Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/02—Manufacture of substantially flat articles, e.g. boards, from particles or fibres from particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/06—Fibrous reinforcements only
  • B29C70/08—Fibrous reinforcements only comprising combinations of different forms of fibrous reinforcements incorporated in matrix material, forming one or more layers, and with or without non-reinforced layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N1/00—Pretreatment of moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/005—Manufacture of substantially flat articles, e.g. boards, from particles or fibres and foam
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/08—Moulding or pressing
  • B27N3/18—Auxiliary operations, e.g. preheating, humidifying, cutting-off
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N7/00—After-treatment, e.g. reducing swelling or shrinkage, surfacing; Protecting the edges of boards against access of humidity
  • B27N7/005—Coating boards, e.g. with a finishing or decorating layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/002—Manufacture of substantially flat articles, e.g. boards, from particles or fibres characterised by the type of binder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/04—Manufacture of substantially flat articles, e.g. boards, from particles or fibres from fibres

Definitions

• the present disclosure concerns lightweight polyurethane wood composites and method for manufacturing lightweight polyurethane wood composites in particular panels/boards for furniture, comprising at least 10 % (w/w) of a foamable polyurethane, and at least 40 % (w/w) of wood particles/fibers or other lignocellulosic material in particle form obtainable by sieving, wherein the sieve hole is no more than 7 mm inclusive.
• the furniture industry used conventional wood-panels, such as particleboards, medium density fiberboard, plywood, etc., in the manufacture of furniture.
• the conventional particleboards have a density of about 550 - 900 kg/m3 that is responsible for several problems, such as: design limitation for high thickness elements, impracticality for the consumer to handle, transport and move furniture, high transportation costs both for consumers and industry.
• Conventional wood-based particleboards are formed by three layers of wood particles (wood flakes, chips, shavings, sawdust and similar) and/or other lignocellulosic material in particle form (flax shives, hemp shives, bagasse fragments and similar) with the addition of an adhesive.
• the external face layers are composed by smaller particles, while the core is composed by larger particles.
• wood particles are blended with the adhesive system normally composed by a urea-formaldehyde (UF) resin, paraffin, catalyst and water, in a blender.
• UF urea-formaldehyde
• the particleboards are then pressed until reaching a final thickness between 3 mm and 60 mm in a hot-press, at temperature between 150 e C and 230 e C and for time between 70 and 250 s. This pressing stage enables the cure of the UF-resin which glues the wood particles.
• the final particleboards are characterized according to European standards for density (EN 323) and internal bond strength (EN 319). Depending on the size and shape of particles they are classified as, e.g., chipboard, panels with other particles, e.g. shives (flaxboard). According to the board’s structure they are classified as: single-layer boards; multi-layer boards; boards with gradient structure; extruded boards with hollow tubes.
• the lightweight particleboards are useful substitutes of the conventional wood- based particleboards, and their density is restricted, by a specific European standard (CEN/TS 16368:2014), to values below 600 kg/m3 instead of 550 - 900 kg/m3 of the conventional wood- based particleboards.
• CEN/TS 16368:2014 a specific European standard
• Numerous approaches have been made to obtain lightweight panels. These approaches include using low density wood species (poplar) or other plant fibers (e.g.
• hemp hemp
• sandwich panels with foam or honeycomb core or by incorporating polymeric particles during wood-based panels’ production.
• the reduced weight comes along with a decline of the mechanical properties, namely: bending strength, internal bond strength, resistance to screws withdrawal and machinability, and the increase in the porous edges with decrease in the resistance to axial withdrawal of edge screws, the decrease on edge machinability and edge banding ability.
• the document US8304069 B2 is one of the attempts above-mentioned to obtain lightweight panels.
• This document discloses a light wood-based material comprising a density of less or equal to 600 kg/m3 and wood particles, a filler, a binder and preferably an antistatic coating for the filler before mixing it with the binder and/or the wood particles.
• the process herein unveiled involves the use of a pre-foamed solid polymer (polystyrene and/or styrene copolymers), which are mixed and molded at high temperature (150 e C to 230 e C) to give a wood-based material.
• the polyurethane is used as filler and the light wood-base material complies with the European standard for lightweight particleboards (CEN/TS 16368:2014), the internal bond strength is only of 0.19 [0008]
• the document US5554429 A is also an attempt to obtain polyurethane-wood composite panels, although being based on oriented strand boards (OSB), and not particleboards as in the present invention, and being directed towards flooring applications.
• the inventors claim the production of oriented strand boards (OSB) by using a mixture of a foaming resin (e.g. polyurethane) and a non- foaming resin (e.g. urea resin, phenol resin).
• the final panels have densities slightly lower than 600 kg/m3 and great values of flexural strength.
• the process now disclosed has the advantage of being wholly operated at room temperature.
• the panels have mechanical values that are in accordance to the standard requirements for lightweight wood-based particleboards, even for densities values lower than 400 kg/m3.
• the current available strategies do not fulfil the desirable purposes for the lightweight panels: appropriated mechanical properties, namely bending strength, tensile strength perpendicular to the plane of the board (internal bond strength), and resistance to axial withdrawal of screws.
• the lightweight panels already in the market are used for insulation and non- structural applications as the easier performed objectives, rather than as furniture, furniture components such as tables, chairs, bookshelves, kitchen worktops doors or ceiling panels and/or in the construction industry.
• furniture components such as tables, chairs, bookshelves, kitchen worktops doors or ceiling panels and/or in the construction industry.
• honeycomb core boards which are used in the furniture industry but impose many design restrictions.
• lightweight panels have also a marketing effect on both the fu rniture industry and the lightweight panels manufactures.
• the present disclosure regards to lightweight panels with a polyurethane-wood composite core, from now on named lightweight polyurethane-wood composites and manufacture thereof. This disclosure overcomes the disadvantages of the current available solutions for the furniture industry previously listed.
• the lightweight polyurethane-wood composites for panels/boards may also be applied to the construction industry as it can be used as building materials, for laminate floors, walls sheathings, doors, furniture and sound and/or temperature insulation.
• the panels/boards are characterized according to European standards for density (EN 323) and internal bond strength (EN 319). Depending on the size and shape of particles they are classified as e.g., chipboard, panels with other particles, e.g. shives (flaxboard). According to the board’s structure they are classified as: single-layer boards; multi-layer boards; boards with graduated structure; extruded boards with tubes.
• the present disclosure relates to a lightweight composite for panels/boards, in particular panels/boards for furniture, comprising at least 10 % (w/w) of a foamable polyurethane , and at least 40 % (w/w) of wood particles/fibers or other lignocellulosic material in particle form obtainable by sieving, wherein the sieve hole is no more than 7 mm inclusive.
• the lightweight composite of the present invention comprising at least 10 % (w/w) of a foamable polyurethane, and at least 40 % (w/w) of wood particles/fibers or other lignocellulosic material in particle form obtainable by sieving.
• the particles/fibers of wood or other lignocellulosic size is between 0.18 to 7 mm preferably between 2-5 mm.
• the sieve hole can be from 0.18 to 7 mm, preferably between 2-5 mm.
• the composite comprises between 30 - 50 % (w/w) of foamable polyurethane and 50 - 30 % (w/w) of wood particles.
• the internal bond strength of the composite is 0.20 - 0.55 N/mm2;
• the density at 20 °C of the composite is 300 - 465 kg/m3;
• the resistance to axial withdrawal of screws of the composite is 200 - 550 N.
• the foamable polyurethane have an intrinsic density at 20 °C of 25 kg/m3.
• the disclosed composite is coated with external layers, such as a wood veneer, a laminate based on resin impregnated papers, or a melamine-impregnated decor paper, among others.
• external layers such as a wood veneer, a laminate based on resin impregnated papers, or a melamine-impregnated decor paper, among others.
• the present subject-matter also relates to articles comprising the composite described previously, wherein said article is a board, a panel, a layer or a furniture.
• said furniture is a table, a chair, a bookshelf, a door, a kitchen worktop door, ceiling panel, laminate floor, a wall sheathing or sound and/or temperature insulation.
• the thickness of the board/panel is 10 - 60 mm, preferably 32 mm.
• the present disclosure also relates to a method to produce a lightweight composite characterized in that it comprises the following steps:
• step (b) mixing the wood particles obtainable by sieving in step (a) with at least 10 % (w/w) of a foamable polyurethane;
• step (c) pouring the obtained mixture of step (b) into a closed mold at 20-25 °C; and d) wherein the molding step of the mixture of step (c) is performed for at least 5 or 30 minutes, preferably for at least 15 minutes at 20-25 °C
• step (c) molding the mixture of step (c) is performed at 20-25 e C for 1 - 3 hours, preferably 2 hours.
• the step (b) is mixing the wood particles obtainable by sieving in step (a) with foamable polyurethane.
• the sieved particles in combination with polyurethane form an adhesive system which guarantees the low density of the product and good cohesion between the wood particles and the foam.
• the foam is produced during the panel manufacture, providing separation of the wood particles, while simultaneously adhering to them.
• the average wood particles size or other lignocellulosic material in particle form is between 0.18 mm and 5 mm, preferably between 2 mm and 5 or between 0.18 mm and 2.
• Other aspect of the present invention relates to the method to produce a panel or a board comprising a lightweight composite obtained by the method described before characterized in that it comprises applying at least one external layer to the lightweight composite with an adhesive.
• the adhesive is a resin or a polyurethane monocomponent adhesive, in particular urea formaldehyde.
• the external layer is selected from a wood veneer, a laminate based on resin impregnated papers, and a melamine-impregnated decor paper.
• This disclosure also relates to the use of lightweight composites described before for furniture, furniture components and construction materials, wherein the furniture, furniture components and construction materials are tables, chairs, bookshelves, doors, kitchen worktop doors, ceiling panels, laminate floors, walls sheathings or sound and/or temperature insulation.
• the disclosure also relates to Furniture comprising at least a panel or a board described before.
• the furniture is a table, a chair, bookshelves, a door, a kitchen worktop, ceiling panel, laminate floor, a wall sheathing or sound and/or temperature insulation.
• the present disclosure relates to lightweight panels with a polyurethane-wood composite and the development of a process for their manufacture.
• the first approach to produce lightweight panels did not involve the use of polyurethane.
• the panels produced by this approach were composed by three layers of wood particles that had an irregular morphology, mostly pine wood, with a dry density in the range of 400 - 500 kg/m 3 .
• the wood particles were obtained directly from the furnish that was fed to the blender of an industrial line of a particleboard producer.
• the size distribution of the particles was determined by sieving and the resulting core and face layers had the following distributions: core layer, withheld in screen hole size in the range of 0.18 - 7 mm, and face layers, withheld in screen hole size in the range of 0.18 - 1 mm.
• the second approach attempted was based on using the larger wood particles (core layer) and pieces of foamable polyurethane.
• the pieces of foamable polyurethane were obtained by shattering a foamable polyurethane block attained after the expansion of a commercial polyurethane mixture.
• the commercial polyurethane is a combination of polymethylene polyphenyl isocyanate (p-MDI), 4,4'- methylene diphenyl diisocyanate (MDI) and a polyol and available in pressurized containers.
• the foamed polyurethane pieces had the dimensions of 10 10 10 mm3 and a density of 25 kg/m3.
• Another approach attempted to obtain a lightweight panel with foamable polyurethane consisted in blending the wood particles (obtained from the fed of the core layer of a standard particleboard) directly with 50 % (w/w) of the commercial polyurethane mixture and keep the resulting blend at room temperature. After a period of 30 minutes, a rigid composite of wood species linked by the foamable polyurethane was formed. It is noteworthy that the foamable polyurethane mixture itself needed about 24 hours till its complete cure and it had much less rigidity than the lightweight panels with the polyurethane-wood composite.
• the rigid composite of wood species linked by the foamable polyurethane is named lightweight panel with a polyurethane-wood composite.
• the lightweight panels were prepared and the standard UF- adhesive system of the core was replaced by the commercial foamable polyurethane mixture.
• the larger wood particles, withheld after sieving (in particular screen holes between 0.5 - 7 mm) were first blended with the foamable polyurethane mixture and the resulting mixture was laid in a mold.
• the external faces were veneers coated with a monocomponent PU - adhesive system on the core-side.
• the resulting mat was then shaped in a mold with a thickness predefined, in particular with a thickness of 32 mm.
• This first pressing stage pre-pressing was performed, in particular, for 15 minutes at 20 - 25 °C or room temperature conditions.
• a first expansion of the lightweight panel core occurred, maybe due to the carbon dioxide release during the reaction between the isocyanate groups of the foamable polyurethane mixture and water both from the wood and the surrounding atmosphere. Furthermore, the carbon dioxide diffuses into existing bubbles already nucleated in the liquid, causing the expansion of the foamable polyurethane till the restricted thickness. The foam has been expanded during pressing and then it is mixed with the particles.
• a second pressing stage is then initiated, in particular, at 80 e C for 15 minutes.
• the high temperature increases the hardening speed of the gelation reaction between the isocyanate groups and hydroxyl functionalities of the wood particles.
• the entire process can be performed at room temperature, in particular for 2 hours till the expansion and cure of the PU foam.
• the lightweight polyurethane wood composites for a panel/broad comprise wood particles/fibers and foamed polyurethane without the need of adding binder, although binder may be added.
• Table 1 Density and internal bond of panels with a polyurethane-wood composite core and a thickness of 32 mm.
• the panel P-3 had the lowest density, while maintaining the internal bond strength above the standard requirements of 0.20 N/mm2 for lightweight panels type LP2 (CEN/TS 16368:2014) and above the 0.30 N/mm2 required for the standard particleboards type P2 (EN 312). For that reason, a more detailed characterization in terms of bending strength (EN 310), formaldehyde content (EN ISO 12469-5) and resistance to axial withdrawal of screws (EN 320) was performed. Maintaining the polyurethane content, panels with less 20 % and 30 % of the total mass were prepared under the same pressing conditions (at room temperature for 2 hours). Just in the first case, the IB value respected the standard requirements.
• the characterization is referred to the panels with 45 % (w/w) of polyurethane and less 20 % of the total mass than the panels presented in table 1 .
• the faces were composed by laminates sheets with a thickness of 0.8 mm.
• the results correspond to average values of at least 3 determinations per test.
• the lightweight panels with a polyurethane-wood composite have important mechanical features and low density, which are the unexpected result of a synergy effect between the wood particles and the foamable polyurethane.
• the lightweight polyurethane-wood composites herein disclosed may be used in the construction industry as well as for furniture and furniture components.
• Some examples of the end products where lightweight polyurethane-wood composites can be used are tables, chairs, bookshelves, doors, in particular kitchen worktops doors, ceiling panels, laminate floors, walls sheathings, sound and/or temperature insulation.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)

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Publications (1)

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Family Applications (1)

Country Status (2)

Citations (5)

• 2019
  • 2019-03-15 PT PT115374A patent/PT115374A/pt unknown
• 2020
  • 2020-03-16 WO PCT/EP2020/057143 patent/WO2020187849A1/en active Application Filing

Patent Citations (5)

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