JP6488118B2 - Rubber composition for bladder, method for producing the same, and bladder - Google Patents

Description

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

  The bladder is used for vulcanization molding of tires. The vulcanization bladder is placed inside the green tire, and the inside of the vulcanization bladder is filled with a heating medium, and the tire is pressed from the inside toward the vulcanization mold. By doing so, the tire is vulcanized.

  Since the bladder is repeatedly used for vulcanization molding of tires under high pressure and high temperature conditions of 180 to 200 ° C., butyl rubber (IIR) excellent in heat resistance is mainly used for the rubber composition constituting the bladder. Furthermore, since the deterioration resistance, crack resistance, chemical resistance and vulcanization speed are comprehensively excellent, a rubber component obtained by adding chloroprene rubber (CR) to butyl rubber is used (for example, Patent Document 1).

  A rubber composition containing a conventional rubber composition for bladders is produced by a production method including a kneading step of kneading raw materials to obtain an uncrosslinked rubber composition and a crosslinking step of crosslinking the uncrosslinked rubber composition. . And a kneading | mixing process can be performed by dividing into the base kneading process which knead | mixes raw materials other than a crosslinking chemical | drug | medicine, and the process including the finishing kneading process which knead | mixes a crosslinking chemical | medical agent in the kneaded material obtained at the base kneading | mixing process. The base kneading process and the finishing kneading process are performed in a kneader such as a closed kneader, and the obtained kneaded material is discharged from the kneader, extruded by a screw extruder, and processed into a sheet shape by sheeting with a calender roll. It is transported to the process.

JP2012-092243A

  However, the kneaded product containing chloroprene rubber reduces the biting into the screw of the screw extruder and the roll of the calender roll. For example, after discharging from the kneader, it takes time to be seated and the productivity is deteriorated. There's a problem.

  The present invention relates to a rubber composition for a bladder, which is excellent in productivity because the kneaded product is well bitten into a screw and a roll, despite being a rubber composition containing a rubber component including chloroprene rubber. And it aims at providing the manufacturing method.

The present invention is a rubber composition for bladder containing a rubber component containing chloroprene rubber, oil, carbon black and a crosslinking chemical,
A base in which rubber components other than chloroprene rubber, oil, and carbon black are started to be kneaded at a rotor rotation speed of 20 to 40 rpm with a closed kneader, and after the rubber component and carbon black are mixed, the base is kneaded at a rotor rotation speed of more than 40 to 60 rpm. Kneading process 1,
The kneaded product obtained in the base kneading step 1 and the chloroprene rubber are kneaded until the temperature of the kneaded product reaches 110 to 130 ° C., and the kneaded product obtained in the base kneading step 2 and the crosslinking chemical The present invention relates to a rubber composition for bladders produced by a production method including a finish kneading step of kneading the above.

  The content of the chloroprene rubber in the rubber component is preferably 1 to 7% by mass.

  The rubber component other than chloroprene rubber is preferably a butyl rubber.

  Moreover, this invention relates to the bladder manufactured using the said rubber composition for bladders.

Furthermore, the present invention is a method for producing a rubber composition for bladder containing a rubber component containing chloroprene rubber, oil, carbon black and a crosslinking chemical,
A base in which rubber components other than chloroprene rubber, oil, and carbon black are started to be kneaded at a rotor rotation speed of 20 to 40 rpm with a closed kneader, and after the rubber component and carbon black are mixed, kneading at a rotor rotation speed of more than 40 to 60 rpm Kneading process 1,
The kneaded product obtained in the base kneading step 1 and the chloroprene rubber are kneaded until the temperature of the kneaded product reaches 110 to 130 ° C., and the kneaded product obtained in the base kneading step 2 and the crosslinking chemical The present invention relates to a method for producing a rubber composition for a bladder, which includes a finishing kneading step of kneading the above.

  A rubber composition for a bladder containing a rubber component containing the chloroprene rubber of the present invention, oil, carbon black and a crosslinking chemical, which is produced by a production method including predetermined base kneading steps 1 and 2 and a finishing kneading step According to the rubber composition, the bladder manufactured using the rubber composition, and the method for manufacturing the rubber composition, the kneaded product can be satisfactorily bited into the screw and the roll, and the bladder is excellent in productivity. A rubber composition, a bladder produced using the rubber composition, and a method for producing the rubber composition can be provided.

<Rubber composition for bladder>
The rubber composition for bladder of the present invention is a rubber composition for bladder containing a rubber component containing chloroprene rubber, oil, carbon black and a crosslinking chemical, and includes predetermined base kneading steps 1 and 2 and a finish kneading step. It is the rubber composition for bladders manufactured by the manufacturing method.

Rubber component The rubber component contains chloroprene rubber. By containing chloroprene rubber, a rubber composition for bladders excellent in deterioration resistance, crack resistance, chemical resistance and crosslinking speed can be obtained.

  The content of the chloroprene rubber in the rubber component is preferably 1% by mass or more, and more preferably 3% by mass or more, from the viewpoint of maintaining performance as a rubber composition for bladders. Moreover, 10 mass% or less is preferable from a viewpoint of cost and productivity, and, as for content of chloroprene rubber, 7 mass% or less is more preferable.

  The rubber component contains a rubber component other than chloroprene rubber. Examples of rubber components other than chloroprene rubber include butyl rubber and diene rubber. Examples of the butyl rubber include halogenated butyl rubber (X-IIR) such as butyl rubber (non-halogenated butyl rubber, IIR), brominated butyl rubber (Br-IIR), and chlorinated butyl rubber (Cl-IIR). Diene rubbers include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and ethylene propylene diene rubber. (EPDM). These rubber components other than chloroprene rubber may be used alone or in combination of two or more.

  Of these, butyl rubber is preferable because of its excellent heat resistance, and non-halogenated butyl rubber is more preferable because of its particularly high heat resistance. Furthermore, it is more preferable to use a rubber component consisting only of chloroprene rubber and butyl rubber, and a rubber component consisting only of chloroprene rubber and non-halogenated butyl rubber, because of its excellent performance as a rubber composition for bladders. Is most preferred.

  The content of isoprene in the non-halogenated butyl rubber is preferably 3 mol% or less, more preferably 2 mol% or less, because it is excellent in the effect of improving heat resistance. Further, 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 further preferably 1.0 mol% or more. If it is less than 0.5 mol%, the rubber strength cannot be improved by crosslinking, and the bladder life may be reduced.

  Note that butyl rubber usually has only a double bond site of 0.5% or less, and the number of crosslinks becomes extremely small even when crosslinks are carried out. The butyl rubber can be usually produced by mixing and reacting isobutylene and isoprene monomers.

  The content of the butyl rubber in the rubber component when the butyl rubber is contained (the total content when two or more types are used in combination) is 90% by mass or more from the reason of maintaining the performance as a rubber composition for bladders. Is preferable, and 93 mass% or more is more preferable. Further, the content of the butyl rubber is preferably 99% by mass or less, and more preferably 97% by mass or less, because it is excellent in air permeation resistance and heat resistance.

Oil By containing the oil, processability can be improved and rubber strength can be increased. As the oil, for example, process oil, vegetable oil, or a mixture thereof can be used. Among these, vegetable oils and fats are preferable, and castor oil is more preferable because it is difficult to volatilize, bleeds on the bladder surface, and can be prevented from sticking to the tire cover.

  The content of oil with respect to 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 1.0 part by mass or more. If the amount is less than 0.5 parts by mass, the bladder and the tire cover may be easily adhered after vulcanization. The oil content is preferably 10 parts by mass or less, and more preferably 7 parts by mass or less. When it exceeds 10 mass parts, there exists a tendency for a bladder life to fall.

Carbon black Reinforcing property can be improved by containing the carbon black. Examples of carbon black include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 40 m ² / g or more, and more preferably 60 m ² / g or more. When it is less than 40 m ² / g, the reinforcing force is insufficient, and the bladder life may be easily lowered. Further, the N ₂ SA is preferably 120 m ² / g or less, and more preferably 100 m ² / g or less. When exceeding 120 m < ² > / g, it is difficult to disperse | distribute a filler, crack resistance (durability) may fall or it may become hard locally, and there exists a possibility that a bladder life may fall. In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

  The content of carbon black with respect to 100 parts by mass of the rubber component is preferably 40 parts by mass or more, and more preferably 50 parts by mass or more. If the amount is less than 40 parts by mass, sufficient reinforcing properties may not be obtained. The carbon black content is preferably 80 parts by mass or less, and more preferably 70 parts by mass or less. When the amount exceeds 80 parts by mass, it is difficult to disperse the filler, crack resistance (durability) may be lowered, or it may be locally hardened, and the bladder life may be reduced.

Crosslinking chemicals Examples of the crosslinking chemicals include crosslinking agents and crosslinking additives, which may be used alone or in combination of two or more. It is preferable to use a crosslinking agent and a crosslinking additive in combination.

  Examples of the crosslinking agent include sulfur and a crosslinked resin, and it is preferable to use a crosslinked resin because the dispersion of zinc oxide and the crosslinked resin itself is good and a sufficient bladder life is obtained. Examples of the crosslinked resin include alkylphenol formaldehyde resins. Although there is no restriction | limiting in particular about the kind of alkylphenol formaldehyde resin, From the point which is excellent in heat resistance, the non-halogenated thing which is not halogenated is preferable. The content of methylol groups in the alkylphenol formaldehyde resin is usually 7 to 10% by mass.

  The content with respect to 100 parts by mass of the rubber component when the crosslinking agent is contained is preferably 5 parts by mass or more, and more preferably 7 parts by mass or more. When the amount is less than 5 parts by mass, crosslinking is insufficient and the bladder life tends to be reduced. Moreover, 10 mass parts or less are preferable and, as for content of a crosslinking agent, 8 mass parts or less are more preferable. When it exceeds 10 mass parts, it will become excessive crosslinking and there exists a tendency for a bladder life and a bladder performance to fall.

  Examples of the cross-linking additive include a cross-linking accelerator, and a cross-linking accelerator is preferably contained because the cross-linking time can be shortened.

  When the crosslinking additive is contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, and more preferably 3 parts by mass or more. When the amount is less than 1 part by mass, the effect of containing a crosslinking additive tends to be insufficient. Moreover, 10 mass parts or less are preferable, and, as for content of a crosslinking additive, 5 mass parts or less are more preferable. When it exceeds 10 mass parts, there exists a tendency for the raise of cost and the dispersion | distribution defect of a crosslinking additive to occur.

Other compounding agents In addition to the above components, the rubber composition for bladders of the present invention comprises zinc oxide, anti-aging agent, mold release agent, stearic acid, inorganic filler (white carbon, silica, activated calcium carbonate, talc, alumina. Etc.), organic reinforcing agents (high impact styrene resin, coumarone indene resin, phenol resin, lignin, modified melamine resin, petroleum resin, etc.), heat resistance improver, flame retardant, heat conduction imparting agent, etc. can be added. .

  The rubber composition of the present invention preferably contains zinc oxide. Since zinc oxide acts as a catalyst for crosslinking, an improvement in bladder life can be expected. Examples of zinc oxide include zinc oxide conventionally used in the rubber industry (such as zinc oxide manufactured by Mitsui Metal Mining Co., Ltd.).

  As the anti-aging agent, for example, a phenol-based anti-aging agent (monophenol-based anti-aging agent, bisphenol-based anti-aging agent, polyphenol-based anti-aging agent) that improves heat resistance is preferably used.

  The rubber composition of the present invention preferably contains a release agent. Thereby, when a crosslinked resin is used, adhesion of the crosslinked resin into the banbury can be suppressed. As a mold release agent, a mixture of a fatty acid metal salt and a fatty acid amide can be suitably used. Here, as for content in the case of containing a mold release agent, 0.1-10 mass parts is preferable with respect to 100 mass parts of rubber components.

<Bladder>
The bladder of the present invention can be produced by performing extrusion reaction with an extruder using the above-mentioned uncrosslinked rubber composition for bladder, forming into the shape of a bladder, and then performing a crosslinking reaction.

<Method for producing rubber composition for bladder>
The manufacturing method of the rubber composition for bladders of the present invention is a manufacturing method including base kneading steps 1 and 2 and a finishing kneading step.

Base kneading process 1
The base kneading step 1 is a base kneading step in which rubber components other than chloroprene rubber, oil, and carbon black are kneaded under a predetermined rotor rotation condition by a closed kneader. Before adding chloroprene rubber, rubber components other than chloroprene rubber, oil and carbon black can be kneaded at high temperature by kneading them under the prescribed rotor rotation conditions, so dispersion of carbon black in rubber components other than chloroprene rubber Can be improved. Furthermore, it can suppress that the kneaded material after adding and kneading chloroprene rubber becomes difficult to bite into a screw or a roll. Since the temperature rises due to friction between the carbon black and the rotor in the kneading machine, it is preferable to knead at a predetermined low rotational speed until the rubber component and the carbon black are mixed.

  The closed kneader used in the base kneading step 1 is not particularly limited as long as it is a closed kneader capable of controlling the number of rotations of the rotor described later and confirming that the rubber component and carbon black are mixed. It is possible to use what has been used in the past.

  In the base kneading step 1, the compounding agent is charged into the kneading chamber of the closed kneader and then kneaded by rotating the rotor in the kneading chamber, kneaded until the temperature of the kneaded product reaches a predetermined discharge temperature, and discharged. It is a process to do. In the base kneading step 1 in the method for producing a rubber composition for a bladder of the present invention, kneading is started at a rotor rotational speed of 20 to 40 rpm, and after the rubber component and carbon black are mixed, the exhaust temperature at a rotor rotational speed of more than 40 to 60 rpm. It is characterized by kneading until it reaches.

  The rotor rotational speed from the start of kneading until the rubber component and carbon black are mixed is 20 to 40 rpm because it suppresses the burden on the equipment and the increase in the wearing temperature, and is excellent in the dispersion effect of carbon black. 40 rpm is preferred. The shorter the kneading time based on the number of revolutions, the better. However, if it is less than 10 seconds, the wearing temperature tends to increase, and therefore it is preferably 10 seconds or more. Moreover, since kneading time will become long and productivity tends to fall when it exceeds 50 seconds, 50 seconds or less are preferable.

  Here, confirmation that the rubber component and the carbon black are mixed can be performed by the transition of the kneading torque or the like.

  The rotor rotational speed after the rubber component and carbon black are mixed is 40 to 60 rpm, and preferably 50 to 60 rpm, because the kneading time can be shortened and the productivity is improved. The kneading time based on the number of rotations is preferably 30 to 150 seconds, and more preferably 60 to 90 seconds. When the kneading time is less than 30 seconds, the carbon black tends to be poorly dispersed. Moreover, when it exceeds 90 seconds, there exists a tendency for productivity to deteriorate.

  120-180 degreeC is preferable and, as for the discharge temperature in the base kneading process 1, 140-160 degreeC is more preferable. When the discharge temperature is less than 120 ° C., the carbon black tends to be poorly dispersed. Moreover, when it exceeds 180 degreeC, there exists a possibility that a rubber component may ignite.

  The amount of the rubber component other than chloroprene rubber added in the base kneading step 1 is preferably 100% by mass of the rubber component content other than the total chloroprene rubber in the rubber composition.

  The amount of oil added in the base kneading step 1 is preferably 100% by mass of the total oil content in the rubber composition. If oil is contained in the same process as carbon black, the rotor may slip.

  The amount of carbon black added in the base kneading step 1 is preferably 100% by mass of the total carbon black content in the rubber composition. When carbon black is divided and added, the dispersibility of carbon black tends to deteriorate.

  Further, in addition to rubber components other than chloroprene rubber, oil and carbon black, kneading a compounding agent other than a cross-linking chemical such as zinc oxide and an anti-aging agent in the base kneading step 1 improves dispersibility and processability. Preferred for reasons.

Base kneading process 2
The base kneading step 2 is a step of kneading the kneaded product obtained in the base kneading step 1 and chloroprene rubber. By kneading the kneaded product obtained in the base kneading step 1 and chloroprene rubber at a predetermined discharge temperature, the rubber component becomes soft and processability is improved, and the kneaded kneaded product is bitten into a screw or a roll. Becomes better.

  The kneader used in the base kneading step 2 is not particularly limited as long as it can adjust the discharge temperature, and a closed kneader conventionally used in the rubber industry can be used.

  The discharge temperature in the base kneading step 2 is 110 to 130 ° C., preferably 115 to 125 ° C., from the viewpoint of suppressing shrinkage and preventing the rubber temperature from being improved.

  The rotor rotational speed in the base kneading step 2 is not particularly limited, and may be set to a rotational speed conventionally used in the rubber industry.

  The amount of chloroprene rubber added in the base kneading step 2 is preferably 100% by mass of the total chloroprene rubber in the rubber composition. When chloroprene rubber is added in another step, processability tends to deteriorate and dispersibility tends to decrease.

Finishing and kneading step The finishing and kneading step is a step of kneading the kneaded product obtained in the base kneading step 2 and the crosslinking chemical.

  The kneader used in the finishing kneading step is not particularly limited as long as the discharge temperature can be adjusted, and a closed kneader conventionally used in the rubber industry can be used.

  80-110 degreeC is preferable and, as for the discharge temperature in a finishing kneading process, 85-100 degreeC is more preferable. When the discharge temperature is less than 80 ° C., the dispersion tends to be poor. Moreover, when it exceeds 110 degreeC, there exists a tendency for vulcanization to start.

  The rotor rotational speed in the finishing kneading process is not particularly limited, and may be set to a rotational speed conventionally used in the rubber industry.

  The manufacturing method of the rubber composition of the present invention can be a conventional manufacturing method except that the kneading step is included. That is, it can be set as the manufacturing method etc. which vulcanize | curing after that the kneaded material obtained with the said kneading | mixing method can be used.

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

Various chemicals used for the production of the test rubber composition and the test tire are shown below.
Butyl rubber 1: BUTYL268 manufactured by ExxonMobil Chemical Co., Ltd. (content of isoprene 1.70 mol%) (non-halogenated butyl rubber)
Butyl rubber 2: BUTYL065 manufactured by ExxonMobil Chemical Co. (content of isoprene: 1.05 mol%) (non-halogenated butyl rubber)
Chloroprene rubber: Neoprene W manufactured by Showa Denko K.K.
Carbon Black: Show Black N330 (HAF, N ₂ SA: 75 m ² / g) manufactured by Cabot Japan
Oil: Industrial No. 1 castor oil anti-aging agent manufactured by Toyokuni Oil Co., Ltd .: Nocrack NS-5 (2,2′-methylenebis (4-ethyl-6-tert-butylphenol) manufactured by Ouchi Shinsei Chemical Co., Ltd. ))
Zinc oxide: 2 types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. (average primary particle size: 270 nm)
Cross-linked resin: Tacroll 201 (alkylphenol formaldehyde resin) manufactured by Taoka Chemical Co., Ltd.
Crosslinking accelerator: Soxinol CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Sumitomo Chemical Co., Ltd.

Examples and Comparative Examples Using a 1.7 L closed Banbury mixer (closed kneader), the chemicals (parts by mass) shown in “Base kneading step 1” in Table 1 are also shown in “Rotor speed” shown in Table 1. ”And“ discharge temperature ”, the base kneading step 1 was performed. The obtained kneaded product was discharged from a Banbury mixer and then sheeted with a screw extruder and a calender roll to obtain a sheet-like kneaded product 1. The mixing of the rubber component and carbon black was confirmed by a kneading chart and visual observation.

  Next, the sheet-like kneaded product 1 and the chemicals (parts by mass) shown in “Base kneading step 2” in Table 1 were charged into a 1.7 L closed Banbury mixer, and the base kneading was performed at the “discharge temperature” shown in Table 1 as well. Step 2 was performed. The obtained kneaded product was discharged from a Banbury mixer and then sheeted with a screw extruder and a calender roll to obtain a sheet-like kneaded product 2. Further, the sheet-like kneaded product 2 and the chemicals (parts by mass) shown in “Finish kneading step” in Table 1 are charged into a 1.7 L closed Banbury mixer, and the finishing kneading step is performed at the discharge temperature shown in Table 1 as well. An uncrosslinked rubber composition was obtained. The following evaluation was performed about the manufacturing process and kneaded material of each Example and the comparative example. The results are shown in Table 1.

<Carbon dispersibility evaluation>
The dispersion state of carbon black in the sheet-like kneaded material 1 obtained in the base kneading step 1 was measured by a microtome method. Larger values indicate better carbon black dispersion. The performance target value is 90% or more, preferably 95% or more.

<Poor polymer crush failure evaluation>
In the sheet-like kneaded product 2 obtained in the base kneading step 2 , the presence or absence of raw material rubber not incorporating carbon black or oil was visually confirmed and evaluated according to the following criteria. Note that ○ is the performance target.
○: A clean rubber sheet without a hole was made. △: There was a hole in the sheet but a rubber sheet was made. ×: A lump of rubber component was clearly left.

<Roll / screw biting evaluation>
The state of biting of the kneaded product obtained in the base kneading step 2 into the calendar roll was visually confirmed and evaluated according to the following criteria. Note that ○ is the performance target value.
○: Immediately bitten into the calendar roll Δ: Bittened into the calendar roll in less than 30 seconds ×: It took 30 seconds or longer to be bitten

<Wearing temperature abnormality evaluation>
The wear ring temperature in the base kneading step 1 was confirmed with a thermometer of a kneader and evaluated according to the following criteria. Note that ○ is the performance target.
○: 100 ° C. or less Δ: More than 100 ° C., 110 ° C. or less ×: More than 110 ° C.

  From the results shown in Table 1, the rubber composition for bladders produced by the production method including the predetermined base kneading steps 1 and 2 and the finish kneading step has good biting into the screw and roll and is excellent in productivity. It can be seen that this is a rubber composition for a bladder.

Claims (5)

Rubber component, an oil, a bladder rubber composition containing carbon black and crosslinking chemicals,
The rubber component consists only of 1 to 10% by mass of chloroprene rubber and 90 to 99% by mass of butyl rubber,
Containing 100 to 10 parts by mass of the rubber component, 0.5 to 10 parts by mass of oil, 40 to 80 parts by mass of carbon black,
Start kneading the whole amount of butyl rubber , oil, and carbon black with a closed kneader at a rotor speed of 20 to 40 rpm, and after the rubber component and carbon black are mixed, knead at a rotor speed of over 40 to 60 rpm. Base kneading process 1,
A base kneading step 2 for kneading the kneaded product obtained in the base kneading step 1 and the total amount of chloroprene rubber until the temperature of the kneaded product becomes 110 to 130 ° C .;
A step of discharging the kneaded product obtained in the base kneading step 2 from the closed kneader and then sheeting with a screw extruder and a calender roll to obtain a sheet-like kneaded product 2 ;
And a rubber composition for a bladder produced by a production method including a final kneading step of kneading the sheet-like kneaded product 2 and a crosslinking chemical. The rubber composition for a bladder according to claim 1, wherein the content of the chloroprene rubber in the rubber component is 1 to 7% by mass. Furthermore, the rubber composition for bladders containing zinc oxide, Comprising: The rubber composition for bladders of Claim 1 or 2 which adds the whole quantity of a zinc oxide at the base kneading process 1. The bladder manufactured using the rubber composition for bladders of any one of Claims 1-3. Rubber component, an oil, a process for the preparation of the bladder rubber composition containing carbon black and crosslinking chemicals,
The rubber component consists only of 1 to 10% by mass of chloroprene rubber and 90 to 99% by mass of butyl rubber,
Containing 100 to 10 parts by mass of the rubber component, 0.5 to 10 parts by mass of oil, 40 to 80 parts by mass of carbon black,
Start kneading the whole amount of butyl rubber , oil, and carbon black with a closed kneader at a rotor speed of 20 to 40 rpm, and after the rubber component and carbon black are mixed, knead at a rotor speed of over 40 to 60 rpm. Base kneading process 1,
A base kneading step 2 for kneading the kneaded product obtained in the base kneading step 1 and the total amount of chloroprene rubber until the temperature of the kneaded product becomes 110 to 130 ° C .;
A step of discharging the kneaded product obtained in the base kneading step 2 from the closed kneader and then sheeting with a screw extruder and a calender roll to obtain a sheet-like kneaded product 2 ;
And a method for producing a rubber composition for a bladder, which includes a finishing kneading step of kneading the sheet-like kneaded product 2 and a crosslinking chemical.