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
2001-07-12
2004-03-30
Sergent, Rabon (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, C524S504000, C524S590000, C524S322000, C525S192000, C525S301500, C525S133500, C525S039000, C526S318500
Reexamination Certificate
active
06713548
ABSTRACT:
FIELD OF INVENTION
This invention relates to waterborne polymer compositions and their applications. More particularly, the invention relates to the utilization of water-dispersible polymers and fatty acid as, surface-active agents in emulsion polymerization reactions to produce waterborne emulsion polymer compositions which exhibit superior grease, water, and chemical resistance properties.
BACKGROUND OF THE INVENTION
Cellulosic fiber products (such as paper, paper board, corrugated paper board, hard board, fiber board, gypsum board, chip board, and the like) have been used for many years in a variety of end uses. These products have the advantages of being relatively inexpensive and readily available. However, these products readily absorb water when exposed to environments where standing water, aqueous mists, aqueous spray, or high humidity is present. Such exposure usually results in a degradation of properties and a loss of strength. Accordingly, it has been a common practice to coat or impregnate cellulosic fiber products with various hydrophobic materials (such as waxes or synthetic resins) in an attempt to impart water and grease resistance properties.
Water-resistant paper is generally produced by first impregnating or coating the paper substrate with a wax melt, wax solution, or wax emulsion, after which the substrate is dried at a temperature lower than the melting point of the wax. The overcoat film of wax allows the paper to have high hydrophobic and water-resistant properties. Should the paper be dried at a temperature higher than the melting point of the wax, the melted wax tends to penetrate into the inside of the paper substrate instead of forming the overcoat film on the paper. However, when the overcoat is applied at a temperature below the melting point of the wax, the overcoat is often brittle. If the paper is subsequently folded, this brittleness often results in poor moisture and water-resistant properties at the creased portion of the coated paper. Furthermore, such waxed paper has relatively poor moisture resistance properties and is difficult to repulp. Also, paper that is wax treated cannot be printed with water or solvent based inks using flexographic or gravure type printing presses. Finally, the moisture and water-resistance properties of the waxed paper normally begin to decrease within about two months of the production of the paper (see U.S. Pat. Nos. 347,200 and 4,117,199). These characteristics limit the employment of wax overcoated paper and paperboard in consumer packaging.
Water-resistant paper can also be produced by coating the surface of the paper with a film-forming hydrophobic synthetic resin solution or latex. Polyethylene, polypropylene, polyvinyl chloride, and copolymers of two or more of the mentioned monomers are commonly employed as hydrophobic synthetic resins. The latex or solution of the hydrophobic synthetic resin may be applied in such a manner as to penetrate into the inside of the paper or, alternatively, may be added into the aqueous slurry of the pulp to be incorporated into the paper. This technology provides paper with high degree of water-resistance. However, as the synthetic resin is firmly fixed to the paper substrate, there can be difficulties in the reuse and repulping of the coated paper (see U.S. Pat. Nos. 3,105,823 and 4,117,199).
Water-resistant paper may be made via another process which employs an aqueous slurry of pulp containing a wax emulsion, sizing agent, aluminum sulfate and a thermosetting resin or wet strength resin. However, the resulting paper has relatively poor moisture and water-resistant properties and is difficult to repulp and reuse.
Another method of producing water-resistant paper is to coat the substrate with an aqueous emulsion containing a synthetic rubber latex and a wax emulsion. The coatings are subsequently dried at a temperature the same as or higher than the melting point of the wax. The rubber latex is the copolymer of butadiene with at least one unsaturated monomer (such as methyl methacrylate, styrene, or acrylonitrile). In this method, the ratio of synthetic rubber latex and wax emulsion is critical for the repulpability, moisture and water-resistant properties of the paper. If the amount of wax employed is less than five parts by weight per one hundred parts by weight of the solid synthetic rubber, the resulting moisture and water-resistant paper will be difficult to repulp (because the rubber is firmly fixed to the paper to an excessive extent). On the other hand, if too much wax is utilized, the resulting aqueous emulsion is too brittle to be securely affixed to the paper. When such paper is bent or folded, the creased portion of the paper has very poor moisture and water-resistance properties. If the drying temperature of the coated paper is lower than the melting point of the wax, the paper will have poor moisture and water-resistance properties (see U.S. Pat. No. 4,117,199).
Paper can also be treated with both a water dispersible copolymer comprised of acrylic polymers, styrene butadiene copolymers, or polyvinylidiene chloride and a wax component separately. The copolymer is applied to a paper substrate followed by a second coat of wax in a two-step process (see U.S. Pat. No. 5,654,039).
Several technologies employed to produce water-resistant paper rely on applying a large amount of melted wax, rosin, or modified starch to the surface of the paper substrate at a relatively high temperature. These processes are commonly energy intensive and require substantial amounts of materials in order to provide any substantial water resistance. There is, therefore, a substantial need for a relatively inexpensive waterproofing composition that can be applied to the paper substrate at near ambient temperature. Additionally, the materials employed to provide moisture and water-resistance should be compatible with aqueous glues, inks, and dyes.
Therefore, an object of this invention is to disclose aqueous polymer compositions which exhibit superior moisture and water resistance characteristics.
When coated on a cellulosic substrate, the water-based polymer compositions of the present invention impart superior moisture and water-resistance to the coated substrate. Such coated paper is environmentally friendly in that the paper can be reused and repulped. Moreover, as the present aqueous polymer compositions do not rely on wax to provide the moisture and water-resistance, the coated substrates can be dried at near ambient temperatures (thereby saving energy). Also, the polymer compositions are not brittle. This characteristic permits the coated paper, when folded or bent, to maintain its moisture and water-resistant properties in the creased portion of the paper. Furthermore, the present polymer compositions are compatible with aqueous glues, inks, and dyes.
Water resistance is also critical for coatings applications on other substrates, such as wood, concrete, brick, and masonry. Water tends to penetrate such porous substrates, thereby causing warping and swelling in wood and cracking and spalling of concrete and masonry.
Traditional waterproofing compounds often contain non-volatile water-repellent components (such as waxes, silicone, silane, siloxane, metallic stearate, acrylics, and preservatives) and surface tension modifying chemicals emulsified in a volatile organic liquid carrier. Growing health and environmental concerns have led to strict regulation of the amounts of volatile organic compound (VOC) which can be released after paint is applied. Such regulations have severely limited the employment of certain water-repellent coating compositions.
In U.S. Pat. No. 4,923,940 hydrophobically modified high molecular weight polyacrylic acid copolymers are used as primary emulsifiers for non-volatile water-repellent components in order to provide low VOC water repellent materials. However, the modified polyacrylic acid copolymers are quite viscous and very difficult to apply. High kinetic energy processing (i.e., a microfluidizer) is employed in U.S. Pat. No. 5,338,345 to produce low
Hayden James George
Moisa Marc Stephen
Rumble Charles Andrew
Srisiri-Sisson Warunee
Zhang Sukun
Asinovsky Olga
McDaniel Terry B.
MeadWestvaco Corporation
Reece IV Daniel B.
Sergent Rabon
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