JP2019112559A - Rubber composition for tires, and pneumatic tire using the same - Google Patents

Abstract

To provide a rubber composition for tires which improves wet grip performance and fuel economy.SOLUTION: The composition contains, based on 100 pts.mass of a rubber component comprising a diene rubber, 1-100 pts.mass of polymer particles which have an alkyl (meth)acrylate unit represented by formula (1) as a constituent unit (where Ris H or a methyl group; R's in the same molecule may be the same or different; Ris a C4-18 alkyl group; and R's in the same molecule may be the same or different) and in which the total amount of an Na concentration and a K concentration is 2,000 ppm or less.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for a tire, and a pneumatic tire using the same.

  Conventionally, in a rubber composition used for a tire, it is required to balance the grip performance (wet grip performance) on a wet road surface and the rolling resistance performance contributing to low fuel consumption at a high level. However, since these are contradictory characteristics, it is not easy to improve them simultaneously.

  With respect to such a problem, Patent Document 1 discloses a (meth) acrylate polymer having a predetermined structural unit and no reactive silyl group per 100 parts by mass of a rubber component consisting of a diene rubber. There is disclosed a rubber composition containing 1 to 100 parts by mass of fine particles having a glass transition temperature of −70 to 0 ° C. and an average particle diameter of 10 nm or more and less than 100 nm.

Unexamined-Japanese-Patent No. 2017-110069

  However, such particles may contain impurities such as an emulsifier depending on the method of synthesis, and if metal elements contained in the emulsifier etc. are present in the composition, they cause heat generation, and therefore low fuel consumption. There was room for further improvement in sex.

  An object of this invention is to provide the rubber composition for tires which can improve the wet grip performance and low fuel consumption property of a tire in view of the above point.

  The rubber composition for a tire according to the present invention has, as a structural unit, an alkyl (meth) acrylate unit represented by the formula (1) with respect to 100 parts by mass of a rubber component consisting of a diene rubber, sodium concentration and potassium It contains 1 to 100 parts by mass of polymer particles having a total concentration of 2000 ppm or less.

In the formula, R ¹ is a hydrogen atom or a methyl group, R ¹ in the same molecule may be the same or different, R ² is an alkyl group having 4 to 18 carbon atoms, R ² in the same molecule It may be the same or different.

  The glass transition temperature of the polymer particles may be -70 to 0 ° C.

  The sodium or potassium in the polymer particles can be present as a fatty acid salt or persulfate.

  The pneumatic tire according to the present invention is manufactured using the above rubber composition for a tire.

  According to the rubber composition for a tire of the present invention, the wet grip performance and fuel economy of the tire can be improved.

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

  The rubber composition for a tire according to the present embodiment is formed by blending polymer particles consisting of a specific (meth) acrylate polymer with a rubber component consisting of a diene rubber.

  Examples of diene rubbers as rubber components include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), And butyl rubber (IIR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, etc., and these are used singly or in combination of two or more. be able to. Among these, at least one selected from the group consisting of NR, BR and SBR is preferable.

  Specific examples of each of the diene rubbers listed above include at least one selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, an alkoxy group, an alkoxysilyl group, and an epoxy group in the molecular terminal or in the molecular chain thereof. The introduction of a functional group of a species also includes a modified diene rubber modified with the functional group. As the modified diene rubber, modified SBR and / or modified BR are preferable. In one embodiment, the diene rubber may be a modified diene rubber alone or may be a blend of a modified diene rubber and an unmodified diene rubber. In one embodiment, 30 parts by mass or more of modified SBR may be contained in 100 parts by mass of diene rubber, and 50 to 90 parts by mass of modified SBR and 50 to 50 parts by mass of unmodified diene rubber (for example, BR and / or NR) 10 parts by mass may be included.

  The polymer particles are made of a (meth) acrylate polymer having an alkyl (meth) acrylate unit represented by the following general formula (1) as a constituent unit (also referred to as a repeating unit), Those having a total amount of sodium concentration and potassium concentration in the polymer particles of 2000 ppm or less are used. The total amount of the sodium concentration and the potassium concentration is preferably as low as possible, more preferably 1800 ppm or less, but may be 100 ppm or more from the viewpoint of cost. Here, the sodium concentration and the potassium concentration are values measured using inductively coupled plasma emission spectrometry (ICP-OES). In addition, sodium and potassium include what exists as fatty acid salt and persulfate in polymer particle.

In the formula, R ¹ is a hydrogen atom or a methyl group, R ¹ in the same molecule may be the same or different, R ² is an alkyl group having 4 to 18 carbon atoms, R ² in the same molecule It may be the same or different. The alkyl group of R ² may be linear or branched. R ² is preferably an alkyl group having 6 to 16 carbon atoms, more preferably an alkyl group having 8 to 15 carbon atoms.

  The (meth) acrylate polymer is obtained by polymerizing a monomer containing one or more alkyl (meth) acrylates. Here, (meth) acrylate means one or both of acrylate and methacrylate. Also, (meth) acrylic acid means one or both of acrylic acid and methacrylic acid.

  Examples of the alkyl (meth) acrylate include n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-nonyl acrylate, n-acrylate Decyl, n-undecyl acrylate, n-dodecyl acrylate, n-tridecyl acrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, n-heptyl methacrylate, n-octyl methacrylate, N-alkyl methacrylates such as n-nonyl methacrylate, n-decyl methacrylate, n-undecyl methacrylate, and n-dodecyl methacrylate; isobutyl acrylate, isopentyl acrylate, isohexyl acrylate, isoheptyl acrylate , Acrylic acid isooct , Isonodecyl acrylate, isodecyl acrylate, isoundecyl acrylate, isododecyl acrylate, isotridecyl acrylate, isotetradecyl acrylate, isobutyl methacrylate, isopentyl methacrylate, isohexyl methacrylate, isoheptyl methacrylate, isooctyl methacrylate, isononyl methacrylate Isodecyl methacrylate, isoundecyl methacrylate, isododecyl methacrylate, isotridecyl methacrylate, and isoalkyl acrylate (meth) acrylates such as isotetradecyl methacrylate; 2-methylbutyl acrylate, 2-ethylpentyl acrylate, 2-methyl acrylate Hexyl, 2-ethylhexyl acrylate, 2-ethylheptyl acrylate, 2-methylpentyl methacrylate, methacrylic acid Acid 2-methylhexyl, 2-ethylhexyl methacrylate, and methacrylic acid 2-ethyl-heptyl and the like. These may be used alone or in combination of two or more.

  Here, isoalkyl refers to an alkyl group having a methyl side chain at the second carbon atom from the end of the alkyl chain. For example, isodecyl refers to a C10 alkyl group having a methyl side chain at the second carbon atom from the chain end, including not only an 8-methylnonyl group but also a 2,4,6-trimethylheptyl group It is.

  As one embodiment, it is preferable that a (meth) acrylate type polymer is a polymer which has a structural unit represented by following General formula (2) as a structural unit represented by Formula (1).

In formula (2), R ³ is a hydrogen atom or a methyl group (preferably a methyl group), and R ³ in the same molecule may be the same or different. Z is a C1-C15 alkylene group, and Z in the same molecule may be same or different. Z may be linear or branched.

The structural unit of Formula (2) is a case where R ² in Formula (1) is represented by the following General Formula (2A).

  Z in Formula (2A) is the same as Z in Formula (2).

  Examples of (meth) acrylates which give rise to such a structural unit include the above-mentioned isoalkyl (meth) acrylates. When a (meth) acrylate (preferably a methacrylate) having such an isoalkyl group is used, the effect of the present embodiment can be easily enhanced. It is preferable that Z in Formula (2) and (2A) is a C5-C12 alkylene group, More preferably, it is a C6-C10 alkylene group. Particularly preferred is an alkylene group having 7 carbon atoms. As an example, the (meth) acrylate polymer is preferably a polymer of a monomer containing isodecyl methacrylate.

  In another embodiment, the (meth) acrylate polymer may be a polymer having a constituent unit represented by the following general formula (3) as a constituent unit represented by the formula (1), or It may be a polymer having a constituent unit represented by Formula (2) and a constituent unit represented by Formula (3). In the latter case, the addition form of both structural units may be random addition or block addition, preferably random addition.

In formula (3), R ⁴ is a hydrogen atom or a methyl group (preferably a methyl group), and R ⁴ in the same molecule may be the same or different. Q ¹ is an alkylene group having 1 to 6 (preferably 1 to 3) carbon atoms, and may be linear or branched (preferably linear), and Q ¹ in the same molecule may be the same or different. Q ² is a methyl group or an ethyl group (preferably an ethyl group), and Q ² in the same molecule may be the same or different.

The structural unit of Formula (3) is a case where R ² in Formula (1) is represented by the following General Formula (3A).

In Formula (3A), Q ¹ and Q ² are respectively the same as Q ¹ and Q ² of Formula (3).

  When the (meth) acrylate polymer is a copolymer of the structural unit of the formula (2) and the structural unit of the formula (3), excellent wet grip performance and rolling resistance performance are easily obtained. Moreover, it is easy to suppress the hardness fall of the rubber composition at normal temperature, and easy to obtain excellent steering stability. Moreover, it is easy to suppress an increase in the elastic modulus of the rubber composition at low temperatures, and an excellent grip performance is easily obtained.

  Here, in the copolymer, specific examples of the (meth) acrylate which gives rise to the structural unit of the formula (2) include the above-mentioned isoalkyl (meth) acrylates, and particularly preferred is isodecyl methacrylate. Moreover, as a specific example of the (meth) acrylate which produces the structural unit of Formula (3), (meth) acrylate n-alkyl and (meth) acrylate isoalkyl are remove | excluded among the alkyl (meth) acrylate of the said listing. Particularly preferred is 2-ethylhexyl methacrylate.

  In the case of such a copolymer, the ratio (copolymerization ratio) of the structural unit of the formula (2) to the structural unit of the formula (3) is not particularly limited. For example, it may be 30/70 to 90/10 or 40/60 to 85/15 in terms of the molar ratio of the constituent unit of the formula (2) / the constituent unit of the formula (3).

  The (meth) acrylate polymer constituting the polymer particles according to the present embodiment may be a homopolymer of the above alkyl (meth) acrylate, but according to a more preferred embodiment, the alkyl (meth) acrylate is It is a polymer of a crosslinked structure formed by crosslinking in the presence of a functional vinyl monomer. That is, in a preferred embodiment, the (meth) acrylate polymer includes a constituent unit derived from a polyfunctional vinyl monomer together with a constituent unit represented by the formula (1), and a constituent unit derived from the polyfunctional vinyl monomer Have a crosslinked structure with a crosslinking point.

  Multifunctional vinyl monomers include compounds having at least two vinyl groups that can be polymerized by free radical polymerization, such as diols or triols (eg ethylene glycol, propylene glycol, 1,4-butanediol, 1,1 6) Hexanediol, trimethylolpropane and the like) di (meth) acrylates or tri (meth) acrylates; methylene di (meth) acrylamides such as methylene bis-acrylamide; diisopropenyl benzene, divinyl benzene, trivinyl benzene and the like The vinyl aromatic compound etc. which have an individual vinyl group etc. are mentioned, These can be used in any 1 type or 2 types or more in combination.

  The (meth) acrylate polymer is not particularly limited, but the molar ratio of the structural unit of the formula (1) to all the structural units (all repeating units) constituting the (meth) acrylate polymer is 50 mol% It is preferable that it is the above, More preferably, it is 80 mol% or more, More preferably, it is 90 mol% or more. The upper limit of the molar ratio of the constituent units of the formula (1) is not particularly limited, but may be 99.5 mol% or less or 99 mol% or less when, for example, the above-mentioned polyfunctional vinyl monomer is added. The molar ratio of the constituent units based on the polyfunctional vinyl monomer may be 0.5 to 20 mol%, 1 to 10 mol%, or 1 to 5 mol%.

  In one embodiment, when the (meth) acrylate polymer is a polymer having a constituent unit of formula (2), the molar ratio of the constituent units of formula (2) to all the constituent units of the polymer is 25% by mole The above content is preferably, more preferably 35 mol% or more, 50 mol% or more, or 80 mol% or more. The upper limit of the molar ratio is not particularly limited, but may be 99.5 mol% or less or 99 mol% or less, for example, when a polyfunctional vinyl monomer is added in the above-mentioned molar ratio.

  In one embodiment, when the (meth) acrylate polymer is a polymer having a constitutional unit of the formula (3), the molar ratio of the constitutional unit of the formula (3) to all the constitutional units of the polymer is 25 mol% The above content is preferably, more preferably 35 mol% or more, 50 mol% or more, or 80 mol% or more. The upper limit of the molar ratio is not particularly limited, but may be 99.5 mol% or less or 99 mol% or less, for example, when a polyfunctional vinyl monomer is added in the above-mentioned molar ratio.

  In another embodiment, in the case where the (meth) acrylate polymer is a copolymer of the structural unit of formula (2) and the structural unit of formula (3), the formula for all structural units of the copolymer The molar ratio of the constituent units of 2) may be 25 to 90 mol%, and the molar ratio of the constituent units of formula (3) may be 5 to 60 mol%, and the molar ratio of the constituent units of formula (2) may be 35 to 85 mol In%, the molar ratio of the structural unit of Formula (3) may be 8-55 mol%. In addition, the total of the molar ratio of the structural unit of the formula (2) and the structural unit of the formula (3) may be 80 mol% or more, or 90 mol% or more. When added in a molar ratio, it may be 99.5 mol% or less, or 99 mol% or less.

  In the present embodiment, it is preferable that the above (meth) acrylate polymer does not have a reactive silyl group. That is, in the present embodiment, the polymer particles are not blended as a reinforcing filler in place of silica, and thus the reactive silyl group in the molecular terminal or molecular chain of the (meth) acrylate polymer constituting the polymer particles. It is preferable that it does not have. Thereby, it is easy to obtain excellent wet grip performance and rolling resistance performance. Moreover, it is easy to suppress the hardness fall of the rubber composition at normal temperature, and easy to obtain excellent steering stability. Moreover, it is easy to suppress an increase in the elastic modulus of the rubber composition at low temperatures, and an excellent grip performance is easily obtained. Here, the reactive silyl group is a functional group represented by the formula: ≡Si-X (wherein, X is a hydroxyl or a hydrolysable group), and 1 to 3 hydroxyl groups or It is a group having a structure in which a hydrolyzable monovalent group is bonded to a tetravalent silicon atom. Examples of X include a hydroxyl group, an alkoxy group, and a halogen atom.

  In the present embodiment, the glass transition temperature (Tg) of the polymer particles composed of the (meth) acrylate polymer is not particularly limited, but it is preferably −70 to 0 ° C., and is −50 to −10 ° C. More preferably, it is -40 to -20 ° C. The setting of the glass transition temperature can be performed by the monomer composition and the like constituting the (meth) acrylate polymer. When the glass transition temperature is 0 ° C. or less, it is easy to more effectively suppress the deterioration of the low temperature performance. Moreover, when a glass transition temperature is -70 degreeC or more, it is easy to heighten the improvement effect of wet grip performance. Here, the glass transition temperature is measured at a temperature rising rate of 20 ° C./min (measurement temperature range: −150 ° C. to 150 ° C.) by differential scanning calorimetry (DSC) according to JIS K7121. It is a value.

  In the present embodiment, the average particle size of the polymer particles is not particularly limited, but is preferably 10 nm to 100 nm, more preferably 20 to 90 nm, and still more preferably 30 to 80 nm. When the (meth) acrylate polymer containing the specific structural unit is added to the diene rubber as such fine particles, excellent wet grip performance and rolling resistance performance can be easily obtained. Moreover, it is easy to suppress the hardness fall of the rubber composition at normal temperature, and easy to obtain excellent steering stability. Moreover, it is easy to suppress an increase in the elastic modulus of the rubber composition at low temperatures, and an excellent grip performance is easily obtained. Here, in the present specification, the “average particle diameter” is a value determined by the cumulant method. Specifically, the particle size (50% diameter: D50) at an integrated value of 50% in the particle size distribution measured by the dynamic light scattering method (DLS) is measured by the photon correlation method (based on JIS Z8826) The angle between the incident light and the detector (90 °), and the value obtained by the cumulant method from the obtained autocorrelation function.

  The method for producing the above-mentioned polymer particles is not particularly limited, and can be synthesized, for example, using known emulsion polymerization. A preferred example is as follows. That is, (meth) acrylate is dispersed in an aqueous medium such as water in which an emulsifying agent is dissolved, together with a polyfunctional vinyl monomer as a crosslinking agent, and a water-soluble radical polymerization initiator (for example, potassium persulfate etc.) is obtained in the obtained emulsion. The polymer particles comprising a (meth) acrylate polymer are formed in the aqueous medium by adding the peroxide of (1) and radically polymerizing the polymer particles, so that the polymer particles are obtained by separating from the aqueous medium. As other methods for producing polymer particles, known polymerization methods such as suspension polymerization, dispersion polymerization, precipitation polymerization, mini-emulsion polymerization, soap-free emulsion polymerization (emulsifier-free emulsion polymerization) and micro-emulsion polymerization can be used.

  The polymer particles obtained by the above-mentioned production method, in particular, the polymer particles produced using polymerization methods such as emulsion polymerization and suspension polymerization using an emulsifying agent have an sp value of 8 to 11 as needed. The polymer particles may be prepared such that the total amount of sodium concentration and potassium concentration is 2000 ppm or less by adding a coagulant after redispersion treatment with a solvent and performing recoagulation treatment.

The organic solvent having an sp value of 8 to 11 is not particularly limited. Examples thereof include tetrahydrofuran (THF), acetone, toluene, methyl ethyl ketone (MEK), xylene, methyl isopropyl ketone, methyl propyl ketone, ethyl benzene, pyridine and the like. Be Here, the sp value (dissolution parameter) referred to in the present specification refers to, for example, pages 71 to 77 of “Practical polymer for engineers” (Kodansha, published Oct. 1, 1981) by Mukai Yuji and Kinjo Tokuyuki. The value δ [(cal / cm ³ ) ^1/2 ] calculated at 25 ° C. according to the Fedors equation described in 1), 1 (cal / cm ³ ) ^1/2 = 2.05 (MJ / m ³ ) ^{1 / 2,} therefore, SP value and 10 (cal ^/ cm ^{3) 1/2} or less means 20.5 ^(MJ / ^{m 3) 1/2} or less.
Formula of Fedors:
SP value (δ) = (E _v / v) ^1/2 = (ΣΔe _i / ΣΔv _i ) ^1/2
E _v: energy of vaporization v: molar volume .DELTA.e _i: evaporation energy Delta] v i atom or atomic group of the _components: the molar volume of each atom or atomic group
The evaporation energy and molar volume of each atom or group used in the calculation of the above equation can be referred to F. Fedors, Polym. Eng. Sci., 14, 147 (1974).

  In the rubber composition according to the present embodiment, the content of the polymer particles composed of the (meth) acrylate polymer is 1 to 100 parts by mass, preferably 100 parts by mass of the rubber component composed of a diene based rubber. It is 2 to 50 parts by mass, more preferably 3 to 30 parts by mass.

  The rubber composition according to the present embodiment includes a reinforcing filler, a silane coupling agent, oil, zinc flower, stearic acid, an antiaging agent, a wax, in addition to the polymer particles comprising the (meth) acrylate polymer. Various additives generally used in rubber compositions such as vulcanizing agents and vulcanization accelerators can be blended.

  As the reinforcing filler, for example, silica such as wet silica (hydrous silicic acid) or carbon black is used. Preferably, in order to improve the balance between the rolling resistance performance and the wet grip performance, it is preferable to use silica alone or a combination of silica and carbon black. The content of the reinforcing filler is not particularly limited, and may be, for example, 20 to 150 parts by mass, or 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. The content of the silica is also not particularly limited, and may be, for example, 20 to 150 parts by mass, or 30 to 100 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, in which case the content of the silane coupling agent is preferably 2 to 20% by mass of the silica mass, more preferably 4 to 15 mass. %.

  Sulfur is preferably used as the above-mentioned vulcanizing agent. The content of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component. Moreover, as said vulcanization accelerator, various vulcanization accelerators, such as a sulfenamide type, a thiuram type, a thiazole type, and a guanidine type, are mentioned, for example, It is used individually by 1 type or in combination of 2 or more types be able to. Although the content of the vulcanization accelerator is not particularly limited, it 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, a kneader, or a mixer such as a roll. That is, for example, in the first mixing step, the diene rubber, the above-mentioned polymer particles, and other additives other than the vulcanizing agent and the vulcanization accelerator are added and mixed, and then the final mixture is added to the obtained mixture The rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator in stages.

  The rubber composition for a tire obtained in this manner is applied to each part of the tire such as treads and sidewalls of pneumatic tires for various applications and various sizes such as tires for passenger cars, large tires for trucks and buses, etc. be able to. That is, the rubber composition is formed into a predetermined shape by, for example, extrusion processing according to a conventional method, and after combined with other parts to produce a green tire, the green tire is vulcanized and formed at, for example, 140 to 180 ° C. Thus, a pneumatic tire can be manufactured. Among these, it is particularly preferable to use as a compound for tread of a tire.

  Hereinafter, although the example of the present invention is shown, the present invention is not limited to these examples.

[Method of measuring average particle size]
The average particle diameter of the polymer particles is the particle diameter (50% diameter: D50) at an integrated value of 50% in the particle size distribution measured by dynamic light scattering (DLS), and dynamic light scattering manufactured by Otsuka Electronics Co., Ltd. It measured by the photon correlation method (JIS Z8826 conformity) using a photometer "DLS-8000" (90 degrees of incident light and a detector), and calculated | required by the cumulant method from the obtained autocorrelation function.

[Method of measuring Tg]
The Tg of the polymer particles was measured at a temperature rising rate of 20 ° C./minute by a differential scanning calorimetry (DSC) method according to JIS K7121 (measurement temperature range: −150 ° C. to 150 ° C.).

Synthesis Example 1
Mix 15.0 g of 2,4,6-trimethylheptyl methacrylate (isodecyl methacrylate), 0.394 g of ethylene glycol dimethacrylate, 1.91 g of sodium dodecyl sulfate, 120 g of water and 13.5 g of ethanol, The monomer is emulsified by stirring for 1 hour, 0.179 g of potassium persulfate is added, nitrogen bubbling is performed for 1 hour, and the solution is kept at 70 ° C. for 8 hours to synthesize a polymer particle dispersion emulsion. did. Polymer particles A were obtained by coagulation with methanol addition in the obtained solution. The average particle size was 60 nm and Tg was -37 ° C.

Synthesis Example 2
The monomer is emulsified by mixing 15.0 g of 2-ethylhexyl methacrylate, 0.450 g of ethylene glycol dimethacrylate, 2.18 g of sodium dodecyl sulfate, 120 g of water and 13.5 g of ethanol and stirring for 1 hour Polymer particles B were obtained in the same manner as in Synthesis Example 1 except that 0.204 g of potassium persulfate was added. The average particle size was 58 nm, and Tg was -10 ° C.

Synthesis Example 3
The monomer is emulsified by mixing 15.0 g of n-dodecyl methacrylate, 0.351 g of ethylene glycol dimethacrylate, 1.70 g of sodium dodecyl sulfate, 120 g of water and 13.5 g of ethanol and stirring for 1 hour Polymer particles C were obtained in the same manner as in Synthesis Example 1 except that 0.159 g of potassium persulfate was added. The average particle size was 62 nm, and Tg was -65 ° C.

Processing Example 1
The polymer particles A obtained in the above Synthesis Example 1 are re-dispersed in a solvent by immersing in a solvent of tetrahydrofuran (THF) having an sp value of 9.1, and then re-added by adding methanol. It was solidified to obtain polymer particles 1.

Processing Example 2
Polymer particles 2 were obtained in the same manner as in Example 1 except that acetone was used instead of tetrahydrofuran and the sp value was 9.9.

Processing Example 3
Polymer particles 3 were obtained in the same manner as in Example 1 except that toluene was used instead of tetrahydrofuran and the sp value was 8.9.

Processing Example 4
Polymer particles 4 were obtained in the same manner as in Example 1 except that n-hexane having an sp value of 7.3 was used instead of tetrahydrofuran, and redispersion and recoagulation were performed.

Processing Example 5
Polymer particles 5 were obtained in the same manner as in Example 1 except that diethyl ether having an sp value of 7.4 was used instead of tetrahydrofuran, and redispersion and recoagulation were performed.

Processing Example 6
Polymer particles 6 were obtained in the same manner as in Example 1 except that isopropyl alcohol having an sp value of 11.5 was used instead of tetrahydrofuran, and redispersion and recoagulation were performed.

Processing Example 7
Polymer particles 7 were obtained in the same manner as in Example 1 except that ethanol was used instead of tetrahydrofuran and the sp value was 12.7.

Processing Example 8
A polymer particle 8 was obtained in the same manner as in Processing Example 1 except that polymer particle B was used instead of polymer particle A.

Processing Example 9
A polymer particle 9 was obtained in the same manner as in Processing Example 1 except that polymer particle C was used instead of polymer particle A.

  The polymer particles 1 to 9 were evaluated for redispersibility and recoagulability, and the polymer particles A to C and the polymer particles 1 to 9 were measured for the amount of impurities, and the results are shown in Table 1. The evaluation method and the measurement method are as follows. The average particle diameter and Tg of the polymer particles after the resolidification treatment were not measured because they can be assumed to be the same as before the treatment.

Re-dispersibility: It was visually confirmed whether the polymer particles were re-dispersed in a solvent, and those well dispersed were designated as “o”, and those not re-dispersed were designated as “x”.

Re-coagulability: It was visually confirmed whether the polymer was re-coagulated, and those that were re-solidified were rated as “○” and those that were not re-solidified were rated as “x”.

Impurity amount ([Na ⁺ + K ⁺ ]): 5 ml of nitric acid was added to 0.1 g of the obtained polymer particles, and it was decomposed by a microwave and diluted to 50 ml with distilled water to obtain a measurement solution. The inductively coupled plasma emission spectrometry (ICP-OES) was performed using Perkin Elmer Co., Ltd. “Оptima 8300” to measure the sodium concentration and the potassium concentration, and the total value was determined.

  Using a laboratory mixer, according to the composition (parts by mass) shown in Table 2 below, at the first mixing stage, other compounding agents other than sulfur and a vulcanization accelerator were added to the diene rubber component and kneaded ( Discharge temperature = 160 ° C). Subsequently, in the final mixing stage, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded (discharge temperature = 90 ° C) to prepare a rubber composition. The details of each component in Table 2 are as follows.

Denatured SBR: "HPR 350" manufactured by JSR Corporation
・ BR: "BR150B" manufactured by Ube Industries, Ltd.
Silica: Tosoh Silica Corporation "Nip Seal AQ"
Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, "Si69" manufactured by Evonik Japan Co., Ltd.
Polymer particles A to C: polymer particles obtained respectively in the above Synthesis Examples 1 to 3 Polymer particles 1 to 9: Polymer particles obtained respectively in the above Treatment Examples 1 to 9 Zinc flower: Mitsui Metal Mining Co., Ltd. Made of "zinc flower type 1"
・ Anti-aging agent: Ouchi Shinko Chemical Co., Ltd. product "Nocrac 6C"
・ Stearic acid: Kao Corporation "Lunack S-20"
・ Sulfur: Powdered sulfur 150 mesh for rubber manufactured by Hosoi Chemical Industry Co., Ltd.
・ Vulcanization accelerator: "Noxceler CZ" manufactured by Ouchi Shinko Chemical Co.
・ Secondary vulcanization accelerator: "Noxceler D" manufactured by Ouchi Shinko Chemical Co., Ltd.

  The obtained rubber compositions were vulcanized at 160 ° C. for 20 minutes to prepare test pieces of a predetermined shape, and the obtained test pieces were used to conduct a dynamic viscoelasticity test to obtain 0 ° C. and 60 ° C. Of tan δ was measured.

Wet grip performance: Using a UBOO rheo spectrometer E4000, the loss coefficient tan δ is 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. Is displayed as an index. The larger the index, the larger the tan δ and the better the wet grip performance.

Fuel economy: The temperature was changed to 60 ° C., and the others were measured in the same manner as tan δ at 0 ° C., and the tan δ was measured. The smaller the index, the less the heat is generated, and the smaller the rolling resistance of the tire is, the better the rolling resistance performance (i.e., fuel economy).

  The results are as shown in Table 2. From the comparison with Comparative Examples 2 to 8, Examples 1 to 5 show that the fuel economy is improved while maintaining excellent wet grip performance.

  The comparison examples 2, 7 and 8 containing the polymer particles A to C show that the improvement effect of the fuel economy is insufficient or the fuel economy is deteriorated according to the comparison with the comparison 1.

The rubber composition for a tire of the present invention can be used for various tire rubber compositions such as passenger cars, light trucks and buses.

Claims (4)

A polymer particle having an alkyl (meth) acrylate unit represented by the formula (1) as a constitutional unit and having a total amount of a sodium concentration and a potassium concentration of 2000 ppm or less based on 100 parts by mass of a rubber component consisting of a diene rubber The rubber composition for tires which contains 1-100 mass parts.

In the formula, R ¹ is a hydrogen atom or a methyl group, R ¹ in the same molecule may be the same or different, R ² is an alkyl group having 4 to 18 carbon atoms, R ² in the same molecule It may be the same or different.   The rubber composition for a tire according to claim 1, wherein the glass transition temperature of the polymer particles is -70 to 0 ° C.   The tire rubber composition according to claim 1, wherein sodium or potassium in the polymer particles is present as a fatty acid salt or a persulfate.   The pneumatic tire produced using the rubber composition for tires of any one of Claims 1-3.