GB2316692A - Polyurethane protection layer for PVC soffit or fascia board - Google Patents

Abstract

A PVC-UE board (1) in which an edge (5) at which the cellular core (2) has been exposed by cutting (e.g. to provide a decorative edge) is provided with a protective layer (10) of a polyurethane formed in situ at the edge (5).

Description

PVC BOARDS The present invention relates to rigid cellular PVC boards intended particularly, but not exclusively, for use on or around the roof of a building as a socalled "roofline board", e.g. a barge, fascia or soffit board or a box-end.

For convenience, rigid cellular PVC is referred to herein by its conventional designation PVC-UE.

For many years, wood was (and in many instances still is) the material of choice for the production of roofline boards. Wood does however have the disadvantage that it requires regular treatment (such as painting or varnishing) and, in any event, may eventually rot and require replacement.

Therefore there is now a trend to manufacture boards of PVC-UE which has the advantage that it does not rot, does not require regular maintenance, and maintains its appearance. Briefly, PVC-UE is an extruded product which comprises a core of cellular PVC and a PVC skin provided on at least those surfaces of the board which will be exposed to the elements. The skin has properties of UV and impact resistance and may be any of a variety of colours.

PVC-UE board is generally extruded such that the skin is provided on only one major face of the board and along the two (lengthwise) side edges. The board is extruded in a width greater than required for the final board and is then slit lengthwise into two boards of the required width. Each such board then has one "unskinned" lengthwise edge and one "unskinned" major face at which the cellular core of the PVC is exposed. When such a board is to be used as a roofline board the "unskinned" edge and "unskinned" face are positioned so as not to be exposed to the elements and are not seen from the ground. Therefore, as viewed from the ground, the roofline boards are seen to have smooth surfaces.

In spite of its disadvantages, wood does however have one advantage over PVC-UE for use as roofline boards. This is in relation to the production of such boards having a decorative lengthwise edge (e.g. a scalloped edge), e.g. by cutting the wooden board. The cut edge is itself likely to be at least fairly smooth and may easily be protected (if desired) by paint or varnish which conceals any marks on the decorative edge.

Whilst PVC-UE may readily be provided with a decorative lengthwise edge using milling techniques, there is the disadvantage that, at the decorative edge, the internal cellular core of the board will be exposed. If the board is then simply used as a roofline board the cellular core as exposed at the decorative edge will be seen from the ground and therefore detract from the appearance of the board. Furthermore the exposed cellular core will attract dust and dirt and will become discoloured. This is obviously unsatisfactory.

It is not possible to overcome this problem simply by painting the decorative edge since paint would not necessarily bind satisfactorily to the edge. As such, the edge would require periodic re-treatment which defeats the object of a "minimum maintenance" roofline board.

It is therefore an object of the present invention to obviate or mitigate the abovementioned disadvantage.

According to a first aspect of the present invention there is provided a PVC UE board having an edge at which the cellular core has been exposed wherein said edge has a protective layer of a cured polyurethane formed in situ at the edge.

According to a second aspect of the present invention there is provided a method of protecting an edge of a cellular core of a PVC-UE board which has been exposed, the method comprising locating the board in a mould such that a mould cavity is defined between the mould and said edge, introducing a mixture of reactants capable of producing a cured polyurethane into said cavity and producing a cured polyurethane.

We have found that cured polyurethanes are eminently suitable for use in protecting/masking edges of a PVC-UE board at which the cellular core has been exposed (e.g. by cutting or milling to produce a decorative edge) since the polyurethanes provide a firm bond to the PVC, may be moulded to be of smooth appearance, may have UV and impact resistance and may be pigmented to be the same colour as the remainder of the board. The polyurethane thus provides a permanent treatment of the edge so that the board is a "minimum maintenance" product which is easy to clean on all exposed surfaces.

The polyurethane may be provided on, and only on, the edge to be protected but may alternatively also extend onto adjacent faces of the board, e.g. as a decorative formation. The polyurethane may, for example have a thickness of 1 mm to 5 mm (e.g. 2 mm to 5 mm) along the length of the edge to be protected. Preferably the polyurethane is of uniform thickness (e.g. 1 mm to 5 mm along) its length.

The method of the second aspect of the invention may be effected by using a mould in which the board to be treated is a close fit and which has a lower surface having a contour corresponding to that of the edge to be treated such that, with the board in position in the mould, a mould cavity of constant depth (along the length of the mould) is defined by said surface, the edge of the board, and the sides of the mould. Thus, for example, if the edge to be treated is scalloped, the aforementioned surface of the mould will be correspondingly scalloped.

The mould will have at least one port through which the chemicals (polyol and multi-functional isocyanate) are introduced into the mould cavity. Preliminary curing of the polyurethane may take place in the mould cavity after which the board may be removed to allow curing to be completed externally of the mould and allow re-use thereof.

The polyurethane precursor chemicals for use in the invention may be obtained from Hyperlast Limited.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 illustrates a PVC-UE board provided with a decorative edge; Fig. 2 illustrates the method of producing a polyurethane layer on the board of Fig. 1; Fig. 3 illustrates the board provided with an edge layer of polyurethane; and Figs 4-7 illustrate production of a box-end.

Referring firstly to Fig. 1, the illustrated PVC-UE board 1 comprises a core 2 of cellular PVC and an outer skin 3 on one major face of the board. The illustrated board (prior to formation of a scalloped edge - see below) was produced by extrusion in the direction of arrow X, using conventional techniques, so that the board as originally extruded has the skin on said major face and also along the two lengthwise edges. The extruded board was then slit to the required width. As such, the board 1 is illustrated as having an upper edge 4 (along which the board was slit) at which the core 2 is exposed. When board 1 is used as a roof edging board, the edge 4 would be uppermost.

The board 1 is illustrated as having a scalloped lower edge 5 produced by milling along the original board edge which was also originally formed with a skin and which is depicted by the dashed line 6. It will thus be appreciated that the core 2 of the board is exposed at the scalloped edge 5, as illustrated in the scrap view of Fig.

1.

Reference is now made to Fig. 2 illustrating the formation of a protective polyurethane layer along the edge 5. For the formation of such a layer, the board 1 is located (with edge 5 lowermost) in a close-fitting mould 7 (which may be of aluminium or fibreboard) having a lower surface 8 which is scalloped in a manner complementary to edge 5. With the board 1 located in position, an undulating mould cavity of constant thickness is defined between edge 5 of the board and surface 8 of the mould.

A mixture of a multi-functional isocyanate and a polyol is produced externally of the mould and then quickly introduced via ports 9 into the mould cavity. The mixture fills this cavity and begins to cure to form a polyurethane layer 10 which covers the edge 5 (see Fig. 3). The board 1 may then be removed from the mould after initial care and the edge 10 allowed to cure fully over a 24 hour period.

The board thus produced is eminently suitable for use as a roofline board.

Reference is now made to Figs. 4-7 which show application of the present invention to the production of a box-end 100 which is to be located at the "junction" of a barge board 101 and a fascia board 102 (see Fig. 7) at the roofline of a building.

More particularly, the described technique is used to produce a box-end having a decorative formation 103a and 103b along its exposed major face (and adjacent the edge thereof) which is intended to match a similar formation on the barge and fascia boards.

The box-end 100 is produced from an extruded PVC-UE board 104 (see Fig.

4) which has a "skinned" major face 105 and a "skinned" lower edge 106. The decorative formation 103a is provided on the face 105 adjacent edge 106.

The box-end is cut from the board 104 as represented by the dashed lines in Fig. 4. The cut-shape is shown on Fig. 5 from which it will be seen that the shape has an edge 107 at which the cellular core is exposed (see also Fig. 6 which is a view looking in the direction of arrow Y of Fig. 5). The cut shape of Fig. 5 is then subjected to a moulding operation which applies a coating of a polyurethane to the edge 107 and applies the decorative formation 103b (matching formation 103a) to the face 105 adjacent edge 107.

The finished box end is illustrated in Fig. 7 and it will be appreciated that its decorative formations 1 03a and 1 03b match corresponding formations on the barge board 101 and fascia board 102.

Although the invention has been particularly described with reference to treatment of an edge along the perimeter of a PVC-UE board, it should be appreciated that the invention may also be applied to "internal edges". Thus, for example, a decorative aperture may be provided in a PVC-UE board so as to extend through the body thereof. The edge surfaces of this aperture (at which the core will be exposed) may be treated with polyurethane as described above.

Claims (5)

1. A PVC-UE board having an edge at which the cellular core has been exposed wherein said edge has a protective layer of a cured polyurethane formed in situ at the edge.

2. A board as claimed in claim 1 wherein the polyurethane is provided on, and only on, the edge to be protected and does not extend onto adjacent faces ofthe board.

3. A board as claimed in claim 1 or 2 wherein the polyurethane has a thickness of 1 mm to 5 mm.

4. A board as claimed in any one of claims 1 to 3 wherein the polyurethane is of uniform thickness along its length.

5. A method of protecting an edge of a cellular core of a PVC-UE board which has been exposed, the method comprising locating the board in a mould such that a mould cavity is defined between the mould and said edge, introducing a mixture of reactants capable of producing a cured polyurethane into said cavity and producing a cured polyurethane.