JP4708208B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a rubber composition and a pneumatic tire using the same, and more particularly, to improve heat generation in a tread and improve cut resistance and chipping resistance, thereby demanding heavy load air. TECHNICAL FIELD The present invention relates to a rubber composition suitable for use in an entering tire and an off-road tire and its pneumatic tire.

Large tires for heavy-duty trucks and buses that often run on rough roads where rocks are exposed, especially off-road road tires used on crushed stones, etc. There are many opportunities to receive cuts, and this cut part grows and causes tire destruction, or rain water or the like that enters from the cut part corrodes the steel cord reinforcing material and easily causes tire destruction. Therefore, there is a need for a rubber composition having excellent cut resistance and chipping resistance, particularly in the tread portion of the tire.
In order to overcome the above-mentioned conventional problems to be solved, the applicant of the present invention blends carbon black having a dibutyl phthalate (DBP) oil absorption of 100 (ml / 100 g) into the rubber composition, At the time of filing, a rubber composition that improved many of the above problems was completed (Patent Documents 1 to 3). However, the rubber compositions disclosed therein still have the disadvantage of high exothermic properties.
Therefore, the present applicant has made further improvement studies, and this time, a rubber composition in which 1,3-dipole compound is blended and modified with NR (natural rubber) or SBR (styrene-butadiene rubber) which is the main component of rubber. Furthermore, by blending carbon black having a dibutyl phthalate (DBP) oil absorption of 90 to 250 (ml / 100 g), it is possible to achieve both cut resistance and chipping resistance and low heat build-up of the rubber composition. The headline and the present invention were completed.
JP 2000-204196 A JP 2001-348461 A JP 2004-231691 A

  In view of the above problems, the present invention provides a rubber composition that achieves both cut-chipping resistance and low heat build-up that can be suitably used for heavy-duty pneumatic tires and off-road tires, and a pneumatic tire using the rubber composition. It is to provide.

In order to solve the above-described problems, the present inventors blend a 1,3-dipole compound and carbon black, which will be described later, in a rubber composition for the purpose of improving cut-chipping resistance and low heat build-up. Thus, the rubber composition of the present invention that solved the above problems was completed.
That is, the present invention is characterized by the following means or configurations.

(1) 1 part having a part Q containing dipolar nitrogen and a 4- to 6-membered cyclic nitrogen-containing heterocyclic part B containing an oxygen atom or sulfur atom with respect to 100 parts by mass of natural rubber and / or diene synthetic rubber , 3-dipole compound at 0.1 to 30 parts by mass, and carbon black having dibutyl phthalate (DBP) oil absorption of 90 to 250 (ml / 100 g) at 30 to 70 parts by mass, respectively , The dipolar nitrogen portion Q is selected from at least one of A1-C (A2) = N (A3) → O, A1-C≡N → O, and A1-C≡N → N-A4, A4 may be different from each other, a hydrogen atom, a methyl group, a phenyl group, a methylphenyl group, a group selected from any one of methoxyphenyl groups, or methylene, phenylene, A connecting chain composed of any one of methylphenylene and methoxyphenylene, wherein the 1,3-dipole compound has at least one of A1 to A4 connected to the nitrogen-containing heterocyclic moiety B, A rubber composition comprising a ring part B selected from at least one of oxetine, thiozetin, oxazoline, thiazoline, tetrahydrooxazine and tetrahydrothioxazine .
(2) the nitrogen-containing heterocyclic ring B moiety oxazoline down or rubber composition according to the above (1) is thiazol down.
( 3 ) The rubber composition according to (1) or (2), wherein the carbon black further has a nitrogen adsorption specific surface area (N ₂ SA) of 70 (m ² / g) to 170 (m ² / g). object.
(4) the 1,3-dipole compound is 4- [2- (4,5-hydro benzoxazolyl)] - phenyl -N- methyl - nitrone, 4- [2- (4,5-Hidorochiazoriru)] - phenyl -N- methyl - nitrone, 4- [2- (4,5-hydro benzoxazolyl)] - phenyl -N- phenyl - nitrone, 4- [2- (4,5-Hidorochiazoriru)] - phenyl - N- phenyl - nitrone, phenyl -N-4-[2- (4,5-hydro benzoxazolyl)] - phenyl - nitrone, phenyl -N-4-[2- (4,5-Hidorochiazoriru)] - phenyl - nitrone, 4-tolyl -N-4- [2- (4,5-hydro benzoxazolyl)] - phenyl - nitrone, 4-tolyl -N-4- [2- (4,5-Hidorochiazoriru)] - Phenyl-nitrone, 4-methoxyphenyl -N-4- [2- (4,5-hydro benzoxazolyl)] - phenyl - nitrone, 4-methoxyphenyl -N-4- [2- (4,5-Hidorochiazoriru)] - phenyl - nitrone, 4- [2- (4,5-hydro benzoxazolyl)] - phenyl - nitrile oxide, 4- [2- (4,5-Hidorochiazoriru)] - phenyl - nitrile oxide, 4- [2- ( 4,5 hydro benzoxazolyl)] - phenyl -N- methyl - nitrilimine, 4- [2- (4,5-Hidorochiazoriru)] - phenyl -N- methyl - nitrile imine, 4 - [2- (4 , 5-hydro benzoxazolyl)] - phenyl -N- phenyl - nitrilimine, 4- [2- (4,5-Hidorochiazoriru)] - phenyl -N- phenyl - nitrile imine, phenylene -N-4-[2- (4,5-hydro benzoxazolyl)] - phenyl - nitrilimine, phenyl -N-4-[2- (4,5-Hidorochiazoriru)] - phenyl - 1 or more nitrile imine The rubber composition according to any one of (1) to (3), comprising:
( 5 ) A pneumatic tire formed by using the rubber composition described in any one of (1) to ( 4 ).
( 6 ) A heavy-duty pneumatic tire using the rubber composition described in any one of (1) to ( 4 ).
( 7 ) A pneumatic tire for off-road using the rubber composition according to any one of (1) to ( 4 ).

According to the above means, a predetermined amount of carbon black having a 1,3-dipole compound and dibutyl phthalate (DBP) oil absorption of 90 to 250 (ml / 100 g) is added to and blended with the rubber composition. Tire performance, uneven wear resistance, and low hysteresis loss can be improved. A prior patent application by the present inventor (Japanese Patent Laid-Open No. 2000-204196) by blending and treating a 1,3-dipole compound with a rubber composition according to the present invention, followed by blending of carbon black treated with dibutyl phthalate. Compared to the rubber composition containing carbon black treated with dibutyl phthalate according to the above as the main compounding component, the effect of improving wear resistance and reducing exothermicity is further brought about.
This is because the 1,3-dipole compound causes the reaction of the following reaction formulas (1) to (3) in the double bond part (P) in the rubber component of SBR and modified SBR and the Q part of the compound. it is conceivable that.

  Furthermore, the reaction of the following reaction formulas (4) to (15) occurs between the carbon black (CB) or white carbon (or silica filler) and the compound B portion.

  Due to the action of such a compound, carbon black and white carbon are sufficiently diffused in the rubber composition. As a result, in addition to wear resistance, the low heat build-up and low hysteresis loss of the tread rubber are further improved, and the use performance as a heavy duty pneumatic tire and off-road tire is further enhanced.

  The 1,3-dipole compound blended in the rubber composition of the present invention includes a part Q containing dipolar nitrogen and a part B containing a 4- to 6-membered cyclic nitrogen-containing heterocyclic ring containing oxygen or sulfur atoms. Compounds having the formula (Formulas I to III) are used. The 1,3-dipole compound is a compound of the present invention as long as it contains a dipolar nitrogen moiety. Specific examples of particularly preferred dipolar nitrogen moieties include A1-C (A2) = N (A3) → O (nitrone system), A1-C≡N → O (nitrile oxide system), and A1-C≡. N → N-A4 (nitrile imine type) can be mentioned. These dipolar nitrogen portions Q are reactively bonded to double bond portions in a polymer such as a rubber component as shown in the above reaction formulas (1) to (3).

  The groups A1 to A4 in the nitrone-based, nitrile oxide-based, and nitrileimine-based dipolar nitrogen portions Q are preferably a hydrogen atom, a group having 20 or less carbon atoms, or a connecting chain. When the number of carbon atoms exceeds 20, the molecular weight of the 1,3-dipole compound itself is increased and the reactivity with the rubber component is deteriorated.

  Since the 1,3-dipole compound has a B portion, A1 to A4 can be a connecting chain that connects the B portions. However, in the case of A1 to A3, in the case of only A1, or in the case of A1 and A4, at least one or more are connected to the B portion, and a plurality of B portions may exist. A1 to A4 may be different or the same.

  As specific groups or connecting chains of A1 to A4 of the 1,3-dipole compound, specifically, a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and 6 to 20 carbon atoms. Any one of the aryl groups in the range (wherein the aromatic ring may have a nitro group, a cyano group, a chloro group, a bromo group, an acyl group, a carbonylalkyl group, an alkyl group, and an alkoxyl group). Or a connecting chain thereof. The alkyl group, acyl group, carbonylalkyl group, and alkoxyl group may have a branched chain or a cyclo ring. A1 to A4 may be different from each other.

  The B portion of the 1,3-dipole compound is composed of a nitrogen-containing heterocycle having oxygen or sulfur such as oxetine, thiozetin, oxazoline, thiazoline, tetrahydrooxazine, and tetrahydrothioxazine. In particular, it consists of a 4- to 6-membered nitrogen-containing heterocyclic ring represented by the following structural formulas (I) to (III) (X in the table is oxygen atom: O or sulfur atom: S). Of these, oxazoline and thiazoline of the structural formula (II) are preferable. In each structural formula, R1 to R7 are a hydrogen atom, a group having 20 or less carbon atoms, or a connecting chain. Moreover, in each structural formula similarly to the case of A1 to A4, in the case of R1 to R3, in the case of R1 to R5, or in the case of R1 to R7, at least one or more of A1 to A4 connected to Q Equivalent to. The B part of the 1,3-dipole compound undergoes a binding reaction of the following reaction formulas (4) to (15), and carbon black and white carbon can be uniformly incorporated into the polymer of the rubber component.

Specific examples of the 1,3-dipole compound include 4- [2- (4,5-hydrooxazolyl)] -phenyl-N-methyl-nitrone, 4- [2- (4,5 -Hydrothiazolyl)] -phenyl-N-methyl-nitrone, 4- [2- (4,5 - hydrooxazolyl)] -phenyl-N-phenyl-nitrone, 4- [2- (4,5-hydrothiazolyl) ] -Phenyl- N-phenyl-nitrone, phenyl-N-4- [2- (4,5-hydrooxazolyl )] -phenyl-nitrone, phenyl-N-4- [2- (4,5-hydrothiazolyl) )] -Phenyl-nitrone, 4-tolyl-N-4- [2- (4,5-hydrooxazolyl)] -phenyl-nitrone, 4-tolyl-N-4- [2- (4,5- Hydrothiazolyl)] - pheni Ru-nitrone, 4-methoxyphenyl-N-4- [2- (4,5-hydrooxazolyl )] -phenyl-nitrone, 4-methoxyphenyl-N-4- [2- (4,5-hydrothiazolyl) )] - phenyl - nitrone, 4- [2- (4,5-hydro benzoxazolyl)] - phenyl - nitrile oxide, 4- [2- (4,5-Hidorochiazoriru)] - phenyl - nitrile oxide, 4- [2- (4,5-hydro benzoxazolyl)] - phenyl -N- methyl - nitrilimine, 4- [2- (4,5-Hidorochiazoriru)] - phenyl -N- methyl - nitrile imine, 4 - [ 2- (4,5-hydro benzoxazolyl)] - phenyl -N- phenyl - nitrilimine, 4- [2- (4,5-Hidorochiazoriru)] - phenyl -N- phenyl - nitrile Min, phenyl -N-4-[2- (4,5-hydro benzoxazolyl)] - phenyl - nitrilimine, phenyl -N-4-[2- (4,5-Hidorochiazoriru)] - phenyl - nitrilimine Etc.

In such a 1,3-dipole compound, for example, 4- [2- (4,5 -hydrooxazolyl )] -phenyl-N-methyl-nitrone (hereinafter referred to as “ 4OPMN ” ) and 4- [ 2- (4,5- Hydroxazolyl )] -phenyl-N-phenyl-nitrone (hereinafter referred to as “ 4OPPN ” ) can be specifically mentioned.

  The method for producing the 1,3-dipole compound used in the present invention can be produced without undue experimentation. For example, with respect to 4OPMN and 4OPPN, the manufacturing method can be shown in the examples described later. Also, other compounds can be produced by typical production methods by appropriately selecting other starting materials and intermediate materials.

  The 1,3-dipole compound is blended in the range of 0.1 to 30 parts by mass with respect to 100 parts by mass of the rubber component. In particular, it is preferably blended in the range of 0.1 to 5 parts by mass. If the amount is less than 0.1 parts by mass, the effects of low heat generation and low hysteresis loss are not sufficient. On the other hand, if the blending amount exceeds 30 parts by mass, the cost is significantly increased, which is not preferable.

  In addition to the 1,3-dipole compound, carbon black described in detail below is blended as an essential component in the rubber composition of the present invention.

As the carbon black treated with dibutyl phthalate, those having a nitrogen adsorption specific surface area (N ₂ SA) in the range of 70 (m ² / g) to 170 (m ² / g) are preferably used. If the N ₂ SA is less than 70 m ² / g, the wear resistance may be insufficient. On the other hand, if the N ₂ SA exceeds 170 m ² / g, a dispersion failure may occur, resulting in low heat generation, wear resistance, Workability may be significantly reduced.
The above _N 2 SA is a one hour drying at 300 ° C., was measured according to ASTM D4820-93 value.
The carbon black has a dibutyl phthalate (DBP) oil absorption of preferably 90 to 250 (ml / 100 g), more preferably 105 to 200 (ml / 100 g). In particular, a numerical value around 110 (ml / 100 g) is most preferable. When the DBP value is less than 90 (ml / 100 g), it is difficult to obtain sufficient wear resistance. On the other hand, when the DBP value exceeds 250 (ml / 100 g), the rubber composition of the present invention is used as a tire. This may be a cause of poor fuel economy. Therefore, the DBP value is preferably 90 to 250 (ml / 100 g). The DBP value is a value measured in accordance with JIS K6221-1982 (A method).
The carbon black as described above is preferably blended in the range of 5 to 80 parts by mass with respect to 100 parts by mass of natural rubber and / or diene synthetic rubber. Furthermore, the preferable compounding quantity of carbon black is the range of 30-70 mass parts. When the blending amount exceeds 80 parts by mass, workability and heat build-up are reduced, although cut resistance and chipping resistance are improved. ("Workability deteriorates and exothermicity increases (deteriorates)") On the other hand, if it is less than 5 parts by mass, effective reinforcement cannot be obtained, and cut resistance and chipping resistance are lowered. Therefore, the numerical range of the blending amount of the carbon black with respect to the total amount of the rubber composition is derived from a balanced viewpoint for achieving both wear resistance and low heat build-up.

The carbon black may be any one selected from channel black, furnace black, acetylene black, thermal black, and the like. Further, this carbon black cannot provide sufficient cut resistance and chipping resistance when the nitrogen adsorption specific surface area (N ₂ SA) is less than 100 (m ² / g), and the nitrogen adsorption specific surface area (N ₂ When the value of (SA) is larger than 170 (m ² / g), exothermic deterioration (increase) is caused when used as a tire.
The value of the nitrogen adsorption specific surface area _(N 2 SA) is a value measured in accordance with ASTM D3037-88, DBP is a value measured according to JIS K6221-1982 (A method) .

You may mix | blend the silica heat-processed with the silicone oil explained in full detail below with the rubber composition of this invention as arbitrary components.
As the silica heat-treated with this silicone oil, those having a nitrogen adsorption specific surface area (N ₂ SA) in the range of 180 to 270 m ² / g are preferably used. If the N ₂ SA is less than 180 m ² / g, the wear resistance may be insufficient. On the other hand, if the N ₂ SA exceeds 270 m ² / g, a dispersion failure may occur, resulting in low heat generation, wear resistance, and factory Workability may be significantly reduced.
The above _N 2 SA is a one hour drying at 300 ° C., was measured according to ASTM D4820-93 value. Examples of the silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Of these, wet silica is particularly preferred.

  The silica heat-treated with the silicone oil as described above is preferably blended in the range of 3 to 50 parts by mass with respect to 100 parts by mass of the rubber composition treated with the 1,3-dipole compound. Furthermore, the compounding quantity of a preferable silica is the range of 5-25 mass parts. When this compounding quantity exceeds 50 mass parts, there exists a possibility that workability may deteriorate remarkably and a fracture characteristic may fall. If it is less than 3 parts by mass, the effect of reducing heat generation is small and the effect of improving chipping is poor.

  Silica heat-treated with the silicone oil can reduce surface energy, weaken aggregation between silica particles, and improve fluidity. Examples of silicone oils used for these purposes include dimethyl silicone oil, methyl hydrogen silicone oil, alkoxy group-containing methyl silicone oil, and the like. Thereafter, a heat baking process is performed as necessary.

When the silica heat-treated with silicone oil is blended in the rubber composition of the present invention, a silane coupling agent is further added to strengthen the bond between the silica and the rubber component and maintain and improve the low heat buildup and wear resistance. It is preferable to add.
Examples of the silane coupling agent used for this purpose include bis (3-triethoxysilylpropyl) polysulfide, bis (2-triethoxysilylethyl) polysulfide, bis (3-trimethoxysilylpropyl) polysulfide, and bis ( 2-trimethoxysilylethyl) polysulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-nitropropyltrimethoxysilane, 3 Nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-tripropyl Toxisilylpropyl-N, N-dimethylthiocarbamoyl polysulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl polysulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl polysulfide, 3-trimethoxysilyl Propylbenzothiazole polysulfide, 3-triethoxysilylpropylbenzothiazole polysulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) polysulfide, 3-mercapto Propyldimethoxymethylsilane, 3-nitropropyldimethoxymethylsilane, 3-chloropropyldimethoxymethylsilane, dimethyl Methyl silyl propyl -N, N-dimethylthiocarbamoyl polysulfide, etc. dimethoxymethylsilylpropyl benzothiazole polysulfides and the like.

The silane coupling agent used in this invention may be used by 1 type, and may use 2 or more types together. Among these, bis (3-triethoxysilylpropyl) polysulfide, 3-trimethoxysilylpropylbenzothiazole polysulfide and the like are preferable.
As a compounding quantity of the said silane coupling agent, 5-20 weight% is preferable with respect to the compounding quantity of the silica heat-processed with silicone oil, and 5-15 weight% is more preferable.

  The rubber composition of the present invention is generally used in the rubber industry as an optional filler other than the carbon black treated with the 1,3-dipole compound and dibutyl phthalate as essential components of the present invention. Various components can be included. Examples of the various components include silica, which has been heat-treated with the above-described silicone oil, for example, fillers (for example, inorganic fillers such as calcium carbonate and calcium carbonate); and vulcanization accelerators; anti-aging agents; zinc oxide; Examples include acids; softeners; and additives such as ozone deterioration inhibitors. Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as MBTS (dibenzothiazyl disulfide) and CZ (N-cyclohexyl-2-benzothiazylsulfenamide); TT (tetramethylthiuram sulfide) and the like. Examples include thiuram vulcanization accelerators; and guanidine vulcanization accelerators such as DPG (diphenylguanidine).

At least one of the optional fillers listed above can be blended as the third component. Among these, silica heat treated with silicone oil is particularly preferable.
About the silica heat-processed with silicone oil, it is preferable that it is 3-50 mass parts compounding with respect to 100 mass parts of rubber compositions of this invention. Furthermore, the compounding quantity of a preferable silica is the range of 5-25 mass parts with respect to 100 mass parts of rubber compositions of this invention. When this compounding quantity exceeds 50 mass parts, there exists a possibility that workability may deteriorate remarkably and a fracture characteristic may fall. If the amount is less than 3 parts by mass, the effects of low heat generation and low chipping are hardly obtained.

  The rubber component (first component) used in the rubber composition of the present invention may be either natural rubber or diene rubber, but natural rubber alone or a blend rubber system of natural rubber and synthetic rubber. Can be preferably used. Since these rubber components are rich in reactivity with the 1,3-dipole compound as the second component in the present invention, they can be well modified. Furthermore, the improvement effect by the silica heat-treated with the silicone oil that is subsequently added / blended is combined with the object of obtaining the wear resistance and low heat build-up of the rubber composition that is the object of the present invention. When the rubber component (first component) contains natural rubber, the amount of the natural rubber polymer gel can be reduced without reducing the molecular weight of the natural rubber molecule, and the slip between the rubber molecules can be increased. Thus, the workability of molding can be improved, the physical properties of unvulcanized or vulcanized rubber can be suppressed, and the dispersibility of the silica filler can be remarkably improved.

  The rubber composition of the present invention can be used for general rubber products such as hoses and belts. In particular, the rubber composition is preferably used for a pneumatic tire. In the case of a pneumatic tire, it is desirable to apply to the tread portion. Since the tread portion contributes greatly to wear resistance and low heat generation, it can be suitably used as a heavy-duty pneumatic tire and an off-road pneumatic tire requiring long-term durability on rough roads. Such a pneumatic tire of the present invention can use air or an inert gas such as nitrogen as the gas to be filled.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Various measurements were performed by the following methods.

[hardness]
The hardness was measured by a spring hardness test (type A) in accordance with JIS K 6301. The larger the value, the higher the hardness.

[Evaluation of heat generation]
A drum test under a step load condition at 10 km / h was carried out to measure the temperature at a depth of 90 mm inside the tire, and the value of the control (Comparative Example 1) was set to 100 and evaluated by an index. The larger the index value, the greater the effect of reducing heat generation.

[Evaluation of wear resistance]
The wear resistance index A of the tread rubber in the tire after running for 2000 hours is expressed by the following formula.
A = M / (D ₀ -D ₁ )
And the value of the control (Comparative Example 1) was taken as 100 and expressed as an index.
A larger index value indicates a greater improvement in wear resistance.
(Here, A is the wear resistance index, M is the travel distance km after traveling for 2000 hours, D ₀ is the groove depth mm before traveling, and D ₁ is the groove depth mm after traveling.)

[Evaluation of chipping resistance]
The chipping resistance was expressed as an index by obtaining the area ratio of rubber not missing per 30 cm × 30 cm of the tread rubber surface in a tire after running for 2000 hours, with the value of the control (Comparative Example 1) being 100. The larger the index, the better the chipping resistance.
The respective evaluation results are shown in Table 1.

(Examples 1-9 and Comparative Examples 1-4)
The rubber composition of each Example and Comparative Example is shown in Table 1 below. A rubber composition before crosslinking is prepared using a Banbury mixer according to the formulation table in Table 1 below, and 3700R57 is prepared using the prepared rubber composition. Standard tires were created.

* 1) # 1500; Emulsion polymerization SBR
* 2) 4OPPN; 4- [2- (4,5-Hydroxazolyl)]-phenyl-N-phenylnitrone
* 3) 4OPMN; 4- [2- (4,5-hydrooxazolyl)]-phenyl-N-methylnitrone)
* 4) Vulcanization accelerator MBTS; dibenzothiazyl disulfide * 2) 4OPPN and * 3) 4OPMN were produced as follows.

<Manufacture of 4OPPN>
To a solution obtained by stirring and mixing 15.0 g of 4-formyl-benzoyl chloride (1 equivalent) in 300 ml of chloroform, a solution obtained by adding 10.9 g of 2-aminoethanol (2 equivalents) to 200 ml of chloroform was added dropwise at −10 ° C. And added. After the solution was placed at 25 ° C. for 2 hours, the white precipitate was removed by filtration. The filtrate was dried by a rotary evaporator to obtain 17.4 g of 4-formyl-N- (2-hydroxyethyl) -benzamide as a yellow liquid.
To 50 ml of concentrated sulfuric acid, 17.4 g of 4-formyl-N- (2-hydroxyethyl) -benzamide was added dropwise with stirring, and the mixture was heated at 100 ° C. for 1 hour. To this solution, 500 ml of 20% sodium hydroxide and chloroform were added dropwise with stirring and mixing, and the temperature was maintained at 15 ° C. or lower. The product layer was separated and dried to give 6.3 g of 4- [2- (4,5-hydrooxazolyl)] -benzaldehyde.
4- [2- (4,5-Hydroxazolyl)] -benzaldehyde (1 eq, 6.3 g) and N-phenyl-hydroxyamine (1 eq, 3.9 g) in 100 ml ethanol Refluxed for 30 minutes and concentrated to a volume of 50 ml. The same amount of 50 ml of water was added and the mixture was cooled to 5 ° C. overnight in a refrigerator. White crystals were obtained by filtration separation and drying to produce 6.7 g of 4- [2- (4,5-hydrooxazolyl)] -phenyl-N-phenylnitrone.

<Manufacturing of 4OPMN>
To a solution obtained by stirring and mixing 4-formyl-benzoyl chloride (15.0 g, 89 mmol) in 300 ml of chloroform, a solution obtained by adding 2-aminoethanol (10.9 g, 178 mmol) to 200 ml of chloroform was added dropwise at −10 ° C. added. After the solution was placed at 25 ° C. for 2 hours, the white precipitate was removed by filtration. The filtrate was dried by a rotary evaporator to obtain 17 g (88 mmol) of yellow liquid 4-formyl-N- (2-hydroxyethyl) -benzamide.
4-Formyl-N- (2-hydroxyethyl) -benzamide (17 g, 88 mmol) was added dropwise to 50 ml of concentrated sulfuric acid with stirring, and the mixture was heated at 100 ° C. for 1 hour. To this solution, 500 ml each of 20% sodium hydroxide solution and chloroform were mixed and added dropwise with stirring, and the temperature was maintained at 15 ° C. or lower. The product layer was separated and dried to give 6.3 g (36 mmol) of 4- [2- (4,5- hydrooxazolyl )] -benzaldehyde (41% yield).
4- [2- (4,5- Hydroxazolyl) ] -benzaldehyde (1 eq, 6.3 g) and N-methyl-hydroxyamine (1.7 g, 36 mmol) in 30 ml of 100 ml ethanol. Refluxed for minutes and concentrated to 50 ml volume. The same amount of 50 ml of water was added and the mixture was cooled to 5 ° C. overnight in a refrigerator. White crystals were obtained by filtration separation and drying to produce 5.1 g of 4- [2- (4,5 -hydrooxazolyl )] -phenyl-N-methylnitrone (yield 69%).

<Preparation of silica heat-treated with silicone oil>
Silica is charged into a fluid mixer (Henschel mixer manufactured by Mitsui Miike Co., Ltd.), and 10 parts by mass of dimethyl silicone oil KF96 (manufactured by Shin-Etsu Chemical Co., Ltd.) is added to 100 parts by mass of the silica and mixed for 5 minutes. Stir. The obtained mixed powder was allowed to stand at 50 ° C. for 1 day to obtain the expression “silica heat-treated with silicone oil”, that is, surface-treated silica.

  Next, a tire performance test was conducted for each of the examples and comparative examples. The results are also shown in Table 1 above. The performance test of the rubber composition was performed by evaluating low heat build-up and wear resistance as described below.

<Evaluation of low heat generation>
A drum system with a speed / step load condition of 10 km / h was implemented, the temperature at a position where the tread was 90 mm in depth was measured, and each example was displayed as an index, with Comparative Example 1 as the control value (control) 100. It shows that it is excellent in low exothermic property, so that the value of an index | exponent is large.
When comparing the results of Examples 1-8 and Comparative Examples 1-5, the exothermic property of each of the Examples is lower than the control of the Comparative Example, and the rubber composition of the present invention is excellent in low exothermic property. I understand that. This indicates that exothermic properties can be reduced by blending carbon black treated with dibutyl phthalate into a rubber composition.

<Evaluation of wear resistance>
The tread rubber in the tire after running for 2000 hours is calculated by the formula: travel distance / (groove depth before running−groove depth after running), and Comparative Example 1 is used as a control value (control) 100 for each example. Is expressed as an index. The larger the index value, the more effective the wear resistance.
When comparing the results of Examples 1 to 4 and Comparative Example 1, it can be seen that each of Examples 1 to 4 is superior in wear resistance compared to the control of Comparative Example 1. This indicates that the greater the amount of carbon black treated with dibutyl phthalate in the rubber composition, the better the wear resistance of the rubber composition.

  As described above, according to the rubber composition of the present invention, it is possible to achieve both low heat buildup, cut resistance and chipping resistance. This means that the rubber composition of the present invention is excellent as a rubber composition for a tire tread or as another industrial rubber composition.

  The rubber composition of the present invention and the pneumatic tire using the rubber composition are excellent in low heat buildup and wear resistance (based on cut-and-chipping resistance). Since it can be used suitably for heavy duty tires and off-road tires, and the factory workability is also improved, the industrial utility value is high.

Claims (5)

Against natural rubber and / or diene synthetic rubber 100 parts by weight parts component, and an oxygen atom or a 1,3-dipole compound having a nitrogen-containing heterocyclic ring unit content of 5-membered ring containing a sulfur atom containing dipolar nitrogen And 30 to 70 parts by mass of carbon black having a dibutyl phthalate (DBP) oil absorption of 90 to 250 (ml / 100 g), respectively, and the dipolar compound is 4- [2- (4,5-hydrooxazolyl)]-phenyl-N-methyl-nitrone, 4- [2- (4,5-hydrothiazolyl)]-phenyl-N-methyl-nitrone, 4- [ 2- (4,5-hydrooxazolyl)]-phenyl-N-phenyl-nitrone, 4- [2- (4,5-hydrothiazolyl)]-phenyl-N-phenyl-nitrone, phen Ru-N-4- [2- (4,5-hydrooxazolyl)]-phenyl-nitrone, phenyl-N-4- [2- (4,5-hydrothiazolyl)]-phenyl-nitrone, 4-tolyl -N-4- [2- (4,5-hydrooxazolyl)]-phenyl-nitrone, 4-tolyl-N-4- [2- (4,5-hydrothiazolyl)]-phenyl-nitrone, 4- Methoxyphenyl-N-4- [2- (4,5-hydrooxazolyl)]-phenyl-nitrone, 4-methoxyphenyl-N-4- [2- (4,5-hydrothiazolyl)]-phenyl-nitrone 4- [2- (4,5-hydrooxazolyl)]-phenyl-nitrile oxide, 4- [2- (4,5-hydrothiazolyl)]-phenyl-nitrile oxide, 4- [2- (4 5-Hydroxazolyl ] -Phenyl-N-methyl-nitrileimine, 4- [2- (4,5-hydrothiazolyl)]-phenyl-N-methyl-nitrileimine, 4- [2- (4,5-hydrooxazolyl)] -Phenyl-N-phenyl-nitrileimine, 4- [2- (4,5-hydrothiazolyl)]-phenyl-N-phenyl-nitrileimine, phenyl-N-4- [2- (4,5-hydrooxazolyl) )]-Phenyl-nitrileimine , a rubber composition selected from at least one of phenyl-N-4- [2- (4,5-hydrothiazolyl)]-phenyl-nitrileimine . Said carbon black ^{further, 70 (m 2 / g)} ~170 (m 2 / g) Nitrogen adsorption specific surface area _(N 2 SA) of a is claim 1 rubber composition according to. A pneumatic tire using the rubber composition according to claim 1 . A heavy duty pneumatic tire using the rubber composition according to claim 1 or 2 . An off-road pneumatic tire using the rubber composition according to claim 1.