Note: Descriptions are shown in the official language in which they were submitted.
1078733
This invention relates to bandages and their pre-
paration.
Bandages according to the present state of the art
consist of woven or knitted materials which may also be com-
bined with plastic sheets. Both natural and synthetic fibers
may be used for the manufacture of the woven or knitted ;
fabrics. Bandages which are required to have a cooling effect
for the treatment of inflammatory swellings are usually dipped
in water, but such swellings may also be treated with wet
towels, handkerchiefs or other woven or knitted materials
inqtead of bandages. The same method of treatment is also
used for reducing high body temperatures, for example, in
infants and small children. -In that case, wet towels or
handkerchiefs are wrapped around the patient's calves. This
procedure has numerous disadvantages. The main disadvantage
is that textile materials of the above-mentioned type may
only hold a very limited quantity of water and any excess
would drip from the bandage and wet the surrounding areas.
It has now been found that the disadvantages of the
bandages previouqly used may be overcome by using bandages
made of materials based on polyurethane urea gels~
The materials used according to the present invention
may consist of the gels alone or they may advantageously
consist of combinations of the gels with any supporting
layers of textile or non-textile products. These supporting
layers may be bonded to the polyurethane on one or both sides.
The hydrogels and alcohol gels to be used according
to the present invention, which are based on polyurethane
polyureas, have been essentially disclosed in German DOS
2,347,299. They may be obtained by reacting isocyanate pre-
polymers of polyethers containing at least 40YO o~ ethylene
~. ~
rA ~ - 1 -
., j~ ,
.: '' ` .. :
``-`` 10~8733
, .
oxide units with diamines or higher polyamines or water as
chain lengthening agents in the presence of water and/or
alcohols as dispersing agents, as well as perfumes and
optionally other additives. The term "gel" is used herein to
described the physical nature of the gel-like end product
rather than the exact polymer physical structure according to
the present day views of the colloid chemistry of this state.
It has been found that bandages based on such gels,
preferably polyurethane polyurea hydrogels, have numerous
surprising advantages:
~ The water content in the gels may be greater
than 9~h, by weight, and have any value below this figure.
The water is absolutely-firmly fixed in the polymer network
even if the water content is 95%, by weight and will not
migrate from the gels.
2. The gels are mechanically strong and may be
elastically stretched. They are found to have a high
ultimate tensile strength.
3. Syneresis does not take place when the gels
or bandages are left to stand. The water is immobilized
so that the gel may be regarded as consiting of "solid
water".
4. The gels or bandages containing the gels
may be frozen at temperatures below the freezing point of
water without destruction of or damage to the gel structure.
Freezing is reversible and thawing and refreezing may be
repeated indefinitely.
5. When the bandage is applied, a cooling
effect takes place and water is slowly liberated from the gel
30- or bandage. The water lost by this process may be restored
to the polymer structure by leaving the gel or bandage in water,
r - 2 -
1078733
that is to say the liberation and absorption of water are
reversible.
6. The gel products may easily be combined with
the support materials. One particularly striking feature
is the firm bond obtained between the gel and textile sheets.
7. The gel masses may easily be shaped. They may
be obtained as flat structures or they may be converted into
any desired shapes in suitable molds. This shaping is
particularly useful if the dressings are required for the
treatment of parts of the body which are difficult to bandage
in the conventional way.
The present invention thus relates to the use, as
dressing, of polyurethane urea gels-containing water and/or
alcohols and optionally also comprising supporting layers,
intermediate layers and/or covering layers.
In particular the invention relates to a bandage
comprising (A) a polyurethane urea gel comprising (i) a
polyaddition product of an isocyanate prepolymer which has
been prepared from a polyisocyanate and a polyether polyol,
said polyether polyol containing at least 4~/O, by weight, of
ethylene oxide units, and a chain lengthening agent selected
from the group consisting of water, polyamines and mixtures
thereof, and (ii) 30 to 95%, by weight~ based on the total
weight of the gel, of a dispersing agent selected from the
group consisting of water, aliphatic monohydric alcohols,
aliphatic polyhydric alcohols and mixtures thereof, (B) bonded
to at least one textile support layer.
The present invention also relates to a process
for the manufacture of bandages based on polyurethane urea
gels containing water and/or alcohols, characterized in that
isocyanate group-containing prepolymers which are obtained from
~'
10~8733
polyethers containing at least 4G%~ by weight, of ethylene
oxide units are mixed with water and/or polyamine~ as chain
lengthening agents in the presence of water and/or alcohols
and optionally also perfumes, pharmaceutical preparation~
and other additives. The re~ulting mixture is applied to or ~-
between layers of support materials before the components
complete their reaction. This procedure is optionally
accompanied by a shaping process.
In particular the invention relates to a process
for the preparation of a bandage comprising i) preparing
an isocyanate prepolymer from a polyisocyanate and a poly-
ether polyol which contains at least 40 weight percent of
ethylene oxide units, and ii) forming a polyurethane urea
gel on a textile substrate by cross-linking said prepolymer
with an agent selected from the group consisting of water,
polyamines and mixture~ thereof in the presence of 30 to
95 wt. %, based on the weight of the gel, of a dispersing
agent ~elected from the group consisting of water, aliphatic
monohydric alcohols aliphatic polyhydric alcohols and mixtures ~-
thereof.
Either water or alcohols or mixtures of both may be
used for the preparation of the gels. The products of the
process may therefore be divided into hydrogels and alcohol
gels. The alcohols used may be either readily volatile
monohydric alcohols, such as ethanol, isopropanol or butanol,
or comparatively non-volatile polyhydric alcohols, such as
ethylene glycol, diethylene glycol, glycerol or trimethylol-
propane. In the preferred gels acc~rding to the present
invention, at least 5~/0, by weight, of the dispersing agent
consists of water.
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~ ~078733
Preparation of the gels may be carried out by various
methods. For example, all the components, i.e., the prepolymer
the dispersing agent, i.e. water and/or alcohol, perfumes,
pharmacuetical preparations, chain lengthening agents and
any other additives may be added all at once, but ~ey are
- preferably added stepwise. In that case, the perfumes,
pharmaceutical preparations and any other additives, as well
as cross-linking agents if used, e.g, polyamines, are dis-
solved in the dispersing agent. At the same time, an emulsion
or solution of the prepolymer in the dispersing agent is
prepared and the two batches are-then mixed in suitable stoi-
chiometric proportions. The resulting mixture is poured
- :
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1~78'733
into molds or applied to textile or non-textile support
materials. Whichever procedure is adopted, the reaction
to form the gel which is used as bandage or part of a bandage
takes place within a few seconds or minutes.
The end-product obtained may be a non-cellular solid
or a foam, depending on the chain lengthening agent used.
Non-cellular gels are obtained when amines are used as chain
lengthening agents. However, when water is used the products
are foams due to the concomitant reaction of the isocyanate
groups with water to produce gaseous carbon dioxide.
Vigorous mixing of the starting components facilitates
the preparation of the gels and improves their quality.
In the simplest case, mixing may be achieved in a zone
of high turbulence produced by mechanical stirrers. Better
results are obtained by using high speed mixing apparatus,
such as impeller homogenizers or mixing chambers with
agitators of the type described in the literature or used
in commercial polyurethane foaming machines. Vigorous
mixing may also be achieved with the aid of mixing devices
of polyurethane foaming machines in which the components
are mixed by counterflow injection.
The gels may be poured or spread out to form endless
webs of any desired thickness befoxe they are cross-linked,
and, if desired, these webs may be profiled.
It is particularly advantageous to apply the gels
to support materials before they are cross-linked. These
support materials may consist, for example, of woven or
knitted fabrics, non-woven webs, foils or mesh fabrics
based on natural and/or synthetic polymers. These support
LeA 16,684 -5-
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1078733
.
materials may also have a foam structure. Suitable foams for
use as support materials are, in particular, the well known
soft and semi-hard polyurethane foams. The thickness of the
layers of gel may vary within wide limits and basically
depends only on the requirements of the bandage. The gel
layers generally have thicknesses of from about 1 to about
50 mm.
. :
The prepolymers used for the preparation of the gels,
consisting of polyethers containing at least 40%,by weight,
of ethylene oxide and of higher functional polyisocyanates
still containing free isocyanate end groups, are prepared
by reacting suitable polyethers with an excess quantity
of polyisocyanate, i.e. using an isocyanate: hydroxyl
ratio greater than 1:1, preferably from 1.5:1 to 20:1 and
, 15 most preferably from 2:1 to 10:1.
The optimum ratio for carrying out the process depends
on the molecular weight, functionality and structure of the
polyether. The isocyanate contents of the prepolymers
should generally be from about 2 to about 20%, by weight,
preferably from 3.5 to 10%, by weight.
When amines are used as chain lengthening agents,
the prepolymers and amines are required to be used in
substantially stoichiometric quantities for producing the
bandage gels, but when carrying out the process on a technical
scale, it has been found that in order to obtain a suitable
residence time of the reactants in the mixing assemblies it
is advantageous to use an excess of amine component, i.e.
an NH2:NCO ratio greater than 1:1 and preferably from 1:1 to
1.2:1.
LeA 16,684 -6-
.. . .
1078733 ~`
When water is used as chain lengthening agent,
the isocyanate groups and water may also be used in stoi-
chiometrically equivalent proportions. However, if desired
and especially for producing foam gels, a substantially
larger quantity of water may used. In that case, it is
particularly advantageous also to use water as dispersing
agent so that hydrogels in ~he form of foams are obtained.
Water in that case fulfills a double function, first as
reactant for the reaction with isocyanate groups and second
as dispersing agent.
The quantity of water and/or alcohol present when
the gels are being formed may vary within wide limits and is
not critical. The weight of alcohol and/or water may be
up to 98%, based on the total mass of gel. However, the
properties of the gels obtained are strongly influenced by
the proportion of polymer to dispersing agent. As a
general rule, the gels obtained are progressively more
stable and harder with increasing polymer content and
softer and structurally less rigid with decreasing polymer
content down to the lower limit of about 2~, by weight.
The gels used according to the present invention preferably
contain from about 30 to 95~, by weight, of water and/or
alcohol.
It is particularly surprising that the gel-based
bandages according to the present invention are exceptionally
stable. Even after prolonged storage, the gels undergo no
visible phase separation which would be noticed, for example,
by the material becoming cloudy. The dimensional stability
is preserved even when the gels are stored at elevated
temperatures and again no phase separation is observed. The
dispersing agent is very firmly fixed in the gel, but may be
LeA 16,684 -7-
1078733
liberated from it quite rapidly, depending on its vapor
pressure, and the body of the gel then gradually shrinks
proportionately to its external dimensions. At this stage,
perfumes and pharmaceutical preparationsmay also diffuse
5 from the gel to be liberated to its surroundings, for example `~
to the patient's skin. The liberation of dispersing agent
causes additional cooling, especially if the dispersing
agent is water. The liberation and reabsorption of dis-
persing agent from and into the gel is reversible. This
means that when the gels have lost some of their dispersing
agent, they may reabsorb fresh dispersing agent and build
it into the polymer structure when stored in pure dispersing
agent.
Another surprising characteristic of the gels is
that they may be frozen and thawed repeatedly any number of
times without destruction of their structure. This property
is particularly advantageous when water is used as dispersing
agent by virtue of its high thermal or cooling capacity.
The bandages according to the present invention may therefore
be stored indefinitely in refrigerators or cooling chests
until they are required.
The starting materials required for the ~els used
according to the present invention include polyethers having
a molecular weight of from about 500 to about 10,000,
preferably from 2,000 to 8,000, which have at least two active
hydrogen atoms and contain at least 40~, by weight, of ethylene
oxide groups. Polyethers of this type may be prepared by
reacting compounds containing reactive hydrogen atoms, e.g.
polyhydric alcohols, with ethylene oxide and optionally also
other alkylene oxides, such as propylene oxide, butylene
oxide, styrene oxide, epichlorohydrin or mixtures of these
alkylene oxides.
LeA 16,684 -~-
1078733
Suitable polyhydricalcohols and phenols include
ethylene glycol, diethylene glycol, polyethylene glycol,
propane-1,2-diol, propane-1,3-diol, butane-1,4-diol, hexane-
1,6-diol, decane-1,2-diol, butyne-2-diol-(1,4),glycerol,
butane-2,4-diol, hexane-1,3,6-triol, trimethylolpropane,
resorcinol, hydroquinone, 4,6-di-tert.-butyl pyrocatechol,
3-hydroxy-2-naphthol, 6,7-dihydroxy-1-naphthol, 2,5-dihydroxy-
l-naphthol, 2,2-bis-(_-hydroxyphenyl)-propane, bis-(_-hydroxy-
phenyl)-methane and ~ -tris-(hydroxyphenyl)-alkanes, such
as 1,1,2-tris-(hydroxyphenyl)-ethane or 1,1,3-tris-(hydroxy-
phenyl)-propane.
Other suitable polyethers include the 1,2-alkylene
oxide derivatives of aliphatic or aromatic monoamines or poly-
amines, such as ammonia, methylamine, ethylene diamine,
N,N-dimethylethylenediamine, tetra- or hexamethylenediamine,
diethylene triamine, ethanolamine, diethanolamine, oleyl-
diethanolamine, methyl diethanolamine, triethanolamine,
aminoethyl piperazine, o, _ and ~-phenylene diamine, 2,4-
and 2,6-diaminotoluene, 2,6-diamino-~-xylene and multinuclear
20 and condensed aromatic polyamines, such as 1,4-naphthylene ~:
diamine, 1,5-naphthylene diamine, benzidine, toluidine,
2,2-dichloro-4,4'-diaminodiphenylmethane, l-fluorenamine,
1,4-anthradiamine, 9,10-diaminophenanthrene and 4,4'-diamino-
azobenzene. Resinous materials, such as phenols and resols,
may also be used as starting molecules for the polyethers.
Ethylene oxide is included in the synthesis of all
these polyethers.
The starting components used according to the present
invention also include aliphatic, cycloaliphatic, araliphatic, ;-
LeA 16,684 -9-
~078733
aromatic and heterocyclic polyisocyanates of the type which
have been described, for example, by W. Siefken in Justus
Liebigs Annalen der Chemie, 562, pages 75 to 136. The
following are examples: ethylene diioscyanate; tetramethylene-
1,4-diisocyanate; hexamethylene-1,6-diisocyanate; dodecane-
1,12-diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-
1,3- and -1,4-diisocyanate and mixtures of these isomers;
l-isocyanato-3,3,5-trimethyl-5-isocyanato-methyl-cyclohexane
(German Auslegeschrift No. 1,202,785); hexahydrotolylene-
2,4- and -2,6-diisocyanate and mixtures of these isomers;
hexahydrophenylene-1,3- and/or -1,4-diisocyanate; perhydro-
diphenylmethane-2,4'- and/or 4,4'-diisocyanate; phenylene-
1,3- and-1,4-diisocyanate; tolylene-2,4- and -2,6-diisocyanate
and mixtures of these isomers; diphenylmethane-2,4'- and/or
4,4'-diisocyanate; naphthylene-1,5-diisocyanate; triphenyl-
methane-4,4',4"-triisocyanate; polyphenyl-polymethylene
polyisocyanates which may be obtained by aniline-formaldehyde
condensation followed by phosgenation and which have been
described, for example, in British Patents 874,430 and
848,671; perchlorinated aryl polyisocyanates as described,
e.g. in German Auslegeschrift No. 1,157,601; polyisocyanates
containing carbodiimide groups as described in German Patent
1,092,007; the diisocyanates described in U.S. Patent
3,492,330; polyisocyanates having allophanate groups according
to British Patent 994,890, Belgian Patent 761,626 and published
Dutch Patent Application 7,102,524; polyisocyanates having
; isocyanurate groups as described, e.g. in German Patents
1,022,789; 1,222,067 and 1,027,394 and in German Offenlegung-
sschrift Nos. 1,929,034 and 2,004,048; polyisocyanates having
urethane groups as described, e.g. in Belgian Patent 752,261
or in U.S. Patent 3,394,164; polyisocyanates having acylated
urea groups according to German Patent 1,230,778; poly-
- LeA 16,684 -10-
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~(~78733
isocyanates containing biuret groups as described, e.g.
in German Patent 1,101,394, British Patent 889,050 and
in French Patent 7,017,514; polyisocyanates prepared
by telomerization reactions, e.g. as described in Belgian
Patent 723,640; polyisocyanates containing ester groups
as mentioned, e.g. in British Patents 956,474 and
1,072,956, in U.S. Patent 3,567,763 and in German Patent
1,231,688; and reaction products of the above-mentioned
isocyanates with acetals according to German Patent
1,072,385.
The low molecular weight cross-linking or chain
lengthening agents used may be aliphatic, cycloaliphatic,
or aromatic diamines or higher polyamines, for example,
ethylene diamine, hexamethylene diamine, diethylene triamine,
hydrazine, guanidine carbonate, N,N'-bis-(3-aminopropyl)-
ethylene diamine, N,N'-bis-(2-aminopropyl)-ethylenediamine,
N,N'-bis-(2-aminoethyl)-ethylenediamine, 4,4'-dimethylamino-
diphenylmethane, 4,4'-diamino-diphenyl-methane and 2,4-
and 2,6-diaminotoluene.
Preparation of the prepolymers from polyethers and
polyisocyanate is carried out by known methods, using NCO:OH
ratios greater than 1:1.
A considerable quantity of both water-soluble and
water-insoluble additives (i.e. additives which may be
25 emulsified in water, if required with the addition of ;
dispersing agents) may be added to the reaction mixtures for
preparing the gels used in the manufacture of the bandages.
Examples of suitable additives include: haemostatic agents,
various pharmaceutical preparations, disinfectants, dyes,
LeA 16,684 -11-
1078733
perfumes and cosmetic preparations for the skin, for example
to regulate its moisture content. Other suitable additives
include natural or other synthetic gel formers, such as
gelatin, carrageenates, alginates, polyvinyl alcohol and
methyl cellulose. All these additives may be added to the
gel compositions in quantities of up to about 20 volumes
percent.
Considerable quantities (up to about 50 volume
percent)of various fillers may also be added in the preparation
of the gels. These include silicates obtained from various
silicic acids, aluminum oxides, tin oxides, antimony tri-
oxide, titanium dioxide, graphite and graphitic carbon,
carbon black, retort carbon, air-borne sand, pulverulent
cements and various inorganic and organic dye pigments,
such as iron oxide pigments, lead chromate, lead oxide and
red lead. Short or long fibers of natural or synthetic
materials, for example powdered cellulose, may also be
used as fillers.
` One advantage of using fillers is that it delays
the liberation of the dispersing agent, i.e. of water and/or
alcohol, as well as of any other additives, and therefore
~` prolongs the time during which the bandage may be left on
the patient before it must be removed.
If desired, a gaseous component (generally air)
may be added to the reaction mixture during gel formation.
Gel bandages with a foam structure are thereby obtained,
; in which the unit weight (kg/m ) is substantially lower
than that of the non-cellular materials, depending on the
~` quantity of gas incorporated.
LeA 16,684 -12-
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1078733
One particular advantage of the process according
to the present invention is that it may very easily be
rendered continuous.
In a continuous process, the isocyanate prepolymers
and, separately therefrom, the chain lengthening agent and
dispersing agent are continuously introduced into a mixing
zone at a temperature above the melting point and below
the decomposition point of the isocyanate prepolymer and
chain lengthening agent at such a rate that the isocyanate
polyaddition reaction is not completed in the mixing zone.
The polyurethane gel obtained in a still fluid and deformable
state with a high water or alcohol content is continuously
removed from the mixing zone. If required, the still fluid
gel is passed through a short reaction tube fitted with a
shaped mouthpiece so that the resulting polyurethane gel
is obtained as a completely shaped endless strand, band or
sheet.
. .
This gel may then be used as a bandage on its own,
but it is preferably combined with a support material.
This may be done by applying the vigorously mixed mass of
gel continuously or intermittently to the textile or non-
textile supports in conventional coating installations,
for example, by means of coating knives or by brush
; coating or casting.
The bandages obtained in this way may be sold
:~ open, but they are preferably sealed into waterproof foils
which may be opened as required. This method of packaging
may be carried out in conventional commercial automatic
heat sealing machines.
LeA 16,684 -13-
~78733
The term "bandage" used in this application is
intended to encompass a broad category of materials made
from the polyurethane urea gels. The opportunity to shape
the gel allows for the bandage to be useful in a number of
applications, particularly for the external treatment of
animals or the human body for cosmetic and/or medicinal
purposes. A bandage may be generally defined as a flexible
strip or band used to cover, strengthen or compress the
external body or to dress or bind up wounds. For example,
the gels may be used as bandages for the treatment of
inflammatory swellings, as leg compresses for reducing
the body temperature of infants, as compresses for localized
or general lowering of the body temperature, for carrying
out operations on undercooled patients, and as face masks
and ice packs.
LeA 16,684 -14-
~078733
EXAMPLES
Example 1
; (a) Preparation of the prepolymer:
159 parts, by weight, of tolylene diisocyanate
(80% 2,4- and 20% 2,6-isomer) are heated to 80C in a reaction
; vessel.
1,200 parts, by weight, of a polyether having a
polyhydroxyl number of 28 which has been obtained by the
chemical addition of 60%, by weight, of ethylene oxide and
40%, by weight, of propylene oxide to glycerol are added
dropwise with stirring over a period of 3 hours. The
reaction mixture is then heated for one more hour at 80C
and left to cool to room temperature with stirring. The
resulting prepolymer has an isocyanate content of 4.2%,
by weight, and a viscosity of 5,200 centipoises at 25C.
(b) Manufacture of the bandage:
7 parts, by weight of the prepolymer described .=
under (a) are added to 59 partsj by weight, of water over
a period of 3 seconds with mechanical stirring (rate of
stirring 1165 revs/min). When the reaction mixture has been
stirred for 50 seconds, it is poured into a mold.
~; The interior of the mold measures 25 x 8 x 0.5
cm. A cotton fabric (muslin bandage, 34 g/m2) 8 cm in
width is placed longitudinally on the base measuring 25 x8 cm
so that 10 cm of bandage overhangs the base at both ends.
60 seconds after the beginning of mixing, the
reaction sets in with slight foaming (cream time). The
gel time is 90 seconds. 10 minutes later, the foaming
reaction is ccmpleted. The shaped product is removed from the
mold after 5 minutes and sealed into an aluminum foil which
LeA 16,684 -15-
1~178733
has been coated with polyethylene on the side facing the
bandage. The density of the gel product is 660 kg/m3.
The sealed bandage is stored at -20C for 24 hours.
The water in the bandage i8 then left to thaw and return to
room temperature. The use properties of the bandage are
not altered even when this process is repeated several
times.
Example 2
The procedure is exactly the same as in Example
l(b), but a polyamide-based fabric with a mesh of 1 mm and
a weight of 130 g/m2 is used instead of the cotton fabric.
Example 3
The procedure is exactly the same as in Example
l(b), but a polyamine -based fabric (130 g/m2) i9 used
insted of a cotton fabric and a polyethylene foil con-
forming to the dimensions of the base of the mold (25 x 8 cm)
is placed on the reaction mixture at the beginning of the
reaction so that the mixture is completely covered by the
~ foil.
i~ 20 Example 4
'~'
The procedure is exactly the same as in Example
l(b), but in~tead of 59 parts, by weight, of water there
- is used an emulsion of 0.2 parts, by weight, of a dye of
color index No. 42,085, 3.5 parts, by weight, of a perfume
oil (mixture of 60%, by weight, of isobornyl acetate and
40%, by weight, of the condensation product of 1 mol of
nonyl phenol and 10 mol of ethylene oxide) and 55.3 parts,
by weight, of water.
LeA 16,684 -16-
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1~78733
Example 5
The procedure is exactly the same as in Example
l(b), but the 59 parts, by weight, of water are replaced
by an emulsion of 56 parts, by weight, of water and 3 parts,
by weight, of an ointment for cuts and burns having the
following composition: Phenolum liquefactum 1 g, Bismutum
sUbgallicum S g, Emplastrum Lithargyri 20 g, ointment base
; ad 100 g.
Example 6
The procedure is exactly as in Example l(b),
but using a suspension of 55 parts, by weight, of water
and 4 parts, by weight, of pulverulent titanium dioxide
instead of 59 parts, by weight, of water.
Example 7
The procedure is exactly the same as in Example
l(b), but using a mixture of 46 parts, by weight, of water
and 13 par~s, by weight, of propan-2-ol instead of 59
parts, by weight, of water.
., .
. Example 8
The procedure is exactly the same as in Example
l(b), but the reaction mixture used is a mixture of 9O5
parts, by weight, of the prepolymer described in Example
l(a) and 53.5 parts, by weight, of a solution consisting
of 52 parts, by weight, of water and 1.5 parts, by weight,
of the aluminum salt of acetic acid. The gel mass has a
density of 630 kg/m .
LeA 16,684 -17-
107~733
Example 9
The procedure is exactly the same as in Example 1
(b), but the reaction mixture used is a mixture of 9.5 parts,
by weight, of the prepolymer described in Example l(a),
and 53.5 parts, by weight, of a mixture of 52 parts, by
weight, of water and 1.5 parts, by weight, of menthol.
Measured from the beginning of the process of mixing the
two reactants, the stirring time is 45 seconds, the cream
time 60 seconds and the gel time 70 seconds. The density
of the gel i= 630 kg/m3.
., ,
., :
:.
LeA 16,684 -18-
