CA2335591A1

CA2335591A1 - Man-made vitreous fibres

Info

Publication number: CA2335591A1
Application number: CA002335591A
Authority: CA
Inventors: Marianne Guldberg; Soren Lund Jensen
Original assignee: Individual
Current assignee: Rockwool AS
Priority date: 1998-06-30
Filing date: 1999-06-30
Publication date: 2000-01-06
Also published as: GB9814179D0; EP1098858A1; HUP0102949A2; DE19840397A1; WO2000000444A1; AU4902899A; PL345280A1

Abstract

The invention provides a product comprising man-made vitreous fibres formed from a composition which includes, by weight of oxides, SiO2: 46 to 58 %, Al2O3: 0.8 to 3 %, FeO: 5 to 6.8 %, TiO2: 0 to 4 %, CaO: 0 to 40 %, MgO: 0 t o 30 %, Na2O + K2O: 0 to 1 %, P2O5: 0.2 to 10 %, others: 0 to 10 %.

Description

WO 00/00444 PCT/EP99l04513 MAN-MADE VITREOUS FIBRES
The preseni~ invention concerns man-made vitreous fibres (MMVF), which have a solubility in biological fluid (biosolubility) which is considered to be acceptable, which are durable in use and which give goad fire resistance properties.
It is well known to make MNIV fibres from mineral melt.
A combination of raw materials is melted in a furnace to provide a mineral melt having the desired chemical composition and ~Ls then formed into fibres. These are used for various purposes including heat insulation, fire protection, sound insulation etc.
Although there is no scientific evidence establishing that there is a health risk associated with manufacture and use of MMV fibres, it is nevertheless commercially desirable to provide MMV fibres which can be said to be of improved biological safety. Biological safety is usually measured on the basis of an in vitro test which assesses the dissolution rate of the fibres in a liquid which is intended to simulate lung liquid, such as Gamble's solution at about pH 7.5.
Various patent applications have been published describing fibres which are said to give improved dissolution rate in such an in vitro test. These include EP-A-459897, W09<'!/09536, W093/22251 and DE 4443022. We also describe biosolulble fibres in our publications W090/02713 and W095/21799.
Although fibres disclosed in, in particular, W095/21799 have proved to be interesting and valuable as fibres which are soluble in biological media, there remains a desire to ach:Leve improved biological solubility. In particular there is a desire to achieve improved biological solubility when determined by in vivo tests. It is also desirable to achieve this biological solubility together with ease and efficiency of manufacture and with good physical properties of the fibres.
CQ~NFI~NIATtO~ C4~'l In particular, there is a desire to provide fibres which have improved bio solubility. Fox instance, there is a probability that the required standards of biosolubility will continue to increase. In particular, 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 Ab:achatzung der Biobestandigkeit and vum verstaubungsverhalten (Fibres - Tests for estimating the biopersistence and dust conditions). The result of such a test is the elimination half-time, T5p of WHO-fibres, i.e.
the time until half of the WHO-fibres injected into the rat lung have beem eliminated.
A T5o of less than or equal to 65 days is normally satisfactory ai;. present but it would be desirable to produce fibres :having even lower TSO.
According to the invention we provide a product comprising man-made vitreous fibres formed from a composition which includes, by weight of oxides, 5102 46 to 58 %
A1203 0.8 to 3%
Fe0 5 to 6.8%
Ti02 0 to 4 Ca0 0 to 40%
Mg0 0 to 30%
Na20 + K20 0 to 1%
P205 0 . 2 to 10 Others O to 10%.
We find that this particular combination of components in the defined ,amounts, in particular the selected ranges of FeO, Al~o~ and alkali metal (Na20 + K20) , especially the narrow range of FeO, give a good combination of durability in use and bio:aolubility. It is particularly surprising that biosolubility can be obtained with the very low levels of alkali metal, since these elements tend to enhance biosolubility. 7:n addition, the fibres can be produced from readily available starting materials and the fibres have good thermal stability, fire resistance and insulation properties.
In this specification the amounts of all elements are given by weight of their oxide. For simplicity, all iron oxide is quoted a,s Fe0 even though some iron may be present as Fe2o3.
The amount of Si02 is from 46 to 58%. Usually it is at least 50 % , preferably at least 54 % . In some cases it can be preferred that S.i02 is not more than 56%.
The amount of A1203 is from 0 . 8 to 3 % . Usually it is at least 0.9 or at least 1%. In some cases it may be at least 1.1%. In general it is not more than 2.5%, preferably not more than 2 % .
The amount of Fe0 is from 5 to 6.8%. In particular it is often at least 5.5%.
In the invention it is preferred that the iron should mainly be in the ferrous state (rather than in the ferric state). Preferably at least 7~%, more preferably at least 80%, of the iron is ferrous. For instance at least 90 or 95 % by weight of the iron is present in ferrous form in the product of the invention.
The amount of Ti02 is not more than 4%. It may be at least 0.2%, prefE~rably at least 0.5%. In some compositions it can be at least 0.8 or 1%. It is generally not more than 2% and preferably not more than 1.5%. In some cases it is preferably not more than 0.5 or 0.2%.
The amount of Ca0 is from 0 to 40 % . Generally it is at least 10%, preferably at least 15%. In general it is not mare than 30 or 25%. It can be not more than 20% but in some cases amounts of at least 20% are beneficial, in particular if Mg~O is below 10 or 8%.
The amount of Mg0 is from 0 to 30%. It may be at least 8 or 100, although it can be below this, eg from 6 to 8 or 9%, in particular if Ca0 is at least 15 or 20%. Preferably it is not more than 20%, more preferably not more than 18%
and most preferably not mare than 15%.

- . WO 00/00444 PCT/EP99104513 The tota l amount o f. a lka l i meta l { Na20 + K2o ) in the invention is very low and ranges from 0 to 1%. In particular it is not more than o.8%, preferably not more than 0.6%. Generally the amount of NazO + K20 is at least 0.1%, and can be at least 0.2%, although in some preferred cases it is partLcularly low and is below 0.2%.
In the product of the invention the fibres must contain P205. It is present in an amount of 0.2 to 10%. In some fibres preferred according to the invention the amount is not. more than 5%, preferably not more than 4%. The amount of P205 can preferably be not more than 2%. In these cases it is particularly surprising that we obtain good biosolubility properties, since it has been stated in various publicatp.ons that the inclusion of a high amount of P205 is required to achieve good biosolubility. The amount of P205 is preferably at least 0 . 5 % . The amount of P205 can in some cases be from 0.2 to 3%. In other preferred compositions the amount of P205 is at least 4%.
In the invention the ratio of P205/ (A1203 + Feo) is preferably not more than 0.8, more preferably not more than 0.7 and in particular not more than 0.45. It is also surprising that we can obtain, with the claimed compositions, good biosolubility at this value of that ratio, since in the publication W092/09536 it is stated that the ratio should be as high as possible {whilst not exceeding 6} and in the examples of the invention in that publication it is always at least 0.9. In the invention the ratio can preferably be below 0.35.
We also find that in the invention it is preferred that the sum of Ca0 + Mg0 + Na20 + K20 + 2P205 - 4A12O3 (based on wt.% of each oxide) is at least 25. Preferably it is at least 3t), more preferably at least: 31, most preferably at least 32 or 33. It may in particular be at least 34. This is necessarily an approximation and solubility should be determined experimentally using an appropriate protocol, but we find in general that as the value of this sum increases, the solubility of the fibres can increase.
The fibres in the product of the invention may contain various other elements in a total amount up to 10%.

5 Preferably the amount of other elements is not more than o, more preferably not more than 3% and in particular not more than 2%. Other elements which can be contained in the fibres include B~_o3, BaO, Zro2, MnO, Zn~, F, C1, Cr203 and V20$. If B203 is present it is usually present in an amount of not more than 5 p . In particular the amount of B203 is preferably less than the amount of P205.
An advantage of the composition of the invention is that it can be produced as a mineral melt having advantageous melt viscosity. In this specification melt viscosity is viscosity in poise at 1400°C, measured by rotation viscomet:.ry or calculated according to Bottinga and Weill, American ,:journal of Science, Volume 272, May 1972, pages 455 to 475. Since P205 is not included in this calculation the presence of P205 is taken into consideration by equalising 1 mole % of P205 with 2 mole % Si02 plus 1 mole o Cad. Laboratory tests have shaven that this approximation is valid within actual chemical ranges.
The composit:.ion of the invention preferably provides a melt which has, viscosity at 1400°C at least 10 poise, preferably at least 15 poise and often at least 17 poise.
Although it may be as high as 60 poise, generally it is not more than 40 poise and preferably is not more than 30 poise. The rangEa of 24 to 28 poise is advantageous. The viscosity can be not more than 25 poise and in particular not more than 20 poise.
In this specification biosolubility is measured in terms of dissolution rate in Gamble's solution. Dissolution rate is determined by a flaw-through technique, as follows.
The modified Gamble's solution used has the following composition .
MgCl-~ . 6H~0 0 . 212 NaCI 7.120 CaCl2. 2H20 0. 029 Na250q 0 . 079 Na2HP09 0. 148 Na2HC03 1. 950 (Na2-tartrat:e) .2H20 0.180-(Na3-citrate:) .2H20 0.152 90% lactic .acid 0.156 Glycine 0.118 Na-pyruvate 0.172 Formalin 1 ml The fibre diameter distribution is determined for each sample by measuring the diameter of at least 200 individual fibres by means of the intercept method and a scanning electron micro.~cope ar optical microscope (100 x magnification). The readings are used for calculating the specific surface of the fibre samples, taking into account the density of the fibres.
Based on the dissolution of Si02 (network dissolution), i~he specific thickness dissolved is calculated and the rate of dissolution established (nm/day). The ca:Lculatians are based on the Si02 content in the fibres, the specific surface and the dissolved amount of Si.
The dissolution rate by the flow-through method is determined as follows. lOmg of fibres are placed in a flow cell in a polyca:rbonate filter holder {diameter, 40 mm). A
0.8~cm filter is ;placed on the inlet side (top) and a 0.2~Cm filter is placed on the outlet side (bottom) to avoid loss of fibres during the test. Both filters are made of cellulose nitrate. The flow rate of the modified Gamble's solution is around 200m1/day and is maintained at this rate by a peristaltic pump. The ratio of liquid flow to surface area of the fibres is 1 to 2~m/second.
The pH of the solution is maintained at 7.6 ~ 0.2 by bubbling with Nz/C02 (95/5) . The entire set--up, including storage containers, is maintained at 37 ~ 0.7°C. Effluent solution is collected once a week for a two hour period and analysed for Si a.nd Ca. Analyses are made on a Perkin-Elmer atomic absorption spectrophotometer (AAS). Further details axe given in Environmental Health Perspectives, Volume 102, Supplement 5, October 1994, page 83.
In the invention the fibres preferably have solubility measured by this test of at least 60 nm/day, more preferably at least 80 or 100nm/day. More preferably the solubility is at least 120 or 130nm/day. It may even be at least 150 or 160:nm/day.
Biological solubility can also be measured by the in vivo test discussed above which gives a value of TSO. The fibres of the invention preferably have T5o not more than 60, more preferably not mare than 50 and in particular not more than 45, especially not more than 40.
In the invention we can provide products which give good solubility in the test described above but give T5o values which are unexpectedly low in view of this in vitro solubility.
The fibre products of the invention are made in conventional manner. The composition is usually formed by blending appropriate amounts of naturally occurring raw materials, such as rock and sand materials and recovered waste materials. These include converter slag, other stags, glass, foundry sand, limestone, magnesite, brucite, talc, serpentinite, pyroxenite, apatite, wollastonite, quartz sand, olivine sand, iron ore, dolomite, and MMVF waste.
The composition ran be converted to a melt in conventional manner, for instance by melting the raw materials in an electric furnace or in a cupola furnace.
The melt is preferably produced in a cupola furnace.
The melt is formed into fibres by canventional processes comprising pouring the melt into or onto a rapidly spinning; fiberising rotor and causing the melt to be flung from the periphery of the rotor as fibres. The rotor may be a spinning cup type of rotor or a rotor having a solid periphery which is usually mounted about a - . WO 00/00444 PCT/EP99/045I3 substantial horizontal axis. Rotors of this type can be arranged as a ca:~cade system.
The fibres can be formed into MMVF in conventional manner by laying down the fibres in the presence of binder typically in an amount of from 0.5 to 4%, often around 1 to 2% by weight of the product. Conventional MMVF binders can be used.
The product: may be used for any of the purposes for which MMVF products are known. These include thermal insulation, fire insulation and protection, noise reduction and regulation, horticultural growing media or as free fibres for rein:Eorcement of cement, plastics or other products or as a f i l ler . They may be provided in any of the conventional forms such as slabs or batts, sheets, pipe sections or other shaped products, or may be comminuted to a granular produces.
The invention will now be illustrated with reference to the following examples.
Examples In each of the examples below, raw materials are melted to form a smelt which has the composition given below in Table 1. The :melt is formed into fibres by means of a cascade rotor system. The fibres are collected as an air laid web and treated to form a product. The melt viscosity at 1400°C is given below for each composition. For each fibre compositio?n the solubility under the in vitro test discussed above :is also given.

Table 1 Composition wt% 1 2 3 4 Si02 57.2 55.7 55.9 55.2 A1203 0.9 1.0 1.0 1.8 Ti02 1.2 1.2 1.2 0.1 Fe0 5.8 6.5 6.8 5.7 Ca0 18.2 20.1 18.1 22.1 Mg0 13.0 11.1 12.9 7.4 Na20 0.3 0.6 0.3 <0:1 K20 0 . 1 0 . 2 0 . 1 < 0 .

p20~ 3.2 3.5 3.7 5.0 P20~,/ (A120~+Fe0) 0.44 0.43 0.44 0. 66 Viscosity at 19.5 17.7 17.2 25.7 1400C poise Solubility nm/day 15C 168 161 102

Claims

1. A product comprising man-made vitreous fibres formed from a composition which includes, by weight of oxides, SiO2 ~ 46 to 58 %
AlO3 ~0.8 to 3%
FeO ~ 5 to 6.8%
TiO2 ~ 0 to 4 CaO ~ 0 to 40%
MgO ~ 0 to 30%
Na2O + K2O 0 to 1 P2O5 ~0.2 to 10 Others ~ 0 to 10%.

2. A product according to claim 1 in which the composition includes P2O5 in an amount of at least 0.5%.

3. A product according to claim 1 or claim 2 in which the composition includes P2O5 in an amount of not more than 5%.

4. A product according to claim 1 in which the composition includes P2O5 in an amount of from 0.2 to 3%.

5. A product according to claim 1 in which the composition includes P2O5 in an amount of not more than 2%.

6. A product according to any preceding claim in which the composition includes Al2O3 in an amount of not more than 2.5%, preferably not more than 2%.

7. A product according to any preceding claim in which the composition includes Al2O3 in an amount of at least 1%.

8. A product according to any preceding claim in which the composition includes TiO2 in an amount of at least 0.8%, preferably at least 1%.

9. A product according to any of claims 1 to 7 in which the composition includes TiO2 in an amount of not more than 0.5%, preferably not more than 0.2%.

10. A product according to any preceding claim in which the ratio P2O5/(Al2O3+FeO) in the composition is not more than 0.7.

11. A product according to claim 10 in which the ratio P2O5/ (Al2O3 + FeO) in the composition is not more than 0.45.

12. A product according to claim 11 in which the ratio P2O5/ (Al2O3 + FeO) is not more than 0.35.

13. A product according to any preceding claim in which the composition includes FeO in an amount of at least 5.5%.

14. A product according to any preceding claim in which the composition includes CaO in an amount of at least 20%.

15. A product according to any preceding claim in which the composition includes MgO in an amount of not more than 9%.

16. A product according to any preceding claim in which the sum of Na2O + K2O is not more than 0.2 %.

17. A product according to claim 1 in which the composition includes P2O5 in an amount of at least 4%.

18. A product according to any preceding claim in which the amount of other elements is not more than 3%.

19. A product according to any preceding claim in which the sum of (CaO + MgO + Na2O + K2O + P2O5 - 4Al2O3) is at least 32%.

20. A product according to claim 19 in which the sum of (CaO + MgO + Na2O + K2O + 2P2O5 - 4Al2O3) is at least 34%.

21. A product according to claim 19 in which the composition comprises 54 to 56% SiO2, 1.1 to 2% Al2O3, not more than 2% TiO2, at least 5.5% FeO, at least 15% CaO, not more than 15% MgO, not more than 0.6% Na2O + K2O, at least 0.5% P2O5, and not more than 3% other elements.

22. A product according to claim 21 in which the composition includes from 1.5 to 2% Al2O3, not more than 0.5% TiO2, 5.5 to 6% FeO, 20 to 25% CaO, 6 to 9% MgO, less than 0.2% Na2O + K2O and at least 4% P2O5.