A method for preparing a polythiol compound

Abstract

This invention belongs to the field of new materials and provides a method for preparing polythiol compounds, which are prepared by reacting 2-mercaptoethanol and epichlorohydrin compounds. The content of the compound represented by formula (1) in the 2-mercaptoethanol is 0.001-0.2 wt% by vacuum distillation. By strictly controlling the content of the above-mentioned specific compounds in the raw material 2-mercaptoethanol, polythiol compounds can be obtained. Even when the content of the compound represented by formula (2) in the epichlorohydrin compound is less than 200 ppm, polythiol compounds for optical resin lenses with low haze and high light transmittance can be obtained. Furthermore, the use of the polythiol compounds provided by this invention in optical materials can improve the pass rate of optical materials, reduce the local bursting phenomenon and the yield of defective products with textures, reduce production costs, and improve the scratch resistance of optical materials.

Description

Technical Field

[0001] This invention belongs to the field of new materials, specifically providing a method for preparing polythiol compounds and a corresponding method for preparing optical plastic lenses. Background Technology

[0002] Optical plastics possess advantages such as high transparency, lightweight, ease of plastic processing, and excellent surface quality, and have been widely used in eyeglasses, lighting equipment, automotive parts, electronic products, and optical instruments. In the future, with the development and innovation of science and technology, optical plastics will become an indispensable material in various industrial sectors. Based on this, the demand for optical plastics in various fields will continue to grow, which will place higher demands on the quality and yield of optical plastic products.

[0003] Currently, existing technologies for preparing polythiol compounds mainly involve the reaction of 2-mercaptoethanol and epichlorohydrin compounds to synthesize polyols, the reaction of polyols with thiourea and hydrochloric acid to synthesize isothiourea salts, and the alkaline hydrolysis reaction of isothiourea salts with ammonia water (as shown in CN101400648A). Existing technologies for preparing optical plastic lenses involve mixing and dissolving polythiol compounds, isocyanate compounds, and catalysts, followed by heating and curing to prepare optical plastic lenses. During research, researchers discovered that the prepared optical plastic lenses have fine lines and a small number of white bubbles in some areas. This not only affects the use and aesthetics of the optical plastic lenses but also their scratch resistance. Such optical plastic lenses are considered substandard products. An increase in substandard products will increase production costs, reduce the output of qualified products entering the market, and affect downstream users. Furthermore, existing technologies also suffer from issues such as fogging, unclear images, and even opacity in the lenses. To address these problems, CN117304082A discloses a method that limits the content of impurities represented by formula (I) in epichlorohydrin compounds to below 30 ppm, which can improve the haze and light transmittance of optical resin lenses, resulting in low-haze, high-transmittance optical resin lenses. The inventors are considering whether there are other solutions that can better solve the aforementioned problems. Summary of the Invention

[0004] This invention provides a method for preparing polythiol compounds, which are obtained by reacting 2-mercaptoethanol and epichlorohydrin compounds. The content of the compound represented by formula (1) in the 2-mercaptoethanol is 0.001-0.2 wt% by vacuum distillation, wherein the vacuum degree of the distillation column is -0.005 ~ -0.2 MPa, the top temperature of the distillation column is 100~120℃, and the reflux ratio is 1:1 ~ 5:1. Compared with the prior art, this invention can obtain polythiol compounds by strictly controlling the content of specific compounds in the raw material 2-mercaptoethanol. Even when the content of the compound represented by formula (2) in the epichlorohydrin compound is greater than 30 ppm, but is 30-200 ppm, a polythiol compound for optical resin lenses with low haze and high light transmittance can still be obtained. Furthermore, using the polythiol compounds provided by this invention in optical materials can improve the pass rate of optical materials, reduce the local bursting phenomenon and the yield of defective products with textures, reduce production costs, and improve the scratch resistance of optical materials.

[0005] The inventor first provides a method for preparing polythiol compounds, the specific steps of which are: reacting 2-mercaptoethanol and epichlorohydrin to synthesize polyols, reacting the polyols with thiourea and hydrochloric acid to synthesize isothiourea salts, and the isothiourea salts undergoing an alkaline hydrolysis reaction with ammonia.

[0006] The content of the compound represented by formula (1) in the 2-mercaptoethanol is 0.001-0.2 wt%.

[0007] Equation (1);

[0008] The CAS number of the thiol compound with the structure shown in formula (1) above is 98026-19-8.

[0009] The method for controlling the content of the compound shown in formula (1) in the 2-mercaptoethanol to be 0.001-0.2wt% can be any of the existing suitable removal methods, among which the inventors prefer to use vacuum distillation as an example; the conditions for vacuum distillation in this method are that the vacuum degree of the distillation column is -0.005 ~ -0.2MPa, the top temperature of the distillation column is 100~120℃, and the reflux ratio is 1:1 ~ 5:1.

[0010] The inventors discovered that the content of the compound shown in formula (1) in 2-mercaptoethanol used in the synthesis of polythioethanol compounds significantly affects the stability of the polythioethanol compound components. When the content of the compound shown in formula (1) in 2-mercaptoethanol is too high, the side reactions that occur during the synthesis process increase, the content of the main component in the generated polythioethanol compound decreases, the types of impurities that can react with isocyanate compounds increase, and the composition becomes too complex. This leads to different reaction rates in the reaction system when polythioethanol compounds react with isocyanate compounds, resulting in many fine lines appearing in the prepared optical plastic lenses. Furthermore, local white bubbles may be generated due to localized polymerization. Such optical plastic lenses are considered defective products, which greatly reduces the pass rate of optical plastic lenses, increases production costs, and reduces the output of optical plastic lenses entering the market.

[0011] In addition, more importantly, the inventors unexpectedly discovered in their research that when the content of the compound shown in formula (1) of 2-mercaptoethanol is controlled at 0.001-0.2wt%, even if the content of the compound shown in formula (2) of the other raw material epichlorohydrin compound is greater than 30ppm, the stability and other properties of the final polythiol compound can be maintained at a high level; the prepared polythiol compound can also be used to obtain optical resin lenses with low haze and high light transmittance.

[0012] Equation (2).

[0013] The compound shown in formula (2) above is the same compound shown in formula (I) of the epichlorohydrin compound disclosed in CN117304082A in the background art. In other words, the technical solution of this application allows the compound shown in formula (2) of the epichlorohydrin compound to meet the product requirements as long as it is less than 200 ppm, thus reducing the purity requirements of the epichlorohydrin compound. The content of the compound shown in formula (2) in the conventional commercially available qualified epichlorohydrin compound with a content of 99.9% wt is within the above range. Therefore, this application can directly select the commercially available qualified epichlorohydrin compound with a content of 99.9% wt as raw material, further reducing the production cost and increasing the yield. According to the verification, the polythiol compound obtained by the above technical solution can improve the pass rate of optical materials, reduce the local bursting phenomenon and the output of unqualified products with textures, reduce the production cost, and improve the scratch resistance of optical materials.

[0014] In addition to the features mentioned above, the preparation method of the polythiol compound defined in this application, including the stages of "synthesizing polyols by reacting 2-mercaptoethanol and epichlorohydrin compounds, synthesizing isothiourea salts by reacting polyols with thiourea and hydrochloric acid, and the alkaline hydrolysis reaction of isothiourea salts with ammonia water", are all completed using existing conventional processes. The inventors have provided examples in the embodiments, and they will not be repeated here.

[0015] Based on this discovery, the present invention provides a method for preparing polythiol compounds, which can prepare polythiol compounds with stable components, and thus prepare qualified optical plastic lenses free from fine lines and white bubbles.

[0016] In addition, the inventors also provide an optical material and its preparation method, which is prepared from the polythiol compound, isocyanate compound and catalyst described in the above technical solution as raw materials.

[0017] Preferably, the isocyanate compound is selected from tetramethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, isophorone diisocyanate, norbornane diisocyanate, phenylenediamine diisocyanate, hydrogenated phenylenediamine diisocyanate, tetramethyl-m-phenylenediamine diisocyanate, dithiodipropyl diisocyanate, dithiodiethyl diisocyanate, 2,5-diisocyanate methylthiophene, 2,5-diisocyanate methyl-1,4-dithiane, 2,5 -Diisocyanate-1,4-dithiane, thiodihexyl diisocyanate, thiodipropyl diisocyanate, bis(isocyanate methyl)adamantane, bis(isocyanate methyl)tetrahydrothiophene, 2,6-bis(isocyanate methyl)naphthalene, 1,5-naphthalene diisocyanate, diethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine triisocyanate, toluene diisocyanate, o-toluidine diisocyanate, diphenylmethane diisocyanate, diphenyl ether diisocyanate, and triphenylmethane triisocyanate.

[0018] More preferably, the isocyanate compound is selected from at least one of hexamethylene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, isophorone diisocyanate, norbornene diisocyanate, phenyldimethyl diisocyanate, and hydrogenated phenyldimethyl diisocyanate.

[0019] Preferably, in addition to the polythiol compounds defined in this application, the raw materials for optical materials may also include other polythiol compounds; said other polythiol compounds are selected from 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, methanedithiol, methanetrithiol, bis(2-mercaptoethyl) ether, tetra(mercaptomethyl)methane, 1,2-dimercaptopropane, 1,3-dimercaptopropane, 1,4-dimercaptobutane, 1,6-dimercaptohexane, 2,2-dimercaptopropane, 1,2-bis(2-mercaptoethyl)propane, 2,3-dimercaptopropane, 2 ...2,3-dimercaptopropane, 2,4-dimercaptobutane, 2,3-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-dimercaptopropane, 2,4-di Ethoxyethane, 1,2-bis(2-mercaptoethylthio)ethane, 2,3-dimercapto-1-propanol, 1,2-dimercaptoethane, 1,3-dimercapto-2-propanol, 2-mercaptomethyl-1,3-dimercaptopropane, 2-mercaptomethyl-1,4-dimercaptobutane, 1,2,3-trimercaptopropane, 2-(2-mercaptoethylthio)-1,3-dimercaptopropane, 2,4-dimercaptomethyl-1,5-dimercapto-3-thiapentane, bis(2-mercaptoethyl)sulfide, ethylene glycol bis(3-mercaptopropionate), diethylene glycol bis(2-mercaptoacetate), ethylene glycol bis(2-mercaptoacetate), 1,4-butanediol bis(2-mercaptoacetate), trimethylolpropane trimercaptopropionate, pentaerythritol tetramercaptopropionate Glucono-ethyl acetate, diethylene glycol bis(3-mercaptopropionate), pentaerythritol tetramercaptopropionate, 1,2-dimercaptocyclohexane, 1,1,1-tris(mercaptomethyl)propane, 1,4-butanediol bis(3-mercaptopropionate), 1,3-dimercaptocyclohexane, trimethylolpropane trimercaptoacetate, 1,4-dimercaptocyclohexane, 1,3-bis(mercaptomethyl)cyclohexane, 1,4-bis(mercaptomethyl)cyclohexane, bis(4-mercaptophenyl)sulfone, 2,5-dimercaptomethyl-1,4-dithiane, 2,5-bis(2-mercaptoethylthiomethyl)-1,4-dithiane, 2,5-dimercaptomethyl-1-thiane, 2,5-dimercaptoethyl-1-thiane, 2,5-dimercaptomethylthiophene, bis(4-mercaptophenyl) The sulfide, 1,2-dimercaptobenzene, 1,3-dimercaptobenzene, 1,4-dimercaptobenzene, 1,3-bis(mercaptomethyl)benzene, 2,5-dimercaptomethyl-1,4-dithiane, 1,4-bis(mercaptomethyl)benzene, 2,2'-dimercaptobiphenyl, bis(4-mercaptophenyl)methane, 2,2-bis(4-mercaptophenyl)propane, 4,4'-dimercaptobiphenyl, bis(4-mercaptophenyl)ether, bis(4-mercaptomethylphenyl)methane, 1,1,3,3-tetratetra(mercaptomethylthio)propane, 2,2-bis(4-mercaptomethylphenyl)propane, bis(4-mercaptomethylphenyl)ether, bis(4-mercaptomethylphenyl)sulfide, 2,5-dimercapto-1,3,4-thiadiazole, and 3,4-thiophene dithiol.

[0020] More preferably, the other polythiol compound is selected from at least one of 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, pentaerythritol tetramercaptoacetate, and pentaerythritol tetramercaptopropionate.

[0021] The catalyst is selected from one or more of dibutyltin dilaurate, dibutyltin dichloride, dibutyltin oxide, and stannous octoate.

[0022] In addition, the raw materials for preparing the optical material may also include additives; the additives are selected from at least one of release agents, ultraviolet absorbers and toners.

[0023] The aforementioned additives can be based on existing conventional techniques and are not particularly limited. The release agent can be selected from one or more of phosphate esters, acidic phosphate esters, oxidized olefinic acidic phosphate esters, alkali metal salts of acidic phosphate esters, alkali metal salts of oxidized olefinic acidic phosphate esters, alkali metal salts of higher fatty acids, and higher fatty acid esters. Phosphate esters, acidic phosphate esters, and oxidized olefinic acidic phosphate esters are preferred.

[0024] The ultraviolet absorber may be selected from one or more of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, phenyl benzoate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole, and resorcinol monobenzoate. Preferably, it is 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole or 2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole.

[0025] The preferred colorant is a boron reagent.

[0026] Preferably, the molar ratio of thiol groups in all polythiol compounds to isocyanate groups in isocyanate compounds can be 0.5-3.0, more preferably 0.6-2.0, and more preferably 0.7-1.3.

[0027] Preferably, based on 100 parts by weight of the total mass of all polythiols and isocyanates, the catalyst accounts for 0.001 to 0.5 parts by weight, and the auxiliaries account for 0.01 to 1.5 parts by weight.

[0028] In addition, the preparation method of the above-mentioned optical materials also directly adopts existing technology, which is illustrated by the inventors in the embodiments and will not be repeated here.

[0029] In summary, by controlling the content of the compound shown in formula (1) in 2-mercaptoethanol within the range of 0.001-0.2 wt%, this application can prepare polythiol compounds with higher stability. More importantly, it reduces the purity requirements for epichlorohydrin compounds, allowing most commercially available epichlorohydrin compounds to be directly used in the preparation of this application, greatly reducing production costs. The resulting polythiol compounds, when used in optical materials, can improve the yield of optical materials, reduce localized burst polymerization and the production of defective products with textures, reduce production costs, and improve the scratch resistance of optical materials. Detailed Implementation

[0030] The following detailed embodiments further illustrate the above-described content of the present invention, but should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Unless otherwise specified, the following embodiments are all implemented using conventional prior art.

[0031] Upon testing, the conventional commercially available epichlorohydrin compound with a content of 99.9% wt used in the embodiments of this application contained compounds represented by formula (2) with a content of less than 200 ppm. Therefore, this application directly selected commercially available epichlorohydrin compound with a content of 99.9% wt as raw material. The epichlorohydrin compound used in Comparative Example 4 was a commercially available product that had been stored for a long time, in which the compound represented by formula (2) was enriched and the content reached 201.12 ppm. The inventor hereby makes this statement.

[0032] Commercially available 2-mercaptoethanol has a purity of 99.5 wt% or higher. In order to obtain 2-mercaptoethanol containing the specific compound shown in formula (1), the inventors adopted the following technical solution:

[0033] Take 10 kg of 2-mercaptoethanol with a purity of 99.5 wt% or higher purchased from the market and perform vacuum distillation. The vacuum degree of the distillation column is -0.1 MPa, the top temperature of the distillation column is 110℃, and the reflux ratio is 3:1. Finally, 9.50 kg of purified 2-mercaptoethanol and 500 g of heavy components can be obtained.

[0034] In addition, the above parameters can also be set as follows: distillation column vacuum degree -0.15MPa, -0.2MPa; distillation column top temperature 115℃, 120℃; reflux ratio 2:1, 4:1.

[0035] Gas chromatography was used to analyze the purchased raw 2-mercaptoethanol, purified 2-mercaptoethanol, and the residue from distillation. The results showed that the content of the compound represented by formula (1) in the purchased raw 2-mercaptoethanol was 0.85 wt%, the purified 2-mercaptoethanol did not contain the compound represented by formula (1), and the content of the compound represented by formula (1) in the residue from distillation was 17.93 wt%. Experiments showed that other impurities in the residue from distillation did not affect the purpose of this application, therefore the influence of other impurities in the residue from distillation on the burst polymerization phenomenon, lens texture, lens haze, and light transmittance can be ignored.

[0036] 1g of the residue from distillation was taken and added to 10g, 12g, 50g, 85g, 100g, 150g, 350g, and 850g of purified 2-mercaptoethanol, respectively, to obtain 2-mercaptoethanol containing different amounts of the specific compound shown in formula (1). After gas chromatography, the contents of the compound shown in formula (1) in the above-mentioned 2-mercaptoethanol containing different amounts of the specific compound shown in formula (1) were 1.79wt%, 1.49wt%, 0.36wt%, 0.21wt%, 0.18wt%, 0.12wt%, 0.05wt%, and 0.02wt%, respectively.

[0037] Meanwhile, 0.1g of the residue from the distillation vessel was added to 1000g of purified 2-mercaptoethanol. After detection by gas chromatograph, the content of the compound shown in formula (1) in the 2-mercaptoethanol was 0.001wt.

[0038] The inventors used 2-mercaptoethanol containing different amounts of the specific compound shown in formula (1) obtained above as raw materials to prepare the following examples.

[0039] The content of the compound shown in formula (1) in the above-mentioned 2-mercaptoethanol was determined using an Agilent 7820A VL gas chromatograph.

[0040] In the examples below, the content of the compound represented by formula (2) in the epichlorohydrin compound was determined by ionization using an Agilent 6530 Q-TOF LC / MS liquid chromatography-mass spectrometry system with an accuracy of 2 ppm.

[0041] Furthermore, in the process of manufacturing optical plastic lenses, the oven polymerization and curing procedure is as follows:

[0042] Program 1

[0043] 25℃-25℃ for 5 hours;

[0044] 25℃-45℃ for 4 hours;

[0045] 45℃-50℃ for 3 hours;

[0046] 50℃-60℃ for 3 hours;

[0047] 60℃-120℃ for 5 hours;

[0048] 120℃-120℃ for 4 hours;

[0049] 120℃-70℃ for 1 hour.

[0050] Program 2

[0051] 25℃-25℃ for 7 hours;

[0052] 25℃-45℃ for 3 hours;

[0053] 45℃-50℃ for 3 hours;

[0054] 50℃-60℃ for 1 hour;

[0055] 60℃-120℃ for 6 hours;

[0056] 120℃-120℃ for 4 hours;

[0057] 120℃-70℃ for 2 hours.

[0058] Program 3

[0059] 25℃-25℃ for 20 hours;

[0060] 25℃-45℃ for 3 hours;

[0061] 45℃-60℃ for 2 hours;

[0062] 60℃-90℃ for 3 hours;

[0063] 90℃-120℃ for 1 hour;

[0064] 120℃-120℃ for 4 hours;

[0065] 120℃-70℃ for 2 hours.

[0066] The evaluation method for whether the obtained optical plastic lenses are qualified is as follows:

[0067] Twenty people visually inspected optical plastic products to determine whether they were qualified, based on whether the products had fine textures.

[0068] The method for evaluating the haze of optical plastic lenses is as follows:

[0069] The haze of the optical plastic lenses obtained in the examples and comparative examples was determined using an UltraScan PRO spectrophotometer. Lower haze indicates better transparency of the optical plastic lens.

[0070] The method for evaluating the light transmittance of optical plastic lenses is as follows:

[0071] The transmittance of the optical plastic lenses obtained in the examples and comparative examples was determined using an UltraScan PRO spectrophotometer. Higher transmittance indicates better light transmission of the optical plastic lens.

[0072] Example 1: A method for preparing a polythiol compound and an optical plastic lens.

[0073] (1) Synthesis of 2,3-dithio(2-mercapto)-1-propanethiol:

[0074] 86.8 g of 2-mercaptoethanol (containing 0.02 wt% of the specific compound shown in formula (1)) was placed in a 1-liter four-necked flask equipped with a stirrer, nitrogen purging tube and thermometer. After 40 minutes of adding 77.5 g of 36 wt% sodium hydroxide aqueous solution at 50 °C, 56.3 g of epichlorohydrin (purity 99.96 wt%, containing 178.73 ppm of the specific compound shown in formula (2)) was added dropwise over 1.5 hours and kept warm for 1 hour. Then, 260 g of 37 wt% hydrochloric acid and 165 g of 99.30 wt% thiourea were added and refluxed at 130 °C for 4 hours to obtain isothiourea salt.

[0075] After cooling to room temperature, 300g of 18wt% ammonia solution was added and the mixture was reacted at 75℃ for 4 hours. After standing and separating the layers, the lower organic phase was separated to obtain a crude polythiol compound with 2,3-dithio(2-mercapto)-1-propanethiol as the main component. Hydrochloric acid was added to adjust the pH to about 6, and water was added for two washings. The mixture was then heated and dehydrated under reduced pressure to obtain 2,3-dithio(2-mercapto)-1-propanethiol.

[0076] (2) Preparation of optical plastic lenses:

[0077] Take 52g of phenylenediamine diisocyanate, 0.01g of dibutyltin dichloride as a catalyst, 0.08g of acidic phosphate ester as a release agent, 0.50g of ultraviolet absorber (2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole), and 0.08g of boron reagent as a colorant, mix and dissolve them; then add and mix 48g of 2,3-dithio(2-mercapto)-1-propanethiol obtained in step (1) above to obtain a mixture.

[0078] The mixture was degassed at 200 Pa for 1 hour, then filtered through a PTFE (polytetrafluoroethylene) filter with a pore size of 5.0 μm. The filtered mixture was then injected into a 75 mm diameter, 0.00 D glass mold sealed with tape. The mold was placed in an oven and heated through polymerization curing process 1 to carry out the polymerization and curing reaction. After polymerization and curing, the mold was removed from the oven and allowed to cool to room temperature. The sealing tape was then removed, allowing the optical plastic lens inside the mold cavity to be demolded, thus obtaining an optical plastic lens with the internal shape of the mold cavity. A total of 100 optical plastic lenses were obtained.

[0079] The optical plastic lens obtained in Example 1 was evaluated for its conformity; the evaluation results are shown in Table 1.

[0080] Example 2: A method for preparing a polythiol compound and an optical plastic lens.

[0081] (1) Synthesis of bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol:

[0082] Add 80.0 g of 2-mercaptoethanol (containing 0.05 wt% of the specific compound shown in formula (1)), 41.5 g of ultrapure water, and 0.25 g of 49 wt% sodium hydroxide aqueous solution to a 1-liter four-necked flask equipped with a stirrer, nitrogen purging tube, and thermometer; add 97.1 g of epichlorohydrin (purity 99.96 wt%, containing 154.67 ppm of the specific compound shown in formula (2)) dropwise over 6.5 hours at 10°C, stirring for 60 minutes; then add 234.8 g of 17.3 wt% sodium sulfide aqueous solution dropwise over 5.5 hours at 22°C, stirring for 120 minutes; then add 35 g of 2-mercaptoethanol (containing 0.05 wt% of the specific compound shown in formula (1)) dropwise to a 1-liter four-necked flask equipped with a stirrer, nitrogen purging tube, and thermometer ...2)) dropwise to a 1-liter four-necked flask equipped with a stirrer, nitrogen purging tube, and thermometer, stirring for 120 minutes; then 436.8 g of 0.5 wt% hydrochloric acid and 198.1 g of thiourea with a purity of 99.30 wt% were refluxed at 110 °C for 3 hours with stirring to carry out the thiourea onium salting reaction. After cooling to 45 °C, 335.0 g of toluene was added, and the mixture was cooled to 26 °C. Then, 322.8 g of 25 wt% ammonia solution was added at 38 °C for 30 minutes and stirred at 58 °C for 1 hour to carry out the hydrolysis reaction, thereby obtaining a toluene solution of polythiols with bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol as the main component.

[0083] Then, 93.0 g of 36 wt% hydrochloric acid was added, and the toluene solution was acid-washed at 36 °C for 30 minutes, twice. 185.8 g of ultrapure water was added, and the solution was washed at 40 °C for 30 minutes, five times. Toluene and trace amounts of water were removed under reduced pressure by heating, and then the solution was filtered under reduced pressure using a 1.2 μm PTFE membrane filter to obtain bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol.

[0084] (2) Fabrication of optical plastic lenses:

[0085] Take 51.2 g of isophthalimide diisocyanate, 0.01 g of dibutyltin dichloride as a catalyst, 0.08 g of acidic phosphate ester as a release agent, 0.60 g of ultraviolet absorber (2-(2'-hydroxy-3',5'-ditert-phenyl)-5-chlorobenzotriazole), and 0.08 g of toner boron reagent, mix and dissolve them; then add and mix 48.8 g of bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol obtained in step (1) above to obtain a mixture.

[0086] The mixture was degassed at 200 Pa for 1 hour, then filtered through a PTFE (polytetrafluoroethylene) filter with a pore size of 5.0 μm. The filtered mixture was then injected into a 75 mm diameter, 0.00 D glass mold sealed with tape. The mold was placed in an oven and heated through polymerization curing process 2 for polymerization curing. After polymerization curing, the mold was removed from the oven and allowed to cool to room temperature. The sealing tape was then removed, allowing the optical plastic lens inside the mold cavity to be demolded, thus obtaining an optical plastic lens with the internal shape of the mold cavity. A total of 100 optical plastic lenses were obtained.

[0087] The optical plastic lens obtained in Example 2 was evaluated for its conformity; the evaluation results are shown in Table 1.

[0088] Example 3

[0089] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 0.12 wt%, and the content of the specific compound shown in formula (2) in epichlorohydrin was 149.33 ppm, everything else was the same as in Example 1, and 2,3-dithio(2-mercapto)-1-propanethiol was prepared by the same method as in Example 1; further, optical plastic lenses were prepared by the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Example 3 were evaluated for their suitability; the evaluation results are shown in Table 1.

[0090] Example 4

[0091] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 0.18 wt% and the content of the specific compound shown in formula (2) in epichlorohydrin was 100.35 ppm, everything else was the same as in Example 1, and 2,3-dithio(2-mercapto)-1-propanethiol was prepared by the same method as in Example 1; optical plastic lenses were further prepared by the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Example 4 were evaluated for their suitability; the evaluation results are shown in Table 1.

[0092] Example 5

[0093] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 0.001 wt% and the content of the specific compound shown in formula (2) in epichlorohydrin was 163.50 ppm, everything else was the same as in Example 1, and 2,3-dithio(2-mercapto)-1-propanethiol was prepared by the same method as in Example 1; optical plastic lenses were further prepared by the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 4 were evaluated for their suitability; the evaluation results are shown in Table 1.

[0094] Example 6

[0095] 2,3-Dithio(2-mercapto)-1-propanethiol was prepared using the same method as in Example 1;

[0096] Take 56.0 g of m-isophorone diisocyanate, 0.05 g of dibutyltin dichloride as a catalyst, 0.10 g of acidic phosphate ester as a release agent, 0.80 g of ultraviolet absorber (2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole), and 0.07 g of colorant, mix and dissolve them; then add and mix 44.0 g of 2,3-dithio(2-mercapto)-1-propanethiol prepared in the same manner as in Example 1 to obtain a mixture.

[0097] The mixture was degassed at 200 Pa for 1 hour, then filtered through a PTFE (polytetrafluoroethylene) filter with a pore size of 5.0 μm. The filtered mixture was then injected into a 75 mm diameter, 0.00 D glass mold sealed with tape. The mold was placed in an oven and heated through polymerization curing process 1 for polymerization and curing. After polymerization and curing, the mold was removed from the oven and allowed to cool to room temperature. The sealing tape was then removed, allowing the optical plastic lens inside the mold cavity to be demolded, thus obtaining an optical plastic lens with the internal shape of the mold cavity. A total of 100 optical plastic lenses were obtained.

[0098] Example 7

[0099] 2,3-Dithio(2-mercapto)-1-propanethiol was prepared using the same method as in Example 1;

[0100] 47.56 g of hydrogenated phenylenediamine diisocyanate, 0.05 g of dibutyltin dichloride as a catalyst, 0.10 g of acidic phosphate ester as a release agent, 1.00 g of ultraviolet absorber (2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole), and 0.08 g of colorant were mixed and dissolved; then, 29.97 g of 2,3-dithio(2-mercapto)-1-propanethiol and 22.47 g of pentaerythritol tetramercaptopropionate prepared in the same manner as in Example 1 were added and mixed to obtain a mixture.

[0101] The mixture was degassed at 200 Pa for 1 hour, then filtered using a PTFE (polytetrafluoroethylene) filter with a pore size of 5.0 μm. The filtered mixture was then injected into a 75 mm diameter, 0.00 D glass mold sealed with tape. The mold was placed in an oven and heated through polymerization curing process 3 for polymerization and curing. After polymerization and curing, the mold was removed from the oven and allowed to cool to room temperature. The sealing tape was then removed, allowing the optical plastic lens inside the mold cavity to be demolded, thus obtaining an optical plastic lens with the internal shape of the mold cavity. A total of 100 optical plastic lenses were obtained.

[0102] Example 8

[0103] 2,3-Dithio(2-mercapto)-1-propanethiol was prepared using the same method as in Example 1;

[0104] Take 49.09 g of norbornane diisocyanate, 0.05 g of dibutyltin dichloride as a catalyst, 0.15 g of acidic phosphate ester as a release agent, 1.10 g of ultraviolet absorber (2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole), and 0.07 g of colorant, mix and dissolve them; then add and mix 25.5 g of 2,3-dithio(2-mercapto)-1-propanethiol and 25.41 g of pentaerythritol tetramercaptopropionate prepared in the same manner as in Example 1 to obtain a mixture.

[0105] The mixture was degassed at 200 Pa for 1 hour, then filtered using a PTFE (polytetrafluoroethylene) filter with a pore size of 5.0 μm. The filtered mixture was then injected into a 75 mm diameter, 0.00 D glass mold sealed with tape. The mold was placed in an oven and heated through polymerization curing process 3 for polymerization and curing. After polymerization and curing, the mold was removed from the oven and allowed to cool to room temperature. The sealing tape was then removed, allowing the optical plastic lens inside the mold cavity to be demolded, thus obtaining an optical plastic lens with the internal shape of the mold cavity. A total of 100 optical plastic lenses were obtained.

[0106] Comparative Example 1

[0107] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 0.21 wt%, and the content of the specific compound shown in formula (2) in epichlorohydrin was 130.77 ppm, everything else was the same as in Example 1, and 2,3-dithio(2-mercapto)-1-propanethiol was prepared by the same method as in Example 1; optical plastic lenses were further prepared by the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 1 were evaluated for their suitability; the evaluation results are shown in Table 1.

[0108] Comparative Example 2

[0109] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 0.36 wt% and the content of the specific compound shown in formula (2) in epichlorohydrin was 124.91 ppm, everything else was the same as in Example 1, and 2,3-dithio(2-mercapto)-1-propanethiol was prepared by the same method as in Example 1; optical plastic lenses were further prepared by the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 2 were evaluated for their suitability; the evaluation results are shown in Table 1.

[0110] Comparative Example 3

[0111] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 1.49 wt%, and the content of the specific compound shown in formula (2) in epichlorohydrin was 150.07 ppm, everything else was the same as in Example 1, and 2,3-dithio(2-mercapto)-1-propanethiol was prepared by the same method as in Example 1; optical plastic lenses were further prepared by the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 3 were evaluated for their suitability; the evaluation results are shown in Table 1.

[0112] Comparative Example 4

[0113] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 1.79 wt%, and the content of the specific compound shown in formula (2) in epichlorohydrin was 201.12 ppm, everything else was the same as in Example 1, and 2,3-dithio(2-mercapto)-1-propanethiol was prepared by the same method as in Example 1; optical plastic lenses were further prepared by the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 4 were evaluated for their suitability; the evaluation results are shown in Table 1.

[0114] Comparative Example 5

[0115] Except that the 2-mercaptoethanol used was a commercially available original sample of 2-mercaptoethanol, and the content of the specific compound shown in formula (2) in epichlorohydrin was 141.66 ppm, everything else was the same as in Example 1. 2,3-Dithio(2-mercapto)-1-propanethiol was prepared using the same method as in Example 1; furthermore, optical plastic lenses were prepared using the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 5 were evaluated for conformity; the evaluation results are shown in Table 1.

[0116] Comparative Example 6

[0117] Except that the 2-mercaptoethanol used was purified by distillation and the content of the specific compound shown in formula (2) in epichlorohydrin was 163.50 ppm, everything else was the same as in Example 1. 2,3-Dithio(2-mercapto)-1-propanethiol was prepared using the same method as in Example 1; optical plastic lenses were further prepared using the same method as in Example 1. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 6 were evaluated for conformity; the evaluation results are shown in Table 1.

[0118] Comparative Example 7

[0119] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 0.36 wt% and the content of the specific compound shown in formula (2) in epichlorohydrin was 124.91 ppm, everything else was the same as in Example 2. Bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol was prepared using the same method as in Example 2; optical plastic lenses were further prepared using the same method as in Example 2. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 7 were evaluated for conformity; the evaluation results are shown in Table 1.

[0120] Comparative Example 8

[0121] Except that the content of the specific compound shown in formula (1) in 2-mercaptoethanol was 1.49 wt%, and the content of the specific compound shown in formula (2) in epichlorohydrin was 150.07 ppm, everything else was the same as in Example 2. Bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol was prepared using the same method as in Example 2; optical plastic lenses were further prepared using the same method as in Example 2. A total of 100 optical plastic lenses were obtained. The optical plastic lenses obtained in Comparative Example 8 were evaluated for conformity; the evaluation results are shown in Table 1.

[0122] Table 1. Evaluation Results of Whether Optical Plastic Lenses Meet Standards

[0123]

[0124] A comparison of the optical plastic lenses obtained in Examples 1-5, Comparative Example 6, and Comparative Examples 1-5 and 7-8 shows that the optical plastic lenses in the comparative examples all exhibited burst polymerization, producing white bubbles and textures, with a lens pass rate of less than 60%. In contrast, the lenses in Examples 1-5 did not exhibit burst polymerization, thus producing no white bubbles and no textures.

[0125] The lens pass rate of Examples 1-5 was 100%; this shows that when the content of the compound shown in Formula (1) in 2-mercaptoethanol is <0.20wt%, the optical plastic lens does not produce white bubbles or textures due to burst polymerization, and the lens pass rate is 100%. In addition, Comparative Example 6 used 2-mercaptoethanol purified by distillation, in which the content of the compound shown in Formula (1) was 0. Although there was no burst polymerization, the lens pass rate was 0%. This is because when the content of the compound shown in Formula (1) is 0, the content of the compound shown in Formula (2) in epichlorohydrin is greater than 30ppm, which causes the lens to be opaque. It can be seen that the technical effect described in this application can only be achieved when the content of the compound shown in Formula (1) in 2-mercaptoethanol is between 0.001-0.2wt%.

[0126] A comparison of the optical plastic lenses obtained in Examples 1-5, Comparative Examples 1-3, 5, 7-8, and Comparative Examples 4 and 6 shows that although the lens of Comparative Example 6 did not exhibit polymerization or texture, it lacked transparency; the lens of Comparative Example 4 exhibited white bubbles caused by polymerization, texture, and also lacked transparency. This indicates that when the content of the compound represented by formula (1) in 2-mercaptoethanol is 0.001-0.20 wt% and the content of the compound represented by formula (2) in epichlorohydrin is less than 200 ppm, the optical plastic lens exhibits no white bubbles caused by polymerization, no texture, a 100% pass rate, and also possesses transparency, thus solving the problem of fogging and opacity in the lens.

[0127] Since the commercially available qualified epichlorohydrin compounds with a content of 99.9%wt contain less than 200ppm of the compound shown in formula (2), the present invention does not limit the content of the compound shown in formula (2) in the epichlorohydrin compound. If necessary, the content of the compound shown in formula (2) in the qualified epichlorohydrin compound can be tested before use. As long as it is within the above range, it can be used directly as a raw material.

[0128] The above embodiments enable those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a polythiol compound, comprising a reaction stage of synthesizing a polyol from 2-mercaptoethanol and an epichlorohydrin compound; characterized in that, The content of the compound represented by formula (1) in the 2-mercaptoethanol is 0.001-0.2 wt%; Equation (1).

2. The method for preparing the polythiol compound according to claim 1, characterized in that, The content of the compound represented by formula (2) in the epichlorohydrin compound is less than 200 ppm; Equation (2).

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