WO2001060754A1

WO2001060754A1 - Man-made vitreous fibres and products containing them

Info

Publication number: WO2001060754A1
Application number: PCT/EP2001/001958
Authority: WO
Inventors: Marianne Guldberg; Soren Lund Jensen; Vermund Rust Christensen
Original assignee: Rockwool International A/S
Priority date: 2000-02-15
Filing date: 2001-02-09
Publication date: 2001-08-23
Also published as: AU2001237407A1

Abstract

Man-made vitreous fibres have a composition which includes, SiO2 40.0 to 44.0 %; Al2O3 17.0 to 21.0 %; CaO + MgO 20.0 to 30.0 %; TiO2 0 to 3 %; Na2O + K2O 0.5 to 5.0 %; FeO 3.0 to 10.0 %; Other Elements 0 to 5 %; and have particularly beneficial solubility and other properties, for instance having T50 below 40 days.

Description

Man-Made Vitreous Fibres and Products containing them

This invention relates to man-made vitreous fibres (MMVF) which are durable in use but which can be shown to be biologically advantageous.

Initial proposals for MMVF which were alleged to be advantageous as a result of being soluble in biological liquids involved the provision of fibres which generally had a low content of alumina. In 096/14454 and W096/14274 we described that advantageous biological solubility properties were obtained with higher amounts of alumina, with values of 14 or 16% upwards being exemplified in 096/14274 and amounts of 18% upwards being described and exemplified in 096/14454. Many of the fibres disclosed in 096/14454 and 096/14274 had Al₂0₃ above 21 or 22%. Many of the fibres have proved to be very interesting and valuable as fibres which are soluble in biological media, but there remains a desire to achieve an improved combination of biological solubility (especially when determined by in vivo tests such as rat lung tests) , and ease, efficiency and economy of manufacture.

The ease of manufacture problems arise because the compositions that provide the required analyses of MMVF are preferably fiberised using a cascade rotor process, for instance as described in WO92/06047. In a cascade rotor process, molten composition is poured on to the first rotor in a set of substantially horizontally mounted rotors, and the melt is thrown from that rotor on to a second rotor in the set off which it is thrown as fibres. Some melt is usually thrown off the second rotor onto a third rotor in the set off which melt is thrown as fibres, and in preferred processes melt is also thrown off the third rotor onto a fourth rotor off which it is thrown as fibres. In order that the fiberisation is conducted efficiently it is necessary to optimise the viscosity. Some of the materials and procedures required for making fibres having high Al₂0₃ contents (e.g. above 21%) are rather expensive. None of the fibres specifically exemplified in 096/14454 or W096/14274 achieve an entirely satisfactory combination of ease and cost of manufacture and solubility properties. In particular, there is a desire to provide fibres which have high biosolubility, but which can still be made by methods which are generally conventional and cost effective .

One method for determining biosolubility is by intra- tracheal tests, as described e.g. by Muhle et al in BIA- Report 2/98: Fasern - Tests zur Abschatzung der Biobestandigkeit und vum Verstaubungsverhalten (Fibres - Tests for estimating the biopersistence and dust conditions) . The result of such a test is the elimination half-time, T₅₀ of WHO-fibres, i.e. the time until half of the WHO-fibres injected in the rat lung have been eliminated.

Present standards are usually all satisfied if the fibres have a T₅₀ of less than or equal to 65 days using the above mentioned method for determining biosolubility but it would be desirable to be able to produce fibres having lower T₅₀ values, preferably below 50 days and most preferably 40 days or less for instance down to 35 or 30 days or less. In order to facilitate manufacture, the melt from which they are made should have a satisfactory viscosity, for instance 12 to 50 poise, more preferably 17 to 45 poise, most preferably 20 to 27 poise, at 1400°C. All viscosities herein are calculated in accordance with Bottinga and Weill, American Journal of Science 272, May 1972, pages 455 to 475.

Although a large number of fibres having a high Al₂0₃ content and which are described as having good biosolubility are known, none satisfy the new requirements that we specify above. For instance, other workers in the field have attempted to develop improved fibres. In WO97/30002 it is proposed to make fibres containing 35 to 45% Si0₂, 18 to 25% Al₂0₃, 0 to 3% iron oxide and 0 to 3% total alkali. In the only example, the fibre contains 40% Si0₂, 0.4% alkali and 1.7% iron. These fibres also contain phosphorous . Other phosphorous-containing fibres are described in WO99/08970 in which the amount of Si0₂ is 38 to 47%, Al₂0₃ 16 to 20%, alkali 0 to 6% and iron 3 to 10%. In each of the examples the amount of Si0₂ is 42% or more and the amount of alkali is 3% or less. In WO97/29057 the amount of Si0₂ is 30 to 51%, Al₂0₃ 11.5 to 25% and alkali 10 to 19%. A somewhat similar definition is given in DE-U-29709025 but the highest exemplified amount of Al₂0₃ is 15%.

In WO98/15503 various fibres having more than 18% alumina are exemplified. The highest amount of alkali is 2.3%.

The use of very high amounts of iron, as in example P of W096/14274 means that the fibre cannot conveniently be made using a cupola or other shaft furnace because of the inconvenience of handling the necessary very high iron- containing melts in such furnaces. Also, the fibres containing such high contents are esthetically unattractive. The use of the very low iron contents of, for instance, WO97/30002 tends to be associated with inferior thermal properties.

We have now found that it is possible to obtain a high biological solubility, and in particular having low T₅₀ as indicated above, by making the fibres from a composition which additionally has the property that it permits ease and economy of manufacture and provide fibres which have good physical and mechanical (including thermal) properties. In order to achieve this object it is necessary to select a very narrowly defined range of compositions within the general ranges disclosed in W096/14454.

In particular, we now provide novel MMV fibres having a composition which includes, by weight of oxides, Si0₂ 40.0 to 44.0% preferably 40.6 to 43.0% A1₂0₃ 17.0 to 21.0% preferably 17.5 to 20.3% CaO + MgO 20.0 to 30.0% preferably 24.2 to 28.2% Ti0₂ 0 to 3% preferably 0.6 to 2.6% Na₂0 + K₂0 0.5 to 5.0% preferably 1.0 to 4.0% FeO 3.0 to 10.0% preferably 4.8 to 7.8% Other Elements 0 to 5% preferably 0 to 2% It should be understood that any of the preferred lower or upper limits may be used in combination with any of the essential or preferred upper or lower limits for each element, and that any combination of the essential and preferred amounts for the different elements may be made. It is particularly preferred that the amount of Si0₂ should be at least 41.0% but not more than 43.0%, preferably from 41.5 or 42.0% up to 42.9%, and preferably 42.3 up to 42.9%. Either independently of this or combined with this, the amount of Al₂0₃ is preferably above 18.0% and most preferably above 18.5%. The amount of Al₂0₃ is preferably not more than 20%, most preferably not more than 19.2%, preferably below 19.0%.

The amount of Si0₂ + Al₂0₃ is generally below 63.0% and preferably below 62.0%. Preferably it is at least 60.0%, most preferably at least 60.8%, preferably at least 61.0%. The amount of Si0₂ + Al₂0₃ + 2R₂0 (where R is sodium and potassium) is preferably in the range 63.0% to 75.0%. Preferably it is at least 64.0% and often it is at least 65.0%. Generally it is not more than 70.0% and preferably it is not more than 69.0%.

Preferred amounts of CaO are generally in the range 15.0 to 22.0%. The amount is preferably above 16.0%, most preferably above 17.0%. The amount is usually not more than 20.0%, and preferably not more than 19.0%.

Preferred amounts of MgO are generally in the range 5.0% to 13.0%. The amount is usually at least 6.5% and often at least 7.5%. It is preferably not more than 11.0% and often not more than 9.0%. The ratio of CaO:MgO is preferably at least 1.8:1, generally at least 2.0:1 and usually below 3.0:1. The amount of CaO + MgO is usually not more than 27.0%.

The amount of Na₂0 + K₂0 is preferably at least 1.5% and often at least 2.0%. The amount is usually not more than 3.5%, often not more than3.0%. The ratio Na₂0 : K₂0 is usually at least 1:1, often 2:1 to 10:1.

If the amount of iron is too low the physical properties of the fibres, especially when heated, are likely to be adversely influenced. For instance the fibres will shrink and will not have good sintering properties. However if the amount is too high, as mentioned above, this makes the process of melting unsatisfactory when using a cupola or shaft furnace. The amount of iron is preferably at least 4.0 and usually at least 5.0%, for instance 5.5 to 7.0%. It is usually not more than7.5%. Throughout this specification, the amount of iron is quoted as FeO.

Preferably the amount of FeO + MgO is at least 10.0%, especially at least 13.0%, but is often below 18.0%.

The amount of P₂0₅ is usually in the range 0 to 5.0%, usually 0-1% preferably 0 to 0.3%, for instance 0.1 to 0.3%. Generally therefore the composition is free of P₂0₅ or, at least, no deliberate addition of phosphorous is made. Other elements may be present in minor quantities, for instance as impurities in raw materials, or as a result of deliberate additions.

The preferred fibres of the invention are formed from melts which have a viscosity under these conditions of 12 to 50 poise, preferably 17 to 45 poise. The viscosity is usually above 20 or 23 poise. It is usually not more than

32, 30 or 27 poise.

The analytical values quoted above can be determined by averaging the result of three analyses of the same product in conventional manner. As a result of selecting the amounts within the narrowly defined ranges we have provided fibres which do give an improved balance of ease of good economy of manufacture, physical and mechanical properties in use and good in vivo solubility. The predominant advantage of the invention is that the fibres can have very satisfactory T₅₀, in particular can provide T₅₀ values which are desired, as indicated above, and can be made in an economically efficient manner. Thus the invention provides fibres having T₅₀ below 50, preferably below 40 and often even lower, as indicated above, having a composition which facilitates cost effective manufacture.

The fibres can be made by forming a melt using an appropriate mineral charge which is combination of rock and/or briquettes that will provide the desired composition, melting this in a cupolar or other shaft furnace or other appropriate furnace then forming the melt into fibres by any convenient fibre-forming process. Preferably the melting occurs while the charge is in the form of a self-supporting stack.

Many of the fibre compositions which we have previously found to give particularly beneficial biosolubility results have an overall analytical content, and in particular an alumina content, which necessitates the use of raw materials which increase the cost of the product compared to other fibres having inferior biosolubility. For instance it may be necessary to use finely divided raw materials, which in practice therefore have to be introduced in the form of briquettes, especially when the charge is to be melted as a self-supporting stack in a cupola or other appropriate furnace.

As a result of the composition which is now used, it is possible to increase the proportion of coarse material in the charge and to reduce (or eliminate) the proportion of briquetted material which has to be used.

The fibre-forming process may be a spinning cup process but is usually a cascade spinner process such as is described in WO92/06047. The fibres may be collected as a web and converted into MMVF products, such as a bonded batt, all as described in W096/14454 and W096/14274.

The fibres may be made in conventional manner, for instance by melting a mineral charge in a cupola furnace to provide a melt which has an analysis such as to provide the defined fibre analyses.

Instead of or in addition to defining the biosolubility by in-vivo tests, the fibres can also be characterised by having a high dissolution rate in buffered Gamble's solution of pH 4.5, for instance when tested by the in-vitro flow through test described by Knudsen et al "New type of stonewool (HT fibres) with a high dissolution rate at pH = 4.5 (Glastechnische Berichte, Glass Science and Technology 69 (1996) ) . The fibres also have a moderately increased dissolution rate at pH 7.5.

Additionally, the fibres have good resistance to atmospheric humidity and so can be used for insulation purposes where they will be exposed to atmospheric conditions. They also have good resistance to degradation by aqueous nutrients and other aqueous liquids which would be encountered when the fibres are used as products which serve as horticultural growth substrates.

Preferred fibres have the following compositions in % by weight of oxides:

Fibre A B C D

Si0₂ 41.1 43.2 41.3 42.6

A1₂0₃ 19.7 18.6 19.9 18.9

Ti0₂ 1.3 1.1 1.0 1.6

FeO 7.2 6.3 3.2 6.3

CaO 15.3 16.4 16.8 18.1

MgO 10.3 6.8 12.7 7.8

Na₂0 2.7 3.4 2.6 1.9

K₂0 0.7 1.6 0.9 0.9

P₂0₅ 0.3 0.1 0.2 0.2

MnO <0.1 0.2 <0.1 <0.1

Viscosit-' 26 44 26 29 The viscosity of the composition is the value at 1400°C calculated as defined above and is quoted in poise. The fibres have T₅₀ below 40 days and often even lower.

The invention includes the use of a melt composition to provide fibres having the defined composition and which are biosoluble, in particular as indicated by T₅₀ of not more than 40 days, preferably not more than 35 days and most preferably less.

The invention also includes the use of a melt composition to make fibres which are shown to be biodegradable, for instance preferably by the T₅₀ method given above but alternatively by any of the other available methods as mentioned above or in W096/14274, and wherein the fibres have the analysis given above, especially when the fibres are the fibres of a bonded product, for instance which is used as thermal insulation, fire insulation or protection or noise regulation protection, or as horticultural growth medium, or wherein the fibres are used in free form as reinforcement or as a filler. The invention also includes a method of making man- made vitreous fibre products comprising forming one or more mineral melts and forming fibres from the or each melt wherein the melt viscosity and biosolubility of fibres are determined (for instance by any of the methods described in W096/14274 or by the T₅₀ method or other methods described above) and a composition is selected which has a suitable viscosity (generally 10 to 40, preferably 10 to 30 poise, at 1400°C) and an appropriate biosolubility and fibres are made from the selected composition, and bonded or unbonded products are made from the fibres.

The selected fibres may be provided in any of the forms conventional for man-made vitreous fibres. Thus they may be provided as loose unbonded fibres, for instance being used as free fibres for reinforcement of cement, plastics or other products or as a filler as an unbonded insulation. More usually the fibres are provided with a bonding agent, generally as a result of forming the fibres and collecting them in conventional manner in the presence of a bonding agent. The resultant product is consolidated as a slab, sheet or other shaped article. Bonded products may take the form of slabs, sheets, tubes or other shaped articles that are to serve as thermal insulation, fire insulation and protection or noise reduction and regulation, or in appropriate shapes as horticultural growing media.

The entire disclosure of W096/14454 and W096/14274, and US patents 5,932,500 and 5,935,886 filed by the present inventors, is incorporated herein by reference.

Claims

1. Man-made vitreous fibres having a composition which includes

Si0₂ 40.0 to 44.0% A1₂0₃ 17.0 to 21.0% CaO + MgO 20.0 to 30.0% Ti0₂ 0 to 3% Na₂0 + K₂0 0.5 to 5.0% FeO 3.0 to 10.0% Other Elements 0 to 5%

2. Fibres according to claim 1 having a composition which includes, by weight of oxides

Si0₂ 40.9 to 43.0%

A1₂0₃ 17.5 to 20.

3% CaO + MgO 24.2 to 28.2%

Ti0₂ 0.6 to 2.6%

Na₂0 + K₂0 1.0 to 4.0%

FeO 4.8 to 7.8%

Other Elements 0 to 2% 3. Fibres according to any preceding claim in which the amount of Al₂0₃ is not more than 19.0%.

4. Fibres according to any preceding claim in which the ratio CaO: MgO is at least 1.8:1.

5. Fibres according to any preceding claim in which the amount of CaO is from 17.0 to 22.0% and the amount of MgO is from 5.0 to 9.0%.

6. Fibres according to any preceding claim in which the amount of FeO is at least 5.0%.

7. Fibres according to any preceding claim in which the amount of CaO + MgO is not more than 27.0%.

8. Fibres according to any preceding claim in which the amount of Si0₂+Al₂0₃ is 60.8 to 62.0%.

9. Fibres according to any preceding claim in which the amount of Al₂0₃ is 18.5 to 19.5%.

10. Fibres according to any preceding claim in which the amount of Si0₂ is 42.0 to 42.9%.

11. Fibres according to any preceding claim m which the amount of CaO is 16.0 to 19.0%.

12. Fibres according to any preceding claim having T₅₀ not more than 40 days.

13. Use of a melt composition to make man-made vitreous fibres which are shown to be biodegradable in the lung wherein the fibres have T₅₀ below 40 days and have a composition as defined in any of claims 1 to 12.

14. Use according to claim 13 in which the fibres are the fibres of a bonded product.

15. Use of fibres according to any of claims 1 to 12 in the manufacture of insulation or horticultural growth substrate products.

16. A method of making fibres according to any of claims 1 to 12 comprising forming a melt from a mineral charge in a shaft furnace wherein melting occurs while the charge is in the form of a self-supporting stack, and forming fibres from the melt by a cascade spinning process.