JP7095716B2 - Rubber composition for tires and tires using them - Google Patents

Description

The present invention relates to a rubber composition for a tire and a tire using the same. Specifically, the present invention relates to a rubber composition for a tire having an increased vulcanization rate and excellent heat generation, rupture property and wear resistance. It is about the tire used.

In recent years, tires are required to have low rolling resistance for the purpose of reducing the environmental load, and in order to satisfy this point, a high blending ratio and a high blending ratio of silica have been carried out.
However, if a high amount of silica is added, problems such as a decrease in breaking strength; a deterioration in wear resistance; and the like occur.

On the other hand, the rubber composition containing silica also has a problem that the vulcanization rate is lowered due to the deterioration of the surface activity and the thermal conductivity peculiar to silica. Therefore, it is possible to improve the productivity of the tire by further adding a vulcanization accelerator or the like to increase the vulcanization rate, but there is a problem that the rupture physical properties are lowered due to the increase in modulus. Therefore, it is important to increase the vulcanization rate from the viewpoint of tire productivity, but it is necessary to balance it with other physical characteristics.

A technique of blending a thermosetting resin with a rubber composition is known (see, for example, Patent Document 1). However, when a thermosetting resin is blended, there are problems that heat generation is deteriorated and breaking strength is lowered.

Therefore, it has been a difficult matter in the industry to improve heat generation, breaking strength and wear resistance at the same time while improving the vulcanization rate.

Japanese Unexamined Patent Publication No. 2009-269961

Therefore, an object of the present invention is to provide a rubber composition for a tire having an increased vulcanization rate and excellent heat generation property, breaking physical characteristics and wear resistance, and a tire using the same.

As a result of diligent research, the present inventors have found that the above-mentioned problems can be solved by blending silica having a specific specific surface area and a specific phenol resin in a specific amount with a diene-based rubber having a specific composition. I was able to find out and complete the present invention.
That is, the present invention is as follows.

1. 1. For 100 parts by mass of diene rubber containing 65 to 100 parts by mass of styrene-butadiene copolymer rubber and 0 to 35 parts by mass of butadiene rubber, 50 to 200 mass of silica having a CTAB specific surface area of 200 to 300 m ² / g. A rubber for tires, which comprises 0.5 to 20 parts by mass of a phenol resin having at least one structural unit derived from an alkylene amine represented by the following chemical formula (1) in a portion and a molecule. Composition.

(In the above general formula (1), R ₁ independently represents a linear or branched alkylene group having 1 to 10 carbon atoms.)
2. 2. The rubber composition for a tire according to 1 above, wherein the phenol resin has at least one structural unit derived from ethyleneamine represented by the following chemical formula (2) in the molecule.

3. 3. The rubber composition for a tire according to 2, wherein the content ratio of the structural unit derived from ethyleneamine in the phenol resin is 3% by mass or more and 50% by mass or less.
4. The rubber composition for a tire according to any one of 1 to 3, wherein the softening point of the phenol resin is 60 ° C. or higher and 150 ° C. or lower.
5. The rubber composition for a tire according to any one of 1 to 4, wherein the terminal-modified styrene-butadiene copolymer rubber is contained in an amount of 65 parts by mass or more in 100 parts by mass of the diene-based rubber.
6. A tire using the rubber composition for a tire according to any one of 1 to 5 above for a cap tread.

According to the present invention, since a specific amount of silica having a specific specific surface area and a specific phenol resin are blended with a diene-based rubber having a specific composition, the vulcanization rate can be increased, and heat generation, rupture properties, and rupture properties can be increased. It is possible to provide a rubber composition for a tire having excellent wear resistance and a tire using the same.
In the present invention, by blending a specific phenol resin, the silanol group on the silica surface and the structural unit derived from the alkylene amine in the phenol resin interact with each other to promote vulcanization, and at the same time, heat generation, fracture resistance and resistance to breakage. It is presumed that wear resistance can be improved at the same time.

Hereinafter, the present invention will be described in more detail.

The diene-based rubber used in the present invention contains styrene-butadiene copolymer rubber (SBR) as an essential component. The blending amount of SBR needs to be 65 to 100 parts by mass when the entire diene rubber is 100 parts by mass. If the blending amount of the SBR is less than 65 parts by mass, the breaking strength deteriorates.
Further, in the present invention, butadiene rubber (BR) can be blended if necessary. The blending amount of BR is preferably, for example, 0 to 35 parts by mass, and more preferably 10 to 30 parts by mass, when the entire diene rubber is 100 parts by mass.
In addition to SBR and BR, other diene-based rubbers can be used, and examples thereof include natural rubber (NR), synthetic isoprene rubber (IR), and acrylonitrile-butadiene copolymer rubber (NBR). These may be used alone or in combination of two or more. The molecular weight and microstructure thereof are not particularly limited, and may be terminal-modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized.

Further, in the rubber composition of the present invention, the effect of the present invention can be further enhanced by containing 65 parts by mass or more, preferably 70 to 90 parts by mass of the terminal-modified SBR in 100 parts by mass of the diene-based rubber. Examples of such terminal-modified SBR include amines, amides, silyls, alkoxysilyls, carboxyls, hydroxyl groups, epoxy groups and the like, or SBRs whose ends are modified with a combination thereof.

(silica)
The silica used in the present invention is not particularly limited, and for example, any conventionally known silica blended in a rubber composition for tire applications can be used.
Specific examples of silica include wet silica, dry silica, fumed silica and the like. As the silica, one kind of silica may be used alone, or two or more kinds of silica may be used in combination.
Further, the silica used in the present invention needs to have a CTAB specific surface area of 200 to 300 m ² / g. When the CTAB specific surface area is less than 200 m ² / g, the breaking strength is lowered. On the contrary, when the CTAB specific surface area exceeds 300 m ² / g, the mixing processability deteriorates.
A more preferred CTAB specific surface area of the silica used in the present invention is 200-270 m ² / g.
In the present specification, the CTAB specific surface area is a value obtained by measuring the amount of CTAB adsorbed on the silica surface according to JIS K6217-3: 2001 "Part 3: How to obtain the specific surface area-CTAB adsorption method".

(Phenol resin)
The phenol resin used in the present invention has at least one structural unit derived from an alkylene amine represented by the following chemical formula (1) in the molecule.

In the above general formula (1), R ₁ independently represents a linear or branched alkylene group having 1 to 10 carbon atoms. The alkylene group of R ₁ has, for example, 1 to 10, preferably 2 to 6, and more preferably 2 to 4.

From the viewpoint of improving the effect of the present invention, the phenol resin may contain at least one structural unit derived from ethyleneamine represented by the following chemical formula (2) in the molecule.

The lower limit of the content ratio of the structural unit derived from alkyleneamine or ethyleneamine in the phenol resin is, for example, 3% by mass or more, preferably 5% by mass or more, and more preferably 10% by mass or more. Thereby, the elastic modulus can be improved. On the other hand, the upper limit of the content ratio of the structural unit derived from ethyleneamine in the phenol resin may be, for example, 50% by mass or less, preferably 45% by mass or less, and more preferably 40% by mass or less. Thereby, the softening point can be appropriately adjusted.
The content of the ethyleneamine-derived structure can be calculated based on the following formula. The nitrogen content (% by mass) in the formula can be measured by an elemental analysis method.
Ethyleneamine-derived structure content = nitrogen content x (43/14)

The softening point of the phenol resin is, for example, 60 ° C. to 150 ° C., preferably 65 ° C. to 130 ° C., and more preferably 70 ° C. to 120 ° C. The softening point of the phenol resin can be appropriately controlled according to the heating temperature at the time of heating and kneading when blended with rubber. As a result, it is possible to realize rubber with little variation in rubber physical characteristics.

The phenolic resin may be composed of a polymer of phenols, aldehydes, and alkyleneamines. The phenolic resin may or may not contain these unreacted monomers.

Examples of phenols are not particularly limited, but for example, phenol; cresols such as orthocresol, metacresol, paracresol; 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6- Xylenol, xylenol such as 3,5-xylenol; 2,3,5-trimethylphenol, 2-ethylphenol, 4-ethylphenol, 2-isopropylphenol, 4-isopropylphenol, n-butylphenol, isobutylphenol, tert-butylphenol Alkylphenol such as hexylphenol, octylphenol, nonylphenol, phenylphenol, benzylphenol, cumylphenol, allylphenol, cardanol, ursiol, thithiol, laccol; naphthol such as 1-naphthol and 2-naphthol; fluorophenol, chlorophenol, Halogenated phenols such as bromophenol and iodophenol, monovalent phenol substitutions such as p-phenylphenol, aminophenol, nitrophenol, dinitrophenol, trinitrophenol; resorcin, alkylresorcin, pyrogallol, catechol, alkylcatechol, hydroquinone, Examples thereof include polyhydric phenols such as alkylhydroquinone, fluoroglucin, bisphenol A, bisphenol F, bisphenol S, dihydroxynaphthalin, and naphthalene. These may be used alone or in combination of two or more. Among these, phenols can contain one or more selected from the group consisting of phenol, cresol, xylenol and alkylphenol, and phenol can be used from the viewpoint of low cost.

The aldehydes are not particularly limited, but for example, formaldehydes such as formalin and paraformaldehyde; trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glioxal, n-butylaldehyde, caproaldehyde, etc. Examples thereof include allylaldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like. These aldehydes may be used alone or in combination of two or more. Among these, aldehydes can contain formaldehyde or acetaldehyde, and formalin or paraformaldehyde can be used from the viewpoint of productivity and low cost.

As the alkylene amine, an aliphatic amine having one or more linear or branched alkylene groups having 1 to 10 carbon atoms in the molecule can be used. The aliphatic amine may be a compound containing one or more primary amines and / or secondary amines. For example, examples of the aliphatic amine include diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, dipropylenetriamine, tripropylenetetraamine, tetrapropylenepentamine, pentapropylenehexamine, polypropyleneimine and the like. Examples include polyalkylene polyamines. These may be used alone or in combination of two or more.

Although the detailed mechanism is not clear, it is thought that aldehydes react with both phenols and alkyleneamines.

The catalyst used for synthesizing the phenol resin may be non-catalyst, or an acidic catalyst can be used from the viewpoint of producing a novolak type phenol resin. The acidic catalyst is not particularly limited, and examples thereof include acids such as oxalic acid, hydrochloric acid, sulfuric acid, diethylsulfuric acid, and paratoluenesulfonic acid, and metal salts such as zinc acetate, which may be used alone or in combination of two or more. Can be used.

As the reaction solvent used when synthesizing the phenol resin, water may be used, or an organic solvent may be used. As the organic solvent, a non-polar solvent can be used and a non-aqueous system can be used. Examples of organic solvents include alcohols, ketones and aromatics, alcohols include methanol, ethanol, propyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, glycerin and the like, and ketones include ketones. Acetone, methyl ethyl ketone and the like, and examples of the aromatics include toluene, xylene and the like. These may be used alone or in combination of two or more.

The molar ratio (F / P molar ratio) of the phenols (P) and the aldehydes (F) may be, for example, 0.2 to 1.0 mol of the aldehydes with respect to 1 mol of the phenols, which is preferable. Can be 0.3 to 0.9 mol. By setting the aldehydes in the above range, the amount of unreacted phenol can be reduced and the yield can be increased. Further, by controlling the reaction molar ratio (F / P) of the phenols (P) and the aldehydes (F) to 1.0 or less, that is, the phenol-rich condition in terms of molar ratio, an appropriate softening point is obtained. A phenol resin containing a structural unit derived from an alkylene amine having the above can be obtained, and such a phenol resin can be satisfactorily compatible or dispersed in rubber by mixing and kneading under heating conditions.

The reaction temperature may be, for example, 40 ° C to 120 ° C, preferably 60 ° C to 110 ° C. The reaction time is not particularly limited and may be appropriately determined according to the type of starting material, compounding molar ratio, amount and type of catalyst used, and reaction conditions.

From the above, the phenol resin used in the present invention can be obtained. The phenol resin may contain a novolak-type phenol resin having a novolak skeleton and a structural unit derived from the ethyleneamine in the molecule.

(Rubber composition ratio for tires)
The rubber composition of the present invention contains 50 to 200 parts by mass of silica having a CTAB specific surface area of 200 to 300 m ² / g with respect to 100 parts by mass of a diene rubber, and is represented by the above chemical formula (1) in the molecule. It is characterized by blending 0.5 to 20 parts by mass of a phenol resin having at least one structural unit derived from alkyleneamine.
If the blending amount of the silica is less than 50 parts by mass, the heat generation property deteriorates. If it exceeds 200 parts by mass, the breaking strength, wear resistance, and heat generation property deteriorate.
If the blending amount of the phenol resin is less than 0.5 parts by mass, the blending amount is too small to achieve the effect of the present invention. On the contrary, if it exceeds 20 parts by mass, the heat generation property and the breaking strength deteriorate.

Further, in the rubber composition of the present invention, the blending amount of the silica is preferably 70 to 150 parts by mass with respect to 100 parts by mass of the diene-based rubber.
The blending amount of the phenol resin is preferably 8 to 18 parts by mass with respect to 100 parts by mass of the diene rubber.

(Other ingredients)
In addition to the above-mentioned components, the rubber composition in the present invention includes a vulcanization or cross-linking agent; a vulcanization or cross-linking accelerator; various fillers such as zinc oxide, carbon black, clay, talc, and calcium carbonate; anti-aging. Agents; various additives commonly blended in rubber compositions such as plasticizers can be blended, and such additives can be kneaded in a common manner to form a composition for vulcanization or cross-linking. Can be used. The blending amount of these additives can also be a conventional general blending amount as long as it does not contradict the object of the present invention.

Further, the rubber composition of the present invention is preferably used for a tire cap tread because it accelerates the vulcanization rate and is excellent in heat generation, fracture property and wear resistance. Further, the tire of the present invention is preferably a pneumatic tire, and can be filled with an inert gas such as air or nitrogen and other gases.
Further, the rubber composition of the present invention can manufacture a pneumatic tire according to a conventional method for manufacturing a tire, for example, a pneumatic tire.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples. In the example, the part is based on mass unless otherwise specified.

<Synthesis of phenolic resin>
(Manufacturing Example 1)
A reactor equipped with a stirrer, a reflux condenser and a thermometer was charged with 1000 parts of phenol, 561 parts of a 37% formalin aqueous solution, and 55 parts of triethylenetetraamine, and reacted under reflux conditions for 2 hours. Then, the reaction was carried out at 200 ° C. for 3 hours while removing water by distillation. Further, water and unreacted monomers were distilled and removed under reduced pressure until the predetermined water content and free monomer amount were reached, and then the mixture was taken out from the reactor to obtain phenol resin 1.
The softening point of the phenol resin 1 was 110 ° C., the nitrogen content was 2.2% by mass, and the content of the ethyleneamine-derived structure was 6.8% by mass.

(Manufacturing Example 2)
Phenol resin 2 was obtained in the same manner as in Production Example 1 except that the blending amount of the 37% formalin aqueous solution was 518 parts and the blending amount of triethylenetetraamine was 110 parts.
The softening point of the phenol resin 2 was 108 ° C., the nitrogen content was 4.1% by mass, and the content of the ethyleneamine-derived structure was 12.6% by mass.

(Manufacturing Example 3)
The phenol resin 3 was obtained in the same manner as in Production Example 1 except that the blending amount of the 37% formalin aqueous solution was 500 parts and the blending amount of triethylenetetraamine was 165 parts.
The softening point of the phenol resin 3 was 102 ° C., the nitrogen content was 6.4% by mass, and the content of the ethyleneamine-derived structure was 19.7% by mass.

Standard Example 1, Examples 1 to 5 and Comparative Examples 1 to 6
Sample preparation In the formulation (parts by mass) shown in Table 1, the vulcanization accelerator and the components excluding sulfur were kneaded with a 1.7 liter closed Banbury mixer for 5 minutes, and the rubber was discharged to the outside of the mixer and cooled to room temperature. .. Then, the rubber was put into the same mixer again, a vulcanization accelerator and sulfur were added, and the mixture was further kneaded to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized in a predetermined mold at 160 ° C. for 20 minutes to obtain a vulcanized rubber test piece, and the unvulcanized rubber composition and the vulcanized rubber were obtained by the test method shown below. The physical properties of the test piece were measured.

Vulcanization rate (T95): In accordance with JIS K6300, the time (T95, min) to reach 95% vulcanization degree at an amplitude of 1 degree and 150 ° C. was measured with a vibrating disk vulcanization tester. The results are shown exponentially with the value of Standard Example 1 as 100. The smaller this value is, the faster the vulcanization rate is and the better the productivity is.
Exothermic (tan δ 60 ° C.): Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., tan δ (60 ° C.) was measured under the conditions of initial strain 10%, amplitude ± 2%, frequency 20 Hz, and temperature 60 ° C. .. The results are shown exponentially with the value of Standard Example 1 as 100. The smaller this value is, the lower the heat generation is.
Breaking strength (TB): Tested at 20 ° C. according to JIS K 6251. The results are shown exponentially with the value of Standard Example 1 as 100. The larger this value is, the higher the breaking strength is.
Abrasion resistance: Using a Ramborn wear tester manufactured by Iwamoto Seisakusho Co., Ltd., the wear was measured under the conditions of a load of 15 N, a slip ratio of 25%, a time of 10 minutes, and room temperature to determine the wear reduction. The results are shown exponentially with the value of Standard Example 1 as 100. The larger the index, the better the wear resistance.
The results are also shown in Table 1.

* 1: SBR (SBR E581 manufactured by Asahi Kasei Corporation, oil spread = 37.5 parts by mass with respect to 100 parts by mass of SBR)
* 2: BR (Nipol BR1220 manufactured by Nippon Zeon Corporation)
* 3: Silica 1 (Zeosil 1165MP manufactured by Solvay, CTAB specific surface area = 155m ² / g)
* 4: Silica 2 (ULTRASIL 9100GR manufactured by Evonik, CTAB specific surface area = 210 m ² / g)
* 5: Carbon black (N339 manufactured by Cabot Japan)
* 6: Cashew-modified phenolic resin (PSM-9450 manufactured by Sumitomo Bakelite Co., Ltd., which does not have a structural unit derived from alkyleneamine)
* 7: Phenol resin 1 (Phenol resin 1 produced in Production Example 1)
* 8: Phenol resin 2 (Phenol resin 2 produced in Production Example 2)
* 9: Phenol resin 3 (Phenol resin 3 produced in Production Example 3)
* 10: Silane coupling agent (Si69 manufactured by Evonik)
* 11: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 12: Stearic acid (beaded stearic acid YR manufactured by NOF CORPORATION)
* 13: Anti-aging agent (6PPD manufactured by EASTMAN)
* 14: Wax (paraffin wax manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
* 15: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu Co., Ltd.)
* 16: Sulfur (oil-treated sulfur from Hosoi Chemical Industry Co., Ltd.)
* 17: Vulcanization accelerator CBS (Sun Cellar CM-G manufactured by Sanshin Chemical Industry Co., Ltd.)
* 18: Vulcanization accelerator DPG (Sulfur DG manufactured by Sumitomo Chemical Co., Ltd.)
* 19: Terminal-modified SBR (Toughden F3420 manufactured by Asahi Kasei Corporation. The terminal is modified with a glycidylamine group.)

From the results in Table 1, the rubber compositions of Examples 1 to 6 contained silica having a specific specific surface area and a specific phenol resin in a specific amount with respect to a diene-based rubber having a specific composition, and thus were standard examples. Compared with No. 1, heat generation, breaking strength and wear resistance are improved at the same time.
On the other hand, in Comparative Example 1, since the specific phenol resin was not blended, the breaking strength was deteriorated.
In Comparative Example 2, since the CTAB specific surface area of silica was less than the lower limit specified in the present invention, the breaking strength was deteriorated.
In Comparative Example 3, since the blending amount of SBR was less than the lower limit specified in the present invention, the breaking strength was deteriorated.
In Comparative Example 4, since the blending amount of the specific phenol resin exceeded the upper limit specified in the present invention, the heat generating property and the breaking strength deteriorated.
In Comparative Example 5, since the blending amount of silica was less than the lower limit specified in the present invention, the heat generating property and the breaking strength were deteriorated.

Claims (5)

For 100 parts by mass of diene-based rubber containing 65 to 100 parts by mass of styrene-butadiene copolymer rubber and 0 to 35 parts by mass of butadiene rubber, 50 to 200 mass of silica having a CTAB specific surface area of 200 to 300 m ² / g. 0.5 to 20 parts by mass of a phenol resin having at least one structural unit derived from alkylene amine represented by the following chemical formula (1) is blended in parts and molecules.
The content ratio of the structural unit derived from the alkylene amine in the phenol resin is 3% by mass or more and 50% by mass or less.
A rubber composition for tires, characterized in that.

(In the above general formula (1), R ₁ independently represents a linear or branched alkylene group having 1 to 10 carbon atoms.) The rubber composition for a tire according to claim 1, wherein the phenol resin has at least one structural unit derived from ethyleneamine represented by the following chemical formula (2) in the molecule.

The rubber composition for a tire according to claim 1 or 2 , wherein the softening point of the phenol resin is 60 ° C. or higher and 150 ° C. or lower. The rubber composition for a tire according to any one of claims 1 to 3 , wherein the terminal-modified styrene-butadiene copolymer rubber is contained in an amount of 65 parts by mass or more in 100 parts by mass of the diene-based rubber. A tire using the rubber composition for a tire according to any one of claims 1 to 4 for a cap tread.