WO2010143633A1

WO2010143633A1 - Rubber composition and tire obtained using same

Info

Publication number: WO2010143633A1
Application number: PCT/JP2010/059706
Authority: WO
Inventors: 基之間宮
Original assignee: 株式会社ブリヂストン
Priority date: 2009-06-10
Filing date: 2010-06-08
Publication date: 2010-12-16

Abstract

Provided is a rubber composition which comprises natural rubber and, as a reinforcing filler, carbon black and/or silica and which has been regulated so as to satisfy relationship (1): -30ºC tanδ/60ºC tanδ > -1026.5Ln(x) + 10256 (1) wherein x = CTAB×A, where CTAB is the specific surface area (m²/g) of the reinforcing filler as determined through cetyltrimethylammonium bromide adsorption in accordance with ISO 6810, A is the amount in parts by mass of the reinforcing filler per 100 parts by mass of the natural rubber, and x is a number in the range of 2,500-13,000; Ln(x) means the natural logarithm of x; and tanδ means the loss tangent of the vulcanized rubber composition. Also provided is a tire which includes a tire member obtained from the rubber composition. The rubber composition gives a tire combining low heat buildup with wear resistance, in particular, a large tire such as a tire for off-road vehicles. The tire, which includes a tire member obtained from the rubber composition, has such performances.

Description

Rubber composition and tire using the same

The present invention relates to a rubber composition and a tire using the rubber composition. More specifically, the present invention relates to a rubber composition that provides a large tire such as a tire for low heat generation and wear resistance, particularly an off-the-road tire, and a tire member such as tread rubber or case rubber. It relates to a tire having the above performance.

In recent years, demands for reducing the fuel consumption of automobiles are becoming more severe in connection with the movement of global carbon dioxide emission regulations due to the social demand for energy saving and the increasing interest in environmental problems. In order to meet such demands, tires with low heat build-up with reduced rolling resistance have been demanded. In particular, heavy duty pneumatic tires used for trucks, buses and the like are required to have further improved heat generation. Further, in a large tire such as an off-the-road tire, the tread has a large volume, so that the internal rubber is likely to store heat and deteriorates remarkably. Therefore, low heat generation (low rolling resistance) and wear resistance of the tread rubber are required.
As a technique for reducing the rolling resistance of the tire, although a technique by optimizing the tire structure has been studied, the most common technique is to use a material having lower heat generation as the rubber composition. In general, in order to improve low heat buildup, it is preferable to suppress deformation of the tread rubber and lower tan δ in a high temperature range.

Especially for off-the-road tires, conventionally, a synthetic rubber component such as styrene-butadiene copolymer (SBR) has been used in the tread rubber composition in order to improve wear resistance. It has been improved. It has also been proposed to add a modified conjugated diene polymer such as a modified styrene-butadiene copolymer in order to improve low heat build-up. However, if the amount of the modified conjugated diene polymer is excessively increased, the wear resistance cannot be sufficiently improved, and the fracture resistance is deteriorated.

Until now, as a method of obtaining a low heat-generating rubber composition, improvement of a reinforcing filler and improvement of a rubber component have been performed.
Conventionally, carbon black has been used as a reinforcing filler for rubber. This is because carbon black can impart high wear resistance to the rubber composition. When trying to reduce heat generation, there are methods such as reducing the carbon black filling amount and using a large particle size, but rolling resistance is improved when using a large particle size carbon black. Inevitably, wear resistance is reduced. On the other hand, in order to improve the wear resistance, carbon black is atomized, the filling amount is increased, or the carbon black is made to have a high structure or have pores, thereby strengthening the interaction with the polymer and increasing the resistance. Although wear resistance is improved, there is a problem that the rolling resistance of the tire increases. Therefore, in order to solve these problems, a rubber composition in which carbon black having colloidal characteristics in a specific relationship with natural rubber and / or diene-based synthetic rubber has been proposed.

Silica is known as a filler to improve low heat build-up (for example, Patent Documents 1 to 4), but silica tends to aggregate particles and has wettability with rubber. Inferior, not well dispersed in rubber. If the silica is not sufficiently dispersed in the rubber, the rubber composition has a high Mooney viscosity, and there is a problem that the processability such as extrusion is poor.

On the other hand, as a method for improving the rubber component, many technical developments have been made on modified rubbers that interact with fillers such as carbon black and silica. For synthetic rubber, a method of modifying the polymerization active terminal of a conjugated diene polymer with an alkoxysilane derivative containing a functional group that interacts with a filler has been proposed as an effective method (for example, Patent Documents 5 and 6). . As for natural rubber, modified natural rubber obtained by graft-polymerizing polar group-containing monomers to natural rubber molecules in natural rubber latex improves affinity with fillers, low heat buildup and wear resistance. A technique for improving the above has been proposed (for example, Patent Document 7). Furthermore, in order to improve the dispersibility of the filler, a technique of blending a rubber-filler coupling agent having a specific structure into a rubber composition (for example, Patent Document 8), a diene rubber and a filler A rubber composition having low heat buildup and wear resistance obtained by adding a vulcanizing agent or a vulcanization accelerator to a heat treated rubber obtained by heat treatment under specific conditions after mixing (for example, Patent Document 9) Has been proposed.
However, recently, it has been required to further improve the low heat buildup and wear resistance of the tread rubber.

JP-A-6-248116 Japanese Patent Laid-Open No. 7-70369 JP-A-8-245838 JP-A-3-252431 JP 2006-37046 A Japanese Examined Patent Publication No. 6-53763 International Publication No. 2004/106397 Pamphlet US Patent Application Publication No. 2007/0161756 JP 2008-156548 A

The present invention has been made under such circumstances, and a rubber composition that provides a large tire such as a tire having low heat build-up and wear resistance, particularly an off-the-road tire, and a tire member using the rubber composition. It is an object of the present invention to provide a tire having the above performance.

In order to obtain a tire having both low heat buildup and wear resistance, particularly a large tire such as an off-the-road tire, a rubber composition excellent in low heat buildup and wear resistance is required. Paying attention to the importance of selecting the type of rubber component and the type of reinforcing filler together with the technology for highly dispersing reinforcing fillers, the following findings were obtained as a result of repeated research. .
Many experiments were conducted to achieve both low heat buildup and wear resistance of tires, particularly large tires such as off-the-road tires. Natural rubber was used as the rubber component, and carbon black and / or silica was used as the reinforcing filler. In the rubber composition, the total surface area of the reinforcing filler and the dispersibility of the reinforcing filler are important, that is, the dispersibility of the reinforcing filler is good at a specific total surface area of the reinforcing filler. It was found that the low heat buildup of the rubber composition is improved, the wear resistance is improved if the total surface area of the reinforcing filler is large and the dispersibility of the reinforcing filler is good.
Furthermore, the inventors have conducted various experimental studies on indices that can universally evaluate the dispersibility of the reinforcing filler at a specific total surface area of the reinforcing filler. In order to obtain a good rubber composition, it has been found through numerous experiments that the (-30 ° C. tan δ / 60 ° C. tan δ) ratio of the vulcanized rubber composition should be increased. The greater the difference between −30 ° C. tan δ and 60 ° C. tan δ of the vulcanized rubber composition, the better the dispersibility of the reinforcing filler, and the total surface area of the reinforcing filler is the dispersibility of the filler. And involved in the wear resistance of the rubber composition,
In addition, in relation to the (−30 ° C. tan δ / 60 ° C. tan δ) ratio, it is also found that cetyltrimethylammonium bromide adsorption specific surface area (m ² / g) is most preferable as an indicator of the specific total surface area of the reinforcing filler. did.
As a result of further experiments based on the above findings, a rubber composition containing natural rubber as a rubber component, carbon black and / or silica as a reinforcing filler, and -30 of vulcanized rubber composition. It has been found that the above problem can be solved by adjusting the ℃ / 60 ° C. tan δ ratio to be larger than a specific formula using the total surface area of the reinforcing filler as a variable.
The rubber composition is prepared by using, for example, a natural rubber and carbon black masterbatch or a modified natural rubber as a natural rubber of the rubber component, or using a dispersibility improver of a reinforcing filler in the rubber composition. It discovered that it could achieve by mix | blending.
The present invention has been completed based on such findings.

That is, the present invention
(1) It contains natural rubber and carbon black and / or silica as a reinforcing filler, and the following formula (1)
−30 ° C. tan δ / 60 ° C. tan δ> −1026.5 Ln (x) +10256 (1)
(Where x = CTAB × A, where CTAB is the cetyltrimethylammonium bromide adsorption specific surface area (m ² / g) measured according to ISO 6810 of the reinforcing filler, and A is per 100 parts by mass of natural rubber. And x is a number in the range of 2500 to 13000. Ln (x) is the natural logarithm of x, and tan δ is the loss tangent of the vulcanized rubber composition.)
A rubber composition characterized by being adjusted to satisfy the relationship of
(2) The rubber composition according to (1), wherein the content of carbon black and / or silica is 20 to 120 parts by mass with respect to 100 parts by mass of natural rubber.
(3) The rubber composition according to (1) or (2) above, which contains natural rubber in the form of a masterbatch of natural rubber and carbon black,
(4) The rubber composition according to (3) above, which contains natural rubber in the form of a wet masterbatch of natural rubber latex and carbon black,
(5) A tire characterized by using the rubber composition according to any one of (1) to (4) as a tire member,
(6) The tire according to (5) above, wherein the tire member is tread rubber or case rubber, and (7) the tire according to (5) or (6) above, which is for large heavy loads or off-the-road use,
Is to provide.

According to the present invention, a rubber composition that provides a tire having both low heat build-up and wear resistance, particularly a large tire such as an off-the-road tire, and the tire composition such as tread rubber and case rubber is used for the tire composition. A tire having performance can be provided.

FIG. 3 is a plot diagram showing the relationship between x in Formula (1) and −30 ° C. tan δ / 60 ° C. tan δ in the rubber compositions obtained in Examples and Comparative Examples. In the tire obtained by the Example and the comparative example, it is a plot figure which shows the relationship between the internal temperature change in a driving | running | working test, and abrasion resistance.

The rubber composition of the present invention contains natural rubber and carbon black and / or silica as a reinforcing filler, and has the following formula (1):
−30 ° C. tan δ / 60 ° C. tan δ> −1026.5 Ln (x) +10256 (1)
(Where x = CTAB × A, where CTAB is the cetyltrimethylammonium bromide adsorption specific surface area (m ² / g) measured according to ISO 6810 of the reinforcing filler, and A is per 100 parts by mass of natural rubber. Wherein x is a number in the range of 2500 to 13000. Ln (x) is the natural logarithm of x, and tan δ is the loss tangent of the vulcanized rubber composition. It is characterized by adjusting to satisfy the relationship.
By adjusting the rubber composition of the present invention such that the value of the -30 ° C. tan δ / 60 ° C. tan δ ratio is larger than the y value when the value of “−1026.5Ln (x) +10256” is y, A rubber composition excellent in low heat generation and wear resistance is obtained, and by using this rubber composition for a tire member, a tire having both low heat generation and wear resistance, particularly a tire for large heavy loads or off-the-road use. Can be given.

In the above formula (1), x is “CTAB × A”, CTAB is the cetyltrimethylammonium bromide adsorption specific surface area (m ² / g) measured according to ISO 6810 of the reinforcing filler, and A is Since it is a mass part of the reinforcing filler per 100 parts by mass of natural rubber, x means the total surface area of the reinforcing filler.
In the present invention, x is a number in the range of 2500 to 13000.
The −30 ° C. tan δ and 60 ° C. tan δ of the vulcanized rubber composition are values measured by the following method.
<Measurement of −30 ° C. tan δ and 60 ° C. tan δ>
A vulcanized rubber composition obtained by vulcanizing a rubber composition at 150 ° C. for 90 minutes was measured from 100 ° C. to −60 ° C. using a shear viscoelasticity measuring apparatus [“Ares” manufactured by Rheometrics Co., Ltd.]. The tan δ at ℃ and the tan δ at −30 ° C. were determined. The tan δ at 60 ° C. was a value at a frequency of 10 Hz and a dynamic strain of 3%, and the tan δ at −30 ° C. was a value at a frequency of 10 Hz and a dynamic strain of 0.1%.

In order to adjust the rubber composition of the present invention so as to satisfy the relationship of the above formula (1), the type of carbon black or silica that is the reinforcing filler in the rubber composition, the selection of the quantity ratio, (1) Use natural rubber in the form of a masterbatch of natural rubber and carbon black, (2) Use modified natural rubber, (3) Reinforcing fillers such as rubber-filler coupling agents This is achieved by taking measures such as using a dispersibility improver, (4) using a heat treatment masterbatch obtained by mixing natural rubber and a reinforcing filler, and then heat-treating under predetermined conditions. be able to.

[Carbon black and / or silica]
In the rubber composition of the present invention, carbon black and / or silica is used as the reinforcing filler.
There is no restriction | limiting in particular as said carbon black, From what is conventionally used as a reinforcing filler of rubber | gum, arbitrary things can be selected suitably and can be used. For example, SRF, GPF, FEF, HAF, ISAF, and SAF are used, and HAF, ISAF, and SAF that are particularly excellent in wear resistance are preferable.
This carbon black preferably has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) measured in accordance with ISO 6810 in the range of 20 to 200 m ² / g, and in the range of 70 to 160 m ² / g. Those are more preferred.
This carbon black may be used alone or in combination of two or more.

On the other hand, examples of silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Among these, wet silica is preferable.
The wet silica preferably has a CATB specific surface area of 100 to 300 m ² / g. Silica having a CATB specific surface area within this range has an advantage that both rubber reinforcement and dispersibility in a rubber component can be achieved. From this viewpoint, silica having a CATB specific surface area in the range of 150 to 250 m ² / g is more preferable. As such silica, commercially available products such as “Nipsil AQ”, “Nipsil KQ” manufactured by Tosoh Silica Co., Ltd., “Ultrasil VN3” manufactured by Degussa Co., Ltd. can be used.
This silica may be used alone or in combination of two or more.

In the present invention, as the reinforcing filler, only carbon black may be used, silica alone may be used, or carbon black and silica may be used in combination. The reinforcing filler is preferably 20 to 120 parts by weight, more preferably 25 to 100 parts by weight, still more preferably 100 parts by weight of natural rubber, from the viewpoint of reinforcing properties and the effect of improving various properties thereby. It is blended at a ratio of 30 to 90 parts by mass. By making the amount of carbon black and / or silica in the above range, excellent workability such as kneading workability can be obtained, and desired abrasion resistance can be obtained as a rubber composition.

In the rubber composition of the present invention, the natural rubber can be used in the form of a masterbatch of natural rubber and carbon black (hereinafter sometimes referred to as a natural rubber masterbatch). This master batch is preferably a wet master batch of natural rubber latex and carbon black.
[Natural rubber masterbatch]
This natural rubber masterbatch is preferably a wet masterbatch in which carbon black is mixed with natural rubber latex, and the production method is preferably such that after decomposing the amide bond in the latex, the natural rubber latex and carbon black are dispersed in water. And a step of mixing, coagulating, and drying the resulting aqueous slurry.

(Preparation of aqueous dispersion slurry solution)
Prior to mixing the natural rubber latex and the aqueous dispersion slurry liquid, a slurry liquid in which carbon black is dispersed in water in advance is produced. The manufacturing method of this slurry can use a well-known method, and is not specifically limited.
The water dispersion slurry of carbon black can be prepared, for example, by putting a predetermined amount of carbon black and water in a homomixer and stirring for a certain time. The concentration of carbon black in the slurry is preferably from 0.5 to 30% by mass, particularly preferably from 1 to 15% by mass, based on the slurry.

Regarding the particle size distribution of the carbon black in the water-dispersed slurry, the volume average particle size (mv) is preferably 25 μm or less and the 90 volume% particle size (D90) is preferably 30 μm or less. When the volume average particle size is 25 μm or less and the 90% by volume particle size is 30 μm or less, the carbon black dispersion in the rubber is further improved, and the reinforcing property and wear resistance are further improved.
When excessive shearing force is applied to the slurry to reduce the particle size of the carbon black, the structure of the carbon black is destroyed and the reinforcing property is deteriorated. Therefore, 24M4DBP oil absorption of the carbon black recovered by drying from the aqueous dispersion slurry liquid The amount is preferably mixed so as to maintain 93% or more, more preferably 96% or more of the 24M4DBP oil absorption before being dispersed in water.

(Mixing process)
The amount of carbon black mixed when mixing the natural rubber latex and the water-dispersed slurry is usually about 10 to 100 parts by mass with respect to 100 parts by mass of the natural rubber component in the natural rubber latex. If it is less than 10 parts by mass, sufficient wear resistance cannot be obtained, and if it exceeds 100 parts by mass, the low heat build-up is reduced. The mixing amount of carbon black is preferably 20 to 80 parts by mass, and more preferably 30 to 60 parts by mass.
Through this mixing step, a natural rubber wet masterbatch is obtained.

(Coagulation process)
The natural rubber wet masterbatch obtained through the mixing step is preferably coagulated in the coagulation step.
The wet masterbatch is solidified by using a solidifying agent such as formic acid or sulfuric acid or a salt such as sodium chloride as usual. Alternatively, coagulation may be performed by adding natural rubber latex and the slurry liquid without adding a coagulant.

(Drying process)
It is preferable to perform a drying process as the final step of master batch production. As the dryer, ordinary dryers such as vacuum dryers, air dryers, drum dryers, band dryers, etc. can be used, but in order to further improve the dispersibility of carbon black, while applying mechanical shearing force It is preferable to dry. Thereby, rubber excellent in processability and reinforcement can be obtained. Although this drying can be performed using a general kneader, it is preferable to use a continuous kneader. Furthermore, it is more preferable to use a multi-axis kneading extruder that rotates in the same direction or in different directions.
In the step of drying while applying a shearing force, the moisture in the master batch before the drying step is preferably 10% by mass or more. This is because when the water content is less than 10% by mass, the dispersion improvement width of the carbon black in the drying process becomes small.

(Amide bond decomposition process)
The natural rubber latex used in the mixing step may be subjected to a step of decomposing amide bonds in the latex. If the amide bond is decomposed in advance, molecules are entangled by the hydrogen bondability of the amide bond, the viscosity increase of the rubber is small, and the processability can be improved.
In the amide bond decomposition step, it is preferable to use a protease and / or an aromatic polycarboxylic acid derivative. Proteases have the property of hydrolyzing amide bonds present in the surface layer components of natural rubber latex particles, and examples include acidic proteases, neutral proteases, and alkaline proteases. In the present invention, alkaline protease is particularly preferred from the viewpoint of effect. When the amide bond is decomposed by a protease, it may be carried out under conditions suitable for the enzyme to be mixed. For example, when mixing a natural rubber latex with Alkalase 2.5L type DX manufactured by Novozym, the temperature is usually 20 to 80 ° C. It is desirable to process with a range. The pH at this time is usually in the range of 6.0 to 12.0. The amount of protease added is usually in the range of 0.01 to 2% by mass, preferably 0.02 to 1% by mass, based on the natural rubber latex.

In the method using an aromatic polycarboxylic acid derivative, the addition amount of the aromatic polycarboxylic acid derivative is preferably 0.01 to 30% by mass with respect to the natural rubber latex. If the addition amount is less than 0.01% by mass, the Mooney viscosity may not be sufficiently reduced. On the other hand, if it exceeds 30% by mass, not only the effect corresponding to the increase is obtained but also the vulcanized rubber is destroyed. May adversely affect properties. The addition amount varies within the above range depending on the type and grade of the natural rubber latex used, but it is preferably in the range of 0.05 to 20% by mass from the physical properties and cost.
The aromatic polycarboxylic acid derivative is preferably a derivative of phthalic acid, trimellitic acid, pyromellitic acid and its anhydride, specifically, monostearyl phthalate, monodecyl phthalate, monophthalic acid Examples include octylamide, polyoxyethylene lauryl phthalate, monodecyl trimellitic acid, monostearyl trimellitic acid, monostearyl pyromellitic acid, and distearyl pyromellitic acid.

In the amide bond decomposition step, it is desirable to add a surfactant for the purpose of improving the stability of the latex. As the surfactant, anionic, cationic, nonionic and amphoteric surfactants can be used, and anionic and nonionic surfactants are particularly preferable. The addition amount of the surfactant can be appropriately adjusted according to the properties of the natural rubber latex, but is usually 0.01 to 2% by mass, preferably 0.02 to 1% by mass with respect to the natural rubber latex. . The addition of the surfactant is preferably performed in the amide bond decomposition step, but is not particularly limited as long as it is at least before the mixing step.

In the rubber composition of the present invention, modified natural rubber can be used as the natural rubber.
[Modified natural rubber]
In the production of the modified natural rubber, natural rubber latex may be used as a raw material, or at least one solid natural rubber raw material selected from natural rubber, natural rubber latex coagulum and natural rubber cup lamp is used. May be.
The natural rubber latex is not particularly limited, and for example, a field latex, an ammonia-treated latex, a centrifugal concentrated latex, a deproteinized latex treated with a surfactant or an enzyme, and a combination thereof can be used. .

In the production of modified natural rubber, for example, when natural rubber latex is used as a raw material, a polar group-containing modified natural rubber can be obtained by producing a polar group-containing modified natural rubber latex and further coagulating and drying. Here, the production method of the polar group-containing modified natural rubber latex is not particularly limited. For example, (1) a polar group-containing monomer is added to the natural rubber latex, and the polar group-containing monomer is used as a natural rubber. (2) A method of adding a polar group-containing mercapto compound to natural rubber latex and adding the polar group-containing mercapto compound to the natural rubber molecule in natural rubber latex (3) ) A method of adding a polar group-containing olefin and a metathesis catalyst to natural rubber latex, and reacting the polar group-containing olefin with a natural rubber molecule in the natural rubber latex using the metathesis catalyst, (4) perbenzoic acid, Reaction of organic peracids such as acetic acid, performic acid, perphthalic acid, perpropionic acid, trifluoroperacetic acid under severe conditions A method of obtaining a rubber having a main chain reactive functional groups such as epoxidized natural rubbers by.

The polar group-containing monomer added to the natural rubber latex is not particularly limited as long as it has at least one polar group in the molecule and can be graft-polymerized with the natural rubber molecule. Here, the polar group-containing monomer preferably has a carbon-carbon double bond in the molecule for graft polymerization with a natural rubber molecule, and is preferably a polar group-containing vinyl monomer. . Specific examples of the polar group include 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, and oxycarbonyl. Preferred examples include a group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, alkoxysilyl group, and tin-containing group. These monomers containing a polar group may be used alone or in combination of two or more.

Examples of the 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, a tertiary amino group-containing monomer such as dialkylaminoalkyl (meth) acrylate is particularly preferable. These amino group-containing monomers may be used alone or in combination of two or more. Here, examples of the primary amino group-containing monomer include acrylamide, methacrylamide, 4-vinylaniline, aminomethyl (meth) acrylate, aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, aminobutyl (meth) ) Acrylate and the like.

The secondary amino group-containing monomer includes (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-anilino Anilinostyrenes such as styrene, 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-anilinophenyl-2-chloro-1,3-butadiene, 2-anilinophenyl-1,3-butadiene, 2 -Anilinophenyl butadienes such as anilinophenyl-3-methyl-1,3-butadiene, 2-anilinophenyl-3-chloro-1,3-butadiene, (3) N-methyl (meth) acrylamide, N And N-monosubstituted (meth) acrylamides such as ethyl (meth) acrylamide, N-methylolacrylamide, N- (4-anilinophenyl) methacrylamide and the like.

Furthermore, examples of the tertiary amino group-containing 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, and 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) ac And esters of acrylic acid or methacrylic acid such as N, N-dihexylaminoethyl (meth) acrylate, N, N-dioctylaminoethyl (meth) acrylate, and acryloylmorpholine. Among these, N, N -Dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dioctylaminoethyl (meth) acrylate, N-methyl-N -Ethylaminoethyl (meth) acrylate and the like are particularly preferred.

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- Acrylamide compounds such as butylaminobutyl (meth) acrylamide, N, N-dihexylaminoethyl (meth) acrylamide, N, N-dihexylaminopropyl (meth) acrylamide, N, N-dioctylaminopropyl (meth) acrylamide, or methacrylamide Examples thereof include N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, N, N-dioctylaminopropyl (meth) acrylamide and the like.

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

Examples of the monomer containing a hydroxyl group include polymerizable monomers having at least one 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 unsaturated carboxylic acid monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxy Hydroxyalkyl (meth) acrylates such as butyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 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) ( Me ) Hydroxyl group-containing unsaturated amides such as acrylamide; o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, o-hydroxy-α-methylstyrene, m-hydroxy-α-methylstyrene, p-hydroxy-α -Hydroxy group-containing vinyl aromatic compounds such as methylstyrene and p-vinylbenzyl alcohol. Among these, a hydroxyl group-containing unsaturated carboxylic acid monomer and a hydroxyl group-containing vinyl aromatic compound are preferable, and a hydroxyl group-containing unsaturated carboxylic acid monomer is particularly preferable. Here, examples of the hydroxyl group-containing unsaturated carboxylic acid 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 monomers may be used alone or in a combination of two or more.

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

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

In the 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, pteridine, Examples include melamine. The nitrogen-containing heterocycle may contain other heteroatoms in the ring. Here, as a monomer containing a pyridyl group as a nitrogen-containing heterocyclic group, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 5-methyl-2-vinylpyridine, 5-ethyl-2- Examples thereof include a vinyl compound containing a pyridyl group such as vinylpyridine, and among these, 2-vinylpyridine, 4-vinylpyridine and the like are particularly preferable. These nitrogen-containing heterocyclic group-containing monomers may be used alone or in a combination of two or more.

Examples of the monomer containing the alkoxysilyl group include (meth) acryloxymethyltrimethoxysilane, (meth) acryloxymethylmethyldimethoxysilane, (meth) acryloxymethyldimethylmethoxysilane, and (meth) acryloxymethyltrimethylsilane. Ethoxysilane, (meth) acryloxymethylmethyldiethoxysilane, (meth) acryloxymethyldimethylethoxysilane, (meth) acryloxymethyltripropoxysilane, (meth) acryloxymethylmethyldipropoxysilane, (meth) acryloxy Methyldimethylpropoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meta Acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyldimethylethoxysilane, γ- (meth) acryloxypropyltripropoxysilane, γ- (meth) acryl Roxypropylmethyldipropoxysilane, γ- (meth) acryloxypropyldimethylpropoxysilane, γ- (meth) acryloxypropylmethyldiphenoxysilane, γ- (meth) acryloxypropyldimethylphenoxysilane, γ- (meth) acrylic Roxypropylmethyldibenzyloxysilane, γ- (meth) acryloxypropyldimethylbenzyloxysilane, trimethoxyvinylsilane, triethoxyvinylsilane, 6-trimethoxysilyl-1,2-hexene, p-trimethoxysilyl Rustyrene and the like. These alkoxysilyl group-containing monomers may be used alone or in a combination of two or more.

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

When the polar group-containing monomer is graft-polymerized to the natural rubber molecule in the natural rubber latex, the graft polymerization of the polar group-containing monomer to the natural rubber molecule is preferably performed by emulsion polymerization. Here, in the emulsion polymerization, in general, the polar group-containing monomer is added to a liquid obtained by adding water and, if necessary, an emulsifier to natural rubber latex, and a polymerization initiator is further added thereto. It is preferable to polymerize the polar group-containing monomer by stirring at the temperature. In addition, in the addition of the polar group-containing monomer to the natural rubber latex, an emulsifier may be added in advance to the natural rubber latex, or after emulsifying the polar group-containing monomer with the emulsifier, May be added. In addition, it does not specifically limit as an emulsifier which can be used for emulsification of a natural rubber latex and / or a polar group containing monomer, Nonionic surfactants, such as polyoxyethylene lauryl ether, are mentioned.

The polymerization initiator is not particularly limited, and various polymerization initiators for emulsion polymerization can be used, and the addition method is not particularly limited. 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 heat buildup and wear resistance without reducing the processability of the rubber composition using the modified natural rubber, a small amount of the polar group-containing monomer is uniformly introduced into 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 monomer.

The above-mentioned components are charged into a reaction vessel and reacted at about 30 to 80 ° C. for about 10 minutes to 7 hours to obtain a modified natural rubber latex in which the polar group-containing monomer is graft copolymerized with natural rubber molecules. . The modified natural rubber latex is coagulated, washed, and then dried using a dryer such as a vacuum dryer, an air dryer, a drum dryer or the like to obtain a modified natural rubber. Here, the coagulant used for coagulating the modified natural rubber latex is not particularly limited, and examples thereof include acids such as formic acid and sulfuric acid, and salts such as sodium chloride.

The polar group-containing mercapto compound that is added to the natural rubber latex and undergoes an addition reaction with the natural rubber molecule in the natural rubber latex, as long as it has at least one mercapto group and a polar group other than the mercapto group in the molecule. It is not limited. Specific examples of the polar group include 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 Preferred examples include a group, a nitrogen-containing heterocyclic group, a mixed oxygen heterocyclic group, an alkoxysilyl group, and a tin-containing group. These mercapto compounds containing polar groups 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. Examples of 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. Of these amino group-containing mercapto compounds, 2-mercaptoethylamine and N, N-dimethylaminoethanethiol are preferred. 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 singly or in combination of two or more.

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 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 mercapto compounds 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, 2-mercapto. Examples include benzimidazole and 2-mercaptoimidazole. Among these, 2-mercaptopyridine, 4-mercaptopyridine and the like 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 containing an alkoxysilyl group include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, 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 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.

When adding the polar group-containing mercapto compound to the natural rubber molecule in the natural rubber latex, generally, the polar group-containing mercapto compound is added to a solution obtained by adding water and an emulsifier as necessary to the natural rubber latex, By stirring at a predetermined temperature, the polar group-containing mercapto compound is added to the double bond of the main chain of the natural rubber molecule in the natural rubber latex. In addition, in the addition of the polar group-containing mercapto compound to the natural rubber latex, an emulsifier may be added to the natural rubber latex in advance, or the polar group-containing mercapto compound may be added to the natural rubber latex after being emulsified with the emulsifier. good. Moreover, an organic peroxide can also be added as needed. In addition, it does not specifically limit as an emulsifier which can be used for emulsification of natural rubber latex and / or a polar group containing mercapto compound, Nonionic surfactants, such as polyoxyethylene lauryl ether, are mentioned.

In order to improve low heat build-up and wear resistance without reducing the processability of the rubber composition, it is important that the polar group-containing mercapto compound is introduced in a small amount and uniformly into each natural rubber molecule. The modification reaction is preferably performed with stirring. For example, the above components such as natural rubber latex and a polar group-containing mercapto compound are charged into a reaction vessel and reacted at about 30 to 80 ° C. for about 10 minutes to 24 hours. A modified natural rubber latex in which the polar group-containing mercapto compound is added to natural rubber molecules is obtained.

The polar group-containing olefin added to the natural rubber latex has at least one polar group in the molecule, and also has a carbon-carbon double bond for cross-metathesis reaction with the natural rubber molecule. Here, specific examples of the polar group include amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, and epoxy group. Preferable examples include oxycarbonyl group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, alkoxysilyl group, and tin-containing group. These polar group-containing olefins may be used singly or in combination of two or more.

When the polar group-containing olefin is reacted with the natural rubber molecule in the natural rubber latex by the metathesis catalyst, generally, the polar group-containing olefin is added to a liquid obtained by adding water and an emulsifier as necessary to the natural rubber latex, Further, a metathesis catalyst is added and stirred at a predetermined temperature to cause a metathesis reaction between the natural rubber molecule and the polar group-containing olefin. Here, in the addition of the polar group-containing olefin to the natural rubber latex, an emulsifier may be added to the natural rubber latex in advance, or the polar group-containing olefin may be added to the natural rubber latex after emulsifying the polar group-containing olefin with the emulsifier. good. In addition, it does not specifically limit as an emulsifier which can be used for emulsification of natural rubber latex and / or a polar group containing olefin, Nonionic surfactants, such as polyoxyethylene lauryl ether, are mentioned.

The metathesis catalyst is not particularly limited as long as it has a catalytic action on the metathesis reaction between the natural rubber molecule and the polar group-containing olefin, and various metathesis catalysts can be used. The metathesis catalyst contains a transition metal, but since it is used in a natural rubber latex, it is preferable that the stability to water is high. Therefore, the transition metal constituting the metathesis catalyst is preferably any one of ruthenium, osmium, and iridium. Specific examples of the metathesis catalyst include bis (tricyclohexylphosphine) benzylideneruthenium dichloride [RuCl ₂ (= CHPh) (PCy ₃ ) ₂ ], as well as RuCl ₂ (═CH—CH═CPh ₂ ) (PPh ₃ ). ₂ , RuCl ₂ (= CHPh) (PCp ₃ ) ₂ , RuCl ₂ (= CHPh) (PPh ₃ ) ₂ , RuCl ₂ (= CHPh) [Cy ₂ PCH ₂ CH ₂ N (CH ₃ ) ₃ ⁺ Cl] ₂ etc. Can be mentioned. In the chemical formula, Cy represents a cyclohexyl group, Cp represents a cyclopentyl group, and Ph represents a phenyl group. The addition amount of the metathesis catalyst is preferably in the range of 1 to 500 mol%, more preferably in the range of 10 to 100 mol% with respect to the polar group-containing olefin.

The above-mentioned components are charged into a reaction vessel and reacted at about 30 to 80 ° C. for about 10 minutes to 24 hours, thereby obtaining a modified natural rubber latex in which the polar group is introduced into natural rubber molecules.
In addition, when using at least one natural rubber raw material selected from natural rubber, natural rubber latex coagulated material, and natural rubber cup lamp as a raw material, a polar group-containing compound is given a mechanical shearing force, A modified natural rubber is obtained by graft polymerization or addition to a raw material.
As the natural rubber raw material, various solid natural rubbers after drying, various natural rubber latex coagulates (including unsmoked sheets) or natural rubber cup lamps can be used, and these natural rubber raw materials are used alone. It may also be used in combination of two or more.

When the polar group-containing compound is graft-polymerized to a natural rubber molecule in a natural rubber raw material, the polar group-containing compound preferably has a carbon-carbon double bond in the molecule, and the polar group-containing vinyl monomer It is preferable that On the other hand, when a polar group-containing compound is subjected to an addition reaction with a natural rubber molecule in a natural rubber raw material, the polar group-containing compound preferably has a mercapto group in the molecule, and is preferably a polar group-containing mercapto compound.

As a means for giving a mechanical shearing force to the mixture of the natural rubber raw material and the polar group-containing compound, a biaxial extrusion kneader and a dry prebreaker are preferable. Here, in the case where the polar group-containing compound is graft-polymerized to the natural rubber molecule in the natural rubber raw material, the natural rubber raw material and the polar group-containing compound (preferably, the polar group-containing vinyl are contained in the apparatus to which the mechanical shearing force is applied. By introducing a polymerization initiator together with a system monomer) and applying a mechanical shearing force, a polar group-containing compound can be introduced into the natural rubber molecule in the natural rubber raw material by graft polymerization. In addition, when a polar group-containing compound is subjected to an addition reaction with a natural rubber molecule in a natural rubber raw material, the natural rubber raw material and the polar group-containing compound (preferably, a polar group-containing mercapto compound are contained in the above-described mechanical shear force device. ) And, if necessary, organic peroxides and the like are further added to give mechanical shearing force, so that a polar group-containing compound is added to the double bond of the main chain of the natural rubber molecule in the natural rubber raw material. An addition reaction can be performed. Examples of the polar group-containing compound used here include the above-described polar group-containing monomers, polar group-containing mercapto compounds, polar group-containing olefins, and the like.

The modified natural rubber in which the above-mentioned polar group-containing compound is graft-polymerized or added to the natural rubber molecule is obtained by charging each component described above into a device that can be applied with a mechanical shear force and applying the mechanical shear force. At this time, the modification reaction of the natural rubber molecule may be carried out by heating, and preferably at 30 to 160 ° C., more preferably 50 to 130 ° C., the modified natural rubber with sufficient reaction efficiency. Can be obtained.

The polar group content of the modified natural rubber is preferably in the range of 0.001 to 0.5 mmol / g, more preferably in the range of 0.002 to 0.3 mmol / g, relative to the rubber component in the modified natural rubber. A range of 0.003 to 0.2 mmol / g is even more preferable. When the polar group content of the modified natural rubber is less than 0.001 mmol / g, the low heat build-up and wear resistance of the rubber composition may not be sufficiently improved. Also, if the polar group content of the modified natural rubber exceeds 0.5 mmol / g, the physical properties inherent to natural rubber such as viscoelasticity and SS characteristics (stress-strain curve in a tensile testing machine) will be 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 the rubber composition of the present invention, various low exothermic improvers or low exothermic deterioration inhibitors shown below can be blended.
[Low exothermic improver]
In the rubber composition of the present invention, compounds that can be used as a low exothermic improver or a low exothermic decrease inhibitor include (1) a compound that becomes a rubber-filler coupling agent, a nitrosoquinoline compound, a hydrazide compound, QAB type compounds having a bipolar nitrogen-containing moiety can be used.

(Rubber-filler coupling agent)
Examples of the rubber-filler coupling agent include disulfide compounds having a heterocyclic group such as bis [2- (2-oxazolyl) phenyl] disulfide or bis [2- (2-thiazolyl) phenyl] disulfide. .
Each of these compounds has a structure in which a 2- (2-oxazolyl) phenyl group or 2- (2-thiazolyl) phenyl group is bonded to each sulfur atom of the disulfide moiety. , The sulfur atom of the disulfide moiety is cleaved to form two 2- (2-oxazolyl) phenyl sulfide groups or 2- (2-thiazolyl) phenyl sulfide groups, and the sulfide moieties of these groups bind to natural rubber At the same time, the oxazolyl moiety or thiazolyl moiety binds to carbon black to exert a coupling action.
By such a coupling action, carbon black is highly dispersed in the rubber composition, and the low heat buildup and wear resistance of the rubber composition are improved.
The coupling agent is blended in an amount of about 0.1 to 10 parts by mass with respect to 100 parts by mass of natural rubber.

(Nitrosoquinoline compounds)
Nitrosoquinoline compounds are known as compounds to be incorporated into rubber compositions in order to realize low heat buildup and high reinforcement of tread rubber. Specifically, 5-nitroso-8-hydroxyquinoline, 7-nitroso -8-hydroxy-5-methylquinoline, 5-nitroso-8-hydroxy-6-methylquinoline, 8-nitroso-5-hydroxy-6-methylquinoline, 5-nitroso-8-hydroxy-7-methylquinoline, 6 -Nitroso-5-hydroxy-8-methylquinoline is preferable, among which 5-nitroso-8-hydroxyquinoline is preferable.
The nitrosoquinoline compound is blended in an amount of about 0.1 to 10 parts by mass with respect to 100 parts by mass of natural rubber.

(Hydrazide compound)
Hydrazide compounds, especially when blended into rubber compositions suitable for tread rubber of heavy duty pneumatic tires, suppress the decrease in elastic modulus due to overvulcanization due to reversion, and reduce low heat buildup and wear resistance. It is known to have an inhibitory action.
Examples of the hydrazide compound that can be used in the present invention include 1-hydroxy-N ′-(1-methylethylidene) -2-naphthoic acid hydrazide, 1-hydroxy-N ′-(1-methylpropylidene) -2-naphthoyl. Acid hydrazide, 1-hydroxy-N ′-(1-methylbutylidene) -2-naphthoic acid hydrazide, 1-hydroxy-N ′-(1,3-dimethylbutylidene) -2-naphthoic acid hydrazide, 1-hydroxy -N '-(2,6-dimethyl-4-heptylidene) -2-naphthoic acid hydrazide, 2-hydroxy-N'-(1-methylethylidene) -3-naphthoic acid hydrazide, 2-hydroxy-N '-( 1-methylpropylidene) -3-naphthoic acid hydrazide, 2-hydroxy-N ′-(1-methylbutylidene) -3-naphthoic acid hydrazide, 2-hydride Xylon-N ′-(1,3-dimethylbutylidene) -3-naphthoic acid hydrazide, 2-hydroxy-N ′-(2,6-dimethyl-4-heptylidene) -3-naphthoic acid hydrazide, isophthalic acid di ( 1-methylethylidene) hydrazide, isophthalic acid di (1-methylpropylidene) hydrazide, isophthalic acid di (1-methylbutylidene) hydrazide, isophthalic acid di (1,3-dimethylbutylidene) hydrazide, isophthalic acid di (2 , 6-Dimethyl-4-heptylidene) hydrazide, isonicotinic acid (1-methylethylidene) hydrazide, isonicotinic acid (1-methylpropylidene) hydrazide, isonicotinic acid (1-methylbutylidene) hydrazide, isonicotinic acid ( 2,6-dimethyl-4-heptylidene) hydrazide, isonicotinic acid (1,3 Dimethylbutylidene) hydrazide, N ′-(1-methylethylidene) -salicylic acid hydrazide, N ′-(1-methylpropylidene) -salicylic acid hydrazide, N ′-(1-methylbutylidene) -salicylic acid hydrazide, N′- (1,3-dimethylbutylidene) -salicylic acid hydrazide, N ′-(2,6-dimethyl-4-heptylidene) -salicylic acid hydrazide, and the like.
The hydrazide compound is blended in an amount of about 0.05 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

(QAB type compound having a bipolar nitrogen-containing moiety)
In the rubber composition of the present invention, a QAB type compound having a bipolar nitrogen-containing portion can be used. This QAB type compound has the following general formula QAB
Wherein Q represents a dipolar nitrogen atom-containing moiety, B represents an oxazoline moiety, a thiazoline moiety, an alkoxysilane moiety or an allyltin moiety, and A represents a linking atom or group that forms a bridge between Q and B. Show.)
It is a compound which has a structure represented by these.
Q in the compound represented by this general formula is preferably a dipolar nitrogen-containing moiety capable of adding a 1,3-dipole to an unsaturated carbon-carbon bond in the molecular structure of natural rubber. . Examples of such Q include nitrone, nitrile oxide, and nitrile imine.

The QAB type compound has, as Q, a dipolar nitrogen-containing moiety such as nitrone, nitrile oxide, nitrileimine, etc., and this dipolar nitrogen-containing moiety is unsaturated in the molecular structure of natural rubber. Add a 1,3-dipole to the carbon-carbon bond. On the other hand, B has an oxazoline portion, a thiazoline portion, an alkoxysilane portion, an allyltin portion, and the like, and these react with the surface group of the component silica and / or carbon black which is a reinforcing filler.
Therefore, the QAB type compound has an action of coupling natural rubber and reinforcing filler, and improves the dispersion of reinforcing filler such as silica and carbon black in the natural rubber. As a result, the rubber composition of the present invention is excellent in low heat buildup and wear resistance.

Examples of the QAB compound represented by the general formula include 4- (2-oxazolyl) -phenyl-N-methyl-nitrone, 4- (2-thiazolyl) -phenyl-N-methyl-nitrone, 4- (2-oxazolyl) -phenyl-N-phenyl-nitrone, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrone, phenyl-N-4- (2-oxazolyl) -phenyl-nitrone, phenyl- N-4- (2-thiazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-oxazolyl) -phenyl-nitrone, 4-tolyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- (2-oxazolyl) -phenyl-nitrone, 4-methoxyphenyl-N-4- (2-thiazolyl) -phenyl-nitrone, 4- (2-oxazolyl) -phenyl-nitrile oxide, 4- (2-thiazolyl) -phenyl-nitrile oxide, 4- (2-oxazolyl) -phenyl-N-methyl-nitrileimine, 4- (2-thiazolyl) -phenyl -N-methyl-nitrileimine, 4- (2-oxazolyl) -phenyl-N-phenyl-nitrileimine, 4- (2-thiazolyl) -phenyl-N-phenyl-nitrileimine, phenyl-N-4- (2 -Oxazolyl) -phenyl-nitrileimine, phenyl-N-4- (2-thiazolyl) -phenyl-nitrileimine and the like. These may be used alone or in combination of two or more. Among these compounds, 4- (2-oxazolyl) -phenyl-N-methyl-nitrone (4OPMN), 4- (2-oxazolyl) -phenyl-N-phenyl-nitrone (4OPPN) and phenyl-N-4 -(2-Oxazolyl) -phenyl-nitrone (P4OPN) is preferred.
The QAB type compound is blended in an amount of about 0.1 to 10 parts by mass with respect to 100 parts by mass of natural rubber.

[Master batch heat treatment method]
The wet masterbatch or dry masterbatch used in the rubber composition of the present invention is preferably used after heat treatment. The heat treatment of the masterbatch is performed by mixing natural rubber and the reinforcing filler by a wet masterbatch or dry masterbatch method and then heat-treating them under predetermined conditions.
Specifically, after mixing natural rubber with carbon black and / or silica, the treatment temperature T (° C.) is 50 ° C. or more, preferably 200 ° C. or less, and the treatment time t (min) is 2 × 10 ⁺²⁰ ×. obtained by heat treatment at ^{T -8.42>t> 1 × 10} +13 × T -5.4228 -3.3 conditions. The resulting heat-treated masterbatch does not contain a vulcanizing agent.
In this way, by heat-treating a masterbatch composed of natural rubber and carbon black and / or silica which is a reinforcing filler, the natural rubber is more firmly attached to the reinforcing filler and the polymer in the natural rubber is free. The rubber composition using this heat-treated master batch has sufficient low heat buildup and wear resistance.
As a method for obtaining the heat treatment masterbatch, a method in which the masterbatch is allowed to remain in a constant temperature apparatus such as an oven for a predetermined time under the above conditions may be used, or natural rubber and a reinforcing filler may be placed in a Banbury mixer or the like under the above conditions. A kneading method may be used. The treatment temperature T is more preferably in the range of 90 to 180 ° C, still more preferably 100 to 170 ° C. If the treatment temperature T is less than 50 ° C., even if the treatment time is sufficiently long, it is difficult to obtain the above effect. If the treatment temperature T exceeds 200 ° C., the main chain of natural rubber may be decomposed.
On the other hand, if the treatment time t (min) is in a range satisfying the above formula, a heat-treated master batch that provides a rubber composition having sufficient low heat buildup and wear resistance can be obtained.

[Preparation of rubber composition]
The rubber composition of the present invention contains natural rubber and carbon black and / or silica as a reinforcing filler, and has a ratio of −30 ° C. tan δ / 60 ° C. tan δ, “CTAB × A” (reinforcing filler The total surface area) is prepared by taking the above-mentioned various means so as to satisfy the relationship of the formula (1).
In the rubber composition of the present invention, natural rubber and carbon black may be used in the form of a wet masterbatch, or natural rubber and carbon black and / or silica may be used in the heat treatment masterbatch (dry masterbatch) described above. (Batch) may be used. Furthermore, modified natural rubber can be used as the natural rubber.
As a compounding agent for the rubber composition, at least one compound selected from the aforementioned compound serving as a rubber-filler coupling agent, a nitrosoquinoline compound, a hydrazide compound, and a QAB compound having a dipolar nitrogen-containing portion is used. Can be used.

Furthermore, as long as the object of the present invention is not impaired, various chemicals usually used in the rubber industry, for example, vulcanizing agents other than sulfur, vulcanization accelerators, silane coupling agents, process oils, plasticizers, An anti-aging agent, an anti-scorch agent, zinc white, stearic acid and the like can be contained.

The vulcanization accelerator that can be used in the present invention is not particularly limited, and examples thereof include M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), and CZ (N-cyclohexyl-2-benzothiazyl). Sulfenamide) and other guanidine vulcanization accelerators such as DPG (diphenylguanidine) can be used, and the amount used is 0.1-5. 0 parts by mass is preferable, and 0.2 to 3.0 parts by mass is more preferable.

Also, examples of the process oil used as a softening agent that can be used in the rubber composition of the present invention include paraffinic, naphthenic, and aromatic oils. Aromatics are used for applications that emphasize tensile strength and wear resistance, and naphthenic or paraffinic systems are used for applications that emphasize hysteresis loss and low-temperature characteristics. The amount used is preferably 0 to 100 parts by mass with respect to 100 parts by mass of natural rubber, and if it is 100 parts by mass or less, the deterioration of the tensile strength and low heat build-up (low fuel consumption) of the vulcanized rubber is suppressed. can do.

Furthermore, examples of the anti-aging agent that can be used in the rubber composition of the present invention include 3C (N-isopropyl-N′-phenyl-p-phenylenediamine), 6C [N- (1,3-dimethylbutyl) -N ′. -Phenyl-p-phenylenediamine], AW (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline), high-temperature condensate of diphenylamine and acetone, and the like. The amount to be used is preferably 0.1 to 6.0 parts by mass, more preferably 0.3 to 5.0 parts by mass with respect to 100 parts by mass of natural rubber.

The rubber composition of the present invention can be prepared by kneading the above components using a kneader such as an open kneader such as a roll or a closed kneader such as a Banbury mixer.
In the preparation of the rubber composition, components other than zinc white, vulcanization accelerator and vulcanizing agent are kneaded in the first stage, and then the remaining zinc white and vulcanized are added to the kneaded product. It is preferable to prepare by adding an accelerator and a vulcanizing agent and kneading in the second stage.
The rubber composition of the present invention thus obtained has excellent low heat buildup and excellent wear resistance, and can be used for tire members of large heavy duty tires and off-the-road tires. Examples of the tire member include tread rubber and case rubber including a sidewall.

[tire]
The tire of the present invention is characterized by using the above-described rubber composition of the present invention for a tire member. Examples of the tire member include a case rubber including a tread rubber and a sidewall. The rubber composition of the present invention can be used for any of these, and it is particularly preferable to use the rubber composition for the tread rubber.
A tire using the rubber composition of the present invention as a case rubber including a tread rubber and a sidewall has low rolling resistance and excellent fuel efficiency, and excellent wear resistance, and is particularly suitable as a large heavy duty tire or an off-the-road tire. It is. 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. When the rubber composition of the present invention is used for a tread, for example, it is extruded on a tread member, and is pasted and molded by a usual method on a tire molding machine to form a raw tire. The green tire is heated and pressed in a vulcanizer to obtain a tire.

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.
Various characteristics in each example were measured according to the following methods.
<Reinforcing filler>
(1) CTAB
The cetyltrimethylammonium bromide adsorption specific surface area (CTAB: m ² / g) was measured for carbon black and silica in accordance with JIS K 6217-3: 2001.
<Performance of vulcanized rubber composition>
(2) -30 ° C. tan δ / 60 ° C. tan δ
According to the method described in the specification, -30 ° C. tan δ and 60 ° C. tan δ were measured in the vulcanized rubber composition, and the ratio of −30 ° C. tan δ / 60 ° C. tan δ was determined.
<Tire performance>
(3) Abrasion resistance A tire of size 2400R35 was produced, the amount of wear was determined from the remaining groove when traveling on a rough road for 10,000 km, and the amount of wear in Example 3 was taken as 0, and the wear resistance was displayed as an index. The greater the value of +, the better the wear resistance, and the greater the value of-, the worse the wear resistance.
(4) Internal temperature change of tire The internal temperature when a tire of size 2400R35 was run on a drum at a speed of 40 km / h for 24 hours was measured, and the temperature of Example 3 was displayed as an index. The internal temperature was changed. A numerical value of + indicates that the numerical value is higher than the internal temperature of the tire of Example 3, and a numerical value of-indicates that the numerical value is lower than the internal temperature of the tire of Example 3.

Production Example 1 Production of wet masterbatch of natural rubber and carbon black In advance, 5% by mass of carbon black (carbon black species shown in Table 2) and 95 were used in a homomixer (High Shear mixer manufactured by Silverson). Mass% water was added and finely dispersed to obtain an aqueous dispersion slurry of carbon black. In any water-dispersed slurry, the volume average particle size (mv) was 25 μm or less, and the 90 volume% particle size (D90) was 30 μm or less.
Next, the aqueous dispersion slurry of carbon black and the natural rubber latex are stirred in a homomixer so that the mass part of the carbon black in Table 2 is 100 parts by mass of the natural rubber component in the natural rubber latex. After mixing, this was adjusted to pH 4.5 with formic acid and solidified to obtain each wet masterbatch.

Production Example 2 Production of dry masterbatch Untreated natural rubber or modified natural rubber and carbon black of the type and content shown in Table 2 were kneaded in a Banbury mixer as in the first stage shown in Table 1. A dry masterbatch was obtained. In Example 5 and Comparative Example 11, a dry masterbatch was prepared using untreated natural rubber, and in Example 12 using modified natural rubber.

Production Example 3 Production of Modified Natural Rubber (Modification Reaction Process of Natural Rubber Latex)
The field latex was centrifuged using a latex separator [manufactured by Saito Centrifugal Industries Co., Ltd.] at a rotational speed of 7500 rpm to obtain a concentrated latex having a dry rubber concentration of 60%. 1000 g of this concentrated latex was put into a stainless steel reaction vessel equipped with a stirrer and a temperature control jacket, and 10 mL of water and 90 mg of emulsifier (trade name “Emulgen 1108” manufactured by Kao Corporation) were added in advance to N, N-diethylamino. What was emulsified in addition to 3.0 g of ethyl methacrylate was added with 990 mL of water, and these were stirred at room temperature for 30 minutes while purging with nitrogen. Next, 1.2 g of tert-butyl hydroperoxide and 1.2 g of tetraethylenepentamine were added as polymerization initiators and reacted at 40 ° C. for 30 minutes to obtain a modified natural rubber latex.

(Coagulation and drying process)
Formic acid was added to the modified natural rubber latex to adjust the pH to 4.7 to coagulate the modified natural rubber latex. The solid material thus obtained was treated with a creper five times, passed through a shredder and crushed, and then dried at 110 ° C. for 210 minutes with a hot air dryer to obtain modified natural rubber A. From the mass of the modified natural rubber A thus obtained, it was confirmed that the conversion rate of N, N-diethylaminoethyl methacrylate added as a monomer was 100%. In addition, the modified natural rubber A was extracted with petroleum ether and further extracted with a 2: 1 mixed solvent of acetone and methanol, but when the extract was analyzed, no homopolymer was detected. It was confirmed that 100% of the added monomer was introduced into the natural rubber molecule. Accordingly, the polar group content of the resulting modified natural rubber A is 0.027 mmol / g with respect to the rubber component in the natural rubber latex.

Production Example 4 Heat treatment method of master batch A wet master batch or a dry master batch was heat-treated in an oven at a temperature of 140 ° C for 30 minutes.

Production Example 5 Production of Rubber-Filler Coupling Agent A mixture was prepared by adding 20 g (65 mmol) of 2,2′-dithio-bis (benzoic acid) to 28.6 mL (390 mmol) of thionyl chloride. The mixture was refluxed for 12 hours and then filtered. The filtrate was dried using a rotary evaporator to obtain 15.0 g (44 mmol) of 2,2′-dithio-bis (benzoyl chloride) powder. The yield of this reaction was 68%.
Next, the obtained 2,2′-dithio-bis (benzoyl chloride) was added to 300 mL of chloroform and mixed. To this mixture, a solution containing 10.7 g (175 mmol) of 2-aminoethanol in 200 mL of chloroform was added dropwise with stirring. After the addition was complete, the mixture was stirred at 25 ° C. for 2 hours while a precipitate was formed. This precipitate was collected by filtration and washed with 200 mL of water. The precipitate was then dried and collected as a pale brown powder of 13.5 g (34 mmol) of 2,2′-dithio-bis [N- (hydroxyethyl) -benzamide]. The yield was 77%.
To this 2,2′-dithio-bis [N- (hydroxyethyl) -benzamide] powder, 15 mL (204 mmol) of thionyl chloride was added dropwise with stirring. This mixture was poured into 150 mL of ether to form a white precipitate. Thereafter, the precipitate was filtered and dissolved in water. The dissolved precipitate was neutralized with chilled 20% sodium hydroxide and extracted with chloroform. The chloroform extract was dried and recrystallized from hexane. 7 g (20 mmol) of bis [2- (2-oxazolyl) phenyl] disulfide was obtained. The yield was 59%. The overall yield was 15%.

Examples 1 to 15 and Comparative Examples 1 to 11
According to the formulation shown in Table 1, natural rubber in the form shown in Table 2, carbon black of the type and amount shown in Table 2, or a combination of carbon black and silica, and rubber-filler shown in Table 2 Twenty-six types of rubber compositions were prepared using a coupling agent.
The rubber composition was prepared by first kneading each component of the first stage shown in Table 1 in a Banbury mixer, and then adding each component of the second stage shown in Table 1 to the obtained kneaded product. In addition, it was carried out by kneading.
Each rubber composition was vulcanized at 150 ° C. for 90 minutes to prepare a test piece for measuring −30 ° C. tan δ and a test piece for measuring 60 ° C. tan δ, and measuring −30 ° C. tan δ and 60 ° C. tan δ, The 30 ° C. tan δ / 60 ° C. tan δ ratio was calculated. The results are shown in Table 2.
Next, 26 types of tires of size 2400R35 were manufactured using each rubber composition, and the tire performance was evaluated. The results are shown in Table 2.
FIG. 1 is a plot diagram showing the relationship between x and −30 ° C. tan δ / 60 ° C. tan δ ratio in the formula (1) in the rubber compositions obtained in Examples and Comparative Examples, and FIG. In the tire obtained by the comparative example, it is a plot figure which shows the relationship between the internal temperature change in a driving | running | working test, and abrasion resistance.

[note]
1) Untreated natural rubber or treated natural rubber: Untreated natural rubber is ordinary natural rubber, which is obtained by directly coagulating and drying natural rubber latex. The natural rubber and the modified natural rubber in the wet masterbatch or the dry masterbatch shown in FIG.
2) Carbon black: types and amounts are shown in Table 2.
3) Silica: Types and amounts are shown in Table 2.
4) Rubber-filler coupling agent: bis [2- (2-oxazolyl) phenyl] disulfide obtained in Production Example 5 5) Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, Degussa Product name "Si69"
6) Anti-aging agent 6C: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”
7) Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “Noxeller CZ”

[note]
1) Wet masterbatch: wet masterbatch of natural rubber and carbon black obtained in Production Example 1 2) Dry masterbatch: dry masterbatch obtained in Production Example 2 3) Modified natural rubber: obtained in Production Example 3 Modified natural rubber A
4) Heat treatment of master batch: Heat treatment was performed by the method of Production Example 4.
5) Rubber-filler coupling agent: bis [2- (2-oxazolyl) phenyl] disulfide obtained in Production Example 5 6) Silica: manufactured by Degussa, trade name “Ultrasil VN3”
As can be seen from FIG. 1, the rubber compositions obtained in Examples 1 to 15 all have a -30 ° C./60° C. tan δ ratio larger than the value of y = 1026.5 Ln (x) +10256. Further, as can be seen from FIG. 2, the tire temperature using the rubber composition obtained in the example is compared with the tire wear resistance using the rubber composition obtained in the comparative example. When the change is the same, the tire using the rubber composition obtained in the examples has good wear resistance.

Industrial application fields

The rubber composition of the present invention can give a tire having both low heat buildup and wear resistance, particularly a large tire such as an off-the-road tire.

Claims

Natural rubber and carbon black and / or silica as a reinforcing filler, and the following formula (1)
−30 ° C. tan δ / 60 ° C. tan δ> −1026.5 Ln (x) +10256 (1)
(Where x = CTAB × A, where CTAB is the cetyltrimethylammonium bromide adsorption specific surface area (m 2 / g) measured according to ISO 6810 of the reinforcing filler, and A is per 100 parts by mass of natural rubber. And x is a number in the range of 2500 to 13000. Ln (x) is the natural logarithm of x, and tan δ is the loss tangent of the vulcanized rubber composition.)
A rubber composition, which is adjusted to satisfy the relationship.
The rubber composition according to claim 1, wherein the content of carbon black and / or silica is 20 to 120 parts by mass with respect to 100 parts by mass of natural rubber.
The rubber composition according to claim 1 or 2, comprising natural rubber in the form of a masterbatch of natural rubber and carbon black.
The rubber composition according to claim 3, comprising natural rubber in the form of a wet masterbatch of natural rubber latex and carbon black.
A tire comprising the rubber composition according to any one of claims 1 to 4 as a tire member.
The tire according to claim 5, wherein the tire member is a tread rubber or a case rubber.
The tire according to claim 5 or 6, wherein the tire is for large heavy loads or for off-the-road use.