JP6141118B2 - Rubber composition for studless tire and studless tire - Google Patents

Description

  The present invention relates to a rubber composition for a studless tire and a studless tire using the rubber composition. More specifically, the studless tire exhibits excellent characteristics in performance on snow and ice and wet grip performance while maintaining wear resistance. The present invention relates to a tire rubber composition.

  Conventionally, spike tires have been used for running on snow and ice roads, and chains have been attached to tires, but in order to deal with environmental problems such as dust problems, studless tires have been used as alternative snow and ice road running tires. Developed (Patent Document 1). Studless tires are more uneven on the road surface on snow than ordinary road surfaces, and are devised in terms of material and design. For example, rubber compositions containing a diene rubber excellent in low temperature characteristics and a large amount of a softening material have been developed in order to enhance the softening effect. In order to pursue low temperature characteristics, diene rubber is often blended with high cis butadiene rubber (butadiene rubber having a high cis 1,4 content).

  In general, in order to improve the performance on snow and ice, means for increasing the amount of butadiene rubber have been taken. However, if the amount of butadiene rubber is increased too much, the mobility in the rubber becomes too high and blooming of various chemicals occurs. Therefore, it is generally said that the limit of butadiene rubber is about 70 phr (per hundred rubber). Further, as the amount of butadiene rubber increases, the ratio of natural rubber decreases, so that there is a tendency that the required rubber toughness is insufficient and the wear resistance performance deteriorates. Furthermore, since the normally used high cis butadiene rubber crystallizes at a low temperature around -20 ° C., it deteriorates the viscoelastic properties of the rubber near the low temperature and inhibits the improvement of the performance on snow and ice.

  In order to cope with the above problem, there is a method of blending low cis butadiene rubber (butadiene rubber having a low cis 1,4 content). Certainly, low cis butadiene rubber has lower crystallinity compared to high cis butadiene rubber, so it can inhibit low temperature crystallization of butadiene rubber, but it increases Tg of rubber composition. As a result, there is a problem that the wear resistance performance is deteriorated.

  Furthermore, studless tires have the disadvantage that they are slippery on general road surfaces, especially when the surface is wet.

JP 2012-136581 A

  The present invention aims to solve the above-described problems. Specifically, the rubber composition for studless tires exhibits excellent characteristics in terms of snow and ice performance and wet grip performance while maintaining wear resistance. And a studless tire using the rubber composition.

  As a result of intensive studies, the present inventor has found that the above-mentioned problems can be solved by blending a predetermined amount of silica and an aromatic vinyl compound oligomer in a predetermined diene rubber component. Completed the invention.

That is, the present invention
For 100 parts by mass of a diene rubber component comprising 20% by mass or more of natural rubber and 30% by mass or more of butadiene rubber having a cis 1,4 content of 90% or more,
10 to 80 parts by mass of silica, and
A rubber composition for studless tires comprising 1 to 5 parts by mass of an aromatic vinyl compound oligomer,
The present invention relates to a rubber composition for a studless tire in which the low-temperature crystallization-derived peak for the butadiene rubber has disappeared.

  In the studless tire rubber composition, the aromatic vinyl compound oligomer preferably has a weight average molecular weight of 300 to 10,000.

  In the rubber composition for a studless tire, the aromatic vinyl compound includes styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, and 2,4,6- One or more selected from the group consisting of trimethylstyrene are preferred.

  The present invention also relates to a studless tire using the studless tire rubber composition in a tread.

  According to the present invention, a rubber composition for a studless tire, in particular, a rubber composition for a tread of a studless tire, and the rubber exhibiting excellent characteristics in snow and ice performance and wet grip performance while maintaining wear resistance. A studless tire using the composition can be provided.

  Hereafter, each element which comprises this invention is demonstrated.

<Diene rubber component>
The diene rubber component according to the present invention comprises 30% by mass or more of butadiene rubber having a natural rubber content of 20% by mass or more and a cis 1,4 content of 90% or more. Here, the total amount of the natural rubber and the butadiene rubber is 50% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, and most preferably 100% by mass. The greater the total of natural rubber and butadiene rubber, the better the low-temperature characteristics and the necessary performance on snow and ice.

  The content of natural rubber in the diene rubber component is preferably 30% by mass or more, more preferably 40% by mass or more. On the other hand, the content of butadiene rubber having a cis 1,4 content of 90% or more in the diene rubber component is preferably 40% by mass or more, more preferably 50% by mass or more. The cis 1,4 content in the butadiene rubber is preferably 93% or more, more preferably 96% or more. When the cis 1,4 content is less than 90%, the grip properties of the snow and ice road surface tend to decrease and the wear resistance tends to decrease. Here, the cis 1,4-content is a value measured by carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR).

  As the other rubber component contained as the diene rubber component, any ordinary diene rubber can be used, but preferably modified natural rubber, isoprene rubber, low cis 1,4 butadiene rubber, styrene butadiene. Examples thereof include rubber, acrylonitrile butadiene rubber, chloroprene rubber and butyl rubber. These rubbers may be used alone or in combination of two or more.

<Aromatic vinyl compound oligomer>
The weight average molecular weight (Mw) of the aromatic vinyl compound oligomer according to the present invention is in the range of 300 to 10,000, and the lower limit is preferably 350 or more. If Mw is less than 300, the grip on the snow and ice road surface tends to be insufficient. On the other hand, the upper limit is 8000 or less. When Mw exceeds 10,000, the grip performance on the snow and ice road surface tends to decrease.

  The content of the aromatic vinyl compound oligomer is 1 to 5 parts by mass with respect to 100 parts by mass of the diene rubber component. If it is less than 1 part by mass, the low-temperature crystallization of butadiene tends to be inhibited, whereas if it exceeds 5 parts by mass, the wear resistance tends to deteriorate. The lower limit of the content is preferably 1.5 parts by mass, more preferably 2 parts by mass. On the other hand, the upper limit of the content is preferably 4.5 parts by mass, more preferably 4 parts by mass.

  Examples of the monomer component of the aromatic vinyl compound oligomer include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. And aromatic vinyl compound monomers. Of these, styrene or α-methylstyrene is preferable from the viewpoint of economy, easy processing, and excellent grip characteristics.

  The aromatic vinyl compound oligomer used in the present invention is a (co) polymer obtained by homopolymerization or copolymerization of one or more aromatic vinyl compound monomers, and is a monomer other than the aromatic vinyl compound monomer. Contains no ingredients.

<Silica>
In the present invention, as the silica, general-purpose ones can be preferably used. Specifically, for example, dry method white carbon used as a reinforcing material, wet method white carbon, colloidal silica and the like can be mentioned. Wet method white carbon mainly composed of hydrous silicic acid is preferred. The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably in the range of 40 to 250 m ² / g, more preferably 60 to 220 m ² / g. When N ₂ SA is less than 40 m ² / g, the reinforcing effect is not sufficient, and the wear resistance of the tire cannot be improved efficiently. On the other hand, when N ₂ SA exceeds 250 m ² / g, the dispersibility of silica tends to decrease and the heat generation of the rubber composition tends to increase. The nitrogen adsorption specific surface area (N ₂ SA) is measured by the BET method according to ASTM D3037-81.

  The content of silica according to the present invention is 10 to 80 parts by mass with respect to 100 parts by mass of the diene rubber component. If the content is less than 10 parts by mass, the performance on snow and ice tends to be insufficient. On the other hand, if it exceeds 80 parts by mass, the workability and workability deteriorate, or the low-temperature characteristics tend to decrease due to an increase in filler content. is there. The lower limit of the content is preferably 15 parts by mass or more, and more preferably 20 parts by mass or more. On the other hand, the lower limit of the content is preferably 70 parts by mass or less, more preferably 60 parts by mass or less.

  In the present invention, a silane coupling agent can be blended in addition to silica. As the silane coupling agent, any of those usually used in this field can be used. Specifically, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) Tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide Bis (3-triethoxysilylpropyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N -Dimethylthio Rubamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyltetra Sulfide systems such as sulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltri Mercapto series such as ethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyltriethoxysilane, vinyl Vinyl bases such as rutrimethoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxy Amino systems such as silane; glycidoxy systems such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane Nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltri And the like, such as chloro-system, such as Tokishishiran. Among these, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide and the like are preferable.

  When mix | blending a silane coupling agent, it is preferable that the compounding quantity is 5 mass parts or more with respect to 100 mass parts of silica. When the content of the silane coupling agent is less than 5 parts by mass, effects such as improvement in dispersibility tend not to be obtained sufficiently. Moreover, it is preferable that it is 20 mass parts or less, and, as for content of a silane coupling agent, it is more preferable that it is 15 mass parts or less. When the content of the silane coupling agent exceeds 20 parts by mass, a sufficient coupling effect cannot be obtained and the reinforcing property tends to be lowered.

  A silane coupling agent may be used individually by 1 type, and may use 2 or more types together.

<Other reinforcing fillers>
The rubber composition for tires of the present invention can contain a reinforcing filler other than silica. The reinforcing filler is not particularly limited as long as it is conventionally used in rubber compositions for tires, such as carbon black, calcium carbonate, magnesium carbonate, clay, alumina, talc, etc., but mainly carbon black is preferred. These reinforcing fillers may be used alone or in combination of two or more.

  The type of carbon black is not particularly limited, and any of those commonly used in this field can be used, but preferably, for example, those of GPF, HAF, ISAF, SAF grade, etc. It is done. Among these, HAF, ISAF, and SAF grades are more preferable from the viewpoint of improving wear resistance.

The CTAB (Cetyl Tri-methyl Ammonium Brimide) adsorption specific surface area of carbon black is preferably 70 m ² / g or more, and more preferably 80 m ² / g or more. If it is less than 70 m < ² > / g, there exists a tendency for a reinforcement property to fall. Further, CTAB adsorption specific surface area is preferably at most 200m ² / g, and more preferably 150 meters ² / g or less. When the CTAB adsorption specific surface area exceeds 200 m ² / g, kneading workability tends to deteriorate. The CTAB adsorption specific surface area of carbon black is measured according to JIS K 6217-3: 2001.

  When carbon black is added, the content of carbon black is preferably 1 part by mass or more and more preferably 5 parts by mass or more with respect to 100 parts by mass of the diene rubber. When the carbon black content is less than 1 part by mass, the weather resistance tends to deteriorate. The content of carbon black is preferably 70 parts by mass or less and more preferably 50 parts by mass or less with respect to 100 parts by mass of the diene rubber. When the content of carbon black exceeds 70 parts by mass, the performance on snow and ice tends to deteriorate.

<Other ingredients>
In addition to the above, the rubber composition of the present invention includes various additives usually used in this field, such as a vulcanizing agent, a vulcanization accelerator, a softening agent (oil), a plasticizer, an antiaging agent, an oxidation agent. Zinc, stearic acid, an antioxidant, an ozone degradation inhibitor and the like can be appropriately added within a range that does not impair the object of the present invention.

  The rubber composition of the present invention thus obtained can be suitably used as a rubber composition for studless tires, particularly as a rubber composition for tire treads.

  The rubber composition of the present invention is excellent in low-temperature crystallization of butadiene rubber, in particular, -15 to -25 ° C, so that the viscoelastic properties at such low temperatures are not deteriorated. It shows the performance on snow and ice. The presence or absence of such low-temperature crystallization can be easily determined by measuring a viscoelastic temperature dispersion curve of the vulcanized rubber composition. For example, using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), tan δ is measured under the condition of dynamic strain of 0.5%, and from the tan δ curve thus obtained, −15 to −25 ° C. (− What is necessary is just to discriminate | determine the presence or absence of the low temperature crystallization origin peak of butadiene rubber in 20 degreeC vicinity.

<Tire>
The rubber composition of the present invention is used for manufacturing a tire and can be made into a tire by a usual method. That is, if necessary, a mixture containing the above components is kneaded using a kneader such as a roll or an internal mixer (usually in the first stage, other raw materials excluding sulfur and vulcanization accelerators). Are added to the kneaded product, and further kneaded with sulfur and a vulcanization accelerator), and extruded according to the shape of each member of the tire at an unvulcanized stage. An unvulcanized tire is formed by molding by an ordinary method. A tire can be obtained by heating and pressurizing the unvulcanized tire in a vulcanizer, and ordinary air can be introduced into the tire as an injection gas to obtain a pneumatic tire. In addition to normal air, inert gas such as air with adjusted partial pressure of oxygen, nitrogen, argon, or helium can be used as the injection gas.

  The present invention will be described based on examples, but the present invention is not limited to the examples.

Below, the various chemical | medical agents used for manufacture of the rubber composition of an Example and a comparative example are shown collectively. Various chemicals were purified according to conventional methods as needed.
<Various chemicals used in the production of rubber composition>
Natural rubber (NR): RSS # 3
Butadiene rubber 1 (BR1): BR1220 manufactured by Nippon Zeon Co., Ltd. (cis 1,4 content: 96%)
Butadiene rubber 2 (BR2): NF35 manufactured by Asahi Kasei Corporation (cis 1,4 content: 32%)
Carbon black (CB): Seast N220 manufactured by Mitsubishi Chemical Corporation (CTAB: 111 m ² / g)
Silica: Ultrasil VN3 manufactured by Evonik Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent (coupling agent): Si75 manufactured by Evonik Degussa
Aromatic vinyl compound oligomer: Styrene oligomer oil synthesized as follows: Process X-140 manufactured by Japan Energy Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid “Kun” manufactured by NOF Corporation
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. (1): Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator (2): Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(Synthesis of aromatic vinyl compound oligomer (styrene oligomer))
In a 50 ml container sufficiently purged with nitrogen, 15 ml of toluene, 5 ml of styrene, and 800 mg of n-butyllithium were added, polymerized at 0 ° C. for 1 hour, and then the reaction was stopped by adding a methanol-hydrochloric acid (2%) solution. A styrene oligomer was obtained.

  For the styrene oligomer thus obtained, the weight average molecular weight (Mw) was measured using a differential refractometer as a detector using a GPC-8000 series device manufactured by Tosoh Corporation, and calibrated with standard polystyrene. there were. The melting point was 19 ° C. as measured by DSC.

Example 1
(Preparation of unvulcanized rubber composition)
According to the formulation shown in Table 1, the rubber chemicals (excluding sulfur and vulcanization accelerator) were kneaded at 150 ° C. for 5 minutes with a Banbury mixer to obtain a kneaded product. Sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at about 80 ° C. using an open roll to obtain an unvulcanized rubber composition.

(Production of studless tires)
The unvulcanized rubber composition was molded into a tread shape, bonded to another tire member, and press vulcanized at 170 ° C. for 15 minutes to obtain a studless tire.

Examples 2-6 and Comparative Examples 1-9
The corresponding raw material compounds were treated in the same manner as in Example 1 in accordance with the formulation shown in Table 1, and the corresponding unvulcanized rubber composition and studless tire were obtained, respectively.

<Evaluation>
According to the following method, the glass transition temperature (Tg), the performance on snow and ice, the wet grip performance, and the wear resistance were evaluated for each of the examples and comparative examples. The results are shown in Table 1.

(Glass transition temperature (Tg))
A rubber sample was sampled from the studless tires of the examples and comparative examples, and the temperature was −100 to 100 ° C. and the dynamic strain was 0.5% using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho). Then, tan δ was measured, and the peak value of the tan δ curve thus obtained was defined as Tg. Further, from the same curve, the presence or absence of a peak derived from low-temperature crystallization of butadiene rubber at −15 to −25 ° C. (around −20 ° C.) was determined.

(Abrasion resistance)
Each studless tire of tire size 195 / 65R15 is mounted on a domestic FF vehicle, the groove depth of the tire tread part after mileage of 8000 km is measured, and the mileage when the tire groove depth is reduced by 1 mm is calculated as follows. The wear resistance index was evaluated by the following formula. In addition, abrasion resistance is so favorable that an index | exponent is large.
Abrasion resistance index = (mileage when tire grooves in each example and comparative example are reduced by 1 mm) /
(Travel distance when the tire groove of Comparative Example 1 is reduced by 1 mm) × 100

(Performance on snow and ice)
Using the studless tires of the examples and comparative examples, the actual vehicle performance was evaluated on snow and ice under the following conditions. The studless tire was manufactured as a 195 / 65R15 size DS-2 pattern studless tire for passenger cars and was mounted on a domestic 2000cc FR car.
(1) On-ice performance test location: Hokkaido Nayoro Test Course Temperature: -6 to -1 ° C
Braking stop distance: The distance required to stop by stepping on the lock brake at 30 km / h was measured.
(2) Performance test on snow Location: Same as above Temperature: -10 to -2 ° C
Braking stop distance: Same as above

From the obtained braking stop distance, a performance index on snow (performance index on snow) and a performance index on ice (performance index on ice) were respectively calculated by the following formulas, and the average value was defined as the performance index on snow and ice. The larger the index, the better the performance on snow and ice.
Performance index on snow = (braking stop distance of Comparative Example 1) ÷
(Brake stop distance of each example / comparative example) × 100
Performance index on ice = (braking stop distance of Comparative Example 1) /
(Brake stop distance of each example / comparative example) × 100

(Wet grip performance)
Using the studless tires mounted on the actual vehicle as described above, the actual vehicle was run on the wet asphalt road test course, and the grip performance (grip feeling, brake performance, traction performance) at this time was evaluated. The feeling evaluation is based on the criteria that the comparative example 1 is 100, the test driver can judge that the performance is clearly improved, 120, and the good level that has never been seen so far is evaluated as 140. , Graded.

  In the embodiment of the present invention, the wear resistance is maintained within a predetermined range (wear resistance index: 91 to 99), and excellent performance on snow and ice (performance index on snow and ice: 110 to 125) and wet grip performance. (100 to 107). On the other hand, in the comparative example, the wear resistance is extremely lowered (Comparative Examples 2 to 4), the performance on snow and ice is not excellent (Comparative Examples 1 and 3 to 9), or the wet grip performance is not excellent (Comparison) Examples 6-9).

  According to the present invention, by blending a predetermined amount of silica and an aromatic vinyl compound oligomer with a predetermined diene rubber component, excellent properties in snow and ice performance and wet grip performance while maintaining wear resistance. It is possible to provide a rubber composition for a treadless tire tread and a studless tire using the rubber composition.

Claims (4)

For 100 parts by mass of a diene rubber component comprising 20% by mass or more of natural rubber and 30% by mass or more of butadiene rubber having a cis 1,4 content of 90% or more,
Silica 30-60 parts by weight, and,
A rubber composition for studless tires comprising 1 to 5 parts by mass of an aromatic vinyl compound oligomer,
A low-temperature crystallization-derived peak for the butadiene rubber has disappeared, a rubber composition for studless tires ,
A rubber composition for studless tires, wherein the disappearance of the low-temperature crystallization-derived peak is determined from a tan δ curve at -15 to -25 ° C. The rubber composition for studless tires according to claim 1, wherein the aromatic vinyl compound oligomer has a weight average molecular weight of 300 to 10,000. The aromatic vinyl compound is selected from the group consisting of styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene and 2,4,6-trimethylstyrene. The rubber composition for a studless tire according to claim 1 or 2, wherein the rubber composition is one type or two or more types. The studless tire which used the rubber composition for studless tires of any one of Claims 1-3 for a tread.