Note: Descriptions are shown in the official language in which they were submitted.
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Cladding Boards
Field of the Invention
The invention relates to cladding boards.
Background to the Invention
Cladding boards are typically designed for covering vertical surfaces. These
can be used
inside and outside. Wooden cladding has been used for many years with well-
known
drawbacks of expanding and contracting dependent upon the weather conditions;
requiring frequent treatments to prevent boards from rotting; and being prone
to igniting.
Plastic cladding is also available in various forms. These are generally
provided as
extruded boards which are by definition formed with a layer of relatively thin
plastics
material which may or may not be coated for extra weather resistance.
The following prior art documents are acknowledged: W001/26899, US2010/064611,
US2010/242398, EP0550873, and EPO192627.
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Summary of the Invention
In a first broad independent aspect, the invention provides a cladding board
comprising a
side with a tongue and a side with a groove or cut-out portion to facilitate
the attachment
of the cladding board to another such cladding board; wherein said board
incorporates a
backing layer of primarily rigid foamed plastics material; and a further layer
located over
said backing layer being primarily of an elastomer or polyurea; said groove
being of
exposed rigid foamed plastics material without any elastomer or polyurea
covering being
provided in said groove or cut-out portion.
In a subsidiary aspect, the further layer covers at least the front of said
tongue.
Consequently, when the tongue is in contact with the groove of an adjacent
board a
watertight seal is achieved between the boards.
The provision of the rigid foamed plastics material layer provides enhanced
insulation for
buildings or other structures which are clad by this board. This would assist
in retaining
the heat in a building during the colder months whilst retaining the coolth
during the
warmer months. The provision of the foamed rigid layer may also increase the
rigidity of
a building. The provision of the elastomer located over the backing layer
improves the
weather resistance. If the rigid foamed plastics material layer were simply
left exposed,
the weather would erode the surface. It also allows the layer which is most
exposed to the
weather conditions to withstand cycles of expansion and contraction which
might arise
even though they would arise at a much lower level than a prior art wood-based
cladding
board. This configuration is also particularly advantageous in terms of the
inter-
connection between adjacent cladding boards.
In a subsidiary aspect, said layer of primarily rigid foamed plastics material
has a shore D
hardness of 35 to 75. In this range, the cladding board rigidity achieves
optimal
constructional strength. It can for example be used as a conventional wood-
based
cladding board i.e. it can be cut or trimmed using carpenter's tools.
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In a further subsidiary aspect, said further layer is an inherently flexible
layer. In a further
subsidiary aspect, said further layer has a cushioning effect. In a further
subsidiary aspect,
the inherent flexibility of said further layer is higher than that of the
rigid backing layer.
This aspect particularly improves its weather resistance properties due to for
example the
impact of hail stones.
In a further subsidiary aspect, said further layer has a shore A hardness of
35 to 90. This
allows the layer to absorb impacts and to weather in an improved manner. The
likelihood
of the outer layer peeling back due to several cycles of differing weather
conditions is
substantially reduced.
In a further subsidiary aspect, said layer of primarily rigid foamed plastics
material is
primarily polyurethane. This material is particularly suited for retaining its
configuration
and has improved thermal properties. Furthermore, it allows the use of a
variety of fillers.
The cladding board may be further improved if the layer of primarily rigid
foamed
plastics material incorporates 20% to 50% fillers by weight. This reduces the
percentage
of plastics material used whilst by selecting the appropriate filler
improvements with
regards to the board's fire retarding properties, structural strength and
weather resistance
are improved.
In a further subsidiary aspect, said fillers comprise one or more from the
group consisting
o ground glass, ground limestone, mineral filler, flour, pulverised fuel ash
(PFA), and
fibres. The provision of fibres is particularly advantageous in terms of
providing
improved structural strength and since the further layer may be provided
without the use
of any fibres, the risk of an operator accidently interacting with a fibre is
almost entirely
done away with.
In a further subsidiary aspect, said layer of primarily rigid foamed plastics
material
incorporates glass fibres. These substantially improve the rigidity of the
cladding board
whilst an operator can still cut or trim the board using carpenter's tools.
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In a further subsidiary aspect, the layer of primarily rigid foamed plastics
material
incorporates a rice-based fibre. The use of a natural product of this kind
provides a
product which is not only of improved strength but with reduced negative
environmental
impact.
In a further subsidiary aspect, said layer of primarily rigid foamed plastics
material
incorporates 30% to 60% air by volume. This allows the cladding board to
appear
relatively bulky whilst being of sufficient strength. It also substantially
improves the
thermal insulation properties of the board.
In a further subsidiary aspect, said further layer is primarily of a
polyurethane elastomer.
This is particularly advantageous in order to create a chemical bond between
the backing
layer and the further layer. This does away with any requirement for employing
adhesives between the several layers.
In a further subsidiary aspect, said polyurethane elastomer incorporates no
air bubbles.
This allows the elastomeric layer to cope with weather fluctuations whilst a
relatively
smooth finish can be obtained. Alternatively, the polyurethane elastomer layer
can
incorporate in certain embodiments a relief in order for the cladding board to
take the
shape and configuration of a wood-based board, plastics, and/or stone.
In a further subsidiary aspect, said polyurethane elastomer incorporates one
or more fillers
selected from the group comprising ground glass, water scavengers, liquid fire
retardants,
recycled rubber, minerals and pulverised fuel ash (PFA).
The provision of liquid and powder fire retardants is particularly beneficial
in terms of
preventing the spread of a fire within a structure which has been clad by the
cladding
board. It also prevents an external fire from spreading into an enclosure
which has been
protected.
In a further subsidiary aspect, the cladding board further comprises a coating
provided
over said further layer, said coating being at least in part an aliphatic
isocyanate. This is
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particularly beneficial for improving the aesthetic appeal of the board but as
well
providing an extra protective layer.
In a further subsidiary aspect, said backing layer and said further layer are
chemically
5 cross-linked; thereby no separate adhesive links one layer to the other.
This allows the
cladding board to appear as a single unitary composition despite the various
layers
fulfilling different functions.
In a second broad independent aspect, the invention provides a moulding
process of
producing a cladding board, comprising the steps of selecting a mould for
forming a
cladding board with a side with a tongue and a side with a groove to
facilitate the
attachment of the cladding board to another such cladding board; forming a
layer which is
primarily of an elastomer; forming a backing layer which is primarily of rigid
foamed
plastics material; and preventing said groove from being covered by said
elastomer.
The advantages achieved in the context of the cladding board which have
already been
detailed above are in part due to the manufacturing process adopted.
Furthermore, it
allows the configuration of the board to not only achieve the improvements
mentioned
above but it allows the board to be made to more closely resemble wood-based
cladding
products.
In a further subsidiary aspect, the method comprises the step of starting the
moulding
process with an in-mould coating of aliphatic isocyanate based medium.
Brief Description of the Figures
Figure 1 shows a cross-sectional view of a cladding board.
Figure 2 shows a perspective view of the end of a cladding board.
Figure 3 shows a perspective view of the end of a cladding board in accordance
with a
further embodiment of the invention.
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Figure 4 shows a perspective view of the end of a cladding board in accordance
with a
further embodiment.
Figure 5 shows a cladding board according to a further embodiment of the
invention.
Detailed Description of the Figures
Figure 1 shows a section 1 of a typical cladding board according to the
invention. It
incorporates a backing layer 2, a further layer 3 and a coating 4. The backing
layer 2 is of
1o filled polyurethane rigid foam. This layer may itself have a thickness of
between 10mm
and 30mm. It has a relatively large proportion of air bubbles such as air
bubble 5
distributed randomly throughout the layer. The air bubbles or closed cells of
gas are of
greater size in the centre of the backing layer whilst they are compressed in
the outer
portions of the backing layer. This allows the material to be denser in the
outer portions
compared to the core of the backing layer where the cells occupy a greater
volume. The
content of air in this layer may be between 30% and 70% in volume. In addition
to the air
bubbles a number of fibres such as fibres 6 are provided throughout the layer
in order to
increase its rigidity. The fibres may be of chopped glass fibre strands or
other appropriate
man-made fibrous material. Alternatively, a natural fibre such as that
obtained from rice
husks might be employed to provide the necessary increased rigidity. In
addition to the
fibres, other fillers are envisaged. In this layer of the cladding board 20%
to 50% fillers
by weight is envisaged. The fillers may be mineral fillers coupled with ground
glass or
pulverised fuel ash (PFA). In addition, the backing layer which could also be
referred to
as a core layer may employ fire retardants.
Layer 3 is provided to cover the backing layer with regards to at least its
top face. Layer 3
may be either an unfilled or a filled polyurethane elastomer. This elastomer
may be
pigmented. It may also contain fire retardants in either liquid or powder form
along with
other fillers such as water scavengers, recycled rubber, further elastomers,
or even
minerals. The shore A of the layer 3 may be selected between 35 and 90.
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The further layer may alternatively have a much higher inherent flexibility.
The shore
level may be selected to offer a cushioning effect. The inherent flexibility
of the further
layer may be higher than that of the rigid backing layer. This aspect
particularly improves
its weather resistance properties due to for example the impact of hail
stones.
Due to the selection of materials for both layer 2 and layer 3 chemical cross-
linking arises
which creates excellent adhesion between the core and its topping without any
requirement for a separate adhesive.
Optionally, a further top layer is provided such as top layer 4 which provides
an improved
finish. This top layer maybe based on aliphatic isocyanate. Other materials of
a similar
category may be employed in this context. This selection of material however
is
particularly suited for cross-linking with layer 3 in order to provide a layer-
wise
construction which holds together as an integral unit without the use of
adhesives. The
thickness of layer 4 may be much less than a millimetre and typically of the
order of the
thickness of a typical paint. Layer 3 however is preferably of Imm to 5mm in
thickness.
The process which is preferred in the production of the cladding board is a
moulding
process. The first step in the process is to place an in-mould coating
consisting of an
aliphatic isocyanate based medium applied in one or more full or partial
layers (each layer
having a thickness similar to that of paint). Layer 3 which might be a hybrid
polyurethane
is applied to cross-link with the coating 4 to form a hard or alternatively a
resilient
backing to the coating. Once this is applied, another form of polyurethane is
applied.
This polyurethane is that of layer 2 and would contain a wide spectrum of
fillers. This
layer would also readily cross-link with the previous layer 3 during the
curing process. In
order to control the expansion of the foam polyurethane an encapsulating mould
box is
employed which constrains the expansion within the mould itself. The cladding
board
lends itself to being cut or trimmed using carpenter's tools.
Figure 2 shows a cladding board 7 with a filled polyurethane rigid foam layer
8 in which
are formed a tongue 9 and a groove 10 in its respective upper and lower side.
The groove
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may either be formed during the moulding process or cut out as a separate step
in the
manufacturing process. Directly over the outer face of layer 8, there is
provided a
polyurethane elastomer 11 which protects and seals the closed or open cell
portions of
layer 8. In this configuration layer 11 covers the outside portion 12 of
tongue 9. This
5 configuration may facilitate an improved attachment of the tongue into the
groove of a
corresponding cladding board.
Figure 3 shows a further cladding board generally referenced 13 with a
polyurethane
elastomer provided on both the outer and inner surfaces of tongue 14.
In a further embodiment, as shown in figure 4, both the tongue and the groove
can be
entirely free of any polyurethane elastomer. Elastomer 15 of cladding board 16
is limited
to the outer most surface of the board.
Figure 5 shows a cladding board with a front face 18 of polyurethane elastomer
18 and a
backing layer 19 of closed-cell foamed polyurethane. Closed-cell foamed
polyurethane is
potentially an inventive option for any of the preceding embodiments. The rear
face 20 of
the backing layer is sloped. In a lower portion of the board, a cut-out
portion 21 is
provided. A projection 22 is provided on one side of the lower portion whilst
said cut-out
portion 21 fulfils the function of a groove. The board progressively narrows
towards the
upper portion which forms in effect a tongue for engagement with cut-out 21.
The
elastomeric layer extends over said tongue in order to facilitate the seal
between adjacent
boards when assembled together.
