US20150361253A1 - Rubber composition and method for producing same - Google Patents
Rubber composition and method for producing same Download PDFInfo
- Publication number
- US20150361253A1 US20150361253A1 US14/828,133 US201514828133A US2015361253A1 US 20150361253 A1 US20150361253 A1 US 20150361253A1 US 201514828133 A US201514828133 A US 201514828133A US 2015361253 A1 US2015361253 A1 US 2015361253A1
- Authority
- US
- United States
- Prior art keywords
- rubber
- mass
- natural rubber
- parts
- master batch
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- 229920001971 elastomer Polymers 0.000 title claims abstract description 190
- 239000005060 rubber Substances 0.000 title claims abstract description 190
- 239000000203 mixture Substances 0.000 title claims abstract description 100
- 238000004519 manufacturing process Methods 0.000 title description 4
- 239000004594 Masterbatch (MB) Substances 0.000 claims abstract description 99
- 239000006229 carbon black Substances 0.000 claims abstract description 94
- 235000019241 carbon black Nutrition 0.000 claims abstract description 94
- 244000043261 Hevea brasiliensis Species 0.000 claims abstract description 91
- 229920003052 natural elastomer Polymers 0.000 claims abstract description 91
- 229920001194 natural rubber Polymers 0.000 claims abstract description 91
- 229920006173 natural rubber latex Polymers 0.000 claims abstract description 61
- 238000001035 drying Methods 0.000 claims abstract description 46
- 238000002156 mixing Methods 0.000 claims abstract description 31
- 239000002002 slurry Substances 0.000 claims abstract description 31
- 229920002857 polybutadiene Polymers 0.000 claims abstract description 27
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims abstract description 24
- 238000007580 dry-mixing Methods 0.000 claims abstract description 13
- 239000007791 liquid phase Substances 0.000 claims abstract description 6
- 239000011369 resultant mixture Substances 0.000 claims abstract description 4
- 239000002904 solvent Substances 0.000 claims description 21
- 239000008187 granular material Substances 0.000 claims description 18
- 241000196324 Embryophyta Species 0.000 claims description 12
- 239000002245 particle Substances 0.000 claims description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 239000011162 core material Substances 0.000 claims description 7
- 238000001179 sorption measurement Methods 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 37
- 239000003795 chemical substances by application Substances 0.000 description 32
- 238000000034 method Methods 0.000 description 32
- 239000004636 vulcanized rubber Substances 0.000 description 32
- 239000003921 oil Substances 0.000 description 30
- 230000003712 anti-aging effect Effects 0.000 description 21
- 229920000126 latex Polymers 0.000 description 20
- 239000000945 filler Substances 0.000 description 19
- 230000003247 decreasing effect Effects 0.000 description 16
- 238000004073 vulcanization Methods 0.000 description 16
- 239000007787 solid Substances 0.000 description 14
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 13
- 241000894007 species Species 0.000 description 13
- 229910052717 sulfur Inorganic materials 0.000 description 13
- 239000011593 sulfur Substances 0.000 description 13
- 238000004898 kneading Methods 0.000 description 10
- 239000002994 raw material Substances 0.000 description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 9
- 235000013339 cereals Nutrition 0.000 description 9
- 235000019589 hardness Nutrition 0.000 description 8
- 238000007493 shaping process Methods 0.000 description 8
- 239000004094 surface-active agent Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 239000004816 latex Substances 0.000 description 7
- 238000010008 shearing Methods 0.000 description 7
- 238000005299 abrasion Methods 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 6
- 239000003054 catalyst Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000000704 physical effect Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 description 4
- 239000011701 zinc Substances 0.000 description 4
- 229910052725 zinc Inorganic materials 0.000 description 4
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- 229920000459 Nitrile rubber Polymers 0.000 description 3
- 239000005062 Polybutadiene Substances 0.000 description 3
- 235000021355 Stearic acid Nutrition 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 235000019253 formic acid Nutrition 0.000 description 3
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 3
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 description 3
- 239000008117 stearic acid Substances 0.000 description 3
- 244000144730 Amygdalus persica Species 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- ZRALSGWEFCBTJO-UHFFFAOYSA-N Guanidine Chemical compound NC(N)=N ZRALSGWEFCBTJO-UHFFFAOYSA-N 0.000 description 2
- 240000007049 Juglans regia Species 0.000 description 2
- 235000009496 Juglans regia Nutrition 0.000 description 2
- 244000018795 Prunus mume Species 0.000 description 2
- 235000011158 Prunus mume Nutrition 0.000 description 2
- 235000006040 Prunus persica var persica Nutrition 0.000 description 2
- 239000006087 Silane Coupling Agent Substances 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000004902 Softening Agent Substances 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 2
- 240000008042 Zea mays Species 0.000 description 2
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 2
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- DKVNPHBNOWQYFE-UHFFFAOYSA-N carbamodithioic acid Chemical class NC(S)=S DKVNPHBNOWQYFE-UHFFFAOYSA-N 0.000 description 2
- 239000000084 colloidal system Substances 0.000 description 2
- 235000005822 corn Nutrition 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 235000013399 edible fruits Nutrition 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 235000014571 nuts Nutrition 0.000 description 2
- 229920001084 poly(chloroprene) Polymers 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 235000020234 walnut Nutrition 0.000 description 2
- 235000017060 Arachis glabrata Nutrition 0.000 description 1
- 244000105624 Arachis hypogaea Species 0.000 description 1
- 235000010777 Arachis hypogaea Nutrition 0.000 description 1
- 235000018262 Arachis monticola Nutrition 0.000 description 1
- 240000001548 Camellia japonica Species 0.000 description 1
- 244000209117 Castanea crenata Species 0.000 description 1
- 235000003801 Castanea crenata Nutrition 0.000 description 1
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 description 1
- 244000058871 Echinochloa crus-galli Species 0.000 description 1
- 235000008247 Echinochloa frumentacea Nutrition 0.000 description 1
- 235000011201 Ginkgo Nutrition 0.000 description 1
- 244000194101 Ginkgo biloba Species 0.000 description 1
- 235000008100 Ginkgo biloba Nutrition 0.000 description 1
- 240000005979 Hordeum vulgare Species 0.000 description 1
- 235000007340 Hordeum vulgare Nutrition 0.000 description 1
- 239000006237 Intermediate SAF Substances 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- CHJJGSNFBQVOTG-UHFFFAOYSA-N N-methyl-guanidine Natural products CNC(N)=N CHJJGSNFBQVOTG-UHFFFAOYSA-N 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- 241000872198 Serjania polyphylla Species 0.000 description 1
- 240000005498 Setaria italica Species 0.000 description 1
- FZWLAAWBMGSTSO-UHFFFAOYSA-N Thiazole Chemical compound C1=CSC=N1 FZWLAAWBMGSTSO-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 235000021307 Triticum Nutrition 0.000 description 1
- 244000098338 Triticum aestivum Species 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 239000002280 amphoteric surfactant Substances 0.000 description 1
- 239000003945 anionic surfactant Substances 0.000 description 1
- 239000000427 antigen Substances 0.000 description 1
- 102000036639 antigens Human genes 0.000 description 1
- 108091007433 antigens Proteins 0.000 description 1
- 150000004982 aromatic amines Chemical class 0.000 description 1
- 239000003093 cationic surfactant Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 235000018597 common camellia Nutrition 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- SWSQBOPZIKWTGO-UHFFFAOYSA-N dimethylaminoamidine Natural products CN(C)C(N)=N SWSQBOPZIKWTGO-UHFFFAOYSA-N 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000003273 ketjen black Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000004060 metabolic process Effects 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- DEQZTKGFXNUBJL-UHFFFAOYSA-N n-(1,3-benzothiazol-2-ylsulfanyl)cyclohexanamine Chemical compound C1CCCCC1NSC1=NC2=CC=CC=C2S1 DEQZTKGFXNUBJL-UHFFFAOYSA-N 0.000 description 1
- 229930014626 natural product Natural products 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000002736 nonionic surfactant Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 235000002252 panizo Nutrition 0.000 description 1
- 235000020232 peanut Nutrition 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 1
- 229920001195 polyisoprene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000002685 polymerization catalyst Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 238000013040 rubber vulcanization Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 230000002393 scratching effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- -1 sodium chloride Chemical class 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- QAZLUNIWYYOJPC-UHFFFAOYSA-M sulfenamide Chemical compound [Cl-].COC1=C(C)C=[N+]2C3=NC4=CC=C(OC)C=C4N3SCC2=C1C QAZLUNIWYYOJPC-UHFFFAOYSA-M 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- KUAZQDVKQLNFPE-UHFFFAOYSA-N thiram Chemical compound CN(C)C(=S)SSC(=S)N(C)C KUAZQDVKQLNFPE-UHFFFAOYSA-N 0.000 description 1
- 229960002447 thiram Drugs 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/005—Processes for mixing polymers
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
- C08J3/09—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids
- C08J3/11—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids from solid polymers
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/20—Compounding polymers with additives, e.g. colouring
- C08J3/22—Compounding polymers with additives, e.g. colouring using masterbatch techniques
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/01—Hydrocarbons
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L7/00—Compositions of natural rubber
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L91/00—Compositions of oils, fats or waxes; Compositions of derivatives thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2307/00—Characterised by the use of natural rubber
- C08J2307/02—Latex
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2409/00—Characterised by the use of homopolymers or copolymers of conjugated diene hydrocarbons
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/002—Physical properties
- C08K2201/006—Additives being defined by their surface area
Definitions
- the present invention relates to a rubber composition, and a method for producing the same, specifically, a rubber composition that can be largely decreased in E′ storage elastic modulus in a low temperature range, can be greatly improved, particularly, in braking performance on an ice and snow road surface (referred to also as an “ice road surface” hereinafter) when used as a raw material for tires, for example, their treads, and can be further improved in low-thermogenic performance.
- a rubber composition that can be largely decreased in E′ storage elastic modulus in a low temperature range, can be greatly improved, particularly, in braking performance on an ice and snow road surface (referred to also as an “ice road surface” hereinafter) when used as a raw material for tires, for example, their treads, and can be further improved in low-thermogenic performance.
- Rubbers for treads of studless tires used for running on ice road surfaces are required to have excellent on-ice and on-snow performances.
- the following method has been hitherto adopted: a method of not only using a polybutadiene rubber, which is low in glass transition temperature, or blending a softening agent, such as oil, into a tread rubber to maintain a low hardness of the tread rubber even at low temperatures, thereby improving the rubber in hysteresis frictional performance, but also blending a hard material such as hollow particles, glass fiber or plant granular material thereinto, thereby improving the rubber in scratch frictional performance.
- a method is adopted in which the blend proportion of a filler or a softening agent such as oil is increased in the composition of the rubber.
- a vulcanized rubber obtained therefrom tends to be lowered in low-thermogenic performance and abrasion resistance.
- the use of the natural rubber wet master batch gives a rubber composition better in filler dispersibility therein and in rubber physical properties such as workability and reinforceability as compared with the use of a rubber dry master batch obtained by dry-mixing a filler with a rubber.
- Patent Document 2 listed below describes a rubber composition for ice-and-snow-road tire treads which contains: a natural rubber wet master batch containing a carbon black having a nitrogen adsorption specific surface area of 105 to 155 m 2 /g, and a CTAB adsorption specific surface area of 100 to 150 m 2 /g; and a polybutadiene rubber.
- Patent Document 3 states that a rubber wet master batch which is one wherein a filler is evenly dispersed and the filler is restrained from being re-aggregated with time, and which is usable as a raw material for a vulcanized rubber excellent in low-thermogenic performance, endurance and rubber strength can be produced by a rubber-wet-master-batch-producing method including step (I) of adding, when the filler is dispersed into a dispersing solvent, at least one portion of a rubber latex solution thereto, thereby producing a slurry solution containing the filler to which rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the rubber latex solution to produce a rubber latex solution containing the just-above described rubber-latex-particle-adhering filler, and step (III) of solidifying and drying the rubber latex solution containing the rubber-latex-particle-adhering filler.
- Patent Document 1 JP-A-2004-99625
- Patent Document 2 JP-A-2004-107482
- Patent Document 3 Japanese Patent No. 4738551
- the rubber-wet-master-batch-containing rubber composition described in Patent Document 3 is excellent in filler dispersibility therein, and is improved in low-thermogenic performance. However, it has become evident that when this rubber composition is used for, for example, a tire tread, there remains room for a further improvement in braking performance, particularly, on ice road surfaces.
- An object thereof is to provide a rubber composition that can be largely decreased in E′ in a low temperature range, can be greatly improved, particularly, in braking performance on an ice and snow road surface when used as a raw material for tires, for example, their treads, and can be further improved in low-thermogenic performance; and a method for producing the composition.
- the present invention relates to a rubber composition obtained by dry-mixing a natural rubber wet master batch yielded by mixing at least a natural rubber latex and a carbon-black-containing slurry solution with each other in a liquid phase and drying the resultant mixture, a dry rubber made mainly of a polybutadiene rubber, and an oil, wherein when the total amount of rubber components in the rubber composition is regarded as 100 parts by mass, the natural rubber is contained in an amount of 50 parts or more by mass, and the polybutadiene rubber is contained in an amount of 20 to 50 parts by mass, and the oil has a pour point of ⁇ 10° C. or lower, and an aniline point of 90° C. or higher, and the blend amount of the oil is from 15 to 40 parts by mass for 100 parts by mass of the rubber components.
- the rubber composition according to the present invention is a composition obtained by dry-mixing the natural rubber wet master batch with the dry rubber, which is made mainly of the polybutadiene rubber, at the specific ratio, the composition is excellent in carbon black dispersibility therein and can be decreased in E′ in a low temperature range. Furthermore, the specific amount of the oil having specific physical properties (the pour point and the aniline point) is blended into the composition; thus, the composition can keep the rubber hardness thereof at a low level even in a low temperature range to be improved in braking performance on ice road surfaces.
- the rubber composition is especially excellent in filler dispersibility therein: step (I) in which when a carbon black is dispersed into a dispersing solvent to prepare the carbon-black-containing slurry solution, at least one portion of the natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the natural rubber latex to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, and step (III) of solidifying and drying the natural rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black. Consequently, when these rubber components are used together with the specific oil, the composition is improved, with an especially good balance, in braking performance on ice road surfaces and low-thermogenic performance.
- a vulcanized rubber from the rubber composition according to the present invention is excellent in low-thermogenic performance, and further in braking performance on ice road surfaces. Accordingly, the rubber composition according to the present invention is particularly useful as a rubber composition for studless tires.
- the natural rubber wet master batch contains the carbon black in an amount of 40 to 70 parts by mass for 100 parts by mass of the rubber components of the master batch. It is more preferred that the carbon black contained in the natural rubber wet master batch has a nitrogen adsorption specific surface area (N 2 SA) of 100 m 2 /g or less. According to this form, the rubber composition is further improved in low-thermogenic performance and can keep the viscosity thereof at a low level to be also excellent in workability.
- N 2 SA nitrogen adsorption specific surface area
- the total amount of the present rubber components in the rubber composition is regarded as 100 parts by mass
- at least one of a plant granular material, a grain granular material, and a granular region of a grain core material may be further contained in an amount of 0.5 to 10 parts by mass.
- the vulcanized rubber is improved in scratch frictional performance to be further improved in braking performance on ice road surfaces.
- the present invention relates to a method for producing a rubber composition
- a method for producing a rubber composition comprising a natural rubber wet master batch obtained by use of a carbon black, a dispersing solvent and a natural rubber latex as raw materials, a dry rubber made mainly of a polybutadiene rubber, and an oil, including: step (I) in which when the carbon black is dispersed into the dispersing solvent, at least one portion of the natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the natural rubber latex solution to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, step (III) of solidifying the rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black to produce the carbon-black-containing natural rubber solidified product, and then drying the solidified product
- This producing method makes it possible to produce a rubber composition improved, with an especially good balance, in braking performance on ice road surfaces, and low-thermogenic performance.
- the step (III) has at least a dehydrating step (III-A) of using a first uniaxial extruder to dehydrate the carbon-black-containing natural rubber solidified product while the product is heated up to 100 to 180° C., thereby producing a natural rubber wet master batch, and a drying plasticizing step (III-B) of using a second uniaxial extruder to plasticize the natural rubber wet master batch while the master batch is heated up to 120 to 180° C., thereby producing the just-above described natural rubber wet master batch further decreased in water content by percentage; and this rubber composition producing method has no cooling step between the dehydrating step (III-A) and the drying plasticizing step (III-B).
- the first uniaxial extruder is used to dehydrate the carbon-black-containing natural rubber solidified product while the product is heated up to 100 to 180° C., thereby producing a natural rubber wet master batch (the dehydrating step (III-A)); thus, the water content by percentage in the resultant natural rubber wet master batch can be efficiently decreased while the applied heat capacity and mechanical energy are restrained as much as possible.
- the second uniaxial extruder is used to plasticize this natural rubber wet master batch while the master batch is heated up to 120 to 180° C. (the drying plasticizing step (III-B)), thereby making it possible to produce the natural rubber wet master batch which is further decreased in water content by percentage and is hardly rubber-deteriorated.
- a rubber composition can be finally obtained which is improved in rubber physical properties, such as tearing resistance and stress property in its high-strain region.
- the present producing method has no cooling step between the dehydrating step (III-A) and the drying plasticizing step (III-B); thus, the water content by percentage in the resultant natural rubber wet master batch can be efficiently decreased while the heat capacity and mechanical energy applied to the master batch are restrained as much as possible.
- a manner for preventing the natural rubber wet master batch from being cooled between the dehydrating step (III-A) and the drying plasticizing step (III-B) may be, for example, a manner of connecting the first uniaxial extruder and the second uniaxial extruder to each other.
- the “cooling step” referred to in the present invention denotes, for example, a step in which the rubber wet master batch after the dehydrating step is cooled to a temperature of 40° C. or lower; and denotes, in a broader sense, a step in which the master batch is cooled to a temperature of 60° C. or lower.
- the water content by percentage of the natural rubber wet master batch obtained through the dehydrating step (III-A) is preferably from 1 to 10%.
- the water content by percentage of the natural rubber wet master batch obtained through the drying plasticizing step (III-B) is preferably 0.9% or less.
- the drying plasticizing step (III-B) a mechanical energy of 70 W/kg or less is applied to the rubber wet master batch inside the second uniaxial extruder.
- the final vulcanized rubber can be prevented from being rubber-deteriorated with a higher certainty while the water content by percentage is efficiently decreased.
- the natural rubber wet master batch is plasticized in the drying plasticizing step (III-B), an anti-aging agent is added and blended thereinto.
- the anti-aging agent can be more evenly dispersed in the natural rubber wet master batch, so that the final vulcanized rubber can be prevented from being rubber-deteriorated with an even higher certainty.
- the water content by percentage is decreased; thus, at the time of the drying plasticizing step (III-B), it hardly happens that the anti-aging agent flows out with the volatilization of water.
- the step (III) includes, after the drying plasticizing step (III-B), a shaping plasticizing step (III-C) of using a mixer further to plasticize the natural rubber wet master batch.
- a mechanical energy of 70 W/kg or less is applied to the rubber wet master batch inside the mixer.
- the mixer may be, for example, an open roll or a uniaxial extruder.
- a natural rubber wet master batch is used which is yielded by mixing at least a natural rubber latex and a carbon-black-containing slurry solution with each other in a liquid phase and drying the resultant mixture.
- step (I) in which when a carbon black is dispersed into a dispersing solvent to prepare the carbon-black-containing slurry solution, at least one portion of the natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the natural rubber latex to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, and step (III) of solidifying and drying the natural rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black.
- the natural rubber latex solution is a natural product produced by a metabolism effect of a plant, and is in particular preferably a natural rubber/water system solution, in which a dispersing solvent therein is water.
- the number-average molecular weight of a natural rubber in the natural rubber latex used in the present invention is preferably 2,000,000 or more, more preferably 2,500,000 or more.
- About the natural rubber latex, a concentrated latex, and a fresh latex called a field latex are usable without any discrimination.
- the total amount of the rubber components in the rubber composition is regarded as 100 parts by mass, it is preferred that the natural rubber (solid) is contained in an amount of 50 parts or more by mass.
- the carbon black may be any carbon black species usable in an ordinary rubber industry, such as SAF, ISAF, HAF, FEF or GPF, or may be any electroconductive carbon black species such as acetylene black or Ketjenblack.
- the carbon black may be a granulated carbon black species, which has been granulated, considering the handleability thereof in an ordinary rubber industry, or a non-granulated carbon black species.
- the resultant vulcanized rubber is more remarkably good in low-thermogenic performance, and further the rubber composition can keep the viscosity thereof at a low level to be also remarkably good in workability, which is preferred.
- N 2 SA nitrogen adsorption specific surface area
- the dispersing solvent is in particular preferably water, and may be, for example, water containing an organic solvent.
- the step (I) is a step of adding, when a carbon black is dispersed into a dispersing solvent, at least one portion of a natural rubber latex thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere. It is allowable to mix the natural rubber latex beforehand with the dispersing solvent, and then add the carbon black thereto to disperse the carbon black therein.
- the addition amount of the natural rubber latex is, for example, from 0.075 to 12% by mass of the whole of the used natural rubber latex (the total of the amounts added in the steps (I) and (II)).
- the percentage by mass of the solid (rubber) to the carbon black therein is preferably from 0.25 to 15%, more preferably from 0.5 to 6% by mass.
- the solid (rubber) concentration in the added natural rubber latex is preferably from 0.2 to 5% by mass, more preferably from 0.25 to 1.5% by mass.
- the method in the step (I) for mixing the carbon black with the dispersing solvent in the presence of the natural rubber latex may be a method of using an ordinary disperser, such as a high-shearing mixer, a High Shear Mixer, a homo-mixer, a ball mill, a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer or a colloid mill, to disperse the carbon black.
- an ordinary disperser such as a high-shearing mixer, a High Shear Mixer, a homo-mixer, a ball mill, a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer or a colloid mill, to disperse the carbon black.
- the “high-shearing mixer” denotes a mixer having a rotor rotatable at a high velocity and a fixed stator in which the rotor is rotated in the state that a precise clearance is set between the rotor and the stator, whereby a high-shearing effect acts.
- Such a high-shearing mixer may be a commercially available product. An example thereof is a product “High Shear Mixer” manufactured by Silverson.
- a surfactant may be added thereto to improve the carbon black in dispersibility.
- the surfactant may be a surfactant known in the rubber industry. Examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.
- an alcohol such as ethanol may be used.
- it is feared that the use of the surfactant is to make rubber properties of the final vulcanized rubber low.
- the blend amount of the surfactant is preferably 2 parts or less by mass, more preferably 1 part or less by mass for 100 parts by mass of the solid (rubber) in the natural rubber latex. It is preferred not to use any surfactant substantially.
- an anti-aging agent may be added thereto.
- the anti-aging agent may be an anti-aging agent known in the rubber industry. Examples thereof include amine type, phenol type, organic phosphite type, and thioether type agents.
- the 90% volume particle size ( ⁇ m) (“D90”) is preferably 31 ⁇ m or more, more preferably 35 ⁇ m or more.
- the carbon black is excellent in dispersibility in the slurry solution and can be further prevented from being re-aggregated, so that the slurry solution is excellent in storage stability and further the final vulcanized rubber is also excellent in low-thermogenic performance, endurance and rubber strength.
- the D90 of the natural-rubber-latex-particle-adhering carbon black means a value obtained by making a measurement about the carbon black plus the adhering natural rubber latex particles.
- the step (II) is a step of mixing the slurry solution with the rest of the natural rubber latex to produce a rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black.
- the method for mixing the slurry solution with the rest of the natural rubber latex in a liquid phase is not particularly limited, and may be a method of using an ordinary disperser, such as a high-shearing mixer, a High Shear Mixer, a homo-mixer, a ball mill, a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer or a colloid mill, to mix the slurry solution with the rest of the natural rubber latex solution.
- the whole of the mixing system, such as the disperser may be optionally heated.
- the solid (rubber) concentration is preferably higher than in the natural rubber latex added in the step (I) when the drying period and labor thereof in the next step (III) are considered.
- the solid (rubber) concentration is preferably from 10 to 60% by mass, more preferably from 20 to 30% by mass.
- the step (III) is a step of solidifying the rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black to produce a carbon-black-containing rubber solidified product.
- the method for the solidification is, for example, a method of incorporating a solidifier into the rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black to solidify the latex solution.
- the solidifier used in the solidifying step may be an acid, such as formic acid or sulfuric acid, or a salt, such as sodium chloride, that is usable usually for solidifying a rubber latex solution.
- the filler is contained in an amount of 40 to 70 parts by mass for 100 parts by mass of the rubber (solid). This case makes it possible to produce a natural rubber wet master batch which is improved, with a good balance, in carbon black dispersibility therein, and in low-thermogenic performance and endurance to be attained when the master batch is finally made into a vulcanized rubber.
- the rubber composition according to the present invention is a composition obtained by dry-mixing the above-mentioned natural rubber wet master batch with a dry rubber made mainly of a polybutadiene rubber, and an oil.
- the species of the polybutadiene rubber may be a species synthesized, using a cobalt (Co) catalyst, neodymium (Nd) catalyst, nickel (Ni) catalyst, titanium (Ti) catalyst, or lithium (Li) catalyst; or a species synthesized, using a polymerization catalyst composition containing a metallocene complex described in WO 2007/129670.
- a cobalt (Co) catalyst neodymium (Nd) catalyst, nickel (Ni) catalyst, titanium (Ti) catalyst, or lithium (Li) catalyst
- a species synthesized using a polymerization catalyst composition containing a metallocene complex described in WO 2007/129670.
- a polybutadiene rubber having a mass-average molecular weight of 350,000 to 1,000,000 and a cis-1,4-isomer content of 95% or more.
- the blend amount of the polybutadiene rubber is set preferably into the range of 20 to 50 parts by mass.
- the rubber composition in the present invention contains at least not only 50 parts or more by mass of the natural rubber but also 20 to 50 parts by mass of the polybutadiene rubber in 100 parts by mass of the rubber components
- a rubber different from any polybutadiene rubber may be blended as another species of the dry rubber.
- the blendable different rubber include polyisoprene rubber (IR), polystyrenebutadiene rubber (SBR), chloroprene rubber (CR), and nitrile rubber (NBR). These may be used alone or in the form of a blend of two or more thereof.
- the oil used in the present invention is an oil having a pour point of ⁇ 10° C. or lower, and an aniline point of 90° C. or higher.
- this oil By blending, in the rubber composition, this oil, the natural rubber wet master batch, and the polybutadiene rubber at a ratio in the specific range, the rubber composition is largely improved in braking performance on ice road surfaces and low-thermogenic performance when used as a raw material for tires, for example, their treads.
- this oil a commercially available product is also suitably usable.
- Examples thereof include a product “PROCESS P200” (pour point: ⁇ 15° C., aniline point: 102.3° C.) manufactured by JOMO, and a product “PS-32” (pour point: ⁇ 20° C., aniline point: 110° C.) manufactured by Idemitsu Kosan Co., Ltd.
- the blend amount of the oil in the rubber composition is preferably from 15 to 40 parts by mass.
- the rubber composition according to the present invention can be produced by, for example, a rubber composition producing method including step (I) in which when a carbon black is dispersed into a dispersing solvent, at least one portion of a natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the natural rubber latex solution to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, step (III) of solidifying the rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black to produce a carbon-black-containing natural rubber solidified product, and then drying the solidified product to produce a natural rubber wet master batch, and step (IV) of dry-mixing this natural rubber wet master batch with a dry rubber made mainly of a polybutadiene rubber, and an oil, wherein when the total amount of rubber
- the step (III) has at least the following dehydrating step (III-A) and drying plasticizing step (III-B) and no cooling step is set between the dehydrating step (III-A) and the drying plasticizing step (III-B): the dehydrating step (III-A) of using a first uniaxial extruder to dehydrate the carbon-black-containing natural rubber solidified product while the product is heated up to 100 to 180° C., thereby producing a natural rubber wet master batch; and the drying plasticizing step (III-B) of using a second uniaxial extruder to plasticize the natural rubber wet master batch while the master batch is heated up to 120 to 180° C., thereby producing the natural rubber wet master batch further decreased in water content by percentage.
- This case makes an improvement of a vulcanized rubber from the resultant rubber composition in rubber physical properties such as tearing resistance and high-strain-region stress property.
- the step (III) will be detailed.
- the dehydrating step (III-A) is a step of using a first uniaxial extruder to dehydrate the carbon-black-containing natural rubber solidified product while the product is heated up to 100 to 180° C., thereby producing a natural rubber wet master batch.
- the first uniaxial extruder may be any uniaxial extruder usable in an ordinary rubber industry.
- the barrel diameter (D), the barrel length (L), and further the ratio of the barrel length to the barrel diameter (L/D) may be set at will.
- the gap width (slit width) between the inner wall of the barrel and its screw is preferably from 0.1 to 0.9 mm.
- a uniaxial extruder having no pin portions projected inward from the barrel inner wall of a discharging port side region (expander region) of the uniaxial extruder. If the expander region has pin portions, a high shearing force acts onto the rubber components passing by the pin portions so that polymer chains in the rubber components are cleaved. Thus, deterioration of the rubber components advances easily. As a result, the vulcanized rubber to be finally obtained tends to be deteriorated in tearing resistance and high-strain-region stress property.
- the set temperature of the inside of the barrel of the first uniaxial extruder (the heating temperature for the filler-containing rubber solidified product) is preferably from 160 to 220° C., more preferably from 180 to 200° C. to decrease the water content by percentage efficiently in the resultant rubber wet master batch while the heat capacity and mechanical energy applied thereto are restrained as much as possible.
- the water content by percentage is preferably from 1 to 10%, more preferably from 1 to 8%.
- the drying plasticizing step (III-B) is a step of using a second uniaxial extruder to plasticize the natural rubber wet master batch while the master batch is heated up to 120 to 180° C., thereby producing the natural rubber wet master batch further decreased in water content by percentage.
- the second uniaxial extruder may be equivalent to the first uniaxial extruder.
- the second uniaxial extruder preferably has no pin portions in the barrel inner wall of its expander region.
- the set temperature of the inside of the barrel of the second uniaxial extruder (the heating temperature for the natural rubber wet master batch) is preferably from 160 to 220° C., more preferably from 160 to 200° C. to decrease the water content by percentage efficiently in the resultant rubber wet master batch while the heat capacity and mechanical energy applied thereto are restrained as much as possible.
- the mechanical energy applied to the natural rubber wet master batch in the second uniaxial extruder is 70 W/kg or less. This case finally gives, from the natural rubber wet master batch as a raw material, a vulcanized rubber excellent in tearing resistance and high-strain-region stress property.
- the water content by percentage is preferably 0.9% or less.
- the anti-aging agent may be an anti-aging agent usable ordinarily for rubbers, and examples thereof include aromatic amine type anti-aging agents, amine-ketone type anti-aging agents, monophenolic type anti-aging agents, bisphenolic type anti-aging agents, polyphenolic type anti-aging agents, dithiocarbamic acid salt type anti-aging agents, and thiourea type anti-aging agents.
- the content of the anti-aging agent(s) is preferably from 0.3 to 3 parts by mass, more preferably from 0.5 to 1.5 parts by mass for 100 parts by mass of the rubber components (solid) in the rubber wet master batch.
- the method for preventing the natural rubber wet master batch from being cooled between the dehydrating step (III-A) and the drying plasticizing step (III-B) may be, for example, a method of connecting the first and second uniaxial extruders to each other through a connecting tool, such as a heatable cylinder having a short barrel length, or a method of connecting the first and second uniaxial extruders directly to each other.
- the following temperature is set preferably to 40° C. or higher, more preferably to 60° C. or higher, in particular preferably to 120° C. or higher: the temperature of the natural rubber wet master batch before the master batch is charged from the first uniaxial extruder into the connecting tool; or the temperature of the natural rubber wet master batch before the master batch is charged into the second uniaxial extruder when the first and second uniaxial extruders are connected directly to each other.
- the step (III) may have, after the drying plasticizing step (III-B), a shaping plasticizing step (III-C) of using a mixer further to plasticize the above-mentioned natural rubber wet master batch.
- the mixer is preferably, for example, an open roll or a uniaxial extruder.
- the mechanical energy applied to the natural rubber wet master batch in the mixer is 70 W/kg or less since this case is to make the vulcanized rubber to be finally obtained from the natural rubber wet master batch as a raw material excellent in tearing resistance and high-strain-region stress property.
- the shaping machine may be a baler.
- the water content by percentage in the natural rubber wet master batch has been sufficiently decreased; accordingly, the water content by percentage in the natural rubber wet master batch obtained through the shaping plasticizing step (III-C) may be about 0.9% or less as in the case with the natural rubber wet master batch after the drying plasticizing step (III-B).
- the natural rubber wet master batch is dry-mixed with a dry rubber made mainly of a polybutadiene rubber, and an oil.
- a dry rubber other than the polybutadiene rubber the same as described above as the different rubber may be optionally blended.
- at least one of a plant granular material, a grain granular material, and a granular region of a grain core material may be blended into the rubber composition.
- the plant granular material is a granular material obtained by pulverizing shells of seeds of a walnut, a camellia or the like, or nuclei of fruits of a peach, a Japanese apricot or the like by a known method, these shells or nuclei having a hardness larger than ices, i.e., a Mohs' hardness of 2 or more.
- the plant granular material is projected from the rubber surface to produce a road-surface scratching effect, thereby exhibiting an effect of preventing the rubber from slipping on ice road surfaces.
- the material is preferably a plant granular material subjected to surface treatment for improving the rubber-bondability thereof.
- the blend amount thereof is preferably from 0.5 to 10 parts by mass for 100 parts by mass of the rubber components in the rubber composition.
- Specific examples thereof include a pulverized material of nuts or shells of fruits such as a peach, Japanese apricot, walnut, ginkgo nut, peanut, or Japanese chestnut; grains such as rice, barley, wheat, foxtail millet, Japanese millet and corn; and core materials thereof.
- the dry-mixing step (IV) further has at least a kneading step (IV-A) and a vulcanization-related blending agent kneading step (IV-B).
- the kneading step (IV-A) is a step of charging the polybutadiene rubber, the oil, and one or more optional blending agents other than any vulcanization-related blending agent into the natural rubber wet master batch obtained through the drying plasticizing step (III-B) or the shaping plasticizing step (III-C), and then using a mixing/dispersing device to knead all the components.
- the blending agent(s) include another rubber, stearic acid, zinc flower, an anti-aging agent, silica, a silane coupling agent, a wax, and a working aid.
- a rubber product after the master batch is vulcanized is to be heightened in strength; the rubber is made good in rubber-kneading workability; and the rubber is prevented from being deteriorated by radicals generated by the cleavage of the rubber molecular chains.
- a gear-engaging type Banbury mixer for example, a gear-engaging type Banbury mixer, a tangential line type Banbury mixer, or a kneader is usable. In particular, the use of a gear-engaging type Banbury mixer is preferred.
- One or more vulcanization-related blending agents such as a vulcanizer, for example, sulfur, and/or a vulcanization promoter, are charged into the rubber composition obtained through the kneading step (IV-A), and then the entire components are kneaded and mixed with each other.
- a vulcanizer for example, sulfur, and/or a vulcanization promoter
- the rubber composition obtained through the vulcanization-related blending agent kneading step (IV-B) is heated to a predetermined temperature or higher, the vulcanizer in the rubber composition reacts with the rubber molecules so that crosslinkage structures are formed between the rubber molecules. Thus, the molecules are made into a three-dimensional network to give rubber elasticity to the rubber composition.
- the sulfur is a sulfur species for ordinary rubbers. Examples thereof include powdery sulfur, precipitated sulfur, insoluble sulfur, and highly dispersed sulfur.
- the sulfur content in the rubber composition according to the present invention is preferably from 0.3 to 6 parts by mass for 100 parts by mass of the rubber components. If the sulfur content is less than 0.3 parts by mass, the vulcanized rubber is short in crosslinkage density to be lowered in rubber strength and others. If the sulfur content is more than 6.5 parts by mass, the vulcanized rubber is deteriorated, particularly, in both of heat resistance and endurance. In order for the vulcanized rubber to ensure rubber strength satisfactorily and be further improved in heat resistance and endurance, the sulfur content more preferably ranges from 1.5 to 5.5 parts by mass for 100 parts by mass of the rubber components.
- the vulcanization promoter may be a vulcanization promoter commonly used for rubber vulcanization. Examples thereof include sulfenamide type vulcanization promoters, thiuram type vulcanization promoters, thiazole type vulcanization promoters, thiourea type vulcanization promoters, guanidine type vulcanization promoters, and dithiocarbamic acid salt type vulcanization promoters. These may be used alone or in the form of an appropriate mixture.
- the content of the vulcanization promoter(s) is preferably from 1 to 5 parts by mass, more preferably from 1.5 to 4 parts by mass for 100 parts by mass of the rubber components.
- Carbon black “N339” “SEAST KH”; N 2 SA: 91 m 2 /g (manufactured by Tokai Carbon Co., Ltd.),
- Carbon black “N234” “SEAST 7HM”; N 2 SA: 119 m 2 /g (manufactured by Tokai Carbon Co., Ltd.), and
- Carbon black “N550” “SEAST SO”; N 2 SA: 40 m 2 /g (manufactured by Tokai Carbon Co., Ltd.);
- Solidifier Formic acid (adjusted into a pH of 1.2 by diluting a 10% solution of a first class 85%-concentration agent) (manufactured by Nacalai Tesque, Inc.); e) Natural rubber: RSS #3; f) Polybutadiene rubber: “HIGHCIS BR” (manufactured by JSR Corporation; g) Silica: “NIPSIL AQ” (manufactured by Nippon Silica Industrial Co., Ltd.); h) Silane coupling agent: “Si75” (manufactured by Degussa);
- Oil A “PROCESS NC140”; pour point: 7.5° C., and aniline point: 91.2° C. (manufactured by JOMO),
- Oil B “PROCESS P200”; pour point: ⁇ 15° C., and aniline point: 102.3° C. (manufactured by JOMO), and
- Oil C “PS-32”; pour point: ⁇ 20° C., and aniline point: 110° C. (manufactured by Idemitsu Kosan Co., Ltd.),
- Anti-aging agent “ANTIGEN 6C” (manufactured by Sumitomo Chemical Co., Ltd.); m) Wax: “OZOACE 0355” (manufactured by Nippon Seiro Co., Ltd.); n) Vulcanization promoter: “SOXINOL CZ” (manufactured by Sumitomo Chemical Co., Ltd.); o) Sulfur: “Powdery sulfur” (manufactured by Tsurumi Chemical Industry Co., Ltd.); p) Plant granular material: “SOFT GRIT #46” (manufactured by Nippon Walnut Co., Ltd.) treated with an ordinary RF adhesive; and q) Granular material of a grain core material: CORN COBS GRIT 40/60 (corncob) manufactured by Nippon Walnut Co., Ltd.
- Carbon black (N339) was added into a diluted natural rubber latex, the concentration therein being adjusted to 0.5% by mass, so as to give a carbon black concentration of 5% by mass.
- a device, ROBOMIX, manufactured by Primix Corp. was used to disperse the carbon black therein (ROBOMIX conditions: rotation at 9000 rpm for 30 minutes) to produce a slurry solution containing the carbon black to which natural rubber latex particles adhered (step (I)).
- step (I) To the slurry solution produced in the step (I), which contained the natural-rubber-latex-particle-adhering carbon black, was added the rest of the natural rubber latex solution (the solid (rubber) concentration therein was adjusted to 25% by mass by the addition of water) to adjust the total of the solid (rubber) content therein and that in the natural rubber latex solution used in the step (I) to 50 parts by mass.
- a mixer for household use, model SM-L56, manufactured by Sanyo Electric Co., Ltd. was used to mix these components with each other (mixer conditions: rotation at 11300 rpm for 30 minutes) to produce a carbon-black-containing natural rubber latex solution (step (II)).
- the carbon-black-containing natural rubber latex solution 25 parts by mass of the carbon black was contained for 50 parts by mass of the rubber components (solid).
- a 10%-by-mass solution of formic acid in water as a solidifier was added to the carbon-black-containing natural rubber latex solution produced in the step (II) until the pH of the whole turned to 4 (step (III)).
- a screen ( ⁇ 2 punching, manufactured by Toyo Screen Kogyo Co., Ltd.) was used to remove water from the solution containing the resultant carbon-black-containing natural rubber solidified product, thereby producing a carbon-black-containing rubber solidified product having a water content of 65.1%.
- the solidified product may be centrifuged.
- An instrument, model H-22 (BS-030) manufactured by Kokusan Co., Ltd., may be used to subject the solidified product to solid-liquid separation (separating conditions: rotation at 29000 rpm for 10 minutes), thereby producing a filler-containing rubber solidified product having a water content of 46.2%.
- the natural rubber wet master batch was subjected to the above-defined dehydrating step and drying plasticizing step while the following were each set into a value described in Table 1: the heating temperature, and the mechanical energy applied to the natural rubber wet master batch (WMB) in each of the steps; and the water content by percentage in the natural rubber wet master batch obtained after each of the steps.
- Table 1 the temperature change between the dehydrating step (III-A) and the drying plasticizing step (III-B) was only 30° C. Thus, it is understood that the present process had no cooling step between the dehydrating step (III-A) and the drying plasticizing step (III-B).
- the rubber hardnesses of the vulcanized rubber were measured at 23° C. and ⁇ 5° C., respectively, in accordance with JIS K6253.
- a viscoelasticity meter manufactured by Toyo Seiki Seisaku-sho, Ltd. was used to measure the storage elastic moduli E′ of the rubber composition at respective temperatures of ⁇ 5° C. and ⁇ 25° C. and at a frequency of 10 Hz, a static strain of 10%, and a dynamic strain of ⁇ 0.25%.
- the reciprocal number of each of the resultant values was shown as an index under the condition that the value of Comparative Example 1 was regarded as 100. As the index is larger, the composition is smaller in storage elastic modulus E′ so that the composition product is wider in contact area at low temperatures to be better in low-temperature performance.
- the 2000-cc FF car was run at a speed of 40 km/h on an ice road surface ( ⁇ 3 ⁇ 3° C.), and then the braking distance thereof was measured (the average value under the condition that n was 10) when the car was subjected to ABS operation.
- the resultant value was shown as an index under the condition that the value of Comparative Example 1 was regarded as 100. As the numeral value is larger, the rubber composition is better in that the braking distance is shorter.
- the low-thermogenic performance of the produced vulcanized rubber was evaluated on the basis of the loss tangent tans thereof.
- the tans was measured at 50 Hz, 80° C. and a dynamic strain of 2%, using a rheospectrometer, E4000 manufactured by UBM, and the measured value was converted to an index.
- the index was an index under the condition that the value of Comparative Example 1 was regarded as 100, and the index was used to make an evaluation. As the numerical value is smaller, the vulcanized rubber is lower-thermogenic to be better.
- the rubber composition was measured at a slip ratio of 30%, an applied load of 40 N and a dropping sand amount of 20 g/minute, and then evaluated on the basis of the measured result.
- the resultant value was shown as an index under the condition that the value of Comparative Example 1 was regarded as 100. As the numeral value is larger, the rubber composition is better in abrasion resistance.
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Abstract
A rubber composition obtained by dry-mixing a natural rubber wet master batch yielded by mixing at least a natural rubber latex and a carbon-black-containing slurry solution with each other in a liquid phase and drying the resultant mixture, a dry rubber made mainly of a polybutadiene rubber, and an oil, wherein when the total amount of rubber components in the rubber composition is regarded as 100 parts by mass, the natural rubber is contained in an amount of 50 parts or more by mass, and the polybutadiene rubber is contained in an amount of 20 to 50 parts by mass, and the oil has a pour point of −10 C or lower, and an aniline point of 90 C or higher, and the blend amount of the oil is from 15 to 40 parts by mass for 100 parts by mass of the rubber components.
Description
- This Application is a Divisional of U.S. application Ser. No. 14/372,932 filed Jul. 17, 2014, which is a 371 National Stage of PCT/JP2012/081683 filed Dec. 6, 2012, which claims priority to Japanese Patent Application No. 2012-067543 filed Mar. 23, 2012, all of which are herein incorporated by reference.
- The present invention relates to a rubber composition, and a method for producing the same, specifically, a rubber composition that can be largely decreased in E′ storage elastic modulus in a low temperature range, can be greatly improved, particularly, in braking performance on an ice and snow road surface (referred to also as an “ice road surface” hereinafter) when used as a raw material for tires, for example, their treads, and can be further improved in low-thermogenic performance.
- Rubbers for treads of studless tires used for running on ice road surfaces are required to have excellent on-ice and on-snow performances. In order to improve tires in frictional performances on ice road surfaces, for example, the following method has been hitherto adopted: a method of not only using a polybutadiene rubber, which is low in glass transition temperature, or blending a softening agent, such as oil, into a tread rubber to maintain a low hardness of the tread rubber even at low temperatures, thereby improving the rubber in hysteresis frictional performance, but also blending a hard material such as hollow particles, glass fiber or plant granular material thereinto, thereby improving the rubber in scratch frictional performance. In order to improve the tread rubber, particularly, in gripping performance on a wetting road surface (referred to also as a “wet road surface” hereinafter), a method is adopted in which the blend proportion of a filler or a softening agent such as oil is increased in the composition of the rubber. However, a vulcanized rubber obtained therefrom tends to be lowered in low-thermogenic performance and abrasion resistance.
- Apart from the above, in the rubber industry, known is the use of a natural rubber wet master batch for improving a rubber composition containing a filler, such as carbon black, in workability when this composition is produced, or in filler dispersibility therein (for example, Patent Document 1 listed below). This is a technique of: mixing, in a liquid phase, a natural rubber latex with a filler-containing slurry solution obtained by mixing a filler and a dispersing solvent with each other at a predetermined ratio beforehand and then dispersing the filler into the dispersing solvent by mechanical force; subsequently adding a solidifier such as an acid to the mixture to solidify the mixture; collecting the solidified product; and then drying the product. The use of the natural rubber wet master batch gives a rubber composition better in filler dispersibility therein and in rubber physical properties such as workability and reinforceability as compared with the use of a rubber dry master batch obtained by dry-mixing a filler with a rubber.
- Patent Document 2 listed below describes a rubber composition for ice-and-snow-road tire treads which contains: a natural rubber wet master batch containing a carbon black having a nitrogen adsorption specific surface area of 105 to 155 m2/g, and a CTAB adsorption specific surface area of 100 to 150 m2/g; and a polybutadiene rubber.
- Furthermore, Patent Document 3 listed below states that a rubber wet master batch which is one wherein a filler is evenly dispersed and the filler is restrained from being re-aggregated with time, and which is usable as a raw material for a vulcanized rubber excellent in low-thermogenic performance, endurance and rubber strength can be produced by a rubber-wet-master-batch-producing method including step (I) of adding, when the filler is dispersed into a dispersing solvent, at least one portion of a rubber latex solution thereto, thereby producing a slurry solution containing the filler to which rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the rubber latex solution to produce a rubber latex solution containing the just-above described rubber-latex-particle-adhering filler, and step (III) of solidifying and drying the rubber latex solution containing the rubber-latex-particle-adhering filler.
- Patent Document 1: JP-A-2004-99625
- Patent Document 2: JP-A-2004-107482
- Patent Document 3: Japanese Patent No. 4738551
- However, the inventor has made eager investigations so that a vulcanized rubber from the rubber composition described in each of Patent Documents 1 and 2 has turned out to be raised in E′ in a low temperature range so as to be deteriorated in braking performance on an ice road surface, and be also deteriorated in low-thermogenic performance.
- The rubber-wet-master-batch-containing rubber composition described in Patent Document 3 is excellent in filler dispersibility therein, and is improved in low-thermogenic performance. However, it has become evident that when this rubber composition is used for, for example, a tire tread, there remains room for a further improvement in braking performance, particularly, on ice road surfaces.
- In light of this actual situation, the present invention has been made. An object thereof is to provide a rubber composition that can be largely decreased in E′ in a low temperature range, can be greatly improved, particularly, in braking performance on an ice and snow road surface when used as a raw material for tires, for example, their treads, and can be further improved in low-thermogenic performance; and a method for producing the composition.
- The object can be attained by the present invention as described hereinafter. Accordingly, the present invention relates to a rubber composition obtained by dry-mixing a natural rubber wet master batch yielded by mixing at least a natural rubber latex and a carbon-black-containing slurry solution with each other in a liquid phase and drying the resultant mixture, a dry rubber made mainly of a polybutadiene rubber, and an oil, wherein when the total amount of rubber components in the rubber composition is regarded as 100 parts by mass, the natural rubber is contained in an amount of 50 parts or more by mass, and the polybutadiene rubber is contained in an amount of 20 to 50 parts by mass, and the oil has a pour point of −10° C. or lower, and an aniline point of 90° C. or higher, and the blend amount of the oil is from 15 to 40 parts by mass for 100 parts by mass of the rubber components.
- Since the rubber composition according to the present invention is a composition obtained by dry-mixing the natural rubber wet master batch with the dry rubber, which is made mainly of the polybutadiene rubber, at the specific ratio, the composition is excellent in carbon black dispersibility therein and can be decreased in E′ in a low temperature range. Furthermore, the specific amount of the oil having specific physical properties (the pour point and the aniline point) is blended into the composition; thus, the composition can keep the rubber hardness thereof at a low level even in a low temperature range to be improved in braking performance on ice road surfaces. When the natural rubber wet master batch is, particularly, a master batch produced through the following steps, the rubber composition is especially excellent in filler dispersibility therein: step (I) in which when a carbon black is dispersed into a dispersing solvent to prepare the carbon-black-containing slurry solution, at least one portion of the natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the natural rubber latex to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, and step (III) of solidifying and drying the natural rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black. Consequently, when these rubber components are used together with the specific oil, the composition is improved, with an especially good balance, in braking performance on ice road surfaces and low-thermogenic performance.
- As described above, a vulcanized rubber from the rubber composition according to the present invention is excellent in low-thermogenic performance, and further in braking performance on ice road surfaces. Accordingly, the rubber composition according to the present invention is particularly useful as a rubber composition for studless tires.
- In the rubber composition, it is preferred that the natural rubber wet master batch contains the carbon black in an amount of 40 to 70 parts by mass for 100 parts by mass of the rubber components of the master batch. It is more preferred that the carbon black contained in the natural rubber wet master batch has a nitrogen adsorption specific surface area (N2SA) of 100 m2/g or less. According to this form, the rubber composition is further improved in low-thermogenic performance and can keep the viscosity thereof at a low level to be also excellent in workability.
- When the total amount of the present rubber components in the rubber composition is regarded as 100 parts by mass, further when the total amount of the present rubber components in the rubber composition is regarded as 100 parts by mass, at least one of a plant granular material, a grain granular material, and a granular region of a grain core material may be further contained in an amount of 0.5 to 10 parts by mass. In this case, the vulcanized rubber is improved in scratch frictional performance to be further improved in braking performance on ice road surfaces.
- Additionally, the present invention relates to a method for producing a rubber composition comprising a natural rubber wet master batch obtained by use of a carbon black, a dispersing solvent and a natural rubber latex as raw materials, a dry rubber made mainly of a polybutadiene rubber, and an oil, including: step (I) in which when the carbon black is dispersed into the dispersing solvent, at least one portion of the natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the natural rubber latex solution to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, step (III) of solidifying the rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black to produce the carbon-black-containing natural rubber solidified product, and then drying the solidified product to produce a natural rubber wet master batch, and step (IV) of dry-mixing this natural rubber wet master batch with the dry rubber, which is made mainly of the polybutadiene rubber, and the oil, wherein when the total amount of rubber components in the rubber composition is regarded as 100 parts by mass, the natural rubber is contained in an amount of 50 parts or more by mass, and the polybutadiene rubber is contained in an amount of 20 to 50 parts by mass, and the oil has a pour point of −10° C. or lower, and an aniline point of 90° C. or higher, and the blend amount of the oil is from 15 to 40 parts by mass for 100 parts by mass of the rubber components. This producing method makes it possible to produce a rubber composition improved, with an especially good balance, in braking performance on ice road surfaces, and low-thermogenic performance.
- In this producing method, it is preferred that: the step (III) has at least a dehydrating step (III-A) of using a first uniaxial extruder to dehydrate the carbon-black-containing natural rubber solidified product while the product is heated up to 100 to 180° C., thereby producing a natural rubber wet master batch, and a drying plasticizing step (III-B) of using a second uniaxial extruder to plasticize the natural rubber wet master batch while the master batch is heated up to 120 to 180° C., thereby producing the just-above described natural rubber wet master batch further decreased in water content by percentage; and this rubber composition producing method has no cooling step between the dehydrating step (III-A) and the drying plasticizing step (III-B).
- According to this producing method, the first uniaxial extruder is used to dehydrate the carbon-black-containing natural rubber solidified product while the product is heated up to 100 to 180° C., thereby producing a natural rubber wet master batch (the dehydrating step (III-A)); thus, the water content by percentage in the resultant natural rubber wet master batch can be efficiently decreased while the applied heat capacity and mechanical energy are restrained as much as possible. Furthermore, the second uniaxial extruder is used to plasticize this natural rubber wet master batch while the master batch is heated up to 120 to 180° C. (the drying plasticizing step (III-B)), thereby making it possible to produce the natural rubber wet master batch which is further decreased in water content by percentage and is hardly rubber-deteriorated. As a result, a rubber composition can be finally obtained which is improved in rubber physical properties, such as tearing resistance and stress property in its high-strain region.
- For example, if the natural rubber wet master batch after the dehydrating step (III-A) is cooled down to room temperature not later than the drying plasticizing step (III-B), a larger heat capacity and mechanical energy would be given to the natural rubber wet master batch when the drying plasticizing step (III-B) is performed. However, the present producing method has no cooling step between the dehydrating step (III-A) and the drying plasticizing step (III-B); thus, the water content by percentage in the resultant natural rubber wet master batch can be efficiently decreased while the heat capacity and mechanical energy applied to the master batch are restrained as much as possible. A manner for preventing the natural rubber wet master batch from being cooled between the dehydrating step (III-A) and the drying plasticizing step (III-B) may be, for example, a manner of connecting the first uniaxial extruder and the second uniaxial extruder to each other. The “cooling step” referred to in the present invention denotes, for example, a step in which the rubber wet master batch after the dehydrating step is cooled to a temperature of 40° C. or lower; and denotes, in a broader sense, a step in which the master batch is cooled to a temperature of 60° C. or lower.
- In the present rubber composition producing method, the water content by percentage of the natural rubber wet master batch obtained through the dehydrating step (III-A) is preferably from 1 to 10%. The water content by percentage of the natural rubber wet master batch obtained through the drying plasticizing step (III-B) is preferably 0.9% or less. Ina case where in the present invention a drying process extending over the two stages (the dehydrating step (III-A) and the drying plasticizing step (III-B)) is performed, and further the water content by percentage after each of the steps is set in the range described just above, the rubber wet master batch can be efficiently decreased in water content by percentage while a vulcanized rubber to be finally obtained therefrom is certainly prevented from being rubber-deteriorated.
- In the rubber composition producing method, it is preferred that in the drying plasticizing step (III-B), a mechanical energy of 70 W/kg or less is applied to the rubber wet master batch inside the second uniaxial extruder. In this case, the final vulcanized rubber can be prevented from being rubber-deteriorated with a higher certainty while the water content by percentage is efficiently decreased.
- In the rubber composition producing method, it is preferred that when the natural rubber wet master batch is plasticized in the drying plasticizing step (III-B), an anti-aging agent is added and blended thereinto. In this case, the anti-aging agent can be more evenly dispersed in the natural rubber wet master batch, so that the final vulcanized rubber can be prevented from being rubber-deteriorated with an even higher certainty. In the natural rubber wet master batch that has undergone the dehydrating step (III-A), the water content by percentage is decreased; thus, at the time of the drying plasticizing step (III-B), it hardly happens that the anti-aging agent flows out with the volatilization of water.
- In the rubber composition producing method, it is preferred that the step (III) includes, after the drying plasticizing step (III-B), a shaping plasticizing step (III-C) of using a mixer further to plasticize the natural rubber wet master batch. In the shaping plasticizing step (III-C), it is more preferred that a mechanical energy of 70 W/kg or less is applied to the rubber wet master batch inside the mixer. In this case, the water content by percentage can be more efficiently decreased while the final vulcanized rubber is certainly prevented from being rubber-deteriorated. The mixer may be, for example, an open roll or a uniaxial extruder.
- About the rubber composition according to the present invention, as a raw material thereof, a natural rubber wet master batch is used which is yielded by mixing at least a natural rubber latex and a carbon-black-containing slurry solution with each other in a liquid phase and drying the resultant mixture. It is preferred to use, particularly, a natural rubber wet master batch produced through the following steps since the rubber composition is remarkably good in carbon black dispersibility therein and a vulcanized rubber therefrom is improved in low-thermogenic performance: step (I) in which when a carbon black is dispersed into a dispersing solvent to prepare the carbon-black-containing slurry solution, at least one portion of the natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the natural rubber latex to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, and step (III) of solidifying and drying the natural rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black.
- The natural rubber latex solution is a natural product produced by a metabolism effect of a plant, and is in particular preferably a natural rubber/water system solution, in which a dispersing solvent therein is water. The number-average molecular weight of a natural rubber in the natural rubber latex used in the present invention is preferably 2,000,000 or more, more preferably 2,500,000 or more. About the natural rubber latex, a concentrated latex, and a fresh latex called a field latex are usable without any discrimination. When the total amount of the rubber components in the rubber composition is regarded as 100 parts by mass, it is preferred that the natural rubber (solid) is contained in an amount of 50 parts or more by mass.
- The carbon black may be any carbon black species usable in an ordinary rubber industry, such as SAF, ISAF, HAF, FEF or GPF, or may be any electroconductive carbon black species such as acetylene black or Ketjenblack. The carbon black may be a granulated carbon black species, which has been granulated, considering the handleability thereof in an ordinary rubber industry, or a non-granulated carbon black species.
- In the case of using, as the carbon black, one having a nitrogen adsorption specific surface area (N2SA) of 100 m2/g or less, the resultant vulcanized rubber is more remarkably good in low-thermogenic performance, and further the rubber composition can keep the viscosity thereof at a low level to be also remarkably good in workability, which is preferred.
- The dispersing solvent is in particular preferably water, and may be, for example, water containing an organic solvent.
- Hereinafter, a description will be made about the natural rubber wet master batch produced through the steps (I) to (III).
- The step (I) is a step of adding, when a carbon black is dispersed into a dispersing solvent, at least one portion of a natural rubber latex thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere. It is allowable to mix the natural rubber latex beforehand with the dispersing solvent, and then add the carbon black thereto to disperse the carbon black therein. It is also allowable to add the carbon black into the dispersing solvent, and next disperse the carbon black in the dispersing solvent while the natural rubber latex is added thereto at a predetermined adding speed; or add the carbon black into the dispersing solvent, and next disperse the carbon black in the dispersing solvent while multiple divided fractions of the natural rubber latex are added thereto, these fractions being equal to each other in volume. By dispersing the carbon black into the dispersing solvent in the state that the natural rubber latex is present, the above-mentioned slurry solution can be produced, which contains the natural-rubber-latex-particle-adhering carbon black. In the step (I), the addition amount of the natural rubber latex is, for example, from 0.075 to 12% by mass of the whole of the used natural rubber latex (the total of the amounts added in the steps (I) and (II)).
- In the step (I), in the added natural rubber latex, the percentage by mass of the solid (rubber) to the carbon black therein is preferably from 0.25 to 15%, more preferably from 0.5 to 6% by mass. The solid (rubber) concentration in the added natural rubber latex is preferably from 0.2 to 5% by mass, more preferably from 0.25 to 1.5% by mass. In these cases, a rubber wet master batch can be produced which is heightened in carbon black dispersibility therein while the natural rubber latex particles are certainly caused to adhere onto the carbon black.
- The method in the step (I) for mixing the carbon black with the dispersing solvent in the presence of the natural rubber latex may be a method of using an ordinary disperser, such as a high-shearing mixer, a High Shear Mixer, a homo-mixer, a ball mill, a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer or a colloid mill, to disperse the carbon black.
- The “high-shearing mixer” denotes a mixer having a rotor rotatable at a high velocity and a fixed stator in which the rotor is rotated in the state that a precise clearance is set between the rotor and the stator, whereby a high-shearing effect acts. In order to generate such a high-shearing effect, it is preferred to set the clearance between the rotor and the stator, and the peripheral velocity of the rotor to 0.8 mm or less, and 5 m/s or more, respectively. Such a high-shearing mixer may be a commercially available product. An example thereof is a product “High Shear Mixer” manufactured by Silverson.
- In the case of mixing the carbon black and the dispersing solvent with each other in the presence of the natural rubber latex in the present invention to produce the slurry solution containing the natural-rubber-latex-particle-adhering carbon black, a surfactant may be added thereto to improve the carbon black in dispersibility. The surfactant may be a surfactant known in the rubber industry. Examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Instead of the surfactant or in addition to the surfactant, an alcohol such as ethanol may be used. However, it is feared that the use of the surfactant is to make rubber properties of the final vulcanized rubber low. Thus, the blend amount of the surfactant is preferably 2 parts or less by mass, more preferably 1 part or less by mass for 100 parts by mass of the solid (rubber) in the natural rubber latex. It is preferred not to use any surfactant substantially. In order to restrain a deterioration of the solid (rubber) in the natural rubber latex in the steps (I) and (II), an anti-aging agent may be added thereto. The anti-aging agent may be an anti-aging agent known in the rubber industry. Examples thereof include amine type, phenol type, organic phosphite type, and thioether type agents.
- About the natural-rubber-latex-particle-adhering carbon black in the slurry solution produced in the step (I), the 90% volume particle size (μm) (“D90”) is preferably 31 μm or more, more preferably 35 μm or more. In this case, the carbon black is excellent in dispersibility in the slurry solution and can be further prevented from being re-aggregated, so that the slurry solution is excellent in storage stability and further the final vulcanized rubber is also excellent in low-thermogenic performance, endurance and rubber strength. In the present invention, the D90 of the natural-rubber-latex-particle-adhering carbon black means a value obtained by making a measurement about the carbon black plus the adhering natural rubber latex particles.
- The step (II) is a step of mixing the slurry solution with the rest of the natural rubber latex to produce a rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black. The method for mixing the slurry solution with the rest of the natural rubber latex in a liquid phase is not particularly limited, and may be a method of using an ordinary disperser, such as a high-shearing mixer, a High Shear Mixer, a homo-mixer, a ball mill, a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer or a colloid mill, to mix the slurry solution with the rest of the natural rubber latex solution. At the time of the mixing, the whole of the mixing system, such as the disperser, may be optionally heated.
- In the rest of the natural rubber latex, the solid (rubber) concentration is preferably higher than in the natural rubber latex added in the step (I) when the drying period and labor thereof in the next step (III) are considered. Specifically, the solid (rubber) concentration is preferably from 10 to 60% by mass, more preferably from 20 to 30% by mass.
- The step (III) is a step of solidifying the rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black to produce a carbon-black-containing rubber solidified product. The method for the solidification is, for example, a method of incorporating a solidifier into the rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black to solidify the latex solution.
- The solidifier used in the solidifying step may be an acid, such as formic acid or sulfuric acid, or a salt, such as sodium chloride, that is usable usually for solidifying a rubber latex solution.
- In the natural rubber wet master batch obtained through step (III), it is preferred about the ratio between the rubber components and the carbon black that the filler is contained in an amount of 40 to 70 parts by mass for 100 parts by mass of the rubber (solid). This case makes it possible to produce a natural rubber wet master batch which is improved, with a good balance, in carbon black dispersibility therein, and in low-thermogenic performance and endurance to be attained when the master batch is finally made into a vulcanized rubber.
- The rubber composition according to the present invention is a composition obtained by dry-mixing the above-mentioned natural rubber wet master batch with a dry rubber made mainly of a polybutadiene rubber, and an oil.
- The species of the polybutadiene rubber (BR) may be a species synthesized, using a cobalt (Co) catalyst, neodymium (Nd) catalyst, nickel (Ni) catalyst, titanium (Ti) catalyst, or lithium (Li) catalyst; or a species synthesized, using a polymerization catalyst composition containing a metallocene complex described in WO 2007/129670. In order to improve the rubber composition in abrasion resistance, workability, tearing resistance and low-thermogenic performance with a good balance, it is preferred to blend thereinto a polybutadiene rubber having a mass-average molecular weight of 350,000 to 1,000,000. It is particularly preferred to blend thereinto a polybutadiene rubber having a mass-average molecular weight of 350,000 to 1,000,000 and a cis-1,4-isomer content of 95% or more. When the total amount of the rubber composition is regarded as 100 parts by mass, the blend amount of the polybutadiene rubber is set preferably into the range of 20 to 50 parts by mass.
- As far as the rubber composition in the present invention contains at least not only 50 parts or more by mass of the natural rubber but also 20 to 50 parts by mass of the polybutadiene rubber in 100 parts by mass of the rubber components, a rubber different from any polybutadiene rubber may be blended as another species of the dry rubber. Examples of the blendable different rubber include polyisoprene rubber (IR), polystyrenebutadiene rubber (SBR), chloroprene rubber (CR), and nitrile rubber (NBR). These may be used alone or in the form of a blend of two or more thereof.
- The oil used in the present invention is an oil having a pour point of −10° C. or lower, and an aniline point of 90° C. or higher. By blending, in the rubber composition, this oil, the natural rubber wet master batch, and the polybutadiene rubber at a ratio in the specific range, the rubber composition is largely improved in braking performance on ice road surfaces and low-thermogenic performance when used as a raw material for tires, for example, their treads. As this oil, a commercially available product is also suitably usable. Examples thereof include a product “PROCESS P200” (pour point: −15° C., aniline point: 102.3° C.) manufactured by JOMO, and a product “PS-32” (pour point: −20° C., aniline point: 110° C.) manufactured by Idemitsu Kosan Co., Ltd. The blend amount of the oil in the rubber composition is preferably from 15 to 40 parts by mass.
- The rubber composition according to the present invention can be produced by, for example, a rubber composition producing method including step (I) in which when a carbon black is dispersed into a dispersing solvent, at least one portion of a natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere, step (II) of mixing this slurry solution with the rest of the natural rubber latex solution to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, step (III) of solidifying the rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black to produce a carbon-black-containing natural rubber solidified product, and then drying the solidified product to produce a natural rubber wet master batch, and step (IV) of dry-mixing this natural rubber wet master batch with a dry rubber made mainly of a polybutadiene rubber, and an oil, wherein when the total amount of rubber components in the rubber composition is regarded as 100 parts by mass, the natural rubber is contained in an amount of 50 parts or more by mass, and the polybutadiene rubber is contained in an amount of 20 to 50 parts by mass, and the oil has a pour point of −10° C. or lower, and an aniline point of 90° C. or higher, and the blend amount of the oil is from 15 to 40 parts by mass for 100 parts by mass of the rubber components.
- It is particularly preferred that the step (III) has at least the following dehydrating step (III-A) and drying plasticizing step (III-B) and no cooling step is set between the dehydrating step (III-A) and the drying plasticizing step (III-B): the dehydrating step (III-A) of using a first uniaxial extruder to dehydrate the carbon-black-containing natural rubber solidified product while the product is heated up to 100 to 180° C., thereby producing a natural rubber wet master batch; and the drying plasticizing step (III-B) of using a second uniaxial extruder to plasticize the natural rubber wet master batch while the master batch is heated up to 120 to 180° C., thereby producing the natural rubber wet master batch further decreased in water content by percentage. This case makes an improvement of a vulcanized rubber from the resultant rubber composition in rubber physical properties such as tearing resistance and high-strain-region stress property. Hereinafter, the step (III) will be detailed.
- The dehydrating step (III-A) is a step of using a first uniaxial extruder to dehydrate the carbon-black-containing natural rubber solidified product while the product is heated up to 100 to 180° C., thereby producing a natural rubber wet master batch. The first uniaxial extruder may be any uniaxial extruder usable in an ordinary rubber industry. The barrel diameter (D), the barrel length (L), and further the ratio of the barrel length to the barrel diameter (L/D) may be set at will. The gap width (slit width) between the inner wall of the barrel and its screw is preferably from 0.1 to 0.9 mm. In the present invention, it is preferred to use a uniaxial extruder having no pin portions projected inward from the barrel inner wall of a discharging port side region (expander region) of the uniaxial extruder. If the expander region has pin portions, a high shearing force acts onto the rubber components passing by the pin portions so that polymer chains in the rubber components are cleaved. Thus, deterioration of the rubber components advances easily. As a result, the vulcanized rubber to be finally obtained tends to be deteriorated in tearing resistance and high-strain-region stress property.
- In the dehydrating step (III-A), the set temperature of the inside of the barrel of the first uniaxial extruder (the heating temperature for the filler-containing rubber solidified product) is preferably from 160 to 220° C., more preferably from 180 to 200° C. to decrease the water content by percentage efficiently in the resultant rubber wet master batch while the heat capacity and mechanical energy applied thereto are restrained as much as possible.
- In the natural rubber wet master batch obtained through the dehydrating step, the water content by percentage is preferably from 1 to 10%, more preferably from 1 to 8%.
- The drying plasticizing step (III-B) is a step of using a second uniaxial extruder to plasticize the natural rubber wet master batch while the master batch is heated up to 120 to 180° C., thereby producing the natural rubber wet master batch further decreased in water content by percentage. The second uniaxial extruder may be equivalent to the first uniaxial extruder. In the same manner as in the first uniaxial extruder, the second uniaxial extruder preferably has no pin portions in the barrel inner wall of its expander region.
- In the drying plasticizing step (III-B), the set temperature of the inside of the barrel of the second uniaxial extruder (the heating temperature for the natural rubber wet master batch) is preferably from 160 to 220° C., more preferably from 160 to 200° C. to decrease the water content by percentage efficiently in the resultant rubber wet master batch while the heat capacity and mechanical energy applied thereto are restrained as much as possible.
- In the drying plasticizing step (III-B), it is preferred that the mechanical energy applied to the natural rubber wet master batch in the second uniaxial extruder is 70 W/kg or less. This case finally gives, from the natural rubber wet master batch as a raw material, a vulcanized rubber excellent in tearing resistance and high-strain-region stress property.
- In the natural rubber wet master batch obtained through the drying plasticizing step (III-B), the water content by percentage is preferably 0.9% or less.
- When the natural rubber wet master batch is plasticized in the drying plasticizing step (III-B), the addition and incorporation of an anti-aging agent thereinto make it possible to disperse the anti-aging agent more evenly in the natural rubber wet master batch. The final vulcanized rubber can be favorably prevented, with a higher certainty, from being rubber-deteriorated. The anti-aging agent may be an anti-aging agent usable ordinarily for rubbers, and examples thereof include aromatic amine type anti-aging agents, amine-ketone type anti-aging agents, monophenolic type anti-aging agents, bisphenolic type anti-aging agents, polyphenolic type anti-aging agents, dithiocarbamic acid salt type anti-aging agents, and thiourea type anti-aging agents. These may be used alone or in the form of an appropriate mixture. The content of the anti-aging agent(s) is preferably from 0.3 to 3 parts by mass, more preferably from 0.5 to 1.5 parts by mass for 100 parts by mass of the rubber components (solid) in the rubber wet master batch.
- Since the producing method according to the present embodiment has no cooling step between the dehydrating step (III-A) and the drying plasticizing step (III-B), the water content by percentage can be efficiently decreased in the resultant natural rubber wet master batch while the heat capacity and mechanical energy applied to the master batch are restrained as much as possible. The method for preventing the natural rubber wet master batch from being cooled between the dehydrating step (III-A) and the drying plasticizing step (III-B) may be, for example, a method of connecting the first and second uniaxial extruders to each other through a connecting tool, such as a heatable cylinder having a short barrel length, or a method of connecting the first and second uniaxial extruders directly to each other. In order to prevent the natural rubber wet master batch from being cooled, the following temperature is set preferably to 40° C. or higher, more preferably to 60° C. or higher, in particular preferably to 120° C. or higher: the temperature of the natural rubber wet master batch before the master batch is charged from the first uniaxial extruder into the connecting tool; or the temperature of the natural rubber wet master batch before the master batch is charged into the second uniaxial extruder when the first and second uniaxial extruders are connected directly to each other.
- In the rubber composition producing method according to the present embodiment, the step (III) may have, after the drying plasticizing step (III-B), a shaping plasticizing step (III-C) of using a mixer further to plasticize the above-mentioned natural rubber wet master batch. The mixer is preferably, for example, an open roll or a uniaxial extruder. In the shaping plasticizing step (III-C) also, it is preferred that the mechanical energy applied to the natural rubber wet master batch in the mixer is 70 W/kg or less since this case is to make the vulcanized rubber to be finally obtained from the natural rubber wet master batch as a raw material excellent in tearing resistance and high-strain-region stress property. The shaping machine may be a baler. In the drying plasticizing step (III-B), the water content by percentage in the natural rubber wet master batch has been sufficiently decreased; accordingly, the water content by percentage in the natural rubber wet master batch obtained through the shaping plasticizing step (III-C) may be about 0.9% or less as in the case with the natural rubber wet master batch after the drying plasticizing step (III-B).
- In the dry-mixing step (IV), the natural rubber wet master batch is dry-mixed with a dry rubber made mainly of a polybutadiene rubber, and an oil. As a dry rubber other than the polybutadiene rubber, the same as described above as the different rubber may be optionally blended. In the dry-mixing step (IV), at least one of a plant granular material, a grain granular material, and a granular region of a grain core material may be blended into the rubber composition.
- The plant granular material is a granular material obtained by pulverizing shells of seeds of a walnut, a camellia or the like, or nuclei of fruits of a peach, a Japanese apricot or the like by a known method, these shells or nuclei having a hardness larger than ices, i.e., a Mohs' hardness of 2 or more. The plant granular material is projected from the rubber surface to produce a road-surface scratching effect, thereby exhibiting an effect of preventing the rubber from slipping on ice road surfaces. In order for the plant granular material to ensure bondability onto the rubber, the material is preferably a plant granular material subjected to surface treatment for improving the rubber-bondability thereof. When the material drops away from the phase of the rubber, fine voids are generated to produce a water absorbing effect. When at least one of the plant granular material, the grain granular material, and the granular region of the grain core material is blended, the blend amount thereof is preferably from 0.5 to 10 parts by mass for 100 parts by mass of the rubber components in the rubber composition. Specific examples thereof include a pulverized material of nuts or shells of fruits such as a peach, Japanese apricot, walnut, ginkgo nut, peanut, or Japanese chestnut; grains such as rice, barley, wheat, foxtail millet, Japanese millet and corn; and core materials thereof.
- The dry-mixing step (IV) further has at least a kneading step (IV-A) and a vulcanization-related blending agent kneading step (IV-B).
- The kneading step (IV-A) is a step of charging the polybutadiene rubber, the oil, and one or more optional blending agents other than any vulcanization-related blending agent into the natural rubber wet master batch obtained through the drying plasticizing step (III-B) or the shaping plasticizing step (III-C), and then using a mixing/dispersing device to knead all the components. Examples of the blending agent(s) include another rubber, stearic acid, zinc flower, an anti-aging agent, silica, a silane coupling agent, a wax, and a working aid. When the blending agent(s) is/are mixed with the rubber components in the kneading step (IV-A), for example, the following advantages are produced: a rubber product after the master batch is vulcanized is to be heightened in strength; the rubber is made good in rubber-kneading workability; and the rubber is prevented from being deteriorated by radicals generated by the cleavage of the rubber molecular chains. In the kneading step (IV-A), for example, a gear-engaging type Banbury mixer, a tangential line type Banbury mixer, or a kneader is usable. In particular, the use of a gear-engaging type Banbury mixer is preferred.
- One or more vulcanization-related blending agents, such as a vulcanizer, for example, sulfur, and/or a vulcanization promoter, are charged into the rubber composition obtained through the kneading step (IV-A), and then the entire components are kneaded and mixed with each other. When the rubber composition obtained through the vulcanization-related blending agent kneading step (IV-B) is heated to a predetermined temperature or higher, the vulcanizer in the rubber composition reacts with the rubber molecules so that crosslinkage structures are formed between the rubber molecules. Thus, the molecules are made into a three-dimensional network to give rubber elasticity to the rubber composition.
- It is sufficient that the sulfur is a sulfur species for ordinary rubbers. Examples thereof include powdery sulfur, precipitated sulfur, insoluble sulfur, and highly dispersed sulfur. The sulfur content in the rubber composition according to the present invention is preferably from 0.3 to 6 parts by mass for 100 parts by mass of the rubber components. If the sulfur content is less than 0.3 parts by mass, the vulcanized rubber is short in crosslinkage density to be lowered in rubber strength and others. If the sulfur content is more than 6.5 parts by mass, the vulcanized rubber is deteriorated, particularly, in both of heat resistance and endurance. In order for the vulcanized rubber to ensure rubber strength satisfactorily and be further improved in heat resistance and endurance, the sulfur content more preferably ranges from 1.5 to 5.5 parts by mass for 100 parts by mass of the rubber components.
- The vulcanization promoter may be a vulcanization promoter commonly used for rubber vulcanization. Examples thereof include sulfenamide type vulcanization promoters, thiuram type vulcanization promoters, thiazole type vulcanization promoters, thiourea type vulcanization promoters, guanidine type vulcanization promoters, and dithiocarbamic acid salt type vulcanization promoters. These may be used alone or in the form of an appropriate mixture. The content of the vulcanization promoter(s) is preferably from 1 to 5 parts by mass, more preferably from 1.5 to 4 parts by mass for 100 parts by mass of the rubber components.
- Hereinafter, this invention will be more specifically described by demonstrating examples thereof. Raw materials and devices used therein are as follows:
- a) Carbon blacks:
- Carbon black “N339”: “SEAST KH”; N2SA: 91 m2/g (manufactured by Tokai Carbon Co., Ltd.),
- Carbon black “N234”: “SEAST 7HM”; N2SA: 119 m2/g (manufactured by Tokai Carbon Co., Ltd.), and
- Carbon black “N550”: “SEAST SO”; N2SA: 40 m2/g (manufactured by Tokai Carbon Co., Ltd.);
- b) Dispersing solvent: Water;
c) Natural rubber latex: - Natural rubber concentrated latex solution, manufactured by Regitex Co., Ltd. (DRC (dry rubber content)=60%), mass-average molecular weight (Mw)=236,000;
- d) Solidifier: Formic acid (adjusted into a pH of 1.2 by diluting a 10% solution of a first class 85%-concentration agent) (manufactured by Nacalai Tesque, Inc.);
e) Natural rubber: RSS #3;
f) Polybutadiene rubber: “HIGHCIS BR” (manufactured by JSR Corporation;
g) Silica: “NIPSIL AQ” (manufactured by Nippon Silica Industrial Co., Ltd.);
h) Silane coupling agent: “Si75” (manufactured by Degussa); - Oil A: “PROCESS NC140”; pour point: 7.5° C., and aniline point: 91.2° C. (manufactured by JOMO),
- Oil B: “PROCESS P200”; pour point: −15° C., and aniline point: 102.3° C. (manufactured by JOMO), and
- Oil C: “PS-32”; pour point: −20° C., and aniline point: 110° C. (manufactured by Idemitsu Kosan Co., Ltd.),
- j) Stearic acid: “LUNAC S-20” (manufactured by Kao Corporation);
k) Zinc flower: - “Zinc flower class-1” (manufactured by Mitsui Mining & Smelting Co., Ltd.);
- l) Anti-aging agent: “ANTIGEN 6C” (manufactured by Sumitomo Chemical Co., Ltd.);
m) Wax: “OZOACE 0355” (manufactured by Nippon Seiro Co., Ltd.);
n) Vulcanization promoter: “SOXINOL CZ” (manufactured by Sumitomo Chemical Co., Ltd.);
o) Sulfur: “Powdery sulfur” (manufactured by Tsurumi Chemical Industry Co., Ltd.);
p) Plant granular material: “SOFT GRIT #46” (manufactured by Nippon Walnut Co., Ltd.) treated with an ordinary RF adhesive; and
q) Granular material of a grain core material: CORN COBS GRIT 40/60 (corncob) manufactured by Nippon Walnut Co., Ltd. - Natural rubber wet master batches were each produced by the following method:
- Carbon black (N339) was added into a diluted natural rubber latex, the concentration therein being adjusted to 0.5% by mass, so as to give a carbon black concentration of 5% by mass. A device, ROBOMIX, manufactured by Primix Corp. was used to disperse the carbon black therein (ROBOMIX conditions: rotation at 9000 rpm for 30 minutes) to produce a slurry solution containing the carbon black to which natural rubber latex particles adhered (step (I)).
- To the slurry solution produced in the step (I), which contained the natural-rubber-latex-particle-adhering carbon black, was added the rest of the natural rubber latex solution (the solid (rubber) concentration therein was adjusted to 25% by mass by the addition of water) to adjust the total of the solid (rubber) content therein and that in the natural rubber latex solution used in the step (I) to 50 parts by mass. Next, a mixer for household use, model SM-L56, manufactured by Sanyo Electric Co., Ltd. was used to mix these components with each other (mixer conditions: rotation at 11300 rpm for 30 minutes) to produce a carbon-black-containing natural rubber latex solution (step (II)). In the carbon-black-containing natural rubber latex solution, 25 parts by mass of the carbon black was contained for 50 parts by mass of the rubber components (solid).
- A 10%-by-mass solution of formic acid in water as a solidifier was added to the carbon-black-containing natural rubber latex solution produced in the step (II) until the pH of the whole turned to 4 (step (III)). A screen (φ2 punching, manufactured by Toyo Screen Kogyo Co., Ltd.) was used to remove water from the solution containing the resultant carbon-black-containing natural rubber solidified product, thereby producing a carbon-black-containing rubber solidified product having a water content of 65.1%. In order to further decrease the water content by percentage, the solidified product may be centrifuged. An instrument, model H-22 (BS-030) manufactured by Kokusan Co., Ltd., may be used to subject the solidified product to solid-liquid separation (separating conditions: rotation at 29000 rpm for 10 minutes), thereby producing a filler-containing rubber solidified product having a water content of 46.2%.
- A first uniaxial extruder (product number: model V-02, manufactured by Suehiro EPM Corporation; barrel diameter: 90 mm; “barrel length”/“barrel diameter” (L/D)=8.6; and slit widths between the barrel and the screw: 0.7 mm, 0.5 mm, and 0.2 mm) was connected directly to a second uniaxial extruder (a uniaxial extruder identical with the first uniaxial extruder). The natural rubber wet master batch was subjected to the above-defined dehydrating step and drying plasticizing step while the following were each set into a value described in Table 1: the heating temperature, and the mechanical energy applied to the natural rubber wet master batch (WMB) in each of the steps; and the water content by percentage in the natural rubber wet master batch obtained after each of the steps. As shown in Table 1, the temperature change between the dehydrating step (III-A) and the drying plasticizing step (III-B) was only 30° C. Thus, it is understood that the present process had no cooling step between the dehydrating step (III-A) and the drying plasticizing step (III-B).
- Into a B-type Banbury mixer (manufactured by Kobe Steel, Ltd.) were charged each of the natural rubber wet master batches obtained through the drying plasticizing step (III-B), a polybutadiene rubber, an oil, and various blending agents shown in Table 1, and then these components were mixed with each other to produce a rubber composition. This rubber composition was vulcanized at 150° C. for 30 minutes to produce a vulcanized rubber.
- The rubber hardnesses of the vulcanized rubber were measured at 23° C. and −5° C., respectively, in accordance with JIS K6253.
- A viscoelasticity meter manufactured by Toyo Seiki Seisaku-sho, Ltd. was used to measure the storage elastic moduli E′ of the rubber composition at respective temperatures of −5° C. and −25° C. and at a frequency of 10 Hz, a static strain of 10%, and a dynamic strain of ±0.25%. The reciprocal number of each of the resultant values was shown as an index under the condition that the value of Comparative Example 1 was regarded as 100. As the index is larger, the composition is smaller in storage elastic modulus E′ so that the composition product is wider in contact area at low temperatures to be better in low-temperature performance.
- The 2000-cc FF car was run at a speed of 40 km/h on an ice road surface (−3±3° C.), and then the braking distance thereof was measured (the average value under the condition that n was 10) when the car was subjected to ABS operation. The resultant value was shown as an index under the condition that the value of Comparative Example 1 was regarded as 100. As the numeral value is larger, the rubber composition is better in that the braking distance is shorter.
- In accordance with JIS K6265, the low-thermogenic performance of the produced vulcanized rubber was evaluated on the basis of the loss tangent tans thereof. The tans was measured at 50 Hz, 80° C. and a dynamic strain of 2%, using a rheospectrometer, E4000 manufactured by UBM, and the measured value was converted to an index. The index was an index under the condition that the value of Comparative Example 1 was regarded as 100, and the index was used to make an evaluation. As the numerical value is smaller, the vulcanized rubber is lower-thermogenic to be better.
- In accordance with JIS K6264, the rubber composition was measured at a slip ratio of 30%, an applied load of 40 N and a dropping sand amount of 20 g/minute, and then evaluated on the basis of the measured result. The resultant value was shown as an index under the condition that the value of Comparative Example 1 was regarded as 100. As the numeral value is larger, the rubber composition is better in abrasion resistance.
-
TABLE 1 Com- parative Com- Com- Com- Exam- parative parative parative ple 1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3 Example 4 Example 5 Step (I) Carbon black Species — N339 N339 N339 N339 N339 N550 N339 N339 Blend amount for 100 parts by — 50 50 50 50 50 70 50 50 mass of rubber components Added Rubber content in NR — 5 5 5 5 5 5 5 5 rubber “Added rubber latex — 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% latex species concentration” (solid (rubber) concentration (% by mass)) Step (II) Added Rubber content in NR — 95 95 95 95 95 95 95 95 rubber “Added rubber latex — 25% 25% 25% 25% 25% 25% 25% 25% latex species concentration” (solid (rubber) concentration (% by mass)) Rubber amount in rubber wet master batch — 100 100 100 100 100 100 100 100 (the number of parts by mass when the total amount of rubber components was regarded as 100 parts by mass) Step (III-A) Used mixer — Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial extruder extruder extruder extruder extruder extruder extruder extruder Heating temperature — 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. Water content (%) — 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 Mechanical energy (Wh/kg) applied to WMB — 93 93 93 93 93 93 93 93 Step (III-B) Used mixer — Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial extruder extruder extruder extruder extruder extruder extruder extruder Heating temperature — 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. Water content (%) — 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 Mechanical energy (Wh/kg) applied to WMB — 61 61 61 61 61 61 61 61 Step (III-C) Used mixer — Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial Uniaxial extruder extruder extruder extruder extruder extruder extruder extruder Heating temperature — 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. 160° C. Water content (%) — 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 Mechanical energy (Wh/kg) applied to WMB — 63 63 63 63 63 63 63 63 Step (IV) NR 50 — — — — — — — — WMB — 75 75 75 75 75 85 75 75 BR 50 50 50 50 50 50 50 50 50 Carbon black Species N339 — — — — — — — — Blend amount for 100 parts by 25 — — — — — — — — mass of rubber components Silica 25 25 25 25 25 25 25 25 25 Si75 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Oil A 20 20 — — — — — — — Oil B — — 10 50 20 — 20 35 20 Oil C — — — — — 20 — — — Stearic acid 2 2 2 2 2 2 2 2 2 Zinc flower 2 2 2 2 2 2 2 2 2 Anti-aging agent 2 2 2 2 2 2 2 2 2 Wax 2 2 2 2 2 2 2 2 2 Plant granular material 2 2 2 2 2 2 2 2 — Granular material of grain core material — — — — — — — — 2 Vulcanization promoter 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Sulfur 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 Vulcanized rubber properties Hardness (23° C.) 51 48 49 42 47 47 47 47 47 Hardness (−5° C.) 61 55 58 45 51 50 50 51 51 Low-temperature performance E′ (−5° C.) 100 96 97 92 95 95 96 95 95 indexes E′ (−25° C.) 100 107 87 147 140 145 140 145 140 Ice braking performance index 100 100 92 117 125 130 125 130 125 Low-thermogenic performance (tanδ) 100 92 87 110 89 89 90 90 89 Abrasion resistance 100 100 105 80 97 97 97 98 97 - It is understood from the results in Table 1 that the vulcanized rubber from the rubber composition according to each of Examples 1 to 4 was largely decreased in E′ in the range of low temperatures, and was further improved in ice braking performance and low-thermogenic performance. However, the vulcanized rubber from the rubber composition according to each of Comparative Examples 2 and 3 was deteriorated in ice braking performance and low-thermogenic performance, and the vulcanized rubber from the rubber composition of Comparative Example 4 was deteriorated in low-thermogenic performance and abrasion resistance.
Claims (5)
1. A rubber composition obtained by dry-mixing a natural rubber wet master batch yielded by mixing at least a natural rubber latex and a carbon-black-containing slurry solution with each other in a liquid phase and drying the resultant mixture, a dry rubber made mainly of a polybutadiene rubber, and an oil,
wherein when the total amount of rubber components in the rubber composition is regarded as 100 parts by mass, the natural rubber is contained in an amount of 50 parts or more by mass, and the polybutadiene rubber is contained in an amount of 20 to 50 parts by mass, and
the oil has a pour point of −10 C or lower, and an aniline point of 90 C or higher, and the blend amount of the oil is from 15 to 40 parts by mass for 100 parts by mass of the rubber components.
2. The rubber composition according to claim 1 , wherein the natural rubber wet master batch is a master batch produced through the following steps:
step (I) in which when a carbon black is dispersed into a dispersing solvent to prepare the carbon-black-containing slurry solution, at least one portion of the natural rubber latex is added thereto, thereby producing a slurry solution containing the carbon black to which natural rubber latex particles adhere,
step (II) of mixing this slurry solution with the rest of the natural rubber latex to produce a natural rubber latex solution containing the just-above described natural-rubber-latex-particle-adhering carbon black, and
step (III) of solidifying and drying the natural rubber latex solution containing the natural-rubber-latex-particle-adhering carbon black.
3. The rubber composition according to claim 1 , wherein the natural rubber wet master batch contains the carbon black in an amount of 40 to 70 parts by mass for 100 parts by mass of the rubber components of the master batch.
4. The rubber composition according to according to claim 1 , wherein the carbon black contained in the natural rubber wet master batch has a nitrogen adsorption specific surface area (N2SA) of 100 m2/g or less.
5. The rubber composition according to according to claim 1 , wherein when the total amount of the rubber components in the rubber composition is regarded as 100 parts by mass, at least one of a plant granular material, a grain granular material, and a granular region of a grain core material is further contained in an amount of 0.5 to 10 parts by mass.
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CN111171413A (en) * | 2018-11-12 | 2020-05-19 | 固特异轮胎和橡胶公司 | Footwear and rubber soles comprising corn cob granules |
US11478040B2 (en) | 2018-11-12 | 2022-10-25 | The Goodyear Tire & Rubber Company | Footwear and rubber sole containing zinc rosinate |
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JP6153257B2 (en) | 2013-09-10 | 2017-06-28 | 東洋ゴム工業株式会社 | Manufacturing method of rubber wet masterbatch |
JP6195504B2 (en) * | 2013-11-11 | 2017-09-13 | 東洋ゴム工業株式会社 | Rubber composition |
CN104311903B (en) * | 2014-11-04 | 2016-04-13 | 天长市高新技术创业服务中心 | A kind of high-strength abrasion-proof modified natural rubber material |
JP6475008B2 (en) * | 2014-12-22 | 2019-02-27 | Toyo Tire株式会社 | Anti-vibration rubber |
JP6555526B2 (en) * | 2015-10-13 | 2019-08-07 | 住友ゴム工業株式会社 | Semi-conductive roller |
JP6706050B2 (en) | 2015-11-16 | 2020-06-03 | Toyo Tire株式会社 | Rubber wet masterbatch and method for producing rubber composition |
CN116635454A (en) * | 2020-12-09 | 2023-08-22 | 超越莲花有限责任公司 | Method for producing a compound having an elastomer and a filler |
JP7255625B2 (en) * | 2021-04-07 | 2023-04-11 | 横浜ゴム株式会社 | Nanocellulose masterbatch and manufacturing method thereof |
US20230242715A1 (en) * | 2022-02-01 | 2023-08-03 | GranBio Intellectual Property Holdings, LLC | Processes and systems for making particulate masterbatches, and compositions obtained therefrom |
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JPS61268743A (en) * | 1985-05-23 | 1986-11-28 | Toyoda Gosei Co Ltd | Curing rubber composition |
JPH08269243A (en) * | 1995-03-31 | 1996-10-15 | Toyo Tire & Rubber Co Ltd | Rubber composition for tire and its production |
JPH09132671A (en) * | 1995-11-09 | 1997-05-20 | Yokohama Rubber Co Ltd:The | Rubber composition |
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DE60238358D1 (en) | 2001-07-27 | 2010-12-30 | Bridgestone Corp | Natural rubber masterbatch its manufacturing process, and natural rubber composition |
JP2004107482A (en) * | 2002-09-18 | 2004-04-08 | Yokohama Rubber Co Ltd:The | Rubber composition for tread of tire for ice/snow-covered road |
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2012
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-
2015
- 2015-08-17 US US14/828,133 patent/US20150361253A1/en not_active Abandoned
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN111171413A (en) * | 2018-11-12 | 2020-05-19 | 固特异轮胎和橡胶公司 | Footwear and rubber soles comprising corn cob granules |
US11478040B2 (en) | 2018-11-12 | 2022-10-25 | The Goodyear Tire & Rubber Company | Footwear and rubber sole containing zinc rosinate |
Also Published As
Publication number | Publication date |
---|---|
US20150011677A1 (en) | 2015-01-08 |
US9139705B2 (en) | 2015-09-22 |
CN104144979A (en) | 2014-11-12 |
JP5850778B2 (en) | 2016-02-03 |
WO2013140676A1 (en) | 2013-09-26 |
DE112012006084B4 (en) | 2016-12-22 |
JP2013199543A (en) | 2013-10-03 |
DE112012006084T5 (en) | 2015-04-16 |
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Legal Events
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AS | Assignment |
Owner name: TOYO TIRE & RUBBER CO., LTD, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KIMURA, TAKAYOSHI;REEL/FRAME:036374/0570 Effective date: 20140707 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |