JP2015006759A - Method for kneading rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for kneading rubber capable of stably obtaining the final Mooney viscosity as a target with a predetermined kneading time without bringing about a rise of cost even when there is a large fluctuation on the initial Mooney viscosity of natural rubber upon the execution of mastication of natural rubber or kneading of a carbon master batch prepared by adding carbon black to natural rubber by the use of a kneader.SOLUTION: In a method for kneading rubber, mastication of natural rubber or kneading of a carbon master batch prepared by adding carbon black to natural rubber is performed by using a kneader, an electric power value of a motor of the kneader and a temperature of the natural rubber are measured after the elapse of a predetermined time from the start of rubber mastication, based on the measured electric power value and the temperature, an initial Mooney viscosity of the natural rubber is estimated and, based on the estimated initial Mooney viscosity, rotation number of the motor of the kneader upon the rubber kneading on and after and the temperature of the natural rubber are controlled.

Description

  The present invention relates to a rubber kneading method, and more particularly, to a rubber kneading method in which kneading of natural rubber and kneading of a carbon master batch produced by adding carbon black to natural rubber is performed using a kneader.

  Rubber products such as pneumatic tires are manufactured using a rubber composition in which synthetic rubber or natural rubber is blended. In producing these rubber compositions, in general, pre-kneaded rubber, Rubber materials processed to have a low Mooney viscosity (rubber plasticity) such as a carbon masterbatch (CB M / B) processed by adding carbon black to rubber are used.

  Conventionally, the desired final Mooney viscosity (Mooney viscosity after rubber kneading) can be obtained in rubber kneading such as kneading of rubber and kneading for adding carbon black to rubber to produce CB M / B. Based on prior trial kneading, kneading conditions such as kneading temperature and kneading time were empirically determined.

  However, natural rubber, unlike synthetic rubber, has a large initial Mooney viscosity (Moone viscosity before the start of rubber kneading) due to differences in sippers (origin), so even when rubber kneading is performed under the same kneading conditions , The load applied to rubber (shearing force, torque, etc.) changes, resulting in variations in the final Mooney viscosity, resulting in large variations in physical properties and processability of the rubber composition after rubber mixing There was something to do.

  Specifically, for example, as shown in FIG. 2, when three kinds of natural rubbers A, B, C having different sippers are masticated, the load applied to the rubber is different and even before the kneaded rubber is discharged. , The load height, that is, the final Mooney viscosity varies.

  Therefore, various rubber kneading methods have been proposed that are devised so that the target final Mooney viscosity can be stably obtained even with natural rubber having different initial Mooney viscosity due to different shippers.

  For example, in Patent Document 1, the power value of a kneader at the time of completion of predetermined rubber kneading is obtained in advance, and when the power value during rubber kneading becomes equal to or less than the power value at the time of completion of rubber kneading, rubber kneading is performed. To stop. That is, it has been proposed to change the kneading time by monitoring the power value during rubber kneading.

  Patent Document 2 proposes to monitor the load of a motor in a kneader during rubber kneading, and to change the amount of the kneading accelerator (squacking agent) as appropriate based on the measured load. Yes.

JP-A-2-227209 JP 2003-320524 A

  The present invention has a large variation in the initial Mooney viscosity of natural rubber when kneading natural rubber or kneading a carbon masterbatch prepared by adding carbon black to natural rubber using a kneader. However, it is an object of the present invention to provide a rubber kneading method capable of stably obtaining a target final Mooney viscosity within a predetermined kneading time without causing an increase in cost.

The invention described in claim 1
A method of kneading natural rubber, or a kneading process of a carbon masterbatch prepared by adding carbon black to natural rubber, using a kneader,
After a predetermined time from the start of rubber kneading, measure the power value of the motor of the kneader and the temperature of the natural rubber,
Based on the measured power value and temperature, estimate the initial Mooney viscosity of the natural rubber;
The rubber kneading method is characterized in that, based on the estimated initial Mooney viscosity, the number of rotations of the motor of the kneading machine and the temperature of the natural rubber in the subsequent rubber kneading are controlled.

The invention described in claim 2
2. The rubber kneading method according to claim 1, wherein the predetermined time is set based on an average time from the start of the rubber kneading to a primary torque peak at which the torque of the kneader rapidly increases.

The invention according to claim 3
3. The rubber kneading method according to claim 1, wherein the initial Mooney viscosity is estimated based on a product of the measured power value and the temperature.

The invention according to claim 4
Control of the motor speed of the kneader and the temperature of the natural rubber during the rubber kneading time after estimation of the initial Mooney viscosity is based on a standard chart prepared in advance corresponding to the initial Mooney viscosity. The rubber kneading method according to any one of claims 1 to 3, wherein the rubber kneading method is performed.

  According to the present invention, when performing kneading of natural rubber or carbon masterbatch prepared by adding carbon black to natural rubber using a kneader, the initial Mooney viscosity of natural rubber varies greatly. Even if it exists, the rubber kneading method which can obtain the target final Mooney viscosity stably by predetermined kneading | mixing time, without causing a raise in cost can be provided.

It is a block diagram which shows the kneading | mixing system in the rubber kneading method which concerns on one embodiment of this invention. It is a graph which shows the time-dependent change of the load concerning the kneader during rubber kneading.

  Hereinafter, the present invention will be specifically described based on embodiments.

1. First, a kneading system used in the rubber kneading method according to the present embodiment will be described.

  FIG. 1 is a block diagram showing a kneading system in the rubber kneading method according to the present embodiment. As shown in FIG. 1, this kneading system includes a closed kneader 1 and a motor for operating the closed kneader 1. 2 and a personal computer 3.

  As the closed kneader 1, a closed rubber kneader having a rotating rotor, such as a Banbury mixer and a kneader, is used as in the prior art. The rotating rotor is connected to the motor 2 and rotates in accordance with the rotation of the motor 2 to perform rubber kneading.

  The closed kneader 1 is provided with a temperature measuring means 1a for measuring the temperature of the kneaded rubber and a temperature control means 1b for controlling the temperature of the kneaded rubber in the closed kneader 1. The motor 2 includes a power value measuring means 2a for measuring the power value (torque) of the motor 2, and a rotation speed control means for adjusting the power value of the motor 2 to control the rotation speed of the motor in the subsequent rubber kneading. 2b is provided. These means are connected to the personal computer 3.

  The personal computer 3 estimates the initial Mooney viscosity based on the kneaded rubber temperature measured by the temperature measuring means 1a and the power value of the motor 2 measured by the power value measuring means 2a. In order to obtain the final Mooney viscosity, control signals are transmitted to the temperature control means 1b and the rotation speed control means 2b to control the rotation speed of the motor of the kneader and the temperature of the natural rubber in the subsequent rubber kneading.

  In order to estimate the initial Mooney viscosity and transmit each control signal as described above, the personal computer 3 includes an estimated value of the initial Mooney viscosity corresponding to the product of the power value of the motor 2 and the rubber temperature, and the initial Mooney viscosity. A database composed of standard charts showing kneading conditions (the number of rotations of the motor and the kneading rubber temperature) corresponding to the estimated value is stored in advance.

  The estimated value of the initial Mooney viscosity is set by grasping the relationship between the product of the electric power value of the motor 2 and the rubber temperature and the initial Mooney viscosity in advance by experiments. Similarly, each standard chart is created by obtaining kneading conditions for obtaining a target final Mooney viscosity from an initial Mooney viscosity by a prior experiment.

2. Rubber Kneading Method Next, the rubber kneading method according to the present embodiment will be described. The rubber kneading according to the present embodiment is performed based on the kneading system.

(1) Start of rubber kneading First, natural rubber and a shaky agent are introduced into a closed kneader 1 whose interior is heated to a predetermined temperature (in the case of CB M / B kneading, carbon is also added. ), By operating the motor 2, the rotating rotor is rotated and rubber kneading is started.

(2) Estimation of initial Mooney viscosity After rubber kneading for a predetermined time, the temperature of the kneaded rubber is measured by the temperature measuring means 1a, and the power value of the motor 2 is measured by the power value measuring means 2a.

  The measured temperature of the kneaded rubber and the power value of the motor 2 are transmitted to the personal computer 3. The personal computer 3 calculates the product of the received temperature of the kneaded rubber and the electric power value of the motor 2, and compares this value with the value stored in the database stored in the personal computer 3 in advance, so that the natural computer is used. Estimate the initial Mooney viscosity of the rubber.

  In addition, as a specific timing for estimating the initial Mooney viscosity, the average time of the primary torque peak in which the torque of the kneader suddenly increases after the start of rubber kneading and the difference in load on the rubber is the largest is preferable, Specifically, about 30 seconds after the start of rubber kneading is preferable.

(3) Adjustment of kneading conditions Next, based on the estimated value of the initial Mooney viscosity obtained, the Mooney viscosity is measured within a predetermined time from the database stored in advance in the personal computer 3 without excessively raising the kneading rubber temperature. Select a standard chart in which kneading conditions (motor rotation speed, kneading rubber temperature) are set so that can be obtained.

  Then, the personal computer 3 transmits a control signal based on the kneading conditions (motor rotation speed, kneading rubber temperature) shown in the selected standard chart to the temperature control means 1b and the rotation speed control means 2b.

  Based on the received control signal, the temperature control means 1b and the rotation speed control means 2b control the rotation speed of the motor and also control the rise in the kneading rubber temperature to perform subsequent rubber kneading.

(4) Discharge of kneaded rubber After rubber kneading is completed, the kneaded rubber is discharged from the discharge port of the closed kneader 1.

3. As described above, according to the rubber kneading method according to the present embodiment, the initial Mooney viscosity is estimated during rubber kneading based on the power value of the motor and the rubber temperature, and the initial Mooney viscosity is estimated. Because the motor speed and the temperature of the rubber that affect changes in the Mooney viscosity during rubber kneading are controlled based on the above, the temperature of the kneading rubber must be raised too much even for natural rubber with a high initial Mooney viscosity. It is possible to stably obtain a kneaded rubber with a target final Mooney viscosity in a predetermined kneading time, and scrap of scraps caused by trouble such as "rubber boil" caused by not controlling the rotation speed of the motor. Occurrence can be prevented appropriately.

  Also, by controlling the motor speed and rubber temperature based on a standard chart that defines the motor speed and rubber temperature suitable for the initial Mooney viscosity, the kneaded rubber with the target final Mooney viscosity Therefore, even if natural rubber having a high initial Mooney viscosity is used, it is not necessary to add an expensive squirt agent, and the cost is not increased.

  Then, by preparing a rubber composition using a kneaded rubber having a stable final Mooney viscosity in this way, a rubber product having stable properties such as physical properties and processability can be provided.

  Hereinafter, based on an Example, this invention is demonstrated more concretely.

1. Natural rubber mastication (1) Examples 1-5
Five types of natural rubber (NR) with different sippers (Examples 1 to 5) were prepared, and a natural rubber 100.0PHR was blended with a shaky agent 0.30PHR, and the natural rubber using the rubber kneading method described above. I went through the training.

  At this time, by a prior experiment, the relationship between the product of the torque based on the motor power value and the rubber temperature and the initial Mooney viscosity and a standard chart for obtaining the target final Mooney viscosity from the initial Mooney viscosity are obtained. The data was stored in advance in the personal computer 3 as a database shown in Table 1.

  The initial Mooney viscosity was estimated about 30 seconds after the start of rubber kneading.

  In accordance with the estimated initial Mooney viscosity, the number of rotations of the motor (rpm) and the kneading rubber temperature (° C.) at the time of discharge shown in Table 1 were set, and the subsequent rubber kneading was performed.

(2) Comparative Example 1
As Comparative Example 1, natural rubber having the same composition as above was kneaded (scoured) in the same manner as above except that the rotation speed was uniformly set to 50 rpm and the discharge temperature was set to 140 ° C.

(3) Evaluation of Final Mooney Viscosity Each example was subjected to mastication 30 times, the final Mooney viscosity was measured for each kneaded rubber, and the average value (Ave.) and dispersion (σ) were determined for each example. . The results are shown in Table 2.

  From Table 2, in each of Examples 1 to 5, the dispersion σ of the final Mooney viscosity is smaller than that in Comparative Example 1, and the number of rotations of the motor and the kneaded rubber are based on the product of temperature and power value (torque). It was confirmed that the variation of the final Mooney viscosity value can be reduced by appropriately controlling the temperature of.

2. Production of carbon master batch (CB M / B) (1) Examples 6 to 10 and Comparative Example 2
Using the same five kinds of natural rubber as in Examples 1 to 5, blending 0.30 PHR and carbon 25.0 PHR to natural rubber 100.0 PHR, and using the data shown in Table 3 as a database Except for the above, rubber kneading of Examples 6 to 10 was performed in the same manner as described above. Further, the rubber kneading of Comparative Example 2 was performed in the same manner as Comparative Example 1 except for the blending.

(2) Evaluation of Final Mooney Viscosity For each kneaded rubber, the final Mooney viscosity was measured in the same manner, and the average value (Ave.) and dispersion (σ) were determined for each example. The results are shown in Table 4.

  From Table 4, in all of Examples 6 to 10, the dispersion σ of the final Mooney viscosity is smaller than that in Comparative Example 2, and similarly in the rubber kneading for producing the carbon master batch, the temperature and power value ( It was confirmed that the variation in the final Mooney viscosity value can be reduced by appropriately controlling the motor speed and the temperature of the kneaded rubber based on the product of the torque.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to said embodiment. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Sealing-type kneader 1a Temperature measuring means 1b Temperature control means 2 Motor 2a Electric power value measuring means 2b Rotational speed control means 3 Personal computer

Claims (4)

A method of kneading natural rubber, or a kneading process of a carbon masterbatch prepared by adding carbon black to natural rubber, using a kneader,
After a predetermined time from the start of rubber kneading, measure the power value of the motor of the kneader and the temperature of the natural rubber,
Based on the measured power value and temperature, estimate the initial Mooney viscosity of the natural rubber;
A rubber kneading method characterized by controlling the number of revolutions of the motor of the kneading machine and the temperature of the natural rubber in the subsequent rubber kneading based on the estimated initial Mooney viscosity.   2. The rubber kneading method according to claim 1, wherein the predetermined time is set based on an average time from a start of the rubber kneading to a primary torque peak at which the torque of the kneader suddenly increases.   The rubber kneading method according to claim 1 or 2, wherein the initial Mooney viscosity is estimated based on a product of the measured power value and the temperature.   Control of the motor speed of the kneader and the temperature of the natural rubber during the rubber kneading time after estimation of the initial Mooney viscosity is based on a standard chart prepared in advance corresponding to the initial Mooney viscosity. The rubber kneading method according to any one of claims 1 to 3, wherein the rubber kneading method is performed.

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