Note: Descriptions are shown in the official language in which they were submitted.
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Multilayer lightweight woodbase materials composed of lignocellulosic
materials
having a core and two outer layers with treated pulp, treated natural fibers,
synthetic fibers or mixtures thereof in the core
Description
The present invention relates to lignocellulosic materials having a core and
two
outer layers, the core comprising treated pulps, treated natural fibers,
synthetic
fibers or mixtures thereof.
WO-A-2011/018373 discloses compression-molded materials which are light in
weight and at the same time compressively strong, these materials consisting
of
woodchips or wood fibers, a binder, and a porous foamable or partly foamable
plastic which acts as a filler.
The compression-molded materials comprising wood chips or wood fibers leave
something to be desired in terms of their mechanical properties, such as the
flexural strength or the transverse tensile.
EP-A-2 338 676 discloses lightweight construction boards having a top outer
board and a bottom outer board comprising a lignocellulose-containing
material,
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and a lightweight middle ply with honeycomb structure. In these boards, the
outer
boards are bonded to the middle ply using an adhesive bonding agent.
Since only the outer boards in these lightweight construction boards hold
screws,
these so-called honeycomb boards exhibit a substantial reduction in screw
pullout resistance. Moreover, because of the honeycomb structure of the middle
ply, edging can be accomplished only with extra cost in complexity and with
specialty machinery.
It was an object of the present invention, therefore, to remedy the
disadvantages
identified above.
Found accordingly have been new, lignocellulosic materials having a core and
two outer layers, comprising, preferably consisting of, in the core
A) 30 to 98% by weight of lignocellulose particles,
B) 0 to 25% by weight, preferably 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, phenol-formaldehyde resin, and organic
isocyanate having at least two isocyanate groups, and
D) 0 to 10% by weight of additives
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and in the outer layers
E) 70 to 99% by weight of lignocellulosic particles, fibers or mixtures
thereof,
F) 1 to 30% by weight of one or more binders selected from the group
consisting of aminoplast resin, phenol-formaldehyde resin, and organic
isocyanate having at least two isocyanate groups, and
G) 0 to 10% by weight of additives
wherein 2% to 30% of the lignocellulose particles A) have been replaced by
treated pulps, treated natural fibers, synthetic fibers or mixtures thereof,
and also
the production thereof and the use thereof.
The statement of the weight percentages 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 percentages by weight of 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 comprises 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 additionally added water, for dilution of the
binders or for moistening of the outer layers, for example, from the
additives,
examples being aqueous curing agent solutions or aqueous paraffin emulsions,
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or from the expanded plastics particles if they are foamed, for example, using
steam.
Suitable pulps are compressed and dried cellulose fibers, and suitable
products,
for example, are paper, paperboard, cardboard or mixtures thereof, preferably
paper, paperboard or mixtures thereof, more preferably paper.
The pulps may be used in any dimensions, as for example in the form of strips,
folded or bent strips, nested strips which form a lattice, sheets, sheets with
cutouts, folded or bent sheets, or folded or bent sheets with cutouts;
preferably
strips, folded or bent strips, or nested strips which form a lattice; more
preferably
folded or bent strips or nested strips which form a lattice.
Suitable natural fibers include vegetable fibers such as seed fibers, for
example,
those of cotton or kapok, bast fibers such as bamboo fibers, jute, hemp
fibers,
kenaf, flax, hops, ramie or leaf fibers such as aback pineapple, caroa,
curaua,
henequen, macarimba, flax, sisal or fruit fibers such as coconut or fibers of
animal origin such as wool and animal hairs or silks or mixtures thereof,
preferably vegetable fibers, bast fibers, leaf fibers or mixtures thereof,
more
preferably bast fibers, leaf fibers or mixtures thereof.
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Suitable synthetic fibers include fibers of synthetic polymers such as
polycondensation fibers, examples being polyester, polyamide, polyimide,
polyamideimide, and polyphenylene disulfide, aramid or polyaddition fibers, as
for example polyurethane, or other polymerization fibers, examples being
5 polyacrylonitrile, polytetrafluoroethylene, polyethylene, polypropylene,
and
polyvinyl chloride; preferably polycondensation fibers, examples being
polyester,
polyamide, polyimide, polyamideimide, and polyphenylene disulfide, aramid, or
other polymerization fibers, as for example polyacrylonitrile,
polytetrafluoroethylene, polyethylene, polypropylene, and polyvinyl chloride;
more preferably polycondensation fibers, examples being polyesters, polyamide,
polyimide, polyamideimide, and polyphenylene disulfide, and aramid.
The natural fibers or synthetic fibers may be used in any length and any
diameter
or in a form in which they have been spun/linked to form ropes, cords or
tapes,
preferably as cords or tapes, more preferably as cords.
The pulps, natural fibers and/or synthetic fibers may be impregnated or
sprayed
in a conventional way with aminoplast resins, phenol-formaldehyde resin,
organic
isocyanate having at least two isocyanate groups, or mixtures thereof. The
amounts applied to the pulps, natural fibers and/or synthetic fibers may vary
within wide limits and are situated generally in a weight ratio of aminoplast
resin,
phenol-formaldehyde resin, organic isocyanate having at least two isocyanate
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groups, or mixtures thereof to the pulp or to the natural fiber of 0.5:1 to
5:1,
preferably 0.75:1 to 4:1, more preferably 1:1 to 3:1.
After the spraying or impregnation, the treated pulps, natural fibers or
synthetic
fibers may be subjected to drying and/or preliminary curing.
In the lignocellulosic materials of the invention, generally 2% to 30% by
weight,
preferably 3% to 20% by weight, especially 4% to 15% by weight of the
lignocellulose particles A) have been replaced by treated pulps, treated
natural
fibers, synthetic fibers or mixtures thereof.
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
generally mixed 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., a
plurality of constituents, such as substances or compounds, for example, from
the group of one component) in any desired order. Components A, B, C and D
may in each case be composed of one, two (Al, A2 or B1, B2, or Cl, C2 or D1,
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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 02 is added
immediately after Cl or Cl is added immediately after 02, or that one or more
other components or component constituents, component B for example, are
added between the addition of Cl and 02. 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, 02, 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
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constituent (i.e., a plurality of constituents, such as substances or
compounds,
for example, from the group of the component) and then added.
For the outer layers, the lignocellulosic particles or fibers 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,
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 atop another,
the
pulps, natural fibers, synthetic fibers or mixtures thereof are incorporated
into the
middle layer, and this system is compressed by a customary process, at
elevated
temperature, to give a lignocellulosic molding.
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For this purpose, first of all half of the mixture E, F, G is scattered on a
support.
Thereafter, some of the mixture A, B, C, D is applied as a layer over it, and
the
pulps, natural fibers or synthetic fibers are pressed gently into this
mixture. These
pulps, natural fibers or synthetic fibers are arranged parallel to one another
at a
distance of 1-2 cm, overlaying one another to form a lattice, in spiral
format, or
unordered, preferably parallel at a distance of 1-2 cm or overlaying one
another
to form a lattice, more preferably overlaying one another to form a lattice.
Now
the remaining A, B, C, D mixture, followed by the E, F, G mixture, are applied
in
layers over the pulps or natural or synthetic fibers ("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.
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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.
5
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,
10 pine, larch, lime, poplar, 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¨ like those 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 shives or mixtures thereof, more
preferably flax or hemp fibers or mixtures thereof, like those used in
manufacturing MDF and HDF boards.
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Starting materials for lignocellulose particles are customarily lumber from
forestry
thinning, residual industrial lumber, and used lumber, and also woody plants.
Processing to the desired lignocellulosic particles, to wood particles for
example,
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).
After the chipping of the wood, the chips are dried. Then any coarse and fine
fractions are removed. The remaining chips are sorted by sieving or
classifying in
a stream of air. The coarser material is used for the middle layer (component
A),
the finer material for the outer layers (component E).
The lignocellulosic fibers of component E are present within the
lignocellulosic
materials of the outer layer in amounts of 70 to 99% by weight, preferably 75
to
97% by weight, more preferably 80 to 95% by weight. Raw materials which can
be used are woods of any of the wood varieties listed under component A, or
woody plants. Following mechanical comminution, the fibers may be produced by
grinding operations, for example, after a hydrothermal pretreatment.
Fiberizing
methods are known from, for example, Dunky, Niemz, Holzwerkstoffe and Leime,
Technologie und Einflussfaktoren, Springer, 2002, pages 135 to 148.
Suitable expanded plastics particles (component B) include expanded plastics
particles, preferably expanded thermoplastic particles, having a bulk density
from
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to 150 kg/m3, preferably 30 to 130 kg/m3, 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).
5 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-
10 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%.
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-Cio olefin homopolymers, C2-Cio olefin copolymers, and
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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.
Customary additives may additionally be admixed with the polymers, preferably
the thermoplastics, forming a basis for the expandable or expanded plastics
particles B), examples of such additives 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 separately, 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
a change in pressure (this expansion often also being referred to as
"foaming")
(Kunststoff 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
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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 plastics particles", generally have no
cell
structures, in contrast to the expanded plastics particles. The expanded
plastics
particles generally have only 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 03 to C10
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,
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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
5 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
10 "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-
15 Handbuch 1996, volume 4 "Polystyrol", pages 567 to 598.
The expandable polystyrene and/or styrene copolymer is/are generally prepared
in a conventional way by suspension polymerization or by means of extrusion
processes.
The overall amount of the expanded plastics particles B, based on the overall
dry
mass of the core, is generally in the range from 0% to 25% by weight,
preferably
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1% to 25% by weight, more preferably 3% to 20% by weight, more particularly
5% to 15% by weight.
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 amino-plast resin, phenol-formaldehyde 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 phenol-formaldehyde resins 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
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diphenylmethane diisocyanate), it relates to the isocyanate component per se,
in
other words, for example, without solvent or emulsifying medium.
As aminoplast resin it is possible to use all aminoplast resins known to the
skilled
person, preferably those known for the production of wood base 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 (MF resins) or melamine-containing urea-
formaldehyde resins (MUF resins), more preferably urea-formaldehyde resins,
examples being Kaurit glue products from BASF SE.
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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.
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.
The stated aminoplast resins are used customarily in liquid form, usually in
solution, customarily as a 25% to 90% by weight strength solution, preferably
as
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 Gunter 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. 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 combinations preferably comprise
an aminoplast resin and/or phenol-formaldehyde 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, 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 if the
binder C and/or F comprises aminoplasts or phenol-formaldehyde resins. These
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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 phenol-formaldehyde resin.
5
Curing agents for the aminoplast resin component or for the phenol-
formaldehyde 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
10 suitable group of curing agents for aminoplast resin or phenol-
formaldehyde resin
are organic acids, inorganic acids, acidic salts of organic acids, and acidic
salts
of inorganic acids, 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
15 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 phenol-formaldehyde resin are organic or
inorganic acids such as nitric acid, sulfuric acid, formic acid, acetic acid,
and
polymers with acid groups, such as homopolymers or copolymers of acrylic acid
20 or methacrylic acid or maleic acid.
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Phenol-formaldehyde resins can also be cured alkalinically. 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 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.
The thickness of the lignocellulose materials of the invention 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.
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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 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, 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, material-intensive decorative parts, relatively thick worktops
and
side panels in kitchens.
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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
Production of the boards
Production of the mixtures (A, B, C, D), (E, F, G) and also of the impregnated
pulps and natural fibers/synthetic fibers
The glue used was urea-formaldehyde glue (Kaurit glue 347 from BASF SE).
The solids content was adjusted with water in each case to 67% by weight.
Details are evident from the table.
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Production of a mixture A, B, C, D:
In a mixer, 330 g of chips (component A) and 33 g of expanded polymer
(component B) were mixed as per the table. Then 62.7 g of a glue liquor
comprising 100 parts of Kaurit glue 347 and 4 parts of a 52% strength aqueous
ammonium nitrate solution, 1.3 parts of urea, and 0.8 part of a 60% aqueous
paraffin dispersion were applied.
Production of a mixture E, F, G:
Furthermore, in a mixer, 179.6 g of chips or fibers (component E) as per the
table
were applied with 30.4 g of a glue liquor comprising 100 parts of Kaurit glue
347
and 1 part of a 52% strength aqueous ammonium nitrate solution, 0.5 part of
urea, 0.5 part of a 60% aqueous paraffin dispersion, and 40 parts of water.
Production of the impregnated paper strips:
Standard commercial paper (200 g/m2) was cut into strips measuring 1.3 x 30 cm
long and impregnated twice in an impregnating bath with melamine-
formaldehyde impregnating resin, consisting of 100 parts of Kauramin
impregnating resin 783, 7.1 parts of water, 0.35 part of Kauropal 930, and
0.3
part of Harter 529 curing agent, drawn through two coating bars, and dried.
Compressing of the glue-treated chips
CA 02875209 2014-11-28
The glue-treated chips were filled into a 30 x 30 cm mold as follows:
First of all, half of mixture (E, F, G) was scattered into the mold. Then 15%
to
50% of the mixture (A, B, C, D) was applied as a layer over it. Pressed
subsequently into this cake of chips were the reinforcing elements (paper,
cord,
5 rope; see table), in the geometry indicated in the table, and the
remainder of the
mixture (A, B, C, D) was scattered over this. Finally, the second half of the
mixture (E, F, G) was applied as a layer over this, and subjected to cold
precompaction. This was followed by pressing in a hot press (pressing
temperature 210 C, pressing time 120 s). The target thickness of each board
10 was 16 mm.
Investigation of the lightweight, wood-containing substance
Density:
15 The density was determined 24 hours after production. For this purpose,
the ratio
of mass to volume of a test specimen was determined at the same moisture
content. The square test specimens have a side length of 50 mm, with an
accuracy of 0.1 mm. The thickness of the test specimen was measured in its
center, to an accuracy of 0.05 mm. The accuracy of the balance used for
20 determining the mass of the test specimen was 0.01 g. The gross density
p
(kg/m3) of a test specimen was calculated by the following formula:
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26
p = m/(bi*b2*d) * 106
Here:
m is the mass of the test specimen, in grams, and
bi, b2, and d are the width and thickness of the test specimen, in
millimeters.
A precise description of the procedure can be found in DIN EN 323, for
example.
Transverse tensile strength:
The transverse tensile strength is determined perpendicular to the board
plane.
For this purpose, the test specimen was loaded to fracture with a uniformly
distributed tensile force. The square test specimens had a side length of 50
mm,
with an accuracy of 1 mm, and angles of exactly 90 . Moreover, the edges were
clean and straight. The test specimens were bonded to the yokes by means of a
suitable adhesive, an epoxy resin, for example, and dried for at least 24
hours in
a controlled-climate cabinet at 20 C and 65% atmospheric humidity. The test
specimen prepared in this way was then clamped into the testing machine in a
self-aligning manner with a shaft joint on both sides, and then loaded to
fracture
at a constant rate, with the force needed to achieve this being recorded. The
transverse tensile strength ft (N/mm2) was calculated by the following
formula:
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fi = Fmax/(a * b)
Here:
Frna, is the breaking force in newtons
a and b are the length and width of the test specimen, in millimeters.
A precise description of the procedure can be found in DIN EN 319, for
example.
Flexural strength
The flexural strength was determined by applying a load in the middle of a
test
specimen lying on two points. The test specimen had a width of 50 mm and a
length of 20 times the nominal thickness plus 50 mm, but not more than
1050 mm and not less than 150 mm. The test specimen was then placed flatly
onto two bearing mounts, the inter-center distance of which was 20 times the
thickness of the test specimen, and the test specimen was then loaded to
fracture in the middle with a force, this force being recorded. The flexural
strength
fm (N/mm2) was calculated by the following formula:
Urn= (3*Fmax*I)/(2*b12)
Here:
Fmax is the breaking force in newtons
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I is the distance between the centers of the bearing mounts, in millimeters
b is the width of the test specimen, in millimeters
t is the thickness of the test specimen, in millimeters.
A precise description of the procedure can be found in DIN EN 310.
Screw pullout resistance
The screw pullout resistance was determined by measuring the force needed to
pull out a screw in an axially parallel fashion from the test specimen. The
square
test specimens had a side length of 75 mm, with an accuracy of 1 mm. First of
all, guide holes with a diameter of 2.7 mm ( 0.1 mm), and depth of 19 ( 1
mm)
were drilled perpendicular to the surface of the test specimen into the
central
point of the surface. Subsequently, for the test, a steel screw with nominal
dimensions of 4.2 mm x 38 mm, having a ST 4.2 thread in accordance with ISO
1478 and a pitch of 1.4 mm, was inserted into the test specimen, with 15 mm (
0.5 mm) of the whole screw being inserted. The test specimen was fixed in a
metal frame and, via a stirrup, a force was applied to the underside of the
screw
head, the maximum force with which the screw was pulled out being recorded.
A precise description of the procedure can be found in DIN EN 320.
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The results of the tests are summarized in the table.
The quantity figures are based in each case on the dry substance. When parts
by
weight are stated, the dry wood or the sum of the dry wood and the filler was
taken as 100 parts. When % by weight is stated, the sum of all the dry
constituents of the lightweight, wood-containing material is 100%.
The tests in the table without addition of component reinforcements serve as a
comparison and were carried out in accordance with WO-A-2011/018373.
Test Target density Component A Component B UF glue [g]
Paper Paper geometry
[kg/m3] (wood) [g] (expanded density
polymer) [g] [g/m2]
1 400 330 33 63 75
Bent strips
2 450 368 37 70 75
arranged in
3 500 393 39 75 75
parallel p
.
,,
4 400 330 33 63 120
Bent strips ,
rõ
N)
450 368 37 70 120
arranged in .
,
,
,
,
,
ca
rõ
6 500 393 39 75 120
parallel o '
7 400 330 33 63 200
Bent strips
8 450 368 37 70 200
arranged in
9 500 393 39 75 200
parallel
400 330 33 63 120
Arranged in a
11 450 368 37 70 120
lattice
12 500 393 39 75
120
13 400 330 33 63
200
Arranged in a
14 450 368 37 70
200
lattice
15 500 393 39 75
200
16[1] 400 330 33 63 -
-- 17[1] 450 368 37 70 --- P
.
N)
0
,
18[1] 500 393 39 75 -
--
rõ
rõ
.
,
,
,
,
,
ca
rõ
[1] = Comparative test as per the sole example in WO-A-2011/018373 _. 0
Test Density Transverse tensile Flexural strength Screw
pullout resistance
[kg/m3] strength [N/mml [N/mnn2] [NJ]
1 428 0.56 9.83 335
2 462 0.67 13.27 387
3 502 0.77 15.22 523
P
.
,,
,
4 436 0.60 10.98 350
rõ
rõ
486 0.73 14.85 410
,
,
,
,
,
La
rõ
6 513 0.83 17.42 547
7 456 0.76 11.67 371
8 504 0.81 14.82 510
9 530 0.92 18.21 632
446 0.64 11.67 363
11 491 0.74 14.46 481
12 528 0.82 17.39
554
13 474 0.82 11.88
495
14 512 0.91 15.66
593
15 543 0.95 18.52
578
16[1] 417 0.42 8.23
262
17[1] 465 0.42 11.11
340
18(1] 493 0.58 14.43
418
[1] = Comparative test as per the sole example in WO-A-2011/018373
