WO1997045498A1

WO1997045498A1 - Highly tintable, abrasion-resistant coating compositions

Info

Publication number: WO1997045498A1
Application number: PCT/US1997/007852
Authority: WO
Inventors: Tuan H. Ho; Mark G. Tilley; Mark S. Sollberger
Original assignee: Sdc Coatings, Inc.
Priority date: 1996-05-29
Filing date: 1997-05-08
Publication date: 1997-12-04
Also published as: AU2833197A; ZA974475B; ID16987A

Abstract

In accordance with the present invention, there are provided coating compositions that are especially useful for providing both abrasion resistance and excellent tintability. Upon application to a solid substrate and subsequent curing, the invention coatings strongly adhere to the underlying solid substrate. The present invention also provides methods for coating solid substrates with tintable, abrasion-resistant, adhesive coatings, and resulting articles.

Description

HIGHLY TINTABLE, ABRASION-RESISTANT COATING COMPOSITIONS

FIELD OF THE INVENTION

The present invention relates to coating compositions that are highly tintable and abrasion-resistant, methods for coating solid substrates with these highly tintable, abrasion- resistant coatings, as well as articles having highly tintable, abrasion-resistant coatings thereon.

BACKGROUND OF THE INVENTION

Plastic materials have become an attractive alternative to glass in a variety of applications because of their substantially lighter weight (relative to glass) , ease of handling, relative ease of processability into various shapes and articles, greater resistance to shattering, and for some plastic materials, the capacity to accept organic dyes. For example, polycarbonates and acrylics are widely used in the windows of buildings and various vehicles, as well as in optical lenses. In addition, plastic materials are also widely used as glazing materials for automobiles, buses, and aircraft. Unfortunately, however, the use of plastic materials has been limited by their tendency to be soft and readily scratched.

Protective polymeric coatings have been utilized to impart abrasion resistance to these relatively soft and easily scratched materials. An example of such a polymeric coating is a heat curable polyurethane resin. Although economically attractive because they are less expensive than other polymeric coating materials, the abrasion resistance of polyurethane coatings is still inadequate for many applications.

In order to provide exceptionally hard, abrasion- resistant coatings, new siloxane-based curable resin systems were developed. An example of such a resin system can be found in U.S. Patent No. 3,986,997, issued to Clark. Although the siloxane resins described in this patent have been very successful as coatings for plastic lenses, sheets, and other articles, they have the major drawback that, once cured, they are not tintable. Tintability is a desirable property in plastic materials used, for example, in windows and sunglasses. Accordingly, a new coating system in which the cured coating possesses the characteristics of high tintability, coupled with the abrasion resistance exhibited by the siloxane-based coatings, described above, would be highly desirable.

Unfortunately, attempts to produce tintable, abrasion- resistant coatings have been met with limited success. For example, U.S. Patent No. 4,355,135, issued to January, discloses tintable polysiloxane-based coating compositions which importantly do not provide the level or speed of tinting or abrasion resistance desired for many applications.

One approach for enhancing the tintability of abrasion- resistant coatings has been through the incorporation of tint enhancing compounds into coating compositions. For example, U.S. Patent No. 5,013,608, issued to Guest et al . , describes the use of polyhydroxy functional and butylated urea formaldehyde compounds as tintability enhancing compounds. Unfortunately, although tint speed is enhanced with the incorporation of these compounds, the hardness of the cured coating is significantly compromised.

U.S. Patent No. 5,232,964, issued to Evans, describes the use of quaternary ammonium salts to enhance the tintability of coating compositions that contain non-silylated acrylate monomer. However, results reported in Examples XXXV, XXXVI, and XXXVII of this patent indicate that quaternary ammonium salts were not effective at enhancing the tintability of non- acrylate-containing polysiloxane-based compositions.

Accordingly, a need exists for coating compositions that are both highly tintable and highly abrasion-resistant when cured.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with the present invention, we have developed coating compositions that provide both significant abrasion resistance and substantial tintability when cured. In accordance with other aspects of the present invention, we have developed methods for coating a solid substrate with the coating compositions of the present invention. In accordance with yet another aspect of the present invention, we have developed articles having highly tintable, abrasion-resistant coatings thereon. Coating compositions of the present invention are highly desirable in a variety of applications, in particular, the ophthalmics industry.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is provided a coating composition comprising:

(A) a base resin that does not contain non- silylated acrylate monomer;

(B) a tint-enhancing quantity of a quaternary ammonium salt; and (C) an effective quantity of crosslinking agent, wherein said coating composition forms a highly tintable, abrasion-resistant, adhesive coating upon curing.

As used herein, the term "base resin" refers to one or more polymerizable substituents, including, for example, monomeric, oligomeric, prepolymeric, polymeric compounds, and the like, or mixtures thereof, optionally mixed with water, solvents, or solvent mixtures, and/or compounds that function to modify the properties of the invention coating compositions and/or resulting cured coatings, such as, for example, colloidal metal oxides, and epoxy functional substituents, as described herein, and the like. However, base resins containing non-silylated acrylate monomers are considered to be outside the scope of base resins contemplated for use herein. The term "non-silylated acrylate monomer, " as used herein, refers to acrylate monomer that does not contain any silicon atoms. The term "prepolymeric" or "prepolymer, " refers herein to a reactive chemical species that is partially polymerized

(i.e., a species that retains additional polymerizable functionality) . Base resins suitable for use in the practice of the present invention include those that exhibit film forming properties desirable for coating applications. Thus, a base resin is considered suitable if it is capable of forming a continuous coating on a solid substrate. The film forming character of a particular base resin can be generally predicted according to the relative physicochemical properties of the resin with respect to a particular substrate (e.g., interfacial tensions, polarity, contact angle, and the like) . For example, resins that form relatively low contact angles on a particular surface are more likely to form continuous coatings on that surface as compared to resins that form higher contact angles on the same surface. Accordingly, those of ordinary skill in the art can readily identify suitable base resins for particular substrates based on these properties.

The base resin typically contains one or more types of substituents that polymerize upon exposure to heat, free radicals, and the like, during curing of the invention coating compositions. As contemplated in the practice of the present invention, polymerization can occur in a variety of ways, such as, for example, by condensation polymerization, ring scission polymerization, free-radical polymerization, and the like, or by a combination of any two or more polymerization methods thereof. As used herein, the terms "curing" and "cured" refer to the process by which coating compositions of the present invention are solidified.

Suitable base resin substituents include reactive substituents, such as, for example, hydroxyl-functional substituents (e.g., partial condensates of one or more silanols, polyols, and the like) , precursors to hydroxyl- functional substituents (e.g., alkoxysilanes and the like) , epoxy-functional substituents, and substituents that undergo free radical polymerization {e.g., substituents containing unsaturated bonds that are used to form polymers such as, for example, silylated acrylates, vinyl functional silanes, allylic functional silanes, and the like, as well as combinations of any two or more thereof) , and the like, as well as combinations of any two or more thereof. The term "silanols" refers herein to mixtures of partially and fully hydrolyzed alkoxysilanes and oligomeric and polymeric products thereof.

When a free radical polymerization system is employed in the present invention, polymerization is initiated either thermally or by exposure to ultraviolet radiation using thermal- and photo-initiator chemical compounds for free radical polymerization that are well known in the art . Free radical polymerization of base resin components of the present invention can also be initiated without a chemical initiator compound by exposing the base resin to radiation, such as, for example, e-beam or gamma-radiation.

When silanols are used as base resin substituents, they are preferably generated in si tu , by hydrolysis, by adding water to the corresponding alkoxysilanes. Alkoxysilanes contemplated to be within the scope of the present invention include, for example, monoalkoxy, dialkoxy, trialkoxy, and tetraalkoxy substituted silanes, and the like, as well as combinations of any two or more thereof. Preferably, alkoxysilanes of the present invention are organically substituted. As used herein, the term "organically substituted" refers to a substituted alkoxysilane which contains at least one silicon-carbon bond. Suitable organic moieties for substitution include those containing one or more alkyl, alkenyl, alkynyl, aryl, and other like functionalities, epoxy functionality, and the like, as well as combinations of any two or more thereof. Organically substituted alkoxysilanes employed in the practice of the present invention include those containing methoxy, ethoxy, propoxy, butoxy, and other like alkoxy substituents, as well as combinations of any two or more thereof .

The water for hydrolysis can be introduced from optional base resin components described herein, such as, for example, an aqueous colloidal metal oxide. Upon hydrolysis, the alkoxysilanes are partially or fully converted into the corresponding silanol(s) and alcohol (s) , thus generating at least a portion of the alcohol present in the base resin. Alcohol, as well as mixtures of two or more alcohols, can optionally be added to the base resin prior to the addition of the alkoxysilanes.

Following their formation, the hydroxyl groups of the silanols can condense with one another to form siloxane bonds. Sometimes the condensation reactions can be enhanced by the addition of small amounts of acid or base catalysts. Acids and bases can also be used to enhance the in si tu hydrolysis of alkoxysilane to silanol . Acid and base catalysts that are suitable for enhancing hydrolysis and condensation reactions are well known to those of ordinary skill in the art and include both organic and inorganic materials.

When partial condensates of silanols are employed as part of the base resin, up to about 100 percent of the base resin can be formed from the partial condensate of one or more silanols. Preferably, the base resin contains from about 10 to about 100 percent of a partial condensate of one or more silanols, based on the total weight of base resin.

Epoxy-functional substituents can also be incorporated into the base resin to modify properties of the cured composition (e.g., abrasion resistance and tintability) . For example, base resins containing a partial condensate of silanols preferably also contain at least one epoxy-functional silanol. When an epoxy-functional substituent, such as an epoxy-functional silanol, is employed in coating compositions of the present invention, the quantity of epoxy-functional substituent can vary widely, and can be up to about 100 weight percent, based on the total weight of base resin. Preferably, the quantity of epoxy-functional substituent in the base resin is from about 0.1 to about 50 weight percent, based on the total weight of base resin. Most preferably, the quantity of epoxy-functional substituent in the base resin is from about 20 to about 45 weight percent, based on the total weight of base resin. Epoxy-functional silanols employed in the practice of the present invention can be generated in si tu , by hydrolysis, as described above, from the corresponding epoxy-functional alkoxysilanes. Exemplary epoxy-functional silanols include silanols having the formula:

(I) Q—Si(OH)₃._n R_n

where n is a number selected from 0 to 2, R is selected from a hydrogen atom, an optionally substituted (e.g., hydroxy, carboxy, amino, epoxy, and the like) , branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 10 atoms in the backbone which typically contains carbon, and optionally contains nitrogen, oxygen, sulfur, and the like, and Q is selected from

(A) —W HC -CH W;

mixtures of (A) and (B) , where W is independently selected from a hydrogen atom, an optionally substituted (e.g., hydroxy, carboxy, amino, and the like) , branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 10 atoms in the backbone. Typically, the backbone contains carbon, and optionally contains nitrogen, oxygen, sulfur, and the like.

Preferably, the epoxy-functional silanol is gamma- glycidoxypropyl silanol. Gamma-glycidoxypropyl silanol can be generated in si tu , by hydrolysis, from a corresponding alkoxysilane, such as, for example, gamma-glycidoxypropyl trimethoxysilane.

Base resins of the present invention can also be prepared by mixing one or more epoxy-functional silanols with one or more non-epoxy-functional silanols. Suitable non-epoxy- functional silanols include, for example, mono-, di-, and tri- methyl silanol, mono-, di-, and tri-propyl silanol, mono-, di-, and tri-butyl silanol, and the like, and mixtures of any two or more thereof. An exemplary mixture of epoxy-functional and non-epoxy functional silanols is the mixture of gamma- glycidoxypropyl silanol and methyl silanol.

When a mixture of epoxy-functional silanol and non- epoxy-functional silanol is employed, the weight ratio of epoxy-functional silanol to non-epoxy-functional silanol can vary widely and is typically within the range of about 10:90 to about 99:1 (ratio of parts epoxy-functional silanol to parts non-epoxy-functional silanol, by weight) . Preferably, the weight ratio of epoxy-functional to non-epoxy-functional silanol is within the range of about 50:50 to about 90:10

(ratio of parts epoxy-functional silanol to parts non-epoxy- functional silanol, by weight) .

The base resin can optionally contain colloidal metal oxides to further improve the abrasion resistance of the cured coating. The term "colloidal metal oxide" refers herein to stable dispersions or solutions of discrete particles of one or more metal oxides. As used herein, the term "metal" includes semiconductor materials, such as, for example, silicon. Colloidal metal oxide dispersions function to modify various physical attributes of the cured coating, including, for example, hardness, refractive index, impact resistance, capacity to absorb or block ultraviolet light, and the like.

Colloidal metal oxides employed in the practice of the present invention include colloids of silicon oxide, aluminum oxide, antimony oxide, tin oxide, cerium and other lanthanide oxides, zirconium oxide, titanium oxide, and the like, as well as composites and combinations of any two or more thereof. The continuous phase of suitable colloidal metal oxide systems can be either aqueous or non-aqueous. A preferred colloidal metal oxide suitable for use in the practice of the present invention is colloidal silica because of its relative widespread availability, attractive performance characteristics, ease of handling, and low cost. Colloidal metal oxides employed in the practice of the present invention typically contain metal oxide particles having particle sizes in the particle size range of about 4 to about 50 millimicrons in diameter. Preferably, the metal oxide particles have particle sizes in the particle size range of about 4 to about 30 millimicrons in diameter. Suitable colloidal metal oxide compositions can be acidic, neutral, or basic, and can contain additives that prolong the stability of the colloidal composition. The quantity of colloidal metal oxide employed in the practice of the present invention can be varied in proportion with the weight percents of the other base resin substituents. This adjustment in metal oxide content will, in turn, influence the physical properties of the cured coating. Preferably, the base resin of the present invention contains up to about 90 weight percent of the colloidal metal oxide, based on total weight of base resin. However, those of ordinary skill in the art will recognize that the appropriate quantity of colloidal metal oxide sufficient to achieve a particular level of abrasion resistance can be readily determined empirically.

Methods for determining the abrasion resistance of coatings are well known to those of ordinary skill in the art . Such methods include the Taber method, ASTM D 1044, and the Bayer Abrasion Resistance Test, ASTM F735-81. Typically, abrasion resistance is measured as a function of the gain in haze which a coated article acquires as a result of the test procedure. The gain in haze is expressed by the parameter, "Δ%H", which is a quantitative measure of the abrasion resistance of coated products. As the metal oxide content becomes a greater percentage of the total solids in the cured coating, the value of Δ%H decreases for that particular coating. It will be recognized that lower values of Δ%H indicate improved abrasion resistance. Typically, enough colloidal metal oxide is added to the coating composition such that the resultant ΔH₅₀₀ (i.e., the Δ%H for a coating after 500 cycles of abrasive contact) , as measured by the Taber Abrasion Resistance Test, is less than about 15%. As used herein, the term "quaternary ammonium salt" refers to tetra-substituted ammonium salts. Quaternary ammonium salts that are suitable for use in compositions of the present invention include those that are capable of being distributed substantially uniformly throughout the coating composition. Preferred quaternary ammonium salts are soluble or miscible with the base resin.

Suitable quaternary ammonium salts employed in the practice of the present invention include, for example, quaternary ammonium salts having the formula:

(II) Z₄N⁺ X^"

where each Z is independently selected from an optionally substituted (e.g., alkoxy, hydroxy, carboxy, amino, epoxy, and the like, as well as combinations of any two or more thereof) , branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 20 atoms (e.g., carbon, nitrogen, oxygen, silicon, sulfur, and the like) , and where X is a counterion selected from a halogen, a nitrate, a sulfate, a sulfonate moiety, or other like negatively charged moiety. Coating compositions of the present invention can contain one or more quaternary ammonium salts of the above formula.

Quaternary ammonium salts that are particularly suitable for use in the practice of the present invention include 3-lauramidopropyltrimethylammonium sulfate, N,N-bis(2- hydroxyethyl) -N- (3 ' -dodecyloxy-2 ' -hydroxypropyl) methylammonium methosulfate, tetraethylammonium p-toluene sulfonate, glycidyltrimethylammonium chloride, and the like, and combinations of any two or more thereof .

Preferably, the quaternary ammonium salt is a silylated quaternary ammonium salt. As used herein, the term "silylated quaternary ammonium salt" refers to a quaternary ammonium salt, where "Z" in Formula II is substituted with one or more silylated groups (i.e., where at least one of the four Z moieties in (II) contains a silicon atom) . Exemplary silylated quaternary salts include quaternary ammonium salts substituted with one or more alkoxysilane moieties, such as, for example, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride, N- trimethoxysilylpropyl-N,N,N-tri-n-butylammonium chloride, N- trimethoxysilylpropyl-N,N,N-tri-n-butylammonium bromide, N- triethoxysilylpropyl-N,N,N-trimethylammonium chloride, and the like, as well as combinations of any two or more thereof.

When the quaternary ammonium salt is silylated and contains silicon-bonded alkoxy groups, such as, for example, methoxy, ethoxy, propoxy, and the like, the alkoxy groups within the quaternary ammonium salt undergo hydrolysis in the presence of water, resulting in the conversion of the alkoxy groups to hydroxy groups. Through these hydroxy groups, the quaternary ammonium salt can then react, via condensation, with condensable base resin substituents. As used herein, the term "a tint-enhancing quantity" of quaternary ammonium salt is the amount of quaternary ammonium salt sufficient to achieve the desired level of tintability after exposure of the cured composition to a tinting solution. Exposure of cured composition to tinting solution is typically carried out for about 30 minutes, and preferably for about 15 minutes, to achieve the desired level of tintability. The tint-enhancing quantity of quaternary ammonium salt for a particular composition of the present invention can be readily determined empirically by testing the tintability of cured test coatings containing different quantities of quaternary ammonium salt. Tintability can be tested in a variety of ways, such as, for example, by using the methods described herein, in Example 1.

The quantity of quaternary ammonium salt employed in the coating composition can vary widely depending on the level of tintability desired. Typically, coating compositions of the present invention contain from about 0.5 to about 50 weight percent of the quaternary ammonium salt, based on the total weight of base resin. Preferably, coating compositions of the present invention contain from about 0.5 to about 40 weight percent of the quaternary ammonium salt, based on the total weight of base resin. Most preferably, coating compositions of the present invention contain from about 2 to about 20 weight percent of the quaternary ammonium salt, based on the total weight of base resin.

As used herein, the terms "crosslinker" and "crosslinking agent" are used interchangeably and refer to chemical compounds containing two or more functional groups that are capable of forming chemical bond(s) with base resin substituents. Such chemical bonding can be by either covalent or ionic means. Crosslinking agents that are of relatively small molecular size and relatively low molecular weight, i.e., monomeric and non-resinous, are preferred.

For example, when the base resin contains condensable substituents, exemplary crosslinking agents include compounds having one or more hydroxyl groups that are capable of reacting by condensation, such as, for example, di- and tri- silanols, glycols, glycerol, and the like, and combinations of any two or more thereof. As used herein, the term "disilanol" refers to a molecule containing two silicon atoms, each having one or more hydroxy functional groups bonded thereto. The term "trisilanol" refers herein to a molecule containing three silicon atoms, each having one or more hydroxy functional groups bonded thereto. The di- and tri- silanols react by condensation with condensable base resin substituents, thus forming a chemical link between formerly separate molecules. Exemplary disilanols include disilanols having the general formula (III) , set forth below.

(Ill) B_n(OH)₃__nSi A Si(0H)₃-_nB_n

where A is selected from an optionally substituted, branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 10 atoms (e.g., carbon, nitrogen, oxygen, sulfur, and the like) , and each B is independently selected from a hydrogen atom, an optionally substituted, branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 10 atoms (e.g. carbon, nitrogen, oxygen, sulfur, and the like) , and n is a number selected from 0 to 2. Di- and tri- silanols employed in the practice of the present invention can be generated in si tu, by hydrolysis of the corresponding precursor alkoxysilanes, as described previously herein. Such alkoxysilanes can readily be identified by one of ordinary skill in the art. For example, a suitable alkoxysilane for use as a trisilanol precursor in the practice of the present invention is tris [3- (trimethoxysilyl)propyl] isocyanurate (Osi Specialties Inc., Endicott, NY) .

Epoxy-functional base resin substituents can be crosslinked by crosslinking agents that are reactive with epoxy groups, such as, for example, polycarboxylic acids, polyanhydrides, polyimides, and the like, as well as combinations of any two or more thereof . Polycarboxylic acids employed in the practice of the present invention include succinic, maleic, itaconic, malic, malonic, glutaric, fumeric, adipic, pimelic, suberic, azelaic, sebacic, tartaric, trimesic, trimellitic, pyromellitic, phthalic, and other like acids, as well as combinations of any two or more thereof .

Suitable polyanhydrides contemplated for use as crosslinking agents in the practice of the present invention include succinic, maleic, malonic, itaconic, glutaric, fumeric, adipic, pimelic, suberic, azelaic, sebacic, tartaric, trimesic, trimellitic, pyromellitic, phthalic, and other like anhydrides, as well as combinations of any two or more thereof.

Suitable polyimides contemplated for use as crosslinking agents in the practice of the present invention include succinimide, phthalimide, glutarimide, maleimide, and other like imides, as well as combinations of any two or more thereof .

An effective amount of crosslinking agent is added to the coating composition to impart the desired level of abrasion resistance to the cured coating. This quantity can readily be determined empirically, for example, by adding different quantities of crosslinking agent to test batches of coating composition of the present invention and testing the cured composition for degree of abrasion resistance using standard test methods, such as, for example, the Taber Abrasion Resistance Test, ASTM No. D 1044 or the Bayer Abrasion Resistance Test, ASTM No. F735-81, both incorporated herein by reference, and other like methods, as well as actual-use tests, which will vary depending on the particular end-use application.

The quantity of crosslinking agent in the coating composition can vary widely and is typically up to about 25 weight percent, based on the total weight of base resin. Preferred coating compositions of the present invention contain from about 0.1 to about 20 weight percent of crosslinking agent, based on the total weight of base resin. Most preferably, coating compositions contain from about 0.1 to about 15 weight percent of crosslinking agent, based on the total weight of base resin.

As contemplated in the practice of the present invention, the coating composition may optionally contain a curing catalyst. As used herein, the term "curing catalyst" refers to an agent that promotes polymerization. Although a curing catalyst is not needed to cure the coating composition, a curing catalyst can be incorporated into the coating composition to speed up the curing process. Suitable curing catalysts include chemical compounds that catalyze reactions by condensation, such as, for example, amines, metal acetylacetonates, diamides, imidazoles, organic sulfonic acids, amine salts of organic sulfonic acids, alkali metal salts of carboxylic acids, ammonium perchlorate, and the like, as well as combinations of any two or more thereof.

Exemplary amines include 1, 2-diaminocyclohexane, benzyldimethylamine, boron trifluoride monoethylamine, and the like, as well as combinations of any two or more thereof. Suitable metal acetylacetonates include, for example, aluminum acetylacetonate, zinc acetylacetonate, iron acetylacetonate, cobalt acetylacetonate, and the like, as well as combinations of any two or more thereof. Suitable amides includes dicyanodiamide, polyamides, such as those that are the condensation products of dimerized fatty acids and aliphatic amines (e.g., diethylene triamine) , and the like, as well as combinations of any two or more thereof. Imidazoles suitable for use as curing catalysts include, for example, methylimidazole, 2-ethyl-4-methylimidazole, l-cyanoethyl-2- propylimidazole, 4 , 5-dihydro-l- (3-triethoxysilylpropyl) - imidazole, and the like, as well as combinations of any two or more thereof. Exemplary alkali metal salts of carboxylic acids include, for example, sodium acetate, dibutyltindilaurate, and the like, as well as combinations of any two or more thereof.

The actual quantity of curing catalyst can vary widely and is typically up to about 5 weight percent, based on the total weight of base resin. Preferred coating compositions contain from about 0.1 to about 3 weight percent of curing catalyst, based on the total weight of base resin. Most preferably, coating compositions contain from about 0.1 to about 1 weight percent of curing catalyst, based on the total weight of base resin. Optionally, it is sometimes desirable to incorporate water-soluble or water-miscible solvents in the practice of the present invention, such as, for example, alcohols, ketones, ethers, Cellosolves™, Dowanols™ and the like. Dowanols™ include, for example, glycol monoethers, which are manufactured by The Dow Chemical Co., Midland, MI. Such solvents can be used to modify the viscosity of the coating composition to facilitate the coating process or to modify the kinetics of the hydrolysis and condensation reactions and subsequent curing step with respect to the base resin. The order of addition of coating composition components can vary. For example, the base resin can be premixed and added to a mixing vessel, followed by the crosslinking agent, the optional catalyst, and the quaternary ammonium salt. Other suitable addition orders include, for example, the following: 1) crosslinking agent, base resin, quaternary ammonium salt, and optional catalyst; 2) base resin, optional catalyst, crosslinking agent, and quaternary ammonium salt; and 3) base resin, quaternary ammonium salt, crosslinking agent, and optional catalyst.

In accordance with another aspect of the present invention, there is provided a method for coating a solid substrate with a highly tintable, abrasion-resistant coating, said method comprising:

(i) preparing a coated substrate by contacting at least one surface of a solid substrate with a coating composition as described herein, then

(ii) subjecting said coated substrate to curing conditions such that the cured coating can subsequently be tinted, if desired, wherein said cured coating composition is adhesive, highly tintable and abrasion-resistant.

Solid substrates suitable for use in the practice of the present invention include, for example, those made from mineral matter, glass, polymer, metal, wood, ceramic, and the like, as well as composite and laminated materials. Useful polymeric substrates include polycarbonates, acrylics, polyesters, cellulose acetates, acrylonitrile-butadiene-styrene and its derivatives, and the like.

The term "contacting, " as used herein, refers to the application of the coating composition to the solid substrate. Suitable methods for contacting solid substrate with coating composition include dip coating, roll coating, gravure coating, spray coating, and other like coating methods that are well known to those of ordinary skill in the art. Dip coating and other coating techniques that coat both sides of a substrate may also be used, or single side coating techniques may be repeated on the other side of a substrate, if desired. These various methods of coating allow the coating to be placed on at least one side of the substrate at variable thicknesses, thus allowing a wider range of uses of the coating. Coating compositions of the present invention typically perform best when the cured coating thickness is in the range of about 1 to about 7 micrometers. Preferably, the cured coating thickness is in the range of about 2 to about 6 micrometers. Most preferably, the cured coating thickness is in the range of about 2 to about 5 micrometers. Thicknesses in these ranges allow optimum tinting in shorter treatment times without impairing the optical clarity of the coated substrates caused by cracking and other defects that can occur if the coating is too thin or too thick.

After the contacting step, the coating composition and substrate are subjected to curing conditions that are sufficient to cure the composition so that it can be subsequently tinted. The coating composition and substrate are normally heated to expedite curing of the coating composition. Temperatures in the range of about 120°F to about 310°F (about 49°C to about 154°C) , for a time period in the range of about 1 to about 6 hours can typically be used for most polymeric substrates. Preferred curing conditions are temperatures in the range of about 200°F to about 275°F (about 93°C to about 135°C) , for a time period in the range of about 2 to about 5 hours.

Suitable curing conditions (i.e., temperature and duration) will vary depending on the material properties of the coating composition and the underlying substrate. In general, curing conditions should be selected so that the selected substrate is not softened and distorted during curing. However, certain materials may be able to withstand more severe conditions. For example, if the substrate is glass or metal, higher curing temperatures and longer curing times can be used. In general, when higher curing temperatures are used to cure coating compositions of the present invention, shorter curing times are required and vice-versa.

Optionally, a pre-curing step can be employed in between the contacting step and the curing step. Pre-curing the coated substrate produces a tack-free coated surface that can be handled for inspection or stored for later completion of the curing process. Coated substrates are pre-cured by exposing the coated substrate to temperatures within the same range of temperatures as in the curing step, but for shorter time periods (e.g., less than about one hour) .

Once cured, coatings of the present invention are highly adhesive to the underlying substrate. As used herein, the term "adhesive" refers to the tendency of the invention coatings to strongly adhere to the underlying substrate upon curing. A particularly desirable property exhibited by cured coatings of the present invention is that they do not delaminate upon exposure to typical tinting conditions. Prior to coating, surfaces of the solid substrate can be primed or otherwise treated to further promote adhesion and the formation of a continuous coating with the invention compositions. The primer can also be used to impart additional properties to the cured coating, such as, for example, impact resistance, light absorption, toughness, and the like. Surfaces of the solid substrate can be primed in a number of ways to alter the surface properties therein in order to promote the formation of a uniform coating. Such methods for priming coating surfaces include chemical and physical methods that are well known to those of ordinary skill in the art. For example, the substrate can be chemically or physically etched, or coated with either a water-based primer (e.g., a water-based urethane emulsion) or a solvent-based primer (e.g., a solvent- based acrylic primer) . In yet another embodiment of the present invention, there are provided articles that are prepared in accordance with the method of the present invention. The articles generally are solid substrates having a tintable abrasion- resistant coating thereon. When a tinted coating is desired, the surface of the coated article of the present invention is immersed in a dye bath containing a suitable colored dye, e.g. BPI Sun Gray or BPI Black, both of which are dyes sold by Brain Power Incorporated of Miami, FL. The intensity of the tint can be adjusted by varying such variables as coating thickness, primer type, mode of surface treatment, time immersed in the dye bath, and the like. The degree of tint obtained can be determined by using a colorimeter, such as a Gardner XL-835^® (Gardner Laboratory, Inc., Bethesda, MD) , which measures the percent of light transmitted through the coating and the substrate.

Significantly, upon curing, coating compositions of the present invention exhibit both high abrasion resistance and high tintability. Characterization of the abrasion resistance of coatings of the present invention is set forth herein in the Examples below. As used herein, the term "high tintability" refers to the capacity of a cured coating to absorb substantial amounts of dye within a reasonable length of time. For example, in the ophthalmic industry, two levels of light transmittance ("LT") are generally used in connection with the application of tints to lenses for eyeglasses. A 50 percent LT means that the amount of dye absorbed is sufficient to allow only 50 percent of the light to pass through the tinted lens. This is generally the level of light transmittance applicable to "fashion" tints for eyeglasses. A darker tint such as that used for sunglasses generally has about 20 percent LT, which means that the amount of dye absorbed allows only 20 percent of the light to pass through the lens. Coated articles of the present invention are typically capable of achieving about 20 percent LT after about 15 to about 30 minutes of exposure to a tinting solution.

The invention will now be described in greater detail with reference to the following non-limiting examples.

Example 1 TESTING METHODS Tinting Test

The lenses were tinted using commercially available dyes from Brain Power, Inc., Miami, FL., namely, BPI Sun Gray and BPI Black dyes. The tinting was carried out at either about 88°C or about 96°C by immersing the lenses into the dye bath for up to 45 minutes. In Table I of Example 12, the indicated properties are measured after the indicated number of minutes of total lens immersion. The lower the percent of light transmitted ("%LT") , the greater is the amount of dye absorbed by the cured coating during the selected time period. The degree of tint obtained is quantified by the percent of light transmitted through the lens, as measured using a Gardner XL-835^® colorimeter manufactured by Gardner Laboratory, Inc., Bethesda, MD, and is reported as %LT.

Baver Abrasion Resistance Test

Abrasion resistance was measured using a Bayer abrader in accordance with the abrasion resistance test, ASTM No. F735- 81. The Bayer abrader generates an increase in sample haze after subjecting a sample to a set of 300 4-inch strokes, rotating the sample 180°, then subjecting the sample to another set of 300 4-inch strokes. The Bayer abrader has positions for coated sample lenses and uncoated reference lenses. Typically, uncoated CR-39 piano lenses are used in the reference positions. The Bayer abrader results are then reported as the ratio of the Δ%H for the reference lenses over the Δ%H for the sample lenses . This ratio is commonly referred to as the Bayer ratio. The Δ%H is calculated as the difference between the final and initial haze readings on the Gardner XL-835 colorimeter. A Bayer ratio of greater than 1 indicates a coating with abrasion resistance better than the CR-39 reference. Likewise a Bayer ratio of 1, or less than 1, indicates that the abrasion resistance for the coating is equivalent to, or less than, what is typically achieved with the CR-39 reference, respectively.

Taber Abrasion Resistance Test

Abrasion resistance was also measured using the Taber Abrasion Resistance Test, ASTM No. D 1044. The Taber Abrader generates an increase in sample haze after being subjected to

100 and 500 cycles of an abrasive CS-10F wheel. Results are reported as percent change in haze ("Δ%H") . Coating Adhesion Test

The adhesion of the cured coating to the substrate was measured using the Crosshatch adhesion test, ASTM No. D 3359. This involves scribing a criss-cross pattern (grid) on the coated surface, applying a 3M 600 tape, and pulling it away sharply in one quick motion. Three tape pulls with no adhesion loss is considered passing, and is reported as 100% adhesion. Adhesion below 100% is estimated as the percentage of coating that remains on the surface after three tape pulls.

Example 2

A 1 liter flask was charged with 198 parts Nalco^® N-

1042 (Nalco Chemical Co., Naperville, IL) . Next, a precombined mixture of 68.4 parts gamma-glycidoxypropyl trimethoxy silane

(Z-6040, Dow Corning, Midland, MI) and 45.6 parts methyltrimethoxy silane (Z-6070, Dow Corning, Midland, MI) was added to the vessel with stirring. After 30 minutes of stirring at ambient temperature, 85 parts propylene glycol monomethyl ether and 85 parts n-butanol were added to the vessel. Next, 14 parts itaconic acid, 3 parts benzyldimethylamine, and 1 part paint flow additive PA-57 (Dow- Corning, Midland, MI) in 10% n-butanol were added with agitation to the vessel. After additional agitation for 1 hour at ambient temperature, the coating composition was filtered and aged at 90°F for 18 hours. The aged coating was applied to polycarbonate ("PC") lenses and plaques primed with water-based primer, XF1133 (SDC Coatings, Inc., Garden Grove, CA) , using a dip-coating process with a withdrawal speed of 4 inches/minute. After a 20 minute air dry time, the parts were cured for 4 hours at 265°F. The coating was also applied to unprimed, etched CR-39^®

(Aceto Corp., Waterbury, CT) lenses and plaques. The CR-39* was etched for 15 minutes at room temperature in a 10% potassium hydroxide solution of 50:50 propylene glycol -.water. The coating was applied to the CR-39* lenses and plaques by dip coating at a withdrawal rate of 4 inches/minute. The coated lenses and plaques were allowed to air dry for 20 minutes before curing for 2 hours at 250°F.

The coated, primed and coated, unprimed lenses and plaques were evaluated for abrasion resistance and tintability. Results from abrasion resistance and tintability testing are shown in Table I in Example 12.

Example 3 To the composition of Example 2 was added 30.8 parts trimethoxysilylpropyltrimethylammonium chloride (Huls America, Inc., Piscataway, New Jersey) with agitation at room temperature. This coating was applied to polycarbonate lenses and plaques primed with XF1133 (SDC Coatings, Inc., Garden Grove, CA) according to the manufacturer's directions and unprimed CR-39^® under the conditions described in Example 2. The coated, primed and coated, unprimed lenses and plaques were evaluated for abrasion resistance and tintability. Results from this testing are shown in Table I in Example 12.

Example 4 A reaction vessel was charged with a mixture of colloidal silicas 115.1 parts Nalco^® N-1042 (Nalco Chemical Co., Naperville, IL) and 67.9 parts Nyacol 830LS (The PQ Corp. Valley Forge, PA) . Then, 88.3 parts gamma-glycidoxypropyl trimethoxysilane (Z-6040, Dow Corning, Midland, MI) was added to the vessel with agitation, followed by 60.2 parts of isopropyl alcohol and 128.5 parts propyleneglycol monomethyl ether. Next, 22.9 parts itaconic acid and 17.6 parts Silwet^® L-77 (OSi Specialties, Inc., Danbury CT) in propylene glycol monomethyl ether were added with agitation at room temperature followed by 0.5 parts of 10% ammonium perchlorate in distilled water.

This coating was applied to primed polycarbonate plaques and lenses primed with XF1133 (SDC Coatings, Inc., Garden Grove, CA) according to the manufacturer's directions by dip coating at a withdrawal rate of 4 inches/minute. After a 20 minute air dry period, the coating was cured for 4 hours at 265°F.

The coating was also applied to unprimed, etched CR-39^® by dip coating at 4 inches/minute withdrawal speed. The coating was cured at 250°F for 2 hours.

The coated, primed lenses and plaques were evaluated for abrasion resistance and tintability. Results from this testing are shown in Table I in Example 12.

Example 5 A quantity of 29.6 parts trimethoxysilylpropyl- trimethylammonium chloride (Huls America, Inc., Piscataway, New Jersey) was added to a composition prepared as described in Example 4. This coating was applied to primed polycarbonate and unprimed CR-39^® as described in Example 4. The coated, primed lenses and plaques were evaluated for abrasion resistance and tintability. Results from this testing are shown in Table I in Example 12.

Example 6 A quantity of 1.5 parts 3-lauramido-propyl- trimethylammonium sulfate Cyastat LS (Cytec Industries, Inc., West Patterson, NJ) was added to the composition prepared as described in Example 2. This coating was applied to primed polycarbonate lenses and plaques and unprimed CR-39^® as described in Example 2. The coated, primed lenses and plaques were evaluated for abrasion resistance and tintability. Results from this testing are shown in Table I in Example 12.

Example 7

A quantity of 15.1 parts 3-lauramido-propyl- trimethylammonium sulfate (Cytec Industries, Inc., West

Patterson, NJ) was added to the composition prepared in Example

2. This coating was applied to primed polycarbonate plaques and lenses and unprimed CR-39^® as described in Example 2. The coated, primed lenses and plaques were evaluated for abrasion resistance and tintability. Results from this testing are shown in Table I in Example 12.

Example 8 A quantity of 21.7 parts N,N-bis (2-hydroxyethyl) -N-

(3 ' -dodecyloxy-2 ' -hydroxypropyl) methylammonium methosulfate (Cyastat 609, Cytec Industries, Inc., West Patterson, NJ) was added to the composition prepared as described in Example 2. The coating was applied to primed polycarbonate lenses and plaques and unprimed CR-39^® as described in Example 2.

Example 9 A quantity of 11.8 parts N,N-bis (2-hydroxyethyl) -N- (3 ' - dodecyloxy-2 ' -hydroxypropyl) -methylammonium methosulfate (Cyastat 609, Cytec Industries, Inc., West Patterson, NJ) and 7.6 parts aliphatic polyglycidyl ether (Heloxy 5044, Shell Chemical Co. , Houston, TX) was added to the composition prepared as described in Example 4 with agitation. This coating was applied to primed polycarbonate plaques and lenses and unprimed CR-39^® as described in Example 4.

Example ιo

A quantity of 15.3 parts tetraethylammonium p- toluenesulfonate (Aldrich Chemical Co., Inc., Milwaukee, Wisconsin) was added to the coating prepared in Example 2 and stirred for 30 minutes at room temperature. The coating was aged for 2 days at room temperature and applied to primed polycarbonate and cured under the conditions described in Example 2. The coated, primed lenses and plaques were evaluated for abrasion resistance and tintability. Results from this testing are shown in Table I in Example 12.

Example 11 A quantity of 23.5 g of 3- tπethoxysilylpropyl- trimethylammonium chloride (Aldrich Chemical Co., Inc., Milwaukee, Wisconsin) was added with agitation to the coating prepared m Example 2 at room temperature. The coating was stirred for 30 minutes at room temperature. This coating was applied to primed polycarbonate plaques and lenses under the conditions described in Example 2.

The coated, primed lenses and plaques were evaluated for abrasion resistance and tintability. Results from this testing are shown m Table I in Example 12.

Example 12

Data from TABLE I demonstrates the effect of quaternary ammonium salts on the tintability and abrasion resistance of the unmodified coating compositions described in Examples 2 and 4. Examples 3, 6, 7, 8, 10, and 11 demonstrate the effect of adding quaternary ammonium salts to the coating composition described m Example 2. Examples 5 and 9 demonstrate the effect of adding quaternary ammonium salts to the coating composition described in Example 4. These examples demonstrate the high tintability and abrasion resistance of coating compositions of the present invention. Examples 3, 5 and 11 additionally demonstrate that use of silylated quaternary ammonium salts actually enhances abrasion resistance of the cured coatings. TABLE I. Abrasion Resistance, Tintability, and Adhesion

While the invention has been described in detail with reference to certain preferred embodiments thereof, it will be understood that modifications and variations are within the spirit and scope of that which is described and claimed.

Claims

1. A coating composition comprising:

(A) a base resin that does not contain non- silylated acrylate monomer;

(B) a tint-enhancing quantity of a quaternary ammonium salt; and

(C) an effective quantity of a crosslinking agent wherein said coating composition forms a highly tintable, abrasion-resistant, adhesive coating upon curing.

2. The composition according to claim 1, wherein said base resin comprises condensable substituents.

3. The composition according to claim 2, wherein said base resin further comprises epoxy-functional substituents .

4. The composition according to claim 1, wherein said base resin comprises a partial condensate of one or more silanols .

5. The composition according to claim 4, wherein said partial condensate comprises at least one epoxy functional silanol.

6. The composition according to claim 5, wherein said base resin comprises up to about 100 percent of epoxy functional silanol, based on the total weight of base resin.

7. The composition according to claim 5, wherein said base resin comprises from about 0.1 up to about 50 percent of epoxy functional silanol, based on the total weight of base resin.

8. The composition according to claim 5, wherein said base resin comprises from about 20 to about 45 percent of epoxy functional silanol, based on total weight of base resin.

9. The composition according to claim 5, wherein said epoxy functional silanol is selected from silanols having the formula:

^■Si(0H)₃._n R_n

wherein n is a number selected from 0 to 2, R is selected from a hydrogen atom, an optionally substituted, branched or straight chain, alkyl, alkenyl, alkynyl radical having from about 1 to about 10 atoms in the backbone, and Q is selected from

mixtures of (A) and (B) , where W is independently selected from a hydrogen atom, an optionally substituted, branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 10 atoms in the backbone.

10. The composition according to claim 5, wherein said epoxy functional silanol is gamma-glycidoxypropyl silanol .

11. The composition according to claim 4, wherein said partial condensate comprises a mixture of gamma- glycidoxypropyl silanol and methyl silanol .

12. The composition according to claim 1, wherein said composition comprises from about 0.5 to about 50 weight percent of the quaternary ammonium salt, based on the total weight of base resin.

13. The composition according to claim 1, wherein said composition comprises from about 0.5 to about 40 weight percent of the quaternary ammonium salt, based on the total weight of base resin.

14. The composition according to claim 1, wherein said composition comprises from about 2 to about 20 weight percent of the quaternary ammonium salt, based on the total weight of base resin.

15. The composition according to claim 1, wherein said quaternary ammonium salt is selected from quaternary ammonium salts having the formula:

Z,N X^"

wherein each Z is independently selected from an optionally substituted, branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 20 atoms, and wherein X is a counterion selected from a halogen, a nitrate, a sulfate, or a sulfonate moiety.

16. The composition according to claim 4, wherein said quaternary ammonium salt is selected from quaternary ammonium salts having the formula:

Z„N⁺ X^"

wherein each Z is independently selected from an optionally substituted, branched or straight chain, alkyl , alkenyl , alkynyl , or aryl radical having from about 1 to about 20 atoms, and wherein X is a counterion selected from a halogen, a nitrate, a sulfate, or a sulfonate moiety.

17. The composition according to claim 16, wherein said quaternary ammonium salt is selected from 3- lauramidopropyltrimethylarnmonium sulfate, N,N-bis(2- hydroxyethyl) -N- (3 ' -dodecyloxy-2 ' -hydroxypropyl} - methylammonium methosulfate, tetraethylammonium p-toluene sulfonate, glycidyltrimethylammonium chloride, or combinations of any two or more thereof .

18. The composition according to claim 16, wherein said quaternary ammonium salt is a silylated quaternary ammonium salt .

19. The composition according to claim 18, wherein said silylated quaternary ammonium salt comprises one or more alkoxysilane moieties.

20. The composition according to claim 19, wherein said silylated quaternary ammonium salt is selected from N- trimethoxysilylpropyl-N,N,N-trimethylammonium chloride, N- trimethoxysilylpropyl-N,N,N-1ri-n-butylammonium bromide, trimethoxysilylpropyl-N,N,N-tri-n-butylammonium chloride, N- triethoxysilylpropyl-N,N,N-trimethylammonium chloride, or combinations of any two or more thereof.

21. The composition according to claim 1, wherein said coating composition comprises up to about 25 weight percent of crosslinking agent, based on the total weight of base resin.

22. The composition according to claim 1, wherein said coating composition comprises from about 0.1 to about 20 weight percent of crosslinking agent, based on the total weight of base resin.

23. The composition according to claim 1, wherein said coating composition comprises from about 0.1 to about 15 weight percent of crosslinking agent, based on the total weight of base resin.

24. The composition according to claim 1, wherein said crosslinking agent is a disilanol .

25. The composition according to claim 24, wherein said disilanol is selected from disilanols having the formula:

B_n (OH) _VnSi A Si (OH) ₃__nB_n

wherein A is selected from an optionally substituted branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 10 atoms in the backbone, B is selected from a hydrogen atom, an optionally substituted, branched or straight chain, alkyl, alkenyl, alkynyl, or aryl radical having from about 1 to about 10 atoms in the backbone, and wherein n is a number selected from 0 to 2.

26. The composition according to claim 1, wherein said crosslinking agent is a trisilanol.

27. The composition according to claim 26, wherein said trisilanol comprises the hydrolysis product of tris[3- (trimethoxysilyl)propyl] isocyanurate.

28. The composition according to claim 3, wherein said crosslinking agent is selected from a polycarboxylic acid, a polyanhydride, a polyimide, a polyamine, or combinations of any two or more thereof.

29. The composition according to claim 1, wherein said base resin further comprises a colloidal metal oxide.

30. The composition according to claim 29, wherein said base resin comprises up to about 90 weight percent of the colloidal metal oxide, based on total weight of base resin.

31. The composition according to claim 30, wherein said colloidal metal oxide is colloidal silica.

32. The composition according to claim 1 further comprising a curing catalyst.

33. The composition according to claim 32, wherein said composition comprises up to about 5 weight percent of said curing catalyst, based on total weight of base resin.

34. The composition according to claim 32, wherein said composition comprises from about 0.1 to about 3 weight percent of said curing catalyst, based on the total weight of base resin.

35. The composition according to claim 32, wherein said composition comprises from about 0.1 to about 1 weight percent of curing catalyst, based on total weight of base resin.

36. A coating composition comprising:

(A) a base resin that does not contain non- silylated acrylate monomer, said base resin comprising from about 0 to about 90 percent colloidal silica, and from about 10 to about 100 percent of a partial condensate of one or more silanols, wherein all percentages are based on total weight of base resin;

(B) an effective quantity of a crosslinking agent; and

(C) a tint-enhancing quantity of a quaternary ammonium salt ; wherein said composition forms a highly tintable, abrasion-resistant, adhesive coating upon curing.

37. A method for coating a solid substrate comprising:

(i) preparing a coated substrate by contacting at least one surface of a solid substrate with a coating composition which forms a transparent, highly tintable, abrasion- resistant coating upon curing, said coating composition comprising:

(A) a base resin that does not contain non-silylated acrylate monomer;

(B) a tint-enhancing quantity of a quaternary ammonium salt; and

(C) an effective quantity of a crosslinking agent; then

(ii) subjecting said coated substrate to curing conditions such that the cured coating can subsequently be tinted, if desired, wherein said method produces a solid substrate with a highly tintable, abrasion-resistant, adhesive coating thereon.

38. An article comprising a solid substrate having a highly tintable, abrasion-resistant coating thereon, prepared in accordance with the method of claim 37.