A tire includes a circular tire frame formed from a resin material, in which the resin material has a tear strength of 10 N/mm or greater.

TECHNICAL FIELD

The present invention relates to a tire that is fitted onto a rim, and in particular relates to a tire in which at least a part of a tire case is formed from a resin material.

BACKGROUND ART

Pneumatic tires constructed from rubber, organic fiber materials, steel members, and the like have been conventionally employed in vehicles such as passenger cars.

Recently, the use of resin materials, in particular thermoplastic resins, thermoplastic elastomers, and the like, as tire materials have been investigated from the perspectives of weight reduction, ease of molding, and ease of recycling.

For example, Patent Document 1 (Japanese Patent Application Laid-Open (JP-A) No. 2003-104008) and Patent Document 2 (JP-A No. H03-143701) disclose a pneumatic tire formed from a thermoplastic polymer material.

There is also a proposal for a pneumatic tire constructed from polymer materials such as a plurality of rubbers, thermoplastic resins, or the like, wherein the rigidity is gradually decreased from a center position of a crown portion to a shoulder portion and furthermore to a maximum width position of a side wall portion, and the rigidity is also gradually increased from the maximum width position of the side wall portion to a bead portion (see, for example, Patent Document 3 below (Japanese Patent No. 4501326)).

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SUMMARY OF INVENTION

Technical Problem

A tire using a thermoplastic polymer material is easily manufactured and lower in cost, compared to conventional tires made of rubber. However, in a case in which a tire frame, which does not have a reinforcement member such as a carcass ply or the like installed therein, is formed with a uniform thermoplastic polymer material, there is still room for improvement from the viewpoints of stress resistance, internal pressure resistance, and the like, compared to conventional tires made of rubber.

In particular, in ordinary conventional tires made of rubber, shape is maintained under application of internal pressure to the tire by employing a carcass and ply. However, in tires employing a polymer material (resin) such as described above, there are proposals for, for example, forms in which hoops of steel cord are applied in a circumferential direction of a tire without using reinforcement members such as a carcass and ply as essential constituent elements. In such tires employing polymer materials, since it is assumed that reinforcement members are not employed in side portions, there is demand for a polymer material that in itself is capable of maintaining tire shape. In particular, there is demand for the development of a tire having suitable tear strength from the viewpoints of maintaining tire shape and puncture resistance under abrasion against curbs or the like.

In this regard, a tire is disclosed in Patent Document 3 that combines a plurality of polymer materials to give a specified rigidity. However, although Patent Document 3 describes improving the ground contact shape in a standard air pressure-filling state by forming a rigidity distribution in a portion of a tire, there is no reference in Patent Document 3 related to tear strength.

In consideration of the above circumstances, an object of the invention is to provide a tire that is formed using a resin material and has excellent shape maintaining ability and puncture resistance.

Solution to Problem

(1) A tire includes a circular tire frame formed from a resin material, in which the resin material, the resin material has a tear strength of 10 N/mm or greater.

Advantageous Effects of Invention

According to the invention, a tire formed using a resin material, and having excellent shape maintaining ability and puncture resistance can be provided.

DESCRIPTION OF EMBODIMENTS

The tire of the invention includes a circular tire frame formed from a resin material, in which the resin material has a tear strength of 10 N/mm or greater. The “tear strength” refers to the tear strength as defined in JIS K7128-3 (1998). In testing, angle shaped test samples without an insection (right angled tear test samples) are employed as test samples. Samples cut in a longitudinal direction and a lateral direction, with respect to a processing direction, as illustrated in FIG. 1 of 6. Test Sample Production in JIS K7128-3, are employed as the test samples. At this time, measurement is made under a condition of a testing speed of 500 mm+50 mm per minute. Measurements may be performed employing a tension tester such as an autograph or the like, such as a Shimadzu Autograph AGS-J (5 KN), manufactured by Shimadzu Corporation.

According to the tire of the invention, when a resin material having a tear strength of 10 N/mm or greater is used for a resin material contained in a tire frame, the shape maintaining ability and puncture resistance of a tire can be improved. Moreover, since the tire is formed with a resin material, a vulcanization process, which has been an essential process for a conventional rubber tire made of rubber, is not necessary, and for example, the tire frame can be formed by injection molding or the like. Moreover, when a resin material is used for the tire frame, the structure of a tire can be simplified compared to a conventional tire made of rubber, and as a result thereof, a tire weight reduction can be achieved. The “shape maintaining ability” of a tire can be an index of whether or not the shape of the tire is maintained when internal pressure (for example, 200 kPa) is applied to the tire. Regarding puncture resistance, when the tear strength is less than 10 N/mm, the tear strength is too low and side portions of the tire frame cannot withstand the internal pressure to bulge out in the tire width direction or the like, whereby tire shape cannot be maintained. Further, the tear strength is preferably 15 N/mm or greater. The upper limit of tear strength is not particularly limited, but is preferably 20 N/mm or less, more preferably 19 N/mm or less, and particularly preferably 18 N/mm or less, in view of balance of tensile elastic modulus and loss coefficient (tan δ).

Hereinafter, the resin material contained in the tire frame in the invention is explained, and then specific embodiments of the tire of the invention are explained with reference to the drawings.

Resin Material

A resin material in the invention is a resin material that includes a resin, and the resin is selected such that the tear strength of the resin material is 10 N/mm or greater.

In the invention, the “resin material” contains at least a resin (a resin component), and may contain other components such as additives. When the resin material does not contain any components other than a resin component, the resin material is formed from resin alone.

In the present specification, a concept of “resin” encompasses thermoplastic resins and thermoset resins; however, it does not encompass natural rubber. Moreover, thermoplastic resins encompass thermoplastic elastomers.

“Elastomer” used here refers to a resin formed of a copolymer including a crystalline polymer which forms a hard segment having a high melting point or forms a hard segment having a high cohesion force, and an amorphous polymer which forms a soft segment having a low glass transition temperature.

Resin

Examples of the resin include thermoplastic resins (which also include thermoplastic elastomers) and thermoset resins. The resin material may, for example, contain a thermoplastic elastomer described below alone, may contain a combination of two or more thereof, or may contain a combination of a thermoplastic elastomer and a non-elastomer thermoplastic resin. In cases in which the resin material contains a single resin alone, the tear strength of the resin is the tear strength of the resin material.

The resin material contained in the tire frame is preferably a thermoplastic resin, and is more preferably a thermoplastic elastomer. Hereinafter, the resin used in the resin material which forms the tire frame is explained, with a focus on thermoplastic resins.

A thermoplastic resin (including a thermoplastic elastomer) is a polymer compound in which a material is soften and fluidized with increasing temperature and changes to a relatively hard and strong state when it is cooled.

In the present specification, among these thermoplastic resins, a polymer compound in which a material is soften and fluidized with increasing temperature and changes to a relatively hard and strong state when it is cooled, and which has a rubber-like elasticity is considered as a thermoplastic elastomer. In contrast, among these thermoplastic resins, a polymer compound in which a material is soften and fluidized with increasing temperature, and changes to a relatively hard and strong state when it is cooled, but which does not have a rubber-like elasticity, is referred to as a non-elastomer thermoplastic resin and distinguished from the thermoplastic elastomer.

Examples of the thermoplastic resin (including the thermoplastic elastomer) include a thermoplastic polyolefin-based elastomer (TPO), a thermoplastic polystyrene-based elastomer (TPS), a thermoplastic polyamide-based elastomer (TPA), a thermoplastic polyurethane-based elastomer (TPU), a thermoplastic polyester-based elastomer (TPC), and a dynamic crosslinking-type thermoplastic elastomer (TPV), as well as a non-elastomer thermoplastic polyolefin-based resin, a non-elastomer thermoplastic polystyrene-based resin, a non-elastomer thermoplastic polyamide-based resin, and a non-elastomer thermoplastic polyester-based resin. The thermoplastic resin contained in the resin material is preferably at least one selected from the thermoplastic polyester-based elastomer, the thermoplastic polyamide-based elastomer, the thermoplastic polyolefin-based elastomer, and the thermoplastic polyurethane-based elastomers.

Examples of the thermoplastic polyester-based elastomer include a material in which at least a polyester is crystalline and forms a hard segment having a high melting point and another polymer (for example, a polyester, a polyether, or the like) is amorphous and forms a soft segment having a low glass transition temperature.

The thermoplastic polyester-based elastomer is also referred to as “TPC” (ThermoPlastic polyester elastomer).

An aromatic polyester may be employed as the polyester that forms the hard segment. The aromatic polyester may be formed from, for example, an aromatic dicarboxylic acid or an ester-forming derivative thereof, and an aliphatic diol. The aromatic polyester is preferably polybutylene terephthalate derived from terephthalic acid and/or dimethyl terephthalate, and 1,4-butanediol. Moreover, the aromatic polyester may be a polyester derived from a dicarboxylic acid component such as isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxyethane dicarboxylic acid, 5-sulfoisophthalic acid, or an ester-forming derivative thereof, and a diol having a molecular weight of 300 or less, for example: an aliphatic diol such as ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, or decamethylene glycol; an alicyclic diol such as 1,4-cyclohexane dimethanol or tricyclodecane dimethylol; an aromatic diol such as xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4′-dihydroxy-p-terphenyl, or 4,4′-dihydroxy-p-quaterphenyl. The aromatic polyester may be a copolymer polyester that employs two or more of the above dicarboxylic acid components and diol components in combination. A polyfunctional carboxylic acid component having three or more functional groups, a polyfunctional oxyacid component, or a polyfunctional hydroxy component can be copolymerized in a range of 5% by mol or less.

Examples of the polyester which forms a hard segment include polyethylene terephthalate, polybutylene terephthalate, polymethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, and polybutylene terephthalate is preferable.

Examples of a polymer which forms a soft segment include an aliphatic polyester and an aliphatic polyether.

Example of the aliphatic polyether include poly(ethylene oxide)glycol, poly(propylene oxide)glycol, poly(tetramethylene oxide)glycol, poly(hexamethylene oxide)glycol, a copolymer of ethylene oxide and propylene oxide, an ethylene oxide addition polymer of poly(propylene oxide)glycol, and a copolymer of ethylene oxide and tetrahydrofuran.

Examples of the aliphatic polyester include poly(ε-caprolactone), polyenantholactone, polycaprylolactone, polybutylene adipate, and polyethylene adipate.

Of these aliphatic polyethers and aliphatic polyesters, poly(tetramethylene oxide)glycol, ethylene oxide adduct of poly(propylene oxide)glycol, poly(ε-caprolactone), polybutylene adipate, polyethylene adipate, or the like is preferable from the viewpoint of the elasticity characteristics of a polyester block copolymer to be obtained.

Moreover, from the viewpoints of toughness and flexibility at low temperature, the number average molecular weight of the polymer which forms a soft segment is preferably from 300 to 6000. Moreover, from the viewpoint of formability, the mass ratio (x:y) of the hard segment (x) to the soft segment (y) is preferably from 99:1 to 20:80, and still more preferably from 98:2 to 30:70.

Examples of the combination of the hard segment and the soft segment may include respective combinations of the hard segment and the soft segment described above. Of these, a combination in which the hard segment is polybutylene terephthalate and the soft segment is an aliphatic polyether is preferable, and a combination in which the hard segment is polybutylene terephthalate and the soft segment is poly(ethylene oxide)glycol is still more preferable.

In the invention, “thermoplastic polyamide-based elastomer” refers to a thermoplastic resin material that is formed of a copolymer having a crystalline polymer which forms a hard segment having a high melting point, and an amorphous polymer which forms a soft segment having a low glass transition temperature, in which the polymer which forms the hard segment has an amide bond (—CONH—) in a main chain thereof.

The thermoplastic polyamide-based elastomer is also simply referred to as “TPA” (ThermoPlastic Amid elastomer).

Examples of the thermoplastic polyamide-based elastomer include a material in which at least a polyamide is crystalline and forms a hard segment having a high melting point and another polymer (for example, a polyester, a polyether, or the like) is amorphous and forms a soft segment having a low glass transition temperature. A chain extender such as a dicarboxylic acid may also be used in the thermoplastic polyamide-based elastomer, in addition to the hard segment and the soft segment. Examples of a polyamide that forms the hard segment include a polyamide formed from a monomer represented by the following Formula (1) or Formula (2).

In Formula (1), R1represents a molecular chain of a hydrocarbon having from 2 to 20 carbon atoms, or a alkylene group having from 2 to 20 carbon atoms.

In Formula (2), R2represents a molecular chain of a hydrocarbon having from 3 to 20 carbon atoms, or an alkylene group having from 3 to 20 carbon atoms.

In Formula (1), R1is preferably a molecular chain of a hydrocarbon having from 3 to 18 carbon atoms or an alkylene group having from 3 to 18 carbon atoms, still more preferably a molecular chain of a hydrocarbon having from 4 to 15 carbon atoms or an alkylene group having from 4 to 15 carbon atoms, and particularly preferably a molecular chain of a hydrocarbon having from 10 to 15 carbon atoms or an alkylene group having from 10 to 15 carbon atoms. In Formula (2), R2is preferably a molecular chain of a hydrocarbon having from 3 to 18 carbon atoms or an alkylene group having from 3 to 18 carbon atoms, is still more preferably a molecular chain of a hydrocarbon having from 4 to 15 carbon atoms or an alkylene group having from 4 to 15 carbon atoms, and is particularly preferably a molecular chain of a hydrocarbon having from 10 to 15 carbon atoms or an alkylene group having from 10 to 15 carbon atoms.

Examples of the monomer represented by Formula (1) or Formula (2) above include an w-aminocarboxylic acid and a lactam. Examples of the polyamide that forms the hard segment include a condensation polymer of the w-aminocarboxylic acid and lactam and a condensation copolymer of a diamine and a dicarboxylic acid.

Examples of the w-aminocarboxylic acid may include an aliphatic ω-aminocarboxylic acid having from 5 to 20 carbon atoms such as 6-aminocaproic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 10-aminocapric acid, 11-aminoundecanoic acid, or 12-aminododecanoic acid. Examples the lactam may include an aliphatic lactam having from 5 to 20 carbon atoms such as lauryl lactam, ε-caprolactam, undecane lactam, ω-enantholactam, or 2-pyrrolidone.

As the polyamide that forms the hard segment, a polyamide obtained by ring-opening polycondensation of lauryl lactam, ε-caprolactam or undecane lactam can be preferably employed.

Examples of the polymer that forms the soft segment include a polyester and a polyether, for example. polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and ABA-type triblock polyether. These may be employed singly, or in a combination of two or more thereof. Moreover, a polyether diamine or the like obtained by a reaction of ammonia or the like with a terminal end of a polyether can be employed.

Here, “ABA-type triblock polyether” means a polyether represented by the following Formula (3).

In Formula (3), x and z each represent integers of from 1 to 20. y represents an integer of from 4 to 50.

As the respective values of x and z in Formula (3), an integer of from 1 to 18 is preferable, an integer of from 1 to 16 is still more preferable, an integer of from 1 to 14 is particularly preferable, and an integer of from 1 to 12 is most preferable. As y in Formula (3), an integer of, respectively, from 5 to 45 is preferable, an integer of from 6 to 40 is more preferable, an integer of from 7 to 35 is particularly preferable, and an integer of from 8 to 30 is most preferable.

Examples of a combination of the hard segment and the soft segment may include Respective combinations of the hard segment and the soft segment described above. Among these, a combination of a ring-opening condensation polymer of lauryl lactam/polyethylene glycol, a combination of a ring-opening condensation polymer of lauryl lactam/polypropylene glycol, a combination of a ring-opening condensation polymer of lauryl lactam/polytetramethylene ether glycol, and a combination of a ring-opening condensation polymer of lauryl lactam/an ABA-type triblock polyether are preferable. The combination of a ring-opening condensation polymer of lauryl lactam/an ABA-type triblock polyether is particularly preferable.

From the viewpoint of melting-formability, the number average molecular weight of the polymer (polyamide) which forms the hard segment is preferably from 300 to 30000. From the viewpoints of toughness and low temperature flexibility, the number average molecular weight of the polymer which forms the soft segment is preferably from 200 to 20000. From the viewpoint of formability, the mass ratio (x:y) of the hard segment (x) to the soft segment (y) is preferably from 50:50 to 90:10, and is more preferably from 50:50 to 80:20.

The thermoplastic polyamide-based elastomer can be synthesized by copolymerizing the polymer which forms the hard segment and the polymer which forms the soft segment, by a known method.

Examples of the “thermoplastic polyolefin-based elastomer” include a material in which at least a polyolefin which is crystalline and forms a hard segment having a high melting point and another polymer (for example the polyolefin or another polyolefin) which is amorphous and forms a soft segment having a low glass transition temperature. Examples of the polyolefin which forms a hard segment include, for example, polyethylene, polypropylene, isotactic polypropylene, and polybutene.

Thermoplastic polyolefin-based elastomers are also imply referred to as “TPO” (ThermoPlastic Olefin elastomers).

The thermoplastic polyolefin-based elastomer is not particularly limited, and examples thereof include a copolymer in which a crystalline polyolefin forms a hard segment having a high melting point and an amorphous polymer forms a soft segment having a low glass transition temperature.

Moreover, two or more polyolefin resins, such as ethylene and propylene, may be used in combination. Moreover, a content ratio of the polyolefin in the thermoplastic polyolefin-based elastomer is preferably from 50% by mass to 100% by mass.

The number average molecular weight of the thermoplastic polyolefin-based elastomer is preferably from 5,000 to 10,000,000. When the number average molecular weight of the thermoplastic polyolefin-based elastomer is from 5,000 to 10,000,000, the resin material has sufficient mechanical physical properties and excellent workability. From similar viewpoints, the number average molecular weight is more preferably from 7,000 to 1,000,000, and is particularly preferably from 10,000 to 1,000,000. Accordingly, the mechanical physical properties and workability of the resin material can be further improved. From the viewpoint of toughness and low temperature flexibility, the number average molecular weight of the polymer which forms the soft segment is preferably from 200 to 6000. From the viewpoint of formability, the mass ratio (x:y) of the hard segment (x) to the soft segment (y) is preferably from 50:50 to 95:5, and is still more preferably from 50:50 to 90:10.

The thermoplastic polyolefin-based elastomer can be synthesized by copolymerizing a polymer which forms a hard segment and a polymer which forms a soft segment by a known method.

Moreover, a product obtained by acid-modifying a thermoplastic elastomer may be used as the thermoplastic polyolefin elastomer.

The “product by acid-modifying a thermoplastic polyolefin elastomer” refers to a product obtained by bonding an unsaturated compound having an acid group such as a carboxylic acid group, a sulfuric acid group, or a phosphoric acid group, with a thermoplastic polyolefin elastomer. For example, in a case in which an unsaturated carboxylic acid (generally, maleic acid anhydride) is employed as the unsaturated compound having an acid group, an unsaturated bond site of the unsaturated carboxylic acid is bonded with (for example, a graft polymerization) a thermoplastic olefin-based elastomer.

From the viewpoint of suppressing degradation of the thermoplastic polyolefin elastomer, the compound having an acid group is preferably a compound having a carboxylic acid group that is a weak acid group, and examples thereof include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid.

Examples of the thermoplastic polyurethane-based elastomer include a material in which at least a polyurethane forms a hard segment in which a pseudo-crosslink is formed by physical aggregation and another polymer is amorphous and forms a soft segment having a low glass transition temperature.

The thermoplastic polyurethane-based elastomer is also referred to simply as “TPU” (ThermoPlastic Urethan elastomer).

Specifically, the thermoplastic polyurethane-based elastomer can be represented by a copolymer including a soft segment including a unit structure represented by the following Structural Unit (U-1) and a hard segment including a unit structure represented by the following Structural Unit (U-2), for example.

In the Structural Unit (U-1) and the Structural Unit (U-2), P represents a long-chain aliphatic polyether, or a long-chain aliphatic polyester. R represents an aliphatic hydrocarbon, an alicyclic hydrocarbon, or an aromatic hydrocarbon. P′ represents a short-chain aliphatic hydrocarbon, an alicyclic hydrocarbon, or an aromatic hydrocarbon.

In the Structural Unit (U-1), as the long-chain aliphatic polyether or the long-chain aliphatic polyester represented by P, for example, one having a molecular weight of from 500 to 5000 can be employed. P is derived from a diol compound including a long-chain aliphatic polyether or a long-chain aliphatic polyester, represented by P. Examples of the diol compound include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, poly(butylene adipate)diol, poly-ε-caprolactone diol, poly(hexamethylene carbonate)diol, and the ABA-type triblock polyether (polyether represented by Formula (3) above), each of which has a molecular weight within the range described above.

These compounds may be employed singly, or two or more thereof may be used in combination.

In the Structural Unit (U-1) and the Structural Unit (U-2), R is derived from a diisocyanate compound including an aliphatic hydrocarbon, an alicyclic hydrocarbon, or an aromatic hydrocarbon, represented by R. Examples of the aliphatic diisocyanate compound including an aliphatic hydrocarbon represented by R include 1,2-ethylene diisocyanate, 1,3-propylene diisocyanate, 1,4-butane diisocyanate, and 1,6-hexamethylene diisocyanate.

Examples of the diisocyanate compound including an alicyclic hydrocarbon represented by R include 1,4-cyclohexane diisocyanate and 4,4-cyclohexane diisocyanate. Moreover, examples of the aromatic diisocyanate compound including the aromatic hydrocarbon represented by the R include 4,4′-diphenylmethane diisocyanate and tolylene diisocyanate.

These compounds may be employed singly, or two or more thereof may be used in combination.

In the Structural Unit (U-2), as a short-chain aliphatic hydrocarbon, alicyclic hydrocarbon, or aromatic hydrocarbon, represented by P′, for example, one having a molecular weight of less than 500 may be employed. P′ is derived from a diol compound including a short-chain aliphatic hydrocarbon, an alicyclic hydrocarbon, or an aromatic hydrocarbon, represented by P′. Examples of the aliphatic diol compound including a short-chain aliphatic hydrocarbon, represented by P′ include a glycol, and a polyalkylene glycol, and examples thereof include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

Examples of the alicyclic diol compound including an alicyclic hydrocarbon represented by P′ include cyclopentane-1,2-diol, cyclohexane-1,2-diol, cyclohexane-1,3-diol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol.

These compounds may be employed singly, or two or more thereof can be used in combination.

From the viewpoint of melting-formability, the number average molecular weight of the polymer (polyurethane) which forms the hard segment is preferably from 300 to 1500. Moreover, from the viewpoints of flexibility and thermal stability of the thermoplastic polyurethane-based elastomer, the number average molecular weight of the polymer which forms the soft segment is preferably from 500 to 20000, more preferably from 500 to 5000, and particularly preferably from 500 to 3000. Moreover, from the viewpoint of formability, the mass ratio (x:y) of the hard segment (x) to the soft segment (y) is preferably from 15:85 to 90:10, and more preferably from 30:70 to 90:10.

The thermoplastic polyurethane-based elastomer can be synthesized by copolymerizing a polymer which forms a hard segment and a polymer which forms a soft segment, by a known method. The thermoplastic polyurethane described in JP-A H05-331256, for example, may be employed as the thermoplastic polyurethane-based elastomer.

Specifically, the thermoplastic polyurethane-based elastomer is preferably a combination of a hard segment formed from an aromatic diol and an aromatic diisocyanate and a soft segment formed from a polycarbonate ester, a tolylene diisocyanate (TDI)/polyester-based polyol copolymer, a TDI/polyether-based polyol copolymer, a TDI/caprolactone-based polyol copolymer, a TDI/polycarbonate-based polyol copolymer, a 4,4′-diphenylmethane diisocyanate (MDI)/polyester-based polyol copolymer, an MDI/polyether-based polyol copolymer, an MDI/caprolactone-based polyol copolymer, an MDI/polycarbonate-based polyol copolymer, and an MDI+ hydroquinone/polyhexamethylene carbonate copolymer are preferable, and a TDI/polyester-based polyol copolymer, a TDI/polyether-based polyol copolymer, an MDI/polyester polyol copolymer, an MDI/polyether-based polyol copolymer, and an MDI+ hydroquinone/polyhexamethylene carbonate copolymer are more preferable.

Examples of the thermoplastic polystyrene-based elastomer include a material in which at least polystyrene forms a hard segment and another polymer (for example, polybutadiene, polyisoprene, polyethylene, hydrogenated polybutadiene, hydrogenated polyisoprene, or the like) forms a soft segment having a low glass transition temperature. A synthetic rubber such as a vulcanized SBR resin or the like may be used as the thermoplastic polystyrene-based elastomer.

Thermoplastic polystyrene-based elastomer is also referred to as “TPS” (ThermoPlastic Styrene elastomer).

Both an acid-modified thermoplastic polystyrene-based elastomer modified with an acid group, and an unmodified thermoplastic polystyrene-based elastomer may be employed as the thermoplastic polystyrene-based elastomer.

As the polystyrene which forms the hard segment, for example, one obtained by a known radical polymerization method or ionic polymerization method can be suitably used, and examples thereof include a polystyrene having anionic living polymerization. Examples of the polymer which forms the soft segment include polybutadiene, polyisoprene, and poly(2,3-dimethyl-butadiene). The acid-modified thermoplastic polystyrene-based elastomer can be obtained by acid-modifying an unmodified thermoplastic polystyrene-based elastomer, as described below.

Examples of a combination of the hard segment and the soft segment may include respective combinations of the hard segment and the soft segment described above. Of these, a combination of polystyrene/polybutadiene and a combination of polystyrene/polyisoprene are preferable. Moreover, to suppress unintended crosslinking reactions of the thermoplastic elastomer, the soft segment is preferably hydrogenated.

The number average molecular weight of the polymer (polystyrene) which forms the hard segment is preferably from 5000 to 500000, and preferably from 10000 to 200000. Moreover, the number average molecular weight of the polymer which forms the soft segment is preferably from 5000 to 1000000, more preferably from 10000 to 800000, and particularly preferably from 30000 to 500000. Moreover, from the viewpoint of formability, the volume ratio (x:y) of the hard segment (x) to the soft segment (y) is preferably from 5:95 to 80:20, and still more preferably from 10:90 to 70:30.

The thermoplastic polystyrene-based elastomer can be synthesized by copolymerizing the polymer which forms a hard segment and the polymer which forms a soft segment by a known method.

“Acid-modified thermoplastic polystyrene-based elastomer” refers to a thermoplastic polystyrene-based elastomer that is acid-modified by bonding an unsaturated compound having an acid group such as a carboxylic acid group, a sulfuric acid group, a phosphoric acid group, or the like with an unmodified thermoplastic polystyrene-based elastomer. The acid-modified thermoplastic polystyrene-based elastomer can be obtained by, for example, bonding an unsaturated bond site of an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride (for example, graft polymerization) with a thermoplastic polystyrene-based elastomer.

From the viewpoint of suppressing degradation of the thermoplastic polyamide-based elastomer, the (unsaturated) compound having an acid group is preferably a compound having a carboxylic acid group that is a weak acid group, and examples thereof include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid.

Examples of the acid-modified thermoplastic polystyrene-based elastomer include TUFTEC such as M1943, M1911, and M1913, manufactured by Asahi Kasei Corporation, and FG19181G manufactured by Kraton Inc.

The acid value of the acid-modified thermoplastic polystyrene-based elastomer is preferably more than 0 mg (CH3ONa)/g and 20 mg (CH3ONa)/g or less, more preferably more than 0 mg (CH3ONa)/g and 17 mg (CH3ONa)/g or less, and particularly preferably more than 0 mg (CH3ONa)/g and 15 mg (CH3ONa)/g or less.

The thermoplastic elastomer can be synthesized by copolymerizing the polymer which forms a hard segment and the polymer which forms a soft segment by a known method.

The non-elastomer polyolefin-based resin is a polyolefin-based resin having a higher elastic modulus than the thermoplastic polyolefin-based elastomers described above.

Examples of the non-elastomer thermoplastic polyolefin-based resin include a homopolymer, a random copolymer, and a block copolymer, of an α-olefin such as propylene or ethylene, and of a cyclic olefin such as a cycloolefin. Specific examples thereof include a thermoplastic polyethylene-based resin, a thermoplastic polypropylene-based resin, and a thermoplastic polybutadiene-based resin, and a thermoplastic polypropylene-based resin is particularly preferable from the viewpoints of heat resistance and workability.

Specific examples of the non-elastomer thermoplastic polypropylene-based resin include a propylene homopolymer, a propylene-α-olefin random copolymer, and a propylene-α-olefin block copolymer. Examples of such the α-olefin include an α-olefin having approximately from 3 to 20 carbon atoms, such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene.

The thermoplastic polyolefin-based resin may be a chlorinated polyolefin-based resin in which a part or all of the hydrogen atoms in the molecule are substituted with a chlorine atom. Examples of the chlorinated polyolefin-based resin include a chlorinated polyethylene-based resin.

The non-elastomer thermoplastic polystyrene-based resin is a thermoplastic polystyrene-based resin having a higher elastic modulus than the thermoplastic polystyrene-based elastomer described above.

As the thermoplastic polystyrene-based resin, for example, one obtained by a known radical polymerization method or ionic polymerization method is suitably used, and examples thereof include polystyrene having an anionic living polymerization. Moreover, examples of the thermoplastic polystyrene-based resin may include a polymer containing a styrene molecular skeleton and a copolymer of styrene and acrylonitrile.

Of these, an acrylonitrile/butadiene/styrene copolymer and a hydrogenated product thereof, a blend of an acrylonitrile/styrene copolymer and polybutadiene and a hydrogenated product thereof are preferable. Specific examples of the thermoplastic polystyrene-based resin include a polystyrene (so-called a PS resin), an acrylonitrile/styrene resin (so-called an AS resin), an acrylic-styrene-acrylonitrile resin (so-called an ASA resin), an acrylonitrile/butadiene/styrene resin (so-called an ABS resin (including a blended-form and a copolymer-form)), a hydrogenated product of an ABS resin (so-called an AES resin), and an acrylonitrile-chlorinated polyethylene-styrene copolymer (so-called an ACS resin).

As stated above, the AS resin is an acrylonitrile/styrene resin, and is a copolymer having styrene and acrylonitrile as the main components. However, the AS resin may be further copolymerized with an aromatic vinyl compound such as α-methylstyrene, vinyltoluene, or divinylbenzene; a cyanated vinyl compound such as dimethacrylonitrile; an alkylester of (meth)acrylic acid such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, or stearyl acrylate; a maleimide-based monomer such as maleimide, N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide, or N-cyclohexylmaleimide; a diene compound; a dialkylester of maleic acid; an allyl alkyl ether; an unsaturated amino compound, a vinyl alkyl ether, or the like.

Moreover, as the AS resin, one obtained by further graft-polymerizing or copolymerizing with unsaturated monocarboxylic acids, unsaturated dicarboxylic acids, an unsaturated fatty acid anhydride, or a vinyl-based monomer having an epoxy group is preferable, and one obtained by further graft-polymerizing or copolymerizing with an unsaturated fatty acid anhydride or a vinyl-based monomer having an epoxy group is more preferable.

The vinyl-based monomer having an epoxy group is a compound having both a radically polymerizable vinyl group and an epoxy group in a molecule thereof. Specific examples thereof include glycidyl esters of an unsaturated organic acid such as glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, or glycidyl itaconate; glycidyl ethers such as allyl glycidyl ether; and derivatives thereof such as 2-methyl glycidyl methacrylate. Of these, glycidyl acrylate, and glycidyl methacrylate can be preferably employed. Moreover, these compounds can be employed singly, or two or more thereof can be used in combination.

Moreover, unsaturated fatty acid anhydrides are compounds having both a radically polymerizable vinyl group and an acid anhydride in a molecule thereof. Specifically, preferable examples thereof include a maleic acid anhydride.

The ASA resin is a substance made of an acrylate monomer, a styrene monomer, and an acrylonitrile monomer, and that has rubbery properties and thermoplasticity.

Examples of the ABS resin include a resin produced by a graft-polymerization, with an acrylonitrile-styrene-based resin, of an olefin-based rubber (for example, polybutadiene rubber) at approximately 40% by mass or less. Moreover, examples of the AES resin include a resin produced by graft-polymerization, with an acrylonitrile-styrene-based resin, of an ethylene-propylene copolymer rubber (for example, EP rubber) at approximately 40% by mass or less.

The non-elastomer polyamide-based resin is a polyamide-based resin having a higher elastic modulus than the thermoplastic polyamide-based elastomer described above.

Examples of the thermoplastic polyamide-based resin may include the polyamide which forms the hard segment of the thermoplastic polyamide-based elastomer described above. Examples of the thermoplastic polyamide-based resin may include a polyamide that is a ring-opening polycondensate of ε-caprolactam (amide 6), a polyamide that is a ring-opening polycondensate of undecane lactam (amide 11), a polyamide that is a ring-opening polycondensate of lauryl lactam (amide 12), a polyamide that is a condensate of a diamine and a dibasic acid (amide 66), and a polyamide having meta-xylene diamine as a structural unit (amide MX).

The amide 6 can be represented by, for example, {CO—(CH2)5—NH}n(wherein n represents the number of repeating units).

The amide 11 can be represented by, for example, {CO—(CH2)10—NH}n(wherein n represents the number of repeating units).

The amide 12 can be represented by, for example, {CO—(CH2)11—NH}n(wherein n represents the number of repeating units).

The amide 66 can be represented by, for example, {CO(CH2)4CONH(CH2)6NH}n(wherein n represents the number of repeating units).

The amide MX having meta-xylene diamine as a structural unit can be represented by, for example, the following structural unit (A-1) (wherein, in (A-1), n represents the number of repeating units).

The thermoplastic polyamide-based resin may be a homopolymer formed only from the structural unit described above, or may be a copolymer of the structural unit (A-1) and other monomers. In the case of a copolymer, a content ratio of the structural unit (A-1) in each thermoplastic polyamide-based resin is preferably 60% by mass or more.

The number average molecular weight of the thermoplastic polyamide-based resin is preferably from 300 to 30000. Moreover, from the viewpoint of toughness and flexibility at low temperature, the number average molecular weight of the polymer which forms the soft segment is preferably from 200 to 20000.

A commercial product may be employed as the non-elastomer polyamide-based resin.

As the amide 6, for example, a commercial product of “UBE Nylon” 1022B, 1011FB, or the like manufactured by Ube Industries, Ltd., can be used.

As the amide 12, for example, “UBE Nylon” 3024U or the like manufactured by Ube Industries, Ltd. can be used. As the amide 66, for example “UBE Nylon 2020B” or the like can be used. Moreover, as the amide MX, for example, a commercial product of MX Nylon (S6001, S6021, or S6011) or the like manufactured by Mitsubishi Gas Chemical Company, Inc. can be used.

The non-elastomer polyester-based resin is a resin having ester bonds in a main chain thereof and having a higher elastic modulus than the thermoplastic polyester-based elastomers described above.

Although the thermoplastic polyester-based resin is not particularly limited, it is preferably the same type of resin as the thermoplastic polyester-based resin included in the hard segment in the thermoplastic polyester-based elastomer described above. Moreover, the non-elastomer polyester-based resin may be crystalline or amorphous, and examples thereof include an aliphatic-type polyester, and an aromatic polyester. The aliphatic-type polyester may be a saturated aliphatic-type polyester or an unsaturated aliphatic-type polyester.

The aromatic polyester is generally crystalline, and can be formed by, for example, an aromatic dicarboxylic acid or an ester-forming derivative thereof, and an aliphatic diol.

Examples of the aromatic polyester include polyethylene terephthalate, polybutylene terephthalate, polystyrene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, and polybutylene terephthalate is preferable.

One example of the aromatic polyester may be, for example, polybutylene terephthalate derived from terephthalic acid and/or dimethylterephthalate, and 1,4-butanediol; and moreover, it may be, for example, a polyester derived from: a dicarboxylic acid component such as isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxyethane dicarboxylic acid, 5-sulfoisophthalic acid, or ester-forming derivatives thereof; and a diol having a molecular weight of 300 or less (for example, an aliphatic diol such as ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentylglycol, or decamethylene glycol; an alicyclic diol such as 1,4-cyclohexane dimethanol, or tricyclodecane dimethylol; or an aromatic diol such as xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4′-dihydroxy-p-terphenyl, or 4,4′-dihydroxy-p-quaterphenyl), or a copolymer-polyester in which two or more of these dicarboxylic acid components and these diol components are used in a combination. Copolymerization can also be performed with a polyfunctional carboxylic acid component, a polyfunctional oxyacid component, or a polyfunctional hydroxy component, each of which has three or more functional groups, in a range of 5% by mol or less.

As the non-elastomer thermoplastic polyester-based resin, a commercial product can be used, and examples thereof include “DURANEX” series (for example, 2000, 2002 and the like) manufactured by Polyplastics Co., Ltd., NOVADURAN series (for example, 5010R5, 5010R3-2, and the like) manufactured by Mitsubishi Engineering-Plastics Corporation, and “TORAYCON” series (for example, 1401X06, 1401X31, and the like) manufactured by Toray Industries, Inc.

As the aliphatic polyester, any of dicarboxylic acid/diol condensates or hydroxycarboxylic acid condensates may be used. Examples thereof include polylactic acid, polyhydroxy-3-butylbutyrate, polyhydroxy-3-hexylbutyrate, poly(ε-caprolactone), polyenantholactone, polycaprylolactone, polybutylene adipate, and polyethylene adipate. Polylactic acid is a representative resin as a biodegradable plastic, and a preferable embodiment of polylactic acid is described below.

A dynamic-crosslinking type thermoplastic elastomer may be used as the resin material.

The dynamic-crosslinking type thermoplastic elastomers is a thermoplastic elastomer produced by performing a crosslinking reaction of rubber components under a condition in which rubber is added and mixed to the thermoplastic resin in a molten state and then a crosslinking agent is added thereto and kneaded.

Hereinafter, the dynamic-crosslinking type thermoplastic elastomer is also simply referred to as “TPV” (ThermoPlastic Vulcanizates Elastomer).

Examples of a thermoplastic resin that can be used in a production of the TPV include the thermoplastic resin described above (including the thermoplastic elastomers).

Examples of a rubber component that can be used in production of the TPV include a diene-based rubber and a hydrogenated product thereof (for example, NR, IR, epoxidized natural rubber, SBR, BR (high-cis BR, and low-cis BR), NBR, hydrogenated NBR, and hydrogenated SBR); an olefin-based rubber (for example, an ethylene propylene rubber (EPDM, EPM), a maleic acid-modified ethylene propylene rubber (M-EPM), IIR, a copolymer of isobutylene and an aromatic vinyl or a diene-based monomer, an acrylic rubber (ACM), or an ionomer); a halogen-containing rubber (for example, Br-IIR, Cl-IIR, a brominated product of an isobutylene para-methylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHR), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CM), or maleic acid-modified chlorinated polyethylene (M-CM)), a silicone rubber (for example, methyl vinyl silicone rubber, dimethyl silicone rubber, or methyl phenyl vinyl silicone rubber), a sulfur-containing rubber (for example, a polysulfide rubber), a fluorine rubber (for example, a vinylidene fluoride-based rubber, a fluorine-containing vinylether-based rubber, a tetrafluoroethylene-propylene-based rubber, a fluorine-containing silicone-based rubber, and a fluorine-containing phosphazene-based rubber); in particular, a halogen-containing copolymer rubber of an isomonoolefin and a p-alkylstyrene such as, as a modified polyisobutylene-based rubber, a isobutylene-isoprene copolymer rubber in which a halogen group is introduced and/or a isobutylene-paramethylstyrene copolymer rubber in which a halogen group is introduced is effectively used. “Exxpro” manufactured by ExxonMobil is suitably employed as the latter.

Various additives such as a rubber, various fillers (for example, silica, calcium carbonate, and a clay), an antioxidant, oil, a plasticizer, a coloring agent, a weather proofing agent, and a reinforcing material may be contained in the resin material as needed. The content of the additive in the resin material (tire frame) is not particularly limited, and may be used as is appropriate within a range that does not impair the effects of the invention. When components other than the resin, such as the additive, are added to the resin material, the content of the resin component in the resin material is preferably 50% by mass or greater, and is more preferably 90% by mass or greater, with respect to the total amount of resin material. The content of the resin component in the resin material is a remaining part obtained by subtracting the total content of each additive from the total amount of the resin component.

Physical Characteristics of Resin Material

Hereinafter, preferable physical characteristics of the resin material included in the tire frame are explained.

In the tire frame of the invention, a resin material having a tear strength of 10 N/mm or greater is used. The tire frame therefore also preferably has a tear strength of 10 N/mm or greater, more preferably 11 N/mm or greater, and particularly preferably 12 N/mm or greater. There are no particular limitations to the upper limit of the tear strength of the tire frame; however it is preferably 20 N/mm or less, is more preferably 19 N/mm or less, and is particularly preferably 18 N/mm or less, in view of balance of tensile elastic modulus and loss coefficient (tan δ). The tear strength of the tire frame can be measured using test samples cut from the tire frame. The measurement method for tear strength and the size of the test samples are the same as the case for the resin material described above.

At least the tear strengths of the crown portion and the side portions of the tire frame are preferably each 10 N/mm or greater, more preferably 11 N/mm or greater, and particularly preferably 12 N/mm or greater. In view of balance of tensile elastic modulus and loss coefficient (tan δ), the upper limits thereof are preferably each 20 N/mm or less, are more preferably 19 N/mm or less, and are particularly preferably 18 N/mm or less. In particular, since the tear strength of the side portions of the tire frame exerts a large influence on shape maintaining ability and puncture resistance, when at least the tear strength of the side portions is set within the range described above, an improvement in puncture resistance is effectively exhibited while securing the shape maintaining ability which is an advantageous effect of the invention, and thus is preferable. Accordingly, the tear strength of at least the side portions is preferably set in the above range. The tear strength of the side portions of the tire frame refers to the tear strength obtained from a test sample containing a site on the tire side section at which a width of the tire frame in the tire width direction is maximal. The tear strength of the tire crown portion refers to the tear strength obtained from a test sample containing a site of the tire frame at a center in the tire width direction. The tear strength of the tire frame may be the same in the crown portion and the side portions, or may be different, as needed. For example, in a case in which the tear strength of the tire frame differs depending on its site on the tire frame, for example, the tear strength of the tire frame differs between the crown portion and the side portions or the like, the tear strength of each site may be adjusted by employing the same type of resin material in the crown portion and the side portions of the tire frame and adjusting the thickness or the like, and the tear strength of each site may be adjusted at each site by employing different types of resin material as the material in the crown portion and the side portions of the tire frame.

In such cases, the thickness of the crown portion of the tire frame may be appropriately selected to adjust the tear strength; however, in consideration of the tire weight and the like, the thickness is preferably from 0.5 mm to 10 mm, more preferably from 1 mm to 5 mm, and particularly preferably from 1 mm to 4 mm. Similarly, the thickness of each of the side portions of the tire frame is more preferably from 0.5 mm to 10 mm, and particularly preferably from 1 mm to 5 mm. Regarding the thickness of the crown portion and the side portions of the tire frame, the average thickness of test samples at the measurement of tear strength can be used as a reference. The thickness of the tire frame may be appropriately measured using a known method and device.

The crown portion and the side portions of the tire frame are described later.

The melting point (or the softening point) of the resin material (tire frame) itself is generally from 100° C. to 350° C., and is preferably approximately from 100° C. to 250° C., and from the viewpoint of tire manufacturability, is preferably approximately from 120° C. ° C. to 250° C., and more preferably from 120° C. to 200° C.

By employing resin material having a melting point of from 120° C. to 250° C. as described above, for example, in a case in which the tire frame is formed by fusing divided bodies thereof (frame pieces), adhesion strength is sufficient among the tire frame pieces even for a frame fused in a surrounding temperature range of from 120° C. to 250° C. Accordingly, the tire of the invention has excellent durability during running, such as puncture resistance, abrasion resistance and the like. The heating temperature is preferably a temperature from 10° C. to 150° C. higher, and more preferably a temperature from 10° C. to 100° C. higher, than the melting point (or softening point) of the resin material which forms the tire frame pieces.

Various additives can be added, if necessary, and mixed appropriately by a known method (for example, melt-mixing) to obtain the resin material.

The resin material obtained by melt-mixing may be employed in pellet form, if necessary.

The tensile elastic modulus, as defined by JIS K7113:1995, of the resin material (tire frame) itself, is preferably from 100 MPa to 1000 MPa, is more preferably from 100 MPa to 800 MPa, and is particularly preferably from 100 MPa to 700 MPa. When the tensile elastic modulus of the resin material is from 100 MPa to 700 MPa, efficient rim fitting can be performed while maintaining the shape of the tire frame.

The tensile yield strength, as defined by JIS K7113:1995, of the resin material (tire frame) itself is preferably 5 MPa or greater, is preferably from 5 MPa to 20 MPa, and is more preferably from 5 MPa to 17 MPa. When the tensile yield strength of the resin material is 5 MPa or greater, resistance to deformation due to the loads imparted to the tire such as during running can be achieved.

The tensile yield elongation, as defined by JIS K7113:1995, of the resin material (tire frame) itself, is preferably 10% or greater, is preferably from 10% to 70%, and is more preferably from 15% to 60%. When the tensile yield elongation of the resin material is 10% or greater, a large elastic region and favorable rim fitting properties can be achieved.

The tensile fracture elongation, as defined by JIS K7113:1995, of the resin material (tire frame) itself is preferably 50% or greater, is preferably 100% or greater, is more preferably 150% or greater, and is particularly preferably 200% or greater. When the tensile fracture elongation of the resin material is 50% or greater, rim fitting properties can be favorable, and there can be a less tendency toward breaking due to impact.

The deflection temperature under load (at loading of 0.45 MPa), as defined by ISO75-2 or ASTM D648, of the resin material (tire frame) itself, is preferably 50° C. or more, is preferably from 50° C. to 150° C., and is more preferably from 50° C. to 130° C. When the deflection temperature under load of the resin material is 50° C. or more, deformation of the tire frame can be suppressed even in a case in which vulcanization is performed during manufacture of the tire.

First Embodiment

Hereinafter, a tire according to a first embodiment of the tire of the invention is explained with reference to the drawings.

A tire10of the present embodiment is explained.FIG. 1Ais a perspective view illustrating a cross-section of a part of the tire according to the first embodiment of the invention.FIG. 1Bis a cross-section of a bead portion fitted to a rim. As illustrated inFIG. 1A, the tire10of the present embodiment shows a cross-sectional configuration that is almost the same as that of an ordinary conventional pneumatic tire made of rubber.

As illustrated inFIG. 1A, the tire10is equipped with a tire case17including a pair of bead portions12each of which contacts a bead sheet21and a rim flange22of the rim20illustrated inFIG. 1B, side portions14each of which extends outward in a radial direction of the tire from the bead portions12, and a crown portion16(outer peripheral portion) which connects the outside end of one side portion14in a radial direction of the tire to the outside end of the other side portion14in a radial direction of the tire.

The tire case17in the present embodiment is configured with, as a resin material, a resin material containing a single thermoplastic polyester-based resin (for example, “HYTREL 4767”, manufactured by Du Pont-Toray Co., Ltd.), to be used. In such a case, the tear strength of the resin material is 13.8 N/mm, and the tear strength of both the side portions14and the crown portion16of the tire case17is also 13.8 N/mm (side portion14thickness: 3 mm, crown portion16thickness: 3 mm).

The tire case17in the present embodiment is formed with a single resin material (the thermoplastic polyester-based resin); however, the invention is not limited to such a configuration, and similarly to ordinary conventional pneumatic tires made of rubbers, a thermoplastic resin material having different characteristics may be employed for each of the sites of the tire case17(such as the side portions14, the crown portion16and the bead portions12). The tire case17may be reinforced with a reinforcement material by embedding of the reinforcement material (such as fibers, cord, nonwoven fabric, or cloth of a polymer material or metal, and the like) in the tire case17(for example, in the bead portions12, the side portions14, the crown portion16, and the like).

The tire case17in the present embodiment is a product formed by bonding a pair of tire case half parts (tire frame pieces)17A formed of a resin material. The tire case half parts17A are formed such that annular tire case half parts17A having the same shape, each of which formed by injection-molding or the like, in an integrated manner, one of the bead portions12, one of the side portions14, and a half-width of the crown portion16are arranged to face each other and bonded at a tire equatorial plane portion. The tire case17is not limited to being formed by bonding two members, and may be formed by bonding three or more members.

The tire case half parts17A formed from the resin material can, for example, be formed by vacuum molding, pressure molding, injection molding, melt casting, or the like. Therefore, it is not necessary to perform vulcanization in contrast to cases in which a tire case is conventionally formed from rubber, whereby a tire manufacturing process can be greatly simplified, and molding time can be reduced.

In the present embodiment, since the tire case half parts17A are formed in bilateral symmetrical shapes, that is, one of the tire case half parts17A is formed in the same shape as the other of the tire case half parts17A, it is advantageous that one type of mold suffices for forming the tire case half parts17A.

In the present embodiment, as illustrated inFIG. 1B, an annular bead core18, formed from steel cord, is embedded in each of the bead portions12, similarly to in ordinary conventional pneumatic tires. However, the invention is not limited to such a configuration, and the bead core18may be omitted as long as the rigidity of the bead portions12is secured and there are no issues with fitting to the rim20. Other than steel cord, the bead core18may also be formed from, for example, organic fiber cord, organic fiber cord coated with a resin, or a hard resin.

In the present embodiment, an annular sealing layer24, that is formed from a material having superior sealing properties to the resin material which forms the tire case17, for example, rubber, is formed at a portion at which the bead portions12contacts the rim20, or at least at a portion at which the rim20contacts the rim flanges22. The sealing layer24may also be formed at a portion at which the tire case17(the bead portions12) contacts the bead sheets21. A softer material than the resin material which forms the tire case17can be employed as the material having superior sealing properties to the resin material which forms the tire case17. As a rubber which can be employed as the sealing layer24, the same type of rubber is preferably employed as the rubber employed on bead portion external faces of ordinary conventional pneumatic tires made of rubber. The sealing layer24of rubber may also be omitted as long as sealing properties with the rim20can be secured by the resin material which forms the tire case17alone, and other thermoplastic resins (thermoplastic elastomer) having superior sealing properties to the resin material may also be employed. Examples of such other thermoplastic resins include resins such as polyurethane-based resins, polyolefin-based resins, thermoplastic polystyrene-based resins, polyester resins, and blends of these resins and a rubber or elastomer, or the like. A thermoplastic elastomer may also be employed, and examples thereof include a thermoplastic polyester-based elastomer, a thermoplastic polyurethane-based elastomer, a thermoplastic polystyrene-based elastomer, a thermoplastic polyolefin-based elastomer, a combination of such elastomers, and blends with rubber.

As illustrated inFIG. 1A, a reinforcement cord26having higher rigidity than the resin material which forms the tire case17is wound around the crown portion16in a circumferential direction of the tire case17. The reinforcement cord26is wound in a spiral shape in such a state that at least a part thereof is embedded in the crown portion16in a cross-sectional view along an axial direction of the tire case17, to form a reinforcement cord layer28. The crown30, formed from a material, for example rubber, having superior abrasion resistance to the resin material which forms the tire case17, is placed on an outer peripheral side of the reinforcement cord layer28in a radial direction of the tire.

The reinforcement cord layer28formed from the reinforcement cord26is explained with reference toFIG. 2.FIG. 2is a cross-sectional view along the tire rotation axis and illustrating a state in which reinforcement cord is embedded in the crown portion of the tire case of the tire of the first embodiment. As illustrated inFIG. 2, the reinforcement cord26is wound in a spiral shape in such a state that, in a cross-sectional view along an axial direction of the tire case17, at least a part is embedded in the crown portion16, to form, together with a part of the outer peripheral portion of the tire case17, the reinforcement cord layer28as illustrated by the dashed line portion inFIG. 2. The part of the reinforcement cord26embedded in the crown portion16is in a state of closely-contacting with the resin material which forms the crown portion16(the tire case17). As the reinforcement cord26, a monofilament (single strand) such as metal fiber, organic fiber or the like, or a multifilament (twisted strands) formed from twisted fibers such as a steel cord formed from twisted steel fiber, or the like, can be employed. In the present embodiment, a steel cord is employed as the reinforcement cord26.

InFIG. 2, the depth L of embedding indicates a depth of embedding of the reinforcement cord26with respect to the tire case17(the crown portion16) to the rotation axis direction of the tire. The depth L of embedding of the reinforcement cord26with respect to the crown portion16is preferably ⅕ or greater of the diameter D of the reinforcement cord26and more preferably more than ½. It is most preferable that the whole of the reinforcement cord26is embedded in the crown portion16. When the depth L of embedding of the reinforcement cord26is more than ½ of the diameter D of the reinforcement cord26, from a dimensional perspective of the reinforcement cord26, the reinforcement cord26is less likely to come out from the embedded portion. When the whole of the reinforcement cord26is embedded in the crown portion16, a surface (outer peripheral face) is flat, whereby incorporation of air to a peripheral part of the reinforcement cord can be suppressed even when a member is placed on the crown portion16in which the reinforcement cord26is embedded. The reinforcement cord layer28corresponds to a belt disposed on an outer peripheral face of a carcass of a conventional pneumatic tire made of rubber.

As described above, the crown30is placed on an outer peripheral side of the reinforcement cord layer28in a radial direction of the tire. Rubber employed in the crown30is preferably a similar type of rubber to the rubber employed in a conventional pneumatic tire made of rubber. In place of the crown30, a crown formed from another type of resin material having superior abrasion resistance to the resin material which forms the tire case17may be employed. A crown pattern formed from a plurality of grooves is formed on a face of the crown30which contacts the road, similarly to a conventional pneumatic tire made of rubber.

Hereinafter, a manufacturing method of a tire according to the present embodiment is explained.

Tire Case Molding Process

First, tire case half parts supported by a thin metal support ring are arranged to face each other. Then a bonding mold which is omitted from the drawings is placed so as to contact an outer peripheral face of the contact part of the tire case half part. The bonding mold is configured to press the circumference of the bonding part (the contact part) of the tire case half part17A with a specific pressure. Subsequently, the circumference of the contact part of the tire case half part is pressed at the melting point (or softening point) or higher of the resin material which forms the tire case. The bonding part of the tire case half parts is heated and pressed by the bonding mold, whereby the bonding part is melted, the tire case half parts are fused together, and these members form into the tire case17in an integrated manner. Although in the present embodiment the bonding part of the tire case half parts is heated using the bonding mold, the invention is not limited thereto, and, for example, the bonding parts may be heated by a radio frequency heater separately provided, or the like, or may be softened or melted in advance by using hot air, irradiation with infrared radiation, or the like, and then pressed by the bonding mold to bond the tire case half parts together.

Reinforcement Cord Member Winding Process

Next, a reinforcement cord winding process is explained, with reference toFIG. 3.

FIG. 3is an explanatory diagram to explain an operation of embedding of the reinforcement cord in the crown portion of a tire case using a cord heating device and rollers. InFIG. 3, a cord supply device56is equipped with: a reel58which is wound with the reinforcement cord26; a cord heating device59which is disposed in a downstream side of the reel58in the cord conveyance direction; a first roller60which is disposed in a downstream side of the reinforcement cord26in the conveyance direction; a first cylinder device62which moves the first roller60in a direction towards or away from, the outer peripheral face of the tire; a second roller64which is disposed in a downstream side of the reinforcement cord26in a conveyance direction of the first roller60; and a second cylinder device66which moves the second roller64in a direction towards or away from, the outer peripheral face of the tire. The second roller64can be employed as a cooling roller made of metal. In the present embodiment, the surface of the first roller60or the second roller64is coated with a fluororesin (TEFLON (registered trademark) in the present embodiment) to suppress adhering of the melted or softened resin material. In the present embodiment, the cord supply device56is configured to have the two rollers, the first roller60and the second roller64; however, the invention is not limited to such a configuration, and may be configured to have one of the rollers alone (that is, one roller).

The cord heating device59is equipped with a heater70and a fan72, for generating hot air. The cord heating device59is also equipped with a heating box74in which hot air is supplied to the inside thereof and the reinforcement cord26passes through an interior space thereof; and a discharge outlet76through which the heated reinforcement cord26is discharged.

In the present process, first, the temperature of the heater70on in the cord heating device59is raised, and the surrounding air heated by the heater70is delivered into the heating box74by means of an airflow generated by rotation of the fan72. The reinforcement cord26unwound from the reel58is then delivered into the heating box74, of which the internal space has been heated by the hot airflow, and heated (for example, the temperature of the reinforcement cord26is heated to approximately 100° C. to 200° C.). The heated reinforcement cord26passes through the discharge outlet76, and is wound helically at a certain tension on the outer peripheral face of the crown portion16of the tire case17which rotates in the arrow R direction inFIG. 3. When the heated reinforcement cord26contacts the outer peripheral face of the crown portion16, the resin material of the contact part is melted or softened, and at least a part of the heated reinforcement cord26is embedded in the outer peripheral face of the crown portion16. At this time, since the heated reinforcement cord26is embedded in the melted or softened resin material, a state in which there are no gaps between the resin material and the reinforcement cord26, that is, a closely-contacting state is achieved. Accordingly, incorporation of air into the portion where the reinforcement cord26is embedded is suppressed. When the reinforcement cord26is heated to a temperature higher than the melting point (or softening point) of the resin material which forms the tire case17, melting or softening of the resin material at the portion which contacts the reinforcement cord26is promoted. In this manner, the reinforcement cord26is readily embedded in the outer peripheral face of the crown portion16, and the incorporation of air can be effectively suppressed.

The depth L of embedding of the reinforcement cord26can be adjusted using the heating temperature of the reinforcement cord26, the tension acting on the reinforcement cord26, the pressure of the first roller60, and the like. In the present embodiment, the depth L of embedding of the reinforcement cord26is set to be ⅕ or greater of the diameter D of the reinforcement cord26. The depth L of embedding of the reinforcement cord26is more preferably more than ½ the diameter D of the reinforcement cord26, and most preferably the whole of the reinforcement cord26is embedded.

In this manner, by winding the heated reinforcement cord26while being embedded in the outer peripheral face of the crown portion16, the reinforcement cord layer28is formed on the outer peripheral side of the crown portion16of the tire case17.

Subsequently, a vulcanized-belt shaped crown30is wound a single turn around the outer peripheral face of the tire case17, and the crown30is adhered to the outer peripheral face of the tire case17with an adhesive or the like. As the crown30, for example, a precure crown can be employed in conventional known recycled tires. The present process is similar to the process for adhering a precure crown to the outer peripheral face of a base tire of a recycled tire.

Then, the seal layers24which is formed from a vulcanized rubber are adhered to the bead portions12of the tire case17with an adhesive or the like, whereby the tire10is completed.

Effects

In the tire10of the present embodiment, since the tire case17is formed with a resin material including a thermoplastic polyester-based resin having a tear strength in the range of 10 N/mm or greater, excellent shape maintaining ability and puncture resistance can be exhibited. Moreover, the tire10has a structure simpler than that of a conventional tire made of rubber, and is hence lighter in weight. Accordingly, the tire10of the present embodiment has high abrasion resistance and durability. In particular, since the tire10has the tear strength of the side portion14in the range of 10 N/mm or greater and has a thickness of 3 mm, the shape maintaining ability can be sufficiently improved while maintaining light weight characteristics.

In the tire10of the present embodiment, the puncture resistance, cutting resistance, and the circumferential direction rigidity of the tire10is improved since the reinforcement cord26which has a higher rigidity than the resin material is wound helically onto the outer peripheral face of the crown portion16of the tire case17formed from the resin material in a circumferential direction. As the circumferential direction rigidity of the tire10is improved, creep of the tire case17formed of the resin material is prevented.

Since at least a part of the reinforcement cord26is embedded in the outer peripheral face of the crown portion16of the tire case17which is formed of the resin material to be in close contact with the resin material, in a cross-sectional view along the axial direction of the tire case17(the cross-section illustrated inFIG. 1A), incorporation of air during manufacture is suppressed, and moving of the reinforcement cord26by the input force or the like during running is suppressed. Accordingly, the occurrence of detachment or the like in the reinforcement cord26, the tire case17, or the crown30is suppressed, and the durability of the tire10is improved.

As such, when the reinforcement cord layer28is configured to contain the resin material, the difference in hardness between the tire case17and the reinforcement cord layer28is reduced, compared to a case in which the reinforcement cord26is fixed with cushion rubber, whereby the reinforcement cord26can be further closely contact and fixed to the tire case17. Accordingly, the incorporation of air described above can be effectively prevented, movement of the reinforcement cord member during running can be effectively suppressed. Moreover, when the reinforcement cord26is a steel cord, easy separation and recovery of the reinforcement cord26from the resin material by heating when disposing of the tire can be achieved, and thus it is advantageous from the perspective of recycling characteristics of the tire10. Since the loss coefficient (tan δ) of resin material is lower than that of vulcanized rubber, the tire rolling characteristics can be improved when the reinforcement cord layer28contains a large amount of the resin material. Moreover, the resin material has an advantage that the in-plane shear rigidity is larger than that of vulcanized rubber and steering stability and abrasion resistance during tire running are excellent.

As illustrated inFIG. 2, the depth L of embedding of the reinforcement cord26is ⅕ or greater of the diameter D, and thus the incorporation of air during manufacture is effectively suppressed, and the movement of the reinforcement cord26by input force during running or the like is further suppressed.

Since the crown30which contacts the road surface is formed from a rubber material which has greater abrasion resistance than the resin material which forms the tire case17, the abrasion resistance of the tire10is improved.

Moreover, since the annular bead core18formed from a metal material is embedded in the bead portion12, the tire case17, that is, the tire10, is firmly retained onto the rim20, similarly to a conventional pneumatic tire made of rubber.

Moreover, since the sealing layer24which is formed from a rubber material having superior sealing properties to the resin material which forms the tire case17is provided at the part that contacts the rim20of the bead portion12, the sealing properties between the tire10and the rim20are improved. Accordingly, the leakage of air from inside the tire is even further suppressed, compared to a case in which sealing is performed between the rim20and the resin material which forms the tire case17alone. The rim fitting properties are also improved by providing the sealing layer24.

The above embodiment has a configuration in which the reinforcement cord26is heated and the surface of the tire case17at the part with which the heated reinforcement cord26is in contact is melted or softened; however, the invention is not limited to such a configuration, and the reinforcement cord26may be embedded in the crown portion16after the outer peripheral face of the crown portion16in which the reinforcement cord26is to be embedded is heated using a hot airflow generation device, without heating the reinforcement cord26.

In the first embodiment, a heat source of the cord heating device59is a heater and a fan; however, the invention is not limited to such a configuration, and a configuration of directly heating the reinforcement cord26with radiation heat (such as, for example, by infrared radiation) may be employed.

The first embodiment is configured such that the part of the resin material melted or softened in which the reinforcement cord26is embedded is cooled forcibly with the metal second roller64; however, the invention is not limited to such a configuration, and a configuration of directly flowing a cooling airflow onto the part of the resin material that is melted or softened, thereby forcibly-cooling and solidifying the melted or softened part of the resin material.

The first embodiment is configured to heat the reinforcement cord26; however, for example, a configuration of covering the outer periphery of the reinforcement cord26with the same a resin material as that of the tire case17. In such a case, by heating the reinforcement cord26together with the coating resin material when the coated reinforcement cord is wound onto the crown portion16of the tire case17, incorporation of air during embedding in the crown portion16can be effectively suppressed.

Helically winding the reinforcement cord26is facile in manufacturing; however, other methods such as providing reinforcement cord26discontinuously in the width direction may also be considered.

The tire10of the first embodiment is so-called a tubeless tire in which the bead portion12is fitted to the rim20to form an air chamber between the tire10and the rim20; however, the invention is not limited to such a configuration, and the tire may be formed into a complete tube shape.

Second Embodiment

A manufacturing method of a tire and a tire of a second embodiment in the invention are explained with reference to the drawings. The tire of the present embodiment, similarly to the first embodiment described above, shows a cross-sectional configuration that is almost the same as that of an ordinary conventional pneumatic tire made of rubber. Thus, in the following drawings, the same reference numerals are appended to the same configuration to that of the first embodiment.FIG. 4Ais a cross-sectional view along the tire width direction of the tire of the second embodiment, andFIG. 4Bis an enlarged cross-sectional view along the tire width direction of a bead portion in a state in which the tire of the second embodiment is fitted to a rim.FIG. 5is a cross-sectional view along the tire width direction illustrating the circumference of a reinforcement layer of a tire according to the second embodiment.

In the tire of the second embodiment, similarly to in the first embodiment described above, a tire case17is configured with a resin material containing a thermoplastic polyamide-based resin (for example, UBESTA XPA9048X1, manufactured by Ube Industries, Ltd.). In such a case, the tear strength of the resin material is 14.6 N/mm, and the tear strengths of the side portions14and the crown portion16of the tire case17are both 14.6 N/mm (side portion14thickness: 3.0 mm, crown portion16thickness: 3.0 mm).

In a tire200in the present embodiment, as illustrated inFIG. 4AandFIG. 5, a reinforcement cord layer28(illustrated by the dashed line inFIG. 5) in which a coating cord member26B is wound in the circumferential direction is superposed on the crown portion16. The reinforcement cord layer28forms an outer peripheral portion of the tire case17and reinforces the rigidity in the circumferential direction of the crown portion16. The outer peripheral face of the reinforcement cord layer28is included in an outer peripheral face17S of the tire case17.

The coating cord member26B is formed by coating a cord member26A having higher rigidity than the resin material which forms the tire case17, with a coating resin material27that is different from the resin material which forms the tire case17. The coating cord member26B and the crown portion16are bonded (for example by welding or by adhering with an adhesive) at the contact part of the covered cord member26B with the crown portion16.

The tensile elastic modulus of the coating resin material27is preferably set to be within a range of from 0.1 times to 20 times as that of the tensile elastic modulus of the resin material which forms the tire case17. When the tensile elastic modulus of the coating resin material27is 20 times or less of the tensile elastic modulus of the resin material which forming the tire case17, the crown portion is not excessively hard, and good rim fitting property is facilitated. When the tensile elastic modulus of the coating resin material27is 0.1 times or more of the tensile elastic modulus of the resin material which forms the tire case17, the resin which forms the reinforcement cord layer28is not excessively soft, the in-plane shear rigidity of the belt is excellent, and cornering force is improved. In the present embodiment, as the coating resin material27, the material the same as the resin material which forms the tire frame.

As illustrated inFIG. 5, the coating cord member26B has a substantially trapezoidal shape in a cross-sectional configuration. In the following, the reference numeral26U indicates the top face of the coating cord member26B (the outside face in a radial direction of the tire), and the reference numeral26D indicates the bottom face (the inside face in a radial direction of the tire). In the present embodiment, the cross-sectional configuration of the coating cord member26B is configured to have a substantially trapezoidal shape; however, the invention is not limited to such a configuration, and any shape may be employed as long as it is a shape other than a shape in which the width increases from the bottom face26D side (the inside in the tire radial direction) toward the top face26U side (the outside in the tire radial direction) in the cross-sectional configuration.

As illustrated inFIG. 5, since the coating cord members26B are arranged at intervals in the circumferential direction, gaps28A between adjacent coating cord members26B are formed. Accordingly, the outer peripheral face of the reinforcement cord layer28is corrugated, whereby the outer peripheral face17S of the tire case17in which the reinforcement cord layer28forms the outer peripheral portion is also corrugated.

Fine roughened corrugations are uniformly formed on the outer peripheral face17S of the tire case17(including the corrugations), and a cushion rubber29is bonded thereon with a bonding agent therethrough. The inside of the rubber part in the radial direction of the cushion rubber29has flowed into the roughened corrugations.

The crown30formed from a material having superior abrasion resistance to the resin material which forms the tire case17, such as rubber, is bonded onto (the outer peripheral face of) the cushion rubber29.

Regarding the rubber (crown rubber30A) employed in the crown30, preferably a similar type of rubber is employed to that employed in conventional pneumatic tires made of rubber. In place of the crown30, a crown formed from another type of resin material having superior abrasion resistance to the resin material which forms the tire case17may be employed. A crown pattern (not illustrated in the drawings) formed from a plurality of grooves is formed on a face of the crown30which contacts the road, similarly to a conventional pneumatic tire made of rubber.

Next, a manufacturing method of a tire of the present embodiment is explained.

Tire Case Molding Process

First, similarly to in the first embodiment described above, the tire case half parts17A are formed, and then heated and pressed by a bonding mold to form the tire case17.

Reinforcement Cord Member Winding Process

A manufacturing device for the tire in the present embodiment is similar to that of the first embodiment described above, the cord supply device56illustrated inFIG. 3of the first embodiment in which the coating cord member26B which has a substantially trapezoidal shape in a cross-sectional configuration and in which the cord member26A is coated with the coating resin material27(the same resin material as that of the tire case in the present embodiment) winds on the reel58is used.

First, the temperature of the heater70is raised, and the surrounding air heated by the heater70delivered into the heating box74by means of an airflow generated by rotation of the fan72. The coating cord member26B unwound from the reel58is then delivered into the heating box74, of which the internal space has been heated by the hot airflow, and heated (for example, the temperature of the outer peripheral face of the coating cord member26B is heated to the melting point (or softening point) or more of the coating resin material27). The coating resin material27is in a melted or softened state by heating the coating cord member26B.

The coating cord member26B passes through the discharge outlet76, and is wound helically at a certain tension on the outer peripheral face of the crown portion16of the tire case17which rotates in the direction coming out from the paper. At this time, the bottom face26D of the coating cord member26B contacts the outer peripheral face of the crown portion16. Then, the coating resin material27which is in the melted or softened state at the contact part spreads out over the outer peripheral face of the crown portion16, and the coating cord member26B is welded to the outer peripheral face of the crown portion16. In this manner, the bonding strength between the crown portion16and the coating cord member26B is enhanced.

Roughening Treatment Process

Subsequently, using a blasting apparatus, which is not illustrated in the drawings, a blasting abrasive is ejected at high speed to the outer peripheral face17S of the tire case17, while rotating the tire case17. The ejected blasting abrasive impacts the outer peripheral face17S, and forms finely roughened corrugations96having an arithmetic mean roughness Ra of 0.05 mm or more on the outer peripheral face17S.

When the finely roughened corrugations96are formed on the outer peripheral face17S of the tire case17in this manner, the outer peripheral face17S is hydrophilic, thereby improving the wetting properties of the bonding agent, described below.

Superposition Process

Next, a bonding agent is applied onto the outer peripheral face17S of the tire case17in which a roughening treatment has been performed.

Examples of the bonding agent include a triazinethiol-based adhesive, a chlorinated rubber-based adhesive, a phenol-based resin adhesive, an isocyanate-based adhesive, a halogenated rubber-based adhesive, and a rubber-based adhesive, and there is no particular limitation; however, the bonding agent preferably reacts at a temperature at which the cushion rubber29can be vulcanized (from 90° C. to 140° C.).

Next, the cushion rubber29in an unvulcanized state is wound a single turn around the outer peripheral face17S coated with the bonding agent, then a bonding agent such as a rubber cement composition is applied onto the cushion rubber29, and the crown rubber30A which is in a fully vulcanized or semi-vulcanized state is wound a single turn therearound to give a tire case in a raw state.

Vulcanization Process

Next, the raw tire case is then housed in a vulcanization can or mold, and then vulcanized. At this time, the non-vulcanized cushion rubber29flows into the roughened corrugations96formed to the outer peripheral face17S of the tire case17by the roughening treatment. When vulcanization is completed, an anchor effect is exhibited by the cushion rubber29that has flowed into the roughened corrugations96, thereby improving the bonding strength between the tire case17and the cushion rubber29. That is, the bonding strength between the tire case17and the crown30is improved through the cushion rubber29.

The sealing layer24formed from a soft material which is softer than the resin material is then adhered to the bead portions12of the tire case17using an adhesive or the like, thereby completing the tire200.

Effects

In the tire200of the present embodiment, since the tire case17is formed from a resin material including a thermoplastic polyamide-based resin having a tear strength in the range of 10 N/mm or greater, excellent shape maintaining ability and puncture resistance can be exhibited. Moreover, the tire200has a structure simpler than that of a conventional tire made of rubber, and is hence lighter in weight. Accordingly, the tire200of the present embodiment has high abrasion resistance and durability. In particular, since the tire200has the tear strength of the side portion14in the range of 10 N/mm or greater and has a thickness of 3 mm, thereby sufficiently improving the shape maintaining ability and the puncture resistance while retaining lightweight characteristics.

In the manufacturing method of the tire of the present embodiment, since the outer peripheral face17S of the tire case17is subjected to roughening treatment at integrating the tire case17with the cushion rubber29and the crown rubber30A, thereby improving the bondability (adhesiveness) due to the anchor effect. Since the resin material which forms the tire case17is dug up by an impact of the blasting abrasive, the wetting properties of the bonding agent are improved. In this manner, the bonding agent is retained in a uniformly applied state on the outer peripheral face17S of the tire case17, whereby the bonding strength between the tire case17and the cushion rubber29can be secured.

In particular, even though corrugations are formed in the outer peripheral face17S of the tire case17, roughening treatment is performed on the circumference of concave parts (dented walls and dented bottoms) by impact of a blasting abrasive to the concave parts (the gaps28A), and the bonding strength between the tire case17and the cushion rubber29can be secured.

Since the cushion rubber29is superposed within the region in which roughening treatment of the outer peripheral face17S of the tire case17is performed, the bonding strength between the tire case17and the cushion rubber can be effectively secured.

In the vulcanization process, when the cushion rubber29is vulcanized, the cushion rubber29flows into the roughened corrugations formed on the outer peripheral face17S of the tire case17by roughening treatment. When the vulcanization is completed, the anchor effect is exhibited by the cushion rubber29that has flowed into the roughened corrugations, thereby improving the bonding strength between the tire case17and the cushion rubber29.

The tire200manufactured by such a tire manufacturing method secures the bonding strength between the tire case17and the cushion rubber29, that is, the bonding strength between the tire case17and the crown30is secured through the cushion rubber29. In this manner, detachment between the outer peripheral face17S of the tire case17of the tire200and the cushion rubber29during running or the like is suppressed.

Since the reinforcement cord layer28forms the outer peripheral portion of the tire case17, the puncture resistance and cut resistance is improved in comparison to a configuration in which the outer peripheral portion is formed from a member other than the reinforcement cord layer28.

Since the reinforcement cord layer28is formed by winding the coating cord member26B, the rigidity in the circumferential direction of the tire200is improved. As the rigidity in the circumferential direction is increased, creep of the tire case17(a phenomenon in which plastic deformation of the tire case17increases with time under constant stress) is suppressed, and pressure resistance against air pressure from the inside in the tire radial direction is improved.

Moreover, when the reinforcement cord layer28is configured to include the coating cord member26B, a smaller difference in hardness between the tire case17and the reinforcement cord layer28can be achieved, compared to a case in which the reinforcement cord26A is simply fixed with the cushion rubber29, whereby the coating cord member26B can be further closely adhered and fixed to the tire case17. Accordingly, incorporation of air as described above can be effectively prevented, and movement of the reinforcement cord member during running can be effectively suppressed.

Moreover, when the reinforcement cord26A is steel cord, easy separation and recovery of the cord member26A from the coating cord member26B can be achieved by heating when disposing of the tire, and thus it is advantageous from the perspective of recycling characteristics of the tire200. Since the loss coefficient (tan δ) of resin material is lower than that of vulcanized rubber, the tire rolling characteristics can be improved when the reinforcement cord layer28contains a large amount of the resin material. Moreover, the resin material has an advantage that the in-plane shear rigidity is larger than that of vulcanized rubber and steering stability and abrasion resistance during tire running are excellent.

In the present embodiment, corrugations are formed on the outer peripheral face17S of the tire case17; however, the invention is not limited thereto, and a configuration in which the outer peripheral face17S is formed to be flat may be employed.

In the tire case17, the reinforcement cord layer may be formed such that a coating cord member that has been wound on and bonded to the crown portion of a tire case is covered with a coating thermoplastic material. In such a case, a coating layer can be formed by ejecting the coating thermoplastic material in a melted or softened state onto the reinforcement cord layer28. Alternatively, without employing an extruder, the coating layer may be formed by heating a welding sheet into a melted or softened state, and then attaching the welding sheet to the surface (outer peripheral face) of the reinforcement cord layer28.

The second embodiment described above is configured to form the tire case17by bonding case divided bodies (the tire case half parts17A); however, the invention is not limited to such a configuration, and the tire case17may be integrally formed by using a mold or the like.

The tire200of the second embodiment is so-called a tubeless tire in which an air chamber is formed between the tire200and the rim20by fitting the bead portions12to the rim20, however, the invention is not limited to such a configuration, and the tire200may be formed into a complete tube shape, for example.

In the second embodiment, the cushion rubber29is disposed between the tire case17and the crown30; however, the invention is not limited thereto, and a configuration in which the cushion rubber29is not disposed may be employed.

The second embodiment has a configuration in which the coating cord member26B is wound helically on the crown portion16; however, the invention is not limited thereto, and a configuration in which the coating cord member26B is wound discontinuously in the width direction may be employed.

In the second embodiment, a configuration in which a thermoplastic material is used as the coating resin material27which forms the coating cord member26B and the coating cord member26B is welded to the outer peripheral face of the crown portion16by heating the coating resin material27into a melted or softened state is employed. However, the invention is not limited to such a configuration, and a configuration in which the coating cord member26B is adhered to the outer peripheral face of the crown portion16by using an adhesive or the like without heating the coating resin material27may be employed.

A configuration in which a thermoset resin is used as the coating resin material27which forms the coating cord member26B, and the coating cord member26B is adhered to the outer peripheral face of the crown portion16by using an adhesive or the like without heating may be employed.

Moreover, a configuration in which a thermoset resin is used as the coating resin material27which forms the coating cord member26B and the tire case17is formed of a resin material may be employed. In such a case, the coating cord member26B may be adhered to the outer peripheral face of the crown portion16by an adhesive or the like, and the site of the tire case17in which the coating cord member26B is disposed may be heated into a melted or softened state to weld the coating cord member26B to the outer peripheral face of the crown portion16.

Furthermore, a configuration in which a thermoplastic material is uses as the coating resin material27which forms the coating cord member26B and the tire case17is formed of a resin material may be employed. In a such case, the coating cord member26B may be adhered to the outer peripheral face of the crown portion16by an adhesive or the like, and the coating resin material27may be heated into a melted or softened state while the site of the tire case17in which the coating cord member26B is disposed may be heated into a melted or softened state, thereby welding the coating cord member26B to the outer peripheral face of the crown portion16. When both the tire case17and the coating cord member26B are heated into a melted or softened state, both are well-mixed, whereby bonding strength is improved. When the resin material which forms the tire case17and the coating resin material27which forms the coating cord member26B are both resin materials, the same type of thermoplastic material is preferable, and the same thermoplastic material is particularly preferable.

After the outer peripheral face17S of the tire case17which has been subjected to roughening treatment may be subjected to corona treatment, plasma treatment or the like to activate the surface of the outer peripheral face17S, and the hydrophilic properties are increased, an adhesive may be applied.

Moreover, the sequence for manufacturing the tire200is not limited to the sequence of the second embodiment, and may be appropriately modified.

Embodiments of the invention have been described by way of exemplary embodiments, however, these embodiments are merely examples, and various modifications can be implemented to the extent of not departing from the gist of the invention. Furthermore, it is needless to say that the scope of rights of the invention is not limited to these embodiments.

EXAMPLES

Hereinafter, more specific explanation regarding the invention is given based on Examples. However the invention is not limited thereto.

Measurement of Tensile Elastic Modulus

Using an injection molding machine (SE 30D, manufactured by Sumitomo Heavy Industries Co., Ltd.), injection molding was performed at a molding temperature of from 180° C. to 260° C., with a mold temperature of from 50° C. to 70° C., to obtain samples of 130 mm×30 mm with a thickness of 2.0 mm.

Each sample was punched out to produce dumbbell shaped test samples (No. 5 test samples) in accordance with JIS K6251:1993. In Comparative Example 1, a test sample was produced in a similar manner to in the other Examples, using rubber.

Then, using Shimadzu Autograph AGS-J (5KN), manufactured by Shimadzu Corporation, the tensile elastic modulus of each of the dumbbell shaped test samples was measured with an elongation speed set at 200 mm/min. The results are shown in the Tables below.

Measurement of Loss Coefficient (tan δ)

Regarding the loss coefficient (tan δ), the tan δ was measured using an ARESIII, manufactured by TA Instruments, Ltd. under conditions of 30° C., 20 Hz, and shear strain of 1%, using the test samples.

Evaluation of Tear Strength

Using the resin materials listed in the following Table, test samples were produced and the tear strength was measured, according to JIS K7128 (1998). At this time, the test speed was set to 500±50 mm per minute. Measurements were performed using Shimadzu Autograph AGS-J (5KN), manufactured by Shimadzu Corporation.

Shape Maintaining Ability

Using the resin materials listed in the following Table, tires were formed in the same manner as in the first embodiment above. A thickness of the side portion was 3 mm and a thickness of the crown portion was 3 mm. Each of the tear strengths of the side portions and the crown portions was the same numerical value as that of the resin material shown in the Tables. Each of the tires was fitted to a rim, filled with air such that an internal pressure was 200 kPa, and the evaluation was performed as to whether or not the shape of the tire was maintained, according to the following criteria.

Criteria

A: Tire shape was maintained.

C: Unable to be produced as a tire, or tire shape was not maintained.

The components shown in the Tables above are as follows.TPC 1: thermoplastic polyester-based elastomer

(“ELASTOLLAN ET858D”, manufactured by BASF SE)Rubber: The following compositions were kneaded with a Banbury mixer, and press-vulcanized at 145° C. for 30 minutes to obtain a sample of 120 mm×120 mm with a thickness of 2 mm.

Butadiene rubber: “BRO1”, manufactured by JSR Corporation

As understood from the Tables above, when a tear strength was 10 N/mm or greater, shape maintaining ability of the tire was excellent and puncture resistance was excellent. In contrast, the rubber of Comparative Example 1 had a tear strength of 10 N/mm, and was not able to maintain shape against internal pressure. Similarly, in Comparative Example 2, it was understood that, although one type of polystyrene-based elastomer was employed, the shape maintaining ability of the tire was inferior when the tear strength was 10 N/mm, even if the thermoplastic elastomer was used. The tensile elastic modulus was also not sufficient in either of the Comparative Examples.

The disclosure of Japanese Patent Application No. 2012-044592 is incorporated by reference into the present specification.