Method for preparing a polyallyl-functional prepolymer composition, and method for manufacturing an optical article wherein said prepolymer composition is used

Abstract

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; - from 0.5 to 3.0 wt.% of at least one aromatic peroxide compound as free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer; (b) heating the reaction mixture at a temperature within the range of from 12 to 3 Celsius degrees (°C) lower than the ten-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having viscosity at 25 °C within the range of from 40 to 350 mm2 / s (from 40 to 350 cSt). The invention also relates to a method for manufacturing an optical article wherein said prepolymer composition is used.

Description

METHOD FOR PREPARING A POLYALLYL-FUNCTIONAL PREPOLYMER COMPOSITION, AND METHOD FOR MANUFACTURING AN OPTICAL ARTICLE WHEREIN SAID PREPOLYMER COMPOSITION IS USED

[0001] The present invention relates to a method for preparing a polyallyl-functional prepolymer composition and a method for manufacturing an optical article wherein said prepolymer composition is used.

[0002] Polyallyl-functional monomers are polymerized using free radical initiators to produce hard polymers. Many of these polymers are substantially transparent to visible light, are substantially colorless, have refractive indices of from about 1.45 to about 1.6, and possess good mechanical resistance. For these reasons, such monomers are widely employed as precursors for optical articles such as optical lenses and optical lens blanks, safety lens, and flat or curved transparent sheets. Light transmission characteristics may be altered by incorporating dyes, light absorbing compounds, pigments, and the like, in the polymerizable composition containing the monomer before polymerization, or by dying the polymer.

[0003] The polymerization reaction of a polyallyl-functional monomer is normally carried out in the presence of a peroxide initiator, especially a dialkylperoxy carbonate, such as for example diisopropylperoxy carbonate (IPP) or mixtures of IPP and di-s-butylperoxy carbonate, which allow to obtain hard polymers having excellent optical properties, in particular transparency, and low colouring.

[0004] Dialkylperoxy carbonate initiators, especially IPP, however, have the disadvantage of being highly expensive and highly thermally instable, with explosive decomposition, and thus require quite severe transportation and storage conditions. Even when they are formulated in diluted form, using for example a polyallyl-functional monomer for dilution, they require transportation and storage temperatures as low as about -20 °C to -10 °C.

[0005] In the state of the art, peroxide initiators are also known that are stable at ambient temperature (also called Ambient Stable Initiators - ASI) and therefore potentially capable of overcoming the above-mentioned drawbacks of the dialkylperoxy carbonate initiators. As used herein, an Ambient Stable Initiator is a free radical initiator compound that does not require storage under refrigerated conditions, namely it can be stored without substantial degradation taking place at temperatures within the range of 20 to 36 °C. As used herein, an ASI initiator has therefore a “high” ten-hour half-life temperature, where “high” means a ten-hour half-life temperature of at least about 55°C.

[0006] However, ASI compounds such as for example certain diacyl peroxides, alkyl peroxyesters, alkyl peroxyketals and peroxymonocarbonates, also have some disadvantages that have so far limited in the practice their use as initiators for the polymerization of polyallyl-functional monomers.

[0007] Certain ASI compounds, for example, have low solubility in polyallyl-functional monomers thus leading to unsatisfactory level of curing of the hard polymers. Furthermore, hard polymers obtained using ASI compounds like diacyl peroxides initiators (e.g. benzoyl peroxide) exhibit considerable yellowing and poor resistance to UV light. Moreover, compared to the hard polymer materials obtained using IPP as initiator, the materials polymerized using ASI compounds normally exhibit relatively high hardness and brittleness as well as high levels of shrinkage. As used herein, the term “shrinkage” (S) refers to the ratio

[0008] where Dpolis the density of the final thermoset polymer at 23 °C and Dmonand 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.

[0009] High levels of shrinkage are particularly detrimental in casting processes such as those customarily used to produce ophthalmic lenses and ophthalmic lens blanks, wherein a liquid monomer composition is introduced into a mold and thereafter polymerized to the final polymer in a thermoset state.

[0010] When polymerization is carried out in the presence of ASI compounds as initiators, in fact the liquid polymerizable composition has to be heated to a relatively high initial temperature to start the curing cycle of the polymerization reaction, e.g. for benzoyl peroxide that has a ten-hour half-life temperature of 73°C the initial temperature is about 60 °C, that is a much higher initial temperature compared to about 40 °C for IPP that has a ten-hour half-life temperature of 45°C. This initial heating step, however, is accompanied by a volume expansion of the polymerizable composition within the mold with the consequent non-negligible reduction of its density. Since the initial volume expansion in the case of curing with ASI compounds is higher than that occurring when the same polymerizable composition is cured with IPP or other non-ASI initiators, the shrinkage observed for the hard polymers cured with the ASI initiator is significantly higher than that of the hard polymers obtained by cured with IPP or other non-ASI initiators.

[0011] Such a high level of shrinkage within the molds brings about numerous defects in the hard polymer, such as change of dimension and internal stresses as well as detachment of the material from the mold walls that yields surfaces of inadequate smoothness and causes breakages of the polymerized material or of the molds. Because of these negative aspects the manufacturing processes using ASI initiators are characterized by low production yields.

[0012] The above drawbacks especially affect the production of semi-finshed lenses (also called “blanks”) of complex design and geometry, such as blanks having a high radius of curvature (6-base or higher) and bifocal semi-finished blanks (e.g. semi-finshed lenses whose front surfaces have a double power correction to simultaneously compensate myopia and presbyopia).

[0013] In a bifocal blank, in fact, the mechanical stresses generated by the shrinkage are different in each of the two power segments of the blank therefore frequently resulting in damages of the lens during demolding, such as generation of chips, pits or entire fracture along the separation surface of the two power segments. The fracture issue is particularly relevant in the casting of the flat top bifocal blanks, namely bifocal blanks featuring two power segements separated by a flat separation surface.

[0014] In the state of the art, it is known that shrinkage may be reduced by using 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 used polyallyl-functional monomer for the production of optical articles - having the following formula (II)

[0015] wherein n is a positive integer (for example in the range 1-10), shrinkage can be reduced by including in the formulation of the polymerizable composition one or more mono- or poly-ethylenically unsaturated compounds that are not poly(allyl carbonate)-functional monomers.

[0016] Examples of these mono- or poly-ethylenically unsaturated compounds, also called co-monomers or reactive diluents, are mono- or polyethylenically unsaturated compounds such as vinyl esters of versatic acid 9 and 10. The comonomers may be liquid components having a lower density of polymerizable double bonds (i.e. number of double bonds per unit mass of the compound) than the diethylene glycol bis(allyl carbonate) monomer. These comonomers allow to obtain a final hard polymer having a lower level of crosslinking (i.e. a lower value of the term Dpolin the above shrinkage equation) compared to the hard polymer obtained from diethylene glycol bis(allyl carbonate) monomer devoid of comonomers and therefore a lower shrinkage.

[0017] Alternatively, or in addition to the above effect, the comonomers may have a higher density (i.e. mass / volume ratio) than the diethylene glycol bis(allyl carbonate) monomer so that the casted polymerizable composition containing the polyallyl-functional monomer and the comonomers has an increased density (i.e. a higher value of the Dmonterm in the above shrinkage equation) and therefore a lower final shrinkage. This is the case for example of compounds having high molar mass or polyfunctional structure, i.e. having three or more ethylenically unsaturated functional groups per molecule, as disclosed in US 4144262 where these compounds are also used as single monomer as an alternative to the diethylene glycol bis(allyl carbonate) monomer.

[0018] This approach to reduce shrinkage using comonomers is described in WO 2004090002A1, US 2021 / 0263197A1, EP3381951A1 and EP 0241997.

[0019] In an alternative approach, when the polyallyl-functional monomer is diethylene glycol bis(allyl carbonate) of above formula (II), the polymerizable composition may include a relatively high content of oligomeric species, that is species of above formula (II) wherein n is an integer equal to 2 or more. As these oligomeric species have a lower density of polymerizable double bonds compared to the linear species of the diethylene glycol bis(allyl carbonate) monomer (i.e. the species of formula (II) with n = 1), they allow to achieve hard polymers with a lower level of crosslinking (i.e. lower value of the term Dpolin the shrinkage equation) and therefore having a lower shrinkage.

[0020] This approach to reduce shrinkage is described in WO 00 / 27794 and WO 2017 / 168325A1.Problem that the Invention is to Solve

[0021] Another way to reduce shrinkage known in the art is based on the introduction in the mold of a liquid prepolymer composition, which is then polymerized to obtain the final thermoset polymer.

[0022] The prepolymer composition (hereinafter also indicated as “prepolymer”) is usually produced by partially polymerizing the polyallyl-functional monomer so as to consume a portion of the allylic groups. The partial polymerization (hereinafter also indicated as “prepolymerization”) is stopped, however, before more than a trivial amount of gelation occurs so that the prepolymer composition can be introduced into the mold as a liquid having an increased density than the initial polyallyl-functional monomer.

[0023] The prepolymerization reaction requires accurate control. Typically, the prepolymerization reaction is controlled by dosing the initiator in small amounts so as 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 the initiator, moreover, ensure that at the end of the prepolymerization reaction the initiator is fully consumed so that the liquid prepolymer composition is stable at ambient temperature and has an adequate shelf-life, namely the liquid prepolymer composition can be stored for quite a long time before being used to produce hard polymer articles without gelation taking place.

[0024] The prepolymerization reaction, moreover, is controlled by adjusting the heat provided to the reaction mixture of monomer and initiator in the reactor. Particularly, it may be necessary cooling the reaction mixture once the desired viscosity for the prepolymer is achieved so as to stop the reaction and prevent subsequent gelling, which may be caused by the thermal inertia of the prepolymer mass (so called “bulk effect”).

[0025] To produce hard 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 can be the same or different from the one 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 having low ten-hour half-life temperatures (i.e. non-ASI initiators such as IPP) are used in the curing cycle, once they are admixed with the monomer, the resultant liquid polymerizable formulation must be promptly used because its shelf-life is short. If not used immediately, the formulation must be refrigerated, with consequent high-energy consumption, for being used at a later time. This drawback imposes on the manufacturer the preparation of small batches of polymerizable formulations.

[0026] To increase the shelf-life of the formulation, it is possible increase the concentration of the initiator in the formulation and carry out the casting at low temperatures, i.e. 10 °C or lower. This way of operating, however, has the disadvantage of increasing the viscosity of the cooled prepolymer, which results in longer and less efficient operations of filling of the molds and consequently limited productivity, especially in the manufacturing of lenses of complex design and geometry.

[0027] 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 dissolving also the partially polymerized monomer and then heated in the presence of a small amount of the initiator. At the end of the prepolymerization, the solvent is removed, e.g. by evaporation or distillation, and the liquid prepolymer composition is subjected to polymerization, after a new addition of an initiator, to produce the hard polymer.

[0028] US 4623708 discloses a method for the preparation of a prepolymer in which the prepolymerization step includes adding a small amount of a free radical type initiator, which may be the same or different than that used just prior to casting, and heating to a temperature higher than the one-hour half-lifetime temperature of the initiator. In this manner, most of the added initiator is consumed and the prepolymerization produces the highest possible conversion while preventing over-polymerization.

[0029] US 6057411 discloses a process for forming a polymerizable, liquid, substantially gel-free, poly(allyl carbonate)-functional prepolymer composition, which comprises heating a neat composition comprising at least one poly(allyl carbonate)-functional monomer and free radical initiator having a ten-hour half-life temperature of at least 85 °C at temperatures in the range of from 5 Celsius degrees below the ten-hour half-life temperature of the free radical initiator to 150 °C, to form a reaction mixture having an increased 25 °C viscosity in the range of from 25 to 10,000 centipoises and an ethylenic double bond utilization of at least 3 percent; and over a period of less than 90 minutes cooling the reaction mixture to a temperature at least 20 Celsius degrees below the ten-hour half-life temperature of the initiator.

[0030] The monomer and prepolymer compositions of the above-discussed state of the art that are used for reducing shrinkage, however, involve high costs because of the use of additional raw materials and complex preparation processes (i.e. comonomers and the provision of special polyallyl-monomer and prepolymer compositions).

[0031] Particularly, the known methods of preparation of the prepolymer compositions and the methods of use thereof are not practical for several reasons. First, a number of variables has to be accurately controlled during the prepolymerization process, namely the dosage of the initiator and the reaction temperature, which makes it difficult to obtain the desired characteristic for the prepolymer in a reproducible manner. Second, the need of a step of dosage of an initiator to the liquid prepolymer composition prior to casting to produce the final polymerized articles and the consequent short shelf-life of the polymerizable composition makes the manufacturing process quite complicated and inefficient. Third, when the prepolymer is prepared by solution polymerization the complete removal of solvent is time consuming, expansive and, where the solvent is toxic or flammable, also hazardous.

[0032] The need is therefore felt for new methods of preparation and use of polyallyl-functional monomers, especially in the form of prepolymer compositions, that allows to overcome the drawbacks of the state of the art.Means for solving the problem

[0033] A method has now been found that allows to prepare hard allyl-based polymers using ambient stable polymerization initiators, the hard polymers having mechanical and optical properties that are substantially comparable to those of hard polymers obtainable by curing with highly effective initiators such as IPP or other conventional peroxy carbonate initiators.

[0034] 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 select group of ambient stable free radical initiators, which are admixed with the polyallyl-functional monomer in such an amount that the initiator is not fully consumed during the prepolymerization reaction; the prepolymerization reaction is carried out by heating the resulting mixture at a temperature close to but lower than the ten-hour half-life temperature of the initiator (and thus also lower than its one-hour half-life temperature) for a period of time sufficient to obtain a prepolymer composition having the desired increased viscosity.

[0035] Since a sufficient amount of initiator remains in the prepolymer composition, its capability of genereating free radical species is exploited in the subsequent step of thermal curing of the the prepolymer composition, thus avoiding any further step of dosing additional initiator to the prepolymer composition prior to casting in the molds.

[0036] The ambient stable free radical initiator is an aromatic peroxide compound (e.g. benzoyl peroxide), which is highly soluble in the polyallyl-functional monomer and can be dosed therefore in effective amounts to also convert the liquid prepolymer composition thereof in a hard polymer using conventional curing cycles, e.g. at temperatures up to 80 to 120 °C and in about 24 to 30 hours.

[0037] Moreover, since the initiator is stable at ambient temperature the shelf-life of the ready-to-cast liquid prepolymer composition at ambient temperature (i.e. 25 °C) is quite long (about 1-2 weeks) and even longer (several months) if stored under refrigeration e.g. at a range between 0 to 4°C. Particularly, the shelf-life is significantly longer than that of the ready-to-cast liquid prepolymer compositions containing IPP (1 hour at ambient temperature) or similar non-ASI initiators.

[0038] The prepolymer composition prepared as described herein is very effective at controlling the shrinkage during the polymerization step to form the hard polymer, the observed shrinkage values being substantially identical to those of the hard polymers obtained using the IPP initiator (about 12% or less).

[0039] The methods described herein, moreover, allow to use ambient stable initiators such as benzoyl peroxide to produce hard polymers and thus optical articles in a very efficient and simple way. The hard polymers have mechanical and optical properties comparable to those of the hard polymers cured using IPP, while overcoming the disadvantages associated to the handling and use of IPP and other non-ASI initiators. Furthermore, thanks to the effective control of the shrinkage of the material the methods described herein enable the use of ASI initiators to manufacture lenses also of complex design and geometry, e.g. semi-finshed lenses of high radius of curvature and bifocal semi-finished lenses, with improved manufacting yields.

[0040] Since the overall amount of aromatic peroxide initiator employed to prepare the prepolymer and then the final polymerized articles is lower than the amount customarily used to directly covert the same poly-allyl functional monomer compositions, the methods described herein have the additional advantage of reducing the negative effects associated to the use of relatively high amount of aromatic peroxide initiators, such as modification of the refractive index of the lenses, increased hardness and brittleness, intrinsic yellowing as well as yellowing induced by exposure to UV light.

[0041] 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 they are obtained with easier and more cost-effective preparation processes than the monomers specifically prepared to have intrinsic reduced shrinkage properties.

[0042] Therefore, 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; - from 0.5 to 3.0 wt.% of at least one aromatic peroxide compound as free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer; (b) heating the reaction mixture at a temperature within the range of from 12 to 3 Celsius degrees (°C) lower than the ten-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having a viscosity at 25 °C within the range of from 40 to 350 mm2 / s (from 40 to 350 cSt).

[0043] According to a third aspect, the present invention relates to a method for manufacturing an optical article comprising: (i) providing a reaction mixture comprising: - at least one polyallyl-functional monomer; - from 0.5 to 3.0 wt.% of at least one aromatic peroxide compound as free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer; (ii) heating the reaction mixture at a temperature within the range of from 12 to 3 Celsius degrees (°C) lower than the ten-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having viscosity at 25 °C within the range of from 40 to 350 mm2 / s (from 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.

[0044] Further characteristics of the present invention are the object of the dependent claims annexed to the present description.

[0045] The compositions of the present invention can comprise, consist essentially of, or consist of, the essential components as well as optional ingredients described herein. As used herein, “consisting essentially of” means that the composition or component may include additional ingredients, but only if the additional ingredients do not materially alter the basic and novel characteristics of the claimed compositions or methods.

[0046] As used herein, the articles "a", "an" and “the” should be read to include one or at least one and the singular also includes the plural, unless it is obvious that it is meant otherwise. This is done merely for convenience and to give a general sense of the disclosure.

[0047] Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified in all instances by the term “about”.

[0048] Polyallyl-functional monomer For the preparation of the prepolymer composition according to the present invention a reaction mixture comprising at least one polyallyl-functional monomer and at least one aromatic peroxide compound as free radical initiator is provided. This mixture may comprise two or more polyallyl-functional monomers.

[0049] The polyallyl-functional monomer can be selected among a wide variety of liquid polyallyl compounds, which may include monomers and oligomers having at least two allyl groups as polymerizable functional groups.

[0050] The polyallyl-functional monomer may comprise, for example, compounds containing two or more allyl groups, such as diallyl esters, diallyl carbonate and diallyl phtalate.

[0051] In one embodiment, the polyallyl-functional monomer comprises the liquid poly(allyl carbonates) of polyhydroxy organic materials. Examples of such monomers include poly(allyl carbonates) of linear or branched aliphatic polyols, poly(allyl carbonates) of cycloaliphatic-containing polyols, and poly(allyl carbonates) of aromatic-containing polyhydroxy compounds. These monomers are themselves known and can be prepared by procedures well known in the art.

[0052] In one embodiment, the polyallyl-functional monomer is selected from: diethylene glycol bis(allyl carbonate), ethylene glycol bis(allyl carbonate), oligomers of diethylene glycol bis(allyl carbonate), oligomers of ethylene glycol bis(allyl carbonate), bisphenol A bis(allyl carbonate), diallylphthalates such as diallyl phthalate, diallyl isophthalate, diallyl terephthalate, diallyl orthophthalate and mixtures thereof.

[0053] The polyallyl-functional monomer is a liquid product at ambient temperature, the kinematic viscosity measured at 25°C is 10 to 1000 mm2 / s (10 to 1000 cSt).

[0054] In one embodiment, the polyallyl-functional monomer has a kinematic viscosity within the range of from 10 mm2 / s to 300 mm2 / s (from 10 cSt to 300 cSt), preferably from 10 to 100 mm2 / s (from 10 to 100 cSt), more preferably from 10 to 40 mm2 / s (from 10 to 40 cSt).

[0055] As used herein, the kinematic viscosity of a compound, including a polyallyl-functional monomer or a prepolymer composition, is determined in accordance with ASTM D446 using a KPG Ubbelodhe viscosimeter (capillary type 1C, 2C or 3C).

[0056] Preferably, the polyallyl-functional monomer has a density at 25 °C within the range of from 1.10 g / ml to 1.30 g / ml, more preferably from 1.11 g / ml to 1.20 g / ml.

[0057] Compound (A) including two or more allyloxycarbonyl groups In one embodiment, the polyallyl-functional monomer can be represented as a compound (A) including two or more allyloxycarbonyl groups according to the following formula (1)

[0058] wherein, in the formula, n is an integer from 2 to 6, R1indicates a hydrogen atom or a methyl group, a plurality of present R1’s 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 which may have an oxygen atom, a divalent to hexavalent organic group b derived from an alicyclic polyol having 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 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.

[0059] These polyols normally include 2 to 6 hydroxyl groups in the molecule, and it is possible for these polyols to include 2 to 4 hydroxyl groups in the molecule, which is preferable.

[0060] Examples of the aliphatic polyol a1 include diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, trimethylolpropane, tris(hydroxyethyl) isocyanurate, pentaerythritol, dipentaerythritol, and the like.

[0061] Examples of the alicyclic polyol b1 include 1,4-dimethylolcyclohexane, 4,8-bis(hydroxymethyl)-[5.2.1.02,6] tricyclodecane, and the like.

[0062] Examples of the aromatic compound c1 include benzene, toluene, xylene, naphthalene, and the like.

[0063] Specific examples of the compound including two or more allyloxycarbonyl groups include an allyl carbonate polymerizable compound (A1), an allyl ester polymerizable compound (A2), and a polymerizable compound (A3) including at least one of an allyl carbonate group and an allyl ester group.

[0064] It is possible for the compound (A) including two or more allyloxycarbonyl groups to include an oligomer thereof.

[0065] A compound including two or more allyloxycarbonyl groups is a liquid product at ambient temperature, the kinematic viscosity measured at 25°C is 10 to 1000 mm2 / s (10 to 1000 cSt), and it is possible to change the oligomer content in a wide range, for example, from 0% to approximately 80% by weight.

[0066] In one embodiment, the compound including two or more allyloxycarbonyl groups has a kinematic viscosity within the range of from 10 mm2 / s to 300 mm2 / s (from 10 cSt to 300 cSt), preferably from 10 to 100 mm2 / s (from 10 to 100 cSt), more preferably from 10 to 40 mm2 / s (from 10 to 40 cSt). Preferably, the density at 25 °C of the compound including two or more allyloxycarbonyl groups is within the range of from 1.10 g / ml to 1.30 g / ml, more preferably from 1.11 g / ml to 1.20 g / ml.

[0067] Allyl Carbonate Polymerizable Compound (A1) The allyl carbonate polymerizable compound (A1) can be represented by Formula (2)

[0068] wherein, 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 of 2 to 6.

[0069] The allyl carbonate polymerizable compound (A1) of Formula (2) may include an oligomer thereof. The oligomer is a poly(allyl carbonate) in which two or more molecules of a polyol are linked via a carbonate group produced by transesterification reaction of allyl carbonate produced in the production step and a polyol.

[0070] The allyl carbonate polymerizable 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 mixed poly(allyl carbonate) compound, that is, a compound which is derived from at least two kinds of polyols and which can be obtained by mechanical mixing of the respective polyol poly(allyl carbonate) compounds, or a compound obtained directly by a chemical reaction starting from a mixture of polyols and diallyl carbonate.

[0071] Finally, it is possible for all these poly(allyl carbonate) compounds to be in the form of monomers or mixtures of monomers and oligomers.

[0072] Generally, the allyl carbonate polymerizable compound is a liquid product at ambient temperature, the kinematic viscosity measured at 25°C is 10 to 1000 mm2 / s (10 to 1000 cSt), and it is possible to change the oligomer content in a wide range, for example, from 0% to approximately 80% by weight.

[0073] In one embodiment, the allyl carbonate polymerizable compound has a kinematic viscosity within the range of from 10 mm2 / s to 300 mm2 / s (from 10 cSt to 300 cSt), preferably from 10 to 100 mm2 / s (from 10 to 100 cSt), more preferably from 10 to 40 mm2 / s (from 10 to 40 cSt). Preferably, the density at 25 °C of the allyl carbonate polymerizable compound is within the range of from 1.10 g / ml to 1.30 g / ml, more preferably from 1.11 g / ml to 1.20 g / ml.

[0074] 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)-[5.2.1.02,6] tricyclodecane, glycerol, trimethylolpropane, tris(hydroxyethyl) isocyanurate, pentaerythritol, diglycerol, ditrimethylolpropane, dipentaerythritol, and the like.

[0075] The the polyols forming X in General Formula (2) may also be extended polyols, such as lactone extended polyols and alkyl oxide extended polyols. By an extended polyol is meant the reaction product having terminal hydroxyl groups of polyol and a suitable reactant, e.g. a lactone or an alkyl oxide.

[0076] Examples of lactone extended polyols include epsilon-caprolactone extended diethylene glycol, epsilon-caprolactone extended dipropylene glycol, epsilon-caprolactone extended triethylene glycol, epsilon-caprolactone extended tetraethylene glycol, epsilon-caprolactone extended pentaerythrite and epsilon-caprolactone extended trimethylol propane.

[0077] Examples of alkyl oxide extended polyols include ethylene oxide or propylene oxide extended diethylene glycol, ethylene oxide or propylene oxide extended dipropylene glycol, ethylene oxide or propylene oxide extended triethylene glycol, ethylene oxide or propylene oxide extended tetraethylene glycol, ethylene oxide or propylene oxide extended pentaerythrite, ethylene oxide or propylene oxide extended trimethylol propane.

[0078] Accordingly, examples of the allyl carbonate compounds include at least one kind selected from bis(allyl carbonate) compounds of at least one kind of diol selected from diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-dimethylolcyclohexane, and 4,8-bis(hydroxymethyl)- [5.2.1.02,6] tricyclodecane; tris (allyl carbonate) compounds of at least one kind of triol selected from glycerol, trimethylolpropane, and tris(hydroxyethyl) isocyanurate; tetra(allyl carbonate) compounds of at least one kind of tetraol selected from pentaerythritol, diglycerol, and ditrimethylol propane; dipentaerythritol hexa (allyl carbonate) compounds; and a mixed poly(allyl carbonate) compound of at least two kinds of compounds selected from the diols, the triols, the tetraols, and the dipentaerythritol.

[0079] The "bis(allyl carbonate) of a mixture of at least two kinds of diols" is, for example, obtained as a mixture of the following monomer components and oligomer components in a case where the diols are diethylene glycol and neopentyl glycol: monomer component: (1) diethylene glycol bis(allyl carbonate); (2) neopentyl glycol bis(allyl carbonate); oligomer component:

[0080] (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);

[0081] (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);

[0082] (5) complex oligomer including both hydrocarbons (and ethers) derived from diethylene glycol and a hydrocarbon derived from neopentylglycol in the same molecule (a compound having a structure in which two hydroxyl groups of a compound in which diethylene glycol and neopentyl glycol are linearly oligomerized in an arbitrary sequence in the same molecule via a carbonate bond are replaced with allyl carbonate groups).

[0083] The following are preferable examples of the allyl carbonate polymerizable compound (A1) suitable for the purposes of the present invention:

[0084] (i) Mixture with diethylene glycol bis(allyl carbonate) and oligomers thereof, where diethylene glycol bis(allyl carbonate) can be defined by Formula (I)

[0085] In addition, it is possible to define an oligomer of diethylene glycol bis(allyl carbonate) by Formula (II)

[0086] wherein, in the formula (II), n is equal to or higher than 2 and equal to or lower than 10.

[0087] It is possible to manufacture compound (I) by reacting diethylene glycol bis (chloroformate) with allyl alcohol as described in, for example, "Encyclopedia of Chemical Technology", Kirk-Othmer, Third Edition, Volume 2, pages 111-112. It is possible to easily produce mixtures of diethylene glycol-bis(allyl carbonate) (Formula (I)) and an oligomer (Formula (II)) thereof by ester replacement between diallyl carbonate and diethylene glycol in the presence of a basic catalyst, for example, as described in EP 35304. These mixtures usually include up to approximately 80% by weight of oligomers;

[0088] (ii) Mixture of bis(allyl carbonate) compound of a mixture of diethylene glycol and neopentyl glycol with oligomers thereof

[0089] This bis(allyl carbonate) compound is the same as the bis(allyl carbonate) compound of point (i) above except that diethylene glycol is replaced with a mixture of diethylene glycol and neopentyl glycol;

[0090] (iii) Mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol and tris (hydroxyethyl) isocyanurate with oligomers thereof

[0091] It is possible to obtain the poly(allyl carbonate) compound by ester replacement of a diallyl carbonate of a mixture of diethylene glycol and tris(hydroxyethyl) isocyanurate, for example, as described in US 4,812,545.

[0092] (iv) Mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol and trimethylolpropane with oligomers thereof.

[0093] This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound of point (iii) above, except that tris(hydroxyethyl) isocyanurate is replaced with trimethylol propane.

[0094] (v) Mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol and pentaerythritol with oligomers thereof.

[0095] This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound of point (iii) above, except that tris(hydroxyethyl) isocyanurate is replaced with pentaerythritol.

[0096] (vi) Mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol, neopentyl glycol, and pentaerythritol with oligomers thereof.

[0097] This poly(allyl carbonate) compound is the same as the poly(allyl carbonate) compound of point (v) above, except that diethylene glycol is replaced with two kinds of diols of diethylene glycol and neopentyl glycol.

[0098] (vii) Poly(allyl carbonate) mixture including a mixture of poly(allyl carbonate) compound of a mixture of diethylene glycol, neopentyl glycol, and pentaerythritol with oligomers thereof and a mixture of diethylene glycol bis(allyl carbonate) compound with oligomers thereof.

[0099] In one embodiment the polyallyl-functional monomer comprises or is a diethylene glycol bis(allyl carbonate) compound of general formula (II)

[0100] wherein, in the formula (II), n is equal to or more than 1 and equal to or less than 10.

[0101] Preferably, the polyallyl-functional monomer comprises 70 wt.% or more, preferably 80 wt.% or more, of the diethylene glycol bis(allyl carbonate) compound of formula (II) for which n is equal to 1 (i.e. the monomer compound of above formula (I)), the weight percentage being based on the weight of the polyallyl-functional monomer.

[0102] The above wt.% relative concentrations of monomer species (n = 1) and oligomer species (n = 2-10) of formula (II) in the polyallyl-functional monomer can be determined by means of known methods. In particular, the concentration values can be determined by means of HPLC or GPC analysis under conditions which are such to obtain sufficiently separate peaks corresponding to the monomeric species and each of the oligomeric species and the subsequent calculation of the percentage area of the chromatographic peaks associated with each of the monomeric and oligomeric species.

[0103] In one embodiment the polyallyl-functional monomer comprises or is the reaction product (RP) of components comprising: diallylcarbonate (A), one or more linear or branched aliphatic diols (B) containing from three to ten carbon atoms in the molecule and optionally a linear or branched aliphatic polyol (C) containing from four to twenty carbon atoms and from three to six hydroxyl groups in the molecule; wherein the molar ratio A / (B+C) is within the range from 4 / 1 to 20 / 1 and the quantity of the optional component (C) in the mixture (B+C) is equal to or lower than 5 wt.%, with respect to the weight of said mixture (B+C).

[0104] Preferably, the molar ratio A / (B+C) is within the range from 5 / 1 to 10 / 1 and the quantity of (C) in the mixture (B+C) is equal to or lower than 3 wt.% with respect to the weight of said mixture (B+C).

[0105] Diols (B) are linear or branched aliphatic diols, preferably containing from 3 to 10 carbon atoms in the molecule.

[0106] Examples of suitable diols (B) are: diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-propanediol, neopentyl glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol and 1,4- cyclohexane dimethanol.

[0107] Preferably, diols (B) are selected from: diethylene glycol, neopentyl glycol and combinations thereof.

[0108] Polyols (C) are linear or branched aliphatic polyols, preferably containing from 4 to 20 carbon atoms and from 3 to 6 hydroxyl groups in the molecule.

[0109] Examples of suitable polyols (C) are: pentae- rythrite, trimethylol propane, dipentaerythrite, ditrimethylol propane and tris (hydroxy-ethyl) isocyanurate.

[0110] Preferably, polyols (C) are selected from: pentaerythrite, trimethylol propane and combinations thereof.

[0111] The polyallyl-functional monomer can be obtained as reaction product (RP) by reacting diallyl carbonate (A) with diol (B) or a mixture of diol (B) and polyol (C) under transesterification conditions and in the presence of a basic catalyst, as described for example in WO 2004 / 090002.

[0112] The reaction product (RP) is a liquid product at ambient temperature, the kinematic viscosity measured at 25°C is 10 to 1000 mm2 / s (10 to 1000 cSt).

[0113] In one embodiment, the reaction product (RP) at 25 °C has a kinematic viscosity within the range of from 10 mm2 / s to 300 mm2 / s (from 10 cSt to 300 cSt), more preferably from 10 to 100 mm2 / s (from 10 to 100 cSt), even more preferably from 10 to 40 mm2 / s (from 10 to 40 cSt). Preferably, the density of the reaction product RP at 25 °C is within the range of from 1.10 g / ml to 1.30 g / ml, more preferably from 1.11 g / ml to 1.20 g / ml.

[0114] The reaction product (RP) is normally obtained as a mixture of allyl carbonates species of components (B) and (C), if present, in monomeric and oligomeric form, as well as in the form of mixed oligomeric allyl carbonates of said components (B) and (C), the relative quantities of said allyl carbonate species mainly depending on the selected ratios of the reagents (A), (B) and (C).

[0115] Allyl Ester Polymerizable Compound (A2) and Polymerizable Compound (A3) Examples of the allyl ester polymerizable compound (A2) include diallyl phthalate represented by General Formula (3) and oligomers thereof, and allyl ester compounds represented by General Formula (4) and oligomers thereof obtained by 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 oligomers thereof.

[0116] 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 transesterification reaction of a mixture of dialkyl phthalate, allyl alcohol, diallyl carbonate, and a polyol.

[0117] In the present embodiment, the compounds of general Formulas (3) to (5) include regioisomers.

[0118] The diallyl phthalate represented by General Formula (3) is at least one kind selected from diallyl isophthalate, diallyl terephthalate, and diallyl orthophthalate.

[0119] 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 of 2 to 6.

[0120] 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 of 0 to 6, and the sum of m and n is an integer of 2 to 6.

[0121] Specific examples of the polyol (aliphatic diol, aliphatic polyol) forming X in Formula (4) and Formula (5) include 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.

[0122] It is possible for the compounds of Formula (4) and Formula (5) to include oligomers thereof. The oligomer in Formula (4) is produced by transesterification reaction of an allyl ester compound produced in a production step and a polyol. The oligomer in Formula (5) is produced by transesterification reaction of the allyl ester compound or the allyl carbonate compound produced in the production step and the polyol.

[0123] Accordingly, the allyl ester polymerizable compound (A2) or the polymerizable compound (A3) includes at least one kind 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 transesterification reaction between the diallyl phthalate compound and a mixture of at least one kind 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, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-dimethylolcyclohexane, and the like; a polyallyl ester compound and an oligomer thereof obtained by transesterification reaction between the diallyl phthalate and a mixture of at least one kind of polyol selected from triols of glycerol and trimethylolpropane, tris(hydroxyethyl) isocyanurate, pentaerythritol, diglycerol, ditrimethylol propane, 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 transesterification reaction of a mixture of at least one kind of dialkyl phthalate having 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.

[0124] More specifically, the allyl ester polymerizable compound (A2) or the polymerizable compound (A3) preferably includes at least one kind selected from (i) a mixture of diallyl terephthalate and a diethylene glycol bis (allyl carbonate) compound at 30% by weight with respect to the diallyl terephthalate and an oligomer thereof; (ii) an allyl ester compound obtained by 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 with respect to 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 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.

[0125] The following are preferable examples of the allyl ester polymerizable 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 transesterification reaction of a mixture of dimethyl terephthalate, allyl alcohol, diallyl carbonate, and diethylene glycol.

[0126] It is possible for the allyl ester polymerizable compound (A2) or the polymerizable compound (A3) described above to be defined by the Formulas (III) to (V), the diallyl terephthalate of Formula (III) is the main component thereof, and each includes an oligomer obtained by transesterification reaction with a polyol.

[0127] According to the present invention, it is possible to select the compound (A) including two or more allyloxycarbonyl groups as a mixture of the allyl ester polymerizable compound (A2) and / or the polymerizable compound (A3) and oligomers thereof with the allyl carbonate polymerizable compound (A1) and an oligomer thereof.

[0128] Polymerizable comonomers The reaction mixture may also comprise an ethylenically unsaturated compound (as a monomer or oligomer) that is capable of polymerizing with the polyallyl-functional monomer described above. Herein, this optional ethylenically unsaturated compounds are also named “comonomers”. Examples of suitable comonomers include: aromatic vinyl compounds such as styrene, alpha-methylstyrene, vinyltoluene, chlorostyrene, chloromethylstyrene and divinylbenzene; alkyl mono(meth)acrylates such as methyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, glycidyl (meth)acrylate and benzyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-phenoxy-2-hydroxypropyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1 ,3-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 2-hydroxy-1 ,3-di(meth)acryloxypropane, 2,2-bis[4-((meth)acryloxyethoxy)phenyl]propane, 2,2-bis[4-((meth)acryloxydiethoxy)phenyl]propane and 2,2-bis[4-((meth)-acryloxypolyethoxy)phenyl]propane; tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate and tetramethylolmethane tri(meth)acrylate; tetra(meth)acrylates such as tetramethylolmethane tetra(meth)acrylate. These comonomers may be used singly or in combination of two or more. In the above description, "(meth)acrylate" means "methacrylate" or "acrylate", and "(meth)acryloxy" means "methacryloxy" or "acryloxy".

[0129] The total amount of comonomer in the reaction mixture according to the present invention may be from 1% to 80% by weight, in particular from 1 to 50% by weight, more particularly from 2% to 20% by weight, even more particularly from 3% to 10% by weight, based on the total weight of the reaction mixture.

[0130] In one preferred embodiment, the reaction mixture is free of ethylenically unsaturated compounds, which means that the reaction mixture is not added with polymerizable comonomers; the only polymerizable compound present in the reaction mixture is therefore the polyallyl-functional monomer.

[0131] In one preferred embodiment, the reaction mixture comprises a polyallyl-functional monomer that is diethylene glycol bis(allyl carbonate) compound of general formula (II) wherein n is an integer equal to or higher than 1 and equal to or lower than 10 and is free of ethylenically unsaturated compounds as comonomers; the only polymerizable compound present in the reaction mixture is therefore said diethylene glycol bis(allyl carbonate) compound of general formula (II).

[0132] In one embodiment, the reaction mixture comprises a polyallyl-functional monomer that is the above-described reaction product (RP) of components comprising diallylcarbonate (A), one or more aliphatic diols (B) and optionally an aliphatic polyol (C), and the 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 optional C.

[0133] Free radical polymerization initiator The radical initiator is an aromatic peroxide compound. Preferably, the aromatic peroxide compound has the following general formula (F1)

[0134] wherein X is selected from: hydrogen, C1to C12alkoxy groups, chlorine and bromine. In one embodiment, X is selected from hydrogen, a Clto C4alkoxy group or bromine. Examples of suitable aromatic peroxide initiators include benzoyl peroxide (BPO), bis(p-methoxy benzoyl) peroxide, bis(p-ethoxy benzoyl) peroxide, bis(p-propoxy benzoyl) peroxide, bis(p-isopropoxy benzoyl) peroxide, bis(p-butoxy benzoyl) peroxide, and bis (p-chloro benzoyl) peroxide. Especially preferred initiator is benzoyl peroxide [CAS 94-36-0].

[0135] The half-life of a free radical initiator at any specified temperature is defined as the time in which the initiator loses half of its activity. It is determined through studies of the decomposition kinetics of the initiator. The ten-hour half-life temperature of an initiator is the temperature at which one half of the initiator originally present will decompose in 10 hours.

[0136] The half-life temperature is determined by measuring the rate of the initiator decomposition in the aromatic solvent monochlorobenzene by periodically sampling solutions of the peroxide maintained at several selected constant temperatures and determining the amount of undecomposed peroxide remaining in the sampled solution by conventional iodometric titration techniques. Such half-life measurement techniques are well known by those skilled in the art. Suitable techniques for determining such half-life temperatures in the same solvent using differential scanning calorimetry which provide a direct measurement of the desired half-life temperature are also known to those skilled in the art and may be substituted for iodometric measurements. The two techniques provide equivalent results for the same solvent within the expected standard experimental deviation for the procedures. It is well known in the art that half-life temperatures are dependent on the solvent in which the determination is made, thus, for precision in comparing the half-life temperature of one peroxide to another, the solvent in which the half-life is determined must be specified.

[0137] The aromatic peroxide initiator suitable for use in the present invention has a ten-hour half-life temperature equal to or higher than 55 °C, preferably equal to or higher than 60 °C. For example, the ten-hour half-life temperature of the initiator may be within the range of from 55 °C to 100 °C, preferably from 60 °C to 95 °C, even more preferably from 60 °C to 85 °C. In one embodiment, the ten-hour half-life temperature of the initiator is within the range of from 60 °C to 80 °C. Especially preferred aromatic peroxide is benzoyl peroxide, which has a ten-hour half-life temperature of 73°C.

[0138] In one embodiment, the reaction mixture includes only one aromatic peroxide compound as free radical polymerization initiator. However, combinations of two or more aromatic peroxide compounds having the same or different ten-hour half-life temperature may be used when desired.

[0139] The amount of the single free radical initiator or the total amount of a combination of initiators in the reaction mixture is within the range of from 0.5 to 3.0 wt.% based on the weight of the polyallyl-functional monomer to be prepolymerized, preferably from 1.0 to 2.0 wt.%, more preferably from 1.3 to 1.8 wt.% (the above wt% refer to the amount of initiator excluded any solid or liquid diluiting component). Amounts of the initiator higher than 3.0 wt.% are disadvantageous as they generate excessive heat thus increasing the risk of possible cracks and optical defects in the hard polymers; moreover, they would result in higher yellowness index and hardness, which may be undesired for ophthalmic lenses.

[0140] Aromatic peroxide initiators are commercially available, usually in the form of compositions containing phlagmatizers and / or stabilizers such as alkyl benzoate-based phlegmatizers, phthalate-based phlegmatizers and cresol-based phlegmatizers or water as stabilizer. It has been observed that the use of initiators containing phthalate-based and cresol-based phlegmatizers may lead to optical articles having defects (so-called “dots”), which become particularly visible on coated lenses. Moreover, phthalate-based and cresol-based phlegmatizers have a relatively low solubility in the polyallyl-functional monomer and prepolymer thereof which is reflected in a higher haziness of the optical articles.

[0141] The use of water-stabilized peroxides may also have some disadvantages in the manufacturing process, if the water content exceeds certain concentrations in the prepolymer composition before casting. The presence of residual water, for example above 0.5 wt% based on the weight of the prepolymer composition, in fact, may result in the premature detachment of the optical article from the mold during the curing cycle or in inhomogenous conversions of the polyallyl-functional monomer in different molds. However, since water can be more easily removed from the prepolymer composition prior to casting it 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.

[0142] Espacially preferred initiator is water-stabilized benzoyl peroxide, which is commercially available as wet-powder. Preferably, the water content is equal to or lower than 50 wt%, more preferably equal to or lower than 25 wt%, the weight percentages being based on the weight of the water-stabilized aromatic peroxide (e.g. benzoyl peroxide).

[0143] In one embodiment, therefore, the step of preparation of the reaction mixture comprises adding the aromatic peroxide compound, preferably benzoyl peroxide, in water-stabilized form.

[0144] Other components The reaction mixture and the prepolymer composition may also include further additive compounds such as an internal release agent, a UV and / or HEV light-absorbing agent, a resin modifier (e.g. a chain extender, a cross-linking agent, a light stabilizer), an antioxidant, filler, adhesion improver, a bleaching agent and the like.

[0145] As the internal release agent, for example, it is possible to use an acidic phosphate ester or a nonreactive silicone oil. Examples of acidic phosphate esters include phosphoric monoesters and phosphoric diesters and it is possible to use the above alone or in a combination of two or more kinds.

[0146] Examples of resin modifiers include an olefin compound including an episulfide compound, an alcohol compound, an amine compound, an epoxy compound, an organic acid and an anhydride thereof, a (meth)acrylate compound, and the like.

[0147] Examples of suitable bleaching agent are those based on inorganic pigments or organic dyes dispersed in allyl resins, such as those disclosed in WO 2021095774A1 and WO 2022224928A1 in the name of the same Applicants.

[0148] Examples of UV and / or HEV light-absorbing agent comprise: benzotriazole, benzophenone, triazine and oxalanilide.

[0149] These additional compounds may be introduced in either or both of the reaction mixture and prepolymer composition, in the latter case prior to casting into the molds.

[0150] In one embodiment, the reaction mixture and prepolymer composition are solventless, namely they do not contain inert organic solvent that would need to be eliminated from the prepolymer composition at the end of the prepolymerization reaction.

[0151] 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.

[0152] The mixing of the components and the prepolymerization reaction may be carried in a reactor, such as a stainless steel reactor, equipped with heating and cooling means to adjust the temperature of the reaction mixture.

[0153] The prepolymerization reaction is carried out by heating the reaction mixture at a temperature within the range of from 12 to 3 °C lower than the ten-hour half-life temperature of the aromatic peroxide compound. Preferably, the reaction mixture is heated at a temperature within the range of from 10 to 5 °C lower than the ten-hour half-life temperature of the aromatic peroxide compound. For example, when benzoyl peroxide is used as initiator (ten-hour half-life temperature equal to 73°C), the temperature of the prepolymerization reaction may be selected within the range of from 61 °C to 70°C, for example from 63 °C to 70°C or from 65 °C to 68°C.

[0154] While it is maintained at the aforementioned temperature, the reaction mixture is preferably degassed in order to remove substantially all the oxygen and water present therein. Degassing can be carried with any suitable means, for example by treating the reaction mixture under reduced pressure (e.g. 50 mbar or less) or by sparging with a non-reactive gas such as nitrogen, helium or argon.

[0155] In one embodiment, at the end of the prepolymerization reaction, the prepolymer composition has a water content equal to or lower than 0.5 wt% based on the weight of the prepolymer composition.

[0156] While it is maintained at the aforementioned temperature, the reaction mixture may remain quiescent or it may be agitated.

[0157] As the reaction mixture is heated and the polymerization progresses, its viscosity increases. The reaction mixture is heated to form a prepolymer composition having viscosity, measured at 25 °C, within the range of from 40 to 350 mm2 / s (from 40 to 350 cSt). Preferably, the reaction mixture is heated until the formed prepolymer composition reaches a viscosity, measured at 25 °C, within the range of from 60 to 200 mm2 / s (from 60 to 200 cSt), more preferably from 70 to 120 mm2 / s (from 70 to 120 cSt). At the end of the prepolymerization reaction the prepolymer composition is liquid and substantially gel-free. By liquid, it is meant that the prepolymer composition is suitable for being casted in a mold.

[0158] The duration of the prepolymerization reaction may very widely depending on the prepolymerization temperature, the type of polyallyl-functional monomer, the desired increased viscosity. Generally, the duration of the prepolymerization reaction is within the range of from 0,5 to 15 hours, in most cases from 1 to 10 hours.

[0159] As said, a combination of two or more aromatic peroxide compounds having the same or different ten-hour half-life temperature may be used when desired. In such a case, if the ten-hour half-life temperatures are the same, the prepolymerization temperature is selected according to the principle of the present invention, i.e. from 12 to 3 °C lower than the ten-hour half-life temperature, or preferred ranges thereof as indicated above. If the ten-hour half-life temperatures of the two or more initiators are different, it is preferred that the prepolymerization temperature is from 12 to 3 °C, or the above-indicated preferred ranges thereof, lower than the lowest ten-hour half-life temperature among those of the initiators of the combination.

[0160] In one preferred embodiment, the reaction mixture and the prepolymer composition thereof include only one aromatic peroxide compound as initiator.

[0161] Once the prepolymer composition has formed, i.e. the reaction mixture has the desired increased viscosity, the prepolymer composition may be casted into moulds or cooled, for example to ambient temperature, for storage.

[0162] In one embodiment, therefore, the method of preparation includes a step of cooling the prepolymer composition to ensure that the polymerization reaction does not progress further. This is advantageous, for example, when large batches of prepolymer are prepared as it avoids the occurrence of an undesired viscosity increase before or during the time of the casting operation.

[0163] In one embodiment, the process includes a step of cooling the prepolymer composition to a temperature of at least 20 °C below the ten-hour half-life temperature of the initiator. For example, when benzoyl peroxide is used as initiator, the prepolymer composition may be cooled to a temperature of 53°C or less.

[0164] Cooling may be achieved over a period of less than 90 minutes, preferably less than 60 minutes, more preferably less than 30 minutes.

[0165] The prepolymer composition has a relatively high stability at the ordinary ambient temperatures. Although the prepolymer composition contains part of the initiator initially dosed and that has not been consumed during the prepolymerization reaction, it has a quite long storage shelf-life and working shelf-life. The storage shelf-life, for example, may be up to about more than 20 weeks depending on the amount of initiator used and the viscosity increase achieved at the end of the prepolymerization reaction.

[0166] The prepolymer composition may be polymerized to the thermoset state, i.e. a hard polymer, by known conventional techniques for polymerizing formulations containing polyallyl-functional monomers.

[0167] In one embodiment, the prepolymer composition is placed in a mold, as for instance a glass mold, and polymerized to form a shaped article such as a lens blank or a lens. This procedure is particularly advantageous for the preparation of ophthalmic lens blanks and ophthalmic lenses.

[0168] According to the present invention, before casting the prepolymer composition into the molds, it is not necessary to introduce therein any further amount of free radical initiator. However, a prepolymer formulation comprising the prepolymer composition and further optional components (e.g. UV absorbers and bluing agents) may be prepared when desired.

[0169] The prepolymer composition may be casted right after that the prepolymerization reaction is completed, for example at the end of the cooling step to a temperature of at least 20°C below the ten-hour half-life temperature of the initiator. For example, in the case of benzoyl peroxide, the prepolymerization may be interrupted at about 50 °C or lower and the prepolymer composition may be casted in the molds at that temperature. Alternatively, the prepolymer composition may be cooled to ambient temperature or refrigerated (e.g. at a temperature within the range of from 0 °C to 6 °C) and stored for later use.

[0170] The casted prepolymer composition may be polymerized by heating it in the mold, the heating being accomplished for example in an oven or in a water bath.

[0171] As curing cycle, namely the temperature-time profile used for polymerizing the prepolymer composition to a hard polymer, a conventional curing cycle may be used, such as those customarily emplyed for curing allyl polymers with IPP.

[0172] Typically, polymerization is conducted at temperatures in the range of from about 80 °C to about 120 °C over a time of from 10 hour to 48 h to achieve full polymerization of the optical article. Full polymerization is deemed achieved when the liquid prepolymer composition has been transformed into a hard polymer suitable for being demolded.

[0173] After that a hard polymer has been obtained, it is generally cooled down before being demolded. Preferably, the hard polymer within the mold is cooled to a temperature within the range of from 40 to 80°C, more prefereably from 50 to 70°C. To this end, the mold containing the polymerized optical material may be left standing at ambient temperature outside the heating apparatus.

[0174] The demolded optical material may be subjected to post-curing, that is heating at temperatures at or above the maximum temperature of the curing cycle, but below those temperatures at which thermal degradation of the material may take place. The post-curing treatment allows to neutralize radical species of the polymerization initiator that may still be present in the optical article and eliminate internal stresses from the optical article.

[0175] When a bleaching agent containing tetraazaporphyrin (TAP) dyes is added to the polymerizable formulation in order to compensate the yellow colour of the optical article (e.g. owing to the presence of UV absorbing compounds or as caused by the initiator), post-curing may also serve to increase the efficiency of the TAP dyes as disclosed in WO 2022224928 A1.

[0176] In most instances the post-curing treatment is accomplished at temperatures in the range of from 90°C to 130 °C.

[0177] The polymerization of the prepolymer composition can be carried out in conventional apparatus, such as a convection oven or a water bath. The molds can be conventional molds, for example made from two mold pieces and a gasket forming a cavity that defines the shape and dimensions of the final optical material. The mold pieces can be made of glass, metal or plastic.

[0178] The optical material of the present invention can be used for a variety of application, particularly ophtalmic lens, lens for protective masks, optical filters and alike. The ophthalmic lens is herein defined as a lens which is designed to fit a spectacles frame so as to protect the eye and / or correct the sight. Said ophthalmic lens can be an uncorrective ophthalmic lens (also called plano or afocal lens) or a corrective ophthalmic lens. Corrective lens may be a unifocal, a bifocal, a trifocal or a progressive lens.

[0179] The optical material may be coated with one or more functional coatings selected from the group consisting of an anti-abrasion coating, an anti-reflection coating, an antifouling coating, an antistatic coating, an anti-fog coating, a polarizing coating, a tinted coating and a photochromic coating.

[0180] The invention will now be described in more detail by means of the following examples, which are given for purely illustrative purposes and are not intended to limit the scope of the invention in any manner.

[0181] EXAMPLESCHARACTERIZATION METHODS The optical materials were evaluated by means of the following methods.

[0182] Density / specific gravity: The density of the poly-allyl functional monomer and the different pre-polymerized resins was determined by using a volume certified glass picnometer(25ml) submersed in a water bath conditioned at 23°C and adjusting the volume of the resin so as to reach the meniscus. The density rho(grams / cm3) is defined as: weigh of the loaded monomer / 25.

[0183] Density / specific gravity of the polymer (ASTM D-792): The density of the resulting polymer is determined by displacement in accordance with ASTM D-792. The scale used for lift gain determination is model E42 ex Gibertini SRL.

[0184] Kinematic viscosity (ASTM D-446): The viscosity at 25°C in accordance with ASTM D-446 is determined with a KPG Ubbelodhe viscometer, capillary type 1C for the poly-allyl functional monomer or alternatively 2C / 3C for the prepolymer composition.

[0185] Percent shrinkage: Shrinkage has been determined using the following formula where Dpolis the density of the final thermoset polymer at 23 °C and Dmonand is the density at 23°C of the liquid polymerizable composition containing the monomer before polymerization.

[0186] Yellowness Index (YI) (ASTM D-1925): The YI was determined on the optical material in the form of a 4 mm-plano lens with a GretagMacbeth 1500 Plus spectrophotometer taking the standard illuminant C and the observer into account (angle of 2°). The YI is defined as: YI = (100 / Y)(1.277X - 1.06Z).

[0187] Total light transmittance and Haze value: The total light transmittance and haze value of the optical material in the form of a flat plate having a thickness of 2 mm was measured in accordance with ASTM D 1003 with a digital haze meter haze-gard plus manufactured by BYK-Gardner.

[0188] Light Transmittance at a given wavelength: The transmittance at a given wavelength of an optical material in the form of a flat plate having a thickness of 2 mm was measured with an UV-Visible spectrophotometer Agilent Cary 60. The expressions “UV-cut” and “HEV-cut” as used herein represent the highest wavelength in the UV region (280 nm to 380 nm) and HEV region (380 nm to 500 nm), respectively, for which the light transmittance of an optical material is lower than 1% as measured in accordance with ASTM D 1003.

[0189] Tinting test of 2mm plano lenses: The capacity of the material to absorb a dye on its surface is determined by dip-dyeing a neutral plano 2mm lenses in a BPITMgrey solution for 15 minutes @ 93°C in a tintometer bath, model COLORADO Electronic ex ORGANIZZAZIONE GF. After rinsing with demineralized water, the lens transmittance was determined by measuring the total light transmittance as described above. In addition, the evenness / unevenness of the tinted lens was visually evaluated upon exposing the tinted lens on a back - lighted visor, model Professional 20 - 5000K ex LUPO DAYLIGHT.

[0190] Refractive index nD20: The polymer refractive index is measured at 20°C on an ATAGO ABBE Refractometer model NAR-3T.

[0191] Mechanical properties - Rockwell hardness M The Rockwell Hardness M (ASTM D-785) of the optical material has been evaluated on a 5mm-thick flat sheet.

[0192] Materials In the Examples, the following compounds were used.

[0193] Polyallyl-functional monomer A polyallyl-functional monomer was prepared by reacting diallyl carbonate (component A), diethylene glylcol as diol (component B) and pentaerythrite as polyol (component C) in a molar ratio A / (B+C) equal to 7.2 and a ratio C / (B+C) equal to 2,29 wt.%. The following compounds were charged into a three-necked jacketed flask, equipped with a thermometer and magnetic stirrer, surmounted by a distillation column with ten perforated plates of 30 mm in diameter: - pentaerythrite (PE): 5 g (about 0.04 moles); - diethylene glycol (DEG): 213 g (about 2.01 moles); - diallyl carbonate (DAC): 2100 g (about 14.80 moles); - 20% weight solution of sodium methylate in methanol: 1.0 ml.

[0194] The reaction was carried out for three hours at a temperature of 85 °C to 120 °C and a decreasing pressure from 200 to 130 mbar, by distilling the allyl alcohol during its formation (total 242 g, about 285 ml; purity >99%). After cooling, the reaction mixture was washed with two aliquots of 500 ml of demineralized water.

[0195] The excess DAC was distilled at a pressure of about 1 mbar, by operating at an increasing temperature up to 130 C: the product obtained was filtered through a mem- brane filter of 0.45 m.

[0196] 512 g of a liquid product were obtained, having the following characteristics: - Viscosity (25 C): 17 mm2 / s (17 cSt); - Density (20 C): 1.152 g / ml; - Refractive index nD20: 1.453; - Apha colour: 1.

[0197] The above polyallyl-functional monomer was obtained as a mixture of monomer and oligomers of bis(allyl carbonate) diethylene glycol, monomer and oligomers of tetrakis(allyl carbonate) of pentaerythrite, and mixed poly(allyl carbonates) of the above diols and polyol.

[0198] The amount of diethylene glycol bis(allyl carbonate) compound of formula (II) with n = 1 was about 83 wt% based on the weight of the mixture of monomer and oligomers. This amount was determined through HPLC analysis of the reaction product under the following conditions: temperature = 25°C; sample of the reaction product subjected to analysis in the form of a 10% by weight solution of acetonitrile; sample injected = 5 microliters; eluent: mixture of acetonitrile / water (45 / 55% by volume); UV detector.

[0199] UV absorbers - BP6 (2,2'-dihydroxy-4,4'-dimethoxybenzophenone, manufactured by MFCI). - Lowilite 20 by Addivant: 2-dihydroxy-4- methoxybenzophenone.

[0200] Peroxide radical polymerization initiators - Luperox A75 (registered trademark) by ARKEMA; water-stabilized benzoyl peroxide (25 wt.% water) in the form of granular wet-powder - PERKADOX CH50-L by Nouryon; phthalate-stabilized benzoyl peroxide (50 wt.% alkyl phthalates) in the form of granular wet-powder. - Trigonox ADC-NS30(registered trademark) by NOURYON; the commercial product contains about 70% by weight of diethylene glycol bis(allyl carbonate) and 30% by weight of a mixture of isopropyl peroxydicarbonates, sec-butyl and isopropyl / sec-butyl peroxydicarbonates.

[0201] TAP dye (bleaching agent) As bleaching agent the commercial product FDG-005 by Yamada Chemicals (Pd-containing TAP compound having a main absorption peak at 583 nm). The product FDG-005 was used as a masterbatch, i.e. pre-dispersed in the polyallyl-functional monomer at a concentration of 0.05 wt. based on the weight of the monomer.

[0202] UV&Blue cut MBTM(bleaching agent) A bleaching agent masterbatch based on a proprietary composition of pigments dispersed in poly-allyl functional monomers supplied by Acomon SRL (about 2.0 wt.% pigments in polyallyl-functional monomer based on the weight of the monomer).

[0203] Prepolymerization process The polyallyl-functional monomer was loaded into a three-necked jacketed flask equipped with a magnetic stirrer and a thermocouple. When needed in the formulation, optional additives such as light stabilizers, UV absorbers, anti-oxidants and bleaching agents were also introduced into the flask at this stage.

[0204] The monomer (or formulation containing the optional additives) was heated up to the prepolymerization temperature (Tp) under vigorous mixing and reduced pressure (Pabs< 50mbar). Once the set Tpwas reached, the atmospheric pressure was restored in the flask by fluxing nitrogen gas. The BPO initiator was then introduced in the flask. The pressure was reduced again (<50mbar) and the mixing continued until the desired viscosity was obtained owing to the polymerization reaction. The increased viscosity of the prepolymer composition was measured on a series of samples of the reaction mixture, which was withdrawn from the reaction flask at predetermined intervals. The prepolymer composition was discharged from the flask and directly casted (i.e. without prior cooling) into glass molds.

[0205] Examples1. 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 comparative purposes, the peroxy dicarbonate initiator Trigonox ADC-NS30, and optional additives in the ratios reported in Table 1.

[0206] The shelf-life of each the prepolymer composition was evaluated by determining the viscosity trend at different prepolymerization temperatures and prepolymerization time periods. The shelf-life at a given temperature is meant here as the time period in which the prepolymer composition can be maintained at that temperature until its viscosity increases to such an extent that its use for mold filling operations becomes impractical.

[0207]

[0208] In comparative example CC1, the polyallyl-functional monomer has been prepolymerized using the following conventional procedure of curing with peroxy dicarbonate initiators. A minor amount of initiator (0.1 parts by weight) was added to the monomer at the temperature Tpof 80 °C and the mixture degassed under reduced pressure (Pabs< 50mbar) for 3 hours. The temperature Tpof 80°C was selected so as to be higher than the one-hour half-life temperature of the initiator (equal to 66°C for ADC NS-30). The minor amount of initiator and the relatively high Tpallowed to obtain a prepolymer composition having the desired increase of viscosity (and consequently increased density), yet a good shelf life thanks to the complete consumption of the initiator compound.

[0209] In order to obtain a ready-to-cast polymerizable formulation, the prepolymer composition CC1 was admixed with a major amount of the same initiator (comparative sample CC2). However, as showed in Table 1, the ready-to-cast CC2 composition showed a significant reduction in shelf life at ambient temperature compared to CC1 (about 1 hour at 25°C). Such a short shelf-life makes storage at low temperature a substantially indispensable practice for manufacturing optical article with these compositions (shelf life of more than 6 months at 4 °C).

[0210] As shown in Table 1, the prepolymer compositions of the present invention (PP1 to PP3) are ready-to-cast compositions exhibiting good processability and very satisfactory shelf life. Samples PP1 - PP3 exhibit an increased viscosity, which is effective to ensure a shrinkage level comparable to that of curing using the peroxy carbonate initiator and, at the same time, does not increase so rapidly over time thus allowing proper casting operations notwithstanding the presence of a full amount of initiator.

[0211] 2. Preparation of optical articles EX2 and EX3 and comparative EX1* and EX1-PP* Ready-to-cast polymerizable formulations according to the invention (EX2 and EX3) were converted into hard polymers. For comparison, a hard polymer (EX1) was prepared by curing the non-prepolymerized polyallyl-functional monomer using the conventional peroxy dicarbonate ADC NS-30.

[0212] EX2 and EX3 formulations were prepared by charging the polyallyl-functional monomer, the initiator and the additives in a jacketed stainless-steel reactor equipped with a mechanical stirrer, a thermocouple and a bottom draining line for mould filling. The pre-polymerization process was carried out at the conditions described for prepolymer PP3 at above point 1 by mixing and degassing (Pabs< 50mbar) the reaction mixture at 65 °C for 3 hours (final viscosity of 90 mm2 / s (90 cSt) at 25 °C). At the end of the reaction period, the prepolymer composition was cooled to 50°C. The vacuum was then substituted by nitrogen gas (Pabs= 1.2 bar). Prior to casting, the prepolymer composition was filtered by passing it on a stainless-steel disk holder containing a 0.45 micrometers PTFE membrane (47 mm diameter) located on the draining line and then used for filling glass molds.

[0213] The comparative formulation EX1 was prepared in the same way of EX2 and EX3 except for mixing and degassing it at ambient temperature for 2 hours (Pabs< 50mbar).

[0214] The polymerization to form the hard polymers was accomplished by heating the molds containing the polymerizable compositions in a forced-air-circulation oven according to one of the curing cycles reported in Tables 2 to 3.

[0215]

[0216]

[0217] At the end of the curing cycle, the molds were removed from the oven and allowed to cool down. Demolding was carried out at a temperature within the range of from 50 to 70°C. The polymerized articles were than subjected to post-curing treatments in a forced-air-circulation oven under the following conditions: - 1 hour at 100°C for EX1 - 2 hours at 120°C for EX2 and EX3.

[0218] The polymerizable compositions EX1 to EX3 were casted and cured in glass molds in the form of plano lenses having a thickness of 2 mm for the determination of the total transmittance, haze% and the dyeability test (T% after tinting and evenness of the dye uptake); cast as flat sheets with thickness of 5mm for the determination of YI and Rockwell hardness.

[0219] The characterization data reported in Tables 4 and 5 were determined on post-cured lenses. Lenses having complex design and geometry were also prepared in order to assess the manufacturing yield of the compositions of the present invention under more particularly severe conditions. The lenses prepared for each casting test were:

[0220] - 10 semi-finished blanks, front and back molds of curvature base 6 and base 8 respectively (5 pieces each curvature), central thickness 10mm; - 5 bifocals lenses, front and back molds of curvature base 6 with additional power equal to +2.00 and flat segment line.

[0221] The process yield was evaluated by determining the ratio of the number of rejected articles exhibiting defects (i.e. cracks, flow lines or defective segments in the bifocal lens) over the total number of casted articles regardless the type of design.

[0222]

[0223] The data of Table 4 demonstrate that using BPO according to the prepolymerization method of the present invention (EX2 and EX3), it is possible to obtain optical articles having good mechanical and optical characteristics, which are comparable with those of the composition EX1 polymerized using the peroxy dicarbonate ADC NS-30 initiator and, moreover, with a limited difference in refractive index. EX2 exhibit a slightly higher yellowness then the comparative material EX1, which however can be easily compensated through a minor addition of the TAP-based bleaching agent without detrimental effects on other features.

[0224] In addition, both EX2 and EX3 show T% and tinting aspect similar to those of the comparative material EX1 (the ability of two lenses to uptake the dyes hue can be considered the same when the difference in the total T% values of the lenses is within + / -5 units).

[0225] Moreover, the lenses EX2 and EX3 show excellent manufacturing yield thanks to the control of the shrinkage that can obtained by the prepolymerization method of the present invention. In fact, compared to the curing of the polyallyl-functional monomer with standard peroxy dicarbonate ADC NS-30 initiator, no lenses with early release, cracks and flow lines were observed in all the prepared semi-finished blanks; moreover, all the bifocal lenses were successfully casted without defective segment line.

[0226] This is the same achievement that can be obtained by means of pre-polymerization of the polyl-allyl functional monomer with the peroxy dicarbonate ADC NS-30 initiator as shown in the comparative example EX1-PP* of Table 4, but with the significant improvement that the prepolymer composition according to the invention is a ready-to-cast composition with enhanced shelf-life and that does not require any subsequent dosage of initiator before casting.

[0227] 3. Preparation of optical articles EX5, EX7, EX9 and comparative EX4*, EX6*, EX8* Polymerizable formulations according to the invention (EX5, EX7, EX9) were prepared by prepolymerizing the polyallyl-functional monomer in the same conditions above described for prepolymer PP3. UV absorber compounds and bluing agent were dosed in the formulation subjected to prepolymerization to obtain final lenses having different cut off ratios. For comparison, formulations comprising the non-prepolymerized polyallyl-functional monomer and optional components were cured with the peroxy dicarbonate ADC NS 30 initiator (comparative EX4*, EX6*, EX8*).

[0228] The composition of each formulation is reported in Table 5 along with the characterization data. Curing and post-curing conditions were as described under above point 2.

[0229]

[0230] The polymerizable composition from EX4 to EX9 refer to alternative UV and HEV compositions including a significantly higher dosage of the UV absorber BP6, introduced in powder form. The high amount of UV absorber did not influence the outcome of the prepolymerization reaction, the resulting prepolymer composition showing an increased viscosity within the desired range of 70-110 mm2 / s (70-110 cSt) at 25°C.

[0231] The data of 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 the high-quality lenses obtained from the non-prepolymerized monomer after curing with the peroxy dicarbonate ADC NS-30 initiator.

[0232] Regarding the optical articles having 400 nm-cut and 410 nm-cut (EX6 to EX9), it is observed that the higher dosage of the UV absorber that is necessary to reach the desired cut off ratio induces higher yellowness in the optical articles regardless of the type of initiator used. Yellowness, however, can be kept to acceptable values by adequately dosing the bluing agent.

[0233] Notably, the optical articles according to the present invention also exhibit better features compared to the comparative materials when high dosage of UV absorber are 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 (EX5, EX7 and EX9) with respect to the comparative articles (EX4*, EX6* and EX8*) where a decreasing trend is observed. Moreover, better and more uniform dyeability of the final lenses are observed for the materials according the present invention (EX 9), where high UV absorber dosage does not influence the color uptake and final homogeneity of the hue, compared to the TX ADC NS30 cured lens (EX8), where the lower hardness is reflected in faster dyes penetration along with the presence of some homogeneity defects.

[0234] Lastly, the comparative compositions showed high occurrence of cracks, flow lines and frequent defective segments when demolding bifocal lenses. On the contrary, the formulation according to the present invention showed excellent casting results thanks to the reduced level of polymerization shrinkage.

Claims

1. A method for preparing a polyallyl-functional prepolymer composition comprising: (a) providing a reaction mixture comprising: - at least one polyallyl-functional monomer; - from 0.5 to 3.0 wt.% of at least one aromatic peroxide compound as free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer; (b) heating the reaction mixture at a temperature within the range of from 12 to 3 Celsius degrees (°C) lower than the ten-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having kinematic viscosity at 25 °C within the range of from 40 to 350 mm2 / s (from 40 to 350 cSt), the kinematic viscosity being determined in accordance with ASTM D446.

2. The method according to claim 1, wherein in step (b) the reaction mixture is heated at a temperature within the range of from 10 °C to 5 °C lower than the ten-hour half-life temperature of the aromatic peroxide compound.

3. The method according to any one of the claims 1 to 2, wherein the prepolymer composition having a viscosity at 25 °C within the range of from 60 to 200 mm2 / s (from 60 to 200 cSt), preferably 70 to 120 mm2 / s (70 to 120 cSt).

4. The method according to any one of the claims 1 to 3, wherein the at least one aromatic peroxide compound has the following general formula (F1) wherein X is selected from: hydrogen, C1to C12alkoxy groups, chlorine and bromine.

5. The method according to claim 4, wherein the at least one aromatic peroxide compound is benzoyl peroxide.

6. The method according to any one of the claims 1 to 5, wherein step (b) comprises degassing the reaction mixture.

7. The method according to any one of the claims 1 to 6, wherein in step (a) the viscosity at 25°of the at least one polyallyl-functional monomer is within the range of from 10 to 300 mm2 / s (from 10 to 300 cSt), preferably from 10 to 100 mm2 / s (from 10 to 100 cSt), more preferably from 10 to 40 mm2 / s (from 10 to 40 cSt).

8. The method according to any one of the claims 1 to 7, comprising cooling the prepolymer composition to a temperature of at least 20 °C below the ten-hour half-life temperature of the aromatic peroxide compound.

9. The method according to any one of the 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 of 2 to 6, R1indicates a hydrogen atom or a methyl group, a plurality of present R1’s 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 which may have an oxygen atom, a divalent to hexavalent organic group (b) derived from an alicyclic polyol having 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 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. The method according to any one of the claims 1 to 9, wherein the at least one polyallyl-functional monomer comprises a diethylene glycol bis(allyl carbonate) compound of general formula (II) wherein, in the formula (II), n is an integer equal to or higher than 1 and equal to or lower than 10.

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

12. The method according to any one of the claims 1 to 9, wherein the at least one polyallyl-functional monomer comprises the reaction product (RP) of components comprising: diallylcarbonate (A), one or more linear or branched aliphatic diols (B) containing from three to ten carbon atoms in the molecule and optionally a linear or branched aliphatic polyol (C) containing from four to twenty carbon atoms and from three to six hydroxyl groups in the molecule; wherein the molar ratio A / (B+C) ranges from 4 / 1 to 20 / 1 and the quantity of the optional component (C) in the mixture (B+C) is equal to or less than 5 wt.%, preferably equal to or less than 3 wt.%, with respect to the total weight of said mixture (B+C).

13. The method according to any one of the claims 1 to 9, wherein the at least one polyallyl-functional monomer comprises the reaction product (RP) of components comprising: diallylcarbonate (A), one or more linear or branched aliphatic diols (B) containing from three to ten carbon atoms in the molecule and a linear or branched aliphatic polyol (C) containing from four to twenty carbon atoms and from three to six hydroxyl groups in the molecule; wherein the molar ratio A / (B+C) is within the range of from 4 / 1 to 20 / 1, preferably from 5 / 1 to 15 / 1, and the quantity of the component (C) in the mixture (B+C) is equal to or less than 5 wt.%, preferably equal to or less than 3 wt.%, with respect to the total weight of said mixture (B+C).

14. The method according to any one of the claims 10 to 11, wherein the reaction mixture is free of ethylenically unsaturated compounds that are not the diethylene glycol bis(allyl carbonate) compound of general formula (II) wherein n is equal to or higher than 1 and equal to or lower than 10.

15. The method according to any one of the claims 12 to 13, wherein the reaction mixture is free of ethylenically unsaturated compounds that are not the reaction product (RP) of components comprising: diallylcarbonate (A), one or more linear or branched aliphatic diols (B) containing from three to ten carbon atoms in the molecule and optionally a linear or branched aliphatic polyol (C) containing from four to twenty carbon atoms and from three to six hydroxyl groups in the molecule; wherein the molar ratio A / (B+C) is within the range of from 4 / 1 to 20 / 1 and the quantity of the optional component (C) in the mixture (B+C) is equal to or less than 5 wt.%, with respect to the total weight of said mixture (B+C).

16. A method for manufacturing an optical article comprising: (i) providing a reaction mixture comprising: - at least one polyallyl-functional monomer; - from 0.5 to 3.0 wt.% of at least one aromatic peroxide compound as free radical initiator, the weight percentage being based on the total weight of the polyallyl-functional monomer; (ii) heating the reaction mixture at a temperature within the range of from 12 to 3 Celsius degrees (°C) lower than the ten-hour half-life temperature of the aromatic peroxide compound to form a prepolymer composition having kinematic viscosity at 25 °C within the range of from 40 to 350 mm2 / s (from 40 to 350 cSt), the kinematic viscosity being determined in accordance with ASTM D446; (iii) casting the prepolymer composition into a mold; (iv) curing the prepolymer composition in the mold to form the optical article.

17. The method according to claim 16, wherein the prepolymer composition is not added with any additional free radical initiator other than at least one aromatic peroxide before being casted in the mold.

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