JP5132133B2 - Rubber composition for inner liner and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition for an inner liner and a pneumatic tire using the rubber composition, and more particularly to a pneumatic tire that improves the handling stability and the ride comfort in a balanced manner.

  Conventionally, a rubber composition using a rubber component having low air permeability such as butyl rubber or halogenated butyl rubber has been used for an inner liner of a pneumatic tire in order to prevent air leakage of the tire and keep the air pressure constant. .

  However, the inner liner is not arranged for the purpose of making a direct contribution to additional characteristics such as improvement of tire motion performance, in particular, handling stability or riding comfort, and also handling stability and riding comfort. There are no examples of technology mentioned for improvement.

  In Patent Document 1 below, a reinforcing sheet having a specific range of tensile rigidity along the tire circumferential direction or axial direction is arranged on the inner liner lumen surface of the tread portion to improve driving stability without impairing riding comfort. Although it is described that the inner liner emphasizes air retention, it does not exhibit substantial resistance to tensile and compressive deformation during travel and does not contribute to improvement of steering stability at all Has been.

  In addition, it is known that increasing the hardness and energy loss of treads and sidewalls are effective in achieving both steering stability and riding comfort, which are conflicting tire characteristics. It has been proposed to arrange the rubber sheet layer and the high loss sheet layer adjacent to each other, and it is described that dynamic viscoelasticity such as E ′ and tan δ of the rubber composition contributes to the hard rubber and the high loss ( Patent Document 2).

Many techniques for controlling the tan δ of the rubber composition have been disclosed. For example, in Patent Documents 3 and 4 below, an isobutylene block copolymer, a thermoplastic resin, and a tackifier are blended with a diene rubber. Although it is described that wet grip properties are improved without damaging the breaking strength by controlling tan δ, there is no disclosure of compatibility between steering stability and riding comfort.
JP 2006-151328 A Japanese Patent Application Laid-Open No. 11-151917 JP 2003-113286 A JP 2003-113287 A

  In view of the above circumstances, the object of the present invention is to focus on an inner liner that has not been conventionally considered to contribute to tire characteristics such as steering stability and ride comfort, and rubber hardness and energy loss are within an appropriate range. By providing an inner liner made of a specific rubber composition, to provide a pneumatic tire capable of improving both steering stability and riding comfort in a well-balanced manner while maintaining air retention and durability. is there.

  As a result of diligent studies to solve the above problems, the present inventor does not target a portion having a large influence on wear resistance or rolling resistance, such as a tread or a sidewall, and has a certain degree of hardness and energy loss as an inner liner rubber. To improve the rigidity and rebound resilience from the inner surface of the tire and improve both driving stability and ride comfort without compromising other characteristics such as air retention, durability, and rolling resistance. And reached the present invention.

  That is, the present invention is a polymer component comprising 40 parts by weight or more of butyl rubber and / or halogenated butyl rubber, 3 to 30 parts by weight of a block copolymer comprising a styrene polymer block and an isobutylene polymer block, and a diene rubber. It is a rubber composition for an inner liner, containing less than 1 part by weight of sulfur with respect to 100 parts by weight.

In the present invention, the block copolymer may be a triblock copolymer having a structure of styrene polymer block-isobutylene polymer block-styrene polymer block.

  The rubber composition for an inner liner preferably has a JIS-A hardness measured at 23 ° C. of 55 to 70 and a JIS rebound resilience measured at 23 ° C. of 10 to 20%.

  The pneumatic tire of the present invention is characterized in that the rubber composition for an inner liner is used for an inner liner of a tire.

  According to the pneumatic tire of the present invention, the inner liner disposed on the inner surface of the tire has a certain degree of hardness and energy loss, so that the rigidity and rebound resilience (damping property) from the tire inner surface are within an appropriate range, and the air The steering stability and ride comfort can be balanced and improved without impairing the air retention and durability of the tire.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a half sectional view of a pneumatic tire 1 according to the present invention, showing an example in which the present invention is applied to a radial tire for a passenger car.

  A pneumatic tire 1 includes a carcass 6 made of a single carcass ply using an organic fiber cord such as polyester that is folded and locked around a bead core 5 embedded in a pair of bead portions 4 from the inside to the outside of the tire. A steel cord disposed between the tread portion 2 located on the outer periphery of the crown portion of the carcass 6, the sidewall portion 3 located on the side portion of the carcass 6, and the carcass 6 inside the tread portion 2. And a cap 7 made of a nylon cord wound in a spiral shape in the tire circumferential direction on the outer periphery of the belt 7.

  The inner liner 10 is disposed so as to cover the tread portion 2, the sidewall portion 3, and the bead portion 4 on the tire inner peripheral surface, and retains the air pressure of the tire 1 when the tire 1 is incorporated in the rim and filled with the internal pressure. It is.

  In the present invention, the rubber composition used for the inner liner 10 includes butyl rubber and / or halogenated butyl rubber and diene rubber as rubber components, and the rubber component includes a styrene polymer block and an isobutylene polymer block. It consists of 100 parts by weight of a polymer component to which a block copolymer (thermoplastic elastomer) has been added, and contains less than 1 part by weight of sulfur with respect to 100 parts by weight of this polymer component.

  As the rubber component, 40 parts by weight or more of butyl rubber (IIR) and / or halogenated butyl rubber (X-IIR) having a small gas permeability coefficient are blended as essential components.

  The halogen X of X-IIR is not particularly limited as long as it is a halogen usually used in rubber components, but generally includes chlorine and bromine.

  In the inner liner according to the present invention, IIR alone has drawbacks such as poor adhesion between an adjacent rubber such as a bead portion and a carcass and the inner liner rubber, and a delay in vulcanization speed. Therefore, X-IIR is preferably used, and IIR and X-IIR can be blended at an arbitrary ratio.

  As these X-IIRs, various grades of chlorobutyl rubber and bromobutyl rubber such as JSR Corporation, Exxon and Bayer can be used as commercial products.

  The IIR and / or X-IIR is required to be contained in at least 40 parts by weight or more in 100 parts by weight of the polymer component from the viewpoint of air retention, and preferably 50 parts by weight or more. In addition, when content of IIR and / or X-IIR exceeds 95 weight% of a rubber part, it exists in the tendency for the adhesiveness with adjacent rubber | gum, and the workability of a rubber composition to fall.

  Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), and styrene isoprene butadiene rubber (SIBR), which are selected from these groups. At least one of these can be used. In particular, blends of NR and SBR, IR, and BR are preferable because they are effective in improving the adhesiveness and vulcanization rate of IIR and X-IIR.

  The rubber composition for an inner liner according to the present invention is used by blending the rubber component with a styrene-isobutylene block copolymer (SIBS). The block copolymer exhibits an effect of appropriately increasing the hardness of the rubber composition and improving the rigidity, and suppresses an increase in rebound resilience and imparts a damping property to the rubber, so that the steering stability and riding performance of the tire can be improved. It will contribute to the improvement of comfort.

  The block copolymer is a block copolymer comprising a styrene polymer block (A) and an isobutylene polymer block (B).

  The styrenic polymer block (A) is a polymer block containing styrene as a monomer, and is a monomer block other than styrene as long as the effect of the present invention is not impaired as long as it is mainly composed of styrene. It may contain. The content of monomer components other than styrene is preferably 30% by weight or less as a proportion of the block (A). The monomer component other than styrene is not particularly limited as long as it is a monomer component capable of cationic polymerization, but aromatic vinyls other than styrene, aliphatic olefins, dienes, vinyl ethers, pinene and Monomers such as its analogs can be exemplified. These may be used alone or in combination of two or more.

  The isobutylene-based polymer block (B) is a polymer block having isobutylene as a monomer, and if it is mainly composed of isobutylene, a monomer component other than isobutylene is used as long as the effects of the present invention are not impaired. It may contain. The content of monomer components other than isobutylene is preferably 30% by weight or less as a proportion of the block (B). Examples of monomer components other than isobutylene include aliphatic olefins other than isobutylene, aromatic vinyls, dienes, and vinyl ethers, and are not particularly limited.

  The structure of the block copolymer is particularly limited, such as a block copolymer having a linear, branched, or star structure, a diblock copolymer, a triblock copolymer, or a multiblock copolymer. However, preferably, a diblock copolymer having a structure (AB) of a styrene polymer block (A) -isobutylene polymer block (B), and a styrene polymer block (A) -isobutylene system A triblock copolymer having a structure (ABA) of a polymer block (B) -styrene polymer block (A), particularly a fully saturated styrene-isobutylene-containing no diene component Styrene triblock copolymers are preferred. The block copolymer may have various substituents such as an alkenyl group at the terminal.

  The ratio of the styrene polymer block (A) to the isobutylene polymer block (B) is not particularly limited, but from the balance between physical properties and processability, (A) is 2 to 60% by weight, and (B) is It is particularly preferably 98 to 40% by weight, (A) 5 to 40% by weight, and (B) 95 to 60% by weight.

The styrene content of the block copolymer is not particularly limited, but is preferably 20 to 40% by weight. Here, the styrene content is a value calculated by the integration ratio of the ¹ HNMR spectrum. The number average molecular weight of the block copolymer is not particularly limited, but generally about 10,000 to 300,000 is used.

  The number average molecular weight of the block copolymer is not particularly limited, but is preferably 3,000 to 500,000 from the viewpoint of physical properties and processability. If the molecular weight is less than 3,000, the rubber composition is not sufficiently hard, and if it exceeds 500,000, the processability is lowered.

  Moreover, it does not specifically limit as a manufacturing method of the said block copolymer, Although a well-known polymerization method can be used, For example, commercial products (SIBSTAR-072T, 103T etc.) marketed by Kaneka Corporation. Etc. can be used.

  The blending amount of the block copolymer is used in the range of 3 to 30 parts by weight in 100 parts by weight of the total polymer components of the IIR and / or X-IIR, the diene rubber and the block copolymer.

  If the blended amount of the block copolymer is less than 3 parts by weight, an increase in rubber hardness and a decrease in impact resilience cannot be obtained, and the balance between handling stability and riding comfort is not balanced, while if it exceeds 30 parts by weight, resilience is achieved. The elasticity decreases too much and heat generation increases and durability such as peeling of the liner joint decreases.

  In the rubber composition for an inner liner according to the present invention, the content of sulfur as a crosslinking agent is less than 1 part by weight with respect to 100 parts by weight of the polymer component. When the sulfur content is 1 part by weight or more, the synergistic action with the block copolymer is strong, the rubber is easily cured, the inner liner is easily cracked, and the durability is lowered.

  The vulcanized rubber (vulcanized at 160 ° C. × 25 minutes) of the rubber composition for the inner liner has a spring type A hardness of 55 to 70 measured at 23 ° C. according to JIS K6253 and conforms to JIS K6255. The rebound resilience measured at 23 ° C. is preferably 10 to 20%. If the hardness is less than 55, the rigidity is inferior and the steering stability cannot be satisfied. If the hardness is more than 70, the rigidity is obtained, but the liner joint is liable to crack and the durability is lowered. If the impact resilience is less than 10%, the rubber tends to generate heat and the liner joint is easily peeled off. If it exceeds 20%, the damping effect cannot be obtained and the riding comfort is not improved.

  In addition to the rubber component, the styrene-isobutylene block copolymer, and sulfur, the rubber composition according to the present invention includes a compounding agent usually used in a rubber composition for an inner liner, such as carbon black, silica, and carbonic acid. Reinforcing agents such as calcium, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, alumina, clay, talc, magnesium oxide, plasticizers such as oil, stearic acid, petroleum resins, zinc white, crosslinking agents other than sulfur, crosslinking aids An agent, a vulcanization accelerator, and the like can be appropriately blended.

There is no restriction | limiting in particular as a kind of said carbon black, For example, HAF, ISAF, SAF, GPF, FEF etc. are mentioned. Among them, GPF grade carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 20 to 80 m ² / g, preferably 25 to 50 m ² / g is desirable. The compounding amount of carbon black is preferably 20 to 60 parts by weight with respect to 100 parts by weight of the rubber component. When the blending amount of carbon black is less than 20 parts by weight, the reinforcing effect tends to be small, and when it exceeds 60 parts by weight, the rubber hardness increases too much due to the synergistic effect of the rubber hardness increasing effect of the block copolymer. It tends to occur, and the workability during kneading and rolling tends to decrease.

  The rubber composition can be obtained by kneading using a normal rubber kneading apparatus such as a roll, a Banbury mixer, a kneader or the like.

  The method of processing the rubber composition into an inner liner is not particularly limited, but is usually rolled into a sheet having a predetermined thickness by a calender device having 2 to 4 rolls for rubber rolling. It is placed on the tire inner surface and vulcanized.

  EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to only these examples. The rubber components and compounding agents used in Examples and Comparative Examples are the following materials.

[material]
Bromobutyl rubber: manufactured by Bayer, Bromobutyl 2030
・ Natural rubber: Made in Thailand, RSS # 3
Styrene butadiene rubber (SBR): manufactured by JSR Corporation, SBR1502
Styrene-isobutylene block copolymer (SIBS): manufactured by Kaneka Corporation, SIBSTAR-072T (styrene content = 23% by weight)
・ Carbon black GPF: manufactured by Tokai Carbon Co., Ltd., Seast V
Aroma oil: JOMO Process X-140, manufactured by Japan Energy Co., Ltd.
・ Petroleum resin: Fujikosan Co., Ltd., Fukkor Resin 120
・ Stearic acid: Lunac S-25, manufactured by Kao Corporation
・ Vulcanization accelerator NS: Sanshin Chemical Industry Co., Ltd., Sunseller NS-G
・ Vulcanization accelerator DM: Sanshin Chemical Industry Co., Ltd., Sunseller DM-G
・ Sulfur: Tsurumi Chemical Co., Ltd., powdered sulfur ・ Zinc flower: Sakai Chemical Industry Co., Ltd., 2 types of zinc oxide

  According to each compounding prescription (part by weight) shown in Table 1, compounding agents other than sulfur, zinc white and vulcanization accelerator, rubber component and SIBS were kneaded by a conventional method with a Banbury mixer to prepare a master batch. Thereafter, sulfur, zinc white, and a vulcanization accelerator were blended into the masterbatch and kneaded again with a Banbury mixer to obtain each unvulcanized rubber composition.

  Each sample was prepared by vulcanizing each rubber composition obtained at 160 ° C. for 25 minutes, hardness (spring type A according to JIS K6253, measurement temperature 23 ° C.), rebound resilience (measurement temperature according to JIS K6255) 23 ° C.) and air permeability.

  Next, these rubber compositions were rolled by a reverse L-shaped calendar to produce an inner liner having a thickness of 0.5 mm. A radial tire having a general structure of size 215 / 45R17 using this inner liner was manufactured, and steering stability, riding comfort and durability were evaluated. Each test method is as follows. The results are shown in Table 1.

[Air permeability]
Using the rubber composition described above, a rubber sheet having a thickness of 1 mm was prepared by press vulcanization at 160 ° C. for 25 minutes under a pressure of 50 kgf / cm ² , and conformed to the differential pressure method (A method) described in JIS K7126. The air permeability ratio was measured. The comparative example 1 is indicated by an index indicating 100, and the smaller the value, the lower the air permeability and the better.

[Steering stability]
Four radial tires are adjusted to 200 kPa in air pressure using JIS standard standard rims, mounted on “GOLF V”, and on the dry road surface for driving stability evaluation of the applicant's own tire test course. The steering stability of the car was sensorially evaluated by three test drivers. “± 0” on the basis of Comparative Example 1 is slightly better than Comparative Example 1 (the driver can see a significant difference in steering stability, but the level that the passenger does not understand) is “+1”, which is good (passenger) ) Is slightly inferior (a level that can be understood by the driver but not understood by the passenger) is -1 and inferior (a level that the passenger can understand) It is shown in the table as “-2”.

[Ride comfort]
Four radial tires were adjusted to a pressure of 200 kPa using a JIS standard standard rim, mounted on “GOLF V”, and on the dry road for ride comfort evaluation of the applicant's own tire test course. Ride comfort was sensorially evaluated by three test drivers. “± 0” on the basis of Comparative Example 1 is slightly better than Comparative Example 1 (the driver can see a significant difference in steering stability, but the level that the passenger does not understand) is “+1”, which is good (passenger) ) Is slightly inferior (a level that can be understood by the driver but not understood by the passenger) is -1 and inferior (a level that the passenger can understand) It is shown in the table as “-2”.

[durability]
The drum running test of each radial tire was carried out under the tire durability conditions specified in FMVSS109, and the tires were run until failure occurred. Indicates the distance traveled until the failure occurred. If there was no failure at the time of 7000 km travel, the travel test was terminated and passed as N.P. F (No. Failure).

  The tires of Examples 1 and 2 according to the present invention have improved handling stability and ride comfort compared to Comparative Example 1 with a small amount of SIBS, and have excellent durability and good air permeability. it can. On the other hand, Comparative Example 2 in which the amount of SIBS is too large improves the handling stability and ride comfort compared with Comparative Example 1, but the liner joint peels off at the time of running 3,000 km due to heat generation in the durability test, Further, in Comparative Example 3 in which the amount of carbon black was increased, the rubber hardness increased and a liner crack occurred when the durability test was run at 4,500 km. Further, in Comparative Example 4 in which the amount of oil was increased in order to suppress an increase in rubber hardness, the air permeability was deteriorated and the riding comfort was improved, but the steering stability was lowered and the tire performance was unbalanced. In Comparative Example 5 in which the sulfur amount was a large amount of 1.2 parts by weight, the rubber was hardened during running in the durability test, and the inner liner crack occurred at the running time of 5,500 km.

  The rubber composition for an inner liner of the present invention can be used for pneumatic tires of various uses and sizes, and is particularly suitable for a tire for a passenger car having a high demand for both handling stability and riding comfort.

It is a half sectional view of the pneumatic tire of an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire 2 ... Tread part 3 ... Side wall part 4 ... Bead part 5 ... Bead core 6 ... Carcass 7 ... Belt 8 ... Cap ply 10 ... Inner liner

Claims (3)

40 parts by weight or more of butyl rubber and / or halogenated butyl rubber, 3 to 30 parts by weight of a block copolymer composed of a styrene polymer block and an isobutylene polymer block, and 100 parts by weight of a polymer component composed of a diene rubber , Containing 20-60 parts by weight of carbon black and less than 1 part by weight of sulfur ,
A rubber composition for an inner liner, having a JIS-A hardness measured at 23 ° C. of 55 to 70 and a JIS-rebound resilience measured at 23 ° C. of 10 to 20% . The rubber for an inner liner according to claim 1, wherein the block copolymer is a triblock copolymer having a structure of a styrene polymer block-isobutylene polymer block-styrene polymer block. Composition. A pneumatic tire, wherein the rubber composition for an inner liner according to claim 1 or 2 is used for an inner liner of a tire.

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