Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-11-20
2001-05-01
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S417000, C523S428000
Reexamination Certificate
active
06225376
ABSTRACT:
The invention relates to reactive epoxy polymer compositions emulsified in water comprising a polymeric epoxy emulsion and an emulsified reactive polymer curing composition. In another aspect, the invention relates to a process for preparing such water emulsified reactive polymer compositions. In yet another aspect, the invention relates to cured coatings resulting from further reaction of the water emulsified reactive polymer compositions on a suitable substrate.
Two-part epoxy resin based coating systems generally comprise a curable epoxy resin and a curing agent for the epoxy resin, and are commonly dispersed or dissolved in a solvent, primarily an organic solvent, to prepare coating compositions, for example paints and floor sealants. The use of such organic solvent-based coating compositions is discouraged on environmental grounds. On the other hand, such cured epoxy resin based coatings provide hard and abrasion resistant coatings which are resistant to, among others, hydrocarbons and aqueous media.
Water-based resin systems consisting of an epoxy resin and a curing agent dissolved or emulsified in water have been developed, and create less environmental and health concerns. The development of such systems is reviewed by Chou (Polymers Paint Colour Journal, Vol. 184,1994, pp 413-417). Water-based resin systems are described in U.S. Pat. No. 4,289,826, in GB-A-1,533,825, and in GB-A-1,380,108. Known two part water-based epoxy resin emulsion coating compositions have significant disadvantages as described by Chou. In particular, the deficiencies of amidoamine adducts or modified polyamines which disperse liquid epoxy resin at the point of application is clearly described: these curing agents are normally made water dispersible by salt formation with volatile organic acids. These acids often create odor, flash rusting and water sensitivity problems. The problems of flash rusting and corrosion are dealt with in detail by M. A. Jackson, “Guidelines to Formulation of Waterborne Epoxy Primers”, Polymers Paint Colour Journal, October 1990, Vol. 180, No 4270, pp 608-621 and by H. Leidheiser, Jr., “Mechanism of Corrosion Inhibition with Special Attention to Inhibitors in Organic Coatings”, Journal of Coatings Technology, October 1988, pp 97-106.
In general, it is difficult to develop stable emulsions which have high solids content and low viscosity, and therefore good flowability. Furthermore, many of the known systems display poor coating properties, as they do not readily coalesce without solvents when coated on a substrate, resulting in cured coatings with poor mechanical flexibility and adhesion, high porosity and excessively high film formation temperature for ambient cure applications. Such systems have a limited balance between hydrophobic and hydrophilic properties, resulting in limited flexibility in the formulation of coatings. Such systems may also suffer from the inability to effectively incorporate pigments into the coating composition. Therefore, pigments are often blended with the curing agent by means of grinding or agitation.
U.S. Pat. No. 5,118,729 describes improved aqueous epoxy dispersions obtained by grafting an emulsifier containing polyoxyethylene residues by reaction on to a terminal epoxy reactive group of the epoxy molecule prior to dispersion.
U.S. Pat. No. 5,344,856 describes an emulsifiable epoxy resin composition which forms a water stable emulsion comprising the reaction product of a polyepoxide type compound with nominally difunctional C
12-36
fatty acids, dispersed by means of the addition of a surfactant wherein the surfactant comprises an alkyl aryloxy poly (propyleneoxy) poly (ethyleneoxy) ethanol or a C
12-36
hydrocarbyloxy poly (propyleneoxy) poly (ethyleneoxy) ethanol wherein the hydrocarbyloxy moiety is the residue of a C
12-36
fatty alcohol or C
12-36
fatty acid: standard chain terminating agents may be employed.
U.S. Pat. No. 3,297,519 describes epoxy resins which are self-dispersible in water without further dispersing aids in a concentration up to 10 percent by weight: the resins described are selected glycidyl ethers based on bisphenol-A containing tailored blocks of polyoxyethylene bridging the two bisphenol-A residues in the molecule. These products are used as components of paper finishes.
U.S. Pat. No. 5,319,004 describes water dispersible hardeners for epoxy resins produced from the reaction of specific polyamidoamides with specific polyamines and specific adducts of polyepoxy compounds with polyalkylene polyether polyols.
WO-A-9501387 describes the preparation of self-dispersible curable epoxy compositions prepared by the reaction of an epoxy resin with a polyhydric phenol and an amine-epoxy adduct: the amine-epoxy adduct is a reaction product of an aliphatic polyepoxide and a polyoxyalkyleneamine. The products described are asserted to require a catalyst to promote the amine-epoxy adduct reaction with the polyhydric phenol and epoxy resin, and the dispersion of the self dispersible, curable epoxy resin is stated to require high shear in specially designed equipment. Specific reaction sequencing is stated to be necessary in order to avoid post-addition of the amine-epoxy adduct to the epoxy resin, with such addition leading to unstable aqueous dispersions.
DE-A-4405148 describes water dispersible epoxy compositions derived from the reaction of aromatic epoxy resins, bisphenol-A and polyglycidyl ether polyepoxides, which resins may be cured with conventional amine curing agents for aqueous systems. Dispersion of the water-dispersible epoxy compositions are stated to require high shear.
JP-A-H6-179801 describes water-based curable epoxy resin compositions prepared from an epoxy resin, a self-emulsifiable active organic amine curing agent and water. Ease of dispersion is obtained by choice of the curing agent. The application of the technology described two epoxy resins with an epoxy equivalent weight of less than 200 is asserted: good leveling and film forming properties are asserted.
EP-A-EP 0617726 describes a water miscible or soluble amine-terminated resin useful as a curing agent for water-dispersible epoxy resins which amine-terminated resin is the reaction product of: 1) a polyamine component comprising one or more hydrophilic amine-terminated polyalkylene glycols, and, optionally, one or more hydrophobic polyamines; 2) a polyepoxide derived from a polyalkylene glycol or cycloalkylene glycol, and optionally hydrophobic polyglycidyl ethers, and, optionally, an amine extender having two active amine hydrogen atoms, and reaction products therefrom; 3) optionally a reactive diluent; and 4) optionally a catalyst for the reaction of an amine with an epoxy resin.
Despite the improvements made to date, the formation of stable aqueous dispersions of emulsified reactive polymer compositions derived from epoxy resins with an epoxy equivalent weight greater than 350 and aqueous dispersed or dispersible curing agents is generally difficult. Dispersions of such compositions containing no solvent, exhibit a viscosity higher than optimal. In particular, two-component pre-dispersed compositions are desired which cure at low ambient temperature to provide final coatings with good mechanical properties.
It is desirable to provide emulsified reactive epoxy polymer compositions which can be produced in presently employed industrial reactors. It is also desirable that such reactive epoxy polymer compositions should be stable without the addition of acid or a significant quantity of organic solvent, in order to optimize final coating properties. It is further desirable that such reactive epoxy polymer compositions should also accept and disperse the commonly used hydrophobic curing agents, which may be required in certain applications to allow economically attractive low ambient temperature curing while still providing final coatings with excellent mechanical properties.
The present invention provides a reactive polymer emulsion preparable by:
(i) reacting at least one polyepoxide (II) with at least one polyoxyalkylene glycol diglycidyl ether
Joerg Karin C.
Klein Dieter H.
Aylward D.
Dawson Robert
The Dow Chemical Company
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