Note: Descriptions are shown in the official language in which they were submitted.
CA 02239790 1998-06-17
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~ 7
Microcellular polyurethane elastomer contA;n;ng urea groups
Field of the invention
The present invention relates to a microcellular polyurethane
elastomer cont~;n;ng urea groups which is based essentially on
diphenylmethane 4,4'--diisocyanate (4,4~-- MDI) as isocyanate
component and has improved static and dynamic properties. The
lO invention also relates to a process for preparing such a
microcellular polyurethane elastomer and to its use for producing
damping elements.
Prior art
The preparation of cellular polyurethane elastomers, their use
and their mechanical and chemical performance parameters are
comprehensively described in Kunststoffhandbuch, Volume VII,
Polyureth~nes, 1966, 1983 and 1993 by R. Vieweg and A. Hochtlen
20 or G. Oertel (Carl Hanser Verlag, Munich). Essentially, in
comparison with rubber types used in a similar way, microcellular
7polyurethane elastomers have significantly improved damping
properties with excellent volume compressibility, as a result of
which they are favored as constituents of vibration- and shock-
25 damping systems, particularly in the automobile sector.
The most typical example of a microcellular polurethane elastomerfor the above application is probably the reaction product of
naphthylene 1,5-diisocyanate (NDI) and polyethylene glycol
30 adipate having a mean molecular weight of about 2000 g/mol, which
is reacted as NCO prepolymer with an activator-cont~;nn;g 50%
strength aqueous solution of a fatty acid sulfonate. Although the
performance level of this basic formulation has not hitherto been
equalled in respect of its damping characteristics and other
3S static and dynamic performance parameters, the literature does
disclose a few efforts made to replace the NDI responsible for
the excellent elastomeric properties by the far cheaper and
significantly easier-to-handle 4,4'-MDI as isocyanate component,
with distinct property losses being reckoned with. Characteristic
40 differences in perform~nce values between NDI-based and 4,4'-MDI-
based compact polyurethane elastomers in general and micro-
cellular formulations in particular are given by E.C. Proling-
heuer, J.J. Lindsay and ~. Kleimann in Journal of Elastomers and
Plastics, Vol. 21, April 1980. Important disadvantages of a
45 microcellular polyurethane elastomer based on 4,4'-MDI are here
given as a significantly higher degree of damping with greater
material heating and significantly increased consolidation values
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under dynamic loading, which lead to more rapid material wear
compared with NDI.
Despite these obvious disadvantages, it is known from the
5 literature, as already mentioned above, that attempts have been
made to use 4,4'-MDI in place of NDI as isocyanate component in
microcellular polyurethane elastomers. However, these experiments
have been restricted to the use of new raw material components,
in particular relatively high molecular weight polyhydroxyl
lO compounds, by means of which certain property advantages of the
resulting microcellular polyurethane elastomer are to be
achieved.
Thus, EP-A-0496204 describes a process for preparing cellular
15 polyurethane elastomers using polyether carbonate diols con-
t~;n;ng polyoxytetramethylene glycol units having a number-
average molecular weight Mn of from 150 to 500 g/mol as oligomeric
polyhydroxyl compound. This is supposed to improve the mech~n;cal
properties, in particular the extension at break, even at
20 relatively low temperatures. An improvement according to the
invention in the static compressive sets in accordance with DIN
53 572, 70~C, which are known to correlate with the dynamic
consolidation values, cannot be found. Even when using NDI and an
aqueous foaming component as described in the original
25 preparation instructions ~cf. Kunststoffhandbuch, Volume VII, Po-
lyurethane, 1966, 1983 and 1993), only average static compressive
sets are obtained.
EP-A-0243832, which likewise claims the use of 4,4'-MDI, inter
30 alia in combination with water as blowing agent, for preparing
microcellular polyurethane elastomers, enCo~rAcses as significant
inventive concepts the use of a hydroxyl-cont~;n;ng
polycondensate of a short-chain polyoxytetramethylene glycol and
an aliphatic dicarboxylic acid as oligomeric polyhydroxyl
35 compound with the objective of obt~;ning a polyol contA;n;ng
ester groups and capable of being readily metered by pumping for
cellular or compact polyurethane elastomers having improved
mech~n;cal and hydrolytic properties. However, there is no
indication of degrees of perm~nent set on static or dynamic
40 loading, by means of which vibration-resistant materials are
customarily characterized. There is therefore no apparent
relationship between inventive content and the permanent
deformation on static and dynamic loading relevant to
shock-damping materials.
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on the other hand, DE-A-3613961 describes a microcellular
polyurethane elastomer based on 4,4'-MDI which, owing to a
defined composition of the oligomeric polyhydroxyl compound,
namely a copolymer of polytetrahydrofuran and ~-caprolactone, has
5 mechanical properties which represent a favorable compromise
between static strength and dynamic stressability. Despite the
use of expensive polyol starting materials, the performance gain
achieved thereby is only small in terms of the test values
"product lifen, flexural strength by the de Mattia method and
10 perm~nent set at 50% compression. For example, the measured
values for the compressive set, which are directly related to the
dynamic consolidation value which is relevant in practice, show
insufficient implvv~~ -nt for practical use when the invention is
employed. The test criteria ~product life" and flexural strength
15 by the de Mattia method which are used are also not sufficiently
suitable for a realistic evaluation of the dynamic properties,
since they are unable, specifically in the case of partial
property i...~,ove~ents~ to sufficiently differentiate the actual
performance differences between polyurethane elastomers based on
20 ~DI and NDI.
In addition to the improvement described in the abovementioned
DE-A-3613961 by appropriate selection of the oligomeric
polyhydroxyl compound, the isocyanate component has a decisive
25 influence, as can readily be seen from the example of ~DI which
has already been discussed and leads to polyurethane products
having excellent static dynamic elastomeric properties. Thus, the
use of the isocyanates 3,3~-dimethylbiphenyl 4,4~-diisocyanate
(TODI) and para-phenylene diisocyanate (PPDI) likewise results in
30 microcellular and compact polyurethane elastomers having
excellent static and long-term elastic properties. The reason for
this is said to be the very good crystallizability of the rigid
segment formed from urea or urethane groups, which leads to good
separation of this segment from the flexible segment formed from
35 oligomeric polyhydroxyl compounds. On the other hand, the poorer
crystallization tendency of the urea or urethane groups based on
4,4'-MDI resulting from their more angled 3-dimensional structure
is regarded as the essential reason for the significantly
worsened static and long-term elastic properties.
In DE-A-195 09 819, an OH prepolymer is used in addition to the
NCO prepolymer. According to our studies, this variant does give
good demoldability, ie. no destruction of the parts on removal
from the mold, and in addition good technical processability, but
4S the compressive set and tear propagation resistance are
completely unsatisfactory.
~Nn~ SHEE~
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~~ Summary of the invention
It is an object of the present invention to develop as the main
isocyanate component a microcellular polyurethane elastomer on
5 the basis of 4,4 '--MDI which is far cheaper and significantly
easier--to--handle than NDI, TODI and PPDI, which polyurethane
elastomer has, regardless of the type of oligomeric polyhydroxyl
compound used, clearly improved static mechanical properties, in
particular compressive sets, and dynamic consolidation values and
10 is thus particularly suitable for shock-damping systems in motor
vehicle construction.
We have found that this object is achieved by using 4,4'-MDI as
the main isocyanate component to prepare a microcellular
15 polyurethane elastomer cont~;n;ng urea groups, hereinafter
referred to as microcellular PU elastomer, having a urea content
of from 14 to 18% by weight and a structure which, after heating
at from 100 to 120~C for from 8 to 24 hours, is characterized by a
melting range from 130~C as the m;n;r.lm lower limit to 230~C as
20 the m;n; upper limit, measured by the differential sc~nning
calorimetry (DSC) method at a heating rate of 20~C/min, which
melting range can be set by adding Bronstedt or ~ewis acid
reagents in an amount of from 0.01 to 5% by weight, based on the
weight of the components a), b), e) and, if used, c).
The present invention accordingly relates to a microcellular PU
elastomer based on
a) an isocyanate component consisting essentially of
diphenylmethane 4,4'-diisocyanate together with
b) at least one oligomeric polyhydroxyl compound having a ~nmhe~
average molar mass of from 1000 to 5000 g/mol and a
functionality of from 1.7 to 3, preferably 2,
c) if desired, low molecular weight chain extenders and/or
crosslinkers and
d) blowing agents
and also
e) catalysts and, if desired,
45 f) auxiliaries and/or additives,
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which ha~ a urea content of from 14 to 18% by weight, defined as
the amount in percent of urea of the empirical formula Cl4H12ON2
formed from diphenylmethane diisocyanate, based on the total
amount of the elastomer after urea formation, and has, after
5 heating at from 100 to 120~C for from 8 to 24 hours, a melting
range of from 130~C as the ~in;mllm lower limit to 230~C as the
m; nimnm upper limit, measured by differential scanning
calorimetry (DSC) at a heating rate of 20~C/min, which melting
range can be set by adding Bronstedt or Lewis acid reagents in an
10 amount of from 0.01 to 5% by weight, based on the weight of the
components a), b), e) and, if used, c).
The present invention also relates to a process for preparing
such a microcellular PU elastomer having improved dynamic
15 mechanical properties, wherein Bronstedt acid or Lewis acid
reagents are added in an amount of from 0.01 to 5% by weight,
based on the weight of the components a), b), e) and, if used,
c), and the microcellular polyurethane elastomer contA;n;ng urea
groups is heated at from 100 to 120~C for from 8 to 24 hours, and
20 the use of the microcellular PU elastomers for producing damping
elements.
Surprisingly, studies of many variants having different chem;c~
and physical structures of the microcellular PU elastomer based
25 on 4,4'-MDI have shown us that a structure which, after heating
at from 100 to 120~C for from 8 to 24 hours, is characterized by a
melting range from 130~C as the min;mllm lower limit to 230~C as
the minimllm upper limit, measured by DSC at a heating rate of
20~C/min gives a m;ni~-lm compressive set at 80~C. This compressive
30 set, measured after 60% compression for 22 hours at 80~C,
correlates with the consolidation after long-term dynamic
loading, which is important in terms of ~ n~ made in practice,
in that a lower compressive set also corresponds to a desired
lower consolidation value. The elastomers based on 4,4'-MDI and
35 having different chemical structures can be prepared in a known
mAnner, in particular by use of oligomeric polyhydroxyl compounds
comprising various basic building blocks, e.g. contA;n;ng
polyester and/or polyether groups. The structures of the present
invention which can be built up using such chemical building
40 blocks can be produced by use of various means, e.g. an
appropriate reaction procedure involving measures which retard
the isocyanate addition reaction, by an appropriate thermal
post-treatment or the introduction of materials promoting the
formation of these structures by acting as nucleating agents for
45 the structures of the present invention. These measures for
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producing the structures of the present invention can also be
employed in combination for reinforcing the action.
In addition to being characterized by DSC, the novel structures
5 can preferably additionally be described by gel permeation
chromatography (GPC) in a solvent mixture comprising
N,N-dimethylformamide with l ~ of di-n-butyl~m; ne after
dissolution of the microcellular PU elastomer in this mixture at
9O~C by signals at apparent molar masses above 250,000 g/mol. The
lO typical feature of these signals is that they disappear or become
smaller after the addition of lithium chloride. The GPC itself is
carried out using this solution, both with and without LiCl, on a
column set cont~i n ing Ultrastyragel of suitable pore sizes and is
c~l;hrated against PMMA samples as st~ndArd. The detection can be
lS effected both by measurement of the refractive index and by W
- absorption.
The term "apparent molar mass means that these typical high
molecular weight structures o~ greater than 250,000 g/mol result
20 completely or partially not from chemical but pr~Aom;n~ntly from
physical compounds, since they disappear or become smaller in the
presence of O.l mol of LiCl per liter of solution.
It is generally recognized that structures can be described and
25 characterized using DSC and GPC. It is also known that, quite
generally, different structures can be produced from polymers
having the same chemical composition per se: these structures are
important in determ;n;ng the properties which are influenced not
only by the chemical composition alone. A new structure of this
30 type is to be regarded as a new material modification, as is
indicated in known textbooks on the description and characteri-
zation of polymers, e.g. the book "Polymeranalytik" by
Martin Hoffmann, Herbert Krohmer and Rainer Kuhn, published by
Georg Thieme Verlag Stuttgart 1977.
When the material modification of the present invention, which
ca~n be characterized by means of DSC and possibly also GPC under
prescribed conditions, is produced in the microcellular PU
elastomers, these elastomers lln~pectedly have a low compressive
40 set at 80~C and a low dynamic consolidation value.
It is known that there are also quite generally relationships
between such structures and properties of polyurethane elastomers
and that the DSC describes, for example, the degree of molecular
45 order as a structural parameter. Such relationships are described
for PU elastomers by, for example, Th. Timm in the journal
Kautschuk und Gummi Kunststoffe, Year 35, ~o. 7/82. However, it
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~ can in no way be deduced from the general knowledge of
relationships between structure and properties that the
structures claimed in the present invention give the desired good
properties of the cellular PU elastomers based on 4,4'-MDI. It
5 can be easily shown experimentally that cellular PU elastomers
having the same chemical composition but not the structures of
the present invention give only undesirably high compressive sets
and dynamic consolidation values. Bowever, the ch~;cal
composition cannot be selected completely freely, but it should
lO adhere as optimum to a urea content of from 14 to 18% by weight
in the microcellular PU elastomers. Within this urea
concentration range, the compressive sets and dynamic
consolidation values are lowered only when the structures of the
present invention have been produced.
The structures of the present invention cannot be produced using
elastomer building blocks comprising NCO and OH prepolymers
described, for example, in DE-A-195 09 819. These consistently
give only unsatisfactorily high compressive sets and low tear
20 propagation resistances.
The preparation of cellular PU elastomers based on 4,4'-MDI and
having such structures which are favorable for the properties is
not previously known.
Kunststoffhandbuch, Volume VII, Polyurethane 1993 describes as
significant means for improving the compressive set in flexible
foam systems and compact polyurethane elastomers the creation of
additional chemical crosslinking points, for example by means of
30 a limited increase in functionality in the polyurethane-forming
raw materials or by means of sulfur, peroxide and isocyanate
vulc~ni~tion. However, in the case of the microcellular PU
elastomers, these measures worsen, ie. increase, the compressive
set and the dynamic consolidation behavior.
The conventional higher chemical crosslinking for improving the
compressive set thus fails in the case described in the present
invention, and it is completely unexpected that the structures of
the present invention lower the compressive set and the dynamic
40 consolidation without higher chemical crosslinking.
As a result of extensive studies it has been found that the
desired structures of the present invention can be produced using
reaction-retarding substances which are added to the reaction
45 mixture in limited amounts.
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The addition of these reaction-retardinq substances to the
reaction mixture can be carried out at the beginning of or during
the preparation of the prepolymer and/or at the beginning of the
foaming process.
Subst~nc~s which have this action are known Lewis acid or
sronstedt acid reagents which are used in polyurethane chem;stry
primarily for setting reaction times required for technical
process reasons or for obt~;n;ng storage-stable isocyanate-
lO cont~;n;ng polyurethane preparations. These include, ~or example,benzoyl chloride, diethylene glycol bis(chloroformate),
p-toluenesulfonic acid, n-alkylbenzenesulfonic acid and
ethanolamine salts thereof, acetylacetone, ethyl acetoacetate and
mineral acids such as phosphoric and hydrochloric acid.
Type and amount used depend on the particular application.
The production of the structures of the present invention, which
may be characterized by DSC and possibly GPC in the m~nner
20 mentioned, is the main criterion here. It has surprisingly been
found that these structures can be particularly easily produced
by means of latent or delayed-action catalyst systems. These
catalysts become active only after a certain time after mixing
the reacting components, by first retarding the polyurethane and
25 urea formation reactions. Such catalyst systems can, for example,
be mixtures of reaction retardants and reaction accelerators or
materials bearing chemical groups for accelerating and retarding
the reaction in one molecule. The monoethanol~m;ne salt of
n-alkylbenzenesulfonic acid with Cg to C15 is a useful example of
30 such a catalyst.
These reaction-retarding substances are used in an amount of from
0.01 to 5% by weight, preferably from 0.05 to 2% by weight, based
on the weight of the components a), b), e) and, if used, c). In
35 this way, the structures described can be produced in micro-
cellular PU elastomers just by simple foaming in closed molds of
bench batches or of mixtures of the reacting components prefer-
ably prepared in lower pressure foaming m~ch;nes.
40 The production of the structures of the present invention is
considerably aided if the heating of the microcellular PU
elastomer comm~nces ; -~;ately or at the latest 2 hours after
demolding. The characterization of the structures of the present
invention also allows their relative quantification. Thus, for
45 example, when the use of reaction-retarding materials or
molecular groups is combined with immediate thermal post-
treatment directly after demolding, the ratio of the area or the
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height o~ sai~ peaks above 250,000 g/mol in the GPC to the main
peak of the PU elastomer in the range below 250,000 g/mol
increases. This higher ratio ; n~- c~tes a higher content of the
structures of the present invention, which does not occur, or
5 occurs only insufficiently, if the heating is commenced only
after 2 hours after demolding. Owing to the higher amount of
structures of the present invention in the microcellular PU
elastomer, the compressive set and the dynamic consolidation
decrease.
It is an advantage that this measure does not adversely affect
the demoldability or the prescribed cycle times.
It has surprisingly been found that a proportion of dispersed
15 urea in the components a), d) and, if used, e) and f), for
example as reaction product of 4,4'-MDI with water, promotes the
formation of the structures o~ the present invention. The urea
content should here be from 0.05 to 5% by weight, preferably from
0.1 to 1% by weight, based on the total elastomer. This dispersed
20 urea is preferably produced by addition of the appropriate amount
of isocyanate to the aqueous crosslinker component.
The percentage of urea is defined as the amount in percent of
urea of the empirical formula C14Hl20Nz formed from MDI, based on
25 the total amount after urea formation. The stoichiometric amount
of CO2 which is evolved in the formation of the urea from water
and isocyanate is then no longer included in the total amount, as
is shown, for example, in the calculation formula for the total
amount of urea in the microcellular PU elastomer in our Example 1
30 for illustrating the invention.
The urea which promotes the formation of the structures of the
present invention can also be generated in another way, e.g. from
MDI and an amine such as 4,4'-diphenylmethane~; ~mi ne.
Apart from the parameter compressive set as static measure for
the rebound behavior of an elasto~.er ar.d ac a correlation parame-
ter for the consolidation value which is determ;ned under dynamic
conditions and better characterizes the practical ~m~n~ made of
40 a shock-damping system in the motor vehicle sector, further
properties such as tensile strength, elongation at break and tear
propagation resistance serve to comprehensively characterize an
elastomer. The knowledge of these properties determined under
static conditions is particularly important for assessing the de-
45 molding strength and the mechanical stability under dynamicstresses, with the tear propagation resistance having special
significance. It is known that the value of the tear propagation
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resistance in compact polyurethanes is primarily determined by
the respective rigid segment content set by the formulation, ie.
ultimately by its formulation hardness. In the case of cellular
polyureth~nes, the bulk density of the foam is an additional im-
5 portant influencing parameter and must be taken into account whencomr~ring foams of different bulk density.
Microcellular PU elastomers in which polymer structure and cell
formation essentially occur by means of the main reaction between
10 isocyanate and water have a rigid segment based on urea struc-
tures. Increasing the content of rigid urea segments, which can
be achieved by increasing the isocyanate content of the formula-
tion or by increasing the molecular weight of the oligomeric
polyhydroxyl compound while keeping the isocyanate content un-
15 changed, leads to improved tear propagation resistances and ten-
sile moduli, analogously to the compact elastomers. However, this
modification method has only restricted utility, since, on the
one hand, the material-specific parameter compressive strength is
undesirably increased at a particular bulk density and, on the
20 other hand, the carbon dioxide evolution which ~cc~ anies urea
formation and is utilized for the blowing process is significant-
ly increased, so that even when the compressive strength is still
acceptable there are expansion effects in the demolded body with
m~ch~n;cal damage resulting from crack formation.
It has surprisingly been found that the structures of the present
invention are particularly effective for lowering compressive set
and dynamic consolidation, together with good demolding behavior,
only in combination with a urea content of from 14 to 18% by
30 weight. Good demolding behavior requires a comparatively high
strength at the instant of demolding, so that, particularly in
the case of demolding parts having a complicated construction, no
mechanical damage occurs to the microcellular PU elastomer mold-
ing.
The urea content of from 14 to 18% by weight can be set with the
aid of the amount of water in the formulation corresponding to
the formula given in Example 1 for illustrating the invention.
Any urea which may be added or generated prior to prefoaming for
40 promoting the formation of the structures of the present inven-
tion is included in the total amount of urea. However, this
amount is usually negligible compared with the total urea con-
tent.
45 In the urea concentration range below 14% by weight, the struc-
tures of the present invention can no longer be reliably produced
using the abovedescribed measures and/or their action in lowering
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11
compressive set and dynamic consolidation is restricted. In the
concentration range above 18% by weight, the generation of these
structures is likewise no longer reliably possible. In addition,
the expAn~ion effect of the simultaneous Co2 evolution resulting
5 from the reaction of water and isocyanate for producing the urea
is so great that undesired cracks can form in the moldings after
demolding.
For preparing the microcellular PU elastomers of the present in-
lO vention, use is made of, apart from the materials already men-
tioned, the starting components known per se, about which the
following may be said:
a) According to the present invention, the isocyanate component
a) essentially comprises 4,4'-MDI.
However, it can additionally contain further organic and/or
modified organic polyisocyanates. In addition to the
4,4'-MDI, preference is given to using 2,4-- and/or 2,2'- MDI
as well as mixtures of MDI isomers with polyphenylpolymethy-
lene polyisocyanates ~raw MDI) and mixtures of raw MDI and
tolylene diisocyanate.
It is also possible to use modified polyfunctional diphenyl-
methane di- or polyisocyanates, ie. products which are formed
by chemical reaction of the MDI. Examples which may be men-
tioned are di- and/or polyisocyanates based on the diphenyl-
methane structure and cont~;n;ng ester, urea, biuret, allo-
phanate and preferably carbodiimide, isocyanurate and/or ure-
thane groups.
Specific examples based on the diphenylmethane structure are:aromatic polyisocyanates cont~;ning urethane groups and
having NCO contents of from 3 to 33.6~ by weight, preferably
from 4 to 8% by weight, 4,4'-MDI modified, for example, with
low molecular weight diols, triols, oxyalkylene glycols,
dioxyalkylene glycols or polyoxyalkylene glycols having
molecular weights of up to 800, with examples of di- or poly-
oxyalkylene glycols which can be used individually or as
mixtures being: diethylene, dipropylene, polyoxyethylene,
polyoxypropylene and polyoxypropylene-polyoxyethylene
glycols. Also suitable are NCO-cont~;n;ng prepolymers having
NCO contents of from 3 to 31% by weight, preferably from 4 to
8% by weight, with polyester alcohols, for example based on
dicarboxylic acids having from-2 to 12 carbon atoms and
dihydric alcohols. Polyester alcohols which can be used are
those described in more detail under the polyhydroxyl
pr~n~n S~EET
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12
compounds. S;~;l ~rly, it is also possible to use ester-
modified polyethers or ether-modified polyesters.
Also useful are liquid polyisocyanates cont~in;ng carbodiim-
ide groups and/or isocyanurate rings and having NC0 contents
of from 3 to 33.6% by weight, for example those based on
4,4~-, 2,4'- and/or 2,2'-MDI and the corresponding isomer
mixtures, e.g. from 4,4~- and 2,4'- MDI ~ raw MDI and mixtures
of tolylene diisocyanates and raw MDI.
The use of prepolymers of polyisocyanates and representatives
of the components (b) and, if desired, (c) having isocyanate
end groups in place of the isocyanates or together with these
as a mixture is likewise possible.
The diisocyanates mentioned can, if desired, be used together
with about 15 mol% (based on diisocyanate) of a higher-func-
tional polyisocyanate. However, the amount of the higher-
functional polyisocyanate has to be limited in such a way
that a product which is still at least partially soluble in
N,N-dimethylformamide cont~;n;ng 1% of di-n-buty-Am;ne is ob-
tained. A larger amount of higher-functional isocyanates
generally has to be compensated for by the concomitant use of
compounds having an average functionality in the reaction
with isocyanates of less than two and/or isocyanates having
an average functionality of less than two, so that excessive
chemical crosslinking of the product is avoided.
b) Suitable oligomeric polyhydroxyl compounds b) are particu-
larly those having an essentially ~;ne~r molecular chain.
Preference is given to using polyoxyalkylene glycols, essen-
tially polyoxytetramethylene glycols, polyoxyalkylene glycols
modified with carbonate and ester groups, essentially poly-
oxytetramethylene glycols and polyester glycols modified with
carbonate and ester groups and having a number-average molar
mass of from 1000 to 5000 g/mol.
Both the polyoxytetramethylene glycols and modified polyoxy-
tetramethylene glycols cont~;n;ng carbonate and ester groups
can be employed as individual components or in the form of
mixtures. Likewise, the polyester polyols can be employed in-
dividually or in admixture with one another.
Suitable essentially linear polyester polyols can be pre-
pared, for example, from dicarboxylic acids having from 2 to
12 carbon atoms and dihydric alcohols. Examples of suitable
dicarboxylic acids are: aliphatic dicarboxylic acids such as
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succinic acid, glutaric acid, adipic acid, suberic acid, aze-
laic acid and sebacic acid and aromatic dicarboxylic acids
such as phthalic acid, isoph~h~lic acid and terephthalic
acid. The dicarboxylic acids can be used individually or as
mixtures. To prepare the polyester polyols, it may be advan-
tageous to use, in place of the carboxylic acid, the corre-
sponding carboxylic acid derivatives such as carboxylic es-
ters having from 1 to 4 carbon atoms in the alcohol radical,
carboxylic anhydrides or carboxylic acid chlorides. Examples
of dihydric alcohols are glycols having from 2 to 16 carbon
atoms, preferably from 2 to 6 carbon atoms, for example eth-
ylene glycol, diethylene glycol, 1,4-but~ne~iol, 1,5-pentane-
diol, 1,6-he~ne~iol, l,10-dec~ne~iol, 2,2-dimethylpro-
pane-1,3-diol, 1,3-propanediol and dipropylene glycol. De-
pending on the properties desired, the dihydric alcohols canbe used individually or in admixture with one another.
Also suitable are hydroxyl-cont~in;ng polyesters of carbonic
acid with the glycols mentioned, in particular those having
from 4 to 6 carbon atoms, such as 1,4-but~ne~iol and/or
1,6-h~x~ne~iol, condensation products of hydroxycarboxylic
acids, for example ~-hydroxycaproic acid and preferably poly-
merization products of lactones, for example unsubstituted or
substituted ~-caprolactones.
As polyester polyols, preference is given to using ethanediol
polyadipate, 1,4-butanediol polyadipate, eth~ne~iol butane-
diol polyadipate, 1,6-h~x~ne~iol-neopentyl glycol polyadi-
pate, 1~6-hex~nediol-l~4-butanediol polyadipate and polyca-
prolactones.
Suitable polyoxyalkylene glycols, essentially polyoxytetrame-
thylene glycols, cont~ining ester groups are polycondensates
of organic, preferably aliphatic, dicarboxylic acids, in par-
ticular adipic acid, with polyoxymethylene glycols having anumber-average molecular weight of from 162 to 600 and
aliphatic or non-aliphatic diols, in particular 1,4-butane-
diol. Other suitable polyoxytetramethylene glycols cont~in;ng
ester groups are the polycondensates formed with ~-caprolac-
tone.
Suitable polyoxyalkylene glycols, essentially polyoxytetra-
methylene glycols, cont~;n;ng carbonate groups are polycon-
densates of these with alkyl or aryl carbonates or phosgene.
AMENDED SHEET
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14
c) In the preparation according to the present invention of the
microcellular PU elastomer, it is possible to use low molecu-
lar weight chain extenders and/or crosslinkers c).
Suitable chain exten~e~s and/or crosslinkers usually have
molecular weights of less than 500, preferably from 60 to
400. Examples of chain exter~ rs/crossl; nk~rs which can be
used are ~lkAnediols having from 2 to 12 carbon atoms,
preferably having 2, 4 or 6 carbon atoms, such as ethanediol,
1,3-prop~n~iol, 1,5-pentanediol, 1,6-heY~ne~iol, 1,7-hepta-
nediol, 1,8-oct~neA;ol, l,9-nonAn~;ol, 1,10-~ec~ne~;ol and
preferably 1,4-but~ne~;ol, dialkylene glycols having from 4
to 8 carbon atoms, such as diethylene glycol and dipropylene
glycol, and difunctional to tetrafunctional polyoxyalkylene
polyols having a molecular weight of up to 500. However,
other suitable c~ po~nds include br~nche~-chain and/or unsat-
urated alkanediols having usually not more than 12 carbon
atoms, such as 1,2-prop~neA;ol, 2-methylpropane-1,3-diol,
2,2-dimethylpropane-1,3-diol, 2-butyl-2-ethylpropane-
1,3-diol, but-2-ene-1,4-diol and but-2-yne-1,4-diol, diesters
of terephthalic acid with glycols having from 2 to 4 carbon
atoms, such as the bis(ethylene glycol) or bis(1,4-butane-
diol) ester of terephthalic acid, hydroxyalkylene ethers of
hydroquinone or resorcinol, such as 1,4-di(~-hydroxyethyl)-
hydroquinone or 1,3-di(~-hydroxyethyl)resorcinol~
~lk~nolamines having from 2 to 12 carbon atoms, such as
ethanol;lm;ne~ 2-aminopropanol and 3-amino-2,2-dimethyl-
propanol, N-alkyl~;~lk~nolamines such as N-methyldiethanola-
mine and N--ethyl--diethanol~m;ne~
Examples of higher-functional crossl ;nk~rs are trihydric and
higher-functional alcohols such as glycerol, trimethylolpro-
pane, pentaerythritol and trihydroxycyclohexanes, and also
tr;~lk~nolamines such as triethanol ~m; ne
Chain exten~ers which have been found to be very useful and
are therefore preferably used are alkyl-substituted aromatic
poly~m;nes having molecular weights of preferably from 122 to
400, in particular primary aromatic ~ m;r~es having in the
ortho position relative to the amino groups at least one
alkyl substituent which reduces the reactivity of the amino
group by steric hindrance, which are liquid at room tempera-
ture and are at least partially, but preferably completely,
miscible with the relatively high molecular weight, at least
difunctional compounds (b) and N-perethoxylated polyoxyalky-
lene polyamines (c) under the processing conditions.
AMFNn~n SHEET
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To prepare the microcellular Pu elastomers, use is advanta-
geously made of the industrially readily available
1,3,5-triethyl-2,4-phenylene~i~m ine, 1-methyl-3,5-di-
ethyl-2,4-phenylene~i~ine, mixtures of 1-methyl-3,5-di-
ethyl-2,4- and 2,6-phenylene~i~mines, known as DETDA, isomer
mixtures of 3,3'-dialkyl- or 3,3',5,5'-tetraalkyl-substituted
4,4~ minodiphenylmethanes having from 1 to 4 carbon atoms
in the alkyl radical, in particular 3,3',5,5'-tetraalkyl-
substituted 4,4'~ minodiphenylmethAn~s cont~ining bonded
methyl, ethyl and isopropyl radicals, and also mixtures of
said tetraalkyl-substituted 4,4'-~i~inodiphenylmethanes and
DETDA.
To achieve specific ~ch~nical properties, it can also be ad-
vantageous to use the alkyl-substituted aromatic poly~m;nes
in admixture with the abov ~ntioned low molecular weight
polyhydric alcohols, preferably dihydric and/or trihydric
alcohols or dialkylene glycols.
The low molecular weight chain exten~rs and/or crosslink~rs
are thus selected, in particular, from the group consisting
of low molecular weight difunctional and/or trifunctional
alcohols, difunctional to tetrafunctional polyoxyalkylene
polyols having a molecular weight of up to 500 and alkyl-
substituted aromatic ~iAm;neS or mixtures of at least two ofthe chain ext~n~ers and/or crossl;nkers mentioned.
d) According to the present invention, the blowing agent d) used
is preferably water which reacts with isocyanate groups to
form carbon dioxide.
The amounts of water which can be advantageously used are
from 0.01 to 5% by weight, preferably from 0.3 to 3.0% by
weight, based on the weight of the components (b) to (c).
However, it is also possible to use other blowing agents cus-
tomary in the preparation of polyure~h~nes. Examples of suit-
able blowing agents are low-boiling liquids which vaporize
under the action of the exothermic polyaddition reaction.
Suitable liquids are those which are inert toward the organic
polyisocyanate and have boiling points below 100~C. Examples
of such preferred liquids are halogenated, preferably fluori-
nated, hydrocarbons such as methylene chloride and dichloro-
monofluoromethane, perfluorinated or partially fluorinated
hydrocarbons such as trifluoromethane, difluoromethane,
difluoroethane, tetrafluoroethane and heptafluoropropane,
hydrocarbons such as n- and iso-butane, n- and iso-pentane
AM~NDED SHEET
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16
and the industrial mixtures of these hydrocarbons, propane,
propylene, hex~ne, heptane, cyclobutane, cyclopentane and
cyclohe~nQ, dialkyl ethers such as dimethyl ether, diethyl
ether and furan, carboxylic esters such as methyl formate and
ethyl formate, ketones such as acetone, and fluorinated and/
or perfluorinated tertiary alkyl~;nes such as perfluorodi-
methylisopropylamine. Mixtures of these low-boiling liquids
with one another and/or with other substituted or unsubsti-
tuted hydrocarbons can also be used.
The most advantageous amount of low-boiling liquid for
producing such cellular elastomer moldings from elastomers
cont~;n;ng bonded urea groups depends on the desired density
and on the amount of water concomitantly used. In general,
amounts of from l to 15% by weight, preferably from 2 to 11%
by weight, based on the weight of the components (b~ and (c),
give satisfactory results.
e) To accelerate the reaction, catalysts (e)r either individual-
ly or in admixture with one another, are added to the reac-
tion mixture. These are preferably organic metal compounds
such as tin(II)salts of organic carboxylic acids, e.g.
tin(II) dioctoate, tin(II) dilaurate, dibutyltin diacetate
and dibutyltin ~ ~ate, and tertiary amines such as tetra-
methylethylene~;~m;ne, N-methylmorpholine, diethylbenzyl-
amine, triethylamine, dimethylcyclohexyl~mine, diazabicy-
clooctane, N,N'-dimethylpiperazine, N-methyl-N'-(4,N-dime-
thylaminobutyl)piperazine, N,N,N',N",N"-pentamethyldiethyl-
ene~;~;ne or the like.
Further suitable catalysts are:
amidines, such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine,
tris(dialkylaminoalkyl)-s-hexahydrotriazines, in particular
tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine, tetra-
alkylammonium hydroxides such as tetramethylammonium hydrox-
ide, alkali metal hydroxides such as sodium hydroxide and
alkali metal alkoxides such as sodium methoxide and potassium
isopropoxide, and also alkali metal salts of long-chain fatty
acids having from 10 to 20 carbon atoms and possibly lateral
OH groups.
Depending on the reactivity required, the activators are
employed in amounts of from 0.001 to 0.5% by weight, based on
the prepolymer.
AMENDED SHEET
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-j OOSO/46847
17
f) In the preparation according to the present invention of the
microcellular PU elastomer, use can be made of, in addition
to the reaction-retarding substances mentioned above, further
a~lx;l;~ies and additives f).
These include, for example, surface-active substances, hydro-
lysis inhibitors, antioxidants, cell regulators, flame retar-
dants and dyes.
Suitable surface-active substances are compounds which aid
the homogenization of the starting materials and may also be
suitable for regulating the cell structure. Examples which
may be mentioned are emulsifiers such as the sodium salts of
castor oil sulfates or of fatty acids and also amine salts of
fatty acids, e.g. diethyl~m;ne oleate, diethanolamine stea-
rate, diethanolamine ricinoleate, salts of sulfonic acids
e.g. ~lk~l; metal or ammonium salts of dodecylbenzene- or
dinaphthylme~hAne~iculfonic acid and ricinoleic acid; foam
stabilizers such as siloxane-oxyalkylene copolymers and other
organopolysiloxanes, ethoxylated alkylphenols, ethoxylated
fatty alcohols, paraffin oils, esters of castor oil or rici-
noleic acid, Turkey red oil and peanut oil; and cell regula-
tors such as paraffins, fatty alcohols and dimethylpolysilox-
anes. The surface-active substances are usually employed in
amounts of from 0.01 to 5 parts by weight, based on 100 parts
by weight of the components (b) to (d).
For the purposes of the present invention, fillers are the
customary organic and inorganic fillers known per se. Spe-
cific examples are: inorganic fillers such as silicieous min-
erals, for example sheet silicates such as antigorite, ser-
pentine, hornblends, amphiboles, chrysotile, talc and zeo-
lites, metal oxides suGh as kaolin, aluminum oxides, titanium
oxides and iron oxides, metal salts such as chalk, barite and
inorganic pigments such as cadmium sulfide and zinc sulfide.
Preference is given to using kaolin (china clay), alllminllm
silicate and coprecipitates of barium sulfate and alnminllm
silicate and also natural and synthetic fibrous minerals such
as wollastonite or glass fibers of various lengths, which may
if desired be coated with a size. Examples of suitable
organic fillers are: carbon black, melamine, rosin, cyclo-
pentadienyl resins and graft polymers based on styrene-
acrylonitrile which can be prepared by in situ polymerization
of acrylonitrile/styrene mixtures in polyoxyalkylene polyols
as described in the German patents 11 11 394, 12 22 669,
(US 3 304 273, 3 383 351, 3 523 093), ll 52 536
(GB 1 040 452) and 11 52 537 (GB 987 618) and can then, if
AM~ nFn SHEET
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18
desired, be aminated, and also polyoxyalkylene polyol or
polyoxyalkylene polyamine fillers in the case of which
aqueous polymer dispersions are converted into polyoxy-
alkylene polyol or polyoxyalkylene polyamine dispersions. The
inorganic and organic fillers can be used individually or as
mixtures.
The inorganic and/or organic fillers can be incorporated into
the reaction mixture in amounts of, for example, from 0.5 to
35% by weight, preferably from 3 to 20% by weight, based on
the weight of the components (a) to (d).
Suitable flame retardants are, for example, tricresyl phos-
phate, tris-2-chloroethyl phosphate, tris(chloropropyl) phos-
phate and tris-2,3-dibromopropyl phosphate.
Apart from the halogen-substituted phosphates mentioned
above, it is also possible to use inorganic flame retardants
such as hydrated aluminum oxide, antimony trioxide, arsenic
oxide, ammonium polyphosphate and caloium sulfate or
melamine, expanded graphite or mixtures thereof, for example
mixtures of mel~m;ne, expAn~e~ graphite and/or ammonium
polyphosphate ! for making the moldings flame resistant. In
general, it has been found to be advantageous to use from 5
to 50 parts by weight, preferably from 5 to 25 parts by
weight, of the flame retardants mentioned per 100 parts by
weight of the components (b) to (d).
Further details regarding the abovementioned other customary
~ ries may be found in the specialist literature, for
example the monograph by J.H. Saunders and R.C. Frisch ~High
Polymers" Volume XVI, Polyurethanes, Parts 1 and 2, Inter-
science Publishers 1962 or 1964, or the Kunststoff-Handbuch,
Polyurethane, Volume VII, Hanser-Verlag, Munich, Vienna, 1st
and 2nd editions, 1966 and 1983.
... .. .
T~e microcellular PU elastomers of the present invention are
advantageously prepared by the one-shot process by means of the
low-pressure technique or, in particular, the reaction injection
40 molding (RIM) technique in open or preferably closed molds. In
particular, the reaction is carried out with compaction in a
closed mold. The reaction injection molding technique is des-
cribed, for example, by H. Piechota and H. Rohr in "Integral-
sch~llmctoffe", Carl Hanser-Verlag, Munich, Vienna 1975;
45 D.J. Prepelka and J.L. Wharton in Journal of Cellular Plastics,
~ ~NV :V SHEET
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CA 02239790 1998-06-17
0050~46847
19
March/April 1975, pages 87 to 98 and U. Knipp in Journal of Cel-
lular Plastics, March/April 1973, pages 76-84.
When using a ~;x;~g chamber having a plurality of feed nozzles,
5 the starting components can be fed in indiv;~ y and inten-
sively mixed in the mixing chAmh~r. It has been found to be
advantageous to use the two-component process.
According to a particularly advantageous embodiment, a prepolymer
lO contA;n;ng NCO groups is first prepared. For this purpose, the
oligomeric polyhydroxyl compounds b), if desired together with
low molecular weight chain ext~rs and/or crosslinkers c), are
reacted with the isocyanate component a) consisting essentially
of 4,4'-MDI at from 80~C to 160~C, preferably from 110~C to 150~C.
15 The reaction time is such that the theoretical NCO content is
reached.
Blowing agents d) and catalysts e) and any further anxil;Aries
and/or additives f) used are usually combined in a crossl;nk~r
20 component.
The production of the microcellular moldings is advantageously
carried out using only water as blowing agent and chain extender
at an NCO/OH ratio of from 0.85 to 1.20 and also catalysts e) in
25 the presence of auxiliaries and/or additives f), with the NCO
prepolymer heated to from 80 to 110~C being intensively mixed with
water, catalyst and auxiliaries and/or additives and placed, in
an amount corresponding to the desired density of the molding, in
a heated, tightly closing mold. The moldings are cured and there-
30 fore Le.,.o~able from the mold after from 10 to 40 minutes.
The amount of reaction mixture introduced into the mold is usual-
ly such that the moldings obtA;neA have a density of from 250 to
1400 kg/m3, with the compact moldings having a density of prefer-
35 ably from 1000 to 1400 kg/m3 and in particular from 1000 to1200 kg/m3, and the microcellular moldings preferably having a
density of from 300 to 1000 kg/m3, in particular from 350 to
800 kg/m3. On introduction into the mold, the starting components
usually have a temperature of from 15 to 80~C, preferably from 30
40 to 65~C. The mold temperature is advantageously from 20 to 110~C,
preferably from 35 to 95~C. The degrees of compaction for
producing the microcellular or cellular moldings are from 1.1 to
8, preferably from 2 to 6.
AMENDED S~EET
CA 02239790 1998-06-17
DD~/46847
Comr~ed with the microcellular PU elastomers based on NDI, the
internal mold pressure in the case of the PU elastomers of the
present invention based on MDI is considerably increased (up to
about 50%), so as to obtain the same foam density.
~o improve the demolding of the elastomer moldings produced
according to the present invention, it has been found to be
advantageous to coat the inner surfaces of the mold with
customary external mold release agents, for example those based
10 on wax or silicone, or in particular with aqueous soap solutions,
at least at the commencement of a production run. However,
release agents which have been found to be particularly useful
and are therefore preferably used are internal mold release
agents as are described, for example, in EP-A-153 639, EP-A-
15 180 749 (AU 85/47 498), EP-A-173 888 (US 4 519 965), WO 84/03288
(EP-A-119 471) and Wo 86/01215. The molding times are on average
from 3 to 60 seconds, depending on the size and geometry of the
molding.
20 The microcellular PU elastomers prepared according to the present
invention have bulk densities of from 350 to 800 g/l and are pre-
ferably used as spring and damping elements in the motor vehicle
sector and the industrial sector.
25 The following examples illustrate the invention.
Example 1
Preparation of the prepolymer cont~;n;ng NCO groups
100 parts by weight (ppw) of a previously dewatered linear poly-
ether-polyester polyol having a mean OH number of 56 mg ROH/g,
namely a polycondensate of a short-chain polytetrahydrofuran
having an average molecular weight of 250 g/mol and adipic acid,
35 were reacted with 0.3 ppw of trimethylolpropane and 38 ppw of
4,4'-MDI at 115~C while stirring continually. This gave a
prepolymer having an NCO content of 5.68%.
a) Production of the moIding (comparison)
To 100 ppw of this prepolymer which had previously ~een brought
to a temperature of 90~C were added, while stirring vigorously,
4.2 ppw of a crosslinker component having a water content of
26.7% by weight and comprising a mixture of St~h~ol 1, a
45 sterically h; nfl~red carbodiimide known to those skilled in the
AME~DED S~EET
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21
art for hydrolysis inhibition, and ethoxylates of ricinoleic and
oleic acid.
In addition, 0.05 ppw of Desmorapid PP (Rhein-Chemie GmbH) for
5 catalyzing the blowing reaction and 0.2 ppw of silicone oil DC
193 (Air Products and Chemicals, Inc.) for improving the cell
structure were added to the reaction mixture. After a total stir-
ring time of 8 s, the reaction mixture was placed in a closable
mold heated to 90~C and was cured for 25 minutes. After removing
O the microceliuiar product f r 0111 the rold, the ...old L.g wa~ given
24 hours' int~rm~ te storage in order to guarantee ~;~Anciona
stability; this is necessary because of expansion effects. The
material was then subjected to further ~herm~l curing at 110~C for
16 hours.
The microcellular PU elastomer produced in this way did not have
the structures of the present invention, since melting above 230~C
no longer took place. Moreover, GPC signals in the range above
250,000 g/mol were not observed.
b) Production of the molding (according to the present inven-
tion)
100 ppw of the same prepolymer were reacted under identical pro-
25 cess conditions with 4.2 ppw of the crosslinker mixture described
in Example la) with addition of 0.07 ppw of a mixture of ethoxy-
lated oleic acid having on average 9 ethoxy units and of the
monoethanol~m;ne salt of n-alkylbenzenesulfonic acid having alkyl
radicals from CgHl9 to Cl5H31. The blowing reaction here proceeded
30 visibly more slowly. The further procedure was then similar to
that of Example la).
For the products produced according to la) and lb), melting
graphs were recorded at a heating rate of 20~C/min using a DSC 7
35 from Perkin-Elmer. In addition, characteristic static properties
were determ;ne~ in accordance with DIN standards and gel permea-
tion chromatograms were recorded. For this purpose, the heated
samples were dissolved with good stirring in a mixture of
N,N-dimethylformamide (DMF) cont~;n;ng l~ of di-n-butyl~m;ne at
40 90~C. The dissolution time was 2 hours, the concentration was 10%.
These 10% strength solutions were chromatographed without dilu-
tion. Chromatography was carried out using DMF as mobile phase on
a column set with Ultrastyragel 106 A, 104 A, 103 ~, 500 A, loo A.
In addition to the main peak at a retention time of 48.2 minutes,
45 a peak appeared at 39.8 minutes. After addition of 0.1 M lithium
~M~NnFn SHEET
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22
chloride (~.1 mol of LiCl per 1 1 of the total solution ), the
peak at 39.8 min disappeared completely.
Both the peak at 39.8 min which according to the table below cor-
5 responds to a molar mass far above 250,000 g/mol and the disap-
pearance of this peak in the presence of LiCl, in our case
0.1 mol per liter, are characteristics of the structures of the
present invention.
10 The calibration using defined polymethyl methacrylate (PMMA) sam-
ples is shown in the table below:
Retention time Molar mass
in min in g/mol
39.68 810,000
41.25 530,000
43.45 280,000
46.24 152,000
47.96 85,100
53.32 30,500
58.47 7100
59.81 3500
Plotting the logarithm of the molar mass against the retentiontime gave, in a known manner, a straight calibration line between
30 the retention times 39.68 and 58.47 min. The chromatogram also
displayed signals at molar masses greater than 810,000 g/mol
which can likewise be designated as ~greater than 250,000 g/mol~'
as per the present invention and disappear on addition of LiCl,
thus indicating the structures of the present invention although
35 they lie outside the calibration range. Detection was carried out
by measurement of the index of refraction and/or of ultraviolet
absorption at 265 nm. The detection method has no influence on
the results in the context of this invention.
40 The compressive stress was measured by a modification of the
method of DIN 53 572, at 80~C, 22 hours and 60% compression using
spacers having a height of lô mm and test specimens having a base
area of 40 x 40 mm and a height of 30 ~ 1 mm.
45 The calculation is in accordance with the following equation
~F~n~n SHEET
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23
Cs (%) = h~ h2 x 100 %
ho = original height of the test specimen in mm
5 hl = height of the test specimen in the deformed state in mm
h2 - height of the test specimen after release of the load in mm.
The microcellular PU elastomers produced as described in Examples
1 a and 1 b had a urea content of 16.3% by weight.
The urea content was calculated under the assumption of complete
conversion of the polyurethane-forming reactants and complete
evolution of CO2 according to the following equation
% UR mHzO + mMDI ~ mCO2 x 100
20 m~~ ~ amount of polyol used in the formulation
mMDI = amount of 4,4'-MDI available for the reaction with water
mMDI = amount of 4,4~-- MDI used in the formulation
mcOZ ~ amount of CO2 formed in g at stoichiometric conversion
mH20 = amount of water used
25 mCC = amount of chain extender/crosslinker used
In Example 1 b, the structures of the present invention were
present, as a result of which the compressive set dropped consid-
erably in comparison with the microcellular elastomer of Example
30 1 a which had the same chemical composition but not the
structures (see Table 1).
Example 2 a (according to the present invention)
35 Preparation of the prepolymer
The preparation of the NCO-cont~;n;ng prepolymer from a linear
polyether-polyester polyol was carried out in a S;mi 1 ~r way to
Example 1. 100 ppw of this polyol were reacted with 0.3 ppw of
40 trimethylolpropane and 33 ppw of 4,4~-- MDI at 120~C with continual
stirring. The prepolymer formed had, after complete reaction, an
NC0 content of 4.78% by weight.
A~NnFn SHEET
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24
Production of the molding
lOO ppw of the prepolymer were reacted at 9O~C with 2.64 ppw of a
crosslinker mixture having a water content of 36.3% by weight and
5 comprising St~h~Xol 1, a mixture of ethoxylated oleic and ricino-
leic acid, the monoethanol ~mi ne salt of n-alkylsulfonic acid and
the sodium salt of sulfated castor oil with vigorous stirring and
addition of 0.03 ppw of Desmorapid PP and 0.2 ppw of silicone oil
DC 193 and poured into a mold heated to 9O~C. After a molding time
10 of 25 minutes and an int~rm~i~te storage time of 24 hours, the
microcellular polyurethane was heated at 110~C for 16 hours. The
static -chAn;cal parameters and a DSC melting graph and a gel
permeation chromatogram were then recorded.
15 The product tested had a calculated urea content of 13.4% by
weight. It thus displayed essential features of the invention,
but a somewhat lower urea content compared with the recomm~n~e~
value of - 14~ by weight.
20 Example 2 b (according to the present invention)
Preparation of the prepolymer
The NCO prepolymer was prepared as described in Example 2 a
25 except that 37 ppw of the isocyanate were used in place of 33 ppw
of 4,4~- MDI . The completely reacted prepolymer had an NCO content
of 5.65% by weight.
Production of the molding
100 ppw of the prepolymer which had been brought to a temperature
of 90~C were reacted with 3.1 ppw of the crosslinker mixture used
in Example 2 a. Demolding and further treatment of the material
were likewise carried out as described in Example 2 a.
The static mechanical parameters, the DSC melting behavior and a
gçl permeation chromatogram were measured on the microcellular
polyurethane elastomer which had a calculated urea content of
15.7% by weight.
In ~omr~rison with Example 2 a, there was a distinct increase in
the size of the GPC peak at greater than 250,000 g/mol relative
to the main peak indicating the actual polymer chain at about
lO0,000 g/mol and thus there was an increase in the content of
45 the structures of the present invention in the elastomer. This
was also reflected in a somewhat higher DSC melting range and, as
AMENDED SHEET
CA 02239790 1998-06-17
0050/46847
a result, a lower compres~ive set acc~r~n;ed by impLuvl -nt in
other mechanical parameters
Example 3 a (according to the present invention, heating after 30
5 minutes' intel -~;Ate storage)
Preparation o~ the NC0 prepolymer
100 ppw of a dewatered linear polyether-polyester polyol having
10 the composition corresponding to Example 1 were reacted with
0.3 ppw of trimethylolpropane and 38 ppw of 4,4'-MDI at 115~C with
intensive mixing. The NC0 content of the finished prepolymer was
measured as 5.65% by weight.
15 Production of the molding
100 ppw of the prepolymer were reacted at 90~C with 3.1 ppw of a
crosslinker whose composition corresponded to that of the cross-
1; nker component of Example 2 a with addition of 0.03 ppw of Des-
20 morapid PP and 0.2 ppw of silicone oil DC 193 and poured into atightly closing mold heated to 90~C.
After a molding time of 30 minutes and int~ te storage for
30 minutes, the polyurethane molding was further cured at 110~C
25 for 16 hours.
The usual static parameters, a DSC melting curve and a gel
permeation chromatogram were measured on the microcellular poly-
urethane elastomer thus obt~; ne~ .
Example 3 b (according to the present invention, heating after
24 hours~ inte ~;~te storage)
The preparation of the NC0 prepolymer and the production of the
35 molding, including its post-treatment and characterization, were
carried out as described in Example 3 a, except that the inter-
mediate storage time of the molding was 24 hours.
Examples 4 a and b
Preparation of the NC0-cont~; n; ng prepolymer (according to the
present invention)
a) 100 ppw of a polyesterol mixture comprising equal parts of
45 polycondensates of an equimolar mixture of monoethylene glycol
and 1,4-butanediol having average molecular weights of 2000 g/mol
were reacted with 0.3 ppw of trimethylolpropane and 35 ppw of
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4,4'-MDI, to which 15 ppm of diethylene glycol bis(chloroformate)
had been added beforehand, at 115~C with intensive stirring. After
the reaction was complete, the NCO content was measured as 5.12
by weight.
b) The synthesis of the prepolymer was carried out using the same
amounts of raw materials and identical process conditions as des-
cribed under 4 a, except that the addition of the diethylene gly-
col bis(chloroformate) was omitted. The NCO content of the prepo-
lO lymer was measured as 5.26% by weight.
For Examples 4 a and 4 b, the moldings were produced in the sameway, with lO0 ppw of the prepolymer being reacted at 90~C with
2.82 ppw in the case of Example 4 a and with 2.90 ppw in the case
15 of Example 4 b of the crosslinker mixture described under
Example 2 a, with good homogenization of the mixture. The reac-
tion mixture was subsequently poured into a mold heated to 90~C.
After a molding time of 25 minutes, the mold was opened, the
microcellular polyurethane molding was taken out and, after
20 int~rm~ te storage for 24 hours, was further cured for 16 hours
at 110~C. The fully reacted material which had a calculated urea
content of 14.6~ by weight was tested in respect of its static
m~ch~n;cal parameters, it dynamic consolidation, the GPC behavior
and its DSC melting characteristics.
Example 4 c (Comparison)
The prepolymer was synthesized as in Example 4 b.
30 In contrast to Examples 4 a and 4 b, the moldings were produced
using the crossl; nk~r mixture described in Example 1 a, with
100 ppw of the prepolymer being reacted at 90~C with 3.94 ppw of
crossl inker mixture, with good homogenization of the reaction
mixture, and poured into a mold heated to 90~C. The elastomer
35 molding taken from the mold after a molding time of 25 minutes
was further treated and tested as described under 4 b.
Example 5 (Comparison)
40 Preparation of the NCO prepolymer
100 ppw of a dewatered li ne~r polyether-polyester polyol having
the composition corresponding to Example 1 were reacted with
24 ppw of Desmodur lS ~naphthylene diisocyanate) at 140~C with
45 intensive homogenization of the reaction mixture. The Desmodur 15
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was added as a solid. The NCO content of the fully reacted
prepolymer was 3.92% by weight.
Production of the molding
100 ppw of the prepolymer heated to 90~C were reacted with 2.9 ppw
of the crosslinker mixture described in Example 1 a with addition
of 0.03 ppw of Desmorapid and 0.2 ppw of silicone oil DC 193. The
reaction mixture was then, as in the previous examples, poured
lO into a mold heated to 9O~C. After a molding time of 25 minutes,
the molding was given 24 hours' intermediate storage, heated at
120~C for 16 hours and tested in respect of its mechanical para-
meters.
15 Examples 6 a to c (machine test)
Preparation of the NCO prepolymer
14 000 ppw of a previously dewatered polyester polyol mixture
20 contA;n;ng ether groups and comprising 12 838 ppw of a polycon-
densate of a short-chain polytetrahydrofuran having an average
molecular weight of 250 g/mol and adipic acid and 1162 ppw of a
polycondensate of the same short-chain polytetrahydrofuran, tri-
methylolpropane and adipic acid, with the mixing ratio of the
25 polyols being selected in such a way that the trimethylolpropane
content was 3 g/1000 g of the total polyol mixture, were reacted
with 5320 ppw of 4,4'-MDI at 115~C with intensive stirring. The
NCO content of the prepolymer was measured as 5.97% by weight.
30 a) Foaming was carried out using a low-pressure foaming machine
at a mixer rotation rate of 2700 rpm and a total output of
18.9 g/s. The mixing ratio of prepolymer to crosslinker
component was 100:4.25.
The crosslinker mixture, which had a water content of 28.1%,
comprised Stabaxol 1, a mixture of ethoxylated oleic and
rlcinoieic acids, the monoethanolamine salt of n-alkyl-
sulfonic acid having Cg-Cl5-alkyl radicals and the sodium salt
of sulfated castor oil. 0.03 ppw of Desmorapid PP and 0.2 ppw
of silicone oil DC 193, based on the prepolymer component,
were added to the crossl ;nker mixture. The reaction mixture
was placed in tightly closing test spring and block molds
heated to 90~C, and these were opened after 30 minutes. After
an intermediate storage time of at most 30 minutes, the
moldings were heated for 16 hours at 110~C.
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b) Prepolymer preparation, formulation and technical process
conditions for production of moldings corresponded completely
to the procedures of Example 6 a except for the way in which
the thermal post-treatment was carried out. The only change
made was in the int~ te storage time between demolding
and heating, which was increased to 24 hours.
c) Formulation and preparation of the prepolymer and also the
method by which the thermal post-treatment was carried out
corresponded to Example 6 a. However, the composition of the
cross-; nker mixture was modified from that given in Example 6
a, viz. 0.02 ppw of 4,4'-MDI, based on 100 ppw of the
prepolymer, were added to the crossl; nke~ mixture with
vigorous stirring. This gave, within 30 seconds, a finely
divided urea-crossl ;nker dispersion which was stable on
storage for at least 4 hours. The urea content calculated for
complete conversion of the isocyanate groups and for a
stoichiometric reaction was about 0.017 ppw per 4.25 ppw of
crosslinker component. The further procedure for production
of moldings including post-treatment was as described in
Example 6 a.
For the microcellular PU elastomers obtained as described in
Examples 6 a to 6 c, which had a urea content of 16.3% by weight,
25 the DSC melting curves, gel permeation chromatograms and the
usual static parameters were recorded and in addition constant-
energy dynamic tests on a test spring were carried out by means
of a hydropulser. The test spring had a cylindrical shape with a
height of 100 mm, an external diameter of 50 mm and an internal
30 diameter of 10 mm and possessed three segment constrictions.
After subjecting the test spring to lO0,000 loading cycles at a
load of 6 kN and a frequency of 1.2 Hz, the consolidation was
measured as the difference between the final and the initial
heights of the spring and was a measure of the compressive
35 deformation during the cyclic fatigue test. The greater the
rebound measured, the lower was the consolidation and the better
the dyn&.,ic perfor.-.,a,.ce of the r..aterial. The test under lorce-
regulated conditions thus allowed a realistic prediction of
material suitability for shock-damping systems in motor vehicle
40 construction.
Example 7 Machine test (Comparison)
Preparation of the prepolymer
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14,000 ppw of the previously dewatered polyol mixture having a
composition as in Example 6 a were reacted with 4900 ppw of
4,4~-MDI at 115~C with intensive mixing. The NCO content of the
completely reacted prepolymer was measured as 5.39% by weight.
Production of the molding
Foaming was carried out by a method similar to Example 6 a using
a low-pressure machine at a mixer rotation rate of 2700 rpm and
10 an output of 18.9 g/s.
The mixing ratio of prepolymer and crosslinker component was
adjusted to 100:4.28. The composition of the crosslinker mixture
was the same as in Example 1 a. 0.03 ppw of Desmorapid PP and
15 0.2 ppw of silicone oil DC 193, based on the prepolymer compo-
nent, were added to the crosslinker mixture prior to foaming. The
reaction mixture was introduced into test spring and block molds
heated to 90~C, and the molds were ;~ tely closed tightly.
After a molding time of 25 minutes, the molds were opened, the
20 microcellular moldings were given 24 hours' intermediate storage
and were subsequently subjected to further curing for 16 hours at
110~C.
Apart from the testing of the static parameters of DSC and GPC
25 analysis, the dynamic consolidation of the test springs was de-
termined under constant-energy conditions.
The parameters determined in Examples 1 to 7 are summarized in
Tables 1 and 2.
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