Rubber composition and tire bladder

Abstract

To provide a rubber composition capable of obtaining a vulcanizate and a vulcanized molding having highly excellent elongation at break at a high temperature and highly excellent flexural fatigue resistance than conventional ones.SOLUTION: There is provided a rubber composition for a tire bladder which comprises a chloroprene-based rubber and a butyl-based rubber, wherein the chloroprene-based rubber includes a chloroprene-based rubber containing an unsaturated nitrile monomer unit, the rubber composition comprises a processing aid, carbon black, a plasticizer, a metal oxide and a vulcanization accelerator, the elongation at break of a vulcanized molding of the rubber composition measured at 190°C based on JIS K 6251 is 500% or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition and a tire bladder. [Background technology]

[0002] Taking advantage of their properties, rubber compositions are used in a wide range of fields, such as general industrial power transmission belts and conveyor belts, automotive air springs, anti-vibration rubber, hoses, wipers, immersion products, sealing parts, adhesives, boots, rubber-coated cloth, rubber rolls, etc. Furthermore, in recent years, the properties required of rubber parts have increased significantly.

[0003] Patent Document 1 discloses a rubber composition for tire vulcanization bladders, which is characterized by blending 1 to 20 parts by mass of an alkylphenol formaldehyde condensate and 0.1 to 10 parts by mass of a citraconic imide compound with 100 parts by mass of a rubber component containing 90 parts by mass or more of a butyl-based rubber consisting of a butyl rubber and / or a halogenated butyl rubber. Patent Document 2 discloses a rubber composition for bladders, which contains a rubber component containing a butyl-based rubber and zinc oxide having an average primary particle size of 15 to 190 nm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-098294 A [Patent Document 2] JP 2010-285525 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, vulcanizates and vulcanized molded articles obtained from conventional rubber compositions have room for improvement in elongation at break and resistance to flex fatigue at high temperatures, and specifically, sufficient studies have not been conducted on further improving the elongation at break in environments exceeding 100° C., and at the same time, further enhancing resistance to flex fatigue. In addition, for example, there have been cases where the vulcanizates and vulcanized molded articles cannot withstand use in extremely harsh environments where repeated stress is applied at high temperatures, such as in tire bladders.

[0006] The present invention has been made in consideration of the above circumstances, and provides a rubber composition for tire bladders that can give vulcanizates and vulcanized molded articles having highly excellent elongation at break at high temperatures and highly excellent flex fatigue resistance, which were difficult to achieve with conventional rubber compositions. [Means for solving the problem]

[0007] According to the present invention, there is provided a rubber composition for tire bladders, comprising a chloroprene-based rubber and a butyl-based rubber, wherein the chloroprene-based rubber comprises a chloroprene-based rubber containing unsaturated nitrile monomer units, and the rubber composition comprises a processing aid, carbon black, a plasticizer, a metal oxide, and a vulcanization accelerator, and the elongation at break of a vulcanized molded product of the rubber composition measured at 190°C based on JIS K 6251 is 500% or more.

[0008] As a result of intensive research, the present inventors have found that, in a rubber composition containing a chloroprene-based rubber and a butyl-based rubber as the rubber, by specifying the type of chloroprene-based rubber and adjusting the type and amount of rubber and the type and amount of additives so that the high-temperature elongation at break of a vulcanized molded article obtained from the rubber composition is a certain value or above, a rubber composition for tire bladders can be obtained which can give a vulcanizate and vulcanized molded article having highly excellent elongation at break at high temperatures and highly excellent flex fatigue resistance compared to conventional rubbers, and have thus completed the present invention.

[0009] Various embodiments of the present invention will be described below. The embodiments described below can be combined with each other. [1] A rubber composition for tire bladders, comprising a chloroprene-based rubber and a butyl-based rubber, wherein the chloroprene-based rubber comprises a chloroprene-based rubber containing an unsaturated nitrile monomer unit, and the rubber composition comprises a processing aid, carbon black, a plasticizer, a metal oxide, and a vulcanization accelerator, and wherein the elongation at break of a vulcanized molded product of the rubber composition measured at 190°C based on JIS K 6251 is 500% or more. [2] The rubber composition according to [1], wherein when a vulcanized molded product of the rubber composition is subjected to a De Mattia flexural fatigue test based on JIS K 6260 under conditions of a stroke of 58 mm, a speed of 300±10 rpm, and 23°C, the number of flexural fatigue tests at which cracks occur is 2 million or more. [3] The rubber composition according to [1] or [2], wherein the rubber composition contains 1 to 30 parts by mass of a chloroprene-based rubber containing an unsaturated nitrile monomer unit per 100 parts by mass of rubber contained in the rubber composition. [4] The rubber composition according to any one of [1] to [3], wherein the vulcanization accelerator contains a compound having an alkylphenol structure, and the rubber composition contains 1 to 10 parts by mass of the compound having an alkylphenol structure per 100 parts by mass of rubber contained in the rubber composition. [5] The rubber composition according to any one of [1] to [4], wherein a vulcanized molded product of the rubber composition has a Type A durometer hardness of less than 68, as measured in accordance with JIS K 6253. [6] A tire bladder comprising a vulcanized molded product of the rubber composition according to any one of [1] to [5]. Effect of the Invention

[0010] According to the rubber composition of the present invention, it is possible to obtain a vulcanizate and a vulcanized molded article having a highly excellent elongation at break at high temperatures and a highly excellent resistance to flex fatigue compared to conventional products. Furthermore, the obtained vulcanizate and vulcanized molded article can be used as a member to be used in an extremely severe environment where stress is repeatedly applied at high temperatures, making use of their properties. Specifically, they can be used as a tire bladder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below by illustrating the embodiments of the present invention. The present invention is not limited by these descriptions. The features of the embodiments of the present invention described below can be combined with each other. In addition, each feature can be an invention independently.

[0012] 1. Rubber composition The rubber composition according to the present invention is a rubber composition containing a chloroprene-based rubber and a butyl-based rubber. The chloroprene rubber according to the present invention contains a chloroprene rubber containing an unsaturated nitrile monomer unit, and further contains a processing aid, carbon black, a plasticizer, a metal oxide, and a vulcanization accelerator. In addition, the elongation at break of a vulcanized molded product of the rubber composition measured at 190° C. based on JIS K 6251 is 500% or more. The rubber composition of the present invention contains a chloroprene-based rubber and a butyl-based rubber as rubber, and by specifying the type of chloroprene-based rubber and adjusting the type and amount of rubber and the types and amounts of additives, specifically, the types and amounts of processing aids, carbon black, plasticizers, metal oxides, and vulcanization accelerators, so that the high-temperature elongation at break of a vulcanized molded product obtained from the rubber composition is a certain value or higher, the rubber composition is a rubber composition for tire bladders that can give vulcanizates and vulcanized molded products having highly excellent elongation at break at high temperatures and highly excellent flex fatigue resistance compared to conventional rubber compositions.

[0013] 1.1 Chloroprene rubber The chloroprene rubber according to the present invention refers to a rubber containing a chloroprene polymer having chloroprene (2-chloro-1,3-butadiene) as a monomer unit (monomer unit = structural unit). Examples of the chloroprene polymer include a chloroprene homopolymer and a chloroprene copolymer (a copolymer of chloroprene and a monomer copolymerizable with chloroprene). The polymer structure of the chloroprene polymer is not particularly limited.

[0014] In addition, commercially available 2-chloro-1,3-butadiene may contain a small amount of 1-chloro-1,3-butadiene as an impurity. 2-chloro-1,3-butadiene containing such a small amount of 1-chloro-1,3-butadiene can also be used as the chloroprene monomer of this embodiment.

[0015] The chloroprene rubber according to the present invention contains a chloroprene rubber containing an unsaturated nitrile monomer unit. The rubber composition according to the present invention uses a chloroprene rubber containing an unsaturated nitrile monomer unit in combination with a butyl rubber, and further adjusts the types and amounts of other additives so that the elongation at break at high temperatures is a certain value or more, thereby making it possible to highly improve the elongation at break at high temperatures and the flex fatigue resistance.

[0016] The chloroprene rubber according to the present invention may contain one or more types of chloroprene rubber. The chloroprene rubber according to one embodiment of the present invention may contain a chloroprene rubber containing one or more unsaturated nitrile monomer units. The chloroprene rubber according to one embodiment of the present invention may further contain a chloroprene rubber that does not contain one or more unsaturated nitrile monomer units.

[0017] The chloroprene-based rubber according to one embodiment of the present invention (chloroprene-based rubber containing unsaturated nitrile monomer units and chloroprene-based rubber not containing unsaturated nitrile monomer units) may also have monomer units derived from monomers other than chloroprene monomers and unsaturated nitrile monomers. The monomers other than chloroprene monomers and unsaturated nitrile monomers are not particularly limited as long as they can be copolymerized with chloroprene monomers, and examples of such monomers include esters of (meth)acrylic acid (methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.), hydroxyalkyl (meth)acrylates (2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.), 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, and sulfur. As an example, the chloroprene-based rubber according to an embodiment of the present invention may include 2,3-dichloro-1,3-butadiene monomer units.

[0018] In the chloroprene rubber containing the unsaturated nitrile monomer unit according to one embodiment of the present invention, when the chloroprene rubber containing the unsaturated nitrile monomer unit is taken as 100 mass%, the content of the unsaturated nitrile monomer unit can be 1 to 25 mass%, preferably 1 to 20 mass%, and more preferably 5 to 20 mass%. The content of the unsaturated nitrile monomer unit in the chloroprene rubber containing the unsaturated nitrile monomer unit according to one embodiment of the present invention is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 mass%, and may be within any two of the numerical values ​​exemplified here. By setting the content of the unsaturated nitrile monomer unit in the rubber composition within the above numerical range, it is easier to improve the elongation at break at high temperature and the flex fatigue resistance.

[0019] When the chloroprene rubber according to one embodiment of the present invention contains two or more kinds of chloroprene rubbers, the content based on the total amount of the unsaturated nitrile monomer units contained in the two or more chloroprene rubbers is preferably within the above-mentioned numerical range, based on the total 100 mass% of the two or more chloroprene rubbers contained in the rubber composition. That is, the chloroprene rubber according to one embodiment of the present invention has a content of the unsaturated nitrile monomer units in the chloroprene rubber contained in the rubber composition of 1 to 25 mass% relative to 100 mass% of the chloroprene rubber contained in the rubber composition, and the content of the unsaturated nitrile monomer units may be within a range between any two of the numerical values ​​exemplified above. Also, the chloroprene rubber according to one embodiment of the present invention has a content of the acrylonitrile monomer units in the chloroprene rubber contained in the rubber composition of 1 to 25 mass% relative to 100 mass% of the chloroprene rubber contained in the rubber composition, and the content of the acrylonitrile monomer units may be within a range between any two of the numerical values ​​exemplified above.

[0020] Examples of the unsaturated nitrile include acrylonitrile, methacrylonitrile, ethacrylonitrile, and phenylacrylonitrile. The unsaturated nitrile may be used alone or in combination of two or more. The unsaturated nitrile preferably contains acrylonitrile from the viewpoint of easily obtaining excellent moldability and from the viewpoint of easily obtaining excellent breaking strength, breaking elongation, hardness, tear strength, and oil resistance in the vulcanized molded product.

[0021] The content of unsaturated nitrile monomer units contained in chloroprene rubber can be calculated from the content of nitrogen atoms in the chloroprene rubber. Specifically, the content of nitrogen atoms in 100 mg of chloroprene rubber can be measured using an elemental analyzer (Sumigraph 220F: manufactured by Sumika Chemical Analysis Center Co., Ltd.), and the content of structural units derived from unsaturated nitrile monomers can be calculated. Elemental analysis can be performed under the following conditions. For example, the electric furnace temperatures are set to 900°C for the reactor, 600°C for the reduction furnace, 70°C for the column, and 100°C for the detector, and oxygen is flowed at 0.2 mL / min as the combustion gas and 80 mL / min as the carrier gas. A calibration curve can be created using aspartic acid (10.52%) with a known nitrogen content as a standard substance.

[0022] The chloroprene rubber according to one embodiment of the present invention preferably contains 75 to 100 mass% of chloroprene monomer units, and more preferably 80 to 100 mass%, when the chloroprene rubber is taken as 100 mass%. The content of the chloroprene monomer units in the chloroprene rubber may be, for example, 75, 80, 85, 90, 95, 99, or 100 mass%, and may be within a range between any two of the numerical values ​​exemplified here. By setting the content of the chloroprene monomer units within the above numerical range, a rubber composition can be obtained that can give a molded product having an excellent balance of hardness, tensile strength, and cold resistance.

[0023] The chloroprene rubber according to one embodiment of the present invention may contain 0 to 20% by mass of monomer units other than the chloroprene monomer unit and the unsaturated nitrile monomer unit, when the chloroprene rubber is taken as 100% by mass. The content of the monomer units other than the chloroprene monomer unit and the unsaturated nitrile monomer unit in the chloroprene rubber may be, for example, 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, or 20% by mass, and may be within a range between any two of the numerical values ​​exemplified here. By adjusting the copolymerization amount of the monomer other than the chloroprene monomer and the unsaturated nitrile monomer to the above range, the effect of copolymerizing these monomers can be expressed without impairing the properties of the obtained rubber composition.

[0024] When the rubber composition according to one embodiment of the present invention contains two or more types of chloroprene-based rubber, it is preferable that the content based on the total amount of each monomer unit contained in the two or more types of chloroprene-based rubbers is within the above numerical range relative to 100 mass % in total of the two or more types of chloroprene-based rubbers contained in the rubber composition.

[0025] The chloroprene polymer (such as a chloroprene homopolymer or a chloroprene copolymer) contained in the chloroprene rubber according to the present invention may be a sulfur-modified chloroprene polymer, a mercaptan-modified chloroprene polymer, a xanthogen-modified chloroprene polymer, a dithiocarbonate-based chloroprene polymer, a trithiocarbonate-based chloroprene polymer, a carbamate-based chloroprene polymer, or the like.

[0026] 1.2 Chloroprene rubber manufacturing method The method for producing the chloroprene rubber according to the present invention is not particularly limited, but the rubber can be obtained by a production method including an emulsion polymerization step of emulsion-polymerizing raw material monomers including a chloroprene monomer. In the emulsion polymerization step according to one embodiment of the present invention, raw material monomers including chloroprene monomers are emulsion-polymerized using an appropriate amount of an emulsifier, a dispersant, a catalyst, a chain transfer agent, etc., and when the target final conversion rate is reached, a polymerization terminator is added to obtain a latex including a chloroprene-based polymer including chloroprene monomer units. Next, unreacted monomers can be removed from the polymerization liquid obtained by the emulsion polymerization step. The method is not particularly limited, and examples of the method include a steam stripping method. Thereafter, the pH is adjusted, and a chloroprene rubber including a chloroprene-based polymer is obtained through conventional processes such as freeze coagulation, water washing, and hot air drying.

[0027] The polymerization initiator used in emulsion polymerization is not particularly limited, and any known polymerization initiator generally used in emulsion polymerization of chloroprene can be used. Examples of the polymerization initiator include organic peroxides such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and t-butyl hydroperoxide.

[0028] The emulsifier used in emulsion polymerization is not particularly limited, and any known emulsifier generally used in emulsion polymerization of chloroprene can be used. Examples of the emulsifier include alkali metal salts of saturated or unsaturated fatty acids having 6 to 22 carbon atoms, alkali metal salts of rosin acid or disproportionated rosin acid (e.g., potassium rosinate), and alkali metal salts of formalin condensates of β-naphthalenesulfonic acid (e.g., sodium salt).

[0029] The molecular weight regulator used in emulsion polymerization is not particularly limited, and any known molecular weight regulator generally used in emulsion polymerization of chloroprene can be used, such as mercaptan compounds, xanthogen compounds, dithiocarbonate compounds, trithiocarbonate compounds, and carbamate compounds. As the molecular weight regulator for the chloroprene rubber according to one embodiment of the present invention, xanthogen compounds, dithiocarbonate compounds, trithiocarbonate compounds, and carbamate compounds can be suitably used.

[0030] The polymerization temperature and the final conversion rate of the monomer are not particularly limited, but the polymerization temperature may be, for example, 0 to 50° C. or 10 to 50° C. The polymerization may be carried out so that the final conversion rate of the monomer falls within the range of 40 to 95% by mass. In order to adjust the final conversion rate, a polymerization terminator that terminates the polymerization reaction may be added to terminate the polymerization when the desired conversion rate is reached.

[0031] The polymerization terminator is not particularly limited, and any known polymerization terminator generally used in emulsion polymerization of chloroprene can be used. Examples of the polymerization terminator include phenothiazine (thiodiphenylamine), 4-t-butylcatechol, 2,2-methylenebis-4-methyl-6-t-butylphenol, etc.

[0032] The chloroprene rubber according to one embodiment of the present invention can be obtained, for example, by removing unreacted monomers by a steam stripping method, adjusting the pH of the latex, and then passing through conventional steps such as freeze coagulation, water washing, and hot air drying.

[0033] Chloroprene rubbers are classified into mercaptan-modified, xanthogen-modified, sulfur-modified, dithiocarbonate-based, trithiocarbonate-based and carbamate-based types depending on the type of molecular weight modifier.

[0034] 1.3 Butyl rubber The rubber composition according to the present invention may contain a butyl-based rubber. In the present invention, the butyl-based rubber means a rubber containing a butyl-based polymer containing a monomer unit derived from isobutylene. That is, the butyl-based rubber contains an isobutylene monomer unit. The butyl-based rubber according to one embodiment of the present invention may contain an isobutylene monomer unit and an isoprene monomer unit, that is, may contain a copolymer obtained by copolymerizing raw monomers containing isobutylene and isoprene. The butyl-based rubber may contain 0.5 to 10 mol% of the isoprene monomer unit. The content of the isoprene monomer unit indicates the content ratio (mol%) of the isoprene monomer unit when the total of the number of moles of the isobutylene monomer unit, the number of moles of the isoprene monomer unit, and the number of moles of other monomer units, if contained, contained in the butyl-based rubber is 100 mol%.

[0035] The butyl-based rubber according to the present invention may contain one or more kinds of butyl-based rubber. The butyl-based rubber according to one embodiment of the present invention may contain one or more kinds selected from regular butyl rubber (non-halogenated butyl rubber) and halogenated butyl rubber. Examples of the halogenated butyl rubber include chlorinated butyl rubber and brominated butyl rubber. The halogenated butyl rubber may contain 0.1 to 5.0 mass% of halogen when the halogenated butyl rubber is taken as 100 mass%, and is preferably 0.5 to 3.0 mass%. The halogen content in the halogenated butyl rubber may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0036] The butyl rubber according to one embodiment of the present invention preferably contains 75 to 100 mass % of isobutylene monomer units, and more preferably 80 to 100 mass %, when the butyl rubber is taken as 100 mass %. The content of chloroprene monomer units in the butyl rubber is, for example, 75, 80, 85, 90, 95, 99, or 100 mass %, and may be within a range between any two of the numerical values ​​exemplified here.

[0037] 1.4 Other rubbers The rubber composition according to one embodiment of the present invention may contain other rubbers besides chloroprene-based rubber and butyl-based rubber. Examples of other rubbers include natural rubber (NR), hydrogenated acrylonitrile butadiene rubber (H-NBR), acrylonitrile butadiene rubber (NBR), chlorosulfonated polyethylene (CSM), ethylene-propylene-diene rubber (EPDM), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), epoxidized natural rubber (ENR), acrylonitrile butadiene rubber (NBR), styrene-isoprene-butadiene copolymer rubber (SIBR), epichlorohydrin rubber (CO), acrylic rubber (ACM), urethane rubber (U), silicone rubber (Q), fluororubber (FKM), and polysulfide rubber (T). The rubber composition according to one embodiment of the present invention may contain chloroprene-based rubber, butyl-based rubber, and natural rubber.

[0038] 1.5 Rubber content The rubber composition according to the present invention preferably contains 1 to 30 parts by mass of chloroprene rubber, based on 100 parts by mass of rubber contained in the rubber composition. The amount of chloroprene rubber is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, or 30 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0039] The rubber composition according to the present invention preferably contains 1 to 30 parts by mass of a chloroprene rubber containing an unsaturated nitrile monomer unit, based on 100 parts by mass of the rubber contained in the rubber composition. The content of the chloroprene rubber containing an unsaturated nitrile monomer unit is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, or 30 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0040] The rubber composition according to the present invention preferably contains 70 to 99 parts by mass of butyl rubber when the rubber contained in the rubber composition is taken as 100 parts by mass. The content of the butyl rubber is, for example, 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0041] The rubber composition according to the present invention preferably contains 70 to 100 parts by mass, more preferably 90 to 100 parts by mass, of the chloroprene rubber and the butyl rubber in total, relative to 100 parts by mass of the rubber contained in the rubber composition. The total content of the chloroprene rubber and the butyl rubber is, for example, 70, 75, 80, 85, 90, 95, or 100 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here. The rubber composition according to the present invention may contain 0 to 30 parts by mass, or 0 to 10 parts by mass, of a rubber other than the chloroprene rubber and the butyl rubber, relative to 100 parts by mass of the rubber contained in the rubber composition.

[0042] 1.6 Vulcanizing agents and vulcanization accelerators The rubber composition according to the present invention contains a vulcanization accelerator. The rubber composition according to the present invention may also contain a vulcanizing agent. The types of vulcanizing agent and vulcanization accelerator are not particularly limited as long as they do not impair the effects of the present invention. The vulcanizing agent and vulcanization accelerator preferably contribute to the vulcanization of chloroprene-based rubber, preferably contribute to the vulcanization of butyl-based rubber and / or chloroprene-based rubber, and more preferably contribute to the vulcanization of butyl-based rubber and chloroprene-based rubber.

[0043] One or more vulcanizing agents can be freely selected and used. Examples of the vulcanizing agent include sulfur. When the rubber composition according to one embodiment of the present invention contains regular butyl rubber as the butyl rubber, it can contain sulfur. The content of the vulcanizing agent can be 0 to 10.0 parts by mass, preferably 0 to 5.0 parts by mass, for example, 0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7, 8, 9, 10.0 parts by mass, relative to 100 parts by mass of the rubber contained in the rubber composition, and may be within a range between any two of the numerical values ​​exemplified here. The rubber composition according to the present invention may not contain a vulcanizing agent.

[0044] The rubber composition according to the present invention contains a vulcanization accelerator. The rubber composition according to one embodiment of the present invention may contain 1.0 to 10.0 parts by mass of the vulcanization accelerator relative to 100 parts by mass of the rubber contained in the rubber composition, and preferably 3.0 to 8.0 parts by mass. The content of the vulcanization accelerator is, for example, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0045] The vulcanization accelerator according to one embodiment of the present invention preferably contains a compound having an alkylphenol structure. The compound having an alkylphenol structure is a compound having a structure derived from an alkylphenol. The compound having an alkylphenol structure can have a function of promoting the formation of a three-dimensional network between rubbers. It is preferable that the compound having an alkylphenol structure itself is incorporated into the three-dimensional network, and it is more preferable that it forms a crosslinked structure that bonds rubbers together. As described above, when the rubber composition according to the present invention contains a chloroprene rubber containing an unsaturated nitrile monomer unit and further contains a compound having an alkylphenol structure, it is presumed that the unsaturated nitrile monomer unit contained in the chloroprene rubber reacts with the compound having an alkylphenol structure having an alkylphenol structure to form a bond, thereby further improving the elongation at break and flex fatigue resistance at high temperatures. The compound having an alkylphenol structure does not include compounds having an alkylphenol structure that are generally used as antioxidants.

[0046] The rubber composition according to one embodiment of the present invention may contain 1 to 10 parts by mass, and preferably 3 to 8 parts by mass, of a compound having an alkylphenol structure relative to 100 parts by mass of rubber contained in the rubber composition. The content of the compound having an alkylphenol structure is, for example, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0047] The compound having an alkylphenol structure preferably has a chemical structure represented by the following formula (1). [ka]

[0048] In formula (1), R 1 and R 2are S k , C.H. 2 and C.H. 2 OCH 2 It is one selected from the above. k is an integer from 1 to 8.

[0049] Y 1 and Y 2 Y is any one selected from hydrogen, halogen, and a hydrocarbon group which may be substituted with halogen. 1 and Y 2 can be hydrogen or halogen. The hydrocarbon group which may be substituted with halogen means an unsubstituted hydrocarbon group and a hydrocarbon group in which one or more hydrogen atoms contained in the hydrocarbon group are substituted with halogen. The number of carbon atoms in the hydrocarbon group can be 2 to 20, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and may be within a range between any two of the numerical values ​​exemplified here. The hydrocarbon group can be an alkyl group, a vinyl group, or an aryl group, and can be an alkyl group, and can be a linear alkyl group or a branched alkyl group. The halogen can be any one selected from fluorine, chlorine, bromine, and elements, and preferably contains bromine.

[0050] Z 1 Z is a hydrocarbon group which may be substituted with halogen. 1may contain a hydrocarbon group having 2 to 20 carbon atoms and optionally substituted with halogen. The number of carbon atoms in the hydrocarbon group may be 2 to 20, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, and may be within a range between any two of the numerical values ​​exemplified here. The hydrocarbon group may be an alkyl group, a vinyl group, or an aryl group, and may be an alkyl group, and may be a linear or branched alkyl group. Examples of the alkyl group include an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a tert-pentyl group, and a 1,1-dimethyl-3,3-dimethylpropyl group. The halogen may be any one selected from fluorine, chlorine, bromine and iodine, and preferably includes bromine.

[0051] The compound having an alkylphenol structure preferably has a structure capable of forming a bond with rubber at at least one end, and preferably has a structure capable of forming a bond with rubber at both ends. As an example, the compound having an alkylphenol structure preferably contains a chemical structure represented by the following formula (2) at at least one end. The compound having an alkylphenol structure preferably contains a structure represented by the following formula (2) at both ends. The structure represented by the following formula (2) is a structure represented by the formula (1) R 1 and / or R 2 can be combined with

[0052] [ka]

[0053] In formula (2), X 1 is any one selected from OH and halogen. The halogen can be any one selected from fluorine, chlorine, bromine, and elements, and preferably includes bromine. Y 3 and Y4 is any one selected from hydrogen, halogen, and a hydrocarbon group which may be substituted with halogen. Specifically, Y 1 and Y 2 The same can be said. Z 2 Z is a hydrocarbon group which may be substituted with halogen. 2 may contain a hydrocarbon group having 2 to 20 carbon atoms and optionally substituted with halogen, specifically, Z 1 The same can be said.

[0054] The compound having an alkylphenol structure can have two or more alkylphenol structures in one molecule. The number of alkylphenol structures that the compound having an alkylphenol structure has in one molecule can be 2 to 10, for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10, and may be within a range between any two of the numerical values ​​exemplified here. The alkylphenol structure can be represented by the following formula (3).

[0055] [ka]

[0056] In formula (3), R 3 are S k , C.H. 2 and C.H. 2 OCH 2 It is one selected from the above. k is an integer from 1 to 8. Y 5 and Y 6 is any one selected from hydrogen, halogen, and a hydrocarbon group which may be substituted with halogen. Specifically, Y 1 and Y 2 The same can be said. Z 3 Z is a hydrocarbon group which may be substituted with halogen. 3may contain a hydrocarbon group having 2 to 20 carbon atoms and optionally substituted with halogen, specifically, Z 1 The same can be said.

[0057] The compound having an alkylphenol structure may have one type of alkylphenol structure or may have two or more types of alkylphenol structures. When the compound having an alkylphenol structure has one type of alkylphenol structure, the compound having an alkylphenol structure can be represented by the following formula (4).

[0058] [ka]

[0059] In formula (4), R 4 and R 5 are S k , C.H. 2 and C.H. 2 OCH 2 It is one selected from the above. k is an integer from 1 to 8. X 2 and X 3 is any one selected from OH and halogen. 2 and X 3 X 1 The same can be said. Y 7 , Y 8 , Y 9 , Y 10 , Y 11 , and Y 12 is any one selected from hydrogen, halogen, and a hydrocarbon group which may be substituted with halogen. Specifically, Y 1 and Y 2 The same can be said. Z 4 , Z 5 , and Z 6 Z is a hydrocarbon group which may be substituted with halogen. 4 , Z 5 , and Z 6may contain a hydrocarbon group having 2 to 20 carbon atoms and optionally substituted with halogen, specifically, Z 1 The same can be said. n can be 0 or more, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or within a range between any two of the numbers exemplified herein.

[0060] The compound having an alkylphenol structure may have two or more kinds of alkylphenol structures. When the compound having an alkylphenol structure has a plurality of kinds of alkylphenol structures, the compound having an alkylphenol structure may have a structure in which a plurality of kinds of alkylphenol structures are randomly arranged. As an example, when the compound having an alkylphenol structure has two kinds of alkylphenol structures, that is, when the compound having an alkylphenol structure has an alkylphenol structure X and an alkylphenol structure Y, the compound having an alkylphenol structure may have a structure in which the alkylphenol structure X and the alkylphenol structure Y are randomly arranged. The compound having an alkylphenol structure may have a structure other than the structure represented by formula (1) and formula (2), and may have a repeating unit other than the alkylphenol structure. The compound having an alkylphenol structure may have a content of the structure other than the structure represented by formula (1) and formula (2) relative to 100 mass% of the compound having an alkylphenol structure, for example, 0, 10, 20, 30, 40, 50 mass%, and may be within a range between any two of the numerical values ​​exemplified here. The compound having an alkylphenol structure may be composed only of the structure represented by formula (1) and formula (2).

[0061] The compound having an alkylphenol structure may be any one selected from a condensation product of an alkylphenol and formaldehyde, a condensation product of an alkylphenol and a sulfide, and halogenated modifications thereof. The alkylphenol may include an alkylphenol having an alkyl group having a carbon number of 2 to 20. The alkyl group may be a linear alkyl group or a branched alkyl group. The number of sulfur atoms in the sulfide can be 1 to 8, for example, 1, 2, 3, 4, 5, 6, 7, or 8, and may be within a range between any two of the numerical values ​​exemplified here. The compound having an alkylphenol structure may contain a halogen. When the compound having an alkylphenol structure contains a halogen, the halogen concentration of the compound having an alkylphenol structure is preferably 1 to 10 mass%, more preferably 2 to 7 mass%, and can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mass%, and may be within a range between any two of the numerical values ​​exemplified here. The compound having an alkylphenol structure preferably has a softening point of 120°C or lower, and more preferably 70 to 100°C.

[0062] The rubber composition according to one embodiment of the present invention may contain a vulcanization accelerator other than the compound having an alkylphenol structure, or may not contain a vulcanization accelerator other than the compound having an alkylphenol structure. Examples of vulcanization accelerators other than the compound having an alkylphenol structure include thiourea-based compounds, 3-methyl-thiazolidine-2-thione, thiadiazole-based compounds, thiuram-based compounds, thiazole-based compounds, and sulfenamide-based compounds. In the rubber composition according to one embodiment of the present invention, the content of the vulcanization accelerator other than the compound having an alkylphenol structure (for example, the total content of thiourea-based compounds, 3-methyl-thiazolidine-2-thione, thiadiazole-based compounds, thiuram-based compounds, thiazole-based compounds and sulfenamide-based compounds) can be 5.0 parts by mass or less, and can be less than 1.0 part by mass. The content of the vulcanization accelerator other than the compound having an alkylphenol structure is, for example, 0, 0.5, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0% by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0063] 1.7 Metal oxides The rubber composition according to one embodiment of the present invention contains a metal oxide. The metal oxide can function as a vulcanizing agent and / or an acid acceptor. Examples of the metal oxide include zinc oxide, magnesium oxide, lead oxide, trimead tetroxide, iron trioxide, titanium dioxide, and calcium oxide. The metal oxide preferably contains at least one of zinc oxide and magnesium oxide, and may contain zinc oxide.

[0064] The rubber composition according to one embodiment of the present invention may contain at least 0.1 parts by mass of metal oxide relative to 100 parts by mass of rubber contained in the rubber composition, preferably 0.1 to 15.0 parts by mass, and more preferably 0.5 to 10.0 parts by mass. The content of the metal oxide is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, or 15.0 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0065] The rubber composition according to one embodiment of the present invention may contain zinc oxide. Zinc oxide can function as a vulcanizing agent and / or an acid acceptor. The rubber composition according to one embodiment of the present invention may contain 0.1 parts by mass or more of zinc oxide, preferably 0.1 to 10.0 parts by mass, and more preferably 0.5 to 5.0 parts by mass, per 100 parts by mass of rubber contained in the rubber composition. The content of zinc oxide is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0066] The rubber composition according to one embodiment of the present invention may contain a metal oxide other than zinc oxide. The metal oxide other than zinc oxide may function as an acid acceptor. The rubber composition according to one embodiment of the present invention may contain 0.1 to 10.0 parts by mass of the metal oxide other than zinc oxide, and more preferably 0.5 to 5.0 parts by mass, per 100 parts by mass of the rubber contained in the rubber composition. The content of the metal oxide other than zinc oxide may be, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 parts by mass, or may be within a range between any two of the numerical values ​​exemplified here.

[0067] 1.8 Plasticizers The rubber composition according to one embodiment of the present invention contains a plasticizer. The plasticizer is preferably a plasticizer compatible with chloroprene-based rubber, butyl-based rubber, and / or a vulcanizing agent, particularly a compound having an alkylphenol structure, and more preferably a plasticizer compatible with a vulcanizing agent, particularly a compound having an alkylphenol structure. Examples of the plasticizer include vegetable oils such as rapeseed oil and castor oil, phthalate-based plasticizers, DOS (dioctyl sebacate), DBS (dibutyl sebacate), DOA (dioctyl adipate), ester-based plasticizers, ether-ester-based plasticizers, thioether-based plasticizers, aromatic oils, naphthenic oils, and paraffinic oils. These can be used alone or in combination of two or more.

[0068] The rubber composition according to one embodiment of the present invention preferably contains vegetable oil and / or aromatic oil, and more preferably contains castor oil. The rubber composition according to one embodiment of the present invention preferably contains triacylglycerol having one or more hydroxy groups and a molecular weight of at least 500. The triacylglycerol may have one or more hydroxy groups, for example, 1, 2, or 3 hydroxy groups, and may be within a range between any two of the numerical values ​​exemplified here. The triacylglycerol can have a molecular weight of 500 or more, for example, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, or within a range between any two of the values ​​exemplified herein. An example of a triacylglycerol having one or more hydroxy groups and a molecular weight of 500 or more is castor oil, and the main component of castor oil is represented by the following formula.

[0069] [ka]

[0070] The rubber composition according to one embodiment of the present invention may contain more than 0 and 50 parts by mass or less of a plasticizer, and preferably 0.1 parts by mass or more, per 100 parts by mass of rubber contained in the rubber composition. The content of the plasticizer may be, for example, 0.1, 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts by mass, or may be within a range between any two of the numerical values ​​exemplified here. A rubber composition according to one embodiment of the present invention may contain, per 100 parts by mass of rubber contained in the rubber composition, 0.1 parts by mass or more of triacylglycerol having one or more hydroxy groups and a molecular weight of 500 or more. The content of triacylglycerol having one or more hydroxy groups and a molecular weight of 500 or more is, for example, 0, 0.1, 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0071] 1.9 Fillers The rubber composition according to one embodiment of the present invention may contain a filler. Examples of the filler include furnace carbon black such as SAF, ISAF, HAF, EPC, XCF, FEF, GPF, HMF, and SRF, modified carbon black such as hydrophilic carbon black, channel black, lamp black, thermal carbon such as FT and MT, acetylene black, ketjen black, silica, clay, talc, and calcium carbonate. The rubber composition according to one embodiment of the present invention may contain one or more types of fillers.

[0072] The rubber composition according to one embodiment of the present invention may contain a total of 20 to 90 parts by mass of the filler relative to 100 parts by mass of the rubber contained in the rubber composition, and preferably contains 35 to 80 parts by mass. The amount of the filler is, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here. In the rubber composition according to one embodiment of the present invention, the hardness of the vulcanizate and vulcanized molded article can be adjusted by containing the filler content within the above numerical range.

[0073] 1.10 Processing aids The rubber composition according to the present invention may further contain a processing aid. The processing aid is mainly added to improve processability, such as making the rubber composition easier to peel off from rolls, molding dies, extruder screws, etc. Examples of the processing aid include fatty acids such as stearic acid, paraffin-based processing aids such as polyethylene, fatty acid amides, petrolatum, factice, etc. The rubber composition according to one embodiment of the present invention may contain one or more types of processing aids.

[0074] The rubber composition according to the present invention may contain 0 to 15 parts by mass of a processing aid relative to 100 parts by mass of rubber contained in the rubber composition, and may also contain 1 to 10 parts by mass. The content of the processing aid is, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0075] 1.11 Other In addition to the above-mentioned components, the rubber composition according to the present invention may further contain components such as organic peroxides, silane coupling agents, co-crosslinking agents (e.g., maleimide-based compounds), stabilizers, flame retardants, and vulcanization retarders, as long as the effects of the present invention are not impaired. Examples of the antiaging agent and antioxidant include ozone antiaging agents, phenolic antiaging agents, amine antiaging agents, acrylate antiaging agents, waxes, and phosphorus antiaging agents. Examples of the amine antiaging agents include 4,4'-bis(α,α-dimethylbenzyl)diphenylamine and octylated diphenylamine. The rubber composition according to the present invention may contain 0.1 to 10 parts by mass of the antiaging agent and antioxidant in total, relative to 100 parts by mass of rubber contained in the rubber composition. The content of the antiaging agent and the antioxidant is, for example, 0, 0.1, 0.3, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0076] 2. Manufacturing method of rubber composition The rubber composition according to one embodiment of the present invention is obtained by kneading rubber and other necessary components at a temperature equal to or lower than the vulcanization temperature. The method for producing the rubber composition according to one embodiment of the present invention may include a mixing step of mixing rubber and other necessary components at a temperature equal to or lower than the vulcanization temperature. Examples of kneading devices include conventional kneading devices such as mixers, Banbury mixers, kneader mixers, and open rolls.

[0077] 3. Characteristics of rubber composition <Elongation at break of vulcanized molded body at high temperatures> The rubber composition of the present invention has a vulcanized molded product of the rubber composition having an elongation at break of 500% or more at 190°C measured in accordance with JIS K 6251. The elongation at break at 190°C is, for example, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650, 660, 670, 680, 690, or 700%, and may be within a range between any two of the numerical values ​​exemplified here.

[0078] The elongation at break at 190°C can be measured using a sample prepared by press-vulcanizing a rubber composition at 180°C for 20 minutes to produce a sheet-like vulcanized molding having a thickness of 2 mm, and molding the sheet-like vulcanized molding into a dumbbell-shaped No. 3 test piece, according to JIS K 6299. The elongation at break at 190°C can be measured according to JIS K 6251. In addition, the rubber composition according to one embodiment of the present invention preferably has the following properties.

[0079] According to the rubber composition of the present invention, by adjusting the type and amount of rubber and the type and amount of additives so that the high-temperature elongation at break of a vulcanized molded article obtained from the rubber composition is a certain value or more, it is possible to obtain a rubber composition that can give a vulcanized product and a vulcanized molded article having highly excellent elongation at break at high temperatures and highly excellent flex fatigue resistance compared to conventional products.

[0080] <Hardness of vulcanized molded body> In the rubber composition according to one embodiment of the present invention, the durometer hardness (type A) of a vulcanized molded product of the rubber composition, as defined by JIS K 6253, may be less than 68, and is preferably 55 to 67. The durometer hardness (type A) of the vulcanized molded product of the rubber composition may be, for example, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, or 67, and may be within a range between any two of the numerical values ​​exemplified here.

[0081] <Flexural fatigue resistance of vulcanized molded products> In the rubber composition according to one embodiment of the present invention, when a vulcanized molded product of the rubber composition is subjected to a De Mattia bending fatigue test under conditions of a stroke of 58 mm, a speed of 300±10 rpm, and room temperature based on JIS K 6260, the number of bending tests at the time when cracks occur is preferably 2 million or more. The number of bending tests at the time when cracks occur may be, for example, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, or 10 million, and may be within a range between any two of the numerical values ​​exemplified here.

[0082] The properties of the rubber composition can be values ​​obtained when the rubber composition is made into a vulcanized molded product under the conditions and methods described in the examples, and measured by the method described in the examples. The properties of the vulcanized molded product of the rubber composition can be controlled by adjusting the type and amount of the rubber composition. As an example, the flex fatigue resistance of the vulcanized molded product can be adjusted by specifying the type of chloroprene-based rubber, and adjusting the type and amount of rubber and the type and amount of additives so that the high-temperature elongation at break of the vulcanized molded product obtained from the rubber composition is a certain value or more. The hardness of the vulcanized molded product can be adjusted by specifying the type of chloroprene-based rubber, and adjusting the type and amount of rubber and the type and amount of additives so that the high-temperature elongation at break of the vulcanized molded product obtained from the rubber composition is a certain value or more, for example, by adjusting the type and amount of filler.

[0083] 4. Unvulcanized molded bodies, vulcanized bodies and vulcanized molded bodies The unvulcanized molded body according to one embodiment of the present invention uses the rubber composition according to one embodiment of the present invention, and is a molded body (molded product) of the rubber composition (unvulcanized state) according to one embodiment of the present invention. The manufacturing method of the unvulcanized molded body according to one embodiment of the present invention includes a step of molding the rubber composition (unvulcanized state) according to one embodiment of the present invention. The unvulcanized molded body according to one embodiment of the present invention is made of the rubber composition (unvulcanized state) according to one embodiment of the present invention.

[0084] A vulcanizate according to one embodiment of the present invention is a vulcanizate of the rubber composition according to one embodiment of the present invention. A method for producing a vulcanizate according to one embodiment of the present invention includes a step of vulcanizing the rubber composition according to one embodiment of the present invention.

[0085] The vulcanized molded article according to one embodiment of the present invention is a vulcanized molded article of the rubber composition according to one embodiment of the present invention. The vulcanized molded article according to one embodiment of the present invention uses the vulcanizate according to one embodiment of the present invention, and is a molded article (molded product) of the vulcanizate according to one embodiment of the present invention. The vulcanized molded article according to one embodiment of the present invention is made of the vulcanizate according to one embodiment of the present invention.

[0086] The vulcanized molded article according to one embodiment of the present invention can be obtained by molding a vulcanized product obtained by vulcanizing the rubber composition (unvulcanized state) according to one embodiment of the present invention, and can also be obtained by vulcanizing a molded product obtained by molding the rubber composition (unvulcanized state) according to one embodiment of the present invention. The vulcanized molded article according to one embodiment of the present invention can be obtained by vulcanizing the rubber composition according to one embodiment of the present invention after molding or during molding. The method for producing the vulcanized molded article according to one embodiment of the present invention includes a step of molding the vulcanized product according to one embodiment of the present invention, or a step of vulcanizing the unvulcanized molded article according to one embodiment of the present invention.

[0087] The vulcanized molded product according to one embodiment of the present invention preferably has the above-mentioned hardness, elongation at break at high temperatures, and / or flex fatigue resistance.

[0088] The unvulcanized molded product, vulcanized product, and vulcanized molded product according to the present embodiment have highly excellent elongation at break at high temperatures and highly excellent flex fatigue resistance, and therefore can be used as a member that particularly requires these properties, and is used for a tire bladder. The rubber composition according to one embodiment of the present invention can be used particularly for a tire bladder used at 150 to 220°C. The rubber composition according to one embodiment of the present invention can be used as a rubber composition for a bladder for tire vulcanization, particularly a rubber composition for a bladder for tire vulcanization used at 150 to 220°C.

[0089] Methods for molding the rubber composition (unvulcanized state) and vulcanizate according to the present embodiment include press molding, extrusion molding, calendar molding, etc. The temperature for vulcanizing the rubber composition may be appropriately set according to the composition of the rubber composition, and may be 140 to 220° C. or 160 to 190° C. The vulcanization time for vulcanizing the rubber composition may be appropriately set according to the composition of the rubber composition, the shape of the unvulcanized molded product, etc. EXAMPLES

[0090] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0091] <Manufacturing method of chloroprene rubber (10% by mass of acrylonitrile (AN))> In a polymerization vessel having an internal volume of 3 L equipped with a heating / cooling jacket and an agitator, 24 parts by mass of chloroprene (monomer), 24 parts by mass of acrylonitrile (monomer), 0.5 parts by mass of diethyl xanthogen disulfide, 200 parts by mass of pure water, 5.00 parts by mass of potassium rosinate (manufactured by Harima Chemicals Co., Ltd.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation) were added. Next, 0.1 parts by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out under a nitrogen gas flow at a polymerization temperature of 40°C. The above-mentioned chloroprene was added in portions starting 20 seconds after the start of polymerization, and the portion-added flow rate was adjusted with an electromagnetic valve based on the change in the heat quantity of the refrigerant for 10 seconds from the start of polymerization, and the flow rate was readjusted every 10 seconds thereafter, so that the polymerization was carried out continuously. When the polymerization rate relative to the total amount of chloroprene and acrylonitrile reached 50%, 0.02 parts by mass of phenothiazine, a polymerization terminator, was added to terminate the polymerization. Thereafter, unreacted monomers in the reaction solution were removed under reduced pressure to obtain a chloroprene-based rubber latex containing a chloroprene-acrylonitrile copolymer.

[0092] The above-mentioned polymerization rate [%] of the chloroprene-based latex was calculated from the dry mass when the chloroprene-based latex was air-dried. Specifically, it was calculated from the following formula (A). In the formula, the "solid content concentration" is the concentration [mass %] of the solid content obtained by heating 2 g of the sampled chloroprene-based latex at 130°C and excluding volatile components such as the solvent (water), volatile chemicals, and raw materials. The "total charge amount" is the total amount [g] of the raw materials, reagents, and solvent (water) charged in the polymerization vessel from the start of polymerization to a certain time. The "evaporation residue" is the mass [g] of the chemicals and raw materials charged from the start of polymerization to a certain time that do not volatilize under the condition of 130°C and remain as solids together with the polymer. The "charge amount of monomer" is the total amount [g] of the monomer charged in the polymerization vessel at the beginning and the amount of the monomer added in portions from the start of polymerization to a certain time. The "monomer" here is the total amount of chloroprene and acrylonitrile. Conversion rate = {[(total charge amount × solid concentration / 100) - evaporation residue] / charge amount of monomer} × 100 (A)

[0093] The content of acrylonitrile monomer units contained in the chloroprene rubber was calculated from the content of nitrogen atoms in the chloroprene-acrylonitrile copolymer rubber. Specifically, the content of nitrogen atoms in 100 mg of the chloroprene rubber was measured using an elemental analyzer (Sumigraph 220F: manufactured by Sumika Chemical Analysis Center Co., Ltd.), and the content of acrylonitrile monomer units was calculated.

[0094] The above elemental analysis was carried out as follows. The electric furnace temperatures were set to 900°C for the reactor, 600°C for the reduction furnace, 70°C for the column, and 100°C for the detector, and oxygen gas was flowed at 0.2 mL / min as the combustion gas, and helium gas was flowed at 80 mL / min as the carrier gas. The calibration curve was created using aspartic acid (10.52%), which has a known nitrogen content, as the standard substance. The chloroprene rubber obtained by the above manufacturing method had a content of acrylonitrile monomer units of 10.0 mass%. This was designated as chloroprene rubber AN10%.

[0095] <Manufacturing method of chloroprene rubber (20% by mass of acrylonitrile (AN))> The amount of acrylonitrile monomer added in the polymerization step was changed to obtain chloroprene rubber AN20% having an acrylonitrile monomer unit content of 20.0 mass%.

[0096] <Preparation of Rubber Composition> The components were mixed as shown in Table 1 and kneaded with an 8-inch open roll to obtain rubber compositions of the examples and comparative examples.

[0097] The components used to obtain the rubber composition are as follows: (Chloroprene rubber) Acrylonitrile-containing chloroprene rubber: chloroprene rubber AN10%, chloroprene rubber AN20%,

[0098] (Butyl rubber) Non-halogenated butyl rubber RIIR268: Regular butyl rubber, manufactured by ENEOS Materials Corporation, RIIR268, isoprene 1.7mol%, Halogenated Butyl Rubber CIIR1066: Chlorinated butyl rubber, manufactured by ENEOS Materials Corporation, CIIR1066, Cl 1.2% by mass

[0099] (Vulcanization accelerator) Non-halogenated alkylphenol formaldehyde resin Tackirol 201: Alkylphenol formaldehyde resin (formaldehyde-4-nonylphenol-4-tert-pentylphenol polymer), manufactured by Taoka Chemical Co., Ltd., Tackirol 201, halogen concentration 3.5% by mass Halogenated alkylphenol formaldehyde resin Tackirol 250-III: Brominated alkylphenol formaldehyde resin (brominated modified product of alkyl (C5-10) phenol formaldehyde polycondensate), manufactured by Taoka Chemical Co., Ltd., Tackirol 250-III

[0100] (Plasticizer) Hydroxy group-containing triacylglycerol Castor oil: Manufactured by Fukoku Oil Co., Ltd., Industrial No. 1 castor oil, the main component has a molecular weight of 933.4 and is represented by the following formula

[0101] [ka]

[0102] (Filler) Carbon Black N330: Asahi Carbon Co., Ltd., Asahi #70, HAF N550: Asahi Carbon Co., Ltd., Asahi #60, FEF

[0103] (Metal oxides) Zinc oxide type 2: Zinc oxide manufactured by Sakai Chemical Industry Co., Ltd.

[0104] (Processing aids) Stearic acid: Stearic acid 50S, manufactured by New Japan Chemical Co., Ltd.

[0105] The rubber compositions thus obtained were evaluated by the following methods, and the results are shown in Table 1.

[0106] <Hardness (Type A durometer)> The obtained rubber composition was press-vulcanized at 180°C for 20 minutes to produce a sheet-like vulcanized molded product having a thickness of 2 mm, based on JIS K 6299. The durometer hardness (type A) of the obtained sheet-like vulcanized molded product, as defined in JIS K 6253, was measured at room temperature (23°C) using GS-610 (manufactured by Techclock Corporation).

[0107] <Elongation at break at high temperatures> The obtained rubber composition was press-vulcanized at 180°C for 20 minutes to produce a sheet-like vulcanized molded product having a thickness of 2 mm in accordance with JIS K 6299. The obtained sheet-like vulcanized molded product was molded into a dumbbell-shaped No. 3 test piece, and the elongation at break was measured at 190°C in accordance with JIS K 6251.

[0108] <Flex fatigue resistance> The obtained rubber composition was press-vulcanized at 180°C for 20 minutes to prepare a vulcanized molded body for the De Mattia flex fatigue test. Using the obtained vulcanized molded body, the De Mattia flex fatigue test was carried out based on JIS K 6260. The number of flex tests (unit: 10,000 times) at which cracks occurred was measured under the conditions of stroke 58 mm, speed 300±10 rpm, and room temperature (23°C), to evaluate the flex fatigue resistance.

[0109] [Table 1]

Claims

1. A rubber composition comprising a chloroprene-based rubber and a butyl-based rubber, The chloroprene-based rubber includes a chloroprene-based rubber containing an unsaturated nitrile monomer unit, The rubber composition includes a processing aid, carbon black, a plasticizer, a metal oxide, and a vulcanization accelerator, A rubber composition for tire bladders, wherein the elongation at break of a vulcanized molded product of said rubber composition, measured at 190°C according to JIS K 6251, is 500% or more.

2. 2. The rubber composition according to claim 1, wherein when a De Mattia flexural fatigue test is performed on a vulcanized molded product of the rubber composition under conditions of a stroke of 58 mm, a speed of 300±10 rpm, and 23° C. based on JIS K 6260, the number of flexural fatigue tests at which cracks occur is 2 million or more.

3. The rubber composition according to claim 1 or claim 2, wherein the rubber composition contains 1 to 30 parts by mass of a chloroprene-based rubber containing the unsaturated nitrile monomer unit per 100 parts by mass of rubber contained in the rubber composition.

4. The vulcanization accelerator includes a compound having an alkylphenol structure, The rubber composition according to claim 1 or 2, wherein the rubber composition contains 1 to 10 parts by mass of the compound having an alkylphenol structure per 100 parts by mass of rubber contained in the rubber composition.

5. 3. The rubber composition according to claim 1, wherein a vulcanized molded product of the rubber composition has a type A durometer hardness of less than 68 as measured in accordance with JIS K 6253.

6. A tire bladder comprising a vulcanized molded article of the rubber composition according to claim 1 or 2.

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