JP2006168031A - Kneading method of silica type compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a kneading method of a silica type compound capable of reconciling silica dispersibility and extrusion dimensional stability. <P>SOLUTION: In the kneading method of the silica type compound by kneading a compound prepared by compounding 30 PHR or above of silica with a diene type synthetic rubber or a blended rubber composed of a natural rubber and the diene type synthetic rubber, the compound is kneaded under a condition that the temperature of a drop door 5 at the time of start of kneading is 50°C or below, the shearing speed of a kneading rotor during kneading is 50-100/s, the pressure of a ram is 0.20-0.25 MPa, the temperature of cooling water is 15-25°C, and the flow rate of cooling water is 150 l/min or above in the kneading rotor, 200 l/min or above in a kneading casing and 20 l/min or above in the drop door 5 and kneading is completed when the compound during kneading reaches 145-155°C to discharge the compound from the drop door 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for kneading a compound containing silica, and more particularly, to a method for kneading a silica-based compound that achieves both silica dispersibility and extrusion dimensional stability.

  In recent years, in order to improve rolling resistance and wet performance of pneumatic tires, rubber compounds containing silica have been used for the surface rubber layer of the tread portion. The silica-based compound used in such a tire is a kneading rotor that uses cooling water when kneading the compound in a kneading casing provided with a drop door at the outlet while applying shear deformation by a pair of rotating kneading rotors. The drop door and the kneading casing are cooled and kneaded while applying a ram pressure to the compound, and the mixture is kneaded by using a closed batch kneader that discharges the compound from the drop door after the kneading is finished ( For example, see Patent Document 1). The compound discharged from the kneader is roll-mixed with the addition of the vulcanizing material. Then, it is supplied to an extruder, where it is extruded into a sheet shape with a predetermined dimension, and then cooled.

  The kneaded silica-based compound is required to have good silica dispersibility in relation to the tire performance. On the other hand, the compound extruded into a sheet form by the extruder shrinks after cooling, but the one with as little shrinkage as possible is required from the viewpoint of extrusion dimensional stability.

However, when the dispersibility of silica is increased by a kneader, shrinkage of the sheet-like compound extruded by the extruder increases, and there is a problem that it is extremely difficult to achieve both silica dispersibility and extrusion dimensional stability.
JP 2000-246731 A

  An object of the present invention is to provide a method for kneading a silica-based compound capable of achieving both silica dispersibility and extrusion dimensional stability.

  The present invention that achieves the above object is to provide cooling water when kneading a compound in a kneading casing provided with a drop door at a discharge port while applying shear deformation by a pair of rotating kneading rotors, a kneading rotor, a drop door, Circulating the kneading casing, kneading while applying ram pressure to the compound, and using a closed batch kneader that discharges the compound from the drop door after kneading is completed. A silica compound kneading method for kneading a compound before blending a vulcanized raw material containing 30 parts by weight or more of silica with 100 parts by weight of a rubber blended with a synthetic rubber, and dropping at the start of kneading The temperature of the door is 50 ° C. or less, the shearing speed of the kneading rotor during kneading is 50-100 / s, and the ram pressure is 0.20. The compound is used under the conditions of 0.25 MPa, cooling water temperature of 15 to 25 ° C., cooling water flow rate of 150 l / min or more with a kneading rotor, 200 l / min or more with a kneading casing, and 20 l / min or more with a drop door. When kneading and the compound being kneaded reaches the range of 145 to 155 ° C., the kneading is finished and discharged from the drop door.

  According to the present invention described above, by defining each condition during kneading as described above, the silica dispersibility of the compound after kneading can be enhanced, and the extrusion dimensional stability of the compound after extrusion can be improved. Therefore, both silica dispersibility and extrusion dimensional stability can be achieved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an example of a closed batch kneader used in the silica compound kneading method of the present invention. Reference numeral 1 denotes an elliptical shape arranged in a kneading chamber 3 in a kneading casing 2 having a cross-sectional glasses shape. A pair of kneading rotors rotate in the direction of the arrow shown in the figure, and knead while applying shear deformation to the compound charged into the kneading chamber 3 from the hopper 4. A drop door 5 that can move up and down is provided at the lower discharge port of the kneading casing 2, and after the kneading is finished, the drop door 5 is lowered to open the discharge port so that the compound can be discharged to the outside.

  Reference numeral 6 denotes a pressurizing device for applying pressure (ram pressure) to the compound being kneaded from above, and a ram (protrusion rod) 9 is connected to a piston 8 slidably disposed in the cylinder 7 up and down. At 10 the ram pressure is applied by pressing the compound being kneaded. The vertical movement of the piston 8 is performed by compressed air supplied to and discharged from the cylinder 7 via the ports 11 and 12.

  The kneading rotor 1, the kneading casing 2 and the drop door 5 are formed with cooling water circulation paths 1a, 2a and 5a for circulating cooling water, respectively, and the cooling water is circulated in the cooling water circulation paths 1a, 2a and 5a. The compound being kneaded can be cooled. A temperature sensor 13 made of a thermocouple is exposed on the inner surface of the top of the drop door 5 so that the temperature on the inner surface of the drop door 5 can be measured. The temperature sensor 13 detects the temperature of the compound during kneading, but can be used for measuring the temperature of the drop door after discharging the compound.

The silica compound kneading method of the present invention uses a closed kneader as described above, and silica is added to 100 parts by weight of diene synthetic rubber or rubber blended with natural rubber and diene synthetic rubber. Mixing of the compound before blending the vulcanized raw material blended by 30 parts by weight or more, preferably 30 to 120 parts by weight is performed as follows. First, the kneading machine is operated, and the pair of kneading rotors 1 are rotated and cooled. Circulate water. After confirming that the temperature measured by the temperature sensor 13 is 50 ° C. or less, that is, the temperature of the drop door 5 when starting kneading is 50 ° C. or less, the raw material is fed into the kneading chamber 3 from the hopper 4 and the kneading is started. To do.

  The shearing speed of the kneading rotor 1 during kneading is in the range of 50 to 100 / s. Further, after the raw materials are charged, the compound being kneaded is pressed by the head 10 of the ram 9 to apply the ram pressure. The range of the ram pressure is 0.20 to 0.25 MPa. Further, the temperature of the cooling water during kneading is in the range of 15 to 25 ° C., the flow rate of the cooling water circulation path 1a of each kneading rotor 1 is 150 l / min or more, and the flow rate of the total cooling water circulation path 2a of the kneading casing 2 is 200 l / min or more. The flow rate of the total cooling water circulation path 5a of the drop door 5 is set to 20 l / min or more.

  When the compound reaches the range of 145 to 155 ° C. during the kneading, the kneading is finished, and the kneaded compound is discharged from the drop door 5. Then, the vulcanized raw material is added to the released compound by an open roll or the like.

  The inventors of the present invention diligently studied to make both silica dispersibility and extrusion dimensional stability compatible, and as a result of repeating experiments using a normally used closed batch kneader and an extruder, I discovered that.

  That is, the compound extruded and cooled in a sheet form by an extruder has a close relationship with the kneading state of the compound kneaded by the kneader, and the kneading machine uses the drop door 5 at the start of kneading. Temperature, shear rate of the kneading rotor 1 during kneading, ram pressure for pressing the compound by the head 10 of the ram 9, temperature and flow rate of cooling water circulating in the kneading rotor 1, kneading casing 2, and drop door 5; Further, it was found that the temperature greatly depends on the temperature at which the compound is discharged from the kneader.

  In an experiment conducted by changing each condition during kneading, as described above, the temperature of the drop door 5 at the start of kneading is 50 ° C. or less, the shear rate of the kneading rotor 1 during kneading is 50 to 100 / s, and the ram pressure. The flow rate of cooling water at a temperature of 0.20 to 0.25 MPa, 15 to 25 ° C. was kneaded with the kneading rotor 1 at 150 l / min or more, the kneading casing 2 with 200 l / min or more, and the drop door 5 with 20 l / min or more. When the temperature at the time of releasing the compound satisfies the condition of 145 to 155 ° C, a compound having high silica dispersibility can be obtained and extrusion dimensional stability can be improved, and both silica dispersibility and extrusion dimensional stability are compatible. It can be made.

  When the temperature of the drop door 5 exceeds 50 ° C., the dispersibility of silica is lowered when the kneaded compound is discharged at the above temperature. The lower limit value of the temperature of the drop door 5 is preferably 20 ° C. or more from the viewpoint of simplification of the cooling water supply device.

  Even if the shear rate of the kneading rotor 1 is less than 50 / s, the silica dispersibility is lowered. On the other hand, if it is greater than 100 / s, the extrusion dimensional stability decreases.

  When the ram pressure is less than 0.20 MPa, the extrusion dimensional stability is lowered. Conversely, when it exceeds 0.25 MPa, silica dispersibility will fall.

  When the flow rate of the cooling water of 15 to 25 ° C. is less than the above values in the kneading rotor 1, the kneading casing 2 and the drop door 5, silica dispersibility and extrusion dimensional stability are deteriorated. The flow rate of the cooling water at 15 to 25 ° C. is preferably in the range of 150 to 300 l / min for the kneading rotor 1, 200 to 300 l / min for the kneading casing 2, and 20 to 30 l / min for the drop door 5. .

  Even if the temperature of the compound at the time of release is lower than 145 ° C., silica dispersibility is lowered. On the other hand, when it is higher than 155 ° C., the extrusion dimensional stability is lowered.

  Using compounds A and B having the blending ratios shown in Table 1, knead in a closed batch kneader with the temperature of the drop door at the start of kneading shown in Table 2, and then sulfur and added by an open roll. A sulfur accelerator was added. When the silica dispersibility and extrusion dimensional stability of the compound thus obtained were evaluated under the following measurement conditions, the results shown in Table 2 were obtained.

  The shearing speed of the kneading rotor is 75 / s, the ram pressure is 0.20 MPa, the cooling water temperature is 20 ° C., the cooling water flow rate is 200 l / min for the kneading rotor, 250 l / min for the kneading casing, and 30 l / min for the drop door. The discharge temperature of the kneaded compound is constant at 150 ° C.

Silica dispersibility The number of remaining white grains (silica grains) of 2 cm ² (projected area) or more in the compound obtained as described above was counted. The smaller this value, the better the silica dispersibility.

Extrusion dimensional stability The dimension A after cooling was measured with respect to the dimension 500 mm immediately after the compound obtained as described above was extruded into a sheet with an extruder, and the shrinkage ratio C (%) was obtained by the following formula. . The smaller this value, the better the dimensional stability.
C = 100 (500-A) / 500

  From Table 2, the kneading methods 1 and 2 of the present invention in which the temperature of the drop door at the start of kneading is 50 ° C. or less have little white grain residue, excellent silica dispersibility, and good extrusion dimensional stability. I understand.

  Using compound A shown in Table 1, the silica dispersibility and extrusion dimensional stability of the compound obtained by kneading in a closed batch kneader by changing the shear rate of the kneading rotor as shown in Table 3 were carried out. When evaluated in the same manner as in Example 1, the results shown in Table 3 were obtained.

  The conditions are the same as in Example 1 (except for the shearing speed of the kneading rotor) except that the temperature of the drop door at the start of kneading was set to 48 ° C.

  From Table 3, it can be seen that the kneading methods 5 to 7 of the present invention in which the shear rate of the kneading rotor is 50 to 100 / s have little white grain residue, excellent silica dispersibility, and good extrusion dimensional stability. Recognize.

  Example 1 shows the silica dispersibility and extrusion dimensional stability of the compound obtained by kneading using compound A shown in Table 1 and changing the ram pressure as shown in Table 4 in a closed batch kneader. When evaluated in the same manner, the results shown in Table 4 were obtained.

  The temperature of the drop door at the start of kneading is the same as in Example 2, and the other conditions except for the ram pressure are the same as in Example 1.

  From Table 4, it can be seen that the kneading methods 10 to 12 of the present invention having a ram pressure of 0.20 to 0.25 MPa have little white grain residue and excellent silica dispersibility and good extrusion dimensional stability. .

  Example 1 shows the silica dispersibility and extrusion dimensional stability of the compound obtained by kneading using compound A shown in Table 1 and changing the cooling water temperature as shown in Table 5 in a closed batch kneader. As a result, the results shown in Table 5 were obtained.

  The temperature of the drop door at the start of kneading is the same as in Example 2, and the other conditions except for the cooling water temperature are the same as in Example 1.

  From Table 5, it can be seen that the kneading methods 15 to 17 of the present invention in which the cooling water temperature is set to 15 to 25 ° C. have little white grains remaining and excellent silica dispersibility and excellent extrusion dimensional stability.

Using compound A shown in Table 1, the silica dispersibility and extrusion dimensional stability of the compound obtained by kneading by changing the cooling water amount of the compound kneaded in a batch kneader as shown in Table 1 as shown in Table 6 Evaluation was conducted in the same manner as in Example 1, and the results shown in Table 6 were obtained.

  The temperature of the drop door after the start of kneading is the same as in Example 2, and the other conditions except for the cooling water amount are the same as in Example 1.

  From Table 6, the kneading methods 23 and 24 of the present invention in which the cooling water amount is 150 l / min or more with a kneading rotor, 200 l / min or more with a kneading casing, and 20 l / min or more with a drop door are less silica remaining and the silica dispersion It can be seen that it has excellent properties and has good extrusion dimensional stability.

  Using compound A shown in Table 1 and changing the discharge temperature of the compound kneaded in a closed batch kneader as shown in Table 7, silica dispersibility and extrusion dimensional stability of the compound obtained by kneading Was evaluated in the same manner as in Example 1, and the results shown in Table 7 were obtained.

  The temperature of the drop door at the start of kneading is the same as in Example 2, and the other conditions except the discharge temperature are the same as in Example 1.

  From Table 7, it can be seen that the kneading methods 26 to 28 of the present invention in which the temperature at the time of releasing the compound is set to 145 to 155 ° C. has little residual white grains and is excellent in silica dispersibility and also has good extrusion dimensional stability. .

It is sectional explanatory drawing which shows an example of the airtight batch type kneader used for the kneading | mixing method of the silica type compound of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Kneading rotor 1a Cooling water circulation path 2 Kneading casing 2a Cooling water circulation path 3 Kneading chamber 4 Hopper 5 Drop door 5a Cooling water circulation path 6 Pressurizer 9 Ram 10 Head 13 Temperature sensor

Claims (1)

When kneading the compound in a kneading casing provided with a drop door at the discharge port while applying shear deformation by a pair of rotating kneading rotors, the cooling water is circulated in the kneading rotor, drop door, kneading casing and the compound. 100 weight of rubber blended with diene-based synthetic rubber or natural rubber and diene-based synthetic rubber using a closed batch kneader that kneads while applying ram pressure and releases the compound from the drop door after kneading is completed A silica compound kneading method for kneading a compound before blending a vulcanized raw material containing 30 parts by weight or more of silica with respect to parts,
The temperature of the drop door at the start of kneading is 50 ° C. or less, the shear rate of the kneading rotor during kneading is 50 to 100 / s, the ram pressure is 0.20 to 0.25 MPa, the temperature of the cooling water is 15 to 25 ° C., and the cooling is performed. The compound is kneaded under the condition that the flow rate of water is 150 l / min or more with a kneading rotor, 200 l / min or more with a kneading casing, and 20 l / min or more with a drop door, and the compound during kneading is in the range of 145 to 155 ° C. A method for kneading a silica-based compound in which the kneading is terminated and the mixture is discharged from the drop door.

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