JP5023367B2 - Rubber composition, method for producing the same, and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition excellent in tire durability and steering stability and capable of reducing rolling resistance, and a pneumatic tire using the rubber composition, particularly a pneumatic tire for passenger cars.

  In recent years, it has become important to reduce rolling resistance as well as durability, wear resistance, and steering stability as basic required characteristics of pneumatic tires under high-speed conditions of vehicles on a developed highway. In rubber compositions used for tires, workability in the kneading process is an important basic characteristic.

Conventionally, in order to improve the basic characteristics, the rubber composition is reinforced by using carbon black, silica, short fibers, or the like for the tire rubber composition. These reinforcing agents can enhance the reinforcing effect by using a large amount of those having a relatively small particle diameter. However, in this case, the viscosity of the rubber composition increases, and the molding processability decreases. Further, for example, Patent Document 1 proposes a method of using a thermosetting resin in order to suppress an increase in the viscosity of the rubber composition, but this method reduces the durability of the rubber composition and increases the cost. .
Japanese Patent No. 2735471

  The present invention is excellent in processability, and further has excellent durability, wear resistance and steering stability, a tire rubber composition capable of reducing rolling resistance, a method for producing the rubber composition, and a pneumatic composition using the rubber composition Regarding tires.

  The present invention relates to a diene-based chitin fiber and / or chitosan fiber having a fiber diameter D of 100 nm or less and an aspect ratio (L / D) represented by a ratio of the fiber diameter D to the fiber length L of 5 or more. A rubber composition containing 5 to 100 parts by mass with respect to 100 parts by mass of the rubber component. The fiber diameter D of the chitin fiber and / or chitosan fiber is preferably 50 nm or less, and the aspect ratio (L / D) represented by the ratio of the fiber diameter D to the fiber length L is preferably 10 or more.

  Moreover, it is preferable that 20-100 mass parts of carbon black is mix | blended with respect to a diene-type rubber component. The present invention relates to a pneumatic tire using the rubber composition in a tread portion. In particular, the present invention relates to a pneumatic tire using the rubber composition in a tread portion or a bead apex.

  Furthermore, the present invention relates to a method for producing the rubber composition obtained by coagulating the latex after dispersing chitin fibers and / or chitosan fibers in the latex.

  In the present invention, since a predetermined amount of chitin fiber and / or chitosan fiber is blended in the diene rubber, the processability is maintained without increasing the viscosity of the rubber, the strength of the rubber composition can be improved, and the hardness can be increased. Contributes to improving wear resistance, durability and handling characteristics. In particular, chitin fibers and / or chitosan fibers have an aminopolysaccharide molecular structure, so that they are highly compatible with diene rubber components and have a high reinforcing effect on rubber composites. Moreover, since these fibers have a lower specific gravity than carbon black, they contribute to weight reduction of the tire, that is, low fuel consumption.

  The present invention relates to a diene-based chitin fiber and / or chitosan fiber having a fiber diameter D of 100 nm or less and an aspect ratio (L / D) represented by a ratio of the fiber diameter D to the fiber length L of 5 or more. A rubber composition containing 5 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

<Diene rubber component>
In the present invention, the diene rubber is natural rubber, butadiene rubber, epoxidized natural rubber, deproteinized natural rubber, synthetic isoprene rubber (IR), low cis-polybutadiene rubber (L-BR), styrene butadiene rubber (SBR), acrylonitrile butadiene. Examples thereof include rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), ethylene-propylene-diene rubber (EPDM), and these rubbers may be used alone or in combination of two or more. Among these, it is preferable to mix SBR in order to improve the grip performance and wear resistance in a highly balanced manner.

  In particular, the diene rubber component preferably contains 20% by mass or more of natural rubber and 15% by mass or more of butadiene rubber. Natural rubber and butadiene rubber are excellent in compatibility with chitin fibers and chitosan fibers and excellent in uniform dispersion thereof, and can be effectively reinforced by blending chitin fibers and / or chitosan fibers. In particular, the natural rubber preferably contains 50% by mass or more of the diene rubber component, and particularly preferably 60% by mass or more. Moreover, 20 mass% or more of polybutadiene is preferable. The polybutadiene is more preferably contained in an amount of 80% by mass or less, particularly 50% by mass or less.

  The diene rubber can be mixed with chitin fibers and / or chitosan fibers in the form of latex or solid rubber. When mixing with chitin fiber and / or chitosan fiber using a solid rubber, dry mixing can be performed using a biaxial roller or a Banbury mixer. On the other hand, when a latex such as natural rubber is used, an aqueous dispersion of chitin fibers and / or chitosan fibers can be mixed with the natural rubber latex.

<Chitin fiber and / or chitosan fiber>
Chitin is a natural material contained in shrimp, crab and other insects, shellfish and mushrooms. Chitin is industrially separated from shrimp and crab shells. Its molecular structure is an amino polysaccharide in which N-acetyl-D-glucosamine is connected in a long chain.

  Further, chitosan is treated with alkali to remove chitin, the acetyl group is removed, the ratio of D-glucosamine units is increased to about 70-95%, and it becomes soluble in an acid aqueous solution.

  Chitin also contains some D-glucosamine units. The main structural unit of chitosan is D-glucosamine, but N-acetyl-D-glucosamine may also be included.

  Hereinafter, in this specification, what is soluble in an acidic aqueous solution is chitosan, and what is not soluble is chitin.

  In the present invention, chitin and chitosan are concepts including derivatives thereof. For example, as chitosan derivatives, carboxymethyl chitosan (CM-CS), chitosan-hydroxybenzotriazole (CS-HOBt), chitosan-acetate (CS-) Acetate), O-{(2-dimethylamino) ethylamine chitosan} (DETNH-CS), and iodo-CS (Iodo-CS).

  Examples of chitin derivatives include acetylated chitin, hydroxyethylated chitin, carboxymethylated chitin, and benzoylated chitin.

  Chitin fibers and / or chitosan fibers are blended in an amount of 5 to 100 parts by mass with respect to 100 parts by mass of the diene rubber component. Hardness and rigidity can be increased by blending chitin fiber and chitosan fiber into rubber. Conventionally, a large amount of carbon black having a small particle diameter is blended to increase the hardness and rigidity of rubber. In this case, the viscosity of the rubber composition is increased and the energy loss is increased, so that the rolling resistance of the tire is deteriorated.

  By blending chitin fibers or chitosan fibers, the rigidity of the rubber composition can be increased, and since the energy loss during running is small, the rolling resistance can be reduced and the degree of heat generation due to friction is also small. Moreover, since the rigidity of the rubber composition is high, good steering stability can be obtained.

  From the above viewpoint, the blending amount of chitin fiber and / or chitosan fiber is preferably 5 to 60 parts by mass and more preferably 15 to 35 parts by mass with respect to 100 parts by mass of the diene rubber component.

  In the present invention, chitin fibers and / or chitosan fibers are obtained as chitin whiskers or chitosan whiskers that are needle-like crystals. These fiber diameters D are 100 nm or less, preferably 50 nm or less. The aspect ratio (L / D) represented by the ratio between the fiber diameter D and the fiber length L is preferably 5 or more, and more preferably 10 or more. By setting the fiber diameter D to 100 nm or less, dispersibility is improved and a rubber reinforcing effect is obtained. Further, by setting the aspect ratio (L / D) to 5 or more, rigidity can be increased in the fiber orientation direction (extrusion direction), while flexibility can be maintained in the non-orientation direction.

  The aspect ratio (L / D) is not particularly limited, but is preferably 1000 or less, more preferably 500 or less, and particularly preferably 100 or less from the viewpoint of improving processability and dispersibility.

<Carbon black>
In the present invention, it is preferable to use carbon black in combination. The content of carbon black is preferably 20 parts by mass or more and more preferably 30 parts by mass or more with respect to 100 parts by mass of the diene rubber. If the carbon black content is less than 20 parts by mass, the rubber composition has insufficient rigidity. Further, the content of carbon black is 100 parts by mass or less and more preferably 70 parts by mass or less with respect to 100 parts by mass of the diene rubber. When the carbon black content is 100 parts by mass or less, workability can be maintained, heat generation due to friction during tire running can be suppressed, energy loss can be reduced, and rolling resistance can be reduced. Become.

  The iodine adsorption amount of carbon black is preferably 60 to 220 mg / g. When the iodine adsorption amount is 60 mg / g or more, properties such as the strength of the rubber composition can be improved, and when it is 220 mg / g or less, heat generated by friction can be reduced.

The nitrogen adsorption specific surface area (N ₂ SA) is preferably 42 m ² / g or more, and more preferably 100 m ² / g or more. When the nitrogen adsorption specific surface area (N ₂ SA) is less than 42 m ² / g, grip performance and wear resistance tend to decrease. Further, the nitrogen adsorption specific surface area (N ₂ SA) is preferably 280 m ² / g or less, and more preferably 200 m ² / g or less. When the nitrogen adsorption specific surface area (N ₂ SA) exceeds 280 m ² / g, good dispersion is difficult to obtain, and the wear resistance tends to decrease. The nitrogen adsorption specific surface area (N ₂ SA) is measured by the BET method according to ASTM-D3037-81.

<Silica>
In this invention, a silica can be mix | blended and the compounding quantity is 5 to 150 mass parts with respect to 100 mass parts of a diene rubber component. When the amount of silica is less than 5 parts by mass, the reinforcing effect is not sufficient. When it exceeds 150 parts by mass, workability and rolling resistance tend to deteriorate. Silica is preferably blended in an amount of 10 to 120 parts by mass with respect to 100 parts by mass of the rubber component.

As the silica, those generally used for general-purpose rubber can be used, and examples thereof include dry method white carbon, wet method white carbon and colloidal silica used as a reinforcing material. Among these, wet method white carbon mainly containing hydrous silicic acid is preferable. The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably in the range of, for example, 100 to 300 m ² / g, more preferably 120 to 280 m ² / g. If the nitrogen adsorption specific surface area (N ₂ SA) of silica is less than 100 m ² / g, the reinforcing effect is not sufficient. On the other hand, when the nitrogen adsorption specific surface area exceeds 300 m ² / g, the dispersibility of silica tends to decrease and the heat generation of the rubber composition tends to increase.

  When silica is blended in the rubber composition, a silane coupling agent, preferably a sulfur-containing silane coupling agent, is usually blended in an amount of 1% by mass to 20% by mass with respect to the silica mass. By blending 1% by mass or more of the silane coupling agent, the wear resistance of the tire is improved and the rolling resistance can be reduced. On the other hand, when the compounding amount of the silane coupling agent is 20% by mass or less, there is little risk of scorching in the rubber kneading and extrusion processes.

  As sulfur-containing silane coupling agents, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethyl Examples include silylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, bis- [3- (triethoxysilyl) -propyl] tetrasulfide, 3-mercaptopropyltrimethoxysilane and the like. Other silane coupling agents include vinyltrichlorosilane, vinyltris (2-methoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ- (2-aminoethyl) Aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and the like can be used.

  In the present invention, other coupling agents such as aluminate coupling agents and titanium coupling agents can be used alone or in combination with a silane coupling agent depending on the application.

  In the present invention, the rubber composition for the base rubber can contain other reinforcing fillers. For example, calcium carbonate, magnesium carbonate, clay, alumina, talc and the like are not particularly limited as long as they are conventionally used in rubber compositions for tires. These reinforcing fillers may be used alone or in combination of two or more.

  In addition to the above, it is preferable to add a vulcanizing agent, a vulcanization accelerator, a softener, a plasticizer, an anti-aging agent, stearic acid, an antioxidant, an ozone deterioration preventing agent, and the like to the rubber composition.

  As the vulcanizing agent, an organic peroxide or a sulfur vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, 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 (benzoylperoxy) 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-butylperoxy-3,3,5-trimethylsiloxane, n-butyl-4, - it can be used such as 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.

  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.

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

  Softeners include process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petroleum jelly such as petroleum jelly, fatty oil softener such as castor oil, linseed oil, rapeseed oil, coconut oil, tall oil, , Waxes such as beeswax, carnauba wax and lanolin, and fatty acids such as linoleic acid, palmitic acid, stearic acid and lauric acid.

  As plasticizers, DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (phthalate) Acid diisodecyl), BBP (butylbenzyl phthalate), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrophthalic anhydride ester, DOZ (di-2-ethylhexyl azelate), DBS (dibutyl sebacate), DOS (Dioctyl sebacate), acetyl triethyl citrate, acetyl tributyl citrate, DBM (dibutyl maleate), DOM (2-ethylhexyl maleate), DBF (dibutyl fumarate) and the like.

<Pneumatic tire>
The present invention is a pneumatic tire using the rubber composition in a bead apex, a tread portion, a sidewall portion, a chafer or a bead portion. The rubber composition containing the various compounding chemicals is extruded in accordance with a predetermined shape of the tire member at an unvulcanized stage. This is molded by a normal method on a tire molding machine to form an unvulcanized tire. This unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

  FIG. 1 shows a right half of a cross section of the pneumatic tire of the present invention. The tire 1 includes a tread portion 7, a pair of sidewall portions 8 extending inward in the tire radial direction from both ends thereof, a bead portion 3 located at the inner end of each sidewall portion, and a chafer 2 located at the rim upper portion. With. A carcass 10 is bridged between the bead portions 3 on both sides, and a breaker portion 9 is disposed on the outer side in the tire radial direction of the carcass 10.

  The carcass 10 is formed of one or more carcass plies on which carcass cords are arranged. The carcass ply includes a bead core 4 extending from a tread portion through a sidewall portion and a bead core 4 extending from the upper end of the bead core 4 toward the sidewall. The area around the apex 5 is folded back from the inside to the outside in the tire axial direction and locked. The breaker unit 9 is composed of two or more breaker plies in which breaker cords are arranged, and is arranged in different directions so that each breaker cord intersects between the breaker plies. A band 6 is disposed on the upper side of the breaker portion in order to reduce lifting at both ends of the breaker during running of the tire. In the present invention, the tire rubber composition is used for the tread portion 7 or the bead apex. In addition, although FIG. 1 illustrated about the tire for passenger cars, it is applicable also to a truck bus tire, a light truck tire, etc.

<Tread rubber>
When using the rubber composition of this invention for a tread rubber, it is preferable that JIS-A hardness is adjusted to the range of 50-80. By setting the JIS-A hardness to 50 or more, the durability of the tread rubber is improved. By setting the JIS-A hardness to 80 or less, the hardness becomes appropriate for improving the handling stability of the tread rubber.

  The loss tangent (tan δ) value of the tread rubber is preferably adjusted to 0.05 to 0.25, preferably 0.10 to 0.20. Here, tan δ is a value measured with a viscoelastic spectrometer at a temperature of 60 ° C. under conditions of a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%. By setting the value of tan δ to 0.05 or more, it has an appropriate viscosity and can reduce heat generation.

  On the other hand, by setting the value of tan δ to 0.20 or less, it is possible to reduce energy loss during traveling and reduce rolling resistance. The complex elastic modulus (E *) of the base rubber measured under the same conditions as tan δ is preferably adjusted in the range of 3.0 to 6.0 MPa.

<Bead Apex>
When using the rubber composition of this invention for a bead apex, it is preferable that JIS-A hardness is adjusted to the range of 70-100. By setting the JIS-A hardness to 70 or more, the rigidity of the bead portion is increased and the steering stability is improved. On the other hand, when the JIS-A hardness exceeds 100, the durability of the bead apex associated with repeated bending deformation of the bead portion decreases. The height H from the bead base portion of the bead apex is preferably adjusted within a range of 10 to 80% of the height of the tire maximum width position.

<Method for producing rubber composition>
The rubber composition of the present invention can be prepared by mixing chitin fibers and / or xanthone fibers with solid rubber, but can be prepared by mixing an aqueous dispersion of chitin fibers and / or xanthone fibers with rubber latex. For example, this chitin whisker can be added to NR latex and coagulated with a low-concentration sulfuric acid solution to obtain a rubber composite of NR latex and chitin whisker.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these.

(1) Example 1
3 g of chitin (manufactured by Aldrich) is added with 50 g of 3N hydrochloric acid, and the mixture is allowed to stand for 3 hours at room temperature under reduced pressure by an aspirator to infiltrate hydrochloric acid. And it is made to react at 105 degreeC for 6 hours. This solution is transferred to a dialysis cellulose tube and dialyzed against deionized water for 2 days. Most of the water was removed under reduced pressure and freeze-dried to obtain chitin whiskers with white needle crystals. The fiber diameter D of the chitin whisker is 40 nm, and the aspect ratio (L / D) is 5.

  This chitin whisker was added to NR latex and coagulated with a 2% sulfuric acid solution to obtain a rubber composite of NR latex and chitin whisker. This rubber composite contains 30 parts by mass of chitin whisker with respect to 100 parts by mass of the rubber component.

  Components obtained by removing sulfur and a vulcanization accelerator from the compounding agents shown in Table 1 were kneaded using a 1.7 L Banbury mixer manufactured by Kobe Steel. Thereafter, sulfur and a vulcanization accelerator were added and further kneaded with a biaxial roller. The obtained mixture was vulcanized at 175 ° C. for 10 minutes to obtain a rubber composition. The same method was used for the adjustment method of the rubber composition in Example 2 and Comparative Example 1 described below.

(2) Example 2
75 g of a 40 wt% sodium hydroxide aqueous solution is added to 3 g of chitin whiskers and allowed to stand for 3 hours at room temperature under reduced pressure by an aspirator to infiltrate the alkali. Add 25 g of ice and stir at 0 ° C. to prepare an aqueous alkaline chitin solution. This solution is transferred to a dialysis cellulose tube and dialyzed against deionized water for 2 days. Most of the water was removed under reduced pressure and lyophilized to obtain white crystalline chitosan whiskers. The fiber diameter D of the chitosan whisker is 85 nm and the aspect ratio (L / D) is 6.

  This chitosan whisker was added to NR latex and coagulated with a 2% sulfuric acid solution to obtain a rubber composite of NR latex and chitosan whisker. This rubber composite contains 30 parts by mass of chitosan whisker with respect to 100 parts by mass of the rubber component.

(3) Comparative Example 1
Based on the recipe shown in Table 1, a rubber composition was prepared in the same manner as in Example 1 described above.

The formulations used in Table 1 are as follows.
(Note 1) RSS # 3 grade was used for natural rubber.
(Note 2) Carbon black is N330 (Iodine adsorption amount: 85 mg / g, nitrogen adsorption specific surface area: 280 m ² / g) manufactured by Showa Cabot Corporation.
(Note 3) The anti-aging agent is “Sant Flex 13” manufactured by Flexis Co., Ltd.
(Note 4) Stearic acid is “paulownia” manufactured by NOF Corporation.
(Note 5) Zinc flower is “Zinc oxide No. 2” manufactured by Mitsui Kinzoku Co., Ltd.
(Note 6) Sulfur is “Seimi Sulfur” manufactured by Nippon Kiln Kogyo Co., Ltd.
(Note 7) The vulcanization accelerator is “Noxeller NS” manufactured by Ouchi Shinsei Chemical Co., Ltd.

The properties of the vulcanized rubbers of the examples and comparative examples based on Table 1 were evaluated by the following methods.
<Processability>
The Mooney viscosity (ML _{1 + 4} ) was measured at 130 ° C. according to the Mooney viscosity measurement method defined in JIS-K6300. The Mooney viscosity index was expressed by the following formula. The larger the index, the lower the Mooney viscosity and the better the processability.

(Mooney viscosity) = (ML _{1 + 4} of Comparative Example 1) / (ML _{1 + 4 of} each formulation) × 100
<Tensile strength>
The rubber composition after vulcanization of the rubber composition was subjected to 300% elongation tensile stress M, breaking strength (Tb) and elongation using a test piece punched with dumbbell No. 3 in accordance with JIS-K6301. Eb) was measured. The larger the tensile strength value, the better the tire wear resistance.

<Hardness (JIS-A)>
The rubber composition after vulcanization of the rubber composition was measured for JIS-A hardness at 25 ° C. according to JIS-K6301.

<Evaluation results>
From Table 1, since Example 1 of the present invention uses an NR / chitin whisker composite and Example 2 uses an NR / chitosan whisker composite, the modulus, tensile strength (Tb) and hardness are not impaired without impairing workability. And the tire using the rubber composition has improved steering stability.

(4) Examples 3 and 5
3 g of chitin (manufactured by Aldrich) is added with 50 g of 3N hydrochloric acid, and the mixture is allowed to stand for 3 hours at room temperature under reduced pressure by an aspirator to infiltrate hydrochloric acid. And it is made to react at 105 degreeC for 6 hours. This solution is transferred to a dialysis cellulose tube and dialyzed against deionized water for 2 days. Most of the water was removed under reduced pressure and freeze-dried to obtain chitin whiskers with white needle crystals. The fiber diameter D of the chitin whisker is 43 nm, and the aspect ratio (L / D) is 8.

  Components obtained by removing sulfur and a vulcanization accelerator from the compounding agents shown in Table 2 were kneaded using a 1.7 L Banbury mixer manufactured by Kobe Steel. Thereafter, sulfur and a vulcanization accelerator were added and further kneaded with a biaxial roller. The obtained mixture was vulcanized at 175 ° C. for 10 minutes to obtain a rubber composition. The adjustment method of the said rubber composition employ | adopted the same method also in the Example and comparative example which are demonstrated below.

(5) Examples 4 and 6
75 g of a 40 wt% sodium hydroxide aqueous solution is added to 3 g of chitin whiskers and allowed to stand for 3 hours at room temperature under reduced pressure by an aspirator to infiltrate the alkali. Add 25 g of ice and stir at 0 ° C. to prepare an aqueous alkaline chitin solution. This solution is transferred to a dialysis cellulose tube and dialyzed against deionized water for 2 days. Most of the water was removed under reduced pressure and lyophilized to obtain white crystalline chitosan whiskers. Chitosan whisker has a fiber diameter D of 40 nm and an aspect ratio (L / D) of 9.5.

(6) Comparative Examples 2-5
Based on the formulation shown in Table 2, a rubber composition was prepared in the same manner as in Example 3 except that chitin whisker and chitosan whisker were blended.

The formulations used in Table 2 are as follows.
(Note 1) Natural rubber is RSS # 3 grade.
(Note 2) SBR is SBR1502 manufactured by Sumitomo Chemical Co., Ltd.
(Note 3) Carbon black N550 is a seast made by Tokai Carbon Co., Ltd. (nitrogen adsorption specific surface area: 42 m ² / g).
(Note 4) Stearic acid is “paulownia” manufactured by NOF Corporation.
(Note 5) Zinc oxide is "Zinc oxide type 2" manufactured by Mitsui Kinzoku Kogyo Co., Ltd.
(Note 6) Sulfur is “Seimi Sulfur” manufactured by Nippon Kiln Kogyo Co., Ltd.

(7) Production of Pneumatic Tire Each unvulcanized rubber composition was extruded with a bead apex having a predetermined shape and bonded with a pre-molded cap rubber to form a tread rubber. This was molded together with other tire members and press vulcanized at 170 ° C. for 10 minutes to produce a tire (size 185 / 70R14) with the structure shown in FIG. The carcass of the prototype tire has polyester cords (1670 tex / 2) arranged at an angle of 90 degrees in the tire circumferential direction. In the breaker, two layers of steel cords were arranged at an angle of 24 ° × 24 ° and the cord angles were arranged in opposite directions.

<Rolling resistance: Viscoelastic properties>
The rubber composition after vulcanization of the rubber composition was cut with a knife and molded into a test piece of 50 mm × 4 mm × 2.5 mm. Using the viscoelastic spectrometer “VES-F-3” manufactured by Iwamoto Seisakusho Co., Ltd., the prepared test piece was complex elastic modulus (E *) at a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2% at 60 ° C. ) And loss tangent (tan δ).

  The loss tangent (tan δ) value of Comparative Example 1 was set to 100, and the rolling resistance was evaluated based on the relative value. Larger values indicate better rolling resistance.

<Steering stability>
The above-mentioned prototype tire (185 / 70R14) was mounted on a passenger car, and the vehicle was driven at an air temperature of 25 ° C., and the steering wheel response was evaluated by the driver's feeling. Relative evaluation was performed by setting the evaluation of Comparative Example 1 to 6. The larger the value, the better the steering stability.

<Workability and hardness>
Workability and hardness were measured by the methods described above.

<Characteristic evaluation>
In Examples 3 to 6 of the present invention, since chitin fibers or chitosan fibers are blended in the bead apex, the strength and hardness of the rubber composition are increased, and the rolling resistance and steering stability of the tire are improved. Is recognized.

  In the present invention, since a predetermined amount of chitin fiber and / or chitosan fiber is blended in the structural member of the tire, the heat generation is reduced, the hardness and rigidity of the rubber composition can be increased, and the steering characteristics can be improved. The present invention can be applied not only to passenger car tires but also to tires of various categories such as truck bus tires and light truck tires.

The right half of sectional drawing of the pneumatic tire of this invention is shown.

Explanation of symbols

  1 tire, 2 chafer, 3 bead part, 4 bead core, 5 bead apex, 6 band, 7 tread part, 8 side wall part, 9 breaker part, 10 carcass.

Claims (6)

  A chitin fiber and / or chitosan fiber having a fiber diameter D of 100 nm or less and an aspect ratio (L / D) represented by a ratio of the fiber diameter D to the fiber length L of 5 or more is 100 masses of a diene rubber component. The rubber composition which mix | blended 5-100 mass parts with respect to part.   The fiber diameter D of the chitin fiber and / or chitosan fiber is 50 nm or less, and the aspect ratio (L / D) represented by the ratio of the fiber diameter D and the fiber length L is 10 or more. Rubber composition.   The rubber composition according to claim 1, wherein 20 to 100 parts by mass of carbon black is blended with the diene rubber component.   A pneumatic tire using the rubber composition according to any one of claims 1 to 3 in a tread portion.   A pneumatic tire using the rubber composition according to any one of claims 1 to 3 for a bead apex.   The manufacturing method of the rubber composition of Claim 1 obtained by coagulating the latex after disperse | distributing chitin fiber and / or chitosan fiber in latex.

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