BE1023018A1 - EMAIL COMPOSITIONS WITH METAL GLOSS - Google Patents

Abstract

The present invention provides new enamels or compositions that are specifically useful for coating metal surfaces consisting of cast iron or sheet steel and creating a metallic luster effect.

Figure 1

Description

EMAIL COMPOSITIONS WITH METAL GLOSS TECHNICAL WORK AREA

The invention is situated in the field of enamel (vitreous enamel) compositions, in particular in enamel compositions that give a metallic luster effect to the end product, in particular cast-iron utensils, such as pots and pans.

BACKGROUND OF THE INVENTION

From an aesthetic and design point of view, people are always looking for new techniques to improve the appearance of utensils such as (cooking) pots and pans. Adding a metallic luster to such utensils is therefore very interesting. For aluminum and steel pots and pans, enamels are known that give a metallic luster effect to the end product, the end product also being resistant to high temperatures and the presence of acids that may occur during the cooking process. For cast iron utensils, however, a different type of enamel is required to achieve this effect due to the long burn-in time. Standard emails for cast-iron utensils are generally composed of a combination of network-building and network-breaking components. The combination of and the balance between the two ensures the perfect flow of enamel during the burn-in process, an appropriate expansion coefficient and chemical resistance. To achieve a metallic luster effect, a certain pigment (luster, pailette) must be administered, such as irriodine. However, this irriodine is very susceptible to degradation by mainly the network-breaking components in the frit, as a result of which the metal luster effect in standard frits for cast iron is not obtained.

There is therefore a need for enamel compositions (enamels) for use on cast iron, which give a metallic luster effect to the end product, without sacrificing coefficient of expansion and chemical resistance.

The present invention offers a solution to the above problem.

SUMMARY OF THE INVENTION

The invention provides the following aspects:

Aspect 1. A frit composition useful for coating cast iron containing the following components: a) 35 - 50 wt. % SiO 2, b) 14-20 wt. % K 2 O + Na 2 O, c) 0 - 0.5 wt. % Li 2 O,

Aspect 2. An email composition that is made up of 1 or more frits, with frit composition according to aspect 1, and to which 1 -10 wt. % luster pigment was added.

Aspect 3. The enamel composition according to aspect 2, which is usable for burning in (firing) in a temperature fork from 700 to 900 ° C, preferably from 750 to 800 ° C, and more preferably from 770 to 790 ° C.

Aspect 4. The email composition according to any of aspects 2 to 3, used as an email top layer.

Aspect 5. The enamel composition according to any of aspects 1 to 4, wherein the enamel composition after burning on a cast iron surface has the following reflection coefficient:

Si -15 ° is higher than or equal to 35;

Si is 45 ° higher than or equal to 20; and / or

Si 75 ° is higher than or equal to 15.

Aspect 6. The use of the enamel composition according to any aspects 1 to 5, for coating cast iron surfaces.

Aspect 7. The use according to aspect 6, for coating any object selected from the list comprising: pots, rollers, sauce pans, (sauce) pans, frying pans, wok pans and any associated lids thereof; roasting or grilling plates, and roasting or grilling grills; barbecues, oven walls, stoves, ornamental fireplaces, and fireplaces; billboards and bathtubs.

Aspect 8. A process for forming an enamel coating on a cast iron surface, which includes the following steps: (a) provided with a cast iron surface, optionally provided with a primer enamel composition; (b) depositing the enamel composition according to any of claims 2 to 5 on the cast iron surface of a); (c) burning in (firing) the enamel layer on the surface, at a temperature between 700 and 900 ° C, preferably between 750 and 800 ° C, more preferably between 770 and 790 ° C, whereby a crystal-hard enamel coating becomes formed on the surface.

Aspect 9. The process according to aspect 8, wherein the enamel layer has a thickness of 50 to 1000 µm, preferably of 100 to 700 µm, more preferably of 100 to 500 µm.

Aspect 10. The process according to any of aspects 8 to 9, wherein the enamel composition is burned in for about 10 to 20 minutes, preferably 12 to 16 minutes.

Aspect 11. The process according to any of the aspects 8 to 10, wherein the reflection coefficient of the end product is as follows:

Si -15 ° is higher than or equal to 35;

Si is 45 ° higher than or equal to 20; and / or

Si 75 ° is higher than or equal to 15.

Aspect 12. Metal object coated with one of the enamel compositions according to any of the aspects 2 to 5.

Aspect 13. Metal article coated according to any of aspects 8 to 11. DETAILED DESCRIPTION OF THE INVENTION

All terms used herein are to be understood as known in the technical field of the invention and have the meaning known therein.

The term "weight percent" refers to percent on a weight basis, abbreviated "% w / w" or "wt. % ”And is the weight percentage on the total weight of the email composition.

As used herein, the singular forms "a" and "de" include both singular and plural unless the context clearly dictates otherwise.

The terms "contains", "includes", "includes" and "includes" as used herein are synonymous and should be construed as open and do not exclude additional, non-recruited members, elements or steps. The term also includes "consisting of" and "consisting essentially of".

The numerical end points of the concentration ranges include the actual end points as well as a variation thereof of less than 1.0% by weight, preferably less than 0.5% by weight, more preferably less than 0.2% by weight, even more preferably less than 0.1% by weight or less. All numbers and fractions that fall within the respective range, as well as the stated end points, form part of the invention.

The term "about" as used herein to refer to a measurable value such as a parameter, an amount, a certain time, and the like, is intended to mean variations of the prescribed value, in particular variations of + / -10% or less, at preferably + / -5% or less, more preferably + / -1% or less, and even more preferably + / -0.1% or less of the prescribed value, to the extent such variations are suitable in the respective embodiments of the invention . It is clear that the value to which the determination "approximately" refers is also specifically and preferably described.

The term "substantially none" refers to less than 0.1% by weight, preferably less than 0.01% by weight, more preferably 0% by weight.

The term "frit" refers to the flakes or granalis, which is obtained by melting the mixed components (eg) at a temperature of 1200 to 1400 ° C at which a glass structure is formed, and afterwards cooling this molten glass to room temperature between cooling rollers or in water.

The term "enamel" refers to the enamel composition, which is obtained by grinding frit in combination with auxiliaries and dyes into fine powder or sludge. The enamel is reacted with burnt and attached to the substrate. In the current context, the terms "email" and "email composition" are considered synonymous.

The term "burn-in" refers to the English term "firing", the heating step that is done to make the enamel composition finally react with the substrate or surface and can be carried out by any known technology. The enamel composition hereby changes into a crystal-hard coating. Burn-in typically takes place in specially developed ovens, which can have different sizes and use different energy sources for burning in the enamel compositions. Examples are so-called lightweight room ovens (box-furnaces), charged ovens (charge furnaces), tunnel ovens (tunnel-furnaces), conveyor belt ovens (conveyer-belt furnaces), continuous ovens (continuous furnaces), with U- or L-type heating chambers . It is important that the ovens have a uniform heat distribution in the oven chamber, with the smallest possible temperature fluctuation in function of time and place in the oven.

The term "applying the enamel composition" includes all possible techniques for applying the enamel layer (also called "enamel") to the substrate or surface. More specifically, the term includes: wet dipping (wet dipping), liquid coating (flow coating), spraying (spraying), wet electrostatic coating (electrostatic coating), electrophoretic coating (electrophoretic coating), powder coating (dusting or dipping) ), powder electrostatic coating (powder electrostatic coating), or combinations thereof.

The enamels according to the invention are specially designed for coating cast iron surfaces that must be able to withstand large temperature fluctuations and chemical components from foodstuffs such as acids, salts and bases. Examples of such cast iron surfaces are cooking utensils such as pots, boiler rolls, sauce pans, saucepans, frying pans, wok pans, as well as any associated lids thereof, as well as barbecues, roasting or grilling plates, and roasting or grilling grills. The enamel compositions according to the present invention can of course also be used for coating other cast-iron surfaces such as ovens, stoves, fireplaces, bathtubs, billboards, etc .. The enamels described herein are also suitable for coating steel.

Cast iron cooking utensils must typically meet the following requirements issued by the European Enamel Authority (EEA) (EEA quality requirements vs.4.1, 2014)

The following table shows the test methods for the respective quality requirements listed above:

The enamels described herein are suitable for application as a top layer, which must adhere to an enamel base layer, specifically aimed at cast iron and / or steel. An example of such a primer for cast iron is the product GC5028 (Prince Belgium bvba). An example of such a primer for steel is the product PM 1/10/5800/1 (Prince Belgium bvba).

The base layer and top layer are typically applied to the surface via a two-coat-two-fire process. A first primer coating is applied via eg. a spray gun and burned in at a typical temperature between 820 ° C-850 ° C. A second coating is then applied, also with eg. a spray gun and burned in again but at a lower temperature (760 ° C-840 ° C).

The enamels described herein are also suitable for application as a single enamel layer, specifically aimed at cast iron and / or steel. Such a single enamel layer is applied to the surface by a one-coat-one-fire process. No primer coating is applied, and the top coat is applied directly to the substrate and burned in at 760 ° C-840 ° C.

The term "luster pigment" as used herein refers to pigments that cause a pearl effect or metallic luster in the final enamel coating. Luster pigments can be natural or synthetic and are basically constructed from coated inert materials. The coating that is used is often Titanium dioxide. Iriodine (Merck), for example, is a natural mica coated with titanium dioxide (TiO 2).

The term "reflection coefficient" is a measure of the amount of metallic luster that the end product after burning in the enamel according to the invention. Such a coefficient can be measured, for example, by means of a BYK mac i type (BYK-Gardner GMBH) spectrophotometer, whereby the surface is illuminated from different angles and the glistening region (Sa) as well as the ginkering intensity (Si) is measured, so that the shimmer can be quantitatively expressed as a function of Sa and Si (f (Sa; Si)). The grain size (uniform / fine vs. grainy / coarse) can also be measured with such a device and can be indicated on a scale from 0 (uniform / fine) to 15 (grainy / coarse).

EXAMPLES

The present invention is further described herein in the form of the following non-limiting examples.

Example 1: Testing the compositions according to the invention

Enamel compositions with different compositions (cf. Table 1) were tested for their metallic luster effect.

The test methods used are briefly outlined below, but can be replaced by any similar methodology known in the art. “Lab” values: color values based on the Lab color space annotation, where L represents the lightness (100 is very light, 0 is very dark), A represents the amount of red or green, and B represents the amount of yellow and blue.

The different frits were applied to the same cast iron substrate and the metal gloss reflection was determined (Figure 1). An appropriate grinding formula for use as a top coat on cast iron was used, with the addition of 3 wt. % luster pigment. The substrates, after drying, are baked for about 12 minutes at 780 ° C.

The impression effect (Si, Sa, AG) was measured with a BYK-mac i Sensor 23mm (BYK gardner GMBH) according to the manufacturer's manual. The reflection coefficient is mainly determined by determining the different Si values (reflection) when illuminating the product from different angles.

The gloss was measured with a BYK gardner - micro Tri gloss 20/60/85 ° gloss meter (BYK gardner GMBH) according to the manufacturer's manual.

Table 1: overview of the specific example frits and their components (in% by weight) before burn-in (firing) and the resulting metallic luster after application to substrate after two-coat-two-fire.

As indicated in the table, a good metallic luster intensity was only obtained if the sum of K2O + Na2O was between 14 and 20 wt. % and if the amount of Li 2 O is less than 0.5 wt. %. We note that the same amount of luster pigment (3% by weight) was added in all examples. The graininess also depends on the composition of the frit.

If these requirements are not met, the final product will not get enough metallic luster.

Claims (13)

CONCLUSIONS A frit composition useful for coating cast iron containing the following components: a) 35 - 50 wt. % SiO 2, b) 14-20 wt. % K 2 O + Na 2 O, c) 0 - 0.5 wt. % Li 2 O, An enamel composition composed of 1 or more frits, with a frit composition according to claim 1, and to which 1 -10 wt. % luster pigment was added. The enamel composition according to claim 2, which is usable for burn-in (firing) in a temperature fork from 700 to 900 ° C, preferably from 750 to 800 ° C, and more preferably from 770 to 790 ° C. The enamel composition according to any of claims 2 to 3, used as an enamel top layer. The enamel composition according to any of claims 1 to 4, wherein the enamel composition after burning on a cast iron surface has the following reflection coefficient: Si -15 ° is higher than or equal to 35; Si is 45 ° higher than or equal to 20; and / or Si is 75 ° higher than or equal to 15. The use of the enamel composition according to any of claims 1 to 5, for coating cast iron surfaces. The use according to claim 6, for coating any item selected from the list comprising: pots, rollers, sauce pans, sauce pans, frying pans, wok pans and any associated lids thereof; roasting or grilling plates, and roasting or grilling grills; barbecues, oven walls, stoves, ornamental fireplaces, and fireplaces; billboards and bathtubs. A process for forming an enamel coating on a cast iron surface, which includes the following steps: (a) provided with a cast iron surface, optionally provided with a primer enamel composition; (b) depositing the enamel composition according to any of claims 2 to 5 on the cast iron surface of a); (c) burning in (firing) the enamel layer on the surface, at a temperature between 700 and 900 ° C, preferably between 750 and 800 ° C, more preferably between 770 and 790 ° C, whereby a crystal-hard enamel coating becomes formed on the surface. The process of claim 8, wherein the enamel layer has a thickness of 50 to 1000 µm, preferably of 100 to 700 µm, more preferably of 100 to 500 µm. The process according to any of claims 8 to 9, wherein the enamel composition is burned in for about 10 to 20 minutes, preferably 12 to 16 minutes. The process according to any one of claims 8 to 10, wherein the reflection coefficient of the end product is as follows: Si -15 ° is higher than or equal to 35; Si is 45 ° higher than or equal to 20; and / or Si is 75 ° higher than or equal to 15. A metal article coated with one of the enamel compositions according to any of claims 2 to 5. A metal article coated according to any of claims 8 to 11.