Aluminum Flake Dispersions

Dispersions of aluminum flake have been made in mixtures of kerosene and ethylene glycol monobutyl ether and other petroleum distillates such as "Solvesso 150" from Exxon Chemicals Co. for use with solvent-based dispersions of poly(arylene sulfide) such as poly(phenylene sulfide) (PPS) and known fluorocarbon polymers such as polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene and hexafluoropropylene (FEP). Such solvent-based dispersions are quite suitable for spray application, but they can exhibit less than desirable settling and flow characteristics for application by coil coating techniques.

The present invention provides a dispersion of aluminum flake in a mixture of ethylene glycol and ethylene glycol monobutyl ether.

Preferably, each of the ethylene glycol and ethylene glycol monobutyl ether are present in amounts of about 40-60% by weight of the two combined; more preferably at levels of about 55% ethylene glycol, 45% ethylene glycol monobutyl ether.

The invention also provides for using such dispersions of aluminum flakes in solvent-based dispersions of poly(phenylene sulfide) and optionally particulate fluorocarbon resin, preferably PTFE or FEP.

By changing the solvent mix and substituting ethylene glycol for kerosene in the prior art, the stability and flow characteristics of coating compositions of the invention are improved to an extent desirable for coil coating. The advantages of the invention are especially noticeable in the wetting of the aluminum flake and the production of stable dispersions in polyphenylene sulfide.

The invention will now be illustrated by an example. Parts, percentages and proportions herein are by weight except where indicated otherwise.

Prepare a premix by grinding in a pebble mill for 48 hours or grinding in a Dyno-mill for 5 passes a blend of

This premix is then mixed in the following proportions:

The coating composition has satisfactory dispersion stability and has desirable viscosity and flow characteristics for application to coiled substrate of any suitable material such as aluminum by suitable techniques such as doctor blade or rolling coating. The coating can be cured by heating 10 minutes at 400.degree. C. This drives off the liquid carrier and coalesces into a desirable coating. Alternately, the coating can be cured at 370.degree. C. for 15 minutes, at 425.degree. C. for 5-7 minutes or under equivalent conditions.