Process for the production of polyurethane urea products

This invention relates to a process for the production of polyurethane urea products from isocyanate product blends and preferably less reactive, aromatic diamines, or solutions of aromatic diamines in relatively high molecular weight polyhydroxyl compounds, the reaction components being reacted in a casting process with commercially-reasonable casting times and comparatively short demolding times. For this purpose, relatively high-molecular weight polyhydroxyl compounds, optionally in the presence of low molecular weight diols are reacted with excess quantities of toluene, phenylene or hexamethylene diisocyanate to produce a substantially diisocyanate-free NCO-prepolymer. This NCO-prepolymer is mixed with from 0.1 to 25%, by weight, of less reactive, monomeric tetra-alkyl-diphenylmethane diisocyanates corresponding to the general formula: ##STR1## wherein R.sub.1 to R.sub.4, which may be the same or different, represent C.sub.1 -C.sub.4 alkyl radicals. These isocyanate blends may be easily processed into elastomer moldings having favorable properties in the casting process using moderately-reactive aromatic diamines from the series of di- to tetra-alkyl-diphenylmethane diamines and/or dialkyl-toluene diamines and/or using substituted 3,5-diamino-4-alkyl-benzoic acid alkyl esters, optionally dissolved in the relatively high molecular weight polyhydroxyl compounds.

This invention relates to a process for the production of polyurethane urea 
products, which may be either cellular or elastomeric, from 
NCO-prepolymers which have increased NCO contents, and aromatic diamines, 
or solutions thereof in relatively high molecular weight polyhydroxyl 
compounds. According to this process, the reaction components are reacted 
in a casting process employing favorably long casting times and 
comparatively short demolding times. 
For this purpose, relatively high molecular weight polyhydroxyl compounds, 
optionally in the presence of low molecular weight diols, are reacted with 
excess quantities of toluene, phenylene or hexamethylene diisocyanate to 
produce a substantially diisocyanate-free NCO-prepolymer. Then, from 0.1 
to 25%, by weight, of less reactive, monomeric tetra-alkyl-diphenylmethane 
diisocyanates, corresponding to the general formula: 
##STR2## 
wherein R.sub.1 to R.sub.4, which may be the same or different, represent 
C.sub.1 -C.sub.4 alkyl radicals, 
are mixed with this NCO-prepolymer in order to increase the NCO content. 
These isocyanate blends may then be easily processed, with moderately 
reactive diamines from the series of di- to tetra-alkyl-diphenylmethane 
diamines, dialkyl-toluene diamines, and/or with 
3,5-diamino-4-alkyl-benzoic acid alkyl esters or with solutions of these 
diamines in relatively high molecular weight polyhydroxyl compounds, into 
elastomer moldings having favorable properties using the known casting 
process employing favorable processing conditions. Aromatic diamines, 
without alkyl substituents in the vicinity of each amino group and without 
deactivating substituents, such as, for example, 
diphenylmethane-4,4'-diamine, may also be used, but must be in the form of 
solutions thereof in relatively high molecular weight polyhydroxyl 
compounds. 
BACKGROUND OF THE INVENTION 
Polyurethane elastomers are preferably produced, according to the known 
casting process from, for example, NCO-prepolymers with glycols as 
chain-lengthening agents. Particularly favorable properties are obtained 
using naphthylene diisocyanate or diphenylmethane diisocyanate with butane 
diol-1,4 (see Kunststoff-Handbuch, Vol. 7, Polyurethanes, Vieweg and 
Hochtlen, Carl-Hanser-Verlag, Munich, 1966, pages 207-227). In order to 
achieve a high hardness in the elastomers, the diisocyanate is reacted 
with the relatively high molecular weight polyhydroxyl compounds in NCO:OH 
ratios of greater than 2:1 to produce NCO-prepolymers which thus still 
contain portions of free diisocyanates, in addition to the 
NCO-prepolymers. 
However, it has also been proposed to increase the NCO content of 
NCO-prepolymers, such as those based on toluene diisocyanate, by adding 
other, different diisocyanates and then to further react them with 
chain-lengthening agents (see Japanese Patent Application No. 53,133,298). 
As the NCO content increases, the hardness of the elastomer increases, but 
the casting time of the reaction mixture is also reduced, and casting is 
practicable only with glycol-lengthening. With aromatic diamines as the 
chain-lengthening agents, elastomers having improved elastic and thermal 
properties are, indeed, generally accessible, but they have a higher 
reactivity. Consequently, the casting time is shortened in many cases to 
impracticably short times, unless diamines, such as 
3,3'-dichloro-4,4'-diamino-diphenylmethane, which have considerably 
reduced reactivities (but, unfortunately, also high melting points), are 
used. Even with these diamines, however, the casting time is extremely 
short (particularly with NCO-enriched prepolymer mixtures) and partly as a 
result of this, the casting process cannot be carried out on a practical 
basis. 
The reaction of conventional NCO-prepolymers with chain-lengthening agents, 
such as, for example, diethyl-tolamines, 
tetra-alkyl-4,4'-diamino-diphenylmethanes or 4-alkyl-3,5-diamino-benzoic 
acid alkyl esters, is also difficult because of similar short 
reactivities. Thus, processing with commercially available isocyanates, 
such as diphenylmethane diisocyanate or naphthylene diisocyanate, in the 
form of NCO-prepolymers, is only possible with very short, impracticable 
casting times (i.e., .ltoreq.5 seconds). Large cast parts or comparatively 
long flow paths are, thus, hardly feasible (see, Example 4, Table 1, 
herein). 
If reduction of the reactivity of these diamines is attempted by diluting 
them with relatively high molecular weight polyhydroxyl compounds (such 
as, for example, adipic acid/C.sub.2 -C.sub.6 -diol polyesters), the 
results are unsatisfactory. A slight increase in the casting time is 
indeed achieved, but this has to be balanced against a concurrent and 
disproportionate increase in the demolding time (see, Example 10, Table 2, 
herein). 
It has now been found that NCO-prepolymers, based on toluene diisocyanate, 
phenylene diisocyanate or hexamethylene diisocyanate with polyester and/or 
polyether diols and blended with tetra-alkyl-diphenylmethane diisocyanate, 
then combined with liquid or low-melting aromatic diamines, may easily be 
processed into cast parts, even in high pressure installations. These 
diamines may be less reactive diamines used alone, or in the form of 
solutions of less reactive diamines in relatively high molecular weight 
polyhydroxyl compounds and/or, surprisingly, even in the form of solutions 
of reactive, aromatic diamines, such as diphenylmethane-4,4'-diamine, in 
relatively high molecular weight polyhydroxyl compounds. During 
processing, a gradual change in hardness may be obtained by varying the 
quantity of the added diisocyanates. Moreover, the casting times are long 
enough for large-volume parts to be produced (see Examples 5 to 9, Table 1 
and Examples 11 to 13, Table 2, herein) and the parts may be released from 
the mold after relatively short molding times. 
It is surprising that, in spite of the simultaneous use of different 
diisocyanates in the casting mixture, the mechanical properties of the end 
products, which are obtained according to the present invention, are 
outstanding. Normally, the mixing of several different isocyanate 
components in the polyurea system causes the production of different urea 
segments which interfere with each other and thus exert a negative 
influence on the mechanical property spectrum (particularly on the heat 
stability and the pressure deformation residue) of the end product. 
However, good values are actually found precisely in the critical 
characteristics of heat stability and pressure deformation residue in the 
products obtained according to the instant invention. The reactivity 
gradation, and thus the processibility, is also very favorably effected. 
In contrast to high-melting diamines, such as 
3,3'-dichloro-4,4'-diamino-diphenylmethane, which are slow to react, 
liquid or low-melting chain-lengthening diamines have a moderate 
reactivity. Examples of these low-melting diamines include 
diethyl-tolamines or the (liquid) mixtures thereof, or the mixed 
condensates from, for example, diethyl aniline, diisopropyl aniline and 
formaldehyde (such as tetra-alkyl-4,4'-diamino-diphenylmethane), which may 
be easily processed as diamine melts in high pressure installations. 
Alkylated diphenylmethane diisocyanate compounds, and the use thereof in 
polyurethanes, have been known for a long time. Thus, British Pat. No. 
852,651 describes the production of tetra-alkylated diphenylmethane 
diisocyanates and indicates the suitability thereof for the production of 
polyurethanes. However, experiments have now shown that formulations which 
are composed exclusively of tetra-alkyl-diphenylmethane diisocyanates 
produce waxy-brittle bodies during the reaction with aromatic diamines as 
chain-lengthening agent, which bodies may only be strengthened by an 
abnormally-long subsequent heating operation (see Table 1, Examples 1 and 
2, herein). Due to this peculiarity, a commercial use of the resulting 
products is impossible, in spite of some useful mechanical properties. 
In the method according to the present invention, the production of a 
brittle, waxy structure is not observed, in spite of the use of 
tetra-alkyl-diphenylmethane diisocyanate. On the contrary, moldings which 
have favorable properties are obtained with practicable casting times and 
short molding times. 
DESCRIPTION OF THE INVENTION 
Thus, the present invention provides a process for the production of 
polyurethane urea products, which may be either cellular or elastomeric, 
by the reaction of NCO-prepolymers and blended with quantities of certain 
monomeric polyisocyanates, with aromatic diamines, or with solutions of 
these diamines in relatively high molecular weight polyhydroxyl compounds, 
and optionally catalysts and conventional additives. 
These substantially-linear NCO-prepolymers, which contain less than 0.2%, 
preferably less than 0.05%, unreacted monomeric diisocyanate (optionally 
by distilling off unreacted diisocyanates), are produced from 
substantially-linear relatively high molecular weight polyhydroxyl 
compounds which have a molecular weight of from 400 to 12,000, preferably 
of from 400 to 5000, to which, optionally, have been added low molecular 
weight diols which have a molecular weight of from 62 to 399, preferably 
of from 62 to 350, reacted with toluene diisocyanate, phenylene 
diisocyanate or hexamethylene diisocyanate, preferably toluene 
diisocyanate, in an NCO:OH ratio of greater than 1.1:1, preferably of from 
1.1:1 to 2.5:1 and more preferably, of from 1.5:1 to 2.1:1. This 
NCO-prepolymer is then blended with from 0.1 to 25%, by weight, preferably 
from 0.5 to 20%, by weight, and more preferably, from 0.5 to 15%, by 
weight, of diphenylmethane diisocyanates which are tetra-alkyl-substituted 
in the o-positions to the NCO groups, which correspond to the general 
formula: 
##STR3## 
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4, which may be the same or 
different represent straight- or branched-chain C.sub.1 -C.sub.4 alkyl 
groups. 
This blended product is then reacted with aromatic diamines, optionally 
dissolved in relatively high molecular weight polyhydroxyl compounds, said 
diamine selected: 
(a) from the series of di- to tetra-alkyl-diphenyl diamines corresponding 
to the general formula: 
##STR4## 
wherein R.sub.1 to R.sub.4, which may be the same or different, represent 
straight- or branched-chain C.sub.1 -C.sub.4 alkyl groups, and/or wherein 
R.sub.2 and/or R.sub.4 may represent hydrogen; and/or 
(b) from the series of dialkyl-toluene diamines corresponding to the 
general formulae: 
##STR5## 
wherein R.sub.5, which may be the same or different, represents straight- 
or branched-chain C.sub.1 -C.sub.5 alkyl groups, preferably ethyl; and/or 
(c) from the 3,5-diamino-4-alkyl-benzoic acid alkylester series, 
corresponding to the general formula: 
##STR6## 
wherein X represents a C.sub.1 -C.sub.12 alkyl, preferably methyl, ethyl, 
isopropyl or isobutyl; and 
R.sub.6 represents straight- or branched-chain C.sub.1 -C.sub.10 alkyl 
radicals; and/or 
(d) solutions of reactive aromatic diamines without alkyl groups in the 
vicinity of each amino group and without deactivating substituents, such 
as, preferably, diphenylmethane-4,4'-diamine, in relatively high-molecular 
weight polyhydroxyl compounds. 
These diamines or diamine mixtures are used in substantially equivalent 
quantities (NH.sub.2 :NCO or OH+NH.sub.2 :NCO of from 0.8:1 to 1.2:1, 
preferably of from 0.9:1 to 1.05:1). Included among suitable 
substantially-linear polyols with molecular weights of from 400 to 12000, 
which preferably contain 2, optionally up to 3, Zerewitinoff-active 
H-groups, which are reactive against NCO-groups (substantially hydroxyl 
groups), are the known polyesters, polylactones, polyethers, 
polythioethers, polyesteramides, polycarbonates and polyacetals. Also, 
hydroxyl-terminated vinyl polymers, such as, for example, polybutadiene 
diols; polyhydroxyl compounds which contain urethane or urea groups; 
optionally modified natural polyols, and compounds containing other 
Zerewitinoff-active groups, such as amino, carboxyl or thiol groups may be 
used. These compounds correspond to the prior art and are described in 
detail, for example, in German Auslegeschriften Nos. 2,302,564; 2,423,764; 
2,549,372 (U.S. Pat. No. 3,963,679); 2,402,840 (U.S. Pat. No. 3,984,607); 
2,497,387 (U.S. Pat. No. 4,035,213) and, in particular, U.S. Pat. No. 
2,854,384. 
The preferred polyols according to the instant invention include polyesters 
containing hydroxyl groups, obtained from dihydricalcohols and adipic 
acid; polycarbonates; polycaprolactones; polyethylene oxide polyethers; 
polypropylene oxide polyethers; polytetrahydrofuran polyethers and mixed 
polyethers of ethylene oxide and propylene oxide and/or optionally 
tetrahydrofuran. Adipic acid diol ester, in particular, adipic 
acid/C.sub.2 -C.sub.6 diol polyester, caprolactone polyester or 
polycarbonate diols, in particular, hexane diol polycarbonates, which are 
optionally modified by co-components, are particularly preferred. However, 
mixtures of the relatively high molecular weight compounds containing 
hydroxyl groups may also be used. 
Preferred low molecular weight diols, optionally to be used simultaneously, 
include ethylene glycol, di- and triethylene glycol, and, in particular, 
1,6-hexane diol, neopentyl glycol, 2-methyl-propane diol and 
hydroquinone-di-.beta.-hydroxyethyl ether. In most cases, 1,4-butane diol 
is most preferable. 
As described, toluene diisocyanates, phenylene diisocyanate and 
hexamethylene diisocyanate are particularly preferred as diisocyanates, 
due to the ease of distillation thereof. Toluene diisocyanates, in 
conventional isomer mixtures, are particularly preferred, and 
toluene-2,4-diisocyanate is most particularly preferred. 
The NCO-prepolymers are formed by reacting the relatively high molecular 
weight polyhydroxyl compounds with excess quantities (.gtoreq.1.1:1 
NCO:OH) of diisocyanates. The low molecular weight diols may optionally be 
used as chain-lengthening agents in admixture with the relatively high 
molecular weight polyhydroxyl compounds, or they may be added subsequently 
to the formation of the NCO-prepolymer. 
The quantity of diisocyanates which is used is preferably from 1.5 to 2.5, 
and most preferably from 1.5 to 2.1, NCO equivalents per OH equivalent. 
During the production of the NCO-prepolymers, it is possible to use a very 
much higher NCO:OH ratio (for example, up to 10.0:1), but the content of 
free diisocyanates of the type mentioned must then be removed again by 
distillation in order that the effective NCO:OH ratios specified are 
observed. It is even preferred initially to carry out the NCO-prepolymer 
formation using a very great NCO excess, approaching the ideal NCO:OH 
ratio of 2:1, in order to limit the linking of two relatively high 
molecular weight polyhydroxyl compounds. After unreacted diisocyanates 
have been distilled off, for example, in a thin-film evaporator, a 
substantially monomer-free NCO-prepolymer which contains less than 0.2%, 
by weight, more preferably less than 0.05%, by weight, of monomeric 
diisocyanate, should remain. 
The NCO content of this substantially monomeric-free NCO-prepolymer is 
blended with 0.1 to 25%, by weight, preferably from 0.5 to 20%, by weight, 
and more preferably from 0.5 to 15%, by weight, diphenylmethane 
diisocyanates which are tetra-alkyl-substituted in o-positions to the NCO 
groups and which correspond to the general formula: 
##STR7## 
In this general formula for these tetra-alkyl-diphenylmethane 
diisocyanates, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 represent the same or 
different alkyl radicals having from 1 to 4 carbon atoms, such as, for 
example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or t-butyl 
groups. Mixtures of such individual compounds with any radicals R.sub.1 to 
R.sub.4 may also be used. 
Suitable diisocyanates for blending with the NCO-prepolymers include the 
tetramethyl, tetraethyl, tetrapropyl, tetraisopropyl, tetra-n-butyl, 
tetraisobutyl and/or tetra-t-butyl derivatives of diphenylmethane 
diisocyanates, in particular, 4,4'-diisocyanates. However, the derivatives 
having asymmetric alkyl substitution on the two phenyl nuclei are also 
suitable. Such derivatives include, for example, 
3,5-diethyl-3',5'-diisopropyl-diphenylmethane-4,4'-diisocyanate, 
3,5-diethyl-3',5'-diisobutyl-diphenylmethane-4,4'-diisocyanate or other 
asymmetrically-substituted tetra-alkyl-diphenylmethane diisocyanates, 
which are produced by the condensation of differently alkyl-substituted 
dialkyl anilines with formaldehyde and subsequent phosgenation. Product 
mixtures comprising asymmetrically-substituted tetra-alkyl-diphenylmethane 
diisocyanates mixed with its symmetrical components are particularly 
preferred. Examples of these preferred mixtures include mixtures of, for 
example, from 45 to 65%, by weight, of 3,5-diethyl-3', 
5'-diisopropyl-diphenylmethane-4,4'-diisocyanate and from 27.5 to 17.5%, 
by weight, of 3,5,3', 5'-tetraethyl-diphenylmethane-4,4'-diisocyanate and 
from 27.5 to 17.5%, by weight, of 
3,5,3',5'-tetra-isopropyl-diphenylmethane-4,4'-diisocyanate. The 
production of asymmetrically-substituted alkyl-diphenylmethane diamines 
which may be phosgenated into the corresponding isocyanates is described, 
for example, in German Auslegeschrift No. 2,920,501. 
The resulting isocyanate blends of NCO-prepolymer with 
tetra-alkyl-diphenylmethane diisocyanates, should preferably contain at 
least 4%, by weight, of NCO, preferably from 4 to 9%, by weight, and more 
preferably from 4 to 7%, by weight, of NCO. 
In the production of these isocyanate blends, minor quantities, generally 
less than 5 mol percent of higher functional compounds, for example, 
trifunctional compounds, may optionally be used in each of the starting 
materials, but the quantity must be restricted such that the properties 
are not substantially modified and merely the molecular weight is 
affected. In the alternative, monofunctional compounds (monofunctional 
hydroxy compounds, monofunctional isocyanates or monofunctional amines) 
may optionally be simultaneously used as chain-terminators to control the 
molecular weight. 
Of course, the conventional hydrolysis and oxidation stabilizers may also 
be added to the starting compounds. It is advisable to add anti-oxidants 
for stabilizing the polyurethane, such anti-oxidants being 
sterically-hindered phenols, organic phosphites and/or phosphonites, 
and/or conventional UV absorbers and light protecting agents based on 
benzotriazole, 2,2,6,6-tetramethylpiperidine, 
1,2,2,6,6-pentamethylpiperidine or benzophenone, and/or other types of UV 
absorbers. Other additives, pigments, dyes or reinforcing fibers may also 
be admixed according to the prior art. 
The isocyanate blends are lengthened according to the present invention 
using aromatic diamines, optionally dissolved in relatively high molecular 
weight polyhydroxyl compounds and/or using solutions of reactive aromatic 
diamines in relatively high molecular weight polyhydroxyl compounds. 
The preferred aromatic diamines from the series of di- to 
tetra-alkyl-diphenylmethane diamines correspond to the general formula: 
##STR8## 
wherein R.sub.1 to R.sub.4, which may be the same or different, represent 
straight- or branched-chain aliphatic alkyl radicals having from 1 to 4 
carbon atoms, and/or wherein 
R.sub.2 and/or R.sub.4 may represent hydrogen. 
Examples of such diamines include tetramethyl-, tetraethyl-, tetrapropyl-, 
tetraisopropyl-, tetrabutyl-, tetraisobutyl- and/or, optionally, 
tetra-t-butyl-diphenylmethane-4,4'-diamines, with 
asymmetrically-alkyl-substituted tetra-alkyl-diphenylmethane diamines 
prepared from differently-substituted dialkyl anilines and formaldehyde 
preferred. Examples of such preferred diamines include 
3,5-diethyl-3',5'-diisopropyl-diphenylmethane-4,4'-diamine, 
3,5-dimethyl-3',5'-diisobutyl-diphenylmethane-4,4'-diamine, 
3,5-dimethyl-3',5'-diisopropyl-diphenylmethane diamine, and mixtures of 
the asymmetrically-substituted and symmetrically-substituted 
tetra-alkyl-diphenylmethanes. The production of such 
asymmetrically-substituted tetra-alkyl-diphenylmethane diamines and of the 
mixtures thereof with symmetrically-substituted 
tetra-alkyl-diphenylmethane diamines is described, for example, in German 
Auslegeschrift No. 2,920,501. 
Trialkyl-substituted diphenylmethane diamines, such as, for example, 
3,5,3'-triisopropyl-diphenylmethane-4,4'-diamine and 
3,5-diisopropyl-3'-ethyl-diphenylmethane-4,4'-diamine may also be used. 
Dialkyl-diphenylmethane diamines, such as 
3,3'-diisopropyl-diphenylmethane-4,4'-diamine, may also be used, but are 
less preferred. However, mixtures of from about 45 to 65%, by weight, of 
3,5-diethyl-3',5'-diisopropyl-diphenylmethane-4,4'-diamine, from 27.5 to 
17.5%, by weight, of 3,5,3',5'-tetraethyl-diphenylmethane-4,4'-diamine, 
and from 27.5 to 17.5%, by weight, of 
3,5,3',5'-tetraisopropyl-diphenylmethane-4,4'-diamine are particularly 
preferred. 
Another preferred group of aromatic diamines include dialkyl-toluene 
diamines and the isomeric mixtures thereof. Examples of these diamines 
include 1-methyl-3,5-diisopropyl-2,4-diaminobenzene, 
1-methyl-3,5-diisopropyl-2,6-diaminobenzene, and preferably 
1-methyl-3,5-diethyl-2,4-diaminobenzene and 
1-methyl-2,5-diethyl-2,6-diaminobenzene and mixtures thereof, preferably 
in ratios of from 8:20 to 40:60. 
Additional diamines which may be used include those of the 
3,5-diamino-4-alkyl-benzoic acid alkyl ester series which correspond to 
the formula: 
##STR9## 
wherein X represents C.sub.1 -C.sub.12 alkyl, preferably methyl, ethyl, 
isopropyl or isobutyl, and 
R.sub.6 represents straight- or branched-chain C.sub.1 -C.sub.10 alkyl 
radicals, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, 
t-butyl, amyl, isoamyl, n-hexyl, n-octyl, n-decyl or 2-ethylhexyl 
radicals. 
The members in which X=CH.sub.3 and R=isopropyl, isobutyl or 2-ethylhexyl 
are particularly preferred. 
The above-described diamines are to be used alone or in admixture with 
relatively high-molecular weight, substantially-linear polyhydroxyl 
compounds having molecular weights of from 400 to 12,000, preferably of 
from 400 to 5000. All the polyols which have already been listed in 
connection with the preparation of the NCO-prepolymers are included as 
relatively high-molecular weight polyhydroxyl compounds. Adipic 
acid/C.sub.2 -C.sub.6 diol polyesters are again preferred according to the 
present invention. 
As suitable reactive aromatic diamines, the toluene diamines and isomer 
mixtures thereof, and particularly, the 4,4'-, 2,4'- and/or 
2,2'-diphenylmethane diamines (and isomer mixtures thereof), in the form 
of from 3 to 70%, by weight, preferably from 5 to 40%, by weight, and more 
preferably, from 10 to 35%, by weight, solutions thereof in relatively 
high-molecular weight polyhydroxyl compounds, may also be used according 
to the present invention. However, processing difficulties are encountered 
when reactive aromatic diamines, such as diphenylmethane-4,4'-diamine, are 
used alone. 
The NCO-prepolymers and the aromatic diamines are mixed according to known 
processes, for example, by metered mixing in chambers equipped with 
stirrers or by high pressure injection mixing in known elastomer casting 
machines.

EXAMPLES 
The same apparatus and the same operational conditions for casting were 
used in all the Examples and Comparative Examples. 
Equipment: 
Toothed-weel metering pump and mixing head equipped with a 5000 r.p.m. 
spiked stirrer. 
Processing temperatures: 
______________________________________ 
NCO-pre- 80.degree. C. Both components were metered and 
polymer mixed in an NCO/(OH+)NH.sub.2 - 
Chain extender 
80.degree. C. ratio as given in the examples. 
(diamine etc.) The reaction mixture is cast in 
open molds (test panels). 
______________________________________ 
EXAMPLES 1 AND 2 
(Not According to the Present Invention) 
Show the lower quality and the poor solidification behavior of the 
elastomers which were prepared using only tetra-alkyl-diphenylmethane 
diisocyanates as the isocyanate component (see Table 1). 
EXAMPLE 1 (Comparative) 
Synthesis of the NCO-prepolymer 
2000 g of an adipic acid ethylene glycol polyester diol having a molecular 
weight of 2000 are reacted with 832 g of a tetra-alkyl-diphenylmethane 
diisocyanate mixture consisting of: 
##STR10## 
to produce an NCO-prepolymer containing 3.4%, by weight, of NCO. 
Preparation of the Elastomer 
A hot melt at about 60.degree. C. of a chain-lengthening agent consisting 
of: 
##STR11## 
is metered into the mixing head with the NCO-prepolymer and the reaction 
takes place in an NCO:NH.sub.2 ratio of 1.05:1. A product is obtained 
which is still of such a waxy and brittle nature, even after being heated 
for 10 hours at 100.degree. C., that a mechanical test could not be 
performed on the elastomer. 
EXAMPLE 2 
(Comparative) 
1500 g of a polypropylene oxide ether diol of molecular weight 1500 are 
reacted with 820 g of the tetra-alkyl-diphenylmethane diisocyanate mixture 
according to Example 1 to produce an NCO-prepolymer containing 3.7%, by 
weight, of NCO. The reaction between the NCO-prepolymer and the 
chain-lengthening agent according to Example 1 takes place in an 
NCO:NH.sub.2 ratio of 1.05:1. The resulting elastomers are still of a waxy 
brittle nature after 2 hours at 100.degree. C., and exhibit only moderate 
properties. 
EXAMPLES 3 TO 9 
(Examples 3 and 4 Not According to the Present Invention) 
(Examples 5-9 According to the Present Invention) 
These Examples demonstrate the advantage of the blending operation with 
tetra-alkyl-diisocyanato-diphenylmethane and the use of different 
chain-lengthening agents (Table 1). 
The base prepolymer used is prepared by reacting one mol of a polyester 
diol of adipic acid and ethylene glycol having a molecular weight of 2000 
with 2 mols of 2,4-toluene diisocyanate to produce an NCO-prepolymer 
containing 3.5%, by weight, of NCO. 
EXAMPLE 3 
(Comparative) 
The base prepolymer is cast with the chain-lengthening diamine mixture of 
Example 1 in a ratio of NCO:NH.sub.2 of 1.05:1. Heating time of the cast 
elastomer=10 hours at 80.degree. C. 
EXAMPLE 4 
(Comparative) 
To the base prepolymer is added an isocyanate mixture to give a total NCO 
content of 4.5%. The isocyanate mixture comprises 40%, by weight, of 
4,4'-diisocyanato-diphenylmethane and 60%, by weight, of 
2,4'-diisocyanato-diphenylmethane. Processing takes place using the 
chain-lengthening diamine of Example 1 with an NCO:NH.sub.2 ratio of 
1.05:1. The moldings are heated for 10 hours at 80.degree. C. 
EXAMPLE 5 
To the base prepolymer is added an isocyanate mixture to give an NCO 
content of 4.7%, by weight. The isocyanate mixture is the 
tetra-alkyl-diphenylmethane diisocyanate mixture corresponding to the 
mixture of Example 1. The diamine mixture according to Example 1 is used 
as the chain-lengthening agent in an NCO:NH.sub.2 ratio of 1.05:1 and the 
molding is subsequently heated for 10 hours at 80.degree. C. 
EXAMPLES 6 TO 9 
To the base prepolymer is added an isocyanate to give an NCO content of 
4.5%. The isocyanate added is 
3,3',5,5'-tetraethyl-4,4'-diisocyanato-diphenylmethane. This blend is 
reacted with the following chain-lengthening agents in an NCO:NH.sub.2 
ratio of 1.05:1. 
EXAMPLE 6 
Diamine Mixture of Example 1 
EXAMPLE 7 
##STR12## 
EXAMPLE 8 
##STR13## 
EXAMPLE 9 
##STR14## 
The moldings are subsequently heated for 10 hours at 80.degree. C. The 
casting time (pot life) in these Examples in relatively short (Example 3) 
or is extremely short when the blending operation is carried out using 
diphenylmethane diisocyanate mixtures (Example 4). In contrast thereto, 
the casting time, when the diisocyanates according to the present 
invention are used, is sufficiently long without impairing the 
solidification times. The elastomers produced exhibit a good strength and 
good elongation, a good elasticity and a very good tear propagation 
resistance. 
TABLE 1 
__________________________________________________________________________ 
Example No. 2 3 4 5 6 7 8 9 
__________________________________________________________________________ 
Hardness Shore D 
36 35 42 43 41 37 33 38 
Tensile Test 
.sigma..sub.100 
(MPa) 
5.96 
6.63 
7.50 
8.67 
8.05 
7.87 
6.28 
7.56 
.sigma..sub.300 
(MPa) 
8.57 
12.6 
14.0 
12.7 
11.0 
10.7 
8.09 
10.9 
.sigma..sub.B 
(MPa) 
15.5 
58.3 
51.7 
54.9 
51.9 
47.9 
43.6 
57.7 
.epsilon..sub.R 
% 506 535 
514 580 562 
546 
622 
566 
Tear propagation 
(KN/m) 
-- 50 65.3 
79 68 71.1 
60.3 
73.0 
resistance 
Rebound elasticity 
(%) 40 41 41 40 42 42 43 44 
Compression set 
(24 h/70.degree. C.) 
(%) 43 42 42 58 50 45 50 54 
Abrasion (mm.sup.3) 
190 53 49 51 46 47 56 35 
(1 kp/40 m) 
Dyn. shear 
(MPa) 
32.6 
-- 37.2 
43.3 
-- -- -- -- 
modulus (20.degree. C.) 
Tan .delta. (20.degree. C.) 
-- 0.069 
-- 0.092 
0.089 
-- -- -- -- 
T.sub. tan .delta. Max. 
(.degree.C.) 
-30 -- -23 -23 -- -- -- -- 
T.sub.tan .delta. Min. 
(.degree.C.) 
+110 
-- +110 
+120 
-- -- -- -- 
Casting time 
(sec) 
35" 20" 
&lt;5" 30" 45" 
25" 
55" 
40" 
Solidification 
(min) 
120' 
10' 
8' 5' 8' 3' 9' 5' 
__________________________________________________________________________ 
No values were measured for the material according to Example 1, as the 
material did not solidify. 
The DIN test numbers were: Hardness 53505; Tension tests 53504; Tear 
propagation resistance 53515; Impact elasticity 53512; Pressure 
deformation 53517; Abrasion 53516; Dyn. shear modulus 53445; Tan 
.delta. 53445. 
EXAMPLES 10 TO 13 
These Examples show the effect of the blending operation using 
tetraethyl-4,4'-diisocyanato-diphenylmethane, and the use of solutions of 
the chain-lengthening diamines in a relatively high molecular weight 
polyhydroxyl compound (Table 2) in the casting process. 
Base prepolymer: 
Adipic acid polyester diol of molecular weight 2000 based on butane 
diol-4,4/ethylene glycol (diol mol ratio 1:1). 
Toluene diisocyanate isomer mixture (65%, 2,4-isomer+35% 2,6-isomer). 
mol ratio of toluene diisocyanate:polyester=2.0:1. 
NCO content of NCO-prepolymer=3.5%. 
EXAMPLE 10 
(Comparative) 
To the base prepolymer is added diisocyanato-diphenylmethane (60% 
4,4'-isomer+40% 2,4'-isomer) to yield an NCO content of 4.5%. 
Chain-lengthening (casting) is carried out using a mixture of: 
##STR15## 
NCO:OH+NH.sub.2 ratio=1.05:1. 
After-heating of the elastomer: 10 hours at 80.degree. C. 
EXAMPLES 11 TO 13 
To the base prepolymer is added 
3,3',5,5'-tetraethyl-4,4'-diisocyanato-diphenylmethane to give an NCO 
content of 4.5%. This blend is processed with solutions of 30 parts, by 
weight, of diamine in 70 parts, by weight, of the polyadipate used for the 
prepolymer in an NCO:OH+NH.sub.2 ratio of 1.05:1. These diamine solutions 
contained diaza-bicyclo-octane as catalyst. The following diamines were 
used: 
EXAMPLE 11 
##STR16## 
Catalysis: 0.3%, by weight, of diazabicyclo-octane, calculated on the 
diamine solution. 
EXAMPLE 12 
##STR17## 
Catalysis: 0.3%, by weight, of diazabicyclo-octane, calculated on the 
diamine solution. 
EXAMPLE 13 
##STR18## 
Catalysis: 0.15%, by weight, of diazabicyclo-octane, calculated on the 
diamine solution. 
After-heating conditions in Examples 11 to 13: 10 hours at 80.degree. C. 
Comparative Example 10 provides a very long consolidation time with a very 
short casting time. In Examples 11 and 12, very fast consolidation times 
are achieved with a favorable casting time. Example 13 shows that, 
according to the present invention, reactive amines, such as 
4,4'-diamino-diphenylmethane, in the form of the solutions thereof in 
relatively high molecular weight polyhydroxyl compounds may also be 
processed. 
EXAMPLES 14 AND 15 
These Examples show that the effect of the blending operation with 
tetra-alkyl-4,4'-diisocyanato-diphenylmethane is still maintained into 
higher NCO contents (Table 2). 
Base prepolymer: 
Polypropylene glycol of molecular weight 1500 is reacted with toluene 
diisocyanate (65% 2,4-isomer+35% 2,6'-isomer) to produce an NCO-prepolymer 
containing 47% of NCO. 
EXAMPLE 14 
(Comparative) 
To the base prepolymer is added diphenylmethane diisocyanate (60% 
4,4'-isomer+40% 2,4'-isomer) to a resulting NCO content of 6.0%. 
The chain-lengthening diamine mixture according to Example 1 is then added 
to the prepolymer in an NCO:NH.sub.2 ratio of 1.05:1. 
EXAMPLE 15 
To the base prepolymer is added 
3,3',5,5'-tetraethyl-4,4'-diisocyanato-diphenylmethane to give an NCO 
content of 6.0%. 
The diamine mixture of Example 1 is then added to the prepolymer in an 
NCO:NH.sub.2 ratio of 1.05:1. After-heating conditions in both Examples: 
10 hours at 80.degree. C. 
Comparative Example 14 clearly shows shorter, impracticable casting times. 
On the other hand, there are obvious processing advantages of Example 15 
which is according to the present invention. 
TABLE 2 
__________________________________________________________________________ 
Example No. 10 11 12 13 14 15 
__________________________________________________________________________ 
Hardness Shore A 
83 86 81 70 47 46 
Tensile test 
.sigma..sub.100 
MPa 4.27 
5.60 
4.62 
2.51 
12.3 
12.0 
.sigma..sub.300 
MPa 6.72 
8.07 
6.50 
3.86 
22.8 
25.0 
.sigma..sub.B 
MPa 39.3 
49.9 
52.4 
34.5 
31.7 
35.0 
.epsilon..sub.R 
% 662 557 612 
692 361 357 
Tear propagation 
KN/m 53.5 
41.5 
37.9 
25.0 
63.0 
70.5 
resistance 
Rebound elasticity 
% 45 48 49 36 42 43 
Compression set 
(24h/70.degree. C.) 
% 42.4 
40.3 
45.7 
43.5 
-- -- 
Abrasion mm.sup.3 
64 43 53 58 64 65 
(1 kp/40 m) 
Dyn. shear modulus 
MPa -- 17.8 
-- 17.6 
-- -- 
(20.degree. C.) 
Tan .delta. (20.degree. C.) 
-- -- 0.061 
-- 0.12 
-- -- 
T.sub.tan .delta. max 
.degree.C. 
-- -30 -- -23 -- -- 
T.sub.tan .delta. min 
.degree.C. 
-- + 110 
-- +120 
-- -- 
Casting time 
sec 8-10" 
20" 20" 
20" &lt;5"* 
25" 
Solidification 
min 30' 9' &lt;1' 
&lt;1' 4.5' 
3.5' 
__________________________________________________________________________ 
*complications in casting 
Although the invention has been described in detail in the foregoing for 
the purpose of illustration, it is to be understood that such detail is 
solely for that purpose and that variations can be made therein by those 
skilled in the art without departing from the spirit and scope of the 
invention except as it may be limited by the claims.