A multi-layered building element and a use thereof

Abstract

According to an example aspect of the present invention, there is provided a multi-layered building element, comprising: a first wood-based panel; a second wood-based panel; between the wood-based panels, a sound insulation layer which has been attached to the wood-based panels, wherein the sound insulation layer comprises a multi-layered structure made of a plurality of fibrous sheets comprising cellulosic and / or lignocellulosic fibres, which fibrous sheets have been stacked and joined to each other so that a plurality of discrete areas in each fibrous sheet have been joined to adjacent fibrous sheets, wherein the fibrous sheets are oriented substantially parallel with the wood-based panels.

Description

TITLEA multi-layered building element and a use thereofFIELD

[0001] The present application relates to building elements, particularly sandwich- structured building elements exhibiting sound insulation properties.BACKGROUND

[0002] Previously known are various types of composite boards which are manufactured by combining wood-based materials and at least one other material. When manufacturing a composite board, it is sought to maximize the good properties and to minimize the bad properties in the end product.

[0003] It is previously known to form composite boards by mixing or combining together various raw materials, for example various layers, and bonding the materials or layers to each other, in order to create a composite board or a sandwich board. It is also known to form composite boards by coating methods, for example wood panels with various coatings comprising non-wood materials.

[0004] The use of various types of gluing and pressing methods in the manufacture of composite boards is also previously known.

[0005] It is known to use mineral wool insulation between cross-laminated timber (CLT) boards in walls.

[0006] Embodiments of the present invention are intended to overcome at least some of the disadvantages in the known building elements and sandwich boards.SUMMARY OF THE INVENTION

[0007] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0008] According to a first aspect of the present invention, there is provided a multilayered building element, comprising: a first wood-based panel; a second wood-based panel; between the wood-based panels, a sound insulation layer which has been attached to the wood-based panels, wherein the sound insulation layer comprises a multi-layered structure made of a plurality of fibrous sheets comprising cellulosic and / or lignocellulosic fibres, which fibrous sheets have been stacked and joined to each other so that a plurality of discrete areas in each fibrous sheet have been joined to adjacent fibrous sheets, wherein typically the fibrous sheets are oriented substantially parallel with the wood-based panels.

[0009] According to a second aspect of the present invention, there is provided use of the multi-layered building element according to the first aspect in a wall, such as in a load-bearing partition wall in a building, typically as a load-bearing part of said wall.

[0010] According to a third aspect of the present invention, there is provided use of a paper cushion pad as a sound-insulating layer in a building element, such as a wall element or a door element.

[0011] Various embodiments of the first aspect or the second aspect or the third aspect may comprise one or more features from the following bulleted list:• The multi-layered building element according to any of the preceding claims, wherein the sound insulation layer comprises, in each interspace between the fibrous sheets, air-filled spaces enclosing said discrete areas and preferably extending across the sound insulation layer in a direction that is orthogonal to the thickness of the sound insulation layer.• The multi-layered structure comprises a cushion structure, such as a cellular cushion structure.• The multi-layered structure comprises or consists of a plurality of paper or paperboard sheets, such as 3 to 100, for example 10 to 50 paper or paperboard sheets, which paper or paperboard sheets have been stacked and partially joined to each other.The fibrous sheets comprise or consist of structured or embossed paper sheets and / or flat paper sheets.The fibrous sheets comprise or consist of alternating embossed paper sheets and flat paper sheets.• At least an innermost paper sheet in said plurality of paper sheets is an embossed paper sheet.• The outermost paper sheets in said plurality of paper sheets are flat paper sheets.• The multi-layered structure comprises a paper cushion pad.• The fibrous sheets have a thickness in the range 0.05 to 0.5 mm.• The thickness of the sound insulation layer is in the range 20 to 80 mm, such as 25 to 60 mm.• The density of the sound insulation layer is in the range 1 to 20 kg / m3, such as 3 to 15 kg / m3.• The air content of the sound insulation layer is at least 90 vol-%, such as at least 95 vol-%, calculated from the total volume of the sound insulation layer.• The fibrous sheets have been joined to each other by adhesive at said discrete areas.• The combined surface area of said plurality of discrete areas is less than 20%, such as 1 to 10% of the total surface area of each fibrous sheet.• The sound insulation layer comprises a three-dimensional air-filled space or spaces defined by the partially joined paper sheets.• The fibrous sheets have been manufactured by a paper making process or a paperboard making process.• The cellulosic and / or lignocellulosic fibres of the fibrous sheets comprise or consists of wood pulp, preferably the cellulosic and / or lignocellulosic fibres are selected from chemical pulp, mechanical pulp, thermomechanical pulp, chemi- thermomechanical pulp, and any combinations thereof.• The wood-based panel comprises an engineered wood product, such as laminated veneer lumber (LVL), plywood or cross-laminated timber (CLT).The wood-based panel comprises a multi-layered wood veneer product, such as plywood or LVL.• The wood-based panel comprises a wooden board, such as particle board, wood fibre board or plywood.• The wood-based panels and the sound insulation layer have been joined to each other by adhesive layers, preferably directly without any further layers between the wood-based panels and the sound insulation layer.• The interspace between each wood-based panel and the sound-insulation layer consists of an adhesive layer.• The multi-layered building element has a sandwich structure, such as a symmetrical sandwich structure.• The sound insulation layer is deformable or flexible in the direction of its thickness.• The sound insulation layer is non-deformable or stiff in a direction that is orthogonal to its thickness.• The stiffness of the sound insulation layer is lower in a direction of its thickness than in a direction that is orthogonal to its thickness.

[0012] Advantages of the invention

[0013] The present invention may enable easy assembling of the building element as a ready element, without any onsite gluing steps or layer-by-layer assembling steps.

[0014] The present building element may have a robust and strong structure which may be easily manipulated during assembly.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIGURE 1 shows schematically a multi-layered building element in accordance with an embodiment of the present invention.

[0016] FIGURE 2 shows experimental R values as a function of frequency for a sample structure in accordance with an embodiment of the present invention.

[0017] FIGURE 3 shows paper cushions pads suitable for use in some embodiments of the present invention.

[0018] FIGURE 4 shows a cross-sectional photograph of a sample structure in accordance with an embodiment of the present invention.EMBODIMENTS

[0019] DEFINITIONS

[0020] Unless otherwise stated herein or clear from the context, any percentages referred to herein are expressed as percent by weight based on a total weight of the respective composition.

[0021] In the present context, the term “cellulosic fibres” typically refers to cellulosic and / or lignocellulosic fibres.

[0022] Unless otherwise stated herein or clear from the context, the term “fibres” typically refers to cellulosic and / or lignocellulosic fibres.

[0023] The term “board” is used interchangeably with “panel” and stands for a structure that has at least one planar surface. Preferably the “board” (or “panel”) has two opposite planar surfaces which are generally orientated in parallel. The term “board” or “panel” may refer to a separate, discrete object or to a layer that forms an integral part of a larger object.

[0024] In the present invention it has been surprisingly observed that a combination of wood-based panels and particular low-density wood-based materials may provide significant improvements in sound insulation properties of composite boards.

[0025] Typically, “wood-based material” or “wood-based panel” or “wood-based layer” refers to a material or panel or layer of which at least 50 wt-% is wood or derived from wood.

[0026] In an embodiment, the building element is a multi-layered structure comprising several layers, typically planar boards or planar sheets, stacked on top of each other and joined to each other for example by adhesive layers.

[0027] The building element may be a wall element.

[0028] The building element may be a door element or a door blank.

[0029] In an embodiment, all layers of the building element consist of a wood-based material and optionally adhesive or resin, the layers being joined to each other by adhesive layers.

[0030] The present building element typically comprises at least two wood-based panels, which preferably form the outermost or exposed layers of the building element.

[0031] In some embodiments, the building element comprises at least three woodbased panels, such as at least four wood-based panels, for example at least five wood-based panels.

[0032] In some embodiments, the building element comprises 2 to 15, such as 2 to 10, such as 2 to 5 wood-based panels.

[0033] In some embodiments, the building element comprises at least one, such as at least two, such as at least three sound insulation layers.

[0034] In some embodiments, the building element comprises 1 to 10, such as 1 to 5, such as 1 to 3 sound insulation layers.

[0035] In some embodiments, there is a sound insulation layer in each interspace between the wood-based panels, providing alternation of wood-based panels and sound insulation layers. The outermost layers are generally wood-based panels.

[0036] In one embodiment, the building element comprises exactly two wood-based panels, such as panels with a thickness of at least 10 mm, which preferably form the outermost or exposed layers of the building element.

[0037] In one embodiment, the building element consists of exactly two wood-based panels, which form the outermost layers of the building element, and a sound insulation layer between the wood-based panels. The wood-based panels and the sound insulation layer have been joined together by an adhesive.

[0038] In one embodiment, the building element consists of exactly three layers, and each of said layers comprises or consists of a wood-based material and optionally adhesiveor resin. Two wood-based panels form the outermost layers of the building element, and a sound insulation layer between the wood-based panels forms the inner layer of the building element. Preferably the structure of the building element is symmetrical across its thickness.

[0039] In one embodiment, the building element consists of 2 to 10 wood-based panels and respectively 1 to 9 sound insulation layers. There is a sound insulation layer in each interspace between the wood-based panels, providing alternation of wood-based panels and sound insulation layers. The outermost layers are wood-based panels. The wood-based panels and the sound insulation layers have been joined together by an adhesive.

[0040] One or more of the wood-based panels may still be coated by a wood based layer, such as a wood veneer or a paper-based coating. Such a wood-based coating layer may have a thickness of less than 10 mm, for example less than 5 mm.

[0041] Said two wood-based panels are separated from each other by at least one sound insulation layer.

[0042] Preferably, the wood-based panels and the sound insulation layer or layers are connected to each other only via adhesive or glue layers. Thus, there are typically no further layers or materials between the wood-based panels and the sound insulation layer or layers.

[0043] Typically, the wood-based material in the wood-based panel is produced from softwood or hardwood, such as spruce, pine, larch, birch, poplar, aspen, alder, maple, eucalyptus, balsa or mixed tropical hardwood or from mixtures thereof.

[0044] In some embodiments, the wood-based material in the wood-based panel comprises softwood, such as spruce. In particular, the wood-based panel or panels comprise only softwood, such as spruce, as the wood-based material.

[0045] In some embodiments, the wood-based material in the wood-based panel comprises hardwood, such as birch. In particular, the wood-based panel or panels comprise only hardwood, such as birch, as the wood-based material.

[0046] The thickness of the wood-based panel is generally from about 0.5 to 50 mm, such as 5 to 40 mm, in particular about 10 to 30 mm.

[0047] The thickness of the wood-based panel may be at least 5 mm, such as at least 10 mm, for example at least 15 mm.

[0048] The wood-based panel may have a single-layer structure or a multi-layer structure. A multi-layered wood-based panel may comprise both wood-based layers and additionally layers of other materials, such as adhesive layers and / or functional non-wood layers.

[0049] In an embodiment, the wood-based panel comprises an engineered wood product, such as an engineered wood panel.

[0050] In an embodiment, the wood-based panel comprises a solid wood-based panel or a solid wood panel.

[0051] For example, each of the wood-based panels may be independently selected from the following group: wood board, wood beam, wood veneer, fibreboard, chipboard, lumber, plywood board, LVL (laminated veneer lumber) board, LVL beam, OSB (oriented strand board) board, and any combinations thereof.

[0052] In an embodiment, the wood-based panel comprises an engineered wood product, such as laminated veneer lumber (LVL), plywood or cross-laminated timber (CLT).

[0053] In an embodiment, the wood-based panel comprises a multi-layered wood veneer product, such as plywood or LVL.

[0054] In an embodiment, the wood-based panel comprises a wooden board, such as particle board, wood fibre board or plywood.

[0055] In one embodiment, the wood-based panel comprises a multi-layered wood veneer board or a multi-layered wood veneer product.

[0056] In one embodiment, the wood-based panel comprises an LVL board. In the LVL board, preferably at least 10%, such as at least 20% of the veneers have a grain direction which is in 90 degrees’ angle to the grain direction of the other veneers.

[0057] In one embodiment, the wood-based panel comprises a plywood board.

[0058] In one embodiment, the wood-based panel comprises a plywood board incorporating one or more functional layers.

[0059] In a preferred embodiment, the wood-based panels have been manufactured by a process involving single pressing of the layers of the wood-based panel to join them together, for example by hot-pressing.

[0060] In one embodiment, the wood-based panel consists of a wood veneer.

[0061] In one embodiment, the wood-based panel comprises a solid wood panel, such as a spruce panel or a birch panel. The solid wood panel may be edge-glued or vertically glued.

[0062] In some embodiments, the wood-based panel comprises a cross-grain panel or board, such as an LVL board or a CLT board. Also other wood-based panels in which grain directions are not parallel are advantageous. Examples include an OSB board and chipboard. The advantage of having a cross-grain structure or a non-oriented grain structure is that the panel has better flatness and dimensional stability.

[0063] The wood-based panel may be a coated panel or an uncoated panel.

[0064] In some embodiments, the two or outermost wood-based panels are similar, such as made of or comprising the same wood-based material, to provide a substantially symmetrical structure for the building element.

[0065] Preferably, at least 50 wt-%, such as at least 80 wt-%, such as at least 90 wt- % of the material of the wood-based panel is wood material, such as wood chips, wood strands, wood fibres, wood veneers and / or solid wood, calculated from the dry weight of the wood-based panel.

[0066] In an embodiment, the sound insulation layer comprises less than 20 wt-%, such as less than 15 wt-%, such as less than 5 wt-%, such as less than 2 wt-% plastic materials, calculated from the dry weight of the sound insulation layer. In an embodiment, the sound insulation layer does not comprise any plastic materials. In an embodiment, the sound insulation layer is free from or substantially free from plastic materials.

[0067] Preferably, at least 50 wt-%, such as at least 80 wt-%, such as at least 90 wt- % of the material of the building element is wood material, such as wood chips, woodstrands, wood fibres, wood veneers and / or solid wood, calculated from the dry weight of the building element.

[0068] In an embodiment, the building element comprises less than 5 wt-%, such as less than 2 wt-% plastic materials, calculated from the dry weight of the building element. In an embodiment, the building element does not comprise any plastic materials. In an embodiment, the building element is free from or substantially free from plastic materials.

[0069] The plastic material may comprise or consist of a thermoplastic material.

[0070] In an embodiment, the density of the wood-based panel is at least 300 kg / m3, such as at least 400 kg / m3, such as at least 500 kg / m3, or 300 to 1 000 kg / m3.

[0071] Sound insulation layer

[0072] Typically, the sound insulation layer is attached or glued between the woodbased panels, generally after said manufacturing of the wood-based panels.

[0073] In one embodiment, the sound insulation layer is attached or glued to the wood-based panels, preferably directly onto surfaces of the wood-based panels, whereby the sound insulation layer becomes located between the wood-based panels.

[0074] In an embodiment, the interspace between each wood-based panel and the sound-insulation layer consists of an adhesive layer.

[0075] The sound insulation layer is preferably made of or comprises a wood-based material, such as a paper cushion pad material. Additionally, the manufacturing process of the building element may be simplified as the materials of the wood-based panels and the sound insulation layer are more compatible and similar to each other.

[0076] Typically, said sound insulation layer is a layer that is distinct from the wood-based panels and has a different composition.

[0077] In an embodiment, the sound insulation layer is in the form of a planar board.

[0078] In an embodiment, the sound insulation layer is deformable or flexible in the direction of its thickness.

[0079] In an embodiment, the sound insulation layer is non-deformable or stiff in a direction that is orthogonal to its thickness.

[0080] In an embodiment, sound insulation properties of the sound insulation layer are better in a direction of its thickness than in a direction that is orthogonal to its thickness.

[0081] In an embodiment, the stiffness of the sound insulation layer is lower in a direction of its thickness than in a direction that is orthogonal to its thickness.

[0082] In an embodiment, the stiffness of the sound insulation layer is higher in a direction that is orthogonal to its thickness than in the direction of its thickness.

[0083] In an embodiment, the sound insulation layer comprises or substantially consists of cellulosic and / or lignocellulosic fibres.

[0084] In an embodiment, the sound insulation layer or at least a part of it which exhibits sound insulation properties comprises at least 50 wt-%, such as at least 60 wt-%, for example at least 80 wt-%, for example at least 90 wt-% of cellulosic and / or lignocellulosic fibres, calculated from the dry weight of the sound insulation layer.

[0085] In an embodiment, the cellulosic and / or lignocellulosic fibres are selected from chemical pulp, mechanical pulp, thermomechanical pulp, chemi-thermomechanical pulp, sawdust, and any combinations thereof.

[0086] In an embodiment, the thickness of the sound insulation layer is at least 10 mm, such as at least 20 mm, such as at least 30 mm.

[0087] In an embodiment, the thickness of the sound insulation layer is in the range 1 to 100 mm, such as 20 to 80 mm, such as 40 to 70 mm.

[0088] In an embodiment, the cellulosic and / or lignocellulosic fibres originate from a pulping process, such as a wood pulping process or a non-wood pulping process.

[0089] The cellulosic and / or lignocellulosic fibres of the fibrous sheets typically comprise plant fibres, such as wood fibres.

[0090] In some embodiments, the cellulosic and / or lignocellulosic fibres of the fibrous sheetsmay be selected from bleached or unbleached chemical pulp, such as bleached or unbleached softwood chemical pulp and / or bleached or unbleached hardwood chemical pulp, or sawdust. In some preferred embodiments, the cellulosic and / or lignocellulosic fibresmay be selected from chemical pulp, mechanical pulp, for examplebleached chemi-thermomechanical pulp (BCTMP), or non- wood pulp. In other embodiments, the cellulosic and / or lignocellulosic fibrescomprise semi-chemical pulp, thermomechanical pulp, or recycled pulp. In some embodiments, the pulp may be made from any broad-leaved tree such as a tree from the betulaceae family, for example birch or aspen, from the salicaceae family, from eucalyptus, mixed tropical hardwood or pines or from any combination of the aforementioned. The pulp may be also made from any conifer such as spruce or pine or from any combination thereof. The pulp may be also made from a combination of broad-leaved trees and conifers. In another embodiment, the pulp may be made from any annuals such as straw, common reed, reed canary grass, bamboo, sugarcane, bagasse or any grass plant.

[0091] The sound insulation layer may comprise in some embodiments at least 50 wt-%, such as at least 60 wt-%, for example at least 80 wt-%, of the cellulosic and / or lignocellulosic fibres, calculated from the dry weight of the sound insulation layer. In preferred embodiments, the sound insulation layer may comprise for example at least 80 wt-%, 85 wt-%, 90 wt-%, 95 wt-% or 98 wt-% of the cellulosic and / or lignocellulosic fibres, calculated from the dry weight of the sound insulation layer. In some embodiments, the sound insulation layer may consist of the cellulosic and / or lignocellulosic fibres.

[0092] Usually the fibrous sheets are made by a papermaking process and comprise wood pulp, such as chemical wood pulp.

[0093] The sound insulation layer may further comprise one or more additive chemicals selected from flame-retardants, foaming agents, mould inhibitors, barrier agents, barrier and binding agents, or combinations thereof. Preferably, the amount of such additives is below 40 wt-%, such as below 30 wt-%, such as below 20 wt-%, such as below 10 wt-%, calculated from the dry weight of the sound insulation layer.

[0094] In an embodiment, the sound insulation layer comprises at least one flame retardant, which may be selected from the following group: minerals, organohalogen compounds, organophosphorus compounds, inorganic phosphorus compounds, and organic compounds, and combinations thereof.

[0095] Examples of mineral flame retardants include: aluminium trihydroxide (ATH), magnesium hydroxide (MDH), huntite and hydromagnesite, various hydrates, red phosphorus, and boron compounds, mostly borates.

[0096] Examples of organohalogen flame retardants include: organochlorines such as chlorendic acid derivatives and chlorinated paraffins; organobromines such as decabromodiphenyl ether (decaBDE), decabromodiphenyl ethane (a replacement for decaBDE), polymeric brominated compounds such as brominated polystyrenes, brominated carbonate oligomers (BCOs), brominated epoxy oligomers (BEOs), tetrabromophthalic anyhydride, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD).

[0097] Examples of organophosphorus flame retardants include: organophosphates such as triphenyl phosphate (TPP), resorcinol bis(diphenylphosphate) (RDP), bisphenol A diphenyl phosphate (BADP), and tricresyl phosphate (TCP); phosphonates such as dimethyl methylphosphonate (DMMP); and phosphinates such as aluminium diethyl phosphinate. In one embodiment, the flame retardant comprises both phosphorus and a halogen, for example tris(2, 3 -dibromopropyl) phosphate (brominated tris) and chlorinated organophosphates such as tris(l,3-dichloro-2-propyl)phosphate (chlorinated tris or TDCPP) and tetrakis(2-chlorethyl)dichloroisopentyldiphosphate (V6).

[0098] Examples of inorganic phosphorus flame retardants include ammonium polyphosphate (APP) and melamine polyphosphate (MPP).

[0099] Examples of organic flame retardants include carboxylic acid and dicarboxylic acids.

[0100] The sound insulation layer may carry a surface coating, such a functional surface coating, on one or both of its surfaces facing a wood-based panel. The coating may comprise an additive chemical or additive chemicals.

[0101] A plurality of fibrous sheets as the sound insulation layer

[0102] In some embodiments, it is provided a multi-layered building element, comprising: a first wood-based panel; a second wood-based panel; between the woodbased panels, a sound insulation layer which has been attached to the wood-based panels, wherein the sound insulation layer comprises a multi-layered structure made of a plurality of fibrous sheets comprising cellulosic and / or lignocellulosic fibres, which fibrous sheets have been stacked and joined to each other so that a plurality of discrete areas in each fibrous sheet have been joined to adjacent fibrous sheets.

[0103] The fibrous sheets are typically thin and bendable, to enable joining the fibrous sheets at the discrete areas so that void space remains in each interspace between adjacent fibrous sheets.

[0104] The sound insulation layer may be embodied as a paper cushion pad. In an embodiment, the multi-layered structure comprises a paper cushion pad.

[0105] In some embodiments, the sound insulation layer comprises a multi-layered cushion structure made of a plurality of paper layers partially joined to each other, such as a paper cushion pad structure.

[0106] Typically, the term “paper cushion pad” typically refers to a multi-layered paper-based structure which has a cellular structure deformable in the direction of its thickness.

[0107] In an embodiment, the multi-layered cushion structure has a multi-layer structure comprising 3 to 100 paper sheets.

[0108] In an embodiment, the thickness of the sound insulation layer is at least 10 mm, such as at least 20 mm, such as at least 30 mm.

[0109] In an embodiment, the thickness of the sound insulation layer is in the range 3 to 100 mm, such as 20 to 80 mm, such as 40 to 70 mm.

[0110] In an embodiment, the paper sheets comprise or consists of structured or embossed paper sheets and / or flat paper sheets.

[0111] In an embodiment, said plurality of paper sheets consist of alternating embossed paper sheets and flat paper sheets.

[0112] In an embodiment, at least an innermost paper sheet in said plurality of paper sheets is an embossed paper sheet.

[0113] In an embodiment, the outermost paper sheets in said plurality of paper sheets are flat paper sheets..

[0114] In an embodiment, the paper sheets have a thickness of at least 0.05 mm, such as at least 0.1 mm, such as at least 0.2 mm, such as at least 0.5 mm.

[0115] In an embodiment, the paper sheets have a thickness in the range 0.05 to 0.5 mm.

[0116] In an embodiment, the paper sheets have been partially joined to each other by adhesive. Generally, only parts of the facing surfaces of adjacent paper sheets have been attached to each other, for example by adhesive.

[0117] In an embodiment, the paper sheets have been partially joined to each other so that a plurality of discrete areas in each paper sheet have been joined to adjacent paper sheets. For example, the attachment points or areas between adjacent paper sheets may be arranged in the form of discrete spots, such as with a matrix layout, or by any other suitable, typically regular, arrangement of discrete areas of attachment. In an embodiment, the average distance from an attachment point to the nearest adjacent attachment point is less than 50 mm, such as less than 20 mm, such as less than 10 mm.

[0118] In an embodiment, wherein the combined surface area of said plurality of discrete areas is less than 20%, such as 1 to 10% of the total surface area of each paper sheet.

[0119] Advantageously, the sound-insulation layer has a cellular structure.

[0120] In some embodiments, the sound insulation layer comprises a three- dimensional air-filled space or spaces defined by the partially joined paper sheets.

[0121] In an embodiment, there is only a single continuous air-filled space between each pair of adjacent paper sheets. Typically, said continuous air-filled space encloses the discrete areas of attachment between the paper sheets.

[0122] In an embodiment, there are a plurality of separate or discrete air-filled spaces between each pair of adjacent paper sheets.

[0123] In some embodiments, at least one of the air-filled spaces extends across at least 50% of the length or the width of the sound insulation layer, such as across the entire length or the width of the sound insulation layer.

[0124] In an embodiment, the density of the sound insulation layer is less than 20 kg / m3, such as less than 15 kg / m3.

[0125] In an embodiment, the density of the sound insulation layer is in the range 1 to 20 kg / m3, such as 3 to 15 kg / m3.

[0126] Typically, the air content of the sound insulation layer is at least 90 vol-%, such as at least 95 vol-%, calculated from the total volume of the sound insulation layer.

[0127] In an embodiment, the wood-based panels and the sound insulation layer have been joined to each other by adhesive layers.

[0128] The building element typically has a sandwich structure, such as a symmetrical sandwich structure.

[0129] Bonding

[0130] The wood based panels and the sound insulation layer are preferably bonded together with an adhesive.

[0131] The adhesive may be an adhesive resin. The adhesive resin may be provided in the form or a dry powder, for example as a hot melt adhesive, or as a liquid or as a combination thereof.

[0132] The adhesive may be applied so as to form an adhesive layer or adhesive layers which uniformly cover at least a part, in particular all or essentially all, of the adjacent surfaces. The adhesive may also or alternatively be applied in the form of discontinuous spots or stripes.

[0133] The adhesive may comprise or consist of a thermosetting polymer. Such thermosetting polymer may be selected from the groups of phenol-formaldehyde adhesives, melamine-formaldehyde adhesives, urea-formaldehyde adhesives, polyurethane adhesives and lignin based resins and combinations thereof.

[0134] The adhesive may comprise a bio-based adhesive.

[0135] The adhesive may be applied on the wood-based panels and / or the sound insulation layer in manners known per se, for example by coating or spraying. In one embodiment, the adhesive is applied in the form of fibrous sheets which have been impregnated with adhesive.

[0136] The adhesive is preferably in room temperature during its application.

[0137] In some embodiments, the wood based panels, or the layers that are to constitute the wood-based panels, and the at least one sound insulation layer, or the layers that are to constitute the sound insulation layer, are stacked and bonded together with adhesive layers, for example in room temperature or in an elevated temperature. Typically, the panels and the sound insulation layer are stacked to form a vertical stack, whereby preferably the weight of the uppermost wood-based panel provides a sufficient pressure to achieve curing of the adhesive. In some embodiments, elevated or additional pressure may be applied.

[0138] Advantageously, the sound insulation layer is a multilayered structure, such as a coated board, whereby it may better tolerate pressing without any significant increase of density.

[0139] Coatings

[0140] One or both of the wood-based panels may comprise a coating.

[0141] There may be a coating on one or both sides, i.e. on one or both outer surfaces, of the wood-based panel.

[0142] In one embodiment, the wood-based panel comprises a coating on the side of the panel that is facing the sound-insulation layer. Such a coating may improve or facilitate the adhesive bonding between the wood-based panel and the sound insulation layer, which is mainly provided by an adhesive layer placed between the wood-based panel and the sound insulation layer.

[0143] In one embodiment, the wood-based panel comprises a coating on the side of the panel that is on the opposite side with regard to (i.e. not facing) the sound insulation layer. Such a coating may provide a surface that can be easily painted or otherwise finished, optionally by first arranging a primer layer on said surface to be painted.

[0144] Typically, the coating comprises at least one polymer resin coating layer having a surface weight of about 100 to 500 g / m2, for example 120 to 250 g / m2.

[0145] The coating may comprise 1 to 10, typically 1 to 5 coating layers of the indicated kind.

[0146] The “polymer resin” layer is preferably a layer formed by a resin selected from phenol-formaldehyde adhesives, melamine-formaldehyde adhesives, ureaformaldehyde adhesives, polyurethane adhesives and lignin based resins and combinations thereof. In particular, the overlay comprises phenol-formaldehyde resin.

[0147] The wood-based panel can have a coating comprising a film or paper. For example, the coating may comprise a resin coating, such as a phenolic resin coating, in the form of a paper substrate impregnated with a resin, such as a phenolic resin. The paper substrate, before impregnation, typically has a grammage of 40 to 80 g / m2. After impregnation, the paper substrate may contain 80 to 140 g / m2of a resin, in particular of a phenolic resin.

[0148] In one embodiment, wherein the coating comprises a paper substrate impregnated with a resin, the coating is applied on the surface of the wood-based panel, such an LVL board, by pressing, in particular by hot pressing.

[0149] In another embodiment, the coating is attached to the wood-based panel by using a separate layer of a phenolic resin, in particular a heat-activated phenolic resin, impregnated in a substrate, such as a non-woven substrate. Such a glue layer (or adhesive layer), will firmly bind the coating layer to the surface of the wood-based panel.

[0150] In some embodiments, the coating of the wood-based panel comprises or consists of a resin and / or plant-based fibres.

[0151] Shape and applications of the building element

[0152] Typically, the building element is a planar structure, such as an elongated planar structure. The width of the building element is usually less than 2.5 m, such as less than 2.0 m. The length of the building element may be less than 5 m, such as less than 3 m.

[0153] In an embodiment, the thickness of the building element is at least 100 mm, such as at least 150 mm, such as at least 200 mm, such as at least 250 mm.

[0154] In some embodiments, the thickness of the building element is less than 300 mm, such as less than 250 mm.

[0155] Typically, the combined thickness of the wood-based panels is at least 50 mm, such as at least 100 mm, such as at least 150 mm.

[0156] FIGURE 1 shows schematically a multi-layered building element 10 in accordance with an embodiment of the present invention. The element comprises a sound insulation layer 11 (curved hatch pattern) and wood-based panels 12a, 12b (straight hatch pattern) on both sides of the sound insulation layer 11. The sound insulation layer may have a smaller thickness than the wood-based panels. The sound insulation layer 11 exhibits flexibility in the horizontal direction (horizontal arrows) and rigidity in the vertical direction (vertical arrows). The horizontal direction is the direction of the thickness of the sound insulation layer.

[0157] Additionally, the element 10 comprises fire-resistant layers 13 a, 13b as the outermost layers, for example gypsum boards. The sound insulation layer 11 exhibits flexibility in the horizontal direction (horizontal arrows) and rigidity in the vertical direction (vertical arrows).

[0158] In other embodiments, the fire-resistant layers may be absent or there may be only a single fire-resistant layer 13a or 13b.

[0159] Example

[0160] Acoustic properties of an exemplary wall element were studied by determining Rw values according to the standards EN ISO 10140-1 :2021 and EN ISO 10140-2 :2022. The Rw value is the sound insulation rating for airborne sound. The values Rw, Rw + C and Rw + Ctr were determined according to the standard EN ISO 717— 1 :2020. The terms C and Ctr are the spectrum adaptation values for the frequency range 100 to 3150 Hz. C is the adjustment for noise sources containing few low frequencies (residential noise, such as children playing, daily activities, etc.). Ctr is the adjustment for noise sources containing many low frequencies (traffic noise, such as urban traffic, long- haul aircraft etc.).

[0161] The studied wall element was assembled between two rooms, to form a partition wall. The volume of the sound-sending room was 102 m3and the volume of the sound-receiving room was 131 m3. The area of the wall element was 5.13 m2. In the test rooms, the air humidity was 33 to 34% the air temperature was 20 °C, and the air pressure was 102 kPa.

[0162] The studied wall element had outer layers of gypsum board. However, such gypsum layers may also be dispensed with or replaced with other finishing or coating layers.

[0163] Sample 1 had the following 5-layered sandwich structure (i.e. a stack of the below listed first to fifth layers joined to each other) in which the wood-based panels were LVL boards and the sound insulation layer was a paper cushion pad layer:First layer: a gypsum board (GFL15) with a thickness 15 mmSecond layer: an LVL board with a thickness 120 mmThird layer: a 36-layered paper cushion pad layer with a total thickness 36 mmFourth layer: an LVL board with a thickness 120 mmFifth layer: a gypsum board (GFL15) with a thickness 15 mm

[0164] For Sample 1, the value of C was -1 dB and the value of Ctr was -5 dB.

[0165] The results are shown in Table 1. It can be seen that Sample 1 provides adequate resistance against residential noise (C).

[0166] Table 1.

[0167] FIGURE 2 shows R value (dB) as a function of frequency (Hz) for Sample 1 (thin solid line). The reference graph (ISO 717-1) is depicted by the thick solid line. The frequency area 100 to 3150 Hz is shown with the vertical dashed lines.

[0168] FIGURE 3 shows paper cushions pads suitable for use in some embodiments of the present invention.

[0169] FIGURE 4 shows a cross-sectional photograph of a sample structure in accordance with an embodiment of the present invention.

[0170] It is to be understood that the embodiments of the invention disclosed are notlimited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0171] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0172] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0173] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0174] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from theprinciples and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0175] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.INDUSTRIAL APPLICABILITY

[0176] The present invention may be industrially applicable at least in the manufacturing of building elements.ACRONYMSLVL Laminated Veneer LumberCLT Cross-Laminated TimberOSB Oriented Strand BoardREFERENCE SIGNS10 multi-layered building element11 sound insulation layer (curved hatch pattern)12a, 12b wood-based panels (straight hatch pattern)13 a, 13b fire-resistant layers

Claims

CLAIMS:

1. A multi-layered building element, comprising:- a first wood-based panel;- a second wood-based panel;- between the wood-based panels, a sound insulation layer which has been attached to the wood-based panels, wherein the sound insulation layer comprises a multi-layered structure made of a plurality of fibrous sheets comprising cellulosic and / or lignocellulosic fibres, which fibrous sheets have been stacked and joined to each other so that a plurality of discrete areas in each fibrous sheet have been joined to adjacent fibrous sheets, wherein the fibrous sheets are oriented substantially parallel with the wood-based panels.

2. The multi-layered building element according to any of the preceding claims, wherein the sound insulation layer comprises, in each interspace between the fibrous sheets, airfilled spaces enclosing said discrete areas and preferably extending across the sound insulation layer in a direction that is orthogonal to the thickness of the sound insulation layer.

3. The multi-layered building element according to any of the preceding claims, wherein the multi-layered structure comprises a cushion structure, such as a cellular cushion structure.

4. The multi-layered building element according to any of the preceding claims, wherein the multi-layered structure comprises or consists of a plurality of paper or paperboard sheets, such as 3 to 100, for example 10 to 50 paper or paperboard sheets, which paper or paperboard sheets have been stacked and partially joined to each other.

5. The multi-layered building element according to any of the preceding claims, wherein the fibrous sheets comprise or consist of alternating embossed paper sheets and flat paper sheets.

6. The multi-layered building element according to any of the preceding claims, wherein at least an innermost paper sheet in said plurality of paper sheets is an embossed paper sheet.

7. The multi-layered building element according to any of the preceding claims, wherein the outermost paper sheets in said plurality of paper sheets are flat paper sheets.

8. The multi-layered building element according to any of the preceding claims, wherein the multi-layered structure comprises a paper cushion pad.

9. The multi-layered building element according to any of the preceding claims, wherein the fibrous sheets have a thickness in the range 0.05 to 0.5 mm.

10. The multi-layered building element according to any of the preceding claims, wherein the thickness of the sound insulation layer is in the range 20 to 80 mm, such as 25 to 60 mm.

11. The multi-layered building element according to any of the preceding claims, wherein the density of the sound insulation layer is in the range 1 to 20 kg / m3, such as 3 to 15 kg / m3.

12. The multi-layered building element according to any of the preceding claims, wherein the air content of the sound insulation layer is at least 90 vol-%, such as at least 95 vol-%, calculated from the total volume of the sound insulation layer.

13. The multi-layered building element according to any of the preceding claims, wherein the fibrous sheets have been joined to each other by adhesive at said discrete areas.

14. The multi-layered building element according to any of the preceding claims, wherein the combined surface area of said plurality of discrete areas is less than 20%, such as 1 to15. The multi-layered building element according to any of the preceding claims, wherein the sound insulation layer comprises a three-dimensional air-filled space or spaces defined by the partially joined paper sheets.

16. The multi-layered building element according to any of the preceding claims, wherein the fibrous sheets have been manufactured by a paper making process or a paperboard making process.

17. The multi-layered building element according to any of the preceding claims, wherein the cellulosic and / or lignocellulosic fibres of the fibrous sheets comprise or consists of wood pulp, preferably the cellulosic and / or lignocellulosic fibres are selected from chemical pulp, mechanical pulp, thermomechanical pulp, chemi-thermomechanical pulp, and any combinations thereof.

18. The multi-layered building element according to any of the preceding claims, wherein the wood-based panel comprises an engineered wood product, such as laminated veneer lumber (LVL), plywood or cross-laminated timber (CLT).

19. The multi-layered building element according to any of the preceding claims, wherein the wood-based panels and the sound insulation layer have been joined to each other by adhesive layers, preferably directly without any further layers between the wood-based panels and the sound insulation layer.

20. The multi-layered building element according to any of the preceding claims, wherein the sound insulation layer is deformable or flexible in the direction of its thickness.

21. The multi-layered building element according to any of the preceding claims, wherein the sound insulation layer is non-deformable or stiff in a direction that is orthogonal to its thickness.

22. The multi-layered building element according to any of the preceding claims, wherein the stiffness of the sound insulation layer is lower in a direction of its thickness than in a direction that is orthogonal to its thickness.

23. Use of the multi-layered building element according to any of the preceding claims in a wall, such as in a load-bearing partition wall in a building, typically as a load-bearing part of said wall.

24. Use of a paper cushion pad as a sound-insulating layer in a building element, such as a wall element or a door element.

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