Thermal insulation product based on mineral wool and method of fabrication of the product

Abstract

The invention relates to a thermal insulation product based on mineral wool comprising mineral fibers, the product comprising two main faces and longitudinal and transverse edges perpendicular to the main faces, the product being characterized by the following orientation fractions: a longitudinal orientation fraction greater than or equal to 48%, or even 50%, along an angle of more or less 6? with respect to the plane of the main faces, when the mineral fibers are counted only in a longitudinal cross-section, and a mean orientation fraction greater than or equal to 40%, or even 45%, along an angle of more or less 6? with respect to the plane of the main faces, when the mineral fibers are counted both in a transverse cross-section and in a longitudinal cross-section. The invention allows the insulating power of a thermal insulation product based on mineral wool to be improved without increasing its thickness.

Claims

1. A method of fabricating a thermal insulation product based on mineral wool, the method comprising: fabricating mineral fibers from molten glass in a centrifuge, receiving the mineral fibers on a reception belt having a speed V.sub.0, conveying the mineral fibers on a first group of conveyers, a speed V.sub.1 of a last conveyer of the first group of conveyers being in the range between greater than 100% and 105% of V.sub.0, and conveying the mineral fibers on a second group of conveyers, a speed V.sub.2 of a last conveyer of the second group of conveyers being in the range between 108% and 120% of V.sub.0, wherein the thermal insulation product based on mineral wool produced by the method comprises two main faces and longitudinal and transverse edges perpendicular to the main faces, the product being characterized by the following orientation fractions: a longitudinal orientation fraction TO.sub.L(0?+/?6?) greater than or equal to 48% along an angle of more or less 6? with respect to the plane of the main faces, when the mineral fibers are counted only in a longitudinal cross-section, and a mean orientation fraction TO.sub.m(0?+/?6?) greater than or equal to 40% along an angle of more or less 6? with respect to the plane of the main faces, when the mineral fibers are counted both in a transverse cross-section and in a longitudinal cross-section.

2. The method of claim 1, wherein the conveyers of the second group all have a speed greater than that of the conveyers of the first group.

3. The method of claim 1, wherein a number of conveyers of the first group is in the range between 3 and 10.

4. The method of claim 1, wherein a number of conveyers of the second group is in the range between 2 and 5.

5. The method of claim 1, wherein the speed of each conveyer of the first group increases by the same amount as for a preceding conveyer.

6. The method of claim 1, wherein the speed of each conveyer of the second group increases by the same amount as for a preceding conveyer or the speed of each conveyer of the second group increases faster than that of the preceding conveyer.

7. The method of claim 1, wherein, for the two last conveyers at least, the mineral fibers are progressively compressed when going between at least the last two conveyers and at least two upper driving devices.

8. The method of claim 1, wherein the thermal insulation product based on mineral wool produced by the method has a thermal conductivity less than or equal to 32 mW/m.Math.K and a density of 15 kg/m.sup.3-60 kg/m.sup.3.

9. The method of claim 1, wherein the thermal insulation product based on mineral wool produced by the method has a thermal conductivity less than or equal to 29 mW/m.Math.K and a density of 55-80 kg/m.sup.3.

Description

(1) Exemplary embodiments of the invention will be presented hereinbelow.

(2) The method of fabrication of the insulation product according to the invention will now be described.

(3) The mineral wool is fabricated by an internal centrifugation method starting from molten mineral material. One example of internal centrifugation method is described hereinbelow.

(4) A fillet of molten glass is introduced into a centrifuge, otherwise known as a fiber-forming plate, rotating at high speed and having opened on its periphery a very large number of orifices via which the glass is projected in the form of filaments under the effect of the centrifugal force. These filaments are then subjected to the action of a gaseous drawing current at high temperature and speed, produced by a ring burner. By running along the wall of the centrifuge, the gaseous drawing current thins the filaments and transforms them into fibers. The fibers formed are driven by the gaseous drawing current toward a reception belt generally formed by a band that is permeable to the gas, associated with aspiration means. A binder, needed to bind the fibers together into a woolen product, is sprayed onto the fibers as they are drawn toward the reception belt. The accumulation of fibers on the reception belt under the effect of the aspiration provides a carpet of fibers whose thickness can vary depending on the final product to be obtained.

(5) The reception belt moves forward at a speed V.sub.0. The mineral fibers are subsequently conveyed toward an oven in order to allow the binder to polymerize, by means of conveyers disposed between the reception belt and the oven. According to the method of the invention, the conveyers are divided into two groups: a first group at the exit of the reception belt, followed by a second group between the first group and the oven.

(6) The first group of conveyers comprises between 3 and 10 conveyers, preferably between 4 and 8 conveyers, in particular between 5 and 7 conveyers. The speed of each conveyer of the first group can be equal to that of the reception belt. The speed V.sub.1 of the last conveyer of the first group of conveyers is, as a minimum, equal to 100% of V.sub.0. As a variant, in order to ensure a sufficient tension for the conveyers, the speed of each conveyer of the first group can increase progressively from one conveyer to the next. Preferably, the speed of each conveyer of the first group increases by the same amount as for the preceding conveyer. Thus, for example, the first conveyer has a speed of 101% of V.sub.0, the second conveyer has a speed of 102% of V.sub.0, the third conveyer has a speed of 103% of V.sub.0, etc . . . . In that case, the increase is 101% of V.sub.0 at each conveyer. The speed V.sub.1 of the last conveyer of the first group of conveyers is however, as a maximum, equal to 105% of V.sub.0. Between these two extremes, all the variants may be envisioned, but the speed V.sub.1 of the last conveyer of the first group of conveyers is in the range between 100% and 105% of V.sub.0.

(7) The second group of conveyers comprises between 2 and 5 conveyers, preferably 2 or 3 conveyers. The speed V.sub.2 of the last conveyer of the second group of conveyers is in the range between 108% and 120% of V.sub.0, preferably between 110% and 115% of V.sub.0. The speed of each conveyer of the second group preferably increases from one conveyer to the next. And preferably, all the conveyers of the second group have a speed greater than that of the conveyers of the first group. Preferably, the speed of each conveyer of the second group increases by the same amount as for the preceding conveyer or the speed of each conveyer of the second group increases faster than that of the preceding conveyer.

(8) In addition, for the last two conveyers at least, the mineral fibers are progressively compressed when passing between the at least last two conveyers and at least two upper driving devices, the upper driving devices driving the mineral fibers at the same speed as the conveyers situated underneath. At least one upper driving conveyer/device pair can be symmetrical with respect to the horizontal. This progressive compression can be initiated within the first group of conveyers. The progressive compression may be applied in stages with a succession of compression steps then of driving steps while maintaining the compression between two successive compressions.

(9) The upper driving devices and the conveyers of the first and second groups may be of any type, for example of the belt, band or roller type.

(10) The presence of the second group of conveyers with a speed equal to at least 108% of V.sub.0 allows more horizontal fibers to be obtained in all the directions of the product, more particularly in the longitudinal direction and, thus, the thermal properties of the product to be improved.

(11) With particular reference to FIG. 1, a method of fabricating a thermal insulation product based on mineral wool is provided. As depicted in FIG. 1, centrifuge(s) 10 are provided for fabricating mineral fibers 2 from molten glass. Fabricated mineral fibers are transferred to a reception belt 12 having a speed V.sub.0. The mineral fibers are conveyed to a first group of conveyers 14. A speed V.sub.1 of a last conveyer 15 of the first group of conveyers 14 is in the range between 100% and 105% of V.sub.0. Then, the mineral fibers are conveyed to a second group of conveyers 16. A speed V.sub.2 of a last conveyer 17 of the second group of conveyers is in the range between 108% and 120% of V.sub.0.

(12) Two examples of product according to the invention have been fabricated by internal centrifugation producing mineral fibers having a micronaire of 10 L/min.

(13) In order to produce the first example, the conveyers of the first group all went at the same speed as the reception belt. In the second group of conveyers, the two conveyers respectively went, from upstream to downstream, at a speed of 103% of V.sub.0 and at a speed of 110% of V.sub.0, in other words a non-uniform progression of the speed. The product obtained has a thickness of 100 mm, a density of 20 kg/m.sup.3 and a thermal conductivity of 31.77 mW/m.Math.K. The product obtained has a longitudinal orientation fraction TO.sub.L(0?+/?6?) of 53% along an angle of more or less 6? with respect to the plane of the main faces of the product when the mineral fibers are counted only in a longitudinal cross-section. The mean orientation fraction TO.sub.m(0?+/?6?) of the product obtained is 46% along an angle of more or less 6? with respect to the plane of the main faces of the product when the mineral fibers are counted both in a transverse cross-section and in a longitudinal cross-section.

(14) In order to produce the second example, the five conveyers of the first group respectively went, from upstream to downstream, at a speed of 101% of V.sub.0, 102% of V.sub.0, 103% of V.sub.0, 104% of V.sub.0 and 105% of V.sub.0. In the second group of conveyers, the two conveyers respectively went, from upstream to downstream, at a speed of 105% of V.sub.0 and at a speed of 110% of V.sub.0, in other words a uniform progression of the speed. The product obtained has a thickness of 60 mm, a density of 55 kg/m.sup.3 and a thermal conductivity of 28.95 mW/m.Math.K. The product obtained has a longitudinal orientation fraction TO.sub.L(0?+/?6?) of 50% along an angle of more or less 6? with respect to the plane of the main faces of the product when the mineral fibers are counted only in a longitudinal cross-section. The mean orientation fraction TO.sub.m(0?+/?6?) of the product obtained is 45% along an angle of more or less 6? with respect to the plane of the main faces of the product when the mineral fibers are counted both in a transverse cross-section and in a longitudinal cross-section.

(15) The method has also allowed products to be obtained with a conductivity of less than or equal to 32 mW/m.Math.K with fibers of micronaire notably in the range between 8 and 11 L/min with a substantial weight gain with respect to a conventional product.

(16) Thanks to the method according to the invention, the fabrication of products with an improved thermal conductivity for a reasonable thickness has successfully been achieved.