JP2014111787A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition having excellent dry grip performance and wet grip performance, low heat generating property and high elasticity, and a pneumatic tire using the composition.SOLUTION: The rubber composition comprises a rubber component (A) comprising natural rubber and/or a synthetic isoprene rubber by 50 mass% or more, a resin composition (B) comprising a novolac resorcin-based resin and a resol phenolic resin, and a thermoplastic resin (C) having a haze value of 40% or less that indicates a solubility degree with the rubber component (A), measured by a specified method. The content of the thermoplastic resin (C) is 8 parts by mass or more with respect to 100 parts by mass of the rubber component (A).

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same. More specifically, the present invention may be referred to as driving stability on a dry road surface (hereinafter referred to as dry grip performance) by blending natural rubber or synthetic isoprene rubber with a thermoplastic resin incompatible with the natural rubber or synthetic isoprene rubber. And a rubber composition excellent in braking performance on a wet road surface (hereinafter sometimes referred to as wet grip performance), low heat generation and high elasticity, 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 heat build-up, although the wet grip performance and the dry grip performance can be secured due to the high glass transition temperature (Tg). There is.
For example, there is a method of blending with a low Tg rubber such as natural rubber or butadiene rubber as a problem of low heat generation, 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, in any method, it is difficult to improve low heat generation, wet grip performance and dry grip performance at a high level in a well-balanced manner.

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 heat generation 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 in 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 heat generation and grip performance. .

  Further, conventionally, a highly elastic rubber has been used for a carcass member of a tire, and as a means for increasing the elasticity of the rubber, the amount of filler such as carbon black is increased (for example, see Patent Document 4), Techniques such as increasing the sulfur of the sulfurizing agent to increase the crosslinking point are known, but when the amount of filler such as carbon black is increased, the workability of the rubber composition and the fracture resistance such as elongation at break are reduced. There exists a subject that it deteriorates or the exothermic characteristic of a rubber composition deteriorates. Furthermore, even when the amount of sulfur in the vulcanizing agent is increased, there is a problem that the elongation at break decreases and the change in physical properties due to thermal deterioration increases.

  On the other hand, as a means for achieving high elasticity while suppressing a decrease in elongation at break of the rubber composition, for example, an unmodified novolak-type phenol obtained by condensation reaction of phenols and aldehydes under an acidic catalyst Add a resin, an unsaturated oil such as tall oil or cashew oil, or a modified novolac phenolic resin modified with an aromatic hydrocarbon such as xylene or mesitylene, and hexamethylenetetramine that hardens these resins as a curing agent. A method has been proposed (see, for example, Patent Documents 5 and 6).

JP 2008-208265 A JP 2008-189725 A JP-A-8-208888 Japanese Patent Laid-Open No. 9-272307 Japanese Patent Laid-Open No. 5-98081 JP 2001-226528 A

  The present invention has been made under such circumstances, and provides a rubber composition which is excellent in dry grip performance and wet grip performance, has low heat buildup and high elasticity, and a pneumatic tire using the rubber composition. It is intended.

  As a result of intensive studies to achieve the above-mentioned object, the present inventor has blended a specific resin compound and a thermoplastic resin in a predetermined ratio with natural rubber or synthetic isoprene rubber. It has been found that a rubber composition that can be adapted to the above can be obtained. The present invention has been completed based on such findings.

More specifically, the present invention has the following configuration.
[1] A rubber component (A) containing 50% by mass or more of natural rubber and / or synthetic isoprene rubber;
Heat having a haze value of 40% or more indicating a degree of incompatibility between the resin composition (B) containing a novolac-type resorcin resin and a resole-type phenol resin and the rubber component (A) measured by the following method A rubber composition comprising a plastic resin (C), wherein the content of the thermoplastic resin (C) is 8 parts by mass or more with respect to 100 parts by mass of the rubber component (A).
<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 above-mentioned [1], wherein the novolac-type resorcin resin is obtained by reacting resorcin and aldehydes at a molar ratio (aldehydes / resorcin) of 0.4 or more and 0.8 or less. } The rubber composition as described in.

[3] The amount of dimethylene ether groups in the resol-type phenolic resin is 20 mol% or more and 80 mol% with respect to the total amount of linking groups derived from aldehydes bonding aromatic rings derived from phenols. The rubber composition as described in [1] above, wherein:

[4] The rubber composition as described in [1] above, wherein the content of the novolac-type resorcin resin in the resin composition (B) is 18% by mass or more and 50% by mass or less.

[5] The rubber according to [4], wherein the content of the resin composition (B) is 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component (A). Composition,

[6] The rubber composition as described in [1] above, wherein the resin composition (B) contains a filler in advance.

[7] The rubber composition as described in [1] above, wherein the filler is dry silica.

[8] The rubber composition as described in [1] above, wherein the rubber component (A) contains natural rubber and / or synthetic isoprene rubber in a proportion of 70 to 100% by mass.

[9] The rubber composition as described in [1] above, wherein the thermoplastic resin (C) has a haze value indicating a degree of incompatibility with the rubber component (A) of 80% or more.

[10] The rubber composition as described in [1] above, wherein the content of the thermoplastic resin (C) is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component (A).

[11] The rubber composition as described in [10] above, wherein the content of the thermoplastic resin (C) is 10 to 50 parts by mass with respect to 100 parts by mass of the rubber component (A).

[12] The thermoplastic resin (C) is at least one selected from a C9 resin, a C5 to C9 resin, a rosin resin, an alkylphenol resin, and a terpene-aromatic compound resin. The rubber composition according to the above [1].

[13] The rubber composition as described in [1] above, further comprising a reinforcing filler (D).

[14] The reinforcing filler (D) 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 rubber component (A). The rubber composition according to [13] above.

[15] A pneumatic tire using the rubber composition according to the present invention as a constituent member.

[16] The pneumatic tire according to [15], which is a radial tire for a passenger car.

  According to the present invention, it is possible to provide a rubber composition that is excellent in dry grip performance and wet grip performance, has low heat buildup and high elasticity, and a pneumatic tire using the rubber composition.

First, the rubber composition of the present invention will be described.
[Rubber composition]
The rubber composition of the present invention includes (A) a rubber component containing 50% by mass or more of natural rubber and / or synthetic isoprene rubber, a resin composition (B) containing a novolac-type resorcin resin and a resole-type phenol resin, Containing a thermoplastic resin (C) having a haze value of 40% or more indicating the degree of incompatibility with the rubber component (A) measured by the following method, and the content of the thermoplastic resin (C) is It is 8 mass parts or more with respect to 100 mass parts of said rubber components (A).

(Rubber component (A))
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).
By using natural rubber and / or synthetic isoprene rubber as the rubber component (A), low heat build-up due to its low Tg can be realized.
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) is a rubber composition capable of exhibiting good low heat build-up, wet grip performance and dry grip performance in a balanced manner. From the viewpoint of obtaining, it needs 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.

(Resin composition (B))
In the rubber composition of the present invention, the resin composition (B) includes a novolac-type resorcin resin and a resole-type phenol resin.
In order to increase the elastic modulus of the rubber composition, it is effective to add a phenolic resin composition, which is a thermosetting resin, but the novolac-type resorcinol resin alone has no curing agent because there is no methylol group at the end. Cannot be cured. On the other hand, since the resol type phenolic resin has a methylol group at the end or the like, it can be cured without a curing agent. However, the resole phenolic resin alone has a slow resin curability, and the resin does not sufficiently cure during rubber vulcanization. Therefore, in this embodiment, by adding a novolac-type resorcin resin and a resole-type phenol resin to the resin composition, the elastic modulus in the rubber composition is increased without using a curing agent, and the elongation at break is large. I found out that That is, by using the above-mentioned novolac-type resorcin resin and resole-type phenol resin together, a bulky cured product is formed by the reaction between the resole-type phenol resin and the novolac-type resorcin resin, and this is a pseudo-crosslinked structure in the rubber component. As such, it is considered that it is effective in increasing elasticity and increasing elongation at break.
In the present embodiment, the above “phenolic resin” refers to a wide range of phenolic resins including not only polycondensates made only of phenol but also polycondensates made of phenols such as cresol and xylenol. That means.

  The resol type phenolic resin is synthesized by reacting phenols with aldehydes. Actually, the above-mentioned resol type phenolic resin is obtained as a precursor before curing, but when an alkali catalyst is used in the above reaction, an addition reaction mainly proceeds to form a low polymerization degree resol type phenolic resin.

Examples of phenols used in the resol type phenolic resin include cresols such as phenol, o-cresol, m-cresol, and p-cresol; 2,3-xylenol, 2,4-xylenol, 2,5 -Xylenols such as xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol; ethylphenols such as o-ethylphenol, m-ethylphenol, p-ethylphenol; isopropylphenol, butylphenol, Butylphenols such as p-tert-butylphenol; alkylphenols such as p-tert-amylphenol, p-octylphenol, p-nonylphenol, p-cumylphenol; fluorophenol, chlorophenol, bromophenol, iodophe Halogenated phenols such as diol; monovalent phenol substitutes such as p-phenylphenol, aminophenol, nitrophenol, dinitrophenol and trinitrophenol; and monovalent phenols such as 1-naphthol and 2-naphthol; And polyphenols such as resorcin, alkylresorcin, pyrogallol, catechol, alkylcatechol, hydroquinone, alkylhydroquinone, prologurcine, bisphenol A, bisphenol F, bisphenol S, and dihydroxynaphthalene. These can be used individually or in mixture of 2 or more types.
Among these phenols, those selected from economically advantageous phenols, cresols, and bisphenol A are preferable.

Examples of aldehydes used in the above-mentioned resol type phenolic resin and novolak type resorcinic resin include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butyl. Examples include aldehyde, caproaldehyde, allyl aldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like. These can be used alone or in combination of two or more.
Among these aldehydes, preferred are those selected from formaldehyde and paraformaldehyde, which are excellent in reactivity and inexpensive.

The resol type phenolic resin can be synthesized by reacting the above-described phenols and aldehydes in the presence of a catalyst such as an alkali metal, an amine, or a divalent metal salt.
Examples of the catalyst used in the above synthesis include hydroxides of alkali metals such as sodium hydroxide, lithium hydroxide and potassium hydroxide; oxides of alkaline earth metals such as calcium, magnesium and barium and hydroxides. Substances such as substances; amines such as sodium carbonate, aqueous ammonia, triethylamine, hexamethylenetetramine; divalent metal salts such as magnesium acetate and zinc acetate; can be used alone or in combination of two or more.

  In the synthesis of the resol type phenolic resin, the reaction molar ratio of phenols and aldehydes is preferably 0.80 mol or more and 2.50 mol or less with respect to 1 mol of phenols, More preferably, it is 1.00 mol or more and 2.30 mol or less. When the molar ratio is in the above range, reaction control is easy and a resol type phenolic resin can be obtained reliably.

  Moreover, the amount of dimethylene ether groups of the resol-type phenolic resin is 20 mol% or more and 80 mol% or less with respect to the total amount of bonding groups derived from aldehydes bonding aromatic rings derived from phenols. It is preferable that it is 25 mol% or more and 75 mol% or less. When the amount of dimethylene ether groups is in the above range, a phenolic resin composition having good curability and excellent thermal stability and no quality variation can be obtained.

In addition, the ratio of the bonding group in the above-mentioned resol type phenol resin is measured based on 1H-NMR method. Specifically, a resol type phenol resin was treated with acetic anhydride in a pyridine catalyst to acetylate a methylol group, and 1H-NMR of this acetylated product was measured.
The amount of each linking group was determined based on the acetone peak (2.04 ppm) from the measured spectrum, respectively, with a methylene group (about 3.8 ppm), a dimethylene ether group (about 4.5 ppm), and a methylol group (about 5. 0 ppm), and the ratio of the integrated intensity of these peaks is ½ times for methylene and methylol groups and ¼ times for dimethylene ether groups. The ratio (mol%) of the amount of dimethylene ether groups to the sum of the amounts of methylene groups, dimethylene ether groups and methylol groups was calculated.

  Further, as a measuring apparatus, an NMR measuring apparatus “JNM-AL300” (frequency: 300 MHz) manufactured by JEOL Ltd. was used. Here, the above measurement method is the case where phenol and formaldehyde are used as raw materials for the resol type phenolic resin, but even when other phenols and aldehydes are used, the measurement is basically based on the same principle. can do.

On the other hand, examples of the resorcins used in the novolac-type resorcin resin include methyl resorcins such as resorcin, 2-methyl resorcin, 5-methyl resorcin and 2,5-dimethyl resorcin, 4-ethyl resorcin, 4-chloro resorcin 2-nitroresorcin, 4-bromoresorcin, 4-n-hexylresorcin, and the like. These can be used alone or in admixture of two or more.
Among these resorcins, those selected from economically advantageous resorcin and methyl resorcins are preferable.

  The novolac-type resorcinol resin can be synthesized by reacting resorcin and the above-mentioned aldehydes in the presence of an acidic catalyst, and then removing water by a dehydration step. Moreover, as a catalyst used for the synthesis | combination of a novolac-type resorcinol-type resin, acids, such as an oxalic acid, hydrochloric acid, a sulfuric acid, diethyl sulfuric acid, and paratoluenesulfonic acid, can be used individually or in combination of 2 or more types. In addition, since resorcin itself exhibits acidity, it can be synthesized without a catalyst.

  In the synthesis of the novolac type resorcin resin, the reaction molar ratio of resorcin to aldehydes is preferably 0.40 mol or more and 0.80 mol or less, more preferably 1 mol of resorcin. Contains 0.45 mol or more and 0.75 mol or less of aldehydes. When the molar ratio is in the above range, it becomes easy to control the reaction and handle the resin.

The content of the novolac-type resorcin resin in the resin composition (B) is preferably 18% by mass or more and 50% by mass or less, and 20% by mass or more and 45% by mass or more with respect to the entire resin composition. More preferably.
By setting the content of the novolac-type resorcin-based resin in the above range, the curability of the resin component in the present embodiment can be improved, and a rubber composition having high elasticity and low heat generation can be obtained.

Furthermore, a filler may be added in advance to the resin composition (B) in order to improve the blocking property due to its standing. Various fillers can be used, but examples include calcium carbonate, calcium stearate, silica, barium sulfate, talc, clay, graphite, and the like. These may be used alone or in combination of two or more. Can do. Among these, it is preferable to use silica, and dry silica is particularly preferable from the viewpoint of few demerits with respect to physical properties when a rubber composition is obtained.
The addition amount of the filler is preferably 1 part by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the resin composition (B). Thereby, the blocking property by leaving the resin composition can be improved without inhibiting the elastic modulus and elongation at break of the rubber composition.

  In order to obtain the resin composition (B) in the present embodiment, the method of mixing the resol type phenolic resin and the novolac type resorcinic resin may be any method in which both components can be uniformly mixed and dispersed. It is not limited. For example, a method of adding and mixing a novolac type phenolic resin into a resol type phenolic resin in the middle of a reaction, a method of adding a resol type phenolic resin to a novolak type phenolic resin in the middle of a reaction, or a resol type There are a method of simply pulverizing and mixing a phenolic resin and a novolac-type phenolic resin, and a method of kneading with a twin screw extruder, an open roll, a pressure kneader, or the like.

  Moreover, it is preferable that the said resin composition (B) is the shape of a powder or solid. When the shape is not powder or solid, but semi-solid or liquid, it is not preferable because it causes a problem of poor workability when blended into a molded product.

  Furthermore, it is preferable that content of the said resin composition (B) shall be 1 to 30 mass parts with respect to 100 mass parts of said rubber components (A), and shall be 5 to 20 mass parts. It is more preferable. When the content is in the above range, a rubber composition having high elasticity and high elongation at break can be obtained.

(Thermoplastic resin (C))
In the rubber composition of the present invention, the thermoplastic resin (C) needs to have a haze value of 40% or more indicating the degree of incompatibility with the rubber component (A) measured by the following method.
<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.
By blending an incompatible resin with the above natural rubber or synthetic isoprene rubber, the resin remains incompatible and remains at a high temperature, so that the storage elastic modulus E ′ at 30 ° C. can be increased. Grip performance is improved. In other words, by blending an incompatible resin with natural rubber or synthetic isoprene rubber, it is possible to ensure low heat buildup and wet grip performance, and to obtain a rubber composition with excellent dry grip performance by the action of the resin. it can.

  The higher the haze value, the greater the turbidity and the higher the incompatibility. When the haze value is less than 40%, the degree of incompatibility with the rubber 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.

The thermoplastic resin (C) is not particularly limited as long as the haze value is 40% or more, and various thermoplastic resins can be exemplified. For example, one or more types of resins having a haze value of 40% or more are appropriately selected from C9-based resins, C5-C9-based resins, rosin-based resins, alkylphenol-based resins, terpene-aromatic compound-based 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 the present invention, as the C5 to C9 resin, a resin having many components of C9 or more is preferable from the viewpoint of incompatibility with the rubber component (A).

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 the present invention, one type of thermoplastic resin (C) may be used alone, or two or more types may be used in combination. 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 (C) in an amount as described above, it is possible to obtain a rubber composition that can achieve both low heat buildup, wet grip performance and dry grip performance.

The rubber composition of the present invention can further contain a reinforcing filler (D).
(Reinforcing filler (D))
As the reinforcing filler, carbon black and / or silica is preferably used.
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 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 reinforcing filler (D), preferably the carbon black and / or silica content is 20 to 120 parts by mass with respect to 100 parts by mass of the rubber component (A). It is preferable that it is 35 to 100 parts by mass. 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 (D), 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.

(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 heat build-up, 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 as a constituent member. The constituent members are not particularly limited, and can be used for, for example, tread rubber, undertread, carcass, sidewalls, beads, and the like.
The pneumatic tire of the present invention is manufactured by a usual method. For example, when used as a tread member, the rubber composition of the present invention containing various chemicals as described above is extruded into a tread member at an unvulcanized stage, and is usually used on a tire molding machine. Affixed and molded by the method to form a green tire. The green tire is heated and pressed in a vulcanizer to obtain a tire.
The pneumatic tire of the present invention is particularly preferably 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. In the following description, “part” means part by mass and “%” means mass% unless otherwise specified.

(Resol type phenol resin)
To a reaction apparatus equipped with a stirrer, a reflux condenser and a thermometer, 1000 parts of phenol and 1294 parts of 37% formaldehyde aqueous solution were added (molar ratio (formaldehyde / phenol) = 1.50), and 5 parts of zinc acetate was further added. . The mixture was refluxed for 1 hour, and water generated by the reaction was removed in vacuum. When the temperature reached 90 ° C., the mixture was further reacted for 1 hour to obtain 1145 parts of a solid resol type phenol resin at room temperature (25 ° C.).
As a result of analyzing this resol type phenol resin by 1H-NMR under the above-mentioned conditions, the amount of dimethylene ether groups relative to the total amount of linking groups derived from aldehyde was 45 mol%.

(Novolac type resorcin resin)
To a reactor equipped with a stirrer, a reflux condenser and a thermometer, 1000 parts of resorcin and 3 parts of oxalic acid were added. The internal temperature was heated to 100 ° C., and after reaching the temperature, 369 parts of 37% formaldehyde aqueous solution was added successively over 30 minutes (molar ratio (formaldehyde / phenol) = 0.50). Thereafter, the mixture was refluxed for 1 hour, and normal pressure removal of water generated by the reaction and vacuum removal were performed until the temperature reached 170 ° C., thereby obtaining 1040 parts of a novolac-type resorcin resin solid at room temperature.

(Production of resin composition (B))
Each novolac-type resorcinol resin and resole-type phenolic resin obtained above are mixed in the combinations and compositions shown in Table 1, and pulverized by an impact pulverizer to obtain powdered resin compositions 1 to 3 It was.

<Examples 1-20 and Comparative Examples 1-5>
An unvulcanized rubber composition obtained by kneading the mixture shown in Table 3 using a Banbury mixer was sheeted to a thickness of 2 mm, and then vulcanized at 145 ° C. for 30 minutes. Each characteristic by the following method was evaluated with respect to the test sample of the obtained vulcanized rubber. Table 2 shows the types of the thermoplastic resin (C) used.

Moreover, about the haze value which shows the incompatibility with respect to the rubber component (A) of a thermoplastic resin (C), it measured with the following method.
A solution obtained by dissolving 3 g of synthetic isoprene rubber (manufactured by JSR, trade name “JSR IR2209”) and 1.125 g of a sample thermoplastic resin at a temperature of 25 ° C. in 50 mL of tetrahydrofuran is cast-molded. The haze value of a film having a thickness of 600 μm obtained by hot pressing under the condition of 20 MPa was measured based on JIS K 6714 using “TRIBIDIMETER NDH5000W” manufactured by Nippon Denshoku Industries Co., Ltd.

<Evaluation>
The following evaluation was performed on each test sample.
For each test sample, (1) Mooney viscosity (ML1 + 4), (2) Stress strain (rubber hardness (HD), tensile stress (M100), elongation at break (EB), and break strength ( TB) measurement) and (3) evaluation of viscoelasticity (measurement of dynamic elastic modulus (E ′) at 25 ° C. and 60 ° C. and measurement of loss tangent (tan δ) at 25 ° C. and 60 ° C.). went.
The measurement results for each evaluation item are shown in Table 3.

(1) Mooney Viscosity The Mooney Viscosity (ML1 + 4) was measured according to JIS K 6300 for the rubber composition samples of each Example and Comparative Example before vulcanization. Table 3 shows the measurement results.

(2) Stress strain characteristics About each test sample, the tensile stress (M100) (MPa) at the time of 100% elongation was measured.
Further, each test sample was punched into JIS dumbbell shape No. 3 and subjected to a tensile test at 25 ° C. in accordance with JIS K 6251. Elongation at break (EB) (%) and breaking strength (TB) ( MPa).

(3) Viscoelasticity Using a spectrometer (manufactured by Toyo Seiki Co., Ltd.), storage elastic modulus (E ′) and loss tangent (tan δ) at 25 ° C. and 60 ° C. under conditions of an initial load of 100 g, a strain of 2%, and a frequency of 50 Hz. It was measured.

In addition to the above formulation, stearic acid: 2 parts, anti-aging agent Nocrack 6C: 1 part, zinc oxide: 4 parts, vulcanization accelerator Noxeller CZ: 3 parts, sulfur: 5.6 parts.
[note]
1) Natural rubber: “SIR20” made in Indonesia
2) Type of resin composition (B): described in Table 1 3) Type of thermoplastic resin (C): described in Table 2 4) Carbon black N339: “Seast KH” manufactured by Tokai Carbon Co., Ltd.

  From Table 3, it can be seen that for Examples 1 to 20 according to the present invention, good results were obtained with respect to stress-strain characteristics and viscoelasticity.

The rubber composition of the present invention is excellent in dry grip performance and wet grip performance, has low heat buildup and high elasticity, and is suitably used for pneumatic tire members and the like.

More specifically, the present invention has the following configuration.
[1] A rubber component (A) containing 50% by mass or more of natural rubber and / or synthetic isoprene rubber;
A resin composition (B) comprising a novolac-type resorcin resin and a resole-type phenol resin;
Containing a thermoplastic resin (C) having a haze value of 40% or more indicating the degree of incompatibility with the rubber component (A) measured by the following method, wherein the content of the resin composition (B) is the is a rubber component (a) 12 parts by mass or more with respect to 100 parts by weight, the thermoplastic resin (C) is a phenol-based resin, the content of that is, the rubber component (a) 100 parts by mass of 8 parts by mass or more based on the rubber composition.
<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.

[ 5 ] The rubber composition as described in [1] above, wherein the resin composition (B) contains a filler in advance .

[ 6 ] The rubber composition as described in [ 5 ] above, wherein the filler is dry silica.

[ 7 ] The rubber composition as described in [1] above, wherein the rubber component (A) contains natural rubber and / or synthetic isoprene rubber in a proportion of 70 to 100% by mass.

[ 8 ] The rubber composition as described in [1] above, wherein the thermoplastic resin (C) has a haze value indicating a degree of incompatibility with the rubber component (A) of 80% or more.

[ 9 ] The rubber composition as described in [1] above, wherein the content of the thermoplastic resin (C) is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component (A).

[ 10 ] The rubber composition as described in [ 9 ] above, wherein the content of the thermoplastic resin (C) is 10 to 50 parts by mass with respect to 100 parts by mass of the rubber component (A).

[ 11 ] The rubber composition as described in [1] above, further comprising a reinforcing filler (D).

[ 12 ] The reinforcing filler (D) 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 rubber component (A). The rubber composition as described in [ 9 ] above.

[ 13 ] The rubber composition as described in [1] above, wherein the rubber component (A) and the thermoplastic resin (C) previously blended are used in the preparation of the rubber composition.

[ 14 ] A pneumatic tire using the rubber composition according to the present invention as a constituent member.

[ 14 ] The pneumatic tire according to [ 13 ], which is a radial tire for a passenger car.

<Examples and Reference Examples 1 to 20 and Comparative Examples 1 to 5>
An unvulcanized rubber composition obtained by kneading the mixture shown in Table 3 using a Banbury mixer was sheeted to a thickness of 2 mm, and then vulcanized at 145 ° C. for 30 minutes. Each characteristic by the following method was evaluated with respect to the test sample of the obtained vulcanized rubber. Table 2 shows the types of the thermoplastic resin (C) used.

From Table 3, it can be seen that for each of the examples and the respective reference examples , good results are obtained for the stress strain characteristics and the viscoelasticity.

Claims (16)

A rubber component (A) containing 50% by mass or more of natural rubber and / or synthetic isoprene rubber;
A resin composition (B) comprising a novolac-type resorcin resin and a resole-type phenol resin;
Containing a thermoplastic resin (C) having a haze value of 40% or more indicating the degree of incompatibility with the rubber component (A) measured by the following method,
The rubber composition, wherein a content of the thermoplastic resin (C) is 8 parts by mass or more with respect to 100 parts by mass of the rubber component (A).
<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 novolac-type resorcin resin is obtained by reacting resorcin and aldehydes in a molar ratio (aldehydes / resorcin) of 0.4 or more and 0.8 or less. Rubber composition.   The amount of dimethylene ether groups in the resol-type phenolic resin is 20 mol% or more and 80 mol% or less with respect to the total amount of bonding groups derived from aldehydes bonding aromatic rings derived from phenols. The rubber composition according to claim 1.   2. The rubber composition according to claim 1, wherein the content of the novolac-type resorcin resin in the resin composition (B) is 18% by mass or more and 50% by mass or less.   Content of the said resin composition (B) is 1 to 30 mass parts with respect to 100 mass parts of said rubber components (A), The rubber composition of Claim 1 characterized by the above-mentioned.   The rubber composition according to claim 1, wherein the resin composition (B) contains a filler in advance.   The rubber composition according to claim 6, wherein the filler is dry silica.   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.   2. The rubber composition according to claim 1, wherein the thermoplastic resin (C) has a haze value of 80% or more indicating a degree of incompatibility with the rubber component (A).   Content of the said thermoplastic resin (C) is 10-100 mass parts with respect to 100 mass parts of said rubber components (A), The rubber composition of Claim 1 characterized by the above-mentioned.   11. The rubber composition according to claim 10, wherein a content of the thermoplastic resin (C) is 10 to 50 parts by mass with respect to 100 parts by mass of the rubber component (A).   The thermoplastic resin (C) is at least one selected from a C9 resin, a C5 to C9 resin, a rosin resin, an alkylphenol resin, and a terpene-aromatic compound resin. Item 2. The rubber composition according to Item 1.   The rubber composition according to claim 1, further comprising a reinforcing filler (D).   The reinforcing filler (D) 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 rubber component (A). 14. The rubber composition according to 13.   A pneumatic tire comprising the rubber composition according to claim 1 as a constituent member.   The pneumatic tire according to claim 15, which is a radial tire for a passenger car.