METHOD AND DEVICE FOR FINISHING AN ENGINEERED WOOD
BOARD
The invention relates to a method for finishing an
engineered wood board comprising a decor on at least
the top and/or the bottom.
Such engineered wood boards are widely used in many
different fields. A particularly significant field of
use is use as a floor panel. With this use in
particular the engineered wood boards are exposed to
immense loading in particular as a result of being
walked on. To ensure that they withstand this loading,
the decorative layer has to be covered with a
protective layer. This generally consists of a
synthetic resin, for example melamine resin, to which
various additives have been added. The various layers
applied to the engineered wood board result in tensile
stresses, which may lead to cupping of the engineered
wood board. Therefore, both the top and bottom of the
engineered wood board may be coated to allow these
forces to occur evenly on both sides and thus to avoid
cupping.
Application of the synthetic resin layer to the
engineered wood board may proceed in a very wide range
of ways. It is known, for example, to apply the
synthetic resin as granules or powder to the side of
the engineered wood board to be coated and to sprinkle
in any additives provided. During final pressing, the
powder applied melts under the action of pressure and
heat and forms a homogeneous layer. In this method
bilateral coating of the engineered wood board is of
course impossible, since the sprinkled-on powder merely
lies on the surface of the engineered wood board and is
only bonded therewith during pressing.

It is known from EP 1 454 763 A2 to apply a protective
layer of melamine resin to the decor on the top of an
engineered wood board. At the same time, a protective
layer of melamine resin is likewise to be applied to
the bottom of the engineered wood board. The applied
resin layers are then intended to melt during pressing
and so enclose the decor.
EP 2 098 304 A2 describes the use of liquid resin,
which is applied to both the top and bottom of the
engineered wood board.
Taking this statement of the problem as basis, the
intention is to improve the above-described method for
finishing an engineered wood board.
The problem is solved by a method of the above type
having the following steps:
a) cleaning the top and bottom of the engineered wood
board,
b) applying a first top resin layer, which contains
corundum particles, to the top and a first bottom
resin layer to the bottom of the engineered wood
board,
c) drying the first top resin layer and the first
bottom resin layer to a residual moisture content
of 3% to 6%,
d) applying a second top resin layer, which contains
cellulose, to the top and a second bottom resin
layer to the bottom of the engineered wood board,
e) drying the second top resin layer and the second
bottom resin layer to a residual moisture content
of 3% to 6%,

f) applying an at least third top resin layer, which
contains glass particles, to the top and an at
least third bottom resin layer to the bottom of
the engineered wood board,
g) drying the third top resin layer and the third
bottom resin layer to a residual moisture content
of 3% to 6%,
h) pressing the multilayer structure under the action
of pressure and heat.
By cleaning the top and the bottom of the engineered
wood board in the first method step, dust or other
impurities, which have become attached to the relevant
sides of the engineered wood board during storage or
preceding production steps, are reliably removed. This
is important for ensuring that even resin layers
requiring very thin application are applied uniformly
and homogeneously to the top and no unevennesses or
inclusions arise in these layers.
The corundum particles in the first top resin layer
increase the abrasion resistance of this layer. This is
of the greatest importance in particular in the event
of use as a floor panel in order to withstand the
abovementioned loading to which a floor panel is
exposed. The corundum in this case assumes the form,
for example, of a mixture of conventional varieties of
silanized corundum of different grain sizes and may
simply be added to the resin. A first bottom resin
layer is applied to the bottom of the engineered wood
board, so compensating the tensile forces acting on the
engineered wood board as a result of the first top
resin layer. The first bottom resin layer may in
particular be colored. Both resin layers may have
additives added to them, such as for example curing
agents or wetting or release agents. The first top
resin layer and the first bottom resin layer are then

dried, to ensure clean application of a next resin
layer. Drying proceeds for example by means of hot air,
wherein the resin is dried and the chemical
crosslinking reaction of the melamine resin is stopped.
In the process, water is extracted from the coating
compound and the latter is adjusted to a residual
moisture content of for instance 3% to 6%. The other
resin layers applied are brought to said residual
moisture content during their respective drying
operations.
The cellulose which is present in the second top resin
layer assumes the form of conventional commercial
fibers which may likewise be added to the resin layers
to be applied. The glass introduced in the third top
resin layer assumes the form of conventional commercial
microglass beads. These are also easy to store and to
introduce into the resin layer to be applied. The resin
layers applied to the bottom of the engineered wood
board may be colored. All the resin layers may have
additives such as curing agents or wetting and release
agents added to them.
Drying to a residual moisture content of 3% to 6% stops
the crosslinking process of the applied resin layers.
During subsequent pressing under the action of pressure
and heat, the resin layers melt again and the
crosslinking process continues. This ensures that the
individual resin layers are not only themselves
crosslinked but are also crosslinked to one another and
may thus be pressed into a large laminate. Conventional
short-cycle presses operate for example at a pressure
of 30 to 60 kg/cm2, a temperature at the engineered
wood surface of for instance 165°C and a pressing time
of 6 to 12 seconds. In this way, the melamine resin
layers applied are crosslinked, enclosing the decor. If
textured pressing plates are used, textures may also be
embossed into the resin layers, in addition to the
decor. These may be largely congruent with the decor,

in which case they are known as Embossed-In-Register
textures.
The third top resin layer preferably contains glass
particles in a proportion of 20%. For the second top
resin layer 5% cellulose has for instance proven
advantageous. The first top resin layer contains in
particular 20% corundum particles.
Advantageously the top resin layers and the bottom
resin layers are applied in an amount of from 20 to
50 g/m2. Because the melamine resin layers applied in
each case to the top and bottom are applied in equal
amounts, it is at the same time ensured that the
tensile forces to which the engineered wood board is
exposed during drying due to the applied layers cancel
each other out. The counter layer applied to the bottom
of the engineered wood board thus precisely matches the
layer sequence applied to the top in layer structure
and respective layer thickness. As a result of this
small amount applied of 20 to 50 g/m2, it is ensured at
the same time that no curtaining arises in particular
on the bottom of the engineered wood board.
The top resin layers and the bottom resin layers may
contain a 60% synthetic resin solution.
A primer and an undercoat may be applied under the
decor of the engineered wood board to be finished. The
decor has been printed onto this undercoat and covered
with a covering. Alternatively, the decor may be
applied to the engineered wood board by lamination in
the form of a decorative paper layer.
A device for finishing an engineered wood board, at
least a top and/or a bottom of the engineered wood
board comprising a decor, comprises the following
according to the invention:

a) a first double-sided application device,
b) a first drying device arranged downstream of the
first double-sided application device in a
processing direction,
c) a second double-sided application device arranged
downstream of the first drying device in the
processing direction,
d) a second drying device arranged downstream of the
second double-sided application device in the
processing direction,
e) at least one third double-sided application device
arranged downstream of the second drying device in
the processing direction,
f) at least one third drying device arranged
downstream of the at least one third double-sided
application device in the processing direction and
g) a short-cycle press,
each double-sided application device comprising a
top application device for applying a resin layer
to the top of the engineered wood board and a
bottom application device for applying a resin
layer to the bottom of the engineered wood board
and each top application device and each bottom
application device in each case comprising a
mixing vessel, in which the resin to be applied in
each case may be mixed with at least one additive.
The engineered wood boards provided with the decor and
requiring finishing are introduced into such a device.
The top and bottom of the engineered wood board are
coated simultaneously with a resin layer in the at
least three double-sided application devices. This

shortens the production time and thus reduces
manufacturing costs. By means of the drying devices
provided downstream of the double-sided application
devices, in which drying devices the engineered wood
boards just coated are dried down to the desired
residual moisture content, for example by hot air, it
is quickly made possible to apply the in each case
first resin layer and to bring the crosslinking process
of the resin layers applied to a standstill at an early
stage. Intermediate storage of the coated engineered
wood boards to dry the resin layers or turning of the
engineered wood boards to allow coating of the other
side too is no longer necessary.
Because both each top application device and each
bottom application device comprises a mixing vessel, in
which the resin to be applied in each case may be mixed
with the desired additives, it is possible to make
particularly rapid adjustments between different
product requirements, for example the desired abrasion
class. It is possible to dispense with protracted
changeovers or holding large amounts of different
resin/additive mixtures in stock, so meaning that both
the amounts of material needing to be held in stock and
the space requirement of the installation are markedly
reduced. At the same time, different product
properties, for example surface smoothness, or acid or
abrasion resistance may be adjusted rapidly and
straightforwardly. In addition, the use of highly
reactive resin mixtures is also possible, since
intermediate storage of the coated engineered wood
boards is no longer necessary, continuous processing
taking place instead. In this way, the cycle times of
the short-cycle press are also reduced markedly,
resulting in a further reduction in manufacturing
costs.
A device according to the invention preferably
comprises a storage magazine with a plurality of

storage vessels, in which the resin to be applied and
the additives may be stored separately from one
another, and feed lines from the storage vessels to the
mixing vessels. In this way, the resin and the
additives may be conveyed separately from one another
into the mixing vessels and mixed only at this point
into the desired resin layer to be applied.
The device may in particular comprise a controller,
which is designed to control the amount of resin and of
additives conveyed by the feed lines into the mixing
vessels. This makes possible automatic adjustment of
various product properties and application amounts or
rates of addition.
Each top application device and each bottom application
device may here be an application roller set, so
ensuring a constant and finely adjustable layer
thickness. In addition, application of the applied
layers takes place very homogeneously and uniformly in
this way.
Peristaltic pumps may be provided to pump the contents
of the mixing vessels to the respective top and bottom
application devices. This increases the service life of
the device by up to 20 times compared with if diaphragm
pumps are used. In addition, the hoses of the
peristaltic pumps may be simply and quickly replaced by
a quick change system, so markedly reducing the time
expended on maintenance and repair of the device.
It is preferably possible for at least one hold-down
member for the engineered wood board to be arranged
upstream of each double-sided application device. In
this way, any deformation of the engineered wood board
which may occur during production may be remedied and
the engineered wood board to be coated may be fed
accurately and reproducibly to the respective double-
sided application device.

To convey the engineered wood boards inside the device
a pointed bar conveyor is used, in the form of pointed
bar conveyor chains, which are themselves robust and
not liable to break down and which ensure a high
surface quality of the coated engineered wood board.
The pointed bars may be cleaned automatically by means
of cleaning brushes.
Transfer of an engineered wood board from a double-
sided application device to the conveyor chain and vice
versa here proceeds by means of sheaves. On entry into
a double-sided application device or a drying device,
the above-described hold-down members in the form of
sheaves are additionally used.
In addition, a device for finishing an engineered wood
board may comprise further double-sided application
devices, with which the overall layer thickness and the
number and proportions of functional additives may be
increased. In this way, products may also be produced
which may be assigned to higher usage classes. The same
is true of the method according to the invention, in
which more than three resin layers may likewise be
applied to the top and bottom of the engineered wood
board to be coated.
If an electrical, in particular computer-aided,
controller is used to control a device as described
herein, it is possible to achieve a high level of
reproducibility of the resin layers applied, since both
the mixing proportions of resin and additives and also
the temperature control means, for example of the
drying devices and the short-cycle press, are
controlled automatically. In this way, a high quality
standard may be achieved for the products produced in
this manner. In addition, different states of curvature
of the engineered wood board to be coated, which may
arise for example due to the application of different

undercoat and decor layers, may be automatically
compensated by adjustment of the amounts applied to the
top and/or bottom.
An exemplary embodiment of the device according to the
invention will now be explained in greater detail with
reference to drawings, in which:
Figure 1 is a schematic plan view of an exemplary
embodiment of a device according to the
invention,
Figure 2 is a schematic plan view of a double-sided
application device and
Figure 3 shows the section along line A-A in Figure 2.
Figure 1 shows a device according to the invention in a
schematic plan view. The engineered wood boards 2 to be
finished are introduced into the device from the top
right in Figure 1. First of all, the top and bottom of
the engineered wood boards 2 are cleaned in a cleaning
device 4. Then, the engineered wood boards 2 are fed to
the first double-sided application device 6. The first
double-sided application device 6 comprises a top
application device 8 and a bottom application device
10, which in the exemplary embodiment shown take . the
form of application roller sets. In these application
roller sets a resin layer is applied to the top and
bottom of the engineered wood board to be coated.
Once the engineered wood boards 2 have passed through
the first double-sided application device 6, they reach
the first drying device 12. Here the resin layers
applied in the first double-sided application device 6
are dried down to a residual moisture content of 3%
to 6%.

A second double-sided application device and a second
drying device are not shown in Figure 1 for reasons of
space and clarity. These adjoin the first drying device
12 in the processing direction V, which is indicated by
small arrows in Figure 1.
In Figure 1 a third double-sided application device 14
follows in the processing direction V. This is of
identical construction to the first double-sided
application device 6. Once the engineered wood boards 2
have passed through the third double-sided application
device 14, the resin layers applied in the third
double-sided application device 14 are dried down in a
third drying device 16 to a residual moisture content
of 3% to 6%. Then the engineered wood boards pass
through the processing stations indicated merely as
squares in Figure 1, involving intermediate stacking
18, pressing in a short-cycle press 20 and quality
control 22.
Both the first double-sided application device 6 and
the second double-sided application device 14 each have
two mixing vessels 24, of which in each case one is
assigned to the top application devices 8 and one to
the bottom application device 10. In these mixing
vessels 24 the resin to be applied in the respective
application devices 8, 10 is mixed with the desired
additives.
These ingredients are stored separately from one
another in a storage magazine 26 in various storage
vessels 28. Each of these storage vessels 28 is
connected to the mixing vessels 24 via a feed line 30.
The desired ingredients are conveyed to the mixing
vessels 24 via these feed lines 30. In Figure 1 the
quantity of the individual ingredients is controlled by
an electrical controller 32, which is connected via
control lines 34 both to the storage magazine 26 and to
the ' mixing vessels 24. This makes it possible to

achieve a high quality standard and excellent
reproducibility of the resin layers applied.
In Figure 1 both the first double-sided application
device 6 and the third double-sided application device
14 are mounted on rails 36. The same is true of all the
double-sided application devices which are not shown.
In this way they may be straightforwardly moved out of
the production line for maintenance or repair or if
they are not needed for the desired layer structure and
subsequently moved back in again.
Figure 2 shows a schematic plan view of one of the
double-sided application devices 6, 14 shown in Figure
1. The engineered wood board 2 is fed in the processing
direction V to the double-sided application device 6,
14. The double-sided application device 6, 14 shown
comprises a top application device 8, which in Figure 2
takes the form of an application roller set. The same
is true of the bottom application device 10, which, as
in Figure 1 above, is not shown in Figure 2. The
double-sided application device 6, 14 in Figure 2
comprises two mixing vessels 24, the right-hand one of
which is assigned to the top application device 8. The
synthetic resin/additive mixture desired for the top
application device 8 is produced therein using an
agitator 38. The ingredients for this mixture are fed
via feed lines, not shown, from the storage vessels 28
of the storage magazine 26 of Figure 1 to the mixing
vessel 24. Both the filling level and the temperature
of the mixture are detected by way of sensors 40. The
material mixed in the right-hand mixing vessel 24 is
fed by way of a peristaltic pump 42 via material feed
lines 44 to the top application device 8.
Figure 3 shows a section along line A-A according to
Figure 2. The top application device 8 and the bottom
application device 10 each take the form of application
roller sets, which each have an application roller 46

and a metering roller 48. Along the material feed lines
44, which in Figure 3 as in Figure 2 are provided with
an arrow at the end, the material to be applied, which
has been mixed in the mixing vessels 24, is introduced
between the application roller 4 6 and the metering
roller 48. It is applied by the application roller 46
to the top or bottom of the introduced engineered wood
board 2. The engineered wood board 2 is conveyed both
upstream and downstream of the double-sided application
device 6, 14 shown via a "pointed bar conveyor" 50.
Because this apparatus 50 has only very few very small-
area contact points with the engineered wood board 2,
the good quality of the already coated engineered wood
board is ensured. The individual pointed bars 52 are
cleaned by means of automatic cleaning brushes 54.
To ensure reproducible and accurate feed of the
engineered wood board 2 into the application device 6,
14, hold-down members 56 may be arranged upstream and
downstream of the respective application devices 8, 10.
In this way it is ensured that the layers may be
applied reproducibly and accurately to the top and
bottom of the engineered wood board 2.
The further double-sided application devices not shown
in Figures 1 to 3 are of like construction. By means of
the rails 36 shown in Figure 1 they may be introduced
simply and without major effort into the production
line or moved out therefrom. They also make it possible
to change the device over quickly and simply to the
finishing of engineered wood boards with a different
layer structure.

List of reference signs
2 Engineered wood boards
4 Cleaning device
6 First double-sided application device
8 Top application device
10 Bottom application device
12 First drying device
14 Third double-sided application device
16 Third drying device
18 Intermediate stacking
20 Short-cycle press
22 Quality control
24 Mixing vessel
26 Storage magazine
28 Storage vessel
30 Feed line
32 Electrical controller
34 Control line
36 Rails
38 Agitator
40 Sensors
42 Peristaltic pump
44 Material feed line
46 Application roller
48 Metering roller
50 Pointed bar conveyor
52 Pointed bar
54 Cleaning brush
56 Hold-down member
V Processing direction

Patent claims
1. A method for finishing an engineered wood board
(2) comprising a decor on at least the top and/or the
bottom, which method comprises the following steps:
(a) cleaning the top and bottom of the engineered
wood board (2),
(b) applying a first top resin layer, which
contains corundum particles, to the top and a first
bottom resin layer to the bottom of the engineered wood
board (2),
(c) drying the first top resin layer and the first
bottom resin layer to a residual moisture content of 3%
to 6%,
(d) applying a . second top resin layer, which
contains cellulose, to the top and a second bottom
resin layer to the bottom of the engineered wood board
(2),
(e) drying the second top resin layer and the
second bottom resin layer to a residual moisture
content of 3% to 6%,
(f) applying an at least third top resin layer,
which contains glass particles, to the top and an at
least third bottom resin layer to the bottom of the
engineered wood board (2),
(g) drying the third top resin layer and the third
bottom resin layer to a residual moisture content of 3%
to 6%,
(h) pressing the multilayer structure under the
action of pressure and heat.

2. The method as claimed in claim 1, characterized
in that the third top resin layer contains around 20%
glass.
3. The method as claimed in claim 1 or claim 2,
characterized in that the second top resin layer
contains around 5% cellulose.
4. The method as claimed in claim 1, 2 or 3,
characterized in that the first top resin layer
contains around 20% corundum particles.
5. The method as claimed in one or more of the
preceding claims, characterized in that the top resin
layers and the bottom resin layers are applied in an
amount of 20 to 50 g/m2.
6. The method as claimed in one or more of the
preceding claims, characterized in that the top resin
layers and the bottom resin layers contain a 60%
synthetic resin solution.
7. The method as claimed in one or more of the
preceding claims, characterized in that a primer and an
undercoat are applied under the decor of the engineered
wood board (2) to be finished and the decor is printed
onto the undercoat and covered with a covering.
8. The method as claimed in one or more of claims
1 to 6, characterized in that the decor was applied to
the engineered wood board (2) by lamination in the form
of a decorative paper layer.
9. A device for finishing an engineered wood board
(2), at least a top and/or a bottom of the engineered
wood board (2) comprising a decor, having
(a) a first double-sided application device (6),

(b) a first drying device (12) arranged downstream
of the first double-sided application device (6) in a
processing direction (V),
(c) a second double-sided application device
arranged downstream of the first drying device (12) in
the processing direction (V),
(d) a second drying device arranged downstream of
the second double-sided application device in the
processing direction (V),
(e) at least one third double-sided application
device (14) arranged downstream of the second drying
device in the processing direction (V),
(f) at least one third drying device (16) arranged
downstream of the at least one third double-sided
application device (14) in the processing direction (V)
and
(g) a short-cycle press (20),
each double-sided application device comprising a top
application device (8) for applying a resin layer to
the top of the engineered wood board (2) and a bottom
application device (10) for applying a resin layer to
the bottom of the engineered wood board (2) and each
top application device (8) and each bottom application
device (10) in each case comprising a mixing vessel
(24), in which the resin to be applied in each case may
be mixed with at least one additive.
10. The device as claimed in claim 9, characterized
by a storage magazine (26) with a plurality of storage
vessels (28), in which the resin to be applied and the
additives may be stored separately from one another,

and feed lines (30) from the storage vessels (28) to
the mixing vessels (24).
11. The device as claimed in claim 10,
characterized by a controller (32), which is designed
to control the amount of resin and of additives
conveyed by the feed lines (30) into the mixing vessels
(24) .
12. The device as claimed in one or more of claims
9 to 11, characterized in that each top application
device (8) and each bottom application device (10) is
an application roller set.
13. The device as claimed in one or more of claims
9 to 12, characterized by peristaltic pumps (42) for
pumping the contents of the mixing vessels (24) to the
respective top application devices (8) and bottom
application devices (10).
14. The device as claimed in one or more of claims
9 to 13, characterized in that at least one hold-down
member (56) for the engineered wood board (2) is
arranged upstream of each double-sided application
device.

A method for finishing an engineered wood board (2)
comprising a decor layer on at least the top and/or the
bottom comprises the following steps:
(a) cleaning the top and bottom of the engineered wood
board (2),
(b) applying a first top resin layer, which contains
corundum particles, to the top and a first bottom
resin layer to the bottom of the engineered wood
board (2),
(c) drying the first top resin layer and the first
bottom resin layer to a residual moisture content
of 3% to 6%,
(d) applying a second top resin layer, which contains
cellulose, to the top and a second bottom resin
layer to the bottom of the engineered wood board
(2),
(e) drying the second top resin layer and the second
bottom resin layer to a residual moisture content
of 3% to 6%,
(f) applying an at least third top resin layer, which
contains glass particles, to the top and an at
least third bottom resin layer to the bottom of
the engineered wood board (2),
(g) drying the third top resin layer and the third
bottom resin layer to a residual moisture content
of 3% to 6%,

(h) pressing the multilayer structure under the action
of pressure and heat.