Method for curing polythiourethane substrates from prepolymers

Abstract

The present invention relates to a method for curing a polythiourethane transparent casting substrate, comprising the steps of: providing a first component A comprising a polythiourethane prepolymer having iso(thio)cyanate end groups, wherein the prepolymer is prepared from at least one polythiol monomer and at least one polyiso(thio)cyanate monomer, used in an amount adapted such that the molar ratio R2 of NCX groups to SH groups is in the range of 2 to 35; providing a second component B comprising at least one polythiol monomer; mixing the first and second components A and B together and filling the resulting polymerizable mixture into a molding cavity; and the weight The present invention relates to a method comprising the steps of curing a composite mixture to obtain a polythiourethane transparent substrate, wherein the prepolymer is prepared by mixing at least one polyiso(thio)cyanate monomer and at least one polythiol monomer in initial amounts such that the initial molar ratio R1 of the NCX groups / SH groups of the monomers is in the range of 0.3R2 to 0.95R2; polymerizing the mixture; and adding an additional amount of at least one polyiso(thio)cyanate monomer to the mixture such that the molar ratio of the NCX groups / SH groups of all monomers used in the preparation of the prepolymer is equal to R2, where X is O or S.

Description

[Technical Field]

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

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

[0003] International Publication No. 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 crown ether).

[0004] The rapid curing process is highly desirable over conventional processes because it dramatically improves productivity due to shorter residence times in the curing oven, allows for better yield of complex and demanding lens shapes due to lower shrinkage of the final polymerizable mixture compared to mixtures obtained directly from monomers, offers better compatibility with adhesives for tapes used in mold assembly, and reduces energy consumption during the polymerization cycle.

[0005] It is known that replacing monomers with prepolymers (or oligomers) at least partially shortens the curing time required for polymerizable compositions poured into a template assembly. The monomer 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 poured into a template assembly to undergo 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 transparent castable polythiourethane substrate, and this method is 1) A step of providing a first component A comprising an isocyanate or a polythiourethane prepolymer having an isocyanate terminal group, 2) A step of providing a second component B comprising a polythiourethane prepolymer having thiol-terminated groups, 3) Mix the first and second components A and B together, and fill the resulting mixture into the molding cavity of the casting mold assembly. 4) In order to significantly reduce the curing time of the polymerizable composition, typically to within 2 hours, the mixture is cured in the presence of a highly reactive catalyst in an amount of 0.001 to 2.5% by weight, based on the total weight of the polymerizable monomers, to obtain a transparent solid substrate. Includes.

[0007] U.S. Patent Application Publication No. 2007 / 098999 discloses a similar process involving two types of prepolymers.

[0008] If viscosity is controlled, some of the available bond-forming energy is already released during oligomer formation (prepolymerization), limiting the formation of localized hot spots in the final polymerizable mixture. Therefore, batch mixing of such mixtures is inherently safer than the usual process from monomers. Using prepolymers allows for stable and uniform reactions.

[0009] In WO 2021 / 182526 pamphlet, EP 3916470 specification, and EP 3919967 specification, another approach for rapidly curing polythiourethane optical materials is selected, which combines the use of monomers and prepolymers in the presence of a polymerization catalyst.

[0010] A prepolymer is obtained from a variable ratio blend of at least two monomers reacted to obtain an oligomer, specifically, from a small amount of a given monomer in an excess of other monomers. To prepare a prepolymer, prior art processes involve directly blending the total amounts of two monomers and subjecting the entire mixture to a heat treatment to enable the formation of the prepolymer.

[0011] Despite the above advantages associated with the use of prepolymers, their production is time-consuming and costly because large heating tanks are required to process the amount of material necessary to meet production needs.

[0012] Therefore, an alternative polymerization method for thiourethane resins will be needed. It would be advantageous to reduce the amount of material undergoing the prepolymerization process. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [[ID=​​​​​​​​

[0015] The inventors have found that the method of producing the intermediate prepolymer affects the properties of the final polymer. The inventors have discovered that modifying the preparation process of a polythiourethane prepolymer having isocyanate or isothiocyanate-terminated groups by first blending a small amount of monomer (polythiol) with a portion of the main monomer (polyisocyanate or polyisothiocyanate), second subjecting this mixture to thermal polymerization to enable oligomer formation, and third diluting this concentrated mixture with the remaining portion of the main monomer, surprisingly results in an improvement in the thermal properties of the final cast polythiourethane polymer.

[0016] The present invention provides a method for rapidly curing a polythiourethane-based transparent casting substrate usable in the manufacture 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) A step of providing a first component A comprising a polythiourethane prepolymer A1 having an isocyanate or isothiocyanate terminal group of formula -NCX (wherein X is O or S), wherein the prepolymer A1 is prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, the monomer is used in an amount adapted such that its NCX group / SH group molar ratio R2 is in the range of 2:1 to 35:1, preferably 3:1 to 35:1, and X is O or S. 2) A step of providing a second component B comprising at least one polythiol monomer B2, A step of providing a second component B comprising a polythiourethane prepolymer B1 having a 2') thiol-terminated group, wherein the prepolymer B1 is prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer. 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) The step of curing the polymerizable mixture to obtain a polythiourethane transparent substrate, and 5) Step of recovering the polythiourethane transparent substrate from the casting mold assembly. The prepolymer A1 includes, a) A step of mixing the at least one polyisocyanate or polyisothiocyanate monomer and the at least one polythiol monomer in an initial amount such that the initial molar ratio R1 of the NCX group / SH group (where X is O or S) of the monomer in the mixture obtained from step a) is in the range of 0.3R2 to 0.95R2, b) A step of polymerizing the mixture obtained from step a), The present invention provides a method for preparing prepolymer A1 by adding an additional amount of at least one polyisocyanate or polyisothiocyanate monomer to the mixture obtained from step b) such that the molar ratio of NCX groups / SH groups (where X is O or S) of all monomers used in the preparation of prepolymer A1 is equal to R2.

[0017] The aforementioned and other objects, features, and advantages of the present invention will be readily apparent to those skilled in the art when considered in conjunction with the accompanying drawings and by reading the following detailed description. [Brief explanation of the drawing]

[0018] [Figure 1] The graph shows the glass transition temperature of the polythiourethane substrate as a function of the amount of urethidion byproducts formed for various lenses prepared in the experimental section. [Modes for carrying out the invention]

[0019] The substrate of the present invention is an organic glass substrate manufactured from a thermosetting resin. In some embodiments, the polymer matrix of the substrate is obtained from a material composition ("substrate composition") comprising at least one polymerizable prepolymer and at least two polymerizable prepolymers.

[0020] This substrate is preferably an optical article substrate, and more preferably an optical lens substrate. This optical article is preferably an eye lens, such as a plastic spectacle lens.

[0021] In this specification, unless otherwise specified, a substrate is understood to be transparent if the observation of an image through the substrate is perceived without a significant loss of contrast. That is, it is understood to be transparent if the formation of an image through the substrate is obtained without adversely affecting the quality of the image. This definition of the term "transparent" may apply to all objects as described herein unless otherwise specified.

[0022] The term “ocular lenses” is used to mean lenses adapted to eyeglass frames for the purpose of protecting the eye and / or correcting vision. The lenses may be selected from afocal, monofocal, bifocal, trifocal, progressive, Fresnel lenses, or any other type of lens having discontinuities. While ocular optics are a preferred area of ​​the present invention, it will be understood that the present invention may also be applied to other types of optical elements, such as lenses for optical instruments, particularly filters for photography or astronomy, optical aiming lenses, ocular visors, optics for illumination systems, screens, and plate glass.

[0023] If the optical article is an optical lens, it may have one or more functional coatings on the front principal surface, the rear principal surface, or both sides. As used herein, the rear surface of the substrate is intended to mean the surface closest to the wearer's eye when the article is in use. This is usually a concave surface. In contrast, the front surface of the substrate is the surface furthest from the wearer's eye when the article is in use. This is usually a convex surface. The optical article may also be a plano article or a biplano article.

[0024] In the context of this invention, the substrate should be understood as an uncoated substrate, generally having two main surfaces. The substrate may, in particular, be an optically transparent material having the shape of an optical article, such as an eye lens mounted on glass. In this context, the term “substrate” is understood as meaning the base component material of an optical lens, more specifically an eye lens. This material may function as a support for one or more coatings or stacks of layers.

[0025] The refractive index of the polythiourethane substrate is preferably 1.52 or higher, more preferably 1.54 or higher, more preferably 1.56 or higher, more preferably 1.58 or higher, more preferably 1.60 or higher, even more preferably 1.65 or higher or 1.67 or higher, preferably 1.80 or lower, more preferably 1.70 or lower, and even more preferably 1.67 or lower. Unless otherwise specified, the refractive index referred to in this application is expressed at a wavelength of 550 nm at 25°C.

[0026] The rapidly curing polymerizable composition that yields polythiourethane-based materials is composed of two main components.

[0027] A first component A, comprising a polythiourethane prepolymer A1 having an isocyanate or isothiocyanate end group, is provided in step 1), which is prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, the latter of which is used in excess. Thus, the first component A comprises an oligomer and an unpolymerized initial monomer (if present).

[0028] In the first embodiment of this method, the second component B provided in step 2) is composed of at least one polythiol monomer B2.

[0029] In a second embodiment of the present method, the second component B provided in step 2') comprises at least one polythiourethane prepolymer B1 having a thiol-terminated group, the prepolymer B1 being prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, the former being used in excess. Thus, the second component B comprises an oligomer and an unpolymerized initial monomer (if present).

[0030] In contrast to conventional processes that use only iso(thio)cyanate monomers or thiol monomers, the present invention uses at least one polythiourethane prepolymer.

[0031] A prepolymer refers to a polymer or oligomer that contains a prepolymer molecule. A prepolymer molecule is a polymer or oligomer molecule that can undergo further polymerization via a reactive (polymerizable) group, thereby providing multiple monomer units to at least one chain of the final polymer. Prepolymer molecules are generally formed from two or more different monomers.

[0032] Polythiourethane prepolymer A1 having isocyanate or isothiocyanate-terminated groups is prepared by a multi-step process which will be described in detail later. This is obtained by reacting at least one polyisocyanate or polyisothiocyanate monomer with at least one polythiol monomer in a ratio such that the molar ratio R2 of isocyanate or isothiocyanate groups to thiol groups NCX / SH (where X is O or S) of the monomers is in the range of 2:1 to 35:1, preferably 3:1 to 35:1, preferably without a catalyst, and preferably at a temperature in the range of 50°C to 150°C.

[0033] When used in this method, the polythiourethane prepolymer B1 having thiol-terminated groups is prepared by reacting at least one polyisocyanate or polyisothiocyanate monomer with at least one polythiol monomer in a ratio such that the molar ratio R'2 of thiol groups to isocyanate or isothiocyanate groups SH / NCX (where X is O or S) is preferably in the range of 3:1 to 35:1, preferably without the presence of a catalyst.

[0034] In one embodiment, the polythiourethane prepolymer B1 having thiol-terminated groups, when used in this method, is prepared by directly blending the total amount of two monomers (at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer) and heat-treating the entire mixture to enable the formation of the prepolymer. As described separately, in this embodiment, the polythiourethane prepolymer B1 having thiol-terminated groups, when used in this method, is prepared by directly mixing at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer in a desired R'2 ratio.

[0035] Polythiol compounds and polyisocyanates or polyisothiocyanate compounds used in the preparation of polythiourethane prepolymers A1 or B1 are considered monomers in this specification, even if they are oligomers.

[0036] Polyisocyanate refers to any compound containing at least two isocyanate groups, in other words, diisocyanate, triisocyanate, 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.

[0037] Polyisocyanates may be selected from aliphatic, aromatic, alicyclic, or heterocyclic polyisocyanates, and mixtures thereof.

[0038] Polyisothiocyanates are defined in the same way as the polyisocyanates described above by replacing the "isocyanate" group with another "isothiocyanate" group.

[0039] In one embodiment of the present invention, the polyisocyanate or polyisothiocyanate monomer is of formula (VI): R 2 (NCX) n2 (VI) It is a compound in which X represents O or S, n² represents an integer in the range of 2 to 6, and R 2 This represents an aliphatic group, alicyclic group, heterocyclic group, or aromatic group.

[0040] Preferred polyisocyanate monomers or isothiocyanate monomers are those of the formula: [ka] It has the following characteristics: In the formula, R 1 These are independently H or a C1-C5 alkyl group, preferably CH3 or C2H5. R 2This is H, a 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 in the range of 1 to 4, b is an integer in the range of 2 to 4, and a + b ≤ 6, and x is an integer between 1 and 10, preferably between 1 and 6.

[0041] The polyisocyanate of the present invention is preferably a diisocyanate. Among the available diisocyanates, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, paraphenylenediisocyanate, xylylenediisocyanate, biphenyl-diisocyanate, 3,3'-dimethyl-4,4'-diphenylenediisocyanate, 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 Examples include annetes, 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.

[0042] Other non-limiting examples of polyisocyanates are isocyanurates derived 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 International Publication No. 98 / 37115, International Publication No. 2014 / 133111, or European Patent No. 1877839.

[0043] The polythiols that can be used in the present invention are defined as compounds containing at least two sulfhydryl (mercapto) groups, in other words, dithiols, trithiols, tetrathiols, etc. Polythiol prepolymers can be used. The polythiol may be any suitable polythiol having two or more, preferably two or three thiol functional groups. The polythiol can be used for the preparation of polythiourethane prepolymer A1 or B1, but it can also be used directly as compound B2 in component B in step 2) of this method.

[0044] In one embodiment of the present invention, the polythiol monomer is of the formula: R 1 (SH) n1 (I) It is a compound in which n1 represents an integer in the range of 2 to 6, and R 1 This represents an aliphatic group, alicyclic group, heterocyclic group, or aromatic group.

[0045] Among preferred polythiol monomers and / or oligomers suitable for the present invention, trimethylolpropanetris(2-mercaptoacetate), trimethylolpropanetris(3-mercaptopropionate), trimethylolethanetris(2-mercaptoacetate), trimethylolethanetris(3-mercaptopropionate), pentaerythritoltetrakis(2-mercaptoacetate), pentaerythritoltetrakis(3-mercaptopropionate), bis(mercaptomethyl)sulfide, bis(mercaptomethyl)di Sulfide, bis(mercaptoethyl)sulfide, bis(mercaptoethyl)disulfide, bis(mercaptopropyl)sulfide, bis(mercaptopropyl)disulfide, 2,3-bis((2-mercaptoethyl)thio)-1-propanethol, 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'-mercappropylthio)-2,3-dimercaptopropane, 1-(3'-mercappropylthio)-2,3-dimercaptopropane, 1-(4'-mercapbutylthio)-2,3-dimercaptopropane, 1-(5'-mercapentylthio)-2,3-dimercaptopropane, 1-(6'-mercahexylthio)-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 can be cited. Further examples of polythiols are shown in the following formula or can be found in International Publication No. 2014 / 133111, European Patent No. 394495, U.S. Patent No. 4775733, or European Patent No. 1877839. [ka]

[0046] In one embodiment of the present invention, the polythiol monomer is pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(thioglycolate), tris(3-mercaptopropionate)trimethylolpropane, tris(mercaptoacetate)trimethylolpropane, and formulas (II) and (III): [ka] It is selected from the group consisting of the following compounds.

[0047] Preferred embodiments include combinations of xylylene diisocyanate and pentaerythritol tetrakis(3-mercaptopropionate); combinations of xylylene diisocyanate and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol; combinations of 2,5(or 2,6)-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, pentaerythritol tetrakis(3-mercaptopropionate) and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol; combinations of xylylene diisocyanate and 4,8(or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane; combinations of dicyclohexylmethane diisocyanate and 4,8(or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane; or combinations 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).

[0048] In one embodiment, the polythiol has a viscosity at 25 °C of 1 Pa·s or less, more preferably 5×10 -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 1×10 -1 Pa·s or less, even more preferably 0.5×10 -1 Pa·s or less.

[0049] Specific examples of polythiourethane resins suitable for the present invention are those commercially available from Mitsui Chemicals, Inc. as the MR® series, particularly 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 in particular in U.S. Patent Nos. 4,689,387, 4,775,733, 5059,673, 5087,758, and 5191,055.

[0050] Depending on the embodiment of the present invention, components A and B are prepared by polymerizing a mixture of at least one polyisocyanate and / or at least one polyisothiocyanate monomer, at least one polythiol monomer, and an optional polyol monomer or polyamine monomer. Typically, components A and B can be prepared by induction heating and conventional thermal polymerization such as infrared heating or UV irradiation.

[0051] The total amount of polyisocyanate or polyisothiocyanate monomer and polythiol monomer in the reaction medium is preferably adapted such that, in each case, the molar ratio R2 of NCX groups / SH groups of the mixture of polyisocyanate or polyisothiocyanate monomer and polythiol monomer is in the range of 2:1 to 35:1, preferably 3:1 to 30:1, more preferably 5:1 to 10:1 or 6:1 to 10:1, and even more preferably 6:1 to 9:1 or 7:1 to 9:1 for the preparation of polythiourethane prepolymer A1. A preferred R2 ratio is about 8:1.

[0052] The amounts of polyisocyanate or polyisothiocyanate monomer and polythiol monomer in the reaction medium are preferably adapted so that the molar ratio of SH groups to NCX groups of the mixture of polyisocyanate or polyisothiocyanate monomer and polythiol monomer is in the range of 3:1 to 35:1, preferably 3:1 to 30:1, more preferably 6:1 to 10:1, when such a prepolymer is used for the preparation of polythiourethane prepolymer B1, where X is O or S.

[0053] In one embodiment, both components A and B are prepared without the use of a catalyst system, which allows for better control of the polymerization reaction and yields a prepolymer with high time stability. However, at least one or both of them can also be prepared using a catalyst, as described below.

[0054] Generally, the first and second components A and B are included in the polymerizable mixture of step 3) in amounts such that the molar ratio of NCX groups to SH groups is in the range of 0.8 to 1.2, preferably 0.9 to 1.1, and more preferably about 1. This molar ratio of the reactive groups can be calculated from the amount of starting material used to prepare the polythiourethane substrate.

[0055] The preparation of prepolymer B1 having thiol-terminated groups has already been described in U.S. Patent No. 5,908,876 or U.S. Patent Application Publication No. 2003 / 125410. Component B of the present invention can be prepared using a similar process.

[0056] Here, we will describe the preparation of polythiourethane prepolymer A1 having isocyanate or isothiocyanate terminal groups.

[0057] According to this method, the prepolymer A1 is a) A step of mixing the at least one polyisocyanate or polyisothiocyanate monomer and the at least one polythiol monomer in an initial amount such that the initial molar ratio R1 of the NCX group / SH group (where X is O or S) of the monomer in the mixture obtained from step a) is in the range of 0.3R2 to 0.95R2, b) A step of polymerizing the mixture obtained from step a), c) Adding an additional amount of at least one polyisocyanate or polyisothiocyanate monomer to the mixture obtained from step b) such that the molar ratio of NCX groups / SH groups (where X is O or S) of all monomers used in the preparation of the prepolymer A1 is equal to R2. It is prepared by [method].

[0058] The at least one polyisocyanate or polyisothiocyanate monomer used in step a) is preferably the same as the at least one polyisocyanate or polyisothiocyanate monomer used in step c).

[0059] In the conventional process, prepolymer A1 is directly prepared by mixing at least one polyisocyanate or polyisothiocyanate monomer with at least one polythiol monomer in a desired R2 ratio.

[0060] According to this method, prepolymer A1 is prepared by first mixing at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer at a specific starting molar ratio R1 of isocyanate / isothiocyanate functional group to thiol functional group (NCX / SH, where X is O or S) lower than the desired final molar ratio R2, and then diluting the prepolymer by adding the remainder of at least one polyisocyanate or polyisothiocyanate monomer to obtain the final NCX / SH (where X is O or S) ratio R2.

[0061] Therefore, the mixture obtained from step c) of this method is a mixture comprising the prepolymer A1 itself and an additional amount of at least one polyisocyanate or polyisothiocyanate monomer.

[0062] Surprisingly, the glass transition temperature of the final polymer material is higher when using the prepolymer A1 manufacturing process according to the present invention than when using the conventional process in which the prepolymer A1 components are directly mixed. The gap between the two processes in terms of the difference in glass transition temperature is highest when the molar ratio R1 of major monomer to trace monomer is lowest in the mixture undergoing prepolymerization (oligomerization) step b).

[0063] The method according to the present invention exhibits several other advantages. Limiting the volume subjected to the heating process during polymerization step b) is more attractive because it requires smaller equipment and less energy. Furthermore, if heat-sensitive additive molecules such as dyes are used, their decomposition is limited by introducing them in step c) of this method.

[0064] While we do not wish to be bound by any theory, the inventors believe that the decrease in the glass transition temperature of the final polythiourethane polymer at a high initial NCX / SH R1 ratio, as in the prior art process, is due to the self-condensation of isocyanates or isothiocyanate monomers to form uretidione or thiouretidione dimer byproducts, and that this situation is advantageous compared to situations with a lower initial NCX / SH ratio.

[0065] In fact, thiourethane polycondensation involves the reaction of isocyanates with thiols. Depending on the conditions, side reactions such as the autoreaction of isocyanates may occur in addition to the main reaction. Cyclopolymerization of isocyanates can yield several species, but the most common is urethidione.

[0066] The formation of a significant amount of urethidion byproducts leads to an increase in the amount of unreacted thiol groups in the final polymer. The lower glass transition temperature of the materials of the prior art can be explained by the consumption of NCX groups by side reactions, and therefore the reduction in overall crosslinking, resulting in free unreacted thiol groups or shorter polymer chains remaining in the final product.

[0067] The side reaction forming an iso(thio)cyanate dimer during the preparation of prepolymer A1 is thought to occur to a greater extent when there is an excess of NCX groups compared to thiol groups, and therefore favorable for the formation of the self-reaction product, and to a lesser extent when the NCX / SH ratio is lower, because there are fewer NCX groups available for self-condensation. Formula R 1 The formation of urethidion byproducts starting from two isocyanate compounds of -NCO is illustrated below: [ka]

[0068] In this specification, by reducing the starting concentration of polyisocyanate / polyisothiocyanate monomers compared to polythiol monomers, more thiourethane bonds are formed, while fewer free iso(thio)cyanates are exposed to heat, reducing the likelihood of self-reaction to form byproducts and causing the presence of thiol residues in the final product.

[0069] In embodiments of the present invention, the initial molar ratio R1 of the NCX group / SH group is in the range of 0.3R2 to 0.8R2, 0.35R2 to 0.7R2, or 0.35R2 to 0.55R2. The R1 and R2 ratios are calculated by summing the amounts of polyisocyanate and polyisothiocyanate monomers when a mixture of such monomers is used. Preferably, polyisocyanate monomers are used.

[0070] The R1 ratio is preferably in the range of 2.4 to 7.6, more preferably 2.5 to 7.5, even more preferably 2.8 to 6, 2.8 to 5, or 2.8 to 4.4. In other embodiments, R1 is preferably in the range of 3 to 6, 3 to 5 (i.e., 3:1 to 5:1) or 3 to 4.4.

[0071] A polyisocyanate or polyisothiocyanate monomer in an amount too small compared to the amount of polythiol monomer (i.e., too low an R1 ratio) should be avoided during step a) of this method to prevent premature gelation of the mixture before it is introduced into the template.

[0072] In order to avoid obtaining a final polymer with a glass transition temperature that is too low, the amount of polyisocyanate or polyisothiocyanate monomer that is too high compared to the amount of polythiol monomer (i.e., too high an R1 ratio) should be avoided during step a) of this method.

[0073] The polythiol / polyiso(thio)cyanate mixture for obtaining prepolymer A1 may contain at least one polyol in an amount of 90% by weight or less. Preferably, the mixture may contain at least one polyol in an amount of 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, or 10% by weight or less. Similarly preferably, no polyol is used. Polyiso(thio)cyanate means polyisocyanate or polyisothiocyanate.

[0074] The polythiol / polyiso(thio)cyanate mixture for obtaining component B, or prepolymer B1, may contain at least one polyol in an amount of 90% by weight or less. Preferably, the mixture may contain at least one polyol in an amount of 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, or 10% by weight or less. Similarly preferably, no polyol is used.

[0075] The mixture of components A and B according to the present invention may also contain, in conventional proportions, additives conventionally used in polymerizable compositions for molding optical articles, particularly eye lenses, namely inhibitors, dyes, photochromic agents, UV absorbers, fragrances, deodorants, antioxidants, resin modifiers, color balance adjusters, chain extenders, crosslinking agents, free radical scavengers, such as antioxidants or hindered amine light stabilizers (HALS), dyes, pigments, fillers, adhesion promoters, anti-yellowing agents, and release agents.

[0076] In one embodiment, the additive is added to the first component A before being mixed with the second component B.

[0077] UV absorbers are often incorporated into optical articles (particularly in 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 to the visible blue light range of the electromagnetic spectrum (400-450 nm), particularly 420-450 nm.

[0078] The UV absorber protects the user's eyes from UV light and protects the substrate material itself, thereby preventing the substrate from weathering, becoming brittle, and / or yellowing. The UV absorber according to the present invention may be, but is not limited to, a benzophenone compound, a benzotriazole compound, or a dibenzoylmethane compound, preferably a benzotriazole compound. Suitable UV absorbers include, but are not limited to, 2-(2-hydroxyphenyl)-benzotriazole, such as 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole (Seesorb® 703 / Tinuvin® 326) or other allylhydroxymethylphenylchlorobenzotriazoles, 2-(5-chloro-2H-benzotriazole-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol (Viosorb® 550), n-octyl-3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazole-2-yl)phenyl]propionate (Eversorb® 109), 2-(2-hydroxy-5-methoxyphenyl)benzotriazole, 2-(2-hydroxy-5-butoxyphenyl)benzotriazole, and BASF's Tinuvin® CarboProtect®. The preferred absorbers are the benzotriazole class. Other examples of benzotriazole UV absorbers that protect against blue light can be found in International Publication No. 2017 / 137372.

[0079] The amount of the UV absorber compound according to the present invention used herein is sufficient to obtain 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 of 0.05 to 4% by weight, preferably 0.1 to 3% by weight, and more preferably 0.1 to 2% by weight, relative to 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 relative to the weight of the optical material composition).

[0080] Among the release agents that can be used in the present invention are mono and dialkyl phosphates, alkyl ester phosphates, silicones, fluorinated hydrocarbons, fatty acids, and ammonium salts. Preferred release agents are mono and dialkyl phosphates, alkyl ester phosphates, and mixtures thereof. Such release agents are disclosed in particular in U.S. Patent No. 4,975,328 and European Patent No. 0271,839. 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.

[0081] The polymerizable mixture of the present invention may contain a solvent, for example, a solvent to promote the dissolution of the catalyst, especially when the catalyst is in the form of a salt. In one embodiment, the curing step 4) is carried out in the presence of at least one solvent, preferably two mercaptoethanol, of the salt catalyst.

[0082] Any polar organic solvent can 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 to less than 2% by weight, preferably 0-0.5% by weight, based on the total weight of the polymerizable compounds present in the mixture of components A and B, in order 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.

[0083] In the present invention, at least one catalyst can be used to catalyze bond formation in the process prior to the curing step 4). In one embodiment, the mixture obtained in step 3) contains at least one catalyst.

[0084] A catalyst is a system for promoting a polymerization reaction. The catalyst may include one or more latent thermal catalysts.

[0085] The catalyst shall be used in the polymerizable composition in an effective amount, i.e., an amount sufficient to promote polymerization of the mixture. Typically, at least one catalyst is used in a proportion of 0.01 to 5% by weight, more preferably 0.02 to 2% by weight, relative to the total weight of the polymerizable compounds present in the mixture of components A and B. In particular, when prepolymer A1 is combined with polythiol monomer B2, too much catalyst should be avoided to prevent premature gelation of the polymerizable mixture before it is introduced into the template.

[0086] The catalyst can be added at various stages of this method.

[0087] In one embodiment, the catalyst is added to the polythiol monomer B2 during the preparation of component B, or to the polythiourethane prepolymer B1 having thiol-terminated groups, depending on the circumstances. In other words, at least one catalyst is added to the second component B before step 4). In another embodiment, at least one catalyst is added to the first component A before step 4). In a preferred embodiment, the catalyst is added to the polythiol monomer B2 during the preparation of component B, before mixing step 3).

[0088] In one embodiment, the catalyst is added to the first component A obtained in step 1) before being mixed with component B, or to the second component B obtained in step 2) or 2') before being mixed with component A. In this embodiment, the catalyst may, depending on the circumstances, be added to prepolymers A1 and / or B1 after the preparation of prepolymers A1 and / or B1.

[0089] In another preferred embodiment, the catalyst is added to the mixture of components A and B in step 3) of the present method.

[0090] In one embodiment, the catalyst is an anionic catalyst. Preferred catalysts are transition metal catalysts and ammonium salts of acids, which preferably satisfy the condition 0.5 ≤ pKa ≤ 14.

[0091] In this application, pKa is 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.

[0092] In one embodiment, the catalyst is of the formula

number

[0093] The preferred metal cation of the salt is Li + kaNa + , K + , Cs + Mg 2+ Ca 2+ Mn 2+ Ag + Ba 2+ and Al 3+ A particularly preferred metal cation is Li, since it is colorless and soluble in the composition. + kaNa + and K + Therefore, transition metals are less preferred because their salts may result in colored compositions and thus colored polymerized resins. In one embodiment, the method according to the present invention does not use a tin-containing catalyst.

[0094] Preferred NR + The four groups are such that R is a C1-C8 alkyl group, more preferably a methyl group, ethyl group, propyl group, butyl group, or hexyl group.

[0095] Preferably, Y- This is an anion such that the corresponding acid YH satisfies the condition 0.5 ≤ pKa ≤ 10, more preferably 0.5 ≤ pKa ≤ 8.

[0096] Preferably, anion Y - These include thiocyanates, carboxylate anions, thiocarboxylate anions, acetylacetonates, diketone anions, acetoacetates, malonic acid anions, cyanoacetates, ketonitrile anions, malononitrile anions, and formula RS - (wherein R is preferably a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or preferably an aryl group having 6 to 12 carbon atoms) selected from the group consisting of anions.

[0097] Preferred anion Y - SCN - These include acetylacetonate, acetate, thioacetate, formate, and benzoate. A preferred salt catalyst is KSCN.

[0098] Additional catalysts that may be used in the method of the present invention include amines, such as tertiary amines (e.g., triethylamine or 3,5-lutidine), organometallic compounds, such as alkyltin or alkyltin oxides, particularly dibutyltin dilaurate, dibutyltin dichloride, and dimethyltin dichloride. Several catalysts may be combined in this method.

[0099] In a preferred embodiment, the method according to the present invention does not use any catalyst other than a salt catalyst.

[0100] In particular, if the reactivity of the thiol and / or iso(thio)cyanate contained in the polymerizable composition is insufficient, an electron donor compound can also be used in combination with a catalyst, preferably a salt catalyst. Generally, electron donor compounds stabilize the cations of the salt catalyst. Therefore, electron donor compounds contribute to the dissociation of anion / cation ion pairs, thereby increasing the anionic reactivity in the polymerization medium and thus promoting the polymerization reaction.

[0101] The electron donor compound is preferably selected from acetonitrile compounds, for example, from malononitrile, amide, amine, imine, phosphine, sulfone, sulfoxide, trialkyl phosphite, triaryl phosphite, ethylene glycol ether, crown ether, and cryptand. Preferred electron donor compounds are crown ether, cryptand, trialkyl phosphite, triaryl phosphite, alkylene glycol, and alkylene glycol ether, with the most preferred being 18-crown-6.

[0102] In one embodiment, the curing step 4) is carried out in the presence of at least one electron-donating compound.

[0103] Examples of acetonitrile compounds are: [ka] In this formula, R is an alkyl group, preferably a C1-C6 alkyl group, such as methyl, ethyl, propyl, or butyl.

[0104] Amide compounds can be primary, secondary, or tertiary amide compounds. Trialkyl phosphites and triaryl phosphites have the formula: [ka] It can be represented by the formula, where R, R', and R''' are either an alkyl group (preferably a C1-C6 alkyl group) or an aryl group having 6 to 12 carbon atoms (e.g., a phenyl group). A trialkyl phosphite, for example (C2H5O)3P, is preferred.

[0105] The electron donor compound can also be selected from crown ethers and cryptands.

[0106] These cyclic molecules are typically selected to have a good balance between the size of the heteroatoms or metal and the size of the "cage." That is, they are selected to have a good balance between the number and size of the heteroatoms and the size of the "cage," and that is, they are selected to have a good balance between the number of heteroatoms and the size of the ring.

[0107] Preferred crown ethers and cryptands are given by the following formula: [ka] It can be expressed by, where X 1 x1 represents O, S, or NH, x1 is an integer between 3 and 6, preferably between 3 and 4, and n1 is 2 or 3. X 2 , X 3 X4 represents O and S, n2, n3, n4, y2, y3, y4 are 2 or 3, and x2, x3, x4 are 2 or 3.

[0108] Among preferred crown ethers and cryptondans, the following compounds: [ka] One could list these:

[0109] Preferred crown ethers include 18-crown-6, 18-crown-7, 15-crown-5, and 15-crown-6.

[0110] The electron donor compound is preferably present in an amount ranging from 0 to 5% by weight, preferably 0 to 1% by weight, more preferably 0.06% to 0.6% by weight, and even more preferably 0.17% to 0.408% by weight, relative to the total weight of polymerizable compounds present in the mixture of components A and B.

[0111] The weight ratio of the catalyst to the electron donor compound is preferably in the range of 1 / 3 to 1 / 5 when the latter is present.

[0112] 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 those referred to in U.S. Patent No. 5,973,098. Preferably, components A and B to be mixed are placed in a small reactor chamber and then mixed in 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 0.05 Pa.s to 0.5 Pa.s, and more preferably 0.1 Pa.s to 0.3 Pa.s.

[0113] 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.

[0114] A casting mold assembly generally includes two mold components that define two molding surfaces that cooperate to form a molding cavity when moved from an open position to a closed position. Each molding surface may be concave, convex, or planar, depending on the desired shape of the article. The molding surface may be convex, for example, to form a concave substrate surface, or concave, for example, to form a convex substrate surface.

[0115] More specifically, the optical material composition may be poured into the cavity of two mold components held together using annular fasteners such as gaskets or adhesive tape. Conventional molds typically consist of two pieces (referred to herein as components) made of mineral glass, with annular fastener members positioned around their periphery to define the required molding cavity.

[0116] Annular fastening members can be positioned around and attached to two mold pieces. A conventional method for filling such a two-piece mold is to inject a (liquid) optical material composition into the molding cavity through a casting opening provided for this purpose in the fastening member. In at least a partially automated process, the molding cavity to be filled is aligned perpendicularly with a filling device adapted to deliver a specific amount of molding material through a nozzle.

[0117] 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.

[0118] After pouring the composition, the resin inside the mold assembly can be cured by heating the casting mold assembly, preferably a lens casting mold assembly, in an oven or a heating device immersed in water according to a predetermined temperature program.

[0119] In one embodiment, the mixture of the first and second components A and B is maintained at room temperature (20-30°C) in the casting mold assembly until gelation occurs before initiating the curing step 4).

[0120] Step 4), which involves curing the mixture to obtain a polyurethane-based transparent substrate, may be carried out in the presence of at least one catalyst and may be carried out using any known polymerization technique, particularly thermal polymerization or radiation polymerization including induction heating and infrared heating. The curing time for 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. As used herein, curing refers to a chemical process of converting monomers or oligomers into polymers with a higher molar mass, and then into a network structure.

[0121] Curing is generally carried out at high temperatures in an oven, such as an air oven, to complete polymerization. This can be done at temperatures in the range of 50-150°C or 100-130°C. After that, the mold assembly is removed from the heat source, the annular fastener members are removed, and the mold components are disassembled.

[0122] Next, the resin molded product can be annealed, if necessary, preferably at a temperature in the range of 100°C to 150°C.

[0123] In step 5) of this method, the polythiourethane transparent substrate is recovered from the mold. The recovered substrate or article is then subjected to edge grinding to obtain a lens.

[0124] This method can be used to manufacture a finished lens in which both sides have the required geometric shape, or to manufacture a semi-finished lens in which one side still needs to be surface-treated to the required geometric shape.

[0125] Subsequently, the substrate or article may be colored or coated to improve various properties such as scratch resistance or reflective properties.

[0126] The present invention also relates to a polythiourethane transparent casting substrate obtained by the method described above. This can be distinguished from a polythiourethane transparent casting substrate obtained by the conventional method by its improved thermomechanical properties, particularly its higher glass transition temperature, as demonstrated in the experimental section.

[0127] Articles obtained by this method have satisfactory color characteristics that can be quantified by a yellowness index Yi. The whiteness of the optical material of the present invention can be quantified by colorimetric measurement based on CIE tristimulus values ​​X, Y, and Z as described in standard ASTM E313 by luminescent material observer C2°, for example. Optical articles according to the present invention preferably have a low yellowness index Yi when measured according to the above standard, i.e., a yellowness index YI of less than 10, more preferably less than 8, and even more preferably less than 6. The yellowness index Yi is calculated by ASTM method E313 with the relation Yi = (127.69X - 105.92Z) / Y (wherein X, Y, and Z are CIE tristimulus values).

[0128] The substrate according to the present invention preferably has a colorimetric coefficient b* (transmittance) defined in the CIE (1976) L*a*b* International Color System that is 10, 5, 4, 2, or 1 or less, and is generally 0 or greater. A low colorimetric coefficient b* may correlate with an appearance (transmitted color) that is limited to yellow or not yellow at all. In fact, a positive value on the b* axis indicates the amount of yellow, while a negative value indicates the amount of blue.

[0129] The following embodiments illustrate the present invention in a more detailed but non-limiting manner. Unless otherwise specified, all thicknesses disclosed in this application refer to physical thicknesses. [Examples]

[0130] 1. Chemical substances used The optical material was prepared from a composition comprising polymerizable monomers and a catalyst solution containing Zelec UN® (CAS 3896-11-5) as a release agent, 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-propantheol (CAS 131538-00-6). The monomers were used as received without any treatment to remove moisture.

[0131] 2. Evaluation of polymerizable composition and cured lens The compositions and optical articles prepared according to the invention were evaluated using the following test procedure. Several samples were prepared for measurement for each system, and the data to be reported was calculated using the average of various samples.

[0132] The glass transition temperature (Tg) of the lens was evaluated by DMA (dynamic mechanical analysis) and DSC (differential scanning calorimetry).

[0133] Viscosity was measured using a viscometer (Brookfield Cone&Plate viscometer, Model CAP 2000+L).

[0134] The infrared transmission spectrum under perpendicular incidence was obtained using a Nicolet iS50 FTIR spectrometer instrument at 4 cm. -1 Depending on the resolution, it ranges from 500 to 4000 cm. -1 Measurements were taken within the specified range. The urethidione parameter was calculated based on the spectrum of the final polythiourethane substrate obtained from FTIR (Fourier Transform Infrared Spectroscopy) using the following formula:

number

[0135] Transmittance (%T) corresponding to the resonance frequency of the urethidione functional group u ) 1785cm -1 And, assigned to the CH2 bond (including the CH2 bond of the thiol monomer) is 2920 cm². -1 Peak at (%T c The normalization signal was used. A higher urethidion parameter indicates lower urethidion transmittance, and therefore more urethidion bonds are present (higher urethidion parameter). Uretidion is a byproduct, and a low urethidion parameter is desired.

[0136] 3. Preparation of polythiourethane prepolymer A1 having isocyanate-terminated groups for Examples 1-5 and Comparative Example 1 A predetermined amount of m-xylylene diisocyanate (XDI), a polyisocyanate monomer, was added to a reactor equipped with a thermal probe and a stirrer, and heated to 120°C. Then, 2,3-bis((2-mercaptoethyl)thio)-1-propanechiol was introduced and mixed with the polyisocyanate in an amount such that the "initial" molar ratio of isocyanate functional groups to thiol functional groups NCO / SH was equal to R1 (process step a). R1 ​​ranged from 2:1 (Comparative Example 1) to 7:1 (Example 5), as shown in Table 1.

[0137] The mixture was heated at 120°C for 3.5 hours, then cooled to room temperature. To this mixture, an additional predetermined amount (see Table 1) of the polyisocyanate monomer m-xylylene diisocyanate (XDI) was added so that the "final" molar ratio (R2) of isocyanate functional groups to thiol functional groups NCO / SH of the monomer used in this process was equal to 8:1 (process step c)). The resulting prepolymer A1 was then transferred to a suitable drum and stored in a cold room. Prepolymer A1 was prepared without the use of a catalyst.

[0138] 4. Preparation of polythiourethane prepolymer A1 having isocyanate-terminated groups for Comparative Example 2 A predetermined amount of the polyisocyanate monomer, m-xylylene diisocyanate (XDI), was added to a reactor equipped with a thermal probe and a stirrer, and heated to 120°C. Next, 2,3-bis((2-mercaptoethyl)thio)-1-propanechiol was introduced and mixed with the polyisocyanate in an amount such that the molar ratio of isocyanate functional groups to thiol functional groups (NCO / SH) was 8:1 (89.66 wt% polyisocyanate, 10.34 wt% polythiol). This 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.

[0139] 5. Preparation of transparent polythiourethane casting substrate Convex and concave biplano molds were assembled using tape. The thickness of the center was 2 mm.

[0140] In all examples and comparative examples, a predetermined amount of the cooled prepolymer A1 prepared as described above was mixed with a predetermined amount of Zelec UN®. This mixture was stirred at 5-15°C, degassed for 1 hour, and then degassed for 15 minutes without stirring to form component A. In parallel, a predetermined amount of the polythiol monomer 2,3-bis((2-mercaptoethyl)thio)-1-propantheol B2 was mixed with a predetermined amount of the catalyst solution described above (8.5% by weight KSCN, 34.84% by weight 18-crown-6, 56.66% by weight 2-mercaptoethanol). This mixture was stirred at 5-15°C, degassed for 1 hour, and then degassed for 15 minutes without stirring to form component B.

[0141] Next, in a small reactor, components A and B were mixed at 15°C for 5 minutes with stirring and degassing, adjusting the molar ratio of SH:NCO to 1:1. Then, without stirring, degassing was performed for another 2 minutes at 15°C to prevent gelation. After mixing was complete, the mixture was packed into the mold assembly through a filter with the help of a syringe. The mixture contained 58 parts by weight of the starting material of component A, 42 parts by weight of monomer B2, 0.4 parts by weight of the catalyst solution, and 0.16 parts by weight of Zelec UN®.

[0142] The assembled mold was held at room temperature for 10 minutes, then placed in a convection oven preheated to 120°C. The mixture of the example began to gel within the mold assembly at room temperature. The polymerization reaction was carried out by leaving the mold assembly in the oven at 120°C for 2 hours.

[0143] In relation to the present invention, "gel" refers to the reaction product of components A and B, which have a remarkably high conversion rate of reactive functional groups. For example, the conversion rate is in the range of 50 to 80%, and preferably about 70%.

[0144] Next, the mold assembly was disassembled to obtain a lens with a central thickness of 2 mm, containing a body made of a transparent thermosetting polythiourethane substrate. This lens was then annealed at 120°C for 1 hour after disassembly. The lens had a refractive index of 1.67 and was free from optical defects such as striations.

[0145] 6. Composition and Results The ratios of monomers used and the characterization results are shown in Table 1. The percentages shown for the monomers used are weight percentages compared to the total weight of monomers used in the preparation of prepolymer A1 having isocyanate end groups. Casting was repeated, and the data are the average of at least three tests.

[0146] [Table 1]

[0147] After a perfectly controlled polymerization reaction, a lens free of any optical defects was obtained.

[0148] Surprisingly, although the same total amounts of thiol and isocyanate monomers were used in all examples and comparative examples, the glass transition temperature (Tg) was affected by the initial NCO / SH molar ratio R1 during the preparation of prepolymer A1.

[0149] Increasing the initial R1 molar ratio of NCO groups / SH groups tends to lower the glass transition temperature of the resulting polythiourethane substrate and increase the amount of uretidione byproducts formed. As shown in Figure 1, the glass transition temperature of the final material increases as the amount of uretidione byproducts formed decreases.

[0150] Furthermore, in Comparative Example 1 (low R1 ratio of 2), where too little polyisocyanate monomer was used compared to the amount of polythiol monomer, undesirable premature gelation occurred, and the mixture solidified during polymerization step b). Consequently, measurement of viscosity and thermomechanical properties was impossible. In Examples 1-5, the mixture did not begin gelling before being transferred to the mold.

[0151] Therefore, the novel method proposed by the present inventors for preparing prepolymer A1 having isocyanate or isothiocyanate-terminated groups makes it possible to improve the thermal properties of the resulting polythiourethane substrate compared to the conventional method shown in Comparative Example 2.

Claims

1. A method for curing a polythiourethane transparent casting substrate, comprising the following steps 1), 2), 3), 4), and 5), or 1), 2'), 3), 4), and 5): 1) A step of providing a first component A comprising a polythiourethane prepolymer A1 having an isocyanate or isothiocyanate-terminated group of formula -NCX (wherein X is O or S), wherein the prepolymer A1 is prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, the monomer is used in an amount adapted such that its molar ratio R2 of NCX group / SH group is in the range of 2:1 to 35:1, and X is O or S. 2) A step of providing a second component B comprising at least one polythiol monomer B2, or 2') A step of providing a second component B comprising a polythiourethane prepolymer B1 having a thiol-terminated group, wherein the prepolymer B1 is prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer. 3) Mix the first and second components A and B together, and fill the resulting polymerizable mixture into the molding cavity of the casting mold assembly. 4) The step of curing the polymerizable mixture to obtain a polythiourethane transparent substrate, and 5) Step of recovering the polythiourethane transparent substrate from the casting mold assembly. The prepolymer A1 includes, a) A step of mixing the at least one polyisocyanate or polyisothiocyanate monomer and the at least one polythiol monomer in an initial amount such that the initial molar ratio R1 of the NCX group / SH group (where X is O or S) of the monomer in the mixture obtained from step a) is in the range of 0.3R2 to 0.95R2, b) A step of polymerizing the mixture obtained from step a), c) Adding an additional amount of at least one polyisocyanate or polyisothiocyanate monomer to the mixture obtained from step b) such that the molar ratio of NCX groups / SH groups (where X is O or S) of all monomers used in the preparation of the prepolymer A1 is equal to R2. A method prepared by [the specified method].

2. The method according to claim 1, wherein the molar ratio R2 of the NCX group / SH group is in the range of 5:1 to 10:1, preferably 6:1 to 9:

1.

3. The method according to claim 1 or 2, wherein the initial molar ratio R1 of the NCX group / SH group is in the range of 0.35R2 to 0.55R2.

4. The method according to any one of claims 1 to 3, wherein the first and second components A and B are included in the polymerizable mixture of step 3) in an amount such that the molar ratio of the NCX group to the SH group (where X is O or S) is in the range of 0.8 to 1.2, preferably 0.9 to 1.

1.

5. The method according to any one of claims 1 to 4, wherein the curing step 4) is carried out in the presence of at least one catalyst.

6. The method according to any one of claims 1 to 5, wherein the at least one catalyst is added to the second component B before step 4) or to the first component A before step 4).

7. The catalyst is, [Math 1] It is a salt compound of In the formula, M ｐ＋ These include alkali metal cations, alkaline earth metal cations, transition metal cations and formula NR ４ ＋ Y is a cation with a valence p selected from the group consisting of ammonium groups (wherein R is preferably an alkyl group having 1 to 10 carbon atoms), and － The method according to claim 5 or 6, wherein the corresponding acid YH is an anion having a pKa that satisfies the condition 0.5 ≤ pKa ≤ 14, and m, n, and p are integers such that n = m × p.

8. The method according to any one of claims 1 to 7, wherein the curing time in step 4) is less than 10 hours, preferably less than 5 hours.

9. The aforementioned polythiol monomer has the formula: R １ (SH) ｎ１ (I) The compound is such that n1 represents an integer in the range of 2 to 6, and R １ The method according to any one of claims 1 to 8, wherein is an aliphatic group, an alicyclic group, a heterocyclic group, or an aromatic group.

10. The aforementioned polythiol monomers are pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(thioglycolate), tris(3-mercaptopropionate)trimethylolpropane, tris(mercaptoacetate)trimethylolpropane, and formulas (II) and (III): 【Chemistry 1】 The method according to any one of claims 1 to 9, selected from the group consisting of the compounds.

11. The polyisocyanate or polyisothiocyanate monomer is of formula (VI): R ２ (NCX) ｎ２ (VI) It is a compound in which X represents O or S, n² represents an integer in the range of 2 to 6, and R ２ The method according to any one of claims 1 to 10, wherein is an aliphatic group, an alicyclic group, a heterocyclic group, or an aromatic group.

12. The aforementioned polyisocyanates or polyisothiocyanate monomers include toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, paraphenylenediisocyanate, xylylenediisocyanate, biphenyl-diisocyanate, 3,3'-dimethyl-4,4'-diphenylenediisocyanate, 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, cyclohexane- The method according to any one of claims 1 to 11, selected from the group consisting of 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.

13. Step 2 below): 2) A step of providing a second component B comprising at least one type of polythiol monomer B2. A method according to any one of claims 1 to 12, including the method described in any one of claims 1 to 12.

14. The method according to any one of claims 1 to 13, wherein the substrate is an optical lens substrate.

15. A polythiourethane-based transparent casting substrate obtained by the method described in any one of claims 1 to 14.

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