JP6332206B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire using a rubber composition, and more particularly to a pneumatic tire using a rubber composition that suppresses a decrease in tensile strength at break while increasing an expansion ratio.

  In recent years, it has been proposed to use a rubber composition as a constituent member of a pneumatic tire. For example, Patent Document 1 proposes that a tread portion of a studless tire is constituted by a rubber composition containing a chemical foaming agent.

  Such a rubber composition is characterized in that by increasing the expansion ratio, the mass can be reduced, the material characteristics can be made flexible, and the functionality due to a large number of bubbles can be added. However, when the expansion ratio is increased, there is a problem that the rubber strength such as the tensile strength at break of the rubber composition is lowered. For this reason, development of the rubber composition which suppressed the fall of the tensile strength at break while raising a foaming ratio is calculated | required.

JP 2006-274045 A

An object of the present invention is to provide a pneumatic tire using a rubber composition that suppresses a decrease in tensile strength at break while increasing the expansion ratio.

The pneumatic tire of the present invention that achieves the above object is a rubber formed by blending 0.1 to 8.0 parts by weight of a chemical foaming agent and 1 to 20 parts by weight of acid-modified polyolefin with respect to 100 parts by weight of a diene rubber. It is characterized by using a composition .

According to the pneumatic tire of the present invention, a rubber composition comprising 0.1 to 8.0 parts by mass of a chemical foaming agent and 1 to 20 parts by mass of an acid-modified polyolefin with respect to 100 parts by mass of a diene rubber. Since it was used , the expansion ratio of the vulcanized foamed rubber molded product can be increased, and the tensile strength at break can be increased to the conventional level.

  As said chemical foaming agent, at least 1 sort (s) chosen from a carbonamide type | system | group foaming agent, a nitroso type | system | group foaming agent, and a sulfonyl hydrazine type | system | group foaming agent is preferable, and the foaming ratio of a rubber composition can be made higher.

  It is preferable to mix 1 to 30 parts by mass of a polyamide polyether elastomer with respect to 100 parts by mass of the diene rubber, and the tensile elongation at break of the vulcanized foamed rubber molded product can be further increased.

  The rubber composition of the present invention is preferably used for a pneumatic tire, particularly a sidewall portion. A pneumatic tire having a sidewall portion made of a foamed rubber molded body obtained by vulcanizing this rubber composition has excellent tire durability, for example, in curb collision, and also reduces tire mass and heat generation. Fuel efficiency can be improved.

  In the rubber composition of the present invention, examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). ), Chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-IIR), chloroprene rubber (CR) and the like, and can be used alone or as any blend. Also, olefin rubbers such as ethylene propylene diene rubber (EPDM), styrene isoprene rubber, styrene isoprene butadiene rubber, isoprene butadiene rubber and the like can be blended. Of these, natural rubber, styrene butadiene rubber, butadiene rubber, and butyl rubber are preferred as the diene rubber. In particular, natural rubber is preferably contained, and the natural rubber is preferably contained in an amount of 20% by mass or more, more preferably 30 to 100% by mass in 100% by mass of the diene rubber. By setting the content of natural rubber in such a range, the tensile strength at break of the rubber composition can be further increased.

The rubber composition of the present invention can foam a rubber molded body by including a chemical foaming agent. The compounding amount of the chemical foaming agent is 0.1 to 8.0 parts by weight, preferably 1.0 to 8.0 parts by weight, more preferably 1.5 to 7.5 parts by weight with respect to 100 parts by weight of the diene rubber. It is good to. When the compounding amount of the chemical foaming agent is less than 0.1 parts by mass, foaming during vulcanization becomes insufficient, and the foaming ratio cannot be increased. Moreover, when the compounding quantity of a chemical foaming agent exceeds 8.0 mass parts, although the cost increases, the effect of the increase in the foaming ratio reaches a peak and the smoothness of the foam surface is impaired.

  Examples of the chemical foaming agent include a carbonamide foaming agent, a nitroso foaming agent, a sulfonyl hydrazide foaming agent, an azo foaming agent, and an azide foaming agent. Among these, at least one selected from a carbonamide foaming agent, a nitroso foaming agent, and a sulfonylhydrazine foaming agent is preferable.

  Azodicarbonamide (ADCA) or the like as the carbonodiamide foaming agent, N, N'-dinitrosopentamethylenetetramine (DPT), N, N'-dimethyl-N, N'-dinitrosotephthale as the nitroso foaming agent Examples include amides. Examples of the sulfonyl hydrazide-based blowing agent include benzenesulfonyl hydrazide (BSH), p, p′-oxybis (benzenesulfonyl hydrazide) (OBSH), toluenesulfonyl hydrazide (TSH), diphenylsulfone-3,3′-disulfonyl hydrazide, and the like. Illustrated. Examples of the azo foaming agent include azobisisobutyronitrile (AZBN), azobiscyclohexylnitrile, azodiaminobenzene, barium azodicarboxylate and the like. Examples of the azide-based blowing agent include calcium azide, 4,4′-diphenyldisulfonyl azide, p-toluenesulfonyl azide and the like. These chemical foaming agents can be used alone or in admixture of two or more.

  The decomposition temperature of the chemical foaming agent is preferably 130 ° C to 190 ° C, more preferably 150 ° C to 170 ° C. By controlling the decomposition temperature of the chemical foaming agent within such a range, chemical foaming and vulcanization can be easily controlled. In this specification, the decomposition temperature of a chemical foaming agent is a temperature calculated | required by measuring a decomposition heat and mass loss using the thermal analysis chosen from differential scanning calorimetry (DSC) and thermal mass measurement (TGA). is there.

  The rubber composition may contain urea together with a chemical blowing agent. Urea acts as a foaming aid. By blending the urea-based foaming aid, the temperature at which the chemical foaming agent is thermally decomposed can be adjusted to be low. The blending amount of the urea foaming aid is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the diene rubber. When the blending amount of the urea foaming auxiliary is less than 0.1 parts by mass, the thermal decomposition temperature of the chemical foaming agent cannot be adjusted sufficiently. When the blending amount of the urea foaming auxiliary exceeds 20 masses, it does not react and becomes a foreign substance in the composition, resulting in a decrease in mechanical strength.

The rubber composition of the present invention can increase the tensile strength at break of the foamed rubber molded article by including the acid-modified polyolefin. Surprisingly, the expansion ratio can be increased. The compounding amount of the acid-modified polyolefin is 1 to 20 parts by mass, preferably 2.5 to 20 parts by mass, and more preferably 3.0 to 20 parts by mass with respect to 100 parts by mass of the diene rubber. When the compounding amount of the acid-modified polyolefin is less than 1 part by mass, the tensile strength at break of the foamed rubber molded product cannot be increased. Moreover, when the compounding quantity of acid-modified polyolefin exceeds 20 mass parts, the tensile breaking strength of a foamed rubber molded object will become low on the contrary.

  The acid-modified polyolefin is a modified polymer obtained by modifying a polyolefin resin and / or a polyolefin elastomer with an unsaturated carboxylic acid. Examples of polyolefin resins and polyolefin elastomers include polyethylene, polypropylene, polybutene, polyoctene, their interpolymers, propylene-ethylene copolymers (propylene-ethylene block copolymers, propylene-ethylene random copolymers, etc.), Ethylene-α-olefin copolymer (ethylene-propylene rubber, ethylene-propylene-diene rubber), ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer Examples thereof include an union (EEA), an ethylene-methyl acrylate copolymer (EMA), an ethylene-methyl methacrylate copolymer (EMMA), and an ethylene-methacrylic acid copolymer (EMAA). Of these, ethylene-α-olefin copolymers, propylene-ethylene copolymers, polyethylene, and polypropylene are preferable. These polyolefin resins and polyolefin elastomers can be used alone or in admixture of two or more.

  Examples of the unsaturated carboxylic acid include maleic acid, fumaric acid, acrylic acid, crotonic acid, methacrylic acid, itaconic acid, and acid anhydrides thereof. Of these, maleic acid, maleic anhydride, acrylic acid, and methacrylic acid are preferable. These unsaturated carboxylic acids can be used alone or in admixture of two or more.

  The acid-modified polyolefin can be obtained by modifying a polyolefin resin and a polyolefin elastomer with an unsaturated carboxylic acid by a conventional method. The acid modification rate of the acid-modified polyolefin is such that the unsaturated carboxylic acid content is preferably 0.1 to 3.0% by mass, more preferably 0.15 to 2.0% by mass.

  The rubber composition of the present invention can optionally contain a polyamide polyether elastomer. By blending the polyamide polyether elastomer, the tensile elongation at break of the foamed rubber molded product can be made higher than the conventional level. The blending amount of the polyamide polyether elastomer is preferably 1 to 30 parts by mass, more preferably 2.5 to 25 parts by mass, and further preferably 3.0 to 20 parts by mass with respect to 100 parts by mass of the diene rubber. Good. When the blending amount of the polyamide polyether elastomer is less than 1 part by mass, the effect of improving the tensile elongation at break of the foamed rubber molded article cannot be sufficiently obtained. Moreover, when the compounding quantity of a polyamide polyether elastomer exceeds 30 mass parts, the tensile fracture strength of a foamed rubber molded object will become low.

  The polyamide polyether elastomer is an elastomer having a hard segment made of polyamide and a soft segment made of polyether, and is disclosed in detail, for example, in WO 2007/145324, including its production method. As the polyamide polyether elastomer, those having a hard segment made of nylon 12 and a soft segment made of polyether are suitable, and the weight average molecular weight is particularly preferably 10,000 to 200,000. Such a polyamide polyether elastomer can use what is marketed, for example, UBESTAXPA P9040X1 by Ube Industries, Ltd. is mentioned.

  In the present invention, the tensile break strength of the rubber composition can be further increased by blending the filler. The blending amount of the filler is preferably 20 to 100 parts by mass, more preferably 40 to 80 parts by mass with respect to 100 parts by mass of the diene rubber. If the blending amount of the filler is less than 20 parts by mass, the tensile strength at break of the rubber composition cannot be sufficiently increased. Moreover, when the compounding quantity of a filler exceeds 100 mass parts, the workability of a rubber composition will fall.

  Examples of the filler include carbon black, silica, calcium carbonate, clay, mica, diatomaceous earth, talc and the like. Of these, carbon black, silica, and calcium carbonate are preferable. Such fillers can be used alone or as any blend.

  A rubber composition is composed of a vulcanizing agent, a vulcanization accelerator, a vulcanizing aid, a rubber reinforcing agent, a softening agent (plasticizer), an anti-aging agent, a processing aid, a foaming aid, a defoaming agent, an activator, a gold Additives usually used in industrial rubber compositions and foamed rubber molded articles such as mold release agents, heat stabilizers, weathering stabilizers, antistatic agents, colorants, lubricants, thickeners and the like can be added. These compounding agents can be used in the usual compounding amounts as long as they do not contradict the object of the present invention, and can be added, kneaded or mixed by a usual preparation method.

  The expansion ratio of the rubber composition of the present invention is preferably 1.2 times or more, more preferably 1.3 to 2.0, and still more preferably 1.4 to 1.8 times. By setting the foaming ratio of the foamed rubber molded body to 1.2 times or more, the specific gravity of the foamed rubber molded body can be reduced. Moreover, the tensile fracture strength of the foamed rubber molded article can be made excellent by setting the expansion ratio to 2.0 times or less.

  The rubber composition of the present invention can be molded into a foamed rubber molded body by molding a molded body of unvulcanized rubber and heating and foaming / vulcanizing it. The shape, size and thickness of the unvulcanized rubber molded product can be appropriately adjusted according to the shape, size and thickness of the foamed rubber molded product after vulcanization molding. Moreover, the molding method generally used can be applied to the molding method of the unvulcanized rubber molded body.

  The foamed rubber molded article made of the rubber composition of the present invention is useful as a pneumatic tire or an industrial buffer material. The part to be used for the pneumatic tire is not particularly limited. For example, it is used as a sound absorbing material on the side rubber constituting the sidewall portion, the cap tread constituting the tread portion, or the radially inner surface of the tire lumen. be able to. Since the pneumatic tire using the rubber composition of the present invention can achieve light weight and low heat buildup while ensuring mechanical strength and maintaining durability, fuel efficiency can be improved.

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

Preparation of rubber composition and creation of unvulcanized molded article 15 types of rubber compositions (Examples 1 to 7, Comparative Examples 1 to 1) having the rubber composition shown in Table 3 as a common formulation and the formulations shown in Tables 1 and 2 For 8), the components other than sulfur, vulcanization accelerator, chemical foaming agent and foaming aid were weighed and kneaded for 5 minutes with a 1.7 L closed Banbury mixer, and the master batch was discharged at a temperature of 150 ° C. at room temperature. Cooled down. Thereafter, this master batch is subjected to a heating roll, and sulfur, a vulcanization accelerator, a chemical foaming agent and a foaming aid are added and mixed to prepare 15 types of rubber compositions, and an unvulcanized composition comprising these rubber compositions. The rubber molded body was molded.

Vulcanization molding and evaluation of foamed rubber molded body An unvulcanized rubber molded body composed of the 15 types of rubber compositions (Examples 1 to 7, Comparative Examples 1 to 8) obtained was formed into a predetermined shape (length 100 mm, width 100 mm). ). These were heated at a temperature of 180 for 15 minutes to be vulcanized. As a result, vulcanization and foaming of the unvulcanized rubber moldings excluding Comparative Examples 1 and 2 proceeded simultaneously, and a foamed rubber molding having a thickness of about 15 mm was molded. Further, the unvulcanized rubber molded articles of Comparative Examples 1 and 2 became vulcanized rubber sheets which were vulcanized and not foamed.

  Specific gravity, average foaming ratio and tensile breaking strength of the obtained foamed rubber molded bodies (comparative examples 1 and 2 are unfoamed vulcanized rubber sheets) were measured by the following methods, respectively. It was shown in 2.

Specific gravity and average foaming ratio The specific gravity of the unvulcanized rubber molding and the specific gravity of the foamed and vulcanized foamed rubber molding were measured at 23 ° C. in accordance with JIS K-6268, respectively. The ratio between the specific gravity of the unvulcanized rubber molded product and the specific gravity of the foamed rubber molded product was calculated and used as the average foaming ratio. Tables 1 and 2 show the results of specific gravity and average foaming ratio of the obtained foamed rubber molded bodies.

Tensile rupture strength The tensile rupture strength of the foamed rubber molded body was measured in accordance with JIS K-6251 by cutting out a JIS No. 3 dumbbell-shaped test piece at 23 ° C. and a tensile speed of 500 mm / min. Tables 1 and 2 show the results of the tensile breaking strength of the obtained foamed rubber moldings.

The types of raw materials used in Tables 1 and 2 are shown below.
Acid modified PO: maleic anhydride modified polypropylene, Mitsui Chemicals Admer HE810
Polyamide polyether: Polyamide polyether elastomer, Ube Industries, Ltd. XPAP 9040X1
Polyolefin: Polypropylene, Prime Polymer S119
・ Chemical foaming agent 1: Nitroso-based foaming agent, N, N'-dinitrosopentamethylenetetramine, Cella D manufactured by Eiwa Chemical Industry Co., Ltd., and the following foaming aid (urea) are combined to adjust the decomposition start temperature to 130 ° C. Chemical foaming agent 2: Sulfonyl hydrazide foaming agent, p, p'-oxybis (benzenesulfonyl hydrazide) (OBSH), Neocelbon N # 5000 manufactured by Eiwa Kasei Kogyo Co., Ltd., decomposition start temperature is 164 ° C
-Foaming aid: urea, cell paste K4 manufactured by Eiwa Kasei Kogyo Co., Ltd.

The types of raw materials used in Table 3 are shown below.
NR: natural rubber, PT. NURISA SIR20
BR: Butadiene rubber, Nippon Zeon BR1220
・ CB: Carbon black, Seast F made by Tokai Carbon
-Zinc oxide: 3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.-Stearic acid: Bead stearic acid paulownia manufactured by Chiba Fatty Acid Company-Anti-aging agent: VULKANOX 4020 manufactured by Bayer
・ Oil: Idemitsu Kosan Diana Process NH-60
・ Sulfur: Tsurumi Chemical Industry Co., Ltd. Jinhua stamp fine powder sulfur 150 mesh
・ Vulcanization accelerator: Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.

  From the results in Table 1, it was confirmed that the foamed rubber molded bodies of Examples 1 to 7 ensure a tensile fracture strength substantially equivalent to that of the unfoamed rubber molded body while increasing the average foaming ratio. On the other hand, the vulcanized rubber sheets of Comparative Examples 1 and 2 have high tensile strength but high specific gravity because they are not foamed. Since the foamed rubber molded article of Comparative Example 3 does not contain acid-modified polyolefin, the tensile strength at break is lowered, and the foaming ratio is also smaller than those of Examples 1 to 3.

  The foamed rubber molded article of Comparative Example 4 cannot maintain the tensile strength at break because it contains unmodified polyolefin instead of acid-modified polyolefin. Further, the expansion ratio is smaller than that of the foamed rubber molded body of Example 1.

Since the foamed rubber molded article of Comparative Example 5 does not contain acid-modified polyolefin, the tensile strength at break is lowered, and the foaming ratio is smaller than that of the foamed rubber molded article of Example 6.
In the foamed rubber molded article of Comparative Example 6, since the blending amount of the acid-modified polyolefin exceeds 30 parts by mass, the elongation at break is lowered, and the breaking strength is also lowered after all.
The foamed rubber molded article of Comparative Example 7 cannot maintain the tensile strength at break because it contains unmodified polyolefin instead of acid- modified polyolefin. Further, the expansion ratio is smaller than that of the foamed rubber molded body of Example 6.
In the foamed rubber molded body of Comparative Example 8, since the compounding amount of the chemical foaming agent exceeds 8.0 parts by mass, gas leakage that cannot be dissolved in the rubber during vulcanization occurs, or foaming becomes irregular and breaks. The strength is lowered, and the foaming ratio becomes too large, so that it is not a practical foam.

Claims (3)

To diene rubber 100 parts by weight of 0.1 to 8.0 parts by weight of a chemical foaming agent, a pneumatic tire using the acid-modified polyolefin from 1 to 20 parts by mass to such Lugo rubber composition. The pneumatic tire according to claim 1, wherein the chemical foaming agent is at least one selected from a carbonamide foaming agent, a nitroso foaming agent, and a sulfonylhydrazine foaming agent. The pneumatic tire according to claim 1 or 2, wherein 1 to 30 parts by mass of a polyamide polyether elastomer is blended with 100 parts by mass of the diene rubber.