JP2008019401A - Rubber composition and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition that can satisfy both the rolling resistance and the wet grip simultaneously by modifying the main chain of styrene-butadiene in the mixture of the rubber composition, in no need of increase of polymer kinds for modification and without plant investment. <P>SOLUTION: Styrene-butadiene rubber, a modifier having functional group reactive with the vinyl group in the styrene-butadiene rubber, amino or amide group, and a radical initiator are mixed to prepare the premixture, and filler is added to the premixture thereby producing the rubber composition. As a modifier, is cited a compound having mercapto group and amino group (for example, cysteamine) and acid amide such as acryl amide or the like. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition that can be suitably used as a tread for a pneumatic tire, for example, and a method for producing the same.

  Conventionally, automobiles have been desired to achieve both fuel economy (environmental property) and safety. Therefore, in tires mounted on automobiles, rolling resistance and grip performance on wet road surfaces (wet grip properties) are desired. Yes. In particular, in a rubber composition for tire treads for passenger cars, silica may be used as a filler and solution-polymerized styrene butadiene rubber (SSBR) may be used as a rubber component in order to achieve both of these. As SSBR, there is terminal-modified SSBR in which the terminal is modified with a functional group that interacts with carbon black or silica, and recently, SSBR in which both terminal chains are modified has been developed.

  However, the use of a large number of such modified polymer species is not desirable at the manufacturing site where the rubber composition is prepared and processed because of increased factory inventory management. On the other hand, enormous capital investment is required to polymerize the modified polymer on its own. Therefore, it is required to modify the polymer by using a general-purpose polymer having an unmodified main chain without increasing the number of modified polymer species and without making capital investment.

  In Patent Document 1 below, a main chain modification in which hydroxyl mercaptan, which is a compound having a hydroxyl group and a mercapto group, is used as a modifier to introduce a hydroxyl group into a polymer molecule and enhance the interaction with silica. SSBR is disclosed. However, this document modifies SSBR in a solution such as cyclohexane by adding a modifier. Therefore, in order to carry out at the production site of a rubber composition, capital investment for modification is required. It is necessary separately, and thus the above-mentioned problem cannot be solved.

Patent Document 2 listed below discloses (A) diene rubber, (B) inorganic filler, and (D) maleic acid and fumaric acid in the molecule for the purpose of improving the dispersibility of the inorganic filler. A rubber composition containing a compound derived from an unsaturated carboxylic acid selected from itaconic acid and sorbic acid and having at least one reactive group A and one amino group for the rubber (A) is disclosed. However, in this document, since the compound (D) is added and mixed simultaneously with the filler that is the inorganic filler (B), a sufficient effect cannot be obtained in achieving both rolling resistance and wet grip properties.
JP-T-2002-541289 JP 2003-176378 A

  The present invention has been made in view of the above points, and by modifying the main chain of the styrene butadiene rubber during mixing of the rubber composition, without increasing the number of modified polymer species and without making capital investment. The purpose is to achieve both rolling resistance and wet grip.

  A method for producing a first rubber composition according to the present invention includes a styrene butadiene rubber, a modifier having a functional group that reacts with a vinyl group in the styrene butadiene rubber and an amino group or an amide group, and a radical generator. Are mixed to prepare a pre-mixture, and the resulting pre-mixture is added with a filler and mixed.

  A method for producing a second rubber composition according to the present invention includes Sn-coupled styrene butadiene rubber, and a modification having a functional group that reacts with a vinyl group and an amino group or an amide group in the styrene butadiene rubber. An agent is mixed to prepare a pre-mixture, and a filler is added to the obtained pre-mixture and mixed. In this case, it is preferable to mix a radical generator together with the modifier when preparing the pre-mixture.

  In the production method of the present invention, at the time of preparing the pre-mixture, the functional group of the modifier reacts with the vinyl group of the styrene butadiene rubber, so that the polymer main chain of the styrene butadiene rubber is modified and an amino group or an amide group. Is introduced. And by adding a filler after that, coexistence of rolling resistance and wet grip property is achieved by interaction with an amino group or an amide group, and a filler.

The present invention also provides at least one modification selected from the group consisting of a compound having a mercapto group or disulfide bond and an amino group, and an acid amide represented by the following general formula (1) on a styrene butadiene rubber. The present invention provides a rubber composition characterized by blending an agent and a radical generator.

In the formula, R ¹ is hydrogen, an alkyl group having 1 to 18 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and R ² is hydrogen or a methyl group.

  The present invention also provides at least a compound selected from the group consisting of a Sn-coupled styrene butadiene rubber, a compound having a mercapto group or a disulfide bond and an amino group, and an acid amide represented by the general formula (1). The present invention provides a rubber composition characterized by blending one type of modifier. .

  Furthermore, this invention provides the pneumatic tire which has a tread which consists of these rubber compositions.

  According to the present invention, pre-mixing is performed prior to mixing with the filler, and at that time, the modifier and the styrene-butadiene rubber are mixed to modify the polymer main chain, without increasing the number of modified polymer species, Further, the main chain of the general-purpose polymer can be modified without making capital investment. And by adding a filler to the styrene butadiene rubber modified in this way and mixing it, both rolling resistance and wet grip properties can be achieved.

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

  In the rubber composition of the present invention, solution-polymerized styrene-butadiene copolymer rubber (SSBR) is preferable as the styrene butadiene rubber (SBR) used as the rubber component. SSBR can be produced by a known solution polymerization method, that is, obtained by copolymerizing 1,3-butadiene and styrene in a hydrocarbon solvent using organolithium as an initiator. As said organic lithium, what is generally used by the solution polymerization method can be used, For example, n-butyl lithium, hexyl lithium, dilithiomethane etc. are mentioned.

As said SBR, what has the coupling | bonding amount of the vinyl unit in a butadiene part is 20 mol% or more is preferable. In the present invention, since a vinyl group is modified with a modifier, it is preferable to use SBR having a high vinyl unit bond amount in order to enhance the modification effect. The upper limit of the amount of vinyl units bonded is not particularly limited, but is preferably 70 mol% or less. The amount of bound styrene in the SBR is preferably 15 to 40 mol%. Here, the bond amount of the vinyl unit and the bond styrene amount are values measured by ¹ H-NMR according to ISO 21561: 2006.

  As the SBR, Sn-coupled styrene butadiene rubber can also be used. If it is Sn coupling polymer, since it will act as a radical generating polymer itself, it becomes unnecessary to mix | blend a radical generator. However, a radical generator described later can be added separately, and is preferably added in order to further increase the reactivity with the modifier. Sn-coupled SBR can be produced by a known method described in, for example, JP-A-63-308011. That is, it can be produced by copolymerizing 1,3-butadiene and styrene by a solution polymerization method using organolithium as an initiator in a hydrocarbon solvent and then coupling with a tin halide compound.

  In the rubber composition of the present invention, the rubber component is the SBR alone or a combination of the SBR and another diene rubber. When used in combination, the SBR is preferably used in an amount of 10% by weight or more of the rubber component. That is, the rubber component is preferably composed of 10 to 100% by weight of the SBR and 90 to 0% by weight of another diene rubber. If the SBR is less than 10% by weight, it is difficult to achieve both rolling resistance and wet grip properties. More preferably, SBR is used in an amount of 50% by weight or more of the rubber component.

  Examples of other diene rubbers include butadiene rubber, natural rubber, isoprene rubber, styrene-isoprene copolymer rubber, and butadiene-isoprene copolymer rubber. These may be used alone or in combination of two or more. May be.

  In the rubber composition of the present invention, a compound having a functional group that reacts with a vinyl group and an amino group or an amide group is used as a modifier for modifying the SBR. Examples of the functional group that reacts with the vinyl group include a mercapto group, a disulfide bond that generates a mercapto group, and a carbon-carbon double bond. More specifically, preferred examples of the modifier include (A) a compound having a mercapto group or disulfide bond and an amino group, and (B) an acid amide represented by the above general formula (1). The amino group may be in the form of a crystalline salt such as hydrochloride or hydrobromide by acting with an acid.

  Examples of the compound (A) include aminoalkyl thiols such as cysteamine, 6-amino-1-hexanethiol, 8-amino-1-octanethiol, 11-amino-1-undecanethiol (wherein the alkyl group The number of carbon atoms is preferably 2 to 12.), or disulfides thereof such as cystamine.

  Examples of the acid amide (B) include cinnamic acid amide, crotonic acid amide, acrylamide, and methacrylamide.

  These modifiers are preferably added in an amount of 0.05 to 1.5 parts by weight, more preferably 0.1 to 0.5 parts by weight, based on 100 parts by weight of the SBR. If it is less than 0.05 part by weight, the effect of modifying SBR is insufficient. Conversely, if it exceeds 1.5 part by weight, the processability is poor.

  In the rubber composition of the present invention, (C) carbon black, (D) an organic peroxide and / or an azo initiator are preferable as the radical generator for initiating the reaction of the modifier to the SBR. These may be used alone or in combination.

  The carbon black (C) used as the radical generator is preferably furnace black, and the blending amount thereof is preferably 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the SBR. It is.

  Examples of the organic peroxide (D) include dicumyl peroxide and tert-butyl cumyl peroxide. Examples of the azo initiator include azobisisobutyronitrile and azobiscyclohexanenitrile. These organic peroxides and azo initiators are preferably added in an amount of 0.001 to 0.02 parts by weight, more preferably 0.005 to 0.01 parts by weight, based on 100 parts by weight of the SBR.

  Examples of the filler in the rubber composition of the present invention include silica, carbon black, and inorganic fillers such as titanium oxide, aluminum silicate, clay, and talc. Preferably, silica alone or a combination of silica and carbon black is used. The filler is preferably blended in an amount of 15 to 150 parts by weight with respect to 100 parts by weight of the rubber component. In addition, when carbon black is blended as the radical generator at the time of premixing, the blending amount of the carbon black is considered to be included in the blending amount of the filler.

  In the rubber composition of the present invention, in addition to the above components, tire rubber compositions such as silane coupling agents, anti-aging agents, zinc white, stearic acid, softeners, vulcanizing agents, vulcanization accelerators, etc. Various commonly used additives can be blended.

  The method for producing a rubber composition of the present invention includes at least two steps: a premixing step in which a modifier is reacted with the SBR, and a filler mixing step in which a filler is mixed into the obtained premixture.

  In the pre-mixing step, the rubber component containing the SBR, the modifier, and the radical generator are mixed (kneaded) to prepare a pre-mixture. When using an Sn coupling polymer as the SBR, the radical generator is not essential as described above, and the Sn coupling SBR and the modifier may be premixed. However, also in this case, the radical generator may be premixed at the same time. Such pre-mixing can be performed using a mixer that is usually used for mixing rubber compositions. The mixing conditions are not particularly limited as long as SBR and the modifier can react to denature SBR. For example, stirring and mixing until 140 ° C. or higher (more preferably 160 to 200 ° C.) is performed. do it.

  In the pre-mixing, the functional group that reacts with the vinyl group of the modifier reacts with the vinyl group of SBR and is bonded. For example, when the compound (A) is used as a modifier, a mercapto group or a disulfide bond moiety reacts with a vinyl group, or when the acid amide (B) is used as a modifier, The moieties react with vinyl groups and each binds to the vinyl group of SBR. Thereby, an amino group or an amide group is introduced into the main chain of SBR. That is, the main chain modification of the polymer molecule can be performed by premixing with respect to SBR whose main chain is unmodified.

  Next, a filler is added to the pre-mixture obtained above and mixed (kneaded). Such a filler mixing step may be carried out as it is in the same mixer following the pre-mixing step, or may be carried out in a separate mixing stage after cooling once after the pre-mixing step. In the filler mixing step, the above-mentioned various additives are usually added and mixed at the same time.

  The rubber composition thus obtained is suitably used as a rubber composition for a tread of a pneumatic tire, and a tread can be formed by vulcanization molding according to a conventional method.

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

(Examples 1-6 and Comparative Examples 1-2)
For Examples 1 to 6 and Comparative Example 2, rubber compositions were prepared as follows. That is, using a 1.7 liter hermetic Banbury mixer, in the pre-mixing step, the SBR, the modifier and the radical generator are stirred for 6 to 8 minutes so that the discharge temperature is 180 ° C., and then the filler In the mixing process, the filler and each additive as a common blend were mixed and stirred so as to be discharged in 3 minutes, and the discharge temperature was 145 to 165 ° C.

  On the other hand, about the comparative example 1, the rubber composition was prepared by mix | blending a filler and each additive with a rubber component, without pre-mixing.

  The details of each component in Table 1 are as follows.

SSBR1: solution polymerization SBR “VSL5025-0HM” manufactured by LANXESS Corporation (bound styrene amount = 26 mol%, bond amount of vinyl unit of butadiene portion = 62 mol%),
Cysteamine: “2-mercaptoethylamine hydrochloride” manufactured by Nacalai Tesque,
-Acrylamide: "acrylamide (monomer)" manufactured by Nacalai Tesque,
Cinnamic amide: “AG835” manufactured by Merck & Co., Inc.
Carbon black: “Diamond Black N339” manufactured by Mitsubishi Chemical Corporation
・ Dicumyl peroxide: “Park Mill D” manufactured by NOF Corporation
AIBN: “α, α′-azobisisobutyronitrile” manufactured by Nacalai Tesque Co., Ltd.

  Further, in each rubber composition, 80 parts by weight of silica (“AQ” manufactured by Tosoh Silica) as a filler is blended with respect to 100 parts by weight of the rubber component, and a silane coupling agent (manufactured by Degussa “ 6.4 parts by weight of Si69 ”), 1 part by weight of wax (“ paraffin wax 155 ”manufactured by Nippon Seiki), 1 part by weight of anti-aging agent 6PPD (“ NOCRACK 6C ”manufactured by Ouchi Shinsei Chemical Industry), zinc white (Mitsui Metals) 2 parts by weight of “Zinc oxide 2 types” manufactured by Mining Co., Ltd. 2 parts by weight of stearic acid (“Lunac S-25” manufactured by Kao), 2 parts by weight of vulcanization accelerator DPG (“Noxeller D” manufactured by Ouchi Shinsei Chemical Industry) Vulcanization accelerator CZ (“Noxeller CZ” manufactured by Ouchi Shinsei Chemical Industry) 1.8 parts by weight and sulfur (“5% oil-filled fine sulfur powder” manufactured by Tsurumi Chemical Industries) 2 parts by weight were blended.

  Each rubber composition was evaluated for processability, rolling resistance, and wet grip properties. Each evaluation method is as follows.

Processability: The case where the rubber was not well packed after being discharged from the filler was unacceptable, and the case where it was acceptable was evaluated as “◯”.

Rolling resistance: tan δ was measured (50 Hz, 1% strain, 60 ° C.) using a viscoelasticity tester manufactured by Ueshima Seisakusho, and displayed as an index with the value of Comparative Example 1 being 100. The smaller the index, the better the rolling resistance.

-Wet grip property: It measured at room temperature using BPST (British portable skid tester), and displayed by the index | exponent which set the value of the comparative example 1 to 100. It shows that it is excellent in wet grip property, so that an index | exponent is large.

  The results are as shown in Table 1, and in Examples 1 to 6 according to the present invention, both rolling resistance and wet grip properties could be achieved without impairing workability. In Comparative Example 2 in which the blending amount of the modifier is out of the range of Claim 5, the rolling resistance and wet grip properties are excellent, but the workability is inferior.

(Examples 7 and 8 and Comparative Example 3)
For Examples 7 and 8, rubber compositions were prepared as follows. That is, using a 1.7 liter hermetic Banbury mixer, in the pre-mixing step, SBR and a modifier (further a radical generator in Example 8) are removed for 6 to 8 minutes so that the discharge temperature is 180 ° C. Then, in the filler mixing step, the filler and the additive as a common formulation were mixed and stirred so as to be discharged in 3 minutes, and the discharge temperature was 145 to 165 ° C. On the other hand, for Comparative Example 3, a rubber composition was prepared by blending a rubber component with a filler and each additive without pre-mixing.

  Details of each component in Table 2 are as follows.

SSBR2: Sn coupled solution polymerization SBR “SL552” manufactured by JSR Corporation (bonded styrene amount = 24 mol%, bond amount of vinyl unit of butadiene part = 32 mol%),
Cysteamine: “2-mercaptoethylamine hydrochloride” manufactured by Nacalai Tesque,
Dicumyl peroxide: “Park Mill D” manufactured by NOF Corporation.

The filler and other additives blended in each rubber composition are the same as in Example 1 described above. Each rubber composition was evaluated for processability, rolling resistance, and wet grip properties in the same manner as in Example 1. The control of rolling resistance and wet grip was set to Comparative Example 3.

  The results are as shown in Table 2. In Examples 7 and 8 according to the present invention, it was possible to achieve both rolling resistance and wet grip properties without impairing workability.

  The rubber composition of the present invention can be used for various rubber compositions filled with a filler, including a rubber composition for tires.

Claims (11)

A styrene butadiene rubber, a modifier having a functional group that reacts with a vinyl group in the styrene butadiene rubber and an amino group or an amide group, and a radical generator are mixed to prepare a pre-mixture,
A method for producing a rubber composition, wherein a filler is added to and mixed with the obtained pre-mixture. A Sn-coupled styrene butadiene rubber and a modifier having a functional group that reacts with a vinyl group and an amino group or an amide group in the styrene butadiene rubber are mixed to prepare a pre-mixture,
A method for producing a rubber composition, wherein a filler is added to and mixed with the obtained pre-mixture.   3. The method for producing a rubber composition according to claim 2, wherein a radical generator is mixed together with the modifier when preparing the pre-mixture. The modifying agent is at least one selected from the group consisting of a compound having a mercapto group or disulfide bond and an amino group, and an acid amide represented by the following general formula (1). Item 4. A method for producing a rubber composition according to any one of Items 1 to 3.

(In the formula, R ¹ is hydrogen, an alkyl group having 1 to 18 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and R ² is hydrogen or a methyl group.)   The method for producing a rubber composition according to any one of claims 1 to 4, wherein 0.05 to 1.5 parts by weight of the modifier is blended with 100 parts by weight of the styrene butadiene rubber.   The method for producing a rubber composition according to claim 1 or 3, wherein the radical generator is carbon black and is blended in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the styrene butadiene rubber.   The radical generator is at least one selected from the group consisting of organic peroxides and azo initiators, and is blended in an amount of 0.001 to 0.02 parts by weight with respect to 100 parts by weight of the styrene butadiene rubber. The method for producing a rubber composition according to claim 1 or 3, wherein:   The rubber composition according to any one of claims 1 to 7, wherein the filler is blended in an amount of 15 to 150 parts by weight with respect to 100 parts by weight of a rubber component containing 10% by weight or more of the styrene butadiene rubber. Method. To styrene butadiene rubber,
A compound having a mercapto group or disulfide bond and an amino group, and at least one modifier selected from the group consisting of acid amides represented by the following general formula (1);
A radical generator,
A rubber composition comprising:

(In the formula, R ¹ is hydrogen, an alkyl group having 1 to 18 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and R ² is hydrogen or a methyl group.) To Sn-coupled styrene butadiene rubber,
A compound having a mercapto group or a disulfide bond and an amino group, and at least one modifier selected from the group consisting of acid amides represented by the following general formula (1):
A rubber composition comprising:

(In the formula, R ¹ is hydrogen, an alkyl group having 1 to 18 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and R ² is hydrogen or a methyl group.)   A pneumatic tire having a tread made of the rubber composition according to claim 9.