Preparation method of zinc ethylphenyl dithiocarbamate

Abstract

The invention discloses a preparation method of zinc ethyl phenyl dithiocarbamate, belongs to the technical field of rubber vulcanization, and particularly relates to a preparation method of zinc N, N '-ethyl phenyl dithiocarbamate. The preparation method comprises the following steps: firstly, uniformly mixing water, triethylamine, zinc oxide and N-ethylaniline, and then adding carbon disulfide into the mixed solution for reaction; and after the reaction is finished, separating triethylamine, and finally filtering, washing, drying and crushing the reactant, thereby obtaining the N, N '-ethyl phenyl zinc dithiocarbamate in a single reactor. The zinc N, N '-ethyl phenyl dithiocarbamate prepared by the method does not generate salt-containing waste liquid and surfactant residue, the product appearance is white, the amine residue is less than or equal to 0.1%, the heating loss is less than or equal to 0.2%, the melting point is more than or equal to 207.0 DEG C, the yield is more than or equal to 99.0%, and the purity is more than or equal to 99.0%; and the high-end rubber product is applied to medical latex and thin, transparent, bright-color and other high-end rubber products, is excellent in performance and free of color pollution, and has a very good market prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber vulcanization accelerator preparation, and in particular to a preparation method of zinc ethyl phenyl dithiocarbamate. Background Art

[0002] Today, with the integration of the global economy, China's rubber auxiliaries have experienced a development process from scratch and from weak to strong, and now have become the leader of the industry. Zinc ethyl phenyl dithiocarbamate belongs to rubber vulcanization accelerators, which can effectively vulcanize rubber at low temperatures; it is mainly used in latex thin, transparent, and brightly colored products, and has the characteristics of non-toxic, odorless, fast vulcanization speed, and good anti-scorching performance. With the continuous improvement of product standards and the increasing intensity of environmental protection management, as well as the excellent requirements of downstream enterprises for product performance; the existing methods for preparing zinc ethyl phenyl dithiocarbamate can no longer meet the requirements of the industry.

[0003] Currently, the preparation methods of zinc ethyl phenyl dithiocarbamate mainly have the following routes: Patent (CN 106588727A) discloses a method for preparing rubber vulcanization accelerator zinc N-ethyl-N-phenyl dithiocarbamate by a one-step method. In this method, water is added to a reaction flask, and then zinc oxide, N-ethylaniline, and a surfactant are added in sequence. The mixture is stirred at 100 revolutions per minute for 30 minutes. Carbon disulfide is divided into 3 equal parts, and 1 part of carbon disulfide is slowly added dropwise at 20 °C, which takes about 1 hour to finish dropping. After dropping, the temperature is raised to 30 °C and another 1 part of carbon disulfide is added dropwise, which takes about 1 hour to finish dropping. Then the temperature is raised to 40 °C and the last 1 part of carbon disulfide is added dropwise, which takes about 1 hour to finish dropping. The mixture is kept warm at 40 °C for 2 hours, cooled to room temperature, centrifuged, dried and pulverized to obtain the finished product zinc ethyl phenyl dithiocarbamate. The disadvantage of this method is that the amino group (-NH2) of aniline forms a conjugated system with the benzene ring through lone pair electrons. The lone pair electrons of the nitrogen atom can delocalize into the π system of the benzene ring to form multiple resonance structures. This delocalization results in a decrease in the electron density on the nitrogen atom, and the lone pair electrons are no longer completely localized on the nitrogen atom, thus weakening its ability as a nucleophile. As a result, the reaction is slow, the amine residue is high, and the appearance has a color. Although using a surfactant as a catalyst to disperse zinc oxide is beneficial to the reaction, it is difficult to completely remove the surfactant mixed in the product, and it is difficult to meet the requirements of high-end products.

[0004] The production method of zinc ethylphenyl dithiocarbamate disclosed in the patent (CN 101215249A) is as follows: into a reaction kettle filled with purified water, a specified amount of N-ethylaniline and sodium hydroxide are added successively under stirring. The temperature is controlled at 10 - 35 °C, and then a specified amount of carbon disulfide liquid is added dropwise, with the time controlled for 4 - 6 hours. After the dropwise addition is completed, stir for 1 - 2 hours, then filter and decolorize to remove impurities. The temperature of the filtrate is controlled at 20 - 40 °C, and a zinc chloride solution is added dropwise to carry out a metathesis reaction. After the reaction ends, the pH value of the reaction solution is adjusted with sulfuric acid to the range of 5 - 9, and then the reaction ends. Then stir for 1.5 hours, carry out solid-liquid separation, discard the liquid, and dry, crush, screen, and package the solid.

[0005] Journal of Wenzhou Normal College (Natural Sciences), Vol. 19, No. 3, June 1998, pp. 48 - 50 reported the catalytic synthesis method of zinc N-ethyl-N-phenyl dithiocarbamate. First, a nucleophilic addition reaction occurs between N-ethylaniline and carbon disulfide to form N-ethyl-N-phenyl dithiocarbamic acid, which is then neutralized with sodium hydroxide to form sodium N-ethyl-N-phenyl dithiocarbamate, and then a metathesis reaction occurs with an aqueous zinc chloride solution to form zinc N-ethyl-N-phenyl dithiocarbamate, which is the accelerator PX. This literature claimed that a catalyst was added in the two-step production process, but did not disclose the specific components of the catalyst used.

[0006] The above two methods generally have the following problems: there are a large number of sodium chloride by-products in the reaction system, and a large amount of water is needed for desalting and washing; the mother liquor also needs to be distilled and concentrated, resulting in high manufacturing costs. In addition, the sodium chloride mixed in the product is difficult to completely remove, which limits its application in fields such as latex, wire and cable.

[0007] In view of the above problems, the present invention discloses a preparation method of zinc N,N'-ethylphenyl dithiocarbamate. The zinc N,N'-ethylphenyl dithiocarbamate prepared according to this method has a fast reaction rate, does not produce waste liquid containing salt, has no surfactant residue, the product appearance is white, the amine residue ≤ 0.1%, the heating loss ≤ 0.2%, the yield ≥ 99.0%, and the purity ≥ 99.5%, which can meet the performance requirements of various products. Summary of the Invention

[0008] The purpose of the present invention is to address the technical defects existing in the prior art, and the present invention provides a preparation method of zinc N,N'-ethylphenyl dithiocarbamate.

[0009] The present invention is implemented through the following technical solutions:

[0010] A preparation method of zinc N,N'-ethylphenyl dithiocarbamate includes the following steps:

[0011] (1) Put water, triethylamine, zinc oxide, and N-ethylaniline into the reactor in sequence, control the temperature at 35 - 40 °C, and stir for 10 - 15 min;

[0012] (2) At 35 - 40 °C, slowly add carbon disulfide. After completion, control the temperature at 35 - 40 °C and react for 2 - 3 h;

[0013] (3) While slowly raising the temperature to 40 - 100 °C, separate triethylamine;

[0014] (4) After reaching 100 °C, hold for 0.5 - 1 h;

[0015] (5) After completion, cool the reaction solution to 25 - 30 °C, filter, wash, dry, and pulverize to obtain the zinc N,N'-ethylphenyldithiocarbamate.

[0016] Preferably, the molar ratio of N-ethylaniline, carbon disulfide, and zinc oxide is 1.0 - 1.01:1.0:0.5 - 0.51.

[0017] Preferably, the particle size of the zinc oxide is 20 - 50 nm.

[0018] Preferably, the mass of water is 2.5 - 3 times that of N-ethylaniline.

[0019] Preferably, the mass of triethylamine is 1 - 1.5 times that of N-ethylaniline.

[0020] For the zinc N,N'-ethylphenyldithiocarbamate prepared by the present invention, the amine residue ≤ 0.1%, the heating loss ≤ 0.2%, the yield ≥ 99.0%, and the purity ≥ 99.5%.

[0021] The preparation method of zinc ethylphenyldithiocarbamate proposed by the present invention has the following beneficial effects:

[0022] 1. For the zinc N,N'-ethylphenyldithiocarbamate prepared by this method, the reaction rate is fast, no salt-containing waste liquid is generated, no surfactant residue remains, the product appearance is white, the amine residue ≤ 0.1%, the heating loss ≤ 0.2%, the yield ≥ 99.0%, and the purity ≥ 99.5%, which can meet the performance requirements of various products; and this method can be carried out on conventional equipment, with simple operation and high safety;

[0023] 2. It was first proposed to synthesize zinc N,N'-ethylphenyldithiocarbamate by catalyzing N-ethylaniline, carbon disulfide and zinc oxide in water with triethylamine. This increased the fusion of each phase and component of the reaction substrates and solvents, raised the reaction temperature of the system, greatly enhanced the reaction rate and process. Triethylamine was recovered during the reaction and could be reused repeatedly. Triethylamine had a synergistic effect, its triple functions (catalysis / dispersion / azeotropy) in the reaction system, and the synergistic effect it could produce with the properties of nanomaterials. In this application, the nucleophilicity of the amino group of activated N-ethylaniline was used as a catalyst and also as a reaction solvent, and it was recovered by azeotropic distillation to achieve a salt-free and surfactant-free process;

[0024] 3. Zinc oxide with a particle size of 20 - 50 nm was used in synergy with triethylamine for dispersion to improve the reaction efficiency and make it fully dispersed in the reaction solution. Using the azeotropic principle, unreacted N-ethylaniline and carbon disulfide were separated from the product while separating triethylamine. Moreover, this application had simple operations, completed complexation - condensation - salification in a single reactor, avoided the intermediate separation step, realized an integrated reaction system, and was convenient for automated control. Limiting the particle size range of zinc oxide to 20 - 50 nm could ensure that the initial melting point of the product was ≥207.3°C, while taking into account both dispersion stability and industrial feasibility. Specific embodiments

[0025] The following specific examples illustrate the implementation modes of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] Unless otherwise specified, the examples and comparative examples are parallel tests with the same components, component contents, preparation steps, and preparation parameters. The test methods in the following examples are all conventional methods unless otherwise specified; the test materials used in the following examples are all obtained from commercial channels unless otherwise specified.

[0027] Unless otherwise stated, all reagents were used as received without further purification.

[0028] In the preparation examples and examples of the present invention, unless otherwise specified, "parts" are all parts by weight, and percentage concentrations are all weight concentrations unless otherwise specified.

[0029] The yield of zinc N,N'-ethylphenyldithiocarbamate is calculated by the ratio of the actual yield to the theoretical yield. The theoretical yield is calculated based on the molar ratio of the reactants (N-ethylaniline: carbon disulfide: zinc oxide). After the reaction is completed, the product is filtered, dried, and weighed. Then the yield = (actual yield / theoretical yield) × 100%; the purity is measured by high-performance liquid chromatography using a reverse-phase C18 column, with methanol / water at a volume ratio of 80:20 as the mobile phase, a flow rate of 1.0 mL / min, a wavelength of 254 nm, and a column temperature of 30°C; a standard curve is plotted using a standard product of known purity to calculate the content of the target substance in the sample; the amine residue is measured by liquid chromatography using a C18 column as the chromatographic column, with methanol / water as the mobile phase and a wavelength of 220 nm; the heat loss on drying is measured by the oven drying method. Weigh about 2 g of the sample, dry it at 105°C for 2 hours, cool it to room temperature, and then weigh it. The heat loss on drying = (mass before drying - mass after drying) / mass before drying × 100%; the initial melting point is measured by differential scanning calorimetry in a nitrogen atmosphere, with a heating rate of 5°C / min and a temperature range of 50 - 250°C, and the starting point of the endothermic peak is taken as the initial melting point; the D90 particle size of zinc N,N'-ethylphenyldithiocarbamate is measured by dynamic light scattering to judge the dispersion stability of zinc N,N'-ethylphenyldithiocarbamate, and the test standard is ISO1332.

[0030] Example 1

[0031] At room temperature, 165.00 g of water, 61.57 g (wt99.0%, 0.503 mol) of N-ethylaniline, 20.49 g (wt99.5%, 0.235 mol) of zinc oxide with a particle size of 20 nm, and 80.00 g of triethylamine were successively added into a four-necked flask equipped with a condenser. The temperature was raised to 35°C, and the mixture was stirred at this temperature for 15 min; while controlling the temperature at 35°C, 39.05 g of carbon disulfide (wt97.5%, 0.5 mol) was added dropwise. After completion, the mixture was stirred at 35°C for 2.5 h; the recovery device was opened, and while slowly raising the temperature to 100°C, triethylamine was separated by azeotropic distillation; after reaching 100°C, it was maintained for 30 min. The reaction solution was cooled to 25°C, filtered, washed, dried at 105°C, and pulverized to obtain 113.9 g of zinc N,N'-ethylphenyldithiocarbamate in a single reactor. The yield of zinc N,N'-ethylphenyldithiocarbamate was 99.5%, the purity detected by liquid chromatography was 99.7%, the N-ethylaniline residue detected by liquid chromatography was 0.05%, the heat loss on drying was 0.13%, the initial melting point was 207.7°C, the appearance was white, and the dispersion stability was 180.

[0032] Example 2

[0033] At room temperature, 330.00 g of water, 123.14 g (wt 99.0%, 1.006 mol) of N-ethylaniline, 40.98 g (wt 99.5%, 0.470 mol) of zinc oxide with a particle size of 50 nm, and 160.00 g of triethylamine were successively added into a four-necked flask equipped with a condenser. The temperature was raised to 40 °C, and the mixture was stirred at this temperature for 15 min. While controlling the temperature at 40 °C, 78.10 g of carbon disulfide (wt 97.5%, 1.000 mol) was added dropwise. After completion, the mixture was stirred at 40 °C for 2.5 h. The recovery device was opened, and while slowly raising the temperature to 100 °C, triethylamine was separated by azeotropic distillation. After reaching 100 °C, it was maintained for 30 min. The reaction solution was cooled to 30 °C, filtered, washed, dried at 105 °C, and pulverized to obtain 228.3 g of zinc N,N'-ethylphenyldithiocarbamate in a single reactor. The yield of zinc N,N'-ethylphenyldithiocarbamate was 99.7%, the purity detected by liquid chromatography was 99.8%, the residual amount of N-ethylaniline detected by liquid chromatography was 0.02%, the heating loss was 0.11%, the initial melting point was 207.3 °C, the appearance was white, and the dispersion stability was 300.

[0034] Example 3

[0035] At room temperature, 165.00 g of water, 61.57 g (wt 99.0%, 0.503 mol) of N-ethylaniline, 20.49 g (wt 99.5%, 0.235 mol) of zinc oxide with a particle size of 30 nm, and 80.00 g of recycled triethylamine were successively added into a four-necked flask equipped with a condenser. The temperature was raised to 35 - 40 °C, and the mixture was stirred at this temperature for 15 min. While controlling the temperature at 35 - 40 °C, 39.05 g of carbon disulfide (wt 97.5%, 0.5 mol) was added dropwise. After completion, the mixture was stirred at 35 - 40 °C for 2.5 h. The recovery device was opened, and while slowly raising the temperature to 100 °C, triethylamine was separated by azeotropic distillation. After reaching 100 °C, it was maintained for 30 min. The reaction solution was cooled to 25 - 30 °C, filtered, washed, dried at 105 °C, and pulverized to obtain 114.1 g of zinc N,N'-ethylphenyldithiocarbamate in a single reactor. The yield of zinc N,N'-ethylphenyldithiocarbamate was 99.7%, the purity detected by liquid chromatography was 99.7%, the residual amount of N-ethylaniline detected by liquid chromatography was 0.07%, the heating loss was 0.15%, the initial melting point was 207.5 °C, the appearance was white, and the dispersion stability was 250.

[0036] Application Example 1

[0037] The product of Example 1 was used in the production of medical latex gloves. Performance tests were carried out on the medical latex gloves prepared with the product of Example 1 and the medical latex gloves prepared with a commercially available PX accelerator, including vulcanization time test (ASTM D5289, 130 °C × 3 min vs 5 min), light transmittance test (ASTM D1746), and hemolysis rate test (ASTM F756). The vulcanization time of the medical latex gloves prepared with Example 1 was shortened by 40%. The light transmittance of the medical latex gloves prepared with Example 1 was 91%, that of the medical latex gloves prepared with the commercially available PX accelerator was 85%, the hemolysis rate of the medical latex gloves prepared with the commercially available PX accelerator was 0.8%, and that of the medical latex gloves prepared with Example 1 was 0.12%.

[0038] Comparative Example 1

[0039] 1000 g of water was added to a four-necked flask equipped with a condenser. 41 g (wt 99.5%, 0.501 mol) of zinc oxide, 121 g (wt 99.0%, 0.988 mol) of N-ethylaniline, and 0.06 g of sodium butylnaphthalenesulfonate were successively added and mixed for 30 min under stirring at 100 rpm. 87.6 g (wt 97.5%, 1.12 mol) was divided into three equal parts. 29.2 g of carbon disulfide was slowly added dropwise at 20 °C over about 1 h. After the addition was completed, the temperature was raised to 30 °C and another 29.2 g of carbon disulfide was added dropwise over about 1 h. Then the temperature was raised to 40 °C and another 29.2 g of carbon disulfide was added dropwise over about 1 h. It was kept warm at 40 °C for 2 h, cooled to room temperature, centrifuged, dried, and pulverized to obtain 222.9 g of the finished product zinc N-ethyl-N-phenyldithiocarbamate. The yield of zinc N-ethyl-N-phenyldithiocarbamate was 98.5%. The purity detected by liquid chromatography was 99.1%. The residual N-ethylaniline detected by liquid chromatography was 0.7%. The heating loss was 0.19%. The initial melting point was 205.0 °C. The appearance was a light yellow powder.

[0040] This comparative example was repeatedly tested according to the preparation method disclosed in the patent (CN 106588727A). The optimal experimental results were that the product yield was 98.7%, the purity detected by liquid chromatography was 99.1%, the residual N-ethylaniline was 0.7%, the heating loss was 0.19%, the initial melting point was 205.0 °C, and the appearance was a light yellow powder. The main reasons for the low yield, purity, and initial melting point, and the high residual N-ethylaniline were the poor nucleophilicity of N-ethylaniline, the residual surfactant, the uneven dispersion of zinc oxide, and the failure to remove the residual N-ethylaniline and carbon disulfide.

[0041] Comparative Example 2

[0042] At room temperature, 252.5 g (wt 99.0%, 2.063 mol) of N-ethylaniline and 20 g of triethylamine were successively added into a four-necked flask equipped with a condenser. The temperature was raised to 35 ± 2 °C, and the mixture was stirred at this temperature for 15 min. While controlling the temperature at 35 ± 2 °C, 183.96 g of carbon disulfide (wt 97.5%, 2.356 mol) was added dropwise. After completion, the mixture was stirred at 35 ± 2 °C for 1.0 h, and then 826.0 g of sodium hydroxide (wt 10.0%, 2.065 mol) was added dropwise for neutralization. Another 5000 ml flask was equipped with an electric stirrer. First, 5 g of concentrated hydrochloric acid was added, and then 142 g (wt 98.5%, 1.026 mol) of zinc chloride solid was added. The stirrer was started to dissolve it, and then 1000 ml of water was added for dilution. The prepared intermediate was added while stirring, maintaining the pH at 5. After the addition, the mixture was stirred for 1 h. It was filtered, washed until neutral, and dried to obtain 453.6 g of zinc N,N'-ethylphenyldithiocarbamate. The yield of zinc N,N'-ethylphenyldithiocarbamate was 96.0%, the purity detected by liquid chromatography was 97.9%, the residual amount of N-ethylaniline detected by liquid chromatography was 0.5%, the loss on heating was 0.3%, the initial melting point was 205.3 °C, and the appearance was a pale yellow powder.

[0043] This comparative example was repeatedly tested according to the "Catalytic Synthesis Method of Zinc N-Ethyl-N-phenyldithiocarbamate" published by Ye Fangchen, Wu Xiangbiao, Journal of Wenzhou Normal College (Natural Science Edition), Vol. 19, No. 3, June 1998. The optimal experimental results were that the product yield was 96.0%, the purity detected by liquid chromatography was 97.9%, the residual amount of N-ethylaniline was 0.5%, the loss on heating was 0.3%, the initial melting point was 205.3 °C, and the appearance was a pale yellow powder. The main reasons for the low yield, purity, and initial melting point; and the high residual amount of N-ethylaniline were that zinc N,N'-ethylphenyldithiocarbamate was easily decomposed under acidic or alkaline conditions; there were a large amount of sodium chloride by-products in the reaction system, and it was difficult to completely remove the impurities in the product.

[0044] Comparative Example 3

[0045] The difference from Example 1 was that the triethylamine in Example 1 was replaced with an equimolar amount of trimethylamine, and other conditions remained unchanged. Then the reaction time was extended to 5 h, the product was pale yellow, the yield was 94.3%, and the amine residue was 0.68%.

[0046] Comparative Example 4

[0047] The difference from Example 1 was that zinc oxide with a particle size of 55 nm of an equal mass was used, and other contents were the same as in Example 1. Then the reaction time was extended to 4.5 h, and the product yield decreased to 93.8%.

[0048] Comparative Example 5

[0049] The difference from Example 1 is that zinc oxide with a particle size of 15 nm and equal mass is used. Other contents are the same as those in Example 1. Then the reaction time is 1.8 h, the residual amount of N-ethylaniline is 0.3%, but the dispersion stability is 150, and the initial melting point is 208.5 °C. In industry, ultrasonic waves are used to improve the dispersion stability, but the industrial cost will increase significantly.

[0050] Comparative Example 6

[0051] The difference from Example 1 is that the azeotropic distillation in step (3) is omitted, and the temperature is directly raised to 100 °C for reaction. The amine residue in the product is 1.05%, and the heat loss on heating is 0.45%.

[0052] The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A preparation method of zinc ethyl phenyl dithiocarbamate, characterized in that, include: (1) Mix water, triethylamine, zinc oxide and N-ethylaniline and stir; (2) adding carbon disulfide to the mixed solution of step (1) for reaction; (3) heating and separating triethylamine, and keeping warm; (4) The reaction solution is post-treated to obtain zinc N,N'-ethylphenyldithiocarbamate.

2. The preparation method of zinc ethyl phenyl dithiocarbamate according to claim 1, characterized in that, The method comprises the steps of: (1) mixing water, triethylamine, zinc oxide and N-ethylaniline at 35-40° C. and stirring; adding carbon disulfide to the mixed solution of step (1) and reacting the mixture at 35-40° C. for 2-3 hours.

3. The preparation method of zinc ethyl phenyl dithiocarbamate according to claim 1, characterized in that, The step (3) of heating the reaction solution to 100° C. and separating the triethylamine is then carried out, and the temperature is maintained for 0.5-1 hour. The post-treatment of the reaction solution comprises cooling the reaction solution to 25-30° C., filtering, washing, drying and crushing.

4. The preparation method of zinc ethylphenyldithiocarbamate according to claim 1, characterized in that, The molar ratio of the N-ethylaniline, carbon disulfide and zinc oxide is 1.0-1.01:1.0:0.45-0.

51.

5. The preparation method of zinc ethyl phenyl dithiocarbamate according to claim 1, characterized in that, The particle size of the zinc oxide is 20-50 nm.

6. The preparation method of zinc ethyl phenyl dithiocarbamate according to claim 1, characterized in that, The mass of the water is 2.5-3 times the mass of N-ethylaniline.

7. The preparation method of zinc ethyl phenyl dithiocarbamate according to claim 1, characterized in that, The mass of the triethylamine is 1-1.5 times that of N-ethylaniline; and in the step (3), the triethylamine is separated by azeotropic distillation.

8. The preparation method of zinc ethyl phenyl dithiocarbamate according to claim 3, characterized in that, The drying condition is drying at 105° C. until the heating loss is ≤0.2%.

9. The preparation method of zinc ethyl phenyl dithiocarbamate according to claim 1, characterized in that, The residual N-ethylaniline content in the obtained N,N'-ethylphenyldithiocarbamate zinc is less than or equal to 0.1%, and the purity is greater than or equal to 99.5%. No surfactant or salt-containing reagent is added during the reaction process.

10. The preparation method of zinc ethylphenyl dithiocarbamate according to claim 1, characterized in that, The preparation method is completed in a single reactor without any intermediate separation step.