Note: Descriptions are shown in the official language in which they were submitted.
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LIGNOCELLULOSIC MATERIALS WITH EXPANDED PLASTICS PARTICLES PRESENT IN
NONUNIFORM DISTRIBUTION IN THE CORE
Description
The present invention relates to lignocellulosic materials having a core and
two outer layers, the
core comprising expanded plastics particles in nonuniform distribution.
CH-A-370 229 discloses compression moldings which possess both light weight
and compressive
strength and which consist of wood chips or wood fibers, a binder, and a
porous, foamable or
partly foamable, plastic that serves as filler.
A disadvantage of these compression moldings is that they do not have plastics-
free outer layers,
meaning that customary coating technologies (e.g., lining with furniture foil
or short-cycle coating
with melamine films) lead to poor results.
DE-U-20 2007 017 713 discloses weight-reduced chipboard panels through
combination of wood
chips and evenly distributed foamed polystyrene beads in the middle ply of the
panel.
A disadvantage of these materials is that the flexural strength, the screw
pullout resistance and
the surface quality are not sufficient for all applications.
WO-A-2008/046890 discloses lightweight, single-ply and multi-ply woodbase
materials which
comprise wood particles, a filler of polystyrene and/or styrene copolymer
having improved
transverse tensile strengths, a bulk density of 10 to 100 kg/ma, and binder.
The filler is
advantageously evenly distributed within the woodbase material.
A disadvantage of these materials is that an improvement in the properties for
a given panel
density is achievable only with an increase in the amount of glue and/or the
amount of polymer
and hence with an increase in the costs.
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It was an object of the present invention, therefore, to remedy the
disadvantages recited above,
and more particularly to provide lightweight lignocellulosic materials having
improved transverse
tensile strengths, improved flexural strengths, improved screw pullout values
and/or good surface
properties, these materials continuing to possess good processing properties,
like conventional
high-density woodbase materials.
Found accordingly have been new and improved lignocellulosic materials having
a core and two
outer layers and comprising or, preferably, consisting of, in the core
A) 30% to 98% by weight of lignocellulose particles;
6) 1% to 25% by weight of expanded plastics particles having a bulk density
in the range
from 10 to 150 kg/m3,
C) 1% to 50% by weight of one or more binders selected from the group
consisting of
aminoplast resin, phenoplast resin, and organic isocyanate having at least two
isocyanate
groups, and
D) 0% to 10% by weight of additives
and in the outer layers
E) 70% to 99% by weight of lignocellulose particles,
F) 1% to 30% by weight of one or more binders selected from the group
consisting of
aminoplast resin, phenoplast resin, and organic isocyanate having at least two
isocyanate
groups, and
G) 0% to 10% by weight of additives,
wherein the lignocellulose particles of the outer layers E comprise at least
25% by weight of
lignocellulosic chips and the expanded plastics particles B are present in
nonuniform distribution
in the core, and also processes for producing them, and their use.
The statement of the percent by weight of components A, B, C, D, E, F and G
relates to the dry
weight of the component in question as a proportion of the overall dry weight.
The sum total of the
percent by weight figures for components A, B, C and D is 100% by weight. The
sum total of
components E, F and G likewise makes 100% by weight. In addition, not only the
outer layers but
also the core comprise water, which is not taken into account in the weight
figures. The water may
originate from the residual moisture present in the lignocellulose particles,
from the binder, from
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additionally added water, for dilution of the binders or for moistening of the
outer layers, for
example, or from the additives, such as aqueous curing agent solutions or
aqueous paraffin
emulsions, for example, or else from the expanded plastics particles when they
are foamed, for
example, using steam. The water content of the core and of the outer layers
can be up to 20% by
weight, i.e., 0% to 20% by weight, preferably 2% to 15% by weight, more
preferably 4% to 10% by
weight, based on 100% by weight overall dry weight. The ratio of the overall
dry mass of the core
to the overall dry mass of the outer layers is generally 100:1 to 0.25:1,
preferably 10:1 to 0.5:1,
more preferably 6:1 to 0.75:1, more particularly 4:1 to 1:1.
Expandable plastics particles B nonuniformly distributed in the core means
that the weight ratio X
(based on dry mass) of expanded plastics particles B to lignocellulose
particles A in the outer
regions of the core ("exterior") is different from the weight ratio Y of
expanded plastics particles B
to lignocellulose particles A in the inner region of the core ("interior"), in
other words is greater or
lesser in the outer regions of the core ("exterior") than in the inner region
of the core ("interior").
The inner region of the core is generally separated from the two outer regions
of the core by faces
extending parallel to the panel plane. The inner region of the core is
understood to be the region
which comprises 20% to 80% by weight, preferably 30% to 70% by weight, more
preferably 40%
to 60% by weight, more particularly 45% to 55% by weight, very preferably 50%
by weight of the
overall dry mass of the core and is situated between the two outer regions.
The two outer regions
may have the same mass, in other words in each case 25% by weight, or
approximately the same
mass, i.e., 25.01:24.99% to 25.99:24.01% by weight, preferably 25.01:24.99% to
25.8:24.2%,
more preferably 25.01:24.99% to 25.6:24.4%, more particularly 25.01:24.99% to
25.4:24.6%, or a
different mass, based on the overall dry mass of the core, i.e., 26:24% to
40:10% by weight,
preferably 26:24% to 30:20% by weight, more preferably 26:24% to 27:23% by
weight, more
particularly 26:24% to 26.5:23.5% by weight. The sum total of the inner region
and of the two
outer regions of the core makes up 100% by weight. For determining the weight
ratio X of
expanded plastics particles B to lignocellulose particles A in the outer
regions of the core, it is
possible to employ all expanded plastics particles B and all lignocellulose
particles A which are
present in both outer regions. The ratio X' here, which describes the ratio of
plastics particles B to
lignocellulose particles A in one of the two outer regions, may differ from or
be the same as the
ratio X", which describes the ratio in the other of the two outer regions.
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The lignocellulosic materials (lignocellulose materials) of the invention can
be produced as
follows:
The components for the core and the components for the outer layers are mixed
generally
separately from one another.
For the core, the lignocellulose particles A may be mixed with the components
B, C and D and/or
with the component constituents comprised therein (i.e., two or more
constituents, such as
substances or compounds, for example, from the group of one component) in any
desired order.
Components A, B, C an D may in each case be composed of one, two (Al, A2 or
B1, B2, or Cl,
C2 or D1, D2) or a plurality of component constituents (Al, A2, A3,..., or B1,
B2, B3,..., Cl, C2,
C3,..., or D1, D2, D3, ...).
Where the components consist of a plurality of component constituents, these
component
constituents may be added either as a mixture or separately from one another.
In the case of
separate addition, these component constituents may be added directly after
one another or else
at different points in time not following directly on from one another. In the
event, for example, that
component C is composed of two constituents Cl and C2, this means that C2 is
added
immediately after Cl or Cl is added immediately after C2, or that one or more
other components
or component constituents, component B for example, are added between the
addition of Cl and
C2. It is also possible for components and/or component constituents to be
premixed with other
components or component constituents before being added. For example, an
additive constituent
D1 may be added to the binder C or to the binder constituent Cl before this
mixture is then added
to the actual mixture.
Preferably, first of all, the expanded plastics particles B are added to the
lignocellulose particles
A, and this mixture is thereafter admixed with a binder C or with two or more
binder constituents
Cl, C2, etc. Where two or more binder constituents are used, they are
preferably added
separately from one another. The additives D are preferably partially mixed
with the binder C or
with a binder constituent (i.e., a plurality of constituents, such as
substances or compounds, for
example, from the group of the component) and then added.
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For the outer layers, the lignocellulose particles E are mixed with the
components F and G and/or
with the component constituents present therein (i.e., a plurality of
constituents, such as
substances or compounds, for example, from the group of one component) in any
desired order.
For the two outer layers it is possible to use either the same mixture or two
different mixtures,
5 preferably the same mixture.
Where the components consist of a plurality of component constituents, these
constituents can be
added either as a mixture or separately from one another. In that case, these
component
constituents can be added directly after one another or else at different
points in time not following
directly on from one another. The additives G are preferably partially mixed
with the binder F or a
binder constituent and then added.
The resulting mixtures A, B, C, D and E, F, G are layered one on top another
and compressed by
a customary process, at elevated temperature, to give a lignocellulosic
molding. For this purpose,
a mat is produced on a support, said mat being composed of these mixtures in
the order E, F,
G/A, B, C, DIE, F, G ("sandwich construction"). This mat is compressed
customarily at
temperatures from 80 to 300 C, preferably 120 to 280 C, more preferably 150 to
250 C, and at
pressures from 1 to 50 bar, preferably 3 to 40 bar, more preferably 5 to 30
bar, to form moldings.
In one preferred embodiment, the mat is subjected to cold precompaction ahead
of this
hotpressing. Compression may take place by any of the methods known to the
skilled person (see
examples in "Taschenbuch der Spanplatten Technik", H.-J. Deppe, K. Ernst, 4th
edn., 2000, DRW
¨ Verlag Weinbrenner, Leinfelden Echterdingen, pages 232 to 254, and "MDF-
Mitteldichte
Faserplatten" H.-J. Deppe, K. Ernst, 1996, DRW- Verlag Weinbrenner, Leinfelden-
Echterdingen,
pages 93 to 104). These methods use discontinuous pressing techniques, on
single-stage or
multistage presses, for example, or continuous pressing techniques, on double-
belt presses, for
example.
The nonuniform distribution of the plastics particles B in the core may be
generated as follows:
A plurality of mixtures of components A, B, C and D can be produced,
containing different mass
ratios of components A and B. These mixtures can be scattered in succession.
In this case, there
ought generally to be only slight mixing, or none, of the mixtures with
different mass ratios of
components A and B. As a result, a nonuniform distribution of the expanded
plastics particles in
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the core of the lignocellulose material can be achieved. In this context, both
the wood particles A
and the plastics particles B can be separated beforehand into different
fractions, by screening, for
example. Each of the mixtures may comprise different fractions of the wood
particles A and/or of
the plastics particles B.
In another embodiment, the nonuniform distribution of the plastics particles B
in the core may be
accomplished by separative scattering. In this case, scattering takes place
using a means which
ensures that the spheres accumulate either in the outer regions or in the
inner regions of the core,
depending on the size and/or on the weight. This can be accomplished, for
example, by scattering
the mixture A, B, C, D using a screening system. In one preferred embodiment,
this system is
equipped with screens of different hole sizes which are arranged mirror-
symmetrically. With
particular preference, a support bearing the material for the lower outer
layer is conveyed beneath
a scattering means in which a screen system is disposed in such a way that at
the beginning of
the scattering means (in production direction) there are screens with a small
hole size, with the
hole size of the screens increasing inwardly toward the middle of the
scattering station, and
decreasing again at the end of the station. The disposition of the screens
means that small
lignocellulose particles enter into the outer regions of the core, those close
to the outer layer, and
large lignocellulose particles enter the inner region of the core. At the same
time, small plastics
particles enter the outer regions of the core, those close to the outer layer,
and large plastics
particles enter the inner region of the core. Depending on the size
distribution of the lignocellulose
particles and of the plastics particles, this produces different mass ratios
of lignocellulose particles
A to plastics particles B. Scattering stations of this kind are described in
EP-B-1140447 and
DE-C-19716130.
For example, the lignocellulose particle scattering station may comprise two
metering silos each
housing a plurality of back-scraping rakes. The bulk material, composed of
different large particles
A and of components B, C and D ("core mixture"), can be supplied to the
metering silos (e.g.,
from above). Disposed on the underside of each of the metering silos may be a
bottom belt which
runs over two deflecting rollers and which, in each case together with a
discharge roll, forms a
discharge unit for the core mixture. Beneath each of the discharge rolls there
may be a
continuous scraper belt which is guided over two deflecting rollers and whose
lower tower can be
guided in each case over screen devices with different hole sizes, thus
forming different sections
of the screen devices. Together with the scraper belts, the screen devices
form fractionating
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means by which the lignocellulosic particles A and the plastics particles B of
the core mixture can
be fractionated according to their sizes. The sections of the screen devices
may be disposed in
such a way that the fine lignocellulose particles A and/or plastics particles
B are each scattered, in
those regions of the scattering station that lie externally in the transport
direction of the web, onto
the lower outer layer, while the coarse lignocellulose particles A and/or
plastics particles B are
scattered, via the internal regions of the fractionating means, onto the outer
layer (see in detail
EP-B-1140447).
According to another advantageous embodiment of the invention, at least a part
of the
apportioning sections in each case comprises an abrasive element which bears
against the
surface of the screen means and, when the apportioning sections are moved, is
guided
abradingly over the surface of the screen means. An abrasive element bearing
under gentle
pressure against the surface of the screen means for each apportioning section
or at least some
of the apportioning sections further strengthens the cleaning effect which
comes about when the
apportioning sections are moved over the surface of the screen means. At the
same time, the
abrasive elements reinforce the force component that acts on the particles in
a direction
perpendicular to the screen surface, thereby producing an increase in the
throughput. The
transport means is preferably designed as a scraper belt, more particularly as
a continuous
scraper belt. In this way, particularly simple and inexpensive configuration
of the transport means
is possible. Here, advantageously, the scraper belt is formed perviously for
the particles at least
over a subregion in a direction perpendicular to the surface of the screen
means, thereby allowing
the particles to be tipped from the metering silo via its feed unit through
the scraper belt and onto
the screen means. This does away with the need for any complicated
configuration of the feed
unit. According to a further advantageous embodiment of the invention, the
scraper belt
comprises drivers, more particularly platelike drivers, which are provided
preferably at regular
intervals on a continuous support element in chain or belt form. In this case,
the support element
may be mounted in each case centrally on the drivers. It is also possible,
however, for a plurality
of support elements, more particularly two chain or belt support elements, to
be provided, each
fastened in the region of the lateral outside edges of the drivers. This
increases the stability of a
scraper belt designed in accordance with the invention. Preferably, the
drivers are fastened
detachably on the support element or support elements, and/or are of air-
impervious design. This
ensures that, on the one hand, the drivers used can be optimally tailored to
the screen means
employed, and on the other hand that worn drivers can be replaced by new ones.
According to
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another advantageous embodiment of the invention, the abrasive elements are
formed in each
case by a section of the drivers. In this way, the design of the means of the
invention can be
particularly cost-effective, since no separate components are needed for the
abrasive elements.
In particular, at least in their sections forming the abrasive elements, the
drivers are of flexible
design, being made from hard rubber, for example. This allows the abrasive
elements to conform
to the surface of the screen means, thereby ensuring, even in the event of a
certain irregularity in
the screen surface, that the abrasive elements bear on the surface of the
screen means with a
certain pressure over their entire width and also over their entire range of
movement. According to
another preferred embodiment of the invention, the drivers are of abrasion-
resistant design, at
least in their sections forming the abrasive elements, and more particularly
possess an abrasion-
resistant coating, such as a Teflon coating, for example. The sections of the
drivers that form the
abrasive elements may be designed either in one piece with the drivers or else
as separate
components. Where the abrasive elements are designed as separate components,
they are
preferably mounted detachably on the drivers, so that they can be replaced in
the event of wear.
According to another advantageous embodiment of the invention, the drivers, at
least in their
sections forming the abrasive elements, are formed from water-repellent
nonadhering material.
This prevents the particles wetted with binder remaining stuck to the drivers,
which could limit the
pickup capacity of the apportioning sections. According to a further preferred
embodiment of the
invention, the screen means comprises screen zones, more particularly two
screen zones, with
different screen openings. In this way, particles of different size are
fractionated by the screen
zones with different-sized screen openings. In this context, in particular,
the screen zones are
arranged one after another along the direction of movement of the apportioning
sections that are
movable over the surface of the screen means, and preferably the screen
openings of the screen
zone/zones situated in the direction of movement of the apportioning sections
are larger than the
screen openings of the screen zone/screen zones situated counter to the
direction of movement.
This ensures that, as they pass over the screen surface, the particles with
small diameter pass
first through the screen means, while in the next screen zone, after this, the
next-larger particles
pass through the screen. Depending on the number of screen zones and on the
size of the screen
openings, therefore, the desired fractioning of the particles is achieved.
These fractionated
particles may either be tipped, in accordance with the screen zones, into
different collecting
means for the different particle sizes, or, for example, may be tipped onto a
moving conveyor belt
which is disposed beneath the screen means and on which, in this way, a web
with different
distributions of particle sizes over its thickness can be produced.
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According to a further advantageous embodiment of the invention, the
continuous scraper belt is
guided via two deflection rolls, and so a lower belt section runs directly on
the surface of the
screen means, and an upper belt section runs at a particular distance from the
surface of the
screen means, more particularly in each case substantially parallel to the
surface of the screen
means. In this way, a particularly compact design is possible for a means of
the invention.
Preferably in this case, at least at one end of the scraper belt, more
particularly in the region of
the deflection rolls, there is a pickup means provided for picking up expelled
particles. These
particles may be alien bodies present in the bulk material, such as screws or
nails, for example;
alternatively, they may be aggregations or particles which exceed a maximum
permissible size,
and which are expelled and taken away in order that even the largest screen
openings of the
screen means cannot become clogged. According to another preferred embodiment
of the
invention, at least in regions between the upper and lower belt sections, an
intermediate base is
provided, and the drivers bear, with their ends opposed to the sections
forming the abrasive
elements, against the intermediate base, meaning that, when the apportioning
sections are
moved, these ends are guided abradingly over the intermediate base. With this
embodiment, bulk
material applied from the metering silo via its feed unit initially to the
intermediate base can be
brought in a defined way to a particular position between the deflection
rollers. In this case,
according to one preferred embodiment, the intermediate base may extend from
one deflection
roller in the direction of movement of the upper belt section toward the
opposite, other deflection
roller; between this other deflection roller and the end of the intermediate
base that faces this
other deflection roller, a region is formed which is pervious for the
particles in a direction
perpendicular to the surface of the screen means. Particularly when this
region is formed from
further screen means possessing relatively large screen openings, it is
possible here for there to
be a preliminary deposition of alien bodies or particles having a size which
is above the size of
these screen openings. Only those particles that pass through the further
screen means fall onto
the underlying screen means, over which they are moved by means of the
transport means.
According to another preferred embodiment of the invention, there are two
scraper belts situated
one after the other in the longitudinal direction, and the scraper belts are
in particular arranged
mirror-symmetrically to one another. In this case, advantageously, a
distribution means, more
particularly in the form of a shuttle distributor, is positioned downstream of
the feed unit of the
metering silo, and can be used to supply the particles taken from the metering
silo through the
feed unit to the two scraper belts, more particularly in alternation. By means
of this design it is
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possible, starting from one metering silo, to distribute particles to two
different scraper belts.
Especially when the two scraper belts can be driven in opposing directions,
and so the two upper
belt sections can be moved in a mutually divergent way, and, between the upper
and the lower
belt sections, in a manner already described, an intermediate base is
provided, it is possible for
5 the particles applied via the distribution means to the respective
intermediate bases to be
transported to the ends of the scraper belts that are situated in opposite
directions, where they
are applied in each case to the screen means disposed beneath the scraper
belts. Given
appropriate sizing of the screen openings of these screen means, particularly
when the size of the
screen openings increases in the direction of movement of the lower belt
sections, the material for
10 the core can be formed on a moving conveyor belt disposed beneath the
screen means, and on
which the lower outer layer has already been scattered, the formation of the
core material being
such that the fine lignocellulose particles A and/or plastics particles B are
accumulated in the
outer layers of the core, and the coarse lignocellulose particles A and/or
plastics particles B are
accumulated in the inner layer of the core. Instead of a distribution means,
it is also possible, for
example, for there to be two metering silos by which the two scraper belts are
charged with
particles. In all embodiments, the screen means and/or the further screen
means is preferably
designed as an oscillating screen or as a vibrating shaker screen. In this
case, the bulk material
fed to the screen means is loosened further, meaning that fine particles and,
subsequently,
medium-sized particles at a distance from the screen pass more quickly toward
the screen
openings and through them (see in detail DE-C-197 16 130).
Another preferred embodiment is the use of a roller scattering system with
specially profiled rolls
(roll screen). In this case as well, preferably, a symmetrical construction is
selected, meaning that
small lignocellulose particles A and/or small plastics particles B enter the
outer regions of the
core, those close to the outer layer, and large lignocellulose particles A
and/or large plastics
particles B enter the inner region of the core. One particularly preferred
embodiment is the use of
one or more ClassiForrnerTM devices. Suitability is possessed, for example, by
the Classiformer
CC from Dieffenbacher, which has a symmetrical construction. Alternatively it
is possible to use
two Classiformers C, arranged opposite and one after the other.
The lignocellulose materials of the invention generally have an average
density of 300 to
600 kg/m3, preferably 350 to 590 kg/m3, more preferably 400 to 570 kg/m3, more
particularly 450
to 550 kg/m3.
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The lignocellulose particles of component A are present in the lignocellulosic
materials of the core
in amounts from 30% to 98% by weight, preferably 50% to 95% by weight, more
preferably 70%
to 90% by weight, and their base material is any desired wood variety or
mixtures thereof,
examples being spruce, beech, pine, larch, lime, poplar, eucalyptus, ash,
chestnut and fir wood or
mixtures thereof, preferably spruce, beech or mixtures thereof, more
particularly spruce, and may
comprise, for example, wood parts such as wood laths, wood strips, wood chips,
wood fibers,
wood dust or mixtures thereof, preferably wood chips, wood fibers, wood dust
and mixtures
thereof, more preferably wood chips, wood fibers or mixtures thereof¨ of the
kind used for
producing chipboard, MDF (medium-density fiberboard) and HDF (high-density
fiberboard)
panels. The lignocellulose particles may also come from woody plants such as
flax, hemp, cereals
or other annual plants, preferably from flax or hemp. Particular preference is
given to using wood
chips of the kind used in manufacturing chipboard. Where mixtures of different
lignocellulose
particles are used, such as mixtures of wood chips and wood fibers, or of wood
chips and wood
dust, for example, the fraction of wood chips is preferably at least 75% by
weight, in other words
75% to 100% by weight, more preferably at least 90% by weight, in other words
90% to 100% by
weight. The average density of component A is generally 0.4 to 0.85 g/cm3,
preferably 0.4 to
0.75 g/cm3, more particularly 0.4 to 0.6 g/cm3.
Starting materials for lignocellulose particles are customarily roundwoods,
lumber from forestry
thinning, residual lumber, waste forest lumber, residual industrial lumber,
used lumber, production
waste from the production of woodbase materials, used woodbase materials, and
also
lignocellulosic plants. Processing to the desired lignocellulosic particles,
to wood particles for
example, such as wood chips or wood fibers, may take place in accordance with
known methods
(e.g., M. Dunky, P. Niemz, Holzwerkstoffe und Leime, pages 91 to 156, Springer
Verlag
Heidelberg, 2002).
In the outer layers, the lignocellulose particles are present in amounts of
from 70% to 99% by
weight, preferably 75% to 97% by weight, more preferably 80% to 95% by weight.
They consist of
at least 25% by weight, in other words 25% to 100% by weight, of
lignocellulosic chips, more
particularly wood chips, preferably at least 75% by weight, in other words 75%
to 100% by weight,
more preferably at least 95% by weight, in other words 95% to 100% by weight,
and very
preferably exclusively, in other words 100% by weight of, lignocellulosic
chips are used, more
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particularly wood chips. Raw materials used may be lignocellulosic materials,
in particular wood
from all lignocellulose or wood sources listed under component A. Preparation
to give the desired
lignocellulosic particles may take place as described for component A. The
average density of
component E is generally 0.4 to 0.85 g/cm3, preferably 0.4 to 0.75 g/cm3, more
particularly 0.4 to
0.6 g/cm3.
Component A may comprise the customary small amounts of water, from 0% to 10%
by weight,
preferably 0.5% to 8% by weight, more preferably 1% to 5% by weight (in a
customary low range
of fluctuation of 0% to 0.5% by weight, preferably 0% to 0.4% by weight, more
preferably 0% to
.. 0.3% by weight). This quantity figure is based on 100% by weight of
absolutely dry wood
substance, and describes the water content of component A after the drying (by
customary
methods known to the skilled person) immediately prior to mixing with the
first component or with
the first component constituent or with the first mixture selected from B, C
and D.
In one preferred embodiment, component E may comprise small amounts of water
from 0% to
10% by weight, preferably 0.5% to 8% by weight, more preferably 1% to 5% by
weight (in a
customary low range of fluctuation of 0% to 0.5% by weight, preferably 0% to
0.4% by weight,
more preferably 0% to 0.3% by weight). This quantity figure is based on 100%
by weight of
absolutely dry wood substance, and describes the water content of component E
after the drying
(by customary methods known to the skilled person) immediately prior to mixing
with the first
component or component constituent or mixture selected from F and G.
Suitable expanded plastics particles (component B) include expanded plastics
particles,
preferably expanded thermoplastics particles, having a bulk density from 10 to
150 kg/m3,
preferably 30 to 130 kg/m', more preferably 35 to 110 kg/m3, more particularly
40 to 100 kg/m3
(determined by weighing a defined volume filled with the bulk material).
Expanded plastics particles B are used generally in the form of spheres or
beads having an
average diameter of 0.01 to 50 mm, preferably 0.25 to 10 mm, more preferably
0.4 to 8.5 mm,
.. more particularly 0.4 to 7 mm. In one preferred embodiment the spheres have
a small surface
area per unit volume, in the form of a spherical or elliptical particle, for
example, and
advantageously are closed-cell spheres. The open-cell proportion according to
DIN ISO 4590 is
generally not more than 30%, i.e., 0% to 30%, preferably 1% to 25%, more
preferably 5% to 15%.
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Suitable polymers on which the expandable or expanded plastics particles are
based are
generally all known polymers or mixtures thereof, preferably thermoplastic
polymers or mixtures
thereof, which can be foamed. Examples of highly suitable such polymers
include polyketones,
polysulfones, polyoxymethylene, PVC (rigid and flexible), polycarbonates,
polyisocyanurates,
polycarbodiimides, polyacrylimides and polymethacrylimides, polyamides,
polyurethanes,
aminoplast resins and phenolic resins, styrene homopolymers (also referred to
below as
"polystyrene" or "styrene polymer), styrene copolymers, C2-C10 olefin
homopolymers, C2-Clo
olefin copolymers, and polyesters. For producing the stated olefin polymers it
is preferred to use
the 1-alkenes, examples being ethylene, propylene, 1-butene, 1-hexene and 1-
octene.
The polymers, preferably the thermoplastics, may additionally be admixed with
the customary
additives forming a basis for the expandable or expanded plastics particles
B), examples being
UV stabilizers, antioxidants, coating materials, hydrophobing agents,
nucleators, plasticizers,
flame retardants, soluble and insoluble, organic and/or inorganic dyes,
pigments, and
athermanous particles, such as carbon black, graphite or aluminum powder,
together or spatially
separate, as adjuvants.
Component B may customarily be obtained as follows:
Suitable polymers, using an expansion-capable medium (also called "blowing
agent") or
comprising an expansion-capable medium, can be expanded by exposure to
microwave energy,
thermal energy, hot air, preferably steam, and/or to a change in pressure
(this expansion often
also being referred to as "foaming") (Kuntstoff Handbuch 1996, volume 4,
"Polystyrol" , Hanser
1996, pages 640 to 673 or US-A-5,112,875). In the course of this procedure,
generally, the
blowing agent expands, the particles increase in size, and cell structures are
formed. This
expanding can be carried out in customary foaming apparatus, often referred to
as "prefoamers".
Such prefoamers may be installed permanently or else may be portable.
Expanding can be
carried out in one or more stages. In the one-stage process, in general, the
expandable plastics
particles are expanded directly to the desired final size. In the multistage
process, in general, the
expandable plastics particles are first expanded to an intermediate size and
then, in one or more
further stages, are expanded via a corresponding number of intermediate sizes
to the desired
final size. The compact plastics particles identified above, also referred to
herein as "expandable
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plastics particles", generally have no cell structures, in contrast to the
expanded plastics particles.
The expanded plastics particles generally have a low residual blowing agent
content, of 0% to 5%
by weight, preferably 0.5% to 4% by weight, more preferably 1% to 3% by
weight, based on the
overall mass of plastic and blowing agent. The expanded plastics particles
obtained in this way
can be placed in interim storage or used further without other intermediate
steps for producing
component B of the invention.
The expandable plastics particles can be expanded using all of the blowing
agents known to the
skilled person, examples being aliphatic C3 to Cio hydrocarbons, such as
propane, n-butane,
isobutane, n-pentane, isopentane, neopentane, cyclopentane and/or hexane and
isomers thereof,
alcohols, ketones, esters, ethers or halogenated hydrocarbons, preferably n-
pentane, isopentane,
neopentane and cyclopentane, more preferably a commercial pentane isomer
mixture of n-
pentane and isopentane.
The amount of blowing agent in the expandable plastics particles is generally
in the range from
0.01% to 7% by weight, preferably 0.01% to 4% by weight, more preferably 0.1%
to 4% by
weight, based in each case on the expandable plastics particles containing
blowing agent.
One preferred embodiment uses styrene homopolymer (also called simply
"polystyrene" herein),
styrene copolymer or mixtures thereof as the sole plastic in component B.
Polystyrene and/or styrene copolymer of this kind may be prepared by any of
the polymerization
techniques known to the skilled person; see, for example, Ullmann's
Encyclopedia, Sixth Edition,
2000 Electronic Release or Kunststoff-Handbuch 1996, volume 4 "Polystyrol",
pages 567 to 598.
The expandable polystyrene and/or styrene copolymer is generally prepared in a
conventional
way by suspension polymerization or by means of extrusion processes.
In the case of the suspension polymerization, styrene, optionally with
addition of further
comonomers, can be polymerized in aqueous suspension in the presence of a
customary
suspension stabilizer by means of radical-forming catalysts. The blowing agent
and optionally
other customary adjuvants may be included in the initial charge for the
polymerization or else
added to the batch in the course of the polymerization or after the
polymerization has ended. The
15
resultant beadlike, expandable styrene polymers impregnated with blowing
agent, after the
end of the polymerization, can be separated from the aqueous phase, washed,
dried and
screened.
In the case of the extrusion process, the blowing agent can be mixed into the
polymer via an
extruder, for example, conveyed through a die plate and pelletized under
pressure to form
particles or strands.
The preferred or particularly preferred expandable styrene polymers or
expandable styrene
copolymers described above have a relatively low blowing agent content. Such
polymers are
also referred to as "low in blowing agent". A highly suitable process for
producing expandable
polystyrene or expandable styrene copolymer low in blowing agent is described
in
US-A-5,112,875.
As described, it is also possible to use styrene copolymers. Advantageously,
these styrene
copolymers contain at least 50% by weight, i.e., 50% to 100% by weight,
preferably at least
80% by weight, i.e., 80% to 100% by weight, of copolymerized styrene, based on
the mass of
the plastic (without blowing agent). Examples of comonomers contemplated
include
a-methylstyrene, ring-halogenated styrenes, acrylonitrile, esters of acrylic
or methacrylic acid
with alcohols having 1 to 8 C atoms, N-vinylcarbazole, maleic acid, maleic
anhydride,
(meth)acrylamides and/or vinyl acetate.
The polystyrene and/or styrene copolymer may advantageously include a small
amount of a
copolymerized chain-branching agent, in other words a compound having more
than one
double bond, preferably two double bonds, such as divinylbenzene, butadiene
and/or
butanediol diacrylate. The branching agent is used generally in amounts from
0.0005 to
0.5 mol%, based on styrene. Mixtures of different styrene (co)polymers can be
used as well.
Highly suitable styrene homopolymers or styrene copolymers are crystal-clear
polystyrene
(GPPS), high-impact polystyrene (HIPS), anionically polymerized polystyrene or
high-impact
polystyrene (A-IPS), styrene-a-methylstyrene copolymers, acrylonitrile-
butadiene-styrene
polymers (ABS), styrene-acrylonitrile (SAN), acrylonitrile-styrene-acrylic
ester (ASA), methyl
acrylate-butadiene-styrene (M BS), methyl methacrylate-acrylonitrile-butadiene-
styrene
(MABS) polymers or mixtures thereof, or used with polyphenylene ether (PPE).
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Preference is given to using plastics particles, more preferably styrene
polymers or styrene
copolymers, more particularly styrene homopolymers, having a molecular weight
in the range
from 70 000 to 400 000 g/mol, more preferably 190 000 to 400 000 g/mol, very
preferably 210 000
to 400 000 g/mol.
These expanded polystyrene particles or expanded styrene copolymer particles
may be used,
with or without further measures for blowing agent reduction, for producing
the lignocellulosic
substance.
The expandable polystyrene or expandable styrene copolymer or the expanded
polystyrene or
expanded styrene copolymer customarily has an antistatic coating.
The expanded plastics particles B are generally in an unmelted state even
after compression to
form the lignocellulose material, this meaning that the plastics particles B
have generally not
penetrated or impregnated the lignocellulose particles, but instead are
distributed between the
lignocellulose particles. The plastics particles B can customarily be
separated from the
lignocellulose by physical methods, as for example after the comminuting of
the lignocellulose
material.
The overall amount of the expanded plastics particles B, based on the overall
dry mass of the
core, is generally in the range from 1% to 25% by weight, preferably 3% to 20%
by weight, more
preferably 5% to 15% by weight.
It has emerged as being advantageous to match the dimensions of the above-
described
expanded plastics particles B to the lignocellulose particles, preferably wood
particles A), or vice
versa.
This matching is expressed below by the relationship of the respective d'
values (from the Rosin-
Rammler-Sperling-Bennet function) of the lignocellulose particles, preferably
wood particles A,
and of the expanded plastics particles B.
The Rosin-Rammler-Sperling-Bennet function is described in DIN 66145, for
example.
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The d' values are determined by conducting sieve analyses first of all for
determining the particle
size distribution of the expanded plastics particles B and lignocellulose
particles, preferably wood
particles, A, in analogy to DIN 66165, Parts 1 and 2.
The values from the sieve analysis are then inserted into the Rosin-Rammler-
Sperling-Bennet
function, and d' is calculated.
The Rosin-Rammler-Sperling-Bennet function is:
R = 100*exp((d/d')n))
The definitions of the parameters are as follows:
R residue (c/0 by weight) remaining on the respective sieve tray
d particle size
d' particle size at 36.8% by weight of residue
n width of the particle size distribution
Highly suitable lignocellulose particles A, preferably wood particles, have a
d' value according to
Rosin-Rammler-Sperling-Bennet (definition and determination of the d' value as
described above)
in the range from 0.1 to 5, preferably 0.3 to 3, and more preferably 0.5 to
2.75.
Highly suitable lignocellulose materials are obtained when the d' values
according to Rosin-
Rammler-Sperling-Bennet of the lignocellulose particles, preferably wood
particles A and for the
particles of the expanded plastics particles B are subject to the following
relationship:
d' of the particles A s 2.5 x d' of the particles B, preferably
d' of the particles A s 2.0 x d' of the particles B, more preferably
d' of the particles A S 1.5 x d' of the particles B, very preferably
d' of the particles A 5 d' of the particles B.
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The overall amount of the binder C, based on the overall mass of the core, is
in the range from
1% to 50% by weight, preferably 2% to 15% by weight, more preferably 3% to 10%
by weight.
The overall amount of the binder F, based on the overall dry mass of the outer
layer(s), is in the
range from 1% to 30% by weight, preferably 2% to 20% by weight, more
preferably 3% to 15% by
weight.
The binders of component C and of component F may be selected from the group
consisting of
aminoplast resin, phenoplast resin, and organic isocyanate having at least two
isocyanate groups,
using identical or different binders or binder mixtures of components C and F,
preferably identical
binders, with particular preference aminoplast in both cases. The weight
figure in the case of
aminoplasts or phenoplasts relates to the solids content of the corresponding
component
(determined by evaporating the water at 120 C over the course of 2 hours in
accordance with
Gunter Zeppenfeld, Dirk Grunwald, Klebstoffe in der Holz- und Mobelindustrie,
2nd edition, DRW-
Verlag, page 268), while in relation to the isocyanate, more particularly the
PMDI (polymeric
diphenylmethane diisocyanate), it relates to the isocyanate component per se,
in other words, for
example, without solvent or emulsifying medium.
Phenoplasts are synthetic resins which are obtained by condensing phenols with
aldehydes and
which may optionally be modified. In addition to unsubstituted phenol, phenol
derivatives as well
can be used for preparing phenoplasts. These derivatives may be cresols,
xylenols or other
alkylphenols, as for example p-tert-butylphenol, p-tert-octylphenol, and p-
tert-nonylphenol,
arylphenols, as for example phenylphenol and naphthols, or divalent phenols,
examples being
resorcinol and bisphenol A. The most important aldehyde for the preparation of
phenoplasts is
formaldehyde, which can be used in a variety of forms ¨ for example, as an
aqueous solution, or
in solid form, as para-formaldehyde, or as a formaldehyde donor. Other
aldehydes, as for
example acetaldehyde, acrolein, benzaldehyde or furfural, and ketones, may
also be used.
Phenoplasts can be modified by chemical reactions of the methylol groups or of
the phenolic
hydroxyl groups, and/or by physical dispersion in a modifying agent (EN ISO
10082).
Preferred phenoplasts are phenol-aldehyde resins, particularly preferably
phenol-formaldehyde
resins (also called PF resins) are known from, for example, Kunststoff-
Handbuch, 2nd edition,
Hanser 1988, volume 10, "Duroplaste", pages 12 to 40.
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As aminoplast resin it is possible to use all aminoplast resins known to the
skilled person,
preferably those known for the production of woodbase materials. Resins of
this kind and also
their preparation are described in, for example, Ullmanns Enzyklopadie der
technischen Chemie,
4th, revised and expanded edition, Verlag Chemie, 1973, pages 403 to 424
"Aminoplaste", and
Ullmann's Encyclopedia of Industrial Chemistry, vol. A2, VCH
Verlagsgesellschaft, 1985, pages
115 to 141 "Amino Resins", and also in M. Dunky, P. Niemz, Holzwerkstoffe und
Leime, Springer
2002, pages 251 to 259 (UF resins) and pages 303 to 313 (MUF and UF with a
small amount of
melamine). Generally speaking, they are polycondensation products of compounds
having at
least one - optionally substituted partially with organic radicals - amino
group or carbamide group
(the carbamide group is also called carboxamide group), preferably carbamide
group, preferably
urea or melamine, and an aldehyde, preferably formaldehyde, Preferred
polycondensation
products are urea-formaldehyde resins (UF resins), melamine-formaldehyde
resins (ME resins) or
melamine-containing urea-formaldehyde resins (MUF resins), more preferably
urea-formaldehyde
resins, examples being Kaurit glue products from BASF SE.
Particularly preferred polycondensation products are those in which the molar
ratio of aldehyde to
the - optionally substituted partially with organic radicals - amino group
and/or carbamide group
is in the range from 0.3:1 to 1:1, preferably 0.3:1 to 0.6:1, more preferably
0.3:1 to 0.55:1, very
preferably 0.3:1 to 0.5:1. Where the aminoplasts are used in combination with
isocyanates, the
molar ratio of aldehyde to the - optionally substituted partially with organic
radicals - amino group
and/or carbamide group is in the range from 0.3:1 to 1:1, preferably 0.3:1 to
0.6:1, more
preferably 0.3:1 to 0.45:1, very preferably 0.3:1 to 0.4:1.
The stated aminoplast resins are used customarily in liquid form, usually in
solution, customarily
as a 25% to 90% by weight strength solution, preferably a 50% to 70% by weight
strength
solution, preferably in aqueous solution, but may also be used in solid form.
The solids content of the liquid aqueous aminoplast resin can be determined in
accordance with
GOnter Zeppenfeld, Dirk Grunwald, Klebstoffe in der Holz- und Mobelindustrie,
2nd edition, DRW-
Verlag, page 268.
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The constituents of the binder C and of the binder F can be used per se alone
¨ that is, for
example, aminoplast resin or organic isocyanate or PF resin as sole
constituent of binder C or of
binder F. In addition, however, the resin constituents of binder C and of
binder F may also be
used as a combination of two or more constituents of the binder C and/or of
the binder F; these
5 combinations preferably comprise an aminoplast resin and/or phenoplast
resin.
In one preferred embodiment a combination of aminoplast and isocyanate can be
used as binder
C. In this case, the total amount of the aminoplast resin in the binder C,
based on the overall dry
mass of the core, is in the range from 1% to 45% by weight, preferably 4% to
14% by weight,
10 more preferably 6% to 9% by weight. The overall amount of the organic
isocyanate, preferably of
the oligomeric isocyanate having 2 to 10, preferably 2 to 8 monomer units and
on average at least
one isocyanate group per monomer unit, more preferably PMDI, in the binder C,
based on the
overall dry mass of the core, is in the range from 0.05% to 5% by weight,
preferably 0.1% to 3.5%
by weight, more preferably 0.5% to 1.5% by weight.
Components D and G may each independently of one another comprise different or
identical,
preferably identical curing agents that are known to the skilled person, or
mixtures thereof. These
components are customarily used lithe binder C and/or F comprises aminoplasts
or phenoplast
resins. These curing agents are preferably added to the binder C and/or F, in
the range, for
example, from 0.01% to 10% by weight, preferably 0.05% to 5% by weight, more
preferably 0.1%
to 3% by weight, based on the overall amount of aminoplast resin or phenoplast
resin.
Curing agents for the aminoplast resin component or for the phenoplast resin
component are
understood herein to encompass all chemical compounds of any molecular weight
that accelerate
or bring about the polycondensation of aminoplast resin or phenol-formaldehyde
resin. One highly
suitable group of curing agents for aminoplast resin or phenoplast resin are
organic acids,
inorganic acids, acidic salts of organic acids, and acidic salts of inorganic
acids, or acid-forming
salts such as ammonium salts or acidic salts of organic amines. The components
of this group
can of course also be used in mixtures. Examples are ammonium sulfate or
ammonium nitrate or
organic or inorganic acids, as for example sulfuric acid, formic acid or acid-
regenerating
substances, such as aluminum chloride, aluminum sulfate or mixtures thereof.
One preferred
group of curing agents for aminoplast resin or phenoplast resin are organic or
inorganic acids
CA 02854701 2014-05-06
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such as nitric acid, sulfuric acid, formic acid, acetic acid, and polymers
with acid groups, such as
homopolymers or copolymers of acrylic acid or methacrylic acid or maleic acid.
Phenoplast resins, preferably phenol-formaldehyde resins, can also be cured
alkylenically. It is
preferred to use carbonates or hydroxides such as potassium carbonate and
sodium hydroxide.
Further examples of curing agents for aminoplast resins are known from M.
Dunky, P. Niemz,
Holzwerkstoffe und Leime, Springer 2002, pages 265 to 269, and further
examples of curing
agents for phenoplast resins, preferably phenol-formaldehyde resins, are known
from M. Dunky,
P. Niemz, Holzwerkstoffe und Leime, Springer 2002, pages 341 to 352.
The lignocellulose materials of the invention may comprise further,
commercially customary
additives and additives known to the skilled person, as component D and as
component G,
independently of one another identical or different, preferably identical
additives, in amounts from
0% to 10% by weight, preferably 0.5% to 5% by weight, more preferably 1% to 3%
by weight,
examples being hydrophobizing agents such as paraffin emulsions, antifungal
agents,
formaldehyde scavengers, such as urea or polyamines, for example, and flame
retardants.
In the material of the invention, the ratio Z between the weight ratio X of
expanded plastics
particles to lignocellulose particles in the outer regions of the core
("exterior") and the weight ratio
Y of expanded plastics particles to lignocellulose particles in the inner
region of the core
("interior") is 1.05:1 to 1000:1, preferably 1.1:1 to 500:1, more preferably
1.2:1 to 200:1. In a
further preferred embodiment, this ratio Z is 0.001:1 to 0.95:1, preferably
0.002:1 to 0.9:1, more
preferably 0.005:1 to 0.8:1.
The thickness of the lignocellulose materials of the invention with expanded
plastics particles
present in nonuniform distribution in the core varies with the field of
application and is situated in
general in the range from 0.5 to 100 mm, preferably in the range from 10 to 40
mm, more
particularly 15 to 20 mm.
Lignocellulose materials, as for example woodbase materials, are an
inexpensive and resource-
protecting alternative to solid wood, and have become very important
particularly in furniture
construction, for laminate floors and as construction materials. Customarily
serving as starting
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materials are wood particles of different thicknesses, examples being wood
chips or wood fibers
from a variety of woods. Such wood particles are customarily compressed with
natural and/or
synthetic binders and optionally with addition of further additives to form
woodbase materials in
panel or strand forms.
Lightweight woodbase materials are very important for the following reasons:
Lightweight woodbase materials lead to greater ease of handling of the
products by the end
customers, as for example when packing, transporting, unpacking or
constructing the furniture.
Lightweight woodbase materials result in lower costs for transport and
packaging, and it is also
possible to save on materials costs when producing lightweight woodbase
materials. Lightweight
woodbase materials may, as when used in means of transport, for example,
result in a lower
energy consumption by those means of transport. Furthermore, using lightweight
woodbase
materials, it is possible to carry out more cost-effective production of, for
example, materials-
intensive decorative parts, relatively thick worktops and side panels in
kitchens.
There are numerous applications, as for example in the bathroom or kitchen
furniture segment or
in interior outfitting, where lightweight and economic lignocellulosic
materials having improved
mechanical properties, as for example improved flexural strengths, are sought
after. Moreover,
such materials are to have an extremely good surface quality, in order to
allow application of
coatings, for example a paint or varnish finish, having good properties.
Examples
1. Production of the expanded plastics particles
The starting material used was the expandable polystyrene Kaurit Light 200
from BASF SE. The
polystyrene particles were treated with steam in a batch preliminary foamer,
and were foamed to
a bulk density of 50 g/I. The resultant expanded plastics particles (component
B) were stored in
an air-permeable fabric bag at room temperature for 7 days before further use.
2. Production of the woodbase materials
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For each woodbase material board, three different mixtures of the starting
materials were
prepared.
Mixture 1: components E, F, G for the outer layers
Mixture 2: components A, B, C, D for the outer region of the core
Mixture 3: components A, B, C, D for the inner region of the core
For comparative example 1, there is no component B - in other words, mixtures
2 and 3 in that
case contain only components A, C and D.
The mixtures were each prepared in a laboratory mixer, with the solid
constituents first being
introduced and mixed. The liquid constituents were premixed in a vessel and
then sprayed on
through nozzles.
Spruce chips with a moisture content of 3.5% were used (components A and E).
The binder used
was Kaurit0 Leim 347 size with a solids content of 67%, from BASF SE
(components C and F).
For mixture 1, the size was admixed with 10 parts by weight of water and 1
part by weight of 52%
strength ammonium nitrate solution (based in each case on 100 parts by weight
of Kaurit0 Leim
347 size) before the size was applied to the solid constituents of the
mixture. For mixtures 2 and
3, the size was admixed with 4 parts by weight of 52% strength ammonium
nitrate solution (based
on 100 parts by weight of Kaurit0 Leim 347 size) before the size was applied
to the solid
constituents of the mixtures. The amount of size liquor is made such as to
produce a degree of
sizing of 8.5%, in other words 8.5 parts by weight of size (based on solids)
per 100 parts by
weight of E (based on solids) in mixture 1 and 8.5 parts by weight of size
(based on solids) per
100 parts by weight of the mixture of A and B (based on solids) in mixtures 2
and 3.
The mixtures were then placed one above another in layers in a 30 x 30 cm mold
in such a way
as to produce, in a symmetrical construction, a cake of chips with 5 layers
(sequence: mixture 1,
mixture 2, mixture 3, mixture 2, mixture 1). The amounts here were selected
such that the weight
ratio of the layers (based on dry mass) was in each case
12.5:18.8:37.5:18.8:12.5.
In examples 2 to 8, the mass ratio of the total amount of component B present
in the inner three
layers to the total amount of component A present in the inner three layers is
the same (based on
solid substance.
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The total weight of the woodbase material mat was selected so as to result in
the desired density
at a target thickness of 16 mm at the end of the pressing operation.
After this, the cake of chips was subjected to cold preliminary compressing
and then pressed in a
hot press. A thickness of 16 mm was set. The pressing temperature was 210 C in
each case, and
the pressing time 150 S.
3. Investigation of the woodbase materials
3.1 Density
The density was determined 24 hours after production, in accordance with EN
1058.
3.2 Transverse tensile strength
The transverse tensile strength was determined in accordance with EN 319.
3.3 Flexural strength and flexural elasticity modulus
The flexural strength and flexural elasticity modulus were determined in
accordance with
DIN EN 310.
.3.4 Screw pullout resistance
The screw pullout resistance was determined in accordance with DIN EN 320.
Only the screw
pullout resistances for the surfaces were measured.
3.5 Peeling strength
The peeling strength, as a measure of the surface quality, was determined in
accordance with
DIN EN 311.
Examples
Examples 1 and 2: comparative examples without expanded plastics particles or
with
homogeneous distribution of the plastics particles in the core
Examples 3 to 8: inventive examples
,
Example Ratio X Ratio Y Ratio Z Density
Transverse Flexural Flexural Screw Peeling
("exterior") ("interior") (= X:Y) tensile
elasticity strength pullout strength
strength modulus
resistance
,
[kg/m1 [N/mm2] [N/mm2] ,
[N/mm2] [N] [N/mm2]
1 a) a) - 507 0.48 1520 7.4
620 0.7
2 0.075 0.075 1 503 0.63 1575 8.4
680 0.8
3 0.108 0.043 2.50 498 0.64 1575 8.6
750 1.1
4 , 0.043 0.108 0.40 502 0.75 1620 9.3
690 0.8
0.086 0.065 1.33 495 0.62 1580 8.6 720 1.0
6 0.065 0.086 0.75 498 0.72 1605 9.1
680 0.8 9
2
7 0.081 0.070 1.15 499 0.64 1585 8.5
710 1.0 coo,
Ni
.
,
8 0.070 0.081 0.87 503 0.68 1600 8.8
680 0.8 <.ri Fe
..
5 a) this comparative example contains no expanded plastics particles
(component B) ,
o,
i
.
