JP2007217677A - Method for producing natural rubber and/or synthetic isoprene rubber masterbatch using powder rubber and filler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method having low energy cost for treating a rubber piece or rubber powder and to provide a method for serving a material obtained by treating those in recycling. <P>SOLUTION: The present invention enables production of a natural rubber and/or synthetic isoprene rubber wet masterbatch by mixing a slurry solution in which carbon black and/or silica is dispersed with powder rubber with a natural rubber latex and/or synthetic isoprene rubber latex. A rubber composition in which high physical properties are kept can be obtained by formulating a natural rubber and/or synthetic isoprene rubber masterbatch obtained by drying the natural rubber and/or synthetic isoprene rubber wet masterbatch therein. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a natural rubber and / or synthetic isoprene rubber masterbatch using powder rubber and a filler, and a rubber composition containing the same.

  Waste tires have a higher recovery rate than ordinary plastic products, and are reused as fuel, especially in cement factories. However, with the recent increase in environmental problems, there is a demand for an improvement in the so-called material recycling rate in which rubber pieces or rubber powder obtained by cutting or crushing waste tires are reused. In addition to the mechanical crushing method at room temperature, such as a roll crushing method, there are a freezing crushing method that crushes after freezing with liquid nitrogen or the like, and a water hammer crushing method that uses ultra-high pressure water, Attempts have been made to produce fine particles at low cost.

  On the other hand, in order to mix powder rubber with unvulcanized rubber and use it as a vulcanized rubber product, it is important to vulcanize and bond powder rubber and new unvulcanized rubber. Recycled rubber made by mixing, desulfurizing by heating and making into a sheet with a roll has been used for a long time. Various desulfurization methods for the surface of the powder rubber have been proposed. For example, there is a method in which a large shear force is applied to the powder rubber by a twin screw extruder or the like to pulverize and desulfurize. However, these methods have a drawback that the processing cost is high and the energy cost is high because the processing is performed with a high shearing force.

JP 2004-99625 A

  Accordingly, it is an object of the present invention to provide a method having a low energy cost for treating rubber pieces or rubber powder, and further providing a method for recycling the product obtained by the treatment.

  In order to solve the above problems, the present inventors have intensively studied. As a result, the slurry obtained by previously dispersing powder rubber and carbon black and / or silica pulverized by a conventional method in water, natural rubber latex and / or Natural rubber and / or synthetic isoprene rubber wet masterbatch could be obtained by mixing synthetic isoprene rubber latex. Furthermore, the present inventors have found that the rubber composition containing the natural rubber and / or synthetic isoprene rubber masterbatch obtained by drying the natural rubber and / or synthetic isoprene rubber wet masterbatch has a breaking strength, elongation at break, etc. In this respect, it was found that high physical properties were maintained as rubber, and the present invention was completed.

The present invention comprises the following (1) to (10).
(1) A natural rubber and / or synthetic isoprene rubber characterized by mixing a slurry solution in which carbon black and / or silica and rubber powder are previously dispersed in water and a natural rubber latex and / or synthetic isoprene rubber latex solution. Manufacturing method of wet masterbatch.
(2) The method according to (1) above, wherein the powder rubber has an average particle size of 200 microns or less.
(3) The method according to (1) above, wherein a surfactant is added to the slurry solution and / or the natural rubber latex and / or the synthetic isoprene rubber latex.
(4) The method according to (1) above, wherein the slurry concentration of the rubber powder in the slurry solution is 0.5 wt% to 60 wt% with respect to the slurry solution.
(5) The blending amount of the carbon black and / or silica in the natural rubber and / or synthetic isoprene rubber wet masterbatch is 100 parts by weight of the rubber component resulting from the natural rubber latex and / or synthetic isoprene rubber latex. The method according to (1) above, wherein the amount is 5 to 100 parts by weight.
(6) The blending amount of the powder rubber in the natural rubber and / or synthetic isoprene rubber wet masterbatch is 0.1 to 100 parts by weight with respect to 100 parts by weight of the rubber component resulting from the natural rubber latex and / or synthetic isoprene rubber. The method according to (1) above, wherein the method is by weight.
(7) A natural rubber and / or synthetic isoprene rubber wet masterbatch obtained by the method according to any one of (1) to (6) above.
(8) Natural rubber and / or synthetic isoprene rubber masterbatch prepared by coagulating and drying the natural rubber and / or synthetic isoprene rubber wet masterbatch described in (7) above .
(9) A rubber composition containing the natural rubber and / or synthetic isoprene rubber masterbatch described in (8) above.
(10) The amount of the powder rubber contained in the natural rubber and / or synthetic isoprene rubber master batch is 0.1 to 50 parts by weight with respect to 100 parts by weight of the rubber component other than the powder rubber of the rubber composition. The rubber composition as described in (9) above, wherein

  According to the present invention, a natural rubber and / or synthetic isoprene rubber wet master is mixed by mixing a slurry solution in which carbon black and / or silica and powder rubber are previously dispersed in water, and natural rubber latex and / or synthetic isoprene rubber latex. It became possible to produce batches. By blending the natural rubber and / or synthetic isoprene rubber master batch obtained by drying the natural rubber and / or synthetic isoprene rubber wet master batch, a rubber composition maintaining high physical properties as rubber can be obtained.

Embodiments of the invention will be specifically described below.
The present invention relates to a natural rubber and / or synthetic isoprene rubber wet, characterized by mixing a slurry solution in which carbon black and / or silica and powder rubber are previously dispersed in water, and natural rubber latex and / or synthetic isoprene rubber latex. The manufacturing method of the master batch is the gist. In general, a slurry in which a filler such as carbon black and silica and water are mixed in advance at a certain ratio, and the filler is finely dispersed in water by mechanical force, natural rubber latex and / or synthetic isoprene rubber. A latex is mixed, and then a coagulant such as an acid is added for coagulation. The obtained coagulum is recovered and further dried to produce a carbon wet masterbatch. On the other hand, in the present invention, a slurry in which filler such as carbon black and / or silica and powdered rubber are mixed in water at a certain ratio and the filler is finely dispersed in water by mechanical force, natural rubber latex and / or Synthetic isoprene rubber latex is mixed to prepare a powder rubber carbon wet master batch in advance.

  In order to obtain a stable slurry in the present invention, the average particle diameter of the rubber powder is preferably 200 microns or less. This is because if the particle size of the powder rubber is large, the particle size difference from the carbon black is large, and it is difficult to produce a uniform slurry.

  In order to obtain a more stable slurry solution, a certain amount of the above-mentioned rubber powder, filler and surfactant are added to water, and a high speed mixer is used such as a high shear mixer, high pressure homogenizer, ultrasonic homogenizer, colloid mill, impeller mill, etc. To stir for a certain time. In the present invention, anionic, cationic, nonionic and amphoteric surfactants can be used, and anionic and nonionic surfactants are particularly preferred. The addition amount of the surfactant is usually 0.01% by weight to 2% by weight with respect to the natural rubber latex and / or the synthetic isoprene rubber latex.

  The carbon black used in the present invention is not particularly limited, and those used in the normal rubber industry can be used. For example, various grades of carbon black such as SAF, HAF, ISAF, FEF, and GPF can be used alone or in combination. The silica used in the present invention is not particularly limited to these, but wet silica, dry silica, and colloidal silica are preferable.

  The slurry concentration of the slurry in which the carbon black and / or silica and rubber powder are dispersed in water is preferably 0.5 wt% to 60 wt%, and particularly preferably 1 wt% to 30 wt%. Furthermore, carbon black and / or silica is preferably added in an amount of 5 to 100 parts by weight, particularly 10 parts by weight based on 100 parts by weight of the rubber component resulting from the natural rubber latex and / or synthetic isoprene rubber latex of the wet masterbatch. It is preferably in the range of -70 parts by weight. This is because if the amount of the filler is less than 5 parts by weight, sufficient reinforcing properties may not be obtained, and if it exceeds 100 parts by weight, the workability may deteriorate.

  Moreover, it is preferable that the compounding part number of powder rubber exists in the range of 0.1 weight part-100 weight part with respect to 100 weight part of rubber components resulting from natural rubber latex and / or synthetic isoprene rubber latex of this wet masterbatch. This is because if the amount of powder rubber added is small, the recyclability becomes low, and if there is too much powder rubber, the physical properties deteriorate.

  The wet masterbatch can be coagulated in the same manner as usual using an acid such as formic acid or sulfuric acid or a salt coagulant such as sodium chloride. In the present invention, coagulation may be performed by adding natural rubber latex and / or synthetic isoprene rubber latex and the slurry without adding a coagulant. Additives such as inorganic fillers other than carbon black and silica, vulcanizing agents, anti-aging agents, coloring agents, and dispersing agents can be added to the wet masterbatch as desired.

  Drying is usually performed as the final step of master batch production. In the present invention, ordinary dryers such as a vacuum dryer, an air dryer, a drum dryer, and a hand dryer can be used. However, in order to improve the dispersibility of the filler and powder rubber, a mechanical shearing force is applied. It is preferable to perform drying. Although this drying can be performed using a general kneader, it is preferable to use a continuous kneader from the viewpoint of industrial productivity. Furthermore, it is preferable to use a twin-screw kneading extruder that rotates in the same direction or in different directions.

  In the step of drying while applying the shearing force, the water content in the master batch before the drying step is preferably 10% or more. If this moisture content is less than 10%, the improvement width of the filler dispersion in the drying process will be small.

  Further, a final rubber composition can be obtained by blending the master batch, and other rubber types can be kneaded with the rubber composition. The amount of powder rubber contained in the masterbatch compounded in the rubber composition is preferably 0.01 to 50 parts by weight with respect to 100 parts by weight of the rubber component other than powder rubber of the finally obtained rubber composition. .

  In addition, a vulcanizing agent, a vulcanization accelerator, an antiaging agent, an anti-scorching agent, zinc white, stearic acid, and the like can be added to the rubber composition as long as the object of the present invention is not impaired.

  And when the physical properties of the rubber composition containing the master batch obtained by the method of the present invention were evaluated, as shown in the following examples, the physical properties as rubber such as breaking strength and elongation at break were excellent. .

EXAMPLES Next, although this invention is demonstrated using an Example and a comparative example, this invention is not limited at all by the following Example.

Example 1
A rubber composition of Example 1 in which a master batch was blended was obtained as follows.
(1) Preparation of latex solution It was diluted with water so that the rubber content of natural rubber field latex (DRC 26.2%, pH 10.5) was 20%.

(2) Preparation of slurry A certain amount of powder rubber with an average particle size of 100 microns and carbon black HAF were added to water, followed by high-speed operation at a high speed in a colloid mill. The total slurry concentration of carbon black and powder rubber was 10% by weight of carbon black and 1% by weight of powder rubber based on the slurry.

(3) Coagulation step Add the latex and slurry prepared above into a homomixer to 100 parts by weight of the rubber component to 50 parts by weight of carbon black, and add formic acid to pH 4.7 while stirring. And got a wet masterbatch. The solidified wet masterbatch was collected, washed with water and dehydrated.

(4) Drying step The solidified sample was dried with an air dryer to obtain a master batch.

(5) Rubber composition 3 parts by weight of zinc oxide, 1.2 parts by weight of sulfur, 2 parts by weight of stearic acid, NS1 for the above master batch (100 parts by weight of rubber, 50 parts by weight of carbon black, 5 parts by weight of rubber powder) Part by weight and 1 part by weight of 6C were kneaded to obtain a rubber composition.

(Comparative Example 1)
The rubber composition of Comparative Example 1 was obtained as follows.
(1) Preparation of latex solution It was diluted with water so that the rubber content of natural rubber field latex (DRC 26.2%, pH 10.5) was 20%.

(2) Coagulation step Formic acid was added to the latex prepared as described above in a homomixer while stirring until the pH reached 4.7. The solidified natural rubber was recovered, washed with water and dehydrated.

(3) Drying process The solidified natural rubber was dried with an air dryer.

(4) Rubber composition Based on 100 parts by weight of the natural rubber obtained above, carbon black 50 parts by weight, powdered rubber 5 parts by weight, zinc oxide 3 parts by weight, sulfur 1.2 parts by weight, stearic acid 2 parts by weight, NS1 Part by weight and 1 part by weight of 6C were kneaded to obtain a rubber composition.

  The physical properties of the rubber composition of Example 1 blended with the master batch of the present invention and the rubber composition of Comparative Example 1 blended with no master batch were evaluated using fracture strength and elongation at break as indices. The breaking strength and elongation at break were measured by a method based on JIS K6251-1993. The results are shown in Table 1. As shown in Table 1, the rubber of Example 1 showed higher physical properties in both breaking strength and elongation at break than Comparative Example 1.

(Example 2)
A rubber composition of Example 2 in which a master batch was blended was obtained as follows.
(1) Preparation of latex solution It was diluted with water so that the rubber content of natural rubber field latex (DRC 26.2%, pH 10.5) was 20%.

(2) Preparation of slurry A certain amount of powder rubber with an average particle size of 100 microns and carbon black HAF were added to water, followed by high-speed operation at a high speed in a colloid mill. The total slurry concentration of carbon black and powder rubber was 10% by weight of carbon black and 2% by weight of powder rubber based on the slurry.

(3) Coagulation step In a homomixer, the latex and slurry prepared as described above were added to 100 parts by weight of the rubber component so that the total amount of carbon black and powdered rubber was 60 parts by weight. A wet masterbatch was obtained until .7 was reached. The solidified wet masterbatch was collected, washed with water and dehydrated.

(4) Drying step The solidified sample was dried with an air dryer to obtain a master batch.

(5) Rubber composition 3 parts by weight of zinc oxide, 1.2 parts by weight of sulfur, 2 parts by weight of stearic acid, NS against the above master batch (100 parts by weight of rubber, 50 parts by weight of carbon black, 10 parts by weight of powdered rubber) 1 part by weight and 1 part by weight of 6C were kneaded to obtain a rubber composition.

(Example 3)
Only the latex was prepared according to the following procedure, and the others were performed in the same manner as in Example 2.

(1) Preparation of latex Commercially available synthetic polyisoprene latex (Sepolex IR-100K DRC: 65.4% manufactured by Sumitomo Seika Co., Ltd.) was diluted with water so that the rubber content was 20%.

(Comparative Example 2)
The rubber composition of Comparative Example 2 was obtained as follows.
(1) Preparation of latex solution It was diluted with water so that the rubber content of natural rubber field latex (DRC 26.2%, pH 10.5) was 20%.

(2) Coagulation step Formic acid was added to the latex prepared as described above in a homomixer while stirring until the pH reached 4.7. The solidified natural rubber was recovered, washed with water and dehydrated.

(3) Drying process The solidified natural rubber was dried with an air dryer.

(4) Rubber composition 10 parts by weight of powder rubber having an average particle size of 100 microns, 50 parts by weight of HAF, 3 parts by weight of zinc oxide, 1.2 parts by weight of sulfur, 2 parts by weight of stearic acid, A rubber composition was obtained by kneading 1 part by weight of NS and 1 part by weight of 6C.

(Comparative Example 3)
(1) Preparation of latex Commercially available synthetic polyisoprene latex (Sepolex IR-100K DRC: 65.4% manufactured by Sumitomo Seika Co., Ltd.) was diluted with water so that the rubber content was 20%.

(2) Coagulation step Formic acid was added to the latex prepared as described above in a homomixer with stirring until the pH reached 4.7. The solidified synthetic isoprene rubber was recovered, washed with water and dehydrated.

(3) Drying step The above-mentioned solidified synthetic isoprene rubber was dried with an air dryer.

(4) Rubber composition 10 parts by weight of powder rubber having an average particle size of 100 microns, 50 parts by weight of HAF, 3 parts by weight of zinc oxide, 1.2 parts by weight of sulfur, and 2 parts by weight of stearic acid with respect to 100 parts by weight of the above synthetic isoprene rubber 1 part by weight of NS and 1 part by weight of 6C were kneaded to obtain a rubber composition.

  Physical properties of the rubber compositions of Examples 2 and 3 blended with the masterbatch of the present invention and the rubber compositions of Comparative Examples 2 and 3 blended with no masterbatch, using the fracture strength and the results of the constant elongation fatigue test as indices evaluated. (Table 2) The fracture strength was measured by a method based on JIS K6151-1993. In the constant elongation fatigue test, dumbbell-shaped test pieces were repeatedly pulled at a speed of 300 rpm and a strain of 100%, and evaluation was performed by logarithm of the number of times of fracture. As a result, as shown in Table 2, the physical properties of Examples 2 and 3 were superior to those of Comparative Examples 2 and 3, respectively.

  According to the present invention, a natural rubber and / or synthetic isoprene rubber wet masterbatch is produced by mixing a slurry solution in which carbon black and / or silica and powder rubber are dispersed with natural rubber latex and / or synthetic isoprene rubber latex. It became possible to do. Rubber that maintains high physical properties in terms of breaking strength and elongation at break by blending natural rubber and / or synthetic isoprene rubber masterbatch obtained by drying the natural rubber and / or synthetic isoprene rubber wet masterbatch A composition can be obtained. The rubber treatment method of the present invention has the advantage of low energy cost, and the natural rubber and / or synthetic isoprene rubber masterbatch obtained by the method of the present invention is useful for rubber recycling.

Claims (10)

  A natural rubber and / or synthetic isoprene rubber wet masterbatch characterized by mixing a slurry solution in which carbon black and / or silica and powder rubber are previously dispersed in water, and natural rubber latex and / or synthetic isoprene rubber latex. Production method.   2. The method according to claim 1, wherein the powder rubber has an average particle size of 200 microns or less.   2. The method according to claim 1, wherein a surfactant is added to the slurry solution and / or the natural rubber latex and / or the synthetic isoprene rubber latex.   The method according to claim 1, wherein the slurry concentration of the rubber powder in the slurry solution is 0.5 wt% to 60 wt% with respect to the slurry solution.   The blending amount of the carbon black and / or silica in the natural rubber and / or synthetic isoprene rubber wet masterbatch is 5 to 100 based on 100 parts by weight of the rubber component resulting from the natural rubber latex and / or synthetic isoprene rubber latex. 2. A method according to claim 1, characterized in that it is parts by weight.   The blending amount of the powdered rubber in the natural rubber and / or synthetic isoprene rubber wet masterbatch is 0.1 to 100 parts by weight with respect to 100 parts by weight of the rubber component resulting from the natural rubber latex and / or synthetic isoprene rubber latex. The method according to claim 1, wherein:   A natural rubber and / or synthetic isoprene rubber wet masterbatch obtained by the method according to any one of claims 1 to 6.   A natural rubber and / or synthetic isoprene rubber masterbatch prepared by coagulating and drying the natural rubber and / or synthetic isoprene rubber wet masterbatch according to claim 7.   A rubber composition containing the natural rubber and / or synthetic isoprene rubber masterbatch according to claim 8.   The amount of powder rubber contained in the natural rubber and / or synthetic isoprene rubber masterbatch is 0.01 to 50 parts by weight with respect to 100 parts by weight of rubber components other than the powder rubber of the rubber composition. The rubber composition according to claim 9.