JP5415813B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same. More specifically, the present invention blends natural rubber and synthetic isoprene rubber with a thermoplastic resin that is incompatible with natural rubber and synthetic isoprene rubber, thereby reducing low temperature characteristics and driving stability on dry road surfaces (hereinafter referred to as dry grip performance and And a rubber composition that can achieve both braking performance on a wet road surface (hereinafter sometimes referred to as wet grip performance) and a pneumatic tire using the rubber composition.

  In recent years, with the improvement of automobile performance, road paving and the development of highway networks, there is an increasing demand for pneumatic tires with high movement performance. The higher the high exercise performance, the faster and more accurately and safely it is possible to travel. In particular, grip performance represented by acceleration performance and brake performance is an important required characteristic.

For tire tread rubber, especially tread rubber for small tires, wet grip performance and dry grip performance are required. Therefore, a rubber composition in which oil is blended with styrene-butadiene rubber (SBR) is often used. Yes. However, this SBR / oil-based rubber composition has a problem that it is difficult to achieve a balance with low-temperature characteristics, although the wet grip performance and the dry grip performance can be secured due to the high glass transition temperature (Tg). is there.
For example, there is a method of blending with low Tg rubber such as natural rubber or butadiene rubber as a problem of low temperature characteristics, but in this case, there arises a problem that wet grip performance and dry grip performance are deteriorated. In addition, there is a technique for increasing the amount of oil, but in this case, there arises a problem that the dry grip performance is lowered. Further, it is conceivable to reduce the amount of filler, but in this case as well, there arises a problem that the dry grip performance is lowered. As described above, it is difficult to improve the low-temperature characteristics, the wet grip performance, and the dry grip performance at a high level in a well-balanced manner by either method.

On the other hand, various rubber compositions obtained by blending a resin with a rubber component have been proposed. Specifically, as a rubber composition used for a tire tread that can exhibit excellent grip performance, for example, a rubber component containing 40 parts by mass or more of a styrene / butadiene copolymer rubber is selected from alkylphenol resins. In the rubber composition (refer patent document 1) characterized by mix | blending the above resin (A) and 1 or more types of resin (B) chosen from terpene resin and terpene phenol resin, and a rubber component On the other hand, a rubber composition (see Patent Document 2) characterized in that a layered clay mineral and a phenolic resin are blended is disclosed.
However, although these techniques can achieve high grip performance, they are not techniques that can achieve both low temperature characteristics and grip performance.
Further, a rubber-reinforced thermoplastic resin comprising 10% by weight or more of a conjugated diene rubber component and a resin component having the balance of a glass transition temperature (Tg) of 100 to 140 ° C. is 2 to 50 wt. A pneumatic tire using a partially blended rubber composition is disclosed (see Patent Document 3). However, the rubber composition used for this pneumatic tire is for pneumatic tires used on road surfaces that are susceptible to trauma, such as bad roads and construction sites, and does not achieve both low temperature characteristics and grip performance.

JP 2008-208265 A JP 2008-189725 A JP-A-8-208888

  The present invention has been made under such circumstances, and an object thereof is to provide a rubber composition capable of achieving both low temperature characteristics, dry grip performance and wet grip performance, and a pneumatic tire using the rubber composition. To do.

  As a result of intensive research to achieve the above object, the present inventor blended a specific thermoplastic resin incompatible with natural rubber and synthetic isoprene rubber at a predetermined ratio. It has been found that a rubber composition suitable for the purpose can be obtained. The present invention has been completed based on such findings.

That is, the present invention
[1] (A) a natural rubber and / or rubber component containing a synthetic isoprene rubber least 50 mass%, with respect to the 100 parts by weight, unrealized, the vulcanizing agent (B) is more than 8 parts by mass of the thermoplastic resin 1.0-5.0 the mass parts including rubber composition, the component (B) of the thermoplastic resin, haze value indicating the incompatibility of the said measured by the following method (a) component There Ri der 80% or more, (B) the rubber composition component of the thermoplastic resin is characterized alkylphenol resin der Rukoto,
<Method for measuring haze value>
The haze value of a film having a thickness of 600 μm obtained by casting a solution prepared by dissolving 3 g of synthetic isoprene rubber and 1.125 g of a sample thermoplastic resin at a temperature of 25 ° C. in 50 mL of tetrahydrofuran is defined in JIS K 6714. Measure based on.
[2] The rubber composition according to [1], wherein the rubber component (A) contains natural rubber and / or synthetic isoprene rubber in a proportion of 70 to 100% by mass,
[ 3 ] The rubber composition according to [1] or [2] , wherein the content of the component (B) is 10 to 100 parts by mass with respect to 100 parts by mass of the component (A).

[ 4 ] The rubber composition according to [ 3 ] above, wherein the content of the component (B) is 10 to 50 parts by mass,
[ 5 ] The rubber composition according to any one of [1] to [ 4 ], further including (C) a reinforcing filler,
[ 6 ] (C) In the above [ 5 ], the reinforcing filler is carbon black and / or silica, and the content thereof is 20 to 120 parts by mass with respect to 100 parts by mass of the component (A). The rubber composition according to the description,
[ 7 ] A pneumatic tire characterized by using the rubber composition according to any one of [1] to [ 6 ] as a tread member, and [ 8 ] a radial tire for a passenger car, [ 7] ], A pneumatic tire according to
Is to provide.

  According to the present invention, a rubber composition capable of achieving both low temperature characteristics, wet grip performance and dry grip performance by blending natural rubber and synthetic isoprene rubber with an incompatible thermoplastic resin, and A pneumatic tire using the same can be provided.

First, the rubber composition of the present invention will be described.
[Rubber composition]
The rubber composition of the present invention comprises (A) a rubber component containing 50% by mass or more of natural rubber and / or synthetic isoprene rubber, and 100 parts by mass of (B) a rubber containing 8 parts by mass or more of a thermoplastic resin. It is a composition, Comprising: The haze value which shows the incompatibility with the said (A) component measured by the below-mentioned method of the thermoplastic resin of the said (B) component is 40% or more, It is characterized by the above-mentioned.

((A) rubber component)
In the rubber composition of the present invention, a rubber component containing 50% by mass or more of natural rubber and / or synthetic isoprene rubber is used as the rubber component (A).
The natural rubber and synthetic isoprene rubber are not particularly limited and can be appropriately selected from conventionally known rubbers. As the synthetic isoprene rubber, those having a weight average molecular weight of 4 × 10 ⁵ or more and a cis bond content of 95% or more are preferable. This weight average molecular weight is a value in terms of polystyrene measured by a gel permeation chromatography method (GPC method).

In the present invention, the content of the natural rubber and / or synthetic isoprene rubber in the rubber component (A) provides a rubber composition capable of exhibiting good low temperature characteristics, wet grip performance and dry grip performance in a balanced manner. From the viewpoint, it is required to be 50% by mass or more, preferably 70 to 100% by mass, more preferably 90 to 100% by mass, and still more preferably 100%.
In the rubber component (A), the rubber component that can be used in combination with the natural rubber and / or synthetic isoprene rubber in a proportion of 50% by mass or less, preferably 30 to 0% by mass, more preferably 10 to 0% by mass. Examples thereof include butadiene rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, and mixtures thereof. Further, some of them may have a branched structure by using a polyfunctional type, for example, a modifier such as tin tetrachloride or silicon tetrachloride.

((B) thermoplastic resin)
In the rubber composition of the present invention, the thermoplastic resin used as the component (B) needs to have a haze value of 40% or more indicating the degree of incompatibility with the component (A) measured by the following method. .
The higher the haze value, the greater the turbidity and the higher the incompatibility. If the haze value is less than 40%, the degree of incompatibility with the component (A) decreases, and the object of the present invention cannot be achieved. The haze value is preferably 80% or more, more preferably 90% or more.
<Method for measuring haze value>
The haze value of a film having a thickness of 600 μm obtained by casting a solution prepared by dissolving 3 g of synthetic isoprene rubber and 1.125 g of a sample thermoplastic resin at a temperature of 25 ° C. in 50 mL of tetrahydrofuran is defined in JIS K 6714. Measure based on.
Details of the method for measuring the haze value will be described later.

<Types of thermoplastic resin>
As the thermoplastic resin of the component (B) in the rubber composition of the present invention, the haze value measured by the above method indicating the degree of incompatibility with the rubber component (A) is 40% or more. There is no particular limitation, and various thermoplastic resins can be mentioned. For example, one or more kinds of resins having a haze value of 40% or more are appropriately selected from C9 series resins, C5 to C9 series resins, rosin series resins, alkylphenol series resins, terpene-aromatic compound series resins, and the like. Can be used.
Here, the C9-based resin refers to a C9-based synthetic petroleum resin, which is a solid polymer obtained by polymerizing a C9 fraction using a Friedel-Crafts-type catalyst such as AlCl ₃ or BF ₃ , indene, Examples thereof include a copolymer mainly composed of methylindene, α-methylstyrene, vinyltoluene and the like.
The C5-C9 resin refers to a C5-C9 synthetic petroleum resin, which is a solid polymer obtained by polymerizing a C5-C11 fraction using a Friedel-Crafts catalyst such as AlCl ₃ or BF _3. For example, a copolymer containing styrene, vinyltoluene, α-methylstyrene, indene or the like as a main component can be used. In this invention, as this C5-C9 resin, resin with many components of C9 or more is preferable from a viewpoint of incompatibility with (A) component.

On the other hand, rosin resins include natural resin rosin, gum rosin, tall oil resin, wood rosin, etc. contained in raw pine ani and tall oil. Hydrogenated rosins; glycerin ester rosins, partially hydrogenated rosins and fully hydrogenated rosins; pentaerythritol ester rosins, partially hydrogenated rosins and polymerized rosins.
Examples of the alkylphenol resin include alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resin, and low-polymerization alkylphenol-formaldehyde resins.
A typical example of the terpene-aromatic compound-based resin is a terpene-phenol resin. This terpene-phenol resin can be obtained by a method in which a terpene and various phenols are reacted using a Friedel-Crafts type catalyst or further condensed with formalin. The starting terpenes are not particularly limited, and monoterpene hydrocarbons such as α-pinene and limonene are preferable, those containing α-pinene are more preferable, and α-pinene is particularly preferable. In the present invention, a terpene-phenol resin having a high ratio of the phenol component is preferable.
In addition, coumarone-indene resin, xylene-based resin, vinyl toluene-α-methylstyrene copolymer, and the like can also be used.

In the rubber composition of this invention, 1 type may be used individually as a thermoplastic resin of (B) component, and it may be used in combination of 2 or more type. Moreover, the content needs to be 8 mass parts or more with respect to 100 mass parts of (A) rubber components mentioned above. If the content is less than 8 parts by mass, the object of the present invention cannot be achieved. Therefore, the content of the thermoplastic resin is preferably in the range of 10 to 100 parts by mass, more preferably 10 to 50 parts by mass, still more preferably 15 to 50 parts by mass, and particularly preferably 20 to 50 parts by mass.
In the present invention, by using the thermoplastic resin of component (B) in the amount as described above, it is possible to obtain a rubber composition that can achieve both low temperature characteristics, wet grip performance and dry grip performance.

The rubber composition of the present invention can further contain a reinforcing filler as the component (C).
((C) Reinforcing filler)
As the reinforcing filler, carbon black and / or silica is preferably used.
The carbon black is not particularly limited, and any carbon black conventionally used as a reinforcing filler for rubber can be appropriately selected and 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 may be used individually by 1 type, and may be used in combination of 2 or more type.
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 BET specific surface area of 40 to 350 m ² / g. Silica having a BET 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 BET specific surface area in the range of 80 to 300 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 individually by 1 type, and may be used in combination of 2 or more type.

  In the rubber composition of the present invention, the content of the reinforcing filler, preferably the carbon black and / or silica, is 20 to 120 parts by mass with respect to 100 parts by mass of the (A) rubber component. Preferably, it is 35-100 mass parts. If this content is 20 parts by mass or more, the reinforcing effect is exhibited, while if it is 120 parts by mass or less, the rolling resistance does not become too large.

(Silane coupling agent)
In the rubber composition of the present invention, when silica is used as the reinforcing filler, a silane coupling agent can be blended for the purpose of further improving the reinforcing property.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxy). Silylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyl Trimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamo Yl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzoyltetrasulfide, 3-triethoxysilyl Propyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide , Dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide, and the like. Among these, bis (3-trieth Shi silyl propyl) polysulfide and 3-trimethoxysilylpropyl benzothiazyl tetrasulfide are preferable.
One of these silane coupling agents may be used alone, or two or more thereof may be used in combination.

  In the rubber composition of the present invention, the amount of the preferred silane coupling agent varies depending on the type of the silane coupling agent, but is preferably selected in the range of 2 to 20 parts by mass with respect to 100 parts by mass of silica. The If this amount is less than 2 parts by mass, the effect as a coupling agent is hardly exhibited, and if it exceeds 20 parts by mass, the rubber component may be gelled. From the viewpoint of the effect as a coupling agent and the prevention of gelation, the preferred amount of the silane coupling agent is in the range of 5 to 15 parts by mass.

(Function)
In the rubber composition of the present invention, by using natural rubber and / or synthetic isoprene rubber as the rubber component (A), it is possible to ensure low temperature characteristics due to its low Tg. Furthermore, by blending an incompatible resin with the natural rubber or synthetic isoprene rubber, the resin does not become compatible and remains at a high temperature, so that the storage elastic modulus E ′ at 30 ° C. can be increased. , Dry grip performance is improved. That is, by blending an incompatible resin with natural rubber or synthetic isoprene rubber, a low-temperature characteristic and wet grip performance can be secured, and a rubber composition having excellent dry grip performance can be obtained by the action of the resin. .

(Preparation of rubber composition)
In the rubber composition of the present invention, various chemicals usually used in the rubber industry, for example, a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, an anti-scorch agent, as desired, as long as the object of the present invention is not impaired. , Zinc white, stearic acid and the like.
As said vulcanizing agent, sulfur etc. are mentioned, The usage-amount is 0.1-10.0 mass parts as a sulfur content with respect to 100 mass parts of rubber components, More preferably, it is 1.0-5. 0 parts by mass. If the amount is less than 0.1 parts by mass, the rupture strength, wear resistance, and low heat build-up of the vulcanized rubber may be reduced. If the amount exceeds 10.0 parts by mass, rubber elasticity is lost.

  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 mass part is preferable, More preferably, it is 0.2-3.0 mass part.

  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, etc. The amount used is rubber. 0.1-6.0 mass parts is preferable with respect to 100 mass parts of matrices, More preferably, it is 0.3-5.0 mass parts.

The rubber composition of the present invention can be prepared by kneading the above-described components using a kneader such as a Banbury mixer, a roll, or an internal mixer.
The rubber composition of the present invention thus prepared can achieve both low temperature characteristics, dry grip performance and wet grip performance, and is particularly suitably used as a tread member for a pneumatic tire.

[Pneumatic tire]
The pneumatic tire of the present invention is characterized by using the above-described rubber composition of the present invention for a tread member.
The pneumatic tire of the present invention is manufactured 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 tread member at an unvulcanized stage and pasted on a tire molding machine by a usual method. The green tire is molded. The green tire is heated and pressed in a vulcanizer to obtain a tire.
As the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.
The pneumatic tire of the present invention is particularly suitably used as a radial tire for passenger cars.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. Various measurements and evaluation methods were performed based on the following methods.
(1) Measurement of haze value indicating incompatibility of component (B) with component (A) In 50 mL of tetrahydrofuran, 3 g of synthetic isoprene rubber (manufactured by JSR, trade name “JSR IR2209”) and a sample thermoplastic resin A solution obtained by dissolving 1.125 g at a temperature of 25 ° C. is cast-molded, and then the haze value of a film having a thickness of 600 μm obtained by hot pressing at 100 ° C. and 20 MPa is made by Nippon Denshoku Industries Co., Ltd. Measurement was performed based on JIS K 6714 using “TRIBIDIMETER NDH5000W”.
(2) Evaluation with rubber composition <Low-temperature characteristics [-20 ° C. storage elastic modulus E ′]>
Using a spectrometer [Toyo Seiki Co., Ltd.], the storage elastic modulus (E ′) was measured under the conditions of −20 ° C., dynamic strain 0.1%, and frequency 52 Hz. Comparative example 3 was set to 100 and displayed as an index. A lower index value is better.
<Dry grip performance [30 ° C. storage elastic modulus E ′]>
Using a spectrometer [Toyo Seiki Co., Ltd.], the storage elastic modulus (E ′) was measured under the conditions of 30 ° C., dynamic strain 1%, and frequency 52 Hz. Comparative example 3 was set to 100 and displayed as an index. A higher index value is better.
<Wet grip performance (BPST method)>
The resistance value when the wet concrete road surface was rubbed with a vulcanized rubber test piece was measured with a British portable skid tester (BPST) at room temperature. The larger the index value, the better the wet grip performance.

(3) Evaluation with tires Using 185 / 70R14 tires, with an indoor ice turntable testing machine,
Internal pressure: 200 kPa
Load: 4.71kN
Ice surface temperature: -1 ° C, fluctuation range ± 1 ° C
Road surface condition: wet on ice (wet on ice, slippery road surface that gets wet when touched)
Evaluation speed: 20 km / h → 0 km / h (braking)
The friction coefficient at the time of braking was measured under the following conditions. A larger index value indicates better wet grip performance.

Example 1 , Reference Examples 1 to 11 and Comparative Examples 1 to 4
Based on the content of each compound shown in Table 3, rubber compositions of Examples , Reference Examples and Comparative Examples were prepared. The type of thermoplastic resin used is shown in Table 1, and the formulation of each component is shown in Table 2.
The rubber composition is vulcanized by a conventional method to prepare each test sample, and for each sample, the storage elastic modulus (E ′) at −20 ° C. and 30 ° C. is measured and the wet grip performance is evaluated by the BPST method. went. The measurement results are shown in Table 3.
Next, a test passenger radial tire and tire size 185 / 70R14 were manufactured by a conventional method using each of the obtained rubber compositions as a tread. Using the obtained tire, the braking performance on a wet road surface was evaluated by an indoor ice turntable tester. The evaluation results are shown in Table 3.

[Note] The haze value when aroma oil is used instead of resin is 35%.

[note]
1) Natural rubber: “SIR20” made in Indonesia
2) SBR: Emulsion polymerization SBR
3) Resin: Resins listed in Table 1 4) Carbon black N339: “Seast KH” manufactured by Tokai Carbon Co., Ltd.
5) Anti-aging agent 6C: “NOCRACK 6C” manufactured by Ouchi Shinko Kogyo Co., Ltd., N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine 6) Vulcanization accelerator CZ: Ouchi Shinko Kogyo "Noxeller CZ", N-cyclohexyl-2-benzothiazylsulfenamide

[note]
7) (St / Vi%): St represents the bound styrene content (mass%) in SBR, and Vi represents the vinyl bond content (mol%) in SBR.
8) Glass transition temperature [Tg]: Tg of a mixture of a rubber component and a resin.

7) (St / Vi%): Same as the footnote in Table 3.
8) Glass transition temperature [Tg]: Tg of the mixture of the rubber component and the aroma oil.

  The rubber composition of the present invention can achieve both low temperature characteristics, wet grip performance and dry grip performance by blending a natural rubber or synthetic isoprene rubber with an incompatible thermoplastic resin. It is suitably used for a tread member of a pneumatic tire.

Claims (8)

(A) natural rubber and / or rubber component containing a synthetic isoprene rubber least 50 mass%, with respect to the 100 parts by mass, seen contains the (B) thermoplastic resin 8 parts by mass or more, a vulcanizing agent 1.0 5.0 the mass parts including rubber composition, the component (B) of the thermoplastic resin, 0 haze value 8 showing the incompatibility of the component (a) was measured by the following method % or more der is, the (B) a rubber composition component of the thermoplastic resin is characterized der Rukoto alkylphenol resin.
<Method for measuring haze value>
The haze value of a film having a thickness of 600 μm obtained by casting a solution prepared by dissolving 3 g of synthetic isoprene rubber and 1.125 g of a sample thermoplastic resin at a temperature of 25 ° C. in 50 mL of tetrahydrofuran is defined in JIS K 6714. Measure based on.   The rubber composition according to claim 1, wherein the rubber component (A) contains natural rubber and / or synthetic isoprene rubber in a proportion of 70 to 100% by mass. The rubber composition according to claim 1 or 2 , wherein the content of the component (B) is 10 to 100 parts by mass with respect to 100 parts by mass of the component (A). The rubber composition according to claim 3 , wherein the content of component (B) is 10 to 50 parts by mass. Furthermore, the rubber composition in any one of Claims 1-4 containing the filler for reinforcement (C). The rubber composition according to claim 5 , wherein the reinforcing filler (C) is carbon black and / or silica, and the content thereof is 20 to 120 parts by mass with respect to 100 parts by mass of the component (A). object. A pneumatic tire using the rubber composition according to any one of claims 1 to 6 for a tread member. The pneumatic tire according to claim 7 , which is a radial tire for a passenger car.