MASTERBATCH MANUFACTURING METHOD AND TIRE MANUFACTURING METHOD

Abstract

A masterbatch manufacturing method comprises: an operation in which carbon black is dispersed in dispersion medium in presence of a surface active agent having an aromatic ring to prepare a carbon black slurry; an operation in which at least the carbon black slurry and a rubber latex are mixed to prepare a liquid mixture; and an operation in which the liquid mixture is coagulated.

Claims

1. A masterbatch manufacturing method comprising: an operation in which carbon black is dispersed in dispersion medium in presence of a surface active agent having an aromatic ring to prepare a carbon black slurry; an operation in which at least the carbon black slurry and a rubber latex are mixed to prepare a liquid mixture; and an operation in which the liquid mixture is coagulated.

2. The masterbatch manufacturing method according to claim 1 wherein the aromatic ring is one among a plurality of intramolecular aromatic rings possessed by the surface active agent.

3. The masterbatch manufacturing method according to claim 1 wherein the surface active agent is a sodium salt of a β-naphthalene sulfonic acid-formaldehyde condensate.

4. The masterbatch manufacturing method according to claim 1 wherein the surface active agent is an anionic surface active agent.

5. The masterbatch manufacturing method according to claim 1 wherein, at the operation in which the carbon black slurry is prepared, the surface active agent is present in an amount that is not less than 0.1 part by mass but not greater than 5 parts by mass per 100 parts by mass of the dispersion medium.

6. The masterbatch manufacturing method according to claim 1 wherein the carbon black is present in an amount that is not less than 1 mass % but not greater than 30 mass % per 100 mass % of the carbon black slurry.

7. The masterbatch manufacturing method according to claim 1 wherein the rubber latex is natural rubber latex.

8. The masterbatch manufacturing method according to claim 1 wherein the rubber latex is natural rubber latex; and at the operation in which the liquid mixture is prepared, the carbon black is present in the carbon black slurry in an amount that is not less than 1 part by mass but not greater than 80 parts by mass per 100 parts by mass of dry rubber content in the natural rubber latex.

9. The masterbatch manufacturing method according to claim 1 further comprising an operation in which a coagulum obtained at the operation in which the liquid mixture is coagulated is dewatered.

10. The masterbatch manufacturing method according to claim 1 further comprising an operation in which an extruder is used to dewater a coagulum obtained at the operation in which the liquid mixture is coagulated.

11. The masterbatch manufacturing method according to claim 1 wherein, at the carbon black slurry, a (volume-based) particle diameter corresponding to 90% at an integrated particle diameter distribution of the carbon black is not less than 0.5 μm but not greater than 4.0 μm.

12. A tire manufacturing method comprising: an operation in which a masterbatch is prepared by the masterbatch manufacturing method according to claim 1; an operation in which the masterbatch is used to prepare a rubber composition; and an operation in which the rubber composition is used to prepare an unvulcanized tire.

13. The tire manufacturing method according to claim 12 wherein the operation in which the rubber composition is prepared comprises kneading at least the masterbatch and a compounding ingredient to prepare a rubber mixture, and kneading at least the rubber mixture and a vulcanizing agent to obtain the rubber composition.

14. The tire manufacturing method according to claim 12 wherein the operation in which the unvulcanized tire is fabricated comprises fabrication of a tire member comprising the rubber composition, and fabrication of the unvulcanized tire that comprises the tire member.

Description

WORKING EXAMPLES

[0063] Working examples in accordance with the present invention are described below.

[0064] The raw materials and reagents that were used at the Working Examples are indicated below. [0065] Surface Active Agent A “Demol NL” manufactured by Kao Corporation anionic surface active agent sodium salt of β-naphthalene sulfonic acid-formaldehyde condensate [0066] Surface Active Agent B “Emulgen A060” manufactured by Kao Corporation nonionic surface active agent [0067] Natural rubber latex “NR Field Latex” manufactured by Golden Hope [0068] Solid natural rubber Solid rubber obtained by drying “NR Field Latex” manufactured by Golden Hope [0069] Carbon black “Diablack A” manufactured by Mitsubishi Chemical Corporation [0070] Zinc oxide “Zinc Oxide Variety No. 2” manufactured by Mitsui Mining & Smelting Co., Ltd. [0071] Stearic acid “Stearic Acid” manufactured by Nippon Oil & Fats Co., Ltd. [0072] Wax “OZOACE 0355” manufactured by Nippon Seiro Co., Ltd. [0073] Antioxidant A “Santoflex 6 PPD” manufactured by Flexsys [0074] Antioxidant B “NOCRAC 224” manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. [0075] Sulfur “Oil-Treated 150-Mesh Powdered Sulfur” manufactured by Tsurumi Chemical Industry Co., Ltd. [0076] Vulcanization accelerator “Sanceler NS-G” manufactured by Sanshin Chemical Industry Co., Ltd.

Preparation of Masterbatch at Comparative Example 1

[0077] Following addition of carbon black to solid natural rubber, this was kneaded. As a result of this, a masterbatch was obtained.

Preparation of Masterbatch at Comparative Example 2

[0078] Following addition of carbon black and surface active agent to solid natural rubber, this was kneaded. As a result of this, a masterbatch was obtained.

Preparation of Masterbatch at Comparative Example 3

[0079] 30 parts by mass of carbon black was added to 100 parts by mass of water, and a ROBO MIX manufactured by PRIMIX Corporation was used to agitate this at normal temperature to prepare a carbon black slurry. Natural rubber latex was added to the carbon black slurry in accordance with the blended amount shown in TABLE 1, and this was agitated at 90° C. in a device called a mixer (SMV-20 Supermixer) manufactured by Kawata Co., Ltd., to obtain a liquid mixture. Formic acid serving as coagulant was added to the liquid mixture in an amount sufficient to achieve a pH of 4 to obtain a coagulum. A Model V-02 screw press manufactured by Suehiro EPM Corporation (squeezer-type single-screw dewatering extruder) was used to dewater the coagulum, and this was discharged at 120° C. In this way, a masterbatch was obtained.

Preparation of Masterbatch at Working Example 1 and at Comparative Example 4

[0080] 30 parts by mass of carbon black and 1 part by mass of surface active agent were added to 100 parts by mass of water, and a ROBO MIX manufactured by PRIMIX Corporation was used to agitate this at normal temperature to prepare a carbon black slurry. Natural rubber latex was added to the carbon black slurry in accordance with the blended amount shown in TABLE 1, and this was agitated at 90° C. in a device called a mixer (SMV-20 Supermixer) manufactured by Kawata Co., Ltd., to obtain a liquid mixture. Formic acid serving as coagulant was added to the liquid mixture in an amount sufficient to achieve a pH of 4 to obtain a coagulum. A Model V-02 screw press manufactured by Suehiro EPM Corporation (squeezer-type single-screw dewatering extruder) was used to dewater the coagulum, and this was discharged at 120° C. In this way, a masterbatch was obtained.

Preparation of Unvulcanized Rubber at the Various Examples

[0081] The compounding ingredients except for sulfur and vulcanization accelerator were added to masterbatch in accordance with TABLE 1, and a Banbury mixer was used to carry out kneading (i.e., nonproductive mixing) to obtain a rubber mixture. The rubber mixture was kneaded (i.e., productive mixing was carried out) with sulfur and vulcanization accelerator in a Banbury mixer to obtain unvulcanized rubber.

Preparation of Vulcanized Rubber

[0082] The unvulcanized rubber was vulcanized for 30 minutes at 150° C. to obtain vulcanized rubber.

tan δ

[0083] tan δ of vulcanized rubber was measured in accordance with JIS K-6394 2007. More specifically, measurement was carried out using a viscoelasticity testing machine manufactured by Toyo Seiki under conditions of temperature 60° C., frequency 10 Hz, static strain 10%, and dynamic strain 1%. tan δ of the respective Examples are shown at TABLE 1 as indexed relative to a value of 100 for the tan δ obtained at Comparative Example 1. The lower the index the less the tendency for heat generation to occur, and thus the better the ability to achieve reduction in fuel consumption when used as a tire.

Tensile Strength (i.e., Rupture Strength)

[0084] Tensile strength of vulcanized rubber was measured in accordance with JIS K-6251 2017. More specifically, a dumbbell-shaped test piece was cut from vulcanized rubber in the shape of a No. 3 dumbbell, a tensile test apparatus was used to measure the tensile force at the dumbbell-shaped test piece, and the tensile strength (i.e., the value of the maximum tensile force recorded when the test piece is elongated until breakage occurs divided by the cross-sectional area of the test piece prior to testing) was determined. The tensile strengths for the respective Examples are shown at TABLE 1 as indexed relative to a value of 100 for the tensile strength obtained at Comparative Example 1. The higher the index the higher the tensile strength.

Carbon Black Slurry Particle Size Distribution (D90 Value)

[0085] Water was added to the carbon black slurries prepared at Comparative Examples 3 and 4 and Working Example 1 to prepare 0.005 mass % carbon black diluents. A particle size distribution image analyzer (“IF-3200” manufactured by Jasco International Co., Ltd.; “PIA-Pro Image Analysis Software, Ver. 2016” analytic software; measurement conditions: cell thickness=50 μm, sample concentration=0.005 wt %, cumulative number of particles used for analysis=15,000 to 30,000 particles) was used to determine the D90 values of these diluents. That is, the (volume-based) particle diameter corresponding to 90% at the integrated particle diameter distribution was determined. D90 values are shown in TABLE 1 in units of μm.

TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Working Comparative Example 1 Example 2 Example 3 Example 1 Example 4 Carbon Addition of Surface Active Agent A — — — Yes — black Addition of Surface Active Agent B — — — — Yes slurry D90 in units of μm — — 10.3 1.9 4.9 Masterbatch Parts by Natural rubber latex (dry rubber content) — — 100 100 100 mass Solid natural rubber 100 100 — — — Carbon black 30 30 30 30 30 Addition of Surface Active Agent A — Yes — — — Nonproductive Parts by Masterbatch 130 130 130 130 130 mixing and mass Carbon black 18 18 18 18 18 productive Zinc oxide 1 1 1 1 1 mixing Stearic acid 2 2 2 2 2 Wax 1 1 1 1 1 Antioxidant A 2 2 2 2 2 Antioxidant B 1 1 1 1 1 Sulfur 2 2 2 2 2 Vulcanization accelerator 1 1 1 1 1 Vulcanized Properties tanδ 100 102 96 92 94 rubber Tensile strength 100 98 101 106 102

[0086] At the vulcanized rubbers of Comparative Example 4 and Working Example 1, at which carbon black slurries were prepared with addition of surface active agent, the tan δ was lower, and the tensile strength was higher, than the vulcanized rubber at Comparative Example 3, at which the carbon black slurry was prepared without addition of surface active agent. This is thought to be due to the fact because the D90 values of the carbon black slurries at Comparative Example 4 and Working Example 1 were less than the D90 value at Comparative Example 3, this made it possible for the surface active agent to improve carbon black dispersion.

[0087] At the vulcanized rubber of Working Example 1, at which Surface Active Agent A was used to prepare the carbon black slurry, the tan δ was lower, and the tensile strength was higher, than the vulcanized rubber at Comparative Example 4, at which Surface Active Agent B was used to prepare the carbon black slurry. This is thought to be due to the fact because the D90 value of the carbon black slurry at Working Example 1 was less than the D90 value at Comparative Example 4, this made it possible for Surface Active Agent A to cause carbon black to be dispersed to an even higher degree.