JPS6264842A - Method for improving extrudability of rubber composition - Google Patents

Abstract

PURPOSE:To improve the extrudability of a rubber compsn., particularly the edge breakage and the surface profile, by adding a metal salt of a fatty acid to a rubber compsn. contg. a polybutadiene rubber in a specified weight ratio. CONSTITUTION:A rubber compsn. contg. a diene rubber comprising 10-100wt% polybutadiene rubber is prepd. A metal salt of a fatty acid in a quantity of 0.02-3pts.wt. per 100pts.wt. diene rubber is added to said rubber compsn. to improve extrudability. Preferred examples of the metal salt of a fatty acid are calcium stearate and calcium palmitate. As the polybutadiene rubber, a rubber having a Mooney viscosity of 30-60 and a cis-1,4 structure content of 25% or above is preferred. The rubber compsn. is suitable for use as rubber for tires.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for improving the extrusion processability of a rubber composition, and more specifically, to improving the extrusion processability of a rubber composition. By adding a specific amount of Improves the extrusion processability of polybutadiene rubber compositions without affecting
In particular, it relates to a method for improving the edge breakage and surface condition of extrudates during extrusion processing, and the rubber composition whose extrusion processability has been improved by the method of the present invention is particularly suitable for use as tire rubber. .

[Conventional technology and its problems]

Polybutadiene rubber has come to be widely used as a material for forming tire rubber, mainly tire sidewalls, trends, beads, carcass, etc. this is,
This is because polybutadiene rubber has superior performance compared to the conventionally most used natural rubber, such as better abrasion resistance, better resistance to flex cracking, and higher repulsion. be.

However, compared to natural rubber, polybutadiene rubber cannot be extruded at high speed, has inferior green properties, and has poor tackiness (
There are processing problems such as low adhesion (rubber-to-rubber adhesion) and poor roll winding properties. Currently, it is used in limited quantities by blending it with natural rubber.

Recently, in the tire industry, there has been a trend toward lower modulus of elasticity for sidewalls due to the shift to radial tires and lower profile ratios.Also, to improve fuel efficiency, the amount of carbon blank blended has been reduced, and carbon materials with low reinforcing properties are being used. There is a tendency to shift to Therefore, polybutadiene rubber is also required to have good processability, especially extrusion processability. Furthermore, in order to improve productivity, there is a demand for polybutadiene rubber that has good high-speed extrudability. However, if the formulation is changed, such as by reducing the amount of carbon compounded, or if the extrusion speed is increased, edge breakage tends to occur in the extrudate during extrusion processing, and the surface texture of the extrudate becomes poor. When such an extrudate is used as a tire forming material, it becomes difficult to form the tire, and edge breakage becomes a defective point, which poses a practical problem.

Therefore, as methods for improving the processability, particularly the extrusion processability, of polybutadiene rubber compositions, methods such as adding a reactive low molecular weight polymer, adding a softener or a plasticizer, etc. have been proposed. However, these methods improve the processability of the rubber composition by lowering its Mooney viscosity, and improve the mechanical properties of the rubber composition after vulcanization.
For example, there is a problem that the tensile modulus, hardness, tensile strength, etc. are reduced, and it is not sufficient for practical use.

Therefore, it is an object of the present invention to provide a polybutadiene rubber composition without adversely affecting the vulcanization system, without reducing the Mooney viscosity of the polybutadiene rubber composition, and without adversely affecting the various physical properties of the polybutadiene rubber composition after vulcanization. It is an object of the present invention to provide a method for improving the extrusion processability of a polybutadiene rubber composition, particularly for improving the edge breakage and surface condition of an extrudate during extrusion processing, without causing any problems.

[Means for solving problems]

The present invention includes adding 0.02 to 3 parts by weight of a metal salt of a fatty acid per 100 parts by weight of the diene rubber to a rubber composition containing a diene rubber containing 10 to 100% by weight of polybutadiene rubber. The above object has been achieved by providing a method for improving the extrusion processability of a rubber composition.

The method for improving the extrusion processability of the rubber composition of the present invention will be described in detail below.

The diene rubber constituting the rubber composition of the present invention contains 10 to 100% by weight of polybutadiene rubber. Among them, the Mooney viscosity of raw rubber (MLI+, 10
(0°C) 25 to 60 and a cis-1,4 structure content of 30% or more is preferred. Further, the diene rubber may include natural rubber as a diene rubber other than the polybutadiene rubber.

This natural rubber has a Mooney viscosity (M L ++
a, 100°C) 30 to 130, and preferred natural rubbers include, for example, R3S# type 1, R3S#
Examples include type 2, R3S# type 3, and SMR.

When the rubber composition of the present invention is used as a tire rubber, it is preferable to use a diene rubber consisting of 10 to 100% by weight of the above polybutadiene rubber and 0 to 90% by weight of the above natural rubber.

In addition, examples of the metal salts of fatty acids added to the rubber composition in item 1 include curved salts and sodium salts of fatty acids.

Metal salts selected from groups Ia to TVa of the periodic table, such as calcium salts, magnesium salts, and potassium salts, may be mentioned, and examples of the fatty acids include lauric acid, stearic acid,
Saturated fatty acids with 12 to 24 carbon atoms such as palmitic acid, 12 to 24 carbon atoms such as oleic acid, linoleic acid, liluic acid, etc.
unsaturated fatty acids, etc.

1) The amount of the metal salt of the fatty acid added is as follows:
0.02 to 3 parts by weight, preferably 0.00 parts by weight.
0.05 to 1 part by weight, particularly preferably 0.1 to 1 part by weight. If the amount added is less than 0.02 parts by weight, there is no effect of improving the extrusion processability of the rubber composition, and if it is more than 3 parts by weight,
Although it is effective in improving the extrusion processability of the rubber composition, the vulcanization rate slows down and the mechanical properties such as the tensile modulus of the rubber composition after vulcanization deteriorate.

1. Methods for adding the metal salt of fatty acid include adding it during the manufacturing process of polybutadiene rubber, dissolving the polybutadiene rubber in a solvent, adding to it and drying it, and adding other substances such as carbon black during kneading. Any method such as adding it together with a compounding agent may be used.

The rubber composition of the present invention includes a vulcanizing agent such as sulfur and a vulcanizing agent such as N-oxydiethylene-2-benzothiazolyl sulfenamide or dihenzothiazyl disulfide in order to vulcanize the diene rubber. An accelerator is added.

Further, carbon black, aromatic oil, zinc white, stearic acid, wax, anti-aging agent, etc. may be appropriately added to the rubber composition of the present invention depending on its use. For example, when the rubber composition of the present invention is used as a tire rubber, it is preferable to add 30 to 80 parts by weight of carbon black to 100 parts by weight of diene rubber.

Extrusion processing and vulcanization of the rubber composition of the present invention are carried out by conventional methods.

〔Example〕

EXAMPLES The present invention will be explained in more detail below by giving examples of the present invention together with comparative examples.

Examples 1 to 4 and Comparative Examples 1 to 6 Compounds according to the compound numbers shown in Table 1 below (rubber compositions)
were created respectively. Calcium stearate, low molecular weight polymer, and oil were all added during kneading along with other ingredients such as carbon blank.

For each of the above formulations, the Mooney viscosity (MI-
1+4, lO0°C), tackiness was measured, extrusion processability was evaluated, the surface texture of the extrudate was observed, and the tensile modulus and hardness of the vulcanizate were measured. The results are shown in Table 1 below.

The Mooney viscosity (ML++, 100°C) of the formulation was measured according to US K6300. The tackiness was measured using a Toyo Seiki tack meter Bikumata Tsuku Model H at room temperature of 25° C. under a load of 500 g and contact for 6 seconds. Further, extrusion processability was evaluated using a capillary rheometer manufactured by Intesco, by extruding through a triangular cross-section die at 80° C. and counting the number of edge breaks that occurred when the extrudate was pulled with a take-up roll. Also,
The vulcanizate was prepared by press vulcanization at 150° C. for 30 minutes. In addition, the tensile modulus and hardness of this vulcanizate were measured by JI
SK6301ζ followed.

Note] *1: Mooney viscosity (MT-1+, 100℃) 1
Polybutadiene rubber with a cis-1,4 structure content of 97% *2: Natural rubber with a Mooney viscosity (MLI+, 100°C) of 70 *3: Carbon blank consisting of a blending ratio of 30 parts by weight of FEF and 20 parts by weight of GPF *4 : Aroma oil (manufactured by Esso, #type 1) 0)
*5: Intrinsic viscosity [η] (toluene, 30°C) = 0°2
Cis-polybutadiene*6: The following components were blended as other compounding agents.

10 parts by weight of aromatic oil, 3 parts by weight of zinc white No. 1,
2 parts by weight of stearic acid, 2 parts by weight of wax, 2 parts by weight of anti-aging agent (N-phenyl-N'-isopropyl-p-phenylenediamine), vulcanization accelerator NBS (N-oxydiethylene-2-benzothiazolyl sulfate) phenamide) 0.4 parts by weight, 0.3 parts by weight of vulcanization accelerator DM (dihenzothiazyl disulfide), 1 part by weight, and 1.5 parts by weight of sulfur.

The following is clear from the results shown in Table 1 above.

The rubber compositions obtained in Examples 1 to 3 had different Mooney viscosity, tensile stress rate and hardness of the vulcanizate compared to the rubber composition obtained in Comparative Example 1 without the addition of calcium stearate. Improvements in extrusion processability (reduction in the number of edge breaks in the extrudate, improvement in surface texture) and improvement in tackiness can be seen without any damage. On the other hand, the rubber composition obtained in Comparative Example 2, in which a large amount of calcium stearate was added, improved extrusion processability and tackiness, but the tensile stress rate and hardness of the vulcanizate decreased, causing practical problems. occurs. Although the rubber compositions obtained in Comparative Examples 3 to 5 have an increased amount of oil or a low molecular weight polymer, the tensile stress rate and hardness of the vulcanizate are reduced, and the effect of improving extrusion processability is small. Furthermore, in Example 4 and Comparative Example 6, the effect of adding calcium stearate was examined when 50 parts by weight of polybutadiene rubber and 50 parts by weight of natural rubber were blended. is Comparative Example 6 without addition of calcium stearate
Mooney viscosity of the formulation compared to the rubber composition obtained with
Improvements in extrusion processability (reduction in the number of edge breaks in the extrudate, improvement in surface texture) and tackiness were observed without any change in the tensile stress rate and hardness of the vulcanizate.

〔Effect of the invention〕

According to the method for improving extrusion processability of a rubber composition of the present invention,
The polybutadiene rubber composition can be produced without adversely affecting the vulcanization system, without lowering the Mooney viscosity of the polybutadiene rubber composition, and without adversely affecting the various physical properties of the polybutadiene rubber composition after vulcanization. It is possible to improve the extrusion processability of products, especially the edge breakage and surface condition of extrudates during extrusion processing, and the rubber composition whose extrusion processability has been improved by the method of the present invention is particularly useful as rubber for tires. It is suitable for use.

Claims (7)

[Claims] (1) A metal salt of a fatty acid is added in an amount of 0.02 to 3 parts by weight based on 100 parts by weight of the diene rubber to a rubber composition containing a diene rubber containing 10 to 100% by weight of polybutadiene rubber. A method for improving extrusion processability of a rubber composition. (2) A method for improving extrusion processability of a rubber composition according to claim (1), wherein the metal salt of a fatty acid is calcium stearate. (3) The polybutadiene rubber has a Mooney viscosity (ML_1
_+_4, 100°C) 30 to 60 and a cis-1,4 structure content of 25% or more. (4) A method for improving extrusion processability of a rubber composition according to claim (1), wherein the diene rubber contains 0 to 90% by weight of natural rubber. (5) Natural rubber has a Mooney viscosity (ML_1_+_4,
A method for improving the extrusion processability of a rubber composition according to claim (4), wherein the rubber composition has a temperature of 100°C) 30 to 130°C. (6) A method for improving extrusion processability of a rubber composition according to claim (1), wherein the rubber composition contains 30 to 80 parts by weight of carbon black per 100 parts by weight of diene rubber. (7) A method for improving extrusion processability of a rubber composition according to any one of claims (1) to (6), which reduces edge breakage that occurs when an extrudate is stretched during extrusion.