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...
Patent
1997-07-15
2000-03-07
Reddick, Judy M.
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...
524379, 524502, 524504, 524539, 524540, 523423, C08K 506
Patent
active
060341602
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method for the preparation of water-borne thermoplastic polyhydroxyethers having narrow polydispersity, coating compositions containing the same, and the use of such compositions for providing flexible coatings.
Coatings that contain no solvents have been prepared from very low molecular weight epoxy resins. The resin in the coating serves as the wetting agent and as the vehicle for any pigments or fillers desired. Because there is no solvent, coatings of this type tend to be free from pinholes, but have disadvantages such as brittleness, poor thermal stability and relatively high costs.
Coating compositions based on higher molecular weight epoxy resins have been prepared as solutions, formulated with solvent, curing agents, modifiers and pigments. These higher molecular weight epoxy resins are often in the form of an ester, obtained by reacting the epoxy resin with a fatty acid. While suitable for many purposes, epoxy ester-based coatings also have disadvantages such as being vulnerable to caustic attack.
In more recent years, there has been a trend toward water-based coating compositions containing epoxy resins, because of ease of handling and cleanup. One such resin is a modified epoxy resin made by grafting an addition monomer component onto the aliphatic backbone of the epoxy resin. For water-dispersible coatings, the addition polymerizable monomer is usually acrylic acid. Such water-dispersed epoxy coatings are particularly useful for the formulation of can coatings. These resins perform well when sprayed onto the surface of an already formed can body but have not found success for use in coating surfaces that are later formed into various shapes, including can ends. This is due to the inflexibility of the resins and their relatively low molecular weight. Increasing the molecular weight of the epoxy resin in order to achieve the desired properties results in the use of strong organic solvents, in order to dissolve the higher molecular weight resin, which must later be removed.
Another form of water-borne resins is based on thermoplastic polyhydroxyether resins, a family of amorphous, high molecular weight phenoxy resins derived from diphenols and epichlorohydrin. These "phenoxy" resins are known for their excellent flexibility, impact and abrasion resistance and adhesive strength. Because of these properties, they are used commercially for a variety of water-borne coatings. However, because of their high molecular weight and chain rigidity, again, a large amount of strong organic solvent must be employed to achieve a satisfactory applicable production process. To prevent pollution of the atmosphere, environmental standards require that such strong organic solvents be either recovered or burned at considerable costs.
The need exists for water-borne thermoplastic polyhydroxyether resin dispersions for use in coating compositions that provide coatings having the desired toughness and flexibility for use on flexible substrates, while having low viscosities which do not require additional steps of solvent reclamation from the dispersions.
SUMMARY OF THE INVENTION
It has been found that by preparing water-borne coating compositions from thermoplastic polyhydroxyether resins having a narrow polydispersity, the removal of organic solvents from such compositions can be reduced or even eliminated. Polydispersity, as used herein is defined as the ratio of weight average molecular weight (M.sub.w) to number average molecular weight (M.sub.n) for a particular thermoplastic polyhydroxyether resin. Narrow polydispersity, as used herein, is defined as a ratio of weight average molecular weight to number average molecular weight of less than 4.0, preferably less than 3.8, more preferably less than 3.5 and most preferably less than 3.1, with a number average molecular weight greater than 7,000 and less than 12,000 (M.sub.w /M.sub.n <4; 7,000<M.sub.n <12,000). These thermoplastic polyhydroxyether resins, having narrow polydispersity, provide coatings
REFERENCES:
patent: 4355122 (1982-10-01), Fan
patent: 4374875 (1983-02-01), Fan
patent: 4476260 (1984-10-01), Salensky
patent: 4544688 (1985-10-01), Salensky
patent: 4564648 (1986-01-01), Huybrechts et al.
patent: 4711924 (1987-12-01), Salensky
patent: 4954553 (1990-09-01), Johnson et al.
patent: 5574079 (1996-11-01), Eaton et al.
Eaton Robert Francis
Johnson Robert Norman
InChem Corp.
Johnston Michael G.
Reddick Judy M.
LandOfFree
Method for the preparation of water-borne coating compositions u does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the preparation of water-borne coating compositions u, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the preparation of water-borne coating compositions u will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-363937