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WO1998001508A1 - Coating compositions - Google Patents

Coating compositions Download PDF

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Publication number
WO1998001508A1
WO1998001508A1 PCT/AU1997/000415 AU9700415W WO9801508A1 WO 1998001508 A1 WO1998001508 A1 WO 1998001508A1 AU 9700415 W AU9700415 W AU 9700415W WO 9801508 A1 WO9801508 A1 WO 9801508A1
Authority
WO
WIPO (PCT)
Prior art keywords
silicic acid
monomer
blend
acrylic
coating composition
Prior art date
Application number
PCT/AU1997/000415
Other languages
French (fr)
Inventor
David Robert Diggins
Huan Kiak Toh
George Philip Simon
Yi-Bing Cheng
David George Hewitt
Jana Habsuda
Original Assignee
Sola International Holdings Ltd.
Monash University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sola International Holdings Ltd., Monash University filed Critical Sola International Holdings Ltd.
Priority to AU32478/97A priority Critical patent/AU3247897A/en
Publication of WO1998001508A1 publication Critical patent/WO1998001508A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
    • C09D183/10—Block or graft copolymers containing polysiloxane sequences
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • G02B1/041—Lenses

Definitions

  • the present invention relates to an organically modified silicate coating and a method for preparing same and in particular the use of such coatings on ophthalmic lenses.
  • Plastics are widely used in the optical industry because they offer several advantages over glass in optical applications in that they are easy to form, are lighter, readily tintable and have a high impact strength compared to glass.
  • Diethylene glycol bis allyl carbonate polymer, CR-39 is widely used in the ophthalmic industry to fabricate plastic eyeglass lenses and has excellent clarity and high temperature resistance. However, transparent coatings are still required for the plastic lens to ensure good scratch resistance.
  • Ormosils may be prepared in a conventional sol-gel process.
  • oligomeric components By incorporating oligomeric components through a sol-gel reaction scheme, the characteristics common to the sol-gel glasses, i.e. high stiffness, brittleness and optical transparency can be controlled and modified.
  • a silicate coating composition including an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent.
  • the coating composition according to this aspect of the present invention may be utilised for forming a coating on an ophthalmic article, for example an ophthalmic lens element.
  • the coating so formed may be characterised in that it forms an abrasion-resistant coating.
  • a coated optical article including an optical article formed from a polymeric or glass material; and an abrasion-resistant coating on at least a portion of the surface thereof formed from a silicate coating composition including an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent.
  • the coating may provide improved abrasion resistance, hardness, toughness or clarity, or a combination thereof to the optical article.
  • the optical article is a lens element.
  • the acrylic-modified silicic acid nano-blend may be of any suitable type.
  • An acrylate or methacrylate modified silicic acid nano-blend may be used.
  • the acrylic-modified silicic acid nano-blend may be derived from an hydroxy substituted acrylate or methacrylate.
  • 2-Hydroxyethyl acrylate (HEA) or 2- hydroxyethyl methacrylate (HEMA) poly(silicic acid) nano-blend has been found to be suitable.
  • the polyfunctional unsaturated cross-linking agent according to the present invention may be a di-, tri- or tetra-functional vinyl, an acrylic or methacrylic monomer.
  • the cross-linking agent may be a short chain monomer for example a polyoxy alkylene glycol diacrylate or methacrylate, trimethylol propane trimethacrylate, pentaerythritol triacrylate or tetraacrylate, or the like.
  • NK Ester TMPT NK Ester A-TMPT
  • NK Ester A-TMM-3 NK Ester A-TMMT
  • di-trimethylol propane tetraacrylate trimethylolpropane triacrylate
  • pentaerythritol tetramethacrylate dipentaerythritol monohydroxypenta acrylate
  • pentaerythritol triacrylate ethoxylated trimethylolpropane triacrylate
  • ethoxylated trimethylol-propane trimethacrylate ethoxylated trimethylol-propane trimethacrylate.
  • the polyfunctional unsaturated cross-linking agent may be present in amounts of from approximately 0.001 to 15% by weight, preferably approximately 0.05% to 5% by weight based on the total weight of the silicate coating composition.
  • the polyoxy alkylene glycol diacrylate or dimethacrylate compound according to the present invention when present, may include ethylene oxide or propylene oxide repeating units in its backbone.
  • a polyethylene glycol dimethacrylate is preferred.
  • Suitable materials include dimethylacrylates where the number of repeating ethylene oxide groups is between 1 and 9.
  • Suitable materials include those sold under the trade names NK Ester 1G, 4G, 6G or 9G. A 1G monomer is preferred.
  • the polyoxy alkylene glycol diacrylate or dimethacrylate component may be present in amounts of from 0 to approximately 15% by weight, preferably approximately 0.001% to 10% by weight, based on the total weight of the coating composition.
  • the acrylic-modified silicic acid nano-blend may have a relatively high molecular weight (MW) for example in the range of approximately 4,000 to 12,000.
  • the silicate coating composition may optionally further include a polymerisable comonomer.
  • the polymerisable comonomer may be selected to improve the properties and/or processability of the coating composition.
  • the polymerisable comonomer may be selected to improve tint rate, hardness, abrasion resistance, refractive index and the like of the resulting polymer.
  • the polymerisable comonomer may be an unsaturated or epoxy comonomer.
  • the polymerisable comonomer may be selected from any suitable type, e.g. from one or more of the group consisting of methacrylates, acrylates, vinyls, vinyl ethers, allyls, epoxides, and the like.
  • the polymerisable comonomer may preferably be selected from one or more of epoxidised monomer or oligomer vinyls, allyiics, polyoxyalkylene glycol di-, tri-, tetra- and higher acrylates or methacrylates, polymerisable bisphenol monomers, urethane monomers having 2 to 6 terminal acrylic or methacrylic groups, fluorene acrylates or methacrylates, and thioacrylate or thiomethacrylate monomers.
  • the epoxidised monomer may function to improve curing and casting characteristics.
  • the epoxidised monomer or oligomer may fall into one or more of the following classes: internal, terminal, mono-functional, di-functional, tri-functional, tetra- functional, aliphatic, aromatic, cyclic, structurally simple, structurally complex, esters, ethers, amines.
  • An epoxidised soybean material may be used.
  • the epoxidised monomer or oligomer may be selected from one or more of the following
  • the epoxidised monomer may be present in amounts of from approximately 0.001% to 10% by weight, preferably 0.01% to 5%, more preferably approximately 0.01% to 2%, based on the total weight of the coating composition.
  • the vinyl comonomer may be selected from the group consisting of styrene, substituted styrenes, 3,9-divinyl- 2,4,8, 10-tetraoxaspiro[5.5]undecane (DTU), a divinyl ester monomer of a bi- or polycyclic compound and mixtures thereof.
  • the vinyl comonomers may be present in amounts of from 0.01% to approximately 20% by weight, preferably approximately 5 to 15% by weight, based on the total weight of the silicate coating composition.
  • a thiodiacrylate or dimethacrylate is included, the thiodiacrylate or dimethacrylates may be selected from bis(4-methacryloylthioethyl)sulf ⁇ de (BMTES) and bis(4-methacryloylthiophenyl)sulf ⁇ de (BMTS).
  • BMTES bis(4-methacryloylthioethyl)sulf ⁇ de
  • BMTS bis(4-methacryloylthiophenyl)sulf ⁇ de
  • the thioacrylate or methacrylate may be present in amounts of from 0.01% to approximately 20% by weight, preferably approximately 5 to 15% by weight, based on the total weight of the silicate coating composition.
  • the fluorene diacrylate or dimethacrylate monomer may be selected from a bisphenol fluorene dihydroxy acrylate (BFHA) or a bisphenol fluorene dimethacrylate (BFMA) or mixtures thereof.
  • the fluorene diacrylate or dimethacrylate monomer may be present in amounts of from 0 to approximately 20% by weight, preferably approximately 1 to 10% by weight.
  • the high index bisphenol monomer component in the cross-linkable casting composition when present may be selected from: dimethacrylate and diacrylate esters of bisphenol A; dimethacrylate and diacrylate esters of 4,4'bishydroxy-ethoxy-bisphenol A and the like.
  • Preferred high index bisphenol compounds include bisphenol A ethoxylated dimethacrylate and tetra brominated bisphenol A ethoxylated dimethacrylates.
  • a bisphenol A ethoxylate dimethacrylate sold under the trade designation ATM 20 by Ancomer has been found to be suitable.
  • the high index bisphenol monomer may be present in amounts of from 0 to approximately 20% by weight, preferably 5 to 15% by weight based on the total weight of the coating composition.
  • a method for preparing an acrylic-modified silicic acid nano-blend which method includes providing a silicic acid oligomer; and an acrylic monomer; mixing the silicic acid oligomer and reactive acrylic monomer; and permitting the mixture to react at elevated temperature whilst continuously removing the water of reaction formed in the reaction.
  • the acrylic monomer may be of any suitable type.
  • An acrylate or methacrylate is preferred.
  • An hydroxy acrylic monomer may be used.
  • 2- Hydroxyethyl methacrylate is particularly preferred.
  • the reaction is conducted at elevated temperature, but surprisingly relatively low temperatures may be successfully used to produce the acrylic- modified silicic acid nano-blend. Temperatures in the range of approximately 60°C to 80°C may be used.
  • the method may include a distillation step.
  • An azeotropic distillation may be used.
  • An azeotropic distillation utilising tetrahydrofuran (THF) has been found to be suitable.
  • the silicic acid oligomer in a preferred aspect, is prepared by a method including the preliminary step of providing an alkali metal silicate; and subjecting the silicate to acid hydrolysis wherein the molar ratio of acid to silicate and duration of hydrolysis are such that a relatively high molecular weight silicic acid oligomer is produced.
  • the alkali metal silicate utilised in the method according to this aspect of the present invention may be a sodium silicate.
  • a sodium metasilicate (Na 2 Si0 3 ) has been found to be suitable.
  • the molar ratio of acid to silicate may be carefully controlled. For example by varying concentration of acid used in the reaction, e.g in the range of 1-6M , it is possible to vary the properties of the final product. For example, concentration of acid increases, the level of branching (Q value) and molecular weight of the final product will tend to increase.
  • a mineral acid may be used, for example hydrochloric acid.
  • Hydrochloric acid with a molarity of approximately 3.0 to 4.5 molar (M) may be used.
  • the acid hydrolysis may continue for an extended period of up to approximately 42 hours. A period of 4 hours or 24 hours is preferred.
  • the acrylic-modified silicic acid oligomer or poly(silicic acid) may be utilised in the preparation of a silicate coating as described above. Accordingly, there is provided a method for preparing a silicate coating, which method includes providing an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent; mixing the nano-blend and polyfunctional unsaturated cross-linking agent to form a silicate coating composition; and subjecting the mixture to a curing step.
  • the acrylic-modified silicic acid nano-blend may be an acrylate or methacrylate derivative of a poly(silicic acid) prepared as described above.
  • the acrylic-modified silicic acid nano-blend may further be utilised in the preparation of an ophthalmic article, for example an ophthalmic lens.
  • a cross-linkable polymeric casting composition including an effective amount of an acrylic-modified silicic acid nano-blend; a monomer capable of forming a transparent homopolymer, preferably a homopolymer having a high refractive index; and optionally a polymerisable comonomer.
  • the casting composition may be heat and/or UV-curable.
  • the optical article formed from the casting composition of the present invention may exhibit improved properties including one or more of improved refractive index in the high to very high range, increased toughness, high rigidity, improved abrasion resistance, hardness, toughness, clarity and tint rate.
  • high refractive index we mean a polymer having a refractive index of at least approximately 1.55, preferably 1.57.
  • very high refractive index we mean a polymer having a refractive index of approximately 1.59 or above, preferably 1.60 or above.
  • high rigidity we mean a polymer having a glass transition temperature (Tg) of at least approximately 65°C, preferably approximately 70°C, more preferably approximately 75°C or above.
  • the acrylic-modified silicic acid nano-blend may be of any suitable type.
  • the nano-blend may be of the form as described above.
  • a 2-hydroxyethyl acrylate (HEA) or 2-hydroxyethyl methacrylate (HEMA) poly(silicic acid) nano- blend has been found to be suitable.
  • the acrylic-modified silicic acid nano-blend may be present in amounts of from approximately 5 to 60% by weight, preferably approximately 10 to 35% by weight, more preferably approximately 10 to 20% by weight, based on the total weight of the casting composition have been found to be suitable.
  • the transparent polymer-forming monomer component may be a high index monomer as discussed above.
  • the high index monomer may include a repeating unit derived from a radical polymerisable bisphenol monomer.
  • the high index bisphenol monomer component in the cross-linkable casting composition may include recurring units capable of forming a homopolymer having a refractive index of approximately 1.55, or greater.
  • the high index bisphenol monomer component may be a polyacrylate or polymethacrylate ester of a bisphenol compound.
  • the high index bisphenol monomer may be selected from compounds
  • R 1 is methyl, ethyl or hydrogen
  • R 2 is hydrogen, methyl or ethyl
  • R 3 is hydrogen, methyl or hydroxyl
  • R 4 is hydrogen, methyl or ethyl
  • X is a halogen, preferably chlorine, bromine or iodine, or hydrogen
  • n is an integer having a value of 0 to 8.
  • Representative monomers of the above-described class include: dimethacrylate and diacrylate esters of bisphenol A; dimethacrylate and diacrylate esters of 4,4'bishydroxyethoxy-bisphenot A.
  • a preferred high index bisphenol compound is bisphenol A ethoxylated dimethacrylate.
  • a bisphenol A ethoxylated dimethacrylate sold under the trade designation ATM20 by Ancomer has been found to be suitable.
  • a glycidyl ester of bisphenol A sold under the trade designation Bis GMA by Freeman Chemicals has been found to be suitable.
  • Halogenated high index bisphenol compounds which may be used include those sold under the trade designation and NK Ester 534M by Shin Nakamura.
  • High index brominated bisphenol monomers sold under the trade designations SR803, SR804, GX6099 and GX6094 by Dia-lchi- Kogyo Seiyaku (DKS) Co. Ltd. have also been found to be suitable.
  • Other monomers which may be used in the casting composition according to the present invention include styrene, and derivatives thereof; preferably high index acrylate and methacrylate esters including benzyl and phenyl methacrylate; n-vinyl pyrrolidone; and preferably high index aromatic urethanes.
  • a secondary high index monomer component may be included to modify overall refractive index of the optical article formed therefrom.
  • the transparent polymer-forming monomer may be present in amounts of from approximately 10 to 60% by weight, preferably 20 to 55% by weight based on the total weight of the casting composition.
  • the cross-linkable polymeric casting composition may optionally further include a polymerisable comonomer.
  • the polymerisable comonomer may be selected to improve the properties and/or processability of the cross-linkable polymeric casting composition.
  • the polymerisable comonomer may be selected to improve refractive index tint rate, hardness, abrasion resistance and the like of the resulting polymer.
  • the polymerisable comonomer may be an unsaturated or epoxy comonomer.
  • the polymerisable comonomer may be selected from any suitable type, e.g. di- or polythiol compounds methacrylates, acrylates, including polyoxyalkylene glycol diacrylates or dimethacrylates, vinyls, including di- or polyvinyl monomers, vinyl ethers, allyls, epoxides, and mixtures thereof.
  • the polymerisable comonomer may be present in amounts of approximately 0.001% to 60% by weight, based on the total weight of the polymeric casting composition.
  • the polymerisable comonomer may preferably be selected from one or more of di- or polythiol compound epoxidised monomer or oligomer vinyls, allyiics, polyoxyalkylene glycol di-, tri-, tetra- and higher acrylates or methacrylates, polymerisable bisphenol monomers, urethane monomers having 2 to 6 terminal acrylic or methacrylic groups, fluorene acrylates or methacrylates, and thioacrylate or thiomethacrylate monomers.
  • the di- or polythiol compound when present, may be of any suitable type.
  • a di- r tri- or tetra polythiol compound may be used.
  • a tri- or tetra-polythiol is preferred.
  • the thiol may be selected from one or more of the following: • 4-mercaptomethyl-3,6-dithia-1 ,8-octanedithiol [MDO]
  • TPIC Tris-(3-mercaptopropyl)isocyanurate 4-mercaptomethyl-3,6-dithia-1 ,8-octanedithiol [MDO] is particularly preferred.
  • the di- or polythiol compound may preferably be present in amounts of from approximately 15 to 60% by weight, more preferably approximately 20 to 55% by weight and particularly about 25 to 45% by weight based on the total weight of the casting composition.
  • the divinyl or polyvinyl monomer when present may be a di- or tri- vinyl monomer.
  • An aromatic divinyl is preferred.
  • the aromatic divinyl monomer may include divinyl benzene, divinyl naphthene or derivatives thereof. 1,5-divinyl naphthene may be used. Divinyl benzene is particularly preferred.
  • the divinyl or polyvinyl monomer may preferably be present in amounts sufficient to provide rigidity and high index in optical articles formed from the casting composition, but not so much as to cause brittleness or low tintability. Amounts of from approximately 5 to 50% by weight, preferably approximately 15 to 40% by weight, more preferably about 20 to 30% by weight based on the total weight of the casting composition are preferred.
  • the epoxidised monomer may function to improve curing and casting characteristics.
  • the epoxidised monomer or oligomer may be as described above with reference to the abrasion-resistant coating.
  • the epoxidised monomer may be present in amounts of from approximately 0.001% to 10% by weight, preferably 0.01% to 5%, more preferably approximately 0.01% to 2%, based on the total weight of the casting composition.
  • the comonomer may similarly be as described above with reference to the abrasion-resistant coating.
  • the crosslinkable polymeric casting composition according to the present invention may be utilised in the preparation of an optical article.
  • the optical article may exhibit improved properties including one or more of improved refractive index in the high to very high range, increased toughness, high rigidity, improved abrasion resistance, hardness, toughness, clarity and tint rate.
  • the optical article is a lens element.
  • a method for preparing an optical article which method includes providing a cross-linkable polymeric casting composition including an effective amount of an acrylic-modified silicic acid nano-blend; a monomer capable of forming a homopolymer having a high refractive index; and optionally a polymerisable comonomer; and a heat and/or UV curing agent; mixing the polymeric casting composition and curing agent; and subjecting the mixture to a cross-linking step.
  • the casting composition may be formed into a suitable article by mixing in a convenient vessel the components making up the material, and then adding the curing catalyst.
  • the mixed material may then be degassed or filtered.
  • the casting process may be undertaken on a continuous or semi-continuous basis.
  • the silicate coating composition and/or cross-linkable casting composition utilised in the methods according to the present invention may include a polymerisation curing agent.
  • the polymerisation curing agent may be a radical heat, cationic or radical initiator.
  • a radical heat or photoinitiator is preferred.
  • the compositions may be cured by a combination of UV radiation and heat.
  • the amount of curing agent may vary with the monomers selected.
  • the amount of curing agent may very between approximately 0.05% to 15% by weight, preferably approximately 7% to 10% b weight. It has been found to be possible to operate with a relatively low level of curing agent for the casting composition of between approximately 0.05 and 1.5%, preferably 0.4% to 1.0% by weight. The following curing agents have been found to be suitable.
  • AIBN Azo radical heat initiator
  • Azodiisobutyronitrile • Trigonox TX-29 (Dialkyl Peroxide radical heat initiator) 1,1-di-(-butyl peroxy-3,3,5-trimethyl cyclohexane)
  • Lucirin TPO (radical photoinitiator) 2,4,6-Trimethylbenzoyldiphenylphosphine oxide • Vicure 55 (radical photoinitiator) methyl phenylglycoxylate
  • Amicure DBU and/or Amicure BDMA are preferred.
  • Initiator may be a single component or combination of initiator components.
  • additives may be present which are conventionally used in coating compositions such as inhibitors, dyes, UV stabilisers and materials capable of modifying refractive index. Mould release agents may be added. Such additives may include: UV Absorbers including
  • HALS Hindered amine light stabilisers
  • Ciba Geigy Irganox 245 triethylene glycol-bis-3- (3-tertbutyl-4-hydroxy-5- methyl phenyl)propionate • Irganox 1010 -2,2-bis[[3-[3,4-bis(1 ,1-dimethylethyl)-4-hydroxyphenyl]-1- oxopropoxy]methyl]-1,3-propanediyl 3,5-bis(1 ,1-dimethyl ethyl)-4-hydroxy benzene propanoate
  • Nitroso compounds such as Q1301 from Wako • Nofmer from Nippon Oils and Fats
  • monomeric additives can be present in amounts up to 10% by weight as viscosity modifiers, and include monomers such as methacrylic acid, vinyl silanes, and other functional monomers.
  • monomers such as methacrylic acid, vinyl silanes, and other functional monomers.
  • Other monomeric additives may be included to improve processing and/or material properties, these include:
  • adhesion promoters/modifiers such as Sartomer 9008, Sartomer 9013, Sartomer 9015 etc.
  • mould release agents such as Phosphoric acid esters, e.g. octyl acid phosphate, etc, Alkyl quaternary ammonium salts, e.g. cetyl trimethyl ammonium bromine, etc., Zonyl Series, e.g. Zonyl FSO 100, Zonyl FSN 100, etc., Zelec Series, e.g. Zelec DP, Zelec UN, etc., and Unidain DS
  • Phosphoric acid esters e.g. octyl acid phosphate, etc
  • Alkyl quaternary ammonium salts e.g. cetyl trimethyl ammonium bromine, etc.
  • Zonyl Series e.g. Zonyl FSO 100, Zonyl FSN 100, etc.
  • Zelec Series e.g. Zelec DP, Zelec UN, etc.
  • Infrared spectra were recorded on a Perkin Elmer 1600 FTIR spectrophotometer.
  • Proton nuclear magnetic resonance ( 1 H NMR) spectra were recorded at 200 MHz with a Bruker AC-200 spectrometer.
  • Silicon nuclear magnetic resonance ( 29 Si NMR) spectra were recorded at 59.6 MHz with a Bruker AM-300 spectrometer with pulse width of 10 ⁇ s and a relaxation delay of 1 s.
  • Q values for poly(silicic acids) were determined by integration after subtracting the residual resonance from the glass tube.
  • Gel permeation chromatography (GPC) was performed on a Waters GPC system (Waters 6000S as a solvent pump and Waters R-401 as a detector). Hardness tests were measured using a Matsuzawa Microhardness Tester (Vickers) with a load of 100 g or 1 kg.
  • poly(silicic acid)-2-ethoxyethylmethacrylate ester may be prepared by hydrolysis of sodium metasilicate to form poly(silicic acid) (2) which could be reacted with 2-hydroxyethylmethacrylate.
  • the nano-blend can then undergo polymerisation to form the desired composite material. This synthetic approach was attractive because
  • Silicon in the poly(silicic acid) was analysed as silicon dioxide, the poly(silicic acid)/tetrahydrofuran solution was washed several times with 5% sodium chloride solution to remove the excess of chloride anions present in the solution and this was later checked. The washed solution was allowed to evaporate to dryness and concentrated sulphuric acid and a mixture of ammonium sulphate and nitrate added. After decomposition by heating the mixture was poured into water. The precipitate was filtered off, ignited and weighed as Si0 2 .
  • Poly(siIicic acid)-2-ethoxyethylmethacrylate nano-blend was prepared by azeotropic distillation of water with tetrahydrofuran from a reaction mixture of the poly(silicic acid) and 2-hydroxymethylmethacrylate (HEMA). Removal of tetrahydrofuran and water resulted in the formation of the ester. The solvent was removed in vacuo to yield ester as a colourless liquid which was used in the next step.
  • Poly(silicic acid)-2-ethoxyethylmethacrylate nano-blend, 2-hydroxyethyl- methacrylate, ethylene glycol dimethacrylate and benzoyl peroxide were stirred and the reaction mixture was poured into a Teflon mould or a glass conical flask and held under nitrogen at 60°C for 3 h to allow the polymerisation to start and then at 80°C under vacuum for 24 h. Samples of the composite material of different thicknesses were obtained.
  • RESULTS AND DISCUSSION Preparation of Polv(silicic acid) (2) Preparation of poly(silicic acid) (2) involves hydrolysis and condensation of sodium metasilicate under acidic conditions.
  • the best extractant of poly(silicic acid) from the aqueous solution is tetrahydrofuran (THF).
  • THF tetrahydrofuran
  • hydrochloric acid concentration and the molar ratio of acid to sodium metasilicate were varied. Concentrations of 3.0 M, 4.5 M and 6.0 M hydrochloric acid were used with reaction times of 1 hour, 24 hours, 48 hours and 72 hours respectively.
  • the reaction for preparation of poly(silicic acids) proceeded with either no gelation, gelation occurring after standing of the sample of poly(silicic acid) or immediately when extraction was attempted. In cases where gelation occurred after standing, it was still possible to use the extracted poly(silicic acids) in the esterification step.
  • the nano-blends were prepared by addition of HEMA to the poly(silicic acid)/tetrahydrofuran solution and azeotropic distillation of water with tetrahydrofuran at 64°C. The reaction was monitored by 1 H NMR spectroscopy.
  • the composite material was prepared by polymerisation of poly(silicic acid nano-blends in the presence of 2-hydroxyethylmethacrylate (HEMA), benzoyl peroxide and ethyleneglycoldimethacrylate as cross-linking agent.
  • HEMA 2-hydroxyethylmethacrylate
  • benzoyl peroxide ethyleneglycoldimethacrylate
  • ethyleneglycoldimethacrylate as cross-linking agent.
  • the maximum temperature required for polymerisation is 80°C.
  • the hybrid materials formed were transparent and colouriess or slightly yellow.
  • the cured material has a very good adhesion with glass and initial tests showed it also adhered well to CR-39 ophthalmic lenses.
  • a possible structure of the hybrid material is proposed to consist of ceramic (SiO 2 ) domains interconnected by polymer chains.
  • Example 2 The method of Example 1 was repeated using HCI concentration of 5.5 M for 1 hour to form a poly(silicic acid)-2-ethoxyethylmethacrylate nano-blend.
  • Example 2 was repeated except that 4.5 M HCI was used. A number of abrasion and durability tests were conducted utilising standard techniques. The results of the tests are given in Table 3 below.
  • Example 2 CR-39 coated 0.30
  • Example 3 CR-39 coated 0.44
  • Example 2 CR-39 coated 0.6
  • Example 3 CR-39 coated 1.3
  • Example 3 CR-39 coated No delamination Outdoor Weathering 4 weeks - Cross Hatch Adhesion Testing
  • Example 2 CR-39 coated No delamination

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Abstract

The present invention relates to an organically modified silicate coating and a method for preparing same and in particular the use of such coatings on ophthalmic lenses. Accordingly, in a first aspect of the present invention there is provided a silicate coating composition including an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent. In a further aspect of the present invention there is provided a coated optical article including an optical article formed from a polymeric or glass material; and an abrasion-resistant coating on at least a portion of the surface thereof formed from a silicate coating composition including an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent.

Description

COATING COMPOSITIONS The present invention relates to an organically modified silicate coating and a method for preparing same and in particular the use of such coatings on ophthalmic lenses. Plastics are widely used in the optical industry because they offer several advantages over glass in optical applications in that they are easy to form, are lighter, readily tintable and have a high impact strength compared to glass. Diethylene glycol bis allyl carbonate polymer, CR-39, is widely used in the ophthalmic industry to fabricate plastic eyeglass lenses and has excellent clarity and high temperature resistance. However, transparent coatings are still required for the plastic lens to ensure good scratch resistance.
There has been increasing interest in the prior art in making new organic- inorganic hybrid materials by the sol-gel method. They are called "organically modified silicates" (ormosils) or "organically modified ceramics" (ormocers or ceramers). These materials are synthesised by chemically incorporating organic polymers into an inorganic silicon or titanium based network and have unique properties since they are essentially a composite with nano-dispersion of polymers and ceramic phases. Ormosils combine the hardness and strength of an inorganic glass with the fracture toughness of a polymer hence ormosil coatings have great potential to improve the surface properties of organic polymers and protect them from scratching.
Ormosils may be prepared in a conventional sol-gel process. By incorporating oligomeric components through a sol-gel reaction scheme, the characteristics common to the sol-gel glasses, i.e. high stiffness, brittleness and optical transparency can be controlled and modified.
However, such known ormosils suffer from significant disadvantages. These include the huge shrinkage involved and the need to dry the coatings (and substrates) at very high temperatures.
Accordingly it would be a significant advance in the art if new sol-gel materials could be provided which do not suffer from such disadvantages.
M.W. Ellsworth and B.M. Novak, Chem. Mater., 5(6) (1993) 839 and B.M. Novak, M.W. Ellsworth and C. Verrier, p. 86, in Hybrid Organic-Inorganic Composites: Nanostructured Organic-Inorganic Hybrid Materials Synthesised Through Simultaneous Processes, Ed., J.E. Mark, C.Y.C Lee and P.A. Bianconi, ACS Publ., Washington, 1995 have recently reported the use of silicic acid oligomers. Poly(siiicic acids) can be readily prepared by allowing sodium metasilicate to hydrolyse and condense in acidic aqueous-organic solutions. Addition of salt forces the system to phase-separate and the extraction of poly(silicic acid) into organic solvent is relatively high.
It is accordingly an object of the present invention to overcome, or at least alleviate, one or more of the difficulties or deficiencies relating to the prior art.
Accordingly, in a first aspect of the present invention there is provided a silicate coating composition including an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent.
The coating composition according to this aspect of the present invention may be utilised for forming a coating on an ophthalmic article, for example an ophthalmic lens element. The coating so formed may be characterised in that it forms an abrasion-resistant coating.
Accordingly, in a first aspect of the present invention there is provided a coated optical article including an optical article formed from a polymeric or glass material; and an abrasion-resistant coating on at least a portion of the surface thereof formed from a silicate coating composition including an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent. The coating may provide improved abrasion resistance, hardness, toughness or clarity, or a combination thereof to the optical article. Preferably the optical article is a lens element.
By the term "lens element" we mean all forms of refractive optical bodies employed in the ophthalmic arts, including, but not limited to, lenses, lens wafers and semi-finished lens blanks requiring further finishing to a particular patient's prescription. Also included are formers used in the manufacture of progressive glass lenses and moulds for the casting of progressive lenses in polymeric material such as the material sold under the trade designation CR-39. The acrylic-modified silicic acid nano-blend may be of any suitable type. An acrylate or methacrylate modified silicic acid nano-blend may be used. The acrylic-modified silicic acid nano-blend may be derived from an hydroxy substituted acrylate or methacrylate. 2-Hydroxyethyl acrylate (HEA) or 2- hydroxyethyl methacrylate (HEMA) poly(silicic acid) nano-blend has been found to be suitable.
The polyfunctional unsaturated cross-linking agent according to the present invention may be a di-, tri- or tetra-functional vinyl, an acrylic or methacrylic monomer. The cross-linking agent may be a short chain monomer for example a polyoxy alkylene glycol diacrylate or methacrylate, trimethylol propane trimethacrylate, pentaerythritol triacrylate or tetraacrylate, or the like. Other polyfunctional cross-linking agents which may be used include NK Ester TMPT, NK Ester A-TMPT, NK Ester A-TMM-3, NK Ester A-TMMT, di-trimethylol propane tetraacrylate, trimethylolpropane triacrylate, pentaerythritol tetramethacrylate, dipentaerythritol monohydroxypenta acrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated trimethylol-propane trimethacrylate.
The polyfunctional unsaturated cross-linking agent may be present in amounts of from approximately 0.001 to 15% by weight, preferably approximately 0.05% to 5% by weight based on the total weight of the silicate coating composition.
The polyoxy alkylene glycol diacrylate or dimethacrylate compound according to the present invention, when present, may include ethylene oxide or propylene oxide repeating units in its backbone. A polyethylene glycol dimethacrylate is preferred. Suitable materials include dimethylacrylates where the number of repeating ethylene oxide groups is between 1 and 9. Suitable materials include those sold under the trade names NK Ester 1G, 4G, 6G or 9G. A 1G monomer is preferred.
The polyoxy alkylene glycol diacrylate or dimethacrylate component may be present in amounts of from 0 to approximately 15% by weight, preferably approximately 0.001% to 10% by weight, based on the total weight of the coating composition. ln a further preferred aspect of the present invention, the acrylic-modified silicic acid nano-blend may have a relatively high molecular weight (MW) for example in the range of approximately 4,000 to 12,000.
In a preferred aspect of the present invention the silicate coating composition may optionally further include a polymerisable comonomer.
The polymerisable comonomer may be selected to improve the properties and/or processability of the coating composition. The polymerisable comonomer may be selected to improve tint rate, hardness, abrasion resistance, refractive index and the like of the resulting polymer. The polymerisable comonomer may be an unsaturated or epoxy comonomer.
The polymerisable comonomer may be selected from any suitable type, e.g. from one or more of the group consisting of methacrylates, acrylates, vinyls, vinyl ethers, allyls, epoxides, and the like. The polymerisable comonomer may preferably be selected from one or more of epoxidised monomer or oligomer vinyls, allyiics, polyoxyalkylene glycol di-, tri-, tetra- and higher acrylates or methacrylates, polymerisable bisphenol monomers, urethane monomers having 2 to 6 terminal acrylic or methacrylic groups, fluorene acrylates or methacrylates, and thioacrylate or thiomethacrylate monomers.
Where an epoxidised monomer or oligomer is included, the epoxidised monomer may function to improve curing and casting characteristics. The epoxidised monomer or oligomer may fall into one or more of the following classes: internal, terminal, mono-functional, di-functional, tri-functional, tetra- functional, aliphatic, aromatic, cyclic, structurally simple, structurally complex, esters, ethers, amines. An epoxidised soybean material may be used. The epoxidised monomer or oligomer may be selected from one or more of the following
• Epoxidised soybean oil - Triglycerides of a mixture of epoxidised oleic acid, linoleic acid or linolinic acid
• Propylene Oxide • Hexanediol diglycidyl ether (HDGE)
• 1 ,2 epoxy butane
• Bisphenol fluorene diglycidyl ether (BPGE) • Epolight 100MF
• AK-601
• MY 721
The epoxidised monomer may be present in amounts of from approximately 0.001% to 10% by weight, preferably 0.01% to 5%, more preferably approximately 0.01% to 2%, based on the total weight of the coating composition.
Where a vinyl comonomer is included, the vinyl comonomer may be selected from the group consisting of styrene, substituted styrenes, 3,9-divinyl- 2,4,8, 10-tetraoxaspiro[5.5]undecane (DTU), a divinyl ester monomer of a bi- or polycyclic compound and mixtures thereof.
The vinyl comonomers may be present in amounts of from 0.01% to approximately 20% by weight, preferably approximately 5 to 15% by weight, based on the total weight of the silicate coating composition. Where a thiodiacrylate or dimethacrylate is included, the thiodiacrylate or dimethacrylates may be selected from bis(4-methacryloylthioethyl)sulfιde (BMTES) and bis(4-methacryloylthiophenyl)sulfιde (BMTS). The thioacrylate or methacrylate may be present in amounts of from 0.01% to approximately 20% by weight, preferably approximately 5 to 15% by weight, based on the total weight of the silicate coating composition.
Where a fluorene diacrylate or dimethacrylate is included, the fluorene diacrylate or dimethacrylate monomer may be selected from a bisphenol fluorene dihydroxy acrylate (BFHA) or a bisphenol fluorene dimethacrylate (BFMA) or mixtures thereof. The fluorene diacrylate or dimethacrylate monomer may be present in amounts of from 0 to approximately 20% by weight, preferably approximately 1 to 10% by weight.
The high index bisphenol monomer component in the cross-linkable casting composition when present may be selected from: dimethacrylate and diacrylate esters of bisphenol A; dimethacrylate and diacrylate esters of 4,4'bishydroxy-ethoxy-bisphenol A and the like.
Preferred high index bisphenol compounds include bisphenol A ethoxylated dimethacrylate and tetra brominated bisphenol A ethoxylated dimethacrylates. A bisphenol A ethoxylate dimethacrylate sold under the trade designation ATM 20 by Ancomer has been found to be suitable.
The high index bisphenol monomer may be present in amounts of from 0 to approximately 20% by weight, preferably 5 to 15% by weight based on the total weight of the coating composition.
Accordingly, in a further aspect of the present invention there is provided a method for preparing an acrylic-modified silicic acid nano-blend, which method includes providing a silicic acid oligomer; and an acrylic monomer; mixing the silicic acid oligomer and reactive acrylic monomer; and permitting the mixture to react at elevated temperature whilst continuously removing the water of reaction formed in the reaction.
The acrylic monomer may be of any suitable type. An acrylate or methacrylate is preferred. An hydroxy acrylic monomer may be used. 2- Hydroxyethyl methacrylate is particularly preferred.
The reaction is conducted at elevated temperature, but surprisingly relatively low temperatures may be successfully used to produce the acrylic- modified silicic acid nano-blend. Temperatures in the range of approximately 60°C to 80°C may be used.
In order to remove the water of reaction formed, the method may include a distillation step. An azeotropic distillation may be used. An azeotropic distillation utilising tetrahydrofuran (THF) has been found to be suitable.
The silicic acid oligomer, in a preferred aspect, is prepared by a method including the preliminary step of providing an alkali metal silicate; and subjecting the silicate to acid hydrolysis wherein the molar ratio of acid to silicate and duration of hydrolysis are such that a relatively high molecular weight silicic acid oligomer is produced.
The alkali metal silicate utilised in the method according to this aspect of the present invention may be a sodium silicate. A sodium metasilicate (Na2Si03) has been found to be suitable.
In order to achieve a desired level of branching (Q value) such that the final product will exhibit gelation only on standing, the molar ratio of acid to silicate may be carefully controlled. For example by varying concentration of acid used in the reaction, e.g in the range of 1-6M , it is possible to vary the properties of the final product. For example, concentration of acid increases, the level of branching (Q value) and molecular weight of the final product will tend to increase.
A mineral acid may be used, for example hydrochloric acid. Hydrochloric acid with a molarity of approximately 3.0 to 4.5 molar (M) may be used. The acid hydrolysis may continue for an extended period of up to approximately 42 hours. A period of 4 hours or 24 hours is preferred.
The acrylic-modified silicic acid oligomer or poly(silicic acid) may be utilised in the preparation of a silicate coating as described above. Accordingly, there is provided a method for preparing a silicate coating, which method includes providing an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent; mixing the nano-blend and polyfunctional unsaturated cross-linking agent to form a silicate coating composition; and subjecting the mixture to a curing step.
The acrylic-modified silicic acid nano-blend may be an acrylate or methacrylate derivative of a poly(silicic acid) prepared as described above.
The acrylic-modified silicic acid nano-blend may further be utilised in the preparation of an ophthalmic article, for example an ophthalmic lens.
Accordingly, in a further aspect of the present invention there is provided a cross-linkable polymeric casting composition including an effective amount of an acrylic-modified silicic acid nano-blend; a monomer capable of forming a transparent homopolymer, preferably a homopolymer having a high refractive index; and optionally a polymerisable comonomer. The casting composition may be heat and/or UV-curable. The optical article formed from the casting composition of the present invention may exhibit improved properties including one or more of improved refractive index in the high to very high range, increased toughness, high rigidity, improved abrasion resistance, hardness, toughness, clarity and tint rate. By the term "high refractive index", as used herein, we mean a polymer having a refractive index of at least approximately 1.55, preferably 1.57. By the term "very high refractive index" as used herein, we mean a polymer having a refractive index of approximately 1.59 or above, preferably 1.60 or above.
By the term "high rigidity" as used herein, we mean a polymer having a glass transition temperature (Tg) of at least approximately 65°C, preferably approximately 70°C, more preferably approximately 75°C or above.
The acrylic-modified silicic acid nano-blend may be of any suitable type. The nano-blend may be of the form as described above. A 2-hydroxyethyl acrylate (HEA) or 2-hydroxyethyl methacrylate (HEMA) poly(silicic acid) nano- blend has been found to be suitable.
The acrylic-modified silicic acid nano-blend may be present in amounts of from approximately 5 to 60% by weight, preferably approximately 10 to 35% by weight, more preferably approximately 10 to 20% by weight, based on the total weight of the casting composition have been found to be suitable. The transparent polymer-forming monomer component may be a high index monomer as discussed above. The high index monomer may include a repeating unit derived from a radical polymerisable bisphenol monomer.
The high index bisphenol monomer component in the cross-linkable casting composition may include recurring units capable of forming a homopolymer having a refractive index of approximately 1.55, or greater.
The high index bisphenol monomer component may be a polyacrylate or polymethacrylate ester of a bisphenol compound.
The high index bisphenol monomer may be selected from compounds
Figure imgf000010_0001
wherein R1 is methyl, ethyl or hydrogen; R2 is hydrogen, methyl or ethyl; R3 is hydrogen, methyl or hydroxyl; R4 is hydrogen, methyl or ethyl; X is a halogen, preferably chlorine, bromine or iodine, or hydrogen; and n is an integer having a value of 0 to 8.
Representative monomers of the above-described class include: dimethacrylate and diacrylate esters of bisphenol A; dimethacrylate and diacrylate esters of 4,4'bishydroxyethoxy-bisphenot A.
A preferred high index bisphenol compound is bisphenol A ethoxylated dimethacrylate. A bisphenol A ethoxylated dimethacrylate sold under the trade designation ATM20 by Ancomer has been found to be suitable. A glycidyl ester of bisphenol A sold under the trade designation Bis GMA by Freeman Chemicals has been found to be suitable. Halogenated high index bisphenol compounds which may be used include those sold under the trade designation and NK Ester 534M by Shin Nakamura. High index brominated bisphenol monomers sold under the trade designations SR803, SR804, GX6099 and GX6094 by Dia-lchi- Kogyo Seiyaku (DKS) Co. Ltd. have also been found to be suitable.
Other monomers which may be used in the casting composition according to the present invention include styrene, and derivatives thereof; preferably high index acrylate and methacrylate esters including benzyl and phenyl methacrylate; n-vinyl pyrrolidone; and preferably high index aromatic urethanes. A secondary high index monomer component may be included to modify overall refractive index of the optical article formed therefrom.
The transparent polymer-forming monomer may be present in amounts of from approximately 10 to 60% by weight, preferably 20 to 55% by weight based on the total weight of the casting composition. The cross-linkable polymeric casting composition may optionally further include a polymerisable comonomer.
The polymerisable comonomer may be selected to improve the properties and/or processability of the cross-linkable polymeric casting composition. The polymerisable comonomer may be selected to improve refractive index tint rate, hardness, abrasion resistance and the like of the resulting polymer. The polymerisable comonomer may be an unsaturated or epoxy comonomer. The polymerisable comonomer may be selected from any suitable type, e.g. di- or polythiol compounds methacrylates, acrylates, including polyoxyalkylene glycol diacrylates or dimethacrylates, vinyls, including di- or polyvinyl monomers, vinyl ethers, allyls, epoxides, and mixtures thereof.
The polymerisable comonomer may be present in amounts of approximately 0.001% to 60% by weight, based on the total weight of the polymeric casting composition.
The polymerisable comonomer may preferably be selected from one or more of di- or polythiol compound epoxidised monomer or oligomer vinyls, allyiics, polyoxyalkylene glycol di-, tri-, tetra- and higher acrylates or methacrylates, polymerisable bisphenol monomers, urethane monomers having 2 to 6 terminal acrylic or methacrylic groups, fluorene acrylates or methacrylates, and thioacrylate or thiomethacrylate monomers.
The di- or polythiol compound, when present, may be of any suitable type. A di-r tri- or tetra polythiol compound may be used. A tri- or tetra-polythiol is preferred. The thiol may be selected from one or more of the following: • 4-mercaptomethyl-3,6-dithia-1 ,8-octanedithiol [MDO]
Trimethylolpropane Tris (3-mercaptopropionate) [TTMP]
Pentaerythritol Tetrakis (3-mercaptoacetate) [PTMA]
Trimethylolpropane Tris (3-mercaptoacetate) [TTMA]
4-t-butyl-1 ,2-benzenedithiol • Bis-(2-mercaptoethyl)sulfide
4,4'-thiodibenzenethiol benzenedithiol
Glycol Dimercaptoacetate
Glycol Dimercaptopropionate Ethylene bis(3- Mercaptopropionate) • Polyethylene Glycol Dimercaptoacetates
Polyethylene Glycol Di(3-Mercaptopropionates)
Pentaerythritol Tetrakis (3-mercapto-propionate) [PTMP]
Mercapto-methyl tetrahydrothiophene [MMTHT]
Tris-(3-mercaptopropyl)isocyanurate [TMPIC] 4-mercaptomethyl-3,6-dithia-1 ,8-octanedithiol [MDO] is particularly preferred.
The di- or polythiol compound may preferably be present in amounts of from approximately 15 to 60% by weight, more preferably approximately 20 to 55% by weight and particularly about 25 to 45% by weight based on the total weight of the casting composition.
The divinyl or polyvinyl monomer when present may be a di- or tri- vinyl monomer. An aromatic divinyl is preferred. The aromatic divinyl monomer may include divinyl benzene, divinyl naphthene or derivatives thereof. 1,5-divinyl naphthene may be used. Divinyl benzene is particularly preferred.
The divinyl or polyvinyl monomer may preferably be present in amounts sufficient to provide rigidity and high index in optical articles formed from the casting composition, but not so much as to cause brittleness or low tintability. Amounts of from approximately 5 to 50% by weight, preferably approximately 15 to 40% by weight, more preferably about 20 to 30% by weight based on the total weight of the casting composition are preferred.
Where an epoxidised monomer or oligomer is included, the epoxidised monomer may function to improve curing and casting characteristics. The epoxidised monomer or oligomer may be as described above with reference to the abrasion-resistant coating.
The epoxidised monomer may be present in amounts of from approximately 0.001% to 10% by weight, preferably 0.01% to 5%, more preferably approximately 0.01% to 2%, based on the total weight of the casting composition.
Where a vinyl comonomer, polyoxyalkylene glycol diacrylate or dimethacrylate, thiodiacrylate or dimethacrylate, fluorene diacrylate or methacrylate, urethane monomer or high index bisphenol monomer is included, the comonomer may similarly be as described above with reference to the abrasion-resistant coating.
The crosslinkable polymeric casting composition according to the present invention may be utilised in the preparation of an optical article. The optical article may exhibit improved properties including one or more of improved refractive index in the high to very high range, increased toughness, high rigidity, improved abrasion resistance, hardness, toughness, clarity and tint rate.
Preferably the optical article is a lens element.
In a preferred aspect of the present invention there is provided a method for preparing an optical article which method includes providing a cross-linkable polymeric casting composition including an effective amount of an acrylic-modified silicic acid nano-blend; a monomer capable of forming a homopolymer having a high refractive index; and optionally a polymerisable comonomer; and a heat and/or UV curing agent; mixing the polymeric casting composition and curing agent; and subjecting the mixture to a cross-linking step.
The casting composition may be formed into a suitable article by mixing in a convenient vessel the components making up the material, and then adding the curing catalyst. The mixed material may then be degassed or filtered. As the curing time is substantially reduced, the casting process may be undertaken on a continuous or semi-continuous basis.
In a further aspect of the present invention there is provided an optical article prepared by the method as described above.
The silicate coating composition and/or cross-linkable casting composition utilised in the methods according to the present invention may include a polymerisation curing agent.
The polymerisation curing agent may be a radical heat, cationic or radical initiator. A radical heat or photoinitiator is preferred. The compositions may be cured by a combination of UV radiation and heat.
The amount of curing agent may vary with the monomers selected. For the coating composition, the amount of curing agent may very between approximately 0.05% to 15% by weight, preferably approximately 7% to 10% b weight. It has been found to be possible to operate with a relatively low level of curing agent for the casting composition of between approximately 0.05 and 1.5%, preferably 0.4% to 1.0% by weight. The following curing agents have been found to be suitable.
• AIBN (Azo radical heat initiator) Azodiisobutyronitrile • Trigonox TX-29 (Dialkyl Peroxide radical heat initiator) 1,1-di-(-butyl peroxy-3,3,5-trimethyl cyclohexane)
• TBPEH (Alkyl Perester radical heat initiator) t-butyl per-2-ethylhexanoate • (Diacyl Peroxide radical heat initiator)
Benzoyl Peroxide
• (Peroxy Dicarbonate radical heat initiator) Ethyl Hexyl Percarbonate
• (Ketone Peroxide radical heat initiator) Methyl ethyl ketone peroxide
• Cyracure UV1-6974 (cationic photoinitiator) Triaryl sulfonium hexafluoroantimonate
• Lucirin TPO (radical photoinitiator) 2,4,6-Trimethylbenzoyldiphenylphosphine oxide • Vicure 55 (radical photoinitiator) methyl phenylglycoxylate
• Bis(t-butyl peroxide) diisopropylbenzene
• t-butyl perbenzoate
• t-butyl peroxy neodecanoate • Amicure DBU
• Amicure BDMA
• DABCO
• Amicure DBU and/or Amicure BDMA are preferred.
Initiator may be a single component or combination of initiator components.
Other additives may be present which are conventionally used in coating compositions such as inhibitors, dyes, UV stabilisers and materials capable of modifying refractive index. Mould release agents may be added. Such additives may include: UV Absorbers including
• Ciba Geigy Tinuvin P - 2(2'-hydroxy-5'methyl phenyl) benzotriazole • Cyanamid Cyasorb UV 531 -2-hydroxy-4-n-octoxybenzophenone
• Cyanamid Cyasorb UV5411-2(2-hydroxy-5-t-octylphenyl)- benzotriazole
• Cyanamid UV 2098 - 2 hydroxy-4-(2-acryloyloxyethoxy) benzophenone
• National Starch and Chemicals Permasorb MA - 2 hydroxy-4-(2 hydroxy- 3- methacryloxy)propoxy benzophenone
• Cyanamid UV24 - 2,2'-dihydroxy-4-methoxybenzophenone
• BASF UVINUL 400 - 2,4 dihydroxy-benzophenone
• BASF UVINUL D-49 - 2,2,-dihydroxy-4,4' dimethoxy- benzophenone
• BASF UVINUL D-50 - 2,2', 4,4' tetrahydroxy benzophenone • BASF UVINUL D-35-ethyl-2-cyano-3,3-diphenyl acrylate
• BASF UVINUL N-539-2-ethylhexyl-2-cyano-3,3-diphenyl acrylate
• Ciba Geigy Tinuvin 213
Hindered amine light stabilisers (HALS), including
• Ciba Geigy Tinuvin 765/292 - bis (1 ,2,2,6,6-pentamethyl-4-piperidyl) sebacate
• Ciba Geigy 770 - bis (2,2,6,6-tetramethyl-4- piperidinyl) sebacate Antioxidants including
• Ciba Geigy Irganox 245 - triethylene glycol-bis-3- (3-tertbutyl-4-hydroxy-5- methyl phenyl)propionate • Irganox 1010 -2,2-bis[[3-[3,4-bis(1 ,1-dimethylethyl)-4-hydroxyphenyl]-1- oxopropoxy]methyl]-1,3-propanediyl 3,5-bis(1 ,1-dimethyl ethyl)-4-hydroxy benzene propanoate
• Irganox 1076 - octadecyl 3-(3, )5'-di-tert-butyl(-4'- hydroxyphenyl) propionate Anticolouring agents including
• 9, 10 dihydro-9-oxa-10-phosphaphenanthrene-1 -oxide Cure modifiers including
• Dodecyl mercaptan
• Butyl mercaptan • Thiophenol
• Nitroso compounds such as Q1301 from Wako • Nofmer from Nippon Oils and Fats
Other monomeric additives can be present in amounts up to 10% by weight as viscosity modifiers, and include monomers such as methacrylic acid, vinyl silanes, and other functional monomers. Other monomeric additives may be included to improve processing and/or material properties, these include:
• methacrylic acid, maleic anhydride, acrylic acid
• adhesion promoters/modifiers such as Sartomer 9008, Sartomer 9013, Sartomer 9015 etc.
• dye-enhancing, pH-adjusting monomers like Alcolac SIPOMER 2MIM • a charge-reducing cationic monomer to render the material more antistatic, example Sipomer Q5-80 or Q9-75
• mould release agents such as Phosphoric acid esters, e.g. octyl acid phosphate, etc, Alkyl quaternary ammonium salts, e.g. cetyl trimethyl ammonium bromine, etc., Zonyl Series, e.g. Zonyl FSO 100, Zonyl FSN 100, etc., Zelec Series, e.g. Zelec DP, Zelec UN, etc., and Unidain DS
Series, e.g. DS 401, DS 202, etc.
EXAMPLE 1 EXPERIMENTAL
Preparation of the Composite Material Methods of Characterisation
Infrared spectra were recorded on a Perkin Elmer 1600 FTIR spectrophotometer. Proton nuclear magnetic resonance (1H NMR) spectra were recorded at 200 MHz with a Bruker AC-200 spectrometer. Silicon nuclear magnetic resonance (29Si NMR) spectra were recorded at 59.6 MHz with a Bruker AM-300 spectrometer with pulse width of 10 μs and a relaxation delay of 1 s. Q values for poly(silicic acids) were determined by integration after subtracting the residual resonance from the glass tube. Gel permeation chromatography (GPC) was performed on a Waters GPC system (Waters 6000S as a solvent pump and Waters R-401 as a detector). Hardness tests were measured using a Matsuzawa Microhardness Tester (Vickers) with a load of 100 g or 1 kg.
It was proposed that poly(silicic acid)-2-ethoxyethylmethacrylate ester may be prepared by hydrolysis of sodium metasilicate to form poly(silicic acid) (2) which could be reacted with 2-hydroxyethylmethacrylate. The nano-blend can then undergo polymerisation to form the desired composite material. This synthetic approach was attractive because
• sodium metasilicate is a commercially available cheap starting material • production of the nano-blend and polymerisation are carried out at low temperatures (<80°C)
• easy manipulation is possible throughout the process
• no production of water occurs and thus no need for drying Preparation of Polv(silicic acid)(2) Poly(silicic acid) (2) was prepared according to the method of Y. Abe and
T. Misono, J. Polym. Sci, Polym. Chem. Ed., 21 (1980) 41 and 20 (1982) 205. Silica content of the sample was determined and 29Si NMR was run on a concentrated solution to assign the Q values (degree of branching). The same general procedure was used for the reaction with different molarites of hydrochloric acid (3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 4.0, 4.5, 6.0 M) and extended reaction times of 24 h, 48 h and 72h. Silica Content Determination
Silicon in the poly(silicic acid) was analysed as silicon dioxide, the poly(silicic acid)/tetrahydrofuran solution was washed several times with 5% sodium chloride solution to remove the excess of chloride anions present in the solution and this was later checked. The washed solution was allowed to evaporate to dryness and concentrated sulphuric acid and a mixture of ammonium sulphate and nitrate added. After decomposition by heating the mixture was poured into water. The precipitate was filtered off, ignited and weighed as Si02.
Preparation of Polvfsilicic acid)-2-ethoxyethylmethacrylate nano-blend
Poly(siIicic acid)-2-ethoxyethylmethacrylate nano-blend was prepared by azeotropic distillation of water with tetrahydrofuran from a reaction mixture of the poly(silicic acid) and 2-hydroxymethylmethacrylate (HEMA). Removal of tetrahydrofuran and water resulted in the formation of the ester. The solvent was removed in vacuo to yield ester as a colourless liquid which was used in the next step. Preparation of Composite Material
Poly(silicic acid)-2-ethoxyethylmethacrylate nano-blend, 2-hydroxyethyl- methacrylate, ethylene glycol dimethacrylate and benzoyl peroxide were stirred and the reaction mixture was poured into a Teflon mould or a glass conical flask and held under nitrogen at 60°C for 3 h to allow the polymerisation to start and then at 80°C under vacuum for 24 h. Samples of the composite material of different thicknesses were obtained. RESULTS AND DISCUSSION Preparation of Polv(silicic acid) (2) Preparation of poly(silicic acid) (2) involves hydrolysis and condensation of sodium metasilicate under acidic conditions. The best extractant of poly(silicic acid) from the aqueous solution is tetrahydrofuran (THF). In early stages of this work significant variation in the properties of the poly(silicic acids) was observed. To determine optimum reaction conditions hydrochloric acid concentration and the molar ratio of acid to sodium metasilicate were varied. Concentrations of 3.0 M, 4.5 M and 6.0 M hydrochloric acid were used with reaction times of 1 hour, 24 hours, 48 hours and 72 hours respectively. The reaction for preparation of poly(silicic acids) proceeded with either no gelation, gelation occurring after standing of the sample of poly(silicic acid) or immediately when extraction was attempted. In cases where gelation occurred after standing, it was still possible to use the extracted poly(silicic acids) in the esterification step. Gelation of the samples was possibly due to the further polymerisation and cross-linking of poly(silicic acids) when the concentration of hydrochloric acid was 4.5 or 6.0 M and reaction time 42 hours and 72 hours. Hydrochloric acid concentration influences the degree of branching in poly(silicic acids), Q values which can be estimated from 29Si NMR spectra. Q4 represents the amount of fully substituted silicon with no OH groups attached and hence is an indication of the extent of the cross-linking of silica polyhedra. It can be seen from Table 1 that Q4 is especially sensitive to the changes in hydrochloric acid concentration and increases with increasing HCI concentration. TABLE 1
Q values determined by 29aSi: NMR spectra of polv(silicic acids
UHCI[M] Q1 [%] Q* [%] QJ [%] Q4 [%]
1.3 <0.1 20.0 72.2 7.8
3.0 <0.1 13.9 62.4 23.7
3.5 <0.1 12.0 49.9 38.1
3.8 <0.1 9.3 48.4 42.3
4.0 <0.1 9.7 42.6 47.7
Preparation of Polvfsilicic acid)-2-ethoxyethylmethacrylate nano-blend
The nano-blends were prepared by addition of HEMA to the poly(silicic acid)/tetrahydrofuran solution and azeotropic distillation of water with tetrahydrofuran at 64°C. The reaction was monitored by 1H NMR spectroscopy.
TABLE 2 Molecular weights of polvfsilicic acid nano-blend) (GPC relative to polystyrene)
Figure imgf000020_0001
As can be seen from Table 2 the molecular weights of the nano-blends vary with the concentration of hydrochloric acid used in the first reaction step. It is noted that the molecular weights of the nano-blends have demonstrated an increasing trend with increasing Q4 values of the nano-blends. Preparation of Composite Material
The composite material was prepared by polymerisation of poly(silicic acid nano-blends in the presence of 2-hydroxyethylmethacrylate (HEMA), benzoyl peroxide and ethyleneglycoldimethacrylate as cross-linking agent. The maximum temperature required for polymerisation is 80°C. The hybrid materials formed were transparent and colouriess or slightly yellow. The cured material has a very good adhesion with glass and initial tests showed it also adhered well to CR-39 ophthalmic lenses. A possible structure of the hybrid material is proposed to consist of ceramic (SiO2) domains interconnected by polymer chains.
EXAMPLE 2 The method of Example 1 was repeated using HCI concentration of 5.5 M for 1 hour to form a poly(silicic acid)-2-ethoxyethylmethacrylate nano-blend.
7.9 g of ρoly(silicic acid)-2-ethoxyethylmethacrylate nano-blend was added to 0.09 g 2-hydroxyethylmethacrylate, 4.7 mg ethylene glycol dimethacrylate and 4.7 mg benzoyl peroxide to form a coating resin. The resin was then spin coated onto CR-39 and cured for 3 hours at
95°C.
EXAMPLE 3 Example 2 was repeated except that 4.5 M HCI was used. A number of abrasion and durability tests were conducted utilising standard techniques. The results of the tests are given in Table 3 below.
TABLE 3 Taber Abrasion Test
CR-39 uncoated 1.00
Example 2 CR-39 coated 0.30 Example 3 CR-39 coated 0.44
(No scratching is given a value of 0) Bayer Oscillating Sand Test
CR-39 uncoated 1.0
Example 2 CR-39 coated 0.6 Example 3 CR-39 coated 1.3
(The higher the number the more abrasion resistant the material) Primary Adhesion - Cross Hatch Adhesion Testing
Example 2 CR-39 coated No delamination
Example 3 CR-39 coated No delamination Suntester Durability 72 hours - Cross Hatch Adhesion Testing Example 2 CR-39 coated No delamination
Example 3 CR-39 coated No delamination Outdoor Weathering 4 weeks - Cross Hatch Adhesion Testing Example 2 CR-39 coated No delamination
Example 3 CR-39 coated No delamination
3 Hour Boil - Cross Hatch Adhesion Testing
Example 2 CR-39 coated No delamination
Example 3 CR-39 coated No delamination
Finally, it is to be understood that various other modifications and/or alterations may be made without departing from the spirit of the present invention as outlined herein.

Claims

Claims 1. A silicate coating composition including an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent.
2. A silicate coating composition according to Claim 1 , wherein the acrylic modified silicic acid nano-blend is an acrylate or methacrylate modified silicic acid nano-blend.
3. A silicate coating composition according to Claim 2, wherein the acrylate or methacrylate modified silicic acid nano-blend is derived from an hydroxy- substituted acrylate or methacrylate.
4. A silicate coating composition according to Claim 3, wherein the acrylic modified silicic acid nano-blend has a molecular weight (MW) in the range of approximately 4,000 to 12,000.
5. A silicate coating composition according to Claim 1 , wherein the polyfunctional unsaturated cross-linking agent is present in amounts of from approximately 0.01% to 15% by weight, based on the total weight of the silicate coating composition, and is selected from the group consisting of di-, tri- or tetra- functional vinyl acrylic or methacrylic monomers.
6. A silicate coating composition according to Claim 5, wherein the polyfunctional unsaturated cross-linking agent is a polyethylene glycol diacrylate or dimethacrylate wherein the number of repeating ethylene oxide groups is between 1 and 9.
7. A silicate coating composition according to Claim 1 , further including a polymerisable co-monomer selected from one or more of the group consisting of methacrylates, acrylates, vinyls, vinyl ethers, allyls and epoxides.
8. A silicate coating composition according to Claim 7, wherein the polymerisable co-monomer is an epoxidised monomer or oligomer selected from the group consisting of internal, terminal, mono-functional, di-functional, tri- functional, tetra-functional, aliphatic, aromatic, cyclic, structurally simple, structurally complex, esters, ethers, amines or mixtures thereof.
9. A silicate coating composition according to Claim 8, wherein the epoxidised monomer or oligomer is present in amounts of from approximately 0.001% to 10% by weight, based on the total weight of the coating composition.
10. A silicate coating composition according to Claim 7, wherein the polymerisable co-monomer is a vinyl co-monomer selected from the group consisting of styrene, substituted styrenes, 3,9-divinyl-2,4,8,10- tetraoxaspiro[5.5]undecane (DTU), a divinyl ester monomer of a bi- or polycyclic compound and mixtures thereof.
11. A silicate coating composition according to Claim 10, wherein the vinyl co-monomer is present in amounts of from approximately 0.01% to approximately 20% by weight of the silicate coating composition.
12. A coated optical article including an optical article formed from a polymeric or glass material; and an abrasion-resistant coating on at least a portion of the surface thereof formed from a silicate coating composition including an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent.
13. A coated optical article according to Claim 12, wherein the acrylic modified silicic acid nano-blend is an acrylate or methacrylate modified silicic acid nano-blend.
14. A coated optical article according to Claim 13, wherein the polyfunctional unsaturated cross-linking agent is present in amounts of from approximately 5% to 15% by weight, based on the total weight of the silicate coating composition, and is selected from the group consisting of di-, tri- or tetra-functional vinyl acrylic or methacrylic monomers.
15. A coated optical article according to Claim 14, further including a polymerisable co-monomer selected from one or more of the group consisting of methacrylates, acrylates, vinyls, vinyl ethers, allyls and epoxides.
16. A coated optical article according to Claim 12, wherein the optical article is a lens element.
17. A method for preparing an acrylic-modified silicic acid nano-blend, which method includes providing a silicic acid oligomer; and an acrylic monomer; mixing the silicic acid oligomer and reactive acrylic monomer; and permitting the mixture to react at elevated temperature whilst continuously removing the water of reaction formed in the reaction.
18. A method according to Claim 17, wherein the acrylic monomer is an acrylate or methacrylate monomer.
19. A method according to Claim 18, wherein the reaction is conducted at temperatures of from approximately 60 to 80°C.
20. A method according to Claim 17, which method includes the preliminary step of providing an alkali metal silicate; and subjecting the silicate to acid hydrolysis wherein the molar ratio of acid to silicate and duration of hydrolysis are such that a relatively high molecular weight silicic acid oligomer is produced.
21. A method according to Claim 20, wherein the alkali metal silicate is a sodium metasilicate.
22. A method for preparing a silicate coating, which method includes providing an acrylic-modified silicic acid nano-blend; and a polyfunctional unsaturated cross-linking agent; mixing the nano-blend and polyfunctional unsaturated cross-linking agent to form a silicate coating composition; and subjecting the mixture to a curing step.
23. A method according to Claim 22, wherein the acrylic modified silicic acid nano-blend is an acrylate or methacrylate derivative of poly(silicic acid).
24. A cross-linkable polymeric casting composition including an effective amount of an acrylic-modified silicic acid nano-blend; a monomer capable of forming a transparent homopolymer; and optionally a polymerisable comonomer.
25. A cross-linkable polymeric casting composition according to Claim 24, wherein the acrylic modified silicic acid nano-blend is an acrylate or methacrylate derivative of a poly(silicic acid).
26. A cross-linkable polymeric casting composition according to Claim 25, wherein the acrylic modified silicic acid nano-blend is present in amounts of from approximately 5% to 60% by weight, based on the total weight of the casting composition.
27. A cross-linkable polymeric casting composition according to Claim 24, wherein the transparent polymer-forming monomer is a high index bisphenol monomer.
28. A polymeric casting composition according to Claim 24, wherein the polymerisable co-monomer is present in amounts of from approximately 0.001% by weight to 60% by weight, based on the total weight of the polymeric casting composition and is selected from one or more of the group consisting of di- or polythiol compounds, methacrylates, acrylates, vinyls, vinyl ethers, allyls, epoxides, and mixtures thereof.
29. A method for preparing an optical article, which includes providing a cross-linkable polymeric casting composition including an effective amount of an acrylic-modified silicic acid nano-blend; a monomer capable of forming a transparent homopolymer; and optionally a polymerisable comonomer; and a heat and/or UV curing agent; mixing the polymeric casting composition and curing agent; and subjecting the mixture to a cross-linking step.
30. An optical article whenever prepared according to the method of Claim 29.
31. An optical article according to Claim 30, wherein the optical article is a lens element.
32. A silicate coating composition substantially as hereinbefore described with reference to any one of the examples.
PCT/AU1997/000415 1996-07-05 1997-06-30 Coating compositions WO1998001508A1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4011253A (en) * 1975-02-21 1977-03-08 Blount David H Process for the production of silicic acrylate compounds and resinous products
US5322889A (en) * 1991-09-24 1994-06-21 Mitsubishi Rayon Co., Ltd. Composite composition having high transparency and process for producing same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4011253A (en) * 1975-02-21 1977-03-08 Blount David H Process for the production of silicic acrylate compounds and resinous products
US5322889A (en) * 1991-09-24 1994-06-21 Mitsubishi Rayon Co., Ltd. Composite composition having high transparency and process for producing same

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
CHEMICAL MATERIALS, 1993, 5(6), M.W. ELLSWORTH et al., "Inverse Organic-Inorganic Composite Materials", pp. 839-844. *
MAT. RES. SOC. SYMP. PROC., 1992, 271, K. ROSE et al., "Multifunctional Acrylate Alkoxysilanes for Polymeric Materials", pp. 731-736. *

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