WO2013054602A1

WO2013054602A1 - Method for producing pneumatic tire

Info

Publication number: WO2013054602A1
Application number: PCT/JP2012/071648
Authority: WO
Inventors: 洋二井本; 睦樹杉本
Original assignee: 住友ゴム工業株式会社
Priority date: 2011-10-11
Filing date: 2012-08-28
Publication date: 2013-04-18
Also published as: JP5319752B2; JP2013082139A

Abstract

A method for producing a pneumatic tire provided with an inner liner (2) inside the tire, wherein the molding of a green tire includes: an assembly step for joining together a width direction end part of the inner liner (2) and a width direction end part of an unvulcanized rubber sheet (3), displaced from each other in the width direction, to produce a laminate (1); a cutting step for slicing the laminate (1) to a certain length corresponding to a drum width, to produce a cut sheet; and a bonding step for winding the cut sheet around the entire periphery of the drum so that the cut surface becomes the peripheral direction of the drum and the inner liner (2) becomes the inner surface, and bonding together positions of an end part of the inner liner (2) and an end part of the unvulcanized rubber sheet (3), displaced by a certain distance. The inner liner is a thermoplastic elastomer composition including SIBS, a polyamide-based polymer, and organoclay, and is the laminate (1) of the first layer having a thickness of 0.05-0.6 mm and the second layer having a thickness of 0.01-0.3 mm.

Description

Method of manufacturing pneumatic tire

The present invention relates to a method of manufacturing a pneumatic tire, and more particularly, to a method of forming an inner liner, comprising the steps of manufacturing a laminate of an unvulcanized rubber sheet such as a carcass ply and the inner liner and forming a green tire. The present invention relates to a method of manufacturing a tire.

In recent years, due to strong social demand for low fuel consumption of the car, the weight of the tire has been reduced, and among the tire members, it is disposed inside the tire to reduce air leakage from the inside to the outside of the pneumatic tire. Also in the air blocking layer (inner liner) which is required to be done, the weight reduction is required.

At present, the rubber composition for air barrier layer improves the air permeation resistance of the tire by using a rubber compound mainly composed of butyl rubber containing, for example, 70 to 100% by mass of butyl rubber and 30 to 0% by mass of natural rubber. The thing is done. In addition to butylene, the rubber composition containing butyl rubber contains about 1% by mass of isoprene, which can be combined with sulfur, vulcanization accelerator, and zinc flower to enable co-crosslinking between molecules with adjacent rubber layers. I have to. The above butyl rubber needs to have a thickness of about 0.6 to 1.0 mm for passenger car tires and about 1.0 to 2.0 mm for truck and bus tires in a normal composition, but the weight reduction of the tires is achieved. For this reason, there is a demand for a polymer which is more excellent in air permeation resistance than butyl rubber and which can further reduce the thickness of the air blocking layer.

In forming a green tire of a pneumatic tire, as shown in FIG. 7, when forming the inner liner P on the drum 5A, the inner liner film P2 is elongated on the conveyor to the unvulcanized inner liner rubber P1. Both end edges of the direction are aligned and attached in advance to form a laminate, and the inner liner film P2 of the laminate is wound on the band with the inner liner film P2 on the inner side, and both ends of the laminate are circumferentially Generally, it is common to overlap at one place to form a joint PJ, and then use a stitching roller to press the joint PJ of the laminate to perform air bleeding.

In this technique, when the inner liner film P2 and the non-vulcanized inner liner rubber P1 are wound on the drum, the positions of both end edges in the longitudinal direction are aligned and adhered in advance. During overlapping bonding on the drum, the thickness of the bonding portion PJ formed on the periphery of the drum 5A inevitably becomes large. For this reason, even if a stitching roller is applied to the joint portion PJ, air may remain between the joint portions PJ, and when the residual air expands by vulcanization molding of a green tire, the joint portion PJ of the laminate P peels off There was a risk of

Moreover, in this technology, since the end of the laminate P forms a joint at one point on the circumference of the drum 5A, the adjacent carcass may be separated if peeling occurs at the joint of the inner liner of the molded green tire. It may cause damage to the ply.

In the prior art, it is proposed to use a thermoplastic elastomer for the inner liner in an attempt to reduce the weight of the pneumatic tire. However, a material that is thinner than the butyl rubber inner liner and has high air permeability is inferior in vulcanization adhesion to the insulation rubber or carcass ply rubber adjacent to the inner liner than the butyl rubber inner liner. It will be.

In particular, when the adhesive strength is weak at the joint portion of the inner liner, the joint portion peels off during traveling, and the tire internal pressure may decrease, which may cause a burst of the tire. Further, since the joint portion has a structure in which other members are exposed to the inner surface, it becomes a path of air leakage, and the internal pressure of the tire is easily reduced.

In JP 2009-208444 A (Patent Document 1), an inner liner film and an unvulcanized rubber sheet are pasted with both ends in the extending direction mutually offset, and this adhesive body is wound on a drum Techniques for molding unvulcanized tires are disclosed.

However, in order to shift the both ends in the extending direction from each other, each member must be cut to a fixed size one by one and separately shifted for lamination, which may reduce productivity. Further, depending on the bonding method, the accuracy may be deteriorated, and air may be accumulated between the films to cause damage at the time of tire vulcanization.

In JP-A-2007-291256 (Patent Document 2), an ethylene-vinyl alcohol copolymer is contained in an amount of 15 to 30 parts by mass with respect to 100 parts by mass of a rubber component consisting of a natural rubber and / or a synthetic rubber. Disclosed is a pneumatic tire provided with the contained inner liner rubber composition. However, this technique is not preferable from the viewpoint of reducing the weight of the tire, since the thickness of the inner liner is as large as 1 mm.

JP-A-9-165469 (Patent Document 3) discloses a nylon film used as an inner liner. Here, it is disclosed that after the nylon film is subjected to RFL treatment, it is adhered to the inner surface of the tire or the carcass layer with a rubber paste made of a rubber composition to produce a pneumatic tire.

However, this technique has a problem that the process becomes complicated. Furthermore, in the vulcanization process, vulcanization molding is generally performed by pressing the inner surface of the uncured tire housed in the mold against the inner surface of the mold, but since the inner liner is a nylon film, nylon is heated when heating the bladder during vulcanization. There is a problem that the film adheres to the bladder and adheres and breaks.

JP, 2009-208444, A JP 2007-291256 A JP-A-9-165469

The present invention is a method of forming a tire by winding a laminate of an inner liner and an unvulcanized rubber sheet such as a carcass ply on a forming drum, and providing uniformity in thickness at a joint on the periphery of the drum. An object of the present invention is to increase air pressure, prevent air from remaining, and effectively reduce peeling of a joint between an inner liner and a carcass ply. Another object of the present invention is to provide a pneumatic tire having low flex crack growth, rolling resistance and low static air pressure reduction rate.

The present invention relates to a method of manufacturing a pneumatic tire having an inner liner on the inside of the tire, wherein molding of the green tire is
(A) an assembly step of manufacturing a laminate by laminating the end portions in the width direction of the inner liner and the end portions in the width direction of the unvulcanized rubber sheet by shifting them 50 mm to 500 mm in the width direction;
(B) a cutting step of manufacturing the cut sheet by cutting the laminate to a predetermined length corresponding to a drum width;
(C) The cut sheet is wound around the entire circumference of the drum so that the cut surface is in the circumferential direction of the drum and the inner liner is on the inner side, and the end of the inner liner and the end of the unvulcanized rubber sheet Has a bonding step of bonding by shifting the position of the part by a fixed distance,
The inner liner is a polymer composition comprising 60 to 99% by mass of a styrene-isobutylene-styrene block copolymer and 100 parts by mass of a polymer mixture containing 1 to 40% by mass of a styrene-maleic anhydride copolymer,
A first layer having a thickness of 0.05 mm to 0.6 mm and a second layer having a thickness of 0.01 mm to 0.3 mm, which is disposed on an unvulcanized rubber sheet side and made of a thermoplastic elastomer The present invention relates to a method of manufacturing the pneumatic tire which is a body.

In the present invention, in the assembling step, the width of the inner liner and the width of the unvulcanized rubber sheet are different, and the laminate is manufactured by shifting in the width direction such that both ends in the width direction do not overlap each other. be able to.

The styrene-isobutylene-styrene triblock copolymer preferably has a styrene component content of 10 to 30% by mass. The styrene-maleic anhydride copolymer has a molar ratio of styrene component / maleic anhydride component of 50/50 to 90/10, a weight average molecular weight of 4,000 to 20,000, and further, maleic anhydride It is preferable to include a styrene-maleic anhydride copolymer base resin in which the acid value of the acid component is 50 to 600.

The styrene-maleic anhydride copolymer is a styrene-maleic anhydride copolymer having a monoester group and a monocarboxylic acid group, which is obtained by esterifying the styrene-maleic anhydride copolymer base resin. It is preferable to include an ester resin of

Furthermore, the styrene-maleic anhydride copolymer preferably includes an aqueous solution of styrene-maleic anhydride copolymer ammonium salt, in which the styrene-maleic anhydride copolymer base resin is dissolved in an ammonium salt.

In the present invention, an inner liner comprising a composite layer of a first layer containing a mixture of SIBS and a styrene-maleic anhydride copolymer and a second layer of a thermoplastic elastomer is mutually offset from the unvulcanized rubber sheet in the width direction The laminated body is wound around the entire circumference of the drum so that the inner liner is on the inner surface side, and the respective end portions of the inner liner and the unvulcanized rubber sheet are mutually separated in the circumferential direction of the drum By bonding at the above positions, it is possible to ease the difference in thickness between the bonded portion of the inner liner and the bonded portion of the unvulcanized rubber sheet. And in the case of stitching, the air of those junctions can be removed certainly, and the exfoliation of the junctions resulting from residual air can be reduced.

Furthermore, since the thickness in the circumferential direction of the tire becomes uniform and the tire becomes close to a true circle, the radial force variation (RFV) can be reduced and the uniformity of the tire is improved.

Further, since the formed inner liner and the unvulcanized rubber sheet such as the carcass ply will form a joint separated in the circumferential direction from each other, even if peeling occurs in the joint of the carcass ply Since the peeled portion is reinforced by the inner liner, damage and breakage of the product tire will be alleviated.

In the present invention, in particular, the inner liner is disposed on the tire inner side, a first layer having a thickness of 0.05 mm to 0.6 mm, and disposed on the unvulcanized rubber sheet side, having a thickness of 0.01 mm. The composite layer of the second layer having a thickness of ̃0.3 mm enhances the adhesion of the adjacent carcass ply to the rubber. The reinforcing effect by the inner liner when the joint of the carcass ply is peeled is enhanced, while the reinforcing effect by the carcass ply when the joint of the inner liner is peeled is enhanced.

It is the schematic which shows an assembly process. It is a perspective view which shows the outline of an assembly process. It is the schematic which shows a cutting process. (A) is sectional drawing of a laminated body, (b) is schematic which shows the state which winds a laminated body on a drum. It is the schematic which shows a cutting process. (A) is sectional drawing of a laminated body, (b) is schematic which shows the state which winds a laminated body on a drum. It is the schematic of the shaping | molding method of the conventional inner liner. 1 is a schematic cross-sectional view of a pneumatic tire. It is a schematic sectional drawing of a polymer laminated body.

Embodiment 1
The present invention is a method of manufacturing a pneumatic tire having an inner liner on the inside of the tire, and the manufacturing method is performed in the following green tire molding process.
(A) An assembly step of manufacturing a laminate by shifting and bonding the widthwise end of the inner liner and the widthwise end of the unvulcanized rubber sheet mutually in the width direction in the range of 50 mm to 500 mm.
(B) A cutting step of manufacturing the cut sheet by cutting the laminate to a predetermined length corresponding to a drum width.
(C) The cut sheet is wound around the entire circumference of the drum so that the cut surface is in the circumferential direction of the drum and the inner liner is on the inner side, and the end of the inner liner and the end of the unvulcanized rubber sheet Bonding process to shift the position of the fixed distance a certain distance.

Here, a method of manufacturing a pneumatic tire according to the present invention will be described with reference to the drawings.
<Assembling process>
FIG. 1 is a lateral schematic view showing an assembling process, and FIG. 2 is a perspective schematic view showing the assembling process. In FIG. 1 and FIG. 2, the film-like inner liner 2 is fed from the storage roll R1 through the first drive roller R2 in the direction of the arrow in the state covered with the release paper and It is separated. Then, the inner liner 2 is sent to the pair of calendar rolls R7.

On the other hand, the unvulcanized rubber sheet 3 is fed to the pair of calender rolls R7 via the second drive roller R6. Here, the inner liner 2 and the unvulcanized rubber sheet 3 are bonded to produce the laminate 1. The laminate 1 is taken up by a take-up roll R8 and temporarily stored, or is continuously sent to the subsequent cutting process. Here, the inner liner 2 and the unvulcanized rubber sheet 3 having substantially the same width are used, and the positions of these both ends are mutually offset, and an offset distance L is formed. .

Here, the shift distance L is prepared in the range of 50 mm to 500 mm, preferably in the range of 100 mm to 300 mm. If the shift distance L is smaller than 50 mm, the distance between the joint of the unvulcanized rubber sheet and the joint of the inner liner becomes narrow, and adhesion failure at the joint tends to occur. On the other hand, if the shift distance L exceeds 500 mm, tire molding on the drum becomes difficult.

The inner liner is made of a styrene-isobutylene-styrene block copolymer, is a first layer having a thickness of 0.05 mm to 0.6 mm, is disposed on the unvulcanized rubber sheet side, and is made of a thermoplastic elastomer. It is composed of a composite layer of a second layer having a thickness of 0.01 mm to 0.3 mm. The width of the inner liner is adjusted by the tire size.

In the present invention, since the inner liner and the unvulcanized rubber sheet are pressure-bonded using a roll, there is no air accumulation, which can be reliably adhered, and the efficiency is good and the productivity is good.

<Cutting process>
FIG. 3 is a schematic perspective view showing the cutting process. The laminate 1 is sent from the take-up roll R8 by a belt conveyor to a cutter, or continuously sent from an assembling process. The laminate 1 is cut at a predetermined length in the longitudinal direction according to the size of the tire, and a cut sheet 4 is manufactured. In addition, the conventional techniques, such as a knife cut, can employ | adopt the cutting | judgement of a laminated body. The cutting direction of the cut sheet 4 corresponds to the circumferential direction of the drum, and the cut length in the longitudinal direction corresponds to the width direction of the drum 5. In addition, the length of the inner liner is appropriately adjusted depending on the tire size.

<Joining process>
The joining process which joins the above-mentioned cutting sheet 4 which consists of a layered product based on Drawing 4 is explained. Here, FIG. 4A is a cross-sectional view of the cut sheet 4, and FIG. 4B is a schematic view showing a method of winding the cut sheet 4 on the drum 5. The laminate is wound so that the inner liner 2 is adjacent to the surface of the drum 5. Here, the position where the

end portions

2a and 2b of the inner liner are joined to each other to form a joint, and the position where the

end portions

3a and 3b of the unvulcanized rubber sheet are joined to each other to form a joint are mutually Will be offset.

Tire molding and vulcanization process
As described above, in the bonding step, a laminate of the inner liner and the unvulcanized carcass ply is produced and formed into a drum shape and a cylindrical shape. After the bonding process, both ends of the laminate located at both ends of the drum are wound around the bead cores, and then the central portion of the laminate comprising the inner liner and the unvulcanized carcass ply is bulged and deformed while narrowing the spacing between the bead cores. Let

Along with this operation, a belt member, tread rubber and the like are attached to the central portion of the laminate, and other rubber members such as side walls and bead apex are also attached to form a green tire. A green tire thus formed is put into a mold and vulcanized by a conventional method to obtain a product tire.

<Inner liner>
In the present invention, the inner liner is a polymer composition comprising 60 to 99% by mass of a styrene-isobutylene-styrene block copolymer and 100 parts by mass of a polymer mixture containing 1 to 40% by mass of a styrene-maleic anhydride copolymer. First layer having a thickness of 0.05 mm to 0.6 mm, and a second layer having a thickness of 0.01 mm to 0.3 mm, which is disposed on the unvulcanized rubber sheet side and made of a thermoplastic elastomer Is composed of a laminate of

<First layer>
The inner liner is a polymer composition including 60 to 99% by mass of a styrene-isobutylene-styrene block copolymer and 100 parts by mass of a polymer mixture containing 1 to 40% by mass of a styrene-maleic anhydride copolymer.

(SIBS)
The first layer comprises a composition of a thermoplastic elastomer based on styrene-isobutylene-styrene block copolymer (SIBS). Due to the isobutylene block origin of SIBS, polymer films made of SIBS have excellent resistance to air permeation. Therefore, when a polymer composed of SIBS is used for the inner liner, a pneumatic tire excellent in air permeation resistance can be obtained.

Furthermore, due to complete saturation of molecular structures other than aromatics, SIBS is inhibited from deterioration and hardening and has excellent durability. Therefore, when a polymer film made of SIBS is used for the inner liner, a pneumatic tire excellent in durability can be obtained.

When a pneumatic tire is manufactured by applying a polymer film made of SIBS to the inner liner, the air permeation resistance can be secured. Therefore, it is not necessary to use a high specific gravity halogenated rubber, which has been conventionally used to impart air resistance, such as halogenated butyl rubber, and the amount can be reduced even when used. This makes it possible to reduce the weight of the tire and to improve the fuel consumption.

The molecular weight of SIBS is not particularly limited, but it is preferable that the weight average molecular weight by GPC measurement is 50,000 to 400,000, from the viewpoint of flowability, molding process, rubber elasticity and the like. If the weight average molecular weight is less than 50,000, the tensile strength and the tensile elongation may be lowered, and if it exceeds 400,000, the extrusion processability may be deteriorated, which is not preferable. The content of the styrene component in SIBS is preferably 10 to 30% by mass, and more preferably 14 to 23% by mass, from the viewpoint of improving air permeability and durability of SIBS.

In the copolymer, the degree of polymerization of each block of the SIBS is about 10,000 to 150,000 for isobutylene from the viewpoints of rubber elasticity and handling (the degree of polymerization is less than 10,000 becomes liquid), and styrene And preferably about 5,000 to 30,000.

SIBS can be obtained by a common living cationic polymerization method of vinyl compounds. For example, in JP-A-62-48704 and JP-A-64-62308, living cationic polymerization of isobutylene with another vinyl compound is possible, and by using isobutylene and another compound as the vinyl compound. It is disclosed that polyisobutylene-based block copolymers can be produced.

(Styrene-maleic anhydride copolymer)
In the present specification, a styrene-maleic anhydride copolymer (SMA) means a styrene-maleic anhydride copolymer base resin (hereinafter also referred to as "SMA base resin"), a styrene-maleic anhydride copolymer base An ester resin of a styrene-maleic anhydride copolymer having a monoester group and a monocarboxylic acid group obtained by esterifying a resin (hereinafter also referred to as SMA ester resin) and a styrene-maleic anhydride copolymer base It is described as a concept including a styrene-maleic anhydride copolymer ammonium salt aqueous solution (hereinafter also referred to as "SMA resin ammonium salt aqueous solution") in which a resin is dissolved in an ammonium salt.

Styrene-maleic anhydride copolymer (SMA) is used as a polymeric surfactant in dispersion and emulsification, and a high functional crosslinking agent, and has very excellent vulcanization adhesion to rubber. In addition, the adhesive effect is also excellent because it imparts wettability to rubber.

In the polymer component of the polymer composition for the inner liner, the content of SMA is 0.5 to 40% by mass. When the content of SMA is 0.5% by mass or more, an inner liner excellent in adhesion to the second layer can be obtained. In addition, when the content of SMA is 40% by mass or less, an inner liner having excellent air permeation resistance and durability can be obtained. The content of SMA in the polymer component is more preferably 2 to 30% by mass.

(Styrene-maleic anhydride copolymer based resin)
In one embodiment of the present invention, SMA preferably comprises an SMA base resin from the viewpoint of unvulcanized tackiness and post-vulcanization adhesion.

The SMA base resin preferably has a molar ratio of styrene component / maleic anhydride component of 50/50 to 90/10 from the viewpoint of high softening point and high thermal stability. The SMA base resin preferably has a weight average molecular weight of 4,000 to 20,000 from the viewpoint of adhesion after vulcanization and fluidity. More preferably, the weight average molecular weight is 5,000 to 15,000.

From the viewpoint of unvulcanized tackiness, it is preferable that the SMA base resin has an acid value of 50 to 600 for the maleic anhydride component in the styrene-maleic anhydride copolymer. Furthermore, the acid value of the maleic anhydride component is more preferably 95 to 500.

(Styrene-maleic anhydride copolymer ester resin)
In one embodiment of the present invention, a styrene-maleic anhydride copolymer is a styrene- having a monoester group and a monocarboxylic acid group, which is obtained by esterifying a styrene-maleic anhydride copolymer base resin. It is preferable to contain an ester resin of maleic anhydride copolymer (hereinafter also referred to as SMA ester resin).

The SMA ester resin has the property of being excellent in vulcanization adhesion. Therefore, the polymer composition for inner liners excellent in the vulcanized adhesion with the rubber layer can be obtained by blending the SMA ester resin with SIBS. From the viewpoint of vulcanization adhesion, the SMA ester resin preferably has a molar ratio of styrene component / maleic anhydride component of 50/50 to 90/10.

The SMA ester resin preferably has a weight average molecular weight of 5,000 to 12,000 from the viewpoint of adhesion after vulcanization and fluidity. Further, the weight average molecular weight is more preferably 6,000 to 11,000. In the SMA ester resin, the acid value of the maleic anhydride component is preferably 50 to 400 from the viewpoint of adhesion to the unvulcanized rubber. More preferably, the acid value of the maleic anhydride component is 95 to 290.

The SMA ester resin can be produced, for example, by introducing a base resin and an alcohol into a reaction vessel and heating and stirring under an inert gas atmosphere.

(Styrene-maleic anhydride copolymer ammonium salt aqueous solution)
In one embodiment of the present invention, a styrene-maleic anhydride copolymer is an aqueous solution of styrene-maleic anhydride copolymer ammonium salt (hereinafter also referred to as an SMA ammonium salt aqueous solution) in which an SMA base resin is dissolved in an ammonium salt. Is preferred.

The aqueous solution of SMA ammonium salt has the property of being excellent in wettability. Therefore, the polymer composition for inner liners excellent in adhesiveness can be obtained by mix | blending SMA ammonium salt aqueous solution with SIBS.

The aqueous solution of SMA ammonium salt preferably has a solid concentration of 10.0 to 45.0% from the viewpoint of adhesion to unvulcanized rubber and molding processability. The aqueous solution of SMA ammonium salt preferably has a pH of 8.0 to 9.5 from the viewpoint of adhesiveness. For example, an aqueous solution of SMA ammonium salt solution is charged with water in a reaction vessel, a base resin is added while vigorously stirring, and an exothermic reaction occurs when ammonium hydroxide is gradually added. It can then be manufactured by heating to a predetermined temperature and continuing stirring until dissolution is complete.

(Additives of polymer composition)
The polymer composition is compounded in tire or general polymer compositions such as other reinforcing agents, vulcanizing agents, vulcanization accelerators, various oils, antioxidants, softeners, plasticizers, coupling agents, etc. Various ingredients and additives can be blended.

(Thickness of first layer)
The thickness of the first layer of SIBS is 0.05 to 0.6 mm. If the thickness of the first layer is less than 0.05 mm, the first layer may be broken by the press pressure during vulcanization of a green tire in which the polymer laminate is applied to the inner liner, which may cause an air leak phenomenon in the tire. is there. On the other hand, if the thickness of the first layer exceeds 0.6 mm, the weight of the tire increases and the fuel economy performance decreases.

The first layer can be obtained by film-forming SIBS by a conventional method of film-forming a thermoplastic resin or a thermoplastic elastomer such as extrusion, calendaring and the like.

<Second layer>
In the present invention, the second layer is composed of a thermoplastic elastomer, in particular a styrenic thermoplastic elastomer composition. Here, the styrene-based thermoplastic elastomer refers to a copolymer containing a styrene block as a hard segment. For example, styrene-isoprene-styrene block copolymer (hereinafter also referred to as "SIS"), styrene-isobutylene block copolymer (hereinafter also referred to as "SIB"), styrene-butadiene-styrene block copolymer (hereinafter referred to as "SIB") Hereinafter, it is also referred to as “SBS”), styrene-isobutylene-styrene block copolymer (hereinafter, also referred to as “SIBS”), and styrene-ethylene · butene-styrene block copolymer (hereinafter, also referred to as “SEBS”). ), Styrene-ethylene-propylene-styrene block copolymer (hereinafter also referred to as "SEPS"), styrene-ethylene-ethylene-propylene-styrene block copolymer (hereinafter also referred to as "SEEPS"), styrene- Butadiene-butylene-styrene block copolymer (hereinafter referred to as "SBB Also referred to as ".) There is.

In addition, the styrenic thermoplastic elastomer may have an epoxy group in its molecular structure. For example, Epofriend A 1020 (made by Daicel Chemical Industries, Ltd., weight average molecular weight is 100,000, epoxy equivalent is 500) Epoxy modified styrene-butadiene-styrene copolymer (epoxidized SBS) can be used.

Among the styrenic thermoplastic elastomers used in the second layer, SIS and SIB are particularly preferred. Since the isoprene block of SIS is a soft segment, the polymer film made of SIS is easy to cure and adhere to the rubber component. Therefore, when a polymer film made of SIS is used for the inner liner, the inner liner is excellent in adhesion to, for example, the rubber layer of the carcass ply, so that a pneumatic tire excellent in durability can be obtained.

The molecular weight of the SIS is not particularly limited, but in view of rubber elasticity and moldability, it is preferable that the weight average molecular weight by GPC measurement is 100,000 to 290,000. If the weight average molecular weight is less than 100,000, the tensile strength may be lowered, and if it exceeds 290,000, the extrusion processability is unfavorably deteriorated. The content of the styrene component in SIS is preferably 10 to 30% by mass from the viewpoints of tackiness, adhesiveness and rubber elasticity.

In the present invention, the degree of polymerization of each block in SIS is preferably about 500 to 5,000 for isoprene and about 50 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

The SIS can be obtained by a general polymerization method of a vinyl compound, and can be obtained, for example, by a living cationic polymerization method. The SIS layer can be obtained by film-forming the SIS by a conventional method of film-forming a thermoplastic resin such as extrusion molding, calendar molding, or a thermoplastic elastomer.

Since the isobutylene block of the styrene-isobutylene block copolymer (SIB) is a soft segment, the polymer film made of SIB is easy to cure and adhere to the rubber component. Therefore, when a polymer film made of SIB is used for the inner liner, the inner liner is excellent in adhesion to the adjacent rubber forming, for example, the carcass and the insulation, so that a pneumatic tire excellent in durability is obtained. be able to.

As SIB, it is preferable to use a linear one from the viewpoint of rubber elasticity and adhesiveness. The molecular weight of SIB is not particularly limited, but from the viewpoint of rubber elasticity and moldability, it is preferable that the weight average molecular weight by GPC measurement is 40,000 to 120,000. If the weight average molecular weight is less than 40,000, the tensile strength may be lowered, and if it exceeds 120,000, the extrusion processability may be deteriorated, which is not preferable.

The content of the styrene component in the SIB is preferably 10 to 35% by mass from the viewpoints of tackiness, adhesiveness and rubber elasticity.

In the present invention, the degree of polymerization of each block in SIB is preferably about 300 to 3,000 for isobutylene and about 10 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

The SIB can be obtained by a general living polymerization method of a vinyl compound, and for example, methylcyclohexane, n-butyl chloride and cumyl chloride are added to a stirrer, cooled to -70 ° C, and reacted for 2 hours Then, the reaction can be stopped by adding a large amount of methanol and vacuum dried at 60 ° C. to produce SIB.

The SIB layer can be formed by a conventional method of film-forming styrenic thermoplastic elastomer such as extrusion or calendaring of SIB. The thickness of the second layer is preferably 0.01 mm to 0.3 mm. If the thickness of the second layer is less than 0.01 mm, the second layer may be broken by the press pressure during vulcanization of a green tire in which the polymer laminate is applied to the inner liner, and the vulcanization adhesion may be reduced. There is. On the other hand, if the thickness of the second layer exceeds 0.3 mm, the weight of the tire may increase and the low fuel consumption performance may decrease. The thickness of the second layer is preferably 0.05 to 0.2 mm.

<Polymer laminate>
In the present invention, the inner liner is a polymer laminate composed of a composite layer of a first layer and a second layer. Here, the first layer and the second layer are thermoplastic elastomer compositions, and are in a softened state in the mold at a vulcanization temperature, for example, 150 ° C. to 180 ° C. The softened state is an intermediate state between solid and liquid by improving molecular mobility. In addition, when the thermoplastic elastomer composition is in a softened state, the reactivity is improved more than in a solid state, so that it adheres and adheres to adjacent members. Therefore, in order to prevent the shape change of the thermoplastic elastomer, the adhesion with the adjacent member, and the fusion, a cooling process is required when manufacturing the tire. In the cooling step, after tire curing, quenching is performed to 50 to 120 ° C. for 10 to 300 seconds, and the inside of the bladder portion is cooled. As a cooling medium, one or more selected from air, water vapor, water and oil are used. By employing such a cooling process, the inner liner can be formed into a thin inner liner in the range of 0.05 to 0.6 mm.

Second Embodiment
In the second embodiment, the width W 2 of the inner liner 2 is formed wider than the width W 1 of the unvulcanized rubber sheet 3.

<Cutting process>
FIG. 5 is a schematic view showing a cutting process. The laminate 1 is sent from the take-up roll R8 to a cutter by a belt conveyor or continuously sent from an assembling process. The laminate 1 is cut at a predetermined length in the longitudinal direction according to the size of the tire, whereby a cut sheet 4 is manufactured. In addition, the conventional techniques, such as a knife cut, can employ | adopt the cutting | judgement of a laminated body. The cutting direction of the cutting sheet 4 corresponds to the circumferential direction of the drum, while the cutting length in the longitudinal direction corresponds to the width direction of the drum 5.

<Joining process>
Fig.6 (a) is sectional drawing of a laminated body, FIG.6 (b) is schematic which shows the state which winds a laminated body on a drum. Here, the inner liner 2 is wound on the drum 5 so as to be in contact with the inner liner 2, and the

joints

2a and 2b overlap to form a joint. In order to join the both ends 3a and 3b of unvulcanized rubber sheets 3 such as insulation on that, unvulcanized rubber pieces 6 are used. In this case, two joints are formed, but they are offset from the joint position with the inner liner.

<Structure of tire>
A pneumatic tire provided with an inner liner inside the tire according to the present invention will be described based on FIG. FIG. 8 is a schematic cross-sectional view of the right half of the pneumatic tire. The pneumatic tire 11 has a tread portion 12 and sidewall portions 13 and bead portions 14 so as to form a toroidal shape from both ends of the tread portion. Furthermore, the bead core 15 is embedded in the bead portion 14. Further, a carcass ply 16 is provided from one bead portion 14 to the other bead portion, and is wound around the bead core 15 at both ends so as to be locked, and at least two at the outside of the crown portion of the carcass ply 16. And a belt layer 17 made of ply.

The belt layer 17 usually crosses two plies of cords such as steel cords or aramid fibers between the plies so that the cords are at an angle of usually 5 to 30 ° with respect to the tire circumferential direction. Arranged as. A topping rubber layer can be provided on the outer sides of both ends of the belt layer to reduce the peeling of both ends of the belt layer. The carcass ply has organic fiber cords such as polyester, nylon, aramid or the like arranged at approximately 90 ° in the tire circumferential direction, and in the region surrounded by the carcass ply and its turn, from the upper end of the bead core 15 to the sidewall direction An extending bead apex 18 is disposed. Further, an inner liner 19 extending from one bead portion 14 to the other bead portion 14 is disposed on the inner side in the tire radial direction of the carcass ply 16.

Next, an arrangement state of the inner liner and the carcass ply in the vulcanized tire is shown in FIG. In FIG. 9, the polymer laminate PL is composed of a first layer PL1 and a second layer PL2. When the polymer laminate PL is applied to the inner liner of a pneumatic tire, when the second layer PL2 is installed outward in the tire radial direction so as to be in contact with the carcass ply C, in the tire vulcanization step, the second layer PL2 And the adhesion strength between the carbon and the carcass C can be enhanced. The resulting pneumatic tire has excellent air permeation resistance and flex crack growth resistance because the inner liner and the rubber layer of the carcass ply C are well adhered.

<Method of manufacturing pneumatic tire>
The method of manufacturing a pneumatic tire according to the present invention can use a conventional manufacturing method. An inner liner is manufactured using the polymer laminate PL. The inner liner is applied to a green tire of a pneumatic tire 11 and manufactured by vulcanization molding with other members. When disposing the polymer laminate PL in a green tire, the second layer PL2 of the polymer laminate PL is disposed radially outward of the tire so as to be in contact with the carcass ply C. When arranged in this manner, the adhesive strength between the second layer PL2 and the carcass 6 can be enhanced in the tire vulcanization step. The resulting pneumatic tire has excellent air permeation resistance and flex crack growth resistance because the inner liner and the rubber layer of the carcass ply C are well adhered.

<Manufacture of inner liner>
Various compounding agents were introduced into a twin-screw extruder (screw diameter: φ 50 mm, L / D: 30, cylinder temperature: 220 ° C.) and pelletized in accordance with the compounding formulas shown in Tables 1 and 2. The sheet was extruded using an extruder (screw diameter: φ 80 mm, L / D: 50, die gap width: 40 mm, cylinder temperature: 220 ° C.) at a screw rotational speed of 80 RPM and an extrusion speed of about 9 m / min.

(Note 1) IIR: “Exxon chlorobutyl 1068” manufactured by ExxonMobil Co., Ltd. (Note 2) SIBS: “Sibustar SIBSTAR 102T” (Shore A hardness: 25, styrene content: 25% by mass) manufactured by Kaneka Co., Ltd.
(Note 3) SMA base resin: “SMA 1000” manufactured by Sartomer (styrene component / maleic anhydride component: 50/50, weight average molecular weight: 5,500, acid value of maleic anhydride: 490).
(Note 4) SMA ester resin: “SMA1440” manufactured by Sartmar (styrene component / maleic anhydride component: 80/20, weight average molecular weight: 7,000, acid value of maleic anhydride: 200).
(Note 5) SMA ammonium salt aqueous solution: "SMA1000H" (pH 9.0) manufactured by Sartmar.
(Note 6) Carbon: “Siest V” (N 660, N ₂ SA: 27 m ² / g) manufactured by Tokai Carbon Co., Ltd.
(Note 7) Stearic acid: "Runac Stearate S30" manufactured by Kao Corporation.
(Note 8) Zinc oxide: "Zinc flower No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
(Note 9) Anti-aging agent: "NOCRAC 6C" (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) manufactured by Ouchi Emerging Chemical Co., Ltd.
(Note 10) Vulcanization accelerator: "Noxceler DM" (di-2-benzothiazolyl disulfide) manufactured by Ouchi New Chemical Co., Ltd.
(Note 11) Sulfur: "Powder sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.
(Note 12) SIS: D1161 JP manufactured by Kraton Polymers (styrene content: 15% by mass, weight average molecular weight: 150,000).
(Note 13) SIB.

In a 2 L reaction vessel equipped with a stirrer, 589 mL of methylcyclohexane (dried with molecular sieves), 613 ml of n-butyl chloride (dried with molecular sieves), and 0.550 g of cumyl chloride were added. The reaction vessel was cooled to −70 ° C., and then 0.35 mL of α-picoline (2-methylpyridine) and 179 mL of isobutylene were added. Further, 9.4 mL of titanium tetrachloride was added to initiate polymerization, and the solution was reacted at -70 ° C. for 2.0 hours with stirring. Next, 59 mL of styrene was added to the reaction vessel and the reaction was continued for further 60 minutes, and then the reaction was stopped by adding a large amount of methanol. After removing the solvent and the like from the reaction solution, the polymer was dissolved in toluene and washed twice with water. The toluene solution was added to a methanol mixture to precipitate a polymer, and the obtained polymer was dried at 60 ° C. for 24 hours to obtain a styrene-isobutylene diblock copolymer.

Styrene component content: 15% by mass
Weight average molecular weight: 70,000
<Unvulcanized rubber sheet>
In the present invention, the unvulcanized rubber sheet uses a carcass ply, and the composition of the topping rubber is as follows.

<Formulation of topping rubber A>
Natural rubber (Note 1) 100 parts by mass Carbon black (Note 2) 50 parts by mass Zinc white (Note 3) 3 parts by mass Antidegradant (Note 4) 0.2 parts by mass Sulfur (Note 5) 1 part by mass Vulcanization acceleration Agent (Note 6) 1 part by mass Vulcanization auxiliary (Note 7) 1 part by mass (Note 1) TSR 20
(Note 2) “Seast V” manufactured by Tokai Carbon Co., Ltd. (N 660, N ₂ SA: 27 m ² / g)
(Note 3) Zinc oxide (ZnO): "Zinc flower No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
(Note 4) Nocchi 6C, made by Ouchi emerging chemical company
(Note 5) "Powder sulfur" manufactured by Tsurumi Chemical Industries, Ltd.
(Note 6) "Nocceller DM" manufactured by Ouchi Emerging Chemical Company
(Note 7) Stearic acid: Kao Corporation "Runac Stearate S30"
<Manufacture of pneumatic tire>
Production of the pneumatic tire of the present invention was carried out based on the above-mentioned assembling step, cutting step and joining step. As shown in Table 1 in detail, pneumatic tires of the comparative example and the example were manufactured. C. for 20 minutes at 170.degree. C., and after cooling for 3 minutes at 100.degree. C. without taking it out of the vulcanizing mold, it is taken out of the vulcanized tire and has the 195 / 65R15 size having the basic structure shown in FIG. Manufactured ones.

In each of the examples, the shift distance (amount) L is changed to 50 mm, 500 mm, and 250 mm, respectively, by setting the inner liner to 1300 mm and changing the dimension of the carcass ply based on FIG.

In Examples 1 to 3, 0.5 parts by mass of the SMA base resin was blended in SIBS of the first layer, and in Examples 4 to 6, 20 parts by mass of the SMA base resin was blended in SIBS of the first layer. is there. Examples 7 to 9 are examples in which 0.5 parts by mass of each of the SMA base resin and the SMA ester resin were blended in SIBS in the first layer, and in Examples 10 to 12, the SMA base resin and SMA in SIBS of the first layer It is an example which mix | blended 0.5 mass part of ammonium aqueous solution, respectively.

Comparative Example 1 is an example in which IIR is used in the first layer, and Comparative Examples 2 to 4 are examples in which 0.5 mass% of SMA base resin is mixed in IIR in the first layer. Comparative Example 5 is an example in which only SIBS is used in the first layer, and Comparative Examples 6 and 7 are examples in which 50 mass% of SMA is mixed with SIBS in the first layer.

All of the embodiments of the present invention are excellent in air-in performance, flex crack growth, rolling resistance and static air reduction rate comprehensive evaluation, and further excellent in uniformity.

<Performance test>
The performance evaluation was performed by the following method regarding the pneumatic tire manufactured as mentioned above.

<Air-in performance>
The inside of the tire after vulcanization was inspected by appearance and the evaluation was as follows.

A: In appearance, when the number of air-ins with a diameter of 5 mm or less is 0 and the number of air-ins with a diameter of 5 mm or more is 0 per tire B: Appearance, a diameter of 5 mm or less per tire When the number of air-ins is 1 to 3 and the number of air-ins exceeding 5 mm in diameter is 0 C: In terms of appearance, the number of air-ins of 5 mm or less in diameter per tire is 4 or more, and 5 mm in diameter When the number of air-ins exceeding 1 is 1 or more <Bending crack growth test>
The flex crack growth test was evaluated by whether the inner liner was broken or peeled off. The prototype tire is assembled on a JIS standard rim 15 x 6 JJ, the internal pressure of the tire is set to 150 KPa lower than usual, the load is 600 kg, the speed is 100 km / h, the inside of the tire is observed with a traveling distance of 20,000 km, The number of peels was measured. The crack growth of each Example and Comparative Example was expressed as an index based on the following formula based on Comparative Example 1. The larger the number, the smaller the flex crack growth.

Flexural crack growth index = (number of cracks in comparative example 1) / (number of cracks in each example) × 100
<Rolling resistance index>
Using a rolling resistance tester manufactured by Kobe Steel, Ltd., assemble a prototype tire to JIS standard rim 15 × 6JJ, load 3.4 kN, air pressure 230 kPa, speed 80 km / h, room temperature (30 ° C) The rolling resistance was measured. And the rolling resistance change rate (%) of the Example was displayed by the index | exponent based on the following formula, making Comparative example 1 into 100 the reference | standard. The larger the rolling resistance change rate, the lower the rolling resistance.

Rolling resistance index = (rolling resistance of comparative example 1) / (rolling resistance of example) × 100
<Static air pressure reduction rate>
The prototype tire is assembled on a JIS standard rim 15 × 6JJ, sealed with an initial air pressure of 300 kPa, left at room temperature for 90 days, and the reduction rate of the air pressure is calculated. As the numerical value is smaller, the air pressure is less likely to decrease and is preferable.

<Uniformity index>
The radial force variation (RFV) was measured using a tire uniformity tester in accordance with JASOC 607: 2000 "Test method for uniformity of automobile tires". The relative value which makes comparative example 1 100 is displayed as an index. The larger the index, the better the uniformity. As the measurement conditions, the rim was 8.0 × 17, the tire rotational speed was 60 rpm, the air pressure was 200 kPa, and the longitudinal load was 4000 kN.

<Overall judgment>
Judgment A is one that satisfies all the following conditions.

(A) Air-in performance evaluation A (b) Flex crack growth index 100 or more (c) Rolling resistance change rate 100 or more (d) Static air pressure reduction rate (% / month) is 2.6 or less Judgment B is The case where any one of the following conditions is satisfied. In the case of multiple judgments, the lower of the evaluation was adopted.

(A) Air-in evaluation is B or C evaluation (b) flex crack growth index is less than 100 (c) rolling resistance change rate is less than 100 (d) static air pressure reduction rate (% / month) is 2.7 or more

The method of manufacturing a pneumatic tire according to the present invention can be applied to a method of manufacturing a pneumatic tire for trucks, buses, heavy machinery, etc. besides pneumatic tires for passenger cars.

Reference Signs List 1 laminate, 2 and 19 inner liner, 3 unvulcanized rubber sheet, 4 cut sheet, 5 drums, L displacement distance (amount), 11 pneumatic tire, 12 tread portion, 13 sidewall portion, 14 bead portion, 15 Bead core, 16 carcass plies, 17 belt layers, 18 bead apexes, PL polymer laminate, PL1 first layer, PL2 second layer.

Claims

In the method of manufacturing a pneumatic tire (11) having the inner liner (2) inside the tire, molding of the green tire is
(A) An assembly for manufacturing a laminate (1) by pasting the end portions in the width direction of the inner liner (2) and the end portions in the width direction of the unvulcanized rubber sheet (3) by shifting them 50 mm to 500 mm in the width direction. Process,
(B) a cutting step of manufacturing the cut sheet (4) by cutting the laminate (1) into a predetermined length corresponding to a drum width;
(C) Wrap the cut sheet (4) around the entire circumference of the drum so that the cut surface is in the circumferential direction of the drum and the inner liner (2) is on the inner side, and the end of the inner liner (2) And a bonding step of bonding by shifting the position of the end of the unvulcanized rubber sheet (3) by a fixed distance,
The inner liner (2) is
A polymer composition comprising 100 parts by mass of a polymer mixture containing 60 to 99% by mass of styrene-isobutylene-styrene block copolymer and 1 to 40% by mass of styrene-maleic anhydride copolymer, and having a thickness of 0.05 mm The first layer, which is ~ 0.6 mm,
The pneumatic tire (11), which is a laminate of a second layer (1) which is disposed on the unvulcanized rubber sheet (3) side, is made of a thermoplastic elastomer, and has a thickness of 0.01 mm to 0.3 mm. Production method.
In the assembling process, the width of the inner liner (2) and the width of the unvulcanized rubber sheet (3) are different from each other so that both end portions in the width direction do not overlap with each other. The method for producing a pneumatic tire (11) according to claim 1, wherein the tire is produced.
The method for producing a pneumatic tire (11) according to claim 1 or 2, wherein the styrene-isobutylene-styrene triblock copolymer has a styrene component content of 10 to 30% by mass.
The styrene-maleic anhydride copolymer has a styrene component / maleic anhydride component molar ratio of 50/50 to 90/10, a weight average molecular weight of 4,000 to 20,000, and further, maleic anhydride The method for producing a pneumatic tire (11) according to any one of claims 1 to 3, comprising a styrene-maleic anhydride copolymer base resin wherein the acid value of the component is 50 to 600.
The styrene-maleic anhydride copolymer is a styrene-maleic anhydride copolymer having a monoester group and a monocarboxylic acid group, which is obtained by esterifying the styrene-maleic anhydride copolymer base resin. The method for producing a pneumatic tire (11) according to any one of claims 1 to 4, which comprises an ester resin.
The styrene-maleic anhydride copolymer comprises an aqueous solution of styrene-maleic anhydride copolymer ammonium salt, wherein the styrene-maleic anhydride copolymer base resin is dissolved in an ammonium salt. The manufacturing method of the pneumatic tire (11) as described in.