JPH0570656B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a rubber processing aid that promotes the incorporation and dispersion of fillers into rubber during rubber kneading and processing, and at the same time contributes to improving the physical properties of rubber. Prior Art The present inventors have previously developed a polybasic acid in which two or more carboxyl groups are introduced into a hydrocarbon having four or more carbon atoms.
Alternatively, he invented a rubber processing aid mainly composed of a salt of the polybasic acid and a divalent metal, or a mixture thereof, and filed a patent application as Japanese Patent Application No. 1983-225256. Problems to be Solved by the Invention However, these rubber processing aids have a remarkable effect on synthetic rubbers such as styrene-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, and butadiene rubber. ,
It did not give much effect to highly versatile natural rubber. Means to Solve the Problems The inventors have conducted intensive research to provide an effective rubber processing aid for natural rubber, and have found that fatty acids having one or more hydroxyl groups in the molecule, or divalent and It was discovered that salts with metals, or mixtures thereof, are effective as rubber processing aids for natural rubber, styrene-butadiene or polyisoprene rubber, leading to the completion of the present invention. As the fatty acid used in the present invention, monobasic acids having 8 to 22 carbon atoms are suitable, and those into which at least one hydroxyl group has been introduced can be used as the rubber processing aid of the present invention. However, among these, 12-hydroxystearic acid is particularly preferred. Effects of the Invention By adding the rubber processing aid of the present invention to rubber in advance or adding it together with a filler, the filler can be easily mixed and dispersed into the rubber, and the filler can be quickly and uniformly added. Dispersed in rubber. Therefore,
The kneading time of the rubber is short, the physical properties of the rubber are less likely to deteriorate due to long-time kneading, and the reinforcing effect is enhanced because the filler is well dispersed. Therefore, a rubber compound using the rubber processing aid of the present invention has significantly improved modulus and tensile strength in vulcanization physical properties. The rubber processing aid of the present invention is effective when used on natural rubber, but it also provides sufficient effects when used on other synthetic rubbers. Examples Example 1 A commercially available product with an acid value of 179, a hydroxyl value of 157, and an iodine value of 3.
12-Hydroxystearic acid. Example 2 Hydroxytall oil fatty acid having an acid value of 150, a hydroxyl value of 210, and an iodine value of 20, obtained by hydroxylating tall oil fatty acid. Example 3 Calcium salt of 12-hydroxystearic acid formed from the 12-hydroxystearic acid of Example 1 by metathesis. Example 4 Calcium salt of hydroxytol oil fatty acid formed from the hydroxytol oil fatty acid of Example 2 by metathesis process. Comparative Example 1 Commercially available stearic acid. Comparative Example 2 Commercially available calcium stearate. Dispersibility test of carbon black Natural rubber: Regarding the substances of each example and comparative example,
When this was blended into natural rubber, the effect on the dispersibility of carbon black into the natural rubber was investigated. Test method: 100 parts of masticated natural rubber with a Mooney viscosity of 65 was wound around a 10-inch diameter kneading roll machine with a roll spacing of 1.5 mm and a roll surface temperature of 50°C, and was rolled for 3 minutes. 5 parts of zinc white and 2 parts of the materials from each of the Examples and Comparative Examples described above were added. Then add 10 parts of HAF carbon black,
After 2 minutes, switch back twice on each side. This operation was repeated five times and a total of 50 parts of HAF carbon black was added. During the process of adding carbon black, the carbon black that falls from the roll onto the tray is
It was left on a tray without being re-added onto the roll, and after all the above operations were completed, the amount of carbon black that had fallen onto the tray was measured, and the amount of carbon black mixed into the natural rubber was calculated. Results The results of the test were as shown in the table below.

[Table] Styrene-butadiene rubber: Example 4 and Comparative Example 2
The effect on the dispersibility of carbon black in styrene-butadiene rubber when it was blended with styrene-butadiene rubber was investigated. Test method Equipped with a Banbury type blade, the blade
100 parts of SBR1502 was charged into a plastometer driven at 95 rpm and the circulating water temperature was set at 40°C, followed by 5 parts of zinc white. After 1 minute, 2 parts of the compounding agent was added and kneaded for 2 minutes. Next, 80 parts of HAF carbon black was added, and BT was determined from the torque-time relationship required for kneading. The filling rate of the plastometer is 78%. The torque-time relationship obtained after adding HAF carbon black is that first, by adding HAF carbon black, the occupied volume inside the plastometer increases and the torque increases. Next, the viscosity of the rubber decreases due to the temperature generated by kneading, carbon black is mixed into the rubber, and the volume occupied within the plastometer begins to decrease, causing the torque to begin to decrease. This torque peak is defined as the first peak. Furthermore, as carbon black is mixed into the rubber, the viscosity of the rubber increases and the torque increases again. When the carbon black is sufficiently mixed and dispersed, the compound progresses to plasticization and the torque decreases again. The torque peak at this time is defined as a second peak. After adding HAF carbon black, the time from reaching the first peak to reaching the second peak
(Incorporation Time). Results The results of the test were as follows.

[Table] Basic plastic property test of compounded rubber The basic physical properties of the rubber compositions to which the substances of Examples 1 and 4 were added were measured. Blended natural rubber compound RSS#3 100 Stearic acid 1 Zinc white No. 1 5 Rubber processing aid 2 HAF carbon black 50 Sulfur 2 Thiazole vulcanization accelerator 1 Polyisoprene compound IR2200 100 Stearic acid 1 Zinc white No. 1 5 Rubber Processing aid 2 Naphthenic oil 20 HAF black 50 Sulfur 2 Thiazole vulcanization accelerator 1 The above formulation allows rubber processing aids using the substances of Examples 1 and 4, and these rubber processing aids. A blank containing no additive was kneaded using a kneading roll machine to prepare an unvulcanized rubber composition. Unvulcanized Rubber Test The Mooney viscosity of the unvulcanized rubber composition roll-kneaded according to the above formulation was measured according to JIS-K-6300. Vulcanization: Using a sample plate molding machine with a 2mm thick mold, 150℃,
Vulcanization was carried out at approximately 40 kg/cm ² for 10, 15 and 20 minutes to obtain a press vulcanizate. Vulcanized product physical property test Hardness was measured using a JIS hardness meter (spring type A type). Modulus, tensile strength and elongation were measured using a Schottsper tensile strength tester. The test piece is
Use dumbbell JIS-3 type, pulling speed is 500
mm/min, and the measurement temperature was 20°C. Test Results The test results were as follows.

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Claims (1)

[Claims] 1 Carbon number 8 or more with one or more hydroxyl groups in the molecule
22 fatty acids, salts of the fatty acids and divalent metals, or mixtures thereof.