Note: Descriptions are shown in the official language in which they were submitted.
`` ` 21375~0
.~
, _
, .
Preparation of compact or cellular polyurethanes, polyisocyanate
compositions contA;ning urethane groups which can be used for
this purpose, and their use
The invention relates to a process for the preparation of compact
or preferably cellular polyurethanes, in particular rigid poly-
urethane (PU) foams, by reacting relatively high-molecular-weight
polyhydroxyl compounds (a) with a liquid polyisocyanate composi-
lO tion (b) contA; n; ~g bonded urethane groups in the presence orabsence of chain extenders and/or crosslinking agents (c), where
this polyisocyanate composition (b) is itself obtA;nAhle by
reacting a mixture of diphenylmethane Ai isocyanates (MDI) and
polyphenylpolymethylene polyisocyanates, known as crude MDI, and
15 linear, branched or cyclic, ~aturated or oiefinically unsatura-
ted, low-molecular-weight monoalcohols, expediently having 1 to
6 carbon atoms, to novel polyisocyanate compositions (b) of this
type, and to their use for the preparation of preferably highly
crosslinked polyurethanes, in particular rigid polyurethane
20 foams.
The preparation of compact or cellular polyurethanes, also
abbreviated to PU below, preferably soft and elastic, semirigid
or rigid polyurethane foams, by reacting relatively high-molecu-
25 lar-weight polyhydroxyl compounds, preferably polyester- or in
particular polyether-polyols, with organic and/or modified organ-
ic polyisocyanates in the presence or absence of chain extenders
and/or crosslinking agents is known and is described in numerous
patents and other publications.
By way of example, reference may be made to Runststoff-Handbuch,
Volume VII, Polyurethanes, Carl Hanser Verlag, Munich, Vienna,
1st Edition, 1966, edited by Dr. R. Vieweg and Dr. A. ~ochtlen,
and 2nd Edition, 1983, edited by Dr. G. Oertel.
Compact and cellular polyurethanes are usually prepared by the
two-component process, in which a component A cont~in;ng the rel-
atively high-molecular-weight polyhydroxyl compounds, if desired
chain extenders, crosslinking agents, blowing agents, catalysts,
40 auxiliaries and/or additives, and component B, which usually com-
prises organic and/or modified organic polyisocyanates, are mixed
vigorously and brought to reaction. Although the t-~ c~mponent
process i8 widely used in industry, it still has deficiencies.
For example, an evident problem is the poor compati hi lity of the
45 polyhydroxyl component (A) and the polyisocyanate cnmronent (B),
which occurs, in particular, in the reaction of highly functional
polyether-polyols based on at least trifunctional initiator
~1375~0
molecules, for example glycerol, trimethylolpropane, pentaery_
thritol, sorbitol and sucrose, with crude MDI having a function-
ality of greater than 2.5. This therefore requires longer stir-
ring times before compatibility of the starting components i8
5 achieved owing to commencement of urethane formation or special
mixing techniques, by means of which the sometimes coarse disper-
sions of one ~tarting component in the other can be converted
into fine emulsions. The polyurethane formation thus takes place
at the beginning of a reaction from 2 heterogeneous phases to a
10 certain conversion, presumably due to the oligomers which become
effective solubilizers, from which fine emulsions and/or true
solutions are formed. This phase change is evident, for example,
from the conversion of the yellow-brown, cloudy di~persions or
emulsions into a dark-brown, clear solution.
There i8 thus a close relationship between the quality of the
compact or cellular polyurethanes formed and the starting materi-
als used, their physical and chemical properties, the mixing
technigue used and the reaction mixture obtained, which can be in
20 the form, for example, of a coarse dispersion, fine emulsion or
clear solution, or anywhere in between.
There has therefore been no lack of attempts to improve the
mechanical properties of polyurethanes by a ~uitable choice of
25 starting materials or by modification thereof in order largely to
overcome the abovementioned disadvantages.
Reference may be made, for example, to processes for the lique-
faction of MDI isomer mixtures or processes for improving the
30 low-temperature shelf life of crude MDI, in particular crude MDI
having a relatively high content of MDI isomers, by partial reac-
tion of the polyisocyanates with polyhydric alcohols.
According to DE-C-16 18 3~0 (US-A-3,644,457), this is achieved by
35 reacting 1 mol of 4,4'- and/or 2,4'-MDI with from 0.1 to 0.3 mol
of tri-1,2-oxypropylene glycol and/or poly-1,2-oxypropylene gly-
col having a molecular weight of up to 700.
According to G3-A-1,369,334, the modification is carried out in
40 two reaction steps and the modifier used is dipropylene glycol or
polyoxypropylene glycol having a molecular weight of less
than 2000.
DE-A-29 13 126 (U~-A-4,229,347) describes MDI compositions in
45 which from 10 to 35~ by weight of the isocyanate groups are
reacted with a mixture of at least 3 alkylene glycols, one of
Z1375~
.
these glycols being di-, tri- or a relatively high-molecular-
weight polyoxypropylene glycol.
By contrast, the modifiers used in DE-A-24 04 166
5 (GB-A-1,430,455) are mixtures of a polyoxyethylene glycol or
polyoxyethylene glycol mixture having a mean molecular weight of
less than 650 and at least one alkylene glycol cont~;n;ng at
least 3 carbon atoms.
10 DE-A-23 46 996 (GB-A-1,377,679) relates to MDI compositions in
which from 10 to 35~ by weight of the isocyanate groups have been
reacted with a commercially available polyoxyethylene glycol.
EP-A-10 850 uses a crude MDI composition comprising a mixture of
15 crude MDI with an MDI which has been modified by means of poly-
oxyalkylene polyols having a functionality of from 2 to 3 based
on polyoxypropylene-polyol and, if desired, polyoxyethylene-
polyol having a molecular weight of from 750 to 3000.
20 According to DE-B-27 37 338 (UA-A 4,055,548), a liguid crude MDI
composition i8 obtained by combining crude MDI with a polyoxy-
ethylene glycol having a mean molecular weight of from 200
to 600.
25 In DE-B-26 24 526 (GB-A-1,550,325), a crude MDI which has been
prepared by a special process and contains from 88 to g5% by
weight of MDI is reacted with polyoxypropylene glycol having a
molecular weight in the range from 134 to 700.
30 DE-A-25 13 796 (GB-A-1,444,192) and DE-A-25 13 793
(GB-A-1,450,660) relate to crude MDI compositions in which the
crude MDI has been modified by means of alkylene glycols or poly-
oxyalkylene glycols in certain amounts.
35 Although said alkylene glycols or polyoxyalkylene glycols cause
liquefaction of the 4,4'- or 2,4'-MDI isomers, which melt at 42
and 28 C respectively, it i8 disadvantageous that the polyisocyan-
ate c~mpositions exhibit crystalline deposits after extended
storage at temperatures around 10 C.
It is furthermore known that flexible PU foams can be produced
using, as the polyisocyanate component, crude MDI compositions
which have been modified by means of urethane groups.
45 In EP-A-22 617, this i8 achieved by reacting a difunctional to
trifunctional polyoxypropylene-polyoxyethylene-polyol cont~i~;ng
at least 50S by weight of the polymerized oxyethylene groups with
- 2137540
.
a mixture of MDI isomer6 and sub~equently diluting the resultant
guasi-prepolymer with crude MDI. A particular di9advantage of the
PU foams described iB their low tensile ~trength and tear propa- -
gation ~trength.
Polyisocyanate mixtures based on crude MDI which have been modi-
fied by means of urethane groups and contain from 12 to 30% by
weight of NC0 groups are also described in EP-B-0 111 121
(US-A-4,478,960). The MDI or crude MDI is modified using a poly-
10 oxypropylene-polyoxyethylene-polyol having a functionality of
from 2 to 4, a hydroxyl number of from 10 to 65 and a content of
polymerized ethylene oxide units of from 5 to 30~ by weight.
Using these polyisocyanate mixtures which have been modified by
means of urethane groups, ~U foams having increased elongation at
15 break, improved tensile strength and tear propagation strength
can be produced.
However, the modification of the MDI isomer mixtures and rela-
tively highly functional crude MDI by means of low-molecular-
20 weight alkanediols and/or oxyalkylene glycol~ and/or relativelyhigh-molecular-weight, at least difunctional polyoxyalkylene-
polyols is severely restricted, since even partial reaction of
these 6tarting materials causes a very considerable increase in
the functionality and thus in the viscosity of the resultant
25 polyisocyanate c~mrositions which have been modified by means of
urethane groups. The high viscosities of crude NDI compositions
of this type mean that they can only be processed with difficulty
in conventional metering and foAm;ng equipment.
30 EP-A-0 320 134 states that the compatibility of the polyhydroxyl
component (A) and the polyisocyanate component (B) can be im-
proved by using polyisocyanate compositions having a functional-
ity of at least 2.3 which comprise, based on the total weight,
from 30 to 45~ by weight of MDI, from 28 to 67~ by weight of
35 polyphenylpolymethylene polyisocyanates contA;ning more than
2 isocyanate groups and from 3 to 27% by weight of a prepolymer
prepared from MDI and a compound contAi ni ng at least 2 radicals
which react with isocyanate groups and having a molecular weight
of less than 1000. Disadvantages of theQe MDI compositions are
40 their two-step preparation method and, as a consequence of the
increase in viscosity, the fact that compounds ContA; n; ng at
least 2 radicals which react with isocyanate groups can only be
used in limited amounts.
45 In order to overcome these disadvantages, DE-A-39 28 330
(US-A-5,028,636) reacts MDI or crude MDI having an MDI content of
at least 30~ by weight with substoichiometric amounts of at least
1375q~
one alkoxylation product obtained using monoalcohols having 8 to
24 carbon atoms, primary amines or organic carboxylic acids as
initiator molecules. EP-A-031 650 describes the modification of
MDI mixtures contA;ning at least 15% by weight of 2,4'-MDI by
5 means of a monohydric alcohol having 9 to 16 carbon atoms or a
polyoxyalkylene alcohol contA; n; ng 1 to 58 alkylene oxide groups
and an alkyl terminal group having 1 to 12 carbon atoms. Through
incorporation of the relatively high-molecular-weight alkyl radi-
cals or polyoxyalkylene groups into the crude MDI or MDI, the
10 adducts obtained are said to be effective in the form of an
"internaln emulsifier and to improve the miscibility of polyoxy-
alkylene-polyols and crude MDI compositions. However, these meas-
ures do not adequately solve the main problem of incompatibility
or immiscibility of highly functional, hydrophilic polyhydroxyl
15 compounds, in particular polyoxyalkylene-polyols, and hydrophobic
polyisocyanates, in particular crude MDI.
It is an object of the present invention to improve the mechani-
cal properties of compact snd cellular polyurethanes, preferably
20 rigid PU foams. To this end, it i8 an object to use measures
which can readily be carried out industrially to improve the mis-
cibility of the starting materials, preferably the miscibility of
the polyhydroxyl component (A) and the polyisocyanate compo-
nent (B).
We have found that, surprisingly, this object is achieved by
increasing the content of urethane groups in the polyisocyanate
composition, which allows the compatibility of polyisocyanate
compositions based on MDI with polyhydroxyl compounds, preferably
30 polyether-polyols, to be improved, ~o that, for example, directly
after c~mpo~ents (A) and (~) have been mixed, true solutions or
fine emulsions are formed.
The present invention accordingly provides a process for the
35 preparation of compact or preferably cellular polyurethanes, in
particular rigid polyurethane foams, by reacting
a) relatively high-molecular-weight polyhydroxyl compounds con-
tAin;ng at least two reactive hydrogen atoms with
b) liquid, diphenylmethane diisocyanate-based polyisocyanate
compositions contA;ning bonded urethane groups,
in the presence or absence of
c) chain extenders and/or crossl; nki ng agents,
` ~1375~
. . . --
d) blowing agents,
e) catalysts and
5 f) auxiliaries,
wherein the polyisocyanate compositions (b) used are obtainable
by reacting mixtures of diphenylmethane diisocyanates and poly-
phenylpolymethylene polyisocyanates with a substoichiometric
10 amount of at least one linear, branched or cyclic, saturated or
olefinically unsaturated, low-molecular-weight monoalcohol.
The present invention furthermore provides the liquid polyisocya-
nate compositions contA;ning urethane groups which can be used
15 according to the invention, which are obtainable by reacting mix-
tures of diphenylmethane diisocyanates and polyphenylpoly-
methylene polyisocyanates with a substoichiometric amount of at
least one linear, branched or cyclic, saturated or olefinically
unsaturated, low-molecular-weight monoalcohol having 1 to 6 car-
20 bon atoms as claimed in claim 6, and the use of these liquidpolyisocyanate compositions cont~ni~g urethane groups for the
production of, in particular, rigid polyurethane foams as claimed
in claim 10.
25 Partial reaction of crude MDI with the low-molecular-weight,
monohydric alcohols allows the urethane group content, which is
advantageously greater than or equal to 0.1 mol~kg of polyisocya-
nate composition, to be increased as desired in accordance with
requirements, for example its compatibility depending on the type
30 of polyhydroxyl component (A), without any excessive increase in
the viscosity of the polyisocyanate composition (b) and thus
without making its processibility more difficult or even impossi-
ble. When the monohydric alcohols suitable according to the
invention are used to form the urethane groups, crude MDI com-
35 positions having a content of urethane groups of, for example,0.4 mol/kg are of low viscosity and preferably give clear solu-
tions on mixing with the polyhydroxyl component (A), while crude
MDI compo6itions having the 6ame urethane group content, but pre-
pared using dihydric and/or trihydric alcohols are no longer pro-
40 cessible in conventional foA~ng eguipment due to their highviscosity.
~eaction of the crude MDI with the monohydric alcohols reduces
the functionality of the polyi~ocyanate composition ~b), but,
45 surprisingly, this measure has virtually no adverse effect on the
mechanical properties of the resultant compact or cellular poly-
urethanes, in particular rigid PU foams. The crucial factor for
`` Z1375~0
this may well be that fine emulsions are rapidly converted into
homogeneous solutions, or homogeneou5 solutions directly, which
readily give reproducible polyurethanes of constant quality are
already obtained at the beginning of the mixing operation from
5 the crude MDI compositions cont~;ning urethane groups and modi-
fied according to the invention and the polyhydroxyl compon-
ent (A), irrespective of the mixing guality of the mixing device.
In the case of rigid PU foams, it is not only the mechanical
properties in general terms, but in particular its compressive
10 strength that has been improved by means of the process according
to the invention.
It is furthermore sdvantageous that the Dy; ~ reaction tempera-
ture which occurs during the preparation of the rigid PU foam can
15 be significantly reduced, so that discoloration or tarring of the
core of the rigid PU foam is prevented.
The following details apply to the novel process for the prepara-
tion of the compact or preferably cellular polyurethanes, in par-
20 ticular rigid PU foams, and to the starting materials which can
be used for this purpose:
a) Suitable relatively high-molecular-weight polyhydroxyl com-
pounds (a) usually have a functionality of from 2 to 8 and a
molecular weight of from 400 to B000, the flexible polyure-
thanes expediently being prepared using polyhydroxyl com-
pounds having a functionality of, preferably, from 2 to 3 and
a molecular weight of, preferably, fro~ 2400 to 7200, in par-
ticular from 3200 to 6000, and rigid polyurethanes ex-
pediently being prepared using polyhydroxyl compounds having
a functionality of, preferably, from 3 to 8, in particular
from 3 to 6, and a molecular weight of, preferably, from 400
to 3600, in particular from 1200 to 3200. Preferred poly-
hydroxyl compounds are linear and/or branched polyester-
polyols, in particular polyoxyalkylene-polyols. However,
polymer-modified polyoxyalkylene-polyols, polyoxyalkylene-
polyol dispersions and other hydroxyl-cont~ n~ ng polymers and
polycondensates having the abovementioned functionalities and
molecular weights, for example polyester-amides, polyacetals
and/or polycarbonates, in particular those prepared from di-
phenyl carbonate and 1,6-hexanediol by transe6terification,
or mixtures of at least two of said relatively high-molecu-
lar-weight polyhydroxyl compounds, are also suitable.
Suitable polyester-polyols may be prepared, for example, from
organic dicarboxylic acids having from 2 to 12 carbon atoms,
preferably aliphatic dicarboxylic acids having from 4 to
-` .. ' 2137~g~
6 carbon atoms and polyhydric ~lcohols, preferably alkane-
diols, having from 2 to 12 carbon atoms, preferably from 2 to
6 carbon atoms and/or dialkylene glycols. Example6 of suit- -
able dicarboxylic acids are succinic acid, glutaric acid,
adipic acid, 8uberic acid, azelaic acid, sebacic acid,
decanedicarboxylic acid, maleic acid, fumaric acid, phthalic
acid, isophthalic acid and terephthalic acid. The dicarboxy-
lic acids may be used either individually or mixed with one
another. The free dicarboxylic acids may also be replaced by
the corresponding dicarboxylic acid derivatives, for example
dicarboxylic esters of alcohols having 1 to 4 carbon atoms or
dicarboxylic anhydrides. Preference is given to dicarboxylic
acid mixtures comprising succinic acid, glutaric acid and
adipic acid in ratios of, for eXAmrle~ from 20 to 35: 35
to 50: 20 to 32 parts by weight, and in particular adipic
acid. Examples of dihydric and polyhydric alcohols, in par-
ticular alkanediols and dialkylene glycols, are ethanediol,
diethylene glycol, 1,2- and 1,3-propanediol, dipropylene gly-
col, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,
l,10-decanediol, glycerol and trimethylolpropane. Preference
is given to ethanediol, diethylene glycol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol and mixtures of at least two
of said alkanediols, in particular mixtures of 1,4-butane-
diol, 1,5-pentanediol and 1,6-hexanediol. ~urthermore, poly-
ester-polyols made from lactones, eg. -caprolactone or
hydroxycarboxylic acids, eg. ~-hydroxycaproic acid, may also
be employed.
The polyester-polyols may be prepared by polycondensing the
organic, eg. aromatic and preferably aliphatic polycarboxylic
acids and~or derivatives thereof and polyhydric alcohols and/
or alkylene glycols without using a catalyst or preferably in
the presence of an esterification catalyst, expediently in an
inert gas atmosphere, eg. nitrogen, helium, argon, inter
alia, in the melt at from 150 to 250-C, preferably from 180
to 220 C, at atmospheric pressure or under reduced pressure
until the desired acid number, which is advantageously less
than 10, preferably less than 2, is reached. In a preferred
~m~o~iment, the esterification mixture is polycondensed at
the abovementioned temperature under atmospheric pressure and
subsequently under a pressure of less than 500 mbar, prefer-
ably from 50 to 150 mbar, until an acid number of from
80 to 30, preferably from 40 to 30, has been reached.
Examples of suitable esterification catalysts are iron,
cadmium, cobalt, lead, zinc, antimony, magnesium, titanium
and tin catalysts in the form of metals, metal oxides or
metal salts. However, the polycondensation may also be
` - ~137S4~
carried out in the liquid phase in the presence of diluents
and/or entrainers, eg. benzene, toluene, ~ylene or chloroben-
zene, for removal of the water of condensation by azeotropic
distillation.
The polyester-polyols are advantageously prepared by polycon-
densing the organic polycarboxylic acids and/or derivatives
thereof with polyhydric alcohols in a molar ratio of from 1:1
to 1.8, preferably from 1:1.05 to 1.2.
The polyester-polyols obtained preferably have a functional-
ity of from 2 to 4, in particular from 2 to 3, and a molecu-
lar weight of from 800 to 3600, preferably from 1200 to 3200,
in particular from 1800 to 2500.
However, the preferred polyhydroxyl compounds are polyoxy-
alkylene-polyols prepared by conventional processes, for
example by anionic polymerization using AlkAli metal
hydroxides such as sodium hydroxide or potassium hydroxide,
or ~lkali metal AlkQxides, such as sodium methoxide, sodium
ethoxide, potassium ethoxide or potassium isopropoxide as
catalysts and with addition of at least one initiator
molecule contAining from 2 to 8, preferably 2 or 3, reactive
hydrogen atoms in bound form for the preparation of polyoxy-
alkylene-polyols for flexible polyurethanes and preferably
from 3 to 8 reactive hydrogen atoms in bound form for the
preparation of polyoxyalkylene-polyols for semirigid and
rigid polyurethanes, or by cationic polymerization using
Lewis acids, such as antimony pentachloride, boron fluoride
etherate, inter alia, or bleaching earth as catalysts, from
one or more alkylene oxides having from 2 to 4 carbon atoms
in the alkylene moiety.
Examples of suitable alkylene oxides are tetrahydrofuran,
1,3-propylene oxide, 1,2- and 2,3-butylene oxide and
preferably ethylene oxide and 1,2-propylene oxide. The
alkylene oxides may be used individually, alternatively one
after the other or as mixtures. Examples of ~uitable initia-
tor molecules are water, organic dicarboxylic acids, ~uch as
~uccinic acid, adipic acid, phthalic acid and terephthalic
acid, aliphatic and aromatic, unsubstituted or N-mono-, N,N-
and N,N'-dialkyl-substituted diamines having from 1 to
4 carbon atoms in the alkyl moiety, such as unsubstituted or
mono- or dialkyl-substituted ethylenediamine, diethylene-
triamine, triethylenetetramine, 1,3-propylenediamine, 1,3-
and 1,4-butylenediamine, 1,2-, 1,~-, 1,4-, 1,~- and
1,6-hexamethylenediamine, phenylenediamines, 2,3-, 2,4- and
~13~5~
- 10
2,6-tolylenediamine and 4,4'-, 2,4'- and 2,2 ~ - diAm; no~; -
phenylmethane.
Other suitable initiator molecules are alkanola~nes, eg.
ethanolamine, N-methyl- and N-ethyl-ethanolamine, ~ kAnol-
amines, eg. diethanol~jne, N-methyl- and N-ethyl-diethanol-
amine, and trialkanol~m;nes, eg. triethanolPm~ne, and
ammonia. Preference is given to polyhydric alcohols, in par-
ticular dihydric to octahydric alcohols and/or alkylene gly-
0 c015, eg. ethanediol, 1,2- and 1,3-propanediol, diethylene
glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol,
glycerol, trimethylolpropane, pentaerythritol, sorbitol and
sucrose or mixtures of at least two polyhydric alcohols.
The polyoxyalkylene-polyols, preferably polyoxypropylene- and
polyoxypropylene-polyoxyethylene-polyols, have a functional-
ity of from 2 to 8 and molecular weights of from 400 to 8000,
where, as stated above, polyoxyalkylene-polyols having a
functionality of from 2 to 3 and a molecular weight of from
2400 to 7200 are preferred for flexible polyurethanes and
polyoxyalkylene-polyols having a functionality of from 3 to 8
and a molecular weight of from 400 to 3600 are preferred for
rigid polyurethanes, and suitable polyoxytetramethylene gly-
cols have a molecular weight of from 400 to approxi-
mately 3500.
Other suitable polyoxyalkylene-polyols are polymer-modified
polyoxyalkylene-polyols, preferably graft polyoxyalkylene-
polyols, in particular those based on styrene and/or acrylo-
nitrile and prepared by in situ polymerization of acrylo-
nitrile, styrene or preferably mixtures of styrene and
acrylonitrile, for example in a weight ratio of from 90:10 to
10:90, preferably from 70:30 to 30:70, expediently in the
abovementioned polyoxyalkylene-polyols by a method similar to
that of German Patents 11 11 394, 12 22 669 (US 3,304,273,
3,383,351 and 3,523,093), 11 52 536 (GB 1,040,452) and
11 52 537 (GB 987,618), and polyoxyalkylene-polyol disper-
6ions which contain, as the disperse phase, usually in an
amount of from 1 to 50~ by weight, preferably from 2 to 25
by weight, for example polyureas, polyhydrazides, poly-
urethanes containing tert-amino groups in bound form, and/or
melamine and are described, for example, in EP-B-011 752
(US 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 may be mixed with the graft polyoxyalkylene-polyols or
- ~13754~
polyester-polyol6 and the hydroxyl-contAin~ng polyester-
amides, polyacetals and/or polycarbonates. ~YAmrles of mix-
tures which have proven highly suitable for flexible polyure_
thanes are those having a functionality of from 2 to 3 and a
molecular weight of from 2400 to 8000 which contain at least
one polyoxyalkylene-polyol and at least one polymer-modified
polyoxyalkylene-polyol from the group consi~ting of graft
polyoxyalkylene-polyols or polyoxyalkylene-polyol dispersions
contA;n~ng, as disperse phase, polyureas, polyhydrazides or
polyurethanes contA;n;ng bonded tertiary amino groups.
Examples of suitable hydroxyl-cont~Ain;ng polyacetals are the
compounds which can be prepared from glycols, ~uch as
diethylene glycol, triethylene glycol, 4,4'-dihydroxyethoxy-
diphenyldimethylmethane, hexanediol and formaldehyde. Suit-
able polyacetals can also be prepared by polymerizing cyclic
acetals.
Suitable hydroxyl-contA;ning polycarbonates are those of a
conventional type, 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, eg. diphenyl
carbonate, or phosgene.
The polyester-A~;des include, for example, the pre~om~nantly
linear condensates obtained from polybasic, saturated and/or
unsaturated carboxylic acids or anhydrides thereof and poly-
hydric, saturated and/or unsaturated amino alcohols, or mix-
tures of polyhydric alcohols and A~i no alcohols and/or poly-
amines.
b) The organic polyisocyanates used according to the invention
are liguid, diphenylmethane diisocyanate-based polyisocyanate
compositions (b) contAin;ng urethane groups which are obtain-
able by reacting mixtures of diphenylmethane diisocyanates
(MDI) and polyphenylpolymethylene polyisocyanates, usually
k~own as crude MDI, with a substoichiometric amount of at
least one linear, branched or cyclic, saturated or olefinic-
ally unsaturated, low-molecular-weight monoalcohol.
Suitable crude MDI grades advantageously have, in addition to
higher homologs, a content of MDI isomers of from 30 to 95S
by weight, preferably from 35 to 80~ by weight, 3ased on the
total weight, and NCO contents of from approximately 30 to
213~5~
. _
12
32% by weight. Highly suitable are crude MDIs which contain
or preferably comprise, based on the total weight:
bIl)from 29 to 65% by weight, preferably from 33 to 60% by
weight, of 4,4'-MDI,
bI2)from 1 to 30% by weight, preferably from 2 to 20% by
weight, of 2,4'-MDI,
bI3)from 0 to 4% by weight, preferably from 0.5 to 2.5% by
weight, of 2,2'-MDI and
bI4)from 70 to 5% by weight, preferably from 65 to 20% by
weight, of at least trifunctional polyphenylpolymethylene
polyisocyanates.
For the purposes of the present invention, liguid polyiso-
cyanate compositions cont~ining urethane groups which can be
used according to the invention are also taken to mean poly-
isocyanate compositions obtained by reacting mixtures of MDI
isomers with the low-molecular-weight monoalcohol~ and subse-
quently blending the resultant MDI mixtures contAining ure-
thane groups with the abovementioned crude MDI and/or the
crude MDI compositions contAining urethane groups prepared
according to the invention or by blending the crude MDI com-
positions ocntAining urethane groups prepared according to
the invention with MDI mixtures and/or MDI mixtures contain-
ing urethane groups.
Suitable mixtures of MDI isomers expediently contain or pre-
ferably comprise, based on the total weight
bIIl) from 90 to 48% by weight, preferably from B0 to 60% by
weight, of 4,4'-MDI,
bII2) from 10 to 48~ by weight, preferably from 20 to 40% by
weight, of 2,4'-MDI and
bII3) from 0 to 4% by weight, preferably from 0 to 2.5% by
weight, of 2,2'-MDI.
Preferred low-molecular-weight monoalcohols for the prepara-
tion of the liguid diphenylmethane diisocyanate-based poly-
isocyanate compositions (b) contAining bonded urethane groups
are those having 1 to 6 carbon atoms, in particular 1 to
3 carbon atoms, from the group consisting of linear or
branched, ~aturated, monohydric alcohols. It is also possible
, ~ 21375~0
13
to use linear or branched, olefinically unsaturated, monohyd-
ric alcohols having 3 to 6 carbon atoms and saturated or ole-
finically unsaturated, cyclic, monohydric alcohols having 4
to 6 carbon atoms, preferably 5 or 6 carbon atoms. Specific
mention may be made, by way of example, of the following:
linear and branched, ~aturated monoalcohols, eg. methanol,
ethanol, n-propanol, isopropanol, n-butanol, n-pentanol and
n-hexanol and the corresponding ctructurally isomeric mono-
hydric alcohols, linear and branched, olefinically unsaturat-
ed monoalcohols, eg. allyl alcohol, 2-methyl-2-propen-1-ol,
2- and 3-buten-1-ol, and cyclic, saturated or olefinically
unsaturated monoalcohols, eg. cyclobutanol, cyclopentanol,
cyclopentenol, cyclohexanol and cyclohexenol. Monoalcohols
which have proven highly successful snd are therefore pre-
ferred are methanol, ethanol, n-propanol, isopropanol and
allyl alcohol. The low-molecular-weight monoalcohols can be
employed in technical-grade or preferably pure form, individ-
ually or as mixtures of at least two monoalcohols.
As mentioned above, the compatibility of the polyhydroxyl
component (A) and the polyisocyanate component (B) depends on
the type of the polyhydroxyl component (A) and the content of
urethane groups in the polyisocyanate crmronent (B), which is
expediently at least 0.1 mol, preferably from 0.1 to 2 mol,
in particular from 0.4 to 1 mol, of urethane groups per kg of
polyisocyanate composition. If the polyisocyanate composition
has a urethane group content of from 0.1 to 0.3 mol/kg, a
fine emulsion which is very rapidly converted into a clear,
homogeneous mixture is in some cases initially formed on mix-
ing the polyhydroxyl component (A) and the polyisocyanatecomponent (~), depending on the type of the polyhydroxyl com-
ponent (A), while polyisocyanate compositions have a ure-
thane group content of approximately 0.4 mol/kg or greater
usually form clear solutions directly on mixing. The polyiso-
cyanate compositions cont~in~ng urethane groups which havebeen modified according to the invention by means of monohyd-
ric alcohols usually have, in the range from 0.4 to 1 mol of
urethane groups/kg, a viscosity, measured at 23-C by means of
a Haake viscometer, of from 1000 to 3000 mPa-s and are there-
fore readily processible, while analogous polyisocyanatec~mrositions having the ~ame urethane group content/kg, but
modified, for example, by mean~ of dipropylene glycol, are
already solid.
-
The polyisocyanate compositions according td the inventionhaving a urethane group content of from 0.1 to 2 mol/kg usu-
ally have a content of NC0 groups of from 18 to 30% by
. -, , 213~5qO
14
weight, preferably from 24 to 28% by weight, based on the
total weight.
The novel crude MDI romrositions cont~in~ng urethane groups
can be used for the preparation of any, preferably highly
crosslinked polyisocyanate polyaddition products. They have
proven particularly successful and are therefore preferred
for the preparation of polyisocyanate polyaddition products
for wbose preparation relatively highly functional polyiso-
cyanates, for example those having a functionality of at
least 2.5, must be mixed with polyhydroxyl components (A)
contA; ni ng polyoxyalkylene-polyols having a functionality of
at least 3 and a hydroxyl number of at least 250, preferably
at least 350. Polyisocyanate polyaddition products of this
type are in particular crosslinked PV elastomers and rigid PU
(molded) foams.
c) The compact or cellular polyurethanes can be prepared by the
novel process in the presence or absence of chain extenders
and crosslinking agents (c). In the preparation of flexible,
compact or cellular polyurethanes, the addition of chain
extenders, crossljnking agents or, if desired, mixtures
thereof may prove advantageous for modification of the me-
chanical properties, for example the hardness. In the produc-
tion of rigid PU foams, the use of chain extenders and/or
crosslinking agents (c) is usually unnecessary. Chain extend-
ers which can be used are difunctional compounds, and cross-
linking agents which can be used are trifunctional and higher
functional compounds, in each case having a molecular weight
of less than 400, preferably from 62 to approximately 300.
Specific examples of chain extenders which may be mentioned
are alkanediols, for example those having 2 to 6 carbon atoms
in the alkylene radical, eg. ethanediol, 1,3-propanediol,
1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol, and dial-
kylene glycols, eg. diethylene glycol, dipropylene glycol and
dibutylene glycol, and specific exampleg of crosslinki~g
agents which can be used are alkanolamines, eg. ethanolamine,
dialkanolamines, eg. diethanolamine, and trialkanolamines,
eg. triethanolamine and triisopropanolam;ne, trihydric and
polyhydric alcohols, eg. glycerol, trimethylolpropane and
pentaerythritol, and aliphatic and/or aromatic diamines, eg.
1,2-ethanediamine, 1,4-butanedi~ine~ 1,6-hexanediamine,
2,3-, 2,4- and/or 2,6-tolylenediamine, 4,4'-diaminodiphenyl-
methane, 3,5-diethyl-2,4- and/or 2,6-tolylenediamine,
3,3'-di- and/or 3,3',5,5'-tetraalkyl-3,3-diaminodiphenyl-
methanes, eg. tetraisopropyl-4,4'-diaminodiphenylmethane.
Other suitable chain extenders or crosslin~;ng agents are
213754~
low-molecular-weight ethoxylation and/or propoxylation prod-
ucts, eg. those having molecular weights of up to approxi-
mately 400, of the abovementioned polyhydric alcohols,
alkylene glycols, alkanolamines and diamines.
S
Preferred chain extenders are alkanediols, in particular
1,4-butanediol and/or 1,6-hexanediol, alkylene glycols, in
particular ethylene glycol and propylene glycol, and pre-
ferred crosslink;ng agents are trihydric alcohols, in partic-
ular glycerol and trimethylolpropane, dialkanolamines, in
particular diethanolamine, and trialkanolamines, in particu-
lar triethanolamine.
The chain extenders and/or crossl1nking agents preferably
used for the preparation of flexible, compact or cellular
polyurethanes can be employed, for example, in amounts of
from 2 to 60~ by weight, preferably from 10 to 40~ by weight,
based on the total weight of formative components (a)
and (c).
d) The blowing agent (d) for the preparation of the cellular
polyurethanes, preferably rigid PU foams, i8, in particular,
water, which reacts with isocyanate groups to form carbon
dioxide. The amounts of water expediently employed are from
0.1 to 8 parts by weight, preferably from 1 to 5 parts by
weight, in particular from 1.5 to 3 parts by weight, based on
100 parts by weight of the polyhydroxyl compounds (a).
Other suitable blowing agents are liquids which are inert
toward the liquid polyisocyanate compositions (b) modified by
means of urethane groups and which have boiling points of
below 100 C, preferably below 50 C, in particular from -50-C
to 30 C, at atmospheric pressure, 80 that they evaporate
under the conditions of the exothermic polyaddition reaction,
and mixtures of these physical blowing agents and water.
Examples of preferred liquids of this type are alkanes, eg.
heptane, hexane, n- and isopentane, preferably technically-
grade mixtures of n- and isopentanes, n- and isobutane and
propane, cycloalkanes, ~uch as cyclopentane and/or cyclo-
hexane, ethers, eg. furan, dimethyl ether and diethyl ether,
ketones, eg. acetone and methyl ethyl ketone, alkyl
carboxylates, such as methyl formate, dimethyl oxalate and
ethyl acetate, and halogenated hydrocarbons, such as methy-
lene chloride, dichloromonofluoromethane, difluoromethane,
trifluoromethane, difluoroethane, tetrafluoroethane, chloro-
difluoroethanes, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-di-
chloro-2-fluoroethane and heptafluoropropane. It is also
213~540
~ . .
16
possible to use mixtures of these low-boiling liquids with
one another and/or with other substituted or unsubstituted
hydrocarbons. Also suitable are organic carboxylic acids, eg.
formic acid, acetic acid, oxalic acid, ricinoleic acid and
carboxyl-cont~in~ng compounds.
Other blowing agents (d) which can be used are compounds
which are pulverulent at room t~p~rature and which decompose
at elevated temperature through eli mi n~tion of gases, eg.
steam, carbon dioxide, carbon monoxide, oxygen or nitrogen.
Specific examples which may be mentioned are silica gels,
bicarbonates, ammonium formate, oxalic acid derivative~, urea
and urea derivatives, peroxides and preferably azo compounds,
eg. azoisobutyronitrile and azodicarbon~mide, hydrazines, eg.
4,4~-oxybis(benzenesulfohydrazide) and diphenyl ~ulfone
3,3'-disulfohydrazide, semicarbazides, eg. p-tolylenesulfo-
nylsemicarbazide, and triazoles, eg. 5-morpholyl-1,2,3,4-
thiatriazole.
Preferred blowing agents are chlorodifluoromethane, chlorodi-
fluoroethanes, dichlorofluoroethanes, pentane mixtures,
cyclopentane, cyclohexane and in particular water, and mix-
tures of at least two of these blowing agents, eg. mixtures
of water and cyclopentane, mixture~ of chlorodifluoromethane
and 1-chloro-2,2-difluoroethane and, if desired, water.
Chlorofluorocarbons, which damage the ozone layer, are not
used as blowing agents.
The requisite amount of physical blowing agents can readily
be determined experimentally depending on the foam density
required and any water employed and is from about O to
25 parts by weight, preferably from O to 15 parts by weight,
per 100 parts by weight of the polyhydroxyl compounds (a). It
may be expedient to mix the polyisocyanate composition (b)
contAini~g bonded urethane groups with the inert physical
blowing agent and thus to reduce its viscosity.
e) If the compact or cellular polyurethanes are prepared in the
presence of catalysts, preferred compounds for this purpose
are those which greatly accelerate the reaction of the
hydroxyl-contAining compounds of formative component (a) and,
if used, (c) with the liquid, MDI-based polyisocyanate com-
positions (b) containing bonded urethane group~. Suitable
compounds are organometallic compounds, preferably organotin
compounds, such as tin(II) ~alt~ of organic carboxylic acids,
eg. tin(II) acetate, tin(II) octanoate, tin(II) ethylhexan-
oate and tin(II) laurate, and the dislkyltin(IV) ~alts of
` - 21~S9U
. .
17
organic carboxylic acids, eg. dibutyltin diacetate, dibutyl_
tin dilaurate, dibutyltin maleate and dioctyltin diacetate,
and highly ba8ic amines, for example ~m;dines, eg. 2,3-dime-
thyl-3,4,5,6-tetrahydropyr~ mi dine, tertiary amines, eg. tri-
ethylamine, tributylamine, dimethylbenzylamine, N-methyl-,
N-ethyl- and N-cyclohexylmorpholine, N,N,N',N'-tetramethyl-
ethylenediamine, N,N,N',N'-tetramethylbutanediamine,
N,N,N',N'-tetramethyl-1,6-hexanedi~mine~ di(4-dimethylamino-
cyclohexyl)methane, pentamethyldiethylenetriamine, tetra-
methyldiaminoethyl ether, bis(dimethylaminopropyl)urea,dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicy-
clo[3.3.0]octane and preferably 1,4-diazabicyclo[2.2.2]oct-
ane, and alkanolamine compounds, such as triethanolamine,
trii~opropanol~mine, N-methyl- and N-ethyldiethanolamine and
dimethylethanolamine.
Other suitable catalysts are: tris(dialkylam;noalkyl)-s-hexa-
hydrotriazines, in particular tris(N,N-dimethylaminoprop-
yl)-s-hexahydrotriazine, tetraalkylammonium hydroxides, such
as tetramethylammonium hydroxide, Al kal ~ metal hydroxides,
such as sodium hydroxide, and Alk~li metal alkoxides, such as
sodium methoxide, sodium ethoxide, potassium ethoxide and
potassium isopropoxide, and al kAl i metal salts of long-chain
fatty acids having 10 to 20 carbon atoms and possibly pendant
OH groups, and combinations of the organometallic compounds
and highly basic amines. It i8 preferred to use from 0.001 to
5S by weight, in particular from 0.05 to 2% by weight, of
catalyst or catalyst combination, based on the weight of the
polyhydroxyl compound (a).
f) Auxiliaries (f) can, if desired, also be incorporated into
the reaction mixture for the preparation of the compact and
cellular polyurethanes. Examples which may be mentioned are
surfactants, foam stabilizers, cell regulators, fillers,
dyes, pigments, flameproofing agents, antihydrolysis agents
and fungistatic and bacteriostatic substances.
Examples of suitable surfactants are compounds which serve to
support homogenization of the starting materials and may also
regulate the cell structure. Specific examples are emulsi-
fiers, such as the sodium salts of castor oil sulfates, or of
fatty acids, and the salts of fatty acids with ~mi nes, for
example diethylamine oleate, diethanolamine stearate and
diethanolamine ricinoleate, 6alts of sulfonic acids, eg.
alkali metal salts or ammonium salts of dodecylbenzene- or
dinaphthylmethanedisulfonic acid and ricinoleic acid; foam
stabilizers, such as siloxane-oxyalkylene copolymers and
- 213754~
18
other organopolysiloxanes, oxyethylated alkylphenols, oxy-
ethylated fatty alcohols, paraffin oils, castor oil esters,
ricinoleic acid esters, Turkey red oil and groundnut oil, and
cell regulators, such as paraffins, fatty alcohols and di-
methylpolysiloxanes. Suitable compounds for improving theemulsification action, the cell structure and/or stabilizing
the foam are furthermore oligomeric polyacrylates ContAi ni ng
polyoxyalkylene and fluoro~lkAne radicals a~ side groups. The
surfactants are usually used in amounts of from 0.01 to
5 parts by weight, based on 100 parts by weight of the poly-
hydroxyl compounds (a).
For the purposes of the present invention, fillers, in par-
ticular reinforcing fillers, are conventional organic and
inorganic fillers and reinforcing agents. Specific examples
are inorganic fillers, such as silicate minerals, for example
phyllosilicates, such as antigorite, serpentine, hornblendes,
amphiboles, chrysotile, talc; metal oxides, such as kaolin,
aluminum oxides, aluminum silicate, titanium oxides and iron
oxides, metal salts, such as chalk, barytes and inorganic
pigments, ~uch as cadmium ~ulfide, zinc 6ulfide and glass
particles. Examples of suitable organic fillers are carbon
black, melamine, colophony, cyclopentadienyl resins and graft
polymers.
The inorganic and organic fillers may be used individually or
as mixtures and are advantageously introduced into the reac-
tion mixture in amounts of from 0.5 to 50% by weight, prefer-
ably from 1 to 40% by weight, based on the weight of
components (a) to (c).
Examples of suitable flameproofing agents are tricresyl phos-
phate, tris(2-chloroethyl) phosphate, tris(2-chloropropyl)
phosphate, tris(l,3-dichloropropyl) phosphate, tris(2~3-di
bromopropyl) phosphate and tetrakis(2-chloroethyl)ethylene
diphosphate.
In addition to the abovementioned halogen-substituted phos-
phates, it is also possible to use inorganic flameproofing
agents, ~uch as red phosphorus, aluminum oxide hydrate, anti-
mony trioxide, arsenic oxide, ammonium polyphosphate, expand-
able graphite and calcium sulfate, or cyanuric acid deriva-
tives, eg. mel~;ne, or mixtures of two or more flameproofing
agents, eg. ammonium polyphosphates and melamine and/or
expandable graphite and, if desired, starch, in order to
flameproof the compact or cellular polyurethanes prepared ac-
cording to the invention. In general, it has proven expedient
- 21~75~0
. .
19
to use from 5 to S0 parts by weight, preferably from 5 to
25 parts by weight, of said flameproofing agents or mixtures
per 100 parts by weight of components (a) to (c).
Further details on the other conventiopal auxiliaries men-
tioned above can be obtained from the specialist literature,
for eYAmrle from the monograph by J.~. Saunders and
R.C Frisch, High Polymers, Volume XVI, Polyurethanes, Parts 1
and 2, Interscience Publishers 1962 and 1964 respectively, or
Runststoff-~andbuch, Polyurethane, Volume VII, Carl-Hanser-
Verlag, Munich, Vienna, 1st and 2nd Editions, 1966 and 1983.
In order to prepare the compact or cellular polyurethanes, the
liquid polyisocyanate compositions (b) contA~ni~g bonded urethane
15 groups, the relatively high-molecular-weight polyhydroxyl com-
pounds (a) and, if desired, chain extenders and/or crossl;nk;ng
agents (c) can be reacted in the absence or preferably presence
of catalysts (e) and auxiliaries (f) and in the presence of blow-
ing agents (d) for the formation of cellular polyurethanes at
20 from 0 to 100 C, preferably from 15 to 80 C, in such mixing ratios
that from 0.5 to 2, preferably from 0.8 to 1.3, in particular
approximately one, reactive hydrogen atom(s) bonded to formative
component (a) and, if used, (c) are present per NC0 group and, if
water is used as blowing agent, the molar ratio between the num-
25 ber of equivalents of water and the number of eguivalents of NC0
groups is from 0.5 to 5 : 1, preferably from 0.7 to 0.95 : 1, in
particular from 0.75 to 0.85 : 1.
The compact and cellular polyurethanes can be prepared by the
30 prepolymer process or preferably by the one-shot process by mix-
ing two cnmronents (A) and (B), where formative components (a)
and, if used, (c), (d), (e) and (f) are combined to form the
polyhydroxyl component (A) and the polyisocyanate component (B)
comprises the diphenylmethane diisocyanate-based polyisocyanate
35 composition (b) contAining bonded urethane groups, if desired
mixed with (f) and inert, physical blowing agents. Since the
polyol component (A) and the polyisocyanate component (B) have
very good shelf lives, they need only be mixed intensively before
preparation of the compact or cellular polyurethanes. The reac-
40 tion mixture can be brought to reaction in open or closed molds,
expediently at from 15 to 80-C.
In order to prepare cellular polyurethanes, eg. flexible, semi-
rigid or preferably rigid polyurethane foams, preferably PU
45 molded foams, the foamable reaction mixture can be introduced
into an expediently metallic, t~mperature-controllable, open or
closed mold at, for example, from 15 to 80 C, preferably at from
2137s4a
18 to 45 C. The mold tPmperature i5 u~ually from 20 to 90 C, pre-
ferably from 35 to 70 C. The reaction mixture is allowed to cure
in the closed mold, usually with compaction, for example with
degrees of compaction of from 1.1 to 8, preferably from 2 to 6,
5 in particular from 2.5 to 4. The novel process i8 also suitable
for the production of polyurethane slabstock foams.
The compact polyurethanes generally have densities of from 1.0 to
1.2 g/cm3, products of higher density being obtained with addition
lO of reinforcing materials and/or fillers. Cellular elastomers and
PU structural foams usually have densities of from 240 to less
than 1000 g/l, densities of from 400 to 600 g/l being preferred.
The flexible, ~emirigid and preferably rigid PU foams expediently
have densitie~ of from 30 to 80 g/l, preferably from 35 to
15 60 g/l.
The compact polyurethanes prepared by the novel proce~s are used,
for example, in the automotive, construction and furniture indus-
tries, for example as rain gutters, side strips, cover panels and
20 table edges; the cellular PU elastomers are used, for example, as
damping elements, sun visors, armrests, shoe inners and shoe
soles; and the PU foams are used, for example, as cushioning
materials, ~afety covers, furniture housings, for foam-filling
refrigeration equipment housings, for example chest freezers and
25 refrigerators, hot-water eguipment, district heating pipes and
cavities of all types, and for rock con~olidation.
~YA~ples
30 Preparation of the liquid polyisocyanate compositions cont~;ning
urethane groups
Example 1
35 0.1 part by weight of benzoyl chloride was added with stirring to
4000 parts by weight of crude MDI having an NC0 content of 314 by
weight and a content of MDI isomers of 40~ by weight under a
nitrogen atmosphere in a reactor fitted with stirrer, reflux con-
denser and feed and withdrawal device for gases, the reaction
gO mixture was warmed to 50 C, and 211 parts by weight of isopropanol
were added dropwise at this temperature over a period of 30 min-
utes, during which the reaction temperature rose to 70-C. The
reaction mixture was then warmed to 80-C and the reaction was com-
pleted at this temperature in 2 hours, giving a clear, flowable
45 polyisocyanate composition having a urethane group content of
0.84 mol/kg, and an NC0 content of 25.94 by weight and a
" - 213 75~
21
viscosity at 23 C of 2100 mPa-s, measured using a Haake viscometer
(Rotovisko RV 20 type).
By varying the amount of i~opropanol, polyisocyanate c~mrositions
5 having different concentrations of urethane groups were prepared
analogously.
The amount of isopropanol used, the percentage contents of ure-
thane and isocyanate groups and the viscosity of the polyiso-
10 cyanate compositions and their miscibility with trioxypropyleneglycol are shown in Table 1.
Examples 2 and 3
15 The procedure was similar to that of ~x~mrl e 1, but the isoprop-
anol was replaced as monohydric alcohols by methanol snd allyl
alcohol in the amounts shown below.
Comparative Example I
The procedure was similar to that of Example 1, but the isoprop-
anol was replaced by difunctional dipropylene qlycol.
Miscibility with polyoxyalkylene-polyols
In order to test the miscibility, e~uimolar amounts of the crude
MDI compositions cont~i ni ng urethane groups and trioxypropylene
glycol (TPG) were mixed at 23 C.
30 The test substance u ed in place of polyoxyalkylene-polyols was
trioxypropylene glycol, since this compound has a similar hyd-
roxyl number to rigid foam polyoxyalkylene-polyols, but has low
viscosity and is therefore more ~uitable for mixing trials of
this type than, for example, sucrose-based polyoxyalkylene-
35 polyols, which have high viscosity.
~ 1 3 7 5
.
D~r A-trlenge~iell-Cn~2t930503
22
0 J 0
K J
E~ U o O
L ~ o ~ V C
c , O a ~ ' ~ L
tJ' ~ 0 -- _
'~ 0 ~ C
., -- ~ .
O r p~ O ~ ~ ~ ~~D O ~
-- '' 3 V~ ~ --4 ~ 0 ~ ~
o c ~ ~
C
o~ ~ o~ ~ 0 ~ O Ltl N N
O O O O O O O ~ O O O ~1 0 0 0 0
r 3
C ~ '--
3 ~ ~ ~ o .-1 ~D 0 o ~
0 O
O ~ C
h ,_ ~ c c
~a ~ H
213~540
23
Preparation of cellular polyurethanes
~Yamp]e 4
Rigid PU foam
Polyhydroxyl c~mronent (A): a mixture comprising
0 93 parts by wt.of trioxypropylene glycol (hydr
number 584),
2.4 parts by wt.of polysiloxane foam ~t~hil~zer
(Tegostab~B8406 from Goldschmidt AG),
1.9 parts by wt.of dimethylcyclohexylamine and
2.7 parts by wt.of water.
Polyisocyanate component (2)s
Crude MDI composition having a urethane group content of
20 0.79 mol~kg, an NCO content of 26% by weight and a viscosity at
23 C of 1990 mPas, measured using a Haake viscometer,
Rotovisko RV 20 type, prepared as described under Example 1 by
reacting 200 parts by weight of isopropanol with 4000 parts by
weight of the crude MDI described in ~YAmrle 1.
In order to prepare the rigid PU foam, 100 parts by weight of the
polyhydroxyl component (A) and 229 parts by weight of the
polyisocyanate component (B) were mixed vigorously at 23 C, and
the clear reaction mixture was transferred into a plastic bucket,
30 where it was allowed to expand.
~mp~rative Example II
Polyhydroxyl component (A): as in Example 4
Polyisocyanate component (D): crude MDI hav$ng an NCO content of
31~ by weight and an MDI isomer content of 40~ by weight.
100 parts by weight of the polyhydroxyl c~mponent (A) and
40 188 parts by weight of the polyisocyanate component (B) were
mixed and allowed to expand as described in Example 4.
` 2~13 7~40 :
24
Table 2
.
Mechanical properties of the rigid PU foams, prepared as
5 described in Example 4 and Comparative ~yA~rle II
Mechanical properties Ex. 4 Comp. Ex. II
Density [g/l] 52.5 47.1
10 Thermal conductivity, lmW/mR~ 20.1 21.5
measured using a
Hesto la_bda control A 50-A
Proportion of closed cells, [%] 87 88
measured using a Beckmann air
comparative pycnometer, Model 930
Compressive strength in accordance with 494 306
DIN 53421 tkPa]
iml-m reaction t~mr~rature [oc] 181 206
in the foam core, measured using a
Cr-Ni thermocouple with a thickness
20 of 0.2 mm.
Example 5
Rigid PU foam
Polyhydroxyl component (A): a mixture comprising
81.6 parts by wt.of a glycerol-initiated polyoxypropylene-polyol
having a hydroxyl number ~of 400,
9.9 parts by wt.of trioxypropylene glycol,
2.5 parts by wt.of polysiloxane foam ~tabilizer
(polyurax~ SR 321 from Union Carbide),
2.0 parts by wt.of dimethylcyclohexylamine and
3.0 parts by wt.of water.
Polyisocyanate component (B)s as in Example 4
In order to prepare the rigid PU foam, 100 parts by weight of the
polyhydroxyl rnmponent (A) and 179 parts by weight of the
40 polyisocyanate component (B) were mixed as in Example 4 and
allowed to expand freely.
Comr~Fative Example III
45 Polyhydroxyl ~mponent (A): as in Example 5
`~ 213754~
.
.
. . .
Polyisocyanate c~mronent (B): as in ComrArative ~Y~mple II
100 parts by weight of the polyhydroxyl r~mrQnent (A) and
152 parts by weight of the polyisocyanate c~mponent (~) were
S mixed and allowed to expand as in Example 4.
Table 3
Hechanical properties of the rigid PU foams, prepared as
10 described in Example 5 and C- ,~rative Example III
Mechanical properties Ex. 5 Comp.
Ex. III
15 Density [g/l] 44.6 40.8
Thermal conductivity, [mW/mR] 20.9 22.1
measured using a
Hesto lambda control A 50-A
Proportion of closed cells, [%] 89 89
measured using a Beckmann air
20 comparative pycnometer, Model 930
Compressive strength in accordance with 368 287
DIN 53421 [kPa]
Example 6
Compact PU molding composition
100 parts by wt.of a polyoxypropylene glycol having a hydroxyl
number of 105 prepared by polyaddition of
3 1,2-propylene oxide onto 1,2-propanediol
were dried for 2 hours at 100 C under reduced pressure (about
10 mbar) and then mixed with
0,1 part by wt. of dibutyltin dilaurate.
33 parts by wt. of the flowable, crude HDI/i80propanol-based
polyisocyanate composition described in
Example 1, having an NCO content of 25.9%
by weight,
were added at 23 C with vigorous stirring using a prDpeller
~tirrer.
` ~13754~
26
The reaction mixture was transferred into a metallic mold having
the internal dimensions 20xlOx0.5 cm which was held at a
temperature of 50 C, and allowed to react there, ~nd the PU
elastomer formed was demolded after one hour.
A clear, bubble-free, dark-brown PU sheet was obtained on which
the following mechanical properties were measured:
Tear strength [N/mm2] 0.92
10 Elongation at break [~]: 102
C; rative Example IV
The procedure was similar to that described in Example 6, but the
15 flowable crude MDI/isopropanol-based polyi~ocyanate composition
was replaced by unmodified crude MDI having ~n NCO content of 31%
by weight.
An inhomogeneous, yellow-brown PU sheet cont~i~jng numerous gas
20 bubbles was obtained on which the following mechanical properties
were measured:
Tear strength [N/mm2] 0.26
Elongation at break [~]: 44
