JP5587692B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

The present invention relates to a rubber composition for a tire and a pneumatic tire using the same.

In order to prevent tire deterioration (such as generation of cracks) due to ozone, a method of blending wax and blooming the surface of the tire to form a film is used. Petroleum wax such as paraffin wax is usually used as the wax, but it may be difficult to obtain when fossil resources are depleted in the future, and there is also a problem that environmental considerations are insufficient. is there. Therefore, it has been studied to incorporate natural waxes (natural waxes) such as carnauba wax, jojoba wax, rice bran wax, beeswax, and candelilla wax.

In general, when wax has a broad carbon number distribution, ozone resistance is exhibited over a wide temperature range. However, the carbon number distribution (molecular weight distribution) of natural wax, that is, the softening point distribution varies depending on the organism of origin. In many cases, it is not broad. For this reason, there is a problem that sufficient ozone resistance cannot be obtained with natural waxes. On the other hand, even if an attempt is made to cope with the problem by increasing the amount of wax, the bloom on the surface of the tire is excessively whitened and the appearance of the tire is impaired.

Patent Document 1 discusses the use of natural waxes such as candelilla wax and beeswax in tires, and discloses a tire rubber composition in which the content ratio of petroleum resources is suppressed. However, measures against ozone resistance and whitening are insufficient, and improvement is desired.

JP 2008-303249 A

The present invention provides a tire rubber composition that solves the above-mentioned problems and is excellent in ozone resistance and can prevent discoloration (whitening, etc.) while considering the environment, and a pneumatic tire using the same. Objective.

As a result of intensive studies on the cause of insufficient ozone resistance when using natural waxes, the present inventor has found that the carbon number distribution (molecular weight distribution) of natural waxes is not broad, and natural Wax-based wax has less branched component (iso component) than petroleum-based wax, so that it is not possible to form an effective film over the entire temperature range, and sufficient ozone resistance is obtained. I came up with the hypothesis that it was not. By blending a natural linear isoprenoid hydrogenated product (component having a branched structure (iso component)) with a natural wax, the molecular weight distribution of the wax can be broadened. The present inventors have found that the amount of a branched structure component (iso component) can be increased, sufficient ozone resistance can be obtained while considering the environment, and discoloration of the rubber surface can be sufficiently suppressed.
That is, the present invention relates to a tire rubber composition containing a hydrogenated natural linear isoprenoid having 20 to 55 carbon atoms and a natural wax.

It is preferable that the total content of the natural linear isoprenoid hydrogenated product and the natural wax is 2 to 25 parts by mass with respect to 100 parts by mass of the rubber component.

Of the total content of the natural linear isoprenoid hydrogenated product and the natural wax, 100% by mass, the content of the natural linear isoprenoid hydrogenated product is preferably 5 to 25% by mass.

The present invention also relates to a pneumatic tire having a tire member produced using the rubber composition.

According to the present invention, since it is a rubber composition for tires containing a hydrogenated natural linear isoprenoid having 20 to 55 carbon atoms and a natural wax, ozone resistance is improved while considering the environment. it can. Further, discoloration of the rubber surface can be sufficiently suppressed.

The rubber composition for tires of the present invention contains a natural linear isoprenoid hydrogenated product having 20 to 55 carbon atoms and a natural wax. By using the hydrogenated product instead of the natural linear isoprenoid, double bonds are reduced and ozone resistance can be improved. Further, the hydrogenation increases the melting point (softening point) of the natural linear isoprenoid. Therefore, the combined use of the hydrogenated product and the natural wax provides a broad and broad molecular weight distribution, and also includes a hydrocarbon (iso component) having a branched structure derived from the hydrogenated product. An effective film can be formed on the surface, and excellent ozone resistance is exhibited in a wide temperature range. In addition, the broad molecular weight distribution can prevent whitening due to excessive bloom.

Furthermore, natural linear isoprenoid hydrogenated products and natural waxes are produced (produced) using non-petroleum resources as raw materials, and are therefore desirable from the viewpoint of environmental considerations.

The rubber composition of the present invention contains a hydrogenated product of a natural linear isoprenoid having 20 to 55 carbon atoms (hereinafter also simply referred to as “hydrogenated product”). The hydrogenated product of natural linear isoprenoid is a hydrogenated product of isoprenoid derived from non-petroleum resources having a chain structure in which carbon number 5 isoprene units are linearly bonded in a basic skeleton. Examples thereof include those having a structure (basic skeleton) represented by the formula. With such a basic skeleton, excellent ozone resistance and discoloration resistance can be obtained.

The hydrogenated product of the natural linear isoprenoid is obtained by hydrogenating a natural linear isoprenoid having 20 to 55 carbon atoms.
The natural linear isoprenoid satisfying the above carbon number is not particularly limited as long as it is produced (produced) using something other than petroleum, for example, a product obtained from a living organism such as a plant (biologically derived product). And those synthesized by enzymatic reaction, those synthesized by callus culture, and the like. Examples of enzymes that can be used include linear prenyl diphosphate synthases such as farnesyl diphosphate synthase, geranylgeranyl diphosphate synthase, squalene synthase, and phytoene synthase. As methods for obtaining natural linear isoprenoids by callus culture, JP 2007-215518 A, and for synthesis of natural linear isoprenoids by enzymatic reaction, JP 2004-24275 A, JP 11-178590 A, Examples include the method described in the publication. In the case of enzyme or callus culture, a genetically modified one may be used.

Examples of the natural linear isoprenoid include those having a chain structure in which 2 to 11 (preferably 4 to 11, more preferably 6 to 10) isoprene units are linearly bonded.

Specific examples of the natural linear isoprenoid include geranylgeranyl diphosphate, geranylgeraniol, geranylfarnesyl diphosphate, squalene, hexaprenyl diphosphate, heptaprenyl diphosphate, phytoene, lycopene, carotene, octaprenyl diphosphate Acid, nonaprenyl diphosphate, decaprenyl diphosphate and the like can be mentioned. The natural linear isoprenoid may have a cyclic structure in the molecule such as the above-mentioned carotenes, but preferably does not have the cyclic structure in the molecule. In this case, excellent ozone resistance and discoloration resistance can be obtained.

The hydrogenation reaction of the natural linear isoprenoid can be performed by a known hydrogenation method. For example, a hydrogenation catalyst (homogeneous hydrogenation catalyst, heterogeneous hydrogenation catalyst) is used, and 1-100 It can be carried out by hydrogenation under pressurized hydrogen at atmospheric pressure. Examples of the hydrogenation catalyst include compounds containing at least one metal selected from titanium, zirconium, hafnium, molybdenum, iron, cobalt, nickel, rhenium, ruthenium, rhodium, palladium, platinum, and group 1-3 organic metals. Specifically, nickel organic carboxylate, cobalt organic carboxylate and the like can be used.

When the natural linear isoprenoid has a phosphate group (hexaprenyl diphosphate, heptaprenyl diphosphate, etc.), the hydrogenated product is dephosphorylated (dephosphorylated) by a conventionally known method. Then, after being converted to alcohol, those obtained by hydrogenation are preferred. Thereby, more excellent ozone resistance is obtained.

The hydrogenated product preferably has 30 or more carbon atoms. If it is less than 30, there is a possibility that it will dissolve with the rubber and the hydrogenated product will not precipitate on the tire surface (does not form a film). The carbon number is preferably 50 or less. If it exceeds 50, precipitation of hydrogenated products and natural wax tends to be delayed, and crack resistance (ozone resistance) tends to decrease.

The hydrogenation rate of double bonds in the hydrogenated product is preferably 30 mol% or more, more preferably 40 mol% or more, based on the number of original double bonds. When the hydrogenation rate is less than 30 mol%, there are too many double bonds and the desired ozone resistance tends not to be obtained. Further, the upper limit of the hydrogenation rate is not particularly limited, and may be 100 mol%.
Here, the hydrogenation rate can be calculated from the spectrum reduction rate of the unsaturated bond portion of the spectrum obtained by measuring proton NMR.

The rubber composition of the present invention preferably contains two or more hydrogenated products having different numbers of carbon atoms and / or isoprene units. As a result, a broad molecular weight distribution can be obtained, and hydrocarbons (isocomponents) with different numbers of branch structures can be included, so that a more effective film can be formed and better ozone resistance and discoloration resistance can be formed. Sex is obtained.

In a total content of 100% by mass of the hydrogenated product and the natural wax, the content of the hydrogenated product is 5% by mass or more, preferably 10% by mass or more. If it is less than 5% by mass, discoloration resistance tends to deteriorate. The content is 25% by mass or less, preferably 20% by mass or less. When it exceeds 25% by mass, the precipitation of the wax is excessively reduced and the crack resistance (ozone resistance) tends to deteriorate.

The rubber composition of the present invention contains a natural wax.
Natural waxes are not particularly limited as long as they are derived from non-petroleum resources. For example, plant waxes such as candelilla wax, carnauba wax, wood wax, rice wax, jojoba wax; beeswax, lanolin, whale wax, etc. Animal waxes; mineral waxes such as ozokerite, ceresin, petrolactam; natural fats and oils such as castor oil, soybean oil, rapeseed oil, and beef fat oil; and refined products thereof. Among them, plant waxes and animal waxes are preferred because they can have a broad molecular weight distribution, exhibit ozone resistance in a wide temperature range, and prevent whitening due to bloom. Wax, carnauba wax, rice wax, and beeswax are more preferable.

When carnauba wax is contained, the content of carnauba wax in 100% by mass of the natural wax is preferably 10% by mass or more. The content is preferably 40% by mass or less. By making this content within the above range, weather resistance in all temperature ranges can be provided.

When the candelilla wax is contained, the content of the candelilla wax in 100% by mass of the natural wax is preferably 10% by mass or more. The content is preferably 40% by mass or less. By making this content within the above range, weather resistance in all temperature ranges can be provided.

When the rice wax is contained, the content of the rice wax in 100% by mass of the natural wax is preferably 10% by mass or more. The content is preferably 40% by mass or less. By making this content within the above range, weather resistance in all temperature ranges can be provided.

When beeswax is contained, the content of beeswax in 100% by mass of the natural wax is preferably 10% by mass or more. The content is preferably 40% by mass or less. By making this content within the above range, weather resistance in all temperature ranges can be provided.

The total content of the natural wax and the hydrogenated product is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and still more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 25 parts by mass or less, and more preferably 18 parts by mass or less. In the present invention, by using a hydrogenated product and a natural wax in combination, even when the total content is within the above range (particularly 15 parts by mass or more), excessive bloom is suppressed, and thus whitening can be prevented.

The rubber component that can be used in the present invention is not particularly limited, and natural rubber (NR), epoxidized natural rubber (ENR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and other tire industries. A general one can be used. In particular, when a hydrogenated product and a natural wax are blended with NR, ENR, and BR, the effects of the present invention can be sufficiently obtained.

As ENR, commercially available ENR may be used, or natural rubber (NR) may be epoxidized. The method for epoxidizing NR is not particularly limited, and can be carried out using a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, or a peracid method (Japanese Patent Publication No. 4). No. -26617, JP-A-2-110182, British Patent Application No. 2113692, etc.). Examples of the peracid method include a method of reacting NR with an organic peracid such as peracetic acid or performic acid.

The NR to be epoxidized is not particularly limited, and those generally used in the rubber industry such as RSS # 3 and TSR20, and latexes thereof can be used. ENRs may be used alone or in combination of two or more.

The epoxidation rate of ENR is preferably 30 mol% or more, more preferably 40 mol% or more. If it is less than 30 mol%, the effect of the modification tends not to be sufficiently exhibited. The epoxidation rate of ENR is preferably 60 mol% or less, more preferably 55 mol% or less. If it exceeds 60 mol%, the polymer tends to gel.
The epoxidation rate means the ratio of the number of epoxidized out of the total number of carbon-carbon double bonds in the natural rubber component before epoxidation. For example, titration analysis, nuclear magnetic resonance (NMR) analysis, etc. Is required.

When the rubber composition of the present invention contains ENR, the content of ENR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 50% by mass or more. Moreover, this content becomes like this. Preferably it is 90 mass% or less, More preferably, it is 65 mass% or less. By making it within the above range, the effects of the present invention can be obtained satisfactorily.

When the rubber composition of the present invention contains NR, the content of NR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 35% by mass or more. If it is less than 10% by mass, the wear resistance tends to deteriorate. The content is preferably 70% by mass or less, more preferably 50% by mass or less. If it exceeds 70% by mass, grip performance tends to decrease.

When the rubber composition of the present invention contains BR, the content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more. If it is less than 10% by mass, the wear resistance tends to deteriorate. The content is preferably 90% by mass or less, more preferably 70% by mass or less. If it exceeds 90% by mass, grip performance tends to decrease.

The tire rubber composition of the present invention preferably contains carbon black. Thereby, good ozone resistance and a reinforcing effect are obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² / g or more, and more preferably 70 m ² / g or more. When N ₂ SA is less than 30 m ² / g, there is a tendency that sufficient reinforcing properties cannot be obtained. Also, _N 2 SA of carbon black is preferably 250 meters ² / g or less, more preferably 150m ² / g. When N ₂ SA exceeds 250 m ² / g, fuel efficiency tends to deteriorate.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

The content of carbon black is preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, ozone resistance tends to deteriorate. The carbon black content is preferably 15 parts by mass or less, more preferably 8 parts by mass or less. If it exceeds 15 parts by mass, the dispersibility and processability tend to deteriorate.

The tire rubber composition of the present invention preferably contains silica. Thereby, while being able to obtain good fuel economy and a reinforcing effect, it is preferable in terms of fracture resistance and workability.

The nitrogen adsorption specific surface area (N ₂ SA) of silica by the BET method is preferably 40 m ² / g or more, and more preferably 100 m ² / g or more. If it is less than 40 m ² / g, the rubber strength tends to decrease. Further, the BET of silica is preferably 220 m ² / g or less, and more preferably 200 m ² / g or less. When it exceeds 220 m ² / g, the workability tends to deteriorate.
In addition, the nitrogen adsorption specific surface area by the BET method of silica can be measured by a method based on ASTM D3037-81.

The content of silica is preferably 20 parts by mass or more, more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. The silica content is preferably 80 parts by mass or less, more preferably 60 parts by mass or less. By making the content of silica within the above range, good fuel economy and reinforcing effect can be obtained, and it is preferable in terms of fracture resistance and workability.

In the present invention, it is preferable to use a silane coupling agent together with silica. Examples of the silane coupling agent include sulfide, mercapto vinyl, amino, glycidoxy, nitro, and chloro silane coupling agents. Among them, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, etc. Sulfide systems are preferred, with bis (3-triethoxysilylpropyl) disulfide being particularly preferred.

When the silane coupling agent is contained, the content of the silane coupling agent is preferably 2 parts by mass or more and more preferably 5 parts by mass or more with respect to 100 parts by mass of silica. The content is preferably 20 parts by mass or less, and more preferably 10 parts by mass or less. By setting the content of the silane coupling agent within the above range, good fuel economy and reinforcement can be obtained.

In addition to the above components, the rubber composition for tires of the present invention generally contains compounding agents generally used in the production of rubber compositions such as zinc oxide, stearic acid, various anti-aging agents, oils, vulcanizing agents, vulcanizing agents. A sulfur accelerator or the like can be appropriately blended.

The rubber composition of the present invention preferably contains an anti-aging agent together with a hydrogenated product and a natural wax. Thereby, ozone resistance can be improved.

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. Of these, amines are preferable, and N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine is more preferable. Here, the content of the anti-aging agent is preferably 1.5 parts by mass or more, more preferably 1.8 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 4 parts by mass or less, more preferably 3 parts by mass or less. By setting the content of the anti-aging agent within the above range, the effect of the present invention can be obtained satisfactorily. Even if the content is within the above range (1.5 parts by mass or more), since the hydrogenated product and the natural wax are used in combination, discoloration can be suppressed. Therefore, discoloration resistance can be improved and ozone resistance can be improved without particularly reducing the amount of anti-aging agent.

The tire rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading each component with a kneader such as a Banbury mixer, a kneader, or an open roll, and then vulcanizing. The rubber composition for tires of the present invention is suitably used as a rubber composition for producing members (particularly sidewalls) disposed outside.

The pneumatic tire of the present invention is produced by a normal method using the tire rubber composition. That is, if necessary, a rubber composition containing various additives is extruded in accordance with the shape of the tire sidewall, etc. at an unvulcanized stage, and molded on a tire molding machine by a normal method. Then, they are bonded together with other tire members to form an unvulcanized tire. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce a tire.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described.
Squalane: Squalane NR: SIR20 from Maruha Nichiro Foods, Inc.
ENR: ENR50 (Epoxidation rate: 50 mol%) manufactured by Kunpu Langursley
BR: Hisys BR150B manufactured by Ube Industries, Ltd.
Carbon black: N220 (N ₂ SA: 119 m ² / g) manufactured by Cabot Japan
Silica: Ultrasil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Petroleum wax: Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd.
Carnauba wax: TOA-131 manufactured by Toa Kasei Co., Ltd.
Natural mixed wax: TOA-200289 manufactured by Toa Kasei Co., Ltd. (formulation: carnauba wax 30% by mass, candelilla wax 30% by mass, rice wax 20% by mass, beeswax 20% by mass)
Wax Example 1: (Formulation: 85% by mass of natural mixed wax, 7.5% by mass of hydrogenated squalene having 30 carbon atoms, 7.5% by mass of hydrogenated phytoene having 40 carbon atoms (Production Example 2))
Wax Example 2: (Formulation: 85% by mass of natural mixed wax, 15% by mass of hydrogenated product obtained in Production Example 1)
Anti-aging agent: Antigen 6C (6PPD) (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Process oil: Aroma oil manufactured by JOMO Co., Ltd. Stearic acid: Stearic acid manufactured by NOF Co., Ltd. Sulfur accelerator: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

Production Example 1 Production method (production) of geranylgeraniol having 20 carbon atoms and hydrogenated product thereof
20 ml of YM medium (manufactured by Difco) was placed in a 100 ml baffled Erlenmeyer flask and autoclaved at 121 ° C. and 1.2 atm for 20 minutes. Saccharomyces cerevisiae ATCC 204660 strain was inoculated and cultured at 30 ° C. with shaking at 130 rpm for 3 days.
(Dephosphorylation)
The culture solution was disrupted with an ultrasonic disrupter and suspended in 100 ml of pH 8.0 Tris-HCL buffer solution containing 6 mM magnesium chloride. For the purpose of hydrolyzing geranylgeranyl nitric acid present in the cells and the culture solution, 0.1 ml of alkaline phosphatase (E. coli) (manufactured by Takara) was added and heat treatment was performed at 65 ° C. for 30 minutes.
(Extraction)
Pentane (300 ml) was added, extracted, and concentrated by evaporating pentane in a fume hood to obtain 5 g of concentrate. The production of geranylgeraniol was confirmed by GC / MS.
(Hydrogenation)
To 4 g of geranylgeraniol, a 0.2% amount of a flake nickel hydrogenation catalyst mainly composed of nickel and held in diatomaceous earth was added to bring the reaction solution to 130 ° C., and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 Mpa for 15 minutes. After cooling to 50 ° C., 3.4 g of hydrogenated product was obtained by removing the catalyst by filtration.

Production Example 2 Production Method of Phytoene and its Hydrogenated Product To a culture medium in which 3 g of geranylgeraniol obtained in Production Example 1 was added to PDA medium (4% potassium extract agar, 1.5% agar) (Phycomyces brakesleanus ( phycomyces blackesleeanus) carB mutant was inoculated and incubated at 30 ° C. for 10 days. Extraction was performed using 100 ml of an organic solvent of pentane: methanol = 2: 1, and concentration was performed by evaporating the solvent in a fume hood to obtain 1 g of a concentrate. The product was confirmed by GC / MS. Hydrogenation was performed in the same manner as in Production Example 1.

(Measurement of hydrogenation rate)
A solution having a concentration of 15% by mass using carbon tetrachloride as a solvent was prepared and calculated from the spectrum reduction rate of the unsaturated bond portion of proton NMR at 100 MHz, and 77.4 mol% of a squalene hydrogenated product (squalane), The hydrogenated product of phytoene was 81.1 mol%, and the hydrogenated product of geranylgeraniol was 81.3 mol%.

Examples 1-8 and Comparative Examples 1-7
According to the blending contents shown in Table 1, a chemical other than sulfur and a vulcanization accelerator was kneaded using a 1.7 L Banbury mixer to obtain a kneaded product. Next, using an open roll, sulfur and a vulcanization accelerator were kneaded into the obtained kneaded material to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was pressed with a 2 mm-thick mold at 150 ° C. for 30 minutes to obtain a vulcanized rubber composition.
The obtained unvulcanized rubber composition was molded into a sidewall shape, bonded to another tire member, and vulcanized at 150 ° C. for 30 minutes to obtain a test tire.

The following evaluation was performed using the obtained vulcanized rubber composition and test tire. The results are shown in Table 1.

(Static ozone test)
The test tire manufactured as described above was left in a 50 pphm ozone chamber with an internal pressure of rim 5J × 13 and 200 KPa, and the number of days until cracking was measured.

(appearance)
The test tires that were left outdoors for 180 days were visually observed and evaluated in four stages so as not to be exposed to rainwater.
◎: No discoloration ○: Partial discoloration △: Most discoloration ×: Discoloration throughout the tire

From Table 1, good ozone resistance and discoloration resistance were obtained in the examples containing hydrogenated natural linear isoprenoid having a specific carbon number and natural wax.

Claims (5)

A tire rubber composition comprising a hydrogenated natural linear isoprenoid having a structure represented by the following formula and having 20 to 55 carbon atoms and a natural wax.

2. The tire rubber composition according to claim 1, wherein the total content of the natural linear isoprenoid hydrogenated product and the natural wax is 2 to 25 parts by mass with respect to 100 parts by mass of the rubber component. 3. The natural linear isoprenoid hydrogenated product and the natural wax in a total content of 100% by mass, wherein the content of the natural linear isoprenoid hydrogenated product is 5 to 25% by mass. The rubber composition for tires as described. The tire according to any one of claims 1 to 3, comprising at least one selected from the group consisting of natural rubber, epoxidized natural rubber, and butadiene rubber, carbon black and / or silica, and an antioxidant. Rubber composition. The pneumatic tire which has a tire member produced using the rubber composition in any one of Claims 1-4 .