METHOD FOR MANUFACTURING WET RUBBER MASTERBATCH, METHOD FOR MANUFACTURING RUBBER COMPOSITION, AND METHOD FOR MANUFACTURING TIRE

Abstract

A method of manufacturing a wet rubber masterbatch includes preparing latex containing magnesium in an amount which is not greater than 150 ppm; and making a liquid mixture that includes a rubber component and carbon black. The latex may include rubber particles for which the 90 vol % particle diameter is not greater than 2 m. The liquid mixture can be made by a step (a) in which the latex and a dispersion solvent are mixed; and a step (b) in which a latex solution obtained at step (a) and a slurry containing the carbon black are mixed. The method for manufacturing a wet rubber masterbatch may satisfy: 0.1<b/a<1.0, where a indicates amount (ppm) of magnesium present in latex; and b indicates amount (parts by mass) of carbon black in the liquid mixture for every 100 parts by mass of rubber component in the liquid mixture.

Claims

1. A method for manufacturing a wet rubber masterbatch satisfying Formula I, below, the method comprising: an operation in which a latex that comprises rubber particles for which 90 vol % particle diameter is not greater than 2 m and that has magnesium present therein in an amount which is not greater than 150 ppm is prepared; and an operation in which a liquid mixture that comprises a rubber component and carbon black is made; wherein the operation in which the liquid mixture is made comprises a step (a) in which the latex and a dispersion solvent are mixed; and a step (b) in which a latex solution obtained at the foregoing step (a) and a slurry containing the carbon black are mixed; wherein Formula I is given by
0.1<b/a<1.0; and wherein, at Formula I, a indicates amount, expressed in units of ppm, of magnesium present in the latex; and b indicates amount, expressed in units of parts by mass, of the carbon black in the liquid mixture for every 100 parts by mass of the rubber component in the liquid mixture.

2. The method for manufacturing the wet rubber masterbatch according to claim 1 wherein the operation in which the latex is prepared comprises a step in which diammonium phosphate is added to latex raw material; and a step in which magnesium phosphate produced as a result of the foregoing step is removed.

3. A rubber composition manufacturing method comprising the method for manufacturing the wet rubber masterbatch according to claim 1.

4. A tire manufacturing method comprising the method for manufacturing the wet rubber masterbatch according to claim 1.

5. The method for manufacturing the wet rubber masterbatch according to claim 1 further comprising an operation in which the liquid mixture is coagulated to obtain a coagulum.

6. The method for manufacturing the wet rubber masterbatch according to claim 5 further comprising an operation in which the coagulum is dewatered.

7. The method for manufacturing the wet rubber masterbatch according to claim 1 wherein the 90 vol % particle diameter is not less than 1.0 m.

8. The method for manufacturing the wet rubber masterbatch according to claim 1 wherein the magnesium is present therein in an amount which is not less than 40 ppm.

9. The method for manufacturing the wet rubber masterbatch according to claim 1 wherein the dispersion solvent comprises water.

10. The method for manufacturing the wet rubber masterbatch according to claim 1 wherein the latex is natural rubber latex.

Description

WORKING EXAMPLES

[0037] Working examples and the like which illustrate the constitution and effect of the present invention in specific terms are described below. Raw materials employed were as follows.

TABLE-US-00001 Raw Materials Employed DAP Diammonium hydrogen phosphate manufactured by Wako Pure Chemical Industries, Ltd. Coagulant Formic acid (reagent-grade 85%; diluted to obtain 10% solution; pH adjusted to 1.2) manufactured by Nacalai Tesque, Inc. Carbon Black (A) SEAST 9 manufactured by Tokai Carbon Co., Ltd. Carbon Black (B) SEAST V manufactured by Tokai Carbon Co., Ltd. Zinc oxide Zinc Oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid LUNAC S-20 manufactured by Kao Corporation Antioxidant (A) NOCRAC 6C manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Antioxidant (B) RD manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Sulfur Powdered Sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator NOCCELER NS-P manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.

Comparative Example 1

Manufacture of Wet Rubber Masterbatch

[0038] Natural rubber latex was collected. Water was added to natural rubber latex to manufacture a natural rubber latex solution having a solids (rubber) concentration that was 27 mass %. 55 parts by mass of Carbon Black (A) was added to water. An agitator (Flashblend manufactured by Silverson) was used to disperse the Carbon Black (A) (Flashblend conditions: 3600 rpm; 30 min) to manufacture a carbon black slurry. The natural rubber latex solution was added to the carbon black slurry in such amount as to cause solids (rubber) to be present therein in an amount that was 100 parts by mass to manufacture a pre-coagulation liquid mixture. The pre-coagulation liquid mixture was maintained at 90 C. in a mixer (SMV-20 Supermixer manufactured by Kawata Co., Ltd.) while formic acid was added thereto in an amount sufficient to achieve a pH of 4. A squeezer-type single-screw dewatering extruder (Model V-02 screw press manufactured by Suehiro EPM Corporation) was used to dry the coagulum until water content was not greater than 1.5% to manufacture a wet rubber masterbatch.

Manufacture of Rubber Composition

[0039] The respective compounding ingredients were blended in amounts as listed at TABLE 1, and a Model B Banbury mixer manufactured by Kobe Steel, Ltd., was used to knead these together to manufacture a rubber composition.

Comparative Example 2

Manufacture of Natural Rubber

[0040] Natural rubber latex was collected. DAP as a fraction of the total weight of the natural rubber latex was added in the amount shown at TABLE 1, and the magnesium phosphate which precipitated was removed therefrom to obtain a liquid supernatant. The liquid supernatant was maintained at 90 C. in a mixer (SMV-20 Supermixer manufactured by Kawata Co., Ltd.) while formic acid was added thereto in an amount sufficient to achieve a pH of 4. A squeezer-type single-screw dewatering extruder (Model V-02 screw press manufactured by Suehiro EPM Corporation) was used to dry the coagulum until water content was not greater than 1.5% to manufacture natural rubber.

Manufacture of Rubber Composition

[0041] The respective compounding ingredients were blended in amounts as listed at TABLE 1, and a Model B Banbury mixer manufactured by Kobe Steel, Ltd., was used to knead these together to manufacture a rubber composition.

Comparative Example 3 and Working Examples 1-3

Manufacture of Wet Rubber Masterbatch

[0042] Natural rubber latex was collected. DAP as a fraction of the total weight of the natural rubber latex was added in the amount shown at TABLE 1, and the magnesium phosphate which precipitated was removed therefrom to obtain a liquid supernatant. Water was added to the liquid supernatant to manufacture a natural rubber latex solution having a solids (rubber) concentration that was 27 mass %. 55 parts by mass of Carbon Black (A) was added to water. An agitator (Flashblend manufactured by Silverson) was used to disperse the Carbon Black (A) (Flashblend conditions: 3600 rpm; 30 min) to manufacture a carbon black slurry. The natural rubber latex solution was added to the carbon black slurry in such amount as to cause solids (rubber) to be present therein in an amount that was 100 parts by mass to manufacture a pre-coagulation liquid mixture. The pre-coagulation liquid mixture was maintained at 90 C. in a mixer (SMV-20 Supermixer manufactured by Kawata Co., Ltd.) while formic acid was added thereto in an amount sufficient to achieve a pH of 4. A squeezer-type single-screw dewatering extruder (Model V-02 screw press manufactured by Suehiro EPM Corporation) was used to dry the coagulum until water content was not greater than 1.5% to manufacture a wet rubber masterbatch.

Manufacture of Rubber Composition

[0043] The respective compounding ingredients were blended in amounts as listed at TABLE 1, and a Model B Banbury mixer manufactured by Kobe Steel, Ltd., was used to knead these together to manufacture a rubber composition.

First Evaluation

Magnesium Content

[0044] Magnesium content of liquid supernatantComparative Examples 2-3 and Working Examples 1-3was measured in accordance with ISO 11852; 2011. Magnesium content of natural rubber latexComparative Example 1was measured in accordance with ISO 11852; 2011.

90 Vol % Particle Diameter

[0045] D90 (m) of liquid supernatantComparative Examples 2-3 and Working Examples 1-3was measured using a SALD 2200 manufactured by Shimadzu Corporation (latex refractive index: 1.6-0.10i), absorbance being set to 0.05 to 0.1 at the time of measurement. D90 (m) of natural rubber latexComparative Example 1was measured under the same conditions.

Second Evaluation: Properties of Vulcanized Rubber

[0046] The rubber composition was vulcanized at conditions of 150 C. for 30 min to obtain vulcanized rubber. Fatigue resistance, heat generation, and tensile stress of the vulcanized rubber were evaluated. Conditions under which evaluation was performed are as indicated below. Results are shown in TABLE 1.

Fatigue Resistance

[0047] Performance of vulcanized rubber with respect to fatigue resistance was evaluated in accordance with JIS K 6260 (flex cracking testing). Results of evaluation are shown as indexed relative to a value of 100 for Comparative Example 1. This means that the larger the value the more excellent it was in terms of performance with respect to fatigue resistance.

Heat Generation

[0048] Heat generation of vulcanized rubber was evaluated using loss tangent tans in accordance with JIS K 6265. Measurements were carried out under conditions of 50 Hz, 80 C., and dynamic strain 2% using an E4000 rheospectrometer manufactured by UBM. Results of evaluation are shown as indexed relative to a value of 100 for Comparative Example 1. This means that the smaller the value the lowerand thus the betterwas the heat generation.

Tensile Stress

[0049] Tensile stress was evaluated at an elongation of 300% (hereinafter M300) in accordance with JIS K 6261. Results of evaluation are shown as indexed relative to a value of 100 for Comparative Example 1. This means that the larger the value the more excellent it was with respect to tensile stress.

TABLE-US-00002 TABLE 1 Comparative Comparative Comparative Working Working Working Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Liquid supernatant or natural rubber latex Amount of DAP added 0.8 1.5 0.25 0.4 0.9 mass % Evaluation Magnesium 110 50 144 131 101 content of liquid supernatant ppm D90 particle 1.53 3.80 1.29 1.40 1.60 diameter of rubber particles within liquid supernatant m Magnesium 180 content of natural rubber latex ppm D90 particle 1.20 diameter of rubber particles within natural rubber latex m Pre-coagulation liquid mixture Blended Natural rubber 100 100 100 100 100 amount Carbon Black 55 55 55 55 55 (parts by (A) mass) N.sub.2SA of Carbon Black (A) 142 142 142 142 142 m.sup.2/g Conditions b/a 0.31 1.10 0.38 0.42 0.54 (b d)/(c 1000) 6.51 2.06 6.05 5.58 4.88 Wet rubber masterbatch Blended Natural rubber 100 100 100 100 100 amount Carbon Black 55 55 55 55 55 (parts by (A) mass) Rubber composition Blended Wet rubber 155 155 155 155 155 amount masterbatch (parts by Natural rubber 100 mass) Carbon Black 55 (A) Zinc oxide 3 3 3 3 3 3 Stearic acid 4 4 4 4 4 4 Antioxidant (A) 2 2 2 2 2 2 Antioxidant (B) 1 1 1 1 1 1 Sulfur 2 2 2 2 2 2 Vulcanization 1 1 1 1 1 1 accelerator Vulcanized rubber Evaluation Fatigue 100 75 96 113 116 120 resistance (relative to index value) Heat generation 100 113 111 98 94 92 (relative to index value) M300 (relative 100 93 92 107 111 113 to index value)

[0050] At Working Example 1, where DAP was 0.25 mass %, fatigue resistance, ability to achieve reduced heat generation, and tensile stress were better than at Comparative Example 1.

[0051] At Working Example 2, where DAP was 0.4 mass %, fatigue resistance, ability to achieve reduced heat generation, and tensile stress were better than at Working Example 1. And at Working Example 3 as well, where DAP was 0.9 mass %, fatigue resistance, ability to achieve reduced heat generation, and tensile stress were better than at Working Example 1. At Working Examples 2-3, it is speculated that the frequency of contact between Carbon Black (A) and rubber particles was high.

[0052] At Comparative Example 3, where DAP was 1.5 mass %, fatigue resistance, ability to achieve reduced heat generation, and tensile stress were worse than at Comparative Example 1. It is speculated that there may have been increased tendency for agglomeration to occur due to the fact that particle diameter of rubber particles was too large.

[0053] At Comparative Example 2, Comparative Example 2 being an example in which dry-blending was carried out, fatigue resistance, ability to achieve reduced heat generation, and tensile stress were worse than at Comparative Example 1.

Comparative Example 4

Manufacture of Wet Rubber Masterbatch

[0054] Natural rubber latex was collected. Water was added to natural rubber latex to manufacture a natural rubber latex solution having a solids (rubber) concentration that was 27 mass %. 40 parts by mass of Carbon Black (B) was added to water. An agitator (Flashblend manufactured by Silverson) was used to disperse the Carbon Black (B) (Flashblend conditions: 3600 rpm; 30 min) to manufacture a carbon black slurry. The natural rubber latex solution was added to the carbon black slurry in such amount as to cause solids (rubber) to be present therein in an amount that was 100 parts by mass to manufacture a pre-coagulation liquid mixture. The pre-coagulation liquid mixture was maintained at 90 C. in a mixer (SMV-20 Supermixer manufactured by Kawata Co., Ltd.) while formic acid was added thereto in an amount sufficient to achieve a pH of 4. A squeezer-type single-screw dewatering extruder (Model V-02 screw press manufactured by Suehiro EPM Corporation) was used to dry the coagulum until water content was not greater than 1.5% to manufacture a wet rubber masterbatch.

Manufacture of Rubber Composition

[0055] The respective compounding ingredients were blended in amounts as listed at TABLE 2, and a Model B Banbury mixer manufactured by Kobe Steel, Ltd., was used to knead these together to manufacture a rubber composition.

Working Examples 4-5

Manufacture of Wet Rubber Masterbatch

[0056] Natural rubber latex was collected. DAP as a fraction of the total weight of the natural rubber latex was added in the amount shown at TABLE 2, and the magnesium phosphate which precipitated was removed therefrom to obtain a liquid supernatant. Water was added to the liquid supernatant to manufacture a natural rubber latex solution having a solids (rubber) concentration that was 27 mass %. 40 parts by mass of Carbon Black (B) was added to water. An agitator (Flashblend manufactured by Silverson) was used to disperse the Carbon Black (B) (Flashblend conditions: 3600 rpm; 30 min) to manufacture a carbon black slurry. The natural rubber latex solution was added to the carbon black slurry in such amount as to cause solids (rubber) to be present therein in an amount that was 100 parts by mass to manufacture a pre-coagulation liquid mixture. The pre-coagulation liquid mixture was maintained at 90 C. in a mixer (SMV-20 Supermixer manufactured by Kawata Co., Ltd.) while formic acid was added thereto in an amount sufficient to achieve a pH of 4. A squeezer-type single-screw dewatering extruder (Model V-02 screw press manufactured by Suehiro EPM Corporation) was used to dry the coagulum until water content was not greater than 1.5% to manufacture a wet rubber masterbatch.

Manufacture of Rubber Composition

[0057] The respective compounding ingredients were blended in amounts as listed at TABLE 2, and a Model B Banbury mixer manufactured by Kobe Steel, Ltd., was used to knead these together to manufacture a rubber composition.

First Evaluation

Magnesium Content

[0058] Magnesium content of liquid supernatantWorking Examples 4-5was measured in accordance with ISO 11852; 2011. Magnesium content of natural rubber latexComparative Example 4was measured in accordance with ISO 11852; 2011.

90 Vol % Particle Diameter

[0059] D90 (m) of liquid supernatantWorking Examples 4-5was measured using a SALD 2200 manufactured by Shimadzu Corporation (latex refractive index: 1.6-0.10i), absorbance being set to 0.05 to 0.1 at the time of measurement. D90 (m) of natural rubber latexComparative Example 4was measured under the same conditions.

Second Evaluation: Properties of Vulcanized Rubber

[0060] The rubber composition was vulcanized at conditions of 150 C. for 30 min to obtain vulcanized rubber. Fatigue resistance, heat generation, and tensile stress of the vulcanized rubber were evaluated. Conditions under which evaluation was performed were identical to those at Working Example 1. Results of evaluation are shown as indexed relative to a value of 100 for Comparative Example 4.

TABLE-US-00003 TABLE 2 Comparative Working Working Example 4 Example 4 Example 5 Liquid supernatant or natural rubber latex Amount of DAP added mass % 1.1 0.4 Evaluation Magnesium content 80 131 of liquid supernatant ppm D90 particle 1.92 1.40 diameter of rubber particles within liquid supernatant m Magnesium content 180 of natural rubber latex ppm D90 particle 1.20 diameter of rubber particles within natural rubber latex m Pre-coagulation liquid mixture Blended Natural rubber 100 100 100 amount Carbon 40 40 40 (parts Black (B) by mass) N.sub.2SA of Carbon 27 27 27 Black (B) m.sup.2/g Conditions b/a 0.22 0.50 0.31 (b d)/(c 1000) 0.90 0.56 0.77 Wet rubber masterbatch Blended Natural rubber 100 100 100 amount Carbon 40 40 40 (parts Black (B) by mass) Rubber composition Blended Wet rubber 140 140 140 amount masterbatch (parts Zinc oxide 3 3 3 by mass) Stearic acid 4 4 4 Antioxidant (A) 2 2 2 Antioxidant (B) 1 1 1 Sulfur 2 2 2 Vulcanization 1 1 1 accelerator Vulcanized rubber Evaluation Fatigue 100 118 111 resistance (relative to index value) Heat generation 100 97 92 (relative to index value) M300 (relative 100 109 105 to index value)

[0061] At Working Example 4, where DAP was 1.1 mass %, fatigue resistance, ability to achieve reduced heat generation, and tensile stress were better than at Comparative Example 4. At Working Example 5, where DAP was 0.4 mass %, ability to achieve reduced heat generation was better than at Working Example 4. At Working Example 5, it is speculated that the frequency of contact between Carbon Black (B) and rubber particles was high.

Comparative Example 5

Manufacture of Wet Rubber Masterbatch

[0062] Natural rubber latex was collected. Water was added to natural rubber latex to manufacture a natural rubber latex solution having a solids (rubber) concentration that was 27 mass %. 70 parts by mass of Carbon Black (A) was added to water. An agitator (Flashblend manufactured by Silverson) was used to disperse the Carbon Black (A) (Flashblend conditions: 3600 rpm; 30 min) to manufacture a carbon black slurry. The natural rubber latex solution was added to the carbon black slurry in such amount as to cause solids (rubber) to be present therein in an amount that was 100 parts by mass to manufacture a pre-coagulation liquid mixture. The pre-coagulation liquid mixture was maintained at 90 C. in a mixer (SMV-20 Supermixer manufactured by Kawata Co., Ltd.) while formic acid was added thereto in an amount sufficient to achieve a pH of 4. A squeezer-type single-screw dewatering extruder (Model V-02 screw press manufactured by Suehiro EPM Corporation) was used to dry the coagulum until water content was not greater than 1.5% to manufacture a wet rubber masterbatch.

Manufacture of Rubber Composition

[0063] The respective compounding ingredients were blended in amounts as listed at TABLE 3, and a Model B Banbury mixer manufactured by Kobe Steel, Ltd., was used to knead these together to manufacture a rubber composition.

Working Examples 6-7

Manufacture of Wet Rubber Masterbatch

[0064] Natural rubber latex was collected. DAP as a fraction of the total weight of the natural rubber latex was added in the amount shown at TABLE 3, and the magnesium phosphate which precipitated was removed therefrom to obtain a liquid supernatant. Water was added to the liquid supernatant to manufacture a natural rubber latex solution having a solids (rubber) concentration that was 27 mass %. 70 parts by mass of Carbon Black (A) was added to water. An agitator (Flashblend manufactured by Silverson) was used to disperse the Carbon Black (A) (Flashblend conditions: 3600 rpm; 30 min) to manufacture a carbon black slurry. The natural rubber latex solution was added to the carbon black slurry in such amount as to cause solids (rubber) to be present therein in an amount that was 100 parts by mass to manufacture a pre-coagulation liquid mixture. The pre-coagulation liquid mixture was maintained at 90 C. in a mixer (SMV-20 Supermixer manufactured by Kawata Co., Ltd.) while formic acid was added thereto in an amount sufficient to achieve a pH of 4. A squeezer-type single-screw dewatering extruder (Model V-02 screw press manufactured by Suehiro EPM Corporation) was used to dry the coagulum until water content was not greater than 1.5% to manufacture a wet rubber masterbatch.

Manufacture of Rubber Composition

[0065] The respective compounding ingredients were blended in amounts as listed at TABLE 3, and a Model B Banbury mixer manufactured by Kobe Steel, Ltd., was used to knead these together to manufacture a rubber composition.

First Evaluation

Magnesium Content

[0066] Magnesium content of liquid supernatantWorking Examples 6-7was measured in accordance with ISO 11852; 2011. Magnesium content of natural rubber latexComparative Example 5was measured in accordance with ISO 11852; 2011.

90 Vol % Particle Diameter

[0067] D90 (m) of liquid supernatantWorking Examples 6-7was measured using a SALD 2200 manufactured by Shimadzu Corporation (latex refractive index: 1.6-0.10i), absorbance being set to 0.05 to 0.1 at the time of measurement. D90 (m) of natural rubber latexComparative Example 5was measured under the same conditions.

Second Evaluation: Properties of Vulcanized Rubber

[0068] The rubber composition was vulcanized at conditions of 150 C. for 30 min to obtain vulcanized rubber. Fatigue resistance, heat generation, and tensile stress of the vulcanized rubber were evaluated. Conditions under which evaluation was performed were identical to those at Working Example 1. Results of evaluation are shown as indexed relative to a value of 100 for Comparative Example 5.

TABLE-US-00004 TABLE 3 Comparative Working Working Example 5 Example 6 Example 7 Liquid supernatant or natural rubber latex Amount of DAP added mass % 0.25 1.1 Evaluation Magnesium content 144 80 of liquid supernatant ppm D90 particle 1.29 1.92 diameter of rubber particles within liquid supernatant m Magnesium content 180 of natural rubber latex ppm D90 particle 1.20 diameter of rubber particles within natural rubber latex m Pre-coagulation liquid mixture Blended Natural rubber 100 100 100 amount Carbon 70 70 70 (parts Black (A) by mass) N.sub.2SA of Carbon 142 142 142 Black (A) m.sup.2/g Conditions b/a 0.39 0.49 0.88 (b d)/(c 1000) 8.28 7.71 5.18 Wet rubber masterbatch Blended Natural rubber 100 100 100 amount Carbon 70 70 70 (parts Black (A) by mass) Rubber composition Blended Wet rubber 170 170 170 amount masterbatch (parts Zinc oxide 3 3 3 by mass) Stearic acid 4 4 4 Antioxidant (A) 2 2 2 Antioxidant (B) 1 1 1 Sulfur 2 2 2 Vulcanization 1 1 1 accelerator Vulcanized rubber Evaluation Fatigue 100 110 118 resistance (relative to index value) Heat 100 98 93 generation (relative to index value) M300 (relative 100 113 115 to index value)

[0069] At Working Example 6, where DAP was 0.25 mass %, fatigue resistance, ability to achieve reduced heat generation, and tensile stress were better than at Comparative Example 5. At Working Example 7, where DAP was 1.1 mass %, ability to achieve reduced heat generation was better than at Working Example 6. At Working Example 7, it is speculated that the frequency of contact between Carbon Black (A) and rubber particles was high.