JP2006206636A - Side tread composition for heavy-duty tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a side tread composition for heavy-duty tires suitable for use in retreading. <P>SOLUTION: The side tread rubber composition for heavy-duty tires comprises 100 pts.wt. vulcanizable rubber component (i) having a compounding ratio (weight ratio) of a natural rubber (NR) and/or a polyisoprene rubber (IR) to a vinyl cis-butadiene rubber (VCR) of (NR and/or IR)/(VCR)=20/80 to 60/40, 40-60 pts.wt. HAF grade carbon black (ii), 0.1-10 pts.wt. cyclic polysulfide (iii) represented by formula (I) (wherein R is a 2-20C substituted or nonsubstituted alkylene group, an oxyalkylene group or an aromatic-containing alkylene group; x is an integer of 2-6; and n is a constant of 1-20), and a vulcanization accelerator (iv) at a ratio (weight ratio) of the vulcanization accelerator (iv) to the cyclic polysulfide (iii) of 0.1-0.5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a side tread composition for heavy duty tires, and more particularly, a side tread composition for heavy duty tires suitable for retreading and reuse, which has good crack resistance and good initial performance retention. About.

  Heavy duty tires such as trucks and buses are often re-tread and reused using casings that have been worn out and recovered. The side tread of heavy duty tires that need to be used for such a long time is resistant to abrasion such as rubbing, has good crack resistance, and retains the initial performance as much as possible (with little change over time) There is a need for a composition (Patent Document 1).

JP-A-8-164713

  Therefore, an object of the present invention is to provide a side-tread composition for heavy-duty tires that has good crack resistance even after long-term use and good initial performance retention and is suitable for retreading and reuse. There is to do.

  According to the present invention, the blending ratio (weight ratio) of (i) natural rubber (NR) and / or polyisoprene rubber (IR) and vinyl cisbutadiene rubber (VCR) is (NR and / or IR) / (VCR). ) = 100 parts by weight of vulcanizable rubber component of 20 / 80-60 / 40, (ii) 40-60 parts by weight of HAF grade carbon black, (iii) general formula (I):

(In the formula, R is a substituted or unsubstituted alkylene group having 2 to 20 carbon atoms, an oxyalkylene group or an alkylene group containing an aromatic group, x is an integer of 2 to 6, and n is a constant of 1 to 20. )
0.1 to 10 parts by weight of a cyclic polysulfide represented by the formula (iv) and a vulcanization accelerator (iv), and the ratio (weight ratio) of vulcanization accelerator (iv) / cyclic polysulfide (iii) is 0.1 to 10 parts by weight. A side tread rubber composition for heavy duty tires of 0.5 is provided.

  According to the present invention, by adding a specific amount of vinyl cis polybutadiene rubber (VCR) to the rubber component and using the cyclic polysulfide of the formula (I) as a vulcanizing agent, the hardness and breaking elongation of the resulting rubber composition are increased. The rate of change can be improved, and the wear resistance and crack resistance can be improved.

  In the present invention, natural rubber (NR) and / or polyisoprene rubber (IR) and vinyl cisbutadiene rubber (VCR) are used as the rubber component, and the ratio (weight ratio) of NR and / or IR to VCR is as follows. A blend with a ratio of (NR and / or IR) / (VCR) = 20/80 to 60/40, preferably 50/50 to 60/40 is used. If the VCR ratio is too small, fatigue resistance and crack resistance are deteriorated, which is not preferable. Conversely, if the ratio is too large, cut resistance is deteriorated, which is not preferable.

  The vinyl cis-butadiene rubber (VCR) used in the present invention is, for example, JP-B-49-17667, JP-B-61-57858, JP-B-62-171, JP-B-63-36324, JP-B-2. -37827, JP-B-2-30881, JP-B-3-63566 and the like. This VCR has a boiling n-hexane insoluble content of 1 to 25% by weight and a boiling n-hexane soluble content of 99 to 75% by weight as described in JP-A-11-349732, for example. A cis-butadiene rubber, the boiling n-hexane insoluble matter is syndiotactic 1,2-polybutadiene (hereinafter abbreviated as SPBD). The boiling n-hexane soluble content is high cis-1,4-polybutadiene, and the microstructure is 90% by weight or more of the cis-1,4 structure. The boiling n-hexane insoluble matter mentioned here means a portion recovered as an insoluble matter when the VCR is refluxed in boiling n-hexane, and the boiling n-hexane soluble matter means the VCR in boiling n-hexane. It is the part that dissolves when refluxed. The boiling n-hexane insoluble matter has a reduced viscosity (135 ° C., concentration of 0.20 g / dl tetralin solution) measured with a tetralin solution of 0.5 to 4, preferably 0.8 to 3. When the reduced viscosity of the boiling n-hexane insolubles is less than 0.5, the die swell of the formulation is not sufficiently improved. On the other hand, when the reduced viscosity of the boiling n-hexane insoluble matter is larger than 4, SPBD forms an agglomerate in the high cis-1,4-polybutadiene at the time of polymerization, causing poor dispersion and reducing workability and durability. This is not preferable. Moreover, it is preferable that the weight average molecular weight of the boiling n-hexane soluble part is in the range of 300,000 to 800,000. If it exceeds 800,000, the Mooney viscosity of the formulation becomes too high, and the processing becomes difficult.

  In addition, the thing of various product numbers is marketed as UBE-POL VCR from Ube Industries, Ltd., and VCR can also use these commercial products also in this invention.

The carbon black blended in the rubber composition of the present invention is HAF great carbon black, preferably having a particle diameter of 20 to 30 nm and a nitrogen adsorption specific surface area N ₂ SA of 60 to 90 m ² / g is used for fatigue resistance and cut resistance. From the viewpoint of the balance of heat generation, it is preferable. This carbon black is blended in an amount of 40 to 60 parts by weight, preferably 40 to 48 parts by weight, based on 100 parts by weight of rubber. If the amount is too small, the hardness is low and the cut resistance deteriorates, which is not preferable. On the other hand, if the amount is too large, the hardness is too high and crack resistance deteriorates, the heat generation becomes high, and the fuel consumption deteriorates. Absent.

  The cyclic polysulfide of the formula (I) used as a vulcanizing agent in the rubber composition of the present invention is blended in an amount of 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of the rubber component. If the amount is too small, the desired effect cannot be obtained, which is not preferable. Conversely, if the amount is too large, the hardness is large and the elongation at break is not preferable.

The cyclic porsulfide of the formula (I) to be blended in the rubber composition of the present invention has the formula: X—R—X (wherein X is independently fluorine, chlorine, bromine, iodine, preferably chlorine, A halogen atom of bromine, wherein R is a substituted or unsubstituted C _{2 to} C ₂₀ alkylene group or a substituted or unsubstituted C _{2 to} C ₂₀ oxyalkylene alkylene group, preferably the substituted or unsubstituted C ₂ -C ₂₀ substituted, more preferably an alkylene group or an aromatic ring C ₄ -C _10. dihalogen compound in polysulfide M-S _x -M (wherein the alkali metal), M is an alkali A metal such as sodium, potassium, lithium and the like, and x is an integer of 2-6, preferably 4-6, in a two-phase system in an incompatible mixed solvent of hydrophilic and lipophilic solvents. By letting or M-S _x -M solution (can be water and C ₁ -C ₄ aliphatic alcohol as solvent, use of water is most preferred) to X-P-X in M-S _x -M and X It is produced by adding and reacting at a rate such that -R-X reacts at the interface (see, for example, JP-A-2002-29383). If the addition rate of X-R-X is too fast in the latter method, the concentration of X-R-X will increase, and reactions other than at the interface will occur, giving priority to intermolecular reactions and becoming chained. It is not preferable. Therefore, it is preferable that the reaction between M-S _x -M and X-M-X is performed in a heterogeneous system as much as possible at the interface only in order to obtain a cyclic polysulfide.

Examples of the group R in the general formula X-R-X and the formula (I) are substituted with a substituent such as ethylene, propylene, butylene, pentylene, hexylene, octylene, nonylene, decylene, 1,2-propylene, and benzyl group. May be. The group R further includes an alkylene group containing an oxyalkylene group, for example, a group (CH ₂ CH ₂ O) p and a group (CH ₂ ) q (wherein p is an integer of 1 to 5, and q is 0 to 2). (Which is an integer) can be an alkylene group including an oxyalkylene group optionally bonded thereto. Preferred group R is

In particular, x is preferably 3 to 5 on average, and n is preferably 1 to 10, more preferably 1 to 5.

  There is no particular limitation on the hydrophilic solvent and the lipophilic solvent used in the above reaction, and any solvent that forms two phases incompatible with each other in an actual reaction system can be used. Specifically, examples of the hydrophilic solvent include water and alcohols such as methanol, ethanol, ethylene glycol, and diethylene glycol, and these can be used as an arbitrary mixture. Examples of the hydrophilic solvent include aromatic hydrocarbons such as toluene, xylene and benzene, aliphatic hydrocarbons such as pentane and hexane, ethers such as dioxane and dibutyl ether, and esters such as ethyl acetate. These can be used as any mixture.

  The reaction at the interface between the dihalogen compound and the alkali metal polysulfide is an equivalent reaction. Practically, both compounds are reacted at 0.95: 1 to 1: 0.95 (equivalent ratio), The reaction temperature is preferably 50 to 120 ° C, more preferably 70 to 100 ° C.

In the reaction, a catalyst is not necessary, but in some cases, a quaternary ammonium salt, a phosphonium salt, a crown ether, or the like can be used as a catalyst. For example, (CH ₃ ) ₄ N ⁺ Cl ⁻ , (CH ₃ ) ₄ N ⁺ Br ⁻ , (C ₄ H ₉ ) ₄ N ⁺ Cl ⁻ , (C ₄ H ₉ ) ₄ N ⁺ Br ⁻ , C ₁₂ H ₂₅ N ⁺ (CH ₃ ) ₃ Br ⁻ , (C ₄ H ₉ ) ₄ P ⁺ Br ⁻ , CH ₃ P ⁺ (C ₆ H ₅ ) ₃ l ⁻ , C ₁₆ H ₃₃ P ⁺ (C ₄ H ₉ ) ₃ Br ^- , 15-crown-5, 18-crown-6, benzo-18-crown-6, and the like can be used. In particular, when a cyclic polysulfide (I) having an average x exceeding 4 to 6 or less is used, a catalyst is preferably used.

  The rubber composition of the present invention further contains a vulcanization accelerator as an essential component. The vulcanization accelerator is blended so that the vulcanization accelerator / cyclic polysulfide ratio (weight ratio) is 0.1 to 0.5, preferably 0.2 to 0.4. If the blending ratio is too small, the rate of change in hardness and elongation at break increases, which is not preferable. On the other hand, if it is too large, cut resistance and crack resistance deteriorate, which is not preferable. As the vulcanization accelerator, for example, those used for conventional sulfur vulcanization such as sulfenamide and thiuram can be used.

  In addition to the above-described essential components, the rubber composition according to the present invention includes other reinforcing agents (fillers) such as silica, other vulcanization or crosslinking agents, other vulcanization or crosslinking accelerators, various oils, aging Various additives that are generally blended for tires such as inhibitors and plasticizers, and other general rubbers can be blended, and these additives are kneaded and vulcanized by a general method to form a composition. Can be used for vulcanization or crosslinking. The blending amounts of these additives may be conventional conventional blending amounts as long as the object of the present invention is not adversely affected.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Examples 1-3 and Comparative Examples 1-7
Sample preparation In the formulation shown in Table I, ingredients other than the vulcanization accelerator and vulcanizing agent (cyclic polysulfide) were kneaded for 4 minutes with a 1.8 liter closed mixer and released when the temperature reached 145 ± 5 ° C. To obtain a master batch. A vulcanization accelerator and a vulcanizing agent were kneaded with this masterbatch with an open roll to obtain a rubber composition.

  The resulting rubber composition was vulcanized by vulcanization at 148 ° C. for 30 minutes in a 15 × 15 × 0.2 cm mold and a mold for a pico abrasion test sample having a disk-shaped portion having a diameter of 32 mm. A rubber sample was prepared, and physical properties of the vulcanized rubber were measured by the following test method. The results are shown in Table I.

Rubber physical property evaluation test method

Hardness (Hs) change rate: compliant with JIS K6301. A blank sample and an aged sample (heated at 80 ° C. × 96 hours) were measured, and the difference was displayed as an index based on the value of Comparative Example 1. It shows that it is so favorable that this value is small.
Breaking elongation change rate: compliant with JIS K6251. The breaking elongation of the blank sample and the breaking elongation of the aging sample (heated at 80 ° C. × 96 hours) were measured, and the difference was displayed as an index based on the value of Comparative Example 1. It shows that it is so favorable that this value is small.

Pico wear: Conforms to JIS K6264. The reciprocal of the amount of wear was displayed as an index based on the value of Comparative Example 1. It shows that it is so favorable that this value is large.
Crack growth (30 × 10 ³ times): Conforms to JIS K6301. Measures the growth length of cracks after 30,000 times of expansion and contraction. The difference was displayed as an index with the value of Comparative Example 1 as a reference. It shows that it is so favorable that this value is small.

Table I footnote * 1: STR20
* 2: Nipol BR1220 (manufactured by Zeon Corporation)
* 3: VCR412 (manufactured by Ube Industries)
* 4: Seast N (manufactured by Tokai Carbon Co., Ltd.)
* 5: 6PPD (manufactured by Flexis Co., Ltd.)
* 6: Noxeller NS (made by Ouchi Shinsei Chemical Co., Ltd.)

* 7: A cyclic polysulfide of general formula (I) with R = (CH ₂ ) ₆ , x (average) = 5 and n = 1 to 4 was synthesized as follows.
80% water, 48 g (0.15 mol) of sulfur and 1.16 g (0.0045 mol) of tetrabutylammonium bromide as a catalyst were added to 89.76 g (0.15 mol) of 30% sodium polysulfide (Na ₂ S ₄ ) aqueous solution. After reacting at 2 ° C. for 2 hours, 100 g of toluene was added, and 23.3 g (0.15 mol) of 1,6-dichlorohexane was added dropwise at 90 ° C. for 1 hour, followed by further reaction for 4 hours. After completion of the reaction, the organic layer was separated and concentrated at 90 ° C. under reduced pressure to obtain 35.2 g (yield 95%) of the desired cyclic polysulfide.

* 8: In general formula (I), R = (CH ₂ ) ₂ O (CH ₂ ) O (CH ₂ ) ₂ , x (average) = 4 and n = 1 to 2 cyclic polysulfide, as follows: And synthesized.
100 g of toluene was added to 89.76 g of 30% sodium polysulfide (Na ₂ S ₄ ) aqueous solution, and 26.0 g (0.15 mol) of 1,2-bis (2-chloroethoxy) methane was added dropwise at 90 ° C. for 1 hour. The reaction was further continued for 4 hours. After completion of the reaction, the organic layer was separated and concentrated at 90 ° C. under reduced pressure to obtain 35.0 g (yield 96%) of the desired cyclic polysulfide.

  As described above, according to the present invention, a rubber composition excellent in the rate of change in hardness (Hs) before and after aging and the rate of change in elongation at break, and excellent in pico abrasion and crack resistance can be obtained. It is useful as a rubber composition.

Claims (2)

(I) The blending ratio (weight ratio) of natural rubber (NR) and / or polyisoprene rubber (IR) and vinyl cisbutadiene rubber (VCR) is (NR and / or IR) / (VCR) = 20 / 80- 60/40 vulcanizable rubber component 100 parts by weight, (ii) HAF grade carbon black 40-60 parts by weight, (iii) general formula (I):

(In the formula, R is a substituted or unsubstituted alkylene group having 2 to 20 carbon atoms, an oxyalkylene group or an alkylene group containing an aromatic group, x is an integer of 2 to 6, and n is a constant of 1 to 20. )
0.1 to 10 parts by weight of a cyclic polysulfide represented by the formula (iv) and a vulcanization accelerator (iv), and the ratio (weight ratio) of vulcanization accelerator (iv) / cyclic polysulfide (iii) is 0.1 to 10 parts by weight. A side tread rubber composition for heavy duty tires of 0.5. The cyclic polysulfide compound has the formula: X-R-X (wherein, X independently represents a halogen atom, R represents an alkylene group or an oxyalkylene group of C ₂ -C ₁₈ substituted or unsubstituted ) And an alkali metal polysulfide of the formula M ₂ S _x (wherein M is an alkali metal and x is an integer from 2 to 6), a non-hydrophilic and lipophilic solvent. The side tread rubber composition for heavy-duty tires according to claim 1, which is obtained by reacting in a compatible mixed solvent in a two-phase system.