Method for producing rubber wet master batch

Abstract

In the step (I), the period (minute(s)) for dispersing the carbon black species A showing a nitrogen adsorption specific surface area (N.sub.2SA-(A)value) of 130 m.sup.2/g or less in the dispersing solvent and that minute(s)) for dispersing the carbon black species B showing an N.sub.2SA-(B) value lower than the N.sub.2SA-(A) value by 25 m.sup.2/g or more in the dispersing solvent by (A) and (B), respectively, and further representing the rotation number (rpm) of a rotor of a dispersing machine used in the dispersing when the carbon black species A is dispersed, and that (rpm) of a rotor of a dispersing machine used in the dispersing when the carbon black species B is dispersed by (A) and (B), respectively, the following expression is satisfied:
1.1(B)(B)(A)(A)1.5(B)(B) (1).

Claims

1. A method for producing a rubber wet master batch obtained by using at least a filler, a dispersing solvent and a rubber latex solution as raw materials, the method comprising a step (I) of dispersing the filler into the dispersing solvent to produce a filler-containing slurry solution, a step (II) of mixing the filler-containing slurry solution with the rubber latex solution to produce a filler-containing rubber latex solution, and a step (III) of solidifying and drying the filler-containing rubber latex solution, wherein the filler comprises two filler species that are a carbon black species A showing a nitrogen adsorption specific surface area (N.sub.2SA-(A) value) of 130 m.sup.2/g or less, and a carbon black species B showing an N.sub.2SA-(B) value lower than the N.sub.2SA-(A) value by 25 m.sup.2/g or more; and in the case of representing, in the step (I), following expression is satisfied:
1.1(B)(B)(A)1.5(B)(B) wherein (A) is the period (minute(s)) for dispersing the carbon black species A in the dispersing solvent, (B) is the period (minute(s)) for dispersing the carbon black species B in the dispersing solvent, (A) represented the rotation number (rpm) of a rotor of a dispersing machine used in the dispersing when the carbon black species A is dispersed, and (B) represented the (rpm) of a rotor of a dispersing machine used in the dispersing when the carbon black species B is dispersed.

2. The method for producing a rubber wet master batch according to claim 1, wherein in the step (I), the dispersing of the carbon black species A and that of the carbon black species B are performed separately from each other to satisfy the expression, and after the dispersings, the resultants are mixed with each other in advance.

3. The method for producing a rubber wet master batch according to claim 1, wherein the step (I) is a step (I-(a)) in which when the filler is dispersed into the dispersing solvent, at least one portion of the rubber latex solution is added thereto, thereby producing the filler-containing slurry solution that is a slurry solution in which rubber latex particles are bonded to the filler, and the step (II) is a step (II-(a)) in which the rubber-latex-particle-bonded-filler-containing slurry solution is mixed with the rest of the rubber latex solution, thereby producing the filler-containing rubber latex solution that is a rubber latex solution in which the rubber latex particles are bonded to the filler.

4. A rubber wet master batch, produced by the producing method recited in claim 1.

5. A rubber composition, comprising the rubber wet master batch recited in claim 4.

6. A pneumatic tire, comprising the rubber composition recited in claim 5.

Description

EXAMPLES

(1) Hereinafter, working examples of this invention will be more specifically described.

(2) Used Materials:

(3) a) Fillers

(4) Carbon black N110: SEAST 9, manufactured by Tokai Carbon Co., Ltd. (N.sub.2SA: 142 m.sup.2/g)

(5) Carbon black N220: SEAST 6, manufactured by Tokai Carbon Co., Ltd. (N.sub.2SA: 119 m.sup.2/g)

(6) Carbon black N234: SEAST 7HM, manufactured by Tokai Carbon Co., Ltd. (N.sub.2SA: 126 m.sup.2/g)

(7) Carbon black N330: SEAST 3, manufactured by Tokai Carbon Co., Ltd. (N.sub.2SA: 79 m.sup.2/g)

(8) Carbon black N339: SEAST KH, manufactured by Tokai Carbon Co., Ltd. (N.sub.2SA: 93 m.sup.2/g)

(9) Carbon black N550: SEAST SO, manufactured by Tokai Carbon Co., Ltd. (N.sub.2SA: 42 m.sup.2/g)

(10) Carbon black N774: SEAST S, manufactured by Tokai Carbon Co., Ltd. (N.sub.2SA: 27 m.sup.2/g) b) Dispersing solvent: Wafer c) Rubber latex solutions:

(11) Natural rubber latex solution (NR concentrated latex), manufactured by Regitex Co., Ltd. (latex solution obtained by adjusting a latex having a DRC (dry rubber content) of 60% to give a rubber concentration of 25% by mass; mass-average molecular weight Mw=236,000)

(12) Natural rubber latex solution (NR field latex), manufactured by a company, Golden Hope (latex solution obtained by adjusting a latex having a DRC of 31.2% to give a rubber concentration of 25% by mass; mass-average molecular weight Mw=232,000) d) Solidifier: Formic acid (solution obtained by diluting a first-class 85% solution thereof into a 10% solution, and adjusted into a pH of 1.2), manufactured by Nacalai Tesque, Inc.; e) Zinc flower: Zinc flower No. 3, manufactured by Mitsui Mining & Smelting Co., Ltd. f) Stearic acid, manufactured by NOF Corp. g) Wax, manufactured by Nippon Seiro Co., Ltd. h) Anti-ageing agents:

(13) (A) N-phenyl-N-(1,3-dimethylbutyl)-p-phenyienediamine 6PPD, manufactured by the company Monsanto; melting point: 44 C.

(14) (B) 2,2,4-trimethyl-1,2-dihydroquinoline polymer RD, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.; melting point: 80 to 100 C. i) Sulfur:

(15) Sulfur, manufactured by Tsurumi Chemical Industry Co., Ltd. j) Vulcanization promoters:

(16) (A) N-cyclohexyl-2-benzothiazole sulfenamide: SANCELER CM, manufactured by Sanshin Chemical Industry Co., Ltd.

(17) (B) 1,3-Diphenylguanidine: Nocceler D, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.

Example 1

(18) To one of the diluted latex solutions in water that was adjusted to set the concentration thereof to 0.5% by mass were added 40 parts by mass of the N220 as a carbon black species A, and then a ROBOMIX manufactured by PRIMIX Corp. was used to disperse the carbon black species therein (ROBOMIX condition ((A))=9000 rpm; and dispersing period (minutes) (A)=35 minutes) to produce a carbon-black-species-A-containing slurry solution in which natural rubber latex particles were bonded to the carbon black species A (step I-(a)). Separately, to one of the diluted latex solutions in wafer that was adjusted to set the concentration thereof to a 0.5% by mass were added 20 parts by mass of the N550as a carbon black species B, and then a ROBOMIX manufactured by PRIMIX Corp. was used to disperse the filler therein (ROBOMIX condition (B))=9000 rpm; and dispersing period (minutes) (B)=30 minutes) to produce a carbon-black-species-B-containing slurry solution in which natural rubber latex particles were bonded to the carbon black species B (step (I-(a)).

(19) Next, the carbon-black-species-A-containing slurry solution and the carbon-black-species-B-containing slurry solution each produced in the step (I-(a)), and the rest of the natural rubber latex solution (solution adjusted into a solid (rubber) concentration of 25% by mass by the addition of water) were used together, and these slurry solutions were added to the latex solution to set the solid (rubber) amount to 100 parts by mass. Next, a mixer, for household use, manufactured by Sanyo Electric Co., Ltd. (mixer condition: 11300 rpm) was used (for 30 minutes) to produce a natural rubber latex solution containing the carbon black species A/B to which natural rubber latex particles were bonded (step II-(a)).

(20) To the natural rubber latex solution produced through the step II-(a)), which contained the carbon black species A/B to which the natural rubber latex particles were bonded, was added a 10%-by-mass solution of formic acid in water as a solidifier until the pH of the latex solution turned to 4. In the state that the latex solution was heated to 90 C., the natural rubber latex solution, which contained the carbon black species A/B to which the natural rubber latex particles were bonded, was solidified (step (III)).

(21) A punching metal 2.0 and 3.5P made of stainless steel was used to separation-filtrate the latex solution to separate the solidified product from the solution. A squeezer-type monoaxial extrusion-dehydrating machine(V-02 model) manufactured by Suehiro EPM Corp. was used to dry the solidified product. In this way, a natural rubber wet master batch was produced (step (III)).

(22) A B-type Bunbury mixer manufactured by Kobe Steel, Ltd.) was used to blend various additives described in Table 1 into the resultant natural rubber wet master batch to prepare a rubber composition. Physical properties of a vulcanized rubber of the rubber composition were measured. The results are shown, in Table 1.

Example 2, and Comparative Examples 2 to 4, 6 and 8

(23) In each of the examples, a rubber wet master batch was produced under the same conditions except that the respective types of the carbon black species A and B, the respective dispersing periods (minutes) (A) and (B) of the carbon black species A and B, and the respective rotor rotation numbers (rpm) (A) and (B) of the dispersing machines used when these species were dispersed were partially or wholly changed to ones described in Table 1 or 2.

Examples 3 to 9

(24) In each of the examples, the respective types of the carbon black species A and B, the respective dispersing periods (minutes) (A) and (B) of the carbon black species A and B, and the respective rotor rotation numbers (rpm) (A) and (B) of the dispersing machines used when these species were dispersed were partially or wholly changed to ones described in Table 1 or 2. Furthermore, a mixer, for household use, manufactured by Sanyo Electric Co., Ltd. was used to mix the carbon-black-species-A-containing slurry solution in advance with the carbon-black-species-B-containing slurry solution (mixer condition: 11300 rpm; and in-advance-mixing period: 5 minutes). Thereafter, in the step (II), the mixture was mixed with the same rubber latex solution to produce a carbon-black-species-A/B-containing rubber latex solution. Under the same conditions as used in Example 1 except the operations described hereinbefore, a rubber wet master batch was produced.

Comparative Examples 1, 5, 7 and 9

(25) In each of the examples, various blending agents described in Table 1 or 2 were dry-mixed with each other instead of using any process of producing a rubber master batch and then using this master batch as a raw material to produce a rubber composition. In this way, a rubber composition was produced. The results are shown in Table 1 or 2.

(26) Evaluations:

(27) Evaluations were made about a rubber obtained by using a predetermined mold to heat each of the rubber compositions at 150 C. for 30 minutes to be vulcanized.

(28) Low Exothermic Performance:

(29) In accordance with JIS K6265, the low exothermic performance of each of the produced vulcanized rubbers was evaluated on the basis of the loss tangent tan thereof. A rheospectrometer E4 000 manufactured by a company, UBM was used to measure the rubber at 50 Hz and 80 C. under a condition of a dynamic strain of 2%. In the evaluation, the value of Comparative Example 1 was regarded as 100, and Examples 1 to 5 and Comparative Examples 2 to 8 were each evaluated on the basis of an index relative thereto; and further the value of Comparative Example 9 was regarded as 100, and Examples 6 to 9 were each evaluated on the basis of an index relative thereto. It is denoted that as the numerical value is lower, the low exothermic performance is better. The results are shown in Tables 1 and 2.

(30) Fatigue Resistance:

(31) In accordance with JIS K6260, the fatigue resistance 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 2 to 8 were each evaluated on the basis of an index relative thereto; and further the value of Comparative Example 9 was regarded as 100, and Examples 6 to 9 were each evaluated on the basis of an index relative thereto. It is denoted that as the numerical value is higher, the fatigue resistance is better. The results are shown in Tables 1 and 2.

(32) TABLE-US-00001 TABLE 1-1 Comparative Comparative Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Carbon Rotor rotation number [rpm] (A) 9000 9000 10500 9000 black of dispersing machine species A Dispersing period [minutes] (A) 30 35 40 35 dispersing ((A) (A)) + 1000 270 315 420 315 conditions Carbon Rotor rotation number [rpm] (B) 9000 9000 9000 9000 black of dispersing machine species B Dispersing period [minutes] (B) 30 35 30 30 dispersing ((B) (B)) + 1000 270 315 270 270 conditions ((A) (A))/ 1.0 1.0 1.6 1.2 ((B) (B)) (N.sub.2SA (A)) (N.sub.2SA (B)) 77 77 77 77 7 7 100 Mixing of Not Not Not Not carbon-black-species-A-containing slurry performed performed performed performed solution in advance with carbon-black-species-B-containing slurry solution Comparative Example 8 Example 1 Example 2 Example 3 Example 4 Example 5 Carbon Rotor rotation number [rpm] (A) 9000 9000 10500 9000 9000 9000 black of dispersing machine species A Dispersing period [minutes] (A) 35 35 30 25 40 40 dispersing ((A) (A)) + 1000 315 315 315 315 360 360 conditions Carbon Rotor rotation number [rpm] (B) 9000 9000 9000 9000 9000 9000 black of dispersing machine species B Dispersing period [minutes] (B) 30 30 30 30 30 30 dispersing ((B) (B)) + 1000 270 270 270 270 270 270 conditions ((A) (A))/ 1.2 1.2 1.2 1.2 1.3 1.3 ((B) (B)) (N.sub.2SA (A)) (N.sub.2SA (B)) 100 77 77 77 77 92 Mixing of Not Not Not Performed Performed Performed carbon-black-species-A-containing slurry performed performed performed solution in advance with carbon-black-species-B-containing slurry solution

(33) TABLE-US-00002 TABLE 1-2 Comparative Comparative Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Blending Blending Carbon black N110 components components species A N220 40 40 40 40 in rubber in rubber Carbon black N234 20 composition wet master species B N550 20 20 20 batch N774 Natural rubber 100 100 100 100 (solid) Natural rubber 100 100 100 Carbon black species N110 40 N220 40 40 N234 20 N550 20 20 Zin flower 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 Wax 2 2 2 2 2 2 2 Anti-ageing agents (A) 2 2 2 2 2 2 2 (B) 1 1 1 1 1 1 1 Sulfur 2 2 2 2 2 2 2 Vulcanization promoters (A) 1.5 15 1.5 1.5 1.5 1.5 1.5 (B) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Vulcanized rubber Low exothermic 100 97 95 94 108 106 131 properties performance (tan) Fatigue resistance 100 115 111 103 112 115 151 Comparative Example 8 Example 1 Example 2 Example 3 Example 4 Example 5 Blending Blending Carbon black N110 40 components components species A N220 40 40 40 40 40 in rubber in rubber Carbon black N234 composition wet master species B N550 20 20 20 20 20 batch N774 20 Natural rubber 100 100 100 100 100 100 (solid) Natural rubber Carbon black species N110 N220 N234 N550 Zin flower 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 Wax 2 2 2 2 2 2 Anti-ageing agents (A) 2 2 2 2 2 2 (B) 1 1 1 1 1 1 Sulfur 2 2 2 2 2 2 Vulcanization promoters (A) 1.5 1.5 1.5 1.5 1.5 1.5 (B) 0.5 0.5 0.5 0.5 0.5 0.5 Vulcanized rubber Low exothermic 127 89 86 84 81 77 properties performance (tan) Fatigue resistance 156 127 129 125 121 133

(34) TABLE-US-00003 TABLE 2 Comparative Example 9 Example 6 Example 7 Example 8 Example 9 Carbon black species A Rotor rotation number [rpm] 9000 9000 9000 9000 dispersing conditions (A) of dispersing machine Dispersing period [minutes] 40 40 40 40 (A) ((A) (A)) + 1000 360 360 360 360 Carbon black species B Rotor rotation number [rpm] 9000 9000 9000 9000 dispersing conditions (B) of dispersing machine Dispersing period [minutes] 30 30 30 30 (B) ((B) (B)) + 1000 270 270 270 270 ((A) (A))/ 1.3 1.3 1.3 1.3 ((B) (B)) (N.sub.2SA (A)) (N.sub.2SA (B)) 37 37 52 51 66 Mixing of carbon-black-species-A-containing slurry solution Performed Performed Performed Performed in advance with carbon-black-species-B-containing slurry solution Blending Blending Carbon black species A N330 40 40 components in components in N339 40 40 rubber rubber wet Carbon black species B N550 20 20 composition master batch N774 20 20 Natural rubber (solid) 100 100 100 100 Natural rubber 100 Carbon black species N330 40 N550 20 40 Zin flower 3 3 3 3 3 Stearic acid 2 2 2 2 2 Wax 2 2 2 2 2 Anti-ageing agents (A) 2 2 2 2 2 (B) 1 1 1 1 1 Sulfur 2 2 2 2 2 Vulcanization promoters (A) 1.5 1.5 1.5 1.5 1.5 (B) 0.5 0.5 0.5 0.5 0.5 Vulcanized rubber properties Low exothermic performance (tan) 100 86 79 88 83 Fatigue resistance 100 131 126 137 133

(35) It is understood from the results in Tables 1 and 2 that the vulcanized rubber of the rubber composition containing the rubber wet master batch obtained by the producing method according to each of Examples 1 to 9 was excellent in low exothermic performance and fatigue resistance. In the meantime, although in Comparative Example 2 the carbon black species A and the carbon black species B were dispersed under the same conditions, the carbon black species A was insufficient in dispersibility so that the vulcanized rubber was improved in neither low exothermic performance nor fatigue resistance. In Comparative Example 3, the carbon black species A and the carbon black species B were dispersed under the same conditions; however, the dispersing period was made longer than in Comparative Example 2. As a result, a fracture of the structure of the carbon black species B advanced so that the vulcanized rubber was deteriorated in fatigue resistance. In Comparative Example 4, the conditions for dispersing the carbon black species A were too intense. As a result, a fracture of the structure of the carbon black species A advanced so that the vulcanized rubber was deteriorated in fatigue resistance. In Comparative Example 6, the difference in N.sub.2SA between the carbon black species A and B was less than 25 so that neither the low exothermic performance nor the fatigue resistance of the vulcanized rubber was Improved. In Comparative Example 8, the N.sub.2SA of the carbon black species A was more than 130 m.sup.2/g so that the vulcanized rubber was largely deteriorated in low exothermic performance.