Rubber composition

Abstract

To provide a rubber composition having superior ozone resistance.SOLUTION: A rubber composition comprises 100 pts.mass of a diene rubber and 0.1 to 20 pts.mass of a compound represented by formula (1). R1 to R3 and X1 to X3 represent a hydrogen atom or a substituent, where at least one of X1 to X3 is an unsaturated ether-containing group, and at least one is a hydroxyl group or a C1-5 aliphatic hydrocarbon group having a hydroxyl group.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition.

Background Art

[0002] Conventionally, a rubber composition containing a phenylenediamine-based antioxidant (for example, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD)) as an antioxidant has been known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recently, with the improvement of the required safety level, further improvement in ozone resistance has been demanded. When the present inventors evaluated the ozone resistance of the rubber composition described in Patent Document 1, it became clear that further improvement is desirable in consideration of future increasing requirements.

[0005] Therefore, an object of the present invention is to provide a rubber composition having excellent ozone resistance in view of the above circumstances.

Means for Solving the Problems

[0006] As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by blending a specific compound in a predetermined amount, and thus have reached the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) 100 parts by mass of a diene rubber, A rubber composition containing 0.1 to 20 parts by mass of a compound represented by the following formula (1). (2) Among the above X 1 ~X 3 Two of them are groups represented by the above formula (A), and the rubber composition according to the above (1). (3) Among the above X 1 ~X 3 One of them is a hydroxyl group, and the rubber composition according to the above (1) or (2).

Advantages of the Invention

[0008] As shown below, according to the present invention, a rubber composition excellent in ozone resistance can be provided.

Modes for Carrying Out the Invention

[0009] The rubber composition of the present invention will be described below. In the present specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In addition, each component may be used alone or in combination of two or more. Here, when two or more of each component are used in combination, the content of that component refers to the total content unless otherwise specified. In addition, being excellent in ozone resistance and having a large elongation at break is also referred to as "the effects of the present invention are excellent".

[0010] The rubber composition of the present invention (hereinafter, also referred to as "the composition of the present invention") is 100 parts by mass of a diene rubber and a rubber composition containing 0.1 to 20 parts by mass of a compound represented by the following formula (1) (hereinafter, also referred to as "specific compound").

[0011] The composition of the present invention is considered to solve the above-described problems because it has such a configuration. The reason is not clear, but it is considered approximately as follows.

[0012] Diene rubbers are known to be deteriorated by ozone in the atmosphere. Deterioration of diene rubbers is a problem because it leads to cracks and breaks. The specific compound contained in the composition of the present invention is considered to react with ozone much faster than diene rubbers and to suppress the deterioration of diene rubbers by ozone. As a result, the composition of the present invention is considered to be less likely to deteriorate even when exposed to ozone (excellent ozone resistance). Here, it is considered that the group represented by the formula (A) in the specific compound reacts with ozone. Also, the hydroxyl group in the specific compound is considered to promote the above reaction. The extremely excellent reactivity of the above-mentioned specific compound with respect to ozone is considered to be due to the fact that the group represented by the formula (A) and the hydroxyl group are present at relatively close positions. This is also inferred from the fact that, as shown in Comparative Example 3 described later, the ozone resistance becomes insufficient when Compound 3 having both the group represented by the formula (A) and the hydroxyl group but with a large distance between their positions is used.

[0013] Hereinafter, each component contained in the composition of the present invention will be described.

[0014] [Diene rubber] The diene rubber contained in the composition of the present invention is not particularly limited. The composition of the present invention may contain one kind of diene rubber or two or more kinds of diene rubbers.

[0015] [Specific examples] Specific examples of the above diene rubbers include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), and the like. Specific examples of the above aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, and the like. Among them, natural rubber is preferred because of the more excellent effects of the present invention and the like.

[0016] 〔Molecular weight〕 The weight average molecular weight (Mw) of the above diene rubber is not particularly limited, but for reasons such as more excellent effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000.

[0017] In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are standard polystyrene conversion values obtained by gel permeation chromatography (GPC) measurement.

[0018] [Specific compound] The composition of the present invention contains a compound represented by the following formula (1).

[0019] [Chemical formula]

[0020] In formula (1), R 1 ~R 3 each independently represents a hydrogen atom or a substituent, and X 1 ~X 3 each independently represents a hydrogen atom or a substituent. However, among X 1 ~X 3 , at least one is a group represented by the following formula (A), and at least one is a hydroxyl group or an aliphatic hydrocarbon group having 1 to 5 carbon atoms and having a hydroxyl group.

[0021] [R 1 ~R 3 As described above, in formula (1), R 1 ~R 3 each independently represents a hydrogen atom or a substituent (for example, specific examples described later). A plurality of R 1 and R 3 may be the same or different from each other.

[0022] R 1 and R​3 is preferably a hydrogen atom because the effects of the present invention are more excellent.

[0023] R 2 is preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom, because the effects of the present invention are more excellent. Examples of the hydrocarbon group include an aliphatic hydrocarbon group, an aromatic hydrocarbon group (aryl group), and a group combining these. The aliphatic hydrocarbon group may be linear, branched, or cyclic. Specific examples of the aliphatic hydrocarbon group include an alkyl group (especially having 1 to 30 carbon atoms), an alkenyl group (especially having 2 to 30 carbon atoms), an alkynyl group (especially having 2 to 30 carbon atoms), and the like. Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups having 6 to 18 carbon atoms such as a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. The hydrocarbon group is preferably an aliphatic hydrocarbon group, more preferably an alkyl group (especially having 1 to 10 carbon atoms), because the effects of the present invention are more excellent.

[0024] [X 1 ~X 3 As described above, in formula (1), X 1 ~X 3 each independently represents a hydrogen atom or a substituent (for example, specific examples described later). However, among X 1 ~X 3 , at least one is a group represented by formula (A) described later, and at least one is a hydroxyl group or an aliphatic hydrocarbon group having 1 to 5 carbon atoms and having a hydroxyl group.

[0025] [Group represented by formula (A)] As described above, among X 1 ~X 3 , at least one is a group represented by formula (A). Hereinafter, the group represented by formula (A) will be described.

[0026] ​[Chemistry]

[0027] In formula (A), R A represents a hydrogen atom or a substituent (for example, specific examples described later). * represents the bonding position.

[0028] R A is preferably a hydrogen atom or a hydrocarbon group, and more preferably a hydrocarbon group, for reasons such that the effects of the present invention are more excellent. Specific examples and preferred embodiments of the above hydrocarbon group are the same as those of R 2 described above.

[0029] <Hydroxyl group, or an aliphatic hydrocarbon group having 1 to 5 carbon atoms and a hydroxyl group> As described above, among X 1 ~X 3 , at least one is a hydroxyl group (-OH) or an aliphatic hydrocarbon group having 1 to 5 carbon atoms and a hydroxyl group.

[0030] Specific examples of the aliphatic hydrocarbon group in the aliphatic hydrocarbon group having 1 to 5 carbon atoms and a hydroxyl group are the same as those of R 2 described above. The above carbon number is preferably 1 to 3 for reasons such that the effects of the present invention are more excellent. The above aliphatic hydrocarbon group is preferably an alkyl group. Specific examples of the aliphatic hydrocarbon group having 1 to 5 carbon atoms and a hydroxyl group include a methylol group (-CH 2 OH), an ethylol group (-C 2 H 4 OH), etc.

[0031] <Preferred embodiment> For reasons such that the effects of the present invention are more excellent, two of the above X 1 ~X 3 (particularly X 1 and X 3 ) are preferably groups represented by formula (A). For reasons such that the effects of the present invention are more excellent, the above X 1~X 3 Of these, one (especially X 2 ) is preferably a hydroxyl group or an aliphatic hydrocarbon group having 1 to 5 carbon atoms and having a hydroxyl group, and more preferably a hydroxyl group.

[0032] 〔Preferred embodiment〕 The specific compound is preferably a compound obtained by a dehydration reaction between glycerol (glycerin) and a compound in which a hydrogen atom is bonded to the bonding position of the group represented by the above formula (A) because the effects of the present invention are more excellent.

[0033] 〔Specific examples of substituents〕 Specific examples of the substituents in the present specification include a halogeno group (halogen atom), an alkyl group (for example, tert-butyl group) (including a cycloalkyl group, a bicycloalkyl group, and a tricycloalkyl group), an alkenyl group (including a cycloalkenyl group and a bicycloalkenyl group), an alkynyl group, an aryl group, a heterocyclic group (which may also be referred to as a heterocyclic group), a cyano group, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an aryloxy group, a silyloxy group, a heterocyclic oxy group, an acyloxy group, a carbamoyl group, a carbamoyloxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group (including an anilino group), an ammonio group, a dialkylamino group, an acylamino group, an aminocarbonylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfamoylamino group, an alkyl or arylsulfonylamino group, a mercapto group, an alkylthio group, an arylthio group, a heterocyclic thio group, a sulfamoyl group, a sulfo group, an alkyl or arylsulfinyl group, an alkyl or arylsulfonyl group, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group, an aryl or heterocyclic azo group, an imide group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, a phosphono group, a silyl group, a hydrazino group, a ureido group, a boronic acid group (-B(OH) 2 ), a phosphato group (-OPO(OH) 2 ), a sulfato group (-OSO 3 H), and other known substituents and the like.

[0034] [Content] In the composition of the present invention, the content of the specific compound is 0.1 to 20 parts by mass with respect to 100 parts by mass of the diene rubber described above. Among them, for the reason that the effects of the present invention are more excellent, it is preferably 1 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 2 to 4 parts by mass.

[0035] [Optional Component] The composition of the present invention can further contain other components (optional components) as necessary within the range that does not impair its effects and purposes. Examples of the above optional components include various additives generally used in rubber compositions such as fillers (e.g., silica, carbon black), silane coupling agents, terpene resins (e.g., aromatic-modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators, etc.

[0036] [Carbon Black] The composition of the present invention preferably contains carbon black for the reason that the effects of the present invention are more excellent. The above carbon black is not particularly limited, and for example, those of various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF can be used. Among them, the HAF grade is preferred for the reason that the effects of the present invention are more excellent. The nitrogen adsorption specific surface area (N 2 SA) of the above carbon black is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 50 to 200 m 2 / g, and more preferably 70 to 150 m 2 / g. Here, the nitrogen adsorption specific surface area (N 2SA) is the value obtained by measuring the nitrogen adsorption amount on the carbon black surface in accordance with JIS K6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0037] <Content> In the composition of the present invention, the content of carbon black is not particularly limited. However, for the reason that the effects of the present invention are more excellent, it is preferably 1 to 100 parts by mass, more preferably 2 to 50 parts by mass, based on 100 parts by mass of the above-mentioned diene rubber.

[0038] [Silica] The composition of the present invention may contain silica. The above silica is not particularly limited, and any conventionally known silica can be used. Examples of the above silica include wet silica, dry silica, fumed silica, diatomaceous earth, etc. The above silica may be used alone or in combination of two or more kinds of silica.

[0039] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of the above silica (hereinafter, the "CTAB adsorption specific surface area" is also simply referred to as "CTAB") is not particularly limited. However, for the reason that the effects of the present invention are more excellent, it is preferably 100 to 300 m 2 / g, more preferably 150 to 200 m 2 / g. Here, the CTAB adsorption specific surface area is the value obtained by measuring the CTAB adsorption amount on the silica surface in accordance with JIS K6217-3:2001 "Part 3: Method for determining specific surface area - CTAB adsorption method".

[0040] <Content> In the composition of the present invention, the content of silica is not particularly limited. However, for the reason that the effects of the present invention are more excellent, it is preferably 10 to 150 parts by mass, more preferably 50 to 100 parts by mass, based on 100 parts by mass of the above-mentioned diene rubber.

[0041] [Manufacturing method] The manufacturing method of the composition of the present invention is not particularly limited. Specific examples thereof include, for example, a method of kneading the above-described respective components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). When the composition of the present invention contains a vulcanizing agent (for example, sulfur) and a vulcanization accelerator, from the reason that the effects of the present invention are more excellent for the obtained composition, components other than the vulcanizing agent and the vulcanization accelerator are first mixed at a high temperature (preferably 100 to 155 ° C), cooled, and then the vulcanizing agent and the vulcanization accelerator are mixed. The composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0042] [Use] The composition of the present invention is suitably used as a rubber material. For example, it is suitably used for tires (especially pneumatic tires), conveyor belts, hoses, vibration isolators, rubber rolls, the outer covers of railway vehicles, etc. Among them, it is suitably used for tires (especially treads).

Examples

[0043] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0044] [Manufacture of rubber composition] The respective components in Table 1 below were mixed in the composition (parts by mass) shown in the same table. Specifically, first, the components other than sulfur and the vulcanization accelerator in Table 1 were mixed in a 1.8 L closed mixer under the condition of 130 ° C for 5 minutes, and the masterbatch was discharged. Thereafter, sulfur and the vulcanization accelerator were added to the above masterbatch and mixed using an open roll under the condition of 80 ° C to produce each rubber composition.

[0045] [Evaluation] Each of the obtained rubber compositions (unvulcanized) was press-vulcanized in a mold (15 cm × 15 cm × 0.2 cm) at 150 ° C for 30 minutes to produce a vulcanized rubber sheet.

[0046] [Elongation at break] For the obtained vulcanized rubber sheet, the elongation at break was evaluated in accordance with JIS K6251. Specifically, a JIS No. 3 dumbbell-shaped test piece (thickness: 2 mm) was prepared from the vulcanized rubber sheet, and the elongation at break was evaluated under the conditions of a temperature of 20°C and a tensile speed of 500 mm / min. The results are shown in Table 1. The results were expressed as an index with the reference example being 100. Practically, it is preferably 130 or more.

[0047] 〔Ozone resistance〕 For the obtained vulcanized rubber sheet, the ozone resistance was evaluated in accordance with JIS K6259. Specifically, the vulcanized rubber sheet was placed in a sealed container (ozone: 500 ppb), left standing for 1 week in a state of 20% elongation, and then the vulcanized rubber sheet was observed. And the ozone resistance was evaluated according to the following criteria. The results are shown in Table 1. Practically, it is preferably C1 or C2, and more preferably C1. C1: No cracks were confirmed visually, but cracks were confirmed with a 10-fold magnifying glass. C2: Small cracks (0.5 mm or less) were confirmed visually. C3: Relatively large cracks (less than 1 mm) were confirmed. C4: Deep and large cracks (1 mm or more and less than 3 mm) were confirmed. C5: Cracks of 3 mm or more were confirmed, or it seemed likely to cause cutting.

[0048]

Table 1

[0049] For each component (other than Compounds 1 to 3) in Table 1, it is as follows.

[0050] · Natural rubber: STR-20 · Carbon black: HAF grade · Zinc oxide: Three types of zinc white (manufactured by Shodo Chemical Industry Co., Ltd.) · Stearic acid: Bead stearic acid YR (manufactured by NOF Corporation) · Anti-aging agent: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) · Sulfur: Oil-treated sulfur (manufactured by Karuizawa Refinery Co., Ltd.) · Vulcanization accelerator: Sanseler NS-G (manufactured by Sanshin Chemical Industry Co., Ltd.) (TBBS)

[0051] Compounds 1 to 3 in Table 1 are as follows.

[0052] · Compound 1: The following compound (corresponding to a specific compound) (however, in formula (1), R 1 ~R 3 are all hydrogen atoms, X 1 and X 3 are both groups represented by formula (A) (however, in formula (A), R A are all methyl groups), and X 2 is a hydroxyl group)

Chemical formula

[0053] · Compound 2: The following compound (corresponding to a specific compound) (however, in formula (1), R 1 and R 3 are all hydrogen atoms, R 2 is an ethyl group, X 1 and X 3 are both groups represented by formula (A) (however, in formula (A), R A are all hydrogen atoms), and X 2 is a methylol group (-CH 2 OH))

Chemical formula

[0054] · Compound 3: Unionox PKA-5001 (polyethylene glycol allyl ether) (the following compound, n ≒ 4) (manufactured by NOF Corporation) (not corresponding to a specific compound)

Chemical formula

[0055] As can be seen from Table 1, Examples 1 to 3 containing the specific compound showed excellent ozone resistance as compared with Comparative Examples 1 to 2 containing 6PPD. Among them, X in the formula (1) 1 ~X 3 Examples 1 to 2 in which one of them is a hydroxyl group showed more excellent ozone resistance. Comparative Example 3 containing Compound 3 (a compound having a group represented by the formula (A) and a hydroxyl group but not satisfying the formula (1)) instead of the specific compound had insufficient ozone resistance.

Claims

1. A rubber composition containing 100 parts by mass of a diene rubber and 0.1 to 20 parts by mass of a compound represented by the following formula (1). 【Chemical 1】 In formula (1), R １ ~R ３ each independently represents a hydrogen atom or a substituent, and X １ ~X ３ each independently represents a hydrogen atom or a substituent. However, among X １ ~X ３ at least one is a group represented by the following formula (A), and at least one is a hydroxyl group or an aliphatic hydrocarbon group having 1 to 5 carbon atoms and having a hydroxyl group. 【Chemical 2】 In formula (A), R Ａ represents a hydrogen atom or a substituent. * represents the bonding position.

2. Said X １ ~X ３ The rubber composition according to claim 1, wherein two of them are groups represented by the formula (A).

3. Said X １ to X ３ The rubber composition according to claim 1 or 2, wherein one of them is a hydroxyl group.

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