JP2017088818A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome facts that many means for enhancing on-ice performance of a tire have been proposed, for example a means that a water film generated on a surface of ice by blending a hard debris or a hollow polymer to a rubber and thereby forming micro convexoconcave on a rubber surface and on-ice friction is enhanced is known, however there are problems that cavity is formed in a tread rubber by blending the hollow polymer, rubber strength is reduced and wet performance is reduced, and therefor enhancing on-ice performance and wet performance are enhanced at the same time is difficult issue in this field.SOLUTION: The above described problem is solved by a rubber composition containing 100 pts.mass of a diene rubber having glass transition temperature (Tg) of -60°C or less and 0.1 to 20 pts.mass of a polymer containing a fluorine-containing acrylic monomer unit.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same, and more particularly to a rubber composition capable of improving both on-ice performance and wet performance and a pneumatic tire using the same.

Conventionally, many means have been proposed in order to improve the performance on ice of the tire (braking performance on ice). For example, there is known a method of improving friction on ice by removing a water film generated on the surface of ice by blending hard foreign matter or a hollow polymer with rubber and thereby forming micro unevenness on the rubber surface.
However, when a hollow polymer is blended, cavities are formed in the tread rubber, the rubber strength is lowered, and the braking performance (wet performance) on a wet road surface is lowered.
As described above, it has been difficult in the industry to simultaneously improve the performance on ice and the wet performance.

  Patent Document 1 listed below discloses a technique in which a surface layer of a tire tread contains polytetrafluoroethylene. However, this technology cannot improve on-ice performance and wet performance at the same time.

JP 2006-240583 A

  Accordingly, an object of the present invention is to provide a rubber composition capable of improving both on-ice performance and wet performance, and a pneumatic tire using the same.

As a result of intensive studies, the present inventors can solve the above problems by blending a diene rubber having a specific glass transition temperature range with a polymer containing a fluorine-containing acrylic monomer unit in a specific amount. The present invention was completed.
That is, the present invention is as follows.

1. A rubber composition comprising 0.1 to 20 parts by mass of a polymer containing a fluorine-containing acrylic monomer unit with respect to 100 parts by mass of a diene rubber having a glass transition temperature (Tg) of −60 ° C. or less.
2. 2. The rubber composition as described in 1 above, further comprising 1 to 10 parts by mass of thermally expandable microcapsules with respect to 100 parts by mass of the diene rubber.
3. A pneumatic tire using the rubber composition according to 1 or 2 as a tread.

  According to the present invention, since a specific amount of a polymer containing a fluorine-containing acrylic monomer unit is blended with a diene rubber having a specific glass transition temperature range, the rubber composition capable of improving both on-ice performance and wet performance. And a pneumatic tire using the same can be provided.

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

(Diene rubber)
The diene rubber used in the present invention is not particularly limited, and any diene rubber that can be blended in the rubber composition can be used. For example, natural rubber (NR), isoprene rubber (IR), Examples thereof include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and ethylene-propylene-diene terpolymer (EPDM). These may be used alone or in combination of two or more. The molecular weight and microstructure are not particularly limited, and may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized.
Of these, NR and BR are preferable.
If NBR is used, the effects of the present invention may not be fully exhibited.

  The diene rubber used in the present invention needs to have a glass transition temperature (Tg) of −60 ° C. or lower. When Tg exceeds −60 ° C., both on-ice performance and wet performance are degraded. When a plurality of diene rubbers are used, Tg is calculated as an average Tg. The average Tg is an average value of the glass transition temperature, and can be calculated as an average value from the glass transition temperature of each diene rubber and the blending ratio of each diene rubber.

(Polymer containing fluorine-containing acrylic monomer unit)
In the polymer containing a fluorine-containing acrylic monomer unit used in the present invention (hereinafter sometimes referred to as a specific polymer), the fluorine-containing acrylic monomer unit is, for example, a part or all of hydrogen atoms of an alkyl group. Fluoro (meth) acrylate having a fluoroalkyl group having 2 to 20 carbon atoms in which is substituted with a fluorine atom. In this invention, the fluoro (meth) acrylate which has a C2-C20 fluoroalkyl group by which all the hydrogen atoms of the alkyl group were substituted by the fluorine atom is preferable.
In addition, the specific polymer used in the present invention may be a copolymer obtained by copolymerizing the fluorine-containing acrylic monomer unit and other known comonomer units. The comonomer unit is not particularly limited, and a known comonomer can be appropriately selected. In the specific polymer, the fluorine-containing acrylic monomer unit preferably constitutes 20% by mass or more.
Moreover, 5-80 mass% is preferable and, as for the fluorine content in the specific polymer used by this invention, 10-50 mass% is more preferable.
Moreover, the weight average molecular weight (polystyrene conversion value by GPC method) of the specific polymer used in the present invention is preferably 100 to 100,000, and more preferably 1,000 to 50,000.

  Since the acrylate unit contained in the specific polymer has high polarity, it tends to be unevenly distributed on the tire surface. Thereby, high water repellency based on a fluoroalkyl group can be imparted to the tire surface. In order to improve the performance on ice, it is important to eliminate the water present on the ice. However, in the present invention, since the tire has high water repellency as described above, the water present between the tire and the ice Can be eliminated well, and the performance on ice is improved. Moreover, the frictional force of the tire against the wet road surface is increased by the action of eliminating such water. Thus, according to the present invention, the performance on ice and the wet performance can be improved at the same time.

(Thermal expansion microcapsule)
In the present invention, thermally expandable microcapsules can be blended for the purpose of further enhancing the performance on ice and the wet performance.
The thermally expandable microcapsule has a configuration in which a thermally expandable substance is encapsulated in a shell formed of a thermoplastic resin. The shell material of the thermally expandable microcapsule can be formed of a nitrile polymer.
In addition, the thermally expandable substance encapsulated in the shell of the microcapsule has a property of being vaporized or expanded by heat, and examples thereof include at least one selected from the group consisting of hydrocarbons such as isoalkane and normal alkane. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, 2,2,4-trimethylpentane, and examples of normal alkanes include n-butane, n-propane, n-hexane, Examples thereof include n-heptane and n-octane. These hydrocarbons may be used alone or in combination. As a preferable form of the thermally expandable substance, a substance obtained by dissolving a hydrocarbon which is gaseous at normal temperature in a hydrocarbon which is liquid at normal temperature is preferable. By using such a mixture of hydrocarbons, a sufficient expansion force can be obtained from the low temperature region to the high temperature region in the vulcanization molding temperature range (150 ° C. to 190 ° C.) of the unvulcanized tire.
Examples of such thermally expandable microcapsules include trade names “EXPANCEL 091DU-80” and “EXPANEL 092DU-120” manufactured by EXPANSEL, Sweden, or trade names “Matsumoto Micros Co., Ltd. “Fair F-85D” or “Matsumoto Microsphere F-100D” or the like can be used.

(Rubber composition ratio)
The rubber composition of the present invention includes 0.1 to 20 parts by mass of a specific polymer with respect to 100 parts by mass of the diene rubber.
When the blending amount of the specific polymer is less than 0.1 parts by mass, the blending amount is too small to achieve the effects of the present invention. Conversely, when it exceeds 20 mass parts, wet performance will deteriorate.
Furthermore, the compounding quantity of a preferable specific polymer is 1-10 mass parts with respect to 100 mass parts of diene rubbers.

  Moreover, in the rubber composition of this invention, when mix | blending a thermally expansible microcapsule, the compounding quantity has preferable 1-10 mass parts with respect to 100 mass parts of diene rubbers.

(Other ingredients)
In the rubber composition of the present invention, in addition to the above-described components, a vulcanization or crosslinking agent; a vulcanization or crosslinking accelerator; various fillers such as zinc oxide, carbon black, silica, clay, talc, calcium carbonate; Anti-aging agent: Various additives generally blended in rubber compositions such as plasticizers can be blended, and these additives are kneaded by a general method to form a composition and vulcanized or crosslinked. Can be used for 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 of the present invention is suitable for producing a pneumatic tire in accordance with a conventional method for producing a pneumatic tire, and is preferably applied to a tread, particularly a cap tread. The pneumatic tire of the present invention can be a studless tire.

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

Standard Example, Examples 1 to 4 and Comparative Examples 1 to 6
Preparation of Sample In the formulation (parts by mass) shown in Table 1 below, the components other than the vulcanization accelerator and sulfur were kneaded with a 1.7 liter closed Banbury mixer for 5 minutes, and then the vulcanization accelerator and sulfur were added. Further, kneading was performed to obtain a rubber composition. Next, the obtained rubber composition was press vulcanized at 160 ° C. for 20 minutes in a predetermined mold to obtain a vulcanized rubber test piece, and the physical properties of the vulcanized rubber test piece were measured by the following test method.

Performance on ice: Pneumatic tires of tire size 215 / 60R16 with various vulcanized rubber test pieces incorporated in the tread are assembled into a 16 × 7J rim, filled with air pressure (220 [kPa]), and tested vehicle (domestic 2 liters) It was mounted on a sedan FF vehicle. Subsequently, the braking distance from the initial speed of 40 [km / h] to the complete stop was measured by the test vehicle on the test course which is an ice board road. The results are shown as an index with Comparative Example 1 as 100. A larger index means better performance on ice.
Wet performance: In the above performance test on ice, instead of the test course, which is a icy road, the braking distance from the initial speed of 40 [km / h] to a complete stop by a test vehicle on a flooded asphalt surface Was measured. The results are shown as an index with Comparative Example 1 as 100. A larger index means better wet performance.
The results are shown in Table 1.

* 1: NR (RSS No. 3, Tg = −55 ° C.)
* 2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd., Tg = -105 ° C)
* 3: SBR (Nipol 1723 manufactured by Nippon Zeon Co., Ltd., oil extended amount = 37.5 parts by mass with respect to 100 parts by mass of SBR, Tg = −55 ° C.)
* 4: Silica (Zeosil 1165MP manufactured by Solvay)
* 5: Carbon black (Cabot Japan Show Black N339)
* 6: Silane coupling agent (Si69 manufactured by Evonik Degussa)
* 7: Process oil (Extract No. 4 S, Showa Shell Sekiyu KK)
* 8: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 9: Stearic acid (Stearic acid YR manufactured by NOF Corporation)
* 10: Anti-aging agent (Santoflex 6PPD manufactured by Solutia Europe)
* 11: Wax (Sannok, Ouchi Shinsei Chemical Co., Ltd.)
* 12: Specific polymer (specific polymer synthesized as follows)
* 13: Polytetrafluoroethylene PTFE (LM-720AP manufactured by Asahi Glass Co., Ltd.)
* 14: Fluorosilicone (LS63U manufactured by Toray Dow Corning)
* 15: Thermally expandable microcapsules (Matsumoto Microsphere F-100D manufactured by Matsumoto Yushi Seiyaku Co., Ltd.)
* 16: Sulfur (Karuizawa Refinery refined sulfur)
* 17: Vulcanization accelerator 1 (Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 18: Vulcanization accelerator 2 (Perkacit DPG manufactured by Flexsys)

Synthesis of specific polymer Monomer (perfluoroalkylethyl acrylate (FA) [C _n F _{2n + 1} CH ₂ CH ₂ COOCH═CH ₂ (n = 6, 8, 10, 12, 14 (n average 9)) mixture of compounds ]] = 70 g, lauryl acrylate (LA) = 25 g, N-methylolacrylamide (N-MAM) = 2.5 g, 3-chloro-2-hydroxypropyl methacrylate (CHPMA) = 2.5 g, emulsifier (di-cured tallow alkyl) Dimethylammonium chloride (cationic surfactant A) = 2 g, lauryltrimethylammonium chloride (cationic surfactant B) = 2 g, polyoxyethylene (8) distearate (nonionic surfactant A, HLB value 8.5) = 7 g), solvent (tripropylene glycol (TPG) = 30 ), A chain transfer agent (dodecyl mercaptan = 0.5 g), and water (191 g) were added, stirred with a homomixer, and emulsified with an ultrasonic emulsifier.Substituted with nitrogen, the initiator (2,2 ′ -Azobis (2-amidinopropane) dihydrochloride = 0.6 g) was added and polymerized for 4 hours at 60 ° C. The disappearance of the monomer was confirmed by GC, and the solid content of the resulting composition (130 ° C., 2 hours) The evaporation residue was 33% .In this way, a specific polymer was synthesized.

As is clear from the results in Table 1, the rubber compositions obtained in Examples 1 to 4 are polymers containing fluorine-containing acrylic monomer units with respect to the diene rubber having a specific glass transition temperature range. Therefore, the performance on ice and the wet performance are both improved as compared with the conventional representative standard example. In particular, Examples 3 and 4 blended with thermally expandable microcapsules further improved on-ice performance and wet performance.
On the other hand, since the compounding quantity of the specific polymer was less than the lower limit prescribed | regulated by this invention in the comparative example 1, neither on-ice performance nor wet performance was improved.
In Comparative Example 2, since the blending amount of the specific polymer exceeds the upper limit defined in the present invention, the wet performance deteriorated.
Since the comparative example 3 is an example which mix | blends a thermally expansible microcapsule and does not mix | blend a specific polymer, wet performance deteriorated.
In Comparative Example 4, since the average Tg of the diene rubber exceeded the upper limit defined in the present invention, the on-ice performance and the wet performance were both deteriorated.
Comparative Example 5 was an example in which PTFE was blended in place of the specific polymer, and both on-ice performance and wet performance deteriorated.
Comparative Example 6 is an example in which fluorosilicone was blended in place of the specific polymer, and both on-ice performance and wet performance deteriorated.

Claims (3)

  A rubber composition comprising 0.1 to 20 parts by mass of a polymer containing a fluorine-containing acrylic monomer unit with respect to 100 parts by mass of a diene rubber having a glass transition temperature (Tg) of −60 ° C. or less.   The rubber composition according to claim 1, further comprising 1 to 10 parts by mass of thermally expandable microcapsules per 100 parts by mass of the diene rubber.   A pneumatic tire using the rubber composition according to claim 1 for a tread.