Note: Descriptions are shown in the official language in which they were submitted.
PATENT
Case D 7093
A W~SIIING ADDI'~IV~ EMBED~ED IN ORGANIC, FLEXIBLE,
FILM-FORMING, WATER-SOLUBLF. POLYMERS
.
BACKGROVND OE' THE INVENTION
This invention relates to a washing additive
embedded in a film of organic, flexible, film-forming,
water-soluble polymers, containing active ingredients
for improving removability by washing of bleachable
stains, fatty or oil~ stains and pigment-containing
soil, which may be added to wash liquors to increase
their detergent effect. The addition oE the additive
according to the invention improves the removal of
bleachable stains and of fat-, oil- and pigment-
containing soil Erom the fabrics to be washed~
In the washing oE fabrics, the wash liquor isgenerally heated to a temperature considerably beyond
room tempera~ure. ~rhis measure increases the detergent
effect oE the detergents used, in some cases to a con-
siderable extent. However, the heating of the washliquor and oE the fabrlcs involves increased energy
consumption ~uring washing. Since, in addition, cer-
tain fabrics, particularly fabrics of wool or synthetic
Eibersl cannot be washed at. high temperature Eor
various reasons, attempts have repeatedly been made to
-1-
obtain good washin~ results at low temperatures. At low
washing temperatures, however, the effect oE the per
compounds frequently used for removing bleachable
stains is reduced, in some cases considerably, or even
weakened to such an extent that the stains in question
cannot be removed. For this reason, so-called bleach
activators are added to detergents to increase their
bleaching efEect, intensifying the bleaching effect of
the per compounds and allG~ing it to be developed even
at low washing temperatures. However, the simultaneous
presence of per compounds and bleach activators in
detergents reduces their stability in storage, par-
ticularly, if the materials cannot be protected against
moisture during storage.
~ttempts to improve stability generally resulted
in a considerable reduction in the bleaching effect of
the detergents. Because of this, it has already been
proposed to store the bleach activator separately from
the detergent containing the per compound and to add at
least part of the activator to the wash liquor just
before it is used. With a view to solving this problem,
DE-OS 27 44 642 proposed a detergent additive which
contains an organic bleach activator in water-
releasable combina-tion with a non-particulate
substrate. In addition to the bleach activator and
optional release aids, the deteryent additive according
to DE-OS 27 44 642 may contain further additives such
as, for example foam modifiers, chelating agents, soil
suspending agents, opticaL brightener~, bactericides,
anti-clouding agents, enzymes, Eabric softeners,
fragrances. By separating the bleach acti~ator and the
bleactling per compound Erom one another until just
b~fore use, it is possible to avoid the problems
arising where per compounds and bleach activators are
stored together.
9~
A furtller improvement in the detergency oE
deteryents based on anionic surEactallts ~nd inorganic
per salts may be obtained by using the additive
according to DE-OS 28 57 153 (corresponding to ~P-OS
0000226) which, in addition to a bleacl~ activator,
contains other detergent ingredients, namely a com-
bination oE an alkoxylated nonionic surfactant and a
cationic surfactant containing a C8-C20 radical and,
for the rest, short Cl-C4 xadicals, in releasable form
]0 on a substrate. ~ silnilar proposal to apply detergent
ingredientsj Eor example a surEactant, in releasable
form to a substrate is knowll Erom DE-OS 28 12 G63. rhe
substrate used in VÆ-OS 28 12 663 is a water-insoluble
polyuretllane foam which contairls t)le active substances
to be released in its cellsO
~ non-cellular, i.e. non-porous, wate~-insoluble
substrate servin~ as a storage for active substances,
Eor examp]e detergellt3 Ol' waslling aids, is described in
Dl3-OS 23 47 299 and in D~-OS 32 03 499. The substrates
; 20 described in tllose publications are respectively water-
~ontainilly and water-rree films oE po]yuretllane gel.
()ne disadvalltage of tl)ese additives lies in tlle fact
tl~nt, after wasllincJ, tl~e water-insolubLe substrate has
to be disentanyled Erom the waslled Labrics. In addi-
tlon, tl)e active substances are, in general, never
coln~letely released frolll tlle substrate.
~ccordingly, it llaS beell proposed to use
detergency-improving readily soluble active substance
combinatiolls in bays oE water-soluble film (~an. pa-tent
applicatioll Serial No. ~80,062 filed ~pril 2~, l9B5)
or in -the form of tablets dissolving spo~ta;neously in
water. US-PS 4 115 292 describes an additive for
dishwashing prepara-tions which consists of
~z~
a combination oE an enæyme and a surEactant, optionally
in conj~nction with othe ingredients of dishwashing
preparations where the e~lzyme is embedded in a film of
a water-soluble polymer.
OBJECTS OE TEIE INVENTION
~n object of the present invention is to provide a
washing additive for increasing the detergency of fabric
detergents which contains detergency-boosting compounds
and which does not require a substrate that has to be
disentangled from the fabrics after they have been
washed.
Another object of the present invention is the
development of a washing additive comprising a mixture
o detergent ingredients embedded in a film of organic,
flexible, film-forming, water-soluble polymers, said
mixture containing at least two of the following a~tive
substances:
a) at least one nonionic surEace-active compound
or at least one nonionic surace-active compound and at
least one an-tigel agent capable of preventing gelation
of said nonionic surace-active compound on contact
with waterr
b) at least one activator for per compounds,
c) at least one nitroyen-containing compound
selected from the group consis-ting oE 1) quaternary
ammonium compounds containing a Clo-C20 alkyl or alke-
nyl and three CL-C4 alkyls, 2) adducts o 1 to 6 mols
of ethylene oxide with 1 mol oE a primary Eatty amine
having a Clo-Cl~ alkyl or akenyl, 3) compounds having
the fortnula:
R - NH - CH2-CEl2-~ONa
where R is a Clo-Clg alkyl or alkenyl, and mixtures
thereof, said waslling additive being readily soluble in
cold water and in cold wash liquors.
These and other objects oE the invention will
become more apparent as the description thereof
proceeds~
DESCRIPTION OF T~IE INV~NTION
The washing additive according to the invention
comprises a mixture of detergent ingredients and,
optionally, auxiliaries which are releasably embedded
in organic, Elexible, Eilm-forming water-soluble poly-
mers. The mixture contains at least two of the
following active substances:
a) at least one nonionic surEace-active compound,
optionally together with an antigel agent for the
nonionic surface-active compound,
b) at least one activator for per compounds,
c) at least one nitrogen-containing compound from
the group comprising quaternary ammonium compounds con-
taining a long-chain Cl~-C20 alkyl or alkenyl and, for
tl)e rest, Cl-C4 alkyls, aclducts of from 1 to 6 mols of
et!lylene o~ide with 1 mol of a primary fatty amine con-
taining a long-chain Clo-C16 alkyl or alkenyl radical,
compounds corresponding to the Eormula:
R-NH-CH2-CI-12-COONa
where R is an alkyl or alkenyl radical containing
from 10 to 18 carbon atoms, more particularly 14 carbon
atoms. The washing additive is readily soluble in cold
water and in cold wash liquors.
More particularLy, the present invention relates
to a washing additive comprising a mixture of detergent
ingredients embedded in a Eilm of organic, flexible,
Eilm-forming, water-soluble polymers, said mixture con-
taining at least two of the following active
substances:
a) at least one nonionic surface-active corrlpollnd
~.2~
or at least one nonionic surface-active compound ancl at
least one antigel agent capable oE preventing gelation
of said nonionic surface-active compound on contact
with water,
b) at ]east one activator Eor per compounds,
c) at least one nitrogen-containing compound
selected from the group consistirlg o~ 1) quaternary
alnmonium compounds containing a Clo-C20 alkyl or alke-
nyl and three Cl-C4 alkyls, 2) adducts oE 1 to 6 mols
oE ethylene oxide with 1 mol of a primary Eatty amine
having a Clo-C16 alkyl or alkenyl, 3) compounds having
the formula:
R-NH-C1l2-CH~-COONa
where R is a C1o-C18 alkyl or alkenyl, and mixtures
lS thereof, said washing additive being readily soluble in
cold water and in cold wash liquors, as well as the
process oE preparing the washing additive.
Suitable nonionic surface-ac~ive compounds (or
tensides) arer above all, adducts of ethylene oxide
onto fatty alcohols containing from 12 to 18 carbon
a-toms, containing from 3 to 10, preferably Erom 6 to 8
and, more particularly 7 mols of ethylene oxide per mol
of alcohol~ The best effects are obtained with adducts
of 6 to 8, more particularly 7 mols of ethylene oxide
onto a C14-C15 oxoalcohol. The presence of tlle
nonionic surfactants in the washing additive according
to the invention promotes above all the removal of fatty
or oily stains during washing.
In many cases, it is best to add foam regulators.
Foaming generally has to be suppressed. Suitable
foaming inhibitors are, for example, the known silicone
oils, such as polydimethyl siloxane.
N-Acyl and O-acyl compounds are suitable activa-
tors for per compounds. Acetyl compounds have proved
to be particularly effective. Examples of suitable
.3~
acetyl compounds are tetraacetyl glycoluril, or pen-
taacetyl glucose or, in particular, tetraacetyl
ethylene diamine. In conjunction with the per compounds oE
the type employed in standard heavy-duty detergents and
particularl~ in conjunction with the perborate normally
used, the bleach activators mentioned lead to an impro-
vement in the removal of bleachable Eabric stains,
especially when washing at temperatures oE Erom 20C to
50C.
Suitable nitrogen-containing compounds are, for
example, quaternary ammoniurn compounds containing a
long-chain Clo-C20 alkyl or alkenyl, preferably alkyl
`- having from 10 to 16 and, more particularly, approxima-
tely 14 carbon atoms. For the rest, the suitable
quaternary ammonium compounds contain three identical
or different Cl-C4 alkyls. These short alkyl chains
are, in particular, methyl. A particularly suitable
and, therefore, preferred quaternary ammonium compound
is tetradecyl trimethylammonium brornide. The quater-
nary ammonium compound may be completely or partlyreplaced by the fatty amine ethoxylate mentioned above.
One example of a particularly suitable fatty amine
ethoxylate is the adduct oE 2 mols oE ethylene oxide
onto primary cocosalkylamine; accordingly, this product
is also preEerred. Inst:ead oE or together with the
quaternary ammonium compoul-d and the fatty amine deri-
vative, it is also possible to use a compound
corresponding to the formula R-NH-~2-~l2 COONa. A
compound in which R is a cocosalkyl radical is pre-
ferred. In the above cocosalkyl is the alkyl derivedfrom coconut oil Eatty acids by hydrogenationO An
improvement in the removal oE pigment-containing soils
erom fabrics is brought ahout by the presence oE the
above surEace-active nitrogen-contaitling compound in
the wash liquor.
\
I necessary, the washing ~dditive oE the inven-
tion may contain small quantities of chelating agents
Eor complexing troublesome heavy metal ions.
Particularly suitable chelating agents are water-
soluble salts o alkane polyphosphonic acids Erom thegroup comprising phosphonoalkane polycarboxylic acids
and amino- and hydroxy-substituted alkane polyphospho-
nic acids, more especially the alkali metal salts oE
a~nino-trls-(methylenepllosphonic acid), dimethyleneami-
nomethane diphosphonic ~cids, l-hydroxyethane-l,
l-diphosphonic acid, l-phosphonoethane-1,2-dicarboxylic
acid, 2-dicarboxylic acid, 2-phosphonobutane-1,2,3-tri-
carboxylic acid and, in particular, the hexasodium salt
of ettlylene diamino-tetrarnethylene phosphonic acid.
The washing additive according to the invention
optionally contains an antigel agent for the nonionic
surfactant. An antigel agent of the type in question
must be capable of preventing the well-known gelation
of the nonionic surfactant on contact with water.
Preferred antigel agents are polyhydric alcohols or
alkanepolyols containing from 2 to 4 carbon atoms which
are thoroughly mixed with the nonionic surfactant. The
antigel efect o the polyhydric alcohol may be inten-
sified by using a mixture of a polyhydric alcohol and
condensation products of Clo C20-fatty alcohols with 1
to 4 mols of ethylene oxide per mol of fatty alcohol
instead of the polyhydric alcohol alone. Polyhydric
alcohols suitable or use as antigel agents are, for
example, l,2-propylene glycol, ethylene glycol or gly-
cerin or mixtures of these alcohols. One example of aparticularly suitable fatty alcohol ethoxylate which
may be used in admixture with the polytlydric alcohol to
intensify the antigel effect is tallow-alkanol ethoxy-
lated with 2 mols of ethylene oxide. However, C12-C
Eatty alcohol ethoxylated witll 3 mols of ethylene
oxide, which contains approximately 70~ of C12 atty
~.2~ 9
alcohol ethoxylate, is also suitable for use as the
antigel agent. If a polyhydric alcohol is used alone
as the antigel agent, a favorable an~igel effect is
obtained if the ratio by weight of nonionic surfactan-t
to polyhydric alcohol is in the range Erom about 1:1
to 1:2. If, by contrast, a mixture of a polyhydric
alohol and a Eatty alcohol ethoxylate is used, very
good results are obtained iE the ratio by weight of
nonionic surfactant to polyhydric alcohol to fatty
alcohol ethoxylate is in the range from (7 to 12) : t5
to 16) : (0.5 to 4). The antigel effect of the antigel
agent may be further increased by using compounds
readily soluble in water, particularly sodium chloride,
sodium acetate, magnesi~l chloride, urea or even
sugars, in addition to the antigel agents described in
the foregoing. The addition of an antigel agent
guarantees the problem-Eree dissolution not only oE the
nonionic surfactant, but also of the water soluble
polymer in which the active substances are embedded.
The mixture of active substances may additionally con-
tain as auxiliaries adducts of from 15 to 25 mols o
ethylene oxide onto 1 mol of a C12-Clg fatty alcohol.
The organic, flexible, film-forming, water-soluble
polymer in which the active substances are embedded in
accordance with the invention is preferably a polyvinyl
alcohol soluble in cold water and hydrolyzed to a level
of from 70 to 90% and preferably rom 78 to 88%.
Particularly good results are obtained with polyvinyl
alcohol which, in addition to this degree of hydroly--
sis, is characterized by a degree of polymeri~ation offrom 225 to 2250 and more particularly from 500 to
1000. A molecular weight of from about 10,000 to
100,000 and, more particularly Erom about 10,000 to
50,000 corresponds to that degree of polymerization.
polyvinyl alcohol such as this quarantees the rapid
dissolution oE the wash.ing additive according to the
invention during the washing cycle in automatic washing
machines, even when the laundry is being washed with
relatively little wash liquor. However, water-soluble
film-forming polymers other than polyvinyl alcohol are
also suitable carriers for the combination o~
detergency-boosting compounds. If these other polymers
are to qualify as suitable carriers, films produced
~rom them must dissolve completely in cold water and in
cold wash liquors in at most lS minutes under the
washing conditions prevailing in automatic washing
machines. In many cases, a mixture of several dif-
ferent water-soluble polymers shows better solubility
than each oE the polymers forming the mixture on its
own.
In order to impar-t a certain flexibility to the
washing additive according to the invention, it is best
to add plasticizers to the preferred polyvinyl alcol-ol.
Suitable plasticizers are polyhydric alcohols, pre-
ferably glycerin and/or polyethylene gLycol. If the
films are intended to be elastic Witil a rough surface
after drying, so that they are readily entrained by the
pieces of laundry during their circulation in the
washing machine, methyl cellulose and/or cellulose
fibers are added to them, in each case in quantities of
up to 15% by weight, based on the quantity of polyvinyl
alcohol.
A particularly efEective and, hence, preferred
washing additive accorcling to the invention contains a
combination o~ at least one nonionic surEace-active
compound together with an antigel agent, at leat cne
activator for per compounds, at least one nitrogen-
containing compound selected from the group consisting
of 1) quaternary ammonium compounds containing a
Clo-C20 alkyl or alkenyl and three CL-C4 alkyls, 2)
adducts of 1 to 7 mols of ethylene oxide with 1 mol of
--10--
a primary fatty amine havirlg a C1o-C16 alkyl or alke-
nyl, 3) compouncls having the formula
R - N~ -CH2-CH2-COONa
where R is a Clo-C18 alkyl or alkenyl, and mixtures
thereoE, and at least one water-soluble salt of an
alkane polyphosphonic acid. The active substances are
preferably present in the fcjllowincJ ratio by weight in
the washing additives according to the invention:
from 2 to 30 parts by weight of nonionic surfactant,0 from 2 to 30 parts by weight o~ activator for per
compounds,
from 0.5 to 10 parts by weight of nitrogen-containing
compound,
from O to 5 parts by weight oE chelating agent.
lS In addition, the washing additive according to the
invention contains from 2 to 50 parts ~y weight oE
antigel agent Eor the nonionic surfactant.
The present invention also relates to a process
for producing the washing aclditive according to the
invention. This process is characterised in that the
active substances and auxiliaries, that is the nonionic
surface-active compound, the activator for the per com-
pound, the nitrogen-containing compound, the antigel
agent, readi]y water-soluble sodium salts or sugars,
adducts of Erom 15 to ~5 mols of ethylene oxide onto 1
mol of fatty alcohol, the water-soluble salt of an
alkane polyphosphonic acid and, optionally, water are
mixed at elevated temperature, preferably at 40 to
60C, with a water-soluble Eilm-forming polymer, to
which the auxiliaries optionally used, i.e. optionally
the polyhydric alcohol and optionally methyl cellulose
and/or cellulose Eibers are added, the ratio by weight
of ~active substances plus auxiliaries) to (polymers
plus their auxiliaries) beiny adjusted to between 1:10
and 5:1 ancl preferably to between 1.5:1 and 3.0:1.
_Jl_
This water-containing mixture of all the components oE
the washing additive forms a highly viscous, tacky
mass. It is formed into Eilms which are so thick that,
after drying at 60 to 80C to a residual water content
of 2 to 10~ by weight, based on the water-free Eilm
containing active substances and auxiliaries, and
optionally aEter rolling, they have a tllickness of Erom
0.4 to 1.5 mm. This thickness guarantees on the one
hand adequate mechanical s~ability and, on the other
hand, sufficiently safe dissolution when the washing
additive is used in a washing machine. The film-
forming process is carried out, for example, on a pre-
heated roll stand, being accompanied by the evaporation
of water. After the residual water conten~ has been
reached and the rolls cooled to aroun~ 35 to 40C, the
elastic film may be removed and, optionally, rolled out
to the thickness mentioned above.
However, the film may also be formed by extrusion
from a die, followed by calendering and drying.
Other forms oE washing additives according to the
inventon may be obtained, for example, by applying the
combination of active substances to a film of water-
soluble polymers and covering the active substances
with another water-soluble film so that the combination
of active substances is firmly anchored between the
films and is only released during dissolution. To this
endt the two films are joined, i.e. for example bonded
or welded, together at their edges or over their
entire surEaces.
Before the use, the film is cut or stamped into
pieces oE the 5ame 5ize which contain active substances
in a quantity sufficient to increase the detergency oE
commercial detergents. This quantity is between about
10 and 50 g for domestic washing machines.
The following examples are illustrative oE the
~12- -
practice of the invention witllout being lilnitative
thereto in any manner.
XAMPLUS
F,YAMPLE 1
90 g o water, 39 g oE polyvinyl alcohol
(molecular weigllt approx. 15,000, de~ree oE hydrolysis
83~) and 39 y o~ polyvinyl alcol-lol ~internally plasti-
cised by copolymerizatiorl; rnolecular weigllt approx.
22,000, degree oE hydrolysis 86~) were dissolve~ at
100C in a heatable stirrer-equipped vessel. 20 g oE
glycerin, ~ g of polyethylene ~lycol (Inolecular weigllt
4000), 4 g oE metllyl ci~llulose an(l ~ g oE cellulose
flbers, max lellgttl 1 min, were added to the resulting
solution (= mixture ~).
Ln anottler mixing ul3it, 97 9 oE tetraacetyl
el:hylenedialllirle, 10~ g o~ C14-Cls~oxoalcohol ~ 7 nlols
o~ etl~ylelle oxide, 37 g of tetradecyl trimethylaln~
motllum bromide, 12 g of a 50% by weight aqueous soLu-
tiOI) oE the hexasodiuln salt oE ettlylenedialllino
tetrallletllylel)e~l~ospllollic acid, 37 y of 1,2-propylene
g]ycol, 37 g oE glycerin, 11 g of oleyl/cetyl alcol~ol -
~2 mols oE etllylelle oxlde and 6 g oE polydimetl-lyl
2S silo.~ane were mixed at 50C to Eorm a paste
(- mi~ture B).
Mixtu~e ~ and mixture B were tl)~n homo~ellize~ Eor
20 mill~tes at 40C in a ~ig-zag kneader (- mixture C).
Mix~ure C was Eed to a rolL stand heatell to 70 oE
whicll the gap width had been adjusted to 0.7 mln. A~ter
treatlnent tor 3 minutes on the roll stalld, the residual
water content amounted to 63 by weight. The roll stand
was cooled to 40C and a 0.7 mm tllick Eilmw~ removed
Erom the roll. The ~ l was cut up into pieces
me.lsuritl~ 25 x 16 cm. 'L'llese pieces contained a
quantity of active substances sufficient for the desired
improvement in detergency. When the pieces of Eilm
were added to the wash liquor of an automatic domestic
washing machine in addition to the quantity of
detergent prescribed Eor one load o~ washin~, a better
washing efEect was obtained than without tlle addition
of the washing adclitive according to the invention when
operating at a wash temperature of 30C.
EXAMPI.E 2
. .
In a heatable stirrer-equipped vessel, 515 g of
polyvinyl alcohol granula-te (molecular weight approx.
15,000, degree of hydrolysis 83~) and 515 g oE an
internally plasticised polyvinyl alcohol granulate were
suspended in 1195 g of deioni~ed cold water and 375 g
of glycerin and a solution was formed by heating the
mixture to 80C. To this solution were added while
stirrin~ 619 g oE Cl~-C15-oxoalcollol -~ 7 mols oE ethy-
lene oxide, 330 g of 1,2-propylene glycol, 61.7 g oE
oleyl/cetyl alcohol -~ 2 mols oE ethylene oxide, 35.2 oE
polydimethyl siloxane, 1~6 g oE a 50~ by weight aqueous
solution oE the hexasodium salt of ethylenediamino
tetramethylenephosphonic acid and quantities oE 53 g
each oE polyethylene glycol (rnolecular weight 4000),
methyl cellulose and cellulose fibers ~length up to
1 mm~. During the addition, the solution cooled to
around 60C. 222 g oE tetradecyl trimethylammonium
bromide, 575 g of tetraacetyl ethylenediamine, 222 g oE
highly disperse precipitated silica, 35 g of sodium
chloride and 0.09 g oE a blue dye were then suspended
in the warm mass.
The mass thus produced had a viscosity oE 9650
mPa.s ~Brookfield viscosimeter, 60C). The mixture
was fed to a roll stand preheated to 70C on which the
water was evaporated to a residual content oE 7~ by
~ .
-14-
weight In 3 minutes, the mixture Eormed a film of
which the thickness was adjusted to 0.8 mm through the
roll gap. After cooling of the roll stand to 40C, the
film wa5 removed and cut into pieces measuring 24 x
15 cm which contained a sufEicient quantity of active
substance foc the desired improvement in detergency.
The Eilms thus produced dissolved completely in 15
minutes in a Miele domestic automatic washing rnachine
with a 30C washing program. Despite being washed with
two thirds of the prescribed dosage oE an ordinary
detergent, the dirty laundry was distinctly cleaner
after washing than without the addition of the washing
additive according -to the invention.
EXAMPLE 3
As in Example 2, an active substance film
according to the invention was produced by suspending
the polyvinyl alcohol granulate in 500 ml of water and
applying the heat during dissolution in the Eorm oE
directly injected steam. By condensation oE the steam,
a ~0% by weight aqueous glycerin-containing polyvinyl
alcohol solution was prepared and then mixed as in
Example 2 with the remaining active substances and
auxlllaries .
EXAMPLE 4
An active substance mass prepared in accordance
with the Eormulation described in Example 2 was applied
by a hand coating kniEe to a metal plate in a film
thickness oE 0.9 mm. This film was dried Eor 60 minu-
tes at 80C in a recirculating air drying cabinet. The
film Eormed corresponded in its dissolving and
detergency-boosting properties to the rolled Eilm oE
Example 2.
-15-
EXAMPLE 5
2~0 kg of an active substance mass containing 23%
of water were prepared according to the formulation
described in Example 2. This mass was concentrated to
a residual water content of 6~ by weight in a thin-
layer evaporator ~Luwa Filmtruder HS) at 50 mbar using
steam under a pressure of 1 bar oE heating. The cut
resistant mass thus obtained was extruded at 70C
through a flat sheeting die into a roll stand (Berstorff
roller head) and processed to a 0.9 mm thick film which
has the perEormance properties described in Example 2.
EXAMPL _
An active substance film was prepared in the same
way as in Example 2, except that instead o:~ 35 g oE
sodiu~ chloride, it contained 35 g of urea. The film
had the same elastic and per:Eormance properties as the
fi1m described in Example 2.
The preceding specific embodiments are illustra-
tive o.E the practice oE the invention. It is to beunderstood however, that other ernbodiments known to
those skilled in the art or described herein may be
employed without departing .Erom the spirit of the inven-
tion or the scope oE the appended claims.
., , ~ .
