JP2010285525A - Rubber composition for bladder, and bladder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a bladder, capable of sufficiently achieving the elongation of the life of the bladder, and to provide the bladder produced by using the composition. <P>SOLUTION: The rubber composition for the bladder includes a rubber component containing a butyl rubber and zinc oxide having an average primary particle diameter of 15-190 nm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a rubber composition for bladder and a bladder using the same.

In the tire manufacturing process, the green tire obtained in the molding process is changed to a vulcanized rubber structure having elasticity in the vulcanization process. In the vulcanization step, the green tire is usually heated from the outer surface by a method such as attaching a mold to a jacket type hot platen. Further, from the inner surface of the green tire, a bladder having a bag shape is inserted into the tire, and steam or the like is injected and heated.

Since the bladder is repeatedly used under heating conditions, high heat resistance is required. Therefore, in the rubber composition for bladder, there is a case where not the vulcanization using sulfur but the metal crosslinking using zinc oxide or the above-mentioned metal crosslinking and crosslinking using a crosslinking resin such as a reactive alkylphenol resin may be used in combination. Is almost.

Conventionally, zinc oxide having an average primary particle size of 200 to 600 nm (JIS grades 1 to 3) has been used as zinc oxide, increasing the amount of zinc oxide or improving the dispersion of zinc oxide during mixing. Attempts have been made to improve the life of the bladder. However, in the method of increasing the amount, the effect of improving the life of the bladder is small for increasing the amount of expensive zinc oxide, and the method of improving the dispersion during mixing has a certain effect, but it is dispersed to some extent. If this happens, there is a problem that the life of the bladder cannot be improved any more, and the life of the bladder will end, and there is still room for improvement in extending the life of the bladder.

Patent Document 1 discloses a rubber composition for a bladder that prevents aggregation of zinc oxide and extends the life of the bladder by blending a large amount of sulfur. However, there is still room for improvement in extending the life of bladders. Patent Document 2 discloses a tread rubber composition containing fine particle state zinc oxide. However, the addition of fine particle state zinc oxide does not improve the strength of the rubber, but destroys zinc oxide. It only prevents it from becoming a nucleus. Moreover, application to a rubber composition for bladders has not been studied.

JP-A-2005-75891 JP 2008-101127 A

An object of the present invention is to solve the above-mentioned problems, and to provide a rubber composition for a bladder that can sufficiently achieve a long life of the bladder, and a bladder manufactured using the rubber composition.

As a result of intensive studies, the inventor has drastically improved the life of the bladder by blending zinc oxide having a smaller average primary particle size than the zinc oxide blended in the rubber composition for bladders. I came to find.
That is, the present invention relates to a rubber composition for a bladder containing a rubber component containing a butyl rubber and zinc oxide having an average primary particle size of 15 to 190 nm.

It is preferable to contain 2 to 12 parts by mass of the zinc oxide with respect to 100 parts by mass of the rubber component.

The content of butyl rubber in 100% by mass of the rubber component is preferably 90% by mass or more.

The content of chloroprene rubber in 100% by mass of the rubber component is preferably 3 to 10% by mass.

The butyl rubber is preferably a non-halogenated butyl rubber.

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

According to the present invention, since it is a rubber composition containing a specific rubber component and zinc oxide having a specific average primary particle size, the life of a bladder manufactured using the rubber composition can be dramatically improved. Can do. Conventionally, carbon black has been used to improve rubber reinforcement, and it is known that reducing the average primary particle size of carbon black increases the surface area in contact with the polymer, thus improving the strength of the rubber. Yes. On the other hand, since zinc oxide has a significantly smaller reinforcing property than carbon black, even when zinc oxide is finely divided, there is hardly any improvement in rubber strength due to an increase in specific surface area. In the present invention, the life of the bladder could be dramatically improved because when the bladder is used for vulcanization of the tire, the polymer contained in the bladder is gradually pyrolyzed, but the average primary particle By using zinc oxide with a small diameter, the specific surface area of zinc oxide is increased, and the radical generated when the polymer is thermally decomposed can be more effectively captured by the zinc oxide, thereby suppressing thermal decomposition of the polymer. This is presumably because the heat resistance of the bladder was improved.
Moreover, by using the bladder produced using the rubber composition of the present invention, it is possible to reduce the number of times the bladder is replaced at the time of tire production, and it is possible to increase the productivity of tire production. Furthermore, since a small amount of bladder is required to manufacture a certain amount of tire, the amount of rubber necessary to manufacture the bladder can be reduced. In this way, it is possible to achieve significant cost reduction and resource saving.

The rubber composition for bladders of the present invention contains a rubber component containing butyl rubber and zinc oxide having an average primary particle size of 15 to 190 nm.

In the present invention, butyl rubber is used as the rubber component. Examples of the butyl rubber include halogenated butyl rubber (X-IIR) such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR), butyl rubber (IIR) (hereinafter, distinguished from halogenated butyl rubber, Also referred to as non-halogenated butyl rubber). These butyl rubbers may be used alone or in combination of two or more. Of these, non-halogenated butyl rubber is preferable from the viewpoint of high heat resistance.

The content of isoprene in the non-halogenated butyl rubber is preferably 2 mol% or less, and more preferably 1.6 mol% or less. When it exceeds 2 mol%, the heat resistance of the bladder is lowered, and it may be difficult to obtain the effect of improving the bladder life. The content of isoprene in the non-halogenated butyl rubber is preferably 0.5 mol% or more, and more preferably 0.7 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.

The content of butyl rubber in 100% by mass of the rubber component is preferably 90% by mass or more, more preferably 92% by mass or more. If the content of butyl rubber is less than 90% by mass, the heat resistance of the rubber composition is lowered, and even if zinc oxide having a specific average primary particle size is used, the life of the bladder may not be dramatically improved. is there. The butyl rubber content is preferably 97% by mass or less, more preferably 95% by mass or less. When the content of butyl rubber exceeds 97% by mass, crosslinking by rubber other than butyl rubber is insufficient and the rubber becomes soft, and it may be difficult to maintain the rigidity required for the bladder.

Other rubber components include ethylene-propylene-diene rubber (EPDM), natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and epoxidized natural rubber (ENR). Diene rubbers such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), styrene-isoprene-butadiene copolymer rubber (SIBR) may be blended. These diene rubbers may be used alone or in combination of two or more. Among these, CR is preferable from the viewpoint of ensuring the vulcanization speed of the bladder rubber.

When CR is blended as a rubber component, the CR content in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more. If the CR content is less than 1% by mass, it may be difficult to maintain the rigidity required for the bladder. The CR content is preferably 10% by mass or less, more preferably 7% by mass or less. When the content of CR exceeds 10% by mass, the content of butyl rubber is lowered and sufficient heat resistance may not be obtained.

Examples of the shape of zinc oxide include a spherical shape, a circular shape, an elliptical shape, a plate shape, a square shape, a hexagonal shape, a polygonal shape, a rhombus shape, a rectangular shape, and a random shape. In the present invention, the shape of zinc oxide was measured using an electron microscope.

The average primary particle diameter of zinc oxide is 15 nm or more, preferably 25 nm or more, more preferably 30 nm or more. If it is less than 15 nm, it is difficult to uniformly disperse zinc oxide in the rubber composition, and there is a possibility that the intended life enhancement effect of the bladder cannot be obtained. The average primary particle diameter of zinc oxide is 190 nm or less, preferably 120 nm or less, more preferably 75 nm or less. If it exceeds 190 nm, the effect of suppressing the thermal decomposition of the polymer by zinc oxide is reduced, and there is a possibility that the intended life enhancement effect of the bladder may not be obtained.

In the present invention, the average primary particle diameter of zinc oxide is the primary particle diameter when converted from a specific surface area measured by the BET method to a true spherical particle model.
Here, the primary particle diameter when converted from the specific surface area to the true spherical particle model can be calculated by the following relational expression. When the primary particles are regarded as ideal spheres, the relationship represented by the following formula is established between the surface area S, volume V, density ρ, and specific surface area SSA of each particle.
SSA = 1 / (V · ρ) × S
Here, since V and S are physical quantities that are uniquely determined by the particle diameter, the particle diameter can be obtained from the specific surface area and density. The density can be easily determined by, for example, a commercially available pycnometer.

The content of zinc oxide is preferably 2 parts by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 2 parts by mass, the absolute amount of zinc oxide is insufficient, and the life of the bladder may not be dramatically improved. Further, the content of zinc oxide is preferably 12 parts by mass or less, more preferably 10 parts by mass or less. When the amount exceeds 12 parts by mass, the life of the bladder commensurate with the amount of zinc oxide blended cannot be achieved, the blending cost increases, and there is a tendency to become ineffective.

The rubber composition of the present invention preferably contains a crosslinked resin. Examples of the crosslinked resin include alkylphenol formaldehyde resins. There is no restriction | limiting in particular about the kind of alkylphenol formaldehyde resin. The content of methylol groups in the alkylphenol formaldehyde resin is usually 7 to 10% by mass.

When the crosslinked resin is blended, the content of the crosslinked resin is preferably 2 parts by mass or more, and more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, the reinforcing property is inferior and the durability tends to be poor. Further, the content of the crosslinked resin is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. If it exceeds 20 parts by mass, the workability during kneading tends to deteriorate.

The rubber composition of the present invention preferably contains carbon black. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited. By blending carbon black, it is possible to enhance the reinforcement.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 40 m ² / g or more, more preferably 60 m ² / g or more. If 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 of the carbon black is preferably 120 m ² / g or less, more preferably 100 m ² / g or less. When it exceeds 120 m ² / g, the finished bladder becomes too hard, and the fit with the tire cover to be vulcanized is deteriorated, and a defective tire may be easily generated.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

When carbon black is blended, the content of carbon black is preferably 40 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 40 parts by mass, it may be difficult to obtain sufficient reinforcement. Further, the carbon black content is preferably 80 parts by mass or less, more preferably 70 parts by mass or less. When the amount exceeds 80 parts by mass, the finished bladder becomes too hard, and the fit with the tire cover to be vulcanized is deteriorated, and a defective tire may be easily generated.

The rubber composition of the present invention preferably contains oil. By blending oil, processability can be improved and the strength of the rubber can be increased. As the oil, for example, process oil, vegetable oil, or a mixture thereof can be used.

Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil (aromatic process oil). As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut hot water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Among these, vegetable oils and castor oil are preferably used from the viewpoint of bleeding on the bladder surface and preventing adhesion to the tire cover.

When the rubber composition contains oil, the oil content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.5 parts by mass, there is a risk that adhesion between the bladder and the tire cover is likely to occur after vulcanization. The oil content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. When it exceeds 10 mass parts, the ratio of butyl rubber will fall and a bladder life will fall.

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 increases heat resistance is preferably used.
Examples of monophenol antioxidants include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butylphenol, 1 -Oxy-3-methyl-4-isopropylbenzene, butylhydroxyanisole, 2,4-dimethyl-6-tert-butylphenol, n-octadecyl-3- (4'-hydroxy-3 ', 5'-di-tert- Butylphenyl) propionate, styrenated phenol and the like.
Examples of bisphenol aging inhibitors and polyphenol aging inhibitors include 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2′-methylene-bis- (4-ethyl-6). -Tert-butylphenol), 4,4'-butylidene-bis- (3-methyl-6-tert-butylphenol), 1,1'-bis- (4-hydroxyphenyl) -cyclohexane, tetrakis- [methylene-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane and the like.

When the rubber composition contains an anti-aging agent, the content of the anti-aging agent is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component. .
If it is less than 0.1 parts by mass, the heat resistance of the bladder rubber is lowered, and the bladder life may be lowered. Further, the content of the anti-aging agent is preferably 5 parts by mass or less, more preferably 3 parts by mass or less. If it exceeds 5 parts by mass, the effect of improving the heat resistance due to the increased amount may not appear clearly, and the blending cost may increase.

In addition to the above components, the rubber composition for bladder of the present invention comprises stearic acid, inorganic fillers (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, thermal conductivity imparting agent and the like can be added.

The rubber composition for bladders of the present invention can be produced, for example, by the following method.
First, the kneading process will be described. The kneading process of the present embodiment includes a base kneading process and a finishing kneading process. In the kneading step, for example, the components are kneaded using a kneader. A conventionally known kneader can be used, and examples thereof include a Banbury mixer, a kneader, and an open roll.

<Base kneading process>
In the base kneading step, for example, components other than zinc oxide and the crosslinked resin (butyl rubber, carbon black, oil, chloroprene rubber, anti-aging agent, etc.) among the above components are kneaded using a kneader.
The base kneading step has the following two steps (first base) because it ensures dispersibility of the carbon black used and suppresses thermal decomposition of other rubbers (eg, chloroprene rubber) that are inferior in heat resistance to butyl rubber. The kneading step and the second base kneading step are preferably performed separately.

<First base kneading step>
In the first base kneading step, for example, components such as butyl rubber, carbon black, and oil are kneaded using a kneader.
In the first base kneading step, it is preferable to knead a rubber composition having a temperature at the start of kneading of 10 to 40 ° C. until the temperature (kneading temperature) of the rubber composition reaches 150 to 180 ° C. If it is lower than 150 ° C., it may be difficult to ensure the dispersibility of the carbon black. On the other hand, if it exceeds 180 ° C., a gelation phenomenon due to carbon black occurs, and the kneaded rubber sheet may not be neatly organized.
In the first base kneading step, the rotational speed of the kneader is preferably 40 to 70 rpm from the viewpoint of ensuring productivity and dispersibility of carbon black.

<Second base kneading process>
In the second base kneading step, components such as chloroprene rubber and anti-aging agent are kneaded with the rubber composition obtained by kneading in the first base kneading step using a kneader. In the second base kneading step, it is preferable to knead a rubber composition having a temperature at the start of kneading of 10 to 40 ° C. until the temperature (kneading temperature) of the rubber composition reaches 120 to 140 ° C. If it is lower than 120 ° C., it may be difficult to ensure dispersion of the chloroprene rubber, and the homogeneity of the finished bladder rubber may be reduced, and as a result, the bladder life may be reduced.
On the other hand, when it exceeds 140 ° C., the thermal decomposition of the chloroprene rubber proceeds, and the bladder life tends to decrease.
In the second base kneading step, it is preferable that the rotational speed of the kneader is 30 to 55 rpm from the viewpoint of dispersibility of chloroprene rubber and suppression of thermal decomposition.

<Finish kneading process>
In the final kneading step, components such as zinc oxide and a crosslinked resin are kneaded with the rubber composition obtained by kneading in the second base kneading step, for example, using a kneader.
In addition, since the average primary particle diameter of zinc oxide used in the present invention is small, it is difficult for zinc oxide to disperse, and further, after the kneaded rubber composition is cooled and then kneaded again, This finish kneading step is performed in the following 3 steps because the uniform diffusibility of zinc oxide is improved, the re-aggregation rate of zinc oxide when using the bladder is delayed, and the lamination phenomenon due to the thermal deterioration of the bladder rubber can be suppressed. It is preferable to divide into the steps (first finishing kneading step, cooling step, second finishing kneading step). This is presumed to be because the shear stress acting on the rubber composition increases when the kneading is performed again after the cooling, and the uniform diffusibility of zinc oxide is improved.

<First finishing kneading process>
In the first finishing kneading step, components such as zinc oxide and a crosslinked resin are kneaded with the rubber composition obtained by kneading in the second base kneading step, for example, using a kneader. In the first finishing kneading step, it is preferable to knead a rubber composition having a temperature at the start of kneading of 10 to 40 ° C. until the temperature (kneading temperature) of the rubber composition reaches 90 to 105 ° C. If the temperature is lower than 90 ° C, the uniform diffusibility of zinc oxide may be insufficient. On the other hand, if the temperature exceeds 105 ° C, the crosslinking reaction may start.
In the first finishing kneading step, it is preferable that the rotational speed of the kneader is 20 to 45 rpm from the viewpoint of dispersibility of zinc oxide and prevention of the crosslinking reaction.

<Cooling process>
Next, in the cooling step, it is preferable that the temperature of the rubber composition (kneaded material) containing at least butyl rubber and zinc oxide kneaded in the first finishing kneading step is preferably 20 to 40 ° C. . The method of cooling is not particularly limited, and examples thereof include a method of cooling by contact with air (cold air), a method of cooling by contacting a metal plate or the like, a method of cooling in a water tank, and the like. When the temperature after cooling is less than 20 ° C., there is no adverse effect on the present invention, but the cooling time becomes long and the productivity may be lowered. On the other hand, when the temperature after cooling exceeds 40 ° C., the shearing force in the second finishing kneading step is insufficient, and the uniform diffusibility of zinc oxide is lowered, which may make it difficult to obtain the effects of the present invention.

<Second finishing kneading process>
Next, using a kneader, the rubber composition cooled in the cooling step is heated from a temperature of 20 to 40 ° C. at the start of kneading until the temperature of the rubber composition (kneading temperature) reaches 90 to 105 ° C. It is preferable to knead. If the kneading temperature is less than 90 ° C., the uniform diffusibility of zinc oxide may be insufficient. On the other hand, if the kneading temperature exceeds 105 ° C., the crosslinking reaction may start.
In the second finishing kneading step, it is preferable to set the rotational speed of the kneader to 20 to 45 rpm from the viewpoint of dispersibility of zinc oxide and prevention of the crosslinking reaction.

In the present invention, it is preferable to carry out each of the above steps within the above temperature range, but the temperature at the start of kneading in the second base kneading step and the temperature at the start of kneading in the first finishing kneading step are the above. In order to adjust the temperature range, a cooling step may be introduced between the first base kneading step and the second base kneading step and between the second base kneading step and the first finishing kneading step. . The cooling step can be performed in the same manner as the cooling step described above. Alternatively, the rubber composition prepared in the first base kneading step and the second base kneading step may be allowed to cool until it reaches the temperature at the start of kneading in the next step.

<Crosslinking reaction process>
After performing the above kneading process, the rubber composition for bladders of the present invention is obtained by performing a crosslinking reaction process. The said crosslinking reaction process can be implemented by performing a crosslinking reaction for 240 to 30 minutes at 170-210 degreeC, for example by the rubber composition (non-crosslinked rubber composition) obtained by the 2nd finishing kneading | mixing process.

The rubber composition for bladders of the present invention can be suitably used as a bladder for tire production.

The bladder of the present invention is extruded by an extruder using the rubber composition for uncrosslinked bladder of the present invention (the above-mentioned uncrosslinked rubber composition) and molded into the shape of a bladder. It can be produced by performing a crosslinking reaction for 30 minutes.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Butyl rubber 268: BUTYL268 manufactured by ExxonMobil Chemical Co., Ltd. (content of isoprene 1.6 mol%) (non-halogenated butyl rubber)
Butyl rubber 065: BUTYL065 manufactured by ExxonMobil Chemical Co., Ltd. (content of isoprene 0.8 mol%) (non-halogenated butyl rubber)
Chloroprene rubber: Neoprene W manufactured by Showa Denko K.K.
Carbon Black: Show Black N330 (N ₂ SA75m ² / g) manufactured by Cabot Japan
Castor oil: No. 1 castor oil for industrial use manufactured by Toyokuni Oil Co., Ltd. Zinc oxide: Two types of zinc white (average primary particle size 270 nm) manufactured by Mitsui Mining & Smelting Co., Ltd.
Fine zinc oxide 1: Ultra fine zinc oxide F-1 (average primary particle size 100 nm) manufactured by Hakusuitec Co., Ltd.
Fine particle zinc oxide 2: Ultra fine particle zinc oxide F-2 (average primary particle size 65 nm) manufactured by Hakusui Tech Co., Ltd.
Fine zinc oxide 3: Ultra fine zinc oxide FINEX-30 (average primary particle size 35 nm) manufactured by Sakai Chemical Industry Co., Ltd.
Fine zinc oxide 4: Ultra fine zinc oxide FINEX-50 (average primary particle size 20 nm) manufactured by Sakai Chemical Industry Co., Ltd.
Cross-linked resin: Tacroll 201 (alkylphenol formaldehyde resin) manufactured by Taoka Chemical Co., Ltd.
Anti-aging agent: Nocrack NS-5 (2,2′-methylenebis (4-ethyl-6-tert-butylphenol)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

Examples 1-8 and Comparative Examples 1-2
In accordance with the formulation shown in Table 1, using a 240 L Banbury mixer, the non-halogenated butyl rubber (butyl rubber 065 and butyl rubber 268), carbon black, and castor oil were first heated to 160 ° C. at a filling rate of 70%. Until kneading (temperature at the start of kneading 30 ° C.) (kneading speed 55 rpm). Thereafter, chloroprene rubber and an antioxidant were added, and a rubber composition having a temperature of 30 ° C. at the start of kneading was kneaded until the temperature of the rubber composition reached 130 ° C. (rotation speed: 45 rpm). Further, zinc oxide and an alkylphenol formaldehyde resin were added, and a rubber composition having a temperature at the start of kneading of 30 ° C. was kneaded until the temperature of the rubber composition reached 100 ° C. (rotation speed: 35 rpm). The kneaded rubber composition was once cooled to 30 ° C. and then charged again into a Banbury mixer, and kneaded until the temperature of the rubber composition reached 100 ° C. (rotation speed: 35 rpm) 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, whereby a bladder (tire size: 195 / 65R15, bladder stretch (periphery: 1.08, Circum: 1. 25), bladder gauge: 5 mm).

The obtained bladder is used for tire molding (180 ° C, tire vulcanization conditions for 12 minutes), and the number of times of use is 600 to 1000 times. As a result of observing the presence / absence of occurrence, when the lamination grew in the state of the bladder rubber and the length was 5 mm or more, the number of times of use was defined as the number of times of bladder life.

According to Table 1, an example using zinc oxide having a specific average primary particle size dramatically improves the number of times of bladder life compared to a comparative example using zinc oxide having a larger average primary particle size. I was able to.

Claims (6)

A rubber composition for a bladder comprising a rubber component containing a butyl rubber and zinc oxide having an average primary particle size of 15 to 190 nm. The rubber composition for bladders according to claim 1, comprising 2 to 12 parts by mass of the zinc oxide with respect to 100 parts by mass of the rubber component. The rubber composition for bladders according to claim 1 or 2, wherein the content of butyl rubber in 100% by mass of the rubber component is 90% by mass or more. The rubber composition for bladders according to any one of claims 1 to 3, wherein the content of chloroprene rubber in 100% by mass of the rubber component is 3 to 10% by mass. The rubber composition for a bladder according to any one of claims 1 to 4, wherein the butyl rubber is a non-halogenated butyl rubber. The bladder produced using the rubber composition for bladders in any one of Claims 1-5.