Note: Descriptions are shown in the official language in which they were submitted.
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Multilayer lignocellulose-containing moldings having low formaldehyde emission
Description
The present invention relates to a multilayer lignocellulose-containing
molding as
defined in the claims.
Furthermore, the present invention relates to a process for the production of
a multilayer
lignocellulose-containing molding and the use of a multilayer lignocellulose-
containing
molding for the production of articles of all types and in the construction
sector and for
the production of pieces of furniture and furniture parts, of packaging
materials, in house
building or in interior finishing or in motor vehicles.
Materials based on lignocellulose are known. Important examples of
lignocellulose-
containing materials are wood parts, such as wood layers, wood strips, wood
chips or
wood fibers, it being possible for the wood fibers, optionally, also to
originate from wood
fiber-containing plants, such as flax, hemp, sunflowers, Jerusalem artichoke
or rape.
Starting materials for such wood parts or wood particles are usually timbers
from the
thinning of forests, residual industrial timbers and used timbers and wood
fiber-
containing plants.
The processing to give the desired lignocellulose-containing materials, such
as wood
particles, is effected by known processes, cf. for example M. Dunky, P. Niemt,
Holzwerkstoffe and Leime, pages 91-156, Springer Verlag Heidelberg, 2002.
Lignocellulose-containing moldings, also referred to as woodbase materials
here in the
case of wood as lignocellulose, are an economical and resource-protecting
alternative to
solid wood and have become very important, particularly in furniture
construction and as
building materials. As a rule, wood layers of different thickness, wood
strips, wood chips
or wood fibers of various timbers serve as starting materials for woodbase
materials.
Such wood parts or wood particles are usually pressed at elevated temperature
with
natural and/or synthetic binders and, optionally, with addition of further
additives to give
board-like or strand-like woodbase materials. Examples of such lignocellulose-
containing moldings or woodbase materials are medium density fiber boards
(MDF),
wood particle materials, such as particle boards and oriented strand boards
(OSB),
plywood, such as veneered plywood, and glued wood.
Binders used are as a rule formaldehyde-containing binders, for example urea-
formaldehyde resins or melamine-containing urea-formaldehyde resins. The
resins are
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prepared by polycondensation of formaldehyde with urea and/or melamine. The
use of
such formaldehyde resins can lead to the presence of free formaldehyde in the
finished
woodbase material. By hydrolysis of the polycondensates, additional
formaldehyde may
be liberated. The free formaldehyde present in the woodbase material and the
formaldehyde liberated by hydrolysis during the life of the woodbase material
can be
released to the environment.
Above certain limits, formaldehyde can cause allergies and irritation of the
skin,
respiratory tract and eyes in humans. The reduction of the formaldehyde
emission in
components, especially in the interior sector, is therefore an important
challenge.
The prior art discloses the following measures for reducing or suppressing the
formaldehyde emission from woodbase materials:
- use of aminoplast glues which were prepared with little formaldehyde
- addition of formaldehyde scavengers to the aminoplast glue, for example urea
and/or melamine
- aftertreatment of the finished woodbase materials with so-called
formaldehyde
scavengers, such as compounds comprising amine groups
However, such measures are still not completely satisfactory. The preparation
of the
aminoplast glues with little formaldehyde or the addition of formaldehyde
scavengers to
the aminoplast glue leads to the glue curing more slowly, which increases the
residence
times in the hot press and thus adversely affects the cost-efficiency of the
production of
the woodbase material.
WO 2010/031718 Al (BASF SE) describes a multilayer lignocellulose-containing
molding comprising a middle layer and a covering layer in which the binder for
the
middle layer is formaldehyde resin and/or organic isocyanate and the binder
for the
covering layer comprises a (co)polymer of ethylenically unsaturated carboxylic
acids
with further ethylenically unsaturated monomers and, under certain
preconditions, a
formaldehyde scavenger. WO 2010/031718 Al does not disclose an organic
isocyanate
as a component of the binder for the covering layer.
The multilayer moldings described in the prior art still leave room for
improvements with
respect to mechanical strengths (for example transverse tensile strength,
peeling
strength of the layers according to the corresponding test standard mentioned
in the
examples) and also moisture resistance (for example 24 hour swelling or water
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absorption according to the test standard or test prescription mentioned in
the
examples).
The object of the present invention is accordingly to overcome the
disadvantages
described in the prior art. In particular, it was intended to provide
multilayer
lignocellulose-containing moldings whose formaldehyde emission was to be
reduced or
virtually absent, and the multilayer lignocellulose-containing moldings being
intended to
have good mechanical properties.
The object was achieved by a multilayer lignocellulose-containing molding
comprising
A) a middle layer or a plurality of middle layers comprising lignocellulose-
containing
particles which is/are obtainable by using a binder (a) and
B) a covering layer or a plurality of covering layers containing
lignocellulose-
containing particles which is/are obtainable by using a binder (b),
the binder (a) being selected from the group consisting of (al) formaldehyde
resins and (a2) an organic isocyanate having at least two isocyanate groups;
the binder (b) comprising the following components:
an aqueous component (I) comprising
(i) a polymer A which is composed of the following monomers:
a) from 80 to 100% by weight of at least one ethylenically unsaturated mono-
and/or dicarboxylic acid (monomer(s) Al) and
b) from 0 to 20% of at least one further ethylenically unsaturated monomer
which differs from the monomers Al (monomer(s) A2)
optionally
(ii) a low molecular weight crosslinking agent having at least two functional
groups which are selected from the group consisting of hydroxyl, carboxyl
and derivatives thereof, primary, secondary and tertiary amine, epoxy,
aldehyde,
an organic isocyanate having at least two isocyanate groups as component (II)
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and, optionally, a component (III), as an aqueous dispersion, comprising
one or more polymer(s) M which is/are composed of the following monomers:
a) from 0 to 50% by weight of at least one ethylenically unsaturated monomer
which comprises at least one epoxide and/or at least one hydroxyalkyl group
(monomer(s) M1) and
b) from 50 to 100% by weight of at least one further ethylenically unsaturated
monomer which differs from the monomers M1 (monomer(s) M2)
and, optionally, customary additives as component (IV),
and the binder (b) optionally comprises a formaldehyde scavenger.
The term lignocellulose is known to the person skilled in the art. Important
examples of
lignocellulose are wood, bark, cork, bagasse, straw, flax, bamboo, alfa grass,
rice shells,
sisal fibers and coir fibers. The material can be present in the form of
granules, strands,
shavings, fibers or flour. Very suitable examples of lignocellulose-containing
particles
are wood parts, such as wood layers, wood strips, wood chips or wood fibers,
it being
possible for the wood fibers to originate, if appropriate, also from wood
fiber-containing
plants, such as flax, hemp, sunflowers, Jerusalem artichoke or rape.
Wood particles, flax particles, in particular wood fibers or wood chips, and
flax fibers or
flax chips, the latter generally being referred to as flax shives, are
preferred as
lignocellulose-containing particles.
The abovementioned lignocellulose in the abovementioned forms can naturally
also be
used in mixtures, for example mixtures of wood fibers with flax fibers or wood
chips with
flax shives.
The binder (a) comprises a formaldehyde resin, preferably aminoplast resin
(al) and/or
an organic isocyanate having at least two isocyanate groups (a2).
If the binder (a) comprises an aminoplast resin, the binder (a) as a rule also
comprises
the substances known to the person skilled in the art, generally used for
aminoplasts
and usually designated as curing agents, such as ammonium-sulfate or ammonium-
nitrate or inorganic or organic acids, for example sulfuric acid, formic acid,
or acid-
generating substances, such as aluminum chloride, aluminum sulfate, in each
case in
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the customary, small amounts, for example in the range from 0.1% by weight to
6% by
weight, based on the total amount of aminoplast resin in the binder (a).
A formaldehyde resin is understood here as meaning polycondensates of
compounds
having at least one carbamido group (the carbamido group also called a
carboxamido
group) optionally partly substituted by organic radicals and an aldehyde,
preferably form
aldehyde; these resins are also called aminoplast resins. Formaldehyde resins
are
furthermore understood herein as meaning phenol-formaldehyde resins (PF
resins).
All formaldehyde resins known to the person skilled in the art, preferably
those known
for the production of woodbase materials, can be used as suitable formaldehyde
resin.
Such resins and their preparation are described, for example, in Ullmanns
Enzyklopadie
der technischen Chemie, 4th, revised and extended 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 in
M.
Dunky, P. Niemz, Holzwerkstoffe and Leime, Springer 2002, pages 251 to 259 (UF
resins) and pages 303 to 313 (MUF and UF with small amount of melamine, the
latter
also known as melamine-fortified UF resins (UFm)). Phenol-formaldehyde resins
(PF
resins) are also suitable formaldehyde resins.
Preferred formaldehyde resins are polycondensates of compounds having at least
one
carbamido group, including those partly substituted by organic radicals, and
formaldehyde.
Particularly preferred formaldehyde resins are urea-formaldehyde resins (UF
resins),
melamine-formaldehyde resins (MF resins) or melamine-containing urea-
formaldehyde
resins (MUF resins and UFm resins) and melamine-urea-phenol-formaldehyde
resins
(MUPF resins).
Very particularly preferred formaldehyde resins are urea-formaldehyde resins
(UF
resins) and melamine-formaldehyde resins (MUF resins and UFm resins), for
example
Kaurit or Kauramin glue types from BASF SE.
In addition to the described conventional formaldehyde resins having a very
high molar
formaldehyde: amino group ratio, it is also possible to use formaldehyde
resins having a
lower molar formaldehyde: amino group ratio.
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Such suitable formaldehyde resins, in particular aminoplast resins, are
polycondensates
of compounds having at least one amino group, including those partly
substituted by
organic radicals, and aldehyde, in which the molar ratio of aldehyde to amino
group
optionally partly substituted by organic radicals is in the range from 0.3 to
1.0, preferably
from 0.3 to 0.6, particularly preferably from 0.4 to 0.5.
Further suitable formaldehyde resins of this type, in particular aminoplast
resins, are
polycondensates of compounds having at least one amino group-NH2 and
formaldehyde, in which the molar ratio of formaldehyde to -NH2 group is in the
range
from 0.3 to 1.0, preferably from 0.3 to 0.6, particularly preferably from 0.4
to 0.5.
Further suitable formaldehyde resins of this type, in particular aminoplast
resins, are
urea-formaldehyde resins (UF resins) or melamine-containing urea-formaldehyde
resins
(MUF resins and UFm resins), in which the molar ratio of formaldehyde to -NH2
group is
in the range from 0.3 to 1.0, preferably from 0.3 to 0.6, particularly
preferably from 0.4 to
0.5.
Further suitable formaldehyde resins of this type, in particular aminoplast
resins, are
urea-formaldehyde resins (UF resins), in which the molar ratio of formaldehyde
to -NH2
group is in the range from 0.3 to 1.0, preferably from 0.3 to 0.6,
particularly preferably
from 0.4 to 0.5.
The abovementioned conventional formaldehyde resins, in particular aminoplast
resins,
having a lower formaldehyde content are usually used in liquid form, in
general
suspended in a liquid suspending medium, preferably in aqueous suspension, but
can
also be used as a solid.
The solids content of the formaldehyde resin suspensions, preferably aqueous
suspension, is usually from 25 to 90% by weight, preferably from 50 to 70% by
weight.
The solids content of an aminoplast resin as a representative of formaldehyde
resins in
aqueous suspension can be determined, for example, according to Gunter
Zeppenfeld,
Dirk Grunwald, Klebstoffe in der Holz- und Mobelindustrie, 2nd edition, DRW-
Verlag,
page 268. For determining the solids content of aminoplast glues, 1 g of
aminoplast glue
is accurately weighed into a weighing dish, finely distributed on the bottom
and dried for
2 hours at 120 C in a drying oven. After thermostating at room temperature in
a
desiccator, the residue is weighed and is calculated as a percentage of the
weight
taken.
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The anninoplast resins are prepared by known processes (cf. abovementioned
Ullmann
literature "Aminoplaste" and "Amino Resins", and abovementioned literature
Dunky
et al.) by reacting compounds containing carbannido groups, preferably urea
and/or
melamine, with the aldehydes, preferably formaldehyde, in the desired molar
carbamido
group: aldehyde ratios, preferably in water as a solvent.
The desired molar ratio of aldehyde, preferably formaldehyde, to amino group
optionally
partly substituted by organic radicals can also be established by adding
monomers
carrying -NH2 groups to prepared, preferably commercial, aminoplast resins
having a
relatively high formaldehyde content. Monomers carrying NH2 groups are
preferably
urea and melamine, particularly preferably urea.
An optional component of the binder (a) (hereinafter referred to as (a2)) and
a
mandatory component of binder (b) (hereinafter referred to as (II)) is an
organic
isocyanate having at least two isocyanate groups.
All organic isocyanates known to the person skilled in the art, preferably
those known for
the production of woodbase materials or polyurethanes, can be used as suitable
organic
isocyanate (a2) and/or (II). Such organic isocyanates and their preparation
and use are
described, for example in Becker/Braun, Kunststoff Handbuch, 3rd revised
edition,
volume 7 "Polyurethane", Hanser 1993, pages 17 to 21, pages 76 to 88 and pages
665
to 671.
Preferred organic isocyanates (a2) and/or (II) are oligomeric isocyanates
having 2 to 10,
preferably 2 to 8, monomer units and on average at least one isocyanate group
per
monomer unit.
A particularly preferred organic isocyanate (a2) and/or (II) is the oligomeric
organic
isocyanate PMDI ("Polymeric Methylenediphenylene diisocyanate") which is
obtainable
by condensation of formaldehyde with aniline and phosgenation of the isomers
and
oligomers formed in the condensation (cf. for example Becker/Braun, Kunststoff
Handbuch, 3rd revised edition, volume 7 "Polyurethane", Hanser 1993, page 18,
last
paragraph to page 19, second paragraph and page 76, fifth paragraph).
The organic isocyanate (a2) and/or (II) can also be present in aqueous-
emulsifiable
form, as obtainable for example by (i) adding emulsifiers, for example
polyethylene
glycols, glue, polyvinylpyrrolidone, polyacrylamides, or (ii) by modifying
with
monofunctional polyethylene oxide derivatives or by adding phosphoric or
sulfonic acids.
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In the context of the present invention, very suitable PMDI products (a2)
and/or (II) are
the products of the LUPRANAr series of BASF SE, in particular LUPRANAT M 20
FB
of BASF Polyurethanes GmbH or the water-emulsifiable form of the ELASTAN
series of
BASF Polyurethanes GmbH.
It is also possible to use mixtures of the organic isocyanates described, the
mixing ratio
not being critical on the basis of current knowledge.
The binder (a) may comprise the components (al) and (a2) in all mixing ratios
or alone.
In a preferred embodiment, the binder (a) comprises only the component (al),
preferably an aminoplast resin, particularly preferably a UF resin and/or MUF
resin
and/or UFm resin.
In a further preferred embodiment, the binder (a) comprises only the component
(a2),
preferably PMDI.
In a further preferred embodiment, the binder (a) comprises the component
(al),
preferably an aminoplast, particularly preferably a UF resin and/or UFm resin
and/or
MUF resin, in the range from 70 to 99.9% by weight, and the component (a2),
preferably
PMDI, in the range from 0.1 to 30% by weight, based in each case on the sum of
(al)
and (a2) of the pure undiluted substances.
In a very particularly preferred embodiment, the binder (a) comprises a UF
resin in the
range from 70 to 99.9% by weight and PMDI in the range from 0.1 to 30% by
weight,
based in each case on the sum of (al) and (a2) of the pure, undiluted
substances.
The binders (al) and (a2) can be used in an already mixed form, but it is also
possible
to bring the binders (al) and (a2), as a rule initially unmixed, into contact
with the
lignocellulose-containing particles, usually in separate steps.
The total amount of the binder (al), preferably of the UF resin, as pure,
undiluted
substance, based on the dry mass of the lignocellulose-containing particles,
preferably
wood particles, is in the range from 3 to 50% by weight, preferably from 5 to
15% by
weight, particularly preferably from 6 to 12% by weight.
The total amount of the binder (a2), preferably of the PMDI, as pure,
undiluted
substance, based on the dry mass of the lignocellulose-containing particles,
preferably
wood particles, is in the range from 0.5 to 30% by weight, preferably from 1
to 10% by
weight, particularly preferably from 2 to 6% by weight.
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Where the binder (a) is composed of (al) and (a2), the total amount of the
binder (a), as
pure undiluted substance, based on the dry mass of the lignocellulose-
containing
particles, preferably wood particles, is in the range from 0.5 to 30% by
weight, preferably
from 1 to 15% by weight, particularly preferably from 2 to 12% by weight.
The binder (b) comprises:
An aqueous component (I) comprising
(i) a polymer A which is composed of the following monomers:
a) from 70 to 100% by weight of at least one ethylenically unsaturated mono-
and/or
dicarboxylic acid (monomer(s) Al) and
b) from 0 to 30% by weight of at least one further ethylenically unsaturated
monomer
which differs from the monomers Al (monomer(s) A2),
optionally
(ii) a low molecular weight crosslinking agent having at least two functional
groups
which are selected from the group consisting of hydroxyl, carboxyl and
derivatives
thereof, primary, secondary and tertiary amine, epoxy, aldehyde,
an organic isocyanate having at least two isocyanate groups as component (II)
and, optionally, a component (III) as an aqueous dispersion comprising one or
more
polymer(s) M, which is composed of the following monomers:
a) from 0 to 50% by weight of at least one ethylenically unsaturated
monomer, which
comprises at least one epoxide group and/or at least one hydroxyalkyl group
(monomer(s) M1) and
b) from 50 to 100% by weight of at least one further ethylenically
unsaturated
monomer which differs from the monomers M1 (monomer(s) M2)
and, optionally, customary additives as component (IV),
and the binder (b) optionally comprises a formaldehyde scavenger.
The polymer A is composed of the following monomers:
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a) from 70 to 100% by weight of at least one ethylenically unsaturated mono-
and/or
dicarboxylic acid (monomer(s) Al) and
b) from 0 to 30% by weight of at least one further ethylenically unsaturated
monomer
which differs from the monomers Al (monomer(s) A2).
The preparation of polymers A is familiar to the person skilled in the art and
is effected in
particular by free radical solution polymerization, for example in water or in
an organic
solvent (cf. for example A. Echte, Handbuch der Technischen Polymerchemie,
chapter
6, VCH, Weinheim, 1993 or B. Vollmert, Grundriss der Makromolekularen Chemie,
volume 1, E. Vollmert Verlag, Karlsruhe, 1988).
Suitable monomers Al are in particular a,f3-monoethylenically unsaturated mono-
and
dicarboxylic acids having three to six carbon atoms, the possible anhydrides
thereof and
the water-soluble salts thereof, in particular the alkali metal salts thereof,
such as, for
example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic
acid,
citraconic acid, tetrahydrophthalic acid, or the anhydrides thereof, such as,
for example,
maleic anhydride, and the sodium or potassium salts of the abovementioned
acids.
Acrylic acid, methacrylic acid and/or maleic anhydride are particularly
preferred, acrylic
acid and the binary combinations of acrylic acid and maleic anhydride or
acrylic acid and
maleic acid being especially preferred.
Suitable monomer(s) A2 are ethylenically unsaturated compounds which can be
subjected to free radical copolymerization in a simple manner with monomer(s)
Al, for
example ethylene, C3-C24-a-olefins, such as propene, 1-hexene, 1-octene, 1-
decene;
vinylaromatic monomers, such as styrene, a-methylstyrene, o-chlorostyrene, or
vinyltoluenes; vinyl halides, such as vinyl chloride or vinylidene chloride;
esters of vinyl
alcohol and monocarboxylic acids having 1 to 18 carbon atoms, such as vinyl
acetate,
vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate; esters
of a,13-mono-
ethylenically unsaturated mono- and dicarboxylic acids, preferably having 3 to
6 carbon
atoms, such as, in particular, acrylic acid, methacrylic acid, maleic acid,
fumaric acid and
itaconic acid, with alkanols having in general 1 to 12, preferably 1 to 8 and
in particular 1
to 4 carbon atoms, such as, in particular, methyl, ethyl, n-butyl, isobutyl,
pentyl, hexyl,
heptyl, octyl, nonyl, decyl and 2-ethylhexyl acrylate and methacrylate,
dimethyl or di-n-
butyl fumarate and maleate; nitrites of a,13-nnonoethylenically unsaturated
carboxylic
acids, such as acrylonitrile, methacrylonitrile, fumaronitrile, maleonitrile,
and conjugated
C4.8-dienes, such as 1, 3-butadiene (butadiene) and isoprene. Said monomers
form as a
rule the main monomers which, based on the total amount of monomers A2,
together
account for a proportion of 50% by weight, preferably 80% by weight and
particularly
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preferably 90% by weight or even the total amount of the monomers A2. As a
rule,
these monomers have only moderate to low solubility in water under standard
conditions
of temperature and pressure (20 C, 1 atm (absolute)).
Further monomers A2, which however have a high water solubility under the
abovementioned conditions, are those which comprise either at least one sulfo
group
and/or the corresponding anion thereof or at least one amino, amido, ureido or
N-heterocyclic group and/or the ammonium derivatives thereof which are
protonated or
alkylated on the nitrogen. Acrylamide and methacrylamide and furthermore
vinylsulfonic
acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid and the
water-
soluble salts thereof and N-vinylpyrrolidone; 2-vinylpyridine, 4-
vinylpyridine;
2-vinylimidazole; 2-(N,N-dimethylamino)ethyl acrylate, 2-(N,N-
dimethylamino)ethyl
methacrylate, 2-(N,N-diemethylamino)ethyl acrylate, 2-(N,N-diethylamino)ethyl
methacrylate, 2-(N-tert.-butylamino)ethyl methacrylate, N-(3-N',N'-
dimethylamino-
propyl)methacrylamide and 2-(1-imidazolin-2-onyl)ethyl methacrylate may be
mentioned
by way of example.
Usually, the abovementioned water-soluble monomers A2 are present only as
modifying
monomers in amounts 5 10% by weight, preferably 5% by weight and particularly
preferably 5 3% by weight, based on the total amount of monomers A2.
Further monomers A2 which usually increase the internal strength of the films
of a
polymer matrix usually have at least one epoxy, hydroxyl, N-methylol or
carbonyl group
or at least two nonconjugated ethylenically unsaturated double bonds. Examples
of
these are monomers having two vinyl radicals, monomers having two vinylidene
radicals
and monomers having two alkenyl radicals. The diesters of dihydric alcohols
with a,f3-
monoethylenically unsaturated monocarboxylic acids are particularly
advantageous,
among which acrylic and methacrylic acid are preferred. Examples of such
monomers
having two noncojugated ethylenically unsaturated double bonds are alkylene
glycol
diacrylates and dimethacrylates, such as ethylene glycol diacrylate, 1,2-
propylene glycol
diacrylate, 1,3-propylene glycol diacrylate, 1,3-butylene glycol diacrylate,
1,4-butylene
glycol diacrylates and ethylene glycol dimethacrylate, 1,2-propylene glycol
dimethacrylate, 1,3-propylene glycol dimethacrylate, 1,3-butylene glycol
dimethacrylate,
1,4-butylene glycol dimethacrylate, and divinylbenzene, vinyl methacrylate,
vinyl
acrylate, ally' methacrylate, allyl acrylate, diallyl maleate, diallyl
fumarate,
nnethylenebisacrylamide, cyclopentadienyl acrylate, triallyl cyanurate or
triallyl
isocyanurate. Also of particular importance in this context are Ci-08-
hydroxyalkyl esters
of methacrylic acid and of acrylic acid, such as n-hydroxyethyl, n-
hydroxypropyl or n-
.
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hydroxybutyl acrylate and nnethacrylate, and compounds such as
diacetoneacrylannide
and acetylacetoxyethyl acrylate or methacrylate.
Frequently, the abovementioned crosslinking monomers A2 are used in amounts of
10% by weight, but preferably in amounts of 5% by weight, based in each case
on
the total amount of monomers A2. Particularly preferably, however, no such
crosslinking monomers A2 at all are used for the preparation of the polymer A.
According to the invention, the proportion of monomers A2 which is
incorporated in the
form of polymerized units in the polymer A is advantageously 5_ 10% by weight
or 5%
by weight.
Particularly advantageously, the polymer A comprises no monomers A2 at all
incorporated in the form of polymerized units.
Preferred polymers A are obtainable by free radical solution polymerization of
only
monomers Al, particularly preferably from 65 to 100% by weight, very
particularly
preferably from 70 to 90% by weight, of acrylic acid with particularly
preferably from 0 to
35% by weight, very particularly preferably from 10 to 30% by weight, of
maleic acid or
maleic anhydride.
Advantageously, polymer A has a weight average molecular weight Mw in the
range
from 1000 g/mol to 500 000 g/mol, preferably from 10 000 g/mol to 300 000
g/mol,
particularly preferably from 30 000 g/mol to 120 000 g/mol.
Establishing the weight average molecular weight Mw in the preparation of
polymer A is
familiar to the person skilled in the art and is advantageously effected by
free radical
aqueous solution polymerization in the presence of free radical chain-transfer
compounds, the so-called free radical chain regulators. The determination of
the weight
average molecular weight Mw is also familiar to the person skilled in the art
and is
effected, for example, by means of gel permeation chromatography.
Suitable commercial products for polymers A are, for example, the SokalanO
products of
BASF SE, which are based, for example, on acrylic acid and/or maleic acid.
Further
suitable polymers are described in WO 99/02591 A.
The component (I) optionally comprises a low molecular weight crosslinking
agent (ii)
having at least two functional groups which are selected from the group
consisting of
hydroxyl, carboxyl and derivatives thereof, primary, secondary and tertiary
amine,
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epoxy, aldehyde.
Suitable crosslinking agents of this type are those having a (weight-average)
molecular
weight in the range from 30 to 10 000 g/mol. The following may be mentioned by
way of
example: alkanolamines, such as triethanolamine; carboxylic acids, such as
citric acid,
tartaric acid, butanetetracarboxylic acid; alcohols, such as glucose, sucrose
or other
sugars, glycerol, glycol, sorbitol, trimethylolpropane; epoxides, such as
bisphenol-A or
bisphenol-F and also resins based thereon and further polyalkylene oxide
glycidyl ethers
or trimethylolpropane triglycidyl ether. In a preferred embodiment of the
invention, the
molecular weight of the low molecular weight crosslinker (ii) used is in the
range from 30
to 4000 g/mol and more preferably in the range from 30 to 500 g/mol.
Polymer M is composed of the following monomers:
a) from 0 to 50% by weight of at least one ethylenically unsaturated monomer
which
comprises at least one epoxide group and/or at least one hydroxyalkyl group
(monomer(s) M1) and
b) from 50 to 100% by weight of at least one further ethylenically unsaturated
monomer which differs from the monomers M1 (monomer(s) M2).
Polymer M is obtainable by free radical emulsion polymerization of the
corresponding
monomers M1 and/or M2 in an aqueous medium. Polymer M may be present in a
single-phase form or multiphase form, and can have a core/shell morphology.
The procedure for free radical emulsion polymerizations of ethylenically
unsaturated
monomers in an aqueous medium has been described before many times and is
therefore sufficiently well known to the person skilled in the art (cf. for
example:
Emulsion Polymerisation in Encyclopedia of Polymer Science and Engineering,
vol. 8,
page 659 et seq. (1987); D.C. Blackley, in High Polymer Latices, vol. 1, page
35 et seq.
(1966); H. Warson, The Applications of Synthetic Resin Emulsions, chapter 5,
page 246
et seq. (1972); D. Diederich, Chemie in unserer Zeit 24, pages 135 to 142
(1990);
Emulsion Polymerisation, Interscience Publishers, New York (1965); DE-A 40 03
422
and Dispersionen synthe-tischer Hochpolymerer, F. Holscher, Springer-Verlag,
Berlin
(1969)).
The free radical aqueous emulsion polymerization reactions are usually
effected in such
a way that the ethylenically unsaturated monomers are dispersed with a
concomitant
use of dispersants in an aqueous medium in the form of monomer droplets and
polymerized by means of a free radical polymerization initiator.
CA 02810275 2013-03-04
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Suitable monomer(s) M1 are in particular glycidyl acrylate and/or glycidyl
methacrylate
and hydroxyalkyl acrylates and methacrylates having C2- to Clo-hydroxyalkyl
groups, in
particular C2- to C4-hydroxyalkyl groups and preferably 02- and C3-
hydroxyalkyl groups,
for example 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-
hydroxypropyl
acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate and/or 4-
hydroxybutyl
methacrylate. One or more, preferably one or two, of the following monomers M1
are
particularly advantageously used: 2-hydroxyethyl acrylate, 2-hydroxyethyl
methacrylate,
glycidyl acrylate, glycidyl methacrylate.
According to the invention, it is possible, optionally, initially to take a
portion or the total
amount of monomers M1 in the polymerization vessel. However, it is also
possible to
meter in the total amount or any remaining amount of monomers M1 during the
polymerization reaction. The total amount or any remaining amount of monomers
M1
can be metered into the polymerization vessel batchwise in one or more
portions or
continuously at constant or varying flow rates. Particularly advantageously,
the metering
of the monomers M1 is effected during the polymerization reaction continuously
at
constant flow rates, in particular as a constituent of an aqueous monomer
emulsion.
Suitable monomer(s) M2 are in particular ethylenically unsaturated compounds
which
can undergo free radical copolymerization in a simple manner with monomer(s)
Ml, for
example ethylene, vinylaromatic monomers, such as styrene, a-methyl styrene,
o-chlorostyrene or vinyltoluenes; vinyl halides, such as vinyl chloride or
vinylidine
chloride; esters of vinyl alcohol and monocarboxylic acids having 1 to 18
carbon atoms,
such as vinyl acetate, vinyl propionate, vinyl-n-butyrate, vinyl laurate and
vinyl stearate;
esters of a,p-monoethylenically unsaturated mono- and dicarboxylic acids
having
preferably 3 to 6 carbon atoms, such as, in particular, acrylic acid,
methacrylic acid,
maleic acid, fumaric acid and itaconic acid, with alkanols having in general 1
to 12,
preferably 1 to 8 and in particular 1 to 4 carbon atoms, such as, in
particular, methyl,
ethyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl and 2-
ethylhexyl acrylate
and methacrylate, dimethyl or di-n-butyl fumarate and maleate; nitriles of a,p-
monoethylenically unsaturated carboxylic acids, such as acrylonitrile,
methacrylonitrile,
funnaronitrile, maleonitrile, and conjugated C4_8-dienes, such as 1,3-
butadiene
(butadiene) and isoprene. Said monomers form as a rule the main monomers
which,
based on the total amount of monomers M2, together account for a proportion of
50%
by weight, preferably 80% by weight and in particular ?_ 90% by weight. As a
rule,
these monomers have only moderate to low solubility in water under standard
conditions
of temperature and pressure (20 C, 1 atm (absolute)).
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Monomers M2 which have a high water solubility under the abovementioned
conditions
are those which comprise either at least one acid group and/or the
corresponding anion
thereof or at least one amino, amido, ureido or N-heterocyclic group and/or
the
ammonium derivatives thereof which are protonated or alkylated on the
nitrogen.
a,P-Monoethylenically unsaturated mono- and dicarboxylic acids having 3 to 6
carbon
atoms and the amides thereof, such as, for example, acrylic acid, nnethacrylic
acid,
maleic acid, fumaric acid, itaconic acid, acrylamide and methacrylamide, and
furthermore vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid,
styrenesulfonic acid and the water-soluble salts thereof and N-
vinyipyrrolidone,
2-vinylpyridine, 4-vinylpyridine, 2-vinylimidazole, 2-(N,N-dimethylamino)ethyl
acrylate, 2-
(N,N-dimethylamino)ethyl methacrylate, 2-(N,N-diethylamino)ethyl acrylate, 2-
(N,N-
diethyl-amino)ethyl methacrylate, 2-(N-tert.-butylamino)ethyl methacrylate, N-
(3-N',N'-
dinnethylaminopropyl)methacrylamide, 2-(1-imidazolin-2-onyl)ethyl methacrylate
and
ureido methacrylate may be mentioned by way of example. Usually, the
abovementioned water-soluble monomers M2 are present only as modifying
monomers
in amounts of 5 10% by weight, preferably 5 5% by weight and particularly
preferably
5 3% by weight, based on the total amount of monomers M2.
Monomers M2, which usually increase the internal strength of the films of a
polymer
matrix, usually have at least one N-methylol or carbonyl group or at least two
nonconjugated ethylenically unsaturated double bonds. Examples of these are
monomers having two vinyl radicals, monomers having two vinylidene radicals
and
monomers having two alkenyl radicals. The diesters of dihydric alcohols with
a,p-monoethylenically unsaturated monocarboxylic acids are particularly
advantageous,
among which acrylic and methacrylic acid are preferred. Examples of such
monomers
having two nonconjugated ethylenically unsaturated double bonds are alkylene
glycol
diacrylates and dimethacrylates, such as ethylene glycol diacrylate, 1,2-
propylene glycol
diacrylate, 1,3-propylene glycol diacrylate, 1,3-butylene glycol diacrylate,
1,4-butylene
glycol diacrylates and ethylene glycol dimethacrylate, 1,2-propylene glycol
dimethacrylate, 1,3-propylene glycol dimethacrylate, 1,3-butylene glycol
dimethacrylate,
1,4-butylene glycol dimethacrylate, and divinylbenzene, vinyl methacrylate,
vinyl
acrylate, ally' methacrylate, ally' acrylate, diallyl maleate, diallyl
fumarate,
methylenebisacrylamide, cyclopentadienyl acrylate, triallyl cyanurate or
triallyl
isocyanurate. Also of importance in this context are compounds such as
diacetoneacrylamide and acetylacetoxyethyl acrylate or methacrylate.
Frequently, the
abovementioned crosslinking monomers M2 are used in amounts of 5 10% by
weight,
preferably in amounts of 5 5% by weight and particularly preferably in amounts
of 5 3%
by weight, based in each case on the total amount of monomers A2. Frequently,
however, no such crosslinking monomers M2 at all are used.
CA 02810275 2013-03-04
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According to the invention, it is possible, optionally, initially to take a
portion or the total
amount of monomers M2 in the polymerization vessel. However, it is also
possible to
meter in the total amount or any remaining amount of monomers M2 during the
polymerization reaction. The total amount or any remaining amount of monomers
M2
can be metered into the polymerization vessel batchwise in one or more
portions or
continuously at constant or varying flow rates. Particularly advantageously,
the metering
of the monomers M2 during the polymerization reaction is effected continuously
at
constant flow rates, in particular as a constituent of an aqueous monomer
emulsion.
For the preparation of the aqueous dispersion of the component (II),
frequently
dispersants are concomitantly used which keep both the monomer droplets and
the
polymer particles obtained by the free radical polymerization dispersed in the
aqueous
phase and thus ensure the stability of the aqueous polymer composition
produced. Both
the protective colloids usually used for carrying out free radical aqueous
emulsion
polymerizations and emulsifiers are suitable as such.
Suitable protective colloids are, for example, polyvinyl alcohols, cellulose
derivatives or
copolymers comprising vinylpyrrolidone or acrylic acid, for example those
defined herein
as component I(i). A detailed description of further suitable protective
colloids is to be
found in Houben-Weyl, Methoden der organischen Chemie, volume XIV/1,
Makromolekulare Stoffe, pages 411 to 420, Georg-Thieme-Verlag, Stuttgart,
1961.
Of course, mixtures of emulsifiers and/or protective colloids can also be
used.
Frequently, exclusively emulsifiers whose relative molecular weights in
contrast to the
protective colloids are usually below 1000 are used as dispersants. They may
be
anionic, cationic or nonionic. When mixtures of surface-active substances are
used, the
individual components must of course be compatible with one another, which in
case of
doubt can be checked by means of a few preliminary experiments. In general,
anionic
emulsifiers are compatible with one another and with nonionic emulsifiers. The
same
also applies to cationic emulsifiers, while anionic and cationic emulsifiers
are generally
not compatible with one another.
Customary emulsifiers are, for example, ethoxylated mono-, di- and
trialkylphenoles
(degree of EO: 3 to 50, alkyl radical: C4 to C12), ethoxylated fatty alcohols
(degree of EO:
3 to 50; alkyl radical: 08 to Cm) and alkali metal and ammonium salts of
alkylsulfates
(alkyl radical: 08 to 012), of sulfuric monoesters of ethoxylated alkanols
(degree of EO: 3
to 30, alkyl radical: C12 to 018) and of ethoxylated alkylphenoles (degree of
EO: 3 to 50,
alkyl radical: 04 to C12), of alkanesulfonic acids (alkyl radical: C12 to C18)
and of
CA 02810275 2013-03-04
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alkylarylsulfonic acids (alkyl radical: C9 to 018). Further suitable
emulsifiers are to be
found in Houben-Weyl, Methoden der organischen Chemie, volume XIV/1,
Makromolekulare Stoffe, pages 192 to 208, Georg-Thieme-Verlag, Stuttgart,
1961.
Nonionic and/or anionic emulsifiers are preferably used for the process
according to the
invention.
As a rule, the amount of dispersant, in particular emulsifiers, used is from
0.1 to 5% by
weight, preferably from 1 to 3% by weight, based in each case on the total
amount of the
monomer mixture M. In the event that protective colloids are used as sole
dispersing
auxiliaries, the amount used will be distinctly higher; the amount used is
typically from
5% to 40% by weight of dispersing auxiliary, preferably from 10% to 30% by
weight, all
based on the total weight of the monomer mixture M.
According to the invention, it is possible, optionally, initially to take a
portion or the total
amount of dispersant in the polymerization vessel. However, it is also
possible to meter
in the total amount or any remaining amount of dispersant during the
polymerization
reaction. The total amount or any remaining amount of dispersant can be
metered into
the polymerization vessel batchwise in one or more portions or continuously at
constant
or varying flow rates. Particularly advantageously, the metering of the
dispersants during
the polymerization reaction is effected continuously at constant flow rates,
in particular
as a constituent of an aqueous monomer emulsion.
Preferred polymers M comprise a) from 0.01 to 50% by weight of at least one
ethylenically unsaturated monomer which comprises at least one epoxide group
and/or
at least one hydroxyalkyl group (monomer(s) M1) and b) from 50 to 99.99% by
weight of
at least one further ethylenically unsaturated monomer which differs from the
monomers
M1 (monomer(s) M2).
Particularly preferred polymers M of this type are obtainable by free radical
solution
polymerization of from 10 to 30% by weight, preferably from 15 to 22% by
weight, of
esters of acrylic acid and/or methacrylic acid with Ci_8-alcohols - preferably
methanol,
n-butanol, 2-ethylhexanol - with from 40 to 70% by weight, preferably from 55
to 65% by
weight, of styrene and of from 5 to 50% by weight, preferably from 20 to 30%
by weight,
of 2-hydroxyethyl acrylate and/or 2-hydroxyethyl methacrylate and/or glycidyl
acrylate
and/or glycidyl methacrylate, the sum of the components being 100% by weight.
Further preferred polymers M comprise no monomer(s) M1 and are obtainable by
free
radical solution polymerization of from 80 to 99% by weight, preferably from
85 to 95%
CA 02810275 2013-03-04
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by weight, of esters of acrylic acid and/or methacrylic acid with C1_8-
alcohols - preferably
methanol, n-butanol, 2-ethylhexanol - with from 0 to 5% by weight, preferably
from 1 to
3% by weight, of ureido methacrylate and of from 0.5 to 5% by weight,
preferably from 1
to 4% by weight, of a,[3-monoethylenically unsaturated mono- and dicarboxylic
acids
having 3 to 6 carbon atoms - preferably acrylic acid, methacrylic acid -
and/or amides of
these acids, the sum of the components being 100% by weight.
Further preferred polymers M are obtainable by using dispersing auxiliaries
based on
poly(acrylic acid)s as described in EP 1240205 A or DE19991049592 A.
Such polymers preferably have a core/shell morphology (isotropic distribution
of the
phases, for example in the form of onion skins) or a Janus morphology
(anisotropic
distribution of the phases).
By targeted variation of type and amount of monomers M1 and M2, it is possible
for the
person skilled in the art, according to the invention, to prepare aqueous
polymer
compositions whose polymers M have a glass transition temperature Tg or a
melting
point in the range from -60 to 270 C.
Advantageously, the glass transition temperature Tg of the polymer M is in the
range
from 10 C to 120 C and preferably in the range from 30 C to 90 C.
The glass transition temperature Tg, is understood as meaning the limit of the
glass
transition temperature toward which the glass transition temperature tends
with
increasing molecular weight, according to G. Kanig (Kolloid-Zeitschrift &
Zeitschrift fur
Polymere, vol. 190, page. 1, equation 1). The glass transition temperature or
the
melting point is determined by the DSC method (Differential Scanning
Calorimetry,
20 K/min, midpoint measurement, DIN 53765).
The Tg values for the homopolymers of most monomers are known and are listed,
for
example, in Ullmann's Encyclopedia of Industrial Chemistry, part 5, vol. A21,
page 169,
VCH Weinheim, 1992; further sources of glass transition temperatures of
homopolymers
are, for example, J. Brandrup, E.H. Immergut, Polymer Handbook, 1st Ed., J.
Wiley, New
York 1966, 2nd Ed. J.Wiley, New York 1975, and 3rd Ed, J. Wiley, New York
1989).
The components (I) and (III) according to the invention usually have polymer
solids
contents (total amount of polymer A or total amount of polymer M) of 10 and 5
70% by
weight, frequently 20 and 5 65% by weight and often 40 and 5 60% by weight,
based on the respective aqueous component (I) or (II).
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The number average particle diameter (cumulant z average) of the polymer M,
determined via quasielastic light scattering (ISO standard 13321), in the
aqueous
component (III) is as a rule from 10 to 2000 nm, frequently from 20 to 1000 nm
and often
from 50 to 700 nm or from 80 to 400 nm.
The components of the binder (b), preferably the components (I) and (III), can
be used
ready-mixed, but it is also possible for the components of the binder (b) to
be in a
generally initially unmixed state when they are brought into contact with the
lignocellulose-containing particles, typically in separate steps.
The total amount of the components (I) and (Ill) of the binder (b) as a pure,
undiluted
substance, based on the dry mass of the lignocellulose-containing particles,
preferably
wood particles, is in the range from 0.5% to 50% by weight, preferably in the
range from
0.75% to 12% by weight and more preferably in the range from 1% to 6% by
weight.
The total amount of the component (I) of the binder (b) as a pure, undiluted
substance,
based on the dry mass of the lignocellulose-containing particles, preferably
wood
particles, is in the range from 0.5% to 30% by weight, preferably in the range
from 1% to
10% by weight and more preferably in the range from 1.5% to 6% by weight.
The total amount of the component (III) of the binder (b) as a pure, undiluted
substance,
based on the dry mass of the lignocellulose-containing particles, preferably
wood
particles, is in the range from 0.5 to 30% by weight, preferably in the range
from 0.75%
to 10% by weight and more preferably in the range from 1 to 6% by weight.
The weight ratio of component (I): component (III) of the binder (b) as a
pure, undiluted
substance is in the range from 10:1 to 1:10 preferably 5:1 to 1:5 and more
preferably 3:1
to 1:3.
The pH of the binder (b) is in the range from 0 to 5, preferably in the range
from 2 to 4.
The desired pH of the binder B arises as a rule by the combination of the
components (I)
and (III) and, optionally, component (IV) and/or formaldehyde scavenger.
The pH of the binder (b) at the place of action can, however, be adjusted to
the desired
value in the range from 0 to 5, preferably in the range from 2 to 4, in a
customary
manner by addition of inorganic or organic acids and/or salts thereof, for
example
CA 02810275 2013-03-04
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mineral acids, such as sulfuric acid, hydrochloric acid, phosphorus-containing
acids
such as phosphoric acid, phosphorous acid or hypophosphorous acid and salts
thereof,
for example sodium phosphate, sodium phosphite, sodium hypophosphite; organic
sulfonic acids, such as methanesulfonic acid, carboxylic acids, such as formic
acid or
acetic acid, or sodium formate, sodium acetate, sodium citrate, or inorganic
or organic
bases, for example sodium hydroxide (aqueous or as such), calcium oxide or
calcium
carbonate (in each case aqueous or as such) or ammonia, aqueous or as such.
In general, the ready-mixed binder (b) having the abovementioned pH ranges can
be
used. The desired pH - as described above - can, however, also be adjusted by
applying
the individual components of the binder (b) and the acids or bases described
above
separately to the lignocellulose-containing substrate. Through the choice of
the pH of
the components of the binder (b) and of the added acids or bases, the person
skilled in
the art can combine them so that the desired pH is established on the
lignocellulose-
containing substrate.
The term additive as component (IV) is to be understood as meaning all
additives known
to the person skilled in the art, for example waxes, paraffin emulsion, flame-
retardant
additives, wetting agents, salts, but also inorganic or organic acids and
bases, for
example mineral acids, such as sulfuric acid or nitric acid, phosphorus-
containing acids
such as phosphoric acid, phosphorous acid or hypophosphorous acid; organic
sulfonic
acids, such as methanesulfonic acid, carboxylic acids, such as formic acid or
acetic
acid, or inorganic or organic bases, for example sodium hydroxide (aqueous or
as such),
calcium oxide or calcium carbonate (in each case aqueous or as such) or
ammonia,
aqueous or as such. These additives can be added in an amount of from 0 to 20%
by
weight, preferably from 0 to 5% by weight, in particular from 0 to 2% by
weight, based
on the dry mass of the lignocellulose-containing particles, for example
absolutely dry
wood.
The lignocellulose-containing particles, preferably wood particles,
particularly preferably
wood chips or fibers, are coated with glue as a rule by bringing into contact
with the
binder (a) or (b). So-called glue application methods of this type are known
for the
production of conventional woodbase materials with customary aminoplast resins
and
are described, for example, in "Taschenbuch der Spanplatten Technik", H.-J.
Deppe,
K. Ernst, 40, edition, 2000, DRW - Verlag Weinbrenner GmbH & Co., Leinfelden-
Echter-
dingen, chapter 3.3.
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The binder (a) or (b) can be brought into contact with the lignocellulose-
containing
particles, preferably wood particles, particularly wood chips or fibers, in
various ways,
preferably by spraying (a) or (b) onto the lignocellulose-containing
particles.
In the glue application, the binder (a) or (b) is usually used in such amounts
as
described above.
As far as the binder (b) is concerned, it is preferable for the component (II)
not to be
premixed with the further components (I) and/or (III) and/or (IV) when it is
brought into
contact with the lignocellulose-containing particles. The component (II) can
be brought
into contact with the lignocellulose-containing particles at a time before or
after the other
aforementioned components.
The binder (b) optionally comprises a formaldehyde scavenger.
The binder (b) preferably comprises a formaldehyde scavenger if the binder (a)
comprises a formaldehyde resin as described above.
Formaldehyde scavenger refers to chemical substances which as a rule have a
free
electron pair which reacts chemically with the formaldehyde, i.e. chemically
binds the
formaldehyde, as a rule virtually irreversibly. Such free electron pairs are
present, for
example, on the following functional groups of organic or inorganic compounds:
primary,
secondary and tertiary amino groups, hydroxyl group, sulfite group, amides,
imides.
Examples of suitable formaldehyde scavengers are: ammonia, urea, melamine,
organic
CI-C10-amines, polymers which carry at least one amino group, such as
polyamines,
polyimines, polyureas, polylysines, polyvinylamine, polyethylenimine. Urea is
a
particularly preferred formaldehyde scavenger.
The amount of the formaldehyde scavengers in the binder (b) is in the range
from 0.1 to
10% by weight, preferably from 0.5 to 7% by weight, based on the dry mass of
the
lignocellulose-containing particles, for example absolutely dry wood, and
pure, undiluted
formaldehyde scavenger.
The multilayer lignocellulose-containing moldings may have a regular or
irregular three-
dimensional shape. The following are examples of suitable desired shapes: all
regular
moldings, such as spheres, cylinders, cuboids, boards; all irregular shapes,
such as
irregular cavities, ornaments.
Preferred desired shapes are sheet-like, the form of a board being
particularly preferred.
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Further preferred multilayer lignocellulose-containing moldings comprise more
than 70%
by weight of lignocellulose-containing particles, preferably wood fibers, wood
chips, flax
fibers or flax shives.
The average density of the multilayer lignocellulose-containing moldings is
usually in the
range from 300 kg/m3 to 950 kg/m3, preferably from 450 kg/m3 to 850 kg/m3.
The multilayer lignocellulose-containing moldings according to the invention
have a
middle layer or a plurality of middle layers A) comprising lignocellulose-
containing
particles and a binder (a) and a covering layer or two covering layers (B)
comprising
lignocellulose-containing particles and a binder (b).
In the context of the invention, middle layer or middle layers is or are all
layers which are
not the outer layers.
The outer layer or the outer layers of the multilayer lignocellulose-
containing moldings
according to the invention are also referred to here as covering layer or
covering layers.
Preferred multilayer lignocellulose-containing moldings according to the
invention are
sheet-like, preferably in the form of a board, comprising, for example, flax
particles
and/or wood particles, particularly preferably wood chips or wood fibers, as
lignocellulose-containing particles, and have three layers; a middle layer A)
and one
covering layer B) each on the top and bottom thereof.
For the production of the multilayer lignocellulose-containing moldings, for
example of
the abovementioned, three-layer lignocellulose-containing moldings, the
following
binders are preferably used for the respective layers:
In a very suitable embodiment, the binder (b) comprises a component (III) but
no low
molecular weight crosslinker (ii), as will now be described by way of example
under
variants 1 and 2.
Variant 1:
For the middle layer A) or the middle layers A), the binder (a) comprises only
the
component (al), preferably an aminoplast resin, particularly preferably a UF
resin and/or
MUF resin.
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For a covering layer B) or the two covering layers B), the binder (b) is used;
for example,
the binder (b) comprises an aqueous solution of a polymer A according to the
invention,
obtainable by free radical solution polymerization of 70% by weight of acrylic
acid and
30% by weight of maleic anhydride in water. The component (I) comprises no
further
crosslinking component. The component (III) of the binder (b) is an aqueous
dispersion
of a polymer M according to the invention, obtainable by free radical emulsion
polymerization of from 50 to 65% by weight of styrene and from 5 to 15% by
weight of
methyl methacrylate, from 5 to 15% by weight of n-butyl acrylate, from 10 to
30% by
weight of hydroxyethyl acrylate and from 2 to 20% by weight of glycidyl
methacrylate in
water, the sum of the monomers being 100% by weight.
The binder (b) furthermore comprises the component (II) in the amounts defined
above
and a formaldehyde scavenger as defined above, in the amounts as defined
there.
Variant 2:
For the middle layer A) or the middle layers A), the binder (a) comprises the
component
(al), preferably an aminoplast, particularly preferably a UF resin and/or MUF
resin, and
the component (a2), preferably PM Dl, in the amounts defined above for the
combination
(al) and (a2).
For a covering layer B) or the two covering layers B), the binder (b) is used;
for example,
the binder (b) comprises an aqueous solution of a polymer A according to the
invention,
obtainable by free radical solution polymerization of 70% by weight of acrylic
acid and
30% by weight of maleic anhydride in water. The component (I) comprises no
further
crosslinking component. The component (III) of the binder (b) is an aqueous
dispersion
of a polymer M according to the invention, obtainable by free radical emulsion
polymerization of from 50 to 65% by weight of styrene and from 5 to 15% by
weight of
methyl methacrylate, from 5 to 15% by weight of n-butyl acrylate, from 10 to
30% by
weight of hydroxyethyl acrylate and from 2 to 20% by weight of glycidyl
methacrylate in
water, the sum of the monomers being 100% by weight.
The binder (b) furthermore comprises the component (II) in the amounts defined
above
and a formaldehyde scavenger as defined above, in the amounts as defined
there.
In a further very suitable embodiment, the binder (b) comprises a low
molecular weight
crosslinker (ii) and no component (III), as will now be described by way of
example
under variants 3 to 5.
CA 02810275 2013-03-04
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Variant 3:
For the middle layer A) or the middle layers A), the binder (a) comprises only
the
component (al), preferably an aminoplast resin, particularly preferably a UF
resin and/or
MUF resin.
For a covering layer B) or the two covering layers B), the binder (b) is used;
for example,
the binder (b) comprises an aqueous solution of a polymer A according to the
invention,
obtainable by free radical solution polymerization of 70% by weight of acrylic
acid and
30% by weight of maleic anhydride in water. The component (I) additionally
comprises a
crosslinker component (ii), preferably having more than two functional groups
per
crosslinker molecule, particularly preferably triethanolamine.
The binder (b) further comprises the component (II) in the amounts defined
above and a
formaldehyde scavenger as Clefined above, in the amounts as defined there.
Variant 4:
For the middle layer A) or the middle layers A), the binder (a) comprises only
the
component (a2), preferably PMDI.
For a covering layer B) or the two covering layers B), the binder (b) is used;
for example,
the binder (b) comprises an aqueous solution of a polymer A according to the
invention,
obtainable by free radical solution polymerization of 70% by weight of acrylic
acid and
30% by weight of maleic anhydride in water. The component (I) additionally
comprises
a crosslinker component (ii), preferably having more than two functional
groups per
crosslinker molecule, particularly preferably triethanolamine.
The binder (b) further comprises the component (II) in the above-defined
amounts but
no formaldehyde scavenger.
Variant 5:
For the middle layer A) or the middle layers A), the binder (a) comprises the
components
(al) and (a2), preferably PMDI.
For a covering layer B) or the two covering layers B), the binder (b) is used,
but without
the component (III); for example, the binder (b) comprises an aqueous solution
of a
polymer A according to the invention, obtainable by free radical solution
polymerization
CA 02810275 2013-03-04
25
of 70% by weight of acrylic acid and 30% by weight of maleic anhydride in
water. The
component (I) additionally comprises a crosslinker component (ii), preferably
having
more than two functional groups per crosslinker molecule, particularly
preferably
triethanolamine.
The binder (b) further comprises a component (II) in the above-defined amounts
and a
formaldehyde scavenger as defined above, in the amounts as defined there.
In a further highly suitable embodiment, the binder (b) comprises both a low
molecular
weight crosslinker (ii) and a component (III), as described hereinbelow by way
of
example under variant 6.
Variant 6:
For the middle layer A) or the middle layers A), the binder (a) comprises the
component
(al), preferably an amino resin, particularly preferably a UF resin and/or MUF
resin,
and/or the component (a2), preferably PMDI in the amounts defined above for
the
combination (al) and (a2).
For a covering layer B) or the two covering layers B), the binder (b) is used;
for example,
the binder (b) comprises an aqueous solution of a polymer A according to the
invention,
obtainable by free radical solution polymerization of 70% by weight of acrylic
acid and
30% by weight of maleic anhydride in water. The component (I) additionally
comprises a
crosslinker component (ii), preferably having more than two functional groups
per
crosslinker molecule, particularly preferably triethanolamine. The component
(III) of the
binder (b) is an aqueous dispersion of a polymer M according to the invention,
obtainable by free radical emulsion polymerization in water of 50% to 65% by
weight of
styrene and 5% to 15% by weight of methyl methacrylate, 5% to 15% by weight of
n-butyl acrylate, 10% to 30% by weight of hydroxyethyl acrylate and 2% to 20%
by
weight of glycidyl methacrylate, the sum total of the monomers being 100% by
weight.
The binder (b) further comprises the component (II) in the above-defined
amounts and a
formaldehyde scavenger as defined above in the amounts as defined there.
The thickness of the nnultilayer lignocellulose-containing moldings,
preferably the board-
like moldings, according to the invention varies with the field of application
and is
generally in the range from 0.5 to 300 mm; preference is given to relatively
thin board-
like moldings having a thickness in the range from 4 to 100 mm and in
particular in the
range from 6 to 40 mm.
CA 02810275 2013-03-04
26
The thickness ratios of the layers of the multilayer lignocellulose-containing
moldings
according to the invention, preferably of the board-like moldings, are
variable. Usually,
the outer layers A), also referred to as covering layers, by themselves or in
total, are
thinner than the layer or layers of the middle layer(s) B).
The mass of the individual covering layer is usually in the range from 5 to
30% by
weight, preferably from 10 to 25% by weight, of the total mass of the
multilayer
lignocellulose-containing molding according to the invention.
In the preferred multilayer lignocellulose-containing molding according to the
invention,
preferably the board-like molding, the thickness of the middle layer(s) B),
based on the
total thickness of the multilayer lignocellulose-containing molding according
to the
invention, preferably the board-like molding, is in the range from 20% to 99%,
preferably
from 50% to 99%, particularly preferably from 60% to 99%.
The multilayer lignocellulose-containing moldings according to the invention,
preferably
those in which the lignocellulose-containing particles are wood particles
and/or flax
particles, particularly preferably wood chips or wood fibers, or flax chips or
flax shives,
are produced in the customary manner, as described in "Taschenbuch der
Spanplatten
Technik" H.-J. Deppe, K. Ernst, 4th edition, 2000, DRW - Verlag Weinbrenner
GmbH &
Co., Leinfelden-Echterdingen, chapter 3.5.
Usually, first lignocellulose-containing particles, for the middle layer(s) A)
and the
covering layer(s) B), for example wood or flax, preferably wood, for example
in the form
of fibers, chips, veneers or strands, as described above, are brought into
contact (also
referred to as "glue-coated") with the respective binder (a) (for the middle
layer(s) A)) or
(b) (for the covering layer(s) B)).
Thereafter, the lignocellulose-containing particles, for example wood or flax,
preferably
wood, for example in the form of fibers, chips, veneers or strands, glue-
coated in this
manner are placed in layers one on top of the other according to the desired
sequence
of the multilayer lignocellulose-containing molding to be produced and are
pressed at
elevated temperature by a customary method to give multilayer lignocellulose-
containing
moldings, preferably those in which the lignocellulose-containing particles
are wood, for
example in the form of fibers, chips, veneers or strands.
For this purpose, a fiber/chip mat is usually produced by sprinkling the
lignocellulose-
containing particles glue-coated in this manner, for example wood or flax -
preferably
CA 02810275 2013-03-04
27
wood, particularly preferably wood in the form of chips or fibers - onto a
substrate and
said mat is usually pressed at temperatures of from 80 C to 250 C and at
pressures of
from 5 to 50 bar to give multilayer lignocellulose-containing moldings
according to the
invention (cf. for example: "Taschenbuch der Spanplatten Technik" H.-J. Deppe,
K. Ernst, 4th edition, 2000, DRW - Verlag Weinbrenner GmbH & Co., Leinfelden-
Echterdingen, pages 232 - 254. "MDF - Mitteldichte Faserplatten" H.-J. Deppe,
K. Ernst,
1996, DRW - Verlag Weinbrenner GmbH & Co., Leinfelden-Echterdingen, pages 93 -
104).
The pressing times needed for board production are typically specified in
"seconds per
mm of board thickness"; or s/mm (often also referred to as pressing time
factor).
Multilayer lignocellulose-containing moldings according to the invention
generally require
pressing time factors of the kind known for the quick formaldehyde resins; a
Siempelkamp laboratory press (dimensions 520 mm x 520 mm) generally requires
pressing time factors of 8 to 10 s/mm for moldings according to the invention,
and also
for boards produced using anninoplast-containing binders only; moldings
produced with
formaldehyde-free binders, for example products of the Acrodur0 product range
from
BASF SE, require pressing time factors of more than 25 s/mm.
Particularly preferred multilayer lignocellulose-containing moldings according
to the
invention are all those which are produced from wood strips, for example
veneer sheets
or plywood sheets, or multilayer lignocellulose-containing moldings produced
from wood
chips, for example particle boards or OSB boards, and multilayer wood fiber
materials,
such as LDF, MDF and HDF boards.
Woodbase materials comprising formaldehyde-free binders are advantageously
produced by the process according to the invention. Multilayer OSB boards,
wood fiber
boards and particle boards are preferred.
The present invention furthermore relates to the use of the multilayer
lignocellulose-
containing moldings according to the invention, preferably the multilayer wood-
containing moldings according to the invention, for the production of pieces
of furniture,
of packaging materials, in house building, in drywall construction or in
interior finishing,
for example as laminate, insulating material, wall or ceiling element, or in
motor vehicles.
The multilayer lignocellulose-containing moldings according to the invention
show a
greatly reduced emission of formaldehyde or virtually no emission of
formaldehyde and
are obtainable using very short pressing times.
CA 02810275 2013-03-04
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The multilayer lignocellulose-containing moldings according to the invention
moreover
show increased peel strength for the covering layers, good transverse tensile
strength
and good moisture resistance.
Examples
General
Amounts reported in % OD are weight percent based on the net mass of dry wood;
OD
stands for oven dry.
Methods of measurement and measured results
Formaldehyde emissions were determined by the following test methods for
woodbase
materials (see also Bundesgesetzblatt 10/91, p. 488/489):
perforator value: DIN EN 120, ISO 12460-5;
gas analysis: DIN EN 717-2;
test chamber method (option 2: 1 m3 chamber): DIN EN 717-1;
desiccator method: JIS A 1460.
The mechanical properties of woodbase materials were evaluated by determining
the
following parameters:
peel strength to EN 311;
transverse tensile strength to EN 319;
water resistance or "swell values" to EN 317
and a "water absorption" method described hereinbelow.
Water absorption was determined similarly to DIN EN 317 except that it is not
the
thickness of the test specimen which is determined before and after 24 hour
water
immersion but its mass, by weighing. The water absorption WA of each test
specimen
as a percentage of the initial mass must be computed by the following formula:
WA =
100 x (m2 - m1)/ m1.
In this formula:
ml is the mass of the test specimen before water immersion, in grams
(measured to 0.01 g)
m2 is the mass of the test specimen after water immersion, in grams
(measured to 0.01 g)
Water absorption is reported to one decimal place.
CA 02810275 2013-03-04
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Wood moisture was determined to DIN 52183.
Production of multilayer lignocellulose-containing moldings,
in particular the production of 3-layer laboratory chipboard
A certain amount of sprucewood chips (conditioned at 20 C and 65% relative
humidity)
plus additives was resinated with the stated amounts of binder and binder
components
in a Laclige mixer. Resination was done in two steps when isocyanates were
used as
binders, otherwise unless otherwise stated in one step. The resinated chips
were
measured for chip moisture content. The chips for covering and middle layers
were
treated separately from each other.
Thereafter, the chips were manually formed into mats: first a covering layer,
then the
middle layer and finally the second covering layer in a mass ratio of 1 part
of covering
layer chips, then 4 parts of middle layer chips and again 1 part of covering
layer chips.
The mat was hot-pressed at 210 C using the molding pressure profile reported
in the
examples.
The three-layer lignocellulose-containing moldings produced in the tests were
tested for
their properties using the methods indicated above.
Binders according to the present invention were used in the examples which
follow,
specifically:
Polymer mixture A-mix
A commercially available aqueous solution of a polymer B52, obtainable by free
radical
solution polymerization of 70% by weight of acrylic acid and 30% by weight of
maleic
anhydride in water. The weight average molecular weight Mw was 80 000 g/mol.
To 100
parts of this polymer were added, as crosslinker component, 30 analogous parts
of
triethanolamine, based on the solids content of the polymer solution. The
solids content
of the admixture was 50% by weight.
For clarity, each individual component of polymer mixture B is listed
separately in the
tables of the examples.
Middle layer binders
The middle layer binders used were KAURIT resins from BASF SE (KL = Kaurit0
resin).
CA 02810275 2013-03-04
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Example 1
PMDI in covering layer improves mechanicals in chipboard giving reduced
formaldehyde
emissions (level F****)
Several laboratory chipboard panels having dimensions of 56.5 cm * 44.0 cm *
16.0 mm
were produced using different binder compositions. The target envelope density
for the
panels was 680 kg/m'.
Molding pressure profile: 65 s at 4 bar, 65 s at 2 bar, 90 s at 1 bar
Table 1A reports the binder batches for the various board panels. Amount
recitations
without explicit units are by mass. Columns headed "MS" identify the binder
for the
middle layer, columns headed "DS" identify the binder for the covering layers.
Table 1A: production parameters
Batch 1 2 3
DS MS DS MS DS MS
A KL 337 % OD 8.50 8.50 8.50
NH solution % v/v of
B (curative) A 5.00 5.00 5.00
Hydrowax 560
C (60%) "Yo OD 0.50 0.50 0.50
D Polymer B52 % OD 2.56 2.56 2.31
E triethanolamine % OD 0.77 0.77 0.69
F Hydrowax Q (50%) % OD 0.03 0.03 0.03
G urea % OD 1.67 2.51 2.25
H water % 00 5.57 5.57 5.56
J Lupranat M20 A OD 0.50
Results (in table 1B)
Batches 1 and 2 constitute conventional comparative boards corresponding to
the prior
art as described in W0/2010/031718. The resin used in the middle layer was
BASF
product KL337.
Batch 3 is an inventive chipboard where the covering layer comprises PM Dl.
CA 02810275 2013-03-04
31
The inventive chipboard 3 clearly evinces, compared with 1 and 2, reduced 24 h
swelling and water absorption and also increased transverse tensile strength
and peel
strength.
Table 1B: results
Batch 1 2 3
Thickness
at testing mr11 15.55 15.55 15.55
Transverse tensile strength V 20
Density (n = 10) kg/m3 673 666 661
Transverse tensile strength N/mm2 0.56 0.54 0.67
Broken in covering layer of 10 10 8 0
Swelling (50 * 50 mm)
Density (n = 10) kg/m3 678 667 665,
Swelling after 24 h 42.6 39.7 34.5
Water absorption after 24 h 118.3 118.4 109.0
Peel strength
Peel strength, top (n = 5) N/mm2 0.97 1.02 0.98
Peel strength, bottom (n = 5) N/mm2 0.96 0.83 1.29
Perforator value
based on 6.5% moisture
mg HCHO / 100 g OD sample 2.38 2.38 2.29
Formaldehyde emission via
desiccator method mg/I 0.35 0.29 0.31
Example 2
PMDI in covering layer improves mechanicals in chipboard giving reduced
formaldehyde
emissions (level CARB-2)
Several laboratory chipboard panels having dimensions of 56.5 cm * 44.0 cm *
16.0 mm
were produced using different binder compositions. The target envelope density
for the
panels was 680 kg/m3.
CA 02810275 2013-03-04
32
Molding pressure profile: 65 s at 4 bar, 65 s at 2 bar, 90 s at 1 bar
Table 2A reports the binder batches for the various board panels. Amount
recitations
without explicit units are by mass. Columns headed "MS" identify the binder
for the
middle layer, columns headed "DS" identify the binder for the covering layers.
Table 2A: production parameters
Batch 1 2 3
DS MS DS MS DS MS
A KL 340 % OD 8.50 8.50 8.50
B NH solution (curative) % v/v of A 5.00 5.00 5.00
C Hydrowax 560 (60%) % OD 0.50 0.50 0.50
D Polymer B52 % OD 2.56 2.56 2.31
E triethanolamine % OD 0.77 0.77 0.69
F Hydrowax Q (50%) % OD 0.03 0.03 0.03
G urea `)/0 OD 1.67 2.51 2.25
H water % OD 5.57 5.57 5.56
J Lupranat M20 FB "Yo OD 0.50
Results (in table 2B)
Batches 1 and 2 constitute conventional comparative boards corresponding to
the prior
art as described in WO/2010/031718. The resin used in the middle layer was
BASF
product KL340.
Batch 3 is an inventive chipboard where the covering layer comprises PMDI.
The inventive chipboard 3 clearly evinces, compared with 1 and 2, reduced 24 h
swelling and water absorption and also increased transverse tensile strength
and peel
strength.
Table 2B: results
Batch 1 2 3
Thickness
at testing mm 15.53 15.52 15.54
Transverse tensile strength
V 20
CA 02810275 2013-03-04
33
Density (n = 10) kg/m3 687 685 696
Transverse tensile strength N/mm2 0.59 0.63 0.78
Broken in covering layer of 10 10 10 1
Swelling (50 * 50 mm)
Density (n = 10) kg/m3 687 688 699
Swelling after 24 h 41.2 39.2 33.8
Water absorption after 24 h 110.5 107.9 99.1
Peel strength
Peel strength, top (n = 5) N/mm2 0.93 1.04 1.24
Peel strength, bottom (n = 5) N/mm2 0.92 0.97 1.13
Perforator value
based on 6.5% moisture
mg HCHO / 100 g OD sample 2.99 2.51 2.51
Formaldehyde emission via
desiccator method mg/I 0.44 0.38 0.38
Example 3
PMDI in covering layer improves nnechanicals in chipboard giving reduced
formaldehyde
emissions (level CARB-2)
Several laboratory chipboard panels having dimensions of 56.5 cm * 44.0 cm *
16.0 mm
were produced using different binder compositions. The target envelope density
for the
panels was 680 kg/m3.
Molding pressure profile: 65 s at 4 bar, 65 s at 2 bar, 90 s at 1 bar
Table 3A reports the binder batches for the various board panels. Amount
recitations
without explicit units are by mass. Columns headed "MS" identify the binder
for the
middle layer, columns headed "DS" identify the binder for the covering layers.
Table 3A: production parameters
Batch 1 2 3
DS MS DS MS DS MS
A KL 347 % OD 9.00 9.00
9.00
CA 02810275 2013-03-04
34
ammonium nitrate solution % v/v of
B (52%) A 4.00 4.00 4.00
C Hydrowax 560 (60%) % OD 0.50 0.50 0.50
D Polymer B52 % OD 2.56 2.31 2.05
E triethanolannine % OD 0.77 0.69 0.62
F urea solid % OD 2.51 2.44 2.16
G Hydrowax Q (50%) % OD 0.03 0.03 0.03
H water % OD 5.57 5.56 4.93
J Lupranat M20 FB % OD 0.50 0.30
Results (in table 3B)
Batch 1 constitutes conventional comparative boards corresponding to the prior
art as
described in WO/2010/031718.
Batches 2 and 3 are an inventive chipboard where the covering layer comprises
PMDI.
The inventive chipboards 2 and 3 clearly evince, compared with 1, reduced 24 h
swelling and water absorption and also increased transverse tensile strength
and peel
strength.
Table 3B: results
Batch 1 2 3
Thickness
at testing mm 15.68 15.67 15.68
Transverse tensile strength
/ 20
Density (n = 8) kg/m' 688 681 675
Transverse tensile strength N/mm2 0.61 0.80 0.70
Broken in covering layer of 8 8 0 1
Swelling (50 * 50 mm)
Density (n = 8) kg/m3 691 682 675
Swelling after 24 h 40.8 31.8 32.4
Water absorption after 24 h % 106.2 97.1 99.0
Peel strength
CA 02810275 2013-03-04
35
Peel strength (n = 4) N/mm2 0.90 1.17 1.10
Formaldehyde emission
Perforator value
based on 6.5% moisture
mg HCHO / 100 g OD
sample 3.37 5.04 3.85
1m3 chamber value
(EN 717-1) ppm 0.058 0.059 0.068
Example 4
Purpose: improved mechanicals through addition of an acid as component (IV) in
the
covering layer
Several laboratory chipboard panels having dimensions of 56.5 cm * 44.0 cm *
16.0 mm
were produced using different binder compositions. The target envelope density
for the
panels was 670 kg/m'.
Molding pressure profile: 65 s at 4 bar, 65 s at 2 bar, 90 s at 1 bar
Table 4A reports the binder batches for the various board panels. Amount
recitations
without explicit units are by mass. Columns headed "MS" identify the binder
for the
middle layer, columns headed "DS" identify the binder for the covering layers.
The mass ratio of the covering layers to the middle layer was DS:MS:DS =
1:4:1. The
layers were formed by hand and then hot-pressed at 210 C using the following
molding
pressure profile: 50 s at 4 bar, 50 s at 2 bar, 40 s at 1 bar.
Table 4A: production parameters
Batch 1 2 3 4
DS MS DS MS DS MS DS MS
A KL 337 % OD 8.50 8.50 8.50 8.50
NH solution % v/v of
B (curative) A 5.00 5.00 5.00 5.00
Hydro Wax 560
C (60%) % OD 0.40 0.40 0.40 0.40
D Polymer B52 `)/0 OD 2.31 2.31 2.31 2.31
CA 02810275 2013-03-04
36
E triethanolamine % OD 0.69 0.69 0.69
0.69
Hydro Wax Q
F (50%) % OD , 0.02 0.02 0.02
0.02
G urea (solid) % OD 2.25 2.25 2.25
2.25
H water `)/0 OD 5.56 5.56 5.56
5.56
methanesulfonic
J acid % OD 0.30 0.50 1.00
K Lupranat M20 FB % OD 0.50 0.50 0.50
0.50
Results (in table 4B)
Batch 4 constitutes an inventive comparative board similar to boards 2 and 3
of example
1. In batches 1 to 3 the covering layer additionally incorporates
methanesulfonic acid.
Particularly batches 2 and 3 are observed to give increased transverse tensile
strength,
reduced swelling values and slightly reduced formaldehyde emissions. In all
three cases
(1-3) peel strength is improved over the board without added acid (4).
Table 4B: results
Batch 1 2 3 4
Thickness
at testing (sanded) mm 15.74 15.72 15.74 15.73
Transverse tensile strength V 20
Density (n = 8) kg/m3 597 670 677 672
Transverse tensile strength NI/rnm2 0.56 0.69 0,61 0.57
Broken in covering layer of 8 0 0 0 0
Swelling (50 * 50 mm)
Density (n = 8) kg/m3 602 672 674 663
Swelling after 24 h 29.2 31.3 31.9 35.4
Water absorption after 24 h 114.1 97.5 98.1 104.7
Peel strength
Peel strength (n = 4) 1\l/rnrre 1.42 1.62 1.53 1.17
= CA 02810275 2013-03-04
37
Formaldehyde emission
Desiccator method mg/I 0.22 0.21 0.20 0.22
Example 5
Improved coatability
Several laboratory chipboard panels having dimensions of 56.5 cm *44.0 cm *
16.0 mm
were produced using different binder compositions. The target envelope density
for the
panels was 670 kg/m3.
Molding pressure profile: 65 s at 4 bar, 65 s at 2 bar, 90 s at 1 bar
Table 5A reports the binder batches for the various board panels. Amount
recitations
without explicit units are by mass. Columns headed "MS" identify the binder
for the
middle layer, columns headed "DS" identify the binder for the covering layers.
Table 5A: production parameters
Batch 1 2 3
DS MS DS MS DS MS
A KL 337 % OD 8.50 8.50
B KL 465 % OD 11.50 12.00
ammonium nitrate
C solution (52%) % v/v of A 4.00 4.00 0.87 5.83
D Hydrowax 560 (60%) % OD 0.50 0.50 0.50 0.50
E Polymer B52 % OD 3.33 2.83
F triethanolamine % OD 1.00 0.85
G urea solid % OD 2.33 2.53 0.30
H Hydrowax Q (50%) % OD 0.50 0.50
chip moisture
(resinated) % OD 9.20 13.40 8.60
Lupranat M2OFB % OD 0.50 0.50
,
The chipboard panels thus produced were coated with decor paper and tested for
the quality of the coating. The results are shown in
table 58.
Table 5B: results
Batch from Tab. 5A 1 2
3
n
Size 20cm*40cm 20cm*40cm 20cm*40cm 20cm*40cm 20cm*40cm
20cm*40cm
0
Coating A B A B
A B 1.)
co
Overlay AC3 x x
x 0
1.)
.,1
Wood brown decor x x
x
.
I.)
Light granite decor
0
1-
co
(KTS820) x x
x 1
0
CA
Brown backer x x
x 1
0
A,
w
_ cz>
i
Visually good good good good
good good
underside slightly underside slightly
Saw cut broken out good broken out good
good good
underside badly underside badly underside badly
Drilling broken out good broken out good
broken out good
Milling good good good good
good good
Cross hatch test slightly spelled good good good i
good good
_
CA 02810275 2013-03-04
39
Columns at left (designations 1-A, 2-A and 3-A): melamine short cycle coating
The boards were coated with already pre-impregnated papers from DKB Dekor
Kunststoffe GmbH (Erndtebnick-Schameder). The sequence of the layers was as
follows: backer chipboard decor foil overlay
Molding conditions: 180 C / 2.5 N/mm2/ 40 sec.
Columns at right (designations 1-B, 2-B and 3-B): lamination with furniture
foil (adhered
with white glue)
Unimpregnated decor paper (light granite decor) having a raw weight of 200
g/m2 had a
liquor batch based on Kaurit -Tranksystem impregnating system (see
hereinbelow)
applied to it by means of a "0/0" rod blade (resin application 48%). The
papers thus
impregnated were dried at 120 C for 175 seconds, the residual moisture content
of the
furniture foil thus produced was found to be 6.7%. The chipboard to be tested
was
coated with the same furniture foil on both sides.
Molding conditions: 95 C / 0.5 N/mm2/ 4 min.
Liquor batch
100 parts by weight of KTS820 (= KauritO-Tranksystem 820) impregnating system
60 parts by weight of water
2 parts by weight of a 60% solution of para-toluenesulfonic acid
The liquor resulting therefrom has a 100 C gel time of about 200 sec.
Resin add-on and residual moisture content of the furniture foil were
determined by
differential weighing (unimpregnated paper/impregnated paper after above
drying/
impregnated paper after additional drying at 180 C/2 min).
Tests
The saw cut involved sawing 3 times in each case with the circular saw into
the coated
board to a depth of about 5 cm. The drill test was done by drilling 3 times
through each
board with a 6 mm drill from above and below. In the milling test a 6 mm
countersinking
head was used to cut into the upper side of the previously produced drill-
hole.
The crosshatch test involves using a carpet knife to make cuts in the form of
a square
grid (4 x 4, separation about 1 cm) through the coating down to the wood. A
strip of
adhesive tape (Tesa/Scotch) is then stuck onto the grid, pushed down by hand
and torn
off again abruptly. To make the test tougher, a knife can then be used to
mechanically
work over the crossing points of the cuts.
CA 02810275 2013-03-04
40
Experimental series A corresponds to a chipboard as described in
WO/2010/031718.
Experimental series B corresponds to an inventive chipboard with PMDI in
binder (b).
Experimental series C corresponds to a chipboard fully bonded with aminoplast
resin.
While no qualitative differences are observable between the furniture foil-
laminated test
specimens (designations 1-B, 2-B and 3-B), the short cycle-coated test
specimens
(designations 1-A, 2-A and 3-A) produce distinct differences in some
instances:
improved quality is discernible for inventive test specimen 2-A compared with
the 1-A
test specimens without PMDI in the covering layer bonded with a formaldehyde-
free
binder; this quality is equivalent to that of conventionally aminoplast-bonded
woodbase
materials (cf. 3-A).
Example 6
Adjustability of formaldehyde emission via dosage of formaldehyde scavenger
Results table with mechanicals and FA values
Several laboratory chipboard panels having dimensions of 51.0 cm * 51.0 cm *
16.0 mm
were produced using different binder compositions. The target envelope density
for the
panels was 650 kg/m3. The boards were produced to using a pressing time factor
of
14 s/mm.
Table 6A reports the binder batches for the various board panels.
Columns headed "MS" identify the binder for the middle layer, columns headed
"DS" identify the binder for the covering layers.
The mass ratio of the covering layers to the middle layer was DS:MS:DS =
1:4:1. The layers were formed by hand and then
hot-pressed at 210 C using the following molding pressure profile: 50 s at 4
bar, 50 s at 2 bar, 40 sat 1 bar.
Table 6A: production parameters
Batch 1 2 3
4 5 n
DS MS DS MS DS MS DS MS DS MS
0
I.)
co
A KL 337 % OD 8.50 8.50
8.50 8.50 8.50 H
0
IV
B ammonium nitrate solution (52%) % v/v of A 4.00 4.00
4.00 4.00 4.00 -A
A in
C Hydrowax 560 (60%) % OD 0.50 0.50
0.50 0.50 0.50 I.)
0
H
D Polymer B52 % OD 2.83 2.83 2.83
2.83 2.83 LO
I
0
E triethanolamine % OD 0.85 0.85 0.85
0.85 0.85 u.)
i
0
F urea solid % OD 2.33 2.53 2.73
2.93 4.00 .1,.
G Hydrowax Q (50%) % OD 0.50 0.50 0.50
0.50 0.50
.
H chip moisture (resinated) % OD 9.20 10.90 12.30
11.10 10.90
,
J Lupranat M2OFB % OD 0.50 0.50 0.50
0.50 0.50
= CA 02810275 2013-03-04
42
Results (in table 6B)
Batch 1 constitutes an inventive comparative board similar to boards 2 and 3
of example 1.
In batches 2 to 5, the amount of urea in the covering layer as formaldehyde
scavenger is
additionally increased compared with batch 1.
The mechanical properties of all the boards are comparable. Only formaldehyde
emission
decreases with increasing amount of urea in the covering layers. The
formaldehyde
emissions in batch 4 are almost 50% reduced compared with the emissions of
batch 1
(F****).
Table 6B: results
Batch 1 2 3 4 5
Thickness
at testing mm 15.60 15.80 15.90 15.80 15.90
transverse tensile strength V 20
density (n = 8) kg/m' 610 643 613 634 634
transverse tensile strength N/mm2 0.44 0.45 0.40 0.43 0.37
swelling (50 * 50 mm)
density (n = 8) kg/m' 623 639 601 641 639
swelling after 24 h 28.1 29.4 25.9 29.0 29.4
water absorption after 24 h 101.4 102.2 108.9 102.5 101.4
peel strength
peel strength (n = 4) N/mm2 1.01 1.15 1.02 0.90 0.96
formaldehyde emissions
desiccator mg/L 0.18 0.14 0.14 0.13 0.11
gas analysis mg/(h*m2) 0.90 0.60 0.60 0.40 0.40
Example 7
CA 02810275 2013-03-04
43
Mixing ratio in binder (b): component I vs. II
Several laboratory chipboard panels having dimensions of 51.0 cm * 51.0 cm *
16.0 mm
were produced using different binder compositions. The target envelope density
for the
panels was 650 kg/m'. The boards were produced to using a pressing time factor
of
14 s/mm.
Table 7A reports the binder batches for the various board panels. Columns
headed "MS"
identify the binder for the middle layer, columns headed "DS" identify the
binder for the
covering layers.
The mass ratio of the covering layers to the middle layer was DS:MS:DS =
1:4:1. The layers
were formed by hand and then hot-pressed at 210 C using the following molding
pressure
profile: 50 s at 4 bar, 50 s at 2 bar, 40 s at 1 bar.
Table 7A: production parameters
Batch 1 2 3 4
DS MS DS MS DS MS DS MS
A KL 337 OD 8.50 8.50 8.50 8.50
ammonium nitrate % v/v
B solution (52%) of A 4.00 4.00 4.00 4.00
C Hydrowax 560 (60%) OD 0.50 0.50 0.50 0.50
D Polymer B52 OD 2.83 2.66 2.49 2.32
E triethanolamine OD 0.85 0.80 0.75 0.70
F urea solid OD 2.33 2.33 2.33 2.33
G Hydrowax Q (50%) OD 0.50 0.50 0.50 0.50
chip moisture
H (resinated) OD 9.20 10.90 12.30 11.10
J Lupranat M2OFB OD 0.50 0.67 1.00 1.00
= CA 02810275 2013-03-04
44
Results (in table 7B)
Batch 1 constitutes an inventive comparative board similar to boards 2 and 3
of example 1.
In batches 2 to 4, the covering layer has an increased amount of isocyanate in
the binder
and at the same time a reduced amount of polymer B52.
The mechanical properties of all the boards are comparable. Only water
stability increases
with increasing amount of isocyanate in the covering layers: the swell values
decrease from
batch 1 to batch 4.
Table 7B: results
Batch 1 2 3 4
transverse tensile strength V 20
transverse tensile strength N/mm2 0.44 0.45 0.44 0.43
swelling (50 *50 mm)
swelling after 24 h 28.1 25.7 25.0 24.9
formaldehyde emissions
desiccator mg/L 0.18 0.18 0.18 0.18
gas analysis mg/(h*m2) 0.90 1.00 0.90 1.10
The codes used in the tables for the substances have the following meanings:
KL 337 or KL 340, or KL 347: each Kaurite-Leim resin from BASF SE, in each
case an
aqueous solution or dispersion of a UF resin; dry resin content 65% to 70% by
weight.
KL 465: KauritO-Leim from BASF SE, aqueous solution or dispersion of a UFm
resin; dry
resin content 65% to 70% by weight.
Hydrowax 560 or Hydrowax0 Q: each a hydrophobicizing agent from Sasol based on
paraffin, each aqueous emulsions; solids content 60% and 50%, respectively.
Lupranat 0 M20 FB: PMDI from BASF Polyurethanes GmbH
