Rubber composition, laminate, and tire

Abstract

To provide a rubber composition capable of bonding rubber layers to each other with sufficient adhesive strength and having sufficient strength, a laminate in which the rubber layers are bonded to each other with sufficient adhesive strength and having sufficient strength, and a tire having sufficient durability.SOLUTION: The rubber composition contains a diene rubber (a), a metal salt (b) and a heterocyclic compound (c) having a triazolinedione skeleton, a laminate is provided with a rubber layer (A) consisting of the rubber composition and a rubber layer (B) laminated on the rubber layer (A), and a tire is provided with the laminate.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Conventionally, when the tread rubber of large tires such as aircraft tires, truck and bus tires, wears out, the tread rubber is removed to obtain a base tire, and retread rubber is attached to the base tire in place of the worn tread rubber to retread the tire (Patent Document 1). Known methods for retreading tires are the cold method (pre-cure method) and the hot method (remolding method), but the cold method is preferred from the viewpoint of preventing over-vulcanization of the base tire. Here, the important thing in cold retreading is the adhesion between the vulcanized rubbers, and to ensure adhesion between the vulcanized rubbers, pre-treatment such as cementing the retreaded rubber or wrapping unvulcanized cushion rubber around the base tire is usually necessary. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-112010 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the cementing process and wrapping of unvulcanized cushion rubber described above reduce the productivity of tire retreading. Therefore, in order to retread tires more efficiently, it is extremely important to establish technology that can sufficiently bond the rubber layers together without pre-processing such as cementing or wrapping of unvulcanized cushion rubber. It is also important to ensure that the retreaded rubber (rubber layer) itself has sufficient strength (such as breaking strength).

[0005] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a rubber composition that can bond rubber layers with sufficient adhesive strength and has sufficient strength (breaking strength, etc.). Another object of the present invention is to provide a laminate using such a rubber composition, in which rubber layers are bonded to each other with sufficient adhesive strength and have sufficient strength (such as breaking strength), and to provide a tire comprising such a laminate and having sufficient durability. [Means for solving the problem]

[0006] The rubber composition, laminate, and tire of the present invention that solve the above problems have the following essential features.

[0007] [1] A rubber composition comprising a diene rubber (a), a metal salt (b), and a heterocyclic compound (c) having a triazolinedione skeleton. The rubber composition of the present invention described in [1] above can be applied to at least one rubber layer of a laminate having multiple rubber layers, thereby making it possible to bond the rubber layers with sufficient adhesive strength and providing sufficient strength (such as breaking strength).

[0008] [2] The heterocyclic compound (c) is represented by the following general formula (1): [ka] The rubber composition according to [1], represented by the formula [wherein X is an aryl group, an alkyl group, or a heteroaryl group]. The rubber composition described in [2] above has high strength, and when applied to at least one rubber layer of a laminate having multiple rubber layers, it is possible to bond the rubber layers together with high adhesive strength.

[0009] [3] The rubber composition according to [1] or [2], wherein the metal salt (b) contains an element of Groups 3 to 12 of the periodic table. The rubber composition described in [3] above has high strength, and by applying it to at least one rubber layer of a laminate having multiple rubber layers, it is possible to bond the rubber layers together with high adhesive strength.

[0010] [4] The rubber composition according to any one of [1] to [3], wherein the metal salt (b) is at least one selected from the group consisting of metal halide salts, metal acrylate salts, metal methacrylate salts, and metal acetate salts. In the rubber composition described in [4] above, the metal halide salt, metal acrylate salt, metal methacrylate salt, and metal acetate salt are easy to handle and easily form a bond with the heterocyclic compound (c).

[0011] [5] The rubber composition according to any one of [1] to [4], wherein the content of the metal salt (b) is 10 parts by mass or more per 100 parts by mass of the diene rubber (a). The rubber composition described in [5] above has improved strength.

[0012] [6] The rubber composition according to any one of [1] to [5], wherein the diene rubber (a) is modified with the heterocyclic compound (c). In the rubber composition described in [6] above, the main chains of the diene rubbers (a) can be crosslinked simply by complexing the heterocyclic compound (c) moieties with the metal salt (b) to form coordinate bonds.

[0013] [7] The rubber composition according to any one of [1] to [6], wherein the diene rubber (a) is modified by blending the heterocyclic compound (c) in an amount of 0.5 mol % or more based on the diene monomer units of the diene rubber (a). The rubber composition described in [7] above has a high network density of coordinate bond crosslinks and improved strength.

[0014] [8] A laminate comprising a rubber layer (A) made of the rubber composition according to any one of [1] to [7], and a rubber layer (B) laminated on the rubber layer (A). In the laminate of the present invention described in [8] above, the rubber layer (A) and the rubber layer (B) are bonded with sufficient adhesive strength, and the laminate has sufficient strength (breaking strength, etc.).

[0015] [9] The laminate according to [8], wherein the rubber layer (B) is made of a rubber composition containing a diene rubber (a). In the laminate described in the above [9], a crosslinked structure is easily formed in the rubber layer (B), and the strength of the rubber layer (B) is easily ensured.

[0016]

[10] The laminate according to [9], wherein the diene rubber (a) in the rubber composition constituting the rubber layer (B) is modified with a heterocyclic compound (c) having a triazolinedione skeleton. In the laminate described in the above item

[10] , a crosslinked structure is easily formed in the rubber layer (B).

[0017]

[11] The laminate according to

[10] , wherein the diene rubber (a) in the rubber composition constituting the rubber layer (B) is modified by blending the heterocyclic compound (c) in an amount of 0.5 mol % or more based on the diene monomer units of the diene rubber (a). In the laminate described in the above

[11] , the network density of the coordinate bond crosslinks in the rubber layer (B) is increased, and the strength of the rubber layer (B) is improved.

[0018]

[12] The laminate according to any one of [9] to

[11] , wherein the rubber composition constituting the rubber layer (B) contains a metal salt (b), and the metal salt (b) contains an element of Groups 3 to 12 of the periodic table. In the laminate described in the above item

[12] , a crosslinked structure is easily formed in the rubber layer (B).

[0019]

[13] A tire comprising the laminate according to any one of [8] to

[12] . The tire of the present invention described in

[13] above has sufficient durability. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a rubber composition that can bond rubber layers together with sufficient adhesive strength and has sufficient strength (breaking strength, etc.). Furthermore, according to the present invention, it is possible to provide a laminate using such a rubber composition, in which rubber layers are bonded to each other with sufficient adhesive strength and have sufficient strength (such as breaking strength), as well as a tire comprising such a laminate and having sufficient durability. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view in the thickness direction, schematically illustrating a laminate of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] The rubber composition, laminate, and tire of the present invention will be described in detail below with reference to examples based on embodiments thereof.

[0023] <Definition> The compounds described herein may be derived in part or in whole from fossil sources, biological sources such as plant sources, recycled sources such as used tires, or a mixture of two or more of fossil, biological, and recycled sources.

[0024] <Rubber composition> The rubber composition of this embodiment is characterized by containing a diene rubber (a), a metal salt (b), and a heterocyclic compound (c) having a triazolinedione skeleton (hereinafter also simply referred to as a "heterocyclic compound" or a "triazolinedione compound").

[0025] In the rubber composition of this embodiment, a heterocyclic compound (c) having a triazolinedione skeleton is added to the main chain of the diene rubber (a). Furthermore, the metal salt (b) easily complexes with the heterocyclic compound (c) portion added to the diene rubber (a). Therefore, in the rubber composition of this embodiment, the metal salt (b) forms a coordinate bond with the heterocyclic compound (c) portion added to the diene rubber (a) to form a complex. The metal salt (b) then forms multiple coordinate bonds, resulting in crosslinking of multiple diene rubbers (a). The crosslinking by the coordinate bond is a reversible crosslink in which bonding (crosslinking) and dissociation (cleavage) are reversible. Although the bond is weaker than the sulfur crosslinking in typical crosslinked rubbers, it still has sufficient strength. Therefore, the rubber composition of this embodiment has sufficient strength (e.g., breaking strength). Furthermore, when the rubber composition of this embodiment is applied to at least one layer of a laminate having multiple rubber layers as described below, the rubber layer to which the rubber composition of this embodiment is applied has sufficient adhesion to the adjacent rubber layer. Therefore, by applying the rubber composition of this embodiment to at least one layer of the laminate, the rubber layers of the laminate can be bonded with sufficient adhesive strength without performing pretreatments such as cementing or wrapping unvulcanized cushion rubber, which are used in conventional cold retreading technology. Therefore, when the rubber composition of this embodiment is applied to at least one rubber layer of a laminate having multiple rubber layers, it is possible to bond the rubber layers with sufficient adhesive strength and has sufficient strength (breaking strength, etc.).

[0026] -Diene rubber (a)- The rubber composition of this embodiment contains a diene rubber (a). When the rubber composition contains the diene rubber (a), it becomes possible to form a crosslinked structure together with the metal salt (b) and the heterocyclic compound (c).

[0027] The diene rubber (a) is a rubber containing units derived from diene monomers (hereinafter also simply referred to as "diene monomer units"), and may further contain units derived from copolymerizable comonomers. The diene monomer-derived units enable the diene rubber to be crosslinked and can exhibit rubber-like elongation and strength. In the crosslinked rubber, the diene rubber (a) is usually present in a crosslinked state, but a portion of the diene rubber may be uncrosslinked. Specific examples of diene monomers (diene compounds) include 1,3-butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. On the other hand, examples of the copolymerizable comonomer include aromatic vinyl compounds, such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, and p-ethylstyrene.

[0028] Examples of the diene rubber (a) include natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), etc. These diene rubbers (a) may be used alone or as a blend of two or more.

[0029] In the rubber composition of this embodiment, the diene rubber (a) preferably has a weight average molecular weight (Mw) of 10,000 to 3,000,000. When the weight average molecular weight (Mw) of the diene rubber (a) is 10,000 or more, the strength (breaking strength, etc.) of the rubber composition is improved, and when it is 3,000,000 or less, the workability in kneading the rubber composition is improved. From the viewpoint of the strength (breaking strength, etc.) of the rubber composition, the weight average molecular weight (Mw) of the diene rubber (a) is more preferably 100,000 or more, and even more preferably 120,000 or more. Furthermore, from the viewpoint of the workability in kneading the rubber composition, it is more preferably 2,000,000 or less, and even more preferably 1,800,000 or less. Here, the weight average molecular weight of the diene rubber (a) is determined as a value converted into standard polystyrene by gel permeation chromatography (GPC) measurement.

[0030] -Metal salt (b)- The rubber composition of this embodiment contains a metal salt (b). The metal salt (b) easily forms a bond (easily complexes) with the heterocyclic compound (c) moiety added to the diene rubber (a). The metal salt (b) forms coordinate bonds with multiple heterocyclic compound (c) moieties, thereby crosslinking multiple diene rubbers (a).

[0031] The metal salt (b) preferably contains an element of Groups 3 to 12 of the periodic table. Elements of Groups 3 to 12 of the periodic table tend to bond strongly with the heterocyclic compound (c). Therefore, a rubber composition containing metal salt (b) containing an element of Groups 3 to 12 of the periodic table has high strength, and by applying the composition to at least one rubber layer of a laminate having multiple rubber layers, the rubber layers can be bonded together with high adhesive strength.

[0032] Specifically, elements of Group 3 of the periodic table include scandium and yttrium. Examples of elements in Group 4 of the periodic table include titanium and zirconium. Examples of elements in Group 5 of the periodic table include vanadium and niobium. Examples of elements in Group 6 of the periodic table include chromium, molybdenum, and tungsten. Furthermore, examples of elements in Group 7 of the periodic table include manganese and rhenium. Examples of elements in Group 8 of the periodic table include iron, ruthenium, and osmium. Furthermore, examples of elements in Group 9 of the periodic table include cobalt, rhodium, and iridium. Examples of elements in Group 10 of the periodic table include nickel, palladium, and platinum. Furthermore, examples of elements in Group 11 of the periodic table include copper. Furthermore, examples of elements in Group 12 of the periodic table include zinc. When the metal salt (b) contains an element of Groups 8, 10, 11, or 12 of the periodic table, the bond with the heterocyclic compound (c) tends to be stronger. Furthermore, the valence of the metal ions in the metal salt (b) is not particularly limited and can be any valence that each element can have, but is preferably divalent or greater.

[0033] It is particularly preferable that the metal salt (b) contains iron, copper, nickel, or zinc. Iron ions, copper ions, nickel ions, and zinc ions are likely to form particularly strong bonds with the heterocyclic compound (c), and can form a stronger crosslinked structure. The valence of the iron ion is divalent (Fe 2+ ) or trivalent (Fe 3+ ) is preferred.

[0034] Examples of the metal salt (b) include metal halides, metal acrylates, metal methacrylates, metal sulfates, metal nitrates, and metal acetates. Among these, metal halides, metal acrylates, metal methacrylates, and metal acetates are preferred. Metal halides, metal acrylates, metal methacrylates, and metal acetates are easy to handle and easily form bonds with the heterocyclic compound (c). The form of the metal salt (b) is not particularly limited, and may be, for example, a hydrate.

[0035] Examples of the metal halide salt include metal fluorides, metal chlorides, metal bromides, and metal iodides, and among these, metal chlorides are preferred because they are easy to handle and can easily form a bond with the tetrazine derivative moiety.

[0036] Specific examples of the metal salt (b) include zinc diacrylate, zinc dimethacrylate (ZDMA), FeCl, FeCl·4H0, FeCl, FeCl·6H0, CuCl, CuCl, CuBr, Ni(CHCOO)·4H0, etc. The metal salt (b) may be a single type or a combination of two or more types. Among these, zinc dimethacrylate (ZDMA) is preferred as the metal salt (b). A rubber composition containing zinc dimethacrylate (ZDMA) has higher strength (such as breaking strength), and when applied to at least one rubber layer of a laminate having multiple rubber layers, it is possible to bond the rubber layers with higher adhesive strength.

[0037] In the rubber composition of this embodiment, the content of the metal salt (b) is preferably 10 parts by mass or more and preferably 80 parts by mass or less per 100 parts by mass of the diene rubber (a). When the content of the metal salt (b) is 10 parts by mass or more per 100 parts by mass of the diene rubber (a), the network density of the coordinate bond crosslinks increases, improving the strength of the rubber composition. When the content of the metal salt (b) is 80 parts by mass or less per 100 parts by mass of the diene rubber (a), the rubber composition is likely to have sufficient rubber elasticity (elastomeric properties). Furthermore, from the viewpoint of the strength (breaking strength, etc.) of the rubber composition, the content of the metal salt (b) is more preferably 20 parts by mass or more per 100 parts by mass of the diene rubber (a), and more preferably 60 parts by mass or less from the viewpoint of the rubber elasticity of the rubber composition.

[0038] -Heterocyclic compound (c) having a triazolinedione skeleton- The rubber composition of this embodiment includes a heterocyclic compound (c) having a triazolinedione skeleton. Here, the "triazolinedione skeleton" refers to a structure in which oxygen atoms are added to two carbon atoms constituting a triazoline ring to form two carbonyl groups. The triazolinedione skeleton has multiple nitrogen atoms in the skeleton (heterocycle) and also multiple carbonyl groups, and can form coordinate bonds with multiple metal salts (b). Furthermore, the heterocyclic compound (c) having a triazolinedione skeleton, together with the metal salt (b), can crosslink multiple diene rubbers (a).

[0039] The heterocyclic compound (c) is represented by the following general formula (1): [ka] [wherein X is an aryl group, an alkyl group, or a heteroaryl group.] In other words, the heterocyclic compound (c) preferably has a 1,2,4-triazoline-3,5-dione skeleton. The compound represented by general formula (1) has high reactivity with the main chain of the diene rubber (a), and is easily combined with the metal salt (b) to form a crosslink through a coordinate bond, thereby forming a high-strength crosslinked structure. Therefore, a rubber composition containing the compound represented by general formula (1) has high strength, and by applying it to at least one rubber layer of a laminate having multiple rubber layers, it is possible to bond the rubber layers with high adhesive strength.

[0040] In the general formula (1), X is an aryl group, an alkyl group, or a heteroaryl group. The aryl group preferably has 6 to 20 carbon atoms, more preferably 6 to 10 carbon atoms, the alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and the heteroaryl group preferably has 1 to 20 carbon atoms, more preferably 3 to 10 carbon atoms. Examples of heteroatoms contained in the heteroaryl group include nitrogen atoms, sulfur atoms, oxygen atoms, selenium atoms, tellurium atoms, phosphorus atoms, silicon atoms, and boron atoms. Of these, nitrogen atoms are preferred. Examples of the aryl group represented by X include a phenyl group, a tolyl group, a dimethylphenyl group, a diisopropylphenyl group, and a naphthyl group. Of these, a phenyl group is preferred. Examples of the alkyl group represented by X include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a neopentyl group, a hexyl group, and an octyl group. Examples of the heteroaryl group represented by X include a pyridyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a triazinyl group, a triazolyl group, a tetrazolyl group, an indolyl group, an indazolyl group, a pteridinyl group, a quinoxalinyl group, a cinnolinyl group, a phthalazinyl group, a quinolyl group, an isoquinolyl group, a quinazolyl group, a benzimidazolyl group, an imidazopyridinyl group, a carbazolyl group, an acridinyl group, a phenanthridinyl group, a furyl group, a benzofuryl group, a dibenzofuryl group, a thienyl group, a benzothienyl group, a thiazolyl group, a benzothiazolyl group, an isothiazolyl group, a benzisothiazolyl group, a dibenzothienyl group, an oxazolyl group, a thiadiazolyl group, a benzoxazolyl group, an isoxazolyl group, a benzisoxazolyl group, and an oxadiazolyl group. Among these, a pyridyl group is preferred. The pyridyl group may be a 2-pyridyl group, a 3-pyridyl group, or a 4-pyridyl group.

[0041] The aryl group, alkyl group, or heteroaryl group represented by X may have a hydrogen atom in the aryl group, alkyl group, or heteroaryl group substituted with a substituent. Examples of such a substituent include an alkyl group, an aryl group, a halogen group, and a nitrile group. Examples of the alkyl group and aryl group as the substituent include the same aryl group and alkyl group as described above for X, and examples of the halogen group include a fluoro group, a chloro group, a bromo group, and an iodo group.

[0042] Specific examples of the compound represented by the general formula (1) include 4-phenyl-1,2,4-triazoline-3,5-dione, 4-(o-tolyl)-1,2,4-triazoline-3,5-dione, 4-(m-tolyl)-1,2,4-triazoline-3,5-dione, 4-(p-tolyl)-1,2,4-triazoline-3,5-dione, 4-methyl-1,2,4-triazoline-3,5-dione, 4-ethyl-1,2,4-triazoline-3,5-dione, 4-(n-tolyl)-1,2,4-triazoline-3,5-dione, ...phenyl-1,2,4-triazoline-3,5-dione, 4-phenyl-1,2,4-triazoline-3,5-dione, 4-phenyl-1,2,4-triazoline-3,5-dione, 4-phenyl-1,2,4-triazoline-3,5-dione, 4-phenyl-1,2,4- Examples of the 4-pyridyl-1,2,4-triazoline-3,5-dione include 4-isopropyl-1,2,4-triazoline-3,5-dione, 4-(2-pyridyl)-1,2,4-triazoline-3,5-dione, 4-(3-pyridyl)-1,2,4-triazoline-3,5-dione, and 4-(4-pyridyl)-1,2,4-triazoline-3,5-dione. Of these, 4-phenyl-1,2,4-triazoline-3,5-dione (Ph-TAD) is preferred.

[0043] The content of the heterocyclic compound (c) in the rubber composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, and preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the diene rubber (a). When the content of the heterocyclic compound (c) is 0.1 parts by mass or more per 100 parts by mass of the diene rubber (a), the network density of the coordinate bond crosslinks increases, improving the strength (breaking strength, etc.) of the rubber composition. When the content of the heterocyclic compound (c) is 10 parts by mass or less per 100 parts by mass of the diene rubber (a), the rubber composition is likely to have sufficient rubber elasticity (elastomeric properties).

[0044] The diene rubber (a) is preferably modified with the heterocyclic compound (c). When the diene rubber (a) is modified with the heterocyclic compound (c), the main chains of the diene rubbers (a) can be crosslinked simply by complexing the heterocyclic compound (c) moieties with the metal salt (b) to form coordinate bonds. Here, the modification of the diene rubber (a) with the heterocyclic compound (c) may be performed at the compounding stage of the rubber composition. Alternatively, the diene rubber (a) may be modified with the heterocyclic compound (c) before compounding the rubber composition, and the diene rubber (a) modified with the heterocyclic compound (c) may be compounded with the metal salt (b) or the like at the compounding stage of the rubber composition to crosslink the main chains of the diene rubbers (a).

[0045] The diene rubber (a) is preferably modified by blending the heterocyclic compound (c) in an amount of 0.1 mol% or more, more preferably 0.2 mol% or more, and even more preferably 0.5 mol% or more, based on the diene monomer units of the diene rubber (a). By using a modified diene rubber obtained by blending the heterocyclic compound (c) in an amount of 0.5 mol% or more, based on the diene monomer units of the diene rubber (a), the network density of the coordinate bond crosslinks is increased, thereby improving the strength (e.g., breaking strength) of the rubber composition. Furthermore, from the viewpoint of the rubber elasticity (elastomeric properties) of the rubber composition, the diene rubber (a) is preferably modified by blending the heterocyclic compound (c) in an amount of 10 mol% or less, more preferably 7 mol% or less, and even more preferably 4 mol% or less, based on the diene monomer units of the diene rubber (a).

[0046] The modified diene rubber preferably has a bond amount of the heterocyclic compound (c) of 0.1 mol% or more, more preferably 0.2 mol% or more, and even more preferably 0.5 mol% or more, relative to the diene monomer units of the diene rubber (a). It is also preferably 10 mol% or less, more preferably 7 mol% or less, and even more preferably 4 mol% or less. When the bond amount of the heterocyclic compound (c) is 0.5 mol% or more relative to the diene monomer units of the diene rubber (a), the network density of the coordinate bond crosslinks increases, improving the strength (e.g., breaking strength) of the rubber composition. When the bond amount of the heterocyclic compound (c) is 4 mol% or less relative to the diene monomer units of the diene rubber (a), the rubber composition is likely to have sufficient rubber elasticity (elastomer properties).

[0047] In the rubber composition of this embodiment, for example, the diene rubber (a), the metal salt (b), and the heterocyclic compound (c) can be mixed (kneaded) to form crosslinks through coordinate bonds. Here, it is preferable that the kneading conditions, such as temperature and time, be appropriately selected depending on the types and reactivities of the diene rubber (a), metal salt (b), and heterocyclic compound (c) used.

[0048] As an example, the reaction scheme for the modification of the diene rubber (a) and the coordination bond crosslinking (complexation) of the modified diene rubber is shown below when synthetic isoprene rubber (IR) (a-1) is used as the diene rubber (a), zinc dimethacrylate (ZDMA) (b-1) is used as the metal salt (b), and 4-phenyl-1,2,4-triazoline-3,5-dione (Ph-TAD) (c-1) is used as the heterocyclic compound (c). Note that the structures of the modified diene rubber and complexed diene rubber shown here are only assumed examples and are not limited thereto. For example, they may be tautomeric isomers or oxidized forms. [ka]

[0049] As shown in the upper part of the above reaction scheme, in one embodiment of the present invention, Ph-TAD (c-1) is added to the main chain of synthetic isoprene rubber (a-1) to produce modified diene rubber (ac-1).

[0050] As shown in the lower part of the above reaction scheme, in one embodiment of the present invention, the modified diene rubber (ac-1) and ZDMA (b-1) are complexed to produce a diene rubber (complexed diene rubber) (abc-1) crosslinked by a coordinate bond. While the above reaction scheme shows a complexation between a nitrogen atom in the triazoline ring moiety of the triazolinedione skeleton, an oxygen atom in the carbonyl moiety of the triazolinedione skeleton, and a zinc ion, the diene rubber (complexed diene rubber) crosslinked by a coordinate bond can take various crosslinking forms.

[0051] -others- In addition to the diene rubber (a), metal salt (b), and heterocyclic compound (c), the rubber composition of this embodiment may contain compounding agents commonly used in the rubber industry, such as zinc oxide (zinc white), fillers (carbon black, silica, etc.), softeners, stearic acid, wax, antioxidants, silane coupling agents, etc., which may be appropriately selected and compounded within a range that does not impair the object of the present invention. Commercially available products can be suitably used as these compounding agents.

[0052] -Method of manufacturing rubber composition- The method for producing the rubber composition is not particularly limited, but the rubber composition can be produced, for example, by blending various components appropriately selected as necessary with the diene rubber (a), metal salt (b), and heterocyclic compound (c) described above, and kneading, heating, extruding, etc.

[0053] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0054] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roller typically used for heat-in of a rubber composition.

[0055] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0056] For example, in the first stage of kneading, the diene rubber (a), the heterocyclic compound (c), and various other components appropriately selected as necessary are blended and kneaded to form a mixture containing a modified diene rubber in which the heterocyclic compound (c) is bonded to the main chain of the diene rubber (a), and in the second or subsequent stages of kneading, the metal salt (b) and various other components appropriately selected as necessary are blended and kneaded to complex the diene rubber (a) modified with the heterocyclic compound (c), thereby forming a crosslinked structure through a coordinate bond. This method for producing a rubber composition is excellent in productivity because the crosslinked structure through a coordinate bond can be formed during the production of the rubber composition (kneading of the rubber composition).

[0057] Alternatively, for example, a modified diene rubber having a heterocyclic compound (c) bonded to the main chain of a diene rubber (a) may be prepared in advance, and the modified diene rubber may be kneaded with optional compounding ingredients in the first stage of kneading. In the second or subsequent stages of kneading, metal salt (b) and various components appropriately selected as necessary may be added and kneaded to complex the diene rubber (a) modified with the heterocyclic compound (c), thereby forming a crosslinked structure through a coordinate bond. This method for producing a rubber composition also allows for the easy formation of a crosslinked structure through a coordinate bond, and is also excellent in productivity.

[0058] <Laminate> The laminate of this embodiment is characterized by comprising a rubber layer (A) made of the rubber composition of this embodiment described above, and a rubber layer (B) laminated on the rubber layer (A). That is, the rubber layer (A) of the laminate of this embodiment is made of the rubber composition containing the diene rubber (a), the metal salt (b), and the heterocyclic compound (c).

[0059] In the rubber layer (A) of the laminate of this embodiment, a heterocyclic compound (c) is added to a diene rubber (a), and a metal salt (b) is coordinated to the heterocyclic compound (c) added to the diene rubber (a) to form a complex. The metal salt (b) forms multiple coordinate bonds, thereby crosslinking multiple diene rubbers (a). The crosslinks formed by the coordinate bonds have sufficient strength, so the rubber layer (A) of the laminate of this embodiment has sufficient strength (such as breaking strength). Furthermore, the rubber layer (A) of the laminate of this embodiment contains the metal salt (b) and the heterocyclic compound (c), and has sufficient adhesiveness to adjacent rubber members. Therefore, in the laminate of this embodiment, the rubber layer (A) and the rubber layer (B) can be bonded with sufficient adhesive strength without performing pretreatments such as cementing or wrapping of unvulcanized cushion rubber, which are used in conventional cold retreading technology. Therefore, in the laminate of this embodiment, the rubber layer (A) and the rubber layer (B) are bonded with sufficient adhesive strength, and the laminate has sufficient strength (breaking strength, etc.).

[0060] Next, a laminate according to one embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view in the thickness direction that schematically illustrates a laminate according to this embodiment. The laminate 1 shown in FIG. 1 comprises a rubber layer (A) 2 and a rubber layer (B) 3, and the rubber layer (A) 2 and the rubber layer (B) 3 are bonded together. For example, the laminate 1 can be produced by laminating the rubber layer (B) 3 on the rubber layer (A) 2, and applying heat and / or pressure as desired. Here, the rubber layer (A) 2 and the rubber layer (B) 3 may be composed of a cross-linked rubber that has been cross-linked in advance, or may be composed of an uncross-linked rubber. However, the laminate according to one embodiment of the present invention is composed of a cross-linked rubber that has been cross-linked in advance. Although the laminate 1 shown in FIG. 1 is composed of two layers, the rubber layer (A) 2 and the rubber layer (B) 3, the laminate of the present invention may be composed of three or more layers.

[0061] -Rubber layer (A)- The laminate of this embodiment includes a rubber layer (A) made of the rubber composition of this embodiment. Because the rubber layer (A) is made of the rubber composition of this embodiment, it has sufficient strength (such as breaking strength) and sufficient adhesion to adjacent rubber members. The rubber layer (A) is made of a rubber composition containing a diene rubber (a), a metal salt (b), and a heterocyclic compound (c). The rubber composition and its components constituting the rubber layer (A), as well as the method for producing the same, are as described above. The rubber layer (A) can be produced by molding the produced rubber composition into a desired shape.

[0062] -Rubber layer (B)- The laminate of this embodiment includes a rubber layer (B) laminated on the rubber layer (A). The rubber layer (B) is not particularly limited as long as it has rubber elasticity. The rubber layer (B) may be composed of the same rubber composition as that used in the rubber layer (A) described above, or may be composed of a different rubber composition.

[0063] --Diene rubber (a)-- The rubber layer (B) is preferably made of a rubber composition containing a diene rubber (a). Examples of the diene rubber include natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), and chloroprene rubber (CR). These diene rubbers may be used alone or as a blend of two or more. When the rubber composition constituting the rubber layer (B) contains the diene rubber (a), a crosslinked structure is easily formed in the rubber layer (B), which makes it easier to ensure the strength (e.g., breaking strength) of the rubber layer (B).

[0064] The diene rubber (a) in the rubber composition constituting the rubber layer (B) may be the same as or different from the diene rubber (a) in the rubber composition constituting the rubber layer (A), and the embodiments and preferred aspects described above for the diene rubber (a) in the "rubber composition of the present embodiment" are also applicable to the diene rubber (a) in the rubber composition constituting the rubber layer (B). For example, the diene rubber (a) in the rubber composition constituting the rubber layer (B) preferably has a weight average molecular weight (Mw) of 10,000 to 3,000,000.

[0065] --Metal salt (b)-- The rubber composition constituting the rubber layer (B) preferably contains a metal salt (b). The metal salt (b) preferably contains an element of Groups 3 to 12 of the periodic table. The metal salt (b) is the same as the metal salt (b) described above in relation to the "rubber composition of the present embodiment." When the rubber composition constituting the rubber layer (B) contains a metal salt (b), particularly a metal salt (b) containing an element of Groups 3 to 12 of the periodic table, a crosslinked structure is easily formed in the rubber layer (B).

[0066] When the rubber composition constituting the rubber layer (B) contains a metal salt (b), the metal salt (b) of the rubber composition constituting the rubber layer (B) may be the same as or different from the metal salt (b) of the rubber composition constituting the rubber layer (A), and the embodiments, preferred aspects, preferred ranges of content, etc. described above for the metal salt (b) in the "rubber composition of the present embodiment" also apply to the metal salt (b) of the rubber composition constituting the rubber layer (B). For example, when the rubber composition constituting the rubber layer (B) contains a metal salt (b), zinc dimethacrylate (ZDMA) is preferred as the metal salt (b), and the content of the metal salt (b) is preferably 10 parts by mass or more per 100 parts by mass of the diene rubber (a).

[0067] --Heterocyclic compounds (c)-- The rubber composition constituting the rubber layer (B) preferably contains a heterocyclic compound (c) having a triazolinedione skeleton. The diene rubber (a) in the rubber composition constituting the rubber layer (B) is preferably modified with the heterocyclic compound (c) having a triazolinedione skeleton. The heterocyclic compound (c) having a triazolinedione skeleton and the diene rubber (a) modified with the heterocyclic compound (c) having a triazolinedione skeleton are the same as those described for the rubber composition of this embodiment above. When the diene rubber (a) in the rubber composition constituting the rubber layer (B) is modified with the heterocyclic compound (c), a crosslinked structure is easily formed in the rubber layer (B).

[0068] The diene rubber (a) in the rubber composition constituting the rubber layer (B) is preferably modified by blending the heterocyclic compound (c) in an amount of 0.1 mol % or more, more preferably 0.2 mol % or more, and even more preferably 0.5 mol % or more, based on the diene monomer units of the diene rubber (a). By using a modified diene rubber obtained by blending the heterocyclic compound (c) in an amount of 0.5 mol % or more based on the diene monomer units of the diene rubber (a), the network density of the coordinate bond crosslinks in the rubber layer (B) is increased, and the strength (breaking strength, etc.) of the rubber layer (B) is improved. From the viewpoint of the rubber elasticity (elastomeric properties) of the rubber layer (B), the diene rubber (a) is preferably modified by incorporating the heterocyclic compound (c) in an amount of 10 mol % or less, more preferably 7 mol % or less, and even more preferably 4 mol % or less, based on the diene monomer units of the diene rubber (a).

[0069] The modified diene rubber preferably has a bond amount of the heterocyclic compound (c) of 0.1 mol% or more, more preferably 0.2 mol% or more, and even more preferably 0.5 mol% or more, relative to the diene monomer units of the diene rubber (a), and preferably 10 mol% or less, more preferably 7 mol% or less, and even more preferably 4 mol% or less. When the bond amount of the heterocyclic compound (c) is 0.5 mol% or more relative to the diene monomer units of the diene rubber (a), the network density of the coordinate bond crosslinks increases, improving the strength (e.g., breaking strength) of the rubber layer (B). When the bond amount of the heterocyclic compound (c) is 4 mol% or less relative to the diene monomer units of the diene rubber (a), the rubber layer (B) is likely to have sufficient rubber elasticity (elastomer properties).

[0070] In addition, when the rubber composition constituting the rubber layer (B) contains a heterocyclic compound (c), the heterocyclic compound (c) of the rubber composition constituting the rubber layer (B) may be the same as or different from the heterocyclic compound (c) of the rubber composition constituting the rubber layer (A) described above, and the embodiments, preferred aspects, preferred ranges of content, etc. described for the heterocyclic compound (c) in the "rubber composition of this embodiment" above can also be applied to the heterocyclic compound (c) of the rubber composition constituting the rubber layer (B). For example, when the rubber composition constituting the rubber layer (B) contains a heterocyclic compound (c), the heterocyclic compound (c) is preferably a compound represented by general formula (1).

[0071] --others-- The rubber composition constituting the rubber layer (B) may contain, in addition to the diene rubber (a), metal salt (b), and heterocyclic compound (c) having a triazolinedione skeleton, compounding agents commonly used in the rubber industry, such as zinc oxide (zinc white), fillers (carbon black, silica, etc.), softeners, stearic acid, wax, antioxidants, silane coupling agents, etc., selected appropriately within the scope of the present invention. Commercially available products can be suitably used as these compounding agents.

[0072] --Method for manufacturing rubber layer (B)-- The method for producing the rubber composition constituting the rubber layer (B) is not particularly limited, and the rubber layer (B) can be produced, for example, by blending various components appropriately selected as necessary, and kneading, heating, extruding, etc. The conditions and devices for kneading, heating, extruding, etc. are the same as those described in the section on the production method of the "rubber composition of the present embodiment" above. The rubber layer (B) can be produced by molding the produced rubber composition into a desired shape.

[0073] <Tires> The tire of this embodiment is characterized by including the laminate of this embodiment described above. The tire of this embodiment has sufficient durability because it includes the laminate of this embodiment described above.

[0074] The laminate in the tire of this embodiment is preferably applied to a combination of the tread layer (tread rubber) and the outermost layer (belt layer, belt reinforcing layer, cushion rubber, etc.) of the tread portion of the tire case (or tire casing).

[0075] The tire can be manufactured by a conventional method. For example, components typically used in tire manufacturing, such as a carcass layer, a belt layer, and a tread layer, each composed of an uncrosslinked rubber composition and / or cords, are laminated on a tire-building drum in this order, and the drum is removed to form a green tire. The green tire is then crosslinked to manufacture a desired tire (e.g., a pneumatic tire).

[0076] Alternatively, a desired retread tire (e.g., a pneumatic tire) can be manufactured by removing the tread layer (tread rubber) from a used tire to obtain a base tire, using the rubber layer (B) as the outermost layer of the base tire, preparing retread rubber as the rubber layer (A), and laminating the rubber layer (A) on the rubber layer (B). [Example]

[0077] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0078] <Synthesis of modified isoprene rubber> Dichloromethane as a solvent, synthetic isoprene rubber (manufactured by ENEOS Materials Corporation, trade name "IR2200"), and 4-phenyl-1,2,4-triazoline-3,5-dione (Ph-TAD, manufactured by Tokyo Chemical Industry Co., Ltd., triazolinedione compound of general formula (1)) in the amount shown in Table 1 were added to a reactor, and the mixture was stirred at room temperature for 5 minutes to synthesize modified isoprene rubber (modified IR). The amount of 4-phenyl-1,2,4-triazoline-3,5-dione (triazolinedione compound) bonded to the resulting modified isoprene rubber was measured by the following method. The results are shown in Table 1.

[0079] (1) Method for measuring the amount of triazolinedione compound bound The resulting modified isoprene rubber is 1 H-NMR analysis was carried out to measure the amount of triazolinedione compound bound.

[0080] [Table 1]

[0081] *1 The amount of triazolinedione compound added to the isoprene unit of synthetic isoprene rubber (IR) *2 The amount of triazolinedione compound bonded to the isoprene unit of synthetic isoprene rubber (IR)

[0082] <Preparation and Evaluation of Rubber Compositions> Rubber compositions were produced using a conventional open roll mill according to the formulation shown in Table 2. The breaking strength (Tb) and adhesive strength of the resulting rubber compositions were measured by the following methods. The results are shown in Table 2.

[0083] (2) Breaking strength (Tb) measurement method A JIS No. 7 test piece was prepared from the rubber composition, and a tensile test was performed using a universal testing machine manufactured by Instron to determine the breaking strength (Tb) of the rubber composition. The value of each sample was indexed, with the value of Comparative Example 1 being set to 100, so that the larger the value, the better the result.

[0084] (3) Measurement method for adhesive strength The rubber composition was heated at 145°C for 30 minutes to prepare a crosslinked rubber sheet (approximately 0.8 to 1.0 mm thick). Two of the obtained crosslinked rubber sheets were laminated to prepare a laminate, which was then thermocompressed at 145°C for 30 minutes under a pressure of 15 MPa and punched out to prepare a 10 mm wide test piece. A T-peel test was performed on the obtained test piece using an Instron universal testing machine to determine the adhesive strength (peel resistance). The value of Comparative Example 1 was set to 100, and the values ​​of each sample were indexed so that a higher value indicates better results.

[0085] [Table 2]

[0086] *2 Same as Table 1 *3 IR: Synthetic isoprene rubber, manufactured by ENEOS Materials Corporation, product name "IR2200", weight average molecular weight (Mw) = 1378 x 10 3 *4 Modified IR-1: Modified isoprene rubber synthesized above, see Table 1 *5 Modified IR-2: Modified isoprene rubber synthesized above, see Table 1 *6 Modified IR-3: Modified isoprene rubber synthesized above, see Table 1 *7 DCP: Dicumyl peroxide, manufactured by SIGMA-ALDRICH *8 ZDMA: Zinc dimethacrylate, manufactured by Cray Valley, product name "DYMALINK 708" *9 NA: Indicates that measurement was not possible because crosslinked rubber could not be formed.

[0087] It can be seen from Table 2 that in the laminates of Examples 1 to 3 according to the present invention, the rubber layers are bonded together with sufficient adhesive strength, and the laminates have sufficient breaking strength (Tb). On the other hand, it is clear that the laminates of Comparative Examples 2 to 4, which were crosslinked with organic peroxide (DCP), had low adhesive strength between the rubber layers. In addition, Comparative Example 5, in which only zinc dimethacrylate (ZDMA) was blended with synthetic isoprene rubber, and Comparative Example 6, in which no metal salt was blended, did not become crosslinked rubber, so it was not possible to prepare JIS No. 7 test pieces, crosslinked rubber sheets, and laminates, and it was not possible to measure the breaking strength (Tb) and adhesive strength. [Industrial Applicability]

[0088] The rubber composition and laminate of the present invention can be used in tires.

[0089] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is thought to be a technology that can contribute to the achievement of goals such as "No. 12: Responsible Consumption and Production" and "No. 13: Take concrete action against climate change." [Explanation of symbols]

[0090] 1: Laminate 2: Rubber layer (A) 3: Rubber layer (B)

Claims

1. A rubber composition comprising: a diene rubber (a); a metal salt (b); and a heterocyclic compound (c) having a triazolinedione skeleton.

2. The heterocyclic compound (c) is represented by the following general formula (1): 【Chemistry 1】 The rubber composition according to claim 1, wherein X is an aryl group, an alkyl group, or a heteroaryl group.

3. The rubber composition according to claim 1, wherein the metal salt (b) contains an element of Groups 3 to 12 of the periodic table.

4. The rubber composition according to claim 1, wherein the metal salt (b) is at least one selected from the group consisting of metal halide salts, metal acrylate salts, metal methacrylate salts, and metal acetate salts.

5. The rubber composition according to claim 1, wherein the content of the metal salt (b) is 10 parts by mass or more per 100 parts by mass of the diene rubber (a).

6. The rubber composition according to claim 1, wherein the diene rubber (a) is modified with the heterocyclic compound (c).

7. 2. The rubber composition according to claim 1, wherein the diene rubber (a) is modified by blending the heterocyclic compound (c) in an amount of 0.5 mol % or more based on the diene monomer units of the diene rubber (a).

8. A laminate comprising a rubber layer (A) made of the rubber composition according to any one of claims 1 to 7, and a rubber layer (B) laminated on the rubber layer (A).

9. The laminate according to claim 8 , wherein the rubber layer (B) is made of a rubber composition containing a diene rubber (a).

10. The laminate according to claim 9, wherein the diene rubber (a) in the rubber composition constituting the rubber layer (B) is modified with a heterocyclic compound (c) having a triazolinedione skeleton.

11. 11. The laminate according to claim 10, wherein the diene rubber (a) in the rubber composition constituting the rubber layer (B) is modified by blending the heterocyclic compound (c) in an amount of 0.5 mol % or more based on diene monomer units of the diene rubber (a).

12. The laminate according to claim 9, wherein the rubber composition constituting the rubber layer (B) contains a metal salt (b), and the metal salt (b) contains an element of Groups 3 to 12 of the periodic table.

13. A tire comprising the laminate of claim 8.

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