JP2021004274A - Tire rubber composition and pneumatic tire obtained using same - Google Patents

Abstract

To solve following problems in which: in a tire rubber composition, there is a method of blending a thermoset resin for increased hardness and elastic moduli, but it causes a deterioration of exothermicity; while an increased rate of vulcanization enables increased tire productivity but requires balancing with other properties.SOLUTION: The present invention provides a tire rubber composition that has 100 pts.mass of a diene-based rubber compounded with 1-200 pts.mass of carbon black and 0.1-20 pts.mass of a phenolic resin having, in the molecule, at least one ethyleneamine-derived structural unit represented by -(NH-C2H4)-.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition for a tire and a pneumatic tire using the same. Specifically, the present invention uses a rubber composition capable of achieving both high elastic modulus and low heat generation and increasing the vulcanization rate. It's about the pneumatic tires that were there.

There is known a technique for blending a thermosetting resin in a rubber composition for a tire for the purpose of increasing hardness and elastic modulus (see, for example, Patent Document 1). However, when a thermosetting resin is blended, there is a problem that heat generation is deteriorated.
On the other hand, it is possible to improve the productivity of the tire by increasing the vulcanization rate of the rubber composition for the tire, but there is a problem that the fracture physical property is lowered due to the increase in the 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.

Japanese Unexamined Patent Publication No. 2009-269961

Therefore, an object of the present invention is to provide a rubber composition capable of increasing the vulcanization rate while achieving both high elastic modulus and low heat generation, and a pneumatic tire using the same.

As a result of diligent research, the present inventors have found that the above problems can be solved by blending carbon black and a specific phenol resin in a specific amount with a diene rubber, and complete the present invention. did it.
That is, the present invention is as follows.

1. 1. 0.1 parts by mass of carbon black and 0.1 parts of phenol resin having at least one structural unit derived from alkyleneamine represented by the following chemical formula (1) in the molecule with respect to 100 parts by mass of diene rubber. A rubber composition for a tire, which is characterized by blending up to 20 parts by mass.

(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. 2. 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 above, 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 0.1 to 5 parts by mass of methylene donor is further blended with respect to 100 parts by mass of the diene rubber.
6. The rubber composition for a tire according to 5 above, wherein the methylene donor is hexamethylenetetramine or a polyvalent methylolmelamine derivative.
7. A pneumatic tire using the rubber composition for a tire according to any one of 1 to 6 above.

According to the present invention, since carbon black and a specific phenol resin are blended in a specific amount with the diene rubber, a rubber composition for a tire capable of achieving both high elastic modulus and low heat generation and increasing the vulcanization rate. It is possible to provide an object and a pneumatic tire using the object.
In the present invention, by blending a specific phenol resin, carbon black and the structural unit derived from alkylene amine in the phenol resin interact with each other to promote vulcanization, and at the same time, increase the elastic modulus and reduce the heat generation. It is presumed that it can be achieved.

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

(Diene rubber)
The diene rubber used in the present invention is not particularly limited, and for example, natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), acrylonitrile- Examples thereof include butadiene copolymer rubber (NBR). Of these, NR, IR and SBR are preferable. 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.

(Carbon black)
The carbon black used in the present invention preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 33 to 500 m ² / g from the viewpoint of improving the effect of the present invention. The nitrogen adsorption specific surface area (N ₂ SA) is a value obtained in accordance with JIS K6217-2.

(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 its 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 carbon atoms, preferably 2 to 6 carbon atoms, and more preferably 2 to 4 carbon atoms.

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 (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 heat kneading when blended with rubber. As a result, it is possible to realize a rubber having 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 such as xylenol, 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, Polyhydric phenols such as alkylhydroquinone, fluoroglucin, bisphenol A, bisphenol F, bisphenol S, dihydroxynaphthalin, naphthalene; and the like can be mentioned. These may be used alone or in combination of two or more. Among these, phenols can include one or more selected from the group consisting of phenol, cresol, xylenol and alkylphenol, and phenol can be used from an inexpensive viewpoint.

The aldehydes are not particularly limited, but for example, formaldehyde such as formalin and paraformaldehyde; trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glioxal, n-butylaldehyde, caproaldehyde, etc. Examples thereof include allyl aldehyde, benz aldehyde, croton aldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolu aldehyde and salicyl aldehyde. These aldehydes may be used alone or in combination of two or more. Among these, aldehydes can include 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, as aliphatic amines, 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 when 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, diethyl sulfate, 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, for example, alcohols, ketones, and aromatics, alcohols include methanol, ethanol, propyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, and the like, and ketones include. 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 phenols (P) and aldehydes (F) may be, for example, 0.2 to 1.0 mol of aldehydes with respect to 1 mol of 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 phenols (P) and 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, the compounding molar ratio, the amount and type of catalyst used, and the 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.

(Mixing ratio of rubber composition for tires)
The rubber composition of the present invention contains 1 to 200 parts by mass of carbon black and at least one structural unit derived from the alkylene amine represented by the chemical formula (1) in the molecule with respect to 100 parts by mass of the diene rubber. It is characterized by blending 0.1 to 20 parts by mass of the phenol resin contained therein.
If the blending amount of carbon black is less than 1 part by mass, the blending amount is too small to achieve the effect of the present invention. On the contrary, if it exceeds 200 parts by mass, the heat generation property deteriorates.
If the blending amount of the phenol resin is less than 0.1 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 wear resistance deteriorates.

Further, in the rubber composition of the present invention, the blending amount of carbon black is preferably 1 to 200 parts by mass with respect to 100 parts by mass of the diene rubber.
The blending amount of the phenol resin is preferably 0.1 to 20 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, silica, clay, talc, and calcium carbonate; an antiaging agent. Various additives generally blended in rubber compositions such as plasticizers can be blended, and such additives are kneaded by a common method to form a composition, which is used for vulcanization or cross-linking. can do. 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.

In the rubber composition of the present invention, a methylene donor can be used for curing the phenol resin, and the type thereof is not particularly limited. For example, hexamethylenetetramine and HMMM (partial condensate of hexamethoxymethylol melamine). ), Polyvalent methylol melamine derivatives such as PMMM (partial condensate of hexamethylol melamine pentamethyl ether), hexaethoxymethyl melamine, para-formaldehyde polymers, N-methylol derivatives of melamine, etc., and the effects of the present invention. From the viewpoint of improvement, hexamethylenetetramine or polyvalent methylolmelamine derivative is preferable.

The blending amount of the methylene donor is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the diene rubber.

Further, the rubber composition for a tire of the present invention can produce a pneumatic tire according to a conventional method for producing a pneumatic tire, for example, a tire cap tread, an under tread, a sidewall, a belt coat, a belt cushion, a rim cushion, and the like. It can be suitably used for inner liners, bead fillers and the like.

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)
A phenol resin 2 was obtained in the same manner as in Production Example 1 except that the amount of the 37% formalin aqueous solution was 518 parts and the 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 amount of the 37% formalin aqueous solution was 500 parts and the 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.

Examples 1-6 and Comparative Examples 1-3
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 sealed 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 Comparative Example 1 as 100. The smaller this value is, the faster the vulcanization rate is and the better the productivity is.
Storage elastic modulus: Measured at 20 ° C. with a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho under the conditions of initial strain 10%, amplitude ± 2%, and frequency 20 Hz in accordance with JIS K6394. The results are shown exponentially with the value of Comparative Example 1 as 100. The larger this value is, the higher the elastic modulus is.
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 of 10%, amplitude of ± 2%, frequency of 20 Hz, and temperature of 60 ° C. The results are shown exponentially with the value of Comparative Example 1 as 100. The smaller this value is, the lower the heat generation is.
The results are also shown in Table 1.

* 1: NR (STR20)
* 2: Carbon black (N339 manufactured by Cabot Japan, nitrogen adsorption specific surface area (N ₂ SA) = 90 m ² / g)
* 3: Straight phenol resin (PR50731 manufactured by Sumitomo Bakelite Co., Ltd., which does not have a structural unit derived from alkyleneamine)
* 4: Phenol resin 1 (phenol resin 1 produced in Production Example 1)
* 5: Phenol resin 2 (phenol resin 2 produced in Production Example 2)
* 6: Phenol resin 3 (phenol resin 3 produced in Production Example 3)
* 7: Hexamethylenetetramine (hexamethylenetetramine manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
* 8: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 9: Stearic acid (bead stearic acid YR manufactured by NOF CORPORATION)
* 10: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu Co., Ltd.)
* 11: Sulfur (oil-treated sulfur from Hosoi Chemical Industry Co., Ltd.)
* 12: Vulcanization accelerator (Suncellor NS-P manufactured by Sanshin Chemical Industry Co., Ltd.)

From the results in Table 1, the rubber compositions of Examples 1 to 6 contained carbon black and a specific phenol resin in a specific amount with respect to the diene rubber, so that the vulcanization rate was higher than that of Comparative Example 1. The result was fast, high storage elastic modulus, and low heat generation.
On the other hand, Comparative Example 2 was an example in which a straight phenol resin and a methylene donor having no structural unit derived from alkyleneamine were used, and the vulcanization rate was slower than that of Comparative Example 1.
Comparative Example 3 is an example in which a phenol resin is not blended, and the storage elastic modulus is worse than that of Comparative Example 1.

Claims (7)

0.1 parts by mass of carbon black and 0.1 parts of phenol resin having at least one structural unit derived from alkyleneamine represented by the following chemical formula (1) in the molecule with respect to 100 parts by mass of diene rubber. A rubber composition for a tire, which is characterized by blending up to 20 parts by mass.
(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 2, wherein the content ratio of the structural unit derived from ethylene amine in the phenol resin is 3% by mass or more and 50% by mass or less. The rubber composition for a tire according to any one of claims 1 to 3, 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 4, wherein 0.1 to 5 parts by mass of methylene donor is further blended with respect to 100 parts by mass of the diene rubber. The rubber composition for a tire according to claim 5, wherein the methylene donor is hexamethylenetetramine or a polyvalent methylolmelamine derivative. A pneumatic tire using the rubber composition for a tire according to any one of claims 1 to 6.