JP2006070093A - Rubber composition for sidewall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for sidewalls which, with an increased ratio in the content of non-petroleum resources, is friendly to the earth, provides against future decreases in the supply amount of petroleum, and besides shows excellent resistance to flex cracking and tear strength. <P>SOLUTION: The rubber composition for sidewalls contains 15-60 pts. wt. of silica based on 100 pts. wt. of a rubber component consisting of 30-90 wt% of natural rubber and 70-10 wt% of an epoxidized natural rubber. Alternatively, the rubber composition for sidewalls contains a rubber component consisting of 60-100 wt% of natural rubber and a filler consisting of 80 wt% or more of white filler and the rubber composition has a degree of swelling of ≥320 in toluene. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition for a side wall when oil is exhausted.

  Conventional rubber compositions used for tire sidewalls include natural rubber, which exhibits excellent tear strength, and butadiene rubber blended in order to improve flex crack resistance, as well as weather resistance and reinforcement. Carbon black has been used to improve this.

However, in recent years, environmental issues have become more important, regulations on CO ₂ emission control have been tightened, and the supply of oil has been declining year by year. The price is expected to rise, and there are limits to the use of raw materials made of petroleum resources such as butadiene rubber and carbon black. Therefore, assuming that the oil will be depleted in the future, it will be necessary to use non-oil resources such as natural rubber, silica, and white fillers such as calcium carbonate. However, in that case, a performance similar to or better than the resistance to flex cracking and reinforcement obtained by the use of petroleum resources that have been used conventionally is required.

  Patent Document 1 discloses a technique that shows a tire raw material that assumes a case where petroleum is depleted, but does not disclose a rubber composition for a sidewall that exhibits sufficient bending cracking resistance and tear strength. Absent.

JP 2003-63206 A

  The present invention provides a rubber composition for a sidewall which is earth-friendly by increasing the content ratio of non-petroleum resources, prepares for future reduction of petroleum supply, and exhibits excellent bending crack resistance and tear strength. The purpose is to do.

  The present invention relates to a rubber composition for a sidewall containing 15 to 60 parts by weight of silica with respect to 100 parts by weight of a rubber component comprising 30 to 90% by weight of natural rubber and 70 to 10% by weight of epoxidized natural rubber.

  The rubber composition preferably further contains 10 to 40 parts by weight of calcium carbonate.

  The rubber composition is preferably obtained by a production method comprising (1) a step of kneading natural rubber and silica, and (2) a step of kneading epoxidized natural rubber.

  The present invention also provides a rubber composition for a sidewall containing a rubber component comprising 60 to 100% by weight of a natural rubber and a filler comprising 80% by weight or more of a white filler, the toluene swelling of the rubber composition The present invention relates to a rubber composition for a sidewall having a degree of 320 or more.

  The rubber composition preferably further contains a butadiene rubber and / or a syndiotactic butadiene rubber.

  According to the present invention, by increasing the content ratio of non-petroleum resources, it is possible to provide a rubber composition for a sidewall that is used for a tire that is kind to the earth and is prepared for a future reduction in the supply of oil. The composition exhibits excellent flex crack resistance and tear strength.

  First, a rubber composition for a sidewall containing 15 to 60 parts by weight of silica with respect to 100 parts by weight of a rubber component composed of 30 to 90% by weight of natural rubber and 70 to 10% by weight of epoxidized natural rubber will be described below. To do.

  The rubber component in the rubber composition for a sidewall of the present invention comprises natural rubber (NR) and epoxidized natural rubber (ENR).

  As the epoxidized natural rubber, commercially available epoxidized natural rubber may be used, or natural rubber may be epoxidized. The method for epoxidizing natural rubber 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. Examples thereof include a method of reacting natural rubber with an organic peracid such as peracetic acid or performic acid.

  The epoxidation rate of the epoxidized natural rubber is preferably 12 to 50 mol%. If the epoxidation rate is less than 12 mol%, the effect of the epoxidized natural rubber becomes incompatible with the natural rubber, and the effect tends to be low. Tend.

  The content of natural rubber in the rubber component is 30% by weight or more, preferably 40% by weight or more, and the content of epoxidized natural rubber is 70% by weight or less, preferably 50% by weight or less. When the content of the natural rubber is less than 30% by weight and the content of the epoxidized natural rubber exceeds 70% by weight, the rubber strength of the obtained rubber composition is not sufficient. The content of natural rubber is 90% by weight or less, preferably 80% by weight or less, and the content of epoxidized natural rubber is 10% by weight or more, preferably 20% by weight or more. If the content of the natural rubber is greater than 90% by weight and the content of the epoxidized natural rubber is less than 10% by weight, the flex crack resistance is deteriorated.

  In addition to natural rubber and epoxidized natural rubber, rubber such as polybutadiene rubber, styrene butadiene rubber, butyl rubber, halogenated butyl rubber, halide of copolymer of isobutylene and p-methylstyrene can be used as the rubber component. However, since it is obtained from non-petroleum resources, it is preferable to consist only of natural rubber and epoxidized natural rubber.

  There is no restriction | limiting in particular as a silica in the rubber composition for sidewalls of this invention, The thing generally used in the tire industry can be used.

  The content of silica is 15 parts by weight or more, preferably 20 parts by weight or more with respect to 100 parts by weight of the rubber component. If the content of silica is less than 15 parts by weight, the tear strength is low, and cutting may occur when it comes into contact with protrusions during running. The silica content is 60 parts by weight or less, preferably 50 parts by weight or less. When the content of silica exceeds 60 parts by weight, the flex crack resistance is inferior.

  In the present invention, a silane coupling agent can be used in combination with silica. There is no restriction | limiting in particular as a silane coupling agent, What is generally used in the tire industry like Si69 can be used.

  The content of the silane coupling agent is preferably 4 to 20 parts by weight with respect to 100 parts by weight of silica. If the content is less than 4 parts by weight, the flex crack resistance tends to be inferior, and even if it exceeds 20 parts by weight, the flex crack resistance tends to be inferior.

  The rubber composition for a side wall of the present invention may further contain calcium carbonate.

  The content of calcium carbonate is preferably 10 parts by weight or more and more preferably 20 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content is less than 10 parts by weight, the obtained rubber composition has low resistance to crack growth after heat aging. The calcium carbonate content is preferably 40 parts by weight or less. If the content exceeds 40 parts by weight, the tear strength becomes insufficient.

  The rubber composition for a sidewall of the present invention is intended to utilize resources other than petroleum, and it is preferable not to use aroma oil.

  Further, the rubber composition for a sidewall of the present invention is intended to use resources other than petroleum, and it is preferable not to use petroleum-based resins.

  The rubber composition for a sidewall of the present invention is obtained by a production method comprising the kneading steps (1) and (2).

  In the kneading step (1), it is preferable to knead natural rubber and silica.

  The blending amount of natural rubber in the kneading step (1) is preferably 40 to 100% by weight of the blending amount of all natural rubber used in the entire kneading step. If the blending amount is less than 40% by weight, the ratio of the silica amount to the natural rubber becomes high, so that the viscosity of the kneaded product becomes very high and tends to be difficult to process. The blending amount is most preferably 100% by weight.

  The blending amount of silica in the kneading step (1) is preferably 80 to 100% by weight of the blending amount of all silica used in the entire kneading step. When the blending amount is less than 80% by weight, since a large amount of silica is blended in ENR in Step 2 to form a hard layer, the flex crack resistance tends to be inferior. The blending amount is most preferably 100% by weight.

  In the kneading step (1), other chemicals blended in the rubber composition such as a softening agent, an anti-aging agent, stearic acid, and zinc oxide can also be blended.

  In the kneading step (2), it is preferable to knead the epoxidized natural rubber.

  The blending amount of the epoxidized natural rubber in the kneading step (2) is preferably 50 to 100% by weight of the blending amount of all the epoxidized natural rubber used in the entire kneading step. When the blending amount is less than 50% by weight, since a large amount of silica is blended in ENR to form a hard layer, the flex crack resistance tends to be inferior. The blending amount of the epoxidized natural rubber is most preferably 100% by weight.

  In the kneading step (2), by kneading calcium carbonate, the resulting rubber composition has good bending cracking resistance and tear strength.

  A tire containing a sidewall comprising the rubber composition of the present invention can be produced by a conventional method of the rubber composition for a sidewall of the present invention. That is, if necessary, the rubber composition for a sidewall of the present invention blended with the additive is extruded in accordance with the shape of the sidewall of the tire at an unvulcanized stage, and is usually used on a tire molding machine. An unvulcanized tire is formed by molding by the method. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

  Next, a rubber composition for a sidewall containing a rubber component comprising 60 to 100% by weight of natural rubber and a filler comprising 80% by weight or more of a white filler, and further having a toluene swelling degree of 320 or more. A thing is demonstrated below.

  The rubber component in the rubber composition for sidewalls is made of natural rubber.

  The content of natural rubber in the rubber component is 60% by weight or more, preferably 70% by weight or more. When the content of natural rubber is less than 60% by weight, the ratio of non-petroleum resources becomes small. The content of natural rubber can be 100% by weight or less, preferably 70% by weight or less. The content of natural rubber is most preferably 100% by weight because the effect of suppressing the use of petroleum resources is obtained.

  As the rubber component of the rubber composition for the sidewall, butadiene rubber or butadiene rubber having a syndiotactic structure (syndiotactic butadiene rubber), butyl rubber, halogenated butyl rubber, isobutylene and p-methylstyrene are used in addition to natural rubber. A rubber such as a halide of the above copolymer may be contained, and it is particularly preferred to contain a butadiene rubber and / or a syndiotactic butadiene rubber from the viewpoint of improving the flex cracking resistance.

  The content of butadiene rubber and / or syndiotactic butadiene rubber in the rubber component is preferably 40% by weight or less, and more preferably 30% by weight or less. When the content exceeds 40% by weight, the content ratio of petroleum resources in the rubber component increases, which is not preferable from an environmental viewpoint. From an environmental viewpoint, it is preferable not to contain a butadiene rubber and / or a syndiotactic butadiene rubber.

  Examples of the filler used in the rubber composition for a sidewall of the present invention include silica, calcium carbonate, sericite, carbon black, aluminum hydroxide, and clay. As the rubber composition for a sidewall of the present invention, it is preferable to use a white filler such as silica, calcium carbonate, sericite, aluminum hydroxide, or clay. By using these white fillers, unlike the case of fillers such as carbon black, there is an advantage of suppressing the use of petroleum resources.

  The content of the white filler in the filler is 80% by weight or more, preferably 95% by weight or more. If the content is less than 80% by weight, the ratio of petroleum resources becomes high, which is not preferable from an environmental viewpoint.

  When silica is used as the white filler, it is preferable to use a silane coupling agent in combination.

  It is preferable that the compounding quantity of a silane coupling agent shall be 4-20 weight part with respect to 100 weight part of silica. If the blending amount is less than 4 parts by weight, the flex crack resistance tends to be inferior.

  The rubber composition for a side wall of the present invention comprises the above-mentioned rubber component, filler, silane coupling agent and wax, petroleum resin, anti-aging agent, stearic acid, zinc white, vulcanizing agent and vulcanization accelerator. Can be blended.

The toluene swelling degree of the rubber composition for a side wall of the present invention is 320 or more, preferably 340 or more. When the toluene swelling degree is less than 320, the flex crack resistance is deteriorated. Further, the degree of toluene swelling is preferably 500 or less, and more preferably 480 or less. When toluene swelling degree exceeds 500, the micro crack produced by ozone will generate | occur | produce and there exists a tendency which is not preferable. Here, the toluene swelling degree is an index of the crosslinking density of rubber and is represented by the following formula.
Toluene swelling degree (%)
= (Weight after immersion in toluene (g)) / (Weight before immersion in toluene (g)) × 100

  The higher the degree of toluene swelling, the lower the crosslinking density, which is not preferable. The high crosslinking density in the rubber composition of the present invention is attributed to the amount of sulfur, and the toluene swelling degree can be increased by reducing the amount of sulfur and the vulcanization accelerator.

  A tire containing a sidewall comprising the rubber composition of the present invention can be produced by a conventional method of the rubber composition for a sidewall of the present invention. That is, if necessary, the rubber composition for a sidewall of the present invention blended with the additive is extruded according to the shape of the sidewall of the tire at an unvulcanized stage, and is usually used on a tire molding machine. An unvulcanized tire is formed by molding by the method. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

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

Examples 1-11 and Comparative Examples 1-14
Below, the various chemical | medical agents used in Examples 1-11 and Comparative Examples 1-14 are demonstrated in detail.

(Explanation of reagents)
NR: TSR20
BR: BR150B manufactured by Ube Industries, Ltd.
ENR25: manufactured by Kumpulan Guthrie Berhad (Malaysia) (epoxidation rate 25 mol%)
ENR50: Made by Kumpulan Guthrie Berhad (Malaysia) (epoxidation rate 50 mol%)
Carbon black: FEF manufactured by Mitsubishi Chemical Corporation
Silica: VN3 manufactured by Degussa
Calcium carbonate: White glazed CC manufactured by Shiraishi Kogyo Co., Ltd.
Silane coupling agent: Si69 manufactured by Degussa
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Petroleum-based resin: SP1068 resin wax manufactured by Nippon Shokubai Co., Ltd .: Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd.
Anti-aging agent: Antigen 6c manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Tsubaki stearic acid manufactured by Nippon Oil & Fats Co., Ltd.
Zinc oxide: Zinc oxide sulfur manufactured by Mitsui Mining & Smelting Co., Ltd .: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. NS: Noxeller NS (N-tert-butyl- manufactured by Ouchi Shinsei Chemical Co., Ltd.) 2-benzothiazolylsulfanamide)

(Manufacture of rubber composition)
The rubber component, filler, softener, petroleum-based resin, wax, anti-aging agent, stearic acid and zinc oxide described in step (1) of Table 1 and Table 2 are added so that the filling rate is 58% (stock) ) Filled in a 1.7 L Banbury made by Kobe Steel, and kneaded until reaching 140 ° C. at 80 rpm.

  Regarding Examples 3 to 6 and Example 9, and Comparative Examples 6 to 7 and Comparative Example 14, the chemicals shown in Step (2) of Tables 1 and 2 were then added to the kneaded product obtained in Step (1). And kneaded for 3 minutes at 70 rpm using a Banbury mixer. For the kneaded materials obtained in other examples and comparative examples, step (2) was not performed.

  Unmixed rubber obtained by blending the kneaded product obtained in step (1) or step (2) with the amount of sulfur and vulcanization accelerator described in step (3) shown in Tables 1 and 2. A rubber composition was produced by vulcanizing the composition at 160 ° C. for 20 minutes. The following tests were conducted using the obtained rubber composition.

<Test>
(hardness)
The hardness was measured with a spring type A according to the test method of “Hardness test method of vulcanized rubber and thermoplastic rubber” of JIS-K6253.

(Tear test)
The tear strength (N / mm) was measured by using an angle-shaped test piece without cutting according to the test method of “vulcanized rubber and thermoplastic rubber—determining the tear strength” of JIS-K6252.

(De mattia test)
In accordance with the test method of “Dematcher flex crack growth test method for vulcanized rubber and thermoplastic rubber” of JIS-K6260, the number of times until a 1 mm breakage occurs in a rubber composition sample at a room temperature of 25 ° C. is measured. This is the logarithm of the obtained number of times. The larger the value, the better the flex crack resistance. Here, 70% and 110% represent elongation rates with respect to the length of the original rubber composition sample.

(Heat aging test)
According to the test method of “Dematcher bending crack growth test method of vulcanized rubber and thermoplastic rubber” of JIS-K6260, bending until 1 mm fracture occurs in the rubber composition sample for 48 hours at 100 ° C. The number of times is measured, and the number of times obtained is expressed in logarithm. The larger the value, the better the bending crack resistance.

  The results are shown in Tables 1 and 2.

  As in Examples 1 to 6, by using epoxidized natural rubber modified from natural resources as a polymer that can be separated from natural rubber, the resistance to flex cracking can be improved. However, in Examples 3 to 6 in which natural rubber and silica were kneaded in the kneading step (1) and epoxidized natural rubber was kneaded in the kneading step (2), the tear strength and the bending crack resistance can be improved in a balanced manner. it can.

  In addition, as in Examples 7 to 11, by using epoxidized natural rubber and calcium carbonate as the rubber component, it is possible to improve the resistance to bending cracks, and in particular, in the kneading step (1), natural rubber and In Example 9 in which silica was kneaded and epoxidized natural rubber and calcium carbonate were kneaded in the kneading step (2), the tear strength and the flex crack resistance performance could be improved in a balanced manner, and the flex crack resistance after heat aging was further improved. Performance can also be improved.

  When only natural rubber is used as a rubber component as in Comparative Example 3, the resistance to bending cracking is low.

  As in Comparative Examples 4 and 5, when only the natural rubber is used as the rubber component and the filler is further reduced, the tear strength is reduced. Therefore, when the rubber composition is used as the sidewall portion, the sidewall is easily damaged. .

  When the natural rubber and silica were kneaded in the kneading step (1) and the remaining natural rubber was kneaded in the kneading step (2) without using epoxidized natural rubber as in Comparative Example 6, the tear strength and resistance The effect of improving flex crack performance is low.

  As in Comparative Example 8, when only natural rubber is used as the rubber component and calcium carbonate is blended in place of silica, the tear strength is greatly reduced.

  As in Comparative Example 9, when only natural rubber is used as a rubber component and a large amount of silica and calcium carbonate is blended, the resistance to flex cracking is lowered.

  As in Comparative Examples 10 to 14, when only natural rubber is used as the rubber component and silica and calcium carbonate are used, the bending crack resistance after heat aging can be improved, but the tear strength is not sufficient. There wasn't.

Examples 12-20 and Comparative Examples 15-17
Hereinafter, various chemicals used in Examples 12 to 20 and Comparative Examples 15 to 17 will be described in detail.

(Explanation of reagents)
NR: TSR20
SBR: SBR1502 manufactured by Sumitomo Chemical Co., Ltd.
BR: BR150B manufactured by Ube Industries, Ltd.
Syndiotactic BR: VCR412 manufactured by Ube Industries, Ltd.
Carbon black: HAF manufactured by Mitsubishi Chemical Corporation
Silica: VN3 manufactured by Degussa
Calcium carbonate: White glazed CC manufactured by Shiraishi Kogyo Co., Ltd.
Vegetable oil: Soybean oil silane coupling agent manufactured by Nippon Oilio Co., Ltd .: Si69 manufactured by Degussa
Petroleum-based resin: SP1068 resin wax manufactured by Nippon Shokubai Co., Ltd .: Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd.
Anti-aging agent: Antigen 6c manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Tsubaki stearic acid manufactured by Nippon Oil & Fats Co., Ltd.
Zinc flower: Zinc flower sulfur manufactured by Mitsui Mining & Smelting Co., Ltd .: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. TBBS: Noxeller NS (N-tert-butyl- manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) 2-benzothiazolylsulfanamide)

  Among these chemicals, non-petroleum resources are NR, silica, sulfur, calcium carbonate, sericite, vegetable oil, silane coupling agent, stearic acid, and zinc white.

(Manufacture of rubber composition)
Various chemicals other than sulfur and vulcanization accelerators listed in Table 3 were charged into a 1.7 L Banbury manufactured by Kobe Steel, and kneaded at 77 rpm until reaching 145 ° C.

  To the obtained kneaded product, sulfur and a vulcanization accelerator are blended in the amounts shown in Table 3, and kneaded with an open roll at 80 ° C. for 6 minutes. The resulting unvulcanized rubber composition is treated at 150 ° C. for 30 minutes. A rubber composition was produced by vulcanization. The following tests were conducted using the obtained rubber composition.

<Test>
(Toluene swelling degree)
A test sample cut out from the rubber composition and measured in advance and having a thickness of 0.5 cm or less was immersed in a toluene solution for one day and night. A test sample was taken out of the toluene solution, excess toluene on the surface was wiped off, and the weight after toluene swelling was measured. From the change in weight before and after swelling, the degree of toluene swelling was calculated by the following formula. It shows that a crosslinking density is so high that a numerical value is large.
Toluene swelling degree (%)
= (Weight after immersion in toluene (g)) / (Weight before immersion in toluene (g)) × 100

(hardness)
The hardness of the rubber composition was measured according to the test method of “Dematcher bending crack growth test method for vulcanized rubber and thermoplastic rubber” of JIS-K6260.

(Crack growth test)
According to JIS-K6260 “Dematcher bending crack growth test method for vulcanized rubber and thermoplastic rubber”, the rubber composition after heat aging was stretched by 50%, and the number of bending until the crack grew to 1 mm was evaluated. . The larger the value, the better the bending crack resistance.

  The results are shown in Table 3. In addition, the non-petroleum ratio in Table 3 indicates the content ratio of non-petroleum resources during the blending of the rubber composition.

  As in Examples 12 to 14, the degree of toluene swelling is high, and the resistance to flex cracking is improved by containing a white filler.

  As in Examples 15 to 20, the flex crack resistance can be further improved by blending a small amount of butadiene rubber or syndiotactic butadiene rubber with the rubber component.

  When the white filler is not blended as the filler as in Comparative Example 16, the bending crack resistance is inferior.

  As in Comparative Example 17, when the degree of toluene swelling is low, the resistance to flex cracking is poor.

Claims (5)

A rubber composition for a sidewall, comprising 15 to 60 parts by weight of silica with respect to 100 parts by weight of a rubber component comprising 30 to 90% by weight of natural rubber and 70 to 10% by weight of epoxidized natural rubber. Furthermore, the rubber composition for sidewalls of Claim 1 which contains 10-40 weight part of calcium carbonate. The rubber composition for a side wall according to claim 1 or 2, obtained by a production method comprising (1) a step of kneading natural rubber and silica, and (2) a step of kneading epoxidized natural rubber. A rubber composition for a sidewall comprising a rubber component comprising 60 to 100% by weight of natural rubber and a filler comprising 80% by weight or more of a white filler,
A rubber composition for a sidewall, wherein the rubber composition has a toluene swelling degree of 320 or more. Furthermore, the rubber composition for sidewalls of Claim 4 containing a butadiene rubber and / or a syndiotactic butadiene rubber.