Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-04-09
2003-11-11
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C524S441000
Reexamination Certificate
active
06646070
ABSTRACT:
TECHNICAL FIELD
This invention generally relates to a stable aqueous metallic flake containing coating composition that utilizes a phosphated polymer. In particular, this invention is directed to a stable aqueous aluminum flake containing a coating composition that utilizes a segmented phosphated copolymer.
BACKGROUND OF THE INVENTION
It is well known to use metallic flakes in coating compositions for imparting metallic glamour, particularly in exterior finishes applied on automobile and truck bodies. Though there are relatively few problems associated with the use of these metallic flakes in solvent based coating compositions, when utilized in waterborne coating compositions, the metallic flake, particularly aluminum flake, reacts with water and any acid constituents present in such coating compositions. As a result, the flake deteriorates and produces hydrogen gas, which is a potential safety hazard. Furthermore, finishes resulting from such coating compositions have a reduced brightness and glamour.
To avoid the foregoing problems, Frangou [U.S. Pat. No. 4,675,358 (1987)] and Antonelli et al. U.S. Pat. No. 5,104,922 (1992)] used phosphated linear random polymers in metallic flake containing coating compositions. The phosphated portion of the polymer provides passivation of the flake. Residual phosphorousic acid groups attached to the polymer are neutralized with an amine or an inorganic base to disperse the polymer into water. These polymers must be sufficiently hydrophobic to associate with the metallic flake, typically an aluminum flake whose surface is hydrophobic. However, it is very difficult to obtain a balance of properties with these polymers. If more passivation is needed for the flake, the phosphated hydrophobic portion of the polymer is increased but at the expense of the hydrophilic portion of the polymer which reduces the dispersibility of the polymer. On the other hand, if more dispersibility is needed, the phosphated hydrophobic portion of the polymer is reduced but the protection provided to the flake is reduced proportionately. As a result, the glamour in the long term is reduced. Thus, as these properties of passivation and dispersibility of the polymer have to be balanced against one another, it becomes very difficult to achieve an optimal balance and still produce acceptable glamour. Even though, aforedescribed phosphated polymers offer some improved protection to metallic flake pigments against the evolution of gases and exhibit some improvement in the stability of coating compositions formulated with metallic pigments, additional improvements in glamour for the resultant coatings are still desirable.
Thus, a polymeric dispersant is still needed for producing a stable aqueous metallic flake containing coating composition that protects the underlying substrate, suppresses the deterioration of the metallic flake and formation of gases, does not deteriorate on weathering, has compatibility with a variety of solvents used in aqueous coating compositions and still produces coatings having improved glamour over the aforedescribed prior art metallic flake containing coating compositions.
SUMMARY OF THE INVENTION
The present invention is directed to an aqueous metallic flake containing coating composition comprising:
metallic flakes and a neutralized phosphated segmented copolymer dispersed in an aqueous carrier, said neutralized segmented copolymer comprising a neutralized phosphated graft copolymer, neutralized phosphated block copolymer or a combination thereof, wherein
said graft copolymer comprises one or more nonionic hydrophilic segments attached at single terminal points to a hydrophobic segment, and said block copolymer comprises one or two of nonionic hydrophilic segments linearly attached to a hydrophobic segment, wherein
a molar ratio of said hydrophobic segment to said nonionic hydrophilic segment in said graft and block copolymers varies in the range of from 96:4 to 4:96 and wherein said nonionic hydrophilic segment is polymerized from one or more nonionic monomers selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, vinyl pyrolidone, oxazoline, hydroxyethyl (meth)acrylate and a combination thereof; and
wherein said segmented phosphated copolymer is provided in the range of from 0.4 weight percent to 12 weight percent with phosphate moieties, all percentages being based on composition solids.
The present invention is also directed to a method for procucing aqueous metallic flake containing coating coposition comprising:
preparing a segmented copolymer comprising a graft copolymer, block copolymer or a combination thereof,
wherein said graft copolymer is prepared by:
polymerizing one or more ethylenically unsaturated monomers, one or more phosphate moiety reactive monomers and one or more nonionic macromonomers terminated with a polymerizable double bond to produce said graft copolymer having a hydrophobic segment with one or more nonionic hydrophilic segments attached at single terminal points thereto, said hydrophobic segment having one or more phosphate reactive moieties positioned thereon, said nonionic macromonomer being selected from the group consisting of polyethylene glycol monomethacrylate methyl ether, polypropylene glycol monomethacrylate methyl ether, polybutylene glycol monomethacrylate methyl ether, polyvinyl pyrolidone, polyoxazoline, polyhydroxyethyl methacrylate and a combination thereof, and wherein a molar ratio of said hydrophobic segment to said nonionic hydrophilic segment in said graft copolymer varies in the range of from 96:4 to 4:96:
wherein said block copolymer is prepared by:
polymerizing one or more of nonionic monomers selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, vinyl pyrolidone, oxazoline and hydroxy ethyl (meth)acrylate, one or more phosphate moiety reactive monomers and one or more ethylenically unsaturated macromonomers to produce said block copolymer having a hydrophobic segment with one or two nonionic hydrophilic segments linearly attached thereto, said hydrophobic segment having one or more phosphate reactive moieties positioned thereon and wherein a molar ratio of said hydrophobic segment to said nonionic hydrophilic segment in said block copolymer varies in the range of from 96:4 to 4:96;
contacting orthophosphoric acid, phosphorus pentoxide, a phosphorus compound containing —O—PO(OH)
2
group, or a combination thereof with said segmented copolymer to provide said segmented copolymer with one or more said phosphate moieties thereon;
neutralizing said phosphate moieties on said segmented copolymer by contacting with a neutralizing agent to produce a neutralized phosphated segmented copolymer; and
mixing metal flakes with said neutralized phosphated segmented copolymer in an aqueous carrier to produce said aqueous metallic flake containing coating composition.
One of the advantages of the coating composition of the present invention is that a coating resulting therefrom has improved glamour when compared against the glamour of coatings obtained from conventional waterborne metallic flake containing coating compositions.
Another advantage of the present invention is the flexibility it affords to the formulator in selecting from a wide variety of solvents, especially from the HAPs-free (hazardous air pollutants) solvents, in formulating the composition. As a result, the formulator, especially in the United States, is in a better position to meet the increasingly stringent legal requirements that deal with the acceptable level of release of VOC (volatile organic content) in the atmosphere.
Still another advantage of the present invention is the flexibility it affords to the formulator in selecting from a wide variety of metallic flakes, such as non-passivated or pre-passivated metallic flakes. As a result, the formulator has greater freedom in tailoring the resulting coating composition having desired coating properties, such as, for example, etch and mar resistance.
Yet another advantage of the novel aqueous metallic coa
Berge Charles T.
Fryd Michael
Huybrechts Josef
Kirshenbaum Kenneth S.
Visscher Karyn B.
Cheung William
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
Wu David W.
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