Polythiols, method for producing same, and polymerizable composition

Abstract

The present invention provides a polythiol composition comprising: a) a polythiol according to formula (I) wherein each n is independently 2 to 4; and b) a polythiol according to formula (II) wherein each n is independently 2 to 4, and m is 1 or 2. The invention also provides a method for preparing the polythiol composition and a polymerizable composition containing the polythiol composition and aliphatic polyisocyanate.

Description

Technical Field

[0001] The present disclosure relates to polythiols, methods of making the same, and polymerizable compositions containing these polythiols. Background Art

[0002] Polythiols are used to form polythiourethane materials by reacting with polyisocyanate compounds to create optical articles with good thermomechanical properties. Polythiols with high sulfur content facilitate the production of optical articles exhibiting high refractive indices. Numerous methods exist for synthesizing polythiols, but most techniques involve more than one reaction process step.

[0003] Thioacetals have a high sulfur to carbon ratio (yielding a higher refractive index than typical aliphatic polythiols). In addition, thioacetals can be prepared from aldehydes, which are abundant in the chemical industry and therefore inexpensive, often from bio-based sources, generally benign to environmental and safety concerns, and offer higher selectivity and reactivity for the formation of thioacetals (compared to alcohols). However, when di- or higher thiols react with di- or higher aldehydes via step-growth, the high reactivity can easily lead to undesirable reactions such as oligomerization, polymerization, and cross-linking.

[0004] To address this issue, protection / deprotection reaction schemes have been proposed, which increase the number of steps and cost associated with polythiol production. Furthermore, during protection, a mixture of binary, monobasic, and unprotected thiols is unavoidable, requiring intermediate purification steps, further increasing the cost and complexity of the polythiol synthesis process. Other methods exploit the selectivity of thiols relative to alcohols by reacting mercaptohydroxy compounds with aldehydes to produce polyols as intermediate compounds, which are then converted to polythiols by conventional means; this also increases the complexity, time, and cost of polythiol synthesis.

[0005] It would be desirable to provide a polythiol that can be prepared using a minimum of reaction steps without the need for removal of by-products or intermediates and that is suitable for preparing high refractive index polymers. Summary of the Invention

[0006] Provided is a polythiol composition comprising:

[0007] a) a polythiol according to formula (I),

[0008]

[0009] wherein each n is independently 2 to 4; and

[0010] b) Polythiols according to formula (II)

[0011]

[0012] wherein each n is independently 2 to 4, and m is 1 or 2.

[0013] Also provided is a method for preparing the above-mentioned polythiol composition, the method comprising:

[0014] a. preparing a reaction mixture comprising a dithiol, a dialdehyde and a catalyst, wherein the molar ratio of the dithiol to the dialdehyde is at least 4:1; and

[0015] b. subjecting the reaction mixture to conditions sufficient to form a polythiol composition.

[0016] There is further provided a polymerizable composition comprising

[0017] a) the above-mentioned polythiol composition; and

[0018] b) Aliphatic polyisocyanate. The equivalent ratio of isocyanate groups (—NCO) in the polyisocyanate b) to thiol (—SH) groups in the polythiol composition a) is 1:0.9 to 1:1.1. DETAILED DESCRIPTION

[0019] Except in the operating examples, or where otherwise indicated, all numerical values ​​expressing quantities of ingredients, reaction conditions, and the like used in the specification and claims should be understood as modified by the term "about," even if the term does not explicitly appear. Therefore, unless otherwise indicated, the numerical parameters listed in the following specification and the appended claims are approximate values ​​that can vary depending on the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be interpreted in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0020] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0021] Any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between and including the recited minimum value of 1 and the recited maximum value of 10, i.e., having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0022] The plural encompasses the singular and vice versa; for example, the singular forms "a," "an," and "the" include plural referents unless expressly and obviously limited to one referent. For example, when describing a composition in terms of "a" polythiol compound or "an" isocyanate, the plural may be used to include mixtures of such compounds.

[0023] The present disclosure provides polythiols suitable for preparing optical articles exhibiting high refractive indices. It has been discovered that when a suitable excess of a dithiol is reacted with a dialdehyde, a product mixture is obtained that is suitable for forming optical materials / polythiourethanes, eliminating the need for by-product removal. The reaction to form the polythiol is performed in a single step, in a single pot, without the need for protecting groups or intermediates that require further reaction or conversion to the desired polythiol. Thus, a wide range of compounds containing a thioacetal / ketal core can be readily synthesized using the methods described herein.

[0024] The polythiol composition comprises:

[0025] a) a polythiol according to formula (I),

[0026]

[0027] wherein each n is independently 2 to 4; and

[0028] b) Polythiols according to formula (II)

[0029]

[0030] wherein each n is independently 2 to 4, and m is 1 or 2. It is noted that each of components a) and b) may comprise one or more different polythiols having the structures of formula (I) and (II).

[0031] In certain examples, the polythiol composition may further comprise c) a polythiol according to formula (III),

[0032]

[0033] wherein n is 2 to 4. Typically in formula (III), n=2; however, polythiol c) may comprise one or more different polythiols having the structure of formula (III). When the polythiol composition comprises polythiol c) of formula (III), polythiol c) may be present in an amount of at least 10% (such as at least 20%) and at most 50% (such as at most 40%) based on the total polythiols in the composition as determined by the LCMS procedure defined below. For example, based on the total polythiols in the composition as determined by the LCMS procedure defined below, polythiols according to formula (III) may be present in the composition in an amount of 10% to 50%, or 10% to 40%, or 20% to 50%, or 20% to 40%. The percentage composition reported by the procedure refers to the sum of the area under the curve of a particular compound relative to the area under the curve of all major UV peaks (>5%) observed in the LC-MS chromatogram. The percentage of each compound is approximately the same as the weight percentage, but not exactly the same. This is partly because the absorbance of a given compound may not be proportional to its weight.

[0034] Polythiol compositions can be prepared from a reaction mixture comprising dithiols, dialdehydes and catalysts. Exemplary dithiols have sufficient chain lengths (such as greater than 5 atoms) to prevent cyclization. Particularly suitable dithiols include those according to formula (III), such as 2,2'-thiobis(ethane-1-thiol) or 2,2'-(ethane-1,2-diylbis(sulfanediyl))bis(ethane-1-thiol). Higher polythiols, such as trithiols, tetrathiols, etc., can also be included in the reaction mixture, but their usage should be sufficiently low to minimize the formation of high molecular weight oligomers.

[0035] Suitable dialdehydes include low molecular weight aliphatic dialdehydes that can maximize the refractive index of the polythiourethane polymer product and reduce unwanted oligomerization; aromatic dialdehydes can also be used. Difunctional ketocarbonyl compounds (aliphatic or aromatic) can also be used, but exhibit lower reactivity to the formation of thioketals and have a higher carbon to carbonyl ratio, resulting in a lower refractive index of the polythiourethane polymer product. Polyaldehyde / ketone compounds can also be used, but exhibit a higher tendency to form high molecular weight oligomers. Specific examples of suitable dialdehydes include glyoxal, benzene-1,2-dicarboxaldehyde, benzene-1,3-dicarboxaldehyde, benzene-1,4-dicarboxaldehyde, cyclohexane-1,4-dicarboxaldehyde, succinaldehyde, or malondialdehyde.

[0036] As described above, when a suitable excess of dithiol reacts with a dialdehyde, a product mixture is obtained, but the mixture is still soluble and suitable for forming an optical material (such as a polythiourethane), so that no by-product removal is required. Typically, the molar ratio of dithiol to dialdehyde in the reaction mixture is at least 4:1, or at least 6:1, such as 6:1 to 12:1.

[0037] Suitable catalysts for the reaction mixture include, for example, acid catalysts. Inorganic and organic protic acids (Brønsted acids) (such as toluenesulfonic acid or hydrochloric acid, etc.) can be used in sub-equimolar loadings relative to the dialdehyde. In particular, Lewis acid catalysts such as lithium tetrafluoroborate are suitable; other Lewis acids (such as organometallic compounds, (alkyl) metal chlorides and trifluoromethanesulfonates, organoboranes, etc.) are also suitable. The amount of catalyst in the reaction mixture can vary and can depend on a variety of factors, such as the type and amount of the reactive compound used, as well as the reaction conditions, reaction rate, and desired degree of reaction. Typically, a substantially equimolar loading of the Lewis acid relative to the dialdehyde is particularly suitable.

[0038] The reaction mixture may further comprise an organic solvent, typically a polar aprotic solvent known in the art that is less likely to react with carbonyl functional groups. Examples include acetonitrile, tetrahydrofuran, dihalomethanes, trihalomethanes, aprotic polyethers, and mixtures thereof. The solvent may be present in an amount of 25% to 95% by weight, based on the total mass of the reaction mixture.

[0039] After the reaction mixture is prepared, it is subjected to conditions sufficient to form the polythiol composition in a one-step, one-pot reaction. The reaction can be carried out at ambient temperature. Ambient conditions mean that the reaction is carried out without the aid of heating or other energy. The ambient temperature is typically in the range of 60 to 90°F (15.6 to 32.2°C), such as typical room temperature, 72°F (22.2°C). The reaction conditions can include heating to 30°C to 85°C (such as 40°C to 75°C, or 55°C to 65°C) for 1 to 24 hours (such as 10 to 15 hours). Exemplary reaction conditions are 58°C to 62°C for 11 to 13 hours. The water released from the carbonyl species can be actively removed from the reaction by adding a desiccant or distillation, but this is generally not necessary for the reaction to proceed.

[0040] The polythiol composition may have a thiol equivalent weight of at least 100 g / equivalent, or at least 110 g / equivalent, or at least 120 g / equivalent, and at most 250 g / equivalent, such as at most 220 g / equivalent, or at most 200 g / equivalent, or at most 160 g / equivalent, based on the total mass of polythiols present in the composition. For example, the polythiol composition can have a thiol equivalent weight of 100 to 250 g / equivalent, or 100 to 220 g / equivalent, or 100 to 200 g / equivalent, or 100 to 160 g / equivalent, or 110 to 250 g / equivalent, or 110 to 220 g / equivalent, or 110 to 200 g / equivalent, or 110 to 160 g / equivalent, or 120 to 250 g / equivalent, or 120 to 220 g / equivalent, or 120 to 200 g / equivalent, or 120 to 160 g / equivalent, based on the total mass of polythiols present in the composition.

[0041] Typically, the polythiol of formula (I) may be present in the polythiol composition in an amount greater than 20%, such as at least 25%, or at least 30%, and up to 50%, or up to 45%, based on the total polythiols in the composition as determined by the LCMS procedure defined below. For example, the polythiol of formula (I) may be present in the polythiol composition in an amount from 20% to 50%, or from 20% to 45%, or from 25% to 50%, or from 25% to 45%, or from 30% to 50%, or from 30% to 45%, based on the total polythiols in the composition as determined by the LCMS procedure defined below.

[0042] The use of the above reactants in the given ratios allows the formation of polythiols having a thioacetal "core," which provides the advantages discussed above for the polythiourethane polymers. Thus, the above polythiol compositions can be used in polymerizable compositions to form polymers having a refractive index (n) e 20 ) is greater than or equal to 1.60. Such polymerizable compositions comprise: a) a polythiol composition as described above; and b) an aliphatic polyisocyanate.

[0043] Polyisocyanates are aliphatic, but may further include aromatic polyisocyanates. Isocyanate-functional uretdiones, allophanates, biuret and isocyanurates are also suitable. Diisocyanates and triisocyanates are often used, such as isocyanurates of diisocyanates. Isocyanate-functional prepolymers may also be used, for example, reaction products of polyisocyanates with polyols. Mixtures of polyisocyanates may be used.

[0044] Polyisocyanates can be prepared from a variety of isocyanate-containing materials. Other examples of suitable polyisocyanates include trimers prepared from the following diisocyanates: 4,4'-methylene-bis(cyclohexyl isocyanate), isophorone diisocyanate, an isomeric mixture of 2,2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 4,4'-diphenylmethylene diisocyanate.

[0045] Suitable diisocyanates include 4,4'-methylene-bis(cyclohexyl isocyanate) (i.e., 4,4'-diisocyanatodicyclohexylmethane), isophorone diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and an isomeric mixture of 2,4,4-trimethylhexamethylene diisocyanate, and 1,6-hexamethylene diisocyanate. Typically, the equivalent ratio of isocyanate groups (-NCO) in the polyisocyanate b) to thiol (-SH) groups in the polythiol composition a) is 1:0.9 to 1:1.1, typically 1:1.

[0046] In addition to aliphatic polyisocyanates, examples of aromatic polyisocyanates that can be used include toluene diisocyanate, tetramethylxylylene diisocyanate, and m-xylene diisocyanate. Uretdiones, allophanates, biuret, isocyanurates, and isocyanate-functional prepolymers prepared therefrom are also suitable.

[0047] The polythiol composition may further comprise art-known urethanization catalysts, color correction dyes, mold release agents, degassing agents, UV absorbers, etc., present in art-recognized amounts. The amount of each additive will vary depending on the desired properties and intended use of the article.

[0048] Suitable carbamate catalyst can change;For example, suitable carbamate catalyst can include those catalysts that can be used for forming thiocarbamate by the reaction of NCO and SH-containing material.The non-limiting example of suitable catalyst can be selected from Lewis base, Lewis acid and insertion catalyst, as described in Ullmann's Encyclopediaof Industrial Chemistry, the 5th edition, 1992, volume A21, page 673 to 674.Catalyst can be the stannous salt of organic acid, such as but not limited to stannous octoate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin mercaptide, dibutyltin dimaleate, dimethyltin diacetate, dimethyltin dilaurate, dibutyltin dichloride, dimethyltin dichloride, 1,4-diazabicyclo [2.2.2] octane and mixtures thereof.Alternatively, catalyst can be zinc octoate, bismuth or ferric acetylacetonate.

[0049] Other non-limiting examples of suitable catalysts can include tin compounds, such as dibutyltin oxide, phosphine, tertiary ammonium salts and tertiary amines, such as but not limited to triethylamine, triisopropylamine, dimethylcyclohexylamine, N, N-dimethylbenzylamine, pyridine and mixtures thereof. Amine compounds and alkyltin halide compounds are most commonly used and are most suitable for use in combination. Catalyst levels can vary depending on the type used; for example, organotin catalysts are typically present in an amount of up to 1000ppm (such as 100 to 1000ppm; typically about 250ppm). Mixtures of two or more of the above catalysts are also suitable.

[0050] Polymerization of the above-described compositions results in the formation of a polymeric product that can be made into shaped articles, such as by casting to form sheets or by molding.The polymeric product obtained by polymerizing the polymerizable compositions of the present disclosure is a thermosetting solid and, in some embodiments, is transparent.

[0051] Alternatively, the polymerizable composition can be sprayable, castable, extrudable, 3-D printable or moldable. The polymerized product prepared from the polymerizable composition is often used to form a solid article, such as an optical element or device. As used herein, the term "optical" means relating to or associated with light and / or vision.

[0052] When manufacturing an optical article, a polymerizable composition can be introduced into a mold of any desired shape at a certain temperature and for a certain period of time to form a polymerized product. After the components of the polymerizable composition are mixed to form a reaction mixture, it is typically introduced into the mold by injection. The mold can have any shape desired for the final product, as described above. It is typically a lens mold, typically a mold for an ophthalmic lens. The molded article can then be demolded from the mold.

[0053] Optical articles may include ophthalmic elements and devices, as well as sheet products such as display elements and devices, windows, mirrors and / or active and passive liquid crystal cell elements and devices. As used herein, the term "ophthalmic" means relating to or associated with the eyes and vision. Non-limiting examples of ophthalmic elements include corrective and non-corrective (plano) lenses, including single vision or multi-vision lenses, which may be segmented or non-segmented multi-vision lenses (such as, but not limited to, bifocal lenses, trifocal lenses, and progressive lenses), and other elements for correcting, protecting, or enhancing (cosmetic or otherwise) vision, including, but not limited to, contact lenses, intraocular lenses, magnifying glasses, sun lenses, fashion lenses, sports masks, face shields, and goggles. As used herein, the term "display" means a visible or machine-readable representation of information in the form of text, numbers, symbols, patterns, or graphics. Non-limiting examples of display elements and devices include screens (including touch screens), displays, and security elements (such as security markings). As used herein, the term "window" means an aperture through which radiation is transmitted. Non-limiting examples of windows include automotive and aircraft transparencies, filters, blinds, and optical switches. As used herein, the term "mirror" means a surface that specularly reflects incident light.

[0054] The polymerized product prepared from the polymerizable composition can have: a refractive index of at least 1.57, or at least 1.58, or at least 1.59; an Abbe number of at least 30, or at least 33, or at least 35; and a thermal conductivity of at least 50 N / mm 2 , or at least 70N / mm 2 , or at least 90N / mm 2 The refractive index, Abbe number, and Fisher hardness values ​​can be determined according to methods generally recognized in the art; for example, the refractive index value (n) can be determined using a Metricon Model 2010 Prism Coupler, Thin Film Thickness / Refractive Index Measurement System according to the manufacturer's operating and maintenance instructions.e 20 ) and Abbe number; and Fisher hardness values ​​are determined according to ISO 14577 using a Fischer Technologies H100C microhardness measuring system.

[0055] The following working examples are intended to further illustrate the disclosed compositions. It should be understood that the disclosure described in this specification is not necessarily limited to the examples described in this section. Components mentioned elsewhere in the specification as suitable alternative materials for use in the compositions but not shown in the working examples below are expected to provide results comparable to their shown counterparts. Unless otherwise indicated, all parts are by weight.

[0056] Examples

[0057] Definition / Methodology:

[0058] Part 1.

[0059] Example 1: Preparation of polythiol composition

[0060] Glyoxal (64.90 g of a 40 wt / wt% aqueous solution in water, 0.45 mol), 2,2'-thiobis(ethane-1-thiol) (482.8 g, 3.13 mol), and lithium tetrafluoroborate (75.4 g, 0.80 mol) were sequentially charged into acetonitrile (1621 mL) and dissolved in a 5 L four-necked round-bottom flask to form a solution. The reaction solution was heated to 60 ° C for 12 hours and then cooled to room temperature, whereby the mixed phases were separated and the bottom layer containing the product was collected. The product layer was washed sequentially with two portions of acetonitrile, the first 300 mL and then 150 mL; the acetonitrile wash layer was discarded. The remaining acetonitrile insoluble portion was concentrated under vacuum at 50 ° C -60 ° C to form a clear, viscous liquid product (206 g) and passed through a 5 μm filter. Before use, the polythiol mixture was dried under high vacuum for at least 8 hours to remove residual moisture.

[0061] Part 2. Characterization of the polythiol composition of Example 1.

[0062] The following procedure was used to determine the thiol equivalent weight. A sample of the polythiol (0.0500–0.1000 g) was weighed to the ten-thousandth decimal place on an analytical balance and dissolved in 30 mL of tetrahydrofuran or a 60 / 40 wt / wt toluene / isopropanol solution, depending on the solubility of the polythiol. One to three drops of pyridine were added to the solution, which was then stirred at room temperature until the sample dissolved. A 0.1 N iodine solution in water was titrated using a Metrohm 865 Dosimat Plus with stirring until the solution exhibited a distinct yellow color. This process was repeated and the SH equivalent weight was calculated using the following equation (3), with the average of the two results used for the calculation. It should be noted that some of the polythiol mixtures used in the Examples / Comparative Examples may contain a small amount of residual hydroxyl functional groups; this may affect the total active hydrogen equivalent weight and, therefore, the ratio of active hydrogen groups to isocyanate groups. However, this difference is expected to be negligible and only the thiol equivalent weight can be used to calculate the amount of isocyanate groups required to achieve an approximately 1:1 ratio of active hydrogen groups:isocyanate groups.

[0063] Equation (3):

[0064] The mercaptan equivalent weight of Example 1 was determined according to the procedure and found to be 224 g / eq.

[0065] The product was also characterized by liquid chromatography-mass spectrometry according to the following procedure ("LCMS procedure") to determine the amount of each polythiol component in the product mixture. The product mixture was diluted with tetrahydrofuran (THF) and analyzed by reverse phase ultrahigh pressure liquid chromatography online UV / Vis and mass spectrometry detection. The product mixture was separated on a Dionex UHPLC (with a WatersCortecs UPLC C18 column, 1.6 μm pore size, 100 x 2.1 mm size). The mobile phase was a gradient mixture of deionized water and acetonitrile, ranging from 60% DIH2O / 40% acetonitrile at T0 to 2% DIH2O / 98% acetonitrile at the end of the run. The analytes were detected using a Vanquish UV-Vis set at 230 nm. Mass spectrometry analysis of the UPLC effluent was performed on a QExactive mass spectrometer using full MS in AIF ESI positive mode and full MS in AIF ESI negative mode over a scan range of 133.4–2000 m / z. Data analysis was performed using Xcalibur 4.2 software. Similarly, the percent composition reported for this analysis refers to the area under the curve for a specific compound relative to the sum of the areas under the curve for all major UV peaks (>5%) observed in the LC-MS chromatogram.

[0066] The compositions according to this analysis are shown in Table 1.

[0067] Table 1: Decomposition of the polythiol composition of Example 1.

[0068]

[0069]

[0070] Complex of molecular ion and supporting electrolyte

[0071] Part 3. Preparation of curable compositions.

[0072] Table 2: Composition of Examples / Comparative Examples

[0073]

[0074] 1 Internal mold release agent mixture containing 13.8% triethylamine based on GC-FID analysis available from PPG Industries, Inc. 2 Release agents available from Stepan

[0075] 3 A mixture of primarily 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol and related isomers, available from PPG Industries, Inc.

[0076] 4 Available from TCIAMERICA, >90% purity 5 A 2 / 1 (mol / mol) adduct of 2,2'-thiobis(ethane-1-thiol) and propargyl alcohol previously described in US 7,687,597 B2.

[0077] 6 The equivalent weight of the mixture determined by titration.

[0078] 7 Determined by titration as described above.

[0079] Comparative Example CE-2: Optical Articles Cast from Cycloaliphatic Diisocyanates and Industry Standard Polythiols

[0080] The components of charge 1 are added to a 250mL flask equipped with a vacuum joint and a magnetic stirring bar. Charge 2 and charge 3 are added to this. The mixture is placed under vacuum and degassed for about 30 minutes. The thiol mixture of charge 4 (calculated to achieve a thiol:isocyanate equivalent ratio of 1:1) is loaded into a reaction flask, sealed and placed under vacuum again. The mixture is stirred at room temperature for about 2 hours, and then the temperature is raised to 60°C by placing the flask in an oil bath. After 5 minutes, the mixture is poured into a preheated (60°C) flat glass mold with a rubber gasket of about 3.5mm in thickness. The mold is placed in an oven initially set at 60°C. The oven temperature is raised to 140°C over the course of 9.16 hours, maintained at this temperature for 5.16 hours, and finally reduced to 70°C over the course of 1.16 hours, then the oven is turned off, and the sample is allowed to return to room temperature, and the sample is removed from the mold at room temperature. Another polymer product mixture was prepared using the same procedure and reagent ratios; this mixture was cast into a pre-assembled finished single-photon negative "-" dynamic mold, with the center thickness of the mold set to 2.2 mm. The same curing conditions were used.

[0081] Comparative Example CE-3: Optical Article Cast from the Aromatic Diisocyanate and Polythiol of Example 1

[0082] Charge 1 was added to a 250 mL flask with a vacuum connection and equipped with a magnetic stirring bar. Charges 2 and 3 were added to the flask simultaneously. The mixture was placed under vacuum and degassed for approximately 35 minutes. The polythiol of charge 4 (calculated to achieve a thiol:isocyanate equivalent ratio of 1:1) was charged into the reaction flask and returned to vacuum. The mixture was immediately uniform and stirred at room temperature for approximately 15 minutes before being dispensed into a pre-assembled finished single-photon negative "-" power mold, the center thickness of which was set to 2.2 mm. The mold was placed in an oven initially set at 60°C. The oven temperature was raised to 140°C over the course of 9.16 hours, maintained at this temperature for 5.16 hours, and finally reduced to 70°C over the course of 1.16 hours, the oven was then turned off, and the sample was allowed to return to room temperature and removed from the mold at room temperature.

[0083] Example 4: Flat Sheets Cast from IPDI and the Polythiol of Example 1

[0084] Charge 1 was added to a 100 mL round-bottom flask equipped with a magnetic stir bar and degassed under high vacuum for approximately 20 minutes. The components of charges 2 and 3 were added, the flask was resealed and degassed again. The polythiol mixture of charge 4 was then added to the flask, calculated to achieve a thiol:isocyanate equivalent ratio of 1:0.99. The flask was resealed and placed under high vacuum. The reaction mixture was stirred in an oil bath at 60°C until uniform for approximately 30 minutes. The mixture was further aged at 60°C for approximately 20 minutes and then poured into a flat glass mold with a rubber gasket having a thickness of approximately 3.5 mm. The polymerized product in the mold was transferred to an oven initially at ambient conditions. The oven temperature was raised to 140°C over the course of 9.75 hours, maintained at this temperature for 5.16 hours, and finally lowered to 70°C over the course of 1.16 hours. The oven was turned off and the sample was allowed to return to room temperature before being removed from the mold at room temperature.

[0085] Example 5: Optical articles cast from alicyclic diisocyanates and the polythiol of claim 1

[0086] The components of Charge 1 were added to a 250 mL flask with a vacuum connection and equipped with a magnetic stir bar; Charges 2 and 3 were also added to the same flask. This mixture was placed under vacuum and degassed for approximately 20 minutes. The polythiol of Charge 4 (calculated to achieve a thiol:isocyanate equivalent ratio of 1:1.01) was added to the reaction flask and returned to vacuum. The mixture was placed in a 60°C oil bath under vacuum and aged for 60 minutes, during which time the mixture became homogeneous. The reaction mixture was dispensed into a pre-assembled single-photon negative "-" dynamic mold set to a center thickness of 2.2 mm and a flat glass mold with a rubber gasket approximately 3.5 mm thick. The mold was placed in an oven initially set to 60°C. The oven temperature was increased to 140°C over the course of 9.16 hours, maintained at this temperature for 5.16 hours, and finally decreased to 70°C over the course of 1.16 hours. The oven was then turned off and the sample allowed to return to room temperature, where it was removed from the mold.

[0087] Example 6: Optical articles with lower SH equivalent weight cast from alicyclic diisocyanates and the polythiol of claim 1

[0088] The components of charge 1 were added to a 250 mL flask equipped with a vacuum connection and a magnetic stirring bar. Charges 2 and 3 were added to the same flask. The mixture was placed under vacuum and degassed for approximately 50 minutes. The polythiol mixture of charge 4 (calculated to achieve a thiol:isocyanate equivalent ratio of 1:1.04) was loaded into the reaction flask and returned to vacuum. The mixture was placed in a 60 ° C oil bath and aged for approximately 15 minutes so that the mixture became uniform. After aging for approximately 30 minutes, the reaction mixture was distributed into a pre-assembled single-photon negative "-" power mold with a center thickness of 2.2 mm and a flat glass mold with a rubber gasket having a thickness of approximately 3.5 mm. The mold was placed in an oven initially set at 60 ° C. The oven temperature was raised to 140°C over the course of 9.16 hours, held at that temperature for 5.16 hours, and finally lowered to 70°C over the course of 1.16 hours before the oven was turned off and the sample was allowed to return to room temperature where it was removed from the mold.

[0089] Part 4. Evaluation of polymeric products of Examples and Comparative Examples.

[0090] By use according to ISO 14577-07 Fisher Microhardness (FMH) was determined by testing using an H-100 SMC (available from Fisher Technology, Inc.). The FMH of the polymer was measured under a load of 300 mN after applying a load of 0-300 mN over 15 seconds. The result is the arithmetic mean of at least 3 measurements.

[0091] Glass transition temperatures were measured on a TA Instruments Q200 differential scanning calorimeter (DSC).

[0092] The refractive index was measured using a Metricon 2010 / M prism coupler equipped with a monochromatic light source at 453, 543, and 633 nm and corrected for temperature. The Abbe number was calculated from the refractive index values ​​according to the following equations (1) and (2), where V D and V e are the Abbe numbers relative to the Fraunhofer d line and the green mercury E line, n d 、n F 、n C 、n e 、n F ' and n C ' are the refractive indices of the material at the Fraunhofer D-line, F-line, C-line, green mercury E-line, and blue and red cadmium lines, respectively. The refractive indices for wavelengths not directly measured are calculated by best fitting empirical data to the Cauchy equation.

[0093] Equation (1):

[0094] Equation (2):

[0095] Light transmittance and color were measured using a HunterLab Ultra Scan Pro spectrophotometer (available from Hunter Associates Laboratory, Inc.) according to ASTM E313-10° / D65 standards and the manufacturer's instructions. The path length of the sheet sample was equal to the sample thickness.

[0096] Table 3: Physical / Optical Properties of Examples 4-6 and Comparative Examples CE-2 and CE-3; Data presented here were obtained from flat sheets

[0097]

[0098] As shown above, Examples 4, 5, and 6 exhibit higher refractive indices compared to CE-2, which has a lower thiol equivalent weight component. Furthermore, the aromatic polyisocyanate of CE-3 forms a very soft polymer with poor light transmittance. Specifically, the above examples demonstrate that high refractive indices can be achieved while maintaining acceptable thermomechanical properties.

[0099] Although specific examples have been described above for purposes of illustration, it will be apparent to those skilled in the art that many changes in detail may be made to the present disclosure without departing from the scope of the present disclosure as defined in the appended claims. Therefore, it should be understood that this disclosure is not limited to the specific aspects disclosed, but is intended to cover modifications within the spirit and scope of the present disclosure as defined in the appended claims.

Claims

1. A polythiol composition comprising: a) Polythiols according to formula (I) wherein each n is independently 2 to 4; and b) Polythiols according to formula (II) wherein each n is independently 2 to 4, and m is 1 or 2.

2. The polythiol composition according to claim 1, wherein the polythiol composition has a thiol equivalent weight of 100 to 250 g / equivalent based on the total mass of polythiol present in the composition.

3. The polythiol composition according to claim 2, wherein the polythiol composition has a thiol equivalent weight of 120 to 160 g / equivalent based on the total mass of polythiol present in the composition.

4. The polythiol composition according to any one of the preceding claims, further comprising c) a polythiol according to formula (III), wherein n is 2 to 4. The polythiol composition according to claim 4 , wherein in formula (III), n=2.

6. The polythiol composition according to claim 5, wherein the polythiol according to formula (III) is present in the composition in an amount of 10% to 50% based on the total polythiol in the composition as determined by LCMS procedure.

7. The polythiol composition according to any one of the preceding claims, wherein the polythiol composition is prepared from a reaction mixture comprising a dithiol, a dialdehyde, and a catalyst, and wherein the molar ratio of the dithiol to the dialdehyde is at least 4:

1.

8. The polythiol composition according to claim 7, wherein the molar ratio of dithiol to dialdehyde is 6:1 to 12:

1.

9. The polythiol composition according to any one of claims 7 to 8, wherein the dithiol comprises the polythiol according to formula (III), wherein n=2.

10. The polythiol composition according to any one of claims 7 to 9, wherein the dialdehyde comprises glyoxal.

11. The polythiol composition according to any one of claims 7 to 10, wherein the catalyst comprises lithium tetrafluoroborate.

12. A method for preparing a polythiol composition according to any one of the preceding claims, the method comprising: a. preparing a reaction mixture comprising a dithiol, a dialdehyde and a catalyst, wherein the molar ratio of the dithiol to the dialdehyde is at least 4:1; as well as b. subjecting the reaction mixture to conditions sufficient to form the polythiol composition.

13. The method of claim 12, wherein the molar ratio of dithiol to dialdehyde is at least 6:

1.

14. The process according to any one of claims 12 to 13, wherein the molar ratio of dithiol to dialdehyde is 6:1 to 12:

1.

15. The method according to any one of claims 12 to 14, wherein the dithiol comprises A polythiol according to formula (III), wherein n is 2 to 4.

16. The method of any one of claims 12 to 15, wherein the dialdehyde comprises glyoxal.

17. The method of any one of claims 12 to 16, wherein the catalyst comprises lithium tetrafluoroborate.

18. The method of any one of claims 12 to 17, wherein the conditions sufficient to form the polythiol composition comprise heating to a temperature of 30°C to 85°C for 1 to 24 hours.

19. A polymerizable composition comprising a) a polythiol composition according to any one of claims 1 to 11; and b) an aliphatic polyisocyanate, wherein the equivalent ratio of isocyanate groups (—NCO) in the polyisocyanate b) to thiol (—SH) groups in the polythiol composition a) is 1:0.9 to 1:1.

1.

20. The polymerizable composition of claim 19, wherein the polyisocyanate b) comprises 4,4'-methylene-bis(cyclohexyl isocyanate), isophorone diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and an isomeric mixture of 2,4,4-trimethylhexamethylene diisocyanate, and 1,6-hexamethylene diisocyanate, or a mixture thereof.

21. An optical article formed from the polymerizable composition of any one of claims 19 to 20.

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