JPH0662809B2 - Vulcanizable rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention discloses that fine needle-shaped syndiotactic-1,2-polybutadiene (hereinafter abbreviated as 1,2-PBD) is uniformly dispersed in rubber. The present invention relates to a vulcanizable rubber composition having excellent reinforcing property, fracture resistance property, fatigue resistance property and extrusion processability.

[Conventional technology]

In recent years, due to the demand for energy saving, attention has been paid to coloring of rubber products such as tires due to weight reduction and individualization of products. In order to achieve this, the ratio of carbon black that has been conventionally used to enhance the reinforcing properties of rubber is reduced or eliminated altogether, and instead, short fibers such as nylon, vinylon, glass, etc. are blended to shorten the ratio. Many attempts have been made to make fiber reinforced rubber.

Such short fiber reinforced rubber has a high reinforcing property, but since the rubber and the mixed short fibers have different elastic moduli, when the rubber composition is strained, stress concentrates at the short fiber end, The rubber is destroyed from. Moreover, in this type of short fiber reinforced rubber, because the adhesion between the rubber and the short fibers is not sufficient,
The broken portion easily grows along the surface of the short fiber,
As a result, the adhesive surface is destroyed, causing large creep,
It has the disadvantage that the breaking life of the rubber is extremely short when cyclic elongation is applied.

Therefore, an attempt was made to blend 1,2PBD short fibers having an average diameter of 0.2 to 10 μm as short fibers (Japanese Patent Publication No. 57-31746).
It cannot be said that the reinforcing performance and the fracture resistance are sufficient, and further, there is a problem that the short fibers are oriented in the direction in which a shearing force is applied at the time of compounding to cause anisotropy in the rubber reinforcing property.

[Problems to be solved by the invention]

Therefore, the present inventors have conducted various studies to improve the above-mentioned drawbacks of conventional short fiber reinforced rubbers, and as a result, were able to improve the fracture resistance and the fatigue resistance, and, surprisingly, the reinforcement and the extrusion. The inventors have found that the workability is remarkably excellent and have reached the present invention described below.

[Means for solving problems]

That is, the present invention provides a needle-shaped 1,2-PBD having a maximum diameter of 1 μm or less, an average diameter of 0.05 μm or less, and a length-to-diameter ratio L / D of 2 to 100, which is obtained by the following specific production method. 1 in rubber
It is a vulcanizable rubber composition containing about 50% by weight.

The needle-shaped 1,2-PBD contained in the rubber composition of the present invention may be any rubber obtained by coagulating latex produced by the method of JP-A-59-142222 or JP-A-59-271888. Can be used.

The method disclosed in the above invention is a completely new polymerization method in which 1,2-PBD is polymerized in a seed latex particle using a cobalt catalyst. When this method is used, the polymerization is carried out in a very small rubber matrix called seed latex particles, so the resulting 1,2-PBD is uniformly dispersed in the rubber matrix in the form of ultrafine needles, and a rubber that has never existed before. −
A composite polymer of ultrafine needle-like polymers is obtained, and in the present invention, this composite polymer is used as it is, or is further blended with another rubber within the specified range of 1,2-PBD of the present invention.

The maximum length of needle-shaped 1,2-PBD contained in the composite polymer is 2
It is extremely fine with an average length of 0.1 μm or less and an average length of 0.1 μm or less. The diameter of needle-shaped 1,2-PBD is 0.0001 to 1.0μ.
m, preferably 0.001 to 0.5 μm, and the average value is 0.05 μm at the maximum, preferably 0.003 to 0.05 μm.
μm, and more preferably 0.005 to 0.03 μm. Acicular
The length-to-diameter ratio L / D of 1,2-PBD is usually 2 to 100, preferably 5 to less than 20. (Refer to the figure) The amount of needle-shaped 1,2-PBD contained in the rubber is 1 to 50% by weight, preferably 5 to 25% by weight.

If the amount of needle-shaped 1,2-PBD is less than 1% by weight, the reinforcing property is lost, and if it exceeds 50% by weight, the elongation is reduced, which is not preferable.

The 1,2-structure content of the acicular 1,2-PBD is preferably 70% or more. When the 1,2-structure content is less than 70%, the reinforcing property to rubber is deteriorated, which is not preferable. Further, the melting point of needle-shaped 1,2-PBD is preferably 190 ° C or higher, and if it is lower than 190 ° C, the temperature dependence of the reinforcing property becomes large, which is not preferable.

Natural rubber latex and synthetic rubber latex are used as seed latex used in the production of needle-shaped 1,2-PBD, and synthetic rubber latex is polybutadiene latex, styrene-butadiene copolymer latex, acrylic rubber. Preferred are latex, ethylene-propylene terpolymer re-emulsifying latex, polyisoprene re-emulsifying latex, diene synthetic rubber re-emulsifying latex such as butyl rubber.

Further, the rubber further blended with the needle-shaped 1,2-PBD composite polymer may be the same as or different from the rubber constituting the composite polymer, and NBR may be used in addition to the rubber exemplified as the seed latex.

It is preferred to optionally add an anti-aging agent prior to coagulating the latex. Total rubber as an anti-aging agent,
It is possible to use those normally used for natural rubber.

The rubber containing the needle-shaped 1,2-PBD of the present invention, by a kneading method usually performed, process oil as a softening agent,
Stearic acid, liquid rubber and the like, carbon black, silica, titanium oxide and the like as a walking agent or pigment can be optionally mixed and used.

The rubber composition of the present invention is particularly useful for tires, and can be advantageously used for treads, rubber chafers, sidewalls, stiffeners, bead fillers, inner liners, belt under cushions and other applications.

[Action]

Due to the small particle size of the needle-shaped 1,2-PBD and the fact that it is absorbed and polymerized in the rubber, the 1,2-PBD is evenly dispersed in the rubber, which results in the reinforcement and fracture resistance. It is thought that it will contribute greatly to the improvement. It is not clear why this form also has a positive effect on extrusion processability, but the stress concentration applied to the edge during extrusion is uniform and finely dispersed.
-Since it is softened by PBD, it is considered that it can realize a sharp edge that is not found in ordinary formulations.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition,
“Parts” and “%” represent parts by weight and% by weight. The sample was manufactured by the following method.

Sample A 15.5 parts of natural rubber latex (produced by Felda, Malaysia) having an average particle diameter of dispersed particles of 0.4 μm and 48 parts of distilled water were put in a pressure resistant reaction vessel, and the inside diameter was sufficiently bubbled with nitrogen gas. Then, after cooling the system to 5 ° C, 1,3
-Butadiene (4.7 parts) was added, and the mixture was stirred for 30 minutes to allow 1,3-butadiene to be absorbed by the latex particles, which was designated as "seed dispersion A".

Cobalt octylic acid in a pressure-resistant container that had been previously replaced with nitrogen.
After adding 0.50 parts of a 0.2 mol / n-hexane solution, 0.84 parts of cyclohexane was added and well stirred. After cooling the system to 5 ° C, 0.17 part of 1,3-butadiene was added and stirred for 30 minutes. Triisobutylaluminum 0.5mol /
0.59 parts of the n-hexane solution of was added and stirred for 30 minutes while cooling to obtain a first catalyst component solution. To the first catalyst component solution was added 0.3 part of sodium dodecylbenzenesulfonate and 15 parts of distilled water bubbled with nitrogen, and the mixture was predispersed with a homomixer under a nitrogen gas atmosphere, and then a homogenizer (manton gaurin "15M type"). Was emulsified and dispersed to obtain an aqueous dispersion having dispersed particles having a particle diameter of 0.1 to 0.3 μm. This was designated as "first catalyst dispersion A".

The "first catalyst dispersion A" was added to the "seed dispersion A" prepared above, and the mixture was stirred for 30 minutes while maintaining the temperature at 5 ° C.
Next, a 0.6 mol / carbon n-hexane solution of carbon disulfide (hereinafter referred to as "second catalyst solution A") was added to this solution, and
Polymerization was carried out while slowly stirring for 3 hours while controlling the temperature at ℃. In the above polymerization,
The polymerization yield was 98%. No coagulum formation was observed. This is designated as latex A. Steam was directly blown into the latex A obtained by polymerization to strip residual monomers, and then 0.5 parts of antioxidant A [Wingstay 200 (manufactured by Good Tire Co.)] was added and mixed well, followed by coagulation by a conventional method. Then, the mixture was left to stand in a hot air dryer at 100 ° C. for 2 hours and dried to obtain “needle-shaped 1,2-PBD reinforced natural rubber A”.

Sample B When a "seed dispersion" was prepared in Sample A, "seed dispersion B" was obtained in the same manner except that 2.3 parts of 1,3-butadiene was added instead of 4.7 parts of 1,3-butadiene.

In Sample A, "Seed Dispersion B" was used instead of "Sheet Dispersion A", and "First catalyst dispersion A" and "Second catalyst solution" were 1/2 times the amount used in Sample A. Polymerization was performed in the same manner except that the amount was changed to obtain latex B with a polymerization yield of 97%.

Latex B was used in place of latex A in sample A, and coagulation and drying were performed in the same manner except that 0.45 parts were added instead of 0.5 parts of anti-aging agent A, and "needle-shaped 1,2-PBD reinforced natural rubber B "was obtained.

Sample C A "Seed Dispersion C" was prepared in the same manner as in Preparation of the "Seed Dispersion" in Sample A, except that 1.3 parts of 1,3-butadiene was added in place of 4.7 parts of 1,3-butadiene.

In Sample A, "Seed Dispersion C" was used instead of "Sheet Dispersion A", and the "first catalyst dispersion A" and the "second catalyst solution" were made 0.27 times the amount used in Sample A. Polymerization was carried out in the same manner except that the procedure was repeated to obtain latex C at a polymerization yield of 95%.

In sample A, latex C was used instead of latex A, and coagulation and drying were performed in the same manner except that 0.42 parts were added instead of 0.5 parts of anti-aging agent A, and "needle-shaped 1,2-PBD reinforced natural rubber C Was obtained.

Sample D SB Latex ^# 1500 manufactured by Nippon Synthetic Rubber Co., Ltd. was continuously polymerized from the final reaction vessel into another pressure resistant reaction vessel which had been previously N ₂ -substituted to obtain 15.5 parts of solid content, and 0.02 part of N, N-diethylhydroxylamine was polymerized. Was added to stop the reaction. As a result of gas chromatography analysis, the latex contained 4.7 parts of 1,3-butadiene as a residual monomer. This was designated as "seed dispersion D".

Polymerization was performed in exactly the same manner as in Sample A except that "Seed Dispersion A" was used in place of "Seed Dispersion A" to obtain Latex D with a polymerization yield of 97%. Also, in sample A, "latex D" was used in place of "latex A"
Instead of adding 0.5 part of A, the antioxidant B (2,2'-dihydroxy-3,3'-di (α-methylcyclohexyl) -5,
Coagulation and drying were carried out in the same manner except that 0.5 parts of 5'-dimethyldiphenylmethane dissolved in a solvent and dispersed in water (concentration 40%) were added, and "needle-shaped 1,2-PBD reinforced synthetic rubber D "was obtained.

Sample E In Sample A, “Seed Dispersion D” was used instead of “Sheet Dispersion A”, and “First Catalyst Dispersion A” and “Second Catalyst Solution” were used in an amount 1 / Polymerization was performed in the same manner except that the amount was doubled to obtain "latex E" with a polymerization yield of 49%.

Latex E was used in place of latex A in sample A, and coagulation and drying were performed in the same manner except that 0.45 parts were added instead of 0.5 parts of the antioxidant, to obtain "needle-shaped 1,2-PBD reinforced natural rubber E". Obtained.

Sample F In Sample A, "Seed Dispersion D" was used instead of "Sheet Dispersion A", and the "first catalyst dispersion A" and the "second catalyst solution" were 0.27 times the amount used in Sample A. Polymerization was performed in the same manner except that the amount was changed to obtain "latex F" with a polymerization yield of 26%.

In sample A, latex F was used instead of latex A, and coagulation and drying were all performed in the same manner except that 0.42 parts were added instead of 0.5 parts of anti-aging agent A, and "needle-shaped 1,2-PBD reinforced synthetic rubber F Was obtained.

Sample G According to the method disclosed in JP-B-57-31746, 15 parts of syn-1,2-polybutadiene particles (melting point 200 ° C.) having a particle diameter of 10 to 700 μm (melting point 200 ° C.) were added to 100 parts of natural rubber and kneaded at 180 ° C. The resulting kneaded product was extruded from a circular die having an inner diameter of 1 mm and a length / inner diameter ratio of 20 at 210 ° C. and cooled to room temperature to obtain “short fibers 1,2−
Polybutadiene-blended natural rubber G "was obtained.

Regarding the polymers obtained in A to F, the melting point was dyed by a differential scanning calorimeter, the vinyl group content was dyed by osminium oxide (OsO ₄ ) by the Morero analysis method of infrared absorption spectrum. The results obtained by observing with a transmission electron microscope and measuring the diameter of the ultrafine fibers are shown in (Table 1). An electron micrograph of needle-shaped 1,2-PBD reinforced natural rubber B is shown in FIG.

The dark part is natural rubber and the whitish line is 1,2-PBD. It can be seen that the acicular 1,2-PBD is uniformly dispersed in the natural rubber matrix without any anisotropy.

Examples 1 to 11 and Comparative Examples 1 to 5 Various rubber compositions shown in Table 2 were prepared and each item was evaluated. The carbon black used was N-330 (HAF manufactured by Tokai Carbon Co., Ltd.), and the silica used was NIPPON SEAL VN-3 (manufactured by Nippon Silica Co., Ltd.).

(1) Tensile strength, elongation, 300% modulus: Measured according to JIS K6301.

(2) Flex resistance: After vulcanizing various rubber compositions, the number of flexures until cracks were generated was evaluated using a demacher tester (300 cycles / minute). However, the value in the evaluation item column was multiplied by the number of times of bending to obtain an appropriate value, which was taken as the bending resistance index. The larger the value, the better the bending resistance.

(3) Fatigue resistance: A dumbbell-shaped No. 3 punched sample described in JIS K6301 is subjected to 150% elongation strain at 300 cycles / minute, and the time until the sample is cut is multiplied by an appropriate coefficient and displayed as an index. did.

(4) Creep: A ring-shaped No. 5 punching die sample described in JIS K6301 is loaded at 100 ° C so that it stretches 100%, and an appropriate coefficient is applied to the time until it stretches to 150%.
Displayed as an index.

(5) Extrudability: ASTM D2230 Garvey Die Screw diameter 10φ L / D = 8 Die temperature 100 ℃ Rotation speed 20r
It was performed under the condition of pm and evaluated with a maximum of 16 points.

(6) Specific gravity: Determined from the weight of the sample section in air and in water at 20 ° C.

(7) Goodrich fever: 143 pounds / (inch) ² weighted by Goodrich flexometer, 0.175 inch /
The heat generation was measured under the conditions of stroke, 1800 rpm, and 20 minutes.

(8) Blackness: According to the Color Harmony Manual, blackness is set to 8
It was classified into stages and evaluated.

[Effects of the Invention] As is clear from Table 2, the rubber composition of the present invention has sufficient reinforcing properties, is light in specific gravity, and has a small Goodrich heat generation even without being filled with carbon black or silica. Therefore, it can be suitably used for rubber products, particularly energy-saving tires.

Further, as is clear from Table 2, the rubber composition of the present invention has remarkably excellent physical properties as compared with a normal light-colored rubber composition, and the light-colored rubber composition is used for applications requiring strength. It became possible to do it.

As described above, it is clear that the rubber composition of the present invention is excellent in reinforcing property as compared with the conventional short fiber reinforced rubber composition, and is also extremely excellent in fracture property, fatigue resistance property, and workability. is there.

[Brief description of drawings]

The figure is an electron micrograph of the needle-shaped 1,2-PBD reinforced natural rubber B of the present invention.

Claims (1)

[Claims] 1. Polymerized by a cobalt catalyst in rubber seed latex particles, having a maximum diameter of 1 μm or less, an average diameter of 0.05 μm or less, and a length-to-diameter ratio L / D of 2 to 100.
Vulcanizable rubber composition containing 1 to 50% by weight of syndiotactic-1,2-polybutadiene in rubber