JP5466471B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

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

In order to prevent tire deterioration (such as generation of cracks) due to ozone, a method is used in which a film is formed by blending wax into the tire and blooming the wax on the surface of the tire. As the wax, paraffin wax (Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd.), which is a petroleum wax, is usually used.

The speed at which the wax moves to the tire surface varies depending on the molecular weight (carbon number) of the wax. Therefore, in order to maintain the weather resistance for a long period of time, it is desirable that the carbon number distribution of the wax (weight frequency distribution of each carbon number component) is broad in the range of 20 to 50 carbon atoms (see Patent Document 1). Although the above paraffin wax satisfies this condition, it is expected that it will be difficult to obtain in the future when the oil is depleted because it uses petroleum as a fossil resource. In addition, when a large amount of paraffin wax is used, there is a problem that the tire may be discolored due to the migration of the anti-aging agent to the surface, which may impair the appearance of the tire.

The above problems can be solved by using biomass-derived natural waxes such as carnauba wax, jojoba wax, and rice wax, but these waxes depend on biological resources, and the harvest also depends on human hands. There is a problem that mass production is difficult.

Moreover, the natural wax derived from biomass tends to have a narrow molecular weight (carbon number) and a narrow carbon number distribution depending on the type of biomass as a raw material. Furthermore, a natural wax derived from biomass having a carbon number distribution having a peak in the range of 30 to 40 carbon atoms is not generally known. Therefore, when only biomass-derived natural wax is used, a broad carbon number distribution cannot be obtained in the range of 20 to 50 carbon atoms, and the weather resistance may not be maintained for a long time.

Patent Document 2 discloses a rubber composition containing vegetable wax. However, all the plant waxes mentioned here are natural waxes derived from biomass and depend on biological resources, so there is room for improvement in that mass production is difficult.

JP 2008-031433 A JP 2007-308624 A

The present invention solves the above-mentioned problems and can maintain the weather resistance for a long period of time without impairing the appearance of the tire, can reduce the amount of petroleum resources used, and can easily secure the raw material. It aims at providing a composition and a pneumatic tire using the same.

The present invention relates to a tire rubber composition containing a rubber component, a biomass-derived synthetic wax, and a biomass-derived natural wax.

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

According to the present invention, since it is a rubber composition for a tire containing a biomass-derived synthetic wax and a biomass-derived natural wax, weatherability can be maintained for a long time without impairing the appearance of the tire, It is possible to provide a pneumatic tire that can reduce the amount of petroleum resources used and can easily secure raw materials.

The rubber composition of the present invention contains a biomass-derived synthetic wax (hereinafter also referred to as a first wax) and a biomass-derived natural wax (hereinafter also referred to as a second wax). By using these waxes in combination, it is possible to obtain a broad carbon number distribution in the range of 20 to 50 carbon atoms, as well as petroleum-based waxes such as paraffin wax, while being derived from biomass. Can be maintained. Further, unlike the case of using petroleum-based wax, even if it is used in a large amount, the aesthetic appearance of the tire is not impaired. Furthermore, since it is not necessary to use petroleum-based wax, the amount of petroleum resources used can be reduced and future oil depletion can be accommodated.

The first wax is not particularly limited as long as it is a wax produced by chemical synthesis using biomass (a biological organic resource excluding fossil resources) as a raw material. The first wax can be produced, for example, based on a substance obtained by heat-treating biomass. Since biomass that exists in large quantities on the earth is used as a raw material, the amount of the first wax necessary for manufacturing tires can be easily secured, mass production can be performed, and costs can be reduced. In addition, quality variations can be reduced. Examples of the substance include biogas (methane, carbon monoxide, hydrogen, etc.), alcohols (methanol, ethanol, butanol, etc.), fatty acids, glycerin fatty acid esters (oils and fats), polyglycols (polyethylene glycol, etc.) Is mentioned. Although 1st wax may be used independently, it is preferable to use 2 or more types together from the point that a desired carbon number profile can be obtained easily.
In this specification, chemical synthesis refers to production of a target compound using a chemical reaction (including a microbial reaction and an enzyme reaction).

The method for producing the first wax is not particularly limited. For example, the Fischer-Tropsch method (FT method) in which carbon monoxide and hydrogen are catalyzed (described in JP 2008-56817 A, JP 2008-231270 A, and the like) is described. And a method using an enzyme or a microorganism (methods described in JP-A No. 2006-211924, JP-A No. 63-28396, etc.) can be used. Among these, a method using Stenotrophomonas maltophilia (ATCC 17674) is preferable because a desired carbon distribution can be easily obtained.

The wax obtained using the FT method (FT wax) usually has a carbon number distribution in the range of 20 to 50 carbon atoms, and the carbon number distribution has a peak between 30 and 40 carbon atoms. As described above, a natural wax derived from biomass having a carbon number distribution having a peak in the range of 30 to 40 carbon atoms is not generally known. Therefore, by using the FT method, it is possible to easily obtain a wax having a carbon number distribution different from that of a general second wax. Therefore, the wax compounded in the rubber composition (the first wax and the second wax) The carbon number distribution of the mixture can be easily made to have a desired profile (profile broad in the range of 20 to 50 carbon atoms).

In the case of a method using an enzyme or a microorganism, a wax having a desired carbon number distribution can be easily obtained by appropriately selecting a raw material (such as a substrate for an enzyme reaction). A person skilled in the art can appropriately select a raw material necessary for producing a wax having a desired carbon number distribution (for example, a carbon number distribution having a peak in the range of 30 to 40 carbon atoms).

By obtaining the first wax having the desired carbon number distribution (for example, the carbon number distribution having a peak in the range of 30 to 40 carbon atoms) by the above method and the like, and mixing with the second wax, the rubber composition The carbon number distribution of the wax (a mixture of the first wax and the second wax) can be easily set to a desired profile (a broad profile in the range of 20 to 50 carbon atoms).
The desired carbon number distribution of the first wax can be appropriately changed according to the composition of the second wax mixed with the first wax, but can be easily selected by those skilled in the art.

When only the first wax is used, it is difficult or impractical to obtain a carbon number distribution having a desired profile. For example, in the case of the FT method, the carbon number distribution of the obtained FT wax usually has a peak in the range of 30 to 40, and is not sufficiently broad in the range of 20 to 50 carbon atoms. In the case of a method using an enzyme or a microorganism, the number of carbons of the obtained wax (microorganism conversion wax) depends on the raw material, so that a wax having a carbon number distribution of a desired profile is obtained by using a plurality of raw materials. Although it is theoretically possible, it is not realistic to prepare a plurality of raw materials because it is very complicated and the manufacturing process is complicated. On the other hand, according to the present invention, the carbon number distribution of a desired profile can be efficiently obtained by using the first wax and the second wax in combination.

The second wax is not particularly limited as long as it is a wax produced by refining biomass as a raw material without using chemical synthesis, for example, carnauba wax, candelilla wax, rice wax, wax, Plant waxes such as jojoba wax and animal waxes such as beeswax, lanolin and spermaceti can be used. Especially, it is preferable to use a carnauba wax from the point that a weather resistance can be improved more, and it is more preferable to use carnauba wax and other 2nd wax together.

The carbon number distribution profile of the wax can be determined by a value obtained by dividing the standard deviation of the carbon number distribution by the average carbon number. It shows that carbon number distribution is broad, so that this value is large.
In addition, the standard deviation and average carbon number of the carbon number distribution described below are values obtained for a range of 20 to 50 carbon atoms. The standard deviation of the carbon number distribution is a value obtained by opening the sum of (individual carbon number−average carbon number) ² to a square. Individual and average carbon numbers can be measured by gas chromatography analysis.

The value obtained by dividing the standard deviation of the carbon number distribution of the wax (mixture of the first wax and the second wax) blended in the rubber composition by the average carbon number is preferably 1.00 or more, more preferably 1.05 or more. It is. If it is less than 1.00, the variation in the carbon number distribution is too small, and there is a possibility that the weather resistance cannot be maintained for a sufficient period. The upper limit of the value is not particularly limited.

The carbon number distribution of wax varies depending on the production method and raw materials. Therefore, when mixing the first wax and the second wax, they may be appropriately mixed so as to obtain a carbon number distribution of a desired profile, and the respective mass ratios are not particularly limited.

The total content of the first wax and the second wax is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, and most preferably 15 parts by mass with respect to 100 parts by mass of the rubber component. More than a part. If it is less than 2 parts by mass, the weather resistance may not be sufficiently improved. The total content is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and still more preferably 20 parts by mass or less. If it exceeds 30 parts by mass, the breaking strength tends to decrease.

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), styrene isoprene butadiene. Common materials in the tire industry such as rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) can be used. Among these, NR, ENR, BR, and SBR are preferably used because the required performance can be easily secured in each member of the tire. Note that NR, ENR, BR, and SBR are not particularly limited, and those commonly used in the tire industry can be used. However, from the viewpoint of reducing the amount of fossil resources such as petroleum, raw materials other than fossil resources are used. It is preferable to use those manufactured by

The tire rubber composition of the present invention includes a rubber component, a first wax and a second wax, a filler such as silica and carbon black, a silane coupling agent, an oil, a tackifier, an antioxidant, and an ozone deterioration preventive agent. Additives as required, such as an agent, an anti-aging agent, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerating aid can be appropriately blended.

As a method for producing the rubber composition for a tire of the present invention, a known method can be used, for example, the above components are kneaded using a rubber kneader such as an open roll, a Banbury mixer, a closed kneader, Thereafter, it can be produced by a method of vulcanization. The rubber composition can be particularly suitably used for treads and sidewalls because of its excellent performance.

In the step of kneading each component, the first wax and the second wax may be added alone, but it is preferable to add the first wax and the second wax after mixing in advance. Thereby, wax can be uniformly dispersed in the rubber composition.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, the rubber composition containing the above components is extruded in accordance with the shape of a tire member such as a sidewall at an unvulcanized stage, and is molded together with other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The use of the pneumatic tire of the present invention is not particularly limited, but it can be suitably used particularly for passenger cars, trucks and buses.

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

Production Example 1
(FT wax)
A Fischer-Tropsch reactor filled with 2 ml of a cobalt catalyst held on a silica support containing 18 L of biogas (obtained by livestock manure compost) containing carbon dioxide and hydrogen and having a hydrogen / carbon dioxide ratio of 2.0. It supplied over 1 hour and reacted on 240 degreeC and 0.1 Mpa conditions. Then, the product (FT wax) was obtained by cooling and removing water vapor | steam. When the composition of the product was examined by gas chromatography analysis, it was found that the wax having 30 or less carbon atoms was 4.12 mmol, the wax having 32 carbon atoms was 0.18 mmol, the wax having 34 carbon atoms was 0.14 mmol, and the wax having 36 carbon atoms was obtained. 0.11 mmol, the wax having 38 carbon atoms was 0.08 mmol, and the wax having 40 or more carbon atoms was 0.17 mmol.

Production Example 2
(Microbial conversion wax)
50 mL of M9 medium was inoculated with Stenotrophomonas maltophilia (ATCC 17674), added with 100 mM soybean oil containing 11% by mass of palmitic acid, 20% by mass of oleic acid having 18 carbon atoms, and 48% by mass of linoleic acid. The product (microorganism conversion wax) was obtained by culturing for 3 days under conditions of 250 rpm and 28 ° C. The composition of the product was examined by gas chromatography analysis. As a result, the wax having 28 or less carbon atoms was 3.2 mmol, the wax having 29 carbon atoms was 30.18 mmol, the wax having 30 carbon atoms was 27.28 mmol, and the carbon number was 31. The wax was 5.11 mmol and the wax having 32 or more carbon atoms was 1.08 mmol.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: SIR20
ENR: ENR50 manufactured by Kunpu Langursley
BR: BR150B manufactured by Ube Industries
Carbon Black: Show Black N220 manufactured by Cabot Japan
Silica: Ultrasil VN3 manufactured by Degussa
Silane coupling agent: Si266 (bis- (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Paraffin wax: Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd. (standard deviation of carbon number distribution / average carbon number: 1.2)
Carnauba wax: Carnauba wax manufactured by Toa Kasei Co., Ltd. (standard deviation of carbon number distribution / average carbon number: 1.0)
Mixed wax (1): Mixed wax manufactured by Toa Kasei Co., Ltd. (a mixture of carnauba wax, candelilla wax, rice wax, beeswax. Standard deviation of carbon number distribution / average carbon number: 1.5)
Mixed wax (2): Mixture of FT wax produced in Production Example 1 and microbial conversion wax produced in Production Example 2 (standard deviation of carbon number distribution / average carbon number: 1.4)
Mixed wax (3): Mixture of mixed wax (1) and (2) (standard deviation of carbon number distribution / average carbon number: 1.2)
Mixed wax (4): Mixture of mixed wax (1) and FT wax produced in Production Example 1 (standard deviation of carbon number distribution / average carbon number: 0.8)
Mixed wax (5): Mixture of mixed wax (1) and microbial conversion wax produced in Production Example 2 (standard deviation of carbon number distribution / average carbon number: 0.7)
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine (6PPD)) manufactured by Sumitomo Chemical Co., Ltd.
Process oil: JOMO process X140 (Aroma oil) manufactured by Japan Energy Co., Ltd.
Stearic acid: Zinc oxide manufactured by NOF Co., Ltd .: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide)

Examples 1-6 and Comparative Examples 1-9
According to the formulation shown in Table 1, chemicals other than sulfur and a vulcanization accelerator were kneaded for 6 minutes at 150 ° C. using a Banbury mixer to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 70 ° C. using an open roll to obtain an unvulcanized rubber composition. Further, the obtained unvulcanized rubber composition was formed into a sidewall shape, bonded together with other tire members, press-vulcanized for 8 minutes at 185 ° C., and a test tire (tire size: 165R13 × SP10) was produced.

The following evaluation was performed using the obtained test tire. The test results are shown in Tables 1 and 2.

(Static ozone test)
The test tire was assembled on a rim (5 J × 13), placed side by side in an ozone chamber under conditions of an internal pressure of 200 kPa, a temperature of 25 ° C., and an ozone concentration of 50 pphm, and the number of days until cracks were generated was measured. In the table, “> 120 days” indicates that cracks did not occur even after 120 days, and “<1 days” indicates that cracks occurred in less than one day. The longer the number of days, the longer the weather resistance can be maintained.

(appearance)
The state of the test tires left for 180 days outdoors covered with rainwater was visually observed and evaluated according to the following criteria.
◎: No discoloration ○: Partial discoloration △: Most discoloration ×: Discoloration throughout the tire

From Table 1 and 2, the Example which used either mixed wax (3)-(5) was able to maintain a weather resistance for a long period of time. Moreover, when the blending amount of any of the mixed waxes (3) to (5) was increased, the weather resistance could be maintained for a longer period. Furthermore, even if the blending amount of any of the mixed waxes (3) to (5) was increased, no discoloration occurred.

In Comparative Example 1 in which a small amount of paraffin wax was blended, weather resistance could not be maintained for a long time, and discoloration occurred. In Comparative Example 2 in which the blending amount of the paraffin wax was larger than that in Comparative Example 1, although the weather resistance could be maintained for a long time, the occurrence rate of discoloration was higher than that in Comparative Example 1.

In Comparative Examples 3 and 4 in which carnauba wax was blended, discoloration did not occur, but the period in which the weather resistance could be maintained was shorter than in Examples 1 and 2 where the blending other than the wax was the same.

In Comparative Example 5 in which no wax was blended, the period during which the weather resistance could be maintained was very short.

Although the discoloration did not generate | occur | produce in Comparative Examples 6 and 7 which mix | blended the mixed wax (1), the period which was able to maintain a weather resistance was shorter than Example 1, 2 which is mixing | blending except wax. Comparative Examples 8 and 9 containing the mixed wax (2) had the same tendency.

Claims (5)

A method for producing a rubber composition for a tire , comprising a step of chemically synthesizing a synthetic wax from a biomass raw material, and a step of kneading a rubber component, a natural wax derived from biomass and the synthetic wax obtained in the above step . The method for producing a rubber composition for a tire according to claim 1, wherein the step of chemically synthesizing the synthetic wax from the biomass raw material is chemically synthesized using a Fischer-Tropsch method. The manufacturing method of the rubber composition for tires of Claim 1 or 2 which manufactures the rubber composition whose sum total content of the said natural wax with respect to 100 mass parts of said rubber components and the said synthetic wax is 5-30 mass parts. The manufacturing method of the rubber composition for tires in any one of Claims 1-3 including the process of previously mixing the said natural wax and the said synthetic wax before kneading | mixing with the said rubber component. A method for producing a pneumatic tire , comprising: a step of chemically synthesizing a synthetic wax from a biomass raw material; and a step of kneading a rubber component, a natural wax derived from biomass and the synthetic wax obtained in the above step .