JP2012082323A - Rubber composition for tire and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire and a pneumatic tire using the composition achieving high hardness, high elasticity, and low heat generation properties and giving excellent controlling stability, low rolling properties, and fracture life characteristics.SOLUTION: The rubber composition for a tire includes: 100 pts.mass of a diene rubber; 30-100 pts.mass of a reinforcing filler; 5-20 pts.mass of at least one novolak type phenol resin selected from a phenol resin, a resorcinol resin and a cresol resin; 0.1-6 pts.mass of a methylene donor; and 0.2-5 pts.mass of a benzoic acid or its derivative having pKa of 1.5-4.0. In the pneumatic tire, the rubber composition for a tire is used for a bead filler 6.

Description

  TECHNICAL FIELD The present invention relates to a tire rubber composition and a pneumatic tire using the same, and more specifically, in a tire rubber composition formed by blending a resin, high hardness, high elasticity, and low heat build-up are achieved. The present invention relates to a tire rubber composition imparted with excellent steering stability, low rolling property, and fracture life characteristics, and a pneumatic tire using the same.

The performance required for the rubber composition for tire bead filler includes high hardness, low heat build-up, low compression set, and high fracture property. Conventionally, in order to increase high hardness, it is known to blend a novolak type phenol resin and a melamine derivative such as hexamethylenetetramine or hexamethoxymethylolmelamine as a curing agent.
In order to obtain a desired hardness as a rubber composition for a tire bead filler, it is necessary to increase the amount of the resin or increase the amount of the curing agent. However, if the amount of the resin is increased, as a matter of course, the amount of unreacted resins increases, and these unreacted resins are merely foreign substances, which reduce the mechanical properties of the rubber composition, particularly fatigue life and creep properties. In addition, there is a problem that heat generation becomes large and the fracture life of the tire is shortened.
On the other hand, as a technique for reducing the rolling resistance of tires, it is known to vulcanize at low temperatures. However, in rubber compositions for tire bead fillers containing a large amount of resin, curing of the resin is insufficient when vulcanized at low temperatures. Thus, there is a problem that the elastic modulus is lowered.

  Patent Document 1 below discloses a rubber composition obtained by blending a diene rubber with a cobalt salt of an aliphatic or alicyclic carboxylic acid, a benzoate, carbon black, a novolac type phenol resin, and a methylene group donor. ing. However, Patent Document 1 does not describe benzoic acid or a derivative thereof having a specific range of pKa used in the present invention. In addition, there is no disclosure or suggestion of using a benzoic acid having a specific range of pKa or a derivative thereof to improve the curing efficiency of the resin and achieve high hardness, high elasticity, and low exothermicity.

JP 2004-18687 A

  An object of the present invention is for a tire rubber composition obtained by blending a resin, achieving high hardness, high elasticity, and low heat generation, and imparting excellent handling stability, low rolling property, and fracture life characteristics. The object is to provide a rubber composition and a pneumatic tire using the same.

As a result of extensive research, the present inventors have found that diene rubber has a specific amount of reinforcing filler, a specific amount of a specific thermosetting resin, a specific amount of methylene donor, and a benzoic acid having a specific pKa range or It has been found that the above problem can be solved by blending a specific amount of the derivative, and the present invention has been completed.
That is, the present invention is as follows.
1. 30-100 parts by mass of reinforcing filler with respect to 100 parts by mass of diene rubber; 5-20 parts by mass of at least one novolac type phenolic resin selected from phenol resin, resorcin resin and cresol resin; methylene donor 0.1 to 6 parts by mass; and 0.2 to 5 parts by mass of benzoic acid having a pKa of 1.5 to 4.0 or a derivative thereof.
2. 2. The rubber composition for tires according to 1 above, wherein the novolac phenolic resin is a phenol resin.
3. 3. The tire rubber composition according to 1 or 2 above, wherein the tire rubber composition has a hardness (20 ° C.) of 85 or more after vulcanization.
4). The pneumatic tire which used the rubber composition for tires in any one of said 1-3 for a bead filler.

  According to the present invention, a specific amount of a reinforcing filler, a specific amount of a specific thermosetting resin, a specific amount of a methylene donor, and a specific amount of benzoic acid or a derivative thereof having a specific pKa range are added to the diene rubber. To provide a rubber composition for a tire that achieves high hardness, high elasticity, low heat build-up, excellent driving stability, low rolling property, and fracture life characteristics, and a pneumatic tire using the same. Can do. The above characteristics can be obtained even by low-temperature vulcanization.

It is a fragmentary sectional view of an example of a pneumatic tire.

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

FIG. 1 is a partial cross-sectional view of an example of a pneumatic tire for a passenger car.
In FIG. 1, the pneumatic tire is composed of a pair of left and right bead portions 1 and sidewalls 2, and a tread 3 connected to both sidewalls 2, and a carcass layer 4 in which fiber cords are embedded between the bead portions 1 and 1 is mounted. Then, the end portion of the carcass layer 4 is turned up around the bead core 5 and the bead filler 6 from the tire inner side to the outer side. Further, in the tread 3, a belt layer 7 is disposed over the circumference of the tire outside the carcass layer 4.
The tire rubber composition of the present invention described below is useful for various members for tires as described above, and particularly useful for the bead filler 6.

(Diene rubber)
As the diene rubber used in the present invention, any diene rubber that can be blended into the tire rubber composition can be used. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber ( BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and the like. These may be used alone or in combination of two or more. The molecular weight and microstructure of the diene rubber are not particularly limited, and may be terminal-modified with an amine, amide, silyl group or the like.
The diene rubber in the present invention is preferably NR and SBR from the viewpoint of the effect of the present invention.

(Reinforcing filler)
The reinforcing filler used in the present invention is not particularly limited, and examples thereof include carbon black and inorganic filler. Examples of the inorganic filler include silica, clay, talc, calcium carbonate and the like.

When carbon black is used in the present invention, the CTAB specific surface area is 20 to 120 (m ² / g) and the nitrogen adsorption specific surface area (N ₂ SA) is 30 to 150 (m ² ) from the viewpoint of the effect of the present invention. / g), DBP oil absorption amount is preferably 50~120 ^(cm 3 / 100g). The CTAB specific surface area is a value determined in accordance with JIS K6217-3, the nitrogen adsorption specific surface area (N ₂ SA) is a value determined in accordance with JIS K6217-2, and the DBP oil absorption is JIS K6217. -4 is a value determined according to the oil absorption amount A method.

(Novolac type phenolic resin)
The novolak-type phenolic resin used in the present invention is at least one resin selected from a phenol resin, a resorcin resin, and a cresol resin, all of which are known resins. The novolac-type phenolic resin may be modified with oil or fatty acid, and examples thereof include resins modified with oils such as rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, and linolenic acid.
From the viewpoint of the effects of the present invention, the novolac type phenol resin is preferably a phenol resin.

(Methylene donor)
Examples of the methylene donor used in the present invention include hexamethylenetetramine and melamine derivatives. Melamine derivatives include, for example, hexamethylol melamine, hexamethoxymethyl melamine, pentamethoxymethylol melamine, hexaethoxymethyl melamine, hexakis- (methoxymethyl) melamine, N, N ′, N ″ -trimethyl-N, N ′, N '' -Trimethylol melamine, N, N ', N''-trimethylol melamine, N-methylol melamine, N, N'-(methoxymethyl) melamine, N, N ', N''-tributyl-N, N ', N ″ -trimethylolmelamine is mentioned. In particular, hexamethoxymethylol melamine or pentamethoxymethylol melamine is preferable.

(Benzoic acid or its derivatives)
The benzoic acid or derivative thereof used in the present invention needs to have a pKa (acid dissociation constant) in the range of 1.5 to 4.0. If the pKa is less than 1.5, the mold may oxidize and corrode. Conversely, if it exceeds 4.0, the desired effect is not achieved. A more preferable pKa range is 1.5 to 3.0.
Specific examples of benzoic acid or derivatives thereof used in the present invention include benzoic acid (pKa = 4.0), 2,4-hydroxybenzoic acid (pKa = 3.2), and salicylic acid (pKa = 2.7). O-aminobenzoic acid (pKa = 2.0), m-aminobenzoic acid (pKa = 3.3), 4-aminosalicylic acid (pKa = 2.0), 2,4-diaminobenzoic acid (pKa = 1) .5) 2,3-hydroxybenzoic acid (pKa = 3.1), 2,4-hydroxybenzoic acid and the like (pKa = 3.1), 2,3-hydroxybenzoic acid (pKa = 3.2), 2 , 5-hydroxybenzoic acid (pKa = 3.0), 3,5-hydroxybenzoic acid (pKa = 3.8), 5-sulfosalicylic acid (pKa = 2.4), 2,3,4-hydroxybenzoic acid (PKa = 3.1).

(Combination ratio of tire rubber composition)
The rubber composition for tires according to the present invention comprises 30 to 100 parts by mass of a reinforcing filler with respect to 100 parts by mass of a diene rubber; 5 to 20 parts by mass of resin; 0.1 to 6 parts by mass of methylene donor; and 0.2 to 5 parts by mass of benzoic acid having a pKa of 1.5 to 4.0 or a derivative thereof. And
When the compounding amount of the reinforcing filler is less than 30 parts by mass, the hardness is lowered and steering stability is deteriorated.
When the compounding amount of the reinforcing filler exceeds 100 parts by mass, workability deteriorates.
When the blending amount of the novolac phenolic resin is less than 5 parts by mass, the hardness is lowered and the steering stability is deteriorated.
When the compounding amount of the novolac-type phenolic resin exceeds 20 parts by mass, the green modulus increases and processability deteriorates.
When the blending amount of the methylene donor is less than 0.1 parts by mass, the resin becomes insufficiently cured and desired hardness cannot be obtained.
When the blending amount of the methylene donor exceeds 6 parts by mass, the vulcanization speed becomes slow and the productivity is deteriorated.
If the amount of the benzoic acid or derivative thereof is less than 0.2 parts by mass, the amount added is too small to achieve the desired effect.
When the amount of the benzoic acid or its derivative exceeds 5 parts by mass, bloom tends to occur.

In the tire rubber composition of the present invention, a more preferable blending amount of the reinforcing filler is 50 to 80 parts by mass.
A more preferable blending amount of the novolac type phenolic resin is 8 to 16 parts by mass.
A more preferable blending amount of the methylene donor is 7 to 13% by mass with respect to the novolac phenolic resin when hexamethylenetetramine is used, and with respect to the novolac phenolic resin when a melamine derivative is used. 22 to 28% by mass. When the blending amount of hexamethylenetetramine is 7% by mass or more with respect to the novolac-type phenolic resin, the resin is sufficiently cured, and when it is 13% by mass or less, it is easy to burn and adjacent. Wet heat deterioration of the polyester carcass is suppressed. When the blending amount of the melamine derivative is 22% by mass or more with respect to the novolak type phenol resin, the resin is sufficiently cured, and when it is 28% by mass or less, the decrease in the vulcanization rate is suppressed. The
The more preferable compounding quantity of the said benzoic acid or its derivative (s) is 0.5-3 mass parts.

  In addition to the above-described components, the tire rubber composition of the present invention is generally used for tire rubber compositions such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, and plasticizers. Various additives blended in the above can be blended, and such additives can be kneaded by a general method to form a composition, which can be used for vulcanization or crosslinking. The blending amounts of these additives can be set to conventional general blending amounts as long as the object of the present invention is not violated.

  The rubber composition for tires of the present invention can be used for producing a pneumatic tire according to a conventional method for producing a pneumatic tire.

  The hardness at 20 ° C. of the vulcanized rubber of the tire rubber composition of the present invention is, for example, preferably 85 or more, particularly preferably 90 or more. The hardness in the present invention means a value measured at 20 ° C. in accordance with JIS K6253.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Examples 1-7 and Comparative Examples 1-12
Sample preparation In the formulation (parts by mass) shown in Table 1 or 2, the ingredients other than the vulcanization accelerator and sulfur were kneaded for 5 minutes in a 1.5 liter closed Banbury mixer, then discharged outside the mixer and cooled to room temperature. did. Subsequently, the composition was put into the Banbury mixer again, and a vulcanization accelerator and sulfur were added and kneaded to obtain a tire rubber composition. Next, the obtained rubber composition for tire was press vulcanized at 150 ° C. for 30 minutes in a predetermined mold to prepare a vulcanized rubber test piece. The physical properties of the obtained vulcanized rubber specimens were measured by the following test methods.

tan δ (60 ° C.): Measured at an initial strain of 5%, an amplitude of ± 1%, a frequency of 20 Hz, and a temperature of 60 ° C. using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho. The value of Comparative Example 1 was taken as 100 and indicated as an index. The smaller the index, the lower the exothermic property and the lower the rolling property.
30% Modulus: Based on JIS K6251, a tensile test was performed with a fully automatic tensile tester with a thermostatic bath, Strograph AR-T, manufactured by Toyo Seiki Seisakusho. A 2 mm thick sheet-like vulcanized rubber specimen was punched with a JIS No. 3 dumbbell, pulled at a pulling speed of 500 mm / min and a temperature of 23 ° C., and the stress at 30% elongation at that time was used as an index. The value of Comparative Example 1 was taken as 100 and indicated as an index. The larger the index, the higher the elasticity and the better.
Hardness: Shore A hardness at 20 ° C. was measured according to JIS K6253.
The results are also shown in Table 1 or 2. In Table 2, the results of Comparative Example 1 and Example 4 are also shown.

* 1: NR (RSS # 3)
* 2: SBR (Nipol 1502 manufactured by Nippon Zeon Co., Ltd.)
* 3: Carbon black (Tokai Carbon Co., Ltd. Seast N, CTAB specific surface _{^{= 76m 2 / g, N 2}} SA = 70m 2 / g, DBP oil absorption ⁼ 102cm 3/100 g)
* 4: Zinc Hana (Zinc Oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 5: Stearic acid (Nippon Oil Co., Ltd. beads stearic acid NY)
* 6: Aroma oil (Extract No. 4 S manufactured by Showa Shell Sekiyu KK)
* 7: Phenol resin (Sumitite Resin PR-NR-1 manufactured by Sumitomo Bakelite Co., Ltd.)
* 8: Resorcin resin (Sumikanol 620 manufactured by Taoka Chemical Industry Co., Ltd.)
* 9: Cresol resin (Sumikanol 610 manufactured by Taoka Chemical Co., Ltd.)
* 10: Hexamethylenetetramine (Ouchi Shinsei Chemical Industry Noxeller H)
* 11: PMMM (Sumikanol 507A from Bara Chemical, pentamethoxymethylol melamine, 65% melamine derivative)
* 12: Sulfur (manufactured by Tsurumi Chemical Co., Ltd., Jinhua Stamp fine powder sulfur 150 mesh)
* 13: Vulcanization accelerator (Noxeller NS-P manufactured by Ouchi Shinsei Chemical Co., Ltd.)

As is clear from the above table, the rubber compositions for tires prepared in Examples 1 to 9 include diene rubber, specific amount of reinforcing filler, specific amount of specific thermosetting resin, methylene donor. And a specific amount of benzoic acid or a derivative thereof having a specific pKa range, and achieves high hardness, high elasticity and low exothermicity with respect to the conventional representative comparative example 1, and is excellent It can be seen that handling stability, low rolling property, and fracture life characteristics are imparted.
On the other hand, Comparative Example 2 did not contain a novolac-type phenolic resin and benzoic acid or a derivative thereof, so that the 30% modulus and hardness were lowered.
Comparative Example 3 was an example in which benzoic acid or a derivative thereof was blended in the blending system of Comparative Example 2, but the 30% modulus and hardness decreased.
In Comparative Example 4, the amount of the novolak-type phenolic resin was less than the lower limit specified in the present invention, and benzoic acid or its derivative was not blended, so that the 30% modulus and hardness were lowered.
Comparative Example 5 is an example in which benzoic acid or a derivative thereof was blended in the blending system of Comparative Example 4, but the 30% modulus and hardness decreased.
Comparative Example 6 was an example in which phenylpropionic acid was blended in place of benzoic acid or its derivative, and tan δ (60 ° C.), 30% modulus and hardness were not improved.
Comparative Example 7 was an example in which L-ascorbic acid was blended in place of benzoic acid or its derivative, and tan δ (60 ° C.), 30% modulus and hardness were not improved.
In Comparative Example 8, since the pKa of benzoic acid or a derivative thereof exceeded the upper limit defined in the present invention, no improvement was observed in tan δ (60 ° C.) and 30% modulus.
In Comparative Example 9, since the blending amount of benzoic acid or a derivative thereof was less than the lower limit specified in the present invention, tan δ (60 ° C.), 30% modulus and hardness were not improved.
Since the compounding quantity of the benzoic acid or its derivative exceeded the upper limit prescribed | regulated by this invention, the tan-delta (60 degreeC) deteriorated in the comparative example 10.
Comparative Example 11 is an example in which benzoic acid or a derivative thereof was not blended in the blending system of Example 8. Compared to Example 8, tan δ (60 ° C.), 30% modulus, and hardness were all deteriorated. I understand.
Comparative Example 12 is an example in which benzoic acid or a derivative thereof is not blended in the blending system of Example 9, and tan δ (60 ° C.), 30% modulus, and hardness are all deteriorated as compared with Example 9. I understand.
Further, when Comparative Example 1 and Example 4 in Table 2 are compared, it can be seen that Example 4 to which salicylic acid is added has improved tan δ (60 ° C.), 30% modulus and hardness.

1 Bead part 2 Side wall 3 Tread 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer

Claims (4)

  30-100 parts by mass of reinforcing filler with respect to 100 parts by mass of diene rubber; 5-20 parts by mass of at least one novolac type phenolic resin selected from phenol resin, resorcin resin and cresol resin; methylene donor 0.1 to 6 parts by mass; and 0.2 to 5 parts by mass of benzoic acid having a pKa of 1.5 to 4.0 or a derivative thereof.   The tire rubber composition according to claim 1, wherein the novolac-type phenolic resin is a phenol resin.   The tire rubber composition according to claim 1 or 2, wherein the tire rubber composition has a vulcanized hardness (20 ° C) of 85 or more.   The pneumatic tire which used the rubber composition for tires in any one of Claims 1-3 for a bead filler.

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