JP5172215B2 - Rubber composition for inner liner and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition used for a tire, and more particularly to a rubber composition for an inner liner of a pneumatic tire. Moreover, this invention relates to a pneumatic tire provided with the inner liner rubber which consists of the said rubber composition.

  Conventionally, in a pneumatic tire, particularly a tubeless tire, an inner liner rubber made of rubber having a low air permeability is formed so as to form a tire cavity surface for the purpose of maintaining the tire internal pressure. As the inner liner rubber, butyl rubber, halogenated butyl rubber or the like having excellent air permeation resistance is used, and carbon black for improving the flex crack growth resistance has been blended. Synthetic rubbers such as butyl rubber and halogenated butyl rubber, and carbon black are all derived from petroleum resources.

  However, in recent years, environmental issues have become more important and regulations on carbon dioxide emissions have been strengthened. In addition, since the existing amount of petroleum is limited, the use of raw materials derived from petroleum resources is limited. This environment-oriented orientation is no exception in the tire field, and the development of rubber compositions for inner liners that replaces some or all of the petroleum-derived raw materials currently used with raw materials derived from non-petroleum resources. Is required.

  Patent Document 1 discloses an eco-tire that uses natural rubber, epoxidized natural rubber, silica, or the like as a raw material derived from resources other than petroleum, and has reduced dependence on petroleum resources. However, the air permeation resistance and the bending crack growth resistance are not considered, and there is room for improvement.

  Patent Document 2 discloses a rubber obtained by dividing and kneading a specific amount of zinc oxide into a rubber component containing a halogenated butyl rubber and / or a halide of a copolymer of isobutylene and p-methylstyrene. A composition and an inner liner made of the rubber composition are described, whereby a rubber gauge such as an inner liner can be kept thin without lowering the viscosity, and weight reduction of a tire can be achieved. It is shown. However, no consideration is given to achieving both air permeation resistance and flex crack growth resistance of the inner liner rubber.

Thus, in the rubber composition in which the raw material derived from petroleum resources is replaced with the raw material derived from resources other than petroleum, the rubber having excellent air permeation resistance and bending crack growth resistance that can be sufficiently used for the inner liner rubber. The present condition is that the composition is not obtained.
JP 2003-63206 A JP 2005-264114 A

  The present invention has been made in order to solve the above-mentioned problems, and the purpose of the present invention is to sufficiently consider resource saving and environmental protection by increasing the content ratio of materials made of resources other than petroleum. In addition, a rubber composition for an inner liner exhibiting characteristics suitable for the inner liner rubber, in particular, excellent air permeation resistance and bending crack growth resistance, and a pneumatic tire comprising the inner liner rubber made of the rubber composition Is to provide.

  The present invention is a rubber composition for an inner liner containing 0.1 to 10 parts by mass of zinc oxide particles having an average particle diameter of 200 nm or less with respect to 100 parts by mass of a rubber component. Here, the rubber component preferably contains epoxidized natural rubber (ENR).

  Moreover, it is preferable that the rubber composition for inner liners of this invention further contains 30-50 mass parts silica with respect to 100 mass parts of rubber components.

  Furthermore, this invention provides a pneumatic tire provided with the inner liner rubber which consists of said rubber composition.

  According to the present invention, by increasing the content ratio of materials made from non-petroleum resources, consideration for resource saving and environmental protection is sufficient, as well as excellent air permeation resistance and flex crack growth resistance. The rubber composition for an inner liner shown and a pneumatic tire provided with the inner liner rubber which consists of the said rubber composition are provided.

  The rubber composition for an inner liner of the present invention contains 0.1 to 10 parts by mass of zinc oxide particles having an average particle diameter of 200 nm or less with respect to 100 parts by mass of the rubber component.

<Rubber component>
In the rubber composition for an inner liner of the present invention, as a rubber component, natural rubber (NR), epoxidized natural rubber (ENR), deproteinized natural rubber (DPNR) and other natural rubbers, diene synthetic rubbers and the like Is blended.

  The rubber composition for an inner liner of the present invention preferably contains epoxidized natural rubber (ENR) as a rubber component. Epoxidized natural rubber (ENR) is obtained by epoxidizing an unsaturated double bond of natural rubber (NR), and its molecular cohesion is increased by epoxy groups that are polar groups. Therefore, the glass transition temperature (Tg) is higher than that of natural rubber (NR), and the mechanical strength, wear resistance, and air permeation resistance are excellent. In particular, when silica is compounded in the rubber composition, due to the reaction between the silanol group on the silica surface and the epoxy group of the epoxidized natural rubber, the same degree as when carbon black is compounded in the rubber composition. The mechanical strength and wear resistance can be obtained.

  As the epoxidized natural rubber (ENR), a commercially available product may be used, or an epoxidized natural rubber (NR) may be used. The method for epoxidizing NR is not particularly limited, and examples thereof include a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, and a peracid method. Examples of the peracid method include a method of reacting an organic peracid such as peracetic acid or formic acid with natural rubber.

  The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 5 mol% or more, and more preferably 10 mol% or more. When the epoxidation rate of ENR is less than 5 mol%, gas retention tends to be poor. The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 60 mol% or less, and more preferably 55 mol% or less. When the epoxidation rate of ENR exceeds 60 mol%, the heat durability tends to be poor. The epoxidation rate of the epoxidized natural rubber (ENR) means (number of epoxidized double bonds) / (number of double bonds before epoxidation) × 100 (%).

  When the rubber composition for an inner liner of the present invention contains epoxidized natural rubber (ENR), the content of ENR in the rubber component can be, for example, about 5% by mass or more. However, when natural rubber other than NR is contained as a rubber component, it may be less than this. On the other hand, when the rubber composition for an inner liner contains only ENR as a natural rubber component, the ENR in the rubber component is preferably 90% by mass or more, and more preferably 95% by mass or more. If the ENR content is less than 90% by mass, the ratio of non-petroleum resources in the rubber composition will be reduced.

  The content of ENR in the natural rubber component blended in the rubber composition is preferably higher, for example, 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more. By increasing the ratio of ENR in the natural rubber component, the gas retention can be further increased. Moreover, the rubber composition for an inner liner of the present invention may contain only ENR as a rubber component. Thereby, gas retainability can further be improved.

  The rubber composition for an inner liner of the present invention may contain natural rubber (NR) as a rubber component. As the natural rubber (NR), those conventionally used in the rubber industry can be used, and examples thereof include natural rubber of grades such as RSS # 3, TSR20, SIR20 and the like.

  When the rubber composition for an inner liner of the present invention contains natural rubber (NR), the content of NR in the rubber component is not particularly limited, but can be, for example, about 5% by mass or more. However, when natural rubber other than NR is contained as a rubber component, it may be less than this. Moreover, when natural rubber other than NR is contained as a rubber component, NR may not be contained. On the other hand, when the rubber composition for an inner liner contains only NR as a natural rubber component, the NR in the rubber component is preferably 90% by mass or more, and more preferably 95% by mass or more. When the content of NR is less than 90% by mass, the ratio of non-petroleum resources in the rubber composition will decrease.

  The rubber composition for an inner liner of the present invention may contain deproteinized natural rubber (DPNR) as a rubber component. Natural rubber (NR) usually contains about 5 to 10% by mass of non-rubber components such as proteins and lipids. These non-rubber components, particularly proteins, are said to cause entanglement of molecular chains and cause gelation. In order to avoid such a problem, it is very advantageous to blend a deproteinized natural rubber (DPNR) from which the non-rubber component in the natural rubber is removed into the rubber composition.

  Here, it is preferable that the weight average molecular weight (gel permeation chromatography (GPC), polystyrene conversion) of deproteinized natural rubber (DPNR) is 1.4 million or more. When the weight average molecular weight is less than 1,400,000, the strength of raw rubber is lowered. The nitrogen content of the deproteinized natural rubber (DPNR) is preferably 0.1% by mass or less, more preferably 0.08% by mass or less, and further preferably 0.05% by mass or less. preferable. When the nitrogen content exceeds 0.1% by mass, it becomes a factor causing gelation. The nitrogen content of deproteinized natural rubber (DPNR) is measured by the RRIM method (Rubber Research Institute of Malaysia method).

  When the rubber composition for an inner liner of the present invention contains a deproteinized natural rubber (DPNR), the content of the deproteinized natural rubber (DPNR) in the rubber component is not particularly limited, but is, for example, about 5% by mass or more. be able to. However, when natural rubber other than DPNR is contained as a rubber component, the amount may be less. Further, when the rubber component contains a natural rubber other than DPNR, DPNR may not be contained. On the other hand, when the rubber composition for an inner liner contains only DPNR as a natural rubber component, the DPNR in the rubber component is preferably 90% by mass or more, and more preferably 95% by mass or more. If the DPNR content is less than 90% by mass, the ratio of non-petroleum resources in the rubber composition will decrease.

Deproteinized natural rubber (DPNR) can be obtained by deproteinizing natural rubber (NR). Examples of the deproteinization treatment of natural rubber (NR) include the following methods.
(1) A method of degrading protein by adding a proteolytic enzyme or bacteria to natural rubber latex,
(2) A method in which alkali is added to natural rubber latex and heated to decompose proteins,
(3) A method for liberating proteins adsorbed on natural rubber latex by a surfactant.

  The natural rubber latex used for the deproteinization treatment is not particularly limited, and field latex, ammonia-treated latex and the like can be used.

  As the proteolytic enzyme used in the above method (1), conventionally known proteolytic enzymes can be used, and are not particularly limited. For example, protease is preferably used. Protease may be derived from bacteria, filamentous fungi, or yeast. Among these, bacteria-derived proteases are preferred. In addition, enzymes such as lipase, esterase, amylase, laccase and cellulase may be used in combination.

  When alkaline protease is used as the proteolytic enzyme, the activity is preferably in the range of 0.1 to 50 APU / g, preferably 1 to 25 APU / g. Here, the activity of the proteolytic enzyme is determined by the Anson-hemoglobin method [Anson. M.M. L. , J .; Gen. Physiol. , 22, 79 (1938)]. That is, after reacting at a temperature of 25 ° C. and a pH of 10.5 for 10 minutes in a solution adjusted so that the final concentration of urea-modified hemoglobin used as a substrate is 14.7 mg / ml, trichloroacetic acid is terminated in the reaction solution. Add to a concentration of 31.25 mg / ml. Subsequently, the soluble content of trichloroacetic acid is colored with a phenol reagent, and the activity per 10 minutes of reaction is obtained by a calibration curve with the coloration degree of 1 mol of tyrosine as 1 APU, and this is converted per 1 minute. Measure. In addition, 1 APU indicates the amount of protease that gives a soluble amount of trichloroacetic acid having the same coloration degree as 1 mol of tyrosine is colored by a phenol reagent in one minute.

  The addition amount of the proteolytic enzyme is appropriately set depending on the enzyme activity, but is usually 0.0001 to 20 parts by mass, preferably 0.001 to 10 parts by mass with respect to 100 parts by mass of the solid content of natural rubber latex. It is. If the amount of the proteolytic enzyme added is less than 0.0001 parts by mass, the protein in the natural rubber latex may not be sufficiently decomposed. If the amount exceeds 20 parts by mass, the activity of the enzyme is reduced and the cost is reduced. Becomes higher.

  The treatment time with the proteolytic enzyme is not particularly limited and can be appropriately set according to the enzyme activity. Usually, it is preferable to perform the treatment for several minutes to one week. During the proteolytic treatment, the natural rubber latex may be agitated or allowed to stand. Moreover, you may adjust temperature as needed, and it is 5-90 degreeC as a suitable temperature, Preferably it is 20-60 degreeC. If the treatment temperature exceeds 90 ° C., the enzyme is rapidly deactivated, and if it is less than 5 ° C., the enzyme reaction is difficult to proceed.

  As the surfactant used in the above method (3), for example, one or more of an anionic surfactant, a nonionic surfactant, and a zwitterionic surfactant can be used. Examples of the anionic surfactant include carboxylic acid type, sulfonic acid type, sulfate ester type, and phosphate ester type. As the nonionic surfactant, for example, polyoxyalkylene ether, polyoxyalkylene ester, polyhydric alcohol fatty acid ester, sugar fatty acid ester, alkyl polyglycoside, and the like are preferably used. Examples of zwitterionic surfactants include amino acid type, betaine type, and amine oxide type.

  In the method (3), the natural rubber latex is washed with a surfactant to liberate proteins adsorbed on the natural rubber latex. As a method for cleaning the natural rubber latex particles with the surfactant, either a method for cleaning the natural rubber latex not treated with enzyme or a method for cleaning the natural rubber latex that has been subjected to the enzyme treatment may be used. Specific cleaning methods include, for example, a method in which a surfactant is added to natural rubber latex that has not been treated with enzyme or natural rubber latex that has been treated with enzyme, and a method in which natural rubber latex particles are aggregated and separated. Can be mentioned. When the natural rubber latex is washed by centrifugation, the centrifugation can be performed once to several times. Usually, a deproteinized natural rubber latex from which protein is highly removed can be obtained by one centrifugation. Moreover, you may perform a centrifugation process, after diluting with water so that the rubber component of a natural rubber latex may be 5-40 mass%, Preferably it is 10-30 mass%.

  The addition amount of the surfactant is 0.001 to 20 parts by mass, preferably 0.001 to 15 parts by mass with respect to 100 parts by mass of the solid content of the natural rubber latex.

  In the above methods (1) and (3), when using a proteolytic enzyme or a surfactant, other additives such as a pH adjusting agent and a dispersing agent may be added.

  Examples of pH adjusters include phosphates such as potassium dihydrogen phosphate, potassium hydrogen phosphate, sodium dihydrogen phosphate, and sodium hydrogen phosphate; acetates such as potassium acetate and sodium acetate; sulfuric acid, acetic acid, hydrochloric acid, Examples thereof include acids such as nitric acid, citric acid and succinic acid or salts thereof; ammonia, potassium hydroxide, sodium hydroxide, sodium carbonate, sodium hydrogen carbonate and the like. The addition amount of the pH adjuster is usually 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the rubber solid content of the natural rubber latex.

  Examples of the dispersant include styrene sulfonic acid copolymer, naphthalene sulfonic acid formalin condensate, lignin sulfonic acid, polycyclic aromatic sulfonic acid copolymer, acrylic acid, maleic anhydride homopolymer and copolymer, isobutylene- Examples thereof include a copolymer of acrylic acid and isobutylene-maleic anhydride.

  The deproteinized natural rubber latex obtained as described above may be coagulated after removing the non-rubber component by centrifugation or the like, or may be coagulated without removing the non-rubber component. The coagulation method is not particularly limited and can be performed by a known method. Usually, a latex rubber particle is destabilized and solidified by adding a coagulant such as formic acid or sulfuric acid or a salt such as sodium chloride. A method of destabilizing and solidifying is used.

  In addition, it is preferable that the gel content rate of deproteinized natural rubber is 10 mass% or less. When the gel content exceeds 10% by mass, the viscosity of the unvulcanized rubber increases and the processability tends to decrease. The gel content is measured as a toluene insoluble matter.

  The rubber composition for an inner liner of the present invention may contain a modified natural rubber or a diene synthetic rubber other than those described above. Examples of the diene synthetic rubber include styrene butadiene rubber (SBR), butadiene rubber (BR), styrene isoprene copolymer rubber, isoprene rubber (IR), butyl rubber (IIR), chloroprene rubber (CR), acrylonitrile butadiene rubber ( NBR), halogenated butyl rubber (X-IIR), and halides of copolymers of isobutylene and p-methylstyrene.

  When the rubber composition for an inner liner of the present invention contains a diene synthetic rubber, the content of the diene synthetic rubber in the rubber component is preferably 10% by mass or less. In view of resource saving and environmental protection, it is more preferable not to include a diene synthetic rubber from the viewpoint of increasing the content of non-petroleum resources.

<Zinc oxide>
The rubber composition for an inner liner of the present invention contains zinc oxide particles having an average particle size of 200 nm or less. Here, in the present invention, the average particle diameter of the zinc oxide particles is measured by a laser beam scattering method using a nanoparticle size distribution measuring apparatus manufactured by Shimadzu Corporation.

  Zinc oxide is blended as a vulcanization accelerator, but by containing zinc oxide particles having an average particle size of 200 nm or less, it is possible to effectively prevent the destruction of rubber due to zinc oxide, The air permeability resistance of the obtained inner liner rubber can be improved. Further, by containing zinc oxide particles having an average particle size of 200 nm or less, the resistance to bending crack growth can be improved. Zinc oxide is a non-petroleum resource, and the rubber composition for the inner liner containing this can be said to be a rubber composition friendly to the earth with sufficient consideration for resource saving and environmental protection.

  The average particle diameter of the zinc oxide particles to be blended is 200 nm or less. When the average particle diameter of the zinc oxide particles exceeds 200 nm, it often becomes a base point for rubber breakage, and the improvement of the air permeability resistance and flex crack growth resistance of the obtained inner liner rubber is not sufficient. In order to further improve the air permeation resistance and the bending crack growth resistance, the average particle diameter of the zinc oxide particles is preferably 150 nm or less, and more preferably 100 nm or less. Moreover, the average particle diameter of the zinc oxide particles is preferably 1 nm or more, and more preferably 10 nm or more. When the average particle diameter of the zinc oxide particles is less than 1 nm, the dispersibility of the zinc oxide particles in the rubber composition tends to be inferior.

  The content of zinc oxide particles having an average particle size of 200 nm or less is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, with respect to 100 parts by mass of the rubber component. It is. When the content of zinc oxide particles having an average particle size of 200 nm or less is less than 0.1 part by mass, the effect as a vulcanization acceleration aid by blending zinc oxide tends to be difficult to obtain. Further, the content of zinc oxide particles having an average particle size of 200 nm or less is 10 parts by mass or less, preferably 5 parts by mass or less, with respect to 100 parts by mass of the rubber component. When the content of zinc oxide particles having an average particle size of 200 nm or less exceeds 10 parts by mass, the flex crack growth resistance tends to be lowered.

  In the rubber composition for an inner liner of the present invention, zinc oxide particles having an average particle diameter exceeding 200 nm may be used in combination with zinc oxide particles having an average particle diameter of 200 nm or less. However, the content of zinc oxide particles having an average particle size exceeding 200 nm is preferably 2.5 parts by mass or less, more preferably 1.5 parts by mass or less, relative to 100 parts by mass of the rubber component. . When the content of zinc oxide particles having an average particle size exceeding 200 nm exceeds 2.5 parts by mass, the flex crack growth resistance tends to be inferior. When zinc oxide particles having an average particle diameter exceeding 200 nm are used in combination, the ratio (mass ratio) of the content of zinc oxide particles having an average particle diameter exceeding 200 nm to the content of zinc oxide particles having an average particle diameter of 200 nm or less is It is preferably 5 or less, and more preferably 3 or less. When the ratio exceeds 5, the flex crack growth resistance tends to be inferior.

<Silica>
The rubber composition for an inner liner of the present invention preferably further contains silica. Silica functions as a reinforcing filler, and by blending silica, the air permeability resistance and the flex crack growth resistance of the resulting inner liner rubber can be further improved.

  Silica may be prepared by a wet method or may be prepared by a dry method.

The BET specific surface area of silica is preferably 150 m ² / g or more, and more preferably 170 m ² / g or more. If the BET specific surface area of silica is less than 150 m ² / g, sufficient flex crack growth resistance tends to be difficult to obtain. Further, BET specific surface area of silica is preferably not more than 200 meters ² / g, more preferably at most 180 m ² / g. When the BET specific surface area of silica exceeds 200 m ² / g, the viscosity of the unvulcanized rubber tends to increase too much.

  30 mass parts or more are preferable with respect to 100 mass parts of rubber components, and, as for content of a silica, 33 mass parts or more are more preferable. When the content of silica is less than 30 parts by mass, sufficient air permeation resistance improving effect tends not to be obtained. Moreover, 50 mass parts or less are preferable with respect to 100 mass parts of rubber components, and, as for content of a silica, 40 mass parts or less are more preferable. When the content of silica exceeds 50 parts by mass, the flex crack growth resistance tends to decrease.

<Silane coupling agent>
When silica is blended in the rubber composition for an inner liner of the present invention, it is preferable to blend a silane coupling agent together with silica. As the silane coupling agent, a conventionally known silane coupling agent can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4- Triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxy Silylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) ) Resulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3 -Trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxy Ethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthio Sulfide systems such as rubamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane Mercapto type such as 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; Vinyl type such as vinyltriethoxysilane, vinyltrimethoxysilane; 3-aminopropyltriethoxysilane 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxy Amino systems such as silane; glycidoxy systems such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane Nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltri Chloro-based compounds such as ethoxysilane; These silane coupling agents may be used alone or in combination of two or more.

  Of these, Si69 (bis (3-triethoxysilylpropyl) tetrasulfide), Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa are preferably used because of their good processability. It is done.

  The content of the silane coupling agent is preferably 1 part by mass or more and more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. When the content is less than 1 part by mass, effects such as improvement in dispersibility tend not to be obtained sufficiently. Moreover, 20 mass parts or less are preferable with respect to 100 mass parts of silica, and, as for content of a silane coupling agent, 15 mass parts or less are more preferable. When the content exceeds 20 parts by mass, a sufficient coupling effect cannot be obtained, and the reinforcing property and wear resistance tend to decrease.

The rubber composition for an inner liner of the present invention may contain carbon black. The BET specific surface area of carbon black is preferably 20 m ² / g or more, and more preferably 25 m ² / g or more. If the BET specific surface area of carbon black is less than 20 m ² / g, the effect of improving the resistance to flex crack growth tends to be difficult to obtain. Further, BET specific surface area of carbon black is preferably not more than 40 m ² / g, more preferably at most 30 m ² / g. When the BET specific surface area of carbon black exceeds 40 m ² / g, the rolling resistance of the tire tends to increase.

  The DBP (dibutyl phthalate) oil absorption of carbon black is preferably 70 to 100 ml / 100 g or more, and more preferably 80 to 90 ml / 100 g. When the DBP oil absorption is less than 70 ml / 100 g, the viscosity of the unvulcanized rubber tends to be low and the rubber residue tends to be poor, and when it exceeds 100 ml / 100 g, the viscosity of the unvulcanized rubber tends to be high and burns tend to occur. is there.

  The content of carbon black is preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, and still more preferably 0 to 1 part by mass with respect to 100 parts by mass of the rubber component. When the content of carbon black exceeds 10 parts by mass, the ratio of non-petroleum resources decreases. From the viewpoint of resource saving and environmental protection, it is preferable not to contain carbon black.

<Other ingredients>
In addition to the above-described components, the rubber composition for an inner liner of the present invention includes other additives conventionally used in the rubber industry, such as vulcanizing agents, vulcanization accelerators, stearic acid, stearic acid metal salts, oils. Further, it may contain a curing resin, wax, various anti-aging agents and the like.

  As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, and di-t-butyl peroxide. , T-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoyl) Peroxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy- Diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1-di t- butyl peroxy-3,3,5-trimethyl siloxane, and the like can be used n- butyl-4,4-di -t- butyl peroxy valerate. Of these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferred. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred. These vulcanizing agents may be used alone or in combination of two or more. Further, sulfur may be oil-treated.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used. Examples of the sulfenamide system include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (N-tert-butyl-2-benzothiazylsulfenamide), N, N-dicyclohexyl-2- Sulfenamide compounds such as benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and N, N-diisopropyl-2-benzothiazolesulfenamide can be used. Examples of the thiazole type include MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitro). Thiazole compounds such as phenyl) mercaptobenzothiazole and 2- (2,6-diethyl-4-morpholinothio) benzothiazole can be used. Examples of thiurams include TMTD (tetramethyl thiuram disulfide), tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram monosulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram hexasulfide. Further, thiuram compounds such as tetrabutylthiuram disulfide and pentamethylenethiuram tetrasulfide can be used. As the thiourea series, for example, thiourea compounds such as thiacarbamide, diethylthiourea, dibutylthiourea, trimethylthiourea, diortolylthiourea and the like can be used. Examples of guanidine-based compounds include guanidine-based compounds such as diphenylguanidine, diortolylguanidine, triphenylguanidine, orthotolylbiguanide, and diphenylguanidine phthalate. Examples of dithiocarbamate include zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate , Complex salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecyl (or octadecyl) isopropyldithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, diamyl Di, such as cadmium dithiocarbamate And the like can be used Okarubamin acid compound. As the aldehyde-amine system or aldehyde-ammonia system, for example, an aldehyde-amine system such as an acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, an acetaldehyde-ammonia reaction product, or an aldehyde-ammonia system compound is used. can do. As the imidazoline-based compound, for example, an imidazoline-based compound such as 2-mercaptoimidazoline can be used. As the xanthate type, for example, a xanthate type compound such as zinc dibutylxanthate can be used. These vulcanization accelerators may be used alone or in combination of two or more.

  Examples of metal stearates include magnesium stearate, magnesium 12-hydroxystearate, calcium stearate, calcium 12-hydroxystearate, barium stearate, barium 12-hydroxystearate, zinc stearate, and zinc 12-hydroxystearate. Can be mentioned. Among the metal stearates, alkaline earth metal salts of stearic acid are preferable from the viewpoint of heat resistance improvement effect and compatibility with epoxidized natural rubber, and calcium stearate, 12-hydroxycalcium stearate, barium stearate, 12- More preferred is barium hydroxystearate. The content of the stearic acid metal salt is 1 part by mass or more, preferably 1.5 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of the stearic acid metal salt is less than 1 part by mass, a sufficient compatibility effect and heat resistance improvement effect tend not to be obtained. Moreover, content of a stearic acid metal salt is 10 mass parts or less, Preferably it is 8 mass parts or less. When the content of the stearic acid metal salt exceeds 10 parts by mass, the hardness and modulus decrease, and the wear resistance tends to decrease.

  As the anti-aging agent, amine-based, phenol-based, imidazole-based, carbamic acid metal salts, and the like can be appropriately selected and used.

  The pneumatic tire of the present invention is provided with an inner liner portion obtained using the rubber composition for an inner liner. That is, the pneumatic tire of the present invention includes a pneumatic tire having any conventionally known structure as long as such an inner liner portion is provided.

  For example, as shown in FIG. 1, such a pneumatic tire 1 includes a tread portion 2 including a cap tread portion and a base tread portion, and a pair of sides extending inward in the tire radial direction from both ends of the tread portion 2. In general, it has a structure including a wall portion 3 and a bead portion 4 positioned at the inner end of each sidewall portion 3. A carcass 6 is bridged between the bead portions 4, and a belt layer 7 that reinforces the tread portion 2 with a tagging effect is disposed outside the carcass 6 and inside the tread portion 2. .

  The carcass 6 is formed of one or more carcass plies 6a in which the carcass cord is arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator CO. The carcass ply 6a extends from the tread portion 2 to the sidewall portion. 3, the periphery of the bead core 5 of the bead portion 4 is folded back and locked from the inner side to the outer side in the tire axial direction.

  The belt layer 7 is composed of two or more belt plies 7a in which the belt cord is arranged at an angle of, for example, 40 ° or less with respect to the tire equator CO. It is location.

  Further, a bead apex rubber 8 extending radially outward from the bead core 5 is disposed in the bead portion 4, and an inner liner rubber 9 forming a tire lumen surface is adjacent to the inside of the carcass 6. The outside of the carcass 6 is protected by clinch rubber 4G and sidewall rubber 3G.

  The rubber composition for an inner liner of the present invention is used for the inner liner rubber 9.

  The pneumatic tire of the present invention is produced by a conventionally known method using the rubber composition for an inner liner of the present invention. That is, the rubber composition for an inner liner having the above-described configuration is kneaded and extruded in accordance with the shape of the inner liner portion of the tire at an unvulcanized stage, and usually on a tire molding machine together with other members of the tire. By molding by this method, an unvulcanized tire is formed. The pneumatic tire of the present invention can be obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

  The pneumatic tire of the present invention has a higher content ratio of the material composed of non-petroleum resources in the inner liner rubber, has sufficient consideration for resource saving and environmental protection, and has excellent air permeation resistance and bending resistance. Since a rubber composition exhibiting crack growth is used, it can be suitably used as, for example, a passenger car as an “eco tire” that is friendly to the global environment.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Examples 1-5 and Comparative Examples 1-5>
According to the formulation shown in Table 1, the compounding components excluding sulfur and the vulcanization accelerator were kneaded for 3 minutes under the conditions of a rotational speed of 80 rpm and 150 ° C. using a Banbury mixer. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded material in the amounts shown in Table 1, and then kneaded at 80 ° C. for 5 minutes using an open roll to obtain an unvulcanized rubber composition. . Next, the unvulcanized rubber composition was vulcanized at 150 ° C. for 30 minutes to produce vulcanized rubber sheets of Examples 1 to 5 and Comparative Examples 1 to 5.

The details of various blending components used in Examples and Comparative Examples are as follows.
(1) Epoxidized natural rubber (ENR): “ENR25” (25% by mole of epoxidation) manufactured by Kumpoulang Guthrie
(2) Chlorinated butyl rubber: “Chlorobutyl HT1066” manufactured by Exxon Chemical
(3) Silica: “Ultra Gil VN3” manufactured by Degussa (BET: 175 m ² / g)
(4) Carbon Black: “Dia Black G” manufactured by Mitsubishi Chemical Corporation (BET: 27 m ² / g, DBP oil absorption 87 ml / 100 g)
(5) Silane coupling agent: “Si266” (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
(6) Anti-aging agent: “Antioxidant FR” manufactured by Matsubara Sangyo (purified product of 2,2,4-trimethyl-1,2-dihydroquinoline derivative)
(7) Calcium stearate: “GF200” manufactured by Calcium Shiraishi
(8) Stearic acid: “Koji” manufactured by Nippon Oil & Fats Co., Ltd.
(9) Zinc oxide fine particles (zinc oxide used in Examples 1 to 5): “Zincox Super F-2” (average particle diameter: 65 nm) manufactured by Hakusui Tech Co., Ltd.
(10) Zinc oxide (zinc oxide used in Examples 3 to 5 and Comparative Examples 1 to 5): 2 types of zinc oxide (average particle size: 500 nm) manufactured by Mitsui Mining & Smelting Co., Ltd.
(11) Sulfur: 5% oil-treated powder sulfur manufactured by Tsurumi Chemical Co., Ltd. (12) Vulcanization accelerator CZ: “Noxeller CZ” (N-cyclohexyl-2-benzothiazyl) manufactured by Ouchi Shinsei Chemical Co., Ltd. -Sulfenamide)
(13) Vulcanization accelerator DPG: “Parcasit DPG” (1,3-diphenylguanidine) manufactured by Flexis
(14) Vulcanization accelerator M: “Sunseller M” (2-mercapto-benzothiazole) manufactured by Sanshin Chemical Industry Co., Ltd.
(15) Vulcanization accelerator DM: “Sunseller DM” (dibenzothiazyl disulfide) manufactured by Sanshin Chemical Industry Co., Ltd.
The test shown below was implemented about the vulcanized rubber of Examples 1-5 and Comparative Examples 1-5. The results are shown in Table 1.

(hardness)
In accordance with JIS-K6253, the type A durometer hardness was measured.

(Rolling resistance test)
Vulcanization of Examples 1-5 and Comparative Examples 1-5 under conditions of initial strain 10%, dynamic strain 1%, frequency 10 Hz and temperature 60 ° C. using a viscoelastic spectrometer manufactured by Ueshima Seisakusho Co., Ltd. The loss tangent (tan δ) of the rubber sheet was measured. The numerical values in Table 1 are relative values when the loss tangent of Example 1 is 100. In addition, it shows that rolling resistance is reduced and the low exothermic property is excellent, so that the said numerical value is large.

(Air permeability test)
Using a gas permeation tester manufactured by Ueshima Seisakusho, the air permeability of the vulcanized rubber sheets of Examples 1 to 5 and Comparative Examples 1 to 5 was measured under normal temperature and normal pressure conditions. The results are shown in Table 1. In Table 1, the air permeability “A” means that the permeability coefficient is 5 or more and less than 10 (× 10 ¹¹ cm ³ · cm ² · s · cmHg), and is “B”. Indicates that the transmission coefficient is 10 or more and less than 15 (× 10 ¹¹ cm ³ · cm / cm ² · s · cmHg), and “C” indicates that the transmission coefficient is 15 or more and less than 20 ( × 10 ¹¹ cm ³ · cm / cm ² · s · cmHg).

(Bending crack growth test)
According to JIS-K6260 “Dematcher bending crack growth test method for vulcanized rubber and thermoplastic rubber”, the number of times until the vulcanized rubber sample breaks 1 mm is obtained under the condition of room temperature 25 ° C. The number of times is shown as a relative value when the number of times in Example 1 is 100. Note that 70% in Table 1 indicates the elongation percentage with respect to the length of the original vulcanized rubber sample.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic sectional drawing which shows an example of the pneumatic tire of this invention.

Explanation of symbols

  1 tire, 2 tread part, 2a cap tread part, 2b base tread part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layer, 8 bead apex rubber, 9 inner liner rubber, 4G clinch rubber.

Claims (3)

0.1 to 10 parts by mass of first zinc oxide particles having an average particle diameter of 1 to 150 nm and second zinc oxide particles having an average particle diameter exceeding 200 nm with respect to 100 parts by mass of a rubber component containing epoxidized natural rubber 2.5 parts by mass or less ,
A rubber composition for an inner liner , wherein a ratio of the content of the second zinc oxide particles to the content of the first zinc oxide particles is 5 or less . Per 100 parts by mass of the rubber component The rubber composition for an inner liner according to claim 1, further containing 30 to 50 parts by weight of the silica. A pneumatic tire provided with the inner liner rubber which consists of a rubber composition of Claim 1 or 2 .

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