Method for producing mineral fibres

Abstract

A process for forming mineral fibers by internal centrifugation using a device including a basket and a fiberizing spinner suitable for rotating jointly about an axis of rotation, the basket including an annular wall pierced by orifices and the fiberizing spinner including an annular wall pierced by orifices, the process including feeding the basket with material to be fiberized at a temperature T.sub.a; centrifuging the material to be fiberized by joint rotation of the basket and of the fiberizing spinner. The factor F is greater than 2000, the factor F being defined by F=μ.sub.adN/Q; wherein μ.sub.a is the viscosity of the material to be fiberized at the temperature T.sub.a; d is the distance between the annular walls of the basket and of the fiberizing spinner; N is the number of orifices of the basket; and Q is the feed flow rate of the material to be fiberized.

Claims

1. A process for forming mineral wool by internal centrifugation using a device comprising a basket and a fiberizing spinner which are suitable for rotating jointly about an axis of rotation, the basket comprising an annular wall pierced by a plurality of orifices and the fiberizing spinner comprising an annular wall pierced by a plurality of orifices, said process comprising: feeding the basket with material to be fiberized at a temperature T.sub.a; centrifuging the material to be fiberized by joint rotation of the basket and of the fiberizing spinner, wherein a factor F is greater than 2000, the factor F being defined by $F=\frac{{\mu }_{a}dN}{Q},$ wherein: μ.sub.a is the viscosity, expressed in Pa.Math.s, of the material to be fiberized at the temperature T.sub.a; d is the distance, expressed in m, between the annular wall of the basket and the annular wall of the fiberizing spinner; N is the number of orifices of the basket; and Q is the feed flow rate, expressed in kg/s, of the material to be fiberized, and wherein the annular wall of the basket comprises from 220 to 1,000 orifices.

2. The process as claimed in claim 1, wherein the viscosity of the material to be fiberized at the temperature T.sub.a is from 50 to 150 Pa.Math.s.

3. The process as claimed in claim 1, wherein the distance between the annular wall of the basket and the annular wall of the fiberizing spinner is from 0.05 to 0.2 m.

4. The process as claimed in claim 1, wherein the feed flow rate of the material to be fiberized is from 0.01 to 0.5 kg/s.

5. The process as claimed in claim 1, wherein the material to be fiberized comprises the constituents below, in the weight proportions defined by the following limits: TABLE-US-00007 SiO.sub.2 35 to 80%,  Al.sub.2O.sub.3 0 to 30%, CaO + MgO 2 to 35%, Na.sub.2O + K.sub.2O 0 to 20%.

6. The process as claimed in claim 5, wherein the material to be fiberized is fed into the basket at a temperature of from 1000 to 1550° C.

7. The process as claimed in claim 1, wherein the factor F is greater than 5000.

8. The process as claimed in claim 7, wherein the factor F is greater than 10000.

9. A process for forming mineral wool by internal centrifugation using a device comprising a basket and a fiberizing spinner which are suitable for rotating jointly about an axis of rotation, the basket comprising an annular wall pierced by a plurality of orifices and the fiberizing spinner comprising an annular wall pierced by a plurality of orifices, said process comprising: feeding the basket with material to be fiberized at a temperature T.sub.a; centrifuging the material to be fiberized by joint rotation of the basket and of the fiberizing spinner, wherein a factor F is greater than 2000, the factor F being defined by F=μ.sub.adN/Q, wherein: μ.sub.a is the viscosity, expressed in Pa.Math.s, of the material to be fiberized at the temperature T.sub.a; d is the distance, expressed in m, between the annular wall of the basket and the annular wall of the fiberizing spinner; N is the number of orifices of the basket; and Q is the feed flow rate, expressed in kg/s, of the material to be fiberized, wherein the orifices of the annular wall of the basket have a diameter of from 1.5 to 3 mm, and wherein the annular wall of the basket comprises from 220 to 1,000 orifices.

Description

EXAMPLES

(1) The reference example (Ref.), the comparative examples (C1 and C2) and examples 1 and 2 according to the invention were produced with a material to be fiberized having the following composition, in weight percentages:

(2) TABLE-US-00004 SiO.sub.2 65.3% Al.sub.2O.sub.3 2.1% CaO 8.1% MgO 2.4% Na.sub.2O 16.4% K.sub.2O 0.7% B.sub.2O.sub.3 4.5%

(3) The features of the fiberizing device used and also the fiberizing conditions are described in detail in table 1 below.

(4) For the reference example, the fiberizing device used is a device without a basket comprising a fiberizing spinner with a bottom. The fibers obtained do not therefore comprise bubbles. For examples C1, 1 and 2, the fiberizing device used is identical except for the basket which has a larger number of holes for examples 1 and 2 compared to comparative example C1 which uses a conventional basket.

(5) TABLE-US-00005 TABLE 1 Ref. C1 Ex. 1 Ex. 2 Flow rate (kg/s) 0.23 0.23 0.23 0.23 T.sub.a (°C.) 1036 1036 1036 1036 μ.sub.a (Pa .Math. s) 147 147 147 147 Basket: Diameter (mm) — 200 200 200 Number of orifices 30 240 600 Orifice diameter (mm) 5.0 2.9 2.3 Fiberizing spinner: Diameter (mm) 400 400 400 400 Number of orifices 30270 30270 30270 30270 Orifice diameter (mm) 0.7 0.7 0.7 0.7 Annular burner: Temperature (°C.) 1300 1300 1300 1300 Induction ring: Power (kW) 20 20 20 20 F — 1900 15250 38120

(6) The light scatterings of the fibers thus obtained were measured as described above and are presented in table 2 below:

(7) TABLE-US-00006 TABLE 2 Fiber Ref. C1 Ex. 1 Ex. 2 LS 0.13 0.30 0.53 0.71

(8) The fibers from examples 1 and 2 have a light scattering which is much greater than that of the reference fibers and fibers from comparative example C1, which demonstrates the presence of bubbles in the fibers from examples 1 and 2.