JP2010031118A - Rubber composition for member for proofing air permeation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a member for proofing air permeation allowing balance of enhancement of fuel economy due to lightweighting with air permeation proofness and durability. <P>SOLUTION: The rubber composition, in which an organic filler having an aspect ratio of 4-100 and a short fibrous shape is blended in an amount of 3-15 parts by weight based on 100 parts by weight of diene rubber containing a butyl rubber as a principal constituent, is characterized in that the organic filler includes a thermoplastic elastomer composition in which a thermoplastic resin is blended with an elastomer, and the thermoplastic resin forms a continuous phase and the elastomer forms a dispersed phase, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for an air permeation prevention member, and more specifically, relates to a rubber composition for an air permeation prevention member that can achieve both low fuel consumption due to weight reduction, air permeation prevention and durability.

  As a method for improving the fuel efficiency of a pneumatic tire, it is conceivable to reduce the thickness by reducing the thickness of a rubber member such as an inner liner. However, when the thickness of the air permeation preventive member such as the inner liner is reduced, there is a problem that air easily leaks and the air permeation preventive performance is deteriorated and the durability is lowered.

  As a countermeasure, Patent Document 1 discloses a rubber composition for an inner liner that has improved air permeation preventive properties by blending a thermoplastic resin with butyl rubber, and by using this, the gauge thickness of the inner liner is reduced. Has proposed. However, the rubber composition for the inner liner has a drawback that the butyl rubber and the thermoplastic resin have a large difference in elastic modulus, so that the rubber composition is easily damaged due to repeated bending load, and the tire durability is inferior. There was a problem.

Therefore, it has been a very difficult task to achieve both low fuel consumption by reducing the weight of the air permeation preventive member, air permeation preventive properties and durability.
JP-A-7-70372

  An object of the present invention is to provide a rubber composition for an air permeation preventive member that can achieve both low fuel consumption due to weight reduction and air permeation preventive properties and durability.

  The rubber composition for an air permeation preventive member according to the present invention that achieves the above object comprises 3 short fiber organic fillers having an aspect ratio of 4 to 100 with respect to 100 parts by weight of a diene rubber containing a butyl rubber as a main component. A rubber composition containing -15 parts by weight, wherein the organic filler comprises a thermoplastic elastomer composition in which a thermoplastic resin is used as a continuous phase and an elastomer is blended as a dispersed phase.

  The organic filler may be formed in a scale shape. The organic filler may be blended after being coated with an adhesive. The content of butyl rubber in the diene rubber is preferably 60% by weight or more.

  This rubber composition for an air permeation preventive member is suitable for constituting an inner liner of a tubeless pneumatic tire or a tube of a pneumatic tire with a tube.

  According to the rubber composition for an air permeation preventive member of the present invention, 3 to 15 weights of short fiber organic filler having an aspect ratio of 4 to 100 with respect to 100 weight parts of diene rubber containing butyl rubber as a main component. This organic filler is formed from a thermoplastic elastomer composition obtained by blending a thermoplastic resin and an elastomer so that the thermoplastic resin is a continuous phase and the elastomer is a dispersed phase. The air permeation preventive property of the rubber composition is improved, and excellent air permeation preventive property is ensured even if the thickness of the air permeation preventive portion such as an inner liner or a tube is reduced. At the same time, because the difference in mechanical properties such as elastic modulus between diene rubber and organic filler is small, the tire durability is not reduced, so the tire weight is reduced while maintaining air permeation prevention and durability. And fuel consumption can be improved.

  In the rubber composition for an air permeation preventive member of the present invention, the rubber component contains butyl rubber as a main component. The butyl rubber is butyl rubber or halogenated butyl rubber. As the halogenated butyl rubber, brominated butyl rubber and chlorinated butyl rubber are preferable. The butyl rubber content in the diene rubber is preferably 60% by weight or more, more preferably 65 to 100% by weight. If the butyl rubber is less than 60% by weight, sufficient air permeation preventing performance cannot be obtained.

  Rubber components other than butyl rubber are diene rubber. The diene rubber may be any rubber that can be blended with the air permeation preventing member rubber such as an inner liner, and examples thereof include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, and acrylonitrile-butadiene rubber. Of these, natural rubber, isoprene rubber and the like are preferable. These diene rubbers may be used alone or in combination of a plurality of types.

  In the rubber composition for an air permeation preventive member of the present invention, a short fiber organic filler composed of a thermoplastic elastomer composition is blended with the above-described diene rubber containing butyl rubber as a main component. By blending the short fibrous organic filler, the air permeation preventive property can be improved without deteriorating the durability of the rubber composition. For this reason, even if the thickness of the air permeation preventive member is reduced, the air permeation preventive property can be ensured without deteriorating durability against a bending load repeatedly applied during tire traveling.

  In the present invention, the air permeation preventive property is improved by configuring the organic filler in a short fiber shape. The aspect ratio of the organic filler is 4 to 100, preferably 20 to 60. When the aspect ratio of the organic filler is less than 4, the air permeation preventing property cannot be sufficiently improved. On the other hand, if the aspect ratio of the organic filler exceeds 100, the elongation characteristics may be deteriorated and the durability may be adversely affected. The aspect ratio of the organic filler is the ratio (L / d) of the length (L) of the short fiber to the diameter (d) of the short fiber. The diameter (d) is the diameter when the cross-sectional shape of the short fiber is circular, and the equivalent diameter when the cross-sectional shape of the short fiber is other than circular. The equivalent diameter refers to the diameter of a circle having the same area as the cross-sectional area perpendicular to the longitudinal direction of the short fibers.

  The diameter of the short fibrous organic filler is not particularly limited, but is preferably 1 to 50 μm, more preferably 10 to 30 μm. When the diameter of the organic filler is less than 1 μm, the air permeation prevention property cannot be sufficiently improved. Further, if the diameter of the organic filler exceeds 50 μm, the physical properties of the rubber composition may be adversely affected.

  The compounding amount of the organic filler is 3 to 15 parts by weight, preferably 5 to 15 parts by weight with respect to 100 parts by weight of the diene rubber. When the blending amount of the organic filler is less than 3 parts by weight, the air permeation preventive property of the rubber composition cannot be sufficiently improved. Moreover, when the compounding quantity of an organic filler exceeds 15 weight part, since the tensile characteristic of a rubber composition will fall, high-speed durability will deteriorate.

  The short fiber organic filler can be formed by melt spinning a thermoplastic elastomer composition to form long fibers, and then chopping the obtained long fibers. Short fibers having a desired aspect ratio can be obtained by adjusting the fiber diameter and chopping length during spinning.

  Further, the organic filler can be formed in a scale shape. Here, the scale-like organic filler means a flat fiber-like organic filler that is compressed and flattened in a direction perpendicular to the longitudinal direction. The scaly organic filler can be formed by melt spinning a thermoplastic elastomer composition to form long fibers, flattening the long fibers, and then chopping the fibers. Alternatively, the rubber composition for an air permeation preventive member blended with a short fiber organic filler is extruded, and the resulting extruded molded body is rolled to remove the short fiber organic filler in the extruded molded body. It may be flattened into a shape. By flattening the organic filler into a scaly shape, the air permeation preventing performance of the rubber composition can be further improved.

  In the present invention, the organic filler comprising the thermoplastic elastomer composition may be coated with an adhesive in advance before blending with the rubber composition. As a result, the interface between the diene rubber and the organic filler can be strengthened, and the fatigue resistance of the rubber composition can be further increased. Examples of the adhesive include an epoxy-modified styrene-butadiene-styrene block copolymer.

  The thermoplastic elastomer composition used in the present invention is constituted by blending a thermoplastic resin and an elastomer. In the thermoplastic elastomer composition, the thermoplastic resin forms a continuous phase (matrix), and the elastomer forms a dispersed phase (domain). Thus, by using a thermoplastic resin as a continuous phase and an elastomer as a dispersed phase, the molding processability can be improved and the reinforcing effect on the rubber composition can be enhanced. The dispersion diameter of the elastomer in the thermoplastic elastomer composition is not particularly limited, but is preferably 1 to 50 μm, more preferably 10 to 30 μm. If the dispersion diameter of the elastomer is smaller than 1 μm, the air permeation preventing property cannot be sufficiently improved. On the other hand, if the dispersion diameter of the elastomer is larger than 50 μm, the flexibility of the thermoplastic elastomer composition cannot be optimized and the tire durability may be adversely affected.

  In the thermoplastic elastomer composition, the composition ratio between the specific thermoplastic resin and the elastomer is not particularly limited, but the weight ratio of the thermoplastic resin / elastomer is preferably 30/70 to 70/30. Preferably it is 35 / 65-55 / 45. By setting the weight ratio of the thermoplastic resin / elastomer within such a range, the difference in elastic modulus between the organic filler made of the thermoplastic elastomer composition and the diene rubber is reduced, and the durability is improved. The reinforcement effect with respect to the system rubber can be increased.

  Examples of the thermoplastic resin constituting the thermoplastic elastomer composition forming the organic filler include, for example, polyamide resins [eg, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11 ), Nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6/66 copolymer (N6 / 66), nylon 6/66/610 copolymer (N6 / 66/610), Nylon MXD6 (MXD6), nylon 6T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer] and their N-alkoxyalkylated products, for example, methoxymethylated nylon 6 , Methoxymethylated nylon 6/610 copolymer, methoxymethyl nylon 612 Products, polyester resins [for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET / PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal Polyesters, aromatic polyesters such as polyoxyalkylene diimide diacid / polybutylene terephthalate copolymer], polynitrile resins (for example, polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), ( (Meth) acrylonitrile / styrene copolymer, (meth) acrylonitrile / styrene / butadiene copolymer], polymethacrylate resin [for example, polymethyl methacrylate (PMMA), polymethacrylate ], Polyvinyl resins [for example, vinyl acetate, polyvinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PDVC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer Polymer, vinylidene chloride / methyl acrylate copolymer, vinylidene chloride / acrylonitrile copolymer], cellulose resin [eg, cellulose acetate, cellulose acetate butyrate], fluorine resin [eg, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer], an imide resin [for example, aromatic polyimide (PI)] and the like can be preferably used.

  Examples of the elastomer constituting the thermoplastic elastomer composition forming the organic filler include diene rubbers and hydrogenated products thereof (for example, natural rubber (NR), isoprene rubber (IR), epoxidized natural rubber, styrene butadiene) Rubber (SBR), butadiene rubber (BR, high cis BR and low cis BR), nitrile rubber (NBR), hydrogenated NBR, hydrogenated SBR], olefin rubber [for example, ethylene propylene rubber (EPDM, EPM), malee Acid-modified ethylene propylene rubber (M-EPM), butyl rubber (IIR), isobutylene and aromatic vinyl or diene monomer copolymer, acrylic rubber (ACM), ionomer], halogen-containing rubber [for example, Br-IIR, CI- IIR, bromide of isobutylene paramethylstyrene copolymer (B -IPMS), chloroprene rubber (CR), hydrin rubber (CHR), chlorosulfonated polyethylene rubber (CSM), chlorinated polyethylene rubber (CM), maleic acid modified chlorinated polyethylene rubber (M-CM)], silicone rubber [for example , Methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (for example, polysulfide rubber), fluorine rubber (for example, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber) , Fluorine-containing silicon rubber, fluorine-containing phosphazene rubber), thermoplastic elastomers (for example, styrene elastomer, olefin elastomer, ester elastomer, urethane elastomer, polyamide elastomer) It can be preferably used mer] and the like.

  A method for producing a thermoplastic elastomer composition is such that a thermoplastic resin and an elastomer are previously melt-kneaded with a twin-screw kneading extruder or the like, and the elastomer is used as a dispersed phase (domain) in the thermoplastic resin forming a continuous phase (matrix). By dispersing. When the elastomer is vulcanized, a vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer. Further, various compounding agents (excluding the vulcanizing agent) for the thermoplastic resin or elastomer may be added during the kneading, but it is preferable to mix them in advance before kneading. The kneading machine used for kneading the thermoplastic resin and the elastomer is not particularly limited, and a screw extruder, a kneader, a Banbury mixer, a biaxial kneading extruder, or the like can be used. Among them, it is preferable to use a twin-screw kneading extruder for kneading the thermoplastic resin and the elastomer and for dynamic vulcanization of the elastomer.

The rubber composition for an air permeation preventive member of the present invention can improve the reinforcing performance of the rubber composition by blending carbon black. Although the property of carbon black is not particularly limited, the nitrogen adsorption specific surface area is preferably 20 to 90 m ² / g, more preferably 25 to 50 m ² / g. When N ₂ SA of carbon black is less than 20 m ² / g, the reinforcing effect is insufficient. If N ₂ SA is more than ^90m 2 / g, the rolling resistance and workability is deteriorated.

  The compounding amount of carbon black is preferably 30 to 90 parts by weight, and more preferably 40 to 60 parts by weight with respect to 100 parts by weight of the diene rubber. When the blending amount of carbon black is less than 30 parts by weight, the reinforcing effect of the rubber composition becomes insufficient. If the blending amount of carbon black exceeds 90 parts by weight, the rolling resistance is deteriorated and the fuel efficiency cannot be improved.

  In the rubber composition of the present invention, other fillers such as silica, clay, calcium carbonate, talc, mica, aluminum hydroxide and magnesium carbonate can be blended. In addition, various additives commonly used in rubber compositions such as vulcanization or cross-linking agents, anti-aging agents, plasticizers, softeners, processing aids, coupling agents, and the like can be blended. Can be kneaded by a general method to obtain a rubber composition, which can be used for vulcanization or crosslinking. The blending amount of these additives can be a conventional general blending amount as long as the object of the present invention is not violated.

  The rubber composition for an air permeation prevention member obtained by the present invention is preferably used for an air permeation prevention member such as an inner liner and a tube of a pneumatic tire. The tubeless pneumatic tire provided with the inner liner made of the rubber composition for an air permeation preventive member of the present invention or the pneumatic tire with a tube provided with a tube made of the rubber composition for the air permeation preventive member has an air permeation preventive property and durability. The fuel efficiency can be improved while maintaining the characteristics.

  Hereinafter, the present invention will be described with reference to examples, but the scope of the present invention is not limited thereby.

Preparation of thermoplastic elastomer composition and molding of organic filler 40 parts by weight of nylon 6/66 copolymer (Alamine CM6001 manufactured by Toray Industries Inc.), brominated product of isobutylene paramethylstyrene copolymer (MDX90- manufactured by ExxonMobil Chemical Co., Ltd.) 10) 60 parts by weight, zinc white (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.), 1 part by weight, and 1 part by weight of stearic acid (beef stearic acid manufactured by NOF Corporation) were melt-kneaded and pelletized. A thermoplastic elastomer composition was prepared.

  The obtained thermoplastic elastomer composition was melt-spun to form a long fiber having a diameter of 15 μm. By cutting the long fibers into a predetermined length, the short fiber-like organic filler 1 and organic filler 2 were obtained. The obtained organic filler 1 had an aspect ratio of 54, and the organic filler 2 had an aspect ratio of 127.

Examples 1-4, Comparative Examples 1-5
Nine kinds of rubber compositions (Examples 1 to 4 and Comparative Examples 1 to 5) having the composition shown in Table 1 were weighed with respect to the composition components except for sulfur, vulcanization accelerator, and vulcanization retarder, respectively. The mixture was kneaded for 4 minutes with a 7 L Banbury mixer, and when reaching 155 ± 5 ° C., the master batch was discharged and cooled to room temperature. This master batch was subjected to a 1.7 L Banbury mixer, and sulfur, a vulcanization accelerator and a vulcanization retarder were added and mixed to prepare a rubber composition for an air permeation prevention member.

  Nine kinds of obtained rubber compositions (Examples 1 to 4 and Comparative Examples 1 to 5) were used to form unvulcanized rubber sheets having a predetermined thickness. The obtained unvulcanized rubber sheet was vulcanized in a mold having a predetermined shape at 170 ° C. for 10 minutes, and the elastic modulus and air permeability coefficient of the vulcanized rubber sheet were measured by the following test methods.

  In addition, tube-less pneumatic tires having a tire size of 195 / 65R15 each comprising an inner liner made of nine types of unvulcanized rubber sheets (thickness: 1 mm) were vulcanized. The high-speed durability of the obtained nine types of pneumatic tires was evaluated by the following test method.

Elastic modulus The elastic modulus of the vulcanized rubber sheet obtained was measured at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, and the storage elastic modulus at a temperature of 20 ° C. E 'was measured. The obtained results are shown in Table 1 with an index with the value of Comparative Example 1 as 100. A larger index means a higher elastic modulus.

Air Permeability Coefficient Using the vulcanized test piece of the obtained rubber composition, the test gas is equivalent to air in accordance with Method A (differential pressure type) of JIS K7126 “Gas Permeability Test Method for Plastic Film and Sheet”. Nitrogen: oxygen = 8: 2), and the air permeability coefficient was measured at a test temperature of 30 ° C. The obtained results are shown in Table 1 as an index with Comparative Example 1 as 100. A smaller index means a smaller air permeability coefficient and better air permeation prevention performance.

High speed durability The obtained pneumatic tire is assembled on a rim (15 × 6J) and mounted on a drum testing machine having a drum diameter of 1707 mm. After performing a high speed durability test in accordance with JIS D4230, a speed of 30 The speed was increased by 10 km / h every minute, and the speed when the tire broke was measured. The obtained results are shown in Table 1 as an index with Comparative Example 1 as 100. Higher index means higher speed durability.

In addition, the kind of raw material used in Table 1 is shown below.
IIR: Brominated butyl rubber, Bromobutyl 2255 manufactured by Nippon Butyl
NR: natural rubber, RSS # 3
Organic fillers 1 and 2: Short fiber organic filler obtained as described above Organic filler 3: Organic fiber made of nylon resin, fiber diameter 0.3 μm, aspect ratio 100, Daiwa SHP-HA1060 manufactured by Daiwa Chemical Industry Co., Ltd.
CB: Carbon black, Niteron # 55S GPF (Nitrogen Carbon Specific Surface Area = 28 m ² / g) manufactured by Nippon Kayaku Carbon
Zinc Hana: Zinc Oxide Type 3 resin manufactured by Shodo Chemical Industry Co., Ltd .: Aromatic petroleum resin, FR-120 manufactured by Air Water
Oil: Extract No. 4 manufactured by Showa Shell Sekiyu KK Sulfur: Oil processing sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Sunseller DM-PO manufactured by Sanshin Chemical Co., Ltd.
Vulcanization retarder: Toray Fine Chemicals retarder CTP

Examples 2 and 5
Unvulcanized rubber sheets having different thicknesses were produced by changing the production conditions when extruding an unvulcanized rubber sheet from the same rubber composition as in Example 2 described above. A tubeless pneumatic tire having a tire size of 195 / 65R15, in which an inner liner was constituted by the obtained unvulcanized rubber sheet, was vulcanized and molded under the same conditions as in Example 2 described above. The weight and air permeation prevention performance of the obtained pneumatic tires (Examples 2 and 5) were evaluated by the following test methods. Moreover, the high-speed durability was measured by the test method described above, and the obtained results are shown in Table 2 as an index with Example 2 as 100.

Tire Weight The weights of the pneumatic tires of Examples 2 and 5 were measured, and the obtained results are shown in Table 2 as an index with Example 2 as 100. The smaller this index is, the lighter it is.

Air permeation prevention performance The pneumatic tires of Examples 2 and 5 were mounted on a rim (15 × 6J), and the internal pressure was changed every 4 days while being allowed to stand for 3 months at an initial pressure of 250 kPa, a room temperature of 21 ° C. and no load. It was measured. As the initial pressure P0 (kPa), the measured pressure Pt (kPa), and the elapsed time t (days), the regression coefficient α was calculated by the following equation (1).
Pt / P0 = exp (−αt) (1)
From the obtained regression coefficient α, t = 30 (day), and the pressure decrease rate β (% / month) per month was calculated by the following formula (2).
β = (1-exp (−αt)) × 100 (2)
The obtained β value was an index with the value of Example 2 as 100, and the air permeation preventing performance is shown in Table 2. The smaller this index is, the better the air permeation preventing performance is.

Claims (6)

  A rubber composition in which 3 to 15 parts by weight of a short fiber organic filler having an aspect ratio of 4 to 100 is blended with 100 parts by weight of a diene rubber containing butyl rubber as a main component, and the organic filler is heated A rubber composition for an air permeation prevention member comprising a thermoplastic elastomer composition in which a plastic resin is used as a continuous phase and an elastomer is blended as a dispersed phase.   The rubber composition for an air permeation preventive member according to claim 1, wherein the organic filler is formed in a scale shape.   The rubber composition for an air permeation preventive member according to claim 1 or 2, wherein the organic filler is coated with an adhesive.   4. The rubber composition for an air permeation prevention member according to claim 1, wherein the diene rubber has a butyl rubber content of 60% by weight or more.   The tubeless pneumatic tire which comprised the inner liner with the rubber composition for air permeation prevention members in any one of Claims 1-4.   The pneumatic tire with a tube which comprised the tube with the rubber composition for air permeation | blocking prevention members in any one of Claims 1-4.