SCREEN PRINTING APPARATUS AND METHOD

Abstract

Apparatus and method for the screen printing manufacture of a layer of silicone material. The method and apparatus provide for the deposition of a layer of silicone material having a controllable thickness and shape profile as determined by a template forming part of a screen printing assembly. The present apparatus and method provide a fully controlled automated or semi-automated manufacturing process enabling the deposition of a silicone layer onto a substrate layer serving as a conveyor to transport the silicone layer between different units of the process line including a heating/curing unit, a drying unit and a lamination unit.

Claims

1. A method of manufacturing a layer of a silicone material comprising: delivering the silicone material from a reservoir to a dispensing nozzle at a print head whilst the silicone material is a liquid or flowable gel; dispensing the silicone material onto a template having at least one aperture to allow the silicone material to pass through the template; depositing the silicone material from the aperture onto a substrate; and allowing the silicone material to cure on the substrate as a layer.

2. The method as claimed in claim 1 further comprising spreading the silicone material over the template using a wiper blade.

3. The method as claimed in claim 1 wherein the reservoir comprises a first reservoir and a separate second reservoir, both the first and second reservoirs being connected to a mixing body that is connected to the dispensing nozzle such that the silicone material flows from the first and second reservoirs to the dispensing nozzle via the mixing body.

4. The method as claimed in claim 3 wherein the silicone material is formed from a first part and a second part stored respectively within the first and second reservoirs.

5. The method as claimed in claim 4 wherein the first part comprises a vinyl siloxane polymer and the second part comprises a silicone hydride (Si—H) containing crosslinker.

6. The method as claimed in claim 4 comprising delivering the first and second parts to the mixing body at a temperature below a curing temperature of the silicone material.

7. The method as claimed in 1 wherein the step of allowing the silicone material to pass through the aperture comprises passing the silicone material through a mesh screen extending across the aperture.

8. The method as claimed in claim 7 wherein a size of the mesh screen is in the range 20 to 100, 30 to 90, 30 to 80, 30 to 70 or 40 to 60 threads per linear cm in both x and y directions.

9. The method as claimed in claim 1 wherein the silicone material is delivered to and dispensed from the nozzle in predefined dose volumes.

10. The method as claimed in claim 7 comprising raising and lowering the template and the screen relative to the substrate between the dispensing of the silicone material onto the template from the nozzle.

11. The method as claimed in claim 10 further comprising conveying the silicone material deposited on the substrate linearly from a position under the print head once the template has been raised relative to the substrate.

12. The method as claimed in claim 11 comprising maintaining the substrate substantially stationary under the print head when the silicone material is dispensed onto the template and allowed to pass through the aperture.

13. The method as claimed in 1 further comprising heating the silicone material on the substrate to a temperature at or above a curing temperature of the silicone material.

14. The method as claimed in claim 13 comprising maintaining the silicone material above the gel temperature for a curing time period in a range 30 seconds to 5 minutes; 1 minute to 5 minutes; 2 minutes to 5 minutes or 2 minutes to 4 minutes.

15. The method as claimed in claim 14 further comprising drying the cured silicone material within a dryer at a temperature below the curing temperature and above 20° C. for a drying time period.

16. The method as claimed in claim 15 wherein after the step of drying the silicone material creating a tension in the substrate using a tensioning device.

17. The method as claimed in claim 16 wherein after the step of tensioning the substrate, applying a release liner to an exposed surface of the silicone material positioned on the substrate.

18. The method as claimed in claim 17 further comprising after the step of tensioning the substrate, applying a support layer to an exposed surface of the substrate opposite to a surface in contact with the silicone material.

19. An apparatus to manufacture a layer of silicone material comprising: at least one reservoir to store at least a part of the silicone material in a liquid or gel phase; a fluid dispensing nozzle positioned at a print head and connected to the reservoir for dispensing the silicone material; a template having at least one aperture to allow the silicone material to flow through the template; and a substrate positionable to receive the silicone material from the aperture of the template.

20. The apparatus as claimed in claim 19 wherein the substrate is provided at or is a part of conveyor arrangement to enable the substrate to move linearly relative to the print head.

21. The apparatus as claimed in claim 19 further comprising an actuating mechanism to raise and lower the print head relative to the substrate.

22. The apparatus as claimed in claim 19 wherein the at least one reservoir comprises a first reservoir and a second reservoir each connected to a mixing body, the mixing body connected to the dispensing nozzle.

23. The apparatus as claimed in claim 22 comprising a first pump coupled to the first reservoir and a second pump coupled to the second reservoir to control a delivery speed and/or volume of the silicone material to the nozzle.

24. The apparatus as claimed in claim 23 wherein the first reservoir comprises a first part of silicone material and the second reservoir comprises a second part of the silicone material, the first and second parts combinable and curable to form the silicone layer on the substrate.

25. The apparatus as claimed in claim 1 when dependent on claim 20 wherein the conveyor arrangement comprises a first supply roll of the substrate and a spatially separated second collecting roll of the substrate; and drive means coupled to at least the first or second roll wherein a linear section of the substrate extends between the first and second rolls and the print head and the template are positioned adjacent a region of the linear section.

26. The apparatus as claimed in 19 further comprising a heater unit to heat the silicone material deposited on the substrate to a temperature at or above a curing temperature the silicone material.

27. The apparatus as claimed in claim 19 further comprising a mesh screen extending across the at least one aperture.

28. The apparatus as claimed in claim 27 wherein a hole or opening size of the mesh screen is in a range 200 to 1500 μm; 300 to 1400 μm; 400 to 1300 μm; 500 to 1200 μm; 600 to 1000 μm; 700 to 1000 μm; 800 to 900 μm.

29. A silicone material layer produced by the method of claim 1 or the apparatus of claim 19.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0042] A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0043] FIG. 1 is a side elevation view of screen printing apparatus for the manufacture of a silicone material layer via a screen printing process;

[0044] FIG. 2 is a perspective view of a print head and a print station according to a specific implementation of the present invention;

[0045] FIG. 3 is a further perspective view of the print head and print station of FIG. 2;

[0046] FIG. 4 is a flow diagram of the screen printing process according to one aspect of the present invention;

[0047] FIG. 5A is a cross section through a substrate to form a conveyor assembly to receive the silicone material;

[0048] FIG. 5B is a cross section of the substrate of FIG. 5A including the silicone material deposited on an upper surface of the substrate;

[0049] FIG. 5C is a cross section through the substrate of FIG. 5B including the silicone material laminated with additional layers;

[0050] FIG. 6A is a plan view of an ostomy appliance coupling according to a specific implementation of the present invention;

[0051] FIG. 6B is a cross section through A-A of the ostomy coupling of FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

[0052] Apparatus and method are provided for the automated or semi-automated manufacture of a layer of silicone material being controllable to achieve relatively thin and uniform layer thicknesses of the order of 1000 μm or less and optionally 200 μm to 1500 μm. The present method utilises screen printing in which the silicone material in a flowable state is delivered onto a substrate that forms a conveyor assembly in which the silicone material is cured on the substrate as a continuous automated or semi-automated process.

[0053] Referring to FIG. 1, the screen printing apparatus comprises a source roll 10 of a substrate material being a polyurethane (PU) film provided on a paper carrier. The PU film and paper carrier are drawn from source roll 10 to a collection roll indicated schematically by reference 23 at an end point of the present apparatus. The PU film and paper carrier are tensioned between the rolls 10, 23 to provide a taut webbing substrate (film) 11 extending through the various stations of the present apparatus and between the rolls 10 and 23.

[0054] The apparatus comprises a screen printing station 12. Referring to FIGS. 2 and 3, the printing station 12 comprises a print head 16 and a screen assembly 34 positioned in a vertical plane between the print head 16 and taut PU film 11. Print head 16 comprises an inclined plate 24 extending from a lower region of a print head body 33. A blade 25 also extends from an underside of print head body 33 opposed to a lower region of inclined plate 24. A nozzle 26 extends downwardly from body 33 having a dispensing end positioned opposed to inclined plate 24. Print head 16 is provided at a mechanical actuator mount unit 35 adapted to move print head 16 backwards and forwards in a generally horizontal plane relative to screen assembly 34.

[0055] Referring to FIG. 3, screen assembly 34 comprises a frame 31 that mounts within its perimeter a solid base plate 27 having a central aperture 32. A generally plate like template 28 is mounted within aperture 32. Template 28 comprises a pair of circular apertures 30. A mesh screen 29 extends across and underside of template 28. Print head 16 is mounted directly above template 28 such that a flow of silicone material is capable of being dispensed from nozzle 26 to flow down inclined plate 24 onto template 28 so as to flood the template 28 at the region of the aperture 32. As head 16 is adapted to traverse in a horizontal plane backwards and forwards over plate 27, blade 25 is adapted to wipe the silicone material over template 28 and across mesh screen 29 extending across template apertures 30.

[0056] Referring again to FIG. 1, the apparatus further comprises a first and second reservoir 13, 14 containing respectively a first and a second part of a silicone formulation being a two-part addition curable silicone formulation. A respective gear pump (not shown) is coupled to each respective reservoir 13, 14 to control a volume and speed of each silicone part pumped from each reservoir 13, 14 to a static mixer 15 via a conduit network 17. Static mixer 15 is formed from an Archimedes type screw mixer. The homogenous mixed silicone formulation is then supplied to the print head 16 via suitable tubing (17) to be delivered onto the template 28 and mesh screen 29 exposed via template apertures 30. PU film 11 is fed through the screen printing station 12 to pass directly underneath template 28 and mesh screen 29. The pre-cured formulation is deposited by print head 16 through screen assembly 34 and onto the PU film 11 as deposited silicone layers 19.

[0057] A flat bed dryer 18 is positioned in the conveying direction downstream of the screen printing station 12 to receive the pre-cured silicone layers 19 deposited on PU film 11. Dryer 18 is thermostatically controlled to a temperature in a range 110 to 120° C. corresponding to the curing and/or gel temperature of the silicone formulation. A drive motor is coupled to one or both of the rolls 10, 23 so as to control a speed by which silicone layers 19 are passed through flatbed dryer 18. Optionally, the deposited silicone layers 19 may be stationary for a predetermined time period within dryer unit 18. Typically, the layers of silicone 19 may be maintained within dryer 18 for 2 to 4 minutes. A tower dryer 20 is positioned downstream of flatbed dryer 18 to receive the cured or partially cured silicone layers 19 adhered to the PU film 11. A ‘nip out-feed’ and tensioner unit 21 is positioned in a conveying direction downstream of tower dryer 20 to receive the fully cured and dry silicone layers 19 on PU film 11. A lamination station 22 is positioned in a conveying direction downstream of the nip out-feed web tensioner unit 21. Lamination station 22 may comprise or be fed by rolls of additional material to be laminated with the PU film 11 and silicone layers 19 as described referring to FIGS. 5A to 5C to create a multilayer laminate structure. The resulting laminate may then be further processed according to supplementary downstream procedures that may include cutting, trimming, stamping or punching operations.

[0058] An overview of the manufacturing process is described referring to FIG. 4 in which the two-part flowable silicone formulation is initially delivered from reservoirs 13, 14 to the static mixer 15 at stage 40. The homogenous silicone material is then fed to the print head 16 from the static mixer 15 at stage 41. The flowable silicone formulation is then deposited from nozzle 26 onto the template 28 and screen 29 within the screen printing station 12 at stage 42. The silicone material is then forced through mesh 29 via wiper blade 25 traversing to and fro over template 28 to be deposited onto the underlying PU substrate 11 at stage 43. The size of the mesh screen 29 is configured specifically to control a rate of flow of the silicone material from the template 28 to the underlying PU substrate 11. According to the specific implementation, mesh screen 29 comprise an opening size in a range 600 to 1000 μm. Such an arrangement provides an appropriate balance between sufficient through-flow and the need to avoid flooding of the PU substrate by the silicone material that would otherwise destroy the predetermined deposition shape corresponding to the template apertures 30.

[0059] The deposited silicone layers 19 are then conveyed via the PU substrate 11 to the flatbed dryer at stage 44. The silicone layers 19 are then heated at around their gel point (110 to 120° C.) for a predetermined time at stage 45. The cured or partially cured silicone layers 19 are then dried (via a tower dryer 20) at stage 46 before being fed to the nip out-feed web tensioner unit 21. The silicone layers and PU layer are then laminated at stage 47 within the lamination station 22 to create a multi-layer laminate structure at stage 47. Optionally, the resulting structure may then be finished according to various downstream finishing processes such as cutting and trimming at stage 48 before or after collection on roll 23 at stage 48.

[0060] Referring to FIGS. 5A to 5C, PU film 11 according to one embodiment includes an elongate sheet of polyurethane (PU) 50 having an exposed upward facing surface 55. A sheet of a carrier paper 51 is adhered to an underside surface 54 of the PU layer 50. Paper carrier layer 51 may be removed at any position within the apparatus of FIG. 1 but is conveniently removed during or prior to the processing at lamination station 22. As illustrated in FIG. 5B, the silicone material deposited on surface 55 of PU layer 50 as circular layers/disks of silicone material 19. Each silicone layer comprises a corresponding upward facing surface 53. Referring to FIG. 5C, after exiting lamination station 22, the fully assembled composite structure comprises a silicone layer 19 having a release liner layer 52 attached to the exposed silicone surface 53 and a polyethylene (PE) secondary substrate 56 layer attached to the underside surface 54 of PU layer 50 (in place of the carrier paper layer 51). As will be appreciated, the paper carrier layer 51 is removed from surface 54 prior to lamination with the PE secondary substrate 56. The four layer structure is then cut and trimmed to create a multilayer laminate disk as illustrated in FIGS. 6A and 6B where FIG. 6B is a cross section through A-A of FIG. 6A. The multilayer structure 61 of FIGS. 6A and 6B is specifically adapted as a skin contactable ostomy coupling in which silicone layer 19 is adapted for positioning in direct contact with the peri-stomal skin surrounding a stoma. The multilayer structure is provided with a central aperture 64 for alignment and interfacing with the stoma. As illustrated, each of the layers 52, 19, 50 and 56 are annular having a generally circular disk-like shape profile with central aperture 64 provided though all or most of the layers.

[0061] According to the specific implementation, silicone layer 19 comprises a thickness in a range 100 to 1500 μm, PU layer 50 comprises a thickness in a range 20 to 50 μm and PE substrate layer 56 comprises a thickness in a range 80 to 150 μm with a release liner layer 52 having a thickness in a range 100 to 250 μm. PE layer 56 may be secured to PU layer 50 via heat treatment, ultrasonic welding or via an adhesive. PE layer 56 provides a mount for a first part 63 of an ostomy appliance coupling mechanism (not shown) to releasably engage with a second part of a coupling mechanism provided at an ostomy appliance, in particular an ostomy bag. The first part 63 is preferably formed as an annular flange capable of frictionally integrating and releasably locking with the coupling mechanism second part so as to provide a sealed coupling between an ostomy bag (not shown) and the multilayer structure 61. Release liner 52 may comprise a low density polyethylene (LDPE) of thickness 100 to 250 μm positioned over silicone layer surface 53 and capable of being removed conveniently prior to mounting of the structure 61 into contact with the skin of a person via silicone surface 53.