JPH0464624B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention provides a pneumatic tire that generates less heat in the tire tread when running, has excellent fuel efficiency, and has significantly improved braking performance on wet roads and on snowy and icy roads. Regarding. [Prior Art] In recent years, the demand for low fuel consumption in automobiles has increased significantly due to social demands for resource and energy conservation. For this reason, not only the development of automobiles themselves, such as engines that consume less gasoline, but also fuel-efficient tires that reduce energy loss have been rapidly investigated. Conventionally, rubber materials with low hysteresis loss have been required as tire materials for fuel-efficient tires, and in particular, natural rubber with low hysteresis loss has been used as a rubber component for the tread portion, which is said to account for more than 50% of the hysteresis loss of tires. , polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber with a low glass transition point (Tg), and blends thereof have been used. Furthermore, as far as rubber compositions have been concerned, there have been rubber compositions that contain a comparatively small amount of carbon black with a relatively large particle size and also contain as little as possible the amount of a softener such as aromatic oil. has been used. By the way, recently, more and more functions have been required of tires at a very high level. For example, the fuel-efficient tires developed as described above do not reduce their fuel-efficiency performance, and from the standpoint of safety, have high braking performance that can be used on various road surfaces such as wet roads, snow-covered roads, and icy roads. Performance is highly desired. However, as mentioned above, when using natural rubber, polyisoprene rubber, polybutadiene rubber, or styrene-butadiene copolymer rubber with low Tg, which has low hysteresis loss, braking performance (wet skid resistance), especially on wet road surfaces, is poor. The problem was that the running stability was extremely poor. Furthermore, when carbon black with a large particle size was used, although the fuel efficiency performance was excellent, deterioration of properties such as braking performance on wet road surfaces and wear resistance could be avoided. Furthermore, the tread rubber of conventional fuel-efficient tires contains a small amount of softener, so it tends to harden at low temperatures, and therefore has sufficient braking performance (ice skid resistance) on snowy or icy roads. had not reached a satisfactory level. On the other hand, recently, so-called high vinyl polybutadiene rubber and high vinyl styrene-butadiene copolymer rubber containing 50% or more of 1,2-vinyl bonds have been developed as materials that satisfy both fuel efficiency and wet skid resistance properties of tires. Proposed.
However, all of these rubbers have a high glass transition point (Tg), so they have poor abrasion resistance, and they also harden easily at low temperatures, resulting in significantly inferior braking performance on snowy and icy roads. However, it is still insufficient to satisfy all such characteristics. Thus, at present, no tire has been proposed that satisfies all of the characteristics of low fuel consumption, high braking performance on wet road surfaces, and high braking performance on snowy and icy roads. Particularly in the winter, when roads become slippery due to snow and ice, conventional tires, including fuel-efficient tires, have very poor braking performance on these surfaces, forcing the use of snow tires. . However, it takes a considerable amount of time and effort for users to change tires, and there is a strong desire for an all-season tire that satisfies the above three characteristics while being a regular summer tire. [Objective of the Invention] The present invention has been made to meet these demands, and has low heat generation in the tire lead portion during driving, excellent fuel efficiency, and improved braking performance on wet road surfaces and improved snow and snow accumulation. The purpose of the present invention is to provide a pneumatic tire that has significantly improved braking performance on icy road surfaces. This tire is a so-called all-season pneumatic tire that can be used throughout the year, regardless of summer or winter. [Structure of the Invention] In order to achieve this object, the present inventors have made extensive research and have developed a novel styrene-based material for the tread portion.
We have discovered that by using a rubber composition containing butadiene copolymer rubber, a pneumatic tire with low fuel consumption and excellent braking performance on wet road surfaces and snowy/icy roads can be obtained, and we have developed the present invention. . Therefore, the present invention provides a pneumatic tire in which the tread portion is composed of at least two layers, an outer surface rubber layer and an inner surface rubber layer, (1) The outer surface rubber layer has 100 parts by weight of raw material rubber. Rubber and/or polyisoprene rubber
20 to 90 parts by weight and 80 to 10 parts by weight of styrene-butadiene copolymer rubber, the copolymer rubber has a bound styrene content of 5 to 30% by weight, and a 1,2-vinyl bond content of the butadiene moiety of 10 to 10% by weight. In 85% of cases, an atomic group represented by the following formula () is introduced at the end of the molecular chain or into the molecular chain. and the ratio A/B of the branched polymer (A) bonded by a tin-butadienyl bond to the polymer (B) into which at least one atomic group represented by the above formula () has been introduced is 0.1 or more and less than 4.0. and
(2) As a reinforcing agent, the specific surface area (N ₂ SA) is 60~
140m ² /g, dibutyl phthalate oil absorption (DBP)
The pneumatic tire is characterized by containing 30 to 80 parts by weight of carbon black having an oil absorption of 100 to 150 ml/100 g per 100 parts by weight of raw rubber. Hereinafter, the configuration of the present invention will be explained in detail. FIG. 1 is an explanatory diagram of a meridional half cross section of an example of the tire of the present invention. In FIG. 1, T is a tread portion, and this tread portion T includes a cap layer (outer surface rubber layer) 1 and an under layer (inner surface rubber layer).
Consists of 2. 3 is a pair of left and right bead portions 4,
A belt layer 5 is disposed so as to surround the outer periphery of the carcass layer 3 in the tread portion T. 6 is a tread groove, and 7 is a side portion. (1) In the present invention, the rubber layer 1 on the outer surface side is made of natural rubber and/or polyisoprene rubber of 20 to 90%
parts by weight and 10 to 80 parts by weight of a specific styrene-butadiene copolymer rubber (total rubber content: 100 parts by weight). This is because a blending ratio outside this range is undesirable because any of the characteristics of fuel efficiency, braking performance on wet road surfaces, and braking performance on snowy/icy road surfaces will deteriorate. However, it may also contain 30 parts by weight or less of other diene rubbers, such as polybutadiene rubber, acrylonitrile-butadiene copolymer rubber, unmodified styrene-butadiene copolymer rubber, and the like. The styrene-butadiene copolymer rubber used here has an atomic group represented by the following formula introduced at the end or into the molecular chain. The introduction of the atomic group shown in the above formula () is the bond of the following formula (In the formula, M represents an O atom or an S atom) (hereinafter referred to as compound A) is reacted with a styrene-butadiene copolymer. Compound A includes N,N-dimethylformamide, N,N-diethylformamide;
N-diethylacetamide; aminoacetamide, N,N-dimethyl-N',N'-dimethylaminoacetamide, N-phenyldiacetamide; N,N-dimethylacrylamide, N,N
-dimethylmethacrylamide; propionamide, N,N-dimethylpropionamide; 4
-pyridylamide, N,N-dimethyl-4-pyridylamide; N,N-dimethylbenzamide, p-aminobenzamide, N',N'-(p-
dimethylamino)benzamide, N,N-dimethyl-N'-(p-ethylamino)benzamide, N-acetyl-N-2-naphthylbenzamide; nicotinamide, N,N-diethylnicotinamide; succinic acid amide, maleic acid Amide, N,N,N',N'-tetramethylmaleic acid amide; succinimide, maleimide, N-methylmaleimide, N-methylphthalimide,
1,2-cyclohexanedicarboximide, N
-Methyl-1,2-cyclohexanedicarboximide; oxamide, 2-furamide, N,N,
N',N'-tetramethyloxamide, N,N-
Dimethyl-2-furamide; N,N-dimethyl-
8-quinolinecarboxamide; N,N-dimethyl-p-amino-benzalacetamide;
N,N-dimethyl-N',N'-(p'-dimethylamino)cinnamylideneacetamide; N,N-
Dimethyl-N',N'-(2-dimethylamino)vinylamide, N'-(2-methylamino)vinylamide; urea, N,N'-dimethylurea, N,
N,N',N'-tetramethylurea; methyl carbamate, N,N-methyl diethylcarbamate; ε-caprolactam, N-methyl-ε-caprolactam, N-acetyl-ε-caprolactam, 2-pyrrolidone, N -Methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, 2-
piperidone, N-methyl-2-piperidone, 2
-quinolone, N-methyl-2-quinolone, 2-
Examples include indolinone, N-methyl-2-indolinone; isocyanuric acid, N,N',N"-trimethylisocyanuric acid, etc., and their corresponding sulfur-containing compounds. Among these, particularly preferred compounds are those in which an alkyl group is bonded to nitrogen. The method for producing the styrene-butadiene copolymer rubber into which the atomic group represented by the formula () is introduced includes, for example, (a) an alkali metal-based catalyst and/or an alkaline earth metal-based catalyst; A method of polymerizing styrene and butadiene using a catalyst and adding compound A to the solution after the polymerization reaction is completed,
(b) A method in which a styrene-butadiene copolymer is dissolved in a suitable solvent, an alkali metal and/or an alkaline earth metal is added to the copolymer, and then Compound A is added and reacted, etc. can be exemplified. In this case, the alkali metal-based catalyst used in the polymerization reaction and addition reaction is a metal itself such as lithium, rubidium, or cesium, or a complex of these metals with a hydrocarbon compound or a polar compound (for example, n-butyllithium, 2 -naphthyllithium, potassium-tetrahydrofuran complex, potassium-diethoxyethane complex, etc.). In addition, alkaline earth metal-based catalysts are disclosed in JP-A-51-115590, JP-A-52-9090, and JP-A-Sho 52-9090.
Barium, which is listed in No. 57-100146, etc.
Examples include catalyst systems containing compounds such as strontium and calcium as main components. Any metal-based catalyst may be used as a catalyst for normal solution polymerization, and is not particularly limited. After the reaction is completed, the unsaturated rubbery polymer into which Compound A has been introduced is treated by adding a coagulant such as methanol,
It is recovered from the reaction solution using conventional separation methods such as steam stripping. The obtained unsaturated rubbery polymer contains at the end of the molecular chain or in the molecular chain, Compound A is introduced as an atomic group. The site into which compound A is introduced may be at the end of the molecular chain or any other site, but is preferably at the end of the molecular chain. This is because by using a polymer obtained by reacting a copolymer having a dienyl structure at the end of the molecular chain with Compound A, the fuel efficiency can be further improved. It is an essential condition of the present invention that the styrene-butadiene copolymer rubber has an atomic group represented by the above formula () in its molecular chain. A rubber composition containing this styrene-butadiene copolymer rubber is significantly improved compared to a rubber composition containing a normal styrene-butadiene copolymer rubber that does not have the atomic group represented by the above formula (). Shows rebound resilience. Therefore, a pneumatic tire using this rubber composition in its tread can greatly improve fuel efficiency while maintaining other characteristics at a high level. Furthermore, the styrene-butadiene copolymer rubber used in the present invention has a bound styrene content of 5 to 30% by weight, preferably 10 to 30% by weight, and a 1,2-vinyl bond content of the butadiene moiety of 10 to 30% by weight. 85
%, preferably 30-75%. If the amount of bound styrene is less than 5% by weight, the wet skid resistance of the rubber composition decreases, which impairs the braking performance of the tire on wet road surfaces, which is undesirable. On the other hand, if it exceeds 30% by weight, braking performance on wet road surfaces increases, but braking performance on snowy/icy roads and abrasion resistance deteriorate, which is not preferable. If the amount of 1,2-vinyl bond is less than 10%, it is difficult to manufacture and the effect of improving braking performance on wet roads is small. On the other hand, if it exceeds 85%, heat generation increases and braking performance on icy roads increases. This is not preferred because the wear resistance is significantly reduced. Further, the styrene-butadiene copolymer rubber used in the present invention may contain a branched polymer bonded with tin-butadienyl bonds in order to obtain good processability during tire manufacturing. However, if the molecular chain ends of the styrene-butadiene copolymer rubber are used too much to form tin-butadienyl bonds, the effective molecular chain ends for introducing the atomic group represented by the above formula () will decrease. In order to obtain the tire performance that is the objective of the present invention while maintaining good processability during tire manufacturing, it is necessary to combine the branched polymer (A) bonded with tin-butadienyl bonds with the formula () in the molecular chain. The ratio A/B to the polymer (B) into which at least one atomic group represented by is introduced is 0.1 or more.
Preferably, it is in a range of less than 4.0. (2) In addition, in the present invention, the outer surface side rubber layer 1
However, carbon black is contained as a reinforcing agent in an amount of 30 to 80 parts by weight per 100 parts by weight of raw rubber. If the amount of carbon black is less than 30 parts by weight, the tire will not have sufficient braking performance on wet roads.
Abrasion resistance cannot be obtained. On the other hand, if it exceeds 80 parts by weight, the fuel efficiency of the tire will deteriorate, and in addition, the hardness of the tread portion will increase at low temperatures, making it easier to slip on icy roads, which is undesirable. The carbon black used here has a specific surface area (N ₂ SA) of 60% by nitrogen adsorption method.
~140m ² /g, preferably 75-120m ² /g, with dibutyl phthalate oil absorption (DBP oil absorption) of 100
~150ml/100g, preferably 110-140ml/100g
It is necessary to be within the range of . If the N ₂ SA is less than 60 m ² /g, the tire will have excellent fuel efficiency, but its braking performance and wear resistance on wet road surfaces will deteriorate significantly. On the other hand, N ₂ SA is 140
If it exceeds m ² /g, the fuel efficiency of the tire will deteriorate, which is undesirable. If the DBP oil absorption amount is less than 100ml/100g, it is not preferable because the wear resistance of the tire decreases and the steering stability deteriorates. If it exceeds 150 ml/100 g, the tread portion tends to harden at low temperatures and braking performance on snowy or icy roads decreases, which is undesirable. Furthermore, it is preferable that the carbon black has a half-value width (ΔDst) of aggregate distribution measured by centrifugal sedimentation of 85 to 130 mμ, since it is more effective in improving fuel efficiency. In the present invention, the tread portion is characterized in that a rubber composition comprising the above-mentioned rubber component and carbon black is used for the outer surface rubber layer of a pneumatic tire comprising at least two layers.
This rubber composition may contain compounding agents commonly used in the rubber industry, such as a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, an anti-aging agent, and a softening agent. Further, the tire of the present invention can be applied to all tires such as tires for passenger cars, tires for trucks and buses, and the type of tire is not particularly limited. Examples and comparative examples are shown below. Examples and Comparative Examples The properties of the styrene-butadiene copolymer rubber (SBR) used here are shown in Table 1, and the properties of carbon black are shown in Table 1. A rubber having a composition shown in Table 1 is used in the cap layer of a tire having a two-layer tread structure shown in FIG.
We created 18 types of 165SR13 tires. Each tire was evaluated by performing a wet road braking test, an icy road braking test, and a rolling resistance test using actual vehicle tests using the following methods. The results are also listed in Table 1. (1) Wet road braking test: Water was sprinkled on the asphalt paved road surface, the braking distance from 40 km/hr was measured, and the index was evaluated with the tire of Comparative Example 1 set as 100. The larger the index, the better the braking performance. (2) Icy road braking test: The brakes were applied while driving at a speed of 40 km/hr on a completely frozen road in an atmosphere of -5 to -10°C, and the distance until it came to a complete stop was measured. Evaluation was made using an index when a tire of 1 is set as 100.
The larger the index, the better the braking performance. (3) Rolling resistance test: On an indoor test drum with a diameter of 707 mm, a tire internal pressure of 1.9 Kg/cm ² and a load of 420 Kg were applied, and after 30 minutes of preliminary running at a speed of 100 Km/hr, a test of 60 Km/hr was performed. The rolling resistance was measured at speed, and the tire of Comparative Example 1 was
It was evaluated using the index when The smaller the index, the lower the rolling resistance and the better fuel efficiency.

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〔Effect of the invention〕

As explained above, according to the present invention, a rubber composition containing a novel styrene-butadiene copolymer rubber is used in the tread portion, and branched polymers bonded by tin-butadienyl bonds in this copolymer rubber are used. By keeping the content of the coalesces within a specific range, this all-season tire maintains good workability during tire manufacturing, has excellent fuel efficiency, and also satisfies braking performance on wet, snowy, and icy roads. You can get pneumatic tires for.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a meridional half cross section of an example of the tire of the present invention. 1...Rubber layer on the outer surface side, 2...Rubber layer on the inner surface side,
3...Carcass layer, 4...Bead part, 5...Belt layer, 6...Tread groove, 7...Side part, T...
...Torezdo department.

Claims (1)

[Scope of Claims] 1. A pneumatic tire in which the tread portion is composed of at least two layers, an outer surface rubber layer and an inner surface rubber layer, (1) the outer surface rubber layer is made of raw material rubber, 100 parts by weight of which is natural rubber. It consists of 20 to 90 parts by weight of rubber and/or polyisoprene rubber and 80 to 10 parts by weight of styrene-butadiene copolymer rubber, and the copolymer rubber has a bound styrene content of 5 to 30% by weight and a butadiene content of 1,2% by weight. - The amount of vinyl bonds is 10 to 85%, and an atomic group represented by the following formula () is introduced at the end of the molecular chain or into the molecular chain, and the ratio A/B of the branched polymer (A) bonded by a tin-butadienyl bond to the polymer (B) into which at least one atomic group represented by the above formula () has been introduced is 0.1 or more and less than 4.0. (2) As a reinforcing agent, the specific surface area (N ₂ SA) is 60~
140m ² /g, dibutyl phthalate oil absorption (DBP)
A pneumatic tire characterized by containing 30 to 80 parts by weight of carbon black having an oil absorption of 100 to 150 ml/100 g per 100 parts by weight of raw rubber.