Note: Descriptions are shown in the official language in which they were submitted.
2~~84~4
Mo-3847
LeA 28 830-US
PROCESS FOR PREPARING OPEN CELL, RESILIENT,
F~XIBLE POLYURETHANE FOAMS
BACKGROUND OF THE INVENTION
Flexible polyurethane foams are familiar in a wide range
of upholstering material applications in the furniture and
motor vehicle industries. Physical blowing agents, such as,
e.g., monofluorotrichloromethane (R11) have been used to adjust
the relationship between apparent density and compression
stress value in the manner required for each field of
to application. Such blowing agents do not increase the polyurea
content of the polymer as does water. Many physical blowing
agents which are currently known have considerable dis-
advantages, such as potential to destroy ozone, greenhouse .
effect, combustibility or toxicity.
is An object of the present invention was therefore to adjust
the compression stress value of flexible polyurethane foams
(hot foams) in the desired way without using the physical
blowing agents which have been used to date.
It is known that the compression stress value of a
Zo flexible polyurethane foam can be reduced by reducing the
isocyanate index. For example, if a compression stress value
of 2.0 kPa is to be obtained with an apparent density of
23 kg/m3 (a specification which is widely used), it is
necessary to reduce the isocyanate index from 107 to 92. As
25 can be seen from Examples A and C herein, however, reducing the
index leads to an unacceptable loss in mechanical properties.
Another known method of reducing compression stress value
consists of proportionally co-using polyethers having a high
oxyethylene unit content (DE-OS 1 248 286). However, polyethylene glycols
3o frequently have high melting points which makes them difficult
35052JCG1896
LeA 28 830-US
CA 02088414 2003-05-14
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to process. In addition, their co-use in the quantities required to reduce
hardness gives rise to problems in the foaming process (specifically, a
tendency to form closed cells in the case of linear polyethers and unstable
foam in the case of higher-function polyethers).
DESCRIPTION OF THE INVENTION
It has now surprisingly been found that it is possible to prepare open ceH
polyurethane foams of reduced hardness and good resilience if small quantities
of oxyethylene-group-rich polyethers having oxyethylene group contents of
more than 50% and functionalities at least two are co-used and an isocyanate
index range of between 95 and 110 is simultaneously used. In this manner, the
compression stress values can be reduced by more than 40% while still
maintaining such values at an excellent level. In addition, foams of excellent
resilience are produced.
A surprising observation in the comparison with Examples A and B
herein where a normal isocyanate index is used, is the fact that resilience is
even further increased by use of the special polyether mixture according to
the
invention (Examples B and E). The prior art discloses that high quantities of
water and low indices produce inelastic, or "tired" foams.
More particularly, the present invention is directed to a process for the
preparation of resilient, flexible, open cell polyurethane foams comprising
reacting
a) polyisocyanates,
b) a polyether mixture comprising:
1 ) from 5 to 10% by weight, based on 100% by weight of b)
the polyether mixture, of a polyether
i) having a molecular weight of from 3000 to 5000,
ii) containing three hydroxyl groups,
and
iii) having an oxyethylene group content of more than
70% by weight, based on 100% by weight of
alkylene oxide present in polyether b)1), and
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CA 02088414 2003-05-14
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2) from 95 to 80% by weight, based on 100% by weight of b)
the polyether mixture, of a polyether
i) produced by the addition of one or more alkylene
oxides to glycerol,
ii) having a molecular weight of from 3000 to 5000,
and
iii) having an oxyethylene group content of 13% by
weight or less, based upon 100% by weight of
alkylene oxide present in polyether b)2),
c) water, and optionally organic blowing agents,
d) catalysts,
e) optionally, compounds having at least two hydrogen atoms
capable of reacting with isocyanate groups, and having molecular
weights of from 32 to 399, and
f) optionally, surface-active or flame-retardant additives,
whereby the reaction is conducted in an isocyanate index range of from 95 to
110, and preferably from 98 to 100.
It is particularly preferred that anionic, cationic or nonionic emulsifying
agents, and preferably alkane sulphonates as emulsifying agents, are used,
and that water is used as blowing agent in a quantity of from 2 to 15 wt-%,
based upon the amount of component b).
Substantially any isocyanates may be used in order to prepare the
foams herein. Aliphatic, cycloaliphatic, aromatic and heterocyclic
polyisocyanates, as described for example by
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W. Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75
to 136 can be used. More specifically, isocyanates of the
following formula are suitable herein:
Q(NCO)n
s where n a 2 to 4, and preferably 2 t~ 3, and Q represents an
aliphatic hydrocarbon radical having from 2 to 18 (and
preferably from 6 to 10) carbon atoms, a cycloaliphatic
hydrocarbon radical having from 4 to 15 (and preferably from 5
to 10) carbon atoms, an aromatic hydrocarbon radical having
to from 6 to 15 (and preferably from 6 to 13) carbon atoms or an
araliphatic hydrocarbon radical having from 8 to 15 (and
preferably from 8 to 13) carbon atoms. Specific isocyanates
are known in the art and are described, e.9., in German
Offenlegungsschrift 2,832,253, pages 10 to 11. Particularly
1s preferred are aromatic polyisocyanates, and particularly the
technically readily available aromatic polyisocyanates, e.g.
2,4- and 2,6-toluylene diisocyanate, and mixtures of such
isomers ("TDI"); polyphenyl-polymethylene polyisocyanates, as
prepared by condensing aniline with formaldehyde and subsequent
2o reaction with phosgene ("crude MDI"); and polyisocyanates
containing carbodiimide groups, urethane groups, allophanate
groups, isocyanurate groups, urea groups or biuret groups
("modified polyisocyanates"), especially such modified
polyisocyanates as are derived from 2,4- and/or 2,6-toluylene
2s diisocyanate or 4,4'- and/or 2,4'-diphenylmethanediisocyanate,
respectively.
Component b) comprises a mixture of
1. from 0.5 to 20 wt-% of a polyether containing at
least two hydroxyl groups, having an oxyethylene
so group content greater than 50 wt-% (calculated on
total alkylene oxide), and having an average
molecular weight of from 400 to 10,000; the polyether
polyol contains predominant amounts of primary OH
groups; it is preferred that from 5 to 10 wt-% of a
triol of an average molecular weight of from 3,000 to
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5,000 and comprising more than 70 wt-% oxyethylene
groups (calculated on total alkylene oxide) is used;
and
2. from 99.5 to 80 wt-% of a polyether produced by the
addition of alkylene oxide to glycerol or a mixture
of glycerol and ethylene glycol, having an average
molecular weight of from 400 to 10,000, and
preferably from 3,000 to 5,000, and comprising a
maximum of 20 wt-% oxyethylene groups (calculated on
to total alkylene oxide), preferably having an
oxyethylene group content of up to 13 wt-%
(calculated on total alkylene oxide); this polyether
contains predominant amounts of secondary OH groups;
Catalysts of the type known in the art in guantities of up
15 to 10 wt-%, based upon the amount of component b) are also
used.
Compounds having at least two hydrogen atoms capable of
reacting with isocyanate groups arid having molecular weights of
from 32 to 399 are optionally used. These include compounds
2o containing hydroxyl groups and/or amino groups and/or thiol
groups and/or carboxyl groups, preferably compounds containing
hydroxyl groups and/or amino groups, which compounds serve to
increase chain length or serve as cross-linking agents. The
compounds generally contain from 2 to 8, and preferably from 2
25 to 4, hydrogen atoms which are capable of reacting with
isocyanates. Examples of such compounds are described in
German Offenlegungsschrift 2,832,253, pages 19 to 20.
Additional materials may also be included in the reaction
mixture. Such materials include surface-active additives such
3o as emulsifying agents and foam stabilizers; porosity regulators
of the type known in the art (such as paraffins or fatty
alcohols or dimethyl polysiloxanes); pigments or dyes and
flameproofing agents of the type known in the art, e.g.
trischloroethyi phosphate, triscresyl phosphate; stabilizers to
guard against the effects of ageing and weathering;
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plasticizers and substances having a fungistatic and
bacteriostatic action; and fillers such as barium sulphate,
diatomaceous earth, carbon black or prepared chalk. These
additional substances and additives which may be added are
described, for example, in German Offenlegungsschrift
2,732,292, pages 21 to 24. Further examples of surface-active
additives and foam stabilizers, cell regulators, reaction
retardants, stabilizers, flame-retardants, plasticizers, dyes
and fillers, plus substances having fungistatic and
io bacteriostatic action, any of which may also be used according
to the invention, and details regarding the method of use and
the mode of action of these additives are described in the
Kunststoff-Handbuch (Manual of Plastics), Vol. VII, edited by
Vieweg and Hbchtlen, and published by Carl-Hanser-Verlag,
15 Munich 1966, e.g. on pages 103 to 1I3.
According to the invention the reaction components are
reacted by the one-shot process, the prepolymer process or the
semi-prepolymer process, which processes are known in the art.
Mechanical equipment is frequently used, e.g. such as that
2o described in U.S. Patent 2,764,565. Details concerning
processing equipment which may also be used for the invention,
are described in the Kunststoff-Handbuch, Vol. VII, edited by
Vieweg and Hochtlen, and published by Carl-Hanser-Verlag>
Munich 1966, e.g. on pages 121 to 205.
2s All components are reacted according to the invention at
an isocyanate index of from 95 to 110, and preferably at an
index of from 98 to 100. The isocyanate index, a concept which
is frequently used in the preparation of polyurethane foams, is
indicative of the degree of cross-linking of a foam. It is
customary to regard a foam as having been produced at an index
30 of 100 if the actual quantity of isocyanate equivalents is
equal to the theoretical quantity of isocyanate equivalents
necessary to react with all the active hydrogens present. It
is therefore possible with the aid of the index to define more
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precisely the degree of under- or over-cross-linking. The
index is calculated by the following general formula:
Index a isocyanate quantity (actual equivalents)
isocyanate quantity (theoretical)
x 100
The flexible polyurethane foams which may be obtained
according to the invention find applications as, for example,
furniture for reclining and for seating, and as seats in
passenger vehicles and, automobiles.
1o The invention is further illustrated but is not intended
to be limited by the following examples in which all parts and
percentages are by weight unless otherwise specified.
EXAMPLES
In the examples, all the components listed below were
mixed together intensively and expanded in a manner which is
known per se.
Foams were prepared by the following handmix procedure:
200g of polyol were weighed together with all other ingredients
2o except isocyanate and tin catalyst in a papex cup and premixed
with a Pendraulik 7~M 34 stirrer for 5 seconds at 3000 rpm.
After adding the required amount of tin catalyst and another 5
seconds of stirring the isocyanate is added under continously
mixing . 8 seconds later the mixture is poured into a 12x12x25 cm
open papex box.
When rising of the mixture has completed, the fresh foam is
transferred to a microwave oven (Panasonic NE 1440) and cured for
25 3 minutes with an irradiation power of 340 W Afterwards the foam
is cured for further 45 minutes in a conaentional oven at 110
Degr. Celsius.
Physical properties of the foams were determined 3 days after
preparation.
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Examples A B C
(control) (control)
Polyol A 100 90 100
Polyol B 10
Water 4.5 4.5 4.5
Foam stabilizer 1.0 1.5 1.0
OS 20 (Bayer AG)
Dimethylethanolamine 0.3 0.3 0.3
Tin(II)-octoate 0.2 0.2 0.35
TDI*) 54.2 54.1 46.4
io
Isocyanate index 107 107 92
Apparent density (kgm 3) 23 23 23
1)
Tensile strength (kPa) 2) 124 102 25
Elongation at break (%) 3) 214 165 54
Compression stress (kPa) 3.5 3.4 2.0
4)
15
value (40%)
DVR (90%a) (%) 5) 6.2 4.9 adheres
Ball rebound resilience (%) 6) 42 44 39
*isomer mixture of 2,4- and 2,6-toluylenediisocya nate in an
80/20 weight ratio
20
Test methods according to:
1 ) DIN 53420
2) DIN 53571
3) " .,
25
4) DIN 53577
5) DiN 53572
6) In house method:
2xH
30 according ~
The resilience is calculatedto the
formula:
1 ()D
H is the return height of diameter;
a steel ball (14 mm 13.6
g weight)
falling
from
a height
of 50 cm on a foam (8 x 8
x 5 cm) sample.
20~~~14
_g_
Examples D E F
(control)
Polyol A 100 90 90
Polyol 8 10 10
Water 4.5 4.5 4.5
Foam stabilizer 1.0 1.5 1.5
OS 20 (Bayer AG)
Dimethylethanolamine 0.3 0.3 0.3
Tin(II)-octoate 0.28 0.24 0.22
TDI~) 47.9 47.8 49.4
Isocyanate index 95 95 98
Apparent density (kgm 3) 23 23 23
Tensile strength (kPa) 79 94 118
Elongation at break (%) 189 249 282
Compression stress (kPa) 2.7 2.0 2.6
val ue (40fo)
DVR (90%) (%) 5.5 4.3 4.2
Ball rebound resilience (%) 40 46 44
Polyol A: adduct of PO/EO and a mixtureof glyceroland
ethylene glycol having an oxyethyl ene contentof about
10
2o and having
wt-%, predominantly secondary an
OH (>97%) end groups
average molecular weight of about3,500.
Polyol B: adduct of PO/E0 and glycerolcontainingabout 72
wt-
oxyethylene groups, pred ominantlyprimary (85%)groupsand
OI-1
lar ,700.
having an average molecu weight
of
about
4
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