JP2006083264A - Rubber composition and tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition that hardly discolors in the presence of ozone, has sufficient gloss and hardly develops a surface crack. <P>SOLUTION: The rubber composition comprises 100 parts by mass of a rubber component with 0.1-10 parts by mass of at least one kind of a nonionic surfactant selected from the group consisting of a compound represented by formula (I), a compound represented by formula (II), their mixture and a compound represented by formula (III) R<SP>2</SP>-O-(CH<SB>2</SB>CH<SB>2</SB>O)<SB>p</SB>H (R<SP>1</SP>and R<SP>2</SP>are each independently a 15-24C alkyl group or alkenyl group and the alkyl group and the alkenyl group each may be a straight-chain group, a branched-chain group or a cyclic group; l, m, n and p are each independently 1-10; l+m+n is 6-18) and 0.5-10 parts by mass of an organic short fiber having 0.5-20μm average diameter and 10-2,000μm average length. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition and a tire using the rubber composition for a sidewall, and relates to a rubber composition for a tire sidewall, which can maintain a good appearance of the tire and hardly develop surface cracks. It is.

  In general, a rubber article made from natural rubber or a diene synthetic rubber is deteriorated in the presence of ozone, and a crack occurs on the surface. This crack progresses due to static and dynamic stress applied to the rubber article, and as a result, the rubber article is broken.

  In order to suppress the occurrence and progression of cracks due to ozone, N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine is used as an anti-aging agent in rubber articles, particularly tire sidewalls. The rubber composition which mix | blended amine type anti-aging agent, such as, is applied. The rubber composition contains a wax for forming a protective film on the surface of the rubber article for the purpose of static protection from ozone.

  On the other hand, JP-A-2002-206036 (Patent Document 1) describes a specific average diameter and average length for color rubbers other than black, instead of an anti-aging agent having high coloring and staining properties. It is disclosed that the ozone crack resistance of the rubber composition can be improved without coloring and contaminating the rubber composition by blending the organic short fibers.

  Japanese Patent Application Laid-Open No. 5-194790 (Patent Document 2) discloses blending a rubber composition for tire sidewalls with a polyoxyethylene ether type nonionic surfactant to change the color due to an amine anti-aging agent and wax. A technique for preventing the above is disclosed.

JP 2002-206036 A JP-A-5-194790

  However, although the amine-based anti-aging agent and the wax are effective in suppressing the generation and progress of cracks in the presence of ozone, they are easy to move through a polymer substrate such as a rubber component, and in a short period, particularly rubber articles. It shifts to the surface of the tire and deteriorates the appearance by changing the color of the rubber article during storage and use. Here, when the amine-based anti-aging agent moves to the surface, the surface turns brown, and when the wax moves to the surface, the surface turns white.

  In recent years, in rubber articles, particularly tires, it is required not only to suppress discoloration but also to give gloss to make the appearance more beautiful, and the technology described in JP-A-2002-206036 described above. Then, by not using a coloring anti-aging agent, it was possible to improve the ozone crack resistance while suppressing discoloration, but it was not possible to impart gloss and make the appearance beautiful.

  Furthermore, in the technique described in JP-A-5-194790, although discoloration can be prevented, the bloom on the surface of the used surfactant is large and an appropriate gloss cannot be maintained. Even if the appearance could not be beautiful.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, to use a rubber composition that does not easily discolor in the presence of ozone, has a sufficient gloss, and that does not easily develop surface cracks, and the rubber composition. Is to provide the tires that were.

  As a result of diligent investigations to achieve the above object, the present inventor, by blending a rubber component with a nonionic surfactant having a specific structure and a specific organic short fiber, hardly discolors even in the presence of ozone. A rubber composition that has excellent gloss and is less prone to surface cracks, and by applying the rubber composition to a tire sidewall, the tire has a good appearance and excellent ozone crack resistance. Has been found, and the present invention has been completed.

［式(I)及び式(II)において、Ｒ¹は、それぞれ独立して炭素数１５〜２４のアルキル基又はアルケニル基を表し、該アルキル基及びアルケニル基は直鎖状、分枝鎖状及び環状のいずれでもよく；ｌ、ｍ及びｎはそれぞれ独立して１〜１０であり、ｌ＋ｍ＋ｎは６〜１８である。］
Ｒ²−Ｏ−(ＣＨ₂ＣＨ₂Ｏ)_pＨ ・・・ (III)
［式中、Ｒ²は、炭素数１５〜２４のアルキル基又はアルケニル基を表し、該アルキル基及びアルケニル基は直鎖状、分枝鎖状及び環状のいずれでもよく；ｐは１〜１０を示す。］ That is, the rubber composition of the present invention is a compound represented by the following formula (I), represented by the following formula (II) with respect to 100 parts by mass of at least one rubber component selected from natural rubber and diene synthetic rubber. 0.1 to 10 parts by mass of at least one nonionic surfactant selected from the group consisting of the compound represented by the following formula (III) and a mixture thereof, and an average diameter of 0.05 to 20 μm and It is characterized by blending 0.5 to 10 parts by mass of organic short fibers having an average length of 10 to 2000 μm.

[In the formula (I) and the formula (II), each R ¹ independently represents an alkyl group or alkenyl group having 15 to 24 carbon atoms, and the alkyl group and alkenyl group are linear, branched and Any of cyclic form may be sufficient; l, m, and n are each independently 1-10, and l + m + n is 6-18. ]
_{^{R 2 -O- (CH 2 CH 2}} O) p H ··· (III)
[Wherein R ² represents an alkyl group or alkenyl group having 15 to 24 carbon atoms, and the alkyl group and alkenyl group may be linear, branched, or cyclic; Show. ]

  In a preferred example of the rubber composition of the present invention, the organic short fibers are composed of at least one of aliphatic polyamide-based, aromatic polyamide-based, polyester-based, polyolefin-based, polyvinyl alcohol-based, and cellulose-based short fibers. . More preferably, the organic short fibers are chemically bonded to the rubber component.

  The rubber composition of the present invention further comprises a polyolefin having a melting point of 100 to 150 ° C., and the organic short fiber is composed of a thermoplastic polymer having an amide group in the main chain, the thermoplastic polymer (A), the rubber component Prepared by kneading in advance at least a part of (B) and each component of the polyolefin (C) at a mass ratio of (A) :( B) :( C) = 1: 1 to 2: 0 to 1. It is preferable that it is what was obtained using the prepared masterbatch.

  In another preferred embodiment of the rubber composition of the present invention, the nonionic surfactant has a balance between hydrophilicity and lipophilicity (HLB value) of 8 to 10.

  The tire of the present invention is characterized in that the rubber composition is applied to a sidewall.

  According to the present invention, a specific amount of a nonionic surfactant having a specific structure and organic short fibers having a specific average diameter and average length are blended in the rubber component, and it is difficult to discolor in the presence of ozone and has good gloss. Thus, it is possible to provide a rubber composition in which surface cracks are difficult to progress, and a tire having a good appearance using the rubber composition as a sidewall and excellent in ozone crack resistance.

  The present invention is described in detail below. The rubber composition of the present invention is represented by the compound represented by the above formula (I) and the above formula (II) with respect to 100 parts by mass of at least one rubber component selected from natural rubber and diene synthetic rubber. 0.1 to 10 parts by mass of at least one nonionic surfactant selected from the group consisting of compounds and mixtures thereof, and compounds represented by the above formula (III), an average diameter of 0.05 to 20 μm and an average length It is characterized by comprising 0.5 to 10 parts by mass of organic short fibers having a length of 10 to 2000 μm.

  In the rubber composition of the present invention, the nonionic surfactant prevents the amine-based anti-aging agent or wax from transferring to the surface and discoloring, and is exposed to ozone in the presence of the nonionic surfactant. The surfactant migrates to the surface and gives gloss. Here, in the rubber composition of the present invention, the compounding amount of the nonionic surfactant needs to be 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. The effect of preventing discoloration due to amine-based anti-aging agent and wax and the effect of giving gloss to the surface are small, and if it exceeds 10 parts by mass, the bloom is excessively glossy or the surface stickiness is caused and the appearance is deteriorated. It deteriorates and the scorch time is remarkably shortened, and workability is deteriorated.

  Moreover, in the rubber composition of this invention, since the said organic short fiber suppresses progress of the fine crack which generate | occur | produced in ozone presence, ozone crack resistance is improved significantly. Here, in the rubber composition of the present invention, the blending amount of the organic short fibers needs to be 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component. When the amount of the rubber composition exceeds 10 parts by mass, the elastic modulus of the rubber composition becomes excessively high. The organic short fibers require an average diameter of 0.05 to 20 μm and an average length of 10 to 2000 μm in order to obtain an appropriate aspect ratio. In general, when the aspect ratio is too small, If the aspect ratio is too large, the breaking strength tends to deteriorate. When the average diameter of the organic short fibers is less than 0.05 μm, the effect of improving the ozone crack resistance is not sufficient, and when the average diameter exceeds 20 μm, the organic short fibers act as fracture nuclei. Further, if the average length of the organic short fibers is less than 10 μm, the effect of improving the ozone crack resistance is not sufficient, and if it exceeds 2000 μm, the workability is deteriorated.

  Examples of the rubber component used in the rubber composition of the present invention include natural rubber and diene synthetic rubber. Examples of the diene synthetic rubber include isoprene rubber (IR), polybutadiene rubber (BR), and styrene-butadiene copolymer. Examples thereof include rubber (SBR). These rubber components may be used alone or in a blend of two or more.

  Nonionic surfactants used in the rubber composition of the present invention include compounds represented by the above formula (I), compounds represented by the above formula (II) and mixtures thereof, and compounds represented by the above formula (III). Selected from the following compounds: This nonionic surfactant may be used individually by 1 type, may use 2 or more types together, and can use a commercial item suitably. Here, in a preferred embodiment of the rubber composition of the present invention, a mixture of the compound represented by the formula (I) and the compound represented by the formula (II) is blended with the rubber component.

R ¹ of formula (I) and Formula (II), and R ² of formula (III) each independently represent an alkyl group or alkenyl group having 15 to 24 carbon atoms, the alkyl and alkenyl groups are straight-chain , Branched, and cyclic. When the number of carbon atoms is less than 15, the HLB value becomes too large, and when it exceeds 24, the HLB value becomes too small. Specific examples of the alkyl group include a hexadecyl group, a heptadecyl group, and an octadecyl group. Specific examples of the alkenyl group include a hexadecenyl group, a heptadecenyl group, and an octadecenyl group. The carbon number of the alkyl group and alkenyl group in R ¹ of formula (I) and formula (II) is preferably 17, and the alkyl group having 17 carbon atoms includes a heptadecyl group, and the alkenyl group having 17 carbon atoms includes A heptadecenyl group is mentioned. On the other hand, the alkyl group and the alkenyl group in R ² of the formula (III) preferably have 18 carbon atoms. The alkyl group having 18 carbon atoms includes an octadecyl group, and the alkenyl group having 18 carbon atoms includes an octadecenyl group. Among them, an oleyl group is preferable. Most stable when the carbon number of the alkyl group and alkenyl group in R ¹ of formula (I) and formula (II) is 17 and when the number of carbon atoms of the alkyl group and alkenyl group in R ² of formula (III) is 18 Can be present in the polymer matrix and can be moderately transferred to the surface upon stimulation.

  L, m and n in formula (I) and formula (II), and p in formula (III) each independently represent 1 to 10. When at least one of l, m, and n in formula (I) and formula (II) is 0, and when p in formula (III) is 0, compatibility with rubber is improved, and a nonionic interface The activator is less likely to migrate to the surface, while if it exceeds 10, the scorch time of the rubber composition becomes too short and workability deteriorates.

  Further, l + m + n in the formula (I) and the formula (II) needs to be 6 to 18, and 6 is particularly preferable from the viewpoint of obtaining an appropriate transition speed. On the other hand, p in the formula (III) is preferably 4 or more from the viewpoint of the transfer speed to the surface, and 4 is particularly preferable from the viewpoint of obtaining an appropriate transfer speed.

The nonionic surfactant preferably has an HLB value (balance between hydrophilicity and lipophilicity) of 2 to 19. Here, in the present invention, the HLB value is defined by the Griffin equation shown below.
HLB = 20 × Mw / M
[Wherein M is the molecular weight of the nonionic surfactant; Mw is the molecular weight of the hydrophilic portion of the nonionic surfactant. ]

  When the HLB value of the nonionic surfactant is less than 2, the lipophilicity is too strong, the compatibility with the rubber is very high, and it is difficult to migrate to the surface. On the other hand, if it exceeds 19, the hydrophilicity is too strong, the compatibility with rubber is poor, and kneading is difficult. Further, the HLB value of the nonionic surfactant is more preferably 8-10. If the HLB value is less than 8, the transition speed to the surface is slow, so the improvement effect is small. If it exceeds 10, the scorch time of the rubber composition is shortened and workability is deteriorated.

  Examples of the organic short fibers used in the rubber composition of the present invention include aliphatic polyamides, aromatic polyamides, polyesters, polyolefins, polyvinyl alcohols, and cellulose short fibers. You may use individually by 1 type and may mix and use 2 or more types. Here, as the aliphatic polyamide, nylon 6, nylon 6,6, nylon 6-nylon 6,6 copolymer, nylon 6,10, nylon 6,12, nylon 4,6, nylon 11, nylon 12, Nylon MXD6, a copolymer of aliphatic diamine and aromatic dicarboxylic acid, and the like. Examples of the aromatic polyamide include Kevlar (trademark) and Twaron. Examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, and aromatic polyester. Examples of the polyolefin include syndiotactic-1,2-polybutadiene, polyethylene, and polypropylene. Examples of the polyvinyl alcohol include vinylon. Examples of the cellulosic fiber include rayon.

  The rubber composition of the present invention further comprises a polyolefin having a melting point of 100 to 150 ° C., and the organic short fiber is composed of a thermoplastic polymer having an amide group in the main chain, the thermoplastic polymer (A), the rubber component Prepared by kneading in advance at least a part of (B) and each component of the polyolefin (C) at a mass ratio of (A) :( B) :( C) = 1: 1 to 2: 0 to 1. It is preferable that it is what was obtained using the prepared masterbatch. In addition, the remainder of a rubber component can be mix | blended by a post process. Here, examples of the thermoplastic polymer having an amide group in the main chain include the above-mentioned aliphatic polyamides and aromatic polyamides. It is preferable that the organic short fiber is made of a thermoplastic polymer having an amide group in the main chain because it can be chemically bonded to the rubber component. Further, by preparing a masterbatch containing organic short fibers, the rubber component and the polyolefin in advance, and producing a rubber composition using the masterbatch, productivity on an industrial scale can be improved. .

  In order to suppress the occurrence and progress of cracks due to ozone, the rubber composition preferably contains an amine anti-aging agent and a wax. Here, examples of the amine-based antioxidant include N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine. Further, the rubber composition is usually used in the rubber industry such as filler such as carbon black, vulcanizing agent, vulcanization accelerator, retarder (anti-scorch agent), softening agent, zinc oxide, stearic acid and the like. The compounding agent to be selected can be appropriately selected and blended within a range that does not impair the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition is produced by kneading, heating, extruding, and the like with a rubber component, a nonionic surfactant, an organic short fiber, and various compounding agents appropriately selected as necessary. be able to.

  The tire of the present invention is characterized in that the rubber composition is applied to a sidewall. In the tire, the amine-based anti-aging agent and wax are prevented from being transferred to the tire surface and discolored, and the nonionic surfactant is transferred to the sidewall surface by exposure in the presence of ozone. Therefore, the appearance is good for a long time. In addition, since the organic short fibers prevent the development of surface cracks on the sidewalls, ozone crack resistance is also good. The tire of the present invention is not particularly limited except that the rubber composition is applied to the sidewall, and can be produced by a usual method.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  A rubber composition containing the vulcanization accelerator, sulfur, retarder, organic short fiber, and nonionic surfactant in the blending formulation shown in Table 1 and in the blending amounts shown in Table 2 was prepared and heated at 145 ° C. for 30 minutes. Sulfurated. For the obtained vulcanized rubber, the scorch time, tensile stress and ozone cracking property were measured and evaluated by the following methods, and the glossiness and blackness were evaluated according to the criteria shown below. Evaluated. In Table 1, o indicates that the appearance is good, Δ indicates that the appearance is normal, and x indicates that the appearance is worse than normal.

(1) Scorch time The initial temperature was set to 130 ° C., the time until the Mooney viscosity increased by 5 units from the lowest viscosity (scorch time) was measured, and Comparative Example 1 was set to 100 and displayed as an index. A larger index value indicates a longer scorch time and better workability.

(2) Tensile stress Tensile stress at 300% elongation was measured as a representative index of rubber physical properties of the sidewall. Specifically, using a JIS No. 3 dumbbell-type test piece, the tensile stress at 300% elongation was measured according to JIS K 6251-1993, and Comparative Example 1 was indicated as 100. A larger index value indicates a higher tensile stress at 300% elongation.

(3) Ozone cracking property The condition of cracks after 72 hours was confirmed under the conditions of ozone concentration 50pphm, temperature 40 ° C, strain 40%, and the number of cracks A to C according to the following evaluation criteria The magnitude | size was shown by 1-5.
A: A small number of cracks B: A large number of cracks C: An infinite number of cracks 1: A thing that can be confirmed with a 10-fold magnifier 2: A thing that can be confirmed with the naked eye 3: A crack that is deep and relatively large (less than 1 mm)
4: The crack is deep and large (1mm or more and less than 3mm)
5: Those that are likely to crack or cut 3mm or more

(4) Glossiness The glossiness of samples was visually evaluated immediately after vulcanization and after being left for 1 week at 40 ° C. in an environment of ozone 50 pphm. Here, 5 is the case where gloss is recognized over the entire surface, 4 is the case where gloss is recognized over a wide area, 3 is the case where gloss is recognized in half of the whole, and 2 is the case where slight gloss is observed. And 1 when no gloss was observed.

(5) Blackness Immediately after vulcanization and after standing for 1 week at 40 ° C. in an environment of ozone 50 pphm, the blackness of the samples was visually evaluated. Here, the case where no discoloration is recognized is set to 5, the case where slight discoloration is recognized is set to 4, the case where discoloration is recognized to half or less of the whole is set to 3, and the case where discoloration is recognized to more than half of the whole 2 and 1 when discoloration was observed over the entire surface. In addition, discoloration refers to white discoloration and brown discoloration.

* 1 JSR "JSR BR01".
* 2 N550, "Asahi # 65" made by Asahi Carbon.
* 3 Process oil, “Fukkor Aromax 3B” manufactured by Fujikosan.
* 4 N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, "NOCRACK 6C" manufactured by Ouchi Shinsei Chemical Industry.
* 5 Microcrystalline wax, Nippon Seiwa "Ozoace-0701".
* 6 "VULKCIT DM / MG" made by dibenzothiazyl disulfide, MBTS, BAYER.
* 7 N-cyclohexylthiophthalimide, “SANTOGARD PVI / PDR / D” manufactured by Flexis.

In Table 2, the nonionic surfactant A is a trademark “Leodol TW-S106” manufactured by Kao Corporation, and is represented by the compound represented by the above formula (I) and the above formula (II). A mixture with a compound, R ¹ is an n-heptadecyl group having 17 carbon atoms [CH ₃ (CH ₂ ) ₁₆ −], l + m + n = 6, and an HLB value of 9.6;
Nonionic surfactant B is a mixture of a compound represented by the above formula (I) and a compound represented by the above formula (II) under the trademark “Leodol TW-S120V” manufactured by Kao Corporation. , R ¹ is a 17-carbon n-heptadecyl group [CH ₃ (CH ₂ ) ₁₆ −], l + m + n = 20, and the HLB value is 14.9;
Nonionic surfactant C is a trademark “Emulgen 404” manufactured by Kao Corporation, represented by the above formula (III), and R ² is an oleyl group having 18 carbon atoms [CH ₃ (CH ₂ ) ₇ CH═ CH (CH ₂ ) ₈ —] wherein p is 4 and the HLB value is 8.8;
Nonionic surfactant D is a trademark “Nissan Nonion NS215” manufactured by Nissan, is polyoxyethylene phenyl ether, and has an HLB value of 15.0.

  The organic short fiber A is “HA1060” manufactured by Daiwa Polymer Co., Ltd., having an average diameter of 1.0 μm and an average length of 500 μm. The product is a master of natural rubber (NR) / polyethylene (PE) / nylon 6. It is a batch (mass ratio is NR: PE: nylon = 1.15: 0.86: 1), and the blending amounts shown in Table 2 indicate the blending amount of nylon short fibers.

As is clear from Table 2, the rubber compositions of the examples have good ozone crack resistance, and the nonionic surfactant migrates to the surface when exposed to ozone, resulting in glossiness and blackness. As the degree increased, the appearance was very good. On the other hand, the rubber compositions of Comparative Examples 1 to 3 that do not contain organic short fibers have poor ozone crack resistance, and the rubber compositions of Comparative Examples 4 to 7 that do not contain the nonionic surfactant defined in the present invention. Even when the product was exposed in the presence of ozone, the glossiness and blackness did not improve, and the appearance was not improved.

Claims (6)

For 100 parts by mass of at least one rubber component selected from natural rubber and diene-based synthetic rubber, a compound represented by the following formula (I), a compound represented by the following formula (II) and a mixture thereof, and the following: 0.1 to 10 parts by mass of at least one nonionic surfactant selected from the group consisting of compounds represented by formula (III), an organic having an average diameter of 0.05 to 20 μm and an average length of 10 to 2000 μm A rubber composition comprising 0.5 to 10 parts by mass of short fibers.

[In the formula (I) and the formula (II), R ¹ each independently represents an alkyl group or an alkenyl group having 15 to 24 carbon atoms, and the alkyl group and the alkenyl group are linear, branched and Any of cyclic form may be sufficient; l, m, and n are each independently 1-10, and l + m + n is 6-18. ]
_{^{R 2 -O- (CH 2 CH 2}} O) p H ··· (III)
[Wherein R ² represents an alkyl group or alkenyl group having 15 to 24 carbon atoms, and the alkyl group and alkenyl group may be linear, branched, or cyclic; Show. ]   2. The rubber according to claim 1, wherein the organic short fibers are made of at least one of aliphatic polyamide-based, aromatic polyamide-based, polyester-based, polyolefin-based, polyvinyl alcohol-based, and cellulose-based short fibers. Composition.   The rubber composition according to claim 1 or 2, wherein the organic short fibers are chemically bonded to the rubber component.   The rubber composition further contains a polyolefin having a melting point of 100 to 150 ° C., and the organic short fiber is composed of a thermoplastic polymer having an amide group in the main chain, the thermoplastic polymer (A), at least of the rubber component A master prepared by previously kneading a part (B) and each component of the polyolefin (C) in a mass ratio of (A) :( B) :( C) = 1: 1 to 2: 0 to 1 The rubber composition according to any one of claims 1 to 3, wherein the rubber composition is obtained using a batch.   The rubber composition according to claim 1, wherein the nonionic surfactant has a balance value (HLB value) between hydrophilicity and lipophilicity of 8 to 10. The tire which applied the rubber composition in any one of Claims 1-5 to sidewall.