Mineral wool composition

Details Mineral wool composition Mineral wool composition

2000-09-12

2001-09-04

Group, Karl (Department: 1755)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C065S469000, C065S470000

Reexamination Certificate

active

06284684

ABSTRACT:

The present invention relates to the field of artificial mineral wools. It is aimed more particularly at mineral wools intended for manufacturing thermal and/or acoustic insulation materials or soilless-culture substrates.
It concerns more particularly mineral wools of the rock-wool type, that is to say the chemical compositions of which wools involve a high liquidus temperature and a high fluidity at their fiberizing temperature, combined with a high glass transition temperature.
Conventionally, this type of mineral wool is fiberized by so-called “external” centrifuging processes, for example of the type of those using a cascade of centrifuging wheels fed with molten material by a static delivery device, as described in particular in Patents EP-0,465,310 or EP-0,439,385.
The so-called “internal” centrifuging fiberizing process, that is to say that using centrifuges rotating at high speed and drilled with holes, is, on the other hand, conventionally reserved for fiberizing mineral wool of the glass-wool type, schematically having a composition richer in alkali metal oxides and having a low alumina content, a lower liquidus temperature and a higher viscosity at the fiberizing temperature than rock wool. This process is described, in particular, in Patents EP-0,189,354 and EP-0,519,797.
However, technical solutions have recently been developed which make it possible to adapt the internal centrifuging process to the fiberizing of rock wool, especially by modifying the composition of the constituent material of the centrifuges and their operating parameters. For further details on this subject, reference may be made especially to Patent WO 93/02977. This adaptation has proved to be particularly beneficial in the sense that it allows properties which hitherto were inherent in one or other of the two types of wool—rock wool or glass wool—to be combined. Thus, the rock wool obtained by internal centrifuging has a quality comparable to that of glass wool, with a lower content of unfiberized material than rock wool obtained conventionally. However, it retains the two major advantages associated with its chemical nature, namely a low chemicals cost and a high temperature withstand capability.
There are therefore now two possible ways of fiberizing rock wool, the choice of one or other depending on a number of criteria, including the quality level required for the intended application and the level of industrial and economic feasibility.
To these criteria have in recent years been added that of biodegradability of mineral wool, namely its ability to be rapidly dissolved in a physiological medium, so as to prevent any potential pathogenic risk associated with the possible accumulation of the finest fibres in the body by inhalation.
One solution to the problem of choosing the composition of a rock-type mineral wool having a biosoluble nature consists in the use of a high content of alumina and moderate alkali contents.
This solution results in particular in high raw materials costs because of the preferred use of bauxite.
The object of the present invention is to improve the chemical composition of rock-type mineral wools, the improvement being aimed especially at increasing their biodegradability with the ability for them to be fiberized especially and advantageously by internal centrifuging, while still maintaining the possibility of obtaining these compositions from inexpensive raw materials.
The subject of the invention is a mineral wool capable of dissolving in a physiological medium, which mineral wool comprises the constituents below in the following percentages by weight:
SiO
2
39-55%,
preferably
40-52%
Al
2
O
3
16-27%,
″
16-25%
CaO
 3-35%,
″
10-25%
MgO
 0-15%,
″
 0-10%
Na
2
O
 0-15%,
″
 6-12%
K
2
O
 0-15%,
″
 3-12%
R
2
O (Na
2
O + K
2
O)
10-17%,
″
12-17%
P
2
O
5
0-3%,
″
0-2%
Fe
2
O
3
 0-15%,
B
2
O
3
0-8%,
″
0-4%
TiO
2
0-3%,
and in that MgO is between 0 and 5%, especially between 0 and 2%, when R
2
O≦13.0%.
According to an advantageous embodiment of the invention, the mineral wool comprises the constituents below in the following percentages by weight:
SiO
2
39-55%,
preferably
40-52%
Al
2
O
3
16-25%,
″
17-22%
CaO
3-35%,
″
10-25%
MgO
0-15%,
″
0-10%
Na
2
O
0-15%,
″
6-12%
K
2
O
0-15%,
″
6-12%
R
2
O (Na
2
O + K
2
O)
13.0-17%,
P
2
O
5
0-3%,
″
0-2%
Fe
2
O
3
0-15%,
B
2
O
3
0-8%,
″
0-4%
TiO
2
0-3%,
In the rest of the text, any percentage of a constituent of the composition should be understood to mean a percentage by weight and the compositions according to the invention may include up to 2 or 3% of compounds to be considered as unanalysed impurities, as is known in this kind of composition.
The selection of such a composition has allowed a whole raft of advantages to be combined, especially by varying the many and complex roles that a number of these specific constituents play.
It has in fact been able to be shown that the combination of a high alumina content, of between 16 and 27%, preferably greater than 17% and/or preferably less than 25%, especially less than 22%, for a sum of network formers—silica and alumina—of between 57 and 75%, preferably greater than 60% and/or preferably less than 72%, especially less than 70%, with a high amount of alkalis (R
2
O: soda and potash) of between 10 and 17%, with an MgO content of between 0 and 5%, especially between 0 and 2%, when R
2
O≦13.0%, makes it possible to obtain glass compositions having the remarkable property of being fiberizable over a very wide temperature range and of endowing the fibres obtained with biosolubility at acid pH. Depending on the embodiiments of the invention, the alkali content is preferably greater than 12%, especially greater than 13.0% and even 13.3%, and/or preferably less than 15%, especially less than 14.5%.
This range of compositions proves to be particularly beneficial as it has been able to be observed that, contrary to the received opinions, the viscosity of the molten glass does not drop significantly with increasing alkali content. This remarkable effect makes it possible to increase the difference between the temperature corresponding to the viscosity for fiberizing and the liquidus temperature of the phase which crystallizes, and thus to considerably improve the fiberizing conditions, and especially makes it possible to fiberize a new family of biosoluble glasses by internal centrifuging.
According to one embodiment of the invention, the compositions have iron oxide contents of between 0 and 5%, especially greater than 0.5% and/or less than 3%, especially less than 2.5%. Another embodiment is obtained with compositions which have iron oxide contents of between 5 and 12%, especially between 5 and 8%, which may allow mineral-wool blankets to exhibit fire resistance.
Advantageously, the compositions according to the invention satisfy the relationship:
(Na
2
O+K
2
O)/Al
2
O
3
≧0.5, preferably (Na
2
O+K
2
O)/Al
2
O
3
≧0.6, especially (Na
2
O+K
2
O)/Al
2
O
3
≧0.7,
which appears to favour the obtaining of a temperature corresponding to the viscosity for fiberizing which is greater than the liquidus temperature.
According to a variant of the invention, the compositions according to the invention preferably have a lime content of between 10 and 25%, especially greater than 12%, preferably greater than 15% and/or preferably less than 23%, especially less than 20%, and even less than 17%, combined with a magnesia content of between 0 and 5%, with preferably less than 2% magnesia, especially less than 1% magnesia and/or a magnesia content of greater than 0.3%, especially greater than 0.5%.
According to another variant, the magnesia content is between 5 and 10% for a lime content of between 5 and 15%, and preferably between 5 and 10%.
Adding P
2
O
5
, which is optional, at contents of between 0 and 3%, especially greater than 0.5% and/or less than 2%, may allow the biosolubility at neutral pH to be increased. Optionally, the composition may also co

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