Disclosure of Invention
In view of the above technical problems, the present invention provides a method for producing a low-chroma polythiol compound, which improves the quality of an optical resin lens. The production method has the advantages of simple operation, easily obtained raw materials, small using amount, low energy consumption, no need of equipment investment and suitability for industrial production.
In order to achieve the purpose, the technical scheme adopted by the application is as follows:
adding a surfactant into an alkaline solution, carrying out hydrolysis reaction to obtain a polythiol crude product mixture, separating, washing with water, and drying to obtain a polythiol compound with low chroma.
The surfactant is one or more of stearic acid, lauric acid, oleic acid, sodium dodecyl sulfate, sodium lauryl sulfate and sodium dodecyl benzene sulfonate.
The dosage of the surfactant is 0.1-1% of the mass of the isothiourea salt. If the ratio is too low, the effective effect cannot be achieved. If the ratio is too high, raw materials are wasted.
Preferably, the alkaline solution has a pH of 10 or more and is subjected to alkaline hydrolysis using isothiourea salt under alkaline conditions to obtain polythiols.
Preferably, the alkali in the alkaline solution is one or a mixture of sodium hydroxide, potassium hydroxide, ammonia water, sodium carbonate and potassium carbonate.
Preferably, the alkali in the alkaline solution is sodium carbonate or potassium carbonate.
Preferably, the hydrolysis reaction temperature is 30-70 ℃.
Preferably, the hydrolysis reaction temperature is 45-60 ℃. If the reaction temperature is low, the reaction rate is slow and the reaction time is long. If the reaction temperature is high, the energy consumption is high, and side reactions occur to generate impurities.
Preferably, the hydrolysis reaction time is 2-5 h.
Preferably, the hydrolysis reaction time is 2.5-3.5 h. If the reaction time is short, the reaction is incomplete; if the reaction time is long, time is wasted, and other reactions may occur.
The synthesis of isothiourea salt is synthesized according to the technical scheme in patent CN105906773B, and the isothiourea salt is formed by salt forming reaction after mixing polyalcohol, thiourea and acid. Wherein thiourea is preferably reacted in an amount of 2.8 to 3.5 moles, preferably 3 to 5 moles, based on 1 mole of the polyol compound, and the acid is preferably reacted at 90 to 120 ℃ for 2 to 10 hours. The acid is one or more of hydrochloric acid, sulfuric acid, hydrobromic acid and phosphoric acid. The synthesis of isothiourea salts is not limited to patent CN105906773B, and isothiourea salts synthesized by other methods can be also applied to the present invention.
The polyol is mainly prepared by the reaction of mercaptoethanol, epichlorohydrin and alkali solution under certain conditions, wherein the polyol comprises the following components in part by weight:
preferably, the drying is adsorption drying, and the drying agent is one or a mixture of silica gel, calcium oxide, magnesium sulfate and phosphorus pentoxide.
The invention firstly provides a process for preparing polythiol compounds, and in the alkaline hydrolysis process of isothiourea salt, the surfactant is added, so that the surfactant has good humidifying and solubilizing effects, and although the surfactant cannot directly participate in the hydrolysis reaction process, the added surfactant can promote the isothiourea salt to carry out hydrolysis reaction, so that the isothiourea salt is hydrolyzed to the maximum extent to obtain the polythiol compound. In the existing process for generating polythiol, no surfactant is added, when a certain amount of intermediate product generated in the hydrolysis process of isothiourea salt reaches, the forward progress of the reaction can be inhibited, so that the hydrolysis reaction is not thorough, the obtained product has high chroma, low purity and low yield, and when the surfactant is added, the hydrolysis reaction can be thoroughly carried out, the alkaline hydrolysis degree of the reaction is increased, the generation of colored impurities is reduced, the purity of the product is improved, and the chroma of the product is reduced.
In view of the foregoing, a method for producing low color polythiol compounds is disclosed. The production method is simple to operate, raw materials are easy to obtain, the using amount is small, the energy consumption is low, the safety and the environmental protection are realized, equipment does not need to be input, the obtained product can meet the requirements of industries such as fine chemical engineering and the like, the quality of downstream products is improved, the optical resin lens with excellent performance is easy to prepare, the requirements of customers and markets are met, and the social and economic values are higher.
Detailed Description
The following further description of the present invention is provided in connection with specific embodiments to enable those skilled in the art to further understand the present invention, and not to limit the present invention, and all techniques based on the principles described herein are within the scope of the present invention.
Example 1
(a) Pouring 190g of polyol A into a four-neck flask, adding 115g (3mol) of thiourea and 152g of hydrochloric acid (3mol) with the mass fraction of 36%, and carrying out reflux reaction at 100 ℃ for 3.5h to form isothiourea salt;
(b) cooling to room temperature, adding a sodium carbonate solution to adjust the pH of the system to 12, simultaneously adding 0.52g of lauric acid, heating to 30 ℃, and carrying out hydrolysis reaction for 2 hours to obtain a polythiol crude product mixture;
(c) and (c) mixing and separating the crude product obtained in the step (b), washing twice, and drying and filtering by using 5% silica gel to obtain the polythiol compound with low chroma.
The chromaticity of the polythiol product obtained in the example 1 of the invention was measured by using a high-precision multifunctional spectrocolorimeter, and the result showed that the chromaticity of the polythiol compound obtained in the example 1 of the invention was 10 Hazen.
Example 2
(a) Pouring 200g of polyol B into a four-neck flask, adding 123g of thiourea (3.2mol) and 177g of hydrochloric acid (3.5mol) with the mass fraction of 36%, and carrying out reflux reaction at 110 ℃ for 2h to form isothiourea salt;
(b) cooling to room temperature, adding an aqueous ammonia solution to adjust the pH of the system to 13, simultaneously adding 4g of sodium dodecyl sulfate, heating to 45 ℃, and carrying out hydrolysis reaction for 2.5 hours to obtain a polythiol crude product mixture;
(c) and (c) mixing and separating the crude product obtained in the step (b), washing twice, and drying and filtering by adopting 6% of phosphorus pentoxide to obtain the polythiol compound with low chroma.
The chromaticity of the polythiol product obtained in the embodiment 2 of the invention is detected by using a high-precision multifunctional spectrocolorimeter, and the result shows that the chromaticity of the polythiol compound obtained in the embodiment 2 of the invention is 9 Hazen.
Example 3
(a) Pouring 180g of polyol A into a four-neck flask, adding 126g of thiourea (3.3mol) and 203g of hydrochloric acid (4mol) with the mass fraction of 36%, and carrying out reflux reaction at 112 ℃ for 2.5h to form isothiourea salt;
(b) cooling to room temperature, adding sodium hydroxide solution to adjust system pH to 10, simultaneously adding 2g sodium dodecyl benzene sulfonate, heating to 70 ℃, and carrying out hydrolysis reaction for 3.5h to obtain a polythiol crude product mixture;
(c) and (c) mixing and separating the crude product obtained in the step (b), washing twice, and drying and filtering by adopting 10% calcium oxide to obtain the polythiol compound with low chroma.
The chromaticity of the polythiol product obtained in the embodiment 3 of the invention is detected by using a high-precision multifunctional spectrocolorimeter, and the result shows that the chromaticity of the polythiol compound obtained in the embodiment 3 of the invention is 8 Hazen.
Example 4
(a) 185g of polyol B is poured into a four-neck flask, 134g of thiourea (3.5mol) and 253g of hydrochloric acid (5mol) with the mass fraction of 36% are added, and reflux reaction is carried out at 115 ℃ for 2h to form isothiourea salt;
(b) cooling to room temperature, adding potassium carbonate solution to adjust the pH of the system to 11, simultaneously adding 5g of lauryl alcohol sodium sulfate, heating to 60 ℃, and carrying out hydrolysis reaction for 5 hours to obtain a polythiol crude product mixture;
(c) and (c) mixing and separating the crude product obtained in the step (b), washing twice, and drying and filtering by adopting 10% calcium oxide to obtain the polythiol compound with low chroma.
The chromaticity of the polythiol product obtained in the embodiment 4 of the invention is detected by using a high-precision multifunctional spectrocolorimeter, and the result shows that the chromaticity of the polythiol compound obtained in the embodiment 4 of the invention is 9 Hazen.
Comparative example 1
(a) Pouring 185g of polyol B into a four-neck flask, adding 110g of thiourea and 200g of hydrochloric acid with the mass fraction of 36%, and carrying out reflux reaction at 112 ℃ for 2h to form isothiourea salt;
(b) cooling to room temperature, adding a potassium hydroxide solution to adjust the pH of the system to 12, and carrying out hydrolysis reaction for 3h at 50 ℃ to obtain a polythiol crude product mixture;
(c) and (c) mixing and separating the crude product obtained in the step (b), washing twice, and drying and filtering by adopting 4% magnesium sulfate to obtain the polythiol compound with low chroma.
The chromaticity of the polythiol product obtained in comparative example 1 was measured with a high-precision multifunctional spectrocolorimeter, and the results showed that the polythiol compound obtained in comparative example 1 had a chromaticity of 15 Hazen.
Comparative example 2
(a) Pouring 185g of polyol A into a four-neck flask, adding 110g of thiourea and 200g of hydrochloric acid with the mass fraction of 36%, and carrying out reflux reaction at 112 ℃ for 2h to form isothiourea salt;
(b) cooling to 40 ℃, adding 250g of toluene into isothiourea salt, introducing 255g of ammonia water with the mass fraction of 20%, and performing hydrolysis reaction for 6 hours at 50 ℃ to obtain a polythiol crude product mixture;
(c) and (c) mixing and separating the crude product obtained in the step (b), performing water washing, acid washing, water washing, alkali washing and water washing, removing toluene and trace moisture under heating and reduced pressure, and performing reduced pressure filtration by using a 1.2-micron PTFE type membrane filter to obtain the polythiol compound.
The chromaticity of the polythiol product obtained in comparative example 2 was measured with a high-precision multifunctional spectrocolorimeter, and the results showed that the polythiol compound obtained in comparative example 2 had a chromaticity of 10 Hazen.
The invention provides a method for producing low-chroma polythiol compound, which firstly proposes a process for preparing polythiol compound, and adds surfactant in the alkaline hydrolysis process of isothiourea salt to obtain low-chroma polythiol. In comparative example 1, the color of the polythiol compound obtained by the conventional alkaline hydrolysis of isothiourea salt was 15Hazen, which is significantly higher than that of the polythiol compound in the examples. In comparative example 2, the color of the polythiol compound obtained by the alkaline hydrolysis method of patent CN105906773B is 10Hazen, which is equivalent to the color of the polythiol compound obtained in the examples of the present invention, but the organic solvent is added in the comparative document 2, the subsequent removal process is complicated, the production process is increased, the production cost is increased, the production period is increased, the efficiency is low, and the steps in the comparative document 2 are complicated and complicated, and are not easy to operate. But the effect is equivalent to that of the comparison document 2, even better than that of the comparison document 2, the reaction time is shortened, the process is simple, the safety and the environmental protection are realized, and the efficiency is high. Accordingly, the present invention provides a process for producing low color polythiol compounds, which can be adapted for industrial production.