Method for curing polythiourethane-based substrates with salt catalysts

Abstract

The present invention relates to a method for curing a polythiourethane-based transparent casting substrate, comprising: preparing a first component A comprising at least one polyisocyanate or polyisothiocyanate monomer A2; preparing a second component B comprising a polythiourethane prepolymer B1 having thiol end groups; mixing the first and second components A and B together and filling the resulting polymerizable mixture into a molding cavity of a casting mold assembly; and curing the polymerizable mixture to obtain a polythiourethane-based transparent substrate, wherein the curing step 4) is carried out in the presence of at least one salt catalyst in an amount ranging from 0.015% to 0.15% by weight, based on the total weight of the polymerizable compounds present in the mixture of the first and second components A and B. Alternatively, the first component A comprises a polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups, and the second component B comprises at least one polythiol monomer B2.

Description

[Technical Field]

[0001] The present invention relates to a method for producing polythiourethane-based substrates, particularly optical substrates such as ophthalmic lenses, generally having a medium or high refractive index, preferably at least 1.52, more preferably at least 1.54, more preferably at least 1.6, and even more preferably at least 1.67, with short curing cycles. [Background technology]

[0002] Ophthalmic lenses made from polythiourethane-based substrates are typically prepared by a process that includes mixing appropriate monomers, such as a mixture of polyisocyanate and polythiol, in a tank, adding catalysts and additives, filling a mold cavity with the liquid mixture of monomers, polymerizing the monomer mixture, and then recovering the polymerized polythiourethane-based substrate from the mold. The mixture is then subjected to a thermal cycle in an oven, typically for a duration of 20 hours.

[0003] WO 00 / 26272 discloses a polymerizable composition for producing a poly(thio)urethane resin, comprising at least one polyiso(thio)cyanate monomer, at least one polythiol monomer, and a salt catalyst system (typically a mixture of KSCN and a crown ether).

[0004] The rapid cure process is highly desirable over conventional processes due to its dramatic increase in productivity due to shorter residence time in the curing oven, its ability to achieve complex and demanding lens shapes at better yields due to lower shrinkage of the final polymerizable mixture than mixtures obtained directly from the monomer, its excellent compatibility with tape adhesives used in mold assembly, and its reduced energy consumption during the polymerization cycle.

[0005] It is known to reduce the time required for curing of a polymerizable composition cast into a mold assembly by at least partially replacing the monomer with a prepolymer (or oligomer) that is first pre-reacted to form an oligomer (prepolymer), then blended with a catalyst that provides high overall reactivity in very small amounts or even via an in-line mixing device, and then cast into the mold assembly and subjected to a short polymerization cycle, typically of a few hours.

[0006] In this regard, U.S. Patent Application Publication No. 2003 / 125410 discloses a method for rapidly curing a polythiourethane transparent casting substrate, which method comprises: 1) providing a first component A comprising a polythiourethane prepolymer having isocyanate or isothiocyanate end groups; 2) providing a second component B comprising a polythiourethane prepolymer having thiol end groups; 3) mixing the first component A and the second component B together and filling the resulting mixture into the molding cavity of the casting mold assembly; 4) curing the mixture to obtain a transparent solid substrate in the presence of 0.001 to 2.5 wt % of a highly reactive catalyst, based on the total weight of polymerizable monomers, to significantly reduce the curing time of the polymerizable composition, typically to within 2 hours. Includes.

[0007] US Patent Application Publication No. 2007 / 098999 discloses a similar process involving two prepolymers.

[0008] Batch mixing of such mixtures is inherently safer than the usual process from monomers, because if the viscosity is controlled, some of the available bond-forming energy is already released during oligomerization (prepolymerization), limiting the formation of localized hot spots in the final polymerizable mixture. The use of prepolymers allows for a stable and uniform reaction. Known catalysts for polythiourethane synthesis are dibutyltin dichloride or a mixture of KSCN and 18-crown-6.

[0009] WO 2021 / 182526, EP 3916470, and EP 3919967 choose a different approach to rapidly cure polythiourethane optical materials, combining the use of monomers and prepolymers in the presence of a polymerization catalyst (typically a basic catalyst such as lutidine).

[0010] The choice of catalyst in the polythiourethane curing process is very important as it not only determines the material curing speed but can also affect the final optical quality of the material in certain cases. Often a compromise must be made between reaction speed and material quality, as faster reaction rates can lead to less controlled polymerization and therefore higher striations and more bubbles. Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to provide a method for rapidly producing polythiourethane resins that overcomes the drawbacks of prior art methods (i.e., allows for better control of the reaction without increasing the cure time and avoids runaway reactions), and which should not impair the thermomechanical properties of the final material.

[0012] Another object of the present invention is to provide a method for curing polythiourethane-based cast substrates that are substantially free of optical defects (particularly free of bubbles and / or striations generated during the polymerization process), have high transmittance and transparency, a low yellowness index, and are resistant to degradation. [Means for solving the problem]

[0013] The present inventors have discovered that the replacement of prior art catalysts with salt catalysts allows for the use of higher amounts of catalyst along with better control of the polymerization of polymerizable mixtures comprising isocyanate-, isothiocyanate-, or thiol-terminated polythiourethane prepolymers and another monomer.

[0014] The present invention relates to a method for rapidly curing polythiourethane-based transparent casting substrates that can be used in the production of optical articles such as ophthalmic lenses, comprising the following steps 1), 2), 3), 4), and 5), or 1'), 2'), 3), 4), and 5): 1) providing a first component A comprising at least one polyisocyanate or polyisothiocyanate monomer A2; 2) preparing a second component B comprising a polythiourethane prepolymer B1 having thiol end groups, said prepolymer B1 being prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer; or 1') preparing a first component A comprising a polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups of formula -NCX, where X is O or S, said prepolymer A1 being prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer; 2') providing a second component B comprising at least one polythiol monomer B2; 3) mixing the first and second components A and B together and filling the resulting polymerizable mixture into the molding cavity of the casting mold assembly; 4) curing the polymerizable mixture to obtain a polythiourethane-based transparent substrate; and 5) Recovering the polythiourethane-based transparent substrate from the casting mold assembly Including, The curing step 4) is carried out in the presence of at least one salt catalyst in an amount ranging from 0.015% to 0.15% by weight relative to the total weight of the polymerizable compounds present in the mixture of the first and second components A and B, A method is provided. DETAILED DESCRIPTION OF THE INVENTION

[0015] The substrate of the present invention is an organic glass substrate made from a thermosetting resin. The polymer matrix of the substrate is obtained, in some embodiments, from a material composition ("substrate composition") comprising at least one polymerizable prepolymer and at least two polymerizable prepolymers.

[0016] The substrate is preferably an optical article substrate, more preferably an optical lens substrate. The optical article is preferably an ophthalmic lens, for example a plastic eyeglass lens.

[0017] In this specification, unless otherwise specified, a substrate is understood to be transparent if the observation of an image through said substrate is perceived without significant loss of contrast, i.e., if the formation of an image through said substrate can be obtained without adversely affecting the quality of this image. This definition of the term "transparent" can be applied to all objects so modified in this specification, unless otherwise specified.

[0018] The term "ophthalmic lens" is used to mean a lens that is fitted to a spectacle frame to protect the eyes and / or correct vision. Said lens may be chosen from afocal, monofocal, bifocal, trifocal, progressive, Fresnel, or any other type of lens with discontinuous surfaces. Although ophthalmic optical systems are the preferred field of the invention, it will be understood that the invention may be applied to other types of optical elements, such as, for example, lenses for optical instruments, in particular filters for photography or astronomy, optical aiming lenses, eye visors, the optics of lighting systems, screens, glass panes, etc.

[0019] When the optical article is an optical lens, it may have one or more functional coatings on the front main surface, the rear main surface, or both surfaces. As used herein, the rear surface of the substrate is intended to mean the surface that is closest to the wearer's eyes when the article is in use. This rear surface is generally a concave surface. In contrast, the front surface of the substrate is the surface that is farthest from the wearer's eyes when the article is in use. This rear surface is generally a convex surface. The optical article may also be a planar article.

[0020] Substrate, in the sense of the present invention, should be understood as meaning an uncoated substrate and generally has two main surfaces. The substrate may in particular be an optically transparent material having the shape of an optical article (for example, an ophthalmic lens to be attached to glass). In this context, the term "substrate" is understood as meaning the base component material of an optical lens (more particularly, an ophthalmic lens). This material may serve as a support for one or more coatings or layer stacks.

[0021] The refractive index of the polythiourethane-based transparent substrate is preferably 1.52 or more, more preferably 1.54 or more, more preferably 1.56 or more, more preferably 1.58 or more, more preferably 1.60 or more, even more preferably 1.65 or more or 1.67 or more, and this refractive index is preferably 1.80 or less, more preferably 1.70 or less, even more preferably 1.67 or less. Unless otherwise specified, refractive indices referred to in this application are expressed at 25°C at a wavelength of 550 nm.

[0022] The fast-setting polymerizable composition for obtaining polythiourethane-based materials is composed of two main components.

[0023] In a first embodiment of the present invention, the first component A prepared in step 1) is composed of at least one polyisocyanate or polyisothiocyanate monomer A2. In step 2) of the first embodiment of the method, a second component B is prepared, comprising a polythiourethane prepolymer B1 having thiol end groups, the second component B being prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, the former being used in excess. The second component B therefore comprises oligomers, if any, and unpolymerized initial monomers.

[0024] In a second embodiment of the present invention, a first component A is prepared in step 1') comprising a polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups, prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, the latter being used in excess. Thus, the first component A comprises oligomers and unpolymerized initial monomers. The second component B, prepared in step 2') of this second embodiment of the method, is composed of at least one polythiol monomer B2.

[0025] In contrast to prior art methods that use only iso(thio)cyanate or thiol monomers, the present invention uses polythiourethane prepolymers.

[0026] A prepolymer refers to a polymer or oligomer that includes a prepolymer molecule. A prepolymer molecule refers to a polymer or oligomer molecule that can enter into further polymerization via reactive (polymerizable) groups, thereby contributing multiple monomer units to at least one chain of the final polymer. A prepolymer molecule is generally formed from two or more different monomers.

[0027] The polythiourethane prepolymer A1 having an isocyanate or isothiocyanate terminal group is prepared by reacting at least one polyisocyanate monomer or polyisothiocyanate monomer with at least one polythiol monomer in such a ratio that the molar ratio of the isocyanate group or isothiocyanate group to the thiol group, NCX / SH (X is O or S), is preferably in the range of 3:1 to 30:1, preferably without a catalyst.

[0028] The polythiourethane prepolymer B1 having thiol terminal groups is prepared by reacting at least one polyisocyanate monomer or polyisothiocyanate monomer with at least one polythiol monomer in such a ratio that the molar ratio of thiol groups to isocyanate groups or isothiocyanate groups SH / NCX (X is O or S) is preferably in the range of 3:1 to 30:1, preferably without a catalyst.

[0029] The polythiol compounds and polyisocyanate or polyisothiocyanate compounds used to prepare the polythiourethane prepolymers A1 or B1 are considered monomers herein, even if they are oligomers.

[0030] By polyisocyanate is meant any compound containing at least two isocyanate groups, i.e., diisocyanates, triisocyanates, etc. Polyisocyanate prepolymers may also be used. The polyisocyanate may be any suitable polyisocyanate having two or more, preferably two or three, isocyanate functional groups. This polyisocyanate may be used to prepare polythiourethane prepolymer A1 or B1, but may also be used directly in component A in step 1) of the process.

[0031] The polyisocyanate may be selected from aliphatic, aromatic, cycloaliphatic, or heterocyclic polyisocyanates, and mixtures thereof.

[0032] The polyisothiocyanates are defined similarly to the polyisocyanates above, with the "isocyanate" group replaced by an "isothiocyanate" group.

[0033] In one embodiment of the present invention, the polyisocyanate or polyisothiocyanate monomer is represented by formula (VI): R 2 (NCX) n2 (VI) wherein X represents O or S, n2 represents an integer ranging from 2 to 6, and R 2 represents an aliphatic group, an alicyclic group, a heterocyclic group, or an aromatic group.

[0034] Preferred polyisocyanate or isothiocyanate monomers are those of the formula: [ka] wherein R 1 are independently H or a C1-C5 alkyl group, preferably CH3 or C2H5; R 2 is H, halogen, preferably Cl or Br, or a C1-C5 alkyl group, preferably CH3 or C2H5; Z is -N=C=X, where X is O or S, preferably O; a is an integer ranging from 1 to 4, b is an integer ranging from 2 to 4, and a+b≦6; x is an integer of 1 to 10, preferably an integer of 1 to 6.

[0035] The polyisocyanates of the present invention are preferably diisocyanates. Among the available diisocyanates are toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, paraphenylene diisocyanate, xylylene diisocyanate, biphenyl-diisocyanate, 3,3'-dimethyl-4,4'-diphenylene diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, 2,2,4-trimethylhexane-1,6-diisocyanate, lysine methyl ester diisocyanate, bis(isocyanatoethyl) fumarate, isophorone diisocyanate (IPDI), ethylene diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, and cyclohexane-1,3-diisocyanate. Examples of suitable isocyanates include cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene-2,4-diisocyanate, tetramethylxylylene diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrophenylene-1,3-diisocyanate, hexahydrophenylene-1,4-diisocyanate, perhydrodiphenylmethane-2,4'-diisocyanate, perhydrophenylmethane-4,4'-diisocyanate (or bis-(4-isocyanatocyclohexyl)methane, or 4,4'-dicyclohexylmethane diisocyanate), bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate, 2,5 (or 2,6)-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, and mixtures thereof.

[0036] Another non-limiting example of a polyisocyanate is the isocyanurate from isophorone diisocyanate and 1,6-hexamethylene diisocyanate, both of which are commercially available. Further polyisocyanates suitable for the present invention are described in detail in WO 98 / 37115, WO 2014 / 133111 or EP 1 877 839.

[0037] The polythiol that can be used in the present invention is defined as a compound containing at least two sulfhydryl (mercapto) groups, i.e., a dithiol, trithiol, tetrathiol, etc. Polythiol prepolymers can also be used. The polythiol can be any suitable polythiol having two or more, preferably two or three, thiol functional groups. This polythiol can be used to prepare polythiourethane prepolymer A1 or B1, but can also be used directly in component B in step 2') of the method.

[0038] In one embodiment of the invention, the polythiol monomer has the formula: R 1 (SH) n1 (I) wherein n1 represents an integer ranging from 2 to 6; R 1 represents an aliphatic group, an alicyclic group, a heterocyclic group, or an aromatic group.

[0039] Among the preferred polythiol monomers and / or oligomers suitable for the present invention are trimethylolpropane tris(2-mercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), trimethylolethane tris(2-mercaptoacetate), trimethylolethane tris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), bis(mercaptomethyl)sulfide, bis(mercaptomethyl)dis ... sulfide, bis(mercaptoethyl) sulfide, bis(mercaptoethyl) disulfide, bis(mercaptopropyl) sulfide, bis(mercaptopropyl) disulfide, 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol, 4,8 (or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 2,5-dimercaptomethyl-1,4-dithiane, and 2,5-bis[(2-mercaptoethyl)thiomethyl]-1,4-dithiane, 1-(1'-mercaptoethylthio) -2,3-dimercaptopropane, 1-(2'-mercaptopropylthio)-2,3-dimercaptopropane, 1-(3'-mercaptopropylthio)-2,3-dimercaptopropane, 1-(4'-mercaptobutylthio)-2,3-dimercaptopropane, 1-(5'-mercapentylthio)-2,3-dimercaptopropane, 1-(6'-mercaptohexylthio)-2,3-dimercaptopropane, 1,2-bis-(4'-mercaptobutylthio)-3-mercaptopropane, 1,2-bis-(5'-mercaptopentylthio)-3-mercaptopropane, 1, 2-bis-(6'-mercaptohexylthio)-3-mercaptopropane, 1,2,3-tris(mercaptomethylthio)propane, 1,2,3-tris-(3'-mercaptopropylthio)propane, 1,2,3-tris-(2'-mercaptoethylthio)propane, 1,2,3-tris-(4'-mercaptobutylthio)propane, 1,2,3-tris-(6'-mercaptohexylthio)propane, methanedithiol, 1,2-ethanedithiol, 1,1-propanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 2,Aliphatic polythiols such as 2-propanedithiol, 1,6-hexanethiol-1,2,3-propanetrithiol, and 1,2-bis(2'-mercaptoethylthio)-3-mercaptopropane may be mentioned. Further examples of polythiols are shown in the formula below or can be found in WO 2014 / 133111, EP 394495, U.S. Pat. No. 4,775,733, or EP 1,877,839: [ka]

[0040] In one embodiment of the present invention, the polythiol monomers include pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(thioglycolate), tris(3-mercaptopropionate)trimethylolpropane, tris(mercaptoacetate)trimethylolpropane, and thiol monomers represented by formulas (II) and (III): [ka] is a compound of

[0041] Preferred embodiments include a combination of xylylene diisocyanate and pentaerythritol tetrakis(3-mercaptopropionate); a combination of xylylene diisocyanate and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol; a combination of 2,5 (or 2,6)-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, a combination of pentaerythritol tetrakis(3-mercaptopropionate) and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol; a combination of xylylene diisocyanate and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol; A combination of an isocyanate and 4,8 (or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane; a combination of dicyclohexylmethane diisocyanate and 4,8 (or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane; or a combination of bis(2,3-epithiopropyl)disulfide and 4,8 (or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane. The most preferred polythiol is 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol of formula (II).

[0042] Preferably, the polythiol has a viscosity of 1 Pa.s or less at 25°C, more preferably 5.10 Pa.s or less. -1 Pa.s or less, more preferably 2.5.10 -1 Pa.s or less, more preferably 2.10 -1 Pa.s or less, more preferably 10 -1 Pa.s or less, and more preferably 0.5.10 -1 Pa.s or less.

[0043] Specific examples of polythiourethane resins suitable for the present invention are those commercially available from Mitsui Chemicals, Inc. under the MR® series, in particular MR6®, MR7® (refractive index: 1.67), MR8 (refractive index: 1.6) resin, and MR10® (refractive index: 1.67). These optical materials and the monomers used in their preparation are described, inter alia, in U.S. Pat. Nos. 4,689,387, 4,775,733, 5,059,673, 5,087,758, and 5,191,055.

[0044] Depending on the embodiment of the present invention, components A and B are prepared by polymerizing a mixture of the required amounts of at least one polyisocyanate and / or at least one polyisothiocyanate monomer, at least one polythiol monomer, and optional polyol or polyamine monomers. Typically, components A and B can be prepared by conventional thermal polymerization, such as induction heating and infrared heating, or UV irradiation.

[0045] The amounts of polyisocyanate monomers or polyisothiocyanate monomers and polythiol monomers in the reaction medium are preferably adjusted in each case so that, for the preparation of polythiourethane prepolymer A1, the molar ratio of NCX / SH groups of the polyisocyanate monomers or mixtures of polyisothiocyanate monomers and polythiol monomers is in the range of 3:1 to 30:1, preferably in the range of 6:1 to 10:1, and / or, for the preparation of polythiourethane prepolymer B1, the molar ratio of SH / NCX groups of the polyisocyanate monomers or mixtures of polyisothiocyanate monomers and polythiol monomers is in the range of 3:1 to 30:1, preferably in the range of 6:1 to 10:1, where X is O or S.

[0046] In one embodiment, both components A and B are prepared without a catalyst system, which allows for better control of the polymerization reaction and results in a prepolymer that is stable over time. However, components A and B may also be prepared using a salt catalyst, as described below, or another catalyst, as described below.

[0047] Generally, in a first embodiment of the present invention, the at least one polyisocyanate or polyisothiocyanate monomer A2 of component A and the prepolymer B1 are contained in the mixture in amounts such that the molar ratio of NCX groups to SH groups is between 0.8 and 1.2, preferably 1.

[0048] Generally, in the second embodiment of the present invention, the prepolymer A1 and the at least one polythiol monomer B2 of component B are contained in the mixture in amounts such that the molar ratio of NCX groups to SH groups is between 0.8 and 1.2, preferably 1.

[0049] The preparation of prepolymer B1 having thiol end groups has already been described in US Patent No. 5,908,876. A similar process can be used to prepare component B of the present invention.

[0050] When component A of the present invention comprises a polythiourethane prepolymer A1, it can be prepared in a similar manner, but using the required ratio of polyisocyanate or polyisothiocyanate monomers to polythiol monomers to obtain a polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups.

[0051] The polythiol / polyiso(thio)cyanate mixture used to obtain prepolymer A1 may contain up to 90% by weight of at least one polyol. Preferably, the mixture may contain up to 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% by weight of at least one polyol. Also preferably, no polyol is used. By polyiso(thio)cyanate is meant polyisocyanate or polyisothiocyanate.

[0052] The polythiol / polyiso(thio)cyanate mixture used to obtain prepolymer B1 may contain up to 90% by weight of at least one polyol. Preferably, the mixture may contain up to 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% by weight of at least one polyol. Also preferably, no polyol is used.

[0053] The mixture of components A and B according to the present invention may also contain additives conventionally employed in polymerizable compositions intended for the molding of optical articles, in particular ophthalmic lenses, namely inhibitors, dyes, photochromic agents, UV absorbers, fragrances, deodorants, antioxidants, resin modifiers, color balancing agents, chain extenders, crosslinkers, free radical scavengers such as antioxidants or hindered amine light stabilizers (HALS), dyes, pigments, fillers, adhesion promoters, anti-yellowing agents, and mold release agents in conventional proportions.

[0054] In one embodiment, the additive is added to the first component A before mixing with the second component B.

[0055] UV absorbers are often incorporated into optical articles (particularly ophthalmic lens materials) to reduce or prevent UV light from reaching the retina. The UV absorbers that can be used in the present invention preferably have the ability to at least partially block light with wavelengths shorter than 400 nm, but may also have an absorption spectrum extending into the visible blue light range of the electromagnetic spectrum (400-450 nm), particularly 420-450 nm.

[0056] The UV absorber not only protects the user's eyes from UV light but also protects the substrate material itself, thereby preventing the substrate from becoming brittle and / or yellowing due to weathering. The UV absorber according to the present invention may be, but is not limited to, a benzophenone-based compound, a benzotriazole-based compound, or a dibenzoylmethane-based compound, and preferably a benzotriazole-based compound. Suitable UV absorbers include, but are not limited to, 2-(2-hydroxyphenyl)-benzotriazoles such as 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole (Seesorb® 703 / Tinuvin® 326) or other arylhydroxymethylphenylchlorobenzotriazoles, 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol (Viosorb® 550), n-octyl-3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate (Eversorb® 109), 2-(2-hydroxy-5-methoxyphenyl)benzotriazole, 2-(2-hydroxy-5-butoxyphenyl)benzotriazole, and BASF's Tinuvin® CarboProtect®. Preferred absorbers are the benzotriazole family. Other examples of benzotriazole UV absorbers that protect against blue light can be found in WO 2017 / 137372.

[0057] The amount of UV absorber compound according to the present invention used herein is sufficient to provide adequate protection from UV light, but not excessive to prevent precipitation. The UV absorber compound according to the present invention is generally present in an amount ranging from 0.05 to 4 wt. %, preferably from 0.1 to 3 wt. %, more preferably from 0.1 to 2 wt. %, based on the total weight of the optical material (or per 100 parts by weight of the polymerizable compound present in the mixture of components A and B, or based on the weight of the optical material composition).

[0058] Among the release agents that can be used in the present invention, mention may be made of mono- and di-alkyl phosphates, alkyl ester phosphates, silicones, fluorinated hydrocarbons, fatty acids, and ammonium salts. Preferred release agents are mono- and di-alkyl phosphates, alkyl ester phosphates, and mixtures thereof. Such release agents are particularly disclosed in U.S. Pat. No. 4,975,328 and European Patent No. 271,839. The release agent is preferably used in an amount of 1% by weight or less, based on the total weight of the polymerizable compounds present in the mixture of components A and B.

[0059] The polymerizable mixture of the present invention may include a solvent to facilitate dissolution of the salt catalyst. In one embodiment, the curing step 4) is carried out in the presence of at least one solvent for the salt catalyst, preferably 2-mercaptoethanol.

[0060] Any polar organic solvent may be used, such as acetonitrile, tetrahydrofuran, dioxane, ethanol, 2-mercaptoethanol, acetone, and 3-methyl-2-buten-1-ol. The amount of solvent is generally kept below 2 wt. % based on the total weight of the polymerizable compounds present in the mixture of components A and B, preferably 0-0.5 wt. % to avoid haze and foaming. In one embodiment, the catalyst is used in the form of a solution of a compound such as 2-mercaptoethanol.

[0061] In the present invention, at least one salt catalyst may be used in the process before the curing step 4). In one embodiment, the mixture obtained in step 3) comprises at least one salt catalyst.

[0062] The salt catalyst is a system for promoting the polymerization reaction, and is used in the polymerizable composition in an amount sufficient to promote polymerization of the mixture, i.e., in an amount ranging from 0.015% to 0.15% by weight, preferably from 0.0425% to 0.102% by weight, based on the total weight of the polymerizable compounds present in the mixture of the first and second components A and B.

[0063] Particularly when the prepolymer B1 is combined with a polyisocyanate or polyisothiocyanate monomer A2, an excessively small amount of catalyst should be avoided to prevent the generation of bubbles which may result from thermal convection occurring during polymerization.

[0064] Excessively large amounts of catalyst should also be avoided, especially when prepolymer A1 is combined with polythiol monomer B2, to prevent premature gelling of the polymerizable mixture before it is introduced into the mold.

[0065] In a first embodiment of the method, in which first component A is composed of at least one polyisocyanate or polyisothiocyanate monomer A2 and second component B comprises a thiol-terminated polythiourethane prepolymer B1, the at least one salt catalyst is preferably present in an amount ranging from 0.03% to 0.15% or from 0.034% to 0.102% by weight, more preferably from 0.0595% to 0.102% by weight, based on the total weight of polymerizable compounds present in the mixture of first and second components A and B. In one embodiment, the amount is in the range of 0.0595% to 0.15% by weight, based on the total weight of polymerizable compounds present in the mixture of first and second components A and B.

[0066] In a second embodiment of the method, in which the first component A is composed of a polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups and the second component B is composed of at least one polythiol monomer B2, the at least one salt catalyst is preferably present in an amount ranging from 0.015% to 0.0765% by weight, more preferably from 0.017% to 0.068% by weight, and even more preferably from 0.0425% to 0.068% by weight, based on the total weight of the polymerizable compounds present in the mixture of the first and second components A and B.

[0067] The use of the present salt catalyst is advantageous because other catalysts used in similar amounts as the present process, such as amine (e.g., lutidine) or tin-based catalysts, result in runaway reactions, undesirable pre-gelation of the polymerizable mixture, and / or materials with deteriorated optical and thermomechanical properties. The salt catalysts of the present invention can be used in larger amounts without runaway reactions of pre-gelation, allowing for better control of the reaction without increasing cure times.

[0068] The salt catalyst may be added at various stages of the process.

[0069] In one embodiment, a salt catalyst is added to the polythiol monomer B2 or to the thiol-terminated polythiourethane prepolymer B1, depending on the situation, during the preparation of component B. In other words, at least one salt catalyst is added to the second component B prior to step 4). In another embodiment, at least one salt catalyst is added to the first component A prior to step 4).

[0070] In one embodiment, the salt catalyst is added to the first component A obtained in step 1) or 1') before mixing with component B, or to the second component B obtained in step 2) or 2') before mixing with component A. In this embodiment, the salt catalyst may be added to the prepolymers A1 and / or B1, as the case may be, after their preparation.

[0071] In another preferred embodiment, a salt catalyst is added to the mixture of components A and B in step 3) of the process.

[0072] In one embodiment, the salt catalyst is represented by the formula

number

[0073] In this application, pKa is preferably expressed at 25° C. pKa can be measured in water at standard pressure by potentiometric (pH) titration using a glass electrode and a pH meter.

[0074] The preferred metal cation of the salt is Li + , Na + , K. + , Cs + , Mg 2+ , Ca 2+ , Mn 2+ , Ag + , Ba 2+ , and Al 3+A particularly preferred metal cation is Li because it is colorless and soluble in the composition. + , Na + , and K + Transition metals are less preferred because their salts can result in colored compositions, and thus colored polymerized resins. In one embodiment, the method of the present invention does not use a tin-containing catalyst.

[0075] Preferred NR + In the fourth group, R is a C1 to C8 alkyl group, more preferably a methyl group, an ethyl group, a propyl group, a butyl group, or a hexyl group.

[0076] Preferably, Y q- is the corresponding acid YH (q-1)- satisfies the condition 0.5≦pKa≦10, more preferably 0.5≦pKa≦8.

[0077] Preferably, the anion Y q- is an anion of thiocyanate, carboxylate, thiocarboxylate, acetylacetonate, diketone, acetoacetate, malonate, cyanoacetate, ketonitrile, malononitrile, and a compound of formula RS - wherein R is a substituted or unsubstituted alkyl group preferably having 1 to 10 carbon atoms, or an aryl group preferably having 6 to 12 carbon atoms.

[0078] Preferred anion Y q- is the SCN - , acetylacetonate, acetate, thioacetate, formate, and benzoate. A preferred salt catalyst is KSCN.

[0079] Among the additional catalysts that can be used in the process of the invention, mention may also be made of amines, such as tertiary amines (e.g., triethylamine or 3,5-lutidine), organometallic compounds, such as alkyltins or alkyltin oxides, in particular dibutyltin dilaurate, dibutyltin dichloride, and dimethyltin dichloride. Several catalysts can be combined in the process.

[0080] In a preferred embodiment, the method of the present invention does not use any catalyst that is not a salt catalyst.

[0081] In particular, when the reactivity of the thiol and / or iso(thio)cyanate contained in the polymerizable composition is insufficient, an electron donor compound may also be used in combination with the salt catalyst. Generally, the electron donor compound stabilizes the cation of the salt catalyst. Therefore, the electron donor compound contributes to dissociating the anion / cation ion pair, thereby increasing the anion reactivity in the polymerization medium and thus accelerating the polymerization reaction.

[0082] The electron donor compound is preferably selected from acetonitrile compounds, such as malononitrile, amides, amines, imines, phosphines, sulfones, sulfoxides, trialkyl phosphites, triaryl phosphites, ethylene glycol ethers, crown ethers, and cryptands. Preferred electron donor compounds are crown ethers, cryptands, trialkyl phosphites, triaryl phosphites, alkylene glycols, and alkylene glycol ethers, and the most preferred is 18-crown-6.

[0083] In one embodiment, the curing step 4) is carried out in the presence of at least one electron donor compound.

[0084] Examples of acetonitrile compounds are: [ka] In the formula, R is an alkyl group, preferably a C1 to C6 alkyl group, for example, methyl, ethyl, propyl, or butyl.

[0085] The amide compounds can be primary, secondary, or tertiary amide compounds. Trialkyl phosphites and triaryl phosphites have the formula: [ka] where R, R', and R''' are either alkyl groups (preferably C1-C6 alkyl groups) or aryl groups (e.g., phenyl groups) preferably having 6 to 12 carbon atoms. Preferred is a trialkyl phosphite, for example (C2H5O)3P.

[0086] The electron donor compound may also be selected from crown ethers and cryptands.

[0087] These cyclic molecules are usually selected to have a good compromise between the size of the heteroatom or metal and the "cage" size, i.e., a good compromise between the number and size of the heteroatoms and the "cage" size, i.e., a good compromise between the number of heteroatoms and the size of the ring.

[0088] Preferred crown ethers and cryptands are of the formula: [ka] wherein X 1 represents O, S, or NH, x1 is an integer of 3 to 6, preferably an integer of 3 to 4, and n1 is 2 or 3; X 2 , X 3 , and X4 represent O or S; n2, n3, n4, y2, y3, and y4 are 2 or 3; and x2, x3, and x4 are 2 or 3.

[0089] Among the preferred crown ethers and cryptands are the following compounds: [ka] may be mentioned.

[0090] Examples of preferred crown ethers are 18-crown-6, 18-crown-7, 15-crown-5, and 15-crown-6.

[0091] The electron donor compound is preferably present in an amount ranging from 0 to 5% by weight, preferably from 0 to 1% by weight, more preferably from 0.06% to 0.6% by weight, and even more preferably from 0.17% to 0.408% by weight, based on the total weight of the polymerizable compounds present in the mixture of components A and B.

[0092] The weight ratio of salt catalyst / electron donor compound, when the latter is present, is preferably in the range of 1 / 3 to 1 / 5.

[0093] The mixing of the first component A and the second component B in step 3) can be carried out by any known mixing technique, such as that mentioned in U.S. Pat. No. 5,973,098. Preferably, the components A and B to be mixed are placed in a small reactor chamber and then mixed with a screw mixer. In one embodiment, the viscosity of the mixture of components A and B at 25° C. is in the range of 0.01 Pa.s to 5 Pa.s, preferably in the range of 0.05 Pa.s to 0.5 Pa.s, and even more preferably in the range of 0.1 Pa.s to 0.3 Pa.s.

[0094] During step 3), the molding cavity of the casting mold assembly is filled with a mixture of the first component A and the second component B.

[0095] A cast mold assembly generally includes two mold parts that define two molding surfaces that cooperate to form a mold cavity when moved from an open position to a closed position. Each molding surface can be concave, convex, or planar, depending on the desired article shape. The molding surfaces can be convex, for example, to form a concave substrate surface, or concave, for example, to form a convex substrate surface.

[0096] More specifically, the optical material composition can be poured into the cavities of two mold parts that are held together using an annular fastener such as a gasket or adhesive tape.

[0097] An annular fastener member may be disposed around and attached to the two mold pieces. The conventional method for filling such two-piece molds is by allowing the (liquid) optical material composition to flow into the mold cavity through a pouring opening provided for this purpose in the closure member. In at least partially automated processes, the mold cavity to be filled is vertically aligned with a filling device adapted to deliver a specific amount of molding material through a nozzle.

[0098] Depending on the desired properties of the resulting optical material, the optical material composition may be degassed under reduced pressure and / or filtered under pressure or reduced pressure before being poured into the mold assembly. After the composition is poured, the casting mold assembly, preferably a lens casting mold assembly, may be heated in an oven or a heating device immersed in water according to a predetermined temperature program to cure the resin in the mold assembly. The resin molded article may be annealed, if necessary.

[0099] Step 4) of curing the mixture to obtain a transparent polythiourethane-based substrate is carried out in the presence of at least one salt catalyst and can be carried out using any known polymerization technique, in particular thermal polymerization, including induction heating and infrared heating, or radiation polymerization. The curing time of step 4) is preferably less than 10 hours or less than 5 hours, more preferably less than 4 hours, less than 3 hours, or less than 2 hours.

[0100] In step 5) of the method, the polythiourethane-based transparent substrate is recovered from the mold.

[0101] The method can be used to produce a finished lens where both sides are of the required geometry, or to produce a semi-finished lens where one side still needs to be surfaced to the required geometry.

[0102] The article obtained from this method has satisfactory color properties, which can be quantified by the yellowness index Yi. The whiteness of the optical material of the present invention can be quantified, for example, by colorimetric measurement based on the CIE tristimulus values ​​X, Y, and Z as described in standard ASTM E313 with Illuminant C observer 2°. The optical material according to the present invention preferably has a low yellowness index Yi, i.e., a yellowness index YI of less than 10, more preferably less than 8, and even more preferably less than 6, when measured according to the above standard. The yellowness index Yi is calculated according to ASTM method E313 according to the relationship Yi=(127.69X-105.92Z) / Y, where X, Y, and Z are the CIE tristimulus values.

[0103] The substrate according to the present invention preferably has a colorimetric coefficient b* (transmittance) as defined by the CIE (1976) L*a*b* International Colorimetric Designation of less than or equal to 10, 5, 4, 2, or 1, and generally greater than or equal to 0. A low colorimetric coefficient b* may correlate with a limited or no yellow appearance (transmitted color). Indeed, a positive value on the b* axis indicates an amount of yellow, while a negative value indicates an amount of blue.

[0104] The following examples illustrate the invention in a more detailed but non-limiting manner. Unless otherwise specified, all thicknesses disclosed in this application relate to physical thickness. [Example]

[0105] Chemicals used Optical materials were prepared from compositions containing polymerizable monomers, Zelec UN® (CAS 3896-11-5) as a mold release agent, and a catalyst solution containing KSCN (CAS 333-20-0), 18-crown-6 (CAS 17455-13-9), and mercaptoethanol (CAS 60-24-2). The monomers used in this example to produce a polythiourethane transparent matrix with a refractive index of 1.67 were xylylene diisocyanate (CAS 3634-83-1) and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol (CAS 131538-00-6). The monomers were used as received without any treatment to remove moisture.

[0106] In Comparative Examples 3 to 10, dimethyltin dichloride was used as the comparative catalyst.

[0107] Evaluation of the cured lens The following test procedures were used to evaluate optical articles made in accordance with the present invention: Several samples for each system were prepared for measurement, and the reported data was calculated using an average of the various samples.

[0108] The critical temperature of the article was measured 24 hours after its preparation in the manner set out in WO 2008 / 001011 for measuring critical temperature, except that the relative humidity was above 90% rather than 50%, typically 100%.

[0109] The mechanical properties of the lenses are evaluated by DMA (Dynamic Mechanical Analysis): the modulus of elasticity E (or Young's modulus, or storage modulus, or tensile modulus) makes it possible to evaluate the ability of a material to deform under the influence of an applied force.

[0110] Examples 1 to 13, Comparative Examples 1 to 10 Preparation of polythiourethane prepolymer A1 with isocyanate end groups A reactor equipped with a heat probe and agitator was charged with a predetermined amount of polyisocyanate monomer m-xylylene diisocyanate (XDI) and heated to 120°C. 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol was then introduced and mixed with the polyisocyanate in an amount that resulted in a molar ratio of isocyanate functional groups to thiol functional groups of NCO / SH of 8:1 (89.7% polyisocyanate, 10.3% polythiol). The mixture was heated at 120°C for 3.5 hours. The resulting prepolymer A1 was then cooled to approximately 35°C, transferred to a suitable drum, and stored in a cold room. Prepolymer A1 was prepared without the use of a catalyst.

[0111] Preparation of polythiourethane prepolymer B1 with thiol end groups A reactor equipped with a heat probe and agitator was charged with a predetermined amount of polythiol monomer 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol and heated to 95°C. Xylylene diisocyanate was then introduced and mixed with the polythiol in an amount to achieve a final molar ratio of thiol functional groups to isocyanate functional groups SH / NCO of 8:1. This mixture was heated at 95°C for 3.5 hours. The resulting prepolymer B1 was then cooled to approximately 35°C, transferred to a suitable drum, and stored in a cold room. Prepolymer B1 was prepared without the use of a catalyst.

[0112] Preparation of transparent polythiourethane casting substrates The convex and concave molds were assembled using tape. The center thickness was 2 mm. Prepolymers A1 and B1 were prepared as described above.

[0113] In Examples 1-7, a predetermined amount of cooled prepolymer A1 was mixed with a predetermined amount of Zelec UN®. The mixture was stirred at 15°C, degassed for 1 hour, and then degassed for 15 minutes without stirring to form Component A. In parallel, a predetermined amount of polythiol monomer 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol B2 was mixed with 0.2-0.8 wt. % of the above-mentioned catalyst solution (8.5 wt. % KSCN, 34.84 wt. % 18-crown 6, 56.66 wt. % 2-mercaptoethanol). The mixture was stirred at 15°C, degassed for 1 hour, and then degassed for 15 minutes without stirring to form Component B.

[0114] Components A and B were then mixed in a small reactor with a molar ratio of SH:NCO adjusted to 1:1, simultaneously stirred and degassed for 5 minutes at 15° C., and then further degassed without stirring for 2 minutes at 15° C. to prevent gelation. After completion of mixing, it was filled into a mold assembly with the aid of a syringe and filter.

[0115] The assembled mold was held at room temperature for 10 minutes and then placed in a preheated convection oven at 120°C. The mixture began to gel in the mold assembly at room temperature. The polymerization reaction was carried out by leaving the mold assembly in the oven at 120°C for 3 hours. The mold assembly was then allowed to cool to 65°C.

[0116] In the context of the present invention, gel refers to a reaction product of components A and B in which the conversion of reactive functional groups is significantly high, for example, in the range of 50-80%, preferably about 70%.

[0117] The mold assembly was then disassembled to yield a lens with a center thickness of 2 mm comprising a body of polythiourethane transparent thermoset substrate, which was annealed at 120° C. for 1 hour after disassembly. The lens had a refractive index of 1.67 and was free of optical defects such as striations.

[0118] Comparative Examples 3 to 6 were carried out in the same manner as Examples 1 to 7, except that the catalyst dimethyltin dichloride was used instead of KSCN.

[0119] In Examples 8-13, the protocol was the same except that a predetermined amount of polyisocyanate monomer m-xylylene diisocyanate A2 was mixed with a predetermined amount of Zelec UN®. The mixture was stirred at 15°C, degassed for 1 hour, and degassed for 15 minutes without stirring to form Component A. In parallel, a predetermined amount of prepolymer B1 was mixed with 0.4-1.2 wt. % of the above-mentioned catalyst solution (8.5 wt. % KSCN, 34.84 wt. % 18-crown 6, 56.66 wt. % 2-mercaptoethanol). The mixture was stirred at 15°C, degassed for 1 hour, and degassed for 15 minutes without stirring to form Component B.

[0120] Comparative Examples 7 to 10 were carried out in the same manner as Examples 8 to 13, except that the catalyst dimethyltin dichloride was used instead of KSCN.

[0121] In Comparative Examples 1-2, the protocol was the same except that a predetermined amount of polyisocyanate monomer m-xylylene diisocyanate A2 was mixed with a predetermined amount of Zelec UN®. The mixture was stirred at 15°C, degassed for 1 hour, and degassed for 15 minutes without stirring to form Component A. In parallel, a predetermined amount of polythiol monomer 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol B2 was mixed with 0.3-0.4 wt. % of the above-mentioned catalyst solution (8.5 wt. % KSCN, 34.84 wt. % 18-crown 6, 56.66 wt. % 2-mercaptoethanol). The mixture was stirred at 15°C, degassed for 1 hour, and degassed for 15 minutes without stirring to form Component B.

[0122] Composition and Results The amount of catalyst used and the characterization results are shown in Table 1. Castings were replicated and the data are the average of at least three tests.

[0123] [Table 1]

[0124] [Table 2]

[0125] After a perfectly controlled polymerization reaction, lenses without any optical defects were obtained.

[0126] It can be observed that increasing catalyst concentration tends to increase the glass transition temperature of the resulting lens.

[0127] Results from dynamic mechanical analysis and differential scanning calorimetry indicate that the storage modulus (E) and glass transition temperature (Tg) of the product were essentially unaffected by changing the process from polyisocyanate monomer or polyisothiocyanate monomer A2 combined with thiol-terminated polythiourethane prepolymer B1 to a process combining isocyanate-terminated or isothiocyanate-terminated polythiourethane prepolymer A1 with polythiol monomer B2.

[0128] Advantageously, no air bubble problems were observed with the prepolymer system according to the invention.

[0129] In Comparative Examples 3-10, where the catalyst dimethyltin dichloride was used instead of KSCN, undesirable premature gelation occurred; the mixtures solidified during mixing, before filling, or upon filling into the molds at similar catalyst contents. Therefore, thermomechanical property measurements were not possible. In Examples 1-13, the mixtures did not begin to gel before being transferred to the molds, demonstrating the advantages of using the salt catalyst of the present invention over other catalysts, such as tin-based catalysts, at the same catalyst concentration.

Claims

1. 1. A method for curing a polythiourethane-based transparent cast optical lens substrate, comprising the steps of: 1), 2), 3), 4), and 5), or 1′), 2′), 3), 4), and 5): 1) providing a first component A comprising at least one polyisocyanate or polyisothiocyanate monomer A2; 2) preparing a second component B comprising a polythiourethane prepolymer B1 having thiol end groups, said prepolymer B1 being prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer; or 1') preparing a first component A comprising a polythiourethane prepolymer A1 having isocyanate or isothiocyanate end groups of formula -NCX, where X is O or S, said prepolymer A1 being prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer; 2') providing a second component B comprising at least one polythiol monomer B2; 3) mixing the first and second components A and B together and filling the resulting polymerizable mixture into the molding cavity of the casting mold assembly; 4) curing the polymerizable mixture to obtain a polythiourethane-based transparent substrate; and 5) Recovering the polythiourethane-based transparent substrate from the casting mold assembly. Including, The curing step 4) is carried out in the presence of at least one salt catalyst in an amount ranging from 0.015% to 0.15% by weight relative to the total weight of the polymerizable compounds present in the mixture of the first and second components A and B; method.

2. The salt catalyst has the formula [Equation 1] wherein M ｐ＋ is an alkali metal cation, an alkaline earth metal cation, a transition metal cation, and a cation of the formula NR ４ ＋ wherein R is an alkyl group preferably having 1 to 10 carbon atoms, and Y ｑ－ is an anion, so that the corresponding acid YH （ｑ－１）－ 2. The method of claim 1, wherein m, n, p, and q are integers such that n*q=m*p.

3. The method of claim 2 , wherein q=1.

4. The cation M ｐ＋ Li ＋ , Na ＋ , K. ＋ , Cs ＋ , Mg ２＋ , Ca ２＋ , Mn ２＋ , Ag ＋ , Ba ２＋ , and Al ３＋ The method of claim 2 or 3, wherein the compound is selected from the group consisting of:

5. The anion Y ｑ－ is an anion of thiocyanate, carboxylate, thiocarboxylate, acetylacetonate, diketone, acetoacetate, malonate, cyanoacetate, ketonitrile, malononitrile, and anions of the formula RS － 5. The method of any one of claims 2 to 4, wherein R is a substituted or unsubstituted alkyl group, preferably having 1 to 10 carbon atoms, or an aryl group, preferably having 6 to 12 carbon atoms.

6. The method of any one of claims 1 to 5, wherein the salt catalyst is KSCN.

7. 7. The method according to any one of claims 1 to 6, wherein the at least one salt catalyst is present in an amount ranging from 0.0425 wt. % to 0.102 wt. %, based on the total weight of the polymerizable compounds present in the mixture of the first and second components A and B.

8. 8. The method according to any one of claims 1 to 7, wherein the curing step 4) is carried out in the presence of at least one electron donor compound selected from the group consisting of trialkyl phosphites, triaryl phosphites, alkylene glycols, alkylene glycol ethers, crown ethers, and cryptands, preferably in the presence of 18-crown-6.

9. The method according to any one of claims 1 to 8, wherein the curing step 4) is carried out in the presence of at least one solvent for said salt catalyst, preferably in the presence of 2-mercaptoethanol.

10. The method according to any one of claims 1 to 9, wherein the curing time of step 4) is less than 10 hours, preferably less than 5 hours.

11. The method according to any one of claims 1 to 10, wherein the amounts of the polyisocyanate monomer or polyisothiocyanate monomer and the polythiol monomer are adjusted so that the molar ratio of NCX / SH groups in the mixture of the polyisocyanate monomer or polyisothiocyanate monomer and the polythiol monomer is in the range of 3:1 to 30:1 for the preparation of the polythiourethane prepolymer A1, and / or the amounts of the polyisocyanate monomer or polyisothiocyanate monomer and the polythiol monomer are adjusted so that the molar ratio of SH / NCX groups in the mixture of the polyisocyanate monomer or polyisothiocyanate monomer and the polythiol monomer is in the range of 3:1 to 30:1 for the preparation of the polythiourethane prepolymer B1, and X is O or S.

12. The polythiol monomer has the formula: R １ (SH) ｎ１ (I) wherein n1 represents an integer ranging from 2 to 6; R １ The method of any one of claims 1 to 11, wherein represents an aliphatic group, an alicyclic group, a heterocyclic group, or an aromatic group.

13. The polythiol monomers include pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(thioglycolate), tris(3-mercaptopropionate)trimethylolpropane, tris(mercaptoacetate)trimethylolpropane, and thiol monomers of formulas (II) and (III): 【Chemical 1】 The method of any one of claims 1 to 12, wherein the compound is selected from the group consisting of:

14. The polyisocyanate or polyisothiocyanate monomers have the formula (VI): R ２ (NCX) ｎ２ (VI) wherein X represents O or S, n2 represents an integer ranging from 2 to 6, and R ２ The method of any one of claims 1 to 13, wherein represents an aliphatic group, an alicyclic group, a heterocyclic group, or an aromatic group.

15. The polyisocyanate monomer or polyisothiocyanate monomer may be toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, paraphenylene diisocyanate, xylylene diisocyanate, biphenyl-diisocyanate, 3,3'-dimethyl-4,4'-diphenylene diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, 2,2,4-trimethylhexane-1,6-diisocyanate, lysine methyl ester diisocyanate, bis(isocyanatoethyl) fumarate, isophorone diisocyanate, ethylene diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexamethyl 15. The method of any one of claims 1 to 14, wherein the isocyanate is selected from the group consisting of hexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene-2,4-diisocyanate, tetramethylxylylene diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrophenylene-1,3-diisocyanate, hexahydrophenylene-1,4-diisocyanate, perhydrodiphenylmethane-2,4'-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate, 2,5-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, and 2,6-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane.

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