence of a vulcanizing agent. The vulcanization temperature is preferably 160 ° C. or higher and 175 ° C. or lower, and the vulcanization time is preferably 10 minutes or longer and 60 minutes or shorter. Within this range, a rubber laminate having excellent adhesion between the EPDM rubber layer and the diene rubber layer can be obtained.

  Further, pre-vulcanization or preliminary vulcanization may be performed by irradiating an electron beam before vulcanization.

  EPDM rubber composition layer 2 and diene rubber composition layer 3 adjusted at a predetermined blending rate are laminated and vulcanized to provide EPDM excellent in heat resistance, weather resistance, ozone resistance, and chemical resistance It is possible to obtain a rubber laminate, that is, a vulcanized rubber product, that can satisfy the demand for cost reduction while utilizing the advantages of the rubber layer.

  By using the vulcanized rubber product obtained as described above for at least a part of the conveyor belt, a heat-resistant belt excellent in weather resistance, ozone resistance and chemical resistance in addition to heat resistance is realized at low cost. be able to.

  In the above embodiment, the case where the vulcanized rubber product obtained by vulcanizing the laminated body is a conveyor belt has been described as an example. However, the vulcanized rubber product obtained from the laminated body according to the present invention is an EPDM rubber. It can be widely used in fields where inexpensive materials are required while taking advantage of its heat resistance, weather resistance, ozone resistance, chemical resistance, and the like.

  Moreover, since the vulcanized rubber product obtained from the laminated body according to the present embodiment includes a diene rubber layer, it also has oil resistance that cannot be obtained only with EPDM rubber.

  Hereinafter, the composition according to the present embodiment will be specifically described with reference to examples. However, the composition according to the present embodiment is not limited to these.

[Manufacture of laminates]
<Production of EPDM rubber composition>
The components shown in Table 1 were blended in the blending amounts (parts by mass) shown in the same table, and these were uniformly kneaded using a Banbury mixer to prepare EPDM rubber compositions A1 to A3. Table 1 also shows the results of measuring the tensile strength (TB), elongation at break (EB), and tearing strength (TR) for the test pieces in which the obtained EPDM rubber compositions A1 to A3 were formed into a sheet shape by an extruder. Indicated.

The detail of each component described in Table 1 is as follows.
-EPDM: EPDM rubber, trade name "EPT4045M", manufactured by Mitsui Chemicals, Inc.-Resorcinol: trade name "RESORCINOL", manufactured by Sumitomo Chemical Co., Ltd.-Hexamethylenetetramine: trade name "Sunseller HT-PO", Sanshin Chemical Industries Company-made carbon black: Trade name “Seast N”, Tokai Carbon Co., Ltd. • Zinc flower: Vulcanization accelerator, Trade name “Zinc flower No. 3”, Shodo Chemical Co., Ltd., stearic acid: Trade name "Stearic acid YR", manufactured by Nippon Oil & Fats Co., Ltd./Silica: Trade name "Nipp seal AQ", manufactured by Tosoh Silica Co., Ltd., aroma oil: Trade name "A-OMIX", manufactured by Sankyo Oil Chemical Co., Ltd. Sulfur accelerator: Trade name “Noxeller DM-PO”, manufactured by Ouchi Shinsei Chemical Co., Ltd. ・ Sulfur: vulcanizing agent, oil-treated sulfur, manufactured by Hosoi Chemical Co., Ltd.

<Manufacture of diene rubber composition>
The components shown in Table 2 were blended in the blending amounts (parts by mass) shown in the same table, and these were uniformly kneaded using a Banbury mixer to prepare diene rubber compositions B1 to B5. Table 2 also shows the results of measuring the tensile strength (TB), elongation at break (EB), and tearing strength (TR) for the test pieces in which the obtained compositions B1 to B5 were formed into a sheet shape by an extruder. It was.

The detail of each component described in Table 2 is as follows.
NR: Natural rubber “STR-20”, TECK BEE HANG CO. , LTD, SBR: Styrene-butadiene rubber, trade name “NIPOL 1502”, Nippon Zeon Co., Ltd., carbon black: trade name “Seast N”, Tokai Carbon Co., Ltd., zinc white: vulcanization accelerator, product Name “Zinc Hana 3”, manufactured by Shodo Chemical Co., Ltd., stearic acid: trade name “stearic acid YR”, manufactured by Nippon Oil & Fats Co., Ltd., silica: trade name “Nipp seal AQ”, manufactured by Tosoh Silica Corporation Resorcinol: Trade name “RESORCINOL”, manufactured by Sumitomo Chemical Co., Ltd. • Phenolic resin: Trade name “PP 5121”, Gunei Chemical Industry Co., Ltd. • Aroma oil: Trade name “A-OMIX”, Sankyo Oil Chemical Co., Ltd. -Hexamethylenetetramine: Trade name "Sunseller HT-PO", Sanshin Chemical Industry Co., Ltd.-Vulcanization accelerator: Trade name "Noxeller DM-P""Ouchi Shinko Chemical Industrial Co., Ltd. Sulfur: vulcanizing agent, oil processing sulfur, Hosoi Chemical Industry Co., Ltd.

<Vulcanization>
The obtained EPDM rubber compositions A1 to A3 and diene rubber compositions B1 to B5 were laminated and vulcanized for 45 minutes in a vulcanizer at 160 ° C. The combination of each composition is shown in Table 3. As shown in Table 3, the combination of EPDM rubber composition A1 and diene rubber composition B1 is Example 1, and the combination of EPDM rubber composition A2 and diene rubber composition B1 is Example 2, EPDM rubber composition. The combination of the product A3 and the diene rubber composition B1 is Comparative Example 1, the combination of the EPDM rubber composition A1 and the diene rubber composition B2 is Comparative Example 2, the EPDM rubber composition A2 and the diene rubber composition B2 The combination of EPDM rubber composition A3 and diene rubber composition B2 is comparative example 4, the combination of EPDM rubber composition A1 and diene rubber composition B3 is comparative example 5, and EPDM rubber composition Comparative Example 6 is a combination of the product A2 and the diene rubber composition B3, and Comparative Example 7 is a combination of the EPDM rubber composition A3 and the diene rubber composition B3. The combination of PDM rubber composition A1 and diene rubber composition B4 is Comparative Example 8, the combination of EPDM rubber composition A2 and diene rubber composition B4 is Comparative Example 9, EPDM rubber composition A3 and diene rubber composition Comparative Example 10 is a combination with the product B4, Comparative Example 11 is a combination of the EPDM rubber composition A1 and the diene rubber composition B5, and Comparative Example 12 is a combination of the EPDM rubber composition A2 and the diene rubber composition B5. A combination of EPDM rubber composition A3 and diene rubber composition B5 was used as Comparative Example 13.

[Mechanical evaluation]
The adhesion of the laminate obtained as described above was evaluated as follows. Note that “peeling force” and “rubber rupture state” were used as indices of adhesion as follows.

<Preparation of test piece>
A laminate in which an EPDM rubber composition layer having a thickness of 3 mm and a diene rubber composition layer having a thickness of 3 mm are laminated is placed in a mold having a length of 150 mm and a width of 150 mm and held at 160 ° C. for 45 minutes. Vulcanization was performed to obtain a vulcanized laminate (hereinafter referred to as vulcanized laminate or vulcanized product). A test piece (length 150 mm, width 25 mm) was obtained by cutting the vulcanized laminate in the length direction with a width of 25 mm.

<Peeling force>
The peel force was measured according to JIS K6256: 2006 “Adhesion test method for vulcanized rubber and thermoplastic rubber”. Table 4 shows the measurement results.

<Rubber fracture evaluation>
After measuring the peeling force, that is, after performing a peeling test, the state of rubber cutting was visually evaluated. The evaluation criteria are as follows.
-Rubber cut: A state in which the rubber is broken in the state of being laminated without peeling at the interface.
-Material failure rate: The percentage of one rubber layer remaining on the surface of the other rubber layer, expressed as a percentage (residual rate), in the sample where interfacial peeling occurred.

  Table 4 shows the evaluation results of the peel force and rubber breakage.

As is clear from Table 4, in Examples 1 and 2, the peel force was 11.3 N / mm, 10.8 N / mm, which was much higher than 5 N / mm, which is a guide for the peel force. Moreover, in Example 1 and Example 2, since interface peeling does not generate | occur | produce and it has reached the rubber piece, it turns out that the adhesiveness of an interface is favorable.
On the other hand, in Comparative Examples 1-13, the peeling force was a value less than 5 N / mm. In Comparative Example 1, although complete interfacial peeling did not occur, the material failure rate indicating the residual rate of one rubber layer on the other rubber layer surface at the interface was 15%. In Comparative Examples 2 to 13, complete interface peeling occurred, and the material destruction rate was 0%. From these results, it can be seen that the test pieces according to Comparative Examples 1 to 13 have insufficient adhesion at the interface.

DESCRIPTION OF SYMBOLS 1 Laminated body 2 EPDM rubber composition layer 3 Diene type rubber composition layer

Claims (5)

For 100 parts by mass of EPDM rubber,
3 to 6 parts by mass of resorcinol;
EPDM rubber composition layer containing 2 to 4.5 parts by mass of hexamethylenetetramine,
For 100 parts by mass of diene rubber,
3 to 6 parts by mass of resorcinol;
2 parts by mass or more and 4.5 parts by mass or less of hexamethylenetetramine;
A laminate obtained by laminating two layers of a diene rubber composition layer containing 1 part by mass or more and 20 parts by mass or less of silica. The diene rubber is
40 to 60 parts by weight of natural rubber,
60 parts by mass or less and 40 parts by mass or more of SBR (styrene-butadiene rubber);
The laminate according to claim 1, formed by:   A vulcanized rubber product obtained by vulcanizing the laminate according to claim 1.   A conveyor belt comprising the vulcanized rubber product according to claim 3. EPDM rubber composition layer containing resorcinol in an amount of 3 to 6 parts by mass and hexamethylenetetramine in an amount of 2 to 4.5 parts by mass with respect to 100 parts by mass of EPDM rubber, and 100 parts by mass of a diene rubber to parts, 3 mass parts or more 6 parts by weight of resorcinol, and 2 parts by weight and not more than 4.5 parts by weight of hexamethylenetetramine, diene rubber composition containing a 1 part by weight or more and 20 parts by weight of silica A stacking step of stacking two layers of a physical layer and obtaining a stack,
A vulcanization step of vulcanizing the laminate,
A method for producing a vulcanized rubber product.

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