Coating apparatus – Projection or spray type – Plural projectors
Reexamination Certificate
1999-09-28
2002-06-11
Ball, Michael W. (Department: 1733)
Coating apparatus
Projection or spray type
Plural projectors
C156S578000, C425S133100, C222S145100
Reexamination Certificate
active
06402841
ABSTRACT:
The present invention relates to a method for supplying a multicomponent fluid thermosetting resin gluing system. It also relates to a process for production of laminated wood or glue-laminated timber in which the method is applied. Furthermore, it also relates to a device for carrying out the method, particularly in said production process.
Production of laminated wood and glue-laminated timber usually involves agglutination of (i.e. gluing together) two or more wooden members surfaces by means of a multicomponent thermosetting resin gluing system, such as gluing systems based on urea-formaldehyde resins, melamine-formaldehyde resins, phenol-formaldehyde resins, phenol-resorcinol-formaldehyde resins, isocyanate resins, polyurethane resins, polyvinyl acetate resins, etc. Such gluing systems are based on at least two components, a resin component and a hardener component. In the exemplified gluing systems the hardener component is based on formaldehyde, organic isocyanates, or acids like formic acid, i.e. substances known to evaporate into gaseous emissions giving rise to unpleasant odours or even respiratory irritation. This emission problem is particularly evident when the gluing system or its components are applied by means of some curtain coating technique, at which the evaporating substance falls freely through the ambient air down to one of the surfaces to be agglutinated. The problem is particularly outspoken when the evaporating component is applied separate from the other components, as in that case neither the evaporating component nor the emitted vapours may react with any other gluing system component. On the other hand, if the hardener is mixed with the resin component prior to application, the pot life of the gluing system as applied is considerably reduced. Such pre-mixing usually also entails palpable problems regarding cleaning the application equipment, as cured resin may clog the nozzles of the apparatus. This latter problem may of course also reside with resin-hardener system that does not involve any component causing emission problems.
Various solutions have been proposed to the above problems. In the case of pre-mixing, cooling of the mixture has been utilized in order to decrease the reaction rate as well as the vapour pressure of the evaporating substance. This is apparently a technologically complicated solution. In other cases the proposed solutions relate to lowering the content of the evaporating component in the gluing system, or providing additives that may absorb any excess of the evaporating component. Drawbacks of these solutions are that they imply that part of the evaporating component is withdrawn from the intended glue-curing reaction, which in turn means longer curing times or inferior adhesion properties of the cured resin, or both.
The above problems are overcome by the present invention as defined by appended claim 1. More specifically the present invention relates to a method for supplying a multicomponent fluid thermosetting resin gluing system, which is characterised in that a first fluid component is brought to flow in a first stream, and a second fluid component is brought to flow in a second stream, whereby the flow of the second stream is brought to essentially encircle the flow of the first stream.
In the present context the term “stream” refers to a stream as well as to a jet or a ray. The flow of each or both of the component streams may be pumped or propelled by gravitational forces, or a combination thereof. The term “encircle” means that the second stream encircles, encompasses, or circumvents, the first stream, or in other words that the second stream flows in a circumjacent relation to the first stream.
If one of the ingredients of the multicomponent fluid thermosetting resin gluing system causes nauseous or noxious gas emissions this ingredient is suitably comprised in the first fluid component. By encircling the first fluid component with a second fluid component the vapours emitted from the first fluid component is then shielded from the ambient air. In this way it is also possible to use resin-hardener systems with high proportions of hardener.
Although the stream of the first fluid component may be discontinuous or comprise regular or irregular dripping, whereby the portions or droplets are essentially completely encircled by the second fluid component, the stream is preferably continuous, i.e. unbroken, whereby said first stream is encircled by the second stream in the direction transverse to the flow direction of both streams.
The present method is particularly suited for supplying thermosetting resin gluing systems chosen from a group comprising urea-formaldehyde resin gluing systems, melamine-formaldehyde resin gluing systems, melamine-urea-formaldehyde resin gluing systems, phenol resin gluing systems, phenol-formaldehyde resin gluing systems, resorcinol-phenol-formaldehyde resin gluing systems, polyurethane resin gluing systems, polyvinyl acetate gluing systems, emulsion and dispersion isocyanate resin gluing systems, and various combinations of two or more of these gluing systems.
The hardener components of these gluing systems are preferably used as the first fluid component according to the present invention.
In the present context the term “hardener” refers both to catalytic hardeners and reactive curing agents.
As the resin component is not brought in contact with the hardener component until the components exit the supply device, the pot life is prolonged, compared with prior art in which the components are premixed in or prior to entering the supply device. Consequently the clogging problem is also strongly diminished or even removed.
In a particularly preferred embodiment the present method is applied in a process for production of laminated wood or glue-laminated timber by agglutinating surfaces of two or more wooden members. In this process a multicomponent gluing system is prepared by mixing a hardener component and a resin component, whereupon the freshly prepared gluing system is applied on at least one of the surfaces to be agglutinated, whereby the hardener component is brought to flow in a first stream from an application device to said surface and the resin component is brought to flow in a second stream, whereby the second stream is brought to essentially encircle the first stream in the direction transverse to the direction of flow of the first as well as of the second stream.
The present invention also relates to a device specially adapted for the present method and the present process, which comprises a first hollow body provided with at least one outlet conduit, a second hollow body having at least as many outlet apertures as there are outlet conduits of the first hollow body, whereby each conduit is introduced into one aperture, there being an interspace between the conduit and the edges of the aperture.
One embodiment (not shown in the drawings) of the present device furthermore comprises an intermediate hollow body having at least one outlet conduit, whereby substantially all of the conduits of the first hollow body are introduced into one of the conduits in the intermediate hollow body and each conduit of the intermediate hollow body is introduced in the same aperture in the second hollow body as the first hollow body conduit is introduced into itself, and there being an interspace between the conduits of the intermediate and the first hollow body and an interspace between the conduit of the intermediate hollow body and the edges of said aperture. The device may be equipped with additional intermediate hollow bodies arranged in a way corresponding to said intermediate body, the upper number being limited by requirement/demand and economy only.
The first hollow body is preferably provided with an inlet duct, and the outlet conduit has suitably an outlet nozzle. The second hollow body is preferably provided with an inlet duct and comprises suitably a shell having interior and exterior surfaces enveloping the first hollow body. Said nozzle is preferably flushed with the interior or the e
Andersson Sven-Erik
Vesterlund Lennart
Akzo Nobel N.V.
Ball Michael W.
Burns Doane Swecker & Mathis L.L.P.
Musser Barbara J.
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