MXPA01003245A - Preparation of organic pieces of optical quality and especially organic lenses - Google Patents

Abstract

The main aim of the present invention is a method of preparing photochromic or non-photochromic organic pieces of optical quality and especially organic lenses, by radical polymerisation of a mixture of radically polymerisable monomers, characterised in that it comprises:a) adjusting, by pre-polymerisation, the viscosity of said mixture, to a value between 0.4 and 2 Pa.s;b) pouring said pre-polymerised mixture into a mould;c) photogelifying, in said mould, said pre-polymerised mixture until its gel point;d) completing the polymerisation of said pre-polymerised and gelified mixture in said mould, by heat treatment;adding effective amounts of at least one thermal catalyst and of at least one photoinitiator intervening in said mixture of monomers for the implementation of said pre-polymerisation, photogelification and polymerisation;said photoinitiator(s) intervening in an amount less than or equal to 0.009 parts by weight per 100 parts by weight of said mixture of monomers.

Description

PREPARATION OF ORGANIC PIECES OF OPTICAL QUALITY AND ESPECIALLY OF ORGANIC LENSES DESCRIPTIVE MEMORY The invention relates to the preparation of organic parts of optical quality and especially the preparation of organic lenses. More specifically, the main objective of the present invention is an original method of preparing such photochromic and non-photochromic organic parts by radical polymerization of a mixture of radically polymerizable monomers. The object of the present invention is also: • novel organic pieces of that type, which are preparable by a variant of said method; this variant makes use of particular monomers; • novel radically polymerizable compositions - mixtures of radically polymerizable monomers - which can be used to prepare organic pieces of this type according to the method of the invention. The present invention is described below with particular reference to the context of the preparation of organic lenses (eyeglasses for vision correction, protective glasses). The present invention is not limited in any way to such context and the person skilled in the art will easily understand that the claimed method is suitable for obtaining any type of molded organic parts, which are without optical defect, such as, therefore, organic lenses, but also windows, optical parts ... The purely thermal methods of radical polymerization of mixtures of monomers (mainly monomers, acrylics and / or methacrylics and / or alkynyl, especially vinyl monomers) containing or not containing an effective amount of at least one photochromic dye have been described and carried out, especially by the applicant , to prepare photochromic or non-photochromic organic lenses, mainly optic and ophthalmic lenses. Such methods are carried out, in a lens mold, on a mixture containing an effective amount of at least one suitable thermal catalyst or radical polymerization initiator. Said catalyst is selected when at least one photochromic dye intervenes, generally between diazo compounds (known as "soft" catalysts which remain "inert" to the photochromic dyes present). Such methods do not give complete satisfaction to the extent that their execution is long and to the extent that, inevitably, during its execution, the oxygen diffuses into the mixture undergoing polymerization, originating this oxygen from the surrounding air and entering the mold through of its hermetic union to leaks. This generates defects in appearance and restrictions (optical defects) in the lenses thus produced.

An alternative process for preparing such organic lenses is described in the patent E: U: A: US-A-5 621 017. This alternative method is based on the UV-polymerization of the monomer mixture containing an effective amount ( from 0.01 to 1 part by weight, per 100 parts by weight of monomers) of at least one suitable photoinitiator. Such a method does not give complete satisfaction as well, especially: - it can reveal to be delicate, even impossible to find satisfactory operating conditions (nature of the photoinitiator, irradiation band) in view of the nature of the monomers present, in view of the presence at least one photochromic dye (which reveals that it is a competitor of absorption for the photoinitiator) and in view of the specifications set for the final lens ... - its field of application is limited. It may in fact be suitable for preparing lenses of relatively low thickness (finished lenses of 2 mm thick (see examples of US-A-5 621 017)), but it is not suitable for preparing thicker lenses (for example, semi-finished lenses of more than 10 mm thickness). In effect, the penetration of ultraviolet radiation into the material that has been polymerized is then dealt with. In order to overcome this difficulty, it has been possible to visualize the use of a photoinitiator that is absorbed in the visible spectrum. However, in order to ensure that an adequate result is obtained - a complete polymerization that is homogeneous throughout the entire thickness - it remains It is necessary to use a high concentration of photoinitiator and use a large amount of energy. In transmission severe polymerization conditions - lenses are usually obtained that have high degree of enamarillecimiento. In any case, in the use of a low concentration of photoinitiator (which is not likely to generate in enamarillecimiento) is very difficult to achieve a complete polymerization through the entire mass of material. In this context, the applicant has developed a novel method of preparing organic pieces which makes it possible to obtain said pieces that are free, up to relatively consistent thicknesses and this from several types of monomer mixtures (even from mixtures that are known which are relatively difficult to polymerize). This novel method can be qualified as a mixed method, insofar as it includes thermal polymerization and photochemical polymerization. This original method of preparing organic pieces and, especially, organic lenses is described below. Characteristically, it includes photogelification and makes use of a low quantity of photoinitiators. Said method of the invention comprises, in fact, to prepare photochromic or non-photochromic organic parts by polymerization of a mixture of radically polymerizable monomers (said mixture containing, in effect, the constituents of the piece or lens in preparation: principal and secondary constituents of its composition. matrix, the type of monomer, more generally conventional additives, especially such as thermal catalyst, the photochromic dye ...), the following successive steps: a) adjust, by pre-polymerization, the viscosity of said mixture, to a value between 0.4 and 2 Pa.s; b) pouring said prepolymerized mixture into a mold (especially a lens mold for preparing lenses); c) photogelifying, in said mold, said prepolymerized mixture to its gelling point; d) completing the polymerization of said prepolymerized and gelled mixture in said mold, by thermal treatment; performing the steps referred to as prepolymerization (a), photogelication (c) and polymerization (d) by introducing, to said mixture of monomers, effective amounts of at least one thermal catalyst and at least one photoinitiator; said photoinitiators intervening in an amount less than or equal to 0.009 parts by weight per 100 parts by weight of said monomer mixture. According to the method of the invention, the mixture containing the constituent elements of the piece in preparation is first prepolymerized before it is poured into the mold. The execution of such prepolymerization from the mold is very advantageous in that it: - makes it possible to neutralize the inhibitors present in said mixture (such polymerization inhibitors are inevitably present in commercial products); - it makes it possible to increase and adjust the viscosity of the mixture to be then poured into the mold. In this mold, the polymerization carried out is thus carried out on a prepolymerized and therefore viscous mixture, under the best conditions since, within such a viscous mixture, the oxygen diffuses more slowly, the yields of the intervening photoinitiator are improved, shrinkage is reduced and the gel point is reached more quickly; - it can be carried out in a perfectly leak-tight container, ie in the absence of oxygen and, therefore, without restriction in terms of duration. It is highly recommended to execute said prepolymerization in order to adjust the viscosity of the mixture to a value between 0.4 and 2 Pa.s. At less than 0.4, the beneficial effects of said prepolymerization are hardly manifested (especially in view of the problem of oxygen diffusion); more than 2, handling problems of the prepolymerized mixture are addressed and too close to the gel point is reached. The prepolymerization according to the invention is generally a thermal or photochemical prepolymerization which, for its execution, requires the presence, in the mixture to be prepolymerized, of an effective amount of at least one thermal catalyst and at least of a photoinitiator, respectively. At least one thermal catalyst (usually a thermal catalyst) must therefore intervene in the monomer mixture, precisely from the beginning of the method for the execution of a thermal prepolymerization. It is generally added in an effective amount q, in such a way as to guarantee both the execution of said thermal prepolymerization (step a) and then the subsequent step, of the final thermal polymerization (step d). However, it is not excluded in any way from the context of the invention to introduce them in two batches, in a first quantity qi, which is an effective amount for the execution of the thermal prepolymerization, upstream of said prepolymerization and then, a second quantity q2. (qi + q2 = q), which is an effective amount for the execution of the final thermal polymerization, downstream of said thermal prepolymerization, with advantage precisely after the thermal prepolymerization before pouring the prepolymerized mixture into the mold. In the hypothesis of the execution of such thermal prepolymerization, it can also be advantageously carried out that the quantity of photoinitiators necessary for the additional execution of the photogenation intervenes in the mixture to be prepolymerized. Said quantity can, however, intervene later, at the end of the thermal prepolymerization, before pouring the prepolymerized mixture into the mold. Thus, advantageously, the prepolymerization is a thermal prepolymerization carried out on the monomer mixture containing the effective amounts of thermal catalysts and photoinitiators or containing only the effective amount of thermal catalysts then adding the effective amount of photoinitiators to said mixture of monomers, at the end of its thermal prepolymerization, before it is poured into the mold. At least one photoinitiator (usually a photoinitiator) must intervene in the monomer mixture, precisely from the beginning of the method, for the execution of a photochemical prepolymerization. Said photoinitiator can act precisely from the beginning in an effective quantity Q, in such a way as to guarantee both the execution of said photochemical prepolymerization (step a) and then that of the subsequent photogelling step (step c). Advantageously, the photoinitiator can intervene in two batches, in a first quantity Qi, which is an effective amount for the execution of the photochemical prepolymerization, upstream of said prepolymerization and then in a second quantity Q2 (Qi + Q2 = Q), which is an effective amount for the execution of the photogelling, downstream of said photochemical prepolymerization, with advantage precisely after the photochemical prepolymerization, before pouring the prepolymerized mixture into the mold. In the hypothesis of the execution of such photochemical prepolymerization, the thermal catalysts subsequently useful in the thermal polymerization (step d) may intervene, before said prepolymerization or at the end thereof (before pouring the prepolymerized mixture into the mold). Thus, according to this variant of the execution of the step a of the method of the invention, the prepolymerization is a photochemical prepolymerization carried out on the monomer mixture containing a effective amount of photoinitiators or advantageously containing only 40% to 60% of said effective amount expressed by weight, then adding the rest of photoinitiators to said monomer mixture, upon completion of their photochemical prepolymerization, before it is poured into the mold; said effective amount of thermal catalysts being added to said monomer mixture before its photochemical prepolymerization or at the end thereof. The following is further specified with reference to said prepolymerization step of the method of the invention (step a). It has been seen that in general it is a matter of a photochemical thermal prepolymerization. The prepolymerization under the combined action of heat and adequate irradiation, ie carrying out a thermal pre-polymerization and a photochemical pre-polymerization, has not been completely excluded., thus acting together the catalysts and photoinitiators within the monomer mixture ... The prepolymerized mixture is then poured according to the step described above, precisely to a mold. Polymerization is completed in said mold and, characteristically, these in two successive steps: - a photogelification to its point of gelation and - a final or supplementary thermal polymerization. The photoinitiators involved in the execution of the mixed method of the invention, which thus combines the photochemical polymerization (step c and optionally step a) and the thermal polymerization (step d and optionally step a) in three steps (a, b, c), intervene, in any case, in a limited amount - equal to or less than 0.009 parts by weight per 100 parts in weight of monomers - and can not thus reveal to be harmful, especially with respect to the problem of enamarillecimiento. In addition, the intervention of said photoinitiators is optimized by executing photogelling and prepolymerization, if it is a case of photochemical prepolymerization under a radiation that is predominantly in the visible aspect, that is, almost free of ultra violet radiation. The effect, commissionable UV lamps are not adequate or are inadequate. It is strongly suggested to use them when using UV filters. However, it is recommended to execute the photogelification step of the method of the invention and the prepolymerization step, if it is a case of photochemical prepolymerization, as fluorescent tubes as radiation sources that are predominantly in the visible aspect (having their maximum energy more than 400 nm, for example at 410 nm or 460 nm). This type of radiation penetrates the thickness of the irradiated material and interferes with the photochromic dyes that are optionally present. The person skilled in the art will now have all the interest of the mixed method of the invention (including thermal and photochemical polymerization), which comprises three main steps (prepolymerization, photochromic gelation, thermal polymerization) and whose execution makes possible obtain thin and thick pieces (especially lenses), which are free of any appearance or restriction defect, especially as the polymerization is carried out in the mold (especially in the lens mold), rapidly with an oxygen diffusion that reduces to a minimum. The method of the invention is also interesting because it is suitable for the polymerization of mixtures of monomers of different types ((meth) acrylic, vinyl monomers ...) and especially of mixed type ((meth) acrylic and vinyl monomers). The monomer mixture to be polymerized according to the invention can contain acrylic and / or methacrylic and / or alkenyl monomers, especially vinyl or allylic monomers. Advantageously, said mixture contains mainly difunctional monomers of type (a) and difunctional monomers of type (b), as defined below. Some compositions based on these two different types of monomers were described by the applicant in the patent application FR 97 05 458, filed on May 2, 1997, published as FR-A-2, 762,845. Its use for preparing organic parts of optical quality, and especially organic lenses by the method of the invention, has been found to be particularly advantageous. Said compositions were developed by the applicant within the research context for a compromise between the optical properties, including photochromic properties, and the mechanical properties of the plastic material that can be used especially in ophthalmology, and obtained by radical copolymerization (thermal) of monomers. Characteristically, said compositions include at least one short chain (meth) acrylic difunctional monomer and at least one long chain alkenic difunctional monomer. The resin that results from its polymerization is thus a structure that provides the properties sought. Said short chain (meth) acrylic difunctional monomers (of type (a) and of formula (A), (A '): see below) actually produces rigidity, this rigidity being modulated by the presence of said difunctional monomers long chain alkenes (of type (b) and of formula (B), (B '), (B "): see below), which also make it possible, surprisingly, to provide said composition with excellent photochromic properties. , the difference in functionality of said monomers of type (a) and (b) advantageously slows down the gelation of the resulting polymerizable composition This characteristic makes it possible for the resin obtained from said composition to have good optical properties and especially in the case of which incorporates photochromic dyes in the same, to express quickly and, at most, the photochromic properties. Thus, the method of the invention is therefore particularly advantageously carried out with a monomer mixture containing at least one difunctional monomer of type (a) and at least one difunctional monomer of type (b): difunctional monomers of type (a) - (meth) acrylics - of one or other of the following formulas (A) and (A '): Formula (A): (X) p (X ') q wherein: Ri, R'i, and R ', identical or different, are independently a hydrogen or a methyl group; - m and n are, independently, numbers between 0 and 4 (inclusive); and are advantageously independently equal to 1 or 2; - X and X 'identical or different, are a halogen or preferably represent a chlorine and / or bromine atom; - p and q are, independently, integers between 0 and 4 (inclusive); + formula (A '): wherein: Ri and R'i, identical or different, are independently a hydrogen or a methyl group; - R is a straight or branched alkyl radical having from 2 to 8 carbon atoms, a cycloalkyl radical having from 3 to 6 carbon atoms carbon, an ether radical of the formula (R'-O-R ") in which R 'and R", identical or different, are independently a straight or branched alkyl radical having from 2 to 4 carbon atoms; * being the difunctional monomers of type (b) - long chain alternating difunctional oligomer - one or the other of the following formulas (B), (B ') and (B "): + formula (B): wherein: Ri, R'i, R2 and R'2, identical or different, are independently hydrogen or a straight or branched alkyl radical, advantageously straight, having from 1 to 4 carbon atoms; and in a particularly advantageous manner correspond to a methyl group; - R3 and t, different, are independently a hydrogen and the other an alkenyl radical having from 2 to 6 carbon atoms, advantageously from 2 to 4 carbon atoms and particularly advantageously an isopropenyl radical; - R'3? R'4, different, are independently a hydrogen and the other an alkenyl radical having from 2 to 6 carbon atoms, advantageously from 2 to 4 carbon atoms and in a particularly advantageous manner an isopropenyl radical; (advantageously, the two ends of the molecule are identical, ie: R3 = R * 3 and R = RU); - Z represents a carbamate function (-NH-CO-0-), a thiocarbamate function (-NH-CO-S-) or a urea function (-NH-CO-NH-); Z ', independently of Z and advantageously respectively with respect to Z, represents a carbamate function (-0-CO-NH-) a thiocarbamate function (-S-CO-NH-) or a urea function (-NH-) CO-NH-); - R 'represents a straight or branched alkyl radical having 2 to 4 carbon atoms; - R, identical or different when n > 2 is a straight or branched alkyl radical having from 2 to 4 carbon atoms; - And, identical or different when n > 2, is oxygen or sulfur; - n is an integer defined in such a way that the total number of carbon atoms, contained in the long chain located between the two portions Z and Z ', is at least equal to 18 and advantageously is between 18 and 112 (inclusive); + formula (B '): wherein: Ri, R2, R3, R4, R'-i, R'2, R'3, R'4, R and Y are as defined above with reference in formula (B); - n is an integer defined in such a way that the total number of carbon atoms, contained in the long chain of the portion (R-Y) n, is at least equal to 22 and advantageously is between 22 and 104 (inclusive); Formula (BM): wherein: Ri, R2, R3, R4 > R'i, R'2, R'3, RU, R, R 'and Y are as defined above with reference in formula (B); - Z 'is a carbamate function (-O-CO-NH-) or Z' is a thiocarbamate function (-S-CO-NH-); advantageously, Z 'is a carbamate function; - n is an integer defined in such a way that the total number of carbon atoms contained in the long chain of the portion (R-Y) n -R \ is at least equal to 22 and advantageously is between 22 and 104 (inclusive). In addition, said mixture of monomers of types (a) and (b) may also contain: (c) at least one aromatic monovinyl monomer of the formula (C): in which Ri = H or CH3; said monovinyl monomer advantageously consisting of styrene; and / or (d) at least one aromatic divinyl monomer of the formula (C): wherein R1 = H or CH3; advantageously comprising divinyl monomer of divinylbenzene; and / or (e) at least one (meth) acrylic monomer of the formula (E): CH2 = C (R) -COOR 'wherein R = H or CH3 and R' is a straight or branched alkyl radical which has from 4 to 16 carbon atoms an optionally substituted benzyl or phenoxyethyl radical (generally substituted by a C-Cß alkyl group) or a polyethoxy group of the formula - (CH2-CH2-0) nR "in which n is a number whole between 1 and 10 R ") CH3 or C2H5, said (meth) acrylic monomer advantageously consisting of 2-ethylhexyl-methacrylate, and / or (f) diallyphthalate The compounds listed above ((c) to (f)) advantageously intervene with The difunctional monomers of types (a) and (b) advantageously can be involved in any mixture of monomers to be polymerized according to the method of the invention, and it is now proposed to specify a little the nature and quantity of each one of the components that intervene or can intervene in the mixture that is polymerizable according to the method of the invention All the monomers of type (a) may or may not be of the same formula (A) or (A '). Thus, the mixtures to be polymerized according to the invention advantageously comprise: - or monomers of the same formula (A) (at least one); - or monomers of the same formula (A) (at least one), - or mixtures (not mixed) of monomers of different formula the (TO); or mixtures (not mixed) of monomers of different formula (A); - or mixtures (mixed) of monomers of the formulas (A) and of the formulas (A ').

According to the preferred variant of the invention, one or more symmetric monomers of type (a) are used. Said monomers of the type (a), of the formula (A) or (A ') in which the groups Ri and R'i are identical, equal to the groups R and R', as well as the substituents X and X 'for the compounds of the formula (A) are suitable as symmetrical. Said symmetric monomers of type (a) of the formula (A) are known and are commercially available or easily accessible to the person skilled in the art. It can be noted that said monomers which do not have a halogen on the aromatic rings correspond in fact to the first monomers of the formula (I) in the sense of WO-A-92/05209. Said monomers of the type (a) of the formula (A) having halogens on the aromatic rings will be easily obtained by the person skilled in the art, using derivatives that are appropriately substituted on said aromatic rings. Within the context of the invention, the monomers and the formula (A), in which R and R \ are identical, are hydrogen or a methyl group, Ri and R'i are a methyl group, n and m are independently equal to 1 or 2. , and p = q = 0, are preferred. A particularly advantageous variant corresponds to the monomer of formula (A) of the above type, furthermore with R = R '= H and m = n = 2. Said monomer is marketed notably by Akzo Nobel (NL) under the trade designation DIACRYL 121. The The synthesis of the monomers is not a particular problem for the person skilled in the art.

The monomers (a) of the formula (A ') are also well known and result from the conventional reaction of an aliphatic diol or a short chain alkylene glycol (with a maximum of 8 carbon atoms in said chain) of at least one type of (meth) acrylic derivative, depending on whether it is desired to obtain monomers of the formula (A ') which are symmetrical or dissymmetric at their ends. These monomers of type (a) generally intervene in the mixture to be polymerized in a proportion of 40 to 99 parts by weight per 100 parts by weight of the mixture of monomers of types (a) and (b). If they intervene in a smaller amount, the polymerizable composition tends to retract during its polymerization inducing a premature appearance which, in turn, is responsible for the deterioration of the optical properties of the final resin. The monomers (b) of the formulas (B), (B ') and (B ") are long-chain difunctional alkenic monomers, whether or not the monomers have a more or less pronounced symmetry (R? / R \, R2 / R '2, R3 / R'3, All these monomers of type (b) may or may not have the same formulas (B), (B ') or (B ") ... Thus, the mixtures to be polymerized according to the invention advantageously comprise: - or either monomers of the same formula (B) (monomers 1); - or monomers of the same formula (B ') (monomers 1); - or monomers of the same formula (B ") (monomers 1); - or mixtures (not mixed) of monomers of different formulas (B); - or mixtures (not mixed) of monomers of different formulas (B '); - or mixtures (not mixed) of monomers of different formulas (B ") - or mixtures (mixed, binary or ternary) of monomers selected from the monomers of the formulas (B), of the formulas (B ') and of the formulas (B "). The monomers of type (b) are obtained which are long-chain alternating difunctional oligomers, said chain being a polyoxyalkylene or poly-mercaptoalkylene chain, or even a mixed chain, according to the conventional conditions of organic synthesis by the reaction: or various derivatives having a functionality of the alkenyl isocyanate type, of formulas I and / or II: Formula I Formula II in which Ri, R2, R3, R4, R'1, R'2, R'3 and RU are as defined above. According to the preferred variant of the invention, the monomers of type (b) used are symmetrical at their ends. In order to do this, a single type of alkenyl isocyanate derivative is used (thus formulas I and II are identical). In a particularly advantageous manner, a vinyl isocyanate derivative is used in which R? = R2 = CH3 (or R '? = R'2 = CH3), R3 (or R'3) is an isopropenyl radical and R4 (or RU) it is hydrogen corresponding to 3-isopropenyl-aa-dimethylbenzyl isocyanate (of general designation m-TMI®). Oligomers (b) obtained from said derivatives are preferred; - and a compound having intrinsically a long chain, said compound being: * or a compound which is symmetric about its terminal functions and which corresponds: + to a diol of the formula HO- (RY) n-R'-OH; + or to a dithiol of the formula HS- (R-Y) n-R'-SH; + or to a diamine of the formula H2N- (R-Y) n-R'-NH2; which makes it possible to obtain said intrinsically symmetric oligomers of the formula (B) (intrinsically symmetrical means monomers of the formula (B) in which the groups Z and Z 'are functions of an identical nature); + or a biepoxi of the formula thus giving rise to the reaction to the synthesis of said oligomers of the formula (B '); * or a compound that is dissymmetric around its terminal functions: + it being possible that said functions are an alcohol, thiol or amine function; all combinations being possible: making it possible for these compounds to obtain other intrinsically dissymmetric difunctional oligomers of the formula (B) (intrinsically unsymmetrical means monomers of the formula (B) in which the Z and Z 'groups are functions of a different nature); + said functions being respectively an epoxy function and an alcohol function or an epoxy function and a thiol function, the compounds of the formula then being H2C- CH-O- (R-Y) n- R'- (OH) or (SH) thus giving rise to the reaction to the synthesis of said oligomers of the formula (B ") In each case, R, R ', Y and n are as defined above, preferably Y is oxygen (the long chain then being a polyoxyalkylene chain) The molecular mass of the polyoxyalkylene long chain and / or polymercaptoalkylene corresponding to the radical (RY) nR 'or (RY) n in said formulas (B, B', B ") specified above, is generally less equal to 500 g.mol "1 and less than 2000 g.mol" 1; and preferably said molecular mass is between 600 g.mol "1 and 900 g.mol" 1. In a particularly advantageous manner, one or more intrinsically symmetric monomers of type (b) of formula (B) (as defined above) are involved: in which R, R ', Ri, R2, R3, R4, R'1, R'2, R'3 and RU are ta! as defined above (and advantageously so that the two ends of the molecule are identical, ie: R? = R '?, R2 = R'2, even more advantageously with R1 = R'1 = R2 = R'2 = CH3 and R3 = R'3 and R4 = RU being one of R3 and R4 hydrogen and the other being an isopropenyl group) and Y is as defined above and it advantageously consists of an oxygen (X = 0) and: (a) - Z and Z 'are carbamate functions of the formula (-NH-CO-O-) and (-O-CO-NH-) respectively; - n is an integer defined in such a way that the total number of carbon atoms contained in the long chain lying between the two motifs Z and Z 'is between 18 and 112; and advantageously, in the case of a polyoxylene chain, it is between 24 and 112 and particularly advantageously between 26 and 50 in the case of a polyoxylene of molecular mass between 600 and 900 g.mol -1; or (ß) - Z and Z 'are thiocarbamate functions of the formulas (-NH-CO-S-) and (S-CO-NH-) respectively; - n is an integer defined in such a way that the total number of carbon atoms contained in the long chain lying between the two motifs Z and Z 'is between 18 and 108; and advantageously, in the case of a polyoxyalkylene chain, it is between 24 and 108 and particularly advantageously between 28 and 46 in the case of a polyoxyalkylene chain of molecular mass between 600 and 900 g.mol "1; ) - Z and Z 'are functions urea (-NH-CO-NH-); - n is an integer defined in such a way that the total number of carbon atoms contained in the long chain between the two Z and Z motifs is between 18 and 112, and advantageously, in the case of a polyoxyalkylene chain, it is between 24 and 112, and particularly advantageously between 28 and 50 in the case of a polyoxyalkylene of molecular mass between 600 and 900 g.mol "1. The person skilled in the art will have understood that the formula (B), in the case (a) above in which the number of carbon atoms contained in the long chain is equal to 50, can be written for example: In the same way, the person skilled in the art will have understood that generally the minimum values mentioned above that define the number of carbon atoms in the long chain of the motifs (R-Y) n-R 'or (R-Y) n, correspond to the compounds having a poly-mercaptoalkylene chain (Y = S). In a particularly advantageous manner, said monomers of type (b) have a general formula (B) as defined above in which: Ri, R2, R'i and R'2, identical, are methyl radicals; R3 and R'3 are an isopropenyl radical; R4 and RU are hydrogen and + or Z or Z 'are urea functions (NH-CO-NH-) and -R' represents an ethylene or propylene group; - n is an integer equal to 13 or 19 which defines a total number of carbon atoms between Z and Z 'equal to 28 or 40, when (R-Y) n is a polyoxyethylene chain; or n is an integer equal to 10 or 14 which defines a total number of carbon atoms between Z and Z ', equal to 33 or 45, when (R-Y) n is a polyoxypropylene chain; or n is an integer between the lower limit values (10 to 13) and the upper limit values (14 to 19) as defined above, when (R-Y) n is a mixed polyoxyethylene / polyoxypropylene chain; which thus defines the monomers of type (b) of designation RUDI JEF 600 and RUDI JEF 900 (see the examples in document FR 97 05458), respectively when n has one of the values of lower limit (n between 10 and 13 inclusive) and n has one of the upper limit values (n between 14 and 19 inclusive); + or Z and Z 'are carbamate functions of the formulas (-NH-CO-0-) and (-0-CO-NH-) respectively, and - R 1 represents an ethylene group; - (R-Y) n represents a long chain of polyoxyethylene; - n is an integer equal to 13 or 19 which defines the total number of carbon atoms contained in the long chain mentioned between the two Z and Z '-like motifs at 28 or 40; which thus define the monomers of type (b) of designation (b) of designation RUDI 600 and RUDI 900 (see the examples of document FR 97 05458), when n = 13 and n = 19 respectively. It is particularly preferred to execute the original method of the invention with the monomers of type (b) above (in the general formula (B) in which Z and Z 'are urea functions) in a function with monomers of type (a) as specified previously. The monomers of type (b) are generally present in the mixture to be polymerized in a proportion of 1 to 60 parts by weight per 100 parts by weight of the monomer mixture (a) and (b). The mixtures to be polymerized according to the invention can also contain, as already indicated, other monomers in combination or not with monomers of the types (a) and (b) specified above. For 100 parts by weight of the mixture of monomers of types (a) and (b), said mixtures may contain from 1 to 60 parts by weight (advantageously from 10 to 50 parts by weight) of at least one monomer selected from alkylene monomers (such as those of formulas (C) and (D) and diallyl phthalate (f)), advantageously vinyl and allylic monomers, monomers (met) acrylics (such as those of the formulas (E)) and mixtures thereof. In view of the effects procured, when these monomer types are added, with respect to the technique, they will know how to determine and optimize the interfering quantities of each type of said monomer (in each case with the total amount of said monomer involved in the composition of the monomer). to be polymerized is between 1 and 60 parts by weight of the monomer mixture of types (a) and (b)). The vinyl monomers of the formula (C) -styrene and / or methylstyrene are used in combination with the monomers of type (a) in order to loosen the network. The intervention in that stage of styrene can be particularly advantageous, in that it is the polymerized compound having a more or less high refractive index (n = 1,595). Said styrene constitutes a particularly preferred compound of this kind of monomer. The compound of formula (D) consists of divinylbenzene (DVB (or di (methylvinyl) benzene) Divinylbenzene is the particularly preferred compound of formula (D) The intervention of at least one compound of formula (D) may reveal which is advantageous because said compound notably moderates, in a general manner, the effects of the compounds of the formula (C). beneficial to such compounds of the formula (D) in the expression of the photochromic properties. With reference to divinylbenzene, of the majority of this polymerized compound having a relatively high refractive index (n = 1.61), its intervention is also beneficial because it results in an increase in the refractive index of the polymers of the invention. The mixture to be polymerized according to the method of the invention also advantageously contains at least one compounds of the formula (E). It is a (meth) acrylic monomer as defined above. It can also be butyl-, pentyl-, hexyl-, heptyl-, octyl- or 2-ethylhexyl (methacrylate) or even ethyltriglycol (methacrylate). 2-Ethylhexylmethacrylate (EHMA) is the preferred compound of the formula (E). In the presence of this type of compound it has proved to be advantageous for the production of the polymerized material and for the execution of the final treatments of the latter. Finally, the polymerizable composition can contain diallyphthalate which allows remarkably to adjust the index and / or other optical and mechanical properties. As specified above, the intervention of the compounds of the formulas (C) and / or (B) and / or (E) and / or diallyl phthalate is not mandatory. It does not reveal however to be advantageous. Similarly, it can be revealed to be extremely advantageous and to produce at least one acrylic monomer to the mixture of monomers to be polymerized according to the original method of the invention, said acrylic monomer being at least trifunctional (i.e. at least three reactive functions: three double bonds, which advantageously possesses 3 to 6 reactive functions). Said monomer intervenes as a constituent monomer of the final matrix, but above all as an accelerator of the prepolymerization (step a) and of the photogelification (step c). It is advantageously selected from: pentaerythritol triacrylate, pentaerythritol tetraacrylate, propoxylated glycerol triacrylate, trimethylolpropane triacrylate, polyurethane triacrylate, dipentaerythritol hexaperylate, and advantageously consists of pentaerythritol triacrylate. Their intervention, in substitution, at least partially, of a difunctional acrylic monomer by adhesion to a mixture of acrylic and / or methacrylic and / or alkenyl monomers, improves the kinetics of the polymerization, without introducing any defect in the final product. Generally, the accelerators of the polymerization, said at least trifunctional acrylic monomers, are made to intervene at 2 to 10%, advantageously 4 to 6%, by weight, of the total weight of the monomer mixture to be polymerized according to the invention. After having specified the nature of the monomers that can constitute the main constituent elements of the piece prepared by the method of the invention, the subject of the additives is addressed which are to be incorporated into the monomer mixture in order, on the other hand, to be possible polymerization according to the invention, on the other hand, photochromic properties to the prepared part, if desired. The monomer mixture to be polymerized according to the final method of the invention can therefore contain an effective amount of at least one photochromic dye, in order to give photochromic properties to the prepared parts. Such dye is advantageously selected from spiroxazines and chromosomes (or a combination thereof) which are provided with photochromic properties. A large number of such photochromic dyes are described in the literature and commercially obtainable. Spiroxazine dyes that can be used within the context of the present invention, in the patents of E.U.A. 3,562,172, 4,634,767, 4,637,968, 4,7230,547, 4,756,973, 4,785,097, 4,792,224, 4,816,584, 4,831,142, 4,909,963, 4,931,219, 4,936,995, 4,986,934, 5,114,621, 5,139,707, 5,233,038, 4,215,010, 4,342,668, 4,699,473, 4,851, 530, 4,913,544, 5,171, 636, 5,180,524, 5,166,345, in the patent applications EP-A-0 508 219, 0 232 295 and 0 171 909 and in the application FR-A-2 738 248 (of the applicant). The use of 1,3-dihydro-3,3-dimethyl-1-neopentyl-6 '- (4"-N, N-diethyl-amino) -spiro [2H] -indol-2,3' is particularly recommended. -3H-naphthol [2,1- b] [1,4] oxazine, and the use of the spiroxazines described in the application FR-A-2 738 248 within the context of the present invention. The chromene dyes which are usable within the context of the present invention are fully described in the patents, US-A-3,567,608, 4,889,413, 4,931, 221, 5,200,116, 5,066,818, 5,224,602, ,238,981, 5,106,998, 4,980,089, 5,130,058, and in the application EP-A-0 562 915.

These phenomena may consist notably of naphthopyrans. The use of 2,2-bis- (4'-methoxyphenyl) 5,6-dimethyl- [2H] -naphthol [1,2-b] pyran is particularly recommended within the context of the present invention. Spiropyran dyes are described which are also usable within the context of the present invention, in the following texts: POTHOCHROMISM G. Brown, Editor - Techniques of Chemistry - Wiley Interscience - Vol. 111-1971 - chapter III - pages 45- 294 - RC Bertelson. POTHOCROMISM - Molecules & Systems-Edited by H. Dürr - H - Bouas - Laurent-Elsevier 1990 - Chapter 8: Spiropyrans - pages 314-455-R. Gugliemetti. The intervention of other photochromic dyes such as the fulcrums is not excluded, within the context of the present invention. The intervention of spiroxazines and / or less is preferred within the context of the present invention.

It has been indicated that the mixtures to be polymerized according to the invention, which are intended to generate a photochromic part, especially a lens, contain an effective amount of at least one photochromic dye. It is a frequent effect, within the context of the present invention, to involve a combination of dyes in order to obtain a specific dye in the darkened state. Within the context of the particularly preferred embodiments of the invention, the photochromic filler comprises a combination of cromenos. A particularly preferred combination is that of the following phenomena: 2- (P-dimethylaminophenyl) -2- (p-methoxyphenyl) -methyl-7,9-dimethoxy- [2 H] -naphtho- [1,2-b] pyran and 3- (p-methoxyphenyl) -3-phenyl-6-morpholino- [3 H] -n3fto- [2,1-b] pyran. This combination allows obtaining an interesting gray color. By way of reference and not limitingly, it has been indicated that said photochromic dyes generally interfere in the mixtures to be polymerized (and those that have been polymerized) of the invention at a ratio of 0.01 to 1% by weight, advantageously to ratio of 0.05 to 0.5_% by weight with respect to the total weight of the monomers. Said dyes may themselves contain very appropriately a polymerizable and / or reactive group that is equally entangled in its chemical form. They intervene then as comonomers to be polymerized; and they are chemically bonded, ie they are grafted to the matrix of said polymerized composition. Generally, the pieces of the invention contain their free photochromic dyes or linked to their matrix.

The mixture of monomers to be polymerized according to the invention also contain, before the execution of the step a and / or just before the execution of step c (see above), the effective amounts of thermal catalysts and photoinitiators. A single additive of the thermal catalyst type and a single additive of the photoinitiator type can generally be involved. The thermal catalyst is generally used at a ratio of 0.01 to 1% by weight, preferably 0.05 to 0.05%, of the pitch of the monomers present. The thermal catalyst must obviously be "inert" to the photochromic dyes optionally present. The thermal catalyst is optionally selected from the diazo compounds. These compounds are familiar to the person skilled in the art and are commercially obtainable. Examples of such diazo compounds are azobisisobutyronitrile (AIBN), 2,2'-azobis (2-methylbutynitrile) (AMBN), and 2,2'-azobis (2,4-dimethylavaleonitrile) (ADVN). of I invention in the presence of the last diazo compounds: ADVN. In the absence of a thermal catalyst or in the presence of a very low amount thereof, it would be necessary to carry out the thermal prepolymerization and the final thermal polymerization at higher temperatures and this would make the reaction difficult to control ... In the presence of a very large amount of catalyst, an excess of free radicals can be generated, this excess of free radicals inducing a destruction of the optionally present photochromic dyes and an accelerated fatigue of the final material. In this latter hypothesis, prepolymerization and polymerization can also be accelerated and made difficult to control. The person skilled in the art has even to appreciate, instead of the above indications and especially of the nature of the monomers present with the effective amounts involved in each case. The polymerization modifier can advantageously intervene, in a manner known per se, in combination with said thermal catalyst. The polymerization modifier generally intervenes with a maximum content of 5% by weight, advantageously at a ratio of 0.01 to 2% by weight, of the weight of the monomers to be copolymerized. It is noted here that it is possible to suppress the presence of such a polymerization modifier in the hypothesis in which the piece is prepared with a reduced thickness (e <2.0 mm). In this hypothesis the problems of heat evacuation are not faced ... for the preparation of a resin of the invention having a thickness greater than 2.0 mm, the presence of a polymerization modifier in the amounts indicated above is generally timely. It is strongly advised against exceeding the maximum content of 5% indicated above, since the glass transition temperature of the prepared material. It is highly recommended, for the preparation of a piece of thickness between 1.5 and 20 mm, a polymerization modifier content of approximately 1.2%. it has been noted that the coloring ability and the kinetics of darkening of the photochromic parts (especially lenses) prepared according to the invention increases the amount of polymerization modifier that intervenes. In the same way with this amount it rises, the mechanical strength increases and the optical quality improves ... It is obviously appropriate that said polymerization modifier does not destroy the photochromic dyes optionally present during the polymerization and / or does not induce a discoloration of the material itself. alone. Such a polymerization modifier is advantageously a chain transfer agent. Said chain transfer agent can be a non-halogenated chain transfer agent, such as a linear alkanethiol or a bis-mercaptoethyl ether. One can cite dodecanethiol as an example of linear alkanethiol without being limiting. It is not excluded to use other types of chain transfer agents, such as alkanethiols substituted by at least one aryl radical or alkyl or thiophenols. All of these compounds are familiar to the person skilled in the art and are commercially obtainable. It has been previously seen that regardless of the variant embodiment of the method of the invention, the photoinitiators characteristically intervene in a limited amount: less than or equal to 0.009 parts by weight per 100 parts by weight of the monomer mixture that is to be used. polymerize. They advantageously intervene in an amount between 0.002 and 0.009 parts by weight. Below this, the photochromic polymerization (to be executed in step c, even in step a) may be difficult only run. Above this, problems are faced with the photochemical polymerization techniques of the prior art. A single photoinitiator usually intervenes. It can be selected especially between acyl oxides and diacylphosphine oxides. It advantageously consists of a diacylphosphine oxide. It is noted incidentally that the irradiation time for the optional execution of the photochemical prepolymerization and that of the photogelification obviously depends on the wavelength and intensity of the irradiation, and on the shape and thickness of the mixture to be polymerized, of the amount of photoinitiator present ... and said irradiation time is generally selected after the experimental tests. This irradiation is executed for the photogelification through the surface of at least one of the walls of the mold. It is not excluded in the context of the present invention also to introduce, in suitable amounts, other additives for the execution of the photochemical polymerization (step c, and optionally step a). The method of the invention, as described above according to its aspects of methods and materials in which it is possible to carry out, is more particularly suitable for the preparation of organic parts of optical quality, and especially lenses whose thickness is between 0.2 and 20. mm. As indicated in the introduction of the present text, the field of application of the method of the invention is not limited, with reference to lenses, to the development of thin lenses (whose thickness is limited, for example, to 2 mm). In this, the method of the invention is particularly interesting. It has been seen above that the monomer mixture to be polymerized according to the method of the invention advantageously comprises at least one acrylic monomer which is at least trifunctional. The use of this type of monomers with the preparation due organic optical quality and especially organic lenses is totally innovative. Thus, such organic parts, obtained by radical polymerization of a monomer mixture containing at least one of three monomers which is at least trifunctional, are novel and constitute another object of the present invention. Advantageously, said novel organic parts are prepared per se, according to the method described above, which constitutes the first object of the present invention. It is not excluded to obtain them by means of prior technical polymerization which is purely thermal or purely photochemical. According to its last object, the present invention relates to original polymerizable compositions which can constitute the starting product, on which advantageously the method of the invention is executed, in order to obtain organic parts of optical quality and especially organic lenses. Such compositions are, as already specified, mixtures of radically polymerizable monomers. Said mixtures optionally contain at least one photochromic dye. They can be of the type the compositions according to US-A-5 621 017, but characteristically contain at most 0.009 parts by weight (advantageously 0.002 to 0.009 parts by weight), per 100 parts by weight of each monomer, at least they are photoinitiator Characteristically, they can contain at least one thermal catalyst for the subsequent execution of the prepolymerization step, when it is a case of thermal prepolymerization or of the final (thermal) polymerization, in the hypothesis in which it is used for the execution of the method of the invention. They are advantageously of the type of the compositions according to FR-A-2,762,845 and characteristically contain at least one acrylic number having at least three reactive functions (advantageously from three to six reactive functions). Such compositions - mixtures of radically polymerizable monomers, currently claimed in themselves - comprise: - at least one difunctional monomer, of the type (a), of one or other of the formulas (A) and (A ') as defined above; - at least one difunctional monomer, of type (b), of one or other of the formulas (B), (B '), and (B ") as defined above, and - at least one acrylic monomer having at least three reactive functions advantageously selected from the group consisting of: + pentaerythritol triacrylate, + pentaerythritol tetracrylate, + propoxylated glycerol triacrylate, + trimethylolpropane triacrylate, + polyurethane triacrylate, + dipentaerythritol hexaperylate. Such compositions may also have at least one monomer if reacted from the group consisting of: - monomers of the type (c) ), of the formula (C) (see above); - the monomers of type (d), of the formula (D) (see above); - the monomers of type (e), of the formula (E) (see above); - diallyl phthalate (see above). They advantageously contain: - at least one difunctional monomer, of type (a), or formula (A), as defined above; - at least one difunctional monomer, of type (b), or the formula (B), as defined above; - at least one acrylic monomer having at least three reactive functions advantageously selected from the group consisting of: + pentaerythritol triacrylate, + pentaerythritol tetracrylate, + propoxylated glycerol triacrylate, + trimethylolpropane triacrylate, + polyurethane triacrylate, + dipentaerythritol hexaperylate - at least one aromatic divinyl monomer of the formula (D): wherein R? = H or CH3; said divinyl monomer advantageously consists of divinylbenzene; and - at least one (meth) acrylic monomer of the formula (E): CH2 = C (R) -COOR 'in which R = H or CH3 and R' is a straight or branched alkyl radical having from 4 to 16 carbon atoms, an optionally substituted benzyl or phenoxyethyl radical or a polyethoxy group of the formula - (CH2-CH2-0) nR "in which n is an integer between 1 and 10 and R" = CH3 or C2Hs; said (meth) acrylic monomer advantageously consists of 2-ethylexylmethacrylate. The invention is illustrated, in its different aspects, while examples 1, Ibis, 1 ter to 4 following. The interest returns to the consideration of said examples and comparative examples 1 and 2. Monomer mixtures (novel per se, by virtue of the fact that they contain a low amount of photoinitiator) are polymerized according to the invention (thermal polymerization + photochemical polymerization). ) for the purpose of get organic lenses (novel by itself, when you enter an acrylic number that is at least trifunctional, in the starting mixture). • Preparation of the difunctional oligomer terminated in urea of type (b): In a thermostatic glass reactor equipped with a thermometer, stirrer, nitrogen purge and dripper, the following are introduced with agitation: 300 g of JEFFAMINE® ED 2003 (poly (oxyethylene) ) diamine of average molecular mass 2,000) of Huntsman Corp., and 0.0075 g of methoxyphenol. When the JEFFAMINE has melted (homogeneous mixture), 700 g of JEFFAMINE® ED 600 (poly (oxyethylene) diamine of average molecular mass 613) are added from Huntsman Corp. The temperature of the mixture is adjusted to 30 ° C and then added 764 g of benzylmethacrylate. The mixture is cooled to 20 °, and then 528 g of 3-isopropenyl-α, α-dimethylbenzyl isocyanate (m-TMI® from Cytec) is added slowly with vigorous stirring. The difunctional oligomer with urea ends of type (b) is thus obtained, which is ready to be diluted with the other monomers and other additives which may be involved in a polymerizable composition to be polymerized according to the invention. The product obtained in solution in benzyl methacrylate is designated, with the abbreviation JEFF / BzMA. • Abbreviations of the compounds: Diacrilo 121: tetraethoxylated bisphenol A dimethacrylate: difunctional monomer of type (a) BzMA: benzyl methacrylate DVB: divinylbenzene EHMA: ethylhexymethacrylate PETA: pentaerythritol triacrylate NDM: n-dodecyl mercaptan (n-dodecanethiol) JEFF / BzMA: consult the synthesis described above: difunctional oligomer of type (b) IRGACURE 819 from CIBA: bis (2,4,6-trimethylbenzoyl) phenyl-phosphino oxide ADVN: 2,2'-azobis (2,4-dimethylpentanitrile) CR49: 2- (p. -dimethylaminophen) -2-f-methoxyphenyl) -5-methyl-7,9-dimethoxy- [2H] -naphtho [1,2-b] pyran, CR59: 3- (p-methoxyphenyl-3-phenyl-6) -morpholino-3H-naphtho- [2,1-b] pyran, ruby red: S-phenyl-S ^ '- piperidinopheni-β-morpholino-SH-naphtho [2,1 b] pyran.

EXAMPLE 1 a) Preparation of the mixture to be polymerized. A one-liter thermostatic glass reactor equipped with agitation, thermometer and nitrogen purge is charged with: 92 g of DVB, to which is added 0.456 g of CR49, 0.0536 of CR59 as photochromic compounds 2.08 g of ADVN as initiator of the radical polymerization, 0.072 g of IRGACURE 819 as photoinitiator of the radical polymerization. The mixture thus obtained is maintained with agitation until the total dissolution of the compounds at 25 ° C. 345.6 g of the reference monomer JEFF / BzMA, 338.4 g of Diacrilo 121, 23.2 g of EHMA, 40 of PETA and 4 g of NDM are then added. The mixture is kept under stirring and in nitrogen purge for about 30 minutes at room temperature. ß) Thermal prepolymerization The temperature is then maintained at 46 ° C until a partially polymerized viscous mixture having a viscosity of 0.4 Pa.s (approximately 35 min.) is obtained. At this stage, the reaction is stopped by cooling the reaction mixture to 20 ° C, introducing bubbling dry air for 15 minutes.

The mixture (resin) thus obtained is then pumped out in vacuo and kept under stirring for about 2 hours. Photogellation This resin is then poured into a lens mold consisting of a mold and a glass counter-mold having a curved edge of approximately 87 mm and a PVC joint of 11 mm. The assemblies thus prepared are then exposed to the light of fluorescent tubes (Brillant 840 of Mazda, E = 0.30 mW / cm2 at 460 nm) until the resin gels, ie approximately 15 to 30 minutes. d) Thermal polymerization The assemblies are then placed in an oven and subjected to the following cycle: - at 25 to 50 ° C in 5 hours and then at 50 to 95 ° C in 3 hours and finally a plateau at 95 ° C for 2 hours. hours. After sufficient cooling, the samples are removed from their molds and inspected visually. The samples that are prepared following this method of the invention do not possess any visible optical defect, such as striations, ropes, cracking ...

EJEPLOS 1 BIS AND 1TER a) Preparation of the mixtures to be polymerized. A thermostatic glass reactor equipped with a stirrer, thermometer and nitrogen purge was charged with: The mixture thus obtained is maintained with agitation with the total dissolution of the compounds at 25 ° C. The mixture is then maintained with stirring and in nitrogen purge for approximately 30 minutes at room temperature, ß) Thermal prepolymerization?) Photogelling. d) Thermal polymerization These successive operations are identical to those previously described in example 1. Samples prepared following this The method of the invention (gray samples for example 1a, brown samples for example 1ter) do not possess any visible optical defect.

EXAMPLE 2 The operations are identical to those previously described in example 1, except step (ß) of partial thermal polymerization at 46 ° C (prepolymerization) which in this case is replaced by a step (ß ') of partial photopolymerization. In order to do this, the glass reactor is subjected to luminous flux originating from fluorescent tubes that are identical to those described to obtain the viscous mixture having a viscosity of 0.4 Pa.s after the exposure time of about 50. minutes at room temperature. The operations that follow are identical to those described in example 1. The lenses obtained after production are free from defects.

EXAMPLE 3 Carried out in the same way as that described in example 2, except that the photoinitiator IRGACURE 819 is introduced in two batches, as follows: Only 0.032 g of IRGACURE 819 is charged to the reactor in order to make possible the partial polymerization of the mix as indicated in example 2. The remainder, ie 0.04 a of IRGACURE 819 is added to the partially polymerized viscous mixture (at the end of step β '). The lenses obtained by this method are free of optical defects.

EXAMPLE 4 The operations are identical to those described in example 3, except that the thermal polymerization initiator, ADVN, is introduced after the partial photopolymerization of the mixture, at the same time as the rest of IRGACURE 819. As before, the lenses possess a very good optical quality.

COMPARATIVE EXAMPLE 1 Carried out as in example 1, except for the omission of the gelling step (step?) With fluorescent tube (logically, in step a, no IRGACURE 819 intervenes). The partially thermally polymerized mixture having a viscosity of 0.4 Pa.s. is thus poured. directly to the molds and then subjected to the curing cycle in an oven described in example 1. The lenses have numerous striations and ropes, which makes them unsuitable for use, such as for ophthalmic lenses.

COMPARATIVE EXAMPLE 2 Carried out as in example 1, but omitting the partial polymerization step (step β of thermal prepolymerization) of the mixture. Thus, the composition is poured directly into the molds and exposed to the luminous flux that originates from the same fluorescent tubes as those used for the preceding examples in order to ensure gelation of the mixture. The type of gelling is then approximately 1 hour minutes and the lenses obtained have numerous defects (striations, strings).

Claims (18)

NOVELTY OF THE INVENTION CLAIMS

1. - A method of preparing optical photochromic or non-photochromic organic parts and especially organic lenses, by radical polymerization of a radically polymerizable monomer mixture, characterized in that said method comprises: a) adjusting, by pre-polymerization, the viscosity of said mixture, to a value between 0.4 and 2 Pa.s; b) pouring said prepolymerized mixture into a mold; c) photogelifying, in said mold, said prepolymerized mixture to its gelling point; d) completing the polymerization of said prepolymerized and gelled mixture in said mold, by thermal treatment; effective amounts of at least one thermal catalyst and at least one photoinitiator are added to said monomer mixture for the execution of said prepolymerization, photogelling and polymerization; said photoinitiators intervening in an amount less than or equal to 0.009 parts by weight per 100 parts by weight of said monomer mixture.

2. The method according to claim 1, further characterized in that said prepolymerization is a thermal or photochemical prepolymerization.

3. The method according to claim 1 or 2, further characterized in that said prepolymerization is a thermal prepolymerization carried out on the monomer mixture containing the effective amounts of thermal catalysts and photoinitiators or containing only the effective amount of thermal catalysts, then adding the effective amount of photoinitiators to said monomer mixture, upon completion of their thermal prepolymerization before it is poured into the mold.

4. The method according to one of claims 1 or 2, further characterized in that said prepolymerization is a photochemical prepolymerization carried out on the monomer mixture containing the effective amount of photoinitiators or advantageously containing only the 40% to 60% of said effective amount expressed by weight, then adding the remaining photoinitiators to said monomer mixture, at the end of their photochemical prepolymerization, before it is poured into the mold; the effective amount of thermal catalysts is added to said monomer mixture, before its photochemical prepolymerization or at the end thereof.

5. The method according to any of claims 1 to 4, further characterized in that said photogelling and said prepolymerization are carried out, in the case of a photochemical prepolymerization, under an irradiation that is predominantly in the visible spectrum and that is almost free of ultraviolet radiation.

6. The method according to any of claims 1 to 5, further characterized in that said mixture of The monomers contain acrylics and / or methacrylics and / or alkenyl, especially vinyl or allylic monomers.

7. The method according to any of claims 1 to 6, further characterized in that said monomer mixture contains one or more difunctional monomers of type (a) and one or more difunctional monomers of type (b): the difunctional monomers being of type (a) - (met) acrylics - of one or other of the following formulas (A) and (A '): + formula (A): wherein: R1 t R'i, and R ', identical or different, are independently a hydrogen or a methyl group; m and n are, independently, numbers between 0 and 4 (inclusive); and are advantageously independently equal to 1 or 2; X and X 'identical or different, are a halogen or preferably represent a chlorine and / or bromine atom; p and q are, independently, integers between 0 and 4 (inclusive); + formula (A1): wherein: R ^ and R'-i, identical or different, are independently a hydrogen or a methyl group; R is a straight or branched alkyl radical having from 2 to 8 carbon atoms, a cycloalkyl radical having from 3 to 6 carbon atoms, an ether radical of the formula (R'-OR ") in which R 'and R ", identical or different, are independently a straight or branched alkyl radical having from 2 to 4 carbon atoms; the difunctional monomers of type (b) - long chain alternating difunctional oligomer being one or other of the following formulas (B), (B ') and (B "): + formula (B): wherein: Ri, R'i, R2 and R'2, identical or different, are independently hydrogen or a straight or branched alkyl radical, advantageously straight, having from 1 to 4 carbon atoms; and in a particularly advantageous manner correspond to a methyl group; R3 and R4, different, are independently a hydrogen and the other an alkenyl radical having from 2 to 6 carbon atoms, advantageously from 2 to 4 carbon atoms and particularly advantageously an isopropenyl radical; R'3, RU, are independently a hydrogen and the other an alkenyl radical having from 2 to 6 carbon atoms, advantageously from 2 to 4 carbon atoms and particularly advantageously an isopropenyl radical; Z represents a carbamate function (-NH-CO-0-), a thiocarbamate function (-NH-CO-S-) or a urea function (-NH-CO-NH-); Z ', independently of Z and advantageously respectively with respect to Z, represents a carbamate function (-0-CO-NH-) a thiocarbamate function (-S-CO-NH-) or a urea function (-NH-CO) -NH-); R 'represents a straight or branched alkyl radical having from 2 to 4 carbon atoms; R, identical or different when n > 2 is a straight or branched alkyl radical having from 2 to 4 carbon atoms; And, identical or different when n > 2, is oxygen or sulfur; n is an integer defined in such a way that the total number of carbon atoms, contained in the long chain lying between the two portions Z and 71, is at least equal to 18 and advantageously is between 18 and 112 (inclusive); + formula (B '): wherein: Ri, R2, R3, Rt, R'i, R'2, R * 3, RU, R and Y are as defined above with reference in formula (B); n is an integer defined in such a way that the total number of carbon atoms, contained in the long chain of the portion (R-Y) n, is at least equal to 22 and advantageously is between 22 and 104 (inclusive); + formula (B "): wherein: Ri, R2, R3, R4, R'i, R'2, R'3, RU, R, R 'and Y are as defined above with reference in formula (B); Z 'is a carbamate function (-O-CO-NH-) or Z' is a thiocarbamate function (-S-CO-NH-); advantageously, Z 'is a carbamate function; n is an integer defined such that the total number of carbon atoms contained in the long chain of the portion (R-Y) n -R \ is at least equal to 22 and advantageously is between 22 and 104 (inclusive).

8. The method according to claim 7, further characterized in that said monomer mixture contains at least one monomer of the type (b) - vinyl difunctional monomer - of the formula (B) in which: Z and Z 'are urea functions of the formula (-NH-CO-NH-); R1, R'1, R2 and R'2, identical and represent methyl radicals; R3 and R'3, identical, represent an isopropenyl; R4 and RU, identical, are hydrogen; R 'represents an ethylene or propylene group; n is an integer equal to 13 or 19 which defines a total number of carbon atoms between Z and Z 'equal to 28 or 40, when (R-Y) n is a polyoxyethylene chain; or n is an integer equal to 10 or 14 which defines a total number of carbon atoms between Z and 71, equal to 33 or 45, when (R-Y) n is a polyoxypropylene chain; or n is a whole number between the values of the lower limit (n is between 10 and 13 (inclusive)) and the values of the upper limit (n is between 14 and 19 (inclusive)), when (R-Y) n is a mixed polyoxyethylene / polyoxypropylene chain.

9. The method according to any of claims 1 to 8, further characterized in that said monomer mixture also contains: (c) at least one aromatic monovinyl monomer of the formula (C): in which Ri = H or CH3; said monovinyl monomer advantageously consisting of styrene; and / or (d) at least one aromatic divinyl monomer of the formula (C): wherein R1 = H or CH3; advantageously comprising divinyl monomer of divinylbenzene; and / or (e) at least one (meth) acrylic monomer of the formula (E): CH2 = C (R) -COOR 'in which R = H or CH3 and R' is a straight or branched alkyl radical having from 4 to 16 carbon atoms an optionally substituted benzyl or phenoxyethyl radical (generally substituted by an alkyl group of C? -C6) or a group polyethoxy of the formula - (CH2-CH2-0) nR "in which n is an integer between 1 and 10 R") CH3 or C2H5; said (meth) acrylic monomer advantageously consisting of 2-ethylhexyl-methacrylate; and / or (f) diallyphthalate.

10. The method according to any of claims 1 to 9, further characterized in that said monomer mixture contains at least one acrylic monomer having at least three reactive functions, advantageously selected from: pentaerythritol triacrylate, pentaerythritol tetraacrylate , propoxylated glycerol triacrylate, trimethylolpropane triacrylate, polyurethane triacrylate, dipentaerythritol hexaacrylate, and advantageously consisting of pentaerythritol triacrylate.

11. The method according to any of claims 1 to 10, further characterized in that said monomer mixture contains an effective amount of at least one photochromic dye intended to give photochromic properties to the prepared pieces; said dyes are advantageously selected from the group of spiroxazines, cryomena and mixtures thereof.

12. The method according to any of claims 1 to 11, further characterized in that said thermal catalyst is selected from diazo compounds and advantageously consists of 2,2'-azobis (2,4-dimethylvaleronitrile) (ADVN).

13. The method according to any of claims 1 to 12, further characterized by selecting said photoinitiator between acyl oxide and diacylphosphine oxide and advantageously consists of a diacylphosphine oxide.

14. The method according to any of claims 1 to 13, further characterized in that it is used to prepare pieces whose thickness are between 0.2 and 20 mm.

15. Optical quality organic parts and especially organic lenses preparable by the method according to any of claims 10 to 14.

16. Mixtures of radically polymerizable monomers containing or not containing an effective amount of at least one photochromic dye , further characterized in that they have up to 0.009 parts by weight, and advantageously from 0.002 to 0.009 parts by weight, per 100 parts by weight of said monomer mixtures, of at least one photoinitiator.

17. Mixtures of radically polymerizable monomers containing or not containing an effective amount of at least one photochromic dye, further characterized in that they comprise: at least one difunctional monomer, of type (a), of one or other of the formulas ( A) and (A ') as defined in claim 7; at least one difunctional monomer, of type (b), of one or other of the formulas (B), (B ') and (B ") as defined in claim 7, and at least one acrylic monomer having at least three active functions, advantageously selecting from the group consisting of: pentaerythritol triacrylate, pentaerythritol tetraacrylate, propoxylated glycerol triacrylate, trimethylolpropane triacrylate, polyurethane triacrylate, dipentaerythritol hexaacrylate.

18. Mixtures of radically polymerizable monomers according to claim 17, further characterized in that they comprise: at least one difunctional monomer, of the type (a), of the formula (A), as defined in claim 7; at least one difunctional monomer, of type (b), of formula (B), as defined in claim 7; and at least one acrylic monomer having at least three active functions, advantageously selected from the group consisting of: pentaerythritol triacrylate, pentaerythritol tetraacrylate, propoxylated glycerol triacrylate, trimethylolpropane triacrylate, polyurethane triacrylate, dipentaerythritol hexaacrylate; at least one aromatic divinyl monomer of the formula (D): wherein R? = H or CH3; said divinyl monomer advantageously consists of divinylbenzene; and at least one (meth) acrylic monomer of the formula (E): CH2 = C (R) -COOR 'in which R = H or CH3 and R' is a straight or branched alkyl radical having from 4 to 16 carbon atoms, an optionally substituted benzyl or phenoxyethyl radical or a polyethoxy group of the formula - (CH2-CH2-0) nR "in which n is an integer between 1 and 10 and R "= CH3 or C2H5; said (meth) acrylic monomer advantageously consists of 2-ethylexylmethacrylate.