JPH1135754A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition which has improved air permeation resistance and improved workability in processing in an unvulcanized state by adding a specified amount of a metal salt of an unsaturated carboxylic acid to a rubber component containing a halogenated butyl rubber. SOLUTION: A rubber component (100 pts.wt.) comprising at least 50 wt.% halogenated butyl rubber and a diene rubber is compounded with 0.1-10 pts.wt., particularly 0.1-3 pts.wt. metal salt of an unsaturated carboxylic acid and 20-150 pts.wt., desirably 30-120 pts.wt. filler, and the mixture is kneaded to obtain an unvulcanized rubber composition. This composition is compounded with 0.1-5 pts.wt., desirably 0.3-1.5 pts.wt. vulcanizer comprising sulfur and vulcanization-related agents such as a vulcanization accelerator, and the mixture is kneaded. The obtained composition is satisfactory both in rigidity during molding an unvulcanized rubber and in flowability in extrusion and shows improved workability in processing. In addition, the unvulcanized rubber shows good low-temperature brittleness resistance and has improved sheet strength during molding (at room temperature to 50 deg.C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition,
More specifically, it relates to a rubber composition mainly composed of halogenated butyl rubber, which is suitable for a tire inner tube, a tire inner liner, etc., and which has air permeation resistance and excellent workability of unvulcanized rubber. It is.

[0002]

2. Description of the Related Art In the rubber industry, rubbers having a high importance on air permeation resistance include rubbers mainly composed of butyl rubber and halogenated butyl rubber. These rubbers are generally used in vulcanized bladders, tire inners. It is applied to rubber products such as liners, tire inner tubes, and rubber hoses. However, when the content of butyl rubber or halogenated butyl rubber is increased, there arises a problem that the workability of processing unvulcanized rubber is reduced in the rolling, extrusion and molding steps after kneading. The reduction in processing workability refers to, for example, breakage of rubber at the time of elongation of unvulcanized rubber due to a decrease in strength of unvulcanized rubber, and has a significant effect on workability during rubber product production. Therefore, conventionally, in order to improve the processing workability of the unvulcanized rubber, a measure of maintaining the strength by blending with a natural rubber having a high unvulcanized rubber strength or a synthetic rubber such as styrene-butadiene rubber has been taken. As a result, the current situation is that the air permeability resistance is reduced.

[0003] Conventionally, as a method for improving the strength of unvulcanized rubber, when a highly elastic substance such as a resin is compounded (Japanese Patent Laid-Open No. 57-172945, etc.), it is necessary to increase the elasticity of the vulcanized rubber. The low-temperature brittleness is reduced, and when a rubber curing agent is added, there is a disadvantage that the scorch property is deteriorated. Further, JP-A-7-1909 discloses that halogenated butyl rubber 20 to 30% by weight, epichlorohydrin rubber 20
An air-permeable rubber member comprising 5 to 50% by weight of a metal salt graft diene polymer of an unsaturated carboxylic acid is also disclosed. However, in such a rubber member, low-temperature brittleness is deteriorated, and a general-purpose rubber is used. It was economically disadvantageous to use non-rubber.

[0004]

SUMMARY OF THE INVENTION The present invention makes it possible to achieve both rigidity when molding unvulcanized rubber and fluidity during extrusion, without impairing the air permeation resistance under such circumstances. A rubber composition that improves processing workability and has good low-temperature brittleness of vulcanized rubber, and is particularly suitable for rubber products such as tire inner tubes and tire inner liners where air permeability is important. The purpose is to provide things.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop a rubber composition having the above-mentioned preferable properties. It has been found that a composition containing a metal salt of an acid in a specific ratio can achieve the object. The present invention has been completed based on such findings. That is, the present invention provides a rubber composition comprising 0.1 to 10 parts by weight of a metal salt of an unsaturated carboxylic acid per 100 parts by weight of a rubber component containing 50% by weight or more of a halogenated butyl rubber. Is what you do. The present invention also relates to a filler of 20 to 150 parts per 100 parts by weight of a mixed rubber of a halogenated butyl rubber alone or a halogenated butyl rubber of 50% by weight or more and a balance of a diene rubber.
The present invention provides a rubber composition characterized by blending 0.1 to 10 parts by weight of a metal salt of an unsaturated carboxylic acid and sulfur vulcanization.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the rubber composition of the present invention may be any one containing at least 50% by weight of a halogenated butyl rubber, and may be a halogenated butyl rubber alone or a halogenated butyl rubber. It may be a mixture of 50% by weight or more and 50% by weight or less of another rubber. Here, the other rubber is preferably a diene rubber, and examples thereof include natural rubber, polyisoprene synthetic rubber, cis polybutadiene rubber, trans polybutadiene rubber, and styrene-butadiene rubber (SBR). The content of halogenated butyl rubber in this rubber component is 50% by weight.
If it is less than 30, sufficient air permeability resistance cannot be exhibited. From the viewpoint of air permeation resistance, a halogenated butyl rubber alone is preferred.

As such halogenated butyl rubber, chlorobutyl rubber and bromobutyl rubber are preferred.
Particularly preferred halogenated butyl rubbers are halogenated copolymers of isobutylene and isoprene with an unsaturation level of 1 to 5 mol% and a halogen content of 0.5 to 3% by weight. Examples of the chlorobutyl rubber include “En
Jay Butyl HT10-66 "(Enjay
Chemical company, trade name), and bromobutyl rubber is, for example, "bromobutyl 2255" (manufactured by Exxon, trade name). Further, as the halogenated butyl rubber in the present invention, a halogenated modified copolymer of a copolymer comprising isomonoolefin and p-alkylstyrene, particularly preferably a chlorinated copolymer of isobutylene and p-methylstyrene Alternatively, a brominated modified copolymer can be used, and examples thereof include "Exxpro" (trade name, manufactured by Exxon Corporation). Further, the compounding amount of the metal salt of the unsaturated carboxylic acid in the rubber composition of the present invention,
It is necessary to contain 0.1 to 10 parts by weight per 100 parts by weight of the rubber component. When the content is less than 0.1 part by weight, the strength of the unvulcanized rubber is not sufficiently improved, the workability is poor, and the object of the present invention cannot be achieved. on the other hand,
If the amount exceeds 10 parts by weight, no improvement in the effect is recognized for the amount, but rather, it adversely affects the physical properties of the vulcanized rubber and is economically disadvantageous. Workability of unvulcanized rubber,
From the viewpoint of the balance between physical properties and economy of the vulcanized rubber, a preferable content of the metal salt of the unsaturated carboxylic acid is in the range of 0.1 to 10 parts by weight per 100 parts by weight of the rubber component. A range of 0.1 to 3 parts by weight is preferred.

In the present invention, the metal salt of the unsaturated carboxylic acid is usually blended in the first kneading step.
Here, the first kneading step means kneading using a component other than the components involved in rubber crosslinking, such as a vulcanizing agent and a vulcanization accelerator, for example, a rubber component, a filler such as carbon black, and other compounding agents. It is the process of doing. In the second kneading step, the mixture obtained in the first kneading step is
The remaining components, that is, vulcanization-related agents such as a vulcanizing agent and a vulcanization accelerator are blended and kneaded to prepare an unvulcanized rubber composition. When the metal salt of the unsaturated carboxylic acid (hereinafter, sometimes referred to as a metal-based crosslinking aid) is blended in the first kneading step, radicals generated from the metal salt during the kneading cause the rubber component to be mixed. Ionic crosslinking occurs, resulting in a high strength unvulcanized rubber. The metal ion cross-links thus formed are, by their nature, low in temperature (from room temperature to about 50 ° C.).
In this case, the bond is strong, and the bond is weak at high temperatures (about 100 to 130 ° C.), so that the unvulcanized rubber has an excellent balance between the rigidity during molding and the processability such as fluidity during extrusion. In addition, no increase in the elastic modulus at low temperature due to the addition of the metal-based crosslinking aid to the vulcanized rubber is observed, and the low-temperature brittleness does not decrease.

Further, the rubber composition of the present invention containing the above-mentioned metal-based crosslinking aid has good scorch properties and also has a good air permeability resistance with a rubber composition containing no such metal-based crosslinking aid. Equal or better, no adverse effect on air permeation resistance is observed. Examples of the unsaturated carboxylic acid constituting the metal salt of the unsaturated carboxylic acid according to the present invention include α, such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, angelic acid, and cinnamic acid.
β-ethylenically unsaturated carboxylic acids can be mentioned, among which acrylic acid and methacrylic acid are preferred. On the other hand, as the metal constituting the metal salt, for example, sodium, potassium, lithium, calcium, barium,
Examples thereof include magnesium, zinc, aluminum, tin, zirconium, and cadmium, and among them, sodium, magnesium, zinc, and aluminum are preferable. Particularly preferred metal salts of unsaturated carboxylic acids are zinc diacrylate and zinc dimethacrylate. These unsaturated carboxylic acid metal salts may be used alone or in combination of two or more.

[0010] The filler is preferably a particulate inorganic filler such as carbon black, silica, basic magnesium carbonate, calcium carbonate, magnesium silicate and clay. These fillers may be used alone or in combination of two or more. Among them, carbon black is particularly preferred. Examples of the carbon black include channel black and furnace black (SAF, ISA).
F, HAF, MAF, FEF, SRF, GPF),
Thermal black, acetylene black and the like. The filler is added in an amount of usually 20 to 150 parts by weight, preferably 30 to 120 parts by weight, based on 100 parts by weight of the rubber component.

The vulcanizing agent is not particularly limited and may be appropriately selected from those conventionally used as a filler for butyl rubber. Sulfur is particularly preferred. When sulfur is used, the amount of the vulcanizing agent is usually 0.1 to 100 parts by weight of the rubber component.
It is blended in an amount of 5 parts by weight, preferably 0.3 to 1.5 parts by weight. As the vulcanization accelerator, for example, guanidine-based,
There are a thiazole type, a sulfenamide type, a thiourea type, a thiuram type, a dithiocarbamate type and the like, which are used without any particular limitation. As described above, the rubber composition of the present invention can be prepared by performing the first kneading step and the second kneading step.In the first kneading step, zinc white, stearic acid, Softeners, anti-aging agents, etc.
Normally, chemicals used in the rubber industry are appropriately added. The kneading is carried out by a usual kneading apparatus, for example, a roll, a Banbury mixer, a kneader, or the like.

[0012]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 5 and Comparative Examples 1 to 3 First, in the first kneading step, the metal-based crosslinking aid shown in Table 2 was used in the amount shown in Table 3 according to the composition shown in Table 1, The kneading was performed at a temperature of 150 ° C.
Next, in the second kneading step, the amounts of the vulcanization accelerators and sulfur shown in Table 1 were added to the mixture obtained above, and the mixture was kneaded at a maximum temperature of 100 ° C., and the mixture was kneaded. , Simply referred to as unvulcanized rubber).
For this composition, Mooney viscosity ML _{1 + 4} (100 ° C.)
And the scorch time (time until the Mooney viscosity increased by 5 units) was measured according to ASTM-D-1646.
Further, after preparing a sheet having a thickness of 4.0 ± 0.40 mm, the sheet was punched into a ring (JIS-5 type), and the unvulcanized rubber sample was subjected to 100 ± 5 mm / 40 ° C.
The tensile test is performed at the speed of
The modulus was measured. Table 3 shows the results.
Further, with respect to the unvulcanized rubbers of Example 2 and Comparative Example 1, a disk-shaped sample having a diameter of 50 mm and a thickness of 5 mm was used, and an unvulcanized viscoelastic device “RPA2000” (manufactured by Monsanto Co.) was used. The temperature dependence of the dynamic storage (shear) elastic modulus G ′ was measured under the conditions of a shear angle of 1 ° and a frequency of 100 cpm. The results are shown graphically in FIG. Next, temperature 1
The vulcanized rubber obtained by vulcanization at 60 ° C for 20 minutes was used as a strip sample with a length of 50 ± 5mm, a width of 4.65 ± 0.1mm, and a thickness of 2mm, at a temperature of 0 ° C and a strain of 0.1%. The dynamic storage modulus E 'was determined under the conditions of a frequency of 52 Hz. Table 3 shows the results.

[0013]

[Table 1]

Note 1) Bromobutyl rubber: Exxon Corp.
Trade name: bromobutyl 2255 2) Vulcanization accelerator DM: dibenzothiazyl disulfide,

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

As shown in Table 3, unvulcanized rubber compositions containing the metal crosslinking aid according to the present invention (Examples 1 to 5)
The tensile strength and the 100% modulus at 40 ° C. are all higher than those of Comparative Examples 1 to 3, and it can be seen that pseudo-crosslinking by metal ions is formed in the first kneading step. Also, as shown in FIG.
The sheet strength (elastic modulus) at the time of molding (room temperature to about 50 ° C.) is improved, and the working area (100 to 130
(About ° C.), it can be seen that the viscosity is reduced. further,
Table 3 shows that in the vulcanized rubber, the increase in the elastic modulus at low temperature due to the addition of the metal crosslinking aid according to the present invention was not observed, and thus it was found that there was no decrease in brittleness at low temperature. Table 3 also shows that the unvulcanized rubber composition of the present invention has good scorch properties.

[0019]

EFFECT OF THE INVENTION The rubber composition according to the present invention can improve processing workability because it can achieve both rigidity during molding of unvulcanized rubber and fluidity during extrusion without impairing air permeability resistance. The rubber composition is suitable for rubber products, such as a tire inner tube and a tire inner liner, in which resistance to air permeation is important, since the vulcanized rubber has good low-temperature brittleness.

[Brief description of the drawings]

FIG. 1 is a graph showing the temperature dependence of the modulus of elasticity of unvulcanized rubber in Example 2 and Comparative Example 1.

Claims (4)

[Claims] 1. A rubber composition comprising 0.1 to 10 parts by weight of a metal salt of an unsaturated carboxylic acid per 100 parts by weight of a rubber component containing 50% by weight or more of a halogenated butyl rubber. 2. The rubber composition according to claim 1, wherein a metal salt of an unsaturated carboxylic acid is blended in the first kneading step, and then a vulcanization-related agent is blended in the second kneading step. 3. The metal salt of an unsaturated carboxylic acid is a metal salt of acrylic acid and / or a metal salt of methacrylic acid.
The rubber composition as described in the above. 4. A filler of 20 to 150 parts by weight and a metal salt of unsaturated carboxylic acid of 0.1 to 100 parts by weight per 100 parts by weight of a mixed rubber of a halogenated butyl rubber alone or a halogenated butyl rubber of 50% by weight or more and a diene rubber. A rubber composition comprising 10 parts by weight and sulfur vulcanization.