CS209465B2 - Enamwelling frit for making the enamels for the covering layers of the baking oven interiors - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to an enamel frit for the production of enamels for the coating layers of the interior of baking pipes for the oxidation of vegetable oil residues deposited on their enamel surfaces at temperatures between 180 ° C and 320 ° C.

In particular, the invention relates to enamel frits of such a composition that, when added to opaque enamel and used on a suitable substrate, they cause the fine layers of food which usually spatter on the surface of the oven during baking or grilling, easily and completely oxidized. the formation of fine ash which is easily removed from the inside walls of the oven.

While continuous scrubbers have hitherto usually been of the type electric cookers, the frit of the invention allows the production and use of continuously scrubbing gas cookers. Indeed, the design of the electric cooker is such that the cooker may have continuously cleaned parts, heated to the high temperatures at which oxidation takes place, directly by the heaters on a surface facing away from the surface that is exposed to contamination. On the other hand, the gas cooker cannot be designed in such a way as to achieve a controllable increase in the temperature of the continuously cleaning walls of the oven by placing jet burners along the opposite sides of said walls.

Accordingly, in order to efficiently arrive at a continuously scrubbing gas oven, it is essential that its internal working surface be of such a function that it will function at relatively low oxidation temperatures and be capable of being brought to such temperatures in a normal atmosphere, which is in the oven, all using conventional burners for roasting or grilling in their usual arrangement and placement.

For this purpose, a large number of catalytic materials dispersed on the surface of the oven are used for this purpose using various environments to facilitate the oxidation of food residues on the walls of the oven.

It is well known that increasing the oxygen content in the atmosphere lowers the temperature at which the materials are oxidized. This is particularly true of organic materials that are exposed to atmospheres with a high percentage of oxygen content.

It has now been found that some vitreous enamels effectively release oxygen when organic materials, such as fine food residues, come into contact with the vitreous enamel surface, and that oxygen is absorbed from the normal atmosphere into the skin layer, according to theory either being deposited directly into the enamel coating, or diffuses into the enamel layer, thereby providing a sufficient excess of oxygen to effect oxidation of the food residue if the layer is then heated.

This phenomenon of oxygen absorption appears to occur at approximately the same surface temperature as is necessary to oxidize residues of organic materials in contact with the surface, and this process is greatly facilitated by the presence of iron oxide in the glass enamel with which the iron homogeneously sintered.

The subject of the present invention is an enamel frit comprising: 1.35 to 2.99% boron oxide B2O3, 1.70 to 7.81% sodium oxide Na2O, 15.52 to 32.85% silica S1O2 10.22 to 15.85% TiO2 and 17.37 to 61.74% FeaCl3 based on 11a total frit weight.

According to a preferred embodiment of the invention, the enamel frit contains 0.40 to 0.42% by weight of CaO, 5.13 to 5.27% by weight. weight of potassium oxide K2O, 0.76 to 0.80% by weight of lithium oxide LigO and 0.55 to 0.60% by weight of phosphorus pentoxide P2O5. Suitably it contains from 2.30 to 2.40% by weight of zirconia ZrO2.

According to another embodiment of the invention, the enamel frit comprises 1.79-3.59% by weight of CuO and 6.68-14.04% by weight of Al2O3. Suitably it still contains traces of up to 3.57 percent by weight of cobalt dioxide CO2O3 and traces of up to 3.98% (by weight of zinc oxide,

Unexpectedly and completely contrary to the prior art, the invention achieves an absolutely surprising improvement in the oxidation of food residues by incorporating a high amount of ferric oxide into an enamel frit, which is then ground into glass enamel, which is applied to the oven walls.

In this way, the fixation of the enamel coating is such that the binding is so strong that the abrasion loss is almost impossible. This means that if an enamel layer is consumed in use or if abrasion occurs, homogeneous dispersion of iron oxide throughout the enamel coating ensures that there will still be a sufficient amount of oxidation-inducing oxide on the layer or near its surface when oxidizing the rest of the food .

Another advantage of incorporating iron oxide directly into the enamel frit is that it is not necessary to use highly refined glasses as the oxide is directly melted with the glass. Thus, a quite common ceramic degree of purity is sufficient.

Temperatures around 430 degrees Celsius were previously required to efficiently oxidize the remainder of the vegetable oils deposited as a layer on the enamel surface. Celsius. However, using the enamel frit of the present invention, these residues are removed at a temperature of 270 ° C, the heating time being the same as previously heated to 430 ° C. Celsius. Using the enamel frit of the invention, oxidation can be achieved even at lower temperatures of about 180 ° C, but this rate occurs to a lesser extent and at a lower rate.

The enamel frits according to the invention can be used not only for cookers based on an enamel-coated steel sheet, but also for cookers of any other metal resistant to the baking temperatures involved.

In the practice of the present invention, the batch of enamel frit is weighed, mixed and sintered, followed by rapid cooling to obtain product or frit flakes using conventional materials and procedures, except that new amounts of iron oxide are used as described below. described.

As will be mentioned below, the basic composition of the enamel frit, besides containing iron oxide, is not critical, and it is only necessary that the sintered frit with a given percentage of iron oxide exhibit a fusibility and physical properties such as suitable for use on metal substrates, and for firing to form an adhesive layer of vitreous enamel.

Table 1 below lists, as a general guide, the oxides which may be used as ingredients for the preparation of any smoked frit of the invention, generally indicating the range of content of each ingredient in weight concentration.

Table 1

Composition of oxides in frit; data represent weight concentration

AI2O3

B2O3

CaO

C02O3

CuO

K2O

Li ₂ O

NazO

P2O5

S1O2

T1O2

ZnO

ZrO2

Fe2O3 tracks up to 20 1 to 10 feet up to 1 feet up to 5 feet up to 4 feet up to 10 feet up to 5

1.7 to 10 feet to 2 15 to 40 10 to 30 feet to 4 feet to 10 15 to 70

The preceding compounds are 100% in total, although they vary within the ranges indicated.

The amount of ferric oxide used is dependent on other elements used in the manufacture of glass, and only to the extent that a high content of ferric oxide can alter the fusibility of the glass and thereby alter

6 of its workability conditions, which requires adjusting the amount of ferric oxide within the workability range.

And although the preferred range by weight of iron oxide content is in the range of 25 to 55%, calculated on an enamel frit, either singly or in combination, certain recognizable and measurable properties can be achieved using as low a weight concentration as 15%, or · As high as 70%, which all depends on the characteristics of the sinaltier frit, such as fusibility, etc.

It goes without saying that there is no measurable upper limit of the oxidation-inducing ferric oxide content, since the only requirement is that there are sufficient additional glass-forming components in the mixture to produce a workable enamel with the general properties of glass enamels at normal firing temperatures.

Examples of specific compositions of vitreous enamels useful in the practice of the invention are set forth in the following examples. All% (parts) given in the examples represent the concentration (ratio) by weight.

Example 1

The components of the composition below are weighed and mixed in a suitable mixer or blender.

parts boric acid 132 potassium carbonate 149 sodium nitrate 72 feldspar 328 float chalk 21 trisodium polyphosphate 25 red iron oxide 798 ground zirconia 93 spodumen, LiAl (SiO3) 2 283 powdered quartz 400 cobalt oxide 93,3 copper oxide 46,8 titanium dioxide rutile) 359

The above mixture was melted at 1410 ° C, cooled to form a frit with cold water, and then dried in an oven at 94 ° C. The frit obtained has this composition, expressed in% of the total oxide content.

The oxidation-inducing iron oxide enamel frit as prepared above was compared to a similar ferric oxide-free frit as well as conventional baking oven enamel using the test below. In this example and other examples, for comparison, clear enamel is used as a standard, having essentially the same composition as the investigated enamel of the invention, except for oxidizing iron oxide, together with conventional baking oven enamel still used in baking ovens. and which does not contain oxidation-inducing ferric oxide in amounts suitable for the enamel frits of the invention.

In this example and others, the evaluation is performed at 200 ° C and at that temperature an eye dropper is applied to the hot sample one drop of each type of food contamination (shortening, meat residues and water with sugar). The test samples are heated at 290 ° C for two hours and then evaluated after cooling. The staining layer of the present invention with molten iron oxide did not retain a staining stain, whereas in the case of two samples used for comparison and containing no oxidizing iron oxide, a strongly adhering, black unsightly residue was observed at the place where the food sample was applied.

Table 2

The following ingredients were mixed in a mixer after weighing:

Borax 56 anhydrous soda · 158 sodium nitrate 34 roasted aluminum oxide 182 powdered quartz 418 red iron oxide 1664,5 titanium dioxide (rutile j 287

The mixture was melted at 1410 ° C. Celsius, quenched with cold water to form a frit and dried in an oven at 93 ° C. The obtained frit has the following composition:

% % B2O3 2.86 SiO ₂ 15.52 CaO 0.42 B2O3 1.35 CO2O3 3.57 N32O 4.49 CuO 1.79 A12O3 6.68 K2O 5.22 Fe2O3 61.74 Li2O 0.77 TÍO2 10.22 NazO 1.72 P2O5 0.56 The frit was ground in plain ball-mill SiO ₂ 32.15 for adding these components: T1O2 13.21 ZrO2 2.30 Fe2O3 35.35

parts parts glass (as frit) 100 boric acid 5,0 bentonite 3/8 tragacanth rubber 1/16 powdered aluminum oxide 62,5 water 32

The enamel obtained was ground to a fineness such that 10 g passed through a 0.077 mm sieve had a volume of 50 ml, and sprayed directly onto a suitable metal substrate using 323 g per 1 m ^{2 of} surface, and baked at 760 ° C for three minutes. C to produce a matte finish.

The above frit was evaluated against a clear standard and conventional baking enamel according to the procedure of Example 1. After the test time (2 hours), the samples were cooled and leveled. as well as the iron-free standard, the black residue appears firmly adhered to.

Example 3

After weighing, the glass mug containing the following raw materials was mixed in a mixer:

parts

borax 20 May boric acid 114 potassium carbonate 201 sodium nitrate 73 float chalk 19 Dec trisodium polyphosphate 27 Mar: lithium carbonate 51 powdered quartz 846 titanium dioxide (rutile) 426 zinc oxide 103 red iron oxide 921 The mixture was melted at 1410 ° C for 40 minutes, cooled with cold water and was dried in an oven at 93 ° C; herewith. way prepared enamel frita má the following composition: % SiO ₂ 32.72 B2O3 2.99 NazO 1.70 K2O 5.26 LizO 0.79 CaO 0.40 P2O5 0.60 TIO2 15.05 ZnO 3.98 FezO3 35.70

The frit is then ground in a conventional ball mill with the addition of the following ingredients:

enamel frit 100 polytran 1/2 sodium nitrite 1/2 water 45

The obtained enamel was ground to a fineness that 10 g of expired sieve of aperture 0.037 mm had a volume of 50 ml, and then sprayed on a suitably treated substrate using the amount of 323 g per 1 m ² of surface and baked for 3 minutes at 790 ° C.

The samples were further evaluated using the procedure of Example 1. After the test time (2 hours), the samples were cooled and evaluated. There is no residual discolored stain with molten iron enamel, whereas for standard enamel samples as well as 1 blank test using a standard, a solid black residue appears at the place where the food samples were applied.

Example 4

Further portions of the following composition are mixed in a blender after weighing:

parts

borax 28 boric acid 105 potassium carbonate 202 sodium nitrate 73 float chalk 19 Dec trisodium polyphosphate 27 Mar: lithium carbonate 52 ground zirconium dioxide powdered quartz 820 copper oxide 92.7 titanium dioxide (rutile) 362 red iron oxide 927 Said glassy mixture is added melts for heat- 1410 ° C for 50 minutes, cooled cold water and dried in drier for hot- 93 ° C, whereupon: enamel frit of the following composition: % S1O2 32.85 B2O3 2.99 Na20 1.79 K2O 5.27 LizO 0.80 CaO 0.40 ZrO2 2.40 P2O5 0.60 CuO 3.59 TiOz 13.44 Fe2O3 35.86 The frit is then ground with the following ingredients: further use-

parts parts glass frit 100 ALIGN! enamel frit 100 ALIGN! boric acid 5.0 polytran FS 1/2 bentonite 3/8 sodium nitrite 1/2 tragacanth rubber 1/16 water 45 powdered alumina 62.5 water 32 Said enamel is ground to a fineness as in the previous examples, then Said enamel is ground to such fineness. sprayed onto a substrate treated with a suitable 10 g passed through a 0.037 sieve method using 323 g per m ² millimeter has a volume of 50 ml, then directly area and firing is carried out for 3 sprayed, without roughening, to suitably minutes at 760 ° C to achieve substrate 323 g naar kg matt surface. m ² area and fired at 820 ° C Samples are evaluated using of the same for 2 minutes to achieve a peppermint the procedure of Example 1; at the end two- surface. The samples are cooled for one hour Samples are evaluated using the procedure and evaluate. Glass enamel with 17% i according to Example 1. After the cleaning cycle is confessed- sintered iron does not provide the rest barva- enamel with built-in iron oxide dirt stain while on the sample plain in that it is essentially free of residual enamel is a firmly adhered black deposit. stained spots, while samples usual As mentioned above, the composition laughing- enamel as well as blind attempt I mark There are no frits applicable according to the invention firmly adhered to, black. too important. Finally, Example 6, Example 5 containing only the ingredients contained in point 1 defini- Enamel with the following composition After weighing the ingredients, mix in a blender: Example 1 a d 6 parts The following composition is weighed mix in a mixer: borax 123 potassium carbonate 154 parts titanium dioxide (rutile) 450 float chalk 22nd dehydrated borax 3.55 trisodium polyphosphate 27 Mar: sodium carbonate 7.09 lithium carbonate 54 silica 24.16 ground zirconium oxide 100 ALIGN! rutile 12.20 powdered quartz 906 ferric oxide 48.36 potassium nitrate 91 sodium nitrate 4.64 red iron oxide 550 This composition was melted at temperature The mixture is melted for 40 minutes at temperature 1450 ° C for 60 minutes, cooled in 1410 ° C and after cooling by cold water up water and dried in a dryer at temperature dried in an oven at 93 ° C ; obtained 120 [deg.] C. The fused frit had the following slože- enamel frit has the following composition: 0 / n her: % ^υ / 0 B2O3 2.65 FezCb 17.37 Na2O 7.44 B2O.3 2.81 S1O2 26.51 CaO 0.42 T1O2 12.83 K2O 5.13 FezCh 50.57 Li ₂ O 0.76 NažO 7.81 The frit was then ground in a conventional spherical P2O5 0.55 mill using the following ingredients: AI2O3 14.04 SiO2 32.85 parts TÍO2 15 79 ZrO2 2.34 glass frit 100 ALIGN! bentonite 3/8 The frit is then ground in a conventional spherical boric acid 5 mill with the following ingredients: tragacanth rubber 1/16 water 32.5

0 * 847 5

The frit obtained was ground to a fineness such that 10 g passed through a 0.036 mm sieve had a volume of 50 ml.

The ground frit was sprayed onto a suitably prepared substrate using an amount of 300 to 350 g per 1 m ² area and baked for three minutes at 780 ° C.

The self-cleaning ability was verified at 235 ° C for two hours.

Although it has been clearly shown that glass enamels can be used in conjunction with continuous-cleaning baking ovens, it goes without saying that glass enamels' ability to oxidize organic compounds may also have wide applicability in numerous other fields, for example when using enamels in conjunction with exhaust paint systems in kilns, where the vapors, before being discharged into the free space, come into contact with a series of heated enamel-covered surfaces according to the invention and oxidize there to form negligible compounds due to air pollution. The same theory can be used for motor-driven pumping systems whose interiors can be covered with the enamel of the present invention, thereby converting some combustion products into less harmful products that can be so treated before being released into the free atmosphere.

The ability of said vitreous enamels to oxidize organic compounds is a function of time, temperature, and type of organic compounds to be oxidized. Usually, only slight oxidation or ineffective oxidation can be achieved at temperatures below 180 ° C, and it is believed that the upper temperature limit of oxidation using the coatings of the present invention is near 320 ° C. This further ensures exceptional safety, while other safety devices are not at this temperature because the probability of an explosion due to the sudden accessibility of excess oxygen due to the unexpected opening of the oven or oven door is greatly reduced to that extent, while at higher temperatures were necessary in previous processes that utilize the effect of temperature in the oxidation of oven residues, there was always a risk of similar explosion, which required the inclusion of precautions on the oven door using the oxidation process.

From the previous working examples, except that the percentage of oxidation-inducing oxide can be reduced in the frit by the addition of a sintering component such as the alumina of Example 4, it can be seen that the percentage of oxidation-inducing oxide is reflected in the final, burned-out the enamel coating layer at substantially the same percentage as that of the enamel frit.

Claims (5)

1. Enamel frit for the production of enamels for coatings on the inside of baking pipes for the oxidation of vegetable oil residues deposited on their enamelled surface, at a temperature within the range of 180 ° C to 320 ° C, characterized in that it contains 1.35 to 2.99% boron oxide, 1.70 to 7.81% sodium oxide, 15.52 to 32.85% silica, 10.22 to 15.85% titanium dioxide, and 17.37 to 61.74% iron oxide, based on total weight of frit. 2. Enamel frit according to claim 1, characterized in that it contains 0.40 to 0.42% of calcium oxide, 5.13 to 5.27% of potassium oxide, 0.76 to 0.80% of lithium oxide and 0 to 0.5%. 55 to 0.60% by weight of fossil inventive oxide, based on the total weight of the frit. 3. An enamel frit according to claim 1, comprising 2.30 to 2.40 percent zirconia based on the total weight of the frit. 4. An enamel frit according to any one of claims 1 to 3, comprising 1.79 to 3.59% copper oxide and 6.68 to 14.04 percent alumina based on the total weight of the frit. 5. Enamel frit according to claims 1 to 4, characterized in that it contains traces of up to 3.57% of cobalt oxide and traces of up to 3.98% of zinc oxide, based on the total weight of the frit.