IE69373B1 - Thermo-insulating mat of random-orientation mineral fibres - Google Patents

Description

THERMO-INSULATING MAT OF RANDOM-ORIENTATION MINERAL FIBRES Procedures for manufacturing thermoinsulating mats or felts from mineral fibres (glass fibres or rock fibres), the orientation of which is practically random, such as those described in European Patent 0 133 083, are already known. These products are of good quality, but they have a high density (of 50 to 150 kg/m3) and do not possess sufficient flexibility to be used for certain applications, in particular when these insulating mats are to be applied to cylindrical surfaces, of tanks for example, without forming pockets of condensation on the side which is in contact with the cylindrical surface and without cracks forming in the exterior surface.

The object of the present invention is to provide a product having the qualities required for applications of this type.

The inventors of the present invention have found by establishing in an unexpected and even surprising manner, in the course of their research, that, by reducing the diameter of the fibres very considerably in comparison to the state of the art, it is possible to produce a product having the desired qualities, and, furthermore, a density which is substantially lower than that of known similar products.

The object of the present invention is a 5 thermo-insulating mat of mineral fibres from fibres transported by a gaseous current to a conveyor belt which is permeable to gases and which retains the fibres which have previously been coated with a binder, the fibres being deposited substantially in planes which are parallel to the conveyor, the felt which is formed on the conveyor being subjected to at least one compression in the longitudinal direction to obtain a quasi-random orientation, this orientation being rendered permanent by fixing the binder, which is characterised in that it is formed of fibres, the great majority of which have a diameter of between 2.5 and 4.5 micrometers and a length of from 2 to 25 cm, and in that they have a density which is.not more than 40 kg/m3.

An embodiment of the mat according to the invention will be described below by way of example. The attached drawing shows, also by way of example, how the mat according to the invention may be manufactured.

The drawing shows, schematically, an installation for the manufacture of a thermo-insulating mat of mineral fibres having a quasirandom orientation according to the invention.

The known mat of mineral fibres having a quasi-random orientation are formed of glass fibres or rock fibres which have a diameter of 6 to 14 micrometers and a length of some centimetres. According to the invention, the mat is formed of mineral fibres which are substantially finer, where the great majority of them having diameters of less than 2.5 to 4.5 micrometers and a length of 2 to 15 cm.

There will now be described a way in which an insulating mat, having the desired qualities stated above, may be obtained using such a material.

Conventionally the mineral fibre felts are formed in a continuous manner by depositing fibres carried by a gaseous current on a fibreconveyor. The conveyor retains the fibres and allows the gases to pass through.

Before being deposited on the conveyor, the fibres are coated with a resinous composition to bind them together, thus conferring its cohesion on the formed felt. The resinous composition, applied in liquid form, is crosslinked by a thermal treatment performed on the felt which has already been brought to the desired conditions of thickness and density.

Forming the felt by depositing the fibres on a receiving conveyor, or on a similar device, leads to tangling which is not homogeneous in all directions. It has been established, by experiment, that the fibres have a strong tendency to position themselves parallel to the surface. This tendency is the more marked the greater the length of the fibres.

In the installation shown in the drawings, the fibres arrive in the form of a mat 1 which is then subjected, in a manner which will be explained, to a double crimping which is performed at two levels. This mat first passes into an upstream section formed of two zones la and Ila which have different cross-sections. A zone Ilia forms a downstream section the function of which is to conduct the mat with non-polymerised adhesive towards a polymerisation oven which is not shown.

The mat or felt of glass fibres (or other mineral fibres) arrives at 1 with non-polymerised adhesive, coming from the reception (not shown) and passes, at the speed of its reception at 1, 1 between a pair of conveyors 2, 2' and is then engaged between a pair of parallel conveyors downstream.

On passing out from between the conveyors 2, 2' of the zone Ia, the felt arrives at the pair LO of conveyors 3, 3' of the zone Ila at a much lower speed, which produces a longitudinal compression of the product and a first crimping, as shown in the drawing.

On passing out from between the conveyors 3, 3' the felt, crimped for the first time, arrives on the pair of conveyors 4,4' in the zone Ilia, at a speed lower than that of the conveyors 3, 3', which results in a second compression of the product between the conveyors and a second crimping, conferring on the final product a completely random arrangement of the fibres, as shown in the drawing.

The product subsequently arrives at a pair of conveyors 5, 5' which convey the felt into g binder polymerisation oven (not shown).

The direction of orientation of the felt is indicated by the arrow 6·.

Owing to the double crimping and the use of fine fibres, a product is obtained which has a smaller apparent density (AD) and greater flexibility, making it suitable, for example, for the thermal insulation of large open-air cisterns by winding around the outside of these cisterns.

Concrete examples of various values (speeds of the various conveyors and heights at the point of entry and axis of certain conveyors) are given below.

The first longitudinal compression produced by the passage of the felt through the conveyors 2, 2' of the zone Ia on the conveyors 3, 3‘ of the zone Ila is performed by conferring on the latter a speed which is, for example, 2.5 times less than that of the conveyors of zone la. It is this which produces the undulating structure shown on the drawing.

The second longitudinal compression is obtained by providing the conveyors 4f 4e in the zone Ilia with a velocity which is, for example, 2.5 times less than that of the conveyors in sone Ila. It is this that produces a random and homogeneous structure.

The velocity Vj of the conveyors 2, 2' of the sone la is equal to the velocity of entry of the felt at 1. This is adjusted to obtain the desired velocity (or crimping) relationship.

The velocity of the conveyors 4, 4' in the downstream sone Ilia is the same as the velocity of the conveyors 5, 5', which feed the felt to the oven, which avoids accidental blocking or de-crimping during the passage of the mat through sone Ilia to the oven.

The velocity of the conveyors in the sone la is the same as the entry velocity (reception velocity) Vr of the felt into 1.

The velocity of the conveyors in the sone Ila, for the double, crimping, is calculated as a function of the relationship between the entry velocity Vr of the felt and the velocity of the oven Ve? where Vr/Vi, (crimping velocity) is: v F* Control of the thickness of the felt is achieved in the following manner: Upstream section, sones Ia_and Ila let H'l be the height on entry into the conveyors of the zone la; let H'2 be the height on leaving the convevors of the zone Ila; Then: - H'l =(1.2 to 2.3). Ee (depending on the required AD); H'2 - (1.2 to 2.4) . Ee (depending on the required AD); Downstream section, zone IIlas let H'3 be the height on entry into the conveyors 4 and 4'; - let H'4 be the height on leaving the conveyors 4 and 4'; Then: - H'3 = (1.0 to 1.30). required AD); - H'4 = (1.0 to 1.20). required AD).

Ee (depending on the Ee (depending on the The conveyors 3, 3' and 4, 4' act against an increase in the thickness of the mat under the effect of the axial pressure which they exert.

A. ·£ The two sections, upstream (la and Ila) and downstream (Ilia), are connected to one another mechanically and are positioned on a moving path enabling the assembly to be positioned in relation to the oven.

Each conveyor is fitted with a carpet which is driven by a direct-current geared motor assembly which permits the velocities to be adjusted precisely to desired settings.

Owing to the fineness of the fibres and the completely random disposition of the insulating fibres in the finished product, the latter possesses a compact surface, good flexibility and a constant thickness with good insulating properties.

The application of the product to large flat or non-flat (concave or convex) surfaces is easy. The product offers a resistance to compression which is sufficient to permit a protective covering or a supplementary layer of insulation to be applied thereto. The product may take the form of a roll of felt, lending itself well to an application to the external surface of a flame-resistant coating and to cylindrical surfaces.

The product obtained in this manner has the following characteristics: * random or quasi-random distribution of the fibres (glass or rock); * very fine fibres (diameters of 2.5 to 4.5 micrometers); - fibre lengths from 2 to 15 cm; * apparent density (AD) < 40 kg/m3; » resistance to compression (for a compression of 10%) > 0.5 kN/m2; * coefficient of thermal productivity < 0.040 W/mK.

The finished mat may have a thickness of from 20 to 200 mm.

The mat may be surfaced, ie. be covered with one or two adhesive sheets of paper, aluminum, polyethylene or pvc.

The random distribution of the fine fibres that have been used ensures that when the mat is wound around a cylindrical surface, this winding is performed without any deformation of the Interior or exterior surface which are thus perfectly cylindrical, with good application to the body to be insulated, avoiding any pockets of condensation on the interior surface and any fissures on the external surface.

Claims (5)

1. neat-insulating mat of mineral fibres obtained from fibres transported by a gaseous current to a conveyor belt which is permeable to 5 gases and which retains the fibres which have previously been coated with a binder, the fibres being deposited substantially in planes which are parallel to the conveyor, the felt which is formed on the conveyor being subjected to at least one 10 compression in the longitudinal direction to obtain a quasi-random orientation, this orientation being rendered permanent by fixing the binder, characterised in that it is formed of fibres the great majority of which have a diameter 15 of between 2.5 and 4.5 micrometers and a length of between 2 and 15 cm; and in that it has a density of not more than 40 kg/m 3 .

2. Mat according to Claim 1, characterised in that it has resistance to compression which is 20 at least 0.5 kN/m 2 for a compression of 10 %.

3. Mat according to Claim 1 or 2, characterised in that it has a coefficient of heat conductivity of not more than 0.040 W/mK.

4. Mat according to any one of Claims 1 to 3, characterised in that, owing to its mechanical properties, it tolerates being applied to a body having a cylindrical surface the diameter of which 5 is not less than 300 mm, without forming irregularities on its curved surfaces, thus ensuring satisfactory application to said cylindrical surface and a smooth exterior surface, which is free of cracks, and is concentric with 10 said cylindrical surface.

5. Heat-insulating mat of mineral fibres according to claim 1, substantially as herein described with reference to and as shown in the accompanying drawing.