JP2019038122A - Method for manufacturing pneumatic tire - Google Patents

Abstract

An object of the present invention is to prevent film peeling during tire molding when a film of a thermoplastic resin or a thermoplastic elastomer is used for an inner liner member. In a method for manufacturing a pneumatic tire according to an embodiment, a cylindrical inner liner member made of a thermoplastic resin or a thermoplastic elastomer film is prepared, and a pre-expansion for expanding and releasing the inner liner member in advance. And wrapping at least one tire member around the pre-expanded inner liner member to produce a green tire, and vulcanizing the green tire. [Selection diagram] FIG.

Description

  The present invention relates to a method for manufacturing a pneumatic tire.

  An inner liner is provided on the inner surface of the pneumatic tire as an air permeation suppression layer in order to keep the tire air pressure constant. Such an inner liner is generally composed of a rubber layer such as butyl rubber or halogenated butyl rubber that is difficult for gas to permeate. However, in order to reduce the weight of the tire, the use of a resin film that can be thinned has been studied. Yes.

  However, when a resin film having high rigidity is used as the inner liner member, there arises a problem of so-called film peeling in which the inner liner member is peeled off from the green tire (unvulcanized tire) at the time of molding the tire. This is because, when the green tire is molded, the cylindrical inner liner member produced in accordance with the molding drum diameter is expanded to the green tire diameter, and the inner liner member has residual stress in the green tire after molding. In general, materials with better air permeability (ie, gas barrier properties) have higher rigidity and stronger force to return after expansion, which can easily lead to film peeling. Therefore, use of materials with excellent gas barrier properties due to molding problems Will be limited.

  In Patent Document 1, in order to reduce thickness variation due to expansion of the inner liner member at the time of green tire molding, the inner liner member made of a film of a thermoplastic resin or a thermoplastic elastomer is not cylindrical but conforms to the shape of the green tire. As described above, a method for producing a green tire having an inner liner member by blow molding in advance and inserting and integrating the same into a green tire is disclosed. This eliminates the problem of film peeling, but it is necessary to perform special blow molding on the inner liner member.

  On the other hand, in Patent Document 2, in a laminate of a polyamide resin film used as an inner liner member and a rubber composition, in order to improve the adhesive strength at the interface between them, the rubber composition has a specific solubility parameter. It is described that a plasticizer is blended. However, when a plasticizer is added, there is a problem that a gas barrier property is generally lowered.

JP, 2014-043078, A Japanese Patent Laying-Open No. 2015-145129

  In view of the above, the embodiment of the present invention provides a method for manufacturing a pneumatic tire capable of suppressing film peeling at the time of molding a tire when a thermoplastic resin or thermoplastic elastomer film is used for the inner liner member. The purpose is to provide.

  The method for manufacturing a pneumatic tire according to the embodiment includes producing a cylindrical inner liner member made of a film of a thermoplastic resin or a thermoplastic elastomer, and performing preliminary expansion for expanding and releasing the inner liner member in advance. Wrapping at least one tire member around the pre-expanded inner liner member to produce a green tire and vulcanizing the green tire.

  According to this embodiment, by extending the inner liner member in advance, the residual stress of the inner liner member after green tire molding can be reduced, and film peeling can be suppressed.

Sectional drawing of the pneumatic tire which concerns on one Embodiment The schematic diagram for demonstrating the preliminary | backup expansion process in one Embodiment. The schematic diagram for demonstrating the green tire formation process in one Embodiment Graph showing the relationship between time and stress in the film expansion test

  Embodiments of the present invention will be described below with reference to the drawings.

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

  An inner liner 8 is provided inside the carcass ply 6 over the entire inner surface of the tire. In the present embodiment, a low air permeable film made of a thermoplastic resin or a thermoplastic elastomer is used as the inner liner member that forms the inner liner 8. As shown in the enlarged view in FIG. 1, the inner liner 8 is bonded to the inner surface of the carcass ply 6 that is a rubber layer on the tire inner surface side.

  When manufacturing the pneumatic tire 1 which concerns on one Embodiment, the cylindrical inner liner member which consists of a film of a thermoplastic resin or a thermoplastic elastomer is produced in this embodiment. Preferably, the inner liner member is made of a thermoplastic elastomer film.

  Examples of the thermoplastic resin include nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6/66 copolymer, nylon 6/66/610 copolymer, nylon MXD6, Aliphatic polyamide resin (nylon resin) such as nylon 6T, nylon 6 / 6T copolymer; ethylene-vinyl alcohol copolymer (EVOH), vinyl acetate (EVA), polyvinyl alcohol (PVA), polyvinylidene chloride (PVDC) , Polyvinyl resins such as polyvinyl chloride (PVC); polyesters such as polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), polyarylate (PAR), polybutylene naphthalate (PBN) Polyresin resin such as polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile-styrene copolymer (AS); Cellulosic resin such as cellulose acetate and cellulose acetate butyrate; Polyvinylidene fluoride (PVDF), Polyfluoride Fluorine resins such as vinyl (PVF) and polychlorofluoroethylene (PCTFE); and imide resins such as aromatic polyimide (PI) can be used, and these can be used alone or in combination of two or more.

  As the thermoplastic elastomer, those having a structure in which the thermoplastic resin is blended with rubber and the thermoplastic resin is a continuous phase (matrix phase) and the rubber is a dispersed phase (domain phase) may be used. Alternatively, a block copolymer composed of a hard segment (hard segment) forming a thermoplastic frozen phase or crystal phase and a soft segment (soft segment) exhibiting rubber elasticity may be used. Or what blended rubber and resin with such a block copolymer can also be used as a thermoplastic elastomer.

  Examples of the block copolymer include polyester elastomers having polyester as a hard segment, polyamide elastomers having polyamide as a hard segment, and polystyrene elastomers having polystyrene as a hard segment. These are used alone. Or you may use 2 or more types together.

  Examples of the rubber blended with the thermoplastic resin or the block copolymer include natural rubber (NR), epoxidized natural rubber (ENR), isoprene rubber (IR), styrene butadiene rubber (SBR), and butadiene rubber (BR). ), Diene rubbers such as nitrile rubber (NBR) and hydrogenated rubbers thereof; ethylene propylene rubber (EPDM), maleic acid modified ethylene propylene rubber, maleic acid modified ethylene butylene rubber, butyl rubber (IIR), acrylic rubber (ACM), etc. Examples of the olefin rubber include halogenated butyl rubber (for example, brominated butyl rubber (Br-IIR), chlorinated butyl rubber (Cl-IIR)), chloroprene rubber (CR), halogen-containing rubber such as chlorosulfonated polyethylene, and the like. These may be used alone or in combination of two or more.

  In one embodiment, a thermoplastic resin and rubber may be melt-kneaded together with a crosslinking agent to produce a dynamically crosslinked product, and the film may be produced from the dynamically crosslinked product. By the melt-kneading, the rubber is dynamically cross-linked (TPV) to obtain a dynamic cross-linked product having a thermoplastic resin as a continuous phase and a rubber cross-linked product as a dispersed phase. In addition, as a crosslinking agent, vulcanizing agents, such as sulfur, a vulcanization accelerator, a phenol resin, etc. can be used, for example.

  Various additives such as a filler, a compatibilizing agent, an adhesive, and a plasticizer can be blended with the thermoplastic resin and the thermoplastic elastomer. The same applies to the rubber constituting the thermoplastic elastomer. When mixing these, it can carry out using various kneading machines, such as a twin-screw extruder, a screw extruder, a kneader, a Banbury mixer, for example.

The air permeability coefficient of the inner liner member is not particularly limited, but the air permeability coefficient at 80 ° C. is preferably 5 × 10 ¹³ fm ² / Pa · s or less in order to increase the weight reduction effect of the tire. The air permeability coefficient is more preferably 4 × 10 ¹³ fm ² / Pa · s or less. The lower limit is not particularly limited, but is practically 0.5 × 10 ¹³ fm ² / Pa · s or more. Here, the air permeability coefficient is measured in accordance with JIS K7126-1 “Plastics—Films and Sheets—Gas Permeability Test Method—Part 1: Differential Pressure Method” at test gas: air, test temperature: 80 ° C. Value.

  The inner liner member can be formed into a cylindrical shape by inflation molding using a thermoplastic resin or a thermoplastic elastomer. That is, a thermoplastic resin or a thermoplastic elastomer (preferably a dynamically cross-linked product) is melted, and the obtained melt is extruded into a cylindrical shape using an extruder equipped with an inflation die such as a ring die, A cylindrical inner liner member is obtained by cutting the extruded cylindrical film with a predetermined length. In addition, you may produce a cylindrical inner liner member by joining the edge part of a film after extrusion molding using the film shape | molded by the T-die extrusion method, and making it cylindrical.

  The thickness of the cylindrical inner liner member (that is, the thickness of the cylindrical film) is not particularly limited, and can be, for example, 0.02 to 1.0 mm, more preferably 0.05 to 1.0 mm. Yes, it may be 0.05 to 0.5 mm.

  After producing the inner liner member as described above, in this embodiment, preliminary expansion is performed on the inner liner member. The pre-expansion is a step of expanding the inner liner member in advance and releasing the expansion prior to forming the green tire. Specifically, before winding a tire member such as a carcass ply around the inner liner member, the inner liner member is expanded alone, a predetermined tension is applied so that the inner liner member expands, and then the tension is applied. By canceling and returning to a free state, preliminary expansion can be performed.

  Thus, by temporarily expanding the inner liner member prior to green tire molding, the residual stress after green tire molding (ie, the force to return after molding) can be reduced. The film peeling at the time can be suppressed.

  As the expansion direction of the preliminary expansion, for example, the cylindrical inner liner member may be expanded in a toroid shape similar to the expansion direction at the time of forming the green tire, or the cylindrical inner liner member is extended in the axial direction. Alternatively, the cylindrical inner liner member may be expanded radially outward in the entire axial direction. Preferably, it may be inflated in the same manner as the expansion direction at the time of green tire molding. That is, in one preferable embodiment, the preliminary expansion may be performed by expanding the axial center portion of the inner liner member radially outward with respect to both axial end portions.

  FIG. 2 is a conceptual diagram showing an example of the preliminary expansion process. A cylindrical inner liner member 12 is placed on the preliminary expansion drum 10 shown in FIG. 2 (A), and as shown in FIG. 2 (B), both end portions in the axial direction of the inner liner member 12 are annular fixtures 14, Fix with 14. Next, as shown in FIG. 2C, a gas such as air is supplied to the inside of the inner liner member 12 while moving the pair of left and right drum portions 10A, 10A of the pre-expansion drum 10 toward each other. The inner liner member 12 is expanded in a toroid shape, that is, its axially central portion 12A expands radially outward with respect to the axially opposite end portions 12B and 12B. Thereafter, as shown in FIG. 2 (D), the gas inside the inner liner member 12 is discharged to release the expanded state, that is, to return to the initial state, and the fixtures 14 and 14 are removed.

  In the preliminary expansion step, the time for maintaining the expanded state is not particularly limited, but is preferably 60 seconds or less. The preliminary expansion process is performed at room temperature without applying heat.

  The expansion rate (preliminary expansion rate) of the inner liner member in the preliminary expansion step is preferably equal to or greater than the expansion rate of the inner liner member at the time of green tire molding, and film peeling can be more effectively suppressed. The expansion ratio of the inner liner member is a ratio of the expanded dimension (that is, the dimension of the expanded portion) to the original dimension at the most expanded portion. For example, when the inner liner member is expanded in a toroidal shape as shown in FIG. 2C, the preliminary expansion rate is the length expanded at the time of preliminary expansion relative to the original circumferential length in the center portion in the width direction that is most expanded ( That is, the ratio between the circumference at the time of preliminary expansion and the original circumference), and the expansion rate at the time of forming the green tire is the green tire relative to the original circumference at the center in the width direction of the green tire. This is the ratio of the length expanded during molding.

  If the pre-expansion rate is too large, the dimensional change of the inner liner member due to plastic deformation during the pre-expansion becomes large. Therefore, in the green tire molding process, when the inner liner member is mounted on the molding drum, the sag becomes large, and there is a possibility that wrinkles remain after the green tire molding. From this point of view, the pre-expansion rate is preferably not more than 3 times the expansion rate of the inner liner member at the time of green tire molding.

  In the preliminary expansion step, the expansion ratio (preliminary expansion ratio) of the inner liner member may be 20 to 200%, but is preferably 50 to 150%. Generally, since the expansion rate at the time of green tire molding is about 40 to 60%, by setting the preliminary expansion rate to 50 to 150%, the film is peeled off while suppressing the generation of wrinkles after green tire molding. Can be effectively suppressed, and tire durability can also be improved.

  After the inner liner member is pre-expanded as described above, at least one tire member is wound around the pre-expanded inner liner member to produce a green tire. Examples of the tire member to be wound include a carcass ply, a sidewall rubber, and the like. Usually, at least the carcass ply is wound so as to cover the entire inner liner member.

  The green tire molding method itself is not particularly limited, and a known method can be used. For example, as shown in FIG. 3A, the inner liner member 12 after the preliminary expansion is set around the primary forming drum 20. As the primary molding drum 20, the preliminary expansion drum 10 may be used as it is, or another molding drum may be used.

  The inner liner member 12 is usually plastically deformed by pre-expansion to cause a dimensional change in the axial direction. Therefore, when setting to the primary molding drum 20, it is necessary to match the both end positions of the inner liner member 12 with the both end positions before preliminary expansion. That is, even when extending in the axial direction due to the preliminary expansion, both ends are aligned with the position corresponding to the axial dimension before the preliminary expansion, and the primary molding drum 20 is set with the central portion slackened.

  Next, as shown in FIG. 3A, the carcass ply 22 is wound around the inner liner member 12, the bead members 24 are attached to the outer peripheral surfaces of both ends in the width direction of the carcass ply 22, and the side wall rubber 26 is attached. The green case 28 is manufactured by folding the both ends of the carcass ply 22 so as to be disposed at a predetermined position and to enclose the bead member 24.

  Next, as shown in FIG. 3B, the green case 28 is transferred to the secondary forming drum 30 to perform shaping. For shaping, a tread ring 36 comprising a cylindrical belt 32 and a tread rubber 34 laminated on the outer peripheral surface thereof is arranged on the radially outer side of the green case 28, and a pair of left and right drums of the secondary molding drum 30 are arranged. While moving the parts 30A and 30A toward each other, a fluid such as a gas is supplied into the green case 28 to expand the green case 28 in a toroidal shape (that is, the axially central portion is expanded radially outward). And joining and integrating with the tread ring 36. Thereby, the green tire 40 having a cross-sectional shape as shown in FIG. 3C can be formed.

  The obtained green tire can be manufactured into a pneumatic tire by vulcanization molding in a mold according to a conventional method.

  According to the present embodiment, by performing preliminary expansion on the inner liner member, it is possible to reduce the residual stress after forming the green tire, and to suppress film peeling. Therefore, moldability can be improved without changing the film material of the inner liner member. Therefore, a film material having excellent gas barrier properties but high rigidity can also be used as the inner liner member, and both gas barrier properties and moldability can be achieved.

  The pneumatic tire according to the present embodiment is not limited to a pneumatic tire for passenger cars, and can be applied to various types of automobile tires including heavy duty tires such as trucks and buses. It can be applied to various pneumatic tires such as motorcycle tires.

  EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[Examples 1 to 5, Comparative Example 1]
50 parts by mass of butadiene rubber (“BunaCB22” manufactured by LANXESS) and 2.5 parts by mass of a cross-linking agent (“Tacco Roll 201” manufactured by Taoka Chemical Industry Co., Ltd.) are mixed in advance under the condition of not being cross-linked. Produced. 52.5 parts by mass of the obtained rubber masterbatch, 50 parts by mass of nylon resin (nylon 6/66 copolymer, “Novamid 2020” manufactured by DSM), and compatibilizer (“Bond First” manufactured by Sumitomo Chemical Co., Ltd.) BF-E ”)) and 5 parts by mass of adhesive (“ Sumikanol 620 ”manufactured by Taoka Chemical Co., Ltd.) at a temperature of 220 ° C. and a rotation speed of 200 rpm are twin screw extruders (Co., Ltd.). Were put into a plastic engineering laboratory), melt-kneaded and dynamically cross-linked to prepare dynamically cross-linked pellets.

  The obtained pellets were extrusion molded into a cylindrical film having a thickness of 0.2 mm and a diameter of 360 mm using an inflation molding machine. The molding temperature during inflation molding is 240 ° C.

  About the obtained film, the stress relaxation test was done and the relationship between a pre-expansion rate and stress relaxation was investigated. In the stress relaxation test, using a tensile tester, the size of the test piece is 25 mm wide × 100 mm long × 0.2 mm thick, the distance between chucks is 40 mm, and the test piece is listed in Table 1 at a speed of 500 mm / min. It was pulled to the pre-expansion rate (elongation rate) as shown in FIG. 1, and after the pre-expansion, the tensile state was immediately released and returned to the initial state. Thereafter, as the main test, the test piece was pulled again to an expansion rate (main test expansion rate): 50% at a speed of 500 mm / min, and held for 60 seconds in a state where the expansion rate was 50%.

  The relationship between stress and time in this test is as shown in FIG. 4, and the stress increases as the expansion rate increases, and reaches the maximum stress at an expansion rate of 50%. Thereafter, when the expansion ratio is maintained at 50%, the stress decreases and converges to a substantially constant stress value after 60 seconds. Therefore, the maximum stress at the time of expansion and the value of stress 60 seconds after the end of expansion were determined and listed in Table 1.

  The results are as shown in Table 1. In Examples 1 to 5 in which preliminary expansion was performed, the stress value after 60 seconds in this test was reduced compared to Comparative Example 1 in which preliminary expansion was not performed. . In particular, in Examples 2 to 5 in which the preliminary expansion rate was equal to or less than the expansion rate of 50% in this test, the stress value after 60 seconds in this test was significantly lower than that in Comparative Example 1, and the residual The stress was reduced.

  Next, a tire molding test was performed using the cylindrical film as an inner liner member. In the tire molding test, preliminary expansion was performed to expand the cylindrical film into a toroidal shape as shown in FIG. 2 (preliminary expansion ratio is as shown in Table 1), and then a pneumatic tire was molded according to a conventional method. At that time, the film peeling state and the film wrinkle state were evaluated. The evaluation method is as follows.

  -Film peeling state: After forming the green tire, the peeling state of the film (that is, the inner liner member) is observed, and “◯” indicates that there is no film peeling, and “△” indicates that the film is partially peeled. The case where film peeling occurred in most cases was evaluated as “x”.

  -Film wrinkle state: Observe whether or not the film (that is, the inner liner member) is wrinkled after molding the green tire. “△”, and those with large wrinkles and poor appearance were evaluated as “x”.

  Moreover, durability was evaluated about the obtained tire of Examples 1-5. The evaluation method is as follows.

  Tire durability: The tire was run on a steel drum having a diameter of 1707 mm at an air pressure of 0 kPa and a load load of 4.0 kN at a speed of 80 km / h until a failure occurred in the tire. Indicated by an index in which the travel distance of Example 1 is 100. The larger the index, the better the tire durability.

結果は、表１に示す通りである。予備拡張していない比較例１では、大部分でフィルム剥がれが発生したのに対し、予備拡張した実施例１〜５では、フィルム剥がれが抑制され、成形性が改善された。特に、グリーンタイヤ成形時における拡張率と同等以上の拡張率で予備拡張したもの、即ち予備拡張率が５０％以上である実施例２〜５では、フィルム剥がれがなく良好であった。

The results are as shown in Table 1. In Comparative Example 1 which was not pre-expanded, film peeling occurred in the majority, whereas in Examples 1-5 which were pre-expanded, film peeling was suppressed and formability was improved. In particular, in Examples 2 to 5 in which the pre-expansion rate was equal to or higher than the expansion rate at the time of forming the green tire, that is, Examples 2 to 5 in which the pre-expansion rate was 50% or more, the film was not peeled off and was good.

  However, when pre-expanding beyond a certain level, the amount of deflection due to plastic deformation increases, and in Example 5 in which the pre-expansion rate exceeds 150%, there is a problem that wrinkles remain after tire molding. Therefore, from the viewpoints of suppressing film peeling and wrinkle generation, the preliminary expansion rate is preferably 50 to 150%.

  Further, in Examples 2 to 4 in which the preliminary expansion rate was 50 to 150%, the tire durability was also improved as compared with Examples 1 and 5. From this, it can be seen that pre-expansion at a pre-expansion rate of 50 to 150% improves the moldability and also improves the tire durability.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 8 ... Inner liner, 12 ... Inner liner member, 40 ... Green tire

Claims (5)

Producing a cylindrical inner liner member made of a film of thermoplastic resin or thermoplastic elastomer;
Performing pre-expansion to expand and release the inner liner member in advance;
Wrapping at least one tire member around the pre-expanded innerliner member to produce a green tire; and
Vulcanizing the green tire;
A method of manufacturing a pneumatic tire including   The method of manufacturing a pneumatic tire according to claim 1, wherein the preliminary expansion is to expand an axially central portion of the inner liner member radially outward with respect to both axial end portions.   The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein an expansion rate of the inner liner member in the preliminary expansion is equal to or greater than an expansion rate of the inner liner member at the time of forming the green tire.   The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, wherein an expansion rate of the inner liner member in the preliminary expansion is 50 to 150%.   The pneumatic tire according to any one of claims 1 to 4, wherein a thermoplastic resin and rubber are kneaded together with a crosslinking agent to produce a dynamically crosslinked product, and the inner liner member is produced from the dynamically crosslinked product. Manufacturing method.

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