Epithio compound, method for preparing same, and composition for preparing optical resin

Abstract

The invention provides an epithio compound, a preparation method thereof and a composition for preparing optical resin. The epithio compound is shown as a formula (I) or a formula (II), and n is 2-4. The optical resin prepared from the epithio compound provided by the invention has improved refractive index and mechanical strength, and also has thermal stability.

Description

Technical Field

[0001] The present application relates to the technical field of optical resins, and in particular to novel episulfide compounds, preparation methods thereof, and compositions for preparing optical resins. Background Art

[0002] High performance optical resins with episulfide compounds as monomers have excellent properties, such as high refractive index (v D ), high Abbe number (n D ) and low specific gravity, making it a growing topic of interest in the fields of optics, electronics, and high-end materials. This is due to the unique electronic structure of sulfur atoms, which can improve optical properties such as refractive index, particularly in the ultraviolet and visible light bands, while also reducing specific gravity. However, sulfur atoms can also negatively impact high-temperature stability and mechanical strength. Currently, episulfide compounds struggle to simultaneously improve the refractive index of these optical materials while also maintaining these other properties.

[0003] Therefore, it is necessary to provide an improved episulfide compound. Summary of the Invention

[0004] In view of this, the primary objective of this application is to provide an episulfide compound. Optical resins prepared using the episulfide compounds of the present invention exhibit enhanced refractive index and mechanical strength while also maintaining thermal stability. Further objectives of this application are to provide a method for preparing the episulfide compound, a composition for preparing the optical resin, and the optical resin.

[0005] In order to achieve the above objectives, this application provides the following technical solutions.

[0006] The first aspect of the present application provides an episulfide compound represented by formula (I) or formula (II),

[0007]

[0008] Here, n is 2 to 4.

[0009] According to one embodiment of the present application, in the formula (I), n is 2.

[0010] The present application also provides a method for preparing the episulfide compound represented by the above formula (I), comprising: reacting a compound represented by formula (III) with a compound represented by formula (IV) in the presence of a base, wherein the reaction temperature is 0°C to 15°C, and the reaction is carried out in a mixed solvent consisting of water and a polar organic solvent to obtain a compound represented by formula (V), wherein n is 2 to 4, and X is selected from Cl, Br or I; and

[0011]

[0012] The epoxy group of the compound represented by formula (V) is converted into an episulfide group to obtain an episulfide compound represented by formula (I).

[0013] According to one embodiment of the present application, the polar organic solvent is 1,4-dioxane, the volume ratio of water to 1,4-dioxane in the mixed solvent is (0.5-5):1, and the ratio of the compound represented by formula (III) to the mixed solvent is (0.005-2) g / mL.

[0014] The present application also provides a method for preparing the episulfide compound represented by the above formula (II), comprising: performing an oxidation reaction on the compound represented by formula (VI) to obtain a compound represented by formula (VII), wherein X is selected from Cl, Br or I, and the oxidant of the oxidation reaction is selected from at least one of 2,3-dichloro-5,6-dicyanobenzoquinone, dibromohydantoin, O2, H2O2, I2, Br2, and Cl2;

[0015]

[0016] reacting the compound represented by formula (VII) with a base to obtain the compound represented by formula (VIII); and

[0017]

[0018] The epoxy group of the compound represented by formula (VIII) is converted into an episulfide group to obtain an episulfide compound represented by formula (II).

[0019] According to one embodiment of the present application, the oxidant is 2,3-dichloro-5,6-dicyanobenzoquinone, and the temperature of the oxidation reaction is 0°C to 25°C.

[0020] The present application also provides a composition for preparing an optical resin, wherein the composition for optical materials comprises an episulfide compound and a curing agent, wherein the episulfide compound comprises at least one episulfide compound selected from claim 1 or 2, and the curing agent is a compound containing two or more reactive groups, wherein the reactive groups are selected from one or more of thiols, primary amines, secondary amines, alcohols, acid anhydrides, and isocyanates.

[0021] According to one embodiment of the present application, the composition further comprises one or more of a vinyl monomer, a polyepoxy compound and a polyisocyanate.

[0022] According to one embodiment of the present application, the mass content of the episulfide compound is 2% to 50% relative to the total weight of the composition.

[0023] According to one embodiment of the present application, the optical resin is obtained by polymerizing and curing the composition.

[0024] The episulfide compounds of the present application have an increased sulfur element mass content while having a lower molecular weight and a flexible molecular structure, which can improve the compatibility with other components for preparing optical resins, thereby making the optical resins prepared using the episulfide compounds of the present application have an increased refractive index and mechanical strength while taking into account thermal stability.

[0025] In addition to the technical problems solved by this application, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions described above, other technical problems that can be solved by this application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 These are the transmittance curves (a) and refractive index curves (b) of the optical resins P-ESR2 and P-ESR3 of Examples 1 and 2 of the present application and the optical resin P-ESR1 of Comparative Example 1.

[0028] Figure 2 These are the transmittance curves (a) and refractive index curves (b) of the optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application, and the optical resins PESR1 and PETR0 of Comparative Examples 1 and 2.

[0029] Figure 3 These are the XRD spectra of the optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application, and the optical resins PESR1 and PESR0 of Comparative Examples 1 and 2.

[0030] Figure 4 These are the TG and DTG curve spectra of the optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application, and the optical resins PESR1 and PETR0 of Comparative Examples 1 and 2.

[0031] Figure 5 These are differential scanning calorimetry curves of the optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application, and the optical resins PESR1 and PESR0 of Comparative Examples 1 and 2.

[0032] Figure 6 These are the force-displacement curves and stress-strain curves of the optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application, and the optical resins PESR1 and PETR0 of Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solution of this application in conjunction with specific embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. In the event of any conflict, the present specification shall take precedence.

[0035] It should be noted that, except in any operating examples, or in the place where there is otherwise indication, all numerals of the expression component amount, reaction conditions etc. used in the specification and claims should be interpreted as being modified by the term "about" in all cases. Unless otherwise indicated, the numerical parameters of setting forth in the following specification and the appended claims are approximate values, which can change according to the desired properties to be obtained by the application. Although the numerical range and parameters setting forth the application's wide range are approximate values, the numerical value of setting forth in the specific embodiment has been reported as accurately as possible. Each numerical parameter should at least be explained according to the number of reported significant figures and by applying common rounding techniques.

[0036] The various steps are divided only for clarity of description. During implementation, they can be combined into one step or some steps can be split and decomposed into multiple steps. As long as they include the same logical relationship, they are within the scope of protection of this patent.

[0037] As used herein, the term "sulfur content" of a compound refers to the mass percentage of the molecular weight of all sulfur atoms in the compound relative to the molecular weight of the compound.

[0038] Compared to conventional organosilicon optical resins, optical resins prepared using episulfide compounds exhibit improved optical properties such as refractive index, Abbe number, and transmittance, which are particularly important for optimizing the performance of optical components. However, the inventors have discovered that the molecular structure of currently common episulfide compounds is insufficiently compatible with other components used to prepare optical resins, hindering their preparation and negatively impacting mechanical strength, thermal stability, and other aspects.

[0039] Therefore, there remains a need to provide improved episulfide compounds.

[0040] Episulfide compounds

[0041] Based on this, the first aspect of the present application is to provide an episulfide compound represented by formula (I) or formula (II),

[0042]

[0043] wherein n is 2 to 4. The sulfur content of the above-mentioned cyclic sulfide compound is more than 58% by weight, and it does not contain aromatic structures, has greater flexibility, and has a lower molecular weight, which has improved compatibility and is conducive to forming a uniform and stable mixture with other components for preparing optical resins. The cross-linked network formed after the polymer can provide better tensile strength and flexibility, so that the optical resin prepared using the cyclic sulfide compound of the present application can greatly improve the refractive index and mechanical strength, while taking into account thermal stability. In particular, the sulfur content of the cyclic sulfide compound shown in formula (II) is as high as 70.1wt%, and it is a low-viscosity liquid at room temperature, which is convenient for processing by pouring, spraying, scraping, etc. without the need for high-temperature melting. It is energy-saving and has low equipment requirements. It can better penetrate into fiber fabrics or porous substrates, helping to form a dense and uniform composite material structure; it has stronger adjustable performance and can be used in combination with other functional monomers, cross-linking agents, and modifiers. The formulation is flexible and can be adjusted to different properties according to different needs, such as flexibility, hygroscopicity, optical properties, etc.

[0044] For example, the episulfide compound represented by formula (II) can be selected from the following structures:

[0045]

[0046] According to some embodiments, n in formula (I) is 2. This facilitates the formation of a three-dimensional network structure with a moderate crosslink density during the crosslinking reaction, effectively avoiding the brittleness and curing shrinkage common to highly crosslinked systems while achieving good mechanical properties. Furthermore, it combines reactivity with flexibility, providing excellent fatigue resistance and environmental stress cracking resistance while ensuring structural bonding strength. This has excellent system compatibility and application value in fields such as composite materials, elastic protective coatings, and high-performance sealing materials, and is considered an optimal balance of performance in episulfide resin structural design.

[0047] Preparation method

[0048] The present application also provides a method for preparing an episulfide compound represented by the above formula (I), comprising: reacting a compound represented by formula (III) with a compound represented by formula (IV) in the presence of a base, wherein the reaction temperature is 0°C to 15°C, and the reaction is carried out in a mixed solvent consisting of water and a polar organic solvent to obtain a compound represented by formula (V), wherein n is 2 to 4, and X is selected from Cl, Br or I; and

[0049]

[0050] The epoxy group of the compound represented by formula (V) is converted into an episulfide group to obtain an episulfide compound represented by formula (I). The above preparation method is simple, easy to operate, has readily available raw materials, mild reaction conditions and high yield.

[0051] According to some embodiments, the compound represented by formula (III) can be obtained by using the compound represented by formula (IX) as a starting material and converting the hydroxyl group (-OH) into a thiol group (-SH).

[0052] Where n is 2 to 4.

[0053] For example, the compound represented by formula (IX) can be reacted with acetic anhydride to convert the hydroxyl group therein into an acetate group; under the catalysis of boron trifluoride ether, it can be reacted with thioacetic acid to further convert the acetate group into thioacetate; and under the catalysis of hydrochloric acid, the thioacetate thiol.

[0054]

[0055] In the reaction of the compound represented by formula (III) with the compound represented by formula (IV) under the action of a base, the base can be, but is not limited to, an alkali metal hydroxide, a carbonate, a tertiary amine, pyridine, etc.; the polar organic solvent can be, but is not limited to, 1,4-dioxane, dimethyl sulfoxide, tetrahydrofuran, N,N-dimethylformamide (DMF), acetonitrile, diethyl ether, etc.

[0056] The temperature of the reaction of the compound represented by formula (III) and the compound represented by formula (IV) under the action of a base is 0°C to 15°C. Thus, it is beneficial to reduce side reactions, control the reaction rate to be stable, thereby improving the reaction yield, and avoiding excessive reaction time. Exemplarily, the temperature of the reaction can be 0°C, 1°C, 2°C, 4°C, 5°C, 6°C, 8°C, 10°C, 12°C, 14°C, 15°C or a value between the ranges consisting of any two values, but is not limited thereto. Preferably, the temperature of the reaction is 0°C to 5°C.

[0057] According to some embodiments, the polar organic solvent is 1,4-dioxane, and the volume ratio of water to 1,4-dioxane in the mixed solvent is (0.5-5):1, and the ratio of the compound represented by formula (III) to the mixed solvent is (0.005-2) g / mL. This is conducive to the direct precipitation of the compound represented by formula (IV) after the reaction, thereby further simplifying the operation. Preferably, the volume ratio of water to 1,4-dioxane in the mixed solvent is (0.5-2):1, and the ratio of the compound represented by formula (III) to the mixed solvent is (0.01-0.2) g / mL.

[0058] The present application does not particularly limit the reaction conditions for converting the epoxy group of the compound represented by formula (V) into an episulfide group. Those skilled in the art can select appropriate reaction conditions. For example, thiocyanate, thiophosphoryl compound, sulfur chloride, diphenylphosphine sulfide or thiourea can be used as a vulcanizing agent.

[0059] In some embodiments, in the reaction of converting the epoxy group of the compound represented by formula (V) into an episulfide group, the compound represented by formula (V) is mixed with thiourea at a molar ratio of 1:(2-4), preferably 1:(2-2.5), and the mixture is reacted at 10° C. to 15° C. This is more conducive to improving the selectivity and controllability of the reaction, avoiding the reduction in yield due to side reactions (such as excessive sulfurization and unnecessary cross-linking reactions), ensuring the thoroughness of the episulfide reaction, and improving the purity of the episulfide three-membered ring product.

[0060] The present application also provides a method for preparing an episulfide compound represented by the above formula (II), comprising: subjecting a compound represented by formula (VI) to an oxidation reaction to obtain a compound represented by formula (VII), wherein X is selected from Cl, Br or I, and the oxidant of the oxidation reaction is selected from at least one of 2,3-dichloro-5,6-dicyanobenzoquinone, dibromohydantoin, O2, H2O2, I2, Br2, and Cl2;

[0061]

[0062] reacting the compound represented by formula (VII) with a base to obtain the compound represented by formula (VIII); and

[0063]

[0064] The epoxy group of the compound represented by formula (VIII) is converted into an episulfide group to obtain the episulfide compound represented by formula (II). This method for oxidatively coupling dithiols to tetrasulfides is simple to operate, operates under mild reaction conditions (room temperature can be used, and the reaction can be completed in 2-5 hours), has high yields, generates no metal salt byproducts, is suitable for large-scale synthesis, and is environmentally friendly. Furthermore, the thiol-based raw materials involved in this scheme are inexpensive and readily available, making them well-suited for exploring structural diversity.

[0065] According to some embodiments, the compound of formula (VI) can be prepared using the compound of formula (IV) as a raw material. For example, epichlorohydrin is used as a raw material and reacted with thioacetic acid to obtain S-(3-chloro-2-hydroxypropyl)acetylthio; then reacted in a hydrochloric acid methanol solution to obtain 1-chloro-3-mercaptopropane-2-ol; then reacted with thioacetic acid and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) to obtain SS-(3-chloro-2-hydroxypropyl)ethane (dithioperoxyacid); then reacted in a hydrochloric acid methanol solution to obtain 1-chloro-3-dithiopropane-2-ol, which is one of the compounds of formula (VI). The compound of formula (VI) is prone to deprotonation reaction. Preferably, it is immediately subjected to an oxidation reaction after preparation to obtain the compound of formula (VII).

[0066]

[0067] According to some embodiments, the oxidant is 2,3-dichloro-5,6-dicyanobenzoquinone, and the temperature of the oxidation reaction is 0°C to 25°C. For example, the temperature of the oxidation reaction can be 0°C, 2°C, 5°C, 7°C, 10°C, 12°C, 15°C, 17°C, 20°C, 22°C, 25°C, or a value between the ranges consisting of any two values, but is not limited thereto. Preferably, the temperature of the reaction is 0°C to 15°C. As a result, it is more conducive to controlling the reaction smoothly, reducing energy consumption while avoiding violent reactions, reducing safety hazards, and facilitating industrial production. It also improves the selectivity of the reaction, thereby increasing the yield of the compound represented by formula (VII).

[0068] The compound represented by formula (VII) reacts under the action of a base to obtain a compound represented by formula (VIII). This application does not particularly limit the reaction, and those skilled in the art can select appropriate reaction conditions. For example, a 40% by weight aqueous solution of NaOH is added dropwise to a solution of the compound represented by formula (VII) in toluene and methanol at 0°C to 25°C, and the reaction is carried out for 3 hours.

[0069] Regarding converting the epoxy group of the compound represented by formula (VIII) into an episulfide group to obtain the episulfide compound represented by formula (II), the present application does not particularly limit the reaction, and those skilled in the art can select appropriate reaction conditions, for example, thiocyanate, thiophosphoryl compound, sulfur chloride, diphenylphosphine sulfide or thiourea can be used as a vulcanizing agent.

[0070] Composition for preparing optical resin

[0071] This application also provides a composition for preparing an optical material, comprising an episulfide compound and a curing agent. The episulfide compound includes at least one episulfide compound according to any embodiment of the first aspect of this application. The curing agent is a compound containing two or more reactive groups, wherein the reactive groups are selected from one or more of thiols, primary amines, secondary amines, alcohols, anhydrides, and isocyanates. Thus, this composition has at least the same advantages as the episulfide compounds of this application.

[0072] According to some embodiments, the composition further comprises one or more of a vinyl monomer, a polyepoxy compound and a polyisocyanate. Exemplarily, the vinyl monomer may be one or more of trimethylolpropane triacrylate (TMPTA), ethylene, propylene, hydroxyethyl methacrylate, methyl acrylate, ethylene glycol diacrylate, divinylbenzene, but is not limited thereto. Exemplarily, the polyepoxy compound may be one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, 1,4-butanediol diglycidyl ether, epoxy novolac resin, epoxy acrylate, but is not limited thereto. Exemplarily, the polyisocyanate may be one or more of 4,4-dicyclohexylmethane diisocyanate, norbornane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, methylenebiscyclohexyl diisocyanate, hydrogenated xylene dimethylene diisocyanate, but is not limited thereto. This helps reduce costs, and while maintaining the optical properties of the optical material without a significant decrease, reduces shrinkage and prevents cracking; improves the fluidity of the processing process and enhances the efficiency of demolding after curing.

[0073] According to some embodiments, the mass content of the episulfide compound is 2% to 50% relative to the total weight of the composition. This facilitates flexible regulation of the mechanical properties, chemical resistance, optical properties, curing behavior, and process parameters of the composition according to actual performance requirements, thereby meeting the customized requirements of different application scenarios.

[0074] According to some embodiments, an optical resin is obtained by polymerizing and curing the composition for preparing an optical material according to any of the above embodiments. For example, the composition for preparing an optical resin, comprising an episulfide compound, a dithiol, TMPTA, and benzophenone, is injected into a mold and cured by heat curing and UV irradiation to obtain the optical resin.

[0075] Example

[0076] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0077] Example 1

[0078] Preparation of 2,5-bis(cyclothioethyl-2-methylthio)-1,4-dithiane (ESR2)

[0079]

[0080] Step A: 2,5-Diacetyl-1,4-dithiane (1)

[0081] To a 250 mL two-necked flask, dry pyridine (110 mL) and 2,5-dihydroxy-1,4-disulfane (52.00 g, 342.00 mmol) were added dropwise in an ice-water bath under nitrogen. After stirring for 1 hour, a white solid began to precipitate. After 3 hours of reaction, the mixture was poured into water. The precipitate was filtered, dried, and recrystallized from methanol to obtain 49.50 g (209.75 mmol, 61.33% yield) of 2,5-diacetyl-1,4-dithiane as white crystals.

[0082] 1 H NMR (400MHz, CD3Cl) δ5.83 (dt, J = 3.2, 1.4 Hz, 2H), 3.69 (dd, J = 14.5, 1.7 Hz, 2H), 2.81 (dd, J = 14.2, 4.7 Hz, 2H), 2.19 (s, 6H).

[0083] Step B: S,S'-(1,4-dithiane-2,5-diyl)diethylthiocarboxylate (2)

[0084] To a 250 mL two-necked flask were added ultra-dry dichloromethane (50 mL), 2,5-diacetyl-1,4-dithiane (8.32 g, 35.20 mmol), and thioacetic acid (6.43 g, 84.5 mmol). Boron trifluoride etherate (0.19 mL, 3.67 mol / L) was added dropwise at 0°C under a nitrogen atmosphere. The reaction mixture was stirred at 0°C for 2 h and at room temperature for 5 h before being quenched with 20 wt% K2CO3. The organic layer was washed with water, dried over anhydrous magnesium sulfate, filtered, and then concentrated. The crude product was recrystallized from methanol to obtain 6.29 g (23.47 mmol, 66.68% yield) of S,S'-(1,4-dithiane-2,5-diyl)diethylthiocarboxylate as white crystals.

[0085] 1 H NMR (400MHz, CD3Cl) δ4.96-4.81(m,2H),3.67(dd,J=14.2,1.9Hz,1H),3.37(d,J=14.0Hz ,1H),3.15(dd,J=14.0,7.7Hz,1H),2.95(dd,J=14.3,5.4Hz,1H),2.40(d,J=2.7Hz,6H).

[0086] Step C: 1,4-Dithiane-2,5-dithiol (3)

[0087] A 50 mL flask was charged with S,S'-(1,4-dithiane-2,5-diyl)diethylthiocarboxylate (2.14 g, 7.98 mmol), 12 mL of a 2 wt% methanolic hydrochloric acid solution, and 20 mL of chloroform. The mixture was refluxed at 60°C for 15 h. The solution was then cooled to room temperature, rotary evaporated, and the residue washed with methanol, filtered, and then washed with water. The residue was then dried to obtain 0.86 g (4.67 mmol, 58.57% yield) of 1,4-dithiane-2,5-dithiol as an off-white solid.

[0088] 1 H NMR (400MHz, CD3Cl) δ4.22 (t, J = 8.3 Hz, 2H), 3.44 (d, J = 13.9 Hz, 2H), 3.15 (d, J = 8.9 Hz, 2H), 2.74 (d, J = 9.2 Hz, 2H).

[0089] Step D: 2,5-bis(oxiranyl-2-methylthio)-1,4-dithiane (4)

[0090] Under ice bath conditions, epichlorohydrin (18.00 g, 0.198 mmol), potassium hydroxide (10.98 g, 0.198 mmol), ionized water (150 mL) and 1,4-dioxane (150 mL) were added in sequence to a 500 mL flask. After stirring for 30 min, 1,4-dithiane-2,5-dithiol (6.00 g, 0.033 mmol) was slowly added to the flask. After stirring for 30 min, a large amount of ice water was added, and the precipitate was filtered and dried to obtain 7.06 g (0.024 mmol, yield 73.15%) of 2,5-bis(oxiran-2-methylthio)-1,4-dithiane as a white solid.

[0091] 1 H NMR (400MHz, CD3Cl) δ4.27 (ddd, J=36.4, 7.4, 2.5Hz, 2H), 3.64 (t, J=15.8Hz, 2H), 3.26-3.18 (m, 2H), 2.97 (ddt, J=24.0, 11.0, 5.1Hz, 4H), 2.89-2.83 (m, 4H), 2.68 (ddd, J=40.2, 4.9, 2.6Hz, 2H).

[0092] Step E: 2,5-Bis(cyclothioethyl-2-methylthio)-1,4-dithiane (ESR2)

[0093] 2,5-Bis(oxiranyl-2-methylthio)-1,4-dithiane (11.12 g, 0.038 mmol), thiourea (9.50 g, 0.125 mmol), 20 mL of ethanol, and 40 mL of toluene were mixed and stirred at 10°C to 15°C for 15 hours. After completion of the reaction, the mixture was washed with a 4 wt% NaCl solution, a 1 wt% sulfuric acid solution, and a 4 wt% NaCl solution, respectively. The organic phase was separated by stratification and dehydrated with 5% magnesium sulfate (the weight of the organic phase). The organic phase was filtered, the solvent was evaporated, and the product was purified by silica gel column chromatography (PE:EA = 5:1) to obtain 6.87 g (0.021 mmol, 55.12% yield) of 2,5-bis(oxiranyl-2-methylthio)-1,4-dithiane as a white solid.

[0094] 1 H NMR (400MHz, CD3Cl) δ4.24 (dd, J=11.2, 9.0Hz, 2H), 3.56 (d, J=13.7Hz, 2H), 3.24-3.12 (m, 4H), 3.0 3(dd,J=13.4,7.9Hz,2H),2.90-2.75(m,2H),2.61(d,J=6.0Hz,2H),2.32(dd,J=15.2,4.8Hz,2H).

[0095] The above-described process for preparing compound ESR2 utilizes mild reaction conditions, does not require harsh conditions such as high temperature and pressure, is easy to operate, highly safe, and produces high yields. The purification steps primarily consist of simple evaporation, precipitation, and recrystallization. Compound ESR2 has a sulfur content of 58.5 wt%.

[0096] Preparation of optical resin P-ESR2

[0097] 0.1 g of the episulfide compound ESR2 and 5 mg of 1,4-dithiane-2,5-dithiol were dissolved in 2 mL of chloroform. After ultrasonic dissolution, the solution was filtered through a PTFE filter to remove insoluble impurities, yielding a transparent solution. This solution was then spin-coated onto a silicon wafer and allowed to stand at room temperature to evaporate the chloroform. The solution was then heat-cured in a vacuum oven at 120°C for 2 hours. After cooling to room temperature, uniform, transparent, round optical resin P-ESR2 was obtained.

[0098] Preparation of optical resin PETR2

[0099] By mass, 5 parts of the episulfide compound ESR2, 0.01 parts of 1,4-dithiane-2,5-dithiol, 95 parts of TMPTA, and 0.19 parts of benzophenone were mixed evenly to obtain a composition for preparing an optical resin, which was injected into a mold. The curing process was divided into two steps: first, thermal curing at 120°C for 12 hours, and then irradiation with an ultraviolet lamp for 24 hours. After demolding, a disc-shaped optical resin PETR2 with a thickness of 0.5 mm and a diameter of 35 mm was obtained.

[0100] Example 2

[0101] Preparation of 1,4-bis(epoxyethane-2-ylmethyl)tetrasulfide (ESR3)

[0102]

[0103] Step A: S-(3-chloro-2-hydroxypropyl)thioacetate (1)

[0104] At room temperature, epichlorohydrin (50.00 g, 541 mmol), thioacetic acid (49.00 g, 76,645 mmol) and deionized water (100 mL) were added sequentially to a 500 mL flask, and the reaction was stirred under a nitrogen atmosphere for 2 days. After completion of the reaction, the mixture was extracted three times with ethyl acetate, washed with saturated sodium bicarbonate and deionized water, and the organic layer was dried over anhydrous sodium sulfate. Rotary evaporation was used to remove the solvent to give 73.00 g (435 mmol, 80.41% yield) of light yellow liquid S-(3-chloro-2-hydroxypropyl)thioacetate.

[0105] 1H NMR (400MHz, CD3Cl) δ3.90-3.83(m,1H),3.57-3.44(m,2H),3.40(s,1H),3.09-2.93(m,2H),2.27(s,3H).

[0106] Step B: 1-Chloro-3-mercaptopropane-2-ol (2)

[0107] S-(3-chloro-2-hydroxypropyl)thioacetate (60.00 g, 356 mmol) was added to a 2% methanolic HCl solution (400 mL) and stirred at room temperature for 24 hours. After the reaction, the remaining HCl was removed with nitrogen, and the solvent was removed by rotary evaporation. Reducing pressure (75°C, 1800 Pa) resulted in 35.00 g (278 mmol, 78.09% yield) of 1-chloro-3-mercaptopropane-2-ol as a light yellow liquid.

[0108] 1-Chloro-3-mercaptopropane-2-ol: 1 H NMR (400MHz, CD3Cl) δ3.84 (dq, J=6.3, 5.2Hz, 1H), 3.60 (d, J=5.3Hz, 2H), 3.19 (s, 1H), 2.77-2.59 (m, 2H), 1.51 (t, J=8.8Hz, 1H).

[0109] Step C: SS-(3-chloro-2-hydroxypropyl)ethane (dithioperoxyacid) (3)

[0110] To a 250 mL two-necked flask, 1-chloro-3-mercaptopropane-2-ol (10.00 g, 79.37 mmol) and thioacetic acid (6.03 g, 79.37 mmol) were added sequentially, followed by the slow addition of 2,3-dichloro-5,6-dicyanobenzoquinone (18.02 g, 79.37 mmol) at 0°C. A sampling plate was used for tracking, and the reaction time was 24 h. After completion of the reaction, the product was filtered, extracted, concentrated, and purified by column chromatography (PE:EA = 10:1) to obtain 8.00 g (40.00 mmol, 50.40% yield) of SS-(3-chloro-2-hydroxypropyl)ethane (dithioperoxyacid) as a light yellow liquid.

[0111] 1 H NMR(401MHz,CD3Cl)δ3.88(d,J=4.8Hz,1H),3.75(dq,J=8.7,4.5,4.1Hz,1H), 3.62-3.57(m,2H),2.89(dd,J=14.1,4.0Hz,1H),2.75(dd,J=14.1,8.4Hz,1H).

[0112] Step D: 1-Chloro-3-dithiopropane-2-ol (4)

[0113] SS-(3-chloro-2-hydroxypropyl)ethane (dithioperoxyacid) (30.00 g, 150.00 mmol) was added to a 2% methanolic HCl solution (250 mL) and stirred at room temperature for 24 hours. After the reaction, the remaining HCl was removed with nitrogen, and the mixture was extracted three times with ethyl acetate. The solvent was then removed by rotary evaporation to obtain 15.21 g (96.27 mmol, 64.18% yield) of 1-chloro-3-dithiopropane-2-ol as a yellow liquid.

[0114] Step E: 3,3'-Tetrasulfoxide bis(1-chloropropanol) (5)

[0115] To a 250 mL two-necked flask, 1-chloro-3-dithiopropane-2-ol (20.00 g, 126.58 mmol) and 100 mL of chloroform were added sequentially. 2,3-Dichloro-5,6-dicyanobenzoquinone (28.74 g, 126.58 mmol) was then slowly added at 0°C. Sample tracking was performed using a plate. The reaction was allowed to proceed for 24 hours. After completion of the reaction, the mixture was filtered, extracted, concentrated, and purified by silica gel column chromatography (PE:EA = 2:1) to obtain 15.3 g (48.73 mmol, 77.00% yield) of 3,3'-tetrasulfoxidebis(1-chloropropanol) as a light yellow liquid.

[0116] 1 H NMR (400MHz, CD3Cl) δ4.28 (s, 2H), 3.81-3.65 (m, 4H), 3.36-3.03 (m, 6H).

[0117] Step F: 1,4-bis(oxiran-2-ylmethyl)tetrasulfide (6)

[0118] 3,3'-Tetrasulfoxide bis(1-chloropropanol) (5.10 g, 16.24 mmol) was added to a mixture of 50 mL of toluene and 100 mL of methanol. Under nitrogen, a 40 wt% aqueous NaOH solution was slowly added dropwise in an ice-water bath. The reaction temperature was maintained below 10°C throughout the entire process. After the addition, the mixture was stirred at low temperature for 3 hours. After the reaction, an appropriate amount of toluene was added, and the mixture was separated by stirring. The reaction solution was extracted with ethyl acetate, and the organic phases were combined and washed twice with water. Anhydrous sodium sulfate was added to the organic phase to remove water. The organic phase was purified by silica gel column chromatography (PE:EA = 3:1) to obtain 2.67 g (11.00 mmol, 67.92% yield) of 1,4-bis(oxiran-2-ylmethyl)tetrasulfide as a yellow liquid.

[0119] 1H NMR (400MHz, CD3Cl) δ3.34 (dq, J=6.0, 3.6, 3.0Hz, 2H), 3.24-3.03 (m, 4H), 2.95 (t, J=4.3Hz, 2H), 2.76-2.71 (m, 2H).

[0120] Step G: 1,4-bis(epithioethane-2-ylmethyl)tetrasulfide (ESR3)

[0121] 1,4-bis(oxiran-2-ylmethyl)tetrasulfide (9.09 g, 37.56 mmol), thiourea (9.50 g, 124.84 mmol), 20 mL of ethanol, and 40 mL of toluene were stirred and reacted at 10-15°C for 15 hours. After completion of the reaction, the mixture was washed with a 4 wt% NaCl solution, a 1 wt% sulfuric acid solution, and a 4 wt% NaCl solution, respectively. The organic phase was allowed to stand for stratification, and the organic phase was dehydrated with 5 wt% magnesium sulfate (the weight of the organic phase). The organic phase was filtered, the solvent was evaporated, and the product was purified by silica gel column chromatography (PE:EA = 5:1) to obtain 4.14 g (15.10 mmol, 40.21% yield) of 1,4-bis(oxiran-2-ylmethyl)tetrasulfide as a yellow liquid.

[0122] 1 H NMR (400MHz, CD3Cl) δ3.27-3.15 (m, 4H), 2.81-2.71 (m, 2H), 2.65 (dq, J = 4.3, 1.2Hz, 2H), 2.40 (ddt, J = 7.3, 3.7, 1.9Hz, 2H).

[0123] The above process for preparing compound ESR3 has mild reaction conditions, is easy to operate, has low raw material costs, allows for diverse selection of oxidants, and has a high overall yield.

[0124] Preparation of optical resin P-ESR3

[0125] An optical resin was prepared in the same manner as the optical resin P-ESR2 in Example 1, except that ESR2 was replaced by ESR3.

[0126] Preparation of optical resin PETR3

[0127] An optical resin was prepared in the same manner as the optical resin PETR2 in Example 1, except that ESR2 was replaced by ESR3.

[0128] Comparative Example 1

[0129] Preparation of bis(2-((cyclothioethyl-2-methyl))thio)ethyl)sulfane (ESR1)

[0130]

[0131] Step A: Bis(2-((oxiran-2-methyl))thio)ethyl)sulfane (1)

[0132] A 150 mL four-necked flask was equipped with a stirrer, dropping funnel, thermometer, and N2 protection (reaction in an ice-water bath). First, 10 mL of bis-mercaptoethyl sulfide (1.183 g / mL, 76.6 mmol), 0.03 g of NaOH (0.75 mmol) dissolved in 0.3 mL of water, and 7.7 mL of methanol were added. 12 mL of epichlorohydrin (1.18 g / mL, 153 mmol) was slowly added dropwise at 5°C-10°C, over approximately 30 minutes. The reaction was then continued at this temperature for 1 hour. Then, 18.5 g of NaOH (462.5 mmol) dissolved in 27.7 g of water was added dropwise over 1 hour, maintaining the temperature between 5°C and 10°C. After the addition was complete, the reaction was continued for an additional 3 hours to terminate the reaction. 30 mL of toluene and a suitable amount of water were added to completely dissolve the white solid. The organic phase was separated and repeatedly washed with distilled water until neutral, then dried over anhydrous sodium sulfate. The solvent and small molecules were removed by distillation under reduced pressure to obtain 15.00 g (56.39 mmol, 73.62% yield) of bis(2-((oxiran-2-methyl))thio)ethyl)sulfane as a white solid.

[0133] 1 H NMR (400MHz, CD3Cl) δ3.15(dtt,J=4.7,4.0,2.6Hz,2H),2.93-2.86(m,2H),2.86-2.78(m,9H),2.71(dd,J=10.7,5.4Hz,3H),2.60(dd,J=4.9,2.6Hz,2H).

[0134] Step B: Bis(2-((2-((2-thioethyl-2-methyl))thio)ethyl)sulfane (ESR1)

[0135] Bis(2-((oxiran-2-methyl)thio)ethyl)sulfane (10.00 g, 41.9 mmol), thiourea (9.50 g, 125 mmol), 20 mL of ethanol, and 40 mL of toluene were stirred and reacted at 10°C to 15°C for 15 hours. After completion of the reaction, the mixture was washed with a 4 wt% NaCl solution, a 1 wt% sulfuric acid solution, and a 4 wt% NaCl solution, respectively. The organic phase was separated by filtration and the solvent was evaporated after dehydration with 5% by weight of the organic phase. The mixture was then purified by silica gel column chromatography (PE:EA = 10:1) to obtain 8.00 g (26.85 mmol, 64.07% yield) of bis(2-((oxiran-2-methyl)thio)ethyl)sulfane as a white solid.

[0136] 1H NMR(400MHz,CD3Cl)δ3.09(dq,J=7.6,5.4Hz,2H),3.03-2.96(m,2H),2.93-2.74(m,8 H), 2.65 (dd, J = 13.7, 7.7 Hz, 2H), 2.59 ( d, J = 6.1 Hz, 2H), 2.25 ( dd, J = 5.4, 1.4 Hz, 2H).

[0137] The sulfur content of compound ESR1 is 53.7 wt%.

[0138] Preparation of optical resin P-ESR1

[0139] An optical resin was prepared in the same manner as the optical resin P-ESR2 of Example 1, except that ESR2 was replaced by ESR1.

[0140] Preparation of optical resin PETR1

[0141] An optical resin was prepared in the same manner as the optical resin PETR2 of Example 1, except that ESR2 was replaced by ESR1.

[0142] Comparative Example 2:

[0143] Preparation of optical resin PETR0

[0144] The optical resin PETR0 was prepared in the same manner as the optical resin PETR2 of Example 1, except that the episulfide compound and the polythiol were not used.

[0145] Performance Testing

[0146] Test Example 1: Compatibility of episulfide compounds ESR1, ESR2, and ESR3

[0147] 10 mg of each of the episulfide compounds ESR2 and ESR3 from Examples 1 and 2 of the present application, and the episulfide compound ESR1 from Comparative Example 1, were added to 1 mL of the organic solvents listed in Table 1 and dissolved using ultrasound. This process was repeated with the addition of 10 mg of monomer and further dissolution until the solution became turbid or phase separation occurred after standing. The solubility was then measured. Solubility was used as a measure of the compatibility of the compound with the solvent. The test results are summarized in Table 1 below.

[0148] Table 1: Compatibility test results of episulfide compounds ESR1, ESR2, and ESR3.

[0149]

[0150] As can be seen from the above data, compared with ESR1 in Comparative Example 1, the solubility of ESR2 and ESR3 in polar organic solvents of the examples of the present application is increased. The cyclic spatial structure of ESR2 is relatively rigid, and the electron cloud density is concentrated, which makes it difficult to neutralize the generated dipole moment, resulting in an overall polarity greater than that of the flexible sulfur-containing fatty straight chain structure ESR1. ESR3 has more sulfur atoms and an enhanced dipole moment, thereby increasing its solubility in polar solvents. The vinyl monomer, polyepoxy compound and polyisocyanate in the composition for preparing the optical resin are all polar. The episulfide compound of the present application has good compatibility with these polar components, which helps to form a uniform, stable and functionally synergistic system, resulting in better film quality, processing performance, curing performance and material reliability.

[0151] Test Example 2: Optical Properties of Optical Resins P-ESR1, P-ESR2, and P-ESR3

[0152] The thickness of the optical resins P-ESR1, P-ESR2, and P-ESR3 on the silicon wafer substrate was measured, and the refractive index curves of the optical resins P-ESR1, P-ESR2, and P-ESR3 were measured using an ellipsometer (HORIBA France SAS, China) in the range of 300 nm to 900 nm. Figure 1 (b) Read the refractive index n of each resin at 589nm D , refractive index n at 486nm F , refractive index n at 656nm C and calculate the Abbe number formula v D =(n D -1) / (n F -n C ), and obtain the Abbe number v D .

[0153] The optical resins P-ESR1, P-ESR2, and P-ESR3 of the examples and comparative examples of the present application were dissolved in chloroform and evenly coated on a clean glass sheet. The samples were kept in a vacuum oven at 80°C for 10 hours to remove the solvent to obtain the desired test samples. The absorbance of the optical resins at wavelengths of 300nm to 800nm ​​was measured using a UV-visible spectrophotometer (Beijing Puxi Company, TU-1900) and the Lambert-Beer law was used to determine the absorbance of the optical resins. (where A is absorbance and T is transmittance) the transmittance curve is calculated, such as Figure 1 (a) is shown. By calculating the intersection of the tangent line of the absorption curve and the initial horizontal line, the absorption edge λ of the film is obtained. E , reflecting that the film has basically no absorption in the entire visible light region, showing high optical transparency, which is conducive to the application of monomers in optical materials with high optical transmittance in the visible light region. The transmittance T at 400nm was obtained through testing. 400.

[0154] The above test results are summarized in Table 2 below.

[0155] Table 2: Optical performance test results of optical resins P-ESR1, P-ESR2, and P-ESR3.

[0156] serial number Sulfur content (wt%) Thickness (nm) <![CDATA[λ E (nm)]]> <![CDATA[T 400 (%)]]> <![CDATA[n D ]]> <![CDATA[v D ]]> P-ESR1 (Comparative Example 1) 53.69 314 345 93.64 1.68 36.0 P-ESR2 (Example 1) 58.54 505 345 93.84 1.74 34.6 P-ESR3 (Example 2) 70.07 523 414 81.17 1.77 27.0

[0157] From the above data, it can be seen that with the increase of monomeric sulfur, the refractive index of the two optical resins P-ESR2 and P-ESR3 prepared using the episulfide compound of the present application is as high as 1.74 or above, compared with P-ESR1 of Comparative Example 1. In addition, the transmittance of P-ESR2 and P-ESR3 at 400nm is lower than that of P-ESR1 of Comparative Example 1, but T 400 The transmittances of P-ESR2 and P-ESR3 are still above 80%, maintaining high transmittance in the visible light region. In addition, the Abbe numbers of P-ESR2 and P-ESR3 are lower than those of P-ESR1 in Comparative Example 1, but are still above 27.0.

[0158] Test Example 3: Optical properties of optical resins PETR0, PETR1, PETR2, and PETR3

[0159] The optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application and the optical resins PESR1 and PESR0 of Comparative Examples 1 and 2 were tested for transmittance curves at wavelengths of 300 nm to 800 nm using a UV-visible spectrophotometer (Beijing Puxi Company, TU-1900) according to the above method. Figure 2 (a) and the absorption margin λ is obtained E , transmittance T at 400nm 400 , transmittance T at 500nm 500 .

[0160] The refractive index curves of the optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application and the optical resins PESR1 and PESR0 of Comparative Examples 1 and 2 were measured in the range of 300 nm to 900 nm using an ellipsometer (HORIBA France SAS). Figure 2 (b) Read the refractive index n of each resin at 589nm D , refractive index n at 486nm F , refractive index n at 656nm C and calculate the Abbe number formula v D =(n D -1) / (n F -n C ), and obtain the Abbe number v D .

[0161] The above test results are summarized in Table 3 below.

[0162] Table 3: Optical performance test results of optical resins PETR0, PETR1, PETR2, and PETR3.

[0163] serial number <![CDATA[λ E (nm)]]> <![CDATA[T 400 (%)]]> <![CDATA[T 500 (%)]]> <![CDATA[n D ]]> <![CDATA[v D ]]> PETR0 (Comparative Example 2) 335 85.86 89.48 1.477 47.36 PETR1 (Comparative Example 1) 358 82.06 89.47 1.481 42.08 PETR2 (Example 1) 385 72.47 87.00 1.495 43.25 PETR3 (Example 2) 384 35.04 80.87 1.511 41.30

[0164] As can be seen from the above data, with the increase in elemental sulfur, the two optical resins PETR2 and PETR3 prepared by incorporating the episulfide compound of the present application have higher refractive indices than the optical resin PETR1 containing the episulfide compound of Comparative Example 1 and the optical resin PETR0 containing pure TMPTA without doping. Furthermore, the transmittance of PETR3 of Example 2 at 400 nm is significantly lower than that of PETR1 of Comparative Example 1 and PETR0 of Comparative Example 2, primarily due to oxidative yellowing during the curing process of ESR3. However, at wavelengths exceeding 500 nm, the transmittance of PETR3 is still above 80%. Furthermore, this oxidative yellowing can be improved by adjusting the curing method and adjusting the color, thereby optimizing the transmittance.

[0165] Test Example 4: X-ray Diffraction (XRD) Study of Optical Resins PETR0, PETR1, PETR2, and PETR3

[0166] An X-ray diffractometer (Rigaku Corporation, Japan, MiniFlex600 X-ray diffractometer) was used to study the structures of the optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application, as well as the optical resins PESR1 and PESR0 of Comparative Examples 1 and 2. The specific experimental steps were as follows: Optical resin samples with a length and width exceeding 5 mm were cut and placed in the grooves of a test vessel. The X-ray diffraction system was operated at a current of 15 mA and a voltage of 40 kV. The diffraction spectrum was automatically saved at a slow scan speed of 0.02θ° from 5° to 90° using the software provided with the diffractometer. Figure 3 shown.

[0167] With the increase of sulfur content in PETR0, PETR1, PETR2 and PETR3, the diffraction peak of the optical resin decreases significantly, which indicates that the introduction of large sulfur atoms disrupts the regularity of the polymer chain, reduces the fluidity and directional arrangement of the molecular chain, and reduces the crystallinity, which makes the optical resin have better flexibility and processability.

[0168] Test Example 5: Atomic Force Microscopy (AFM) Study of Optical Resins PETR1, PETR2, and PETR3

[0169] The surface profile and roughness of the optical resins PETR1, PETR2, and PETR3 of the present embodiment and the comparative example were studied by atomic force microscopy (manufacturer: Bruker Instruments, Germany, model: Dimension Icon Atomic Force Microscope). The specific test steps are as follows: an area with a length and width of 3 μm on the surface of each resin was scanned using an atomic force microscope, and the obtained data was processed by Nanoscope analysis software to calculate the average roughness S a , root mean square roughness S q , Micro roughness ten-point height S z , maximum roughness depth S max , surface inclination S sk , surface kurtosis S ku , the data are shown in Table 4.

[0170] Table 4 Surface profile data obtained by analyzing AFM spectra using Nanoscope analysis software.

[0171]

[0172] The above data show that the surface roughness of the optical resins PETR1, PETR2, and PETR3 is very low. The addition of the high-sulfur episulfide compound does not affect the flatness and smoothness of the surface profiles of PETR2 and PETR3.

[0173] Test Example 6: Thermal performance test of optical resins PETR0, PETR1, PETR2, and PETR3

[0174] The optical resins PETR0, PETR1, PETR2, and PETR3 of the examples and comparative examples of the present application were subjected to thermogravimetric tests using a STA2500 synchronous thermal analyzer (Netzsch Instrument Manufacturing Co., Ltd., Germany): approximately 20 mg of PETR0, PETR1, PETR2, and PETR3 were taken, and a heating curve mode was used under a nitrogen atmosphere with a heating rate of 10°C / min and a test temperature range of 30°C to 800°C. The thermogravimetric (TG) and differential thermogravimetric (DTG) curves were as follows: Figure 4 As shown, read the temperature T at which weight loss reaches 5% d .

[0175] Differential scanning calorimetry (DSC) tests were performed on PETR0, PETR1, PETR2, and PETR3 using a STA2500 synchronous thermal analyzer (Netzsch Instrument Manufacturing Co., Ltd., Germany): approximately 20 mg of PETR0, PETR1, PETR2, and PETR3 were taken, and the glass transition temperatures of the four optical resins were tested using a differential scanning calorimeter under a nitrogen atmosphere using a heating curve mode at a heating rate of 10°C / min and a test temperature range of 30°C to 300°C. Figure 5 As shown, read the glass transition temperature T g , the results are summarized in Table 5 below.

[0176] Table 5: Thermal performance test results of optical resins PETR0, PETR1, PETR2, and PETR3.

[0177] serial number <![CDATA[T d (℃)]]> <![CDATA[T g (℃)]]> PETR0 (Comparative Example 2) 361.87 226.26 PETR1 (Comparative Example 1) 351.63 213.41 PETR2 (Example 1) 261.35 202.56 PETR3 (Example 2) 187.23 158.16

[0178] The above data demonstrates that the introduction of high-sulfur episulfide compounds lowers the thermal decomposition temperature of optical resins, reducing their thermal stability. However, even for PETR3, which has the highest sulfur content, the 5% weight loss temperature remains as high as 187.23°C, demonstrating high thermal stability. Furthermore, while the introduction of high-sulfur episulfide compounds lowers the glass transition temperature, PETR3's glass transition temperature remains high at 158.16°C, maintaining a relatively high level.

[0179] Test Example 7: Mechanical Properties Test of Optical Resins PETR0, PETR1, PETR2, and PETR3

[0180] The mechanical properties of the optical resins PESR2 and PESR3 of Examples 1 and 2 of the present application and the optical resins PESR1 and PESR0 of Comparative Examples 1 and 2 were studied using a universal testing machine (manufacturer: Jinan Hengsi Shengda Instrument Co., Ltd., model: China-UTM-5105 Universal Testing Machine). The specific testing steps are as follows: According to the national standard GB / T 1040.2-2006, the samples were cut into dumbbell-shaped strips of 2 mm wide and 10 mm long using a blade, and then tested using a universal testing machine. A mechanical extensometer was used during the test, and the loading rate was 1 mm / min. The experimental data were then plotted using Origin software to obtain a force-displacement curve (e.g., Figure 6 (a)) and stress-strain curves (as shown in Figure 6 The test results are summarized in Table 6, where the tensile modulus (E) is the ratio of stress to strain.

[0181] Table 6: Mechanical properties test results of optical resins PETR0, PETR1, PETR2, and PETR3.

[0182]

[0183]

[0184] As can be seen from the above data, as the sulfur content in the episulfide compound increases, the tensile strength of the two optical resins PETR2 and PETR3 prepared by incorporating the episulfide compound of the present application increases to over 6 MPa, and the elongation at break also increases to over 8%, compared to the optical resin PETR1 containing the episulfide compound of Comparative Example 1 and the optical resin PETR0 containing pure TMPTA. The optical resins of the present application exhibit enhanced tensile properties. Furthermore, the tensile modulus E of the two optical resins PETR2 and PETR3 prepared by incorporating the episulfide compound of the present application decreases somewhat, but remains above 120 MPa, and the elongation is significantly increased. This means that the optical resins of the present application can undergo greater deformation while maintaining rigidity, resulting in significantly enhanced flexibility.

[0185] The above descriptions are merely some specific embodiments of the present application, which are intended to illustrate the present application and are not intended to limit the scope of protection claimed in the present application. All modifications, substitutions, or direct / indirect applications in other related technical fields made based on the inventive concept of the present application and using the contents of the present application specification and drawings are included in the scope of protection claimed in the present application.

Claims

1. An episulfide compound represented by formula (I) or formula (II), in, n is 2 to 4.

2. The episulfide compound according to claim 1, characterized in that In the formula (I), n is 2.

3. A method for preparing the episulfide compound represented by formula (I) according to claim 1, comprising: reacting the compound represented by formula (III) with the compound represented by formula (IV) in the presence of a base at a temperature of 0°C to 15°C in a mixed solvent consisting of water and a polar organic solvent to obtain a compound represented by formula (V), wherein n is 2 to 4, and X is selected from Cl, Br, or I; and The epoxy group of the compound represented by formula (V) is converted into an episulfide group to obtain an episulfide compound represented by formula (I).

4. The method according to claim 3, characterized in that The polar organic solvent is 1,4-dioxane, the volume ratio of water to 1,4-dioxane in the mixed solvent is (0.5-5):1, and the ratio of the compound represented by formula (III) to the mixed solvent is (0.005-2) g / mL.

5. A method for preparing the episulfide compound represented by formula (II) according to claim 1, comprising: Performing an oxidation reaction on the compound represented by formula (VI) to obtain a compound represented by formula (VII), wherein X is selected from Cl, Br or I, and the oxidant of the oxidation reaction is selected from at least one of 2,3-dichloro-5,6-dicyanobenzoquinone, dibromohydantoin, O2, H2O2, I2, Br2, and Cl2; reacting the compound represented by formula (VII) with a base to obtain the compound represented by formula (VIII); and The epoxy group of the compound represented by formula (VIII) is converted into an episulfide group to obtain an episulfide compound represented by formula (II).

6. The method according to claim 5, characterized in that The oxidant is 2,3-dichloro-5,6-dicyanobenzoquinone, and the temperature of the oxidation reaction is 0°C to 25°C.

7. A composition for preparing an optical resin, characterized in that: The composition for optical materials includes an episulfide compound and a curing agent, wherein the episulfide compound includes at least one episulfide compound selected from claim 1 or 2, and the curing agent is a compound containing two or more reactive groups, wherein the reactive groups are selected from one or more of thiols, primary amines, secondary amines, alcohols, acid anhydrides, and isocyanates.

8. The composition according to claim 7, characterized in that The composition further comprises one or more of a vinyl monomer, a polyepoxy compound, and a polyisocyanate.

9. The composition according to claim 7 or 8, characterized in that The mass content of the episulfide compound is 2% to 50% relative to the total weight of the composition.

10. The composition according to claim 9, characterized in that The optical resin is obtained by polymerizing and curing the composition.

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