Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1999-12-17
2002-09-24
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S480000, C428S482000, C428S213000, C428S216000, C106S013000, C528S293000, C528S294000, C528S295000, C528S302000, C528S308000, C528S308600, C528S308700, C427S384000, C427S385500, C427S393500
Reexamination Certificate
active
06455142
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method for creating a fog resistant product, typically a polymer film, by means of coating the product with an anti-fog coating. The anti-fog coating is also disclosed.
2. Description of Related Art
Anti-fog coatings are desirable for many applications, such as facemasks and other types of face protection, eyewear such as goggles and glasses, car windshields, windows, bathroom mirrors, see-through packaging materials for moist foods and the like. Disposable and replaceable liners for eyewear such as welding goggles, ski goggles and the like, or for other surfaces subject to fogging, such as windows, are also a desired end use. In many of these applications, it is important that the coating be substantially transparent. However, prior art anti-fog coatings have suffered from numerous limitations, including high cost, need for frequent re-application, inadequate transparency and limited anti-fog properties. There is a need for anti-fog coatings that address one or more of these problems. There is similarly a need for anti-fog coatings that are suitable for use on disposable items such as single-use facemasks. A need also exists for anti-fog coatings that are adapted for application to polymer film substrates. In addition, prior art anti-fog coatings are typically applied off-line. This is a less efficient and more costly alternative. Coatings adapted for in-line application are also desirable.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an anti-fog coating suitable for application to a base polymer film.
It is a further object of the present invention to provide a base polymer film with an anti-fog coating on one or both sides.
It is another object of the present invention to provide an anti-fog coating that is substantially free of streaks and smears, particularly when applied to a base polymer film.
It is yet another object of the present invention to provide an anti-fog coating that is substantially transparent.
The present invention has accomplished these objectives by providing in a preferred embodiment a coated polymer film having an essentially streak-free coated surface that resists the formation of fog. The film includes a self-supporting polymer film layer, and an anti-fog coating on the film layer. The anti-fog coating, which can also be applied to alternate substrates, includes a binder and a surfactant, where the surfactant preferably includes a fluorosurfactant at less than about 0.5 weight percent.
DETAILED DESCRIPTION OF THE INVENTION
The present inventors have surprisingly found that excellent anti-fog properties are provided by a coating that includes a copolyester binder and specific surfactants. The selection of binder and surfactants, and the specific amounts used of the preferred fluorosurfactant, have been found to be critical to the optimal anti-fog results achieved by various coatings of this invention.
The anti-fog coating of the present invention preferably includes a binder to anchor the anti-fog coating to the base polymer film. Polymeric binders have proven to be most effective. One preferred binder is a water soluble copolyester. Preferably, the water soluble copolyester includes a copolyester as disclosed in U.S. Pat. No. 4,493,872 to Funderburk et al. , the disclosure of which is incorporated herein by reference in its entirety. This copolyester is disclosed as the condensation product of the following monomers or their polyester forming equivalents: isophthalic acid, a sulfomonomer containing an alkali metal sulfonate group attached to a dicarboxylic aromatic nucleus and an alkylene glycol with about 2 to about 11 carbon atoms. Optionally, an aliphatic dicarboxylic acid of the formula HOOC(CH
2
)—
n
COOH, where n is about 1 to about 11, can also be employed as a monomer therein. An optimal copolyester is made up of about 90 mol percent isophthalic acid, about 10 mol percent of the sodium salt of 5-sulfoisophthalic acid and about 100 mol percent ethylene glycol.
It is important to note, however, that the preferred percentage of sulfomonomer, isophthalic acid and aliphatic dicarboxylic acid employed is somewhat broader in the context of the present invention than in the Funderburk et al. patent. For example, in the context of the present invention, isophthalic acid is preferably about 50 to about 98 mol percent, aliphatic dicarboxylic acid is preferably about 0 to about 50 mol percent, and the sulfomonomer is preferably about 2 to about 20 mol percent. In addition, the sulfomonomer group of the present invention is not limited to an alkali metal sulfonate group. Any sulfomonomer in which a sulfonate group is attached to a dicarboxylic nucleus is preferred for use herein. In fact, any water soluble copolyester that functions to bind the coating to the surface of the base polymer film, either alone or synergistically in combination with other components, is preferred for use in the anti-fog coating of the present invention.
It is believed that films coated with an anti-fog film containing this binder would possess the improved adhesion to inks and metals that have been previously disclosed in conjunction with this class of compounds.
Another preferred water-soluble copolyester binder is a polymer having a Chemical Abstract Name of 1,3-benzenedicarboxylic acid, 5-sulfo-, 1,3-dimethyl ester, sodium salt, polymer with dimethyl 1,4-benzenedicarboxylate, 1,2-ethanediol and 2, 2′-oxybis[ethanol]. The molecular formula of this polymer is (C
10
H
10
O
7
S.C
10
H
10
O
4
. C
4
H
10
O
3
.C
2
H
6
O
2
.Na)
x
. This copolyester is commercially available as AJ20A polymer from Palmetto Chemicals, Greenville, South Carolina, and contains an antimony catalyst. A similar polymer commercially available from the same company as AJ30 polymer is also preferred for use herein, but it contains a titanium catalyst. It is believed that the antimony catalyst of the AJ20A polymer is preferable because it minimizes the yellowness of reclaimed scrap film. The reclaim (no excessive yellowing or deterioration in physical properties when coated film scrap is mixed with fresh polymer and reextruded) and recycling characteristics of coated polymer film are important. The ability to reuse scrap film, instead of disposing of it, reduces material and waste disposal costs and minimizes unnecessary waste.
Without intending to be bound by theory, it is believed that water soluble and water dispersible binders are preferred for use in the present invention because this water sensitivity contributes to the positive antifog performance, particularly in combination with anionic surfactants. It is postulated that the surfactant induces wet out of the water droplets on the film surface, preventing fog, and the water sensitive binder absorbs the water, conducting it away from the surface. Water-based binders are also preferred for health and safety reasons, due the elimination or reduction of potentially hazardous solvents. In addition, is it believed that the preferred coating layers of the present invention are substantially amorphous, non-crystalline layers. They are preferably hydrophilic, water-wicking or water-dispersing layers.
Binders containing water-dispersing agents are preferred for use in the present invention. Agents having a sulfonated component are particularly useful. Such water-dispersing agents include 5-sulfoisophthalic acid (also known as 5-SIPA), or its 1,3-dimethyl ester sodium salt. Alternate sulfomonomers disclosed in U.S. Pat. No. 5,496,647 to Krejci et al. , the disclosure of which is incorporated herein by reference, are also preferred for use herein.
The binder is preferably present at about 1 to about 30 percent by weight of the coating solution, and in an alternate preferred embodiment, it is present at about 1 to about 6 percent by weight of the coating solution.
It is also preferred that the anti-fog coating of the present invention include a surfactant or mixture of surfactants. In one preferred emb
Donald Robin M.
Funderburk F. Gene
Heberger John M.
Rollins John G.
Westermeier Jan C.
Chen Vivian
Mitsubishi Polyester Film LLC
LandOfFree
Anti-fog coating and coated film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Anti-fog coating and coated film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Anti-fog coating and coated film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2823588