IES81187B2

IES81187B2 - A method for manufacturing a panel

Info

Publication number: IES81187B2
Authority: IE
Inventors: James Mcgee; Roy Lowe; Denis Collins
Original assignee: Athlone Extrusions Dev Ltd
Priority date: 1998-02-06
Filing date: 1999-02-02
Publication date: 2000-06-14
Also published as: IE990070A1; GB9902372D0; GB2333990B; IES990071A2; GB2333990A

Abstract

A panel comprising a substrate layer of acrylonitrile-butadiene-styrene (ABS) material, and a top layer of an ultra violet protective acrylic material is formed using a co-extrusion method. ABS extrudate is delivered through an elongate opening (21, figure 3) in a die plate (15, figure 2), and acrylic extrudate is delivered into a delivery channel (23, figure 3) located above the elongate opening in the die plate. The acrylic extrudate may be delivered through a number of spaced apart sub-channels (24, figure 3) so that a uniform layer of acrylic is dispensed over the ABS substrate. A protective plastics film material is preferably applied from a reel onto at least one face of the composite panel, the film serving to protect the panel in transit (figures 5-8). The side edges of the panel may also be trimmed and de-burred (figures 9-11). The trimmings, which may derive from the panel and/or the film may be removed and recycled. The composite panel may be tested for its dimensional stability, by cutting a sample from the panel, transferring the sample to a heating table, heating the sample for a predetermined period of time, and comparing the dimensions of the sample from before and after heating (figures 12,13). The method for preparing the composite panel has particular application in the manufacture of baths.

Description

“A method for manufacturing a panel” Introduction The invention relates to a method for manufacturing a panel.

Currently, baths for domestic use are manufactured either from moulded ceramic materials, cast iron or cast acrylic sheet. Cast acrylic sheet is widely used as it can be readily thermoformed into a bath at lower cost, of lighter weight, with greater design flexibility and with lower thermal conductivity than other materials.

The term “acrylic” used in this context refers to poly (methyl methacrylate) (PMMA) materials. For the manufacture of acrylic sheet, a bulk polymerisation or cast process is used during which high molecular weights are achieved.

Relative to most other plastics materials, such acrylics are particularly suitable for bath manufacture as they have excellent scratch resistance and a high gloss surface finish. However, the manufacture of cast acrylic is both a difficult and lengthy operation so that the sheet material is consequently expensive.

One possible alternative to using cast acrylic material is to use a composite structure of a substrate coated with a protective layer.

There are, however, major processing difficulties in forming such composite panels to a sufficiently high grade to maintain the integrity of the composite structure on thermoforming into a desired shape such as a hath or the like.

There are also problems in that the surface of the composite panels is easily damaged in normal handling and use. -2There is therefore a need for an improved production process which will overcome at least some of these difficulties.

Statements of Invention According to the invention, there is provided a method of forming a panel comprising a substrate layer of acrylonitrile-butadiene-styrene (ABS) material and a top layer of an ultra violet (UV) protective acrylic material comprising the steps ofio extruding ABS material to a molten condition; extruding acrylic material to a molten condition; delivering the ABS extrudate through an elongate opening in a die block to form a substrate layer of ABS; delivering the acrylic extrudate into a delivery channel in the die block above the elongate opening; and leading the acrylic extrudate through the delivery channel to form a substantially uniform protective layer of acrylic on top of the ABS substrate layer.

In a particularly preferred embodiment the method includes includes the step of leading the acrylic from an inlet part of the delivery channel through a number of laterally spaced-apart sub-channels of an outlet part of the delivery channel to enhance the uniform flow of acrylic extrudate onto the ABS extrudate.

In one embodiment of the invention the method includes the steps of:-3cooling the composite plastics material to form a sheet; leading a protective plastics film material from a reel; and applying the protective film to at least one face of the composite plastics sheet.

Preferably the method includes the step of adjusting the position of the reel of protective plastics film so that the film corresponds with the sheet.

Ideally includes the step of applying a substantially constant tension to the protective film as it is being applied to the composite panel. Preferably a substantially constant tension is applied to the protective film by applying a braking force to the reel from which the film is led.

In a preferred embodiment the protective plastics film is led form one of a number of separate in-line reels of film corresponding to the width of the cooled composite plastics sheet.

Ideally, the method includes the step of trimming the side edges of the composite panel. Preferably the method also includes the step of de-burring the cut side edges of the panel. Ideally, the cut side edges of the panel are de-burred by applying de-burring rollers to the cut side edges of the composite panel.

Preferably excess film at the side edges of the panel is removed and collected for recycling as the side edges are being trimmed. Ideally the method includes the step of collecting the excess film by winding onto to waste film collection reel.

In one embodiment of the invention the trimmings removed from the panel side edges are granulated and recycled. At least portion of the trimmings are chopped to a smaller size in-line prior to granulation. -4In a particularly preferred embodiment of the invention the method includes the step of testing the composite panel for dimensional stability on thermoforming.

In this case preferably the panel is tested by;cutting a defined sample of the plastics panel across the width of the panel; laying the sample on a table; moving the table with the sample in position into a heating position; heating the sample for a preset period corresponding to the thickness of the panel; removing the table with the heated sample in position from the heating position; and comparing the dimensions of the sample, after heating, with those of the sample prior to heating.

Preferably one face of the sample is heated in the heating position by heating the sample-receiving table. Ideally, the table is heated by circulating a heating fluid through the table.

In one embodiment one face of the sample is heated in the heating position by applying radiant heat to the face of the panel. Preferably radiant heat is applied by infra red heating means located above the sample table in the heating position.

The invention also provides a co-extrusion die plate for forming a panel comprising a substrate layer of acrylonitrile-buadiene-styrene (ABS) material and -5a top layer of an ultra violet (UV) protective acrylic layer, the die plate having an elongate opening therein to form molten ABS into a substrate layer of ABS, the die plate also having a delivery channel above the elongate opening, acrylic extrudate being led through the delivery channel to form a substantially uniform protective layer of acrylic on top of the ABS substrate layer.

In a preferred embodiment of the invention the delivery channel is divided into a number of laterally spaced-apart channels at an outlet part thereof to enhance the uniform flow of acrylic extrudate into the ABS substrate.

The invention further provides a panel comprising a substrate layer of acrylonitride-butadiene-strene and a top layer of an ultra violet protective acrylic material whenever formed by a method and/or using an apparatus of the invention.

Brief Description of the Drawings The invention will be more clearly understood from the following description thereof, given by way of example only, in which:20 Fig. 1 is a plan view of a co-extrusion apparatus used in the process of the invention; Fig. 2 is a perspective view of part of the apparatus of Fig. 1; Figs. 3 and 4 are respectively end and side cross sectional views of a coextrusion die plate used in the process of the invention; Fig. 5 is a side view of a multi-stage lamination apparatus used in the 30 process of the invention; -6Fig. 6 is a plan view of the lamination apparatus of Fig. 5; Fig. 7 is a perspective, partially cut-away view of part of the apparatus of Figs 5 and 6; Fig. 8 is a perspective view of one lamination station of the apparatus of Figs 5 to 7; Fig. 9 is a plan view of a trimming station used in the process of the invention; Fig. 10 is a perspective view of the trimming station; Fig. 11 is a side view of the trimming station; Fig. 12 is a perspective view of a testing apparatus used in the process of the invention; and Fig. 13 is a side, partially cross sectional view of the testing apparatus, in use. -7Detailed Description Referring to the drawings, there is illustrated co-extrusion apparatus 1 used in a method of forming a panel comprising a substrate layer of acrylonitrile-butadiene5 styrene (ABS) and a top layer of an ultra violet (UV) protective acrylic material.

ABS material is extruded in a conventional manner and delivered in a molten state to a co-extrusion block 2 from a static mixer 3 fed by a gear pump 4. The gear pump 4 delivers the ABS from a screen changer 5.

Acrylic material is also extruded in a conventional manner and delivered in a molten state along a co-extrusion line 10 to the co-extrusion block 2.

At the co-extrusion block 2, the ABS and acrylic material pass through a co15 extrusion plate 15 (Figs. 3 and 4) and the co-extruded material is then formed into a desired sheet/panel shape by a die 20.

Referring particularly to Figs. 3 and 4, the die plate 15 includes an elongate opening 21 through which molten ABS material is passed. Acrylic material is delivered against a back wall 22 of a delivery channel 23 which has a number of elongate ribs to divide the channel into sub channels 24 to promote the even flow of acrylic material in an even layer on top of the ABS material as it passes through the elongate opening 21. The end of the delivery channel 23 is contoured to further improve the flow characteristics of the acrylic material and to promote the formation of an even layer of acrylic on the ABS. In this way, an acrylic-capped ABS sheet is formed with a substantially even layer distribution.

Referring particularly to Figs. 5 to 8, there is illustrated a multi-stage lamination apparatus 30 used in the method of the invention. This is used to provide a film 31, typically of polyethylene material which is applied over at least one face of the formed plastics sheet material to protect the sheets in transportation and storage. -8The film 31 is led from one of a number of reels 33, 34, 35 over a guide and tensioning roller 32 and applied to a sheet 36 between a pair of spaced-apart nip rollers 37, 38. The upper nip roller 37 is pressed down by means of rams 39a to apply the film 31 to the sheet 36.

Each of the reels 33, 34, 35 of film are typically of different widths to optimally accommodate sheets of different size. The film delivery can be rapidly changed over from one reel to another so that production efficiency is optimised. The film is drawn from a reel at a substantially constant tension by applying a braking force through a brake controller 39 on each of the reels 33, 34, 35.

It will be noted that the reels 33, 34, 35 are mounted on a common carriage 40 having rollers 41 which run along corresponding transverse tracks 42 to accurately adjust the position of the carriage 40 and hence the film 31 to the sheet 36 travelling along a conveyor 45. Adjusting ratchet screws 46 are used to move the carriage 40 on the tracks 42. In this way, film application and usage is optimised.

Referring to Figs. 9 to 11, using cutting knives 50, 51, the side edges of the sheet 36 are trimmed and waste sheet trim 52 is delivered under the conveyor for regrinding in a grinder 53. If desired, particularly for larger sized waste, the waste may he pre-chopped in a chopper 54 prior to grinding.

To improve quality, the side edges of the cut sheet 34 are de-burred by passing the cut sheet 34 between de-burring rollers 55 on opposite sides of the sheet 34.

Referring particularly to Figs. 11 and 12, to check the dimensional stability of sheets or panels manufactured using the process of the invention, sample strips which are typically 500 mm wide and 100 mm long are first cut from the sheets. The sample 80 is laid on a table 81 of a reversion testing apparatus 79. The testing apparatus 79 comprises a bed 83 having tracks 82 on which the table is mounted for movement inwards and outwards illustrated particularly in Fig. 13. The , I. -9apparatus 79 also includes a head part 88 housing two banks 84, 85 of infrared heaters in a carriage 86 which is height adjustable by a handle-operated screw 87, as illustrated. The heaters 84, 85 are positioned over the sample table 81 when the table is in the testing position illustrated in dotted outline in Fig. 13.

The table 81 has a heat exchange surface below the bed which is provided by a pipe network 90 in the bed. The pipes are supplied with heating/cooling fluid lines 91, 92.

In use, with the cut sample 80 in position, the table 81 is moved into the heated position underneath the heaters 84, 85. The sample is then heated from below and on top for a preset period corresponding to the thickness of the panel from which the sample was cut. After heating, the table with the heated sample in position is withdrawn to the position illustrated in Fig. 12, the sample is removed and the dimensions of the sample, after heating, are compared to those of the sample prior to heating. In this way, the sample is rapidly reversion tested to a high level of accuracy. Consequent adjustments may be made to the processing parameters.

The invention is not limited to the embodiments hereinbefore described which may be varied in construction and detail.

Claims

1. A method of forming a panel comprising a substrate layer of acrylonitrilebutadiene-styrene (ABS) material and a top layer of an ultra violet (UV) protective acrylic material comprising the steps of:extruding ABS material to a molten condition; extruding acrylic material to a molten condition; delivering the ABS extrudate through an elongate opening in a die plate to form a substrate layer of ABS; delivering the acrylic extrudate into a delivery channel in the die plate above the elongate opening; and leading the acrylic extrudate through the delivery channel to form a substantially uniform protective layer of acrylic on top of the ABS substrate layer.

2. A method as claimed in claim 1 including the step of leading the acrylic from an inlet part of the delivery channel through a number of laterally spaced-apart sub-channels of an outlet part of the delivery channel to enhance the uniform flow of acrylic extrudate onto the ABS extrudate.

3. A method as claimed in claim 1 or 2 including the steps of:cooling the composite plastics material to form a sheet; leading a protective plastics film material from a reel; and -11 applying the protective film to at least one face of the composite plastics sheet, preferably the method includes the step of adjusting the position of the reel of protective plastics film so that the film corresponds with the sheet, preferably the method includes the step of applying a substantially constant tension to the protective film as it is being applied to the composite panel, preferably a substantially constant tension is applied to the protective film by applying a braking force to the reel from which the film is led, preferably the protective plastics film is led form one of a number of separate in-line reels of film corresponding to the width of the cooled composite plastics sheet, preferably the method includes the step of trimming the side edges of the composite panel, preferably the method includes the step of de-burring the cut side edges of the panel, preferably the cut side edges of the panel are de-burred by applying de-burring rollers to the cut side edges of the composite panel, preferably excess film at the side edges of the panel is removed and collected for recycling as the side edges are being trimmed, preferably the method includes the step of collecting the excess film by winding onto a waste film collection reel, preferably the trimmings removed from the panel side edges are granulated and recycled, preferably at least portion of the trimmings are chopped to a smaller size in-line prior to granulation.

4. A method as claimed in any preceding claim including the step of testing the composite panel for dimensional stability on thermoforming, preferably the panel is tested by:cutting a defined sample of the plastics panel across the width of the panel; -12laying the sample on a table; moving the table with the sample in position into a heating position; heating the sample for a preset period corresponding to the thickness of the panel; removing the table with the heated sample in position from the heating position; and comparing the dimensions of the sample, after heating, with those of the sample prior to heating, preferably one face of the sample is heated in the heating position by heating the sample-receiving table, preferably the table is heated by circulating a heating fluid through the table, preferably one face of the sample is heated in the heating position by applying radiant heat to the face of the panel, preferably radiant heat is applied by infra red heating means located above the sample table in the heating position, preferably the method includes the step of adjusting the process parameters for forming composite panels in accordance with the test results.

5. A co-extrusion die plate for forming a panel comprising a substrate layer of arylonitrile-butadiene-styrene (ABS) material and a top layer of an ultra violet (UV) protective acrylic layer, the die plate having an elongate opening therein to form molten ABS into a substrate layer of ABS, the die plate also having a delivery channel above the elongate opening, the acrylic extrudate being led through the delivery channel to form a substantially uniform protective layer of acrylic on top of the ABS substrate layer.