JP2005219565A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight pneumatic tire excellent in air permeability without damaging a moldability. <P>SOLUTION: The pneumatic tire uses a film of thermoplastic elastomer which has the air permeability of 25 × 10<SP>-12</SP>cm<SP>3</SP>cm/cm<SP>2</SP>sec cmHg or less, and a residual elongation percentage after elongation in a room temperature of 45% or less, preferably of 1 to 25% for an inner liner. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire excellent in lightness and air retention by using a thermoplastic elastomer film having a small residual elongation after stretching at room temperature as an inner liner.

  Thermoplastic elastomers such as nylon resin are less air permeable than rubber, so when used in an inner liner of a pneumatic tire, the thickness of the elastomer is reduced to a film without reducing the air retention rate of the tire. It is known that it can contribute to the weight reduction of a pneumatic tire (for example, refer patent document 1). However, since the thermoplastic elastomer is harder than rubber, there is a problem that the film is peeled off in a lift process at the time of molding a tire when used as an inner liner.

Japanese Patent Laid-Open No. 10-264607

  Accordingly, an object of the present invention is to provide a pneumatic tire that is light in weight and excellent in air retention by improving the inner liner of the pneumatic tire.

According to the present invention, a thermoplastic elastomer having an air permeability of 25 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg or less and a residual elongation after 50% elongation at room temperature of 45% or less. There is provided a pneumatic tire using a film comprising the above as an inner liner.

According to the present invention, a thermoplastic elastomer having an air permeability of 25 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg or less and a residual elongation of 50% or less after 50% elongation at room temperature is used as an inner liner. By using it, a pneumatic tire that is lightweight and excellent in air retention can be obtained.

  A pneumatic tire maintains a tire internal pressure by arranging a rubber having a small air permeability called an inner liner on the inner surface, and a polyisobutylene rubber having a low air permeability is typically used as an inner liner material. (For example, brominated butyl rubber and brominated paramethylstyrene-isobutylene copolymer rubber) are used. The air pressure retention of a general tire that is put into practical use in the tire industry and the automobile industry is a decrease of 2.5% / month or less, and in order to satisfy this, the thickness of the conventional material described above is 500 to 1500 μm. is required. If a thermoplastic elastomer having a lower air permeability than that of the material is used, the thickness of the inner liner can be reduced. However, the thermoplastic elastomer is harder than rubber and has a feeling of other rubber members constituting the pneumatic tire. There is a problem that the adhesiveness is poor.

  In the production process of a pneumatic tire, each member constituting the pneumatic tire is laminated on a molding drum and then inflated (lifted) into a tire shape, but conventionally there has been a problem that the film is peeled off in this inflation process. . Although the general lift rate in the tire manufacturing process is 40 to 85%, the present inventors have conducted research on a radial tire (size: 195 / 65R15) with a lift rate of 60%. The relationship between the elongation and peeling from the tire can be clarified, and the present invention has been achieved.

The thermoplastic elastomer used as the inner liner of the pneumatic tire according to the present invention has an air permeability of 25 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg or less, preferably 15 × 10 ⁻¹² cm ³ · cm / cm. It is necessary that it is not more than cm ² · sec · cmHg and the residual elongation after 50% elongation at room temperature is not more than 45%, preferably 1 to 25%. The residual elongation rate refers to the ratio of the increase in length after elongation (residual elongation length) with respect to the longer increase during elongation due to elongation as 100%. In order to obtain such specific air permeability and residual elongation, for example, the thermoplastic elastomer is adjusted so that the volume fraction and the viscosity of the resin as the matrix and the rubber as the dispersed phase satisfy the following formula.
(Φd / φm) × (ηm / ηd) <1
In the formula, φd: rubber volume fraction φm: resin volume fraction ηd: rubber viscosity ηm: resin viscosity ηm / ηd closer to 1 is preferable because the rubber particle size decreases and the residual elongation decreases.

  The thermoplastic elastomer used in the present invention preferably comprises a thermoplastic resin (for example, a polyamide resin such as nylon 6, nylon 66, nylon 11, nylon 12, and a copolymer thereof, or an arbitrary blend thereof) as a continuous phase. And rubber (for example, brominated product of isobutylene-paraalkylstyrene copolymer rubber, acid-modified product of isobutylene-isoprene copolymer rubber, acid-modified product of ethylene-α olefin copolymer rubber, carboxylated nitrile butadiene copolymer rubber, carboxylated (Ethylene / acrylic copolymer rubber) having a dispersed phase, and the ratio of the thermoplastic resin to the rubber is not particularly limited, but the thermoplastic resin / rubber (weight ratio) is 60 / 40-20. / 80 is preferable, and 50/50 to 30/70 is more preferable. Anti-aging agents, crosslinking agents, plasticizers, and the like can be appropriately blended with the thermoplastic elastomer as general additives.

  The inner liner may be a film made of only a thermoplastic elastomer. However, it is usually preferable from the viewpoint of work to use a laminate of a thermoplastic film and an adhesive layer having adhesiveness to rubber. Examples of such adhesive layers include rubber components (for example, natural rubber, styrene butadiene rubber, isobutylene-isoprene rubber, butadiene rubber, polyisobutylene, polyisoprene, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer). Polymer) 100 to 100 parts by weight of rubber black for reinforcing rubber compounding, 0 to 100 parts by weight, adhesive resin (for example, RF resin) 0.5 to 20 parts by weight, tackifier (for example, terpene resin, terpene phenol resin, modified terpene) Resin, hydrogenated terpene resin, rosin ester, alicyclic saturated hydrocarbon resin) 50 to 200 parts by weight, and further vulcanizing agent, vulcanization accelerator, oil, anti-aging agent, plasticizer, etc. An appropriately blended composition can be used.

  The thickness of the film for an inner liner of the present invention is typically 50 to 300 μm, preferably 100 to 200 μm, and when the adhesive layer is used, the thickness of the adhesive layer is preferably 5 to 50 μm.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Standard Example 1, Examples 1 to 4 and Comparative Examples 1 to 4
Production of Inner Liner Material (1) In Examples 1 to 4 and Comparative Examples 1 to 3, the raw material components shown in Table I were mixed using a biaxial mixer set at 230 ° C. The mixture thus prepared was pelletized and formed into a film at a temperature of 250 ° C. using an extruder equipped with a 400 mm wide T die.
(2) The comparative example 4 and the standard example 1 mixed the raw material component shown in Table I for 10 minutes using the closed mixer set to 60 degreeC. The obtained mixture was formed into a sheet using two rolls (temperature 60 ° C.).

Next, the physical properties of the obtained inner liner material were tested by the following test methods, and the results are shown in Table I.
Method of measuring residual elongation after stretching (1) A sample sheet is punched with a JIS No. 3 dumbbell, and marked with an autograph, and pulled at a speed of 50 mm / min at room temperature until the distance between the marked lines expands by 50%. The tensile load was removed and left at room temperature for 24 hours. Thereafter, the gap between the marked lines was measured, and the residual strain (that is, the residual elongation) was determined.

Air permeability: Film air permeability coefficient measurement method: JIS K7126 “Plastic film and sheet gas permeability test method (Method A)”.
Test piece: The film sample prepared in each example was used.
Test gas: Air (N ₂ : O ₂ = 8: 2)
Test temperature: 30 ° C

Table I footnote * 1: Amilan CM1041 (Toray)
* 2: Nylon 5033B (manufactured by Ube Industries)
* 3: Rilsan BMN O (manufactured by Atofina)
* 4: Exxpro 89-4 (Butyl rubber manufactured by ExxonMobil Chemical)
* 5: Oil-treated sulfur (manufactured by Karuizawa Seisakusho)
* 6: Zinc Hana 3 (manufactured by Shodo Chemical)
* 7: HPR AR201 (Mitsui / DuPont Polychemical)

Manufacture of prototype tire (1) A rubber other than the solvent of Table I (toluene and methyl ethyl ketone) and a compounding agent are mixed in a closed mixer to prepare a master batch, and then the master batch is shredded. The solvent was added and stirred for 24 hours. On the other hand, an adhesive cement having the composition shown in Table II was prepared. On one side of the prepared film, the adhesive cement of Table II was applied and dried with a brush to prepare an inner liner member. This member was wound on a molding drum, and thereafter, a prototype tire was manufactured by a conventional method.

Table II footnote * 1: FEF grade carbon black (manufactured by Nippon Kayaku Carbon)
* 2: Zincification No. 3 (manufactured by Shodo Chemical)
* 3: Heat stearic acid (manufactured by NOF Corporation)
* 4: Nocrack 224 (Ouchi Shinsei Chemical)
* 5: Resorcin formaldehyde resin (manufactured by INDSPEC CHEMICAL)
* 6: Bencel AD (Arakawa Chemical)
* 7: Oil-treated sulfur (manufactured by Karuizawa Seisakusho)
* 8: Sunseller CM-DO (manufactured by Sanshin Chemical Industry)
* 9: CYREZ 964RPC (manufactured by CYTEC INDUSTRIES)
* 10: Toluene (manufactured by Tokyo Chemical Industry)
* 11: Methyl ethyl ketone (manufactured by Tokyo Chemical Industry)

Next, the characteristics of the obtained tire were tested by the following test methods, and the results are shown in Table I.
Tire molding processability: The width of the sheet is the dimension that almost covers the inner surface of the tire, the length is cut to the same length as the forming drum, the sheet is rolled in the length direction, and the cut ends are joined together to obtain a cylindrical sheet member It was. Thereafter, this member was fixed to the molding drum, and another member such as a carcass was stacked thereon and pasted to obtain a first green tire. Next, pressure is applied to the green tire from the inner surface to extend the diameter by extending about 60% in the length direction, and at the same time, the green tire is integrated with other members such as a belt and tread rubber, and the final tire before vulcanization. Two green tires were obtained.
The second green tire was left at room temperature for 6 hours, and the degree of peeling of the sheet member after 6 hours was evaluated according to the following criteria.
○: No peeling △: Peeling of 2% or less of the total internal area ×: Peeling occurred exceeding 2% of the total internal area

Tire internal pressure retention (pressure drop rate): left for 3 months under an initial pressure of 200 kPa, a room temperature of 21 ° C. and no load. The measurement interval of the internal pressure is every 4 days, the measurement pressure Pt, the initial pressure P ₀ , the elapsed days t, and the following formula

The α value is obtained by returning to. Using the obtained α, t = 30 (days) is substituted to obtain β = [1-exp (−αt)] × 100. Let β be the rate of pressure drop per month (% / month). And it evaluated on the following references | standards according to the obtained pressure drop rate.
○: Pressure drop rate of 2.5% or less ×: Pressure drop rate of over 2.5%

  According to the present invention, as shown in the above examples, the film having the air permeability and the residual elongation after stretching at room temperature within the specified range of the present invention is excellent in the tire molding processability and the tire internal pressure retention. It is very useful as a material for an inner liner of a pneumatic tire.

Claims (4)

A film comprising a thermoplastic elastomer having an air permeability of 25 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg or less and a residual elongation after 50% elongation at room temperature of 45% or less. Pneumatic tire used for inner liner.   The pneumatic tire according to claim 1, wherein the thermoplastic elastomer is a thermoplastic resin in a continuous phase and rubber in a dispersed phase.   The pneumatic tire according to claim 1 or 2, wherein the film is a laminate of a thermoplastic elastomer layer and an adhesive layer having adhesiveness to rubber.   The pneumatic tire according to any one of claims 1 to 3, wherein the thermoplastic resin is selected from nylon 6, nylon 66, nylon 11, nylon 12, copolymers thereof, and blends thereof.