A method of bending a PET felt panel

Abstract

A method of bending a rigid fibrous Polyethylene Terephthalate (PET) felt panel 10. The PET panel is positioned on an upper planar surface (Figure 3 - 14) which has at least one heating element (Figur

Description

The present invention relates to a method of bending PET felt, in particular to a method of bending a rigid fibrous PET felt panel, and a PET felt panel. Polyethylene Terephthalate (PET) is a thermoplastic polymer resin of the polyester family. PET is typically used as a fibre for textiles and bottles for liquids. The high volume of PET bottles produced and subsequently discarded has resulted in those bottles being recycled to form PET fibre for use in other products. One such product is acoustic felt panels made from a mixture of recycled PET fibres and virgin polyester fibres which are becoming increasingly favoured for interior walls and ceilings where both noise reduction and aesthetics are considered important. The recycled and virgin fibres are blended together, layered up and heated to form a prefelt or flexible mat type structure. The flexible mat can be pressed between plates to form a flat rigid panel or between male and female moulds to form more complex 3D objects, such as chairs. Acoustic felt panels having a more complex 2D profile compared to a flat panel are becoming increasingly more specified, for both aesthetic and acoustic reasons. The aforementioned method, whilst being suitable for complex 3D shapes, does not lend itself to high volume 2D profiles. One method by which PET felt is shaped to form a 2D profile is to take a thicker, typically 12mm rigid PET felt panel and cut a notch in the surface of the panel such that the panel can be bent to the required 2D profile about that notch. An adhesive is applied inside the notch prior to bending to ensure the panel retains the 2D profile after being bent. Whilst this method enables the thicker felt to be formed with a 2D profile, the method is time consuming, and the resulting bend is often of poor quality and not able to be produced consistently to a given radius. Another method by which PET felt could be shaped to form a 2D profile is using an extrusion process. However, it has not been possible to extrude sheets having a thickness and area suitable for semi-structural applications such as an acoustic panel system. There is a need therefore for an improved method of forming a thicker PET felt panel with a 2D profile. Thus, according to one aspect of the present invention there is provided a method of bending a rigid fibrous PET felt panel, comprising the steps of providing a flat rigid fibrous PET panel, preferably having a thickness between 5mm and 25mm, applying heat to a localised, preferably linear section of the PET panel, and bending the rigid PET panel about the localised heated section to form a bent rigid fibrous PET felt panel.. Advantageously, it is possible to form a rigid fibrous PET felt panel with a 2D profile starting from an easy to produce flat rigid PET felt panel, avoiding the need for more complex pressing or extrusion processes, or the need to cut a notch in the panel to enable it to be bent. An additional advantage is that only a localised section of the PET panel needs to be heated compared to prior art methods which require the whole panel to be heated. Yet a further advantage is that no adhesive is required to retain the PET panel in the bent position, nor is a cut or notch required to facilitate bending the panel. According to another aspect of the present invention there is provided a PET panel having a thickness between 5mm and 25mm, the panel comprising a first linear section and a second linear section joined by a continuous bend, in which the continuous bend does not include a notch. The invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a side view of a flat rigid fibrous PET felt panel, Figure 2 is a plan view of the panel of Figure 1, Figure 3 is a plan view of a bending table without a PET panel being positioned upon it, Figure 4 is a side view of the panel of Figure 1 positioned on the bending table of Figure 3 prior to bending, Figure 5 is a plan view of the bending table of Figure 3 with the PET panel positioned upon it, Figure 6 is a side view of the bending table of Figure 3 with the PET panel positioned upon it, Figure 7 is a side view of the bending table of Figure 3 with the PET panel positioned upon it after bending, Figure 8 is a side view of a bent panel according to the present invention, and Figures 9 to 19 are photographs of PET panels. In Figures 1 and 2, a flat rigid fibrous acoustic PET felt panel 10 is shown prior to bending. The PET panel 10 comprises a mixture of 60% recycled fibre and 40% virgin fibre. It will bs understood that alternative proportions of recycled and virgin fibres can be used, include 100% virgin or recycled fibres, and in any combination in between. The panel 10 has a thickness of 12mm and a density of 2500gsm. In alternative embodiments the panel can have a thickness greater than 9mm and less then 25mm. The density of the panel can also vary up to 4800gsm. In Figures 3 and 4, a line-bending table 12 is provided having an upper planar surface 14. The planar surface 14 has a first section 16 and a second section 18. The first section 16 is hingably connected (not shown) such that it is pivotable relative to the second section 18. In alternative embodiments, the planar surface is a single fixed section. A linear heating element, in the form of a heating wire 20 is provided in a recess 22 positioned between the first 16 and second 18 sections of the upper planar surface 14. It can be seen that the wire 20 is positioned vertically below the upper planar surface 14 such that it does not come into contact with the PET panel 10 but sufficiently close such that it can heat a localised section 24of the PET panel 10. The PET panel 10 is bent as follows: Firstly, the panel 10 is provided in its rigid fibrous state, and optionally trimmed to enable easier manipulation or to achieve the required dimension prior to bending (Figures 1 and 2). The panel 10 is then positioned on the upper planar surface 14 such that the point about which the panel 10 is required to be bent coincides with the heating wire 20 (Figures 3 and 4). The heating wire 20 is then heated to a temperature of between 180 and 210°C. The panel 10 is exposed to the heating wire at the above temperature for a period of between 60 and 240 seconds. After between 60 and 240 seconds, the first section 16 of the table 12 is manually rotated upwards relative to the second section 18 such that the panel 10 is bent to produce a bent panel 10’ (Figure 7). In alternative embodiments the panel itself can be manually moved on a table having a fixed upper planar surface. The panel 10’ is maintained in the bent position for a sufficient period of time after being bent such that it has sufficiently cooled to ensure the panel 10’ remains in the bent position. The final bent PET panel 10’ comprises a first linear section 26 and a second linear section 28 joined by a continuous bend 30 (Figure 8). A bend angle 0 is created between the first linear section 26 and the second linear section 28. It can be seen from Figure 8 that the PET panel 10’ is a continuous bend without any interruptions in its outer surface, for example, a notch. Furthermore, no adhesive is used to retain the panel in the bent position after it has been formed. The heating time, recess width, and temperature is adjusted depending on the thickness of the panel and the bend angle required. For example, a lower bend angle will require one or more of a wider recess, a longer heating time, or a higher temperature Examples of PET panels produced by the method described above, and starting from the flat PET panel shown in Figure 9, are given below in Table 1. Sample No. Thickness (mm) Forming Temperature (°C) Forming Time (s) Recess Width (mm) Bend Angle (°) Figure 1 12 188 150 10 40 10-12 2 12 188 150 10 90 13&14 3 5 188 120 20 0 15-17 4 25 188 180 20 90 18&19 5 12 188 180 20 15&90 20 6 12 188 150 10 30 21 Table 1 It can be seen from Table 1 and Figures 19 to 21 that the samples of PET panels have been bent to form a bend angle between the first linear section 26 and the second linear section 28 of between 0° and 90°. It will be appreciated however that the bend angle can be greater than 90° and up to 180°, that is any angular deviation from a flat panel. It can also been seen from Figure 21 that more than one bend can be formed in the same PET panel, and that the bend angle can be different in each of the more than one bends, to enable complex shapes to be formed according to the end use requirement. It can be seen from Figures 15 to 17 that the bend angle is 0°, that is the panel has been bent back on itself. This is advantageous as, when viewing from the end, as shown in Figure 16, the bent panel gives the appearance of a single panel with a rounded edge, in contrast to the end of a single unbent panel which has a square edge as a result of being cut. It can also be seen in Figures 11, 12 and 14 to 21 that a continuous bend is formed between the first linear section 26 and the second linear section 28.

Claims

1. A method of bending a rigid fibrous PET felt panel (10), comprising the steps of providing a flat rigid fibrous PET panel (10), applying heat to a localised section of the PET panel, and bending the rigid PET panel about the localised heated section to form a bent rigid fibrous PET felt panel (10’), in which the PET panel is positioned on an upper planar surface (14) comprising at least one heating element (20), the heating element being spaced vertically below the planar surface (14) such that, in use, it does not physically come into contact with the PET panel (10).

2. A method according to claim 1 in which step of applying heat comprises applying heat for greater than 60 seconds and less than 240 seconds.

3. A method according to claim 1 or 2 in which the at least one heating element (20) is a linear heating element.

4. A method according to claim 3 in which the at least one heating element (20) is provided inside a recess (22) of the planar surface (14).

5. A method according to any preceding claim in which the step of applying heat to a localised section of the PET panel comprises heating the localised section of the PET to a temperature of between 180°C and 210°C degrees.

6. A method according to any preceding claim in which the planar surface (14) comprises a first section and a second section, the heating element being provided between the first and second sections, in which the step of bending the panel comprises moving the first section relative to the second section.

7. A method according to any preceding claim in which the panel is maintained in the bent position until the localised section has sufficiently cooled.

8. A method according to any preceding claim in which the panel comprises a proportion of recycled PET material.

9. A method according to any preceding claim in which the panel is an acoustic panel.

10. A method according to any preceding claim in which the step of bending the rigid PET panel comprises bending the bending the rigid PET panel to form a bend angle between a first linear section (26) and a second linear section (28) of equal to or greater than 0° and less than 180°.

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