A METHOD AND AN APPARATUS FOR THE MANUFACTURE OF A BITUMINOUS COATING SHEET AND SUCH COATING SHEET

Abstract: The invention relates to a method of manufacturing a bituminous coating sheet, wherein a bitumen-impregnated core material provided with a layer of backface bitumen is caused to be in contact with one or more rotating bodies during the manufacture. The invention is characterised in that a slip material dispersed/emulsified or dissolved in a liquid is applied onto the bituminous backface layer on the side that is to be brought into contact with a rotating body; and that the liquid is evaporated prior to contact with the rotating body; and that subsequently a further bituminous layer is applied onto the side which is provided with said slip material.

Description: A method and an apparatus for the manufacture of a bituminous coating sheet and such coating sheet The invention relates to a method for the manufacture of a bituminous coating sheet wherein a bitumen-impregnated and bitumen-coated core material is advanced across one or more rotating bodies during the manufacturing process. The invention also relates to an apparatus for exercising the method and a coating sheet produced by said method. Such coating sheets are used eg for the coating of roofs. The coating sheet is generally configured with a core material that consists eg of woven or non-woven synthetic fibre. Usually, the core material is impregnated with bi- turaen and on the one or first face it is coated with a bituminous material wherein eg crushed slate is usually incorporated to increase the resistance of said coating sheet to eg sunlight. This side constitutes the outwardly facing, free side of the coating sheet. On the other side of the core material which is opposite the slate material, a bituminous coating is also provided, viz a so- called welding bitumen. Such coating sheets are often used in connection with the coating of eg bridges and the establishment of diffusion-proof underground membranes, eg in waste disposal areas, liquid manure containers, and the like. In a known method of manufacturing a bituminous coating sheet, a core material impregnated with or coated with a bituminous material on the above-mentioned second side is strewn with a layer of sand that prevents, during the further manufacturing process, this side of the coating sheet from adhering to the rotating bodies that convey the coating sheet. In a concluding step of the manufac- turing process, a bituminous material is added on top of the sand layer - preferably a so-called welding bitumen that serves to connect the coating sheet with a support on the site of use. However, the use of a sand layer as an anti-adhesion measure in connection with the manufacturing process is associated with the drawback that the subsequently applied welding bitumen can exhibit poor ad ¬ hesive properties towards the remaining coating sheet. Thus, in connection with eg roof coverings, bridge coverings and the like membrane coatings, powerful external influences such as wind influences that cause a suction in the surface may cause delamination of the bituminous coating sheet. The consequence of such delaminations can be leakages with ensuing damage to the roof structure and/or the remaining part of the building or the plant. Moreover, the sand layer involves a significant increase in the volume of the coating sheet. It is an object of the invention to provide a method for the manufacture of such bituminous coating sheet wherein the finished product possesses considerablyincreased de- lamination strength and a reduced volume compared to the prior art. Moreover, it is an object of the invention to provide an apparatus for exercising this method. Finally, it is an object of the invention to provide a coating sheet that possesses a considerablyincreased delamination strength compared to the prior art coating sheets. According to the invention the method for the manufacture of such bituminous coating sheet is characterised in that a separing material being dispersed/emulsified or dissolved in a liquid is applied onto that side of the bituminous backface layer that is to be brought into contact with a rotating body; that the liquid is evaporated prior to contact with the rotating bodies for advancing the coating sheet; and that subsequently a further bituminous layer is applied onto that side which is provided with the slip material. By such method, even and thin application of the slip material is accomplished, and furthermore it enables use of slip materials having considerablyincreased adhesive properties compared to sand as known from the prior art. Finally, the option of applying the layer very thinly also enables a coating sheet with a considerablyreduced volume, the layer thicknesses being otherwise unchanged as regards core and bitumen coatings. According to a particularly convenient embodiment of the method, the dispersion/emulsion or the solution as the case may be is applied by a spraying process. This method enables safe control of the process and thereby ensures that the thinnest possible layer of slip material can be applied. Moreover, it will also be possible to accomplish the application by means of an anti set-off roller. The dispersion/emulsion/solution is preferably applied onto the coating sheet at such distance from the first rotating body that said liquid is completely evaporated prior to contact with the first rotating body whereby is provided a solid, non-adhesive surface layer consisting of the slip material. In that context it is important that - during application of the liquid slip material - the bituminous material has a suitable temperature. Conveniently it is ranging from 100 to 200°C, preferably, however, from 120 to 160°C. The relatively elevated temperature permits quick evaporation of the liquid contents of the dispersion/emulsion or the solution, thereby accomplishing an advantageous cooling of the bituminous coating sheet that increases the viscosity of the bitumen material. Optionally further coolant can be supplied to the surface of the bitumen layer. In the method, a polymer dispersion/emulsion is preferably used, eg a dispersion/emulsion of a thermoplastic polymer, eg acrylic-based or PVB (Polyvinyl Butyral) that can be admixed with a plasticizer. Alternatively a solution of polyvinylalcohol can be used. An apparatus for exercising the method described above comprises rotating bodies for conveyance of the coating sheet and means for applying a dispersion/emulsion/solution of a slip material. Such means for applying the liquid slip material are conveniently in the form of one or more nozzles to which the disper- sion/emulsion/solution is supplied under pressure. The pressurized supply can be accomplished by means of usual liquid pumps. Such embodiment with nozzles ensures the most homogenous distribution and thus the option of ap ¬ plying the thinnest possible layers of the slip material. These means for applying the liquid slip material are preferably arranged at such distance from the first rotating body that the liquid contents of the disper- sion/emulsion/solution has evaporated completely prior to contact with the rotating body. It is a further option to provide an anti-set off roller for use in the application of the dispersion/emulsion/solution. The invention also relates to a coating sheet which is characterised in comprising a core material, the one side of this core material being provided with a layer of a polymer-based slip material and adjacently this polymer- based slip material a bituminous layer. This is prefera- bly a thermoplastic polymer. Compared to the prior art coating sheets, such coating sheet has a considerablyincreased delamination strength and also has a considerably smaller volume than prior art coating sheets while maintaining as such the layer thick- nesses of core and bitumen coatings. The slip material used is preferably a thermoplastic polymer. Upon melting this is dissolved in bitumen. The oils present in the bituminous material dissolves the dried film of polymer at a relatively low temperature, and thus - by application of the bituminous welding layer - the polymer will be dissolved, with an ensuing increase in the delamination strength since the bituminous welding layer is caused to be in direct contact with the bitumi- nous backface layer. Moreover, the heated thermoplastic polymer will have an adhesive effect. In this context it is important that, following evaporation of the liquid contents of the dispersion/emulsion/solution, there is no longer much heat that the thermoplastic polymer becomes tacky. In order to avoid this, it is an option - as mentioned previously - to supply further coolant, eg water, in order to hereby cause the temperature of the sheet to decrease further. On the basis of solubility parameters for the relevant bitumen, the person skilled in the art will be able to select the desired thermoplastic polymer to ensure that the solubility parameters of that polymer are close to these. In this context, the solubility parameters are de- termined by such conditions as stereoisometry, polarity, van-der-waal forces and molecular weight. The method, the apparatus for exercising the method and the coating sheet produced by said method will now be ex- plained in further detail with reference to the drawings, wherein Figure 1 is a schematic sectional view through a coating sheet according to the invention, and Figure 2 is a schematic view of a production plant for the manufacture of a coating sheet according to the invention. Figure 1 is a sectional view through a coating sheet. It will appear that the coating sheet is composed of a core material 3 consisting of a woven synthetic fibre material, eg polyester fibre. The core material 3 is impreg ¬ nated with bitumen. On the top face of the core layer 3, a bituminous layer 2 is provided and on top of this, a layer of powderous protective material 1 is provided, eg crushed slate. On the bottom face of the core material a further bituminous layer 4 is provided, a so-called backface bitumen, and below this backface bitumen 4, a thin layer of a thermoplastic polymer material 5 is provided, and below this a bituminous welding material 6. Towards the bottom the coating sheet is provided with a film 7 that serves to prevent adhesion of the layer of welding bitumen to other surfaces. A coating sheet as shown in Figure 1 can be manufactured eg in a production plant like the one shown schematically in Figure 2. For the sake of clarity, machinery frames, operating means, etc., are not shown. Such can readily be implemented by the person skilled in the relevant art. The coating sheet is, in the example shown, conveyed from the left towards the right. Starting from the left, a sheet of impregnated core material 3 is introduced into the shown part of the production plant, the top face thereof being provided with a bituminous layer 2 and the bottom face with a bituminous layer 4. The sheet temperature is, at this point, 100-200°C, preferably 120-160°C. At a coating station 8, a powderous coating layer 1 of crushed slate is applied on top of the bituminous layer 2. The sheet is subsequently conveyed around a first ro ¬ tating body 9, where the coated face of the sheet abuts on this rotating body 9. The coating 1 thus prevents the sheet from adhering to the rotating body 9. Immediately after the rotating body 9, is a coating station 10 for a slip material, eg a thermoplastic polymer, dispersed/emulsified/dissolved in liquid. The coating sta- tion 10 is, in the example shown, composed of four jet nozzles arranged on a common suspension means transver- sally to the sheet whereby the entire width of the sheet is coated by the dispersion/emulsion/solution ejected thereby. At a distance from this coating station 10, the sheet is conveyed around a second rotating body 11 and further around a third and a fourth rotating body 12,13 where it is, with the face thereof on which the slip material 5 is applied in dissolved/dispersed/emulsified form, in abutment on these three rotating bodies 11,12,13. In this context it is important that the liquid contents of the applied dispersion/emulsion/solution is substantially evaporated prior to contact with the first rotating body 11, and that the sheet temperature is in this connection also reduced to a suitable level where the thermoplastic polymer does not tack. The sheet is subsequently conveyed into a reservoir 16 by means of two rotating bodies 14,15. In the reservoir the face provided with the slip material 5 is provided with a layer of welding bitumen 6. At this point, the layer of welding bitumen preferably has a temperature that causes dissolution and/or adhesion of the thermoplastic polymer. The thus finished coating sheet is provided with a film layer (not shown) to prevent adhesion, and is conveyed via a further rotating body 17 to the final packaging and stor- ing.

Claims: C l a i m s 1. A method of manufacturing a bituminous coating sheet, wherein a bitumen-impregnated core material (3) onto which a layer of backface bitumen (4) is applied is conveyed to be in contact with one or more rotating bodies during manufacture, c h a r a c t e r i z e d in that, onto the backface bitumen layer (4) on the side to be brought into contact with a rotating body, a slip material (5) is applied which has been dispersed/emulsified or dissolved in a liquid; that the liquid is evaporated prior to contact with the rotating body; and that subsequently a further bituminous layer (16) is applied onto the face which is provided with slip material. 2. A method according to claim 1, c h a r a c t e r i z e d in that the dispersion/emulsion or solution as the case may be is applied in a spraying process. 3. A method according to claim 1 or 2, c h a r - a c t e r i z e d in that the dispersion/emulsion or solution as the case may be is applied at such distance from the first rotating body that the liquid is evaporated prior to contact with the first rotating body. 4. A method according to any one of claims 1-3, c h a r a c t e r i z e d in that the bitumen- impregnated core material (3) and the backface bitumen layer (4) have, during application of the dispersion/emulsion or solution as the case may be, a tempera- ture ranging between 100°C and 200°C, preferably between 120°C and 160°C. 5. A method according to any one of claims 1-4, c h a r a c t e r i z e d in that a dispersion/emulsion or solution as the case may be using a polymer material, eg a thermoplastic polymer material, as slip material, may be used. 6. An apparatus for exercising the method according to any one of claims 1-5, c h a r a c t e r i z e d in comprising rotating bodies (9,11,12,13,14,15,17) for conveying the coating sheet, and means (10) for applying a slip material dispersed/emulsified or dissolved in a liquid. 7. An apparatus according to claim 6, c h a r a c t e r i z e d in that the means (10) for applying the dispersion/emulsion or solution as the case may be consist of one or more nozzles to which the liquid is supplied under pressure. 8. An apparatus according to claim 6 or 7, c h a r a c t e r i z e d in that the means (10) for applying the dispersion/emulsion or solution as the case may be are arranged at such distance from the first, sub- sequent rotating element that the liquid contents of the dispersion/emulsion is evaporated prior to contact with the rotating body. 9. A coating sheet manufactured by the method fea- tured in claims 1-5, c h a r a c t e r i z e d in comprising a bitumen-impregnated core material (3) which is coated with a surface bitumen (2) and a backface bitumen (4), respectively, on respective sides of the core material; a layer of a polymer-based slip material (5) on at least the one side of the sheet; and further bituminous layer (6) provided adjacently the slip material (5) . 10 10. A coating sheet according to claim 9, c h a r a c t e r i z e d in that the slip material (5) is a thermoplastic polymer.

Inventors: OLSEN JOHN EJRUP, OLSEN, JOHN, EJRUP
Applicants: ICOPAL AS, OLSEN JOHN EJRUP, ICOPAL A/S, OLSEN, JOHN, EJRUP
Application year: 1999
Main classification: B32B31
IPC codes: D06N5, E04D5