Process for producing rubber wet master batch, rubber composition and tire

Abstract

Provided are a process for efficiently producing a rubber wet master batch in which a dispersibility of carbon black in the rubber is improved, in which a reinforcing property and an abrasion resistance of the rubber can be enhanced by using carbon black having a high surface activity, in which a yield of the carbon black in the wet master batch obtained is not reduced and in which a handling property of the carbon black is good as compared with master batches prepared by using a granulated and dried substance of carbon black prepared by a conventional wet method and non-granulated carbon black, a carbon black-containing rubber wet master batch obtained by the above process and a rubber composition and a tire prepared by using the master batch. It is a process for producing a rubber wet master batch comprising a step for mixing a slurry (A) in which a filler containing carbon black is dispersed with a rubber liquid (B) in which a rubber component is dispersed or dissolved, wherein the slurry (A) is prepared by using a filler containing a carbon black granulated substance which is granulated by a wet method and which stays in a non-drying state.

Claims

1. A process for producing a rubber wet master batch comprising: a step for taking out a non-drying carbon black granulated substance from an outlet of a wet granulating equipment for producing carbon black; a step for preparing a slurry (A) by using a filler containing the non-drying carbon black granulated substance; and a step for mixing the slurry (A), in which the filler containing the non-drying carbon black granulated substance is dispersed, with a rubber liquid (B), wherein a moisture content of the non-drying carbon black granulated substance is 30 to 65% by mass, and wherein a loss on heating of the non-drying carbon black granulated substance which is determined at 150 to 900 C. by thermogravimetric analysis (TGA) is 0.87 to 1.5% by mass, and a transmittance of toluene extract thereof is 90% or more.

2. The process for producing a rubber wet master batch according to claim 1, wherein a diameter of the non-drying carbon black granulated substance is 0.1 to 10 mm.

3. The process for producing a rubber wet master batch according to claim 1, wherein a hardness of the non-drying carbon black granulated substance is 1.0 to 100 cN.

4. The process for producing a rubber wet master batch according to claim 1, wherein an aggregate size distribution of the filler in the slurry (A) is a volume average aggregate diameter (my) of 25 m or less and a 90 volume % aggregate diameter (D90) of 30 m or less, and a 24M4DBP oil absorption of the dried filler recovered from the slurry (A) is maintained at 93% or more of a 24M4DBP oil absorption of the filler staying in a dried state before dispersed in a dispersing medium.

5. The process for producing a rubber wet master batch according to claim 1, wherein the dispersing medium for the slurry (A) is water.

6. The process for producing a rubber wet master batch according to claim 1, wherein the slurry (A) contains a filler comprising the non-drying carbon black granulated substance and at least one selected from silica and inorganic fillers represented by Formula (1):
nM.xSiO.sub.y.zH.sub.2O(1) wherein M is at least one selected from metal selected from aluminum, magnesium, titanium, calcium and zirconium, oxides or hydroxides of the above metals, hydrates thereof and carbonates of the metals; and n, x, y and z are an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5 and an integer of 0 to 10, respectively.

7. The process for producing a rubber wet master batch according to claim 1, wherein the rubber component in the rubber liquid (B) is a natural rubber and/or a synthetic diene base rubber.

8. The process for producing a rubber wet master batch according to claim 7, wherein the rubber liquid (B) is a natural rubber latex and/or a synthetic diene base rubber latex.

9. The process for producing a rubber wet master batch according to claim 1, wherein (a) the slurry (A) is mixed with the rubber liquid (B); and (b) the above mixed liquid is subjected to chemical and/or physical coagulation treatment to take out a coagulated substance formed.

10. The process for producing a rubber wet master batch according to claim 9, wherein (c) the coagulated substance taken out is subjected to drying treatment.

11. The process for producing a rubber wet master batch according to claim 10, wherein the drying treatment is carried out by means of a hot blast dryer, a vacuum dryer or a freeze dryer.

12. The process for producing a rubber wet master batch according to claim 10, wherein the drying treatment is carried out by means of a continuous kneading equipment or a continuous multiaxial kneading extruding equipment.

Description

EXAMPLES

(1) Next, the present invention shall be explained below in further details with reference to examples, but the present invention shall by no means be restricted by the examples shown below.

(2) Various measurements in the respective examples and comparative examples were carried out by the following methods.

(3) <Non-Drying Carbon Black Granulated Substance>

(4) (1) Average Moisture Content:

(5) The weights of the sample about 1 g put in a crucible were measured before dried and after dried at 105 C. for 5 hours to calculate an average moisture thereof according to the following calculation equation. This procedure was repeated five times, and an average value thereof was set to an average moisture content.
moisture content (%)=(weight (g) before driedweight (g) after dried/(weight (g) before dried)100
(2) Loss on Heating:

(6) A reduction in a mass of the carbon black for test observed when the temperature was elevated from 150 C. up to 900 C. at a heating rate of 15 C./minute under nitrogen atmosphere was measured by means of a conventional thermogravimetric measuring apparatus (TGA), and it was shown by mass %.

(7) (3) Transmittance of Toluene Extract:

(8) The transmittance of toluene extract (%) was measured by a method described in an eighth item B method of JIS K 6218:1997 and shown by a percentage based on purified toluene.

(9) (4) Average Granule Diameter:

(10) The diameters of 1000 granulated substances were measured at a magnification of 30 times by means of an optical microscope, and an average value thereof was set to an average granule diameter.

(11) (5) Average Granule Hardness:

(12) Measured according to JIS K 6219-3.

(13) <Filler-Dispersed Slurry>

(14) (4) Measurement of Aggregate Size Distribution of the Filler in the Slurry Liquid (Volume Average Aggregate Diameter (mv) and 90 Volume % Aggregate Diameter (D90)):

(15) Measured by means of a laser diffraction type aggregate size distribution meter (model MICROTRAC FRA) using a water solvent (refractive index: 1.33). An aggregate refractive index of 1.57 was used in all measurements. In order to prevent the filler from being re-coagulated, the measurement was carried out immediately after dispersed.

(16) (5) 24M4DBP Oil Absorption of the Filler:

(17) Measured according to ISO 6894.

(18) (6) Slurrying Energy Index:

(19) An electric energy required for slurrying was measured and shown by an index, wherein it was based on an electric energy in Comparative Example 2. The smaller the numerical value is, the smaller the energy consumption is, and it is preferred.

(20) <Compounded Rubber>

(21) (7) Carbon Black Gel Content:

(22) A compounded rubber having each composition shown in Table 2 was cut narrowly, and after measuring a mass thereof, it was put in a sample cage made of a metal gauze (150 mesh) having a known tare mass and immersed as it was in toluene for 24 hours. Then, the cage was taken out to sufficiently dry a toluene-insoluble matter (carbon gel), and a mass thereof was measured. A proportion (% by mass) of a mass (a mass obtained by removing the toluene-insoluble matters such as carbon black and the like from the insoluble matter) of the natural rubber contained in the insoluble matter to a mass of the natural rubber contained in the compounded rubber was determined, and it was shown by an index, wherein that of the rubber composition in Comparative Example 5 was set to 100. It is shown that the larger the value is, the more the carbon black gel content is.

(23) (8) Carbon Black Dispersibility:

(24) Measured according to ISO 11345:2006 C method.

(25) (9) Carbon Black Content:

(26) Measured according to JIS K 6227/ISO 1408:1995.

(27) <Vulcanization Physical Properties of Rubber Composition>

(28) (10) Rupture Strength:

(29) A tensile strength was determined when measured at 23 C. according to JIS K 6251-1993. The larger the value is, the higher the reinforcing property is.

(30) (11) Abrasion Resistance:

(31) An abrasion amount was measured at a slip rate of 40% at room temperature by means of a Lambourn type abrasion test equipment, and an inverse number thereof was shown by an index, wherein that of the rubber composition in Comparative Example 5 was set to 100. The larger the value is, the less the mass is reduced, and the better the abrasion resistance is.

(32) (12) Impact Resilience:

(33) Measured at room temperature (25 C.) according to a JIS K 6255:1996 Tripso type impact resilience test method, and it was shown by an index, wherein a value of Comparative Example 5 was set to 100. The larger the value is, the larger the impact resilience is, and it is better.

Example 1

(1) Preparation of Carbon Black Slurry

(34) Carbon black (N220: average granule diameter 1.7 mm, average granule hardness 21.5 cN, taken out from an outlet of a wet granulating equipment in producing carbon black) having an average moisture content of 52% by mass and staying in a non-drying state after wet granulated was put in water in an amount of 45 parts by mass in terms of a dried substance and subjected to slurrying treatment at a revolution rate of 4800 rpm for 30 minutes by means of a high shear mixer manufactured by Silverson Machines, Inc. to prepare a carbon black-containing slurry having a slurry concentration of about 5% by mass. The carbon black slurry was prepared in a scale of the slurry 20 kg. An aggregate size distribution of the carbon black in the slurry obtained above was a volume average aggregate diameter mv=4.9 m and D90 (90 volume % aggregate diameter)=8.3 m.

(35) Also, a 24M4DBP oil absorption of the carbon black (CB) before dispersed was 99 mL/100 g; a 24M4DBP oil absorption of slurry-recovered and dried CB was 96 mL/100 g; and a retention ((24M4DBP oil absorption of slurry-recovered and dried CB)/(24M4DBP oil absorption of CB before dispersed)100) of the oil absorptions was 97%.

(36) Further, the slurrying energy index was 60.

(2) Preparation of Wet Master Batch

(37) A whole amount of the carbon black-containing slurry obtained in (1) described above was mixed with 1000 parts by mass of a natural rubber-condensed latex containing ammonia diluted to 10% by mass while stirring, and then the mixture was coagulated by adding formic acid thereto to control it to pH 4.7. Next, the above coagulated substance was filtrated through a nonwoven cloth and dehydrated, and then it was continuously treated by means of a double shaft extruding equipment at a discharge temperature of 150 C., whereby a wet master batch was prepared.

(38) A content (% by mass) of the carbon black in the above wet master batch was determined. The measurement result is shown in Table 1.

Example 2

(1) Preparation of Carbon Black Slurry

(39) A carbon black-containing slurry having a slurry concentration of about 5% by mass was prepared in the same manner as in Example 1 (1), except that in Example 1 (1), the slurrying treating time was changed to 20 minutes. An aggregate size distribution of the carbon black in the slurry obtained above was a volume average aggregate diameter mv=5.1 m and D90 (90 volume % aggregate diameter)=8.4 m.

(40) Also, a 24M4DBP oil absorption of the carbon black (CB) before dispersed was 99 mL/100 g; a 24M4DBP oil absorption of slurry-recovered and dried CB was 97 mL/100 g; and a retention ((24M4DBP oil absorption of slurry-recovered and dried CB)/(24M4DBP oil absorption of CB before dispersed)100) of the oil absorptions was 98%.

(41) Further, the slurrying energy index was 53.

(2) Preparation of Wet Master Batch

(42) A whole amount of the carbon black-containing slurry obtained in (1) described above was used to produce a wet master batch in the same manner as in Example 1 (2) and evaluate it. The results thereof are shown in Table 1.

Example 3

(1) Preparation of Carbon Black Slurry

(43) A carbon black-containing slurry having a slurry concentration of about 5% by mass was prepared in the same manner as in Example 1 (1), except that in Example 1 (1), the slurrying treating time was changed to 15 minutes. An aggregate size distribution of the carbon black in the slurry obtained above was a volume average aggregate diameter mv=5.3 m and D90 (90 volume % aggregate diameter)=8.5 m.

(44) Also, a 24M4DBP oil absorption of the carbon black (CB) before dispersed was 99 mL/100 g; a 24M4DBP oil absorption of slurry-recovered and dried CB was 98 mL/100 g; and a retention ((24M4DBP oil absorption of slurry-recovered and dried CB)/(24M4DBP oil absorption of CB before dispersed)100) of the oil absorptions was 99%.

(45) Further, the slurrying energy index was 43.

(2) Preparation of Wet Master Batch

(46) A whole amount of the carbon black-containing slurry obtained in (1) described above was used to produce a wet master batch in the same manner as in Example 1 (2) and evaluate it. The results thereof are shown in Table 1.

Example 4

(47) A carbon black-containing slurry having a slurry concentration of about 5% by mass was prepared in the same manner as in Example 1 (1), except that in Example 1 (1), a loss on heating of the carbon black measured by thermogravimetric analysis (TGA) at 150 C. up to 900 C. in a non-drying state was changed to 1.1% by mass. An aggregate size distribution of the carbon black in the slurry obtained above was a volume average aggregate diameter mv=4.8 m and D90 (90 volume % aggregate diameter)=8.2 m.

(48) Also, a 24M4DBP oil absorption of the carbon black (CB) before dispersed was 98 mL/100 g; a 24M4DBP oil absorption of slurry-recovered and dried CB was 98 mL/100 g; and a retention ((24M4DBP oil absorption of slurry-recovered and dried CB)/(24M4DBP oil absorption of CB before dispersed)100) of the oil absorptions was 97%.

(49) Further, the slurrying energy index was 60.

(2) Preparation of Wet Master Batch

(50) A whole amount of the carbon black-containing slurry obtained in (1) described above was used to produce a wet master batch in the same manner as in Example 1 (2) and evaluate it. The results thereof are shown in Table 1.

Example 5

(51) A carbon black-containing slurry having a slurry concentration of about 5% by mass was prepared in the same manner as in Example 1 (1), except that in Example 1 (1), a loss on heating of the carbon black measured by thermogravimetric analysis (TGA) at 150 C. up to 900 C. in a non-drying state was changed to 1.4% by mass. An aggregate size distribution of the carbon black in the slurry obtained above was a volume average aggregate diameter mv=5.0 m and D90 (90 volume % aggregate diameter)=8.4 m.

(52) Also, a 24M4DBP oil absorption of the carbon black (CB) before dispersed was 99 mL/100 g; a 24M4DBP oil absorption of slurry-recovered and dried CB was 97 mL/100 g; and a retention ((24M4DBP oil absorption of slurry-recovered and dried CB)/(24M4DBP oil absorption of CB before dispersed)100) of the oil absorptions was 98%.

(53) Further, the slurrying energy index was 60.

(2) Preparation of Wet Master Batch

(54) A whole amount of the carbon black-containing slurry obtained in (1) described above was used to produce a wet master batch in the same manner as in Example 1 (2) and evaluate it. The results thereof are shown in Table 1.

Example 6

(55) A carbon black-containing slurry having a slurry concentration of about 5% by mass was prepared in the same manner as in Example 1 (1), except that in Example 1 (1), a loss on heating of the carbon black measured by thermogravimetric analysis (TGA) at 150 C. up to 900 C. in a non-drying state was changed to 1.3% by mass. An aggregate size distribution of the carbon black in the slurry obtained above was a volume average aggregate diameter mv=4.9 m and D90 (90 volume % aggregate diameter)=8.4 m.

(56) Also, a 24M4DBP oil absorption of the carbon black (CB) before dispersed was 98 mL/100 g; a 24M4DBP oil absorption of slurry-recovered and dried CB was 96 mL/100 g; and a retention ((24M4DBP oil absorption of slurry-recovered and dried CB)/(24M4DBP oil absorption of CB before dispersed)100) of the oil absorptions was 98%.

(57) Further, the slurrying energy index was 60.

(2) Preparation of Wet Master Batch

(58) A whole amount of the carbon black-containing slurry obtained in (1) described above was used to produce a wet master batch in the same manner as in Example 1 (2) and evaluate it. The results thereof are shown in Table 1.

Comparative Example 1

(1) Preparation of Carbon Black Slurry

(59) A carbon black-containing slurry having a slurry concentration of about 5% by mass was prepared in the same manner as in Example 1 (1), except that in Example 1 (1), fluffy non-granulated carbon black (N220, taken out from an outlet of a crushing equipment subsequent to a bag filter in producing carbon black) was used in place of the non-drying carbon black granulated substance. An aggregate size distribution of the carbon black in the slurry obtained above was a volume average aggregate diameter mv=5.6 m and D90 (90 volume % aggregate diameter)=8.7 m.

(60) Also, a 24M4DBP oil absorption of the carbon black (CB) before dispersed was 99 mL/100 g; a 24M4DBP oil absorption of slurry-recovered and dried CB was 98 mL/100 g; and a retention ((24M4DBP oil absorption of slurry-recovered and dried CB)/(24M4DBP oil absorption of CB before dispersed)100) of the oil absorptions was 99%.

(61) Further, the slurrying energy index was 56.

(2) Preparation of Wet Master Batch

(62) A whole amount of the carbon black-containing slurry obtained in (1) described above was used to produce a wet master batch in the same manner as in Example 1 (2) and evaluate it. The results thereof are shown in Table 1.

Comparative Example 2

(1) Preparation of Carbon Black Slurry

(63) A carbon black-containing slurry having a slurry concentration of about 5% by mass was prepared in the same manner as in Example 1 (1), except that in Example 1 (1), carbon black (N220: average granule diameter 1.0 mm, average granule hardness 7.7 cN) which was dried after wet granulated was used in place of the non-drying carbon black granulated substance. An aggregate size distribution of the carbon black in the slurry obtained above was a volume average aggregate diameter mv=5.4 m and D90 (90 volume % aggregate diameter)=8.9 m.

(64) Also, a 24M4DBP oil absorption of the carbon black (CB) before dispersed was 99 mL/100 g; a 24M4DBP oil absorption of slurry-recovered and dried CB was 97 mL/100 g; and a retention ((24M4DBP oil absorption of slurry-recovered and dried CB)/(24M4DBP oil absorption of CB before dispersed)100) of the oil absorptions was 98%.

(65) Further, the slurrying energy index was 100.

(2) Preparation of Wet Master Batch

(66) A whole amount of the carbon black-containing slurry obtained in (1) described above was used to produce a wet master batch in the same manner as in Example 1 (2) and evaluate it. The results thereof are shown in Table 1.

(67) TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 Kind of CB Comparative Example N220 N220 N220 N220 N220 N220 1 2 Non- Non- Non- Non- Non- Non- N220 N220 drying drying drying drying drying drying Fluffy Dried after wet after wet after wet after wet after wet after wet non- after wet granu- granu- granu- granu- granu- granu- granu- granu- Kind & state of CB lated lated lated lated lated lated lated lated Carbon CB addition amount 45 45 45 45 45 45 45 45 black (mass part) (CB)- Average granule hardness 21.5 21.5 21.5 21.0 22.0 21.5 7.7 containing of granulated substance slurry (cN) TGA loss on heating 0.89 0.89 0.89 1.1 1.4 1.3 0.89 0.82 (mass %) Transmittance of toluene 95 95 95 93 91 92 95 97 extract (%) Slurry concentration 5 5 5 5 5 5 5 5 (mass %) Slurrying time (min.) 30 20 15 30 30 30 30 30 CB average moisture 55 55 55 55 56 56 3.0 1.0 content (mass %) Slurrying energy index 60 53 43 60 60 60 56 100 CB handling property No No No No No No Notable Slight Scatter- Scatter- Scatter- Scatter- Scatter- Scatter- Scatter- Scatter- ing ing ing ing ing ing ing ing Rubber Kind of rubber Natural Natural Natural Natural Natural Natural Natural Natural latex rubber rubber rubber rubber rubber rubber rubber rubber Rubber addition amount 100 100 100 100 100 100 100 100 (mass part) Wet master CB content (mass part) 45.2 44.6 44.5 44.8 45.0 44.7 38.2 44.2 batch
Slurrying energy (index): index in which a slurrying energy in Comparative Example 2 was set to 100.

(68) As can be found from the results shown in Table 1, since the carbon black does not cause scattering in preparing the slurries in the examples, the handling property is good, and a yield of the carbon black in the master batch is high. In contrast with this, the carbon black causes marked scattering in Comparative Example 1, and a yield of the carbon black in the master batch is low. Further, the carbon black was observed to cause slight scattering as well in Comparative Example 2.

Examples 7 to 12 and Comparative Examples 3 to 5

(69) The wet master batches obtained in Examples 1 to 6 and Comparative Examples 1 and 2 were used respectively in Examples 7 to 12 and Comparative Examples 3 and 4 to prepare the respective rubber compositions having blend compositions shown in Table 2 by means of a Banbury mixer.

(70) In Comparative Example 5, the respective components in the blend composition shown in Table 2 were kneaded by means of a Banbury mixer without using the master batch to prepare a rubber composition.

(71) The respective rubber compositions were subjected to vulcanization treatment at 150 C. for 30 minutes to prepare samples for test and evaluate the physical properties of the vulcanized rubbers. The results thereof are shown in Table 2.

(72) In the rubber composition prepared in Comparative Example 5, an index of a carbon black gel content was 100, and a carbon black dispersibility was 5.1.

(73) TABLE-US-00002 TABLE 2 Example Comparative Example 7 8 9 10 11 12 3 4 Example Example Example Example Example Example Comparative Comparative 5 Kind of wet master batch 1 2 3 4 5 6 Example 1 Example 2 Wet master Natural rubber 100 100 100 100 100 100 100 100 batch (mass part) composition Carbon black 45.2 44.6 44.5 44.8 45.0 44.7 38.2 44.2 (mass part) Blended raw Natural rubber 100 materials in Carbon black (N220) 45 the Stearic acid 2 2 2 2 2 2 2 2 2 composition Antioxidant 6C.sup.1) 1 1 1 1 1 1 1 1 1 (mass part) Zinc oxide 4 4 4 4 4 4 4 4 4 Vulcanization 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 accelerator NS.sup.2) Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Compounded CB gel content 140 142 135 145 150 142 98 130 100 rubber (index) characteristic CB dispersibility 9.8 9.6 9.5 9.7 10.0 9.7 9.7 9.5 5.1 Vulcanized Fracture strength 33.2 32.9 32.7 33.1 33.9 32.1 29.2 32.8 28.6 rubber (MPa) characteristic Impact resilience 123 121 120 124 126 122 125 118 100 (index) Abrasion resistance 125 123 122 129 135 124 92 110 100 (index)
Remarks:
1) Antioxidant 6C: N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine
2) Vulcanization accelerator NS: N-t-butyl-2-benzothiazyl-sulfeneamide

(74) As can be found from the results shown in Table 2, the rubber compositions prepared in the examples are excellent in a fracture strength, an impact resilience and an abrasion resistance and have a large carbon black gel content as compared with the rubber compositions prepared in the comparative examples. This is because of the results that the carbon black is increased in a dispersibility due to the wet master batch and that in addition thereto, an excellent reinforcing effect is brought about by using carbon black having a high surface activity. On the other hand, in Comparative Example 3, the same effects are expected to the rubber physical properties, but it is difficult to control an amount of the carbon black in the rubber, and therefore it is difficult to obtain the stable performances. Further, Comparative Example 4 is limited to having received a merit exerted by the effects of the wet master batch, and the rubber performances thereof are not comparable to those of the examples.

INDUSTRIAL APPLICABILITY

(75) According to the production process of the present invention for a rubber wet master batch, using a carbon black granulated substance which is granulated by a wet method and which stays in a non-drying state to prepare a carbon black-containing filler-dispersed slurry makes it possible to efficiently provide a rubber wet master batch in which a dispersibility of the carbon black in the rubber is improved, in which a reinforcing property and an abrasion resistance of the rubber can be enhanced since carbon black having a high surface activity can be used, in which a yield of the carbon black in the wet master batch obtained is not reduced and in which a handling property of the carbon black is good as compared with master batches prepared by using a conventional carbon black granulated and dried substance and non-granulated carbon black.