| Title of Invention | "A PROCESS FOR THE PREPARATION OF MINERAL WOOL". |
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| Abstract | A process for the preparation of mineral wool capable of being dissolved in a physiological medium, said mineral wool comprises the constituents below in the following percentages by weight: SiO2 38-52%, preferably 40-48% Al2O3 17-23% SiO2+Al2O3 56-75%, preferably 62-72% RO(CaO+MgO) 9-26%, preferably 12-25% MgO 4-20%, especially 7-16% MgO/CaO >0.8, preferably 1.0 or > 1.15 R2O(Na2O+K2O) > 2% P2O5 0-5% Fe2O3(total Iron) > 1.7%, preferably >2% B2O3 0-5% MnO 0-4% TIO2 0-3% comprising the steps of melting followed by fiberizing the molten composition by internal centrifugation to obtain the mineral wool. |
| Full Text | The present invention relates to the field of artificial mineral wool. It is aimed more particularly at mineral wool intended for manufacturing thermal and/or acoustic insulation materials or soilless-culture substrates. It concerns more particularly mineral wool of the rock-wool or basalt-wool type, that is to say the chemical compositions of which involve a high liquidus temperature and a high fluidity at their fiberizing temperature. Conventionally, this type of mineral wool is fiberized by so-called "external" centrifuging processes, for example of the type of those using a cascade of centrifuging wheels fed with molten material by a static delivery device, as described in particular in Patents EP-0,465,310.or,ER-0l439,385. The process of fiberizing by so called "internal" centrifuging, that is to say using centrifugers rotating at high speed and drilled with holes, is on the other hand conventionally reserved for fiberizing mineral wool of the glass-wool type, broadly having a composition richer in alkali metal oxides, a lower liquidus temperature and a higher viscosity at the fiberizing temperature than rock wool or basalt wool. This process is, for example, described in Patents EP-0,189,354 or EP-0,519,797. However, technical solutions have recently been developed which allow the internal centrifuging process to be adapted for fiberizing rock wool or basalt wool, especially by modifying the compostion of the material of which the centrifugers are composed and their operating parameters. For more details on this subject the reader may refer in particular to Patent WO 93/02977. This adaptation has proved to be particularly beneficial in that it makes it possible to combine properties which hitherto were not inherent in either of the two types of wool - rock or glass. Thus, 2 the rock wool obtained by internal centrifuging is comparable in quality to that of glass wool, with a lower unfiberized content than that of rock wool obtained conventionally. However, it retains the two key aspects associated with its chemical nature, namely a low chemicals cost and a very high fire resistance. There are therefore two possible ways of fiberizing rock or basalt wool, the choice of one or the other depending on a number of criteria, including the required level of quality with regard to the intended application and that of industrial and economic feasibility. To these criteria have been added in recent years that of biodegradability of mineral wool, namely its ability to be rapidly dissolved in a physiological medium, so as to prevent any potential pathogenic risk associated with the possible accumulation of the finest fibres in the body by inhalation. The object of the invention is therefore to improve the chemical composition of mineral woo! of the rock or basalt type, the improvement being aimed especially at increasing its biodegradability and/or at reconciling biodegradability with ability to be fiberized by internal centrifuging (without, however, excluding other fiberizing methods). The subject of the invention is a mineral wool capable of being dissolved in a physiological medium, which comprises the constituents below in the following percentages by weight: SiO2 38 - 52%, preferably 40 - 48% AI2O3 17-23% SiO2+ AI2O3 56 -75%, preferably 62 - 72% RO (CaO and/or MgO) 9 - 26%, preferably 12 - 25% MgO 4 - 20%, especially 7 -16% MgO/CaO > 0.8, preferably > 1,0 or > 1.15 R2O (Na2O and/or K2O) > 2% P2O5 0 - 5% Fe2O3 (total iron) > 1.7%, preferably > 2% MnO 0 - 4% B2O3 0 - 5% TiO2 0-3% 3 It may also furthermore comprise, preferably, Fe2O3 (total iron) and P2O5 contents such that: 1 0.5% (Throughout the rest of the text, any percentage of a constituent of the composition should be understood to mean a percentage by weight and the compositions according to the invention may include up to 2 or 3% of compounds to be regarded as unanalysed impurities, as is known in this type of family of compositions). The selection of such a composition has allowed a whole raft of advantages to be built up, especially by varying the many complex roles that a number of its specific constituents play. Thus, what is involved is a mineral wool composition of the rock wool type, in which its content of alkali metal oxides (RaO) essentially in the form of Na2O and/or K2O is modest, less than 12 or even less than 10 or even 8%. At the same time, its content of alkaline-earth metal oxides (RO), essentially in the form of CaO and/or MgO, is relatively high, at least 9% and even more at least 12% or even 16%. The iron oxide content (measured in the form of Fe2O3 but, by convention, corresponding to the total iron content) was set at a relatively significant level of at least 1.7% and even more of at least 5%. Such a content present in the composition is most particularly justified when the composition has to be fiberized by internal centrifuging, as it was observed that this made it possible to slow down the rate of corrosion of the materials of which the centrifuger is composed. Manganese oxide MnO could in particular play a similar role - this is why the composition may optionally contain a few percent of MnO, Moreover, the viscosity at fiberizing of such a composition may be high enough for internal centrifuging and it may be termed a "hard rock" composition, this being due in particular to a suitable silica and alumina content. As regards its biodegradability, it was already known that, especially in compositions of the rock-wool type, certain compounds, such as P2O6, could considerably improve this, while other oxides seemed on the contrary to have a tendency to reduce it, at the very least in neutral pH. Reference may be made, for example, to Patents EP-0,459,897 and WO 93/22251. However, a massive addition of P2O5 has not proved in the context of the invention to be the most 4 judicious approach. This is because other considerations may arise, for example economic ones (P2O5 coming from expensive raw materials) and also technical . ones - the changes in the proportions of P2O5, and especially of alumina, in the composition may cause other of its properties to vary in an undesirable or unknown manner. Thus, P2O5 is not without influence on the viscosity of the composition, just like alumina. However, most particularly in the case of compositions of the rock-wool type to be fiberized by internal centrifuging, to which the invention applies most advantageously, the viscosimetric behaviour of the composition is a very critical and important criterion to be controlled and regulated sufficiently. Moreover, certain compounds may be advantageous for certain properties but be unfavourable for obtaining a high degree of biodegradability, something o that seems to be the case with iron, which is advantageous, as mentioned above, for prolonging the life of centrifugers but which could tend to reduce the biodegradability of rock wool, or the case with alumina, which is judicious for regulating the viscosity of the composition but may not be very favourable with regard to biosolubility, especially when measured by in vitro tests in neutral pH. The invention has therefore established a judicious compromise between all this data, essentially in the following manner: the composition may contain P2O5, but in a modest amount of at most 5%, or rather at most 4%. It also contains iron oxide, which is advantageous, but for reasons other than biodegradability. However, the composition achieves a high level of biodegradability without adding an excessive amount of P2O5 (or any other very special compound regarded as being favourable to biodegradability), by another means, which consisted, in particular, in varying the relative proportion of MgO with respect to CaO. In fact, compositions of the rock-wool type generally contained a proportion of lime CaO which is greater than that of magnesia MgO. By reversing this ratio, it has been found that the high level of biodegradability hitherto only able to be obtained with high P2OS contents, in order to "compensate" for the significant alumina and iron contents, could be achieved. A subsidiary, and not insignificant, advantage associated with a low P2O5 content should be noted, namely too much P2O5 tends in fact to jncrease the liquidus temperature of the composition, which is obviously not favourable for fiberizing by internal centrifuging. 5 Another characteristic aspect according to the invention relates to the combination of this particular MgO/CaO ratio with a rather high alumina content, since this is at least 17%. It has been found that this combination allowed the biosolubility criteria, both measured in in vitro tests in neutral pH and in in vitro tests in acid pH, to be satisfactorily met. Indeed, the matter of knowing which pH was most representative of the in vivo physiological medium, especially that of pulmonary regions, has not been definitively resolved. A high alumina content has seemed until now to be favourable to rapid dissolution in acid pH, but weakly/slowly in neutral pH. The invention makes it possible to obtain a high level of biosolubility, at least measured in vitro, whatever the pH, by selecting a high alumina content but by adapting the content of alkaline-earth metal oxides so as to maintain its beneficial effect in acid pH without being made to suffer in neutral pH. It should be noted that the sum SiO2 + AI2O3 allows the viscosimetric behaviour of the compositions to be largely controlled. According to one embodiment of the invention, the compositions satisfy the relationship: R2O/AI2O3 between 0.2 and 0.8. The content of alkali metal oxides R2O, i.e. essentially Na2O and/or K2O, is preferably at feast 5% and especially maintained within ranges of about to 12% (or possibly 13%). As regards the content of iron oxide(s) (total iron), as mentioned above, it is advantageous to provide at least 4%, and even at least 5%, of ron-oxides in order to protect the centrifugers, especially between 5 and 9%. Furthermore, the iron oxides may have a favourable effect on the fire resistance o the mineral wool obtained. Advantageously, the compositions according to the invention also satisfy the following relationship, expressed as a ratio of percentages by weight: MgO/CaO between 1 and 3. Thus, the abovementioned advantageous effect is obtained without too great an excess of MgO with respect to CaO making it excessively complicated orexpensive to procure these oxides as raw materials. The compositions according to the invention preferably have a P2O5 content of at least 0.5 or of at least 1 %, and especially of about 1.5 to 4%. This moderate 6 content has a highly advantageous influence on the biodegradability, without economically penalizing the composition too much or having too great an influence on its liquidus temperature. According to another embodiment, the P2O5 content may be lower, especially from 0% or, for example, from 0.1 to 0.5% or from 0.1 to 1%. The preferred CaO content of the composition of the invention is less than or equal to 15%, especially at least 2% and advantageously between 5 and 14%, In parallel, the preferred MgO content of the composition is less than or equal to 20% and preferably at least 7%, the preferred range lying between 5 and 14%. It may be considered that, apart from the optional P2O5, the two compounds which have the greatest influence on the viscosity at fiberizing of the composition are silica and alumina. It is thus possible to select at least 60% of (SiO2 + AI2O3 + P2O5) in order to guarantee a viscosity high enough for fiberizing by internal centrifuging, especially within values of between 60 and 70% and especially at least 61 or 62%. The oxidation of the composition may, for example, be controlled by the addition of manganese oxide MnO. Adding boron oxide, which remains optional may allow the thermal insulation properties of the mineral wool to be improved, especially by tending to lower its thermal conductivity coefficient in its radiative component. Optionally, the composition may also contain TiO2 as an impurity or intentionally added, for example in an amount up to 2%. According to a non-limiting preferred embodiment, the alumina content of the compositions according to the invention is at least 18%, especially at least 19, or at least 20%. The difference Tog2.5 - Tllq is preferably at least 10°C, preferably at least 20 or 30oC: this difference defines the "working range" of the compositions of the invention, i.e. the temperature range in which they may be fiberized, most particularly by internal centrifuging. The temperature at which the compositions have a viscosity (in poises) such that log = 2.5 is written as Tlog2.5 and the liquidus temperature is written as Tllq, 7 Such mineral wool, as mentioned above, has a satisfactory level of biosolubility, whether the measurement method invofves a neutral or slightly basic pH or an acid pH. Thus, the mineral wool according to the invention generally has a rate of dissolution of at least 30, and preferably at least 40 or 50 ng/cm2 per hour measured at pH 4.5 and at least 30, preferably at least 40 or 50 ng/cm2 per hour measured at pH 7.5. In general, such mineral wool has a rate of dissolution of at least 30 and preferably at least 40 or at least 50 ng/cm2 per hour measured at pH 4.5 and a rate of dissolution of at least 30 and preferably at least 40 or at least 50 ng/cm2 per hour measured at pH 6.9. In general, it also has a rate of dissolution of at least 60 and especially at least 80 ng/cm2 per hour measured at pH 4.5 and/or a rate of dissolution of at least 40 and especially at least 60 ng/cm2 per hour measured at pH 6.9 and/or a rate of dissolution of at least 40 and especially at least 60 ng/cm2 per hour measured at ph 7.5. The mineral wool is mainly used to manufacture thermal and/or acoustic insulation products or soilless-culture substrates. The subject of the invention is also any product comprising, at least partly, the mineral wool defined above. Further details and advantageous characteristics will emerge from the description below of preferred non-limiting embodiments. Table 1 below gives the chemical compositions, as percentages by weight, of seven examples. When the sum of all the contents of all the compounds is slightly less than or slightly more than 100%, it is to be understood that the difference with 100% corresponds to the minor impurities/compounds (not analysed) and/or is due merely to the accepted approximation in the analytical methods used in this field. The compositions according to these examples were fiberized by internal centrifuging, especially according to the teaching of the aforementioned patent WO93/02977. Their working ranges, defined by the difference Tlog2.5 - Tlqi are amply positive. All the compositions have an MgO/CaO ratio of greater than 1 and a very modest (less than 1%) P2O5 content and an iron oxide content of around 7% which has proved to be advantageous in limiting corrosion of the centrifugation dishes. They also have a high alumina content of approximately 18 to 20%, with a fairly high sum (SiO2 + AI2O3) and an alkali metal oxide content of at least 5%. Their biodegradability, especially measured at neutral or slightly acid pH (pH 4.9 or 7.5), or at acid pH (4.5), is high. The composition according to Example 7, which contains more than 0.5% of P2O5 satisfies the Fe2O3/P2O5 ratio of between 1 and 20, here equal to 12.5, in accordance with a preferred embodiment of the invention. -10-WE CLAIM: 1. A process for the preparation of mineral wool capable of being dissolved in a physiological medium, said mineral wool comprises the constituents below in the following percentages by weight: SiO2 38-52%, preferably 40-48% Al2O3 17-23% SiO2+Al2O3 56-75%, preferably 62-72% RO(CaO+MgO) 9-26%, preferably 12-25% MgO 4-20%, especially 7-16% MgO/CaO >0.8, preferably 1.0 or > 1.15 R2O(Na2O+K2O) > 2% P2O5 0-5% Fe2O3(total Iron) > 1.7%, preferably >2% B2O3 0-5% MnO 0-4% TIO2 0-3% comprising the steps of melting followed by fiberizing the molten composition by internal centrifugation to obtain the mineral wool. 2. The process as claimed in claim 1, wherein said mineral wool comprising Fe2O3 (total iron) and P2O5 contents such that 1 0.5% -11- 3. The process as claimed in claim 1 or 2 wherein said mineral wool satisfies the relationship R2O/ AI2O3 0.2-0.8 4. The process as claimed in one of the preceding claims, wherein said mineral wool satisfies the relationship satisfies the relationship: R2O > 5 %, preferably 5-12% 5. The process as claimed in one of the preceding claims, wherein said mineral wool satisfies the relationship: MgO/CaO 1-3 6. The process as claimed in one of the preceding claims, wherein said mineral wool comprises at least 0.5 or at least 1%, especially between 1.5 and 4% by weight of P2O5 7. The process as claimed in one of the preceding claims, wherein said mineral wool comprises MgO in the following percentage by weight: MgO 7%, especially between 7 and 14%. 8. The process as claimed in one of the preceding claims, wherein said mineral wool comprises CaO in the following percentage by weight: CaO 2% especially between 5 and 14%. 9. The process as claimed in one of the preceding claims, wherein said mineral wool comprises at least 4%, especially at least 5% and preferably between 5 and 9% by weight of Fe2O3 (total iron) -12- 10. The process as claimed in one of the preceding claims, wherein said mineral wool comprises, in percentages by weight, the compounds SiO2, Al2O3 and P2O5 in proportions such that: SiO2 +Al2O3 +P2O5: at least 60%, especially 60 to 70%. 11. The process as claimed in one of the preceding claims, wherein said mineral wool comprises Al2O3 > 18%, especially > 19% or 20% 12. The process as claimed In one of the preceding claims, wherein said mineral wool has a rate of dissolution of at least 30 ng/cm2 per hour measured at pH 4.5 and a rate of dissolution of at least 30 ng/cm2 per hour measured at pH7.5. 13. The process as claimed in one of the preceding claims, wherein said mineral wool has a rate of dissolution of at (east 30 ng/cm2 per hour measured at pH 4.5 and a rate of dissolution of at least 30 ng/cm2 per hour measured at pH 6.9. 14.The process as claimed in one of the preceding claims, wherein said mineral wool has a rate of dissolution of at least 60 ng/cm3 per hour measured at pH 4.5 and/or a rate of dissolution of at least 40 ng/cm2 per hour measured at pH 7 5 and/or a rate of dissolution of at least 40 ng/cm2 per hour measured at pH 6.9. 15. The process as claimed In one of the preceding claims, wherein said mineral wool is obtained by infernal centrifuging. -13- 16.Thermal and/or acoustic insulation product or soilless-culture substrate comprising, at least partly, the mineral wool prepared according to one of the preceding claims. A process for the preparation of mineral wool capable of being dissolved in a physiological medium, said mineral wool comprises the constituents below in the following percentages by weight: SiO2 38-52%, preferably 40-48% Al2O3 17-23% SiO2+Al2O3 56-75%, preferably 62-72% RO(CaO+MgO) 9-26%, preferably 12-25% MgO 4-20%, especially 7-16% MgO/CaO >0.8, preferably 1.0 or > 1.15 R2O(Na2O+K2O) > 2% P2O5 0-5% Fe2O3(total Iron) > 1.7%, preferably >2% B2O3 0-5% MnO 0-4% TIO2 0-3% comprising the steps of melting followed by fiberizing the molten composition by internal centrifugation to obtain the mineral wool. |
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| Patent Number | 207474 | ||||||||||||
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| Indian Patent Application Number | IN/PCT/1999/00125/KOL | ||||||||||||
| PG Journal Number | 24/2007 | ||||||||||||
| Publication Date | 15-Jun-2007 | ||||||||||||
| Grant Date | 14-Jun-2007 | ||||||||||||
| Date of Filing | 31-Dec-1999 | ||||||||||||
| Name of Patentee | SAINT GOBAIN ISOVER | ||||||||||||
| Applicant Address | "LES MIROIRS", 18, AVENUE D' ALSSACE, F-92400 COURBEVOLE, | ||||||||||||
Inventors:
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| PCT International Classification Number | A01G 31/00,C03C 13/0 | ||||||||||||
| PCT International Application Number | PCT/FR99/01054 | ||||||||||||
| PCT International Filing date | 1999-05-04 | ||||||||||||
PCT Conventions:
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