JP2018132363A - Method for measuring gel content, rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of measuring gel content capable of measuring the gel content adhered on the filler surface, which are conventionally hardly captured, in a short time, and a rubber composition with improved abrasion resistance and a pneumatic tire manufactured by using the rubber composition.SOLUTION: The method for measuring gel content adhered on the filler surface in a rubber composition mixed with a filler, which includes: a step 1 in which the rubber composition immersed in a solvent (1) is subjected to an ultrasonic processing and measures average particle diameter D(1) of the particles in the solvent (1); a step 2 in which the filler surface immersed in the solvent (2) is subjected to an ultrasonic processing and measures average particle diameter D(2) of filler surface particle in the solvent (2); and a step 3 in which the gel thickness R adhered on the filler surface in the rubber composition is calculated using the formula below: R=(D(1)-D(2))/2.SELECTED DRAWING: None

Description

The present invention relates to a method for measuring a gel content, a rubber composition, and a pneumatic tire.

In the rubber composition containing the filler, there is a gel component that is hardly soluble in a solvent. For example, in Patent Document 1, an unvulcanized rubber sample is immersed in a toluene solvent for 24 hours or more, and a filter paper or mesh is used. The gel fraction when filtered and dried using is measured.

JP-A-2005-206680

At present, in order to improve the wear resistance and rubber strength of the rubber composition, modification of the filler surface such as carbon black is being studied.

The gel fraction is formed by the interaction between the filler and the polymer, and is related to the abrasion resistance of the rubber composition. Therefore, the above-mentioned gel fraction is measured in the evaluation of the filler whose surface is modified. . However, this method measures not only the gel adsorbed on the filler surface but also the occluder bar (the gel remaining between the fillers) due to the structure of the filler, etc. As a result of the examination by the present inventors, it has been found that there is a problem that it is difficult to detect only the change in the gel content due to the quality.

On the other hand, methods such as soxhlet and boiling are also conceivable, but there is a drawback that it takes time to measure. Moreover, although the method of observing with TEM is also considered, it is difficult to measure the gel component adsorbed on the filler surface, and there is a drawback that it takes time even if it can be measured.

The present invention solves the above problems and uses a method for measuring a gel content that can measure the gel content adsorbed on the filler surface, which has been difficult to grasp in the past, a rubber composition with improved wear resistance, and the rubber composition. An object of the present invention is to provide a pneumatic tire manufactured in this way.

The present invention is a method for measuring a gel content adsorbed on a filler surface in a rubber composition containing a filler, wherein the rubber composition immersed in the solvent (1) is subjected to ultrasonic treatment, and particles in the solvent (1) Step 1 for measuring the average particle diameter D (1) of the filler, and step 2 for measuring the average particle diameter D (2) of the filler particles in the solvent (2) by ultrasonically treating the filler immersed in the solvent (2). And a step 3 of calculating a gel thickness R adsorbed on the filler surface in the rubber composition represented by the following formula.
R = (D (1) -D (2)) / 2

It is preferable that the time of the ultrasonic treatment in the steps 1 and 2 is 10 seconds or more.
It is preferable that the output of the ultrasonic wave in the ultrasonic treatment in the steps 1 and 2 is 10 W or more.

The present invention also provides a rubber composition comprising a rubber component and 5-120 parts by mass of carbon black with respect to 100 parts by mass of the rubber component, wherein the gel is calculated by the measurement method in the carbon black. the thickness R, relates to a rubber composition is the ratio R _{/ N} 2 SA of the nitrogen adsorption specific surface area _N 2 SA of 0.16 or more.

The carbon black preferably has a nitrogen adsorption specific surface area of 30 to 400 m ² / g and a DBP oil absorption of 60 to 300 ml / 100 g.

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, there is provided a method for measuring a gel content adsorbed on a filler surface in a rubber composition containing a filler, wherein the rubber composition immersed in the solvent (1) is subjected to ultrasonic treatment, and the solvent (1) Step 1 for measuring the average particle diameter D (1) of the particles and ultrasonically treating the filler immersed in the solvent (2), and measuring the average particle diameter D (2) of the filler particles in the solvent (2) Since it is a measuring method of the gel part containing the process 2 and the process 3 which calculates the gel thickness R adsorbed on the filler surface in the rubber composition represented by the above formula, The adsorbed gel can be measured in a short time.
Further, since the ratio of the gel thickness when calculated by the measurement method and the ratio of the nitrogen adsorption specific surface area is a rubber composition containing carbon black in a specific range, and a pneumatic tire produced using the rubber composition, Abrasion resistance can be improved.

It is a schematic diagram about average particle diameter D (1) of particles, average particle diameter D (2) of filler particles, and gel thickness R.

[Measurement method of the present invention]
The present invention is a method for measuring a gel content adsorbed on a filler surface in a rubber composition containing a filler, wherein the rubber composition immersed in the solvent (1) is subjected to ultrasonic treatment, and particles in the solvent (1) Step 1 for measuring the average particle diameter D (1) of the filler, and step 2 for measuring the average particle diameter D (2) of the filler particles in the solvent (2) by ultrasonically treating the filler immersed in the solvent (2). And a step 3 for calculating a gel thickness R adsorbed on the filler surface in the rubber composition represented by the following formula.
R = (D (1) -D (2)) / 2

In the present invention, the particle means a filler particle (A in FIG. 1) having a gel component adsorbed on the surface. The filler particles mean particles of the filler itself (B in FIG. 1) that do not adsorb gel content on the surface.
Therefore, in the present invention, the average particle diameter of the particles means the average particle diameter of the filler including the gel portion adsorbed on the surface (D (1) in FIG. 1). The average particle diameter of the filler particles means the average particle diameter of the filler itself (D (2) in FIG. 1).

In the method of the present invention, by immersing the rubber composition containing the filler in the solvent (1) and sonicating, the structure of the filler can be destroyed, and it is refined into individual aggregates and adsorbed on the filler surface. The occluded rubber that is not gel can be eliminated.
Furthermore, in the method of the present invention, the average particle diameter D (1) of the particles in the solvent (1) is measured after the ultrasonic treatment to determine the average particle diameter of the particles having the gel adsorbed on the surface. In addition, after immersing the filler in the solvent (2) and ultrasonically treating it, the average particle diameter of the filler particles in the solvent (2) is measured to determine the average of the filler particles that do not adsorb gel content on the surface. Obtain the particle size. Finally, by subtracting the average particle diameter D (2) from the average particle diameter D (1) and dividing by 2, the gel thickness R adsorbed on the filler surface (R in FIG. 1) is calculated. Since the particles after sonication become finer than the filter paper or mesh size, it is difficult to determine the gel content by weight measurement before and after sonication. In the method of the present invention, however, the filler The thickness of the gel adsorbed on the surface can be measured.
As described above, in the method of the present invention, by combining ultrasonic treatment and measurement of the average particle diameter, the gel content adsorbed on the filler surface, which has been difficult to grasp in the past, can be measured in a short time. Therefore, the change of the gel content due to the change of the filler surface can be measured, and can be used for the evaluation of the filler whose surface is modified.

In step 1, the rubber composition containing the filler is immersed in the solvent (1), the rubber composition immersed in the solvent (1) is subjected to ultrasonic treatment, and then the average particle size of the particles in the solvent (1) is determined. taking measurement.

In step 1, first, the rubber composition containing the filler is immersed in the solvent (1).

As the solvent (1), an organic solvent having high affinity for rubber (diene polymer) is preferable.
Examples of the organic solvent include cyclohexane, isobutyl acetate, isopropyl acetate, methyl ethyl ketone, methyl isopropyl ketone, butyl acetate, carbon tetrachloride, methyl propyl ketone, ethylbenzene, xylene, toluene, ethyl acetate, tetrahydrofuran, and benzene. These may be used alone or in combination of two or more.

The time for immersing the rubber composition in the solvent (1) before the ultrasonic treatment may be appropriately set according to the solvent or the like so that components other than the gel component are sufficiently dissolved. Time is preferred.

In step 1, next, the rubber composition immersed in the solvent (1) is subjected to ultrasonic treatment.

The method of ultrasonic treatment in step 1 is not particularly limited, and a conventionally known method can be used. For example, an ultrasonic generator such as an ultrasonic generator with a seismic terminal or an ultrasonic cleaner is used. A method is mentioned.

The output of ultrasonic waves in the ultrasonic treatment in step 1 is preferably 10 W or higher, more preferably 50 W or higher, and still more preferably 100 W or higher. When it is 10 W or more, there is a tendency that the filler can be efficiently miniaturized by individual aggregates, and the gel component not adsorbed on the filler surface can be more efficiently excluded. Although the upper limit of the said output is not specifically limited, Preferably it is 200 W or less.

The frequency of ultrasonic waves in the ultrasonic treatment in step 1 is preferably 20 to 40 kHz. When it is within the above numerical range, the filler can be efficiently made finer by individual aggregates, and the gel component not adsorbed on the filler surface tends to be more efficiently excluded.

The sonication time in step 1 is preferably 10 seconds or longer, more preferably 1 minute or longer. If it is 10 seconds or longer, the filler can be made finer by individual aggregates, and the gel component not adsorbed on the filler surface tends to be more eliminated. In addition, the upper limit of the time is preferably 30 minutes or less from the viewpoint that no further effect tends to be obtained.

In step 1, after the ultrasonic treatment, the average particle diameter D (1) of the particles in the solvent (1) is further measured.
In the solvent (1), particles that have been refined into individual aggregates and excluded gel components that are not adsorbed on the surface are dispersed in the solvent (1). Therefore, the average particle diameter of the particle | grains which adsorb | sucked the gel part only on the surface can be measured.

A method for measuring the average particle diameter D (1) is not particularly limited, and a conventionally known method can be used. For example, a method for measuring a particle size distribution by a laser diffraction scattering method, a dynamic light scattering method, or the like. Is mentioned. Moreover, you may observe directly by TEM etc. The average particle diameter may be any of mode diameter, median diameter, and arithmetic average diameter (number average diameter, volume average diameter, area average diameter, etc.).

Next, in Step 2, after immersing the filler in the solvent (2) and ultrasonically treating the filler immersed in the solvent (2), the average particle diameter of the filler particles in the solvent (2) is measured.

In step 2, first, a filler (the same filler as the filler in the rubber composition) is immersed in the solvent (2).
Examples of the solvent (2) include the same as the solvent (1), and the same as the solvent (1) is preferable.
The time for immersing the filler in the solvent (2) before the ultrasonic treatment is not particularly limited.

In step 2, next, the filler immersed in the solvent (2) is subjected to ultrasonic treatment.
As the ultrasonic treatment method, time, ultrasonic output, and frequency in step 2, the same conditions as in the ultrasonic treatment in step 1 can be applied.

In step 2, after the ultrasonic treatment, the average particle diameter D (2) of the filler particles in the solvent (2) is further measured.
By the ultrasonic treatment, filler particles refined into individual aggregates are dispersed in the solvent (2). Therefore, the average particle diameter of the filler particles that do not adsorb gel content on the surface can be measured.
Examples of the method for measuring the average particle size D (2) include the same methods as the method for measuring the average particle size D (1).

In the present invention, either step 1 or step 2 may be performed first.

In step 3, the gel thickness R adsorbed on the filler surface in the rubber composition represented by the following formula is calculated.
R = (D (1) -D (2)) / 2

By subtracting the average particle diameter D (2) of the filler particles from the average particle diameter D (1) of the particles and dividing by 2, the gel thickness R adsorbed on the filler surface can be calculated.
Here, in order to make the calculated gel thickness R meaningful, in Steps 1 and 2, it is preferable to measure the average particle diameter based on the same reference by the same measurement method.

[Rubber composition to be measured]
The object to be measured in the method of the present invention is a rubber composition (unvulcanized) in which a rubber component and a filler are blended.

Rubber components include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR). ), Ethylene propylene diene rubber (EPDM), butyl rubber (IIR), and halogenated butyl rubber (X-IIR). These diene rubbers may be used alone or in combination of two or more. Of these, isoprene-based rubber, BR, and SBR are preferable, and BR and SBR are more preferable.

Examples of the filler include fine particle fillers such as carbon black and silica; amorphous fillers such as calcium carbonate; plate-like fillers such as clay and talc; organic fillers such as cellulose fibers. Among these, carbon black is preferable because the polymer is easily taken into the internal voids of the structure.

The filler content is preferably 10 to 120 parts by mass with respect to 100 parts by mass of the rubber component in terms of facilitating the change of the gel content due to the dispersion state of the filler and the change of the filler surface.

In addition to the rubber component and filler, other compounding agents (oil softener, wax, stearic acid, zinc oxide, anti-aging agent, sulfur vulcanizing agent, vulcanization accelerator, etc.) may be included as appropriate. Although content of another compounding agent is not specifically limited, It is preferable to make it less than content of a filler.

As a method for producing the rubber composition, a known method can be used. For example, the above components can be produced by a method of kneading each component using a rubber kneading apparatus such as an open roll, a Banbury mixer, or a closed kneader. .

[Rubber composition of the present invention]
The rubber composition of the present invention comprises a rubber component and carbon black, the carbon black content is 5 to 120 parts by mass, and the gel thickness R when calculated by the measurement method in the carbon black, the ratio R _{/ N} 2 SA of the nitrogen adsorption specific surface area _N 2 SA is 0.16 or more.

As a result of the study by the present inventors, the higher the ratio of R / N ₂ SA between the gel thickness calculated by the measurement method of the present invention and the nitrogen adsorption specific surface area, R / N ₂ SA, the more functional groups on the surface of the carbon black, It has been found that the activity of the carbon black surface is large and the wear resistance is good.
That is, the rubber composition of the present invention contains a gel thickness R when calculated by the measurement method of the present invention, the ratio R / N 2 _SA of the nitrogen adsorption specific surface area N ₂ SA of carbon black is a specific range , Can improve wear resistance.

Rubber components include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR). ), Ethylene propylene diene rubber (EPDM), butyl rubber (IIR), and halogenated butyl rubber (X-IIR). These diene rubbers may be used alone or in combination of two or more. Among these, BR and SBR are preferable, and SBR and BR are more preferably used in combination from the viewpoint that the effects of the present invention can be obtained better.

Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. As the NR, for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20 and the like can be used. As IR, it is not specifically limited, For example, IR2200 etc. can use what is common in tire industry. As modified NR, deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B, BR150B and other high cis content BR, Ube Industries, Ltd. VCR412, VCR617, etc. BR containing tactic polybutadiene crystals can be used. These may be used alone or in combination of two or more. In particular, the cis content of BR is preferably 95% by mass or more from the reason that the wear resistance is improved.

As BR, for example, products such as Ube Industries, JSR, Asahi Kasei, Nippon Zeon, and the like can be used.

It does not specifically limit as SBR, For example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more.

As SBR, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used, for example.

The content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more. When it is 10% by mass or more, rubber strength and fuel efficiency tend to be sufficiently obtained. Further, the upper limit of the content is not particularly limited, and may be 100% by mass. However, when other rubber components are used together with NR, 70% by mass or less is preferable.

The content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more. When it is 5% by mass or more, sufficient wear resistance tends to be obtained. The content is preferably 70% by mass or less, more preferably 60% by mass or less, and still more preferably 40% by mass or less.

The content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, and particularly preferably 60% by mass or more. When the content is 5% by mass or more, sufficient wet grip performance tends to be obtained. The content is preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 80% by mass or less.

The rubber composition of the present invention contains the carbon black. Although it does not specifically limit as said carbon black, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762 etc. are mentioned. These may be used alone or in combination of two or more.

The carbon black nitrogen adsorption specific surface area _(N 2 SA) is preferably at least ^{30 m} 2 / g, more preferably not less than ^{60m 2 / g, 100m 2 /} g or more is particularly preferable. When it is 30 m ² / g or more, the reinforcing property is improved and sufficient durability and wear resistance tend to be obtained. Further, the _N 2 SA is preferably 400 meters ² / g or less, more preferably 300 meters ² / g, more preferably from 250 meters ² / g or less, 180 m ² / g or less is particularly preferred. When it is 400 m ² / g or less, good dispersion of carbon black is easily obtained, and good wear resistance, fracture performance, durability, and low fuel consumption tend to be obtained.
In addition, the nitrogen adsorption specific surface area of the said carbon black is calculated | required by JISK6217-2: 2001.

The carbon black has a dibutyl phthalate oil absorption (DBP) of preferably 60 ml / 100 g or more, more preferably 80 ml / 100 g or more. When it is 60 ml / 100 g or more, the reinforcing property is improved, and sufficient durability and wear resistance tend to be obtained. The DBP is preferably 300 ml / 100 g or less, more preferably 200 ml / 100 g or less, still more preferably 150 ml / 100 g or less. When it is 300 ml / 100 g or less, good durability, fatigue resistance, and wear resistance tend to be obtained.
In addition, DBP of the said carbon black is calculated | required by the measuring method of JISK6217-4: 2001.

In the carbon black, the ratio R / N ₂ SA between the gel thickness R and the nitrogen adsorption specific surface area N ₂ SA when calculated by the measurement method of the present invention is 0.16 or more. The ratio is preferably 0.19 or more, more preferably 0.35 or more. The upper limit of the ratio is not particularly limited, but is preferably 1.0 or less. Abrasion resistance can be improved as it is 0.16 or more.
In the invention relating to the rubber composition of the present invention, the gel thickness R calculated by the measurement method of the present invention in the above-mentioned carbon black is more specifically, <gel content measurement method of Examples described later>> Means the gel thickness R calculated by
Carbon black having the above characteristics can be produced, for example, by increasing the number of functional groups on the carbon black surface.

Content of the said carbon black is 5 mass parts or more with respect to 100 mass parts of rubber components, Preferably it is 10 mass parts or more, More preferably, it is 20 mass parts or more. Sufficient reinforcement is acquired as it is 5 mass parts or more. Moreover, the said content is 120 mass parts or less, Preferably it is 80 mass parts or less, More preferably, it is 60 mass parts or less. When the amount is 120 parts by mass or less, good dispersion of carbon black is obtained, and good processability, reinforcement, rolling and low performance are also obtained.

The rubber composition of the present invention preferably contains stearic acid.
A conventionally well-known thing can be used as a stearic acid, For example, products, such as NOF Corporation, NOF company, Kao Corporation, Wako Pure Chemical Industries, Ltd., and Chiba fatty acid company, can be used.

In the rubber composition of the present invention, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

The rubber composition of the present invention preferably contains zinc oxide.
Conventionally known zinc oxide can be used, for example, Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Co., Ltd. Can be used.

In the rubber composition of the present invention, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. If it is within the above numerical range, the effect of the present invention tends to be obtained better.

The rubber composition of the present invention preferably contains a wax.
The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers such as ethylene and propylene. Of these, petroleum waxes are preferred and paraffin waxes are more preferred because the effects of the present invention can be obtained better.

As the wax, for example, products such as Ouchi Shinsei Chemical Co., Ltd., Nippon Seiwa Co., Ltd., Seiko Chemical Co., Ltd. can be used.

In the rubber composition of the present invention, the content of the wax is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

The rubber composition of the present invention preferably contains an antiaging agent.
Examples of the antiaging agent include naphthylamine type antiaging agents such as phenyl-α-naphthylamine; diphenylamine type antiaging agents such as octylated diphenylamine and 4,4′-bis (α, α′-dimethylbenzyl) diphenylamine; N -Isopropyl-N'-phenyl-p-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylenediamine, etc. P-phenylenediamine-based antioxidants; quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer; 2,6-di-t-butyl-4-methylphenol; Monophenolic antioxidants such as styrenated phenol; tetrakis- [methylene-3- (3 ', 5'-di-t-butyl- '- hydroxyphenyl) propionate] bis methane, tris, and the like polyphenolic antioxidants. Of these, p-phenylenediamine-based antioxidants are preferable, and N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine is more preferable.

As the anti-aging agent, for example, products such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Co., Ltd., and Flexis Co. can be used.

In the rubber composition of the present invention, the content of the anti-aging agent is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

The rubber composition of the present invention preferably contains oil.
Examples of the oil include process oil, vegetable oil and fat, or a mixture thereof. As the process oil, for example, a paraffin process oil, an aroma process oil, a naphthenic process oil, or the like can be used. As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut hot water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Of these, process oil is preferred.

Examples of the oil include Idemitsu Kosan Co., Ltd., Sankyo Oil Chemical Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H & R Co., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd. Etc. can be used.

In the rubber composition of the present invention, the oil content is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. If it is within the above numerical range, the effect of the present invention tends to be obtained better.
The oil content includes the amount of oil contained in rubber (oil-extended rubber).

The rubber composition of the present invention preferably contains sulfur.
Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur that are generally used in the rubber industry. These may be used alone or in combination of two or more.

As the sulfur, for example, products such as Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Nihon Kiboshi Kogyo Co., Ltd., Hosoi Chemical Co., Ltd. can be used.

In the rubber composition of the present invention, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

The rubber composition of the present invention preferably contains a vulcanization accelerator.
Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), Tetrabenzylthiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N′-diisopropyl-2-benzothiazolesulfenamide, etc. The sulfenami And guanidine vulcanization accelerators such as diphenyl guanidine, diortolyl guanidine, and orthotolyl biguanidine. Of these, sulfenamide-based vulcanization accelerators are preferable because the effects of the present invention can be obtained more suitably.

As the vulcanization accelerator, products such as Ouchi Shinsei Chemical Industry Co., Ltd. and Sanshin Chemical Industry Co., Ltd. can be used.

In the rubber composition of the present invention, the content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1 part by mass with respect to 100 parts by mass of the rubber component with respect to 100 parts by mass of the rubber component. That's it. Further, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

In addition to the above components, the rubber composition of the present invention can be blended with additives generally used in the tire industry. Inorganic fillers such as silica and vulcanizing agents other than sulfur (for example, organic crosslinking) Agent) and the like.

The rubber composition of the present invention may contain silica as an inorganic filler.

Examples of the silica include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid) and the like, but wet process silica is preferred because of the large number of silanol groups.

Examples of silica that can be used include products such as Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 20 m ² / g or more, more preferably 30 m ² / g or more, and still more preferably 100 m ² / g or more. By setting it to 20 m ² / g or more, wear resistance and the like tend to be improved. N ₂ SA of the silica is preferably 400 m ² / g or less, more preferably 300 m ² / g or less, and still more preferably 280 m ² / g or less.
In addition, the nitrogen adsorption specific surface area of the other silica is a value measured by the BET method according to ASTM D3037-81.

In the rubber composition of the present invention, the content of silica is preferably 5 parts by mass or more, more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it to 5 parts by mass or more, low fuel consumption tends to be improved. The content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 100 parts by mass or less. If it exceeds 200 parts by mass, the balance between processability and fuel efficiency tends to deteriorate.

In addition to silica, the rubber composition of the present invention includes calcium carbonate, calcium silicate, magnesium oxide, aluminum oxide, alumina, alumina hydrate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, barium sulfate, talc, mica, Other inorganic fillers may be included. Even when other inorganic fillers are included in addition to silica, the above range (total content of silica) is suitable for the total content of inorganic fillers.

The organic crosslinking agent is not particularly limited, and examples thereof include maleimide compounds, alkylphenol / sulfur chloride condensates, organic peroxides, and amine organic sulfides. These may be used alone or in combination of two or more, and may be used in combination with sulfur.
An organic crosslinking agent is mix | blended at 10 mass parts or less with respect to 100 mass parts of rubber components, for example.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, kneader, open roll or the like.

The rubber composition of the present invention includes tire components (sidewall, tread (cap tread), base tread, under tread, clinch apex, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chain Fur, inner liner; side reinforcing layer of run flat tire; etc.). Especially, since abrasion resistance etc. are favorable, it can apply suitably for a tread (cap tread).

[Pneumatic tire of the present invention]
The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, if necessary, the rubber composition containing various additives is extruded in accordance with the shape of a tread, etc. at an unvulcanized stage, molded by a normal method on a tire molding machine, etc. After being bonded together with the tire member to form an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

The tire of the present invention is suitably used as a passenger car tire, bus tire, truck tire, motorcycle tire, high performance tire, competition tire and the like.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.
Below, the Example of the measuring method of this invention and the Example of a rubber composition are demonstrated in order.

[Measurement method of the present invention]
Hereinafter, various chemicals used in Examples and Comparative Examples of the measurement method of the present invention will be described together.
SBR: E-SBR (bound styrene content: 23.5% by mass, vinyl content: less than 20% by mass)
Carbon Black (1): Corax N134 (N ₂ SA: 138 m ² / g, iodine adsorption amount: 146 mg / g, DBP oil absorption amount: 124 ml / 100 g) manufactured by Orion Engineered Carbons Co., Ltd.
Carbon black (2): HP1107 manufactured by Orion Engineered Carbons (N ₂ SA: 141 m ² / g, iodine adsorption amount: 140 mg / g, DBP oil absorption amount: 130 ml / 100 g)
Carbon black (3): Seast 9H (N ₂ SA: 142 m ² / g, iodine adsorption amount: 139 mg / g, DBP oil absorption amount: 130 ml / 100 g) manufactured by Tokai Carbon Co., Ltd.
Wax: Paraffin wax oil: Aroma oil Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Zinc oxide anti-aging agent manufactured by Mitsui Mining & Smelting Co., Ltd .: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine sulfur: Powdered sulfur added by Tsurumi Chemical Co., Ltd. Sulfur accelerator: N-tert-butyl-2-benzothiazolylsulfenamide

(Production method of kneaded product and vulcanized rubber composition)
According to the formulation shown in Table 1, materials other than sulfur and a vulcanization accelerator were kneaded using a 1.7 L Banbury mixer until the temperature reached 160 ° C. to obtain a kneaded product.
Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using an open roll to obtain an unvulcanized rubber composition. Further, the obtained unvulcanized rubber composition was press vulcanized for 15 minutes at 170 ° C. to obtain a vulcanized rubber composition.

The obtained vulcanized rubber composition was evaluated for wear resistance by the following method, and the results are shown in Table 1. Moreover, in the obtained kneaded material, the gel fraction or the gel thickness R was calculated by the method shown below, and the results are shown in Table 2.

(Abrasion resistance)
About the said vulcanized rubber composition, the amount of lamborn abrasion was measured on the conditions of temperature 20 degreeC, slip rate 20%, and test time 2 minutes using the lamborn abrasion tester. Further, the volume loss amount was calculated from the measured lamborn wear amount, the lumbar wear index of the vulcanized rubber composition (1) was taken as 100, and the volume loss amount of each vulcanized rubber composition was displayed as an index (wear resistance index). ). The larger the wear resistance index, the better the wear resistance.

<Comparative Example 1: Conventional gel content measurement method>
The kneaded product (1) or (2) was finely chopped, put into a mesh, and immersed in a toluene solvent for 1 day. After extracting a soluble part, it vacuum-dried and weighed the gel mass. The gel fraction was calculated by the following formula. The gel filler mass indicates the weight of the filler present in the kneaded product, and is measured by calculating (mass of the kneaded product) × (mass part of filler) / (total mass part). The total polymer mass of the kneaded product indicates the mass of the polymer present in the kneaded product, and is measured by calculating (mass of the kneaded product) × 100 / (total mass part).
Gel fraction (%) = {(total gel mass) − (gel filler mass)} ÷ (total polymer mass of the kneaded product) × 100

<Example 1>
The kneaded product (1) or (2) was finely chopped and immersed in a toluene solvent for 1 day. Thereafter, the toluene solvent was sonicated (20 kHz, 100 W, 10 seconds, Digital Sonifier manufactured by BRANSON), DLS (dynamic light scattering, cumulant analysis, water temperature 25 ° C., accumulated number 5000 times, manufactured by Otsuka Electronics Co., Ltd.) The average particle diameter D (1) (nm) was measured using ELS-Z2) (Step 1). Next, the same carbon black as the carbon black blended in the kneaded product is put in a toluene solvent, subjected to ultrasonic treatment (20 kHz, 50 W, 2 minutes), and the average particle diameter D (2) (nm) is determined using DLS. Measured (Step 2). And gel thickness R (nm) was computed from the following formula (process 3).
R = (D (1) -D (2)) / 2

<Example 2>
The gel thickness R (nm) was calculated in the same manner as in Example 1 except that the sonication time in Step 1 was changed to 5 minutes.

<Comparative example 2>
The gel fraction was calculated in the same manner as in Comparative Example 1 except that the kneaded product (1) or (3) was used as a measurement target.

<Example 3>
The gel thickness R (nm) was calculated in the same manner as in Example 1 except that the kneaded product (1) or (3) was used as a measurement target.

<Example 4>
A gel thickness R (nm) was calculated in the same manner as in Example 2 except that the kneaded product (1) or (3) was used as a measurement target.

In Tables 1 and 2, rubber compositions having different wear resistance despite the fact that carbon blacks having substantially the same physical properties such as nitrogen adsorption specific surface area and generally equivalent are blended are compared with conventional rubber compositions. In Comparative Example 1 or 2 which is a gel content measurement method, no difference was observed in the gel fraction, whereas in Examples 1, 2 or 3 and 4 which are measurement methods of the present invention, the gel thickness R was There was a difference. From this, it became clear that the gel component adsorbed on the filler surface, which was difficult to grasp in the past, can be measured in a short time by the measurement method of the present invention.

[Rubber composition of the present invention]
Hereinafter, various chemicals used in Examples and Comparative Examples of the rubber composition of the present invention will be described together.
NR: TSR20
SBR: E-SBR (bound styrene content: 23.5% by mass, vinyl content: less than 20% by mass)
BR: BR150B manufactured by Ube Industries, Ltd.
Carbon Black (1): Corax N134 (N ₂ SA: 138 m ² / g, iodine adsorption amount: 146 mg / g, DBP oil absorption amount: 124 ml / 100 g, R / N ₂ SA manufactured by Orion Engineered Carbons Co., Ltd. 0.14)
Carbon black (2): HP1107 (N ₂ SA: 141 m ² / g, iodine adsorption amount: 140 mg / g, DBP oil absorption amount: 130 ml / 100 g, R / N ₂ SA: 0 manufactured by Orion Engineered Carbons Co., Ltd. .16)
Carbon black (3): Seast 9H (N ₂ SA: 142 m ² / g, iodine adsorption amount: 139 mg / g, DBP oil absorption amount: 130 ml / 100 g, R / N ₂ SA: 0.23 manufactured by Tokai Carbon Co., Ltd. )
Carbon black (4): # 4000B (N ₂ SA: 100 m ² / g, DBP oil absorption: 124 ml / 100 g, pH: 10, volatile content: 0.3% by mass, R / N ₂ manufactured by Mitsubishi Chemical Corporation SA: 0.005)
Carbon Black (5): Dia Black I (N ₂ SA: 114 m ² / g, manufactured by Mitsubishi Chemical Corporation), DBP oil absorption: 114 ml / 100 g, pH: 7.5, volatile content: 1.0 mass%, R / N ₂ SA: 0.2)
Silica: N ₂ SA: 175 m ² / g
Silane coupling agent: bis (3-triethoxysilylpropyl) disulfide wax: paraffin wax oil: aroma oil
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Zinc oxide anti-aging agent manufactured by Mitsui Mining & Smelting Co., Ltd .: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine sulfur: Powdered sulfur added by Tsurumi Chemical Co., Ltd. Sulfur accelerator: N-tert-butyl-2-benzothiazolylsulfenamide

R in R / N ₂ SA of carbon blacks (1) to (5) was calculated by the following method.

<Gel content measurement method>
Using a 1.7 L Banbury mixer, 100 parts by mass of SBR was kneaded at a rotational speed of 70 rpm for 1 minute, then 50 parts by mass of each carbon black, 2 parts by mass of wax, 10 parts by mass of oil, 2 parts by mass of stearic acid, and 2 parts by mass of zinc oxide. Part and 1 part by weight of an anti-aging agent were added and kneaded at a rotational speed of 70 rpm until reaching 160 ° C. to obtain a kneaded product.
2 g of the kneaded product was finely chopped and immersed in 100 g of a toluene solvent for 1 day. Thereafter, the toluene solvent was sonicated (20 kHz, 100 W, 2 minutes, Digital Sonifier manufactured by BRANSON), and DLS (dynamic light scattering, cumulant analysis, water temperature 25 ° C., accumulated number 5000 times, manufactured by Otsuka Electronics Co., Ltd.) ELS-Z2) was used to measure the average particle diameter D (1) (nm) (volume average diameter) (Step 1). Next, 0.1 g of carbon black identical to the carbon black blended in the kneaded product is put into 100 g of toluene solvent, subjected to ultrasonic treatment (20 kHz, 50 W, 2 minutes), and average particle diameter D (2) using DLS. (Nm) (volume average diameter) was measured (step 2). And gel thickness R (nm) was computed from the following formula (process 3).
R = (D (1) -D (2)) / 2

<Examples and Comparative Examples>
According to the formulation shown in Tables 3 to 6, materials other than sulfur and a vulcanization accelerator were kneaded at 160 ° C. for 3 minutes using a 1.7 L Banbury mixer to obtain a kneaded product.
Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using an open roll to obtain an unvulcanized rubber composition. Further, the obtained unvulcanized rubber composition was press vulcanized for 15 minutes at 170 ° C. to obtain a vulcanized rubber composition.

In the obtained vulcanized rubber composition, abrasion resistance was evaluated by the method shown below, and the results are shown in Tables 3-6. The reference comparative example of Table 3 is Comparative Example 3, the reference comparative example of Table 4 is Comparative Example 7, the reference comparative example of Table 5 is Comparative Example 11, and the reference comparative example of Table 6 is Comparative Example 15.

(Abrasion resistance)
About the said vulcanized rubber composition, the amount of lamborn abrasion was measured on the conditions of temperature 20 degreeC, slip rate 20%, and test time 2 minutes using the lamborn abrasion tester. Further, the volume loss amount was calculated from the measured amount of lamborn wear, and the volume loss amount of each vulcanized rubber composition was displayed as an index (wear resistance index) with the lamborn wear index of the reference comparative example being 100. The larger the wear resistance index, the better the wear resistance.

From Tables 3 to 6, the rubber component and a predetermined amount of carbon black were included, and the ratio of the gel thickness R when calculated by the measurement method of the present invention to the carbon black and the nitrogen adsorption specific surface area N ₂ SA R / example N ₂ SA is 0.16 or more 5 to 16, it has become clear that the wear resistance is improved.

Claims (6)

A method of measuring a gel content adsorbed on a filler surface in a rubber composition containing a filler,
Sonicating the rubber composition immersed in the solvent (1), and measuring an average particle diameter D (1) of particles in the solvent (1);
Step 2 of ultrasonically treating the filler immersed in the solvent (2) and measuring the average particle diameter D (2) of the filler particles in the solvent (2);
And a step 3 of calculating a gel thickness R adsorbed on the filler surface in the rubber composition represented by the following formula:
R = (D (1) -D (2)) / 2 The method for measuring a gel content according to claim 1, wherein the ultrasonic treatment time in the steps 1 and 2 is 10 seconds or more. The method for measuring a gel content according to claim 1 or 2, wherein an ultrasonic output in the ultrasonic treatment in the steps 1 and 2 is 10 W or more. A rubber composition comprising a rubber component and 5-120 parts by mass of carbon black with respect to 100 parts by mass of the rubber component,
The ratio R / N ₂ SA of the gel thickness R and the nitrogen adsorption specific surface area N ₂ SA when calculated by the measurement method according to claim 1 in the carbon black is 0.16 or more. Rubber composition. The rubber composition according to claim 4, wherein the carbon black has a nitrogen adsorption specific surface area of 30 to 400 m ² / g and a DBP oil absorption of 60 to 300 ml / 100 g. A pneumatic tire produced using the rubber composition according to claim 4.

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