Man-made vitreous fiber wool

Details Man-made vitreous fiber wool Man-made vitreous fiber wool

1996-04-08

1997-11-25

Bell, Mark L.

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

501 38, 501 70, 65454, C03C 1306, C03B 3704

Patent

active

056912552

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to man-made vitreous fibre (MMVF) wool containing iron and a relatively high amount of alkaline earth metals, and a low amount of alkali metals, conventionally known as stone, slag or basalt wool.
Various types of MMV fibres are known.
It is known, in the manufacture of traditional glass fibres, to include in the glass melt components which provide boron oxide (borate). This can improve the glass and the glass melt. However, borate-containing raw materials are expensive and are normally not added at all if possible, especially when the product contains iron and has low alkali and high alkaline earth content, as in conventional rock, stone and slag melts.
Glass wool products usually have a relatively high content of alkali metal (often above 13% Na.sub.2 O+K.sub.2 O). In this specification all analyses are expressed by weight of total composition measured as oxides. Glass filament and glass wool are usually free of iron but often also contain boron. Typically they contain less than 7% Al.sub.2 O.sub.3. However E-Glass is a filamentary or other non-wool product and can have high aluminium and low or zero alkali metal. For instance JP-A-50090719 describes an E-Glass containing 15-16% Al.sub.2 O.sub.3, 9.5-10.5% B.sub.2 O.sub.3 and 5% P.sub.2 O.sub.3. It is free of iron and sodium.
Glass fibres are described in EP-A-9418 which can have a wide range of optional components including, inter alia, iron, boron and phosphorous. None of the exemplified compositions contain both boron and phosphorous and they all have above 13% alkali metal oxide.
WO93/07741 describes fibres containing 0 to 4% P.sub.2 O.sub.5, above 13% Na.sub.2 O, and up to 8% Al.sub.2 O.sub.3 for use in horticulture. B.sub.2 O.sub.3 can be present but the total amount of impurities (including any B.sub.2 O.sub.3 which is included) must be not above 1%.
Glass wool is described in EP-A-412878 which has high alkali metal content (above 13%) and which contains borate. It is free of iron. Phosphorous is an optional component. It is included allegedly to improve solubility of the fibres.
We are concerned with improving the solubility of the fibres in those wools generally referred to as rock, stone, slag or basalt wools and which typically contain iron, a low amount of aluminium (below 10%), a low amount of alkali metal (below 7%) and a significant amount of alkaline earth metal (above 12%).
It has been proposed that it would be desirable to provide such wools in which the MMV fibres are soluble in a physiological medium, in particular lung fluid.
It is known that the composition of a fibre can significantly affect its solubility. For instance, it is illustrated in WO87/05007 that fibres having a low alumina content, in particular alumina below 10% by weight of composition, have improved solubility in a physiological environment. It is also known that inclusion of phosphorus can improve solubility in the physiological medium. This has been illustrated in the case of stone wool fibres in for instance EP-A-459,897. This discloses stone wool fibres which comprise 1 to 10% of phosphorus as P.sub.2 O.sub.3. This component is said to provide solubility in the physiological medium. It can be assumed that increasing the amount of phosphorous within this range increases solubility.
During the manufacture of MMVF wool the components which are to form the fibres are melted in a furnace, such as an electric, shaft, tank or cupola furnace. This produces a melt which may then be fiberised. The melt usually has a melting point of around 1,400.degree. to 1,600.degree. C. and is thus heated to above this temperature in the furnace. It has been found that the inclusion of significant amounts of phosphorous in the melt can lead to some problems. For instance phosphorus may volatilise in the furnace, leading to difficulties of controlling the composition. In particular increasing the amount of phosphorus can adversely influence melt viscosity and properties. It increases the risk of the melt (which contains iron and

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Database WPI, Section Ch, Week 7710, Derwent Publications Ltd., London, GB; Class F, AN 77-16933Y & JP,A,50 090 719 (Nihon Muki Zairyo) 21 Jul. 1975.

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