Note: Descriptions are shown in the official language in which they were submitted.
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A PROCESS FOR T~IE PRODUCTION OF HOT-C~)RING,
FLEXIBLE MOLDED POLYURETHANE FOAMS
8ackqround of the Invention
Hot-curing, flexible, molded polyurethane foams have many
applications and are used in many industries, including the
automotive industry and the furniture industry. The quality of
the flexible, molded polyurethane foams typically used in seats
and armrests is largely determined by their density.
Regardless of the type of basic raw material
(polyols/isocyanates) used in the production of the molded
foams, a certain density level has proved to be appropriate and
to meet practical requirements in the various applications and
the demands they involve, particularly with regard to long-term
performance.
The density to be obtained is largely determined by the
water content of the combination of raw materials used.
Quantities of water of up to 5 parts by weight (typically 2.5
to 3.5 parts by weight) per 100 parts by weight polyol are
typical, depending on the desired density.
It has been found that, depending on the application of
the foam, the relatively low densities often required can only
be obtained in exceptional cases by increasing the water
content beyond the quantities indicated above. The reason for
this is that, with increasing water content ~i.e., above 3.5
parts by weight per 100 parts by weight polyol), the catalytic
coordination of the chemical reactions (polymer formation/gas
formation) essential to the foaming process becomes more
difficult and the overall processing scope is greatly reduced.
Apart from problems with regard to skin quality ~mold
temperature/release agent) and foam stability, the index range
in particular is also limited. For these reasons, desired or
necessary reductions in density are mainly obtained by the use
of physical blowing agents (for example halogenated
hydrocarbons). This procedure is state-of-the-art and applies
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in principle to all hot-curing molded foams. HoweYer, this
method cannot be recommended either, primarily for reasons of
pollution control.
It was known from British patent 892,776 that rigid or
5 semirigid polymer foams could be produced by reaction of 100
parts by weight of a monomeric, organic polyisocyanate with 1
to 30 parts by weight water in the presence of a surface-active
agent and a catalyst and preferably in the presence of 5 to 30
parts by wei~ht of a polyfunctional compound containing two or
o more isocyanate-reactive groups. It is apparent both from the
claims and the Examples of this patent that the "catalysts"
used are inorganic products of calcium acetate or sodium
hydroxide, so that the course of the foaming process is largely
determined by trimerization reactions.
DESCRIPTION OF ~HE INVENTIQN
It has no~ surprisingly been found that relatively large
quantities of water of more than 5.0 parts by weight per 100
parts by weight of "basic polyol" can be processed without
difficulty. Furthermore, densities of down to 15 kg/m3 can be
20 obtained in hot-curing, flexible, molded polyurethane foams.
In contrast to the standard index range of g5 to 105 hitherto
applied in practice, the invention is directed to the discovery
that normally prohibitiYely low index of less than 90 can be
used.
The present invention relates to a process for the
production of hot-curing, flexible, molded polyurethane foams
comprising reacting
a) a polyisocyanate selected from the group consisting
of polyisocyanates based on diphenyl methane
3~ diisocyanate, toluene diisocyanate, hexamethylene
diisocyanate, isophorone diisocyanate, and mixtures
thereof,
b) compounds containing at least two isocyanate-reactive
hydrogen atoms and having molecular weights of from
400 to 10,000 and,
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c) from 5 to 15 parts by weight and preferably from 6
to 12 parts by ~eight to 100 parts by weight of
component b) of water optionally in the presence of
d) cha'n-extending and crosslinking agents containing at
least two isocyanate-reactive hydrogen atoms and
having molecular weights of from From 32 ~o 399, and
optionally in the presence of
e) other blowing agents, catalysts and other auxiliaries
and additives generally known in the art,
in a closed mold, with the reaction of all the components being
carried out at an isocyanate index of less than 90 and
preferably in the range of from 60 to 80.
The polyisocyanates useful herein are selected from the
group consisting of polyisocyanates based on diphenyl methane
diisocyanate, toluene diisocyanate, hexamethylene diisocyanate,
isophorone diisocyanate, and mixtures thereof.
Specific isocyanates include 2,4-and 2,6-toluene
diisocyanate, and mixtures of such isomers ("TDI"); 4,4'-
and/or 2,4'-diphenyl methane diisocyanate (~MDI");
hexamethylene diisocyanate and/or isophorone diisocyanate;
polyphenyl polymethylene polyisocyanates of the type obtained
by phosgenation of aniline-formaldehyde condensates (ncrude
MDI"); carbodiimide, urethane, allophanate, isocyanurate, urea
or biuret polyisocyanates derived from 2,4-and/or 2,6-toluene
diisocyanate or from 4,4'- and/or 2,4'-diphenyl methane
diisocyanate and/or hexamethy1ene diisocyanate and/or
isophorone diisocyanate; and alkyl-substituted MDI types of the
type descnibed, for example, in German Offenlegungsschriften
2,935,318, 3,032,128 and 3,032,358.
According to the invention, the following TDI types are
preferred:
(i) toluene diisocyanate in the form of a mixture of the 2,4-
and 2,6-isomers ;n a ratio of 80:20 (T 80); (ii) toluene
diisocyanate in the form of a mixture of the 2,4- and
2,6-isomers in a ratio of 65:35 (T 65); (iii~ toluene
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diisocyanate prepolymers; and (iv) mixtures of TDI with
diphenyl methane diisocyanate and/or polyphenyl polylnethylene
polyisocyanates.
Compounds containing at least two isocyanate-reactive
hydrogen atoms and having molecular weights of from 400 to
lO,OOO include compounds containing amino groups, thiol groups,
carboxyl groups, and hydroxyl groups. Preferred are compounds
of this type which contain hydroxyl groups, more especially 2
to 8 hydroxyl groups, and particularly those having molecular
weights in the range from 1,000 to 6,000. Specific examples
include, for example polyethers, polyesters, polycarbonates and
polyester amides containing at least 2, generally 2 to 8 and
preferably 2 to 6 hydroxyl groups of the type generally known
for the production of homogeneous and cellular polyurethanes
and described, for example, in German Offenlegungsschrift
2,832,253, pages 11-18. Particularly preferred are those
materials having OH numbers of from 28 to 56.
Optionally, compounds containing at least two
isocyanate-reactive hydrogen atoms and having molecular weights
of from 32 to 399 can also be used. Such compounds generally
contain hydroxyl groups and/or amino groups and/or thiol groups
and/or carboxyl groups. Preferred are compoundc containing p
hydroxyl groups and/or amino groups which serve as
chain-extending or crosslinking agents. These compounds
generally contain 2 to 8 and preferably 2 to 4
isocyanate-reactive hydrogen atoms. Examples of such compounds
can be found in ~erman Offenlegungsschrift 2,832,253, pages
10-20.
Water is used as a blowing agent in a quantity of from 5
to 15 parts by weight and preferably in a quantity of from 6 to
12 parts by weight per 100 parts by weight the component b).
Auxiliaries and additives can also are optionally be used
in the usual quantities. These include readily volatile
organic compounds as further blowing agents; reaction
accelerators and reaction retarders generally known in the art;
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surface-active additives, such as e~ulsifiers and foam
stabilizers; cell regulators, such as ~araffins or fatty
alcohols or dimethyl polysiloxanes; pigments or dyes and
flameproofing agents, such as ~rischloroethyl phosphate and
tricresyl phosphate; stabilizers against ageing and weathering;
plasticizers; fungistatic and bacteriostatic agents; and
fillers, such as barium sulfate~ kieselguhr, carbon black or
whiting.
These optional auxiliaries and additives are known and are
o described, for example, in German Offenleyungsschrift
2,732,292, pages 21 to 24.
Further examples of surface-active additives and foam
stabili~ers, cell regulators, reaction retarders, stabilizers,
flameproofing agents, plasticizers, dyes, fillers, fungistatic
and bacteriostatic agents which may optionally be uscd in
accordance with the invention and information on the use of
these additives and the way in which they work can be found in
Kunststoff-Handbuch, Vol. VII, edited by Vieweg and Hochtlen,
Carl-Hanser-Verlag, Munchen 1966, for example on pages 103 to
113.
According to the invention, the reaction components can be
reacted by the known single-stage (or, one-shot) process, the
prepolymer process or the semiprepolymer process, often using
machines, for example of the type described in U.S. patent
2,764,565. Particulars of processing machines which may also
be used in accordance with the invention can be found in
Kunststoff-Handbuch, Vol. VII, edited by Vieweg and Hochtlen,
Carl-Hanser-Verlag, Munchen 1966, for example on pages 121 to
205.
According to the invention, the reaction of all the
components is carried out at an isocyanate index of less than
90 and preferably at an index in the range from 60 to 80.
The isocyanate index, a term commonly used in the
production of polyurethane foams, is an indication of the
degree of crosslinking of a foam. It is customary to regard
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that foam, in which the quantity of isocyanate corresponding to
the stoichiometric ratios or the theoretically necessary
quantity of isocyanate has been used, as naving been made with
an index of 100. Accordingly, it is possible through the index
5 to more closely define the degree of undercrosslinking or
overcrosslinking. The isocyanate index is calculated in
accordance with the following general equation:
quantity of isocyanate actually used
index = x 100
theoretical quantity of isocyanate
According to the invention, the foaming reaction is
carried out in closed molds. To this end, the reaction mixture
iS introduced into a mold. Suitable mold materials are metals,
for example aluminum, or plastics, for example epoxy resin.
The foamable reaction mixture foams in the mold and forms the
molding. According to the invention, it is possible to
introduce foamable reaction mixture into the mold in such a
quantity that the ~oam formed just fills the mold.
Alternatively, however, more reaction mixture may be introduced
into the mold than is necessary for filling the interior of the
mold with foam. The latter technique is known as overcharging
and is known, for example, from U.S. patents 3,178,490 and
3,182,10~.
The hot-curing, flexi~le, molded polyurethane foams
obtainable in accordance with the invention are used, for
example, as instrument panels, armrests (including car
arm-rests), and seats for motor vehicles, pre~erably cars.
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 speci~ied.
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EXAMPLES
In the examples, the following materials were used:
Polyether A: a glycerol-started trifunctiona1 long-chain
P0/EO polyether (approx. 15% EO), having an OH number
of 36 and a molecular weight of 4800;
Polyether B: a glycerol-started trifunctional long-chain
PO/EO polyether (approx. 10% EO), having an OH number
of 50~ and a molecular weight of 3900;
Catalyst 1: bis-N,N'-dimethylaminodiethyl ether (30%)
in dipropylene glycol (70%);
Catalyst 2: tin (II) octoate
T 80: toluene diisocyar.ate, a mixture of 2,4- and
2,6-isomers in a weight ratio of 80:20.
All the components wer.e intensively mixed and foamed in a
closed mold (22cm x 22cm x 7 cm).
Example I Example 2
Polyether A 70 parts by 65 parts by
w~eight weight
Polyether B 30 " 35 "
Water 7.0 " 8.C "
Foam stabilizer OS 32 1.5 " 1.5 "
(Bayer AG) (polyether poly-
siloxane)
Catalyst 1 0.2 " 0.2 "
Catalyst 2 0.4 " 0.4
TDI 80 X*) X*)
Index 80 75
Gross density 24 kg/m3 22 kg/m3
Compression hardness 3.2 KPa 3.4 KPa
(at 40% compression)
*) Quantity corresponding to the index noted
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Although the invention has been descr;bed 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
5 without departing from the spirit and scope of the invention
except as it may be limited by the claims.
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