Patent Application
20050009937
Finishing drywall to a smooth, level finish is a labor and time-intensive process. The current drywall process involves 34 days during which consecutive applications of drywall compound are applied to the wall to provide a uniform wall surface capable of receiving a coating providing an acceptable aesthetic appearance. Current high-build primer/surfacers can only mask very minor surface flaws and must still be used over fairly uniform substrates.
Previous work by Tampio U.S. Pat. No. 5,620,509 illustrates the use of fiber and foaming agents for the purpose of sound absorption using the fiber as the only filler. A second work by Rothfelder, et al, U.S. Pat. No. 3,839,059 demonstrates the use of fiber in fire retardant coatings using large cellulosic fibers. The present invention is distinctive from these previous works both in purpose and in composition with the former using only fiber as the filler while the invention can use many common filler pigments in conjunction with the fibers and with the latter using fibers of 3-10 times larger size than in the present invention.
It is an object of this invention to provide a high-build coating composition with improved masking and filling capabilities functioning as a primer for the drywall, therefore saving time and labor in the preparation of the drywall. The coating composition of this invention comprises hydrophilic fibers, and/or at least one foam booster, and at least one foam stabilizer. The preferred composition uses fibers, foam booster and foam stabilizer. It is another object of this invention is to provide a novel coating composition having no defoamer present.
According to this invention, there is provided a sag and shrinkage resistant waterborne coating composition comprising hydrophilic fibers, at least one foam booster, and at least one foam stabilizer. The coating composition comprises between about 1% by weight and 5% by weight of hydrophilic fibers; between about 0.1% by weight and 1.0% by weight of at least one foam booster; and between about 0.05% by weight and 0.5% by weight of at least one foam stabilizer. The hydrophilic fibers can be cellulose fibers, having a particle size between about 10 microns to about 50 microns, and a particle diameter of between about 5 microns to about 25 microns. At least one foam booster is generally an anionic surfactant, and the at least one foam stabilizer is generally a nonionic surfactant. The coating composition can further comprise an associative thickener, such as an alkali swellable thickener and/or a cellulosic thickener.
Waterborne coating compositions according to this invention comprise hydrophilic fibers, at least one foam booster and at least one foam stabilizer. The use of these hydrophilic fibers encourages entrapment of more air to improve shrink resistance of the coating and also contributes to a unique coating rheology.
It has been found that the addition of a small amount of foam booster and foam stabilizer, in the absence of defoamer, to the coating compositions comprising hydrophilic fibers significantly improves the masking performance (of substrate imperfections) of paint compositions. The foam booster and foam stabilizer act to produce a stable microfoam produced through surfactant stabilization. The stable microfoam provides a higher film build and greater shrink resistance compared to conventional latex (or waterborne) formulations. The foam is generated through mixing in the manufacturing process. After application, the air pockets are stable enough to be maintained until the paint is dry. These pockets provide build, masking, and shrink resistance.
The synergistic effect of the hydrophilic fibers with foam booster and foam stabilizer gives the optimum results of this invention. Hydrophilic fibers, when used in combination with the foam booster and foam stabilizer, provides more structure to the coating which displays a significant improvement in masking surface defects over the use of foam booster and foam stabilizer alone.
The selection of the hydrophilic fibers of the composition of this invention can be optimized depending on the nature of the substrate or the method of application. Hydrophilic fibers can include, but not limited to, cellulose fibers, for example, mechanical pulp, chemical pulp, semichemical pulp, digested pulp, as obtained from wood; and artificial cellulose fibers. The average length of the fibers is generally between about 20 microns and about 40 microns, and suitable fibers can range from 10 microns to 50 microns. If the average fiber length of the fibers is less than 10 microns, however, the advantageous results of the masking effects of this invention may not be realized.
Also, with respect to fiber length and size, for example, optimum compositions for one-coat or two-coat application by spray application, preferably but not limited to airless spray, may be obtained by using amounts from about 1 percent by weight to about 5 percent by weight of hydrophilic fibers having average fiber lengths of 30 microns and average fiber diameter of about 18-20 microns. The application of the composition of this invention by means of spray delivery makes it possible to easily apply one or more coats of the composition on uneven or curved surfaces, with a dry coating layer of from about 1 mil to 80 mils of wet film build, preferably 20-40 wet mils, without any sagging.
The specific types and amounts of foam boosters and foam stabilizers can vary according to the specific coatings formulation. According to this invention, the foam booster of this invention is an anionic surfactant. Suitable foam boosters can include sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, and others.
The foam stabilizer of this invention is a nonionic surfactant, such as fatty alkanolamides, that can be formed by the reaction of alkanolamines and fatty acids. Fatty alkanolamides are known to stabilize the foaming action of other surfactants. Examples of fatty alkanolamides include tall oil fatty acid diethanolamide, lauric acid diethanolamide, coconut diethanolamide, and oleic acid monoethanolamide, or other fatty acid alkanolamides derived from monoethanolamine and diethanolamine, and others. For example, a commercially available fatty alkanolamide is Witcamide 128T, coconut diethanolamide (contains 6% diethanolamine), available from Akzo Nobel Industrial Specialties of Chicago, Ill.
The coating composition of this invention comprises about 1% to about 5% by weight of hydrophilic fibers, about 0.1% to about 1% of at least one foam booster, and about 0.05% to about 0.5% by weight of at least one foam stabilizer. In addition to the above ingredients, the compositions of this invention may contain any other components generally present in coating compositions.
Additional components such as the use of rheology modifiers can also greatly improve the performance of the coating. Adjustments to the rheology utilizing associative thickeners, such as alkali swellable thickeners or cellulosic thickeners for example, to produce a more thixotropic profile will aid in the foam stability and sag resistance of the final product while the paint dries. Examples of associative thickeners include, but are not limited to, hydrophobically-modified alkali-soluble acrylic copolymers (for example, Acrysol TT 935 from Rohm & Haas, Philadelphia, Pa.), and/or cellulosic thickeners such as hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, etc. (for example, Cellosize ER-52000 from Union Carbide, Danbury, Conn.). These thickeners are typically used to control the viscosity for improved application by brush, roller, or spray. The thickeners may also help entrap foam and enable a high film build without sagging. The level of thickener is present in an amount effective to maintain the coating composition as a sag resistant film.
For airless spray applications, it is also desirable that the coating composition comprise glass microspheres which aid in pump throughput. The microspheres can range from about 15 microns to about 70 microns, with an average size of about 40 microns for airless spray application. The microspheres typically has at least a 6,000 psi crush strength to prevent them from cracking during airless spray. An example of this microsphere is the Scotchlite K-46 from 3M Corporation, St.Paul, Minn., 55144-1000.
In general, the foam and fiber compositions of this invention can be prepared in a charged mixer according to the formulation given in Table I. The percent figures are given as percent by weight.
Example 1 is a latex formulation comprising hydrophilic fibers, a foam booster and a foam stabilizer. The high build latex paint preparation is prepared by adding about 0.34% by weight of 30% active sodium lauryl sulfate (foam booster) and about 0.10% by weight of Witcamide 128T (coconut diethanolamide, a foam stabilizer) according to the following formulation:
The composition according to Examples 1 may be applied using airless spray equipment, rollers or brushes, or any other technique that will apply a sufficiently thick coating to the surface to mask surface defects. In general, coatings up to about 80 wet mil thickness do not exhibit any sagging and are more shrink resistant than a conventional latex coating.
The composition of Example 1 was applied to release paper. The application is carried out in one coat, with a total drawdown of 24 mils wet. The percent shrinkage is 50% as determined using a micrometer.
Example 2 is a latex formulation comprising hydrophilic fibers and also comprising a defoamer, but without a foam booster or foam stabilizer. The high build latex paint preparation is obtained by adding about 2.4% by weight of ARBOCEL® BE 600-30, a cellulose fiber by J. Rettenmaier USA LP, having an average length of 30 microns and an average fiber diameter of 18-20 microns.
The composition is applied to release paper. The application is carried out in one coat, with a total drawdown of 25 mils. The percent shrinkage is 54%, as determined using a micrometer.
Example 3 is a latex formulation with foam booster and foam stabilizer, but without defoamer or fibers. The high build latex paint preparation is prepared by adding about 0.34% by weight of 30% active sodium lauryl sulfate (foam booster) and about 0.10% by weight of Witcamide 128T (coconut diethanolamide, a foam stabilizer).
The composition is applied to release paper. The application is carried out in one coat, with a total drawdown of 25 mils. The percent shrinkage was 57%, as determined using a micrometer.
This application claims the benefit of U.S. Provisional Application No. 60/478,949 filed Jun. 16, 2003.
| Number | Date | Country | |
|---|---|---|---|
| 60478949 | Jun 2003 | US |
