JP2006219618A - Modified natural rubber masterbatch, method for producing the same, rubber composition and tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber masterbatch giving a rubber composition having remarkably lowered mechanical tanδ and improved abrasion resistance and breaking strength and provide a method for the production of the masterbatch. <P>SOLUTION: The method for the production of a modified natural rubber masterbatch comprises (i) a step to mix a natural rubber latex with a slurry solution containing a filler dispersed in water, (ii) a step to coagulate the mixed liquid obtained by the step (i), and (iii) a step to carry out graft polymerization or addition of a compound containing a polar group to a natural rubber molecule in a coagulation product by adding a compound containing a polar group to the coagulation product obtained by the step (ii) and drying the mixture under mechanical shearing force. The modified natural rubber masterbatch is produced by the method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a modified natural rubber masterbatch, a method for producing the same, and a rubber composition and a tire using the modified natural rubber masterbatch, and in particular, greatly reduces the low loss, wear resistance and fracture resistance of the rubber composition. The present invention relates to a modified natural rubber masterbatch comprising a modified natural rubber and a filler, which can be improved.

  In recent years, there is an increasing demand for lower fuel consumption of automobiles, and tires with low rolling resistance are required. Therefore, as a rubber composition used for tire treads or the like, a rubber composition having a low tan δ (hereinafter referred to as low loss property) and excellent in low heat generation properties is required. In addition, a rubber composition for a tread is required to have excellent wear resistance and fracture characteristics in addition to low loss. On the other hand, in order to improve the low loss, wear resistance and fracture characteristics of rubber compositions containing various fillers in the rubber component, the affinity between the filler in the rubber composition and the rubber component is improved. It is effective to make it.

  For example, in order to improve the affinity between the filler and the rubber component in the rubber composition and to improve the reinforcing effect by the filler, synthetic rubber or functional group having improved affinity with the filler by terminal modification Synthetic rubbers and the like have been developed in which the monomers are copolymerized to improve the affinity with the filler.

  On the other hand, although natural rubber is used in large quantities by taking advantage of its excellent physical properties, it is a technology that improves the natural rubber itself to improve the affinity with the filler and greatly enhance the reinforcing effect of the filler. There is no.

  For example, a technology for epoxidizing natural rubber has been proposed. However, since this technology cannot sufficiently improve the affinity between the natural rubber and the filler, the reinforcing effect of the filler can be sufficiently improved. Can not. In addition, a technique (see Patent Documents 1 to 6) in which a vinyl monomer is added to natural rubber latex to perform graft polymerization is known, and the grafted natural rubber obtained by the technique is used for adhesives and the like. It has been put into practical use. However, since the grafted natural rubber is grafted with a large amount (20 to 50% by mass) of a vinyl compound as a monomer in order to change the properties of the natural rubber itself, it has a large viscosity when blended with a filler. Increases and decreases processability. In addition, since a large amount of vinyl compound is introduced into the natural rubber molecular chain, the excellent physical properties of natural rubber (stress-strain curve in viscoelasticity, tensile test, etc.) are impaired.

  On the other hand, as a technique for improving the dispersibility of the filler with respect to the natural rubber, a method of producing a natural rubber master batch by mixing a natural rubber latex and a slurry solution in which the filler is previously dispersed in water is known. However, the rubber composition using the natural rubber masterbatch is not sufficient in terms of reinforcement, and there is still room for improvement in terms of wear resistance and fracture characteristics.

JP-A-5-287121 JP-A-6-329702 Japanese Patent Laid-Open No. 9-25468 JP 2000-319339 A JP 2002-138266 A JP 2002-348559 A

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to produce a rubber master batch capable of greatly improving the low loss property, wear resistance and fracture characteristics of the rubber composition, and production of the master batch It is to provide a method. Another object of the present invention is to use such a masterbatch, a rubber composition having a high affinity between a rubber component and a filler, a reinforcing property, a low loss property, an excellent wear resistance and a fracture property, The object is to provide a tire using the rubber composition.

  As a result of intensive investigations to achieve the above object, the present inventor mixed natural rubber latex and a slurry solution of a filler and coagulated, and added a polar group-containing compound to the obtained coagulated product to mechanical shear. In order to complete the present invention, it is found that by drying while applying force, a modified natural rubber masterbatch capable of significantly improving the low loss property, abrasion resistance and fracture characteristics of the rubber composition can be obtained. It came.

That is, the production method of the modified natural rubber masterbatch of the present invention is:
(i) a step of mixing a natural rubber latex and a slurry solution in which a filler is previously dispersed in water;
(ii) a step of coagulating the liquid mixture obtained in the step (i); and
(iii) A polar group-containing compound is added to the coagulated product obtained in the step (ii) and dried while applying mechanical shearing force, and the polar group-containing compound is graft-polymerized on the natural rubber molecules in the coagulated product. It is characterized by including the process to add.

  In the method for producing a modified natural rubber masterbatch of the present invention, the filler in the slurry solution has a volume average particle size (mv) of 25 μm or less and a 90 volume% particle size (D90) of 30 μm or less. It is preferable that the 24M4DBP oil absorption amount of the filler dried and recovered from the solution retains 93% or more of the 24M4DBP oil absorption amount before being dispersed in water.

In a preferred embodiment of the method for producing a modified natural rubber masterbatch of the present invention, the filler is carbon black, silica and the following general formula (I):
nM · xSiO _y · zH ₂ O (I)
[Wherein, M is a metal selected from the group consisting of aluminum, magnesium, titanium, calcium and zirconium, an oxide or hydroxide of these metals, and a hydrate thereof, or a carbonate of these metals. And n, x, y, and z are each an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10]. Is at least one selected from the group consisting of

  In another preferred embodiment of the method for producing a modified natural rubber masterbatch of the present invention, the polar group of the polar group-containing compound is an amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, Azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxycarbonyl group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, It is at least one selected from the group consisting of a tin-containing group and an alkoxysilyl group.

  In another preferred embodiment of the method for producing a modified natural rubber masterbatch of the present invention, the graft amount or addition amount of the polar group-containing compound is 0.01 to 5.0% by mass with respect to the rubber component in the coagulum.

  In another preferred embodiment of the method for producing a modified natural rubber masterbatch of the present invention, the natural rubber latex and / or the slurry solution further contains a surfactant.

  In another preferred embodiment of the method for producing a modified natural rubber masterbatch of the present invention, the drying is performed using a continuous kneader. Here, as the continuous kneader, a twin-screw kneading extruder is preferable.

  The modified natural rubber masterbatch of the present invention is manufactured by the above method, and the rubber composition of the present invention is characterized by using the modified natural rubber masterbatch. The tire of the invention is characterized in that the rubber composition is used for any of the tire members.

  According to the present invention, natural rubber latex and a slurry solution of a filler are mixed and coagulated, and a polar group-containing compound is added to the coagulated product, followed by drying while applying a mechanical shearing force. By modifying the molecule, it is possible to provide a modified natural rubber masterbatch in which the filler is highly dispersed in the rubber component. Further, by using the modified natural rubber masterbatch, it is possible to provide a rubber composition excellent in low loss property, wear resistance and fracture characteristics, and a tire using the rubber composition.

  The present invention is described in detail below. The method for producing a modified natural rubber masterbatch of the present invention comprises (i) a step of mixing a natural rubber latex and a slurry solution in which a filler is previously dispersed in water; (ii) obtained in the step (i). Solidifying the mixed liquid; and (iii) adding a polar group-containing compound to the coagulated product obtained in the step (ii) and drying it while applying a mechanical shearing force. It includes a step of graft polymerization or addition of a polar group-containing compound to a natural rubber molecule derived from rubber latex, and the modified natural rubber masterbatch of the present invention is manufactured by the method. Features.

  In the method for producing a modified natural rubber masterbatch of the present invention, natural rubber latex and a filler-containing slurry solution are mixed and coagulated, and then a polar group-containing compound is added to the coagulated product, and mechanical shearing force is applied. By drying, the polar group-containing compound is graft-polymerized or added to the natural rubber molecules in the coagulated product. Here, in the modified natural rubber masterbatch of the present invention, since the filler is masterbatched with the rubber component, the dispersibility of the filler in the rubber component is improved. In addition, since the polar group of the polar group-containing compound has excellent affinity for the filler, the modified natural rubber obtained by graft polymerization or addition of the polar group-containing compound to the natural rubber molecule in the coagulated product is not modified. Higher affinity for fillers than natural rubber. And in the modified natural rubber masterbatch of the present invention, due to the synergistic effect of the effect of making the rubber component and filler into a masterbatch and the effect of modifying the natural rubber molecules in the coagulum with a polar group-containing compound, The dispersibility of the filler with respect to the rubber component is greatly improved, and the uniformity is very high. Therefore, the modified natural rubber masterbatch of the present invention exhibits a sufficient reinforcing effect of the filler and is extremely excellent in wear resistance and fracture resistance, as well as greatly improving low heat buildup (low loss). . Further, by using the modified natural rubber masterbatch of the present invention, the fracture resistance, wear resistance and low loss property of the rubber composition can be greatly improved. Further, the rubber composition can be used for a tire, particularly a tire. By using this tread, it is possible to remarkably improve fracture resistance and wear resistance while greatly reducing rolling resistance.

  The natural rubber latex used in the modified natural rubber masterbatch of the present invention is not particularly limited, and examples thereof include field latex, ammonia-treated latex, centrifugal concentrated latex, deproteinized latex treated with a surfactant and an enzyme, and these. A combination or the like can be used.

  The slurry solution used for the modified natural rubber masterbatch of the present invention is obtained by dispersing a filler in water in advance. Here, the slurry solution can be produced by a known method. For example, a mixer such as a rotor / stator type high shear mixer, a high-pressure homogenizer, an ultrasonic homogenizer, or a colloid mill can be used. For example, the slurry solution can be prepared by putting water into a colloid mill, slowly dropping the filler while stirring, and then circulating the mixture with a surfactant in a homogenizer at a constant pressure and a constant temperature. . The pressure in this case is usually in the range of 10 to 1000 kPa, preferably in the range of 200 to 800 kPa. It is also possible to mix a filler and water in a certain ratio and introduce these mixed liquids from one end of an elongated conduit to produce a continuous stream of slurry having a homogeneous composition under conditions of vigorous hydraulic stirring. it can. In addition, the density | concentration of the filler in the said slurry solution has the preferable range of 0.5-30 mass% of a slurry solution, and the range of 1-15 mass% is still more preferable.

  In the slurry solution, the filler in the slurry solution preferably has a volume average particle size (mv) of 25 μm or less and a 90 volume% particle size (D90) of 30 μm or less, and the volume average particle size (mv) is More preferably, it is 20 μm or less and 90% by volume particle size (D90) is 25 μm or less, and the 24M4DBP oil absorption amount of the filler recovered by drying from the slurry solution is 93% or more of the 24M4DBP oil absorption amount before being dispersed in water. It is preferable to hold, more preferably 96% or more. Here, the 24M4DBP oil absorption is a value measured in accordance with ISO 6894, and the volume average particle size and 90% by volume particle size are determined using a laser diffraction type particle size distribution meter, with a water refractive index of 1.33, a filler. This is a value measured as a refractive index of 1.57. If the particle size (volume average particle size and 90% by volume particle size) of the filler in the slurry solution is too large, the dispersibility of the filler in the mixture of the natural rubber latex and the slurry solution deteriorates, and the reinforcing property and Wear resistance may deteriorate. In addition, if an excessive shear force is applied to the slurry solution in order to reduce the particle size, the filler structure is destroyed and the reinforcing property is lowered. Therefore, the 24M4DBP oil absorption amount of the filler recovered by drying from the slurry solution is It is preferable to hold 93% or more of the 24M4DBP oil absorption before being dispersed in water.

  The natural rubber latex and / or the slurry solution preferably further contains a surfactant from the viewpoint of improving the stability of the natural rubber latex. Here, examples of the surfactant include anionic, cationic, nonionic and amphoteric surfactants. Among these, anionic and nonionic surfactants are preferable. The addition amount of the surfactant is usually from 0.01 to 2% by mass, preferably from 0.02 to 1% by mass, based on the natural rubber latex or slurry solution.

  Examples of the filler used in the present invention include carbon black and inorganic filler, and examples of the inorganic filler include silica and an inorganic compound represented by the above general formula (I). These fillers may be used alone or in a combination of two or more.

Examples of the carbon black include GPF, FEF, SRF, HAF, ISAF, and SAF grades, and examples of the silica include wet silica, dry silica, and colloidal silica. Furthermore, the inorganic compound of the above formula (I) includes alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina; alumina monohydrate such as boehmite and diaspore (Al ₂ O ₃ .H ₂ O). Aluminum hydroxide [Al (OH) ₃ ] such as gibbsite and bayerite; aluminum carbonate [Al ₂ (CO ₃ ) ₃ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium oxide (MgO), magnesium carbonate ( MgCO ₃ ), talc (3MgO · 4SiO ₂ · H ₂ O), attapulgite (5MgO · 8SiO ₂ · 9H ₂ O), titanium white (TiO ₂ ), titanium black (TiO _2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca (OH) _2], magnesium aluminum oxide _{(MgO · Al 2 O 3)} , clay _{(Al 2 O 3 · 2SiO 2} ), kaolin _{(Al 2 O 3 · 2SiO 2} · 2 ₂ O), pyrophyllite _{(Al 2 O 3 · 4SiO 2} · H 2 O), bentonite _{(Al 2 O 3 · 4SiO 2} · 2H 2 O), aluminum silicate _{(Al 2 SiO 5, Al 4} · 3SiO 4・ 5H ₂ O etc.), magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), calcium silicate (Ca ₂ SiO ₄ etc.), aluminum calcium silicate (Al ₂ O ₃ · CaO · 2SiO ₂ etc.), Magnesium calcium oxide (CaMgSiO ₄ ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO (OH) ₂ .nH ₂ O], zirconium carbonate [Zr (CO ₃ ) ₂ ], various zeolites Examples thereof include crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals that correct electric charges. In the formula (I), M is preferably at least one selected from aluminum metal, aluminum oxide or hydroxide, hydrates thereof, and aluminum carbonate.

  As a mixing method of the natural rubber latex and the slurry solution, for example, the slurry solution is put in a blender mill and the natural rubber latex is dropped while stirring, or conversely, the natural rubber latex is stirred. A method of adding the slurry solution dropwise thereto can be given. Alternatively, a method of mixing a natural rubber latex stream and a slurry stream having a constant flow rate ratio under vigorous hydraulic stirring conditions may be used. Here, the blending ratio of the natural rubber in the natural rubber latex and the filler in the slurry solution is such that the filler in the slurry solution is 5 to 100 parts by mass with respect to 100 parts by mass of the rubber component in the natural rubber latex. It is preferable to mix | blend so that it may become a ratio of 10 to 70 mass parts, and it is still more preferable to mix | blend. If the blending amount of the filler is less than 5 parts by mass, sufficient reinforcement may not be obtained, and if it exceeds 100 parts by mass, the workability may be deteriorated.

  In the method for producing a modified natural rubber masterbatch of the present invention, the natural rubber latex and the slurry solution are mixed, and then the obtained mixed liquid is solidified. Here, the coagulation of the mixed solution is usually performed using a coagulant such as an acid such as formic acid or sulfuric acid, or a salt such as sodium chloride. However, coagulation may be achieved by mixing the natural rubber latex and the slurry solution without adding a coagulant. In this case, the coagulant may not be used.

  In the method for producing a modified natural rubber masterbatch of the present invention, as a final step, a polar group-containing compound is added to the coagulated product obtained by the above coagulation and dried while applying a mechanical shearing force. A polar group-containing compound is graft-polymerized or added to the rubber molecule to obtain a modified natural rubber masterbatch excellent in processability, reinforcement and low loss. Drying while applying a mechanical shearing force can be performed using a general kneader, but from the viewpoint of industrial productivity, it is preferable to use a screw-type continuous kneader, which rotates in the same direction or is different. It is more preferable to use a biaxial kneading extruder with direction rotation. As the screw-type continuous kneader, commercially available products can be used, for example, a Kobe Steel twin-screw kneading extruder can be used. In addition, it is preferable that the water | moisture content in the solidified material before drying is 10% or more. When the water content in the solidified product before drying is less than 10%, the improvement in the dispersibility of the filler in the drying process may be small.

  In the present invention, when the polar group-containing compound is graft-polymerized to the natural rubber molecule in the coagulated product, the polar group-containing compound preferably has a carbon-carbon double bond in the molecule. A monomer is preferred. On the other hand, when the polar group-containing compound is subjected to an addition reaction with the natural rubber molecule in the coagulated product, the polar group-containing compound preferably has a mercapto group in the molecule, and is preferably a polar group-containing mercapto compound.

  Here, when the polar group-containing compound is graft-polymerized to the natural rubber molecule in the coagulated product, the coagulated product and the polar group-containing compound (preferably the polar group-containing vinyl monomer) The polar group-containing compound can be introduced into the natural rubber molecules in the coagulated product by graft polymerization by adding a polymerization initiator together with the body and drying while applying a mechanical shearing force. In addition, when an addition reaction of a polar group-containing compound with a natural rubber molecule in a coagulated product, the coagulated product and a polar group-containing compound (preferably, a polar group-containing mercapto compound) are introduced into an apparatus that can be given mechanical shearing force. If necessary, add organic peroxide, etc., and dry while applying mechanical shearing force to add a polar group-containing compound to the double bond of the main chain of the natural rubber molecule in the coagulum Can be reacted.

  Specific examples of polar groups of the polar group-containing vinyl monomer suitable for graft polymerization to natural rubber molecules derived from the natural rubber latex in the coagulum include amino groups, imino groups, nitrile groups, ammonium groups. Imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxycarbonyl group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, nitrogen-containing Preferred examples include a heterocyclic group, an oxygen-containing heterocyclic group, a tin-containing group, and an alkoxysilyl group. These polar group-containing vinyl monomers may be used alone or in combination of two or more.

  Examples of the vinyl monomer containing an amino group include polymerizable monomers containing at least one amino group selected from primary, secondary and tertiary amino groups in one molecule. . Among the polymerizable monomers having an amino group, tertiary amino group-containing vinyl monomers such as dialkylaminoalkyl (meth) acrylate are particularly preferable. These amino group-containing vinyl monomers may be used alone or in a combination of two or more.

  Here, the primary amino group-containing vinyl monomers include acrylamide, methacrylamide, 4-vinylaniline, aminomethyl (meth) acrylate, aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, aminobutyl. Examples include (meth) acrylate.

  Secondary vinyl group-containing vinyl monomers include (1) anilinostyrene, β-phenyl-p-anilinostyrene, β-cyano-p-anilinostyrene, β-cyano-β-methyl. -p-anilinostyrene, β-chloro-p-anilinostyrene, β-carboxy-p-anilinostyrene, β-methoxycarbonyl-p-anilinostyrene, β- (2-hydroxyethoxy) carbonyl-p- Anilinostyrene such as anilinostyrene, β-formyl-p-anilinostyrene, β-formyl-β-methyl-p-anilinostyrene, α-carboxy-β-carboxy-β-phenyl-p-anilinostyrene (2) 1-anilinophenyl-1,3-butadiene, 1-anilinophenyl-3-methyl-1,3-butadiene, 1-anilinophenyl-3-chloro-1,3-butadiene, 3 -Anilinophenyl-2-methyl-1,3-butadiene, 1-a Linophenyl-2-chloro-1,3-butadiene, 2-anilinophenyl-1,3-butadiene, 2-anilinophenyl-3-methyl-1,3-butadiene, 2-anilinophenyl-3-chloro- Anilinophenylbutadienes such as 1,3-butadiene, (3) N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-methylolacrylamide, N- (4-anilinophenyl) methacrylamide, etc. N-mono substituted (meth) acrylamides and the like can be mentioned.

  Furthermore, examples of the tertiary amino group-containing vinyl monomer include N, N-disubstituted aminoalkyl (meth) acrylate and N, N-disubstituted aminoalkyl (meth) acrylamide.

  Examples of the N, N-disubstituted aminoalkyl (meth) acrylate include N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) Acrylate, N, N-dimethylaminobutyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N-diethylaminobutyl (meth) acrylate, N-methyl -N-ethylaminoethyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-dibutylaminopropyl (meth) acrylate, N, N-dibutylaminobutyl (meth) acrylate, N, N-dihexylaminoethyl (meth) acrylate, N, N-dioctyl Aminoethyl (meth) acrylate, esters of acrylic acid or methacrylic acid such as acryloyl morpholine and the like. Among these, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dioctylaminoethyl (meth) Particularly preferred are acrylates, N-methyl-N-ethylaminoethyl (meth) acrylate, and the like.

  Examples of the N, N-disubstituted aminoalkyl (meth) acrylamide include N, N-dimethylaminomethyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl ( (Meth) acrylamide, N, N-dimethylaminobutyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, N, N-diethylaminobutyl (meth) acrylamide, N -Methyl-N-ethylaminoethyl (meth) acrylamide, N, N-dipropylaminoethyl (meth) acrylamide, N, N-dibutylaminoethyl (meth) acrylamide, N, N-dibutylaminopropyl (meth) acrylamide, N, N-dibutylaminobutyl (meth) acrylamide, N, N-dihexylaminoethyl ( Data) acrylamide, N, N-dihexyl-aminopropyl (meth) acrylamide, N, N-acrylamide compounds such as dioctyl aminopropyl (meth) acrylamide or methacrylamide compounds and the like. Among these, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, N, N-dioctylaminopropyl (meth) acrylamide and the like are particularly preferable.

  Examples of the vinyl monomer containing a nitrile group include (meth) acrylonitrile and vinylidene cyanide. These nitrile group-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer containing a hydroxyl group include polymerizable monomers having at least one primary, secondary and tertiary hydroxyl group in one molecule. Examples of such monomers include hydroxyl group-containing unsaturated carboxylic acid monomers, hydroxyl group-containing vinyl ether monomers, hydroxyl group-containing vinyl ketone monomers, and the like. Here, specific examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meta ) Acrylate, 3-hydroxybutyl (meth) acrylate, hydroxyalkyl (meth) acrylates such as 4-hydroxybutyl (meth) acrylate; polyalkylene glycols such as polyethylene glycol and polypropylene glycol (the number of alkylene glycol units is, for example, 2 To 23) mono (meth) acrylates; N-hydroxymethyl (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, N, N-bis (2-hydroxymethyl) (meth) acrylamide Hydroxyl group-containing unsaturated amides such as o- Contains hydroxyl groups such as loxystyrene, m-hydroxystyrene, p-hydroxystyrene, o-hydroxy-α-methylstyrene, m-hydroxy-α-methylstyrene, p-hydroxy-α-methylstyrene, p-vinylbenzyl alcohol And vinyl aromatic compounds. Among these, hydroxyl group-containing unsaturated carboxylic acid monomers, hydroxyalkyl (meth) acrylates, and hydroxyl group-containing vinyl aromatic compounds are preferable, and hydroxyl group-containing unsaturated carboxylic acid monomers are particularly preferable. Here, examples of the hydroxyl group-containing unsaturated carboxylic acid-based monomer include esters such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, amides, and anhydrides. Among these, Particularly preferred are esters such as acrylic acid and methacrylic acid. These hydroxyl group-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer containing a carboxyl group include unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, tetraconic acid, cinnamic acid; phthalic acid, succinic acid, adipic acid, etc. Non-polymerizable polyvalent carboxylic acids and free carboxyl group-containing esters such as monoesters of hydroxyl-containing unsaturated compounds such as (meth) allyl alcohol and 2-hydroxyethyl (meth) acrylate, and salts thereof It is done. Of these, unsaturated carboxylic acids are particularly preferred. These carboxyl group-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer containing an epoxy group include (meth) allyl glycidyl ether, glycidyl (meth) acrylate, and 3,4-oxycyclohexyl (meth) acrylate. These epoxy group-containing vinyl monomers may be used alone or in combination of two or more.

  In the vinyl monomer containing the nitrogen-containing heterocyclic group, the nitrogen-containing heterocyclic ring includes pyrrole, histidine, imidazole, triazolidine, triazole, triazine, pyridine, pyrimidine, pyrazine, indole, quinoline, purine, phenazine, Examples include pteridine and melamine. The nitrogen-containing heterocycle may contain other heteroatoms in the ring. Here, as a vinyl monomer containing a pyridyl group as a nitrogen-containing heterocyclic group, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 5-methyl-2-vinylpyridine, 5-ethyl- 2-vinylpyridine and the like can be mentioned, among which 2-vinylpyridine, 4-vinylpyridine and the like are particularly preferable. These nitrogen-containing heterocyclic group-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer having a tin-containing group include allyltri-n-butyltin, allyltrimethyltin, allyltriphenyltin, allyltri-n-octyltin, (meth) acryloxy-n-butyltin, (meth) acryloxy Tin-containing monomers such as trimethyltin, (meth) acryloxytriphenyltin, (meth) acryloxy-n-octyltin, vinyltri-n-butyltin, vinyltrimethyltin, vinyltriphenyltin, vinyltri-n-octyltin Can be mentioned. These tin-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer containing the alkoxysilyl group include (meth) acryloxymethyltrimethoxysilane, (meth) acryloxymethylmethyldimethoxysilane, (meth) acryloxymethyldimethylmethoxysilane, (meth) acryloxy. Methyltriethoxysilane, (meth) acryloxymethylmethyldiethoxysilane, (meth) acryloxymethyldimethylethoxysilane, (meth) acryloxymethyltripropoxysilane, (meth) acryloxymethylmethyldipropoxysilane, (meth) Acryloxymethyldimethylpropoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acryloxy Propyltriethoxy Lan, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyldimethylethoxysilane, γ- (meth) acryloxypropyltripropoxysilane, γ- (meth) acryloxypropylmethyldipropoxy Silane, γ- (meth) acryloxypropyldimethylpropoxysilane, γ- (meth) acryloxypropylmethyldiphenoxysilane, γ- (meth) acryloxypropyldimethylphenoxysilane, γ- (meth) acryloxypropylmethyldibenzyl Examples include loxysilane, γ- (meth) acryloxypropyldimethylbenzyloxysilane, trimethoxyvinylsilane, triethoxyvinylsilane, 6-trimethoxysilyl-1,2-hexene, and p-trimethoxysilylstyrene. These alkoxysilyl group-containing vinyl monomers may be used alone or in a combination of two or more.

  The polymerization initiator used for graft polymerization of the polar group-containing compound onto the natural rubber molecule in the coagulated product is not particularly limited, and various polymerization initiators for emulsion polymerization can be used. There is no particular restriction. Examples of commonly used polymerization initiators include benzoyl peroxide, hydrogen peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, 2,2-azobisisobutyronitrile, 2,2-azobis (2-diaminopropane) hydrochloride, 2,2-azobis (2-diaminopropane) dihydrochloride, 2,2-azobis (2,4-dimethylvaleronitrile), potassium persulfate, sodium persulfate And ammonium persulfate. In order to lower the polymerization temperature, it is preferable to use a redox polymerization initiator. Examples of the reducing agent to be combined with the peroxide in the redox polymerization initiator include tetraethylenepentamine, mercaptans, acidic sodium sulfite, reducing metal ions, ascorbic acid and the like. A preferred combination of a peroxide and a reducing agent in the redox polymerization initiator includes a combination of tert-butyl hydroperoxide and tetraethylenepentamine.

  In order to improve the low loss and wear resistance without reducing the processability of the rubber composition using the modified natural rubber masterbatch of the present invention, a small amount and a uniform amount of the polar group-containing compound are contained in each natural rubber molecule. Therefore, the amount of the polymerization initiator added is preferably in the range of 1 to 100 mol%, more preferably in the range of 10 to 100 mol% with respect to the polar group-containing compound.

  On the other hand, specific examples of polar groups of polar group-containing mercapto compounds suitable for addition reaction with natural rubber molecules derived from natural rubber latex in the coagulum include amino groups, imino groups, nitrile groups, ammonium groups, Imido group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxycarbonyl group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, nitrogen-containing complex Preferred examples include a ring group, an oxygen-containing heterocyclic group, a tin-containing group, and an alkoxysilyl group. These polar group-containing mercapto compounds may be used alone or in combination of two or more.

  Examples of the mercapto compound containing an amino group include mercapto compounds having at least one amino group selected from primary, secondary and tertiary amino groups in one molecule. Among the mercapto compounds having an amino group, a tertiary amino group-containing mercapto compound is particularly preferable. Here, as the primary amino group-containing mercapto compound, 4-mercaptoaniline, 2-mercaptoethylamine, 2-mercaptopropylamine, 3-mercaptopropylamine, 2-mercaptobutylamine, 3-mercaptobutylamine, 4-mercaptobutylamine Etc. The secondary amino group-containing mercapto compounds include N-methylaminoethanethiol, N-ethylaminoethanethiol, N-methylaminopropanethiol, N-ethylaminopropanethiol, N-methylaminobutanethiol, N- And ethylaminobutanethiol. Further, the tertiary amino group-containing mercapto compounds include N, N-dimethylaminoethanethiol, N, N-diethylaminoethanethiol, N, N-dimethylaminopropanethiol, N, N-diethylaminopropanethiol, N, N N, N-disubstituted aminoalkyl mercaptans such as -dimethylaminobutanethiol and N, N-diethylaminobutanethiol. Among these amino group-containing mercapto compounds, 2-mercaptoethylamine, N, N-dimethylaminoethanethiol and the like are preferable. These amino group-containing mercapto compounds may be used alone or in combination of two or more.

  Examples of the mercapto compound having a nitrile group include 2-mercaptopropane nitrile, 3-mercaptopropane nitrile, 2-mercaptobutane nitrile, 3-mercaptobutane nitrile, 4-mercaptobutane nitrile, and the like. These nitrile group-containing mercapto compounds May be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the mercapto compound containing a hydroxyl group include mercapto compounds having at least one primary, secondary, or tertiary hydroxyl group in one molecule. Specific examples of the hydroxyl group-containing mercapto compound include 2-mercaptoethanol, 3-mercapto-1-propanol, 3-mercapto-2-propanol, 4-mercapto-1-butanol, 4-mercapto-2-butanol, 3 -Mercapto-1-butanol, 3-mercapto-2-butanol, 3-mercapto-1-hexanol, 3-mercapto-1,2-propanediol, 2-mercaptobenzyl alcohol, 2-mercaptophenol, 4-mercaptophenol, etc. Among these, 2-mercaptoethanol and the like are preferable. These hydroxyl group-containing mercapto compounds may be used alone or in a combination of two or more.

  Examples of the mercapto compound containing a carboxyl group include mercaptoacetic acid, mercaptopropionic acid, thiosalicylic acid, mercaptomalonic acid, mercaptosuccinic acid, mercaptobenzoic acid and the like. Among these, mercaptoacetic acid is preferred. These carboxyl group-containing mercapto compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the mercapto compound containing the nitrogen-containing heterocyclic group, the nitrogen-containing heterocyclic ring includes pyrrole, histidine, imidazole, triazolidine, triazole, triazine, pyridine, pyrimidine, pyrazine, indole, quinoline, purine, phenazine, pteridine, melamine. Etc. The nitrogen-containing heterocycle may contain other heteroatoms in the ring. Here, as a mercapto compound containing a pyridyl group as a nitrogen-containing heterocyclic group, 2-mercaptopyridine, 3-mercaptopyridine, 4-mercaptopyridine, 5-methyl-2-mercaptopyridine, 5-ethyl-2-mercapto Examples of mercapto compounds containing other nitrogen-containing heterocyclic groups include 2-mercaptopyrimidine, 2-mercapto-5-methylbenzimidazole, 2-mercapto-1-methylimidazole, and 2-mercapto. Examples include benzimidazole and 2-mercaptoimidazole. Among these, 2-mercaptopyridine and 4-mercaptopyridine are preferable. These nitrogen-containing heterocyclic group-containing mercapto compounds may be used alone or in combination of two or more.

  Examples of the mercapto compound having a tin-containing group include 2-mercaptoethyltri-n-butyltin, 2-mercaptoethyltrimethyltin, 2-mercaptoethyltriphenyltin, 3-mercaptopropyltri-n-butyltin, and 3-mercaptopropyl. Mention may be made of tin-containing mercapto compounds such as trimethyltin and 3-mercaptopropyltriphenyltin. These tin-containing mercapto compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the mercapto compound containing an alkoxysilyl group include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, and 2-mercaptoethyltrimethoxysilane. Examples include silane, 2-mercaptoethyltriethoxysilane, mercaptomethylmethyldiethoxysilane, mercaptomethyltrimethoxysilane, and the like. Among these, 3-mercaptopropyltrimethoxysilane is preferable. These alkoxysilyl group-containing mercapto compounds may be used alone or in a combination of two or more.

  The above-mentioned coagulated product and polar group-containing compound are charged into a device that can be given mechanical shearing force, and dried while applying mechanical shearing force in the device, so that the natural rubber molecule in the coagulated product contains the polar group. The natural rubber can be modified by graft copolymerization or addition reaction of the compound. In this case, the modification reaction of the natural rubber may be carried out by heating, preferably 30 to 160 ° C, more preferably 50 to 130 ° C, so that the natural rubber is modified with sufficient reaction efficiency. can do.

  In the modified natural rubber masterbatch of the present invention, the graft amount or addition amount of the polar group-containing compound is preferably in the range of 0.01 to 5.0% by mass with respect to the rubber component derived from the natural rubber latex in the coagulum, 0.02 The range of -3.0 mass% is still more preferable, and the range of 0.03-2.0 mass% is still more preferable. If the grafting amount or addition amount of the polar group-containing compound is less than 0.01% by mass, the low loss and wear resistance of the rubber composition may not be sufficiently improved. Moreover, if the grafting amount or addition amount of the polar group-containing compound exceeds 5.0% by mass, the physical properties inherent to natural rubber such as viscoelasticity and SS characteristics (stress-strain curve in a tensile tester) are greatly changed. In addition, the physical properties inherent to natural rubber are impaired, and the processability of the rubber composition may be greatly deteriorated.

  In addition to the natural rubber latex, slurry solution, polar group-containing compound and surfactant, additives such as vulcanizing agents, anti-aging agents, coloring agents, and dispersing agents are used in the modified natural rubber masterbatch of the present invention. be able to.

  The rubber composition of the present invention is characterized by using the above-mentioned modified natural rubber masterbatch. Since the above-mentioned modified natural rubber masterbatch is excellent in uniformity as described above, the rubber composition of the present invention is uniform. Excellent in low loss, wear resistance and fracture characteristics. In addition to the modified natural rubber masterbatch, the rubber composition of the present invention further includes a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a scorch preventing agent, zinc white, stearic acid, and a silane coupling agent. The compounding agents usually used in the rubber industry, etc. can be appropriately selected and blended within a range not impairing the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition of the present invention can be produced by kneading, adding, extruding, etc. various compounding agents appropriately selected as necessary to a modified natural rubber masterbatch.

  The tire of the present invention is characterized in that the rubber composition is used for any of tire members. Here, in the tire of the present invention, it is particularly preferable to use the rubber composition as a tread rubber, and a tire using the rubber composition as a tread has high fracture resistance and wear resistance, and low rolling resistance. Excellent fuel economy. In addition, as gas with which the tire of the present invention is filled, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen is exemplified.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Preparation of carbon black slurry solution)
A colloid mill with a rotor diameter of 50 mm was charged with 1425 g of deionized water and 75 g of carbon black (N110), and stirred for 10 minutes at a rotor-stator gap of 1 mm and a rotational speed of 1500 rpm. 0.05% Kao Demol N] was added and circulated three times under a pressure of 500 kPa using a pressure homogenizer to prepare a carbon black slurry solution. The 24M4DBP oil absorption of the carbon black used was measured in accordance with ISO 6894. The 24M4DBP oil absorption before being dispersed in water was 98 mL / 100 g, and the 24M4DBP oil absorption after drying and recovery from the slurry solution was 96 mL / 100 g. 100 g (retention rate: 98.0%). The particle size distribution of carbon black in the slurry solution was measured as a water refractive index 1.33 and a particle refractive index 1.57 using a laser diffraction particle size distribution analyzer [MICROTRAC FRA type] immediately after dispersion. (Mv) was 15.1 μm and 90 volume% particle size (D90) was 19.5 μm.

(Coagulation process 1)
In a homomixer, natural rubber latex diluted with deionized water with natural rubber latex and adjusted to a rubber content of 20% and the above carbon black slurry solution were mixed with 50 parts by weight of carbon black with respect to 100 parts by mass of the rubber component. It added so that it might become a mass part, formic acid was added until it was set to pH = 4.7, stirring, and it was made to coagulate | solidify. Next, the obtained solidified product 1 was recovered and washed with water, and dehydrated until the water content was about 40%. The amount of carbon black in the solidified product 1 was 50 parts by mass with respect to 100 parts by mass of natural rubber.

<Production Example 1>
After determining the dry matter content of the solidified product 1, 900 g of the solidified product 1 in terms of dry matter, 3.0 g of N, N-diethylaminoethyl methacrylate, 1.2 g of tert-butyl hydroperoxide (t-BHPO) Was kneaded in a kneader at room temperature for 2 minutes at 30 rpm to be uniformly dispersed. Next, while uniformly adding 1.2 g of tetraethylenepentamine (TEPA) to the obtained mixture, a twin-screw kneading extruder made of Kobe Steel [same-direction rotating screw diameter = 30 mm, L / D = 35, three vent holes The modified modified natural rubber masterbatch A was obtained by extrusion while applying mechanical shearing force at a barrel temperature of 120 ° C. and a rotation speed of 100 rpm.

  From the mass of the resulting modified natural rubber master batch A, the conversion rate of N, N-diethylaminoethyl methacrylate added as a monomer was 76%. Further, when the modified natural rubber masterbatch A was extracted with petroleum ether and further extracted with a 2: 1 mixed solvent of acetone and methanol, homopolymer separation was attempted. As a result, the homopolymer was detected at 8% of the charged monomer amount. It was done. Therefore, the graft amount of N, N-diethylaminoethyl methacrylate in the modified natural rubber masterbatch A is 0.35% by mass with respect to the natural rubber in the coagulum.

<Production Examples 2-5>
Instead of 3.0 g of N, N-diethylaminoethyl methacrylate, 2.1 g of 2-hydroxyethyl methacrylate was added in Production Example 2, 1.7 g of 2-vinylpyridine was added in Production Example 3, and 1.7 g of acrylonitrile was added in Production Example 4. In Production Example 5, 2.8 g of methacrylamide was added, and modified natural rubber master batches B to E were obtained in the same manner as in Production Example 1 except that. Further, in the same manner as in the modified natural rubber master batch A, the graft amount of the polar group-containing compound added as a monomer in the modified natural rubber master batches B to E was analyzed, and the results shown in Table 1 were obtained.

<Production Examples 6-7>
Instead of adding tert-butyl hydroperoxide (t-BHPO) and tetraethylenepentamine (TEPA), instead of 3.0 g of N, N-diethylaminoethyl methacrylate, in Production Example 6, N, N-dimethylaminoethanethiol was used. 1.7 g was added, 1.8 g of 4-mercaptopyridine was added in Production Example 7, and modified natural rubber master batches F and G were obtained in the same manner as in Production Example 1 except that. Moreover, the addition amount of the polar group-containing compound added as a monomer in the obtained modified natural rubber master batches F and G was analyzed using a pyrolysis gas chromatograph-mass spectrometer, and the results shown in Table 1 were obtained. It was.

<Production Example 8>
A natural rubber masterbatch H was obtained in the same manner as in Production Example 1 except that N, N-diethylaminoethyl methacrylate was not added.

(Preparation of silica slurry solution)
Add 1425 g of deionized water and 75 g of wet silica [Nippal Silica Co., Ltd., nip seal LP] to a colloid mill with a rotor diameter of 50 mm. Prepared. The 24M4DBP oil absorption of the silica used was measured according to ISO 6894. The 24M4DBP oil absorption before being dispersed in water was 150 mL / 100 g, and the 24M4DBP oil absorption after drying and recovery from the slurry solution was 144 mL / 100 g. (Retention rate: 96.0%). Further, when the particle size distribution of silica in the slurry solution was measured as a water refractive index 1.33 and a particle refractive index 1.57 using a laser diffraction particle size distribution analyzer [MICROTRAC FRA type] immediately after dispersion, the volume average particle size ( mv) was 13.2 μm and the 90% by volume particle size (D90) was 24.0 μm.

(Coagulation process 2)
In a homomixer, natural rubber latex diluted with deionized water with natural rubber latex and adjusted to a rubber content of 20% and the silica slurry solution are mixed with 50 parts by mass of silica with respect to 100 parts by mass of the rubber component. The formic acid was added to pH = 4.7 with stirring and solidified. Next, the obtained solidified product 2 was recovered and washed with water, and dehydrated until the water content was about 40%. The amount of silica in the coagulum 2 was 50 parts by mass with respect to 100 parts by mass of natural rubber.

<Production Example 9>
After determining the dry matter content of the coagulum 2, 900 g of the coagulum 2 in terms of dry matter, 3.0 g of N, N-diethylaminoethyl methacrylate, 1.2 g of tert-butyl hydroperoxide (t-BHPO) Was kneaded in a kneader at room temperature for 2 minutes at 30 rpm to be uniformly dispersed. Next, while adding 1.2 g of tetraethylenepentamine (TEPA) uniformly to the resulting mixture, a twin-screw kneading extruder made by Kobe Steel [co-rotating screw diameter = 30 mm, L / D = 35, three vent holes The modified modified natural rubber masterbatch I was obtained by extrusion while applying mechanical shearing force at a barrel temperature of 120 ° C. and a rotation speed of 100 rpm. Further, in the same manner as in the modified natural rubber master batch A, the graft amount of the polar group-containing compound added as a monomer in the modified natural rubber master batch I was analyzed, and the results shown in Table 1 were obtained.

<Production Examples 10-15>
Instead of 3.0 g of N, N-diethylaminoethyl methacrylate, 2.1 g of 2-hydroxyethyl methacrylate was added in Production Example 10, 1.7 g of 2-vinylpyridine was added in Production Example 11, and 1.4 g of methacrylic acid was added in Production Example 12. In Production Example 13, 1.7 g of acrylonitrile was added, 2.3 g of glycidyl methacrylate was added in Production Example 14, 2.8 g of methacrylamide was added in Production Example 15, and the modified natural rubber master batch was prepared in the same manner as in Production Example 9 above. JO were obtained. Further, in the same manner as in the modified natural rubber master batch A, the graft amount of the polar group-containing compound added as a monomer in the modified natural rubber master batches J to O was analyzed, and the results shown in Table 1 were obtained.

<Production Examples 16 to 20>
Instead of adding tert-butyl hydroperoxide (t-BHPO) and tetraethylenepentamine (TEPA), instead of 3.0 g of N, N-diethylaminoethyl methacrylate, in Production Example 16, N, N-dimethylaminoethanethiol was used. 1.7 g was added, 1.8 g of 4-mercaptopyridine was added in Production Example 17, 1.3 g of mercaptoethanol was added in Production Example 18, 1.5 g of mercaptoacetic acid was added in Production Example 19, and 3-mercaptopropyltrimethoxy was added in Production Example 20. Modified natural rubber master batches P to T were obtained in the same manner as in Production Example 9 except that 3.3 g of silane was added. Moreover, the amount of addition of the polar group-containing compound added as a monomer in the obtained modified natural rubber master batches P to T was analyzed using a pyrolysis gas chromatograph-mass spectrometer, and the results shown in Table 1 were obtained. It was.

<Production Example 21>
A natural rubber masterbatch U was obtained in the same manner as in Production Example 9 except that N, N-diethylaminoethyl methacrylate was not added.

  Next, a rubber composition having the formulation shown in Table 2 was prepared by kneading with a plast mill, and the Mooney viscosity, tensile strength (Tb), tan δ, and abrasion resistance were measured for the rubber composition by the following methods. Measured and evaluated. The results of the rubber composition according to Formula 1 are shown in Table 3, and the results of the rubber composition according to Formula 2 are shown in Table 4.

(1) Mooney viscosity The Mooney viscosity ML _{1 + 4} (130 ° C.) of the rubber composition was measured at 130 ° C. according to JIS K6300-1994.

(2) Tensile strength The vulcanized rubber obtained by vulcanizing the rubber composition at 145 ° C for 33 minutes was subjected to a tensile test according to JIS K6301-1995, and the tensile strength (Tb) was measured. . It shows that fracture resistance is so favorable that tensile strength is large.

(3) tanδ
Using a viscoelasticity measuring device [manufactured by Rheometrics Co., Ltd.] for the vulcanized rubber obtained by vulcanizing the rubber composition at 145 ° C. for 33 minutes, loss tangent (tan δ) at a temperature of 50 ° C., a strain of 5%, and a frequency of 15 Hz. ) Was measured. It shows that it is excellent in low-loss property, so that tan-delta is small.

(4) Abrasion resistance For the vulcanized rubber obtained by vulcanizing the above rubber composition at 145 ° C. for 33 minutes, the wear amount at a slip rate of 60% at room temperature was measured using a Lambone type abrasion tester. In Table 3, the reciprocal of the amount of wear of Comparative Example 1 was set to 100, and in Table 4, the reciprocal of the amount of wear of Comparative Example 2 was set to 100, and each index was displayed. The larger the index value, the smaller the wear amount and the better the wear resistance.

* 1 The types of master batch used are shown in Table 3 and Table 4.
* 2 Degussa, “Si69”, bis (3-triethoxysilylpropyl) tetrasulfide.
* 3 N- (1,3-Dimethylbutyl) -N'-phenyl-p-phenylenediamine.
* 4 N-cyclohexyl-2-benzothiazylsulfenamide.
* 5 N-t-butyl-2-benzothiazylsulfenamide.

From the comparison between Examples and Comparative Examples in Tables 3 and 4, a polar group-containing compound was added to the coagulated product, dried while applying mechanical shearing force, and the natural rubber molecule in the coagulated product contained a polar group. It can be seen that the use of a modified natural rubber masterbatch in which a compound is graft-polymerized or added can greatly improve the fracture characteristics, low loss and wear resistance of the rubber composition.

Claims (11)

(i) a step of mixing a natural rubber latex and a slurry solution in which a filler is previously dispersed in water;
(ii) a step of coagulating the liquid mixture obtained in the step (i); and
(iii) A polar group-containing compound is added to the coagulated product obtained in the step (ii) and dried while applying mechanical shearing force, and the polar group-containing compound is graft-polymerized on the natural rubber molecules in the coagulated product. A method for producing a modified natural rubber masterbatch comprising a step of adding.   The filler in the slurry solution has a volume average particle size (mv) of 25 μm or less and a 90% by volume particle size (D90) of 30 μm or less, and the 24M4DBP oil absorption of the filler collected by drying from the slurry solution is: The method for producing a modified natural rubber masterbatch according to claim 1, wherein 93% or more of the 24M4DBP oil absorption before being dispersed in water is maintained. The filler is carbon black, silica and the following general formula (I):
nM · xSiO _y · zH ₂ O (I)
[Wherein, M is a metal selected from the group consisting of aluminum, magnesium, titanium, calcium and zirconium, an oxide or hydroxide of these metals, and a hydrate thereof, or a carbonate of these metals. And n, x, y, and z are each an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10]. The method for producing a modified natural rubber masterbatch according to claim 1 or 2, wherein the method is at least one selected from the group consisting of:   The polar group of the polar group-containing compound is an amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxy It is at least one selected from the group consisting of a carbonyl group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, a nitrogen-containing heterocyclic group, an oxygen-containing heterocyclic group, a tin-containing group, and an alkoxysilyl group. The method for producing a modified natural rubber masterbatch according to claim 1.   The method for producing a modified natural rubber masterbatch according to claim 1, wherein the grafting amount or addition amount of the polar group-containing compound is 0.01 to 5.0 mass% with respect to the rubber component in the coagulated product.   The method for producing a modified natural rubber masterbatch according to claim 1, wherein the natural rubber latex and / or the slurry solution further contains a surfactant.   The method for producing a modified natural rubber masterbatch according to claim 1, wherein the drying is performed using a continuous kneader.   The method for producing a modified natural rubber masterbatch according to claim 7, wherein the continuous kneader is a twin-screw kneading extruder.   A modified natural rubber masterbatch produced by the method according to claim 1.   A rubber composition using the modified natural rubber masterbatch according to claim 9.   A tire, wherein the rubber composition according to claim 10 is used for any tire member.