JP4452317B1 - Manufacturing method of wet masterbatch - Google Patents

Abstract

Provided is a wet masterbatch manufacturing method capable of generating granular coagulates from a mixture of rubber latex and filler slurry in a short time and without containing large lumps. Objective.
A method for producing a wet masterbatch having a mixing / coagulation step 3 in which a rubber latex and a slurry in which a filler is dispersed in water are mixed and a mixture of the rubber and the filler is coagulated from the mixed solution. Then, the crushing blade 9 that solidifies the mixture is provided with a crushing blade 9 that satisfies the following condition (a), and the crushing blade 9 is rotated so that the peripheral speed is 10 m / s or more to solidify while mixing the rubber latex and the slurry. Product.
(A) Area of rotating body drawn by rotation of crushing blade (cm ² ) ≧ total amount of liquid mixture (L) × 10 (cm ² · L ⁻¹ )
[Selection] Figure 2

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.

  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.).

  In the mixing / coagulation step, the coagulation tank into which the natural rubber latex and the filler slurry are charged is provided with a screw type stirring blade for mixing both liquids. A coagulated product is generated by adding a coagulant.

  However, the solidified product tends to be a large lump because the production rate in the mixed liquid is high. When a large lump of coagulum is generated, it becomes difficult to dehydrate in the subsequent dehydration step, and the fluidity is lowered, so that the handling property is lowered.

  As a method for solving the above-mentioned problem, as shown in Patent Document 2, a solidified product is produced while stirring the mixed solution with a stirring blade provided in the coagulation tank, and this solidified product is obtained by a crushing blade provided in the coagulation tank. A method of crushing is known.

Patent Registration No. 2633913 JP 2007-237456 A

  However, since the coagulated substance itself is an elastic body mainly composed of rubber, a large force is required to break it. Moreover, as in Patent Document 2, it takes a considerable amount of time to crush the massive coagulated product generated in the coagulation tank with a crushing blade whose size is limited while it can freely move in the mixed liquid. Was needed.

  Therefore, in the present invention, in view of the above problems, a wet solution capable of generating a granular coagulated material from a mixture of rubber latex and filler slurry in a short time and without containing a large lump. It aims at providing the manufacturing method of a masterbatch.

In order to solve the above-mentioned problems, the present invention is a method for producing a wet masterbatch having a mixing / coagulation step in which a rubber latex and a slurry in which a filler is dispersed in water are mixed and the mixed solution is coagulated. Then, a crushing blade satisfying the following condition (a) is provided in the coagulation tank for coagulating the mixed solution, and the crushing blade is rotated so that the peripheral speed is 10 m / s or more to solidify while mixing the rubber latex and the slurry. It is characterized by generating an object. (A) Area of rotating body drawn by rotation of crushing blade (cm ² ) ≧ total amount of liquid mixture (L) × 10 (cm ² · L ⁻¹ )
That is, a mixed liquid composed of rubber latex and filler slurry is formed by adding a coagulant such as an acid such as formic acid or a metal salt such as aluminum sulfate to produce a coagulated product (a mixture of rubber and filler). In addition, it is possible to generate a coagulum by applying a strong force to the liquid. Therefore, in the present invention, a strong shearing force is given to the mixed solution by rotating a crushing blade having a certain size or more with respect to the amount of the mixed solution at a high speed of a peripheral speed of 10 m / s or more. In the above, a large number of coagulated nuclei were produced in the mixed solution.

  Thereby, since the growth of the solidified product proceeds uniformly, it becomes possible to obtain a granular solidified product having a uniform size in a short time. The peripheral speed of the crushing blade is not particularly limited as long as it is 10 m / s or more. However, when the peripheral speed of the crushing blade exceeds 50 m / s, a large difference is not seen in the solidified product to be generated. The peripheral speed is preferably 10 m / s or more and 50 m / s or less.

  In the present invention, the size of the crushing blade is important. That is, even if the crushing 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 crushing blade is exerted on only 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.

In the present invention, the size of the crushing blade is (a) the area (cm ² ) of the rotating body drawn by the rotation of the crushing blade ≧ the total amount of the mixed solution (L) × 10 (cm ² · L ⁻¹ ). Thus, the size of the crushing blade capable of exerting an impact force on the entire liquid mixture is ensured. In addition, the crushing blade effectively suppresses crushing and agglomeration at an early stage due to the shearing force at the time of rotation of the coagulated material that is growing greatly.

The size of the crushing blade may be any size as long as it satisfies the above condition (a). However, if the crushing blade is large, a power source that rotates the crushing blade requires a large power. (L) × 100 (cm ² · L ⁻¹ ) ”>“ area of rotating body drawn by rotation of crushing blade (cm ² ) ”is preferable.

  As described above, the crushing blade according to the present invention is used mainly for the purpose of preventing the solidified product from growing into a large lump. Therefore, when a large number of massive coagulated products are produced in the mixing / solidifying step, it takes a long time to crush the coagulated products into particles.

  In the present invention, the crushing blade means a blade that mainly gives a shearing force to the mixed liquid, such as a chopper composed of a blade type blade, and a stirring blade such as a propeller type that mainly gives a thrust to the mixed liquid. Is different. In addition, even if it is a crushing blade | wing, after making it an appropriate magnitude | size and rotating at high speed, stirring of a liquid mixture becomes fully possible.

One crushing blade can be provided in the coagulation tank, or a plurality of crushing blades may be provided. When a plurality of crushing blades are provided in the coagulation tank, the total area of the rotating bodies drawn by the rotation of each crushing blade is larger than the total amount (L) × 10 (cm ² · L ⁻¹ ) of the mixed liquid. What should I do? It is also possible to provide a plurality of crushing blades on the same rotating shaft. That is, the crushing blades may be formed in a plurality of stages on one rotating shaft at intervals in the axial direction.

Also in this case, the area of the rotating body drawn by the rotation of the crushing blades is such that the total area of the rotating bodies in each stage is larger than the total amount (L) × 10 (cm ² · L ⁻¹ ) of the mixed liquid. You can do it. When multiple crushing blades are provided in the solidified layer, and each stage is provided with multiple crushing blades, obtain the area of all rotating bodies drawn by crushing blade rotation in units of steps, and add these do it.

  In the coagulation tank, it is also possible to install a propeller-type agitating blade as an auxiliary, assuming that the crushing blade satisfies the above requirements, so that the mixture can be stirred more uniformly. .

  In the present invention, 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 carbon black remaining in the mixed liquid can be reduced, and coagulation can be completed in a shorter time. When adding a coagulant, it is preferable to first start rotation of the crushing blade and add the coagulant to the mixed solution after a predetermined time has elapsed. When a coagulant is added simultaneously with the start of rotation of the crushing blade, the formation of a solidified product proceeds rapidly, the coagulated product tends to be agglomerated, and the coagulated product adheres and accumulates on the crushing blade.

  Most of the coagulated product obtained by the present invention has a size of about 1 mm to 10 mm, so that moisture can be easily removed in the subsequent dehydration / drying process, and since the surface area is large, it can be dried smoothly. . Furthermore, since it is excellent in fluidity, there is no possibility of causing a situation that it becomes clogged in the dehydrating apparatus or the drying apparatus and cannot be discharged in the dehydrating / drying process.

  In particular, in the dehydration process, when using a screw press machine that dehydrates while feeding the coagulum with a screw, the inside of the screw press machine is heated to a temperature at which the water in the coagulum evaporates but the coagulum does not melt. The object is pushed forward of the press by the rotation of the screw.

  In the above configuration, a large load is applied to the screw. When the coagulated product obtained in the present invention is used, the coagulated product is not clogged in the screw press machine, and a large load may be applied to the screw. Therefore, the solidified product can be discharged smoothly from the discharge port, and the dehydration can be performed more efficiently. The coagulated product obtained in the mixing / coagulation step is finally subjected to a dehydration / drying step to obtain a wet master batch.

  The wet masterbatch obtained by the present invention can be suitably used for various rubber compositions including tire rubber compositions such as tire dread rubber and sidewall rubber.

  In the present invention, when a rubber latex and a slurry in which a filler is dispersed in water are mixed and solidified, a crushing blade having a certain size or more with respect to the amount of the liquid mixture is set to a high speed of 10 m / s or more. Therefore, it is possible to obtain a granular coagulate having a uniform size in a short time.

Process drawing which shows the manufacturing method of the wet masterbatch which concerns on this invention Cross-sectional view of the solidification device used in the mixing and solidification process Sectional drawing which shows another aspect of a solidification apparatus Cross-sectional view of crushing blades installed in the coagulator Sectional drawing which shows another aspect of a crushing blade | wing

  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 carbon black 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 for mixing and coagulating rubber latex and carbon black slurry. The coagulation apparatus 7 includes a coagulation tank 8 and a crushing blade 9. In the present embodiment, blade-shaped blades are used as the crushing blades 9, and the blades are symmetrically arranged with respect to the rotary shaft 12 standing on the bottom surface of the coagulation tank 8 so that the surface of the blades faces the horizontal direction. The crushing blade 9 rotates in the horizontal direction so that a strong shearing force acts on the mixed solution.

  One crushing blade 9 may be used, or a plurality of crushing blades 10 and 11 may be used as shown in FIG. Further, the crushing blade is not necessarily installed on the bottom surface of the coagulation tank 8, and may be disposed on the side surface of the coagulation tank 8 like the crushing blades 10 and 11.

The blade size of the crushing blade 9 is adjusted by the total amount of rubber latex and carbon black slurry supplied to the coagulation tank 8. Specifically, as shown in FIG. 4, when the length of the crushing blade 9 is a, the area of the rotating body drawn by the rotation of the crushing blade 9 is a ² π / 4 (cm ² ). Therefore, a may be set such that a ² π / 4 (cm ² ) ≧ total amount of liquid mixture (L) × 10 (cm ² · L ⁻¹ ).

Further, as shown in FIG. 5, when the shape of the crushing blade 9 is not straight and the outer peripheral side end of the crushing blade 9 is bent vertically, the area of the rotating body drawn by the rotation of the crushing blade 9 Is a ² π / 4 + abπ (cm ² ). Therefore, in this case, a and b may be set so that a ² π / 4 + abπ (cm ² ) ≧ total amount of liquid mixture (L) × 10 (cm ² · L ⁻¹ ).

  After supplying both the liquid of rubber latex and carbon black slurry to the coagulation tank 8, or while introducing both liquids into the coagulation tank 8, the crushing blade 9 is rotated so that the peripheral speed is 10 m / s or more to obtain a mixed liquid. Stir while applying a shearing force. 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 greatly affects the shape of the solidified material thereafter. 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 the case of adding a coagulant, it is preferable to start the rotation of the crushing blades 9 and to add the coagulant at a stage where the formation and growth of the coagulum has settled. Specifically, after the start of rotation of the crushing blade 9, about 2 to 4 minutes have passed. 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). Specifically, methods such as centrifugation, screw press, and filter press can be employed. After dehydration, the coagulum is subjected to a drying step 6.

  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.

  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 a filler in the filler slurry preparation step 2, and this was dispersed in water with a high shear mixer to prepare a slurry having a solid content of 5% by weight.

  Thereafter, in the mixing / coagulation step 3, the rubber latex 20L, the carbon black slurry, and 50 L were simultaneously charged into a 100 L capacity coagulation tank, and the crushing blade was immediately rotated at a predetermined peripheral speed for 5 minutes to stir the mixture. In addition, when 2 minutes and 30 seconds passed after the rotation of the crushing 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. After stirring for 5 minutes, the state of formation of the solidified product was observed, and in some cases, the crushing blade was additionally rotated.

  As shown in FIG. 2, the solidification apparatus is of type A in which crushing blades are installed on the bottom surface of the solidified layer, type B in which crushing blades are provided on both the bottom and side surfaces as shown in FIG. Evaluation was carried out with three types of type C, in which the crushing blades on the bottom surface were eliminated in the coagulation tank and crushing blades were provided only on the side surfaces.

[Evaluation item]
The evaluation was performed with three items of a solidified state, a crushed state, and a time merit. The evaluation criteria for each item are described below.

(1) Solidification state In the mixing / solidification step, if there is an unsolidified portion of carbon black, turbidity occurs in the mixed liquid after solidification. This turbidity was judged visually.
◎… Transparent ○… Almost transparent △… Muddy

(2) Size of the solidified product The size of the solidified product was visually determined.
◎ ... Most is 1-10mm, uniform particle size ○ ... Most is 1-10mm
Δ: 10 mm to fist size × ... Huge lump

(3) Time merit Judgment was made by taking into account the mixed state and the crushed state in the total rotation time of the crushed blade.
◎… Effective in a short time ○… Effective in a short time △… No time advantage ×… Very time consuming

[Evaluation results]
Table 1 shows the coagulation apparatus and the evaluation results. In the table, “13 + 13” in the “blade length” item means that blade-shaped crushing blades having a diameter of 13 cm are formed in two stages on the same rotation axis. In this embodiment, the minimum required area of the rotating body is 70 (L) × 10 (cm ² · L ⁻¹ ) = 700 cm ² .

From Table 1, in Examples 1 to 6 where the area of the rotating body is 700 cm ² or more and the peripheral speed of the crushing blade is 10 m / s or more, the size of the solidified product is mostly in the range of 1 mm to 10 mm. The product with excellent fluidity was obtained. Further, the time required for the coagulation step was as short as 10 minutes or less.

  In particular, in Examples 1 and 2 in which the peripheral speed of the crushing blade was set to 20 m / s or more, the time required for the solidification step could be further shortened to 5 minutes, and the obtained solidified product had a uniform size. there were. Thus, as the particle size of the solidified product becomes uniform, the fluidity of the solidified product as a whole becomes better. In addition, since an appropriate gap can be secured between the solidified particles, moisture is easily removed, and drying can be performed efficiently. Moreover, even if the peripheral speed of the crushing blade | wing was 10 m / s, the evaluation regarding the solidification state and the magnitude | size of a solidified substance improved, so that the area of the rotary body increased (Examples 4 and 5).

On the other hand, even if the area of the rotating body is 700 cm ² or more, if the peripheral speed of the crushing blade is less than 10 m / s, a fist large coagulum is generated (Comparative Examples 1 to 3), and the crushing blade Even if the stirring time was extended, a large amount of coagulated material remained (comparative examples 1 and 2).

  As described above, the solidified product obtained by the present invention is advantageous in terms of fluidity, that is, handling properties in terms of shape. In particular, when using a screw press machine that dehydrates while feeding the coagulum with a screw in the dehydration process, the coagulum does not clog in the screw press machine, and does not impose a heavy load on the screw. It becomes possible to discharge smoothly from the discharge port.

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 Coagulator 8 Coagulation tank 9 Crushing blade 10 Crushing blade 11 Crushing blade 12 Rotating shaft

Claims (5)

A method for producing a wet masterbatch having a mixing / coagulation step in which a rubber latex and a slurry in which a filler is dispersed in water are mixed to coagulate the mixed solution. A wet master characterized in that a crushing blade satisfying the following condition (a) is provided, and the crushing blade is rotated so as to have a peripheral speed of 10 m / s or more to generate a coagulum while mixing the rubber latex and slurry. Batch manufacturing method.
(A) Area of rotating body drawn by rotation of crushing blade (cm ² ) ≧ total amount of liquid mixture (L) × 10 (cm ² · L ⁻¹ ) In the mixing / solidifying step, a plurality of crushing blades are provided in the coagulation tank, and the area of the rotating body in the condition (a) is the sum of the areas of the rotating bodies drawn by the rotation of the crushing blades. The method for producing a wet masterbatch according to claim 1. In the mixing / solidifying step, a plurality of crushing blades are provided on the same rotation axis in the coagulation tank, and the area of the rotating body in the condition (a) is the sum of the areas of the rotating bodies drawn by the rotation of each crushing blade. The method for producing a wet masterbatch according to claim 1 or 2, wherein the method is provided. The method for producing a wet masterbatch according to any one of claims 1 to 3, wherein in the mixing / solidifying step, a coagulant is added to the mixed solution after a predetermined time has elapsed since the rotation of the crushing blades. The method for producing a wet masterbatch according to any one of claims 1 to 4, wherein the coagulated product obtained in the mixing and coagulating step is dehydrated with a screw press.

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