JP2024049830A - Rubber composition for bladder and method for producing same - Google Patents

Abstract

[Problem] To provide a rubber composition for bladders that is excellent in various performances while saving energy and improving productivity, a manufacturing method thereof, and a bladder. [Solution] The rubber composition for bladders contains butyl-based rubber A, butyl-based rubber B, and carbon black, and is obtained by a manufacturing method including a base kneading step 1A in which the butyl-based rubber A and a part of the carbon black are kneaded to prepare kneaded product 1A, a base kneading step 1B in which the remaining butyl-based rubber B and the carbon black are kneaded to prepare kneaded product 1B, and a base kneading step 2 in which the kneaded product 1A and the kneaded product 1B are kneaded to prepare kneaded product 2. [Selected Drawings] None

Description

The present invention relates to a rubber composition for bladders, a method for producing the same, and a bladder.

The bladder is used during the vulcanization molding of tires. The vulcanization bladder is placed inside the green tire, a heating medium is filled inside the vulcanization bladder, and the tire is pressed from the inside toward the vulcanization mold to vulcanize the tire. Various performance characteristics are required of the bladder, but recently there has been a demand for energy conservation and productivity improvement while maintaining these various performance characteristics.

The present invention aims to solve the above problems and provide a rubber composition for bladders that is excellent in various performances while saving energy and improving productivity, as well as a manufacturing method thereof and a bladder.

The present invention provides a rubber composition for a bladder, comprising a butyl-based rubber A, a butyl-based rubber B, and carbon black,
A base kneading step 1A in which the butyl-based rubber A and a part of the carbon black are kneaded to prepare a kneaded product 1A;
a base kneading step 1B in which the butyl-based rubber B and the remaining portion of the carbon black are kneaded to prepare a kneaded product 1B;
The present invention relates to a rubber composition for a bladder obtained by a production method including a base kneading step 2 of kneading the kneaded material 1A and the kneaded material 1B to prepare a kneaded material 2.

According to the present invention, the rubber composition for bladder contains butyl-based rubber A, butyl-based rubber B, and carbon black, and is obtained by a manufacturing method including a base kneading step 1A in which the butyl-based rubber A and a portion of the carbon black are kneaded to prepare kneaded product 1A, a base kneading step 1B in which the remaining butyl-based rubber B and the carbon black are kneaded to prepare kneaded product 1B, and a base kneading step 2 in which the kneaded product 1A and the kneaded product 1B are kneaded to prepare kneaded product 2. Therefore, it is possible to provide a rubber composition for bladder that is excellent in various performances while saving energy and improving productivity.

1 is an electron microscope photograph (SEM photograph) of a cross section of a bladder obtained in an example. 1 is an electron microscope photograph (SEM photograph) of a cross section of a bladder obtained in a comparative example.

The present invention is a rubber composition for bladder containing butyl-based rubber A, butyl-based rubber B, and carbon black, and is obtained by a manufacturing method including a base kneading step 1A in which the butyl-based rubber A and a portion of the carbon black are kneaded to prepare kneaded material 1A, a base kneading step 1B in which the remaining butyl-based rubber B and the carbon black are kneaded to prepare kneaded material 1B, and a base kneading step 2 in which the kneaded material 1A and the kneaded material 1B are kneaded to prepare kneaded material 2.

Conventionally, in the case of rubber compositions for bladders using two or more types of butyl rubber, a manufacturing method that involves four steps, for example, a step of kneading the total amount of two or more types of butyl rubber, carbon black, and oil to about 150°C, a step of kneading the resulting kneaded mixture, carbon black, zinc oxide, and antioxidant to about 135°C, a step of kneading the resulting kneaded mixture, chloroprene rubber, and stearic acid to about 130°C, and a step of kneading the resulting kneaded mixture and cross-linking chemicals to about 105°C, has been widely used. However, problems include the need to knead the chloroprene rubber and zinc oxide at a temperature that does not react in the third step, which makes it difficult to reduce viscosity, and the need for four steps, which increases power consumption.

On the other hand, in the present invention, the base kneading process 1A in which the butyl-based rubber A and a portion of the carbon black are kneaded to prepare the kneaded product 1A and the base kneading process 1B in which the remaining butyl-based rubber B and the carbon black are kneaded to prepare the kneaded product 1B are separately carried out, and then the kneaded product 1A and the kneaded product 1B prepared in advance are kneaded to prepare the kneaded product 2, thereby enabling sufficient kneading in each process. As a result, a large amount of the rubber composition for the bladder can be produced in a shorter time, and productivity can be improved. In addition, it is possible to reduce the power consumption of the kneading machine during production, and power consumption can also be reduced. Therefore, according to the present invention, it is possible to provide a rubber composition for the bladder that is excellent in various performances while saving energy and improving productivity.

First, we will explain each component used in the present invention.

(Rubber component)
The rubber component contains at least two kinds of butyl-based rubbers (butyl-based rubber A and butyl-based rubber B).
Examples of butyl-based rubbers include butyl rubber (non-halogenated butyl rubber, IIR); halogenated butyl rubber (X-IIR) such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR); and the like. These may be used alone or in combination of two or more. Among these, non-halogenated butyl rubber is more preferred because of its excellent heat resistance.

The content of isoprene in the non-halogenated butyl rubber is preferably 3 mol% or less, more preferably 2 mol% or less, because it has an excellent effect of improving heat resistance. Also, from the viewpoint of bladder life, the content of isoprene in the non-halogenated butyl rubber is preferably 0.5 mol% or more, more preferably 0.7 mol% or more, and even more preferably 1.0 mol% or more.
In the present invention, at least two types of butyl rubbers, butyl rubber A and butyl rubber B, are used. When butyl rubber A and butyl rubber B are non-halogenated butyl rubbers, it is desirable that both have an isoprene content within the above range.

Butyl rubber usually has less than 0.5% double bond sites, so even if crosslinking is performed, the number of crosslinks is extremely small. Butyl rubber is usually produced by mixing and reacting isobutylene and isoprene monomers.

In the rubber composition for bladder, the content of butyl-based rubber (total content of two or more types of butyl-based rubber) in 100% by mass of the rubber component is preferably 90% by mass or more, and more preferably 93% by mass or more, in order to maintain the performance of the rubber composition for bladder. In addition, the content of butyl-based rubber is preferably 99% by mass or less, and more preferably 97% by mass or less, in order to provide excellent air permeability resistance and heat resistance. The content of non-halogenated butyl rubber is also preferably in the same range.

The rubber composition for the bladder uses at least two types of butyl rubber, butyl rubber A and butyl rubber B. There are no particular limitations on butyl rubber A and butyl rubber B, but from the standpoint of heat resistance and bladder life, it is desirable to use butyl rubber A in which the isoprene content in the non-halogenated butyl rubber is 1.20 to 3.00 mol %, and butyl rubber B in which the isoprene content in the non-halogenated butyl rubber is 0.50 to 1.10 mol %.

The rubber composition for the bladder uses at least two types of butyl rubber, butyl rubber A and butyl rubber B. The compounding ratio of butyl rubber A and butyl rubber B is not particularly limited. For example, the mass ratio of butyl rubber A and butyl rubber B (content of butyl rubber A (parts by mass)/content of butyl rubber B (parts by mass)) is preferably 10/90 or more, more preferably 30/70 or more, and even more preferably 40/60 or more, and is preferably 90/10 or less, more preferably 70/30 or less, and even more preferably 60/40 or less. The same range is desirable when using butyl rubber A with an isoprene content of 1.20 to 3.00 mol% in the non-halogenated butyl rubber and butyl rubber B with an isoprene content of 0.50 to 1.10 mol% in the non-halogenated butyl rubber.

The rubber composition for the bladder may contain other rubber components in addition to the butyl-based rubber.
Examples of other rubber components include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), ethylene propylene diene rubber (EPDM), etc. These may be used alone or in combination of two or more. Among them, chloroprene rubber (CR) is preferable from the viewpoints of deterioration resistance, crack resistance, chemical resistance, and crosslinking speed.

In the rubber composition for bladder, the content of chloroprene rubber in 100% by mass of the rubber component is preferably 1% by mass or more, and more preferably 3% by mass or more, for the reason of maintaining the performance as a rubber composition for bladder. In addition, the content of chloroprene rubber is preferably 10% by mass or less, and more preferably 7% by mass or less, from the viewpoints of cost and productivity.

(Carbon black)
Examples of carbon black include, but are not limited to, GPF, FEF, HAF, ISAF, SAF, etc. By including carbon black, the reinforcing property can be enhanced.

The nitrogen adsorption specific surface area ( _N2SA ) of carbon black is preferably ⁴⁰ m2/g or more, more preferably ⁶⁰ m2/g or more, from the viewpoints of reinforcing power and bladder life, and is preferably ¹²⁰ _m2 /g or less, more preferably ¹⁰⁰ m2/g or less, from the viewpoints of dispersibility and bladder life.
The nitrogen adsorption specific surface area of carbon black is determined by Method A of JIS K6217.

In the rubber composition for bladder, from the viewpoint of reinforcing properties, the carbon black content is preferably 40 parts by mass or more, and more preferably 50 parts by mass or more, per 100 parts by mass of the rubber component. Also, from the viewpoint of dispersibility and bladder life, the carbon black content is preferably 80 parts by mass or less, and more preferably 70 parts by mass or less.

(oil)
The rubber composition for the bladder desirably contains oil, which can improve processability and increase rubber strength.

The oil may be, for example, process oil, vegetable oil, or a mixture thereof. Among them, vegetable oil is preferred, and castor oil is more preferred, because it is less likely to volatilize, bleeds onto the bladder surface, and can prevent adhesion to the tire cover.

In the rubber composition for bladder, from the viewpoint of preventing adhesion between the bladder and the tire cover after vulcanization, the content of the oil is preferably 0.5 parts by mass or more, and more preferably 1.0 parts by mass or more, per 100 parts by mass of the rubber component. Also, from the viewpoint of bladder life, the content of the oil is preferably 10 parts by mass or less, and more preferably 7 parts by mass or less.

(Anti-aging agent)
The rubber composition for the bladder desirably contains an antioxidant.
The antioxidant is not particularly limited, and for example, a phenol-based antioxidant (monophenol-based antioxidant, bisphenol-based antioxidant, polyphenol-based antioxidant) that enhances heat resistance is preferably used.

In the rubber composition for bladder, the content of the antioxidant is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, per 100 parts by mass of the rubber component. Within the above range, an excellent bladder life tends to be obtained.

(Zinc Oxide)
The rubber composition for the bladder preferably contains zinc oxide.
Zinc oxide acts as a crosslinking catalyst, and is therefore expected to improve bladder life. Examples of zinc oxide include zinc oxide that has been used in the rubber industry (such as zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd.).

In the rubber composition for bladder, the content of zinc oxide is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 7 parts by mass or less, per 100 parts by mass of the rubber component. If it is within the above range, an excellent bladder life tends to be obtained.

(Cross-linking agents)
The rubber composition for the bladder preferably contains a crosslinking agent.
Examples of crosslinking chemicals include crosslinking agents and crosslinking additives. These may be used alone or in combination of two or more. Among these, it is preferable to use a crosslinking agent and a crosslinking additive in combination.

The cross-linking agent is not particularly limited, and examples include sulfur and cross-linking resins. Among them, it is preferable to use cross-linking resins because they provide good dispersion of zinc oxide and the cross-linking resin itself, resulting in a sufficient bladder life.

The crosslinked resin may be an alkylphenol formaldehyde resin.
The type of alkylphenol formaldehyde resin is not particularly limited, but a non-halogenated one is preferred because of its excellent heat resistance. The content of methylol groups in the alkylphenol formaldehyde resin is usually 7 to 10 mass %.

When the rubber composition for bladder contains a crosslinking agent, the content of the crosslinking agent is preferably 5 parts by mass or more, and more preferably 7 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of forming sufficient crosslinks and imparting excellent bladder life. Furthermore, from the viewpoint of preventing excessive crosslinking and obtaining good bladder life and bladder performance, the content of the crosslinking agent is preferably 10 parts by mass or less, and more preferably 8 parts by mass or less. The content of the crosslinking resin is also desirably in the same range.

The crosslinking additives include crosslinking promoters.
Among these, it is preferable to contain a crosslinking accelerator from the viewpoint of shortening the crosslinking time.

When the rubber composition for the bladder contains a cross-linking additive, from the viewpoint of obtaining a sufficient effect of the addition, the content of the cross-linking additive is preferably 1 part by mass or more, and more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of cost and dispersibility of the cross-linking additive, the content of the cross-linking additive is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less. The content of the cross-linking accelerator is also preferably in the same range.

(Other compounding agents)
In addition to the above-mentioned components, the rubber composition for the bladder may contain additives such as a release agent, stearic acid, inorganic fillers (white carbon, silica, activated calcium carbonate, talc, alumina, etc.), organic reinforcing agents (high impact styrene resin, coumarone-indene resin, phenolic resin, lignin, modified melamine resin, petroleum resin, etc.), heat resistance improvers, flame retardants, and thermal conductivity imparting agents.

Among these, a release agent is preferable. This can prevent adhesion of the crosslinked resin to the inside of the Banbury when a crosslinked resin is used. A mixture of a fatty acid metal salt and a fatty acid amide can be preferably used as the release agent. Here, when the rubber composition for the bladder contains a release agent, the content of the release agent is preferably 0.1 to 10 parts by mass per 100 parts by mass of the rubber component.

Next, we will explain the method for producing the rubber composition for bladder of the present invention using each of the above components.

<Method of manufacturing rubber composition for bladder>
The rubber composition for bladder of the present invention contains butyl-based rubber A, butyl-based rubber B and carbon black, and is obtained by a production method including a base kneading step 1A of kneading the butyl-based rubber A and a portion of the carbon black to prepare kneaded product 1A, a base kneading step 1B of kneading the remaining butyl-based rubber B and the carbon black to prepare kneaded product 1B, and a base kneading step 2 of kneading kneaded product 1A and kneaded product 1B to prepare kneaded product 2.

(Base kneading process 1A)
In the above-mentioned production method, the butyl-based rubber A and a part of the carbon black are kneaded to obtain a kneaded product 1A.

The type of closed mixer that can be used in the base mixing step 1A is not particularly limited, and for example, any closed mixer that can control the rotor speed and confirm that the butyl rubber A and carbon black have been mixed can be used, and those that have been conventionally used in the rubber industry can be used. It should be noted that confirmation that the butyl rubber A and carbon black have been mixed can be made by monitoring the progress of the mixing torque, etc.

The base kneading process 1A can be carried out, for example, by feeding the compounding ingredients into the kneading chamber of an internal kneader, kneading the ingredients by rotating the rotor in the kneading chamber, kneading the mixture until the temperature of the mixture reaches a predetermined temperature, and then discharging the mixture.

For example, the base kneading step 1A can be carried out by starting kneading at a rotor rotation speed of 25 to 50 rpm and kneading until the kneaded material reaches 150 to 180°C. The rotor rotation speed from the start of kneading until the butyl-based rubber A and carbon black are mixed is preferably 20 to 40 rpm, more preferably 30 to 40 rpm, because this suppresses the burden on the equipment and the rise in the wearing temperature and provides an excellent dispersion effect for the carbon black. The kneading time at this rotation speed is preferably 10 seconds or more from the viewpoint of suppressing the rise in the wearing temperature, and is preferably 50 seconds or less from the viewpoint of productivity.

Among the two or more types of butyl-based rubbers used in the present invention, any of the butyl-based rubbers may be used as the butyl-based rubber A in the base kneading process 1A. When the rubber composition for the bladder contains two or more types of butyl-based rubbers, it is desirable to use a part of the two or more types as the butyl-based rubber A in the base kneading process 1A and use the remaining as the butyl-based rubber B in the base kneading process 1B. Specifically, for example, when it contains three types of butyl-based rubbers, one type of butyl-based rubber may be used as the butyl-based rubber A in the base kneading process 1A and the remaining two types of butyl-based rubber may be used as the butyl-based rubber B in the base kneading process 1B, or two types of butyl-based rubber may be used as the butyl-based rubber A in the base kneading process 1A and the remaining one type of butyl-based rubber may be used as the butyl-based rubber B in the base kneading process 1B.

In the base kneading step 1A, butyl-based rubber A is kneaded. Of the total amount of butyl-based rubber A used in the above manufacturing method (100% by mass), it is preferable to knead 80% by mass or more in the base kneading step 1A, more preferably knead 90% by mass or more, even more preferably knead 95% by mass or more, and particularly preferably knead 100% by mass (total amount).

In the base kneading step 1A, a portion of the carbon black is kneaded, and out of the total amount of carbon black used in the above manufacturing method (100% by mass), it is preferable to knead 50% by mass or more in the base kneading step 1A, more preferably knead 60% by mass or more, and even more preferably knead 70% by mass or more. As for the upper limit, it is preferable to knead 90% by mass or less, more preferably knead 85% by mass or less, and even more preferably knead 80% by mass or less.

In the base kneading step 1A, components other than the above components may be kneaded as appropriate. In particular, it is desirable to knead chloroprene rubber, oil, antioxidants, etc.

When kneading the chloroprene rubber, oil, and anti-aging agent in the base kneading step 1A, it is preferable to knead 80% by mass or more of the chloroprene rubber, oil, and anti-aging agent used in the above manufacturing method in a total amount of 100% by mass in the base kneading step 1A, more preferably knead 90% by mass or more, even more preferably knead 95% by mass or more, and particularly preferably knead 100% by mass (total amount).

(Base kneading process 1B)
In the above-mentioned production method, the butyl-based rubber B and the remaining portion of the carbon black are kneaded to obtain a kneaded product 1B. The base kneading step 1A and the base kneading step 1B are steps carried out separately and independently, and either one may be carried out first, or they may be carried out simultaneously using different kneaders.

The closed mixer that can be used in the base mixing process 1B is not particularly limited, and the same mixer as in the base mixing process 1A can be used, and mixing can be performed in the same manner.

For example, the base kneading step 1B can be carried out by starting kneading at a rotor rotation speed of 25 to 50 rpm and kneading until the kneaded material reaches 150 to 180°C. The rotor rotation speed from the start of kneading until the butyl-based rubber B and carbon black are mixed is preferably 20 to 40 rpm, more preferably 30 to 40 rpm, because this suppresses the burden on the equipment and the rise in the wearing temperature and provides an excellent dispersion effect for the carbon black. The kneading time at this rotation speed is preferably 10 seconds or more from the viewpoint of suppressing the rise in the wearing temperature, and is preferably 50 seconds or less from the viewpoint of productivity.

As described above, any one of the two or more types of butyl-based rubbers used in the present invention may be used as butyl-based rubber B in base kneading step 1B.

In the base kneading step 1B, butyl-based rubber B is kneaded. Of the total amount of butyl-based rubber B used in the above manufacturing method (100% by mass), it is preferable to knead 80% by mass or more in the base kneading step 1B, more preferably knead 90% by mass or more, even more preferably knead 95% by mass or more, and particularly preferably knead 100% by mass (total amount).

In the base kneading step 1B, the remainder of the carbon black is kneaded. Of the total amount of carbon black used in the above manufacturing method (100% by mass), it is preferable to knead 10% by mass or more in the base kneading step 1B, more preferably knead 15% by mass or more, and even more preferably knead 20% by mass or more. As for the upper limit, it is preferable to knead 50% by mass or less, more preferably knead 40% by mass or less, and even more preferably knead 30% by mass or less.

In addition, in the base kneading step 1B, ingredients other than the above ingredients may be kneaded as appropriate. In particular, it is desirable to knead zinc oxide, etc.

When zinc oxide is kneaded in the base kneading step 1B, it is preferable to knead 80% by mass or more of the total amount of zinc oxide used in the present invention (100% by mass) in the base kneading step 1B, more preferably knead 90% by mass or more, even more preferably knead 95% by mass or more, and particularly preferably knead 100% by mass (total amount).

(Base kneading process 2)
In the base kneading step 2 of the above-mentioned production method, the kneaded material 1A obtained in the base kneading step 1A and the kneaded material 1B obtained in the base kneading step 1B are kneaded.

There are no particular limitations on the type of closed mixer that can be used in base mixing process 2, and a mixer similar to that used in base mixing process 1A can be used, and mixing can be performed in the same manner.

For example, the base kneading step 2 can be carried out by kneading the kneaded material 1A and the kneaded material 1B until the kneaded material reaches 110 to 130°C. The rotation speed of the kneader is preferably 30 to 55 rpm, more preferably 30 to 40 rpm. The kneading time at this rotation speed is preferably 10 seconds or more from the viewpoint of suppressing an increase in the wearing temperature, and is preferably 50 seconds or less from the viewpoint of productivity.

In the base kneading step 2, kneaded material 1A and kneaded material 1B are kneaded together. Of the total amount of kneaded material 1A and kneaded material 1B used in the above manufacturing method (100% by mass), it is preferable to knead 80% by mass or more in the base kneading step 2, more preferably knead 90% by mass or more, even more preferably knead 95% by mass or more, and particularly preferably knead 100% by mass (total amount).

In addition, in the base kneading process 2, ingredients other than the above ingredients may be kneaded as appropriate.

(Finishing kneading process)
In the above-mentioned manufacturing method, it is preferable to carry out a finish kneading step after the base kneading step 2 in which the kneaded material 2 and a crosslinking agent are kneaded to prepare the kneaded material 3 .

There are no particular limitations on the type of internal mixer that can be used in the finishing mixing process, and the same mixer as in the base mixing process 1A can be used, and mixing can be performed in the same manner.

For example, the finishing kneading process can be carried out by starting kneading at a rotor rotation speed of 20 to 50 rpm and kneading until the kneaded material reaches 90 to 105°C. The rotor rotation speed is preferably 20 to 45 rpm. The kneading time at this rotation speed is preferably 10 seconds or more from the viewpoint of suppressing an increase in the wearing temperature, and is preferably 50 seconds or less from the viewpoint of productivity.

In the final kneading step, crosslinking chemicals such as crosslinking agents and crosslinking additives are kneaded. Of the total amount of the crosslinking agents and crosslinking additives used in the above manufacturing method (100% by mass), it is preferable to knead 80% by mass or more in the final kneading step, more preferably knead 90% by mass or more, even more preferably knead 95% by mass or more, and particularly preferably knead 100% by mass (total amount).

In the final mixing step, ingredients other than the above ingredients may be mixed in as appropriate. In particular, it is desirable to mix in a release agent, etc.

When the release agent is kneaded in the final kneading step, it is preferable to knead 80% by mass or more of the total amount of the release agent used in the present invention (100% by mass) in the final kneading step, more preferably knead 90% by mass or more, even more preferably knead 95% by mass or more, and particularly preferably knead 100% by mass (total amount).

(Crosslinking reaction process)
After the above steps are performed, a crosslinking reaction step is performed to obtain a crosslinked rubber composition for a bladder. The crosslinking reaction step can be performed, for example, by crosslinking the rubber composition (uncrosslinked rubber composition) obtained in the second finish kneading step at 170 to 210° C. for 2 to 30 minutes.

The present invention will be specifically explained based on examples, but the present invention is not limited to these.

The various chemicals used in the production of the test rubber compositions and test tires are shown below.
Butyl rubber 1: BUTYL 268 (isoprene content 1.70 mol%) manufactured by ExxonMobil Chemical Co. (non-halogenated butyl rubber)
Butyl rubber 2: BUTYL065 (isoprene content 1.05 mol%) manufactured by ExxonMobil Chemical Co. (non-halogenated butyl rubber)
Chloroprene rubber: Neoprene W manufactured by Showa Denko Co., Ltd.
Carbon black: Show Black N330 (HAF, _N2SA : ^75m2 /g) manufactured by Cabot Japan Co., Ltd.
Oil: Industrial No. 1 castor oil manufactured by Toyokuni Oil Mills Co., Ltd. Anti-aging agent: Nocrac NS-5 (2,2'-methylenebis(4-ethyl-6-tert-butylphenol) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Zinc oxide: Zinc oxide type 2 (average primary particle size: 270 nm) manufactured by Mitsui Mining & Smelting Co., Ltd.
Crosslinking resin: Takkiroll 201 (alkylphenol formaldehyde resin) manufactured by Taoka Chemical Co., Ltd.
Crosslinking accelerator: Soxinol CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Sumitomo Chemical Co., Ltd.

<Example>
(Base kneading process 1A)
Using a 1.7 L internal Banbury mixer (internal mixer), the base kneading step 1A was carried out with the chemicals (parts by mass) shown in "Base kneading step 1A" in Table 1 at the "discharge temperature" also shown in Table 1. The obtained kneaded product 1A was discharged from the Banbury mixer and then sheeted with a screw extruder and a calendar roll to obtain a sheet-shaped kneaded product 1A. It was confirmed by the kneading chart and visual observation that the rubber component and the carbon black had been mixed.

(Base kneading process 1B)
Separately, a 1.7 L closed Banbury mixer (closed mixer) was used to carry out the base kneading process 1B with the chemicals (parts by mass) shown in "Base kneading process 1B" in Table 1 at the "discharge temperature" also shown in Table 1. The obtained kneaded product 1B was discharged from the Banbury mixer and then sheeted with a screw extruder and a calendar roll to obtain a sheet-like kneaded product 1B. It was confirmed by a kneading chart and visual observation that the rubber component and the carbon black had been mixed.

(Base kneading process 2)
The sheet-shaped kneaded material 1A and the kneaded material 1B were charged into a 1.7 L closed Banbury mixer, and the base kneading step 2 was carried out at the "discharge temperature" also shown in Table 1. The obtained kneaded material 2 was discharged from the Banbury mixer, and then sheeted by a screw extruder and a calendar roll to obtain a sheet-shaped kneaded material 2.

(Finishing kneading process)
The sheet-shaped kneaded material 2 and the chemicals (parts by mass) shown in the “final kneading step” in Table 1 were charged into a 1.7 L sealed Banbury mixer, and the final kneading step was carried out at the discharge temperature also shown in Table 1 to obtain an uncrosslinked rubber composition.

The obtained uncrosslinked rubber composition was molded into a bladder shape and subjected to a crosslinking reaction at 200°C for 30 minutes to produce a bladder (tire size: 195/65R15, bladder stretch (periphery: 1.08, circum: 1.25), bladder gauge: 5 mm).

Comparative Example
(Base kneading process (1))
A 1.7 L internal Banbury mixer was used to carry out a base kneading process with the chemicals (parts by mass) shown in "Base kneading process (1)" in Table 2 at the "discharge temperature" also shown in Table 2. The obtained kneaded product (1) was discharged from the Banbury mixer and then sheeted with a screw extruder and a calendar roll to obtain a sheet-like kneaded product (1). It was confirmed by a kneading chart and visual observation that the rubber component and the carbon black had been mixed.

(Base kneading process (2))
The sheet-like kneaded material (1) and the chemicals (parts by mass) shown in "Base kneading step (2)" in Table 2 were charged into a 1.7 L closed Banbury mixer, and the base kneading step (2) was carried out at the "discharge temperature" also shown in Table 2. The obtained kneaded material (2) was discharged from the Banbury mixer, and then sheeted using a screw extruder and a calendar roll to obtain a sheet-like kneaded material (2). It was confirmed by a kneading chart and visual observation that the rubber component and the carbon black had been mixed.

(Base kneading process (3))
The sheet-like kneaded material (2) and the chemicals (parts by mass) shown in "Base kneading step (3)" in Table 2 were charged into a 1.7 L sealed Banbury mixer, and the base kneading step (3) was carried out at the "discharge temperature" also shown in Table 2. The obtained kneaded material (3) was discharged from the Banbury mixer, and then sheeted with a screw extruder and a calendar roll to obtain a sheet-like kneaded material (3).

(Finishing kneading process)
The sheet-shaped kneaded product (3) and the chemicals (parts by mass) shown in the “final kneading step” in Table 2 were charged into a 1.7 L sealed Banbury mixer, and the final kneading step was carried out at the discharge temperature also shown in Table 2 to obtain an uncrosslinked rubber composition.

The obtained uncrosslinked rubber composition was molded into a bladder shape and subjected to a crosslinking reaction at 200°C for 30 minutes to produce a bladder (tire size: 195/65R15, bladder stretch (periphery: 1.08, circum: 1.25), bladder gauge: 5 mm).

The manufacturing processes and bladders of the examples and comparative examples were evaluated as follows. The results are shown in Tables 1 and 2 and Figures 1 and 2.

<Energy saving>
In the above manufacturing process, the power consumption (kW/batch) of the kneader per process (batch) was measured.

<Productivity>
In the above production process, the production amount (kg/h) of the uncrosslinked rubber composition per hour was measured.

<Dispersibility of zinc oxide>
The cross section of the resulting bladder was observed under an electron microscope to check the dispersion state of zinc oxide.

From the evaluation results in Tables 1 and 2, the Example was able to reduce energy consumption and improve productivity compared to the Comparative Example. Also, from Figures 1 and 2, it was observed that the bladder of the Example had zinc oxide dispersibility equal to or greater than that of the bladder of the Comparative Example.

The present invention (1) is a rubber composition for a bladder, comprising a butyl-based rubber A, a butyl-based rubber B, and carbon black,
A base kneading step 1A in which the butyl-based rubber A and a part of the carbon black are kneaded to prepare a kneaded product 1A;
a base kneading step 1B in which the butyl-based rubber B and the remaining portion of the carbon black are kneaded to prepare a kneaded product 1B;
The rubber composition for a bladder is obtained by a production method including a base kneading step 2 of kneading the kneaded material 1A and the kneaded material 1B to prepare a kneaded material 2.

The present invention (2) is a rubber composition for bladder according to the present invention (1), in which chloroprene rubber, oil and an antioxidant are further kneaded in the base kneading step 1A.

The present invention (3) is a rubber composition for bladder according to the present invention (1) or (2), in which zinc oxide is further mixed in the base kneading step 1B.

The present invention (4) is further a rubber composition for bladder, which is obtained by a manufacturing method including a finishing kneading step of kneading the kneaded material 2 with a crosslinking agent to produce the kneaded material 3, and is any combination of the present inventions (1) to (3).

The present invention (5) is a rubber composition for a bladder in any combination with any of the present inventions (1) to (4), in which the base kneading process 1A is kneaded until the temperature of the kneaded product 1A reaches 150 to 180°C.

The present invention (6) is a rubber composition for a bladder, which is any combination of the present inventions (1) to (5), in which the base kneading process 1B is kneaded until the temperature of the kneaded product 1B reaches 150 to 180°C.

The present invention (7) is a rubber composition for a bladder, which is any combination of the present inventions (1) to (6), in which the base kneading process 2 is kneaded until the temperature of the kneaded material 2 reaches 110 to 130°C.

The present invention (8) is a rubber composition for bladder in any combination with any of the present inventions (1) to (7), in which the finishing kneading process is performed until the temperature of the kneaded material 3 reaches 90 to 105°C.

The present invention (9) is a bladder using a rubber composition for a bladder in any combination with any of the present inventions (1) to (8).

The present invention (10) is a method for producing a rubber composition for a bladder, comprising:
A base kneading step 1A in which the butyl-based rubber A and a part of the carbon black are kneaded to prepare a kneaded product 1A;
a base kneading step 1B in which the butyl-based rubber B and the remaining portion of the carbon black are kneaded to prepare a kneaded product 1B;
The method for producing a rubber composition for a bladder includes a base kneading step 2 of kneading the kneaded material 1A and the kneaded material 1B to prepare a kneaded material 2.

Claims (10)

A rubber composition for a bladder comprising a butyl-based rubber A, a butyl-based rubber B, and carbon black,
A base kneading step 1A in which the butyl-based rubber A and a part of the carbon black are kneaded to prepare a kneaded product 1A;
a base kneading step 1B in which the butyl-based rubber B and the remaining portion of the carbon black are kneaded to prepare a kneaded product 1B;
The rubber composition for a bladder is obtained by a production method including a base kneading step 2 of kneading the kneaded material 1A and the kneaded material 1B to prepare a kneaded material 2. The rubber composition for bladder according to claim 1, further comprising chloroprene rubber, oil and antioxidant in base kneading step 1A. The rubber composition for bladder according to claim 1 or 2, further comprising zinc oxide mixed in the base mixing step 1B. The rubber composition for bladder according to claim 1 or 2, obtained by a manufacturing method further including a finishing kneading step of kneading the kneaded material 2 with a crosslinking agent to produce the kneaded material 3. The rubber composition for bladder according to claim 1 or 2, wherein the base kneading step 1A is performed until the temperature of the kneaded material 1A reaches 150 to 180°C. The rubber composition for bladder according to claim 1 or 2, wherein the base kneading step 1B is kneaded until the temperature of the kneaded material 1B reaches 150 to 180°C. The rubber composition for bladder according to claim 1 or 2, wherein the base kneading step 2 is performed until the temperature of the kneaded material 2 reaches 110 to 130°C. The rubber composition for bladder according to claim 1 or 2, wherein the finishing kneading step is performed until the temperature of the kneaded material 3 reaches 90 to 105°C. A bladder using the rubber composition for bladders according to claim 1 or 2. A method for producing a rubber composition for a bladder, comprising:
A base kneading step 1A in which the butyl-based rubber A and a part of the carbon black are kneaded to prepare a kneaded product 1A;
a base kneading step 1B in which the butyl-based rubber B and the remaining portion of the carbon black are kneaded to prepare a kneaded product 1B;
A method for producing a rubber composition for a bladder, comprising: a base kneading step 2 of kneading the kneaded material 1A and the kneaded material 1B to prepare a kneaded material 2.

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