TIRE MASTERBATCH, TIRE RUBBER COMPOSITION, TIRE, AND METHODS FOR MANUFACTURE THEREOF

Abstract

A tire masterbatch comprises natural rubber and cellulose nanofiber, wherein at least a portion of the cellulose nanofiber is such that length is 10 μm to 20 μm, and a ratio (i.e., L/D) of the length to a diameter is 1000 to 2000. A tire masterbatch manufacturing method comprises an operation in which at least a cellulose nanofiber slurry and a natural rubber latex are mixed to prepare a liquid mixture, and an operation in which the liquid mixture is coagulated, wherein at least a portion of cellulose nanofiber within the cellulose nanofiber slurry is such that length is 10 μm to 20 μm, and a ratio (i.e., L/D) of the length to a diameter is 1000 to 2000.

Claims

1. A tire masterbatch comprising: natural rubber; and cellulose nanofiber; wherein at least a portion of the cellulose nanofiber is such that length is 10 μm to 20 μm, and a ratio of the length to a diameter is 1000 to 2000.

2. The tire masterbatch according to claim 1 wherein the tire masterbatch further comprises a rubber component that comprises the natural rubber; and the cellulose nanofiber is present in an amount that is not less than 0.1 part by mass but not greater than 60 parts by mass per 100 parts by mass of the rubber component.

3. A tire masterbatch manufacturing method comprising: an operation in which at least a cellulose nanofiber slurry and a natural rubber latex are mixed to prepare a liquid mixture; and an operation in which the liquid mixture is coagulated; wherein at least a portion of cellulose nanofiber within the cellulose nanofiber slurry is such that length is 10 μm to 20 μm, and a ratio of the length to a diameter is 1000 to 2000.

4. The tire masterbatch manufacturing method according to claim 3 wherein at the operation in which the liquid mixture is prepared, at least the cellulose nanofiber slurry, the natural rubber latex, and a carbon black slurry are mixed.

5. The tire masterbatch manufacturing method according to claim 3 wherein the length at the portion of the cellulose nanofiber is not less than 13 μm.

6. The tire masterbatch manufacturing method according to claim 3 wherein the length at the portion of the cellulose nanofiber is not less than 15 μm.

7. The tire masterbatch manufacturing method according to claim 3 wherein the ratio at the portion of the cellulose nanofiber is not less than 1300.

8. The tire masterbatch manufacturing method according to claim 3 wherein the ratio at the portion of the cellulose nanofiber is not less than 1500.

9. The tire masterbatch manufacturing method according to claim 3 wherein the ratio at the portion of the cellulose nanofiber is less than 2000.

10. The tire masterbatch manufacturing method according to claim 3 wherein the cellulose nanofiber is present in the liquid mixture in an amount that is not less than 0.1 part by mass but not greater than 60 parts by mass per 100 parts by mass of dry rubber content in the natural rubber latex.

11. The tire masterbatch manufacturing method according to claim 3 further comprising: an operation in which a coagulum obtained by the coagulation of the liquid mixture is dewatered.

12. A tire manufacturing method comprising: an operation in which a tire masterbatch is prepared by the tire masterbatch manufacturing method according to claim 3; an operation in which the tire 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 tire masterbatch and a compounding ingredient to prepare a rubber mixture, and kneading at least the rubber mixture and sulfur to obtain the rubber composition.

14. A tire rubber composition comprising: natural rubber; and cellulose nanofiber; wherein at least a portion of the cellulose nanofiber is such that length is 10 μm to 20 μm, and a ratio of the length to a diameter is 1000 to 2000.

15. A tire prepared through use of the rubber composition according to claim 14.

Description

WORKING EXAMPLES

[0074] Working examples in accordance with the present invention are described below.

[0075] The raw materials and reagents that were used at the Working Examples are indicated below.

TABLE-US-00001 Concentrated natural rubber latex (dry rubber content 60 mass %) Manufactured by Regitex Co., Ltd. Natural rubber RSS #3 Carbon black “SEAST 3” (N330) manufactured by Tokai Carbon Co., Ltd. CNF1 “IMa-10002” manufactured by Sugino Machine Limited Concentration 2 wt %; fiber diameter 10 nm-50 nm; fiber length 10 μm-20 μm; viscosity 7,000 mPa .Math. s (under conditions of 25° C. and 60 rpm (B-type viscometer)) CNF2 “WFo-10002” manufactured by Sugino Machine Limited Concentration 2 wt %; fiber diameter 10 nm-50 nm; fiber length 1 μm-9 μm; viscosity 6,000 mPa .Math. s (under conditions of 25° C. and 60 rpm (B-type viscometer) CNF3 “Rheocrysta” manufactured by DKS Co. Ltd. Concentration 2 wt %; fiber diameter 3 nm; viscosity not less than 10,000 mPa .Math. s (resulting from concentration 1.0 wt %; measurement conditions: BM- type viscometer; 6 rpm; 3 min; 20° C.) Zinc oxide “Zinc Oxide Variety No. 2” manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid “LUNAC S-20” manufactured by Kao Corporation Wax “OZOACE 0355” manufactured by Nippon Seiro Co., Ltd. Antioxidant A “NOCRAC 6C” (N-phenyl-N′-(1,3-dimethylbutyl)-p- phenylenediamine) manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Antioxidant B “NOCRAC 224” (2,2,4-trimethyl-1,2- dihydroquinoline polymer) manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Sulfur “5% Oil Treated Sulfur Powder” manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator “Sanceler CM” (N-cyclohexyl-2- benzothiazolesulfenamide) manufactured by Sanshin Chemical Industry Co., Ltd.

Measurement of Cellulose Nanofiber Length and Diameter

[0076] Cellulose nanofiber—specifically CNF1, 2, and 3—are slurry-like products. These products were diluted with distilled water. The diluent (i.e., diluted liquid dispersion of CNF) was dripped onto a grid and allowed to dry, following which a Field-Emission Scanning Electron Microscope, i.e., FE-SEM, was used to observe the cellulose nanofiber. The conditions under which observation was carried out are as follows.

TABLE-US-00002 Magnification under which observation carried out 2000x Working distance WD = 2 mm Detector InLens Electron beam accelerating voltage 1 kV

[0077] Length and diameter of cellulose nanofibers appearing in FE-SEM images were measured. Ratio of length to diameter, i.e., L/D, was calculated from these measured values.

[0078] Cellulose nanofiber length and L/D were as follows (representative values).

TABLE-US-00003 CNF1 Length 19 μm L/D 1727 CNF2 Length 8 μm L/D 258 CNF3 Length 30 μm L/D 2500

Preparation of Masterbatch at Comparative Examples 4-6 and 10-12, and at Working Examples 1-3

[0079] The cellulose nanofiber indicated at TABLES 1 and 2 was agitated for 30 minutes at 1000 rpm in a mixer (“SM-20 Supermixer” manufactured by Kawata Co., Ltd.) to obtain a cellulose nanofiber slurry. Concentrated natural rubber latex was added to the cellulose nanofiber slurry in accordance with the blended amounts shown in TABLES 1 and 2, and this was agitated for 30 minutes at 1000 rpm in a mixer (“SM-20 Supermixer” manufactured by Kawata Co., Ltd.) to obtain a liquid mixture. The liquid mixture was placed in an oven and was dried overnight at 70° C. Masterbatch was obtained as a result of such procedure.

Preparation of Masterbatch at Comparative Examples 7-9 and 13-15, and at Working Examples 4-12

[0080] Carbon black was added to water and this was agitated to obtain a carbon black slurry. The cellulose nanofiber indicated at TABLES 1 and 2 was agitated for 30 minutes at 1000 rpm in a mixer (“SM-20 Supermixer” manufactured by Kawata Co., Ltd.) to obtain a cellulose nanofiber slurry. Concentrated natural rubber latex and the carbon black slurry were added to the cellulose nanofiber slurry in accordance with the blended amounts shown in TABLES 1 and 2, and this was agitated for 30 minutes at 1000 rpm in a mixer (“SM-20 Supermixer” manufactured by Kawata Co., Ltd.) to obtain a liquid mixture. The liquid mixture was placed in an oven and was dried overnight at 70° C. Masterbatch was obtained as a result of such procedure.

Preparation of Unvulcanized Rubber at Respective Examples Other than Comparative Examples 1-3 (i.e., Comparative Examples 4-15 and Working Examples 4-12)

[0081] The compounding ingredients except for sulfur and vulcanization accelerator were added to masterbatch in accordance with TABLES 1 and 2, and a Banbury mixer was used to carry out kneading to obtain a rubber mixture. The rubber mixture was kneaded with sulfur and vulcanization accelerator in a Banbury mixer to obtain unvulcanized rubber.

Preparation of Unvulcanized Rubber at Comparative Examples 1-3

[0082] The compounding ingredients except for sulfur and vulcanization accelerator were added to natural rubber in accordance with TABLES 1 and 2, and a Banbury mixer was used to carry out kneading to obtain a rubber mixture. The rubber mixture was kneaded with sulfur and vulcanization accelerator in a Banbury mixer to obtain unvulcanized rubber.

Preparation of Vulcanized Rubber

[0083] The unvulcanized rubber was vulcanized for 30 minutes at 150° C. to obtain vulcanized rubber.

E′ (Storage Modulus)

[0084] E′, i.e., storage modulus, of vulcanized rubber was measured in accordance with JIS K-6394. More specifically, measurement was carried out using a viscoelasticity testing machine under conditions of room temperature, frequency 10 Hz, static strain 5%, and dynamic strain 1%. E of the respective Examples are shown at TABLES 1 and 2 as indexed relative to a value of 100 for the E of Comparative Example 6. The higher the index the greater the E, and thus the better the rigidity.

tan δ

[0085] tan δ of vulcanized rubber was measured in accordance with JIS K-6394. More specifically, measurement was carried out using a viscoelasticity testing machine under conditions of temperature 70° C., frequency 10 Hz, static strain 5%, and dynamic strain 1%. tan δ of the respective Examples are shown at TABLES 1 and 2 as indexed relative to a value of 100 for the tan δ of Comparative Example 6. 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.

TABLE-US-00004 TABLE 1 Comparative Examples 1 2 3 4 5 6 7 8 Amount blended in masterbatch Parts Concentrated natural — — — 100  100  100  100  100  by rubber latex (dry mass rubber content) Carbon black — — — — — — 2 2 CNF1 — — — — — — — — CNF2 — — — 10  20  30  10  20  CNF3 — — — — — — — — Amount blended in rubber composition Parts Masterbatch — — — 110  120  130  112  122  by Natural rubber 100 100 100 — — — — — mass (RSS #3) Carbon black 35 40 50 — — — — — Zinc oxide 3 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 2 Wax 1 1 1 1 1 1 1 1 Antioxidant A 2 2 2 2 2 2 2 2 Antioxidant B 1 1 1 1 1 1 1 1 Sulfur 2 2 2 2 2 2 2 2 Vulcanization 1 1 1 1 1 1 1 1 accelerator Physical E′ 100 106 121 56  82  100  58  83  properties tanδ 109 115 128 83  94  100  86  95  Comparative Examples 9 10 11 12 13 14 15 Amount blended in masterbatch Parts Concentrated natural 100  100 100 100 100 100 100 by rubber latex (dry mass rubber content) Carbon black 2 — — — 2 2 2 CNF1 — — — — — — — CNF2 30  — — — — — — CNF3 — 10 20 30 10 20 30 Amount blended in rubber composition Parts Masterbatch 132  110 120 130 112 122 132 by Natural rubber — — — — — — — mass (RSS #3) Carbon black — — — — — — — Zinc oxide 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 Wax 1 1 1 1 1 1 1 Antioxidant A 2 2 2 2 2 2 2 Antioxidant B 1 1 1 1 1 1 1 Sulfur 2 2 2 2 2 2 2 Vulcanization 1 1 1 1 1 1 1 accelerator Physical E′ 101  96 108 119 98 109 120 properties tanδ 101  109 114 121 109 113 121

TABLE-US-00005 TABLE 2 Working Examples 1 2 3 4 5 6 Amount blended in masterbatch Parts Concentrated natural 100 100 100 100 100 100 by rubber latex (dry mass rubber content) Carbon black — — — 2 2 2 CNF1 10 20 30 10 20 30 CNF2 — — — — — — CNF3 — — — — — — Amount blended in rubber composition Parts Masterbatch 110 120 130 112 122 132 by Natural rubber — — — — — — mass (RSS #3) Carbon black — — — — — — Zinc oxide 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 Wax 1 1 1 1 1 1 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 Physical E′ 120 126 152 125 131 156 properties tanδ 94 96 103 92 93 101 Working Examples 7 8 9 10 11 12 Amount blended in masterbatch Parts Concentrated natural 100 100 100 100 100 100 by rubber latex (dry mass rubber content) Carbon black 5 5 5 10 10 10 CNF1 8 18 28 5 13 23 CNF2 — — — — — — CNF3 — — — — — — Amount blended in rubber composition Parts Masterbatch 113 123 133 115 126 133 by Natural rubber — — — — — — mass (RSS #3) Carbon black — — — — — — Zinc oxide 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 Wax 1 1 1 1 1 1 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 Physical E′ 124 129 152 124 127 149 properties tanδ 90 93 97 91 90 94

[0086] E′, i.e., storage modulus, of vulcanized rubber prepared with CNF1 was better than that of vulcanized rubber prepared with CNF2 and that of vulcanized rubber prepared with CNF3 (see, for example, Working Example 3, Comparative Example 6, and Comparative Example 12).

[0087] Moreover, tan δ of vulcanized rubber prepared with CNF1 was not much different from that of vulcanized rubber prepared with CNF2 (tan δ of vulcanized rubber prepared with CNF2 was smaller than that of vulcanized rubber prepared with CNF3) (see, for example, Working Example 3 and Comparative Example 6).

[0088] Based on such results, it is fair to say that it was possible using CNF1 to manufacture a masterbatch capable of serving as raw material for vulcanized rubber having an excellent balance between ability to achieve reduced heat generation and rigidity.

[0089] It should be noted that the effect whereby CNF1 caused improvement in E was able to be elicited to even greater degree as a result of employment of an operation in which there was mixture of three components, i.e., cellulose nanofiber slurry, concentrated natural rubber latex, and carbon black slurry. For example, where operations were employed in which there was mixture of two components, i.e., cellulose nanofiber slurry and concentrated natural rubber latex, the vulcanized rubber at Working Example 3 prepared with CNF1 was 52 points better than that of the vulcanized rubber at Comparative Example 6 prepared with CNF2, and was 33 points better than that of the vulcanized rubber at Comparative Example 12 prepared with CNF3. On the other hand, where operations were employed in which there was mixture of three components, i.e., cellulose nanofiber slurry, concentrated natural rubber latex, and carbon black slurry, the vulcanized rubber at Working Example 6 prepared with CNF1 was 55 points better than that of the vulcanized rubber at Comparative Example 9 prepared with CNF2, and was 36 points better than that of the vulcanized rubber at Comparative Example 15 prepared with CNF3. Thus, employment of operations in which there was mixture of three components resulted in an increase in the difference between the E of the vulcanized rubber prepared with CNF1 and the E of the vulcanized rubber prepared with CNF2, and employment of such operations also resulted in an increase in the difference between the E of the vulcanized rubber prepared with CNF1 and the E of the vulcanized rubber prepared with CNF3.

[0090] In addition, with CNF1, it was also possible to cause worsening of heat generation due to addition of cellulose nanofiber to be suppressed to even greater degree as a result of employment of an operation in which there was mixture of three components, i.e., cellulose nanofiber slurry, concentrated natural rubber latex, and carbon black slurry. For example, where operations were employed in which there was mixture of two components, i.e., cellulose nanofiber slurry and concentrated natural rubber latex, the vulcanized rubber at Working Example 3 prepared with CNF1 was 3 points worse than (i.e., there was a difference of 3 points as compared with) that of the vulcanized rubber at Comparative Example 6 prepared with CNF2, and was 18 points better than that of the vulcanized rubber at Comparative Example 12 prepared with CNF3. On the other hand, where operations were employed in which there was mixture of three components, i.e., cellulose nanofiber slurry, concentrated natural rubber latex, and carbon black slurry, the vulcanized rubber at Working Example 6 prepared with CNF1 had the same number of points as that of the vulcanized rubber at Comparative Example 9 prepared with CNF2, and was 20 points better than that of the vulcanized rubber at Comparative Example 15 prepared with CNF3.