Water Wash-Up Coating Composition

This invention relates to paint type coating compositions. More particularly, it relates to paint made with resinous binder and which is rendered water wash-up by the incorporation of selected surfactants.

Paints utilizing vegetable oil based resin binders have long been well known. For some time polysaccharide resins have been made available for combination with vegetable oil based resins in formulations which contain a relatively high water content. Such formulations have advantages in that they are economical to produce and have good paint qualities. Typical polysaccharide resins for this use are offered by Lorama Chemicals, Inc., Quebec, Canada, under the tradename JK270. Suggested paint formulations with such polysaccharide resins in combination with long, medium and short oil alkyds are described in "New Low-Cost Stains Exhibit Interesting Features", D. R. Arntfield and V. Altavilla, Journal of Water Borne Coatings, 1984 Buyer's Guide Issue, pages 10-13. The authors are connected with Lorama Chemicals, Inc. As pointed out in this Lorama Chemicals publication, the products produced are solvent based while containing a substantial water content. Most importantly, the Lorama Chemicals publication points out that its products are not water wash-up. The present invention is an improvement upon the Lorama Chemicals teachings and provides similar products but with an important difference in that the present products are water wash-up.

In accordance with the present invention a paint formulation is provided which contains a blend of miscible polysaccharide resin and vegetable oil based resin. The paint formulation contains an effective amount of hydrophilic and lyophilic surfactants to render the paint water wash-up. In the preferred embodiment the hydrophilic and lyophilic surfactants together are present in the amount of about 4-12 weight percent, usually about 7-10 weight percent, based upon the resin solids in the formulations. The hydrophilic and lypophilic surfactants are selected to provide a hydrophilic-lypophilic balance (HLB) value in the range of about 8-15, preferably about 9-12. The amount of surfactants and the particular HLB value chosen will depend upon the properties of the particular blend of resins used.

While the paint formulation of the invention may utilize either organic solvent based or water reducible versions of vegetable oil based resins, from an economic standpoint the resin will usually be of the organic solvent soluble type. The resin may be used in the pure or neat state, but will typically be commercially available in solution in one or more organic solvents, such as hydrocarbon solvents or glycol ether derivatives based upon ethylene, diethylene, or propylene glycols. Typical solvents include butyl Cellosolve and mineral spirits. Generally the resin may be an alkyd including long oil, medium oil and short oil alkyds. Other suitable choices for the formulation include urethane alkyds of various oil lengths, raw and bodied vegetable oils, emulsified alkyds of various oil lengths and alkyd copolymers.

The polysaccharide resin is suitably a hydrolyzed starch that forms a miscible medium with the selected vegetable oil based resin. In general, the hydrolyzed starch will preferably have at least a portion thereof at an average molecular weight of about 20,000-35,000, usually about 24,000-32,000. In the preferred embodiment the hydrolyzed starch has a major portion with a molecular weight of about 28,000 and a minor portion with a molecular weight of less than 10,000. In the preferred embodiment the major portion is present in a weight ratio relative to the minor portion of about 5:1.

The amount of resin solids in the formulation will depend upon the type of paint product being made. The weight ratio of vegetable oil based resin to polysaccharide resin will generally be in the range of about 25:75 to 75:25, with approximately similar amounts by weight of each resin being used in the preferred embodiment.

The resins are dispersed in a solvent system which may include organic solvents of the type commonly used with vegetable oil based resins. Typical of the present formulation is the presence of a high water content. Water may be present in an amount of 0-90 percent by volume, preferably about 10-90 percent by volume. In the preferred embodiment water will constitute more than about 50 percent by volume of the formulation.

The key to making the present paint formulation water wash-up is the presence of an effective amount of properly selected surfactants. This requirement is met by utilizing a blend of hydrophilic and lypophilic surfactants which provides the HLB values noted above. The surfactants selected may be ionic or non-ionic and will generally fall in the following categories:

(1) ethoxylated amines and/or amides

(2) ethoxylated alkyl phenols

(3) ethoxylated alcohols

(4) ethoxylated fatty acids

(5) other glycol esters of fatty acids

(6) alkyl sulfonates

(7) polyamino-amides and their acid esters

(8) amino alkyl aryl sulfonates

The present formulations may contain any of the usual additives found in conventional paint formulations designed for a particular purpose. Thus, the present formulations may contain pigments found in conventional coatings. They may also contain defoamers such as those commercially available under the tradenames Nopco NxZgr and NDW, Nalco 2314 or Patcote 577n. The compositions may also contain suitable metallic driers (water dispersible or solvent soluble) in effective amounts and appropriate to the particular resins used and the purpose for which the paint formulation is made.

A typical water wash-up formulation of this invention designed for use as a light walnut wood toner/stain is formulated as follows: