Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1999-10-21
2002-02-19
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C528S018000, C528S026000, C528S027000, C528S031000, C528S032000, C528S033000, C528S034000
Reexamination Certificate
active
06348269
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to coating compositions, and more particularly but not by way of limitation, to coating compositions which, when cured, provide substantially transparent abrasion resistant coatings having improved adhesion and increased stability to crack formation.
The present invention also relates to liquid coating compositions having improved stability wherein the liquid coating compositions are derived from aqueous-organic solvent mixtures containing effective amounts of epoxy functional silanes, disilanes and carboxylic acid components.
2. Description of Prior Art
The prior art is replete with compositions which, when applied to substrates and cured, provide transparent, abrasion resistant coatings for the substrates. Such coatings are especially useful for polymeric substrates where it is highly desirable to provide substrates with abrasion resistant surfaces. However, adhesion problems and crack formation can result from environmental exposure and usual processing of the coated articles. Thus, a need has long existed for improved compositions having improved stability, and which, when applied to a substrate, such as a polymeric substrate, and cured provide transparent, abrasion resistant coatings with improved adhesion and stability to crack formation. It is to such compositions and processes by which such compositions are manufactured and applied to substrates that the present invention is directed.
BRIEF SUMMARY OF THE INVENTION
The present invention provides coating compositions having improved stability which, when applied to a variety of substrates and cured, form transparent abrasion resistant coatings having improved adhesion and resistance to crack formation. Broadly, the coating compositions of the present invention comprise an aqueous-organic solvent mixture containing from about 10 to about 99.9 weight percent, based on the total solids of the composition, of a mixture of hydrolysis products and partial condensates of an epoxy functional silane, a disilane, and from about 0.01 to about 80 weight percent, based on the total weight of the composition, of a carboxylic acid functional compound selected from the group consisting of carboxylic acids, multifunctional carboxylic acids, anhydrides, and combinations thereof. The epoxy functional silane and the disilane are present in the aqueous-organic solvent mixture in a molar ratio of from about 0.05:1 to about 5:1. The coating compositions of the present invention may further include from about 0.1 to about 80 weight percent of a mixture of hydrolysis products and partial condensates of one or more silane additives, based on the total solids of the composition, and/or an amount of colloidal silica or a metal oxide or combinations thereof, equivalent to from about 0.1 to about 75 weight percent solids, based on the total solids of the composition.
It is an object of the present invention to provide coating compositions having improved stability which form transparent coatings upon curing. It is a further object of the present invention to provide stable coating compositions, which form transparent coatings upon curing having abrasion resistance, improved adhesion, and improved resistance to crack formation.
Other objects, advantages and features of the present invention will become apparent upon reading the following detailed description in conjunction with the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to coating compositions having improved stability which, when applied to a variety of substrates and cured, form substantially transparent abrasion resistant coatings, which provide improved adhesion and improved resistance to crack formation. For testing coated samples, coating compositions were applied to poly (diethylene glycol-bis-allyl carbonate) lenses, hereinafter referred to as ADC lenses and cured at a temperature of 110° C. for a period of 3 hours. Semi-quantitative assessments of the extent of cracking and adhesion were made using the following tests.
For testing adhesion of the coated articles the procedures of ASTM D-3359, i.e. the tape test, were followed.
A typical test for measuring the adhesion and resistance to cracking of a coating composition cured on a substrate consists of immersion of the coated article in boiling aqueous tint for a period of time, e. g. 30 minutes, followed by inspection for crack formation and testing for adhesion. Within the ophthalmic industry it is common to use such tint solutions on lenses to reduce the overall transmission of light through the lens, for example for a sunglass application. Thus, it is necessary for cured coating compositions on ophthalmic lenses not to crack or lose adhesion as a result of treatments in boiling tint. In the boiling tint test, coated and cured lenses were tested in BPI Black Tint (Brain Power, Inc.) under boiling conditions. In this test a bottle of BPI Black Tint (approximately 100 grams) was diluted to about 900 grams with tap water and brought to a boil. The coated article was immersed in the boiling solution for a period of 30 minutes. The coated article was removed from the tint solution and inspected for cracking and tested for adhesion.
For testing abrasion resistance of coated substrates, any of a number of quantitative test methods may be employed, including the Taber Test (ASTM D-4060), the Tumble Test and Standard Method for the Modified Bayer Test, which is described in The AR Council of America Standard Testing Procedures section 5.2.5 and is a variation of the test method, ASTM F735-81. In addition, there are a number of qualitative test methods that may be used for measuring abrasion resistance, including the Steel Wool Test and the Eraser Test In the Steel Wool Test and the Eraser Test, coated substrate samples are scratched under reproducible conditions (constant load, frequency, etc.). The scratched test samples are then compared and rated against standard samples. A semi-quantitative application of these test methods involves the use of an instrument, such as a Spectrophotometer or a Colorimeter, for measuring the scratches on the coated substrate as a haze gain.
The measured abrasion resistance of a cured coating on a substrate, whether measured by the Modified Bayer Test, Taber Test, Steel Wool Test, Eraser Test, Tumble Test, etc. is a function, in part, of the cure temperature and cure time. In general, higher temperatures and longer cure times result in higher measured abrasion resistance. Normally, the cure temperature and cure time are selected for compatibility with the substrate; although, sometimes less than optimum cure temperatures and cure times are used due to process and/or equipment limitations. It will be recognized by those skilled in the art that other variables, such as coating thickness and the nature of the substrate, will also have an effect on the measured abrasion resistance. In general, for each type of substrate and for each coating composition there will be an optimum coating thickness. The optimum cure temperature, cure time, coating thickness, and the like, can be readily determined empirically by those skilled in the art.
In the test method employed to determine the abrasion resistance of the coating compositions of the present invention, a commercially available alundum (grain code 1524, 12 grit, alundum ZF) sold by Norton Advanced Ceramics of Canada Inc., 8001 Daly Street, Niagra Falls, Ontario, was used as the abrasive material. In this test, 540 grams alundum was loaded into a 9 {fraction (5/16)}″×6 ¾″ cradle fitted with four lenses. Each set of four lenses, herein referred to as ADC lenses, and two coated lenses, were subjected to a 4 inch stroke (the direction of the stroke coinciding with the 9 {fraction (5/16)}″ length of the cradle) at an oscillation frequency of 300 strokes per minute for a total of 4 minutes. The lens cradle was repositioned by turning 180 degrees after the initial 2 minutes of oscillations. Repositioning of the cradle wa
Dawson Robert
Dunlap Codding & Rogers P.C.
Feely Michael J
SDC Coatings Inc.
LandOfFree
Composition for providing an abrasion resistant coating on a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composition for providing an abrasion resistant coating on a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composition for providing an abrasion resistant coating on a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2942557