JP2001019806A - Tire tread rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition which can give tire treads reduced in fuel consumption and improved in abrasion resistance and processabitity by compounding a rubber component with carbon black and an organopolysiloxane. SOLUTION: This composition is prepared by compounding 100 pts.wt. rubber component with 40-150 pts.wt. carbon black, 0.5-8 pts.wt. organopolysiloxane represented by the formula: (SiO2)aX22(a+1), and optionally, 1-100 pts.wt. inorganic filler. In the formula, X is O1/2[(CH3)2SiO]bR1 or O1/2R1; at least one X is O1/2[(CH3)2SiO]bR1; R1 is H or a 5C or lower monovalent hydrocarbon group; b is 1-100; and a is 1-20. From the viewpoint of the extrudability of the composition and the dimensional stability of the extrudate, the molecular weight of the organopolysiloxane is desirably 200-10,000. The inorganic filler used is desirably, for example, silica having a CTAB absorption specific surface area of 100-200 m2/g and a BET nitrogen absorption specific surface area of 100-250 m2/g or clay having a mean particle diameter of 0.1-10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a tire tread rubber composition. More specifically, the present invention relates to a tire tread rubber composition having good fuel economy, abrasion resistance and workability.

[0002]

2. Description of the Related Art With the recent increase in demand for tire performance, inorganic fillers such as silica are blended from the viewpoint of improving contradictory performances such as low fuel consumption performance and wet grip performance. Tire tread has increased.

[0003] However, the inorganic filler has a disadvantage that the reinforcing effect is smaller than that of carbon black and the abrasion resistance is lower than that of carbon black.

[0004] Recently, the addition of silica has been increasing, but in order to increase the reinforcing effect as a filler,
For example, bis (3- (triethoxysilyl) propyl)
Tetrasulfide (Si69 (trade name) manufactured by Degussa)
It is becoming common to add a so-called sulfur-containing silane coupling agent that chemically bonds the filler and the polymer. However, in terms of improving abrasion resistance, conventional carbon It does not surpass black, and there is still much room for improvement.

On the other hand, JP-A-9-19464, JP-A-9-111044, and JP-A-10-25364
Japanese Patent Application Laid-Open No. 10-152581 discloses that addition of an organopolysiloxane to a rubber composition improves wear resistance.
Sufficient effects have not been obtained.

[0006] WO 96/29364 discloses a rubber composition containing silica and a specific organopolysiloxane as essential components, and has excellent rebound resilience and a tensile strength equal to or higher than that of carbon black. It describes that it exhibits strength and abrasion resistance, but it is not yet sufficient in terms of abrasion resistance, and there is room for improvement.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the other physical properties can be improved by adding an organopolysiloxane having a specific alkoxysilyl group to a rubber composition. The wear resistance is improved without lowering.

That is, the present invention provides a rubber component having a weight of 100%.
Parts by weight of 40 to 150 parts by weight of carbon black
And general formula (1): (SiO_Two)_aX_{2 (a + 1)} (1) (where X is O_1/2[(CH_Three)_TwoSiO]_bR¹Or O
_1/2R¹And each X may be the same or different,
And one or more of X is O_1/2[(CH_Three)_TwoSiO]_bR ¹so
Must be, R¹Is a hydrogen atom or carbon number 5 or less
B is an integer of 1 to 100, and a is a monovalent hydrocarbon group of
Is an integer of 1 to 20).
Tire tread containing 0.5 to 8 parts by weight of xan
Rubber composition (Claim 1) and 100 parts of the rubber component
1-100 parts by weight of another inorganic filler based on parts by weight
2. The tire tread rubber composition according to claim 1, wherein the tire tread rubber composition is mixed.
(Claim 2).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Raw rubber used as a rubber component in the present invention includes natural rubber (NR) and / or synthetic rubber used in various rubber compositions such as polyisoprene rubber (IR), Styrene butadiene rubber (SBR), various polybutadiene rubbers (BR), acrylonitrile-butadiene copolymer rubber (NBR),
Butyl rubber (IIR) and the like can be mentioned. These natural rubbers and / or synthetic diene rubbers may be used alone or in combination of two or more, for example, as a blend.

The carbon black used in the present invention is:
What is necessary is just to be used for general rubber compounding. Examples of the carbon black include furnace black, acetylene black, thermal black, channel black, graphite, and the like.

The carbon black is a rubber component 1
The amount is 40 to 150 parts by weight, preferably 40 to 100 parts by weight, per 100 parts by weight. When the compounding amount is less than 40 parts by weight, the reinforcing property of carbon black is not sufficient, and it is not practical as a rubber composition for a tire tread, and when it exceeds 150 parts by weight, the composition becomes too hard,
Practicality is lost as a rubber composition for tire treads.

The rubber composition of the present invention has a general formula (1): (SiO_Two)_aX_{2 (a + 1)} (1) (where X is O_1/2[(CH_Three)_TwoSiO]_bR¹Or O
_1/2R¹And each X may be the same or different,
And one or more of X is O_1/2[(CH_Three)_TwoSiO]_bR ¹so
Must be, R¹Is a hydrogen atom or carbon number 5 or less
B is an integer of 1 to 100, and a is a monovalent hydrocarbon group of
Is an integer of 1 to 20).
Loxane is blended. Before carbon black compounded rubber
The specific alkoxysilyl group or silanol group (R¹
Is a hydrogen atom).
Low fuel consumption, abrasion resistance and workability by compounding
A rubber composition having a good value can be obtained.

A in the general formula (1) defines the length of the main chain of the organopolysiloxane. If a exceeds 20, the effect is not changed but the productivity of the compound is deteriorated. Preferred values of a are 1 to 15, more preferably 1 to 10.

X in the general formula (1) is bonded to the main chain of the organopolysiloxane so that the organopolysiloxane has a functional group (alkoxysilyl group or silanol group). X is O _1/2 [(CH ₃ ) ₂ SiO] _b R ¹
Or O _1/2 R ¹ , wherein X is O _1/2 [(CH ₃ ) ₂ Si
When O] _b R ¹ is bonded to the terminal of the main chain of the organopolysiloxane, the main chain is substantially lengthened and

[0015]

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When a group is present and X is O _1/2 R ¹ , there is a —OR ¹ group bonded to the silicon atom. However, if O _1/2 where _{[(CH 3) 2 SiO]} b R 1 with O _1/2 R ¹ at the ends of the main chain of the organopolysiloxane is present,
The structure is substantially the same as the case where O _1/2 R ¹ is bonded to other than the main chain terminal. X is O _1/2 [(CH ₃ ) ₂ SiO] _b R
^{In the case of 1} , in the case of bonding to a position other than the terminal of the main chain of the organopolysiloxane, the end of the side chain where the dimethylsiloxane chain is bonded to the main chain

[0017]

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Wherein X is O _1/2 [(CH ₃ ) ₂ Si
O] _b R ¹ has the same structure as that of the case where it is bonded to the terminal of the organopolysiloxane. In the case of this structure,

[0019]

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The group is preferable because it has a small steric hindrance and easily reacts, and thus easily bonds to another compound. On the other hand, when X is O _1/2 R ¹ and is bonded to other than the terminal of the main chain of the organopolysiloxane,

[0021]

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In the case of this structure, since steric hindrance is large and it is difficult to react, it is difficult to bond to other compounds.
Therefore, 50% of 2 (a + 1) Xs existing
More than 60%, especially more than 70%

[0023]

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It preferably has a group.

In the above O _1/2 [(CH ₃ ) ₂ SiO] _b R ¹ , 1 to 100 can be used as b, but the content of alkoxysilyl group and / or silanol group contained in the organopolysiloxane may be used. The ratio is preferably 1 to 50, and more preferably 1 to 20, from the viewpoint of high ratio and high reactivity.

[0026] The _{O 1/2 [(CH 3) 2} SiO] b R 1 or O _1/2 R ¹ in R ¹ is a hydrogen atom or a 1 to 5 carbon atoms
Is a monovalent hydrocarbon group. In the case of a hydrogen atom, storage stability is not necessarily good but a highly reactive silanol group is contained. In the case of a monovalent hydrocarbon group having 1 to 5 carbon atoms, storage stability is good but reactivity is high. Contains an alkoxysilyl group, which is not always good, and may be properly used as needed. Among the hydrocarbon groups having 1 to 5 carbon atoms, those having 1 to 2 carbon atoms are preferable because they have high reactivity and good storage stability.

Examples of the monovalent hydrocarbon group having 1 to 5 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group and a pentyl group, and a methyl group and an ethyl group are preferred. .

Specifically, the organopolysiloxane represented by the general formula (1) is, for example, in the general formula (1), a = 1, b = 1, and X are all O _1/2 [(CH ₃ ) ₂ S
iO] _{b When} R ¹ is all ethyl groups in R ¹ ,

[0029]

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Where a = 2, b = 2, and X are all O
_{When 1/2} [(CH ₃ ) ₂ SiO] _b R ¹ and R ¹ are all ethyl groups,

[0031]

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Where a = 3, b = 20 and X are all O
_{When 1/2} [(CH ₃ ) ₂ SiO] _b R ¹ and R ¹ are all ethyl groups,

[0033]

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## EQU1 ##

The molecular weight of the organopolysiloxane used in the present invention is from 200 to 10,000, more preferably from 2 to 10,000, in view of the extrusion processability of the composition and the dimensional stability after extrusion.
00-5000, especially 200-2000 is preferred.

Preferred specific examples of the organopolysiloxane include, besides those represented by the above structural formulas, organopolysiloxanes described in Japanese Patent Publication No. 3-17764.

The organopolysiloxane is compounded in an amount of 0.5 to 8 parts by weight, preferably 1 to 7 parts by weight, based on 100 parts by weight of the rubber component. When the amount is less than 0.5 part by weight, the effect of improving the wear resistance is not sufficient,
When the amount is more than the weight part, the effect of improving the wear resistance is smaller than the compounding amount, and the wear resistance is not improved in spite of the increase in cost, which is not desirable.

The organopolysiloxane can be produced, for example, by the method described in JP-A-58-67728.

The rubber composition of the present invention may further contain another inorganic filler. By blending the other inorganic filler in addition to the organopolysiloxane, in addition to low fuel consumption, abrasion resistance and workability, an effect of further improving grip performance is obtained, and the other inorganic filler is blended. A more excellent rubber composition can be obtained than when no rubber composition is used. In general, when other inorganic fillers are blended, the abrasion resistance of the rubber composition tends to decrease, but in the present invention, since the organopolysiloxane is blended, the abrasion resistance is supplemented, and the abrasion resistance is reduced. Good other inorganic filler-filled rubber compositions can be obtained.

Examples of the other inorganic filler include silica, clay, calcium carbonate, aluminum hydroxide, and alumina. These may be used alone or in combination of two or more. Among these, silica, aluminum hydroxide, and clay are particularly preferable because of their high grip performance.

As the silica, those generally used for compounding general-purpose rubber can be used. Also,
CTAB adsorption surface area of silica (hereinafter referred to as CTAB)
Is from 100 to 200 m ² / g, and further from 100 to 170
m ² / g, BET nitrogen adsorption specific surface area (hereinafter, referred to as BET) is 100 to 250 m ² / g, more 150-25
Those having 0 m ² / g are preferred. Examples of the silica having the above characteristics include Ultra Seal VN manufactured by Degussa.
^{3 (CTAB: 165m 2 / g} , BET: 172m 2 /
g), Nipsil VN3 (CTA manufactured by Nippon Silica Co., Ltd.)
^{B: 144m 2 / g, BET} : 210m 2 / g), Nippon Silica Co., Ltd. of Nipsil AQ (CTAB: 150m ² /
g, BET: 227 m ² / g). These may be used alone or in combination of two or more.

As the clay, for example, those having an average particle diameter of 0.1 to 10 μm, more preferably 0.1 to 8 μm are preferable.

The calcium carbonate has, for example, an average particle size of 0.1 to 10 μm, and more preferably 0.1 to 8 μm.
Are preferred.

The aluminum hydroxide has a center particle diameter of, for example, 0.1 to 10 μm, and more preferably 0.1 to 8 μm.
μm, BET is 1~10m ² / g, and even more 1~9m ² /
g are preferred.

As the alumina, for example, the center particle diameter measured by a laser diffraction method is 1 to 10 μm,
Further, the thickness is preferably 1 to 8 μm.

The compounding amount of the other inorganic filler (when two or more kinds are used in combination, the total compounding amount) is 1 to 100 parts by weight, more preferably 1 to 100 parts by weight, based on 100 parts by weight of the rubber component. It is preferably from 50 to 50 parts by weight, particularly preferably from 3 to 50 parts by weight. When the amount is less than 1 part by weight, the effect of using the other inorganic filler is hardly obtained. When the amount exceeds 100 parts by weight, the effect of improving the wear resistance tends to be lost. It should be noted that what is used and in what proportion as the other inorganic filler may be appropriately selected by those skilled in the art according to the properties to be particularly enhanced.

The rubber composition of the present invention comprises the rubber component,
In addition to carbon black, organopolysiloxane and other inorganic fillers, addition of process oils, antioxidants, antioxidants, stearic acid, zinc oxide, wax (WAX), etc. which are generally used as rubber compositions for tire treads A vulcanizing agent such as sulfur or a vulcanization accelerator may of course be appropriately compounded.

[0048]

EXAMPLES Hereinafter, the tread rubber composition of the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

The raw materials and evaluation methods used in the following Examples and Comparative Examples are described below.

(Raw materials) SBR: SL574 (trade name) manufactured by JSR Corporation NR: General RSS # 3 grade carbon black: Diamond Black I (trade name) (N220) manufactured by Mitsubishi Chemical Corporation Silica: Ultra seal VN3 (trade name) manufactured by Degussa Clay: BURGESS manufactured by Burgess Pigment
# 28 (trade name), average particle size 0.2 μm Aluminum hydroxide: C-30 manufactured by Sumitomo Chemical Co., Ltd.
3 (trade name), central particle diameter 0.25 μm organopolysiloxane: prototype In the general formula (1), a is 3 ≦ a ≦ 5, and b is 1 ≦ b ≦
3 and 70% or more of X is O _1/2 [(CH ₃ ) ₂
SiO] _b R ^{1 wherein} R ¹ is an ethyl group and has a molecular weight of 1200
Aroma oil: Diana Process P manufactured by Idemitsu Kosan Co., Ltd.
S32 (trade name) Antioxidant: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
(Trade name) WAX: Sunnock wax manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (trade name) Stearic acid: Paulownia (trade name) manufactured by NOF Corporation Zinc oxide: oxidation manufactured by Mitsui Kinzoku Mining Co., Ltd. Two kinds of zinc Sulfur: Powder sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator NS: Noxeller NS (trade name) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

(Lambourn Abrasion) A predetermined vulcanized rubber was subjected to a wear test for 2 minutes at a load of 2 kg and a slip ratio of 30% using a Lambourn type abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd. The test results were indicated by an index with Comparative Example 1 being 100. The larger the index, the better the wear resistance.

(Mooney Viscosity) The Mooney viscosity of a predetermined unvulcanized rubber composition was measured at 130 ° C. in accordance with JIS K6300. The measurement results were indicated by an index with Comparative Example 1 being 100. The larger the index, the lower the viscosity and the easier the processing.

(Fuel efficiency) A test piece was prepared from a predetermined vulcanized rubber sheet molded to a thickness of 2 mm, and was subjected to a viscoelastic spectrometer of Iwamoto Seisakusho Co., Ltd. at a frequency of 10 Hz and a dynamic strain of 1.
The loss tangent (tan δ) at 60 ° C. was measured under the condition of 0%. The larger the index, the lower the tan δ and the better the fuel economy performance.

(Grip Performance) The grip performance was evaluated on a handling course on a wet road surface at an Okayama test course of Sumitomo Rubber Industries, Ltd. The evaluation was performed by a sensory evaluation using a protest driver.
The index was set to 00. A larger index indicates better grip performance.

Examples 1 to 4 and Comparative Examples 1 to 4 Raw materials were kneaded by a conventional method using a 1.7 L Banbury and an open roll so as to have the composition shown in Table 1. The Mooney viscosity was evaluated using the obtained unvulcanized rubber composition.
Lambourn abrasion was evaluated using a vulcanized rubber vulcanized at g / cm ² for 15 minutes, and fuel economy was evaluated using a 2 mm thick vulcanized rubber sheet vulcanized under the same conditions. In addition, 185 / 65R14 size tires for passenger cars using the unvulcanized rubber composition in a tire tread were prepared by a conventional method, and grip performance was evaluated. Table 1 shows the results.

[0056]

[Table 1]

[0057]

According to the present invention, by adding an organopolysiloxane having a specific alkoxysilyl group or silanol group to a carbon black compounded rubber,
A tire tread rubber composition having good fuel economy, abrasion resistance and workability can be obtained. Further, when other inorganic filler is added, the grip performance can be improved.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08L 83:04)

Claims (2)

[Claims] Claims: 1. A carbohydrate is added to 100 parts by weight of a rubber component.
Black and 40 to 150 parts by weight and the general formula (1): (SiO_Two)_aX_{2 (a + 1)} (1) (where X is O_1/2[(CH_Three)_TwoSiO]_bR¹Or O
_1/2R¹And each X may be the same or different,
And one or more of X is O_1/2[(CH_Three)_TwoSiO]_bR ¹so
Must be, R¹Is a hydrogen atom or carbon number 5 or less
B is an integer of 1 to 100, and a is a monovalent hydrocarbon group of
Is an integer of 1 to 20).
Tire tread containing 0.5 to 8 parts by weight of xan
Rubber composition. 2. The tire tread rubber composition according to claim 1, further comprising 1 to 100 parts by weight of another inorganic filler based on 100 parts by weight of the rubber component.