JP6909097B2 - Thermoplastic elastomer composition, air permeable film for tires, and pneumatic tires using this - Google Patents

Description

The present invention relates to a thermoplastic elastomer composition, an air-permeable film for tires, and a pneumatic tire using the same.

An inner liner is provided on the inner surface of the pneumatic tire as an air permeation suppressing layer in order to keep the tire air pressure constant. The inner liner is generally composed of a rubber layer such as butyl rubber or halogenated butyl rubber, which is difficult for gas to permeate. However, in order to reduce the weight of the tire, the use of a thin resin film is being considered.

The air-resistant resin film is obtained by melt-kneading a rubber component and a thermoplastic resin and dynamically cross-linking them. The thermoplastic resin is a continuous phase (matrix phase) and the rubber component is a dispersed phase (domain phase). ), A thermoplastic elastomer composition (Thermoplastic Vulcanizates; TPV) having a sea-island structure is used.

Conventionally, a thermoplastic elastomer composition used for an air-permeable film has been required to have excellent workability, flexibility, and adhesiveness to rubber. As a method for improving the flexibility, it is conceivable to increase the compounding ratio of the rubber component, but when the compounding ratio of the rubber component is increased, the processability deteriorates, so that it is necessary to add a plasticizer. However, when a plasticizer is added, there is a problem that the air permeability is deteriorated.

As a method of blending a large amount of rubber component in a continuous phase with a small amount of plasticizing agent, for example, in Patent Document 1, dynamic cross-linking of a polyamide resin (A) and a halogenated isoolefin paraalkylstyrene copolymer rubber (B) In the method for producing a thermoplastic elastomer composition, the polyamide resin is modified by melt-kneading the compound (C) that can be bonded to the terminal amino group of the polyamide resin into the polyamide resin (A) in advance to obtain the polyamide resin (A). It is disclosed that a large amount of halogenated isoolefin paraalkylstyrene copolymer rubber is blended while suppressing the reaction with the halogenated isoolefin paraalkylstyrene copolymer rubber (B) and reducing the amount of the plasticizer for polyamide resin (). Claim 1, paragraph 0013, etc.).

However, the invention described in Prior Document 1 has an object of improving the low temperature durability of the polyamide resin, and there is no description about processability, flexibility, and adhesiveness to rubber, and these characteristics are not described. There was room for further improvement.

Patent No. 5668876

In view of the above points, the present invention uses a thermoplastic elastomer composition capable of obtaining a resin film having excellent processability, flexibility, and adhesiveness to rubber while maintaining at least air permeability resistance. It is an object of the present invention to provide an air-permeable film for a tire, and a pneumatic tire using the film.

The thermoplastic elastomer composition of the present invention has a continuous phase made of a thermoplastic resin and a dispersed phase made of sulfide rubber dispersed in the continuous phase, and the vulture rubber is based on 100 parts by mass of butyl rubber. The content ratio of the thermoplastic resin to the rubber component (ratio as a polymer component excluding the component such as a filler) is the mass ratio (thermoplastic resin) containing 1 to 10 parts by mass of chlorosulfonated polyethylene. / Rubber component) is 60/40 to 25/75, and the content of the thermoplastic agent in the vulgarized rubber is less than 1 part by mass with respect to 100 parts by mass of butyl rubber .

The air-permeable film for tires of the present invention can be made of the above-mentioned thermoplastic elastomer composition.

The pneumatic tire of the present invention may use the above-mentioned air-permeable film for tires.

According to the thermoplastic elastomer composition of the present invention, an air-permeable film having excellent workability, flexibility, and adhesiveness to rubber can be obtained while maintaining air permeability, and is suitable for tires. Can be used.

It is sectional drawing of the pneumatic tire which concerns on one Embodiment of this invention.

Hereinafter, matters related to the practice of the present invention will be described in detail.

The thermoplastic elastomer composition according to the present embodiment has a sea-island structure in which the thermoplastic resin is a continuous phase (matrix phase) and the rubber component is a dispersed phase (domain phase).

Examples of the thermoplastic resin constituting the continuous phase include nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6/66 copolymer, and nylon 6/66/610 co-weight. Polycarbonate resins such as coalesced, nylon MXD6, nylon 6T, nylon 6 / 6T copolymer; polybutylene terephthalate (PBT), potiethylene terephthalate (PET), polyethylene isophthalate (PEI), PET / PEI copolymer, poly Polyester resins such as allylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, polyoxyalkylene diimide acid / polybutyrate terephthalate copolymer; polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene Polynitrile resins such as polymers (AS), methacrylonitrile / styrene copolymers, methacrylonitrile / styrene / butadiene copolymers; cellulose-based resins such as cellulose acetate, cellulose acetate butyrate; vinylidene fluoride (PVDF), Fluorine resins such as polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE); imide resins such as aromatic polyimide (PI); ethylene-vinyl alcohol co-weight Coalescence (EVOH) can be mentioned, and these can be used alone or in combination of two or more.

Butyl rubber (IIR) is used as the rubber component constituting the dispersed phase. Further, the rubber component may contain other rubber components as long as the effects of the present invention are not impaired. Examples of such rubber components include natural rubber (NR), epoxidized natural rubber (ENR), isoprene rubber (IR), styrene butadiene rubber (SBR), nitrile rubber (NBR), and hydride nitrile rubber (H-). Diene rubbers such as NBR) and hydride styrene butadiene rubbers and their hydrogenated rubbers; olefin rubbers such as ethylene propylene rubber (EPDM), maleic acid-modified ethylene propylene rubber, maleic acid-modified ethylene butylene rubber, and acrylic rubber (ACM). Halogen-containing rubber such as chloroprene rubber (CR); In addition, silicon rubber, fluororubber, polysulfide rubber and the like can be mentioned.

The content ratio of butyl rubber (IIR) in the rubber component constituting the dispersed phase is preferably 80% by mass or more and less than 100% by mass, and more preferably 90% by mass or more and less than 100% by mass.

The content ratio of the thermoplastic resin to the rubber component (ratio as a polymer component excluding the component such as a filler) varies depending on the type of the thermoplastic resin and is not particularly limited, but is a mass ratio (thermoplastic resin / Rubber component), usually about 60/40 to 25/75, more preferably 50/50 to 30/70.

The rubber component constituting the dispersed phase preferably contains 1 to 10 parts by mass of chlorosulfonated polyethylene (CSM) with respect to 100 parts by mass of butyl rubber, and preferably contains 3 to 10 parts by mass. Is more preferable, and it is more preferable that the content is 5 to 10 parts by mass. The chlorosulfonated polyethylene may be kneaded with butyl rubber in advance before the melt-kneading of the thermoplastic resin and the rubber component, or may be added during the melt-kneading of the thermoplastic resin and the rubber component.

Various components generally added to the rubber composition, such as a cross-linking agent, zinc oxide, stearic acid, a filler, a softening agent, and an anti-aging agent, can be appropriately added to the rubber components constituting the dispersed phase. That is, the rubber component constituting the dispersed phase may be composed of a rubber composition obtained by adding various contained components to butyl rubber.

Examples of the cross-linking agent for cross-linking the rubber component include vulcanizing agents such as sulfur and sulfur-containing compounds, vulcanization accelerators, and phenolic resins. From the viewpoint of heat resistance, it is preferable to use a phenol-based resin. Examples of the phenol-based resin include a resin obtained by a condensation reaction between phenols and formaldehyde, and an alkylphenol-formaldehyde condensate or a brominated alkylphenol-formaldehyde condensate is more preferable.

The content of the cross-linking agent is not particularly limited as long as the rubber component can be cross-linked appropriately, and varies depending on the type thereof, but as a guide, it is about 0.1 to 5 parts by mass with respect to 100 parts by mass of butyl rubber.

Sulfur as a cross-linking agent is not essential, and as the cross-linking system, only a vulcanization accelerator or a phenol-based resin may be blended. When the thermoplastic elastomer composition according to the present embodiment is used as an air-permeable film for tires, it is preferable to co-crosslink the rubber member or rubber layer to be bonded at the time of vulcanization, but when sulfur is added. This is because the cross-linking of the rubber component proceeds too much depending on the temperature at which the air-permeable film is produced, and the above-mentioned co-crosslinking becomes difficult.

The various contained components arbitrarily added to the rubber component may be added to the rubber component in advance, or may be added during the melt-kneading of the thermoplastic resin and the rubber component. In particular, it is preferable to add the vulcanization-based components such as the vulcanization accelerator at the final stage of melt-kneading so that the rubber components are not crosslinked as much as possible. Dynamic cross-linking may be performed at the stage of melt-kneading, but if the rubber component is too cross-linked, it becomes difficult to co-crosslink as described above during vulcanization molding of the member to be attached, so that the rubber component is too cross-linked. It is preferable to set the heating time and temperature so that the heating time and temperature are not set.

Further, it is preferable that the rubber component does not substantially contain a plasticizer. Here, "substantially free" means a content in a range in which no significant action or effect is observed depending on the content thereof, and although it varies depending on the type of plasticizer and the like, it is usually contained in 100 parts by mass of butyl rubber. On the other hand, it is less than 1 part by mass, preferably less than 0.1 part by mass.

Plasticizers include dibutyl phthalate, dioctyl phthalate, dioctyl adipate, dibutyl glycol adipate, dibutyl carbitol adipate, dioctyl sebacate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxydiethyl phosphate, butyl. Benzene sulfonamide and the like can be mentioned.

The thermoplastic elastomer composition according to the present embodiment may be a mixture of a thermoplastic resin, a rubber component, and a compatibilizer. By blending the compatibilizer, the interfacial tension between the thermoplastic resin and the rubber component can be reduced, and the dispersed phase of the sea-island structure can be finely divided. As the compatibilizer, as one embodiment, an ethylene-glycidyl (meth) acrylate copolymer (that is, an ethylene-glycidyl methacrylate copolymer and / or an ethylene-glycidyl acrylate copolymer) may be used. The content of the compatibilizer is not particularly limited, but may be 0.5 to 10 parts by mass with respect to 100 parts by mass of butyl rubber.

When the thermoplastic elastomer composition according to the present embodiment is applied to an air-permeable film for tires, a resorcin-based formaldehyde condensate may be contained as an adhesiveness improver. The adhesiveness improver is blended in order to improve the adhesiveness between the air-permeable film and the adjacent rubber member in the tire. As the resorcin-based formaldehyde condensate, a phenol compound containing at least a part of resorcin and a compound obtained by condensing formaldehyde are used. Preferably, a resorcin-alkylphenol-formaldehyde copolymer or a modified resorcin-formaldehyde resin is used. The modified resorcin-formaldehyde resin is one in which an unsaturated group-containing monomer is bonded to at least a part of a phenol compound forming a skeleton to form a side chain of an arylalkyl group (aralkyl group) or a grafted polymer chain. , Or a polymer of an unsaturated group-containing monomer or a mixture of a polymer thereof and resorcin, or the like. Further, it may partially contain an aldehyde compound other than formaldehyde. For example, at least one selected from styrene, α-methylstyrene, p-methylstyrene, α-chlorostyrene, divinylbenzene, vinylnaphthalene, inden, and vinyltoluene (particularly preferably styrene) coexists with resorcin and formaldehyde. It may be a reaction product obtained by mixing a small amount of butyraldehyde or other aldehyde. The content of the resorcin-based formaldehyde condensate is not particularly limited, but may be 1 to 10 parts by mass with respect to 100 parts by mass of butyl rubber.

The thermoplastic elastomer composition according to the embodiment is not limited to this, but can be obtained by melt-kneading a thermoplastic resin and a rubber component together with a cross-linking agent and dynamically cross-linking the rubber with the cross-linking agent. By dynamically cross-linking the rubber component in this way, the particle size of the dispersed phase can be reduced and the flexibility can be improved. Ingredients such as a cross-linking agent may be added during the above kneading, or may be mixed in advance before kneading. The kneading machine used for kneading is not particularly limited, and examples thereof include a twin-screw extruder, a screw extruder, a kneader, and a Banbury mixer. The melt-kneading conditions are not particularly limited, but for example, kneading can be performed at 200 to 250 ° C. at a rotation speed of 100 to 300 rpm for 1 to 3 minutes. The particle size of the dispersed phase of the thermoplastic elastomer composition is not particularly limited, but the average particle size is preferably 0.1 to 2 μm, more preferably 0.1 to 1 μm.

In one embodiment, a cross-linking agent and a CSM are added to the rubber component to prepare pellets of a rubber master batch, and the pellets are put into a kneader together with a thermoplastic resin and a compatibilizer, and melt-kneaded to be dynamic. Pellets of the thermoplastic elastomer composition may be obtained by cross-linking. Further, even if the thermoplastic resin, the rubber component, the cross-linking agent, the CSM and the compatibilizer are put into a kneader without being premixed, melt-kneaded and dynamically cross-linked to obtain pellets of the thermoplastic elastomer composition. good. The adhesive improver may be added at the same time as the rubber component, and may be before or after the dynamic cross-linking. However, when the phenolic resin is added as the cross-linking agent, the adhesive improver should be added after the dynamic cross-linking. Is preferable. The melt-kneading conditions in this case are not particularly limited, but for example, it is preferable to knead at 200 to 250 ° C. at a rotation speed of 100 to 300 rpm for 1 to 3 minutes.

By filming the pellets of the thermoplastic elastomer composition thus obtained, the air-permeable film according to the embodiment of the present invention can be obtained. The method of forming a film is not particularly limited, and a method of forming a normal thermoplastic resin into a film, such as extrusion molding or calendar molding, can be used.

The thickness of the air-permeable film is not particularly limited because it depends on the application, but for example, in the case of a tire, it can be 0.02 to 1.0 mm, preferably 0.05 to 0.5 mm, and more. It is preferably 0.05 to 0.3 mm.

The air permeability of the air-permeable film is also not particularly limited because it depends on the application, but for tires, it conforms to JIS K7126-1 "Plastic-Film and Sheet-Gas Permeability Test Method-Part 1: Differential Pressure Method". It is preferable that the value measured at test gas: air and test temperature: 80 ° C. is at least as air permeable as an inner liner composed of a rubber layer such as butyl rubber or butyl halogenated rubber. More preferably, it is 0.0 × 10 ¹³ fm ² / Pa · s or less.

The air-permeable film according to the present embodiment is applied to various pneumatic tires such as passenger car tires, various automobile tires including heavy-duty tires such as trucks and buses, and motorcycle tires including bicycles. can do.

FIG. 1 is a cross-sectional view of the pneumatic tire 1 according to the embodiment. As shown in the figure, the pneumatic tire 1 is provided between a pair of bead portions 2 to be rim-assembled, a pair of sidewall portions 3 extending outward in the tire radial direction from the bead portions 2, and the pair of sidewall portions 3. It is composed of a tread portion 4 that comes into contact with the provided road surface. A ring-shaped bead core 5 is embedded in each of the pair of bead portions 2. A carcass ply 6 using an organic fiber cord is provided so as to be folded around the bead core 5 and locked, and to be bridged between the left and right bead portions 2. Further, on the outer peripheral side of the tread portion 4 of the carcass ply 6, a belt 7 composed of two belt plies using a rigid tire cord such as a steel cord or an aramid fiber is provided.

An inner liner 8 is provided inside the carcass ply 6 over the entire inner surface of the tire. In the present embodiment, the air-resistant film is used as the inner liner 8. As shown in the enlarged view in FIG. 1, the inner liner 8 is attached to the inner surface of the carcass ply 6 which is a rubber layer on the inner surface side of the tire. More specifically, the topping rubber covering the cord of the carcass ply 6 It is attached to the inner surface of the layer.

In the pneumatic tire according to the present embodiment, a tie rubber layer is selectively arranged as a part between the layers between the carcass ply 6 and the inner liner 8 in order to prevent the cord of the carcass ply 6 from biting into the inner liner 8. It may be what is done.

As a method for manufacturing a pneumatic tire using the air-permeable film according to the present embodiment, for example, the air-permeable film is used as an inner liner, and the inner liner is mounted in a tubular shape on the outer periphery of the molding drum. A green tire (unvulcanized tire) is produced by pasting a carcass ply on it, further pasting each tire member such as a belt, tread rubber, and sidewall rubber, and inflating, and the green tire is placed in a mold. By vulcanizing and molding with, a pneumatic tire can be obtained. In the example shown in FIG. 1, the air-permeable film is provided on the inner surface side of the carcass ply, but it is possible to prevent the permeation of air from the inside of the tire and maintain the air pressure of the tire, that is, the internal pressure. As long as it is provided as an air permeation suppressing layer for holding, it can be provided at various positions such as, for example, on the outer surface side of the carcass ply, and is not particularly limited.

Hereinafter, examples of the present invention will be shown, but the present invention is not limited to these examples.

According to the formulation (parts by mass) shown in Table 1, the thermoplastic resin and the compatibilizer were dry-mixed in advance, and the rubber component, chlorosulfonated polyethylene, and other components other than the adhesiveness improver were dry-mixed. The material was melt-kneaded at a temperature of 220 ° C. using a twin-screw extruder (Plastic Industry Research Institute) and dynamically crosslinked to obtain pellets of a thermoplastic elastomer composition. The obtained pellets were put into a twin-screw extruder again together with an adhesive improver, kneaded at a temperature of 220 ° C., and then molded into a width of 14 cm and a thickness of 0.2 mm using a single-screw extruder to form a film. A sample was obtained.

Details of each component in Table 1 are as follows.
<Thermoplastic elastomer composition>
-IIR: "IIR268" manufactured by ExxonMobil Chemical Co., Ltd.
-Nylon 6/66: "Novamid 2020J" manufactured by DSM
-Hypalonized polyethylene 1: "TS-320" manufactured by Tosoh Corporation
-Hypalonized polyethylene 2: "TS-530" manufactured by Tosoh Corporation
・ Chloroprene rubber: "B-15" manufactured by Tosoh Corporation
-Plasticizer: "BM-4" manufactured by Daihachi Chemical Industry Co., Ltd.
-Crosslinking agent: "Tackiroll 250-III" manufactured by Taoka Chemical Industry Co., Ltd.
・ Zinc Oxide: “Zinc Oxide No. 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
-Stearic acid: "Lunac S-20" manufactured by Kao Corporation
・ Compatibility agent: "Bond First E" manufactured by Sumitomo Chemical Co., Ltd.
-Adhesive improver: "Sumicanol 620" manufactured by Taoka Chemical Industry Co., Ltd.

<Rubber composition for adhesiveness evaluation>
・ NR: RSS # 3
-SBR: "JSR1502" manufactured by JSR Corporation
-Carbon black: "Showa Black N-330T" manufactured by Cabot Japan Co., Ltd.
-Stearic acid: "Lunac S-20" manufactured by Kao Corporation
・ Zinc Oxide: “Zinc Oxide No. 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Sulfur: "Powdered sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.
-Vulcanization accelerator: "Noxeller NS-P" manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
-Melamine derivative: Hexamethoxymethylmelamine, "Silets 963L" manufactured by Cytec Industries, Ltd. of Japan

For each sample consisting of the obtained thermoplastic elastomer composition, processability (melt viscosity), air permeability, flexibility (10% tensile stress), and adhesiveness were evaluated. Each evaluation method is as follows.

Workability (melt viscosity): Using a capillary rheometer manufactured by Yasuda Seiki Seisakusho Co., Ltd., the melt viscosity at 230 ° C. and a shear rate of 800 (1 / s) was measured, and the value of Comparative Example 1 was set to 100. It is displayed by the index. The larger the index, the higher the melt viscosity and the worse the workability.

-Air permeability: According to JIS K7126-1 "Plastic-Film and Sheet-Gas Permeability Test Method-Part 1: Differential Pressure Method", test gas: air, test temperature: 80 ° C. be. The smaller this value, the better the air permeability.

-Flexibility (10% tensile stress): Measured according to the tensile test of JIS K6251. The dumbbell shape was No. 3 (however, the thickness was 200 μm), and the stress in a 10% stretched state when pulled at a speed of 500 mm / min was measured to determine the median value in the extrusion direction of the film. The smaller this value, the better the flexibility.

-Adhesiveness: A rubber composition for adhesion evaluation having a thickness of 0.3 mm prepared according to the formulation (part by mass) shown in Table 2 was used as a tie rubber layer on the surface of an unvulcanized topping rubber layer of carcass ply. I pasted it. Each sample made of a resin film having a thickness of 0.2 mm is superposed on a tie rubber layer attached to a carcass ply, the press temperature is 160 ° C., the press time is 20 minutes, the press pressure is 30 kg / cm ^2, and press vulcanization is performed. It was carried out and integrated by adhesion. The obtained vulcanized adhesive was cut into strips having a width of 25 mm and subjected to a 180 ° peeling test at a peeling rate of 50 mm / min. The average value between 8 cm was taken as the adhesive strength.

The evaluation results are as shown in Table 1, and the value of air permeability of each Example and Comparative Example is 5.0 × 10 ¹³ fm ² / Pa · s or less, and has excellent air permeability. It was confirmed that. In addition, Examples 1 to 3 using chlorosulfonated polyethylene were improved in processability, flexibility, and adhesiveness as compared with Comparative Examples 1 to 4.

From the comparison between Comparative Example 1 and Comparative Example 2, it was found that the inclusion of the plasticizer deteriorated the air permeability and the adhesiveness.

Further, from the comparison between Comparative Example 1 and Comparative Examples 3 and 4, it was found that when chloroprene, a halogenated rubber different from chlorosulfonated polyethylene, was used, the adhesiveness was deteriorated.

The thermoplastic elastomer composition of the present invention can be used as an inner liner for various tires of passenger cars, light trucks, buses and the like.

1 ... Pneumatic tire 2 ... Bead 3 ... Sidewall 4 ... Tread 5 ... Bead core 6 ... Carcass ply 7 ... Belt 8 ... Inner liner

Claims (3)

It has a continuous phase made of a thermoplastic resin and a dispersed phase made of vulcanized rubber dispersed in this continuous phase.
The vulcanized rubber contains 1 to 10 parts by mass of chlorosulfonated polyethylene with respect to 100 parts by mass of butyl rubber.
The content ratio of the thermoplastic resin to the rubber component (ratio as a polymer component excluding the component such as a filler) is 60/40 to 25/75 in terms of mass ratio (thermoplastic resin / rubber component). ,
A thermoplastic elastomer composition in which the content of the plasticizer in the vulcanized rubber is less than 1 part by mass with respect to 100 parts by mass of butyl rubber. An air-permeable film for tires, which comprises the thermoplastic elastomer composition according to claim 1. A pneumatic tire using the air-permeable film for tires according to claim 2.

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