1, 1, 3, 3-tetra (mercaptomethylthio) propane, preparation method thereof and optical coating material

Abstract

The invention relates to 1, 1, 3, 3-tetra (mercaptomethylthio) propane, a preparation method thereof and an optical coating material, and belongs to the technical field of high-molecular optical materials.The preparation method of the 1, 1, 3, 3-tetra (mercaptomethylthio) propane comprises the steps that 1, 1, 3, 3-tetrachloropropane, tetrabutylammonium bromide and zinc acetate are taken and added into a mixed solvent, and a mixed solution is obtained; dropwise adding a mixed solution containing sodium hydrosulfide, ethanol and water, and carrying out temperature-controlled reaction to obtain a reaction solution; and adjusting the pH value of the reaction solution to 6-7, cooling to room temperature, filtering, drying, eluting an organic phase, and carrying out reduced pressure distillation on the filtrate to recover the solvent, thereby obtaining the 1, 1, 3, 3-tetra (mercaptomethylthio) propane. The preparation method has the characteristics of small environmental pollution, simple process and high yield, and the optical coating material has the advantages of high light transmittance, low haze value, high refractive index and adjustability.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer optical material synthesis, in particular to 1,1,3,3-tetrakis(mercaptomethylthio)propane and a preparation method thereof, and an optical coating material. Background Art

[0002] As a polythiol compound, 1,1,3,3-tetrakis(mercaptomethylthio)propane, with its active thiol (-SH) and methylthio (-SCH2) groups in its molecular structure, has important applications in optical components, polymer optical materials, and high-molecular-weight materials. It can be used as a crosslinker or chain transfer agent in the synthesis of materials such as polyurethane optical resins, improving the refractive index and material properties of polymers.

[0003] In the existing technology, the synthesis of polythiol compounds mainly relies on the preparation route of traditional thiol derivatives, but these methods generally have problems such as low efficiency, high environmental pollution and complex process. Specifically, the synthesis of traditional thiol derivatives often adopts the thiourea method or sodium hydrosulfide method. For example, in the industrial production of mercaptopropionic acid, the acrylic acid-thiourea method has the disadvantages of many by-products (such as disulfide) and high environmental pollution. For example, the preparation of 1,1,3,3-tetramethoxypropane requires the use of sodium methoxide and sodium sulfhydride under high pressure conditions. The reaction has harsh process conditions and the yield is only 75%. For other tetrasubstituted propane derivatives, such as 1,1,3,3-tetramethyldisiloxane, it is obtained by hydrolysis and distillation of low-boiling organic silicon, but this method has extremely high requirements for the purity of the raw materials. In addition, 1,1,3,3-tetramethylbutyl hydroperoxide uses a solid superacid catalytic system. Although it can achieve catalyst recycling, product separation requires complex layering operations. For compounds containing methylthio groups, existing methods mostly rely on metal catalysts such as zinc chloride. For example, the synthesis of 2-bromo-3-ethylsulfonylpyridine requires catalytic condensation using an acetic anhydride / zinc chloride system, which can easily lead to equipment corrosion and waste liquid treatment problems.

[0004] The aforementioned technologies are difficult to directly transfer to the synthesis of the target product, 1,1,3,3-tetrakis(mercaptomethylthio)propane. Therefore, the development of a mild, highly selective, and environmentally friendly 1,1,3,3-tetrakis(mercaptomethylthio)propane and optical coating materials based on this compound has significant industrial value and is in urgent market demand. Summary of the Invention

[0005] The present invention aims to provide 1,1,3,3-tetrakis(mercaptomethylthio)propane and a preparation method thereof, as well as an optical coating material, to solve the problems of severe environmental pollution, harsh process conditions, low yield, and easy oxidation to produce by-products in the synthesis of traditional thiol compounds, and to make the optical coating have the advantages of high transmittance, low haze value, high and adjustable refractive index.

[0006] On the one hand, the preparation method of 1,1,3,3-tetrakis(mercaptomethylthio)propane provided by the present invention adopts the following technical scheme:

[0007] The preparation method of 1,1,3,3-tetrakis(mercaptomethylthio)propane comprises the following steps:

[0008] S1. Take 1,1,3,3-tetrachloropropane, tetrabutylammonium bromide and zinc acetate, add them to a mixed solvent, and stir and mix under nitrogen protection to obtain a mixed solution;

[0009] S2. Add a mixture of sodium hydrosulfide, ethanol, and water dropwise to the mixed solution prepared in step S1, control the temperature to 20-45° C., stir and react for 90-120 min, continue nitrogen protection, and heat to 45-60° C., continue the reaction for 2-4 h to obtain a reaction solution;

[0010] S3. Neutralize the reaction solution obtained in step S2 with dilute hydrochloric acid solution to a pH of 6-7, cool to room temperature, filter, dry, and elute the organic phase. Distill the filtrate under reduced pressure to recover the solvent to obtain 1,1,3,3-tetrakis(mercaptomethylthio)propane.

[0011] Preferably, the weight ratio of 1,1,3,3-tetrachloropropane, tetrabutylammonium bromide, zinc acetate, mixed solvent and sodium hydrosulfide in step S1 and step S2 is (2-3): (0.07-0.2): (0.15-0.3): (7-15): (2.5-4.5);

[0012] In the mixed solution in step S2, the percentage of sodium hydrosulfide is 20-35%, the percentage of ethanol is 40-60%, and the percentage of water is 20-45%.

[0013] Preferably, the mixed solvent comprises: 20-40% water and 60-80% organic solvent;

[0014] The organic solvent is at least one of methanol, ethanol, acetonitrile and acetone.

[0015] On the other hand, the present invention also provides 1,1,3,3-tetrakis(mercaptomethylthio)propane.

[0016] 1,1,3,3-tetrakis(mercaptomethylthio)propane is prepared by the above-mentioned preparation method. The structural formula of the 1,1,3,3-tetrakis(mercaptomethylthio)propane is: (HSCH2S)2CH-CH2-CH(HSCH2S)2;

[0017] The structural formula of the 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0018] .

[0019] In yet another aspect, the present invention further provides an optical coating material.

[0020] An optical coating material, comprising the following components in parts by weight:

[0021] 20-45 parts of 1,1,3,3-tetrakis(mercaptomethylthio)propane prepared by the preparation method according to any one of claims 1 to 3;

[0022] 25-50 parts of isocyanate;

[0023] 5-15 parts of epoxy monomer.

[0024] Preferably, the isocyanate is at least one of toluene diisocyanate, triphenylmethane triisocyanate, cyclohexane diisocyanate, diphenylmethane diisocyanate, diphenyl ether diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, toluene diisocyanate, diethylene diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, m-xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dithiodipropyl diisocyanate, dihexyl thiodiisocyanate, diethyl diisocyanate, dithiodipropyl diisocyanate, lysine triisocyanate, trimethylhexamethylene diisocyanate, and o-tolidine diisocyanate.

[0025] Preferably, the epoxy monomer is at least one of bisphenol A epoxy monomer, 2,2'-dimercaptoethyl sulfide diglycidyl ether, 3,3'-dimercaptodiphenyl sulfone diglycidyl ether, 2,2'-dimercaptobisepoxypropane ethyl sulfide, bisphenol A episulfide monomer and bis((3,4-epoxycyclohexyl)methyl)adipate.

[0026] Preferably, the optical coating material further comprises 0.1-0.9 parts by weight of a wetting and dispersing agent;

[0027] The wetting dispersant is at least one of BYK-163 and BYK-324 dispersants.

[0028] Preferably, the optical coating material further comprises 0.4-4 parts by weight of a diluent;

[0029] The diluent is at least one of n-pentane, dichloromethane, methyl formate, benzyl acrylate, ethoxyphenol acrylate, diphenylmethanol acrylate, o-phenylphenoxyethyl acrylate, 1,6-hexanediol diacrylate, pentaerythritol triacrylate, and trimethylolpropane triacrylate.

[0030] Preferably, the optical coating material further comprises 0.02-0.35 parts by weight of an initiator;

[0031] The initiator is any one of stannous octoate, dibutyltin dilaurate, dibutyltin dichloride, dibutyltin oxide and tetrabutylphosphine bromide.

[0032] In summary, the present invention has the following beneficial technical effects:

[0033] This invention uses sodium hydrosulfide as a sulfur source to enhance reaction activity, ensure complete tetrasubstitution, and avoid residual intermediates. Tetrabutylammonium bromide is used as a phase transfer catalyst to facilitate the transfer of sulfide ions between the aqueous phase and the organic phase (e.g., an ethanol / water mixed solvent). Furthermore, the reaction temperature is controlled in stages to prevent mercaptan oxidation caused by high temperatures. Furthermore, zinc acetate is added during the reaction to reduce disulfide byproducts. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an infrared spectrum of 1,1,3,3-tetrakis(mercaptomethylthio)propane prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The following embodiments and appendix Figure 1 The present invention is described in further detail.

[0036] raw material

[0037] Isocyanate: the isocyanate is at least one of toluene diisocyanate, triphenylmethane triisocyanate, cyclohexane diisocyanate, diphenylmethane diisocyanate, diphenyl ether diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, toluene diisocyanate, diethylene diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, m-xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dipropyl disulfide diisocyanate, dihexyl sulfide diisocyanate, diethyl disulfide diisocyanate, dipropyl sulfide diisocyanate, lysine triisocyanate, trimethylhexamethylene diisocyanate, and o-tolidine diisocyanate;

[0038] Epoxy monomer: The epoxy monomer is at least one of bisphenol A epoxy monomer, 2,2'-dimercaptoethyl sulfide diglycidyl ether, 3,3'-dimercaptodiphenyl sulfone diglycidyl ether, 2,2'-dimercaptobisepoxypropane ethyl sulfide, bisphenol A episulfide monomer, and bis((3,4-epoxycyclohexyl)methyl)adipate; wherein the bisphenol A epoxy monomer is selected from NPEL-128 of Nan Ya Plastics.

[0039] Wetting dispersant: The wetting dispersant is at least one of BYK-163 and 324 dispersants;

[0040] Diluent: the diluent is at least one of n-pentane, methylene chloride, methyl formate, benzyl acrylate, ethoxyphenol acrylate, biphenylmethanol acrylate, o-phenylphenoxyethyl acrylate, 1,6-hexanediol diacrylate, pentaerythritol triacrylate, and trimethylolpropane triacrylate;

[0041] Initiator: The initiator is any one of stannous octoate, dibutyltin dilaurate, dibutyltin dichloride, dibutyltin oxide and tetrabutylphosphine bromide.

[0042] Example 1

[0043] 1,1,3,3-tetrakis(mercaptomethylthio)propane, the specific preparation method is as follows:

[0044] 1) 250 g of 1,1,3,3-tetrachloropropane, 11 g of tetrabutylammonium bromide, and 20 g of zinc acetate were added to a mixed solvent comprising 680 g of ethanol and 200 g of water, and stirred under nitrogen to obtain a mixed solution.

[0045] 2) adding dropwise a mixture of 300 g of sodium hydrosulfide, 680 g of ethanol, and 370 g of water to the mixed solution prepared in step 1) for 60 min, controlling the temperature at 40° C., stirring and reacting for 100 min under continuous nitrogen protection, then heating to 50° C. and continuing the reaction for 2.5 h to obtain a reaction solution;

[0046] 3) The reaction solution obtained in step 2) was neutralized with 6% dilute hydrochloric acid solution to a pH of 6.0. The solution was cooled to room temperature, filtered, dried, and the organic phase was eluted. The filtrate was distilled under reduced pressure to recover the solvent, yielding 412 g of 1,1,3,3-tetrakis(mercaptomethylthio)propane. The yield of 1,1,3,3-tetrakis(mercaptomethylthio)propane was 84.6%.

[0047] The structural formula of 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0048] (HSCH2S)2CH-CH2-CH(HSCH2S)2;

[0049] The structural formula of 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0050] .

[0051] Reference Figure 1 The 1,1,3,3-tetrakis(mercaptomethylthio)propane prepared in Example 1 was subjected to Fourier transform infrared spectroscopy FT-IR test, wherein the 2984~2853cm -1 The strong absorption peak at ) and symmetric and asymmetric stretching vibrations of methine (CH), 2537~2597cm -1 The absorption peak at 1197~1293cm is the characteristic peak of -SH stretching vibration. -1 The absorption peak at is the methylene group connected to sulfur ( ) Bending vibration, 996~1089cm -1 The absorption peak at is the propane chain ( )CC skeleton stretching vibration, 609~696 cm -1 The absorption peak is the stretching vibration of CS bond.

[0052] H NMR nuclear magnetic resonance hydrogen spectrum analysis: δ = 1.50~1.95 ppm (s (br), 4H, 4×-SH, thiol), δ = 2.01~2.29 ppm (m, 2H, -CH2, methylene in the propane chain), 2.53~2.97 ppm (s, 8H, 4×-S-CH2, methylene), δ = 3.51~3.82 ppm (m, 2H, 2×-CH, methine).

[0053] Example 2

[0054] 1,1,3,3-tetrakis(mercaptomethylthio)propane, the specific preparation method is as follows:

[0055] 1) 250 g of 1,1,3,3-tetrachloropropane, 11 g of tetrabutylammonium bromide, and 22 g of zinc acetate were added to a mixed solvent comprising 660 g of ethanol and 200 g of water, and stirred under nitrogen to obtain a mixed solution.

[0056] 2) adding dropwise a mixture of 300 g of sodium hydrosulfide, 680 g of ethanol, and 370 g of water to the mixed solution prepared in step 1) for 60 min, controlling the temperature at 40° C., stirring and reacting for 100 min under continuous nitrogen protection, then raising the temperature to 50° C. and continuing the reaction for 2.6 h to obtain a reaction solution;

[0057] 3) The reaction solution obtained in step 2) was neutralized with 5% dilute hydrochloric acid solution to a pH of 6.0. The solution was cooled to room temperature, filtered, dried, and the organic phase was eluted. The filtrate was distilled under reduced pressure to recover the solvent, yielding 429 g of 1,1,3,3-tetrakis(mercaptomethylthio)propane. The yield of 1,1,3,3-tetrakis(mercaptomethylthio)propane was 88.2%.

[0058] The structural formula of 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0059] (HSCH2S)2CH-CH2-CH(HSCH2S)2;

[0060] The structural formula of 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0061] .

[0062] The 1,1,3,3-tetrakis(mercaptomethylthio)propane compound prepared in Example 2 was subjected to infrared spectroscopy FT-IR and HNMR nuclear magnetic resonance hydrogen spectrum tests, and the test results were basically the same as those of Example 1.

[0063] Example 3

[0064] 1,1,3,3-tetrakis(mercaptomethylthio)propane, the specific preparation method is as follows:

[0065] 1) 250 g of 1,1,3,3-tetrachloropropane, 12 g of tetrabutylammonium bromide, and 20 g of zinc acetate were added to a mixed solvent comprising 700 g of ethanol and 200 g of water, and stirred under nitrogen to obtain a mixed solution.

[0066] 2) adding dropwise a mixture of 300 g of sodium hydrosulfide, 600 g of ethanol, and 300 g of water to the mixed solution prepared in step 1) for 60 min, controlling the temperature at 40° C., stirring and reacting for 100 min under continuous nitrogen protection, then raising the temperature to 50° C. and continuing the reaction for 2.5 h to obtain a reaction solution;

[0067] 3) The reaction solution obtained in step 2) was neutralized with 6% dilute hydrochloric acid solution to a pH of 6.0. The solution was cooled to room temperature, filtered, dried, and the organic phase was eluted. The filtrate was subjected to reduced pressure distillation to recover the solvent, yielding 418 g of 1,1,3,3-tetrakis(mercaptomethylthio)propane. The yield of 1,1,3,3-tetrakis(mercaptomethylthio)propane was 85.7%.

[0068] The structural formula of 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0069] (HSCH2S)2CH-CH2-CH(HSCH2S)2;

[0070] The structural formula of 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0071] .

[0072] Example 4

[0073] 1,1,3,3-tetrakis(mercaptomethylthio)propane, the specific preparation method is as follows:

[0074] 1) 250 g of 1,1,3,3-tetrachloropropane, 12 g of tetrabutylammonium bromide, and 20 g of zinc acetate were added to a mixed solvent comprising 650 g of ethanol and 180 g of water, and the mixture was stirred and mixed under nitrogen to obtain a mixed solution;

[0075] 2) adding dropwise a mixture of 280 g of sodium hydrosulfide, 600 g of ethanol, and 350 g of water to the mixed solution prepared in step 1) for 60 min, controlling the temperature at 40° C., stirring and reacting for 100 min under continuous nitrogen protection, then heating to 50° C. and continuing the reaction for 2.8 h to obtain a reaction solution;

[0076] 3) The reaction solution obtained in step 2) was neutralized with 6% dilute hydrochloric acid solution to a pH of 6.0. The solution was cooled to room temperature, filtered, dried, and the organic phase was eluted. The filtrate was distilled under reduced pressure to recover the solvent, yielding 397 g of 1,1,3,3-tetrakis(mercaptomethylthio)propane. The yield of 1,1,3,3-tetrakis(mercaptomethylthio)propane was 80.7%.

[0077] The structural formula of 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0078] (HSCH2S)2CH-CH2-CH(HSCH2S)2;

[0079] The structural formula of 1,1,3,3-tetrakis(mercaptomethylthio)propane is:

[0080] .

[0081] Application Examples

[0082] Application Example 1

[0083] An optical coating material, the specific preparation method is as follows:

[0084] 1) 45 g of 1,1,3,3-tetrakis(mercaptomethylthio)propane prepared in Example 1 was added to a reaction vessel containing 2.0 g of dichloromethane, 1.5 g of pentaerythritol triacrylate, and 50 g of diphenylmethane diisocyanate. After mixing, 10 g of bisphenol A epoxy monomer (NPEL-128) and 0.4 g of BYK-163 were added, respectively. The mixture was heated to 35° C. and stirred at 80 rpm for 35 minutes to obtain a prepolymerized coating solution.

[0085] 2) Add 0.15 g of dibutyltin dilaurate to the prepolymer coating liquid prepared in step 1), stir evenly, filter and degas through a 0.2 μm pore size PTFE filter membrane, and then spin-coat the prepolymer coating liquid onto the surface of a resin substrate at a speed of 2500 r / min to obtain a coated substrate. Place the coated substrate in a curing oven, heat to 40°C for curing for 5 minutes, heat to 50°C for curing for 10 minutes, and heat to 65°C for curing for 5 minutes. After the coating is completely cured, cool naturally to room temperature and take a sample to obtain an optical coating material.

[0086] Application Example 2

[0087] An optical coating material, the specific preparation method is as follows:

[0088] 1) 50 g of 1,1,3,3-tetrakis(mercaptomethylthio)propane prepared in Example 1 was added to a reaction vessel containing 2.0 g of n-pentane, 1.5 g of trimethylolpropane triacrylate, and 60 g of hexamethylene diisocyanate. After mixing evenly, 10 g of bisphenol A epoxy monomer (NPEL-128) and 0.4 g of BYK-163 were added, respectively. The mixture was heated to 30° C. and stirred at 80 rpm for 35 minutes to obtain a prepolymerized coating solution.

[0089] 2) Add 0.25 g of dibutyltin dilaurate to the prepolymer coating liquid prepared in step 1), stir evenly, filter and degas through a 0.2 μm pore size PTFE filter membrane, and then spin-coat the solution onto the surface of a resin substrate at a speed of 2500 r / min to obtain a coated substrate. Place the coated substrate in a curing oven, heat to 40°C for curing for 5 minutes, heat to 50°C for curing for 10 minutes, and heat to 65°C for curing for 5 minutes. After the coating is completely cured, cool naturally to room temperature and take a sample to obtain an optical coating material.

[0090] Test Case

[0091] Test Example 1

[0092] Optical performance testing experiment

[0093] The transmittance and refractive index of 1,1,3,3-tetrakis(mercaptomethylthio)propane prepared by Examples 1-4 and the prepolymerized coating liquid prepared by Application Example 1-2 were respectively tested. The transmittance was tested using a Lambda 650 S UV-visible spectrophotometer produced by PerkinElmer Chemical Analytical Instruments, Inc., USA, and the refractive index was tested using an Rx-7000 digital refractometer produced by Shanghai Optical Instruments Co., Ltd.

[0094] Detection method: The samples prepared in Examples 1-4 and Application Examples 1-2 were directly coated on the prism of a UV-visible photometer or the prism of a refractometer for detection. The detection results are detailed in Table 1.

[0095] Table 1 Optical properties of prepared samples

[0096] sample Transmittance (T%) Refractive index (nd) Example 1 89.7 1.798 Example 2 89.6 1.799 Example 3 89.7 1.798 Example 4 89.7 1.797 Application Example 1 89.8 1.680 Application Example 2 90.1 1.613

[0097] According to the optical experimental results in Table 1, 1,1,3,3-tetrakis(mercaptomethylthio)propane and the optical coating material containing 1,1,3,3-tetrakis(mercaptomethylthio)propane have the advantages of high transmittance, large refractive index and adjustable refractive index.

[0098] Test Example 2

[0099] Coating adhesion and peeling force test experiment

[0100] A cross-hatch test using a tape method was conducted. A blade was used to scratch the surface of the optical coating material prepared in Example 1-2. The scratches were then made perpendicularly, leaving 20 small squares on the coating surface. 3M invisible tape was then applied to the grid. The tape was then peeled back at a slightly faster and more steady speed. A magnifying glass was used to observe any coating shedding at the intersections of the grid. The scratch test results showed no shedding or peeling of the coating, demonstrating good adhesion.

[0101] Test Example 3

[0102] Coating wear resistance test

[0103] The TH-110 spectrophotometer from Zhejiang Caipu Technology Co., Ltd. was used. The coated substrate prepared in Example 1-2 was placed on the haze meter test port. The transmittance and haze values ​​were measured in the center area at four directions: 0°, 90°, 180°, and 270°. The arithmetic average was taken as the initial value (denoted as ), haze measurement after friction (denoted as ), the haze is calculated by ΔH=H1−H0 and is in the range of 0.34~0.40%. The national standard ΔH ≤ 0.8%, and the result is judged to be qualified.

[0104] The above are all preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. The preparation method of 1,1,3,3-tetrakis(mercaptomethylthio)propane is characterized in that: The following steps are involved: S1. Take 1,1,3,3-tetrachloropropane, tetrabutylammonium bromide and zinc acetate, add them to a mixed solvent, and stir and mix under nitrogen protection to obtain a mixed solution; S2. Add a mixture of sodium hydrosulfide, ethanol, and water dropwise to the mixed solution prepared in step S1, control the temperature to 20-45° C., stir and react for 90-120 min, continue nitrogen protection, and heat to 45-60° C., continue the reaction for 2-4 h to obtain a reaction solution; S3. Neutralize the reaction solution obtained in step S2 with dilute hydrochloric acid solution to a pH of 6-7, cool to room temperature, filter, dry, and elute the organic phase. Distill the filtrate under reduced pressure to recover the solvent to obtain 1,1,3,3-tetrakis(mercaptomethylthio)propane.

2. The method for preparing 1,1,3,3-tetrakis(mercaptomethylthio)propane according to claim 1, wherein The weight ratio of 1,1,3,3-tetrachloropropane, tetrabutylammonium bromide, zinc acetate, mixed solvent and sodium hydrosulfide in step S1 and step S2 is (2-3): (0.07-0.2): (0.15-0.3): (7-15): (2.5-4.5); In the mixed solution in step S2, the percentage of sodium hydrosulfide is 20-35%, the percentage of ethanol is 40-60%, and the percentage of water is 20-45%.

3. The method for preparing 1,1,3,3-tetrakis(mercaptomethylthio)propane according to claim 1, characterized in that The mixed solvent comprises: 20-40% water and 60-80% organic solvent; The organic solvent is at least one of methanol, ethanol, acetonitrile and acetone.

4. 1,1,3,3-tetrakis(mercaptomethylthio)propane prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The structural formula of the 1,1,3,3-tetrakis(mercaptomethylthio)propane is: (HSCH2S)2CH-CH2-CH(HSCH2S)2; The structural formula of the 1,1,3,3-tetrakis(mercaptomethylthio)propane is: 。 5. An optical coating material, characterized in that: The optical coating material comprises the following components in parts by weight: 20-45 parts of 1,1,3,3-tetrakis(mercaptomethylthio)propane prepared by the preparation method according to any one of claims 1 to 3; 25-50 parts of isocyanate; 5-15 parts of epoxy monomer.

6. The optical coating material according to claim 5, characterized in that: The isocyanate is at least one of toluene diisocyanate, triphenylmethane triisocyanate, cyclohexane diisocyanate, diphenylmethane diisocyanate, diphenyl ether diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, diethylene diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, m-xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dithiodipropyl diisocyanate, dihexyl thiodiisocyanate, diethyl diisocyanate, dithiodipropyl diisocyanate, lysine triisocyanate, trimethylhexamethylene diisocyanate, and o-tolidine diisocyanate.

7. The optical coating material according to claim 5, characterized in that: The epoxy monomer is at least one of bisphenol A epoxy monomer, 2,2'-dimercaptoethyl sulfide diglycidyl ether, 3,3'-dimercaptodiphenyl sulfone diglycidyl ether, 2,2'-dimercaptobisepoxypropane ethyl sulfide, bisphenol A episulfide monomer and bis((3,4-epoxycyclohexyl)methyl)adipate.

8. The optical coating material according to claim 5, characterized in that: The optical coating material further comprises 0.1-0.9 parts by weight of a wetting and dispersing agent; The wetting dispersant is at least one of BYK-163 and BYK-324 dispersants.

9. The optical coating material according to claim 5, characterized in that: The optical coating material further comprises 0.4-4 parts by weight of a diluent; The diluent is at least one of n-pentane, dichloromethane, methyl formate, benzyl acrylate, ethoxyphenol acrylate, diphenylmethanol acrylate, o-phenylphenoxyethyl acrylate, 1,6-hexanediol diacrylate, pentaerythritol triacrylate, and trimethylolpropane triacrylate.

10. The optical coating material according to claim 5, characterized in that: The optical coating material further comprises 0.02-0.35 parts by weight of an initiator; The initiator is any one of stannous octoate, dibutyltin dilaurate, dibutyltin dichloride, dibutyltin oxide and tetrabutylphosphine bromide.

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