Coating processes – With pretreatment of the base – Heating or drying pretreatment
Patent
1995-03-01
1997-06-17
Bareford, Katherine A.
Coating processes
With pretreatment of the base
Heating or drying pretreatment
427358, 4273881, 118 68, 118410, 118419, B05D 302
Patent
active
056395140
DESCRIPTION:
BRIEF SUMMARY
This is a nation stage application of PCT/GB93/01418, filed Jul. 6, 1993.
This invention relates to a process for forming a cured thermoset coating on a metal substrate for packaging end uses, including packaging of liquid and dry products, especially for use in the packaging (including processing or holding) of foods and beverages. The invention also relates to thermosettable compositions for use in coating metal substrates for packaging end use.
BACKGROUND OF THE INVENTION
Currently, thermosetting protective and decorative coatings are generally applied to metal strip or sheet for packaging end uses by roller-coating of a solvent-based lacquer (which may comprise water and a co-solvent) typically comprising 30-60% by weight solids. After application of the lacquer to the metal strip or sheet, the solvent is removed by evaporation and the applied coating is cured. For cost and environmental reasons, it would be desirable to be able to reduce the usage of organic solvents in the application of thermosetting coatings, and the present invention is directed to that objective.
U.S. Patent Specification No. 4,990,364 describes solvent-free, low monomer or monomer-free polymerisable or curable compositions for use in coating various classes of substrates, including metal substrates for packaging end use. The compositions are indefinitely stable under the conditions described and are curable only by means of free-radical initiators in conjunction with heat treatment; by means of actinic light, especially ultra-violet radiation; or by electron radiation. There is no disclosure of thermally activated crosslinkable systems.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an apparatus, shown partly in section and partly in diagrammatic form, for carrying out the process of the invention; and
FIG. 2 is another form of apparatus, shown in diagrammatic form, suitable for carrying out the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for coating a metal substrate for packaging end use, which comprises applying to a primary substrate a thermosettable (that is to say, thermally crosslinkable/curable) composition suitable for forming a coating for packaging end use, wherein the thermosettable composition is substantially solvent-free, the composition is applied as a thermosettable film by extrusion in melt (including plastified) form through an extrusion coating die onto a substrate, there being relative movement between the die and the substrate so that successive areas on the substrate are coated with the thermosettable composition so as to form a film, the primary substrate being the metal substrate for packaging end use or an intermediate temporary support from which the applied coating is transferred onto the metal substrate for packaging end use, and the applied coating is thermally cured after extrusion through the extrusion coating die.
It is an important feature of the present invention that the solvent content of the applied composition is to be low as compared with the practice hitherto in applying thermosetting coatings for packaging purposes. Specifically, no solvent is added to the composition at any stage of the process and, moreover, the residual solvent content of the composition derived from the manufacture of any of the ingredients does not exceed 10% by weight, advantageously does not exceed 5% by weight, preferably does not exceed 4% or 3% by weight, and more especially does not exceed 2% by weight. In many cases, the solvent content of the composition will be sufficiently low that it will not be necessary to take any further measures to comply with legislation concerning volatile organic solvent emissions.
It is also an important feature of the process of the invention that it is possible to obtain uniform thin films on the substrate by extrusion of substantially solvent-free thermosettable compositions in molten or plastified form.
Metal substrates coated in accordance with the process of the invention may be employed for any of a wide range of packagin
REFERENCES:
patent: 4899691 (1990-02-01), Fitzgerald, Jr. et al.
patent: 4990364 (1991-02-01), Bolte et al.
Jones Ian Thomas
Port Anthony Brian
Bareford Katherine A.
Courtaulds Coatings (Holdings) Limited
LandOfFree
Process for coating a metal substrate for packaging end use does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for coating a metal substrate for packaging end use, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for coating a metal substrate for packaging end use will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2156225