JPH08176351A - Softener for tire tread rubber and rubber composition for tire tread containing the same softener blended therein - Google Patents

Abstract

PURPOSE: To obtain a softener for tire tread rubber, containing a dimer acid or its esterified substance having a specific structure and capable of enhancing gripping performances at low temperatures and maintaining the gripping performances on dry and wet road surfaces good. CONSTITUTION: This softener contains a compound selected from a dimer acid and its esterified substance of formulas I to III [R<1> and R<2> are each H or a 1-12C alkyl; (m), (n), (p), (q), (m'), (n'), (p') and (q') are each 0 or >=1; (m+n) is 11-13; (p+q) is 13-15; (m'+n') is 10-12; (p'+q') is 10-12]. The dimer acid and its esterified substance are usually obtained by polymerizing a higher unsaturated fatty acid such as oleic acid or its ester. A solid acid catalyst such as a montmorillonitic activated clay is preferred as a polymerization catalyst and preferably used in 2-8% catalytic amount based on the polymerization raw material. The reaction is preferably carried out at 230-250 deg.C under 2-10atm. Furthermore, the softener is preferably blended in an amount of 10-30 pts.wt. based on 100 pts.wt. rubber raw material containing a diene-based rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire tread rubber softening agent and a tire tread rubber composition containing the polymer.

[0002]

2. Description of the Related Art Conventionally, it has been generally known that the hardness of a tread should be lowered in order to improve the grip performance of a rubber for a normal tire tread at a low temperature. An alcohol ester-based plasticizer of a valent fatty acid is added to the rubber composition. However, when these additives are used, the rubber composition causes a decrease in hysteresis loss (tan δ), and further, since the plasticizer has a high volatility, the grip performance on a dry road surface and a wet road surface is consequently increased. Will fall. On the other hand, the rubber composition for a tire tread that emphasizes grip is
A styrene-butadiene copolymer rubber (SBR) having a high styrene content is used as a polymer, and a rubber composition filled with carbon black and a petroleum softener is used. However, since such a rubber composition has a relatively high glass transition point (Tg), there is a problem that the tread becomes stiff and the grip performance deteriorates at low temperatures such as winter.

In order to suppress the deterioration of grip performance at low temperatures, an attempt has been made to mix a petroleum-based softening agent and an ester-based plasticizer into a rubber composition at the same time as disclosed in JP-A-60-76403. However, the combined use of such petroleum-based softeners and ester-based plasticizers results in lower hysteresis loss (tan δ) and higher volatility of the plasticizers, resulting in grip performance on dry and wet road surfaces. However, there was a problem in that Further, if the surface temperature of the tire rises during normal running, the life of the petroleum softener and the ester plasticizer becomes a problem because the volatility of both is high.

Then, the improved rubber compositions for tire treads are disclosed in JP-A-4-300932 and JP-A-6-107866, but the molecular weight of the softening agent is too large, and the commonly used ester is used. There is a problem that the glass transition point (Tg) is higher than that of the system plasticizer, and the tread becomes stiff at a low temperature such as winter and the grip performance is deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention provides a tire tread rubber which not only enhances grip performance at low temperatures, but also maintains good grip performance under normal driving conditions, that is, grip performance on dry and wet road surfaces. The purpose is to provide a softening agent for use. Another object of the present invention is to provide a rubber composition containing such a softening agent for tire tread rubber.

[0006]

The present invention was made based on the finding that a dimer acid having a specific structure or an esterified product thereof has excellent properties as a softening agent for tire tread rubber. That is, the present invention contains one or more compounds selected from the group consisting of dimer acids represented by the following general formulas (I) to (V) and esterified products thereof, a tire tread characterized by the following: Provided is a softening agent for rubber.

[0007]

Embedded image

[0008]

[Chemical 4]

(In the formula, R ¹ and R ² are each hydrogen or an alkyl group having 1 to 12 carbon atoms, which may be the same or different from each other, and m, n, p, q,
m ′, n ′, p ′ and q ′ are each an integer of 0 or 1 or more, m + n = 11 to 13, p + q = 13 to 15,
m '+ n' = 10-12 and p '+ q' = 10-12. Although the method for producing the dimer acid and its esterified product used in the present invention is not particularly limited, it is generally produced by a polymerization reaction using a higher unsaturated fatty acid or its ester. As the higher unsaturated fatty acid or its ester, oleic acid, elaidic acid, octadecenoic acid, linoleic acid, linolenic acid, palmitoleic acid, isooleic acid, branched octadecenoic acid, branched hexadecenoic acid and the like and higher unsaturated fatty acids and the like, methanol, ethanol , Propanol ,,
The carbon number of isopropanol, butanol, isobutanol, tersialibutanol, pentanol, hexanol, octanol, 2-ethylhexanol, decanol, lauryl alcohol is 1 to 12, preferably 1 to 12.
Esters with alcohols of 8 can be used. in this case,
The higher unsaturated fatty acid or its ester is used alone or in the form of a mixture. In addition, this higher unsaturated fatty acid and /
Alternatively, higher saturated fatty acid and / or ester thereof may be mixed in the ester thereof, and the mixing ratio thereof is preferably 40% by weight (hereinafter abbreviated as%) or less, particularly 20%.
The following is recommended.

As the polymerization catalyst, a liquid or solid Lewis acid or Bronsted acid is used, but a solid acid catalyst which is one of Bronsted acids is preferably used.
Examples of such substances include activated clay (preferably montmorillonite activated clay and bentonite activated clay), synthetic zeolite, silica / alumina, silica / magnesia and the like. The catalyst amount is 1 to 20 with respect to the polymerization raw material.
%, Preferably 2-8%. The reaction temperature is 200-
270 ° C is preferable, and more preferably 230 to 250 ° C.
Is. The reaction pressure may be reduced pressure, normal pressure or increased pressure, but is usually 1 to 10 atm, preferably 2 to 10 atm. The reaction time is not constant depending on the amount of catalyst and the reaction temperature, but 5 to 10 hours is usually sufficient. The reaction atmosphere may be air, but in order to obtain a product having a good color tone, it is preferable to use an inert gas atmosphere such as nitrogen or argon. An inert organic solvent may be used in the reaction, but it is preferable to simply add a catalyst to the higher saturated fatty acid and / or its ester without using a solvent.

The polymerization reaction product thus obtained is composed of a mixture of trimer acid (or its alkyl ester) which is a trimer and dimer acid (or its alkyl ester) which is a dimer. , Their mixing ratio is in the range of dimer / trimer = 9/1 to 6/4, and further, unreacted higher unsaturated fatty acid (or its alkyl ester)
including. Usually, unreacted higher unsaturated fatty acid (or its alkyl ester) is separated from this polymerization reaction product and used. In addition, the dimer may be used separately. As the separation method, vacuum distillation method, thin film distillation method, molecular distillation method,
An extraction method, a chromatographic separation method, an adsorption separation method, etc. can be adopted. Further, the polymerization reaction product may contain by-products such as aromatic compounds and polycyclic compounds. The content of these compounds varies depending on the raw materials used and the production conditions, but is usually 1 to 20% of aromatic compounds and 1 to 40% of polycyclic compounds. Compound (I) of the present invention
The dimer acid represented by (V) or its esterified product can be produced by the above production method. Compound (III) can be produced by hydrogenating compound (I) or (II), and compound (V) can be produced by hydrogenating compound (IV). Compound (I), (II) or (II
The ratio of I) to the compound (IV) or (V) varies depending on the production conditions of the dimer acid, but the compound (I), (II) and / or (III): compound (IV) and / or (V) = 9: 1
˜1: 9.

The dimer acid or its esterified product used in the present invention is a styrene-butadiene copolymer rubber (SB
R), natural rubber (NR), polyisoprene rubber (IP)
And 5 to 50 parts by weight, preferably 7 to 40 parts by weight, based on 100 parts by weight of a rubber raw material containing one or more rubbers selected from the group consisting of other diene rubbers.
More preferably, 10 to 30 parts by weight are used in combination. The diene rubber is not limited,
Examples thereof include polybutadiene (BR) and butyl rubber. The raw rubber used for tire tread rubber is
1 selected from SBR, NR, IP and the diene rubber
Type or two or more types of rubber as a main component, and other rubber, for example, about 1 to 10% can be used. The above specific rubber may be used alone, for example, SBR / B
Two blends of R, NR / BR or SBR, NR / IR
It is also possible to use a mixture of two or more types such as a three-type blend of / BR or SBR. Further, the rubber composition of the present invention may optionally contain an appropriate amount of a compounding agent such as a petroleum-based softening agent or another ester-based softening agent.

[0013]

EFFECTS OF THE INVENTION According to the present invention, a tire tread that enhances grip performance at low temperatures such as winter and maintains good grip performance under normal driving conditions, that is, grip performance on dry and wet road surfaces. A softening agent for rubber is provided. Therefore, the dimer acid and / or
Alternatively, the tire tread rubber containing the ester thereof exhibits extremely excellent performance. Next, the present invention will be described with reference to examples.

[0014]

【Example】

Example 1 Using the raw materials shown in Table-1, 100 parts by weight of SBR1500, 50 parts by weight of HAF carbon (Asahi # 70), zinc white
3 parts by weight of # 1, 1 part by weight of stearic acid, 1.7 of sulfur
5 parts by weight, 1 part by weight of accelerator NS, and a softening agent were sequentially supplied to a kneading roll machine [Kansai Roll Co., Ltd.] and kneaded to prepare a rubber composition. After vulcanizing this rubber composition, each physical property was measured. Table 2 shows the measurement results. The kneading conditions, vulcanization conditions and physical property measurement conditions are shown below.

[0015]

[Table 1] Table-1 Raw materials used Sample name Trade name Manufacturer SBR1500 JSR SBR # 1500 Japan Synthetic Rubber HAF Carbon Asahi # 70 (ASTM Ni N300) Asahi Carbon Zinc Hua Zinc Hua No. 1 White Water Chemical Stearic Acid Stearic Acid for Rubber (Camellia) Nippon Oil Fat Sulfur Powder Sulfur 300 Mesh Hosoi Chemical Accelerator NS Noxeller NS Ouchi Shinko Ji (2-Ethylhexyl) Sebacate OS Daihachi Chemical Aromatic Oil JSO AROMA 790 Nippon San Oil

Kneading conditions Roll size: φ6 × 15 inches, Roll speed: 25r
pm (f), roll rotation ratio: 1: 1.32, roll temperature: 50 ± 5 ° C., test method: JIS K 6299 vulcanization degree test condition test device: JSR curastometer type, test temperature: 1
60 ± 1 ° C., amplitude: ± 1 °, frequency: 100 cpm, test method: JIS K 6300 -20 ° C. hardness test Test device: sping type hardness tester JIS A type, test piece shape: 50 × 25 × 2 mm 4 sheets stacked, Treatment time: 5 hours, test method: JIS K 6301 tensile test Specimen shape: JIS No. 3, test speed: 500 mm / m
in, test method: JIS K 6301

Dynamic Viscoelasticity Test (Measurement of Loss Coefficient) Tester: Model RSA-II manufactured by Rheometrics, Test mode: Tensile mode, Specimen shape: 23 × 5 × 1 mm strip, Measurement item: Dynamic elastic modulus, loss elasticity Rate, loss coefficient, measurement frequency: 10 Hz, strain: 0.1%, measurement temperature:-
60 to 100 ° C, heating rate: 2 ° C / min, test method:
JIS K 7198 Heat loss test equipment: Gear type oven, test piece shape: 50x25x
2 mm, treatment condition: 160 ± 1 ° C. × 96 hours, test method: JIS K 6301

The softening agents used in the products 1 to 5 of the present invention are
It was synthesized according to the following method. (1) Softening agent (No1) methyl oleate 75%, methyl linoleate 15
%, Methyl stearate 9%, and other compounds
1000 g of methyl ester of higher unsaturated fatty acid having a composition of 1% and 70 g of montmorillonite activated clay as a catalyst were placed in an autoclave having an internal volume of 2 liters,
The reaction was performed at 230 ° C. for 5 hours under a nitrogen atmosphere. After filtering the reaction product, thin film distillation (150-200 ° C / 0.3-0.
5 mmHg) to remove the monomer fraction, and then thin-film distillation (250-280 ° C./0.3-0.5 mmHg) again,
Dimethyl dimer acid (No. 1) was obtained as a distillate. (2) Softening agent (No. 2 to 4) 1000 g of methyl ester of higher unsaturated fatty acid having the same composition as in the case of the softening agent (No. 1) and 70 g of montmorillonite activated clay as a catalyst were put into an autoclave having an internal volume of 2 liters, and nitrogen atmosphere The reaction was carried out at 230 ° C for 5 hours. After filtering the reaction product, thin film distillation (150-200
(° C / 0.3-0.5 mmHg) to remove the monomer fraction, and then dimeric acid methyl ester was obtained. When this dimer acid methyl ester was analyzed by liquid chromatography (GPC), it was found to be dimethyl dimer acid / trimethyl trimer acid = 70/30 (weight ratio). The methyl ester was used as it was (No 2). In addition, isopropyl ester and 2-ethylhexyl ester were synthesized by the following method. To 500 g of dimer acid methyl ester was added 500 g of a mixed solution of 100 g of sodium hydroxide dissolved in ethanol and water in equal volumes, and saponification reaction was carried out for 8 hours under reflux. Next, excess sulfuric acid was added, the dimer acid was extracted with ether, washed with water, and dried over anhydrous sodium sulfate. The obtained dimer acid was isopropyl esterified with isopropanol (No3) using 2-toluenesulfonic acid as a catalyst (0.5%) or 2-ethylhexanol.
-Ethylhexyl esterification (No 4) was carried out to obtain the corresponding dimer acid derivative.

[0019]

[Table 2] Table-2 Evaluation results Present Invention 1 Present Invention 2 Present Invention 3 Present Invention 4 Softener No. 1 15 0 0 0 Softener No 2 0 15 0 0 Softener No 3 0 0 15 0 Softener No 4 0 0 0 15 Hardness (−20 ° C.) * 1) [Hs (JIS)] 72 71 71 71 70 Tensile strength [kgf / cm ² ] 252 246 246 252 Elongation [%] 600 590 590 610 300% Tensile stress [kgf / cm ² ] 102 101 101 98 Loss factor (-20 ℃) * 2) Tan δ 0.532 0.523 0.523 0.512 Heat loss (%) * 3) 0.15 0.13 0.13 0.08

* 1) The smaller this value, the better the grip performance at low temperature. * 2) The higher the value, the better the grip performance. * 3) The weight loss on heating was calculated as a percentage with respect to the weight loss on heating in Comparative Product 1, which was a product without addition of a softening agent.

[0021]

[Table 3] Table-2 Evaluation results (continued) Invention 5 Comparative product 1 Comparative product 2 Comparative product 3 Softening agent No2 7.5 0 0 0 0 Softening agent No 4 7.5 0 0 0 0 (2-ethylhexyl) sebacate 0 0 15 0 0 Aromatic oil 0 0 0 15 0 Hardness (-20 ° C ) * 1) [Hs (JIS)] 70 82 70 77 Tensile strength [kgf / cm ² ] 252 283 222 258 Elongation [%] 610 400 510 630 300% Tensile stress [kgf / cm ² ] 95 174 102 911 Loss Coefficient (-20 ℃) * 2) tan δ 0.521 0.435 0.258 0.533 Heat loss (%) * 3) 0.10-0.28 0.45

From Table 2, the tire tread rubbers of the present invention (Invention 1 to 5) using dimethyl dimer acid and dimer acid derivative as a softening agent, were prepared from di (2-ethylhexyl) sebacate and aromatic oil. It can be seen that it has overall superior performance as compared with the used ones (Comparative products 2 and 3). In particular, all of the present inventions 1 to 5 have extremely low heating loss values, and when the dimer acid and / or its ester of the present invention is used, the grip performance at low temperatures is enhanced, and the grip performance under normal running conditions, that is, It is possible to provide a tire tread rubber in which the grip performance on a dry road surface and a wet road surface is favorably maintained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kohei Sakuma 1-3-7 Main Office, Sumida-ku, Tokyo Lion Corporation

Claims (2)

[Claims] 1. A tire tread rubber containing one or more compounds selected from the group consisting of dimer acids represented by the following general formulas (I) to (V) and esterified products thereof. Softening agent. Embedded image Embedded image (In the formula, R ¹ and R ² are each hydrogen or C 1
To 12 alkyl groups, which may be the same or different from each other, m, n, p, q, m ', n',
p ′ and q ′ are each an integer of 0 or 1 or more, and m
+ N = 11 to 13, p + q = 13 to 15, m '+ n' =
10-12 and p '+ q' = 10-12. ) 2. 100 parts by weight of a rubber raw material containing one or more rubbers selected from the group consisting of styrene-butadiene copolymer rubber, natural rubber, polyisoprene rubber (IP) and other diene rubbers. On the other hand, a rubber composition for a tire tread, which comprises 5 to 50 parts by weight of the polymer of the higher unsaturated fatty acid according to claim 1.