JP2012131943A - Method for producing wet master batch, rubber composition for tire, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a wet master batch which enables drying of a coagulation in the state of appropriate plasticization and further also enables maintenance of a rubber characteristic after vulcanization.SOLUTION: The method for producing a wet master batch comprises: a dehydration step 5 of mixing a rubber latex with a slurry in which a filler is dispersed in water and coagulating and dehydrating a mixture of a rubber with the filler from this liquid mixture; and a drying step 6 of drying a coagulation obtained by the dehydration step 5, wherein the dehydration step 5 and the drying step 6 are consecutively performed as a series of the steps using a dehydration drying device 20 which includes a dehydration portion 21 having the function of a screw pressing machine and a dry portion 22 having the function of a screw extruder and can supply the coagulation dehydrated in the dehydration portion 21 in the state of being heated and pressurized to the dry portion 22, when the dehydration step 5 and the drying step 6 are performed.

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 method 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.).

  However, if there is a large amount of water in the coagulated product, then when the rubber composition containing other chemicals in the coagulated product (wet masterbatch) is kneaded using a Banbury mixer or the like, the water content is on the surface of the rubber composition. There was a risk of oozing out and slipping between the rubber composition and the rotor of the mixer, resulting in a decrease in kneadability. Moreover, when there is much water | moisture content in a solidified material, when the rubber composition was vulcanized | cured, there also existed a possibility that a void (internal space | gap) might arise because the water | moisture content in a rubber composition evaporated.

  As a method of solving the above problem, as shown in Patent Document 2, the solidified material is put into a multi-screw extruder and extruded with a plurality of screws installed in the barrel of the extruder to remove moisture in the solidified material. A method of evaporating and drying by heating is known.

  By the way, in general, the solidified product obtained by the wet masterbatch method is less flexible and harder than the dry masterbatch near room temperature. This is presumably because, as described above, in the wet masterbatch method, the carbon black dispersibility with respect to the rubber component is excellent, so that the reinforcing effect is enhanced.

  Therefore, in Patent Document 2, as described above, a multi-screw extruder is used as a screw extruder for smooth extrusion, and a strong shearing force is applied to the solidified product by the rotation of a plurality of screws. The solidified material is plasticized to ensure fluidity.

Patent Registration No. 2633913 JP 2006-348237 A

  However, in the method described in Patent Document 2, when the solidified product is repeatedly heated and subjected to shear deformation or extensional deformation in order to heat the solidified product to a temperature at which moisture evaporates, the molecular chains of rubber molecules are excessively cut. There was a problem that the rubber properties after vulcanization were deteriorated.

  Therefore, in the present invention, in view of the above problems, a method for producing a wet masterbatch capable of drying a coagulated product in an appropriately plasticized state and further maintaining good rubber properties after vulcanization. For the purpose of provision.

  In order to solve the above problems, the present invention comprises a dehydration step of mixing a rubber latex and a slurry in which a filler is dispersed in water, and coagulating and dehydrating a mixture of the rubber and the filler from the mixed solution, A method for producing a wet masterbatch comprising a drying step for drying a coagulated product obtained in the dehydration step, and in performing the dehydration step and the drying step, a dehydration unit having a function of a screw press machine, screw extrusion A series of the dehydrating step and the drying step using a dehydrating and drying apparatus that can supply the dried coagulated product dehydrated in the dehydrating unit while being heated and pressurized to the drying unit. It is characterized in that the process is continuously executed.

  According to the said structure, it becomes possible to send the solidified material heated and pressurized by the dehydration part to a drying part as it is. That is, the solidified product softened by being heated and pressurized in the dehydrating unit can be sent to the drying unit while being softened. Therefore, an excessive shearing force is not applied, and an appropriately plasticized solidified product can be obtained.

  In the present invention, it is important to send the solidified product in a heated and pressurized state from the dehydrating unit to the drying unit. That is, when the dehydration step and the drying step are performed separately in a screw press machine and a screw extruder that are provided separately, the coagulum is heated and pressurized from the time when it is discharged from the screw press machine. As soon as it is released, the temperature drops.

  As described above, the solidified product whose temperature has been lowered becomes inflexible and hard at around room temperature, so when it is applied to the screw extruder in that state, the solidified product is heated to a suitable viscosity until it is heated again. On the other hand, excessive shearing force and heat are applied. As a result, the molecular chains of the rubber molecules are excessively cut, the thermal history of the solidified product is increased, and the rubber properties (such as fracture strength) after vulcanization are reduced.

  On the other hand, the solidified substance is hard at around room temperature, but becomes softer as the temperature increases. Therefore, it can prevent that an excessive shear force acts on a solidified material by supplying to a dry part in the state which softened the solidified material like this invention. Furthermore, since the coagulated material supplied to the drying unit is already heated and pressurized, the residence time in the drying unit can be shortened by that amount, and the heat history applied to the coagulated material as a whole is reduced. It is possible to maintain good rubber properties after vulcanization.

  As the dehydrating and drying apparatus, for example, a screw press machine provided separately and a screw extruder can be used and the outlet of the screw press machine connected to the inlet of the screw extruder can be used. However, it is preferable that the dehydrating and drying apparatus has a configuration in which the dehydrating unit and the drying unit are connected to each other and have one screw shaft that passes through the dehydrating unit and the drying unit.

  According to the said structure, since a solidified substance moves along a screw axis | shaft toward a drying part from a dehydration part, it becomes possible to convey a solidified substance smoothly. Furthermore, since only one screw shaft is required, the apparatus can be simplified and made compact, and there is an advantage that the equipment cost can be reduced.

  In the above configuration, the dehydrating and drying apparatus may include an outer cylinder that surrounds the screw shaft in the dehydrating unit and the drying unit, and a mixing pin may be provided on the outer cylinder portion of the drying unit. Thereby, the shear force and pressure which act on a solidified substance can be enlarged. Therefore, compared with a configuration in which the mixing pin is not provided in the outer cylinder portion of the drying unit, the solidified product can be dried and plasticized while the length of the drying unit in the screw axial direction is shortened.

  In other words, by shortening the length of the drying section in the screw axial direction, the time for the solidified material to stay in the drying section can be further shortened, the heat history of the solidified material can be reduced, and the rubber properties after vulcanization can be improved. It becomes possible to maintain better.

  The wet masterbatch obtained by the above production method has a low moisture content, and is excellent in kneadability because it is appropriately plasticized. In addition, the rubber composition using the wet masterbatch according to the present invention has a low moisture content, excellent kneadability, and the rubber molecular chains are not cut excessively, so that the rubber properties after vulcanization are improved. Can be maintained. Furthermore, by using such a rubber composition, a pneumatic tire excellent in breaking strength and wear resistance can be obtained.

  Further, as described above, the drying unit includes a dehydrating unit having a function of a screw press and a drying unit having a function of a screw extruder, and the drying unit remains in a state where the solidified product dehydrated by the dehydrating unit is heated and pressurized. The dehydrating and drying apparatus that can be supplied to the apparatus can make the apparatus compact, and can efficiently dry and plasticize synthetic rubber, wet masterbatch, and the like.

  In the present invention, when the dewatering step and the drying step are performed at the time of manufacturing the wet master batch, the dewatering unit having the function of a screw press and the drying unit having the function of a screw extruder are provided and dewatered by the dewatering unit. Since the dehydration step and the drying step are continuously performed as a series of steps using a dehydration drying apparatus that can be supplied to the drying unit while the coagulum is heated and pressurized, the coagulum is appropriately It can be dried in a plasticized state, and the rubber properties after vulcanization can be maintained well.

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 Schematic of dehydration drying equipment used in dehydration process and drying process Partial cross-sectional enlarged view of FIG. Table showing evaluation results of examples

  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 an example of 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 coagulated 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. The coagulated product thus obtained has excellent fluidity when viewed as an aggregate of granular materials, and is suitable for use in a dehydration step and a drying step.

  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 schematic view showing a dehydration drying apparatus used in the dehydration process 5 and the drying process 6, and FIG. 4 is an enlarged partial cross-sectional view thereof. The dehydrating and drying apparatus 20 includes a dehydrating unit 21 having a function of a screw press and a drying unit 22 having a function of a single screw extruder, and remains in a state where the solidified material dehydrated by the dehydrating unit 21 is heated and pressurized. It is configured to supply to the drying unit 22. That is, in the present invention, using the dehydration drying apparatus 20, the dehydration process 5 and the drying process 6 are continuously performed as a series of processes.

  Specifically, the dehydrating and drying apparatus 20 includes a screw shaft 23 and a cylindrical outer cylinder 24 that houses the screw shaft 23. The outer cylinder 24 is comprised from the 1st barrel part 25 and the 2nd barrel part 26, and the outer cylinder 24 is comprised by connecting both in the state arrange | positioned in series. Of the outer cylinder 24, the portion of the first barrel portion 25 is the dewatering portion 21, and the portion of the second barrel portion 26 is the drying portion 22.

  A plurality of slits 27 are formed in the first barrel portion 25 as filtration openings along the length direction. On the other hand, the second barrel portion 26 is provided in a cylindrical shape, and a steam jacket 28 is formed on the outer peripheral surface thereof so that the second barrel portion 26 can be heated. The drying unit 22 is provided with a mixing pin 29 that penetrates the steam jacket 28 and the second barrel portion 26 and has a tip protruding from the inner peripheral surface of the second barrel portion 26.

  In the present embodiment, two mixing pins 29 are arranged in the second barrel portion 26 at intervals in the screw axis direction to form one row, and are arranged at four locations at 90 ° intervals in the circumferential direction of the second barrel portion 26. It is installed.

  The screw shaft 23 is provided with a steam flow path therein and can be heated. Further, a portion of the screw shaft 23 surrounded by the first barrel portion 25 (a rear portion 23a of the screw shaft) is formed in a tapered shape so that the diameter gradually increases from the rear end side toward the front end side. Thus, the solidified product is compressed between the rear portion 23a of the screw shaft and the first barrel portion 25.

  The rear end portion of the dehydrating and drying apparatus 20, that is, the rear end portion of the first barrel portion 25 is provided with a supply port 30 of the solid matter, and the solid matter introduced into the first barrel portion 25 from here is Due to the rotation of the screw shaft 23, it is heated and pressurized while being fed forward through the first barrel portion 25 and dehydrated. Then, the solidified product is supplied into the second barrel portion 26 while being heated and pressurized. The coagulated product preferably has a moisture content of 10.0% or less, more preferably 5.0% or less when leaving the dehydrating unit 21.

  The solidified substance introduced into the second barrel portion 26 is transferred to the discharge port 31 while receiving a shearing force due to the rotation of the portion of the screw shaft 23 surrounded by the second barrel portion 26 (front portion 23b of the screw shaft). Move towards. At this time, since the solidified product is already heated and pressurized, the length (in the screw axis direction) of the second barrel portion 26 can be shortened as compared with the case where the solidified product is heated from room temperature. .

  Thereby, the time for which the solidified material stays in the dehydrating and drying apparatus 20 can be shortened, and as a result, the thermal history of the solidified material can be reduced. Further, the shearing force necessary for plasticizing the solidified product is secured by the mixing pin 29 by the amount corresponding to the shortening of the length of the second barrel portion 26.

The solidified product dried in the second barrel portion 26 is discharged from the discharge port 31. It is preferable that the moisture content of the coagulated material immediately after being discharged from the discharge port 31 is 2.0% or less. That is, in the present invention, since the dehydration step and the drying step are continuously performed as a series of steps, the solidified product is uniformly dried and plasticized. Therefore, the obtained coagulated product has a small variation in quality, and can be kneaded without problems as long as the moisture content is 2.0% or less, and a uniform rubber composition can be obtained.

  In the present embodiment, no die lip is attached to the discharge port 31 of the second barrel portion 26. This is because the coagulated material supplied to the drying unit 22 is already heated and pressurized, so that the coagulated material can be sufficiently dried without further rapid heating and pressurization. For example, the pin 29 can be used to plasticize the solidified product, and to prevent excessive shearing force from acting on the solidified product by mounting the die lip.

  However, it is also possible to attach a die lip to the outlet of the second barrel portion. In this case, by appropriately adjusting the opening area of the die lip, the arrangement of the mixing pins, the length of the second barrel portion, etc., the solidified product is appropriately plasticized and an excessive shearing force acts on the solidified product. Do not.

  Specifically, the coagulated product discharged from the dehydrating and drying apparatus 20, that is, the coagulated product discharged from the second barrel portion 26, has a temperature immediately after discharge of 100 ° C. to 180 ° C., and Mooney viscosity defined in JIS K6300. Is adjusted to be in the range of 60 ° to 180 °, an excessive shearing force does not act on the solidified product, and a suitably plasticized solidified product can be obtained while suppressing thermal history.

  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).

  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 and drying process]
In this example, the dehydration process and the drying process were continuously performed as a series of processes using the dehydration drying apparatus 20 described in the above embodiment. As the dehydration drying apparatus 20 used, the first barrel part 25 constituting the dehydration part 21 had an inner diameter of 120 mm and a length of 780 mm, and the second barrel part 26 constituting the drying part 22 had an inner diameter of 120 mm and a length of 350 mm. .

  In the dehydrating and drying apparatus 20 having the above-described configuration, the screw shaft 23 was heated to 95 ° C. to treat the solidified product. The temperature of the solidified product after dehydration from the first barrel portion 25 was 122 ° C., and the moisture content was 4.0%. The solidified product after dehydration was supplied to the second barrel portion 26 while being heated and pressurized, and dried. In this example, evaluation was performed on a solidified product (wet masterbatch) obtained by changing the heating temperature of the second barrel portion 26 (Examples 1 to 3). In addition, the solidified product that was dried without attaching the mixing pin 29 to the second barrel portion 26 was also evaluated (Example 4).

  On the other hand, a single screw press machine having the same configuration as the dehydrating unit 21 of the dehydrating and drying apparatus 20 (manufactured by Suehiro EPM, product number: V-05 type, barrel diameter 120 mm, barrel length L / barrel diameter D = 6.5) Comparative Example 1 was obtained by performing only the dehydration step under the same conditions as above. Also, using this screw press and a single screw extruder (manufactured by Nakata Engineering Co., Ltd., product number: 60K extruder, barrel diameter 60 mm, barrel length L / barrel diameter D = 10, barrel temperature 80 ° C.) In Comparative Example 2, the dehydration step and the drying step were performed separately.

  In addition, since the solidified substance supplied to the single screw extruder of Comparative Example 2 was cooled and hardened, no mixing pin was used in consideration of the load applied to the extruder. Instead, by attaching a die lip having an opening ratio of 20% to the outlet of the extruder, the coagulated product was pressurized and heated, and further the shear force was applied to dry-plasticize the coagulated product.

  Furthermore, the above-described screw press machine and a single twin screw extruder (manufactured by Kobe Steel, product number: KTX-37, barrel diameter 37 mm, barrel length L / barrel diameter D = 30, barrel temperature 80 ° C.) are used. Thus, Comparative Example 3 was obtained by separately performing the dehydration step and the drying step, and Comparative Example 4 was obtained by repeating the dehydration step twice using the above-described screw press machine. In Comparative Example 3, the die lip was not attached to the twin screw extruder, and the solidified product was dry plasticized by a strong shearing force acting between the screws.

  The moisture content and Mooney viscosity of the coagulated product (wet masterbatch) obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were measured. In addition, the thermal history of the solidified product was calculated. Measurement conditions or calculation methods are as follows. These results are shown in FIG.

(1) Moisture content: Measured according to JIS K6238-2 using MX-50 manufactured by A & D.
(2) Mooney viscosity: measured in accordance with JIS K6300. In FIG. 5, the value of Comparative Example 2 is displayed as an index (displayed as a relative numerical value) with 100 as the value. The numbers in parentheses below the index display are actually measured values.
(3) Thermal history: A value obtained by dividing the difference between the sample introduction initial temperature (25 ° C.) and the discharge temperature by the residence time in the apparatus and halving.

[Production and Evaluation of Rubber Composition]
A rubber composition was prepared using the wet masterbatch. The composition of the rubber composition is 1 part by weight of stearic acid (manufactured by Nippon Oil & Fats), 1 part by weight of anti-aging agent (manufactured by Monsanto 6PPD), 150 parts by weight of wet masterbatch (of which 100 parts by weight of rubber component), zinc white ( 3 parts by weight of Mitsui Kinzoku No. 1), 1 part by weight of wax (manufactured by Nippon Seiwa), 2 parts by weight of sulfur (manufactured by Tsurumi Chemical Co., Ltd.), and 1 part by weight of an accelerator (CBS made by Sanshin Chemical) were blended.

  The rubber composition was kneaded using a B-type Banbury mixer manufactured by Kobe Steel. The rubber composition after kneading was vulcanized under conditions of 150 ° C. × 30 min, and then measured for breaking strength and exothermicity. The measurement conditions are as follows. These results are shown in FIG.

(1) Breaking strength: The breaking strength was measured according to JIS K6251. FIG. 5 shows an index with the value of Comparative Example 2 as 100. A numerical value becomes small, so that the thermal history of a solidified substance becomes large, or excessive shear force acts on a solidified substance.
(2) Exothermicity (tan δ): a value (loss tangent) measured under the conditions of initial strain 10%, dynamic strain ± 2%, frequency 10 Hz, temperature 60 ° C. using a spectrometer manufactured by Toyo Seiki Co., Ltd. FIG. 5 shows an index with the value of Comparative Example 2 as 100. The smaller this value, the lower the exothermic property and the better.

[Evaluation results]
The evaluation results are shown in the table of FIG. From FIG. 5, Examples 1-4 which performed the spin-drying | dehydration process and the drying process continuously as a series of processes using the spin-drying | dehydration apparatus are made into the screw press machine and screw extruder which carried out the spin-drying | dehydration process and the dry process separately. The breaking strength is improved as compared with Comparative Examples 2 and 3 which were separately executed using the same. On the other hand, the numerical values of tan δ and heat history are such that Examples 1 to 4 are smaller than Comparative Examples 2 and 3, and both Examples 1 to 4 have better results than Comparative Examples 2 and 3. became.

  That is, in Examples 1 to 4, since the solidified product is sent to the drying step in a softened state, the amount of heat applied to the solidified product in the drying step can be smaller than in Comparative Examples 2 and 3, and the entire solidified product A moderate shear force acts on the surface. On the other hand, in Comparative Examples 2 and 3, the solidified product discharged from the screw press machine was once cooled to near normal temperature and supplied to the screw extruder in a hard state. It was considered that the rupture strength of the rubber after vulcanization was lowered because an excessive shearing force acted on the solidified product.

  In general, tan δ increases as the number of rubber molecule ends increases. Therefore, it was considered that in Comparative Examples 2 and 3 in which an excessive shear force acts, the rubber molecular chain was excessively cut as compared with Examples 1 to 4, and as a result, the tan δ value was increased.

  Regarding other comparative examples, Comparative Example 1 was not evaluated for rubber properties after vulcanization because the moisture content of the coagulated product discharged from the screw press machine was high and could not be kneaded well in the next step. Moreover, about the comparative example 4, since the spin-drying | dehydration process of a screw press machine was repeated twice and implemented, the final discharge | emission temperature of the solidified substance rose to 209 degreeC. As a result, although the moisture content was 1.5%, the thermal history was too large. Therefore, when the vulcanized rubber characteristics were compared with Comparative Example 2, the breaking strength decreased and the value of tan δ increased.

  In Examples, in Examples 1 to 3 using a mixing pin, drying treatment is possible in a wide temperature range of 90 ° C. to 150 ° C. of the outer cylinder temperature of the drying section, and rubber properties after vulcanization are excellent. It was confirmed that This was thought to be because the solidified product supplied to the drying section was softened as a whole, and excessive shear force was less likely to act. Moreover, also in Example 4 which did not use a mixing pin, it was confirmed that the vulcanized rubber characteristic comparable as Examples 1-3 can be obtained by adjusting the heating temperature of a drying part.

  In Comparative Example 2 using a single screw extruder and Comparative Example 3 using a twin screw extruder, the latter had lower breaking strength. This is thought to be because, in a twin screw extruder, a strong shearing force is inevitably applied to the coagulated product by the rotation of the screw shaft, resulting in excessive cutting of the rubber molecular chains and an increase in the thermal history. It was.

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 Coagulation apparatus 9 Coagulation tank 10 Shear blade 11 Rotating shaft 20 Dehydration drying apparatus 21 Dehydration part 22 Drying section 23 Screw shaft 24 Outer cylinder 25 First barrel section 26 Second barrel section 27 Slit 28 Steam jacket 29 Mixing pin 30 Supply port 31 Discharge port

Claims (7)

A rubber latex and a slurry in which a filler is dispersed in water are mixed, and a dehydration process for coagulating and dehydrating a mixture of the rubber and the filler from the mixed solution, and a coagulated product obtained in the dehydration process is dried. A method for producing a wet masterbatch having a drying step, comprising: a dehydrating part having a function of a screw press machine and a drying part having a function of a screw extruder in performing the dehydration step and the drying step; The dehydration step and the drying step are continuously performed as a series of steps using a dehydration drying apparatus capable of supplying the coagulated material dehydrated in the dehydration unit to the drying unit while being heated and pressurized. A manufacturing method of a wet masterbatch. The wet dewatering apparatus according to claim 1, wherein the dehydrating and drying apparatus includes the dehydrating unit and the drying unit, and has one screw shaft that passes through the dehydrating unit and the drying unit. Method. 3. The wet masterbatch according to claim 2, wherein the dehydrating and drying apparatus includes an outer cylinder that surrounds the screw shaft in the dehydrating section and the drying section, and a mixing pin is provided in an outer cylinder portion of the drying section. Manufacturing method. The wet masterbatch manufactured by the method in any one of Claims 1-3. A rubber composition for tires, wherein the wet masterbatch according to claim 4 is used. A pneumatic tire using the rubber composition according to claim 5. A dehydrating unit having a screw press machine function and a drying unit having a screw extruder function are provided, and the solidified material dehydrated by the dehydrating unit can be supplied to the drying unit while being heated and pressurized. A dehydrating and drying apparatus characterized by.

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