WO2025023227A1 - Method for manufacturing a polymeric optical article and a composition used therefor - Google Patents

Abstract

The present invention relates to a process for manufacturing a polymeric optical article comprising providing a polymerizable composition comprising: at least one polyallyl-functional monomer containing a small amount of oligomers; from 0.5 to 2 wt.% of at least one aromatic peroxide as free radical initiator. The polymerizable composition is cured according to a predefined curing cycle which allows to obtain optical articles with improved properties without using highly reactive radical initiators, like IPP. Moreover, productivity of the process is increased with a remarkably reduced number of defects in the optical articles. The invention also relates to a polymerizable composition suitable for use in the above process.

Description

METHOD FOR MANUFACTURING A POLYMERIC OPTICAL ARTICLE AND A COMPOSITION USED THEREFOR

The present invention relates to a method for manufacturing a polymeric optical article and a composition used therefor.

Polyallyl-functional monomers are polymerized using free radical initiators to produce hard polymers. Many of these polymers are substantially transparent to visible light, are substantially colorless, have refractive indices of from about 1.45 to about 1.6, and possess good mechanical resistance. For these reasons, such monomers are widely employed as precursors for optical articles such as optical lenses and optical lens blanks, safety lens, and flat or curved transparent sheets. Light transmission characteristics may be altered by incorporating dyes, light absorbing compounds, pigments, and the like, in the polymerizable composition containing the monomer before polymerization, or by dying the polymer.

The polymerization reaction of the polyallyl-functional monomers is normally carried out in the presence of peroxide initiators, especially dialkylperoxy carbonate, such as for example diisopropylperoxy carbonate (IPP) or mixtures of IPP and di-s-butylperoxy carbonate, which allow to obtain polymerized products having excellent optical properties, in particular transparency, and low colouring.

Dialkylperoxy carbonate initiators, especially IPP, however, have the disadvantage of being highly expensive and highly thermally unstable, with explosive decomposition, and thus require quite severe transportation and storage conditions. Even when they are formulated in diluted form, using for example a polyallyl-functional monomer for dilution, they require transportation and storage temperatures as low as about -20 °C to -10 °C.

In the state of the art, peroxide initiators are also known that are stable at ambient temperature (also called Ambient Stable Initiators: ASI) and therefore potentially capable of overcoming the above-mentioned drawbacks of the dialkylperoxy carbonate initiators. However, ASI compounds (e.g. diacyl peroxides, alkyl peroxyesters, alkyl peroxyketals and peroxymonocarbonates) also have certain disadvantages that have so far limited their use in the practice as initiators for the polymerization of polyallyl-functional monomers.

Certain ASI compounds, for example, have low solubility in the polyallyl-functional monomers thus leading to unsatisfactory level of curing of the polymerized material. Furthermore, polymerized materials obtained using ASI compounds like diacyl peroxides initiators (e.g. benzoyl peroxide) exhibit considerable yellowing and poor resistance to UV light. Moreover, compared to the polymerized materials obtained using IPP as initiator, the materials polymerized using ASI compounds normally exhibit relatively high hardness and brittleness as well as high levels of shrinkage.

As used herein, the term “shrinkage” (S) refers to the ratio

where D_pol is the density of the final thermoset polymer at 23 °C and D_mon and is the density of the liquid polymerizable composition at 23°C. The term “percent (%) shrinkage” is equal to shrinkage multiplied by one hundred.

High levels of shrinkage are particularly detrimental in casting processes such as those customarily used to produce ophthalmic lenses and ophthalmic lens blanks, wherein the liquid monomer composition is introduced into a mold and thereafter polymerized to the final polymer in a thermoset state.

When polymerization is carried out in the presence of ASI compounds as initiators, in fact the liquid polymerizable composition has to be heated to a relatively high initial temperature, e.g. about 60 °C for BPO (i.e. much higher than about 40 °C for IPP) in order to start the curing cycle and thus the polymerization reaction. This initial heating step, however, is accompanied by a volume expansion of the polymerizable composition within the mold that leads to a non-negligible reduction of density of the polymerizable composition to be cured. Since the initial volume expansion is higher than that occurring when the same polymerizable composition is cured with IPP or other non-ASI initiators, the shrinkage observed for the polymerized material cured with the ASI initiator is significantly higher than that of the same polymerizable composition cured with IPP or other non-ASI initiators.

Such a high level of shrinkage brings about numerous defects in the polymerized material and frequently causes breakages of the same or of the molds leading therefore to overall low yields for the manufacturing processes using ASI initiators.

In the state of the art, it is known that the shrinkage may be reduced by using special polymerizable compositions. For example, when the polyallyl-functional monomer is diethylene glycol bis(allyl carbonate), which is one of the most used polyallyl-functional monomer for the production of optical articles, having the following formula (II)

wherein n is a positive integer (for example in the range 1-10), shrinkage can be reduced by including in the polymerizable composition one or more mono- or poly-ethylenically unsaturated compounds that are not poly(allyl carbonate)-functional monomers.

Examples of these mono- or poly-ethylenically unsaturated compounds, also called co-monomers or reactive diluents, are mono- or polyethylenically unsaturated compounds such as vinyl esters of versatic acid 9 and 10. The comonomers may be liquid components having a lower density of polymerizable double bonds (i.e. the number of double bonds per unit mass of the compound) than diethylene glycol bis(allyl carbonate) monomer. These comonomers allow to obtain a final polymerized material having a lower level of crosslinking (i.e. a lower value of the term D_pol in the above shrinkage equation) compared to the polymerized material obtained from diethylene glycol bis(allyl carbonate) monomer devoid of comonomers and therefore a lower final shrinkage.

Alternatively, or in addition to the above effect, the comonomers may have a higher density (i.e. mass/volume ratio) than diethylene glycol bis(allyl carbonate) monomer so that the casted polymerizable composition containing the polyallyl-functional monomer and the comonomers has an increased density (i.e. a higher value of the D_mon term in the above shrinkage equation) and therefore a lower final shrinkage. This is the case for example of compounds with high molar mass or polyfunctional structure, i.e. having three or more ethylenically unsaturated functional groups per molecule as disclosed in US 4144262 where they are also used in pure form as an alternative to the use of diethylene glycol bis(allyl carbonate) monomer.

This approach to reduce shrinkage using comonomers is described for example in WO 2004090002A1, US 2021/0263197A1, EP3381951A1 and EP 0241997.

In an alternative approach, when the polyallyl-functional monomer is diethylene glycol bis(allyl carbonate) of above formula (II), the polymerizable composition may include a relatively high content of oligomeric species, that is species of formula (II) wherein n is equal to 2 or more. As these oligomeric species have a lower density of polymerizable double bonds compared to the linear species of the diethylene glycol bis(allyl carbonate) monomer (i.e. the species of formula (II) with n = 1), they allow to achieve a final polymerized material having a lower level of crosslinking (i.e. lower value of the term D_pol in the shrinkage equation) and therefore a lower final shrinkage.

This approach to reduce shrinkage is described for example in in WO 00/27794 and WO 2017/168325A1.

Problem that the Invention is to Solve

Another way to reduce shrinkage known in the art is based on the introduction in the mold of a liquid prepolymer, which is then polymerized to obtain the final thermoset polymer. The prepolymer is usually produced by partially polymerizing the polyallyl-functional monomer so as to consume a portion of the allylic groups. The partial polymerization is stopped, however, before more than a trivial amount of gelation occurs so that the prepolymer may be introduced into the mold as a liquid. An example of this technique is described in US 6057411.

The methods and monomer compositions of the state of the art that are suitable for reducing shrinkage, however, involve high costs because of the use of additional raw materials (i.e. comonomers) and complex preparation processes (the provision of special polyallyl-monomers and prepolymers).

In addition, the use of special polyally-monomers and prepolymers according to the prior art can have detrimental effects on process productivity. In fact, the higher reactivity of prepolymers forces to prepare small batches to avoid undesired premature gelification of the material in the process equipment. Moreover, high molecular weights of special polyallyl-monomers and prepolymers cause higher viscosity and density of the material to be processed, and consequently longer times for filling the glass moulds and thus reduced productivity.

The need is therefore felt in the state of the art for new methods for polymerizing polyallyl-functional monomers with the aid of ambient stable polymerization initiators.

Means for solving the problem

A process has now been found that allows to easily polymerize a polyallyl-functional monomer as defined hereinbelow with the aid of ambient stable polymerization initiators to obtain a polymer material having good mechanical and optical properties, these properties being substantially comparable to those of polyallyl-functional monomers polymerized using IPP initiator.

The polymerization process, i.e. curing, of the polyally-functional monomer described herein enables to substantially minimize the detrimental effects associated to the shrinkage occuring in the processes of the prior art in which ASI compounds are employed as initiators and therefore provide a very efficient and productive way for manufacturing polymeric optical articles.

The present invention is based on the observation that curing a polymerizable composition comprising a polyallyl-functional monomer as defined hereinbelow and a relatively small amount of an ambient stable aromatic peroxide (e.g. benzoyl peroxide) by heating the composition at a sufficiently slow rate as defined hereinbelow leads to a progressive gelification and curing of the polymerizable composition without a significant volume expansion within the molds. The process herein described, therefore, minimizes the occurrence of breakages and optical defects in the polymerized articles with the consequent increase of the process productivity.

In particular, according to the present invention the curing cycle comprises a step of isothermally heat treating the polymerizable composition at a temperature (T_A) close to the ten-hour half-life temperature of the aromatic peroxide and holding the composition at that temperature T_A for a certain priod of time (as defined hereinbelow), which is followed by a step of further heat treating the polymerizable composition by raising its temperature from the temperature T_A up to a final temperature (T_F), which is within the range of from 80 °C to 120 °C. The curing is then completed to obtain the final polymerized material (hereinafter also indicated as “polymerizate”).

Without wishing to be bound to any theory it is believed that by using a small amount of aromatic peroxide initiator (i.e. lower than those customarily employed in the state of the art for ASI compounds) in combination with a curing cycle according to the temperature-time profile herein described, a more uniform distribution of the heat generated by the exothermic polymerization reaction within the mass of the polymerizable composition is achieved and thus a more uniform polymerization reaction of the polyallyl-functional monomer. This, in turn, leads to a polymerized material having the desired mechanical and optical properties with a few or no defects (e.g. flow lines). Moreover, since the isothermal treatment minimizes the volume expansion of the polymerizable composition within the mold, the difference between the density of the final polymerized material and the density of the liquid polymerizable composition at the starting temperature of the curing cycle is maintained low with beneficial effects in terms of shrinkage.

In one embodiment these results may be achieved without resorting to the use of any comonomer, prepolymer or polyallyl-functional monomer requiring complex preparation processes in the polymerizable composition. This is advantageous as it allows to manufacture optical articles starting from polyally-functional monomers that are obtained with easier and more cost-effective preparation processes along with cheaper and easier-to-handle free radical initiators.

Moreover, the use of a relaytively small amount of aromatic peroxide (i.e. lower than the usual amount of about 3 wt.% on the basis of the polyallyl-functional monomer) has the additional advantage of keeping the yellowness and hardness of the final optical article within acceptable levels differently from the prior art.

Furthermore, despite the extended duration of the manufacturing process (about 20 to 48 hours), the present invention allows to use ambient stable initiators instead of more unstable peroxides (like IPP) with significant advantages in terms of personnel safety, manufacturing costs as well as transportation and storage conditions.

Therefore, according to a first aspect the present invention relates to a process for manufacturing a polymeric optical article comprising:
A. providing a polymerizable composition comprising:
- at least one polyallyl-functional monomer having formula (I):

wherein X represents a divalent to hexavalent group derived from a linear or branched aliphatic polyol having 3 to 12 carbon atoms or a divalent to hexavalent group derived from an alicyclic polyol having 5 to 16 carbon atoms, and n represents an integer of 2 to 6;
wherein the polyallyl-functional monomer having formula (I) comprises 70 wt.% or more, preferably 80 wt.% or more, of the polyallyl-functional monomer having formula (I) for which n is equal to 2, the weight percentage being based on the total weight of the polyallyl-functional monomer having formula (I);
- from 0.5 to 2 wt.% of at least one aromatic peroxide as free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer;
B. curing the polymerizable composition according to a curing cycle comprising:
B1. heating the polymerizable composition up to an activation temperature T_A of from 12 °C to 3 °C lower than the ten-hour half-life temperature of the aromatic peroxide;
B2. holding the polymerizable composition at the temperature T_A for a period of from 8 to 24 hours;
B3. heating the polymerizable composition after the step B2 up to a final temperature T_F within the range of from 80 °C to 120 °C;
B4. holding the polymerizable composition at the final temperature T_F to obtain the optical article.

According to a second aspect, the present invention relates to a polymeric optical article obtained by the process according to the first aspect.

According to a third aspect, the present invention relates to an ophthalmic lens comprising the polymeric optical article according to the second aspect.

According to a fourth aspect, the present invention relates to a polymerizable composition comprising:
- at least one polyallyl-functional monomer having formula (I):

wherein X represents a divalent to hexavalent group derived from: (a1) a linear or branched aliphatic polyol having 3 to 12 carbon atoms; or (b1) a divalent to hexavalent group derived from an alicyclic polyol having 5 to 16 carbon atoms, and n represents an integer of 2 to 6;
wherein the polyallyl-functional monomer having formula (I) comprises 70 wt.% or more, preferably 80 wt.% or more, of the polyallyl-functional monomer having formula (I) for which n is equal to 2, the weight percentage being based on the total weight of the polyallyl-functional monomer having formula (I);
- from 0.5 to 2 wt.% of at least one aromatic peroxide as free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer.

According to a preferred embodiment of the present invention, the polymerizable composition is free of ethylenically unsaturated compounds different from the polyallyl-functional monomers having formula (I).

According to a preferred embodiment, the polyallyl-functional monomer is a diethylene glycol bis(allyl carbonate) compound of formula (II):

wherein n is an integer equal to or higher than 1 and equal to or lower than 10;
wherein the diethylene glycol bis(allyl carbonate) compound of general formula (II) comprises 70 wt.% or more, preferably 80 wt.% or more, of the diethylene glycol bis(allyl carbonate) compound of formula (II) for which n is equal to 1, the weight percentage being based on the total weight of the diethylene glycol bis(allyl carbonate) compound of general formula (II).

According to a preferred embodiment of the present invention, the polymerizable composition is free of ethylenically unsaturated compounds different from the diethylene glycol bis(allyl carbonate) compounds having formula (II).

　　　Further characteristics of the present invention are the object of the dependent claims annexed to the present description.

The compositions of the present invention can comprise, consist essentially of, or consist of, the essential components as well as optional ingredients described herein. As used herein, “consisting essentially of” means that the composition or component may include additional ingredients, but only if the additional ingredients do not materially alter the basic and novel characteristics of the claimed compositions or methods.

As used herein, the articles "a", "an" and “the” should be read to include one or at least one and the singular also includes the plural, unless it is obvious that it is meant otherwise. This is done merely for convenience and to give a general sense of the disclosure.

Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified in all instances by the term “about”.

Polyallyl-functional monomer.
The polymerizable composition according to the present invention comprises at least one polyallyl-functional monomer having formula (I). In most cases, the polymerizable composition comprises a mixture of polyallyl-functional monomers having formula (I) (i.e. monomer composition), said mixture comprising 70 wt.% or more, preferably 80 wt.% or more, of the polyallyl-functional monomer having formula (I) for which n is equal to 2, the weight percentage being based on the total weight of the mixture.

The polyallyl-functional monomers can be selected among a wide variety of liquid polyallyl compounds, which may include monomers and oligomers having at least two allyl groups as polymerizable functional groups.

The polyallyl-functional monomer may comprise, for example, compounds containing two or more allyl groups, such as diallyl esters and diallyl carbonate.

In one embodiment, the polyallyl-functional monomer comprises the liquid poly(allyl carbonates) of polyhydroxy organic materials. Examples of such monomers include poly(allyl carbonates) of linear or branched aliphatic polyols, and poly(allyl carbonates) of cycloaliphatic-containing polyols. These monomers are known and can be prepared by procedures well known in the art.

In one embodiment, the polyallyl-functional monomer is selected from: diethylene glycol bis(allyl carbonate), ethylene glycol bis(allyl carbonate), oligomers of diethylene glycol bis(allyl carbonate), oligomers of ethylene glycol bis(allyl carbonate), and mixtures thereof.

In the formula (I) as defined above, X represents a divalent to hexavalent group derived from: (a1) a linear or branched aliphatic polyol having 3 to 12 carbon atoms or (b1) a divalent to hexavalent group derived from an alicyclic polyol having 5 to 16 carbon atoms. Such polyols normally include 2 to 6 hydroxyl groups in the molecule, and it is possible for these polyols to include 2 to 4 hydroxyl groups in the molecule, which is preferable.

Examples of the aliphatic polyol (a1) include: diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, trimethylolpropane, tris(hydroxyethyl) isocyanurate, pentaerythritol, dipentaerythritol, and the like.

Examples of the alicyclic polyol (b1) include: 1,4-dimethylolcyclohexane, 4,8-bis(hydroxymethyl)-[5.2.1.0^2,6] tricyclodecane, and the like.
Specific examples of the compound including two or more allyloxycarbonyl groups include an allyl carbonate polymerizable compound (A1), an allyl ester polymerizable compound (A2), and a polymerizable compound (A3) including at least one of an allyl carbonate group and an allyl ester group.

A compound of formula (I) including two or more allyloxycarbonyl groups is a liquid product at room temperature, the viscosity measured at 25°C is 10 to 1000 cSt.
As used herein, the kinematic viscosity of a polyallyl-functional monomer or a polymerizable composition is determined in accordance with ASTM D446 using a KPG Ubbelodhe viscosimeter (capillary type 1C or 2C).

As reported above, the polyallyl-functional monomer of formula (I) may consist of at least one monomer of formula (I) wherein n = 2, or may be a mixture of siad at least one monomer of formula (I) wherein n = 2 with at least one oligomer thereof, i.e. at least one compound of formula (I) wherein n is from 3 to 6. The oligomer is a poly(allyl carbonate) in which two or more molecules of a polyol are linked via a carbonate group produced by transesterification reaction of allyl carbonate produced in the production step and a polyol.

Specific examples of the polyols forming group X in formula (I) include: diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-dimethylolcyclohexane, 4,8-bis(hydroxymethyl)-[5.2.1.0^2,6] tricyclodecane, glycerol, trimethylolpropane, tris(hydroxyethyl) isocyanurate, pentaerythritol, diglycerol, ditrimethylolpropane, dipentaerythritol, and the like.

The polyols forming group X in formula (I) may also be extended polyols, such as lactone extended polyols and alkyl oxide extended polyols. By an extended polyol is meant the reaction product having terminal hydroxyl groups of polyol and a suitable reactant, e.g. a lactone or an alkyl oxide.

Examples of lactone extended polyols include: epsilon-caprolactone extended diethylene glycol, epsilon-caprolactone extended dipropylene glycol, epsilon-caprolactone extended triethylene glycol, epsilon-caprolactone extended tetraethylene glycol, epsilon-caprolactone extended pentaerythrite and epsilon-caprolactone extended trimethylol propane.

Examples of alkyl oxide extended polyols include: ethylene oxide or propylene oxide extended diethylene glycol, ethylene oxide or propylene oxide extended dipropylene glycol, ethylene oxide or propylene oxide extended triethylene glycol, ethylene oxide or propylene oxide extended tetraethylene glycol, ethylene oxide or propylene oxide extended pentaerythrite, ethylene oxide or propylene oxide extended trimethylol propane.

Accordingly, examples of the allyl carbonate compounds include at least one kind selected from bis(allyl carbonate) compounds of at least one kind of diol selected from diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-dimethylolcyclohexane, and 4,8-bis(hydroxymethyl)- [5.2.1.0^2,6] tricyclodecane; tris (allyl carbonate) compounds of at least one kind of triol selected from glycerol, trimethylolpropane, and tris(hydroxyethyl) isocyanurate; tetra(allyl carbonate) compounds of at least one kind of tetraol selected from pentaerythritol, diglycerol, and ditrimethylol propane; dipentaerythritol hexa (allyl carbonate) compounds; and a mixed poly(allyl carbonate) compound of at least two kinds of compounds selected from the diols, the triols, the tetraols, and the dipentaerythritol.

The "bis(allyl carbonate) of a mixture of at least two kinds of diols" is, for example, obtained as a mixture of the following monomer components and oligomer components in a case where the diols are diethylene glycol and neopentyl glycol:
monomer component:
(1) diethylene glycol bis(allyl carbonate);
(2) neopentyl glycol bis(allyl carbonate);
oligomer component:
(3) oligomer including only hydrocarbons (and ethers) derived from diethylene glycol (a compound having a structure in which two hydroxyl groups of a compound in which diethylene glycol is linearly oligomerized via a carbonate bond are replaced with allyl carbonate groups);
(4) oligomer including only hydrocarbons derived from neopentyl glycol (a compound having a structure in which two hydroxyl groups of a compound in which neopentyl glycol is linearly oligomerized via a carbonate bond are replaced with allyl carbonate groups);
(5) complex oligomer including both hydrocarbons (and ethers) derived from diethylene glycol and a hydrocarbon derived from neopentylglycol in the same molecule (a compound having a structure in which two hydroxyl groups of a compound in which diethylene glycol and neopentyl glycol are linearly oligomerized in an arbitrary sequence in the same molecule via a carbonate bond are replaced with allyl carbonate groups).

The following are preferred examples of allyl carbonate polymerizable compounds of formula (II) suitable for the purposes of the present invention:
(i) Mixture with diethylene glycol bis(allyl carbonate) and oligomers thereof, where diethylene glycol bis(allyl carbonate) can be defined by formula (IIa)

In addition, it is possible to define an oligomer of diethylene glycol bis(allyl carbonate) by formula (IIb)

wherein n is equal to or higher than 2 and equal to or lower than 10.

It is possible to manufacture compound (IIa) by reacting diethylene glycol bis (chloroformate) with allyl alcohol as described in, for example, "Encyclopedia of Chemical Technology", Kirk-Othmer, Third Edition, Volume 2, pages 111-112. It is possible to easily produce mixtures of diethylene glycol-bis(allyl carbonate) (Formula (IIa)) and an oligomer (Formula (IIb)) thereof by ester replacement between diallyl carbonate and diethylene glycol in the presence of a basic catalyst, for example, as described in EP 35304. These mixtures usually include up to approximately 80% by weight of oligomers;

(ii) Mixture of bis(allyl carbonate) compound of a mixture of diethylene glycol and neopentyl glycol with oligomers thereof
This bis(allyl carbonate) compound is the same as the bis(allyl carbonate) compound of point (i) above except that diethylene glycol is replaced with a mixture of diethylene glycol and neopentyl glycol;

(iii) Mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol and tris (hydroxyethyl) isocyanurate with oligomers thereof
It is possible to obtain the poly(allyl carbonate) compound by ester replacement of a diallyl carbonate of a mixture of diethylene glycol and tris(hydroxyethyl) isocyanurate, for example, as described in US 4,812,545.

(iv) Mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol and trimethylolpropane with oligomers thereof.
This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound of point (iii) above, except that tris(hydroxyethyl) isocyanurate is replaced with trimethylol propane.

(v) Mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol and pentaerythritol with oligomers thereof.
This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound of point (iii) above, except that tris(hydroxyethyl) isocyanurate is replaced with pentaerythritol.

(vi) Mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol, neopentyl glycol, and pentaerythritol with oligomers thereof.
This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound of point (v) above, except that diethylene glycol is replaced with two kinds of diols of diethylene glycol and neopentyl glycol.

(vii) Poly(allyl carbonate) mixture including a mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol, neopentyl glycol, and pentaerythritol with oligomers thereof and a mixture of diethylene glycol bis(allyl carbonate) compound with oligomers thereof.
In one preferred embodiment, the polyallyl-functional monomer comprises or is a diethylene glycol bis(allyl carbonate) compound of formula (II)

wherein n is equal to or more than 1 and equal to or less than 10.

Preferably, the polyallyl-functional monomer comprises 70 wt.% or more, preferably 80 wt.% or more, of the diethylene glycol bis(allyl carbonate) compound of formula (II) for which n is equal to 1 (i.e. the monomer compound of above formula (IIa)), the weight percentage being based on the weight of the polyallyl-functional monomer.

The above wt.% relative concentrations of monomer species (n = 1) and oligomer species (n = 2-10) of formula (IIb) in the polyallyl-functional monomer can be determined by means of known methods. In particular, the concentration values can be determined by means of HPLC or GPC analysis under conditions which are such to obtain sufficiently separate peaks corresponding to the monomeric species and each of the oligomeric species and the subsequent calculation of the percentage area of the chromatographic peaks associated with each of the monomeric and oligomeric species.

In one embodiment the polyallyl-functional monomer comprises or is the reaction product (RP) of components comprising: diallylcarbonate (A), one or more linear or branched aliphatic diols (B) containing from three to ten carbon atoms in the molecule and optionally a linear or branched aliphatic polyol (C) containing from four to twenty carbon atoms and from three to six hydroxyl groups in the molecule; wherein the molar ratio A/(B+C) is within the range from 4/1 to 20/1 and the quantity of the optional component (C) in the mixture (B+C) is equal to or lower than 5 wt.%, with respect to the weight of said mixture (B+C).

Preferably, the molar ratio A/(B+C) is within the range from 5/1 to 10/1 and the quantity of (C) in the mixture (B+C) is equal to or lower than 3 wt.% with respect to the weight of said mixture (B+C).

Diols (B) are linear or branched aliphatic diols, preferably containing from 3 to 10 carbon atoms in the molecule.
Examples of suitable diols (B) are: diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-propanediol, neopentyl glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol and 1,4- cyclohexane dimethanol.
Preferably, diols (B) are selected from: diethylene glycol, neopentyl glycol and combinations thereof.

Polyols (C) are linear or branched aliphatic polyols, preferably containing from 4 to 20 carbon atoms and from 3 to 6 hydroxyl groups in the molecule.
Examples of suitable polyols (C) are: pentae- rythrite, trimethylol propane, dipentaerythrite, ditrimethylol propane and tris (hydroxy-ethyl) isocyanurate.
Preferably, polyols (C) are selected from: pentaerythrite, trimethylol propane and combinations thereof.

The polyallyl-functional monomer can be obtained as reaction product (RP) by reacting diallyl carbonate (A) with diol (B) or a mixture of diol (B) and polyol (C) under transesterification conditions and in the presence of a basic catalyst, as described for example in WO 2004/090002.

The reaction product (RP) at 25 °C has preferably a kinematic viscosity within the range of from 10 cSt to 300 cSt, more preferably from 10 to 100 cSt, even more preferably from 10 to 40 cSt. Preferably, the density of the reaction product RP at 25 °C is within the range of from 1.1 g/ml to 1.3 g/ml.

The reaction product (RP) is normally obtained as a mixture of allyl carbonates species of components (B) and (C), if present, in monomeric and oligomeric form, as well as in the form of mixed oligomeric allyl carbonates of said components (B) and (C), the relative quantities of said allyl carbonate species mainly depending on the selected ratios of the reagents (A), (B) and (C).

Polymerizable comonomers.
The polymerizable composition according to the presente invention may also comprise an ethylenically unsaturated compound (as a monomer or oligomer) that is capable of polymerizing with the polyallyl-functional monomer described above. Herein, this optional ethylenically unsaturated compounds are also named “comonomers”. Examples of suitable comonomers include: aromatic vinyl compounds such as styrene, alpha-methylstyrene, vinyltoluene, chlorostyrene, chloromethylstyrene and divinylbenzene; alkyl mono(meth)acrylates such as methyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, glycidyl (meth)acrylate and benzyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-phenoxy-2-hydroxypropyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1 ,3-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 2-hydroxy-1 ,3-di(meth)acryloxypropane, 2,2-bis[4-((meth)acryloxyethoxy)phenyl]propane, 2,2-bis[4-((meth)acryloxydiethoxy)phenyl]propane and 2,2-bis[4-((meth)-acryloxypolyethoxy)phenyl]propane; tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate and tetramethylolmethane tri(meth)acrylate; tetra(meth)acrylates such as tetramethylolmethane tetra(meth)acrylate. These comonomers may be used singly or in combination of two or more. In the above description, "(meth)acrylate" means "methacrylate" or "acrylate", and "(meth)acryloxy" means "methacryloxy" or "acryloxy".

The total amount of comonomer in the polymerizable composition according to the present invention may be from 1% to 80% by weight, in particular from 1 to 50% by weight, more particularly from 2% to 20% by weight, even more particularly from 3% to 10% by weight, based on the total weight of the polymerizable composition.

In one preferred embodiment, the polymerizable composition is free of additional ethylenically unsaturated compounds, which means that the polymerizable composition is not added with polymerizable comonomers; the only polymerizable compound present in the polymerizable composition is therefore the polyallyl-functional monomer of formula (I) or (II).

In one preferred embodiment, the polymerizable composition comprises a polyallyl-functional monomer that is diethylene glycol bis(allyl carbonate) compound of formula (II) wherein n is an integer equal to or higher than 1 and equal to or lower than 10 and is free of ethylenically unsaturated compounds as comonomers; the only polymerizable compound present in the polymerizable composition is therefore said diethylene glycol bis(allyl carbonate) compound of formula (II).

In one embodiment, the polymerizable composition comprises a polyallyl-functional monomer that is the above-described reaction product (RP) of components comprising diallylcarbonate (A), one or more aliphatic diols (B) and optionally an aliphatic polyol (C), and the polymerizable composition is free of ethylenically unsaturated compounds as comonomers; the only polymerizable compound present in the polymerizable composition is therefore the reaction product (RP) of components A, B and optional C.

In one embodiment, the polyallyl-functional monomer present in the polymerizable composition is not a prepolymer, i.e. the polyallyl-functional monomer has not been partially polymerized to consume a portion of the allylic groups before being used to prepare the polymerizable composition. Indeed, an advantage of the present invention is that polymerized optical articles having very low shrinkage can be obtained using polyallyl-functional monomers of simple constitution and preparation, without resorting to the preparation of prepolymers and/or comonomers.

In one embodiment, the polymerizable composition is free of any polymerizable component that has been previously partially polymerized.

Free radical polymerization initiator
According to the present invention, the polymerizable composition includes at least one free radical polymerization initiator. The radical initiator is an aromatic peroxide compound. Preferably, the aromatic peroxide initiator is a compound having the following general formula (F1):

wherein X is selected from: hydrogen, C₁ to C₁₂ alkoxy groups, chlorine and bromine. In one embodiment, X is selected from hydrogen, a C_l to C₄ alkoxy group or bromine. Examples of suitable aromatic peroxide initiators include benzoyl peroxide (BPO), bis(p-methoxy benzoyl) peroxide, bis(p-ethoxy benzoyl) peroxide, bis(p-propoxy benzoyl) peroxide, bis(p-isopropoxy benzoyl) peroxide, bis(p-butoxy benzoyl) peroxide, and bis(p-chloro benzoyl) peroxide. Especially preferred initiator is benzoyl peroxide [CAS 94-36-0].

The half-life of a free radical initiator at any specified temperature is defined as the time in which the initiator loses half of its activity. It is determined through studies of the decomposition kinetics of the initiator. The ten-hour half-life temperature of an initiator is the temperature at which one half of the initiator originally present decomposes in 10 hours.

The half-life temperature is determined by measuring the rate of the initiator decomposition in the aromatic solvent monochlorobenzene by periodically sampling solutions of the peroxide maintained at several selected constant temperatures and determining the amount of undecomposed peroxide remaining in the sampled solution by conventional iodometric titration techniques. Such half-life measurement techniques are well known by those skilled in the art. Suitable techniques for determining such half-life temperatures in the same solvent using differential scanning calorimetry which provide a direct measurement of the desired half-life temperature are also known to those skilled in the art and may be substituted for iodometric measurements. The two techniques provide equivalent results for the same solvent within the expected standard experimental deviation for the procedures. It is well known in the art that half-life temperatures are dependent on the solvent in which the determination is made, thus, for precision in comparing the half-life temperature of one peroxide to another, the solvent in which the half-life is determined must be specified.

Preferably, aromatic peroxide initiators suitable for use in the present invention have a ten-hour half-life temperature equal to or higher than 55 °C, more preferably equal to or higher than 60 °C. For example, the ten-hour half-life temperature of the initiator may be within the range of from 55 °C to 100 °C, preferably from 60 °C to 95 °C, even more preferably from 60 °C to 85 °C. Especially preferred aromatic peroxide is benzoyl peroxide, which has a ten-hour half-life temperature of 73°C.

In one embodiment, the polymerizable composition includes only one aromatic peroxide as free radical polymerization initiator. However, mixture of two or more aromatic peroxides having the same or different ten-hour half-life temperature may be used when desired, provided that the activation temperature T_A at which the isothermal step is carried out is selected according to the principles of the present invention.

The amount of free radical initiator or mixture of initiators in the polymerizable composition is within the range of from 0.5 to 2 wt.% based on the weight of the polyallyl-functional monomer to be polymerized, preferably from 0.7 to 1.8 wt.% (the above wt% refer to the amount of pure initiator). Amounts of the initiator higher than 2 wt.% are disadvantageous as they generate excessive heat thus increasing the risk of possible cracks and optical defects in the polymerizates; moreover higher yellowness index and hardness are achieved, which are undesired for ophthalmic lenses.

Aromatic peroxide initiators are commercially available usually in the form of compositions containing phlagmatizers and/or stabilizers, such as alkyl benzoate-based phlegmatizers, phthalate-based phlegmatizers and cresol-based phlegmatizers or water as stabilizer. It has been observed that the use of initiators containing phthalate-based and cresol-based phlegmatizers may lead to polymerized optical articles having defects (so-called dots) which become particularly visible on coated lenses. Moreover, phthalate-based and cresol-based phlegmatizers a relatively low solubility which is reflected in a higher haziness of the final polimerizates.

The use of water-stabilized peroxides may also have some disadvantages in the manufacturing process, if the water content exceeds certain concentrations in the polymerizable composition before casting. The presence of residual water, for example above 0.5 wt% based on the weight of the polymerizable composition, in fact, may result in the premature detachment of the optical article from the mold during the curing cycle or in inhomogenous conversions of the polyallyl-functional monomer from a mold to another. However, since water can be more easily removed from the polymerizable composition prior to casting it into the molds, for example by degassing or purging with an inert gas the composition, in one embodiment it is preferred to use water-stabilized aromatic peroxides.

Espacially preferred initiator is water-stabilized benzoyl peroxide, which is commercially available as wet-powder. Preferably, the water content is equal to or lower than 50 wt%, more preferably equal to or lower than 25 wt%, the weight percentages being based on the weight of the water-stabilized aromatic peroxide (e.g BPO).

Other components.
The polymerizable composition may also include further additive compounds such as an internal release agent, a UV and/or HEV light-absorbing agent, a resin modifier (e.g. a chain extender, a cross-linking agent, a light stabilizer), an antioxidant, filler, adhesion improver, a bleaching agent and the like.

As the internal release agent, for example, it is possible to use an acidic phosphate ester or a nonreactive silicone oil. Examples of acidic phosphate esters include phosphoric monoesters and phosphoric diesters and it is possible to use the above alone or in a mixture of two or more kinds.

Examples of resin modifiers include an olefin compound including an episulfide compound, an alcohol compound, an amine compound, an epoxy compound, an organic acid and an anhydride thereof, a (meth)acrylate compound, and the like.

Examples of suitable bleaching agent are those based on inorganic pigments or organic dyes dispersed in allyl resins, such as those disclosed in WO 2021095774A1 and WO 2022224928A1 in the name of the same Applicants.

Examples of UV and/or HEV light-absorbing agent comprise: benzotriazole, benzophenone, triazine and oxalanilide.

Preparation of the optical materials.
According to the present invention, the process the polymerizable composition may be prepared by mixing the polyallyl-functional monomer, the free radical polymerization initiator and the optional components (step A).

In one embodiment, the step A comprises combining the polyallyl-functional monomer with benzoyl peroxide that is in water-stabilized form.

The mixing of the components is usually carried out at a temperature of 25°C using a conventional apparatus. Since the peroxide is stable at ambient temperature, the pot life of the polymerizable composition is significantly longer compared to those of the polymerizable compositions containing IPP as initiator.

According to a preferred embodiment, the composition is stirred until homogeneous and subsequently degassed under reduced pressure (e.g.50 mbar or less) and/or filtered before curing to remove as much as possible the water that has been introduced along with its components, especially when water-stabilized peroxides are used.

In one embodiment, the polymerizable composition has a water content equal to or lower than 0.5 wt% based on the weight of the polymerizable composition.

The polymerizable composition may be polymerized to the thermoset state by known conventional techniques for polymerizing formulations containing polyallyl-functional monomers.

In one embodiment, the polymerizable, composition is placed in molds, as for instance glass molds, and polymerized to form shaped articles such as lens blanks or lenses. This procedure is particularly advantageous for the preparation of ophthalmic lens blanks and ophthalmic lenses.

According to the present invention, polymerization is accomplished by heating the polymerizable composition according to the curing cyle (i.e. the temperature-time sequences) described hereinafter.

In step B1, the polymerizable composition is heated up to an activation temperature T_A of from 12 to 3 Celsius degrees (°C) lower than the ten-hour half-life temperature of the aromatic peroxide, preferably from 10 to 3 °C, more preferably from 8 to 3 °C. For example, when BPO is used as initiator (ten-hour half-life temperature equal to 73°C), the T_A may be selected within the range of from 61 °C to 70°C, from 63 °C to 70°C or from 65 °C to 70°C.

As said, a mixture of two or more aromatic peroxides having the same or different ten-hour half-life temperature may be used when desired. In such a case, if the ten-hour half-life temperatures are the same, the activation temperature T_A is from 12 to 3 Celsius degrees lower than the ten-hour half-life temperature, or preferred ranges thereof as indicated above. If the ten-hour half-life temperatures of the two or more initiators are different, it is preferred that the activation temperature T_A is from 12 to 3 Celsius degrees, or the above-indicated preferred ranges thereof, lower than the lowest ten-hour half-life temperature among those of the initiators of the mixture.

Tipycally, the polymerizable composition is at ambient temperature when casted into the molds and the heating apparatus (e.g. oven) used for the polymerization is at a starting temperature of about 35 to 50 °C. Introducing the molds filled with the polymerizable composition into the oven at said temperature, however, is not an issue since such temperatures are quite below the ten-hour half-life temperature of the aromatic peroxide initiators.

The curing cycle according to the invention comprises at least an isothermal step (B2) at the temperature T_A. In this step, the polymerizable composition is held at the temperature T_A for a period of time of from 8 to 24 hours, preferably from 8 to 20 hours, more preferably from 8 to 15 hours, even more preferably from 8 to 12 hours.

If the polymerizable composition that is casted in the molds is at ambient temperature, it is preferred to slowly heat the molds containing the composition up to the activation temperature T_A, for example over a period of from 1 to 6 hours, more preferably over a period of from 1 to 3 hours.

The isothermal heat treatment and possibly the slow ramp rate up to the activation temperature T_A avoid a too fast heat generation within the mass of the polymerizable composition owing to a fast activation of the initiator and therefore allow the progressive gelification of the polymerizable composition without a significant volume expansion.

When a mixture of two or more aromatic peroxides having different ten-hour half-life temperatures (e.g. T_1-10h < T_2-10h < T_3-10h < etc.) is used, it is preferred that a first isothermal heat treatment at a temperature T_A1 is carried out, followed by a second isothermal heat treatment at a temperature T_A2 and a third isothermal heat treatment at the temperature T_A3, and so on for each different further initiator present in the polymerizable composition, wherein T_A1, T_A2, T_{A3 (…)} are temperature values from 12 to 3 Celsius degrees lower than the ten-hour half-life temperature, or preferred ranges thereof as indicated above, of the respective initiator (i.e. T_1-10h, T_2-10h, T_3-10h (…).

After that the polymerizable composition has been isothermally treated at the temperature T_A (or temperatures T_A1, T_A2, T_A3, …), the polymerization is completed at a final temperature T_F that is selected within the range of from 80 °C to 120 °C, preferably from 85 °C to 105 °C, more preferably from 90 °C to 100 °C (step B3).

The choice of the temperature T_F may depend on several factors including the type of ASI selected, its dosage in the polymerizable composition and the desired degree of polymerization conversion as well as type of poly-allyl functional monomer, the duration of the isothermal step B2 and the size of the mold. A person skilled in the art may select the T_F on the basis of his common general knowledge or by means of routine experimentation.

In one embodiment, the temperature T_F is equal to or higher than the one-hour half-life temperature of the initiator, that is the temperature at which one half of the initiator originally present will decompose in one hour. The choice of this temperature ensures that the residual peroxide is consumed in a short time and a full curing of the polymerizate is achieved.

The temperature T_F is preferably reached with a slow ramp rate, namely the temperature of the polymerizable composition is slowly raised from the activation temperature T_A to the final temperature T_F over a period of from 5 to 40 hrs, preferably from 15 to 40 hours, more preferably from 18 to 40 hrs, even more preferably from 20 to 35 hrs, even more preferably from 22 to 30 hrs. The raising of the temperature of the polymerizable composition from T_A to T_F can be carried out with step-wise increments or continuously (i.e. with a constant heating rate). As a general rule, the longer is the duration of the isothermal treatment at the T_A temperature, the quicker is the ramp rate from T_A to T_F.

In order to have a process that can be profitably used on an industrial scale, the overall duration of the curing cycle is preferably within the range of from 40 to 50 hours.

The duration of the heat treatment at the temperature T_F to obtain the optical article (step B4) may vary broadly depending for example on the value of T_F, ramp rates as well as the temperature and duration of the preceding heat treatment. Preferably, the polymerizable composition is maintained at the temperature T_F for a period of from zero to 30 hours, more preferably for a period of from 1 to 25 hours, in order to achieve full polymerization of the optical article. Full polymerization of the polymerizable composition is deemed achieved when the liquid polymerizable composition has been transformed into a solid optical material suitable for being demolded.

After that full polymerization has been achieved, the solid optical material is generally cooled down before being demolded, preferably within a temperature range of from 40 to 80°C, more prefereably from 50 to 70°C. The cooling rate is not a crucial factor. For example, the mold containing the polymerized optical material may be left standing at ambient temperature outside the heating apparatus.

The demolded optical material may be subjected to post-curing, that is heating at temperatures at or above the maximum temperature of the curing cycle, but below those temperatures at which thermal degradation of the material may take place. The post-curing treatment allows neutralizing radical species of the polymerization initiator that may still be present in the polymerized molded article and eliminate possible demolding stresses from the polymerized molded articles

When a bleaching agent containing tetraazaporphyrin (TAP) dyes is added to the polymerizable composition in order to compensate the yellow colour of the polymerized article (e.g. owing to the presence of UV absorbing compounds or as caused by the initiator), post-curing may also serve to increase the efficiency of the TAP dyes as disclosed in WO 2022224928 A1.

The post-curing treatment may be carried out at a temperature in the range of from 90°C to 130 °C.

The polymerization of the polymerizable composition can be carried out in conventional apparatus, such as a convection oven or a water bath. The moulds can be conventional moulds, for example made from two mould pieces and a gasket forming a cavity that defines the shape and dimensions of the final optical material. The mould pieces can be made of glass, metal or plastic.

The optical material of the present invention can be used for a variety of application, particularly ophtalmic lens, lens for protective masks, optical filters and alike. The ophthalmic lens is herein defined as a lens which is designed to fit a spectacles frame so as to protect the eye and/or correct the sight. Said ophthalmic lens can be an uncorrective ophthalmic lens (also called plano or afocal lens) or a corrective ophthalmic lens. Corrective lens may be a unifocal, a bifocal, a trifocal or a progressive lens.

The optical material may be coated with one or more functional coatings selected from the group consisting of an anti-abrasion coating, an anti-reflection coating, an antifouling coating, an antistatic coating, an anti-fog coating, a polarizing coating, a tinted coating and a photochromic coating.

The invention will now be described in more detail with the following examples, which are given for purely illustrative purposes and which are not intended to limit the scope of the invention in any manner.

EXAMPLES
CHARACTERIZATION METHODS
The optical materials were evaluated by means of the following methods.

Yellowness Index (YI) (ASTM D-1925):
The YI was determined on the optical material in the form of a 4 mm-plano lens with a GretagMacbeth 1500 Plus spectrophotometer taking the standard illuminant C and the observer into account (angle of 2°). The YI is defined as: YI = 100/Y (1.277X - 1.06Z).

Total light transmittance and Haze value:
The total light transmittance and haze value of the optical material in the form of a flat plate having a thickness of 2 mm was measured in accordance with ASTM D 1003 with a digital haze meter haze-gard plus manufactured by BYK-Gardner.

Light Transmittance at a given wavelength:
The transmittance at a given wavelength of an optical material in the form of a flat plate having a thickness of 2 mm was measured with an UV-Visible spectrophotometer Agilent Cary 60.
The expressions “UV-cut” and “HEV-cut” as used herein represent the highest wavelength in the UV region (280 nm to 380 nm) and HEV region (380 nm to 500 nm), respectively, for which the light transmittance of an optical material is lower than 1% as measured in accordance with ASTM D 1003.

Tinting test of 2mm plano lenses:
The capacity of the material to absorb a dye on its surface is determined by dip-dyeing a neutral plano 2mm lenses in a BPI^TM grey solution for 20 minutes @ 95°C in a tintometer bath, model COLORADO Electronic ex ORGANIZZAZIONE GF. After rinsing with demineralized water, the lens transmittance was determined by measuring the total light transmittance as described above. In addition, the evenness/unevenness of the tinted lens was visually evaluated upon exposing the tinted lens on a back - lighted visor, model Professional 20 - 5000K ex LUPO DAYLIGHT.

Mechanical properties - Rockwell hardness M
The Rockwell Hardness M (ASTM D-785) of the optical material has been evaluated on a 5mm-thick flat sheet.

Materials
In the Examples, the following compounds were used.
Polyallyl-functional monomer
A polyallyl-functional monomer was prepared by reacting diallyl carbonate (component A), diethylene glylcol as diol (component B) and pentaerythrite as polyol (component C) in a molar ratio A/(B+C) equal to 7.2 and a ratio C/(B+C) equal to 2,29 wt.%.
The following compounds were charged into a three-necked jacketed flask, equipped with a thermometer and magnetic stirrer, surmounted by a distillation column with ten perforated plates of 30 mm in diameter:
- pentaerythrite (PE): 5 g (0.04 moles);
- diethylene glycol (DEG): 213 g (2.01 moles);
- diallyl carbonate (DAC): 2100 g (14.80 moles);
- 20% weight solution of sodium methylate in methanol: 1.0 ml.
The reaction was carried out for three hours at a temperature of 85 °C to 120 °C and a decreasing pressure from 200 to 130 mbar, by distilling the allyl alcohol during its formation (total 242 g (285 ml); purity more than 99%).
After cooling, the reaction mixture was washed with two aliquots of 500 ml of demineralized water.
The excess DAC was distilled at a pressure of about 1 mbar, by operating at an increasing temperature up to 130 C: the product obtained was filtered through a mem- brane filter of 0.45 m.
512 g of a liquid product were obtained, having the following characteristics:
- Viscosity (25 C): 17 cSt;
- Density (20 C): 1.152 g/ml;
- Refractive index nD20: 1.453;
- Apha colour: 1.

The above polyallyl-functional monomer was obtained as a mixture of monomer and oligomers of bis(allyl carbonate) diethylene glycol, monomer and oligomers of bis(allyl carbonate) neopentyl glycol, monomer and oligomers of tetrakis(allyl carbonate) of pentaerythrite, and mixed poly(allyl carbonates) of the above diols and polyol.

The amount of diethylene glycol bis(allyl carbonate) compound of formula (II) with n = 1 was about 83 wt% based on the weight of the mixture of monomer and oligomers. This amount was determined through HPLC analysis of the reaction product under the following conditions: temperature = 25°C; sample of the reaction product subjected to analysis in the form of a 10% by weight solution of acetonitrile; sample injected = 5 microliters; eluent: mixture of acetonitrile/water (45/55% by volume); UV detector.

UV absorbers
- BP6 (2,2'-dihydroxy-4,4'-dimethoxybenzophenone, manufactured by MFCI).
- Lowilite 20 by Addivant: 2-dihydroxy-4- methoxybenzophenone.

Peroxide radical polymerization initiators
- Luperox A75 (registered trademark) by ARKEMA; water-stabilized benzoyl peroxide (25 wt.% water) in the form of granular wet-powder
- PERKADOX CH50-L by Nouryon; phthalate-stabilized benzoyl peroxide (50 wt.% alkyl phthalates) in the form of granular wet-powder.
- Trigonox ADC-NS30 (registered trademark) by NOURYON; the commercial product contains about 70% by weight of diethylene glycol bis(allyl carbonate) and 30% by weight of a mixture of isopropyl peroxydicarbonates, sec-butyl and isopropyl/sec-butyl peroxydicarbonates.

TAP dye (bleaching agent)
As bleaching agent the commercial product FDG-005 by Yamada Chemicals (Pd-containing TAP compound having a main absorption peak at 583 nm). The product FDG-005 was used as a masterbatch, i.e. pre-dispersed in the polyallyl-functional monomer at a concentration of 0.05 wt. based on the weight of the monomer.

UV&Blue cut MB ^TM (bleaching agent)
A bleaching agent masterbatch based on a proprietary composition of pigments dispersed in poly-allyl functional monomers supplied by Acomon SRL (about 2.0 wt.% pigments in polyallyl-functional monomer based on the weight of the monomer).

Example 1 (Samples 1 to 4)
Liquid polymerizable compositions were prepared by mixing 100 parts by weight (pbw) of the polyallyl-functional monomer with BPO initiator or, for comparative purposes, IPP initiator, and additives in the ratios reported in Table 5.

Before casting, each polymerizable composition was vigorously mixed with a magnetic stirrer, degassed for 3 hours at a pressure of 50 mbar or lower and then filtered on a 0.45 micrometers PTFE membrane (47 mm diameter).

The polymerizable compositions were casted and polymerized in glass molds in the form of plano lenses having a thickness of 2 mm for the determination of the total transmittance and haze% and a thickness of 5mm for the determination of YI and Rockwell hardness. Rockwell hardness has been determined also on 10 mm-thick plano lenses.

The polymerization was accomplished by heating the molds containing the polymerizable compositions in a forced-air-circulation oven according to one of the curing cycles reported in Tables 1 to 4. The polymerizable compositions were casted at ambient temperature (25°C) and introduced in the oven set at the initial temperature reported in the Tables 1 to 4.

At the end of the curing cycle, the molds were removed from the oven and allowed to cool to ambient temperature. The polymerized articles were than subjected to post-curing at a temperature of 110 - 130°C for 1-2 hours as reported below in a forced-air-circulation oven.

The process yield was evaluated by determining the ratio of the number of articles exhibiting defects (i.e. cracks or flow lines) over the total number of casted articles.

The optical and mechanical properties of the polymerized materials are reported in Table 5.

The polymerized optical articles have a UV cut of 355 nm.
The data of Table 5 show that using BPO according to the process of the present invention (sample 3) allows to obtain optical articles having good mechanical and optical characteristics, that are comparable with those of IPP-polymerized compositions (sample 4). The yield of the process is also very high.

On the contrary, the use of BPO in higher amount or with shorter curing cycles (samples 1 and 2), besides leading to a decrease of the casting yield, had detrimental effects on the lens quality. The lenses obtained with comparative sample 1 had excessive yellow index and hardness, mainly due to the high ASI content. A too high hardness, especially for thick lenses, is very likely to cause cracks during curing and/or demoulding steps. Conversely, the lenses obtained according to comparative sample 2 are characterized by several optical defects, such as flow lines and striations especially when thick semifinished lenses are produced. This is mainly due to a too short curing cycle and the ASI reactivity.

The difference between the curing conditions and the low amount of initiator in comparative sample 2 is also reflected in the tinting behavior, where samples in practice can be considered as having a similar hue when the difference in total T% value is within +/-5 units.

The lenses obtained with the curing cycle 1 according to the invention show T% and good evenness similar to those of the same composition cured with the conventional IPP curing cycle 4 (benchmark). Comparative samples 1 and 2, on the other hand, are either too hard or too soft with respect to the lenses obtained with the benchmark, where IPP was used with curing cycle 4, with deviations in color tone or undesired unevenness of dye uptake.

Example 2 - Samples 5 to 10
Polymerizable compositions of the samples 5 to 10 were prepared as described in Example 1 except that a bleaching agent was additionally included in the polymerizable composition. In case of pigments based bleaching agent, the final filtration of the polymerizable composition was performed on depth filters with maximum pore size 5 microns.
The tested compositions and their optical and mechanical properties are reported in Table 6.

The data of Table 6 show the optical and mechanical properties of lenses at different cut off ratios (as obtained through the addition of the UV absorber) obtained with conventional IPP curing cycle and the curing cycle of the present invention.

Because of the low amount of initiator and the efficient polymer conversion, with the process of the present invention lenses with properties very similar to those of the IPP-cured lenses (benchmark) are obtained. Moreover, the tinting behavior, which is strictly correlated to the good conversion of the final polymerizates, is very similar for BPO-cured and IPP-cured materials.

Claims (21)

1. A process for manufacturing a polymeric optical article comprising:
   A. providing a polymerizable composition comprising:
   - at least one polyallyl-functional monomer having formula (I):
   

   

   wherein X represents a divalent to hexavalent group derived from a linear or branched aliphatic polyol having 3 to 12 carbon atoms or a divalent to hexavalent group derived from an alicyclic polyol having 5 to 16 carbon atoms, and n represents an integer of 2 to 6;
   wherein the polyallyl-functional monomer having formula (I) comprises 70 wt.% or more, preferably 80 wt.% or more, of the polyallyl-functional monomer having formula (I) for which n is equal to 2, the weight percentage being based on the total weight of the polyallyl-functional monomer having formula (I);
   - from 0.5 to 2 wt.% of at least one aromatic peroxide as free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer;
   B. curing the polymerizable composition according to a curing cycle comprising:
   B1. heating the polymerizable composition up to an activation temperature T_A of from 12 °C to 3 °C lower than the ten-hour half-life temperature of the aromatic peroxide;
   B2. holding the polymerizable composition at the temperature T_A for a period of from 8 to 24 hours;
   B3. heating the polymerizable composition after the step B2 up to a final temperature T_F within the range of from 80 °C to 120 °C;
   B4. holding the polymerizable composition at the final temperature T_F to obtain the optical article.
   
2. The process according to claim 1, wherein in step B1 the polymerizable composition is heated up to an activation temperature T_A of from 10 °C to 3 °C lower than the ten-hour half-life temperature of the aromatic peroxide.
   
3. The process according to claim 1 or 2, wherein in step B2 the polymerizable composition is held at the activation temperature T_A for a period of from 8 to 20 hours, preferably from 8 to 15 hours, more preferably from 8 to 12 hours.
   
4. The process according to any one of claims 1 to 3, wherein in step B3 the polymerizable composition is heated up to the final temperature T_F within the range of from 85 °C to 105 °C, preferably from 90 °C to 100 °C.
   
5. The process according to any one of claims 1 to 4, wherein in step B3 the polymerizable composition is heated up to the final temperature T_F over a period of from 5 to 40 hours, preferably from 15 to 40 hours, more preferably from 18 to 40 hrs, even more preferably from 20 to 35 hrs, even more preferably from 22 to 30 hrs.
   
6. The process according to any one of the claims 1 to 5, wherein in step B4 the polymerizable composition is held at the final temperature T_F for a period of from zero to 30 hours, preferably for a period of from 1 to 25 hours.
   
7. The process according to any one of claims 1 to 6, wherein the polymerizable composition is free of ethylenically unsaturated compounds different from the polyallyl-functional monomers having formula (I).
   
8. The process according to any one of claims 1 to 7, wherein the at least one polyallyl-functional monomer has a 25°C kinematic viscosity within the range of from 10 to 300 cSt, preferably from 10 to 100 cSt, more preferably from 10 to 40 cSt.
   
9. The process according to any one of claims 1 to 8, wherein the polyallyl-functional monomer is a diethylene glycol bis(allyl carbonate) compound of formula (II):
   

   

   wherein n is an integer equal to or higher than 1 and equal to or lower than 10;
   wherein the diethylene glycol bis(allyl carbonate) compound of general formula (II) comprises 70 wt.% or more, preferably 80 wt.% or more, of the diethylene glycol bis(allyl carbonate) compound of formula (II) for which n is equal to 1, the weight percentage being based on the total weight of the diethylene glycol bis(allyl carbonate) compound of general formula (II).
   
10. The process according to claim 9, wherein the polymerizable composition is free of ethylenically unsaturated compounds different from the diethylene glycol bis(allyl carbonate) compounds having formula (II).
    
11. The process according to any one of claims 1 to 10, wherein the at least one polyallyl-functional monomer comprises the reaction product (RP) of components comprising: diallylcarbonate (A), one or more linear or branched aliphatic diols (B) containing from three to ten carbon atoms in the molecule and optionally a linear or branched aliphatic polyol (C) containing from four to twenty carbon atoms and from three to six hydroxyl groups in the molecule; wherein the molar ratio A/(B+C) ranges from 4/1 to 20/1 and the quantity of the optional component (C) in the mixture (B+C) is equal to or less than 5 wt.%, preferably equal to or less than 3 wt.%, with respect to the total weight of said mixture (B+C).
    
12. The process according to any one of claims 1 to 10, wherein the at least one polyallyl-functional monomer comprises the reaction product (RP) of components comprising: diallylcarbonate (A), one or more linear or branched aliphatic diols (B) containing from three to ten carbon atoms in the molecule and a linear or branched aliphatic polyol (C) containing from four to twenty carbon atoms and from three to six hydroxyl groups in the molecule; wherein the molar ratio A/(B+C) is within the range of from 4/1 to 20/1, preferably from 5/1 to 15/1, and the quantity of the component (C) in the mixture (B+C) is equal to or less than 5 wt.%, preferably equal to or less than 3 wt.%, with respect to the total weight of said mixture (B+C).
    
13. The process according to any one of claims 1 to 12, wherein the aromatic peroxide is benzoyl peroxide.
    
14. The process according to any one of claims 1 to 13, wherein in step A the at least one polyallyl-functional monomer is mixed with a water-stabilized benzoyl peroxide.
    
15. The process according to claim 14, wherein the water-stabilized benzoyl peroxide contains water in amount equal to or lower than 50 wt.%, preferably equal to or lower than 25 wt.%, the weight percentage being based on the total weight of the water-stabilized benzoyl peroxide.
    
16. A polymeric optical article obtained by the process according to any one of claims 1 to claim 15.
    
17. An ophthalmic lens comprising the polymeric optical article according to claim 16.
    
18. A polymerizable composition comprising:
    - a polyallyl-functional monomer having formula (I):
    

    

    wherein X represents a divalent to hexavalent group derived from a linear or branched aliphatic polyol having 3 to 12 carbon atoms or a divalent to hexavalent group derived from an alicyclic polyol having 5 to 16 carbon atoms, and n represents an integer of 2 to 6;
    wherein the polyallyl-functional monomer having formula (I) comprises 70 wt.% or more, preferably 80 wt.% or more, of the polyallyl-functional monomer having formula (I) for which n is equal to 2, the weight percentage being based on the total weight of the polyallyl-functional monomer having formula (I);
    - from 0.5 to 2 wt.% of at least one aromatic peroxide as free radical initiator, preferably benzoyl peroxide, the weight percentage being based on the total weight of the polyallyl-functional monomer.
    
19. The polymerizable composition according to claim 18, wherein the polymerizable composition is free of ethylenically unsaturated compounds different from the polyallyl-functional monomers having formula (I).
    
20. The polymerizable composition according to claim 18, wherein the polyallyl-functional monomer is a diethylene glycol bis(allyl carbonate) compound of formula (II):
    

    

    wherein n is an integer equal to or higher than 1 and equal to or lower than 10;
    wherein the diethylene glycol bis(allyl carbonate) compound of general formula (II) comprises 70 wt.% or more, preferably 80 wt.% or more, of the diethylene glycol bis(allyl carbonate) compound of formula (II) for which n is equal to 1, the weight percentage being based on the total weight of the diethylene glycol bis(allyl carbonate) compound of general formula (II).
    
21. The polymerizable composition according to claim 20, wherein the polymerizable composition is free of ethylenically unsaturated compounds different from the diethylene glycol bis(allyl carbonate) compounds having formula (II).