Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Patent
1994-06-22
2000-03-14
Group, Karl
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
501 36, C03C 1306
Patent
active
060372842
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to mineral fibres; more specifically it concerns mineral fibres of which the composition is such that they degrade as soon as they come into contact with a physiological medium.
Thermal and acoustic insulation of buildings is often produced from products which consist substantially of mineral wool, such as rock wool. The specific layout of the places to be insulated often leads people responsible for laying these products to cut them on the spot. This operation gives rise to breakages of the fibres, and can lead to dispersion of some of them in the atmosphere. A fibre can thus be inhaled accidentally.
Users have become aware of this risk, and it is desirable to provide them with replacement fibrous products, which, although they have the required insulation properties, can easily be dissolved by living tissue. This capacity for dissolving in a human organism is generally assessed by measuring the dissolving speed of the fibres in a solution which simulates an extracellular fluid.
The object of the present invention is mineral fibres which dissolve quickly in such a solution, but which maintain good mechanical resistance when they are subjected to heat.
This object is achieved by means of fibres, of which the composition comprises the following components, of which the content is expressed as a percentage by weight, in accordance with the limitations defined hereinafter;
______________________________________ SiO.sub.2 48 to 67%
Al.sub.2 O.sub.3
0 to 8%
Fe.sub.2 O.sub.3
0 to 12%
(total iron expressed in
this form)
CaO 16 to 35%
MgO 1 to 16%
Na.sub.2 O + K.sub.2 O
0 to 6.5%
P.sub.2 O.sub.5
0 to 5%
______________________________________
fact that the contents of these components comply with the following
ratios:
According to the present invention, the presence of alkaline oxides, in particular Na.sub.2 O, and/or the presence of phosphorous pentoxide in the composition of the mineral fibres previously defined, enables their dissolving speed in a solution which simulates an extracellular fluid to be increased.
Furthermore, an excessively high content of alkaline oxides, in particular Na.sub.2 O, detracts from satisfactory mechanical resistance of the mineral fibres according to the invention when they are subjected to heat.
For these reasons the mineral fibres contain at least 2 weight % Na.sub.2 O and or phosphorous pentoxide, the sum of the alkaline oxides not exceeding 6.5 weight %. According to the preferred limits, the sum of the alkaline oxides is between 1 and 6%.
Silica is a component which decreases the speed at which the fibres dissolve. If its content by weight is high, this negative effect must be counterbalanced by increasing the components which promote dissolving of the fibres, such as for example Na.sub.2 O, by increasing the alumina content or by introducing phosphorous pentoxide into the composition. However, as previously stated, there is a limit to this increase. For this reason the SiO.sub.2 content must not exceed 67%.
Iron oxides, expressed only in the form Fe.sub.2 O.sub.3, as well as alumina, play a part in the dissolving speed. An excess of one and/or the other decreases the speed at which the fibres dissolve. A high dissolving speed can be maintained when the sum of the contents of these two oxides remains less than 12%, provided that the alumina content does not exceed 8%.
Although Al.sub.2 O.sub.3 and iron oxides are not essential in the fibres according to the invention, their presence in the composition improves the mechanical resistance thereof, together with the addition of alkaline earth oxides.
The mineral fibres according to the invention thus have good mechanical resistance when they are subjected to heat, owing in particular to the fact that the composition includes lime, magnesium and iron oxides in proportions such that the sum of the contents of these oxides exceeds 23%, and preferably 25%.
The fibres according to the invention advantageously comprise the components listed hereinafter, in accorda
REFERENCES:
patent: 5108957 (1992-04-01), Cohen et al.
patent: 5250488 (1993-10-01), Thelohan et al.
patent: 5332698 (1994-07-01), Nyssen et al.
patent: 5332699 (1994-07-01), Olds et al.
patent: 5401693 (1995-03-01), Bauer et al.
patent: 5843854 (1998-12-01), Karppinen et al.
DeMeringo Alain
Holstein Wolfgang
Lohe Peter
Schwab Wolfgang
Thelohan Sylvie
Group Karl
Isover Saint-Gobain
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