EP0936001A1

EP0936001A1 - Multi-color patterned cookware

Info

Publication number: EP0936001A1
Application number: EP98203949A
Authority: EP
Inventors: Kenneth Batzar; Lori Marie Mason
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1994-12-22
Filing date: 1995-12-06
Publication date: 1999-08-18
Also published as: EP0804293B1; BR9510489A; WO1996019299A1; KR100296070B1; ES2135114T3; DE69510234D1; DE69510234T2; CN1171064A; HK1004122A1; CN1090543C; EP0804293A1; JPH10510760A

Abstract

Cookware with a coating on its cooking surface has a random spattered pattern of globules on or in the coating, applied either in multiple applications or in a manner such as to give a roughness to the coating.

Description

BACKGROUND OF THE INVENTION

This invention concerns non-stick coated cookware, with a decorative pattern visible through a light transmitting topcoat. More specifically, it concerns such cookware with a pattern formed by discontinuous globules..
U.S. Patent 4,259,375- Vassiliou (1981) discloses a article of cookware with a 3-layer coating having a discontinuous speckled or spattered pattern in a partial layer directly beneath the topcoat. The spattered coating is deliberatly sprayed directly on the layer under it while the under layer is still wet and soft so that the spattered layer sinks into the under layer and does not provide roughness that could telegraph through the surface. It was said that roughness would provide a place for a fork or other utensil to catch in the coating and tear the coating. The spattered layer dots were also sprayed on directly, such as at 90 degrees from the sustrate, so as to form more or less round dots. This patent is incorporated by reference herein for its disclosure of materials, processes and equivalents suitable for the present invention.
U.S. Patent 3,961,993 - Palisin (1976) discloses spraying multilayer polymer coatings on a substrate, one layer being sprayed on top of the layer under it after the under layer has become tacky. A tacky underlayer permits the successive layer to adhere better without completely merging indistinguishably with the underlayer. Still, any roughness in the upper layer would tend to smooth out as the two layers interact.
U.S. Patent 3,655,421 - Long (1972) describes means of keeping globules of a intermittent coating from flowing out to make a uniform layer, by controlling surface tension relations.
It is desirable to have a superior non-stick, decorative coating for cookware optionally with a raised or textured surface and with greater flexibility for aesthetic design than just to make smooth round dots.

SUMMARY OF INVENTION

The present invention provides a article of cookware and a method of making it, having a cooking surface which comprises a multi-layer, non-stick coating on a substrate which coating minimizes sticking by food residues and which is heat resisting by being stable at temperatures above 300°C, wherein the coating comprises a primer adhered to the substrate, a non-stick, heat-resisting, light-transmitting topcoat, and optionally one or more intermediate coats, with the topcoat adhered to any such intermediate coats which are adhered to the primer, or in the absence of intermediate coats, the topcoat being adhered directly to the primer, with the coating under the topcoat having a first color or darkness, wherein a discontinuous layer of globules is present on or in and covers no more than 80% of the area of the coating under the topcoat, said globules having at least one color or darkness which is visibly diiferent than said first color or darkness a seen through said topcoat, said discontinuous layer is applied, by at least two applications of globules, with the first application covering 30-80% of the area and the second application covering 20-45% of the area, with the second application covering at least 5% less area than the first.
Included in the invention are a method of making an article in which the coatings are applied by spraying coating compositions successively on the substrate and ultimately heating the article to cure the coating, wherein the coating under the discontinuous coating is dried enough before applying the discontinuous coating so that substantial portions of the spattered coating remains on top of said under coating to create the roughness telegraphing through the topcoat. In another alternative the undercoat is not dried before applying the discontinuous coat which then sinks into the undercoat, resulting in a substantially smooth topcoat.

DETAILED DESCRIPTION

One embodiment of the process for obtaining the present invention is the drying or "flashing" the primer or intermediate coat before applying the discontinuous coat, adequately so the spattered dots do not sink into the primer or the intermediate coat. In normal application, air flow for 30 seconds or longer, or preheating the substrate or the air with a shorter time of air flow, will suffice.
In another embodiment, the globules can be applied wet-on-wet and permitted to sink into the underlayer so long as they do not merge ad lose their distinctiveness.
Those skilled in the art know how to select the ingredients of each coating to avoid wetting which might cause the globules to run together. Wetting is generally not a problem with most heat resistant materials useful for cookware coatings, especially perfluoropolymers such a polytetrafluoroethylene and (PTFE) and copolymers of TFE and fluorovinyl ethers (PFA).
Preferably the coatings contain oxide-coated mica, and preferably the oxide in Ti0₂, a described in U.S. Patents 3,087,827 - Klenke et al., 3,087,828 and 3,087,829 - both to Linton, and granted 1963.
In the examples which follow, parts, percentages and proportions are given by weight except where stated otherwise.

EXAMPLE 1

A primer having the composition of Table 1 is sprayed on a clean, lightly etched aluminum substrate to a dry film thickness (DFT) of 7.5 to 10 microns, the primer is dried at 66°C for 3 minutes and a black midcoat of Table 2 is applied to a DFT of 17.5 to 20 microns. The midcoat is allowed to dry at ambient temperature for 45 seconds and three separate inks or spatter coatings are applied using a De Vilbiss spatter gun to provide a discontinuous coating. The inks of Table 3 or 4 are colored to be significantly different than the black midcoat background and are sprayed at a 45° angle (or at a angle of from 30 to 75°) to provide irregular shapes on the spinning substrate. The effect is to provide an appearance of natural stone. The inks are not limited to solid color pigments but also include color achieved by reflectace with coated mica. A topcoat of Table 5 is then applied wet-on-wet over the spattered particles. The topcoat, in this example, contains mica particles in a 1-15 micron particle size range so as not to interfere with the aesthetics of the spatter coat. The entire system is sintered at 427 to 435°C for 5 minutes with the measured temperatures being that of the substrate metal.

Primer	Coating Composition (Wt.%)	Solids Content in Finished Article (Wt%)
Furfuryl Alcohol	1.82	-
Polyamic acid salt in N-Methyl Pyrrolidone	18.10	24.48
Water	48.33	-
Mica coated with TiO₂	0.05	0.24
PTFE Dispersion	7.93	22.19
FEP Dispersion	5.88	15.08
Colloidal Silica Dispersion	3.58	5.00
Ultramarine blue dispersion	13.74	32.06
Aluminum silicate dispersion	0.58	0.94

Intermediate	Coating Composition (Wt.%)	Solids Content in Finished Article (Wt%)
PTFE Dispersion	56.34	77.43
PFA Dispersion	10.21	14.22
Water	4.62	-
Carbon black dispersion	2.71	3.79
Ultramarine blue dispersion	0.49	3.22
Mica coated with TiO₂	0.75	1.73
Surfactant catalyst soln.	12.63	-
Acrylic dispersion	12.23	-

Typical spatter ink formulation compositions (parts by weight)
	A (white)	B(gray)	C(brown)
PTFE Dispersion	542.0	542.0	542.0
PFA Dispersion	96.0	96.0	96.0
Ceramic Dispersion	50.0	50.0	-
TiO₂ Dispersion	100.0	100.0	20.0
Iron Oxide Dispersion	-	-	80.00
Channel Black Dispersion	-	8.0	2.0
Solvent Surfactant Blend	110.00	110.00	110.00
Acrylic Dispersion	120.00	120.00	120.00
Solvent-Surfactant Blend	30.00	30.00	30.00
Hydroxyl propl cellulose soln.	30.00	15.00	20.00
Viscosity in centipoise as measured by Brookfield #2 spindle, @ 20 rpm	682	608	682

	White	Grey
Spatter Coats	Coating Composition (Wt.%	Solids Content in Finished Article (Wt.%)	Coating Composition (Wt.%)	Solids Content in Finishes Article (Wt.%)
PTFE Dispersion	50.29	71.04	50.61	70.63
PFA Dispersion	8.91	12.58	8.96	12.52
A1₂O₃ Ceramic Dispersion	4.64	5.46	4.67	5.43
TiO₂ Dispersion	9.28	10.92	9.34	10.86
Carbon black Dispersion	-	-	0.75	0.52
Surfactant-Catalyst Solution	12.99	-	13.07	-
Acrylic Dispersion	11.13	-	11.20	-
Hydroxyl propyl cellulose solution	2.78	-	1.40	-
Viscosity in centipoise as measured by Brookfield #2 spindle, @ 20 rpm	682	608

Topcoat	Coating Composition (Wt.%)	Solids Content in Finished Article (Wt%)
PTFE Dispersion	66.73	94.04
PFA Dispersion	3.51	4.95
Water	3.77	-
Mica coated with TiO₂	0.43	1.01
Surfactant catalyst soln.	12.52	-
Acrylic dispersion	13.04	-

In order to achieve a stone-like appearance, we prefer to spray a first discontinuous coat of a relatively darker color or optical density than the second a well as each successive globule coat being of a progressively lighter color or darkness. One preferred combination is to have a black base coat (the intermediate on which the discontinuous globule coats are to be sprayed) with the first globule coat in a dark brown, the second globule coat in a lighter gray, and an optional third globule coat in white.
It is important, for achieving the desired aesthetic flexibility, to have more complete coverage with the first globule coat and progressively less complete coverage with each successive globule coat, in accordance with the following:

% of Area

Globule Coat Range of Coverage Preferred Range

First 30-80 45-65

Second 20-45 30-40

Optional Third 10-35 15-30
There should be at least a 5% difference in area covered between each globule coat. Thus, if the first coat covert 40%, the second should cover no more than 35% and then the third no more than 30%.
The spray is preferably done from a spatter gun, resulting in random coverage and more or less overlap of the globules of one application by those of the next application.

Claims

An article of cookware having a coating thereon, wherein the coating comprises a primer adhered to the substrate and optionally one or more further coats, the uppermost coat having a first color or darkness, wherein a discontinuous layer of globules is present on or in and covers no more than 80% of the area of the uppermost coat, said globules having at least one color or darkness which is visibly different than said first color or darkness, said globules applied in at least two applications with the first application of one color covering 30-80% of the area and the second application of another color covering 20-45% of the area, with the second application covering at least 5% less area than the first.
An article of cookware having a cooking surface which comprises a multi-layer, non-stick coating which minimizes sticking by food residues and which is heat resisting by being stable at temperatures above 300°C on a substrate, wherein the coating comprises a primer adhered to the substrate, a non-stick, heat-resisting, light-transmitting topcoat, and optionally one or more intermediate coats, with the topcoat adhered to any such intermediate coats which are adhered to the primer or in the absence of intermediate coats, the topcoat being adhered directly to the primer, with the coating under the topcoat having a first color or darkness, wherein a discontinuous layer of raised globules is present on or in and covers no more than 80% of the area of the coating under the topcoat, said globules having at least one color or darkness, which is visibly different than said first color or darkness as seen through said topcoat, said globules applied in at least two applications with the first application covering 30-80% of the area and the second application covering 20-45% of the area, with the second application covering at least 5% less area than the first.
A method of making an article of cookware having a cooking surface which comprises a multi-layer, non-stick coating which minimizes sticking by food residues and which is heat resisting by being stable at temperatures above 300°C on a substrate, wherein the coating comprises a primer adhered to the substrate, a non-stick, heat-resisting, light-transmitting topcoat, and optionally one or more intermediate coats, with the topcoat adhered to any such intermediate coats which are adhered to the primer or in the absence of intermediate coats, the topcoat being adhered directly to the primer, with the coating under the topcoat having a first color or darkness, wherein a discontinuous layer of globules is present in and covers no more than 80% of the area of the coating under the topcoat, said globules having at least one color or darkness, which is visibly different than said first color or darkness as seen through said topcoat, wherein said globules are applied in at least two applications while the coating under the topcoat is still wet so that the globules sink into the coating under the topcoat and the topcoat is substantially smooth, with the first application covering 30-80% of the area and the second application covering 20-45% of the area, with the second application covering at least 5% less area than the first.
An article of cookware having a coating thereon, wherein the coating comprises a primer adhered to the substrate and optionally one or more further coats, the topmost coat having a first color or darkness, wherein a discontinuous layer of raised globules is present on and covers no more than 80% of the area of the topmost coat, said globules having at least one color or darkness which is visibly different than said first color or darkness.
An article of cookware having a cooking surface which comprises a multi-layer, non-stick coating which minimizes sticking by food residues and which is heat resisting by being stable at temperatures above 300°C on a substrate, wherein the coating comprises a primer adhered to the substrate, a non-stick, heat-resisting, light-transmitting topcoat, and optionally one or more intermediate coats, with the topcoat adhered to any such intermediate coats which are adhered to the primer or in the absence of intermediate coats, the topcoat being adhered directly to the primer, with the coating under the topcoat having a first color or darkness, wherein a discontinuous layer of raised globules is present on and covers no more than 80% of the area of the coating under the topcoat, said globules having at least one color or darkness, which is visibly different than said first color or darkness as seen through said topcoat, said discontinuous layer creating a texture or roughness in said topcoat.
A method of making an article of cookware having a cooking surface which comprises a multi-layer, non-stick coating which minimizes sticking by food residues and which is heat resisting by being stable at temperatures above 300°C on a substrate, wherein the coating comprises a primer adhered to the substrate, a non-stick, heat-resisting, light-transmitting topcoat, and optionally one or more intermediate coats, with the topcoat adhered to any such intermediate coats which are adhered to the primer or in the absence of intermediate coats, the topcoat being adhered directly to the primer, with the coating under the topcoat having a first color or darkness, wherein a discontinuous layer of raised globules is applied to and covers no more than 80% of the area of the coating under the topcoat, said globules having at least one color or darkness, which is visibly different than said first color or darkness as seen through said topcoat, wherein the coating under the discontinuous coating is dried enough before applying the discontinuous coating such that a portion of the globules remains on top of said undercoating to create a roughness in said topcoat.