JPH1087884A - Rubber composition for tire inner liner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for tire inner liners which gives an unvulcanized compound improved in processability and productivity without detriment to vulcanizate properties such as E' (storage modulus) and tanδ. SOLUTION: This composition is prepared by mixing 100 pts.wt. rubber component composed of at least 50 pts.wt. butyl rubber and at most 50 pts.wt. diene rubber with 20-120 pts.wt. carbon black having a nitrogen adsorption specific surface area of 60m<2> /g or below and at most 10 pts.wt. polysiloxane containing alkoxysilyl groups (≡Si-OR<1> ) or acyloxysilyl groups (≡Si-OCOR<2> ) (wherein R<1> is a 1-18 C substituted or unsubstituted monovalent hydrocarbon group or an ethereal organic group; and R<2> is hydrogen or a 1-21 C hydrocarbon group) and having an average degree of polymerization of 3-10,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to passenger cars and trucks,
More particularly, the present invention relates to a rubber composition for an inner liner of a pneumatic tire such as a bus, and more particularly to a method of reducing viscosity or scorch without substantially impairing vulcanization properties such as storage elastic modulus (E ') and tan δ, which are viscoelastic properties. The present invention relates to a rubber composition for an inner liner of a tire, which can improve the processability of an unvulcanized compound by elongating the time and improve the productivity by shortening the vulcanization time.

[0002]

2. Description of the Related Art In order to improve the processability and productivity of rubber compositions for inner liners of pneumatic tires such as passenger cars, trucks and buses, the amount of process oil is increased or the amount of carbon is reduced. To lower the viscosity of the unvulcanized rubber composition,
In such a method, there is a problem that the viscosity of the unvulcanized compound decreases, but the vulcanization properties such as E1 and tan δ decrease. Although a method by adding a processing aid is also conceivable, there is no existing processing aid that can achieve the above-mentioned object without impairing vulcanization properties.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned problems of the conventional rubber composition for an inner liner and to provide a viscoelastic property of E '(storage modulus).
Without substantially impairing vulcanization properties such as and tan δ,
To provide a rubber composition for an inner liner of a tire capable of improving the processability of an unvulcanized compound by lowering the viscosity or extending the scorch time, and improving the productivity by shortening the vulcanization time. It is in.

[0004]

According to the present invention, the nitrogen specific surface area is 60 parts by weight based on 100 parts by weight of a rubber component containing 50 parts by weight or more of butyl rubber and 50 parts by weight or less of diene rubber.
20 to 120 parts by weight of carbon black of m ² / g or less and the following alkoxysilyl group (I) or acyloxysilyl group (II): {Si-OR ¹ (I)} Si-OCOR ² (II) ¹ is a substituted or unsubstituted 1 having 1 to 18 carbon atoms
R ² is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms), and contains 10 parts by weight or less of a polysiloxane having an average degree of polymerization of 3 to 10,000. The present invention provides a rubber composition for an inner liner of a tire.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As rubber components to be blended in the rubber composition for an inner liner of a tire of the present invention, general-purpose diene rubbers (for example, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR) ), Styrene-butadiene copolymer rubber (SBR)) and butyl rubber (IIR). In the present invention, in order to maintain the air retention of the inner liner (film), the compounding amount of butyl rubber is adjusted to 50 parts by weight of 100 parts by weight of the rubber component.
It is required to be at least 70 parts by weight, preferably at least 70 parts by weight. Other rubber components include diene rubbers, particularly natural rubber (NR), isoprene rubber (IR), because of flex resistance.
It is preferable to use butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR) and the like.

[0006] The carbon black compounded in the rubber composition according to the present invention may be selected from any carbon black conventionally used for tires (for example, carbon black obtained by an oil furnace method) from the viewpoint of heat generation. Specific surface area (N ₂ SA) (ASTM-D3037-78)
Measured by method C) of 60 m ² / g or less, preferably ² m ² / g or less.
0 to 40 m ² / g. If the nitrogen specific surface area of the carbon black exceeds 60 m ² / g, the tan δ of the vulcanized product is increased and the heat generation is undesirably deteriorated.

The amount of carbon black to be compounded in the rubber composition used in the present invention is 20 to 120 parts by weight, preferably 30 to 70 parts by weight, per 100 parts by weight of the rubber component. If the compounding amount of this carbon is too small, the stress at the time of elongation and the physical properties at break decrease, which is not preferable. Conversely, if it is too large, the viscosity of the rubber compound increases and the processability becomes poor or the heat generation increases. It is not preferable.

In the rubber composition according to the present invention, any silica conventionally used in rubber compositions can be blended as a reinforcing agent in place of a part of carbon black. Coupling agents can be used.

According to the present invention, the rubber composition for an inner liner of a tire has an average degree of polymerization of 3 having an alkoxysilyl group and / or an acyloxysilyl group represented by the above formula (I) and / or (II). 1 to 10,000, preferably 10 to 1,000, polymers (oligomers)
10 parts by weight or less per 100 parts by weight, preferably 0.1 to 8 parts by weight
Mix by weight.

As described above, the polysiloxane containing an alkoxysilyl group (I) or acyloxysilyl group (II) blended in the rubber composition according to the present invention has an average degree of polymerization of 3 to 10,000, preferably 10 to 1,000. (Or oligomer). Therefore,
In the polysiloxane of the present invention, a specific amount of ≡Si—O
The presence of a —R ¹ group or a ≡Si—OCOR ² group is essential, and these groups may be in any of the main chain, side chain, and terminal. Further, there may be a hydrogen group or another organic group. Further, the polysiloxane used in the present invention preferably has six or more alkoxy groups and acyloxy groups directly bonded to Si atoms in one molecule. The polysiloxane used in the present invention preferably has at least one hydrocarbon group, preferably an alkyl group, directly bonded to a Si atom in the molecule, from the viewpoint of affinity with the rubber component. Such a polysiloxane is a known substance and can be generally produced, for example, as follows.

The polysiloxane containing an alkoxysilyl or acyloxysilyl group is synthesized by reacting a polysiloxane containing a Si—H group with an alcohol or a carboxylic acid in the presence of a catalyst.

The following can be exemplified as the above-mentioned シ ロ キ サ ン Si-H group-containing polysiloxane.

[0013]

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As the alcohol, methanol, ethanol, propanol, butanol, pentanol,
Examples thereof include heptanol, octanol, octadecanol, phenol, and benzyl alcohol, and further include alcohols having an oxygen atom such as ethylene glycol monomethyl ether and diethylene glycol monomethyl ether.

Examples of the carboxylic acid include acetic acid, propionic acid, palmitic acid, stearic acid, myristic acid and the like.

Further, as the catalyst, chloroplatinic acid, platinum-ether complex, platinum-olefin complex, PdCl
₂ (PPh ₃ ) ₂ and RhCl ₂ (PPh ₃ ) ₂ can be used. It is synthesized by reacting the corresponding ≡Si—H group-containing polysiloxane with an alcohol or a carboxylic acid in the presence of a catalyst. As a method for introducing an organic group, a
It is easily introduced by reacting iH with an organic compound having a double bond using the above catalyst. Examples of the compound having a double bond include styrene, α-methylstyrene, α-methylstyrene dimer, limonene, and vinylcyclohexene.

As another method, it is possible to synthesize by reacting the corresponding ≡Si—H group-containing polysiloxane with a double bond-containing alkoxysilane as shown below in the presence of the above-mentioned catalyst. it can.

[0018]

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As still another method, the polysiloxane used in the present invention can be synthesized by reacting a silanol-terminated polysiloxane with an alkoxysilane in the presence of a catalyst such as a divalent tin compound.
Examples of such a silanol-terminated polysiloxane include the following.

[0020]

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Examples of the alkoxysilane include the following alkoxysilanes, and further include silane coupling agents shown in Table I.

[0022]

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[0023]

[Table 1]

The polysiloxane used in the present invention can be synthesized by reacting a polysiloxane having a reactive functional group on the side chain or terminal with the silane coupling agent shown in Table I above. Examples of the polysiloxane having a reactive functional group include those having an epoxy group, an amino group, a mercapto group, a carboxyl group, and the like.

As described above, the polysiloxane used in the present invention has no particular limitation on the terminal groups and side chains, and is determined by the type of raw materials used in the production.

The amount of the polysiloxane used in the present invention is 10 parts by weight or less, preferably 0.1 to 8 parts by weight, based on 100 parts by weight of the rubber component in the rubber composition.
If the amount of the polysiloxane is too small, the desired effect cannot be obtained, while if it is too large, the polysiloxane that does not bind to silica may exude from the vulcanized product, which is not preferable.

In the present invention, the rubber composition may optionally contain a silane coupling agent. The silane coupling agent that can be used in the present invention can be any silane coupling agent conventionally used in combination with silica, and typical examples include those shown in Table I above. Of these, bis- [3-
(Triethoxysilyl) -propyl] tetrasulfide is most preferred from the viewpoint of processability. Further shown in Table II,
A special silane coupling agent that reacts with rubber during vulcanization can also be suitably used.

[0028]

[Table 2]

When a silane coupling agent is compounded in the rubber composition used in the present invention, it is preferably 40% by weight or less, more preferably 1% by weight, based on the amount of silica.
-20% by weight. If the amount of the silane coupling agent is too large, burning (scorch) may easily occur in the mixing or extrusion step, which is not preferable.

In the rubber composition according to the present invention, a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator,
Various additives commonly used for tires such as various oils, anti-aging agents and plasticizers, and other general rubbers can be compounded, and such compounds are kneaded and vulcanized by a general method. And vulcanized or crosslinked. The compounding amounts of these additives can also be conventional general compounding amounts as long as they do not contradict the object of the present invention.

[0031]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples.

Examples 1 to 7 and Comparative Examples 1 to 5 The polysiloxane used in the present invention was synthesized by the following method. Polysiloxane 1 100 g of polymethylhydrogensiloxane (KF99, manufactured by Shin-Etsu Chemical Co., Ltd.) and 60 g of methanol were mixed, 40 μl of a 1% isopropyl alcohol solution of chloroplatinic acid was added, and the mixture was reacted at 80 ° C. for 10 hours to synthesize. The deduced structure of this compound is as follows: Polysiloxane 2 100 g of polymethylhydrogensiloxane (KF99, manufactured by Shin-Etsu Chemical Co., Ltd.) and 72 g of ethanol were mixed, 40 μl of a 1% isopropyl alcohol solution of chloroplatinic acid was added, and the mixture was reacted at 80 ° C. for 10 hours to synthesize. The deduced structure of this compound is as follows:

[0033]

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The following commercially available products were used as the other components (see Table III) used in the following Examples and Comparative Examples.

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

[Table 5]

Butyl rubber IIR: Brominated isobutylene isoprene rubber (EXXON BROMOBUTYL R)
UBBER 2244) Natural rubber NR: SIR-20 carbon black CB-1: Seast V (Tokai Carbon, N ₂ SA27m)
² / g) CB-2: Seast 300 (Tokai Carbon, N ₂ SA8)
4m ² / g) Silica: Nipsil AQ (Nippon Silica) Silane coupling agent: Si69 (Dexa) (chemical name:
Bis- [3- (triethoxysilyl) -propyl] tetrasulfide) Silicon oil: KF99 (Shin-Etsu Chemical) Aromatic oil: Process oil X-140 (Kyodo Sekiyu) Zinc oxide: Zinc Hua No. 3 (Seido Chemical) Stearic acid: Lunac YA (Kao soap) Sulfur: Oil treated sulfur Vulcanization accelerator: Suncellar DM (Sanshin Chemical) (Dibenzothiazyl disulfide)

Preparation of Samples The vulcanization accelerator and the components other than sulfur were kneaded in a closed mixer for 3 minutes or more, and the vulcanization accelerator and sulfur were kneaded with an open roll into the master batch released when the temperature reached 165 ± 5 ° C. And
A rubber composition was obtained. The unvulcanized physical properties of the obtained rubber composition were measured. Next, this composition was press-vulcanized in a mold of 15 × 15 × 0.2 cm at 160 ° C. for 20 minutes to prepare a target test piece (rubber sheet), and the vulcanization properties were evaluated.

The test methods for the unvulcanized and vulcanized properties of the compositions obtained in the respective examples are as follows. Mooney viscosity The viscosity at a temperature of 100 ° C. was measured according to JIS K 6300. Scorch time The time at which the viscosity increased by 5 Mooney at a temperature of 125 ° C. was measured according to JIS K 6300. Vulcanization time 95% at a temperature of 160 ° C. according to JIS K 6300
The time to reach% vulcanization was measured. E ′ (storage modulus) and tan δ viscoelasticity spectrometer (manufactured by Toyo Seiki Co., Ltd.) at a temperature of 60 ° C., an initial strain of 10%, a dynamic strain of ± 2%, and a frequency of 20 Hz. is there.

The following evaluation results are shown in Table III together with the composition. Comparative Example 1 is a conventional typical compound for an inner liner.

Examples 1 to 7 are formulations within the scope of the present invention.
In each case, good results have been obtained. That is, Examples 1 to
5 is a system in which the polysiloxane is blended with respect to Comparative Example 1, and a decrease in the viscosity of the unvulcanized blend and an extension of the scorch time are recognized, the vulcanization time is shortened, and the processability is improved. The vulcanization properties of E ′ (storage modulus) and tan δ are not substantially impaired. Examples 6 and 7 are systems in which silica is blended with respect to Example 2, so that heat generation is reduced and durability is preferable.

On the other hand, Comparative Example 2 is a system in which silicone oil is blended in place of Polysiloxane in Example 2, and shows that the rubber sheet is foamed and cannot be put to practical use.
In Comparative Example 3, since the polymer system is out of the specified range as compared with Example 2, the heat build-up deteriorates (tan δ increases). Comparative Examples 4 and 5 are systems in which the blending amount of the process oil was increased and the blending amount of the carbon black was decreased to reduce the viscosity as compared with the embodiment 2, but E ′ (storage elastic modulus) decreased. It is not preferable from the viewpoint of durability.

[0044]

As described above, according to the present invention, a specific carbon black 20 is added to 100 parts by weight of a rubber component containing 50 parts by weight or more of butyl rubber and 50 parts by weight or less of diene rubber.
E '(storage modulus) and ta
Without impairing the vulcanization properties such as nδ, lowering the viscosity of the unvulcanized compound and improving the workability by extending the scorch time (suppressing burnt of rubber in the extrusion and rolling processes, improving line speed, etc.) or reducing the vulcanization time Effects such as improvement in productivity due to shortening can be obtained. Therefore, the rubber composition according to the present invention,
It is suitable as a rubber composition for inner liners of tires for passenger cars, trucks and buses.

Claims (1)

[Claims] 1. A rubber component containing 50 parts by weight or more of butyl rubber and 50 parts by weight or less of a diene rubber, and 20 to 120 parts by weight of carbon black having a nitrogen specific surface area of 60 m ² / g or less and an alkoxysilyl group described below. (I) or an acyloxysilyl group (II): ≡Si-OR ¹ (I) ≡Si-OCOR ² (II) (wherein, R ¹ is a substituted or unsubstituted 1-C 1-18 alkyl group)
R ² is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms), and contains 10 parts by weight or less of a polysiloxane having an average degree of polymerization of 3 to 10,000. A rubber composition for an inner liner of a tire comprising: