JP2016084405A - Cushion rubber composition for retreaded tire and retreaded tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability of a retreaded tire.SOLUTION: There is provided a cushion rubber composition by blending 100 pts.mass of a diene rubber, 20 to 100 pts.mass of carbon black and 5 to 20 pts.mass of a modified liquid rubber. There is also provided a retreaded tire by using the cushion rubber composition for a cushion rubber binding a base tire and a tread rubber by inclusion therebetween.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition used as a cushion rubber for a retread tire, and a retread tire using the same.

  For example, in heavy-duty pneumatic tires such as trucks and buses, tires called retreads may be rehabilitated. With regard to such tire retreading, there is a method in which vulcanized tread rubber is attached to a crown portion of a base tire via a cushion rubber, and the tread rubber and the base tire are combined, which is called a precure method. Cushion rubber is important for improving tire durability in retreaded tires manufactured by the precure method.

In order to improve the durability of the retreaded tire, Patent Document 1 discloses that the Mw of the peak derived from the rubber component measured by GPC of the sol in the rubber component of the cushion rubber is 50 × 10 ⁴ or less, and Mw It is disclosed that liquid isoprene rubber is used to reduce the viscosity. Patent Document 2 discloses that a liquid isoprene rubber is blended in the cushion rubber in order to achieve a low modulus while suppressing a decrease in tensile stress. However, the cushion rubber containing the unmodified liquid rubber disclosed in these documents cannot sufficiently improve the durability of the retreaded tire, and further improvement in durability is required.

  On the other hand, blending a modified liquid rubber with a rubber composition for tires is known as described in Patent Document 3, for example. However, in Patent Document 3, the modified liquid rubber is used for improving dispersibility of polar organic materials such as kneaded adhesives and phenolic resins in belt ply blends and bead filler blends. This does not suggest an improvement in durability of the cushion rubber.

  Patent Document 4 discloses that a dihydraside compound such as phthalic acid dihydrazide is blended in a tire rubber composition. However, in the cited document 4, the dihydrazide compound is used as an exothermic improver for imparting low exothermic properties, and it is also used for cushion rubber of retreaded tires, thereby improving the durability of the retreaded tires. Is not disclosed.

JP 2008-094266 A JP 2002-069237 A JP 2005-226016 A Japanese Patent Publication No. 7-57828

  An object of this invention is to provide the cushion rubber composition of the retreaded tire which can improve the durability of a retreaded tire, and a retreaded tire using the same.

  The cushion rubber composition for retread tires according to the present invention is obtained by blending 20 to 100 parts by mass of carbon black and 5 to 20 parts by mass of modified liquid rubber with respect to 100 parts by mass of the diene rubber. In the retread tire according to the present invention, the cushion rubber composition is used as a cushion rubber that is interposed between a base tire and a tread rubber to couple them together.

  ADVANTAGE OF THE INVENTION According to this invention, durability of a retreaded tire can be improved by using modified | denatured liquid rubber for the cushion rubber composition for retreaded tires.

  The cushion rubber composition for retread tire according to the present embodiment is obtained by blending carbon black (B) and modified liquid rubber (C) with diene rubber (A). By using the modified liquid rubber in this way, the durability of the retreaded tire can be improved. The reason is not intended to be limited, but is presumed as follows. That is, liquid rubber can be compounded by substituting at least a part of it as an alternative to oil. Unlike oil, diene rubber (not only diene rubber in the cushion rubber composition but also cushion rubber) In addition, it is possible to improve the durability of retreaded tires by using liquid rubber instead of oil. At the time of general rubber mixing, carbon black agglomerates, and at that time, a rubber component taken into the carbon black agglomerate called an occluder rubber is generated. Since the occluder rubber cannot participate in rubber cross-linking, desired rubber physical properties cannot be obtained, and there is a concern that a weak portion is generated in the rubber. On the other hand, by using the modified liquid rubber, the occluder rubber can be reduced and the number of co-crosslinkable liquid rubber can be increased, so that the durability is further improved.

  In the rubber composition according to the present embodiment, examples of the diene rubber (A) blended as a base rubber component include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), Styrene-butadiene rubber (SBR), styrene-isoprene rubber, butadiene-isoprene rubber, styrene-butadiene-isoprene rubber and the like can be mentioned, and these can be used alone or in admixture of two or more. More preferred is NR, SBR, BR, or a blended rubber of two or more of these, and even more preferred is NR alone or a blend of NR 60 mass% or more with SBR and / or BR 40 mass% or less.

  The diene rubber (A) is a solid rubber that does not have fluidity at room temperature (23 ° C.), and the modified liquid rubber (C) is included in the diene rubber (A). Absent. The number average molecular weight (Mn) of the diene rubber (A) is not limited as long as it is solid at room temperature, but is usually 100,000 or more, and Mn may be 200,000 to 1,200,000 as one embodiment. In this specification, a number average molecular weight is a value (polystyrene conversion value) measured at 40 ° C. by GPC (gel permeation chromatography), solvent: THF (tetrohydrofuran).

  The carbon black (B) is not particularly limited, and various known varieties can be used. For example, various furnace blacks such as SAF class (N100 series), ISAF class (N200 series), HAF class (N300 series), FEF class (N500 series) (both ASTM grade) can be used, one type alone or two You may use combining the carbon black of a seed | species or more.

  The compounding amount of the carbon black is preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, and further preferably 30 to 60 parts by mass with respect to 100 parts by mass of the diene rubber (A). It is.

  The modified liquid rubber (C) is a liquid polymer having fluidity at normal temperature (23 ° C.), and is not included in the diene rubber (A) that is solid at normal temperature. As long as the modified liquid rubber has fluidity at room temperature, its number average molecular weight (Mn) is not particularly limited, but is preferably less than 100,000, more preferably 1000 to 80000, and further preferably 2000 to 20000. 50000.

  Examples of the base polymer constituting the modified liquid rubber (C) include polyisoprene, polybutadiene, styrene butadiene copolymer, styrene isoprene copolymer, butadiene isoprene copolymer, styrene-butadiene-isoprene rubber copolymer, and acrylonitrile. Various diene polymers such as a butadiene copolymer can be used, and these can be used alone or in combination of two or more. Among these, at least one selected from the group consisting of polyisoprene, polybutadiene, styrene butadiene copolymer, and acrylonitrile butadiene copolymer is preferable.

  As the modified liquid rubber (C), those having at least one modified group selected from the group consisting of an epoxy group, a carboxyl group and a carboxylic acid derivative group are preferably used. These modified groups have a strong interaction with carbon black, and can enhance the effect of reducing the occluder rubber, thereby enhancing the effect of improving the durability of the retreaded tire. Here, examples of the carboxyl group include those derived from carboxylic acids such as maleic acid, phthalic acid, acrylic acid, and methacrylic acid. Examples of the carboxylic acid derivative group include a carboxylic acid ester group which is an ester group derived from these carboxylic acids, and a carboxylic acid anhydride group composed of an anhydride of a dicarboxylic acid such as maleic acid or phthalic acid. Although carbon number of the alkyl group couple | bonded with the oxygen atom in a carboxylic acid ester group is not specifically limited, It is preferable that it is 1-6.

  The modifying group of the modified liquid rubber (C) may be introduced at the end (both ends or one end) of the molecular chain of the main chain, or may be introduced at one or a plurality of positions in the molecular chain.

  Specific examples of the modified liquid rubber (C) include, for example, carboxyl group and / or carboxylic ester group-containing liquid polyisoprene, carboxylic acid anhydride group-containing liquid polyisoprene, epoxy group-containing polybutadiene, and carboxyl group-containing liquid acrylonitrile. A butadiene copolymer etc. are mentioned, You may use any 1 type or in combination of 2 or more types.

  The blending amount of the modified liquid rubber (C) is preferably 5 to 20 parts by mass with respect to 100 parts by mass of the diene rubber (A). By setting it as such a compounding quantity, the durable improvement effect of a retreaded tire can be heightened. The blending amount of the modified liquid rubber (C) is more preferably 7 to 18 parts by mass, still more preferably 10 to 15 parts by mass with respect to 100 parts by mass of the diene rubber (A).

  You may mix | blend the dihydrazide compound represented by following General formula (1) with the rubber composition which concerns on this embodiment. By adding such a dihydrazide compound, the durability of the retreaded tire can be further improved. The reason is not intended to be limited, but is presumed as follows. That is, by adding a dihydrazide compound, an increase in co-crosslinking between the modified liquid rubber and the diene rubber occurs due to an improvement in the effect of reducing the occlud rubber and a vulcanization activation action of the dihydrazide compound, resulting in durability. Is thought to improve.

式（１）中、Ａは、２価の芳香環基、置換又は非置換の２価のヒダントイン環基、あるいは炭素数１〜１８の飽和又は不飽和の２価の直鎖状炭化水素基である。上記の芳香環基としては、ヘテロ元素を含んでいてもよい炭素数４〜１８の２価の芳香環基（置換基を有していてもよい）が挙げられ、例えば、フェニレン基、ナフチレン基、ピリジレン基、キノリレン基などが挙げられる。上記のヒダントイン環基としては、置換されているか又は置換されていないヒダントイン環を含む２価の基であればよい。上記の直鎖状炭化水素基としては、例えば、メチレン基、エチレン基、プロピレン基、テトラメチレン基、ヘプタメチレン基、オクタメチレン基、オクタデカメチレン基、７，１１−オクタデカジエニレン基等が挙げられる。これらの中でも、Ａは、２価の芳香環基が好ましく、より好ましくはｏ−フェニレン基、ｍ−フェニレン基、ｐ−フェニレン基が挙げられる。

In the formula (1), A represents a divalent aromatic ring group, a substituted or unsubstituted divalent hydantoin ring group, or a saturated or unsaturated divalent linear hydrocarbon group having 1 to 18 carbon atoms. is there. Examples of the aromatic ring group include divalent aromatic ring groups having 4 to 18 carbon atoms that may contain a hetero element (which may have a substituent), such as a phenylene group and a naphthylene group. , Pyridylene group, quinolylene group and the like. The hydantoin ring group may be a divalent group including a substituted or unsubstituted hydantoin ring. Examples of the linear hydrocarbon group include a methylene group, an ethylene group, a propylene group, a tetramethylene group, a heptamethylene group, an octamethylene group, an octadecamethylene group, and a 7,11-octadecadienylene group. Can be mentioned. Among these, A is preferably a divalent aromatic ring group, more preferably an o-phenylene group, an m-phenylene group, or a p-phenylene group.

  Specific examples of the dihydrazide compound include phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin, succinic acid dibidazide, adipic acid dihydrazide, azelaic acid dihydrazide, Examples thereof include sebacic acid dihydrazide, eicosanedioic acid dihydrazide, 7,11-octadecadien-1,18-dicarbohydrazide, and the like, and any one kind or a combination of two or more kinds can be used.

  It is preferable that the compounding quantity of the said hydrazide compound is 0.1-5 mass parts with respect to 100 mass parts of diene rubber (A). The addition effect can be exhibited by mix | blending 0.1 mass part or more. On the other hand, even if 5 parts by mass or more is added, the effect obtained according to the increase in the amount added is small. The blending amount of the hydrazide compound is more preferably 0.3 to 3 parts by mass, and still more preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the diene rubber (A).

  In the rubber composition according to this embodiment, the modified liquid rubber (C) is preferably compounded by substituting at least a part thereof as an oil substitute. Therefore, it is preferable that the modified liquid rubber (C) and the oil are contained in a total amount of 7 to 30 parts by mass, more preferably 10 to 25 parts by mass with respect to 100 parts by mass of the diene rubber (A). Part. Moreover, it is preferable that the compounding quantity of modified | denatured liquid rubber (C) is larger than the compounding quantity of oil. Here, the oil is preferably a mineral oil mainly composed of hydrocarbons such as paraffinic oil, naphthenic oil, and aroma oil.

  In the rubber composition according to the present embodiment, in addition to the above components, stearic acid, zinc white, anti-aging agent, wax, tackifier, vulcanizing agent, vulcanization accelerator, vulcanization retarder, etc. Various additives generally used in the rubber composition can be blended. Examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount thereof is diene rubber (A). It is preferable that it is 0.1-10 mass parts with respect to 100 mass parts, More preferably, it is 0.5-5 mass parts.

  The rubber composition according to the present embodiment can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer.

  The rubber composition according to this embodiment is used as a cushion rubber for retread tires. That is, when the tread surface of a tire that has been worn out and has finished its primary life is buffed to form a base tire, and the pre-vulcanized tread rubber (precure tread) is attached to the crown portion of the base tire, the rubber composition An unvulcanized sheet-like cushion rubber made of the above is interposed between the two, and the cushion rubber is vulcanized to bond the base tire and the tread rubber. Thereby, the retreaded tire which concerns on one Embodiment is obtained.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, a cushion rubber composition for retreaded tires was prepared according to a conventional method according to the formulation (parts by mass) shown in Table 1 below. The details of each component in Table 1 are as follows.

・ Natural rubber: RSS # 3
・ SBR: “NIPOL1502” manufactured by Nippon Zeon Co., Ltd.
Carbon black 1: “Show Black N326” manufactured by Cabot Japan
・ Carbon Black 2: “Show Black N330T” manufactured by Cabot Japan
・ Stearic acid: “Stearic acid” made by Japanese fats and oils
・ Zinc oxide: “Zinc Hana 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Oil: “Process P200” manufactured by JX Nippon Oil & Energy
Liquid rubber: Liquid polyisoprene, “LIR-50” (unmodified, Mn = 54000) manufactured by Kuraray Co., Ltd.
Modified liquid rubber 1: Maleic acid modified liquid polyisoprene, “LIR-410” manufactured by Kuraray Co., Ltd. (maleic acid monomethyl ester group, Mn = 30000)
-Modified liquid rubber 2: Epoxy-modified liquid polybutadiene, "Ricon657" manufactured by Clay Valley
-Modified liquid rubber 3: carboxyl group-modified liquid NBR, "Nipol DN601" manufactured by Nippon Zeon Co., Ltd.
・ Dihydrazide compound: “Isophthalic acid dihydrazide” manufactured by Otsuka Chemical Co., Ltd.
・ Tackifier: “Escollets 1102” manufactured by EXXON
・ Sulfur: “Sulfur Powder” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator 1: “Noxeller DM” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator 2: “Noxeller M” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator 3: “Noxeller ZTC” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Vulcanization retarder: “Bullcurrent E / C” manufactured by Lances

  Durability was evaluated about the retreaded tire which used each obtained rubber composition as cushion rubber. Specifically, after pasting an unvulcanized cushion rubber sheet with a thickness of 1.5 mm on precure tread, it is left to stand at room temperature for a week, and then affixed to a tire of tire size 11R22.5, and then A retreaded tire was produced by vulcanizing the cushion rubber. The obtained retreaded tire is assembled to a standard rim, grounded to an indoor drum tester, and the speed is increased from 40 km / h to 10 km / h every hour under the conditions of air pressure and load specified by JATMA. The mileage until it broke under the up condition was measured. It represents with the index | exponent which made the value of the comparative example 1 100. The larger the index, the longer the mileage and the higher the durability. If the index is 105 or more, it means that the durability improving effect is excellent.

  The results are as shown in Table 1. In Comparative Example 2 in which the amount of oil was reduced compared to Comparative Example 1 as a control, the durability improvement effect was hardly obtained. Compared to Comparative Example 1, in Comparative Example 3 in which part of the oil was replaced with unmodified liquid rubber, although an effect of improving durability was obtained, it was insufficient. On the other hand, in Examples 1 to 4 in which part or all of the oil was replaced with the modified liquid rubber, not only for Comparative Example 1, but also for Comparative Example 3 using unmodified liquid rubber, A remarkable improvement effect was observed in the durability of the retreaded tire. Further, in Example 5 in which the dihydrazide compound was added together with the modified liquid rubber, an effect of further improving the durability was observed.

Claims (4)

  A cushion rubber composition for retread tires, comprising 20 to 100 parts by mass of carbon black and 5 to 20 parts by mass of modified liquid rubber with respect to 100 parts by mass of diene rubber.   The cushion rubber composition for retread tire according to claim 1, wherein the modified liquid rubber has at least one modified group selected from the group consisting of an epoxy group, a carboxyl group and a carboxylic acid derivative group. The cushion rubber composition for retread tires according to claim 1 or 2, comprising 0.1 to 5 parts by mass of a dihydrazide compound represented by the following general formula (1) with respect to 100 parts by mass of the diene rubber. .

(In the formula, A represents a divalent aromatic ring group, a substituted or unsubstituted divalent hydantoin ring group, or a saturated or unsaturated divalent linear hydrocarbon group having 1 to 18 carbon atoms. )   A rehabilitated tire, wherein the cushion rubber composition according to any one of claims 1 to 3 is used as a cushion rubber that is interposed between a base tire and a tread rubber to couple them together.