DE1421911C - Process and colored thread for the production of green colored glasses - Google Patents

Description

The invention relates to a method for producing green-colored glasses by adding a fritted glass set for low surface tension, made of aluminum oxide and magnesium oxide is free and colored green by chromium oxide, to a colorless raw glass containing aluminum oxide and mixing both glasses in a forehearth. The present invention further relates to a frit enriched with dye.

When mixing in fritted glass, it is desirable to have as high a level as possible in the fritted glass To have dye content, d. H. get by with as little fritted glass as possible, so with the addition of the cold fritted glass within the relatively short time available in the forehearth Mixing section excessive heat losses are avoided; in addition, the addition of the With the fritted glass, the chemical composition is changed as little as possible. Further it is desirable that the fritted glass mix easily and intimately with the molten raw glass.

A .Verfahren of the type specified is known (German Auslegeschrift 1 060 565). It offers the advantages that by omitting the aluminum oxide in the fritted glass, its surface tension and viscosity are reduced, so that mixing with the raw glass is easier, and that the solubility of the chromium oxide used for green coloring is also considerably increased. According to the teaching of the known method, it is also advisable to use as little magnesium oxide as possible in order to increase the solubility for chromium oxide even further, and instead to use an equal amount of calcium oxide. Correspondingly, in the explanation of the known method, examples of the composition of the fritted glass are given which contain no magnesium oxide, but calcium oxide in amounts between 9.0 and 12.5 percent by weight. With regard to the particular combination of frit and base glass, it is desirable according to the known method that the glass compositions are as similar as possible so that the coefficients of thermal expansion do not differ greatly. This can be achieved by using the same general composition for the frit as for the base glass, with the exception of the replacement of Al ₂ O ₃ by SiO ₂ , the total content of CaO + MgO being kept between 6 and 15 percent by weight. It can be seen that, in accordance with the recommendation given to use CaO in exchange for MgO, the glass frit will usually have a higher CaO content than the base glass.

With regard to barium oxide, the explanation of the known method can only be inferred that O to 5 percent by weight of BaO can be used both in the base glass and in the frit.

The present invention is based on the object of the known method described at the outset to improve even further, in particular with regard to the highest possible chromium content and possible easy mixing of the frit in the base glass.

According to the invention, this object is achieved in that a glass is used as the fritted glass which contains 55 to 75 percent by weight SiO ₂ , 15 to 30 percent by weight Na ₂ O and / or K ₂ O and a total concentration of CaO and / or BaO below 5 Contains percent by weight, the surface tension being below about 312 dynes / cm, preferably below 300 dynes / cm, and an addition of more than 2 percent by weight, preferably up to 7 percent by weight, of 5-chromium oxide is made possible, and the fritted glass to the raw glass in a weight ratio of 1 : 40 to 1: 400 is added.

The fritted glass used in the method according to the invention offers a considerably more favorable combination of low surface tension and high solubility for chromium oxide compared to the fritted glass according to the known method, in which relatively high contents of CaO and CaO + BaO are considered. Surface tension values of only about 220 dynes / cm with very high contents of chromium oxide can be obtained according to the invention with frits which are essentially free of Al ₂ O ₃ , MgO, CaO and BaO.
The method according to the invention differs fundamentally from the known method discussed, since the content of CaO and / or BaO in the fritted glass in relation to the raw glass should not be the same or greater than in the known method, but on the contrary can be greatly reduced. An indication of the _{advantages that can be achieved with such a measure r} cannot be seen in the context of the known method.

But the other relevant prior art could not suggest the invention either. So is in one Standard work on glass technology (I. I. K i t a i g ο r ο ds k i, "Technologie des Glases", 1957, pp. 65 and 66) in discussing the relationship between composition and surface tension of glasses indicated that the oxides of the divalent metals have the magnitude of the surface tension from sodium silicate glass almost does not change, and this is also done by a specially designed one for CaO and BaO graphical representation occupied in that of a sodium silicate glass with a surface tension of about 280 dynes / cm is assumed. However, these are not glasses with a high chromium oxide content, and otherwise the findings are contrary to the teachings of the present invention.

In another standard work (Schmidt-Voss, "Die Rohstoffe zur GlaseTrzeugung", 2nd edition, Leipzig 1958, pp. 173, 198 and 310) are information about the influence of the viscosity of glasses made of CaO and BaO, but no reference to the teaching of the present invention can be inferred from them, and moreover, viscosity and surface tension are not parallel. So it says there, for example, that the complete ability to solve of chromium oxide in glass for lime glasses is only 1.2%. In the present invention as well in the known method mentioned above, however, the fritted glass is not lime glass, and its solubility for chromium oxide is in any case above the stated value of 1.2%. Apart from that nothing of this is said about the influence of BaO in the cited literature reference, and in others Passages of the same standard work contain information that suggest an increase in the CaO content. It is stated, for example, that lime increases the viscosity in the relaxation area and in higher areas Temperatures is predominantly reduced, so that - lime-rich glasses are then very thin - a in relation to mixing in a fritted glass

seemingly advantageous peculiarity. Elsewhere in the same standard work it is said with regard to BaO that barite-lime glasses purify better and melt more quickly than pure lime glasses, although one should not exceed 5 to 7% BaO. The teaching cannot be inferred from such information that a restriction of the total content of CaO + BaO in a _{fritted glass colored with Cr 2} O ₃ leads to particular advantages.

For the invention property of the present new teaching, it is also irrelevant whether in other things Related and for other uses similar or identical glass compositions as were already known in the fritted glass used according to the invention.

For example, in another standard work (Thie η e, "Glas", Jena 1939, Vol. II, p. 932, Glas Nr. 2) a "bad dragonfly glass" is given, which does not _{contain Cr 2} O ₃ , but otherwise falls within the range of the compositions of the glasses used in accordance with the invention as tempered glass. The cited literature reference does not give any indication of such usability.

In the method according to the invention, a molten soda-lime glass can be used as the raw glass significantly higher surface tension than the fritted glass can be used. At a temperature in which the fritted glass melts, the fritted glass is mixed with the molten raw glass.

In a particular embodiment of the present invention, a molten raw glass is used which consists of 60 to 75 percent by weight SiO ₂ , 0.3 to 10 percent by weight Al ₂ O ₃ , 6 to 15 percent by weight CaO + MgO, 12 to 18 percent by weight Na ₂ O, O up to 5 percent by weight of K ₂ O and 0 to 5 percent by weight of BaO.

The drawing shows a device that is used to carry out the method can.

The device consists of a melting tank 10, in which the raw glass is melted and is purified. A number of forehearths 11 can be provided in connection with this melting tank being. The molten raw glass 9 flows out of the melting tank 10 via a dam 13 in a channel running along the forehearth. The fritted material is through a funnel 23 and an outlet 25 is introduced into the forehearth 11 in a metered manner. The fritted glass is on its way through a melting portion 15 of the forehearth 11 melted and to some extent with mixed with the raw glass. This mixture flows under a scraper 19. Agitators 20 and 21 cause further mixing of the glass components. The homogeneous glass mass thus obtained is discharged from an outlet 22. The delivery is regulated by a feeder 24, the separates measured batches or lots of the glass and feeds them to the molds of the molding machine.

The fritted glass, which is added to the raw glass mass flowing out of the melting tank 10, is through Melting a corresponding glass offset and then cooling and crushing it into one powder-like, granular mass, for example by directly introducing the molten glass offset in water. In the finely crushed form, the fritted glass in the forehearth 11 is dated Raw glass taken up and melted down at a temperature which is considerably lower than that which is required for melting the frit glass per se would. The fritted glass added to the raw glass is generally only a small fraction the total amount of glass discharged from the melting tank 10. The quantity ratio between raw glass and fritted glass depends on the composition of the fritted glass, the intensity of the in the final product color desired and other variable factors; it lies in general between 40: 1 and 400: 1.

The device described is to be understood only as an example of various possible embodiments that are used to carry out the method can be used, and explains very schematically the alignment of the method to existing forehearth structures.

Preparation of the raw glass

The raw glass preferably used is essentially a known glass of the type generally used is used to make colorless or "milk bottle-colored" containers. It contains the following components:

Table I.

SiO ₂ 60 to 75

Al ₂ O ₃ 0.3 to 10

CaO + MgO 6 to 15

Na ₂ O 12 to 18

K ₂ O 0.0 to 5

BaO .... 0.0 to 5

Se 0.00025 to 0.00035

Raw glass compositions that are within these ranges can be used with fritted glasses of the compositions described herein. It is often desirable that the fritted glass have essentially the same composition as the raw glass, apart from the various oxides which make up the particular nature of the fritted glass, namely Cr ₂ O ₃ , Al ₂ O ₃ , BaO and MgO.

A composition that is as similar as possible can, however, be dispensed with if in the forehearth good mixing can be achieved.

The following Examples A and B are soda lime glass offsets that were used in the manufacture of the fused (clear) raw glass mass can be used.

Table!!

55 Example A.
% Example B.
% SiO ₂
60 Al ₂ O ₃
Fe ₂ O ₃ : ..-....
TiO ₂
CaO
₆₅ MgO ........
Alkalis
selenium 72.01
1.74
0.039
0.029
11.38
1.15
13.65
0.00025
up to 0.00030 71.45
1.32
0.037
0.013
8.32
5.58
13.28
0.00025
up to 0.00035

5 6

The Conditions and Methods of Preparation Table III

of such a molten raw glass are known; _{Q ische N d} j _d .

it is referred to Table XX, B-Il, p. 245 des / ■ _{tt nv} -

"Handbook of Glass Manufacture" before, T ο ο 1 ey, ^{for glasses} _set together

Ogden Publishing Co., New York, N.Y., 1953, verse 5 Georgia green

grasslands. Dominant wavelength. '. 515 to 545 μΐη

In general, the raw glass occurs with a temperature of 2.0 to 5%

temperature from about 1260 to about 143O ⁰ C from the brightness 70 to 80%

Melting furnace or the refining system from and in rum green

the forehearth 11. This temperature is the dominant wavelength .. 542 to 555 μΐη

Adding the fritted glass well suited, which has a purity of 6 to 8%

is in finely divided form, z. B. in a particle brightness of 67 to 70%

size from 0.5 to 2.3 mm. In some cases it turned emerald green

found that the dispersion of the fritted glass dominant wavelength .. 550 to 562 μm

by increasing the forehearth temperature in the addition- 15 purity 55 to 80%

area was favored: For example, a brightness of 26 to 42%

Schfhelzwann temperature of 1250 ° C on the Zu-Grasgrün

point to be ^{increased to 1290 0} C, and the tem- No norms

temperature can then be along the forehearth distance

drop to an outlet temperature of 1190 ° C. 20 Table IV

A forehearth color component made up of glasses that is suitable for such a process

is described in the German patent 1 060 109. (Weight percent)

The specified raw glass compositions ent- - ^r . '·

each hold selenium, as it is in colorless or pearl-normal georgia green

muted flint glass compositions, 25 iron, total 0.04 to 0.06%. -

as well as divalent iron as an impurity, although (as Fe ₂ O ₃ )

at the given analytical values the total Cr ₂ O ₃ -. 0.015 to 0.021%

Iron content is given as Fe ₂ O ₃ . The FeO-CrO ₃ none

Content generally recognized as an impurity CoO 0.0009 to 0.0011%

of the sand is introduced as a measure of 30 normal rum green 0.05 to 0.07%

Quality control to less than 0.2 weight percent '"(as Fe ₂ O ₃ )

limited. Cr ₂ O ₃ 0.031%

_{A corresponding CrO 3 is} not required to produce the frit

Glass offset in an oxidizing atmosphere so CoO 0.0013%

melted that the temperature of the melt 35 normal emerald green

is between 1480 and 1535 ° C. This melt iron, a total of 0.175-0.250%

is as a stream from an outlet of the melting tank (as Fe ₂ O ₃ )

drained and quickly cooled, for example by Cr ₂ O ₃ 0.16 to 0.24%

Introducing into water so that the fritted glass as CrO ₃ no

granular mass is obtained. 40 CoO none

Normal grass green

Iron, total 0.07-0.09%

Desired optical properties (as Fe ₂ O ₃ )

of the finished glass Cr ₂ O ₃ 0.07 to 0.09%

45 CrO ₃ none

In the manufacture of colored glasses, ins- NiO. *. 0.06%

special green glasses, must have certain color CoO 0.004%

standards are met. These standards are usually defined in terms of purity, dominant wavelength and brightness. 50 i _T. . . ',,,,. , _, ...

In this case, the "purity" of the glass makes it possible to absorb ultraviolet steels

that percentage of the leaching rate that has passed through

tes that dominate within the area of georgia green

the wavelength of a certain glass coloration Fe ₂ O ₃ "... 0.054%

located. The rest of the light of this wavelength from 55 chromium, a total of 0.021% (as Cr ₂ O ₃ )

sorbs the glass. When using, for example, CrO ₃ traces · ·

a well-known Georgian green glass forms light CoO. ·. 0.0009%

a wavelength of 515 to 545 πΐμ the range FeO none

the dominant wavelength of this color, and rum green

if a purity of 5% is given, then 60 Fe ₂ O ₃ 0.070%

this means that 5% of the light that is inside this chromium, 'a total of 0.037% (as Cr ₂ O ₃ )

Area through which glass passes. The CrO ₃ traces up to 0.001%

remaining 95% of this wavelength are from CoO 0.0013%

absorbed by the glass. FeO does not use the term "brightness"

here as a percentage of the total through the glass 65 emerald green

transmitted light indicated. If georgia- Fe ₂ O ₃ 0.093 to 0.125%

green glass has a brightness of 75%, so it leaves chromium, a total of 0.140 to 0.17%

75% of the light of all wavelengths passes through. (as Cr ₂ O ₃ )

continuation

CrO ₃ traces up to 0.02%

FeO none

CoO 0.002 to 0.006%

Green grass

Fe ₂ O ₃ 0.05 to 0.08%

Chromium, total 0.06 to 1%

(as Cr ₂ O ₃ )

CrO ₃ : traces up to 0.02%

FeO none

CoO 0.004 to 0.13%

NiO 0.04 to 0.06%

Some examples of compositions of fritted glass which can be used according to the invention are given in Table V below. These glasses all have surface tensions below 300 dyn / am. With some of the following compositions, a particularly strong reduction in surface tension has been achieved _{through B 2} O ₃ and relatively high contents of Na ₂ O and K _{2 O.}

For comparison, a composition according to the known one was shown in Table V below as Example 22 Procedure of the German Auslegeschrift 060 565 included (see example B in tables I and II). It can be seen without further ado that this known composition with 9 percent by weight CaO does not have the very advantageous combination of low surface tension and high chromium solubility offers like the inventive compositions of Examples 1 to

Table V

component

Theoretical compositions (percent by weight) Example

3 4 5

3 __ 4 66.18 67.18 17.65 17.92 4.37 3.89 4.42 4.48 0.32 0.26 7.06 6.27 7.00 6.14 N. D. N. D. 258 259

SiO ₂
Na ₂ O

B ₂ O ₃ ..

BaO

CaO

Fe ₂ O ₃

NOK

CoO

Cr ₂ O ₃ *)

Cr ₂ O ₃ *)

After analysis

CrO ₃ .

Surface tension
(dyn / cm)

71.52

19.09

0.89

4.77 0.89

2.86 2.78

N.D. 292

*) Total chromium oxides as Cr ₂ O ₃

68.04

18.14

1.96

4.54 1.96

5.36 5.36

2.05 284 Table V (continued)

69.12

18.43

1.48

4.61

1.50

0.25 4.61 4.66

1.61 269

68.79

18.34

1.62

4.59

1.62

5.04 5.08

N.D. 268

59.42

20.00 '

4.15

5.00

4.50 0.93 6.00 6.42

N.D. 250

component

Theoretical compositions (percent by weight) Example

10 11 12

10 11th 69.38 61.89 4.63- 18.50 26.80 1.43. 4.14 1.43 1.70 4.63 -5.47 4.74 5.09 1.73 N.D. 269 224

14th

SiO ₂ .
Na ₂ O
K ₂ O.
B ₂ O ₃ .

BaO ....

CaO

Fe ₂ O ₃

NOK

CoO

Cr ₂ O ₃ *)

Cr ₂ O ₃ *)

After analysis

CrO ₃

After analysis

Surface tension
(dyn / cm)

*) Total chromium oxides as Cr ₂ O ₃ .

60.79

20.00

3.71

5.00

4.13 0.87 5.50 5.81

N.D.

252

63.31

20.00

1.54

5.00

1.56 3.38 0.71 4.50 4.83

N.D.

262 68.36

18.23

1.69

4.56

1.69

5.47 5.20

1.91

268

64.77 27.17

4.31 0.89

2.86 2.59

N.D.

243

62.79

26.91

4.25

1.43

4.62 4.05

N.D.

238 629/14

Table V (continued)

component

15 Theoretical compositions (percent by weight) Example

17 18 19 20

17th 18th 60.97 60.56 26.68 25.90 2.84 4.12 3.02 1.94 1.93 0.23 6.29 5.52 5.44 N.D. N.D. 238 247

SiO ₂ .
Na ₂ O
K ₂ O.
B ₂ O ₃ .
BaO ..
CaO.
Fe, O,

69.38

18.50

1.43

4.63
1.43

65.76
17.68
3.20
2.09
1.87
1.98
0.93
2.26
6.23 66.40

17.70

4.39

4.43

67.36

17.96

3.90

4.49

CoO

Cr ₂ O ₃ *) 4.63

Cr ₂ O ₃ *) 4.43

After analysis

CrO ₃ NDND

After analysis

Surface tension

- (dyn / cm) "! 282 287

*) Total chromium oxides as Cr ₂ O ₃ .

The chromium oxide is indicated in each of the examples as Cr ₂ O ₃ and is a measure of the total chromium oxide content; preferably at least part of the specified “Cr ₂ O ₃ ” content of the fritted glass is in the form of hexavalent chromium (as CrO ₃ ). The actual content of hexavalent chromium in a given frit depends on two factors, namely the addition of the chromium to the fritted glass batch as potassium dichromate and, secondly, the state of oxidation of the fritted glass batch during melting. In certain examples, such as Examples 4, 7 and 8, all of the chromium was added in the form of bichromate. In certain other examples, such as Examples 1, 2 and 3, the chromium was added in equal parts by weight as chromite (a mineral containing FeO-Cr ₂ O ₃ ) and potassium dichromate. In the manufacture of UV-absorbing glasses, a residual content of hexavalent chromium is desirable, and an oxidizing _{agent such as KNO 3} is preferably added in order to maintain strongly oxidizing conditions in the fritted glass batch.

summary

The compositions discussed in this specification of green glass frits can be systematically represented as follows:

Table VI

7.08
6.92

3.05

6.29

6.24

2.73

73.5

15.5

2.0

9.0

2.0

258

259

303

Table VII

Component ,

35

SiO ₂

Na ₂ O

K ₂ O ..... '

B ₂ O ₃

CaO

BaO

Chromium oxide

CoO

NOK

Fe ₂ O ₃

Na ₂ O and / or K ₂ O
all in all

CaO and / or BaO
all in all

Weight percent

55 to 75 0 to 20 0 to 30 0 to 20 0 to 5 0 to 5 over 2 0 to 1 0 to 5 0 to 2.

15 to 30 obis 5

Although any amount of B ₂ O _{3 is} acceptable, the compositions of a particularly effective class according to the invention contain the following ingredients in the amounts indicated:

Table VIII

component

SiO ₂

Na ₂ O and / or K ₂ O

B ₂ O ₃

CaO and / or BaO

Chromium oxide

Fe ₂ O ₃

CoO

NOK

More precisely, lie

Weight percent 55

component

the

55 to 75
15 to 30

O to 20

O to 5

over 2

O to 2

O to 1

O to 5
Compositions 65

SiO ₂

Na ₂ O and / or K ₂ O

B ₂ O ₃

CaO and / or BaO

Chromium oxide

Fe ₂ O ₃

CoO

NOK

certain stock (Na ₂ O and / or K ₂ O) within the following ranges

parts: + B ₂ O ₃

Weight percent

58 to 70

19 to 26

1 to 5

Obis 5

over 3

O to 2

O to 1 '

O to 5

at least 23

Claims (6)

1 42 11. _ Patent claims: 1. A process for the production of green-colored glasses by adding a fritted glass which is set to low surface tension, is free of aluminum oxide and magnesium oxide and colored green by chromium oxide, to an aluminum oxide-containing colorless raw glass and mixing both glasses in a forehearth, characterized in that a glass is used as the fritted glass which contains 55 to 75 percent by weight SiO ₂ , 15 to 30 percent by weight Na ₂ O and / or K ₂ O and a total concentration of CaO and / or BaO below 5 percent by weight, the surface tension being below 312 dynes / cm, preferably below 300 dynes / cm, and an addition of more than 2 percent by weight, preferably up to 7 percent by weight, of chromium oxide is made possible, and the glass is added to the raw glass in a weight ratio of 1:40 to 1: 400 .. 2. The method according to claim 1, characterized in that a melted KaIk-Natf as the raw glass onOlas with a significantly higher surface tension than the fritted glass is used. 3. The method according to claim 1 or 2, characterized in that a molten raw glass is used, which consists of 60 to 75 percent by weight SiO ₂ , 0.3 to 10 percent by weight Al ₂ O ₃ , 6 to 15 percent by weight CaO + MgO, 12 to 18 percent by weight Na _2, 0.0 to 5 percent by weight K ₂ O and 0 to 5 Weight percent BaO consists. 4. Green-colored glass frit, characterized by a content of 55 to 75 percent by weight SiO ₂ , 15 to 30 percent by weight Na ₂ O and / or K ₂ O, O to 20 percent by weight B ₂ O ₃ , 0 to 5 percent by weight CaO μη ^ / οαεΓ BaO , over 2 percent by weight Cr ₂ O ₃ , from 0 to 2 percent by weight Fe ₂ O ₃ , from 0 to 1 percent by weight CoO and from 0 to 5 percent by weight NiO. 5. Glass frit according to claim 4, characterized by a maximum content of Cr ₂ O ₃ of 7 percent by weight. 6. Glass frit according to claim 4, characterized by a content of 58 to 70 percent by weight SiO ₂ , 19 to 26 percent by weight Na ₂ O and / or K ₂ O, 1 to 5 percent by weight B ₂ O ₃ , 0 to 5 percent by weight CaO and / or BaO, over 3 percent by weight Cr ₂ O ₃ , O to 2 percent by weight Fe ₂ O ₃ , O to 1 percent by weight CoO and O to 5 percent by weight NiO, the total content of (Na ₂ O and / or K ₂ O) + * B ₂ O _{3 is} at least 23 weight percent. 1 sheet of drawings