JP2007224072A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition suitably used in a heavy-duty pneumatic tire and an off-road tire and having abrasion resistance and low heat build-up properties and a high recycling ratio and to provide the pneumatic tire using the rubber composition. <P>SOLUTION: The rubber composition is obtained by compounding 100 pts.mass of a rubber component with 0.1-30 pts.mass of a compound having a moiety Q containing dipolar nitrogens and a moiety B containing a 4- to a 6-membered nitrogen-containing heterocycle containing an oxygen or a sulfur and further compounding waste rubber. The dipolar nitrogen moiety is specifically selected from at least one or more of A1-C(A2)=N(A3)→O, A1-C≡N→O and A1-C≡N→N-A4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition and a pneumatic tire using the rubber composition, and more specifically, while improving the heat build-up of rubber and wear resistance while being a highly recyclable rubber composition containing waste rubber and the like. The present invention relates to a rubber composition that can be used for heavy-duty pneumatic tires and off-road tires that are demanding, and the pneumatic tires.

In general, a pneumatic tire requires low fuel consumption and stability of an automobile. In particular, heavy duty pneumatic tires used for trucks, buses and the like are required to have further improved heat generation. Further, for off-road tires, the tread rubber is required to have low hysteresis loss (low rolling resistance) and wear resistance. Conventionally, in off-road tires, in order to improve wear resistance, synthetic rubber components such as SBR are used in the tread rubber composition to improve cutability and fatigue resistance.
By the way, in recent years, with the increase in environmental problems, used rubber products such as waste tires and rubber obtained from rubber scraps produced in the manufacturing process of rubber products (hereinafter referred to as waste rubber) are natural rubber and synthetic rubber. The new material rubber (hereinafter simply referred to as the rubber component) is used to improve the material recycling rate in the rubber composition.
Generally, when the content of waste rubber is increased to increase the recycling rate, the wear resistance deteriorates. For this reason, waste rubber is pulverized, and the pulverized product is processed by an oil pan method and blended in an optimized state to increase the recycling rate and improve wear resistance.
However, when the recycling rate is increased, the exothermic property deteriorates. For this reason, unless the exothermic property is fundamentally improved, the recycling rate cannot be increased by adding waste rubber. Even in heavy duty pneumatic tires and off-road tires, improvement of the recycling rate is required.

  In view of the above-mentioned problems, the present invention provides a rubber composition having wear resistance and low heat generation that can be used for heavy-duty pneumatic tires and off-road tires and having a high recycling rate, and a pneumatic tire using the rubber composition. There is to do.

In order to solve the above-mentioned problems, the present inventors have developed a dipolar that shows reactivity in a double bond site such as a rubber component in a rubber composition containing a rubber component such as natural rubber and synthetic rubber. When a compound comprising a part Q containing nitrogen and a part B containing a nitrogen-containing heterocyclic ring containing oxygen or sulfur which shows reactivity with a filler such as carbon black, white carbon (or silica filler), etc. is blended It has been found that the dispersibility of carbon and the like in the rubber component is improved, the low exothermic property of the rubber composition is improved, and that such a composition can be used by sufficiently containing waste rubber or the like, leading to the present invention. It is a thing.
That is, the present invention is characterized by the following means or configurations.

(1) For 100 parts by mass of the rubber component, 0.1 to 30 parts by mass of a compound having a part Q containing dipolar nitrogen and 4 to 6 nitrogen-containing heterocyclic parts B containing oxygen or sulfur are blended, And a rubber composition comprising waste rubber.

(2) The dipolar nitrogen portion is selected from at least one of A1-C (A2) = N (A3) → O, A1-C≡N → O, and A1-C≡N → N-A4. A1 to A4 may be different from each other, hydrogen or a group having 20 or less carbon atoms or a linking chain connecting the B, and the compound is bonded to at least one of A1 to A4 and the B is connected. The rubber composition as described in (1) above.
(3) A1 to A4 of the above compound are hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms (however, the aromatic ring has 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 group thereof selected from the above ( 2) The rubber composition as described.
(4) The rubber composition according to the above (1), wherein the nitrogen-containing heterocycle of the B part is oxazoline or thiazoline.

(5) The above compound is 4- (2-oxazolyl) -phenyl-N-methyl-nitrone, 4- (2-thiazolyl) -phenyl-N-methyl-nitrone, 4- (2-oxazolyl) -phenyl- N-phenyl-nitrone, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrone, phenyl-N-4- (2-oxazolyl) -phenyl-nitrone, phenyl-N-4- (2-thiazolyl)- Phenyl-nitrone, 4-tolyl-N-4- (2-oxazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- ( 2-Oxazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4- (2-oxazolyl) -phenyl-nitrile Oxide, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-methyl-nitrileimine, 4 -(2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-phenyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrileimine, phenyl-N- The rubber composition according to (4) above, comprising at least one of 4- (2-oxazolyl) -phenyl-nitrileimine and phenyl-N-4- (2-thiazolyl) -phenyl-nitrileimine.

(6) The rubber composition according to (1), wherein the waste rubber is a powder rubber obtained by pulverizing.
(7) The rubber composition as described in (6) above, wherein the powder rubber has a fine particle size applied to a sieve of # 80 (sieve screen) or less.
(8) A rubber composition as described in (6) or (7) above, wherein the waste rubber is a recycled rubber obtained by treating the powder rubber with an oil pan method.

(9) A pneumatic tire according to any one of claims 1 to 8, wherein the waste rubber is contained in an amount of 50 parts by mass or less based on the rubber component 100.
(10) The pneumatic tire according to (9), wherein the pneumatic tire is a heavy duty pneumatic tire.
(11) The pneumatic tire according to (9), wherein the pneumatic tire is an off-road tire.

  According to the above means, the wear resistance is improved by adding a predetermined amount of waste rubber, in particular, sufficiently pulverized powder rubber and recycled rubber, to rubber components such as natural rubber and synthetic rubber. When the compound is added, the reaction of the following reaction formulas (1) to (3) occurs between the double bond part (P) in the rubber component and the Q part of the compound.

  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.

このような化合物の作用により、ゴム組成物においてカーボンブラック及びホワイトカーボンが十分に拡散される。その結果として、耐摩耗性の改善に有効な粉末廃ゴム等を配合して耐摩耗性に加えてリサイクル率を高め、ゴムの低発熱性及び低ヒステリシスロス性を更に改善し、重荷重用空気入りタイヤ及びオフロードタイヤとしての使用を可能にするものである。

By the action of such a compound, carbon black and white carbon are sufficiently diffused in the rubber composition. As a result, powder waste rubber effective for improving wear resistance is blended to increase the recycle rate in addition to wear resistance, further improving the low heat build-up and low hysteresis loss of rubber, and entering heavy duty pneumatic It can be used as a tire and an off-road tire.

Hereinafter, embodiments of the present invention will be described in detail.
The rubber composition of the present invention has a compound 0.1 having a part Q containing dipolar nitrogen and a part B containing 4 to 6 nitrogen-containing heterocycles containing oxygen or sulfur with respect to 100 parts by mass of the rubber component. 30 mass parts is mix | blended, It is characterized by the above-mentioned.

  The above 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 hydrogen, 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 compound itself increases, and the reactivity with the rubber component becomes worse.
Since the said compound has B part, A1-A4 can become a connecting chain which connects B part. 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 above compound, specifically, hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms ( However, 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 above compound consists 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: O or sulfur: S). Of these, oxazoline and thiozoline of the structural formula (II) are preferable. In each structural formula, R1 to R7 are hydrogen, 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.
As described above, the B part 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 above compounds include 4- (2-oxazolyl) -phenyl-N-methyl-nitrone, 4- (2-thiazolyl) -phenyl-N-methyl-nitrone, and 4- (2-oxazolyl). -Phenyl-N-phenyl-nitrone, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrone, phenyl-N-4- (2-oxazolyl) -phenyl-nitrone, phenyl-N-4- (2- Thiazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-oxazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4-methoxyphenyl-N- 4- (2-oxazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4- (2-oxazolyl) -fe Ru-nitrile oxide, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-methyl-nitrile Imine, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-phenyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrileimine, phenyl -N-4- (2-oxazolyl) -phenyl-nitrileimine, phenyl-N-4- (2-thiazolyl) -phenyl-nitrileimine and the like can be mentioned.

  Examples of such compounds include 4- (2-oxazolyl) -phenyl-N-methyl-nitrone (hereinafter referred to as 4OPMN) and 4- (2-oxazolyl) -phenyl-N-phenyl-nitrone (hereinafter referred to as 4OPPN). Can be specifically mentioned.

The method for producing the above compound 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.
Said compound is contained in 0.1-30 mass parts with respect to 100 mass parts of rubber components. In particular, it is preferable to contain in 0.1-5 mass parts. If the compounding amount is less than 0.1, the effects of low heat generation and low hysteresis loss are not sufficient. When the compounding amount of the compound exceeds 30 parts by mass, the cost increases significantly, which is not preferable.

  In the rubber composition of the present invention, the rubber component may be appropriately selected from natural rubber and synthetic rubber and may be blended. Moreover, as a synthetic rubber, it can select suitably from well-known things according to the objective. Conjugated rubber is particularly preferable, and it is preferable to appropriately select at least one from styrene-butadiene copolymer (SBR), polyisoprene (IR), polybutadiene (BR), acrylonitrile-butadiene rubber, chloroprene rubber, and butyl rubber. . Particularly preferably, when SBR is selected, the wear resistance is improved.

Waste rubber is blended in the rubber composition of the present invention. The waste rubber is preferably blended at 50 parts by mass or less with respect to 100 parts by mass of the rubber component. Especially preferably, it is 0.1 to 50 mass parts, It is preferable to mix | blend especially in the range of 1 to 10 mass parts.
If the amount of waste rubber exceeds 50 parts by mass, the heat buildup deteriorates and it is not suitable for tire treads. Further, if the amount of waste rubber is less than 0.1 parts by mass, the recycling rate is not sufficient.

Waste rubber is rubber obtained from used rubber products, rubber scraps produced during the manufacturing process of rubber products, and the like. The waste rubber is preferably blended into the rubber composition as crushed rubber, more preferably powder rubber, and recycled rubber obtained by regenerating the powder rubber by the oil pan method.
The use of powder rubber and recycled rubber is not limited in the present invention as long as it can be obtained by conventional methods. Commercially available powder rubber, powder rubber, and recycled rubber may be used. Further, the powder rubber preferably has a fine particle size applied to a sieve screen of # 80 or less, particularly a particle size applied to a # 100 or less.

The powder rubber used in the present invention can be obtained by, for example, the following crusher.
As shown in FIGS. 1 to 3, waste rubber chips G from chipping equipment and the like are put into a crusher 10 arranged in series. The crushed powder rubber is classified by the sieving machine 16, and the classified powder rubber is stored in the storage tanks T1, T2, and T3 according to the classified particle diameter.
The crusher 10 includes a rotary roll 12 and three fixed blades 14 arranged to face the peripheral surface thereof. As shown in FIG. 2A, grooves 12 (1) having a cross-sectional shape of both grooves along the axial direction are formed on the circumferential surface of the rotary roll 12 by knurling at a pitch R of a constant interval. A roll blade having a constant width R is formed on the peripheral surface of the roll 12. Incidentally, when the cross section is one-sided, rubber can be crushed at the time of crushing (in the process of finely pulverizing the rubber, in a state where the small powders are aggregated and can be separated). The pitch R of the groove 12 (1) is appropriately selected according to the crushing stage of the waste rubber chip G, and is particularly preferably selected in the range of 0.25 to 2.5 mm. In particular, the range of 0.6 to 2.5 mm is preferable in rough finishing, and the range of 0.25 to 0.6 mm is preferable in the finishing stage. If it exceeds 2.5 mm, it is too coarse to make the rubber chip G small. Conversely, if it is less than 0.25 mm, the rubber chip G is too fine and wrinkles occur.
The inclined surface of the fixed blade 14 opposed to the rotary roll 12 is formed with an arcuate surface that matches the peripheral surface of the rotary roll, and the peripheral surface and the arcuate surface are opposed to each other so that a gap is not substantially generated. Yes. Six grooves 14 (1) are formed on the isolated surface along the axial direction of the rotary roll, with a gap Q, and a fixed blade is formed. Further, the tip of the blade formed between the groove portions 14 (1) has an arcuate tip width corresponding to the width P. The interval Q is 1 to 20 mm, preferably 6 mm, and if it exceeds 20 mm, rubber curling occurs. The tip width P of the blade is 0.5 to 5 mm, preferably 1 to 2 mm. If it exceeds 5 mm, rubber curls will occur.

  The cross-sectional shape of the groove 14 (1) of the fixed blade 14 is such that the groove side wall surface on the downstream side where the waste rubber chip of the raw material to be moved moves connects the center O of the rotary roll 12 and the blade tip as shown in the figure. Formed on the extension. And the groove part 14 (1) is formed deeply toward the said downstream direction, and the bottom face of the groove part 14 (1) is as shown to FIG. 2B with respect to the above-mentioned arcuate surface or the surrounding surface of the rotary roll 12. And the inclination angle θ is preferably an acute angle. On the other hand, as shown in FIG. 2C, if the groove side wall surface is formed on the extension of the center O on the upstream side where the waste rubber chip moves, rubber stagnation occurs during crushing, which is not preferable. Moreover, as shown in FIG. 2D, it is not preferable to form both side wall surfaces of the groove 14 (1) on the extension of the center O, because rubber curl occurs at the corners of the groove.

As described above, the gap between the rotary roll 12 and the fixed blade 14 is preferably in a state where there is substantially no gap, that is, it is preferable that the two touch lightly, and the straightness of the rotary roll 12 with respect to the fixed blade 14 is zero. . That is, the rotating shaft of the rotating roll 12 is straight with respect to the opposing surface of the fixed blade 14, and the axial direction of the rotating roll and the strip direction of the groove 14 (1) are parallel. If there is a gap between the rotary roll 12 and the fixed blade 14, curling occurs.
When the waste rubber chip G is used as powder rubber in the crusher configured as described above, the waste rubber chip G supplied from the chipping equipment is put into the inclined surface S of the first fixed blade 14 in FIG. 2A. As shown in FIG. 3, the chip G is crushed by a shearing force when passing between the rotary roll 12 and the fixed blade 14. The crushing is repeated by the number of the groove portions 14 (1) of the fixed blade 14 and further multiplied by the number of the fixed blades 14 installed around the rotary roll 12. The processing is also multiplied according to the number of installed rotating rolls 12. Further, the pitch R of the groove portion 12 (1) of the rotary roll 12 is appropriately selected according to the respective stages from the upstream to the downstream of the waste rubber pitch.

Note that the crushed rubber chips G generated by the crushing process by the fixed blade 14 are not constant in size and vary in size. The relatively large rubber chip G falls immediately after leaving the fixed blade 14 and the relatively small rubber chip G. Is sandwiched between the groove portions 12 (1) of the rotary roll 12. For this reason, it is scraped off by the brush 18 arranged at a position substantially symmetrical with the fixed blade 14. In the crusher 10, these can be collected and circulated again to the inlet side to repeat the crushing process.
Further, in the crushing treatment, an aggregation preventing material can be added according to the crushing state of the waste rubber chip G. By adding an anti-agglomeration material, aggregation of rubbers is prevented, and a powder rubber having a low particle size can be obtained efficiently. Examples of the aggregation preventing material include fillers such as general calcium carbonate, alumina, carbon black, talc, and silica. In particular, carbon black is preferable. The addition amount of the aggregation preventing material is in the range of 10 to 20 parts by mass with respect to 100 parts by mass of the waste rubber. If the addition amount is less than 10 parts by mass, a sufficient coagulation effect cannot be obtained, and if it exceeds 20 parts by mass, the selectivity of the rubber composition for use as a final product is narrowed.
The waste rubber chips G crushed by the crusher 10 are classified by the sieving machine 16 and stored in the storage tanks T1, T2, and T3 as they are.
For example, as described in JP-A-2002-155170, recycled rubber is produced by an oil pan treatment method manufactured by Muraoka.

In the rubber composition of the present invention, carbon black and / or white carbon (silica filler) can be blended with the rubber component. These are preferably blended in the range of 30 to 70 parts by mass with respect to 100 parts by mass of the rubber component. When the amount of carbon black and white carbon decreases, the elastic modulus tends to decrease. Further, when the amount of carbon or the like increases, the low heat build-up of the vulcanized rubber composition tends to deteriorate.
The carbon black can be appropriately selected from those usually used in the rubber industry, and examples thereof include SAF, SRF, GPF, FEF, HAF, and ISAF. Incidentally, it is desirable to activate the surface of carbon black or the like by utilizing oil absorption.

  The rubber composition of the present invention can contain various components usually used in the rubber industry in addition to the above rubber component and carbon black. For example, as various components, fillers (for example, reinforcing fillers such as silica; and inorganic fillers such as calcium carbonate and calcium carbonate); vulcanization accelerators; anti-aging agents; zinc oxide; stearic acid; And additives such as an ozone degradation inhibitor. As vulcanization accelerators, thiazole vulcanization accelerators such as MBTS (dibenzothiazyl disulfide) and CZ (N-cyclohexyl-2-benzothiazylsulfenamide); thiurams such as TT (tetramethylthiuram sulfide) And guanidine-based vulcanization accelerators such as DPG (diphenylguanidine).

  The rubber composition of the present invention can be used for environmentally friendly recycled products such as general rubber products such as hoses and belts. Moreover, it is suitable to use for a pneumatic tire. Since pneumatic tires contribute greatly to wear resistance and low heat build-up, they can be used as heavy-duty pneumatic tires and off-road pneumatic tires that require long-term rough road durability. In the pneumatic tire of the present invention, air or an inert gas such as nitrogen can be used as the gas to be filled.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
(Examples 1-8 and Comparative Examples 1-5)
The rubber composition of each Example and Comparative Example is shown in Table 1 below, and a rubber composition before crosslinking was prepared using a Banbury mixer according to the formulation table in Table 1 below. Tires were created on 3700R57.

In each note in Table 1,
* 1) # 1500; Emulsion polymerization SBR
* 2) Powdered rubber / recycled rubber * 3) 4OPPN; (4- (2-oxazolyl) -phenyl-N-phenylnitrone)
* 4) 4OPMN; (4- (2-oxazolyl) -phenyl-N-methylnitrone)
* 5) Anti-aging agent 6PPD; N-phenyl-N'-isopropyl-p-phenylenediamine * 6) Vulcanization accelerator DPG; Diphenylguanidine * 7) Vulcanization accelerator CZ; N-cyclohexyl-2- Benzothiazylsulfenamide * 8) Vulcanization accelerator MBTS; Dibenzothiazyl disulfide

* 2) Powdered rubber / recycled rubber, * 3) 4OPPN and * 4) 4OPMN were produced as follows.
<Powder rubber / Recycled rubber>
Powder rubber was manufactured using the manufacturing equipment shown in FIG. A waste rubber chip having a particle size of 3 mm was used. The blade tip width P of the fixed blade 14 is 1.25 mm, and the pitch Q of the groove 14 (1) is 6 mm. During the crushing process, 20 parts by mass of carbon black as an aggregation preventing material was added to 100 parts by mass of the raw material waste rubber. The obtained powder rubber was classified by passing through a # 200 screen sieve to obtain powder rubber.
<Recycled rubber>
Recycled rubber manufactured by Muraoka Co., Ltd. obtained by treating coarse powder rubber with the PAN method is used.

<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-oxazolyl) -benzaldehyde.
A mixture of 4- (2-oxazolyl) -benzaldehyde (1 eq, 6.3 g) and N-phenyl-hydroxyamine (1 eq, 3.9 g) was refluxed in 100 ml ethanol for 30 min to a volume of 50 ml. Concentrated. The same amount of 50 ml of water was added and the mixture was cooled to 5 ° C. overnight in a refrigerator. Filtration separation and drying gave white crystals, yielding 6.7 g of 4- (2-oxazolyl) -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-oxazolyl) -benzaldehyde (41% yield).
A mixture of 4- (2-oxazolyl) -benzaldehyde (1 eq, 6.3 g) and N-methyl-hydroxyamine (1.7 g, 36 mmol) was refluxed in 100 ml of ethanol for 30 minutes and concentrated to a volume of 50 ml. did. 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 and drying, yielding 5.1 g of 4- (2-oxazolyl) -phenyl-N-methylnitrone (69% yield).

Next, tire performance tests for each of the examples and comparative examples were performed. In the performance test, the following evaluation of low heat buildup and wear resistance was evaluated as follows.
<Evaluation of low heat generation>
A drum system with a speed and step load condition of 10 km / h was implemented, the temperature at a position at a constant depth of the tread was measured, and each example was displayed as an index, with Comparative Example 1 as a control value (control) 100. It shows that it is excellent in low exothermic property, so that the value of an index | exponent is large.

Table 1 above shows the low exothermic results.
When Examples 1 to 4 are compared with the results of Comparative Example 1, the low heat build-up is improved over the rubber composition not using waste rubber. Even in Examples 5 to 8, the low heat build-up is improved as compared with Comparative Examples 2 to 5.

  Since the rubber composition of the present invention and the pneumatic tire using the rubber composition have a high recycling rate and are excellent in low heat generation and wear resistance, when it is used for a tire tread or the like, Since it can be suitably used for off-road tires, the industrial utility value is high.

1 is a schematic view of a crusher for producing powdered rubber by refining waste rubber used in the present invention. 2A is a cross-sectional view showing the crusher 10 used in FIG. 1, FIG. 2B is an enlarged view showing the cross-sectional shape of the groove portion of the fixed blade in FIG. 2A, and FIGS. 2C and 2D are for comparison. It is an enlarged view which shows the cross-sectional shape of this groove part. It is sectional drawing of the crusher for demonstrating the crushing phenomenon estimated at the time of crushing chip rubber with a rotary roll and a fixed blade.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Crusher 12 Rotary roll 12 (1) Groove part 14 Fixed blade 14 (1) Groove part 16 Sieve 18 Brush

Claims (11)

  100 parts by mass of the rubber component is blended with 0.1 to 30 parts by mass of a compound having a part Q containing dipolar nitrogen and 4 to 6 nitrogen-containing heterocyclic parts B containing oxygen or sulfur, and waste rubber A rubber composition comprising:   The dipolar nitrogen portion is selected from at least one of A1-C (A2) = N (A3) → O, A1-C≡N → O, and A1-C≡N → N-A4, and the A1 -A4 is hydrogen which may be different from each other, or a group having 20 or less carbon atoms or a linking chain that links the B, and the compound is bonded to at least one of A1 to A4. The rubber composition according to 1.   A1 to A4 of the above compound are hydrogen, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms (however, the aromatic ring has 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. Rubber composition.   The rubber composition according to claim 1, wherein the nitrogen-containing heterocycle of the B moiety is oxazoline or thiazoline.   The above compounds are 4- (2-oxazolyl) -phenyl-N-methyl-nitrone, 4- (2-thiazolyl) -phenyl-N-methyl-nitrone, 4- (2-oxazolyl) -phenyl-N-phenyl. -Nitrone, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrone, phenyl-N-4- (2-oxazolyl) -phenyl-nitrone, phenyl-N-4- (2-thiazolyl) -phenyl-nitrone 4-tolyl-N-4- (2-oxazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- (2-oxazolyl) ) -Phenyl-nitrone, 4-methoxyphenyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4- (2-oxazolyl) -phenyl-nitrileoxy 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-phenyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrileimine, phenyl-N-4 The rubber composition according to claim 4, comprising at least one of-(2-oxazolyl) -phenyl-nitrileimine and phenyl-N-4- (2-thiazolyl) -phenyl-nitrileimine.   The rubber composition according to claim 1, wherein the waste rubber is a powder rubber obtained by pulverizing.   The rubber composition according to claim 6, wherein the powder rubber has a fine particle size applied to a sieve of # 80 (sieve screen) or less.   The rubber composition according to claim 6 or 7, wherein the waste rubber is a recycled rubber obtained by treating the powder rubber with an oil pan method.   A pneumatic tire according to any one of claims 1 to 8, wherein the waste rubber is contained in an amount of 50 parts by mass or less with respect to the rubber component 100.   The pneumatic tire according to claim 9, wherein the pneumatic tire is a heavy duty pneumatic tire.   The pneumatic tire according to claim 9, wherein the pneumatic tire is an off-road tire.

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