DEVICE FOR THE IMPREGNATION WITH THERMOPLASTIC SUBSTANCES OF BANDS OR SHEETS MADE OF FOAMED RESIN

Abstract: Device for the impregnation of sheets of elastic foamed resin with thermoplastic substances. In particular said sheets, due to their particular molecular structure, once impregnated with bitumen and conveniently compressed, can keep the bitumen ensuring a good impermeabilization. For these reasons they find a good application in the building sector. In particular the device comprises driving and guiding means of the foamed resin sheet, a hopper fed with bitumen and two calendering rollers. The calendering rollers are heated and have, respectively, an external surface with lattice shape and an external surface coated with an elastomer material resistant to high temperatures.

Description: "DEVICE FOR THE IMPREGNATION WITH THERMOPLASTIC SUBSTANCES OF BANDS OR SHEETS MADE OF FOAMED RESIN" The present invention concerns a device for the impregnation with thermoplastic substances of bands or sheets made of elastic foamed resin having an at least partially open cellular structure. Said sheets are particularly effective for the impermeabilization of surfaces that must be weatherproof, and therefore they are mainly used in the building sector. In particular waterproof sealing materials are increasingly used, generally consisting of a supporting structure made of elastically compressible foamed resin (foamed polyurethan) , impregnated with a thermoplastic substance such as for instance bitumen or similar material. Even after having been imbued, the foamed resin maintains its elastic properties so as it can be compressed, and therefore made waterproof, before its installation. In fact an effective impermeabilization of the foamed resin sheet can be obtained during its processing by - means of an appropriate compression. In particular, what happens is that the initially open cells, which are impregnated for example with bitumen, gradually close as they are increasingly compressed, until the element is made completely waterproof. One of the most effective processes for the production of this material is the calendering process. It consists in conveying the foamed resin sheet through a hopper containing thermoplastic material, for example bitumen, and then through a couple of calendering cylinders or rollers operated by a motor. Cylinders are heated so as to keep the bitumen at the viscous state; the foamed resin sheets are guided by driving rollers and suitable guides in such a way that they enter the hopper and then the calendering rollers following a more or less vertical path. However it is necessary that the foamed resin sheet is guided during said process, and this in order to avoid deformations, tearings or breakings. One of the solutions of the known technique provides for instance a supporting belt on the path leading from the driving rollers as far as beyond the calendering rollers. This solution however presents the drawback of hindering the impregnation of the resin sheet through its surface which is in direct contact with the belt, as said belt is impermeable to the bitumen. Said drawback does not appear particularly serious when the foamed resin sheet introduced is made of polyurethan resin derived from polyethers, in that this material has a completely open cellular structure and, the impregnation with bitumen takes place in a uniform way even if occurring only from one side of the foamed resin sheet. This type of resins, however, have limited application since they are photosensitive, and therefore subject to deterioration in time. Polyester-based polyurethan resins are not photosensitive, but they are scarcely suitable to be used with said device, because they have a partially open structure and then, they would be impregnated in a poorly uniform way. Another drawback of said device is due to a not perfect resting of the belt with respect to the resin sheet that during processing often moves. In a more recently known technique it was proposed to overcome said disadvantages by replacing the supporting belt with a wire net that should thus accomplish the function of accompanying the foamed resin band as far as beyond the calendering cylinders without hindering the process of impregnation taking place inside the hopper. In this way, the simultaneous impregnation along both surfaces of the sheet is allowed, because the bitumen easily penetrates the meshes of said net. Nevertheless this solution, "too, proved to be insufficient, in that the net risks to become broken when coming in contact with the calendering cylinders and, causes deformations and tearings in the foamed resin sheets themselves. Therefore, in the light of what said above, there is still the problem of proposing a device for impregnation by calendering of polyurethan resins having partially open cellular structure, that may result to be more effective than the previous ones. An object of the present invention is to overcome said disadvantages, byensuring the function of guiding the foamed resin sheets, but avoiding supporting elements of the known techniques (such as for example wire net or belt) that can break when in contact with the calendering rollers or can hinder the simultaneous impregnation of the band from both surfaces. A device is therefore proposed that accomplishes in a different way the guide function, simultaneously meeting the requirement of a uniform distribution of the thermoplastic substance. This object is achieved by the present invention that concerns a device for the impregnation with thermoplastic substances of elastic foamed resin bands or sheets having an at least partially open cellular structure, of the type comprising driving means and guiding means of said foamed resin sheets, a hopper containing the thermoplastic substance, a couple of calendering cylinders and heating means for said cylinders, characterized in that one of said cylinders has an outher surface shaped according to a metal lattice, while the other one is externally covered with a layer of an elastomeric material resistant to high temperatures, in such a way to form a grip surface cooperating with the action of said lattice shaped cylinder. The features of the invention will become more evident from the following description referring to an example given by way of illustration and with no limiting purposes, made with reference to the accompanying drawings, wherein: figure 1 is a perspective view of the device according to the invention; figure 2 is a section (2a) and a perspective view (2b) a the cylinder having its external surface shaped according to a metal lattice; - figure 3 is a section (3a) and a perspective view (3b) of the other cylinder, covered with rubber; and figure 4 is a schematic view of an equipment comprising the device of figure 1. Figure 1 illustrates a impregnation device according to the present invention during a calendering process, in which a sheet of foamed resin 3 is driven into an hopper 5 through cylinders 1 and 2, latter of which is actuated by a motor. The foamed resin sheet 3 rests on the fixed supporting plate 4 on which it freely slides. On the opposite side a further canalizing plate 6 is provided for, with the function of accompanying the sheet 3 resting on the plate 4 without hindering it from sliding. The distance between the plates 4 and 6 is adjusted at the beginning of the working cycle as a function of the thickness of the treated sheet of resin, and kept constant by means of a locking mechanism provided on the canalizing plate 6. Inside the hopper 5, that is suitably fed with a thermoplastic substance from manifolds 10 and 11 on both sides of the resin sheet, the fixed plate 4 has an end edge in the vicinity of the inlet area of calendering rollers 8 and 9, which, from that moment on, must also accomplish the function of guiding the foamed resin sheet. In particular the distance separating the fixed plate 4 from the calendering rollers 8 and 9 is preferably of about 2 cm and anyway such as to allow the sheet 3 to be accompanied as near as possible to the rollers 8 and 9 without hindering the impregnation of the surface of the sheet 3 itself that rests on the plate 4. Furthermore the sheet 3 is preferably made of foamed resin having partially open structure, for example of the type based on polyesters, since said materials offer high levels of reliability and duration. The roller 8, as shown in figure 2a, has its external surface shaped according to a lattice 12, preferably 0.5 mm thick, on the smooth external surface of the cylinder. The lattice 12 has the double function of guiding the sheet 3 into the calendering cylinders 8 and 9 avoiding the danger of deformations, but also, thanks to the improved adhesion deriving from the combined action of the two calendering rollers 8 and 9, of favouring a good impregnation of the sheet itself, both for the compression to which it is submitted and for the uniformity of distribution of the thermoplastic substance on its surface. The cylinder 8 is moreover heated in a known way, using for example an equipment for oil circulation, to a temperature near the melting temperature of the thermoplastic substance so as to improve the penetration of said substance into the foamed resin sheet avoiding the risk of deformations of the foam resin itself; in the case where said thermoplastic substance is bitumen, the temperature is preferably kept at approximately 150 degrees C. Figure 3a on the contrary illustrates a section of the calendering cylinder 9 that is covered with a layer of elastomer material 13 capable of resisting to oils and high temperatures. In these cases a rubber is preferably used having hardness of about 40 Shore. The roller 9, too, is heated to the same temperature as the roller 8 and preferably, but not necessarily, using the same heating system. The function of the cylinder 9 is that of offering a grip surface to the action of the reticulated roller 8, so as to conveniently compress the foamed resin sheet that slides between the two rollers. The speed of rotation of the feeding roller 2 and of the calendering cylinders 8 and 9 can be adjusted independently from each other as a function of the characteristics of the material to be handled. Figure 4 schematically shows a plant comprising the aforedscribed device, wherein there is provided an equipment for the production of a pressure adhesive tape and means for coupling said adhesive tape to the sheet or band of foamed resin 3 impregnated with bitumen. Said equipment essentially comprises a device 14 to spread one side of the supporting tape 15 with a generally aqueous solution of an adhesive; an element 16 for thermal treatment (e.g., evaporation of the water content) of the tape 15 provided with adhesive and two or more coupling rollers 18. During operation the tape 15 unwinds from the bobbin 17 and passes through the spreading device 14 that applies a layer of generally aqueous solution of adhesive on one side of the tape 15. Said side is preferably the upper one and, in any case, presents a siliconated surface on which the adhesive is deposited but to which it only partially adheres. The tape spread with adhesive then passes through an oven 16 for thermal treatment of the adhesive (for example water evaporation and/or resinification of the adhesive) and reaches the couple of cylinders 18 through which it is coupled with the sheet or band of foamed resin 3 coming, thanks to the guide of idle rollers 19, from the calendering cylinders 8 and 9. The sheet 3 coupled with the adhesive tape 15 at an outlet of the rollers 18 will then be cut and shaped according to final requirements; at the moment of use the tape 15 is taken away leaving the adhesive fixed on one side of the sheet 3 for an easier application. To perform in a continuous way the operations of formation of the band 3 and application of the adhesive thereon, the equipment for treating the paper tape 15, comprising the spreading device 14, the oven 16, is at least partly below the calendering unit 8, 9. It is evident that suitable modifications, additions or replacements of some elements with others accomplishing the same functions can be made without anyway escaping from the scope of the present invention. For instance, - the external surface of the calendering cylinder 8 can present, instead of a metal lattice, some indentations that provide in a different way the corrugated surface, with improved adhesion, necessary for the combined action between the two calendering rollers 8 and 9 .

Claims: C L A I M S 1. Device for the impregnation with thermoplastic substances of bands or sheets of elastic foamed resin having at least partially open cellular structure, of the type comprising driving means and guiding means for said foamed resin sheets, a hopper containing a thermoplastic substance, a couple of calendering cylinders and heating means for said cylinders, characterized in that one of said cylinders has an external surface shaped according to a metal lattice, while the other cylinder is externally coated with a layer of elastomer material resistant to high temperatures, in such a way to constitute a grip surface cooperating with the action of said lattice shaped cylinder. 2. Device according to claim 1, characterized in that said guiding means comprise at least two plates, one as a support for said sheet and the other canalizing the resin sheet, said plates being upperly positioned with respect to said calendering cylinders and along the resin sheet main surfaces, and extending in length as far as the inlet area of said sheets into said cylinders, said sheet sliding between said plates. 3. Device according to claim 2, characterized in that the distance between said supporting plate and said canalizing plate is adjustable as a function of the thickness of said resin sheet, the adjusted distance being kept constant by a locking mechanism. 4. Device according to claim 1, characterized in that said driving means of said foamed resin bands or sheets comprise one or more cylinders, at least one of which is actuated by a motor having an adjustable speed. 5. Device according to claim 4, characterized in that the speeds of said driving means and of said calendering cylinders are separately adjustable. 6. Device according to any of the preceding claims, characterized in that said elastic foamed resin is a polyester-based resin.

Inventors: MORA ALCIDE, MORA, ALCIDE
Applicants: MORA ALCIDE, MORA, ALCIDE
Application year: 1993
Main classification: B29C67
IPC codes: B29C43, B29C44