Coating processes – Solid particles or fibers applied – Uniting particles to form continuous coating with...
Reexamination Certificate
2001-10-04
2003-12-30
Cameron, Erma (Department: 1762)
Coating processes
Solid particles or fibers applied
Uniting particles to form continuous coating with...
C427S195000
Reexamination Certificate
active
06669984
ABSTRACT:
FIELD OF THE INVENTION
The subject invention generally relates to a powder-based coating composition, a cured film of the powder-based coating composition, and a method of improving a color strength of the cured film. More specifically, the subject invention relates to an extruded powder-based coating composition, and a method of improving the color strength of a cured film of the powder-based coating composition, that combine a surface-active agent with a powder-based binder and a pigment to improve the color strength such that the amount of pigment that is used can be reduced.
BACKGROUND OF THE INVENTION
Powder-based coating compositions are known in the art. Conventional powder-based coating compositions typically combine a powder-based binder and a pigment to form a mixture. The mixture is then extruded to form an extrudate that is cooled and ground to form the conventional powder-based coating compositions that are applied to, and cured on, a substrate to form a cured film for both aesthetic and functional purposes.
In the prior art, during the combination of the powder-based binder and the pigment to form the mixture and also during the extrusion of the mixture, it is commonplace that the pigment is not efficiently ‘wetted’ and not uniformly dispersed throughout the mixture and throughout the powder-based coating composition. As a result, to achieve suitable color strength for both the aesthetic and functional purposes, it is necessary that these conventional powder-based coating compositions include excessive amounts of the pigment for combination with the powder-based binder.
As understood throughout the art, an excessive amount of pigment in powder-based coating compositions is very problematic. For instance, the pigment is frequently the most expensive component of the powder-based coating composition. As a result, an excessive amount of pigment drives the cost of the powder-based coating composition upward which is undesirable. Furthermore, an excessive amount of pigment contributes to difficulties in applying the powder-based coating composition to the substrate and also leads directly to poor appearance of the cured film. Finally, without the excessive amount of pigment, the powder-based coating compositions of the prior art are unable to achieve color strengths that are suitable across the various industries.
Due to the inadequacies of the powder-based coating compositions of the prior art, it is desirable to provide a unique and novel powder-based coating composition and method that improve a color strength of a cured film.
SUMMARY OF THE INVENTION
A powder-based coating composition and a method of improving a color strength of a cured film of the powder-based coating composition are disclosed. The method includes the step of combining at least a powder-based binder, a pigment, and a surface-active agent to form a mixture. The mixture is then extruded to form an extrudate of the mixture. The powder-based coating composition is then produced from the extrudate of the mixture. After the powder-based coating composition is produced from the extrudate, the composition is applied to a substrate. Finally, the powder-based coating composition is cured to form the cured film. The surface-active agent in the mixture that is extruded improves the color strength of the powder-based coating composition and the cured film without detrimental effects to the physical properties of the cured film.
Accordingly, the subject invention provides a unique and novel powder-based coating composition and method that utilize a surface-active agent in the powder-based coating composition to affect the pigment and improve the color strength of the cured film of the powder-based coating composition produced according to the method.
DETAILED DESCRIPTION OF THE INVENTION
A method of improving a color strength of a cured film of a powder-based coating composition is disclosed. The method of the subject invention includes the step of combining at least a powder-based binder, a pigment, and a surface-active agent to form a mixture. The mixture is then extruded to form an extrudate of the mixture, and then the powder-based coating composition of the subject invention is produced from the extrudate of the mixture. The step of extruding the mixture into the extrudate, and the step of producing the powder-based coating composition from the extrudate will be described in detail below.
After combination, the mixture includes from 45 to 99, preferably from 60 to 70, parts by weight of the powder-based binder based on 100 parts by weight of the mixture. The powder-based binder in the mixture more specifically includes a resin, having a functional group, and a cross-linking agent. The cross-linking agent is reactive with the functional group of the resin.
The resin of the powder-based binder is preferably selected from the group consisting of acrylic resins, epoxy resins, phenolic resins, polyester resins, urethane resins, and combinations thereof. Furthermore, the mixture includes from 45 to 75, preferably from 55 to 65, parts by weight of the resin based on 100 parts by weight of the mixture. The functional groups of the preferred resins set forth above include, but are not limited to, epoxy functional groups, carboxy functional groups, hydroxy functional groups, and combinations thereof. The most preferred resin of the powder-based binder is a carboxylated polyester resin. One suitable carboxylated polyester resin is commercially available as Uralac® P 3400 from DSM Engineering Plastic Products, Reading, Pa. An alternative carboxylated polyester resin suitable for the resin of the powder-based binder is commercially available as Uralac® P 5998 also from DSM Engineering Plastic Products.
The cross-linking agent that is reactive with the functional group of the resin is preferably selected from the group consisting of aminoplasts, blocked isocyanates, polycarboxylic acids, acid anhydrides, polyamines, polyphenols, epoxy resins, and combinations thereof. Furthermore, the mixture includes from 0.5 to 25.0, preferably from 1 to 15, parts by weight of the cross-linking agent based on 100 parts by weight of the mixture. The most preferred cross-linking agent of the powder-based binder is triglycidyl isocyanurate (TGIC). One suitable TGIC is commercially available as Araldite® PT 810 from Vantico, Brewster, N.Y. Alternatively, if the cross-linking agent is the epoxy resin, then one suitable epoxy resin is commercially available as Araldite® GT 7013 from Vantico, Brewster, N.Y.
The pigment is combined with the powder-based binder and the surface-active agent to form the mixture. Depending on the particular embodiment, the pigment may include an inorganic pigment, an organic pigment, or both. Generally, the mixture includes from 1 to 50, preferably from 30 to 40, parts by weight of the pigment based on 100 parts by weight of the mixture. Carbon black pigment may be used. Other pigments, both inorganic and organic, may also be combined to form the mixture. Suitable inorganic pigments that may be combined to form the mixture include, but are not limited to, titanium dioxide pigment, zinc oxide, zinc sulfide, barium sulfate, inorganic colored pigments, such as iron oxide (red, black, brown, and yellow), chrome yellow, moly orange, titanium yellow, nickel titanate yellow, chrome greens such as chromium oxide green, ferric ferrocyanide, lead chromate, and the like. The most preferred organic pigments are selected from the group consisting of phthalocyanine-based green pigment, phthalocyanine-based blue pigment, and combinations thereof. Other organic pigments may be included. Other suitable organic pigments that may be combined to form the mixture include, but are not limited to, metallized and non-metallized azo pigments such as cromophthal pigments, azomethine pigments, methine pigments, anthraquinone pigments, perinone pigments, perylene pigments, diketopyrrolopyrrole pigments, thioindigo pigments, iminoisoindoline pigments, isoindolinone pigments, iminoisoindolinone pigments, quinacridone pigments such as quina
Alford William H.
Anchor Michael J.
Drewno Gregory W.
BASF Corporation
Cameron Erma
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