Water and oil repellent masonry treatments

Details Water and oil repellent masonry treatments Water and oil repellent masonry treatments

2001-08-23

2004-02-10

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C524S544000, C526S242000, C526S243000, C106S002000

Reexamination Certificate

active

06689854

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to water-soluble, soil-resistant and water and oil repellent fluorochemical polymers. More particularly, the present invention relates to the treatment of masonry and other porous substrates with water-soluble fluorochemical polymers to render them resistant to soil and repellent to water-and oil-based stains.
BACKGROUND OF THE INVENTION
Masonry, a term used generically to describe building materials such as concrete, brick, tile, stone, grout, and like substances, is used extensively in the construction of buildings, roads, parking ramps, driveways, garage flooring, fireplaces, fireplace hearths, and counter tops. When left unprotected, masonry or asphalt surfaces quickly discolor from exposure to water-and oil-based stains and gradually deteriorate from spalling and efflorescence induced by water penetration and weather exposure. Common household liquids are among the most severely discoloring stains including motor oil, brake-oil, transmission fluid, cooking oil, coffee, and wine.
Masonry and other porous surfaces may be made resistant to water and water-based liquids in one of two ways: by rendering the surface waterproof or by rendering the surface water repellent. A waterproofed surface is completely impervious to both liquid water and water vapor. A water repellent surface repels water but is substantially permeable to water vapor. Mason Hayek, “Waterproofing and Water/Oil Repellency,” 24 Kirk-Othmer Encyclopedia Of Chemical Technology 460-62 (3d ed. 19xx), for example, provides an overview of these effects.
Waterproofing of a surface is typically achieved by application of a membrane such as vinyl chloride, polyvinyl chloride, polyethylene, or butyl rubber or by application of a sealant such as tar, asphalt, paints, polyurethane, epoxy or mastics. While these waterproofing agents can offer excellent resistance to penetration by water and water-based liquids, they often disadvantageously alter the appearance of the coated surface, changing the color of the surface and leaving it with a shine. Waterproofing treatments also trap moisture within the treated surface, thereby promoting spalling.
In contrast, water repellents do not alter the appearance of a porous masonry surface when applied as a treatment, and because a water repellent surface is permeable to water vapor, moisture does not become trapped in the masonry and spalling effects can be reduced. Water-repellent treatments used commercially include metal stearates, oils, waxes, acrylates (both polymers and monomers), silicones (solvent-based and emulsion), siliconates, silanes and, more recently, fluorochemicals. These compositions generally contain hydrophobic groups, such as a long-chain alkyl group or polydimethylsiloxane, and functional groups, such as silyl or carboxyl, to bond either covalently or ionically to the masonry surface, which typically contains high concentrations of silicon, calcium and aluminum atoms. Treatments made from these compositions are typically delivered from volatile organic solvents, which are undesirable because of the adverse environmental and health effects associated with them.
Environmental concerns have spawned the development of a number of water-dispersed and water-emulsified masonry treatments. U.S. Pat. No. 4,648,904 (DePasquale et al.), for example, describes a shelf-stable aqueous emulsion useful to render a porous ceramic substrate water-repellent consisting essentially of a C
1
-C
20
hydrocarbyl or halogenated hydrocarbyl silane and a nonionic emulsifying agent having a hydrophillic-lipophilic balance (HLB) value from 4 to 15. Also, U.S. Pat. No. 4,517,375 (Schmidt) discloses aqueous impregnation solutions prepared from hydrolyzed alkyl trialkoxy silanes. While providing ecological advantages over solvent-based treatments, these water-dispersed and water-emulsified silane materials have not been evidenced to provide performance comparable to solvent delivered materials. Additionally, silane compositions do not provide significant protection from oil-based stains.
Only fluorochemical-containing treatments offer significant repellency to oil-based stains. U.S. Pat. No. 5,274,159 (Pellerite et al.), for example, describes certain water-soluble or dispersible fluorocarbylalkoxysilane surfactants which may be cured onto a masonry surface. Additionally, Published World Patent Application WO 9207886 describes an aqueous dispersion of a gelled particulate fluororesin that can form a protective film having good weatherability and good stain-resistance. U.S. Pat. No. 6,037,429 (Linert et al.) describes a water-soluble and shelf-stable aqueous fluorochemical polymeric treatment useful to treat porous substrates to render them repellent to water-and oil-based stains. The treatment comprises a water-soluble fluorochemical polymer containing only carbon atoms in the backbone, with a plurality of each of the following groups pendent from the backbone: (a) fluoroaliphatic groups, (b) carboxyl-containing groups, (c) silyl groups and optionally (d) other non-hydrophilic pendant groups that do not otherwise deleteriously affect one or more of the oil- or water-repellency properties.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a water-soluble and shelf-stable aqueous fluorochemical polymeric treatment useful to treat porous substrates to render them repellent to water-and oil-based stains. The treatment comprises a water-soluble or water-dispersible fluorochemical polymer containing only carbon atoms in the backbone, with a plurality of each of the following groups pendent from the backbone: (a) fluoroaliphatic groups, (b) carboxyl-containing groups, and (c) silyl groups and optionally (d) other non-hydrophilic groups. Typically, the treatment polymers have interpolymerized units derived from one or more, and preferably a plurality, of each of the following monomers:
(a) monomer selected from the group consisting of acrylate, methacrylate, acrylamide, methacrylamide, thioacrylate or meththioacrylate compounds containing a C
4
-C
6
fluoroaliphatic moiety that is linked to the residue of the compound through a divalent, organic linking group;
(b) monomer selected from the group consisting of acrylic acid, methacrylic acid, carboxyalkylacrylate and carboxyalkylmethacrylate compounds; and
(c) monomer selected from the group consisting of acrylate, methacrylate, acrylamide, methacrylamide, thioacrylate or meththioacrylate compounds containing an alkoxysilane moiety linked to the residue of the monomer through a divalent organic group
(d) optionally one or more other monomers having a non-hydrophilic groups and which do not otherwise deleteriously affect the repellency properties of the resulting coating.
Surprisingly, in view of the teachings of U.S. Pat. No. 6,037,429 (Linert et al.), the above-described copolymer having a short-chain fluoroaliphatic moiety is water soluble or water-dispersible despite the absence of the highly water-solubilizing oxyalkylene or polyoxyalkylene groups.
Further, the present coating compositions are surprising effective in providing low surface energy coatings for use in applications such as masonry and other porous substrates to render them resistant to soil and repellent to water- and oil-based stains
The compositions of the invention, comprising fluoroaliphatic groups having less than six carbon atoms, are believed to ultimately degrade to the fluoroaliphatic carboxylic acids (or salts thereof), which are believed to be more effectively eliminated that the higher homologous perfluorooctyl-containing compounds.
The performance of the coating prepared from the present coating compositions are surprising in view of teachings that the lower perfluoroalkyl groups were significantly less effective than longer chain perfluoroalkyl groups, such as the perfluorooctyl group. For example, it has been demonstrated that surfactants derived from perfluorocarboxylic acids and perfluorosulfonic acids exhibit considerable differences in performance as a function of chain length. See, for example
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