KR100665480B1 - Manufacturing method for tread rubber of truck and bus tires - Google Patents

Abstract

The present invention has a pH of 6 to 9, iodine adsorption of 130 to 150 mg / g, nitrogen adsorption specific surface area of 130 to 150 m 2 / g, dibutyl phthalate absorption of 120 to 140 ml / 100 g, coloring degree of 130 to 140%, and centrifugal sedimentation The carbon black having a value of ΔD ₅₀ of the maximum frequency band (ΔD ₅₀ ) by 40 to 60 nm was mixed with natural rubber in the form of a slurry in a liquid phase, and then compressed and dried to prepare a mixture, followed by subsequent compounding. To provide tread rubber for pneumatic tires for truck buses, which is predispersed with natural rubber and carbon black with a small particle size and a large specific surface area, which are excellent for improving wear resistance. By manufacturing, the balance between wear resistance and heat resistance can be achieved, and consequently, the life of the tire can be improved.

Description

Manufacturing method for tread rubber of truck and bus tires}

The present invention relates to a method for manufacturing tread rubber for pneumatic tires for truck buses, and more particularly, to a method of premixing carbon black, a reinforcing agent for improving abrasion resistance of tread rubber, with natural rubber and blending with other compounding agents. A method for producing tread rubber for pneumatic tires for truck buses.

In the case of tread rubber for large radial pneumatic tires used in trucks and buses, the service life of the rubber composition itself is increased along with the heat resistance of the rubber composition itself in order to prevent the explosion and separation of the tires caused by the heat generation of the tread during long-distance high-speed driving. It is important to balance at high levels of wear resistance.

In order to improve the abrasion resistance of the tread rubber, it is a common method to use a carbon black as a reinforcing agent with a large specific surface area or a large structure in consideration of the structural characteristics of the carbon aggregates. In order to reinforce and to improve rubber reinforcement, methods for increasing the blending amount of carbon black have been taken.

However, in general, when carbon black having a large specific surface area is used, reinforcement with rubber may be increased, thereby improving abrasion resistance. However, it is generally known that the larger the specific surface area, the lower the heat generation resistance. Accidents cause significant problems with the performance of the product.

In addition, increasing the blending amount of carbon black is also inevitable deterioration in heat resistance, and also increases the unvulcanized viscosity due to the increase in the carbon black and polymer bonding phase is accompanied by a decrease in processability.

In general, as a method of lowering the heat generation of the rubber, it is widely used to reduce the specific surface area of the carbon black used as the filler, but in this case, the wear resistance of the composition is reduced due to the use of the carbon black having a small specific surface area, and thus the life of the tire is reduced. This results in shortening.

Therefore, in order to achieve the desired wear resistance performance, carbon black having a large specific surface area, that is, having a small particle size, must be used. Due to the poor dispersion, the degradation of physical properties such as tearing resistance and fatigue resistance may result in improved wear resistance. This may result in worse results when blended with natural rubber and synthetic rubber.

 Accordingly, in the present invention, by using an appropriate amount of carbon black having a specific particle characteristic that has a large specific surface area, which is advantageous for abrasion resistance, the wear resistance is improved, and carbon black is used in a natural rubber and liquid state in order to compensate for deteriorated heat generation and dispersibility. It is an object of the present invention to provide a method for producing a tread rubber that can be improved in heat resistance and fatigue resistance with a significantly improved dispersibility by performing a process of mixing with other compounding agents in advance.

Method for producing a tread rubber for pneumatic tires of the truck bus of the present invention for achieving the above object is silica as a reinforcing agent based on 100 parts by weight of the raw material rubber consisting of 60 to 100% by weight of natural rubber and 40% by weight of polybutadiene rubber. 40 to 60 parts by weight of the carbon black alone, 2.0 to 3.0 parts by weight of a vulcanization accelerator and sulfur are added, and other conventional compounding agents are properly blended. In this case, the carbon black is 6 to 9 and iodine adsorption is 130 to 150 mg / g, nitrogen adsorption specific surface area of 130 to 150 m 2 / g, dibutyl phthalate absorption of 120 to 140 ml / 100 g, coloring degree of 130 to 140%, and the maximum half-width value (ΔD ₅₀ ) of the centrifugal sedimentation method. It is characterized by mixing 40 to 60nm with a natural rubber in the form of a slurry in a liquid phase, and then preparing it in a compressed and dry form, followed by subsequent compounding. The.

The present invention will be described in more detail as follows.

The raw material rubber of the present invention is a diene rubber as natural rubber alone or a mixed rubber with polybutadiene rubber, and when mixed with polybutadiene rubber, it can be mixed and used within 40% by weight of the total raw rubber.

The carbon black used in the present invention has a pH of 6 to 9, iodine adsorption of 130 to 150 mg / g, nitrogen adsorption specific surface area of 130 to 150 m 2 / g, dibutyl phthalate absorption of 120 to 140 ml / 100 g, and a degree of coloring of 130 to 130 140%. In addition, the aggregate characteristic is preferably the maximum frequency value of the full width at half maximum of Sir (ΔD ₅₀₎ by centrifugal sedimentation separation 40~60nm.

As a reinforcing agent having such a property, carbon black except silica is used in an amount of 40 to 60 parts by weight based on 100 parts by weight of the raw material rubber alone. Does not obtain a satisfactory level of abrasion resistance, and when blended in excess of 60 parts by weight, the viscosity becomes high, resulting in poor workability. It becomes unfavorable because it becomes high.

In addition, when carbon black having a large specific surface area and a small particle size is used, which is advantageous for improving abrasion resistance, and carbon black having a smaller specific surface area and a larger particle size is used, a carbon black / natural rubber master batch is produced as in the manufacturing method of the present invention. The application of the carbon black is also important because the degree of reinforcement with rubber is lower than that of carbon black having a small particle size, so that the wear resistance can not be satisfactorily improved.

In addition to the raw material rubber and carbon black, the vulcanization accelerator and sulfur are included in an amount of 2.0 to 3.0 parts by weight based on 100 parts by weight of the raw material rubber, and other conventional compounding agents include a vulcanization active agent and an anti-aging agent, and the composition thereof is particularly exceptional. It is not limited.

The manufacturing method of the rubber for tire treads according to the present invention is characterized in that it is in accordance with a conventional manufacturing method, except that carbon black satisfying the above characteristics is premixed with natural rubber. Specifically, the carbon black alone is mixed with water to prepare a liquid phase slurry form, and then mixed with natural rubber latex, and after removing the moisture through an extruder, once again passed through the compactor to compress and hot air dry After cooling, it is made into a certain shape and used. In this way, when carbon black is premixed with natural rubber, dispersibility can be improved, and heat resistance and fatigue resistance can be improved.

Since the compounding process and the raw materials are the same as the conventional method for producing a tire tread rubber, of course, it is not particularly limited.

Hereinafter, the present invention will be described in the following examples, but is not limited to the examples.

Example 1

Rubber additives were prepared by conventional methods using a banbury mixer and an open mill with the additives shown in Table 1 in the following composition ratios. However, carbon black is mixed with water to prepare a liquid phase slurry form, and then mixed with natural rubber latex, water is removed through an extruder, and once again passed through a compactor, compressed, hot air dried and cooled After the formation, the rubber test piece was prepared by a conventional method.

Comparative Examples 1 and 2

 Next, rubber test pieces were prepared in a conventional manner with the compounding agents and the composition ratios of Table 1, and physical properties thereof were measured.

Comparative Example 3

As a compounding agent and a composition ratio of the following Table 1, a rubber test piece was prepared by using a method of premixing carbon black and natural rubber as in Example 1, and physical properties were measured.

Specific evaluation methods for the rubber test pieces obtained according to Example 1 and Comparative Examples 1 to 3 are as follows, the results are shown in Table 1 below.

 [Abrasion Resistance Test]

 The disk-shaped abrasive stone and the disk-shaped rubber composition test specimens of Examples 1 and 3 were rotated independently, respectively, and silicon carbide was dropped between the compressed abrasive stone and the rubber test specimen, and the worn surface of the rubber test specimen Table 1 shows the results of the measurement using a Lambon wear tester which prevents the sticking of the abrasive stone and measures the wear loss of the rubber test piece caused by the difference in the surface speed between the abrasive stone and the rubber test piece. The value shown in Table 1 is the value shown with the value of the comparative example 1 as the reference | standard 100, It shows that it is excellent in abrasion resistance as a number becomes large.

 [Heat resistance test]

 The rubber test pieces of Examples 1 and Comparative Examples 1 to 3 were subjected to a strain of 10HZ and 1% at 60 ° C. to measure the viscous modulus and elastic modulus at this time, and the ratio of these two values, that is, the value of the viscous modulus / elastic modulus, That is, the results measured by a rheometrics tester for calculating tan δ are shown in Table 1 below.

 The value shown in Table 1 is the value shown on the basis of the value of the comparative example 1 as reference | standard 100, and it shows that heat resistance is disadvantageous, so that the number is small.

Carbon Black Dispersion Test

An optical microscope (High Resolution vidicon camera, Hamamatsu C-2702) was used to observe the cut surface of the rubber specimen as an image and calculate the carbon black dispersion according to the following equation. The values shown in Table 1 indicate that the larger the number is, the better the dispersion degree is, based on the value of Comparative Example 1 (100).

 Carbon black dispersion (%) = 100- (U / Lxα)

U: Correction area (unit: pixel ² , 1 pixel ≒ 1 μm) of undispersed carbon black aggregates measured by Image Analyzer divided by 100 μm ²

L: carbon black volume% in the specimen

α: correction factor

Comparative example Example One 2 3 One Natural rubber 100 100 100 100 Carbon Black A ¹⁾ 50 - - 50 Carbon Black B ²⁾ - 50 50 - Zinc oxide 4.0 4.0 4.0 4.0 Stearic acid 2.5 2.5 2.5 2.5 Anti-aging agent ³⁾ 1.5 1.5 1.5 1.5 Anti-aging agent ⁴⁾ 1.0 1.0 1.0 1.0 brimstone 1.5 1.5 1.5 1.5 NS ⁵⁾ 1.0 1.0 1.0 1.0 Abrasion Resistance Index 100 82 83 107 Fever Resistance Index 100 116 118 105 Carbon Black Dispersion Index 100 105 107 112 1) carbon black A; Nitrogen adsorption ratio surface area of 130 to 140 m 2 / g, tint coloring value of 130 to 140% 2) carbon black B; Nitrogen adsorption ratio Surface area 80-100㎡ / g, tint coloring value 100-110% 3) N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine 4) Poly- (2, 2,4-trimethyl-1,2-dihydroquinoline) 5) Nt-butylbenzothiazole-2-sulfenamide

In Table 1, Comparative Example 2 compared carbon black with a relatively large particle size and a small specific surface area compared to Comparative Example 1, and replaced the same amount of carbon black, which is disadvantageous in wear resistance. Compared with the comparative example 1, although it is excellent in heat resistance, abrasion resistance falls and the undesirable result is shown.

Example 1 was prepared by using the same carbon black having a small particle size and a large specific surface area, which were excellent in improving the wear resistance used in Comparative Example 1, in the form of a master batch with natural rubber as mentioned in the above description. It can be seen that the carbon black dispersibility is significantly improved and thus the effect of offsetting the lowering of the heat generation resistance caused by the use of carbon having a small particle size is obtained. In addition, as the carbon black dispersion is improved, it can be seen that the wear resistance is slightly increased due to further improvement in physical properties.

Comparative Example 3 is a case where the carbon black has a large particle size and a small specific surface area, and is produced in a master batch form with natural rubber, which is the same mixing method as Example 1, using carbon black, which is disadvantageous in wear resistance. The degree of increase did not appear as much as the increase of Example 1 compared to Comparative Example 1 due to this, the degree of increase in the wear resistance and heat resistance resistance is insignificant, showing no effect.

On the other hand, Example 1 shows that the wear resistance is improved and the heat resistance is equivalent to that of Comparative Example 1 to achieve a balance between wear resistance and heat resistance, thereby improving the overall tire life without accident of the product during use.

As described in detail above, in the case where rubber is manufactured by predispersing carbon black having a small particle size and a large specific surface area with natural rubber according to the present invention and then performing a conventional rubber compounding method, wear resistance and heat resistance As a result, the life of the tire can be improved.

Claims (1)

(Correction) 40 to 60 parts by weight of carbon black alone, silica, and 2.0 to 3.0 parts by weight of carbon black except silica as a reinforcing agent, based on 100 parts by weight of raw rubber including 60 to 100% by weight of natural rubber and 40% by weight of polybutadiene rubber. In the method for producing a tread rubber by adding a portion and properly blended with other conventional compounding agent, pH 6-9, iodine adsorption 130-150mg / g, nitrogen adsorption specific surface area 130-150m2 / g, dibutyl phthalate absorption 120-140ml / 100g, coloring degree 130-140%, maximum by centrifugal sedimentation Pneumatic tires for truck buses, characterized in that the carbon black having a half width value of ΔD ₅₀ of 40 to ₆₀ nm is mixed with natural rubber in the form of a slurry and then compressed and dried to produce a mixture. Method for producing tread rubber for use.