U.S. patent application number 11/699087 was filed with the patent office on 2007-07-05 for polyurethane cast elastomers made of nco prepolymers based on 2,4'-mdi and a process for their preparation.
Invention is credited to James-Michael Barnes, Hartmut Nefzger, Manfred Schmidt, Matthias Wintermantel.
Application Number | 20070155941 11/699087 |
Document ID | / |
Family ID | 36178252 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070155941 |
Kind Code |
A1 |
Nefzger; Hartmut ; et
al. |
July 5, 2007 |
Polyurethane cast elastomers made of NCO prepolymers based on
2,4'-MDI and a process for their preparation
Abstract
Polyurethane (PUR) cast elastomers are produced from
NCO-functional prepolymers based on 2,4'-MDI satisfying specific
compositional requirements and amine-based chain extenders and/or
crosslinking agents.
Inventors: |
Nefzger; Hartmut; (Pulheim,
DE) ; Schmidt; Manfred; (Dormagen, DE) ;
Barnes; James-Michael; (Breitscheid, DE) ;
Wintermantel; Matthias; (Koln, DE) |
Correspondence
Address: |
BAYER MATERIAL SCIENCE LLC
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
36178252 |
Appl. No.: |
11/699087 |
Filed: |
January 29, 2007 |
Current U.S.
Class: |
528/44 |
Current CPC
Class: |
C08G 65/2615 20130101;
C08G 18/4887 20130101; C08G 65/3311 20130101 |
Class at
Publication: |
528/044 |
International
Class: |
C08G 18/00 20060101
C08G018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 2005 |
DE |
102005012794.0 |
Claims
1. A polyurethane elastomer comprising the reaction product of a.)
an NCO prepolymer which is the reaction product of (1) a
diphenylmethane diisocyanate having (i) a 2,4' isomer content of at
least 85 wt. % and (ii) from at least 1 to 25 wt. %, based on total
weight of the NCO prepolymer of free monomeric 2,4'-diphenylmethane
diisocyanate and (2) a polyol having an OH number of from 20 to 200
mg KOH/g and a functionality of from 1.95 to 2.40, b.) an
amine-based chain extender and/or crosslinking agent, and c.)
optionally, auxiliary substances and additives.
2. The polyurethane elastomer of claim 1 in which component b) is
selected from diethyltoluenediamine,
3,3'-dichloro-4,4'-diaminodiphenylmethane, isobutyl
3,5-diamino-4-chlorobenzoate,
4-methyl-2,6-bis(methylthio)-1,3-diaminobenzene, trimethylene
glycol di-p-aminobenzoate,
4,4'-diamino-2,2'-dichloro-5,5'-diethyldiphenylmethane and mixtures
thereof.
3. A process for the production of the polyurethane elastomer of
claim 1 comprising adding A) the amine-based chain extender and/or
crosslinking agent and any optional auxiliary substance or additive
to B) the NCO prepolymer.
4. An adhesive or sealant comprising the polyurethane elastomer of
claim 1.
5. A molded article produced from the polyurethane elastomer of
claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to polyurethane (PUR) cast
elastomers made from NCO-functional prepolymers based on 2,4'-MDI
and amine-based chain extenders and/or crosslinking agents and to a
process for their preparation.
[0002] MDI (diphenylmethane diisocyanate) is a technically
important group of poly-isocyanates; it has a very heterogeneous
composition in terms of its structure and comprises (a) monomer
grades characterized in that they have two aromatic structural
elements bonded via a single methylene bridge, and (b) higher
oligomers having more than two aromatic structural elements and
possessing more than one methylene bridge, which are referred to as
polymeric MDI.
[0003] Monomeric MDI contains predominantly the 4,4' and 2,4'
isomers as a consequence of its synthesis. The 2,2' isomer also
occurs to a lesser extent, but is largely of no technical
value.
[0004] The ratio of monomeric MDI to polymeric MDI, and the
proportions of the 2,4' and 4,4' isomers in monomeric MDI, can be
varied within wide limits by varying the conditions of synthesis of
the precursor.
[0005] The crude MDI obtained in the MDI synthesis is separated
substantially by distillation, it being possible, depending on
technical expenditure, to separate off either almost isomerically
pure fractions with proportions of 4,4'-MDI, for example, of more
than 97.5 wt. %, or isomer mixtures with, for example, proportions
of 4,4'-MDI and 2,4'-MDI of about 50 wt. % in each case.
[0006] In the past, because of technical conditions, pure 2,4'
isomer was commercially available only in very limited quantities,
if at all. Recently, however, more effort has been devoted to
making this isomer available in high purity as well. A basic reason
for this effort is the difference in reactivity of the 2- and
4'-NCO groups of 2,4'-MDI, in a way similar to the differences in
reactivity of the 2- and 4-NCO groups of 2,4-toluene diisocyanate
(TDI).
[0007] These differences in reactivity allow or facilitate the
synthesis of monomer-poor NCO prepolymers. NCO prepolymers are
materials with terminal NCO groups which are obtained by reacting a
polyol with a polyisocyanate using a molar excess of NCO, based on
the NCO-reactive groups, at a temperature of from room temperature
to about 100.degree. C. Depending on the initial molar proportions,
NCO prepolymers prepared in this way always contain free monomeric
diisocyanate.
[0008] In the case of 2,4-TDI, the driving force behind the
preparation of monomer-poor to practically monomer-free NCO
prepolymers is justified by its high vapor pressure and the
resulting health hazards. NCO prepolymers based on aliphatic
diisocyanates, e.g. hexamethylene diisocyanate (HDI) or isophorone
diisocyanate (IPDI), are to be regarded as even more critical in
this context. This aspect is also relevant to MDI, although to a
markedly reduced extent because its vapor pressure is lower than
that of TDI. Moreover, reducing the monomer content of the
prepolymer results in polyurethanes that are softer than those
prepared from monomer-containing NCO prepolymers.
[0009] Monomer-poor NCO prepolymers can be prepared in several
different ways: [0010] a.) Removal of the free monomeric
diisocyanate by technically expensive film evaporation or
short-path evaporation. This is independent of whether the
diisocyanates used have NCO groups of the same or different
reactivity. Entraining agents, for example, can also be used for
this purpose. [0011] b.) Use of diisocyanates with NCO groups of
different reactivity or NCO groups of the same reactivity, and
specially chosen stoichiometric proportions, e.g. molar proportions
of NCO to NCO-reactive groups of less than 2:1, and/or optionally
under special catalysis conditions. [0012] c.) Combinations of both
of the above-described a.) and b.) processes, e.g., in such a way
that the proportion of free monomeric diisocyanate is initially
limited to a certain extent by process b.) and then minimized
further by process a.).
[0013] Such combination processes can be useful when the viscosity
of the prepolymers is to be minimized. The disadvantage of process
b.) is basically that reactions with stoichiometric proportions
(particularly proportions of less than 2:1) lead to increased
pre-extension, inherently resulting in a marked increase in the
viscosity of the reaction product.
[0014] WO 01/40340 A2 (Crompton Corp.) gives examples of such
combinations wherein, in a first step, the diisocyanate is
converted to an NCO prepolymer with the concomitant use of a
selectivity-increasing catalyst, and the prepolymer is then freed
of excess monomer by film evaporation.
[0015] Particularly critical applications, for instance in the food
sector, are affected by the matter of industrial hygiene, which
applies to a high degree to TDI and also to MDI. This is indicated
by numerous patents dealing with monomer-poor MDI prepolymers,
e.g., WO 03/006521 (Henkel KGaA), WO 03/033562 (Henkel KGaA), WO
03/055929 (Henkel KGaA), WO 03/051951 (Henkel KGaA), WO 93/09158
(Bayer AG) and EP 0 693 511 A1 (Bayer AG).
SUMMARY OF THE INVENTION
[0016] The object of the present invention was therefore to provide
polyurethanes based on 2,4'-MDI which have processing advantages
compared with the state of the art without sacrificing the
mechanical properties of the product. Such processing advantages
include longer casting times and lower prepolymer viscosities.
[0017] Surprisingly, it has now been found that, in terms of
mechanical properties (e.g., abrasion, ultimate strength, tear
propagation resistance, elongation at break), valuable PUR products
are obtained from NCO prepolymers based on 2,4'-MDI with a 2,4'
isomer content of at least 85 wt. % and a proportion of free
monomeric MDI in the prepolymer of at least from about 1 wt. % to
20 wt. %, preferably of from 2 to 18 wt. %, most preferably from at
least 3 wt. % to 15 wt. %, based on the prepolymer. The low
viscosity of the NCO prepolymers is a further advantage.
DETAILED DESCRIPTION OF THE INVENTION
[0018] NCO prepolymers are understood hereafter as meaning NCO
prepolymers which have been prepared from pure 2,4'-MDI, containing
at least 1 wt. % and a maximum amount of 20 wt. % of free monomeric
diisocyanate, based on the prepolymer, which MDI has not been
extracted or distilled.
[0019] Pure 2,4'-MDI is understood hereafter as meaning MDI grades
which have a 2,4' isomer content of at least 85 wt. %, preferably
of at least 90 wt. %, more preferably of at least 95 wt. %, and
most preferably of at least 97.5 wt. %.
[0020] The present invention provides polyurethane elastomers
obtainable (by the casting process) from [0021] a) one or more NCO
prepolymers based on diphenylmethane diisocyanate with a 2,4'
isomer content of at least 85 wt. %, preferably of at least 90 wt.
% and more preferably of at least 95 wt. %, the proportion of free
monomeric 2,4'-MDI being from at least 1 wt. % to 20 wt. %,
preferably from 2 to 18 wt. % and most preferably from 3 to 15 wt.
%, based on the NCO prepolymer, and on one or more polyols having
OH numbers of from about 20 to about 200 mg KOH/g and
functionalities of from about 1.95 to about 2.40, preferably from
about 1.96 to 2.20, [0022] b) one or more amine-based chain
extenders and/or crosslinking agents, preferably aromatic
amine-based chain extenders and/or crosslinking agents, and [0023]
c) optionally, auxiliary substances and additives.
[0024] The polyurethanes of the present invention are superior to
those within the current state of the art because they have
particularly favorable combinations of advantageous properties with
respect to prepolymer viscosity, casting time and mechanical and
mechanico-dynamic properties.
[0025] The present invention also provides a casting process for
the preparation of the polyurethane elastomers according to the
invention. In the process of the present invention, [0026] A) a
prepolymer is formed by reacting diphenylmethane diisocyanate (MDI)
with a 2,4' isomer content of at least 85 wt. %, preferably of at
least 90 wt. % and more preferably of at least 95 wt. % with one or
more polyols having OH numbers of from about 20 to about 200 mg
KOH/g and functionalities of from about 1.95 to about 2.40 to give
NCO prepolymers with a proportion of free monomeric 2,4'-MDI of
from 1 wt. % to 20 wt. %, preferably of from 2 to 18 wt. % and most
preferably of from about 3 to 15 wt. %, based on the NCO
prepolymer, and [0027] B) one or more amine-based chain extenders
and/or crosslinking agents and optionally auxiliary substances and
additives are added to the prepolymer from A) to produce the
elastomer product.
[0028] Preparation of elastomers by the casting process is an
important use for NCO-terminated prepolymers. The NCO prepolymers
are either reacted with a chain extender directly after their
preparation or after being cooled to a lower temperature (storage
temperature) and stored for the purpose of chain extension at a
later stage.
[0029] The synthesis of PUR elastomers from prepolymers is
favorable because part of the heat of reaction is already produced
during the synthesis of the prepolymer, thereby reducing the
exothermic heat of the actual polymer synthesis. This has a
favorable effect on the rate of molecular weight build-up and
allows longer casting times, a processing advantage.
[0030] In one particularly preferred embodiment of the process for
preparation of the PUR elastomers by the prepolymer process, the
prepolymers are first degassed by application of a reduced pressure
at room temperature or elevated temperature, and then stirred with
a chain extender, usually at elevated temperature.
[0031] In the process of the present invention, the prepolymer is
preferably heated to a temperature of from 60.degree. C. to
110.degree. C. and degassed under vacuum, with stirring. The chain
extender and/or crosslinking agent is then added in liquid form,
optionally after having been heated to a temperature typically of
at least 5.degree. C. above its melting point. The reaction mixture
is cast into preheated molds (preferably heated to 90.degree. C. to
120.degree. C.) and cured at 90.degree. C. to 140.degree. C. for
about 24 hours.
[0032] Polyols suitable for use in the practice of the present
invention include polyether polyols, polyester polyols,
polycarbonate polyols and polyetherester polyols having hydroxyl
numbers of from 20 to 200 mg KOH/g, preferably of from 27 to 150 mg
KOH/g and most preferably of from 27 to 120 mg KOH/g.
[0033] Polyether polyols are prepared from an initiator molecule
and epoxide, preferably ethylene oxide and/or propylene oxide, by
either alkaline catalysis or double metal cyanide catalysis, or
optionally by alkaline catalysis and double metal cyanide catalysis
in a stepwise reaction, and have terminal hydroxyl groups.
Initiators which can be used to prepare suitable polyether polyols
for use in the practice of the present invention include the
compounds with hydroxyl and/or amino groups known to those skilled
in the art, and water. The functionality of the initiator(s) is at
least 2 and at most 4. Of course, it is also possible to use
mixtures of several initiators. Mixtures of several polyether
polyols can also be used in the practice of the present
invention.
[0034] Polyether polyols can be hydroxyl terminated oligomers of
tetrahydrofurane.
[0035] Polyester polyols may be prepared in known manner by the
polycondensation of aliphatic and/or aromatic polycarboxylic acids
having from 4 to 16 carbon atoms, optionally their anhydrides and
optionally their low-molecular esters, including cyclic esters,
with the reaction component used being predominantly low-molecular
weight polyol(s) having from 2 to 12 carbon atoms. The
functionality of the structural components for polyester polyols is
preferably 2, but can also be greater than 2 in individual cases,
the components having functionalities greater than 2 only being
used in small amounts so that the arithmetic number-average
functionality of the polyester polyols ranges from 2 to 2.5,
preferably from 2 to 2.1.
[0036] Polyetherester polyols may be prepared by the concomitant
use of polyether polyols in the synthesis of polyester polyols.
[0037] Polycarbonate polyols may be produced by known processes,
e.g., by polycondensation of carbonic acid derivatives (e.g.
dimethyl or diphenyl carbonate or phosgene) and polyols.
[0038] Preferred chain extenders are aromatic amine-based chain
extenders such as diethyltoluenediamine (DETDA);
3,3'-dichloro-4,4'-diaminodiphenylmethane (MBOCA); isobutyl
3,5-diamino-4-chlorobenzoate;
4-methyl-2,6-bis(methylthio)-1,3-diaminobenzene (Ethacure 300);
trimethylene glycol di-p-aminobenzoate (Polacure 740M); and
4,4'-diamino-2,2'-dichloro-5,5'-diethyldiphenylmethane (MCDEA).
MBOCA and isobutyl 3,5-diamino-4-chlorobenzoate are particularly
preferred. Aliphatic amine-based chain extenders can likewise be
used (concomitantly).
[0039] It is also possible to use auxiliary substances and
additives such as catalysts, stabilizers, UV stabilizers,
hydrolysis stabilizers, emulsifiers, and dyestuffs and color
pigments that are preferably capable of incorporation.
[0040] Examples of suitable catalysts are: trialkylamines,
diazabicyclooctane, tin dioctanoate, dibutyltin dilaurate,
N-alkylmorpholine, lead, zinc, calcium or magnesium octanoate and
the corresponding naphthenates and p-nitrophenate.
[0041] Examples of suitable stabilizers are Broensted and Lewis
acids, such as hydrochloric acid, benzoyl chloride, organomineral
acids (e.g., dibutyl phosphate), and also adipic acid, malic acid,
succinic acid, tartaric acid and citric acid.
[0042] Examples of UV stabilizers and hydrolysis stabilizers are
2,6-dibutyl-4-methylphenol and sterically hindered
carbodiimides.
[0043] Dyestuffs capable of incorporation are those which possess
Zerewitinoff-active hydrogen atoms, i.e. atoms which can react with
NCO groups.
[0044] Other auxiliary substances and additives include
emulsifiers, foam stabilizers, cell regulators and fillers. A
survey of such auxiliary substances and additives can be found in
G. Oertel, Polyurethane Handbook, 2nd edition, Carl Hanser Verlag,
Munich, 1994, chap. 3.4.
[0045] The polyurethane elastomers of the present invention can be
used in a very wide variety of applications, e.g., as elastic
moldings produced by the casting process, as well as in coatings
and adhesive bonding agents produced by a spraying process, e.g.,
in parking deck coating systems, concrete repairs and corrosion
protection.
[0046] The invention will be illustrated in greater detail with the
aid of the Examples which follow.
EXAMPLES
[0047] Methods of Measurement Used: TABLE-US-00001 DIN ISO/ASTM
Property Dimensions standard standard Hardness [Shore] DIN 53505
ISO 868 Stress [MPa] DIN 53504 ISO 527 Ultimate strength [MPa] DIN
53504 ISO 527 Elongation at break [%] DIN 53504 ISO 527 Tear
propagation resistance [kN/m] DIN 53515 ISO 527 Abrasion [mm.sup.3]
DIN 53516 ASTM D 1242 Density [g/mm.sup.3] DIN 53420 ISO 1183
Permanent set, PS [%] DIN 53517 DIN ISO 815
Chemicals Used: [0048] Polyester Polyol 1:
poly(ethylene-co-butylene) adipate having an OH number of 56 mg
KOH/g which is commercially available from Bayer MaterialScience
AG; nominal functionality 2.0 [0049] 4,4'-MDI: 4,4'-diphenylmethane
diisocyanate which is commercially available under the name
Desmodur.RTM. 44M from Bayer MaterialScience AG; 98.5 wt. %
4,4'-isomer [0050] 2,4'-MDI: 2,4'-diphenylmethane diisocyanate
(laboratory product) from Bayer MaterialScience AG; 98.5 wt. %
2,4'-isomer [0051] Isobutyl 3,5-diamino-4-chlorobenzoate:
RC-Crosslinker 1604 commercially available from Rheinchemie,
Rheinau.
Example 1
Preparation of MDI-based Ester Prepolymers
[0051] Instructions for the Preparation of Prepolymers Using
Prepolymer 2 as an Example (Table 1):
[0052] 25 parts by weight of 2,4'-MDI were heated to 70.degree. C.
in a stirred flask under nitrogen and stirred rapidly with 100
parts by weight of dehydrated Polyester Polyol 1 heated to
70.degree. C. The reaction was allowed to proceed for 2 hours and
the physical properties of Prepolymer 2 were determined (See Table
1.). TABLE-US-00002 TABLE 1 Formulations of MDI-based ester
prepolymers (according to the invention and Comparative Examples) 1
C 2 3 C 4 C 5 6 C Polyester Polyol 1 [parts by weight] 100 100
Prepolymer 1.sup.1 [parts by weight] 100 100 Prepolymer 2.sup.2
[parts by weight] 100 100 4,4'-MDI [parts by weight] 25 10 10
2,4'-MDI [parts by weight] 25 10 10 NCO (theoretical) [wt. % of
NCO] 3.36 3.36 6.1 6.1 6.1 6.1 NCO (experimental) [wt. % of NCO]
3.4 3.44 6.2 6.1 6.17 6.15 Free MDI [wt. %] 4.8 3.1 11.9 13.4 11.9
13.4 Viscosity at 70.degree. C. [mPas] 10,600 4800 2900 6200 2900
6400 C: Comparison .sup.1Prepolymer 1: Reaction product of 100
parts by weight of Polyester Polyol 1 and 25 parts by weight of
4,4'-MDI .sup.2Prepolymer 2: Reaction product of 100 parts by
weight of Polyester Polyol 1 and 25 parts by weight of 2,4'-MDI
[0053] Comparison of the viscosity values for MDI prepolymers with
a theoretical NCO content of 3.36 wt. % shows the advantages of the
prepolymer based on 2,4'-MDI (Prepolymer 2, according to the
invention) over the 4,4' analogue (Prepolymer 1 C, not according to
the invention).
[0054] Mixing of either of these two prepolymers with additional
MDI to attain NCO contents of 6.1 wt. % of NCO (theoretical)
obviously gives in all cases prepolymers with lower viscosities
than the starting prepolymers (Prepolymers 3 C, 4 C, 5 and 6 C in
Table 1). It is further seen that the equally low viscosity of
Prepolymers 3 C and 5 (in each case, 2900 mPas at 70.degree. C.) is
not sufficient for advantageous processing (e.g., casting time) to
casting elastomers. Only Prepolymer 5 could advantageously be
processed further to an elastomer (See Tables 2 and 3.).
Example 2
Preparation of Casting Elastomers According to the Invention from
Prepolymers 2 and 5 of Example 1
Instructions for the Preparation of Casting Elastomers Using
Casting Elastomer A as an Example:
[0055] 100 parts of Prepolymer 2 were degassed at 90.degree. C.
under vacuum, with slow stirring, until free of bubbles. This
degassed prepolymer was then stirred with 9.05 parts of isobutyl
3,5-diamino-4-chlorobenzoate preheated to 100.degree. C., and the
reacting homogeneous melt was cast into molds preheated to
110.degree. C., having dimensions corresponding to the testing
standards. The melt was then heated for 24 hours at 110.degree. C.
and the mechanical properties listed in Table 2 were determined.
TABLE-US-00003 TABLE 2 Formulations, preparation and properties of
the casting elastomers according to the invention Casting elastomer
No. A B C D E Formulation and preparation: Prepolymer No. 2 2 2 2 5
[parts by weight] 100 80 60 40 100 Prepolymer No. 5 5 5 [parts by
weight] 20 40 60 NCO (theoretical) [wt. % of NCO] 3.36 3.9 4.46
5.04 6.1 Prepolymer temperature [.degree. C.] 90 90 90 90 85
Viscosity of prepolymer mixture, [mPas] 2030 1940 1750 1600 1200
90.degree. C. Isobutyl 3,5-diamino-4- [parts by weight] 9.05 10.5
12.0 13.6 16.4 chlorobenzoate Temperature of crosslinking agent
[.degree. C.] 100 100 100 100 100 Index (theoretical) 107 107 107
107 107 Casting time [s] 225 165 105 105 60 Peeling time [min] 8 8
7 7 5 Mold temperature [.degree. C.] 110 110 110 110 110
Post-heating temperature [.degree. C.] 110 110 110 110 110
Post-heating time [h] 24 24 24 24 24 Mechanical properties:
Hardness [Shore A] 91 92 93 97 99 [Shore D] 37 49 Stress 10% [MPa]
3.61 4.22 5.26 6.45 9.23 Stress 100% [MPa] 6.5 6.9 7.5 8.3 10.0
Stress 300% [MPa] 9.9 10.0 11.4 12.0 14.3 Ultimate strength [MPa]
43.31 36.3 44.4 42.6 46.0 Elongation at break [%] 683 607 591 616
609 Tear propagation resistance, [kN/m] 62.8 67.3 71.6 83 99.2
Graves Impact resilience [%] 47 47 Formulation and preparation:
Abrasion (DIN) [mm.sup.3] 59 57 62 52 Density [g/mm.sup.3] 1.214
1.218 1.224 1.214 PS 22.degree. C. [%] 25.4 64 36.7 PS 70.degree.
C. [%] 47.4 61 56.4 Storage modulus G' [MPa] at 0.degree. C. 36.0
48.4 70.6 86.5 139 at 20.degree. C. 28.2 36.9 53.3 65.9 108 at
50.degree. C. 24.6 31.2 43.9 53.1 84.8 at 80.degree. C. 24.3 29.4
41.0 47.4 74.9 at 110.degree. C. 25.5 29.6 40.7 45.5 70.2 Loss
factor, tan .delta. at 0.degree. C. 0.1302 0.1246 0.1170 0.1045
0.0903 at 20.degree. C. 0.0768 0.0789 0.0756 0.0734 0.0690 at
50.degree. C. 0.0484 0.0494 0.0497 0.0542 0.0543 at 80.degree. C.
0.0302 0.0318 0.0318 0.0392 0.0389 at 110.degree. C. 0.0177 0.0193
0.0193 0.0259 0.0270 Tan .delta. max. -36 -36 -36 -36 -36 Tan
.delta. min. 130 130 130 130 130 Loss modulus G'' [MPa] at
0.degree. C. 4.69 6.0 8.26 9.04 12.5 at 20.degree. C. 2.16 2.9 4.03
4.84 7.46 at 50.degree. C. 1.19 1.5 2.18 2.88 4.61 at 80.degree. C.
0.74 0.9 1.30 1.86 2.91 at 110.degree. C. 0.45 0.6 0.79 1.18 1.89
Softening point [.degree. C.] 190 195 195 210 195
Example 3
Preparation of Casting Elastomers not According to the Invention
from Prepolymers 1 C, 3 C, 4 C and 6 C of Example 1
[0056] The preparation was carried out as described under Example
2. The formulations and properties of these cast elastomers are
reported in Table 3. TABLE-US-00004 TABLE 3 Formulations,
preparation and properties of the cast elastomers not according to
the invention Cast elastomer No. F G H I Formulation and
preparation: Prepolymer No. 1 C 3 C 4 C 6 C [parts by weight] 100
100 100 100 NCO (theoretical) [wt. % of NCO] 3.36 6.1 6.1 6.1
Prepolymer temperature [.degree. C.] 100 90 90 90 Viscosity of
prepolymer, 90.degree. C. [mPas] 4530 1200 2710 2720 Isobutyl
3,5-diamino-4-chlorobenzoate [parts by weight] 9.05 16.4 16.4 16.4
Temperature of crosslinking agent [.degree. C.] 100 100 100 100
Index (theoretical) 107 107 107 107 Casting time [s] 75 30 60 60
Peeling time [min] 9 4 3 4 Mold temperature [.degree. C.] 110 110
110 110 Post-heating temperature [.degree. C.] 110 110 110 110
Post-heating time [h] 24 24 24 24 Mechanical properties: Hardness
[Shore A] 83 99 99 99 [Shore D] 31 49 48 48 Stress 10% [MPa] 1.92
9.91 9.09 8.45 Stress 100% [MPa] 4.0 10.2 9.06 8.6 Formulation and
preparation: Stress 300% [MPa] 8.8 16.0 13.8 12.3 Ultimate strength
[MPa] 10.3 51.5 35.1 33 Elongation at break [%] 325 538 543 589
Tear propagation resistance, Graves [kN/m] 14.9 89.6 89.5 87.8
Impact resilience [%] 50 48 47 46 Abrasion (DIN) [mm.sup.3] 101 69
46 55 Density [g/mm.sup.3] 1.205 1.228 1.228 1.228 PS 22.degree. C.
[%] 8.5 45.9 45.1 47 PS 70.degree. C. [%] 16.2 66.8 57.8 67.4
Storage modulus G' [MPa] at 0.degree. C. 16.6 177 140.4 138.8 at
20.degree. C. 14.6 137 110.5 101.8 at 50.degree. C. 15.0 107 87.6
78.0 at 80.degree. C. 15.8 94.0 78.7 66.2 at 110.degree. C. 16.2
87.2 74.8 60.8 Loss factor, tan .delta. at 0.degree. C. 0.1295
0.0870 0.0807 0.0976 at 20.degree. C. 0.0428 0.0665 0.0605 0.0735
at 50.degree. C. 0.0169 0.0544 0.0468 0.0616 at 80.degree. C.
0.0097 0.0417 0.0358 0.0488 at 110.degree. C. 0.0075 0.0309 0.0231
0.0352 Tan .delta. max. -33 -36 -36 -33 Tan .delta. min. 110 130
190 140 Loss modulus G'' [MPa] at 0.degree. C. 2.15 15 11.32 13.55
at 20.degree. C. 0.63 9.08 6.68 7.48 at 50.degree. C. 0.25 5.81
4.10 4.81 at 80.degree. C. 0.15 3.92 2.82 3.23 at 110.degree. C.
0.12 2.69 1.73 2.14 Softening point [.degree. C.] 165 195 230
200
[0057] The advantages of the present invention are clear upon
comparison of Tables 2 and 3.
[0058] At comparable prepolymer temperatures (starting temperature)
and comparable NCO contents, i.e. comparable formulations, the
casting times of the prepolymers according to the invention (Table
2) are up to 3 times longer than those of the systems not according
to the invention (Table 3), which represents a clear processing
advantage. The particularly favorable combinations of the
properties of "long casting time" and "low prepolymer viscosity"
are only achieved by the systems according to the present
invention.
[0059] The cast elastomers of the present invention also exhibit
advantages with respect to their mechanical properties:
[0060] If, for example, the PUR prepared from Prepolymer 2 (Cast
Elastomer A, Table 2) is compared with a PUR prepared from
Prepolymer 1 C (cast Elastomer F, Table 3)--both prepolymers having
the same NCO value of 3.36 wt. % of NCO--Cast Elastomer A (an
example of the present invention ) has better ultimate strength,
elongation at break, tear propagation resistance and abrasion.
[0061] If the PUR prepared from Prepolymer 5 (Cast Elastomer E,
Table 2) is compared with a PUR prepared from Prepolymers 3 C, 4 C
and 6 C (Cast Elastomers G, H and I, Table 3)--all the prepolymers
having the same NCO value of 6.1 wt. % of NCO--Cast Elastomer E (an
example of the present invention) has comparable good ultimate
strength, elongation at break, tear propagation resistance,
abrasion and permanent set, within the limits of experimental
error.
[0062] The same also applies in terms of the mechanico-dynamic
properties (storage and loss moduli and loss factor).
[0063] The PUR-forming systems of the present invention exhibit a
unique combination of advantageous properties with respect to
prepolymer viscosity, casting time and mechanical and
mechanico-dynamic properties.
[0064] 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.
* * * * *