Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-07-16
2002-03-26
Chen, Vivian (Department: 1773)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C428S421000, C525S199000, C526S242000, C526S250000, C427S189000, C427S195000, C427S212000, C427S222000
Reexamination Certificate
active
06362295
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions of matter classified in the art of chemistry as seed polymers based on fluoropolymers, more specifically homo polymers of vinylidene fluoride (VDF) and copolymers of vinylidene fluoride with comonomers selected from hexafluoropropylene (HFP) tetrafluorethylene (TFE), chlorotrifluorethylene (CTFE), trifluoroethylene (TrFE), and/or vinylfluoride (VF), in combination with polymers based on acrylic acid, acrylic acid esters, methacrylic acid and/or methacrylic acid esters (acrylic polymers), to compositions containing them, more specifically to powder coating compositions containing them, and to processes for the preparation and use of the compositions containing the seed polymers of fluoropolymers and acrylic polymers and for the use of the fluoropolymer and acrylic polymer combinations themselves.
BACKGROUND OF THE INVENTION
There are a number of patents and publications describing PVDF homopolymer and copolymer based powder coatings made by alloying the fluoropolymer with acrylics. In all cases, the fluoropolymer, acrylics and pigment(s) are melt blended and the melt mixed product is ground. See, for example, U.S. Pat. No. 5,346,727 and references cited therein.
The present invention, by avoiding the necessity for melt blending the fluoropolymer, acrylic polymer and pigment, provides a powder coating composition already having the desired relatively uniform particle size or one which can be comminuted to the desired relatively uniform particle size without the necessity of cryogenic or low temperature grinding.
There are numerous published patents and patent applications worldwide which describe the use of particles in a latex of polyvinylidene fluoride homo- or co-polymers as seeds for the polymerization of various acrylic monomers to form latices from which aqueous based paints and other coatings materials are formed directly without isolation of the polymers from the latices. See, for example, U.S. Pat. Nos. 5,439,980, 5,034,460, 4,946,889 and 5,523,346, PCT Application WO 95/08582, EP 0736583A1, EP 0360575A2, Japanese Applications 6-335005 (8-170045), 3-124997 (4-325509), 3-355973 (5-170909), 4-97306 (5-271359), 7-63193 (8-259773) and the following abstracts—Chem. Abstr. 1994: 702216, Chem. Abstr. 1993, 474687, Derwent 94: 080169, Derwent 94: 062223, Derwent 93: 397686, Derwent 94: 107015/13, Derwent 93: 365288, Derwent 93: 365461, Derwent 93: 278324, Derwent 91: 529278, Derwent 87: 082345, Derwent 86: 213626 and the references cited in these publications. None of these publications teach or suggest isolation of the solids from the seed polymerization latex and subsequent use of the solids in formulating powder coating compositions. The present invention provides a more economical way to prepare fused powder coatings having physical properties equal to or better than those of prior art fused powder coatings.
DEFINITIONS
As used herein and in the appended claims, “acrylic modified fluoropolymer” (“AMF”) means the solid resin (particles or agglomerated) prepared by polymerizing ethylenically unsaturated monomers selected from the group acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters and mixtures thereof in the presence of a latex of vinylidene fluoride homo- or co-polymers as described in more detail below.
SUMMARY OF THE INVENTION
The invention provides in a first composition aspect, an improved blend of polyvinylidene fluoride based polymer, acrylic polymer and pigment useful for powder coatings wherein the improvement comprises the polyvinylidene fluoride based polymer and acrylic polymer being combined as an acrylic modified fluoropolymer.
Special mention is made of tangible embodiments of the first composition aspect of the invention wherein the pigment is combined with the acrylic modified fluoropolymer when the acrylic modified fluoropolymer is suspended as a latex.
Special mention is made of tangible embodiments of the invention wherein the pigment is combined with the acrylic modified fluoropolymer by blending both ingredients as a dry powder.
The tangible embodiments of the first composition aspect of the invention possess the inherent applied use characteristic of being suitable for forming powder coatings on substrates, providing good uniform coatings with uniform distribution of pigment and good adherence while avoiding the necessity of a cryogenic or similar grinding step in their preparation.
The invention provides in a first process aspect a process for forming a composition of the first composition aspect of the invention comprising dispersing pigment in a latex of acrylic modified fluoropolymer to create a first mixture; recovering the solids from said first mixture to obtain the first composition aspect of the invention as a powder; and, if necessary, recovering the first composition aspect of the invention as a powder in the desired particle size range by a particle size selection process selected from grinding, sieving or a combination thereof.
The invention provides in a second process aspect a process for the preparation of a composition of the first composition aspect of the invention comprising; recovering the solids from an acrylic modified fluoropolymer latex as a coarse dry powder; if necessary, converting said coarse dry powder to a powder having the desired particle size by a process selected from grinding, sieving or a combination thereof; and combining said dry powder in the desired particle size with pigment particles in the desired particle size to obtain the first composition aspect of the invention.
The invention provides in a third process aspect, a process for the preparation of a composition of the first composition aspect of the invention comprising: combining the dry resin recovered from an acrylic modified fluoropolymer latex, said resin having the desired particle size, with pigment particles in the desired particle size.
The invention provides in a second composition aspect, an article of manufacture comprising a substrate coated on at least one surface thereof with a coating derived from the first composition aspect of the invention.
The invention provides in a fourth process aspect, a process for the preparation of an embodiment of the second composition aspect of the invention which comprises applying to at least one surface of a substrate on which a coating is desired, a layer of a composition of the first composition aspect of the invention and coalescing said layer to a fixed coating by application of heat.
The invention provides in a third composition aspect, an article of manufacture comprising a substrate having on at least one surface thereof a coating derived from an unpigmented acrylic modified fluoropolymer.
The invention provides in a fifth process aspect, a process for the preparation of an embodiment of the third composition aspect of the invention which comprises applying a layer of an unpigmented acrylic modified fluoropolymer powder coating composition to the substrate surface on which said coating is desired and coalescing said layer to a fixed coating application of heat.
An unpigmented acrylic modified fluoropolymer powder coating composition means an acrylic modified fluoropolymer or an acrylic modified fluoropolymer prepared as described in the Detailed Description of the Invention portion of the specification but without incorporation of pigment.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now generally be described with reference to preferred embodiments thereof so as to enable one of skill in the art to make and use same.
The vinylidene fluoride homo- and co-polymer emulsions employed as starting materials are known, as are their methods of preparation. See, for example Humphrey and Dohany, Vinylidene Fluoride Polymers, Encyclopedia of Polymer Science and Engineering, 2nd Edition, Vol. 17, pp. 532 to 548, 1989, John Wiley and Sons, and the references cited therein. See also U.S. Pat. Nos. 3,857,827; 4,360,652; 4,569,978; 3,051,677; 3,178,399; 5,093,427; 4,076,929; 5,543,217; Moggi et al., Polymer Bullet
Drujon Xavier F.
Gaboury Scott R.
Atofina Chemicals, Inc.
Chen Vivian
Mitchell William D.
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