WO1996030314A1

WO1996030314A1 - A mineral fiber composition

Info

Publication number: WO1996030314A1
Application number: PCT/EP1996/001181
Authority: WO
Inventors: Peter Lohe; Wolfgang Holstein; Wolfgang Schwab
Original assignee: Isover Saint-Gobain; Grünzweig + Hartmann AG
Priority date: 1995-03-31
Filing date: 1996-03-19
Publication date: 1996-10-03
Also published as: AU5004596A; DE19512145A1; DE19512145C2

Abstract

A biodegradable mineral fiber composition, characterized by the following constituents in percent by weight: SiO2 45 to 60; Al2O3 0 to 3; CaO 20 to 40; MgO 3 to 15; Na2O 0 to 2; K2O 1 to 10; Na2O + K2O 1 to 12; TiO2 0 to 3; Fe2O3 0 to 3; others 0 to 5.

Description

A mineral fiber composition

This invention relates to a mineral fiber composition which is biodegradable.

The prior art describes some mineral fiber compositions which are said to be biodegradable.

Biodegradability of mineral fiber compositions is of great importance since various studies indicate that mineral fibers with very small diameters in the range of less than 3 microns are suspected to be carcinogenic, while biodegradable mineral fibers with such dimensions show no carcinogenicity.

However, mineral fiber compositions must also have good workability by known methods for producing mineral wool with a small diameter, in particular the jet process. This in¬ volves in particular a sufficient processing range of for ex¬ ample 80°C and suitable viscosity of the glass melt.

The mechanical and thermal properties of mineral fibers, or the products made therefrom, are also of crucial impor¬ tance. Mineral fibers are used for example for insulating purposes to a great extent. Sufficient temperature resistance of the mineral fibers is necessary in particular for use in the industrial sector.

The problem of the invention is to provide a novel min¬ eral fiber composition which is distinguished by biodegrad¬ ability, has good temperature resistance and can be processed well.

The invention is based on the finding that this problem can be solved by a mineral fiber composition which consists substantially of silicon dioxide and alkaline-earth oxides, and further contains substantially potassium oxide as a melt¬ ing accelerator and a considerable proportion of aluminum ox- ide for increasing temperature resistance.

It has turned out that such mineral fiber compositions fulfill the combination of necessary properties, namely bio- degradability, sufficient temperature resistance for insula¬ tion objects in industry, as well as good workability in the production of the mineral wool as such and the products. This simultaneously means that the upper devitrification tempera¬ ture of the melt is preferably under 1320°C. The mean fiber diameter is preferably 3 microns or less.

The inventive glass fiber compositions have considerable amounts of potassium oxide but only small amounts of sodium oxide. The presence of potassium oxide produces a clear in¬ crease in glass viscosity and improves temperature resistance by around 40 to 50°C as compared to sodium-containing glass.

The subject of the invention is a mineral fiber composi¬ tion which is biodegradable, characterized by the following constituents in percent by weight:

Si0₂ 45 to 60

Al₂0₃ 0 to 3

CaO 20 to 40

MgO 3 to 15

Na₂0 0 to 2

K₂0 1 to 10

Na₂0 + K₂0 1 to 12

Ti0₂ 0 to 3

Fe₂0₃ 0 to 3

Others 0 to 5.

The inventive mineral fiber compositions are readily drawable in particular by the jet process, i.e. one obtains a fine, low-shot mineral wool.

The mineral wool reaches a high temperature resistance of at least 740°C and shows good biodegradability.

The inventive mineral fiber compositions can preferably be melted in melting chambers fueled with fossile fuels, in particular natural gas, at melting temperatures from 1350 to 1450°C. Such melting chambers can produce a homogeneous melt, which is a prerequisite for constant product quality. Homoge¬ neity of the glass melt also facilitates the reproducibility of the fiberizing process and thus of the thermal and me¬ chanical product properties. Furthermore, the constant chemi¬ cal composition of the thus produced mineral wool leads to controllable biodegradability.

In particular the addition of aluminum oxide increases the temperature resistance of the mineral wool.

The inventive mineral fiber compositions preferably have the following constituents in percent by weight:

Si0₂ 50 to 58

A1₂0₃ 0.2 to 2.5

CaO 25 to 35

MgO 5 to 10

Na₂0 < 1

K₂0 2 to 8

Na 0 + K₂0 2 to 8

Ti0₂ 0 to 1

Fe₂0₃ 0 to 1

Others 0 to 5.

Mineral fiber compositions are especially preferred with the following constituents in percent by weight: Si0₂ 52 to 57

A1₂0₃ < 2

CaO 28 to 34

MgO 6 to 9

Na₂0 < 1

K₂0 2 to 6

Na₂0 + K₂0 2 to 6

Ti0₂ 0 to 1

Fe₂0₃ 0 to 1

Others 0 to 5.

For assessment of biodegradability the standard powder test of the Deutsche Glasgesellschaft was used. This is an easily performed method and gives a sufficient measure of biodegradability. The method is described in L. Springer, "Laboratoriumsbuch f r die Glasindustrie", 3rd ed. 1950, Halle/S, W. Knapp Verlag.

The thermal behavior of the mineral fibers was deter¬ mined by the so-called "Swedish method". This method uses a silit pipe furnace with a horizontal working pipe open on both sides with a length of 350 mm and an inside diameter of 27 mm. In the center of the furnace there is a ceramic sup¬ porting plate with dimensions of 30 x 20 x 3 mm for position¬ ing the test sample. The test sample has dimensions of 12 x 12 x 12 mm or 12 mm 0 x 12 mm height. The gross density is normally 100 kg/m³. The temperature increase is 5 K/min. The change in test sample height is determined continuously with a reading optic.

The invention will be described more closely in the fol¬ lowing using examples. Example 1

A mineral wool was produced with the following composi¬ tion in percent by weight:

Si0₂ 55.6

A1₂0₃ 0.4

Fe₂0₃ 0.5

CaO 30.5

MgO 7.0

Na₂0 0.2

K₂0 5.6

This composition could be readily fiberized by the jet process at a drawing temperature between 1340 and 1400°C into mineral fibers with a mean diameter of 2.0 to 10 microns.

An investigation by the standard powder test of the Deutsche Glasgesellschaft yielded a value of 40 mg/kg and thus a value for high biodegradability.

Determination of thermal behavior by the "Swedish method" yielded a temperature resistance of 740°C with 5% height reduction.

Example 2

A mineral wool was produced with the following composi¬ tion in percent by weight: Si0₂ 53.4

A1₂0₃ 2.0

Fe₂0₃ 0.3

CaO 32.4

MgO 8.2

Na₂0 0.4

K₂0 2.6

This composition could be readily processed by the jet process at a drawing temperature between 1340 and 1400°C into mineral fibers with a mean diameter of 2.0 to 10 microns.

An investigation by the standard powder test of the Deutsche Glasgesellschaft yielded a value of 48 mg/kg and thus a value for high biodegradability.

Determination of thermal behavior by the "Swedish method" yielded a temperature resistance of 750°C with 5% height reduction.

Claims

1. A mineral fiber composition which is biodegradable, characterized by the following constituents in percent by weight :

Si0₂ 45 to 60

A1₂0₃ 0 to 3

CaO 20 to 40

MgO 3 to 15

Na₂0 0 to 2

K₂0 1 to 10

Na₂0 + K₂0 1 to 12

Ti0₂ 0 to 3

Fe₂0₃ 0 to 3

Others 0 to 5.

2. The mineral fiber composition of claim 1, character¬ ized by the following constituents in percent by weight :

Si0₂ 50 to 58

A1₂0₃ 0.2 to 2.5

CaO 25 to 35

MgO 5 to 10

Na₂0 < 1

K₂0 2 to 8

Na 0 + K₂0 2 to 8 Ti0₂ 0 to 1 Fe₂0₃ 0 to 1

Others 0 to 5.

3. The mineral fiber composition of claim 1 or 2, char¬ acterized by the following constituents in percent by weight

Si0₂ 52 to 57

A1₂0₃ < 2

CaO 28 to 34

MgO 6 to 9

Na₂0 < 1

K₂0 2 to 6

Na 0 + K₂0 2 to 6

Ti0₂ 0 to 1

Fe₂0₃ 0 to 1

Others 0 to 1.