Pneumatic tire and method for manufacturing same

Abstract

Provided is a pneumatic tire in which a resin layer is firmly adhered to an outer surface. This pneumatic tire includes the resin layer on at least a part of the outer surface thereof, and is characterized in that the resin layer is disposed via an adhesive layer containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit.

Description

Pneumatic tire and manufacturing method thereof

[0001] The present invention relates to a pneumatic tire and a method for manufacturing the same.

[0002] Conventionally, studies have been conducted to provide a resin layer on the outer surface of a tire in order to improve performance.

[0003] For example, Patent Document 1 discloses that a tire's crack resistance is improved by forming a rubber layer and a urethane resin layer covering the surface of the rubber layer in at least a partial region of the tire's outer surface. Furthermore, Patent Document 2 discloses a technology in which a resin film including an oxygen barrier resin layer is disposed in at least a portion of the groove bottom of the tire tread in order to enhance the oxygen penetration prevention property of the tire tread.

[0004] JP 2019-089446 A JP 2012-250574 A

[0005] A tire is mainly composed of a rubber component, and when a resin layer is placed directly on a rubber component as in the above-mentioned technology, the adhesion between the rubber component and the resin layer may become insufficient.

[0006] Therefore, an object of the present invention is to provide a pneumatic tire having a resin layer firmly bonded to its outer surface, and a method for manufacturing such a pneumatic tire.

[0007] That is, the gist of the present invention for solving the above problems is as follows.

[0008] [1] A pneumatic tire having a resin layer on at least a part of an outer surface, characterized in that the resin layer is disposed via an adhesive layer containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit.

[0009] [2] The pneumatic tire according to [1], wherein the copolymer has a melting point of 50 to 120°C.

[0010] [3] The pneumatic tire according to [1] or [2], wherein the copolymer has a content of the conjugated diene unit of more than 0 mol% and 50 mol% or less, and a content of the non-conjugated olefin unit of 50 mol% or more and less than 100 mol%.

[0011] [4] The pneumatic tire according to any one of [1] to [3], wherein the copolymer further contains an aromatic vinyl unit.

[0012] [5] The copolymer has a content of the conjugated diene units of 1 to 50 mol%, a content of the non-conjugated olefin units of 40 to 97 mol%, and a content of the aromatic vinyl units of 2 to 35 mol%. The pneumatic tire according to [4].

[0013] [6] The pneumatic tire according to any one of [1] to [5], wherein the thickness of the adhesive layer is 10 μm or more and 2 mm or less.

[0014] [7] The pneumatic tire according to any one of [1] to [6], wherein the resin layer has a thickness of 10 μm or more and 50 mm or less.

[0015] [8] The pneumatic tire according to any one of [1] to [7], wherein the resin layer contains a thermoplastic resin having a melting point of 25°C or higher and 250°C or lower.

[0016] [9] The pneumatic tire according to [8], wherein the thermoplastic resin is one or more selected from polyolefin-based resins, polyamide-based resins, and polyvinyl alcohol-based resins.

[0017]

[10] The pneumatic tire according to any one of [1] to [9], wherein the outer surface on which the resin layer is disposed is at least a part of the outer surface of the tread portion and / or the sidewall portion of the tire.

[0018]

[11] A method for manufacturing a pneumatic tire according to any one of [1] to

[10] , comprising: heating an adhesive layer laminated on an outer surface of unvulcanized rubber; and heating the adhesive layer and a resin layer laminated together.

[0019]

[12] The method for manufacturing a pneumatic tire according to

[11] , comprising: a step of laminating an adhesive layer and a resin layer in this order on an outer surface of unvulcanized rubber; and a step of heating the unvulcanized rubber on which the adhesive layer and the resin layer are laminated.

[0020]

[13] The method for manufacturing a pneumatic tire according to

[11] , comprising: a step of laminating an adhesive layer and a resin layer to obtain a composite layer; a step of heating the composite layer; a step of laminating the heated composite layer on an outer surface of unvulcanized rubber so that the adhesive layer faces the unvulcanized rubber; and a step of heating the unvulcanized rubber on which the composite layer has been laminated.

[0021]

[14] The method for manufacturing a pneumatic tire according to

[11] , comprising: a step of laminating an adhesive layer on an outer surface of unvulcanized rubber; a step of heating the unvulcanized rubber on which the adhesive layer has been laminated to convert the unvulcanized rubber into vulcanized rubber; a step of laminating a resin layer on the adhesive layer laminated on the vulcanized rubber; and a step of heating the vulcanized rubber on which the adhesive layer and the resin layer have been laminated to thermally fuse the adhesive layer and the resin layer together.

[0022]

[15] The method for manufacturing a pneumatic tire according to any one of

[12] to

[14] , wherein the lamination of the adhesive layer is carried out by applying a solution containing the copolymer and an organic solvent, and then drying the solution to remove the organic solvent.

[0023] According to the present invention, it is possible to provide a pneumatic tire having a resin layer firmly bonded to the outer surface, and a method for manufacturing such a pneumatic tire.

[0024] Hereinafter, embodiments of the present invention will be described. However, the description is intended to exemplify the present invention and is not intended to limit the present invention in any way.

[0025] The compounds described herein may be derived partially or entirely from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires, or may be derived from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0026] <Pneumatic tire> A pneumatic tire according to one embodiment of the present invention (hereinafter, may be referred to as "tire of the present embodiment") is characterized in that it includes a resin layer on at least a part of the outer surface, and the resin layer is disposed via an adhesive layer containing a copolymer having conjugated diene units and non-conjugated olefin units.

[0027] In the tire of this embodiment, a copolymer having conjugated diene units and non-conjugated olefin units (hereinafter referred to as "copolymer A") is used as the material for the adhesive layer, and a resin layer is disposed on the outer surface via the adhesive layer. With this configuration, the adhesive layer and the resin layer can be fused to each other, for example, by heating. Note that this fusion is thought to be due in part to the high affinity between the resin in the resin layer and the non-conjugated olefin units in copolymer A. Furthermore, with this configuration, the adhesive layer can be firmly bonded to the tire component that comes into contact with the surface opposite the resin layer. Note that it is thought that the conjugated diene units in copolymer A can contribute to this bonding. Therefore, in the tire of this embodiment, the resin layer is firmly bonded to the outer surface, and therefore, it is possible to fully enjoy the improved effects of disposing the resin layer on the outer surface (e.g., crack resistance, abrasion resistance, fuel economy, wet performance, weather resistance, etc.).

[0028] As used herein, "external surface" means the surface exposed to the external environment.

[0029] In the tire of this embodiment, the resin layer is preferably disposed on a rubber member of the tire (e.g., tread rubber, side rubber, etc.) via an adhesive layer containing copolymer A. In other words, in the tire of this embodiment, the adhesive layer containing copolymer A is preferably in contact with the rubber member of the tire. The rubber member also preferably contains a diene rubber component. The rubber member also preferably contains a vulcanizing agent such as sulfur. In these cases, the adhesive layer and the rubber member can be co-vulcanized, for example, by heating, to further improve bonding strength.

[0030] In the tire of this embodiment, the outer surface on which the resin layer is disposed is preferably at least a part of the outer surface of the tread and / or sidewall of the tire, more preferably the entire outer surface of the tread of the tire, and even more preferably the entire outer surface of the sidewall of the tire. In this case, the performance improvement effect of disposing the resin layer on the outer surface can be further enhanced.

[0031] In the pneumatic tire of the present invention, it is sufficient that a resin layer is disposed on at least a portion of the outer surface of the tire via an adhesive layer. Therefore, for example, one aspect of the present invention is an embodiment in which a resin tread member (resin layer), which is expected to be developed as an alternative concept to tread rubber, is disposed on the base portion of the tire (such as a base tire) via an adhesive layer.

[0032] (Resin Layer) In the tire of the present embodiment, a resin layer is disposed on at least a part of the outer surface. Such a resin layer contains one or more types of resin.

[0033] The resin layer may be a single layer or may be a multi-layer structure of two or more layers. When the resin layer is a multi-layer structure of two or more layers, each layer may be made of substantially the same resin, or each layer may be made of a different resin or a combination of resins.

[0034] The thickness of the resin layer (total thickness when the tire is configured with multiple layers) is not particularly limited, but is preferably 10 μm or more and 50 mm or less. In this case, the effect of improving various performances by disposing the resin layer can be more reliably obtained while avoiding a significant increase in tire weight. From the same viewpoint, the thickness of the resin layer is more preferably 50 μm or more, even more preferably 100 μm or more, more preferably 30 mm or less, even more preferably 20 mm or less, and particularly preferably 10 mm or less.

[0035] The resin contained in the resin layer is not particularly limited, but is preferably a thermoplastic resin that can be thermally fused to the non-conjugated olefin units (particularly the polyolefin portion) in copolymer A. Specifically, the resin layer preferably contains a thermoplastic resin having a melting point of 25°C or higher and 250°C or lower. In this case, the high fusion property between the thermoplastic resin contained in the resin layer and the non-conjugated olefin units in copolymer A contained in the adhesive layer allows the resin layer to be bonded even more firmly. Such thermoplastic resins may be used alone or in combination of two or more. From the same viewpoint, the melting point of the thermoplastic resin is more preferably 40°C or higher, even more preferably 60°C or higher, more preferably 220°C or lower, and even more preferably 180°C or lower.

[0036] Examples of thermoplastic resins having the above-mentioned melting points include polyolefin resins, polyamide resins, and polyvinyl alcohol resins. The thermoplastic resin contained in the resin layer is preferably one or more selected from these.

[0037] Examples of the polyolefin resin include polyethylene, polypropylene, and ethylene-vinyl acetate copolymer (EVA). These polyolefin resins may be used alone or in combination of two or more. Examples of polyethylene include very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE).

[0038] Examples of the polyamide resin include nylon 6 and nylon 66. These polyamide resins may be used alone or in combination of two or more.

[0039] Examples of the polyvinyl alcohol resin include EVAL (EVOH), POVAL (PVOH), etc. These polyvinyl alcohol resins may be used alone or in combination of two or more.

[0040] The resin layer may further contain any other components in addition to the resin. However, from the viewpoint of further enhancing the effect of improving various performances attributable to the resin, the proportion of the resin in the resin layer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0041] The method for producing the resin layer is not particularly limited. For example, the resin layer can be produced using a resin composition containing a resin. Specifically, the components of the resin composition are melt-kneaded using an extrusion kneader, and the resin composition is extruded to produce the resin layer. Alternatively, the resin composition can be pressed to produce the resin layer. Furthermore, a commercially available product (such as a commercially available sheet or film) may be used as the resin layer.

[0042] (Adhesive Layer) In the tire of the present embodiment, when a resin layer is disposed on at least a part of the outer surface, an adhesive layer containing copolymer A is interposed therebetween.

[0043] The thickness of the adhesive layer is not particularly limited, but is preferably 10 μm or more and 2 mm or less. In this case, the resin layer can be bonded efficiently and sufficiently firmly. From the same viewpoint, the thickness of the adhesive layer is more preferably 50 μm or more, even more preferably 100 μm or more, and more preferably 1 mm or less, even more preferably 500 μm or less.

[0044] The adhesive layer may contain a crosslinking agent in addition to the copolymer A. In this case, the adhesive layer can be more firmly bonded to a tire component (particularly a rubber component) that comes into contact with the surface opposite to the resin layer.

[0045] Examples of crosslinking agents include sulfur and peroxides. These crosslinking agents may be used alone or in combination of two or more. Examples of peroxides include ketone peroxides, peroxyketals, dialkyl peroxides, hydroperoxides, diacyl peroxides, peroxyesters, and peroxydicarbonates. These peroxides may be used alone or in combination of two or more.

[0046] The adhesive layer may further contain any other component in addition to the copolymer A and the crosslinking agent. However, from the viewpoint of further enhancing the effect of improving adhesiveness attributable to the copolymer A, the proportion of the copolymer A in the adhesive layer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0047] The method for producing the adhesive layer is not particularly limited. For example, the adhesive layer can be produced using a composition containing copolymer A. Specifically, the components of the composition are melt-kneaded using an extrusion kneader, and the composition is extruded to produce the adhesive layer. Alternatively, the adhesive layer can be produced by heat-pressing the composition. The heat-pressing temperature is preferably 120 to 180°C, and more preferably 140 to 160°C.

[0048] - Copolymer Having Conjugated Diene Units and Non-Conjugated Olefin Units (Copolymer A) - Copolymer A may be a binary copolymer having only conjugated diene units and non-conjugated olefin units, i.e., composed of two types of units. Copolymer A may also be a terpolymer having aromatic vinyl units in addition to conjugated diene units and non-conjugated olefin units, i.e., composed of three types of units. Copolymer A may also be a multi-component copolymer further containing other monomer units.

[0049] The conjugated diene unit is a structural unit derived from a conjugated diene compound as a monomer. Here, the conjugated diene compound refers to a conjugated diene compound. The conjugated diene compound preferably has 4 to 8 carbon atoms. Specific examples of such conjugated diene compounds include 1,3-butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. The conjugated diene compound may be used alone or in combination of two or more types.

[0050] From the viewpoint of improving the mechanical strength of an adhesive layer containing copolymer A, the conjugated diene compound as a monomer of copolymer A preferably contains at least one selected from the group consisting of 1,3-butadiene and isoprene, more preferably consists of only at least one selected from the group consisting of 1,3-butadiene and isoprene, and even more preferably consists of only 1,3-butadiene. In other words, the conjugated diene units in copolymer A preferably contain at least one selected from the group consisting of 1,3-butadiene units and isoprene units, more preferably consists of only at least one selected from the group consisting of 1,3-butadiene units and isoprene units, and even more preferably consists of only 1,3-butadiene units.

[0051] In copolymer A, the proportion of 1,2-adducts (including 3,4-adducts) of conjugated diene units is preferably 10 mol% or less. When the proportion is 10 mol% or less, the heat resistance and flex fatigue resistance of copolymer A can be improved. From the same viewpoint, the proportion of 1,2-adducts (including 3,4-adducts) of conjugated diene units in the binary copolymer is more preferably 8 mol% or less, and even more preferably 6 mol% or less. Note that the proportion of 1,2-adducts (including 3,4-adducts) of conjugated diene units is the proportion in all conjugated diene units, not the proportion in copolymer A as a whole. Furthermore, when the conjugated diene units are butadiene units, the proportion has the same meaning as the 1,2-vinyl bond content.

[0052] In copolymer A, the content of conjugated diene units is preferably more than 0 mol% and not more than 50 mol%. In this case, the elongation and weather resistance of copolymer A can be improved. From the same viewpoint, the content of conjugated diene units in copolymer A is more preferably 40 mol% or less. Furthermore, from the viewpoint of further improving adhesiveness, the content of conjugated diene units in copolymer A is more preferably 3 mol% or more, even more preferably 5 mol% or more, even more preferably 10 mol% or more, and even more preferably 20 mol% or more.

[0053] Furthermore, when copolymer A is a terpolymer or multicomponent copolymer, the content of conjugated diene units is preferably 1 to 50 mol%. In this case, the adhesive properties of the adhesive layer containing copolymer A can be further improved, and the flexibility and mechanical strength can be improved. From the same viewpoint, the content of conjugated diene units in copolymer A is more preferably 3 mol% or more, even more preferably 5 mol% or more, even more preferably 10 mol% or more, and even more preferably 20 mol or more, and more preferably 40 mol% or less, and even more preferably 35 mol% or less.

[0054] The non-conjugated olefin unit is a structural unit derived from a non-conjugated olefin compound as a monomer. Here, the non-conjugated olefin compound refers to an aliphatic unsaturated hydrocarbon compound having one or more carbon-carbon double bonds. The non-conjugated olefin compound preferably has 2 to 10 carbon atoms. Specific examples of such non-conjugated olefin compounds include α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene, and heteroatom-substituted alkene compounds such as vinyl pivalate, 1-phenylthioethene, and N-vinylpyrrolidone. The non-conjugated olefin compound may be a single compound or a combination of two or more compounds.

[0055] The non-conjugated olefin compound as a monomer of copolymer A is preferably an acyclic non-conjugated olefin compound from the viewpoint of improving the mechanical strength of the adhesive layer containing copolymer A, and the acyclic non-conjugated olefin compound is more preferably an α-olefin, even more preferably an α-olefin containing ethylene, and particularly preferably consisting of ethylene alone. In other words, the non-conjugated olefin unit in copolymer A is preferably an acyclic non-conjugated olefin unit, and the acyclic non-conjugated olefin unit is more preferably an α-olefin unit, even more preferably an α-olefin unit containing ethylene, and particularly preferably consisting of ethylene alone.

[0056] When copolymer A is a binary copolymer, the content of non-conjugated olefin units is preferably 50 mol% or more and less than 100 mol%. In this case, the fracture properties at high temperatures of an adhesive layer containing copolymer A can be effectively improved. From the same viewpoint, the proportion of non-conjugated olefin units in copolymer A is more preferably 60 mol% or more.

[0057] Furthermore, when copolymer A is a terpolymer or multipolymer, the content of non-conjugated olefin units is preferably 40 to 97 mol% or less. In this case, the mechanical strength of the adhesive layer containing copolymer A can be improved. From the same viewpoint, the content of non-conjugated olefin units in copolymer A is more preferably 45 mol% or more, even more preferably 55 mol% or more, particularly preferably 60 mol% or more, and more preferably 95 mol% or less, even more preferably 90 mol% or less.

[0058] Copolymer A preferably has an aromatic vinyl unit in addition to the conjugated diene unit and the non-conjugated olefin unit. By having the aromatic vinyl unit, copolymer A cuts crystalline components such as ethylene crystalline components, suppresses excessive crystallization derived from the non-conjugated olefin unit, improves the rigidity of copolymer A while hardly impairing elasticity, and can obtain high crack resistance, thereby improving the crack resistance of an adhesive layer containing said copolymer A.

[0059] The aromatic vinyl unit is a structural unit derived from an aromatic vinyl compound as a monomer. Here, the aromatic vinyl compound refers to an aromatic compound substituted with at least a vinyl group, and is not included in conjugated diene compounds. The aromatic vinyl compound preferably has 8 to 10 carbon atoms. Examples of such aromatic vinyl compounds include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, and p-ethylstyrene. The aromatic vinyl compound may be used alone or in combination of two or more.

[0060] The aromatic vinyl compound as a monomer of copolymer A preferably contains styrene, more preferably consists of styrene, from the viewpoint of improving the mechanical strength of the adhesive layer containing copolymer A. In other words, the aromatic vinyl unit in copolymer A preferably contains styrene unit, more preferably consists of styrene unit. Note that the aromatic ring in the aromatic vinyl unit is not included in the main chain of the copolymer unless it is bonded to an adjacent unit.

[0061] When copolymer A further contains an aromatic vinyl unit, the content of the aromatic vinyl unit is preferably 2 to 35 mol %. In this case, the mechanical strength of the adhesive layer containing copolymer A can be improved. From the same viewpoint, the content of the aromatic vinyl unit in copolymer A is more preferably 30 mol % or less, and even more preferably 25 mol % or less.

[0062] In copolymer A, from the viewpoint of obtaining the desired effects of the present invention, the content of other structural units other than conjugated diene units, non-conjugated olefin units, and aromatic vinyl units is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less of the total copolymer A. It is particularly preferable that no other structural units are contained, that is, the content is 0 mol%. In other words, it is preferable that copolymer A has only conjugated diene units and non-conjugated olefin units, that is, a binary copolymer composed of two types of units, or that has conjugated diene units, non-conjugated olefin units, and aromatic vinyl units, that is, a ternary copolymer composed of three types of units. Furthermore, from the viewpoint of reliably obtaining the desired effects, it is preferable that copolymer A has a butylene unit content of 0 mol%.

[0063] From the viewpoint of improving the mechanical strength of a layer containing the copolymer, copolymer A is preferably a polymer obtained by polymerizing at least one type of conjugated diene compound, one type of non-conjugated olefin compound, and one type of aromatic vinyl compound as monomers. In other words, copolymer A is preferably a copolymer having one type of conjugated diene unit, one type of non-conjugated olefin unit, and one type of aromatic vinyl unit, more preferably a terpolymer consisting of one type of conjugated diene unit, one type of non-conjugated olefin unit, and one type of aromatic vinyl unit, and even more preferably a terpolymer consisting of 1,3-butadiene unit, ethylene unit, and styrene unit. Here, "one type of conjugated diene unit" encompasses conjugated diene units having different bonding modes.

[0064] Copolymer A, particularly when it is a binary copolymer, preferably has a conjugated diene unit content of more than 0 mol% and not more than 50 mol% and a non-conjugated olefin unit content of 50 mol% or more and less than 100 mol%. In this case, the elongation and weather resistance of copolymer A can be improved, and the fracture properties at high temperatures of an adhesive layer containing copolymer A can be effectively improved.

[0065] Furthermore, when copolymer A is a terpolymer or multipolymer, it is preferable that the content of conjugated diene units is 1 to 50 mol%, the content of non-conjugated olefin units is 40 to 97 mol%, and the content of aromatic vinyl units is 2 to 35 mol%. In this case, the flexibility and mechanical strength of the adhesive layer containing copolymer A can be improved.

[0066] The copolymer A preferably has a polystyrene-equivalent number average molecular weight (Mn) of 10,000 to 9,000,000 (10 to 9,000 kg / mol), more preferably 100,000 to 8,000,000 (100 to 8,000 kg / mol). When the Mn of the copolymer A is 10,000 or more, the mechanical strength of the layer containing the copolymer A can be sufficiently ensured, and when the Mn is 9,000,000 or less, good workability can be maintained when using the copolymer A itself or an adhesive layer containing the copolymer A.

[0067] The polystyrene-equivalent weight average molecular weight (Mw) of the copolymer A is preferably 10,000 to 10,000,000 (10 to 10,000 kg / mol), more preferably 50,000 to 9,000,000 (50 to 9,000 kg / mol), and even more preferably 100,000 to 8,000,000 (100 to 8,000 kg / mol). When the Mw of the copolymer A is 10,000 or more, the mechanical strength of the adhesive layer containing the copolymer A can be sufficiently ensured, and when the Mw is 10,000,000 or less, good workability can be maintained when using the copolymer A itself or an adhesive layer containing the copolymer A.

[0068] The copolymer A preferably has a molecular weight distribution [Mw / Mn (weight average molecular weight / number average molecular weight)] of 1.00 to 4.00, more preferably 1.00 to 3.50, and even more preferably 1.80 to 3.00. When the molecular weight distribution of the copolymer A is 4.00 or less, the copolymer A can have sufficient uniformity in its physical properties.

[0069] The number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the copolymer A are determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0070] The copolymer A preferably has a melting point (Tm) of 50 to 120°C. If the melting point of the copolymer A is 50°C or higher, the crystallinity of the copolymer A is increased, and the crack resistance of an adhesive layer containing the copolymer A can be improved. If the melting point of the copolymer A is 120°C or lower, workability when using the copolymer A itself or an adhesive layer containing the copolymer A is improved. From the same viewpoint, the melting point of the copolymer A is more preferably 110°C or lower. The melting point of the copolymer A can be measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121-1987.

[0071] The glass transition temperature (Tg) of the copolymer A, as measured by a differential scanning calorimeter (DSC), is preferably 0°C or lower, and more preferably -110°C to -10°C. When the glass transition temperature of the copolymer A is 0°C or lower, the mechanical strength of the adhesive containing the copolymer A can be further improved. The glass transition temperature of the copolymer A can be measured using a differential scanning calorimeter in accordance with JIS K 7121-1987.

[0072] The degree of crystallinity of the copolymer A is preferably 0.5 to 50%, more preferably 3 to 45%, and even more preferably 5 to 45%. When the degree of crystallinity of the copolymer A is 0.5% or more, the crystallinity of the copolymer A resulting from the non-conjugated olefin units can be sufficiently ensured, and the mechanical strength of the adhesive layer containing the copolymer A can be further improved. Furthermore, when the degree of crystallinity of the copolymer A is 50% or less, the workability during kneading and extrusion processability are improved when using the copolymer A itself or an adhesive layer containing the copolymer A. The degree of crystallinity of the copolymer A can be calculated from the energy ratio between the polyethylene and the copolymer A by measuring the crystalline melting energy of a 100% crystalline polyethylene and the melting peak energy of the copolymer A. The melting peak energy can be measured using a differential scanning calorimeter.

[0073] The main chain of the copolymer A preferably consists solely of an acyclic structure. This can further improve the mechanical strength of an adhesive layer containing the copolymer A. NMR is used as a primary measurement means for determining whether the main chain of the copolymer A has a cyclic structure. Specifically, when no peaks attributable to cyclic structures present in the main chain (for example, peaks appearing at 10 to 24 ppm for three- to five-membered rings) are observed, this indicates that the main chain of the copolymer A consists solely of an acyclic structure. In this specification, the main chain of a polymer means a linear molecular chain in which all other molecular chains (long molecular chains, short molecular chains, or both) are linked together like pendants [see "Glossary of Basic Terms in Polymer Science IUPAC Recommendations 1996", Pure Appl. Chem. , 68, 2287-2311 (1996), Section 1.34. The copolymer A may have either a linear or branched structure, but preferably has a linear structure.

[0074] The copolymer A has conjugated diene units, and therefore can be crosslinked. The copolymer A has conjugated diene units, and therefore acts as an elastic body and is stretchable. The copolymer A can be injection molded and stretched, and therefore can be processed into a film. The copolymer A can also be foamed.

[0075] -Production of Copolymer A- When producing a binary copolymer having only conjugated diene units and non-conjugated olefin units, i.e., composed of two types of units, as the copolymer A, it is possible to produce the copolymer A through a polymerization step using a conjugated diene compound and a non-conjugated olefin compound as monomers. Furthermore, when producing a terpolymer having conjugated diene units, non-conjugated olefin units, and aromatic vinyl units, i.e., composed of three types of units, as the copolymer A, it is possible to produce the copolymer A through a polymerization step using a conjugated diene compound, a non-conjugated olefin compound, and an aromatic vinyl compound as monomers.

[0076] The method for producing copolymer A may further include a coupling step, a washing step, and other steps as necessary. Hereinafter, the method for producing copolymer A will be described, taking the case of producing a terpolymer as a representative example.

[0077] In the production of copolymer A, it is preferable to first polymerize only a non-conjugated olefin compound and an aromatic vinyl compound in the presence of a polymerization catalyst without adding a conjugated diene compound. In particular, when using a catalyst composition described below, the conjugated diene compound is more reactive than the non-conjugated olefin compound and the aromatic vinyl compound, so it is difficult to polymerize either or both of the non-conjugated olefin compound and the aromatic vinyl compound in the presence of the conjugated diene compound. Furthermore, due to the characteristics of the catalyst, it is also difficult to first polymerize the conjugated diene compound and then additionally polymerize the non-conjugated olefin compound and the aromatic vinyl compound.

[0078] The polymerization method may be any method such as solution polymerization, suspension polymerization, liquid phase bulk polymerization, emulsion polymerization, gas phase polymerization, solid phase polymerization, etc. When a solvent is used in the polymerization reaction, any solvent may be used as long as it is inert in the polymerization reaction, and examples thereof include toluene, cyclohexane, and normal hexane.

[0079] The polymerization process may be carried out in one stage or in two or more stages. A single-stage polymerization process is a process in which all types of monomers to be polymerized, i.e., a conjugated diene compound, a non-conjugated olefin compound, an aromatic vinyl compound, and other monomers, preferably a conjugated diene compound, a non-conjugated olefin compound, and an aromatic vinyl compound, are simultaneously reacted and polymerized. A multi-stage polymerization process is a process in which one or two types of monomers are first reacted in part or in whole to form a polymer (first polymerization stage), and then one or more stages (second polymerization stage to final polymerization stage) are carried out to polymerize the monomers not added in the first polymerization stage, the remainder of the monomers added in the first polymerization stage, etc. are added and polymerized. In particular, in the production of the copolymer A, it is preferable to carry out the polymerization process in multiple stages.

[0080] In the polymerization step, the polymerization reaction is preferably carried out in an atmosphere of an inert gas, preferably nitrogen gas or argon gas. The temperature of the polymerization reaction is not particularly limited, but is preferably, for example, in the range of -100°C to 200°C, and can also be set to about room temperature. The pressure of the polymerization reaction is preferably in the range of 0.1 to 10.0 MPa in order to sufficiently incorporate the conjugated diene compound into the polymerization reaction system. The reaction time of the polymerization reaction is also not particularly limited, and is preferably, for example, in the range of 1 second to 10 days, but can be appropriately selected depending on conditions such as the type of polymerization catalyst and the polymerization temperature. In the polymerization step of the conjugated diene compound, the polymerization may be terminated using a polymerization terminator such as methanol, ethanol, or isopropanol.

[0081] The polymerization step is preferably carried out in multiple stages. More preferably, a first step is carried out in which a first monomer raw material containing at least an aromatic vinyl compound is mixed with a polymerization catalyst to obtain a polymerization mixture, and a second step is carried out in which a second monomer raw material containing at least one selected from the group consisting of a conjugated diene compound, a non-conjugated olefin compound, and an aromatic vinyl compound is introduced into the polymerization mixture. Furthermore, it is more preferable that the first monomer raw material does not contain a conjugated diene compound, and the second monomer raw material contains a conjugated diene compound.

[0082] The first monomer starting material used in the first step may contain a non-conjugated olefin compound together with an aromatic vinyl compound. The first monomer starting material may contain the entire amount of the aromatic vinyl compound used, or may contain only a portion of the aromatic vinyl compound. The non-conjugated olefin compound is contained in at least one of the first monomer starting material and the second monomer starting material.

[0083] The first step is preferably carried out in a reactor under an atmosphere of an inert gas, preferably nitrogen gas or argon gas. The temperature (reaction temperature) in the first step is not particularly limited, but is preferably in the range of -100°C to 200°C, and can also be around room temperature. The pressure in the first step is also not particularly limited, but is preferably in the range of 0.1 to 10.0 MPa in order to sufficiently incorporate the aromatic vinyl compound into the polymerization reaction system. The time spent in the first step (reaction time) can be appropriately selected depending on conditions such as the type of polymerization catalyst and the reaction temperature, but is preferably in the range of 5 to 500 minutes, for example, when the reaction temperature is 25 to 80°C.

[0084] In the first step, the polymerization method for obtaining the polymerization mixture can be any method such as solution polymerization, suspension polymerization, liquid phase bulk polymerization, emulsion polymerization, gas phase polymerization, solid phase polymerization, etc. When a solvent is used in the polymerization reaction, any solvent that is inert in the polymerization reaction can be used, and examples thereof include toluene, cyclohexanone, and normal hexane.

[0085] The second monomer raw material used in the second step is preferably a conjugated diene compound alone, or a conjugated diene compound and a non-conjugated olefin compound, or a conjugated diene compound and an aromatic vinyl compound, or a conjugated diene compound, a non-conjugated olefin compound, and an aromatic vinyl compound. When the second monomer raw material contains at least one selected from the group consisting of a non-conjugated olefin compound and an aromatic vinyl compound in addition to the conjugated diene compound, these monomer raw materials may be mixed together with a solvent or the like before being introduced into the polymerization mixture, or each monomer raw material may be introduced individually. The monomer raw materials may be added simultaneously or sequentially. In the second step, the method for introducing the second monomer raw material into the polymerization mixture is not particularly limited, but it is preferable to control the flow rate of each monomer raw material and add them continuously to the polymerization mixture (so-called metering). Here, when a monomer raw material that is gaseous under the conditions of the polymerization reaction system (for example, ethylene as a non-conjugated olefin compound under room temperature and atmospheric pressure conditions) is used, it can be introduced into the polymerization reaction system at a predetermined pressure.

[0086] The second step is preferably carried out in a reactor under an inert gas atmosphere, preferably nitrogen gas or argon gas. The temperature (reaction temperature) in the second step is not particularly limited, but is preferably in the range of -100°C to 200°C, and can also be set to about room temperature. Note that increasing the reaction temperature may decrease the selectivity of cis-1,4 bonds in the conjugated diene units. The pressure in the second step is not particularly limited, but is preferably in the range of 0.1 to 10.0 MPa in order to sufficiently incorporate monomers such as conjugated diene compounds into the polymerization reaction system. The time spent in the second step (reaction time) can be appropriately selected depending on conditions such as the type of polymerization catalyst and the reaction temperature, but is preferably in the range of 0.1 hours to 10 days. In the second step, the polymerization reaction may be terminated using a polymerization terminator such as methanol, ethanol, or isopropanol.

[0087] Here, the polymerization step of the above-mentioned conjugated diene compound, non-conjugated olefin compound, and aromatic vinyl compound preferably includes a step of polymerizing various monomers in the presence of one or more of the following components (a) to (f) as a catalyst component. Note that, although it is preferable to use one or more of the following components (a) to (f) in the polymerization step, it is more preferable to use a combination of two or more of the following components (a) to (f) as a catalyst composition. (a) component: a rare earth element compound or a reaction product of the rare earth element compound and a Lewis base (b) component: an organometallic compound (c) component: an aluminoxane (d) component: an ionic compound (e) component: a halogen compound (f) component: a cyclopentadiene skeleton-containing compound selected from substituted or unsubstituted cyclopentadiene (a compound having a cyclopentadienyl group), substituted or unsubstituted indene (a compound having an indenyl group), and substituted or unsubstituted fluorene (a compound having a fluorenyl group) The above (a) to (f) components can be used in the polymerization step, for example, by referring to WO 2018 / 092733.

[0088] The coupling step is a step of carrying out a reaction (coupling reaction) to modify at least a portion (e.g., terminals) of the polymer chains of the copolymer A obtained in the polymerization step. In the coupling step, the coupling reaction is preferably carried out when the polymerization reaction reaches 100%. The coupling agent used in the coupling reaction is not particularly limited and can be appropriately selected depending on the purpose. Examples include tin-containing compounds such as bis(1-octadecyl maleate)dioctyltin(IV); isocyanate compounds such as 4,4'-diphenylmethane diisocyanate; and alkoxysilane compounds such as glycidylpropyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, bis(1-octadecyl maleate)dioctyltin(IV) is preferred in terms of reaction efficiency and low gel formation. The number average molecular weight (Mn) of the copolymer A can be increased by carrying out the coupling reaction.

[0089] The washing step is a step of washing the copolymer A obtained in the polymerization step. The medium used for washing is not particularly limited and can be appropriately selected depending on the purpose. Examples include methanol, ethanol, and isopropanol. However, when using a Lewis acid-derived catalyst as the polymerization catalyst, an acid (e.g., hydrochloric acid, sulfuric acid, nitric acid, etc.) can be added to these solvents. The amount of acid added is preferably 15 mol% or less relative to the solvent. By adding an amount of 15 mol% or less, the acid is less likely to remain in the copolymer and to adversely affect the reaction during kneading and vulcanization of the composition. This washing step can suitably reduce the amount of catalyst residue in the copolymer A.

[0090] <Method for manufacturing pneumatic tire> The method for manufacturing a pneumatic tire of the present invention is a method for manufacturing the tire of the present embodiment described above. The method for manufacturing a pneumatic tire of the present invention is characterized by including heating an adhesive layer laminated on the outer surface of unvulcanized rubber, and heating the adhesive layer and a resin layer laminated together. The unvulcanized rubber is a so-called intermediate member that will eventually become the rubber member of a tire by vulcanization.

[0091] In this manufacturing method, by heating the unvulcanized rubber and adhesive layer in a state in which the adhesive layer is laminated on the outer surface of the unvulcanized rubber, the adhesive layer and the unvulcanized rubber co-vulcanize, thereby improving the bonding strength between the adhesive layer and the rubber component in the finally obtained pneumatic tire. Also, in this manufacturing method, by heating the unvulcanized rubber and adhesive layer in a state in which the adhesive layer and the resin layer are laminated, the adhesive layer and the resin layer are thermally fused to each other, thereby improving the bonding strength between the adhesive layer and the resin layer in the finally obtained pneumatic tire. Therefore, according to this method of manufacturing a pneumatic tire of the present invention, a pneumatic tire can be manufactured in which the resin layer is firmly bonded to the outer surface.

[0092] In the method for producing a pneumatic tire of the present invention, heating the adhesive layer laminated on the outer surface of the unvulcanized rubber and heating the adhesive layer and the resin layer laminated on each other may be performed at the same time or at different times. Furthermore, the method for producing a pneumatic tire of the present invention may further include heating other than that described above, such as heating to vulcanize only the unvulcanized rubber.

[0093] Hereinafter, the method for manufacturing a pneumatic tire of the present invention will be specifically described based on several embodiments.

[0094] (First Manufacturing Method) The first manufacturing method, which is one aspect of the manufacturing method for a pneumatic tire of the present invention, is a manufacturing method including a step of laminating an adhesive layer and a resin layer in this order on the outer surface of unvulcanized rubber (laminating step), and a step of heating the unvulcanized rubber on which the adhesive layer and the resin layer are laminated (heating step).

[0095] In the first manufacturing method, the unvulcanized rubber and the adhesive layer are co-vulcanized by the heating step described above, and the adhesive layer and the resin layer are heat-sealed to each other. This first manufacturing method is advantageous in that the heating step can be performed only once.

[0096] The temperature in the heating step of the first production method is preferably within a temperature range in which the unvulcanized rubber is appropriately vulcanized and within a temperature range at or above the melting point of the resin contained in the resin layer.

[0097] The temperature range in which unvulcanized rubber is appropriately vulcanized is, for example, 100 to 190° C., preferably 110° C. or higher, or 120° C. or higher, and preferably 180° C. or lower, or 170° C. or lower. If the temperature exceeds the upper limit described above, there is a risk of over-vulcanization and consequent deterioration.

[0098] (Second Manufacturing Method) A second manufacturing method, which is one aspect of the manufacturing method for a pneumatic tire of the present invention, is a manufacturing method including the steps of laminating an adhesive layer and a resin layer to obtain a composite layer (first lamination step), heating the composite layer (first heating step), laminating the heated composite layer onto the outer surface of unvulcanized rubber so that the adhesive layer faces the unvulcanized rubber (second lamination step), and heating the unvulcanized rubber on which the composite layer (adhesive layer and resin layer) has been laminated (second heating step).

[0099] In the second manufacturing method, the adhesive layer and the resin layer can be heat-sealed to each other by the first heating step described above, and the unvulcanized rubber and the adhesive layer can be co-vulcanized by the second heating step described above. Furthermore, the second heating step is expected to reinforce the heat fusion between the adhesive layer and the resin layer. This second manufacturing method is advantageous in that, since the adhesive layer and the resin layer are heat-sealed to each other separately in advance, it is possible to prevent excessive heat from being applied to the unvulcanized rubber, thereby preventing over-vulcanization, for example, when the temperature required for the heat fusion is relatively high. This second manufacturing method is also advantageous in that it further enhances the bonding (heat fusion) between the adhesive layer and the resin layer.

[0100] The temperature in the first heating step of the second manufacturing method is preferably at or above the melting point of the resin contained in the resin layer, and the temperature in the second heating step of the second manufacturing method is preferably within the temperature range (described above) at which the unvulcanized rubber is appropriately vulcanized.

[0101] (Third Manufacturing Method) A third manufacturing method, which is one aspect of the manufacturing method for a pneumatic tire of the present invention, is a manufacturing method including the steps of laminating an adhesive layer on the outer surface of unvulcanized rubber (first lamination step), heating the unvulcanized rubber with the adhesive layer laminated thereon to convert the unvulcanized rubber into vulcanized rubber (first heating step), laminating a resin layer on the adhesive layer laminated on the vulcanized rubber (second lamination step), and heating the vulcanized rubber with the adhesive layer and resin layer laminated thereon (second heating step).

[0102] In the third manufacturing method, the unvulcanized rubber and the adhesive layer can be co-vulcanized by the first heating step described above, and the adhesive layer and the resin layer can be thermally fused to each other by the second heating step described above. Furthermore, the second heating step can be expected to reinforce the co-vulcanization of the unvulcanized rubber and the adhesive layer. This third manufacturing method is advantageous in that it further improves the bonding strength between the vulcanized rubber (rubber member) and the adhesive layer.

[0103] The temperature in the first heating step of the third manufacturing method is preferably within the temperature range (described above) in which the unvulcanized rubber is appropriately vulcanized, and the temperature in the second heating step of the third manufacturing method is preferably within the temperature range (described above) in which the risk of over-vulcanization is avoided and is at or above the melting point of the resin contained in the resin layer.

[0104] (Other Manufacturing Conditions, etc.) In the manufacturing method described above, the time for each heating step is not particularly limited, and can be, for example, 3 minutes to 6 hours.

[0105] In the above-described manufacturing methods, the adhesive layer may be laminated by applying a solution containing the copolymer A and an organic solvent, followed by drying to remove the organic solvent. Specifically, in the first and third manufacturing methods, the solution containing the copolymer A and an organic solvent can be applied onto the outer surface of the unvulcanized rubber. In the second manufacturing method, the solution containing the copolymer A and an organic solvent can be applied onto the resin layer.

[0106] Examples of the organic solvent include aliphatic hydrocarbons such as pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, diethylcyclohexane, decahydronaphthalene, bicycloheptane, tricyclodecane, hexahydroindene, and cyclooctane; aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and 1,2-dichloroethane; halogenated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene; nitrogen-containing hydrocarbons such as nitromethane, nitrobenzene, and acetonitrile; ethers such as diethyl ether and tetrahydrofuran; and mixed solvents of combinations thereof.

[0107] The above-described manufacturing method can be appropriately selected in consideration of the resin used in the resin layer. For example, when a polyamide-based resin (such as nylon 6 or nylon 66) is used in the resin layer, these resins tend to have a relatively high melting point of 200°C or higher, so it is preferable to manufacture a pneumatic tire using the second manufacturing method. On the other hand, when a polyolefin-based resin or a polyvinyl alcohol-based resin is used in the resin layer, it is also preferable to manufacture a pneumatic tire using any of the first to third manufacturing methods.

[0108] The present invention will be described in more detail below with reference to examples. However, these examples are intended to illustrate the present invention and are not intended to limit the present invention in any way.

[0109] <Synthesis of Copolymer Having Conjugated Diene Units and Non-Conjugated Olefin Units> (Synthesis of Copolymer A1) 75 g of styrene and 675 g of toluene were placed in a thoroughly dried 2000 mL pressure-resistant stainless steel reactor. Meanwhile, in a glove box under a nitrogen atmosphere, ((1-benzyldimethylsilyl-3-methyl)indenyl)bis(bis(dimethylsilyl)amide)gadolinium complex {(1-BnMe ２ Si-3-Me]C ９ H ５ Gd[N(SiHMe ２ )２ ] ２} 0.075 mmol, dimethylanilinium tetrakis(pentafluorophenyl)borate [Me ２ NHPhB(C ６ F ５ ) ４ 0.083 mmol of methyl methyl ketone and 0.35 mmol of diisobutylaluminum hydride were added, and 30 g of toluene was further added to obtain a catalyst solution. The obtained catalyst solution was added to the pressure-resistant stainless steel reactor and heated to 60°C. Next, ethylene was charged into the pressure-resistant stainless steel reactor at a pressure of 1.5 MPa, and copolymerization was carried out for a total of 3 hours at 75°C. During the copolymerization, 80 g of a toluene solution containing 20 g of 1,3-butadiene was continuously added at a rate of 0.4 to 0.6 mL / min. Next, 1 mL of a 5% by mass solution of 2,2'-methylene-bis(4-ethyl-6-t-butylphenol) (NS-5) in isopropanol was added to the pressure-resistant stainless steel reactor to terminate the reaction. Next, the copolymer was separated using a large amount of methanol and dried under vacuum at 50°C to obtain copolymer A1.

[0110] (Synthesis of Copolymer A2) In a thoroughly dried 2000 mL pressure-resistant stainless steel reactor, 30 g of styrene, 20 g of a toluene solution containing 5 g of 1,3-butadiene, and 430 g of toluene were placed. Meanwhile, in a glove box under a nitrogen atmosphere, mono(1,3-bis(tert-butyldimethylsilyl)indenyl)bis(bis(dimethylsilyl)amide)gadolinium complex {1,3-[(t-Bu)Me ２ Si] ２ C ９ H ５ Gd[N(SiHMe ２ ) ２ ] ２} 0.075 mmol, dimethylanilinium tetrakis(pentafluorophenyl)borate [Me ２ NHPhB(C ６ F ５ ) ４0.075 mmol of methyl methyl ketone and 0.35 mmol of diisobutylaluminum hydride were added, and 20 mL of toluene was further added to obtain a catalyst solution. The obtained catalyst solution was added to the pressure-resistant stainless steel reactor and heated to 60°C. Next, ethylene was charged into the pressure-resistant stainless steel reactor at a pressure of 1.0 MPa, and copolymerization was carried out for a total of 3 hours at 75°C. During the copolymerization, 120 g of a toluene solution containing 30 g of 1,3-butadiene was continuously added at a rate of 2.5 to 2.8 mL / min. Next, 1 mL of a 5% by mass solution of 2,2'-methylene-bis(4-ethyl-6-t-butylphenol) (NS-5) in isopropanol was added to the pressure-resistant stainless steel reactor to terminate the reaction. Next, the copolymer was separated using a large amount of methanol and dried under vacuum at 50°C to obtain copolymer A2.

[0111] (Synthesis of Copolymer A3) 30 g of styrene, 20 g of a toluene solution containing 5 g of 1,3-butadiene, and 430 g of toluene were placed in a thoroughly dried 2000 mL pressure-resistant stainless steel reactor. Meanwhile, in a glove box under a nitrogen atmosphere, mono(1,3-bis(tert-butyldimethylsilyl)indenyl)bis(bis(dimethylsilyl)amide)gadolinium complex {1,3-[(t-Bu)Me ２ Si] ２ C ９ H ５ Gd[N(SiHMe ２ ) ２ ] ２} 0.075 mmol, dimethylanilinium tetrakis(pentafluorophenyl)borate [Me ２ NHPhB(C ６ F ５ ) ４0.075 mmol of methyl methyl ketone and 0.35 mmol of diisobutylaluminum hydride were added, and 20 mL of toluene was further added to obtain a catalyst solution. The obtained catalyst solution was added to the pressure-resistant stainless steel reactor and heated to 60°C. Next, ethylene was charged into the pressure-resistant stainless steel reactor at a pressure of 1.0 MPa, and copolymerization was carried out for a total of 3 hours at 75°C. During the copolymerization, 240 g of a toluene solution containing 60 g of 1,3-butadiene was continuously added at a rate of 2.5 to 2.8 mL / min. Next, 1 mL of a 5% by mass solution of 2,2'-methylene-bis(4-ethyl-6-t-butylphenol) (NS-5) in isopropanol was added to the pressure-resistant stainless steel reactor to terminate the reaction. Next, the copolymer was separated using a large amount of methanol and dried under vacuum at 50°C to obtain Copolymer A3.

[0112] (Synthesis of Copolymer A4) In a thoroughly dried 2000 mL pressure-resistant stainless steel reactor, 30 g of styrene, 20 g of a toluene solution containing 5 g of 1,3-butadiene, and 430 g of toluene were placed. Meanwhile, in a glove box under a nitrogen atmosphere, mono(1,3-bis(tert-butyldimethylsilyl)indenyl)bis(bis(dimethylsilyl)amido)gadolinium complex {1,3-[(t-Bu)Me ２ Si] ２ C ９ H ５ Gd[N(SiHMe ２ ) ２ ] ２} 0.075 mmol, dimethylanilinium tetrakis(pentafluorophenyl)borate [Me ２ NHPhB(C ６ F ５ ) ４0.075 mmol of methyl methyl ketone and 0.35 mmol of diisobutylaluminum hydride were added, and 20 mL of toluene was further added to obtain a catalyst solution. The obtained catalyst solution was added to the pressure-resistant stainless steel reactor and heated to 60°C. Next, ethylene was charged into the pressure-resistant stainless steel reactor at a pressure of 1.0 MPa, and copolymerization was carried out for a total of 3 hours at 75°C. During the copolymerization, 350 g of a toluene solution containing 90 g of 1,3-butadiene was continuously added at a rate of 2.5 to 2.8 mL / min. Next, 1 mL of a 5% by mass solution of 2,2'-methylene-bis(4-ethyl-6-t-butylphenol) (NS-5) in isopropanol was added to the pressure-resistant stainless steel reactor to terminate the reaction. Next, the copolymer was separated using a large amount of methanol and dried under vacuum at 50°C to obtain Copolymer A4.

[0113] <Measurement of Physical Properties of Copolymers> The synthesized copolymers A1 to A4 were measured for the following physical properties. The results are shown in Table 1.

[0114] (1) Contents of butadiene units, ethylene units, and styrene units The contents (mol%) of butadiene units, ethylene units, and styrene units in the copolymer are determined by １ It was determined from the integral ratio of each peak in the H-NMR spectrum (100°C, d-tetrachloroethane standard: 6 ppm).

[0115] (2) Number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) Gel permeation chromatography [GPC: HLC-8121GPC / HT manufactured by Tosoh Corporation, column: GMH manufactured by Tosoh Corporation] ＨＲ The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the copolymer in terms of polystyrene were determined using a differential refractometer (RI) with a monodisperse polystyrene as a standard. The measurement temperature was 40°C.

[0116] (3) Proportion of 1,4-bonds in butadiene units The proportion of 1,4-bonds was calculated by determining the proportion of 1,2-bonds and 3,4-bonds by an infrared method (Morello method) and subtracting the total amount of 1,2-bonds and 3,4-bonds from 100%.

[0117] (4) Melting Point (Tm) The melting point (Tm) of the copolymer was measured using a differential scanning calorimeter (DSC, manufactured by TA Instruments Japan, "DSCQ2000") in accordance with JIS K 7121-1987.

[0118] (5) Glass Transition Temperature (Tg) The glass transition temperature (Tg) of the copolymer was measured using a differential scanning calorimeter (DSC, manufactured by TA Instruments Japan, "DSCQ2000") in accordance with JIS K 7121-1987.

[0119] (6) Crystallinity The crystalline melting energy of 100% crystalline polyethylene and the melting peak energy of the resulting copolymer at 0 to 120°C were measured, and the crystallinity was calculated from the energy ratio between the polyethylene and the copolymer. The melting peak energy was measured using a differential scanning calorimeter (DSC, manufactured by TA Instruments Japan, Ltd., "DSCQ2000").

[0120] (7) Confirmation of main chain structure For the synthesized copolymer, １３ A C-NMR spectrum was measured. １３ In the C-NMR spectrum chart, no peaks were observed between 10 and 24 ppm, confirming that the main chain of each of the synthesized copolymers A1 to A4 was composed solely of an acyclic structure.

[0121]

[0122] <Preparation of Rubber Sheet> On the other hand, a rubber composition was prepared by blending and kneading each component according to the formulation shown in Table 2. A rubber sheet (unvulcanized rubber) having a thickness of 2 mm was prepared from the obtained rubber composition.

[0123]

[0124] * 1 Carbon black: HAF grade, manufactured by Asahi Carbon Co., Ltd., trade name "Asahi # 70" * 2 Antioxidant: 6PPD, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac (registered trademark) 6C" * 3 Vulcanization accelerator: CZ, N-cyclohexyl-2-benzothiazolyl sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccela (registered trademark) CZ"

[0125] Example 1 Using the copolymer A1 synthesized as described above, a 500 μm-thick adhesive layer 1 was prepared by heat pressing at 160°C. A 500 μm-thick sheet of LLDPE (linear low-density polyethylene, "Yumerit 1540F" manufactured by Ube Maruzen Polyethylene Co., Ltd.) was also prepared and used as the resin layer 1. The adhesive layer 1 and the resin layer 1 were then laminated in this order on the surface of the rubber sheet (unvulcanized rubber) prepared as described above, and then press-molded for 20 minutes while heating to 160°C. This vulcanized the rubber sheet (unvulcanized rubber), yielding a multilayered vulcanized rubber sheet 1 in which the adhesive layer 1 and the resin layer 1 were thermally fused together.

[0126] A peel test was conducted on the obtained multilayered vulcanized rubber sheet 1 at room temperature (25°C), and it was found that peeling occurred at the interface between the vulcanized rubber sheet and the adhesive layer 1, with a peel strength of 37 N / 10 mm. It was confirmed that peeling did not occur at the interface between the adhesive layer 1 and the resin layer 1, and the peel strength was 150 N / 10 mm or more.

[0127] (Example 2) Using the copolymer A2 synthesized as described above, a 500 μm-thick adhesive layer 2 was produced by heat pressing at 160° C. Then, the same procedure as in Example 1 was carried out except that adhesive layer 2 was used instead of adhesive layer 1, and the rubber sheet (unvulcanized rubber) was vulcanized, and a multilayered vulcanized rubber sheet 2 was obtained in which the adhesive layer 2 and the resin layer 1 were heat-fused together.

[0128] A peel test was carried out on the obtained multilayered vulcanized rubber sheet 2 at room temperature, and peeling occurred at the interface between the vulcanized rubber sheet and the adhesive layer 2, with a peel strength of 40 N / 10 mm. At the same time, peeling did not occur at the interface between the adhesive layer 2 and the resin layer 1, and it was confirmed that the peel strength was 150 N / 10 mm or more.

[0129] (Example 3) Using the copolymer A3 synthesized as described above, a 500 μm-thick adhesive layer 3 was produced by heat pressing at 160° C. Then, the same procedure as in Example 1 was carried out except that adhesive layer 3 was used instead of adhesive layer 1, and the rubber sheet (unvulcanized rubber) was vulcanized, and a multilayered vulcanized rubber sheet 3 was obtained in which the adhesive layer 3 and the resin layer 1 were heat-fused together.

[0130] A peel test was carried out on the obtained multilayered vulcanized rubber sheet 3 at room temperature, and peeling occurred at the interface between the vulcanized rubber sheet and the adhesive layer 3, with a peel strength of 58 N / 10 mm. At the same time, peeling did not occur at the interface between the adhesive layer 3 and the resin layer 1, and it was confirmed that the peel strength was 150 N / 10 mm or more.

[0131] (Example 4) Using the copolymer A4 synthesized as described above, a 500 μm-thick adhesive layer 4 was produced by heat pressing at 160° C. Then, the same procedure as in Example 1 was carried out except that adhesive layer 4 was used instead of adhesive layer 1, and the rubber sheet (unvulcanized rubber) was vulcanized, and a multilayered vulcanized rubber sheet 4 was obtained in which the adhesive layer 4 and the resin layer 1 were heat-fused together.

[0132] A peel test was carried out on the obtained multilayered vulcanized rubber sheet 4 at room temperature, and peeling occurred at the interface between the vulcanized rubber sheet and the adhesive layer 4, with a peel strength of 72 N / 10 mm. At that time, peeling did not occur at the interface between the adhesive layer 4 and the resin layer 1, and it was confirmed that the peel strength was 150 N / 10 mm or more.

[0133] (Example 5) A 500 μm thick polypropylene sheet ("Wintec WSX03" manufactured by Japan Polypropylene Corporation) was prepared and used as the resin layer 2. Next, the adhesive layer 1 and the resin layer 2 were laminated together and heated to 180° C. to obtain a laminate 1 in which the adhesive layer 1 and the resin layer 2 were heat-fused together.

[0134] It was confirmed that the peel strength of the interface between the adhesive layer 1 and the resin layer 2 of the obtained laminate 1 was 150 N / 10 mm or more. From this, it is inferred that when a multilayer vulcanized rubber sheet 5 is obtained by the same procedure as in Example 1 except that resin layer 2 is used instead of resin layer 1, and a peel test is carried out at room temperature, peeling at the interface between the adhesive layer 1 and the resin layer 2 will not occur before peeling occurs at the interface between the vulcanized rubber sheet and the adhesive layer 1.

[0135] (Example 6) A 500 μm thick polyamide sheet (UBE Nylon 1013B, manufactured by UBE Corporation) was prepared and used as the resin layer 3. Next, the adhesive layer 1 and the resin layer 3 were laminated together and heated to 240° C. to obtain a laminate 2 in which the adhesive layer 1 and the resin layer 3 were heat-fused together.

[0136] It was confirmed that the peel strength of the interface between the adhesive layer 1 and the resin layer 3 of the obtained laminate 2 was 150 N / 10 mm or more. From this, it is inferred that when a multilayer vulcanized rubber sheet 6 is obtained by the same procedure as in Example 1 except that resin layer 3 is used instead of resin layer 1, and a peel test is carried out at room temperature, peeling at the interface between the adhesive layer 1 and the resin layer 3 will not occur before peeling at the interface between the vulcanized rubber sheet and the adhesive layer 1 occurs.

[0137] Comparative Example 1 An adhesive layer A having a thickness of 500 μm was prepared by using SEBS (styrene-ethylene / butylene-styrene copolymer, "Tuftec H1062" manufactured by Asahi Kasei Corporation) and hot pressing at 180° C. Then, the same procedure as in Example 1 was carried out except that adhesive layer A was used instead of adhesive layer 1, and a multilayer vulcanized rubber sheet A was obtained.

[0138] A peel test was carried out on the obtained multilayered vulcanized rubber sheet A at room temperature, and peeling occurred at the interface between the vulcanized rubber sheet and adhesive layer A, with a peel strength of 6 N / 10 mm. In other words, in this comparative example, the adhesion of the resin layer was insufficient.

[0139] According to the present invention, it is possible to provide a pneumatic tire having a resin layer firmly bonded to the outer surface, and a method for manufacturing such a pneumatic tire.

Claims

1. A pneumatic tire having a resin layer on at least a portion of an outer surface, the resin layer being disposed via an adhesive layer containing a copolymer having conjugated diene units and non-conjugated olefin units.

2. The pneumatic tire according to claim 1, wherein the copolymer has a melting point of 50 to 120°C.

3. The pneumatic tire according to claim 1, wherein the copolymer has a content of the conjugated diene units of more than 0 mol % and not more than 50 mol %, and a content of the non-conjugated olefin units of 50 mol % or more and less than 100 mol %.

4. The pneumatic tire according to claim 1, wherein said copolymer further comprises an aromatic vinyl unit.

5. The pneumatic tire according to claim 4, wherein the copolymer has a conjugated diene unit content of 1 to 50 mol %, a non-conjugated olefin unit content of 40 to 97 mol %, and an aromatic vinyl unit content of 2 to 35 mol %.

6. The pneumatic tire according to claim 1, wherein the adhesive layer has a thickness of 10 μm or more and 2 mm or less.

7. The pneumatic tire according to claim 1, wherein the resin layer has a thickness of 10 μm or more and 50 mm or less.

8. The pneumatic tire according to claim 1, wherein the resin layer contains a thermoplastic resin having a melting point of 25°C or higher and 250°C or lower.

9. The pneumatic tire according to claim 8, wherein the thermoplastic resin is one or more selected from the group consisting of polyolefin-based resins, polyamide-based resins, and polyvinyl alcohol-based resins.

10. The pneumatic tire according to claim 1, wherein the outer surface on which the resin layer is disposed is at least a part of the outer surface of the tread portion and / or the sidewall portion of the tire.

11. A method for producing a pneumatic tire as described in claim 1, comprising: heating the unvulcanized rubber in a state in which an adhesive layer is laminated on the outer surface of the unvulcanized rubber; and heating the adhesive layer and a resin layer in a state in which the adhesive layer and the resin layer are laminated together.

12. A method for producing a pneumatic tire as described in claim 11, comprising the steps of: laminating an adhesive layer and a resin layer in this order on the outer surface of unvulcanized rubber; and heating the unvulcanized rubber on which the adhesive layer and resin layer are laminated.

13. A method for manufacturing a pneumatic tire as described in claim 11, comprising the steps of: laminating an adhesive layer and a resin layer to obtain a composite layer; heating the composite layer; laminating the heated composite layer onto the outer surface of unvulcanized rubber with the adhesive layer facing the unvulcanized rubber; and heating the unvulcanized rubber on which the composite layer is laminated.

14. A method for manufacturing a pneumatic tire as described in claim 11, comprising the steps of: laminating an adhesive layer on an outer surface of unvulcanized rubber; heating the unvulcanized rubber with the adhesive layer laminated thereon to convert the unvulcanized rubber into vulcanized rubber; laminating a resin layer on the adhesive layer laminated on the vulcanized rubber; and heating the vulcanized rubber with the adhesive layer and resin layer laminated thereon to thermally fuse the adhesive layer and the resin layer together.

15. A method for producing a pneumatic tire according to any one of claims 12 to 14, wherein the lamination of the adhesive layer is carried out by applying a solution containing the copolymer and an organic solvent, and then drying to remove the organic solvent.

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