Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-10-29
2002-08-13
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S286000
Reexamination Certificate
active
06432240
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process and an apparatus for laminating pre-forms into laminated glazing assemblies, wherein the pre-forms include two solid panes laid on top of each other with a layer of adhesive in between such that the two solid panes with the layer of adhesive in between are subjected to pressure and temperature differences to form the laminated glazing assembly.
BACKGROUND OF THE INVENTION
The expression “laminated glazing assemblies” should be understood here to mean multi-layer products which consist of at least two solid panes with an adhesive film in between. The adhesive film is made of plastic or similar material for joining the two solid panes together. The two solid panes may both be made of glass or may both be made of plastic. However, it is also possible for a glass pane and a plastic pane to be joined together by an adhesive film. The individual layers (i.e., the solid panes and the layers or films of plastic) are produced separately in a conventional manner. The individual layers are then layered on top of each other to form of a packet of layers (i.e., a “pre-form”), before a final assembly into a laminated glazing assembly.
Modern glazing assemblies made of laminated glass, such as windscreens and side windows in motor vehicles, are often finally laminated in large autoclaves at high pressure and high temperature. Because of the necessary increase in pressure and of the long residence time required, a process using an autoclave step slows down the continuous and highly mechanized sequence of operations in the manufacture of the laminated glass assemblies, which has already been achieved for the manufacture and conversion of the individual layers for forming the pre-forms.
However, processes have also already been described for the manufacture of laminated glass which dispense with the autoclaving for the final bonding. In these autoclave-less processes, the pre-forms are finally bonded at atmospheric pressure.
German Patent No. 2,209,642 (hereinafter “the DE '642 patent”) describes a process for manufacturing three-layer laminated-glass glazing assemblies. During the process of the DE '642 patent, the pre-forms are put under vacuum and heated in a chamber, while the intermediate spaces are simultaneously subjected to vacuum using a suction frame. After having reached a certain temperature, for example, 100° C., the chamber is again vented to atmospheric pressure. However, the lateral vacuum is maintained by the suction frame, which continues to create a vacuum. Consequently, a primary laminate is simply assembled temporarily. This primary laminate is then transferred, with the suction frame under vacuum, into another chamber which is at atmospheric pressure. In the atmospheric pressure chamber, the primary laminate is heated to a temperature above the melting point of the adhesive film, which has been placed between the two solid panes. The pressure difference between the outside and the inside is sufficient to form the final laminated assembly.
German Patent No. 3,044,717 (hereinafter “the DE '717 patent”) describes another autoclave-less process for the manufacture of two-layer laminated products having a thermoplastic sheet located on the outside. According to the process of the DE '717 patent, a chamber at ambient pressure receives the pre-form. The ambient pressure chamber has its pressure temporarily decreased to a pressure even lower than the internal pressure obtained between the layers of the pre-form. The pressure may be reduced with the aid of a suction frame. The pressure difference briefly separates the layers from each other so as to facilitate the outgassing of the intermediate space. Next, the entirety of the pre-form is heated to the bonding temperature. During the time the pre-form is heated to the bonding temperature, the pressure in the chamber is increased back up to ambient pressure so as that the final laminated glazing assembly results and the internal pressure within the pre-form remains below atmospheric.
The two above-described autoclave-less processes rely on separable vacuum systems and also require a suction frame for sealing the packet of layers around the edge. The edge sealing is done, not only during the phase when the pre-form is under vacuum, but also during the subsequent phase wherein the final laminated glazing assembly is produced at atmospheric or higher pressure. For each shape and/or size of the pre-form, depending on the case, a specific variant of the suction frame has to be used. Since positioning and removing the suction frame cannot presently be mechanized, the above-described autoclave-less processes cannot be incorporated into, or can only be incorporated insufficiently into, an at least quasi-continuous manufacturing line. The term “quasi-continuous” should be understood here to mean a sequence of operations during which the flow of product material takes place, in principle, continuously during certain pane cycle periods and must only be interrupted for a short time for certain conversion steps, for example, for pressing between membranes or other pressing molds.
German Reference No. 2,424,085 (hereinafter “the DE '085 reference”) also describes an autoclave-less process during which a plastic film is laminated onto a pane using pressing membranes. In order to carry out the process of the DE '085 reference, the pane and the film are placed in a chamber so that the pane does not contact the film. Next, the chamber is closed and a vacuum is created therein. The plastic film rests on a membrane forming a wall of the chamber. The membrane is subjected to vacuum on both sides (i.e., on a front and rear face away from the chamber). After a necessary vacuum has been obtained in the chamber, the rear face of the membrane is subjected to atmospheric pressure. Because of the pressure difference established, the membrane presses the film against the pane. The film is made of either self-adhesive plastic or is provided with an adhesive layer. In this way, it is possible to produce curved glazing assemblies made of laminated glass. The curved laminated glazing assemblies are then pressed in a similar manner between two membranes.
When a heat-activatable adhesive is used, the pane is pre-heated outside of the chamber and then placed in the chamber. This process has the advantage that both a suction frame and individual pressing molds may be dispensed with.
Finally, German Reference No. 19,712,145 (hereinafter “the DE '145 reference”) describes another laminating process during which a pre-form, consisting of two panes and an adhesive film interlayer, is heated to the assembly temperature. The pre-form is then transferred into a chamber and a vacuum is created therein. PVB adhesive films are usually employed for the manufacture of glazing assemblies of the DE '145 reference. The PVB adhesive films are usually made of laminated glass which has a relatively rough and non-transparent surface so as to guarantee that, after the solid panes and the adhesive film have been joined together, all the air can be sucked out through the channels formed by the unevenness in the film. In order to obtain the required high transparency of the final product, the adhesive film must be fully melted so that the unevenness completely disappears. In the process of the DE '145 reference, after the minimum pressure has been obtained and after sufficient venting, the edge of the pre-form is sealed by mechanical pressing, while the chamber is vented again. Under the action of forces exerted on the main surfaces of the laminated product, preferably in combination with additional heating in order to completely melt the adhesive film, the rise in pressure causes the panes to be joined to the adhesive film so that a virtually continuous flow of material can be achieved.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide an apparatus and process for laminating pre-forms into laminated glazing assemblies, wherein at least a quasi-continuou
Balduin Michael
Havenith Hubert
Labrot Michael
Ball Michael W.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Rossi Jessica
Saint-Gobain Glass France
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