JP2010150481A - Method of producing rubber composition and tire for track and bus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire for a heavy-loading vehicle such as a truck and a bus, wherein the tire is improved in low fuel consumption performance and abrasion resistance with sufficient balance. <P>SOLUTION: The rubber composition contains silica of 5-20 pts.mass based on a rubber component of 100 pts.mass containing an epoxidized natural rubber of 5-50 mass%, and also does not contain a silane coupling agent, wherein a method of producing the rubber composition consists of a step in which silica is mixed with the epoxidized natural rubber and kneaded to produce a masterbatch. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a rubber composition, and a truck and bus tire having a tread composed of the rubber composition.

  Currently, in a passenger car, it is common to blend silica in the tread portion in order to reduce fuel consumption and improve wet grip performance. However, the silica and silane coupling agent compounded rubber composition is inferior to the carbon black compounded rubber composition in wear resistance under severe conditions. Therefore, the adoption of silica is delayed in heavy-duty vehicle tires such as trucks and buses.

  On the other hand, environmental issues have become more important in recent years, and regulations on the suppression of carbon dioxide emissions have been strengthened. The demand for lower fuel consumption is increasing for truck and bus tires. The development of tires that balance both wear resistance and wear resistance is desired.

In Cited Document 1, as a rubber composition with improved processability and rubber strength, 30 parts by weight or more of predetermined silica is added to 100 parts by weight of a rubber component made of natural rubber and / or epoxidized natural rubber, carbon A rubber composition containing 5 parts by weight or less of black and 2 to 10 parts by weight of a fatty acid salt is disclosed. However, there is room for further improvement for use in the tread portion of heavy duty tires.
JP 2007-246808 A

  An object of the present invention is to provide tires for heavy-duty vehicles such as trucks and buses with improved fuel efficiency and wear resistance in a well-balanced manner.

  The present invention is a method for producing a rubber composition containing 5 to 20 parts by mass of silica and 100 parts by mass of a rubber component containing 5 to 50% by mass of epoxidized natural rubber and not containing a silane coupling agent. And a method for producing a rubber composition, comprising the step of blending the epoxidized natural rubber with the silica and kneading to produce a master batch.

  In the method for producing a rubber composition according to the present invention, the epoxidized natural rubber preferably has an epoxidation rate of 5 to 25 mol%.

  The present invention is a tire for trucks and buses having a tread made of the rubber composition produced by the method for producing a rubber composition.

  According to the present invention, it is possible to provide tires for heavy-duty vehicles such as trucks and buses with improved fuel efficiency and wear resistance in a well-balanced manner.

<Rubber composition>
The rubber composition produced in the present invention contains a rubber component including epoxidized natural rubber and silica, and does not contain a silane coupling agent.

<Rubber component>
The rubber component includes epoxidized natural rubber (ENR).

  As ENR, commercially available ENR may be used, or NR may be epoxidized. The method for epoxidizing NR is not particularly limited, and can be carried out using a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, or a peracid method. Examples of the peracid method include a method of reacting NR with an organic peracid such as peracetic acid or performic acid.

  The epoxidation rate of ENR is preferably 25 mol% or less, and more preferably 20 mol% or less. When the epoxidation rate of ENR exceeds 25 mol%, the glass transition point is high, and the wear resistance and rolling resistance performance tend to decrease. On the other hand, the epoxidation rate of ENR is preferably 5 mol% or more. When the epoxidation rate of ENR is less than 5 mol%, the reinforcing effect of the rubber composition cannot be obtained. As the ENR, one type having an epoxidation rate may be used alone, or two or more types having different epoxidation rates may be used in combination.

  The content of ENR is 50% by mass or less and preferably 30% by mass or less in the rubber component. When the content of ENR exceeds 50% by mass, the rolling resistance performance tends to decrease due to the influence of the glass transition point. On the other hand, the content of ENR is 5% by mass or more in the rubber component. If the ENR content is less than 5% by mass, the reinforcing effect of the rubber composition cannot be obtained.

  As the rubber component, in addition to ENR, natural rubber (NR) and / or diene synthetic rubber can be used. Diene-based synthetic rubbers include styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR). ) And the like. These rubbers may be used alone or in combination of two or more.

<Silica>
The content of silica is 20 parts by mass or less and preferably 15 parts by mass or less with respect to 100 parts by mass of the rubber component. When the silica content exceeds 20 parts by mass, the wear resistance performance cannot be maintained. On the other hand, the content of silica is 5 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of silica is less than 5 parts by mass, the rolling resistance performance is not improved.

  Silica is not particularly limited, and silica prepared by a dry method or a wet method can be used.

Silica has a BET specific surface area (BET) of 100 m ² / g or more, preferably 130 m ² / g or more. When the BET of silica is less than 100 m ² / g, a sufficient reinforcing effect due to the blending of silica cannot be obtained. The BET of silica is 250 m ² / g or less, preferably 200 m ² / g or less. If the BET of silica exceeds 250 m ² / g, the dispersibility, low heat build-up and reinforcing properties of silica are deteriorated, and the rolling resistance tends to increase. In addition, the nitrogen adsorption specific surface area by the BET method of a silica can be measured by the method based on ASTM-D-4820-93.

<Silane coupling agent>
The method for producing a rubber composition according to the present invention includes a step of preparing a master batch by previously kneading epoxidized natural rubber and silica. By producing a masterbatch, the epoxidized natural rubber and silica are directly bonded to form a stronger bond than when a silane coupling agent is used, and excellent wear resistance can be obtained even under severe conditions. . Therefore, in this invention, the silane coupling agent normally mix | blended with a silica is not mix | blended.

<Carbon black>
The rubber composition produced in the present invention can contain carbon black as a reinforcing agent. The compounding amount of carbon black is preferably 5 to 80 parts by mass, more preferably 30 to 55 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount of the carbon black is less than 5 parts by mass, sufficient reinforcing properties and rigidity cannot be obtained, and if it exceeds 80 parts by mass, heat tends to be generated.

The carbon black preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 100 to 220 m ² / g, more preferably 120 to ²⁰⁰ m ² / g. When the nitrogen adsorption specific surface area is lower than 100 m ² / g, the reinforcing property is insufficient, and when it exceeds 220 m ² / g, heat is easily generated, which is not preferable.

<Softener>
Softeners include petroleum-based softeners such as process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt and petroleum jelly, and fatty oil-based softeners such as soybean oil, palm oil, castor oil, linseed oil, rapeseed oil and coconut oil. Agents, waxes such as tall oil, sub, beeswax, carnauba wax and lanolin, and fatty acids such as linoleic acid, palmitic acid, stearic acid and lauric acid. The blending amount of the softening agent is preferably 100 parts by mass or less with respect to 100 parts by mass of the rubber component. In this case, there is a risk of reducing wet grip performance when the rubber composition is used in a tire. Less is.

<Anti-aging agent>
As the anti-aging agent, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like can be appropriately selected and used.

<Vulcanization aid>
As the vulcanization aid, stearic acid, zinc oxide (zinc white) or the like can be used.

<Vulcanizing agent>
As the vulcanizing agent, an organic peroxide or a sulfur vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- 3 or 1,3-bis (t-butylperoxypropyl) benzene or the like can be used. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred.

<Vulcanization accelerator>
Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used.

<Other ingredients>
The rubber composition in the present invention can be blended with various compounding agents and additives blended in tires or general rubber compositions such as other plasticizers. Moreover, the content of these compounding agents and additives can also be set to general amounts.

<Method for producing rubber composition>
The method for producing a rubber composition according to the present invention includes a step of preparing a masterbatch by blending silica into epoxidized natural rubber and kneading. By kneading the epoxidized natural rubber and silica in advance, it is possible to obtain a rubber composition having a strong bond between the epoxidized natural rubber and silica and having excellent wear resistance under severe conditions.

Epoxidized natural rubber can be mixed in the form of rubber latex.
Silica can also be mixed with silica before drying, that is, undried silica.

  By mixing the rubber latex and undried silica, the undried silica is kept in a fine particle state, the dispersibility in the polymer solution is improved, the rolling resistance is reduced, and the wear resistance is improved. it can.

  When the epoxidized natural rubber and silica are solid, they can be mixed with a Banbury mixer and a kneader.

  Next, the mixture which added the other compounding agent to the said masterbatch is knead | mixed using a Banbury mixer etc. At this time, the lower limit of the kneading temperature is preferably about 80 ° C., more preferably about 100 ° C. If the kneading temperature is lower than about 80 ° C., the rubber viscosity may increase and workability may decrease. Further, the upper limit of the kneading temperature is preferably about 200 ° C., more preferably 180 ° C. When the temperature exceeds 200 ° C., the rubber tends to be excited (molecules are cut too much).

<Tire structure>
An embodiment of a tire according to the present invention will be described with reference to the drawings.

  In FIG. 1, a truck and bus tire 1 (hereinafter referred to as a tire 1) of the present embodiment is a tire having a maximum load capacity specified by JIS standards of 2500 kg or more, and extends from the tread portion 2 to the sidewall portion 3. A carcass 6 reaching the bead core 5 of the bead part 4 and a belt layer 7 disposed inside the tread part 2 and outside the carcass 6 are configured.

  The carcass 6 is formed from one or more carcass plies 6A in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction, and in this example, one carcass ply 6A. As the carcass cord, a preferable one using a steel cord is illustrated in this example, but an organic fiber cord such as aromatic polyamide, nylon, rayon, polyester, or the like can be used as required. The carcass ply 6A includes a series of ply turn-up portions 6b that are turned back from the inner side in the tire axial direction around the bead core 5 at both ends of the ply main body portion 6a spanned between the bead cores 5 and 5.

  The bead portion 4 is provided with a hard apex rubber rubber 8 that passes between the ply main body portion 6a and the ply turn-up portion 6b and extends radially outward from the bead core 5, and from the bead portion 4 to the sidewall portion 3. It is reinforced over. Reference numeral 10 in the figure denotes a rim slip prevention clinch rubber that forms a bead skin, and is disposed on the bottom and outer surfaces of the bead that can come into contact with the rim. Reference numeral 11 is a reinforcing cord layer using a steel cord disposed between the clinch rubber 10 and the carcass ply 6A, and is provided at the lower end of the rising portion 11A extending along the outer surface of the ply folded portion 6b. It is formed in an L shape in which a lowering portion 11B extending along the bottom surface of the bead is extended.

  Next, the belt layer 7 is composed of two belt plies 7A and 7B in which steel belt cords (steel cords) are arranged at an angle of 16 to 22 ° with respect to the tire circumferential direction. , 7B are placed on the inside and outside in the radial direction with different cord inclination directions so that the belt cords cross between the plies. As a result, the belt rigidity is increased, and the cornering force necessary for steering stability is sufficiently secured.

<Tire manufacturing method>
Truck and bus tires using the rubber composition in the tread portion are formed by preparing an uncrosslinked product of the rubber composition and applying the uncrosslinked product to the tread portion 2 of the tire and performing vulcanization molding. Can be done.

<Examples 1 to 5, Comparative Example 4>
(Production of master batch)
In Examples 1 to 5 and Comparative Example 4, master batches were prepared by previously blending silica with epoxidized natural rubber. Specifically, according to the composition shown in Table 1, epoxidized natural rubber (solid) and silica (solid) were kneaded at 100 ° C. for 5 minutes using a Banbury mixer, and then heat treated at 170 ° C. for 3 minutes to obtain a master batch. Got.

(Production of rubber composition)
The obtained master batch, the composition shown in Table 1 excluding sulfur and the vulcanization accelerator were kneaded at about 150 ° C. for 5 minutes using a Banbury mixer. Sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded at 80 ° C. for 5 minutes with a biaxial open roll. The resulting rubber composition was vulcanized at 160 ° C. for 18 minutes to obtain a vulcanized rubber composition.

<Comparative Examples 1-3, 5>
(Production of rubber composition)
Comparative Examples 1-3, 5 are examples in which a master batch is not produced. First, the formulations shown in Table 1 except for sulfur and a vulcanization accelerator were kneaded at about 150 ° C. for 5 minutes using a Banbury mixer. Sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded at 80 ° C. for 5 minutes with a biaxial open roll. The resulting rubber composition was vulcanized at 160 ° C. for 18 minutes to obtain a vulcanized rubber composition.

The vulcanized rubber composition was subjected to an abrasion resistance test and a rolling resistance test.
<Abrasion resistance test>
A test piece was prepared from the vulcanized rubber composition, and using a Lambourne abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd., the Lambourne wear loss was measured under the conditions of a temperature of 20 ° C., a slip rate of 20% and a test time of 5 minutes. The volume loss amount of each formulation was expressed as an index according to the following formula, with the loss amount of Comparative Example 1 being 100. It shows that abrasion resistance performance is excellent, so that a numerical value is large.

(Abrasion resistance index) = (Volume loss amount of Comparative Example 1) / (Volume loss amount of each formulation) × 100
<Rolling resistance test>
A test piece was prepared from the vulcanized rubber composition, and the loss tangent of each blend was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. (Tan δ) was measured. The tan δ of Comparative Example 1 was set to 100, and the index was displayed by the following calculation formula. The larger the value, the smaller the tan δ, indicating that the rolling resistance is reduced and the fuel efficiency is low.

(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100
The results are shown in Table 1.

NR: natural rubber, RSS # 3
ENR-10: Epoxidized natural rubber, ENR-10 manufactured by Kumplan Guthrie Berhad (epoxidation rate: 10 mol%)
ENR-25: Epoxidized natural rubber, ENR-25 manufactured by Kumplan Guthrie Berhad (epoxidation rate: 25 mol%)
ENR-50: Epoxidized natural rubber, ENR-50 (epoxidation rate: 50 mol%) manufactured by Kumplan Guthrie Berhad
BR: BR150B manufactured by Ube Industries, Ltd.
Carbon Black: Show Black N220 (N ₂ SA: 111 m ² / g) manufactured by Cabot Japan
Silica: Ultrazil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si-69 from Tegussa
Wax: Sunnock wax anti-aging agent manufactured by Ouchi Shinsei Chemical Co., Ltd .: NOCRACK 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylene manufactured by Ouchi New Chemical Co., Ltd.) Diamine)
Stearic acid: Zinc stearate oxide manufactured by Nippon Oil & Fats Co., Ltd .: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. Noxeller NS (N-tert-butyl-2-benzothiazolyl-sulfenamide) manufactured by
<Evaluation results>
In Examples 1, 3, and 4, NR is 50 parts by mass, ENR-10 is 30 parts by mass, and BR is 100 parts by mass. Part of the rubber composition. A master batch was prepared in advance by mixing ENR-10 with silica. As compared with Comparative Example 1 in which only carbon black was used as a reinforcing agent, the wear resistance and fuel efficiency were improved in all cases.

  Example 2 is a rubber composition containing 10 parts by mass of silica with respect to 100 parts by mass of a rubber component containing 50 parts by mass of NR, 30 parts by mass of ENR-25, and 20 parts by mass of BR. A master batch was prepared in advance by mixing silica with ENR-25. Compared to Comparative Example 1, the wear resistance and fuel efficiency were improved.

  Example 5 is a rubber composition containing 20 parts by mass of silica with respect to 100 parts by mass of a rubber component containing 30 parts by mass of NR, 50 parts by mass of ENR-25 and 20 parts by mass of BR. A master batch was prepared in advance by mixing silica with ENR-25. Compared to Comparative Example 1, the wear resistance and fuel efficiency were improved.

  Comparative Example 2 is a rubber composition containing silica and a silane coupling agent with respect to 100 parts by mass of a rubber component containing 80 parts by mass of NR and 20 parts by mass of BR. Although the wear resistance performance was improved as compared with Comparative Example 1, the fuel efficiency was deteriorated.

  Comparative Example 3 is a rubber composition containing 10 parts by mass of silica with respect to 100 parts by mass of a rubber component containing 50 parts by mass of NR, 30 parts by mass of ENR-50, and 20 parts by mass of BR. A masterbatch is not prepared in advance with ENR-50 and silica. Compared to Comparative Example 1, both the wear resistance performance and the low fuel consumption were deteriorated.

  Comparative Example 4 is a rubber composition containing 30 parts by mass of silica with respect to 100 parts by mass of a rubber component containing 50 parts by mass of NR, 30 parts by mass of ENR-10, and 20 parts by mass of BR. A master batch was prepared in advance by mixing ENR-10 with silica. Although the wear resistance performance was improved as compared with Comparative Example 1, the fuel efficiency was deteriorated.

  Comparative Example 5 contains 10 parts by mass of silica and 0.8 parts by mass of the silane coupling agent with respect to 100 parts by mass of the rubber component containing 50 parts by mass of NR, 30 parts by mass of ENR-10, and 20 parts by mass of BR. It is a rubber composition. A master batch was not prepared in advance with ENR-10 and silica. Although the wear resistance performance was improved as compared with Comparative Example 1, the fuel efficiency was deteriorated.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is sectional drawing which shows one Example of the tire for trucks and buses of this invention.

Explanation of symbols

  2 tread part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layers, 7A, 7B inner and outer belt plies.

Claims (3)

A method for producing a rubber composition containing 5 to 20 parts by mass of silica with respect to 100 parts by mass of a rubber component containing 5 to 50% by mass of epoxidized natural rubber, and containing no silane coupling agent,
Including the step of blending the silica with the epoxidized natural rubber and kneading to prepare a masterbatch,
A method for producing a rubber composition.   The manufacturing method of the rubber composition of Claim 1 whose epoxidation rate of the said epoxidized natural rubber is 5-25 mol%.   A truck and bus tire having a tread made of the rubber composition manufactured by the method for manufacturing a rubber composition according to claim 1.

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