JP4938992B2 - Rubber composition for inner liner - Google Patents

Description

  The present invention relates to a rubber composition for an inner liner.

  In recent years, due to the strong social demand for low fuel consumption of vehicles, tire rolling resistance has been reduced and weight reduction has been achieved, and among tire members, it is arranged inside the tire and from the inside of the pneumatic tire to the outside Even inner liners that have a function of improving air retention by reducing the amount of air leakage (air permeation amount) have been reduced in weight.

  Currently, as a rubber composition for an inner liner, the air retention of a tire is improved by blending a butyl rubber and a diene rubber, and blending the butyl rubber in a high amount. However, butyl rubber is excellent in reducing the amount of air permeation, but the energy loss is large, and the higher the butyl rubber content, the greater the tire rolling resistance and the lower the fuel consumption characteristics of the car. there were.

  Further, when the blending ratio of natural rubber is increased in order to improve the fuel efficiency of the vehicle, there is a problem that the air permeation amount increases.

  Patent Document 1 discloses a rubber composition for an inner liner containing a plate-like mica, but it does not sufficiently improve the air retention of a tire and reduce rolling resistance.

JP-A-11-140234

  An object of this invention is to provide the rubber composition for inner liners which can improve the air retention property of a tire and can reduce rolling resistance.

  The present invention comprises a diene rubber and a butyl rubber, and contains more than 30 parts by weight of a phlogopite having an aspect ratio of 45 or more with respect to 100 parts by weight of a rubber component containing 40 to 80% by weight of the butyl rubber. Further, the present invention relates to a rubber composition for an inner liner containing 45 parts by weight or less of carbon black.

  According to the present invention, a rubber composition for an inner liner that improves the air retention of a tire and reduces rolling resistance by containing a specific amount of a phlogopite having a large aspect ratio with respect to a rubber component containing a butyl rubber. Things can be provided.

  The rubber composition for an inner liner of the present invention comprises a rubber component composed of a diene rubber and a butyl rubber, and a phlogopite.

  Diene rubbers include natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR) diene rubber, acrylonitrile-butadiene rubber (NBR), epoxidized natural rubber, epi Examples thereof include chlorohydrin rubber and chloroprene rubber.

  The content of the diene rubber is preferably 20% by weight or more, and more preferably 35% by weight or more in the rubber component. When the content of the diene rubber is less than 20% by weight, the content of the butyl rubber in the rubber component increases, and the rolling resistance tends to increase. The content of the diene rubber is preferably 60% by weight or less and more preferably 55% by weight or less in the rubber component. If the diene rubber content exceeds 60% by weight, the effect of improving air retention tends to be insufficient.

  Examples of the butyl rubber include butyl rubber, brominated butyl rubber, and chlorinated butyl rubber. Of these, halogenated butyl rubber (bromobutyl rubber, chlorobutyl rubber, brominated product of a copolymer of p-methylstyrene and isobutylene) is particularly preferable from the viewpoint of a high vulcanization rate.

  The content of butyl rubber is preferably 40% by weight or more and more preferably 55% by weight or more in the rubber component. When the content of butyl rubber is less than 40% by weight, the effect of improving air retention is not sufficient. Further, the content of the butyl rubber is preferably 80% by weight or less, and more preferably 65% by weight or less in the rubber component. When the content of butyl rubber exceeds 80% by weight, rolling resistance tends to increase.

The rubber composition for an inner liner of the present invention contains a phlogopite (phlogopite, composition formula: K ₂ Mg ₆ (Si ₃ Al) ₂ O ₂₀ (OH) ₄ ). The phlogopite refers to a mica that contains MgO as a chemical component and further contains more Fe ₂ O ₃ and F as impurities. The phlogopite used in the present invention has a relatively large average particle size, and further can reduce the air permeation amount even with the same particle size, the same aspect ratio, and the same blending amount than other mica bites, etc. The improvement effect can be increased.

  The phlogopite preferably has an average particle size of 50 to 250 μm. If the average particle diameter is less than 50 μm, the effect of improving air retention tends to be insufficient. On the other hand, if the average particle diameter exceeds 250 μm, the inner liner tends to crack due to bending fatigue.

  Examples of the resin that covers the surface of the phlogopite include urethane resin, acrylic resin, epoxy resin, nylon resin, and polyester resin. Of these, urethane resins, acrylic resins, and epoxy resins are preferred because they have a relatively high compatibility with rubber. As a coating method, there is used a method in which a resin is melted, a phlogopite is put therein, stirred, then solidified, and pulverized.

  The aspect ratio of the phlogopite is 45 or more, preferably 50 or more, more preferably 52 or more. If the aspect ratio is less than 45, a sufficient effect of improving air retention cannot be obtained. Further, the aspect ratio of the phlogopite is preferably 100 or less, and more preferably 90 or less. When the aspect ratio exceeds 100, the strength of the phlogopite is reduced, and the phlogopite is cracked. Here, the aspect ratio refers to the ratio of the long diameter to the thickness of the phlogopite.

  The phlogopite can be obtained by a grinding method such as wet grinding or dry grinding. Wet pulverization produces a clean surface and has a slightly higher effect of improving air retention. Also, dry pulverization has the respective characteristics that the manufacturing process is simple and the cost is low, and it is better to use them depending on the case.

  The content of the phlogopite is more than 30 parts by weight, preferably 35 parts by weight or more, relative to 100 parts by weight of the rubber component. If the content of the phlogopite is less than 30 parts by weight, the effect of improving air retention is not sufficient. Further, the content of the phlogopite is preferably 80 parts by weight or less, preferably 70 parts by weight or less, and more preferably 55 parts by weight or less with respect to 100 parts by weight of the rubber component. If the phlogopite content exceeds 80 parts by weight, the tear strength of the rubber composition is lowered, and cracks are likely to occur.

  The rubber composition for an inner liner of the present invention further contains carbon black. The rubber composition for the inner liner of the present invention improves air retention by blending a specific amount of phlogopite having a large aspect ratio with a rubber component containing butyl rubber and further blending a small amount of carbon black. Rolling resistance can be reduced.

The nitrogen adsorption specific surface area of carbon black is preferably ²⁰ to 150 m ² / g. When the nitrogen adsorption specific surface area of carbon black is less than 20 m ² / g, the rubber has a remarkably low reinforcing property and the obtained rubber composition tends to be easily cut. On the other hand, if the nitrogen adsorption specific surface area of carbon black exceeds 150 m ² / g, the hardness of the rubber composition increases and cracks tend to occur due to bending fatigue.

  The content of carbon black is preferably 45 parts by weight or less and more preferably 40 parts by weight or less with respect to 100 parts by weight of the rubber component. When the content of carbon black exceeds 45 parts by weight, rolling resistance tends to increase. Further, the content of carbon black is preferably 10 parts by weight or more, and more preferably 15 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of carbon black is less than 10 parts by weight, the rubber composition has insufficient reinforcing properties and tends to be cut easily.

  The rubber composition for the inner liner of the present invention appropriately contains, in addition to the rubber component, phlogopite and carbon black, oil, zinc oxide, a vulcanizing agent, a vulcanization accelerator and the like generally used in the tire industry. Can do.

  The rubber composition for an inner liner of the present invention is used for manufacturing a tire and can be made into a tire by a usual method. That is, if necessary, the rubber composition for an inner liner of the present invention blended with the additive is extruded in accordance with the shape of the inner liner of the tire at an unvulcanized stage, and is usually used on a tire molding machine. An unvulcanized tire is formed by molding by the method. The unvulcanized tire is heated and pressurized in a vulcanizer to produce a tire.

  The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

Various chemicals used in the examples are shown below.
Natural rubber: RSS # 3
Chlorobutyl rubber: 1066 manufactured by Exxon Chemical Co., Ltd.
Carbon black: GPF manufactured by Mitsubishi Chemical Corporation (nitrogen adsorption specific surface area: 28 m ² / g)
Fragobite: Mica S200HG manufactured by Repco Co., Ltd. (average particle size: 55 μm, aspect ratio: 55)
Paraffin process oil: PS-32 manufactured by Idemitsu Kosan Co., Ltd.
Zinc oxide: 2 types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Powder sulfur: Vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller CZ manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(Manufacture of vulcanizates)
The chemicals excluding zinc oxide, sulfur and vulcanization accelerator were kneaded at 125 ° C. for 4 minutes in a 1.7 L Banbury mixer according to the blending amounts shown in Table 1. To the obtained kneaded product, zinc oxide, sulfur and a vulcanization accelerator were added and kneaded with a roll at 50 ° C. for 5 minutes to obtain an unvulcanized rubber composition. Using the obtained unvulcanized material, an inner liner is molded, and it is bonded to another tire member such as a tread to produce an unvulcanized tire, which is subjected to press vulcanization at 170 ° C. for 15 minutes. A tire was manufactured (tire size: 215 / 55R17). Test tires were used in the following tests.

(Air permeability)
A rubber sheet having a thickness of 0.5 mm was cut out from the inner liner of the test tire, and the air permeation amount was measured according to ASTM D-1434-75M method. It shows that the smaller the air permeation amount, the better the air retention of the tire, which is preferable.

(Rolling resistance test)
A sheet having a thickness of 0.5 mm was cut out from the inner liner of the test tire, and the initial strain was 10%, the dynamic strain was ± 2%, and the frequency was 10 Hz, using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho Co., Ltd. The loss tangent tan δ at a measurement temperature of 70 ° C. was measured. Then, from the following formula, the loss tangent tan δ of Comparative Example 1 was set to 100, and other values were expressed as indices (rolling resistance index). A larger index indicates that rolling resistance is reduced, which is preferable.
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

  The measurement results are shown in Table 1.

As in Examples 1 to 5, a rubber composition for an inner liner, in which 30 parts by weight or more of phlogopite and 45 parts by weight or less of carbon black are blended with a rubber component containing 40 to 80% by weight of chlorobutyl rubber. The rolling resistance index can be improved by 10% or more, and at the same time, the air permeation coefficient can be suppressed to 15 × 10 ⁻¹¹ or less, and the air permeation amount can be sufficiently secured.

Claims (1)

Comprising 100 parts by weight of a rubber component comprising a diene rubber and a butyl rubber and containing 40-80% by weight of the butyl rubber,
A rubber composition for an inner liner having an average particle diameter of 50 to 250 μm and an amount of phlogopite having an aspect ratio of 45 or more in an amount of more than 30 parts by weight and further containing carbon black in an amount of 45 parts by weight or less.