JPH0625280B2 - High performance tire with improved low temperature properties - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a high-performance tire (HPT) which is excellent in low-temperature characteristics, that is, steering stability is not significantly deteriorated at low temperatures.
(High Per-formance Tire).

[Prior art]

In the conventional HPT, so-called high styrene SBR having a styrene content of more than 23.5% of a normal styrene-butadiene copolymer rubber is used as a rubber component in the cap tread rubber composition, and carbon black having a small particle size is used. Used in large quantities. Further, among the softeners, since the proportion of aromatic oil is large, the cap tread rubber composition is hardened at a low temperature and the driving stability is remarkably lowered, which is extremely dangerous on an icy road surface. Will end up. Therefore, as a countermeasure against this, conventionally, polystyrene rubber having excellent low temperature characteristics is added to high styrene SBR having a higher styrene content, or paraffin oil having a VGC (viscosity specific gravity constant) of 0.90 or less and sebacic acid having good low temperature characteristics are used. Plasticizers such as derivatives have been used as softeners.

However, the expected effects such as poor compatibility between polybutadiene rubber excellent in low-temperature characteristics and high styrene SBR, (a) no improvement in low-temperature characteristics, and (b) poor abrasion resistance were not obtained. In addition, since the conventional type softener with good low temperature characteristics reduces hysteresis loss,
Despite the use of high styrene SBR, there are problems such as not improving wet skid characteristics.

[Object of the Invention]

An object of the present invention is to provide a high-performance tire in which the cap tread rubber is hardened at a low temperature and the steering stability is remarkably lowered.

[Structure of Invention]

Therefore, the present invention, the tread portion in contact with the road surface, (1) styrene content of 30 wt% ~ less than 38 wt% styrene-butadiene copolymer rubber, the total styrene content is
At least one of styrene-butadiene copolymer rubber, polybutadiene rubber, polybutadiene rubber having a high vinyl content, natural rubber, polyisoprene rubber, and halogenated butyl rubber is used in an amount of 0 to 30 as other rubber content so as to be 28% or more.
70 parts by weight or more of carbon black having a nitrogen specific surface area of 80 m ² / g or more and a dibutyl phthalate oil absorption of 110 ml / 100 g or more, relative to 100 parts by weight of the raw material rubber contained by weight, (3) the following formula (In the formula, R is a hydrogen atom, a hydroxyl group, a methyl group or a general formula. (In the formula, R ′ represents a hydrocarbon group having 3 to 21 carbon atoms)
And may be the same or different, but at least two of R are general formulas. Is a group represented by. n is a number from 0 to 2) Loss tangent (tan) at 0 ° C blended with 5 to 13 parts by weight of a neopentyl type polyol ester having a kinematic viscosity (40 ° C) of 300 cSt or less
A high-performance tire characterized by comprising a rubber composition having a δ) of 0.74 or more and a dynamic storage elastic modulus (E ′) at −20 ° C. of 30 M * Pa or less.

Hereinafter, the configuration of the present invention will be described in detail.

(1) Raw rubber.

Styrene with a styrene content of 30% to less than 38% by weight
Made of butadiene copolymer rubber. As other rubber content,
Styrene content of less than 30 wt% styrene-butadiene copolymer rubber, polybutadiene rubber, polybutadiene rubber with high vinyl content, natural rubber, polyisoprene rubber,
At least one halogenated butyl rubber is contained in an amount of 0 to 30 parts by weight so that the total styrene content is 28% or more. Therefore, when another rubber component is blended, the rubber component is contained in the raw rubber in an amount of 1 to 30 parts by weight.

(2) Carbon black.

Nitrogen specific surface area (N ₂ SA) 80 m ² / g or more, preferably 110 m ² / g or more, dibutyl phthalate oil absorption (DBP oil absorption) 110 ml /
Use 100g or more of carbon black.

(3) Neopentyl type polyol ester.

A compound having the above formula and a kinematic viscosity (40 ° C.) of 300 cSt or less. When the kinematic viscosity (40 ° C) exceeds 300 cSt, the effect of improving ice skid performance is small, which is not preferable.

Preferred examples of such neopentyl-type polyol ester are compounds having the following general formulas (1) to (3). In the formula, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are alkyl groups or alkenyl groups having 3 to 21 carbon atoms and may be the same or different.

Examples of the polyhydric alcohol that constitutes the neopentyl type polyol ester include neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, and dipentaerythritol. Examples of the acid constituting the neopentyl type polyol ester include C ₄
~ C ₂₂ saturated fatty acids, unsaturated fatty acids such as butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid,
Tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, isostearic acid, nonadecanoic acid, heneicoic acid, lauroleic acid,
Fatty acids such as tsuzuic acid, ficetrain acid, myristic acid, zoumaric acid, palmitoleic acid, petrosenoic acid, vaccenic acid, gadrenic acid, oleic acid, linoleic acid, linolenic acid, and mixed fatty acids thereof can be mentioned, but especially these It is not limited to.

(4) In the present invention, with respect to 100 parts by weight of the raw rubber,
70 parts by weight or more of the carbon black and 5 to 13 parts by weight of the neopentyl type polyol ester are blended to obtain a rubber composition.

Two or more kinds of the above neopentyl type polyol ester may be used, or a total of 30 parts by weight or more may be used together with an ordinary softening agent or other plasticizer.

Further, one or more kinds of other commonly used softeners such as ordinary aromatic oil, naphthenic oil, other synthetic plasticizers (DOS, DOP, DOA, etc.) and vegetable oil may be added. Further compounding agents such as zinc oxide, stearic acid, various antioxidants, waxes, vulcanization accelerators,
A vulcanizable rubber composition for tread is obtained by appropriately blending a vulcanizing agent such as sulfur.

This rubber composition has a loss tangent (tan δ) of 0.74 at 0 ° C.
It has physical properties of not less than 0.80, preferably not more than 0.80, and a dynamic storage elastic modulus (E ′) at −20 ° C. of not more than 30 M * Pa, preferably not more than 27 M * Pa. By using this composition for the cap tread rubber, not only the drawback that the steering stability is lowered in a low temperature atmosphere but also the rolling resistance can be reduced.

Examples and comparative examples are shown below.

Examples and Comparative Examples Table 1 shows various compounding examples. In addition to the compounding agents shown in Table 1, 4 parts by weight of zinc white, 2 parts by weight of stearic acid, 2 parts by weight of anti-aging agent, 1 part by weight of wax, etc. are compounded.
Sulfur as a vulcanizing agent 2.00 parts by weight per 100 parts by weight of rubber, N-cyclohexyl-2-benzothiazolesulfenamide as a vulcanization accelerator 1.00 parts by weight per 100 parts by weight of rubber, N, N'-diphenyl It contains 0.20 parts by weight of guanidine. The above raw rubbers and compounding agents except sulfur as a vulcanizing agent and a vulcanization accelerator were mixed for 4 minutes with a Kobe Steel B-type Banbury mixer with a capacity of 1.8 minutes, and then the vulcanizing agent was uniformly dispersed with an 8-inch roll. A rubber composition was obtained.

Then, using a vulcanizing press specified in JIS K6301 this rubber composition, press vulcanization for 30 minutes at 150 ℃, to obtain a 2mm sheet, the vulcanizate tan δ using the following viscoelasticity spectrometer, The value of E'was measured.

The viscoelasticity spectrometer was measured by using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho under the conditions of an initial strain of 10%, a dynamic strain of 2%, an extensional deformation, and a frequency of 20 Hz.

Further, a radial tire of 205/60 R14 size was prepared by using the rubber compositions according to various compounding examples shown in Table 1 for the cap tread, and the wet skid characteristics, ice skid characteristics, and rolling resistance were measured. The wet skid characteristics were indexed with the comparative example (1) being 100 and the ice skid characteristics and rolling resistance being 100 in the comparative example (2). The larger the numerical value for each characteristic, the better. That is, it was determined from the following formula.

Wet skid characteristic = measured value (friction coefficient value) / measured value of comparative example (1) x 100.

Ice skid characteristic = measured value of comparative example (2) / measured value of test sample x 100.

Rolling resistance characteristic = measured value of comparative example (2) / measured value of test sample x 100.

Wet skid characteristics = speed on wet asphalt road surface
The friction coefficient at each speed of 40 km / hr, 60 km / hr, and 80 km / hr was obtained, and the index was obtained from the above formula with Comparative Example (1) as 100 at each level, and the average value of the three levels is shown.

Ice skid characteristic = Calculate the braking distance from an initial speed of 30km / hr on an icy road surface with an ambient temperature of -10 ° C and display it as an index from the above formula.

Rolling resistance = 2.0k air pressure on an iron drum with a diameter of 1707mm
g / cm ² , load 490 kg, speed 40-150 km / hr (40,60,80,100,
120,150km / hr), comparative example from the above formula at each speed
The index for (2) is calculated and shown as the average value.

Comparative Example (1) is a rubber composition used for a tire that emphasizes ordinary steering stability, and E ′ @ − 20 ° C. shows 26.9 M * Pa. This rubber composition is used in a cap compound. If there is, it is possible to drive even in cold regions. Comparative Example (2) is a rubber composition using a styrene-butadiene copolymer rubber having a high styrene content, which is used for a tire called a normal HPT, and has an E '@-20 ° C.
Is 34.0 M * Pa, which is larger than that of Comparative Example (1), and this level is
Driving in cold regions, especially on icy roads, is extremely difficult.

Comparative Examples (3) and (4) are paraffin oil or dioctyl sebacate as a plasticizer, which is a method for improving low-temperature characteristics when a styrene-butadiene copolymer rubber having a high styrene content that has been conventionally used is used. This is an example using 1 part, but in this case, E '@-20 ° C is 26.7M * P for Comparative Example (3), respectively.
a, Comparative Example (4) is improved to 23.2M * Pa, and tire data shows that Comparative Example (3) 115 and Comparative Example (4) 120 have good ice skid characteristics, but tanδ @ 0 ° C is a comparative example. (3) 0.72, comparative example
(4) Comparative example despite using styrene-butadiene copolymer rubber with a high styrene content of 0.69
(1) or less, which is not preferable, and wet skid characteristics have not been improved even in actual tires.

Example (1) is a case where LX-198 manufactured by Asahi Denka Co., Ltd. having a kinematic viscosity (40 ° C.) of 188 cSt, which is one of the neopentyl type polyol esters specified in the present invention, is used.
δ @ 0 ° C is 0.85 and E '@-20 ° C is 27.0, which is a good level, and even the actual tire has a comparative wet skid characteristic.
Compared to (1), it is 110, which is close to that of Comparative Example (2), and the ice skid characteristic is 117, which is equivalent to that of Comparative Example (1), and it is possible to sufficiently run on an icy road surface. If the amount of neopentyl-type polyol ester is less than 5 parts by weight, the improvement effect is small and it is not preferable.

Further, Comparative Example (5) is a neopentyl type polyol ester, but also uses the same Asahi Denka H-450 with a kinematic viscosity (40 ° C.) of 417 cSt. In this case, tan δ @ 0
The temperature was as good as 0.86, but E '@-20 ° C was 33.5M * Pa, which was not an improvement effect, and an insufficient result was obtained in the ice skid test.

As described above, by using the neopentyl type polyol ester having a kinematic viscosity (40 ° C.) of 300 cSt or less, the low temperature characteristics are significantly improved without significantly lowering the wet skid characteristics.

Next, in Comparative Example (6), an attempt was made to improve low temperature properties by blending a styrene-butadiene copolymer rubber having a high styrene content, which is one of the conventional techniques, with a polybutadiene rubber having excellent low temperature properties. As an example, the compatibility between rubber components is poor and the expected effect of improving low temperature characteristics cannot be exhibited.

Examples (2), (3) and Comparative Examples (7), (8) are examples in which a styrene-butadiene copolymer rubber produced by a solution polymerization method is used as a blend, but the styrene content is 30% by weight. ,
1.25 x 30 ÷ 0.65 x 30 = 57 <65 using SBR (1) having 30% of 1,2 vinyl bonds in the butadiene part and (2) with styrene content of 25% by weight and 50 of vinyl bonds. SB which is%
The embodiment (3) using R (2) and 1.25 × 25 + 0.65 × 50 = 63.75 <65 showed improvement effects in both wet skid characteristics and low temperature characteristics, but comparison using SBR (3) Example (7),
Comparative Example (8) using SBR (4) has a SBR (3) styrene content of 38.0 wt%, 1,2 vinyl bond 28%, 1.25 x 38 + 0.65
× 28 = 65.7, SBR (4) styrene content 20.0% by weight, 1,2
Vinyl bond 76%, 1.25 × 20 + 0.65 × 76 = 74.4,
1.25 x styrene content + 0.65 x vinyl bond content exceeds 65. In this case, the effect of improving the low temperature characteristics is small, which is not preferable.

Further, as shown in Examples (2) and (3), the rolling resistance can be improved by using the styrene-butadiene copolymer rubber produced by a specific solution polymerization method.
The cap tread rubber composition for use can be significantly reduced compared to Comparative Example (2). If the specific solution-polymerized styrene-butadiene copolymer rubber is less than 10 parts by weight, the improvement effect is small and it is not preferable.

Next, regarding carbon black, Example (1), Example
(4) and Comparative Example (9) show the nitrogen specific surface area (AS
TM D3037-84), DBP oil absorption (JIS K6221
It was investigated carbon black having characteristics of measurement) by (the carbon black for rubber) A method, N ₂ SA is
Comparative example (9) using N341 carbon black having a DBP oil absorption of less than 110 ml / 100 g at less than 80 m ² / g has good low temperature characteristics,
Wet skid characteristics are poor and not desirable Further, from Examples (1) and (4), it is understood that N ₂ SA is more preferably 110 m ² / g or more in consideration of wet skid characteristics. If the amount of carbon black is less than 70 parts by weight, the wet skid characteristics are insufficient, which is not preferable.

As described above, according to the present invention, excellent low temperature characteristics,
In addition, it becomes possible to provide HPT having excellent wet skid characteristics.

More preferably, the styrene-butadiene copolymer rubber
In 10 parts by weight or more, the styrene content is 20 to 40% by weight, the 1,2 vinyl bond in the butadiene portion is 25 to 60%, and α = 1.25 ×
Rolling resistance by using styrene-butadiene copolymer rubber made by solution polymerization method with α value of 65 or less calculated by styrene content (%) + 0.65 x 1,2 vinyl bond content (%) Can also be reduced.

Claims (2)

[Claims] 1. A tread portion which comes into contact with a road surface is composed of (a) a styrene-butadiene copolymer rubber having a styrene content of 30% by weight to less than 38% by weight.
(B) 70 parts by weight or more of carbon black having a nitrogen specific surface area of 80 m ² / g or more and dibutyl phthalate oil absorption of 110 ml / 100 g or more, relative to 100 parts by weight of raw rubber of 28% or more, (c) the following formula (In the formula, R is a hydrogen atom, a hydroxyl group, a methyl group or a general formula. (In the formula, R ′ represents a hydrocarbon group having 3 to 21 carbon atoms)
And may be the same or different, but at least two of R are general formulas. Is a group represented by. n is a number from 0 to 2) Loss tangent (tan) at 0 ° C blended with 5 to 13 parts by weight of a neopentyl type polyol ester having a kinematic viscosity (40 ° C) of 300 cSt or less
A high-performance tire characterized by comprising a rubber composition having a δ) of 0.74 or more and a dynamic storage elastic modulus (E ') at -20 ° C of 30 M * Pa or less. 2. The tread portion in contact with the road surface is composed of (a) a styrene-butadiene copolymer rubber having a styrene content of 30% by weight to less than 38% by weight.
Styrene-butadiene copolymer rubber, polybutadiene rubber, natural rubber, etc. as other rubber content to be 28% or more.
With respect to 100 parts by weight of the raw rubber containing 1 to 30 parts by weight of at least one of polyisoprene rubber and halogenated butyl rubber, (b) a nitrogen specific surface area of 80 m ² / g or more and a dibutyl phthalate oil absorption of 110 ml / 100 g or more 70 parts by weight or more of carbon black, (c) the following formula (In the formula, R is a hydrogen atom, a hydroxyl group, a methyl group or a general formula. (In the formula, R ′ represents a hydrocarbon group having 3 to 21 carbon atoms)
And may be the same or different, but at least two of R are general formulas. Is a group represented by. n is a number from 0 to 2) loss tangent (tan
A high-performance tire characterized by comprising a rubber composition having a δ) of 0.74 or more and a dynamic storage elastic modulus (E ') at -20 ° C of 30 M * Pa or less.