DE1909187B2 - Process for the production of opal glass objects - Google Patents

Description

CaO

with a ratio of 1.5

MgO

and has approximately the following properties:

Temperature at viscosity
10 ² poise 165O ⁰ C

Melt temperature 1127 ° C

Viscosity at the melting temperature 10 ⁴ · ² poise

Thermal expansion coefficient <45-10 - '/ ° C

(O to 30O ⁰ C)

9. The method according to claim 1, characterized in that a glass is used which has the following Components contains:

Ingredient weight percent

SiO ₂ 55 to 75.5

Al ₂ O ₃ 2 to 6

B ₂ O ₃ O to 12

CaO + MgO 10 to 26

Alkali oxides O to 3

10. The method according to claim 9, characterized in that a glass is used at which the condition

Weight percent CaO _{Λ Λ,. Λ} ,
_ _ 1.4 to 1.5

Weight percent MgO

is satisfied.

11. The method according to any one of claims 8 to 10, characterized in that a glass is used in which the alkali oxides consist of Na ₂ O.

12. The method according to any one of claims 3 to 11, characterized in that the heat treatment is combined with the relaxation heat treatment.

13. The method according to any one of claims 1, 2 or 12, characterized in that temperatures between 565 and 98O ⁰ C for 15 minutes to 64 hours are used in the heat treatment.

14. The method according to claim 13, characterized in that temperatures between 650 and 85O ° C can be applied for 30 minutes to 8 hours.

15. The method according to claim 12, characterized in that temperatures between 565 and 850 ⁰ C are used for 15 minutes to 8 hours in the heat treatment.

16. The method according to claim 15, characterized in that temperatures between 760 and 815 ° C can be applied for one hour.

17. Process for the manufacture of glass objects according to one of the claims with compositions 8 to 11, characterized in that a glass object formed from a glass of the specified composition and in the course of the Forming process is opalesced.

18. The method according to claim 17, characterized in that almost complete opalescence is brought about by cooling the objects to a temperature corresponding to a viscosity of 10 ⁷ · ^Μ poise.

The invention relates to the manufacture of opal glass objects and to those useful therefor

ao glasses.

Opal glasses of various types are known. Most of them use special opalescent agents such as titanium and tin compounds, fluorides, sulfates, chlorides, phosphates and various other salts. Of these, fluoride opal glasses have often been used for lighting purposes, since a wider range of opalescence (degree of opacity) can be set with them.
The manufacture of opal glasses with special opalescent agents brings with it special circumstances in glass manufacture. The most common opalescent agents, especially fluorides, have a highly corrosive effect on the linings of glass melting furnaces, so that the furnaces have to be overhauled at relatively short intervals. A complicating factor here is the fact that under normal working conditions when the furnace is heated up, the opalescent agent may melt out prematurely or preferentially, and this can lead to an accumulation of the opalescent agent at the bottom of the melting tank, so that the corrosion there is considerably increased. The resulting unevenness in the distribution of the opalescent agent leads to correspondingly uneven results, and in general the uniform mixing in of the opalescent agent itself causes difficulties, so that a uniform product cannot easily be obtained. Another disadvantage of known opal glass is that the molten glass itself is often already opalescent: this increases fuel costs, since the thermal radiation from such melts is more strongly reflected and less absorbed than with clear melts.

Opal glasses are also known in which the opacity is not caused by a special opalescent agent, but rather by devitrification. In order to be able to achieve devitrification in a relatively simple manner, such glasses must have compositions that are otherwise avoided in glass production because they are associated with poorer processing properties. For example, known opal glasses of this type are characterized by extreme SiO ₂ - (CaO + MgO) ratios, ie they contain a relatively large amount of SiO ₂ and possibly also B ₂ O ₃ , but in comparison therewith little alkaline earth metal; Such strongly acidic glasses have a particularly strong tendency to devitrify. However, they are considerably more difficult to process than conventional glasses.

The field of application of opal glass has expanded significantly in recent times, and not only For lighting fixtures, light globes, filters, scientific purposes and the like, but also for example in the packaging industry for the production of containers for medicines and personal care products, deodorants, Foods and the like, particularly for the latter Applications it is highly desirable to use opal glass objects with usual high-speed To be able to manufacture glass molding machines in rational mass production, and accordingly the The glass used should be easy to process, chemically stable, heat-resistant and non-corrosive and overall the cost of producing the opal glass objects should be as low as possible. From the For the reasons outlined above, the known opal glasses cannot meet these requirements without only imperfectly fulfill.

According to the invention, the object set is achieved by a method for the production of opal glass objects, which is characterized in that made of an alkaline earth aluminum silicate glass, which has the following Contains components,

component

SiO ₂

Al ₂ O ₃ 1.5 to

Weight percent until 76 15th 5 to 12th Ι, ί until 13th 0 until 20th 5 until 15th 0 to < 11th 1 until 5 0 to < 2 0

B ₂ O ₃

CaO

MgO

Na ₂ O

K ₂ O

Li ₂ O

with the conditions

(CaO + MgO 10 to 30

(Na ₂ O + K ₂ O) <11

Weight percent B ₂ O ₃ .
Weight percent Na ₂ O

(SiO, + Al ₂ O ₃ + B ₂ O ₃
+ CaO + MgO + Na ₂ O)> 95

the glass objects are shaped and an in-situ phase separation is brought about by a heat treatment which makes glass objects opalescent.

According to the method according to the invention, a non-corrosive glass is used that is not special Contains opalescent agents and due to its well-balanced composition is easy to process; the opalescence constituent takes place through a phase separation and not By devitrification, the glasses used according to the invention can, on the contrary, even have a high resistance exhibit against devitrification.

As only common components for the glass attachment that are available in large quantities and at low cost are required, and since the opalescent heat treatment is carried out on the finished articles can be, both the raw material costs and the operating and manufacturing costs are low. Another The advantage is that the degree of opalescence achieved is determined by the manner of the heat treatment can be controlled reproducibly within wide limits.

The glass used in the present invention usually contains six main components, their Meaning should be briefly discussed below.

The predominant glass-forming oxide is silicon dioxide (SiO ₂ ), the importance of which is known for glass.

The glass also contains aluminum oxide (Al ₂ O ₃ ), which serves two purposes:

a) alumina increases resistance to devitrification during opalescent heat treatment;

b) the opalescence speed can be controlled by a suitable choice of the Al ₂ O ₃ content, since with increasing Al ₂ O ₃ content the opal

_t eszierungsgeschwindigkeit decreases.

Both of these effects are dependent on the glass viscosity, and this is largely determined by the Al ₂ O ₃ content.
The alkaline earth oxides (CaO and MgO) are usually both present and have the purpose of increasing the chemical stability of the finely divided opalescent phase. These oxides also affect the glass viscosity.

Boron oxide (B ₂ O ₃ ) primarily promotes opalescence,

that is, the tendency towards opalization increases with increasing BjjO ₃ content. Sodium oxide (Na ₂ O) serves on the one hand as a flux in the usual way and on the other hand counteracts the tendency to opalesce, so that the ratio of NaO to B ₂ O _{3 plays} an important role in determining the time and temperature of the opalescence heat treatment.

Other alkali oxides, such as potassium oxide (K ₂ O) and lithium oxide (Li ₂ O), can also be present in the amounts indicated.

The heat treatment required for opalescence naturally depends on the specific composition, which is selected within the limits given above. It has been shown that, according to the range limits given above, thermal opalescence can also be achieved with glasses that again _{contain Na 2} O and B ₂ O ₃ , but the controllability of the opalescence process is not as good as with glasses that contain these two Contain ingredients. Therefore, glass compositions containing both Na ₂ O and B ₂ O ₃ are preferred. Furthermore, lithium oxide is preferably not used, since this oxide promotes the tendency towards devitrification at elevated temperatures. Accordingly, in a further embodiment of the invention, the specified method is preferably carried out with a glass, since; has the following components:

Weight percent

SiO ₂ 60 to 70

Al ₂ O ₃ 4 to 8

B ₂ O ₃ 1 to 9

CaO 6 to 16

MgO 4 to 12

Na ₂ O 3 to 7

with the conditions

(CaO + MgO) 14 to 21

(Na ₂ O + K ₂ O) 8

Weight percent B ₂ O ₃
Weight percent Na ₂ O

0.2 to 3

(SiO. + Al ₂ O, + B ₂ O ₃ + CaO

+ MgO + Na ₂ O> 98

According to common practice, coloring oxides, for example the oxides of cobalt, copper, Chromium, nickel and manganese, are added to make opalescent glass of various colors and shades to manufacture. The colors and shades can be determined by the oxygen level of the melt, the time and temperature of the heat treatment can be controlled.

Generally, such coloring oxides make up no more than about 2 percent by weight of the glass composition the end.

When carrying out the method according to the invention, an alkaline earth aluminum silicate glass is selected from the composition ranges given above. The small proportions of B ₂ O ₂ and Na ₂ O are advantageous in order to promote and control the desired phase separation. It was found that the presence of both of these components is desirable in order to be able to control the transition from the initially transparent glass to the opalescent state as much as possible.

The glass with the selected composition is melted and made into objects by conventional methods shaped. Ordinary starting materials can be used for the glass offset, provided that that the desired composition can be formed from them. The choice of raw materials is essentially based on economic considerations. It goes without saying that the melted Glass should be as homogeneous as possible before the glass objects are formed from it.

After the glass object has been foimed, it is subjected to a certain heat treatment for a period of time that is sufficient to bring about the desired phase separation.

In a further embodiment of the invention glasses are specified in which the phase separating and thus opalescent heat treatment of the type described with a conventional relaxation heat treatment can be combined. This is seen to be advantageous in the manufacture of the opalescent glass articles. Such a thermally opalescent alkaline earth aluminum silicate glass according to the designation can contain the following components:

Ingredient weight percent

SiO ₂ 66 to 69

Al ₂ O ₃ at 6

B ₂ O ₃ 4 to 8

CaO + MgO 13 to 18

Na ₂ O at 5

under the condition
Weight percent CaO
Weight percent MgO

In embodiments of the present invention glasses are also specified in the context of the above-mentioned compositions in which the phase separation and thus the opalescence occurs under the influence of the thermal conditions that prevail during the molding process, so that the glass is opalescent after molding. This is clearly a very special advantage, since a special heat treatment can be omitted entirely. In such glasses, substantially complete opalescence can be obtained by cooling the articles to a temperature at which the viscosity is about 10 ⁷ x ⁶⁶ poise. Such a thermally opalescent alkaline earth aluminum silicate glass according to the invention can contain the following components:

Ingredient weight percent

SiO ₂ 71

ίο Al ₂ O ₃ 5

CaO + MgO 10

B ₂ O ₃ 12

Alkali oxides 3

CaO

is with a ratio of 1.5

MgO

Other glasses according to the invention performed in a similar manner during the molding process

ao conditions that become opalescent are given below.

Unless a glass composition according to the invention is used, in the case of the one indicated Way the heat treatment used for opalescence with the heat treatment used for relaxation can be combined or even by the conditions prevailing during the molding process can be represented, according to the invention, the glass object after the molding of a subjected to a certain heat treatment in order to achieve a certain degree of opalescence. The invention describes, on the one hand, a large range of possible compositions for thermally opaque materials Glass and on the other hand gives information about the relationship of these compositions to that for the Opalescence required heat treatment.

The relationship between time and temperature in heat treatment depends primarily on the composition of the glass used. It is understood that higher temperatures require a shorter period of time to produce the desired phase separation and opalescence, but that the glass at such high Temperatures is more easily deformed and degassed. For the purposes of the invention temperatures of about 600 or 650 to about 980 ° for 15 minutes to about 64 or more hours is satisfactory. in the in general, for economic reasons, temperatures between 650 and 850 ° are used for 30 minutes up to about 8 hours preferred. With a combined phase separation and relaxation heat treatment according to the invention, temperatures between 565 and 850 ° C. were used for 15 minutes to 8 hours are, preferably temperatures between 760 and 815 ° C for one hour.

In the case of heat treatment, the general rule is that the duration and temperature are shortened of translucent glass, longer periods of time and higher temperatures favor the formation favor of dense opal glass.

If the heat treatment is properly carried out, the glass is essentially separated into two " but continuous glass phases separated (usually no crystalline phase is present.) On green This phase separation will make the glass opalescent. One of these glass phases is rich in aluminum oxide Alkaline earth oxides, sodium oxide and boron oxide. This glass phase is relatively stable and vis-à-vis Acids and alkalis fairly stable. The other

209542/4 «

component

SiO ₂

Al ₂ O ₃

CaO

MgO

Na ₂ O 2.8

Weight percent

71.5

6.5

9.6

6.2

1.2 2.4

Glass phase is rich in silicon dioxide and also very stable. It can be observed that the division ratio of the phases corresponds to the ratio of their corresponding Components in the original glass.

As mentioned earlier, the higher temperatures require a shorter period of time to bring about the desired phase separation, but the glass will at deformed or devitrified more easily at these higher temperatures. Generally speaking, the glass is with that The above-mentioned composition range is fairly stable when subjected to the required heat treatment versus devitrification.

Some embodiments of the glass according to the invention will now be described. The optical Properties of the exemplary embodiments are described in connection with the devices with which the optical Properties were measured, described.

Furthermore, to explain the exemplary embodiments Drawings attached to the invention. It shows

η * ΐ ¹ 'Τ? ^iasramm ', i ^{n dem di} * r ^eflexio " ^s - ^{and 20} The glass beakers are then kept at a temperature permeability _{properties of an example of an} opal glass according to the invention that has been taken out in an electric furnace for 24 hours _{. At the end of this} ^p _{period were.} gigke.t _{the glass} s.nd applied by dei wavelength, ^ cher _{gleichmäßi k. the übfi Ei £ s.}

tJ 'Ζ T Γ ^{"Diagramra' m} .i ^{m αη} *" ^{τ, the} "(Invention density, chemical resistance, particularly suitable range of 25 Glaszu- expansion coefficient) of the glass were transactions is represented by this Wärmesammensetzungen, _ _ not significantly treatment changed

K ₂ O

B ₂ O ₃

Fe ₂ O ₃ (impurity) 0.1

Temperature for viscosity 10 ³ poise 1351 ^C C Temperature for viscosity 10 ⁷ poise 926 ^C C

Liquidus temperature 1227 ⁰ C

Viscosity at liquidus temperature .. 10 ³ · ⁷ Poise thermal expansion coefficient / ⁰ C · 10 ⁷ (0 to 30O ⁰ C) 57

F i g. 3 is a diagram in which the reflection properties of certain opaque glasses according to the invention plotted as a function of the wavelength

The difficulties encountered in measuring and comparing the optical properties of materials that have a tendency to diffuse an incident light beam (e.g. opal and opalescent Glass) are known to occur. The basic problem arises from the fact that some of the radiant energy that is in the sample enters, is scattered within the sample and therefore by ordinary spectrophotometers is not detected as reflected, absorbed or transmitted radiation. The test procedure used in the Ausf ührungsbeispielen was used, tries to compensate for this scattering effect.

Example 2

Starting materials were made into a homogeneous glass by the method of Embodiment 1 melted, which has the following composition and properties:

Ingredient weight percent

SiO ₂ 70.6

Al ₂ O ₃

CaO 9.4

MgO 6.1

example 1

The raw materials

Sand 3618.53 g

Raw dolomite lime 1414.88 g

high calcite lime 72.48 g

Alumina 323.83 g

Borax 175.63 g

Sodium carbonate 146.43 g

Potassium carbonate 85.18 g

45

⁵⁰

Na ₂ O 3.3

K ₂ O 1.4

B ₂ O ₃ 2.2

Fe ₂ O ₃ (impurity) 0.06

Liquidus temperature 1240 ^r C

Thermal expansion coefficient ...

cient / ° C · 10 ⁷ (0 to 30O ⁰ C) 56

The molten glass was poured into several small rectangular plates (25 x 19 x 3 mm). The panels were clear and translucent after casting. Three of these panels were selected and each of the panels was given a specific heat treatment in an electrical laboratory oven. One of the plates was exposed to Wärmebehanc ^one lung and served as a comparison object.

were melted in a crucible made of platinum at glass temperatures around 1600 ⁰ C in an electric furnace with mechanical stirring. The melt time was about 24 hours to ensure homogeneity. A plurality of glass beakers were made from the molten glass by an ordinary blowing method. The finished glass cups were see-through and kept the appearance of ordinary soda lime plate 1

Heat treatment: none, appearance: clear and transparent, no visible Light scattering.

Plate 2 heat treatment: 2 hours at 800 ^° C.,

and features:

a «Appearance of profits auuan.aiR.-" »... ^^ ..» .. χ .-, ^. - ^ ",," ~ .. "" .— ~,

Look at the following composition: very light blue against a black

Eagle owl background, narrow cloudiness.

Background, low haze.

Plate 3 Rods were cut from the molten glass

,. "" ._, which you then drew in the ambient air

Heat treatment: 2 hours at 830 C, left to cool. The rod was placed in test rods

Appearance: clear blue against a black _{part that looks clear and} transparent.

Background clear cloudiness. _{5 Several of the} p _ro bestäbe were measured at 64 hours

800 ⁰ C heat treated. The resulting glass

Plate 4 was uniformly opal. The X-ray spread pattern

.. “This opal glass indicated that noticeable amounts

Heat treatment: 2 hours at 900 C, _the crystal type diopside (CaO · MgO · 2SiO ₂ ) in the

Appearance: completely opaque-opal. ₁₀ surface were available. This means that the

glass according to the invention even with an extended

To improve the optical properties of the plate 4 further heat treatment is devitrified (which for most

to characterize reflection and transmissive glass types were valid), but that the presence of these

speed with respect to radiant energy with spectrophoto- crystal type does not harm the opacity,

determined by metric means after the samples were 15

grinded and polished to surface finish Embodiment 5

remove inaccuracies. The spectral transmission starting materials were according to the method

Release data were obtained by means of a Beckmann Spectrum _of exemplary embodiment 1 for a glass as follows

trophotometer DK-2A determined that melted with an inte- composition and properties:

grating hollow sphere was equipped to

to be able to better absorb scattered radiation. The constituent weight percent

Permeability measurements were obtained by using SiO ₂ 68.8

a parallel monochromatic beam of light through the Al ₂ O ₃ 6.4

Sample has been focused on a detector. The ener- ^ ₃ Q- ^ '3

amount (which is above the wavelengths of interest - 25 '

area was measured) was then expressed as a percentage of MgU

the amount of energy incident on the sample. Na ₂ O 4.0

draws. The integrating hollow sphere K ₂ O mentioned above -

collects that part of the emitted radiation, Jj ₂ Q ₃ 2.4

which due to scattering is not parallel to the 3 ° temperature that occurs at a viscosity of 10 ³ poise 1293 ° C

Radiation escapes. This procedure almost ^r . . ., ". . """

the total energy impinging on the sample, temperature at 10'Poise viscosity 877 ° C

_he f _a B _t . Liquidus temperature 1238 ° C

The reflectance and transmittance curves for viscosity at liquidus temperature .. 10 ³ · ³ poise

Plate 4 as a function of the wavelength are shown in FIG. 35

F i g. 1 shown. These curves are characteristic. The weight of a crucible filling was approximately

for highly opaque-opal types of glass. ⁴ , 5 kg, and the melting was in a refractory

Container at 1593 ⁰ C in a gas-fired oven

Embodiment 3 for 24 hours with mechanical stirring

40 led. Test rods were drawn from the melt.

In order to achieve the properties of the opal of the invention, the test rods were clear and translucent. In order to show the glass further, several samples were made to determine the density influence of the opal coating on the glass stability. The stared glass durability tests were carried out. The density of the clear, transparent glass was measured according to the standard US Pharmacopeia XVII method and was 2.4691 g / cm ³ . Procedure used. This method is referred as follows A similar sample like glass composition: United States Pharmacopeia XVIl, Conwurde heat treated for 21 hours at 930 ⁰ C. tainers-glass, chemical resistance-weter-attack. At the end of this heat treatment the sample was The procedure corresponds to the powdered glass test

evenly opal. The density was 2.5591 g / cm ³ , which corresponds to 5 ° ASTM regulation C-225-59T (Method PW Resis an increase of approximately 3.6%. Tance of Powdered Sample to Attack by Distilled Wa

ter).

_A Generally speaking, the procedure consists in this

Ausiuhrungsbeispiel 4 the _{pull of the G] asp powder sample with emerr}

Starting materials were given volume of water at elevated temperature according to Procedure 55

of embodiment 1 to a homogeneous glass ™ ^ah ™. ^{to establish the} / specific period of time. At

The following composition has melted: After this period of time, the water becomes mat n / 50 H ₂ SO

titrated to the neutral point to remove the powder glass.

^To neutralize part by weight. The test results are i

60 mm of required 7i / 5O H ₂ SO ₄ stated

SiO ₂ 62.0 The lower the number of ml of 7i / 5O H ₂ SO ₄ , the s

J ^ q gO better is the chemical resistance.

^{2 8} 'The following test results were obtained: D

Clarify CaO 10.6 and required transparent test rods

MgO 7.5 65 1.8 ml. N / 50 H ₂ SO ₄ and the opaque-opal sample tubes

_, _ (after heat treatment for 10 hours <

^m * ^{u 5} ' ^υ at 800 ⁰ C) 2.5 ml. n / 50 H ₂ SO ₄ , in order to extract the water

B ₂ O ₃ 9.0 to neutralize. This shows that the chemical B.

1

resistance to water is not significantly reduced by the opalescent heat treatment.

Embodiment 6

Compositions were made from suitable starting materials by following the procedure of Working Example 1 6 A, 6 B and 6 C (see below) melted, and the melt became clear, translucent Test rods drawn. Tests were carried out to determine the minimum time-temperature relationship occurs during opalescence. The times and temperatures listed below are those given Periods of minimum temperatures at which the glass composition becomes slightly cloudy or "milky".

_ ... percent by weight

^Component 6A 6B 6C

SiO ₂ 69.7 69.8 64.8

Al ₂ O ₃ 6.3 6.2 6.7

CaO 10.6 10.6 11.2

MgO 7.3 7.4 7.8

Na ₂ O 3.0 5.0 3.7

K ₂ O - - -

B ₂ O ₃ 2.9 1.0 5.8

Temperature ⁰ C »5

Temperature at viscosity

10 ³ poise 1229 1318 1251

Temperature at viscosity

10 ⁷ poise 877

Liquidus temperature 1331 1248 1215

Viscosity at liquidus temperature (poise) 10 ³ · ⁰ 10 ³ · ¹ 10 ³ · ²

Time 1 hour 800 no 710

Opalescence time 64 hours 725 720 675

Example 7

The following values illustrate more precisely the relationship between the heat treatment and the composition of types of glasses according to the invention.

Glass with the following composition was made after the method of embodiment 1 from suitable Raw materials melted and the melt produced rods 12.7 cm in length and approximately 0.6 cm in diameter drawn. The appearance of these bars was recorded.

The bars were then heat treated to determine the following temperatures:

Tu 1: lowest temperature at which a slight opalescence (weak clouding) is visible after one hour of heat treatment;
ToI: Lowest temperature at which a dense white opal glass is created after one hour of heat treatment;

Tu 64: Lowest temperature at which, after a heat treatment of 64 hours, a faint opalescence is visible;

To 64: Lowest temperature at which, after a heat treatment of 64 hours, a tight white opal glass is created.

These temperatures were determined by placing the rods in a gradient oven with a stabilized temperature profile for the specified period of time. Since the gradient oven had a known uniform temperature gradient of about 350 ^° C. over the length of the rod, the exact temperature for each point on the rod was known. The results are shown in Table 1.

Table I.

No. Al ₂ O ₃ Glass composition
in percent by weight Na ₂ O SiOa CaO MgO D ₂ O ₃ Appearance
the bars TuI
CQ
after Tu.64
( ⁰ C)
after ToI
CC)
after To 64
CC)
after 2 3 73.0 12.9 9.1 0 1 hour 64 hours 1 hour 64 hours 7-1 2 5 73.0 11.7 8.3 9 opal - - - - 7-2 2 5 73.0 10.6 7.4 2 clear 810 725 * * 7-3 2 5 73.0 9.4 6.6 4th clear 760 675 * * 7-4 2 5 69.0 10.6 7.4 6th opalescent - - * * 7-5 2 5 65.0 11.7 8.3 8th opalescent - - * * 7-6 2 5 69.0 8.2 5.8 10 opalescent - - 800 730 7-7 2 7th 73.0 9.4 6.6 2 opalescent - - 780 740 7-8 2 7th 73.0 7.0 5.0 6th clear * * * * 7-9 2 7th 69.0 7.0 5.0 10 clear * 690 * * 7-10 4th 1 69.0 15.3 10.7 0 clear 750 675 * * 7-11 4th 3 69.0 14.1 9.9 0 opal - - - - 7-12 4th 3 69.0 12.9 9.1 2 clear 720 690 * 780 7-13 4th 3 69.0 11.7 8.3 4th opalescent - - - 775 7-14 4th 3 61.0 15.3 10.7 6th opalescent - - - - 7-15 4th 5 73.0 10.6 7.4 0 clear * 715 * * 7-16 4th 5 69.0 10.6 7.4 4th clear * 720 800 7-17 4th 5 62.0 12.9 9.1 7th clear 780 710 * 760 7-18 4th 5 65.0 8.2 5.8 12th clear 750 700 810 750 7-19 4th 7th 70.0 5.3 3.7 10 opalescent - - 740 725 7-20 4th 7th 65.0 5.9 4.1 14th clear 680 * 730 7-21 clear 725-775 670 * 690

A>

Al ₁ O ₃ Glass composition OK SiO ₂ CaO MgO B ₂ O, Appearance TuI
( ⁰ C) Do 64
( ⁰ C) ToI
( ⁰ C) To 64
CQ No. 6th in percent by weight 0 75.5 10.6 7.4 0.5 the bars after after after after 6th 1.5 74.0 10.6 7.4 0.5 1 hour 64 hours 1 hour 64 hours 7-22 6th 1.5 67.0 14.1 9.9 1.5 opal - - - - 7-23 6th 1.5 70.0 10.6 7.4 4.5 opalescent - - - - 7-24 6th 1.5 67.0 10.6 7.4 7.5 opalescent - - 900 810 7-25 6th 3 72.5 10.6 7.4 0.5 opal - - - * 7-26 6th 3 71.5 10.6 7.4 1.5 opal - - - 7-26a 6th 3 70.0 10.6 7.4 3 clear 820 730 925 800 7-27 6th 3 68.5 10.6 7.4 4.5 clear 840 700 * 775 7-28 6th 3 67.0 10.6 7.4 6th clear 825 680 910 760 7-29 6th 3 66.5 10.6 7.4 7.5 opalescent - - 850 - 7-30 6th 3 64.0 10.6 7.4 9 opalescent - - 800 - 7-31 6th 3 58.0 15.8 11.2 6th opal - - - - 7-32 6th 3 55.0 14.1 9.9 12th opal - - - - 7-33 6th 5 71.0 10.6 7.4 0 clear 775 710 880 760 7-34 6th 5 69.5 10.6 7.4 1.5 opal - - - - 7-35 6th 5 68.0 10.6 7.4 3 clear * 720 * 7-36 6th 5 66.5 10.6 7.4 4.5 clear * 720 * 775 7-37 6th 5 65.0 10.6 7.4 6th clear 800 700 * 750 7-38 6th 5 63.5 10.6 7.4 7.5 clear 760 680 * 740 7-39 6th 5 63.0 10.6 7.4 9 clear 750 670 825 720 7-40 6th 5 60.5 10.6 7.4 10.5 clear 740 600 800 710 7-41 6th 5 66.0 10.6 7.4 5 clear 760 655 810 700 7-42 5 5 59.0 10.6 7.4 12th clear 740 640 800 690 7-43 6th 5 71.0 7.0 5.0 6th clear 760 700 * 740 7-44 6th 5 69.0 5.9 4.1 10 opalescent - - 790 670 7-45 6th 7th 73.0 4.7 3.3 6th clear 750 680 825 740 7-46 6th 7th 65.0 8.2 5.8 8th clear 750 670 * 723 7-47 6th 7th 61.0 7.0 5.0 14th clear ♦ 670 * 700 7-48 6th 9 65.0 9.4 6.6 4th clear * 675 * * 7-49 6th 9 65.0 8.2 5.8 6th clear 710 670 700 * 7-50 8th 3 71.0 9.4 6.6 2 clear * 660 * 700 7-51 8th 3 65.0 10.6 7.4 6th clear * 680 * 725 7-52 8th 3 71.0 4.7 3.3 10 clear 850 740 * 800 7-53 8th 3 67.0 4.7 3.3 14th clear 800 725 875 740 7-54 10 3 67.0 8.2 5.8 6th clear 785 790 * * 7-55 10 3 67.0 5.9 4.1 10 clear 775 775 * * 7-56 10 3 55.0 10.6 7.4 14th clear 830 690 - 775 7-57 10 5 63.0 9.4 6.6 6th clear * 750 * * 7-58 10 5 55.0 9.4 6.6 14th clear 760 710 790 730 7-59 clear * 730 * 770 7-60 clear 740 690 785 720

Notes: * means that opalescence did not occur under the test conditions. - means that the special test conditions were not evaluated.

A glass within the compositional range of the present invention has its constituents as follows Have percentages by weight, has commercially 6o desirable shape properties such as viscosity-temperature relationship, Liquidus temperature and thermal expansion capacity can be made out of proportion cheap raw materials, has good chemical resistance and can be made 65 conventional aids during a modified relaxation heat treatment process opalesced will:

Ingredient weight percent

SiO ₂ 66 to 69

Al ₂ O ₃ about 6

B ₂ O ₃ 4 to 8

RO (CaO + MgO) 13 to 18

Na ₂ O about 5

with

CaO percent by weight

about 1.4

MgO weight percent

This glass has the following properties:

Temperature at viscosity 10 ² poise ... <1566 ° C
Temperature at viscosity 10 ³ poise ... <1316 ° C
Temperature at viscosity 10 ⁷ poise ... <927 ⁰ C

Liquidus temperature <1204 ° C

Temperature at viscosity 10 ³ ( ⁰ C)

- Liquidus temperature ( ⁰ C) <112 ° C

Thermal expansion coefficient <60 · 10 ~ '/

° C (0 to
300 ° C)

Preferred compositions within the above range are shown in FIG. 2 shown. Dolomite lime was used as a source of CaO and MgO so that the weight percent CaO to MgO ratio is approximately 1.4. The preferred types of glass are the types of glass represented by the parallelogram in the middle part of the ternary diagram. The boundaries of this parallelogram were determined by evaluating the glass forming and stress relieving properties with regard to the heat treatment required for opalescence. Glass within this preferred composition range has excellent molding properties and becomes thermally opalescent in a very short time at a relatively low temperature. It has been found that articles molded from glasses having these compositions can be opalesced in a modified relaxation cycle. In these glass compositions, B ₂ O _{3 is} the primary opalescent agent, and the tendency of the glass to opalesce increases as the proportion of B ₂ O ₃ increases.

The time and temperature for the opalescent heat treatment this glass agrees with the stress relief heat treatment of conventional lighter weight Glass objects largely match. This means that this type of glass through a heat treatment at temperatures of about 565 to 845 ° C in 15 minutes to about 8 hours can. Preferably, the opalescent heat treatment is carried out at temperatures for economic reasons carried out between 760 and 815 ° C for about an hour.

The following tables give glass compositions which are within this preferred composition range, depending on the B ₂ O ₃ content:

B ₂ O ₃ content is about A ⁰ I ₀ :
Ingredient weight percent

Na ₂ O about 5

Al ₂ O ₃ about 6

SiO ₂ 67 to 69

RO (CaO + MgO) 16 to 18

B ₂ O ₃ content is about 6%:
Ingredient weight percent

Na ₂ O about 5

Al ₂ O ₃ about 6

SiO ₂ 66.5 to 68.5

RO (CaO + MgO) 14.5 to 16.5

B ₂ O ₃ content is about 8%:
Ingredient weight percent

Na ₂ O about 5

S Al _a O _s about 6

SiO ₂ 66 to 68

RO (CaO + MgO) 13 to 15

These types of glass do not require any special melting and refining conditions and can be melted ^{in continuously operated gas-fired furnaces at temperatures of 1425 to 1600 ° C.} Customary starting materials can be used, as can be seen from the following examples. 15th

Embodiment 8

The raw materials

powdered flint 3967.94 g

raw dolomite lime 2069.3Og

Soda ash 517.24 g

Boric anhydride 314.47 g

Alumina 362.17 g

are melted in a platinum crucible at a glass temperature of 1593 ⁰ C in an electric furnace with mechanical stirring. The melting time is around 24 hours to ensure homogeneity.

A rod was drawn from the molten glass, from which test rods were formed, which were then used in Let ambient air cool. The test bars were clear and transparent and had the following composition:

component
SiO ₂ ..

Al ₂ O ₃ ..
CaO ...
MgO ..

Weight percent
66.0

6.0

10.0

7.5

Na ₂ O 5.0

B ₂

5.0

Several of these bars were heat treated for 15 minuter at 815 ⁰ C. At the end of this heat treatment, the rods were slightly opalescent (slightly clouded). The coefficient of thermal expansion in the temperature range from 0 to 30O ⁰ C was measured using conventional methods and was about 59.6 · 10 - '/ ° C.
Other test bars of the same composition were heat-treated at 815 ° C for 16 hours. At the end of this heat treatment, the test bars were uniformly opal and the thermal expansion coefficient was 60.4 · ^{10--1 / 0} C (Obis 300 ° C). This means an increase the thermal expansion coefficient from about 1.3%.

Embodiment 9

From the composition according to the embodiment example 8 clear, transparent test plates were voi about 1.8 mm thick made by molten glass in a shallow, refractory tub underneath was poured in open air. The panels were taking

subjected to various opalescence heat treatments in order to carry out reflection measurements can.

The heat treatment and the appearance of the sample panels are described below. The optical one Reflection of the radiant energy in the visible wavelength range was made by conventional photometric Procedure determined. The results are shown in FIG. 3 shown graphically.

IO

Plate 1

Heat treatment: none,
Appearance: clear and transparent.

Plate 2

Heat treatment: half an hour at 815 ° C,
Appearance: slight opalescence.

Plate 3

Heat treatment: one hour at 815 ⁰ C,
Appearance: slight opalescence.

Plate 4

Heat treatment: eight hours at 815 ° C,
Appearance: almost opaque-opal.

Plate 5

Heat treatment: two hours at 827 ° C,
Appearance: opaque-opal.

30th

35

These sample disks were ground and polished until the surface was smooth and the optical reflective properties were conventionally using a General Electric "Hardy" Model Spectrophotometer with a black background certainly. The results are shown in FIG. 3 shown. These curves show how the time duration and The temperature of the heat treatment can be changed to achieve the desired optical properties to achieve in the glass according to the invention.

Embodiment LO

Following the procedure of Embodiment 8, raw materials were melted and test bars were melted manufactured. The glass had the following composition and properties:

Weight percent

9.3

6.7

SiO ₂ .
Al ₂ O ₃ .
CaO ..
MgO.
Na ₂ O
B ₂ O ₃ ..

50 temperature at viscosity 10 ⁸ poise 1527 ° C

. Temperature at viscosity 10 ^s poise 1274 ° C

Temperature at viscosity ΙΟ ⁷ · ⁸⁸ poise 846 ^ C

Liquidus temperature 1177 ° C

Temperature at viscosity 10 ^s

- Liquidus temperature 97 ° C

Thermal expansion coefficient 58-10- ⁷ / ° C

(0 to 300 ° C)

Relaxation tests were carried out with these test rods and it was found that the test rods were slightly opalescent after one hour at 749 ° C. Further experiments with bars of this composition were carried out and it was found that the rods after a heat treatment of one hour at 821 ⁰ C densely opaque opal were. This shows that the stress relief and opalescence heat treatment can be combined.

With certain glass compositions it is even possible to apply a subsequent heat treatment to renounce entirely and opalescence under the simple influence of the thermal condition, which at Pouring exists to achieve. These types of glass are also characterized by low and good coefficients of expansion chemical resistance.

They correspond to the composition:

Weight percent

SiO ₂ about 71

Al ₂ O ₃ about 4

RO (CaO + MgO) about 10

B ₂ O ₃ about 12

Na ₂ O about 3

the weight ratio of CaO to MgO being 1.5.

This ratio is for the properties of the glass most favorable and advantageously corresponds to the most favorable and advantageously corresponds to straight about the ratio of lime and magnesium about the ratio of lime and magnesia in the Dolomite. Other alkali metal oxides can also be used in place of sodium oxide, though Lithium oxide promotes discharge at high temperatures.

These types of glass have the following properties:

Temperature at viscosity 10 ² poise 1650 ° C

Melting temperature 1127 ° C

Viscosity at melting temperature 10 ⁴ - ^a poise
Expansion coefficient per ° C
(between 0 and 300 ° C) <45

Opalescence of the glass occurs in a temperature range suitable for d'e molding operations and is complete when the glass transition temperature reaches the Littleton point (viscosity 10 ⁷ x ⁶⁶ poise) on cooling. Otherwise, the opalescence develops during the molding process; it occurs instantly when the molten glass is drawn into the open air.

1 sheet of drawings

Claims (8)

Patent claims: 1. Process for the production of opal glass objects, characterized in that an alkaline earth aluminum silicate glass that contains the following components, component Weight percent SiO ₂ 55 to 76 AI ₂ O ₈ 1.5 to 12 B ₂ O ₃ O to 13 CaO 5 to 20 MgO O to 15 Na ₂ O 1 to <11 K ₂ OO to 5 Li ₂ OO to <2 with the conditions (CaO + MgO) 10 to 30 (Na ₂ O + K ₂ O) <11 O to 5 Weight percent B ₂ O ₃
Weight percent Na ₂ O (SiO ₂ + Al ₂ O ₃ + B ₂ O ₃ + CaO + MgO + Na ₂ O)> 95 the glass objects are formed and an in-situ phase separation is carried out by means of a heat treatment is brought about, through which the glass objects become opalescent. 2. The method according to claim 1, characterized in that a glass is used which the contains the following components: Ingredient weight percent SiO ₂ 60 to 70 Al ₂ O ₃ 4 to 8 B ₂ O ₃ 1 to 9 CaO 6 to 16 MgO 4 to 12 Na ₂ O 3 to 7 with the conditions (CaO + MgO) 14 to 21 (Na ₂ O + K ₂ O) <8 35 45 Weight percent B ₂ O ₃
Weight percent Na ₂ O 0.2 to 3 (SiO ₂ + Al ₂ O ₈ + B ₂ O ₃ + CaC + MgO + Na ₂ O)> 98 3. The method according to claim 1, characterized in that a glass is used which has the following Components contains: Ingredient weight percent SiO ₂ 66 to 69 Al ₂ O ₃ at 6 B ₂ O ₃ 4 to 8 CaO + MgO 13 to 18 Na ₂ O at 5 under the condition Weight percent CaO
Weight percent MgO by 1.4 and has the following properties: Temperature at viscosity 10 * poisex <1316 ° C Liquidus temperature <1204 ° C Temperature at viscosity 10 ³ poise ( ⁰ C) -Liquidus temperature ( ⁰ C) <112 ° C Therm. Expansion coefficient <60 · 10- ⁷ / ^o C (O to 30O ⁰ C) 4. The method according to claim 3, characterized in that that a glass is used which contains the following components: Ingredient weight percent SiO ₂ 67 to 69 Al ₂ O ₃ at 6 B ₂ O ₃ at 4 CaO + MgO 16 to 18 Na ₂ O at 5 5. The method according to claim 3, characterized in that a glass is used which the contains the following components: Ingredient weight percent SiO ₂ 66.5 to 68.5 Al ₂ O ₃ at 6 B ₂ O ₃ at 6 CaO + MgO 14.5 to 16.5 Na ₂ O at 5 6. The method according to claim 3, characterized in that a glass is used which has the following Components contains: component Weight percent SiO ₂ 66 to 68 Al ₂ O ₃ at 6 B ₂ O ₃ at 8 CaO + MgO 13 to 15 Na ₂ O at 5 7. The method according to claim 3, characterized in that a glass is used which has the following Components contains: component
SiO ₂
Al ₂ O ₃
CaO.
MgO
Na ₂ O
B ₂ O ₃ . Weight percent 67 9.3 6.7 5 6 and has approximately the following properties: Temperature at viscosity 10 ² poise 1527 ° C Temperature at viscosity 10 ³ poise 1274 ° C Temperature at viscosity 1Ο ' ^β6 poise 846 ° C Liquidus temperature 1177 ⁰ C Temperature at viscosity 10 ³ poise - Liquitustempera- ture 97 ⁰ C Thermal expansion coefficient 58-10 - '/ ⁰ C (O to 300 ° C) 8. The method according to claim 1, characterized in that a glass is used which has the following Components contains: test component weight percent SiO ₂ 71 AUO ₃ 4 B ₂ O, 12 CaO + MgO 10 Alkali oxides 3