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...
Reissue Patent
1999-02-09
2001-01-16
Reddick, Judy M. (Department: 1713)
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...
C524S508000, C524S510000, C524S596000, C524S611000
Reissue Patent
active
RE037023
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
This invention relates to aqueous dispersions of phenolic resin. In particular, this invention relates to stable resin dispersions that are heat-reactive, have outstanding chemical resistance properties, and are safe for use in contact with foodstuffs.
2. Description of Related Art
Phenolic resins are commercially important materials that are used in an array of diverse products. Examples include coatings, binders for inorganic materials, binders for organic materials, rubbers, laminates, moldings, castings, and other uses. Phenolic resin polymers are also widely used as a component in coating materials that are baked to form the coating and to adhere the coating to the substrate. Resins that tend to exhibit hydrophobicity typically provide less resistance to chemical attack. Whereas such hydrophobic polymers can be used to form aqueous heat-reactive coating compositions, they typically are not considered suitable for use in many coating applications because of their limited resistance to chemical attack.
Historically, phenolic resins were only available in organic solvent based formulations. Such formulations have lately come under pressure as manufacturers seek to find formulations that reduce the amount of volatile components. Governmental regulations often mandate significant reduction, or even elimination, of volatile organic solvents from such formulations, particularly for products having selected uses. The reduction or elimination of volatile organic solvent emissions has provided new commercial opportunities for resins dispersions with low levels of volatile organic compounds.
The art has investigated a variety of ways to make a useful, stable aqueous phenolic resin dispersion that do not pose a significant loss in either handling or performance characteristics. Aqueous dispersions have been made with gums or cellulosic materials as the dispersing agent. Such gum and cellulose-containing dispersions were, however, unsatisfactory. The storage stability was poor, and the coating suffered from poor chemical resistance due to the hydrophilic nature of the dispersing agent.
Surfactants, such as phosphate esters, have been tried. Formulations containing such surfactants provide unacceptably poor film properties caused by surface migration of the surfactant.
The use of a protective colloid material, particularly PVA, as a dispersant has been the subject of attention in the art. Such protective colloids have been used with polyacrylamide and an optional aldehyde-reactive modifier in U.S. Pat. No. 4,131,582. A protective colloid is used to stabilize a phenolic resin formed in situ with other components of the adhesive formulation according to U.S. Pat. No. 4,400,229. Novolac resins are stabilized with PVA in U.S. Pat. No. 4,788,236. Protective colloids can also be used in systems relying on an organic coupling solvent for the phenolic resin. See, U.S. Pat. Nos. 4,124,554 and 5,200,455. Unfortunately, PVA resin works well only with hydrophobic phenolic polymers (e.g., bisphenol-A) and does not form a stable dispersion with highly functional, hydrophillic resins. It would be useful to have an aqueous dispersion of such hydrophillic resins because such resins are characterized by better chemical resistance than the hydrophobic bisphenol-A resins.
There exists in the art the need for an aqueous phenolic resin formulation that provides a coating material which exhibits storage stability, chemical resistance, and ease of handling.
SUMMARY OF THE INVENTION
It is an objective of the invention to provide an aqueous dispersion of a phenolic resin that exhibits good storage stability and forms a chemically resistant coating.
It is another objective of the invention to provide a method for making an aqueous dispersion of hydrophillic resins and, in particular, resins that are highly functional.
In accordance with these and other objects that will become apparent from the description herein, compositions according to the invention comprise an aqueous dispersion containing:
(a) a heat-reactive hydrophilic phenolic resin;
(b) a hydrophobic etherified bisphenol-A resin in an amount of at least about 10% based on the weight of said phenolic resin; and
(c) a protective colloid for the dispersed resins.
The ether moieties in the bisphenol-A resin will react to maintain the desired crosslink density for good chemical resistance while simultaneously serving as a more hydrophobic component that, along with the protective colloid component, stabilize the phenolic resin in aqueous solution. The result is that coating materials containing the present aqueous resin dispersion have characteristics that are the best of the hydrophilic resins and the hydrophobic resins. The dispersion of the present invention exhibits excellent stability like hydrophobic resin dispersions, good film forming properties, and coatings that are chemically resistant like those made from hydrophilic resins.
REFERENCES:
patent: 3870669 (1975-03-01), Höfel et al.
patent: 4122054 (1978-10-01), Culbertson
patent: 4124554 (1978-11-01), Fry
patent: 4131582 (1978-12-01), Kako et al.
patent: 4167500 (1979-09-01), Jazenski et al.
patent: 4182696 (1980-01-01), Wynstr et al.
patent: 4255486 (1981-03-01), Burke, Jr. et al.
patent: 4278579 (1981-07-01), Murphy
patent: 4310653 (1982-01-01), Krajewski et al.
patent: 4400229 (1983-08-01), Demmer et al.
patent: 4788236 (1988-11-01), Kopf
patent: 4988753 (1991-01-01), Rullmann et al.
patent: 5036122 (1991-07-01), Auerbach et al.
patent: 5200455 (1993-04-01), Warren
patent: 0 370 595 (1990-05-01), None
patent: WO 90/05154 (1990-05-01), None
Supplementary European Search Report, Mar. 19, 1998.
International Search Report, Mar. 25, 1996.
Bourlier Ken A.
Mulrenin Peggy S.
Banner & Witcoff , Ltd.
Georgia-Pacific Resins, Inc
Reddick Judy M.
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