KR100886119B1 - Mixing method of the compound for tire - Google Patents

Abstract

A mixing method of compound for a tire is provided to improve fatigue resistance and crack resistance by inputting vulcanization accelerator and retarder in rubber firstly. A mixing method of compound for a tire comprises a first step of making compound by inputting vulcanization accelerator and vulcanization retarder in rubber raw material and then mixing them; a second step of inputting carbon black into compound and then mixing them; and a third step of adding sulfur as vulcanizing agent. The mixing temperature of the first step is 120~150°C. The mixing temperature of the second step is 140~160°C.

Description

Mixing method of the compound for tire}

The present invention relates to a method for refining a compound for tires, and more particularly, to form an ideal crosslinked structure by an even distribution of a vulcanizing agent, and to suppress fatigue breakage and crack growth that starts at a relatively weak crosslinked site. A method for refining a dragon compound.

Rubbers, which form the basis of tire materials, are usually made in a compound form and are made of a mixture of a number of compounding agents according to the characteristics required for each part. The compound is thus processed into semi-finished products, and these semi-finished products are formed through a process called a molding process to form a fixed tire and become a final product through a vulcanization process. At this time, the vulcanization process is crosslinked by sulfur and vulcanization accelerator contained in the compound and ultimately acts as an elastic rubber.

The vulcanizing agent is added in the conventional compound for tires up to 10 parts by weight, which is mixed during the kneading process called the refining process.

On the other hand, the refining process has a unit process of two or more stages, generally, the process of mixing the vulcanizing agent is finally made. Specifically, the process in which the vulcanizing agent is mixed is performed at a particularly low temperature, that is, 125 ° C. or less, and finally, after the process including the carbon black and the remill process are performed. The reason for the low temperature is that if it exceeds 125 ° C, scorch occurs due to vulcanization during kneading by the added sulfur and vulcanization accelerator.

In addition, the previous refining step in which the vulcanizing agent is added, that is, the process including the carbon black is usually mixed within 145 ~ 200 ℃, wherein the carbon black is a carbon gel through the dispersion and distribution process on the rubber This creates a strong bond between rubber and carbon black. In general, the amount of carbon gel is increased as the mixing temperature increases, and the reinforcing property of the compound is increased. However, it is effective that the amount is appropriately formed according to the required performance of each compound. Usually, when carbon gel is measured by toluene extraction, about 50 to 70% by weight is carbon gel.

However, among the carbon gels, since the portion immediately adjacent to the carbon black has the strongest bond, a compounding agent such as a vulcanizing agent may not be dispersed or distributed to the carbon gel portion in a subsequent process.

If the vulcanizing agent is not evenly distributed, fatigue resistance and crack resistance will inevitably decrease, but most compound engineers overlook this problem, and are not aware of the degradation of the compound caused by the problem. .

The present invention has been made to solve the above problems, a new mixing method of inverse mixing, that is, by dispersing the vulcanization accelerator and the vulcanization retardant first on the rubber in a conventional Soviet process to finally achieve a uniform crosslinked structure It is to provide a method for refining a compound for tires that can be formed to improve fatigue resistance and crack resistance.

Other objects and advantages of the invention will be described below and will be appreciated by the embodiments of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the claims.

A method for refining a compound for tires according to the present invention includes a first step of generating a compound by simultaneously adding and mixing a vulcanization accelerator and a vulcanization retardant on a raw material rubber; A second step of mixing by mixing carbon black into the compound; And a third step of adding sulfur as a vulcanizing agent.

The inventors of the present invention have developed a new mixing method called inverse mixing, and this inverse mixing method is a method of dispersing the vulcanization accelerator and the vulcanization retardant first in a rubber phase in a conventional Soviet process.

That is, a low-temperature mixing process is performed by adding a vulcanization accelerator and a vulcanization retardant among the vulcanizing agents to be used in the compound to rubber such as natural rubber, and then mixing carbon black with the rubber-vulcanization accelerator / vulcanization retardant compound obtained. to be. This method is a concept first attempted in the present invention in a way that ordinary rubber engineers cannot think of.

Since the vulcanization accelerator is evenly distributed in the rubber phase before the carbon gel is formed by the inverse mixing method as described above, the vulcanization accelerator can be evenly distributed in the carbon gel to be formed later, and thus, The reaction is also induced naturally to finally form a uniform crosslinked structure.

The inverse mixing is a method of mixing the vulcanization accelerator and the vulcanization delayer first, unlike the most common concept in which the vulcanizing agent is added last, and the mixing method is performed through low temperature mixing. This method is possible in both a conventional Banbury mixer and kneader or mill.

Meanwhile, the first kneading step in which the rubber and the vulcanization accelerator and the vulcanization delay agent are mixed is preferably performed at low temperature in the range of 120 to 150 ° C., and the next step in which the carbon black is added is in the range of 140 to 165 ° C. It is preferable to be.

When the temperature is exceeded, the scorch time of the final compound may be shortened, and there is a fear that the scorch may be generated in the extrusion or rolling process, which is a later step.

In particular, when the vulcanization accelerator and the vulcanization retardant are mixed at 120 to 150 ° C., the effect of the Soviet Union on the initial rubber phase may be reduced. That is, the effect of the Soviet Union decreases as the oxidation of the end of the mechanically cut rubber chain decreases and recombines, and when the temperature exceeds 150 ° C., the rubber is too soft to cut the mechanical chain so that the Soviet effect decreases. Done.

In addition, in the step of adding carbon black, which is a step after the first kneading process in which the vulcanization accelerator and the vulcanization delay agent are mixed, the kneading is preferably maintained at 140 to 165 ° C., when the temperature exceeds 165 ° C., a scorch problem occurs. In the case of mixing below 140 ° C, the formation of carbon gel required for reinforcement is not sufficiently induced. Therefore, the temperature range in the two-step carbon black mixing process should be controlled to be 140 ° C to 165 ° C. .

Hereinafter, the structural change of the compound according to the inverse mixing method of the present invention will be described in more detail.

When the rubber and carbon black are first kneaded by a conventional method, the combination of the carbon gels enclosed in the rubber phase is made around the carbon black particles, and the portion immediately adjacent to the carbon black in the carbon gel shows the strongest bond. As a result, the penetration of the compounding agent, such as a vulcanizing agent, is not easy during the post-processing, and thus uniform dispersion of the vulcanizing agent cannot be obtained, resulting in deterioration of fatigue resistance and crack resistance.

However, according to the inverse mixing method of the present invention, the rubber-vulcanization accelerator-vulcanization retardant compound is first formed so that the vulcanization accelerator is already evenly distributed on the rubber. Therefore, the vulcanization accelerator is evenly dispersed in the carbon gel formed by the introduction of carbon black, which is a post-process, so that the reaction with sulfur is naturally induced to obtain a uniform crosslinked structure.

The terms or words used in this specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The rubber composition for tire treads according to the present invention as described above provides the following effects.

According to the method for refining the compound for tires of the present invention, since the uniformity of the crosslinked structure can be obtained, the fatigue resistance and the crack resistance of the compound can be greatly improved, whereby the wear resistance can be improved, thereby improving the tire resistance. Among the materials, it can be applied to various parts from the tread compound to the belt part requiring durability.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but it should be noted that the present invention is not limited by the following examples.

Refining Process

The refining process was performed according to the compounding ratios and compounding conditions as shown in the following [Table 1] and [Table 2].

Example  And Comparative example

<Example 1>

According to the inverse mixing method of the present invention, a rubber-vulcanization accelerator-vulcanization retardant compound is mixed by mixing 100 parts by weight of natural rubber with 1 part by weight of vulcanization accelerator and 0.3 parts by weight of vulcanization retardant based on 100 parts by weight of the natural rubber. 50 parts by weight of carbon black was added and mixed in two steps, and 1.5 parts by weight of sulfur was added as a final step.

On the other hand, in the mixing conditions, the mixing temperature and mixing time of the first stage is 135 ℃, 1 minute 30 seconds, the mixing temperature and mixing time of the second stage 160 ℃, 2 minutes 30 seconds, the mixing temperature and mixing time of the final stage It carried out on the conditions of 110 degreeC and 50 second.

<Example 2>

The mixing was carried out under the same conditions as in Example 1 except that the mixing temperature of step 1 was maintained at 145 ° C.

<Example 3>

Unlike Examples 1 and 2, the sulfur and vulcanization accelerators, which are vulcanizing agents applied to the compound, were reduced by 10%, respectively, and mixing conditions were performed under the same conditions as in Example 1.

Comparative Example 1

According to the conventional refining method in the first step, the Soviet work is carried out, and in the second step, 50 parts by weight of carbon black is added to 100 parts by weight of rubber, and then 1.5 parts by weight of sulfur, 1.0 part by weight of vulcanization accelerator and vulcanization in the final step. 0.3 parts by weight of the retardant was added and kneaded.

Comparative Example 2

The refining process was carried out in the same manner as in Example 1 except that the vulcanization retardant was not added in the first step and the vulcanization retardant was added in the final step.

Comparative Example 3

The refining process was performed similarly to Example 1 except the mixing temperature of 1st stage was kept at 155 degreeC.

<Comparative Example 4>

It proceeded in the same manner as in Example 1 except that the mixing temperature of the second step was maintained at 185 ° C.

Compounding ratio (unit: parts by weight) Mixing stage Compounding agent Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4  Stage 1 Natural rubber 100 100 100 100 100 100 100 Curing accelerator ^{1 )} 1.0 1.0 0.9 - 1.0 1.0 1.0 Delay Retardant ^{2 )} 0.30 0.30 0.30 - - 0.30 0.30  2 steps Carbon Black ^{3 )} 50 50 50 50 50 50 50 Zinc Oxide ^{4 )} 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Stearic acid 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti-aging 2 2 2 2 2 2 2  3 steps brimstone 1.5 1.5 1.35 1.5 1.5 1.5 1.5 Curing accelerator ^{1 )} - - - 1.0 - - - Delay Retardant ^{2 )} - - - 0.30 0.30 - -

Corporation

1): sulfenamide type or mercito benzothiazole type vulcanization accelerator

2): N-cyclohexyl thiophthalimide

3) ISAF grade

4): Zinc oxide (ZnO) manufactured by drying method (surface area: 3 ㎡ / g)

Formulation condition Mixing step Mixed condition Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Stage 1 Mixing time 1 minute 30 seconds 1 minute 30 seconds 1 minute 30 seconds 1 minute 30 seconds 1 minute 30 seconds 1 minute 30 seconds 1 minute 30 seconds Mixing temperature 135 ℃ 145 ℃ 145 ℃ 135 ℃ 135 ℃ 155 ℃ 135 ℃ 2 steps Mixing time 2 minutes 30 seconds 2 minutes 30 seconds 2 minutes 30 seconds 2 minutes 30 seconds 2 minutes 30 seconds 2 minutes 30 seconds 2 minutes 30 seconds Mixing temperature 160 ℃ 160 ℃ 160 ℃ 160 ℃ 160 ℃ 160 ℃ 185 ℃ 3 steps Mixing time 50 seconds 50 seconds 50 seconds 50 seconds 50 seconds 50 seconds 50 seconds Mixing temperature 110 ℃ 110 ℃ 110 ℃ 110 ℃ 110 ℃ 110 ℃ 110 ℃

Physical properties of the Examples and Comparative Examples are shown in the following [Table 3].

Physical property results Properties The details Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Machinability Viscosity 68 63 63 67 73 68 71 Scorch Time 26 minutes 25 minutes 28 minutes 27 minutes 17 minutes 12 minutes 18 minutes  Tensile Properties 300% modulus 165 170 160 160 167 166 150 % Elongation 420 410 435 437 278 365 430 The tensile strength 297 310 285 290 320 298 280 Fatigue resistance Performance index 135 138 120 100 105 108 110 Standard Deviation Index between Specimens (n = 6) 280 285 200 100 161 153 167 Crack resistance Performance index 175 167 145 100 115 128 119 Wear resistance Performance index 140 135 108 100 102 100 102

[Related to tensile properties]

300% Modulus: Tensile Strength at 300% Elongation (kgf / ㎠),

Tensile Strength: Tensile Strength at Break (kgf / ㎠)

Fatigue resistance: We calculated the index of performance by averaging the cycles of failure while simultaneously applying the cyclic deformation of 6 dumbbell-type specimens to 118%, and calculating the difference between the fracture points of each of the six specimens as the standard deviation. Is higher means more advantageous. For example, if the standard deviation index is 280, this means that the deviation is 1/3 compared to 100.

As shown in Table 3, in the case of Example 1, the problem of scorch does not occur at all, and the ultimately reacted with the sulfur introduced in the last step by the well-dispersed vulcanization accelerator before carbon gel formation by inverse mixing Since the effective crosslinking was formed in a balanced manner, it was found that the fatigue resistance was improved by 35% compared to Comparative Example 1.

First of all, it was confirmed that the standard deviation index was lowered to about 1/3 compared to that of Comparative Example 1 as a result of the unstable crosslinking structure occurring in any of the specimens as the fracture time between the specimens became almost the same. In addition, crack resistance was improved by 75%, and the fatigue resistance of rubber, which is affected by the fatigue performance, was improved by 40%.

However, as in the case of Comparative Example 2, inverse mixing without the retardant has improved physical properties, but the scorch stability is poor, it can be seen that there is a problem in the post-process such as actual extrusion. This means that the composition of the present invention must be mixed in the range of 120 to 150 ° C. while the vulcanization accelerator and the vulcanization delay agent are simultaneously added.

Example 2 confirmed that there was no problem by increasing the mixing temperature to 145 ° C. in the one-step inverse mixing step.

Example 3 evaluated the case where the amount of the vulcanizing agent used in the formulations of Examples 1 and 2 was reduced by 10%, respectively. As a result, the results were superior to those of the comparative example, and the results similar to those of Examples 1 and 2 were shown. That is, when the inverse mixing method of the present invention is applied, it is confirmed that even when the amount of the vulcanizing agent is reduced by applying about 10% compared to the comparative example 1 to which the conventional mixing method is applied.

On the other hand, when it exceeds 150 ℃ as in Comparative Example 3 it was confirmed that the scorch time is shortened rapidly. In addition, in Comparative Example 4, which is a case where the mixing temperature of the two stages of 160 ℃ or more, the improved physical properties than Comparative Example 1 was confirmed that the scorch time is shortened. That is, it can be seen that the temperature conditions are important for the inverse mixing of the present invention.

Therefore, when the inverse mixing technology of the present invention is applied, the fatigue resistance and crack resistance of the compound can be obtained since the vulcanizing agent can obtain the uniformity of the crosslinked structure that cannot be obtained from the conventional compound that could not enter the mixing process after the formation of the solid carbon gel. The performance could be greatly improved. Ultimately, the wear resistance is improved, and thus, the tire material can be grafted to a variety of tread compounds and belt parts requiring durability.

Claims (3)

A first step of generating a compound by simultaneously adding and mixing a vulcanization accelerator and a vulcanization retardant on the raw material rubber; A second step of mixing by mixing carbon black into the compound; And A method for refining a compound for tires comprising a third step of adding sulfur as a vulcanizing agent. The method of claim 1, The mixing temperature of the first step is a refining method of a compound for tires, characterized in that 120 to 150 ℃. The method according to claim 1 or 2, Mixing temperature of the second step is a method of refining a compound for tires, characterized in that 140 to 160 ℃.