Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With work feeding or handling means
Patent
1997-04-16
1998-12-15
Engel, James
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With work feeding or handling means
118110, 118245, 118663, 118712, B05C 100
Patent
active
058491457
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a device and the relative process for the continuous, warm smearing of hotmelt adhesive onto a plastic film, that allows the homogenous spreading of a thin adhesive layer onto the films or membranes used for plastic-coating or lining paper objects.
In particular, the device and the process according to the present invention concern the field of plastic-coating of paper industry articles wherein--as already known--the need arises to unite a paper support with a plastic film of different kinds. Usually such film is a polypropylene film, and such film is applied to a paper support by means of interposition of adhesives of different kinds, which all have the purpose of enhancing the paper support, to make it aesthetically more pleasant and to strengthen the surface thereof so that it may better stand the natural deteriorating agents, like dust, humidity, wear, yellowing etc.
Systems for continuous smearing with rolls are already known, which can obtain the spreading of a thin layer of adhesive of different kinds and with different features, onto plastic films.
The employed techologies make use of mainly two particular kinds of processes.
The first one provides for the application of an adhesive compound onto a film that will the be wound into coils, and that may be used a second time in machines for the plastic-coating, by thermic re-activation of the adhesive.
The second process provides for the smearing of the adhesive onto the film directly during the plastic-coating process of the paper support.
The first technology involves the inconvenience that the adhesive film must be stored and transported a plurality of times before use.
Furthermore, it introduces great adhesive waste in the working, because the dimension of the adhesive film, that is smeared over all its width, is not always exactly equal to the one of the supports to be plastic-coated. Finally, the costs of said adhesive films are very high.
The inconveniences of the second process derive from the complexity of the device that manages the smearing and drying process of the adhesive onto the plastic film, and of the following application onto the paper support.
In detail, this second process provides for the use of two fundamental kinds of adhesives: with a solvent base and with watery base.
If adhesives with a solvent base are used, the drying process is quicker because it is favoured by the quick evaporation of the solvent, while causing noxious and polluting gas emissions.
If adhesives with a watery base are used, there are no polluting emissions, but the water evaporation phase is more complex, as it requires more thermic energy, and often the color change of some inks occurs, which are not consistent with the watery base composition of the adhesive.
It is the aim of the present invention to eliminate all above mentioned inconveniences.
The main aim set forth according to the present invention is accomplished by a device that allows the continuously warm smearing of a thin, hotmelt adhesive layer, of the normal or reticulatable kind, commonly used in different fields, especially in paper industry, onto a plastic film by previous spreading and drying of a layer of primer of known kind, with the roller system that may be easily fitted for smearing films of different width without replacing said rollers.
It is a further aim of the present invention by means of a device for the compensation of the thermal expansion between the metal elements of the apparatus, to keep constant the minimum thickness and the dosing of the adhesive according to the variations of the working temperature.
It is another aim of the present invention to introduce a successive phase of spreading and smoothing the plastic film, already smeared with the adhesive.
It is a last aim of the present invention to define a smearing process by means of which the creation of filaments in the adhesive may be avoided, which could compromise the correct and uniform spreading of said adhesive onto the plastic film during the detachment between said film and t
REFERENCES:
patent: 4899691 (1990-02-01), Fitzgerald, Jr. et al.
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