Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Mo3262
LeA 26,554
PROCESS FOR THE PREPARATION OF OPEN-CELL
HYDROPHILIC POLYURETHANE FOAMS
BACKGROUND OF THE INYENTION
The inventlon relates to a novel process for the
preparation of open-cell hydrophilic polyurethane foams and the
5 use of these foams as a fixing substrate for cut flowers.
Processes for the production of open-cell hydrophilic
foams as a fixing substrate are known. See, for example, U.S.
Patents 2,988,441 and 3,373,009, German Auslegeschrift 1,229,662,
and E. Weinbrenner and J. Niggemann, "Stecklingsvermehrung und
Kultur in Blocksubstraten aus Polyurethane-Schaumstoff (Cutting
propagation and culture in block substrates of polyurethane
foam)", Gartenwelt, _ , 71-73 (1970). The disadvantage of this
process is the low water retention capacity of the foams
prepared.
German Offenlegungsschrift 2,304,892 represents a
further development inasmuch as the disadvantages related to
insufficient water retent~on capacity are essentially overcome by
additionally using modified polyisocyanates, such as urethane- or
urea-modifed polyisocyAnates or the like. The use of the
20 expensive 1socyanate modification for the preparation of such
f1xing substrates is, however, A disadvantage. This also applies
to German Offenlegungsschrift 2,441,843, which d1scloses similar
isocyanate mod1ficat~ons with organic sulfonic acids, which
allows the preparation of fixing substrates with an adequate
water retention capacity.
German Offenlegungsschrlft 3,627,236 discloses a
process for the preparation of fixing substrates uslng
chlorofluorocarbon ("CFC") blowing agents without using
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previously modified polyisocyanates. Apart from serious
ecological disadvantages, the water retention capacity of such
fixing substrates is deficient, as shown by the comparison
examples below.
The object of the present invention is to provide a new
process for the preparation of fixing substrates having an
adequate water retent~on capacity and which (a~ dispenses with
expensive prior isocyanate modifications and (b) avoids the use
of CFC blowing agents. It has surprisingly been possible to
10 achieve this object with the process of the invention described
in more detail below.
SUMMARY OF THE INVENTION
The present invention relates to a process for the
preparation of open-cell hydrophilic polyurethane foams having a
15 density of 10 to 60 kg/m comprising reacting
(a) polyisocyanates
with
(b) compounds having at least two hydrogen atoms that are
reactive towards isocyanates and generally having a
molecular weight of from about 400 to about 10,000,
in the presence of
(c) water as a blowing agent,
(d) optionally, compounds having at least two hydrogen atoms
that are reactive towards isocyanates and hav1ng a molecular
weight of from 32 to 399,
(e) optionally, auxiliaries and additives, and
(f) about 1 to about 100 mmole (preferably 5 to 20 mmole) of an
acid (preferably phosphoric acid or a substituted phosphoric
acid) per 100 9 of the total amount of components (b), (c),
(d), and (e).
The invention also relates to the use of the
polyurethane foams prepared according to the invention as a
fixing substrate for cut flowers in order to maintain a wet
35 env1ronment for the cut flowers.
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DETAILED DESCRIPTION OF THE INVENTION
The use of acids, including inorganic or organic acids
or mixtures thereof, is essential to the practice of the
invention. Suitable inorganic acids include hydrochloric acid,
5 sulfuric acid, phosphoric acid, and mixtures thereof. Phosphoric
acid is a preferred inorganic acid. Suitable organic acids
include carboxylic acids; sulfonic acids; and acidic derivatives
of phosphoric acid substituted with organic substituents, such as
phosphoric acid monoesters and diesters. Organic acids having a
10 PKa less than 2, such as sulfon~c acids or phosphoric ac~d
diesters, are preferred. Alkylbenzenesulfonic acid mixtures or
dialkyl phosphates are particularly preferred organic acids.
The acids are employed in the process of the invention
in amounts of about I to about 100 mmole (preferably 5 to 20
15 mmole) per 100 9 of "polyol mixture." As used herein, the term
"polyol mixture" is understood as the sum of the polyols and
other isocyanate-reactive compounds of components (b) and (d),
water, and the optional additives and auxiliaries. The acid is
usually introduced as part of the "polyol side" during foam
20 preparation, although the acld can, of course, also be introduced
separately.
The following components are employed for carrylng out
the process of the lnvention for the preparation of the open-cell
hydrophllic f1xlng substrates:
1. Allphat1c, cycloaliphatic, araliphatic, aromatic, and
heterocycltc polylsocyanates such as descrlbed by W. Slefken in
Justus Lleblgs Annalen der Chemie, 362, pages 75 to I36,
lncluding lsocyanate compounds of the formula
Q(NCO)n
ln which n is a number of from 2 to about 4 (preferably 2 to 3),
and
Q ls an allphatlc hydrocarbon group w1th 2 to about 18
35 ~preferably 6 to lO) carbon atoms, a cycloallphatic hydrocarbon
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group with about 4 to about 15 (preferably 5 to 10) carbon atoms,
or an aromatic hydrocarbon group with 6 to about 15 (preferably 6
to 13) carbon atoms, for example, polyisocyanates such as those
descr~bed in German Offenlegungsschrift 2,832,253, pages 10 to
5 11.
In general, the polyisocyanates that are commercially
readily available, for example, tolylene 2,4- and
2,6-diisocyanate and mixtures of these isomers ("TDI"), and
polyphenyl-polymethylene polyisocyanates such as are prepared by
10 aniline-formaldehyde condensation and subsequent phosgenation
("crude MDI"), are particularly preferred.
2. Compounds having at least two hydrogen atoms that are
reactive towards isocyanates and generally having a molecular
weight of from about 400 to about 10,000. Such compounds
15 include, in addition to compounds containing amino groups, thiol
groups, or carboxyl groups, the preferred compounds containing
hydroxyl groups. Particularly preferred compounds contain two to
eight hydroxyl groups and have a molecular weight of from 1,000
to 6,000 ~most preferably 2,000 to 6,000), for example,
20 polycarbonates and polyester-am~des containing at least two
(generally two to eight, but preferably 2 to 6) hydroxyl groups,
such as those known for the preparation of homogeneous and
cellular polyurethanes and descr~bed, for example, ~n German
Offenlegungsschrift 2,832,253, pages 11 to 18. Products that are
25 rendered hydroph~lic by ~ncorporat~on of ethylene oxide and/or
ethylene glycol or by another manner are preferred, ~n part~cular
those containlng pr~mary hydroxyl groups to the extent of at
least 50 wt.% (based on the total number of hydroxyl groups).
3. Opt~onally, compounds having at least two hydrogen atoms
30 that are reactive towards ~socyanates and hav~ng a molecular
weight of from 32 to 399. Such compounds also include compounds
conta~n~ng hydroxyl groups, am~no groups, th10l groups, carboxyl
groups, or a comb~nation thereof, preferably compounds conta~ning
hydroxyl groups andlor am~no groups, used as cha~n-extending
35 agents or crosslinking agents. In general, such compounds
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contain from 2 to about 8 (preferably 2 to 4) isocyanate-reactive
hydrogen atoms. Examples are described in German Offen-
legungsschrift 2,832,253, pages 19 to 20.
4. Water as the blow~ng agent. Preferably, the water is
S used ln amounts of about S to about 14 percent by weight (more
preferably 6 to 12 percent by weight) based on the
isocyanate-reactive component 2 discussed above (often referred
to as the "polyol component").
5. Optionally, auxiliaries and additives, such as the
10 following:
(a) Known catalysts in amounts of up to 50 wt.%, based on
the amounts of the acid to be used according to the
invention;
(b) Surface-active addit~ves, such as emulsifiers and foam
stabilizers,
(c) Known reaction retarders; cell regulators such as
paraffins or fatty alcohols or dimethylpoly-siloxanes;
pigments or dyestuffs; known flameproofing agents,
such as tris(chloroethyl) phosphate and tricresyl
phosphate; furthermore stabilizers against agelng and
weathering; plasticizers; and fungistatic and
bacteriostatic agents; and fillers, such as barium
sulfate, kieselguhr, carbon black, or prepared chalk.
Such aux11iar1es and additlves are descr~bed, for
25 example, 1n German Offenlegungsschrift 2,732,292, pages 21 to 24.
Other examples of surface-active additives, foam stabil~zers,
cell regulators, reactlon retarders, stabilizers, flameproof~ng
agents, plasticizers, dyestuffs, fillers, and funigistatic and
bacterlostatic agents to be used accord1ng to the invention, as
30 well as details on the method of use and mode of action of these
addit1ves, are described in Kunststoff-Handbuch (Plast1cs
Handbook), Volume VII, publ~shed by Vieweg and Hochtlen,
Carl-Hanser-Verlag, Munich, 1966, for example, on pages 103 to
113.
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The open-cell hydrophilic polyurethane foams are
produced according to methods known in the art.
The following examples further illustrate details for
the process of this invention. The invention, which is set forth
5 in the foregoing disclosure, is not to be limited either in
spirit or scope by these examples. Those skilled in the art will
readlly understand that known variations of the conditions of the
following procedures can be used. Unless otherwise noted, all
temperatures are degrees Celsius and all parts and percentages0 are respectively parts by weight and percentages by weight.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Example 1 (comparison)
This comparison example is a modification of the method
described in German Offenlegungsschrlft 3,627,236 in Example 1
15 (columns 10
A component
15 parts 5:8 mixture of two polyethylene glycol ethers of OH
number 380 and 72, respectively
30 parts 1:3 mixture of two propylene oxide ethers started
with ethylenediamine and having OH numbers of 650
and 810, respectively
10 parts polyoxypropylene polyol having OH number 400
prepared by using a mixture of sucrose and glycerin
as starters5 10 parts glycerin-started polyoxypropylenetriol having OH
number 400
parts graft polyether polyol having OH number 35 (Bayfit
3699 from Bayer AG)
parts diethylene glycol0 15 parts trimethylolpropane
4 parts water (R
0.2 parts polyoxyalkylene polysiloxane (Tegostab B from
Goldschmidt AG)
0.4 parts N,N-dimethylcyclohexylamine
3 parts fluorotrichloromethane
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e component
113 parts crude MDI
The following characteristic data were determined under
laboratory conditions:
Cream tlme 17 sec
Gel time 33 sec
Rise time 40 sec
The cell structure of the foam was uniform and fine.
After cooling (during which time the foam shrinks greatly) the
gross density was 66 kg/m . The gross density of a foam prepared
by this method is much too high. In addition, the fixing
capacity is not adequate. Although the water uptake of about 11
15 volume percent is also considerably higher than that of normal
polyurethane rigid foam~ the water uptake is much too low for use
as a commerclal hydrophilic fixing foam.
Examples 2 to 6
The preparative ingredients and properties of foams
20 prepared according to the invention and of comparison foams are
descrlbed in the following Table:
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TABLE
Example no.: 2 3 4 5 6
~1)
Polyol (parts) 88 88 88 88 88
Water (parts~ 8 8 10 1.8 8
Stabilizer(2 (parts) 2 2 2 2 2
s 85% Phosphoric acid (parts) - 1 -
10~ Hydrochloric acid (parts) - - - 8
Dibutyl phosphate (parts) - - - - 2
Polyisocyanate(3) (parts) - - 135
MDI (crude) (parts) 135 135 135
Stirring tLme (sec) 15 15 15 15 15
Cream time (sec) 30 23 28 28 27
Rise tlme (sec) 72 63 85 62 68
Tack-free time (sec) 78 66 100 75 77
15 Cell size fine fine fine finefine
Cell structure u n i f o r m
Shrinkage at room none none none nonenone
temperature
Gross density (kg/m3) 24.6 26.2 24.5 29 22.3
.
20 Fixing capacity good good good moderate good
Water uptake (volX) 3.4 85.9 25.4 20 80
(1) Polyether m~xture of the following composition: 18 parts by
welght trifunctional polyether (glycerol + 55% propylene
oxide + 45X ethylene oxide, OH number 56); 37 parts by
weight amlno-polyether (ethylenediamine + propylene ox~de,
OH number 630); 15 parts by we~ght glycerol; and 30 parts by
we~ght trifunctional polyether (trimethylolpropane + 33%
polyethylene oxide 67X ethylene ox~de, OH number 615)
(2) Polyether-siloxane from Br~t~sh Petroleum oO.0 (3) Prepolymer prepared from 110 parts by weight crude MDI and
10 parts by weight Marlo AS-3 acid (clo-cl3-alkylbenzenesulfonic
acid from Huls AG), NCO content 28 wt.X
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Example 2 (comparison) shows that although a usable
foam can be produced without phosphoric acid and with a polyol
formulation correspondlng to the standard formulatlon, the water
uptake is completely unsatisfactory.
Example 3 shows the dramatic improvement in water
uptake by addition of phosphoric acid.
Example 4 (comparison) shows the standard recipe using
modifled ~socyanate (as descr~bed in German Offenlegungsschrift
2,441,843).
Example S shows the use of a different inorganic acid.
Example 6 shows the use of a substituted phosphoric
acid.
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