SK283612B6 - Lead-free technical glass - Google Patents

Abstract

The invention relates to lead-free technical glass for application, in particular, in the electrical industry for the production of light bulbs, fluorescent tubes and other light sources or components thereof, comprising SiO2 at 62-72 mass %, Na2O at 5-10 mass %, Al2O3 at 1-6 mass %, CaO at 0.1-4 mass %, MgO at 0.1-3 mass %, K2O at 3-8 mass %, BaO at 6-12 mass %, SrO at 1-4 mass %, Li2O at 0.1-3 mass % B2O3 at 0.1-3 mass % SO3 at 0.1-0.5 mass %, or Sb2O3 at 0.1-0.5 mass %.

Description

Technical field

The invention relates to unleaded technical glass intended for use, in particular, in the electrical industry in the manufacture of lamps, fluorescent lamps and other light sources or parts thereof.

BACKGROUND OF THE INVENTION

Lead and recently unleaded glasses are used for the production of light sources or their components. Lead glass due to its properties such as high electrical resistance, processing time and the ability to produce a high quality vacuum seal weld, whether with glass or electrical supply, is one of the basic materials of the electrical industry. Its disadvantage is high content of PbO in glass, about 20-21%. It is well known that PbO is classified as a toxic substance, and there is currently an environmental effort to eliminate the use of lead and its compounds in products. The professional public has therefore long been involved in the development of glass as an equivalent substitute for lead glass. So-called lead-free glasses are developed and used industrially, but all of them merely come close to lead glasses.

Lead-free glass according to EP 0 603 933A replaces lead glass with its properties such as electrical resistance and thermal expansion. The processability of this glass is also good, but the viscosity profile in the glass processing area is shifted to higher temperatures. Therefore, when processing this glass, it is necessary to use a higher flame temperature and thus a greater amount of energy. When the glass with the glass is sealed despite a suitable thermal expansion, the glass has a higher weld glass stress than the lead glass.

Other lead-free glass according to DE 197 55 005A has, according to the declared parameters, electrical properties similar to lead glass or also lead-free glass according to EP 0 603 933A. Its viscosity properties in the field of glass processing are superior to lead-free glass according to EP 0 603 933A, but not to lead glass. As regards the dilatation properties, it is to be noted here that there is a considerable difference from the aforementioned glasses according to EP 0 603 933A and lead glass. Taking into account the global trend in the development of machinery and technology in the production of light sources (increasing the speed of machines), there is a requirement to reduce the thermal expansion of these glasses. For the safe sealing of two glasses, the limit of the thermal expansion of two glasses is considered to be 3 - 5.10 ' ⁷ ' C ' ¹ . The proposed glass according to DE 197 55 005A with respect to commonly used glass glasses having an expansion of approx. 94 - 96. 10 ' ⁷ ' C ' ¹ ensures this difference, but the weld is subjected to an oppositely oriented tension compared to lead glass but also to EP glass. 0 603,933A. This finding suggests a possible risk of breaking the melting of the glass thus designed with conventional bank glass.

SUMMARY OF THE INVENTION

The object of the present invention was to provide a lead-free technical glass which would replace the previously manufactured lead glass used in the production of light sources and which would have better properties than the previously known lead-free glass.

These requirements are substantially met by the unleaded technical glass according to the invention intended for use, in particular, in the electrical industry in the manufacture of filament lamps, fluorescent lamps and other light sources or parts thereof containing silica, aluminum, sodium, calcium, magnesium, potassium, barium, strontium, lithium, boron, sulfur or antimony, and which comprises 62 to 72% by weight of SiO ₂ , 5-10% by weight of Na ₂ O, 1 - 6% by weight of Al ₂ O ₃ , 0.1-4% by weight CaO, 0.1-3 wt% MgO, 3-8% by weight of K ₂ O, from 7.1 to 12% by weight BaO, 1-4% by weight of SrO, 0.1 to 3% by weight of Li ₂ O, 0.1 - 3% by weight of B ₂ O ₃ , up to 0,5% by weight of SO ₃ or up to 0,5% by weight of Sb ₂ O ₃ .

The glass structure is designed from oxides which by their presence influence the resulting property of glass as follows:

SiO ₂ is a glass-forming oxide that forms the basis of glass construction.

Al ₂ O ₃ improves the chemical resistance of the glass and suppresses the matting of the glass surface during processing above the flame. Additions of Al ₂ O ₃ strongly increase the surface tension of the glass, which is unfavorable when sealing the electrical supply to the glass.

Due to the size of the ionic radius, BaO has little mobility in the glass network and thus increases the electrical resistance. It also has a significant effect on the lengthening of the glass, which makes the glass easier to process. It is a good substitute for PbO.

CaO strengthens the glass structure and has therefore long been used as a stabilizer. It significantly increases the chemical resistance of alkaline glasses, increases the electrical resistance and increases the thermal expansion, decreases the viscosity at high temperatures significantly, but increases it at low temperatures, which makes the glass shorter.

MgO reduces thermal expansion. The addition of MgO as a substitute for CaO significantly prolongs the enamel and improves its processability.

SrO has similar properties to BaO. Increases electrical resistance and increases thermal expansion. It is a good substitute for PbO. However, its price is high.

Na ₂ O reduces glass viscosity, decreases chemical resistance of glass, increases electrical conductivity. Sodium raw materials act as a strong flux. They are one of the basic glass raw materials, without which the glass could not be melted.

K ₂ O has similar properties to Na ₂ O and is also one of the basic components of glass. It shortens glass compared to Na ₂ O, increases glass leachability less than Na ₂ O.

Li ₂ O reduces thermal expansion, reduces viscosity and lengthens glass. Cast iron improves the meltability of glass, shortens the dissolution time of sand grains and increases the melting rate.

B ₂ O ₃ increases chemical resistance, decreases thermal expansion, improves fusibility, reduces surface tension and reduces crystalline ability. Boron raw materials serve as fluxes, reducing the melt viscosity and thereby improving the meltability and clarity, ultimately improving the homogeneity of the glass.

Among the basic properties of glass that affect its usability for the production of light sources in particular are electrical properties, viscosity, dilatation, liquidus temperature, crystallization ability. The lead-free technical glass according to the present invention approaches lead glass in these properties and some properties are superior to those of the prior-art lead-free glasses.

SK 283612 Β6

Example

In a ladle furnace, lead-free technical glass of the following composition was melted:

component Weight. % S1O2 67.5 A12O3 3.2 Na ₂ O 7.6 K, 0 5.3 MgO 0.8 CaO 1.75 BaO 8.6 Ltd 2.8 Li ₂ O 1.17 B ₂ O _p 1.0 Sat ₃ 0.1 Sb ₂ O ₃ - PbO -

Furthermore, glass tubes were made from this unleaded technical glass and light sources were subsequently made.

The following table shows the properties of the glass produced according to the invention and, for comparison, the properties of lead glass with a PbO content of 20.9% by weight and the glass according to EP 0 603 933A and the glass according to DE 197 55 005A. The glass according to this embodiment is designated as glass No. 1, lead glass as glass No. 2, glass according to EP 0 603 933A as glass No. 3 and glass according to DE 197 55 005A as glass No. 4.

property Glass No. 1 Glass No.2 Glass No.3 Glass No.4 ^and (20-300) X10 ⁷ (° C ') «(25-300) x 10 ⁷ (° C')« 150-350) x10 ⁷ (° C ') 93.0 93.0 92.5 98.0 LBM (° C) 670 625 675 665 T _work (° C) 1010 1000 1020 992 T _E (° C) 475 440 480 470 Tkioo (° C) 285 280 290 290 T _li0 . (° C) 790 ' 854 840 680 Density (g / cm ⁵ ) 2.56 2.82 2.62 2.56 Water resistance (ml / g) 0.25 0.82 0.9

The meaning of the symbols used in the table is as follows:

'(20 - 3oo> x 10- ⁷ (C') - the coefficient of thermal expansion between 20 and 300 "C '(> 5-300) x? H' ⁷ (C ^_I) - coefficient of thermal expansion between 25 and 300 ° ~ C «(Sat - 350) x10 ' ⁷ (“ C' ¹ ) - thermal expansion coefficient between 50 and 350 ° C

LBM (° C) - Littleton softening point, glass temperature at viscosity η = 10 ^{7 '65} dPa.s, (° C) - processing temperature, glass temperature at viscosity η = 10 ⁴ dPa.s,

T _g (° C) - transformation temperature, glass temperature at viscosity η = 10 ¹³ ' ³ dPa.s

T _k oo (° C) - temperature at which the specific internal insulation resistance is 100 MQ.cm,

Tiiq (° C) - liquidus temperature - temperature above which no crystalline phase is formed within 24 hours

Water resistance (ml / g) - chemical resistance to distilled water expressed as consumption of 0,01 M HCl solution per 1 g of crushed glass of defined granulometry.

From the above table it can be seen that the electrical properties of the prepared No. 1 glass are comparable to both lead glass and unleaded glass, thus fulfilling the first of the conditions for replacing lead glass. Furthermore, it can be seen from the table that the viscosity profile is shifted to higher values compared to lead glass as well as glass No. 4, but it is closer to lead glass than Glass No. 4. 3. It should be noted here that glass no. 4 has lower viscosity point values, but only at the expense of high dilatation. When evaluating the dilatation to see that the proposed glass no. 1 has the same dilation as lead glass, and approximately the same as glass no. 3. The equality or similarity of the dilatation was the second essential condition in the development of glass. The question of dilatation is very important for achieving a good glass-metal weld (electrical supply) and glass-glass. The general principle here is that the expansion of the glass used to seal the inlets must be less than or equal to the expansion of the bank glass with which it is built. Such a weld on the side of the bank glass creates a compressive stress which increases the strength of the weld. Otherwise, t. j. if the bank glass has less dilatation, a dangerous tensile stress arises, thereby reducing the strength of the weld and the light source thus produced has a low resistance to mechanical stress. Designed glass no. 1 in this regard, it follows the world development in reducing the dilation of bank glass due to increased productivity in the production of flasks using faster machines. Another important feature is the liquidus temperature. Prepared glass no. 1 is 50 ° C lower than glass no. 3 and 64 ° C lower than lead glass. I must note here that the value of 790 ° C was determined after 48 hours and not at 24 hours as prescribed by the standard. No value could be obtained by this standard procedure, because the glass was so stable that it could not crystallize.

The liquidus temperature is very important in forming the tubes with the vello system. In any case, it must be at least 50 ° C lower than the temperature of the glass in the feeder head during molding.

Equally important is the crystallization ability. Prepared glass no. 1 has approximately 6 times less crystallization than glass no. 3, which shows significantly better glass stability. This stability is positively reflected in the corrosive and mechanical properties of the glass, and ultimately in the life of the light sources themselves. This fact can be seen from the values given for water resistance, where glass no. 1 differs diametrically from lead glass and glass no.4.

Glass tubes made of unleaded technical glass, the composition of which is according to this embodiment of the invention, were tested not only for the mentioned properties, but also for the processability of this glass in the production of components and light sources themselves. Tests for the durability of these lamps have also been carried out. The results confirm that the glass according to this patent is useful as a substitute for lead glass in the manufacture of light sources and has some properties better than the previously known unleaded glasses.

Industrial usability

The lead-free technical glass with the composition according to the invention can be used in all areas where the advantages arising from the properties of the glass are required. Especially in the electrotechnical industry in the production of light sources or their components. The lead-free technical glass according to the invention can be used primarily for the production of saucers and pump tubes for incandescent lamps, fluorescent lamps and

286 compact fluorescent lamps. It is also possible to make it from miniature bulbs, but also illuminated advertising. It is also possible to use glass for the production of fuses which are mounted in incandescent lamps.

Claims (1)

PATENT CLAIMS 1. Unleaded technical glass intended for use, in particular, in the electrical industry for the manufacture of filament lamps, fluorescent lamps and other light sources or parts thereof, containing silicon, aluminum, sodium, calcium, magnesium, potassium, barium, strontium, lithium, boron, sulfur or antimony and characterized in that it contains 62-72% SiO ₂ %, 5-10% Na ₂ O, 1-6% Al ₂ O ₃ , 0.1-4% CaO, 0.1-3 % MgO, 3-8% by weight of K ₂ O, 7.1 to 12% by weight BaO, 1-4% by weight of SrO, 0.1 to 3% by weight of Li ₂ O, 0.1 to 3% by weight of B ₂ O _3> up to 0.5% by weight of SO ₃ or up to 0.5% by weight of Sb ₂ O ₃ .