JP5210485B2 - Method for producing rubber composition - Google Patents

Description

  The present invention relates to a method for producing a rubber composition by kneading a compounding material containing rubber in a tire production process.

  A rubber composition for tires is manufactured by kneading raw material rubber with various compounding materials such as oil, filler, vulcanizing agent, vulcanization accelerator using a kneading machine such as a Banbury mixer. . In this case, the kneading is generally performed in two steps depending on the characteristics of the compounding material.

  The first step is a so-called non-pro kneading process, in which carbon black, oil, filler, etc., excluding vulcanization-related compounding materials are added to the raw rubber and kneaded. Non-pro kneading is performed at a high temperature of 160 to 180 ° C. for a long time in order to sufficiently disperse these compounding materials in the raw rubber.

  The second step is a so-called pro-kneading process, in which a vulcanizing agent, a vulcanization accelerator, an accelerator aid and the like are added and kneaded into the rubber compound obtained by the non-pro kneading process. In the professional kneading process, if the kneading temperature is high or the kneading time is long, heat is generated during kneading and the temperature rises, and as a result, the rubber may be crosslinked. Therefore, unlike the non-pro kneading process, the professional kneading needs to be performed by setting the environment temperature to a low (about 130 ° C.) and setting an appropriate time. The rubber composition obtained through the professional kneading process is vulcanized when heat is applied.

  The vulcanizing agent kneaded in the professional kneading process is usually sulfur. However, sulfur is a dangerous substance (flammable solid), but it is already known that it is easily charged due to friction during handling and impact. Therefore, when the charged sulfur is charged into the Banbury mixer in the professional kneading process, there is a risk of a fire being caused by spark discharge or the like.

  In order to solve this problem, it is necessary to suppress the charge amount of sulfur used in the professional kneading process. Conventionally, in order to suppress charging of sulfur, a method of suppressing charging by controlling environmental conditions and a method of adding an antistatic agent to sulfur have been proposed.

  First, sulfur charge suppression by controlling environmental conditions is a method of using a humidifier in a professional kneading process to create a high-humidity working environment. Although this method can surely reduce the charge amount, various problems occur. First, there is a problem that the water content of the rubber composition obtained in the professional kneading process is increased. This is not preferable because it causes problems such as adhesion inhibition and air entry in the subsequent process. Secondly, depending on the chemicals kneaded into the raw rubber, quality change occurs due to water content, which causes problems in the performance of the rubber composition. Thirdly, when the water content that is scattered during kneading is sucked into the dust collector of the Banbury mixer, it adheres to the pipes of the dust collector, the bubble filter, and the like, which may cause problems such as defective equipment and deterioration.

  Next, in the method of adding an antistatic agent, oil treat or zinc white (zinc oxide) is used as the antistatic agent. However, when an oil treat is used, the amount of oil added is limited in order to prevent performance deterioration of the rubber product, and therefore a sufficient antistatic effect due to the addition of the oil treat cannot be expected. Zinc oxide, on the other hand, exhibits a static elimination effect, but cannot be said to be a sufficiently satisfactory antistatic effect.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for producing a rubber composition without causing charging of sulfur in a professional kneading process.

In order to solve this problem, the present invention provides a non-pro kneading process in which carbon black, oil, and other compounding materials are added to a raw rubber and kneaded, and a rubber compound obtained in the non-pro kneading process is vulcanized. a process for preparing a rubber composition by a professional kneading step of kneading a vulcanization accelerator, the amount of carbon black corresponding to at least a portion of the carbon black the total amount to be added as an antistatic agent in the pro kneading step, It is characterized by adding 0.5 to 1.0% by weight with respect to the blending amount of the vulcanizing agent.

  Carbon black is a compounding material that is always added to rubber compounding as a reinforcing agent for rubber products, and as can be seen from the fact that carbon fibers are used in the antistatic cloth, it has excellent electrical conductivity and has a neutralizing effect. There is no quality concern at all. That is, when carbon black is added as an antistatic agent in the professional kneading process, the quality of the rubber composition is not deteriorated as in the case of adding a conventional oil treat, and the environmental conditions are changed and the humidity is increased. There is no need for a working environment. Furthermore, since the amounts of various compounding materials that satisfy the physical properties required for the rubber composition are determined in advance at the design stage, the amount of carbon black added as an antistatic agent is at least the predetermined total amount of carbon black. An amount corresponding to a part, for example, 0.1% by weight of the total amount of carbon black is sufficient. Therefore, according to the present invention, it is possible to obtain a high antistatic effect without disadvantages such as deteriorating the quality of the rubber composition, and it is possible to easily prevent dangers such as fire in the professional kneading process. .

In the present invention, the vulcanizing agent added at the time of professional kneading is sulfur. Since sulfur is highly likely to be charged at the time of charging as described above, a predetermined amount of carbon black is charged simultaneously with sulfur and a vulcanization accelerator as an antistatic agent. In this case, the amount of carbon black added as an antistatic agent is 0.5 to 1.0% by weight with respect to the amount of sulfur as a vulcanizing agent set in advance. For example, when adding 1% by weight of carbon black with respect to the amount of sulfur, if the total amount of carbon black is 26% by weight and sulfur is 1.8% by weight, 0.0018% by weight. The upper limit of the amount of carbon black is not good as long as it is an amount sufficient dispersion can be taken in the rubber in the professional kneading time. If the amount of carbon black exceeds the upper limit, the total amount of carbon black to be charged is determined by design, so the amount charged in the non-pro kneading process decreases, and the physical properties of the final rubber composition may deteriorate, It is not preferable.

  As the carbon black used in the present invention, any commercially available carbon black can be mentioned, and finely powdered carbon black is particularly preferable. For example, a commercially available carbon black usually used for tire manufacture is used in the form of fine powder. Can do. In particular, the carbon black of SAF, ISAF, HAF grade, etc. in the form of fine powder is preferable. The particle size of carbon black is preferably in the range of 10 to 30 μm.

  In the present invention, the neutralizing action of carbon black against the charging of sulfur as a vulcanizing agent is considered to be due to the following mechanism. The particle size of the carbon black is considerably smaller than the sulfur added, for example, the average particle size of sulfur is 7 μm, whereas the average particle size of carbon black is 20 nm, which is about 1/350 of sulfur. When carbon black and sulfur are simultaneously added and kneaded in the professional kneading process, the carbon black particles adhere around the charged sulfur particles, absorb the charge, and discharge into the atmosphere (corona discharge). It is considered that the charged sulfur particles can be neutralized.

  Moreover, as a vulcanization accelerator thrown in at a professional kneading process, the various things normally used for a sulfur bridge | crosslinking type | system | group can be used individually or in combination of 2 or more types. Furthermore, you may add a promoter aid etc. as needed.

  In the present invention, professional kneading is performed at a temperature of 130 ° C. or lower, preferably 110 ° C. or lower. When the kneading temperature exceeds 130 ° C., scorch of the rubber compound is generated, which is not preferable. The kneading time may be any time as long as the introduced sulfur, carbon black, and vulcanization accelerator are sufficiently dispersed and kneaded in the rubber, and are, for example, 1 to 1.5 minutes. The rubber may become too hard after professional kneading. In this case, the rubber composition may be subjected to rubber softening treatment.

  Next, the present invention will be described in detail with reference to experimental examples. In this experimental example, various carbon blacks were charged simultaneously with sulfur in a professional kneading process to confirm the effect of removing static electricity from sulfur, and the results are shown in FIG.

  For comparison, a rubber composition having the formulation shown in Table 1 was produced by conventional non-pro kneading (kneading temperature: 160 ° C.) and pro kneading (kneading temperature: 110 ° C.) treatment, and the charge amount was measured. As shown in FIG. 1 as an A blender, it was 1.25 kV. Note that the charge amount of the rubber composition after professional kneading was approximately 1.25 kV regardless of the type of carbon black.

  A part of the carbon black used for non-pro kneading in Table 1 is used as an antistatic agent in a blending amount corresponding to 0.5% by weight or 1.0% by weight of the blending amount of sulfur as a vulcanizing agent in the professional kneading process. A rubber composition was produced by charging and kneading, and the charge amount was measured to obtain the result shown in FIG. The carbon black used is Sun Black 305 (Asahi Carbon Co., HAF grade) having a particle size of 18 nm, Sun Black 285 (Asahi Carbon Co., SAF grade) having a particle size of 26 nm, and a particle size of 20. MA-100 (SAF grade, manufactured by Mitsubishi Chemical Corporation) having a lamp black (channel type) and a particle size of 22 nm. The charge amount was measured by CYSIDO electrostatic STATIRON-DZ23.

  As shown in FIG. 1, when Sun Black 285 is introduced, the charge amount can be suppressed to 1.02 kV when the blending ratio is 0.5% by weight, and to 0.75 kV when 1.0% by weight. As the amount is increased, the charge suppressing effect becomes more prominent. When Sun Black 305 is added, the charge amount can be suppressed to 0.57 kV at a blending ratio of 0.5% by weight, and to 0.45 kV at 1.0% by weight. The effect becomes remarkable. When lamp black is introduced, the charge amount can be suppressed to 0.75 kV at a blending ratio of 0.5% by weight, and to 0.57 kV at 1.0% by weight. Becomes prominent. When MA-100 is introduced, the charge amount can be suppressed to 0.8 kV at a blending ratio of 0.5% by weight, and to 0.38 kV at 1.0% by weight. The effect becomes remarkable. That is, it can be seen that even if any carbon black is added to the professional kneading process as an antistatic agent, a satisfactory charge suppressing effect can be obtained as compared with the rubber composition obtained by the conventional kneading process. In particular, when carbon black other than recovered carbon is added, the antistatic effect can be improved as the blending ratio is increased.

  The present invention suppresses the charging of the vulcanizing agent during kneading by introducing carbon black as an antistatic agent into a kneading professional kneading process for producing a rubber composition for tires. Disasters such as fire can be prevented.

It is a graph which shows the relationship between the compounding ratio with respect to sulfur of the carbon black thrown in in the professional kneading process, and the charge amount of a rubber composition.

Claims (4)

Starting rubber of carbon black, oils, and other compounding materials nonprofessional kneading step of kneading by introducing, the nonprofessional kneading step obtained in the rubber vulcanizing agent, a vulcanization accelerator kneading and professional kneading step In producing a rubber composition by
An amount of carbon black corresponding to at least a part of the total amount of carbon black to be added is added as an antistatic agent in the pro-kneading step in an amount of 0.5 to 1.0% by weight based on the amount of the vulcanizing agent. A process for producing a rubber composition characterized by the above.   The method for producing a rubber composition according to claim 1, wherein the vulcanizing agent is sulfur.   The method for producing a rubber composition according to claim 1 or 2, wherein the carbon black is fine powdery carbon black.   The method for producing a rubber composition according to any one of claims 1 to 3, wherein a kneading temperature in the professional kneading step is 130 ° C or lower.

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