U.S. patent application number 11/897133 was filed with the patent office on 2008-08-14 for process for the production of polyurethane sandwich elements.
Invention is credited to Michael Begemann, Reiner Raffel, Jurgen Wirth.
Application Number | 20080191374 11/897133 |
Document ID | / |
Family ID | 34177877 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080191374 |
Kind Code |
A1 |
Begemann; Michael ; et
al. |
August 14, 2008 |
Process for the production of polyurethane sandwich elements
Abstract
The present invention relates to a process for the continuous
production of polyurethane sandwich elements comprising an upper
outer layer and a lower outer layer and a layer of cellular
polyurethane lying in between, which is firmly bonded to the outer
layers. This invention also relates to an apparatus suitable for
the production of polyurethane sandwich elements as described
above.
Inventors: |
Begemann; Michael; (Lintach,
DE) ; Wirth; Jurgen; (Koln, DE) ; Raffel;
Reiner; (Siegburg, DE) |
Correspondence
Address: |
LUCAS & MERCANTI, LLP
475 PARK AVENUE SOUTH, 15TH FLOOR
NEW YORK
NY
10016
US
|
Family ID: |
34177877 |
Appl. No.: |
11/897133 |
Filed: |
August 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10942663 |
Sep 16, 2004 |
7278842 |
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11897133 |
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Current U.S.
Class: |
264/46.3 |
Current CPC
Class: |
B29C 67/246 20130101;
B32B 5/20 20130101; Y10T 156/1732 20150115; B29K 2075/00 20130101;
B29C 44/326 20130101; B29C 2043/483 20130101; B32B 2266/0278
20130101 |
Class at
Publication: |
264/46.3 |
International
Class: |
B29C 44/10 20060101
B29C044/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2003 |
DE |
10343745.2 |
Claims
1. A process for the continuous production of polyurethane sandwich
elements comprising an upper outer layer, a lower outer layer and a
layer of cellular polyurethane lying in between and which is firmly
bonded to the outer layers, said process comprising: a)
continuously conveying the two outer layers in the longitudinal
direction such that a gap extending in the longitudinal direction
of the outer layers is formed between the outer layers, b) applying
the polyurethane reaction mixture pro rata from a position above
the upper side of the lower outer layer and onto the upper side of
the lower outer layer, and from a position below the under-side of
the upper outer layer and onto the under-side of the upper outer
layer, c) feeding the outer layers with the polyurethane reaction
mixture into a shaping zone in which the thickness of the
polyurethane sandwich element is established and in which the
polyurethane reaction mixture reacts, and d) removing the resultant
polyurethane sandwich element off the conveying means, wherein the
ratio of the material flow of the polyurethane reaction mixture
applied to the upper outer layer to the material flow of the
polyurethane reaction mixture applied to the lower outer layer is
between 0.001:1 and 0.2:1.
2. The process of claim 1, wherein the ratio of the material flow
of the polyurethane reaction mixture applied to the upper outer
layer to the material flow of the polyurethane reaction mixture
applied to the lower outer layer is between 0.002:1 and 0.1:1.
3. The process of claim 1, wherein the ratio of the material flow
of the polyurethane reaction mixture applied to the upper outer
layer to the material flow of the polyurethane reaction mixture
applied to the lower outer layer is between 0.005:1 and 0.05:1.
4. The process of claim 1, in which applying of the polyurethane
reaction mixture to the upper outer layer is by spraying with a
spray mixing head, and the spray zone is demarcated by films or
paper webs which move at an average advance of 0.1 to 10 m/h, in a
plane parallel to the upper outer layer.
5. The process of claim 4, in which any scattered aerosols or
scattered mists formed during spraying are sucked off at the narrow
sides of the spray zone.
6. The process of claim 4, in which the spray mixing head
oscillates transversely to the direction of movement of the upper
outer layer, the translatory distance covered by the spray mixing
head being set smaller than the width of the upper outer layer and
the spray mixing head being swiveled outwards at the ends of the
distance covered, such that the edge regions of the upper outer
layer are also sprayed.
7. The process of claim 1, in which a first mixing head and a
second mixing head apply the reaction components to the outer
layers with the reaction components conveyed to the first mixing
head and to the second mixing head with common metering units and
the division of the material flows for the first mixing head and
for the second mixing head is effected by a flow distributor.
8. The process of claim 7, in which the common metering units and
flow distributor are adjustable.
9. The process of claims 1, in which an auxiliary substance is
injected online into one or more of the reaction components before
the mixing of the reaction components in the first or second mixing
head.
10. The process of claim 9, wherein said auxiliary substance
comprises a catalyst.
11. The process of claim 1, in which the polyurethane reaction
mixture is applied to the upper and the lower outer layer with a
time interval, such that the polyurethane reaction mixture remains
longer on the upper outer layer than on the lower outer layer,
before both outer layers enter into the shaping zone.
12. The process of claim 1, in which the polyurethane reaction
mixture is applied to the upper outer layer by the dipping
process.
13. An apparatus for the continuous production of polyurethane
sandwich elements comprising an upper outer layer, a lower outer
layer, and a layer of cellular polyurethane lying in between the
outer layers and which is firmly bonded to the outer layers, and
which comprises a circulating upper belt for guiding the upper
outer layer, a circulating lower belt for guiding the lower outer
layer, a feed device for feeding the upper outer layer onto the
circulating upper belt, a feed device for feeding the lower outer
layer onto the circulating lower belt, a first mixing head arranged
above the lower outer layer to apply the polyurethane reaction
mixture to the lower outer layer, a second mixing head arranged
below the upper outer layer to apply the polyurethane reaction
mixture to the upper outer layer, a metering device to meter the
reaction components to the first mixing head, to the second mixing
head, and to the lines between the metering device and the first
and the second mixing heads, with the second mixing head being a
spray mixing head wherein the spray zone in which the scattered
mists caused by the spraying form are demarcated from the
environment by films or paper webs.
14. The apparatus of claim 13, additionally comprising a
length-cutting device for the polyurethane sandwich element.
15. The apparatus of claim 13, in which the films or paper webs are
moved at an average advance of 0.1 to 10 m/h in a direction
perpendicular to the direction of movement of the upper layer, and
this movement is either continuous or intermittent.
16. The apparatus of claim 15, in which the films or paper webs are
in a plane parallel to the upper outer layer and in which suction
devices are arranged at the open narrow sides of the spray
zone.
17. The apparatus of claim 16, having a total of four suction
devices, with the first two suction devices being arranged such
that these are on opposite sides of the spray mixing head with one
suction device being at the open narrow side of the spray zone
close to the outer edges of the upper outer layer, and the last two
suction devices being arranged such that these are on opposite
sides of the spray mixing head with one suction device being in
front of the spray mixing head and the other being behind the spray
mixing head.
18. The apparatus of claim 13, in which the second mixing head
oscillates transversely to the direction of movement of the upper
outer layer, with the translatory distance covered by the second
mixing head being adjustable, and in which the second mixing head
swivels outwardly at the end points of the distance covered.
19. The apparatus of claim 13, in which the second mixing head (34)
and, optionally, the films or paper webs which limit the spray
region can be moved away or swiveled away.
20. The apparatus of claim 13, in which the metering device for
each reaction component comprises only one common metering unit
with which the reaction component is conveyed to the first and to
the second mixing head, and one flow distributor with which the
metered material flow of reaction component is distributed to the
first and the second mixing head.
21. The apparatus of claim 20, in which the metering units and flow
distributors are adjustable.
22. The apparatus of claim 13, additionally comprising means for
injecting additional auxiliary substances in which the means for
injecting are arranged in the lines between the metering device and
the first and/or the second mixing heads.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a process for the
production of polyurethane sandwich elements (so-called panels) in
which the polyurethane reaction mixture is applied both to the
upper and to the lower outer layer, and then the outer layers which
are wetted with polyurethane reaction mixture are brought into
contact with one another. This invention also relates to an
apparatus for the production of these polyurethane sandwich
elements (i.e. panels).
[0002] Polyurethane sandwich elements (i.e. panels) are, in
general, produced by a continuous process. In this process, the
panels are produced as a continuous product on so-called Contimats
in thicknesses of, as a rule, approx. 20 to 200 mm. However,
thicknesses of less than 20 mm and of more than 200 mm are also
possible. Such a Contimat in this context conventionally comprises
a circulating upper belt for guiding the upper outer layer and a
circulating lower belt for guiding the lower outer layer, a feed
device for the upper outer layer, a feed device for the lower outer
layer, a shaping zone within which the polyurethane reaction
mixture foams and reacts between the upper outer layer and the
lower outer layer, a length-cutting device for the panel produced,
and a metering station with a mixing head for application of the
polyurethane reaction mixture to the lower outer layer. A Contimat
according to the prior art is shown in FIG. 1.
[0003] In the case of panels with sheet metal outer layers, a
polyurethane layer with a bulk density of 45.+-.5 kg/m.sup.3 is
conventionally present between the upper and the lower outer layer.
However, it is desirable in this context to establish the lowest
possible bulk densities of, for example, 40 kg/m.sup.3 or, for
example, of even only 38 kg/m.sup.3, in order to minimize the
amount of starting substances consumed.
[0004] For various reasons, however, technical problems arise here.
On the one hand, the complete filling of the canted edge zones of
sheet metal outer layers is inadequate at a low bulk density. On
the other hand, in the case of thin panels, such as, for example 20
mm thick, the distribution of the polyurethane reaction mixture is
not uniform at a low bulk density. This is particularly a problem
at a relatively high belt speed of, for example, above 30 m/min. In
both cases, panels of lesser quality or waste consequently result.
A further problem is the low adhesion between the polyurethane foam
and the upper sheet metal outer layer at low bulk densities. This,
in turn, can lead to panels of lesser quality or waste.
[0005] To avoid problems such as these, the panels are typically
produced with increased bulk densities of conventionally 45 to 50
kg/m.sup.3, i.e. the so-called "overpacking" technique. In
"overpacking", the material flow of polyol, isocyanate, and blowing
agent, and thus of polyurethane foam are increased, and the foaming
pressure is also increased. This results in the adequate filling of
the canted edge zones. The increased foaming pressure results here
from the increased amounts of polyurethane reaction mixture and
blowing agent, which leads to foaming of the polyurethane foam, and
therefore to a build up of pressure in the closed-off space between
the upper outer layer and the lower outer layer in the shaping
zone. At a higher material flow, the distribution of the
polyurethane reaction mixture on the lower outer layer is, of
course, also better. The adhesion of the polyurethane reaction
mixture to the upper sheet metal outer layer is likewise improved
by the higher material flow, but above all by the higher foaming
pressure.
SUMMARY OF THE INVENTION
[0006] The object of the present invention is to provide a simple
and economical process and a suitable apparatus for the production
of polyurethane sandwich elements with low bulk densities of, for
example, 38 to 40 kg/m.sup.3.
[0007] The present invention relates to a process for the
continuous production of polyurethane sandwich elements comprising
an upper outer layer, a lower outer layer, and a layer of cellular
polyurethane lying in between the upper and lower outer layers, and
which is firmly bonded to the upper and lower outer layers. This
process comprises [0008] a) continuously conveying the two outer
layers in the longitudinal direction such that a gap extending in
the longitudinal direction of the outer layers is formed between
the outer layers, [0009] b) applying the polyurethane reaction
mixture pro rata from above to the upper side of the lower outer
layer and from the below to the under-side of the upper outer
layer, [0010] c) feeding the outer layers with the polyurethane
reaction mixture into a shaping zone in which the thickness of the
polyurethane sandwich element is established and in which the
polyurethane reaction mixture reacts, and [0011] d) removing the
resultant polyurethane sandwich element off the conveying
means.
[0012] In this process, the ratio of the material flow of the
polyurethane reaction mixture applied to the upper outer layer to
the material flow of the polyurethane reaction mixture applied to
the lower outer layer is between 0.001:1 and 0.2:1, preferably
between 0.002:1 and 0.1:1 and most preferably between 0.005:1 and
0.05:1.
BRIEF DESCRIPTION OF THE FIGURES
[0013] FIG. 1 shows a side view of a typical prior art
device/apparatus for the production of polyurethane sandwich
elements.
[0014] FIG. 2 shows a side view of a device or apparatus according
to the invention, for the production of polyurethane sandwich
elements in which the second mixing head is a spray mixing
head.
[0015] FIG. 3 shows a side view of a device or apparatus according
to the present invention for the production of polyurethane
sandwich elements in which the second mixing head is a spray mixing
head and the spray zone is limited by a mobile spray booth.
[0016] FIG. 4 shows a cross-section at plane A-A in FIG. 3 through
the mobile spray booth.
[0017] FIG. 5 shows a cross-section at plane B-B in FIG. 4 through
the mobile spray booth.
DETAILED DESCRIPTION OF THE INVENTION
[0018] In the process according to the present invention, the
liquid polyurethane reaction mixture is applied to the lower outer
layer as in conventional processes, and also to the upper outer
layer. This results in the canted edge zones also being filled
completely in the upper metal sheet. At the same time, a
non-uniform distribution of the polyurethane reaction mixture on
the lower outer layer is compensated for. The adhesion of the
polyurethane foam to the upper outer layer is improved decisively
by the liquid wetting.
[0019] The material ratio of the polyurethane reaction mixture
applied to the upper outer layer and to the lower outer layer, and
therefore, the thickness of the film of polyurethane reaction
mixture applied to the under-side of the upper outer layer are of
decisive importance for the process according to the invention. The
thickness of the film must be chosen according to the forces of
adhesion and cohesion, such that dripping of the polyurethane
reaction mixture from the upper outer layer on to the lower outer
layer is avoided. If this is not the case, defects in the panel
occur and waste results.
[0020] The film thicknesses preferably produced in the liquid
polyurethane reaction mixture applied to the under-side of the
upper outer layer are in the range from 10 to 450 .mu.m, more
preferably in the range from 50 to 300 .mu.m, and most preferably
in the range from 100 to 200 .mu.m. These thicknesses can be
increased by a factor of 1.5 to 5 if the polyurethane reaction
mixture is frothed. A frothed polyurethane reaction mixture
comprises, for example, 0.1 to 4 parts by weight of CO.sub.2 per
100 parts of polyurethane reaction mixture.
[0021] To ensure complete adhesion, the surfaces in contact with
the polyurethane reaction mixture are preferably cleaned and
degreased before application of the polyurethane reaction mixture.
To increase the forces of adhesion still further, an additional
chemical or electrochemical pre-treatment, or the application of an
adhesion promotor before application of the polyurethane reaction
mixture is also possible.
[0022] Polyurethane sandwich elements (panels) often have highly
structured lower outer layers, and, when and/or where appropriate,
also upper outer layers. In this case, the outer layers provided
with deeper structures are in principle fed at the bottom in the
processes for the production of the panels, so that the
polyurethane reaction mixture penetrates easily into the structures
by the influence of gravity and can fill these completely. By the
process according to the invention, it is now also possible for the
surfaces present in the upper outer layer to be filled completely
with the polyurethane reaction mixture before the upper and lower
outer layers are brought together in the shaping zone.
[0023] In a preferred embodiment, the polyurethane reaction mixture
is applied to the upper outer layer with a spray mixing head, and
the spray zone is demarcated by films or paper webs so that the
scattered mist which forms is collected. The spray zone here is the
space below the upper outer layer, in which the scattered mists
arises from the spraying form. The films or paper webs here are
arranged substantially planar-parallel to the upper outer layer. In
other words, the films or paper webs are located in planes that are
parallel to the upper outer layer. It is particularly preferred
that one film or paper web is located in the plane above (and
parallel to) the upper outer layer and another film or paper web is
located in the plane below (and parallel to) the upper outer layer.
By placing one film or paper web above and another one below the
upper outer layer, the spray zone is demarcated. The films or paper
webs are preferably moved at an average advance of 0.1 to 10 m/h,
more preferably 0.1 to 5 m/h and most preferably 0.1 to 3 m/h. As
previously stated, the films or paper webs are in planes that are
parallel to the upper outer layer. These films or paper webs
preferably perpendicularly to the direction of movement of the
upper outer layer. The scattered aerosols or scattered mists are
preferably sucked off here at the narrow sides of the spray zone by
suitable suction devices.
[0024] The spray mixing head preferably oscillates transversely to
the direction of movement of the upper outer layer. At relatively
low transportation speeds (i.e. <30 m/min) of the outer layers,
the spray mixing head can traverse the entire width of the spray
region. At higher transportation speeds of the outer layers,
however, the accelerations in the turning points become very
high.
[0025] Thus, the translatory distance covered by the spray mixing
head transversely to the direction of movement of the upper outer
layer can preferably be adjusted. The spray mixing head preferably
oscillates only in a shortened range which can be adjusted, for
example, by or on a linear scale. At the end points of the distance
covered, the spray mixing head is swiveled outwards in the
direction of the distance covered, so that the edge regions of the
upper outer layer are also sprayed, without the spray mixing head
having to travel to the edge of the upper outer layer.
[0026] The canted edges, such as occur, for example, with sheet
metal outer layers, are therefore covered in the present case,
before applying the polyurethane reaction mixture by a protective
film. This film is peeled off after the panel has been
finished.
[0027] As a rule, a polyurethane reaction mixture of the same
composition is applied to both the lower and to the upper outer
layers. The mixing heads assigned to the upper and the lower outer
layers can then be supplied with the reacting components of
isocyanate and polyol from the same working tanks. Two variations
are possible in this context. Either each mixing head and each
component is provided with its own metering pump, or both mixing
heads are supplied by a common metering pump for one component,
with the material flows then being adjusted for each mixing head by
a flow divider downstream of the metering pump. It is preferred
that the metering pumps and the flow dividers are adjustable.
[0028] Toothed wheel flow dividers are suitable, for example, to be
employed as the flow dividers.
[0029] One or more auxiliary substances can also be injected into
the reaction components before they are mixed. For example, a
catalyst can be added into the polyol component which is being
conveyed to the mixing head assigned to the lower outer layer, in
order to influence the rate of the polyurethane reaction on the
lower outer layer. This makes it is possible to accelerate the rate
of the formation of polyurethane on the lower outer layer in
comparison to the rate of formation of polyurethane on the upper
outer layer.
[0030] It is preferred, and in some cases may be necessary, to
accelerate the rate of formation of polyurethane on the lower outer
layer. One reason for this may be that the angle formed by the
upper and the lower outer layer on entry into the shaping zone is
as a rule relative small, e.g. the angle may be 5-40.degree..
Therefore, for construction reasons, the two mixing heads must be
arranged one after the other. As a rule, in this context the mixing
head with which the upper outer layer is charged with polyurethane
reaction mixture is arranged, in the direction of transportation of
the outer layers, before the mixing head with which the lower outer
layer is charged with polyurethane reaction mixture. In order to
achieve reaction and foaming of the polyurethane reaction mixtures
on the upper and the lower outer layer at about the same time, the
reaction of the polyurethane reaction mixture on the lower outer
layer must, therefore, generally be accelerated.
[0031] In a particularly preferred embodiment of the process, the
start times (also commonly referred to as lay times or cream time)
of the polyurethane reaction mixtures on the upper and the lower
outer layers are adjusted. These are typically adjusted such that
the polyurethane reaction mixture on the upper outer layer starts
about when the foam formed from the polyurethane reaction mixture
on the lower outer layer reaches the polyurethane reaction mixture
on the upper outer layer.
[0032] The entire spray region, that is to say the spray mixing
head assigned to the upper outer layer and, where appropriate, the
films or paper webs, can be moved away or swiveled away during
production pauses and/or after the end of production.
[0033] In an alternative embodiment, the polyurethane reaction
mixture can be applied to the upper outer layer by the dipping
process. This process is particularly advantageous when flat upper
outer layers are used, because the polyurethane reaction mixture
can then be applied to the upper outer layer in a thin film. In
this case the edges of the upper outer layers must initially be
masked with a protective film. The protective films are typically
peeled off before bringing together the upper outer layer with the
lower outer layer.
[0034] Furthermore, the present invention relates to a device or
apparatus for the continuous production of polyurethane sandwich
elements comprising an upper outer layer, a lower outer layer and a
layer of cellular polyurethane lying in between the upper outer
layer and the lower outer layer, and which is firmly bonded to the
upper and lower outer layers. This apparatus comprises a
circulating upper belt for guiding the upper outer layer, a
circulating lower belt for guiding the lower outer layer, a feed
device for feeding the upper outer layer onto the circulating upper
belt, a feed device for feeding the lower outer layer onto the
circulating lower belt, optionally a length-cutting device for the
polyurethane sandwich element, a first mixing head arranged above
the lower outer layer for application of the polyurethane reaction
mixture to the lower outer layer and a second mixing head arranged
below the upper outer layer for application of the polyurethane
reaction mixture to the upper outer layer, a metering device for
metering the reaction components to the first mixing head, to the
second mixing head, and to the lines between the metering device
and the first and the second mixing heads. It is preferred that the
second mixing head is a spray mixing head, and the spray zone in
which the scattered mists caused by the spraying form are
demarcated from the environment by films or paper webs.
[0035] A spray mixing head which is arranged below the upper outer
layer and the discharge channel and spray nozzle of which are
directed against the under-side of the upper outer layer is
preferably employed as the second mixing head. It is also possible,
in principle, also to charge the upper outer layer with
polyurethane reaction mixture from the top. However, since the
surface structures which are often present in the upper top layer
(crimping) severely limit the flexibility of the upper outer layer.
These surface structures make the upper outer layer rigid, and
thus, the upper outer layer can no longer be deflected when such
surface structures are present. In the present invention, provision
is therefore made, to spray the upper outer layer with polyurethane
reaction mixture with a spray mixing head from the bottom. The
device according to the invention can therefore be employed very
flexibly for smooth upper outer layers and for surface-structured
upper outer layers. The use of a spray mixing head in the present
invention results in the upper outer layer being coated very
uniformly and homogeneously.
[0036] Spray mixing heads are distinguished in that the
polyurethane reaction mixture to be discharged can be atomized and
discharged at an increased speed by them. The spray mixing heads,
in this context, in general have a mixing device with which the
polyurethane reaction components to be mixed can be mixed. Suitable
mixing devices include, for example, stirrer mixers, nozzle mixers,
counter-current injection mixers or static mixers. A spray device
such as, for example a spray nozzle, is arranged downstream of the
mixing device. In this context both spray nozzles which are
operated without air assistance and spray nozzles in which air or
nitrogen can be admixed to the polyurethane reaction mixture before
the spray nozzle are suitable. Spraying is assisted by the gas
expansion which then develops behind such spray nozzles. However,
spraying with air or nitrogen, in particular, leads to an increased
aerosol formation. However, above approx. 500 mPas, spraying
practically only with air or nitrogen assistance is possible.
[0037] During spraying of the polyurethane reaction mixture,
scattered aerosols or scattered mists are formed. These spread in
the environment and lead to severe contamination in the long term.
For this reason, the spray zone in which the scattered mists caused
by the spraying is demarcated from the environment by films or
paper webs.
[0038] The films or paper webs can be, and preferably are, moved
continuously or intermittently with an average advance of 0.1 to 10
m/h. The direction of movement of the films or paper webs is
preferably perpendicular to the direction of movement of the upper
outer layer.
[0039] It is also preferable that the films or paper webs are
arranged such that they are parallel to, or substantially parallel,
to the upper outer layer. In other words, these films or paper webs
are in a plane that is parallel to or substantially parallel to the
plane the upper outer layer resides in. There are preferably two
films or paper webs, one being above the upper outer layer and one
being below the upper outer layer. In addition, suction devices are
preferably arranged at the open narrow sides of the spray zone.
These suction devices are preferably located below the upper outer
layer but above the film or paper web which is below the upper
outer layer. The films or paper webs arranged approximately
parallel to the upper outer layer and the suction devices arranged
at the narrow sides of the spray zone thus form a spray booth which
is demarcated from the environment in all spatial directions.
[0040] In one advantageous embodiment of the invention, the second
mixing head can be oscillated transversely to the direction of
movement of the upper outer layer, with it being possible to adjust
the translatory distance covered by the second mixing head. This
adjustment to the distant covered can be, e.g. by means of a linear
scale. In addition, the second mixing head can also preferably be
swiveled outwards in the direction of the distance covered at the
end points of the distance covered, so that during spraying the
edge regions of the upper outer layer can also be sprayed, without
the spray mixing head having to move to the edge of the upper outer
layer.
[0041] In a further embodiment, the second mixing head and the
films or paper webs with which the spray region is limited can be
moved away or swiveled away.
[0042] Preferably, the metering device contains, for each reaction
component, only one common metering unit with which the reaction
component is conveyed to the first and to the second mixing heads,
and one flow distributor with which the metered material flow of
reaction component is distributed to the first and the second
mixing heads. The metering units such as, for example metering
pumps, and the flow distributors are preferably adjustable.
[0043] Toothed wheel flow distributors can, for example, be
employed as the flow distributors.
[0044] In one embodiment of the process, a means for passing in or
injection of additional auxiliary substances are arranged in the
lines between the metering device and the first and/or the second
mixing heads. Pressure or servo-controlled nozzles or simple
valves, for example, are suitable. Here, it is essential that they
guarantee complete closure of the injection point when metering is
stopped. A catalyst, for example, can thus be added to the polyol
component in order to influence the rate of the polyurethane
reaction.
DETAILED DESCRIPTION OF THE FIGURES
[0045] Reference will now be made to the figures to more clearly
define the apparatus.
[0046] FIG. 1 illustrates a prior art device 1 for the production
of polyurethane sandwich elements as is known and described in the
prior art. FIG. 1 is a side-view of a prior art apparatus. In this
apparatus, a lower outer layer 2 and an upper outer layer 3 are
conveyed continuously by corresponding upper and lower feed devices
(not shown) into the gap which extends in the longitudinal
direction between the circulating upper belt 4 and the circulating
lower belt 5, the so-called shaping zone, and guided therein.
[0047] The polyol component A and the isocyanate component B are
conveyed from the respectively assigned working tanks 6 and 7 via
assigned pumps and lines to the mixing head 8 where they are mixed.
The polyurethane reaction mixture formed by this mixing is applied
to the lower outer layer 2 by the mixing head 8 as it is traversing
over the width of the lower outer layer 2 transversely to the
direction of transportation of the lower outer layer 2. The
polyurethane reaction mixture applied to the lower outer layer 2
foams and is transported by the longitudinal movement of the lower
outer layer 2 into the shaping zone which is spanned by the
circulating upper belt 4 and the circulating lower belt 5. In the
shaping zone, the polyurethane reaction mixture between the upper
outer layer 3 and the lower outer layer 2 foams and reacts, so that
after passing through the shaping zone a polyurethane sandwich
element is obtained, which can optionally then be cut to any
desired length and worked further.
[0048] Reference will now be made to FIG. 2, a side view in
elevation of an apparatus which illustrates an embodiment of the
present invention. FIG. 2 illustrates an apparatus 21 suitable for
carrying out the process according to the present invention for the
production of polyurethane sandwich elements, in which the upper
outer layer 23 is sprayed with polyurethane reaction mixture with a
spray mixing head 34. In this embodiment, the lower outer layer 22
and the upper outer layer 23 are being conveyed continuously by
correspondingly assigned feed devices 29 and 30 into the gap
extending in the longitudinal direction between the circulating
upper belt 24 and the circulating lower belt 25, and are guided
therein.
[0049] The polyol component A and the isocyanate component B are
conveyed from the respective working tanks 26 and 27 via respective
pumps 31 and 32 and corresponding lines to the mixing head 33 which
is assigned to the lower outer layer and to the mixing head 34
which is assigned to the upper outer layer. In each case, the
polyol component and isocyanate component are mixed in the mixing
heads, and the polyurethane reaction mixture thereby formed is
applied to the lower outer layer 22 and to the upper outer layer
23. The mixing head 34 is constructed here as a spray mixing head.
Conveying of the components is effected here in a manner such that
component A is conveyed by the pump 31 to an adjustable flow
distributor 35, where it is divided into the set ratio there, and
is fed via correspondingly assigned lines to the lower mixing head
33 and to the upper mixing head 34. In an analogous manner,
component B is conveyed by metering pump 32 to the adjustable flow
distributor 36, divided there into the set ratio, and fed to the
upper and lower mixing heads 33 and 34.
[0050] The polyurethane reaction mixture applied to the lower outer
layer 22 and the upper outer layer 23 foams and is transported by
the longitudinal movement of the outer layers 22 and 23 into the
shaping zone, which is spanned by the circulating upper belt 24 and
the circulating lower belt 25.
[0051] In the shaping zone, the polyurethane reaction mixture
between the upper outer layer 23 and the lower outer layer 22 foams
and reacts, so that after passing through the shaping zone a
polyurethane sandwich element is obtained. This resultant
polyurethane sandwich element can then be cut (if desired) to the
desired length in the length-cutting device 37.
[0052] Reference will now be made to FIG. 3 which illustrates a
side view of an advantageous embodiment of the apparatus as shown
in FIG. 2. The apparatus 41 according to the invention additionally
comprises a reservoir tank 48 for an auxiliary substance C which
may be, for example, a catalyst. The auxiliary substance C is
metered via metering pump 54 into the line 56 which runs between
the flow distributor 55 for component A and the mixing head 53
which is assigned to the lower outer layer. This auxiliary
substance C is mixed into component A in the line 56 by means of
the static mixer 57. The auxiliary substance C is introduced into
the line 56 here, for example, by means of a servo-controlled
nozzle 58. In addition, FIG. 3 shows the mobile spray booth 60 by
which the spray zone in which the scattered mists caused by the
spraying are formed are demarcated from the environment by films or
paper webs. The mobile spray booth 60 is shown in detail in FIG. 4
(section A-A in FIG. 3) and in FIG. 5 (section B-B in FIG. 4).
[0053] Reference will now be made to FIG. 4 which illustrates the
cross-section along plane A-A of the spray booth 60 shown in FIG.
3. The spray booth 60 has an upper wind-off roller 61 and a lower
wind-off roller 63, and an upper wind-up roller 62 and a lower
wind-up roller 64 for the upper and lower films or paper webs 65,
and, respectively. Suction devices 67 and 68 which suck up the
scattered aerosols formed during spraying, are arranged at the
narrow sides of the mobile spray booth 60.
[0054] The lower film or paper web 66 is separated approximately in
the middle by means of a fixed blade 71, so that a slit (shown as
slit 72 in FIG. 5) is formed, through which the discharge tube 73
and the spray nozzle 74 of the mixing head 75 can oscillate. While
the upper film or paper web 65 can be supported on the upper outer
layer 76, additional supports 77 are attached for the lower slit
film or paper web 66. The upper film or paper web 65 does not
necessarily touch the upper outer layer 76. As described previously
in a preferred embodiment, the upper film or paper web 65 is
preferably in a plane located parallel (or substantially parallel)
to the plane in which the upper outer layer 76 is located.
[0055] The oscillation range 78 of the spray mixing head 75 can be
adjusted by means of a linear scale 79. Suitable swiveling devices
(not shown) with which the mixing head 75 can be swiveled outwards
in order to spray the entire spray region 82 are provided at the
left-hand and right-hand limits, 80 and 81, respectively, of the
oscillation range 78. The left-hand and right-hand limits 80 and 81
represent the turning points of the spray mixing head 75.
[0056] Reference will now be made to FIG. 5 which illustrates the
cross-section at B-B of the spray booth 60 as shown in FIG. 4. FIG.
5 shows, in particular, the edge of the lower wind-off roller 63,
the edge of the lower wind-up roller 64, the lower film or paper
web 66, the slit 72 produced by means of a blade (shown as blade 71
in FIG. 4). It is through this slit 72 that the discharge tube 73
and the spray nozzle of the mixing head 75 traverse, and the
suction devices 67, 68, 69, and 70 are arranged at the narrow sides
of the spray booth.
[0057] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *