JP2011032424A - Manufacturing method for wet master batch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a wet master batch capable of efficiently performing dehydration of a coagulum and suppressing deterioration of a rubber component at completion of drying treatment. <P>SOLUTION: The manufacturing method for the wet master batch includes a mixing/coagulation step 3 for mixing a rubber latex with a slurry in which a filler is dispersed into water and coagulating the mixture liquid, and a dehydration step 5 for dehydrating the coagulum obtained in the mixing/coagulation step 3. In the dehydration step 5, the coagulum is subjected to dehydration treatment using a screw pressing machine 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a wet masterbatch using a rubber latex and a slurry in which a filler such as carbon black is dispersed, and a rubber composition using the same.

  Conventionally, as a method for producing rubber having excellent dispersibility and processability, as shown in Patent Document 1, natural rubber latex and a filler slurry such as carbon black are mixed, and a natural rubber and a filler are mixed with a coagulant. There is known a method using a so-called wet masterbatch in which a mixture is solidified, and the obtained solidified product is separated from water, further dehydrated and then dried. The wet masterbatch obtained by this method is superior in dispersibility of carbon black to the rubber component as compared with a dry masterbatch obtained by kneading natural rubber and a filler using a kneading roll or the like, and after vulcanization. It has the advantage of excellent rubber properties (breaking strength, wear resistance, etc.).

  By the way, in the manufacturing process of the wet master batch, the coagulated product obtained by coagulating the mixed solution of the rubber latex and the filler slurry contains a large amount of water. A drying step is required. Specifically, as shown in Patent Document 2, a method is known in which a coagulated product is subjected to centrifugal dehydration and then dried using a multi-screw kneading extruder.

Japanese Patent No. 2633913 JP 2006-348146 A

  However, the method of centrifugal dehydration of the coagulated product has a problem that the water content after the dehydration treatment is as high as several tens of percent and the dehydration efficiency is low. Furthermore, in the drying process after the dehydration process, excessive heat and shearing force are applied to the solidified product in the multi-screw kneading extruder in order to reduce the moisture content, which may cause deterioration of the rubber component.

  Therefore, in view of the above problems, the present invention has an object to provide a method for producing a wet masterbatch capable of efficiently dewatering a coagulum and suppressing deterioration of a rubber component at the end of the drying process. And

  Conventionally, a method using a screw press to dehydrate solution-polymerized butadiene rubber or the like is well known. Specifically, the polymer solution obtained by solution polymerization is added to hot water, and the obtained crumb-like rubber is dehydrated with a screw press. However, in this method, when the rubber is heated in order to reduce the moisture content, the rubber is softened to exhibit adhesiveness, and it becomes difficult to discharge the rubber. Accordingly, the rubber had to be dehydrated at a temperature at which the rubber was not softened, and the moisture content could only be reduced to about 10%.

  However, the present inventor found that a coagulated product obtained by coagulating a mixture of rubber latex and filler slurry is not easily softened even when heated to a high temperature in a screw press machine, and also exhibits adhesiveness. As a result, it has been found that the moisture content in the solidified product can be greatly reduced, and the present invention has been completed.

  That is, the present invention is obtained by mixing a rubber latex and a slurry in which a filler is dispersed in water (filler slurry) and coagulating the mixed solution, and the mixing and coagulating step. A method for producing a wet masterbatch having a dehydration step of dewatering a solidified product, wherein the dewatering process is performed while the solidified product is heated using a screw press machine in the dehydration step.

  According to the said structure, it becomes possible to reduce the moisture content of a coagulum continuously and efficiently by compressing mechanically, heating a coagulum in a screw press machine. As a result, the amount of water to be evaporated in the drying process after the dehydration process can be reduced, and there is no fear that excessive heat and shearing force are applied to the solidified product, and deterioration of the rubber component at the end of the drying process can be suppressed. .

  The solidified product is preferably a granular product. It becomes possible to improve fluidity | liquidity by making a solidified material into a granular material. Therefore, when performing a dehydration process using a screw press machine, it becomes possible to compress a solidified material smoothly in a screw press machine, and can dehydrate efficiently.

  Further, the screw press machine includes a heating screw shaft, and an outer cylinder that accommodates the screw shaft, in which a slit extending along the outer cylinder length direction (axial direction) is formed as an opening for filtration. It is preferable to use the same. By adjusting the heating temperature of the screw shaft and the slit width, the moisture content of the solidified product after dehydration can be reduced to 10% by weight or less.

  That is, by forming slits in the length direction of the outer cylinder, the solidified product generates frictional resistance with the slits, thereby gradually dewatering and moving in the outer cylinder. Therefore, in combination with the solidified particles being excellent in fluidity, the solidified materials can be compressed while being smoothly moved toward the discharge port of the screw press machine, and the moisture contained in the solidified materials. Can be efficiently dehydrated. Furthermore, by heating the screw shaft, it becomes possible to evaporate water directly from the dehydrated coagulum, and the moisture content of the coagulum can be further reduced.

  In order to smoothly dehydrate the solidified product, it is preferable that at least 90% of the solidified product has a particle size of 1 mm to 30 mm. At this time, the slit width is adjusted to 0.1 mm to 2.0 mm. If the slit width is narrower than the above range, the slit may be clogged and dewatering may be hindered. If the slit width is wider than the above range, the solidified substance leaks out from the slit and the recovery rate is lowered, and the dewatering efficiency may be lowered without pressure applied to the solidified substance.

  What is interesting here is that even though at least 90% of the coagulated material is present in the range of 1 mm to 30 mm in particle size, it is possible to efficiently dehydrate the coagulated material without leaking from the slit up to a slit width of 2 mm. It is a thing. This is because the solidified substance is not in a state where it can freely move within the outer cylinder, but is present in a state where the solidified substance is in close contact with each other, so that even if the slit width exceeds 1 mm, it remains stable without passing through the slit up to 2 mm. This is considered to be held inside the outer cylinder. Therefore, dehydration can be easily performed by setting the slit width to be close to 2 mm.

  In addition to the above configuration, by heating the screw shaft of the screw press machine to 100 ° C. to 150 ° C., the moisture content of the solidified product after the dehydration treatment can be reduced to 5% by weight or less. The compression ratio of the screw press can be appropriately set within a range where the solidified product can be efficiently compressed, but it is preferable to set the compression ratio to 1 / 1.2 to 1 / 4.0. If the compression ratio is less than 1 / 1.2, dehydration efficiency may be reduced. Moreover, when a compression ratio exceeds 1/4, there exists a possibility that a solidified substance may be clogged in an outer cylinder.

  In addition to the size of the coagulum, the slit width and the heating temperature of the screw shaft, the coagulum is more efficiently dehydrated by setting the compression ratio of the screw press to 1 / 1.3 to 1 / 4.0. It becomes possible. Specifically, the moisture content of the solidified product can be reduced to 1.5% by weight or less, and the drying step of drying the solidified product after the dehydration step can be omitted.

  In the mixing / coagulation step, the above-mentioned coagulated product having a particle size can be produced by applying a strong shearing force to a mixed solution in which a rubber latex and a slurry in which a filler is dispersed in water are mixed. Specifically, like a chopper composed of blade-type blades, a shear blade that mainly gives a shearing force to the mixed solution is used, and this is rotated at high speed in the mixed solution (circumferential speed of 10 m / s or more). To generate a strong shear force.

  Even if it is a shear blade, it is possible to sufficiently stir the mixed liquid by rotating it at an appropriate size and at a high speed. However, a propeller type stirring blade that mainly gives thrust to the mixed liquid Is different. As for the reason why a fine coagulated product is generated by applying a strong shearing force to the mixed solution, when a strong shearing force is applied to the mixed solution, a large number of coagulated nuclei are generated in the mixed solution. Then, it is presumed that the growth of the coagulum progresses evenly around the generated nucleus, so that a fine and granular coagulum can be obtained.

  At this time, the size of the shear blade is important. That is, even if the shear blade is rotated at a speed capable of giving an impact to the mixed solution, if the blade is small, the impact force of the shear blade only affects a part of the mixed solution. The number of nuclei decreases. If it does so, the solidified material produced | generated early will grow faster than the solidified material produced | generated later, and the magnitude | size of a solidified material will vary from a granular form to a lump shape. Therefore, by stirring the mixed liquid while paying attention to the size of the shear blade, a coagulated product having a particle size of 1 mm to 30 mm in at least 90% of the whole can be obtained.

  In the present invention, as described above, it is not always necessary to add a coagulant in the mixing / coagulation step. However, by adding a coagulant, the amount of rubber latex and filler remaining in the mixed liquid can be reduced, and coagulation can be completed in a shorter time. When adding the coagulant, it is preferable to start the rotation of the shear blade and add the coagulant to the mixed solution after a predetermined time has elapsed and the formation of the coagulum has settled. When a coagulant is added at the same time as the rotation of the shear blade, the formation of the solidified product proceeds rapidly, the coagulated product tends to be agglomerated, and the coagulated product adheres to and accumulates on the shearing blade.

  The wet masterbatch obtained by the present invention is excellent in dispersibility between rubber particles and filler particles. Therefore, since the rubber composition using such a wet masterbatch is excellent in processability, fatigue resistance and low heat build-up, various rubber compositions including tire rubber compositions such as tire dread rubber and sidewall rubber are used. Can be suitably used.

  In the present invention, the coagulated product obtained by mixing and coagulating the rubber latex and the filler slurry is dehydrated using a screw press machine, so that the coagulated product can be efficiently dehydrated and dried. It becomes possible to suppress deterioration of the rubber component at the end of the treatment.

Process drawing which shows the manufacturing method of the wet masterbatch which concerns on this invention Schematic cross-sectional view of the solidification device used in the mixing / solidification process Partial cross-sectional schematic diagram of a screw press used in the dehydration process

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a process diagram showing a method for manufacturing a wet masterbatch according to the present invention. First, the rubber latex preparation step 1 and the filler slurry adjustment step 2 are performed to prepare a rubber latex and a filler slurry.

  As rubber latex, it is also possible to use synthetic rubber latex in addition to natural rubber latex. The concentration of the rubber latex is preferably adjusted so that the solid content is 10 wt% to 40 wt% with a dispersion medium such as water.

  As the filler, in addition to carbon black and silica, talc, clay, other inorganic fillers, and the like can be used. When carbon black is used as the filler, various grades that are usually used as rubber fillers can be used. Specific examples include SAF, ISAF, HAF, FEF and the like, and these can be used alone or in admixture of two or more. As for the slurry density | concentration of a filler, solid content is 1 to 20 weight%, and it is more preferable that it is 3 to 15 weight%.

  The prepared rubber latex and filler slurry are subjected to dispersion treatment as necessary. The dispersion treatment can be performed using a high shear (rotor / stator) mixer, a homogenizer, a colloid mill, or the like. These devices can make particles finer by increasing the number of rotations or extending the processing time.

  FIG. 2 is a cross-sectional view showing a coagulation apparatus used in the mixing / coagulation step 3. The coagulation device 8 includes a coagulation tank 9 and a shear blade 10. In the present embodiment, a blade-like blade is used as the shear blade 10, and the blade is disposed symmetrically with respect to the rotating shaft 11 erected on the bottom surface of the coagulation tank 9 so that the surface of the blade faces the horizontal direction. The shear blade 10 rotates in the horizontal direction so that a strong shear force acts on the mixed solution.

  In the mixing / coagulation step 3, after supplying both the rubber latex and the filler slurry to the coagulation tank 9, or while introducing both liquids into the coagulation tank 9, the shear blade 10 is moved at a high speed (at a peripheral speed of 10 m / s). The mixture is stirred so that a shearing force is applied to the mixed solution. As a result, a large number of solidified nuclei are generated in the mixed solution. Thus, the number of nuclei of the solidified product in the initial stage of the mixing / solidifying step 3 greatly affects the shape of the subsequent solidified product. That is, the larger the number of coagulates generated in the initial stage, the smaller the particle size of the final coagulum and the uniform size. In this way, a coagulum having a particle size of 1 mm to 30 mm in at least 90% of the whole can be obtained.

  In the case of adding a coagulant, it is preferable to add the coagulant at the stage where the rotation of the shear blade 10 is started and the formation / growth of the coagulum has settled. Specifically, about 2 to 4 minutes after the rotation of the shear blade 10 is started is preferable. As the coagulant, an acid such as formic acid or a metal salt such as aluminum sulfate can be used.

  The coagulated product obtained as described above is subjected to solid-liquid separation and washing in which the coagulant is washed away alternately in the solid-liquid separation step 4, and then dehydrated in a state where moisture and impurities are removed ( Dehydration step 5).

  FIG. 3 is a partial cross-sectional schematic view showing a screw press used in the dehydration step 5. The screw press machine 20 includes a screw shaft 21 and a cylindrical outer cylinder 22 that houses the screw shaft 21. A plurality of slits 23 are formed in the outer tube 22 as filtration openings along the length direction.

  The slit 23 may be set to have a width of 0.1 mm to 2.0 mm. However, in this range, the recovery rate of the solidified product hardly changes, and therefore it is preferable to approach the upper limit of 2.0 mm. Accordingly, the dehydration process can be performed more smoothly, and the moisture content of the solidified product after dehydration can be further reduced.

  The screw shaft 21 is provided with a steam flow path therein and can be heated. In addition, the heating method of the screw shaft 21 is not particularly limited, but it is easy to raise the temperature and maintain the temperature by heating with steam. The screw shaft 21 is preferably heated to 100 ° C to 150 ° C. Further, the screw shaft 21 is formed in a tapered shape so that the diameter gradually increases from the rear end side toward the front end side, so that the solidified product is compressed between the screw shaft 21 and the outer cylinder 22. It has become.

  A supply port 24 for the solidified product A is provided at the rear end of the screw press 20, and the solidified product A introduced into the outer cylinder 21 from here is fed forward by the rotation of the screw shaft 20. It is compressed and discharged from an outlet 25 formed at the tip of the screw press. In front of the discharge port 25, a pressing plate 26 biased in a direction to close the discharge port 25 is disposed. Therefore, the solidified substance A is discharged from the discharge port 25 against the pressing force of the pressing plate 26, and the compressive force of the solidified substance can be increased.

  By performing dehydration of the solidified product using the screw press machine having the above-described configuration, the moisture content of the solidified product after the dehydration treatment can be reduced to 5% by weight or less. Furthermore, by setting the compression ratio of the screw press to 1 / 1.3 to 1 / 4.0, the moisture content of the solidified product after the dehydration treatment can be reduced to 1.5% by weight or less.

  When the moisture content of the solidified product after the dehydration process exceeds 1.5% by weight, the drying process 6 is generally performed after the dehydration process. In the drying step 6, a band dryer, a conveyor dryer, a drum dryer, an extruder, or the like can be used. Among them, the use of an extruder is particularly preferable in that plasticization can be performed simultaneously with drying. Even when the drying step 6 is executed, in the present invention, the water content of the coagulated product after the dehydration treatment is small, so that the amount of water evaporated in the drying step is small. Therefore, there is no possibility that the rubber component is deteriorated due to excessive heat and shear force applied to the solidified product during the drying process.

  When the moisture content of the coagulated product after the dehydration treatment is 1.5% by weight or less, it is not necessary to further apply the coagulated product to the drying step, and in this case, the drying step 6 can be omitted.

  By passing through the above process, the dried solidified substance, ie, a wet masterbatch, can be manufactured. Furthermore, the rubber composition kneaded uniformly can be obtained by blending other chemicals in the wet masterbatch and kneading with a kneader such as a Banbury mixer (kneading step 7).

  In addition, when the drying process 6 is omitted or when the drying process other than the extruder is used even after the drying process 6, the wet masterbatch is not plasticized. Therefore, in such a case, when the rubber composition is kneaded by a kneader, plasticization can be performed by kneading only the wet master batch in advance before blending other chemicals.

  Furthermore, when the drying step 6 is omitted, it is preferable to supply the solidified product (wet master batch) immediately after being discharged from the screw press machine directly to the kneader. Thereby, it becomes possible to supply the solidified product to the kneader in a sufficiently softened state, and the power and load applied to the kneader can be reduced.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, unless this invention exceeds the summary, it is not limited to these Examples.

[Contents of mixing and solidification process]
In this example, natural rubber latex was used as the rubber latex in the rubber latex preparation step 1, and the concentration was adjusted to 25% by weight of the rubber component. Furthermore, carbon black (Shiast 9 manufactured by Tokai Carbon Co., Ltd.) was used as the filler in the filler slurry preparation step 2, and this was dispersed in water under a condition of 3600 rpm × 30 min using a stirrer manufactured by Silverson Co., Ltd. (flash blend). A 5% by weight slurry was prepared.

  Thereafter, in the mixing / coagulation step 3, using a super mixer SM-20 manufactured by Kawata Co., Ltd. as a coagulation device, the rubber coagulation tank was adjusted to 23 ° C., and 8.0 L of rubber latex and 3.3 L of carbon black slurry (weight) The rubber component: carbon black = 100: 50) was added at the same time.

  Immediately thereafter, the SM-20 shear blade was rotated at a peripheral speed of 24 m / s to produce a solidified product. In addition, when 2 minutes and 30 seconds passed after the rotation of the shear blade was started, a 10% by weight aqueous solution of formic acid as a coagulant was added to the mixed solution to adjust to pH 3-4.

  90% or more of the obtained solidified product had a particle size of 1 mm to 30 mm. The size of the solidified product was classified by a stainless steel sieve conforming to ISO 3301-1 JIS Z-8801, and measured with an opening of 30 mm and an opening of 1 mm.

[Details of dehydration process]
In this step, a screw press manufactured by Suehiro EPM (rotation speed: 20 rpm, screw length: 810 mm) was used as a screw press machine. Table 1 shows the results of evaluating the moisture content of the solidified product after dehydration and the recovery rate of the solidified product when the slit width of the screw press was variously changed. Table 2 shows the results of evaluating the moisture content of the solidified product after dehydration and the recovery rate of the solidified product when the compression ratio of the clew press machine was changed variously. Further, Table 3 shows the results of evaluating the moisture content of the solidified product after dehydration and the recovery rate of the solidified product when the screw shaft temperature of the screw press machine was changed variously.

  In measuring the moisture content, a heat drying moisture meter MX-50 manufactured by A & D was used, and the moisture content was measured according to JIS K6238-2.

[Evaluation results]
The evaluation results are shown in Tables 1 to 3. From Table 1, Examples 1-4 which have a slit width of 0.1 mm to 2 mm have a moisture content of 1.2% to 0.7% by weight by setting the compression ratio and screw temperature appropriately. Turned out to be low. This level of moisture content is usually comparable to the moisture content after the drying process. Therefore, in Examples 1 to 4, after the dehydration process is completed, the drying process can be omitted. Moreover, the recovery rates of the coagulated materials in Examples 1 to 4 were all as high as 97% to 98%.

  On the other hand, Comparative Example 1 having a slit width of less than 0.1 mm cannot efficiently perform dehydration due to clogging of the solidified product, and has a very high moisture content of 38.4% by weight. It was. Further, in Comparative Example 2 in which the slit width exceeded 2 mm, the solidified product leaked out of the outer cylinder through the slit, and the recovery rate was as low as 78%. In addition, since the coagulated material leaked to the outside, it was difficult to apply pressure to the coagulated material inside the outer cylinder, the dehydration efficiency was lowered, and the moisture content was increased to 10.2% by weight.

  Since the recovery rate is an item that varies depending on the slit width, in Tables 2 and 3 where the slit width is constant at an appropriate value, the recovery rate is a high value. Therefore, the description of the recovery rate is omitted below.

  From Table 2, the screw temperature and the slit width are appropriately set for Example 1, Example 5 and Example 6 in which the compression ratio of the screw press machine is set to 1 / 1.3 to 1 / 4.0. As a result, the moisture content was as low as 1.2 wt% to 0.6 wt%. It was confirmed that the moisture content decreased as the compression ratio was increased within the range of the compression ratio.

  On the other hand, in Comparative Example 3 having a compression ratio lower than 1 / 1.3, dehydration hardly progressed, and the moisture content did not change much from before the treatment. Further, in Comparative Example 4 in which the compression ratio exceeded 1/4, the solidified product was excessively pressurized and clogged in the screw press machine, and could not be discharged well.

  From Table 3, in Example 1, Example 7 and Example 8 in which the screw shaft temperature was set to 100 ° C. to 150 ° C., the moisture content was 1.2% by weight by appropriately setting the slit width and the compression ratio. The value was as low as ˜1.3 wt%. However, there was almost no change in the moisture content when the screw shaft temperature was 110 ° C. or higher in the above range.

  On the other hand, in Comparative Example 5 in which the screw shaft temperature was less than 100 ° C., the moisture content was as high as 25.6% by weight. Further, Comparative Example 6 in which the screw shaft temperature exceeded 150 ° C. became soft and became tacky, and was clogged in the screw press machine and could not be discharged well.

DESCRIPTION OF SYMBOLS 1 Rubber latex preparation process 2 Filler slurry preparation process 3 Mixing and coagulation process 4 Solid-liquid separation process 5 Dehydration process 6 Drying process 7 Kneading process 8 Coagulator 9 Coagulation tank 10 Shear blade 11 Rotating shaft 20 Screw press machine 21 Screw shaft 22 Outer cylinder 23 Slit 24 Supply port 25 Discharge port 26 Press plate

Claims (6)

A wet having a mixing / coagulating step of mixing rubber latex and a slurry in which a filler is dispersed in water and coagulating the mixed solution, and a dehydrating step of dehydrating the coagulated product obtained in the mixing / coagulating step. A method for producing a master batch, wherein, in the dehydration step, the solidified product is dehydrated while being heated using a screw press. The coagulated product obtained in the mixing / coagulation step is a granular material, and as the screw press machine, a heating screw shaft and an outer cylinder accommodating the screw shaft, along the outer cylinder length direction as an opening for filtration. The one having a slit formed therein is used, and by adjusting the heating temperature of the screw shaft and the slit width, the water content of the solidified product after the dehydration treatment is 10% by weight or less. The manufacturing method of the wet masterbatch of Claim 1 characterized by the above-mentioned. The method for producing a wet masterbatch according to claim 2, wherein at least 90% or more of the solidified product has a particle diameter of 1 mm to 30 mm, and the slit width is adjusted to 0.1 mm to 2.0 mm. The wet masterbatch according to claim 3, wherein the water content of the solidified product after the dehydration treatment is adjusted to 5 wt% or less by heating the screw shaft of the screw press machine to 100 ° C to 150 ° C. Production method. By setting the compression ratio of the screw press to 1 / 1.3 to 1 / 4.0, the moisture content of the solidified product after the dehydration treatment is 1.5% by weight or less, and the solidified product is removed after the dehydration step. The method for producing a wet masterbatch according to claim 4, wherein a drying step of drying is omitted. The method for producing a wet masterbatch according to any one of claims 1 to 5, wherein the coagulated product is generated by applying a shearing force to the mixed solution in the mixing and coagulating step. .

Images