NZ757092B2 - A method of reducing shrinkage in the production of structural panels for a building - Google Patents
A method of reducing shrinkage in the production of structural panels for a building Download PDFInfo
- Publication number
- NZ757092B2 NZ757092B2 NZ757092A NZ75709219A NZ757092B2 NZ 757092 B2 NZ757092 B2 NZ 757092B2 NZ 757092 A NZ757092 A NZ 757092A NZ 75709219 A NZ75709219 A NZ 75709219A NZ 757092 B2 NZ757092 B2 NZ 757092B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- panel
- mesh
- building
- polyurethane foam
- layer
- Prior art date
Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 6
- 229920005830 Polyurethane Foam Polymers 0.000 claims abstract description 23
- 239000011496 polyurethane foam Substances 0.000 claims abstract description 23
- 229920002635 polyurethane Polymers 0.000 claims abstract description 16
- 239000004814 polyurethane Substances 0.000 claims abstract description 16
- 210000003491 Skin Anatomy 0.000 claims abstract description 15
- 229920002396 Polyurea Polymers 0.000 claims abstract description 12
- 230000002708 enhancing Effects 0.000 claims abstract description 9
- 238000005507 spraying Methods 0.000 claims abstract description 9
- 239000006260 foam Substances 0.000 claims abstract description 7
- 229920000642 polymer Polymers 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- 238000009432 framing Methods 0.000 description 2
- 239000003292 glue Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000000789 fastener Substances 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- 239000011120 plywood Substances 0.000 description 1
- 239000011378 shotcrete Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229920001059 synthetic polymer Polymers 0.000 description 1
Abstract
is known that panels moulded for structural use can be subject to undesirable levels of shrinkage and this can complicate their end use or a building made from them. It is an object of the invention to go at least some way to addressing this problem. Accordingly there is provided a method of significantly reducing panel shrinkage in the production of a structural building panel. The method involves spraying polyurethane foam onto a rigid open mould such that the foam substantially embeds mesh, which prevents or significantly reduces shrinkage of the polyurethane foam. A skin of polyurea is then sprayed over the polyurethane to enhance structural strength of the panel. nificantly reducing panel shrinkage in the production of a structural building panel. The method involves spraying polyurethane foam onto a rigid open mould such that the foam substantially embeds mesh, which prevents or significantly reduces shrinkage of the polyurethane foam. A skin of polyurea is then sprayed over the polyurethane to enhance structural strength of the panel.
Description
TITLE
A method of reducing shrinkage in the production of structural panels for a building.
FIELD OF INVENTION
A preferred form of this invention relates to a method of reducing panel shrinkage in
the context of forming structural panels for use in a building.
BACKGROUND
It is known to form panels from synthetic polymers and the like. They are primarily
used for exterior cladding over framing, or as a non-structural aesthetic finishing for
the interior of buildings. The inventor has discovered that panels moulded for
structural use can be subject to undesirable levels of shrinkage and this can
complicate their end use or compromise a building made from them.
OBJECT OF THE INVENTION
It is an object of the present invention to go at least some way to addressing the
above shrinkage problem.
INTERPRETATION
The term “comprising” or derivatives thereof such as “comprises” when used in this
document in relation to a combination of features should not be interpreted
exclusively. In other words the terms refer to the minimum features present, without
ruling out the option of additional unspecified features. The ‘features’ may for
example be physical items and/or action steps.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a method of substantially
reducing shrinkage in the production of a structural panel for use in a building,
comprising:
• spraying polyurethane foam onto a rigid open mould so that the foam
substantially embeds mesh and such that the mesh prevents or at least
significantly reduces shrinkage of the polyurethane foam; and
• spraying a skin of polyurea over the polyurethane to enhance structural
strength of the panel.
Optionally a first layer of the polyurethane foam is sprayed onto the mould, the mesh
is laid against the first layer, and a second layer of the polyurethane foam is sprayed
onto the first layer to substantially encase the mesh.
Optionally the first layer makes up approximately 70% ± 10%, and the second layer
makes up approximately 30% ± 10%, of the thickness of the panel.
Optionally the first layer is approximately 70mm thick ± 20%, and the second layer is
approximately 30 mm thick ± 20%.
Optionally the mesh is metallic, eg steel, and is formed from strands that are 3-8 mm
thick (eg in diameter).
Optionally the mesh is formed from strands that are approximately 4 mm thick (eg in
diameter).
Optionally the mould is such that the panel curves from bottom to top.
Optionally the panel provides a structural wall section and a structural roof section for
a building.
Optionally the mould is such that the panel is substantially straight or planar from
bottom to top.
Optionally the panel is combined with other same or substantially similar panels,
butted side to side, to form a building.
Optionally the building panel has an R rating of approximately 2 m K/W per 50 mm
thickness.
Optionally the polyurethane used, or used for each layer if applicable on the claim
dependency, has a density of 25-200 kg/m .
Optionally the polyurethane used, or used for each layer if applicable on the claim
dependency, has a density of approximately 32 kg/m .
Optionally shrinkage of the polyurethane foam is no more than 0-2% by 3 months.
Optionally shrinkage of the polyurethane foam is no more than 0.01% by 3 months.
DRAWINGS
Some preferred embodiments of the invention will now be described by way of
example and with reference to the accompanying drawings, of which:
Figure 1 illustrates a cross-section through a mould and part completed panel;
Figure 2 illustrates the mould and panel at a more advanced stage of formation
of the panel;
Figure 3 is an isometric view of a completed panel, formed as per figures 1 and
2;
Figure 4 is a cross-sectional view of the completed panel;
Figure 5 is an isometric view of a building formed by combining a series of the
panels;
Figure 6 is a vertical cross section of a portion of the building showing how the
panel may be fitted to a foundation or floor;
Figure 7 is a vertical cross section of a portion of the building showing how the
panel may be fitted to a foundation or floor in an alternative manner;
Figure 8 is a horizontal cross section through a portion of the building showing
how neighbouring panels may be secured to one another.
DETAILED DESCRIPTION
Referring to Figure 1, a rigid metallic mould 1, in this case made of steel, is formed in
the shape of a structural building panel. The mould 1 has a base 2, side walls 3 and
an open front 4. The mould is shown standing upright, but in use it may be laying on
its base 2.
With further reference to Figure 1, a first layer 5 of foam, eg polyurethane foam, is
sprayed into the mould and hardens in less than one minute. The first layer may for
example be about 70mm thick ±20%. Metallic mesh 6, substantially rigid and made
from welded galvanised steel rods 3-8 mm thick, preferably about 4mm thick, is laid
over the first layer 5. The rods are such that they have been welded together at each
crossing/intersection that makes up the mesh. The mesh openings may be
substantially square or some other shape, and about 150-250 mm across, preferably
about 200 mm across. A second layer 7 of polyurethane foam, the same or different,
is then sprayed over the first layer 5 and mesh 6 so that the mesh is encased about
where the two layers meet. The second layer 7 also hardens in less than one
minute. The second layer 7 may be about 30 mm thick ±20%. In some instances
each of the two layers may be built up from a series of thinner sub-layers, but are still
referred to as ‘first’ and ‘second’ layers to distinguish the polyurethane either side of
the mesh 6.
The thickness of the first and second layers may be other than 70 mm and 30 mm
respectively, although preferably this approximate ratio is maintained regardless of
the combined thickness of the two layers. The combined thickness may for example
be from 90-300 mm depending on the desired heat insulation and overall strength
requirements for the finished panel.
Referring to Figure 2, optionally the mesh 6 is arranged to protrude slightly at the top
and/or bottom of the first and second layers of polyurethane as indicated at 8. The
protruding mesh at the bottom can be used to conveniently tie the panel to a floor or
foundation when forming a building. The protruding mesh at the top can be used to
fasten a roof cap and/or to assist in joining the top of the panel to neighbouring
panels the same or similar, when forming a building.
With further reference to Figure 2, a skin, preferably a polyurea skin 9, is sprayed
completely over and around the two layers of polyurethane 5, 7. The polyurea skin 9
may be applied to the second layer 7 of polyurethane while still in the mould 1, with
further spray application of polyurea skin to envelope the other polyurethane surfaces
after removal from the mould. Alternatively the polyurea skin 9 may be applied to all
of the polyurethane surfaces after removal from the mould. The polyurea skin wraps
completely around the polyurethane to enhance the strength of the panel. The skin
may for example be 2-6 mm thick, but is preferably about 2 mm thick.
Figures 3 and 4 show the completed panel 10. In figure 3 the mesh 6 is illustrated
for ease of understanding, although in reality it would be within the rest of the panel
and therefore not visible. As shown in figure 3, the panel 10 is formed to have a
corner ridge 11 to enhance strength, although this is not essential. In alternative
embodiments the completed panel may be straight or flat over its entire length and
width.
Figure 5 illustrates a building 12 formed from a series of the panels 10. More
specifically, the building 12 is formed by butting a series of the panels 10 together.
The panels 10 are fastened to one another at their side edges with glue and/or screw
or other pin type fasteners. The edges may be ‘stepped’ complimentarily, so that
immediately neighbouring panels overlap one another. The building 12 is generally
hexagonal in its footprint, but in other embodiments it may an alternative shape.
The mesh serves to prevent or at least significantly reduce shrinkage of the
polyurethane in the panel 10 over the days, weeks and months after its completion.
This is important because it enables panels to be produced in a size-reliable manner
so that shrinkage does not compromise the building they are for. It has been found
that shrinkage is more prone at the outside surface of a building when formed as
above, which is why the mesh is preferably positioned nearer the outside surface of
the panel than its interior surface. In addition to addressing shrinkage, having the
imbedded mesh 6 serves to enhance security in that the panels/building walls are
more difficult for a would-be intruder to cut through. The mesh may also enhance the
strength of the building generally.
Figure 6 illustrates one option for securing the panels 10 to the building’s 12 floor or
foundation 13. As shown, the mesh 6 that protrudes 8 at the bottom of the panel is
screw fastened to a beam 14 that forms part of the foundation.
Figure 7 illustrates an alternative way of attaching the panels 10 to the building’s 12
floor or foundation, for example when the foundation or floor is a poured or sprayed
concrete or other pad 15. In this case the portion of the mesh 6, 8 that protrudes at
the bottom of the panel is cast into the pad 15. As also shown, the panel sits in a
complimentary shaped step 16 at the edge of the pad to assist in providing accurate
placement of parts. The ground is indicated at 17.
Figure 8, which is a horizontal section through a portion of the building 12, illustrates
the manner in which the panels 10 may be secured to one another along their upright
sides or edges. As shown, the panels 10 butt one another at complimentary steps 18
and are fastened to one another at such steps by way of screws 19 and/or glue. The
steps 18 incorporate moulded-in beam like strips 20 to give the screws 19 better
purchase for a secure connection between adjoining panels. The strips 20 may be
wooden or any other suitable material. The joins between the edges of the panels
may be sprayed over with a polyurea skin for enhanced strength and water-tightness.
The polyurethane foam in each case above may for example be the product
Endurathane SR42M available from the supplier Polymer Group Ltd which has a
website at www.Polymer.co.nz.
The polyurea skin in each case above may for example be the product Endurathane
P515, also available from the supplier Polymer Group Ltd which has a website at
www.Polymer.co.nz.
Preferably the panels each have a foam density of 32 kg/m . In some preferred
embodiments they may have a density of from 25 to 200 kg/m .
Preferably the panels have an insulation New Zealand ‘R’ rating of about 2.05 m
K/W for every 50 mm. The preferred the ‘R’ rating of each finished panel may
optionally be from 1.5 to 6 depending on how thick it is.
Preferably panels formed as above exhibit less than 1% shrinkage at 3 months after
their completion, and more preferably no more than about 0.01% shrinkage by 3
months. Optionally the shrinkage may be no more than 0% to 2% by 3 months.
Preferably the panels are structural in that they need no framework strengthening, for
example they do not need any upright beams or framing to make them load bearing.
The strips 20 for the screws to gain purchase are not load bearing, preferably they
are approximately 9 mm to approximately 15 mm thick, and most preferably
approximately 12 mm thick. The strips are preferably flexible so as to bend with
curvature in the panel. They may be formed from plywood. They preferably bond
into to the sprayed polyurethane.
In terms of disclosure, this document hereby anticipates and disclosures any feature
mentioned herein in combination with any one or more other features mentioned
herein, even if such combination is not the subject of a claim.
While some preferred forms of the invention have been described by way of example
it should be understood that modifications and improvements can occur without
departing from the scope of the following claims.
Claims (14)
1. A method of substantially reducing shrinkage in the production of a structural panel for use in a building, comprising: • spraying polyurethane foam onto a rigid open mould so that the foam 5 substantially embeds mesh and such that the mesh prevents or at least significantly reduces shrinkage of the polyurethane foam; and • spraying a skin of polyurea over the polyurethane to enhance structural strength of the panel. 10
2. A method according to claim 1, wherein a first layer of the polyurethane foam is sprayed onto the mould, the mesh is laid against the first layer, and a second layer of the polyurethane foam is sprayed onto the first layer to substantially encase the mesh. 15
3. A method according to claim 2, wherein the first layer makes up approximately 70% ± 10%, and the second layer makes up approximately 30% ± 10%, of the thickness of the panel.
4. A method according to claim 2 or 3, wherein the first layer is approximately 70mm 20 thick ± 20%, and the second layer is approximately 30 mm thick ± 20%.
5. A method according to any one of the preceding claims, wherein the mesh is metallic and is formed from strands that are 3-8 mm thick. 25
6. A method according to any one of the preceding claims, wherein the mesh is formed from strands that are approximately 4 mm thick.
7. A method according to any one of the preceding claims, wherein the mould is such that the panel curves, or is straight, from bottom to top.
8. A method according to any one of the preceding claims, wherein the panel is formed to provide a structural wall section and a structural roof section for a building.
9. A building comprising panels, butted side to side and secured in that disposition, each panel comprising: 5 • a polyurethane foam layer that has been created by spraying such foam onto a rigid open mould; • mesh substantially embedded by the polyurethane foam as a result of said spraying, the mesh being such that it has served to significantly reduce shrinkage of the polyurethane foam; and
10 • a polyurea skin over the polyurethane foam layer wherein such skin has been created by spraying and serves to enhance structural strength of the panel. 15 10. A building according to claim 9, each panel having an R rating of approximately 2 m K/W per 50 mm thickness.
11. A building according to claim 9 or 10, wherein each panel has a density of 25-200 kg/m .
12. A building according to claim 11, wherein the polyurethane has a density of approximately 32 kg/m .
13. A building according to any one of claims 9-12 wherein the shrinkage of the 25 polyurethane foam is no more than 0-2% by 3 months.
14. A building according to claim 13, wherein the shrinkage of the polyurethane foam is no more than 0.01% by 3 months.
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NZ757092A NZ757092B2 (en) | 2019-09-09 | A method of reducing shrinkage in the production of structural panels for a building | |
EP20863408.9A EP4028606A4 (en) | 2019-09-09 | 2020-08-07 | A method of reducing shrinkage in the production of structural panels for a building |
CA3153543A CA3153543A1 (en) | 2019-09-09 | 2020-08-07 | A method of reducing shrinkage in the production of structural panels for a building |
PCT/NZ2020/050085 WO2021049952A1 (en) | 2019-09-09 | 2020-08-07 | A method of reducing shrinkage in the production of structural panels for a building. |
AU2020344437A AU2020344437A1 (en) | 2019-09-09 | 2020-08-07 | A method of reducing shrinkage in the production of structural panels for a building. |
US17/641,439 US20220372755A1 (en) | 2019-09-09 | 2020-08-07 | A method of reducing shrinkage in the production of structural panels for a building |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NZ757092A NZ757092B2 (en) | 2019-09-09 | A method of reducing shrinkage in the production of structural panels for a building |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ757092A NZ757092A (en) | 2020-09-25 |
NZ757092B2 true NZ757092B2 (en) | 2021-01-06 |
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