Preparation method of dimethyl thio toluenediamine

Abstract

The invention discloses a preparation method of dimethyl thio toluenediamine, which comprises the following steps: continuously introducing dimethyl disulfide into a reaction system containing diaminotoluene and a catalyst for reaction, and evaporating and condensing the dimethyl disulfide in the reaction process so as to bring out a byproduct methyl mercaptan, after the reaction is finished, purifying and decoloring by adopting a neutralization distillation method to obtain dimethyl thio toluenediamine; the neutralization distillation method comprises the following steps: adding dimethyl disulfide into a reaction solution after the reaction is finished for dilution, then filtering the reaction solution to obtain a filtrate, adding an alkali solution into the filtrate for neutralization, heating and stirring, and finally carrying out reduced pressure distillation. The preparation method disclosed by the invention has the advantages of small catalyst dosage, short reaction time, high product yield and economic and environment-friendly purification and decoloration modes.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of fine chemicals, and particularly relates to a method for preparing dimethylthiotoluenediamine. Background Art

[0002] In the processing and molding of polyurethane (PU) elastomers, a chain extender that simultaneously functions as a chain extender and a crosslinking agent must be added. The basicity of aromatic diamine chain extenders is weaker than that of aliphatic diamines, and their reaction activity with -NCO is relatively low. Therefore, they have a moderate gel time and can endow PU elastomers with good physical and mechanical properties.

[0003] Currently, the most successfully used chain extender is 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA). MOCA is a solid at room temperature and needs to be melted before use, which leads to a shortened pot life and poor operability. Moreover, MOCA is suspected of being carcinogenic and poses a great hazard to on-site operators and the environment.

[0004] Dimethylthiotoluenediamine (DMTDA) can be comparable to MOCA in terms of curing performance. It is a yellow liquid at room temperature, has strong operability, and has no risk of physiological mutagenicity and carcinogenicity. The properties of polyurethane elastomers prepared with DMTDA are also excellent, and some properties are even improved, such as rebound rate and flex cracking resistance.

[0005] Patent documents US4670598A, US4727191A, US4751330A, US5015770A and CN1718571A introduce some synthesis methods of DMTDA, but they generally have disadvantages such as large catalyst consumption, long reaction time, and low conversion rate.

[0006] Therefore, there is a need in the art to develop a new method for preparing dimethylthiotoluenediamine with less catalyst consumption, short reaction time, high product yield, and an economical and environmentally friendly purification and decolorization method. Summary of the Invention

[0007] To solve the problems existing in the prior art, the present invention uses diaminotoluene (TDA) and dimethyldisulfide (DMDS) as raw materials, and uses a combination of metal halides or metal elements and halogen elements as catalysts to synthesize DMTDA. During the reaction process, DMDS is continuously introduced and distilled and condensed, and the by-product of methyl mercaptan continuously generated is taken out, which can eliminate its poisoning of the catalyst, improve the catalytic activity, thereby reducing the catalyst consumption, improving the reaction selectivity, thereby increasing the yield, and increasing the reaction rate, thereby shortening the reaction time; after the reaction, neutralization distillation is used for purification and decolorization, which is economical and environmentally friendly.

[0008] Specifically, the present invention provides a method for preparing dimethylthiotoluenediamine. The method includes continuously introducing dimethyldisulfide into a reaction system containing diamino toluene and a catalyst for reaction, and distilling and condensing dimethyldisulfide during the reaction to carry out by-products methyl mercaptan, and after the reaction, purification and decolorization are carried out by a neutralization distillation method to obtain dimethylthiotoluenediamine; the neutralization distillation method includes: adding dimethyldisulfide to the reaction solution after the reaction to dilute it, then filtering the reaction solution to obtain a filtrate, adding an alkali solution to the filtrate for neutralization, heating and stirring, and finally carrying out vacuum distillation.

[0009] In one or more embodiments, the catalyst is a metal halide, or a combination of a metal element and a halogen element.

[0010] In one or more embodiments, the metal halide is selected from one or more of cuprous iodide, ferrous iodide, and zinc chloride, preferably cuprous iodide.

[0011] In one or more embodiments, the combination of the metal element and the halogen element is a combination of copper element and iodine element.

[0012] In one or more embodiments, the diamino toluene is selected from one or both of 2,4-diamino toluene and 2,6-diamino toluene.

[0013] In one or more embodiments, the molar ratio of the catalyst to diamino toluene is (0.001 - 0.1):1, preferably (0.002 - 0.02):1.

[0014] In one or more embodiments, the molar ratio of dimethyldisulfide to diamino toluene is (2 - 12):1, preferably (8 - 12):1.

[0015] In one or more embodiments, the reaction temperature is 100 - 200 °C, preferably 150 - 190 °C.

[0016] In one or more embodiments, the reaction time is 2 - 10 h, preferably 4 - 6 h.

[0017] In the present invention, the alkali solution is a solution obtained by dissolving an alkali in a solvent.

[0018] In one or more embodiments, the alkali in the alkali solution is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide, preferably sodium hydroxide.

[0019] In one or more embodiments, the solvent in the alkali solution is selected from one or more of water, ethanol, and methanol, preferably water.

[0020] In one or more embodiments, the mass concentration of the base in the base solution is 0.1% to 100%, preferably 1% to 30%.

[0021] In one or more embodiments, the molar ratio of the base in the base solution to the catalyst is (1 to 10):1, preferably (1 to 3):1.

[0022] In one or more embodiments, after adding the base solution, stir at 70 to 90 °C for 0.5 to 1 h.

[0023] In one or more embodiments, during the vacuum distillation process, the distillation pressure is 0 to 1000 Pa, and the distillation temperature is 170 to 190 °C. Detailed implementation manners

[0024] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art with respect to the present invention. In case of conflict, the definition in this specification shall prevail.

[0025] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall in no way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0026] As used herein, terms such as "comprising", "including", "containing" and similar terms encompass the meanings of "consisting essentially of" and "consisting of". For example, when it is disclosed herein that "A comprises B and C", it should be considered that "A consists essentially of B and C" and "A consists of B and C" have been disclosed herein.

[0027] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0028] In this article, unless otherwise specified, the percentage refers to the mass percentage, and the ratio refers to the mass ratio.

[0029] In this article, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all alternatives, improvements and equivalents of the methods and materials described in the present invention can be covered within the scope defined by the claims.

[0030] In this text, for the sake of brevity in description, not all possible combinations of all technical features in each implementation or embodiment are described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation or embodiment can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0031] The present invention discloses a preparation method of dimethylthiotoluenediamine. Dimethyldisulfide is continuously introduced into a reaction system containing diamino toluene and a catalyst for reaction, and dimethyldisulfide is distilled and condensed during the reaction, thereby carrying out by-product methanethiol. After the reaction, neutralization distillation is used for purification and decolorization to obtain dimethylthiotoluenediamine. This preparation method has the advantages of less catalyst consumption, short reaction time, high product yield, etc.

[0032] In the present invention, the neutralization distillation method includes: adding dimethyldisulfide to the reaction solution after the reaction to dilute it, then filtering the reaction solution to obtain a filtrate, adding an alkali solution to the filtrate for neutralization, heating and stirring, and finally carrying out vacuum distillation. This purification and decolorization method has the advantages of economy and environmental protection. The filter cake obtained by filtering the reaction solution is the catalyst and can be recycled.

[0033] In the present invention, the catalyst can be a metal halide, or a combination of a metal element and a halogen element. The metal halide can be one or more selected from cuprous iodide, ferrous iodide, and zinc chloride, preferably cuprous iodide. The combination of the metal element and the halogen element can be a combination of copper element and iodine element.

[0034] In the present invention, the diamino toluene can be one or both selected from 2,4-diaminotoluene (2,4-TDA) and 2,6-diaminotoluene (2,6-TDA). When the diamino toluene is a mixture of 2,4-diaminotoluene and 2,6-diaminotoluene, the molar ratio of 2,4-diaminotoluene to 2,6-diaminotoluene can be 1:100 to 100:1, such as 1:20, 1:10, 1:5, 1:2, 1:1, 2:1, 5:1, 10:1, 20:1. In some embodiments, 2,4-diaminotoluene or 2,6-diaminotoluene can be used alone as the diamino toluene reactant in the reaction system. In some embodiments, 2,4-diaminotoluene and 2,6-diaminotoluene can be mixed as the diamino toluene reactant in the reaction system.

[0035] In the present invention, the molar ratio of the catalyst to diaminotoluene can be (0.001 - 0.1):1, preferably (0.002 - 0.02):1, such as 0.002:1, 0.005:1, 0.01:1, 0.15:1, 0.02:1. Controlling the amounts of the catalyst and diaminotoluene within the above molar ratio range can achieve the effect of maintaining a high product yield with less catalyst input.

[0036] In the present invention, the molar ratio of dimethyldisulfide to diaminotoluene can be (2 - 12):1, preferably (8 - 12):1, such as 8:1, 9:1, 10:1, 11:1, 12:1.

[0037] In the present invention, the reaction temperature can be 100 - 200 °C, preferably 150 - 190 °C, such as 150 °C, 160 °C, 170 °C, 180 °C, 190 °C. Controlling the reaction temperature within the above range is beneficial to improving the product yield.

[0038] In the present invention, the reaction time can be 2 - 10 h, preferably 4 - 6 h, such as 4 h, 4.5 h, 5 h, 5.5 h, 6 h. The reaction of the present invention can be completed within the above reaction time, and the reaction time is short and the reaction efficiency is high.

[0039] In the present invention, the base in the base solution can be one or more selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide, preferably sodium hydroxide.

[0040] In the present invention, the solvent in the base solution can be one or more selected from water, ethanol, and methanol, preferably water.

[0041] In the present invention, the mass concentration of the base in the base solution can be 0.1% - 100%, preferably 1% - 30%, such as 2%, 5%, 10%, 15%, 20%, 25%, 30%.

[0042] In the present invention, the molar ratio of the solute in the base solution to the catalyst can be (1 - 10):1, preferably (1 - 3):1, such as 1:1, 1.2:1, 1.5:1, 1.8:1, 2.1:1, 2.4:1, 2.7:1, 3:1.

[0043] In the present invention, after adding the base solution, stirring can be carried out at 70 - 90 °C for 0.5 - 1 h. In some embodiments, the stirring temperature can be 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, and the stirring time can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h.

[0044] In the present invention, during the vacuum distillation process, the distillation pressure can be 0 to 1000 Pa, such as 100 Pa, 200 Pa, 500 Pa, 800 Pa.

[0045] In the present invention, during the vacuum distillation process, the distillation temperature can be 170 to 190 °C. In the present invention, under a pressure of 0 to 1000 Pa, the boiling point of the product DMTDA is 170 to 190 °C.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) By continuously introducing DMDS and distilling and condensing it, the by-product methyl mercaptan is completely carried out, eliminating its influence on the reaction selectivity, and thus avoiding its influence on the yield.

[0048] (2) By continuously introducing DMDS and distilling and condensing it, the by-product methyl mercaptan is carried out in a timely manner, avoiding its poisoning of the catalyst, thus avoiding the reduction of its catalytic activity, reducing the amount of catalyst used, and reducing the production cost.

[0049] (3) The reaction time of the present invention is short, the production efficiency is high, and the product purity is high.

[0050] (4) The present invention uses the neutralization distillation method for purification and decolorization, having the advantages of economic and environmental protection in the purification process.

[0051] Compared with CN1718571A, the present invention has the following advantages:

[0052] (1) CN1718571A is forced reflux + nitrogen purge, while the present invention is continuously introducing DMDS and distilling and condensing it; the nitrogen purge cannot be completely blown out because methyl mercaptan is easily soluble in dimethyl disulfide, and at the forced reflux position, part of the methyl mercaptan dissolved in dimethyl disulfide cannot be blown out.

[0053] (2) The present invention continuously introduces DMDS and distills and condenses it, with a wide temperature adjustment range (room temperature to 280 °C); while for forced reflux + nitrogen purge, the temperature adjustment range is narrow (room temperature to 160 °C).

[0054] (3) The present invention has the advantages of high yield and high catalytic activity. Whether methyl mercaptan is carried out more cleanly directly affects the selectivity, and thus affects the yield. If methyl mercaptan cannot be carried out in a timely manner, it will poison the catalyst and reduce the catalytic activity.

[0055] (4) The optimal reaction temperature of CN1718571A is 135 to 150 °C and the maximum reaction temperature can only be 160 °C; the present invention can raise the reaction temperature to above 180 °C, maintain a very high conversion rate and reaction selectivity, and the reaction time is shorter and the reaction efficiency is higher.

[0056] (5) The synthesis effect of the present invention at a reaction time of 4 h and a catalyst dosage of 0.78% is superior to that of CN1718571A at a reaction time of 9 h and a catalyst dosage of 5.8%. The catalyst of the present invention has higher activity and higher reaction efficiency.

[0057] (6) The present invention uses the neutralization distillation method for purification and decolorization, which has the advantages of economic and environmental protection in the purification process.

[0058] The present invention will be described below by way of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents, and materials used in the examples are conventional methods, reagents, and materials in the art unless otherwise specified. The raw material compounds in the examples can all be obtained through commercial channels.

[0059] Example 1

[0060] Add 61 g of 2,4-TDA (0.5 mol) and 0.95 g of CuI (0.005 mol) to a 500 mL four-necked flask equipped with a peristaltic pump and a distillation device. Heat up to 150 °C and start pumping in 500 g of DMDS (5.3 mol). DMDS is continuously introduced and condensed and distilled out, carrying out the by-product methyl mercaptan. The reaction is completed after pumping for 5 h. Cool down and sample for gas chromatography (GC) analysis. The conversion rate of TDA is measured to be 100%, and the reaction selectivity is 98.1%.

[0061] Add 100 g of DMDS to the four-necked flask and filter using a Buchner funnel. The filter cake is recycled for the catalyst. Add 1 g of 20% NaOH aqueous solution to the filtrate and heat up to 80 °C and stir for 0.5 h. Finally, carry out vacuum distillation and collect the fraction at 170 - 190 °C under the condition of 200 Pa. GC analysis shows that the purity of DMTDA is 97.5%.

[0062] Example 2

[0063] Add 61 g of 2,4-TDA (0.5 mol) and 0.48 g of CuI (0.0025 mol) to a 500 mL four-necked flask equipped with a peristaltic pump and a distillation device. Heat up to 180 °C and start pumping in 400 g of DMDS (4.2 mol). DMDS is continuously introduced and condensed and distilled out, carrying out the by-product methyl mercaptan. The reaction is completed after pumping for 4 h. Cool down and sample for GC analysis. The conversion rate of TDA is measured to be 100%, and the reaction selectivity is 98.3%.

[0064] Add 100g DMDS into a four-necked flask, filter with a Bush funnel, and use the filter cake to recover the catalyst. Add 1.2g of 10% NaOH aqueous solution to the filtrate, heat to 80℃ and stir for 0.5h. Finally, perform vacuum distillation and collect the fraction of 170-190℃ under 200Pa. The purity of DMTDA measured by GC analysis is 97.8%.

[0065] Example 3

[0066] Add 61g 2,4-TDA (0.5mol) and 0.95g CuI (0.005mol) to a 500mL four-necked flask with a peristaltic pump and a distillation device, raise the temperature to 180°C, start pumping in 400g DMDS (4.2mol), continue to introduce DMDS and evaporate and condense, taking out the by-product methyl mercaptan, and the reaction is completed after 4h of pumping. Cool down and take samples for GC analysis, and the conversion rate of TDA is 100% and the reaction selectivity is 98.5%.

[0067] Add 100g DMDS into a four-necked flask, filter with a Bush funnel, and use the filter cake to recover the catalyst. Add 12g of 2% NaOH aqueous solution to the filtrate, heat to 80℃ and stir for 0.5h. Finally, perform vacuum distillation and collect the fraction of 170-190℃ under 200Pa. The purity of DMTDA measured by GC analysis is 98.3%.

[0068] Example 4

[0069] Add 61g 2,6-TDA (0.5mol) and 0.95g CuI (0.005mol) to a 500mL four-necked flask with a peristaltic pump and a distillation device, raise the temperature to 180°C, start pumping in 400g DMDS (4.2mol), continue to pass DMDS and evaporate and condense, taking out the by-product methyl mercaptan, and the reaction is completed after 4h of pumping. Cool down and take samples for GC analysis, and the conversion rate of TDA is measured to be 99.6%, and the reaction selectivity is 97.0%.

[0070] Add 100g DMDS into a four-necked flask, filter with a Bush funnel, and use the filter cake to recover the catalyst. Add 12g of 2% NaOH aqueous solution to the filtrate, heat to 80℃ and stir for 0.5h. Finally, distill under reduced pressure and collect the 170-190℃ fraction under 200Pa. The purity of DMTDA measured by GC analysis is 97.4%.

[0071] Comparative Example 1

[0072] 61 g of 2,4-TDA (0.5 mol) was charged into a 500 mL four-necked flask, and 0.95 g of CuI (0.005 mol) was added for activation for 0.5 h while maintaining the temperature at 150 °C. Then, 120 g (1.3 mol) of DMDS was added. During the reaction, DMDS continuously escaped and was condensed and refluxed to the reactor through a condenser. After reacting for 1.5 h, nitrogen was intermittently introduced into the four-necked flask at a pressure of 0.2 MPa. A total of 8.7 g of nitrogen was introduced, 1.74 g was introduced between 1.5 and 2 h after the reaction, 3.48 g was introduced between 3 and 5 h after the reaction, and the remaining nitrogen was introduced in the later stage to continuously remove methanethiol in the reaction. After reacting for a certain period of time, a sample was taken for GC analysis. The raw material peak disappeared, the total reaction time was 5 h, and the conversion rate of TDA was 87.4% and the reaction selectivity was 26.1% as analyzed by GC after sampling.

Claims

1. A method for preparing dimethylthiotoluenediamine, characterized in that, The method includes continuously introducing dimethyl disulfide into a reaction system containing diamino toluene and a catalyst for reaction, and distilling and condensing dimethyl disulfide during the reaction to carry out by-products methyl mercaptan, and after the reaction, purification and decolorization are carried out by neutralization distillation to obtain dimethylthio toluenediamine; The neutralization distillation method includes: adding dimethyl disulfide to the reaction solution after the reaction to dilute it, then filtering the reaction solution to obtain a filtrate, adding an alkali solution to the filtrate for neutralization, heating and stirring, and finally carrying out vacuum distillation.

2. The method according to claim 1, characterized in that, The catalyst is a metal halide or a combination of a metal element and a halogen element; the metal halide is preferably selected from one or more of cuprous iodide, ferrous iodide, and zinc chloride, more preferably cuprous iodide; the combination of the metal element and the halogen element is preferably a combination of copper element and iodine element.

3. The method according to claim 1, characterized in that, The diamino toluene is selected from one or two of 2,4-diamino toluene and 2,6-diamino toluene.

4. The method according to claim 1, characterized in that, The molar ratio of the catalyst to diamino toluene is (0.001 - 0.1):1, preferably (0.002 - 0.02):

1.

5. The method according to claim 1, characterized in that, The molar ratio of dimethyl disulfide to diamino toluene is (2 - 12):1, preferably (8 - 12):

1.

6. The method according to claim 1, wherein The reaction temperature is 100 - 200 °C, preferably 150 - 190 °C.

7. The method according to claim 1, characterized in that The reaction time is 2 - 10 h, preferably 4 - 6 h.

8. According to the method described in claim 1, wherein the alkali in the alkali solution is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide, preferably sodium hydroxide; and / or the solvent in the alkali solution is selected from one or more of water, ethanol, and methanol, preferably water.

9. The method according to claim 1, characterized in that, The method has one of the following 239955 or more features: the mass concentration of the alkali in the alkali solution is 0.1% - 100%, preferably 1% - 30%; the molar ratio of the alkali in the alkali solution to the catalyst is (1 - 10):1, preferably (1 - 3):1; stir for 0.5 - 1 h at 70 - 90 °C after adding the alkali solution.

10. The method according to claim 1, characterized in that, During the vacuum distillation process, the distillation pressure is 0 - 1000 Pa, and the distillation temperature is 170 - 190 °C.