JP2020075982A - Rubber composition for inner liner, and pneumatic tire - Google Patents

Abstract

To provide a rubber composition for an inner liner that can give a vulcanized rubber excellent in air permeability resistance and resistance to flexing fatigue.SOLUTION: A rubber composition for an inner liner has a carbon black and a modified silicone oil having a silanol group at a molecular terminal thereof.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for an inner liner and a pneumatic tire.

  In a tubeless pneumatic tire, a rubber layer having low air permeability (having air permeability resistance) called an inner liner is provided on the inner surface of the tire in order to ensure airtightness. Further, the inner liner is usually made of butyl rubber having a lower air permeability (having air permeation resistance) than an ordinary rubber layer constituting a tread, a sidewall, or the like.

  Further, in order to further improve the air permeation resistance, it is known to compound a flat filler into a rubber composition for an inner liner. However, when a flat filler is blended, a problem that the flexural fatigue resistance of the crosslinked rubber obtained from the rubber composition is deteriorated occurs, so that it is possible to improve the air permeation resistance and the flexural fatigue resistance in a well-balanced manner. It is required (Patent Document 1).

  Further, it is known that the rubber composition for the innerliner preferably does not contain a softening agent such as process oil or a plasticizer such as phthalate ester from the viewpoint of suppressing deterioration of air permeation resistance (Patent: Reference 2).

JP, 2011-168666, A JP, 2009-24101, A

  On the other hand, in the rubber composition for the inner liner, it is required to have more excellent air permeation resistance and bending fatigue resistance, but the vulcanized rubber obtained from the rubber composition as in the above Patent Document, There was room for improvement in these characteristics.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition for an inner liner, from which a vulcanized rubber having excellent air permeation resistance and flex fatigue resistance can be obtained.

  The present invention relates to a rubber composition containing carbon black, which contains a modified silicone oil having a silanol group at a molecular end thereof, and a rubber composition for an innerliner.

  Further, the present invention relates to a pneumatic tire including an inner liner made of the rubber composition.

  The details of the mechanism of action of the effect of the rubber composition for an inner liner according to the present invention are unclear, but it is presumed as follows. However, the present invention may not be construed as being limited to this mechanism of action.

  The rubber composition for an inner liner of the present invention contains carbon black and a modified silicone oil having a silanol group at the molecular end. As described in Patent Document 2 above, it is usually not preferable to add a softening agent such as process oil to the rubber composition for the inner liner. However, in the rubber composition for an inner liner of the present invention, the modified silicone oil having a silanol group at the molecular end can react with a hydroxy group or a carboxy group on the surface of carbon black in the rubber composition. Since the crosslinked rubber obtained from contains a highly polar carbon black (carbon black that has reacted with silicone oil), it is estimated that it is difficult for nitrogen and oxygen to dissolve in the crosslinked rubber. Excellent air permeability. Further, it is presumed that the modified silicone oil having a silanol group at the molecular end reacts with a hydroxy group or a carboxy group on the surface of carbon black, whereby the aggregation of carbon blacks can be suppressed during the mixing of the rubber composition. As a result, the crosslinked rubber is excellent in flex fatigue resistance.

<Rubber composition>
The rubber composition of the present invention is a rubber composition for an inner liner containing carbon black and a modified silicone oil having a silanol group at the terminal.

<Carbon black>
As the carbon black of the present invention, for example, a conductive carbon black such as acetylene black or Ketjen black may be used in addition to carbon black used in a usual rubber industry such as SAF, ISAF, HAF, FEF and GPF. You can The carbon black may be a granulated carbon black or a non-granulated carbon black that has been granulated in consideration of its handling property in the usual rubber industry. Carbon black may be used alone or in combination of two or more kinds.

From the viewpoint of improving the adhesiveness of the crosslinked rubber, the carbon black preferably has an iodine adsorption amount of 5 mg / g or more, more preferably 15 mg / g or more, and 150 mg / g or less. It is preferably 100 mg / g or less, more preferably 55 mg / g or less. Further, the carbon black is, DBP (dibutyl phthalate) oil absorption amount ^is preferably at 40 cm 3/100 g or ^more, more preferably 75 cm 3/100 g or more, ^and, not more than 150 cm 3/100 g ^preferably, more preferably not more than 125 cm 3/100 g. Here, the iodine adsorption amount is a value measured according to JIS K6217-1, and the DBP oil absorption amount is a value measured according to JIS K6217-4.

  From the viewpoint of improving the reinforcing property of the vulcanized rubber, the carbon black is preferably 20 parts by weight or more, and more preferably 30 parts by weight or more, based on 100 parts by weight of the rubber component in the rubber composition. The content is preferably 40 parts by weight or more, and more preferably 100 parts by weight or less, and more preferably 70 parts by weight or less, from the viewpoint of suppressing increase in viscosity of the rubber composition. And more preferably 60 parts by weight or less.

<Modified silicone oil having a silanol group at the molecular end>
The modified silicone oil having a silanol group at the molecular end of the present invention is an organopolysiloxane compound having a silanol group introduced into the side chain and / or the end of the silicone oil. The silanol group may be present at both ends of the molecule, or may be present at one end. From the viewpoint of improving the air permeation resistance and flex fatigue resistance of the crosslinked rubber, a modified silicone oil having silanol groups at both ends of the molecule is preferable. The modified silicone oil having a silanol group at the molecular end is preferably an organopolysiloxane compound whose main skeleton is polydimethylsiloxane, from the viewpoint of easy availability.

Modified silicone oils having a silanol group at the molecular end, a viscosity at 25 ° C. under, from the viewpoint of improving the processability of the rubber composition is preferably from 100,000mm ² / s, 10,000mm ² / S or less, more preferably 5,000 mm ² / s or less, further preferably 1,000 mm ² / s or less, further preferably 500 mm ² / s or less. It is most preferably 100 mm ² / s or less.

  Examples of commercial products of the modified silicone oil having a silanol group at the molecular end include, for example, trade names “X-21-5841” and “KF-9701” manufactured by Shin-Etsu Chemical Co., Ltd .; YF3800 "," XF3905 "," YF3057 "," YF3807 "," YF3802 "," YF3897 "," XC96-723 "; product names" DMS-S12 "," DMS-S14 ", and" DMS "manufactured by Gelest. -S15 "," DMS-S21 "," DMS-S27 "," DMS-S31 "," DMS-S32 "," DMS-S33 "," DMS-S35 "," DMS-S42 "," DMS-S45 ". , ”“ DMS-S51 ”and the like.

  From the viewpoint of improving the flex fatigue resistance of the vulcanized rubber, the modified silicone oil having a silanol group at the molecular end is 0.1 part by weight or more based on 100 parts by weight of the rubber component in the rubber composition. Is preferable, more preferably 0.5 part by weight or more, further preferably 1 part by weight or more, and from the viewpoint of improving the air permeation resistance of the crosslinked rubber, 10 parts by weight or less. It is preferably 8 parts by weight or less, more preferably 6 parts by weight or less.

  In the present invention, a rubber composition for an inner liner can be prepared using at least the carbon black and the modified silicone oil having a silanol group at the molecular end. Further, examples of the raw material of the rubber composition for the inner liner include rubber, a flat filler, a tackifier, various compounding agents and the like which are usually used in the rubber industry.

<Rubber>
As the rubber, it is preferable to use a butyl rubber from the viewpoint of improving the air permeation resistance of the crosslinked rubber. Examples of the butyl rubber include halogenated butyl rubber such as brominated butyl rubber and chlorinated butyl rubber; butyl rubber. The butyl rubber may be used alone or in combination of two or more kinds.

  From the viewpoint of improving the air permeation resistance of the crosslinked rubber, the butyl rubber is preferably the halogenated butyl rubber, and is preferably 60% by weight or more in the butyl rubber component of the rubber composition.

  The rubber includes, for example, natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), nitrile rubber (NBR) together with the butyl rubber. ) And other synthetic diene rubbers can be used. Further, the synthetic diene rubber may be a modified diene rubber into which an amino group, an alkoxysilane group, a hydroxy group, an epoxy group, a carboxy group, a cyano group, a halogen or the like is introduced. The synthetic diene rubber and the modified diene rubber may be used alone or in combination of two or more kinds.

  When the butyl rubber and the synthetic diene rubber are used together as the rubber, the butyl rubber is contained in the rubber component of the rubber composition in an amount of 60 parts by weight or more from the viewpoint of improving the air permeation resistance of the crosslinked rubber. Is preferable, 80 parts by weight or more is preferable, and 90 parts by weight or more is more preferable.

<Flat filler>
The tabular filler is a filler in which the main shape of particles is a tabular shape, and the air permeation resistance of the inner liner can be improved by inhibiting air permeation in the rubber layer. That is, since the inner liner composed of a thin rubber layer is usually extruded into a sheet shape by a roll or an extruder, the flat filler is laid in the rubber layer substantially parallel to the layer surface. It is arranged in. Therefore, the air that tries to pass through the rubber layer in the thickness direction is blocked by the flat filler so that the air permeation is hindered.

  Examples of the flat filler include inorganic fillers such as layered minerals such as talc, mica, and clay; organic fillers such as pulverized coal. The pulverized coal is flat particles obtained by pulverizing coal with a pulverizer such as a ball mill. As the flat filler, it is preferable to use crushed coal because it has good compatibility with the rubber component and excellent dispersibility in the rubber component.

  The tabular filler preferably has an average particle size measured by a laser diffraction / scattering method of about 0.5 to 100 μm, more preferably about 1 to 30 μm.

  From the viewpoint of improving the air permeation resistance of the vulcanized rubber, the flat filler is preferably 5 parts by weight or more, and 8 parts by weight or more with respect to 100 parts by weight of the rubber component in the rubber composition. More preferably, and from the viewpoint of improving flex fatigue resistance of the crosslinked rubber, it is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and 20 parts by weight or less. More preferable.

<Tackifier>
The tackifier is an additive that imparts tackiness to the rubber composition, and is also called a tackifier. By blending a tackifier, it is possible to increase the adhesiveness at the joint portion of the inner liner and prevent the joint portion from opening before the vulcanization after molding the green tire, and to prevent the inner liner from sticking to the carcass ply. Adhesiveness can also be improved.

  Examples of the tackifier include alkylphenol resins and hydrocarbon resins. From the viewpoint of improving the air permeation resistance of the crosslinked rubber, it is preferable to use a hydrocarbon resin as the tackifier.

  Examples of the hydrocarbon resin include aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins. The aliphatic petroleum resin is a resin obtained by cationically polymerizing an unsaturated monomer such as isoprene or cyclopentadiene, which is a petroleum fraction having 4 to 5 carbon atoms (C5 fraction) (C5 petroleum). It is also referred to as a resin) or hydrogenated. The aromatic petroleum resin is a resin obtained by cationically polymerizing a petroleum fraction having 8 to 10 carbon atoms (C9 fraction) such as vinyltoluene, alkylstyrene, and indene (C9 fraction). It is also called petroleum resin.), And may be hydrogenated. The aliphatic / aromatic copolymer petroleum resin is a resin obtained by copolymerizing the C5 fraction and the C9 fraction (also referred to as C5 / C9 petroleum resin), and is hydrogenated. May be The hydrocarbon resin is preferably a petroleum resin containing a C5 component as a main component.

  The tackifier is preferably 1 part by weight or more, more preferably 2 parts by weight or more, and 15 parts by weight or less with respect to 100 parts by weight of the rubber component in the rubber composition. Is preferred and 10 parts by weight or less is more preferred.

  Examples of the various compounding agents include vulcanizing agents, vulcanization accelerators, antioxidants, silica, silane coupling agents, zinc oxide, methylene acceptors and methylene donors, organic acid cobalt salts, stearic acid, vulcanizing agents. Examples thereof include accelerator aids, vulcanization retardants, organic peroxides, softeners such as waxes and oils, and processing aids.

  The vulcanizing agent may be an ordinary vulcanizing agent for rubber, and a sulfur-based vulcanizing agent is preferable. The sulfur as the sulfur-based vulcanizing agent may be ordinary sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. The vulcanizing agent may be used alone or in combination of two or more kinds.

  The content of the vulcanizing agent is preferably 0.05 to 2 parts by weight, and more preferably 0.1 to 1 part by weight, based on 100 parts by weight of the rubber component in the rubber composition.

  The vulcanization accelerator may be an ordinary rubber vulcanization accelerator, and may be a sulfenamide vulcanization accelerator, a thiuram vulcanization accelerator, a thiazole vulcanization accelerator, or a thiourea vulcanization accelerator. , Guanidine vulcanization accelerators, dithiocarbamate vulcanization accelerators and the like. The vulcanization accelerator may be used alone or in combination of two or more kinds.

  The content of the vulcanization accelerator is preferably 0.5 to 5 parts by weight, and more preferably 1 to 3 parts by weight with respect to 100 parts by weight of the rubber component in the rubber composition.

  The method of compounding (adding) the carbon black, the modified silicone oil having a silanol group at the molecular end, the rubber, the tabular filler, the tackifier, and the various compounding agents is, for example, a Banbury mixer or a kneader. A method of kneading with a kneader such as a roll used in a usual rubber industry is used.

  The method of kneading is not particularly limited, for example, a component other than the vulcanizing components such as a sulfur-based vulcanizing agent and a vulcanization accelerator, a method of adding and kneading in any order, a method of simultaneously adding and kneading Further, a method of adding all the components at the same time and kneading, and the like can be mentioned. Further, the number of times of kneading may be once or plural times. The kneading time varies depending on the size of the kneading machine used and the like, but is usually about 2 to 5 minutes. The discharge temperature of the kneader is preferably 100 to 170 ° C, more preferably 110 to 160 ° C. The discharge temperature of the kneader is preferably 80 to 110 ° C, and more preferably 80 to 100 ° C when the vulcanizing component is included.

  A method of molding the rubber composition into an inner liner is carried out by extruding it into a sheet form with a roll or an extruder in accordance with a conventional method, and then adhering the extruded sheet form to the inside of the rubber constituting the tread or the sidewall. It may be vulcanized. According to such a molding method, a tubeless pneumatic tire having an inner liner made of a thin rubber layer on the inner surface of the tire can be formed. The thickness of the inner liner varies depending on the tire size and the like, but is usually 0.5 to 3 mm.

  The use of the rubber composition for an inner liner of the present invention is not particularly limited, but it is suitable for heavy-duty pneumatic tires such as trucks and buses that require high air permeation resistance.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Raw materials used)
a) Brominated butyl rubber: "Bromobutyl 2222" (manufactured by Nippon Butyl Co., Ltd.)
b) Carbon black: "Seast V (GPF)" (manufactured by Tokai Carbon Co., Ltd.)
c) Coal pulverized product: pulverized bituminous coal, "Austin Black 325" (manufactured by Coal Fillers), (average particle size 5 μm)
d) Tackifier: "T-REZ RA100" (manufactured by Tonen Chemical Co., Ltd.)
e) Oil (A): Silicone oil modified with silanol at both ends, “X-21-5841” (manufactured by Shin-Etsu Chemical Co., Ltd.), (viscosity at 25 ° C. is 30 mm ² / s).
f) Oil (B): Silicone oil modified with silanol at both ends, “YF3802” (manufactured by Momentive), (viscosity at 25 ° C. is 80,000 mm ² / s)
g) Oil (C): "Process NC-140" (manufactured by JX Nikko Nisseki Energy Co., Ltd.)
h) Zinc oxide: "Three types of zinc oxide" (Mitsui Mining & Smelting Co., Ltd.)
i) Stearic acid: "Palmac 1500 Beads" (manufactured by IOI Acidchem Sdn Bhd)
j) Vulcanization accelerator: "NOXCELLER DM-P" (manufactured by Ouchi Shinko Chemical Co., Ltd.)
k) Sulfur: “Fine powder sulfur containing 5% oil” (manufactured by Tsurumi Chemical Industry Co., Ltd.)

<Examples 1-3, Comparative Examples 1-2>
<Production of rubber composition and unvulcanized rubber composition>
A rubber composition was produced by dry-mixing each raw material (components excluding sulfur and vulcanization accelerator) shown in Table 1 with a Banbury mixer (kneading time: 3 minutes, discharge temperature: 120 ° C.). did. Next, the sulfur and vulcanization accelerator shown in Table 1 were added to the obtained rubber composition, and dry mixing was performed using a Banbury mixer (kneading time: 1 minute, discharge temperature: 90 ° C.). A vulcanized rubber composition was produced. The compounding ratios in Table 1 are shown in parts by weight (phr) when the rubber component contained in the rubber composition is 100 parts by weight.

<Manufacture of vulcanized rubber>
A vulcanized rubber was produced by vulcanizing the unvulcanized rubber compositions obtained in the above Examples and Comparative Examples under conditions of 160 ° C. and 30 minutes. The following evaluation was performed on the obtained vulcanized rubber. The evaluation results are shown in Table 1.

<Evaluation of air permeation resistance>
For the evaluation of the air permeation resistance, the air permeation rate of the vulcanized rubber sheet having a thickness of 1 mm was measured using a gas permeation rate tester (“BT-3” manufactured by Toyo Seiki Seisakusho Ltd.), and Comparative Example 1 was set to 100. Displayed as an index. The larger the value, the better the air permeation resistance.

<Evaluation of flex fatigue resistance>
The evaluation of flex fatigue resistance was based on the evaluation of flex fatigue resistance of JIS K6260 (Demacha flex crack test), and the number of times until the crack growth of the vulcanized rubber test piece became 2 mm was obtained, and Comparative Example 1 The value of was set to 100 and displayed as an index. The larger the value, the better the fatigue resistance.

Claims (3)

A rubber composition containing carbon black,
A rubber composition for an inner liner, which comprises a modified silicone oil having a silanol group at the molecular end.   The inner layer according to claim 1, wherein the modified silicone oil having a silanol group at the molecular end is 0.1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the rubber component in the rubber composition. Rubber composition for liner.   A pneumatic tire comprising an inner liner made of the rubber composition according to claim 1.