Note: Descriptions are shown in the official language in which they were submitted.
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TILE COATING AND PROCESS THEREFOR
FIELD OF INVENTION
The present invention relates to a process for coating a substrate with a
plastic
material and in particular, but not limited to, a process for coating tiles
with a thermo
plastic polyurethane.
BACKGROUND
It is often desirable to improve the properties of 3-Dimensional objects,
for example brittle objects, by coating the object with a protective layer.
One such
instance is tiles, in particular roofing tiles, as described below although it
will be
appreciated that the present invention is not limited to tiles. Tiles are
typically made of
a cementitious material, and as such, are brittle exhibiting a low modulus of
rupture.
For example, when exposed to thermal or physical forces tiles will often crack
and fail
completely breaking into pieces. Such behaviour is, of course, undesirable as
the
broken tiles destroy the integrity of the roof and must be replaced.
Accordingly, there is a need in the art to improve the performance
characteristics
of tiles. These characteristics are not limited to the modulus of rupture of
the tiles, and
include other properties such as UV resistance, application strength, microbe
resistance,
scratch resistance, chipping resistance, colour stability long term, batch
colour stability,
strength, water proofing of concrete enhanced, highly uv stable, non slip
surface,
mixture of colours applied at one time, are also desirable to be incorporated
in a coating
of a tile.
Existing technologies for coating tiles consist of wet based spray/shower
coatings, for example slurry oxide, single and two pack paint systems. Such
coatings
are very susceptible to impact damage due to their cured nature, i.e.
comprising thin flat
layers of organic based pigments encapsulated in water, resin or petro-
chemical based
carriers. These coatings evaporate leaving the base organic compounds which
are
typically stiff and inflexible. This renders the coating prone to chipping and
cracking so
that the coating no longer improves the tiles performance characteristics.
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It is known to improve the performance characteristics of woven and fibrous
materials by a melt blowing process in which a vacuum is applied to draw a
molten
polymer through a woven or fibrous substrate. Unfortunately such technologies
are
limited to the treatment of materials through which a vacuum can be drawn.
It is accordingly an object of the present invention to provide a tile coating
which ameliorates at least some of the aforementioned problems in the art.
BRIEF DESCRIPTION OF THE INVENTION
In a first aspect the present invention provides a method of coating a
substrate
comprising the steps of
supplying to a melt blowing die a monomer in an at least partly flowable form,
discharging said monomer in a flowable state from said melt blowing die,
entraining said monomer in a flowable state in a flow of hot gas from at least
one side of said melt blow die. and
depositing said monomer in a flowable state on a substrate by sputtering under
positive pressure.
Preferably in the deposition step the monomer form a uniforin coating on the
substrate.
Preferably in the discharge step the monomer discharges through an aperture or
apertures in the die.
Preferably the aperture or apertures have a diameter of between 0.1mm to 3mm.
Preferably there are between about 1 and about 70 apertures per square inch.
Preferably in the entraining step the gas is pressurised air.
Preferably the gas is heated to between about 40 C to about 400 C.
Preferably the monomer is selected from the group comprising TPU,
polypropylene, PVDF, EVA, PVC, Nylon, PC, Stryrene's, ABS, HDPE, LDPE and
LLDPE.
Preferably the method further includes a preliminary step of melting the
substrate by heating to a temperature of between about 40 C and about 400 C.
Preferably the substrate is heated to a temperature of between about 140 C
and
about 195 C.
Preferably the method further includes a preliminary step of heating the
monomer to a temperature of between about 40 C and about 400 C.
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Preferably the monomer is Thermoplastic Polyurethane (TPU).
Preferably the monomer is heated to a temperature of between about 210 C and
about 245 C
Preferably the substrate is selected from the group comprising cements,
aggregates, geopolymers, natural stones, tin, aluminium, stainless steel,
plastic and
resinous materials, fibreglass matt and cloth, cotton, hemp cloth, jute cloth.
Preferably the method includes a step of controlled cooling of the substrate
after
deposition.
Preferably the method includes a step of dipping the coated substrate in a
water
bath after deposition.
Preferably the coating deposited on the substrate is between 10 microns to lmm
thick.
Preferably in the depositing step the entrained polymer is at an angle of
between
to 165 relative to the surface of the substrate.
15 In a second aspect the present invention provides a positive pressure
apparatus
to deposit a coating on a substrate comprising:
a melt blowing die having an aperture or apertures through which a flowable
monomer resin is discharged;
a means for supplying the flowable monomer to the melt blowing die;
a pressurised gas supply configured to entrain the flowable monomer resin as
it
discharges from the die; and
a support table to position the substrate relative to the die so that the
substrate is
coated by the entrained monomer.
Preferably the melt blowing die includes a head having an array of apertures
through which the monomer discharges.
Preferably the apertures have a diameter of between 0.1mm to 3mm.
Preferably there are between about 1 and about 70 apertures per square inch.
Preferably the positioning table is stationary and the melt blowing die can be
moved to a position where the entrained monomer resin can coat the or each
substrate.
Alternatively the positioning table is a conveyor capable of advancing the or
each substrate to a position where the entrained monomer resin can coat the or
each
substrate.
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Preferably the entrained polymer can be deposited at an angle of between 15
to
165 relative to the surface of the substrate.
In a third aspect the present invention provides a coated substrate when
prepared
accordingly to a method described above.
In a further aspect the present invention provides a melt blow process
comprising applying a plastic coating to the surface of a tile.
In another aspect the present invention consists in a tile coating of a
plastic
coating or plastic film.
Preferably the plastic film is one formed prior to application to a tile.
Preferably the plastic film is one extruded directly onto a surface of a tile.
Preferably the tile coating is a therinoplastic material.
Preferably said thermo plastic material is polyurethane.
Preferably said polyurethane includes a uv stabilizing additive.
Preferably said polyurethane includes a fire retardant additive.
Preferably said plastic film is adhesion applied to a said tile.
Preferably said plastic coating is a sprayed layup.
Preferably said plastic layup is a fibre re-enforced sprayed layup.
In another aspect the present invention consists in a method coating a tile
(preferably a concrete tile) comprising applying a plastic coating to at least
part of a
surface of a said tile.
Preferably said applying is by extruding a sheet formed plastic coating
directly
to said tile.
Preferably the extruded sheet is at a temperature to still at least be tacky
prior to
it being deposited onto a surface of said tile.
Preferably said applying is by melt blowing the plastic coating onto said
tile.
Preferably said applying is by a spay deposition of a non woven precursor form
of the plastic coating.
Preferably said coating is applied to a thickness of between 10 microns to
1mm.
In a further aspect the present invention consists in a tile which includes a
coating of a plastic coating or plastic film.
Preferably the plastic film is one formed prior to application to a tile.
Preferably the plastic film is one extruded directly onto a surface of a tile.
Preferably the tile coating is a thermoplastic material.
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Preferably said thermo plastic material is a polyurethane.
Preferably said polyurethane includes a uv stabilizing additive.
Preferably said polyurethane includes a fire retardant additive.
Preferably said plastic film is adhesion applied to a said tile.
Preferably said plastic coating is a sprayed layup.
Preferably said plastic layup is a fibre re-enforced sprayed layup.
This invention may also be said broadly to consist in the parts, elements and
features referred to or indicated in the specification of the application,
individually or
collectively, and any or all combinations of any two or more of said parts,
elements or
features, and where specific integers are mentioned herein which have known
equivalents in the art to which this invention relates, such known equivalents
are
deemed to be incorporated herein as if individually set forth. For the
purposes of
illustrating the invention, there is shown in the drawings a form which is
presently
preferred. It is being understood however that this invention is not limited
to the precise
arrangements shown.
As used herein the following terms have the meanings as specified below:
The term 'monomer' includes monomers and derivatives thereof, for example
dimmers, polymers and salts tlzereof.
The tenn 'comprising' as used in this specification and claims means
'consisting
at least in part of, that is to say when interpreting independent claims
including that
term, the features prefaced by that term in each claim will need to be present
but other
features can also be present.
The term 'entrained' refers to discharged filaments of monomer resin carried
in
a flow of gas.
A preferred form and methodologies of the present invention will now be
described with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram of a positive pressure coating apparatus
of the present invention,
Figure 2 is a top view of a bear tile prior to impact testing,
Figure 3 is a top view of a bear tile after impact testing,
Figure 4 is a top view of an oxide treated tile after impact testing,
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Figure 5 is a side view of a coated tile of the present invention,
Figure 6 is a top view of a coated tile of the present invention prior to
impact testing,
Figure 7 is a top view of a coated tile of the present invention after a first
impact test,
Figure 8 is a top view of a coated tile of the present invention after a
second impact test, and
Figure 9 is a back view of a coated tile of the present invention after a
second impact test.
DETAILED DESCRIPTION OF THE INVENTION
The tile coating technology we have developed enables concrete tiles to be
coated with a highly UV stabilised Thermo Plastic Polyurethane. This
technology
enables the outer exposed surface of a concrete tile to be coated with a
vastly superior
colouring agent at a similar cost to the currently used Oxide slurries and
paints.
This coating also provides the tile with significant strength and durability
benefits. This is particularly so if the thickness of the coating is increased
to over about
100 microns. The technology in the specifically designed machinery to enable
the
coating such as by extrusion coating or by melt blown deposition.
The Thermoplastic includes a uv stabilising additive and may include a flame
retardant.
The thermoplastic material may have properties such as UV resistance,
application strength, microbe resistance, scratch resistance, chipping
resistance, colour
stability long term, batch colour stability, strength, water proofing of
concrete
enhanced, highly uv stable, non slip surface, mixture of colours applied at
one time.
A preferred process for coating a tile will now be described with reference to
Figure 1 which illustrates a positive pressure apparatus 100. A Thermo Plastic
Polyurethane (TPU) is heated in extruder 102 to a flowable molten state.
Desirably the
monomer resin is preheated before introduction into the extruder 102, to
ensure a
satisfactory moisture content of, for example 0.1 %. Heat may be applied to
the
monomer resin throughout the deposition process to ensure it is maintained in
a
flowable state. However it is also contemplated that a light cure monomer
resin could
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be employed in the present invention, in which instance no heating step may be
necessary for the resin to be in a sufficiently flowable state for
introduction into the
extruder 102.
Typical temperatures will be between 210 to 245 C. The TPU is then pumped
by gear pump 106 through filter 104 to remove any undesirables from the TPU
resin.
Undesirables include any solid particulates that may subsequently block the
apertures of
the melt blowing die.
The TPU is pumped into the melt blowing die 108 and is discharged via
apertures 112. While in Figure 3 the apertures 112 are formed on a single head
of the
die 108, it is within the scope of the invention to provide multiple die heads
allowing
the molten TPU to be simultaneously or sequentially discharged from different
angles
relative to the substrate tile 116.
As the TPU is discharged it becomes entrained in jets of pressured air 110a
and
110b at between 40 to 400 C. The temperature of the jets of pressurised air
is matched
to the resin being discharged. Typically the air temperature will be between
15 C
below or 400 C above the viscount softening point of the resin, preferably
about 20 C
above or below the melting point of the resin. The flow rate of the air is
dependant on
the type, temperature and quantity of the resin being deposited. For example,
some
resins can be processed at air speeds as low as 5 ms'1, while other resins
having a higher
viscosity require an air flow speed of between 4 to 500 ms-1 to be correctly
orientated
or blown in a consistent direction.
This combination of pressurised heated air entraining TPU filaments forms a
curtain 114 which is deposited onto the surface of a substrate tile 116. The
substrate tile
may be pre-treated by heating up to between 60 C to 285 C, preferably
between 140
C to 195 C in drying and heating chamber 120.
In one embodiment the heating chamber is a tunnel of sufficient length to
allow
a tile passing therethrough to be heated/dried to a desired temperature.
Providing a
tunnel of sufficient lengtll to heat the tile must be balanced against
maintaining an
acceptable production speed. The required thickness of the tile coating, the
desired peel
strength, the tile surface and the type of resin being deposited all influence
the
temperature to which the tile is heated. A typical heater for the tile is an
IR heater bank,
although other heaters such as flame, hot air, among others are also possible.
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Without wish to be bound to any particular theory it is believed that by
sputtering the molten TPU onto a preheated tile surface the viscosity of the
molten TPU
is maintained allowing the TPU to flow on the surface of the tile to form a
uniform
layer. Additionally, by maintaining the viscosity of the TPU, the TPU is able
to
impregnate into the pores of the tile and achieve a mechanical bond between
the tile and
the TPU layer. This results in the high peel strength characteristics of the
coatings
prepared according to the present invention.
When the substrate tile is non-porous, for example an aluminium tile, an
etching
agent may be used to roughen the surface of the tile and encourage the
formation of a
mechanical bond between the TPU layer and the tile. Additionally any number of
known in the art adhesives may be employed to improve the bonding of the TPU
layer
to the tile.
The substrate tile 116 is advanced by conveyor 118 to a position proximate the
die 108 where it is coated by the molten TPU entrained in the pressurised air
flow. The
speed of the conveyor can be between 1 and 300 mis/min. Once the coating is
complete
the substrate tile 116 is removed. Alternatively the substrate tile 116 may be
held in
position by a support table and the melt blowing die moved to coat the tile
with the
TPU. The melt blowing die may be moveable to both track over the substrate
tile 116,
as well as being movable to discharge the molten TPU from varying angles
relative to
the substrate tile 116 and thereby achieve a desired coating.
The coated substrate tile may be subsequently treated in a cooling chamber 122
to control the cooling of the tile and maximise the bonding of the TPU layer
to the tile.
The coated tile may also be treated in a hot water bath to produce a glazed
surface on
the tile.
Desirably any monomer resin overspray from the coating process is recycled.
The process and apparatus described above is amenable to a number of
variations for uptake in other industries. For example, the present invention
may
combine with Photo Voltaic technology to provide improved solar energy
systems. A
substrate tile may be first primed by depositing a base layer of TPU in
accordance with
the present invention. A photo voltaic cell can then be screen printed atop
the TPU
layer according to known in the art processes and finally a sealing top coat
of aliphatic
TPU can be deposited onto the PV cell. This arrangement will protect the PV
cell from
weathering and allow an entire roof to be tiled with solar cells.
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Additionally the process and apparatus described above can be arranged to
deposit multiple coatings upon a substrate, either by providing multiple melt
blowing
die head or by repeatedly passing a substrate through the apparatus/process.
In another embodiment of a multi layer coating process a polycarbonate layer
is
deposited onto a rigid substrate and a TPU layer is coated atop the
polycarbonate layer.
The polycarbonate layer can then be separated from the rigid substrate to
provide a TPU
coated polycarbonate product. Such coated substrates can have selected
properties, for
example being both light weight and photo stable.
The present invention coats a tile substrate with a polymer based resin, with
the
coating improving the impact characteristics of the tile. The coating has been
found to
absorb the initial impact shocks without chipping or cracking. Furthermore
even when
an impact is sufficiently high so as to crack the tile, the polymer based
resin coating will
remain and hold the tile together. The methodology and results of the
experiments are
outlined below:
Impact Testing
The tests were conducted supporting one end of a tile on a 100mm wooden
block to place the tile in a condition having a 4:1 pitch ratio. A 24 oz
hammer was
dropped from a height of 2000mm on a bear tile, an oxide treated tile and a
TPU coated
tile respectively. The results of the testing are set out in Figures 2 to 9.
The TPU coated tile was prepared in accordance with the method described
above by preheating the a tile for 65 seconds at 100% reflective heat so that
the surface
of the tile reached a temperature of between 185 C. The TPU resin was heated
to a
melt temperature of 265 C and entrained in a 200 ms 1 flow of pressurised air
and
coated onto a tile at a thickness of around 100 microns.
Figures 2 and 3 show a bear tile before and after impact testing. The bear
tile
shattered into smaller pieces. Similarly Figure 4 shows the oxide treated tile
also
shattered into smaller pieces.
Figure 5 shows a sectional view of an edge of the TPU coated tile. The tile
had a
TPU coating thickness 504 of around 100 microns. Figure 5 also shows the
penetration
of the TPU coating 504 into the tile to form a mechanical bond between the
coating and
the tile.
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Figures 6, 7 and 8 show a tile prior to impact testing, after one impact test
and
after a second impact test respectively. Figure 9 shows the reverse side of
the tile after
the second impact test. After the first impact the tile substrate had
shattered, but
remained held together by the TPU coating. Even after the second impact test
the tile
substrate remained together.
The tiles not only remain held together, but are strongly held together due to
the
strength of the bond between the TPU coating and the tile substrate. Further
testing was
performed on a series of coated tiles prepared under varying process
conditions to show
the high bond strength between the TPU coating and the tile. This was done by
measuring the load required to separate the TPU layer from the tile. The
results are set
out in Table 1 below:
Table 1- Tile coating parameters and peel strengths
Test Resin Melt Coating Tile preheat Air Peel strength
number Type temp gauge tem erature speed range
C um C mts/sec Load (N)
1 TPU 230 60 130 200 101-148
2 TPU 230 100 120 200 101 - 119
3 TPU 230 120 85 200 35 - 41
