Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-11-09
2001-11-06
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S108000, C525S111000, C525S113000, C525S118000, C525S119000, C525S120000, C525S121000, C525S123000, C525S124000, C525S125000, C525S161000, C525S162000, C525S163000, C525S166000, C525S170000, C525S179000, C525S183000, C525S207000, C525S213000, C525S217000, C428S461000
Reexamination Certificate
active
06313224
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to curable liquid or powder coating compositions containing flow modifiers and such polymeric flow modifiers and multilayered coatings with the curable coating composition in the cured state.
BACKGROUND OF THE INVENTION
Flow or surface modifiers or control agents or additives are used in the coatings industry to control interfacial tension and surface tension gradients of coating compositions. Lower pollution-type coatings such as waterborne coatings, powder coatings, and, to some extent, high solids coatings utilize flow modifiers to control leveling of the coating film. Typical powder coating compositions contain a flow modifier to enhance their rheology or to control cratering and reduce orange-peel characteristics to provide for smoother, better looking coatings. Common flow modifiers include: acrylics such as poly(2-ethylhexyl acrylate), poly(lauryl acrylate), poly(butyl acrylate), poly(ethylacrylate-2-ethylhexyl acrylate), poly(lauryl methacrylate) and the like (see in this regard U.S. Pat. No. 3,787,340 to Labana et al.). Other useful flow additives include silicon-containing polymers and fluorinated polymers, such as the esters of polyethylene glycol or polypropylene glycol, and fluorinated fatty acids.
Coating compositions used in multilayered coatings for metallic and plastic substrates like those for automotive applications must meet a number of performance requirements which can vary depending on the previous and subsequent coating layers and the application methods and chemistries for the coatings. For example, motor vehicle manufacturers who use powder coating compositions as clearcoats require a degree of compatibility between a variety of powder clearcoats from different sources. Poor compatibility can result in the powder clear coating that is applied subsequently on the manufacturing assembly line having defects from components of the powder clear coating that was previously applied on the line. Such components can act as contaminates in the subsequently applied coating, and contaminants can alter the surface tension gradients in the coating composition resulting in cratering defects.
Also in multilayered coatings on substrates, intercoat adhesion and, in some applications, recoatability can be adversely affected by modifications in the powder coatings to reduce the degree of cratering. For powder coatings applied as primer surfacers or chipguard primers or in basecoat/clearcoat composite coatings that are topcoated with typical finishing coat compositions, the presence of the aforementioned types of flow control agents can adversely affect the intercoat adhesion between the topcoat and the powder primer surfacer.
In addition, powder coatings are often applied as chipcoat primers over uncured, dehydrated electrodeposited coatings (see, for example, U.S. Pat. No. 4,804,581). In such an application, the chipguard primer is only applied to a portion of the electrodeposited coating usually in the areas that are subjected to stone chipping, i.e., rocker panels and wheel wells. The composite coating is co-cured in one step and topcoated with a conventional finishing coat. In applying the chipguard primer to only a portion of the dehydrated, uncured electrodeposited primer, there is an area of overspray where the powder coating composition contacts the electrodeposited primer in areas other than that to be coated. When the chipguard primer contains conventional flow control additives such as those described above, severe cratering of the electrodeposited primer often results. Other applications of powder coatings require recoatability, i.e., good recoat adhesion between the cured powder coating and a subsequent coating layer, so that minor imperfections or minor damage that may occur during shipment and transfer of industrial parts can be corrected. Unfortunately, powder coatings containing the common flow modifiers have been found to have poor crater resistance.
It is an object of the present invention to provide a coating composition with improved compatibility with other similar coating compositions while maintaining good appearance and intercoat adhesion.
SUMMARY OF THE INVENTION
In accordance with the present invention, a curable coating composition has:
(A) from 80 to 99.99 percent by weight based on the weight of solids of the curable coating composition of at least one liquid or particulate film-forming resinous material, and
(B) from about 0.01 to 10 percent by weight based on weight of total resin solids of the curable coating composition of a flow modifying agent.
The flow modifying or control agent is an additional polymerized copolymer from polymerizable ethylenically unsaturated monomers; about 40 to 99 percent by weight based on the weight of polymerizable ethylenically unsaturated monomers for the copolymer is from at least one alkyl acrylate or methacrylate containing from 1 to 20 carbon atoms in the alkyl group which is non-amine, non-hydroxyl and non-acid functional. Also polymerized into the copolymer is at least one functional polymerizable ethylenically unsaturated monomer in an amount of about 2 to 50 percent by weight based on weight of polymerizable ethylenically unsaturated monomers for the copolymer. This functional monomer is selected from:
(1) amino functional acrylates and methacrylates in an effective amount for 100 weight percent solids in the copolymer so that the copolymer has an amine value in the range of about 2 to about 70, either present alone or with one or more hydroxyl functional monomers like hydroxyalkyl acrylates and/or methacrylates and/or polycaprolactone polyol monomers in an effective amount so that the hydroxyl number of the copolymer is up to 100, and
(2) acid functional acrylates and methacrylates in an effective amount to give the copolymer an acid value in the range of from 10 to 30 alone or with one or more hydroxyl functional monomers like hydroxyalkyl acrylates and/or methacrylates and/or polycaprolactone polyol monomers in an effective amount to give the copolymer a hydroxyl number up to about 100.
The aforementioned percent by weight and effective amounts for the monomers of the copolymer flow modifying agent are based on the weight percent of the total monomers for the copolymer including (1) and (2) comonomers and any additional monomers. The weight percent of the one or more particular functional monomers (1) or (2) gives the amount in the aforementioned range for the functional monomers of about 5 to 50 percent by weight based on the weight of polymerizable ethylenically unsaturated monomers. The values given are approximate values in that for values other than zero, somewhat lower values can also be used and for values in the upper region of the ranges, somewhat higher values can be used to give similar results as the values within the ranges. All of the aforementioned effective amounts are based on 100 percent of the solids of the copolymer. The amounts in weight percent of the components (A) and (B) equal 100 percent of the solids of the curable composition without the presence of additional components or additional components as described herein may also be included.
The copolymer flow control agent does not adversely affect intercoat adhesion when the curable coating composition is a thermosetting powder coating with a curable particulate resinous material where the powder coating is used in a multilayered coating as the clear coat. When the coating composition with the film-forming resinous material and the flow control agent is a liquid, a carrier may be used. The carrier can make the coating composition a solvent-borne or water-borne coating composition. Also, other additional components usually found in coating compositions can be present in amounts usually used by those skilled in the art. These amounts of the other additional components and film-forming resinous material provide most of the solids for the curable coating composition.
Another aspect of the invention is a multilayered coating composition of a basecoat/clearcoat composition wh
Barkac Karen A.
Humbert Kurt A.
Olson Kurt G.
Singer Debra L.
Wozniak Mark E.
Altman Deborah M.
PPG Industrial Ohio, Inc.
Sellers Robert E. L.
Stachel Kenneth J.
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