Note: Descriptions are shown in the official language in which they were submitted.
21 64467
Lignin-cont~;n;ng isocyanate ~ e~olymer mixtures,
their preparation a~d their use for producing
polyure~h~ne~, and al~o production of the polyurethanes
The present invention relates to lignin-contain-
ing i60cyanate prepolymer mixtures. The invention also
relates to a process for preparing ~uch isocyanate
prepolymer mixtures. Finally, the invention also provides
for the use of the isocyanate prepolymer mixtures of the
invention for producing polyurethanes (PU), particularly
foamed shaped bodies based on polyurethane and also a
process for this purpose.
Polyoxyalkylene polyols prepared using lignin and
tannin as initiator molecule6 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 u~ing
alkylene oxides, for example 1,2-propylene oxide, at from
20 to 250C, at atmospheric or superatmospheric pressure.
The polyoxyalkylene polyol~ prepared have 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 polyisocyanates.
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
diphenylmethane diisocyanate (MDI) at 60C or at room
temperature. According to the publication, the films
obtained therefrom have a good mechanical strength and
foams have a good elasticity. No comparative examples
without lignin are given. The lignin forms the rigid
phase, the PEG the soft phase.
~ ignin can also be dissolved in polyoxyethylene
glycols (PEG) and from this solut on be reacted with
isocyanates to give polyurethane parts, as described in
US-A-3,519,581. For this purpose, the lignin is dissolved
2 1 6446~
- 2 -
in a polyoxyethylene glycol (PEG) or a mixture of PEG and
polyoxypropylene glycol (PPG) and treated, if appropriate
at above 100C, to esterify the carboxyl groups of the
lignin. The lignin/polyoxyalkylene glycol solutions
obtained are advantageously allowed to cool to below
100C, before being reacted with the polyisocyanates 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 purpose of the
reaction. Curing proceeds over a nll~her of hours at room
temperature or alternatively 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 reacted.
However, apart from insufficient reactivity of
solid or even dissolved lignin, e.g. lignin dissolved in
tetrahydrofuran or dioxane, towards isocyanates under the
conditions of polyurethane production, a series of other
disadvantages stand in the way of the direct use of
lignin in polyurethane systems. Their high solvent
content very strongly influences the sensitive catalysis
of the PU systems, particularly if the lignins are used
as solution and not as solid. Industrially, lignins are
predom;n~ntly used as "thickeners", and in relatively
high concentrations they also have a corresponding
viscosity-increasing action in water-containing poly-
etherol components. Incompatibility of the lignin with
other PU polyol components is frequently also to be
observed, which results in the lignin particles, which
themselves are very fine, coalescing after making up the
polyol mixture, 80 that it is no longer processable.
Some of the lignin OH groups are phenolic in nature, 80
that the polyurethane ~onds obtained therefrom are
thermolabile. For the above reasons, lignin polyurethanes
were not satisfactory in their processing and even
21 64467
-- 3
product properties. In general, incorporation of the
lignin impairs the mechanical properties even in poly-
urethane foams. To obtain PU parts having good properties
at all, use is often made of specially fractionated
lignins or lignins which have been obtained by a special
process (eg. organosolv lignins).
Usual disadvantages of lignin in PU production
are insufficient reactivity and insufficient incorpora-
tion of the lignin into the PU matrix. Lignin solutions
are usually highly viscous and not readily miscible with
organic polyisocyanate; in addition, the foams have poor
mechanical properties. Removing the high molecular weight
fractions of lignin and carrying out the reaction in
solution gives PU parts for which a series of advantages
have been reported. For example, a lower index is re-
quired, cf. CA-A-2,052,487. With kraft lignin itself, the
PU polyaddition reaction cannot be carried out in a PEG
solution. 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, eg. that having a low
molecular weight of from 300 to 2000 and better
solubility, gives more homogeneous foams having good
mechanical properties. A one-shot or a prepolymer
procedure can be used. In the latter case, a prepolymer
is prepared from lignin/polyols/isocyanates and this i~
then cast into films or can also be foamed by mixing with
water/catalysts/stabilizers.
To circumvent the above difficulties associated
with the direct processing of lignin, alkoxylation of the
lignin has also been proposed. However, this is
complicated. In general, owing to the above (processing)
difficulties, lignins or lignin derivatives are not
currently used on an industrial scale for producing
polyurethanes. US-A-3,546,199 and US-A-3,654,194 describe
how lignin in solid, pulverulent form or dissolved in
reactive cr unreactive solvents can be reacted to give
21 64467
-- 4
lignin polyetherols, both in the absence of catalysts and
with ROH/aniline catalysis. The OH numbers of the polyols
obtained are used to back-calculate the 0~ numbers of the
lignins. They are from about 600 to 1300. Tannin can also
be used like lignin. The OH numbers of the lignin poly-
ether polyols are from 50 to 1000.
It is an object of the present invention to
provide new readily procesRable isocyanate prepolymer
mixtures. A further object of the invention is to indi-
cate those isocyanate prepolymer mixtures which, in their
further processing into polyurethane products, particu-
larly into polyurethane foams, give products which
possess improved physical properties, particularly afi
regards elongation at break, tensile strength and/or tear
propogation resistance. A further object of the present
invention is the provision of processes for preparing
such isocyanate prepolymer mixtures and for producing
polyurethanes having the improved mechanical properties.
We have found that this object is achieved by
means of isocyanate prepolymer mixtures as defined in the
claims. The process of the invention for preparing such
polyisocyanate prepolymer mixtures and also their use ~or
producing polyurethanes and polyurethane products and a
process for this purpose are likewise defined in the
claimR. Preferred embodiments of the invention are given
in the following description and the subclaims.
According to the invention, a natural material,
ie. a regenerable polyhydroxyl compound, is
advantageously used.
According to the invention, the synthetically
prepared polyhydroxyl compounds are advantageously
replaced co~pletely or at least partially by lignin as a
hydroxyl-containing natural material. The use of this
regenerable hydroxyl-containing natural material requires
no complicated technical syntheses. A further advantage
is that lignin obtained in other areas as a waste product
can be industrially utilized, if appropriate after slight
2 1 64467
-- 5
technical treatment and/or purification. The u~e of novel
starting material6 enables, according to the invention,
the production of polyisocyanate polyaddition products
having different mechanical properties, which in turn
open up new possible applicationR.
The isocyanate prepolymer mixtures provided by
the invention, which contain urethane groups and reactive
isocyanate groups in bonded form, are formed 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
consi6ts at least partially of a ~olution of lignin in
polyoxyethylene glycol. 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) 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate,
an isomer mixture of 4,4'- and 2,4'- or 4,4'-, 2,4'
and 2,2'-diphenylmethane diisocyanates or a mixture
of diphenylmethane diisocyanates and polyphenyl-
polymethylene polyisocyanates with
b2) a solution comprising
b2i) at least one polyoxyethylene glycol hav-
ing a molecular weight of from 400 to
4000, and
b2ii) lignin.
The ratio of lignin to hydroxyl-containing
compound is here preferably such that from 1 to 50% by
weight of lignin and from 99 to 50% by weight of liquid
comprising polyoxyethylene glycol together form 100% by
weight of the solution. The lignin Rolution preferahly
consists of from 99 to 80% by weight, in particular from
99 to 90% by weight, of liquid comprising polyoxyethylene
glycol, in particular a polyoxyethylene glycol, while the
amount of lignin makes up from 1 to 20% by weight, in
21 64467
- 6
particular from 1 to 10% by weight, of the solution. In
particular, the weight ratio of lignin to liquid compris-
ing polyoxyethylene glycol is in the range from 1:5 to
1:20, preferably from 1:6 to 1:14.
The reaction of the lignin solution with the
isocyanate is preferably carried out in the absence of
surface-active agents.
The lignins used are preferably those which have
not been ~ubjected to any special chemical treatment for
their further processing. Rraft li~nins are particularly
preferred. Such lignins advantageously have an acid
number of less than 10.
The preferred solvents for the lignin are poly-
oxyethylene glycols having a molecular weight of from 550
to 1800.
The isocyanate prepolymer mixture i8 preferably
a liquid mixture having an -N=C=0 content of from 5 to
25% by weight, 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 esteri-
fied at least partially with the liquid containing
polyoxyethylene glycol and thus be chemically bound to
tl~e latter. This measure can reduce the acid number to
values of less than 1, preferably of less than 0.1. By
means of the esterification, the COOH groups of the
lignin are transformed and prevented from reacting with
the -N=C=0 group~ with carbon dioxide formation. The
chemical incorporation of the lignin into the isocyanate
prepolymer mixture occurs via the hydroxyl groups present
on the lignin, indeed out of the solution with reaction
with the isocyanate groups of the polyisocyanate com-
ponent.
The isocyanate prepolymers are advantageously
21 64467
-- 7
prepared by reacting organic polyisocyanates initially
_h charged in a heatable stirred vessel-with a defyciency of
polyhydroxyl compounds, preferably in the absence of
catalysts.
The viscosity of the -N=C=O prepolymer is
strongly dependent on the polyoxyethylene glycol and its
molecular weights in the range, for example, from 600 to
lSOO. In PEG having a molecular weight of 600, the
solubility of lignin, in particular unmodified kraft
lignin, is still 40~ by weight. Furthermore, in contrast
to other polyethylene glycols, PEG 600 is available in PU
quality. In the case of polyoxyethylene glycols of higher
molecular weight, the solubility decrea~es (PEG 1500:30%
by weight, PEG 4000:20~ by weight), and in addition the
solutions of lignin in PEG 1500 and PEG 4000 are solid at
room temperature, which necessitates more complicated
handling. Furthermore, the desired -N=C=O content of the
isocyanate prepolymer mixture and the desired lignin
content of the isocyanate prepolymer mixture influence
its viscosity. ~he -N=C=O contents obtained in the
prepolymers correspond to the theoretical values when the
OH groups of the lignin are included. Dark, but clear and
fluid prepolymers are usually obtained. The method of the
invention and the isocyanate prepolymer mixtures of the
invention have numerous advantages in comparison with the
prior art. Lignin dissolved in the polyoxyethylene glycol
can be readily handled and proces~ed.
Incorporation of the lignin into the isocyanate
prepolymer mixture ena~les any other relatively high
molecular weight compounds containing at least two
reactive hydrogen atoms to be used for polyurethane
production.
In the process of the invention for producing
compact or cellular polyurethanes, preferably PU foams,
a) relatively high molecular weight compounds con-
taining at least two reactive hydrogen atoms,
2 1 644 67
preferably polyhydroxyl compounds, are reacted
with
b) li~uid polyisocyanate compositions containing
urethane groups in bonded form.
This occurs 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 isocyan-
ate prepolymer mixture as defined above.
In the process of the invention for producing
polyurethanes, it is preferred that the relatively high
molecular weight compoundq have a functionality of from
2 to 8 and an amine or hydroxyl number of from 25 to 500
and are advantageously fielected from the group of poly-
oxyalkylene polyamines and/or polyhydroxyl compounds, in
particular polyhydroxyl compounds having a functionality
of from 2 to 8 and a hydroxyl numher of from 25 to 500,
which are in turn preferably selected from the group of
polythioether polyols, polyesteramides, hydroxyl-contain-
ing polyacetals, hydroxyl-containing aliphatic poly-
carbonates, 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 indicated, 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
hydroxyl nll~her of preferably from 30 to 80 for producing
flexible PU foams and polyhydroxyl compounds having a
2 1 64467
g
functionality of preferably from 3 to 8 and in particular
of from 3 to 6 and a hydroxyl number of preferably from
100 to 500 for producing 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) also include polymer-modified polyoxy-
alkylene polyols, polyoxyalkylene polyol disper~ions and
other hydroxyl-containing polymers and polycondensates
having the abovementioned functionalities and hydroxyl
number~, for example polyesteramides, polyacetals and/or
polycarbonates, in particular those which are prepared
from diphenyl carbonate and l,6-hexanediol by transester-
ification, or mixtures of at least two of the specified
relatively high molecular weight polyhydroxyl compounds
(a).
Suitable polye~ter polyols can, for example, be
prepared 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 alkanediols having from 2 to 12 carbon atoms,
preferably from 2 to 6 carbon atoms, dialkylene glycols
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 tere-
phthalic acid. The dicarboxylic acids can be used either
individually or in admixture. In place of the dicarboxyl-
ic acids, it is also possible to use the corresponding
carboxylic acid derivatives, for example dicarboxylic
esters of alcohols having from 1 to 4 carbon atoms or
dicarboxylic anhydrides. Preference i~ given to using
dicarboxylic acid mixtures of succinic, glutaric and
21 64467
- 10 -
adipic acid in weight ratios of, for example, 20 to 35 :
35 to 50 : 20 to 32, and in particular adipic acid.
Examples of dihydric and polyhydric alcohols, in particu-
lar alkanediols and dialkylene glycols, are: ethanediol,
diethylene glycol, 1,2- or 1,3-propanediol, dipropylene
glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,
l,10-decanediol, glycerol and trimethylolpropane. Prefer-
ence is given to using ethanediol, diethylene glycol,
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol
or mixtures of at least two of the Rpecified alkanepoly-
ols, in particular, for example, mixtures of 1,4-butane-
diol, 1,5-pentanediol and 1,6-hexanediol. It is also
possible to use polyester polyols from lactones, eg.
~-caprolactone, or hydroxycarboxylic acids, eg.
~-hydroxycaproic acid.
To prepare the polyester polyols, the organic,
for example aromatic and preferably aliphatic,
dicarboxylic acids and/or their derivatives and the
polyhydric alcohols and/or alkylene glycols can be
polycondensed in the absence of catalyst or prefera~ly in
the presence of esterification catalysts, advantageously
in an atmosphere of inert gases such as nitrogen, helium,
argon, etc., in the melt at from 150 to 250C, preferably
from 180 to 220C, at atmospheric pres6ure or under
reduced pre~sure to the desired acid number which is
advantageously less than 10, preferably less than 2.
A-cording to a preferred embodiment, the esterification
mixture is polycondensed at the abovementioned tempera-
tures to an acid number of from 80 to 30, preferably from
40 to 30, under atmospheric pressure and subsequently
under a pressure of less than 500 mbar, preferably from
50 to 150 mbar. Suitable e6terification catalysts are,
for example, iron, cadmium, cobalt, lead, zinc, antimony,
magnesium, titanium and tin cataly~ts in the form of
metals, metal oxides or metal salts. However, the poly-
condensation can also be carried out in the liquid phase
in the presence of diluents and/or entrainers, for
~ 1 64467
- 11
example benzene, toluene, xylene or chlorobenzene, for
azeotropically distilling off the water of condensation.
The polyester polyols are prepared by polyconden-
sing the organic dicarboxylic acids and/or their deriva-
tives with the polyhydric alcohols, advantageou61y in a
molar ratio of 1:1 to 1.8, preferably 1;1.05 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 particularly
preferably used are polyoxyalkylene polyols which are
prepared by known methods, for example by anionic poly-
merisation using alkali metal hydroxides, 6uch as sodium
or potas6ium hydroxide, or using alkali metal alkoxides,
such as sodium methoxide, sodium or potassium ethoxide or
potassium isopropoxide, as cataly6ts and with addition of
at least one initiator molecule containing from 2 to 8,
preferably 2 or 3, reactive hydrogen atoms in bonded form
for preparing polyoxyalkylene polyols for flexible PU
foams and preferably containing from 3 to 8 reactive
hydrogen atoms in bonded form for preparing polyoxyalkyl-
ene polyols for semi-rigid and rigid PU foams, or by
cationic polymerisation using Lewis acids, such as
antimony pentachloride, boron fluoride etherate, etc., or
bleaching earth as catalysts, from one or more alkylene
oxides having from 2 to 4 carbon atoms in the alkylene
radical.
Suitable alkylene oxides are, for example,
tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butyl-
ene oxide and preferably ethylene oxide and 1,2-propylene
oxide. The alkylene oxides can be used individually, in
succe6sion or as mixtures. Suitable initiator molecules
are, for example: water, organic dicarboxylic acids such
as succinic acid, adipic acid, phthalic acid and tere-
phthalic acid, aliphal~c and aromatic, unsubstituted or
N-monoalkylated, N,N- or N,N'-diaikylated diamines having
2 1 64467
- 12 -
from 1 to 4 carbon atoms in the alkyl radical, such as
unsubstituted, monoalkylated or dialkylated ethylene-
diamine, diethylenetriamine, triethylenetetramine,
1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-,
1,3-, 1,4-, l,S- and 1,6-hexamethylenediamine, phenylene-
diamine, 2,3-, 3,4-, 2,4- and 2,6-tolylenediamine and
4,4'-, 2,4'- and 2,2'-diaminodiphenylmethane.
Other suitable initiator molecules are: alkanol-
amines such as ethanolamine, N-methylethanolamine and
N-ethylethanolamine, dialkanolamines such as diethanol-
amine, N-methyldiethanolamine and N-ethyldiethanolamine
and trialkanolamines such as triethanolamine, and
~mmQ~ia. Preference is given to using polyhydric, in
particular dihydric to octahydric, alcohols and/or alkyl-
ene glycols such as ethanediol, 1,2- and 1,3-propanediol,
diethylene glycol, dipropylene glycol, 1,4-butanediol,
1,6-hexanediol, glycerol, trimethylolpropane, penta-
erythritol, sorbitol and sucrose and also mixtures of at
least two polyhydric alcohols.
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 preference being given to u6ing
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 functional-
ity of from 3 to 8 and a hydroxyl number of from 100 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 and prepared by in-situ
polymerisation of acrylonitrile, styrene or preferably
mixtures of styrene and acrylonitrile, for example in a
weight ratio of from 90:10 to 10:90, preferably from
21 64467
- 13 -
70:30 to 30:70, advantageously in the abovementioned
polyoxyalkylene polyols, by a method similar to that
given in the German patents 11 11 394, 12 22 669
(US 3 304 273, 3 383 351, 3 523 093), 11 52 536
(G~ 10 40452) and 11 52 537 (GB 987618), and also poly-
oxyalkylene polyol dispersions which comprise as dis-
persed phase, usually in an amount of from 1 to 50% by
weight, preferably from 2 to 25% by weight: for example
polyureas, polyhydrazides, polyurethanes containing
bonded tert-amino groups, and/or melamine, and which are
described, for example, in EP-B-011 752 (US-A-4,304,708),
US-A-4,374,209 and DE-A-32 31 497.
Like the polyester polyols, the polyoxyalkylene
polyols can be used individually or in the form of
mixtures. Furthermore, they can be mixed with the graft
polyoxyalkylene polyols or polyester polyols and also
with the hydroxyl-containing polyesteramides, polyacetals
and/or polycarbonates.
Suitable hydroxyl-containing polyacetals are, for
example, the compounds which can be prepared from glycols
such as diethylene glycol, triethylene glycol,
4,4'-dihydroxyethoxydiphenyldimethylmethane, hexanediol
and formaldehyde. Suitable polyacetals can also be
prepared by polymerizing cyclic acetals.
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 diaryl0 carbonates, for example diphenyl carbonate, or phosgene.
The polyesteramides include, for example, the
preA~;n~ntly linear condensates obtained from polybasic,
saturated and/or unsaturated carboxylic acids or their
anhydrides and polyhydric saturated and/or unsaturated
aminoalcohols or mixtures of polyhydric alcohols and
aminoalcohols and/or polyamines.
The relatively high molecular weight polyhydroxyl
21 64467
- 14 -
compounds (a) can, depending on the application of the
isocyanate prepolymer mixture~ (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, eg. the hardness. In the production of
rigid PU foams, the use of chain extenders and/or cross-
linkers can usually be omitted. Suitable chain extendersare difunctional compounds, suitable crosslinker6 are
trifunctional and higher-functional compounds, each
having molecular weights of less than 400, preferably
from 62 to about 300. Examples of chain extenders are
alkanediols, for example those having from 2 to 6 carbon
atom~ in the alkylene radical, such as methanediol,
1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and
1,6-hexanediol, and dialkylene glycols such as
diethylene, dipropylene and dibutylene glycol, and
examples of crosslinkers are alkanolamines, eg. ethanol-
amine, dialkanolamines, eg.diethanolamine, and tri-
alkanolamines, eg. triethanolamine and triisopropanol-
amine, and trihydric and/or higher-hydric alcohols such
as glycerol, trimethylolpropane and pentaerythritol.
Useful chain extenders or crosslinkers are also the low
molecular weight ethoxylation and/or propoxylation
products, eg. those having molecular weights up to about
400, of the abovementioned polyhydric alcohols, alkylene
glycols, alkanolamines and also of aliphatic and/or
aromatic diamine6.
Chain extenders which are preferably used are
alkanediols, in particular l,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
trlmethylolpropane, dialkanolamines, in particular
diethanolamine, and trialkanolamines, in particular
2 1 64467
- 15 -
triethanolamine.
The chain extenders and/or crosslinkers (c) which
are preferably used in producing 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).
Further polyisocyanates can be used in admixture
with the isocyanate prepolymer mixtures (b) of the
invention for producing the PU. Specific examples are:
alkylene diisocyanates having from 4 to 12 carbon atoms
in the alkylene radical, for example l,12-dodecane
diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate,
2-methylpentamethylenel,5-diisocyanate,2-ethyl-2-butyl-
pentamethylene 1,5-diisocyanate, tetramethylene
1,4-diisocyanate and preferably hexamethylene 1,6-diiso-
cyanate; cycloaliphatic diisocyanates such as cyclohexane
1,3- and 1,4-diisocyanate and also any mixtures of these
isomers, l-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-
cyclohexane (isophorone diisocyanate), 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
polyisocyanates, 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 diphenyl-
methane 4,4'- and 2,4'-diisocyanates, polyphenyl-poly-
methylene polyisocyanates, mixtures of diphenylmethane
4,4'-, 2,4'- and 2,2'-diisocyanates and polyphenyl-
polymethylene polyisocyanates (raw MDI) and mixtures of
raw MDI and tolylene diisocyanate. The organic diisocyan-
ates and polyisocyanates can be used individually or in
the form of their mixtures.
Organic polyisocyanates which have been found to
be very useful are mixtures of diphenylmethane diisocyan-
ates and polyphenyl-polymethylene polyisocyanates,
21 64467
- 16 -
preferably those having a diphenylmethane diisocyanate
content of at least 35% by weight, eg. from 45 to 95% by
weight and in particular from 48 to 60% by weight, 80
that such raw MDI compositions are particularly prefer-
ably used.
Suitable blowing agents (d) for producing the
cellular polyurethanes are water and/or liquids and gases
which are liquid at room temperature, which are inert
towards the liquid isocyanate prepolymer mixtures and
have boiling points below 50C, in particular from -50C
to 30C, at atmospheric pressure, and also mixtures of
gaseous and liquid blowing agents. Examples of such
preferred gases and liquids are alkanes such as propane,
n- and iso-butane, n- and iso-pentane, preferably indus-
trial 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 halogenated
hydrocarbons such as dichlorofluoromethane, trifluoro-
methane, 1,1-dichloro-1-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
m~xtures thereof. The blowing agents mentioned by way of
example can be used individually or as mixtures. Blowing
agent~ which are not used are chlorofluorocarbons, which
damage the ozone layer.
The liquids having boiling points below 50C can
alAo be mixed with (cyclo)alkanes, eg. hexane and cyclo-
hexane, and alkyl carboxylateR, eg. ethyl formate, ha~ing
boiling points above 50C, as long as the blowing agent
mixture ha~ a boiling point advantageously below 38C.
The amount of blowing agent or mixture required can
be experimentally determined in a simple manner as a
21 64467
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function of the type of blowing agent or blowing agent
mixture and also of the mixing ratios. The blowing agents
are usually used in an amount of ~rom 0.1 to 30 parts 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 PU production
are preferably compounds which strongly accelerate the
reaction of the hydroxyl-containing component (a) with
the isocyanate prepolymer mixtures (b) of the invention
or the mixtures of polyisocyanate 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, eg. tin(II) diacetate, tin(II) diocto-
ate, tin(II) diethylhexanoate and tin(II) dilaurate, and
the dialkyltin(IV) salts of organic carboxylic acids, eg.
dibutyltin diacetate, dibutyltin dilaurate, dibutyltin
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, bis(dimethylaminoethyl)
ether, bis(dimethylaminopropyl)urea, dimethylpiperazane,
1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane, alkan-
olamine compounds such as triethanolamine, triisopropan-
olamine, N-methyldiethanolamine and N-ethyldiethanolamine
and dimethylethanolamine, tris(N~N-dialkanol~miTlo~lkyl)-
s-hexahydrotriazine, in particular tris(N,N-dimethyl-
aminopropyl)-~-hexahydrotriazine, tetraalkylammonium
~.ydroxides such as tetramethyl~m~ium hydroxide, and
preferably 1,4-diazabicyclo[2.2.2]octane. Preference is
given to u~ing from 0.001 to 5% by weight, particularly
21 64467
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from 0.05 to 2% by weight, of catalyst or catalyst
combination, ba6ed on the weight of the component (a).
Auxiliaries (f) can, if desired, additionally be
incorporated into the reaction mixture for producing the
compact or cellular polyurethanes, preferably PU foams.
Examples which may be mentioned are surface-active
substances, foam stabilizers, cell regulators, flame
retardants, fillers, dyes, pigments, antistatic agents,
hydrolysis inhibitors, fungistatic and bacteriostatic
substances.
Suitable surface-active substances are, for
example, compounds which serve to aid the homogenisation
of the isocyanate prepolymer mixtures and may also be
suitable for regulating the cell structure of the PU
foams. Examples which may be mentioned are emulsifiers
such as the sodium salts of castor oil sulfates or of
fatty acids, and also salts of fatty acids with amines,
eg. diethylamine oleate, diethanolamine stearate,
diethanolamine ricinoleate, salts of sulfonic acids eg.
alkali metal or Am~o~ium salts of dodecylbenzenesulfonic
or dinaphthylmethanedisulfonic acid, and ricinoleic acid;
foam stabilizers such as siloxane-oxyalkylene copolymers
and other organopolysiloxanes, ethoxylated alkylphenyls,
ethoxylated fatty alcohols, paraffin oils, castor oil or
ricinoleic esters, Turkey red oil and peanut oil, and
cell regulators such as pyrogenic silica, paraffins,
fatty alcohols and dimethylpolysiloxanes.
Furthermore, oligomeric polyacrylates having polyoxy-
alkylene and fluoralkane radicals as side groups are
suitable for improving the emulsifying action, the cell
structure and/or ~tabilization of the foam. 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).
Suitable flame retardants are, for example,
diphenyl cresyl phosphate, tricresyl phosphate,
tris(2-chloroethyl) phosphate, tris(2-chloropropyl)
2 1 64467
- 19 -
phosphate, tris(1,3-dichloropropyl) phosphate, tris(2,3-
dibromopropyl) phosphate and tetrakis(2-chloroethyl)-
ethylene diphosphate.
Apart from the halogen-substituted phosphates
mentioned, it is also possible to use inorganic flame
retardants such as hydrated aluminum oxide, antimony
trioxide, arsenic oxide, ~ ~n;um polyphosphate, expanded
graphite and calcium sulfate, or cyanuric acid deriva-
tives such as melamine, or mixtures of at least two flame
retardants such as Am~onium polyphosphate and melamine
and/or expanded graphite, and also, if desired, starch
for ~k;ng the PU foams produced from the 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 specified flame retardants or mixtures per 100 part~
by weight of the components (a) to (c).
For the purposes of the present invention,
filleræ, 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, for 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 ~uch as chalk,
barite, and inorganic pigments such as cadmium sulfide,
zinc sulfide, and also glass particles. Suitable organic
fillers are, for example: 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
0.5 to 50% by weight, preferably from 1 to 10% by weight,
based on the weight of the components (a) to (c).
Further details about the abovementioned other
customary auxiliaries (f) can be found in the specialist
21 64467
- 20 -
literature, for example the monograph of J.H. Saunders
and K.C. Frisch "High Polymers" Volume XVI, Poly-
urethanes, Parts 1 and 2, Interscience Publishers 1962 or
1964, or the Kunststoff-Handbuch, Polyurethane, Volume
VII, Carl-Hanser-Verlag, Munich, Vienna, 1st and 2nd
Edition, 1966 and 1983.
Further preferred features and embodiment~ of the
invention are given in the following examples.
Example 1
Preparation of the lignin-containing prepolymers of the
invention
Preparation of the lignin solution:
The proportion of lignin indicated in the table
was dissolved in the corresponding polyoxyethylene glycol
(PEG) and the solution was dewatered for 8 hours at
160C. Partial esterification of the lignin with the PEG
occurred during this phase.
Preparation of the isocyanate prepolymer mixture:
To prepare the iRocyanate prepolymer mixture, the
isocyanate was initially charged at 80C and the lignin-
containing PEG component was allowed to run in slowly
while stirring. Subsequently, stirring was continued for
a further 2 hours at 80C to complete the formation of
the lignin-containing i~ocyanate semiprepolymers.
21 6446/
- 21 -
Table 1
-N=C=O prepolymers from lignin solutions in polyether
glycols
~xperi- Lignin ~ Polyol~ Lignin;Polyol Isocyan-
ment (Weight ratio) ate~
1 Lig AT PEG60058:760 MI
2 Lig AT PEG600110:680 MI
3 Lig AT Peg60040:360 MI
4 Lig AT Pegl500 40:360 MI
~xperi- Lignin solution: -N=C=O Viscosity Lig~in
ment Isocya~ate (Wt.%)mPas (Wt.%)
(Weight ratio)
1 82:118 12.913500 3
2 79:120 14.218400 5
3 300:300 9.25121000 5
4 300:300 11.88180 5
Notes:
Lig AT = Kraft lignin Indulin AT from We~tvaco,
Charle~ton, SC, USA
PEG 600 = Polyethylene glycol having an average
molecular weight of 600
PEG 1500 = Polyethylene glycol having an average
molecular weight of 1500
MI = Mixture of diphenylmethane 4,4'~ and 2,4'-diiso-
cyanate
Exam~le 2
Production of polyurethane parts
Open-celled flexible polyurethane foams were
produced using the liquid, lignin-containing prepolymers
21 64467
- 22 -
of the invention as described in Example 1. The process-
ing properties of the polyols and the properties of the
flexible PU foams were e~m;ned. For comparison, use was
made of a formulation into which no lignin-containing
prepolymers had been incorporated.
The base polyetherol used was a glycerol-
initiated polyoxypropylene-polyethylene block polyol
having a primary hydroxyl end group content of greater
than 80%, a hydroxyl number of 35 mg of ROH/g of-polyol
and a viscosity of 850 mPas (measured in accordance with
DIN 51562 at 25C, using an Ubbelohde viscometer).
The cell-opening polyol used was a glycerol-
initiated polyoxypropylene-polyoxyethylene polyol having
an ethylene oxide content of 70% by weight, based on the
alkylene oxide content, a hydroxl number of 42 mg of
KOH/g of polyol and a viscosity of 980 mPas at 25C
measured using an Ubbelohde viscometer.
As compari~on substance, use was made of a
polyisocyanate mixture cont~ining urethane groups and
having an -N=C=O content of 24.5% by weight obtained from
diphenylmethane diisocyanate (40.7% by weight),
polyphenyl-polymethylene polyisocyanates (30.3% by
weight), polyoxypropylene glycol having an average
molecular weight cf 2000 (10% by weight) and the
abovementioned cell-opening polyol (10% by weight).
To produce the flexible PU foams, the polyol and
isocyanate components were intensively mixed at an NCO
index = 80 (80 -N=C=O group~ per 100 OH groups) and the
reaction mixture was poured 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 dimensions 400x400xlOO mm (determination of
the mechanical propertieR of the foams) and allowed to
foam therein.
Formulation for producing flexible polyurethane foams in
parts by weight.
21 64467
- 23 -
Component (A): Mixture comprising:
Base polyetherol 54.55
Cell-opening polyol 5.0
Water 3.0
Stabilizer ~ 0.20
Diazabicyclo[2.2.2]octane 0.20
33~ by weight in dipropylene glycol
N,N-dimethylaminopropylamine 0.30
N,N,N',N~-tetramethyl-4,4'-diamino-
dicyclohexylmethane 0.45
Glycerol 1.20
Tri 6 ( chloropropyl) phosphate 5.00
' Foam stabilizer based on silicone, Tegostab ~ B8680
from Goldschmidt
Component (B): Isocyanate mixture as described in Table
In the experiments described in Table 2, the
polyisocyanate mixture containing urethane groups which
was used as comparison substance was replaced in the
proportions indicated by the lignin-containing prepoly-
mers of the invention. It can be seen that both the
elongation at break and also the tensile strength and the
tear propogation resistance of the flexible foams are
improved.
In experiment 5, only the comparison substance
was used as isocyanate component, while in experiments 6
and 7, 75 parts by weight of the comparison substance and
25 parts by weight of the respective lignin-containing
prepolymer as described in Example 1 were used in each
case. The actual amounts of the polyisocyanate component
in the three experiments were always selected in such a
way that the indicated -N=C=O/OH ratio of 80:100
resulted.
21 64467
- 24 -
Table 2
~xperiment 5 (Com- 6 (In- 7 (Inven-
parison) vention) tion)
Comparison 6ub~tance 100 75 75
Ligprep 4 25
Ligprep 3 25
Viscosity at 25C, mPas ~ 100 420 780
Beaker times:
Start time [6ec] 12 10 12
Setting time [~ec] 67 52 71
Rising time [eec] 75 62 90
Free-foamed den~ity
[g/l] 48.37 48.48 52.80
Molded foamsO:
Mold temperature [C] 51.2 50.8 51.1
Cushion weight [g] 824 757 792
Core density [g/l] 50.3 49.7 46.8
Open cell content [%] 3 2.5 2.5
Compressive hardne~s
[kPa]
20% 1.8 1.0 1.4
40% 3.0 1.9 2.4
60% 6.0 4.5 4.8
Compressive ~et [%] 7.7 25.8 19.5
Elasticity [cm] 45.9 38.1 40.7
Elongation at break [%]
76 78
Ten6ile strength [kPa]
61 70 75
Tear propogation
resistance [N/mm]
_ 0.20 0.23 0.27
.~otes on Table 2:
100 g of the components (A) (polyol) plu8 ~B) (poly-
isocyanate) corre~ponding to the ratio given were
introduced into a beaker having a capacity of
1000 ml.
O 16 l cu6hion mold, demolding time 5 min,
open cell content: ~ubjective evaluation after 5 min
after demolding. Scale 1 - ~ very open, 5: very
closed.
21 64467
- 25 -
Foam tests were carried out as follows:
Density determination DIN 53420
Elasticity mea~urement: Rebound resilience measured
by an internal BASF method
Compressive set DIN 53572
Compressive hardness DIN 53577
Tear propogation resi~tance DIN 53515
Tensile strength DIN 53571.
The figures in Table 2 6how that the isocyanate
prepolymer mixtures of the invention are suitable for
producing polyurethane foam articles having improved
properties. In particular, the increased elongation at
break, the increased tensile Rtrength and the increase
tear propogation resistance are notable and repre~ent a
surprising result.
