METHOD FOR MANUFACTURING A MULTILAYER PVC SEMIFINISHED PRODUCT AND A CORRESPONDING APPARATUS

Abstract

A method for manufacturing of a multilayer PVC semi-finished product, in particular a multilayer PVC synthetic leather or a multilayer PVC foam sheet, the method comprising the steps of:

a. Coating a coated or uncoated carrier web with a PVC plastisol, whereby a carrier web coated with an ungelled plastisol layer is obtained; thereafter
b. Gelling the ungelled plastisol layer, whereby a carrier web coated with a gelled plastisol layer is obtained; and thereafter
c. Cooling the carrier web coated with the gelled plastisol layer; characterized in that the coating comprises coating the carrier web with at least two PVC plastisols one above the other, simultaneously or in immediate succession. A corresponding apparatus is further described.

Claims

1. A method for manufacturing a multilayer PVC semi-finished product (100), in particular a multilayer PVC synthetic leather or a multilayer PVC foam sheet, said method comprising: a. coating a coated or uncoated carrier web with a PVC plastisol, whereby a carrier web coated with an ungelled plastisol layer is obtained; thereafter b. gelling the ungelled plastisol layer, whereby a carrier web coated with a gelled plastisol layer is obtained; and thereafter c. cooling the carrier web coated with the gelled plastisol layer; wherein the coating in step a. includes coating the carrier web with at least two PVC plastisols one above the other simultaneously or in immediate succession.

2. The method according to claim 1, wherein the ungelled plastisol layers are coated directly on top of each other on the carrier web or a gelled plastisol layer is coated on the carrier web.

3. The method according to claim 1, wherein the gelling comprises simultaneously gelling the at least two ungelled plastisol layers.

4. The method according to claim 1, wherein the step sequence a. to c. is repeated at least once, wherein in at least one of the step sequences in step a. the carrier web is coated with the at least two PVC plastisols simultaneously or in immediate succession.

5. The method according to claim 4, wherein in at least one further one of the sequences of steps a. to c. in step a. the carrier web is coated with exactly one PVC plastisol.

6. The method according to claim 1, in which, during the simultaneous or immediately successive coating of the carrier web with at least two PVC plastisols, two PVC plastisols are applied to the carrier web which differ from one another in at least one material property, the two PVC plastisols preferably differing from one another in at least one material property other than their viscosity.

7. The method according to claim 1, in which, during the simultaneous or immediately successive coating, the at least two PVC plastisols are each applied to the coated or uncoated carrier web via an individual slot of a multilayer slot nozzle having a plurality of fluidically separated individual slots.

8. The method according to claim 7, in which at least one of the individual slots is pressurized by a pump with the associated PVC plastisol.

9. The method according to claim 8, comprising, before coating or during coating, adjusting a layer thickness of at least one of the PVC plastisols applied to the carrier web during coating, for which purpose a delivery rate of the pump, preferably a rotational speed of the pump, and/or an advancing speed of the carrier web with respect to the multilayer slot nozzle is adjusted. The method according to claim 8, in which a delivery rate of the pump is set as a function of an advancing speed of the carrier web with respect to the multilayer slot nozzle (6) and/or as a function of a width of the multilayer slot nozzle perpendicular to the advancing direction of the carrier web.

11. An apparatus, preferably transfer coating apparatus, for the production of a multilayer PVC semi-finished product, in particular a multilayer PVC synthetic leather or a multilayer PVC foam film, the apparatus comprising at least one process stage sequence with a coating unit for coating a coated or uncoated carrier web with a PVC plastisol, a gelling unit adjoining the coating unit for gelling the PVC plastisol, and a cooling unit adjoining the gelling unit for cooling the carrier web coated with the gelled PVC plastisol, wherein the coating unit is configured for simultaneous or directly successive coating of the carrier web with at least two PVC plastisols one above the other. The apparatus according to claim 11, which has a multilayer slot nozzle (6) with at least two fluidically separated individual slots (5) for the simultaneous or directly successive coating of the carrier web (1) with at least two PVC plastisols (2, 3) one above the other.

13. The apparatus according to claim 12, wherein at least one of the individual slots has an adjustable slot width, preferably the slot widths of both individual slots being adjustable independently of each other.

14. The apparatus according to claim 12, wherein the slot width is between 50 and 1000 μm, preferably between 50 and 700 μm, and more preferably between 200 and 500 μm.

15. The apparatus according to claim 1, wherein the viscosities of the at least two PVC plastisols are between 1 and 15 Pa˜s, preferably between 2 and 8 Pa˜s, and more preferably between 3 and 7 Pa˜s, wherein further preferably the viscosity of a first one of the two ungelled PVC plastisols disposed below a second one of the ungelled PVC plastisols is greater than the viscosity of the second PVC plastisol.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further details of the invention are explained in the figures below. Thereby showing:

[0026] FIG. 1 is a schematic diagram of a method for manufacturing of a multilayer PVC semi-finished product as known from the prior art;

[0027] FIG. 2 is a schematic representation of the application of a plastisol to a carrier web using the prior art coating process;

[0028] FIG. 3 is a schematic cross-sectional view of a multilayer plastisol layer formed by the process according to FIG. 2;

[0029] FIG. 4 is a schematic representation of an exemplary embodiment of the multilayer coating of a carrier web according to the invention;

[0030] FIG. 5 is a schematic representation of a further embodiment of a multilayer coating apparatus according to the invention; and

[0031] FIG. 6 is a schematic cross-sectional view of a multilayer plastisol layer formed using the apparatus according to FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0032] Multilayer PVC plastisol products, for example multilayer PVC artificial leather, consist of several layers, each of which is applied individually as plastisol to the carrier web or to a coating previously applied to the carrier web. After coating, the ungelled plastisol layer is changed to a gel by thermal treatment and, after a final cooling, a subsequent layer can be applied again to the carrier web or the plastisol layer previously applied to it using the same process sequence.

[0033] This is made necessary by the product structure of PVC semi-finished products, for example in the case of artificial leather, where each layer fulfills a different task. For example, there is a surface that is supposed to have a special look and surface feel, while softer, underlying layers, often foam layers, influence the flexibility and thickness of the material in a special way.

[0034] FIG. 1 shows in schematic representation an exemplary transfer coating method for manufacturing of a multilayer PVC semi-finished product 100 according to the state of the art. In addition to an unwinding unit 500 for providing the carrier material 1, a number of process stages corresponding to the number of plastisol layers of a multilayer PVC semifinished product 100 to be produced are provided, each consisting of a coating unit 200 for coating the carrier web 1 with a PVC plastisol, a subsequent gelling unit 300 for gelling the PVC plastisol, and a cooling unit 400 subsequent to the gelling unit for cooling the carrier web 1 coated with the gelled PVC plastisol. After all of the process stages consisting of coating unit 200, gelling unit 300 and cooling unit 400 have been passed through by the carrier material 1, the coated carrier material 1 or the PVC semi-finished product 100 formed therefrom can be rolled up and stored in a reeling unit 600.

[0035] Accordingly, in the prior art it is necessary that for each layer of the multilayer PVC semifinished product 100 to be produced, the coated or optionally still uncoated carrier web 1 is first coated with the ungelled plastisol, then the carrier web 1 coated with the still ungelled plastisol is heated, to stimulate gelling of the plastisol, and then the carrier web with the gelled plastisol is cooled again to enable the cooled, gelled plastisol layer to be coated with a next, ungelled plastisol layer. The frequent heating and re-cooling of the semi-finished product 100 or the precursor product is correspondingly energy-intensive.

[0036] FIGS. 2 and 3 show a detail of the coating unit 200 according to FIG. 1 and a plastisol layer 4 obtained thereby. For coating, the carrier web 1 of the coating unit 200 is transported along a transport system in the feed direction x in a reproducible position with respect to a doctor blade 8, wherein the transport system may, for example, comprise a plurality of rollers 9. In the coating system 200, a still plastisol 3 is metered onto the carrier web 1 and is formed into an ungelled plastisol layer with a smooth surface on the carrier web 1 in a coating process by a doctor blade 8, which is arranged while maintaining a gap to the upper side of the carrier web 1. In the manner previously described with reference to FIG. 1, the carrier web 1 with the plastisol layer 4 applied thereto can be treated in a subsequent process step by heating the carrier web 1 with the ungelled plastisol layer applied thereto, so that the plastisol layer 4 gels and, after a cooling process, can be made available for further coating analogous to the process shown in FIG. 2.

[0037] FIG. 3 illustrates another disadvantage, of the prior art brush coating process, which is that unevenness or texture on the top of a previously applied plastisol layer, here formed by the PVC plastisol 3, is leveled by the use of the smoothing blade 8 when another plastisol 2 is applied to it, so that the brush coating process is also not suitable for conveying haptic properties across subsequently applied plastisol layers.

[0038] FIG. 4 shows an exemplary embodiment for coating an uncoated carrier web 1 according to the invention with two PVC plastisols 2, 3, which are applied simultaneously to the carrier web 1 with the aid of a multilayer slot nozzle 6. Using the process according to the invention, several or all of the layers of a multilayer PVC semifinished product can be coated simultaneously and one on top of the other, so that at least two intermediate thermal steps (heating and cooling) can be omitted.

[0039] For this purpose, the carrier web 1 is conveyed by at least two rollers 9, for example of a transfer coating machine. The two plastisol layers 2, 3 are applied directly to each other in their ungelled state, i.e. wet-on-wet, on the carrier web 1. In particular, the preferred E-PVC plastisols have an inherent viscosity which ensures that the two flowable PVC plastisols 2, 3 do not mix with each other, or only insignificantly, so that even after the subsequent gelling of the plastisols 2, 3, the multilayer plastisol layer 4 produced therefrom has the respective functional property of the PVC plastisol 2, 3 concerned on its opposite sides and thus, in particular, no mixing or even mutual cancellation of material properties has to be accepted.

[0040] FIG. 5 shows in cross-section perpendicular to the longitudinal direction of the individual slots 5 an exemplary embodiment of a multilayer slot nozzle 6 which can be used according to the invention and which has a plurality of fluidically separated individual slots 5, with the aid of which the at least two PVC plastisols 2, 3 are applied to the carrier web 1 via one of the two individual slots 5 in each case during simultaneous or directly successive coating.

[0041] The multilayer slot nozzle 6 can be arranged in particular without contact with respect to the material web 1 or the roll 9 and in particular also with respect to the plastisols 2, 3 deposited on the roll 9 or the material web 1. Consequently, a distance of the multilayer slot nozzle 6 in relation to the material web 1 including any previously applied coatings can be greater than the sum of the individual thicknesses of the plastisols 2, 3 in the ungelled state. Accordingly, the multilayer slot nozzle 5 also does not mechanically shape, in particular smooth or level, the upper surface of the outer plastisol 2, which represents a further significant difference from the coating process known from the prior art.

[0042] The metering of the plastisols 2, 3 and thus the respective layer thickness of the plastisols 2, 3 on the carrier web 1 can be adjusted by controlling a delivery rate of the pumps 7, with the aid of which the respective plastisol 2, 3 is fed from a respectively assigned plastisol supply 10 into a respectively assigned individual slot 5 of the multilayer slot nozzle 6. A further factor for the resulting layer thickness of the individual layers of plastisol layer 4 (cf. FIG. 6) is the rotational speed or peripheral speed of the rollers 9. The thickness of the layers of plastisols 2, 3 on the carrier web 1 can thus be determined solely by controlling the volume flow of plastisols 2, 3 leaving the individual slots 5 of the multilayer slot nozzle 6 and the peripheral speed of the roller 9.

[0043] FIG. 6 illustrates that the outer side of the plastisol layer 4 facing away from the carrier web 1, which is formed by the upper side of the outer PVC plastisol 2, essentially adopts the geometry of the underlying PVC plastisol 3, albeit slightly weakened, so that, for example, haptic properties can also be transported across layers.

[0044] The features of the invention disclosed in the foregoing description, in the drawing as well as in the claims may be essential for the realization of the invention both individually and in any combination.