GB2317403A

GB2317403A - A process for the preparation of a layered insulating board

Info

Publication number: GB2317403A
Application number: GB9621079A
Authority: GB
Inventors: Ian Cridland; Luis Norgaard
Original assignee: Rockwool International AS
Current assignee: Rockwool AS
Priority date: 1996-09-20
Filing date: 1996-10-09
Publication date: 1998-03-25
Anticipated expiration: 2016-10-09
Also published as: HU221918B1; EP0927287B1; EP0927287A1; WO1998012395A1; CZ94299A3; HUP9904721A2; ES2144855T3; GB2317403B; DE69701638T2; PL332457A1; AU4295697A; HUP9904721A3; DE69701638D1; GB9621079D0; ATE191528T1

Abstract

The present invention relates to a process for the preparation of a mineral fibre insulating board, which insulating board comprises at least one hard layer and at least one soft layer. The process comprises provision of a primary web, compression of the primary web in one or more longitudinally extending zones, doubling of the primary web to form a secondary web, and curing and optional compression of the secondary web, the amount of binder added to the various zones lying within different ranges.

Description

A process for the preparation of a layered insulating board, and a layered insulating board.

The present invention relates to a process for the preparation of an insulating board having at least dne hard layer, wherein a primary web of mineral fibre material is provided, where the primary web is compressed in at least one longitudinally extending zone in which the primary web is made to overlap itself under formation of a secondary web, and where the secondary web is cured and optionally compressed.

Boards of mineral fibre material for insulation purposes can be prepared with various properties depending on the desired field of application.

In order to increase the dimensional stability of the insulating boards, the mineral fibre material will often comprise an amount of binder, e.g.

in the form of phenol formaldehyde urea which is cured when the secondary web passes through a curing oven.

When erecting new constructions, thermal insulation is often performed with mineral fibre material in the cavity wall. In certain forms of new construction, the inner wall is erected first, whereafter it is clad with a layer of insulating material before the outer wall is erected. The insulating material will typically be secured to the inner wall by means of wall ties which are anchored in the wall and extend throughout and beyond the insulating material. The wall ties retain the insulating material secured to the wall by means of retaining clips in the form of plate shaped end pieces which urge against the outer layer of the insulating material. Thus, it is important that the insulating material possesses sufficient rigidity to be fixed in this way.

Further, insulating boards are often subjected to rough handling during mounting, and consequently it is generally desirable with respect to handling that insulating boards of mineral wool have at least one comparatively dimensionally stable surface.

Finally, the outer wall with the insulating material mounted thereon may risk being exposed to weathering conditions for a prolonged period until the outer wall is erected. Consequently, it is desirable to be able to prepare an insulating board which also has a suitably weather-resistant surface.

On the other hand, as it is, the outer side of an inner wall is often comparatively uneven. In order to avoid formation of ducts through which e.g. cold air may flow, it is consequently desirable to be able to prepare an insulating board which essentially is conformable to the contours of the wall.

Further, it is generally desirable to keep the average density of the insulating material down in view of transport and production economy, as well as for reasons of handling.

It is i.a. known from patent specifications Nos. CA 1 057 183, EP 0 451 186 B1, and DE 3 701 592 C2 to prepare insulating boards comprising layers having different characteristics by gluing or curing a separate compressed layer and another non-compressed or less compressed layer together so as to form one web. Danish utility model No. DK 92 00033 U3 discloses an insulating board thus prepared which is intended for insulating buildings having ventilated outer wall, or as facade cladding.

The insulating board is prepared from mineral wool and comprises a thin layer of about 30 mm having a relatively high density of about 90 kg/m3, and a comparatively thick layer of about 70 mm having a relatively low density of about 45 kg/m3. According to the utility model, the insulating board may be prepared on a dual-density apparatus, e.g. as described in US 4 950 355, and according to the utility model the insulating board may contain 0.5-15 weight-% binder, and preferably 0.5-5 weight-%.

In the above processes for the preparation of insulating boards comprising several layers having different properties, it has been found that the initial costs are very high. Further, in connection with the particular insulating boards problems of delamination may arise, so that after some time the layers after come apart. Further, as it is, if it is a matter of products having low density, the individual layers will not get to cohere sufficiently, because the compression resistance in the light non-cured mineral wool is too low. If sufficiently good bonding between the layers is to be obtained, the light wool layer will be compressed excessively. Hereby the layer gets too thin, which will result in too poor insulating capacity. It is not possible either to prepare products with thin layers having high density by several of the above processes, since it is not possible to cut off a sufficiently thin layer from the secondary mineral fibre web. The cut off, thin non-cured fibre web will further be unable to cohere sufficiently for the web to be treated by the above processes.

From Danish published application No. 155 163 B it is known to prepare mineral fibre webs having a zone with a higher degree of hardness than the rest of the web. This is achieved by compressing a part of the primary web before distribution by a pendulum conveyor, and where the compressed part at the pendulum distribution is made to partly overlap the compressed part of a number of the preceding layers. Hereby a zone of compressed primary web is established which extends in the longitudinal and horizontal direction of the secondary web. By e.g. compressing a zone along the edge of the primary web it is possible by this process to obtain a secondary web of mineral fibre containing insulating material having a hard layer positioned at one of the surfaces.

However, it has turned out to be difficult to obtain a suitably easy-tohandle and weather-resistant layer and simultaneously achieve an adequately soft and conformable layer by the process in question.

Thus, it is the object of the invention to provide a process of the kind stated in the preamble, wherein an insulating board can be prepared which essentially is constituted by mineral fibres, which insulating board comprises at least one hard, easy-to-handle and weather-resistant layer, and at least one soft and conformable layer, the above problems essentially being avoided.

This is achieved by the process according to the invention which is characterized in that an amount of binder of 1-3 weight-% is added to the primary web in zones which are not to be compressed, and an amount of binder of 1.3-5 weight-% in zones which are to be compressed in the longitudinal direction.

The invention rests on the discovery that there is a critical interval for the binder content within which it is possible to prepare insulating boards having the desired properties.

Too little binder in the hard layer will l.a. entail that the primary web does not retain its compression after compressing and till it is fixed by the curing. Further, too low content of binder will result in a layer which is too porous and weak to be capable of fulfilling the above requirements as to insulation of buildings. On the other hand, too large amount of binder will not provide the soft layer with the desired ability to be conformable to the contours of the brickwork, and also for reasons of economy as well as for considerations of fire it is generally desirable to limit the use of binder as far as possible.

It has surprisingly been found that by a process of the above kind where parts of the primary web are compressed before the primary web, e.g. by pendulum distribution or by preceding cutting off in sections as described in EP 0 297 111 B1, is made to overlap itself under formation of a secondary web which is compressed and cured, it is possible to prepare insulating boards having particularly advantageous properties by adding 1-3 weight-% binder to the zones of the primary web which are to constitute the soft layers of the insulating board, and 1.3-5 weight-% binder to the zones of the primary web which are to constitute the hard layers of the insulating board.

The binder intervals stated are particularly expedient when it is desired to prepare an insulating product in one operation, and where the product is to exhibit a combination of zones having different properties, such as a number of layers having a higher density than what is the average of the product, and a number of layers having a lower density than what is the average of the product.

Further, it has surprisingly been found that an improvement of the tensile strength is obtainable for the insulating boards prepared by the process according to the invention by adding an amount of binder of 2 weight-% or more to the zones of the primary web which are to constitute the hard layers of the insulating boards.

According to a preferred embodiment of the process according to the invention, 1-3 weight-% binder are added to the zones of the primary web which are to constitute the soft layers of the insulating board, and 2-5 weight-% binder to the zones of the primary web which are to constitute the hard layers of the insulating board.

It has also been found that there is an interval for the binder content within which insulating boards according to the invention may be prepared under particularly favourable production conditions, because the amount of binder in weight-% can be the same in the two layers. Thus, during production of insulating boards it has been found to be particularly uncomplicated to dose the binder in an essentially uniform amount across the entire primary web.

According to another preferred embodiment of the process according to the invention an amount of binder of 2-3 weight-% is added to the primary web.

According to yet another preferred embodiment of the process according to the invention an amount of binder of 2.1-2.7 weight-% is added to the primary web.

However, it is also possible in a first step to dose a uniform amount of binder to the entire primary web, and subsequently in a second step to dose an additional amount of binder to the zones which are to be compressed.

It is possible directly to prepare a mineral fibre web having a hard layer positioned at one of its surfaces, and a soft layer positioned at the other surface, and where the insulating boards prepared by the process according to the invention can be obtained by cutting off in suitable lengths from the web. This is achievable by a particularly preferred embodiment of the process according to the invention wherein the primary web is compressed in a longitudinally extending zone along one of its edges.

However, it is also possible by the process according to the invention to prepare the above insulating boards by first preparing a mineral fibre web having an easy-to-handle and weather-resistant layer on both sides, whereafter the web is divided symmetrically or asymmetrically in the vertical direction so as to obtain two webs having one easy-to-handle and weather-resistant side and one soft and conformable side, respectively.

Fibre webs may also be prepared where the primary web is compressed at another site or several other sites than along the edges, and the web may be divided into one or more planes parallel to the upper and lower surface in a suitable way so as to obtain insulating boards having the desired combinations of layers with different properties.

The invention also relates to an insulating board prepared by the process according to the invention, which insulating board is characterized in that it comprises at least one hard layer with a binder content of 1.3-5 weight-%, and at least one soft layer with a binder content of 1-3 weight-%.

In addition to the above advantageous properties, the insulating board according to the invention offers the advantage that it can be packed more densely than conventional insulating boards without suffering damage. Hereby transport and handling of the final packaged products are facilitated. Further, the insulating boards have a lower binder content than similar conventional boards.

As described above, the insulating boards according to the invention exhibit an improved tensile strength at a binder content of 2 weight-% or more, corresponding to a preferred embodiment of the insulating boards according to the invention.

An insulating board according to the invention having a hard layer positioned at one surface of the board, and a soft layer positioned at the other surface of the board, is particularly suited for cavity wall insulation where the insulating board is secured with the soft and conformable surface of the insulating board to the outer side of the inner wall by means of wall ties, and where the outer wall is erected at a distance from the insulating boards so as to establish a cavity between the insulating material and the inner side of the outer wall.

A particularly preferred embodiment of the insulating board according to the invention comprises a soft layer positioned at one surface of the board, and a hard layer positioned at. the other surface of the board.

Another particularly preferred embodiment of the insulating board according to the invention is prepared by dividing in the vertical direction a mineral fibre web having several hard and/or soft layers.

Finally, it may for certain types of insulation purposes be expedient to have an insulating board having two hard surfaces with a soft core, or two soft surfaces with one hard core.

Yet another particularly preferred embodiment of the insulating board according to the invention is characterized by having a hard layer on both surfaces.

Still another preferred embodiment of the insulating board according to the invention has a soft layer on both surfaces. In this way the insulating board is conformable to uneven surfaces on both sides, simultaneously with it still being easy-to-handle due to a firm core in the form of a hard layer.

The term insulating board as used herein comprises any board or sheet formed insulating material intended for thermal insulation, sound insulation or sound regulation, fire retardant purposes, or the like.

The term mineral fibre as used herein comprises all types of man-made mineral fibres, such as rock, glass or slag fibres, in particular fibres used in materials for the above purposes, and as filler in cement, plastics or other substances, or which are used as culture medium for plants.

The term binder as used herein comprises any material which is suited as binder in mineral fibre materials for the above products, e.g. phenol formaldehyde urea or melamine resin.

The term layer as used herein denotes areas which essentially exhibit uniform characteristics within the area; but comprises both layers which are sharply delimited, and areas in which there is a stepwise or flowing transition to any neighbouring layers.

The expression hard layer as used herein denotes a layer which has a degree of hardness which is higher than what is the average of the product.

The expression soft layer as used herein denotes a layer which has a degree of hardness which is lower than what is the average of the product.

In the following the invention will be described in more detail by way of an example.

Example 1: Mineral fibres are obtained by spinning in a spinning chamber, and are made to deposit on a conveyor belt under formation of a primary web having a width of about 1.8 m, and a surface weight of about 500 g/m2.

A binder comprising phenol formaldehyde urea in aqueous suspension is continuously distributed to the fibres in the air in the spinning chamber prior to the fibres settling on the conveyor belt, the binder being added in an amount corresponding to a final concentration of phenol formaldehyde urea in the primary web of about 2.1 % of the weight of the web. A zone along both edges of the primary web having a width of about 30 cm is rolled by means of 2 rollers each urging against the web at a pressure of 1 600 kg. The primary web is laid out by pendulum distribution under formation of a secondary web having a width of about 2 m, the secondary web as seen in cross-section comprising about 12 layers of primary web. The secondary web obtained is compressed to a height of 200 mm, and cured in a curing oven, whereafter the secondary web is divided symmetrically in the vertical direction into 2 webs having a height of 100 mm. Finally, the insulating boards are provided by cutting off in the desired sizes from the divided secondary web.

Insulating boards prepared by the process according to the example have a hard layer of about 15 mm positioned at one surface, and a soft layer of about 85 mm positioned at the other surface. The hard layer has a density of about 60 kg/m3, and the soft layer has a density of about 26 kg/m3, the average density of the insulating board being about 29.9 kg/m3.

As mentioned, insulating boards prepared by the process according to the invention exhibit better properties than conventional insulating boards.

A comparison experiment has been carried out with insulating boards prepared according to example 1, and conventional insulating boards intended for mounting in the cavity wall of new constructions. Data for the comparison experiment are stated in table 1 below.

Table 1 Density Tensile Binder stren content Insulating board accord. I 29.9 kg/m3 23.0 kPa 2.1 to invention l | weight-% Ordinary insulating 29.0 kg/m3 B 18.6 kPa 2.4 board weight-% The tensile strength was measured at pull transversely to the longitudinal direction of the secondary web.

Claims

Claims:

1. A process for the preparation of an insulating board having at least one hard layer and at least one soft layer, wherein a prirt t of mineral fibre material is provided, where the primly web is compn sed;n at least one longitud; nally extending zone in which the primary web is made to overlap itself under formation of a secondary web, and where the secondary web is cured and optionally compressed, characterized in that an amount of binder of 1-3 weight-% is added to the primary web in zones which are not to be compressed, and an amount of binder of 1.3-5 weight-% in zones which are to be compressed in the longitudinal direction.

2. A process according to claim 1, characterized in that 1-3 weight-% binder is added to the zones of the primary web which are to constitute the soft layers of the insulating board, and 2-5 weight-% binder to the zones of the primary web which are to constitute the hard layers of the insulating board.

3. A process according to any of the preceding claims, characterized in that an average amount of binder of 1.3-3 weight-% is added to the primary web.

4. A process according to any of the preceding claims, characterized in that an average amount of binder of 2.1-2.7 weight-% is added to the primary web.

5. A process according to any of the preceding claims, characterized in that the primary web is compressed in a longitudinally extending zone along one of its edges.

6. A process according to any of the preceding claims, characterized in that the secondary web is divided in a plane parallel to the surface before or after optional compression and curing.

7. An insulating board of mineral fibres1 where the insulating board comprises a number of layers having different degrees of hardness, including at least one hard layer and at least one soft layer, and where the insulating board is prepared by a process wherein a primary web of mineral fibre material is provided, where the primary web is compressed in at least one longitudinally extending zone in which the primary web is made to overlap itself under formation of a secondary web, and where the secondary web is cured and optionally caTpressed, chaacterised in that the at least one hard layer has a binder content of 1.3-5 weight-%, and the at least one soft layer has a binder content of 1-3 weight-%.

8. An insulating board according to claim 7, characterized in that the hard layer has a binder content of 2-5 weight-%, and the soft layer has a binder content of 1-3 weight-%.

9. An insulating board according to claim 7 or 8, characterized in that it comprises an average anoint of binder of 2-3 weight-%.

10. An insulating board according to claim 7-9, characterized in that it comprises an average arans of binder of 2.1-2.7 weight-%.

11. An insulating board according to claims 7-10, characterized in that it comprises a soft layer positioned at one side, and a hard layer positioned at the other side.

12. An insulating board according to claims 7-11, characterized in that it is prepared by dividing in the vertical direction a mineral fibre web having several hard and/or soft layers.

13. An insulating board according to claims 7-12, characterized in that it comprises a hard layer positioned at both surfaces.

14. An insulating board according to claims 7-13, characterized in that it comprises a soft layer positioned at both surfaces.