Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2001-01-16
2002-08-13
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C525S190000
Reexamination Certificate
active
06432484
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to curable compositions and more particularly to low VOC (volatile organic component) ambient temperature curable coating compositions suitable for use in automotive refinish applications. A number of clear and pigmented coating compositions are utilized in various coatings, such as, for example, primers, basecoats and clearcoats used in automotive refinish coatings, which are generally solvent based.
In repairing damage, such as dents and scratches to autobodies, the original coating in and around the damaged area is typically sanded or ground out by mechanical means. Some times the original coating is stripped off from a portion or off the entire autobody to expose the substrate (e.g., bare metal) underneath. After repairing the damage, the repaired surface is coated, preferably with low VOC coating compositions, typically in portable or permanent low cost painting enclosures vented to the atmosphere to remove the organic solvents from the freshly applied paint coatings in an environmentally safe manner. Generally, the drying and curing of the freshly applied paint takes place within these enclosures. Furthermore, it is preferable to conduct the foregoing drying and curing steps within the enclosure to prevent the wet paint from collecting dirt in the air or other contaminants.
As these paint enclosures take up significant floor space of typical small autobody paint repair shops, these shops prefer to dry and cure these paints as rapidly as possible. More expensive enclosures are frequently provided with heat sources, such as conventional heat or infrared lamps located inside the enclosure to cure the freshly applied paint at accelerated rates. Therefore, to provide more cost effective utilization of shop floor space and to minimize fire hazards resulting from wet coatings from solvent based coating compositions, there exists a continuing need for low VOC fast curing coating formulations which cure under ambient conditions while still providing outstanding performance characteristics such as solvent resistance
One of the approaches used in addressing the foregoing involves utilizing a binder system that contains a conventional polyester resin functionalized with acetoacetate groups and having at least two acrylate moieties. However, the use of acrylate functionalities, such as those disclosed in U.S. Pat. No. 5,288,802, is not the best approach, if rapid cure coatings are desired. Thus, a continuing need still exists for a low VOC coating composition that cures rapidly under ambient conditions.
Another disadvantage of the compositions described in U.S. Pat. No. 5,288,802 is the disagreeable and offensive odor associated with acrylate functionalized diluents used in these compositions.
Thus, it would be most advantageous to provide a composition that not only cures more rapidly than current undercoatings of this type to permit autobody paint repair shops to rapidly complete the repairs, but also has less offensive odors.
STATEMENT OF THE INVENTION
The present invention is directed to a coating composition comprising:
a crosslinking component comprising a polyamine, a polyketimine, or a combination thereof, wherein said polyamine has an average of at least two amine functionalities per polyamine molecule and wherein said polyketimine has an average of at least two ketiniine functionalities per polyketimine molecule; and
a binder component comprising:
at least one structured reactive diluent having a GPC weight average molecular weight in the range of from 100 to 45,000, said diluent being substantially free from acrylate functionalities and having at least two acetoacetate functionalities per diluent molecule.
The present invention is further directed to a method of producing a coating on a substrate, said method comprising:
mixing a crosslinking component with a binder component to form a pot mix, said crosslinking component comprising a polyamine, a polyketimine, or a combination thereof, said polyamine having an average of at least two amine functionalities per polyamine molecule and said polyketimine having an average of at least two ketimine functionalities per polyketimine molecule; said binder component comprising at least one structured reactive diluent having a GPC weight average molecular weight in the range of from 100 to 45,000, said diluent being substantially free from acrylate functionalities and having at least two acetoacetate functionalities per said diluent molecule;
applying a layer of said pot mix on said surface; and
curing said layer under ambient conditions to form said coating on said surface of said substrate.
One of the advantages of the present invention is its low VOC, which is significantly below the current guidelines of Environment Protection Agency (EPA) of the United States.
Another advantage of the composition of the present invention is that it is free from isocyanate groups. As a result, it has less toxicity than conventional isocyanate group-containing coating compositions, such as polyurethanes. This reduced toxicity is particularly helpful for auto paint repair shops that may not have physical facilities required to handle more toxic compositions containing isocyanate functionalities.
Yet another advantage of the composition of the present invention is that it reduces the time-to-sand, before the coating can be sanded without fouling the sandpaper, thereby increasing the number of repairs that could be performed in a day.
Still another advantage of the composition of the present invention is that it does not release pungent odors often associated with low molecular weight compounds containing acrylate functional moieties. Compounds such as these are employed in conventional low VOC non-isocyanate containing coating compositions.
DETAILED DESCRIPTION OF THE INVENTION
As used herein:
“Two-pack coating composition” means a thermosetting composition comprising two components that are stored in separate containers, which are typically sealed for increasing the shelf life of the components of the coating composition. The components are mixed just prior to use to form a pot mix, which has a limited pot life, typically a few minutes, such as 15 minutes to 45 minutes to a few hours, such as 2 hours to 6 hours. The pot mix is applied as a layer of desired thickness on a substrate surface, such as an autobody. After application, the layer dries and cures to form a coating on the substrate surface having desired coating properties, such as solvent resistance.
“Low VOC coating composition” means a coating composition that is less than about 0.6 kilogram of organic solvent per liter (5 pounds per gallon) of the composition, as determined under the procedure provided in ASTM D3960.
“High solids composition” means a coating composition having a solids component of above 30 percent, preferably in the range of from 40 to 95 percent and more preferably in the range of from 45 to 80 percent, all in weight percentages based on the total weight of the composition.
“GPC weight average molecular weight” means a weight average molecular weight measured by utilizing gel permeation chromatography. A high performance liquid chromatograph (HPLC) supplied by Hewlett-Packard, Palo Alto, Calif. was used. Unless stated otherwise, the liquid phase used was tetrahydrofurane and the standard was polymethyl methacrylate.
“Polydispersity” means GPC weight average molecular weight divided by GPC number average molecular weight.
“Polymer solids” or “Binder solids” means a polymer or binder in its dry state.
“(Meth)acrylate” means acrylate and methacrylate.
“Structured reactive diluent” means a structured molecule, such as a macromolecule, oligomer or polymer, which unlike conventional resins, has a very well defined structure. Examples of these diluents include star, expanded star, dendritic (hyper branched), or cyclodextric structured molecules.
One efficient approach to reduce VOC is to use high solids coating compositions containing low weight average molecular weight, i.e., less than about 10,000, structured reacti
Corcoran Patrick Henry
Douglas Carl Brent
Felton Eric Diaz
Huybrechts Josef
Jaycox Gary Delmar
Cameron Erma
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
LandOfFree
Coating compositions containing highly structured... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coating compositions containing highly structured..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coating compositions containing highly structured... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2915520