Preparation method of bis (mercaptomethyl)-3, 6, 9-trithia-n-undecane-1, 11-dimercaptoalcohol and modified polyurethane optical material raw material composition containing bis (mercaptomethyl)-3, 6, 9-trithia-n-undecane-1, 11-dimercaptoalcohol

Abstract

The invention relates to a preparation method of bis (mercaptomethyl)-3, 6, 9-trithia-n-undecane-1, 11-dimercaptan and a raw material composition of a modified polyurethane optical material containing the bis (mercaptomethyl)-3, 6, 9-trithia-n-undecane-1, 11-dimercaptan. The preparation method comprises three steps of nucleophilic substitution, chain extension reaction and thioetherification and chain extension, the prepared compound comprises two structural isomers of 5, 7-bis (mercaptomethyl)-3, 6, 9-trithia-n-undecane-1, 11-dimercapto alcohol (I) and 4, 8-bis (mercaptomethyl)-3, 6, 9-trithia-n-undecane-1, 11-dimercapto alcohol (II), the two structural isomers serve as a core monomer of a modified polyurethane optical material, and the two structural isomers of the modified polyurethane optical material can be used for preparing the modified polyurethane optical material. A modified polyurethane optical material can be prepared from a raw material composition composed of the monomer, polyisocyanate and a flexible hydroxyl bisphenol A glycidyl ether epoxy compound (formula A), and the optical material has the advantages of high light transmittance, high refractive index, excellent mechanical properties and the like. (I) (II) (A)

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer optical material synthesis and preparation, and particularly relates to a preparation method of di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dimercaptanol and an optical material composition containing the compound. BACKGROUND

[0002] Di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dimercaptanol is a polythiol compound, mainly including 5,7-di(mercaptomethyl)-3,6,9-trithia-undecane-1,11-dimercaptanol, 4,7-di(mercaptomethyl)-3,6,9-trithia-undecane-1,11-dimercaptanol and 4,8-di(mercaptomethyl)-3,6,9-trithia-undecane-1,11-dimercaptanol three isomers. Because of its high refractive index (nd≥1.60), low dispersion (Abbe number≥35), high transparency (haze≤1%) and excellent mechanical properties, it has important applications in the fields of material science, optical resin, polymer crosslinking agent, etc. For example, the above polythiol composition is polymerized with a polyisocyanate to prepare optical components.

[0003] Currently, the polythiol composition preparation technology includes the following patent technologies: introducing a specific free radical inhibitor with a specific structure compound such as a phenolic compound, an amine compound or a quinone compound on the polymer matrix or surface coating.

[0004] US company patent: 3M company patent CN107820506B, introduces a dye specific structure compound in the polymer, which has the function of free radical inhibitor, delays thiol oxidation, and reduces side reactions and product stability. PPG industrial Ohio company patent CN201880067352.5, purifies by distillation + acid washing + water washing combined process to reduce nitrogen-containing impurities.

[0005] Japanese company patent: Mitsui Chemicals patent CN118541349A, uses high performance liquid chromatography (HPLC) to separate compounds with specific retention time to improve purity; CN113924326A, through the reaction of 2-mercaptoethanol and haloalcohol compound under the action of catalyst, the compound is obtained; SKC patent CN201811625363.9, optimizes the polymerization and curing process to reduce waste generation; Meiyuan business patent KR1020100119601A, uses a non-H2S route to synthesize thiol compounds, and reduces the dependence on toxic raw materials by catalytic reduction of thiourea or sulfide.

[0006] Chinese company patents: Yifeng New Material Co., Ltd. patents: CN114605605B, adding thiodipropionic acid ester stabilizer to inhibit oxidation side reaction; CN118684609A, controlling metal impurities, optimizing hydrolysis conditions to reduce byproducts; CN119751795A, controlling lens color defect rate by controlling the content of cyclic compounds in the preparation of polythiol composition and isocyanate; CN117285688B, using CO2 instead of H2S to optimize the synthesis process, and using a closed reaction to reduce safety risks.

[0007] Traditional preparation methods still face technical bottlenecks such as high toxicity, many byproducts, difficult isomer separation, and poor product stability. SUMMARY

[0008] The present application aims to provide a preparation method for di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dimercaptol and a raw material composition for modified polyurethane optical material containing the compound. The present application uses a "sulfide bond directional assembly three-step method" combined with the synergistic effect of a microchannel reactor to provide a new technical path for the preparation of polythiol compounds. The preparation method includes three steps of nucleophilic substitution, chain extension, and sulfidation and chain extension, to prepare two structural isomers including 5,7-dimercaptomethyl-3,6,9-trithiaundecane-1,11-dimercaptol (I) and 4,8-dimercaptomethyl-3,6,9-trithiaundecane-1,11-dimercaptol (II). The compound serves as a core monomer for modified polyurethane optical material, and through polymerization reaction of the monomer with polyisocyanate and bisphenol A epoxy resin, a modified polyurethane optical material with high light transmittance, high refractive index, and excellent mechanical properties can be prepared.

[0009] To achieve the above-mentioned purpose, the present application provides the following technical solutions: The present application uses a "sulfide bond directional assembly three-step method" to prepare di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dimercaptol, and the specific reaction is as follows: First step: 2-bromoethyl mercaptan generates thiol anion under alkaline conditions and attacks the carbon atom (beta-carbon) of CH2Br in 2-bromomethyl-1,3-dibromopropane, while bromide ion (Br - ) as a leaving group, forming a new C-S bond to generate 2-bromoethyl 3-bromo-2-(bromomethyl) propyl sulfide (formula a). The specific reaction process is as follows:

[0010] Second step: NaHS is added in steps, so that the thiol group anion (HS-) in NaHS selectively replaces the primary carbon bromine (-Br) with relatively small steric hindrance in 2-bromoethyl 3-bromo-2-(bromomethyl) propyl sulfide (a), and the remaining primary carbon bromine (-Br) is difficult to be replaced due to the time sequence effect of step-by-step addition and intramolecular interaction, to generate a sulfide compound containing a branched thiol group, the introduction of the thiol group increases the number of functional groups, and the molecular chain derives a branch to complete chain extension. The reducing agent dithiothreitol is added during the reaction process to inhibit the formation of disulfide bonds, effectively eliminating side reactions. The specific reaction process is as follows:

[0011] Third step: organic base triethylamine (Et3N) is used, and the weak basicity of Et3N makes the 2-mercaptoethyl mercaptan part deprotonated to generate a monosulfur anion (HSCH2CH2S-), which selectively attacks the terminal -CH2Br of 2-mercaptoethyl 3-bromo-2-(mercaptomethyl) propyl sulfide (b) to form a new C-S bond. Combined with the strong ring jet flow formed by the microchannel reactor, it promotes the instantaneous mixing of materials and promotes directional chain extension and recombination, and finally generates di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dithiol. The specific reaction process is as follows:

[0012] In the above reaction, although the primary carbon thiol (-SH) of the 5,7-isomer has significantly smaller steric hindrance than the 4,8-isomer and the 4,7-isomer, a small amount of it still inevitably participates in the reaction of the 4,8-isomer. Since the steric hindrance of the 4,7-isomer is significantly higher than that of the 4,8-isomer, its generation ratio can be ignored (<0.3%). The specific reaction process is as follows:

[0013] Specifically, the preparation method of di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dithiol of the present application comprises the following steps: (1) Nucleophilic substitution: 2-bromomethyl-1,3-dibromopropane is stirred into a reaction container containing an alcohol solvent, N2 is continuously introduced, the temperature is controlled to 0-25°C, and a 2-bromoethyl mercaptan and sodium ethoxide solution with a concentration of 15-40wt% in ethanol is added dropwise. The dropwise addition is completed within 1-3 hours, and the stirring reaction is carried out for 5-9 hours. The organic phase is separated and eluted, and the solvent is collected by reduced pressure distillation to obtain 2-bromoethyl 3-bromo-2-(bromomethyl) propyl sulfide (formula a); (2) Chain extension reaction: 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) prepared in step (1) is added to a solvent, the whole process is protected by N2, dithiothreitol and 30-50% sodium hydrosulfide are stirred and added, incubated at 20-50℃ for 1-3 hours, the remaining sodium hydrosulfide is added, and the reaction is continued for 3-7 hours, the organic phase is separated and eluted, the solvent is collected by reduced pressure distillation, and 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b) is obtained.

[0014] (3) Thioetherification and chain extension: triethylamine is added to a microchannel reactor containing a mixed solvent, and after complete dissolution, 2-mercaptoethyl mercaptan is added, the flow rate is controlled at 0.1-1 mL / min, after reaction for 30-60 minutes, the temperature is raised to 0-25℃, N2 is continuously introduced, 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b) prepared in step (2) above is added to the reaction solution, and incubated for 6-10 hours, the PH is neutralized to neutral with dilute hydrochloric acid, the organic phase is separated and eluted, the solvent is collected by reduced pressure distillation, and di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol represented by formula I and formula II is obtained.

[0015] The preparation method described above, preferably, the alcohol solvent in step (1) is selected from one of anhydrous methanol, anhydrous ethanol and anhydrous isopropanol.

[0016] The preparation method described above, preferably, the weight ratio of sodium ethoxide, 2-bromoethyl mercaptan, 2-bromomethyl-1,3-dibromopropane and alcohol solvent in step (1) is (1-1.2):(2-3):(3-5):(15-50).

[0017] The preparation method described above, preferably, the solvent in step (2) is selected from one of methanol, ethanol, isopropanol, n-butanol and tetrahydrofuran, or a mixture of the above solvents and water, wherein water accounts for 10-40% of the weight of the mixture.

[0018] The preparation method described above, preferably, the weight ratio of dithiothreitol, sodium hydrosulfide, 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) and solvent in step (2) is (0.02-0.1):(1-1.2):(2-5):(10-45).

[0019] The preparation method described above, preferably, the mixed solvent in step (3) is a mixture of water and an organic solvent selected from at least one of methanol, ethanol, ethyl ether, acetone and tetrahydrofuran; wherein the amount of water accounts for 15-50wt% of the mixed solvent.

[0020] The preparation method as described above, preferably, the weight ratio of the four of 2-mercaptoethanethiol, triethylamine, 2-mercaptoethyl 3-bromo-2-(mercaptomethyl) propyl sulfide (b) and mixed solvent in the step (3) is (0.7~1.5): (2~3): (2.5~5): (15~50).

[0021] In another aspect, the present application provides a modified polyurethane optical material raw material composition, which is composed of: Component A: polyisocyanate, 25~50 parts by weight; Component B: di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dimercaptanol represented by Formula I, Formula II and / or Formula III, 20~45 parts by weight;

[0022] Component C: flexible hydroxyl bisphenol A glycidyl ether epoxy compound represented by Formula A, 3~10 parts by weight.

[0023]

[0024] The modified polyurethane optical material raw material composition as described above, preferably, the polyisocyanate refers to an organic compound containing two or more isocyanate groups in the molecule or a mixture thereof.

[0025] The modified polyurethane optical material raw material composition as described above, preferably, the polyisocyanate is at least one selected from the group consisting of diphenylmethane diisocyanate, diphenyl ether diisocyanate, toluene diisocyanate, diisocyanate dicyclohexyl methane, diethylene diisocyanate, cyclohexane diisocyanate, hexamethylene diisocyanate, dithio diethyl diisocyanate, tetramethylene diisocyanate, thio dihexyl diisocyanate, thio dipropyl diisocyanate, dithio dipropyl diisocyanate, triphenylmethane triisocyanate, isophorone diisocyanate, m-xylylene diisocyanate, phenylene diisocyanate, lysine triisocyanate, trimethyl hexamethylene diisocyanate and o-tolidine diisocyanate.

[0026] In yet another aspect, the present application provides a modified polyurethane optical material, which is polymerized from the modified polyurethane optical material raw material composition as described above.

[0027] In still another aspect, the present application provides a modified polyurethane optical coating, which is prepared into a coating liquid from the modified polyurethane optical material raw material composition as described above, and is formed by spin coating and curing.

[0028] The flexible hydroxyl bisphenol A glycidyl ether epoxy compound represented by Formula A in the present application can be prepared by the following method: (1) Unilateral epoxidation reaction: add bisphenol A and epichlorohydrin into the reaction container containing N, N-dimethylformamide solvent under stirring, the weight ratio of bisphenol A to epichlorohydrin is 1: (0.37-0.44); continuously introduce N2, control the temperature to 65-90℃, add potassium carbonate powder under stirring, and stir for 3-7 hours; separate and elute the organic phase, collect the solvent by distillation under reduced pressure, and obtain bisphenol A monoglycidyl ether; (2) Flexible chain introduction reaction: add bisphenol A monoglycidyl ether prepared in the above step (1) and diethylene glycol into the reaction container containing xylene solvent under stirring, continuously introduce N2, heat to 60-70℃, add p-toluenesulfonamide in batches under stirring, heat to 70-100℃, and react for 4-7 hours; after the reaction is completed, neutralize the acid with lye, remove the catalyst by water washing, collect the solvent by distillation under reduced pressure, and finally obtain flexible hydroxyl bisphenol A glycidyl ether epoxide compound (A).

[0029] The present application has the following advantages: (1) Directional assembly: three-step nucleophilic substitution is adopted to accurately control the positions of thioether bonds and mercapto groups, and random polymerization is avoided.

[0030] (2) Structure controllable: the synergistic design of branched mercapto groups and linear thioether chains is compatible with mercaptan / thioether, and the product is endowed with unique spatial conformation and reactivity.

[0031] (3) Green and mild: no high temperature or strong oxidant is needed, no heavy metal catalyst is used, and the product is easy to purify under mild reaction conditions, which meets the principle of green chemistry.

[0032] (4) The raw material composition of the modified polyurethane optical material of the present application can be used to prepare optical lens materials or coatings, and the composition contains flexible hydroxyl bisphenol A glycidyl ether, which has a flexible ether bond segment in the molecular chain, significantly improves the flexibility of the molecular chain, improves the toughness of the material while maintaining the rigid skeleton; the terminal hydroxyl group provides active hydrogen, enhances the reaction ability with the curing agent and the intermolecular hydrogen bond combination. In the curing process, the epoxy group and the hydroxyl group form a reaction gradient to realize step-by-step curing, reduce the curing stress, reduce the deformation or cracks caused by internal stress, and avoid defects of optical elements caused by stress concentration.

[0033] (5) The modified polyurethane optical material and coating material prepared by the present application have high light transmittance, high refractive index and excellent mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The infrared spectrum of di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol prepared for Example 1.

[0035] Figure 2di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol H NMR nuclear magnetic resonance hydrogen spectrum. DETAILED DESCRIPTION

[0036] The application is further described below by specific examples, but does not mean to limit the scope of protection of the application.

[0037] Example 1 Preparation of di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol (1) 280g of 2-bromomethyl-1,3-dibromopropane was stirred into a reaction vessel containing 1500g of anhydrous ethanol, N2 was continuously introduced, the temperature was controlled to 15°C, and a mixture of 170g of 2-bromoethanethiol, 65g of sodium ethoxide and 250g of anhydrous ethanol was added dropwise, which took 1.5 hours, and the reaction was continuously stirred for 6 hours, then the organic phase was separated and eluted, the solvent was collected by reduced pressure distillation, and 291.2g of 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) was obtained.

[0038] (2) 95g of 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) prepared in the above step (1) was added to a solvent of 180g of water and 720g of ethanol, and after complete dissolution, N2 protection was performed throughout, 1.6g of dithiothreitol and 15g of sodium hydrosulfide were added with stirring, and the reaction was carried out at 30°C for 1.5 hours, 15g of sodium hydrosulfide was continuously added and the reaction was carried out for 5 hours, then the organic phase was separated and eluted, the solvent was collected by reduced pressure distillation, and 69.1g of 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b) was obtained.

[0039] (3) 48g of triethylamine was added to a microchannel reactor (produced by Shanghai Kedeng Technology Co., Ltd., model: GR-50) containing a mixed solvent of 100g of water and 260g of ethanol, and after complete dissolution, 23g of 2-mercaptoethanethiol was added, the flow rate was controlled at 0.6mL / min, and after 50 minutes of reaction, the temperature was controlled at 5°C, N2 was continuously introduced, 65g of 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b) prepared in the above step (2) was added to the reaction solution, and the reaction was carried out for 7.5 hours, then 5% dilute hydrochloric acid was used to neutralize the PH to neutral, the organic phase was separated and eluted, the solvent was collected by reduced pressure distillation, and finally 63.1g of colorless transparent di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol was obtained. The yield was 84.2%.

[0040] (4) Product analysis I. High performance liquid chromatography (HPLC) quantitative detection and analysis: The product prepared in Example 1 was subjected to content determination and analysis. The external standard method was used, and the specific steps were as follows: mixed standard preparation, accurate weighing of pure product, preparation of a series of concentration standard solutions, at least 5 concentration gradients of mixed standard solutions (such as 10%, 5%, 3%, 1%, and 0.5%), injection of the mixed standard series solutions in order from high to low concentration, recording of the chromatogram, and reading of the peak areas of two isomers; taking the standard concentration (x) as the abscissa and the corresponding peak area (y) as the ordinate, a standard curve was drawn by the least square method to obtain the regression equation (such as y = ax + b) and establish a linear relationship. The peak area of the sample of Example 1 was compared with the standard peak area, and the content range of each isomer was calculated. The detection results showed that the content of 5,7-bis (mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol (I) in the sample of Example 1 was 95%, the content of 4,8-bis (mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol (II) was 5%, and 4,7-bis (mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol (III) was not detected.

[0041] Infrared spectroscopy FT-IR test: The product prepared in Example 1 was subjected to Fourier transform infrared spectroscopy (FT-IR) test, and the results are shown in Figure 1 The absorption peak at 2855~2920 cm⁻¹ is the C-H stretching vibration of methylene (-CH2-) and methine (-CH-); the absorption peak at 2553~2590 cm⁻¹ is the S-H stretching vibration, which is the characteristic absorption peak of mercapto group; the absorption peak at 1382~1465 cm⁻¹ is the C-H bending vibration of methine and methylene; and the absorption peak at 622~697 cm⁻¹ is the C-S bond stretching vibration of sulfide bond (-S-).

[0042] Pure 5,7-bis (mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol was subjected to infrared spectroscopy FT-IR test, and the test results were basically the same as those of Example 1; Example 1 and the pure product only had slight differences in the molecular skeleton vibration mode in the fingerprint region (below 1500 cm⁻¹).

[0043] Nuclear magnetic resonance hydrogen spectrum analysis: as Figure 2As shown, δ = 3.65~3.72ppm (t, 4H, 2x-CH2-SH) triplet for methylene hydrogen connected with branched thiol group; δ = 3.31~3.49ppm (m, 2H, 2x-CH-S) multiplet for methine hydrogen connected with sulfur atom; δ = 2.93~3.37ppm (m, 8H, 4x-CH2-S) multiplet for methylene hydrogen connected with sulfur atom (-S) on both sides; δ = 2.56~2.67ppm (t, 4H, 2xCH2-SH) triplet for methylene hydrogen connected with main chain thiol group (-SH); δ = 1.82~2.38ppm (brs, 4H, 4x-SH) broad singlet for -SH hydrogen at different positions.

[0044] The pure product 5,7-di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol was subjected to H NMR nuclear magnetic resonance hydrogen spectrum test, and the test results were basically the same as those of Example 1, except that there were slight differences in the chemical shifts of the corresponding protons, and the coupling modes between the adjacent protons were slightly different.

[0045] Example 2: Preparation of di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol (1) 290g of 2-bromomethyl-1,3-dibromopropane was stirred into a reaction container containing 1450g of anhydrous ethanol, N2 was continuously introduced, the temperature was controlled to 15°C, and a mixture of 175g of 2-bromoethanethiol, 63g of sodium ethoxide and 250g of ethanol was added dropwise. The dropwise addition was completed in 1.5 hours, and the stirring reaction was continued for 6 hours. The organic phase was separated and eluted, and the solvent was collected by reduced pressure distillation to obtain 297.6g of 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a).

[0046] (2) 95g of 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) prepared in the above step (1) was added to a solvent of 190g of water and 700g of ethanol, and after complete dissolution, N2 protection was performed throughout the process. 1.5g of dithiothreitol and 17g of sodium hydrosulfide were added with stirring, and the reaction was carried out at 32°C for 1.5 hours. 15g of sodium hydrosulfide was continuously added and the reaction was carried out for 5 hours. The organic phase was separated and eluted, and the solvent was collected by reduced pressure distillation to obtain 69.3g of 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b).

[0047] (3) To the micro-channel reactor containing 100 g of water and 260 g of ethanol mixed solvent, 45 g of triethylamine was added, and after complete dissolution, 21 g of 2-mercaptoethanethiol was added. The flow rate was controlled at 0.6 mL / min, and after reaction for 50 min, the temperature was controlled at 5°C, and N2 was continuously introduced. To the reaction solution, 60 g of 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b) prepared in the above step (2) was added, and the reaction was carried out at 32°C for 7.5 h. The pH was neutralized to neutral with 5% dilute hydrochloric acid, and the organic phase was separated and eluted. The solvent was collected by distillation under reduced pressure, and finally 57.8 g of colorless transparent di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol was obtained. The yield was 84.2%.

[0048] The di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol compound prepared in Example 2 was tested by infrared spectroscopy FT-IR and H NMR nuclear magnetic resonance hydrogen spectrum, and the test results were basically the same as those of Example 1.

[0049] Example 3 Preparation of di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol (1) 300 g of 2-bromomethyl-1,3-dibromopropane was stirred and added to a reaction container containing 1550 g of anhydrous ethanol, N2 was continuously introduced, and the temperature was controlled to 15°C. A mixture of 165 g of 2-bromoethanethiol, 68 g of sodium ethoxide, and 250 g of ethanol was added dropwise, and the dropwise addition was completed in 1.5 h. The reaction was continuously stirred for 6.5 h, and the organic phase was separated and eluted. The solvent was collected by distillation under reduced pressure, and 308.1 g of 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) was obtained.

[0050] (2) 95 g of 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) prepared in the above step (1) was added to a solvent of 205 g of water and 700 g of ethanol, and after complete dissolution, N2 protection was carried out throughout the process. 1.8 g of dithiothreitol and 18 g of sodium hydrosulfide were added with stirring, and the reaction was carried out at 32°C for 1.6 h. 15 g of sodium hydrosulfide was further added and the reaction was carried out for 5 h. The organic phase was separated and eluted, and the solvent was collected by distillation under reduced pressure to obtain 69.5 g of 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b).

[0051] (3) To the micro-channel reactor containing 100 g of water and 290 g of ethanol mixed solvent, 52 g of triethylamine was added, and after complete dissolution, 25 g of 2-mercaptoethanethiol was added. The flow rate was controlled at 0.6 mL / min, and after 50 minutes of reaction, the temperature was controlled at 5°C, and N2 was continuously introduced. To the reaction solution, 69 g of 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b) prepared in the above step (2) was added, and the reaction was carried out for 7.5 hours while maintaining the temperature. The pH was neutralized to neutral with 5% dilute hydrochloric acid, the organic phase was separated and eluted, the solvent was collected by distillation under reduced pressure, and finally 67.3 g of colorless transparent di(mercaptomethyl)-3,6,9-trithiaundecane-1,11-dithiol was obtained. The yield was 84.3%.

[0052] Preparation of modified polyurethane optical material 1. Preparation of flexible hydroxyl bisphenol A glycidyl ether epoxy compound (Formula A) (1) To the reaction vessel containing 500 g of DMF solvent, 150 g of bisphenol A and 58 g of epichlorohydrin were added with stirring, N2 was continuously introduced, the temperature was controlled at 80°C, 46 g of potassium carbonate powder was added with stirring, and the reaction was carried out for 5 hours. The organic phase was separated and eluted, the solvent was collected by distillation under reduced pressure, and 142.4 g of bisphenol A monoglycidyl ether (compound of formula a) was obtained.

[0053] (2) 120 g of bisphenol A monoglycidyl ether (a) prepared in the above step (1) and 85 g of diethylene glycol were stirred and added to a reaction vessel containing 400 g of xylene solvent, N2 was continuously introduced, the temperature was raised to 65°C, 3 g of p-toluenesulfonamide was added with stirring, the temperature was raised to 85°C, and then 2 g of p-toluenesulfonamide was added. The acid value of the system was titrated with KOH standard solution every 1 hour, the reaction was carried out for 6 hours while maintaining the temperature, and when the acid value no longer changed, the temperature was lowered to 50°C, and neutralized with 10% NaHCO3 solution. The organic phase was separated and eluted, and 132.4 g of colorless transparent flexible hydroxyl bisphenol A glycidyl ether epoxy compound (i) was obtained by distillation under reduced pressure. The yield was 80.4%.

[0054] Nuclear magnetic resonance hydrogen spectrum analysis: δ = 7.15~6.86 ppm (m, 8H, 2xPh hydrogen); 4.19~3.95 (dd, 2H, epoxy-CH2-O-Ph); 3.89~3.77 (t, 2H, -CH2OH- connected to hydroxyl); 376~3.63 (m, 6H, OCH2CH2OCH2); 3.18~3.15 (m, 1H, epoxy-CH-); 2.80~2.65 (dd, 2H, epoxy-CH2-); 2.50 ppm (t, 1H, -OH); 1.63 (s, 6H, -C(CH3)2).

[0055] Preparation of modified polyurethane optical material Take 50 g of the di (mercapto methyl) -3, 6, 9-trithia normal undecane-1, 11-dithiol prepared in example 1, 5 g of flexible hydroxyl bisphenol A glycidyl ether epoxy compound (formula A) into a reactor containing 50 g of diphenyl methane diisocyanate, stirring at 80 rpm for 35 minutes, adding 0.25 g of dibutyl tin dilaurate, stirring to form a prepolymer; after vacuuming the prepolymer to remove bubbles, it is injected into a tempered mold, the tempered mold containing the prepolymer is placed in a curing oven, the temperature is raised to 40℃ and cured for 2.5 hours, the temperature is raised to 65℃ and cured for 3 hours, and then cooled to room temperature to demold and sample, thus obtaining the modified polyurethane optical material.

[0056] Example 5: Preparation of modified polyurethane optical coating Take 40 g of the di (mercapto methyl) -3, 6, 9-trithia normal undecane-1, 11-dithiol prepared in example 2 and 7 g of flexible hydroxyl bisphenol A glycidyl ether epoxy compound (formula A) into a reaction vessel containing 10 g of hexamethylene diisocyanate and 40 g of diphenyl methane diisocyanate, mix well, then add 0.3 g of BYK-163 wetting dispersant, heat to 30℃ and stir at 80 rpm for 35 minutes to obtain a prepolymer coating solution; add 0.15 g of dibutyl tin dilaurate to the coating solution, stir well and filter with a 0.2 um PTFE filter membrane, then spin coat onto the surface of a resin substrate at 1500 rpm, then place the coated substrate in a curing oven, heat to 45℃ and cure for 5 min, heat to 55℃ and cure for 5 min, heat to 65℃ and cure for 5 min, then cool to room temperature and sample.

[0057] Experimental Example 1: Optical performance detection experiment The di (mercapto methyl) -3, 6, 9-trithia normal undecane-1, 11-dithiol prepared in examples 1-3 and the modified polyurethane optical material prepared in examples 4-5 were respectively detected for light transmittance and refractive index. The Lambda 650 S ultraviolet-visible spectrophotometer produced by PerkinElmer Chemical Analysis Instrument Co., Ltd. was selected for light transmittance detection, and the Rx-7000 digital refractometer produced by Shanghai Optical Instrument Equipment Co., Ltd. was selected for refractive index detection. The detection method was to directly coat the sample prepared in examples 1-3 or dilution on the prism of the ultraviolet-visible spectrophotometer or the prism of the refractometer for detection. The detection results are shown in Table 1.

[0058]

[0059] The test results show that the modified polyurethane optical material prepared by the present application has high light transmittance and high refractive index.

[0060] Experimental Example 2: Impact strength detection experiment The impact resistance of the polyurethane optical material prepared in Example 4 was tested. The highest steel ball mass without cracks in the optical material, such as 90 g steel ball impact three times, the material without cracks, 100 g steel ball impact cracks, the impact resistance of the material is 90 g. Test method: the substrate with a certain arc in the center thickness is fixed on the bottom of the instrument with the convex surface upward, different mass steel balls (80 g, 90 g, 100 g and 110 g) are selected and vertically free fall on the center of the substrate material surface from a height of 1.30 m, three times of determination are carried out for each mass of steel ball. The steel ball impact test results show that the impact resistance of the modified polyurethane optical material is higher than 100 g, and the impact resistance is good.

[0061] Experimental Example 3 Adhesion Test Experiment The cross-cut test was carried out by using the adhesive tape method. Test method: a blade was used to scratch the surface of the optical coating prepared in Example 5, and then the scratch was made from a vertical angle, finally 16 small square blocks were left on the surface of the coating, 3M invisible adhesive tape was adhered on the grid, the adhesive tape was torn back at a slightly fast and smooth speed, and the peeling of the coating at the cross-cut intersection of the grid was observed by using a magnifying glass. The scratch test results show that the coating has no peeling and peeling, and the adhesion is good.

Claims

1. A method for preparing di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dimercaprol, characterized in that, The method includes the following steps: (1) Nucleophilic substitution: 2-bromomethyl-1,3-dibromopropane was added to a reaction vessel containing an alcohol solvent with stirring. N2 was continuously introduced and the temperature was controlled at 0~25℃. An ethanol solution containing 2-bromoethanethiol and sodium ethoxide at a concentration of 15~40wt% was added dropwise over 1~3 hours. The reaction was stirred for 5~9 hours. The organic phase was separated and eluted. The solvent was collected by vacuum distillation to obtain 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (formula a). (2) Chain extension reaction: The 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) prepared in step (1) was added to the solvent under N2 protection throughout the process. Dithiothreitol and 30-50% sodium hydrosulfide were added while stirring. The reaction was maintained at 20-50℃ for 1-3 hours. The remaining sodium hydrosulfide was added, and the reaction was continued for 3-7 hours. The organic phase was separated and eluted, and the solvent was collected by vacuum distillation to obtain 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (formula b); (3) Thioetherification and chain extension: Triethylamine was added to a microchannel reactor containing a mixed solvent. After complete dissolution, 2-mercaptoethyl mercaptan was added. The flow rate was controlled at 0.1-1 mL / min. After reacting for 30-60 minutes, the temperature was raised to 0-25°C and N2 was continuously introduced. 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b) prepared in step (2) above was added to the reaction solution. The reaction was kept at a constant temperature for 6-10 hours. The pH was neutralized to neutral with dilute hydrochloric acid. The organic phase was separated and eluted. The solvent was collected by vacuum distillation to obtain di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dimercaprol as shown in Formula I and Formula II.

2. The preparation method according to claim 1, characterized in that, In step (1), the alcohol solvent is selected from one of anhydrous methanol, anhydrous ethanol and anhydrous isopropanol.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the weight ratio of sodium ethoxide, 2-bromoethanethiol, 2-bromomethyl-1,3-dibromopropane and alcohol solvent is (1~1.2):(2~3):(3~5):(15~50).

4. The preparation method according to claim 1, characterized in that, In step (2), the solvent is selected from one of methanol, ethanol, isopropanol, n-butanol and tetrahydrofuran, or a mixture of the above solvents and water, wherein water accounts for 10 to 40% of the weight of the mixture.

5. The preparation method according to claim 1 or 4, characterized in that, In step (2), the weight ratio of dithiothreitol, sodium hydrosulfide, 2-bromoethyl 3-bromo-2-(bromomethyl)propyl sulfide (a) and solvent is (0.02~0.1):(1~1.2):(2~5):(10~45).

6. The preparation method according to claim 1, characterized in that, In step (3), the mixed solvent is a mixture of water and an organic solvent, wherein the organic solvent is selected from at least one of methanol, ethanol, acetonitrile, acetone and tetrahydrofuran; wherein the amount of water accounts for 15 to 50 wt% of the mixed solvent.

7. The preparation method according to claim 1 or 6, characterized in that, In step (3), the weight ratio of 2-mercaptoethanethiol, triethylamine, 2-mercaptoethyl 3-bromo-2-(mercaptomethyl)propyl sulfide (b) and the mixed solvent is (0.7~1.5):(2~3):(2.5~5):(15~50).

8. A modified polyurethane optical material raw material composition, characterized in that, It is composed of the following components: Component A: Polyisocyanate, 25-50 parts by weight; Component B: 20 ​​to 45 parts by weight of di(mercaptomethyl)-3,6,9-trithia-n-undecane-1,11-dimercaptool as shown in Formula I, Formula II and / or Formula III; ; Component C: 3-10 parts by weight of the flexible hydroxybisphenol A glycidyl ether epoxy compound shown in Formula A.

9. The modified polyurethane optical material raw material composition as described in claim 8, characterized in that, The polyisocyanate refers to an organic compound or a mixture thereof containing two or more isocyanate groups in its molecule.

10. The modified polyurethane optical material raw material composition according to claim 9, characterized in that, The polyisocyanate is selected from at least one of diphenylmethane diisocyanate, diphenyl ether diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, diethylene diisocyanate, cyclohexane diisocyanate, hexamethylene diisocyanate, dithiodiethyl diisocyanate, tetramethylene diisocyanate, thiodihexyl diisocyanate, thiodipropyl diisocyanate, dithiodipropyl diisocyanate, triphenylmethane triisocyanate, isophorone diisocyanate, m-phenylenedimethyl diisocyanate, phenylenedimethyl diisocyanate, lysine triisocyanate, trimethylhexamethylene diisocyanate, and o-toluidine diisocyanate.

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