KR20130107014A - Rubber composition for bass tread - Google Patents

Abstract

The present invention provides a rubber composition for a bass tread capable of simultaneously improving low fuel consumption and steering stability, and a pneumatic tire having a bass tread using the same. The present invention contains a rubber component and paper fibers, the rubber component is polymerized by a lithium initiator, the content of tin atoms is 50 to 3000ppm, the amount of vinyl bonds 5 to 90 mass% of 5 to 50 mass% of tin-modified polybutadiene rubber having a molecular weight distribution (Mw / Mn) of 2 or less, and containing 100 parts by mass of the rubber component. The present invention relates to a rubber composition for a base tread having a content of 0.5 to 30 parts by mass of fibers.

Description

Rubber Composition For bass tread

The present invention relates to a rubber composition for a base tread and a pneumatic tire using the same.

BACKGROUND ART Conventionally, automobile fuel economy has been reduced by reducing the rolling resistance of a tire. As a method for low fuel consumption, for example, a tread portion has a two-layer structure (bass tread and cap tread), and a rubber having low heat generation in the bass tread. Although the method of using a composition is known, in recent years, the demand for low fuel consumption becomes increasingly strong, and more excellent low heat generation property is calculated | required.

In addition, due to the improvement of the performance of automobiles and the development of the road network, it is also required to improve the steering stability of the tire, especially the steering stability at high speeds. When a large amount of carbon black is blended into the base tread, the rigidity of the tread portion is increased and the steering stability is improved, but the low fuel consumption is reduced. On the other hand, if carbon black is reduced, low fuel efficiency is improved, but rigidity (steering stability) is lowered. As such, it was difficult to simultaneously improve steering stability and low fuel consumption.

Japanese Patent Laid-Open No. 2006-306955 discloses a rubber composition for a tire in which paper fiber and a silane coupling agent are blended in order to achieve both low fuel efficiency and steering stability. However, there is still room for improvement in terms of such compatibility.

The present invention solves the above problems, and has a rubber composition for the base tread (bass tread) that can improve the low fuel consumption, steering stability at the same time, and a pneumatic tire (tire) having a base tread (bass tread) using the same The purpose is to provide.

The present invention contains a rubber component and paper fibers, the rubber component is polymerized by a lithium initiator, the content of tin atoms is 50 to 3000ppm, the amount of vinyl bonds 5 to 90 mass% of 5 to 50 mass% of tin-modified polybutadiene rubber having a molecular weight distribution (Mw / Mn) of 2 or less, and containing 100 parts by mass of the rubber component. The present invention relates to a rubber composition for a base tread having a content of 0.5 to 30 parts by mass of fibers.

Paper fiber has an average fiber length (L) of 10 microns or more, an average fiber length (D) of 1 to 100 microns, and a ratio (L / D) of 10 to an average fiber length (L) of 10 It is preferable that it is above.

It is preferable that content of carbon black is 15-50 mass parts with respect to 100 mass parts of rubber components.

The present invention also relates to a pneumatic tire having a base tread produced using the rubber composition for the base tread.

According to the present invention, since it is a rubber composition for the base tread containing a specific tin-modified poly butadiene rubber and paper fibers, it is possible to simultaneously improve low fuel efficiency and steering stability. Can be.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

The rubber composition for the base tread of the present invention contains a predetermined amount of specific tin-modified poly butadiene rubber (tin-modified BR) and paper fibers. By using tin-modified BR and paper fiber together, the improvement of low fuel efficiency and steering stability can be improved, and both performances can be improved simultaneously. Especially, even if carbon black is reduced by such a combination, Since good rigidity is obtained, low fuel consumption can be remarkably improved while improving steering stability, and the effect of this invention is exhibited.

The rubber composition of the present invention contains a tin-modified BR polymerized by a lithium initiator as a rubber component. Thereby, low fuel consumption can be improved. This is supposed to improve the dispersibility of the filler (carbon black, etc.) according to the tin modified BR.

As the tin-modified BR, for example, one obtained by adding a tin compound after polymerization of 1,3-butadiene with a lithium initiator can be used. The terminal carbon of the tin-modified BR molecule is preferably bonded to tin.

As the lithium initiator, for example, alkyl lithium, aryl lithium, allyl lithium, vinyl lithium, organotin lithium, organic nitrogen lithium Lithium type compounds, such as a (Lithium) compound, are mentioned. By using a lithium-based compound, a tin-modified BR having a high vinyl bond amount and a low cis bond amount can be easily produced.

As the tin compound, for example, tin tetrachloride, butyls jutori chloride, zibutyls main chloride, geoku chils main chloride, toributchis main chloride, triphenyl tin chloride, di Diphenyl dibutyl tin, toriphenylsjuetokishido, diphenyl dimethyl tin, diphenyl dimethyl tin, zitoryls main chloride, ziphenyl suzuiokutanoeto, divinyl diethyl tin ), Tetra benzyl tin, branched chisel stezireto, tetra allyl tin, p-torbutyl chiles styrene, etc., and these may be used alone or two or more kinds thereof may be used. You may use together.

The tin atom content in tin-modified BR is 50 ppm or more, preferably 60 ppm or more, and more preferably 100 ppm or more. If the content of tin atoms is less than 50 ppm, the effect of improving the dispersibility of the filler becomes small, and the low fuel consumption tends to deteriorate. The content of tin atoms in the tin-modified BR is 3000 ppm or less, preferably 2500 ppm or less, more preferably 1500 ppm or less, and still more preferably 500 ppm or less. If the content of tin atoms is more than 3000 ppm, the kneading of the kneaded material is bad and the edge is not provided, so the extrudability of the kneaded material tends to be deteriorated.

The molecular weight distribution (Mw / Mn) of tin-modified BR is 2 or less, preferably 1.8 or less, and more preferably 1.5 or less. If Mw / Mn exceeds 2, the dispersibility of the filler is deteriorated, and the low fuel consumption tends to deteriorate.

In addition, in this specification, a number average molecular weight (Mn) and a weight average molecular weight (Mw) are the gel permeation chromatograph (GPC) (GPC-8000 series made from ortho); Detector: The differential refraction sum total, column: It was calculated | required by standard polystyrene conversion based on the measured value by TSKGEL SUPERMALTPORE HZ-M made from ortho (stock).

The vinyl bond amount of tin-modified BR is 5 mass% or more, Preferably it is 7 mass% or more. Tin-modified BR having a vinyl bond amount of less than 5% by mass tends to be difficult to polymerize (manufacture). In addition, the vinyl bond amount of tin-modified BR is 50 mass% or less, and 20 mass% or less is preferable.

When the amount of vinyl bonds exceeds 50% by mass, filler dispersibility tends to deteriorate, or the tensile strength of a rubber composition tends to decrease.

In addition, the amount of vinyl bonds (unit amount of 1,2-linked butadiene) can be measured according to an extra-red absorption spectrum analysis method.

The content of tin-modified BR in 100% by mass of the rubber component is 5% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, and more preferably 30% by mass or more. If it is less than 5 mass%, there exists a tendency which cannot fully improve low fuel consumption. The content of tin-modified BR in 100% by mass of the rubber component is 90% by mass or less, preferably 80% by mass or less, and more preferably 60% by mass or less. If it exceeds 90 mass%, the breaking strength of the rubber composition tends to be lowered.

The rubber composition of the present invention is a rubber component other than the tin-modified BR, for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (butadiene). rubber (BR), styrene butadiene rubber (SBR), chloroprene rubber (CR), styrene isoprene butadiene rubber (SIBR), styrene isoprene rubber Diene rubber such as SIR and isoprene butadiene rubber may be used. Among these, it is preferable to use NR or NR and BR simultaneously with tin-modified BR from the reason that both low fuel consumption and steering stability can be compatible.

It does not specifically limit as NR, For example, what is common in the tire industry, such as SIR20, RSS3, TSR20, can be used. Epoxy-ized natural rubber (ENR), deproteinized natural rubber (DPNR) and the like can also be used.

In the rubber composition of the present invention, the content of NR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and more preferably 30% by mass or more. If it is less than 10 mass%, there exists a tendency for sufficient tensile strength not to be obtained.

As for content of this NR, 95 mass% or less is preferable and 75 mass% or less is more preferable. If it exceeds 95% by mass, the content of tin-modified BR is small, so the effect of low fuel efficiency tends not to be obtained.

It does not specifically limit as BR, For example, BR of high cis content, such as BR1220 by Nippon Xeon (stock), BR130B by the Ube Corporation (stock), BR150B, VCR412 by the Ube Corporation (stock), BR (SPB containing BR) etc. which contain syndiotactic poly butadiene crystals, such as VCR617, can be used.

Moreover, in this invention, even if it mix | blends special SPB containing BR and does not raise rigidity, sufficient rigidity (steering stability) is obtained according to the combination of tin modified BR and paper fiber. Therefore, the content rate of tin-modified poly butadiene rubber in a rubber component can be improved, and the low fuel consumption can be improved more significantly. Here, in the rubber composition of the present invention, the content of the SPB-containing BR is within 100% by mass of the rubber component, preferably 5% by mass or less, more preferably 1% by mass or less, and the SPB-containing BR It is not necessary to include it.

Although paper fiber is used in this invention, a reinforcement effect is exhibited by this and favorable rigidity is obtained by this.

The paper fiber is a short fiber made of paper by pulverization or the like, and examples thereof include cellulose fibers produced in a fibrous form by pulverizing and beating wood, pulp, old paper, and the like. Among them, recycled materials can be recycled, and used paper is preferred because of low cost. Moreover, as a paper fiber, what is obtained by the mechanical method (dry grinding etc.) which crushes and pulps a wood with a physical force, etc. are used suitably. As a commercial item of the paper fiber, neo-fiber (newspaper paper, a prince-made bag (stock) product), KC flock coat (product made in Japan paper chemical (stock)), a wheat pie part (Sankyo) Powder (stock)) etc. These paper fibers may be used independently, or may be used in combination of 2 or more type.

The average fiber length L of the paper fibers is preferably at least 10 microns, more preferably at least 50 microns, and more preferably at least 100 microns.

When L is less than 10 micron m, the effect of the rigidity improvement by adding paper fiber tends to become small, and the improvement effect of low fuel consumption also tends to become small. Moreover, the L is preferably 2000 microns or less, more preferably 1500 microns or less, and even more preferably 1000 microns or less. If L exceeds 2000 microns, there is a tendency for poor dispersion of paper fibers.

The average fiber length (D) of the paper fibers is preferably 1 micron m or more, more preferably 3 micron m or more, and further preferably 5 micron m or more. If D is less than 1 micron m, poor dispersion of paper fibers tends to occur. Moreover, 100 micron m or less of this D is preferable, 80 micron m or less is more preferable, and 60 micron m or less is further more preferable. If D exceeds 100 microns m, the reinforcing effect tends not to be obtained, and the improvement effect of low fuel efficiency tends to decrease.

The ratio (L / D, average aspect ratio) of the average fiber length L and the average fiber length D of the paper fibers is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. If the L / D is less than 10, the reinforcing effect tends not to be obtained, and the improvement effect of low fuel efficiency tends to decrease. Moreover, 2000 or less are preferable, as for the L / D, 1000 or less are more preferable, and 500 or less are further more preferable. If the L / D exceeds 2000, the dispersion of paper fibers tends to occur.

In addition, D, L, L / D of paper fiber can be measured by the method etc. which are computed according to image analysis from the image image | photographed using a scanning electron microscope.

The content of the paper fiber is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.5 mass part, there exists a possibility that a reinforcement effect may not be acquired. The content of the paper fiber is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and further preferably 20 parts by mass or less. If it exceeds 30 parts by mass, rubber becomes hard, and workability and ride comfort performance may deteriorate.

It is preferable that the rubber composition for base treads of this invention contains carbon black. The addition of carbon black to tin-modified BR and paper fibers can also impart reinforcement and improve stiffness (steering stability).

As for the nitrogen adsorption ratio surface area (N2SA) of carbon black, 50 m <2> / g or more is preferable, 60 m <2> / g or more is more preferable, 70 m <2> / g or more is also preferable, 77 m <2> / g or more is especially preferable. It exists in the tendency for sufficient tensile strength to not be obtained in less than 50 m <2> / g. Moreover, 110 m <2> / g or less is preferable, as for N2SA of carbon black, 100 m <2> / g or less is more preferable, 90 m <2> / g or less is further more preferable. If it exceeds 110 m 2 / g, workability and low fuel efficiency may deteriorate.

In addition, the nitrogen adsorption ratio surface area of carbon black is calculated | required in accordance with A method of JISK6217.

Dibutyl phthalate (DBP) oil absorption of carbon black is preferably 90 ml / 100 g or more, more preferably 103 ml / 100 g or more. The DBP oil absorption of carbon black is preferably 120 ml / 100 g or less, more preferably 110 ml / 100 g or less.

In addition, the DBP oil absorption amount of carbon black is calculated | required according to the measuring method of JISK6221.

When the rubber composition for the base tread contains carbon black, the content of the carbon black is preferably 15 mass based on 100 parts by mass of the rubber component. 20 parts by mass or more, more preferably 30 parts by mass or more. If it is less than 15 mass parts, there exists a tendency for sufficient reinforcement not to be obtained. The carbon black content is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, further preferably 40 parts by mass or less, still more preferably 35 parts by mass or less, and particularly preferably 32 parts by mass. It is as follows. If it exceeds 50 parts by mass, the low fuel consumption tends to deteriorate.

In the rubber composition of the present invention, the total content of the paper fibers and carbon black is preferably 15 parts by mass or more, more preferably 25 parts by mass or more, based on 100 parts by mass of the rubber component, Moreover, 30 mass parts or more are preferable. The total content thereof is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and further preferably 50 parts by mass or less. By using a specific amount of tin-modified BR and paper fibers together, and adjusting the total content in the above range, low fuel consumption and steering stability can be significantly improved.

In addition to the above components, the rubber composition for the base tread of the present invention may be a compounding agent generally used in the production of a rubber composition, for example, silica, calcium carbonate, clay ( Reinforcing fillers such as clay, zinc oxide, stearic acid, various anti-aging agents, oils such as aroma oils, waxes, vulcanizing agents, vulcanization accelerators and the like can be appropriately blended.

It is preferable that the rubber composition for base treads of this invention contains an anti-aging agent.

As the anti-aging agent, it is possible to appropriately select and use each compound of an amine (amin), a phenol type, an imidazole type, a carbamic acid metal salt, a wax or the like. Among these, an amine system is preferable, and N- (1, 3- dimethyl butyl) -N'-phenyl- p-phenylene diamine is more preferable. As for content of anti-aging agent, 1 mass part or more is preferable with respect to 100 mass parts of rubber components, More preferably, it is 1.3 mass parts or more. The content is preferably 2 parts by mass or less, and more preferably 1.7 parts by mass or less. When adjusting in the said range, the effect of this invention is acquired favorably.

In the rubber composition of the present invention, the oil content is preferably 5 parts by mass or more, more preferably 6 parts by mass or more based on 100 parts by mass of the rubber component. 8.5 mass parts or less are preferable, and, as for the content, 7.5 mass parts or less are more preferable. The effect of this invention is acquired favorably by carrying out content of oil in the said range.

It is preferable that the rubber composition for base treads of this invention contains a vulcanization accelerator. Examples of vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamido (TBBS), N-cyclohexyl-2-benzochiazolylsulfamido (CBS), and N, N'- Indication Kurohecyl-2-benzothiazolyl penamido (DZ), mercapto benzo thiazole (MBT), gibenzothiazolyl sulfido (MBTS), diphenyl guanidine (DPG) etc. are mentioned. These vulcanization accelerators may be used alone or in combination of two or more thereof. Of these, sulfenamide-based vulcanization accelerators such as TBBS and CBS are preferable, and TBBS is more preferable because of excellent vulcanization properties and low fuel efficiency in rubber properties after vulcanization. .

The content of the vulcanization accelerator is preferably 1 part by mass or more and more preferably 1.3 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 1 part by mass, the rubber composition may not be sufficiently vulcanized, and the rubber properties required may not be obtained. As for the compounding quantity, 2 mass parts or less are preferable, and 1.7 mass part or less is more preferable. If it exceeds 2 parts by mass, there is a risk of causing rubber (rubber) glycol.

The rubber composition for the base tread of the present invention is produced by a general method. That is, it can be manufactured by a method of mixing and kneading the above components with a VAN Antoine Louis Barye mixer, a needle, an open roll, and the like, and then vulcanizing the same.

The pneumatic tire of this invention can be manufactured by a conventional method using the said rubber composition for base treads. That is, a base tread may be manufactured using the rubber composition, and the base tread may be fabricated by overlapping with other members and heated and pressurized in a tire forming gas phase.

The pneumatic tire of the present invention can be used in a passenger car, a track, a bus, two cars (bikes), etc. Among these, a passenger car, two cars (bikes) It can be used suitably.

Although this invention is demonstrated concretely based on an Example, this invention is not limited to this example.

Hereinafter, the various medicines used by the Example and the comparative example are demonstrated.

Tin-modified BR: BR1250 (Lithium initiator made by Nippon Xeon Co., Ltd.), polymerization, vinyl bond amount: 10-13 mass%, Mw / Mn: 1.5, tin atom Content: 250ppm, content of components of 105 or less in polystyrene equivalent molecular weight: 2-3% by mass),

NR: RSS # 3,

BR: BR150B (cis content: 97 mass%) made by Ube Heungsan (stock),

Carbon black: diamond black N330 (N2SA: 79m2 / g, DBP oil absorption: 105ml / 100g) made by Mitsubishi Chemical Corporation

Paper fiber: Neofiber (mean fiber length (L): 1000 micron m, average fiber length (D): 20 micron m, L / D: 50) made of a Prince bag (stock),

Wax: Sun knock made by Ohio Shinkou chemical industry (stock),

Anti-aging agent: Crack 6C (N- (1,3-dimethyl butyl) -N-phenyl (phenyl) -p-phenylenediamine (phenylene) of thing made by Ohio Shinko Chemical Co., Ltd.) diamine)),

Zinc oxide: Galvanization No. 1 made by Mitsui Metal Mining (stock),

Stearic acid: Stearic acid `` tsubaki '' made by Nichiyu (stock),

Aroma oil: process X-140 made in Japan energy

Sulfur: Powder sulfur made of Karuizawa sulfur (stock),

Vulcanization accelerator: Nokucera NS (N-tert-butyl (butyl) -2- benzothiazolyl penamido) made by Ohio Shinkou chemical industry (stock)

(Examples 1 to 6 and Comparative Examples 1 to 7)

Using a VAN Antoine Louis Barye mixer, chemicals other than sulfur and a vulcanization accelerator were mixed and kneaded for 4 minutes under conditions of 150 ° C to obtain a kneaded product. Next, using an open roll, sulfur and a vulcanization accelerator were added to the kneaded product obtained above, and beaten for 3 minutes under conditions of 80 ° C to obtain an unvulcanized rubber composition. Furthermore, the obtained unvulcanized rubber composition was press-vulcanized for 20 minutes under the conditions of 160 degreeC, and the vulcanized rubber composition was produced.

The following evaluation was performed using the obtained vulcanized rubber composition. The results are shown in Table 1.

(Viscoelastic test)

Hysteresis loss of vulcanized rubber composition at 70 ° C. under conditions of initial distortion 10%, dynamic distortion amplitude 1%, and frequency 10 Hz, using viscoelastic specutorometa manufactured by Iwamoto Co., Ltd. (tan δ), and double match cloth elastic modulus (E *) was measured. Tanδ of Comparative Example 1 was expressed by 100 by the following formula. The larger the index, the better the rolling resistance (low fuel consumption). In addition, E * of Comparative Example 1 was represented by an index by the following formula. The larger the index, the higher the rigidity and the better the steering stability.

(Low fuel efficiency index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Rubber stiffness index) = (E * of each compound) / (E * of Comparative Example 1) × 100

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7




Compounding (mass part)





Tin Denatured BR 30 30 50 80 50 30 - 30 - 30 50 80 80 NR 70 70 50 20 20 70 70 70 70 70 50 20 20 BR - - - - 30 - 30 - 30 - - - - Carbon black 40 35 30 25 25 20 40 40 40 30 40 40 55 Paper fiber 2 2 5 10 10 25 - - 2 - - - - Wax One One One One One One One One One One One One One Antioxidant 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Zinc oxide 3 3 3 3 3 3 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 2 Aroma oil 7 7 7 7 7 7 7 7 7 7 7 7 7 brimstone 2 2 2 2 2 2 2 2 2 2 2 2 2 Vulcanization accelerator 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

evaluation
Low heat generation index 124 128 130 134 132 133 100 120 99 125 122 124 99 Rubber Stiffness Index 104 102 102 104 104 105 100 100 103 90 99 98 115

As shown in Table 1, in the embodiment using a combination of a specific tin-modified BR and paper fibers, it was possible to improve both the performance of low fuel consumption and rigidity (steering stability), but the comparative example At the same time, there was no improvement. Moreover, it became clear from the result of Example 1 and Comparative Examples 1-3 that both performances improve synergistically with the said combined use.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be apparent to those skilled in the art that changes may be made.

Claims (3)

A rubber component and a paper fiber are contained, and the rubber component is polymerized by a lithium initiator, the content of tin atoms is 50 to 3000 ppm, and the amount of vinyl bonds is 5 to 50. 5% by mass to 90% by mass of tin-modified polybutadiene rubber having a mass% and a molecular weight distribution (Mw / Mn) of 2 or less, wherein the content of the paper fiber is 100 parts by mass of the rubber component. The rubber composition for base treads which is 0.5-30 mass parts.
The paper fiber has an average fiber length (L) of 10 microns or more, an average fiber length (D) of 1 to 100 microns, and a ratio of average fiber length (L) and average fiber length (D). A rubber composition for a base tread, wherein (L / D) is 10 or more.
The rubber for base tread according to claim 1 or 2, wherein the content of carbon black is 15 to 50 parts by mass based on 100 parts by mass of the rubber component. ) Composition.