Mineral fibres

Details Mineral fibres Mineral fibres

1992-07-31

1994-05-17

Group, Karl

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

501 38, C03C 1306

Patent

active

053128060

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to mineral fibres which are resistant at high temperatures, and in particular high-temperature resistant mineral fibres for use in thermal insulation, e.g. in energy intensive furnaces.


THE PRIOR ART

Fireproof ceramic fibres are known which consist substantially of a major amount of SiO.sub.2 and Al.sub.2 O.sub.3, and optionally a minor amount of a further component, and which has a maximum temperature of use (MTU) of about 1500.degree. C. or more, cf. U.S. Pat. Nos. 4,240,833, 2,674,539 and 2,710,261, DE laid open patent applications Nos. 1,075,295 and 1,596,842 and NO laid open patent application No. 145,467. Such fibres are manufactured from a melt composed of a mixture of SiO.sub.2 and Al.sub.2 O.sub.3, and since this mixture does not melt until at a temperature of 1600.degree.-1900.degree. C. is reached the formation of the melt requires an electric furnace. As such, the costs associated with the manufacture of these fibres are relatively high.
Mineral fibres are another kind of fibres and they consist of a mixture of the following oxides: SiO.sub.2, Al.sub.2 O.sub.3, FeO or Fe.sub.2 O.sub.3, CaO, MgO and R.sub.2 O wherein R is Na and K. Examples of such mineral fibres are rock wool fibres which typically have an MTU of up to 750.degree. C. and which may be manfactured at relatively low costs in coke-heated shaft furnaces.
There is a need to provide low-cost mineral fibres having a somewhat higher MTU than ordinary rock wool fibres, viz. having an MTU of up to 850.degree. C.
DK patent application No. 5453/87 discloses inorganic fibres having an MTU of up to 815.degree. C. and having the following composition:


______________________________________ SiO.sub.2 : 55-64% by weight Al.sub.2 O.sub.3 : 0-10% by weight CaO: 29-44% by weight MgO: 0.1-30% by weight ______________________________________
Also, SE patent application No. 8406571-3 describes inorganic fibres having a higher MTU than that of ordinary rock wool fibres, viz. an MTU of up to 800.degree. C. These known fibres are manufactured from a chlorite-containing raw material which contains chlorite in an amount of more than 35%, preferably 40-45%, and has an iron oxide content of between 5 and 20%, preferably between 10 and 15%. The known fibres which may for instance have the following composition:


______________________________________ SiO.sub.2 : 40.9% Al.sub.2 O.sub.3 : 14.7% FeO: 5.3% Fe.sub.2 O.sub.3 : 8.3% CaO: 10.2% MgO: 6.8% K.sub.2 O + Na.sub.2 O: 3.3% MnO: 0.25% TiO.sub.2 : 3.0% ______________________________________ the relatively high from oxide content.
It is the object of the present invention to provide mineral fibres having an MTU which is substantially higher than the MTU of conventional rock wool fibres and which can be manufactured in conventional plants for the manufacture of rock wool fibres and which are not associated with the above-mentioned drawback.


SUMMARY OF THE INVENTION

This object is obtained with the mineral fibres of the invention, which have the following composition:


______________________________________ SiO.sub.2 : 34-42% by weight Al.sub.2 O.sub.3 : 31-38% by weight TiO.sub.2 : 0-1% by weight FeO: 2.5-7.5% by weight CaO: 17-21% by weight MgO: 0.5-4.3% by weight Na.sub.2 O: 0.3-1.5% by weight K.sub.2 O: 0.1-2.3% by weight ______________________________________
This composition is characterized in having a high content of SiO.sub.2 and Al.sub.2 O.sub.3 which provides an increased temperature resistance. The FeO content ensures that a sufficient amount of seed crystal forming agents is present, which is essential to the behaviour of the fibres at temperatures above the crystallization temperature. FeO and CaO reduces the viscosity to a suitable level. The MgO content is kept at a low level as the CaO content is high; thereby a melting temperature minimum which occurs when the MgO and CaO contents are within the same range is avoided.
It has been found that the fibre product according

REFERENCES:
patent: 2674539 (1954-06-01), Harter et al.
patent: 2710261 (1955-06-01), McMullen
patent: 3679443 (1972-07-01), Mechel et al.
patent: 4026715 (1977-05-01), Erickson et al.
patent: 4240833 (1980-12-01), Myles
patent: 4461840 (1984-07-01), Massol et al.
patent: 4720295 (1988-01-01), Bronshtein

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