FR2476062A1 - LEAD AND HEAT-FREE SINKS, GLACES PRODUCED THEREFROM, AND COATING METHOD EMPLOYING SAME - Google Patents

Abstract

THE INVENTION RELATES TO GLASS FRITS. IT CONCERNS A FRIT WITH GOOD GLASS STABILITY, A COEFFICIENT OF THERMAL EXPANSION (20-300C) BETWEEN APPROXIMATELY 65 AND 7510C, A VISCOSITY SUITABLE FOR NEARBY COOKING OF 700 TO 950C, AND EXCELLENT ATTACK RESISTANCE BY ACIDS AND BASES, CHARACTERIZED IN THAT IT IS FORMED, BY WEIGHT BASED ON OXIDES AS CALCULATED FROM THE FURNACE, SIO 35 TO 47, BO 5.5 A 9, BAO 24 A 42, TIO 1.5 A 4, ZRO 6 A 10, LIO 1 A 5, MGO 0 A 5, CAD 0 A 4, SRO 0 A 8, ZNO 0 A 10, BIO 0 A 8, WITH MGOCAOSROZNOBIO 0 A 10. USE FOR TRAINING DECORATIVE GLAZES ON DISHES.

Description

The use of glass parts, in vitro

  ceramics and ceramics in the field of the tableware, being understood by that of conspicuous kitchen and table pieces, is widespread. In the past, such pieces, and in particular those prepared

  from glass and glass ceramics, have been used

  nally marketed in the united state, that is to say without external decoration. However, for the vast majority of articles of the trade, it is on the aesthetic aspect of the product that one counts to attract the consumer. As a result, very intensive research and development work has been devoted to obtaining presentations and decorative finishes for the surfaces of these types of pieces. Most of this work has been devoted to the development of attractive glazes and enamels. If we reduce these terms to their most fundamental sense, we

  glazes are considered to be trans-

  parents and enamels of glazes that contain pigments to give them a color. These two products are applied to the surface of the glass, glass-ceramic or ceramic part to be decorated under

  form of very finely divided particles, usually

  referred to as "frit", and this frit

  is then cooked so that it is

  sionxe with the surface of the piece and form on it

  a continuous film strongly adherent.

  So far, most of the commercial frits for decorating glass items,

  ceramics and ceramics contained valuable

  quantities of lead oxide (PbO) and, in some cases

  case of cadmium oxide (CdO). These compounds were

  in the frit compositions for two reasons.

  main sounds: (1) to make the frit more fusible, that is to say to lower the melting point so that it can merge with the surface of the article at a sufficiently low temperature to be able to avoid the article to be deformed by heat; and (2) to raise its refractive index. CdO has also been used as a dye in some frits. However, cadmium and lead have the disadvantageous property of being very toxic, so that the glazes and enamels containing these metals come into contact with food

  must have extremely good resistance to

  acidic and alkaline materials to prevent the release of appreciable amounts of these metals. the dangers arising from the release of these

  metals, when the compositions containing them come

  in contact with food, have been recognized by the FOOD AND DRUG ADMINISTRATION (F.D.A.)

  regulation of the food industries and

  in the United States. In its "Compliance Guidance Ianual", published on June 15, 1974, this body established the maximum values of release of cadmium and lead that a surface in contact with food does not

must not exceed.

  It goes without saying that the potential toxicity related to cadmium and / or lead could be completely suppressed by the preparation of frits in which

  these metals would be completely absent. The impossibility

  to meet the combination of the following four criteria required for acceptable glaze or enamel has hindered the mere elimination of these metals, and

  particular lead, in frits.

  Firstly, the frit or frying temperature, that is the temperature at which the frit is sufficiently fluid to give a smooth and homogeneous coating, must be sufficiently

  low to prevent thermal deformation

of the coated article.

  Secondly, the coefficient of thermal expansion must be compatible with that of the article in order to prevent splitting and / or

  a peeling of the glaze or enamel obtained. Very good

  the frit will present a coefficient of

  thermal insulation a little lower than that of the coated article. Under these conditions, the decorative coating is placed in a state of compression relative to the article once it is applied to it by cooking. Third, the frit has to have excellent resistance to attack by acids and

  bases and, in china applications, at the

  washing with detergents used in commercial dishwashers. Corrosion of the surface can lead to loss of luster, the onset of cloudiness or iridescence in the glaze or enamel, the appearance of a

  porosity or other untoward effects on the es-

  the physical nature of the decorative coating

  ratif. Fourthly, the sinter must have good glass stability, that is to say resist the

  devitrification during the cooking operation.

  Although it is not imperative, a

  the fourth desirable property for the frit is to

  seduce a sufficiently high refractive index for

  give a coating with a clear high gloss.

  Although we have explored compositions

  which met several of these criteria,

  Supported research was devoted to the development of clean, lead-free cadmium-free frits

  to answer the complete combination of these imperatives.

  It goes without saying that frits can be used

  Used for other purposes than to constitute bases for

  glazes and decorative enamels. In such applications

  For example, a large brightness resulting from the high refractive index of the composition may not be necessary. Of

  more, in some decoration techniques, a coating-

  large-sided surface is not considered advantageous. Nevertheless, here as elsewhere, it will always be advantageous for the frits to satisfy the first four of the above criteria. Thus, the firing temperature of the frit will have to be low enough to avoid the thermal deformation of the support

  to which the coating is applied. The coefficient of di-

  thermal frit of the frit shall be compatible

  with that of the support. The frit will have to present a

  excellent chemical stability. In addition, to ensure

  formation of a transparent coating, the frit exhibited

will have good glass stability.

  Colored glasses have been the subject of research

  depth for all colors produced in the visible spectrum. W. W. Weyl's Colored Glasses, Dawson's of Pall Mall, London, 1959, is a monograph devoted to the study of the effects of different cations and anions in the creation of colors in

  glasses. The interactions between ions to form cou-

  theirs are virtually limitless, and they still do

  the subject of research even at present.

  The use of iron with or without introduction of titanium to obtain colors ranging from yellow

  brown in various glass compositions, and in particular

  glasses containing lead, has been prescribed for many years. Weyl, in the work cited above, dedicates a certain number of pages to this kind of phenomena, and for example page 108 and following and

  - page 212 and following. Similarly, the creation of a

  bright red liner in glasses (ruby glasses) by

  introduction of cadmium sulfoselenide in the

  sition is well known. Since glazes are essential

  glasses applied as coatings

  superficial thin on a support, we formulated and

  marketed pigments containing iron and, optionally,

  Titanium intended to be added to

  frits, as well as pigments containing

cadmium sulfoselenide.

  However, there were serious difficulties

  by attempting to pigment glazes containing cadmium or lead oxides. The degree of release of these toxic oxides by the glazes or, in other words, the chemical durability of the glazes, is function

  of the cooking temperature implemented in the operation

  icing ration. Thus, as a general rule, the degree of release of lead and cadmium will be even more

  low as the cooking temperature is higher.

  However, when preparing lead-containing frits stained with iron + titanium pigments and baked at temperatures above 700 ° C., the sustained coloration from yellow to brown which is

  Wanted did not appear. Instead, we do not get

  Only a pale yellow color is faded. Similarly,

  the cooking of frits containing lead with pigments

  cadmium sulphoselenide at conventional

  high temperatures did not give the usual bright red color desired, but only dull gray hues. The main object of the present invention is to provide sinter compositions useful as base materials for glazes and enamels and which, being essentially free of toxic heavy metals

  cadmium and lead, are eminently suitable for

  well in the decoration of articles of wares.

  Another object of the present invention is to provide frits of the kind defined above which have a good glass stability, high refractive indices, firing temperatures ranging from about 700 to 9500C, coefficients of thermal expansion ( over the range 20-3000C) varying from approximately

  at 75 x 10 7 / oC, and excellent resistance to

  acid and alkali, and in particular

  detergent attack, since the field of application

  The basic application envisaged for the frits according to the invention is that of the decoration of the articles of tableware, these frits also having indices.

  high refraction when you want to get a coating-

transparent with great brilliance.

  Another object of the invention is to provide

  color glazes obtained from the frits according to the invention and providing sustained colors, and in particular colorations ranging from yellow to

  brown or red, which are stable at high temperatures.

  According to the invention, it has been found that frits

  which satisfy these objectives can be obtained from

  firing compositions belonging to the system li20-BaO-TiO2-

  ZrO 2 -3203-SiO 2, in which is optionally

  at least one member of the group formed by MgO, CaO, SrO, ZnO and Bi203. The compositions of the frits according to the invention are essentially formed, in% by weight on the basis of the oxides as calculated from the batch, of: SiO 2 35 to 47%

B203 5.5 to 9

  BaO 24 to 42 TiO2 1.5 to 4 ZrO2 6 to 10 Li20 1 to 5 MgO 0 to 5 CaO 0 to 4 SrO 0 to 8 ZnO O to 10 Bi203 0 to 8 with SrO + MgO + CaO + ZnO + Bi203 0 to 10 As can be seen immediately, cadmium and lead, potentially toxic heavy metals, do not

  not part of the compositions according to the invention, which

  controls their use in articles that come into contact with food. The constituents listed above

  can be combined to produce pre-made frits

  feeling good glass stability and, when

  desires, high refractive indices that make it possible

  hold high gloss glazes and enamels at firing temperatures between about 700 and 9500C, with thermal expansion coefficients (20-300oC)

  ranging from 65 to 75 x 10_7 / oC, and excel-

  slow resistance to attack by acids and alkalis

  lily, and in particular to attack by detergents such as those used in commercial dishwashers. ZrO2 and TiO2 serve two functions. In

  first, the combination gives the frits the

  exceptional chemical stability. Second, these ingredients (in combination with BaO) are useful for obtaining a high refractive index. However, the introduction of large amounts of these constituents, and in particular a large amount of ZrO 2, considerably raises the softening temperature and the viscosity of the frits, which necessitates extensive adjustments to the other components to ensure obtaining the desired combination of the other parameters, in particular with regard to obtaining

  good glass stability and low temperature

cooking.

  BaO has a profound effect on the glass stability and the refractive index of the frits according to the invention. Therefore, when it is desired to obtain glazes and enamels very large brightness, we will use large amounts of BaO. When such a brilliance is

  not required, the amount of BaO can be reduced.

  Preferably, the composition of the frits according to the invention is limited to the constituents listed above. However, the presence of small amounts of compatible metal oxides and fluoride can be tolerated to modify the behavior of the melt sinter and / or their physical properties. However, the total of all foreign additions of this kind shall not be

  exceed about 5%. As examples of this kind of ad-

  Examples include very small amounts of Na 2 O and / or K 2 O and / or F intended to render the frit more fusible. The fluoride content will not normally exceed about 3%. It goes without saying that pigments can be dissolved and / or suspended in

  frits to get a decorative color enamel.

  The dyes and pigments which have been the most widely used industrially in the past are the oxides of the transition metals, such as, for example, CoO, NiO, MnO, Fe 2 O 3, Cr 2 O 3 and V 2 O 5. More recently, we made

  to this effect to various rare earths, and in parti-

  with praseodymium, erbium and neodymium. normally

  the proportion of such a pigment will be less than

  20% by weight, and frequently less than 5%.

  Particularly preferred compositions will have thermal expansion coefficients (20-300oC) of less than about 70 x 10-7 / oc, and may be converted to fired glazes by firing at temperatures of about 700 to 850 C. thermal expansion coefficients allow the frits according to the invention to be compatible with a high proportion of glass parts, glass-ceramics

  and commercial ceramics used in

  warehouses. As a further advantage, these low coefficients of thermal expansion have

  the effect of placing the decorative coating in compres-

  in relation to its support, thereby conferring

  the article with improved mechanical strength

  SOE. The low maturation temperatures allow the frits to be applied by baking on commercial ware items without thermal deformation thereof. These particularly preferred sinter compositions are essentially formed, in% by weight on the basis of the oxides as calculated from the batch, of SiO 2 40 at 45%

B2 0 6 to 8

  BaO 31 to 39 TiO2 2 to 3 ZrO2 8 to 9.5 Li2O 1 to 2.5 MgO O to 4 CaO O to 4 SrOO to 8 ZnO O to 6 Bi203 0 to 7 with MgO + CaO + SrO + ZnO + Bi20 2 to 8

  It has also been found that bright colors

  mically stable from yellow to brown, and most commonly from orange to reddish brown, can be obtained with such frits by adding thereto 0.5 to 10% by weight Fe203 and 0 to 4% by weight of TiO2. In addition, a bright red color can be obtained with such frits by mixing them with 2 to 10% by weight of cadmium sulfoselenide and subjecting them to

  cooking under non-oxidizing or inert atmosphere.

  Consequently, according to another mode of

  In the invention, these additions are made to the frit according to the invention to obtain a sustained color ranging from yellow to brown or red even after cooking.

high temperatures.

  In particular, it is possible to obtain glazes

  feeling a steady color from yellow to brown

  by applying a mixture of the frit according to the invention

  and from 0.5 to 10% by weight of Fe 2 O 3 + O at 4% by weight

  TiO2 to a piece of glass, glass ceramics or ceramics

  baking and cooking at around 700 to 950 C for a time sufficient for the frit to become fluid and

  gives a smooth and homogeneous coating.

  In a similar way, bright red glazes can be obtained by adding to the frit

  according to the invention about 2 to 10% by weight of sulfoselene

  cadmium nitrate and cooking in a

non-oxidizing or inert atmosphere.

  The U.S. Patent No. 4,084,976 is aimed at

  lead-free cures for use in combination with alumina parts. Such glazes essentially comprise, in% by weight: SiO 2 50 to 54%

A1203 5 to 8

3203 from 6 to 12

  CaO 4 to 6 XMgO 2 to 8 Ba0 2 to 5 Sr0 5 to 8 ZnO 1 to 2 Li20 + Na2O + K20 4 to 6

  The examples indicated are subjected to cooking at 1160 C.

  Such glazes are outside the field of composites

according to the invention.

  The U.S. Patent No 4 120 733 is also intended

  lead-free glazes usable with almine parts, and it proposes glazes which are supposed to provide an improvement over those described in the US patent. No. 4,084,976, in that their maturation temperatures are about 25 to 38 ° C.

  lower. Such glazes are essentially

  in% by weight of: SiO 2 48 to 54%

A1203 7 to 11

3203 16.5 to 20

  BaO 11i to 14 CaO 2 to 3 ZnO 2 to 2.5 Na 2 OO 4.25 to 5.25

K20 0.4 to 1

  The examples shown were baked between

  1038 and 12000C. Such compositions are very distant

  glazes according to the invention.

  U.S. Patent Application No. 80 496

  Richard F. Reade, October 1, 1979, describes frits suitable for glazes and decorative enamels that are particularly suitable for

  to articles of wares because the metals

  toxic, such as cadmium and lead in 1 1, are absent. Such frits have compositions belonging to the system R2O-Al2O3-B203-ZrO2-sio2-F, o

  R20 represents Na2O, optionally accompanied by Li2O.

  As such, these frits are outside the scope of the compositions according to the invention. Table I below shows a group of sinter compositions, expressed in parts by weight.

  based on the oxides as calculated from the furnace

  which illustrate the present invention. As the sum

  individual constituents is equal to 100 or very

  100, we can consider for all practical purposes

  that the various constituents are given in% by weight.

  The starting ingredients actually used may be any material, whether it is the oxide or other compound, which, when melted in combination with the combination of the various constituents, is converted into the desired oxide by giving them the same. desired proportions.

  The proportions indicated

  These compositions correspond to the above-described example compositions and are ball-milled to promote a homogeneous melt. Each batch was placed in a platinum crucible, then

  it was introduced into an oven operating at about 1200-1300C.

  After melting for about two to four hours, a portion of the melt batch was shaped into a glass dough, the dimensions of which were about 15.25 x 5 x 0.95 cm, and this dough was immediately transferred to an oven. annealing working at about 500-600oC. We paid

  the rest of the melt in a water bath (fragmen-

  by quenching in the liquid state) to obtain

  finely divided glass particles which, after drying, were passed through the ball mill to

  cross a sieve with 44 micron openings.

  Table I also indicates the point of

  softening (P. Ram.), the annealing point (Rec.), both given in OC, and the coefficient of thermal expansion (Dil.) over the interval 20300 C, given to the multiplying factor 10-7 / C, determined on the above-described annealed dough pieces. Each of the determinations in question was made using conventional glassmaking methods.

TABILEAU I

1 2 3 4 5 6

  SiO2 40.92 41.88 44.38 41.68 42.33 42.52 BaO 33.74 34.48 31.93 38.65 30, 53 35.05

B203 6.49 6.60 7.00 6.61 6.71 6.74

  ZrO2 8.25 8.50 9.00 8.40 8.53 8.57 TiO2 2.45 2.50 2.65 2.49 2.53 2.54 Li2O 1.73 1.34 1.42 2 17 1.35 1.36

Bi203 6.43 - - - - -

MgO - - 3.62 - - -

ZnO - 4.70 -.

SrO - - - - 8,00 -

  CaO - - - - - 3.20 P. Ram. 744 761 766 746 769 767 P. Rec. 598 613 608 599 619 606 Dil. 69.2 66.1 64.6 72.3 70.7 70.8 As just pointed out, the liquid-tempered fragment particles of glass were crushed to a very fine powder. The powder was shaped by hand pressing into a cylinder about 1.3 cm in height and about 1.3 cm in diameter. Each cylinder was placed on a platinum blade about 0.65 mm

  thickness and the blade was introduced into an electric oven

  operating at a desired temperature, we kept

  specimens at this temperature for about 10

  nutes, and then extracted from the oven to make them

  cool to room temperature in the environ-

environment.

  This heating of the cylindrical mass gives rise to a melting of the frit and to a flow which

  has the shape of a button whose diameter

  is a practical indication of viscous flow. Thus, laboratory experiments have revealed that a button diameter of at least about 1.4 cm is required to ensure a good flow of the melted frit and a good

  wetting of the particular support that is to be coated.

  The flow knobs were separated from the slide and then subjected to tests to measure their

  resistance to chemical attack. It is obvious that

  what special frit-support combination

  should be subjected to tests for itself and be examined as to the degree of wetting of the coating, as well as

  than the presence of punctures, cracks and

  burns. To evaluate the resistance of the frits to acids, the melting knobs were weighed and then immersed in an aqueous solution containing 10% by weight

  of citric acid. These immersions were carried out

  24 hours in a stirred solution placed at a

  960C. We considered a weight loss not

  greater than about 0.02% as indicating a good

  resistance to attack by acids. We also

  put each of the knobs in another test that was designed to indicate the durability of the sintered against alkaline detergents such as those used in commercial dishwashers. This test comprises an immersion of weighed buttons in a 0.3% by weight aqueous solution of an alkaline detergent marketed by the firm Economics Laboratories, St Paul, Minnesota, U.A., under the trademark SUPER SOILAX. The immersion is continued for 24 hours at 960C, after which the

  samples of the solution, rinsed with water

  they are dried, examined visually and

  Repetitions to measure the possible weight loss. We are

  The 24-hour exposure time represents an accelerated equivalent of actual multi-year use in chinaware applications. It is estimated that a weight loss of no greater than about 0.02% exhibits excellent detergent resistance. The buttons were visually examined to identify any

alterations of the brightness.

  Table II below indicates the cooking temperature used (OC), the weight loss (%) after 24 hours in the citric acid solution and the weight loss (%) after 24 hours in the solution

detergent "Super Soilax".

TABLE II

Temp. of Detergent, Altered Acid

  Ex% citric alteration cooking, n0 (OC) loss of brightness 9% loss brightness 1 800 0.002 nil 0.01 nil

2,850 0.004 "0.02"

  3,850 0 "0.02 This 4,850 0.007" 0.009 t

850 0.006 "0.002

6,850 0.004 "0.003

* Table II above shows that each

  frits exhibited excellent resistance to

  attack by both acids and alkalis. Each of the samples offered large areas. shine after

  the tests. This advantageous feature is very important

  when the desired products are glazes

  and decorative enamels. For example, gluteals have been

  who show a very low weight loss after immersion in acids and bases, but to which this immersion gives rise to a strong loss of radiance. Of

  such products would clearly be irrelevant

  that one wishes to obtain very elegant pieces of

  operatives. To study the possibilities of using

  in accordance with the invention in combination with various

  of support, the composites have been converted into frits

  Examples of the examples given above were milled so that they pass through the sieve with openings.

  of 44 microns, they were applied to the surface of the

  port and then cooked at maturity.

  Thus, the frit powders of Examples 1 and 2 were mixed with about 5% by weight of commercially available pigments, the mixture was repeatedly blended on plates.

  plates made of PYROCERAMR, which is a vitroceram for

  table goods marketed by the plaintiff and

  having a coefficient of thermal expansion (0-300 C) of about 97 x 10-7 / oC, and then subjected to

  baking for 15 minutes respectively at 875 and 82500.

  The glazes that were fired had a good sheen, and they gave quite convincing results both in the acid test described above and in a 96-hour exposure to the detergent test. Since the coefficient of thermal expansion of Example 1 is 69.2 × 10 -7 / α and that of Example 2 is 66.1 × 10 7 / oC, these

  Glazes form on the flat plate a superficial layer

  in compression which gives it mechanical strength

improved.

  In a similar manner, a sufficient quantity of frit powder of Example 3 was suspended in distilled water to obtain a proportion of

  about 65% by weight, this spray was sprayed

  binds on rods of 6.35 mm diameter to a glass-ceramic having a coefficient of thermal expansion (0-300C) of about 100 x 10o7 / oC, and then subjected to a

  cooking at 90000 for 10 minutes. Here again, the ice

  baked clay had a good shine and gave results

  quite convincing, both acid and acid proof

  the detergent test. The lowest coefficient of di-

  The thermal equilibrium specific to the composition of Example 3 had the effect of increasing the mechanical strength of the rods, expressed by their modulus of rupture, by approximately

82 to 154 MPa.

  Finally, frit powder slurries of the compositions of Examples 5 and 6 were prepared in a manner similar to that described above for Example 3, and applied by spraying.

  on tiles approximately 3.2 cm in diameter

  porcelain having a coefficient of thermal expansion (0-300 0C) of about 95 x 10-7 / oC. By cooking for about 10 minutes at temperatures between

  800 and 90000, a smooth glaze was obtained which

  was a great brilliance and excellent resistance to

  Cide and detergent. Here again, the coefficient of di-

  lower thermal clearance of the glazes compared to that of the support gave mechanical strength

  improved to sample tiles.

  The examples below illustrate the aspects

  advantage of colored glazes according to the invention.

  A frit having a coeffi-

  The thermal expansion (20 ° -300 ° C.) of about 66.4 × 10 -7 / OC which had the following approximate composition, expressed in% by weight on the basis of the oxides as calculated from the batch:

BaO 28.57% -

MgO 2.50 Li 2 O 3.35 SiO 2 46.19

3203 7.33

ZrO2 9.30 TiO2 2.76

  and it was ground so that it goes through the sieve to open

  44 microns. The powder obtained was mixed with 1% by weight of Fe 2 O 3 and 2% by weight of TiO 2, in the form of a powder, it was screen printed on flat plates

  in PYROCERAM (glass ceramics for commercial table

  The present invention provides a thermal expansion coefficient (0-300 °) of about 97 x 10 7 / ooc) and the plates thus coated are fired at 7500C for 15 minutes. The glaze had a

  large luster and a deep brown red color.

  When combining a classic frit with

  lead with Fe203 and TiO2 in similar proportions

  Compared with those of the illustrative example above and that it was baked on flat plates made of PYROCERAM D under the same conditions, only a very pale yellow tint was obtained.

  A frit having a coeffi-

  thermal expansion (20-300C) of approx.

  66.8 x 10-7 / OC which possessed the approximate composition

  Hereinafter, expressed in% by weight on the basis of the oxides as calculated from batch BaO 33 86% SiO2 40.80 Tji2O 1.31 ZnO 4.37

B203 6.47

ZrO2 8.22 TiO2 2.44 CdO 2.53

  and it was ground so that it goes through the sieve to open

  44 microns. The particles were then mixed

  obtained with 5% by weight of a sulphosylated pigment

  powdered cadmium cadmium, it has been

  This was done on flat PYROCERAMN plates, and the plates so coated were baked at 85 ° C. for 15 minutes in a nitrogen atmosphere. The resulting glaze had a large luster and a bright red color. By cooking in other non-oxidizing or inert atmospheres, for example argon and elium, or in slightly reducing atmospheres, for example forming gas (hydrogen + nitrogen) and CO mixtures

  and CO 2, bright red stains are also obtained.

  On the other hand, when the icing is carried out in the air or in another oxidizing atmosphere, the red coloring is not thermally stable and it is obtained only

dull gray hues.

  A lead-containing frit, an alkaline borosilicate frit and a zinc borosilicate frit each were mixed with 5% by weight of the cadmium sulfoselenide pigment, and fired on

  flat plates in PYROCERAM [in an atmosphere of

  zote in a similar way to that described above. Only dull gray colors have been obtained, which means that

  the specificity of the frits according to

  the possibility of providing glazes

of sustained color.

Claims (7)

  1. A frit substantially free of cadmium and lead and having good glass stability, a coefficient of thermal expansion (203,000 ° C.) of between about 65 and 75 × 10 7 / cm, a viscosity suitable for baking in the vicinity of 700 at 950 C, and excellent resistance to attack by acids and bases, characterized in that it is essentially   formed in% by weight on the basis of the oxides as calcu-   from the batch, SiO2 35 to 47% B203 '5.5 to 9   BaO 24 to 42 TiO2 1.5 to 4 ZrO2 6 to 10 Ili20 1 to 5 Ng0 O to 5 CaO O to 4 SrO O to 8 ZnO O to 10 Bi203 0 to 8 with MgO + CaO + SrO + ZnO + Bi203 0 to 10 2. Frit according to claim 1, having   a coefficient of thermal expansion (20-300 C)   between about 65 and 70 x 10-7 / o and a viscosity suitable for baking at about 700 to 850 ° C, characterized in that it is essentially formed in% by weight on the basis of the oxides as calculated from of the batch, SiO2 35 to 47% B203 6 to 8   BaO 31 to 39 TiO 2 2 to 3 MgO 0 to 4 CaO 0 to 4 SrO 0 to 8 ZnO 0 to 6 ZrO 2 8 to 9.5 0i 2 O 1 to 2.5 Bi 2 O 3 to 7 with MgO + CaO + SrO + ZnO + Bi 2 O 3 to 8   3. Glaze with a hue   from yellow to brown which is stable at temperatures   between 700 and 950 ° C., characterized in that it consists essentially of 0.5 to 10% by weight of Fe 2 O 3 and 0 to 4% by weight of TiO 2, the remainder being   constituted by a frit according to claim 1.   4. Glaze with a bright red color that is stable at temperatures between 700   and 95000 C in a non-oxidizing or inert environment,   characterized in that it consists essentially of 2 to 10% by weight of cadmium sulfoselenide, the remainder   being constituted by a frit according to claim 1.   5. Method of coating a glass piece,   glass ceramic or ceramics with a glaze   a sustained color ranging from yellow to brown,   characterized in that it comprises the operations as:   (a) mixing a powdered frit according to the   cation 1 with 0.5 to 10% Fe 2 O 3 and 0 to 4% TiO 2; (b) applying said mixture to the surface of the glass, glass-ceramic or ceramic part; and (c) subjecting said piece to baking in the vicinity of 700 to 9500C for a time sufficient to give rise to a flow of the frit and   form a smooth and homogeneous coating.   6. Process for coating a glass, glass-ceramic or ceramic part with a glaze presenting   a bright red color, characterized in that it com- takes the following steps:   (a) mixing a powdered frit according to the claim   1 with 2 to 10% by weight of cadmium sulfoselenide; (b) applying the mixture to the surface of the glass, glass-ceramic or ceramic part; and (c) subjecting said piece to baking at around 700 to 9500C in a non-oxidizing or inert environment for a time sufficient to give   a flow of the frit and make it   sea a smooth and homogeneous coating.   7. The method of claim 6, wherein   characterized in that the inert atmosphere is a nitrogen atmosphere.