Accelerators for vulcanization of rubbery polymers

Abstract

To provide a 1-functional-valence thiuram compound that can be synthesized at a low cost and can be used as an accelerator for vulcanization giving a high cure rate without generating a bad scorch, and to provide a cured rubber composition containing the 1-functional-valence thiuram compound and having reduced permanent deformation, improved aging curing characteristics, and oxidation resistant cross-linking.SOLUTION: A 1-functional-valence thiuram compound is represented by formula: [where, R1 and R2 may be the same or different, indicate an organyl radical, contain at least 8 carbon atoms in total and can combine with each other to form a ring structure, and R3 indicates an organyl radical containing at least 6 carbon atoms].SELECTED DRAWING: None

Description

[Technical Field]

[0001] [Background technology]

[0002] Accelerators have been used in the vulcanization of natural and synthetic rubber compounds for decades. Their primary function in rubber vulcanization is to increase the speed of the curing process and often allow for a reduction in vulcanization temperatures. This allows for more efficient utilization of curing molds and reduces energy requirements. Increased throughput often translates into lower commercial production costs. However, accelerators must not cause premature curing of the rubber compound until sufficient time has passed for the required rubber chemicals to be mixed into the compound and for the compound to be formed in the curing mold. In the rubber industry, premature crosslinking of a rubber compound is referred to as scorch, and resistance to such premature crosslinking is referred to as scorch safety. Regardless, cure characteristics, including cure rate, cure time, cure temperature, scorch behavior, and degree of cure, are crucial in rubber compound formulations. The use of vulcanization accelerators also generally results in improved tensile strength, better resistance to compression set, lower hysteresis, improved aging properties, and other beneficial cured rubber properties.

[0003] In some instances, a particular accelerator, when used alone, results in an excessively slow cure rate. However, the addition of a small amount of another accelerator is often sufficient to accelerate the cure rate. Such a second accelerator is sometimes referred to as an "activator," and its use is referred to as "activation." The most commonly "activated" accelerators are thiazoles, including thiazole sulfenamides. The accelerators most commonly used as "activators" are thiuram sulfides, dithiocarbamates, and guanidines. A ratio of about 1 phr of thiazole to 0.1 phr to about 0.3 phr of "activator" (parts by weight per 100 parts by weight of rubber) is typically used, characterizing the thiazole as the "primary accelerator" and the activator as the "secondary accelerator."

[0004] Among the "primary accelerators," benzothiazole sulfenamides are commonly used in the vulcanization of a wide range of diene-based rubber compositions. They are often used in combination with thiuram sulfide and dithiocarbamate "secondary accelerators," which are powerful activators that tend to cure quickly and be "scorching," i.e., to cause premature vulcanization. This is evidenced by the small amounts required for activation. A thiazole sulfenamide to activator ratio of 10 to 1 is common.

[0005] One of the most widely used accelerator combinations for diene rubbers consists of a benzothiazole sulfenamide and a thiuram sulfide or dithiocarbamate. It is non-scorching, safe, provides adequate cure rates in reasonable lengths of time, and results in rubber compositions with good physical properties. However, in commercial operations, such as the manufacture of automobile tires, improving productivity and costs is always desirable. One means of increasing productivity is to shorten vulcanization time without sacrificing quality or operational safety. Over the years, various cure systems have been evaluated, some of which have significantly increased cure rates, but at the expense of reduced processing safety and scorch, limiting their use.

[0006] Dithioacid salts, such as dithiocarbamates or thiurams, often referred to as "ultraaccelerators," rapidly accelerate vulcanization at conventional vulcanization temperatures. However, their use often leads to problems with premature vulcanization of rubber compositions during processing steps such as mixing or molding, due to the heat generated by their own activity, which can cause unwanted scorch of the rubber. Sulfenamides, so-called "delayed-acting accelerators," generally do not exhibit scorch problems but tend to slow the rate of vulcanization. In general, conventional accelerators exhibit scorch characteristics that are directly proportional to the rate of vulcanization. In other words, conventional accelerators that accelerate the rate of vulcanization usually cause high levels of scorch (premature crosslinking) susceptibility during vulcanization. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent Application No. 62 / 955,323 [Non-patent literature]

[0008] [Non-Patent Document 1] Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ed., Wiley Interscience, NY 1982, Vol. 20, pp. 365-468, "Vulcanization Agents and Auxiliary Materials," pp. 390-402 Summary of the Invention [Means for solving the problem]

[0009] The present invention is based on the discovery that certain monofunctional thiuram compounds can be produced at low cost and used as vulcanization accelerators that provide excellent cure rates without causing high levels of scorch. The use of monofunctional thiuram compounds as vulcanization accelerators also results in cured rubber compositions that exhibit reduced compression set, improved aging cure properties, and oxidation-resistant crosslinks. These monofunctional thiuram compounds have the structural formula:

[0010] [ka]

[0011] [In the formula, R 1 and R 2 may be the same or different and represent organyl radicals, where R 1 and R 2 contains a total of at least 8 carbon atoms, and R 1 and R 2 can bond together to form a ring structure, R 3represents an organyl radical containing at least six carbon atoms. In these monofunctional thiuram compounds, R 1 and R 2 preferably contains a total of at least 8 carbon atoms.

[0012] The present invention relates to, inter alia, a composition comprising (A) an unsaturated rubber, (B) a reinforcing silica, (C) a silica coupling agent, (D) sulfur, (E) carbon black, and (F) a composition having the structural formula:

[0013] [ka]

[0014] [In the formula, R 1 and R 2 may be the same or different and represent organyl radicals, where R 1 and R 2 contains a total of at least two carbon atoms, and R 1 and R 2 can bond together to form a ring structure, R 3 represents an organyl radical containing at least six carbon atoms. In a preferred embodiment, a rubber composition for production comprising an accelerator of the formula: 1 and R 2 preferably contain a total of at least 8 carbon atoms. Such production rubber compositions also typically contain a metal activator compound. The metal activator compound is typically selected from the group consisting of zinc compounds, cadmium compounds, mercury compounds, calcium compounds, and magnesium compounds, with zinc compounds usually being preferred.

[0015] The subject invention further provides a method of making a rubber article, comprising forming a production rubber composition 1 into a desired geometric shape in a mold and curing the rubber composition in the mold at an elevated temperature in the range of about 132°C to 177°C (about 270°F to 350°F), wherein the production rubber composition comprises (A) an unsaturated rubber, (B) a reinforcing silica, (C) a silica coupling agent, (D) sulfur, (E) carbon black, and (F) a rubber having the structural formula:

[0016] [ka]

[0017] [In the formula, R 1 and R 2 may be the same or different and represent organyl radicals, where R 1 and R 2 contains a total of at least two carbon atoms, and R 1 and R 2 can bond together to form a ring structure, R 3 represents an organyl radical containing at least six carbon atoms. In such a method, R 1 and R 2 preferably contains a total of at least 8 carbon atoms.

[0018] The present invention also provides a rubber article, such as a tire, hose, power transmission belt, conveyor belt, air spring, windshield wiper blade, shoe sole, latex glove, gasket or seal, comprised of a cured unsaturated rubber, wherein the cured unsaturated rubber is crosslinked with monosulfide groups, and the cured unsaturated rubber is pendant -SR 3 The group [wherein, R 3 represents an organyl radical containing at least 6 carbon atoms, and the unsaturated rubber contains reinforcing silica. In these rubber articles, the cured rubber contains multiple thermodynamically stable sulfur bridges and exhibits improved aging resistance, low levels of compression set, and improved aging cure characteristics.

[0019] The subject invention further provides a tire having a generally toroidal carcass having an outer periphery and a tread, two spaced apart beads, at least one ply extending from bead to bead, and sidewalls extending radially from said tread to said beads and connecting said tread with said beads, said tread being adapted for ground contact, wherein the cured unsaturated rubber is crosslinked with monosulfide groups, and the cured unsaturated rubber is pendant-SR 3 The group [wherein, R 3 represents an organyl radical containing at least 6 carbon atoms], and the unsaturated rubber contains reinforcing silica. DETAILED DESCRIPTION OF THE INVENTION

[0020] The accelerators of the present invention can be beneficially used in the vulcanization of virtually any natural or unsaturated synthetic rubber. Some representative examples of rubbery polymers that can be vulcanized according to the present invention include natural rubber, polybutadiene homopolymer, synthetic polyisoprene homopolymer, styrene-butadiene rubber (SBR), α-methylstyrene-butadiene rubber, α-methylstyrene-isoprene rubber, styrene-isoprene-butadiene rubber (SIBR), styrene-isoprene rubber (SIR), isoprene-butadiene rubber (IBR), α-methylstyrene-isoprene-butadiene rubber, α-methylstyrene-styrene-isoprene-butadiene rubber, nitrile rubber, carboxylated nitrile rubber, and the like. Various blends of these and other unsaturated rubbers can, of course, also be cured using the accelerators of the present invention.

[0021] The monofunctional thiuram compounds used in the vulcanized rubbers of the present invention are further described and can be synthesized according to the procedures disclosed in U.S. Patent Application No. 62 / 955,323, filed December 30, 2019. The teachings of U.S. Patent Application No. 62 / 955,323, filed December 30, 2019, are incorporated herein by reference in their entirety. Monofunctional thiuram compounds are typically used at levels ranging from about 0.1 phr to 10 phr in vulcanized rubber formulations. Monofunctional thiuram compounds are more typically used in amounts ranging from 0.3 phr to 5 phr, and often in amounts ranging from 0.5 phr to 3.5 phr.

[0022] Reinforcing silica is typically included in rubber compounds cured using the monofunctional thiuram accelerators of the present invention to fully realize the overall benefits provided by these accelerators. Such rubber compounds also typically include a silica coupling agent (sulfur-containing organosilicon compound) to realize maximum benefit. Some representative examples of suitable sulfur-containing organosilicon compounds that can be used as silica coupling agents are those of the formula: Z-Alk-S n -Alk-Z(I) [Wherein Z is

[0023] [ka]

[0024] and R 1 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl, or phenyl; R 2 is an alkoxy of 1 to 8 carbon atoms or a cycloalkoxy of 5 to 8 carbon atoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms, and n is an integer of 2 to 8. It is of the type.

[0025] Specific examples of sulfur-containing organosilicon compounds that may be used as silica coupling agents in accordance with the present invention include the following: 3,3'-bis(trimethoxysilylpropyl) disulfide, 3,3'-bis(triethoxysilylpropyl) tetrasulfide, 3,3'-bis(triethoxysilylpropyl) octasulfide, 3,3'-bis(trimethoxysilylpropyl) tetrasulfide, 2,2'-bis(triethoxysilylethyl) tetrasulfide. , 3,3'-bis(trimethoxysilylpropyl) trisulfide, 3,3'-bis(triethoxysilylpropyl) trisulfide, 3,3'-bis(tributoxysilylpropyl) disulfide, 3,3'-bis(trimethoxysilylpropyl) hexasulfide, 3,3'-bis(trimethoxysilylpropyl) octasulfide, 3,3'-bis(trioctaoxysilylpropyl) tetrasulfide, 3,3'-bis(trihexaoxysilylpropyl) propyl) disulfide, 3,3'-bis(tri-2"-ethylhexoxysilylpropyl) trisulfide, 3,3'-bis(triisooctoxysilylpropyl) tetrasulfide, 3,3'-bis(tri-t-butoxysilylpropyl) disulfide, 2,2'-bis(methoxydiethoxysilylethyl) tetrasulfide, 2,2'-bis(trippropoxysilylethyl) pentasulfide, 3,3'-bis(tricyclonexoxysilylpropyl) silyl) tetrasulfide, 3,3'-bis(tricyclopentoxysilylpropyl) trisulfide, 2,2'-bis(tri-2"-methylcyclohexoxysilylethyl) tetrasulfide, bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxyethoxypropoxysilyl 3'-diethoxybutoxysilylpropyl tetrasulfide, 2,2'-bis(dimethylmethoxysilylethyl) disulfide, 2,2'-bis(dimethylsec.butoxysilylethyl) trisulfide, 3,3'-bis(methylbutylethoxysilylpropyl) tetrasulfide, 3,3'-bis(di-t-butylmethoxysilylpropyl) tetrasulfide, 2,2'-bis(phenylmethylmethoxysilylethyl) trisulfide, 3,3'-bis(diphenylisopropoxysilylpropyl) tetrasulfide, 3,3'-bis(diphenylcyclohexyloxysilylpropyl) disulfide, 3,3'-bis(dimethylethyl methyl captosilylpropyl) tetrasulfide, 2,2'-bis(methyldimethoxysilylethyl) trisulfide, 2,2'-bis(methylethoxypropoxysilylethyl) tetrasulfide, 3,3'-bis(diethylmethoxysilylpropyl) tetrasulfide, 3,3'-bis(ethyldi-sec.butoxysilylpropyl) disulfide, 3,3'-bis(propyldiethoxysilylpropyl) disulfide, 3,3'-bis(butyldimethoxysilylpropyl) trisulfide Sulfide, 3,3'-bis(phenyldimethoxysilylpropyl)tetrasulfide, 3-phenylethoxybutoxysilyl 3'-trimethoxysilylpropyl tetrasulfide, 4,4'-bis(trimethoxysilylbutyl)tetrasulfide, 6,6'-bis(triethoxysilylhexyl)tetrasulfide, 12,12'-bis(triisopropoxysilyldodecyl)disulfide, 18,18'-bis(trimethoxysilyloctadecyl)tetrasulfide, 18 ,18'-Bis(tripropoxysilyloctadekenyl)tetrasulfide, 4,4'-Bis(trimethoxysilylbuten-2-yl)tetrasulfide, 4,4'-Bis(trimethoxysilylcyclohexylene)tetrasulfide, 5,5'-Bis(dimethoxymethylsilylpentyl)trisulfide, 3,3'-Bis(trimethoxysilyl-2-methylpropyl)tetrasulfide, 3,3'-Bis(dimethoxyphenylsilyl-2-methylpropyl)disulfide.

[0026] The preferred sulfur-containing organosilicon compound is 3,3'-bis(trimethoxy or triethoxysilylpropyl) sulfide. The most preferred compound is 3,3'-bis(triethoxysilylpropyl) tetrasulfide. Thus, with respect to Formula I, preferably, Z is

[0027] [ka]

[0028] [In the formula, R 2 is an alkoxy of 2 to 4 carbon atoms, with 2 carbon atoms being particularly preferred; Alk is a divalent hydrocarbon of 2 to 4 carbon atoms, with 3 carbon atoms being particularly preferred; n is an integer of 3 to 5, with 4 being particularly preferred. The amount of silica coupling agent used is usually in the range of about 0.1 phr to about 20 phr. The amount of silica coupling agent used is more typically in the range of about 0.5 phr to about 4 phr, and preferably in the range of 1 phr to 2 phr.

[0029] Silica fillers may be added in amounts ranging from about 10 phr to about 250 phr. Preferably, silica is present in an amount ranging from about 15 phr to about 80 phr. If carbon black is also present, the amount of carbon black, if used, may vary. Generally, the amount of carbon black varies from about 5 phr to about 200 phr, more typically in an amount ranging from 10 phr to 80 phr. Preferably, the amount of carbon black ranges from about 10 phr to about 40 phr. It should be appreciated that silica couplers may be used in combination with carbon black, i.e., premixed with carbon black prior to addition to the rubber composition, and such carbon black would be included in the rubber composition formulation in the amounts described above for carbon black. In any event, the total amount of silica and carbon black will be at least about 30 phr. As referenced above, the combined weight of silica and carbon black may be at least about 30 phr, preferably from about 45 to about 130 phr.

[0030] Commonly used siliceous pigments used in rubber compounding applications can be used as silica. For example, silica can include pyrogenic and precipitated siliceous pigments (silica), with precipitated silica being preferred. The siliceous pigments used in the present invention are preferably precipitated silicas, such as those obtained by acidifying soluble silicates, e.g., sodium silicate.

[0031] Such silicas may be characterized, for example, by having a BET surface area, as measured using nitrogen gas, preferably in the range of about 40 to about 600 square meters per gram, more typically in the range of about 50 to about 300 square meters per gram. The BET method for measuring surface area is described in Journal of the American Chemical Society, Vol. 60, p. 304 (1930).

[0032] The silica may also be characterized by having a dibutyl phthalate (DBP) absorption value typically ranging from about 100 to about 400, more commonly from about 150 to about 300. The silica can be expected to have an average ultimate particle size in the range of 0.01 to 0.05 microns, as determined, for example, by electron microscopy, although the silica particles may be smaller or possibly larger in size.

[0033] Various commercially available silicas that may be considered for use in the present invention are, for example and by way of example only and without limitation, silicas commercially available from PPG Industries under the Hi-Sil trademark, having the designations 210, 243, etc.; silicas available from Rhone-Poulenc, for example, having the designations Z1165MP and Z165GR, and silicas available from Degussa AG, for example, having the designations VN2 and VN3.

[0034] The carbon black may include any of the commonly available industrially produced carbon blacks, but should be at least 20 m 2 / g, more preferably at least 35m 2 / g to 200m 2 Preferred carbon blacks have a surface area (EMSA) of up to 1 / g or more. The surface area values ​​used in this application are those determined by ASTM test D-1765 using the cetyltrimethylammonium bromide (CTAB) method. Useful carbon blacks include furnace blacks, channel blacks, and lamp blacks. Examples of carbon blacks include, among others, super abrasion furnace (SAF) black, high abrasion furnace (HAF) black, good extrudability furnace (FEF) black, fine particle furnace (FF) black, semi-super abrasion furnace (ISAF) black, medium reinforcing furnace (SRF) black, medium processability channel black, difficult processability channel black, and conductive channel black. Other carbon blacks that may be used include acetylene black. Mixtures of two or more of the above carbon blacks can be used to prepare the carbon black products of the present invention. Typical values ​​for the surface area of ​​usable carbon blacks are summarized in the table below.

[0035] [Table 1]

[0036] The carbon black used in preparing the rubber compound may be in pelletized form or in unpelletized, flocculent form. Unpelletized carbon black is preferred for more uniform mixing. The reinforced rubber compound can be conventionally cured using about 0.5 to about 4 phr of known vulcanizing agents. For example, sulfur- or peroxide-based curing systems may be used. For a general disclosure of suitable vulcanizing agents, see Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, Wiley Interscience, NY 1982, Vol. 20, pp. 365-468, especially "Vulcanization Agents and Auxiliary Materials," pp. 390-402. Vulcanizing agents can, of course, be used alone or in combination. Vulcanizable elastomer or rubber compositions can be prepared by compounding or mixing the polymer with carbon black and other conventional rubber additives, such as fillers, plasticizers, antioxidants, and vulcanizing agents, using standard rubber mixing equipment and procedures and conventional amounts of such additives.

[0037] Rubber compounds cured with the monofunctional thiuram accelerators of the present invention may also contain processing oils, waxes, scorch inhibitors, antioxidants, and processing aids. In most cases, the rubber compounds are compounded with sulfur and / or sulfur-containing compounds, at least one filler, at least one antidegradant, at least one processing oil, zinc oxide, optionally a tackifying resin, optionally a reinforcing resin, optionally one or more fatty acids, optionally a peptizer, and optionally one or more scorch inhibitors. Such blends typically contain about 0.5 to 5 phr (parts per 100 parts by weight of rubber) of sulfur and / or sulfur-containing compounds, with 1 to 2.5 phr being preferred. In cases where bloom is a problem, it may be desirable to use insoluble sulfur.

[0038] Typically, 10 to 150 phr of at least one filler is used in the blend, with 30 to 80 phr being preferred. In most cases, at least a portion of carbon black is used as a filler. The filler, of course, can consist entirely of carbon black. Silica can be included in the filler to improve tear resistance and heat buildup. Clay and / or talc can be included in the filler to reduce cost. The blend also typically contains 0.1 to 2.5 phr of at least one accelerator, with 0.2 to 1.5 phr being preferred. Antioxidants, such as antiozonants, are typically included in the blend in amounts ranging from 0.25 to 10 phr, with 1 to 5 phr being preferred. Processing oil is typically included in the blend in amounts ranging from 2 to 100 phr, with 5 to 50 phr being preferred. The functionalized rubbery polymers of the present invention also typically contain 0.5 to 10 phr of zinc oxide, with 1 to 5 phr being preferred. These blends may optionally contain 0-10 phr of tackifying resins, 0-10 phr of reinforcing resins, 1-10 phr of fatty acids, 0-2.5 phr of peptizers, and 0-1 phr of scorch inhibitors.

[0039] Lignin further improves filler / polymer compatibility and reduces the overall weight of the tire tread formulation. The lignin may be lignosulfonate (also known as lignin sulfonate and sulfite lignin) or kraft lignin (also known as sulfate lignin). Lignin is typically present in tire tread formulations in an amount ranging from 10 phr to 80 phr, more typically in an amount ranging from 15 phr to 30 phr. Starch may also be beneficially used as a filler in such compositions in addition to lignin in an amount ranging from 10 phr to 50 phr, more typically in an amount ranging from 15 phr to 30 phr.

[0040] Rubber compounds, such as tire tread compounds containing silica and organosilicon compounds, are typically mixed using thermomechanical mixing techniques. Mixing of rubber compounds can be accomplished by methods known to those skilled in the art of rubber mixing. For example, raw materials are typically mixed in at least two stages: at least one non-productive stage followed by a productive mix stage. The final curative, including sulfur-vulcanizing agents, is usually mixed in the final stage, conventionally referred to as the "productive" mix stage, where mixing is typically performed at a specific or final temperature that is lower than the mixing temperature(s) of the preceding non-productive mix stage(s). The rubber, silica, and sulfur-containing organosilicon, and, if used, carbon black, are mixed in one or more non-productive mix stages. The terms "non-productive" and "productive" mix stages are familiar to those skilled in the art of rubber mixing.

[0041] The sulfur-vulcanizable rubber composition containing the sulfur-containing organosilicon compound, the vulcanizable rubber, and generally at least a portion of the silica must be subjected to a thermomechanical mixing step. The thermomechanical mixing step generally involves mechanical operation in a mixer or extruder for a period of time appropriate to produce a rubber temperature between 140°C and 190°C. The suitable duration of the thermomechanical operation varies as a function of the operating conditions and the amount and nature of the components. For example, the thermomechanical operation may be carried out for a period ranging from about 2 minutes to about 20 minutes. Typically, the rubber reaches a temperature ranging from about 145°C to about 180°C, preferably maintained at that temperature for a period ranging from about 4 minutes to about 12 minutes. Typically, the rubber reaches a temperature ranging from about 155°C to about 170°C, more preferably maintained at that temperature for a period ranging from about 5 minutes to about 10 minutes.

[0042] The monofunctional thiuram accelerators of the present invention can be used in conjunction with conventional tire production techniques to cure rubber blends used in tire treads. For example, green tires can be vulcanized using typical tire cure cycles employing a wide range of conventional cure temperatures. However, it is generally preferred that tires of the present invention be cured at temperatures ranging from about 132°C (270°F) to about 177°C (350°F). More typically, tires of the present invention are cured at temperatures ranging from about 143°C (290°F) to about 154°C (310°F). The cure cycle used to vulcanize tires of the present invention generally has a duration of about 10 to about 14 minutes, with a cure cycle of about 12 minutes being most preferred.

[0043] The present invention is described by the following examples, which are illustrative only and cannot be considered as limiting the scope of the invention or the manner in which it can be practiced. Unless otherwise indicated, parts and percentages are given by weight, polymer microstructures were determined by nuclear magnetic resonance spectroscopy (NMR), glass transition temperatures (Tg) were determined by differential scanning calorimetry at a heating rate of 10°C per minute, and molecular weights were determined by gel permeation chromatography (GPC). Example 1 and Comparative Examples 2 to 4 Examples 1-4 evaluate the use of various accelerators with equimolar loadings of the R2NCS2-functional group. Example 1 illustrates the use of N,N-di-benzyl-n-dodecanyl benzylsulfenyl dithiocarbamate as an accelerator for use in vulcanizing rubber according to the present invention. Comparative Examples 2-3 were conducted using conventional rubber accelerators known in the prior art.

[0044] [Table 2]

[0045] All rubber compounds were prepared using a two-pass procedure of making a non-production compound followed by the addition of curatives to make the production compound as specified in Table 1. A traveling die rheometer cure was performed at 160°C for 60 minutes with the following results:

[0046] [Table 3]

[0047] Example 5 and Comparative Examples 6 to 8 Examples 5-8 evaluate the use of various accelerators with equimolar loadings of R2NCS2-functional groups in the presence of a second accelerator. Example 5 illustrates the use of N,N-di-benzyl-n-dodecanyl benzylsulfenyl dithiocarbamate as an accelerator for use in vulcanizing rubber according to the present invention. Comparative Examples 6-8 were conducted using conventional rubber accelerators known in the prior art.

[0048] [Table 4]

[0049] All rubber compounds were prepared using a two-pass procedure in which a non-production compound was made, followed by the addition of curatives to make the production compound, as specified in Table 2. Traveling die rheometer cure was carried out at 160°C for 60 minutes.

[0050] [Table 5]

[0051] While certain representative embodiments and details have been set forth for the purpose of illustrating the subject invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the subject invention. [Mode of the invention] [1] (A) unsaturated rubber, (B) reinforcing silica, (C) silica coupling agent, (D) sulfur, (E) carbon black, and (F) structural formula: [ka] [In the formula, R 1 and R 2 may be the same or different and represent organyl radicals, where R 1 and R 2 contains a total of at least two carbon atoms, and R 1 and R 2 can bond together to form a ring structure, R 3 represents an organyl radical containing at least six carbon atoms. Accelerator of A rubber composition for production, comprising: [2] R 3 2. The production rubber composition according to claim 1, wherein the alkyl group has 6 to about 20 carbon atoms. [3] R 1 and R 2 1. The production rubber composition of claim 1, wherein [4] R 1 and R 2 1. The production rubber composition of claim 1, characterized in that [5] R 1 and R 2 1. The production rubber composition of claim 1, wherein [6] R 3 1. The rubber composition for production according to 1, characterized in that after crosslinking, becomes a pendant group on the backbone of the rubber. [7] R 3 1. The rubber composition for production according to claim 1, characterized in that after crosslinking, [8] R 3 2. The production rubber composition according to 1, wherein represents an alkyl group containing 1 to 20 carbon atoms. [9] R 3 2. The production rubber composition according to 1, wherein represents an alkyl group containing 2 to 12 carbon atoms.

[10] R 3 2. The rubber composition for production according to 1, wherein represents an alkyl group containing 4 to 8 carbon atoms.

[11] R 3 2. The production rubber composition according to claim 1, wherein represents a t-butyl group.

[12] R 3 2. The rubber composition for production according to 1, characterized in that: represents a benzyl group.

[13] 2. The production rubber composition according to claim 1, wherein the accelerator is present in an amount ranging from 0.1 phr to 10 phr.

[14] 2. The production rubber composition according to claim 1, wherein the accelerator is present in an amount ranging from 0.3 phr to 5 phr.

[15] 2. The production rubber composition according to claim 1, wherein the accelerator is present in an amount ranging from 0.5 phr to 3.5 phr.

[16] 1. The production rubber composition according to 1, further comprising a metal activator compound.

[17] 17. The production rubber composition of claim 16, wherein the metal activator is selected from the group consisting of zinc compounds, cadmium compounds, mercury compounds, calcium compounds, and magnesium compounds.

[18] 10. The production rubber composition of claim 1, further comprising an additional filler.

[19] 19. The production rubber composition of claim 18, wherein the additional filler is selected from the group consisting of nanocellulose, clay, lignin, and talc.

[20] 2. The production rubber composition of claim 1, wherein the reinforcing silica is present in an amount ranging from about 10 phr to about 250 phr.

[21] 2. The production rubber composition of claim 1, wherein the reinforcing silica is present in an amount ranging from about 15 phr to about 150 phr.

[22] 2. The production rubber composition of claim 1, wherein the reinforcing silica is present in an amount ranging from about 20 phr to about 80 phr.

[23] 2. The production rubber composition of claim 1, wherein the carbon black is present in an amount ranging from about 2 phr to about 150 phr.

[24] 2. The production rubber composition of claim 1, wherein the carbon black is present in an amount ranging from about 5 phr to about 80 phr.

[25] 2. The production rubber composition of claim 1, wherein the carbon black is present in an amount ranging from about 10 phr to about 60 phr.

[26] 1. The production rubber composition according to claim 1, characterized in that the total amount of silica and carbon black is at least 30 phr.

[27] 2. The production rubber composition according to 1, wherein the total amount of silica and carbon black is within the range of about 45 to about 130 phr.

[28] 2. The production rubber composition of claim 1, wherein the silica coupling agent is present in an amount ranging from about 1 phr to about 4 phr.

[29] 2. The production rubber composition of claim 1, wherein the silica coupling agent is present in an amount ranging from about 1 phr to about 20 phr.

[30] 1. A method for producing a rubber article, comprising the steps of: forming the production rubber composition of 1 into a desired geometric shape in a mold; and curing the rubber composition in the mold at an elevated temperature in the range of about 132°C (270°F) to about 177°C (350°F).

[31] 31. The method of claim 30, wherein the elevated temperature is in the range of 143°C (290°F) to about 154°C (310°F).

[32] 31. The method of claim 30, wherein the rubber composition is cured in the mold for about 8 to 30 minutes.

[33] 31. The method of claim 30, wherein the rubber composition is cured in the mold for about 10 to 20 minutes.

[34] 31. The method of claim 30, wherein the rubber composition is cured in the mold for about 10 to 14 minutes.

[35] 31. The method of claim 30, wherein the rubber article is a tire.

[36] A rubber article comprising a cured unsaturated rubber, the cured unsaturated rubber being crosslinked with monosulfide groups, the cured unsaturated rubber being pendant-SR 3 The group [wherein, R 3 represents an organyl radical containing at least 6 carbon atoms, and the unsaturated rubber contains reinforcing silica.

[37] R 3 37. The rubber article of claim 36, wherein the alkyl group has from 6 to about 20 carbon atoms.

[38] R 3 37. The rubber article according to claim 36, characterized in that: represents an alkyl group containing 1 to 20 carbon atoms.

[39] R 3 37. The rubber article according to claim 36, characterized in that represents an alkyl group containing 2 to 12 carbon atoms.

[40] R 3 37. The rubber article according to claim 36, characterized in that represents an alkyl group containing 4 to 8 carbon atoms.

[41] R 3 37. The rubber article according to claim 36, wherein represents a t-butyl group.

[42] R 3 37. The rubber article according to claim 36, wherein represents a benzyl group.

[43] 37. The rubber article according to claim 36, characterized in that it is a tire.

[44] 43. A tire comprising a generally annular carcass having an outer periphery and a tread, two spaced apart beads, at least one ply extending from bead to bead, and sidewalls extending radially from said tread and connecting said tread to said beads, said tread adapted for ground contact.

[45] 37. The rubber article according to claim 36, characterized in that it is a latex glove.

[46] 37. The rubber article according to claim 36, characterized in that it is a gasket.

[47] 37. A rubber article according to claim 36, characterized in that it is a seal.

Claims

1. (A) unsaturated rubber, (B) reinforcing silica, (C) silica coupling agent, (D) sulfur, (E) carbon black, (F) structural formula: 【Chemistry 1】 [In the formula, R １ and R ２ may be the same or different and represent organyl radicals, where R １ and R ２ contains a total of at least 2 carbon atoms, and R １ and R ２ can be linked together to form a ring structure, R ３ represents a benzyl group] (G) optionally a processing oil, (H) optionally a wax, (I) optionally a scorch inhibitor, (J) optionally a processing aid, (K) optionally an antidegradant, (L) optionally zinc oxide, (M) optionally a tackifying resin, (N) optionally a reinforcing resin, (O) optionally a fatty acid, (P) optionally a peptizer, (Q) optionally a filler, and (R) optionally a plasticizer. A rubber composition for production, comprising:

2. R １ and R ２ 10. The production rubber composition of claim 1, wherein: contains a total of at least 8 carbon atoms.

3. R １ and R ２ 10. The production rubber composition of claim 1, wherein: contains a total of at least 10 carbon atoms.

4. R １ and R ２ 10. The production rubber composition of claim 1, wherein: contains a total of at least 12 carbon atoms.

5. R ３ 2. The production rubber composition of claim 1, wherein after crosslinking, becomes a pendant group on the backbone of the rubber.

6. R ３ 10. The production rubber composition of claim 1, wherein after crosslinking, does not become part of the chemical crosslinks.

7. 10. The production rubber composition of claim 1, wherein the accelerator is present in an amount ranging from 0.1 phr to 10 phr.

8. 10. The production rubber composition of claim 1, wherein the accelerator is present in an amount ranging from 0.3 phr to 5 phr.

9. 10. The production rubber composition of claim 1, wherein the accelerator is present in an amount ranging from 0.5 phr to 3.5 phr.

10. (A) unsaturated rubber, (B) reinforcing silica, (C) silica coupling agent, (D) sulfur, (E) carbon black, (F) structural formula: 【Chemistry 2】 [In the formula, R １ and R ２ may be the same or different and represent organyl radicals, where R １ and R ２ contains a total of at least 2 carbon atoms, and R １ and R ２ can be linked together to form a ring structure, R ３ represents a benzyl group] (G) a metal activator compound selected from the group consisting of zinc compounds, cadmium compounds, mercury compounds, calcium compounds, and magnesium compounds; (H) optionally a processing oil; (I) optionally a wax; (J) optionally a scorch inhibitor; (K) optionally a processing aid; (L) optionally an antidegradant; (M) optionally a tackifying resin; (N) optionally a reinforcing resin; (O) optionally a fatty acid; (P) optionally a peptizer; (Q) optionally a filler; and (R) optionally a plasticizer. A rubber composition for production, comprising:

11. 10. The production rubber composition of claim 1 further comprising an additional filler.

12. 12. The production rubber composition of claim 11, wherein the additional filler is selected from the group consisting of nanocellulose, clay, lignin, and talc.

13. 10. The production rubber composition of claim 1, wherein said reinforcing silica is present in an amount ranging from 10 phr to 250 phr.

14. 10. The production rubber composition of claim 1, wherein said reinforcing silica is present in an amount ranging from 15 phr to 150 phr.

15. 10. The production rubber composition of claim 1, wherein said reinforcing silica is present in an amount ranging from 20 phr to 80 phr.

16. 10. The production rubber composition of claim 1, wherein said carbon black is present in an amount ranging from 2 phr to 150 phr.

17. 10. The production rubber composition of claim 1, wherein said carbon black is present in an amount ranging from 5 phr to 80 phr.

18. 10. The production rubber composition of claim 1, wherein said carbon black is present in an amount ranging from 10 phr to 60 phr.

19. 2. The production rubber composition of claim 1, wherein the combined amount of silica and carbon black is at least 30 phr.

20. 2. The production rubber composition of claim 1, wherein the total amount of silica and carbon black is within the range of 45 to 130 phr.

21. 10. The production rubber composition of claim 1, wherein the silica coupling agent is present in an amount ranging from 1 phr to 4 phr.

22. 10. The production rubber composition of claim 1, wherein the silica coupling agent is present in an amount ranging from 1 phr to 20 phr.

23. 11. A method for producing a rubber article, comprising the steps of: molding the production rubber composition of claim 1 or 10 into a desired geometric shape in a mold; and curing the rubber composition in the mold at an elevated temperature in the range of 132°C (270°F) to 177°C (350°F).

24. 24. The method of claim 23, wherein the elevated temperature is in the range of 143°C (290°F) to 154°C (310°F).

25. 24. The method of claim 23, wherein the rubber composition is cured in the mold for 8 to 30 minutes.

26. 24. The method of claim 23, wherein the rubber composition is cured in the mold for 10 to 20 minutes.

27. 24. The method of claim 23, wherein the rubber composition is cured in the mold for 10 to 14 minutes.

28. 24. The method of claim 23, wherein the rubber article is a tire.

29. 11. A rubber article comprising a cured production rubber composition according to claim 1 or 10, wherein the cured production rubber composition is crosslinked with monosulfide groups, and the cured production rubber composition has pendant -S-R ３ A rubber article having a group.

30. 30. The rubber article of claim 29, characterized in that it is a tire.

31. 31. The tire of claim 30, characterized in that it has a generally toroidal carcass having a peripheral tread adapted for ground contact, two spaced apart beads, at least one ply extending from bead to bead, and sidewalls extending radially from said tread and connecting said tread with said beads.

32. 30. The rubber article of claim 29, characterized in that it is a latex glove.

33. 30. The rubber article of claim 29, wherein the rubber article is a gasket.

34. 30. The rubber article of claim 29, which is a seal.

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