IT202300017712A1 - METHOD OF PREPARING A POLYALLYL-FUNCTIONAL PREPOLYMER COMPOSITION AND USE OF SAID PREPOLYMER COMPOSITION TO MANUFACTURE AN OPTICAL ARTICLE. - Google Patents

Description

METHOD FOR PREPARING A POLYALLYL-FUNCTIONAL PREPOLYMER COMPOSITION AND USE OF SAID PREPOLYMER COMPOSITION TO MANUFACTURE AN OPTICAL ARTICLE

Field of invention

The present invention relates to a method of preparing a polyallylfunctional prepolymer composition and to the use of said prepolymer composition to manufacture an optical article.

State of the art of the invention

Polyallyl-functional monomers are polymerized using free radical initiators to produce tough polymers. Many of these polymers are substantially transparent to visible light, are essentially colorless, have refractive indices from about 1.45 to about 1.6, and possess good mechanical strength. For these reasons, these monomers are widely used as precursors for optical products such as optical lenses and optical lens blanks, safety lenses, and flat or curved transparent sheets. The light transmission characteristics can be modified by incorporating dyes, light-absorbing compounds, pigments, and the like into the polymerizable composition containing the monomer prior to polymerization, or by coloring the polymer.

The polymerization reaction of a polyallyl-functional monomer is typically performed in the presence of a peroxide initiator, particularly a dialkylperoxy carbonate, such as diisopropylperoxy carbonate (IPP) or mixtures of IPP and dis-butylperoxy carbonate, resulting in tough polymers with excellent optical properties, particularly transparency, and low coloration.

Dialkylperoxycarbonate initiators, especially IPPs, have the disadvantage of being highly expensive and highly thermally unstable, with explosive decomposition, and therefore require rather harsh transport and storage conditions. Even when formulated in dilute form, for example using a polyallyl-functional monomer for dilution, they require transport and storage temperatures of approximately -20°C to -10°C.

In the prior art, peroxide initiators are also known that are stable at room temperature (also called ambient stable initiators or ASIs) and thus potentially capable of overcoming the above-mentioned drawbacks of dialkylperoxy carbonate initiators. As used herein, an ambient stable initiator is a free radical initiating compound that does not require refrigerated storage, i.e., it can be stored without substantial degradation at temperatures in the range of 20-36°C. As used herein, an ASI initiator therefore has an "elevated" ten-hour half-life temperature, where "elevated" means a ten-hour half-life temperature of at least about 55°C.

However, ASI compounds such as some diacyl peroxides, alkyl peroxyesters, alkyl peroxyketals and peroxymonocarbonates also have some disadvantages that have so far limited their practical use as initiators for the polymerization of polyallyl-functional monomers.

Some ASI compounds, for example, have low solubility in polyallyl-functional monomers, resulting in unsatisfactory hardening of hard polymers. Furthermore, hard polymers obtained using ASI compounds as diacyl peroxide initiators (e.g., benzoyl peroxide) exhibit significant yellowing and poor UV light resistance. Furthermore, compared to hard polymer materials obtained using IPP as the initiator, materials cured using ASI compounds typically exhibit relatively high hardness and brittleness, as well as high levels of shrinkage.

As used herein, the term ?withdrawal? (S) refers to the ratio or

where Dpol is the density of the final thermoset polymer at 23°C and Dmon is the density at 23°C of the liquid polymerizable composition containing the monomer before polymerization. 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 routinely used to produce ophthalmic lenses and ophthalmic lens blanks, in which a liquid monomer composition is introduced into a mold and subsequently polymerized into the final polymer in a thermoset state.

When polymerization is performed in the presence of ASI compounds as initiators, in fact, the liquid polymerizable composition must be heated to a relatively high initial temperature to initiate the curing cycle of the polymerization reaction. For example, for benzoyl peroxide which has a ten-hour half-life temperature of 73°C, the initial temperature is approximately 60°C, which is a much higher initial temperature than approximately 40°C for IPP which has a ten-hour half-life temperature of 45°C. This initial heating phase, however, is accompanied by a volume expansion of the polymerizable composition inside the mold resulting in a non-negligible reduction in its density. Since the initial volume expansion when cured with ASI compounds is higher than that which occurs when the same polymerizable composition is cured with IPP or other non-ASI initiators, the shrinkage observed for hard polymers cured with the ASI initiator is approximately 10°C. significantly higher than that of hard polymers obtained by curing with IPP or other non-ASI initiators.

Such a high level of shrinkage within the molds causes numerous defects in the hard polymer, such as dimensional changes and internal stresses, as well as material detachment from the mold walls, resulting in uneven surfaces and causing failure of the cured material or molds. Because of these negative aspects, manufacturing processes using ASI initiators are characterized by low production yields.

The above drawbacks particularly concern the production of semi-finished lenses (also called "blanks") of complex design and geometry, such as blanks having a high radius of curvature (base 6 or greater) and bifocal semi-finished lenses (e.g. semi-finished lenses whose front surfaces have a double power correction to simultaneously compensate for myopia and presbyopia).

In a bifocal blank, in fact, the mechanical stresses generated by shrinkage are different in each of the two power segments of the blank, thus frequently causing damage to the lens during mold removal, such as the generation of chips, cavities, or complete fracture along the separation surface of the two power segments. The problem of fracture is particularly relevant when casting flat-topped bifocal blanks, i.e., bifocal blanks that have two power segments separated by a flat separation surface.

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

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

Examples of these mono- or polyethylenically unsaturated compounds, also called comonomers or reactive diluents, are mono- or polyethylenically unsaturated compounds such as versatic acid vinyl esters 9 and 10. Comonomers can be liquid components having a lower density of polymerizable double bonds (i.e., number of double bonds per unit mass of the compound) than the diethylene glycol bis(allyl carbonate) monomer. These comonomers yield a final hard polymer with a lower level of crosslinking (i.e., a lower value of the Dpol term in the above shrinkage equation) than the hard polymer obtained from a diethylene glycol bis(allyl carbonate) monomer without comonomers and consequently with lower shrinkage.

Alternatively, or in addition to the above effect, the comonomers may have a higher density (i.e., mass-to-volume ratio) than the diethylene glycol bis(allyl carbonate) monomer, so that the cast polymerizable composition containing the polyallyl-functional monomer and the comonomers has an increased density (i.e., a higher value of the Dmon term in the above shrinkage equation) and consequently a lower final shrinkage. This is the case, for example, with compounds having high molar mass or polyfunctional structure, i.e., having three or more ethylenically unsaturated functional groups per molecule, as disclosed in US 4,144,262 where these compounds are also used as a single monomer as an alternative to the diethylene glycol bis(allyl carbonate) monomer.

This approach to reduce shrinkage using comonomers is described 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 formula (II) above, the polymerizable composition can include a relatively high content of oligomeric species, i.e., species of formula (II) above where n is an integer equal to 2 or higher. Since these oligomeric species have a lower density of polymerizable double bonds than the linear species of the diethylene glycol bis(allyl carbonate) monomer (i.e., the species of formula (II) with n = 1), they allow for tough polymers with a lower level of crosslinking (i.e., a lower value of the Dpol term in the shrinkage equation) and consequently having lower shrinkage.

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

Another way to reduce shrinkage known in the art is based on the introduction into the mold of a liquid prepolymer composition, which is then polymerized to obtain the final thermoset polymer.

The prepolymer composition (hereinafter also referred to as "prepolymer") is typically produced by partially polymerizing the polyallyl-functional monomer, thereby consuming a portion of the allyl groups. The partial polymerization (hereinafter also referred to as "prepolymerization") is terminated, however, before more than a negligible amount of gelation occurs, so that the prepolymer composition can be introduced into the mold as a liquid having an increased density compared to the initial polyallyl-functional monomer.

The prepolymerization reaction requires careful control. Typically, the prepolymerization reaction is controlled by adding the initiator in small amounts to ensure that only a desired portion of the allylic double bonds of the initial polyallyl-functional monomer reacts to form the prepolymer composition. Small amounts of initiator also ensure that at the end of the prepolymerization reaction, the initiator is completely consumed, so the liquid prepolymer composition is stable at room temperature and has an adequate shelf life. That is, the liquid prepolymer composition can be stored for a considerable length of time before being used to produce hard polymer articles without gelling.

The prepolymerization reaction is also controlled by regulating the heat supplied to the monomer-initiator reaction mixture in the reactor. In particular, it may be necessary to cool the reaction mixture once the desired prepolymer viscosity is reached to stop the reaction and prevent subsequent gelation, which can be caused by the thermal inertia of the prepolymer mass (the so-called "mass effect").

To produce tough polymers, the liquid prepolymer composition is then added with an initiator and subjected to a thermal curing cycle to polymerize the composition. The initiator, which may be the same or different from that used to prepare the prepolymer composition, is added to the latter in an amount sufficient to substantially polymerize the allylic double bonds of the prepolymer. However, when initiators with low half-live temperatures of ten hours (i.e., non-ASI initiators such as IPP) are used in the curing cycle, once mixed with the monomer, the resulting liquid polymerizable formulation must be used promptly because its shelf life is short. If not used immediately, the formulation must be refrigerated, resulting in high energy consumption, for later use. This drawback forces the manufacturer to prepare small batches of polymerizable formulations.

To increase the shelf life of the formulation, it is possible to increase the initiator concentration in the formulation and perform casting at low temperatures, i.e., 10°C or lower. This approach, however, has the disadvantage of increasing the viscosity of the cooled prepolymer, resulting in longer and less efficient mold-filling operations and consequently limited productivity, particularly when manufacturing lenses with complex designs and geometries.

According to another known method, the prepolymer composition can be prepared by solution polymerization. The monomer composition is dissolved in a substantially inert organic solvent capable of also dissolving the partially polymerized monomer and then heated in the presence of a small amount of the initiator. After prepolymerization, the solvent is removed, for example by evaporation or distillation, and the liquid prepolymer composition is polymerized, after a further addition of an initiator, to produce the hard polymer.

US 4623708 discloses a method for preparing a prepolymer in which the prepolymerization step includes adding a small amount of a free-radical initiator, which may be the same or different from that used just before casting, and heating to a temperature above the initiator's 1-hour half-life temperature. In this manner, most of the added initiator is consumed and the prepolymerization produces the highest possible conversion while preventing overpolymerization.

US 6057411 discloses a process for forming a substantially gel-free, liquid, polymerizable, poly(allyl carbonate)-functional prepolymer composition, comprising heating a pure composition comprising at least one poly(allyl carbonate)-functional monomer and a free radical initiator having a ten-hour half-life temperature of at least 85°C to temperatures in the range of 5 degrees Celsius below the ten-hour half-life temperature of the free radical initiator to 150°C, to form a reaction mixture having an increased viscosity at 25°C in the range of 25 to 10,000 centipoise and an ethylene double bond utilization of at least 3 percent; and in a period of less than 90 minutes cooling the reaction mixture to a temperature of at least 20 degrees Celsius below the ten-hour half-life temperature of the initiator.

The state-of-the-art monomer and prepolymer compositions discussed above that are used to reduce shrinkage, however, entail high costs due to the use of additional raw materials and complex preparation processes (i.e. comonomers and the supply of special polyallyl monomer and prepolymer compositions).

Specifically, known methods for preparing prepolymer compositions and their use are impractical for several reasons. First, a number of variables must be carefully controlled during the prepolymerization process, namely initiator dosage and reaction temperature, making it difficult to reproducibly achieve the desired prepolymer properties. Second, the requirement for an initiator dosage step into the liquid prepolymer composition prior to casting to produce the final polymerized articles, and the resulting short shelf life of the polymerizable composition, makes the manufacturing process quite complicated and inefficient. Third, when the prepolymer is prepared by solution polymerization, complete solvent removal is time-consuming, costly, and, where the solvent is toxic or flammable, even dangerous.

There is therefore a need for new methods of preparation and use of polyallyl-functional monomers, particularly in the form of prepolymer compositions, which overcome the disadvantages of the state of the art.

Summary of the invention

A method has now been found that allows the preparation of hard allyl-based polymers using environmentally stable polymerization initiators, the hard polymers having mechanical and optical properties that are essentially comparable to those of hard polymers achievable by curing with highly effective initiators such as IPP or other conventional peroxycarbonate initiators.

The method is based on the preparation of a liquid prepolymer composition by partial polymerization of a polyallyl-functional monomer in the presence of a selected group of environmentally stable free radical initiators, which are mixed with the polyallyl-functional monomer in such an amount that the initiator is not completely consumed during the prepolymerization reaction; the prepolymerization reaction is carried out by heating the resulting mixture to a temperature close to, but below, the ten-hour half-life temperature of the initiator (and hence also below its one-hour half-life temperature) for a period of time sufficient to obtain a prepolymer composition having the desired increased viscosity.

Since a sufficient amount of initiator remains in the prepolymer composition, its ability to generate free radical species is exploited in the subsequent step of thermally hardening the prepolymer composition, thus avoiding any further step of dosing an additional initiator to the prepolymer composition before casting into the molds.

The environmentally stable free radical initiator is an aromatic peroxide compound (e.g. benzoyl peroxide), which is highly soluble in the polyallyl-functional monomer and can therefore be dosed in effective quantities to also convert the relevant liquid prepolymer composition into a hard polymer using conventional curing cycles, e.g. at temperatures up to 80 - 120 °C and in approximately 24 - 30 hours.

Furthermore, since the initiator is stable at room temperature, the shelf life of the ready-to-cast liquid prepolymer composition at room temperature (i.e. 25°C) is quite long (approximately 1-2 weeks) and even longer (several months) when stored in a refrigerator, e.g., in the range from 0 to 4°C. In particular, the shelf life is significantly longer than that of ready-to-cast liquid prepolymer compositions containing IPP (1 hour at room temperature) or similar non-ASI initiators.

The prepolymer composition prepared as described herein is very effective in controlling shrinkage during the polymerization step to form the hard polymer, the observed shrinkage values being substantially identical to those of hard polymers obtained using the IPP initiator (approximately 12% or less).

The methods described herein also enable the use of environmentally stable initiators such as benzoyl peroxide to produce hard polymers and thus optical articles very efficiently and simply. The hard polymers have mechanical and optical properties comparable to those of hard polymers toughened using IPP, while overcoming the disadvantages associated with the handling and use of IPP and other non-ASI initiators. Furthermore, thanks to the effective control of material shrinkage, the methods described herein enable the use of ASI initiators to fabricate lenses of even complex designs and geometries, such as high-radius-of-curve blanks and bifocal blanks, with improved manufacturing yields.

Because the overall amount of aromatic peroxide initiator used to prepare the prepolymer and subsequently the final polymerized articles is less than the amount customarily used to directly cap the same polyallyl-functional monomer compositions, the methods described herein have the additional advantage of reducing the adverse effects associated with the use of relatively large amounts of aromatic peroxide initiators, such as changes in the refractive index of the lenses, increased hardness and brittleness, intrinsic yellowing, and yellowing induced by exposure to UV light.

The benefit of the present invention can be achieved with a wide variety of polyallyl-functional monomers, without particular restrictions. The methods described herein, however, are particularly advantageous when the starting material subjected to prepolymerization is a polyallyl-functional monomer having low viscosity and density, as these are obtained with easier and more economical preparation processes than monomers specifically prepared to have low intrinsic shrinkage properties.

Accordingly, according to a first aspect the present invention relates to a method for preparing a polyallyl-functional prepolymer composition comprising:

(a) providing a reaction mixture comprising: - at least one polyallyl-functional monomer;

- 0.5 to 3.0% by weight of at least one aromatic peroxide compound as a free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer;

(b) heating the reaction mixture to a temperature in the range of 12 to 3 degrees Celsius (?C) below the ten-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having a viscosity at 25 ?C in the range of 40 to 350 cSt.

According to a second aspect, the present invention relates to a polyallylfunctional prepolymer composition obtained by the method according to the first aspect.

According to a third aspect, the present invention relates to a method of manufacturing an optical article comprising:

(i) provide a reaction mixture comprising: - at least one polyallyl-functional monomer;

- 0.5 to 3.0% by weight of at least one aromatic peroxide compound as a free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer;

(ii) heating the reaction mixture to a temperature in the range of 12 to 3 degrees Celsius (?C) below the ten-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having a viscosity at 25 ?C in the range of 40 to 350 cSt;

(iii) casting the prepolymer composition into a mold;

(iv) curing the prepolymer composition in the mold to form the optical article.

According to a fourth aspect, the present invention relates to an optical article obtained by the method according to the third aspect.

According to a fifth aspect, the present invention relates to an ophthalmic lens comprising the optical article according to the fourth aspect.

Further features of the present invention are the subject of the dependent claims attached to this description.

The compositions of the present invention may comprise, consist substantially 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 significantly alter the basic and novel characteristics of the claimed compositions or methods.

As used herein, the terms "an," "an," and "the," should be read to include one or at least one, and the singular also includes the plural, unless it is clearly understood otherwise. This is done solely for convenience and to convey a general sense of disclosure.

Other than in the working examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so on, used in the description and claims are to be understood as modified in all cases by the term 'approximately'.

Detailed description of the invention

Polyallyl-functional monomer

For the preparation of the prepolymer composition according to the present invention, a reaction mixture is provided comprising at least one polyallyl-functional monomer and at least one aromatic peroxide compound as a free radical initiator. This mixture may comprise two or more polyallyl-functional monomers.

The polyallyl-functional monomer can be selected from 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 include, for example, compounds containing two or more allyl groups, such as diallyl esters, diallyl carbonate, and diallyl phthalate.

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

In one embodiment the polyallylfunctional monomer is selected from: diethylene glycol bis(allyl carbonate), ethylene glycol bis(allyl carbonate), diethylene glycol bis(allyl carbonate) oligomers, ethylene glycol bis(allyl carbonate) oligomers, bisphenol A bis(allyl carbonate), diallyl phthalates such as diallyl phthalate, diallyl isophthalate, diallyl terephthalate, diallyl orthophthalate, and mixtures thereof.

The polyallyl-functional monomer is a liquid product at room temperature, the kinematic viscosity measured at 25 °C is 10 to 1000 cSt.

In one embodiment, the polyallylfunctional monomer has a kinematic viscosity in the range of 10 cSt to 300 cSt, preferably 10 to 100 cSt, more preferably 10 to 40 cSt.

As used herein, the kinematic viscosity of a compound, including a polyallyl-functional monomer or prepolymer composition, is determined in accordance with ASTM D446 using a KPG Ubbelodhe viscometer (capillary type 1C, 2C, or 3C).

Preferably, the polyallyl-functional monomer has a density at 25 ?C in the range of 1.10 g/ml to 1.30 g/ml, more preferably 1.11 g/ml to 1.20 g/ml.

Compound (A) including two or more allyloxycarbonyl groups

In one embodiment, the polyallylfunctional monomer may be represented as a compound (A) including two or more allyloxycarbonyl groups according to the following formula (1)

wherein, in the formula, n is an integer from 2 to 6, R1 indicates a hydrogen atom or a methyl group, a plurality of R1s present may be the same or different, X is a divalent to hexavalent organic group a derived from a linear or branched aliphatic polyol having 3 to 12 carbon atoms that may have an oxygen atom, a divalent to hexavalent organic group b derived from an alicyclic polyol having 5 to 16 carbon atoms that may have an oxygen atom, or a divalent to hexavalent organic group c derived from an aromatic compound having 6 to 12 carbon atoms, and organic group a or organic group b forms an allyl carbonate group by bonding to an allyloxycarbonyl group via an oxygen atom derived from a hydroxyl group.

These polyols typically 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 α1 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.

Examples of the aromatic compound c1 include benzene, toluene, xylene, naphthalene, and the like.

Specific examples of the compound including two or more allyloxycarbonyl groups include a polymerizable allyl carbonate compound (A1), a polymerizable allyl ester compound (A2), and a polymerizable compound (A3) including at least one of an allyl carbonate group and an allyl ester group.

It is possible that compound (A) including two or more allyloxycarbonyl groups includes a related oligomer.

A compound including two or more allyloxycarbonyl groups is a liquid product at room temperature, the kinematic viscosity measured at 25 °C is 10 to 1000 cSt, and the oligomer content can be varied over a wide range, for example, from 0% to approximately 80% by weight.

In one embodiment, the compound including two or more allyloxycarbonyl groups has a kinematic viscosity in the range of 10 cSt to 300 cSt, preferably 10 to 100 cSt, more preferably 10 to 40 cSt. Preferably, the density at 25 °C of the compound including two or more allyloxycarbonyl groups is in the range of 1.10 g/ml to 1.30 g/ml, more preferably 1.11 g/ml to 1.20 g/ml.

Polymerizable allyl carbonate compound (A1) Polymerizable allyl carbonate compound (A1) can be represented by the Formula (2)

where, in Formula (2), 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 from 2 to 6.

The polymerizable allyl carbonate compound (A1) of Formula (2) may include a related oligomer. The oligomer is a poly(allyl carbonate) in which two or more molecules of a polyol are linked via a carbonate group produced by a transesterification reaction of allyl carbonate produced in the manufacturing step and a polyol.

The polymerizable allyl carbonate compound is a poly(allyl carbonate) compound of a linear or branched aliphatic polyol having 3 to 12 carbon atoms. A poly(allyl carbonate) compound of an alicyclic polyol having 5 to 16 carbon atoms in the molecule is also suitable for this purpose. These polyols usually have 2 to 6 hydroxyl groups in the molecule, and it is possible for these polyols to have 2 to 4 hydroxyl groups in the molecule, which is preferable. It is also possible to use a blended poly(allyl carbonate) compound, that is, a compound that is derived from at least two types of polyols and that can be obtained by mechanical mixing of the respective poly(allyl carbonate) polyol compounds, or a compound obtained directly by a chemical reaction starting from a mixture of polyols and diallyl carbonate.

Finally, it is possible that all of these poly(allyl carbonate) compounds are in the form of monomers or mixtures of monomers and oligomers.

In general, the polymerizable allyl carbonate compound is a liquid product at room temperature, the kinematic viscosity measured at 25 °C is 10 to 1000 cSt, and the oligomer content can be varied over a wide range, for example, from 0% to approximately 80% by weight.

In one embodiment, the polymerizable allyl carbonate compound has a kinematic viscosity in the range of 10 cSt to 300 cSt, more preferably 10 to 100 cSt, still more preferably 10 to 40 cSt. Preferably, the density at 25 °C of the polymerizable allyl carbonate compound is in the range of 1.10 g/ml to 1.30 g/ml, more preferably 1.11 g/ml to 1.20 g/ml.

Specific examples of the polyols forming X in General Formula (2) 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 X in General Formula (2) may also be extended polyols, such as lactone-extended polyols and alkyl oxide-extended polyols. By extended polyol is meant the reaction product having terminal polyol hydroxyl groups and a suitable reagent, 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 pentaerythritol, and epsilon-caprolactone-extended trimethylol propane.

Examples of alkyl oxide-extended polyols include diethylene glycol extended with ethylene oxide or propylene oxide, dipropylene glycol extended with ethylene oxide or propylene oxide, triethylene glycol extended with ethylene oxide or propylene oxide, tetraethylene glycol extended with ethylene oxide or propylene oxide, pentaerythritol extended with ethylene oxide or propylene oxide, trimethylol propane extended with ethylene oxide or propylene oxide.

Accordingly, examples of allyl carbonate compounds include at least one type selected from bis(allyl carbonate) compounds of at least one type 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 type of triol selected from glycerol, trimethylolpropane, and tris(hydroxyethyl)isocyanurate; tetra(allyl carbonate) compounds of at least one type of tetraol selected from pentaerythritol, diglycerol, and ditrimethylolpropane; dipentaerythritol hexa(allyl carbonate) compounds; and a mixed poly(allyl carbonate) compound of at least two types of compounds selected from diols, triols, tetraols, and dipentaerythritols.

The ?bis(allyl carbonate) of a mixture of at least two types of diols? is, for example, obtained as a mixture of the following monomeric components and oligomeric components in a case where the diols are diethylene glycol and neopentyl glycol:

monomeric component:

(1) diethylene glycol bis(allyl carbonate);

(2) neopentylglycol bis(allyl carbonate);

oligomeric 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 neopentyl glycol 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 preferable examples of the polymerizable allyl carbonate compound (A1) suitable for the purposes of the present invention:

(i) Mixture with diethylene glycol bis(allyl carbonate) and related oligomers, where diethylene glycol bis(allyl carbonate) can be defined by Formula (I)

Additionally, an oligomer of diethylene glycol bis(allyl carbonate) can be defined using Formula (II).

where, in formula (II), n is equal to or greater than 2 and equal to or less than 10.

Compound (I) can be manufactured by reacting diethylene glycol bis(chloroformate) with allyl alcohol as described, for example, in the ?Encyclopedia of Chemical Technology?, Kirk-Othmer, third edition, volume 2, pages 111-112. Mixtures of diethylene glycol-bis(allyl carbonate) (Formula (I)) and a related oligomer (Formula (II)) can be readily produced by ester substitution 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 wt. % oligomers;

(ii) Mixture of bis(allyl carbonate) compound of a mixture of diethylene glycol and neopentyl glycol with related oligomers

This bis(allyl carbonate) compound is the same as the bis(allyl carbonate) compound in (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 related oligomers

The poly(allyl carbonate) compound can be obtained by ester substitution 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 related oligomers.

This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound in (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 related oligomers.

This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound in (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 related oligomers.

This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound in (v) above, except that diethylene glycol is replaced with two types of diols 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 related oligomers and a mixture of diethylene glycol bis(allyl carbonate) compound with related oligomers.

In one embodiment, the polyallylfunctional monomer comprises either a diethylene glycol bis(allyl carbonate) compound of general formula (II)

where, in formula (II), n is equal to or greater 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 equals 1 (i.e., the monomeric compound of formula (I) above), the weight percentage being based on the weight of the polyallyl-functional monomer.

The above relative concentrations in % by weight of monomeric species (n = 1) and oligomeric species (n = 2-10) of formula (II) in the polyallyl-functional monomer can be determined by known methods. In particular, the concentration values can be determined by HPLC or GPC analysis under conditions such as to obtain sufficiently separated 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 polyallylfunctional monomer comprises or is the reaction product (RP) of components comprising: diallyl carbonate (A), one or more linear or branched aliphatic diols (B) containing three to ten carbon atoms in the molecule, and optionally a linear or branched aliphatic polyol (C) containing four to twenty carbon atoms and three to six hydroxyl groups in the molecule; wherein the molar ratio A/(B+C) is in the range of 4/1 to 20/1 and the amount of the optional component (C) in the mixture (B+C) is equal to or less than 5% by weight, based on the weight of said mixture (B+C).

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

Diols (B) are linear or branched aliphatic diols, preferably containing 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, neopentylglycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol and 1,4-cyclohexane dimethanol.

Preferably, the diols (B) are selected from: diethylene glycol, neopentyl glycol and combinations thereof.

Polyols (C) are linear or branched aliphatic polyols, preferably containing 4 to 20 carbon atoms and 3 to 6 hydroxyl groups in the molecule.

Examples of suitable polyols (C) are: pentaerythritol, trimethylol propane, dipentaerythritol, ditrimethylol propane and tris(hydroxyethyl)isocyanurate.

Preferably, the polyols (C) are selected from: pentaerythritol, trimethylol propane and combinations thereof.

The polyallyl-functional monomer can be obtained as a 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) is a liquid at room temperature, the kinematic viscosity measured at 25 ?C is 10 to 1000 cSt.

In one embodiment, the reaction product (RP) at 25°C has a kinematic viscosity in the range of 10 cSt to 300 cSt, more preferably 10 to 100 cSt, still more preferably 10 to 40 cSt. Preferably, the density of the reaction product RP at 25°C is in the range of 1.10 g/ml to 1.30 g/ml, more preferably 1.11 g/ml to 1.20 g/ml.

The reaction product (RP) is normally obtained as a mixture of allyl carbonate 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 amounts of said allyl carbonate species depending mainly on the selected ratios of reagents (A), (B) and (C).

Polymerizable allyl ester compound (A2) and polymerizable compound (A3)

Examples of the polymerizable allyl ester compound (A2) include diallyl phthalate represented by General Formula (3) and related oligomers, and allyl ester compounds represented by General Formula (4) and related oligomers obtained by a transesterification reaction of a mixture of diallyl phthalate and a polyol. Examples of the polymerizable compound (A3) include a polymerizable compound represented by General Formula (5) including at least one of an allyl ester group and an allyl carbonate group and related oligomers.

The polymerizable compound represented by General Formula (5) includes a mixture of an allyl ester compound, an allyl carbonate compound, and compounds having an allyl ester group and an allyl carbonate group, obtained by a transesterification reaction of a mixture of dialkyl phthalate, allyl alcohol, diallyl carbonate, and a polyol.

In the present embodiment, the compounds of General Formulas (3) to (5) include regioisomers.

Diallyl phthalate represented by General Formula (3) is at least one type selected from diallyl isophthalate, diallyl terephthalate, and diallyl orthophthalate.

In Formula (4), X represents a divalent group derived from a linear or branched aliphatic diol having 2 to 8 carbon atoms or a trivalent to hexavalent group derived from a linear or branched aliphatic polyol having 3 to 10 carbon atoms and having 3 to 6 hydroxyl groups, and n is an integer from 2 to 6.

In Formula (5), X represents a divalent group derived from a linear or branched aliphatic diol having 2 to 8 carbon atoms or a trivalent to hexavalent group derived from a linear or branched aliphatic polyol having 3 to 10 carbon atoms and having 3 to 6 hydroxyl groups, m and n represent integers from 0 to 6, and the sum of m and n is an integer from 2 to 6.

Specific examples of the polyol (aliphatic diol, aliphatic polyol) forming X in Formula (4) and Formula (5) include the diols of ethylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 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, and 1,4-dimethylolcyclohexane; triols of glycerol and trimethylolpropane; and polyols of tris(hydroxyethyl)isocyanurate, pentaerythritol, diglycerol, ditrimethylol propane and dipentaerythritol.

It is possible that the compounds of Formula (4) and Formula (5) include related oligomers. The oligomer in Formula (4) is produced by a transesterification reaction of an allyl ester compound produced in one production step and a polyol. The oligomer in Formula (5) is produced by a transesterification reaction of the allyl ester compound or the allyl carbonate compound produced in the production step and the polyol.

Accordingly, the polymerizable allyl ester compound (A2) or the polymerizable compound (A3) includes at least one type selected from, for example, a diallyl phthalate compound selected from diallyl isophthalate, diallyl terephthalate, and diallyl orthophthalate; diallyl ester compounds and oligomers thereof obtained by a transesterification reaction between the diallyl phthalate compound and a mixture of at least one type of diol selected from ethylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 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, 2,2diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-dimethylolcyclohexane, and the like; a compound of polyallyl ester and a related oligomer obtained by a transesterification reaction between diallyl phthalate and a mixture of at least one type of polyol selected from glycerol triols and trimethylolpropane, tris(hydroxyethyl)isocyanurate, pentaerythritol, diglycerol, ditrimethylolpropane, dipentaerythritol, and the like; and an allyl ester compound, an allyl carbonate compound, a compound having an allyl carbonate group and an allyl ester group and oligomers thereof, obtained by a transesterification reaction of a mixture of at least one type of dialkyl phthalate having from 1 to 3 carbon atoms selected from dimethyl isophthalate, dimethyl terephthalate, dimethyl orthophthalate, diethyl isophthalate, diethyl terephthalate, diethyl orthophthalate, dipropyl isophthalate, dipropyl terephthalate and dipropyl orthophthalate, an allyl alcohol, diallyl carbonate and the diol or polyol described above.

More specifically, the polymerizable allyl ester compound (A2) or the polymerizable compound (A3) preferably includes at least one type selected from (i) a mixture of diallyl terephthalate and a diethylene glycol bis(allyl carbonate) compound at 30% by weight based on the diallyl terephthalate and an oligomer thereof; (ii) an allyl ester compound obtained by a transesterification reaction of a mixture of diallyl terephthalate and propylene glycol; (iii) a mixture of the allyl ester compound of (ii) and a diethylene glycol bis(allyl carbonate) compound at 20% by weight based on the allyl ester compound and an oligomer thereof; (iv) a mixture of an allyl ester compound, an allyl carbonate compound and a compound having an allyl ester group and an allyl carbonate group, obtained by a transesterification reaction of a mixture of dimethyl terephthalate, allyl alcohol, diallyl carbonate and diethylene glycol, and (v) a mixture of the mixture obtained in (iv) and a diethylene glycol bis(allyl carbonate) compound at 10% by weight with respect to the mixture and an oligomer thereof.

The following are preferable examples of the polymerizable allyl ester compound (A2) or the polymerizable compound (A3) suitable for the purposes of the present invention: a mixture of an allyl ester compound, an allyl carbonate compound, and a compound having an allyl ester group and an allyl carbonate group, obtained by a transesterification reaction of a mixture of dimethyl terephthalate, allyl alcohol, diallyl carbonate, and diethylene glycol.

It is possible that the polymerizable allyl ester compound (A2) or the polymerizable compound (A3) described above are defined by Formulas (III) to (V), the diallyl terephthalate of Formula (III) is the major component thereof and each includes an oligomer obtained by a transesterification reaction with a polyol.

According to the present invention, compound (A) comprising two or more allyloxycarbonyl groups may be selected as a mixture of the polymerizable allyl ester compound (A2) and/or the polymerizable compound (A3) and their oligomers with the polymerizable allyl carbonate compound (A1) and a related oligomer.

Polymerizable comonomers

The reaction mixture may also include an ethylenically unsaturated compound (such as a monomer or oligomer) that is capable of polymerizing with the polyallyl-functional monomer described above. These optional ethylenically unsaturated compounds are also referred to herein as "comonomers." Examples of suitable comonomers include: vinyl aromatic compounds such as styrene, β-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 can be used singly or in combinations 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 reaction mixture according to the present invention may be from 1% to 80% by weight, more particularly 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 reaction mixture.

In a preferred embodiment, the reaction mixture is free of ethylenically unsaturated compounds, meaning that no polymerizable comonomers are added to the reaction mixture; the only polymerizable compound present in the reaction mixture is therefore the polyallyl-functional monomer.

In a preferred embodiment, the reaction mixture comprises a polyallyl-functional monomer which is a diethylene glycol bis(allyl carbonate) compound of general formula (II), wherein n is an integer equal to or greater than 1 and equal to or less than 10 and is free of ethylenically unsaturated compounds as comonomers; the only polymerizable compound present in the reaction mixture is then said to be the diethylene glycol bis(allyl carbonate) compound of general formula (II).

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

Free radical polymerization initiator The radical initiator is an aromatic peroxide compound. Preferably, the aromatic peroxide compound has the following general formula (F1)

where X is selected from hydrogen, C1 to C12 alkoxy groups, chlorine, and bromine. In one embodiment, X is selected from hydrogen, a Cl to C4 alkoxy group, or bromine. Examples of suitable aromatic peroxide initiators include benzoyl peroxide (BPO), bis(p-methoxybenzoyl) peroxide, bis(p-ethoxybenzoyl) peroxide, bis(p-propoxybenzoyl) peroxide, bis(p-isopropoxybenzoyl) peroxide, bis(p-butoxybenzoyl) peroxide, and bis(p-chlorobenzoyl) peroxide. The particularly 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 it takes for the initiator to lose half its activity. It is determined by studying the initiator's decomposition kinetics. The 10-hour half-life temperature of an initiator is the temperature at which half of the originally present initiator decomposes in 10 hours.

The half-life temperature is determined by measuring the rate of decomposition of the initiator 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 using conventional iodometric titration techniques. Such half-life measurement techniques are well known to those skilled in the art. Suitable techniques for determining such half-life temperatures in the same solvent using differential scanning calorimetry that provide a direct measurement of the desired half-life temperature are also known to those skilled in the art and can be replaced with iodometric measurements. The two techniques provide equivalent results for the same solvent within the experimental standard deviation expected for the procedures. It is well known in the art that half-life temperatures depend on the solvent in which the determination is made; therefore, for accuracy in comparing the half-life temperature of one peroxide with another, the solvent in which the half-life is determined must be specified.

The aromatic peroxide initiator suitable for use in the present invention has a ten-hour half-life temperature of or above 55°C, preferably equal to or above 60°C. For example, the ten-hour half-life temperature of the initiator may be in the range of 55°C to 100°C, preferably 60°C to 95°C, even more preferably 60°C to 85°C. In one embodiment, the ten-hour half-life temperature of the initiator is in the range of 60°C to 80°C. In particular, a preferred aromatic peroxide is benzoyl peroxide, which has a ten-hour half-life temperature of 73°C.

In one embodiment, the reaction mixture includes only one aromatic peroxide compound as the free radical polymerization initiator. However, combinations of two or more aromatic peroxide compounds having the same or different ten-hour half-life temperatures may be used if desired.

The amount of the individual free radical initiator or the total amount of a combination of inhibitors in the reaction mixture is in the range of 0.5 to 3.0 wt.% based on the weight of the polyallyl-functional monomer to be prepolymerized, preferably 1.0 to 2.0 wt.%, more preferably 1.3 to 1.8 wt.% (the above wt.% refers to the amount of initiator excluding any solid or liquid dilution component). Initiator amounts above 3.0 wt.% are disadvantageous as they generate excessive heat, thereby increasing the risk of cracking and optical defects in hard polymers; furthermore, a higher yellowing index and hardness may be achieved, which may be undesirable for ophthalmic lenses.

Aromatic peroxide initiators are commercially available, usually in the form of compositions containing phlegmatizers and/or stabilizers, such as alkyl benzoate-based phlegmatizers, phthalate-based phlegmatizers, and cresol-based phlegmatizers or water as a stabilizer. It has been observed that the use of initiators containing phthalate-based and cresol-based phlegmatizers can result in optical articles with defects (so-called "spots") that become particularly visible on coated lenses. Furthermore, phthalate-based and cresol-based phlegmatizers have relatively low solubility in the polyallyl-functional monomer and its prepolymer, which is reflected in increased opacity of the optical articles.

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

The especially preferred initiator is water-stabilized benzoyl peroxide, which is commercially available as a moist powder. Preferably, the water content is 50% or less by weight, more preferably 25% or less by weight, with the weight percentages being based on the weight of the water-stabilized aromatic peroxide (e.g., benzoyl peroxide).

In one embodiment, therefore, the step of preparing the reaction mixture comprises adding the aromatic peroxide compound, preferably benzoyl peroxide, in water-stabilized form.

Other components

The reaction mixture and prepolymer composition may also include additional 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 crosslinking agent, a light stabilizer), an antioxidant, filler, adhesion improver, a bleaching agent, and the like.

For example, an acid phosphate ester or a non-reactive silicone oil can be used as an internal release agent. Examples of acid phosphate esters include phosphate monoesters and phosphate diesters, and these can be used alone or in combination with two or more types.

Examples of resin modifiers include an olefinic compound including an episulfur 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 agents 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 absorbers include: benzotriazole, benzophenone, triazine, and oxalanilide.

These additional compounds can be introduced into either or both the reaction mixture and the prepolymer composition, in the latter case prior to casting into the molds.

In one embodiment, the reaction mixture and the prepolymer composition are solvent-free, i.e., they contain no inert organic solvent that must be removed from the prepolymer composition at the end of the prepolymerization reaction.

Preparation of the prepolymer composition According to the present invention, the prepolymer composition is prepared by heating the reaction mixture comprising the at least one polyallyl functional monomer, the at least one free radical polymerization initiator and the optional components.

The mixing of the components and the prepolymerization reaction can be carried out in a reactor, such as a stainless steel reactor, equipped with heating and cooling means to regulate the temperature of the reaction mixture.

The prepolymerization reaction is carried out by heating the reaction mixture to a temperature in the range of 12 to 3°C below the 10-hour half-life temperature of the aromatic peroxide compound. Preferably, the reaction mixture is heated to a temperature in the range of 10 to 5°C below the 10-hour half-life temperature of the aromatic peroxide compound. For example, when benzoyl peroxide is used as the initiator (10-hour half-life temperature of 73°C), the prepolymerization reaction temperature can be selected in the range of 61°C to 70°C, e.g., 63°C to 70°C or 65°C to 68°C.

Although maintained at the above-mentioned temperature, the reaction mixture is preferably degassed to remove essentially all oxygen and water present. Degassing can be accomplished by any suitable means, such as treating the reaction mixture at reduced pressure (e.g., 50 mbar) or spraying with a nonreactive gas such as nitrogen, helium, or argon.

In one embodiment, at the end of the polymerization reaction, the prepolymer composition has a water content equal to or less than 0.5% by weight based on the weight of the prepolymer composition.

While maintained at the above-mentioned temperature, the reaction mixture can remain quiescent or can be stirred.

As the reaction mixture is heated and polymerization progresses, its viscosity increases. The reaction mixture is heated to form a prepolymer composition having a viscosity, measured at 25°C, in the range of 40 to 350 cSt. Preferably, the reaction mixture is heated until the formed prepolymer composition reaches a viscosity, measured at 25°C, in the range of 60 to 200 cSt, more preferably 70 to 120 cSt. At the end of the prepolymerization reaction, the prepolymer composition is liquid and substantially free of gel. By liquid, it is meant that the prepolymer composition is suitable for casting into a mold.

The duration of the prepolymerization reaction can depend very largely on the prepolymerization temperature, the type of polyallyl-functional monomer, and the desired increased viscosity. Generally, the duration of the prepolymerization reaction ranges from 0.5 to 15 hours, in most cases from 1 to 10 hours.

As stated, a combination of two or more aromatic peroxides having the same or different ten-hour half-life temperatures may be used when desired. In such a case, if the ten-hour half-life temperatures are equal, the prepolymerization temperature is selected according to the principle of the present invention, i.e., 12 to 3°C lower than the ten-hour half-life temperature, or the preferred ranges thereof as indicated above. If the ten-hour half-life temperatures of the two or more initiators are different, it is preferable that the prepolymerization temperature be 12 to 3°C, or the preferred ranges thereof indicated above, lower than the lowest ten-hour half-life temperature of the initiators in the combination.

In a preferred embodiment, the reaction mixture and the associated prepolymer composition include only an aromatic peroxide compound as an initiator.

Once the prepolymer composition is formed, i.e. the reaction mixture has the desired increased viscosity, the prepolymer composition can be cast into molds or cooled, for example to room temperature, for storage.

In one embodiment, therefore, the preparation method includes a step for cooling the prepolymer composition to ensure that the polymerization reaction does not progress further. This is advantageous, for example, when preparing large batches of prepolymer as it prevents an unwanted increase in viscosity before or during the casting operation.

In one embodiment, the process includes a step of cooling the prepolymer composition to a temperature at least 20°C below the ten-hour half-life temperature of the initiator. For example, when benzoyl peroxide is used as the initiator, the prepolymer composition may be cooled to a temperature of 53°C or lower.

Cooling can be achieved in a period of less than 90 minutes, preferably less than 60 minutes, more preferably less than 30 minutes.

The prepolymer composition has relatively high stability at normal ambient temperatures. Although the prepolymer composition contains some of the initiator initially dosed and not consumed during the prepolymerization reaction, it has a relatively long shelf life and working shelf life. The shelf life, for example, can be up to approximately 20 weeks, depending on the amount of initiator used and the increase in viscosity achieved at the end of the prepolymerization reaction.

The prepolymer composition can be polymerized to the thermoset state, i.e., a hard polymer, by conventional techniques known for polymerizing formulations containing polyallyl-functional monomers.

In one embodiment, the prepolymer composition is placed in a mold, such as a glass mold, and polymerized to form shaped articles such as lens blanks or lenses. This procedure is particularly advantageous for preparing ophthalmic lens blanks and ophthalmic lenses.

According to the present invention, no additional free radical initiator needs to be introduced into the molds before casting the prepolymer composition. However, a prepolymer formulation comprising the prepolymer composition and additional optional components (e.g., UV absorbers and blueing agents) can be prepared as desired.

The prepolymer composition may be cast immediately after completion of the prepolymerization reaction, such as at the end of the cooling phase at a temperature at least 20°C below the ten-hour half-life temperature of the initiator. For example, in the case of benzoyl peroxide, prepolymerization may be stopped at approximately 50°C or lower and the prepolymer composition cast into molds at that temperature. Alternatively, the prepolymer composition may be cooled to room temperature or refrigerated (e.g., to a temperature in the range of 0°C to 6°C) and stored for later use.

The cast prepolymer composition can be polymerized by heating it in the mold, for example in an oven or water bath.

As the curing cycle, i.e. the temperature-time profile used to polymerize the prepolymer composition into a hard polymer, a conventional curing cycle, such as that routinely used to cure allylic polymers with IPP, can be used.

Typically, polymerization is conducted at temperatures in the range of about 80°C to about 120°C for 10 to 48 hours to achieve complete polymerization of the optical article. Complete polymerization is considered achieved when the liquid prepolymer composition has been transformed into a hard polymer suitable for removal from the mold.

Once a hard polymer has been obtained, it is generally cooled before being removed from the mold. Preferably, the hard polymer inside the mold is cooled to a temperature in the range of 40 to 80 °C, more preferably 50 to 70 °C. For this purpose, the mold containing the polymerized optical material may be allowed to rest at room temperature outside the heating apparatus.

The optical material removed from the mold can be post-cured, that is, heated to temperatures equal to or above the maximum temperature of the curing cycle, but below the temperatures at which thermal degradation of the material can occur. Post-curing treatment allows for the neutralization of any radical species from the polymerization initiator that may still be present in the optical article and eliminates internal stresses in the optical article.

When a bleaching agent containing tetraazaporphyrin (TAP) dyes is added to the polymerizable formulation in order to offset the yellow color of the optical article (e.g., due to the presence of UV-absorbing compounds or as caused by the initiator), post-polymerization may also serve to increase the efficiency of the TAP dyes as disclosed in WO 2022224928 A1.

In most cases, post-hardening treatment is performed at temperatures in the range of 90°C to 130°C.

Polymerization of the prepolymer composition can be performed in a conventional apparatus, such as a convection oven or a water bath. The molds can be conventional, for example, consisting of two mold pieces and a gasket that form a cavity that defines the shape and dimensions of the final optical material. The mold pieces can be made of glass, metal, or plastic.

The optical material of the present invention can be used for a variety of applications, in particular, ophthalmic lenses, lenses for protective masks, optical filters, and the like. Herein, an ophthalmic lens is defined as a lens designed to fit into an eyeglass frame to protect the eye and/or correct vision. This ophthalmic lens may be a non-corrective ophthalmic lens (also called a plano or afocal lens) or a corrective ophthalmic lens. A corrective lens may be a monofocal, bifocal, trifocal, or 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-reflective coating, an anti-fogging coating, an anti-static coating, an anti-fog coating, a polarizing coating, a tinting coating, and a photochromic coating.

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

EXAMPLES OF CHARACTERIZATION METHODS

Optical materials were evaluated using the following methods.

Density/Specific Gravity: The density of the polyallyl-functional monomer and various prepolymerized resins was determined using a certified volume glass pycnometer (25 ml) immersed in a water bath conditioned at 23 °C and adjusting the resin volume to reach the meniscus. The density (grams/cm<3>) is defined as: weight of loaded monomer/25.

Polymer Density/Specific Gravity (ASTM D-792): The density of the resulting polymer is determined by displacement according to ASTM D-792. The scale used for determining the lift gain is the model E42 ex Gibertini SRL.

Kinematic Viscosity (ASTM D-446): The viscosity at 25°C according to ASTM D-446 is determined with a KPG Ubbelodhe capillary viscometer, type 1C for the polyallyl-functional monomer or alternatively 2C/3C for the prepolymer composition.

Shrinkage Percentage: Shrinkage was determined using the following formula

where Dpol is the density of the final thermoset polymer at 23 μC and Dmon is the density at 23 μC of the liquid polymerizable composition containing the monomer before polymerization.

Yellowness Index (YI) (ASTM D-1925): YI was determined on optical material in the form of a 4 mm plano lens with a GretagMacbeth 1500 Plus spectrophotometer using standard illuminant C and an observer (2° angle). 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 were measured according to ASTM D 1003 with a Haze-Gard Plus digital haze meter manufactured by BYK-Gardner.

Transmittance of light 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 Agilent Cary 60 UV-visible spectrophotometer.

The terms “UV cut” and “HEV cut,” as used herein, represent the highest wavelength in the UV region (280 nm to 380 nm) and the HEV region (380 nm to 500 nm), respectively, for which the transmittance of light of an optical material is less than 1% as measured by ASTM D 1003.

2 mm Plano Lens Coloration Test: The ability of the material to absorb a dye onto its surface is determined by immersion coloring 2 mm plano neutral lenses in a BPI? gray solution for 15 minutes at 93?C in a colorimetric bath, model COLORADO Electronic ex ORGANIZATION GF. After rinsing with demineralized water, the transmittance of the lens was determined by measuring the total light transmittance as described above. Additionally, the uniformity/irregularity of the colored lens was visually evaluated after exposing the colored lens to a backlit visor, model Professional 20 - 5000K ex LUPO DAYLIGHT.

Refractive index nD20: The refractive index of polymer is measured at 20 ?C on an ATAGO ABBE refractometer model NAR-3T.

Mechanical properties? Rockwell hardness M

The Rockwell M hardness (ASTM D-785) of the optical material was evaluated on a 5 mm thick flat sheet.

Materials

The following compounds were used in the examples: Polyallyl-functional monomer

A polyallyl-functional monomer was prepared by reacting diallyl carbonate (component A), diethylene glycol as the diol (component B), and pentaerythritol as the polyol (component C) in a molar ratio A/(B+C) equal to 7.2 and a C/(B+C) ratio equal to 2.29 wt%.

The following compounds were loaded into a three-necked flask, equipped with a thermometer and magnetic stirrer, topped by a distillation column with ten perforated plates of 30 mm diameter:

- pentaerythritol (PE): 5 g (?0.04 moles);

- diethylene glycol (DEG): 213 g (?2.01 moles);

- diallyl carbonate (DAC): 2100 g (?14.80 moles);

- 20% by weight of sodium methylate solution 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, distilling off the allyl alcohol as it formed (total 242 g ?285 ml; purity >99%).

After cooling, the reaction mixture was washed with two 500 ml aliquots of demineralized water.

The excess DAC was distilled at a pressure of approximately 1 mbar, operating at an increasing temperature up to 130 C: the obtained product was filtered through a 0.45 m membrane filter.

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;

- Color Apha: 1.

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

The amount of diethylene glycol bis(allyl carbonate) compound of formula (II) with n = 1 was approximately 83 wt % based on the weight of the monomer and oligomer mixture. This amount was determined by HPLC analysis of the reaction product under the following conditions: temperature = 25 μC; reaction product sample subjected to analysis as a 10 wt % acetonitrile solution; injected sample = 5 μl; eluent: acetonitrile/water mixture (45/55 vol %); UV detector.

UV absorbers

- BP6 (2,2?-dihydroxy-4,4?-dimethoxybenzophenone, manufactured by MFCI).

- Lowilite 20 for adjuvant: 2-dihydroxy-4-methoxybenzophenone.

Peroxide radical polymerization initiators

- Luperox A75? from ARKEMA; water-stabilized benzoyl peroxide (25% water by weight) in the form of a moist granular powder

- PERKADOX CH50-L from Nouryon; phthalate-stabilized benzoyl peroxide (50% by weight of alkyl phthalates) in the form of a moist granular powder.

- Trigonox ADC-NS30? from NOURYON; the commercial product contains approximately 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)

The commercial product FDG-005 from Yamada Chemicals (a Pd-containing TAP compound with a main absorption peak at 583 nm) was used as a whitening agent. 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? (whitening agent)

A bleaching agent masterbatch based on a proprietary composition of pigments dispersed in polyallyl-functional monomers supplied by Acomon SRL (approximately 2.0% by weight of pigments in polyallyl-functional monomer based on the weight of the monomer).

Prepolymerization process

The polyallyl-functional monomer was loaded into a three-necked flask equipped with a magnetic stirrer and a thermocouple. Optional additives such as light stabilizers, UV absorbers, antioxidants, and bleaching agents were also added to the flask at this stage, when necessary in the formulation.

The monomer (or formulation containing optional additives) was heated to the prepolymerization temperature (Tp) under vigorous mixing and reduced pressure (Pabs < 50 mbar). Once the set Tp was reached, atmospheric pressure was restored to the flask by flushing with nitrogen gas. The BPO initiator was then introduced into the flask. The pressure was again reduced (< 50 mbar) and mixing continued until the desired viscosity was achieved by the polymerization reaction. The increased viscosity of the prepolymer composition was measured on a series of samples of the reaction mixture, which were withdrawn from the reaction flask at predetermined intervals.

The prepolymer composition was discharged from the flask and cast directly (i.e. without prior cooling) into glass molds.

Examples

1. Preparation of prepolymer compositions Prepolymer compositions were prepared by mixing 100 parts by weight (pbw) of the polyallyl-functional monomer with BPO initiator or, for comparison purposes, the peroxy dicarbonate initiator Trigonox ADC-NS30, and additional additives in the ratios given in Table 1.

The shelf life of each prepolymer composition was evaluated by determining the viscosity behavior at various prepolymerization temperatures and prepolymerization time periods. Shelf life at a given temperature is defined herein as the length of time the prepolymer composition can be held at that temperature until its viscosity increases to such an extent that its use for mold-filling operations becomes impractical.

Table 1

in quantities of pure BPO

b final polymer density of all samples = 1.313 gr/cm<3 >c hs = hours; dd = days; mo = months

* comparative example

In comparative example CC1, the polyallylfunctional monomer was prepolymerized using the following conventional curing procedure with peroxy dicarbonate initiators. A minor amount of initiator (0.1 part by weight) was added to the monomer at a Tp of 80°C, and the mixture was degassed under reduced pressure (Pabs < 50 mbar) for 3 hours. The Tp temperature of 80°C was selected to be higher than the half-life temperature of 1 hour of the initiator (equal to 66°C for ADC NS-30). The minor amount of initiator and the relatively high Tp resulted in a prepolymer composition that had the desired increase in viscosity (and consequently increased density), but a good shelf life due to complete consumption of the initiator compound.

In order to obtain a ready-to-cast polymerizable formulation, the prepolymer composition CC1 was mixed with a higher amount of the same initiator (comparative sample CC2). However, as shown in Table 1, the ready-to-cast composition CC2 showed a significant reduction in shelf life at room temperature compared to CC1 (approximately 1 hour at 25°C). Such a short shelf life makes low-temperature storage essentially indispensable for the manufacture of optical articles with these compositions (shelf life of over 6 months at 4°C).

As shown in Table 1, the prepolymer compositions of the present invention (PP1 to PP3) are ready-to-cast compositions that exhibit good processability and a very satisfactory shelf life. Samples PP1–PP3 exhibit an increased viscosity, which is effective in ensuring a level of shrinkage comparable to that of curing with the peroxycarbonate initiator and, at the same time, does not increase as rapidly over time, thus allowing adequate casting operations despite the presence of a full amount of initiator.

2. Preparation of ES2 and ES3 and ES1* and ES1-PP* optical articles compared

Ready-to-cast polymerizable formulations according to the invention (ES2 and ES3) were converted into hard polymers. For comparison, a hard polymer (ES1) was prepared by curing the unprepolymerized polyallylfunctional monomer using conventional peroxy dicarbonate ADC NS-30.

The ES2 and ES3 formulations were prepared by charging the polyallyl-functional monomer, initiator, and additives into a jacketed stainless steel reactor equipped with a mechanical stirrer, a thermocouple, and a bottom drain line for mold filling. The prepolymerization process was conducted under the conditions described for the PP3 prepolymer in step 1 above by mixing and degassing (Pabs < 50 mbar) the reaction mixture at 65 μC for 3 h (final viscosity of 90 cSt at 25 μC). At the end of the reaction period, the prepolymer composition was cooled to 50 μC. The vacuum was then replaced by nitrogen gas (Pabs = 1.2 bar). Prior to casting, the prepolymer composition was It was filtered by passing it over a stainless steel disc holder containing a 0.45 micrometer PTFE membrane (47 mm diameter) located on the drainage line and then used for filling glass molds.

Comparative formulation ES1 was prepared in the same manner as ES2 and ES3 except for mixing and degassing at room temperature for 2 hours (Pabs < 50 mbar).

Polymerization to form the hard polymers was accomplished by heating molds containing the polymerizable compositions in a forced-air oven according to one of the curing cycles shown in Tables 2 through 3.

Table 2 - Curing cycle with BPO as initiator (ES2 and ES3)

Table 3 - Curing cycle with Trigonox-NS30 as an initiator (comparative ES1)

After the curing cycle was completed, the molds were removed from the oven and allowed to cool. Mold removal was performed at a temperature range of 50 to 70°C. The cured items were then subjected to post-curing treatments in a forced-air oven under the following conditions:

- 1 hour at 100 ?C for ES1

- 2 hours at 120 ?C for ES2 and ES3.

Polymerizable compositions ES1 to ES3 were cast and cured in glass molds in the form of plano lenses having a thickness of 2 mm for the determination of total transmittance, % opacity and colorability test (T% after coloring and uniformity of paint absorption); cast as flat sheets with a thickness of 5 mm for the determination of YI and Rockwell hardness.

The characterization data reported in Tables 4 and 5 were determined on post-cured lenses.

Lenses with complex designs and geometries were also prepared to evaluate the manufacturing performance of the compositions of the present invention under particularly more severe conditions. The lenses prepared for each casting test were:

- 10 semi-finished blanks, front and rear molds of base 6 and base 8 curvature respectively (5 pieces for each curvature), central thickness 10 mm;

- 5 bifocal lenses, anterior and posterior molds of base curvature 6 with additional power equal to 2.00 and flat segment line.

Process yield was evaluated by determining the ratio of the number of rejected articles showing defects (i.e., cracks, runout lines, or defective segments in the bifocal lens) to the total number of articles cast regardless of design type.

Table 4 - Characterization of optical articles

a pure BPO

b quantity of mother mix dosed

c final polymer density of all samples = 1.313 gr/cm<3 >d prepolymer CC2 of Table 1

* comparative

The data in Table 4 demonstrate that using BPO according to the prepolymerization method of the present invention (ES2 and ES3), it is possible to obtain optical articles having good mechanical and optical characteristics,

which are comparable to those of the ES1 composition polymerized using the peroxy dicarbonate initiator ADC NS-30 and, furthermore, with a limited difference in refractive index. ES2 exhibits slightly greater yellowing than the comparative material ES1, which, however, can easily be compensated for by a small addition of TAP-based whitening agent without detrimental effects on other characteristics.

Furthermore, both ES2 and ES3 show similar T% and coloration appearance to the comparative material ES1 (the ability of two lenses to absorb the shade of colorants can be considered the same when the difference in the total T% values of the lenses is within ±5 units).

Furthermore, the ES2 and ES3 lenses exhibit excellent manufacturing performance thanks to the shrinkage control that can be achieved using the prepolymerization method of the present invention. Indeed, compared to the curing of the polyallylfunctional monomer with standard peroxy dicarbonate ADC initiator NS-30, no premature release lenses, cracks, or glide lines were observed in all the prepared semi-finished blanks; furthermore, all bifocal lenses were successfully cast without segment line defects.

This is the same result that can be achieved by prepolymerization of the polyallylfunctional monomer with the ADC NS-30 peroxy dicarbonate initiator as shown in the comparative example ES1-PP* in Table 4, but with the significant improvement that the prepolymer composition according to the invention is a ready-to-cast composition with a longer shelf life and which does not require any subsequent dosing of initiator before casting.

3. Preparation of optical articles ES5, ES7, ES9 and ES4*, ES6*, ES8* comparison

Polymerizable formulations according to the invention (ES5, ES7, ES9) were prepared by prepolymerizing the polyallyl-functional monomer under the same conditions as described above for the PP3 prepolymer. UV-absorbing compounds and the blue-tinting agent were dosed into the prepolymerized formulation to obtain final lenses with different cut-off ratios. For comparison, formulations comprising the unpolymerized polyallyl-functional monomer and optional components were cured with the peroxy dicarbonate initiator ADC NS 30 (ES4*, ES6*, ES8* comparison).

The composition of each formulation is reported in Table 5 along with the characterization data. The curing and post-curing conditions were as described in point 2 above.

Table 5 - Characterization of optical articles

with pure BPO <b>quantity of masterbatch dosed

c final polymer density of all samples = 1.313 gr/cm<3>

* comparative

Polymerizable compositions ES4 to ES9 refer to alternative UV and HEV compositions that include a significantly higher dosage of the UV absorber BP6, introduced in powder form. The high amount of UV absorber did not affect the outcome of the prepolymerization reaction; the resulting prepolymer composition exhibits an increased viscosity within the desired range of 70–110 cSt at 25°C.

The data in Table 5 show that the prepolymerization method of the present invention can be advantageously used to prepare optical articles having optical and mechanical properties very similar to those of high-quality lenses obtained from the non-prepolymerized monomer after curing with peroxy dicarbonate initiator ADC NS-30.

For optical articles with a cutoff of 400 nm and a cutoff of 410 nm (ES6 to ES9), it has been observed that the higher dosage of UV absorber required to achieve the desired cutoff ratio induces greater yellowing in the optical articles regardless of the type of initiator used. Yellowing, however, can be kept to acceptable levels by appropriate dosage of the blueing agent.

In particular, the optical articles according to the present invention also exhibit better characteristics than the comparative materials when a high dosage of UV absorber is used, i.e. in optical articles having higher cut-off values. In fact, a stable hardness value is observed for the lenses according to the present invention (ES5, ES7 and ES9) compared to the comparative articles (ES4*, ES6* and ES8*) where a decreasing trend is observed. Furthermore, a better and more uniform tintability of the final lenses is observed for the materials according to the present invention (ES 9), in which a high dosage of UV absorber does not influence the color absorption and the final homogeneity of the shade, compared to the TX ADC NS30 hardened lens (ES8), in which the lower hardness is reflected in a faster penetration of dyes together with the presence of some homogeneity defects.

Finally, the comparative compositions showed a high occurrence of cracks, flow lines, and frequent defective segments when bifocal lenses were removed from the mold. In contrast, the formulation according to the present invention showed excellent casting results due to the low level of polymerization shrinkage.

Claims (20)

CLAIMS 1. A method for preparing a polyallyl-functional prepolymer composition comprising: (a) providing a reaction mixture comprising: - at least one polyallyl-functional monomer; - 0.5 to 3.0% by weight of at least one aromatic peroxide compound as a free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer; (b) heating the reaction mixture to a temperature in the range of 12 to 3 degrees Celsius (-4°C) below the 10-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having a viscosity at 25°C in the range of 40 to 350 cSt. 2. The method of claim 1, wherein in step (b) the reaction mixture is heated to a temperature in the range of 10°C to 5°C below the ten-hour half-life temperature of the aromatic peroxide compound. 3. A method according to any of claims 1 to 2, wherein the polymer composition has a viscosity at 25°C in the range of 60 to 200 cSt, preferably 70 to 120 cSt. 4. A method according to any of claims 1 to 3, wherein at least one aromatic peroxide compound has the following general formula (F1). where X is selected from: hydrogen, alkoxy groups from C1 to C12, chlorine, and bromine. 5. The method of claim 4, wherein the at least one aromatic peroxide compound is benzoyl peroxide. 6. A method according to any of claims 1 to 5, wherein step (b) comprises degassing the reaction mixture. 7. A method according to any of claims 1 to 6, wherein in step (a) the 25° viscosity of the at least one polyallyl-functional monomer is in the range of 10 to 300 cSt, preferably 10 to 100 cSt, more preferably 10 to 40 cSt. 8. A method according to any of claims 1 to 7, comprising cooling the prepolymer composition to a temperature at least 20°C below the ten-hour half-life temperature of the aromatic peroxide compound. 9. A method according to any of claims 1 to 8, wherein the at least one polyallyl-functional monomer comprises a compound including two or more allyloxycarbonyl groups according to the following formula (1) wherein, in the formula, n is an integer from 2 to 6, R1 denotes a hydrogen atom or a methyl group, a plurality of R1 present may be the same or different, X is a divalent to hexavalent organic group (a) derived from a linear or branched aliphatic polyol having from 3 to 12 carbon atoms which may have an oxygen atom, a divalent to hexavalent organic group (b) derived from an alicyclic polyol having from 5 to 16 carbon atoms which may have an oxygen atom, or a divalent to hexavalent organic group (c) derived from an aromatic compound having from 6 to 12 carbon atoms, and the organic group (a) or the organic group (b) forms an allyl carbonate group by bonding to an allyloxycarbonyl group via an oxygen atom derived from a hydroxyl group. 10. A method according to any of claims 1 to 9, wherein the at least one polyallyl-functional monomer comprises a diethylene glycol bis(allyl carbonate) compound of general formula (II) where, in formula (II), n is an integer equal to or greater than 1 and equal to or less than 10. 11. The method of claim 10, wherein the diethylene glycol bis(allyl carbonate) compound of general formula (II) comprises 70% by weight or more, preferably 80% by weight or more, of a diethylene glycol bis(allyl carbonate) compound of formula (II) for which n is equal to or greater than 1 and equal to or less than 10. 12. A method according to any of claims 1 to 9, wherein the at least one polyallyl-functional monomer comprises the reaction product (RP) of components comprising: diallyl carbonate (A), one or more linear or branched aliphatic diols (B) containing three to ten carbon atoms in the molecule, and optionally a linear or branched aliphatic polyol (C) containing four to twenty carbon atoms and three to six hydroxyl groups in the molecule; wherein the molar ratio A/(B+C) ranges from 4/1 to 20/1 and the amount of the optional component (C) in the mixture (B+C) is equal to or less than 5% by weight, preferably equal to or less than 3% by weight, based on the total weight of said mixture (B+C). 13. A method according to any of claims 1 to 9, wherein the at least one polyallyl-functional monomer comprises the reaction product (RP) of components comprising: diallyl carbonate (A), one or more linear or branched aliphatic diols (B) containing three to ten carbon atoms in the molecule, and a linear or branched aliphatic polyol (C) containing four to twenty carbon atoms and three to six hydroxyl groups in the molecule; wherein the molar ratio A/(B+C) is in the range of 4/1 to 20/1, preferably 5/1 to 15/1, and the amount of component (C) in the mixture (B+C) is equal to or less than 5% by weight, preferably equal to or less than 3% by weight, based on the total weight of said mixture (B+C). 14. A method according to any of claims 10 to 11, wherein the reaction mixture is free of ethylenically unsaturated compounds other than the diethylene glycol bis(allyl carbonate) compound of general formula (II) wherein n is equal to or greater than 1 and equal to or less than 10. 15. A method according to any of claims 12 to 13, wherein the reaction mixture is free of ethylenically unsaturated compounds that are not the reaction product (RP) of components comprising: diallyl carbonate (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 in the range of 4/1 to 20/1 and the amount of the optional component (C) in the mixture (B+C) is equal to or less than 5% by weight, based on the total weight of said mixture (B+C). 16. Polyallyl-functional prepolymer composition obtained by the method according to any of claims 1 to 15. 17. A method for manufacturing an optical article comprising: (i) providing a reaction mixture comprising: - at least one polyallyl-functional monomer; - 0.5 to 3.0% by weight of at least one aromatic peroxide compound as a free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer; (ii) heating the reaction mixture to a temperature in the range of 12 to 3 degrees Celsius (-C) below the 10-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having a viscosity at 25°C in the range of 40 to 350 cSt; (iii) casting the prepolymer composition into a mold; (iv) curing the prepolymer composition in the mold to form the optical article. 18. The method of claim 17, wherein the prepolymer composition is not added with any additional free radical initiator other than at least one aromatic peroxide before being cast into the mold. 19. Optical article obtained by the method according to any of claims 17 to 18. 20. Ophthalmic lens comprising the optical article according to claim 19.