FR2559758A1 - Lead- and cadmium-free glass frit compositions for glazing, enamelling and decorating tableware - Google Patents

Abstract

Lead-free, cadmium-free and zinc-free glass frit composition in which the softening point of the fibres lies approximately between 535 DEG C and 609 DEG C, composed essentially of the following constituents present in the shown approximate ranges of percentages by weight relative to the total composition: Al2O3 (constituent): 0-30 (percentage by weight); B2O3: 16-32; SiO2: 11-40; Li2O: 4-12; ZrO2: 0-18; SnO2: 0-20; CeO2: 0-2; La2O3: 0-15; CaO: 0-16; SrO: 0-13; BaO: 0-7; Na2O: 0-3.5; F: 0-2.6, with: SnO2 + CaO: 2-23; ZrO2 + Al2O3: 0-26.5; CaO + SrO + BaO: 0-19.25. Application to the decoration of tableware made of glass, of glass-ceramic and of ceramic.

Description

Lead-free and lead-free glass frit compositions
cadmium for glazing, enameling and
tableware decoration
The present invention relates to lead-free and cadmium-free glass frit compositions which have desirable properties and characteristics enabling them to be used for glazing, enamelling and decorating tableware and tableware, for example glassware such as goblets, porcelain, etc. The compositions according to the present invention can also find their use in selected applications such as micro-electronic encapsulation, as well as for the formation of a light diffusion layer on a glass surface. The decorative glazes and the glass compositions according to the present invention have the advantage of containing neither lead compounds nor cadmium compounds.

 Most of the kitchenware that is currently commercially available is marketed with more or less important external ornamentation and decoration. The manufacturers of this tableware have long realized that decorated glassware was more attractive to the consumer and sold better than undecorated tableware. As a result, significant efforts have been made over the years for research and development work on decorative compositions for all types of tableware and tableware, tableware, and kitchenware in general.

 Decorative compositions generally fall into two categories: glazes and enamels.

Glazes are usually considered transparent glasses, while enamels are glazes that contain a coloring matter such as a pigment.

In real use, glazes and enamels are used in a finely divided form called "frit", which is selectively applied to the surfaces of glassware, glass-ceramic dishes, porcelain and ceramic dishes. function of the decorative or ornamental design that we want to obtain. To achieve this result, a number of different decoration techniques are available in the industry. Generally, the frit is in the form of a paste which consists of the finely divided glaze or enamel composition plus a vehicle. After application to the part by screen printing or by another technique, the part is heated or cooked to melt the frit, volatilize the vehicle and make the decoration adhere firmly to the surface of the part.

 According to the current state of the art, various decorative compositions are available which are used for decorating glassware, porcelain and the like, to produce selected designs and ornamentation. Often, these available compositions contain lead and / or cadmium oxides. In the past, lead oxide was used in these compositions to lower the melting point of the frit so that the frit could melt on the surface of the part at a temperature as low as possible to avoid thermal deformation of the part. Cadmium oxide was used in the past as a colorant in some frits. Some American states have now instituted legislation prohibiting the use of cadmium and lead in the glazes used for the decoration of glassware and porcelain, on the grounds that these substances are allegedly toxic and that young children are particularly susceptible to the allegedly toxic effects of these constituents. The present invention therefore eliminates the risks arising from the presence of allegedly toxic substances in the glazing and decoration compositions. Furthermore, the present invention eliminates the risk of a possible "recall" of decorated tableware in either State which could in the future institute legislation prohibiting the use of lead and / or cadmium oxides in decorative compositions.

 The present invention further eliminates the need to analyze decorative glazes and glass compositions to determine whether their content of allegedly toxic substances is well below the minimum required.

This saves the cost of compliance testing.

 The decorative glazing compositions according to the present invention do not contain lead oxide or cadmium oxide, which allows glass manufacturers to resume sales in states which require or prescribe zero lead or cadmium content in the glassware sold. in these same States and which is used to consume drinks, or in porcelain intended to come into contact with food.

 The glasses according to the present invention can have significantly lower densities than glasses containing lead, for example a density of 2.6842 instead of 4.5837.

One kilogram of the new glasses has a larger volume than the decorative materials that were previously used commercially. The number of glass pieces decorated depends on the volume of glass available for printing. For example, one kilogram of lead glass will print approximately 1,100 pieces of glass with a specific design. In comparison, a quantity of one kilogram of a standard lead-free glass according to the present invention will make it possible to print approximately 1870 pieces with the same design. This has been achieved by the following calculation
Volume per kilogram of material
lead glass - specific mass (bl.S, p.34,5837gXcm3
lead-free glass - specific basket (MS p.) 2,6842g / cm3
Weight 1 kg 1000 g
Lead: volume 1 = = = = 218.16 ml
MS p. 4.5837 4.5837
1000
Lead-free: volume 2 = = 372.55 ml 2.6842
Report 1100 pieces x 1.7 = 1870 pieces
The present invention also makes it possible to lower the costs of raw materials due to the elimination of the need to use lead and cadmium compounds which are relatively costly. For the same reason, the present invention can allow the cost of colored pigments to be lowered.

This is illustrated by the following remarks
Glass decoration glazes have at least two components
A - Glass (= fondant) and
B - Colored pigment (= dye)
The pigments in part B are identical or similar in lead glasses and in lead-free glasses to obtain the colors chosen. The raw materials in part A of lead-free glasses, without tin oxide, are cheaper than for lead glasses.

For example, a typical glass according to the present invention can be 20% to 30% less expensive, for equal weight, than a glass containing lead.

 A number of advantages characterize the present invention, including the fact that the decorative compositions which are described here meet the requirements for good decoration of protective glasses, glazes and enamels, without using allegedly toxic substances. It is important, especially for the decoration of glassware and porcelain which are used at home or in restaurants, that the decorative compositions have a sufficient resistance to bases and hardness to be able to be exposed for many years to washing cycles. machine without seriously degrading, which would cause unpleasant deterioration of the decorated dishes.

The present invention provides many compositions which may be harder and therefore more resistant to scuffing than the compositions generally known in the art. Consequently, part of the compositions according to the present invention are those which are particularly suitable for decorating the Porcelain. It has been determined by the applicants that the pigmented glasses according to the present invention are less sensitive to the atmosphere of ovens than the compositions known in the art, in particular those which contain certain cadmium pigments such as cadmium sulfide and selenide. cadmium (CdS and
CdSe, respectively), which are sensitive to oxidation.

According to the specific formulas and constituents, the present invention provides compositions which, in general, have better properties such as less expansion, high hardness, high resistance to chemical agents, in particular to bases, and a vitreous domain which is sufficiently wider than that of other lead-free glasses such as compositions containing zinc oxide.

According to one of the features of the present invention, aluminoborosilicate compositions are proposed which can be used for the decoration of glassware and porcelain as well as for hybrid micro-electronic applications. In general, the compositions of the present invention which have this feature are based on the Al203 - B203 system
SiO2, in which are also present lithium oxide Li2O and at least one other component chosen from the group which comprises ZrO2, SnO2, CeO2, La2O3, CaO, SrO, BaO,
Na2O, ZrF4, NaF and 3NaF.AlF3.

According to another aspect of the invention, compositions are proposed which are devoid of aluminum added in the form of alumina (A2 and which are defined as containing significant amounts of lanthanum oxide
ta2O). These compositions are based on the B203 system
SiO2 - ZrO2 - La203 and also contain lithium oxide Li2O.

 Characterized by good resistance to chemical agents, the glasses according to the present invention also have a good gloss and a good surface polish. In addition, they usually have a hard surface without containing allegedly toxic substances. The glasses according to the present invention include those which can be baked in the temperature range from 580 "C to 6300CI at the normal rate and during the normal residence time in the oven, using conventional baking tunnels for the decoration of glassware and porcelain.

 In today's industry, it is important that the compositions used for the decoration of glassware and porcelain have the characteristics which are described below.

 The decorative compositions must be able to be baked at a temperature between 580 "C and 6300 C. It is generally desirable that the residence time in the oven at the maximum temperature is between 7 and 11 minutes, the temperature rise taking place at at 140C to 150C per minute The time required to reach the maximum temperature should be approximately 40 minutes + 10 minutes.

 The compositions used for decoration must be able to be cooked in a smooth and shiny layer without "flowing" from the printed area, and at the same time be capable of forming fine lines without any casting, that is to say that the drawings obtained on the glassware must be clean and precise and must not be blurred, blurred or indistinct.

 It is desirable that the decorated glassware and porcelain be able to withstand machine wash cycles, preferably in the presence of a relatively strong detergent, for a period of 5 to 20 years.

In addition, the decorated material on the glassware must not be erased or liable to attack by the acids normally found in fruit juices.

 For applications such as glass art, the electronics industry and light-scattering coatings, glasses need not have resistance to acids and / or bases.

 Finally, the decorated material must not show cracks after firing, nor crack during its actual use.

 These properties, features and characteristics can be determined by quantitative tests as well as by observation. Therefore, a specific decorative composition can be evaluated to determine if it will be satisfactory for commercial purposes. For example, decorated glassware can be subjected to machine wash cycle tests. By testing the decorated piece with 5% sodium pyrophosphate at 600C for eight hours and taking measurements at two hour intervals, accelerated laboratory tests can be performed to predict resistance to machine washing.

 For resistance tests to fruit juices, two acids are generally used to determine the susceptibility of decorated glassware to attack. The first test is carried out with 2% citric acid for 30 minutes at room temperature, and the second with 4% acetic acid for 24 hours at room temperature.

 The surface polish and defining characteristics of the printed design after firing can be predicted by a test known as the "flow index" test. This flow index is equal to the ratio of the measured width to the measured height of a baked sample pellet of the decorative composition. The tablet of decorative composition is placed on a glass surface and the height of the tablet is measured above this surface. The width measured is equal to the width of the pellet surface in contact with the glass surface. Good samples will have a flow index between 1 and 1.2. Indices less than 1 make it possible to suppose a less good adhesion to the glass. Indices higher than 1.3 make it possible to suppose a poor definition, with casting of the printed lines, that is to say an excessive fluidity of the dough.

 Bes possible tendencies of the decorated material to break or crack are linked to differences in thermal contraction of the glass or porcelain serving as a substrate (goblet or tableware) and decorative glass between normal temperature and room temperature . These differences can be determined by the residual stress caused in the goblet glass by the decorative glass that contracts.

For example, a test can be carried out on a 2.5 mm-edge sample cube which is cooked in contact with the base glass using the heating speed, the residence time in the oven, the temperature of the latter, and the desired cooling rate. The stress induced by slowing down the polarized light is measured in accordance with procedures known in the art.

 The conversion is measured using a test tube about 2.5 mm thick. The thickness of the baked decorative layer is approximately 0.03 to 0.058 mm. According to the experimental determinations, the values of the measured stresses which are given in Table 1 below are approximately 4 to 6 times greater than the values of the expected stresses for decorative layers printed by screen printing and baked. The possible presence of cracks in the test pieces was observed and these observations were recorded in Table 1. It is obvious that for stresses up to approximately 12 kg / cm2 (1600 psi), the pellets did not show any cracks in thin layers ranging in thickness from 0.03 to 0.058 mm.

 The aforementioned test techniques and procedures are well known in the art of glass technology.

 It should be noted that the compositions according to the present invention can be used in conventional screen printing techniques which are well known and which do not constitute an object of the invention. Any of these conventional screen printing methods can be used for the purposes of the invention.

In its broadest aspects, the present invention relates to compositions based on a borosilicate glass system represented by the constituents listed below in the ranges of percentages by weight indicated, expressed as oxide.
Component Percentage by weight
Al2O3 0 - 30
B203 16 - 32
SiO2 11 - 40
LiO2 4 - 12, the remainder being formed by other compatible components for the manufacture of glass which will be described in more detail below.

In addition to the ingredients listed above, which form the basic glass, the system generally contains one or more of the following oxides: ZrO2, SnO2,
CeO2, La203, CaO, SrO, BaO, Na2O, ZrF4, NaF and 3NaF.AlF3.

 It will be noted that these compositions do not contain zinc. Although zinc has been used in decorative compositions and has been found to be useful in achieving low viscosity in glass at specific temperatures, zinc is considered to be contraindicated in drinking water and its content should therefore be limited to no more than about 5 mg / l.

 More particularly, the glass compositions according to the present invention contain the following constituents expressed as a percentage by weight of oxide relative to the total composition.

Component Percentage by weight
l2 3 0 - 30
B203 16 - 32
SiO2 il - 40
Li2O 4 - 12
ZrO2 0 - 18
SnO2 0 - 20
CeO2 0 - 2
La203 0 - 15
CaO 0 - 16
SrO o - 13
Component Percentage by weight
BaO 0 - 7
Na2O 0
F 0- 2.6 with
Z SnO2 + CaO 2 - 23
Z ZrO2 + La2O3 2 - 33
Z ZrO2 + Al2O3 O - 26.5
Z CaO + SrO + BaO O - 19.25
Table 1 shows representative compositions of the present invention which have been found to materially improve the characteristics of glassware and decorated porcelain.

 These compositions include those which have remarkable resistance to bases and which develop acceptable stresses. The defects of certain compositions developing relatively high stresses which are liable to cause certain cracks can be remedied by adding a filler constituted by an appropriate quantity of a ceramic with a low coefficient of expansion, such as beta-eucryptite. Certain colored pigments also have the effect of lowering the stress, as is known in the art. Clays can be used as well as mullite, quartz, and the like.

According to another embodiment of the present invention, it has been found that the following compositions are particularly suitable for the purposes described here
Component Percentage by weight
AI203 19 - 20
B203 28 - 30
SiO2 11 - 16
LiO2 4 - 8
ZrO2 4 - 7.5
SnO2 6 - 19
La2O3 0 - 0.5
CaO O - 4
Component Percentage by weight
SrO 0 - 13
BaO 0- 7
Na2O 0 - 0.25
F 0 - 1.5
The compositions defined by the parameters indicated above have good fiber softening point characteristics and develop a compressive stress (C) or a low tensile stress (T), when tests have been carried out. constraint.

With the preferred compositions of the invention as defined above, it can be noted that when tin oxide is present in an amount greater than 10% by weight, the amount of strontium oxide should be less than 10 8; conversely, when there is more than 10% of strontium oxide, the quantity of tin oxide must be less than 10%. On the other hand, taking into account the parameters indicated above, the sum of CaO + BaO + SrO must be between 6 and 21% with a maximum of 7% of BaO and 5% of CaO, with this additional condition that there must always be either BaO or CaO. The preferred compositions, the composition of which falls within the above ranges, are those indicated in Table 1,
Examples 5, 13, 14, 22 and 23.

 Certain compositions of the invention are colorless and can therefore be used as a screen layer for or as a top layer on conventional decorative compositions which may optionally contain lead and cadmium, in order to prevent or slow the release of lead and cadmium by the decorated surfaces.

The following examples, with the exception of Example 15, illustrate the invention without being intended to limit it in any way. Example 15 is given for comparison. The compositions were recalculated to the normal and standard percentages of oxides. In compositions 1, 5 to 9, 16, cryolite (3NaF.AlF3) was used; in Examples 5, 7, 8, 12 to 14 and 18, ZrF4 was added, in compositions 3, 4 and 15 zircon was added; and in compositions 4, 11, 15 and 17 NaF was used. Consequently, in the corresponding examples, the zircon was converted into percentages of ZrO2 and SiO2, the NaF into percentages of F and Na2O, ZrF4 into percentages of F and ZrO2, and the cryolite into percentages of F, Na2O and
A1203. In this table, the symbols "A" and "C" denote respectively acetic acid and citric acid. TABLE 1 - GLASS COMPOSITIONS (1-12)
Glass N 1 2 3 4 5 6 7 8 9 10 11 12% Loss at bases 0.62 0.49 1.44 1.08 1.28 1.77 1.99 1.94 1.77 1.61 1, 77 2.3% Loss at acid A 7.34 12.78 5.93 16.33 2.87 2.83 4.78 4.06 8.54 7.40 8.70 11.4% Loss at C acid 4.72 9.18 8.36 11.42 1.74 1.53 1.94 3.82 4.25 5.20 6.60 4.8
Composition
Al2O3 19.0 20.0 20.0 20.0 19.7 20.0 20.0 20.0 19.25 20.0 18.0 20.0
B2O3 29.0 28.0 29.0 29.0 28.25 28.2 28.0 28.0 29.0 28.0 28.0 28.0
Li2O 6.0 8.0 6.0 6.0 7.5 7.5 7.5 7.5 6.0 8.0 8.0 8.0 8.0
SiO2 18.0 16.0 16.0 16.0 12.75 12.75 12.55 12.75 18.0 16.0 18.0 16.0
ZrO2 5.0 5.0 5.0 5.0 6.10 5.0 6.0 6.11 5.0 5.0 5.0 6.5
SnO2 0 10.0 2.0 0 14.22 12.25 12.22 4.25 0 10.0 5.0 10.0
CeO2 0 0 2.0 2.0 0 0 0 0 2.0 0 0 0
La2O3 2.0 0 0 0 0.5 0.5 0.5 0.5 0 0 0 0
CaO 16.0 0 16.0 16.0 4.0 7.5 6.0 14.0 16.0 13.0 13.0 3.0
SrO 0 13.0 0 0 0 0 0 0 0 0 0 5.0
BaO 0 0 1.0 0 5.25 5.25 5.25 5.25 0 0 0 3.0
Na2O 3.0 0 3.0 3.0 0.8 0.8 0.8 0.5 3.0 0 3.0 0
F 2.0 0 0 3.0 0.93 0.25 1.18 1.14 1.75 0 2 0.5
FSP C DTA # 552 567 583 557 538 559 537 556 549 577 556 560
Flow index. 1,144 1,040 1,031 1,181 1,200 1,155 1,209 1,181 1,125 1,010 1,126 1,101
Tension in kg / cm2 119 T 99.8 T 73.5 T 119 T 31.5C 91.7 T 113.4 T 119 T 122.5 T 106.1 T 144.2 T 74.2 T
Voltage in psi 1700T 1425 T 1050 T 1700 T 450 T 1310 T 1620 T 1700 T 1750 T 1515 T 2060 T 1060 T
Cracks Yes No No Yes No No No Yes Yes No Yes No # SnO2 + CaO 16 10 18 16 18.22 19.75 18.22 18.25 16 23 18 13 # ZrO2 + La2O3 7 5 5 5 6.6 5, 5 6.5 6.61 5 5 5 6.5 TABLE 1 - GLASS COMPOSITIONS (continued) (1-12) 1 2 3 4 5 6 7 8 9 10 11 12 # ZrO2 + Al2O3 24 25 25 25 25.8 25 26 26.11 24.25 25 23 26.5 # CaO + SrO + BaO 16 13 17 16 9.25 12.75 11.25 19.25 16 13 13 11 #FSP C DTA: Fiber softening point expressed in degrees Celsius, determined by differential thermal analysis TABLE 1 - GLASS COMPOSITIONS (13-24)
Glass N 13 14 15 16 17 18 19 20 21 22 23 24% Loss on bases 1.99 2.21 3.18 3.07 2.56 4.2 4.46 5.9 2.67 2.05 1, 94 0.7% Loss at acid A 6.80 6.40 15.87 12.3 13.80 13.6 14.97 16.6 16.48 7.54 6.33 8.43% Loss at acid C 2.30 1.40 10.4 7.7 6.20 3.4 4.58 6.23 6.10 3.42 4.21 3.41
Composition
Al2O3 20.0 20.0 20.0 18.70 18.0 20.0 20.0 20.0 20.0 20.0 20.0 0
B2O3 28.0 28.0 29.0 29.0 29.0 28.0 28.0 28.0 28.0 30.0 29.0 30.0
Li2O 8.0 8.0 6.0 6.0 6.0 8.0 8.0 8.0 8.0 4.0 6.0 7.0
SiO2 14.0 11.0 15.80 18.0 18.0 14.0 15.0 10.0 16.0 15.0 16.0 28.0
ZrO2 6.5 6.5 5.0 5.0 5.0 6.5 3.0 6.5 5.0 4.0 5.0 18.0
SnO2 15.0 19.0 0 0 0 15.0 10.0 20.0 7.0 6.0 7.0 0
CeO2 0 0 2.0 2.0 2.0 0 0 0 0 0 0 0
La2O3 0 0 0 0 0 0 0 0 0 0 0 15.0
CaO 3.0 0 14.0 16.0 16.0 0 0 0 2.0 4.0 3.0 2.0
SrO 4.0 0 0 0 0 8.0 16.0 0 11.0 13.0 11.0 0
BaO 0 7.0 0 0 0 0 0 7.0 3.0 4.0 3.0 0
Na2O 0 0 5.60 3.3 3.5 0 0 0 0 0 0 0
F 1.5 0.5 2.60 2.0 2.5 0.5 0 0.5 0 0 0 0
FSP C DTA 567 535 549 558 565 565 557 537 573 565 576 606
Flow index. 1.081 1.272 1.200 1.082 1.082 1.141 1.103 1.381 1.095 1.0210 0.905 1.020
Tension in kg / cm2 75.6 C 56.4 T 136.2 T 165.6 T 136 T 84 T 123.6 T 88.6 T 113.1 T 87.2 C 100.5 C 44.1 C
Voltage in psi 1080 C 805 T 1945 T 2365 T 1800 T 1200 T 1765 T 1265 T 1615 T 1245 C 1435 C 630 C
Cracks No No Yes Yes Yes No Yes No Yes No No No # SnO2 + CaO 18 19 14 16 16 15 10 20 9 10 10 2 # ZrO2 + La2O3 6.5 6.5 5 5 5 6.5 3 6.5 5 4 5 23 # ZrO2 + Al2O3 26.5 26.5 25 23.7 23 26.5 23 26.5 25 24 25 18 # CaO + SrO + BaO 7 7 14 16 16 8 16 7 16 21 17 2.0 TABLE 1 - GLASS COMPOSITIONS (25-37)
Glass N 25 26 27 28 29 30 31 32 33 34 35 36 37
Base loss 0.64 0.85 0.79 0.88 0.42 0.86 1.04 1.45 2.43 3.79 2.77 3.21 2.21
Loss of acid A 7.72 12.22 8.14 8.55 3.33 6.22 5.42 4.20 6.89 4.80 6.41 6.61 2.58
Loss of acid C 2.83 4.81 6.20 3.80 3.66 5.74 6.73 3.47 9.09 5.87 5.79 6.12 2.50
Composition
Al2O3 0 0 0 0 0 0 0 0 2.0 0 30.0 17.0 15.0
B2O3 30.0 30.0 30.0 32.0 30.0 24.0 24.0 24.0 24.0 24.0 16.0 25.0 32.0
Li2O 7.0 7.0 7.0 7.0 8.0 9.0 9.0 8.0 5.0 8.0 12.0 8.0 8.0
SiO2 30.0 30.0 30.0 30.0 35.0 40.0 40.0 40.0 40.0 40.0 40.0 28.0 29.0
ZrO2 16.0 14.0 12.0 12.0 10.0 5.0 5.0 3.0 4.0 0 0 4.0 4.0
SnO2 0 0 0 0 2.0 1.0 1.0 1.0 0 0 0 0 0
CeO2 0 0 0 0 0 0 0 0 0 0 0 0 0 #
La2O3 15.0 15.0 15.0 13.0 15.0 15.0 13.0 13.0 13.0 15.0 2.0 6.0 0
CaO 2.0 4.0 6.0 6.0 0 3.0 5.0 8.0 9.0 10.0 0 9.0 9.0
SrO 0 0 0 0 0 0 0 0 0 0 0 9.0 0
BaO 0 0 0 0 0 0 0 0 0 0 0 0 0
Na2O 0 0 0 0 0 3.0 3.0 3.0 3.0 3.0 0 3.0 3.0
F 0 0 0 0 0 0 0 0 0 0 0 0 0
FSP C DTA 595 609 597 596 590 573 574 578 606 574 581 567 573
Flow index. 1.063 1.010 1.030 1.052 1.030 1.074 1.099 1.021 1.010 1.147 1.117 1.042 1.074
Tension in kg / cm2 29 C 82.6 T 97.3 T 94.5 T 72.8 T 42 T 84 T 59.5 T 74.2 T 125.7 T 82.6 C 26.6 T 21.7 VS
Voltage in psi 415 C 1180 T 1390 T 1350 T 1040 T 600 T 1200 T 850 T 1060 T 1795 T 1180 C 380 T 310 C
Cracks No No No No No No No No No Yes No No No # SnO2 + CaO 2 4 6 6 2 4 6 7 9 10 0 9 9 # ZrO2 + La2O3 31 29 27 25 25 20 18 16 17 15 2 4 4 # ZrO2 + Al2O3 16 14 12 12 10 5 5 3 6 0 30 21 19 # CaO + SrO + BaO 2 4 6 6 0 3 5 8 9 10 0 18 9
From the preceding tables, it will be seen that, for the compositions containing aluminum oxide, the constituents included the following in the ranges of percentages by weight indicated, expressed as oxides
Component Percentage by weight
Al2O3 15 - 30
B203 16 - 32
Li2O 4 - 12
SiO2 8 - 40
ZrO2 3 - 6.5
SnO2 0 - 20
CeO2 0 - 2
La2O3 0 - 6
CaO 0 - 16
SrO 0 - 13
BaO 0 - 7
Na2O 0 - 3.5
F 0 - 3 in which, according to Examples 1 to 23
Z SnO2 + CaO is 9 to 23%
Z ZrO2 + La203 is 3 to 7%
Z ZrO2 + A12O3 is 23 to 26.5%
Z CaO + SrO + BaO is 7 to 21%
The compositions which did not show cracks in the tests were within the above ranges. These compositions contain the following ingredients:
Component Percentage by weight
Al2O3 15 - 30
B203 16 - 32
Li2O 4 - 12
SiO2 10 - 40
ZrO2 4 - 6.5
SnO2 0 - 20
CeO2 0 - 2
La2O3 0 - 6
CaO 0 - 16
SrO 0 - 13
BaO 0 - 7
Na2O 0 - 3
F 0 - 1.5 in which, in general
Z SnO2 + CaO is 10 to 23%
Z ZrO2 + La203 is 4 to 6.5%
Z ZrO2 + Al2O3 is 24 to 26.5%
Z CaO + SrO + BaO is 7 to 21%
The large group of alumino-borosilicate compositions fall within those identified by the numbers 35, 36 and 37 in the table above. In this group of glasses, ESnO2 + CaO is 0-9%, SZrO2 + La203 is 2-4%, SZrO2 + Al203 is 19-30% and SCa + SrO + BaO is 0-18%.

 The preceding tables also show compositions which are free of added aluminum oxide, or which contain only very small amounts thereof, that is to say of the order of 2% or less. These compositions can be defined by the ingredients listed below in the ranges of percentages by weight indicated, expressed as oxides.

Components Percentage by weight
Al2 3 0 - 2
B203 24 - 32
Li2O 5 - 9
SiO @ 16 - 40
ZrO2 0 - 18
CaO 0 - 10
SrO 0 - 3
Na2O 0 - 3 where
Z SnO2 + CaO is 2 - 10%
Z ZrO2 + La203 is 15 - 33%
Z ZrO2 + Al2O3 is 0 - 18%
Z CaO + SrO + BaO is 0 - 10%
Among these compositions, some have not shown cracks and can be defined by the constituents listed below in the ranges of percentages by weight indicated, expressed as oxides.

Component Percentage by weight
B203 24 - 30
Li2O 5 - 9
SiO2 28 - 40
ZrO2 3 - 18
SnO2 0-2
La203 13 - 15
CaO ~ 9
Na2O 0 - 3 where
z SnO2 + CaO is 2 - 9 t
# ZrO2 + La203 is 17 - 33%
# CaO + SrO + BaO is 0 - 9%
To determine the hardness of the glasses according to the invention, the "Knoop hardness indices" (KHN) for the glasses indicated in Table 1 above were measured. These indices ranged from 520 to 594. The same Knoop hardness indices for lead glasses used in commerce were from 250 to 300. KHNs are hardness values expressed by the load in kilograms divided by the area projected from the penetration of a diamond in millimeters, corrected for the separating power of the microscope used. EG

Shand has demonstrated, for ordinary window glass,
KHN from 445 to 490, and of the order of 550 for alumino-silicate glasses (EB Shand, "Glass Engineering Handbook", page 42, McGraw Hill, 1958).

 it therefore appears that the glasses according to the invention are exceptionally harder than decorative glasses containing lead (520 against 250), that they are a little harder than ordinary window glasses (520 against 490) and that they have a hardness comparable to that of aluminosilicate glasses.

 As already mentioned, transparent coatings can be prepared from the compositions of the present invention and then be used as top layers or top layers for other tableware. To illustrate this embodiment of the invention, glasses containing lead and cadmium were overprinted with the glass NO 1 in Table 1 and baked together.

In the base resistance tests, the coated samples were found to be superior. They also showed better shine and a more intense color. Table
A below states the results obtained with the three most critical colors: red, orange and yellow - by comparing coated samples and uncoated samples. The samples had no cracks, even if the NO 1 glass developed a relatively high stress.

TABLE A
Glass samples containing lead and
cadmium, coated and uncoated
Red Orange Yellow
Uncoated Uncoated Uncoated
coated coated coated% of base disturbances 2.19 1.03 1.14 0.70 1.58 1.15
Brilliant Lost retained Weak Strong Weak Medium
Intense Matte Color Good Light- Good Good
lie meiji.

Cracks No No No No No No
The compositions according to the present invention can be used to produce a wide range of pigment colors. The desirable colors are obtained by adding colored pigments to a base glass (as a single constituent) such as those indicated in Table 1, or to a mixture of two or more glasses, or to a mixture of glass added of a charge. The colored pigments are added in a percentage of 0.5% to 15% by weight. The lower limit of 0.5% white titanium oxide is used to obtain white translucent color effects commonly used in so-called "engraved glassware. The upper limit of 15% is used in complex colors requiring several pigments, including opacifiers. The most useful range is 4% to 12% of pigments used for all basic and relatively simple color shades like black, white, yellow, orange, brown and beige.

 Table 2 lists several important colors, yellow, orange, brown and brown with their characteristics.

These results illustrated the stress reductions, from 119 T kg / cm2 to 22.4 C kg / cm2, obtained by adding ss-eucryptite, a load with a low coefficient of expansion. Pigment chemistry appears in row 2 of Table 2. Generally 1 to 15% pigment is used. Line 3 gives the percentage of the colored pigment used. The percentage of S-eucryptite appears in line 4. The weight loss in the accelerated basic test is indicated in line 6. Line 7 shows the induced stress as explained above.

Sample N 6 had a tensile stress of 66kg / cm2 (945 psi) and showed no cracks. The thin printed and baked layer had a tensile stress of 11.2 kg / cm2 (160 psicette this way of reducing the stresses induced has the disadvantage of a lower surface polish and a lower gloss due to the presence of relatively large particles (20 to 44 microns) of ss-eucryptite used to obtain better results It is possible to use approximately 5 to 15 tonnes of fillers with a low coefficient of expansion to prepare a colored enamel conforming to this aspect of the invention.

TABLE 2
COLORS
1 2 3 4 5 6 7
Color Brown Yellow Chamois Brown C t oas Orange
ounce
Pigment Fe 203 CrNbTi FeZr FeZnTi FeZn CrWTi% pigment 2 5 5 5 5 10% charge 13 13 13 13 13 13 Beta
Eucryptite% loss 1.85 1.69 1.76 1.11 1.62 0.89 at bases
Flow index. @@@@@ @@@@@@@@@@ @@@@@ @@@@@@@@@@
Load kg / m2 14 C 22.1 C 22.4 C 56 T 42.7 T 66.2 T Pellet
psi 100 C 315 C 320 C 800 T 610 T 945 T approximately
2.5
Cracks No No No No No No
Basic glass i 1 1 1 1 i
It has been found that it is possible to improve the present compositions as illustrated in the
Table 1, having high tensile stresses and developing cracks, by incorporating loads with a low coefficient of thermal expansion which have the effect of reducing the apparent stress of this composite mixture.

By adding 1% to 15% of B-eucryptite, for example, we effectively reduced the strong pulls. The amount of these charges depends on the original stress of the base glass used. For example, N 21 glass requires only 1% ss-eucryptite for the removal of visible cracks. Composition N 16 requires a maximum of 15% of 8-eucryptite to meet the criteria for the absence of cracks.

 Although many of the glasses in Table 1 can be used as the sole components of base glass, there are some that have high tension stresses. This stress can be reduced to a suitable level by adding another glass from Table 1 having a compression stress or a very low tensile stress.

This second constituent glass is chosen from glasses like N s 5, 13, 22 and 23 in the table. It has been found experimentally that small quantities added, of the order of 2%, of the previous glasses made it possible to reduce the tensile stress below the cracking limit.

These glasses can be added in amounts up to 95% to form usable combinations. Therefore, the range of glasses chosen is 1% to 99%. The appropriate choice is made according to the specific requirements of the flow indices for the specific colored pigments.

Some pigments significantly decrease the flow index, while others have very little or no effect on this index.

 For example, glasses N "4 and NO 13 have good flow indices as single constituents (1,200 1,081; 1,020). On the other hand, glass N" 23 has a lower flow index and requires addition of glass NO 1.

 To illustrate this aspect of the invention, 18 cl curved orange juice cups (Boléro) were printed with hot-melt inks (hot wax) with a "wheat" design, with several colors ranging from yellow to yellow. 'orange, by a technique called "mixing". Two fundamental colors are mixed together in the middle of the screen printing screen to obtain a variety of color shades. In Table 3, the six samples used glass NO 13 and glass NO 1, the ratio of N 13 to N 1 being 1 to 3.

The cup N 6 had a ratio of 1, and the cup N 5 a ratio of 3, as seen below. Small amounts of filler with a low coefficient of expansion were added to this mixture (for example 2% ss-eucryptite + 1% Cer-Vit C-101). Table N 3 gives the results obtained. The best results appear for cups N s 1 to 3. The glass contained in these colored mixtures was finely ground to less than 12 microns. Cups Nos. 4 and 6 were printed with the exact same mixture as Cups Nos. 1 to 3, but with particle sizes of less than 44 microns. The percentages of loss under the effect of the bases were calculated from the total weight loss, by subtracting the weight losses due to the unprinted cup.

TABLE 3
Cup 1 2 3 4 5 6
q, loss
at the bases 0.5 1.0 0.8 1.32 1.38 3.11
% of loss
with acids 2.93 2.57 1.64 5.74 7.45 4.38
Index
1.060 1.020 1.043 1.040 1.020 1.051
Stress kg / cm2 17.5 C 22.1 C 18.2 C 50.1 C 57.8 57.1 T
psi 250 C 315 C 260 C 715 C 825 C 815 C
Glass report 13
glass i 2 2.2 2 2.6 i
The stress values in Table 1 expressed in psi (pound / inch squared) can be converted into standardized coeffi cients of thermal expansion ix lo 7 per degree
Celsius (0-3000C) by a conversion factor determined experimentally and which is equal to 154 - per unit of expansion.

The values of the aforementioned stresses, divided by the factor 154, give the units of differences in thermal expansion between the basic glass (the glass of the cups) with a coefficient (α) of 83 x 10 7 per OC, and the glasses according to the invention. The compression stresses reveal lower thermal expansions than those of cup glass, and the tensile stresses (tension) reveal greater thermal expansions than those of base glass. Consequently, when a tension is observed, the units calculated are added to the coefficient 83 x 10 7 by 0C. On the other hand, when we observe compression constraints, we subtract the calculated units from the coefficient 83 x 10 7 per OC.

For example, in sample N 1, the stress observed is equal to 1700 psi (119 kg / cm2). We then proceed to the calculation as follows
1700 (traction) divided by 154 = 11.04 units 83 + 11.04 = 94.04 x 10 7 per C
This compares favorably to a measured value of 94.1 x 10-7 per C.

 In another example, for sample No. 13, a compressive stress of 1080 psi (75.6 kg / cm2) was measured.

1080C divided by 154 = 7.01
83 -, 01 = 75.99 to compare with the measured value of
76.1.

For sample NO 5, a compressive stress of 450 psi (37.2 kg / cm2) was measured
460 C divided by 154 = 2.99
83 - 2.99 = 80.01 to be compared to a measured value of 80.01
To make the glasses shown in Table 1, various ingredients were melted, in quantities generally ranging between 4.5 and 23 kilograms. Glass NO 1 was made in an amount of 1,360 kilograms using the following compositions which are typical raw materials which can be used to form the glasses according to the invention.

 The following composition is based on 100 kilograms of raw materials, or approximately 85 kilograms of the resulting glass.

Starting ingredients Quantities
Glass sand 7.7
Alumina (A-10) 12.7
Anhydrous boric acid 23.6
Lithium carbonate 12.0
Lanthanum carbonate 2.5
Nepheline-Syenite 7.8
Cryolite 4.0
Ground zircon 6.1
High-grade limestone
calcite 23.6
100 kg
The raw materials identified above were melted at a temperature of 12000C for two hours.

The molten bath was stirred eight times and then allowed to cool.

The glass was put in the form of flakes using a water-cooled rolling mill, in accordance with conventional procedures. Due to the high rate of volatilization, it is desirable to minimize the loss of boron oxide. The flakes formed must be clear and transparent without any optical inclusion which could reveal the presence of undissolved alumina.

Agitation is necessary to minimize the separation of a top layer containing boric acid and silica, and a bottom layer containing alumina and zircon.

 Two other compositions of raw materials are indicated below to illustrate the type of materials used for the purposes of the invention.

Starting raw materials Grams
Ottawa 290 (sand) 27.8566
Anhydrous boric acid 36.8717
Calcined kyanite 59.6637
Ground zircon 11.9792
Borax anhydrous 19.9661
Lithium carbonate 39.3631
Strontium carbonate 25.4686
Lanthanum oxide 11.9393
Total weight 233.1082 grams. Total glass weight 200,000 grams. Loss on fusion 33.1082 grams.

Starting raw materials Grams
Ottawa 290 (sand) 32.4947
Anhydrous boric acid 51.0280
Calcined kyanite 52.5354
Ground zircon 11.9665
Borax anhydrous 19.9441
Lithium carbonate 39.3203
High calcite limestone 32.6886
Total weight 239.9777 grams. Total glass weight 200,000 grams. Loss on fusion 39,777 grams.

 The softening temperature of the fibers of these compositions is between 5350C and 6090C.

Claims (14)

 1. Composition of lead-free, cadmium-free and zinc-free glass frit, the fiber softening point of which is between approximately 5350C and 6090C, consisting essentially of the following constituents present in the approximate ranges indicated in percentages by weight relative to the total composition  Constituent Percentage by weight  Al2O3 0 - 30  B203 16 - 32  SiO2 11 - 40  Li2O 4 - 12  ZrO2 0 - 18  SnO2 o - 2n  CeO2 0 - 2  La2O3 0 - 15  CaO 0 - 16  SrO 0 - 13  BaO 0- 7  Na2O 0 - 3.5  F 0 - 2.6 with  # SnO2 + CaO = 2-23  # ZrO2 + La203 = 2-33  # ZrO2 + Al203 = 0-26.5  # CaO + SrO + BaO = 0-19.25  2. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition  Constituent Percentage by weight  Al2O3 19 - 20  B203 28 - 30  SiO2 11 - 16 LiO2 4 - 8  ZrO2 4 - 7.5  SnO2 6 - 19  La2O3 0 - 0.5  CaO 0 - 4  SrO 0 - 13  BaO 0 - 7  Na2O 0 - 0.25  F 0 - 1.5  3. Composition of glass frit according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition  Constituent Percentage by weight  Al2O3 15 - 30  B203 16 - 32  Li2O 4 - 12  SiO2 11 - 40  ZrO2 3 - 6.5  SnO2 0 - 20  CeO2 0 - 2  La2O3 0 - 6  CaO 0 - 16  SrO 0 - 13  BaO 0 - 7  Na2O 0 - 3.5  F 0 - 3 with  Z SnO2 + CaO between 9 and 23%  # ZrO2 + La2O3 between 3 and 7%  # ZrO2 + Al2O3 between 23 and 26.5%  Z CaO + SrO + BaO between 7 and 19.25%  4. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition  Constituent Percentage by weight  Al2O3 15 - 30  B203 16 - 32  Li2O 4 - 12  SiO2 11 - 40  ZrO2 4 - 6.5  SnO2 0 - 20  CeO2 0 - 2  La2O3 0 - 6  CaO 0 - 16  SrO 0 - 13  BaO 0 - 7  Na2O 0 - 3  F 0 - 1.5 with, in general  Z SnO2 + CaO between 10 and 23%  Z ZrO2 + La2O3 between 4 and 6.5%  Z ZrO2 + Al2O3 between 24 and 26.5%  Z CaO + SrO + BaO between 7 and 19.25%  5. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition  Constituent Percentage by weight  Al2O3 0 - 2  B2O3 24 - 32  Li2O 5 - 9  SiO2 16 - 40  ZrO2 0 - 18  SnO2 0 - 10  La203 13 - 15  CaO 0 - 10  SrO 0 - 3  Na2O 0 - 3 with  Z SnO2 + CaO = 2 - 10%  Z ZrO2 + La203 = 15 - 33%  # ZrO2 + Al2O3 = 0 - 18%  Z CaO + SrO + BaO = 0 - 10%  6. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition  Constituent Percentage by weight  B2O3 24 - 30  Li2O 5 - 9  SiO2 28 - 40  ZrO2 3 - 18  SnO2 0 - 2  La2O3 13 - 15  CaO 0 - 9  Na2O 0 - 3 with  # SnO2 + CaO = 2 - 9%  # ZrO2 + La2O3 = 17 - 33%  # CaO + SrO + BaO = 0 - 9%  7. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition  Constituent Percentage by weight  Al2 3 19.7  B2O3 28., 25  Li2O 7.50  SiO2 12.75  ZrO2 6.10  SnO2 14.22  La2O3 0.5  CaO 4  BaO 5.25  Na2O 0.8  F 0.93  8. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition  Constituent Percentage by weight  Al2O3 20  B203 28  Li2 O 8  SiO2 14  ZrO2 6.5  SnO2 15  CaO 3  SrO 4  F 1.5  9. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition:  Constituent Percentage by weight  Al2O3 20  B203 28  Li2 O 8  SiO2 11  ZrO2 6.5  SnO2 19  BaO 7  F 0.5  10. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentages by weight relative to the total composition:  Constituent Percentage by weight  A12O3 20  B2O3 30  Li 20 4  SiO2 15  ZrO2 4  SnO2 6  CaO 4  SrO 13  BaO 4  11. A glass frit composition according to claim 1, consisting essentially of the following constituents present in the indicated ranges of percentage s by weight relative to the total composition  Constituent Percentage by weight  Al2O3 20  B203 29  Li2 O 6  SiO2 16  ZrO2 5  SnO2 7  CaO 3  SrO 11  BaO 3  12. Colored enamel making it possible to decorate glass, glass-ceramic and ceramic dishes, comprising a frit as defined in any one of claims 1 to 11 and from 4% to 15% of a filler or pigment with a low coefficient of expansion, relative to the weight of the glass frit.  13. Colored enamel according to claim 12, in which the filler consists of ss-eucryptite with a low coefficient of thermal expansion.  14. Method for reducing the stresses in decorative compositions intended to be applied to glass, glass-ceramic and ceramic tableware, characterized in that it consists in incorporating into a glass frit as it is defined in claim 1 from 5 to 15% of a load with a low coefficient of thermal expansion.