JP2003238739A - Rubber composition and pneumatic tire produced by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition improved in the dispersion of silica in a rubber, excellent in failure characteristics, wear resistance, processability, and the like, and suffering little heat build-up (giving low fuel consumption), and to provide a pneumatic tire produced by using the rubber composition. <P>SOLUTION: The pneumatic tire is produced by using the rubber composition containing 100 pts.wt. of (A) a rubber component comprising a conjugated diene copolymer rubber having (a) ethylenically unsaturated nitrile monomer units (b) aromatic vinyl monomer units and (c) conjugated diene monomer units, with the content of the units (a) being 5-45 wt.% based on the total of the units (a), (b) and (c), and 10-85 pts.wt. of (B) a hydrous silicic acid having a nitrogen adsorption specific surface area (BET) of 200-400 m<SP>2</SP>/g and a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 170-270 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition and a pneumatic tire using the same. For more details,
INDUSTRIAL APPLICABILITY The present invention has, as a rubber component, good low heat buildup (fuel economy) and processability, which are obtained by using a modified conjugated diene-based polymer having enhanced interaction with silica as a reinforcing filler. A rubber composition having excellent breaking properties and abrasion resistance,
And a pneumatic tire using this rubber composition.

[0002]

2. Description of the Related Art In recent years, with increasing interest in safety of automobiles, not only fuel consumption performance but also performance on wet road surface (hereinafter referred to as wet performance), particularly braking performance, has been increased. For this reason, the demand for the performance of the rubber composition of the tire tread is not limited to simply reducing the rolling resistance, and there is a need for a highly compatible wet performance and low fuel consumption performance. As a method for obtaining a rubber composition that simultaneously provides a tire with good fuel economy and good wet performance, a hydrated silica is used instead of carbon black that has been generally used as a reinforcing filler. Methods using silica such as acid have already been carried out. In this case, in order to enhance the dispersibility of silica, a rubber material obtained by modifying the polymerization active terminal of a diene polymer obtained by anionic polymerization using an organolithium compound with a functional group that interacts with the silica is used. Is being attempted. For example, a method of using silica as a filler and modifying a polymerization active terminal with a silicon compound having an alkoxyl group (Japanese Patent Publication No. 6-57767, Japanese Patent Application Laid-Open No. 7-233216, Japanese Patent Application Laid-Open No. 9-87426) and the like. It is disclosed.

However, when general hydrous silicic acid (wet process silica) which is widely used in the rubber industry at present is used as silica, the above-mentioned method is used to obtain a rubber composition having low heat build-up and good processability. Although effective, there was a problem that the fracture characteristics and wear resistance were not always sufficiently satisfactory. For this reason, it is known to use silica having a fine particle diameter to increase the surface area thereof to improve the reinforcing property with rubber, but in this case also, the Mooney viscosity of the compound becomes high and the dispersibility is increased. Since it was inferior, sufficient fracture characteristics and wear resistance could not be obtained.

[0004]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a rubber composition using silica as a reinforcing filler, which enhances silica dispersibility in rubber, and also has a destructive property and resistance to fracture. An object of the present invention is to provide a low heat-generating (fuel-efficient) rubber composition having excellent wear properties and processability, and a pneumatic tire using the rubber composition.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a specific rubber containing an unsaturated nitrile monomer is blended with a certain amount of fine particle silica. Was found to be effective. The present invention has been completed based on such findings. That is, the present invention has (A) (a) an ethylenically unsaturated nitrile monomer unit, (b) an aromatic vinyl monomer unit, and (c) a conjugated diene monomer unit, and Based on the total amount of the above (a), (b) and (c) units, a rubber component containing a conjugated diene copolymer rubber containing 5 to 45% by weight of the (a) unit, and 100 parts by weight thereof, (B) Nitrogen adsorption specific surface area (BET) is 200 to 400 m ² / g, and cetyltrimethylammonium bromide adsorption specific surface area (CTA)
B) is 170 to 270 m ² / g and contains 10 to 10 hydrous silicic acid.
The present invention provides a rubber composition containing 85 parts by weight. The present invention also provides a pneumatic tire characterized by using the rubber composition.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the rubber composition of the present invention,
As the component (A), a rubber component containing a conjugated diene copolymer rubber shown below is used. The conjugated diene copolymer rubber has (a) an ethylenically unsaturated nitrile monomer unit, (b) an aromatic vinyl monomer unit, and (c) a conjugated diene monomer unit. , (A) unit is 5 based on the total amount of the above (a), (b) and (c) units.
It is necessary to contain .about.45% by weight. When the content of the ethylenically unsaturated nitrile unit as the unit (a) is less than 5% by weight, the silica dispersibility becomes poor, and the fracture characteristics, abrasion resistance and low heat buildup may not be sufficiently improved. on the other hand,
If this content exceeds 45% by weight, the glass transition point (Tg) of the conjugated diene copolymer rubber becomes too high and the properties as a rubber elastic body are lost. The preferred content of this ethylenically unsaturated nitrile unit is 8 to 35% by weight,
Particularly, 9 to 20% by weight is preferable. Here, the monomer (a)
Examples thereof include acrylonitrile and methacrylonitrile, and of these, acrylonitrile is preferable. These monomers (a) may be used alone or in combination of two or more.

The content of the aromatic vinyl monomer unit as the unit (b) is preferably 10 to 50% by weight. If this content is less than 10% by weight, the vulcanized rubber obtained may have insufficient wear resistance.
If it exceeds 50% by weight, the resulting vulcanized rubber tends to have a low impact resilience, and tan δ tends to increase. The preferable content of the aromatic vinyl monomer unit is 15 to 40% by weight. As the monomer (b), styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α
-Methylstyrene, 2,4-dimethylstyrene, 2,4-
Examples include diisopropyl styrene, 4-tert-butyl styrene and tert-butoxy styrene,
Of these, styrene is particularly preferred. These monomers (b) may be used alone or in combination of two or more. Examples of the monomer (c) include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and chloroprene. Of these, 1,3-butadiene and isoprene are particularly preferable. preferable. These monomers (c) may be used alone or in combination of two or more.

In the repeating unit in the conjugated diene-based copolymer rubber, the content of the monomer unit consisting of the monomer (c) is preferably 20 to 81% by weight, more preferably 50 to 80% by weight. When the content of the monomer unit composed of the monomer (c) is less than 20% by weight, the resulting vulcanized rubber may have a small impact resilience and a large tan δ. The conjugated diene-based copolymer rubber may be obtained by copolymerizing various ester-based monomers in addition to the monomers (a), (b) and (c), if necessary.
As the ester-based monomer, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-amyl (meth) acrylate, n-hexyl (meth ) Acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate and other (meth) acrylates, and vinyl acetate and other vinyl esters. The content of the monomer unit composed of these ester-based monomers can be set to an amount ratio within a range that does not impair the properties of the conjugated diene-based copolymer rubber, but is 20 with respect to the total amount of the monomer unit. It is preferable to set the content to be not more than weight%. Preferred examples of the conjugated diene-based copolymer rubber of the present invention include acrylonitrile-butadiene-styrene copolymer and the like. Further, the copolymer rubber is preferably a random copolymer.

The conjugated diene-based copolymer rubber preferably has a glass transition temperature of -60 ° C to 0 ° C and a Mooney monoviscosity [ML _{1 + 4} (100 ° C)] of 20 to 200. The "glass transition point" varies depending on the compositional ratio of the monomers used, but is not limited to ASTM D3418-82 (Re
It is -60 to 0 ° C, and preferably -50 to -10 ° C when measured by a differential scanning calorimeter (DSC) according to applied 1988). Further, the difference between the extrapolation start temperature and the extrapolation end temperature of the glass transition is preferably 20 ° C or lower, more preferably 18 ° C or lower, further preferably 15 ° C or lower, and particularly 13 ° C or lower. The lower limit is usually 5 ° C. If the temperature difference exceeds 20 ° C., the wet skid resistance of the obtained vulcanized rubber decreases and tan δ also increases, which is not preferable. Further, the content of the monomer unit composed of the monomer (a) is 9 to 15% by weight, and the difference between the extrapolation start temperature and the extrapolation end temperature of the glass transition is 13 ° C. or less, particularly It is preferably 10 ° C or lower. Here, the extrapolation start temperature and the extrapolation end temperature of the glass transition are ASTM D3418-82 (Rea
It was measured by a differential scanning calorimeter (DSC) according to published 1988). The extrapolation start temperature is approximately the straight line portion between the straight line extending the low temperature side baseline and the low temperature side inflection point P ₁ and the high temperature side inflection point Ph in the temperature rising curve of the DSC shown in FIG. The reading of the temperature axis corresponding to the point where the straight line obtained by extending L is intersected. The extrapolation end temperature is the temperature axis reading corresponding to the intersection of the straight line extending the high temperature side baseline and the straight line extending the straight line portion L in the temperature rising curve of the DSC shown in FIG. .

The Mooney viscosity [ML _{1 + 4} (100 ° C.)] of the conjugated diene-based copolymer rubber of the present invention is preferably 20 to 200, more preferably 30 to 150. When the Mooney viscosity is less than 20, abrasion resistance of the obtained vulcanized rubber may decrease. On the other hand, 20
If it exceeds 0, the processability of the rubber composition containing the conjugated diene-based copolymer rubber may be lowered. The polystyrene-equivalent weight average molecular weight of the conjugated diene-based copolymer rubber measured by GPC (gel permeation chromatography) is preferably 100,000 or more, and particularly preferably 100,000 to 2,000,000. If the weight average molecular weight is less than 100,000, the abrasion resistance of the obtained vulcanized rubber tends to decrease, and ta
nδ may become large. On the other hand, when it exceeds 2,000,000, the processability of the rubber composition containing the conjugated diene-based copolymer rubber may deteriorate. This weight average molecular weight can be controlled during polymerization by using a chain transfer agent represented by alkyl mercaptan which is generally used in radical polymerization.

The conjugated diene-based copolymer rubber is obtained by polymerizing the above-mentioned monomers (a), (b) and (c) and optionally an ester-based monomer in a water-based medium by using a radical polymerization initiator. , Can be manufactured. The polymerization method is not particularly limited, but emulsion polymerization is usually preferable. Emulsion polymerization may be a general method, in which a predetermined monomer is emulsified in an aqueous medium in the presence of an emulsifier, polymerization is initiated by a radical polymerization initiator, and polymerization is performed at a predetermined polymerization conversion rate. A method of stopping the polymerization with a terminator can be mentioned.

In the present invention, the method of charging the above-mentioned monomer (a) is important, and it is preferable that the monomer (a) is divided and added to the polymerization system. It is preferable to add a part of the monomer (a) before starting the polymerization and to add the rest intermittently or continuously to the polymerization system in the polymerization process. Further, after the polymerization conversion rate of all the charged monomers measured during the polymerization reaches 10 to 95%, preferably 20 to 80%, the rest of the monomer (a) is collectively or divided. Or continuously added. When the total amount of the monomer (a) is charged into the polymerization system before the polymerization is initiated and copolymerized, the difference between the initiation temperature and the termination temperature of the glass transition of the copolymer rubber becomes larger than 20 ° C. It tends to be unfavorable. The initial charging amount of the above-mentioned monomer (a) before the initiation of polymerization is preferably 20 to 95% by weight, more preferably 20 to 90% by weight, based on the total amount of the monomer (a) used. Preferably 30-
It is 85% by weight.

As the emulsifier, an anionic surfactant,
Examples include nonionic surfactants, cationic surfactants and amphoteric surfactants. Further, a fluorine-based surfactant can also be used. As these emulsifiers, anionic surfactants are frequently used, for example, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid,
In addition to potassium salts or sodium salts of long-chain fatty acids having 10 or more carbon atoms such as stearic acid, rosin acid salts and the like can be used. Radical polymerization initiators include benzoyl peroxide, lauroyl peroxide, ter
t-Butyl hydroperoxide, cumene hydroperoxide, paramenthane hydroperoxide, di-t
Organic peroxides such as ert-butyl hydroperoxide and dicumyl peroxide can be used.
Further, an azo compound represented by azobisisobutyronitrile, an inorganic peroxide represented by potassium persulfate, and a redox catalyst represented by a combination of these peroxides and ferrous sulfate are used. You can also These radical polymerization initiators may be used alone or in combination of two or more.

Further, in order to control the molecular weight of the conjugated diene copolymer rubber, as a chain transfer agent, alkyl mercaptans such as tert-dodecyl mercaptan, n-dodecyl mercaptan, carbon tetrachloride, thioglycols, diterpenes, terpinolene. And chain transfer agents such as γ-terpinenes can also be used. The polymerization can be carried out at 0 to 100 ° C using a reactor from which oxygen has been removed, and the polymerization temperature is particularly preferably 0 to 80 ° C. The polymerization system may be a continuous system or a batch system, and the polymerization temperature and the like or the operating conditions such as stirring and the like can be appropriately changed during the reaction. It is preferable that the polymerization conversion rate is suppressed to 80% or less, because gelation tends to occur when the polymerization conversion rate becomes high. The polymerization can be stopped by adding a polymerization terminator when the predetermined polymerization conversion rate is reached. As the polymerization terminator, hydroxylamine,
An amine compound such as diethylhydroxylamine or a quinone compound such as hydroquinone can be used.
After the termination of the polymerization, from the produced conjugated diene-based copolymer rubber latex, if necessary, after removing unreacted monomers by a method such as steam distillation, sodium chloride, potassium chloride, salts such as calcium chloride, And, if necessary, hydrochloric acid, nitric acid, sulfuric acid or the like may be further added to coagulate the conjugated diene-based copolymer rubber as crumb. The conjugated diene-based copolymer rubber can be obtained by washing this crumb, dehydrating it, and then drying it with a dryer or the like.

Further, the conjugated diene-based copolymer rubber may contain an extender oil. In this case, the content of the extender oil is 100 parts by weight of the conjugated diene-based copolymer rubber. 10 to 60 parts by weight, preferably 2
It is 0 to 50 parts by weight. If the extender oil is less than 10 parts,
If the workability is not sufficiently improved and exceeds 60 parts by weight, the amount ratio of the extender oil blended according to the required workability at the time of preparing the rubber composition is limited, which is not preferable. The Mooney viscosity [ML _{1 + 4} (100 ° C.)] of the obtained oil-extended rubber is preferably 20 to 180, particularly preferably 30 to 150. The extender oil is not particularly limited, and examples thereof include aromatic oils, naphthene oils, and paraffin oils. These may be one kind or a mixture of two or more kinds. Among these, aromatic extender oils are particularly preferable.

The rubber composition of the present invention must contain at least 30% by weight of the conjugated diene copolymer rubber as the rubber component of the component (A). If this amount is less than 30% by weight, a rubber composition having desired physical properties may not be obtained. The content of the conjugated diene-based copolymer rubber in the rubber component is preferably 35% by weight or more, and particularly preferably 40 to 100% by weight. Examples of the rubber component used in combination with the conjugated diene-based copolymer rubber include natural rubber and diene-based synthetic rubber. Examples of the diene-based synthetic rubber include styrene-butadiene copolymer (SB
R), polybutadiene (BR), polyisoprene (I
R), butyl rubber (IIR), ethylene-propylene copolymers and mixtures thereof. Further, a part thereof may have a branched structure by using a polyfunctional modifier, for example, a modifier such as tin tetrachloride.

Next, in the rubber composition of the present invention,
As the component (B), the nitrogen adsorption specific surface area (BET) is 20.
0 to 400 m ² / g, and cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 170 to 27
A hydrous silicic acid of 0 m ² / g is used. The hydrous silicic acid having such properties is finer in particle size and has a larger surface area than the commonly used general hydrous silicic acid, and reacts with the modified conjugated diene-based polymer in the component (A). As a result, the fracture characteristics and wear resistance are improved. The BET is less than 200 m ² / g or the CTAB is 1
If it is less than 70 m ² / g, the effect of improving the fracture characteristics and the wear resistance cannot be sufficiently exhibited. Also, the BET is 400 m ² / g
Or the CTAB exceeds 270 m ² / g, the cohesive force of the hydrous silicic acid becomes too strong, leading to poor dispersion in the rubber composition, and the fracture properties and abrasion resistance are rather reduced, and Sex is also reduced. Considering fracture properties, abrasion resistance, workability, etc., the preferred BET of the hydrous silicic acid is in the range of 200 to 300 m ² / g, while the preferred CTAB is in the range of 180 to 230 m ² / g. In the present invention, the hydrous silicic acid as the component (B) is 1 part with respect to 100 parts by weight of the rubber component as the component (A).
It is compounded in the range of 0 to 85 parts by weight. If this amount is less than 10 parts by weight, the effect of improving the reinforcing property and other physical properties will not be sufficiently exhibited, and if it exceeds 85 parts by weight, workability and the like will deteriorate. Considering the reinforcing property, other physical properties, and processability, the content of the hydrous silicic acid is preferably in the range of 20 to 60 parts by weight.

In the rubber composition of the present invention, if desired, carbon black can be used as the component (C) together with the above-mentioned silica for the purpose of improving the storage elastic modulus and the reinforcing property. The carbon black is not particularly limited, and any one can be selected and used from those conventionally used as a reinforcing filler for rubber. Examples of the carbon black include FEF, SRF, HAF, ISAF, SAF and the like. The iodine adsorption amount (IA) is preferably 60 mg / g
The above is carbon black having a dibutyl phthalate oil absorption (DBP) of 80 ml / 100 g or more. By using this carbon black, the effect of improving various physical properties becomes great, but HAF, ISAF, and SAF, which are excellent in wear resistance, are particularly preferable. In the present invention, the compounding amount of the component (C) carbon black optionally used is within the range of 80 parts by weight or less relative to 100 parts by weight of the component (A), and the component (B). It is preferable to select such that the total amount with the above-mentioned hydrous silicic acid is 120 parts by weight or less. If the compounding amount of this carbon black exceeds 80 parts by weight or the total amount with the component (B) exceeds 120 parts by weight, it is difficult to obtain a rubber composition having desired physical properties, and the object of the present invention cannot be achieved. There is a risk. From the standpoints of compounding effect and physical properties, the preferable blending amount of the component (C) is in the range of 5 to 70 parts by weight, and the total blending amount with the component (B) is preferably 100 parts by weight or less.

In the rubber composition of the present invention, a silane coupling agent may be blended as the component (D), if desired. As this silane coupling agent,
There is no particular limitation, and known compounds conventionally used in rubber compositions such as bis (3-triethoxysilylpropyl) polysulfide, γ-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane,
N-phenyl-γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and the like can be used. The amount of the silane coupling agent used, if desired, is usually 1 to 20% by weight based on the hydrous silicic acid of the component (B).
It is selected in the range of. If this amount is less than 1% by weight, the effect as a coupling agent cannot be sufficiently exerted, and
If it exceeds 20% by weight, gelation of the rubber component may occur. From the viewpoint of the effect as a coupling agent and the prevention of gelation, the preferable amount of the silane coupling agent is in the range of 5 to 15% by weight.

The rubber composition of the present invention contains, if desired, various chemicals usually used in the rubber industry, such as a vulcanizing agent, a vulcanization accelerator, a process oil and an aging, as long as the object of the present invention is not impaired. Inhibitor, anti-scorch agent, zinc white, stearic acid, etc. may be contained. The rubber composition of the present invention is obtained by kneading using a kneading machine such as a roll or an internal mixer. After the molding process, vulcanization is performed to obtain a tire tread, an undertread, a carcass, a sidewall and a bead. It can be used not only for tire applications such as parts, but also for applications such as anti-vibration rubber, belts, hoses and other industrial products, and is particularly preferably used as rubber for tire treads. The pneumatic tire of the present invention,
The rubber composition of the present invention is used to produce it by a usual method. That is, if necessary, the rubber composition of the present invention containing various chemicals as described above is extruded into a member for tread at an unvulcanized stage, and is pasted and molded by a usual method on a tire molding machine. Then, a raw tire is molded.
This raw tire is heated and pressed in a vulcanizer to obtain a tire. The pneumatic tire of the present invention thus obtained has good fuel economy, is particularly excellent in fracture characteristics and wear resistance, and since the processability of the rubber composition is good, It has excellent productivity.

[0021]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The physical properties of the polymer were measured according to the following methods. <Physical Properties of Polymer> The weight average molecular weight (Mw) of the polymer is measured by gel permeation chromatography [GPC;
Tosoh HLC-8020, column; Tosoh GMH-
XL (two in series)] and using the differential refractive index (R1) as a polystyrene conversion using monodisperse polystyrene as a standard. The Mooney viscosity of the polymer was measured at 100 ° C. using an RLM-01 type tester manufactured by Toyo Seiki. The content of bound acrylonitrile units in the polymer was calculated from the nitrogen content by elemental analysis. The content of styrene unit in the polymer was calculated from the integration ratio of ¹ H-NMR spectrum. The glass transition point (Tg) of the polymer was measured by using a differential scanning calorimeter (DSC) Model 7 manufactured by Perkin Elmer Co., Ltd. under the condition that the temperature was raised to 10 ° C./min after cooling to −100 ° C. Further, the physical properties of the vulcanized rubber were measured by the following methods, and the Mooney viscosity of the rubber composition was measured as follows.

<Physical Properties of Vulcanized Rubber> (1) Using a low exothermic viscoelasticity measuring device (manufactured by Rheometrics), tan δ (50 at a temperature of 50 ° C., a strain of 5% and a frequency of 15 Hz.
C) was measured. The smaller the tan δ (50 ° C), the lower the heat buildup. (2) Destructive strength The strength (Tb) at the time of cutting is JIS K6301-1995.
Was measured according to. (3) Abrasion resistance A Lambourn abrasion tester was used to measure the amount of abrasion at a slip ratio of 60% at room temperature, and the abrasion resistance of Comparative Example 4 or 9 was set to 100, and the abrasion resistance index was expressed. The larger the index, the better. <Mooney viscosity of rubber composition> JIS K6300-1
According to 994, Mooney viscosity [ML _{1 + 4} /
130 ° C.] was measured.

Production Example 1 (Polymer A: Oil-Extended Conjugated Diene Copolymer Rubber) In a polymerization container, 200 parts of water (parts by weight, the same applies hereinafter), 4.5 parts of rosin acid soap, and 66 parts of butadiene were used. Parts, 26 parts of styrene, and 5 parts of acrylonitrile. Then, the temperature of the polymerization vessel was set to 5 ° C., and p-menthane hydroperoxide as a radical polymerization initiator was adjusted to 0.
03 parts, sodium ethylenediamine tetraacetate 0.02
Parts, 0.01 parts of ferrous sulfate heptahydrate, and 0.03 parts of sodium formaldehyde sulfoxylate were added to initiate polymerization. When the polymerization conversion rate reached 30%,
When 3 parts of acrylonitrile is further added, the polymerization conversion rate is 60.
When% was reached, diethylhydroxylamine was added to terminate the polymerization. Next, unreacted monomers were recovered by steam stripping to obtain a conjugated diene-based copolymer rubber latex. Then, an emulsion containing 37.5 parts of aroma oil (manufactured by Fuji Kosan Co., Ltd., trade name "Fuccol Aromax # 3") was blended with 100 parts of solid content contained in this latex, and this was added. Coagulated with sulfuric acid and sodium chloride to give crumbs. Then
This crumb was dried by a hot air dryer to obtain a conjugated diene rubber A oil-extended with aroma oil. The Mooney viscosity of the conjugated diene copolymer rubber contained in the latex is 12
7, the amount of bound acrylonitrile is 10% by weight, the amount of bound styrene is 20% by weight, the weight average molecular weight is 640000, the glass transition point is -43 ° C, and the difference between the extrapolation start temperature and the extrapolation end temperature of the glass transition is It was 11 ° C. The Mooney viscosity of the oil-extended conjugated diene copolymer rubber A was 49.

Production Example 2 (Polymer B: Oil-Extended Conjugated Diene Copolymer Rubber) In a polymerization vessel, 200 parts of water and 4.5 parts of rosin acid soap were used.
Parts, 69 parts of butadiene, 19 parts of styrene, and 7 parts of acrylonitrile. Thereafter, the temperature of the polymerization vessel was set to 5 ° C., and as a radical polymerization initiator, 0.03 part of p-menthane hydroperoxide, 0.02 part of ethylenediaminetetraacetic acid sodium salt, and ferrous sulfate heptahydrate were added. Polymerization was initiated by adding 0.01 part and 0.03 part of sodium formaldehyde sulfoxylate. When the polymerization conversion rate reached 30%, 5 parts of acrylonitrile was further added, and when the polymerization conversion rate reached 60%,
Diethylhydroxylamine was added to terminate the polymerization. Then, a conjugated diene-based copolymer rubber B oil-extended with an aromatic oil was obtained in the same manner as in Production Example A. The conjugated diene-based copolymer rubber contained in the latex has a Mooney viscosity of 132, a bound acrylonitrile amount of 14% by weight,
The amount of bound styrene is 15% by weight, and the weight average molecular weight is 640.
000, the glass transition point was -45 ° C, and the difference between the extrapolation start temperature and the extrapolation end temperature of the glass transition was 12 ° C.
The Mooney viscosity of the oil-extended conjugated diene copolymer rubber A was 45.

Production Example 3 (Polymer C: Oil-Extended Conjugated Diene Copolymer Rubber) In a polymerization container, 200 parts of water and 4.5 parts of rosin acid soap were used.
Parts, 66 parts of butadiene, 26 parts of styrene, and 8 parts of acrylonitrile. Thereafter, the temperature of the polymerization vessel was set to 5 ° C., and as a radical polymerization initiator, 0.03 part of p-menthane hydroperoxide, 0.02 part of ethylenediaminetetraacetic acid sodium salt, and ferrous sulfate heptahydrate were added. Polymerization was initiated by adding 0.01 part and 0.03 part of sodium formaldehyde sulfoxylate. When the conversion of the polymerization reached 60%, diethylhydroxylamine was added to terminate the polymerization. Then, a conjugated diene-based copolymer rubber C oil-extended with an aromatic oil was obtained in the same manner as in Production Example A. The conjugated diene-based copolymer rubber contained in the latex has a Mooney viscosity of 125, a bound acrylonitrile amount of 10% by weight, and a bound styrene amount of 2%.
0% by weight, the weight average molecular weight was 640000, the glass transition point was -41 ° C, and the difference between the extrapolation start temperature and the extrapolation end temperature of the glass transition was 25 ° C. The Mooney viscosity of the oil-extended conjugated diene copolymer rubber A was 47.

Production Example 4 (Polymer D: Oil-Extended Conjugated Diene Copolymer Rubber) In a polymerization container, 200 parts of water and 4.5 parts of rosin acid soap were used.
Parts, 58 parts of butadiene and 42 parts of styrene. Thereafter, the temperature of the polymerization vessel was set to 5 ° C., and as a radical polymerization initiator, 0.03 part of p-menthane hydroperoxide, 0.02 part of ethylenediaminetetraacetic acid sodium salt, and ferrous sulfate heptahydrate were added. Polymerization was initiated by adding 0.01 part and 0.03 part of sodium formaldehyde sulfoxylate. When the conversion of the polymerization reached 60%, diethylhydroxylamine was added to terminate the polymerization. Then, a conjugated diene-based copolymer rubber D oil-extended with an aromatic oil was obtained in the same manner as in Production Example A. The conjugated diene copolymer rubber contained in the latex has a Mooney viscosity of 126, a bound styrene content of 35% by weight,
Weight average molecular weight is 760000, glass transition point is -42.
It was ℃. The Mooney viscosity of the oil-extended conjugated diene copolymer rubber A was 47.

Production Example 5 (Polymer E: Non-oil-extended Conjugated Diene Copolymer Rubber) In a polymerization vessel, 200 parts of water and 4.5 parts of rosin acid soap were used.
Parts, 80 parts of butadiene, 12 parts of styrene, and 5 parts of acrylonitrile. Thereafter, the temperature of the polymerization vessel was set to 5 ° C., and as a radical polymerization initiator, 0.03 part of p-menthane hydroperoxide, 0.02 part of ethylenediaminetetraacetic acid sodium salt, and ferrous sulfate heptahydrate were added. Polymerization was initiated by adding 0.01 part and 0.03 part of sodium formaldehyde sulfoxylate. When the polymerization conversion rate reached 30%, 3 parts of acrylonitrile was further added, and when the polymerization conversion rate reached 60%,
Diethylhydroxylamine was added to terminate the polymerization. Next, unreacted monomers were recovered by steam stripping to obtain a conjugated diene-based copolymer rubber latex. The conjugated diene copolymer rubber contained in the latex had a Mooney viscosity of 50, a bound acrylonitrile amount of 10% by weight, a bound styrene amount of 11% by weight, a weight average molecular weight of 450,000, and a glass transition point of -60 ° C.

Production Example 6 (Polymer F: Non-oil-Extended Conjugated Diene Copolymer Rubber) In a polymerization vessel, 200 parts of water and 4.5 parts of rosin acid soap were used.
Parts, 72 parts of butadiene and 28 parts of styrene.
Then, the temperature of the polymerization vessel was set to 5 ° C., and as a radical polymerization initiator, 0.03 part of p-menthane hydroperoxide and ethylenediaminetetraacetic acid sodium salt were added.
Polymerization was initiated by adding 02 parts, 0.01 part of ferrous sulfate heptahydrate, and 0.03 part of sodium formaldehyde sulfoxylate. When the conversion of the polymerization reached 60%, diethylhydroxylamine was added to terminate the polymerization. Next, unreacted monomers were recovered by steam stripping to obtain a conjugated diene-based copolymer rubber latex. The Mooney viscosity of the conjugated diene copolymer rubber contained in the latex is 49, the amount of bound styrene is 23.5%,
Weight average molecular weight 440000, glass transition point is -61 ° C.
Met. Table 1 shows the microstructures and physical properties of the polymers A to F obtained as described above. Here, polymers A to D
Is an oil-extended rubber obtained by adding 37.5 parts by weight of oil to 100 parts by weight of the polymer, but the polymers E and F are not oil-extended.

[0029]

[Table 1]

Table 2 shows the properties of silica (hydrous silicic acid) used in Examples and Comparative Examples. Where KQ,
Each silica of PR and H2000 is the silica in the present invention.

[0031]

[Table 2]

(Note) 1) AQ: manufactured by Nippon Silica Industry Co., Ltd., trademark "Nipsil A"
"Q" 2) KQ: manufactured by Nippon Silica Industry Co., Ltd., trademark "Nipsil K"
Q ”3) PR: manufactured by Tokuyama Corporation, trademark“ Tokushiru PR ”4) H2000: PPG Industries, In
c. Made, trademark "Hisil 2000"

Examples 1 to 5 and Comparative Examples 1 to 7 As the rubber component, the polymers A to D (oil-extended rubber) of Table 1 obtained in Production Examples 1 to 4 were used, and the composition 1 of Table 3 was used. A rubber composition was prepared by kneading in the first stage and then kneading in the second stage by the compounding formulation shown in (the filler is a carbon black / silica combination system).

[0034]

[Table 3]

(Note) * 1; 6C [N- (1,3 dimethylbutyl) -N'-phenyl-p-phenylenediamine] * 2; DPG (diphenylguadinine) * 3; DM (dibenzothiazylsul) Phenamide) * 4; NS (Nt-butyl-2-benzothiazylsulfenamide) Obtained by measuring the Mooney viscosity of each rubber composition as described above and vulcanizing at 160 ° C for 15 minutes. The physical properties of the rubber composition were measured. The results are shown in Table 4.

[0036]

[Table 4]

As a result of the above, Examples 1 to 1 of the present invention
Comparing 3, 4 and 5 with Comparative Examples 5, 6 and 7, respectively, in the examples, the Mooney viscosity is low (workability is good) and the fracture strength is high, even though the same type of silica is used. , Low heat generation and wear resistance are all excellent. In Comparative Examples 1 to 4 using AQ silica, tan δ is low, but since the dispersibility is not good, the breaking strength and abrasion resistance are very poor. Examples 6 and 7 and Comparative Examples 8 to 11 The polymers E and F (non-oil-extended rubber) of Table 1 obtained in Production Examples 5 and 6 were used, and the compounding recipe shown in Compounding 2 of Table 3 (filling A rubber composition was prepared by first-stage kneading with a material of silica alone) and then second-stage kneading. While measuring the Mooney viscosity of this rubber composition,
The physical properties of the rubber composition obtained by vulcanization at 160 ° C. for 15 minutes were measured. The results are shown in Table 5.

[0038]

[Table 5]

From the above results, comparing Examples 6 and 7 of the present invention with Comparative Examples 10 and 11, respectively, the Mooney viscosity is low in the Examples (the processability is high) even though the types of silica are the same. Good), destructive strength, low heat generation,
It can be seen that the wear resistance is all excellent. In Comparative Examples 8 and 9 using AQ silica, ta
Although nδ is low, the fracture strength and wear resistance are very inferior to those in Examples 6 and 7 because of poor dispersibility.

[0040]

EFFECT OF THE INVENTION The rubber composition of the present invention has good silica dispersibility, excellent low exothermicity, good fracture characteristics and abrasion resistance, and is particularly suitable as a rubber for a tire tread. Used.

[Brief description of drawings]

FIG. 1 is a DSC chart showing how to determine an extrapolation start temperature and an extrapolation end temperature of a glass transition of a conjugated diene-based copolymer rubber according to the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiro Tadaki             2-11-21 Tsukiji, Chuo-ku, Tokyo J             Within SRL Co., Ltd. F-term (reference) 4J002 AC021 AC032 AC062 AC071                       AC081 AC082 BB152 BB182                       DA037 DJ006 EX078 EX088                       GN01

Claims (9)

[Claims] 1. (A) (a) ethylenically unsaturated nitrile
A monomer unit, and (b) an aromatic vinyl monomer unit,
(C) a conjugated diene monomer unit, and
Based on the total amount of (a), (b) and (c) units,
(A) Conjugated diene-based copolymer containing 5 to 45% by weight of unit
A rubber component including a united rubber and 100 parts by weight thereof,
(B) Nitrogen adsorption specific surface area (BET) is 200 to 400 m
²/ G and cetyltrimethylammonium bromide
Adsorption specific surface area (CTAB) 170-270m ²/ G
Characterized in that it contains 10 to 85 parts by weight of certain hydrous silicic acid
Rubber composition. 2. The conjugated diene-based copolymer rubber comprises (a),
The rubber composition according to claim 1, which contains 10 to 50% by weight of the unit (b) based on the total amount of the units (b) and (c). 3. The conjugated diene-based copolymer rubber has a glass transition point of −60 ° C. to 0 ° C. and a Mooney viscosity [ML _{1 + 4} (100
C.)] 20 to 200. The rubber composition according to claim 1 or 2. 4. The rubber composition according to claim 1, 2 or 3, wherein the difference between the extrapolation start temperature and the extrapolation end temperature of the glass transition of the conjugated diene copolymer rubber is 20 ° C. or less. 5. The rubber composition according to claim 1, wherein the conjugated diene-based copolymer rubber is a copolymer of acrylonitrile, styrene and butadiene. 6. The rubber composition according to claim 1, wherein the conjugated diene copolymer rubber is contained in the component (A) in an amount of 30% by weight or more. 7. The rubber composition according to claim 1, further comprising 80 parts by weight or less of (C) carbon black per 100 parts by weight of component (A). 8. The rubber composition according to claim 1, further comprising 1 to 20% by weight of a silane coupling agent (D) with respect to the component (B). 9. A pneumatic tire comprising the rubber composition according to claim 1 as a tread rubber.