Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1994-12-16
2001-03-13
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S431000, C428S436000, C428S458000, C428S460000, C428S480000, C428S481000, C428S482000, C428S526000, C428S528000, C525S398000, C525S399000, C525S400000, C525S441000, C525S443000, C525S444000, C525S509000, C525S515000, C525S519000, C525S517000, C528S260000, C528S261000, C528S263000, C528S264000
Reexamination Certificate
active
06200683
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to coating compositions. Particularly, the invention pertains to compositions which can be cured to form a coating having improved stain resistant properties. More particularly, the compositions of this invention can be cured to form a coating having not only improved stain resistant properties, but also low temperature flexibility.
BACKGROUND OF THE INVENTION
It is well known in the coating industry that coil coating is a cost effective and efficient method of applying coating compositions onto a number of different substrates, particularly metals. For example, coil coating processes are often used for finishing panels employed in the fabrication of many major appliances such as refrigerators, vending machines, washers, dryers, and other metal cabinetry.
Compositions which are used to coat a metal substrate prior to the metal being formed into its desired shape must be curable to form a coating which is hard, yet flexible, in order for the pre-coated metal to withstand the various post-coating forming operations. In addition, it is often very desirable that, once cured, these types of coating compositions possess a high level of stain resistance and a high gloss (i.e., a 60° gloss value of at least 70%, preferably at least 80%, as determined by ASTM D 523-78). These features impart on the resulting coated substrate not only functionality, but also an attractive appearance to the finished article made therefrom.
In view of the many advantages associated with the implementation of pre-coated metals, those in the coatings industry are continually attempting to formulate improved compositions which can be used for these purposes. One such attempt is set out in U.S. Pat. No. 5,166,288.
That particular patent discloses that a composition, which contains a high molecular weight polyester (i.e, a number average molecular weight of 15,000 to 30,000) having a glass transition temperature of 5° to 40° C., a melamine resin which contains 60% by weight or more of hexamethoxymethylmelamine monomer, and an amine-blocked derivative of a long-chain alk-ylbenzenesulfonic acid having C
10
-C
20
alkyl group, can be cured to form a coating which is hard, yet flexible, and which resists stains. However, notwithstanding the above, the coating composition disclosed therein has a number of shortcomings associated therewith.
For example, U.S. Pat. No. 5,166,288 reveals that, when the coating is formulated for processability (flexibility) at temperatures below 20° C., the cured coating's stain resistant properties decrease (see, e.g., Example 2, Table 2). This is an expected phenomena since it is known in the coatings industry that ingredients employed to give a coating low temperature flexibility typically reduce the resulting film's stain resistant properties. Accordingly, those in the coatings industry would consider a composition to be an advancement in the art if it can be cured to form a coating which has excellent stain resistant properties and low temperature flexibility (e.g., flexible at temperatures at or below about 10° C.).
Furthermore, it is also known in the coatings industry that the implementation of lower molecular weight binders facilitate the formulation of coatings with a higher solids concentration (i.e., a solids concentration which is greater than about 50 weight percent based upon the total weight of the composition). This higher solids concentration is often a very desirable feature to the end user.
In view of the above, those in the coatings industry would consider a composition to be an advancement in the art if, in addition to having a higher solids concentration, the composition can be cured to form a coating which displays excellent stain resistance and low temperature flexibility properties. It would also be considered as an advancement in the art if, in addition to having the aforementioned properties, the composition can be cured to form a film having a high gloss.
SUMMARY OF THE INVENTION
In view of the above, one object of this invention is to provide a composition which can be cured to form a film having improved stain resistant properties.
Another object of this invention is to provide a composition which can be cured to form a film having not only improved stain resistance, but also low temperature flexibility.
Yet another object of this invention is to provide a coating composition which can be cured to form a coating having not only a high gloss and improved stain resistant properties, but also low temperature flexibility.
Still another object of this invention is to provide an improved composition which is particularly adapted for use in coil coating processes.
These and other objects are achieved through the formulation of a novel coating composition which combines a polyester-based resin, a crosslinker, an acid catalyst, and a urea-aldehyde resin. The polyester-based resin can be a single polyester resin and or a blend of at least two different polyester resins.
The polyester-based resin is typically present in an amount ranging from between 50% to 95% by weight; the crosslinker is typically present in an amount ranging from between 5% to 45% by weight; the acid catalyst is typically present in an amount ranging from between 0.1% to 15.0% by weight; and, the urea-aldehyde is typically present in an amount ranging from between 0.1% to 50% by weight. These weight percentages are based upon the total weight of resin solids in the coating composition.
The compositions of the present invention can be cured to form a film having improved stain resistant properties. The compositions of the present invention can also be formulated such that cured films resulting therefrom not only have improved stain resistant properties, but also have low temperature flexibility. In addition to the aforementioned characteristics, the compositions of the present invention can further be formulated such that cured films resulting therefrom have a high gloss.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art upon reading the specification and the appended claims which follow.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention, there are provided novel compositions which can be cured to form a film having improved stain resistant properties. In a preferred embodiment of the invention, the coating composition can be cured to form coatings having improved stain resistant properties and low temperature flexibility.
As used herein, the term “low temperature flexibility” refers to a cured film's ability to flex at temperatures below about 10° C. without showing any substantial visible cracks at the point of flex, when observed under 10-power magnification.
The coating compositions of the present invention include a combination of a polyester-based resin, a crosslinker, an acid catalyst and a urea-aldehyde resin. Specifically, these coating compositions comprise a polyester-based resin which, in turn, comprises either a single polyester resin or a blend of at least two different polyester resins.
When a single polyester resin is employed in the polyester-based resin component, this polyester resin typically has a number-average molecular weight (Mn) ranging from between 3,000 to 30,000. The “number-average molecular weight” as mentioned above is measured by gel permeation chromatography (GPC) using the calibration curve of polystyrene standards. Moreover, the single polyester resin has a glass transition temperature (T
g
) typically ranging from between −25° to 50° C. The “glass transition temperature” as mentioned herein is measured according to the differential scanning calorimetry (DSC) method.
On the other hand, when a blend of at least two different polyesters are employed in the polyester-based resin component, this blend is typically composed of at least a first polyester resin and a second polyester resin, wherein the first polyester resin typically has a number-average molecular weight (Mn), as determined by GPC, which ranges from
Huffman W. Scott
Montague Robert A.
Richardson Jamel S.
Sundararaman Padmanabhan
Altman Deborah M.
Chen Vivian
Chirgott Paul S.
PPG Industries Ohio Inc.
LandOfFree
Coil coating compositions with low temperature flexibility... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coil coating compositions with low temperature flexibility..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coil coating compositions with low temperature flexibility... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2537687