JP6724558B2 - Method for producing rubber composition for tire - Google Patents

Description

The present invention relates to a method for producing a rubber composition for tires.

Generally, a rubber composition that requires low-temperature grip performance, such as a studless tire containing a rubber component and a large amount of a softening agent, is produced by a method in which these materials are collectively charged and kneaded. In such a studless tire formulation, carbon black is generally used as a filler, but carbon black has a property of being easily adsorbed with a softening agent.

Therefore, when the rubber component, carbon black, and the softening agent are added all at once and kneaded, the softening agent is adsorbed on each particle of carbon black, and the effect of dispersion due to collision/friction of carbon black granules that originally occurs during kneading cannot be expected. .. Therefore, the dispersibility of carbon black is deteriorated and the rubber-reinforcing property is deteriorated. As a result, there is a problem that performance such as abrasion resistance is deteriorated.

An object of the present invention is to provide a method for producing a rubber composition for a tire, which solves the above-mentioned problems, obtains good carbon black dispersibility, and is capable of imparting properties such as excellent abrasion resistance.

The present invention relates to a first base kneading step of kneading a part of a rubber component, carbon black, and a softening agent, a first kneaded product obtained in the first base kneading step, and the remaining part of the rubber component. 2 base kneading step, a second kneading material obtained in the second base kneading step, and a finish kneading step of kneading a vulcanized material, wherein the first base kneading step is a part of the rubber component. The present invention relates to a method for producing a rubber composition for tires, in which 60 parts by mass or more of the carbon black is kneaded with 100 parts by mass.

It is preferable to knead 30 to 95 mass% of the rubber component contained in the rubber composition for tires in the first base kneading step.

It is preferable that the rubber composition for a tire contains 30 to 70 parts by mass of carbon black and 20 parts by mass or more of a softening agent with respect to 100 parts by mass of a rubber component.
The rubber composition for tires is preferably a rubber composition for studless tires.

According to the present invention, the first base kneading step of kneading a part of the rubber component, the carbon black, and the softening agent, the first kneaded product obtained in the first base kneading step, and the rest of the rubber component are kneaded. And a finish kneading step of kneading the second kneaded product obtained in the second base kneading step and the vulcanized material, wherein the first base kneading step comprises: Since it is a method for producing a rubber composition for a tire in which 60 parts by mass or more of the carbon black is kneaded with 100 parts by mass, good carbon black dispersibility can be obtained, and excellent performance such as excellent wear resistance can be obtained. Can be given.

The method for producing a rubber composition for a tire of the present invention comprises a first base kneading step of kneading a part of a rubber component, carbon black, and a softening agent, and a first kneaded product obtained in the first base kneading step, And a second base kneading step of kneading the rest of the rubber component, a second kneading material obtained in the second base kneading step, and a finishing kneading step of kneading a vulcanized material, the first base kneading The step is a method of kneading 60 parts by mass or more of the carbon black with 100 parts by mass of the rubber component.

As described above, the rubber component, the carbon black, the bulk kneading of a large amount of the softening agent, the dispersibility of the carbon black tends to deteriorate, the present invention, a part of the rubber component, carbon black, using a softening agent, First, kneading is performed in a state where the amount of carbon black is relatively large with respect to the rubber component (first base kneading step), and then the first kneaded product obtained in the first base kneading step is mixed with the remaining rubber component. This is a method of kneading (second base kneading step). Therefore, carbon black is sufficiently dispersed in the rubber even in a compound containing a large amount of a softening agent such as a studless tire compound. Therefore, according to the production method of the present invention, a good carbon black dispersibility can be obtained, and a rubber composition excellent in performance such as abrasion resistance can be produced.

First, each component used in the present invention will be described.

(Rubber component)
The rubber component is not particularly limited, and diene rubber or the like can be preferably used. As the diene rubber, natural rubber (NR) or diene synthetic rubber can be used. Examples of the diene synthetic rubber include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and acrylonitrile butadiene rubber. (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like. These may be used alone or in combination of two or more. Among them, SBR and BR are preferable, and SBR is more preferable, from the viewpoint of wear resistance and the like.

Examples of SBR include solution-polymerized styrene-butadiene rubber (S-SBR) and emulsion-polymerized styrene-butadiene rubber (E-SBR), and among them, S-SBR is preferable.

From the viewpoint of wear resistance, low temperature characteristics, etc., SBR preferably has a glass transition point (Tg) of -10 to 10°C. The Tg is more preferably -10 to 0°C. In the present invention, Tg is a value measured by differential scanning calorimetry (DSC) according to JIS K7121 (heating rate 20°C/min).

From the viewpoint of wear resistance and the like, SBR preferably has a weight average molecular weight (Mw) of 900,000 or more. Mw is more preferably 1 million or more, and even more preferably 1.1 million or more. On the other hand, the upper limit of Mw is not particularly limited, but is preferably 2 million or less, more preferably 1.5 million or less. In addition, Mw is a value measured by gel permeation chromatography (GPC, "HCL-8220" manufactured by Tosoh Corporation, measurement temperature 40° C.) using Tetrohydrofuran (THF) as a developing solvent.

SBR has a styrene content of 35 to 50% by mass and a vinyl content in the butadiene part (content of 1,2-vinyl structure when the entire butadiene part is 100% by mass) is 55 to 80% by mass. Is preferred. The styrene content and the vinyl content in the butadiene part are values calculated by the integration ratio of ¹ HNMR spectrum.

From the viewpoint of performance such as abrasion resistance, in the rubber composition obtained by the production method of the present invention, the content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 80% by mass or more. And may be 100% by mass.

(Carbon black)
The average particle size of carbon black is preferably 10 to 35 nm, more preferably 13 to 30 nm or less. If it is less than 10 nm, the dispersibility of carbon black may be lowered, and if it exceeds 35 nm, the reinforcing effect of carbon may be insufficient.
The average particle size of carbon black is the number average particle size and is measured by a transmission electron microscope.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 168 m ² /g or more, more preferably 180 m ² /g or more. If it is less than 168 m ² /g, sufficient abrasion resistance may not be obtained. The upper limit is not particularly limited, but the N ₂ SA is preferably 205 m ² /g or less, more preferably 200 m ² /g or less. If it exceeds 205 m ² /g, it may be difficult to disperse it.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

The dibutyl phthalate oil absorption (DBP) of carbon black is preferably 125 ml/100 g or more, and more preferably 130 ml/100 g or more. If it is less than 125 ml/100 g, sufficient abrasion resistance may not be obtained. The DBP is preferably 137 ml/100 g or less, more preferably 130 ml/100 g or less. If it exceeds 137 ml/100 g, the workability may decrease.
The DBP of carbon black is measured according to JIS K 6217-4:2001.

In the rubber composition obtained by the production method of the present invention, the content of carbon black is preferably 30 parts by mass or more, and more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 30 parts by mass, sufficient abrasion resistance may not be obtained. Further, the content is preferably 70 parts by mass or less, more preferably 60 parts by mass or less. If it exceeds 70 parts by mass, workability tends to deteriorate.

(Softener)
As the softening agent, one known in the tire field in a liquid state at room temperature (20° C.) can be used. Specific examples include oils, aromatic resins, C5-based petroleum resins, C9-based petroleum resins and the like. Of these, oil is preferable.

As the oil, petroleum-based oils and the like can be preferably used in order to improve the processability of the rubber (softening effect, compounding agent dispersing effect, polymer chain lubrication effect, etc.). Specifically, in addition to paraffin-based process oils, naphthene-based process oils, aroma-based process oils, treated distillate aromatic extracts (TDAE (treated distillate aromatic extracts)), solvent residue aromatic extracts ( Alternative aromatic oils such as (SRAE) solvent residue aromatic extracts, and mild extraction solvates (MES) are listed.

In the rubber composition obtained by the production method of the present invention, the content of the softening agent is preferably 20 parts by mass or more, and more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 20 parts by mass, the low temperature characteristics may deteriorate. The upper limit of the content is not particularly limited, but is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and further preferably 120 parts by mass or less. If it exceeds 200 parts by mass, abrasion resistance tends to deteriorate.

(Anti-aging agent)
As the antiaging agent, a conventionally known amine antiaging agent or the like can be used, and specifically, a phenylene amine antiaging agent such as N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. Examples include inhibitors. In the rubber composition obtained by the production method of the present invention, the content of the antioxidant is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

(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 wax and animal wax; and synthetic waxes such as polymers such as ethylene and propylene. In the rubber composition obtained by the production method of the present invention, the wax content is preferably 0.2 to 8 parts by mass with respect to 100 parts by mass of the rubber component.

(Zinc oxide, stearic acid)
As zinc oxide and stearic acid, conventionally known ones can be used. In the rubber composition obtained by the production method of the present invention, the contents of zinc oxide and stearic acid are preferably 0.5 to 8 parts by mass and 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component, respectively.

(Vulcanized material)
As the vulcanization material, for example, sulfur, a vulcanization accelerator or the like can be used.

The sulfur is not particularly limited, and those commonly used in the tire industry can be used, but powdered sulfur is preferable.

From the viewpoint of performance such as abrasion resistance, in the rubber composition obtained by the production method of the present invention, the content of sulfur is preferably 0.1 parts by mass or more, and more preferably 100 parts by mass of the rubber component. It is 0.5 parts by mass or more, preferably 6 parts by mass or less, and more preferably 4 parts by mass or less.

The vulcanization accelerator is not particularly limited, and those commonly used in the tire industry can be used. For example, guanidines, sulfenamides, thiazoles, thiurams, dithiocarbamates, thioureas, xanthates, etc. Are listed.

From the viewpoint of performance such as abrasion resistance, in the rubber composition obtained by the production method of the present invention, the content of the vulcanization accelerator is preferably 0.3 parts by mass or more with respect to 100 parts by mass of the rubber component, It is more preferably 0.5 part by mass or more, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less.

(Other ingredients)
The rubber composition obtained by the production method of the present invention may appropriately contain other compounding agents in addition to the above components.

Next, each kneading step in the manufacturing method of the present invention will be described.

(First base kneading process)
In the first base kneading step, a part of the rubber component, carbon black, and a softening agent are kneaded to obtain a first kneaded product. Good carbon black dispersibility can be obtained even by a method in which a relatively large amount of carbon black and a softening agent are kneaded in advance with the rubber component to simultaneously knead the carbon black and the softening agent.

The kneading method is not particularly limited and, for example, a known kneading machine such as a Banbury mixer or a kneader can be used. The kneading time in the first base kneading step is preferably 1 to 10 minutes, and the kneading temperature is preferably 130 to 160°C.

In the first base kneading step, a part of the rubber component is kneaded, but from the viewpoint of the carbon black dispersibility, the first rubber component contained in the rubber composition obtained by the production method of the present invention is 100% by mass. In the base kneading step, 30 to 95% by mass is preferably kneaded, 40 to 85% by mass is more preferable, and 45 to 75% by mass is further preferable.

In the first base kneading step, 60 parts by mass or more of carbon black is preferably kneaded with 100 parts by mass of the rubber component kneaded in the step, and more preferably 65 to 180 parts by mass. More preferably, 70 to 130 parts by mass are kneaded. If the amount is less than 60 parts by mass, the effect of dividing and kneading the rubber component in the first and second base kneading steps is small, and the effect of sufficiently improving the carbon black dispersibility cannot be obtained. If it exceeds 180 parts by mass, the amount of rubber is small, so that the carbon black agglomerates into a gel, and the dispersion of the carbon black in the rubber component may deteriorate.

The entire amount of carbon black may be kneaded in the first base kneading step, or may be divided and kneaded in the first and second base kneading steps or the like. However, from the viewpoint of ensuring dispersibility, the entire amount of carbon black is the first base kneading step. It is preferable to knead.

The total amount of the softening agent may be kneaded in the first base kneading step, or may be divided and kneaded in the first and second base kneading steps and the like. In the present invention, since a relatively large amount of rubber component and carbon black are kneaded in the first base kneading step, good dispersibility of carbon black can be obtained even if the total amount of the softening agent is kneaded in this step. It is possible.

In the first base kneading step, it is preferable to knead another base kneading material (antiaging agent, wax, stearic acid, zinc oxide, etc.) in addition to the above components.

(Second base kneading process)
In the second base kneading step, the first kneaded material obtained in the first base kneading step and the rest of the rubber component are kneaded to obtain a second kneaded material. A first kneaded product prepared by kneading a part of the rubber component used in the present invention in advance and the remaining rubber component are kneaded to obtain a second kneaded product having good carbon black dispersibility. ..

The kneading method is not particularly limited and, for example, a known kneading machine such as a Banbury mixer or a kneader can be used. The kneading time in the second base kneading step is preferably 1 to 10 minutes, and the kneading temperature is preferably 120 to 160°C.

In the second base kneading step, other components than the remaining rubber component may be appropriately kneaded, but from the viewpoint of carbon dispersibility, it is preferable to knead only the remaining rubber component with the first kneaded product. ..

(Finishing process)
In the finish kneading step, the second kneaded material obtained in the second base kneading step and the vulcanized material are kneaded. The kneading method is not particularly limited, and for example, a known kneader such as an open roll can be used. The kneading time is preferably 0.5 to 15 minutes, and the kneading temperature is preferably 40 to 80°C.

In the finish kneading step, the second kneaded product, sulfur and the vulcanization accelerator are usually kneaded, but in the first and second base kneading steps, when a part of the materials to be normally kneaded in the base kneading is not kneaded The materials may also be appropriately kneaded.

(Other processes)
The kneaded product (unvulcanized rubber composition) obtained in the finishing kneading step is extruded according to the shape of a member such as a tread, and molded by a usual method on a tire molding machine to obtain another tire member. A tire can be manufactured by laminating together with each other to form an unvulcanized tire and then heating and pressing in a vulcanizer. The manufactured tire can be suitably used as a passenger car tire, a bus tire, a truck tire, and the like.

The present invention will be specifically described based on Examples, but the present invention is not limited thereto.

Hereinafter, various chemicals used in Examples and Comparative Examples will be collectively described.
SBR: SE6529 manufactured by Sumitomo Chemical Co., Ltd. (S-SBR, Tg: -4°C, styrene content: 43 mass%, vinyl content: 57 mass%, Mw: 1.2 million, 44.0 phr oil extension)
Carbon black: HPT10 manufactured by Cabot Japan KK (average particle size: 25 nm, N ₂ SA: 188 m ² /g, DBP absorption: 135 ml/100 g)
Oil: Diana Process Oil NH-70S (aroma oil) manufactured by Idemitsu Kosan Co., Ltd.
Zinc oxide: Two kinds of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Camellia anti-aging agent manufactured by NOF CORPORATION 6C: Santoflex 13 (N-phenyl-N'-(1,3-dimethylbutyl) manufactured by Flexis) -P-phenylenediamine)
Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. CZ: Noxceller CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[Examples and Comparative Examples]
(Base kneading process)
The materials described in the item of base kneading in Table 1 were kneaded using a 1.7 L Banbury mixer to obtain a kneaded product. In Table 1, X-1 and X-2 mean that each material was added and kneaded in this order for each item. The kneading temperature and kneading time for each item are as follows.
X-1 (first base kneading step) Kneading temperature: 150°C, kneading time: 5 minutes X-2 (second base kneading step) Kneading temperature: 150°C, kneading time: 5 minutes (finishing kneading step)
Using an open roll, the materials described in the item of finish kneading in Table 1 were added to the second kneaded material obtained in the second base kneading step, and kneaded at 70°C for 8 minutes to give an unvulcanized rubber composition. I got a thing.
(Vulcanization process)
The unvulcanized rubber composition obtained in the finishing kneading step was press-vulcanized at 170° C. for 20 minutes with a 0.5 mm thick mold to obtain a vulcanized rubber composition.

The following evaluations were carried out on the obtained unvulcanized rubber composition and vulcanized rubber composition. The results are shown in Table 1.

(Carbon black dispersity)
A sample having a thickness of 2 to 3 mm and a few mm square is taken from an appropriate portion of the unvulcanized or vulcanized rubber composition, lightly stuck on a sample stand of a microscope microtome, and cooled and cured with liquid nitrogen. Then, a thin blade sample having a thickness of 2 μm was prepared using a steel blade. After immersing in benzene and allowing it to swell appropriately, spread it flat on a microscope plate glass and count the number of agglomerates occupying ½ or more of one eye in the field of view of a mesh of 13×13 μm. 70 to 1000 times) and the carbon black dispersity (%) was evaluated using the following formula. The larger the value, the better the degree of dispersion.
D=100-(US/L)
(D: dispersity of carbon black, U: total aggregate, S: area swelling of the entire material, L: volume of carbon black)

(Abrasion resistance index (pico abrasion test method))
With respect to the vulcanized rubber composition, a top-hat type disk-shaped sample having a polished surface of 31.75 mm in diameter was prepared. The sample was attached to a tester equipped with a grinder and a rotary table, and a wear test was performed to determine the wear resistance index. Taking Comparative Example 1 as 100, each sample was indexed. The smaller the number, the better.

As shown in Table 1, first, a first base kneading step (X-1) of kneading a part of a rubber component, carbon black, and a softening agent was performed, and then, the obtained first kneaded product and rubber were obtained. By performing the second base kneading step (X-2) on the balance of the components, it has been clarified that good carbon black dispersibility can be obtained and performances such as excellent abrasion resistance can be imparted.

Claims (4)

A first base kneading step of kneading a part of the rubber component, carbon black, and a softening agent,
A second base kneading step of kneading the first kneaded material obtained in the first base kneading step and the balance of the rubber component;
A second kneaded product obtained in the second base kneading step, and a finish kneading step of kneading a vulcanized material,
In the first base kneading step, 60 parts by mass or more of the carbon black is kneaded with 100 parts by mass of the rubber component ,
The nitrogen adsorption specific surface area of the carbon black is 168 m ² /g or more,
The tire rubber composition, production method with respect to 100 parts by mass of the rubber component, der Ru tire rubber composition that contains a softening agent 30 parts by mass or more. The method for producing a rubber composition for a tire according to claim 1, wherein 30 to 95% by mass of a rubber component contained in the rubber composition for a tire is kneaded in the first base kneading step. The method for producing a rubber composition for a tire according to claim 1 or 2, wherein the rubber composition for a tire contains 30 to 70 parts by mass of carbon black and 30 parts by mass or more of a softening agent with respect to 100 parts by mass of a rubber component. .. The method for producing a rubber composition for a tire according to claim 1, wherein the rubber composition for a tire is a rubber composition for a studless tire.