METHOD OF MAKING FIBRE MATS

Abstract: For use as carcasse in laminates a mat of fibre material is manufactured by exposing and impregnating the fibres. The fibres are thereafter dried and formed to a web by being deposited on a movable belt (wire). The final forming of the web to a fibre mat is carried out by pressing in at least one step.

Description: Method of making fibre mats This invention relates to a method of making fibre mats to be used as carcasse in laminate by impregnation and forming of fibre material. The laminate in question ' consists of a carcasse and surface layers and may have technical as well as decor¬ ative function. The carcasse in the laminate is assembl¬ ed of a number of sheets of kraft paper, which have been impregnated preferably with phenol resin. At laminates of great thickness which are used as load-carrying structures, the number of paper sheets comprised therein is great. At this type of laminate, thus, first paper sheets must be manufactured which thereafter are impregnated and assembled. To make a detour in this way over paper is a process which requires both energy and labour. A simpl ified method, therefore, would also imply essential economic advantages. The present invention renders it possible that the man¬ ufacture of laminate can be carried out in a simpler and less expensive way. The carcasse or carrying struct¬ ure in the laminate can be made in the form of a fibre mat direcly from the fibre material, so that no paper sheets are required. The fibre material can be of var¬ ious kinds, for example cellulose fibres or artificial fibres, but preferably fibres of cellulose-containing material are used. The characterizing features of the invention are defined in the attached claims. The invention is described in greater detail in the following with reference to the accompanying Figure, which is a flow chart for an embodiment of the method according to the invention. According to the embodiment shown the starting material are wood chips. They are washed in a chip washer 1 and thereafter fed into a refiner 2 via a preheater 3. The refiner 2 is of the type disc-refiner with a pressurized refiner housing 4. The object is to manufacture a fibre pulp which is substantially free of shives. Through a blow conduit 5 coupled to the refiner housing the refined fibre material is transported by means of overpressure in the refinerhousing k . Impregnation chemicals are added in the blow conduit 5 and/or immediately prior to the refining. The chemicals include a suitable binder such as phenol resin in an amount of 10-50, preferably 20-50?_ by of the fibre amount. A small amount of paraffin, up to 2% s may also be added simultaneously with the phenol resin. The impregnation chemicals preferably are supplied in the blow conduit 5 where high speed and turbulence pre¬ vail in the fibre pulp, whereby the resin is effectively distributed on the single fibres. The impregnated fibre material is transferred from the blow conduit 5 to a drier 6, which comprises a fan 7 and a heating device 8 for heating air to a temperature below the curing temperature of the phenol resin (at maximum 200°C, preferably below lβO°C). The hot air and the fibre pulp are transported through a drier pipe 9, in which the drying takes place. The staying time in the drier pipe 9 is very short. By controlling the air temp¬ erature and staying time, the desired dry content of the fibre material can be obtained. In the drier pipe 9 a thus, t^3 solvent supplied with the impregnation medium and also the fibre moisture evaporate. The drier pipe 9 opens into a cyclone 10 where air and fibres are separated. Air outgoing from the cyclone norm¬ ally has a temperarure between 60 and 85 C. Depending on the impregnation chemicals used, this air also can cont- ain substances which must not be emitted freely. At the use of phenol resin, gases are released at the drying which in certain cases must be recovered. Part of the air can then be recirculated to the inlet of the drier fan 7_ and the remaining part is directed to combustion. For preventing the gas components, which are deemed dang¬ erous, from doing harm a temperature of 600 C is required. Suitable equipment for this purpose is commercially available. The fibre material separated in the cyclone 10 is weighed on a pair of fibre scales 11, preferably of the type belt weigher. The fibre amount weighed determine-. ' ".the supply of impregnation agent. The fibre material is transported from there in an air transport conduit to a storage container 12, into which the fibre material is fed via an air separation cyclone 13. From said container 12 the fibre material . is passed by means of an air transport conduit to a .'forming station 14, for example of the type shown in SE-PS 7510795-3. The forming station can be a pneumatic or mechanical one and adjustable to different thicknesses. The forming station 14 comprises a distribution chamber 15 and a conveyor belt 16 in the form of a wire, on which the fibres are deposited. The transport air is sucked through the belt by means of a fan 17. An additional cyclone 18 and fans are provided for separating and returning fibres following along, which fibres are subjected to repeated distribution in the forming station 14. This arrange¬ ment implies that the mat formed can meet reasonable requirements on forming accuracy (surface layer variat¬ ions) . The forming is followed by a continuous prepressing in a press 19, preferably a belt prepress of conventional design for removing remaining air from the fibre mat and for consolidating the mat so that it can be handled in subsequent process steps. Loose fibres are also returned from the prepressing to be used again in the forming station. The fibre mat is thereafter divided into des¬ ired dimensions by means of longitudinal and transverse saws 20 and, respectively, 21. A metal detector 22 pref¬ erably can be located in connection to the saws. Depend¬ ing on the aperture of the laminate press (not shown) subsequent to the saws and on the capacity of said press, a plate prepress may also be provided before the laminate press. In said prepress heat may possibly be supplied to the fibre mat in order to shorten the heating time in the subsequent laminate press. Fibre mats, which are rejected, for example because of nonuniform forming at the start, are passed to a return bin 22 where the material is torn and returned to the process. In cases when the fibres cannot be reused directly, for example when they contain metal, the fibre material is passed to a special reject container for treatment. The invention, of course, is not restricted to the embodiment shown, but can be varied within the scope of the invention idea.

Claims: Claims 1. A method of manufacturing mats of fibre material for use as carcasse in laminates, c h a r a c t e r i z e d i n that the method comprises the steps as follows: a) exposure of single fibres from the fibre material, b) impregnation of the fibres with a binder in a transport conduit where high speed and turbulence prevail, c) drying of the fibres by hot air in an air transport conduit, d) separation of the air from the fibre material, e) forming of a web .of the fibre material by fine distribution and depositing on a movable belt, f) final forming of the fibre web to a fibre mat by pressing in at least one step. 2. ' A method as defined in claim 1, c h a r a c t e r ¬ i z e d i n that the fibre material consists of cellulose-containing material, and fibres are exposed by refining-: wood chips. 3. A method as defined in claim 2, c h a r a c t e r ¬ i z e d i n that the binder contains phenol resin in an amount of 10-50, preferably 20-50?ό by. weight of the fibre amou 4. A method as defined in claim 2 or 3, c h a r a c t ¬ e r i z e d i n that the amount of added binder is controlled by weighing the material immediately after the air separation according to step d).

Inventors: TOLL HARRY, TOLL, HARRY
Applicants: SUNDS DEFIBRATOR, SUNDS DEFIBRATOR AKTIEBOLAG
Application year: 1985
Main classification: B27N3
IPC codes: B27N3, B32B5