Process for making a laminated car window, capable of reflecting infrared rays

The invention relates to a method of manufacturing a laminated glass window, intended in particular for motor vehicles, infrared reflective and provided with a sealing layer of the edges, the glass comprising at least two glass sheets and a laminate placed between them, this laminate comprising a carrier sheet provided with at least one infrared reflective layer, for example made of a metal such as silver, and the outer layers made of a thermoplastic polymer.

A method of manufacturing a laminated glass pane reflecting infrared, using a multilayer laminate containing a metal layer responsible for the reflection of infrared and a seal disposed on the edges, which protects the metal layer, has already been mentioned in EP-A2-0 391 165, in conjunction with US-PS 4,368,945, which are expressly referenced in this document. In terms of the metal layer reflects infrared involve the use of silver. With regard to this known method, the laminated glass pane is manufactured in the usual manner, from the laminate and the two sheets of glass, the laminate extending to the edges of the laminated glass window. The sealing is performed here by depositing on the "slice" (that is to say the song) of the final laminated glass, a sealing adhesive. To form said adhesive layer of sealing edges are used thermoplastic adhesive materials based on polybutene copolymers, adhesives based on fluorine polymers or adhesives based on butyl.

This known method is certainly suitable for the manufacture of fixed automotive glass (that is to say panes fixedly mounted in the frames that surround the edges of which are coated, since they are inserted in the frames ) but it is not always suitable, for example to manufacture retractable side windows. Indeed, as the slices retractable side windows are exposed when the window is open, adhesive materials are not only visible, but are also subject to mechanical stresses that may cause the destruction of the edge sealing.

DE-A1 23 44 616 refers to the means for the manufacture of windscreen provided with an electric heater and made of laminated glass, to attach a carrier sheet made of polyethylene terephthalate (PET) and provided with a conductive layer on two glass sheets, by means of thermoplastic polyvinyl butyral sheeting, and to cancel the risk of corrosion by removing edges in part and that in the edge region, a width of 3 to 12 mm, for example, the metallic coating is present on the PET sheet, which extends itself up to the singing of the glass sheets. This partial removal of the layer can be made by chemical or mechanical processes. In this edge region, wherein the layer has been eliminated, the polyvinyl butyral sheet is directly joined to the surface of the PET sheet and thus acts necessary sealing.

It is also known that it is possible to prevent corrosion of the silver layer, to use a carrier sheet provided with a coating and having dimensions smaller than those of the glass sheets, to coat this sheet carrier between two thermoplastic sheets, whose dimensions correspond to those of the glass sheets, then to assemble the sheets so that the edges of the carrier sheet with the coating are recessed at least 3 mm from the edges of the sheets glass (US-PS 3,794,809).

The polymer of the thermoplastic sheets encapsulating the carrier sheet is then crosslinked by means of a thermal process and overpressure, so as to ensure the desired sealing role.

The two methods described above are of course effective, but they require that the carrier sheets are used provided with a coating, at least the coated surface of this coating is free to access, these carrier sheets to then receive at least one additional sheet, namely a thermoplastic sheet, made for example of polyvinyl butyral. However, the carrier sheets with a layer have reached a decisive disadvantage. Indeed, the sensitive surface layer is not protected during the required manipulations of the carrier sheet with the coating, so that there is risk of damage and / or soiling the surface layer. Such defects are unfortunately visible on the laminated glass window, once completed.

The invention aims to provide a process for manufacturing a glass (or "glazing") laminated glass infrared reflective and provided with a sealing edge, which method is, firstly, adapted to the production industrial and allowing, on the other hand, to ensure effective and durable sealing of the edge region of the laminated glass window, without the sealing layer be a source of problems, including an optical point of view .

The process according to the invention involves the use of a laminate comprising a carrier sheet, provided in at least one of its faces, at least one infrared reflective layer, said laminate further comprising outer layers made from polymer (s) thermoplastic (s), the method according to the invention comprising the following steps:<ul><li>a) is cut out from the laminate plate corresponding to the geometrical shape of the glass sheets, but shorter, for example from 1 to about 10 mm, along those edges thereof that will seal;</li><li>b) the laminate plate is positioned with respect to the glass sheets in accordance with the determined offset space on the edges, then manufacturing a preparatory laminate (or "preliminary") from the set of layers, by removing the air between the layers and forming a provisional assembly, or gluing, and that by rolling or by a low pressure process;</li><li>c) the gap (or "slot" or "groove") remaining on board the preliminary laminate is filled by injection of a polymer-based melt (s) consistent (s) with (s) polymer ( s) thermoplastic (s) already forming the external layers of the laminate;</li><li>d) (s) polymer (s) injected (s) in the edge gap merges (s) with (s) polymer (s) of the laminate of the outer layers and this, by means of an autoclaving process involving heat and pressure. This gives the final laminate.</li></ul>

The term "polymer (s) consistent (s) with (s) polymer (s) of thermoplastic material (s) forming the outer layers" means one (or more) polymer (s) may (s) to merge with the (s) polymer (s) thermoplastic (s) of the outer layers, in particular one (or more) polymer (s) of the same basic composition as the (s) polymer (s) of the outer layers and comprising or not one or more additives (e.g., one or adhesion agents). In the simplest way, the (s) polymer (s) injected (s) is (are) identical (s) to (x) polymer (s) forming the outer layers.

The method according to the invention requires no special security measures to protect the surface layer during the manufacture of the laminated glass window, as this surface layer is completely covered by the outer thermoplastic layer. It was further found that sealing the edges of the laminated glass window is invisible in practice, the sealing adhesive used to seal with preferably the same appearance and the same refractive index as the thermoplastic layers neighbors and merging completely with these layers, without showing a visible dividing line. If the appearance of a laminated glass window manufactured in accordance with the invention corresponds to that of a glass of the same type designed in conformity with the method described in US-PS 3,794,809, this new method provides for the industrial production an essential advantage. Indeed, the sensitive surface layer is covered and one sheet, namely the laminate already made, is required when the laminated creation process.

The sealing process can be easily automated using known methods, as exemplified later.

Thermoplastic polyurethanes, as currently sold and used for making the laminated glass panes, for example to join the sheets of glass plates or polycarbonate sheets, are examples of thermoplastic polymers suitable for the production of the outer layers the laminate and injection into the edge gap. However, for economic reasons we prefer their polyvinylbutyral, which is used to a large extent to the shape or the layer (s) thermoplastic (s) intermediate (s) in the manufacture of laminated glasses. It was found that could easily melt the polyvinyl butyral stream for injection into the edge gap. In this case, simply to ensure that it does not exceed a temperature of 230 ° C upon heating and injection and to prevent as far as possible that of air or oxygen enters in the molten polyvinyl butyral, which could cause polymer coloring.

The composition of polyvinyl butyral usually used to make laminated glass is such that adhesion to glass does not exceed a certain ceiling. Indeed, if the adhesion became too much, the safety features of the laminated glass window would deteriorate. As this factor plays no role in the region of the edges of the laminated glass window and as, on the other hand, it may be advantageous that the polyvinyl butyral firmly adhered to the glass, allowing a particularly effective sealing in the region of the gap edge, it is possible, through a suitable improvement of the invention, to add to (x) polymer (s) thermoplastic (s) chosen (s) for injection into the gap a additive improving adhesion, the silane, for example.

Other advantages and features of the invention appear in the light of the following examples, illustrative but not exhaustive, of an advantageous embodiment of the invention, the description making reference to the figures wherein:<ul><li>Figure 1 shows the different layers of the laminated glass window, as observed during the assembly process,</li><li>2 shows a view of the edge region of the preliminary laminated, during the injection into the gap,</li><li>3 shows an automatic device for injecting material into the gap.</li></ul>

The laminated glass pane consists of two glass sheets 1 and 2, each with a thickness of 4 mm, between which was placed a laminate 3. This laminate 3, whose structure is shown in Figure 2, includes for share a carrier sheet 4 made, for example, polyethylene terephthalate (PET), thick, e.g., 0.02 to 0.1 mm, and which is provided on one of its faces with a surface layer 5 capable of reflecting heat, the laminate also having two outer layers 6 and 7 made, for example, polyvinyl butyral and each having, for example, a thickness of about 0.4 mm. The surface layer 5, capable of reflecting heat, can be made of several sub-layers, the truly useful layer made, for example, silver, thick for example from 8 to 15 nm, being covered on either side by the other layers generally made of metal and / or alloys or combinations of metals. Instead of a single silver layer, layer 5 may contain two or, if necessary, more than two silver layers proportionally thinner and that are separated from each other by layers of alloys dielectric metal.

The structure of the laminate may also be designed so that a PET sheet provided with a coating to be joined to another similar PET sheet, but devoid of coating, on the side, for example, of the coating and that, by means an adhesive layer, the resulting assembly being provided on one side or the other of an outer layer made of a thermoplastic polymer, polyvinyl butyral, for example.

It is for this purpose that the appropriate laminates are described in US Pat patents 4,368,945, EP 0303586 and EP 0303587, for example. The laminates of this type are produced by manufacturers in the form of bands or strips of sheets, in a continuous process, and shipped in roll form.

As can be seen in Figure 1, the two glass sheets 1 and 2 have already before they are assembled their final shape and size, as is necessary and common in the manufacture of laminated glass. When one wants to produce a laminated and curved glass, two sheets 1 and 2 are themselves curved and, if appropriate, more or less hardened, to give them a stronger mechanical strength and / or the characteristics of a safety glass.

A form 3 is cut into the existing laminate, s ccording the outlines of two glass sheets 1 and 2, those of its edges intended to receive the seal being shorter by a few millimeters than the two glass sheets, so that the edge of the form 3 is recessed by a distance a relative to the edges of sheets 1 and 2. This width a is preferably between 3 and 6 mm. As it is, for the laminated glass window shown here, a retractable side window and to which the lower edge region is concealed and inserted into the door, it is not necessary to seal the lower edge corresponding 9 of the laminated glass window, so that in this zone, the laminate plate 3 can reach the edges of the sheets 1 and 2.

The glass sheets 1 and 2, and the shape cut in the laminate 3 are assembled in the desired order, in a plurality of layers, as shown in Figure 1.

A preliminary laminate is then made from this set of layers, as we know usually done to produce laminated glass. The manufacturing process of this preliminary laminate may for example comprise the following steps: the set of layers is heated to a temperature of about 80 to 90 ° C, and then rolled by means of two cylinders, the air present between the layers thus being expelled, allowing assembly (or collage) provisional layers. The manufacture of the preliminary laminated glass may also consist of a vacuum process, the air between the layers being aspirated, the provisional assembly being again obtained by heating of the assembly of layers to a temperature up to 70- 100 ° C.

The preliminary laminated 10 thus obtained has a gap 12 on its edge. It is in this gap 12 that melted polyvinylbutyral is now injected which possibly was added an adhesion. Note that it may be advisable that the preliminary laminate is worn during this injection to a temperature of 70-120 ° C, for example. To this end, it is possible to preheat the preliminary laminated immediately before injection into the gap, or to inject directly after the preparatory joining process, as the preliminary laminated has a high temperature. finally add that we can both perform the injection at room temperature in the edge gap.

This injection into the gap 12 occurs automatically with the aid of an injection nozzle 14, a robot moves along the edge of the pane of laminated glass 10.

A device designed for this purpose is shown in Figure 3.

This device comprises a robot 18, on the handling head 19 surrounding the injection nozzle 14. The injection nozzle 14 is applied against the edge of the preliminary laminate 10 by the robot 18, which moves along this slice maintaining good contact with it. The injection nozzle remote control program 14 is stored in the memory of a central control unit 20 which, in turn, controls the robot 18 via pilot line 21. Similarly, the motor 23 of the extruder 24 is controlled by the CPU 20 via the pilot line 22. in the extruder 24, the pellets of polyvinyl butyral, which can be for example crushed leaf fall of current PVB, are introduced into the feed hopper 25. this extruder can be provided with a worm. The cylinder 26 containing the screw of the extruder is connected to the injection nozzle 14 via a pressure hose 28, a swivel joint 29 being connected to both ends of this tube, so as not to transmit the twisting forces due to the rotation of the injection nozzle 14.

Heating rings 30 have been arranged on the cylinder 26 of the extruder 24, which rings bear the extruder at a temperature of about 180 ° C required to melt the polyvinyl butyral. Similarly, the pipe 28 is equipped with heating resistors 31 and the injection nozzle 14 of a similar resistor 32, the latter ensuring the maintenance of the PVB to a stable temperature throughout the operation, at which temperature the mass melted polymer has a viscosity low enough to allow it to completely fill the gap 12.

Of course, it is possible to perform in a different way the sealing by injection into the gap, for example using a device which allows the preliminary laminated to move past a fixed nozzle or by means of an injection nozzle which is moved by hand along the edges of the preliminary laminated.

After filling the gap in this manner with polyvinyl butyral, the laminated preliminary we will refer to the usual autoclaving process at a temperature of about 140 ° C and a pressure of about 10 bar. During this treatment, polyvinylbutyral injected into the gap edge and the outer layers of the laminate are based on one another to form a completely homogeneous layer and free of imperfections. The line of separation of the carrier layer, provided with a coating, is certainly still visible when examined carefully and in certain lighting conditions, but is so discreet that it does not affect the appearance or the optical qualities of the glass.