Process for producing wet rubber masterbatch

Abstract

A process for producing a wet rubber masterbatch comprises a step (I) of dispersing a filler into a dispersing solvent to produce a filler-containing slurry solution, and a step (II) of adding a rubber latex solution to the filler-containing slurry solution to yield a filler-containing rubber latex solution, and stirring the yielded filler-containing rubber latex solution while heating the filler-containing rubber latex solution, thereby solidifying the filler-containing rubber latex solution, and a step (III) of stirring the resultant while adding an acid thereto, thereby solidifying the filler-containing rubber latex solution. In the step (II), the circumferential speed of a stirring impeller which a mixing tank used at the time of the stirring has is less than 10 m/s, and a calorie of 25 to 250 J both inclusive per unit period and unit mass is given to the filler-containing rubber latex solution by the heating.

Claims

1. A process for producing a wet rubber masterbatch comprising at least a filler, a dispersing solvent and a rubber latex solution as raw materials, wherein the process comprises: a step (I) of dispersing the filler into the dispersing solvent to produce a filler-containing slurry solution, a step (II) of adding the rubber latex solution to the filler-containing slurry solution to produce a filler-containing rubber latex solution, and stirring the filler-containing rubber latex solution while heating the filler-containing rubber latex solution, thereby solidifying the filler-containing rubber latex solution, and then a step (III) of stirring the filler-containing rubber latex solution while adding an acid thereto, thereby further solidifying the filler-containing rubber latex solution, wherein in the step (II), the circumferential speed of a stirring impeller, which a mixing tank used at the time of the stirring, is less than 10 m/s, and a calorie per unit period and unit mass that is given by the heating, is 25 to 250 J both inclusive.

2. The process for producing a wet rubber masterbatch according to claim 1, wherein the period for the stirring in the step (II) is 1.5 times or more that in the step (III).

3. The process for producing a wet rubber masterbatch according to claim 1, wherein the heat is at a temperature of 70 to 180 C.

4. The process for producing a wet rubber masterbatch according to claim 1, wherein the heat is at a temperature of 80 to 160 C.

5. The process for producing a wet rubber masterbatch according to claim 1, wherein the length of time stirring in step (II) is 1.5 times to 10 times longer than the length of time stirring in step (III).

6. A process for producing a wet rubber masterbatch comprising at least a filler, a dispersing solvent and a rubber latex solution as raw materials, wherein the process comprises: a step (I-a) of dispersing the filler into the dispersing solvent while also adding at least one portion of the rubber latex solution to the dispersing solvent to produce a filler-containing slurry solution which contains the filler to which rubber latex particles adhere, a step (II-a) of adding the rest of the rubber latex solution to the filler-containing slurry solution to produce a filler-containing rubber latex solution, in which the rubber latex particles adhere to the filler, and stirring the filler-containing rubber latex solution while heating the filler-containing rubber latex solution, thereby solidifying the filler-containing rubber latex solution, and then a step (III-a) of stirring the filler-containing rubber latex solution while adding an acid thereto, thereby further solidifying the filler-containing rubber latex solution, wherein in the step (II), the circumferential speed of a stirring impeller, which a mixing tank used at the time of the stirring, is less than 10 m/s, and a calorie per unit period and unit mass that is given by the heating, is 25 to 250 J both inclusive.

7. The process for producing a wet rubber masterbatch according to claim 6, wherein the heat is at a temperature of 70 to 180 C.

8. The process for producing a wet rubber masterbatch according to claim 6, wherein the heat is at a temperature of 80 to 160 C.

9. The process for producing a wet rubber masterbatch according to claim 6, wherein the length of time stirring in step (II) is 1.5 times to 10 times longer than the length of time stirring in step (III).

Description

EXAMPLES

(1) Hereinafter, this invention will be more specifically described through a description of working examples thereof. Raw materials and apparatuses used therein are as follows:

(2) Used Materials:

(3) a) Fillers:

(4) Carbon black N110: SEAST 9 manufactured by Tokai Carbon Co., Ltd.,

(5) Carbon black N330: SEAST 3 manufactured by Tokai Carbon Co., Ltd., and

(6) Carbon black N774: SEAST S manufactured by Tokai Carbon Co., Ltd.;

(7) b) Dispersing solvent: Water;

(8) c) Rubber latex solution: Natural rubber latex manufactured by a company Golden Hope, which was used as a rubber latex; concentration: a concentration adjusted by adding water to the natural rubber latex at room temperature to give a rubber component concentration of 25% by weight (DRC (dry rubber content)=31.2%); mass-average molecular weight Mw=232,000, manufactured by a company Golden Hope;
d) Solidifier: Formic acid (solution obtained by diluting a first-class 85% solution thereof into a 10% solution and adjusting the pH of the diluted solution to 1.2), manufactured by Nacalai Tesque, Inc.;
e) Zinc oxide: Zinc flower No. 1, manufactured by Mitsui Mining & Smelting Co., Ltd.;
f) Stearic acid: LUNAC S-20, manufactured by Kao Corp.;
g) Wax: OZOACE 0355, manufactured by Nippon Seiro Co., Ltd.;
h) Antiaging agents:

(9) (A) N-phenyl-N-(1,3-dimethylbutyl)-p-phenylenediamine NOCRAC 6C, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd., and

(10) (B) 2,2,4-Trimethyl-1,2-dihydroxyquinoline polymer RD, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.;

(11) i) Sulfur: Sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.;

(12) j) Vulcanization promoter: N-cyclohexyl-2-benzothiazol sulfonamide SANCELER CM (manufactured by Sanshin Chemical Industry Co., Ltd.); and

(13) k) Additional rubber: BR150L, manufactured by Ube Industries, Ltd.

(14) Evaluations:

(15) Evaluations were made about a rubber obtained by using a predetermined mold to heat and vulcanize each rubber composition at 150 C. for 30 minutes.

(16) Exothermic Property of Vulcanized Rubber:

(17) According to JIS K6265, the exothermic property of each of produced vulcanized rubbers was evaluated through the loss tangent tan thereof. A rheospectrometer, E4000, manufactured by a company UBM was used to measure the loss tangent at 50 Hz and 80 C. under a condition of a dynamic strain of 2%. The measured value was converted to an index. In the evaluation, the value of Comparative Example 1 was regarded as 100, and Examples 1 to 5 and Comparative Examples 1 to 4 were each evaluated through an index relative thereto; the value of Comparative Example 5 was regarded as 100, and Example 6 was evaluated through an index relative thereto; and the value of Comparative Example 6 was regarded as 100, and Example 7 was evaluated through an index relative thereto. It was denoted that as the numerical value was smaller, the exothermic property was better.

(18) Fatigue Resistance Performance of Vulcanized Rubber:

(19) According to JIS K6260, the fatigue resistance performance of each of the produced vulcanized rubbers was evaluated. In the evaluation, the value of Comparative Example 1 was regarded as 100, and Examples 1 to 5 and Comparative Examples 1 to 4 were each evaluated through an index relative thereto; the value of Comparative Example 5 was regarded as 100, and Example 6 was evaluated through an index relative thereto; and the value of Comparative Example 6 was regarded as 100, and Example 7 is evaluated through an index relative thereto. It was denoted that as the numerical value is larger, the fatigue resistance performance was better.

Example 1

(20) To the above-mentioned diluted latex solution in water that had a concentration adjusted to 0.5% by mass were added 50 parts by mass of carbon black. The carbon black was dispersed therein, using a stirring machine (FLASHBLEND) manufactured by a company Silverson (FLASHBLEND conditions: 3600 rpm for 30 minutes) to produce a carbon black-containing slurry solution in which natural rubber latex particles adhered onto the carbon black (step (I)).

(21) Next, the rest of the natural rubber latex solution (adjusted into a solid (rubber) concentration of 25% by mass by adding water to the above-mentioned diluted latex solution) was added to the carbon black-containing slurry solution produced in the step (I), in which the natural rubber latex particles adhered onto the carbon black, so as to adjust the solid (rubber) amount in the rest of the latex solution, and the natural rubber latex solution used in the step (II) to 100 parts by mass. Next, a mixing machine (SUPER MIXER SM-20) manufactured by Kawata Mfg Co., Ltd. used to stir the resultant carbon black-containing natural rubber latex solution in which the natural rubber latex particles adhered onto the carbon black while heating this rubber latex solution, thereby solidifying the rubber latex solution (step (II)).

(22) Thereafter, while the resultant was stirred while adding a 10%-by-mass formic acid solution in water as a solidifier thereto to turn the pH thereof down to 4, thereby solidifying the carbon black-containing natural rubber latex solution, in which the natural rubber latex particles adhered onto the carbon black (step (III)). A screw press V-02 model manufactured by Suehiro EPM Corp. was used to dry the solidified product into a water content of 1.5% or less. In this way, a natural wet rubber masterbatch was produced.

(23) Various additives described in Table 1 were blended into the resultant natural wet rubber masterbatch to prepare a rubber composition. The physical properties of a vulcanized rubber thereof were measured. The results are shown in Table 1.

Comparative Examples 1 to 6, and Examples 2 to 11

(24) In each of the examples, a wet rubber masterbatch, a rubber composition and a vulcanized rubber were each produced in the same way as in Example 1 except that one or more of the following were changed as described in Table 1 or 2: the blend of the various components; whether or not heating was done in the step (II); whether or not an acid was added in the step (III); the circumferential speed of the stirring impellers in the step (II); the calorie in the step (II); the stirring period in the step (II)/stirring period in the step (III) ratio. The physical properties of the vulcanized rubbers are shown in Tables 1 and 2.

(25) TABLE-US-00001 TABLE 1 Com- Com- Com- Com- parative parative parative parative Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Example Example Example Example ample ample ample ample ample ample ample ample ample 1 2 3 4 1 2 3 4 5 6 7 8 9 Blended components: Wet rubber Carbon N110 masterbatch black N330 50 50 50 50 50 50 50 50 50 50 50 50 50 blend N774 components Natural rubber 100 100 100 100 100 100 100 100 100 100 100 100 100 (solid content) Blend Additional rubber components Zinc flower 3 3 3 3 3 3 3 3 3 3 3 3 3 at rubber Stearic acid 2 2 2 2 2 2 2 2 2 2 2 2 2 composition Wax 1 1 1 1 1 1 1 1 1 1 1 1 1 producing Antiaging (A) 2 2 2 2 2 2 2 2 2 2 2 2 2 time agents (B) 1 1 1 1 1 1 1 1 1 1 1 1 1 Sulfur 2 2 2 2 2 2 2 2 2 2 2 2 2 Vulcanization 1 1 1 1 1 1 1 1 1 1 1 1 1 promoter Step (II) and step (III) conditions: Heating in step (II) Done Not Done Done Done Done Done Done Done Done Done Done Done done Stirring period (min.) while 15 15 15 15 30 15 10 15 15 15 45 30 8 heating in step (II) Heating temperature ( C.) 190 60 120 110 100 125 150 105 150 125 80 100 125 in step (II) Addition of acid in step (III) Done Done Not Done Done Done Done Done Done Done Done Done Done done Circumferential speed (m/s) of 5 5 5 30 5 5 5 5 5 8 5 5 5 impellers in step (II) Calorie in step (II) 294 12 102 102 51 102 153 63 153 102 29 51 102 Stirring period (min.) in 5 5 5 5 10 5 3 5 5 5 5 5 5 step (III) Stirring period in step (II)/ 3 3 3 3 3 3 3 3 3 3 9 6 1.6 stirring period in step (III) ratio Vulcanized rubber physical properties: Exothermic property (INDEX) 100 104 103 98 92 90 94 93 94 90 93 91 93 Fatigue resistance (INDEX) 100 95 98 90 110 110 106 107 105 108 115 112 111

(26) TABLE-US-00002 TABLE 2 Com- Com- parative Ex- parative Ex- Example ample Example ample 5 10 6 11 Blended components: Wet rubber Carbon N110 45 45 masterbatch black N330 blend N774 70 70 components Natural rubber 80 80 100 100 (solid content) Blend Additional rubber 20 20 components Zinc flower 3 3 3 3 at rubber Stearic acid 2 2 2 2 composition Wax 1 1 1 1 producing Antiaging (A) 2 2 2 2 time agents (B) 1 1 1 1 Sulfur 2 2 2 2 Vulcanization 1 1 1 1 promoter Step (II) and step (III) conditions: Heating in step (II) Done Done Done Done Stirring period (min.) while 15 15 15 10 heating in step (II) Heating temperature ( C.) in 190 105 190 150 step (II) Addition of acid in step (III) Done Done Done Done Circumferential speed (m/s) of 8 8 5 5 impellers in step (II) Calorie in step (II) 294 63 294 153 Stirring period (min.) in step (III) 5 5 5 5 Stirring period in step (II) 3 3 3 2 Vulcanized rubber physical properties: Exothermic property (INDEX) 100 95 100 89 Fatigue resistance (INDEX) 100 106 100 112

(27) From the results in Tables 1 and 2, it is understood that the vulcanized rubber obtained using the wet rubber masterbatch according to each of Examples 1 to 11 is excellent in exothermic property and fatigue resistance.