JP2019038121A - Pneumatic tire manufacturing method - 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 film of a thermoplastic resin or a thermoplastic elastomer having a hydrophilic group is produced, and a pretreatment is performed on the film to increase the moisture content of the film, A green tire is manufactured by using a film with an increased moisture content as an inner liner member, and the green tire is vulcanized. [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 a green tire is molded, a cylindrical inner liner member made to fit the molding drum diameter is expanded to the green tire diameter, and a high tension remains on a rigid material. It is. In general, a material having excellent low air permeability (that is, gas barrier property) has higher rigidity. Therefore, the use of a material having excellent gas barrier property is limited due to the above-described molding problems.

  Incidentally, in Patent Document 1, in a pneumatic tire using such a resinous film as an inner liner member, gas barrier properties are reduced due to water absorption by the film, and therefore, a hygroscopic filler is added to the sidewall portion. Blending is described. Patent Document 2 describes that a heated gas having a moisture content of 10% or less is used as a heat medium introduced into a green tire at the time of tire molding in order to suppress hydrolysis and oxidative degradation of the thermoplastic resin film. ing. These documents refer to the relationship between the film and water when a resin film is used for the inner liner member, but do not refer to the relationship between the moisture content of the film and the moldability during tire molding. Absent.

JP, 2006-196219, A JP 2002-283808 A

  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 producing a pneumatic tire according to the embodiment includes producing a film of a thermoplastic resin or thermoplastic elastomer having a hydrophilic group, performing a pretreatment for increasing the moisture content of the film on the film, and moisture content. The method includes producing a green tire using the film having an improved thickness as an inner liner member and vulcanizing the green tire.

  According to this embodiment, by increasing the moisture content of the film used as the inner liner member, it is possible to temporarily reduce the stress of the film, and by molding the green tire in that state, Film peeling can be suppressed.

Sectional drawing of the pneumatic tire which concerns on one Embodiment The schematic diagram for demonstrating the manufacturing process of the pneumatic tire which concerns on one Embodiment.

  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.

  In manufacturing the pneumatic tire 1 according to one embodiment, in the present embodiment, a film of a thermoplastic resin or a thermoplastic elastomer having a hydrophilic group is produced as an inner liner member that forms the inner liner 8.

  Examples of the hydrophilic group include an amide group, a hydroxyl group, an amino group, and a carboxyl group.

  Examples of the thermoplastic resin having a hydrophilic group include those having an amide group such as nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6/66 copolymer, nylon 6 and the like. / 66/610 copolymer, nylon MXD6, nylon 6T, nylon 6 / 6T copolymer and other aliphatic polyamide resins (nylon resin). Moreover, as what has a hydroxyl group, ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol (PVA), etc. are mentioned. These can be used alone or in combination of two or more.

  The thermoplastic elastomer having a hydrophilic group is a blend of the above thermoplastic resin having a hydrophilic group and rubber, and has a structure in which the thermoplastic resin is a continuous phase (matrix phase) and the rubber is a dispersed phase (domain phase). A thing may be used. Further, a block copolymer having a hydrophilic group and comprising 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 with a hydrophilic group can also be used as a thermoplastic elastomer with a hydrophilic group. Examples of the block copolymer having a hydrophilic group include polyamide-based elastomers having polyamide as a hard segment.

  Examples of the rubber blended with the thermoplastic resin having a hydrophilic group or the block copolymer include natural rubber (NR), epoxidized natural rubber (ENR), isoprene rubber (IR), styrene butadiene rubber (SBR), Diene rubbers such as butadiene rubber (BR) and 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 Olefin-based rubber such as (ACM); Halogenated butyl rubber (for example, brominated butyl rubber (Br-IIR), chlorinated butyl rubber (Cl-IIR)), halogen-containing rubber such as chloroprene rubber (CR), chlorosulfonated polyethylene, etc. Is mentioned. These may be used alone or in combination of two or more.

  In one embodiment, the thermoplastic resin or thermoplastic elastomer film having a hydrophilic group is preferably a film containing an aliphatic polyamide resin. More preferably, it has a structure in which aliphatic polyamide resin is a continuous phase and rubber is a dispersed phase.

  In one embodiment, a thermoplastic resin having a hydrophilic group (for example, an aliphatic polyamide resin) and rubber are melt-kneaded together with a crosslinking agent to produce a dynamically crosslinked product, and the above film is produced from the dynamically crosslinked product. Good. 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 film 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.

  In one embodiment, the film may be formed into a cylindrical shape as shown in FIG. 2A by inflation molding using a thermoplastic resin or a thermoplastic elastomer. That is, the above-described thermoplastic resin or thermoplastic elastomer (preferably dynamically cross-linked product) having a hydrophilic group is melted, and the obtained melt is cylindered using an extruder equipped with an inflation die such as a ring die. The cylindrical film 10 as an inner liner member may be produced by extrusion molding into a shape. In addition, you may produce a cylindrical film 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. These films do not necessarily have an adhesive layer for adhering to the rubber layer of the tire body.

  The thickness of the film is not particularly limited, and may be, for example, 0.02 to 1.0 mm, 0.05 to 1.0 mm, or 0.05 to 0.5 mm.

  After producing a film as mentioned above, in this embodiment, the film is pretreated to increase its moisture content.

  By increasing the moisture content of the film, the stress of the film can be temporarily reduced. The reason is not intended to be limited by this, but is considered as follows. That is, a water molecule is hydrogen-bonded to the hydrophilic group of the polymer constituting the film, and further attracts the water molecule to the periphery to form a water molecule-water molecule hydrogen bond. These water molecules push the distance between the polymer chains around the hydrophilic group. Thereby, the hydrogen bond between a hydrophilic group and a hydrophilic group is newly cut | disconnected, and a hydrogen bond with a water molecule is formed. As described above, the mobility increases due to the disappearance of the hydrogen bond between the polymer chains, so that the plasticizing effect appears and the stress is considered to decrease.

  As a pretreatment method for increasing the moisture content, a method of directly applying water as a liquid by immersing the film in water, or a method of exposing the film to a humidified atmosphere may be used. The latter method is preferred, and the possibility that water droplets remain on the film surface can be suppressed. That is, in a preferred embodiment, the pretreatment is a treatment for increasing the moisture content of the film 10 by placing the film 10 in a humidified atmosphere as shown in FIG. Specifically, the film is placed in a constant temperature and humidity chamber or a constant temperature and humidity chamber having a humidified atmosphere in which the temperature and relative humidity are controlled, and is exposed to the humidified atmosphere for a predetermined time.

  The humidification conditions are not particularly limited as long as the humidity is increased so that the moisture content of the film can be increased. What is necessary is just the conditions humidified with respect to the standard conditions which are normal environments after the shaping | molding of a film until the time of green tire shaping, for example, temperature: 20-95 degreeC, relative humidity: 60-98% RH, processing time. : The conditions under which the moisture content of the film can be increased from 5 to 48 hours may be set as appropriate.

  In one embodiment, in the pretreatment, the moisture content of the film is preferably 1.0% by mass or more. Since the stress of the film becomes lower as the moisture content becomes higher, it is preferable to make the moisture content as high as possible from the viewpoint of the moldability of the tire, and the moisture content is more preferably 1.05% by mass or more, and 1.1% by mass. % Or more. The upper limit of the moisture content is not particularly limited, but if the pretreatment time is too long, the productivity is impaired, so the moisture content is preferably 3.0% by mass or less. Here, the moisture content is a value measured using a Karl Fischer moisture measuring device.

  In one embodiment, in the pretreatment, it is preferable to increase the moisture content of the film so that the 10% tensile stress of the film is 3.5 MPa or less. When the 10% tensile stress is 3.5 MPa or less, film peeling during tire molding can be more reliably suppressed. The lower limit of the 10% tensile stress is not particularly limited, and may be, for example, 2.0 MPa or more. Here, the 10% modulus is the tensile stress at the time of 10% elongation at 23 ° C. measured according to the tensile test of JIS K6251 (punched in dumbbell shape No. 3).

  After adjusting the moisture content of the film as described above, a green tire is produced using the film as an inner liner member while maintaining the high moisture content. The green tire molding method itself is not particularly limited, and a known method can be used.

  For example, as shown in FIG. 2C, a cylindrical film 10 is set as an inner liner member around a primary forming drum 12, and a carcass ply 14 is wound around the film 10 and both ends of the carcass ply 14 in the width direction. A bead member 16 is mounted on the outer peripheral surface of the rim, and a side wall rubber 18 is disposed at a predetermined position, and both ends of the carcass ply 14 are folded back so as to wind the bead member 16, thereby producing a green case 20. Next, as shown in FIG. 2D, the green case 20 is transferred to the secondary forming drum 22 to perform shaping. For shaping, a tread ring 28 comprising a cylindrical belt 24 and a tread rubber 26 laminated on the outer peripheral surface thereof is arranged outside the green case 20 in the radial direction, and a pair of left and right drums of the secondary forming drum 22 is arranged. While moving the portions 22A and 22A toward each other, a fluid such as a gas is supplied into the green case 20 to expand the green case 20 in a toroid shape (that is, the axial central portion is expanded radially outward). And joining and integrating with the tread ring 28. Thereby, the green tire 30 having a cross-sectional shape as shown in FIG. 2 (E) 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 increasing the moisture content of the film used as the inner liner member, the stress of the film can be temporarily reduced, and the film that is expanded into a toroidal shape when the green tire is molded is flexible. Can be granted. Therefore, film peeling at the time of shaping | molding can be suppressed.

  The moisture content increased during the molding of the green tire returns to the original low moisture content due to the heat in the subsequent vulcanization molding process. Although the gas barrier property of the film is reduced (that is, deteriorated) due to an increase in the moisture content, the gas barrier property is restored to the original high state because the moisture content returns to a low state after vulcanization. Therefore, while the film material itself is the same as the inner liner member (that is, the gas barrier property has the same performance), the moldability is improved by adjusting the moisture content at the time of molding to temporarily make it flexible. be able to.

  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 3, Comparative Examples 1 to 8]
Dynamic cross-linked pellets were obtained by melt-kneading with a biaxial kneader (manufactured by Plastics Engineering Laboratory) according to the formulation (parts by mass) shown in Table 1 below.

  Details in Table 1 are as follows.

Nylon resin: Nylon 6/66 copolymer, “Novamid 2020” manufactured by DSM
・ Butyl rubber: “IIR268” manufactured by ExxonMobil Chemical
-Compatibilizer: ethylene-glycidyl methacrylate copolymer, "Bond First BF-E" manufactured by Sumitomo Chemical Co., Ltd.
・ Plasticizer: “DOS” manufactured by Daihachi Chemical Industry Co., Ltd.
・ Crosslinking agent: alkylphenol-formaldehyde resin, “Tactrol 201” manufactured by Taoka Chemical Co., Ltd.
-Adhesive: Resorcin-based formaldehyde condensate, "Sumikanol 620" manufactured by Taoka Chemical Industry Co., Ltd.

  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.

The air permeability coefficient was measured about the obtained cylindrical film. In addition, pretreatment as shown in Table 1 is performed on the cylindrical film, the moisture content of the pretreated film is measured, and a tensile test is performed on the pretreated film to obtain a 10% tensile stress. It was measured. The pretreatment conditions in Table 1 are as follows.
Standard: A cylindrical film was allowed to stand in an atmosphere of 20 ° C. and 50% RH for 15 hours as equivalent to standard conditions for not humidifying, that is, normal physical property measurement conditions.
Drying: The cylindrical film was dried in an oven at 70 ° C. for 15 hours.
Humidification: As an equivalent to the humidified atmosphere, the cylindrical film was left in a constant temperature and humidity chamber set at 25 ° C. and 80% RH for 15 hours.

  The measuring method of an air permeability coefficient, a moisture content, and 10% tensile stress is as follows.

  -Air permeability coefficient: According to JIS K7126-1 "Plastics-Film and sheet-Gas permeability test method-Part 1: Differential pressure method" Test gas: Air, Test temperature: 80 ° C, Air permeability coefficient Measured and displayed as an index with the value of Comparative Example 4 being 100. The smaller the index, the better the gas barrier property.

  Moisture content: Measured using a Karl Fischer moisture meter (“852Titrando” manufactured by Metrohm) according to JIS K7251 B method (moisture vaporization method). The set temperature was 170 ° C. and the sample amount was 0.5 g.

  10% tensile stress: Measured according to the tensile test of JIS K6251. The dumbbell shape was No. 3 (however, the thickness was 200 μm), and the median value of the stress in a state where the dumbbell was stretched 10% when pulled in the film extrusion direction at a speed of 500 mm / min at a measurement temperature of 23 ° C. was obtained. The smaller this value, the better the flexibility.

  A pneumatic tire was produced using the cylindrical film obtained after the pretreatment as an inner liner member. At that time, the state of peeling of the film (that is, the inner liner member) after the green tire molding was observed. “Good” indicates that there was no film peeling and “△” indicates that the film was partially peeled. The case where film peeling occurred in the part was indicated as “x”.

結果は、表１に示す通りである。比較例４がコントロールであり、前処理を標準条件としてタイヤを成形したところ、水分率が０．６５質量％と低いため、１０％引張応力が３．９ＭＰａと高く、部分的にフィルム剥がれが発生した。比較例１では、成形性を考慮してフィルム材料中のゴム比率を高くしたところ、フィルム剥がれは改善されたが、ガスバリア性が悪化した。比較例２では、成形性を考慮してフィルム材料に可塑剤を添加したところ、同様に、フィルム剥がれは改善されたが、ガスバリア性が悪化した。

The results are as shown in Table 1. Comparative Example 4 was a control, and when a tire was molded using the pretreatment as a standard condition, the moisture content was as low as 0.65% by mass, so the 10% tensile stress was as high as 3.9 MPa, and film peeling occurred partially. did. In Comparative Example 1, when the rubber ratio in the film material was increased in consideration of moldability, film peeling was improved, but gas barrier properties were deteriorated. In Comparative Example 2, when a plasticizer was added to the film material in consideration of moldability, the film peeling was similarly improved, but the gas barrier property was deteriorated.

  Comparative Examples 3 and 4 and Example 1 share the same film material, and the pretreatment conditions are changed. In Comparative Example 3 of the standard conditions, the moisture content in Comparative Example 3 is 10% lower due to drying. % Tensile stress increased and moldability deteriorated. On the other hand, in Example 1 of humidification conditions, the moisture content increased, the 10% tensile stress decreased, and film peeling was improved.

  In Comparative Examples 5 and 6 and Example 2, the film materials are common and the pretreatment conditions are changed. Comparative Examples 7 and 8 and Example 3 share the same film material, and the pretreatment conditions are changed. These are obtained by increasing the resin ratio with respect to Comparative Example 4. In Comparative Examples 6 and 8 under standard conditions, the gas barrier property was improved as compared with Comparative Example 4, but the 10% tensile stress was increased and the moldability was deteriorated. In Comparative Examples 5 and 7, the stress was further increased by 10% due to drying. On the other hand, in Examples 2 and 3 of the humidifying conditions, the gas barrier property was high due to the increase in the resin ratio, but the 10% tensile stress was reduced due to the increase in the moisture content, and the film peeling was improved.

  In addition, since the air permeability coefficient of the comparative example 3 and Example 1 is the same value as the comparative example 4 as a tire, the measurement is abbreviate | omitted. Similarly, Comparative Example 5 and Example 2 have the same value as Comparative Example 6, Comparative Example 7 and Example 3 have Comparative Example 8, and the air permeability coefficient as a tire is the same value.

  According to the results of Examples 1 to 3 and Comparative Examples 3 to 8, the moisture content was adjusted to 1.0% by mass or more and the 10% tensile stress to 3.9 MPa or less by performing pretreatment under humidification conditions on the film. The film peeling could be improved without impairing the gas barrier property.

  As described above, according to the present embodiment, by performing the pretreatment of the humidifying condition, the moldability can be improved by temporarily reducing the stress without changing the film material, and the gas barrier property and the moldability. Can be compatible.

  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, 10 ... Cylindrical film, 30 ... Green tire

Claims (7)

Producing a film of thermoplastic resin or thermoplastic elastomer having a hydrophilic group;
Performing a pretreatment for increasing the moisture content of the film,
Producing a green tire using the film having an increased moisture content as an inner liner member; and
Vulcanizing the green tire;
A method of manufacturing a pneumatic tire including   The method for manufacturing a pneumatic tire according to claim 1, wherein the pretreatment is a treatment for increasing the moisture content of the film by placing the film in a humidified atmosphere.   The manufacturing method of the pneumatic tire of Claim 1 or 2 whose said film is a film containing aliphatic polyamide resin.   The pneumatic tire according to any one of claims 1 to 3, wherein a thermoplastic resin and rubber are kneaded together with a crosslinking agent to produce a dynamically crosslinked product, and the film is produced from the dynamically crosslinked product. Method.   The manufacturing method of the pneumatic tire of any one of Claims 1-4 which makes the moisture content of the said film 1.0 mass% or more in the said pre-processing.   The manufacturing method of the pneumatic tire of any one of Claims 1-5 which raises the moisture content of the said film in the said pre-treatment, and makes the 10% tensile stress of the said film 3.5 MPa or less.   The method for manufacturing a pneumatic tire according to any one of claims 1 to 6, wherein the film is formed into a cylindrical shape by inflation molding using the thermoplastic resin or the thermoplastic elastomer.

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