Synthesis of Monofunctional Thiuram Accelerator

Abstract

To provide a route for synthesizing monofunctional thiuram compounds that is safe, environmentally friendly, and cost effective.SOLUTION: The present invention provides a route for synthesizing monofunctional thiuram compounds that is safe, environmentally friendly, and cost effective. This method specifically involves synthesizing a monofunctional thiuram by (1) reacting a tetraorganylthiuram disulfide with an organyl mercaptan to produce the monofunctional thiuram and a dithiocarbamate metal salt or a dithiocarbamate metalloid salt under basic conditions, (2) separating the monofunctional thiuram in an organic phase from the dithiocarbamate metal salt or the dithiocarbamate metalloid salt in an aqueous phase, and (3) recovering the monofunctional thiuram from the aqueous phase. The monofunctional thiuram compounds made in accordance with this invention are of particular value as accelerators for use in the vulcanization of rubber. The use of these monofunctional thiuram compounds as accelerators provides good cure rates and as well as good scorch safety.SELECTED DRAWING: None

Description

Technical Field

[0001]

Background Art

[0002] A monofunctional thiuram compound is useful as an accelerator for vulcanization (sulfur curing) of rubber and as a starting material for synthesizing or other useful compounds. Such a monofunctional thiuram compound has the structural formula:

[0003]

Chemical Formula

[0004] [wherein R 1 and R 2 may be the same or different and represent an organyl radical, R 1 and R 2 together contain at least 8 carbon atoms, R 1 and R 2 can be linked together to form a cyclic structure, and R 3 represents an organyl radical containing at least 6 carbon atoms] including those having this. The synthesis of this general type of monofunctional thiuram compound is described in the prior art.

[0005] U.S. Patent No. 2,792,394 describes an alkylsulfenyl halide in which the alkyl group contains 1 to 12 carbon atoms and the halide is selected from the group consisting of chloride, bromide, and iodide, having the formula:

[0006]

Chemical Formula

[0007] [wherein,

[0008]

Chemical Formula

[0009] is a substituted amino group in which up to one hydrogen is bonded to a nitrogen atom, and R and R' are hydrogen; alkyl, cycloalkyl, aryl, aralkyl radicals, and together with nitrogen, a saturated carbon-nitrogen, carbon-nitrogen-oxygen and carbon-nitrogen-sulfur ring having at least 4 carbon atoms out of up to 6 members, selected from the group consisting of hydrocarbon radicals selected from the group consisting of radicals forming the ring, and M is a cation forming a salt] Discloses a process for reacting with an aqueous solution of a compound corresponding to at the reaction temperature to produce an alkylsulfenyl dithiocarbamate.

[0010] According to further description of U.S. Patent No. 2,792,394, the product produced by the method disclosed therein has the formula:

[0011] [Chemical formula]

[0012] [wherein,

[0013] [Chemical formula]

[0014] is a primary or secondary amino group, and either or both of R and R' are alkyl, cycloalkyl, aryl, aralkyl hydrocarbon radicals, or radicals having at least 4 carbon atoms and together with a nitrogen atom form a 5- or 6-membered saturated heterocyclic ring, for example, piperidyl, morpholinyl, thiomorpholinyl, 2-methyl-thiomorpholinyl, pyrrolidyl, piperazinyl, pipecolinyl, or either of R and R' may be a hydrogen atom, and R'' is an alkyl group] corresponds to .

[0015] U.S. Patent No. 7,217,834 discloses a method for preparing a salt of an S-alkyl ester of thiosulfuric acid by reacting an organic dihalide with a thiosulfate in water. This prior art patent more specifically discloses a method for preparing a compound of the formula Me 1 O3S S-(CH2) n -S SO3Me 2 [wherein Me 1 and Me 2 are the same or different and are each a monovalent metal ion or an ammonium ion, and n is an integer from 2 to 8], which comprises reacting a compound of the formula X-(CH2) n -X [wherein X is a halogen and n is an integer from 2 to 8] with thiosulfate ions at a reaction temperature of 80°C to 150°C and at a pH in the range of 3 to 9.8, and carrying out the reaction in water without adding an alcohol and / or a glycol.

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0017] A better route for synthesizing monofunctional thiuram compounds is needed today. More specifically, such a synthetic route must be safe, environmentally friendly, and cost-effective. More specifically, such a synthetic route should avoid the use of chlorine species (SO2Cl2 or elemental chlorine). Such a synthetic route should also avoid the formation of RS-Cl intermediates, which can be highly toxic and may be difficult to prepare from thiols in some cases.

Means for Solving the Problems

[0018] The present invention provides a safe, environmentally friendly, and cost-effective route for synthesizing monofunctional thiuram compounds. The method of the present invention more specifically includes (1) reacting tetraorganothiuram disulfide with an organomercaptan under basic conditions to produce a monofunctional thiuram and a metal salt or metalloid salt of dithiocarbamic acid, (2) separating the monofunctional thiuram in the organic phase from the metal salt or metalloid salt of dithiocarbamic acid in the aqueous phase, and (3) recovering the monofunctional thiuram from the aqueous phase to synthesize the monofunctional thiuram. The monofunctional thiuram compounds produced according to the present invention have particular value as vulcanizing agents or accelerators used in rubber. The use of these monofunctional thiuram compounds as accelerators does not cause a high level of scorch and does not cause hard rubber that is very prone to scorch.

[0019] A mixture of monofunctional thiuram and a metal salt of dithiocarbamic acid has been found to be very useful as an accelerator system in the vulcanization of rubber formulations. Such a mixture can be easily and efficiently produced in a specific embodiment of the present invention. More specifically, the present invention further clarifies a method for synthesizing a monofunctional thiuram accelerator composition, which includes (1) reacting tetraorganothiuram disulfide with an organomercaptan in a liquid solvent under basic conditions to produce a monofunctional thiuram and a metal salt or metalloid salt of dithiocarbamic acid, and (2) recovering the monofunctional thiuram accelerator composition from the solvent as a mixture of monofunctional thiuram and a metal salt or metalloid salt of dithiocarbamic acid. In this embodiment of the present invention, zinc hydroxide can be used to generate basic conditions, resulting in the formation of zinc metal salt of dithiocarbamic acid, which is particularly useful in the accelerator system.

Embodiments for Carrying Out the Invention

[0020] The synthesis method of the present invention involves reacting tetraorganothiuram disulfide with an organomercaptan under basic conditions to produce a monofunctional thiuram. Tetraorganothiuram disulfide that can be used in the synthesis of the present invention is commercially available from several suppliers. For example, Methyl Tuads® tetramethylthiuram disulfide, Ethyl Tuads® tetraethylthiuram disulfide, and Butyl Tuads® tetrabutylthiuram disulfide are sold by Vanderbilt Chemicals. Also, Tetraalkylthiuram disulfide is sold by Eastman Chemical. In any case, this reaction produces a metal dithiocarbamate as a reaction by-product as depicted below:

[0021] [Chemical formula]

[0022] [wherein, R 1 , R 2 , R 3 and R 4 may be the same or different and represent an organyl radical]. R 1 , R 2 , R 3 and R 4 usually contain from 1 to about 20 carbon atoms. Preferably, R 1 and R 2 together contain at least 8 carbon atoms in total, and R 1 and R 2 can be linked together to form a cyclic structure. Also, R 3 and R 4 preferably together contain at least 8 carbon atoms in total, and R 3 and R 4 can be linked together to form a cyclic structure. R 1 and R 2 typically together contain at least 10 carbon atoms in total. R 1and R 2 preferably contains at least 12 carbon atoms in total, more preferably contains at least 14 carbon atoms in total. R 3 and R 4 typically contains at least 10 carbon atoms in total. R 3 and R 4 preferably contains at least 12 carbon atoms in total, more preferably contains at least 14 carbon atoms in total. R 1 , R 2 , R 3 and R 4 preferably contains 4 to 6 carbon atoms. For example, R 1 , R 2 , R 3 and R 4 is preferably a butyl group, a pentyl group or a hexyl group, and a butyl group is very preferred. Therefore, it is very preferred that the tetraorganothiuram disulfide is tetrabutylthiuram disulfide. R 5 usually represents an organil radical containing at least 1 carbon atom, and typically contains 6 to about 20 carbon atoms. M represents a metal such as sodium, potassium, manganese, zinc, etc.

[0023] The reaction between tetraorganothiuram disulfide and an organomercaptan is typically carried out in a polar organic solvent. The polar solvent may be a polar aliphatic solvent or a polar aromatic solvent such as an alcohol, a ketone, an ester, acetic acid, a glycol ether, an aprotic amide, an aprotic sulfoxide, an aprotic amine, or a halogenated hydrocarbon. Some representative examples of suitable polar organic solvents include tetrahydrofuran, dioxane, methyl chloride, dichloromethane, chloroform, acetonitrile, methyl ethyl ketone, methyl isobutyl ketone, m-amyl acetate, ethylene glycol butyl ether acetate, propylene glycol monomethyl ether acetate, xylene, toluene, benzene, n-methylpyrrolidone, ethanol, isopropanol, n-butanol, and n-propanol, hexyl acetate, octyl acetate, propylene glycol monomethyl ether acetate, methyl propyl ketone, methyl isobutyl ketone, and methyl hexyl ketone, as well as various mixtures thereof. However, the polar organic solvent must be liquid under the conditions under which the reaction is carried out and should be inert with respect to the reactants and reaction products.

[0024] Tetraorganothiuram disulfide is usually present in a polar organic solvent at a level within the range of about 5 weight percent to about 40 weight percent, more typically at a level within the range of 10 weight percent to about 30 weight percent. Typically, it is preferred that tetraorganothiuram disulfide be present in the polar organic solvent at a level within the range of 15 weight percent to 25 weight percent.

[0025] The organomercaptan is added at a level slightly lower than stoichiometry with respect to the amount of tetraorganothiuram disulfide used during the reaction. In most cases, the molar ratio of organomercaptan to tetraorganothiuram disulfide is in the range of 15:20 to 19.9:20. The molar ratio of organomercaptan to tetraorganothiuram disulfide is usually in the range of 18:20 to 19.9:20, typically in the range of 19:20 to 19.8:20, and more typically in the range of 19.2:20 to 19.7:20.

[0026] A base strong enough to react with the organomercaptan is added to reach and maintain basic conditions. Some representative examples of bases that can be used include sodium hydroxide, potassium hydroxide, calcium carbonate, sodium methoxide, zinc hydroxide, and the like. The base is typically used at a level sufficient to deprotonate the dithiocarbamic acid derivative formed during the reaction.

[0027] The reaction of the present invention proceeds rapidly at room temperature. Therefore, it is typically carried out at room temperature. However, the method of the present invention can be carried out over an extremely wide temperature range typically in the range of about -20°C to about 100°C. More typically, it is carried out at a temperature in the range of 10°C to 70°C. In most cases, the method of the present invention is carried out at a temperature in the range of 15 to 30°C. The reaction of the present invention is usually carried out under a dry inert gas atmosphere.

[0028] Since the monofunctional thiuram is soluble in organic solvents and the metal dithiocarbamate is soluble in water, the monofunctional thiuram can be easily separated from the metal dithiocarbamate. Therefore, phase separation can be used to recover the monofunctional thiuram in the aqueous phase from the metal dithiocarbamate in the aqueous phase.

[0029] The dithiocarbamate can optionally be oxidized to regenerate tetraorganothiuram disulfide, which can be recycled for use in the first step of the method of the present invention later. The metal dithiocarbamate may be a metal salt such as sodium dithiocarbamate, potassium dithiocarbamate, manganese dithiocarbamate, or zinc dithiocarbamate. Also, such metal salts, particularly zinc dithiocarbamate, can then be used as an accelerator for the vulcanization of rubber.

[0030] The present invention will be illustrated by the following examples, which are for illustrative purposes only and should not be considered as limiting the scope of the invention or the ways in which it can be practiced. Unless otherwise indicated, parts and percentages are by weight.

Examples

[0031] In this experiment, 20 mmol (10.88 grams) of tetrabenzylthiuram disulfide (TBnTD) was added to 50 ml of degassed anhydrous tetrahydrofuran (tetramethylene oxide) to prepare a tetrabenzylthiuram disulfide suspension. In another bottle, 20 ml of tetrahydrofuran (THF), 3.65 ml (19.5 mmol) of 4-tert-butylbenzyl mercaptan (4-tert-butylbenzylthiol), and 4.35 ml (19.5 mmol) of sodium methoxide (CH3ONa) were mixed together to form a white slurry. Then, the 4-tert-butylbenzyl mercaptan / sodium methoxide slurry was added dropwise to the tetrabenzylthiuram disulfide suspension over 1 hour while stirring the mixture, and it was maintained at room temperature for another 1 hour. Then, the tetrahydrofuran solvent was removed using a rotary evaporator, the residue was diluted with toluene, and then washed with water to remove sodium dibenzylthiocarbamate in the form of reaction by-products. Then, the organic phase was dried again with a rotary evaporator to recover N,N-di-benzyl-4-tert-butylbenzylsulfenyl dithiocarbamate. In this reaction, 9.01 grams of the product was recovered, resulting in a 95% yield. The recovered monofunctional thiuram had a purity of 97%. The reaction carried out in this experiment can be explained as follows:

[0032] [Chemical formula] [Example]

[0033] In this experiment, 10.88 grams (20 mmol) of tetrabenzylthiuram disulfide was mixed with 25 ml of anhydrous tetrahydrofuran (THF) to prepare a tetrabenzylthiuram disulfide suspension. In another vial, 3.65 ml of 1,1-dimethylheptyl mercaptan was diluted with 10 ml of THF, and 4.35 ml of a 25 wt% solution of sodium methoxide (CH3ONa) was added thereto. The resulting thiol sodium salt solution was poured into the tetrabenzylthiuram disulfide suspension, and the mixture immediately became clear. The reaction was further advanced for 1 hour while stirring. Then, a rotary evaporator was used to remove the THF solvent, and the residue was diluted with toluene. The residue was then washed with water to remove the thiocarbamate. The organic phase was dried with a rotary evaporator, and 8.05 grams of the product was recovered. NMR showed that it had a purity of 91%. An 87% product yield was obtained in this experiment. The reaction conducted in this experiment can be explained as follows:

[0034] [Chemical formula] [Example]

[0035] In this experiment, 4 mmol of tetrabenzylthiuram disulfide was suspended in 5 ml of THF to prepare a tetrabenzylthiuram disulfide suspension. In another mixing container containing 5 ml of THF, 3.8 mmol of sodium methoxide (CH3ONa) was mixed with 3.9 mmol of n-dodecyl mercaptan to prepare a slurry containing 3.9 mmol of n-dodecanethiol-Na salt. When 4-tert-butylbenzyl mercaptan was used as the reactant, it took significantly longer for the mixture to become clear than in Example 1. It was noted that some white solids remained after the completion of the reaction. NMR showed that the product was C 12 H 25 -SS-C 12 H 25, the remaining tetrabenzylthiuram disulfide, and the desired thiuram product (N,N-di-benzyl-4-n-dodecanylbenzylsulfenyl dithiocarbamate) were shown to be a mixture. The reaction carried out in this experiment can be explained as follows:

[0036]

Chem.

Example

[0037] In this experiment, 23.93 (44 mmol) of tetrabenzylthiuram disulfide was suspended in 100 ml of THF. A solution of potassium t-butyl mercaptide (t-butylthiol potassium salt) was prepared by adding 4.72 ml of t-butyl mercaptan (t-butylthiol) to a solution containing 2.49 grams of potassium hydroxide (90%, 40 mmol) (KOH) in 10 ml of methanol. The t-butylthiol potassium salt solution was then transferred by cannula to the tetrabenzylthiuram disulfide suspension, and stirring was maintained until the mixture became clear. The reaction was continued while maintaining stirring for an additional hour. The THF solvent was removed by using a rotary evaporator, the residue was diluted with hexane, and then washed with water to remove the thiocarbamate formed as a reaction by-product. The organic phase was then dried using a rotary evaporator, and 12.23 grams of the solid product (N,N-di-benzyl-tert-butylsulfenyl dithiocarbamate) was recovered. This gave a yield of 80.7%. The reaction carried out in this experiment can be explained as follows:

[0038]

Chem.

Example

[0039] In this procedure, 0.55 ml (4.9 mmol) of t-butyl mercaptan was added to a container containing 3 ml of THF, and subsequently, 1.06 ml of sodium methoxide (CH3ONa) solution (4.8 mmol) was added to form the sodium salt of t-butyl mercaptan. In a separate container, 1.20 grams of tetramethylthiuram disulfide (5 mmol) was suspended in 3 ml of THF and then added all at once to the t-butyl mercaptan sodium salt solution. The solution immediately became clear. The mixture was maintained with stirring for an additional 30 minutes to convert the remaining reactants. The solution was then concentrated under vacuum, diluted with 20 ml of toluene, and washed with 10% potassium carbonate (K2CO3) solution. The organic phase was dried and concentrated to give 0.66 grams of N,N-di-methyl-tert-butylsulfenyl dithiocarbamate in the form of a white powder. This gave a 63% yield. The reaction carried out in this experiment can be explained as follows:

[0040]

Chemical formula

Example

[0041] In this experiment, 8.16 grams of tetrabenzylthiuram disulfide (15 mmol) was suspended in 30 ml of anhydrous THF. In a separate vial, 1.32 ml of isopropyl mercaptan (14.4 mmol) (isopropylthiol) was diluted with 10 ml of THF, and subsequently, 3.15 ml of a 25 weight percent (13.8 mmol) sodium methoxide (CH3ONa) solution was added to the vial to form the sodium salt of isopropyl mercaptan. Then, the sodium salt solution of isopropyl mercaptan was poured into the tetrabenzylthiuram disulfide suspension, and immediately the mixture became clear. The mixture was maintained with further stirring for 40 minutes to convert the remaining reactants. The THF solvent was removed by a rotary evaporator, the residue was diluted with toluene, and then washed with water to remove the thiocarbamate. The organic phase was dried and 4.30 grams of N,N-di-benzyl-isopropylsulfenyldithiocarbamate, which resulted as a pale yellow solid, was recovered by a rotary evaporator once again. The reaction conducted in this experiment can be described as follows:

[0042] [Chemical formula] [Example]

[0043] In this experiment, 2.72 grams of tetrabenzylthiuram disulfide (5 mmol) was suspended in 10 ml of anhydrous THF. In another vial, 0.52 ml of isobutyl mercaptan (4.8 mmol) was diluted with 5 ml of THF, and then 1.06 ml (4.6 mmol) of a 25 weight percent solution of sodium methoxide (CH3ONa) was added to form the sodium salt of isobutyl mercaptan. Next, the sodium salt solution of isopropyl mercaptan was poured into the tetrabenzylthiuram disulfide suspension, and it immediately became clear. The mixture was maintained with further stirring for 40 minutes to convert the remaining reactants. The THF solvent was removed with a rotary evaporator, and the residue was diluted with toluene. Subsequently, it was washed with water to remove the thiocarbamate formed as a by-product. The organic phase was dried once again using a rotary evaporator, and 1.34 grams of N,N-di-benzyl-isobutylsulfenyldithiocarbamate was recovered as a pale yellow solid. This gave a yield of 77%. The reaction carried out in this experiment can be explained as follows:

[0044] [Chemical formula]

[0045] Certain representative embodiments and details have been shown for the purpose of explaining the subject invention, but 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. [Aspects of the Invention] [1] A method for synthesizing a monofunctional thiuram, comprising: (1) reacting a tetraorganothiuram disulfide with an organomercaptan under basic conditions to form a monofunctional thiuram and a metal dithiocarbamate or a metalloid dithiocarbamate; (2) separating the monofunctional thiuram in the organic phase from the metal dithiocarbamate or the metalloid dithiocarbamate in the aqueous phase; and (3) recovering the monofunctional thiuram from the aqueous phase. [2] The step of oxidizing a metal dithiocarbamate or a metalloid dithiocarbamate to regenerate a tetraorganothiuram disulfide, and the step of recycling the regenerated tetraorganothiuram disulfide to step (1), the method according to 1. [3] The method according to 1, characterized in that the metal or metalloid is selected from metals and metalloids of Groups 1 to 15 of the periodic table. [4] The tetraorganothiuram disulfide has the structural formula:

Chemical formula

Chemical formula

[10] The method according to claim 1, wherein the tetraorganothiuram disulfide is tetrabenzylthiuram disulfide.

[11] The method according to claim 1, characterized in that the tetraorganothiuram disulfide is tetrabutylthiuram disulfide.

[12] The method according to claim 1, wherein the metal dithiocarbamate or metalloid dithiocarbamate is selected from the group consisting of sodium dithiocarbamate, calcium dithiocarbamate, potassium dithiocarbamate, magnesium dithiocarbamate, and zinc dithiocarbamate.

[13] The method according to claim 1, characterized in that the metal dithiocarbamate or metalloid dithiocarbamate is a zinc dithiocarbamate salt.

[14] Reacting tetraorganothiuram disulfide with an organomercaptan in the presence of a zinc compound, wherein the zinc compound is the conjugate base anion of an acid having a pK a greater than that of the dithiocarbamate derivative formed by the reaction of the method. The method according to claim 1, characterized in that it is

[15] A method for synthesizing a monofunctional thiuram accelerator composition, comprising: (1) reacting tetraorganothiuram disulfide with an organomercaptan in a liquid solvent under basic conditions to produce a monofunctional thiuram and a metal dithiocarbamate or a metalloid dithiocarbamate; and (2) recovering the monofunctional thiuram accelerator composition from the solvent as a mixture of the monofunctional thiuram and the metal dithiocarbamate or the metalloid dithiocarbamate.

[16] The tetraorganothiuram disulfide has the structural formula:

Chemical formula

[17] The monofunctional thiuram has the structural formula:

Chemical formula

[18] R 5 The method according to 17, characterized in that R contains 6 to about 20 carbon atoms

[19] R 1 and R 2 The method according to 17, characterized in that R and R together contain at least 10 carbon atoms

[20] R 1 and R 2 The method according to 17, characterized in that R and R together contain at least 12 carbon atoms

[21] R 1 and R 2 The method according to 17, characterized in that R and R together contain at least 14 carbon atoms

[22] The method according to 15, characterized in that the tetraorganylthiuram disulfide is tetrabenzylthiuram disulfide

[23] The method according to 15, characterized in that the tetraorganylthiuram disulfide is tetrabutylthiuram disulfide

[24] The method according to 15, characterized in that the method is carried out in the presence of zinc hydroxide

[25] The method according to 15, characterized in that the metal dithiocarbamate is a zinc salt

[26] The method is carried out in the presence of a zinc compound, and the zinc compound is the conjugate base anion of an acid having a pK greater than that of the dithiocarbamate derivative formed by the reaction of the method a The method according to 15, characterized in that it is

Claims

1. A method for synthesizing a monofunctional thiuram, comprising: (1) reacting tetraorganothiuram disulfide with an organomercaptan under basic conditions generated by using zinc hydroxide to produce a monofunctional thiuram and zinc dithiocarbamate; (2) separating the monofunctional thiuram in the organic phase from the zinc dithiocarbamate in the aqueous phase; and (3) recovering the monofunctional thiuram from the aqueous phase.

2. A method for synthesizing a monofunctional thiuram, comprising: (1) reacting tetraorganothiuram disulfide with an organomercaptan under basic conditions to produce a monofunctional thiuram and a zinc dithiocarbamate salt; (2) separating the monofunctional thiuram in the organic phase from the zinc dithiocarbamate salt in the aqueous phase; and (3) recovering the monofunctional thiuram from the aqueous phase, characterized by oxidizing the zinc dithiocarbamate salt to regenerate tetraorganothiuram disulfide, and recycling the regenerated tetraorganothiuram disulfide to step (1). Method.

3. The method according to claim 1 or 2, characterized in that the tetraorganothiuram disulfide has the structural formula: 【Chemical 1】 [wherein, R １ , R ２ , R ３ and R ４ may be the same or different and each represents an organyl radical, R １ and R ２ together contain at least 8 carbon atoms in total, R １ and R ２ can be linked together to form a cyclic structure, R ３ and R ４ together contain at least 8 carbon atoms in total, R ３ and R ４ can be linked together to form a cyclic structure]

4. The method according to claim 3, characterized in that the monofunctional thiuram has the structural formula:

5. 【Chemical 2】 [wherein, R １ and R ２ may be the same or different and each represents an organyl radical, R １ and R ２ collectively contain at least 8 carbon atoms, R １ and R ２ may be linked together to form a cyclic structure, and R ５ represents an organyl radical containing at least 1 carbon atom]

6.

7. R ３ The method according to claim 3, characterized in that R contains 6 to about 20 carbon atoms.

8. R １ and R ２ The method according to claim 5, characterized in that R and R together contain at least 10 carbon atoms in total.

9. R １ and R ２ The method according to claim 5, characterized in that the total number of carbon atoms in R and R is at least 12. The method according to claim 1 or 2, characterized in that the tetraorganothiuram disulfide is tetrabenzylthiuram disulfide. R １ and R ２ The method according to claim 5, characterized in that the total number of carbon atoms contained in R and R is at least 14.

10. The method according to claim 1 or 2, characterized in that the tetraorganothiuram disulfide is tetrabutylthiuram disulfide.

11.

12. A method for synthesizing a monofunctional thiuram accelerator composition, comprising: (1) reacting tetraorganothiuram disulfide with an organomercaptan in a liquid solvent under basic conditions to produce a monofunctional thiuram and a zinc dithiocarbamate salt; and (2) recovering the monofunctional thiuram accelerator composition as a mixture of the monofunctional thiuram and the zinc dithiocarbamate salt from the solvent. Reacting a tetraorganothiuram disulfide with an organomercaptan in the presence of a zinc compound, wherein the zinc compound is a conjugate base anion of an acid having a pK greater than that of the dithiocarbamic acid derivative formed by the reaction of the method. ａ The method according to claim 2, characterized in that it is an anion of a conjugate base of an acid having a pK greater than that of the dithiocarbamic acid derivative formed by the reaction of the method.

13. The tetraorganothiuram disulfide has the structural formula: ​ ​ 【Chemical Formula 3】 [wherein, R １ , R ２ , R ３ and R ４ may be the same or different and each represents an organyl radical, R １ and R ２ together contain at least 8 carbon atoms, R １ and R ２ may be linked together to form a cyclic structure, R ３ and R ４ together contain at least 8 carbon atoms, R ３ and R ４ may be linked together to form a cyclic structure]] The method according to claim 12, characterized by having

14. A monofunctional thiuram having the structural formula: 【Chemical Formula 4】 [wherein, R １ and R ２ may be the same or different and each represents an organyl radical, R １ and R ２ collectively contain at least 8 carbon atoms, R １ and R ２ may be linked together to form a cyclic structure, and R ５ represents an organyl radical containing at least 1 carbon atom] The method according to claim 12, characterized by having

15. R ５ The method according to claim 14, characterized in that R contains 6 to about 20 carbon atoms.

16. R １ and R ２ The method according to claim 14, characterized in that R and R together contain at least 10 carbon atoms in total.

17. R １ and R ２ The method according to claim 14, characterized in that R and R together contain at least 12 carbon atoms in total.

18. R １ and R ２ The method according to claim 14, characterized in that the total number of carbon atoms contained in R and R is at least 14.

19. The method according to claim 12, characterized in that the tetraorganothiuram disulfide is tetrabenzylthiuram disulfide.

20. The method according to claim 12, characterized in that the tetraorganothiuram disulfide is tetrabutylthiuram disulfide.

21. The method according to claim 12, characterized in that the method is carried out in the presence of zinc hydroxide.

22. The method is carried out in the presence of a zinc compound, and the zinc compound is a conjugate base anion of an acid having a pK greater than that of the dithiocarbamic acid derivative formed by the reaction of the method. ａ The method according to claim 12, characterized in that it is an anion of a conjugate base of an acid having a ａ .

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