JP2016117880A - Copolymer, rubber composition and pneumatic tire - Google Patents

Abstract

A copolymer capable of improving the balance between tan δ at 0 ° C. and tan δ at 60 ° C. when used in a rubber composition. A weight average molecular weight of 1000 containing a monomer unit (a) derived from a compound represented by formula (1) and a monomer unit (b) derived from a compound represented by formula (2). A copolymer having a glass transition temperature of -60 to 20 ° C. (R1 is H or methyl group; R2 is H, C1-8 linear alkyl group or C3-8 branched alkyl group; R3 to R8 are each independently at least one C3-8 aliphatic hydrocarbon group. The rest are H or C1-2 aliphatic hydrocarbon groups) [Selection] None

Description

  The present invention relates to a copolymer containing a monomer unit derived from an aromatic vinyl compound and a monomer unit derived from a compound containing a conjugated diene, a rubber composition containing the copolymer, and the rubber composition. It relates to the used pneumatic tire.

  Conventionally, for example, in rubber compositions used for tires, it is required to balance the grip performance (wet grip performance) on wet road surfaces and the rolling resistance performance contributing to low fuel consumption at a high level. Generally, tan δ at 0 ° C. is used as an index for wet grip performance, and the larger one is superior in performance. As for the rolling resistance performance, tan δ at 60 ° C. is used as an index, and a smaller one is superior in performance. Since wet grip performance and rolling resistance performance are contradictory characteristics, it is not easy to improve at the same time.

  In Patent Document 1, in order to improve wet grip performance without deteriorating rolling resistance performance, a copolymer resin (petroleum resin) of styrene or vinyl toluene with a C5 fraction obtained by thermal decomposition of naphtha with respect to a diene rubber. It has been proposed to blend. However, when a petroleum resin is blended, the elastic modulus of the rubber composition increases at low temperatures and the grip performance (low temperature characteristics) deteriorates.

  Patent Document 2 discloses that a low molecular weight styrene butadiene liquid polymer is blended with a diene rubber in order to improve the road surface grip force in a racing tire. However, when the liquid polymer is blended, the hardness of the resulting rubber composition is greatly reduced, and the steering stability when used in a tire is greatly reduced.

  Patent Document 3 discloses that a petroleum resin and a styrene-butadiene liquid polymer are used in combination, but it is not easy to suppress the above-described decrease in low-temperature characteristics and steering stability.

  In Patent Document 4, a branched conjugated diene copolymer in which a diene component such as myrcene is introduced into a styrene-butadiene rubber is used as a rubber component of a tire rubber composition in order to achieve both wet grip performance and rolling resistance performance. Is disclosed. However, this document introduces a branched conjugated diene compound such as myrcene as a monomer unit for the purpose of improving the characteristics of a styrene butadiene rubber having a high styrene content. Since the copolymer is used as a rubber component, it has a high molecular weight and it is not easy to suppress a decrease in low-temperature characteristics.

JP 09-328577 A JP-A-61-203145 JP 2005-154696 A JP 2014-088544 A

  An object of the present embodiment is to provide a copolymer that can improve the balance of tan at 0 ° C. and tan δ at 60 ° C. when used in a rubber composition.

  The copolymer according to this embodiment includes a monomer unit (a) derived from a compound represented by the following general formula (1) and a monomer unit derived from a compound represented by the following general formula (2) ( b), and a copolymer having a weight average molecular weight (Mw) of 1,000 to 50,000.

式（１）中、Ｒ¹は水素原子又はメチル基を表し、Ｒ²は水素原子、炭素数１〜８の直鎖アルキル基、又は炭素数３〜８の分岐アルキル基を表す。

In Formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a hydrogen atom, a linear alkyl group having 1 to 8 carbon atoms, or a branched alkyl group having 3 to 8 carbon atoms.

式（２）中、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶、Ｒ⁷及びＲ⁸は、同一又は異なってもよく、少なくとも１つは炭素数３〜８の脂肪族炭化水素基を表し、残りは水素原子又は炭素数１もしくは２の脂肪族炭化水素基を表す。

In the formula (2), R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different, and at least one represents an aliphatic hydrocarbon group having 3 to 8 carbon atoms, The rest represents a hydrogen atom or an aliphatic hydrocarbon group having 1 or 2 carbon atoms.

  The rubber composition which concerns on this embodiment contains 1-100 mass parts of said copolymers with respect to 100 mass parts of rubber components consisting of a diene rubber. The pneumatic tire according to the present embodiment uses the rubber composition at least in part.

  According to this embodiment, when used in a rubber composition, the balance between tan δ at 0 ° C. and tan δ at 60 ° C. can be improved while suppressing a decrease in hardness and an increase in elastic modulus at low temperature. A polymer can be provided.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The copolymer according to this embodiment is represented by the monomer unit (a) derived from the compound represented by the general formula (1) (hereinafter referred to as an aromatic vinyl compound) and the general formula (2). And a monomer unit (b) derived from a compound (hereinafter referred to as a conjugated diene-containing compound) having a weight average molecular weight (Mw) of 1,000 to 50,000, and flowing at room temperature (23 ° C.) It is a copolymer having the property (hereinafter referred to as a liquid copolymer). When the liquid copolymer obtained by copolymerizing such an aromatic vinyl compound and a conjugated diene-containing compound having a specific structure is used in a rubber composition, the hardness is reduced and the temperature is reduced. The balance between tan δ at 0 ° C. and tan δ at 60 ° C. can be improved while suppressing an increase in elastic modulus. Therefore, the balance between wet grip performance and rolling resistance performance can be improved while suppressing deterioration of steering stability and low temperature characteristics when employed in a tire. Here, a monomer unit (also referred to as a structural unit) is a basic unit of a chemical structure of a copolymer, and is a unit having a chemical structure formed by the reaction of the above compound as a monomer. is there.

In Formula (1), R < ¹ > is a hydrogen atom or a methyl group, More preferably, it is a hydrogen atom. R ² is a hydrogen atom, a linear alkyl group having 1 to 8 carbon atoms, or a branched alkyl group having 3 to 8 carbon atoms, preferably a hydrogen atom or a linear alkyl group having 1 to 4 carbon atoms, or carbon It is a branched alkyl group of the number 3 or 4. R ² may be in any of the ortho (o-) position, the meta (m-) position, and the para (p-) position of the aromatic ring, preferably the meta position and / or the para position.

  Examples of the aromatic vinyl compound represented by the formula (1) include styrene, α-methylstyrene, methylstyrene (ortho position, meta position, para position, or a mixture of two or more thereof), ethyl styrene (ortho position). , Meta-position, para-position or a mixture of two or more thereof), propylstyrene (ortho-position, meta-position, para-position or a mixture of two or more thereof), isopropylstyrene (ortho-position, meta-position, para-position or these) Butyl styrene (ortho, meta, para, or a mixture of two or more thereof), isobutyl styrene (ortho, meta, para, or a mixture of two or more thereof), t-butylstyrene (ortho position, meta position, para position or a mixture of two or more thereof), s-butylstyrene (ortho position, meta position, para position or two or more of these) ), Pentyl styrene (ortho, meta, para, or a mixture of two or more thereof), hexyl styrene (ortho, meta, para, or a mixture of two or more thereof), heptyl styrene (ortho) And octylstyrene (ortho-position, meta-position, para-position or a mixture of two or more thereof), and the like. Any of these may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of styrene, methylstyrene, and tert-butylstyrene is preferable.

In the formula (2), R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different, and at least one is an aliphatic hydrocarbon group having 3 to 8 carbon atoms, The remainder is a hydrogen atom or an aliphatic hydrocarbon group having 1 or 2 carbon atoms. Preferably, one of R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ is an aliphatic hydrocarbon group having 3 to 8 carbon atoms, and 0 to 2 is a fatty acid having 1 or 2 carbon atoms. And the remaining 3 to 5 are hydrogen atoms.

  The aliphatic hydrocarbon group having 3 to 8 carbon atoms is preferably an unsaturated aliphatic hydrocarbon group containing at least one double bond, and may be linear or branched. A branched unsaturated hydrocarbon group having one methyl group as a side chain and one or two double bonds is preferred. It is preferable that carbon number is 4-6. Preferable specific examples include a 4-methyl-3-pentenyl group, a 3-methyl-2-butenyl group, a 2-methyl-1-propenyl group, and a 2-methyl-1,3-butadienyl group. .

  The aliphatic hydrocarbon group having 1 or 2 carbon atoms is preferably a saturated aliphatic hydrocarbon group, that is, a methyl group or an ethyl group, and more preferably a methyl group.

In one preferred embodiment, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are any one of R ³ , R ⁴ and R ⁵ having 3 to 8 carbon atoms (preferably 4 to 6). The remaining 5 are the same or different and are a hydrogen atom or a methyl group, and at least one of R ⁷ and R ⁸ is a hydrogen atom.

  The conjugated diene-containing compound represented by the formula (2) is a compound having a C 3-8 aliphatic hydrocarbon group bonded to a conjugated diene structure. By copolymerizing such a compound having a specific structure with an aromatic vinyl compound, the properties of the rubber composition can be improved as described above in combination with being a liquid polymer. Specific examples of the conjugated diene-containing compound include 2-methyl-4-methylenehexa-1,5-diene, 2-methyl-6-methyleneocta-1,7-diene (ie, α-myrcene), 2- Methyl-8-methylenedeca-1,9-diene, 5-methyl-3-methylenehexa-1,4-diene, 7-methyl-3-methyleneocta-1,6-diene (ie β-myrcene), 9 -Methyl-3-methylenedeca-1,8-diene, 3,7-dimethylocta-1,3,7-triene (i.e., α-ocimene), 3,9-dimethyldeca-1,3,9-triene, 3,7-dimethylocta-1,3,6-triene (i.e., β-cymene), 3,9-dimethyldeca-1,3,8-triene, 2,6-dimethylocta-2,4,6- Triene (ie, alloocimene), 2,8-dimethyldeca-2,6,8-triene, 2,6-dimethylocta-1,3,5,7-tetraene (ie, cosmene), and the like. Any one type or a combination of two or more types can be used. Among these, at least one selected from the group consisting of myrcene, ocimene, alloocimene and cosmene is preferable, and more preferably at least one selected from the group consisting of myrcene, oscymene and alloocimene. The myrcene may be α-myrcene, β-myrcene, or a mixture thereof. Ocymen may be α-cymene, β-osmene (trans or cis), or a mixture thereof. The conjugated diene-containing compound according to a preferred embodiment is at least one selected from the group consisting of β-myrcene, β-osimene and alloocimene.

  In the liquid copolymer, the copolymerization ratio of the monomer unit (b) (that is, the content (molar ratio) of the monomer unit (b) to the total monomer units constituting the liquid copolymer) is It is preferable that it is 20-80 mol%, More preferably, it is 50-80 mol%, and 60-80 mol% may be sufficient. By setting the copolymerization ratio of the monomer unit (b) to 20 mol% or more, it is possible to improve the effect of suppressing the deterioration of the low temperature characteristics. Moreover, the effect which suppresses the fall of hardness can be improved by making the copolymerization ratio of a monomer unit (b) 80 mol% or less.

  In the liquid copolymer, the copolymerization ratio of the monomer unit (a) (that is, the content (molar ratio) of the monomer unit (a) to the total monomer units constituting the liquid copolymer) is It is preferable that it is 20-80 mol%, More preferably, it is 20-50 mol%, and 20-40 mol% may be sufficient. The monomer unit constituting the liquid copolymer basically consists of the monomer units (a) and (b), but other vinyl compounds, diene compounds, etc., as long as the effects are not impaired. A monomer may be used in combination. Although not particularly limited, the total content of the monomer units (a) and (b) with respect to all monomer units constituting the liquid copolymer is preferably 90 mol% or more, more preferably It is 95 mol% or more, More preferably, it is 100 mol%.

  The monomer unit (a) derived from the aromatic vinyl compound is represented by the following general formula (3). Moreover, the monomer unit (b) derived from the said conjugated diene containing compound can be represented by any one or more of following General formula (4)-(6) as an example. Therefore, the liquid copolymer according to one embodiment is selected from the group consisting of the monomer unit represented by the general formula (3) and the monomer unit represented by the general formulas (4) to (6). Containing at least one kind.

式中、Ｒ¹及びＲ²は、式（１）と同じである。

In the formula, R ¹ and R ² are the same as those in the formula (1).

式（４）〜（６）中、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶、Ｒ⁷及びＲ⁸は、式（２）と同じである。なお、式（４）で表される単量体単位には、下記一般式（４Ａ）で表されるトランス型の単量体単位、及び／又は、下記一般式（４Ｂ）で表されるシス型の単量体単位が含まれる。

In formulas (4) to (6), R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are the same as in formula (2). The monomer unit represented by the formula (4) includes a trans monomer unit represented by the following general formula (4A) and / or a cis represented by the following general formula (4B). A monomer unit of the type is included.

式（４）〜（６）で表される各単量体単位の含有量は特に限定されず、例として、単量体単位（ｂ）に対する比率として、式（４）で表される単量体単位が１〜１００モル％、式（５）で表される単量体単位が０〜９９モル％、式（６）で表される単量体単位が０〜９９モル％でもよい。単量体単位（ｂ）に対する比率として、式（４）で表される単量体単位は１０〜９０モル％でもよく、６０〜８０モル％でもよく、式（５）で表される単量体単位は１〜４０モル％でもよく、２〜１５モル％でもよく、式（６）で表される単量体単位は１〜５０モル％でもよく、１０〜３０モル％でもよい。

The content of each monomer unit represented by the formulas (4) to (6) is not particularly limited, and as an example, as a ratio to the monomer unit (b), a single amount represented by the formula (4) The body unit may be 1 to 100 mol%, the monomer unit represented by the formula (5) may be 0 to 99 mol%, and the monomer unit represented by the formula (6) may be 0 to 99 mol%. As a ratio with respect to the monomer unit (b), the monomer unit represented by the formula (4) may be 10 to 90 mol% or 60 to 80 mol%, and the single unit represented by the formula (5) The body unit may be 1 to 40 mol% or 2 to 15 mol%, and the monomer unit represented by the formula (6) may be 1 to 50 mol% or 10 to 30 mol%.

  The weight average molecular weight (Mw) of the liquid copolymer is 1,000 to 50,000 as described above, and preferably 5,000 to 40,000 from the viewpoint of enhancing the effect of improving the properties of the rubber composition. 10,000-30,000 may be sufficient. In addition, the number average molecular weight (Mn) of a liquid copolymer is not specifically limited, For example, 500-30,000 may be sufficient and 5,000-20,000 may be sufficient. Further, the molecular weight distribution (Mw / Mn) of the liquid copolymer is not particularly limited, and may be, for example, 1.01 to 10.0 or 1.10 to 5.00.

  The glass transition temperature (Tg) of the liquid copolymer is preferably -60 to 20 ° C. By having such a glass transition temperature, it is possible to enhance the effect of improving the balance between tan δ at 0 ° C. and tan δ at 60 ° C. when used in a rubber composition. The glass transition temperature of the liquid copolymer is more preferably −40 to 10 ° C., and may be −30 to 5 ° C.

  The liquid copolymer may be a random copolymer or a block copolymer as long as it is copolymerized using the above aromatic vinyl compound and conjugated diene-containing compound as monomer components. A random copolymer is preferable.

  The manufacturing method of this liquid copolymer is not specifically limited, It can synthesize | combine using a well-known polymerization method. For example, it can be synthesized by radical polymerization using an initiator composed of an azo compound. Examples of the azo compound as the radical polymerization initiator include 2,2′-azobisisobutyronitrile (AIBN), 1,1′-azobis (cyclohexanecarbonitrile) (ABCN), 2,2′-azobis ( 2,4,4-trimethylpentane), 2,2'-azobis (2-methylpropane), 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethyl) Valeronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis [ N- (2-propenyl) -2-methylpropionamide] and the like.

  The liquid copolymer thus obtained can be used by blending with a rubber composition as an example. That is, the rubber composition according to this embodiment contains 1 to 100 parts by mass of the above liquid copolymer with respect to 100 parts by mass of a rubber component made of a diene rubber.

  Examples of the diene rubber as the rubber component include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), and chloroprene rubber (CR). , Butyl rubber (IIR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, and the like. These may be used alone or in combination of two or more. Can be used. Among these, at least one selected from the group consisting of NR, BR and SBR is preferable. Further, in these molecular terminals or molecular chains, modification is made with at least one functional group selected from the group consisting of an amino group, hydroxyl group, epoxy group, alkoxy group, alkylsilyl group, alkoxysilyl group, and carboxyl group. Modified diene rubber modified, or modified diene rubber modified with a compound containing tin can also be used. As one embodiment, the rubber component may contain 50% by mass or more of modified SBR. The diene rubber as the rubber component is a solid rubber having no fluidity at normal temperature (23 ° C.), and the liquid copolymer is not included in the rubber component.

  From the viewpoint of improving the balance between wet grip performance and rolling resistance performance, the amount of the liquid copolymer is preferably 1 to 100 parts by weight, more preferably 1 to 50 parts, relative to 100 parts by weight of the rubber component. It is a mass part, More preferably, it is 2-30 mass parts, and 3-20 mass parts may be sufficient.

  In addition to the liquid copolymer, the rubber composition according to this embodiment includes a reinforcing filler, a silane coupling agent, oil, zinc white, stearic acid, an anti-aging agent, a wax, a vulcanizing agent, and a vulcanization accelerator. Various additives generally used in rubber compositions, such as an agent, can be blended.

  As the reinforcing filler, silica such as wet silica (hydrous silicic acid) and / or carbon black is preferably used. More preferably, silica is used to improve the balance between rolling resistance performance and wet grip performance. It is preferable to use silica alone or a combination of silica and carbon black. The reinforcing filler is preferably composed mainly of silica, that is, 50% by mass or more of the reinforcing filler is silica. The compounding quantity of a reinforcing filler is not specifically limited, For example, 20-150 mass parts may be sufficient with respect to 100 mass parts of rubber components, and 30-100 mass parts may be sufficient. The compounding amount of silica is not particularly limited, and may be, for example, 20 to 120 parts by mass or 30 to 90 parts by mass with respect to 100 parts by mass of the rubber component.

  When silica is blended, it is preferable to use a silane coupling agent in combination. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxy). Sulfide silanes such as silylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3- Mercaptosilanes such as mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane; 3-octanoylthio-1-propyltriethoxysilane , Protected mercaptosilanes such as 3-propionylthiopropyltrimethoxysilane and the like can be used, and these can be used alone or in combination of two or more. It is preferable that the compounding quantity of a silane coupling agent is 2-20 mass% of silica mass, More preferably, it is 4-15 mass%.

  As the vulcanizing agent, sulfur is preferably used. Although the compounding quantity of a vulcanizing agent is not specifically limited, It is preferable that it is 0.1-10 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 0.5-5 mass parts. Moreover, as said vulcanization accelerator, various vulcanization accelerators, such as a sulfenamide type | system | group, a thiuram type | system | group, a thiazole type | system | group, and a guanidine type | system | group, can be used, for example, any 1 type individually or in combination of 2 or more types. Can be used. The blending amount of the vulcanization accelerator is not particularly limited, but is preferably 0.1 to 7 parts by mass, more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component. .

  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. That is, for example, in the first mixing stage, to the diene rubber, together with the liquid copolymer, other additives other than the vulcanizing agent and the vulcanization accelerator are added and mixed, and then the final mixture is added to the resulting mixture. In the mixing stage, a rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator.

  The rubber composition thus obtained can be used for various rubber members for tires, vibration-proof rubbers, conveyor belts and the like. Preferably, it is used for tires, and can be applied to various parts of tires such as tread portions and sidewall portions of various sizes of pneumatic tires for passenger cars, trucks and buses, and tires of various sizes. That is, according to a conventional method, the rubber composition is molded into a predetermined shape by, for example, extrusion, and combined with other parts, and then vulcanized and molded at, for example, 140 to 180 ° C. to produce a pneumatic tire. can do. Among these, it is particularly preferable to use as a tire tread formulation.

  Examples are shown below, but the present invention is not limited to these examples.

Each component used in the examples and comparative examples is as follows.
・ SBR: "SL563" manufactured by JSR Corporation
-Modified SBR: alkoxy group and amino group terminal modified SBR, "HPR350" manufactured by JSR Corporation
・ NR: RSS # 3
・ BR: “Ubepol BR150B” manufactured by Ube Industries, Ltd.
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd.
・ Carbon black: “Seast 3” manufactured by Tokai Carbon Co., Ltd.
Silane coupling agent 1: bis (3-triethoxysilylpropyl) tetrasulfide, “Si69” manufactured by Evonik Degussa
Silane coupling agent 2: Mercaptosilane, “Si363” manufactured by Evonik Degussa
・ Zinc flower: “Zinc flower 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Sulfur: Hosoi Chemical Co., Ltd. “Powder sulfur for rubber 150 mesh”
・ Vulcanization accelerator: “Noxeller CZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Secondary vulcanization accelerator: “Noxeller D” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Polymers 1 to 8: those obtained in Synthesis Examples 1 to 8 Polymer 9: Tosoh Co., Ltd., aromatic aliphatic copolymer petroleum resin “Petrotac 100”
-Polymer 10: manufactured by Kuraray Co., Ltd., liquid styrene butadiene rubber "Kuraprene L-SBR820"
Polymer 11: obtained in Synthesis Example 9

The measuring method of Mw, Mn, Mw / Mn, and Tg of the polymer (copolymer) is as follows.
-Mn, Mw, Mw / Mn: It calculated | required in polystyrene conversion by the measurement by a gel permeation chromatography (GPC). Specifically, the measurement sample used was 0.2 mg dissolved in 1 mL of THF. “LC-20DA” manufactured by Shimadzu Corporation was used, the sample was filtered, and passed through a column (“PL Gel 3 μm Guard × 2” manufactured by Polymer Laboratories) at a temperature of 40 ° C. and a flow rate of 0.7 mL / min. Detection was performed by “RI Detector” manufactured by System.
Tg: Measured by a differential scanning calorimetry (DSC) method in accordance with JIS K7121 at a rate of temperature increase of 20 ° C./minute (measurement temperature range: −150 ° C. to 50 ° C.).

[Synthesis Example 1: Synthesis of Polymer 1 (Liquid Copolymer)]
60 g of 4-t-butylstyrene, 12.8 g of β-myrcene (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.77 g of azobisisobutyronitrile and 50 mL of toluene were mixed, and nitrogen was added for 1 hour. After bubbling, the reaction solution was kept at 70 ° C. for 24 hours. 66 g of polymer 1 was obtained by reprecipitation purification of the resulting solution in methanol. The polymerization conversion rate (percentage of “production amount / charge amount”) was 91%. The obtained polymer 1 was a liquid copolymer having Mw of 22000, Mn of 12000, and Mw / Mn of 1.83 and having fluidity at room temperature. Moreover, Tg was -5 degreeC.

Polymer 1 has monomer units represented by the following formulas (3-1), (4-1), (5-1), and (6-1) determined by ¹³ C-NMR (400 MHz CDCl ₃ ) measurement. It is confirmed that the content of the copolymer is a random copolymer having 73 mol% of the monomer unit of the formula (3-1) and the monomer of the formula (4-1). 20 mol% unit, 2 mol% monomer unit of formula (5-1), 5 mol% monomer unit of formula (6-1), formula (4-1), (5-1) And (6-1) was 27 mol% in total (copolymerization ratio of monomer unit (b) derived from β-myrcene = 27 mol%). Here, in the following formula (4-1), the transformer type is shown for convenience, but the transformer type and the cis type are not distinguished in this measurement. The chemical shift of each peak is as shown in Table 1 below. In Table 1, for example, “(3-1) -8” means carbon number 8 in formula (3-1).

[Synthesis Example 2: Synthesis of Polymer 2 (Liquid Copolymer)]
The polymer was prepared in the same manner as in Synthesis Example 1 except that the molar ratio of 4-t-butylstyrene and β-myrcene used in the synthesis of polymer 1 was changed to 4-t-butylstyrene / β-myrcene = 50/50. 2 was obtained. The polymerization conversion rate was 88%. The obtained polymer 2 was a liquid copolymer having Mw of 20000, Mn of 12000, Mw / Mn of 1.67, and fluidity at room temperature. Moreover, Tg was -16 degreeC. The content of each monomer unit of the polymer 2 is 40 mol% of the monomer unit of the formula (3-1), 45% of the monomer unit of the formula (4-1), ) Monomer unit of 3 mol%, monomer unit of formula (6-1) is 12 mol%, and the sum of formulas (4-1), (5-1) and (6-1) is 60 mol. %Met.

[Synthesis Example 3: Synthesis of Polymer 3 (Liquid Copolymer)]
The polymer was prepared in the same manner as in Synthesis Example 1 except that the molar ratio of 4-t-butylstyrene and β-myrcene used in the synthesis of polymer 1 was changed to 4-t-butylstyrene / β-myrcene = 20/80. 3 was obtained. The polymerization conversion rate was 85%. The obtained polymer 3 was a liquid copolymer having Mw of 18000, Mn of 11000, and Mw / Mn of 1.64 and having fluidity at room temperature. Moreover, Tg was -20 degreeC. The content of each monomer unit in the polymer 3 is 20 mol% for the monomer unit of the formula (3-1), 60 mol% for the monomer unit of the formula (4-1), ) Monomer unit of 4 mol%, monomer unit of formula (6-1) is 16 mol%, and the total of formulas (4-1), (5-1) and (6-1) is 80 mol% %Met.

[Synthesis Example 4: Synthesis of Polymer 4 (Liquid Copolymer)]
Synthesizing except that β-cymene (manufactured by Sigma Aldrich) was used instead of β-myrcene used for the synthesis of polymer 2 (4-t-butylstyrene / β-oscymene (molar ratio) = 50/50). Polymer 4 was obtained in the same manner as in Example 2. The polymerization conversion was 90%. The obtained polymer 4 was a liquid copolymer having Mw of 21000, Mn of 13000, and Mw / Mn of 1.62, and having fluidity at room temperature. Moreover, Tg was -5 degreeC. The content of the monomer unit derived from 4-t-butylstyrene was 40 mol%, and the content of the monomer unit derived from β-ocimene was 60 mol%.

[Synthesis Example 5: Synthesis of Polymer 5 (Liquid Copolymer)]
(Methylstyrene / β-myrcene (moles), except that methylstyrene (m-, p-mixture, manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of 4-t-butylstyrene used for the synthesis of polymer 2. Ratio) = 50/50), Polymer 5 was obtained in the same manner as in Synthesis Example 2. The polymerization conversion was 90%. The obtained polymer 5 was a liquid copolymer having Mw of 23000, Mn of 13000, and Mw / Mn of 1.77 and having fluidity at room temperature. Moreover, Tg was -18 degreeC. The content of monomer units derived from methylstyrene was 40 mol%, and the content of monomer units derived from β-myrcene was 60 mol%.

[Synthesis Example 6: Synthesis of Polymer 6 (Liquid Copolymer)]
Polymer 6 was prepared in the same manner as in Synthesis Example 2 except that styrene was used instead of 4-t-butylstyrene used in the synthesis of polymer 2 (styrene / β-myrcene (molar ratio) = 50/50). Got. The polymerization conversion was 90%. The obtained polymer 6 was a liquid copolymer having Mw of 24000, Mn of 13000, and Mw / Mn of 1.85, and fluidity at room temperature. Moreover, Tg was -20 degreeC. The content of monomer units derived from styrene was 40 mol%, and the content of monomer units derived from β-myrcene was 60 mol%.

[Synthesis Example 7: Synthesis of Polymer 7 (Liquid Copolymer)]
The polymer was prepared in the same manner as in Synthesis Example 1 except that the molar ratio of 4-t-butylstyrene and β-myrcene used in the synthesis of polymer 1 was changed to 4-t-butylstyrene / β-myrcene = 90/10. 7 was obtained. The polymerization conversion rate was 95%. The obtained polymer 7 was a liquid copolymer having Mw of 24000, Mn of 13000, and Mw / Mn of 1.85 and having fluidity at room temperature. Moreover, Tg was 0 degreeC. The content of the monomer unit of the polymer 7 is 87 mol% of the monomer unit of the formula (3-1), and the single unit of the formulas (4-1), (5-1), and (6-1) The total amount of the monomer units was 13 mol%.

[Synthesis Example 8: Synthesis of Polymer 8 (Liquid Copolymer)]
The polymer was prepared in the same manner as in Synthesis Example 1 except that the molar ratio of 4-t-butylstyrene and β-myrcene used in the synthesis of polymer 1 was changed to 4-t-butylstyrene / β-myrcene = 10/90. 8 was obtained. The polymerization conversion was almost 100%. The obtained polymer 8 was a liquid copolymer having Mw of 15000, Mn of 9000, and Mw / Mn of 1.67 and having fluidity at room temperature. Moreover, Tg was -28 degreeC. The monomer unit content of the polymer 8 is 10 mol% of the monomer unit of the formula (3-1), and the monomer unit of the formula (4-1), (5-1) and (6-1) The total of the monomer units was 90 mol%.

[Synthesis Example 9: Synthesis of Polymer 11 (Liquid Copolymer) (Comparative Example)]
Polymer 11 was prepared in the same manner as in Synthesis Example 2 except that isoprene was used in place of β-myrcene used in the synthesis of polymer 2 (4-t-butylstyrene / isoprene (molar ratio) = 50/50). Got. The polymerization conversion was almost 100%. The obtained polymer 11 was a liquid copolymer having Mw of 22000, Mn of 13000, and Mw / Mn of 1.69 and having fluidity at room temperature. Moreover, Tg was -10 degreeC.

[Evaluation of rubber composition (1)]
Using a lab mixer (labor plast mill), in accordance with the composition (parts by mass) shown in Table 2 below, first, in the first mixing stage, other compounding agents excluding sulfur and vulcanization accelerator are added to the diene rubber component. Add and knead (discharge temperature = 160 ° C.), and then add and knead sulfur and a vulcanization accelerator (discharge temperature = 90 ° C.) in the final mixing stage to the obtained kneaded product. Prepared. The rubber composition of evaluation (1) is a rubber composition containing silica using a blend of modified SBR and unmodified BR as a rubber component.

  About each obtained rubber composition, it vulcanized | cured at 160 degreeC * 20 minutes, and produced the test piece of the predetermined shape. Using the obtained test piece, a dynamic viscoelasticity test is performed to measure tan δ at 0 ° C. and 60 ° C. and storage elastic modulus (E ′) at −10 ° C., and the hardness at 23 ° C. did. Each measuring method is as follows.

  0 ° C. tan δ: Using a rheometer E4000 manufactured by UBM, the loss factor tan δ was measured under the conditions of a frequency of 10 Hz, a static strain of 10%, a dynamic strain of 2%, and a temperature of 0 ° C. The index was displayed. The larger the index, the larger the tan δ, and the better the wet grip performance.

  60 ° C. tan δ: The temperature was changed to 60 ° C., and tan δ was measured in the same manner as 0 ° C. tan δ, and displayed as an index with the value of Comparative Example 1 being 100. The smaller the index, the less heat is generated, and the smaller the rolling resistance in the tire, the better the rolling resistance performance (low fuel consumption).

  --10 ° C. E ′: The storage elastic modulus E ′ was measured under the same conditions as 0 ° C. tan δ except that the temperature was changed to −10 ° C., and displayed as an index with the value of Comparative Example 1 being 100. The smaller the index, the smaller the E ′ at a low temperature, and the better the grip performance (low temperature characteristics) at a low temperature when the tire is made.

  -23 degreeC hardness: Based on JISK6253, the hardness in the temperature of 23 degreeC was measured with the type A of durometer, and the value of the comparative example 1 was set to 100, and was displayed with the index | exponent. The larger the index, the higher the hardness at normal temperature, and the better the steering stability when made into a tire.

  The results are as shown in Table 2, and with respect to Comparative Example 1 as a control, when Examples 1 to 8 were blended with polymers 1 to 8 which are specific liquid copolymers, the hardness decreased at 23 ° C. The balance of tan δ at 0 ° C. and tan δ at 60 ° C. could be improved while suppressing the increase of E ′ at −10 ° C. Specifically, tan δ at 0 ° C. could be increased while maintaining tan δ at 60 ° C. In particular, in Examples 1 to 6 in which polymers 1 to 6 having a copolymerization ratio of the monomer unit (b) of 20 to 80 mol% were blended, the hardness decrease at 23 ° C. and the E at −10 ° C. 'With no substantial increase, tan δ at 0 ° C and tan δ at 60 ° C could be balanced in a high dimension.

  On the other hand, in Comparative Example 2 in which polymer 9 which is a petroleum resin was blended, the increase of E ′ at −10 ° C. was large and the low temperature characteristics were inferior. In Comparative Example 3 in which the polymer 10 which is a liquid styrene butadiene rubber was blended, the hardness was greatly reduced at 23 ° C., and the steering stability was poor. Also in Comparative Example 4 in which the polymer 11 which is a liquid copolymer of 4-t-butylstyrene and isoprene was blended, the hardness decrease at 23 ° C. was large and the steering stability was poor.

  In Example 7, an increase in E ′ at −10 ° C. was observed, but the increase was smaller than that in Comparative Example 2, and at 23 ° C. as observed in Comparative Example 2. There was no decrease in hardness, and therefore the balance between tan δ at 0 ° C. and tan δ at 60 ° C. could be improved while suppressing the decrease in hardness at 23 ° C. and the increase in E ′ at −10 ° C. In Example 8, a decrease in hardness was observed at 23 ° C., but the decrease was smaller than those in Comparative Examples 3 and 4, and E ′ at −10 ° C. as in Comparative Example 2 was observed. There is no increase, rather, E ′ is small and significantly improved. Therefore, while suppressing the decrease in hardness at 23 ° C., E ′ at −10 ° C. is reduced to improve low temperature characteristics, and 0 ° C. The balance between tan δ at tan δ and tan δ at 60 ° C. could be improved.

[Evaluation of rubber composition (2)]
According to the composition (parts by mass) shown in Table 3 below, after preparing the rubber composition in the same manner as the evaluation (1) of the rubber composition, tan δ at 0 ° C. and 60 ° C. and E ′ at −10 ° C., The hardness at 23 ° C. was measured. Each measurement result was displayed as an index with the value of Comparative Example 5 as 100. The rubber composition of evaluation (2) is a rubber composition containing silica using a blend of unmodified SBR and unmodified BR as a rubber component.

  The results are as shown in Table 3, and even in the unmodified SBR / BR blend system, Examples 9 to 11 were blended with Polymers 1 to 3 as specific liquid copolymers with respect to Comparative Example 5 as a control. As a result, it was possible to balance tan δ at 0 ° C. and tan δ at 60 ° C. at a high level while suppressing a decrease in hardness at 23 ° C. and an increase in E ′ at −10 ° C.

  Further, even when the silane coupling agent is changed from sulfide silane to mercaptosilane, it is 23 ° C. in Example 12 in which Polymer 1 which is a specific liquid copolymer is blended with respect to Comparative Example 8 which is a control. It was possible to balance tan δ at 0 ° C. and tan δ at 60 ° C. in a high dimension without decreasing the hardness at -10 ° C. and increasing E ′ at −10 ° C.

[Evaluation of rubber composition (3)]
According to the composition (parts by mass) shown in Table 4 below, the rubber composition was prepared in the same manner as in the evaluation (1) of the rubber composition, and then tan δ at 0 ° C. and 60 ° C. and E ′ at −10 ° C. The hardness at 23 ° C. was measured. Each measurement result was displayed as an index with the value of Comparative Example 9 as 100. The rubber composition of evaluation (3) is a rubber composition containing silica and carbon black using NR alone as a rubber component.

  A result is as showing in Table 4, and also in NR type | system | group, it is 23 degreeC that it is Examples 13-15 which mix | blended the polymers 1-3 which are specific liquid copolymers with respect to the comparative example 9 which is control. It was possible to balance tan δ at 0 ° C. and tan δ at 60 ° C. in a high dimension while suppressing the decrease in hardness at -10 ° C. and the increase in E ′ at −10 ° C.

Claims (7)

General formula (1)

(In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a hydrogen atom, a linear alkyl group having 1 to 8 carbon atoms, or a branched alkyl group having 3 to 8 carbon atoms.)
A monomer unit (a) derived from a compound represented by formula (2):

(Wherein R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different, at least one represents an aliphatic hydrocarbon group having 3 to 8 carbon atoms, and the rest Represents a hydrogen atom or an aliphatic hydrocarbon group having 1 or 2 carbon atoms.)
And a monomer unit (b) derived from a compound represented by the formula: wherein the weight average molecular weight (Mw) is 1,000 to 50,000.   The copolymer according to claim 1, wherein the monomer unit (b) has a copolymerization ratio of 20 to 80 mol%.   The copolymer according to claim 1 or 2, wherein the glass transition temperature is -60 to 20 ° C.   The copolymer according to any one of claims 1 to 3, wherein the aliphatic hydrocarbon group having 3 to 8 carbon atoms in the general formula (2) includes at least one double bond.   The compound represented by the general formula (1) is at least one selected from the group consisting of styrene, methylstyrene, and tert-butylstyrene, and the compound represented by the general formula (2) is myrcene, oximene. The copolymer according to any one of claims 1 to 4, wherein the copolymer is at least one selected from the group consisting of alloocimene and cosmene.   The rubber composition which contains 1-100 mass parts of copolymers of any one of Claims 1-5 with respect to 100 mass parts of rubber components which consist of diene rubber.   A pneumatic tire using at least a part of the rubber composition according to claim 6.