Rubber composition and rubber product

Abstract

The present invention provides a rubber composition, which can improve the balance between the hysteresis loss under low strain and the hysteresis loss under high strain of the rubber. The rubber composition comprises a rubber component and at least one compound selected from the group consisting of general formulas (1) and (2). General formula (1): HS-R-COOM General formula (2): MOCO-R-(S) n -R-COOM (wherein: the R moieties are each independently a straight chain or branched chain alkylene group in which the number of carbon atoms in the straight chain portion connecting the sulfur atom to the COOM group is 8 or more; the M moieties are each independently an atom selected from the group consisting of alkali metals and alkaline earth metals; and n is an integer of 2 to 8.)

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from Japanese Patent Application No. 2020-080713 filed on April 30, 2020, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a rubber composition and a rubber product. Background Art

[0004] Rubber hysteresis loss (hereinafter may be simply referred to as "loss") is energy lost during the deformation history of rubber, and it refers to the difference between energy applied during deformation of a substance and energy recovered during recovery. This difference is converted into heat or sound. Therefore, it is known that the hysteresis loss of rubber has a great influence on, for example, the fuel efficiency of a tire and the damping property of a seismic isolation rubber.

[0005] For example, JP 2013-108003 A (PTL 1) describes a method for producing a rubber composition having small hysteresis loss, low heat build-up, and improved wear resistance.

[0006] Reference List

[0007] Patent Literature

[0008] PTL 1: JP 2013-108003 A Summary of the invention

[0009] Problem that the invention aims to solve

[0010] By reducing the loss of rubber at low strain, the rubber obtains improved low heat generation (i.e., higher fuel efficiency). However, if the loss of rubber at high strain is also reduced, the energy dissipation performance is degraded, which may lead to reduced durability. Conversely, if the loss is increased to improve durability, the loss at low strain increases, which may lead to deterioration of heat generation.

[0011] Therefore, it would be helpful to provide a rubber composition that can improve the balance between the hysteresis loss of the rubber at low strains and the hysteresis loss of the rubber at high strains.

[0012] Solutions for solving problems

[0013] The rubber composition according to the present invention is a rubber composition comprising:

[0014] The rubber component, and

[0015] At least one compound selected from the group consisting of the following general formulae (1) and (2),

[0016] HS-R-COOM(1), and

[0017] MOCO-R-(S) n -R-COOM(2),

[0018] in

[0019] R is independently a straight chain or branched chain alkylene group having 8 or more carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group;

[0020] M is independently an atom selected from the group consisting of alkali metals and alkaline earth metals; and

[0021] n is an integer from 2 to 8.

[0022] This makes it possible to improve the balance between the hysteresis losses of the rubber at low strains and the hysteresis losses of the rubber at high strains.

[0023] The rubber product according to the present invention is a rubber product produced using any one of the above-mentioned rubber compositions. As a result, it achieves an excellent balance between the hysteresis loss at low strain and the hysteresis loss at high strain.

[0024] Effects of the Invention

[0025] According to the present invention, a rubber composition can be provided that can improve the balance between the hysteresis loss of rubber at low strain and the hysteresis loss of rubber at high strain. Further, according to the present invention, a rubber product can be provided that has an excellent balance between the hysteresis loss at low strain and the hysteresis loss at high strain. DETAILED DESCRIPTION

[0026] The following describes an embodiment of the present invention. It should be noted that the description given below is for illustrative purposes only and should not be construed as limiting the scope of the present invention.

[0027] In the present invention, two or more embodiments may be arbitrarily combined.

[0028] In the present specification, unless otherwise specified, a numerical range includes the lower limit value and the upper limit value of the range. For example, "20 parts by mass to 150 parts by mass" means 20 parts by mass or more and 150 parts by mass or less.

[0029] (Rubber composition)

[0030] The rubber composition according to the present invention is a rubber composition comprising:

[0031] The rubber component, and

[0032] At least one compound selected from the group consisting of the following general formulae (1) and (2),

[0033] HS-R-COOM(1), and

[0034] MOCO-R-(S) n -R-COOM(2),

[0035] in

[0036] R is independently a straight chain or branched chain alkylene group having 8 or more carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group;

[0037] M is independently an atom selected from the group consisting of alkali metals and alkaline earth metals; and

[0038] n is an integer from 2 to 8.

[0039] The rubber component and the compounds of the general formulae (1) and (2) of the rubber composition according to the present invention are listed and described below.

[0040] -Rubber component

[0041] The rubber component is not particularly limited, and the rubber component of a known rubber composition can be used. The example of the rubber component includes natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), chloroprene rubber, ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), polysulfide rubber, silicone rubber, fluororubber and polyurethane rubber. The rubber component can be modified or unmodified.

[0042] The rubber component may be a known diene polymer for rubber compositions.

[0043] The rubber components may be used alone or in combination of two or more.

[0044] In one embodiment, the rubber component is at least one selected from the group consisting of NR, IR, BR, SBR and modified derivatives thereof.

[0045] When using SBR as rubber component, the styrene content in SBR is not particularly limited, and can be appropriately adjusted. The styrene content in SBR is, for example, greater than 0 % by weight and in the range of less than 50 % by weight. In one embodiment, the styrene content in SBR is greater than 0 % by weight, more than 1 % by weight, more than 3 % by weight, more than 5 % by weight, more than 10 % by weight, more than 15 % by weight, more than 20 % by weight, more than 30 % by weight, or more than 40 % by weight. In another embodiment, the styrene content in SBR is less than 50 % by weight, less than 45 % by weight, less than 40 % by weight, less than 30 % by weight, less than 20 % by weight, less than 15 % by weight, less than 10 % by weight, or less than 5 % by weight.

[0046] When using SBR as rubber component, the vinyl content of the butadiene part of SBR is not particularly limited, and can be appropriately adjusted. The vinyl content of the butadiene part of SBR is, for example, 1mol% to 70mol%. In one embodiment, the vinyl content of the butadiene part of SBR is more than 1mol%, more than 5mol%, more than 10mol%, more than 20mol%, more than 30mol%, more than 35mol%, more than 40mol%, more than 45mol%, more than 50mol%, or more than 60mol%. In another embodiment, the vinyl content of the butadiene part of SBR is less than 70mol%, less than 60mol%, less than 50mol%, less than 45mol%, less than 40mol%, less than 35mol%, less than 30mol%, less than 20mol%, less than 10mol%, or less than 5mol%.

[0047] The weight average molecular weight (Mw) of the rubber component is not particularly limited and can be appropriately adjusted. The Mw of the rubber component is, for example, 10,000 to 10,000,000. In one embodiment, the Mw of the rubber component is 10,000 or more, 50,000 or more, 100,000 or more, 150,000 or more, 200,000 or more, 250,000 or more, 300,000 or more, 400,000 or more, 500,000 or more, 1,000,000 or more, or 5,000,000 or more. In another embodiment, the rubber component has an Mw of 10,000,000 or less, 5,000,000 or less, 4,000,000 or less, 3,000,000 or less, 2,000,000 or less, 1,000,000 or less, 500,000 or less, 400,000 or less, 300,000 or less, 250,000 or less, 200,000 or less, 150,000 or less, or 100,000 or less.

[0048] The Mw of the rubber component can be obtained by performing gel permeation chromatography measurement and converting the result into monodisperse polystyrene.

[0049] - Compounds of formula (1) and (2)

[0050] In the rubber composition according to the present invention, the compounds of the general formulae (1) and (2) are blended with the rubber component to obtain the effect of improving the balance between the loss at a low strain and the loss at a high strain.

[0051] HS-R-COOM(1), and

[0052] MOCO-R-(S) n -R-COOM(2),

[0053] in

[0054] R is independently a straight or branched alkylene group having 8 or more carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group;

[0055] M is independently an atom selected from the group consisting of alkali metals and alkaline earth metals; and

[0056] n is an integer from 2 to 8.

[0057] Although not wishing to be bound by theory, the reasons for the improved balance are speculated to be, for example, as follows:

[0058] (i) the sulfur atom in the compound of the general formula (1) and (2) reacts with the rubber component, thereby introducing a COOM group into the rubber component;

[0059] (ii) the M of a plurality of COOM groups coordinate with the COO portion of the COOM group, thereby forming non-covalent bonds between the polymer networks of the rubber component;

[0060] (iii) when the vulcanized rubber composition or rubber product is under low strain, the non-covalent bonds and the sulfur-sulfur bonds generated by vulcanization fix the network and inhibit the occurrence of loss, when under high strain, the weak non-covalent bonds are broken to increase energy dissipation and improve rubber durability, and once the strain is removed, the non-covalent bonds are formed again in response to low strain and high strain.

[0061] In the compounds of the general formulae (1) and (2), R is independently a straight chain or branched alkylene group having 8 or more carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group. For example, in the case of a straight chain alkylene group having 8 carbon atoms, the structure of the compound of the general formula (1) is HS-(CH2)8-COOM. Further, R may be a branched alkylene group as long as the number of carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group is 8 or more. For example, in the case of the structure of HS-CH(CH3)-(CH2)7-COOM, R has 8 carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group, and is an alkylene group branched at the carbon adjacent to the sulfur atom.

[0062] In R of the compounds of the general formulae (1) and (2), the number of carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group is, for example, 8 to 30. In one embodiment, in R of the compounds of the general formulae (1) and (2), the number of carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group is 8 or more, 10 or more, 12 or more, 14 or more, 16 or more, 18 or more, 20 or more, 22 or more, 24 or more, 26 or more, or 28 or more. In another embodiment, in R of the compounds of the general formulae (1) and (2), the number of carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group is 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, 20 or less, 18 or less, 16 or less, 14 or less, 12 or less, or 10 or less.

[0063] In one embodiment, in R of the compounds of general formulae (1) and (2), the number of carbon atoms in the linear portion connecting the sulfur atom and the COOM group is 10 or more. As a result, the compound is easily mixed with the rubber component, and the compound reacts effectively with the rubber component.

[0064] When R of the compounds of the general formulae (1) and (2) is a branched alkylene group, the total number of carbon atoms in the alkylene group is, for example, 9 to 50. In one embodiment, when R of the compounds of the general formulae (1) and (2) is a branched alkylene group, the total number of carbon atoms in the alkylene group is 9 or more, 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, or 45 or more. In another embodiment, when R of the compounds of the general formulae (1) and (2) is a branched alkylene group, the total number of carbon atoms in the alkylene group is 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 25 or less, 20 or less, 15 or less, or 10 or less.

[0065] In one embodiment, when R of the compounds of formula (1) and (2) is a branched alkylene group, the number of carbon atoms in the straight chain connecting the sulfur atom and the COOM group is greater than the number of carbon atoms in the branched chain branching from the straight chain.

[0066] In one embodiment, R is a straight chain alkylene group.

[0067] In one embodiment, R of the compounds of formula (1) and (2) is a branched alkylene group branched at the carbon adjacent to the sulfur atom. Examples of such compounds of formula (1) include HS-CH(CH3)-(CH2)7-COOM.

[0068] In one embodiment, R of the compounds of formula (1) and (2) is a branched alkylene group branched at two carbons adjacent to the sulfur atom. Examples of such compounds of formula (1) include HS-(CH2)-CH(CH3)-(CH2)6-COOM.

[0069] In one embodiment, R of the compounds of formula (1) and (2) is a branched alkylene group, which is branched at 3, 4, 5, 6, 7 or 8 carbons adjacent to the sulfur atom.

[0070] In one embodiment, the compounds of formula (1) and (2) do not include compounds branched from carbons adjacent to a sulfur atom. In another embodiment, the compounds of formula (1) and (2) are branched at more than 2 carbons adjacent to a sulfur atom.

[0071] The two R's in the compound of the general formula (2) may be the same or different.

[0072] In the compounds of the general formulae (1) and (2), M is independently an atom selected from the group consisting of alkali metals and alkaline earth metals. Examples of M include Li, Na, K, Rb, Cs, Fr; Mg, Ca, Sr, Ba, and Ra. In one embodiment, in the compounds of the general formulae (1) and (2), M is at least one independently selected from the group consisting of Li, Na, and K. From the viewpoint of the balance between the hysteresis loss at low strain and the hysteresis loss at high strain, M is preferably Na.

[0073] In the present invention, M of the compounds of the general formulae (1) and (2) is an atom selected from the group consisting of alkali metals and alkaline earth metals. As a result, it is presumed that, as described above, M of a plurality of COOM groups coordinates with the COO portion of the COOM group, thereby forming a non-covalent bond between the polymer networks of the rubber component. Therefore, when a compound having a carboxyl (COOH) group other than a carboxylate is used, a non-covalent bond due to the coordination is not formed, and only a weaker non-covalent bond due to the carboxyl group is formed, which may not suppress the occurrence of loss under low strain.

[0074] In one embodiment, M in R of the compounds of formula (1) and (2) is Na.

[0075] The two M's in the compound of the general formula (2) may be the same or different.

[0076] In the general formula (2), n is an integer selected from 2, 3, 4, 5, 6, 7 and 8.

[0077] In one embodiment, n in the compound of formula (2) is 2-4.

[0078] In one embodiment, the rubber composition according to the present invention includes a compound of the general formula (1). In another embodiment, the rubber composition according to the present invention includes a compound of the general formula (2). In another embodiment, the rubber composition according to the present invention includes compounds of the general formula (1) and (2). In another embodiment, the rubber composition according to the present invention includes a compound of the general formula (1) and does not include any compound of the general formula (2). In another embodiment, the rubber composition according to the present invention includes a compound of the general formula (2) and does not include any compound of the general formula (1).

[0079] In one embodiment, the compound of formula (1) is at least one selected from the group consisting of HS-(CH2)8-COOLi, HS-(CH2)8-COONa, HS-(CH2)8-COOK, HS-(CH2)8-COOMg, HS-(CH2)8-COOCa, ...OLa, HS-(CH2)8-COOLi, HS-(CH2)8-COONa, HS-(CH2)8-COOK, HS-(CH2)8-COOMg, HS-(CH2)8-COOCa, HS-(CH2)8-COOLi, HS- 10 -COOLi, HS-(CH2) 10 -COONa, HS-(CH2) 10 -COOK, HS-(CH2) 10 -COOMg, HS-(CH2) 10 -COOCa, HS-(CH2) 12 -COOLi, HS-(CH2) 12 -COONa, HS-(CH2) 12 -COOK, HS-(CH2) 12 -COOMg, HS-(CH2) 12 -COOCa, HS-(CH2) 14 -COOLi, HS-(CH2) 14 -COONa, HS-(CH2) 14 -COOK, HS-(CH2) 14 -COOMg, HS-(CH2) 14 -COOCa, HS-(CH2) 16 -COOLi, HS-(CH2) 16 -COONa, HS-(CH2) 16 -COOK, HS-(CH2)16 -COOMg, HS-(CH2) 16 -COOCa, HS-(CH2) 18 -COOLi, HS-(CH2) 18 -COONa, HS-(CH2) 18 -COOK, HS-(CH2) 18 -COOMg, and HS-(CH2) 18 -COOCa.

[0080] In one embodiment, the compound of formula (2) is at least one selected from the group consisting of LiOCO-(CH2)8-(S)2-(CH2)8-COOLi, NaOCO-(CH2)8-(S)2-(CH2)8-COONa, KOCO-(CH2)8-(S)2-(CH2)8-COOK, MgOCO-(CH2)8-(S)2-(CH2)8-COOMg, CaOCO-(CH2)8-(S)2-(CH2)8-COOCa, LiOCO-(CH2)8-(S)2-(CH2)8-COOLi, NaOCO-(CH2)8-(S)2-(CH2)8-COONa, KOCO-(CH2)8-(S)2-(CH2)8-COOK, MgOCO-(CH2)8-(S)2-(CH2)8-COOMg, CaOCO-(CH2)8-(S)2-(CH2)8-COOCa, 10 -(S)2-(CH2) 10 -COOLi, NaOCO-(CH2) 10 -(S)2-(CH2) 10 -COONa, KOCO-(CH2) 10 -(S)2-(CH2) 10 -COOK, MgOCO-(CH2) 10 -(S)2-(CH2) 10 -COOMg, CaOCO-(CH2) 10 -(S)2-(CH2) 10 -COOCa, LiOCO-(CH2) 12 -(S)2-(CH2) 12 -COOLi, NaOCO-(CH2) 12 -(S)2-(CH2) 12 -COONa, KOCO-(CH2) 12 -(S)2-(CH2) 12 -COOK, MgOCO-(CH2) 12 -(S)2-(CH2) 12 -COOMg, CaOCO-(CH2) 12 -(S)2-(CH2) 12 -COOCa, LiOCO-(CH2) 14 -(S)2-(CH2) 14-COOLi, NaOCO-(CH2) 14 -(S)2-(CH2) 14 -COONa, KOCO-(CH2) 14 -(S)2-(CH2) 14 -COOK, MgOCO-(CH2) 14 -(S)2-(CH2) 14 -COOMg, CaOCO-(CH2) 14 -(S)2-(CH2) 14 -COOCa, LiOCO-(CH2) 16 -(S)2-(CH2) 16 -COOLi, NaOCO-(CH2) 16 -(S)2-(CH2) 16 -COONa, KOCO-(CH2) 16 -(S)2-(CH2) 16 -COOK, MgOCO-(CH2) 16 -(S)2-(CH2) 16 -COOMg, CaOCO-(CH2) 16 -(S)2-(CH2) 16 -COOCa, LiOCO-(CH2) 18 -(S)2-(CH2) 18 -COOLi, NaOCO-(CH2) 18 -(S)2-(CH2) 18 -COONa, KOCO-(CH2) 18 -(S)2-(CH2) 18 -COOK, MgOCO-(CH2) 18 -(S)2-(CH2) 18 -COOMg, and CaOCO-(CH2) 18 -(S)2-(CH2) 18 -COOCa.

[0081] The compound of the general formula (1) may be used alone or in combination of two or more.

[0082] The compound of the general formula (2) may be used alone or in combination of two or more.

[0083] Regarding the total amount of at least one compound selected from the group consisting of general formula (1) and (2) in the rubber composition, for example, the total amount of COOM groups in the compound is 2 mmol to 20 mmol relative to 100 g of the rubber component. In one embodiment, the total amount of at least one compound selected from the group consisting of general formula (1) and (2) in the rubber composition is 2 mmol or more, 3 mmol or more, 4 mmol or more, 5 mmol or more, 6 mmol or more, 7 mmol or more, 8 mmol or more, 9 mmol or more, 10 mmol or more, 12 mmol or more, 14 mmol or more, 16 mmol or more, or 18 mmol or more relative to 100 g of the rubber component. In another embodiment, the total amount of at least one compound selected from the group consisting of general formula (1) and (2) in the rubber composition is 20 mmol or less, 18 mmol or less, 16 mmol or less, 14 mmol or less, 12 mmol or less, 10 mmol or less, 9 mmol or less, 8 mmol or less, 7 mmol or less, 6 mmol or less, 5 mmol or less, 4 mmol or less, or 3 mmol or less relative to 100 g of the rubber component.

[0084] In addition to the rubber component and the compound of the general formula, the rubber composition according to the present invention may also include the known components used in the rubber composition. Examples of known components include fillers such as silica and carbon black; vulcanizing agent (crosslinking agent), vulcanization accelerator, vulcanization retarder, antioxidant, stearic acid, zinc oxide, reinforcing agent, softener, vulcanization aid, colorant, flame retardant, lubricant, foaming agent, thermoplastic resin, thermosetting resin, plasticizer, processing aid, antioxidant, scorch retarder, ultraviolet protection agent, antistatic agent, coloring preventer and oil. These can be used alone or in combination of two or more.

[0085] -filler

[0086] Known fillers such as carbon black and silica can be appropriately selected and used as the filler.

[0087] (Carbon Black)

[0088] Carbon black is not particularly limited and can be appropriately selected according to the purpose. For example, carbon black can be FEF, SRF, HAF, ISAF, and SAF grade carbon black. Carbon black can be used alone or in combination of two or more.

[0089] The nitrogen adsorption specific surface area (N2SA) of carbon black is not particularly limited, and it may be, for example, 20 m 2 / g~250m 2 / g. N2SA of carbon black is measured according to JIS K 6217-2:2001.

[0090] (Silicon Dioxide)

[0091] The silica is not particularly limited and can be used depending on the application. For example, it may be a general grade silica, or a special silica that has been surface-treated with a silane coupling agent or the like.

[0092] The silica may be used alone or in combination of two or more.

[0093] Examples of silica include wet silica (hydrous silicic acid), dry silica (silicic anhydride), calcium silicate, and aluminum silicate, among which wet silica is preferred.

[0094] The wet silica may be precipitated silica. Precipitated silica is silica obtained by reacting a reaction solution at a relatively high temperature and in a neutral to alkaline pH range to grow silica primary particles in the initial stage of production, and then controlling them in an acidic pH range to aggregate the primary particles.

[0095] The cetyltrimethylammonium bromide adsorption specific surface area (CTAB specific surface area) of silica is not particularly limited and can be appropriately adjusted. The CTAB specific surface area of ​​silica can be, for example, 70 m 2 / g~250m 2 / g.

[0096] In this specification, the CTAB specific surface area refers to a value measured according to ASTM D3765-92. Note that the adsorption cross-sectional area of ​​CTAB per molecule on the silica surface is 0.35 nm 2 , and the specific surface area (m 2 / g) is defined as the CTAB specific surface area.

[0097] The BET specific surface area of ​​silica is not particularly limited and can be appropriately adjusted. The BET specific surface area of ​​silica can be, for example, 100 m 2 / g~250m 2 / g.

[0098] In this specification, the BET specific surface area refers to a specific surface area determined by the BET method. The BET specific surface area can be measured according to ASTM D4820-93.

[0099] The amount of the filler in the rubber composition is, for example, 20 to 150 parts by mass relative to 100 parts by mass of the rubber component.

[0100] In one embodiment, the amount of filler is 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, 80 parts by mass or more, 90 parts by mass or more, 100 parts by mass or more, 110 parts by mass or more, 120 parts by mass or more, 130 parts by mass or more, or 140 parts by mass or more, relative to 100 parts by mass of the rubber component. In another embodiment, the amount of filler is 150 parts by mass or less, 140 parts by mass or less, 130 parts by mass or less, 120 parts by mass or less, 110 parts by mass or less, 100 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0101] -Method for preparing rubber composition

[0102] The method for preparing the rubber composition is not particularly limited except that the rubber composition includes a rubber component and the compound of the above general formula, and a known method for preparing a rubber composition may be used.

[0103] For example, when the preparation of the rubber composition includes a non-production process (also referred to as a non-production mixing process) and a production process (also referred to as a production mixing process), the rubber composition can be prepared by: mixing a rubber component that does not contain a vulcanization system (vulcanizing agent and vulcanization accelerator); a part or all of the compound of the general formula; a filler; and other components such as stearic acid in the non-production process, and adding the vulcanization system and zinc oxide and the like to the mixture obtained from the non-production process, and mixing the mixture in the production process.

[0104] In one embodiment, when the preparation of the rubber composition includes a non-production process and a production process, all of the compound of the general formula is added in the non-production process. In another embodiment, when the preparation of the rubber composition includes a non-production process and a production process, a portion of the compound of the general formula is added in the non-production process, and the remaining compound of the general formula is added in the production process.

[0105] When the preparation of the rubber composition includes a non-production process and a production process, the non-production process may include only one step or include two steps.

[0106] (Rubber products)

[0107] The rubber product according to the present invention is a rubber product prepared using any of the above-mentioned rubber compositions. Examples of rubber products include tires; anti-vibration rubber; seismic isolation rubber; hoses; belts such as conveyor belts; rubber pads (MT pads); rubber tracks; bellows (air springs); pneumatic chucks such as air pickers and air grippers; rubber bearings such as rubber bearings for bridges; rubber-coated chain-type anti-fall devices; and rubber for office equipment such as OA rollers.

[0108] In one embodiment, the rubber article is at least one selected from the group consisting of: tires; anti-vibration rubbers; seismic isolation rubbers; hoses; belts such as conveyor belts; rubber pads (MT pads); rubber tracks; bellows (air springs); pneumatic chucks such as air pickers and air grippers; rubber bearings such as rubber bearings for bridges; rubber-coated chain-type fall prevention devices; and rubber for office equipment such as OA rollers.

[0109] -tire

[0110] The tire according to the present invention is a tire prepared using any one of the rubber compositions described above.

[0111] The tire is not particularly limited except for using any of the above-described rubber compositions, and known tire constructions and manufacturing methods may be employed.Examples of members in the tire include a tread portion, a shoulder portion, a sidewall portion, a bead portion, a belt layer, and a carcass.

[0112] Example

[0113] The present invention will be described in more detail based on Examples, which are for illustrative purposes only and should not be construed as limiting the scope of the present invention. In the Examples, the blending amounts are in parts by mass unless otherwise specified.

[0114] Details of materials used in the examples are as follows.

[0115] Styrene-butadiene rubber (SBR): styrene content 10% by weight, vinyl content 40 mol%, number average molecular weight 201,000, weight average molecular weight 211,000

[0116] Compound of general formula (1): SH(CH2) 10 COONa

[0117] Comparative compound 1: SHCH2COONa

[0118] Comparative compound 2: SH(CH2) 10 COOH

[0119] Filler: Carbon black, manufactured by Tokai Carbon Co., Ltd., "Seast7HM" N234

[0120] Wax: "SUNTIGHT" manufactured by Seiko-Chemical Co., Ltd.

[0121] Antioxidant: "NOCRAC 6C" manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.

[0122] Vulcanization accelerator 1: bis(2-benzothiazolyl) persulfide

[0123] Vulcanization accelerator 2: N-tert-butyl-2-benzothiazole sulfenamide

[0124] (Example 1)

[0125] The vulcanized rubber was obtained by performing the non-production process and the production process with the recipe listed in Table 1. In the non-production process, the maximum temperature of the rubber composition was adjusted to 150° C. In the production process, the maximum temperature of the rubber composition was adjusted to 110° C. The blending amount of the compound of the general formula (1) was such that the molar number of COONa groups was 5 mmol relative to 100 g of SBR.

[0126] (Comparative Examples 1 to 3)

[0127] A vulcanized rubber was obtained in the same manner as in Example 1, except that the formulation of the rubber composition was changed to the formulation listed in Table 1. In Comparative Examples 2 and 3, the comparative compounds were blended so that the number of moles of COONa groups or COOH groups of the comparative compounds was equal to the number of moles of COONa groups of the compound of the general formula (1) of Example 1.

[0128] The obtained vulcanized rubber was subjected to the following hysteresis loss measurement.

[0129] - Hysteresis loss measurement

[0130] Using a universal material testing machine (manufactured by INSTRON), a loading-unloading test was performed at a temperature of 25°C, a strain of 10% or a strain of 300% and a speed of 200 mm / sec, and the ratio of energy loss was measured. Where each hysteresis loss of Comparative Example 1 was 100, the hysteresis losses of the other embodiments and the comparative examples were expressed as indices. The results are shown in Table 1. The results show that the smaller the hysteresis loss at 10% strain, the better the low heat generation property, and the larger the hysteresis loss at 300% strain, the better the durability.

[0131] Table 1

[0132]

[0133] As can be understood from Table 1, the vulcanized rubber using the rubber composition according to the present invention can improve the balance between the hysteresis loss at a low strain and the hysteresis loss at a high strain.

[0134] Industrial Applicability

[0135] According to the present invention, a rubber composition can be provided that can improve the balance between the hysteresis loss of rubber at low strain and the hysteresis loss of rubber at high strain. Further, according to the present invention, a rubber product can be provided that has an excellent balance between the hysteresis loss at low strain and the hysteresis loss at high strain.

Claims

1. A rubber composition comprising: The rubber component, and At least one compound selected from the group consisting of the following general formulae (1) and (2), Between the polymer networks of the rubber component, a plurality of M of COOM groups and COO of COOM groups coordinate to form non-covalent bonds, HS-R-COOM(1), and MOCO-R-(S) n -R-COOM(2), in R is independently a straight chain or branched chain alkylene group having 10 or more and 30 or less carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group; M is independently at least one selected from the group consisting of Li, Na, and K; and n is an integer from 2 to 8. 2 . The rubber composition according to claim 1 , wherein R is a straight-chain hydrocarbylene group. 3 . The rubber composition according to claim 1 , wherein M is Na. 4 . The rubber composition according to claim 1 , wherein the total amount of COOM groups in the compound is 2 mmol to 20 mmol relative to 100 g of the rubber component. 5 . The rubber composition according to claim 1 , further comprising a filler, wherein an amount of the filler is 20 to 150 parts by mass relative to 100 parts by mass of the rubber component.

6. A method for producing a rubber composition, comprising a non-production process and a production process, wherein In the non-production process, the rubber component is kneaded with at least a portion of at least one compound selected from the group consisting of the following general formulas (1) and (2) to form a kneaded product, wherein the total amount of COOM groups in the compound is 2 mmol to 20 mmol relative to 100 g of the rubber component, Between the polymer networks of the rubber component, the M of a plurality of COOM groups and the COO part of the COOM group coordinate to form non-covalent bonds, HS-R-COOM(1), and MOCO-R-(S) n -R-COOM(2), in R is independently a straight chain or branched chain alkylene group having 10 or more and 30 or less carbon atoms in the straight chain portion connecting the sulfur atom and the COOM group; M is independently at least one selected from the group consisting of Li, Na, and K; and n is an integer from 2 to 8, and In the production process, a vulcanizing system is added to the kneaded product obtained in the non-production process, and they are kneaded to produce a rubber composition. 7 . The method for producing a rubber composition according to claim 6 , wherein the R is a straight-chain alkylene group. 8 . The method for producing a rubber composition according to claim 6 , wherein the M is Na. 9 . The method for producing a rubber composition according to claim 6 , comprising adding a filler in the non-production process, wherein the amount of the filler is 20 to 150 parts by mass relative to 100 parts by mass of the rubber component. 10 . A rubber product using the rubber composition according to claim 1 .

Images