JP5169350B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire using a film layer made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer and a thermoplastic resin as an inner liner layer, and more specifically, a tire in a molding process and a vulcanization process. The present invention relates to a pneumatic tire that can effectively prevent peeling of a splice portion of a film layer due to deformation of the tire.

  In recent years, it has been proposed to use a film layer made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer and a thermoplastic resin as an inner liner layer of a pneumatic tire (see, for example, Patent Document 1 and Patent Document 2). ). In forming a pneumatic tire having such a film layer, a sheet-like film layer is wound around a forming drum, and both ends of the film layer are spliced at one place on the tire circumference. It has been proposed to form an inner liner layer that extends continuously in the tire circumferential direction (see, for example, Patent Document 3 and Patent Document 4).

  However, when both ends of the film layer are spliced at one place on the tire circumference, the rigidity of the film layer containing the thermoplastic resin is relatively higher than that of other tire constituent members. When the tire expands, stress concentrates on the splice part of the film layer, and as a result, there is a problem that the splice part peels off.

JP-A-8-217923 JP-A-11-199713 JP-A-9-164805 International Publication No. WO96 / 34736 Pamphlet

  An object of the present invention is to use a film layer formed by deformation of a tire in a molding step and a vulcanization step when a film layer made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin is used as an inner liner layer. It is an object of the present invention to provide a pneumatic tire that can effectively prevent the splice portion from peeling off.

In order to achieve the above object, a pneumatic tire of the present invention is a film having a thickness in the range of 0.002 mm to 0.7 mm and comprising a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin. In a pneumatic tire using a layer as an inner liner layer, the film layer is composed of a plurality of divided pieces divided in the tire circumferential direction, and the divided pieces of the film layer are overlapped with each other in at least two places on the tire circumference. And splicing via a stress relaxation layer.

  In the present invention, when a film layer made of a thermoplastic resin or a thermoplastic elastomer composition is used as the inner liner layer, the film layer is composed of a plurality of divided pieces divided in the tire circumferential direction, and the divided pieces of the film layer Is spliced through the stress relaxation layer at at least two locations on the tire circumference, reducing the stress concentration at each splice and effectively removing the splice from the film layer due to tire deformation in the molding and vulcanization processes Can be prevented. As a result, the yield of pneumatic tires can be improved.

  When the film layer is composed of a plurality of divided pieces divided in the tire circumferential direction as described above, an unvulcanized tire is molded on a molding base having a curved surface such as a rigid core, a profile drum, and a bladder. In doing so, it is possible to obtain a secondary effect that the divided pieces of the film layer can be attached to the molding base having the curved surface without any gap along the shape.

  In this invention, it is preferable that the overlap amount of the tire circumferential direction of the division piece of a film layer is 3 mm or more and 50% or less of the circumferential direction length of this division piece. The stress relaxation layer is preferably a rubber layer. Furthermore, the thickness of the stress relaxation layer is preferably 0.1 mm to 1.0 mm. Thereby, peeling of the splice part of a film layer can be prevented more reliably.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIG. 2 shows an extracted inner liner layer. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3, 3, and an end portion of the carcass layer 4 is folded around the bead core 5 from the inside of the tire to the outside. A plurality of belt layers 6 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 6 are disposed such that the reinforcing cords are inclined with respect to the tire circumferential direction, and the reinforcing cords cross each other between the layers.

  In the pneumatic tire, an inner liner layer (air permeation preventive layer) 7 is disposed on the tire lumen side of the carcass layer 4. As shown in FIG. 2, the inner liner layer 7 includes a film layer 11 made of a thermoplastic resin or a thermoplastic elastomer composition. More specifically, the film layer 11 is composed of four divided pieces 11a to 11d divided in the tire circumferential direction, and these divided pieces 11a to 11d are spliced via stress relieving layers 12 at four locations on the tire circumference. By doing so, the inner liner layer 7 extending continuously in the tire circumferential direction is formed. The film layer 11 is composed of at least two divided pieces divided in the tire circumferential direction, and these divided pieces need to be spliced through the stress relaxation layer 12 in at least two places on the tire circumference. More preferably, it is composed of 4 to 8 divided pieces divided in the tire circumferential direction, and these divided pieces are spliced via the stress relaxation layer 12 at 4 to 8 locations on the tire circumference.

  The overlap amount W in the tire circumferential direction of the divided pieces 11a to 11d of the film layer 11 is set to 3 mm or more and 50% or less of the circumferential length L of each divided piece 11a to 11d. When the overlap amount W is less than 3 mm, the splice part is likely to be peeled off. Further, when the overlapping amount W exceeds 50% of the circumferential length L of each of the divided pieces 11a to 11d, the film layer 11 has a multilayer structure, and the rigidity of the inner liner layer 7 becomes higher than necessary.

The thickness of the film layer 11 may be selected from the range of 0.002Mm～0.7Mm. On the other hand, the thickness of the stress relaxation layer 12 is preferably 0.1 mm to 1.0 mm. If the stress relaxation layer 12 is too thin, the splice part is liable to be peeled off, and if it is too thick, the step of the splice part becomes large.

  As the stress relaxation layer 12, it is preferable to employ a rubber layer. When the stress relaxation layer 12 is a rubber layer, good adhesiveness and good stress relaxation action can be exhibited in an unvulcanized state. The rubber used for the stress relaxation layer 12 is not particularly limited, but diene rubber and its hydrogenated product, butyl rubber, halogenated butyl rubber, and the like can be used.

  In the pneumatic tire configured as described above, the inner liner layer 7 is formed by splicing the divided pieces 11a to 11d of the film layer 11 around the forming drum through the stress relaxation layer 12 at four locations on the tire circumference. Formed, and a tire component such as a carcass layer, a bead core, a bead filler, and a sidewall rubber is laminated thereon to form a primary green tire, and a belt layer and a tread are formed while expanding the primary green tire in a toroidal shape. It is obtained by pasting rubber together to form a secondary green tire (unvulcanized tire) and then vulcanizing the secondary green tire.

  When the film layer 11 made of a thermoplastic resin or a thermoplastic elastomer composition as described above is used as the inner liner layer 7, the film layer 11 is composed of a plurality of divided pieces 11a to 11d divided in the tire circumferential direction, Since these divided pieces 11a to 11d are spliced through the stress relaxation layer 12 at at least two locations on the tire circumference, the stress concentration in each splice portion is relaxed, and the film layer is formed by deformation of the tire in the molding process and the vulcanization process. 11 can be effectively prevented from peeling off.

  Further, when the film layer 11 is composed of a plurality of divided pieces 11a to 11d divided in the tire circumferential direction, a rigid core (a molded base made of a rigid body having a shape approximate to the inner shape of an unvulcanized tire), profile On a molding base having a curved surface such as a drum (a molding base in which a part of the contour in the axial direction of the molding drum is curved) or a bladder (a molding base made of a rubber bag inflated by filling with internal pressure) When the unvulcanized tire is molded, the divided pieces 11a to 11d of the film layer 11 can be attached to the molding base having a curved surface without any gap along the shape. That is, a pneumatic tire using the film layer 11 as the inner liner layer 7 can be molded on the molding base having a curved surface so as not to cause wrinkles in the film layer 11. As a method for manufacturing a pneumatic tire using a rigid core, for example, the methods described in JP 2007-253406 A, JP 2007-253412 A, and JP 2007-69497 A are known. Yes.

  Below, the film layer used by this invention is demonstrated. This film layer can be composed of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer in a thermoplastic resin.

  Examples of the thermoplastic resin used in the present invention include polyamide resins [for example, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6/66 copolymer (N6 / 66), nylon 6/66/610 copolymer (N6 / 66/610), nylon MXD6, nylon 6T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer], polyester resin [for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), polybutylene terephthalate / Tetramethylene glycol copolymer, PET PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, aromatic polyester such as polyoxyalkylene diimide diacid / polybutylene terephthalate copolymer], polynitrile resin [for example, polyacrylonitrile ( PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, methacrylonitrile / styrene / butadiene copolymer], poly (meth) acrylate resin [eg polymethacryl Acid methyl (PMMA), polyethyl methacrylate, ethylene ethyl acrylate copolymer (EEA), ethylene acrylic acid copolymer (EAA), ethylene methyl acrylate resin (EMA)], polyvinyl resin [for example, vinyl acetate (EVA), polyvinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate Copolymer], cellulose resin [eg, cellulose acetate, cellulose acetate butyrate], fluorine resin [eg, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene Copolymer (ETFE)], imide resin [for example, aromatic polyimide (PI)] and the like.

  Examples of the elastomer used in the present invention include diene rubbers and hydrogenated products thereof [for example, NR, IR, epoxidized natural rubber, SBR, BR (high cis BR and low cis BR), NBR, hydrogenated NBR, Hydrogenated SBR], olefin rubber [eg ethylene propylene rubber (EPDM, EPM), maleic acid modified ethylene propylene rubber (M-EPM)], butyl rubber (IIR), isobutylene and aromatic vinyl or diene monomer copolymer, Acrylic rubber (ACM), ionomer, halogen-containing rubber [for example, Br-IIR, Cl-IIR, brominated product of isobutylene paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHC, CHR), Chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM)], silicone rubber (eg, methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (eg, polysulfide rubber), fluoro rubber (eg, Vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorine-containing silicone rubber, fluorine-containing phosphazene rubber), thermoplastic elastomer (eg, styrene elastomer, olefin elastomer, polyester elastomer, And urethane elastomers and polyamide elastomers).

  In the thermoplastic elastomer composition used in the present invention, the composition ratio of the thermoplastic resin component (A) and the elastomer component (B) may be appropriately determined depending on the balance of the thickness and flexibility of the film layer, but is preferably within a preferable range. Is 10/90 to 90/10, more preferably 20/80 to 85/15 (weight ratio).

  In the thermoplastic elastomer composition according to the present invention, in addition to the essential components (A) and (B), as a third component, other polymers such as a compatibilizer and a compounding agent can be mixed. The purpose of mixing other polymers is to improve the compatibility between the thermoplastic resin component and the elastomer component, to improve the film molding processability of the material, to improve heat resistance, to reduce costs, etc. Examples of the material used for this include polyethylene, polypropylene, polystyrene, ABS, SBS, and polycarbonate.

The thermoplastic elastomer composition is prepared by melt-kneading a thermoplastic resin and an elastomer (unvulcanized material in the case of rubber) in advance using a twin-screw kneading extruder or the like, and adding an elastomer component in the thermoplastic resin forming a continuous phase. It is obtained by dispersing. When the elastomer component is vulcanized, a vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer. Further, various compounding agents (excluding the vulcanizing agent) to the thermoplastic resin or the elastomer component may be added during the kneading, but are preferably mixed in advance before kneading. The kneading machine used for kneading the thermoplastic resin and the elastomer is not particularly limited, and examples thereof include a screw extruder, a kneader, a Banbury mixer, and a biaxial kneading extruder. Among these, it is preferable to use a twin-screw kneading extruder for kneading the resin component and the rubber component and for dynamic vulcanization of the rubber component. Further, two or more types of kneaders may be used and kneaded sequentially. As conditions for melt-kneading, the temperature may be higher than the temperature at which the thermoplastic resin melts. The shear rate during kneading is preferably 2500 to 7500 sec ⁻¹ . The entire kneading time is from 30 seconds to 10 minutes, and when a vulcanizing agent is added, the vulcanization time after addition is preferably from 15 seconds to 5 minutes. The thermoplastic elastomer composition produced by the above method is formed into a film by molding with a resin extruder or calender molding. The method for forming a film may be a method of forming a film of a normal thermoplastic resin or thermoplastic elastomer.

  The thin film of the thermoplastic elastomer composition thus obtained has a structure in which the elastomer is dispersed as a discontinuous phase in a thermoplastic resin matrix. By adopting the dispersion structure in such a state, it is possible to set the Young's modulus in a range of 1 to 500 MPa and to impart appropriate rigidity as a tire constituent member.

  The thermoplastic resin or thermoplastic elastomer composition can be molded into a sheet or film and embedded alone in the tire, but an adhesive layer may be laminated to improve the adhesion to the adjacent rubber. good. Specific examples of the adhesive polymer constituting the adhesive layer include ultrahigh molecular weight polyethylene (UHMWPE), ethylene ethyl acrylate copolymer (EEA), ethylene methyl acrylate resin (EMA) having a molecular weight of 1 million or more, preferably 3 million or more. ), Acrylate copolymers such as ethylene acrylic acid copolymer (EAA) and their maleic anhydride adducts, polypropylene (PP) and its maleic acid modification, ethylene propylene copolymer and its maleic acid modification, Polybutadiene resin and its modified maleic anhydride, styrene-butadiene-styrene copolymer (SBS), styrene-ethylene-butadiene-styrene copolymer (SEBS), fluorine thermoplastic resin, polyester thermoplastic resin, etc. Can be mentioned. These can be extruded into a sheet form or a film form by a conventional method, for example, using a resin extruder. The thickness of the adhesive layer is not particularly limited, but it is preferable that the thickness is small for weight reduction of the tire, and 5 μm to 150 μm is preferable.

  In a pneumatic tire having a tire size of 195 / 65R15, a film layer made of a thermoplastic elastomer composition obtained by blending an elastomer (brominated butyl rubber) with a thermoplastic resin (nylon 6, 66) is used as an inner liner layer. Conventional tires 1 and 2 and Examples 1 and 2 having different structures only were manufactured.

  In Conventional Example 1, a film layer having a laminated structure of a thermoplastic elastomer composition (180 μm) and an adhesive (20 μm) having a width of 390 mm and a thickness of 200 μm is extruded by a T-die, and one film layer is formed. An inner liner layer is formed by wrapping around a forming drum having a circumferential length of 1300 mm and splicing both ends of the film layer so that the overlapping amount in the circumferential direction is 10 mm, and then an unvulcanized tire including the inner liner layer is formed. Molded and vulcanized.

  In Conventional Example 2, a film layer having a laminated structure of a thermoplastic elastomer composition (180 μm) and an adhesive (20 μm) having a width of 390 mm and a thickness of 200 μm is extruded by a T-die, and one film layer is formed. The inner liner is wound by winding it around a forming drum having a circumference of 1300 mm and sandwiching an unvulcanized rubber layer having a thickness of 0.5 mm between the films at both ends of the film layer so that the circumferential overlap amount is 10 mm. After forming the layer, an unvulcanized tire including the inner liner layer was formed and vulcanized.

  In Example 1, a film layer having a laminated structure of a thermoplastic elastomer composition (180 μm) and an adhesive (20 μm) having a width of 390 mm and a thickness of 200 μm is extruded by a T-die, and the film layer has a length. Cut into two pieces of 660 mm, wound the two pieces on a molding drum with a circumference of 1300 mm, and these pieces were unvulcanized rubber with a thickness of 0.5 mm between the films at two locations on the tire circumference. An inner liner layer was formed by splicing the layers so that the amount of overlap in the circumferential direction was 10 mm, and then an unvulcanized tire including the inner liner layer was formed and vulcanized.

  In Example 2, a film layer having a laminated structure of a thermoplastic elastomer composition (180 μm) and an adhesive (20 μm) having a width of 390 mm and a thickness of 200 μm was extruded using a T-die, and the film layer had a length. Cut into four pieces of 660 mm, wound the four pieces on a molding drum with a circumference of 1300 mm, and these pieces were unvulcanized rubber with a thickness of 1.0 mm between the films at four locations on the tire circumference. The inner liner layer was formed by splicing the layers so that the circumferential overlap amount was 3.0 mm, and then an unvulcanized tire including the inner liner layer was formed and vulcanized.

  In the manufacturing process of these test tires, the state of the film layer constituting the inner liner layer was visually confirmed. As a result, in Examples 1 and 2, no peeling occurred at the splice portion of the film layer in any of the molding step and the vulcanization step, and no failure such that the splice portion opened was observed. On the other hand, in the conventional examples 1 and 2, peeling occurred in the splice portion of the film layer, and the splice portion was open.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the tire equator line showing an inner liner layer extracted from the pneumatic tire of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 7 Inner liner layer 11 Film layer 11a-11d Divided piece of film layer 12 Stress relaxation layer

Claims (4)

In a pneumatic tire using a film layer made of a thermoplastic elastomer composition in which a thickness is in a range of 0.002 mm to 0.7 mm and a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin as an inner liner layer, the film The air is characterized in that the layer is composed of a plurality of divided pieces divided in the tire circumferential direction, and the divided pieces of the film layer are overlapped with each other in at least two places on the tire circumference and spliced through a stress relaxation layer Enter tire.   2. The pneumatic tire according to claim 1, wherein an overlapping amount in the tire circumferential direction of the segment pieces of the film layer is 3 mm or more and 50% or less of a circumferential length of the segment pieces.   The pneumatic tire according to claim 1, wherein the stress relaxation layer is a rubber layer.   The pneumatic tire according to claim 3, wherein the stress relaxation layer has a thickness of 0.1 mm to 1.0 mm.

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