Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1995-02-03
2001-08-28
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S502000, C525S199000
Reexamination Certificate
active
06281280
ABSTRACT:
This invention relates to paints, and in particular to paints that are used exteriorly. More particularly, this invention relates to exterior use paints having a low gloss and which include polyvinylidene fluoride polymers having a high melt viscosity. This invention also relates to polymerization processes for making polyvinylidene fluoride polymers with high melt viscosities to provide coating formulations with low gloss performance.
Polyvinylidene fluoride (PVDF) containing materials have been used as maintenance-free coatings or paints due to their long-term weatherability. The current commercial PVDF-containing paints provide coatings with a 60° gloss of 30 (ASTM Designation D523-89) using a standard pigmented base formula, such as a blue base formula, after coating development. Because of the evolution of construction materials, however, the need exists to have weatherable coatings with broadened gloss scale. Currently, a PVDF paint or coating having a reduced gloss is available which includes a flatting agent such as fumed silica. Such a coating, however, has reduced weatherability. A PVDF containing paint or coating normally is a thixotropic dispersion and is difficult to formulate into a low-gloss product due to poor application rheology after the addition of an effective amount of flatting agents.
It therefore is an object of the present invention to provide a polyvinylidene fluoride-containing paint which has a low gloss without sacrificing weatherability and appliability of the paint.
In accordance with an aspect of the present invention, there is provided a paint composition comprising from about 30 wt. % to about 70 wt. %, based on the weight of the composition, of a binder component, and from about 30 wt. % to about 70 wt. % of a solvent component. The binder component comprises at least about 35 wt. %, based on the total weight of said binder component, of a polyvinylidene fluoride polymer having a melt viscosity of at least 40 kPoise, and from 0 wt. % up to about 65 wt. %, based on the total weight of the binder component, of a polymer compatible with polyvinylidene fluoride. The composition may further include a pigment, wherein said pigment is present in the composition at a pigment-to-binder weight ratio from 0 to about 0.8.
Current polyvinylidene fluoride resins for use in maintenance-free paints have a melt viscosity of from about 29 kPoise to about 33 kPoise. Applicants have found that, when one polymerizes vinylidene fluoride such that the resulting polyvinylidene fluoride polymer has a melt viscosity of at least 40 kPoise, and formulates a paint including such polymer, that such paint has a reduced gloss while being easy to apply and retaining weatherability.
In one embodiment, the polyvinylidene fluoride polymer has a melt viscosity of from about 40 kPoise to about 100 kPoise, preferably from about 50 kPoise to about 70 kPoise.
In one embodiment, the binder component is present in an amount of from about 40 wt. % to about 60 wt. %, and preferably at about 50 wt. %, based on the weight of the composition.
In another embodiment, the polyvinylidene fluoride is present in an amount of from about 60 wt. % to about 80 wt. %, based on the weight of the binder component. The polymer compatible with polyvinylidene fluoride may be present in an amount of from about 20 wt. % to about 40 wt. %, based on the weight of the binder component.
The term “polymer compatible with polyvinylidene fluoride,” as used herein, means a polymer which may be contained in the paint composition, and which is miscible thermodynamically with polyvinylidene fluoride and does not impair the weatherability of the final paint composition.
Polymers compatible with polyvinylidene fluoride which may be employed include, but are not limited to, acrylic resin polymers such as polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyethyl methacrylic, and copolymers of the above acrylics, as well as polyvinyl acetate. The binder of the paint composition may contain mixtures of these polymers as well. An example of an acrylic polymer composition which may be employed is a 70:30 copolymer of methyl methacrylate and ethyl acrylate polymer having a molecular weight of about 88,000 known as Acryloid B44, a product of Rohm and Haas, Philadelphia, Pa.
In another embodiment, the solvent component is present in the composition in an amount of from about 40 wt. % to about 60 wt. %, preferably at about 50 wt. %. Examples of solvents which may be employed include, but are not limited to, one or more of the following: toluene, isophorone, butyrolactone, carbitol acetate, dimethyl phthalate, and propylene carbonate.
In one embodiment, the pigment is present in the composition at a pigment-to-binder weight ratio of from about 0.3 to about 0.6.
Pigments which may be employed include any pigment which may be employed in paint formulations. Examples of such pigments include, but are not limited to, Arctic blue #3, topaz blue #9, Olympia blue #190, walnut brown #10, golden brown #19, maple yellow #25, honey yellow #29, jade green #4, sherwood green #5, camouflage green #179, and jet black #1, all supplied by Shepherd; titanium dioxide Green No. 5 (a mixture of oxides of nickel, titanium, zinc, cobalt, and antimony described in French Patent Application No. 2,659,973); iron oxide-containing pigments; aluminum oxide containing pigments; silica-containing pigments; zirconium oxide-containing pigments; carbon black; lead carbonate-containing pigments; and lead chromate-containing pigments.
In general, the polyvinylidene fluoride polymers which have an increased melt viscosity also have an increased molecular weight vis-a-vis those polyvinylidene fluoride polymers having lower melt viscosities. The molecular weight of the polyvinylidene fluoride polymer may be increased by reducing the amount of free radical initiator present in the polymerization reaction mixture. In general, the free radical initiator, such as, for example, di-t-butyl peroxide, or DTBP, is added to the polymerization reaction mixture in an amount of from about 0.02 g to about 3.0 g per kg of vinylidene fluoride monomer, preferably from about 0.10 g to about 2.0 g per kg of vinylidene fluoride monomer.
In general, melt viscosity measurement is used to characterize high molecular weight polyvinylidene fluoride polymers. The general relationship between molecular weight, M, and melt viscosity, &eegr;, of a high molecular weight polymer has been established theoretically as:
&eegr;=kM
3.5
, wherein k is a constant. (Meares, Polymers:
Structure and Bulk Properties
, Van Nostrand Reinhold Company, London, pg. 358 (1965)).
In general, such polyvinylidene fluoride polymers in accordance with the present invention, also have an increased gel content and increased branching of the polymer chain vis-a-vis polyvinylidene fluoride polymers having lower melt viscosities.
In a preferred embodiment, the polyvinylidene fluoride polymers are formed by an emulsion polymerization process, which employs a fluorosurfactant, such as, for example, ammonium perfluorooctanoate. Such emulsion polymerization may be effected at a temperature of from about 110° C. to about 125° C. The polymerization may be carried out in the presence of a water soluble or insoluble initiator. The initiator may be DTBP, which may be present in amounts hereinabove described.
The resulting polyvinylidene fluoride product has a melt viscosity of at least 40 kPoise, has an increased molecular weight, and an increased gel content. Such polymer also has increased branching of the polyvinylidene fluoride polymer chain.
The resulting polyvinylidene fluoride polymer, which may be in the form of a powder and which has a melt viscosity of at least 40 kPoise, and preferably from about 40 kPoise to about 100 kPoise, and more preferably from about 50 kPoise to about 70 kPoise, and has an increased gel content and an increased molecular weight, then is mixed with one or more solvents, a pigment, if needed, and a polymer which is compatible with
Burks Steven John
Kamsler Craig Norman
Kent Bradley Lane
Lin Shiow-Ching
Acquah Samuel A.
Ausimont USA, Inc.
Norris & McLaughlin & Marcus
Rajguru U. K
LandOfFree
Low-gloss paints including polyvinylidene fluoride having a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low-gloss paints including polyvinylidene fluoride having a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low-gloss paints including polyvinylidene fluoride having a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2528783