Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Patent
1995-03-20
1997-12-09
Lee, Helen
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
428327, 4285371, B27N 302, B32B 516
Patent
active
056958757
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a homogeneous particle board having considerably increased strength and resistance against moisture as well as the use thereof.
Particle boards have been produced for a very long time. Usually they serve their purpose in a very good way. However there is a problem with these known particle boards. Thus they are sensitive to moisture and swell easily in a moist environment. In addition the strength and the hardness are rather moderate.
There is a need for particle boards having a better strength, resistance against moisture and surface hardness. For instance these particle boards are needed as a carrier for so-called laminate floorings. Usually these floorings consist of a particle board having a thin decorative thermosetting laminate glued to its upper side. A balanced laminate is usually glued to the lower side of the carrier to give a dimensionally stable and even flooring material.
The carrier has usually a thickness of about 6-9 mm and the two laminate sheets a thickness of about 1 mm together. Accordingly the complete flooring material has a thickness of about 7-10 mm.
The laminate coated particle board is sawn up into a number of flooring boards which are provided with groove and tenon in the long sides and the short sides.
Bar patterns are very usual for such laminate floorings. The decorative thermosetting laminate is produced in the usual way. Usually you start with a base layer consisting of a number of paper sheeets impregnated with phenol-formaldehyde resin and a decor paper sheet impregnated with melamine-formaldehyde resin. There may also be an overlay of .alpha.-cellulose impregnated with melamine-formaldehyde resin. These sheets are bonded together to a laminate by pressing under heat and pressure.
Due to the fact that it has not been possible before to produce particle boards with enough strength, resistance against moisture and surface hardness it has not been possible to make laminate floorings which can stand a long time use in a public environment. In such spaces the floors are usually exposed to a higher moisture charge and a greater mechanical strain.
The surface hardness of the particle board is important for the resistance of the laminated floor against impression marks.
A high bending strength and internal bond of the particle board are important for obtaining a strong and resistant laminate floor.
Normally particle boards are manufactured by building up a mat of particles in several layers on a forming belt. Than the central layer or layers is usually built up of considerably bigger particles than the two outermost layers on each side of the central layer. Therefore the particle board made of the mat of particles will get the above mentioned drawbacks.
According to the present invention it has quite inexpectedly been possible to satisfy the above need and bring about a homogeneous particle Board having considerably increased strength and resistance against moisture. The board is characterized in that, it has a density of 600-1200 kg/m.sup.3, preferably 850-1100 kg/m.sup.3 a thickness swelling of 3-12%, preferably 4-7% after 24 hours in water, a water absorption of 14-30% by weight, preferably 15-28% by weight after 24 hours in water, a bending strength of 18-35 MPa, preferably at least 24 MPa and an internal bond of 1.2-3.2 MPa, preferably 2.0-3.2 MPa.
The particle board is built up of wooden particles having a maximal size of 3 mm. At a temperature of 10.degree.-30.degree., preferably 15.degree.-25.degree. C. these particles are mixed with 5-18% by weight of glue calculated as dry glue on dry particles and 0.1-1.0% by weight of an sizing agent. This particle material mixed with glue is spread on a forming belt or the like in such a way that a mat of particles consisting of one to five preferably at least three layers is built up, which mat of particles is possibly prepressed and then flat pressed at a pressure of 15-50 kp/cm.sup.2, preferably 20-40 kp/cm.sup.2 and a temperature of 120.degree.-210.degree. C., preferably 130.degree.-170.degree. C.
REFERENCES:
patent: 3492388 (1970-01-01), Inglin-Knusel
Larsson Roland
Ringo Peter
Lee Helen
Perstorp Flooring AB
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