JPH1029404A - Pneumatic tire and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obviate the destruction of an air permeation preventing layer in a splice part by making a cord of an inner carcass layer out of the two-ply carcass layers forming the splice part discontinue at least one spot between both symmetrically paired bead cores. SOLUTION: A splice part 15, whose one end and the other end in the tire circumferential direction EE' are superposed on each other and extending in the tire cross direction, is formed in a carcass layer 11. An air permeation preventing layer 14 is inserted between an outer carcass layer 11u and an inner carcass layer 11d of this splice part 15. Then, a cord 11c of the inner carcass layer 11d out of both two-ply carcass layers 11 and 11 forming the splice part 15 is discontinued at least in a spot lying between a symmetrical pair of bead cores 10 and 10. This spot to be discontinued should be set to be an equidistance in the tire cross direction or to be symmetry to a tire equatorial plane otherwise, and it is installed in the inner part of a belt layer 13. In addition, for the end of this discontinuity, a notch 16 cutting the cord 11c is installed in the inner carcass layer 11d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a resin film containing a thermoplastic resin as a main component as an air permeation preventing layer and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, an inner liner layer (air permeation prevention layer) made of a low gas permeable rubber such as a halogenated butyl rubber is used on the inner surface of a pneumatic tire to prevent air leakage and keep the tire air pressure constant. Is provided. However, since the halogenated butyl rubber has a large hysteresis loss, when the carcass layer and the inner liner layer are wavy after vulcanization of the tire, the inner liner layer is deformed along with the deformation of the carcass layer and generates heat, so that the tire is rolled. There was a problem that resistance increased. For this reason, the two are generally bonded between a halogenated butyl rubber inner liner layer and a carcass layer via a rubber sheet called a tie rubber having a small hysteresis loss. This increases the thickness of the tie rubber in addition to the thickness of the inner liner layer, and has become a bottleneck in reducing the weight of the tire.

[0003] In order to solve this problem, there has been proposed a method for reducing the weight of the tire by reducing the thickness of the air permeation preventing layer using a resin film having a lower air permeability and a lower mass than halogenated butyl rubber. (Japanese Patent Laid-Open No. 6-4020)
No. 7). However, it has been found that the following problem occurs in the manufacturing process when the resin film is used as the air permeation preventing layer.

That is, when molding a green tire, a composite sheet in which a resin film is adhered to a carcass material is wound around a tire forming drum and spliced so that both ends thereof are overlapped. Shrinkage of the carcass cord by heat immediately after vulcanization causes a contraction force to be generated in the outer and inner carcass layers in the splice portion of the composite sheet. At this time, the outer carcass layer is restrained from being deformed by the contraction force by members (belt layer, side tread layer, etc.) further in contact with the outside, but the contraction force of one inner carcass layer remains as it is. As a result, a peeling force is generated between the outer and inner carcass layers, but since the strength of the resin film near the vulcanization temperature is lower than that of rubber, the resin film is sandwiched between the carcass layers by the peeling force generated at the time of vulcanization. There is a problem that the resin film breaks intolerably and breaks, and the sealing property (air permeation prevention property) of the vulcanized tire is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to use a resin film as an air permeation preventing layer, so that the air permeation preventing layer is not broken at the splice portion, and is lightweight and has excellent sealing properties. An object of the present invention is to provide a pneumatic tire and a method for manufacturing the same.

[0006]

In order to achieve the above object, the present invention provides a carcass layer in which a resin film containing a thermoplastic resin as a main component is internally applied as an air permeation preventing layer on the inner surface of a carcass layer, and a tire circumferential direction is provided. In the pneumatic tire spliced by sandwiching the resin film between both ends of the carcass layer at both ends of the two carcass layers forming the splice, the cord of the inner carcass layer, at least between the pair of left and right bead core It is characterized by being discontinuous at one location.

Since the cord of the inner carcass layer of the two carcass layers forming the splice portion is discontinuous at at least one place between the pair of right and left bead portions, the inner carcass layer at the time of vulcanization is vulcanized. Since the shrinking force of the carcass is reduced, the peeling force between the carcass layers can be reduced,
Destruction of the resin film at the splice portion can be prevented.

The method of manufacturing a pneumatic tire according to the present invention comprises the steps of: forming a composite sheet in which a resin film containing a thermoplastic resin as a main component is bonded to a belt-like carcass material comprising a carcass cord and a coating rubber; On the side of the inner side of the two-layer carcass material forming the splice portion, the cord of the inner carcass material is wound at least in the middle in the tire width direction when the winding is performed with the side inward and the winding start end and the winding end end are overlapped and spliced. It is characterized in that a green tire is formed by splicing at one place as a discontinuity, and then the green tire is vulcanized.

In splicing both ends of the composite sheet in which the resin film and the carcass material are laminated as described above, the cord of the inner carcass material only needs to be discontinuous at at least one position in the middle in the tire width direction. Therefore, a pneumatic tire that can achieve the above object can be easily manufactured.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to the present invention is shown in FIG.
As shown in FIG. 2, a carcass layer 11 is mounted between a pair of left and right bead cores 10, 10, and two belt layers 13, 13 are arranged in the tread portion 12 over one circumference of the tire. On the inner wall surface of the tire, there is formed an air permeation prevention layer 14 which is internally adhered with a resin film mainly composed of a thermoplastic resin and substantially covers the inner surface of the carcass layer 11.

In the carcass layer 11, as shown in FIG. 2, one end and the other end in the tire circumferential direction EE 'overlap each other to form a splice portion 15 extending in the tire width direction. Outer carcass layer 1
1u between the inner carcass layer 11d and the air permeation prevention layer 1
4 is sandwiched. In the splice portion 15, the cord 11c of the inner carcass layer 11d among the two carcass layers forming the splice portion 15 is discontinuous at at least one location between the pair of left and right bead cores 10, 10. To make it discontinuous, for example, as shown in FIG. 2, a notch 16 for cutting the cord 11c may be provided in the inner carcass layer 11d. The number of discontinuities may be one, but it is more effective if the number of discontinuities is two to four. The discontinuous portions are preferably provided at equal intervals in the tire width direction or at symmetrical positions with respect to the tire equatorial plane so that the rigidity of the inner carcass layer 11d in the splice portion 15 in the tire width direction becomes uniform. Further, it is more preferable that the discontinuous portion is provided inside the belt layer 13. This is because the discontinuous portion is protected by the belt layer 13.

In order to manufacture this pneumatic tire, first, as shown in FIG. 3, a resin film 30 containing a thermoplastic resin as a main component was bonded to a belt-like carcass material 31 composed of a carcass cord and coat rubber. Composite sheet 32
With the resin film 30 on the outer peripheral surface of the tire building drum 40.
Is wound so as to be in contact with the tire building drum 40, and as shown in FIG.
A splice portion 15 extending in the tire width direction and sandwiching a part of the resin film 30 is formed. In this case, the carcass material 31 corresponding to the inner carcass layer 11d in the splice portion 15 may be provided with a discontinuous portion in advance.

The thermoplastic resin constituting the resin film 30 used in the present invention has an air permeability coefficient of 25 × 10 ⁻¹² cc · cm.
cm / cm ² · sec · cmHg or less, preferably 5 × 10 ^-12 cc
・ Cm / cm ²・ sec ・ Young's modulus is 1 ~ 500 under cmHg
MPa, preferably 10 to 300 MPa.
Air permeability coefficient is 25 × 10 ^-12 cc · cm / cm ² · sec · cm
If it exceeds Hg, the thickness of the air permeation prevention layer must be increased in order to maintain the tire air pressure, which is against the purpose of reducing the weight of the tire. Further, if the Young's modulus of the film is less than 1 MPa, wrinkles and the like are generated at the time of tire molding, and the moldability is deteriorated. If it exceeds 500 MPa, durability is problematic, which is not preferable.

Examples of the thermoplastic resin include polyamide resins (for example, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 1
1 (N11), nylon 12 (N12), nylon 61
0 (N610), nylon 612 (N612), nylon 6/66 copolymer (N6 / 66), nylon 6/66
/ 610 copolymer (N6 / 66/610), nylon M
XD6 (MXD6), nylon 6T, nylon 6 / 6T
Copolymer, nylon 66 / PP copolymer, nylon 66
/ PPS copolymer), and N-alkoxyalkylated products thereof, for example, methoxymethylated product of 6-nylon,
Methoxymethylated 6-610-nylon, 612-
Methoxymethylated nylon, polyester resin (for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PE10), PET / PEI copolymer,
Polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, aromatic polyester such as polyoxyalkylenediimidic acid / polybutylate terephthalate copolymer), polynitrile resin (for example, polyacrylonitrile (PAN), polymer Polyacrylonitrile, acrylonitrile / styrene copolymer (A
S), methacrylonitrile / styrene copolymer, methacrylonitrile / styrene / butadiene copolymer), polymethacrylate-based resin (eg, polymethyl methacrylate (PMMA), polyethyl methacrylate), polyvinyl-based resin (eg, , Vinyl acetate, polyvinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (E
VOH), polyvinylidene chloride (PDVC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer, vinylidene chloride / acrylonitrile copolymer), cellulose-based resin (for example, Cellulose acetate, cellulose acetate butyrate), fluorinated resins (for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer), imide resin (For example, aromatic polyimide (PI) and the like can be mentioned, and two or more kinds may be used.

Further, as the thermoplastic resin film used in the present invention, a film obtained by blending an elastomer with the above-mentioned thermoplastic resin may be used. As the elastomer component that can be blended with the thermoplastic resin, the composition and the blended state with the thermoplastic resin component, as a result, if it has the above air permeability coefficient and Young's modulus, the type and amount thereof are There is no particular limitation.

Examples of the elastomer to be blended with the thermoplastic resin include diene rubbers and hydrogenated products thereof (for example, NR, IR, epoxidized natural rubber, SBR,
BR (high-dis BR and low-cis BR), NBR, hydrogenated N
BR, hydrogenated SBR), olefin rubber (eg, ethylene propylene rubber (EPDM, EPM), maleic acid-modified ethylene propylene rubber (M-EPM), II
R, isobutylene and aromatic vinyl or diene monomer copolymer), acrylic rubber (ACM), ionomer,
Halogen-containing rubber (for example, Br-IIR, CI-II
R, bromide of isobutylene paramethylstyrene copolymer (Br-IPMS), CR, hydrin rubber (CHR.
CHC), chlorosulfonated polyethylene (CSM),
Chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM)), silicone rubber (eg, methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (eg, polysulfide rubber), Fluorine rubber (for example, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorine-containing silicon rubber, fluorine-containing phosphazene rubber), thermoplastic elastomer (for example, styrene-based elastomer, olefin-based rubber) Elastomer, ester-based elastomer, urethane-based elastomer, polyamide-based elastomer) and the like, and may be two or more kinds.

When the compatibility between the specific thermoplastic resin and the elastomer component is different, it is preferable to add an appropriate compatibilizer as the third component. By mixing the compatibilizer into the system, the interfacial tension between the thermoplastic resin and the elastomer component is reduced, and as a result, the rubber particles forming the dispersion layer become finer, so that the properties of both components are more improved. It will be effectively expressed. Such a compatibilizer is generally a copolymer having a structure of both or one of a thermoplastic resin and an elastomer component, or an epoxy group, a carbonyl group, a halogen group, an amino group capable of reacting with the thermoplastic resin or the elastomer component. It can have a copolymerized structure having a group, an oxazoline group, a hydroxyl group and the like. These may be selected depending on the types of the thermoplastic resin and the elastomer component to be mixed, and those usually used include styrene / ethylene / butylene block copolymer (SEBS) and its maleic acid-modified product, EPDM: E
Examples include PDM / styrene or EPDM / acrylonitrile graft copolymers and their maleic acid-modified products, styrene / maleic acid copolymers, and reactive phenoxines. The amount of the compatibilizer is not particularly limited, but is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the polymer component (total of the thermoplastic resin and the elastomer component).

When the thermoplastic resin and the elastomer are blended, the composition ratio of the specific thermoplastic resin (A) and the elastomer component (B) is not particularly limited, and the thickness of the film, the air permeability, the flexibility, It may be appropriately determined by the balance of the properties, but a preferable range is 10/9 by weight ratio (A) / (B).
0-90 / 10, more preferably 15 / 85-90 / 1
0.

The polymer composition (resin film 30) according to the present invention may further comprise, in addition to the above essential polymer components, other compatibilizer polymers such as the above-mentioned compatibilizer polymer as long as the necessary properties of the tire polymer composition of the present invention are not impaired. Can be mixed. The purpose of mixing the other polymer is to improve the compatibility between the thermoplastic resin and the elastomer component, to improve the film formability of the material, to improve the heat resistance, to reduce the cost, etc. As a material to be used, for example, polyethylene (PE),
Polypropylene (PP), polystyrene (PS), AB
S, SBS, polycarbonate (PC) and the like. Further, olefin copolymers such as polyethylene and polypropylene, maleic acid-modified products thereof, and glycidyl group-introduced products thereof can also be mentioned. The polymer composition according to the present invention further comprises a filler generally incorporated into the polymer blend, carbon black, quartz powder, calcium carbonate, alumina, titanium oxide, etc., having the above-mentioned requirements for the air permeability coefficient and Young's modulus. They can be arbitrarily compounded as long as they are not damaged.

The elastomer component can be dynamically vulcanized when mixed with the thermoplastic resin. The vulcanizing agent, vulcanization aid, vulcanization conditions (temperature, time) and the like for dynamically vulcanizing may be appropriately determined according to the composition of the elastomer component to be added, and are not particularly limited. . As the vulcanizing agent, a general rubber vulcanizing agent (crosslinking agent) can be used. Specifically, examples of the ionic vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, and alkylphenol disulfide, and for example, 0.5 to 4 phr. [Parts by weight per 100 parts by weight of rubber component (polymer)] can be used.

The organic peroxide vulcanizing agents include:
Benzoyl peroxide, t-butyl hydroperoxide, 2,4-bichlorobenzoyl peroxide,
Examples of thiourea-based vulcanization accelerators such as 2, Te-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, and pipecoline pipecolyldithiocarbamate include ethylenethiourea,
Diethylthiourea and the like can be mentioned.

As a vulcanization accelerating auxiliary, a general rubber auxiliary can be used in combination, for example, zinc white (about 5 phr), stearic acid, oleic acid and Zn salts thereof (2 to 2 phr). About 4 phr) can be used. The method for producing a thermoplastic elastomer composition is as follows: a thermoplastic resin component and an elastomer component (an unvulcanized product in the case of rubber) are used in advance.
By melt-kneading with a shaft kneading extruder or the like, and dispersing an elastomer component as a dispersed phase (domain) in a thermoplastic resin forming a continuous phase (matrix phase). When vulcanizing the elastomer component, a vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer component. The various additives (excluding the vulcanizing agent) to the thermoplastic resin or the elastomer component may be added during the kneading, but it is preferable to mix them before kneading. The kneader used for kneading the thermoplastic resin and the elastomer component is not particularly limited, and may be a screw extruder, a kneader,
A Banbury mixer, a twin screw extruder or the like can be used. Among them, for kneading the thermoplastic resin and the elastomer component and for dynamic vulcanization of the elastomer component, it is preferable to use a twin-screw kneading extruder. Further, two or more kinds of kneaders may be used and the kneading may be performed sequentially. As the conditions for the melt-kneading, the temperature may be at least the temperature at which the thermoplastic resin melts. Further, the shear rate during kneading is preferably 1000 to 7500 sec ^-1 . The whole kneading time is 30 seconds to 10 minutes,
When a vulcanizing agent is added, the vulcanization time after the addition is 1
It is preferably from 5 seconds to 5 minutes. The polymer composition produced by the above method is then formed into a sheet-like film by extrusion or calendering. The method of forming a film may be a method of forming a normal thermoplastic resin or thermoplastic elastomer into a film.

The film thus obtained has a structure in which the elastomer component (B) is dispersed as a dispersed phase (domain) in a matrix of the thermoplastic resin (A). By taking such a dispersed structure, thermoplastic processing becomes possible, and sufficient rigidity can be imparted to the film as the belt reinforcing layer by the effect of the resin layer as the continuous phase and the sufficient flexibility. At the same time, regardless of the amount of the elastomer component, at the time of molding, it is possible to obtain molding processability equivalent to that of a thermoplastic resin, so that it can be formed into a film by a usual resin molding machine, that is, extrusion molding, or calender molding. It becomes possible.

The adhesion between these films and the rubber layer opposite to each other is performed by applying an adhesive obtained by dissolving a general rubber-based, phenolic resin-based, acrylic copolymer-based, or isocyanate-based polymer and a crosslinking agent to a solvent. Bonding by heat and pressure at the time of vulcanization molding, or bonding resin such as styrene butadiene styrene copolymer (SBS), ethylene ethyl acrylate (EEA), styrene ethylene butylene block copolymer (SEBS) to thermoplastic There is a method in which a multilayer film is prepared by co-extrusion or lamination with a film, and is adhered to a rubber layer during vulcanization. Examples of the solvent-based adhesive include a phenol resin-based resin (Chemlock 220, Road Co., Ltd.), a chlorinated rubber-based resin (Chemrock 205, Chemlock 234B), and an isocyanate-based resin (Chemrock 402).

In the present invention, an example in which two belt layers 13 are arranged in the above embodiment has been described. However, the present invention is not limited to this, and a plurality of belt layers having three or more belt layers are arranged. Can be suitably used.

[0026]

EXAMPLES A pneumatic tire having a tire size of 165SR13 (rim size: 13 × 41 / 2-J) was manufactured using a film made of the following materials A to D as an air permeation preventing layer (Inventions 1 to 5, conventional examples). 1-2). For forming the films for materials B and C, the thermoplastic component and the elastomer component are kneaded in advance with a twin-screw kneader, the elastomer component is dispersed in the resin component, and then the vulcanizing agent is continuously added, followed by water cooling. A pellet-like thermoplastic elastomer was produced by the above method, and the pellet was formed into a film by ordinary T-die extrusion. Material A,
As an adhesive between B and C and the carcass member, Chemlock 234B (Road Far East Co.)
Was applied. Notches as shown in FIG. 2 were provided as discontinuous portions. The basic structure of each tire is a tire having one carcass layer as shown in FIG. 1 and two belt layers disposed on a tread portion on the carcass layer, and a splice portion of the carcass layer. Was formed such that the outer carcass layer and the inner carcass layer were wrapped with three carcass cords.

For each of the obtained tires, splice open, uniformity, the amount of irregularities in the side wall portion, the air leak test (pressure drop rate), and the tire mass were evaluated by the following methods. Table 1 shows the results. All parts in the materials represent parts by weight. Material A : thermoplastic resin component; nylon 11 (N11)
(Rilsan BESN OTL manufactured by Atochem), air permeability coefficient is 2.13 × 10 ⁻¹² cc · cm / cm ² · sec · cmHg,
A material with a Young's modulus of 257 MPa. The film was formed by ordinary T-die extrusion.

Material B : thermoplastic resin component; nylon 6
(N6) (Toray CM4061) 25.2 parts, nylon MXD6 (MXD6) (Mitsubishi Gas Chemical Reny 600
2) 37.8 parts, elastomer component; masterbatch (modified butyl rubber: bromide of isobutylene-paramethylstyrene copolymer, Exxon EX manufactured by Exxon Chemical)
XPR0 89-4 100 parts, carbon black GPF made by Tokai Carbon: 60 parts Seast V, 1 part stearic acid, petroleum hydrocarbon resin Essolets 11 made by Esso
02 10 parts, paraffinic process oil 10 parts) 4
8.9 parts, compatibilizing component: 10 parts of Mitsui Petrochemical High Sex Million 240M (EEA), and 1.5 parts of zinc oxide, 0.5 part of DM and 0.5 part of sulfur as vulcanizing agent components
Part, air permeability coefficient is 0.84 × 10 ^-12 cc · cm
/ Cm ² · sec · A material whose Young's modulus is 244 MPa at cmHg.

Material C : thermoplastic resin component; nylon 6
(N6) (Toray CM4061) 25.2 parts, nylon MXD6 (MXD6) (Mitsubishi Gas Chemical Reny 600
2) 37.8 parts, 10 parts of nylon 6/66/610 (CM4001 manufactured by Toray), elastomer component; Br
-(Polyisobutylene-p-methylstyrene) (EXXPRO 89-4 manufactured by Exxon Chemical Co.) 27.0 parts, having an air permeability coefficient of 0.63 × 10 ⁻¹² cc · cm / cm ^2.
・ Sec ・ A material whose Young's modulus is 317 MPa at cmHg.

Material D : butyl rubber; Br-IIR rubber composition (air permeability coefficient 55 × 10 ⁻¹² cc · cm / cm ² · sec)
-CmHg, Young's modulus is 15 MPa). Measurement method of air permeability coefficient of film : JIS K7126
The method was based on "Testing method for gas permeability of plastic films and sheets (Method A)".

Test piece: The film sample prepared in each example was used. Test gas: air (N ₂ : O ₂ = 8: 2) Test temperature: 30 ° C. Measuring method of Young's modulus of film : According to JIS K6251 “Tensile test method for vulcanized rubber”.

Test piece: A film sample prepared by extrusion molding in each example was punched out with a JIS No. 3 dumbbell in parallel with the direction of resin flow during extrusion. Obtained stress ~
A tangent was drawn on the curve in the initial strain region of the strain curve, and the Young's modulus was determined from the slope of the tangent. Evaluation method of splice open : Regarding the tire after vulcanization, when the splice portion of the air permeation preventing layer was open, it was evaluated as poor (x), and when it was not open, it was evaluated as good (O).

Uniformity test method : JASO C-6
07-87 (Automobile tire uniformity test method)
The PP value (value from peak to peak) of the RFV was measured according to the following. The measured value of the conventional tire 2 was set to 100 and indicated by an index. The smaller this value, the better the uniformity.

A method for testing the amount of unevenness of the side wall portion : JAT
The tire was mounted on a standard rim specified by MA and the maximum air pressure was sealed, and after 24 hours, the maximum value of the amount of unevenness of the sidewall portion was measured. The measured value of the conventional tire 2 was set to 100 and indicated by an index. The smaller this value is, the more excellent the appearance is because there is no unevenness in the side wall portion.

Air leak test method (pressure drop rate ): The apparatus is left for 3 months at an initial pressure of 200 kPa, a room temperature of 21 ° C. and no load. The measurement interval of the internal pressure is every 4 days, and the measurement pressure Pt,
The following formula is used as the initial pressure P0 and the number of elapsed days t.

[0036]

(Equation 1) To obtain the α value. Using the obtained α, t = 30
(Day) is substituted to obtain β = [1−exp (−αt)] × 100. β is the rate of pressure drop per month (% / month).

[0037]

[Table 1]

In Table 1, the structure of the notch portion of the present inventions 1 to 3 is such that three carcass cords embedded in the inner carcass layer in the splice portion are cut at one place in the tire crown center to be discontinuous. It has become. Invention 4
As the structure of the cutout portion, three carcass cords embedded in the inner carcass layer in the splice portion were cut at two places at both ends of the lower belt layer to be discontinuous.
As the structure of the cutout portion of the fifth aspect of the present invention, three carcass cords embedded in the inner carcass layer in the splice portion are provided at two places at both ends of the lower belt layer and one place at the tire crown center, for a total of three places. Cut to discontinuity.

As is clear from Table 1, the present inventions 1 to 5 do not cause splice open and do not break the air permeation preventing layer and are excellent in uniformity as compared with the conventional examples 1 and 2. In addition, since the value of the amount of unevenness of the sidewall portion is small, the sidewall portion has no unevenness and is excellent in appearance, and the pressure drop rate is small, so that the sealing property is excellent.

[0040]

As described above, the pneumatic tire of the present invention is lightweight and excellent in preventing air permeation, and the air permeation preventing layer is not broken at the carcass layer splice.
Carcass layer splice open does not occur, and furthermore, deterioration of uniformity due to the splice portion does not occur. Further, according to the method for manufacturing a pneumatic tire of the present invention, a pneumatic tire having the above performance can be efficiently manufactured.

[Brief description of the drawings]

FIG. 1 is a meridional half sectional view of an example of a pneumatic tire of the present invention.

FIG. 2 is a perspective view illustrating an example of a carcass layer splice portion of the pneumatic tire of the present invention.

FIG. 3 is an explanatory view showing a state in which a resin film and a carcass material are wound around the outer peripheral surface of a tire building drum in the present invention.

FIG. 4 is a cross-sectional view of a main part showing how a carcass layer splice is formed on the tire building drum after winding in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Carcass layer 14 Air permeation prevention layer 15 Splice part 16 Notch 32 Composite sheet 40 Tire forming drum

Claims (7)

[Claims] 1. A resin film containing a thermoplastic resin as a main component is internally adhered to an inner surface of a carcass layer as an air permeation preventing layer,
In the pneumatic tire spliced by sandwiching the resin film between both ends of the carcass layer at both ends in the tire circumferential direction, the cord of the inner carcass layer of the two carcass layers forming the splice portion is replaced with a pair of right and left bead cores. A pneumatic tire that is discontinuous at least at one point between the pneumatic tires. 2. The pneumatic tire according to claim 1, wherein the discontinuous portions are two to four portions. 3. The pneumatic tire according to claim 1, wherein the discontinuous portions are provided at equal intervals in the tire width direction or at symmetrical positions with respect to the tire equatorial plane. 4. The thermoplastic resin is a polyamide resin,
The pneumatic tire according to claim 1, wherein the pneumatic tire is at least one selected from the group consisting of a polyester resin, a polynitrile resin, a polymethacrylate resin, a polyvinyl resin, a cellulose resin, a fluorine resin, and an imide resin. 5. The pneumatic tire according to claim 1, wherein the resin film contains an elastomer. 6. The pneumatic tire according to claim 5, wherein the elastomer is at least one selected from the group consisting of a diene rubber, an olefin rubber, a sulfur-containing rubber, a fluororubber, and a thermoplastic elastomer. 7. A composite sheet in which a resin film containing a thermoplastic resin as a main component is bonded to a belt-like carcass material composed of a carcass cord and coat rubber, and wound around a tire forming drum with the resin film side inward. In overlapping and splicing the end portion and the winding end portion, the cord of the inner carcass material among the two layers of carcass material forming the splice portion is spliced as discontinuous at at least one position in the middle in the tire width direction. A method for manufacturing a pneumatic tire in which a green tire is formed and then the green tire is vulcanized.