METHOD FOR CURING A POLYTHIOURETHANE-BASED SUBSTRATE FROM A PREPOLYMER

Abstract

The invention relates to a method of curing a polythiourethane-based transparent casted substrate, comprising the steps of providing a first component A comprising a polythiourethane pre-polymer having iso(thio)cyanate end groups, said pre-polymer having been prepared from at least one polythiol monomer and at least one polyiso(thio)cyanate monomer, used in amounts adapted so that the molar ratio R2 of NCX / SH groups ranges from 2 to 35, providing a second component B comprising at least one polythiol monomer, mixing together first and second components A and B and filling a molding cavity with the resulting polymerizable mixture, curing said polymerizable mixture to obtain a polythiourethane-based transparent substrate, wherein said pre-polymer has been prepared by mixing said at least one polyiso(thio)cyanate monomer and said at least one polythiol monomer in initial amounts such that the initial molar ratio R1 of NCX / SH groups for said monomers ranges from 0.3 R2 to 0.95 R2, polymerizing the mixture, and adding to the mixture an additional amount of at least one polyiso(thio)cyanate monomer such that the molar ratio of NCX / SH groups for all the monomers used in the preparation of said pre- polymer is equal to R2, X being O or S.

Description

1 / 33 “METHOD FOR CURING A POLYTHIOURETHANE-BASED SUBSTRATE FROM A PRE-POLYMER”

[0001] The present invention relates to a process for manufacturing polythiourethane-based substrates, and in particular optical substrates, such as ophthalmic lenses, generally having a medium or high refractive index, preferably of at least 1.52, more preferably of at least 1.54, more preferably of at least 1.6 and even more preferably of at least 1.67, within short curing cycles. BACKGROUND AND SUMMARY OF THE INVENTION

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

[0003] Application WO 00 / 26272 discloses a polymerizable composition for manufacturing 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] A fast curing process is highly desirable compared to the usual process, as the shorter residence time in the curing oven allows for a dramatic gain in productivity, complex and demanding lens geometries can be obtained with better yield, as the final shrinkage of the polymerizable mixture is less than that of the mixture obtained directly from monomers, compatibility with the tape adhesive used for the mold assembly is better, and energy consumption during polymerization cycles is reduced.

[0005] It is known that the partial replacement of monomers with prepolymers (or oligomers) reduces the time required to cure the polymerizable composition poured into mold sets. The monomers are first pre-reacted to form oligomers (prepolymers), then mixed with a catalyst that Petition 870250081874, dated 11 / 09 / 2025, page 12 / 54 2 / 33 provides high overall reactivity in very small volumes or even through in-line mixing equipment, and then poured into mold sets where they undergo a short polymerization cycle, typically of a few hours.

[0006] In this regard, US 2003 / 125410 discloses a method for the rapid curing of transparent molten polythiourethane substrate, which comprises the following steps: 1) To provide a first component A comprising a polythiourethane prepolymer having isocyanate or isothiocyanate end groups, 2) To provide a second component B comprising a polythiourethane prepolymer having thiol end groups, 3) Mix the first and second components A and B and fill a molding cavity of a casting mold assembly with the resulting mixture, and 4) Cure the aforementioned mixture to obtain a transparent solid substrate in the presence of 0.001 to 2.5% by weight, based on the total weight of the polymerizable monomers, of a highly reactive catalyst to drastically shorten the curing time of the polymerizable composition to, typically, 2 hours.

[0007] US 2007 / 098999 discloses a similar process involving two prepolymers.

[0008] Provided the viscosity is controlled, batch mixing of such mixtures is inherently safer than the usual monomer process, as some of the available bond-forming energy has already been released during oligomer formation (pre-polymerization), which limits the formation of local heat spots in the final polymerizable mixture. The use of prepolymers allows for a stable and consistent reaction.

[0009] In applications WO 2021 / 182526, EP 3916470 and EP 3919967, a different approach was chosen for the rapid curing of a polythiourethane optical material, combining the use of monomers and prepolymers in the presence of a polymerization catalyst. Petition 870250081874, dated 11 / 09 / 2025, page 13 / 54 3 / 33

[0010] Prepolymers are obtained from non-stoichiometric mixtures of at least two monomers that react to obtain oligomers, specifically from a small amount of one monomer in an excessive amount of the other monomer. To prepare prepolymers, the processes of the prior art involve directly mixing the total amount of the two monomers and subjecting the total mixture to a heat treatment to allow the formation of the prepolymer.

[0011] Despite the advantages mentioned above regarding the use of prepolymers, their manufacture is time-consuming and expensive, since large heating tanks are needed to process the amount of material required to meet production needs.

[0012] Therefore, alternative polymerization methods for thiourethane resins would be necessary. It would be advantageous to reduce the amount of material subjected to the pre-polymerization process.

[0013] One objective of the invention is to provide a rapid manufacturing process for a polythiourethane resin, which solves the disadvantages of prior art methods without increasing the curing time. This process should not compromise the thermomechanical properties of the final material.

[0014] Another objective of the invention is to provide a method for curing fused polythiourethane-based substrates that are substantially free of optical defects, in particular free of bubbles and / or streaks resulting from the polymerization process, having high transmittance and clarity, as well as resistance to aging and a low yellowing index.

[0015] The present inventors found that the manufacturing method of the intermediate prepolymer affected the properties of the final polymer. They discovered that modifying the process of preparing the polythiourethane prepolymer having isocyanate or isothiocyanate terminal groups, firstly mixing the secondary monomer (polythiol) with a portion of the primary monomer (polyisocyanate or polyisothiocyanate), secondly subjecting this mixture to a thermal polymerization treatment to allow the formation of the oligomer, and thirdly diluting this concentrated mixture with the remaining portion of the Petition 870250081874, dated 11 / 09 / 2025, p. 14 / 54 4 / 33 main monomer, surprisingly led to an improvement in the thermal properties of the final molten polythiourethane polymer.

[0016] The present invention provides a method for the rapid curing of a transparent molten substrate based on polythiourethane, usable for making optical articles, such as ophthalmic lenses, which comprises the following steps 1), 2), 3), 4) and 5) or 1), 2'), 3), 4) and 5): 1) To provide a first component A comprising a polythiourethane prepolymer A1 having isocyanate or isothiocyanate terminal groups of formula -NCX where X is O or S, said prepolymer A1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, used in adapted amounts such that the molar ratio R2 of NCX / SH groups for said monomers varies from 2:1 to 35:1, preferably from 3:1 to 35:1, X being O or S. 2) To provide a second component B comprising at least one polythiol monomer B2, or 2') To provide a second component B comprising a polythiourethane prepolymer B1 having thiol terminal groups, said prepolymer B1 having been 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 and fill a molding cavity of a casting mold assembly with the resulting polymerizable mixture. 4) Cure the aforementioned polymerizable mixture to obtain a transparent polythiourethane-based substrate, and 5) Recover the transparent polythiourethane-based substrate from the casting mold assembly, in which the aforementioned A1 prepolymer has been prepared by: a) Mixture of at least one polyisocyanate or polyisothiocyanate monomer and said at least one polythiol monomer in Petition 870250081874, dated 11 / 09 / 2025, p. 15 / 54 5 / 33 initial quantities such that the initial molar ratio R1 of the NCX / SH groups for said monomers varies from 0.3 R2 to 0.95 R2 in the mixture resulting from step a), X being O or S, b) Polymerization of the mixture resulting from step a), c) Addition to the mixture resulting from step b) of an additional quantity of at least one polyisocyanate or polyisothiocyanate monomer such that the molar ratio of the NCX / SH groups for all monomers used in the preparation of said prepolymer A1 is equal to R2, X being O or S.

[0017] The above-mentioned objectives, features and advantages of the present invention will become readily apparent to those skilled in the art from a reading of the following detailed description, when considered in conjunction with the accompanying drawings, in which Figure 1 represents the graph of the glass transition temperature of the polythiourethane substrate as a function of the amount of urethidione byproduct formed for the different lenses prepared in the experimental part. DETAILED DESCRIPTION OF THE INVENTION

[0018] The substrate of the invention is an organic glass substrate, made from a thermosetting resin. The polymeric matrix of the substrate is obtained from a material composition (“substrate composition”) comprising at least one polymerizable prepolymer and at least two polymerizable prepolymers in some embodiments.

[0019] The substrate is preferably an optical article substrate, more preferably an optical lens substrate. The optical article is preferably an ophthalmic lens, such as a plastic spectacle lens.

[0020] In the present description, unless otherwise specified, a substrate is understood to be transparent when the observation of an image through said substrate is perceived without significant loss of contrast, that is, when the formation of an image through said substrate is obtained without adversely affecting the image quality. This definition of the term Petition 870250081874, dated 11 / 09 / 2025, p. 16 / 54 6 / 33 “transparent” can apply to all objects qualified as such in the description, unless otherwise specified.

[0021] The term “ophthalmic lens” is used to mean a lens fitted to a spectacle frame to protect the eye and / or correct vision. Said lens may be chosen from among afocal, single-vision, bifocal, trifocal, progressive lenses and Fresnel lenses or any other type of lens having a discontinuous surface. Although ophthalmic optics is a preferred field of the invention, it will be understood that this invention can be applied to optical elements of other types, such as, for example, lenses for optical instruments, filters particularly for photography or astronomy, optical vision lenses, eyepieces, lighting system optics, screens, glazing, etc.

[0022] If the optical article is an optical lens, it may be coated on its main front surface, main back side, or both sides with one or more functional coatings. As used herein, the back face of the substrate is intended to mean the face which, when the article is being used, is closest to the user's eye. It is generally a concave face. Conversely, the front face of the substrate is the face which, when the article is being used, is furthest from the user's eye. It is generally a convex face. The optical article may also be a planar or biplanar article.

[0023] A substrate, within the meaning of the present invention, should be understood to mean an uncoated substrate, and generally has two main faces. The substrate could, in particular, be an optically transparent material having the shape of an optical article, for example, an ophthalmic lens intended to be mounted in eyeglasses. In this context, the term “substrate” is understood to mean the basic constituent material of the optical lens and more particularly of the ophthalmic lens. This material may function as a support for a stack of one or more coatings or layers.

[0024] The refractive index of the polythiourethane-based 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, and even more preferably 1.65 or higher or 1.67 or higher, and is preferably 1.80 or lower, more Petition 870250081874, dated 11 / 09 / 2025, page 17 / 54 7 / 33 preferably 1.70 or lower, and even more preferably 1.67 or lower. Unless otherwise specified, the refractive indices referred to in this application are expressed at 25 °C at a wavelength of 550 nm.

[0025] The fast-curing polymerizable composition leading to a polythiourethane-based material is composed of two main components.

[0026] A first component A comprises a polythiourethane prepolymer A1 having isocyanate or isothiocyanate terminal groups provided in step 1) and is prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, the latter being used in excess. Therefore, the first component A comprises oligomers and the initial unpolymerized monomers, if any.

[0027] In a first embodiment of the present process, the second component B provided in step 2) is composed of at least one polythiol B2 monomer.

[0028] In a second embodiment of the present process, the second component B provided in step 2') is composed of at least one polythiourethane prepolymer B1 having thiol terminal groups, said prepolymer B1 having been 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 and the initial monomers that did not polymerize, when present.

[0029] Compared to prior art processes, which use only iso(thio)cyanate or thiol monomers, the present invention uses at least one polythiourethane prepolymer.

[0030] Prepolymer means a polymer or oligomer comprising prepolymer molecules. Prepolymer molecule means a macromolecule or oligomer molecule that is able to enter, through reactive (polymerizable) groups, into further polymerization, thus contributing more than one monomeric unit to at least one chain of the final macromolecule. Generally, it is formed from two or more different monomers. Petition 870250081874, dated 11 / 09 / 2025, page 18 / 54 8 / 33

[0031] The A1 polythiourethane prepolymer having isocyanate or isothiocyanate terminal groups is prepared in a multi-step process which will be detailed later. It is obtained by reacting at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer in a proportion such that the molar ratio R2 of isocyanate or isothiocyanate groups to NCX / SH thiol groups for said monomers varies from 2:1 to 35:1, preferably from 3:1 to 35:1 and preferably in the absence of a catalyst, X being O or S, at a temperature preferably ranging from 50 °C to 150 °C.

[0032] The B1 polythiourethane prepolymer having thiol terminal groups, when used in the present process, is prepared by reacting at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer in a proportion such that the molar ratio R'2 of thiol groups to isocyanate or isothiocyanate SH / NCX groups preferably varies from 3:1 to 35:1, preferably in the absence of a catalyst, X being O or S.

[0033] In one embodiment, the B1 polythiourethane prepolymer having thiol end groups, when used in the present process, is prepared by directly mixing the total amount of the two monomers (at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer) and subjecting the overall mixture to a heat treatment to allow the formation of the prepolymer. In other words, in this embodiment, the B1 polythiourethane prepolymer having thiol end groups, when used in the present process, is prepared directly by mixing at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer in the desired R'2 ratio.

[0034] In this document, polythiol and polyisocyanate or polyisothiocyanate compounds used to prepare polythiourethane A1 or B1 prepolymers are considered as monomers, even when they are oligomers.

[0035] Polyisocyanate means any compound comprising at least two isocyanate groups, in other words, diisocyanates, triisocyanates, etc. It is possible to use polyisocyanate prepolymers. Polyisocyanate may be Petition 870250081874, dated 11 / 09 / 2025, page 19 / 54 9 / 33 any suitable polyisocyanate having two or more, preferably two or three, isocyanate functions.

[0036] Polyisocyanates may be selected from aliphatic, aromatic, cycloaliphatic or heterocyclic polyisocyanates and mixtures thereof.

[0037] Polyisocyanates are defined in the same way as the polyisocyanates above, by replacing the “isocyanate” group with the “isothiocyanate” group.

[0038] In one embodiment of the invention, said polyisocyanate or polyisothiocyanate monomer is a compound of formula (VI): R2(NCX)n2(VI) wherein X represents O or S, n2 represents an integer ranging from 2 to 6 and R2 represents an aliphatic, alicyclic, heterocyclic or aromatic group.

[0039] The preferred polyisocyanate or isothiocyanate monomers are those having the following formulas: where R1 is independently H or a C1-C5 alkyl group, preferably CH3 or C2H5; R2 is H, a halogen, preferably Cl or Br, or a C1-C5 alkyl group, preferably CH3 or C2H5; Z is -N=C=X, with X being O or S, preferably O; a is an integer ranging from 1 to 4, b is an integer ranging from 2a to 4a + b < 6; ex is an integer from 1 to 10, preferably from 1 to 6. Petition 870250081874, dated 11 / 09 / 2025, page 20 / 54 10 / 33

[0040] The poly-isocyanates to be invented are preferably di-isocyanates. Among the available di-isocyanates you may find tolueno-2,4-diisocyanate, tolueno-2,6-di-isocyanate, diphenylmethane-4,4'-di-isocyanate, diphenylmethane-2,4'-di-isocyanate, paraphenylene di-isocyanate, xylylene di-isocyanate, biphenyl-di-isocyanate, 3,3'-dimethyl-4,4'-diphenylene di-isocyanate, tetramethylene-1,4-di-isocyanate, hexamethylene-1,6-di-isocyanate, 2,2,4-trimethyl hexano-1,6-di-isocyanate, lysine methyl ester di-isocyanate, bis(isocyanateethyl) fumarate, isophorone di-isocyanate (IPDI), ethylene diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene-2,4-diisocyanate, tetramethylxylylene diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrofenileno-1,3-diisocyanate, hexahydrofenileno-1,4-diisocyanate, perhydro diphenylmethane-2,4'-diisocyanate, perhydrophenylmethane-4,4'-diisocyanate (or bis-(4-isocyanatocyclohexyl)methane, or 4,4'-dicyclohexyl methanediisocyanate), bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate, 2,5(or 2,6)-bis(isocyanatomethyl)bicyclo[2.2.1]heptane and mixtures thereof.

[0041] Other non-limiting examples of polyisocyanates are isophorone diisocyanate and 1,6-hexamethylene diisocyanate isocyanurates, both commercially available. Other polyisocyanates suitable for the present invention are described in detail in WO 98 / 37115, WO 2014 / 133111 or EP 1877839.

[0042] The polythiols that may be used in the present invention are defined as compounds comprising at least two sulfhydryl (mercapto) groups, in other words, dithiols, trithiols, tetrathiols, etc. It is possible to use polythiol prepolymers. The polythiol could be any suitable polythiol having two or more, preferably two or three, thiol functions. The polythiol can be used for the preparation of polythiourethane prepolymers A1 or B1, but also directly as compound B2 in component B during step 2) of the present process.

[0043] In one embodiment of the invention, said polythiol monomer is a compound with the formula: Petition 870250081874, dated 11 / 09 / 2025, p. 21 / 54 11 / 33 R1(SH)ni (I)

[0044] where n1 represents an integer ranging from 2 to 6 and R1 represents an aliphatic, alicyclic, heterocyclic or aromatic group.

[0045] Among the preferred polythiol monomers and / or oligomers suitable according to the present invention, aliphatic polythiols may be mentioned, such as trimethylolpropanetris(2-mercaptoacetate), trimethylolpropanetris(3-mercaptopropionate), trimethylolethanetris(2-mercaptoacetate), trimethylolethanetris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), bis(mercaptomethyl)sulfide, bis(mercaptomethyl)disulfide, 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, 2,5dimercaptomethyl-1,4-dithian and 2,5-bis[(2-mercaptoethyl)thiomethyl]-1,4-dithian, 1-(1'mercaptoethylthio)-2,3-dimercaptopropane, 1-(2'-mercapropylthio)-2,3dimercaptopropane, 1-(3'-mercapropylthio)-2,3-dimercaptopropane, 1-(4'mercabutylthio)-2,3-dimercaptopropane, 1-(5'-mercapentythio)-2,3dimercaptopropane, 1-(6'-mercahexylthio)-2,3-dimercaptopropane, 1,2-bis-(4'mercaptobutylthio)-3-mercaptopropane, 1,2-bis-(5'-mercaptopentylthio)-3mercaptopropane, 1,2-bis-(6'-mercaptohexylthio)-3-mercaptopropane, 1,2,3tris(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-ethaneedithiol, 1,1-propaneedithiol, 1,2-propaneedithiol, 1,3-propanedithiol, 2,2-propanedithiol, 1,6-hexanethiol-1,2,3-propanetrithiol and 1,2-bis(2'-mercaptoethylthio)-3-mercaptopropane. Other examples of polythiols are shown in the formulas below or can be found in WO 2014 / 133111, EP 394495, US 4775733 or EP 1877839. Petition 870250081874, dated 11 / 09 / 2025, page 22 / 54 12 / 33 O II -Hí00C2h4sh= e C2HE.C(CH2COOCH2CH2SH)3

[0046] In one embodiment of the invention, said polythiol monomer is selected from the group consisting of pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakisthioglycolate, trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(mercaptoacetate) and compounds of formulas (II) and (III): CH-SH CH-S-(CH2)2~SH (II) CH-S-(CH2)-SH CHrSH çh2-ch-s-(ch2)2-sh(|||)S CH-SH II CHrCH-S-(CH2)FSH

[0047] xylene and Preferred embodiments are the combination of tetrakis(3-mercaptopropionate) pentaerythritol diisocyanate; the combination of xylylene diisocyanate and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol; the combination 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; the combination of xylylene diisocyanate and 4,8 (or 4,7 or 5,7)-dimercaptomethyl-1,11-dimercapto3,6,9-trithiaundecane; the 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). Petition 870250081874, dated 11 / 09 / 2025, page 23 / 54 13 / 33

[0048] In one embodiment, the polythiols have a viscosity at 25 °C of 1 Pa.s or less, more preferably 5.10⁻¹Pa.s or less, more preferably 2.5.10⁻¹Pa.s or less, more preferably 2.10⁻¹Pa.s or less, more preferably 10⁻¹Pa.s or less, and even more preferably 0.5.10⁻¹Pa.s or less.

[0049] Specific examples of polythiourethane resins suitable for the present invention are those marketed by Mitsui Chemicals as the MR® series, in particular MR6®, MR7® (refractive index: 1.67), MR8® (refractive index: 1.6), and MR10® (refractive index: 1.67) resins. These optical materials, as well as the monomers used for their preparation, are specifically described in US patents 4689387, 4775733, 5059673, 5087758, and 5191055.

[0050] Depending on the embodiment of the invention, components A and B are prepared by polymerizing mixtures of required amounts of at least one polyisocyanate and / or at least one polyisothiocyanate monomer and at least one polythiol monomer, and optionally polyol monomers or polyamine monomers. Typically, components A and B can be prepared by classical thermal polymerization, including induction and infrared heating or UV irradiation.

[0051] The overall amounts of polyisocyanate or polyisothiocyanate monomers and polythiol monomers in the reaction medium are preferably adapted in each case so that the molar ratio R2 of NCX / SH groups for the mixture of polyisocyanate or polyisothiocyanate monomers and polythiol monomers varies from 2:1 to 35:1 for the preparation of the polythiourethane prepolymer A1, preferably from 3:1 to 30:1, more preferably from 5:1 to 10:1 or 6:1 to 10:1, even more preferably from 6:1 to 9:1 or 7:1 to 9:1. The preferred R2 ratio is around 8:1.

[0052] The amounts of polyisocyanate or polyisothiocyanate monomers and polythiol monomers in the reaction medium are preferably adjusted so that the molar ratio of SH / NCX groups for the mixture of polyisocyanate or polyisothiocyanate monomers and polythiol monomers preferably varies from 3:1 to 35:1 for the preparation of the prepolymer of Petition 870250081874, dated 11 / 09 / 2025, page 24 / 54 14 / 33 polythiourethane B1 when such prepolymer is used, preferably from 3:1 to 30:1, more preferably from 6:1 to 10:1, X being 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 results in prepolymers with high stability over time. However, at least one of them, or both, 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 an amount such that the molar ratio of NCX to SH groups ranges from 0.8 to 1.2, preferably from 0.9 to 1.1, and most preferably around 1. This molar ratio of reactive groups can be calculated from the amounts of starting materials used to prepare the polythiourethane substrate.

[0055] The preparation of prepolymer B1 having thiol terminal groups has already been described in US 5908876 or US 2003 / 125410. A similar process can be used to prepare component B of the present invention.

[0056] The preparation of the A1 polythiourethane prepolymer having isocyanate or isothiocyanate terminal groups will be described below.

[0057] According to the present process, prepolymer A1 is prepared by: a) Mixture of at least one polyisocyanate or polyisothiocyanate monomer and said at least one polythiol monomer in initial amounts such that the initial molar ratio R1 of the NCX / SH groups for said monomers varies from 0.3 R2 to 0.95 R2 in the mixture resulting from step a), X being O or S, b) Polymerization of the mixture resulting from step a), c) Addition to the mixture resulting from step b) of an additional quantity of at least one polyisocyanate or polyisothiocyanate monomer such that the molar ratio of NCX / SH groups for all monomers used in the preparation of said prepolymer A1 is equal to R2, where XO or S.

[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). Petition 870250081874, dated 11 / 09 / 2025, page 25 / 54 15 / 33

[0059] In prior art processes, prepolymer A1 is prepared directly by mixing at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer in the desired R2 ratio.

[0060] According to the present process, prepolymer A1 is prepared by first mixing at least one polyisocyanate or polyisothiocyanate monomer and at least one polythiol monomer at an initial molar ratio R1 of isocyanate / isothiocyanate functional groups to thiol functional groups (NCX / SH, X being O or S) lower than the desired final molar ratio R2, and then adding the remainder of at least one polyisocyanate or polyisothiocyanate monomer to dilute the prepolymer and obtain the final NCX / SH ratio R2, X being O or S.

[0061] Thus, the mixture resulting from step c) of the present process 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 manufacturing process of prepolymer A1 according to the invention, instead of the prior art process in which the components of prepolymer A1 are mixed directly. The disparity between the two processes in terms of glass transition temperature difference is greater when the molar ratio R1 of the main monomer to the secondary monomer is the lowest in the mixture subjected to step b) of prepolymerization (oligomerization).

[0063] The process according to the invention presents several other advantages. It is more interesting to limit the volume to be subjected to the heating process during step b) of polymerization, since smaller equipment is needed and requires less energy. Furthermore, when heat-sensitive additive molecules, such as dyes, are used, their introduction in step c) of the present process limits their degradation.

[0064] Without limiting themselves to 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 prior art processes, is due to the self-condensation of isocyanate or isothiocyanate monomers to Petition 870250081874, dated 11 / 09 / 2025, page 26 / 54 16 / 33 form a dimer byproduct of the urethidione or thio-urethidione type, which is favored in this situation compared to the situation where the initial NCX / SH ratio is lower.

[0065] In fact, the polycondensation of thiourethane involves the reaction of iso(thio)cyanates with thiols. Depending on the conditions, secondary reactions may occur in addition to the main reaction, such as the autoreaction of iso(thio)cyanate. The cyclopolymerization of isocyanates can result in several species, but the most common is urethidione.

[0066] If significant amounts of urethidione byproducts were formed, this would result in an increased amount of unreacted thiol groups in the final polymer. The lower glass transition temperature of the prior art materials could be explained by residual unreacted free thiol groups or by shorter polymer chains in the final product, due to the consumption of NCX groups by secondary reactions and, consequently, the overall reduction in crosslinking.

[0067] It is believed that the secondary reaction that forms iso(thio)cyanate dimers during the preparation of prepolymer A1 occurs to a greater extent when there is a greater excess of NCX groups compared to thiol groups, thus favoring the formation of autoreaction products, and to a lesser extent when the NCX / SH ratio is lower, since fewer NCX groups are available to undergo autocondensation. The formation of a urethidione byproduct from two isocyanate compounds of formula R1NCO is schematized below: THE THE R1—NCO ----* R1—N N-R1 Urethidiona

[0068] In this document, by reducing the initial concentration of polyisocyanate / polyisothiocyanate monomers compared to polythiol monomers, more thiourethane linkages are formed, while fewer free iso(thio)cyanates are exposed to heat and have the possibility of autoreacting to form byproducts and cause the presence of thiol residues in the final product. Petition 870250081874, dated 11 / 09 / 2025, page 27 / 54 17 / 33

[0069] In some embodiments of the invention, the initial molar ratio R1 of the NCX / SH groups varies from 0.3 R2 to 0.8 R2, from 0.35 R2 to 0.7 R2, or from 0.35 R2 to 0.55 R2. The ratios R1 and R2 are calculated by adding the amounts of polyisocyanate and polyisothiocyanate monomers, if a mixture of these monomers is used. Preferably, polyisocyanate monomers are used.

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

[0071] A very low amount of polyisocyanate or polyisothiocyanate monomer compared to the amount of polythiol monomer (i.e., a very low R1 ratio) should be avoided during step a) of the present process to prevent premature gelation of the mixture before it is introduced into the mold.

[0072] A very high amount of polyisocyanate or polyisothiocyanate monomer compared to the amount of polythiol monomer (i.e., a very high R1 ratio) should be avoided during step a) of the present process to avoid obtaining a final polymer having a very low glass transition temperature.

[0073] The polythiol / polyiso(thio)cyanate mixture from which prepolymer A1 is obtained may comprise 90% or less by weight of at least one polyol. Preferably, said mixture may comprise 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less by weight of at least one polyol. Also preferably, no polyol is used. Polyiso(thio)cyanate means polyisocyanate or polyisothiocyanate.

[0074] Component B or the polythiol / polyiso(thio)cyanate mixture from which prepolymer B1 is obtained may comprise 90% or less by weight of at least one polyol. Preferably, said mixture may comprise 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, Petition 870250081874, dated 11 / 09 / 2025, page 28 / 54 18 / 33 30% or less, 20% or less, 10% or less by weight of at least one polyol. Preferably, no polyol is used.

[0075] The mixture of components A and B according to the invention may also include additives that are conventionally employed in polymerizable compositions intended for molding optical articles, in particular ophthalmic lenses, in conventional proportions, namely inhibitors, dyes, photochromic agents, UV absorbers, perfumes, deodorants, antioxidants, resin modifiers, color balancing agents, chain extenders, crosslinking agents, free radical scavengers, such as antioxidants or hindered amine light stabilizers (HALS), dyes, pigments, fillers, adhesion accelerators, anti-yellowing agents and mold release agents.

[0076] In one embodiment, additives are added to the first component A before mixing with the second component B.

[0077] UV absorbers are frequently incorporated into optical articles in order to reduce or prevent UV light from reaching the retina (particularly in ophthalmic lens materials). The UV absorber that may be used in the present invention preferably has the ability to at least partially block light having a wavelength shorter than 400 nm, but may also have an absorption spectrum that extends to the visible blue light range of the electromagnetic spectrum (400-450 nm), in particular 420-450 nm.

[0078] The aforementioned UV absorbers protect the user's eye from UV light and the substrate material itself, thus preventing it from wearing out and becoming brittle and / or yellowing. The UV absorber according to the invention may be, without limitation, a benzophenone-based compound, a benzotriazole-based compound or a dibenzoylmethane-based compound, preferably a benzotriazole compound. Suitable UV absorbers include, without limitation, 2-(2-hydroxyphenyl)-benzotriazoles, such as 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole (Seesorb® 703 / Tinuvin® 326), or other allyl-hydroxymethylphenyl chlorobenzotriazoles, 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 Petition 870250081874, dated 11 / 09 / 2025, page 29 / 54 19 / 33 methoxyphenyl)benzotriazole, 2-(2-hydroxy-5-butoxyphenyl)benzotriazole, and also Tinuvin® CarboProtect® from BASF. The preferred absorbers are from the benzotriazole family. Other examples of benzotriazole UV absorbers protecting against blue light can be found in document WO 2017 / 137372.

[0079] The amount of UV absorber compounds according to the invention used herein is sufficient to provide satisfactory protection against UV light, but not excessive so as to prevent precipitation. The inventive UV absorber compounds are generally present in an amount ranging from 0.05 to 4% by weight relative to the total weight of optical material (or per 100 parts by weight of the polymerizable compounds present in the mixture of components A and B or relative to the weight of the optical material composition), preferably from 0.1 to 3% by weight, more preferably from 0.1 to 2% by weight.

[0080] Among the release agents that may be used in the invention, mono- and dialkyl phosphates, alkyl ester phosphates, silicones, fluorinated hydrocarbons, fatty acids, and ammonium salts may be mentioned. Preferred release agents are mono- and dialkyl phosphates, alkyl ester phosphates, and mixtures thereof. These release agents are disclosed inter alia in US 4975328 and EP 0271839. The release agent is preferably used in an amount equal to or less than 1% by weight 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 comprise a solvent, e.g., to promote the dissolution of a catalyst, especially if it is in the form of a salt. In one embodiment, the curing step 4) is carried out in the presence of at least one salt catalyst solvent, preferably 2-mercaptoethanol.

[0082] 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% by weight, based on the total weight of the polymerizable compounds present in the mixture of components A and B, and preferably from 0 to 0.5% by weight, to avoid Petition 870250081874, dated 11 / 09 / 2025, page 30 / 54 20 / 33 hazing and bubbles. In one embodiment, the catalyst is used in the form of a solution in a compound, such as 2-mercaptoethanol.

[0083] In the present invention, at least one catalyst can be used to catalyze the formation of bonds in the process before the curing step 4). In one embodiment, the mixture resulting from step 3) comprises at least one catalyst.

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

[0085] The catalyst should be used in the polymerizable composition in an effective amount, that is, an amount sufficient to promote the polymerization of the mixture. Generally, at least one catalyst is used in a proportion of 0.01 to 5% by weight with respect to the total weight of the polymerizable compounds present in the mixture of components A and B, more preferably 0.02 to 2% by weight. A very high amount of catalyst should be avoided to prevent premature gelation of the polymerizable mixture before it is introduced into the mold, particularly when a prepolymer A1 is combined with a polythiol monomer B2.

[0086] The catalyst can be added at different stages of this process.

[0087] In one embodiment, the catalyst is added to the polythiol monomers B2 during the preparation of component B, or to the polythiourethane prepolymer B1 having thiol terminal groups, depending on the case. In other words, at least one catalyst is added to said second component B before step 4). In another embodiment, at least one catalyst is added to said first component A before step 4). In the preferred embodiment, the catalyst is added to the polythiol monomers 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 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 catalyst can be added to prepolymers A1 and / or B1 after their preparation, depending on the case. Petition 870250081874, dated 11 / 09 / 2025, page 31 / 54 21 / 33

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

[0090] In one embodiment, the catalyst is anionic. Preferred catalysts are transition metal-based catalysts, as well as ammonium salts of acids, these salts preferably satisfying the condition 0.5 < pKa < 14.

[0091] In the present application, pKa is expressed at 25 °C. pKa can be measured in water at standard pressure by potentiometric titration (pH), using a glass electrode and a pH meter.

[0092] In one embodiment, the catalyst is a salt compound of formula, τντP+γ—iVim ϊη , wherein Mp+ is a p-valence cation selected from the group consisting of alkali metal cations, alkaline earth metal cations, transition metal cations and ammonium groups of formula NR4+ in which R is an alkyl group preferably having from 1 to 10 carbon atoms, Y' is an anion, such that the corresponding acid YH has a pKa satisfying the condition 0.5 < pKa < 14, where m, n, peq are integers such that n = mx p.

[0093] The preferred metal cations of the salts are Li+, Na+, K+, Cs+, Mg2+, Ca2+, Mn2+, Ag+, Ba2+, and Al3+. The particularly preferred metal cations are Li+, Na+, and K+ due to their lack of color and solubility in the composition. Transition metals are less preferred because their salts can lead to colored compositions and therefore colored polymerized resins. In one embodiment, the method according to the invention does not use a tin-containing catalyst.

[0094] Preferred NR+4 groups are those in which R is a C1-C1 alkyl group and, more preferably, a methyl, ethyl, propyl, butyl or hexyl group.

[0095] Preferably, Y' is an anion so that the corresponding acid YH satisfies the condition 0.5 < pKa < 10 and more preferably 0.5 < pKa < 8.

[0096] Preferably, the Y' anion is selected from the group consisting of thiocyanate, carboxylate anions, thiocarboxylate anions, acetylacetonate, anions Petition 870250081874, dated 11 / 09 / 2025, p. 32 / 54 22 / 33 diketone, acetoacetic ester, malonic ester anions, cyanoacetic ester anions, ketonitrile anions, malononitrile anion and anions of formula RS where R is a substituted or unsubstituted alkyl group preferably having from 1 to 10 carbon atoms or an aryl group preferably having from 6 to 12 carbon atoms.

[0097] The preferred Y' anions are SCN, acetylacetonate, acetate, thioacetate, formate, and benzoate. The preferred salt catalyst is KSCN.

[0098] Among the additional catalysts that can be used in the method of the invention, 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, may also be mentioned. Various catalysts can be combined in the present process.

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

[0100] Electron-donating compounds may also be used in combination with the catalyst, preferably a salt catalyst, especially when the polymerizable composition comprises poorly reactive thiols and / or iso(thio)cyanates. Generally, electron-donating compounds stabilize the cation of the salt catalyst. They thus contribute to dissociating the anion / cation ion pair and thereby increase the reactivity of the anion in the polymerization medium and thus promote the polymerization reaction.

[0101] Electron donor compounds are preferably selected from acetonitrile compounds, such as malononitriles, 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, with 18-crown-6 being the most preferred.

[0102] In one embodiment, the curing step 4) is performed in the presence of at least one electron donor compound.

[0103] Examples of acetonitrile compounds are: Petition 870250081874, dated 11 / 09 / 2025, p. 33 / 54 23 / 33 O^ΞN N^=C CH2C^N e rÍ—Hno qua I

[0104] R is an alkyl group, preferably a C1-C1 alkyl group, such as methyl, ethyl, propyl, butyl.

[0105] Amide compounds could be primary, secondary, or tertiary amide compounds. Trialkylphosphites and triarylphosphites could be represented by the formula: OR Pçor1 OR'

[0106] wherein R, R', R”' are an alkyl group, preferably a C1-C6 alkyl group or an aryl group preferably having 6 to 12 carbon atoms, such as a phenyl group. Trialkylphosphites are preferred, for example (C2H5O)3P.

[0107] Electron donor compounds may also be selected from among crown ethers and cryptands. These cyclic molecules are usually chosen to exhibit a good compromise between the size of the heteroatom or metal and the size of the “cage”, that is, between the number of heteroatoms and the size of the “cage”, that is, between the number of heteroatoms and the size of the ring.

[0108] The preferred crown ethers and cryptands could be represented by the following formulas: Petition 870250081874, dated 11 / 09 / 2025, pp. 34 / 54 24 / 33 where X1 represents 0, S, or NH, xi is an integer from 3 to 6, preferably from 3 to 4, n-ι is 2 or 3, X2, X3 and X4 represent O, S, n2, n3, n4, y2, y3, y4 are 2 or 3 and x2, xs and x4 are 2 or 3.

[0109] Among the ethers mentioned, the following compounds: ----------|- o [C H-fe ]------------------^[CH;h -O ]-----preferred crown and cryptands, could be — S( CH-fe —S(CH2)3----(CHshSfCH^S----—NH —(CH;h-।----CH2CH;O----CH2CH; 2I N---[CH2CH2O j-^-C^CHs -N ।----[cH2CH;SU^CH2CH; -I

[0110] Examples of preferred crown ethers are 18-crown-6, 18-crown-7, 15-crown-5 and 15-crown-6.

[0111] The electron donor compounds are 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, even more preferably from 0.17% to 0.408% by weight, relative to the total weight of polymerizable compounds present in the mixture of components A and B.

[0112] The weight ratio of catalyst / electron donor compound, when the latter is present, preferably ranges from 1 / 3 to 1 / 5. Petition 870250081874, dated 11 / 09 / 2025, page 35 / 54 25 / 33

[0113] The mixing of the first component A with the second component B in step 3) can be carried out using any known mixing technique, such as those mentioned in US 5973098. Preferably, the components A and B to be mixed are added to a small reactor chamber and then mixed with a rotary mixer. In one embodiment, the viscosity at 25 °C of the mixture of components A and B varies from 0.01 Pa.sa to 5 Pa.s, preferably from 0.05 Pa.sa to 0.5 Pa.s, even more preferably from 0.1 Pa.sa to 0.3 Pa.s.

[0114] During step 3), a molding cavity of a casting mold assembly is filled with the mixture of the first and second components A and B.

[0115] Generally, the casting mold assembly comprises two mold parts defining two molding surfaces that cooperate to form a molding cavity when moved from an open position to a closed position. Each of the molding surfaces can be concave, convex, or flat, depending on the desired article shape. The molding surface can be convex, e.g., to form a concave substrate surface, or concave, e.g., to form a convex substrate surface.

[0116] More specifically, the optical material composition can be poured into the cavity of two mold parts held together using an annular closure, such as a seal or adhesive tape. A traditional mold comprises two pieces, called parts in this document, typically made of mineral glass, around the periphery of which an annular closure member is disposed, defining with them the required molding cavity.

[0117] An annular closing member may be arranged around the periphery of the two mold pieces and fixed to them. The conventional way of filling a two-piece mold is by causing the optical material (liquid) composition to flow into the molding cavity through a casting opening provided for this purpose in the closing member. In at least one partially automated process, the molding cavity to be filled is aligned vertically with a device of Petition 870250081874, dated 11 / 09 / 2025, page 36 / 54 26 / 33 filling that is adapted to distribute a particular quantity of molding material through a nozzle.

[0118] Depending on the desired characteristics of the resulting optical material, degassing can be performed under reduced pressure and / or filtration can be performed under increased or reduced pressure before pouring the optical material composition into the mold assembly.

[0119] After pouring the composition, the casting mold assembly, preferably a lens casting mold assembly, can be heated in an oven or in a water-immersed heating device according to a predetermined temperature program to cure the resin in the mold assembly.

[0120] In one embodiment, the mixture of the first and second components A and B is kept at room temperature (20-30 °C) in the casting mold assembly until gelation occurs, before starting the curing step 4).

[0121] The curing step 4) of the mixture, which provides a transparent polythiourethane-based substrate, can be carried out in the presence of at least one catalyst and can be implemented using any well-known polymerization technique and, in particular, thermal polymerization, including induction and infrared heating, or radiation polymerization. The curing time of step 4) is preferably less than 10 or 5 hours, more preferably less than 4, 3 or 2 hours. As used herein, curing refers to a chemical process of converting a monomer or oligomer into a polymer of higher molar mass and then into a network.

[0122] Curing is generally carried out at elevated temperature in an oven, for example, an air oven, to complete polymerization. This can be done at a temperature ranging from 50 to 150 °C or from 100 to 130 °C. Then, the mold assembly is removed from the heat source, the annular closing element is removed and the mold parts are disassembled.

[0123] The resin-molded product may then be annealed, if necessary, at a temperature preferably ranging from 100 °C to 150 °C. Petition 870250081874, dated 11 / 09 / 2025, p. 37 / 54 27 / 33

[0124] In step 5) of the present process, the transparent polythiourethane-based substrate is recovered from the mold. The recovered substrate or article can then be re-flashed to obtain a lens.

[0125] The present process can be used to manufacture a finished lens, having both sides in the required geometries, or a semi-finished lens, having one face that still needs to be surfaced in the required geometry.

[0126] Subsequently, the substrate or article can be tinted or coated to improve various properties, such as scratch resistance or reflective properties.

[0127] The invention also relates to a transparent fused substrate based on polythiourethane, obtained by the process described above. This differs from transparent fused substrates based on polythiourethane obtained by prior art processes by its improved thermomechanical properties, in particular by its higher glass transition temperature, as demonstrated in the experimental part.

[0128] The article resulting from the present process has satisfactory color properties that can be quantified by the yellowness index Yi. The degree of whiteness of the inventive optical material can be quantified by means of colorimetric measurements, based on the CIE tristimulus values ​​X, Y, Z, as described in the ASTM E313 standard with illuminant C and observer 2o. The optical article according to the invention preferably has a low yellowness index Yi, that is, less than 10, more preferably less than 8 and even better less than 6, measured according to the above standard. The yellowness index Yi is calculated according to the ASTM E313 method through the relation Yi = (127.69 X - 105.92 Z)) / Y, where X, Y, and Z are the CIE tristimulus values.

[0129] The substrate according to the invention preferably has a colorimetric coefficient b* (in transmission) as defined in the international colorimetric system L*a*b* CIE (1976) less than or equal to 10, 5, 4, 2 or 1, and generally greater than or equal to 0. A low colorimetric coefficient b* can be correlated with a limited or non-yellow appearance (transmission color). In fact, positive values ​​on the b* axis indicate amounts of yellow, while negative values ​​indicate amounts of blue. Petition 870250081874, dated 11 / 09 / 2025, page 38 / 54 28 / 33

[0130] The following examples illustrate the present invention in a more detailed, but not limiting, manner. Unless stated otherwise, all thicknesses disclosed in this application relate to physical thicknesses. EXAMPLES 1. Chemical substances used

[0131] Optical materials were prepared from a composition comprising polymerizable monomers, Zelec UN® (CAS 3896-11-5) as a mold release agent and a catalyst solution comprising KSCN (CAS 333-20-0), 18-crown-6 (CAS 17455-13-9) and mercaptoethanol (CAS 6024-2). The monomers used in the present examples were xylylene diisocyanate (CAS 3634-83-1) and 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol (CAS 13153800-6) in order to produce a transparent polythiourethane matrix having a refractive index of 1.67. The monomers were used as received without treatment to eliminate moisture. 2. Evaluation of the polymerizable composition and lenses after curing.

[0132] To evaluate the compositions and optical articles prepared according to the present invention, the following test procedures were used. For each system, several samples were prepared for measurements and the reported data were calculated using the average of the different samples.

[0133] The glass transition temperature (Tg) of the lenses was evaluated by DMA (dynamic-mechanical analysis) and DSC (differential scanning calorimetry).

[0134] Viscosity was measured using a viscometer (Brookfield CAP 2000+L Cone and Plate Viscometer).

[0135] Normal-incidence infrared transmission spectra were measured with the Nicolet iS50 FTIR spectrometer in a range of 500 to 4000 cm⁻¹ with a resolution of 4 cm⁻¹. The urethidione parameter was calculated based on a spectrum of the final polythiourethane substrate obtained by Fourier Transform Infrared Spectroscopy (FTIR) using the equation below: %Tc Urethidione parameter = ---%Tu Petition 870250081874, dated 11 / 09 / 2025, page 39 / 54 29 / 33

[0136] The transmission corresponding to the resonance frequency of the urethidione functional group (%Tu) was obtained at 1785 cm-1, and the peak at 2920 cm-1, attributed to the CH2 linkage (including the CH2 linkage of the thiol monomer) (%Tc), was used as the normalized signal. The higher the urethidione parameter, the lower the urethidione transmittance and therefore the greater the urethidione linkage present (higher urethidione parameter). Since urethidione is a byproduct, a low urethidione parameter is desirable. 3. Preparation of the A1 polythiourethane prepolymer having isocyanate terminal groups for examples 1 to 5 and comparative example 1.

[0137] In a reactor equipped with a thermal probe and a stirrer, a determined quantity of m-xylylene diisocyanate (XDI) polyisocyanate monomer was charged and heated to 120 °C. Then, 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol was introduced and mixed with the polyisocyanate in an amount such that the “initial” molar ratio of isocyanate functions to thiol functions NCO / SH was equal to R1 (step a of the process)). R1 ​​varied from 2:1 (comparative example 1) to 7:1 (example 5), as indicated in Table 1.

[0138] The mixture was heated for 3.5 hours at 120 °C, then cooled to room temperature, and an additional determined quantity (see Table 1) of the polyisocyanate monomer, m-xylylene diisocyanate (XDI), was added to the mixture, so that the final molar ratio between the isocyanate functions and the NCO / SH thiol functions of the monomers used in this process (R2) was equal to 8:1 (step c) of the process). The resulting prepolymer A1 was then transferred to a suitable drum and stored in a cold chamber. Prepolymer A1 was prepared without the use of a catalyst. 4. Preparation of the A1 polythiourethane prepolymer having isocyanate terminal groups for comparative example 2

[0139] In a reactor equipped with a thermal probe and a stirrer, a determined quantity of m-xylylene diisocyanate (XDI) polyisocyanate monomer was charged and heated to 120 °C. Then, 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol was introduced and mixed with the polyisocyanate in an amount such that the molar ratio of isocyanate functions to thiol functions NCO / SH was 8:1 (89.66% polyisocyanate, 10.34% polythiol, by weight). A Petition 870250081874, dated 11 / 09 / 2025, pages 40 / 54 The 30 / 33 mixture was heated for 3.5 hours at 120 °C. The resulting A1 prepolymer was then cooled to approximately 35 °C and transferred to a suitable drum and stored in a cold chamber. The A1 prepolymer was prepared without the use of a catalyst. 5. Preparation of transparent fused polythiourethane substrates

[0140] Convex and concave biplane molds were assembled using adhesive tape. The central thickness was 2 mm.

[0141] In all examples and comparative examples, a determined quantity of cooled prepolymer A1, prepared as described above, was mixed with a determined quantity of Zelec UN®. This mixture was stirred between 5 and 15 °C and degassed for 1 hour, degassed for 15 minutes without stirring, to form component A. In parallel, a determined quantity of 2,3-bis((2-mercaptoethyl)thio)-1propanethiol polythiol monomer B2 was mixed with a determined quantity of the aforementioned catalyst solution (8.5% KSCN, 34.84% 18-crown-6, 56.66% 2-mercaptoethanol, by weight). This mixture was stirred between 5 and 15 °C and degassed for 1 hour, degassed for 15 minutes without stirring, to form component B.

[0142] Components A and B were then mixed with the SH:NCO molar ratio adjusted to 1:1 in a small reactor, under stirring and degassing for 5 minutes at 15 °C and then further degassing without stirring for 2 minutes at 15 °C to prevent gelation. After mixing was complete, the mold sets were filled with the aid of a syringe and through a filter. The mixture contained 58 parts by weight of component A starting materials, 42 parts by weight of B2 monomer, 0.4 parts by weight of catalyst solution and 0.16 parts by weight of Zelec UN®.

[0143] The assembled molds were kept at room temperature for 10 minutes before being placed in a convection oven preheated to 120 °C. The mixture of the samples initiated gelation in the mold assemblies at room temperature. The polymerization reaction was carried out by leaving the mold assemblies in the oven for 2 hours at 120 °C. Petition 870250081874, dated 11 / 09 / 2025, pp. 41 / 54 31 / 33

[0144] In the context of the present invention, a gel designates the reaction product of components A and B in which the conversion rate of the reactive functions is significantly high. For example, said conversion rate ranges from 50 to 80% and is preferably about 70%.

[0145] The mold sets were then disassembled to obtain lenses with a central thickness of 2 mm, comprising a transparent thermoset polythiourethane substrate body, which were annealed at 120 °C for 1 h after disassembly. The lenses had a refractive index of 1.67 and did not exhibit optical defects such as streaks. 6. Compositions and results

[0146] The ratios of the monomers used and the results of the characterizations are shown in Table 1. The percentages given for the monomers used are percentages by weight compared to the total weight of monomers used for the preparation of prepolymer A1 having isocyanate terminal groups. The castings were repeated and the data are the average of at least 3 tests. Table 1 Process Step Step a) Step c) Step 5 NCO / SH (initial molar ratio of R1) Initial amount of isocyanate (%) Initial amount of thiol (%) Additional amount of isocyanate (%) Viscosity (cPo) Tg (°C) Urethidione parameter Comparative example 1* 2:1 22.41 10.34 67.24 - - - Example 3:1 33.62 10.34 56.04 58 80.5 0.858 Petition 870250081874, dated 11 / 09 / 2025, pages 42 / 54 32 / 33 Example 1 8 Example 2 4:1 44.83 10.34 44.83 51 79.5 5 0.866 Example 3 5:1 56.04 10.34 33.62 44 79.6 0 0.864 Example 4 6:1 67.24 10.34 22.41 27 78.1 6 0.875 Example 5 7:1 78.45 10.34 11.21 24 78.7 5 0.881 Comparative example 2 8:1 89.66 10.34 0 38 77.8 4 0.882 The mixture gelled during the pre-polymerization step b).

[0147] Lenses without any optical defects were obtained after a perfectly controlled polymerization reaction.

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

[0149] It is observed that increasing the initial molar ratio R1 of the NCO / SH groups tends to decrease the glass transition temperature of the resulting polythiourethane-based substrate and increase the amount of urethidione byproduct formed. As shown in Figure 1, the glass transition temperature of the final material increases as the amount of urethidione byproduct formed decreases.

[0150] However, in comparative example 1, where a very low amount of polyisocyanate monomer was used compared to the amount of polythiol monomer (low R1 ratio of 2), undesirable premature gelation occurred and the mixture solidified during polymerization step b). Thus, not Petition 870250081874, dated 11 / 09 / 2025, pages 43 / 54 In examples 33 / 33, it was possible to measure viscosity and thermomechanical properties. In examples 1 to 5, the mixtures did not begin gelling before transfer to the mold.

[0151] Therefore, the new method proposed by the present inventors for preparing the A1 prepolymer having isocyanate or isothiocyanate terminal groups, compared with the conventional process represented by comparative example 2, allows for improved thermal properties of the resulting polythiourethane-based substrate. Petition 870250081874, dated 11 / 09 / 2025, pages 44 / 54

Claims

1 / 4 CLAIMS 1. A method for curing a transparent molten substrate based on polythiourethane, characterized by comprising the following steps 1), 2), 3), 4) and 5) or 1), 2'), 3), 4) and 5): 1) providing a first component A comprising a polythiourethane prepolymer A1 having isocyanate or isothiocyanate terminal groups of formula -NCX where X is O or S, said prepolymer A1 having been prepared from at least one polythiol monomer and at least one polyisocyanate or polyisothiocyanate monomer, used in adapted amounts such that the molar ratio R2 of the NCX / SH groups for said monomers varies from 2:1 to 35:1, X being O or S, 2) provide a second component B comprising at least one polythiol monomer B2, or 2') provide a second component B comprising a polythiourethane prepolymer B1 having thiol terminal groups, said prepolymer B1 having been 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 and fill a molding cavity of a casting mold assembly with the resulting polymerizable mixture. 4) cure the aforementioned polymerizable mixture to obtain a transparent polythiourethane-based substrate, and 5) recover the transparent polythiourethane-based substrate from the casting mold assembly, in which said prepolymer A1 was prepared by: a) mixing at least one polyisocyanate or polyisothiocyanate monomer and said at least one polythiol monomer in initial quantities such that the initial molar ratio R1 of the NCX / SH groups for said monomers varies from 0.3 R2 to 0.95 R2 in the mixture resulting from step a), X being O or S, b) polymerization of the mixture resulting from step a), Petition 870250081874, dated 11 / 09 / 2025, page. 51 / 54 2 / 4 c) addition to the mixture resulting from step b) of an additional quantity of at least one polyisocyanate or polyisothiocyanate monomer such that the molar ratio of the NCX / SH groups for all monomers used in the preparation of said prepolymer A1 is equal to R2, X being O or S.

2. Method according to claim 1, characterized in that said molar ratio R2 of the NCX / SH groups varies from 5:1 to 10:

1. 3.A method according to any of the preceding claims, characterized in that the initial molar ratio R1 of the NCX / SH groups varies from 0.35 R2 to 0.55 R2.

4. A method according to any of the preceding claims, characterized in that 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 to SH groups varies from 0.8 to 1.2, X being O or S.

5. A method according to any of the preceding claims, characterized in that the curing step 4) is carried out in the presence of at least one catalyst.

6. A method according to any of the preceding claims, characterized in that at least one catalyst is added to the second component B before step 4) or to the first component A before step 4). 7.A method according to any one of claims 5 and 6, characterized in that said catalyst is a salt compound of formula MP+Y lv±m xn, wherein Mp+ is a p-valence cation selected from the group consisting of alkali metal cations, alkaline earth metal cations, transition metal cations and ammonium groups of formula NR4+ in which R is an alkyl group, Y- is an anion, such that the corresponding acid YH has a pKa satisfying the condition 0.5 < pKa < 14, m, nep being integers such that n = m x p.

8. A method according to any one of the preceding claims, characterized in that the curing time of step 4) is less than 10 hours. Petition 870250081874, dated 11 / 09 / 2025, p. 52 / 54 3 / 4 9.Method, according to any of the preceding claims, characterized in that said polythiol monomer is a compound of formula: R1(SH)n1 (I) wherein n1 represents an integer ranging from 2 to 6 and R1 represents an aliphatic, alicyclic, heterocyclic or aromatic group.

10. Method, according to any of the preceding claims, characterized in that said polythiol monomer is selected from the group consisting of pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakisthiioglycolate, trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(mercaptoacetate) and compounds of formulas (II) and (III): CH2-SH CH-S-(CH2)2-SH CH2-S-(CH2)2-SH CH2-SH CH. CH S (CH.). SH / iin (II) 1 2 2 2 (III) S CH2-SH CH2-CH-S-(CH2)2-SH 11.Method, according to any of the preceding claims, characterized in that said polyisocyanate or polyisothiocyanate monomer is a compound of formula (VI): R2(NCX)n2 (VI) wherein X represents O or S, n2 represents an integer ranging from 2 to 6 and R2 represents an aliphatic, alicyclic, heterocyclic or aromatic group. 12.A method, according to any of the preceding claims, characterized in that said polyisocyanate or polyisothiocyanate monomer is selected from the group consisting of 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(ethyl isocyanate) fumarate, isophorone diisocyanate (IPDI), ethylene diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cycle Petition 870250081874, of 09 / 11 / 2025, p.53 / 54 4 / 4 hexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene-2,4 diisocyanate, tetramethylxylylene diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrophenylene-1,3-diisocyanate, hexahydrophenylene-1,4-diisocyanate, perhydro diphenylmethane-2,4'-diisocyanate, 4,4'-dicyclohexylmethanediisocyanate, 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. Method, according to any of the preceding claims, characterized by comprising the following step 2): 2) providing a second component B comprising at least one polythiol monomer B2.

14. Method, according to any of the preceding claims, characterized in that the substrate is an optical lens substrate. 15.Transparent fused polyurethane substrate characterized by being obtained by the method as defined in any of the preceding claims. Petition 870250081874, dated 11 / 09 / 2025, p. 54 / 54.

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