Method for producing a sip wall element and sip wall element produced by such method

Abstract

The invention relates to a method for producing a SIP wall element (10), the SIP wall element (10) comprising opposing first and second boundary surfaces (11 a, 11 b) and four lateral boundary surfaces (11c), characterised in that the method comprises the steps of: a) arranging a first magnesium oxide board (13a) at the first boundary surface (11a), a second magnesium oxide board (13b) at the second boundary surface (11 b), and shuttering elements (20) at the lateral boundary surfaces (11c), such that the first and second magnesium oxide boards (13a, 13b) and the shuttering elements (20) together define a mould (300) delimiting a cavity (200), the mould (300) being provided with a filling opening (22) and one or more vent openings (23); b) fixing the magnesium oxide boards (13a, 13b) and the shuttering elements (20) against displacement relative to each other; c) heating the mould (300) to a temperature between 45 and 50 degrees Celsius; d) introducing liquid-state PIR foam into the cavity (200) through the filling opening (22), and discharging the air displaced by the PIR foam from the cavity (200) through the one or more vent openings (23); e) sealing the filling opening (22) and the one or more vent openings (23), and allowing the mould (300) to cool; f) removing the shuttering elements (20) after curing of the PIR foam. The invention further relates to a SIP wall element 10 produced by the method according to the invention.

Description

[0001]

[0002] Method for Producing a SIP Wall Element and SIP Wall Element Produced by Such Method

[0003] The invention relates to a method for producing a SIP wall element, the SIP wall element comprising opposing first and second boundary surfaces, as well as four lateral boundary surfaces.

[0004] The invention also relates to a SIP wall element comprising a first and a second magnesium oxide board, and a PIR foam thermal insulation layer fixed to the first and second magnesium oxide boards and enclosed therebetween.

[0005] As in every field, time and cost are key considerations in the construction industry as well. The three most important questions are what, when, and for how much. The aim is to accelerate the construction process in the most cost-effective manner possible. Traditional wall structures using brick require substantial on-site manual labour, and the wet technologies involved are time-consuming. Trends in recent years indicate that skilled construction labour is increasingly scarce and expensive on the market. As a result, prefabricated structures have come to the fore, where the exterior — and in some cases interior — walls of a building are constructed from prefabricated wall elements. Using this technology, the external structural envelope (walls and roof) of a typical family house can be erected within a week following the completion of the foundation works.

[0006] The use of multi-layered versions of wall elements, known as SIP (Structural Insulated Panel) wall elements, has a history spanning several decades. SIP wall elements were already used in the construction of residential buildings in the United States as early as the 1930s. These panels were wood-based, with insulating materials, such as foamed concrete, arranged in the intermediate layers. The next evolutionary milestone in the SIP industry occurred in the 1990s, with the spread of OSB (Oriented Strand Board) sheets. At that time, OSB sheets began to be used as the facing of the panels, while EPS (expanded polystyrene) boards were typically applied as the insulating layer between the sheets.

[0007] Among the various SIP technologies, solutions utilising OSB sheets are currently the most widespread. The main disadvantage of these is that the EPS boards are bonded to the OSB sheets using adhesives, which adds an extra manufacturing step and increases production costs. Furthermore, this method does not always provide sufficiently strong adhesion between the individual layers for all applications. A further drawback of SIP elements with OSB sheets is their poor resistance to fire, water, mould, and pests, which necessitates additional surface treatment and the use of extra layers. The combined thermal conductivity of OSB sheets and EPS boards is relatively high; therefore, additional external thermal insulation layers must be applied to the SIP elements when used in residential buildings. Moreover, since OSB sheets are practically unsuitable for painting, these SIP elements must in any case be covered with a finishing layer.

[0008] Patent document GB 2588833 A discloses a modular building structure system, the main component of which is a SIP panel arranged between a steel frame. The panel consists of two construction boards and an insulating material arranged therebetween, where the construction board may be made of MgO, and the insulating material may be PIR foam.

[0009] Document CN 103059242 A discloses a rigid foam material made of epoxymodified polyisocyanurate resistant to high temperatures, along with a method for its production. The PIR foam disclosed is ideal for homogeneous foam structures, exhibiting excellent thermal stability at high temperatures, adequate strength and thermal insulation properties, as well as outstanding sound absorption and flameretardant characteristics.

[0010] We recognised that by using magnesium oxide sheets instead of OSB sheets as facing layers, and PIR (polyisocyanurate) foam instead of EPS boards as the thermal insulation layer, a SIP wall element can be produced which, due to its particularly high thermal stability, exhibits excellent fire protection properties, while also having a notably low thermal conductivity. The enhanced fire resistance makes it possible to use the wall elements in buildings with higher fire safety classifications, such as nurseries, kindergartens or schools. Owing to the excellent insulation properties, there is no need for additional thermal insulation layers, which significantly reduces construction costs, and the same thermal insulation performance can be achieved with thinner walls, thereby increasing the usable internal floor area of the building. Furthermore, due to their surface characteristics, magnesium oxide sheets can be directly painted, wallpapered, plastered or covered with other internal finishing layers, so unlike OSB-based solutions, there is no need to apply a separate layer (e.g. plasterboard) to enable such finishes.

[0011] We also recognised that if the PIR foam is introduced in liquid state between the magnesium oxide sheets, a particularly strong chemical bond is formed between the cured PIR foam and the sheets. This eliminates the need for a separate bonding step between the layers, while providing the wall elements with excellent structural strength. As a result, the wall elements become self-supporting, meaning that the building does not require a separate frame structure, which further reduces construction costs. The strong bond formed during the curing of the PIR foam between the facing and the insulation layer also improves the fire resistance of the SIP wall elements, since the individual layers are less prone to separation under thermal load, and thus the wall element retains its structural stability for a longer time.

[0012] However, we recognised that if the curing (foaming) of the PIR foam takes place under unsuitable conditions, the resulting PIR foam may be prone to deformation even under normal thermal effects (e.g. sunlight) during use, which is particularly undesirable when used in SIP wall elements. We further recognised that if the liquid-state PIR foam is introduced into a mould preheated to a specific temperature, and the entire assembly is then allowed to cool, the foaming process of the PIR foam can be completed properly, and the foaming will not re-initiate upon later heat exposure. The PIR foam cured in this way will be dimensionally stable and will no longer deform when exposed to heat.

[0013] The aim of the invention is to provide a SIP wall element and a method for producing such a SIP wall element, which are free from the disadvantages of solutions known from the prior art. In particular, our objective is to provide a method for producing a SIP wall element whose fire resistance, thermal and acoustic insulation properties, as well as structural characteristics, exceed those of existing SIP wall elements, and in which the PIR foam thermal insulation layer does not deform under the effect of heat. Owing to their design, the wall elements are self- supporting and load-bearing structures, thus enabling the construction of buildings without a frame structure, at lower cost and with reduced need for specialised labour. The objectives set out above are achieved by the method for producing a SIP wall element according to claim 1 , and by the SIP wall element according to claim 8.

[0014] The SIP wall element according to the invention is suitable for versatile use, including in family houses, small offices, surgeries, shops or smaller-scale public buildings. Using the SIP wall elements according to the invention, building walls can be constructed in a cost-effective and rapid manner, with minimal involvement of specialised labour, and with outstanding thermal and fire insulation properties.

[0015] The problem is solved by forming, in the SIP wall element, a first and a second magnesium oxide board as facing layers, and a PIR foam thermal insulation layer enclosed therebetween, wherein the PIR foam is introduced in liquid state between the magnesium oxide boards, which have been preheated to a predetermined temperature, and the assembly is then allowed to cool, during which the PIR foam cures between the boards.

[0016] In a particularly preferred embodiment, the liquid-state PIR foam is introduced between the magnesium oxide boards at a pressure of between 120 and 140 bar, preferably at a pressure of 130 bar, thereby forming a thermal insulation layer between the boards which, after curing, has a density of at least 45 kg / m3

[0017] In another preferred embodiment, a two-component liquid-state PIR foam is used, which is introduced between the magnesium oxide boards at a temperature between 22 and 25 degrees Celsius, preferably at 23 degrees Celsius.

[0018] Further preferred embodiments of the invention are defined in the dependent claims.

[0019] Further details of the invention are described by way of exemplary embodiments and with reference to the drawings. In the drawings:

[0020] Figure 1 is a schematic perspective view of an exemplary embodiment of a SIP wall element produced by the method according to the invention,

[0021] Figure 2a is a schematic A-A sectional view of the SIP wall element shown in Figure 1 ,

[0022] Figure 2b is a schematic B-B sectional view of the SIP wall element shown in Figure 1 ,

[0023] Figure 3 is a block diagram illustrating the main steps of a method for producing a SIP wall element according to the invention, Figure 4 is a schematic view of a mould used in the method according to the invention, shown with one shuttering element removed,

[0024] Figure 5 is a schematic view illustrating the joining of two adjacent SIP wall elements according to the invention.

[0025] Figure 1 shows a schematic perspective view of an exemplary embodiment of a SIP wall element 10 according to the invention. The SIP wall element 10 comprises opposing first and second boundary surfaces 11 a, 11 b and four lateral boundary surfaces 11 c. In a particularly preferred embodiment, the opposing boundary surfaces 11 a, 11 b and the mutually opposing lateral boundary surfaces 11 c are formed as mutually parallel, substantially planar surfaces, so that the SIP wall element 10 has a flat, substantially cuboid shape, as shown in Figure 1.

[0026] The SIP wall element 10 according to the invention comprises a first magnesium oxide board 13a at the first boundary surface 11 a, a second magnesium oxide board 13b at the second boundary surface 11 b, and a PIR foam thermal insulation layer 13c fixed to the first and second magnesium oxide boards 13a, 13b and enclosed therebetween. In the context of the present invention, the first and second magnesium oxide boards 13a, 13b are generally understood to be sheets known per se, made from a mixture of magnesium oxide and other materials. These boards are often referred to as "magnesium oxide cement boards" or simply "magnesium boards". Magnesium oxide boards offer several advantages in the construction industry, such as fire resistance and water resistance. During the production of magnesium oxide boards, the required raw materials are mixed and prepared. These include magnesium oxide powder as well as other additives such as cellulose fibre, wood chips, perlite or glass fibre, which improve the mechanical properties of the boards. The mixed raw materials are formed into a mouldable paste, which is then poured or pressed into board shapes. The formed boards are allowed to harden and dry. During hardening, the magnesium oxide reacts with water to form hydrated magnesium hydroxide (magnesium hydrate), which solidifies the boards. Finally, the hardened boards are cut to the desired size and shape.

[0027] In a particularly preferred embodiment, the first and second magnesium oxide boards 13a, 13b are chloride-free magnesium oxide boards 13a, 13b, and are therefore resistant to corrosion and discolouration. The SIP wall element 10 is preferably dimensioned such that the width of the boards 13a, 13b in the direction of the lateral boundary surfaces 11 c, i.e. the width of the SIP wall element 10, is preferably 120 cm, and the height of the boards 13a, 13b is between 280 and 300 cm, preferably 285 cm. The advantage of this sizing is that the SIP wall elements 10 can be easily moved, even manually, and that the interior height of a dwelling or family house built from the SIP wall elements 10 corresponds to the typical range of 260-280 cm found in modern residential buildings. The thickness of the magnesium oxide boards 13a, 13b is preferably between 10 and 12 mm.

[0028] The PIR foam thermal insulation layer 13c is arranged between the boards 13a, 13b in such a way that the PIR foam thermal insulation layer 13c is chemically bonded to the boards 13a, 13b, that is, the boards 13a, 13b are essentially joined together by the PIR foam thermal insulation layer 13c. The boards 13a, 13b and the PIR foam thermal insulation layer 13c are arranged in a sandwich-like structure, i.e. in parallel with each other and with the planes of the boundary surfaces 11 a, 11 b (see Figures 2a and 2b). The thickness of the PIR foam thermal insulation layer 13c is preferably between 8 and 18 cm.

[0029] The SIP wall element 10 is produced by the method according to the invention as follows. The main steps of the method are illustrated in Figure 3.

[0030] In the first step a) of the method according to the invention, a first magnesium oxide board 13a is arranged at the first boundary surface 11 a, a second magnesium oxide board 13b is arranged at the second boundary surface 11 b, and shuttering elements 20 are arranged at the lateral boundary surfaces 11 c in such a way that the first and second magnesium oxide boards 13a, 13b and the shuttering elements 20 together define a mould 300 delimiting a cavity 200, as shown for example in Figure 4. The mould 300 may be formed, for example, by placing one of the boards 13a, 13b on a workbench (not shown in the figure), arranging shuttering elements 20 of a height corresponding to the intended thickness of the thermal insulation layer 13c around the edges of the given board 13a, 13b, and then placing the other board 13b, 13a on top of the shuttering elements 20, which act as spacers. The shuttering elements 20 are preferably made of wood or another material with low thermal conductivity. The shuttering elements 20 are configured to fit precisely and essentially without gaps against the boards 13b, 13a. That is, the top and bottom of the shuttering elements 20 lie in planes, preferably in mutually parallel planes. The mould 300 is provided with a filling opening 22 and one or more vent openings 23. The openings 22 and 23 are preferably formed as bores in the shuttering elements 20. The shuttering elements 20 may be arranged directly at the edges of the boards 13a, 13b, but in a preferred embodiment, during the formation of the mould 300, a portion of the shuttering elements 20 are recessed inward from the edges of the magnesium oxide boards 13a, 13b, towards the interior of the cavity 200, as shown in Figure 4. In a particularly preferred embodiment, the shuttering elements 20 are recessed by 5 to 10 cm, preferably 6 cm, from the edges of the magnesium oxide boards 13a, 13b, meaning that the distance between the sides of the shuttering elements 20 facing the cavity 200 and the edges of the boards 13a, 13b is 5 to 10 cm, preferably 6 cm. The function of this arrangement will be explained in more detail below.

[0031] In the next, second step b) of the method, the magnesium oxide boards 13a, 13b and the shuttering elements 20 are fixed against displacement relative to one another. This may be achieved using an external frame structure, a clamp frame, or a hydraulic press (not shown in the drawings), as would be apparent to the skilled person.

[0032] In the next, third step c) of the method, the mould 300, together with the air present in the cavity 200, is heated to a temperature between 45 and 50 degrees Celsius. The mould 300 may be heated, for example, by directly heating the magnesium oxide board 13a, 13b positioned on the workbench, using a heating element arranged in the workbench. Due to thermal conduction, the shuttering elements 20 in direct contact with the heated magnesium oxide board 13a, 13b, as well as the other board 13b, 13a in contact with the shuttering elements, also heat up after a while. In another possible embodiment, the magnesium oxide board 13a, 13b not in contact with the workbench is also heated, thereby causing the mould 300 to reach the desired temperature more quickly. In a third exemplary embodiment, the magnesium oxide boards 13a, 13b are not heated directly; instead, hot air is blown into the cavity 200. In addition to the examples presented above, the mould 300 may of course be heated in other ways known to the skilled person. It should be noted that in certain embodiments, the order of steps b) and c) may be reversed, i.e. the magnesium oxide boards 13a, 13b and the shuttering elements 20 may first be heated and then fixed against displacement.

[0033] In the next, fourth step d) of the method, the cavity 200 is filled with liquid- state PIR foam through the filling opening 22, and the air displaced by the PIR foam is vented from the cavity 200 through one or more vent openings 23. It should be noted that in its liquid state, the PIR foam is not yet foam in texture, and it only becomes foamed upon curing. Nevertheless, for the sake of simplicity, this material is referred to in the description as "liquid-state PIR foam". The liquid-state PIR foam is preferably introduced into the cavity 200 through the filling opening 22 formed in one of the shuttering elements 20, using a pipe (not shown in the drawings) connected to the filling opening 22. In a particularly preferred embodiment, the liquid-state PIR foam is introduced into the cavity 200 at a pressure between 120 and 140 bar, preferably at 130 bar, thereby producing PIR foam in the cavity 200 with a density of at least 45 kg / m3. It should be noted that the density of at least 45 kg / m3refers to the density of the PIR foam after curing. In a preferred embodiment, a two-component liquid-state PIR foam is introduced into the cavity 200 at a temperature between 22 and 25 degrees Celsius, preferably at 23 degrees Celsius. The components are preferably mixed before, and most advantageously directly before, their introduction into the cavity 200. In this embodiment, the term "liquidstate PIR foam" refers to the mixture of the two components.

[0034] In the next, fifth step e) of the method, after the cavity 200 has been filled with the liquid-state PIR foam, the filling opening 22 and the one or more vent openings 23 are sealed, thereby also sealing the cavity 200. The sealed state of the cavity 200 means that the liquid-state PIR foam introduced into the cavity 200, which expands during curing, is not able to escape from the cavity 200. The sealing of the openings 22 and 23 may be carried out, for example, by plugging them. The sealed mould 300 is then allowed to cool, and the liquid-state PIR foam within it is allowed to cure, thereby forming the PIR foam thermal insulation layer 13c. Since in step b) the magnesium oxide boards 13a, 13b and the shuttering elements 20 were fixed against relative displacement, the mould 300 is not deformed by the PIR foam expanding under high pressure.

[0035] In the final, sixth step f) of the method, the shuttering elements 20 are removed after the PIR foam has cured, thereby yielding the SIP wall element 10. During curing, the PIR foam forms a chemical bond with the magnesium oxide boards 13a, 13b, resulting in strong adhesion between the layers of the SIP wall element 10, which makes the wall element 10 structurally self-supporting. In those embodiments where the shuttering elements 20 were arranged recessed inward from the edges of the magnesium oxide boards 13a, 13b towards the interior of the cavity 200, the removal of the shuttering elements 20 creates a groove 19 running parallel to the boards 13a, 13b along the lateral boundary surfaces 11 c.

[0036] The grooves 19 enable an advantageous joining method for the SIP wall elements 10, which is illustrated in Figure 5. In the adjacent SIP wall elements 10 forming the wall structure, a respective groove 19 is formed at the adjacent lateral boundary surfaces 11 c, running parallel to the first and second boards 13a, 13b. Into the grooves 19, two joint inserts 30, preferably made of wood, are inserted from above in such a way that a PIR foam layer 31 is arranged between them. The joint inserts 30 are covered on the outside with a respective covering magnesium oxide board 32. The joint inserts 30 are preferably made of hardwood, such as acacia or beech, and they fill the gap between the SIP wall elements 10 in a sandwich-like manner together with the PIR foam layer 31 and the magnesium oxide boards 32, thereby providing proper mechanical connection as well as excellent thermal and acoustic insulation between the wall elements 10.

[0037] Various modification to the above disclosed embodiment will be apparent to a person skilled in the art without departing from the scope of protection determined by the attached claims.

Claims

Claims1. A method for producing a SIP wall element (10), the SIP wall element (10) comprising opposing first and second boundary surfaces (11 a, 11 b) and four lateral boundary surfaces (11 c), characterised in that the method comprises the steps of: a) arranging a first magnesium oxide board (13a) at the first boundary surface (11a), a second magnesium oxide board (13b) at the second boundary surface (11 b), and shuttering elements (20) at the lateral boundary surfaces (11 c), such that the first and second magnesium oxide boards (13a, 13b) and the shuttering elements (20) together define a mould (300) delimiting a cavity (200), the mould (300) being provided with a filling opening (22) and one or more vent openings (23); b) fixing the magnesium oxide boards (13a, 13b) and the shuttering elements (20) against displacement relative to each other; c) heating the mould (300) to a temperature between 45 and 50 degrees Celsius; d) introducing liquid-state PIR foam into the cavity (200) through the filling opening (22), and discharging the air displaced by the PIR foam from the cavity (200) through the one or more vent openings (23); e) sealing the filling opening (22) and the one or more vent openings (23), and allowing the mould (300) to cool; f) removing the shuttering elements (20) after curing of the PIR foam.

2. The method according to claim 1 , characterised in that the opposing boundary surfaces (11a, 11 b) and lateral boundary surfaces (11 c) are formed as mutually parallel, substantially planar surfaces.

3. The method according to claim 1 or 2, characterised in that the liquidstate PIR foam is introduced into the cavity (200) at a pressure between 120 and 140 bar, preferably at 130 bar, thereby forming PIR foam in the cavity (200) having a density of at least 45 kg / m34. The method according to any one of claims 1 to 3, characterised in that the liquid-state PIR foam introduced into the cavity (200) is a two-component foam having a temperature between 22 and 25 degrees Celsius, preferably 23 degrees Celsius.

5. The method according to any one of claims 1 to 4, characterised in that during the formation of the mould (300), the shuttering elements (20) are arranged recessed inward from the edges of the magnesium oxide boards (13a, 13b), towards the inside of the cavity (200).

6. The method according to claim 5, characterised in that the shuttering elements (20) are recessed by 5 to 10 cm, preferably 6 cm, from the edges of the magnesium oxide boards (13a, 13b).

7. The method according to any one of claims 1 to 6, characterised in that the shuttering elements (20) are made of wood.

8. A SIP wall element (10) comprising a first and a second magnesium oxide board (13a, 13b), and a PIR foam thermal insulation layer (13c) fixed to the first and second magnesium oxide boards (13a, 13b) and enclosed therebetween, characterised in that the PIR foam thermal insulation layer (13c) is produced by steps c) to e) of the method according to any one of claims 1 to 7.

9. The SIP wall element (10) according to claim 8, characterised in that the first and second magnesium oxide boards (13a, 13b) have a thickness of between 10 and 15 mm, preferably 12 mm.

10. The SIP wall element (10) according to claim 8 or 9, characterised in that the first and second magnesium oxide boards (13a, 13b) have a width of 1.2 metres and a height of 2.85 metres.

11. The SIP wall element (10) according to any one of claims 8 to 10, characterised in that the PIR foam thermal insulation layer (13c) has a thickness ofbetween 8 and 25 cm.

12. The SIP wall element (10) according to any one of claims 1 to 11 , characterised in that the first and second magnesium oxide boards (13a, 13b) are chloride-free magnesium oxide boards (13a, 13b).

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