Compositions: coating or plastic – Coating or plastic compositions – Coating repellent
Reexamination Certificate
2002-07-25
2004-02-10
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Coating repellent
C106S241000, C106S285000, C106S287230, C106S287240, C427S384000, C427S372200, C525S301000, C525S193000, C524S457000, C524S458000, C524S460000, C524S510000, C524S515000, C524S522000, C524S533000, C524S539000
Reexamination Certificate
active
06689200
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to aqueous water repellent coating compositions comprising admixtures of (i) water-based water repellent compositions and (ii) water-reducible film-forming polymers. One particularly useful application of these compositions is in making substrates, especially porous substrates, more water repellent. Another aspect of this invention relates to a method for improving the water repellency of coatings comprising a water reducible film-forming polymer by admixing therewith a water-based water repellent composition. Additionally, this invention relates to a method of making a substrate more water repellent by application of the coating composition of this invention to the substrate and allowing the coating composition to cure or dry. Furthermore, this invention relates to the provision of durable color to a substrate by application of these coatings.
2. Description of the Prior Art
Conventional water repellent coating compositions or sealers are generally low viscosity, colorless or semi-transparent, penetrating liquids. One of the primary functions of these water repellent coating compositions is to prevent the penetration of liquid water into the pores of the substrates to which the composition is applied. These water repellent penetrating compositions are designed to waterproof a variety of dry, porous substrates such as wood, brick, masonry, concrete, tile and stucco.
Water repellent coating compositions typically contain a non-volatile composition. This non-volatile composition contains the active water repellent ingredients. These ingredients remain on, and penetrate into, the treated substrate after the coating composition is applied and the liquid carrier evaporates. The active water repellent ingredients contained in the non-volatile composition can include a variety of materials. These materials typically include various waxes, resins, fragrances, preservatives and surface tension modifying chemicals.
The solvent carrier used in many typical water repellent coating compositions is usually a volatile organic compound (VOC) so that the entire composition is organic. These solvent-based compositions, although often having adequate performance as water repellent compositions, are less desirable due to the presence of such organic solvents.
Water-based water repellent compositions have also been developed and have the advantage of minimizing organic solvents. Many of the conventional water-based compositions, however, incorporate conventional surfactants or hydrophilic portions which remain in the compounds and reduce their water repellency.
One approach to overcoming the drawbacks of those conventional approaches is that described in U.S. Pat. No. 5,338,345 issued Aug. 16, 1994, entitled “Water-Based Water-Repellant Coating Compositions” (the “'345 Patent”). In the '345 Patent, the coating composition comprises an emulsion having water as the continuous phase, and as the discontinuous phase, droplets of a non-volatile organic water repellent composition. The emulsion contains an emulsion stabilizing amount of a hydrophobically modified polyacrylic acid polymer wherein the viscosity of the emulsion is less than about 100 Cps and the particle size of the droplets is less than about 50 microns. The relatively low viscosity and small particle size provides for easy application and excellent penetration into porous substrates. The non-volatile organic water repellent composition taught in the '345 Patent includes conventional materials such as liquids (e.g. linseed oil), natural and synthetic waxes, and hydrocarbon resins. The process of making the compositions of the '345 Patent involves the making of a conventional emulsion of this type and then subjecting the emulsion to high kinetic energy processing so as to produce the desired viscosity and particle size.
The compositions taught in the '345 Patent provide excellent performance as a result of their composition, relatively low viscosity, and relatively small particle size. We have now, however, unexpectedly discovered an improvement in water-based water repellent compositions produced according to the '345 Patent. In attempting to improve the performance of the emulsions described in the '345 Patent, we have discovered that admixtures of the emulsions of the '345 Patent and at least one water-reducible film forming polymer provide stable aqueous final formulas having excellent water repellency and improved durability and color retention. These combinations of properties are unexpected because the water-reducible film-forming polymers themselves typically have very poor measured water repellency and would be expected to have a negative impact on the measured water repellency when added to the emulsions described in the '345 Patent. This is particularly true because many water reducible film-forming polymer compositions incorporate non-volatile surfactants, or have hydrophilic groups or polymer segments which will remain in the resulting coating and thus greatly reduce the water repellency.
The combination of the emulsions described in the '345 Patent with water-reducible film-forming polymers surprisingly results in water-based water repellent compositions having excellent water repellent characteristics. Additionally, the water-reducible film-forming polymers allow for the convenient incorporation of colored pigments that add durable color to the substrate and enhance its appearance. The combination of the two components can provide low viscosity products having high application solids, lower levels of volatile organic compounds (“VOC”), excellent water repellent efficiency (% WRE), improved durability, and allow for the ready addition of pigments to the compositions.
BRIEF SUMMARY OF THE INVENTION
This invention relates to coating compositions comprising:
(i) a water based water repellent composition comprising an emulsion having water as a continuous phase and, as a discontinuous phase, droplets of a nonvolatile organic water repellent component, the emulsion containing an emulsion stabilizing amount of a hydrophobically modified polyacrylic acid polymer wherein the viscosity of the emulsion is less than about 100 Cps and the particle size of the droplets is less than 50 microns; and
(ii) at least one water reducible film-forming polymer.
Because of the surprising ability of the water-based water repellent portion (i) to form stable aqueous compositions in admixture with a wide variety of water-reducible film-forming polymers, and to enhance their water repellency, this invention also relates to a process for improving the water-repellency of coatings which comprise a water-reducible film-forming polymer. The process comprises admixing with the water-reducible film-forming polymer an effective amount of the water-based water repellent composition (i) described above.
It is necessary only to admix an effective amount of the water-based water repellent composition to provide the desired degree of water repellency. In general, the organic water repellent component in (i) will be present in the admixture in an amount to provide at least 1% of the total weight solids of that mixture. For many applications, a useful combination of the components (i) and (ii) are such that the organic water repellent composition of emulsion (i) and the film-forming water-reducible polymer (ii) are present at a weight solids ratio of from 1/99 to 99/1. For water repellent coating applications requiring at least a water repellent effectiveness of 60% under ASTM D4446, a preferred weight solids ratio of the organic water repellent composition of emulsion (i) to the film-forming water-reducible polymer would typically be from about 20/80 to about 80/20.
The coating compositions of this invention can be conveniently prepared by admixing the previously prepared water-based water repellent composition (i) and the water-reducible polymer (ii). It is generally convenient to add both of the two materials as their aqueous solution wit
Saunders Heath G.
Scarborough Victoria D.
Teague Timothy G.
Wilson Cedric M.
Koslow C. Melissa
McDonald Robert E.
The Sherwin-Williams Company
Tirey Arthi K.
Tsang Vivien Y.
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