Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2000-04-20
2003-03-25
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C106S287130, C106S287140, C524S783000, C524S785000, C524S789000, C524S837000
Reexamination Certificate
active
06538092
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to coating compositions and methods of making and using same, and more particularly but not by way of limitation, to coating compositions which, when cured, provide substantially transparent coatings having abrasion resistance and a matched refractive index to that of the substrate.
The present invention also relates to liquid coating compositions and methods of making and using same having improved abrasion resistance and improved stability wherein the liquid coating compositions are derived from aqueous-organic solvent mixtures containing effective amounts of an epoxy-functional silane, colloidal metal oxide composite, a tetrafunctional silane, and colloidal silica.
2. Description of Prior Art
Silica based coatings deposited on plastic materials are useful for their abrasion resistance and weatherability and thus extend the useable life of the plastic material. These coatings, in most cases, do not match the refractive index of the plastic material and allow for interference patterns to arise due to the refractive index mismatch between the cured coating film and the plastic substrate material. This mismatch leads to increased reflectivity of the coated plastic material and to exacerbation of material flaws due to the increased reflectivity.
BRIEF SUMMARY OF THE INVENTION
The present invention provides compositions having improved stability which, when applied to a variety of substrates and cured, form transparent coatings having abrasion resistant properties and a matched refractive index to that of the substrate as well as methods of making and using said coating compositions.
Broadly, the coating compositions of the present invention comprise an aqueous-organic solvent mixture containing from about 10 to about 90 weight percent, based on the total solids of the composition, of a mixture of hydrolysis products and partial condensates of an epoxy-functional sijane, from about 1 to about 90 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, from about 1 to 90 weight percent, based on the total solids of the composition, of a metal oxide composite colloid, from about 1 to 75 weight percent, based on the total solids of the composition, of a colloidal silica material, and from about 1 to 75 weight percent, based on the total solids of the composition, of a tetrafunctional silane.
The coating compositions of the present invention may further include from about 0.1 to about 50 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.
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 which have improved adhesion properties, improved resistance to crack formation, and a matched refractive index to that of the substrate.
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
Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.
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 possess improved adhesion, improved resistance to crack formation, and have a matched refractive index to that of the substrate.
For measuring the refractive indexes of the cured coating compositions, each composition was applied to a cleanly etched lead-silicate glass plaque by dip coating at 2 inches per minute and curing for a period of 1 hour at 120° C. The refractive indexes were measured using a Bausch and Lomb Abbe-3L refractometer. Either diiodomethane or 1-bromonaphthalene was used as the contact liquid. The standard procedures for measurement and instrument maintenance contained in the operator's manual for the Bausch and Lomb Abbe-3L refractometer were used for data gathering and processing. For testing coated samples, coating compositions were applied to ADC lenses and cured at a temperature in the range from 95° C. to 120° 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 cracking and adhesion consists of immersion of the coated article in boiling water or boiling tap water tint for a period of time, e. g. 30 minutes, followed by inspection for crack formation and testing for adhesion. Specifically, lenses were tested in BPI Black Tint (Brain Power, Inc.) under boiling conditions. In this test a bottle of BPI 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, sample coated substrates 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
Lembo Bryan S.
Terry Karl W.
Dawson Robert
Dunlap Codding & Rogers P.C.
SDC Coatings Inc.
Zimmer Marc S.
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