WO2008155401A1

WO2008155401A1 - Mineral fibre product

Info

Publication number: WO2008155401A1
Application number: PCT/EP2008/057840
Authority: WO
Inventors: Bent Jacobsen
Original assignee: Rockwool International A/S
Priority date: 2007-06-20
Filing date: 2008-06-20
Publication date: 2008-12-24

Abstract

The invention provides a method of making a mineral fibre product (23) comprising the steps of: (a) forming an air laid web (1 ) of mineral fibres and heat -curable binder on a permeable conveyor (2) and transporting the web on the conveyor, wherein the web has a longitudinal direction Y which is in the direction of transport of the web and the web has upper and lower major surfaces and the lower major surface is in contact with the conveyor and the web has a transverse direction X which is substantially parallel to the major surfaces and substantially perpendicular to longitudinal direction Y, and the fibres of the web are substantially oriented in the XY plane; (b) cutting the web (1 ) in the XY plane to form at least one core layer (8) and at least one covering layer (9); (c) passing the core layer (8) or each of the core layers (8) through a first curing oven (10) so as to cure the binder; (d) cutting the core layer (8) or each of the core layers (8) in either the longitudinal direction Y or the transverse direction X to form lamellae (13), reorienting each lamella by 90° and joining the reoriented lamellae (13) to form a lamellar core section (14) which has upper and lower major surfaces; (e) placing the covering layer (9) or covering layers (9) onto a major surface or major surfaces of the lamellar core section (14) to obtain a covered lamellar core section (20); and (f) passing the covered lamellar core section (20) through a second curing oven (22) to form a mineral fibre product (23).

Description

Mineral Fibre Product Field of the Invention

The present invention is concerned with a method of making a mineral fibre product and products which are obtainable by such a method. The products of the method of the present invention are particularly well suited to use in the building industry as roof insulation boards.

Background to the Invention Mineral wool products are well known and have been used extensively in the building industry to provide heat and sound insulation.

Mineral fibre products are generally made by centrifugal fiberisation of a mineral melt to form a cloud of fibres entrained in air. The fibres are generally collected from the cloud on a permeable conveyor as a primary web. The thickness of the fibres on the conveyor builds up as the fibres are deposited from the cloud but generally the primary web remains relatively thin and it is conventional to cross- lap the primary web to form a thicker web which is often referred to as the secondary web. As a result of the air laying process, the fibres in the primary web and consequently also the secondary web are substantially oriented in the plane of the web, i.e., parallel to the largest surface of the web.

Such mineral fibre products have good heat insulation properties and are frequently used as floor, wall and roof insulation. In the case of roof insulation and floor insulation the products are often required to have relatively high compression strength to enable a person to walk over the insulation product without it collapsing.

In products where the fibres are predominantly oriented parallel to the major surface, it is often necessary to make the product relatively dense in order to provide adequate compression strength. However in general terms a high density product will provide less heat insulation than a low density product of the same weight so this inevitably compromises the insulating properties of the product.

It is known in the art that the mineral fibres can be reoriented to provide improved properties, in particular can be oriented to be substantially perpendicular to the major surface rather than parallel to it. In the art there have been two major ways of achieving the reorientation.

The first method of achieving reorientation is to pleat the web, often using longitudinal compression, to produce a "concertina" effect. This is described in

EP 688,834, WO94/16163 and EP 678,138. This process leads to a product in which the centre of each pleat has fibres which are oriented substantially perpendicular to the major surface but the edge regions have fibres which are predominantly parallel to the surface. A similar effect is achieved in EP 741 ,827. A curing step is carried out following the pleating.

A second and fundamentally different approach to reorienting the fibres is known wherein the web is cut to form lamellae which are turned by 90° and joined back together. An example of this process is given in EP 560,878. In this process the fibres of the lamellae are not folded at any point so the whole structure consists of reoriented fibres which are substantially perpendicular to the major surfaces. This can lead to a significant improvement in the compressive strength of the product.

Other documents such as RU 810,654, RU 810,653 and RU 876,624 disclose the production of products by cutting and turning strips of a mineral fibre web to form a lamellar product. In these publications the lamellar product is covered with a layer of mineral wool that has been separated from the web before reorientation in order to support the lamellar structure and provide a uniform surface. The mineral wool is cured after the reorientation and, where they are present, after the covering layers have been added in order to bind them to the reoriented core section.

DK2352675 discloses a mineral wool lamellar product that is covered with a layer, wherein the layer is preferably mineral wool which has different characteristics to the lamellae.

Known products have performed reasonably well and have been popular for use as insulation, particularly in houses such as on floors, walls and roofs, for many years. However, in recent years increasing environmental concern has led to a greater emphasis being placed on the desire to retain heat energy in both domestic and commercial buildings. Strict regulations have been placed on new buildings and, rather than in the past where each surface of the building (such as the floor, walls and roof) had to meet certain requirements, a more rigorous requirement on the insulation properties has now been applied to the building as a whole.

As a result of this, interest has been increasingly focussed on how to improve the insulation properties of a building as a whole in the most cost-effective and efficient way. As insulation of the floor and walls is relatively difficult to install due to the structure of these elements, attention has been increasingly focussed on roof insulation.

The simplest way to increase the insulating properties of roof insulation is to make the mineral wool boards thicker and this has, to date, been the most popular solution.

However, further regulations have come into force in Europe which limit the weight of a single roof board to 15kg, which is intended to ensure that each board can be handled by one person.

In view of these regulations, there is a desire for a cost-effective and convenient way of making an insulating product which can be used as a roof board and which is well insulating yet relatively light and convenient.

Summary of the Invention

According to a first aspect, the present invention relates to a method of making a mineral fibre product comprising the steps of:

(a) forming an air laid web of mineral fibres and heat-curable binder on a permeable conveyor, and transporting the web on the conveyor, wherein the web has a longitudinal direction Y which is in the direction of transport of the web and the web has upper and lower major surfaces and the lower major surface is in contact with the conveyor and the web has transverse direction X which is substantially parallel to the major surfaces and substantially perpendicular to longitudinal direction Y, and the fibres of the web are substantially oriented in the XY plane; (b) cutting the web in the XY plane to form at least one core layer and at least one covering layer;

(c) passing the core layer or each of the core layers through a first curing oven so as to cure the binder; (d) cutting the core layer or each of the core layers in either the longitudinal direction Y or the transverse direction X to form lamellae, reorienting each lamella by 90° and joining the reoriented lamellae to form a lamellar core section which has upper and lower major surfaces;

(e) placing the covering layer or covering layers onto a major surface or major surfaces of the lamellar core section to obtain a covered lamellar core section; and

(f) passing the covered lamellar core section through a second curing oven to form a mineral fibre product.

According to a second aspect, the present invention relates to a mineral wool product obtainable by a method according to the first aspect of the invention.

The invention provides a method that allows for products that have advantageous properties to be obtained, namely a low density mineral wool core section with advantageously high compressive strength characteristics. The low density of the mineral wool core section means that the product has extremely good insulating properties per unit weight so is suitable for meeting the requirements in the building industry for roof boards that are highly insulating yet light whilst still providing boards that are of a conveniently large size to minimise the number of tiles needed for one roof. Hence, the boards are very well suited for use as roof boards and can meet the building regulations in a cost-effective and efficient manner.

The invention is concerned with mineral fibre products that have a core formed by cutting the web into lamellae and turning the lamellae so as to ensure that the entirety of the core section is reoriented (in contrast to the "pleating" methods discussed above which achieve only partial reorientation).

The invention essentially requires that the core layer or core layers are cured before being cut into lamellae and that the reoriented lamellar core section is covered with at least one covering layer. The curing of the web in the first curing oven prior to cutting of the web into lamellae ensures that the compression strength properties of the web are optimised as reorienting the fibres before curing is destructive for the uncured web and therefore lowers the homogeneity of the properties and causes the resultant product to have inferior insulating and strength properties.

In a preferred embodiment, the density of the air laid web is between 50 and 90 kg/m³, and is preferably about 60 kg/m³. This is considerably lower than the density of conventional mineral wool insulation products and allows for optimum insulation properties to be obtained.

A major advantage of the method of the present invention is that the whole product can be made from a single air laid web. This type of process is commonly known as "on-line". Producing the different layers from a single initial layer results in substantial processing efficiency compared with processes where different layers have different sources.

To improve the balance of insulation and strength properties even further, it is preferred to form an additional layer for each core layer, compress the additional layer(s) to form a reinforcing layer(s) and join the reinforced layer(s) to the core layer(s) prior to curing in the first curing oven.

In a further preferred embodiment, the lamellar core structure comprises two core layers which have a directional relationship with respect to one another. In particular, the largest surface of each lamella of one core layer is at 90° to the largest surface of each lamella in the other core layer.

Detailed Description

In the method of the present invention, the air laid web of mineral fibres and heat curable binder can be made in any conventional way. To form air laid webs, mineral material is made molten, usually in a furnace such as a cupola furnace. A stream of the molten mineral material is then fed to fiberising equipment which converts the melt to fibres.

There are two main types of fiberising equipment. The first is known as a cup- spinner which is mainly used for glass wool, and the second is known as a cascade spinner which is mainly used for rock wool. Either type can be used in the present invention but it is preferred that the composition of the mineral melt is such that it would be described as rock wool and that a cascade spinner is used. Suitable fiberising equipment is described in documents such as EP678138 and WO94/16163.

The fibres produced by the fiberising equipment are entrained in air and collected on a permeable conveyor in a conventional manner, such as that disclosed in EP678138 and WO94/16163. The dimension of the web which corresponds to the direction of travel of the web following formation is termed the longitudinal direction Y and the dimension of the web which is perpendicular to the longitudinal direction in the plane of the web is called the transverse direction X. The fibres build up on the surface of the conveyor (which is in the XY plane) to produce the air laid web. Hence, the fibres are substantially oriented in the XY plane of the web.

The longitudinal and transverse directions are defined with respect to the direction of transport of the web, so that the longitudinal direction is the direction of transport of the web. The location of the web in space is not important so this can change without affecting the directions of the web which will always be defined with regard to the direction of transport of the web.

Where a web is cross-lapped, the longitudinal direction Y is the direction of travel of the cross-lapped web following formation, so that the longitudinal direction Y generally corresponds to the direction of travel of the conveyor on which the cross-lapped web is formed. The fibres remain in the same plane as prior to cross-lapping, the XY plane.

The mineral fibres that are collected include a heat-curable binder, as is conventional. The binder can be added to the fibres when they are entrained in air or can be added to the fibres as they are being collected on the air permeable conveyor.

The air laid web can be cut into lamella used directly following its formation without further processing. In this case the fibres are allowed to build up on the conveyor until they reach a thickness suitable for the final product, which is around 100 to 500mm, preferably 200 to 400mm most preferably 250 to 350 mm. Alternatively, the air laid web can be cross-lapped. This is preferred, as cross- lapping ensures that the web has a more uniform density. In this process the collected air laid web is usually passed to a pair of conveyors that form a pendulum which swings to arrange the web with segments that overlap one another. In this case, a thinner air laid web is collected than with the direct use method as the web is made thicker by cross-lapping. Cross-lapping is well known in the field and any conventional cross-lapping method can be used, such as those disclosed in EP678138 and WO94/16163.

The air laid web, which has optionally been cross lapped, can be subjected to further processing. For example, it can be compressed such as by height and/or longitudinal compression.

The density of the air laid web which is used in the process is preferably low relative to conventional insulation products. In particular, the density of the core layer of the mineral wool product is preferably 50 to 90 kg/m³, preferably about 60 kg/m³. This is usually similar to the density of the air laid web, which is generally not subjected to a substantial degree of compression in the core layer.

The air laid web, optionally following cross-lapping, is cut in the XY plane to form at least one core layer and at least one covering layer. Preferably there is one core layer and two covering layers, one for each of the major surfaces. The covering layer or each covering layer comprises 1 to 15 %, preferably 2 to 10% by weight of the total air laid web. Usually there are two core layers so these together would make up 2 to 30%, preferably 4 to 20 % of the total weight of the air laid web.

The core layer or layers pass through a first curing oven. The curing oven has the effect of curing or "setting" the heat curable binder. The heat of the first curing oven and duration in the oven should be sufficient to ensure that curing occurs. Once the binder has been cured, the fibres in the core layer are fixed in position and the web becomes more robust. It is important in the present invention that the core layer is passed through a first curing oven at this point, i.e. before the core layer has been cut into lamellae. This is due to the fact that the structure of the cured core layer will be less damaged than if cutting were to take place on an uncured web. Following the first curing oven, the core layer is cut into lamellae. The core layer can either be cut in the longitudinal Y or the transverse X direction. It is preferred to cut the core layer in the transverse X direction as this results in a simpler process than cutting in the Y direction. The "lamellae" are the strips of the core layer that are formed by cutting. The direction of cutting is selected to be substantially perpendicular to the major fibre direction.

The lamellae are reoriented by 90°. The purpose of the reorientation is to change the orientation of the fibres from being substantially in the XY plane to being substantially perpendicular to the XY plane. The compression strength in the direction perpendicular to the XY plane is thus greatly improved.

The reoriented lamellae are joined together in any conventional manner, such as with an adhesive, to form a lamellar core section.

Where there is more than one core layer, each core layer is cut into lamellae and these lamellae are joined together to make the lamellar core section. Usually the lamellae of each core layer are joined to one another to form what is termed a lamellar core layer before being joined with the other lamellar core layer to form a lamellar core section. The lamellar core layers can be joined to one another so as to have the same orientation, i.e. the elongate lamellae have their long directions arranged parallel with one another.

However, in a preferred embodiment, the lamellar core layers are arranged so as to have a directional relationship to one another, in particular to be perpendicular to one another. In particular, two core layers are formed, each core layer is cut to form lamellae which have two opposed largest surfaces and other smaller surfaces. The lamellae are reoriented and joined to form the lamellar core section so that the largest surfaces of each lamella of one core layer are at 90° to the largest surfaces of each lamella in the other core layer. Otherwise expressed the elongate lamellae in adjacent core layers have their long directions arranged in substantially perpendicular conformation. This can be achieved either by cutting one of the core layers into lamellae in the longitudinal direction and one in the transverse direction, or by cutting both core layers into lamellae in the same direction, and turning one of the lamellar core layers by 90° with respect to the other lamellar core layer prior to joining the lamellar core layers together. The covering layer or layers are placed onto the major surface or surfaces of the lamellar core section. This is usually the surface in the XY plane. Preferably the covering layer(s) are processed prior to being placed on the lamellar core section.

In the preferred embodiments of the invention the covering layer(s) are compressed, preferably by being subjected to height compression. This increases the density of the covering layers and enables them to provide excellent strength to the final product. Preferably, the covering layer or each covering layer has a density of 100 to 250 kg/m³, preferably 150 to 200 kg/m³, most preferably around 180 kg/m³ (compared to the core layer which has a density of 50 to 90 kg/m³, preferably about 60 kg/m³).

The covering layers can be adhered to the lamellar core section with adhesive or can simply be placed or held onto the lamellar core section until the covered lamellar core section passes through a second curing oven. As with the first curing oven the purpose is to cure the heat curable binder in the uncured mineral wool, of the covering layer(s), and to ensure that the layers of the covered lamellar core section are adhered together. The first and second curing ovens are different entities.

In a preferred embodiment, an additional layer (which is in addition to the covering layer(s)) is formed for each core layer. The additional layers can be formed before or after the core layer has been cured, preferably after curing. The additional layer or additional layers are compressed to form a reinforcing layer or reinforcing layers with a higher density than the core layer. The reinforcing layer can have a density of 100 to 250 kg/m³, preferably 150 to 200 kg/m³, most preferably around 180 kg/m³. The reinforced layer or reinforced layers are joined to the core layer or core layers prior to the core layer(s) being cut into lamellae. The reinforcing layers impart additional strength to the lamellar core layer, which is advantageous.

According to the second aspect, the invention relates to a mineral wool product obtainable according to the method of the invention. The product is defined in claim 9. Such a product has advantageous properties, namely a good balance between strength and insulating properties while being light per unit area and therefore easy and convenient to handle. The characteristics of the product that distinguish it from products made by different methods are that the lamellar core section has been cured twice, while the covering layers have only been cured once. In addition, as the core layer and covering layers all come from the same source, the chemical composition of the mineral fibres and the binder will be substantially the same (although as noted above, the layers can be processed in different ways).

The product of the invention is advantageously used in the insulation field, particularly as a roof board to insulate a roof.

Figures

Figure 1 is an illustration of a process of making a mineral fibre product in accordance with the preferred embodiments of the present invention;

Figure 2 is an illustration of a process of making a mineral fibre product in accordance with the preferred embodiments of the present invention;

Figure 3 shows a product in accordance with the preferred embodiments of the present invention.

A process according to the preferred embodiments of the present invention is described below with reference to the figures.

A mineral melt is fiberised and the fibres collected on a permeable conveyor as an air-laid web (not shown). The air laid web 1 is passed on conveyors 2 to a pair of pendulum conveyors 3 which cross-lap the web 1 to form a cross-lapped web 4. The cross-lapped web 4 is then passed through sets of rollers 5 and 6 to subject the cross-lapped web 4 to height compression and longitudinal compression.

A knife is positioned at point 7 which cuts the web 4 in the XY plane to separate the web into two layers, the core layer 8 and the covering layer 9. The core layer 8 is cured in first curing oven 10 and is then cut into lamellae 13 by circular saws

11. The lamellae are cut into lengths corresponding to the desired dimensions of the final product by circular saw 12 and the lamellae are then turned by 90 degrees to form a lamellar core section 14.

In the embodiment in figure 1 , the covering layer 9 is split into two by cutting the layer in the XY plane with saw 15 to make an upper covering layer 16 and a lower covering layer 17. The upper covering layer 16 and lower covering layer 17 are placed onto the lamellar core section 14 at point 18 to form a covered lamellar section 20.

In the embodiment in figure 2, the covering layer 9 is split into two by cutting the layer in the longitudinal direction Y with saw 15 to make an upper covering layer 16 and a lower covering layer 17. The upper covering layer is placed onto the lamellar core section 15 at point 18 and the partially covered lamellar core layer is moved to point 19 where it is placed onto the lower covering layer 17 to form a covered lamellar section 20.

In the embodiments in figures 1 and 2 the covered lamellar product 20 is passed along conveyor 21 and passed through curing oven 22 to form the final product 23. The final product 23 is used as roofing insulation.

Figure 3 shows a cured covered lamellar core section 23 which includes two lamellar core layers 24, 25. The lamellae core layers are oriented at 90° to one another. The lamellar core section (which is made up from the lamellar core layers 24 and 25) has two covering layers, 16 and 17.

The cured covered lamellar core section 23 is used as a roof board for roof insulation.

Claims

1. A method of making a mineral fibre product (23) comprising the steps of:

(a) forming an air laid web (1) of mineral fibres and heat-curable binder on a permeable conveyor (2) and transporting the web on the conveyor, wherein the web has a longitudinal direction Y which is in the direction of transport of the web and the web has upper and lower major surfaces and the lower major surface is in contact with the conveyor and the web has a transverse direction X which is substantially parallel to the major surfaces and substantially perpendicular to longitudinal direction Y, and the fibres of the web are substantially oriented in the

XY plane;

(b) cutting the web (1) in the XY plane to form at least one core layer (8) and at least one covering layer (9);

(c) passing the core layer (8) or each of the core layers (8) through a first curing oven (10) so as to cure the binder;

(d) cutting the core layer (8) or each of the core layers (8) in either the longitudinal direction Y or the transverse direction X to form lamellae (13), reorienting each lamella by 90° and joining the reoriented lamellae (13) to form a lamellar core section (14) which has upper and lower major surfaces; (e) placing the covering layer (9) or covering layers (9) onto a major surface or major surfaces of the lamellar core section (14) to obtain a covered lamellar core section (20); and

(f) passing the covered lamellar core section (20) through a second curing oven (22) to form a mineral fibre product (23).

2. A method according to claim 1 , wherein the density of the core section of the mineral fibre product is 50 to 90 kg/m³, preferably about 60 kg/m³.

3. A method according to claim 1 or 2, wherein an additional layer is formed for each core layer (8), the additional layer or additional layers are compressed to form a reinforcing layer or reinforcing layers and the reinforced layer or reinforced layers are joined to the core layer or core layers prior to step c).

4. A method according to any preceding claim, wherein the covering layer (9) or each covering layer (9) comprises 1 to 15 %, preferably 2 to 10% by weight of the air laid web.

5. A method according to any preceding claim wherein the covering layer (9) or each covering layer (9) has a density of 100 to 250 kg/m³, preferably 150 to 200 kg/m³, most preferably around 180 kg/m³ and the core layer has a density of 50 to 90 kg/m³, preferably about 60 kg/m³.

6. A method according to any preceding claim, wherein the mineral fibre product (23) is a roof board.

7. A method according to any preceding claim, wherein two core layers (8) are formed and wherein each core layer (8) is cut to form lamellae (13) and the lamellae (13) are joined to form the lamellar core section (14) so that the largest surface of each lamellar of one core layer is at 90° to the largest surface of each lamellar in the other core layer.

8. A method according to any preceding claim, wherein the air laid web (1) is cross-lapped prior to being cut to form at least one core layer (8) and at least one covering layer (9).

9. A mineral wool product (23) which has two opposite major surfaces comprising a lamellae core section comprising several lamellae of mineral fibres and heat cured binder joined side-by-side whereby the fibres are oriented substantially perpendicular to the said major surfaces; and a covering layer positioned over the lamellae core over one of said major surfaces, the covering layer being formed of a layer of mineral fibres of the same composition as those of the core and oriented parallel to the major surfaces and heat cured binder of the same type as the core binder.

10. A mineral wool bound according to claim 9 obtainable by a method according to any preceding claim.

11. Use of a product (23) according to claim 10 or claim 11 as roof insulation.