ZIRCONIUM-BASED AND LANTHANUM-BASED ETHYLENICALLY UNSATURATED METAL SALTS

Abstract

An ethylenically unsaturated and (co)polymerizable metal salt soluble in an ethylenically unsaturated reactive diluent is based on zirconium or on lanthanum and on an ethylenically unsaturated hemi-ester of a dicarboxylic acid. A process for the preparation of the salt and a crosslinkable composition comprising it are also disclosed. Uses of the metal salt include optical and dental uses, uses in composite materials, in moulding compositions, in 3D printing compositions and compositions for 3D articles and for coatings or adhesives. The finished crosslinked product which results from crosslinking the crosslinkable composition comprising the metal salt is also described.

Claims

1. A (Co)polymerizable ethylenically unsaturated metal salt which is soluble in an ethylenically unsaturated reactive diluent, wherein the metal salt is a zirconium or zirconium oxide salt or a lanthanum salt with an ethylenically unsaturated hemi-ester of a dicarboxylic acid of formula (I):
(X).sub.n—R1—O.sub.2C—R—CO.sub.2   (I) and optionally, in addition to the said hemi-ester (I), in the presence of a saturated monocarboxylic acid of formula (II): R2CO.sub.2H, and that the said salt is defined according to one of the following formulae (Ill), (IV) or (V): [(X).sub.nR1—O.sub.2C—R—CO.sub.2—].sub.4-xZr(—O.sub.2CR2).sub.x (III), with x=0 or 1 or 2 or 3, [(X).sub.nR1—O.sub.2C—R—CO.sub.2—].sub.2-xZr(=O)(—O.sub.2CR2).sub.x (IV), with x=0 or 1, and [(X).sub.nR1—O.sub.2C—R—CO.sub.2—].sub.3-xLa(—O.sub.2CR2).sub.x (V), with x=0 or 1 or 2, R being the residue, without the carboxyl groups, of a dicarboxylic acid of aliphatic, cycloaliphatic, aromatic or mixed structure, R1—(X).sub.n being the residue, without OH, of an ethylenically unsaturated monoalcohol carrying n ethylenically unsaturated functional groups X chosen from (meth)acrylate (—CO.sub.2—C(R3)═CH.sub.2, with R3: —H or —CH.sub.3), vinyl (—CH.sub.2═CH.sub.2) or allyl (—CH.sub.2—CH.sub.2═CH.sub.2), with n being an integer ranging from 1 to 5 or from 1 to 3 or n being equal to 1, and R2 being the residue, without carboxylic group, of a saturated (without ethylenic unsaturation) monocarboxylic acid chosen from: a monoacid other than a dicarboxylic acid hemi-ester, the said monoacid being aliphatic, cycloaliphatic, heterocyclic, aromatic or mixed, or an acid hemi-ester of a dicarboxylic acid, of formula (VI): R′1—O.sub.2C—R′—CO.sub.2H, with, in this case, R2═R′1—O.sub.2C—R′— and R′1 being the residue of a saturated monoalcohol of aliphatic, cycloaliphatic, aromatic or mixed structure, and R′ being the residue of a dicarboxylic acid, without carboxyl groups, of saturated structure (without ethylenic unsaturation) of aliphatic, cycloaliphatic, aromatic or mixed structure, which can be identical to R when R is of saturated structure or which can be different from R, and optionally the said metal salt being in the form of a solution in an ethylenically unsaturated reactive diluent copolymerizable with the said salt.

2. The metal salt according to claim 1, wherein the dicarboxylic acid R(—CO.sub.2H).sub.2 is selected from: for aliphatic diacids: maleic, fumaric, succinic, itaconic, butanedioic, pentanedioic, hexanedioic, heptanedioic, octanedioic, nonanedioic, decanedioic or dodecanedioic acid, C.sub.36 dimer fatty acids or from their mixtures for cycloaliphatic diacids: cyclohexane-1,4-, -1,3- or -1,2-dicarboxylic acid, tetrahydrophthalic acid, norbornanedicarboxylic acids or their mixtures for aromatic diacids: ortho-, iso- or terephthalic acid, tetrabromophthalic acid, naphthalenedicarboxylic acids, biphenyldicarboxylic acids, in particular biphenyl-2,2′-dicarboxylic acid (diphenic acid), or their mixtures.

3. The metal salt according to claim 1, wherein the ethylenically unsaturated monoalcohol HO—R1—(X).sub.n is selected from: for X being allyl: allyl alcohol, monoether of allyl alcohol with an aliphatic C.sub.2 to C.sub.36 diol which can be alkoxylated or an oligoether diol or an oligoester diol, diether of allyl alcohol with an aliphatic triol which can be alkoxylated or an oligoether triol or oligoester triol, triether of allyl alcohol with an aliphatic tetrol which can be alkoxylated or with an oligoether or oligoester tetrol, mono-, di- or triallyl ester derivatives of a dicarboxylic acid/allyl alcohol hemi-ester with a polyol of respective OH functionalities of 2, 3 and 4 for X being vinyl: vinyl alcohol, monoether of vinyl alcohol with an aliphatic C.sub.2 to C.sub.36 diol which can be alkoxylated or an oligoether diol or an oligoester diol, diether of vinyl alcohol with an aliphatic triol which can be alkoxylated or an oligoether triol or oligoester triol, triether of vinyl alcohol with an aliphatic tetrol which can be alkoxylated or with an oligoether or oligoester tetrol, mono-, di- or triallyl ester derivatives of a dicarboxylic acid/vinyl alcohol hemi-ester with a polyol of respective OH functionalities of 2, 3 and 4 for X being (meth)acrylate: hydroxyalkyl mono(meth)acrylate with C.sub.2-C.sub.8 alkyl, mono(meth)acrylate of oligoether diol or of oligoester diol, di(meth)acrylate of aliphatic triol which can be alkoxylated, di(meth)acrylate of oligoether triol or of oligoester triol, tri(meth)acrylate of aliphatic tetrol which can be alkoxylated or tri(meth)acrylate of oligoether tetrol or of oligoester tetrol, penta(meth)acrylate of aliphatic hexol which can be alkoxylated or penta(meth)acrylate of oligoether hexol or of oligoester hexol.

4. The metal salt according to claim 1, wherein characterized in that the group X is the (meth)acrylate CH.sub.2═C(R3)—CO.sub.2— group with R3 being —H or —CH.sub.3 and with n ranging from 1 to 5 or from 1 to 3 or with n being equal to 1, and with the following general formulae (III), (IV) and (V) for the said salt: [(CH.sub.2═C(R3)—CO.sub.2—).sub.nR1—O.sub.2C—R—CO.sub.2—].sub.4-xZr(—O.sub.2CR2).sub.x (III) with x=0 or 1 or 2 or 3, [(CH.sub.2═C(R3)—CO.sub.2—).sub.nR1—O.sub.2C—R—CO.sub.2—].sub.2-xZr(═O)(—O.sub.2CR2).sub.x (IV) with x=0 or 1 and [(CH.sub.2═C(R3)—CO.sub.2—).sub.nR1—O.sub.2C—R—CO.sub.2—].sub.3-xLa(—O.sub.2CR2).sub.x (V) with x=0 or 1 or 2,

5. The metal salt according to claim 1, wherein the dicarboxylic acid of residue R comprises aromatic dicarboxylic acids.

6. The metal salt according to claim 5, wherein the dicarboxylic acid of residue R is iso- and terephthalic acid and biphenyl-2,2′-dicarboxylic acid.

7. The metal salt according to claim 1, wherein the group X is the (meth)acrylate group and the monoalcohol HO—R1—(X).sub.n is selected from the group consisting of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, hydroxyhexyl (meth)acrylate, diethylene glycol mono(meth)acrylate, neopentyl glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, tripropylene glycol mono(meth)acrylate, mono(meth)acrylate of polyethylene glycol of Mn<1000, mono(meth)acrylate of polypropylene glycol of Mn<1000, polytetramethylene glycol mono(meth)acrylate, hydroxylated mono(meth)acrylate of polycaprolactone of Mn<1000, monoepoxidized (meth)acrylated compound with a secondary hydroxyl, alkoxylated mono(meth)acrylated diepoxide, optionally ethoxylated and/or propoxylated trimethylolpropane di(meth)acrylate, optionally ethoxylated and propoxylated glycerol di(meth)acrylate, tris(2-hydroxyethyl) isocyanurate di(meth)acrylate, pentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, diglycerol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate.

8. The metal salt according to claim 1, wherein x=0 for the salts of respective formulae (III), (IV) and (V).

9. The metal salt according to claim 1, wherein x=1 or 2 or 3 for the salt of formula (III), that x=1 for the salt of formula (IV) and x=1 or 2 for the salt of formula (V) and the monocarboxylic acid R2CO.sub.2H is a different monocarboxylic acid from a dicarboxylic acid hemi-ester and is selected from the group consisting of: aliphatic monoacid with R2 being a linear C.sub.1-C.sub.21 alkyl or branched C.sub.4-C.sub.21 alkyl cycloaliphatic monoacid with R2 being a C.sub.6 to C.sub.18 cycloalkyl aromatic monoacid with R2 being a C.sub.6 to C.sub.18 aryl and monoacid with R2 comprising a heterocycle comprising a heteroatom from O, N and S and in particular from thiophene, phthalimide or furan rings and more particularly from: thiophenecarboxylic acid, N-phthaloylglycine and furoic acid (also known as furancarboxylic acid).

10. The metal salt according claim 1, wherein x=1 or 2 or 3 for the salt of formula (III), x=1 for the salt of formula (IV) and x=1 or 2 for the salt of formula (V) and the monocarboxylic acid R2CO.sub.2H is a dicarboxylic acid hemi-ester of formula (VI): R′1—O.sub.2C—R′—CO.sub.2H.

11. The metal salt according to claim 1, wherein the metal salt is in solution comprising the ethylenically unsaturated reactive diluent, chosen from (meth)acrylic, vinyl or allyl monomers and their mixtures.

12. A process for the preparation of the metal salt as defined according to claim 1, comprising the following stages: i) preparing the ethylenically unsaturated hemi-ester of formula (I) and optionally of the said saturated hemi-ester of formula (VI) by respective reactions: of the dicarboxylic anhydride of formula R(CO).sub.2O with the said ethylenically unsaturated monoalcohol HO—R1—(X).sub.n, and optionally of the dicarboxylic anhydride R′(CO).sub.2O with the said saturated monoalcohol R′1—OH, ii) neutralizing by a weak base in aqueous medium the hemi-ester of formula (I), optionally as a mixture with the saturated monoacid (without ethylenic unsaturation) of formula (II) which can be a monoacid other than a hemi-ester or a hemi-ester according to formula (VI), in order to obtain a soluble salt of the hemi-ester (I), optionally of the mixture with the monoacid (II) as defined above, iii) adding in aqueous solution with stirring as a function of the targeted salt of respective formulae (II), (IV) or (V) of respectively zirconium tetrachloride (ZrCl.sub.4), zirconium oxydichloride (Zr(═O)Cl.sub.2) or lanthanum trichloride (LaCl.sub.3), with precipitation of the salt, iv) filtering of the precipitated salt with washing with water, drying and recovery of the salt in the solid bulk form.

13. A process for the preparation of the metal salt according to claim 1, wherein the process is done in solution comprising the ethylenically unsaturated reactive diluent, wherein the process comprises the following stages comprises i) preparing the ethylenically unsaturated hemi-ester of formula (I) and optionally of the said saturated hemi-ester of formula (VI) by respective reactions: of the dicarboxylic anhydride of formula R(CO).sub.2O with the ethylenically unsaturated monoalcohol HO—R1—(X).sub.n, and optionally of the dicarboxylic anhydride R′(CO).sub.2O with the said saturated monoalcohol R′1—OH, ii) neutralizing by a weak base in aqueous medium the hemi-ester of formula (I), optionally as a mixture with the saturated monoacid (without ethylenic unsaturation) of formula (II) which can be a monoacid other than a hemi-ester or a hemi-ester according to formula (VI), iii) adding to the aqueous solution of stage ii) an inert organic solvent (unreactive without ethylenic unsaturation) which is a solvent for the metal salt and is immiscible with water, in order to create a two-phase medium, iv) adding with stirring to the two-phase medium as a function of the targeted salt of respective formulae (II), (IV) or (V) respectively zirconium tetrachloride (ZrCl.sub.4), zirconium oxydichloride (Zr(═O)Cl.sub.2) or lanthanum trichloride (LaCl.sub.3), with transfer of the metal salt formed in solution into the organic phase of the water/organic solvent two-phase medium, v) separation by settling with removal of the aqueous phase and addition to the recovered organic phase of at least one ethylenically unsaturated reactive diluent, vi) removal of the inert organic solvent by evaporation under reduced pressure and recovery of the solution of the metal salt in the at least one reactive diluent.

14. A crosslinkable composition comprising at least one metal salt as defined according to claim 1.

15. A composition according to claim 14, wherein the composition is adapted to be crosslinked by the peroxide route and/or by the route under radiation.

16. A composition according to claim 14, further comprising, in addition to the at least one metal salt, at least one reactive diluent copolymerizable with the metal salt selected from mono- or polyfunctional (meth)acrylic, vinyl or allyl monomers.

17. A composition according to claim 16, wherein the reactive diluent is at least one (meth)acrylic monomer selected from the group consisting of optionally alkoxylated C.sub.1-C.sub.18 alkyl (meth)acrylates, optionally alkoxylated hydroxyalkyl (meth)acrylates with C.sub.2-C.sub.4 alkyl, epoxy (meth)acrylates, urethane (meth)acrylates, optionally alkoxylated poly(meth)acrylic esters of aliphatic polyols or of oligoether polyols having from 2 to 4 ether units, with a functionality ranging from 2 to 6.

18. A composition according to claim 14, further comprising at least one ethylenically unsaturated oligomer carrying at least one ethylenically unsaturated group.

19. A composition according to claim 18, wherein the oligomer carries from 1 to 6 ethylenically unsaturated groups chosen from: (meth)acrylate, vinyl and allyl, preferably (meth)acrylate or vinyl.

20. A composition according to claim 18, wherein the oligomer is selected from the group consisting of: vinyl esters, unsaturated polyesters, polyether (meth)acrylates, polyester (meth)acrylates, (meth)acrylic (meth)acrylate copolymers, epoxy (meth)acrylates, oligourethane (meth)acrylates, polycarbonate (meth)acrylates and polycarbonate urethane (meth)acrylates.

21. A composition according to claim 14, wherein the composition is crosslinkable by UV radiation with the presence of a photoinitiator or by an electron beam without a photoinitiator.

22. A composition according to claim 14, wherein the composition is chosen from: a coating composition, an adhesive composition, a moulding composition, a composition of composite material reinforced by glass or carbon fibres, or a 3D printing composition.

23. A method of using the composition according to claim 14 comprising crosslinking the composition.

24. (canceled)

25. A crosslinked product resulting from crosslinking the composition according to claim 14.

26. A product according to claim 25, wherein the product is: a coating, an adhesive, a composite material, a moulded part, a corrective lens or an optical prism having a high refractive index, a dental part, a 3D printing or a 3D article.

Description

EXAMPLES

1) Starting Materials Used

[0057]

TABLE-US-00001 Starting materials Example 1 Example 2 Example 3 Example 4 Ethylenically Hydroxyethyl Hydroxyethyl Phenyl glycidyl Hydroxyethyl unsaturated acrylate methacrylate ether acrylate methacrylate monoalcohol (HEA, Aldrich) (HEMA, Aldrich) (CN131B from (HEMA, Aldrich) Sartomer) Acid anhydride Phthalic anhydride Weak base Sodium bicarbonate (NaHCO.sub.3, Aldrich) Metal salt Zirconyl dichloride octahydrate (ZrOCl.sub.2•8H.sub.2O, Alfa Aesar) Lanthanum trichloride heptahydrate (LaCl.sub.3•8H2O, Aldrich) Ethylenically Biphenylmethanol Cumyl phenol Biphenylmethanol Biphenylmethanol unsaturated acrylate (HOO8 acrylate acrylate (HOO8 acrylate (HOO8 diluent from KPX) (CD590 from from KPX) from KPX) Sartomer)

2) Preparation of the Ethylenically Unsaturated Metal Salts

Example 1 (Invention): Zirconyl Di(HEA Phthalate) Diluted in Biphenylmethanol Acrylate (HOO8 from KPX)

[0058] Stage 1: 29.71 g of hydroxyethyl acrylate (HEA, Mw 116.12 g/mol, Sigma Aldrich), 37.89 g of phthalic anhydride (Mw 148.12, Sigma Aldrich) and 0.07 g of hydroquinone methyl ether (HQME, Aldrich) are introduced into 1 l reactor with stirring and while bubbling with air (0.3 ml/H/kg). The mixture is heated and maintained at 100° C. until the final halting criterion, determined by the measurement of the acid number (AN), expressed in mg KOH/g, is reached. The final theoretical AN value expected is 212.3 mg KOH/g.
Stage 2: A solution of 21.29 g of sodium bicarbonate (NaHCO.sub.3, Mw 84.0 g/mol, Aldrich) dissolved in 70 g of demineralized water is added over 30 minutes to the same reactor at 60° C. and while bubbling with air. Release of CO.sub.2 is observed. At the end of the addition of the sodium bicarbonate solution, the reaction medium is milky but becomes slightly hazy homogeneous after stirring for 1 hour. The pH of the solution is measured at 7.
Stage 3: At 60° C., with stirring and while bubbling with air, 500 g of ethyl acetate are added to the medium and then a solution of 48.19 g of zirconyl dichloride octahydrate (ZrOCl.sub.2.8H.sub.2O, Mw 322.25 g/mol, Alfa Aesar) dissolved in 32.0 g of demineralized water is added to the two-phase medium over 15 minutes. As the addition takes place, a white precipitate is formed in the medium, which precipitate subsequently dissolves in the organic phase. At the end of the addition, with the stirrer halted, two phases are observed: a clear colourless aqueous phase and an opaque white organic phase.
Stage 4: The aqueous phase is removed in a separating funnel and the organic phase is washed once with 50 g of a 20% sodium chloride solution.
Stage 5: After paper filtration, 55 g of biphenylmethanol acrylate (H008, KPX) are added to the organic medium and then the ethyl acetate is evaporated under reduced pressure.
After evaporation of the solvent, the product obtained is a homogeneous liquid of 121.94 g, i.e. a final yield of the zirconyl di(HEA phthalate) salt of 84%. The viscosity at 25° C. of the mixture is 5400 mPa.Math.s and with a refractive index of 1.591.

Example 2 (Invention): Zirconyl Di(HEMA phthalate) Diluted in Cumyl Phenol Acrylate (CD590 from Sartomer)

[0059] Stage 1: 31.62 g of hydroxyethyl methacrylate (HEMA, Mw 130.14 g/mol, Sigma Aldrich), 35.98 g of phthalic anhydride (Mw 148.12, Sigma Aldrich) and 0.07 g of hydroquinone methyl ether (HQME, Aldrich) are introduced into 1 l reactor with stirring and while bubbling with air (0.3 ml/H/kg). The mixture is heated and maintained at 100° C. until the final halting criterion, determined by the measurement of the acid number (AN), expressed in mg KOH/g, is reached. The final theoretical AN value expected is 201.6 mg KOH/g.
Stage 2: A solution of 21.75 g of sodium bicarbonate (NaHCO.sub.3, Mw 84.0 g/mol, Aldrich) dissolved in 70 g of demineralized water is added over 30 minutes to the same reactor at 60° C. and while bubbling with air. Release of CO.sub.2 is observed. At the end of the addition of the sodium bicarbonate solution, the reaction medium is milky but becomes slightly hazy homogeneous after stirring for 1 hour. The pH of the solution is measured at 7.
Stage 3: At 60° C., with stirring and while bubbling with air, 500 g of ethyl acetate are added to the medium and then a solution of 49.22 g of zirconyl dichloride octahydrate (ZrOCl.sub.2.8H.sub.2O, Mw 322.25 g/mol, Alfa Aesar) dissolved in 32.0 g of demineralized water is added to the two-phase medium over 15 minutes. As the addition takes place, a white precipitate is formed in the medium, which precipitate subsequently dissolves in the organic phase. At the end of the addition, with the stirrer halted, two phases are observed: a clear colourless aqueous phase and an opaque white organic phase.
Stage 4: The aqueous phase is removed in a separating funnel and the organic phase is washed once with 50 g of a 20% sodium chloride solution.
Stage 5: After paper filtration, 84.79 g of cumyl phenol acrylate (CD590, Sartomer) are added to the organic medium and then the ethyl acetate is evaporated under reduced pressure.
After evaporation of the solvent, the product obtained is a homogeneous liquid of 155.72 g, i.e. a final yield of the zirconyl di(HEMA phthalate) salt of approximately 88%. The viscosity at 25° C. of the mixture is 4590 mPa.Math.s and with a refractive index of 1.561.

Example 3 (Invention): Zirconyl Di(Phenyl Glycidyl Ether Acrylate Phthalate) Diluted in Biphenylmethanol Acrylate (H008 from KPX)

[0060] Stage 1: 44.32 g of phenyl glycidyl ether acrylate (CN131B, Mw 300 g/mol, Sartomer), 35.98 g of phthalic anhydride (Mw 148.12, Sigma Aldrich) and 0.07 g of hydroquinone methyl ether (HQME, Aldrich) are introduced into 1 l reactor with stirring and while bubbling with air (0.3 ml/H/kg). The mixture is heated and maintained at 100° C. until the final halting criterion, determined by the measurement of the acid number (AN), expressed in mg KOH/g, is reached. The final theoretical AN value expected is 123.5 mg KOH/g.
Stage 2: A solution of 15.38 g of sodium bicarbonate (NaHCO.sub.3, Mw 84.0 g/mol, Aldrich) dissolved in 70 g of demineralized water is added over 30 minutes to the same reactor at 60° C. and while bubbling with air. Release of CO.sub.2 is observed. At the end of the addition of the sodium bicarbonate solution, the reaction medium is milky but becomes slightly hazy homogeneous after stirring for 1 hour. The pH of the solution is measured at 7.
Stage 3: At 60° C., with stirring and while bubbling with air, a solution of 29.45 g of zirconyl dichloride octahydrate (ZrOCl.sub.2.8H.sub.2O, Mw 322.25 g/mol, Alfa Aesar) dissolved in 25.0 g of demineralized water is added to the medium over 15 minutes. A white precipitate very rapidly forms.
Stage 4: The white precipitate is isolated by filtration and then dried overnight in an oven at 100° C. The product recovered is subsequently dissolved in 100 g of toluene. The cloudy solution is filtered through paper in order to obtain a clear and homogeneous filtrate.
Stage 5: After paper filtration, 80.0 g of biphenylmethanol acrylate (H008 from KPX) are added to the organic medium and then the toluene is evaporated under reduced pressure.
After evaporation of the solvent, the product obtained is a slightly hazy homogeneous liquid of 132.0 g, i.e. a final yield of the zirconyl di(phenyl glycidyl ether acrylate phthalate) salt of approximately 66%. The viscosity at 25° C. of the mixture is 35 000 mPa.Math.s and with a refractive index of 1.594.

Example 4 (Invention): Lanthanum Tri(HEMA phthalate) Diluted in Biphenylmethanol Acrylate (H008 from KPX)

[0061] Stage 1: 15.56 g of hydroxyethyl methacrylate (HEMA, Mw 130.14 g/mol, Sigma Aldrich), 17.70 g of phthalic anhydride (Mw 148.12, Sigma Aldrich) and 0.035 g of hydroquinone methyl ether (HQME, Aldrich) are introduced into 1 I reactor with stirring and while bubbling with air (0.3 ml/H/kg). The mixture is heated and maintained at 100° C. until the final halting criterion, determined by the measurement of the acid number (AN), expressed in mg KOH/g, is reached. The final theoretical AN value expected is 201.6 mg KOH/g.
Stage 2: A solution of 10.69 g of sodium bicarbonate (NaHCO.sub.3, Mw 84.0 g/mol, Aldrich) dissolved in 100 g of demineralized water is added over 30 minutes to the same reactor at 60° C. and while bubbling with air. Release of CO.sub.2 is observed. At the end of the addition of the sodium bicarbonate solution, the reaction medium is milky but becomes slightly hazy homogeneous after stirring for 1 hour. The pH of the solution is measured at 7.
Stage 3: At 60° C., with stirring and while bubbling with air, 350 g of ethyl acetate are added to the medium and then a solution of 49.22 g of lanthanum trichloride heptahydrate (LaCl.sub.3.7H.sub.2O, Mw 371.37 g/mol, Aldrich) dissolved in 50.0 g of demineralized water is added to the two-phase medium over 15 minutes. As the addition takes place, a white precipitate is formed in the medium, which precipitate subsequently dissolves in the organic phase. At the end of the addition, with the stirrer halted, two phases are observed: a clear colourless aqueous phase and a slightly cloudy organic phase.
Stage 4: The aqueous phase is removed in a separating funnel and the organic phase is washed once with 50 g of a 10% sodium chloride solution.
Stage 5: After paper filtration, 30 g of biphenylmethanol acrylate (H008 from KPX) are added to the organic medium and then the ethyl acetate is evaporated under reduced pressure.
After evaporation of the solvent, the product obtained is a homogeneous liquid of 65.8 g, i.e. a final yield of the lanthanum tri(HEMA phthalate) salt of approximately 91%. The viscosity at 25° C. of the mixture is 9200 mPa.Math.s and with a refractive index of 1.588.

3) Characteristics of the Prepared Salts

[0062]

TABLE-US-00002 Soluble metal salt/dilution Refractive monomer Appearance Brookfield index Exam- (reactive of the viscosity of the ples diluent) ratio mixture @25° C. mixture Exam- 55/45 Clear 5400 mPa .Math. s 1.591 ple 1 homogeneous Exam- 45/55 Clear 4590 mPa .Math. s 1.561 ple 2 homogeneous Exam- 60/40 Slightly hazy 35 000 mPa .Math. s 1.594 ple 3 homogeneous Exam- 55/45 Clear 9200 mPa .Math. s 1.588 ple 4 homogeneous