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
  • B27N3/08—Moulding or pressing
  • B27N3/10—Moulding of mats
  • B27N3/14—Distributing or orienting the particles or fibres

Definitions

• This invention refers to a method for manufacturing panels in sheet form and the product obtained thereby.
• a typical example of application of this technique consists of panels composed of fragments of wood of suitable particle size, impregnated with thermosetting resin. This material is cold-preformed into the shape of a slab which is subsequently compressed into its final configuration in a heated mould, where the binder is polymerized.
• Panels of this kind have extensive empty spaces inside them, due to the fact that the quantity of binding resin must be maintained within permissible limits from the economic and technological point of view. In certain applications their consequent poor mechanical strength and high hygroscopicity is not appreciated.
• US-A-2 686 143 discloses a method for manufacturing panels made of two layers of fine particle-sized wood shavings, mixed with resins, distributed onto the outside of a mass of shredded fibrous waste material and then compressed, as in the preamble of claim 1.
• the scope of this invention is to obtain panels composed internally of scraps of multilayered materials and externally of fine particle-sized wood shavings. Said panels are consequently characterized by a low degree of hygroscopicity, limited swelling in water, good thermal and acoustic insulation, deriving from the first component material, and an excellent finish and even surface deriving from the second component material.
• the method for manufacturing panels according to the invention is characterized by the fact that fine particle-sized wood shavings, suitably mixed with resins, are distributed on the outside of a mass of fragments of sheet material composed of thermoplastic resin coated cardboard, the composition thus obtained being compressed in a mould at a temperature higher than the softening point of the thermoplastic material and higher than the polymerizing temperature of the resin used, and subsequently cooled.
• the invention also refers to the panel obtained by such method.
• multilayered material refers to a composite material comprising a layer of cardboard and at least one layer of thermoplastic material on one of its outer surfaces.
• Further layers may also be present, such as for example a sheet of aluminium foil.
• a further essential advantage of the invention lies in the fact that scraps of multilayered material are widely available and exceptionally low in cost, in that they can be obtained from material discarded from the manufacture of boxes which use this material as a constituent.
• the plastic layer of the bonded sheet material referred to herein consists of a sheet of polyethylene, even though the presence of other thermoplastic materials is not excluded.
• the sheet material is broken up into fragments, preferably having minimum dimensions of not less than 2 mm and maximum dimensions of around 40 mm, of the most diverse shapes, from substantially circular to elongated in the form of fibres.
• thermoplastic binding material suitable for forming the panel ranges from 5 to 15% in weight of the fragments, and more specifically around 10%, which is the same order of magnitude as the percentage in weight of the thermoplastic fraction contained in cardboard-polyethylene or cardboard-aluminium-polyethylene multilayer sheets, so that the use of fragments made from scraps of this material ensures an adequate quantity of bonding resin.
• thermoplastic resin added to the fragments will have a sufficiently fine particle size so as to be suitably distributed throughout the mass, typically with a basic particle size not exceeding the average size of the fragments.
• thermosetting class in order to favourably affect the properties of the panel, and to facilitate the technique of forming the mass to be introduced into the mould, as well as to enable the panel to be removed easily from the mould.
• Synthetic resins which can be polymerized by adding a catalyst may also be used.
• wood shavings with a particle size ranging from 0.25 to 1.2 mm, with the addition of ureic resin or, preferably, melaminic resin, which gives better characteristics in terms of hygroscopicity and limited swelling.
• the thickness of the layers of wood shavings may vary from 0.3 to 1.5 mm.
• the panels are formed satisfactorily when the initial slab is subjected to pressures in the region of 15-25 kg/cm 2 and heated to a temperature ranging from 120 to 190°C.
• the length of time that the fragments must remain under compression between the hot plates of the press varies according to the final thickness of the panel, in order to ensure a sufficiently even distribution of the temperature throughout the mass. It has proved to be advantageous, for example, to keep the panel under the heated press plates for a period ranging from 15 ⁇ to 30 ⁇ per millimetre of thickness of the panel obtained.
• thermosetting resin or a resin polymerized by catalysis Whenever a thermosetting resin or a resin polymerized by catalysis is used as an additive, it was found that, in the time required for polymerization and cross-linking of the resin, the polyethylene melts to improve the aggregating action between the resin and the fragments of multilayered material, resulting in a singularly compact and sturdy product.
• Resins of the most diverse kinds have proved useful in manufacturing panels according to the invention, such as for example: phenolic resins (phenol-formaldehyde, cresol-formaldehyde, phenol-furfural), amino-plasts (urea-formaldehyde, melamine-formaldehyde), polyesters (phthalic, maleic), epoxy, vinyl, acrylic, polystyrene, polyolefin and isocynate.
• phenolic resins phenol-formaldehyde, cresol-formaldehyde, phenol-furfural
• amino-plasts urea-formaldehyde, melamine-formaldehyde
• polyesters phthalic, maleic
• epoxy vinyl, acrylic, polystyrene, polyolefin and isocynate.
• the mechanical properties and compactness of the end product can be improved by the addition of fillers of various different materials of suitable particle size, in widely varying percentages, typically from 5 to 10%, such as cellulose, cotton staple, sawdust, fibre glass, kaolin, calcium carbonate.
• paraffin to the wood shavings and the use of melamine glues reduces the hygroscopicity and moisture expansion of the material.
• the upper surface composed of fragments of resinated multilayered material, was also covered with a further layer of resinated fine wood shavings.
• the slab thus formed was cut into suitably sized modules with a specific weight of approximately 1000 kg/m3, which were then introduced between the hot plates of a gang press.
• the press plates After having reached the softening point of the polyethylene in the core of the panels, the press plates were cooled to reduce the temperature of the panels to below the softening point, while keeping the panels constantly subjected to a specific pressure higher than the pressure exerted by the water vapour at the same temperature, during the heating and cooling phases.
• the panels were subsequently removed from the press, cut transversally and longitudinally and then smoothed.
• the preheating temperature must obviously be below the point which causes the thermoplastic resin to soften to such a degree as to cause it to run or to adhere excessively on contact, which could negatively affect the distribution of the resin within the mass.
• a further feature of the manufacturing method according to this invention is consequently that of subjecting the fragments after milling to pre-drying in order to reduce the moisture content to values below 4%, preferably around 2%.
• the drying can easily be carried out under a stream of hot air.
• the panel can be cooled under pressure, with release of any vapour that may have formed in the mass of material.
• the panels obtained according to the invention lend themselves to a wide range of applications in the most diverse fields. In addition to the conventional uses for products of this kind, they can also be suitable for uses which call for resistance to passive stress, in view of their good mechanical strength. Moreover, due to their low degree of impregnability and expansion in water, the panels according to the invention can be used in the building industry.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Laminated Bodies (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Refrigerator Housings (AREA)
• Securing Of Glass Panes Or The Like (AREA)
• Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
• Panels For Use In Building Construction (AREA)
• Conveying And Assembling Of Building Elements In Situ (AREA)
• Joining Of Building Structures In Genera (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=11366786

Family Applications (1)

Country Status (14)

Families Citing this family (2)

Family Cites Families (5)

• 1993
  • 1993-08-06 IT IT93MI001786A patent/IT1265062B1/it active IP Right Grant
• 1994
  • 1994-07-12 CA CA002127820A patent/CA2127820C/en not_active Expired - Fee Related
  • 1994-07-15 ES ES94202057T patent/ES2107740T3/es not_active Expired - Lifetime
  • 1994-07-15 DK DK94202057.9T patent/DK0637488T3/da active
  • 1994-07-15 EP EP94202057A patent/EP0637488B1/en not_active Expired - Lifetime
  • 1994-07-15 DE DE69405665T patent/DE69405665T2/de not_active Expired - Fee Related
  • 1994-07-15 AT AT94202057T patent/ATE158220T1/de not_active IP Right Cessation
  • 1994-07-15 SI SI9430104T patent/SI0637488T1/xx unknown
  • 1994-07-22 HU HU9402172A patent/HU215067B/hu not_active IP Right Cessation
  • 1994-07-26 JP JP6192685A patent/JPH0768579A/ja active Pending
  • 1994-08-05 PL PL94304572A patent/PL174630B1/pl unknown
  • 1994-08-05 FI FI943636A patent/FI943636A/fi unknown
  • 1994-08-05 NO NO942916A patent/NO308513B1/no unknown
• 1997
  • 1997-12-02 GR GR970403202T patent/GR3025553T3/el unknown

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