Note: Descriptions are shown in the official language in which they were submitted.
2164!~Q
Lignin-cont~; n~n~ isocyanate prepolymer mi~tures,
their preparation and their use for producing
polyurethanes and also the production of the
polyurethanes
The present invention relates to lignin-contain-
ing isocyanate prepolymer mixtures. The invention also
relates to a process for preparing such isocyanate pre-
polymer mixtures. Finally, the invention also re~ates to
the use of the isocyanate prepolymer mixtures of the
invention for producing polyurethanes (PU), in particular
foamed shaped bodies based on polyurethane, and also a
process for this purpose.
Polyoxyalkylene polyols prepared using lignin and
tannin as initiator molecules are known. According to
US-A-3,546,199 and US-A-3,654,194, lignin or tannin can
be alkoxylated in the presence or absence of solvents
using alkylene oxides, for example 1,2-propylene oxide,
at from 20 to 250C and at atmospheric or elevated
pressure. The polyoxyalkylene polyols prepared pos~ess
hydroxyl numbers in the range from 50 to 1000, preferably
from 200 to 800, and are suitable for producing flexible
to rigid PU foams by reaction with organic polyiso-
cyanates.
EP-A-0 342 781 describes the use of lignin in PU
production. Solutions of lignin in tetrahydrofuran (THF)
or polyoxyethylene glycol (PEG) are reacted with di-
phenylmethane diisocyanates (MDI) at 60C or at room
temperature. The films obtained therefrom have a good
mechanical strength, foams have a good elasticity ac~ord-
ing to the publication. No comparative examples without
lignin are given. The lignin forms the rigid phase, the
PEG the soft phase.
Lignin can also be dissolved in polyoxyethylene
216~49Q
-- 2
glycols (PEG~ and be reacted from this solution with
isocyanates to give polyurethane parts, as d~scribed in
U5-A-3,515,581. For this purpose, the lignin is disso~ved
in a polyoxyethylene glycol (PEG) or a mixture of PEG and
polyoxypropylene glycol ~PPG) and is treated, if desi~ed
at temperatures above 100C, for esterifying the carboxyl
groups of the lignin. The lignin/polyoxyalkylene glycol
solutions obtained are advantageously left to cool to
below 100C before they are reacted with the polyisocyan-
ates to form polyurethanes. The reaction always takes
place in the presence of a surface-active compound.
US-A-3,577,358 describes dissolving the lignin
either in PEG or in dioxane for the purposes of the
reaction. Curing occurs over a nl~her of hours at room
temperature or else at elevated temperature (~ 80C). The
polyurethane is isolated by removing the solvent. Lignin
and isocyanate react when they are mixed at 120C. The IR
spectrum shows that all OH and -N=C=O groups have react-
ed.
However, obstacles to the direct use of lignin in
polyurethane systems are not only insufficient reactivity
of the solid and even dissolved lignin, e.g. lignin
dissolved in tetrahydrofuran or dioxane, towards isocyan-
ates under the conditions of polyurethane production, but
also a series of other disadvantages. Their high salt
content very strongly influences the sensitive catalysis
of the PU systems, particularly when the lignins are used
as solution and not as solid. Industrially, lignins are
used predominantly as thickeners, and in higher concen-
trations they also have a similar viscosity-increasing
effect in water-containing polyetherol components.
Incompatibility of the lignin with other PU polyol compo-
nents is also frequently to be observed, which result8 in
the lignin particles, which in themselves are very fine,
coalescing after making up the polyol mixture, 80 that it
is no longer processable. Some of the lignin 0~ groups
are phenolic in nature, 80 that the polyurethane bonds
21 64~90
-- 3
obtained from them are thermolabile. For the reasons
given, lignin polyurethanes have not had 6atisfactory
processing and product properties. In general, incorpora-
tion of lignin even in polyurethane foams impair~ the
mechanical properties. To obtain PU parts having good
properties at all, u~e is often made of specifically
fractionated lignins or lignins which have been obtained
by a specific process (e.g. organosolv lignins).
Usual disadvantages of lignin in PU production
are insufficient reactivity and insufficient incorpora-
tion of the lignin in the PU matrix. Lignin solutions are
usually highly viscous and are not readily miscible with
organic polyisocyanates; in addition, the foams have pcor
mechanical properties. Separation of the high molecular
weight fractions of the lignin and carrying out the
reaction in solution gives PU parts for which a series of
advantages is reported. For example, a lower index is
required, cf. CA-A-2,052,487. With kraft lignin itself,
the PU polyaddition reaction in a PEG solution cannot be
carried out. The molecular weight of the lignin and the
viscosity of the lignin solution in PEG are too high and
the miscibility with the isocyanate component is too
poor. Special, modified lignin, e.g. one having a low
molecular weight of from 300 to 2000 and better solubili-
ty, gives more homogeneous foams having good mechanical
properties. A one-shot or else a prepolymer method may be
used. In the latter case, lignin/polyols/isocyanates are
used to prepare a prepolymer which can then be cast into
films or can also be foamed by mixing with
water/catalysts/stabilizers.
To circumvent the above difficulties associated
with the direct proce~ing of the lignin, alkoxylation of
the lignin ha~ also been proposed, but this iq compli~
cated. In general, owing to the (processing) difficultie~
mentioned, lignins or lignin derivatives are not current-
ly used on an industrial scale for producing polyur-
ethanes. US-A-3,546,199 and US-A-3,654,194 describe
~16~
reacting solid pulverulent lignin or lignin dissolved in
reactive or unreactive solvents to give lignin polyether-
018, both in the ab~_nce of catalyst and with ROH/aniline
catalysis. The OH numbers of the polyols obtained enable
the OH numbers of the lignins to be back-calculated. They
are from about 600 to 1300. Tannin can also be used like
lignin. The OH numbers of the lignin polyether-polyols
are from 50 to 1000.
It i8 an object of the present invention to
prepare isocyanate prepolymer mixtures which can be
readily processed. A further ob~ect of the invention is
to indicate such isocyanate prepolymer mixtures which in
further processing give polyurethane products, in part-
icular polyurethane foams, which possess improved phy~i-
cal properties, in particular with regard to elongation
at break, tensile strength and/or tear propagation
resistance. It is also an object of the present invention
to devise a process for preparing such isocyanate pre-
polymer mixtures and also a process for producing polyur-
ethanes having the improved mechanical properties.
We have found that this object is achieved byisocyanate prepolymer mixtures as defined in the claims.
The process of the invention for preparing such poly-
isocyanate prepolymer mixtures and their use for produc-
ing polyurethanes and polyurethane products and a process
for this purpose are likewise defined in the claims.
Preferred embodiments of the invention are given in the
following description and the subclaims.
According to the invention, use is advantageously
made of a natural material, i.e. a regenerable poly-
hydroxyl compound.
According to the invention, the synthetically
prepared polyhydroxyl compounds are advantageously
completely or at least partially replaced by lignin as a
hydroxyl-containing natural material. The use of this
regenerable hydroxyl-containing natural material requires
no complicated technical syntheses. It is also
~164490
-- 5
advantageous that lignin formed as waste product in other
areas can be industrially utilized, if appropriate after
slight technical troatment and/or purification. The use
of novel starting materials enables, according to the
invention, the production of polyisocyanate polyaddition
products having different mechanical properties which in
turn open up new application opportunities.
The isocyanate prepolymer mixtures provided
according to the invention, which contain urethane groups
and reactive isocyanate groups in bound form, are
obtained by reacting
bl) at least one organic polyisocyanate based on
diphenylmethane diisocyanate with
b2) at least one polyhydroxyl component.
According to the invention, the polyhydroxyl
component consists at least partially of a suspension of
lignin in a polyoxyalkylene glycol containing oxypropyl-
ene groups. The isocyanate prepolymer mixture of the
invention has an NC0 content of from 2.5 to 30% by
weight, based on the total weight of the isocyanate
prepolymer mixture, and is obtainable by reacting
bl) diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate,
an isomer mixture of diphenylmethane 4,4'- and 2,4'-
or 4,4'-, 2,4'- and 2,2'-diisocyanates or a mixture
of diphenylmethane diisocyanates and polyphenyl-
polymethylene polyisocyanates with
b2) a suspension comprising
b2i) at least one polyoxyalkylene glycol having a
molecular weight of from 400 to 6000, prefer-
ably from 1000 to 3000, selected from the
group of polyoxypropylene glycols, polyoxy-
propylene-polyoxyethylene glycols and mix-
tures thereof and
b2ii) lignin.
The ratio of lignin to hydroxyl-containing
compound is here preferably such that from 1 to 70% by
weight of lignin and from 99 to 30% by weight of poly-
216~490
-- 6
hydroxyl component (b2) containing polyoxypropylene
and/or polyoxypropylene-polyoxyethylene glycol together
form 100% by weight of the suspension. The lignin
6uspension preferably comprises from 70 to 30% by weight,
in particular from 60 to 50% by weight, of the
polyoxypropylene-polyoxyethylene glycols and/or, in
particular, a polyoxypropylene glycol, while the amount
of lignin makes up from 30 to 70% by weight, in
particular from 40 to 50~ by weight, of the suspension.
The reaction of the lignin suspension with the
polyisocyanate is preferably carried out in the absence
of a surfactant.
The lignins used are preferably ones which h2ve
not been subjected to any special chemical treatment for
their further processing. Rraft lignins are particularly
preferred. Such lignins preferably have an acid nl~her of
less than 10.
The preferred suspension media for the lignin are
polyoxypropylene glycols having a molecular weight of
from 1000 to 3000.
The isocyanate prepolymer mixture is preferably
a fluid mixture having an -N=C=0 content of from 5 to
25~, based on the isocyanate prepolymer mixture. The
particularly preferred isocyanate prepolymer mixture has
an -N-C=0 content of from 9 to 15% by weight.
In the process of the invention for preparing the
isocyanate prepolymer mixtures, the abovementioned
components are reacted with one another to form the
isocyanate prepolymer mixture. The lignin can be at least
partially esterified on the surface by the hydroxyl
groups of the polyoxypropylene and/or polyoxypropylene-
polyoxyethylene glycols and any further polyhydroxyl
compounds of the polyhydroxyl component (b2) and be thus
chemically bonded to the latter. The chemical incorpora-
tion of the lignin into the isocyanate prepolymer mixture
occurs via the hydroxyl groups present on the lignin, and
indeed out from the suspension with reaction with the
~164490
i60cyanate groups of the polyisocyanate component.
The bonding of the lignin into the isocyanate
prepolymer mixture- enables any other relatively high
molecular weight compounds having at least two reactive
hydrogens to be used for the production of polyurethane.
Owing to its viscosity and good suitability for
prepolymer preparation, it is easy to suspend lignin as
solid in polyoxypropylene-polyoxyethylene glycols,
preferably polypropylene glycols, to remove water adher-
ing to the lignin (about 5~ by weight) and to react thewater-free lignin suspension thus obtained with isocyan-
ates to give lignin-containing prepolymers.
Suspending in polyoxypropylene-polyoxyethylene
glycol~ and/or polyoxypropylene glycols readily enables
up to about 70% by weight of lignin to be introduced into
the ~uspension and up to about 30~ by weight of lignin to
be introduced into the isocyanate prepolymer mixture. The
viscosity of the i60cyanate prepolymer mixtures of the
invention is low despite the high lignin content and
these are readily processable.
The lignin-containing isocyanate prepolymer
mixtures based on lignin ~u~pensions are storage stable.
Even after standing for a prolonged period at room
temperature, viscosity and -N=C=O content are essentially
unchanged.
The use of the lignin-containing isocyanate
prepolymer mixtures of the invention enable polyurethane
parts to be produced without processing difficulties. The
mechanical properties of the parts obtained are good.
Unmodified lignins, e.g. standard kraft lignin, standard
organosolv lignins or lignins isolated via other
digestion processes can also be used and are readily
processable under the conditions according to the
invention to give high performance polyurethanes.
In the process of the invention for producing
compact or cellular polyurethanes, preferably PU foams,
21644~Q
-- 8
a) relatively high molecular weight compounds having
at least two reactive hydrogens, preferably
polyhydroxyl compounds, are reacted with
b) liquid polyi60cyanate compositions containing
urethane groups in bonded form.
This is carried out in the presence or absence of
c) chain extenders and/or crosslinkers,
d) blowing agents,
e) catalysts and
f) auxiliaries.
According to the invention, the polyisocyanate
composition (b) consists at least partially of an i80-
cyanate prepolymer mixture as defined above.
In the process of the invention for producing
polyurethanes, it is preferred that the relatively high
molecular weight compounds (a) have a functionality of
from 2 to 8 and an amine or hydroxyl number of from 25 to
500 and are advantageously selected from the group of
polyalkylene polyamines and/or polyhydroxyl compounds, in
particular polyhydroxyl compounds having a functionality
of from 2 to 8 and a hydroxyl number of from 25 to 500,
which in turn are preferably selected from the group of
polythioether polyols, polyester amides, hydroxyl-con-
taining polyacetals, hydroxyl-containing aliphatic
polycarbonates, polyester polyols, polymer-modified
polyether polyols, preferably polyether polyols and
mixtures of at least two of the specified polyhydroxyl
compounds.
Suitable relatively high molecular weight poly-
hydroxyl compounds as are used in (a) advantageously
possess, as already mentioned, a functionality of from 2
to 8 and a hydroxyl number of from 25 to 500, with
preference being given to using polyhydroxyl compounds
having a functionality of preferably from 2 to 3 and a
~16~90
g
hydroxyl number of preferably from 30 to 80 for the
production of flexible PU foams and preference being
given to using polyhydroxyl compounds having a
functionality of preferably from 3 to 8 and in particular
from 3 to 6 and a hydroxyl number of preferably from 100
to 500 for the production of rigid PU foams. The
polyhydroxyl compounds used are preferably linear and/or
branched polyester polyols and in particular linear
and~or branched polyoxyalkylene polyols, with
polyhydroxyl compounds from regenerable natural materials
and/or chemically modified regenerable natural materials
being particularly preferred. Suitable lignin-free
polyhydroxyl compounds (a) are also polymer-modified
polyoxyalkylene polyols, polyoxyalkylene polyol
dispersions and other hydroxyl-containing polymers and
polycondensates having the abovementioned functionalities
and hydroxyl numbers, for example polyesteramides,
polyacetals and/or polycarbonates, in particular those
which are prepared from diphenyl carbonate and 1,6-
hexanediol by transesterification, or mixtures of atlea6t two of the specified relatively high molecular
weight polyhydroxyl compounds (a).
Suitable polyester polyols can be prepared, for
example, from organic dicarboxylic acids having from 2 to
12 carbon atoms, preferably aliphatic dicarboxylic acids
having from 4 to 6 carbon atoms and polyhydric alcohols,
preferably alkane diols having from 2 to 12 carbon atoms,
preferably from 2 to 6 carbon atoms, dialkylene glycol~
and/or alkanetriols having from 3 to 6 carbon atoms.
Suitable dicarboxylic acids are, for example: succinic
acid, glutaric acid, adipic acid, suberic acid, azelaic
acid, sebacic acid, decanedicarboxylic acid, maleic acid,
fumaric acid, phthalic acid, isophthalic acid and tereph-
thalic acid. The dicarboxylic acids can here be used
either individually or in admixture. In place of the free
carboxylic acids, it is also possible to use the corre-
sponding carboxylic acid derivatives such as dicarboxylic
216449V
- 10
esters of alcohols having from 1 to 4 carbon atoms or
dicarboxylic anhydrides. Preference is given to using
dicarboxylic acid mixtures of succinic, glutaric and
adipic acid in weight ratios of, for example, 20 to 35:35
to 50:20 to 22, and in particular adipic acid. Examples
of dihydric and polyhydric alcohols, in particular alkane
diols and dialkylene glycols, are: ethanediol, diethylene
glycol, 1,2- or 1,3-propanediol, dipropylene glycol, 1,4-
butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decane-
diol, glycerol and trimethylolpropane. Preference iBgiven to using ethanediol, diethylene glycol, 1,4-butane-
diol, 1,5-pentanediol, 1,6-hexanediol, glycerol or
mixtures of at least two of the specified alkane polyo's,
in particular, for example, mixtures of 1,4-butanediol,
1,5-pentanediol and 1,6-hexanediol. Also usable are
polyester polyols from lactones, e.g. ~-caprolactone, or
hydroxycarboxylic acids, e.g. w-hydroxycaproic acid.
The polyester polyols can be prepared by polycon-
densing the organic, for example aromatic and preferably
aliphatic dicarboxylic acids and/or their derivatives
with the polyhydric alcohols and/or alkylene glycols in
the absence of catalyst or preferably in the presence of
esterification catalysts, advantageously in an atmosphere
of inert gases, for example nitrogen, helium, argon,
etc., in the melt at from 150 to 250C, preferably from
180 to 220C, under atmospheric or reduced pressure, to
the desired acid number which is advantageously less than
10, preferably less than 2. According to a preferred
embodiment, the esterification mixture is polycondensed
at the abovementioned temperatures to an acid number of
from 80 to 30, preferably from 40 to 30, under atmospher-
ic pressure and subsequently under a pressure of less
than 500 mbar, preferably from 50 to 150 mbar. Suitable
esterification catalysts are, for example, iron, cadmium,
cobalt, lead, zinc, antimony, magnesium, titanium and tin
catalysts in the form of metals, metal oxides or metal
salts. However, the polycondensation can also be carried
216 l i~O
- 11
out in the liquid phase in the presence of diluents
and/or entrainers such as benzene, toluene, xylene or
chlorobenzene, for azeotropically distilling off the
water of condensation.
The polyester polyols are advantageously prepared
by polycondensing the organic dicarboxylic acids and/or
their derivatives with the polyhydric alcohols in a molar
ratio of 1:1 to 1.8, preferably l:l.OS to 1.2.
The polyester polyols obtained preferably have a
functionality of from 2 to 4, in particular from 2 to 3,
and a hydroxyl number of from 240 to 30, preferably from
180 to 40.
However, the polyhydroxyl compounds used are
particularly preferably polyoxyalkylene polyols prepared
by known methods, for example by anionic polymerization
using alkali metal hydroxides such as sodium or potas6ium
hydroxide, or using alkali metal alkoxides such as sodium
methoxide, sodium or potassium ethoxide or potassium
isopropoxide as catalysts and with addition of at least
one initiator molecule containing from 2 to 8, preferably
from 2 to 3, reactive hydrogens in bonded form for
preparing polyoxyalkylene polyols for flexible PU foams
and preferably from 3 to 8 reactive hydrogens in bonded
form for preparing polyoxyalkylene polyols for semi-rigid
and rigid PU foams, or by cationic polymerization using
Lewis acids such as antimony pentachloride, boron fluo-
ride etherate, etc., or bleaching earth as catalysts,
from one or more alkylene oxides having from 2 to 4
carbon atoms in the alkylene radicals.
Suitable alkylene oxides are, for example,
tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butyl-
ene oxide and preferably ethylene oxide and l,2-propylene
oxide. The alkylene oxides can be used individually,
alternately in succession or in admixture. Suitable
initiator molecules are, for example: water, organic
dicarboxylic acids such as succinic acid, adipic acid,
phthalic acid and terephthalic acid, aliphatic and
2164~90
aromatic, unsubstituted or N-monoalkylated, N,N-dialkyl-
ated or N,N'-dialkylated diamines having from 1 to 4
carbon atoms in the lkyl radical, such as unsubstituted
or monoalkylated or dialkylated ethylenediamine, diethyl-
ene triamine, triethylene tetramine, l,3-propylenedi-
amine, 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-,
1,5- and 1,6-hexamethylenediamine, phenylene diamines,
2,3-, 3,4-, 2,4- and 2,6-tolylenediamine and 4,4'-, 2,4'-
and 2,2'-diaminodiphenylmethane.
Also ~uitable as initiator molecules are: alkano-
lamines such as ethanolamine, N-methylethanolamine and N-
ethylethanolamine, dialkanolamines such as diethanol-
amine, N-methyldiethanolamine and N-ethyldiethanolamine
and trialkanolamines such as triethanolamine, and ammo-
nia. Preference is given to using polyhydric, in particu-
lar dihydric to octahydric alcohols and/or alkylene
glycols such as ethanediol, 1,2- and 1,3-propanediol,
diethylene glycol, dipropylene glycol, 1,4-butanediol,
1,6-hexanediol, glycerol, trimethylolpropane, pentaeryth-
ritol, sorbitol and sucrose and also mixtures of at lea~t
2 polyhydric alcohol~.
The polyoxyalkylene polyols, preferably polyoxy-
propylene and polyoxypropylene-polyoxyethylene polyols,
have a functionality of from 2 to 8 and hydroxyl numbers
of from 25 to 500, with, as already stated, preference
being given to using polyoxyalkylene polyols having a
functionality of from 2 to 3 and a hydroxyl number of
from 30 to 80 for flexible PU foams and polyoxyalkylene
polyols having a functionality of from 3 to 8 and a
hydroxyl number of from lOO to 500 for semi-rigid and
rigid PU foams and suitable polyoxytetramethylene glycols
having a hydroxyl number of from 30 to about 280.
Other suitable polyoxyalkylene polyols are
polymer-modified polyoxyalkylene polyols, preferably
graft polyoxyalkylene polyols, in particular those based
on styrene and/or acrylonitrile, which are prepared by
in-situ polymerization of acrylonitrile, ~tyrene or
~164490
- 13 -
preferably mixtures of styrene and acrylonitrile, for
example in a weight ratio of from 90:10 to 10:90, prefer-
ably from 70:30 to 30:70 advantageously in the above-
mentioned polyoxyalkylene polyol~ using a method
~imilar to those given in the German Patents 11 11 394,
12 22 669 (US 3 304 273, 3 383 351, 3 523 903), 11 52 536
(GB 10 40 452) and 11 52 537 (GB 987618), and also
polyoxyalkylene polyol dispersions containing as disper~e
phase, usually in an amount of from 1 to 50~, preferably
from 2 to 25~: for example, polyureas, polyhydrazides,
polyurethanes containing tert-amino groups in bonded form
and/or melamine and described, for example, in
EP-B-011 752 (US-A-4,304,708), US-A-4,374,209 and
DE-A-32 31 497.
The polyoxyalkylene polyols can, like the polyes-
ter polyols, be used individually or in the form of
mixtures. Furthermore, they can be mixed with the graft
polyoxyalkylene polyols or polye~ter polyols and also the
hydroxyl-containing polyester amides, polyacetals and/or
polycarbonates.
Suitable hydroxyl-containing polyacetals are, for
example, the compound~ which can be prepared from glycols
6uch as diethylene glycol, triethylene glycol, 4,4'-
dihydroxyepoxydiphenyldimethylmethane, hexanediol and
formaldehyde. Polymerization of cyclic acetals also
allows ~uitable polyacetals to be prepared.
Suitable hydroxyl-containing polycarbonates are
those of the type known per se which can be prepared, for
example, by reacting diols such as 1,3-propanediol, 1,4-
butanediol and/or 1,6-hexanediol, diethylene glycol,
triethylene glycol or tetraethylene glycol with diaryl
carbonates, for example diphenyl carbonate, or phosgene.
The polyester amides include, for example, the
predominantly linear condensates obtained from polybasic,
~aturated and/or unsaturated carboxylic acids or their
anhydrides and polyhydric saturated and/or unsaturated
amino alcohols or mixtures of polyhydric alcohols and
2~ 6A~90
amino alcohols and/or polyamines.
The relatively high molecular weight polyhydroxyl
compounds (a) can, depending on the application of the
isocyanate prepolymer mixtures (b), be completely or
preferably partially replaced by low molecular weight
chain extenders and/or crosslinkers. In the production of
flexible PU foams, the addition of chain extenders,
crosslinkers or, if desired, mixtures thereof can be
advantageous for modifying the mechanical properties of
the PU foams, for example the hardness. In the production
of PU rigid foams, the use of chain extenders and/or
crosslinkers can usually be omitted. Chain extenders
which can be u~ed are difunctional compounds and suitable
cros~linkers are trifunctional and higher-functional
compounds, each having molecular weights less than 400,
preferably from 62 to about 300. Examples of chain
extenders are alkane diols, for example those having from
2 to 6 carbon atoms in the alkylene radical, such as
ethane diol, 1,3-propane diol, 1,4-butane diol, 1,5-
pentane diol and 1,6-hexane diol, and dialkylene glycols
such as diethylene, dipropylene and dibutylene glycol,
and examples of crosslinkers are alkanolamines, e.g.
ethanolamine, dialkanolamines, e.g. diethanolamine, and
trialkanolamines, e.g. triethanolamine and triiso-
propanolamine, and trihydric and/or higher-hydric alco-
hols such as glycerol, trimethylolpropane and pentaeryth-
ritol. Other suitable chain extenders or cros~linkers are
the low molecular weight ethoxylation and/or propoxyl-
ation products, for example those having molecular
weights up to about 400, of the abovementioned polyhydric
alcohols, alkylene glycols, alkanolamines and of aliphat-
ic and/or aromatic diamines.
As chain extenders, preference is given to using
alkanediols, in particular 1,4-butanediol and/or 1,6-
hexanediol, alkylene glycols, in particular ethylene
glycol and propylene glycol, and preferred crosslinkers
are trihydric alcohols, in particular glycerol and
~164~90
- 15 -
trimethylolpropane, dialkanolamine, in particular dieth-
anolamine, and trialkanolamine, in particular triethanol-
amine.
The chain extenders and/or crosslinkers (c) which
are preferably used in the production of flexible PU
foams can be used, for example, in amounts of from 2 to
60% by weight, preferably from 10 to 40~ by weight, based
on the weight of the relatively high molecular weight
compounds (a).
The isocyanate prepolymer mixtures of the inven-
tion (b) can be mixed with further polyisocyanates for
producing the PU. Specific examples are: alkylene diiso-
cyanates having from 4 to 12 carbon atom~ in the alkylene
radical, for example dodecane 1,12-diisocyanate, 2-
ethyltetramethylenel,4-diisocyanate,2-methylpentamethy-
lene 1,5-diisocyanate, 2-ethyl-2-butylpentamethylene 1,5-
diisocyanate, tetramethylene 1,4-diisocyanate and prefer-
ably hexamethylene 1,6-diisocyanate; cycloaliphatic
diisocyanates, for example cyclohexane 1,3- and 1,4-
diisocyanate and also any mixtures of these isomers, 1-
isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane
(iRophorone dii~ocyanate), hexahydrotolylene 2,4- and
2,6-diisocyanate and also the corresponding isomer
mixtures, dicyclohexylmethane 4,4'-, 2,2'- and 2,4'-
diisocyanate and also the corresponding isomer mixtures,
and preferably aromatic diisocyanates and polyiso-
cyanates, for example tolylene 2,4- and 2,6-diisocyanate
and the corresponding isomer mixtures, diphenylmethane
4,4'-, 2,4'- and 2,2'-diisocyanate and the corresponding
isomer mixtures, mixtures of diphenylmethane 4,4'- and
2,4'-diisocyanates, polyphenylpolymethylene polyisocyan-
ates, mixtures of diphenylmethane 4,4'-, 2,4'- and 2,2'-
diisocyanates and polyphenylpolymethylene polyisocyanates
(raw MDI) and mixtures of raw MDI and tolylene
diisocyanates. The organic diisocyanates and polyiso-
cyanates can be used individually or in the form of their
mixtures.
216 4490
- 16 -
Organic polyisocyanates which have been found to
be very useful are mixtures of diphenylmethane diisocyan-
ates and polyphenylp~lymethylene polyisocyanates, prefer-
ably those having a diphenylmethane diisocyanate content
of at least 35~ by weight, e.g. from 45 to 95~ by weight
and in particular from 48 to 60% by weight, 80 that ~uch
raw MDI compo6itions are particularly preferably used.
Suitable blowing agents (d) for producing the
cellular polyurethanes are water and/or gases which are
liquid at room temperature and liquids which are inert to
the liquid isocyanate prepolymer mixtures and have
boiling points at atmospheric pressure below 50C, in
particular from -50C to 30C, and also mixtures of
gaseous and liquid blowing agents. Examples of such ga~es
and liquids which are preferably used are alkanes such as
propane, n- and iso-butane, n- and iso-pentane, prefera-
bly technical grade mixtures of n- and iso-pentane, and
cycloalkanes such as cyclopentane, alkyl ethers such as
dimethyl ether, diethyl ether and methyl isobutyl ether,
alkyl carboxylates such as methyl formate, and halogenat-
ed hydrocarbons such as dichlorofluoromethane, trifluoro-
methane, l,l-dichloro-l-fluoroethane, monochlorotri-
fluoroethane, monochlorodifluoroethane, difluoroethane,
dichlorotrifluoroethane, monochlorotetrafluoroethane,
pentafluoroethane, tetrafluoroethane and dichloromono-
fluoroethane. The cellular polyurethanes, preferably PU
foams, are produced using, in particular, water, linear
and cyclic alkanes having from 5 to 7 carbon atoms and
mixtures thereof.
The blowing agents mentioned by way of example
can be used individually or as mixtures. Blowing agents
which are not used are chlorofluorocarbons which damage
the ozone layer.
It is also possible to mix the liquids having
boiling points below 50C with (cyclo)alkanes such as
hexane and cyclohexane and alkyl carboxylates, such as
ethyl formate having boiling points above 50C, as long
2164490
- 17 -
as the blowing agent mixture advantageously has a boiling
point below 38C. The amount of blowing agent or blowing
agent mixture required can be experimentally determined
in a ~imple manner as a function of the type of blowing
agent or blowing agent mixture and on the mixing ratios.
The blowing agents are usually used in an amount of from
0.1 to 30 part~ by weight, preferably from 1 to 25 parts
by weight, based on 100 parts by weight of the components
a-c.
Catalysts (e) which can be used in the production
of PU are preferably compounds which strongly accelerate
the reaction of the hydroxyl-containing component ~a)
with the isocyanate prepolymer mixtures of the invention
(b) or the mixtures of isocyanate prepolymer mixtures (b)
and further organic polyisocyanates. Suitable catalysts
are, for example, organic metal compounds, preferably
organic tin compounds such as tin(II) salts of organic
carboxylic acids, e.g. tin(II) diacetate, tin(II) diocto-
ate, tin(II) diethylhexanoate and tin(II) dilaurate, and
the dialkyltin(IV) salts of organic carboxylic acids,
e.g. dibutyltin diacetate, dibutyltin dilaurate, dibutyl-
tin maleate, dioctyltin diacetate, and dibutyltin dimer-
captide and strongly basic amines, for example amidines
such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine,
tertiary amines such as triethylamine, tributylamine,
dimethylbenzylamine, N-methylmorpholine, N-ethylmorpho-
line, N-cyclohexylmorpholine, dimorpholino-diethyl ether,
N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetra-
methylbutanediamine, N,N,N',N',tetramethylhexane-1,6-
diamine, di(4-N,N-dimethylaminocyclohexyl)methane,
pentamethyldiethylenetriamine, tetramethyldiaminoethyl
ether, bis(dimethylaminopropyl)urea, dimethylpiperazine,
1,2-dimethylimidazole,l-azabicyclo[3.3.0~octane,alkano-
lamine compounds such as triethanolamine, triisopropanol-
amine, N-methyldiethanolamine and N-ethyldiethanolamine
and dimethylethanolamine, tris(N,N-dialkylaminoalkyl)-s-
hexahydrotriazine, in particular tris(N,N-dimethylamino-
2164~0
- 18 -
propyl)-s-hexahydrotriazine,tetraalkylamoniumhydroxides
such as tetramethylammonium hydroxide and preferably 1,4-
diazabicyclo[2.2.2]o~tane. Preference i8 given to using
from 0.001 to 5% by weight, in particular from 0.05 to 2~
by weight, of catalyst or catalyst combination, based on
the weight of the component (a).
If desired, auxiliaries (f) can also be incorpo-
rated into the reaction mixture for producing the compact
or cellular polyurethanes, preferably PU foams. Examples
are surface-acti~e substances, foam stabilizers, cell
regulators, flame retardants, fillers, dyes, pigments,
antistatic agents, hydrolysis inhibitors, fungistatic and
bacterio6tatic sub6tances.
Suitable surface-active substances are, for
example, compounds which serve to assist the homogeniza-
tion of the isocyanate prepolymer mixtures and may also
be suitable for regulating the cell structure of the PU
foams. Examples are emulsifiers such as the sodium salts
of castor oil sulfates or of fatty acids, and also 6alts
of fatty acids with amines, for example diethanolamine
salts of oleic acid, stearic acid and ricinoleic acid,
salts of sulfonic acids, for example alkali metal or
ammonium salts of dodecylbenzenedisulfonic or dinaphthyl-
methanedisulfonic acid, and ricinoleic acid; foam stabi-
lizers such as siloxane-oxyalkylene copolymer~ and other
organopolysiloxanes, ethoxylated alkylphenols, ethoxyl-
ated fatty alcohols, paraffin oils, castor oil ester~ or
ricinoleic esters, Turkey red oil and peanut oil, and
cell regulators such as pyrogenic silica, paraffins,
fatty alcohol~ and dimethylpolysiloxanes. Other suitable
compounds for impro~ing the emulsifying action, the cell
structure and/or stabilization of the foam are oligomeric
polyacrylates having polyoxyalkylene and fluoroalkane
radicals as side groups. The surface-active substances
are usually used in amounts of from 0.01 to 5 parts by
weight, based on 100 parts by weight of the component
(a).
~l6,l4sn
- 19
Suitable flame retardants are, for example,
diphenyl cre~yl phosphate, tricresyl phosphate, tris(2-
chloroethyl) phosphate, tris(2-chloropropyl) phosphate,
tris(l,3-dichloropropyl) phosphate, tris(2,3-dibromoprop-
yl) phosphate and tetrakis(2-chloroethyl)ethylene diphos-
phate.
Apart from the halogen-substituted phosphates
mentioned, it is also possible to use inorganic flame
retardants such as hydrated aluminum oxide, antimony
10 trioxide, arsenic oxide, ammonium polyphosphate, expanded
graphite and calcium sulfate, or cyanuric acid deriva-
tives such as melamine, or mixtures of at least two flame
retardants such as ammonium polyphosphates and melam'ne
and/or expanded graphite, and also, if desired, starch to
make the PU foams produced from isocyanate prepolymer
mixtures flame resistant. In general, it has been found
to be advantageous to use from 5 to 50 parts by weight,
preferably from 10 to 40 parts by weight, of the flame
retardants or mixtures mentioned per 100 parts by weight
20 of the components (a) to (c).
For the purposes of the present invention,
fillers, in particular reinforcing fillers, are the
customary organic and inorganic fillers and reinforce-
ments known per se. Specific examples are: inorganic
fillers such as siliceous minerals, or example sheet
silicates such as antigorite, serpentine, hornblendes,
amphiboles, chrysotile, zeolites, talc; metal oxides such
as kaolin, aluminum oxides, aluminum silicate, titanium
oxides and iron oxides, metal salts such as chalk, barite
30 and inorganic pigments such as cadmium sulfide, zinc
sulfide, and also glass particles. Examples of suitable
organic fillers are: carbon black, melamine, rosin,
cyclopentadienyl resins and graft polymers.
The inorganic and organic fillers can be used
individually or as mixtures and are advantageously
incorporated into the reaction mixture in amounts of from
O.5 to 5096 by weight, preferably from 1 to 1096 by weight,
2164490
- 20 -
based on the weight of the components (a) to (c).
Further details about the other customary auxil-
iaries (f) mentioned above can be found in the 6pecialist
literature, for example the monograph of J.H. Saunders
and K.C. Frisch "High Polymers", Volume XVI, Polyureth-
anes, part 1 and 2, Verlag Interscience Publishers 1962
and 1964, or the ~unststoff-Handbuch, Polyurethane,
Volume VII, Carl-Hanser-Verlag, Munich, Vienna, 1st and
2nd edition, 1966 and 1983.
Further preferred features and embodiments of the
invention are given in the following examples.
EXAMPLE 1
Preparation of the lignin-containing isocyanate prepoly-
mer mixtures of the invention
Lignin-containing prepolymers according to the
invention were prepared using three different unmodified
lignins: kraft lignin AT and two organosolv lignins. The
lignin powders were first stirred into polyoxypropylene
glycol having a molecular weight of 2000 and were treated
while removing the water for 5 hours at 150C and under
reduced pressure of 2mbar. The dewatered lignin suspen-
sion obtained was subsequently slowly metered while
stirring into the initially charged isocyanate heated to
80C and was stirred for 2 hours at 80C or 120C to
complete the reaction.
This gave lignin-containing isocyanate prepolymer
mixtures whose vi6cosity was strongly dependent on the
lignin type and also on the structure of the polyisocyan-
ate used. The viscosity was down to below 1000 mPas at
25C, measured using a rotation viscometer, at lignin
contents in the prepolymer of > 20% by weight. The
storage stability is evidenced by the testing of viscosi-
ty and -N=C=0 content after 60 days (Table 1, experiment
1) and also the fact that the prepolymer formation at
elevated temperature did not lead to increased viscosi-
ties or significantly altered -N=C=0 contents (Table 1,
2164490
- 21 -
experiments 1 to 3).
Table 1
-N=C=O prepolymers from lignin
suspensions in polyoxypropylene glycols
R2porim~nt Lignln Polyol Lig~in:polyol Ieocyanato
(~oight ratio)
1 Llg PH41)PPG 20002) 42 : 58 M20W3)
2 Lig PH9 PPG 2000 48 : 52 M20W
3 Llg AT PP~ 2000 48 : 52 M20W
4 Llg AT PPG 2000 44 : 56 MI~)
0 ~xperlment Suspenslon:I~ocya- -N=C~O Re~arks
nate ~ by
(welght ratio) wt.)PreparationVl~co~ity
te~peratureat 25C
C
1 1000 : 1050 13.2 80 42400
440050
after 60 13.2 120 58500
day85) 13.3 80 370050
2 500 : 650 14.5 B0 4100
14.4 120 4200
3 500 : 650 16.9 80 6800
16.9 120 6500
4 280 : 320 16.4 80 725
(1) Lig AT: Kraftlignin Indulin AT from Westvaco,
Charleston, SC, USA
Lig PH4 and Lig PH9: organosolv lignins from Organo-
cell GmbH, Munich
(2) A polyoxypropylene glycol having a molecular weight
of 2000
(3) Mixture of diphenylmethane diisocyanates and poly-
phenyl-polymethylene polyisocyanates (raw MDI)
(4) Mixture of diphenylmethane 4,4'- and 2,4'-diisocyan-
ate
'~16 4490
- 22 -
(5) The measurements of the -N=C=O content and the
viscosity using a rotation viscometer were carried
out after storage of the suspension for 60 day~ at
50C
Table 1 shows that the isocyanate prepolymer
mixtures of the invention are very stable both physically
and chemically. This is a particular advantage of the
invention.
EXAMPLE 2
Production of polyurethane parts
Flexible polyurethane foams were produced using
the lignin-containing isocyanate prepolymer mixtures of
the invention as described in Example 1.
The base polyetherol used was a polyoxypropylene-
polyoxyethylene block polyol initiated using a glycerol
and having a content of primary hydroxyl end groups
greater than 80%, a hydroxyl number of 35 mg of KOH/g of
polyol and a viscosity of 850 mPas at 25C measured in
accordance with DIN 51562 using an Ubbelohde viscometer.
The cell opening polyol used was a polyoxypropyl-
ene-polyoxyethylene polyol initiated using glycerol and
having an ethylene oxide content of 70% by weight, based
on the alkylene oxide content, a hydroxyl number of 42 mg
of KOH/g of polyol and a viscosity of 980 mPas at 25C
measured in accordance with DIN 51562 using an Ubbelohde
viscometer.
The comparative substance used was a polyisocyan-
ate mixture containing urethane groups and having an
-N=C=O content of 24.5% by weight, obtained from
diphenylmethane diisocyanates (40.7% by weight),
polyphenyl-polymethylene polyisocyanates (30.4~ by
weight), polyoxypropylene glycol having an average
molecular weight of 2000 (10% by weight) and the
abovementioned cell opening polyol (10~ by weight).
The flexible PU foams were produced by intensive-
~164490
- 23 -
ly mixing the polyol and isocyanate components at an NCO
index = 80 (80 -N=C=O groups per 100 OH groups) and
pouring the reaction mixture into an open beaker (deter-
mination of the reaction times and the free-foamed bulk
density) and into a heatable mold (mold temperature 50C)
having the dimen6ions 400x400x100 mm (determination of
the mechanical propertie~ of the foams) and allowed to
foam therein.
Formulation for producing flexible polyurethane
foams in parts by weight.
Component (A): mixture consisting of:
Ba~e polyetherol 54.55
Cell opening polyol 5.0
Water 3.00
Stabilizer1) 0.20
Diazabicyclo[2.2.2]octane 0.20
33% by weight in dipropyl-
ene glycol
N,N-dimethylaminopropylamine 0.30
N,N,N',N'-tetramethyl-4,4'-
diaminodicyclohexylmethane 0.45
Glycerol 1.20
Tris(chloropropyl) phosphate 5.00
Foam stabilizer based on silicone, Tegostab B 8680
from Goldschmidt.
Component (B): Isocyanate mixture as de~cribed in Table
In the experiments described in Table 2, the
polyisocyanate mixture containing urethane groups used a~
comparative substance was replaced completely or
9 0
partially as indicated by the lignin-containing
iRocyanate prepolymer mixture of the invention.
~154~9~
Table 2
Rrpari~unt 5 ~C~ p~rinon~ 6 lln-~ntion) 7 (ID~antio~
Comparatlve ~ub~tance 100 0 50
IRocy~n-t~ prepolymer
mlxtur- from e~periment 4
in E~ample 1 0 100 50
Viscoaity at 25-C mPas c 100 980 790
5eaker tlme~-:
Start tim- ~eec] 12 10 10
1 0 S-ttlng tlma- [~cl 67 70 48
Rl~lng tlme [nec) 75 105 68
Free-foamed denelty [g/ll 48.37 54.46 50.93
Molded foame-:
Mold t~mp~rat~re [-C] 51.2 50.8 50.9
C~hlon w~lght [g] 824 692 Bl9
Core denPlty [g/l] 50.3 59.7 49.9
Proportlon of open celle
[~] 3 2 3
Compre~slve hardnecR
[ kPal
20~ 1.8 1.0 1.7
40~ 3.0 2.3 2.7
60~ 6.0 5.7 5.1
Compre~ e ~-t [~] 7.7 44.0 13.3
Ela~ticlty [cm] 45.9 35.1 42.7
Elongatlon at break [~] 70 152 106
Ten~ etrength [kPa] 61 85 75
7ear propagatlon re~l~- 0.20 0.45 0.28
tance [N/mml
30 Notes on Table 2:
100 g of the components (A) (polyol) plus (B) (poly-
i60cyanate), in the ratios given, were introduced
into a beaker having a capacity of 1000 ml.
16 1 cu6hion mold, demolding time 5 min,
Proportion of open cells: subjective evaluation
after 5 min after demolding. Scale 1-5, 1: very
open, 5: very closed.
~16449~
- 26 -
Foam tests were carried out as follows:
Den~ity determination DIN 53420
Elasticity measurem-=nt: Rebound resilience measured by
an internal BASF method
Compressive set DIN 53572
Compressive hardness DIN 53577
Tear propagation resistance DIN 53515
Tensile strength DIN 53571.
The figures in Table 2 show that the isocyanate
prepolymer mixtures of the invention are suitable for
producing polyurethane foam articles which have improved
properties. In particular, the increased elongation at
break, the increased tensile strength and the increased
tear propagation resistance are notable and represent a
surprising result.
