CA2299067A1 - Coating composition for a ceramic article and use in repairing defects in glazed ceramic articles - Google Patents
Coating composition for a ceramic article and use in repairing defects in glazed ceramic articles Download PDFInfo
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- CA2299067A1 CA2299067A1 CA 2299067 CA2299067A CA2299067A1 CA 2299067 A1 CA2299067 A1 CA 2299067A1 CA 2299067 CA2299067 CA 2299067 CA 2299067 A CA2299067 A CA 2299067A CA 2299067 A1 CA2299067 A1 CA 2299067A1
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
- C04B41/81—Coating or impregnation
- C04B41/89—Coating or impregnation for obtaining at least two superposed coatings having different compositions
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
- C04B41/81—Coating or impregnation
- C04B41/82—Coating or impregnation with organic materials
- C04B41/83—Macromolecular compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F290/00—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups
- C08F290/02—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups on to polymers modified by introduction of unsaturated end groups
- C08F290/06—Polymers provided for in subclass C08G
- C08F290/062—Polyethers
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- 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
- C09D171/00—Coating compositions based on polyethers obtained by reactions forming an ether link in the main chain; Coating compositions based on derivatives of such polymers
- C09D171/02—Polyalkylene oxides
Abstract
A coating composition for application to a ceramic substrate comprising an undercoat and a clear topcoat, wherein the undercoat comprises a radiation curable oligomer, an extender or filler, aluminum hydroxide and titanium dioxide. The topcoat comprises an urethane acrylate oligomer and an hydrocarbon acrylate diluent. A coating composition is also provided comprising an undercoat and a clear topcoat, wherein the undercoat comprises a radiation curable oligomer, an extender or filler, and a colourant. The topcoat comprises an urethane acrylate oligomer and an hydrocarbon acrylate diluent. A surface defect on a glazed ceramic article can be repaired by first coating or hiding the surface defect with either of the above-described undercoats, curing such undercoat with an energy source, applying the above-described topcoat to the cured undercoat, and curing the topcoat with an energy source.
Description
COATING COMPOSITION FOR A CERAMIC ARTICLE
AND USE IN REPAIRING DEFECTS IN GLAZED CERAMIC ARTICLES
Field of Invention The present invention relates to coating compositions applied to ceramic substrates and the method by which they are applied.
Background of the Invention Vitreous glazes are typically applied to ceramic articles to enhance their aesthetic appearance.
When in their green state, ceramic articles are coated with a slurry which forms a vitreous coating when fired. After application of the slurry, the ceramic article is then subj ected to a high temperature firing process, one consequence of which is the curing of the glaze to the ceramic article.
Unfortunately, the resultant glazed coating may possess any one of several kinds of surface defects. For instance, the coating may contain voids and pinholes caused by trapped air or gas formed from a spot contaminant in the film and insufficient flow during levelling of the coating. In such cases, the appearance of the glazed ceramic article may be unacceptable, requiring further action to correct the defect.
U.S. Patent 2,826,508 discloses a method of repairing surface defects of fired ceramic articles by applying an undercoating to the defect, applying a glaze coating on the undercoating, and then baking the applied coatings to effect curing and adherence to the ceramic substrate. Unfortunately, exposure to such cyclical firing increases the risk of stress fracture in the ceramic article. Further, this manner of repair creates disruption of and introduces inefficiencies into the manufacturing process. It is therefore desirable to provide a coating composition for repairing of surface defects of fired ceramic articles which resembles ceramic glaze upon application but does not requires elevated temperatures to effect curing and adherence to the ceramic substrate.
Summary of Invention The present invention provides an improved coating composition for use in repairing surface defects of fired ceramic articles In accordance with one aspect, the present invention provides a coating composition for application to a ceramic substrate comprising: a radiation curable oligomer, an extender, aluminum hydroxide and titanium dioxide. The aluminum hydroxide can be refined from gibbsite. The aluminum hydroxide can be characterized by a particle size of less than about 1.5 ,um. The radiation curable oligomer can be a polyether acrylate or an urethane acrylate. Suitable polyether acrylates include those characterized by a viscosity of greater than 220 mPa/s. The coating composition can include substantially no monomer. Suitable fillers include aluminum oxide, barium sulfate, or magnesium silicate. Where the coating composition is cured by ultraviolet light, a photoinitiator blend comprising an aromatic ketone and phosphine oxide can further be provided.
In another aspect, the present invention provides a coating composition for applications to a ceramic substrate comprising: a binder, having a radiation curable oligomer and an extender; and a pigment, having aluminum hydroxide and titanium dioxide, wherein the pigment and the binder are combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
In another aspect, the present invention provides a coating composition for application to a ceramic substrate comprising:
AND USE IN REPAIRING DEFECTS IN GLAZED CERAMIC ARTICLES
Field of Invention The present invention relates to coating compositions applied to ceramic substrates and the method by which they are applied.
Background of the Invention Vitreous glazes are typically applied to ceramic articles to enhance their aesthetic appearance.
When in their green state, ceramic articles are coated with a slurry which forms a vitreous coating when fired. After application of the slurry, the ceramic article is then subj ected to a high temperature firing process, one consequence of which is the curing of the glaze to the ceramic article.
Unfortunately, the resultant glazed coating may possess any one of several kinds of surface defects. For instance, the coating may contain voids and pinholes caused by trapped air or gas formed from a spot contaminant in the film and insufficient flow during levelling of the coating. In such cases, the appearance of the glazed ceramic article may be unacceptable, requiring further action to correct the defect.
U.S. Patent 2,826,508 discloses a method of repairing surface defects of fired ceramic articles by applying an undercoating to the defect, applying a glaze coating on the undercoating, and then baking the applied coatings to effect curing and adherence to the ceramic substrate. Unfortunately, exposure to such cyclical firing increases the risk of stress fracture in the ceramic article. Further, this manner of repair creates disruption of and introduces inefficiencies into the manufacturing process. It is therefore desirable to provide a coating composition for repairing of surface defects of fired ceramic articles which resembles ceramic glaze upon application but does not requires elevated temperatures to effect curing and adherence to the ceramic substrate.
Summary of Invention The present invention provides an improved coating composition for use in repairing surface defects of fired ceramic articles In accordance with one aspect, the present invention provides a coating composition for application to a ceramic substrate comprising: a radiation curable oligomer, an extender, aluminum hydroxide and titanium dioxide. The aluminum hydroxide can be refined from gibbsite. The aluminum hydroxide can be characterized by a particle size of less than about 1.5 ,um. The radiation curable oligomer can be a polyether acrylate or an urethane acrylate. Suitable polyether acrylates include those characterized by a viscosity of greater than 220 mPa/s. The coating composition can include substantially no monomer. Suitable fillers include aluminum oxide, barium sulfate, or magnesium silicate. Where the coating composition is cured by ultraviolet light, a photoinitiator blend comprising an aromatic ketone and phosphine oxide can further be provided.
In another aspect, the present invention provides a coating composition for applications to a ceramic substrate comprising: a binder, having a radiation curable oligomer and an extender; and a pigment, having aluminum hydroxide and titanium dioxide, wherein the pigment and the binder are combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
In another aspect, the present invention provides a coating composition for application to a ceramic substrate comprising:
from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate;
from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant;
from about 10 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate;
from about 10 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate;
from about 0.5 to about 20 percent by weight, based on the total weight of the composition, of aluminum hydroxide;
from about 3 to about 6 percent by weight, based on the total weight of the composition, of titanium dioxide;
from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide; and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
In a further aspect, the present invention provides a coating composition for application to a ceramic substrate comprising: a radiation curable oligomer, an extender, and a colourant. The colourant can be pearlescent pigment or tinting paste. The radiation curable oligomer can be a polyether acrylate or an urethane acrylate. Suitable polyether acrylates, include those characterized by a viscosity of greater than 220 mPa/s. The coating composition can include substantially no monomer. Suitable fillers include aluminum oxide, barium sulfate, or magnesium silicate. Where the coating composition is cured by ultraviolet light, a photoinitiator blend comprising an aromatic ketone and phosphine oxide can further be provided.
In even a further aspect, the present invention provides a coating composition for application to a ceramic substrate comprising: a binder, having a radiation curable oligomer and an extender, and a pigment, having a colourant, wherein the pigment and the binder are combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
In yet a further aspect, the present invention provides a coating composition for application to a ceramic substrate comprising:
from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate;
from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant;
from about 15 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate;
from about 15 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate;
from about 1 to about 10 percent by weight, based on the total weight of the composition, of a colourant;
from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide; and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant;
from about 10 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate;
from about 10 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate;
from about 0.5 to about 20 percent by weight, based on the total weight of the composition, of aluminum hydroxide;
from about 3 to about 6 percent by weight, based on the total weight of the composition, of titanium dioxide;
from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide; and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
In a further aspect, the present invention provides a coating composition for application to a ceramic substrate comprising: a radiation curable oligomer, an extender, and a colourant. The colourant can be pearlescent pigment or tinting paste. The radiation curable oligomer can be a polyether acrylate or an urethane acrylate. Suitable polyether acrylates, include those characterized by a viscosity of greater than 220 mPa/s. The coating composition can include substantially no monomer. Suitable fillers include aluminum oxide, barium sulfate, or magnesium silicate. Where the coating composition is cured by ultraviolet light, a photoinitiator blend comprising an aromatic ketone and phosphine oxide can further be provided.
In even a further aspect, the present invention provides a coating composition for application to a ceramic substrate comprising: a binder, having a radiation curable oligomer and an extender, and a pigment, having a colourant, wherein the pigment and the binder are combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
In yet a further aspect, the present invention provides a coating composition for application to a ceramic substrate comprising:
from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate;
from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant;
from about 15 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate;
from about 15 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate;
from about 1 to about 10 percent by weight, based on the total weight of the composition, of a colourant;
from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide; and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
In another aspect, the present invention provides a coating composition for application to a ceramic substrate comprising an undercoat and a clear topcoat, wherein the undercoat comprises a radiation curable oligomer, an extender, aluminum hydroxide and titanium dioxide, and wherein the topcoat comprises an urethane acrylate oligomer and hydrocarbon acrylate diluent.
In yet even a further aspect, the present invention provides a coating composition for application to a ceramic substrate comprising an undercoat and a clear topcoat, wherein the undercoat comprises a radiation curable oligomer, an extender and a colourant, and wherein the topcoat comprises an urethane acrylate oligomer and a hydrocarbon acrylate diluent.
In a further aspect, the present invention provides a method of repairing a surface defect on a glazed ceramic article comprising the steps of coating or hiding a surface defect of a glazed ceramic article with a coating composition comprising a radiation curable oligomer, an extender;
aluminum hydroxide and titanium dioxide and curing the composition with an energy source.
In yet another aspect, the present invention provides a method of repairing a surface defect on a glazed ceramic article comprising the steps of coating or hiding the surface defect with an undercoat comprising a radiation curable oligomer, an extender, aluminum hydroxide and titanium dioxide, curing the undercoat with a first energy source, applying a topcoat to the cured undercoat, the topcoat including an urethane acrylate oligomer and a hydrocarbon acrylate dilment, and curing the topcoat with a second energy source. The first and second energy sources can be ultraviolet light.
In a further aspect, the present invention provides a method of repairing a surface defect on a glazed ceramic article comprising the steps of coating or hiding the surface defect with an undercoat comprising a radiation curable oligomer, an extender and a colourant, curing the undercoat with a first energy source, applying a topcoat to the undercoat, the topcoat including an urethane acrylate oligomer and a hydrocarbon acrylate diluent, and curing the topcoat with a second energy source. The first and second energy sources can be ultraviolet light.
Detailed Description The present invention provides a white coating composition comprising a radiation curable oligomer, an extender or filler, aluminum hydroxide and titanium dioxide.
In one embodiment, the radiation curable oligomer is a polyether acrylate or an urethane acrylate. Preferably, the radiation curable oligomer is a polyether acrylate having a viscosity greater than 220 mPa/s, and even more preferably between 220 - 400 mPa/s. Although small amounts of monomer could be in the coating composition, it is preferable that the coating composition includes substantially no monomer.
Suitable extenders or fillers include barium sulfate, magnesium silicate, and silica oxides.
The extenders or fillers enhance the optical effect of the coating composition.
Preferably, the aluminum hydroxide is refined from gibbsite. The structure of gibbsite is analogous to the basic structure of micas. In particular, the gibbsite structure is formed of stacked sheets of linked octahedrons of aluminum hydroxide. Preferably, the aluminum hydroxide is characterized by a particle size less than 1.5 ~cm.
Preferably, the titanium dioxide is of the ruble grade. Titanium dioxide is used to impart a white colour to the coating composition. Other compounds which could be substituted for titanium dioxide and provide the desired whiteness include lead oxide and zinc sulfide.
_ 'J _ Where the white coating composition is to be cured by ultraviolet light, a photoinitiator is provided. The photoinitiator includes a blend of an aromatic ketone and phosphine oxide. The aromatic ketone can include benzophenone, methyl-o-benzoyl benzoate and 2-isopropyl thioxanthone. The aromatic ketone is a surface curing agent. The phosphine oxide is provided to obtain desired depth of cure. A cationic curing agent, comprising iodonium or sulfonium salts, could also be used as a photoinitiator where the coating composition is cured by ultraviolet light.
Optionally, the coating composition could also be cured using excimer laser, requiring the coating composition to include excimer laser sensitive photoinitiators such as benzoketals. Alternatively, the coating composition can be cured using electron beam technology, which would altogether eliminate the necessity for a photoinitiator.
Optionally, the coating composition could include a dispersant. A suitable dispersant includes solutions of polycarboxylic acid salt of polyamine amides or solutions of high molecular weight block co-polymers with pigment affinic groups. The dispersant could also include any of solutions of alkyl-ammonium salt of an acidic polymer, solutions of salt of unsaturated polyamine amide and lower molecular weight acid polymer, solutions of salt of polyamine amides and a polar acidic ester, solutions of hydroxy-functional carboxylic acid ester with pigment affinic group, solutions of unsaturated poly-carboxylic acid polymer, solutions of alkylammonium salt of a poly-carboxylic acid, solutions of alkanolammonium salt of an unsaturated fatty acid, and solutions of unsaturated acidic polycarboxylic acid polyester.
In a preferred embodiment, the white coating composition of the present invention comprises from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate, from about 0.25 to about 3.0 percent by weight, based on the total weight of the _$_ composition, of a dispersant, from about 10 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate, from about 10 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate, from about 0.5 to about 20 percent by weight, based on the total weight of the composition, of aluminum hydroxide, from about 3 to about 6 percent by weight, based on the total weight of the composition, of titanium dioxide, from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide, and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
In another embodiment, the white coating composition of the present invention comprises a binder and a pigment. The pigment includes a radiation curable oligomer and an extender or filler.
The pigment includes aluminum hydroxide and titanium dioxide. The binder can also include a photoinitiator and/or a dispersant. The pigment and the binder of the white coating composition can be combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
More preferably, the pigment and the binder are combined in a ratio in the range of from about 4:1 to about 6:1 by volume. Even more preferably, the pigment and the binder are combined in a ratio of about 4:1 by volume.
In another embodiment, a coloured coating composition is provided comprising a radiation curable oligomer, an extender or filler, and a colourant. In one embodiment, the radiation curable oligomer is a polyether acrylate or urethane acrylate. More preferably, the radiation curable oligomer is a polyether acrylate having a viscosity greater than 220 mPa/s, and even more preferably between 220 - 400 mPa/s. Although small amounts of monomer could be used in the coating composition, it is preferable that the coating composition includes substantially no monomer.
Suitable extenders or fillers include barium sulfate, magnesium silicate, and silica oxides.
The colourant is used to impart colour to the coating composition. Depending on the desired colour, different colourants can be used in the coating composition to match the colour of the surrounding ceramic glaze. Colourants include opaque pigments, semi-transparent pigments and dyes.
Acceptable colourants include pearlescent pigments. Suitable pearlescent pigments are mica coated with an oxide from the group including TiOz, Zr02, Sn02, ZnO, Fe203, Cr203 and VZOS, or mixtures of two or more of said oxides. Mica as used herein is an all encompassing term for a class of naturally occurring minerals, all of which possess a scaly, plate-like crystal structure. Examples of mica include muscovite, phlogopite and biotite. Preferably, the mica particles are characterized by a particle size within the range of from about 5 ~cm to about 200 ,um.
Acceptable pearlescent pigments include the AFFLAIRT"' line of pearlescent pigments manufactured by BDH Chemicals, including, AFFLAIRT~~ 120, AFFLAIRTM 121, AFFLAIRTM 163, AFFLAIRT"~ 205, AFFLAIRT"~ 215 and AFFLAIRTM 225. Other acceptable pearlescent pigments include the MEARLINTM
line of pearlescent pigments manufactured by Engelhard Corporation such as MEARLINTM
Super Blue 6392. Other colourants which could be used to obtain a pearlescent effect include bismuth oxychloride, lead hydrogen arsenate, and lead carbonate.
Other acceptable colourants include tinting paste comprising pigments such as aryl red or Pigment Red 170, carbon black or Pigment Black 7, medium yellow or Pigment Yellow 151 or Pigment Yellow 83, phtalo blue or Pigment Blue 15:1, and quinacridone red or Pigment Violet 19.
Where the white coating composition is to be cured by ultraviolet light, a photoinitiator is provided. The photoinitiator includes a blend of an aromatic ketone and phosphine oxide. The aromatic ketone can include benzophenone, methyl-o-benzoyl benzoate and 2-isopropyl thioxanthone. The aromatic ketone is a surface curing agent. The phosphine oxide is provided to obtain desired depth of cure. A cationic curing agent, comprising iodonium or sulfonium salts, could also be used as a photoinitiator where the coating composition is cured by ultraviolet light.
Optionally, the coating composition could also be cured using excimer laser, requiring the coating composition to include excimer laser sensitive photoinitiators such as benzoketals. Alternatively, the coating composition can be cured using electron beam technology, which would altogether eliminate the necessity for a photoinitiator.
Optionally, the coating composition could include a dispersant. A preferred dispersant includes solutions of polycarboxylic acid salt of polyamine amides or solutions of high molecular weight block co-polymers with pigment affinic groups. A suitable dispersant could also include any of solutions of alkyl-ammonium salt of an acidic polymer, solutions of salt of unsaturated polyamine amide and lower molecular weight acid polymer, solutions of salt of polyamine amides and a polar acidic ester, solutions of hydroxy-functional carboxylic acid ester with pigment affinic group, solutions of unsaturated poly-carboxylic acid polymer, solutions of alkylammonium salt of a poly-carboxylic acid, solutions of alkanolammonium salt of an unsaturated fatty acid and solutions of unsaturated acidic polycarboxylic acid polyester.
In a preferred embodiment, the coloured coating composition of the present invention comprises from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate, from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant, from about 15 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate, from about 15 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate, from about 1 to about percent by weight, based on the total weight of the composition, of a colourant, from about 0.25 5 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide, and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
In another embodiment, the coloured coating composition of the present invention comprises a binder and a pigment. The pigment includes a radiation curable oligomer and an extender or filler.
10 The pigment includes aluminum hydroxide and titanium dioxide. The binder can also include a photoinitiator and/or a dispersant. The pigment and the binder of the coloured coating composition can be combined in a ratio in the range of from about 3:1 to about 10:1 by volume. More preferably, the pigment and the binder are combined in a ratio in the range of from about 4:1 to about 6:1 by volume. Even more preferably, the pigment and the binder are combined in a ratio of about 4:1 by volume.
In a further embodiment, the coating composition comprises an undercoat, of the white coating composition or the coloured coating composition described above, and a clear topcoat. The clear topcoat, when applied on the associated undercoat, enhances the aesthetic appearance of the coating composition. The clear topcoat comprises an urethane acrylate oligomer and a hydrocarbon acrylate diluent.
Where the coating composition having an undercoat and topcoat is to be cured by ultraviolet light, a photoinitiator can be provided. The photoinitiator includes a blend of an axomatic ketone and phosphine oxide. The aromatic ketone can include benzophenone, methyl-o-benzoyl benzoate and 2-isopropyl thioxanthone. The aromatic ketone is a surface curing agent.
The phosphine oxide is provided to obtain desired depth of cure. A cationic curing agent, comprising iodonium or sulfonium salts, could also be used as a photoinitiator where the coating composition is cured by ultraviolet light. Optionally, the coating composition could also be cured using excimer laser, requiring the coating composition to include excimer laser compatible photoinitiator such as benzoketals. Alternatively, the coating composition can be cured using electron beam technology, which would altogether eliminate the necessity for a photoinitiator.
In a preferred embodiment, the topcoat comprises from about 56 to about 95 percent by weight, based on the total weight of the composition, of an urethane acrylate oligomer. The topcoat also comprises from about 5 to about 40 percent by weight, based on the total weight of the composition, of an hydrocarbon acrylate diluent, from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide, and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
Any of the embodiments of the coating composition of the present invention can be applied to a surface defect of a fired ceramic substrate, and then cured using ultraviolet light, an electron beam, or an excimer laser.
The present invention also provides a method of repairing surface defects on glazed ceramic articles. In one embodiment, the glazed ceramic article has been previously fired. The method comprises the steps of (i) coating or hiding a surface defect of a glazed ceramic article with a white coating composition or a coloured coating composition, and (ii) curing the composition with an energy source. The white coating composition can comprise any of the previously described embodiments of the white coating composition of the present invention.
Similarly, the coloured coating composition can comprise any of the previously described embodiments of the coloured coating composition of the present invention.
The energy source can be an ultraviolet light source, an electron beam, an excimer laser, or a cationic curing agent. Where the energy source is an ultraviolet light source, the white or coloured coating composition comprises a photoinitiator including a blend of an aromatic ketone and phosphine oxide. Another suitable photoinitiator, in this case, is a catonic curing agent. Where the energy source is an excimer laser, the white or coloured coating composition must also comprise an excimer laser sensitive photoinitiator such as a benzoketal. Where the energy source is an electron beam, the white or coloured coating composition requires no photoinitiator.
In another embodiment, the present invention provides a method of repairing surface defects on glazed ceramic articles comprising the steps of (i) coating or hiding a surface defect of a glazed ceramic article with an undercoat of a white coating composition or a coloured coating composition, (ii) curing the undercoat with a first energy source, (iii) applying a topcoat to the cured undercoat, and (iv) curing the topcoat with a second energy source. The white coating composition can comprise any of the previously described embodiments of the white coating composition of the present invention. Similarly, the coloured coating composition can comprise any of the previously described embodiments of the coloured coating composition of the present invention. Also, the clear topcoat composition can comprise any of the previously described embodiments of the topcoat composition of the present invention. The first and second energy sources can be any of those mentioned above. In one embodiment, the glazed ceramic article has been previously fired.
The present invention will be described in further detail with reference to the following non-limitative examples.
Example 1 A coating composition comprising the compounds identified in Table 1 was applied to surface imperfections on a glazed ceramic substrate.
Table 1 . Compound - Percent Weight oligomer 50 monomer 3 6 photoinitiator 4 extender/flattening10 agent The coating composition was cured using a Fusion System Model 450 ultraviolet light source. It was observed that the resultant cured coating failed to adhere to the ceramic substrate.
Further, it was observed that the monomers tended to boil out, leaving a greasy residue on the coating surface.
Example 2 A coating composition was formulated comprising 98 percent by weight, based on the total weight of the composition, of an oligomer, 1 percent by weight, based on the total weight of the composition, of phosphine oxide, and 1 percent by weight, based on the total weight of the composition, of alpha-hydroxy ketone. Several oligomers were tested, namely:
epoxy acrylate, methacrylate acid ester, polyester acrylates and polyether acrylates.
Each of the formulation coating compositions were applied to a ceramic substrate and were cured using a Fusion System Model 450 ultraviolet light source. The coatings were tested for adhesion, discolouration, thermal stability, water soak, aesthetics, resistance to alcohol and chlorines, and resistance to staining from Fuchsin Basic. The adhesion characteristics and aesthetic characteristics of each of the cured coatings containing the various oligomers tested are described in Table 2.
Table 2 Oligomer ' Viscosity Observations (cps) bisphenol-A epoxy > 50,000 yellowed on curing Amine modified bisphenol-A > 50,000 yellowed on epoxy curing Bisphenol A epoxy acrylate > 50,000 yellowed on curing Methacrylate Acid Ester 1500 no adhesion Amine modified polyester acrylate3000 yellowed on curing Polyester acrylate 3500 - 6300 no adhesion Polyester acrylate 100 - 3500 no adhesion Polyester acrylate 30,000 - 55,000no adhesion Polyether acrylate 130 - 220 no adhesion Polyether acrylate 200 - 400 Acceptable curing Of the oligomers tested above, a polyether acrylate would appear to be a suitable candidate.
In particular, a polyether acrylate characterized by a viscosity of greater than 220 cps would appear to be a suitable candidate. A polyether acrylate characterized by a viscosity between 220 cps and 400 cps would appear to be particularly suitable.
Based on similarities between polyether acrylates and urethane acrylates, namely features of low viscosity, high elasticity and low shrinkage, an urethane acrylate would also appear to be a suitable candidate for inclusion in the coating composition of the present invention.
Exam. lp a 3 A coating composition was formulated comprising 60 percent by weight, based on the total weight of the composition, of polyether acrylate, 2.5 percent by weight, based on the total weight of the composition, of dispersant, about 5 to about 20 percent by weight, based on the total weight of the composition, of a filler, 1 percent by weight, based on the total weight of the composition, of phosphine oxide, and 1 percent by weight, based on the total weight of the composition, of alpha hydroxy ketone. Several fillers were tested, namely: calcium carbonate, aluminum hydrate, anahydrous sodium potassium aluminum silicate, hydrated aluminium silicate, aluminium oxide, barium sulfate, and magnesium silicate.
Each of the coating compositions, containing the different fillers tested, were applied to a ceramic substrate and were subjected to a Fusion System Model 450 ultraviolet light source. The adhesion characteristics and curing characteristics of each of the formulations having different fillers were evaluated. The observations made regarding these characteristics are identified in Table 3.
- 1~ -Table 3 Filler Type Observations calcium carbonate no adhesion aluminium hydrate shrinks back anahydrous sodium potassiuminhibits curing aluminum silicate hydrated aluminium silicateinhibits curing aluminium oxide good curing and adhesion barium sulfate good curing and adhesion magnesium silicate good curing and adhesion Therefore, of the fillers tested, aluminum oxide, barium sulfate, and magnesium silicate appear to be acceptable candidates for the coating composition of the present invention.
Example 4 A coating composition was formulated comprising 60 percent by weight, based on the total weight of the composition, of polyether acrylate, 2.5 percent by weight, based on the total weight of the composition, of dispersant, 20 percent by weight, based on the total weight of the composition of the barium sulphate, 20 percent by weight, based on the total weight of the composition, of magnesium silicate, and 1.0 to 2.5 percent by weight, based on the total weight of the composition, of a photoinitiator. Several photoinitiators were tested, including blends of individual photoinitiators.
Each of the coating compositions, containing the different photoinitiators tested, were applied to a ceramic substrate and were subjected to ultraviolet light from an Novacure UV Spot Care EFOS
100 SS Lamp. The adhesion characteristics and curing characteristics of each of the different formulations having different photoinitiators were evaluated. The observations made regarding these characteristics are identified in Table 4.
Table 4 Photoinitiators Observations -hydroxy ketone no adhesion -hydroxy ketone/ no adhesion benzophenone benzophenone no adhesion but surface cured benzyl dimethyl ketone no adhesion phosphine oxide no adhesion or adhesion with sticky surface phosphine oxide/ adhesion with cured benzophenone surface Of the photoinitiators tested, it would appear that a photoinitiator comprising a blend of phosphine oxide and benzophenone would be suitable for the coating composition of the present invention.
Example 5 White coating compositions were formulated comprising the compounds identified in Table 5.
Table 5 Compound Percentage V~eight Polyether acrylate60.0 Dispersant 2.5 Barium sulphate 10 - 20 Magnesium silicate10 - 20 Titanium dioxide5.0 -15.0 Phosphine oxide 0.5 Benzophenone 1.0 The titanium dioxide used was of the rutile grade. The ruble titanium dioxide was included with a view to imparting a white colour to the coating composition and with a view to matching the aesthetic appearance of a glaze. The coating compositions that were tested included varying levels of rutile titanium dioxide, namely between 5 and 15 weight percent.
Each of the coating compositions, containing different levels of rutile titanium dioxide, were applied to a ceramic substrate and cured using an ultraviolet light source. It was observed that the ruble titanium dioxide did not impart the desired optical effects characteristic of a ceramic glaze.
A second formulation was created, comprising the compounds identified in Table 6.
Table 6 Compounds Percentage Weight Polyether acrylate60.0 Dispersant 2.5 Barium sulphate 10 - 20 Magnesium silicate10 - 20 Aluminium hydroxide0.5 - 10.0 Titanium dioxide 5.0 Phosphine oxide 0.5 Benzophenone 1.0 The aluminum hydroxide was refined from gibbsite and was characterized by a particle size distribution between 0.015 and 1.5 ,um.
Each of the coating compositions was applied to a ceramic substrate and cured using ultraviolet light. The cured coating compositions, containing the aluminum hydroxide, were found to resemble the appearance of ceramic glaze. In comparison to the compositions defined in Table 5, the coating compositions having the aluminum hydroxide were found to impart superior overall whiteness. Further, the cured coating compositions having aluminum hydroxide were able to provide a three-dimensional appearance which was not able to be achieved with the coating compositions defined in Table 5.
It would appear, therefore, that inclusion of an aluminum hydroxide in the white coating composition is necessary to provide the appearance of a ceramic glaze.
It will be understood, of course, that modifications can be made in the embodiments of the invention described herein without departing from the scope and purview of the invention as defined by the appended claims.
In yet even a further aspect, the present invention provides a coating composition for application to a ceramic substrate comprising an undercoat and a clear topcoat, wherein the undercoat comprises a radiation curable oligomer, an extender and a colourant, and wherein the topcoat comprises an urethane acrylate oligomer and a hydrocarbon acrylate diluent.
In a further aspect, the present invention provides a method of repairing a surface defect on a glazed ceramic article comprising the steps of coating or hiding a surface defect of a glazed ceramic article with a coating composition comprising a radiation curable oligomer, an extender;
aluminum hydroxide and titanium dioxide and curing the composition with an energy source.
In yet another aspect, the present invention provides a method of repairing a surface defect on a glazed ceramic article comprising the steps of coating or hiding the surface defect with an undercoat comprising a radiation curable oligomer, an extender, aluminum hydroxide and titanium dioxide, curing the undercoat with a first energy source, applying a topcoat to the cured undercoat, the topcoat including an urethane acrylate oligomer and a hydrocarbon acrylate dilment, and curing the topcoat with a second energy source. The first and second energy sources can be ultraviolet light.
In a further aspect, the present invention provides a method of repairing a surface defect on a glazed ceramic article comprising the steps of coating or hiding the surface defect with an undercoat comprising a radiation curable oligomer, an extender and a colourant, curing the undercoat with a first energy source, applying a topcoat to the undercoat, the topcoat including an urethane acrylate oligomer and a hydrocarbon acrylate diluent, and curing the topcoat with a second energy source. The first and second energy sources can be ultraviolet light.
Detailed Description The present invention provides a white coating composition comprising a radiation curable oligomer, an extender or filler, aluminum hydroxide and titanium dioxide.
In one embodiment, the radiation curable oligomer is a polyether acrylate or an urethane acrylate. Preferably, the radiation curable oligomer is a polyether acrylate having a viscosity greater than 220 mPa/s, and even more preferably between 220 - 400 mPa/s. Although small amounts of monomer could be in the coating composition, it is preferable that the coating composition includes substantially no monomer.
Suitable extenders or fillers include barium sulfate, magnesium silicate, and silica oxides.
The extenders or fillers enhance the optical effect of the coating composition.
Preferably, the aluminum hydroxide is refined from gibbsite. The structure of gibbsite is analogous to the basic structure of micas. In particular, the gibbsite structure is formed of stacked sheets of linked octahedrons of aluminum hydroxide. Preferably, the aluminum hydroxide is characterized by a particle size less than 1.5 ~cm.
Preferably, the titanium dioxide is of the ruble grade. Titanium dioxide is used to impart a white colour to the coating composition. Other compounds which could be substituted for titanium dioxide and provide the desired whiteness include lead oxide and zinc sulfide.
_ 'J _ Where the white coating composition is to be cured by ultraviolet light, a photoinitiator is provided. The photoinitiator includes a blend of an aromatic ketone and phosphine oxide. The aromatic ketone can include benzophenone, methyl-o-benzoyl benzoate and 2-isopropyl thioxanthone. The aromatic ketone is a surface curing agent. The phosphine oxide is provided to obtain desired depth of cure. A cationic curing agent, comprising iodonium or sulfonium salts, could also be used as a photoinitiator where the coating composition is cured by ultraviolet light.
Optionally, the coating composition could also be cured using excimer laser, requiring the coating composition to include excimer laser sensitive photoinitiators such as benzoketals. Alternatively, the coating composition can be cured using electron beam technology, which would altogether eliminate the necessity for a photoinitiator.
Optionally, the coating composition could include a dispersant. A suitable dispersant includes solutions of polycarboxylic acid salt of polyamine amides or solutions of high molecular weight block co-polymers with pigment affinic groups. The dispersant could also include any of solutions of alkyl-ammonium salt of an acidic polymer, solutions of salt of unsaturated polyamine amide and lower molecular weight acid polymer, solutions of salt of polyamine amides and a polar acidic ester, solutions of hydroxy-functional carboxylic acid ester with pigment affinic group, solutions of unsaturated poly-carboxylic acid polymer, solutions of alkylammonium salt of a poly-carboxylic acid, solutions of alkanolammonium salt of an unsaturated fatty acid, and solutions of unsaturated acidic polycarboxylic acid polyester.
In a preferred embodiment, the white coating composition of the present invention comprises from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate, from about 0.25 to about 3.0 percent by weight, based on the total weight of the _$_ composition, of a dispersant, from about 10 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate, from about 10 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate, from about 0.5 to about 20 percent by weight, based on the total weight of the composition, of aluminum hydroxide, from about 3 to about 6 percent by weight, based on the total weight of the composition, of titanium dioxide, from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide, and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
In another embodiment, the white coating composition of the present invention comprises a binder and a pigment. The pigment includes a radiation curable oligomer and an extender or filler.
The pigment includes aluminum hydroxide and titanium dioxide. The binder can also include a photoinitiator and/or a dispersant. The pigment and the binder of the white coating composition can be combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
More preferably, the pigment and the binder are combined in a ratio in the range of from about 4:1 to about 6:1 by volume. Even more preferably, the pigment and the binder are combined in a ratio of about 4:1 by volume.
In another embodiment, a coloured coating composition is provided comprising a radiation curable oligomer, an extender or filler, and a colourant. In one embodiment, the radiation curable oligomer is a polyether acrylate or urethane acrylate. More preferably, the radiation curable oligomer is a polyether acrylate having a viscosity greater than 220 mPa/s, and even more preferably between 220 - 400 mPa/s. Although small amounts of monomer could be used in the coating composition, it is preferable that the coating composition includes substantially no monomer.
Suitable extenders or fillers include barium sulfate, magnesium silicate, and silica oxides.
The colourant is used to impart colour to the coating composition. Depending on the desired colour, different colourants can be used in the coating composition to match the colour of the surrounding ceramic glaze. Colourants include opaque pigments, semi-transparent pigments and dyes.
Acceptable colourants include pearlescent pigments. Suitable pearlescent pigments are mica coated with an oxide from the group including TiOz, Zr02, Sn02, ZnO, Fe203, Cr203 and VZOS, or mixtures of two or more of said oxides. Mica as used herein is an all encompassing term for a class of naturally occurring minerals, all of which possess a scaly, plate-like crystal structure. Examples of mica include muscovite, phlogopite and biotite. Preferably, the mica particles are characterized by a particle size within the range of from about 5 ~cm to about 200 ,um.
Acceptable pearlescent pigments include the AFFLAIRT"' line of pearlescent pigments manufactured by BDH Chemicals, including, AFFLAIRT~~ 120, AFFLAIRTM 121, AFFLAIRTM 163, AFFLAIRT"~ 205, AFFLAIRT"~ 215 and AFFLAIRTM 225. Other acceptable pearlescent pigments include the MEARLINTM
line of pearlescent pigments manufactured by Engelhard Corporation such as MEARLINTM
Super Blue 6392. Other colourants which could be used to obtain a pearlescent effect include bismuth oxychloride, lead hydrogen arsenate, and lead carbonate.
Other acceptable colourants include tinting paste comprising pigments such as aryl red or Pigment Red 170, carbon black or Pigment Black 7, medium yellow or Pigment Yellow 151 or Pigment Yellow 83, phtalo blue or Pigment Blue 15:1, and quinacridone red or Pigment Violet 19.
Where the white coating composition is to be cured by ultraviolet light, a photoinitiator is provided. The photoinitiator includes a blend of an aromatic ketone and phosphine oxide. The aromatic ketone can include benzophenone, methyl-o-benzoyl benzoate and 2-isopropyl thioxanthone. The aromatic ketone is a surface curing agent. The phosphine oxide is provided to obtain desired depth of cure. A cationic curing agent, comprising iodonium or sulfonium salts, could also be used as a photoinitiator where the coating composition is cured by ultraviolet light.
Optionally, the coating composition could also be cured using excimer laser, requiring the coating composition to include excimer laser sensitive photoinitiators such as benzoketals. Alternatively, the coating composition can be cured using electron beam technology, which would altogether eliminate the necessity for a photoinitiator.
Optionally, the coating composition could include a dispersant. A preferred dispersant includes solutions of polycarboxylic acid salt of polyamine amides or solutions of high molecular weight block co-polymers with pigment affinic groups. A suitable dispersant could also include any of solutions of alkyl-ammonium salt of an acidic polymer, solutions of salt of unsaturated polyamine amide and lower molecular weight acid polymer, solutions of salt of polyamine amides and a polar acidic ester, solutions of hydroxy-functional carboxylic acid ester with pigment affinic group, solutions of unsaturated poly-carboxylic acid polymer, solutions of alkylammonium salt of a poly-carboxylic acid, solutions of alkanolammonium salt of an unsaturated fatty acid and solutions of unsaturated acidic polycarboxylic acid polyester.
In a preferred embodiment, the coloured coating composition of the present invention comprises from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate, from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant, from about 15 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate, from about 15 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate, from about 1 to about percent by weight, based on the total weight of the composition, of a colourant, from about 0.25 5 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide, and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
In another embodiment, the coloured coating composition of the present invention comprises a binder and a pigment. The pigment includes a radiation curable oligomer and an extender or filler.
10 The pigment includes aluminum hydroxide and titanium dioxide. The binder can also include a photoinitiator and/or a dispersant. The pigment and the binder of the coloured coating composition can be combined in a ratio in the range of from about 3:1 to about 10:1 by volume. More preferably, the pigment and the binder are combined in a ratio in the range of from about 4:1 to about 6:1 by volume. Even more preferably, the pigment and the binder are combined in a ratio of about 4:1 by volume.
In a further embodiment, the coating composition comprises an undercoat, of the white coating composition or the coloured coating composition described above, and a clear topcoat. The clear topcoat, when applied on the associated undercoat, enhances the aesthetic appearance of the coating composition. The clear topcoat comprises an urethane acrylate oligomer and a hydrocarbon acrylate diluent.
Where the coating composition having an undercoat and topcoat is to be cured by ultraviolet light, a photoinitiator can be provided. The photoinitiator includes a blend of an axomatic ketone and phosphine oxide. The aromatic ketone can include benzophenone, methyl-o-benzoyl benzoate and 2-isopropyl thioxanthone. The aromatic ketone is a surface curing agent.
The phosphine oxide is provided to obtain desired depth of cure. A cationic curing agent, comprising iodonium or sulfonium salts, could also be used as a photoinitiator where the coating composition is cured by ultraviolet light. Optionally, the coating composition could also be cured using excimer laser, requiring the coating composition to include excimer laser compatible photoinitiator such as benzoketals. Alternatively, the coating composition can be cured using electron beam technology, which would altogether eliminate the necessity for a photoinitiator.
In a preferred embodiment, the topcoat comprises from about 56 to about 95 percent by weight, based on the total weight of the composition, of an urethane acrylate oligomer. The topcoat also comprises from about 5 to about 40 percent by weight, based on the total weight of the composition, of an hydrocarbon acrylate diluent, from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide, and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
Any of the embodiments of the coating composition of the present invention can be applied to a surface defect of a fired ceramic substrate, and then cured using ultraviolet light, an electron beam, or an excimer laser.
The present invention also provides a method of repairing surface defects on glazed ceramic articles. In one embodiment, the glazed ceramic article has been previously fired. The method comprises the steps of (i) coating or hiding a surface defect of a glazed ceramic article with a white coating composition or a coloured coating composition, and (ii) curing the composition with an energy source. The white coating composition can comprise any of the previously described embodiments of the white coating composition of the present invention.
Similarly, the coloured coating composition can comprise any of the previously described embodiments of the coloured coating composition of the present invention.
The energy source can be an ultraviolet light source, an electron beam, an excimer laser, or a cationic curing agent. Where the energy source is an ultraviolet light source, the white or coloured coating composition comprises a photoinitiator including a blend of an aromatic ketone and phosphine oxide. Another suitable photoinitiator, in this case, is a catonic curing agent. Where the energy source is an excimer laser, the white or coloured coating composition must also comprise an excimer laser sensitive photoinitiator such as a benzoketal. Where the energy source is an electron beam, the white or coloured coating composition requires no photoinitiator.
In another embodiment, the present invention provides a method of repairing surface defects on glazed ceramic articles comprising the steps of (i) coating or hiding a surface defect of a glazed ceramic article with an undercoat of a white coating composition or a coloured coating composition, (ii) curing the undercoat with a first energy source, (iii) applying a topcoat to the cured undercoat, and (iv) curing the topcoat with a second energy source. The white coating composition can comprise any of the previously described embodiments of the white coating composition of the present invention. Similarly, the coloured coating composition can comprise any of the previously described embodiments of the coloured coating composition of the present invention. Also, the clear topcoat composition can comprise any of the previously described embodiments of the topcoat composition of the present invention. The first and second energy sources can be any of those mentioned above. In one embodiment, the glazed ceramic article has been previously fired.
The present invention will be described in further detail with reference to the following non-limitative examples.
Example 1 A coating composition comprising the compounds identified in Table 1 was applied to surface imperfections on a glazed ceramic substrate.
Table 1 . Compound - Percent Weight oligomer 50 monomer 3 6 photoinitiator 4 extender/flattening10 agent The coating composition was cured using a Fusion System Model 450 ultraviolet light source. It was observed that the resultant cured coating failed to adhere to the ceramic substrate.
Further, it was observed that the monomers tended to boil out, leaving a greasy residue on the coating surface.
Example 2 A coating composition was formulated comprising 98 percent by weight, based on the total weight of the composition, of an oligomer, 1 percent by weight, based on the total weight of the composition, of phosphine oxide, and 1 percent by weight, based on the total weight of the composition, of alpha-hydroxy ketone. Several oligomers were tested, namely:
epoxy acrylate, methacrylate acid ester, polyester acrylates and polyether acrylates.
Each of the formulation coating compositions were applied to a ceramic substrate and were cured using a Fusion System Model 450 ultraviolet light source. The coatings were tested for adhesion, discolouration, thermal stability, water soak, aesthetics, resistance to alcohol and chlorines, and resistance to staining from Fuchsin Basic. The adhesion characteristics and aesthetic characteristics of each of the cured coatings containing the various oligomers tested are described in Table 2.
Table 2 Oligomer ' Viscosity Observations (cps) bisphenol-A epoxy > 50,000 yellowed on curing Amine modified bisphenol-A > 50,000 yellowed on epoxy curing Bisphenol A epoxy acrylate > 50,000 yellowed on curing Methacrylate Acid Ester 1500 no adhesion Amine modified polyester acrylate3000 yellowed on curing Polyester acrylate 3500 - 6300 no adhesion Polyester acrylate 100 - 3500 no adhesion Polyester acrylate 30,000 - 55,000no adhesion Polyether acrylate 130 - 220 no adhesion Polyether acrylate 200 - 400 Acceptable curing Of the oligomers tested above, a polyether acrylate would appear to be a suitable candidate.
In particular, a polyether acrylate characterized by a viscosity of greater than 220 cps would appear to be a suitable candidate. A polyether acrylate characterized by a viscosity between 220 cps and 400 cps would appear to be particularly suitable.
Based on similarities between polyether acrylates and urethane acrylates, namely features of low viscosity, high elasticity and low shrinkage, an urethane acrylate would also appear to be a suitable candidate for inclusion in the coating composition of the present invention.
Exam. lp a 3 A coating composition was formulated comprising 60 percent by weight, based on the total weight of the composition, of polyether acrylate, 2.5 percent by weight, based on the total weight of the composition, of dispersant, about 5 to about 20 percent by weight, based on the total weight of the composition, of a filler, 1 percent by weight, based on the total weight of the composition, of phosphine oxide, and 1 percent by weight, based on the total weight of the composition, of alpha hydroxy ketone. Several fillers were tested, namely: calcium carbonate, aluminum hydrate, anahydrous sodium potassium aluminum silicate, hydrated aluminium silicate, aluminium oxide, barium sulfate, and magnesium silicate.
Each of the coating compositions, containing the different fillers tested, were applied to a ceramic substrate and were subjected to a Fusion System Model 450 ultraviolet light source. The adhesion characteristics and curing characteristics of each of the formulations having different fillers were evaluated. The observations made regarding these characteristics are identified in Table 3.
- 1~ -Table 3 Filler Type Observations calcium carbonate no adhesion aluminium hydrate shrinks back anahydrous sodium potassiuminhibits curing aluminum silicate hydrated aluminium silicateinhibits curing aluminium oxide good curing and adhesion barium sulfate good curing and adhesion magnesium silicate good curing and adhesion Therefore, of the fillers tested, aluminum oxide, barium sulfate, and magnesium silicate appear to be acceptable candidates for the coating composition of the present invention.
Example 4 A coating composition was formulated comprising 60 percent by weight, based on the total weight of the composition, of polyether acrylate, 2.5 percent by weight, based on the total weight of the composition, of dispersant, 20 percent by weight, based on the total weight of the composition of the barium sulphate, 20 percent by weight, based on the total weight of the composition, of magnesium silicate, and 1.0 to 2.5 percent by weight, based on the total weight of the composition, of a photoinitiator. Several photoinitiators were tested, including blends of individual photoinitiators.
Each of the coating compositions, containing the different photoinitiators tested, were applied to a ceramic substrate and were subjected to ultraviolet light from an Novacure UV Spot Care EFOS
100 SS Lamp. The adhesion characteristics and curing characteristics of each of the different formulations having different photoinitiators were evaluated. The observations made regarding these characteristics are identified in Table 4.
Table 4 Photoinitiators Observations -hydroxy ketone no adhesion -hydroxy ketone/ no adhesion benzophenone benzophenone no adhesion but surface cured benzyl dimethyl ketone no adhesion phosphine oxide no adhesion or adhesion with sticky surface phosphine oxide/ adhesion with cured benzophenone surface Of the photoinitiators tested, it would appear that a photoinitiator comprising a blend of phosphine oxide and benzophenone would be suitable for the coating composition of the present invention.
Example 5 White coating compositions were formulated comprising the compounds identified in Table 5.
Table 5 Compound Percentage V~eight Polyether acrylate60.0 Dispersant 2.5 Barium sulphate 10 - 20 Magnesium silicate10 - 20 Titanium dioxide5.0 -15.0 Phosphine oxide 0.5 Benzophenone 1.0 The titanium dioxide used was of the rutile grade. The ruble titanium dioxide was included with a view to imparting a white colour to the coating composition and with a view to matching the aesthetic appearance of a glaze. The coating compositions that were tested included varying levels of rutile titanium dioxide, namely between 5 and 15 weight percent.
Each of the coating compositions, containing different levels of rutile titanium dioxide, were applied to a ceramic substrate and cured using an ultraviolet light source. It was observed that the ruble titanium dioxide did not impart the desired optical effects characteristic of a ceramic glaze.
A second formulation was created, comprising the compounds identified in Table 6.
Table 6 Compounds Percentage Weight Polyether acrylate60.0 Dispersant 2.5 Barium sulphate 10 - 20 Magnesium silicate10 - 20 Aluminium hydroxide0.5 - 10.0 Titanium dioxide 5.0 Phosphine oxide 0.5 Benzophenone 1.0 The aluminum hydroxide was refined from gibbsite and was characterized by a particle size distribution between 0.015 and 1.5 ,um.
Each of the coating compositions was applied to a ceramic substrate and cured using ultraviolet light. The cured coating compositions, containing the aluminum hydroxide, were found to resemble the appearance of ceramic glaze. In comparison to the compositions defined in Table 5, the coating compositions having the aluminum hydroxide were found to impart superior overall whiteness. Further, the cured coating compositions having aluminum hydroxide were able to provide a three-dimensional appearance which was not able to be achieved with the coating compositions defined in Table 5.
It would appear, therefore, that inclusion of an aluminum hydroxide in the white coating composition is necessary to provide the appearance of a ceramic glaze.
It will be understood, of course, that modifications can be made in the embodiments of the invention described herein without departing from the scope and purview of the invention as defined by the appended claims.
Claims (34)
1. A coating composition for application to a ceramic substrate comprising a radiation curable oligomer, an extender, aluminum hydroxide and titanium dioxide.
2. The coating composition as claimed in claim 1 wherein the aluminum hydroxide is refined from gibbsite.
3. The coating composition as claimed in claim 2 wherein the aluminum hydroxide is characterized by a particle size of less than about 1.5 µm.
4. The coating composition as claimed in claim 1 wherein the radiation curable oligomer is a polyether acrylate or an urethane acrylate.
5. The coating composition as claimed in claim 1 wherein the radiation curable oligomer is a polyether acrylate characterized by a viscosity greater than about 220 mPa/s.
6. The coating composition as claimed in claim 1 wherein the radiation curable oligomer is a polyether acrylate characterized by a viscosity from about 220 mPa/s to about 400 mPa/s.
7. The coating composition as claimed in claim 3 wherein the radiation curable oligomer is a polyether acrylate or an urethane acrylate.
8. The coating composition as claimed in claim 3 wherein the radiation curable oligomer is a polyether acrylate characterized by a viscosity greater than 220 mPa/s.
9. The coating composition as claimed in claim 3 wherein the radiation curable oligomer is a polyether acrylate is characterized by a viscosity from about 220 mPa/s to about 400 mPa/s.
10. The coating composition as claimed in claim 1 having substantially no monomer.
11. The coating composition as claimed in claim 10 further comprising a photoinitiator blend of an aromatic ketone and phosphine oxide.
12. The coating composition as claimed in claim 11 wherein the filler is selected from the group consisting of aluminum oxide, barium sulfate and magnesium silicate.
13. A coating composition for application to a ceramic substrate comprising:
a binder, having a radiation curable oligomer and an extender; and a pigment, having aluminum hydroxide and titanium dioxide;
wherein the pigment and the binder are combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
a binder, having a radiation curable oligomer and an extender; and a pigment, having aluminum hydroxide and titanium dioxide;
wherein the pigment and the binder are combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
14. The coating composition as claimed in claim 13 wherein the pigment and the binder are combined in a ratio in the range of from about 4:1 to about 6:1 by volume.
15. The coating composition as claimed in claim 13 wherein the pigment and the binder are combined in a ratio in the range of about 4:1 by volume.
16. A coating composition for application to a ceramic substrate comprising:
from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate;
from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant;
from about 10 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate;
from about 10 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate;
from about 0.5 to about 20 percent by weight, based on the total weight of the composition, of aluminum hydroxide;
from about 3 to about 6 percent by weight, based on the total weight of the composition, of titanium dioxide;
from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide; and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate;
from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant;
from about 10 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate;
from about 10 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate;
from about 0.5 to about 20 percent by weight, based on the total weight of the composition, of aluminum hydroxide;
from about 3 to about 6 percent by weight, based on the total weight of the composition, of titanium dioxide;
from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide; and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
17. A coating composition for application to a ceramic substrate comprising a binder, including a radiation curable oligomer and an extender, and a pigment comprising a colourant.
18. The coating composition as claimed in claim 17 wherein the radiation curable oligomer is a polyether acrylate or an urethane acrylate.
19. The coating composition as claimed in claim 17 wherein the radiation curable oligomer is a polyether acrylate characterized by a viscosity greater than about 220 mPa/s.
20. The coating composition as claimed in claim 17 wherein the radiation curable oligomer is a polyether acrylate characterized by a viscosity from about 220 mPa/s to about 400 mPa/s.
21. The coating composition as claimed in claim 18 having substantially no monomer.
22. The coating composition as claimed in claim 21 wherein the colourant is a pearlescent pigment.
23. The coating composition as claimed in claim 21 wherein the colourant is a tinting paste.
24. A coating composition for application to a ceramic substrate comprising:
a binder, having a radiation curable oligomer and an extender; and a pigment, having a colourant;
wherein the pigment and the binder are combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
a binder, having a radiation curable oligomer and an extender; and a pigment, having a colourant;
wherein the pigment and the binder are combined in a ratio in the range of from about 3:1 to about 10:1 by volume.
25. The coating composition as claimed in claim 24 wherein the pigment and the binder are combined in a ratio in the range of from about 4:1 to about 6:1 by volume.
26. The coating composition as claimed in claim 24 wherein the pigment and the binder are combined in a ratio of about 4:1 by volume.
27. A coating composition for application to a ceramic substrate comprising:
from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate;
from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant;
from about 15 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate;
from about 15 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate;
from about 1 to about 10 percent by weight, based on the total weight of the composition, of a colourant;
from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide; and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
from about 55 to about 65 percent by weight, based on the total weight of the composition, of a polyether acrylate;
from about 0.25 to about 3.0 percent by weight, based on the total weight of the composition, of a dispersant;
from about 15 to about 20 percent by weight, based on the total weight of the composition, of barium sulfate;
from about 15 to about 20 percent by weight, based on the total weight of the composition, of magnesium silicate;
from about 1 to about 10 percent by weight, based on the total weight of the composition, of a colourant;
from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of phosphine oxide; and from about 0.25 to about 2 percent by weight, based on the total weight of the composition, of benzophenone.
28. A coating composition for application to a ceramic substrate comprising an undercoat and a clear topcoat, wherein the undercoat comprises a radiation curable oligomer, an extender or filler, aluminum hydroxide and titanium dioxide, and wherein the topcoat comprises an urethane acrylate oligomer and an hydrocarbon acrylate diluent.
29. A coating composition for application to a ceramic substrate comprising an undercoat and a clear topcoat, wherein the undercoat comprises a radiation curable oligomer, an extender or filler, and a colourant, and wherein the topcoat comprises an urethane acrylate oligomer and an hydrocarbon acrylate diluent.
30. A method of repairing a surface defect on a glazed ceramic article comprising the steps of:
coating or hiding a surface defect of a glazed ceramic article with the coating composition as claimed in claim 1; and curing the composition with an energy source.
coating or hiding a surface defect of a glazed ceramic article with the coating composition as claimed in claim 1; and curing the composition with an energy source.
31. A method of repairing a surface defect on a glazed ceramic article comprising the steps of:
coating or hiding the surface defect with an undercoat comprising a radiation curable oligomer, an extender, aluminum hydroxide and titanium dioxide;
curing the undercoat with a first energy source;
applying a topcoat to the cured undercoat, the topcoat including an urethane acrylate oligomer and an hydrocarbon acrylate diluent; and curing the topcoat with a second energy source.
coating or hiding the surface defect with an undercoat comprising a radiation curable oligomer, an extender, aluminum hydroxide and titanium dioxide;
curing the undercoat with a first energy source;
applying a topcoat to the cured undercoat, the topcoat including an urethane acrylate oligomer and an hydrocarbon acrylate diluent; and curing the topcoat with a second energy source.
32. The method as claimed in claim 31 wherein each of the undercoat and topcoat further comprise a photoinitiator, and wherein each of the first and second energy sources is ultraviolet light.
33. A method of repairing a surface defect on a glazed ceramic article comprising the steps of:
coating or binding the surface defect with an undercoat comprising a radiation curable oligomer, an extender and a colourant;
curing the undercoat with a first energy source;
applying a topcoat to the cured undercoat, the topcoat including an urethane acrylate oligomer and an hydrocarbon acrylate diluent; and curing the topcoat with a second energy source.
coating or binding the surface defect with an undercoat comprising a radiation curable oligomer, an extender and a colourant;
curing the undercoat with a first energy source;
applying a topcoat to the cured undercoat, the topcoat including an urethane acrylate oligomer and an hydrocarbon acrylate diluent; and curing the topcoat with a second energy source.
34. The method as claimed in claim 33 wherein each of the undercoat and topcoat further comprises a photoinitiator, and wherein each of the first and second energy sources is ultraviolet light.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2299067 CA2299067A1 (en) | 1999-12-30 | 2000-02-22 | Coating composition for a ceramic article and use in repairing defects in glazed ceramic articles |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2,293,182 | 1999-12-30 | ||
| CA 2293182 CA2293182A1 (en) | 1999-12-30 | 1999-12-30 | Coating composition for a ceramic article |
| CA 2299067 CA2299067A1 (en) | 1999-12-30 | 2000-02-22 | Coating composition for a ceramic article and use in repairing defects in glazed ceramic articles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2299067A1 true CA2299067A1 (en) | 2001-06-30 |
Family
ID=25681433
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2299067 Abandoned CA2299067A1 (en) | 1999-12-30 | 2000-02-22 | Coating composition for a ceramic article and use in repairing defects in glazed ceramic articles |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2299067A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113061054A (en) * | 2021-05-06 | 2021-07-02 | 刘黎明 | Glazing repair process for ceramic crack |
| CN114907105A (en) * | 2022-05-30 | 2022-08-16 | 佛山东鹏洁具股份有限公司 | Composite material for re-burning and repairing sanitary ceramics, preparation method and repairing method |
-
2000
- 2000-02-22 CA CA 2299067 patent/CA2299067A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113061054A (en) * | 2021-05-06 | 2021-07-02 | 刘黎明 | Glazing repair process for ceramic crack |
| CN114907105A (en) * | 2022-05-30 | 2022-08-16 | 佛山东鹏洁具股份有限公司 | Composite material for re-burning and repairing sanitary ceramics, preparation method and repairing method |
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