JP2012051150A - Method for producing pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve air permeability resistance.SOLUTION: A pneumatic tire equipped with an inner liner rubber layer on the inner surface of the tire is vulcanization-molded, and the surface of the inner liner rubber layer after being vulcanization-molded is irradiated with electron beams. By coating the surface of the inner liner rubber layer irradiated with electron beams with a compound having a carbon-carbon double bond and at least one functional group selected from the group consisting of a hydroxyl group, a nitrile group, and a halogen atom in a molecule, the compound is reacted with the surface of the inner liner rubber layer.

Description

  The present invention relates to a pneumatic tire.

  In a pneumatic tire, in order to ensure airtightness, a rubber layer having a low air permeability called an inner liner is provided on the inner surface of the tire. For such an inner liner rubber layer, a halogenated butyl rubber having excellent air permeation resistance as compared with a normal rubber layer constituting a tread, a sidewall or the like is used. Further, in order to further improve the air permeation resistance, there is a method of blending a plate-like filler such as talc or mica having a plate-like structure. However, these methods have a problem in that the strength of the inner liner rubber layer is reduced.

Japanese Patent Laid-Open No. 04-045114 Japanese Patent Application Laid-Open No. 10-025358 JP 2009-132379 A

  The present inventor has intensively studied to improve the air permeation resistance of a tire and uses a compound having a specific functional group for the inner liner rubber layer of a vulcanized pneumatic tire using electron beam irradiation. I thought about combining them.

  As a technique for imparting a compound to a rubber polymer using electron beam irradiation, the above-mentioned Patent Document 1 discloses that a crosslinked silicone rubber is impregnated with a radical polymerizable monomer and then the monomer is polymerized by electron beam irradiation. Is disclosed. Further, Patent Document 2 discloses that a monomer is applied to a natural rubber latex film and a polymer film is formed by electron beam irradiation. However, Patent Document 1 aims to increase the hardness of silicone rubber, and Patent Document 2 aims to improve the adhesiveness of rubber products, both of which are technologies unrelated to pneumatic tires. It is.

  On the other hand, as related to a pneumatic tire, in Patent Document 3, a composition containing a rubber component is laminated on a resin layer, and an electron beam is applied to the composition, whereby a resin layer and a rubber component are disposed. An inner liner for a tire in which partial cross-linking is generated is disclosed, and it is disclosed that the adhesiveness with an adjacent rubber member is thereby improved. However, in this document, the inner liner body is formed of a resin layer, and the rubber component is integrally provided for adhesion to the adjacent rubber member, and electron beam irradiation is performed before being attached to the adjacent rubber member. is there. Accordingly, the electron beam irradiation is not performed on the inner liner rubber layer after vulcanization molding, nor is it disclosed that a compound having a specific functional group is applied.

  An object of this invention is to provide the pneumatic tire which can improve air permeation resistance, and its manufacturing method.

  The method for producing a pneumatic tire according to the present invention includes a step of vulcanizing and molding a pneumatic tire having an inner liner rubber layer on the inner surface of the tire, and irradiating the surface of the inner liner rubber layer after vulcanization with an electron beam. The inner liner rubber after vulcanization molding, a compound having in its molecule at least one functional group selected from the group consisting of a carbon-carbon double bond, a hydroxyl group, a nitrile group and a halogen atom. Applying to the surface of the layer.

  The pneumatic tire according to the present invention is a pneumatic tire provided with an inner liner rubber layer on the inner surface of the tire, and is irradiated with an electron beam on the surface of the inner liner rubber layer, whereby a carbon-carbon double bond, a hydroxyl group, A compound having in the molecule thereof at least one functional group selected from the group consisting of a nitrile group and a halogen atom is reacted with the surface of the inner liner rubber layer.

  According to the present invention, the compound having the specific functional group is bonded to the inner liner rubber layer of the pneumatic tire after vulcanization by electron beam irradiation, thereby self-aggregating on the surface of the inner liner rubber layer. A highly functional group is added, thereby reducing air permeability and improving air permeation resistance.

1 is a half sectional view of a pneumatic tire according to an embodiment.

  Embodiments of the present invention will be described below.

  FIG. 1 shows an example of a pneumatic radial tire according to the embodiment. The tire includes a tread portion (1), a pair of left and right bead portions (2), and a pair of left and right sidewall portions (3) interposed between the tread portion (1) and the bead portion (2). The carcass layer (4) disposed on the radially inner side of the tread portion (1) is wound from the inside of the bead core (5) to the outside by the bead portion (2) through the side wall portions (3) on both sides. It is locked by.

  A belt layer (6) is disposed on the outer peripheral side of the carcass layer (4) in the tread portion (1), and a tread rubber portion (7) constituting a ground contact surface is provided on the outer peripheral side of the belt layer (6). It has been. A sidewall rubber part (8) is provided on the outer surface side of the carcass layer (4) in the sidewall part (3). Further, an inner liner rubber layer (9) is provided on the inner surface side of the carcass layer (4) over the entire inner surface of the tire. The inner liner rubber layer (9) is bonded to the inner surface of the topping rubber layer that covers the cord of the carcass layer (4). A pneumatic tire having such a structure can be produced by producing a green tire (unvulcanized tire) and then vulcanizing it in accordance with a conventional method.

  The rubber composition for forming the inner liner rubber layer (9) may be a butyl rubber alone as a rubber component. However, butyl rubber is generally preferable because it has a low degree of unsaturation and hardly generates radicals by electron beam irradiation. Is to use a rubber composition containing a diene rubber. The rubber component is preferably a blend of butyl rubber and diene rubber, more preferably, from the viewpoint of ensuring air permeability of the rubber composition main body and ensuring the amount of radicals generated by electron beam irradiation. The blend of 30 to 80 parts by mass of butyl rubber and 20 to 70 parts by mass of diene rubber in 100 parts by mass of the rubber component.

  Examples of the butyl rubber include butyl rubber (IIR) and halogenated butyl rubber. Examples of the halogenated butyl rubber include brominated butyl rubber (BIIR) and chlorinated butyl rubber (CIIR). These can be used alone or in combination of two or more. More preferably, halogenated butyl rubber is used. Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer, styrene-isoprene. -A butadiene copolymer rubber etc. are mentioned, These can be used individually or in combination of 2 or more types, respectively.

  The rubber composition may contain a reinforcing filler such as carbon black or silica. Although the compounding quantity of a reinforcing filler is not specifically limited, It is preferable that it is 20-100 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 30-80 mass parts. Although it does not specifically limit as carbon black, The thing of FEF (N500 series), GPF (N600 series), SRF (N700 series) (both ASTM grade) is used preferably. In addition, the flat filler which consists of layered minerals, such as a talc, mica, and clay, can also be mix | blended.

  In addition to the above rubber composition, various additives generally used in rubber compositions such as oil, zinc white, stearic acid, vulcanizing agent, and vulcanization accelerator can be appropriately blended. Examples of the vulcanizing agent include sulfur and sulfur-containing compounds, and are not particularly limited. However, the blending amount is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. More preferably, it is 0.1-2 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-5 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 0.2-3 mass parts.

  The rubber composition is prepared by kneading using a rubber kneader such as a normal Banbury mixer or kneader, extruded into a sheet shape by a roll or the like according to a conventional method, and the extruded sheet material is placed inside the carcass layer. The inner liner rubber layer (9) can be formed on the inner surface of the tire by pasting and vulcanizing at, for example, 140 to 180 ° C. In addition, although the thickness of an inner liner changes with tire sizes etc., it is 0.5-3.0 mm normally.

  After vulcanization molding as described above, in this embodiment, the surface of the inner liner rubber layer (9) is irradiated with an electron beam. By irradiating with an electron beam, radicals are formed in the rubber polymer existing on the surface of the inner liner rubber layer, specifically, in the carbon-carbon double bond (C = C) portion or C—H bond portion of the diene rubber. Can be generated.

  Although it does not specifically limit as irradiation conditions of an electron beam, It is preferable that acceleration voltage is 150-1000 kV, More preferably, it is 200-500 kV, and irradiation dose is 10-400 kGy, More preferably, it is 50-250 kGy.

  In this way, the monomer is applied to the surface of the inner liner rubber layer (9) irradiated with the electron beam when the generated radicals are present (that is, before the radicals disappear). Here, the monomer refers to a low molecular compound having a specific functional group and a carbon-carbon double bond in the molecule.

  Examples of the specific functional group include a hydroxyl group (—OH), a nitrile group (—CN), and a halogen atom that enhance self-aggregation, and a monomer having any one or more thereof in the molecule is used. Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Among these, chlorine and bromine are preferable.

The monomer has at least one unsaturated group represented by H ₂ C═CR— (wherein R is a hydrogen atom or a methyl group) as a radical-polymerizable carbon-carbon double bond, and is self-aggregating. It is preferable to use those having at least one of the above-mentioned specific functional groups having a high molecular weight. More specifically, a compound represented by the following general formula (1) is used as the monomer.

  In the formula, R represents a hydrogen atom or a methyl group, X represents a hydroxyl group, a nitrile group or a halogen atom, A represents a C 1-10 divalent organic group which may contain an oxygen atom, and n represents 0 or 1. A is more preferably a C 1-8 divalent organic group which may contain an ester bond or an ether bond.

More specifically, the monomer includes a vinyl group (H ₂ C═CH—), an isopropenyl group (H ₂ C═C (CH ₃ ) —), an allyl group (H ₂ C═CH—) necessary for radical polymerization. CH _2- ) and a compound having at least one hydroxyl group, nitrile group, or halogen atom, such as allyl alcohol, 3-buten-1-ol, 4-pentene-1- All, 5-hexen-1-ol, 6-hepten-1-ol, 7-octen-1-ol, 8-nonen-1-ol, 9-decene-1-ol, 10-undecen-1-ol Alkenol (A is an alkylene group having 1 to 10 carbon atoms and X is a hydroxyl group) such as 3-methyl-3-buten-1-ol, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate (Meth) acryloyl group-containing compounds (A is an alkylene group containing an ester bond and X is a hydroxyl group), alkene nitriles such as acrylonitrile, allyl cyanide, 4-pentenenitrile, 5-hexenenitrile (the above A is carbon number) 1-10 alkylene groups and X is a nitrile group), allyl chloride, vinyl chloride, vinyl bromide, 4-bromo-1-butene, 3-chloro-2-methyl-1-propene, 5-bromo-1-pentene, Halogenated alkenes such as 6-bromo-1-hexene and 10-bromo-1-decene (wherein A is an alkylene group having 1 to 10 carbon atoms and X is a halogen atom). Any of these may be used alone or in combination of two or more.

  The method for applying the monomer to the surface of the inner liner rubber layer (9) is not particularly limited. For example, when the monomer is liquid, it is diluted as it is or with a solvent such as water, or when the monomer is solid. A monomer liquid (a liquid containing a monomer) may be prepared by dissolving in a solvent such as water, and the monomer liquid may be applied to the surface of the inner liner rubber layer (9). The application method is not particularly limited. For example, various methods such as brushing, spraying, and further immersing the tire, particularly the inner liner rubber layer (9) portion in a tank containing the monomer liquid. Can be adopted. When the monomer is a gas, the monomer can be imparted also by placing a pneumatic tire in an atmosphere filled with the monomer.

  After adding the monomer, it is allowed to stand for a predetermined time. In addition, when letting it stand, you may put in an oven etc. and heat (for example, 30-80 degreeC).

  In the monomer applied to the surface of the inner liner rubber layer (9), the carbon-carbon double bond portion in the molecule reacts with the diene rubber on the surface of the inner liner rubber layer (9) by radical polymerization reaction. . That is, the monomer is bonded to the diene rubber polymer by the reaction of the carbon-carbon double bond of the monomer with the radical of the diene rubber generated by electron beam irradiation. In addition, a graft polymer having a diene rubber polymer as a trunk and a polymer portion formed by linking the monomers as a side chain may be formed by sequentially linking monomers by a radical polymerization reaction.

  Thereby, a functional group having high self-aggregation property of the monomer is introduced on the surface of the inner liner rubber layer (9) (in addition, a surface treatment portion (a film made of the monomer) by the monomer is denoted by a reference numeral in FIG. 10). For this reason, it is speculated that the introduced functional groups attract each other, so that the cohesive force between the rubber polymers into which the monomers are introduced can be increased. Therefore, the air permeability is reduced, and the tires are resistant to air permeation. Can be improved. Since the monomer does not penetrate into the inner liner rubber layer (9), the functional group is introduced only on the surface of the inner liner rubber layer (9). Thus, since only the rubber surface is modified, the weather resistance can be improved without impairing the original characteristics of the rubber composition constituting the inner liner rubber layer (9). Further, even when a diene rubber is used as the rubber composition, the air permeation resistance can be improved, so that the adhesion of the carcass layer (4) to the topping rubber layer is improved by the diene rubber. Moreover, the adhesiveness at the time of joining both edge parts by winding a sheet-like inner liner rubber at the time of tire shaping | molding can also be improved. Furthermore, the breaking strength can be increased by blending a diene rubber.

The amount of the monomer applied to the surface of the inner liner rubber layer (9) is not particularly limited, and can be, for example, 100 to 10,000 g / m ² .

  In the said embodiment, although the monomer was provided after irradiating an electron beam, you may irradiate an electron beam after providing a monomer. That is, in the present invention, the surface of the inner liner rubber layer after vulcanization may be irradiated with an electron beam, and then the monomer may be added to the surface of the inner liner rubber layer irradiated with the electron beam. After the above-mentioned monomer is applied to the surface of the inner liner rubber layer after vulcanization molding, the surface of the inner liner rubber layer may be irradiated with an electron beam. Furthermore, the electron beam irradiation and the monomer application are performed simultaneously. In any case, the monomer can be reacted with the surface of the inner liner rubber layer.

  The pneumatic tire to which the present invention can be applied is not particularly limited, and can be applied to various pneumatic tires such as tires for passenger cars and tires for heavy loads such as trucks and buses.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  A rubber composition for an inner liner was prepared according to a conventional method using a Banbury mixer. The composition of the rubber composition excluding Comparative Example 4 is as shown in Table 1 below. For Comparative Example 4, the composition of the rubber component was BIIR / NR = 70/30 (parts by mass) (see Table 2), and the others were as shown in Table 1.

  Using the resulting rubber composition for inner liner, a 195 / 65R15 pneumatic radial tire was vulcanized and molded in accordance with a conventional method, and then subjected to electron beam irradiation and monomer coating in accordance with the conditions shown in Table 2 to enter pneumatic Tires were manufactured.

In detail, in Example 1, with respect to the tire after vulcanization molding, using an electron beam irradiation device, the surface of the inner liner rubber layer was subjected to the conditions of temperature: room temperature, acceleration voltage: 200 kV, and irradiation dose: 200 kGy. Irradiated with an electron beam. Immediately after the irradiation, a monomer solution was applied to the surface of the inner liner rubber layer of the tire by brushing to give a monomer to the surface of the inner liner rubber layer. As the monomer solution, a 50 mass% aqueous solution of monomer A: allyl alcohol (CH ₂ = CHCH ₂ OH) was used. Then, by leaving it at room temperature for 4 hours, a pneumatic tire in which the monomer was bonded to the surface of the inner liner rubber layer was obtained.

In Example 2, a pneumatic tire was obtained in the same manner as in Example 1 except that a 50% by mass aqueous solution of monomer B: acrylonitrile (CH ₂ = CHCN) was used as the monomer liquid. In Example 3, a pneumatic tire was obtained in the same manner as in Example 1 except that monomer C: allyl chloride (CH ₂ = CHCH ₂ Cl) was used as the monomer liquid.

  Comparative Example 1 is an example in which electron beam irradiation and monomer application were not performed as controls. Comparative Example 2 was an example in which the monomer liquid was applied without electron beam irradiation, and was the same as Example 1 except that no electron beam irradiation was performed. Comparative Example 3 was an example in which the electron beam was irradiated but the monomer liquid was not applied, and was the same as Example 1 except that the monomer liquid was not applied. Comparative Example 4 was an example in which the ratio of the halogenated butyl rubber was increased with respect to Comparative Example 1, and a pneumatic tire was obtained in the same manner as Comparative Example 1 with the rest.

  About each obtained pneumatic tire, air permeation resistance was evaluated. Moreover, the breaking strength was evaluated about the used rubber composition for inner liners. Each evaluation method is as follows.

-Air permeation resistance: A tire was mounted on a 15 × 6 J rim, filled with an internal pressure of 240 kPa, and allowed to stand in an atmosphere of 1 atm at 23 ° C., and then the internal pressure was measured. For each tire, the internal pressure retention rate (= “value after 3 months” / “initial value” × 100 (%)) was measured and displayed as an index with the value of the internal pressure retention rate of Comparative Example 1 being 100. The larger the value, the higher the internal pressure retention rate and the better the air permeation resistance.

Break strength: A rubber sample vulcanized at 160 ° C. for 20 minutes using a rubber composition for an inner liner was prepared, and the rubber sample was irradiated with an electron beam in the same manner as in the corresponding examples and comparative examples. Then, a monomer test was performed, a tensile test was performed according to JIS K6251, and an index with the breaking strength of Comparative Example 1 as 100 was displayed. It shows that breaking strength is so large that a numerical value is large.

  The results are as shown in Table 2, and in comparison with Comparative Example 1 as a control, the break strength was obtained in Examples 1 to 3 in which a monomer having a specific functional group was applied to the inner liner rubber layer surface by electron beam irradiation. The air permeation resistance was improved without impairing the air quality. On the other hand, in Comparative Example 2 in which the electron beam irradiation was not performed and in Comparative Example 3 in which the electron beam irradiation was performed but no monomer was applied, the effect of improving the air permeation resistance was not observed. Further, in Comparative Example 4 in which the ratio of the halogenated butyl rubber was increased, although the air permeation resistance was improved, the breaking strength was greatly impaired.

DESCRIPTION OF SYMBOLS 1 ... Tread part, 2 ... Bead part, 3 ... Side wall part, 4 ... Carcass layer, 5 ... Bead core, 6 ... Belt layer, 7 ... Tread rubber part, 8 ... Side wall rubber part, 9 ... Inner liner rubber layer, 10 ... Surface treatment section

Claims (4)

Vulcanizing and molding a pneumatic tire having an inner liner rubber layer on the inner surface of the tire;
Irradiating the surface of the inner liner rubber layer after vulcanization with an electron beam;
A compound having in the molecule thereof a carbon-carbon double bond and at least one functional group selected from the group consisting of a hydroxyl group, a nitrile group and a halogen atom is formed on the surface of the inner liner rubber layer after vulcanization molding. Applying a process;
The manufacturing method of the pneumatic tire containing this. The carbon - carbon double bond is H _{2 C} = CR- (where, R represents a hydrogen atom or a methyl group) The method of manufacturing a pneumatic tire according to claim 1, wherein a group represented by. The method for producing a pneumatic tire according to claim 1, wherein the compound is represented by the following general formula (1).

(Wherein R represents a hydrogen atom or a methyl group, X represents a hydroxyl group, a nitrile group or a halogen atom, A represents a C 1-10 divalent organic group which may contain an oxygen atom, and n represents 0 or 1. ) A pneumatic tire having an inner liner rubber layer on the tire inner surface,
A compound having a carbon-carbon double bond and at least one functional group selected from the group consisting of a hydroxyl group, a nitrile group, and a halogen atom in the molecule by irradiating the surface of the inner liner rubber layer with an electron beam. A pneumatic tire characterized by reacting with the surface of the inner liner rubber layer.

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