Note: Descriptions are shown in the official language in which they were submitted.
~ ~(3~
l'he i.nvention relates to a composite foil consisting
of a-t leas-t two layers, wherein at least one outer cover layer,
normally insoluble in water, is connected to a water-soluble,
at least single-layer reaction layer which contains a
dissolving intermediary for the cover layer, at least the
cover layer being constructed free from pores by the extrusion
of a foil of a thermoplastic material.
C,erman Offenlegungsschrift 2,703,005 in the Applicant's
name discloses a foil adapted to be used once by being laid on
a toilet seat. In one embodiment the foi.l can take the form
of a composite foil, a water-soluble layer turned towards the
user having on its side remote from the user a cover or seal-
ing layer insoluble in water. This cover laye~r can be
dissolved in an acid or basic medium. For this purpose the
water-soluble layer contains a corresponding basic or acid
additive, so that when completely immersed in water the foil
is soluble as a whole, but not when water merely contacts its
cover layer.
European Patent Application 80 1~8 243.9 in the
2~ Applicant's name (Publication No. 32 244), which is not a
prior publication, discloses a further development of this
toilet seat covering and also mentions that such a composite
foil is also suitable as a packing material and for the
making of carrier bags, sachets and the like.
It has been found that a foil of the kind disclosed
in European Offenlegungsschrift 32 244 is extremely suitable
for many applications, more particularly as a packing material,
not only in flexible form, but also in self-supporting form,
more particularly i~ the form of semi-rigid to rigid sheets.
Such mechanical supporting capacity and rigidity can be
achieved if the polymers of the reaction and/or cover layer
are themselves formulated rigi.d, or the reaction layer and/or
30~L
the cover layer are provided with fillers, more particularly
mineral fillers and/or fibrous material. ~hus, the reaction
layer of the composite foil can be constructed like paper,
cardboard, pasteboard or corrugated pasteboard, the binder
being water-soluble or dissolvable by the dissolving
intermediary which is contained in the reaction layer and
which is preferably at the same time also a dissolving
intermediary for the cover layer. Furthermore, the reaction
layer, also as in papermaking, can be produced by salting
the components from an aqueous solution in an alkaline or
acid medium. The composite foil can take the form of blanks
for packing material and be pre-punched and have embossed
lines for subsequent folding. The foil can also be pre
shaped into boxes, if necessary with lids. The composite
foil is~more particularly suitable as a packing for cigarettes
and other goods whose packaging is normally thrown away pretty
earelessly hy consumers and contaminates the environment,
unless it dissolves or rots away quiekly.
According to one embodiment of the invention, the
composite foil is printed on, more particularly in colours,
this causes no environmental eontamination even if the pack-
ing material is simply thrown away by the consumer, since it
quickly decomposes due to the penetration of moisture. If
the reaction layer is produced separately from the cover
layer, preferably the reaction layer is printed on, capacity
to be printed on ean be aided by the use of suitable fillers.
It has also been found that sueh polymers and other
components are suitable for making the composite foil accord-
ing to the invention and have an even positive effect on the
environment when the foil and the packing produced therefrom
decompose. Thus, components of the foil or the whole foil
can have soil-improving and, in dependence on the dissolving
intermediary selected, even fertilizing properties, if after
use the packings ma~e from them are normally subjected to
deliberate rotting or composting or are merely thrown away.
If after use the packings are normally mixed with liquids
or flushed away by liquids, components with properties of
auxiliary flocculation agents have proved particularly
advantageous, khis will be discussed hereinafter. Very
advantageously the composite foil according to the invention
and the packing produced therefrom consist exclusively of
materials which decompose, or act as dissolving intermediaries
to dissolve one another, when moisture or liquid penetrates to
the side of the reaction layer.
me cover layer and/or the reaction layer can also
have on their fre;e surfaces a textile coating of individual
fibres which are anchored in the top side of the foil or glued
thereto. The length of the fibres, which are felted with one
another to a limited extent, can be in the range of about
0.01 to 2 mm or longer. me fibres reinforce the foil
mechanically and prevent sticking as the result of any
electrostatic charges. Nevertheless, after use the foil
can be completely dissolved, since although the fibres are
to some extent felted to one another, they are not permanent-
ly interconnecte~. The fibres preferably used are cellulose,
more particularly cotton fibres. Other fibrous materials
are however suitable.
The cover layer and the following or any further
layers are preferably interconnected, more particularly
welded together over their whole surfaces. However, they
can also be glued by partly dissolving one and/or the other
surface, or by means of an adhesive. The cover layer and
reaction layer are preferably made of the same plastics,
normally insoluble in water, the reaction layer also contain-
-- 3
ing dissolving intermediary additives for itself and thecover layer. These additives can he uniformly distributed
in the reaction layer or be present at a higher concentration
in the boundary layer with the cover layer. ~s a rule this
depends on the thickness of the reaction layer and the
facility with which the dissolving intermediary can convert
water-insolubility into solubility. If it is made of a
water-soluble material, such as hydroxy-propyl cellulose, the
reaction layer can also be free from dissolvin~ intermediary
additives and have on the side pointing towards the cover
layer an additional intermediate layer which contains the
dissolving intermediary additives for the cover layer.
Since the co~er layer need not be self-supporting,
if the reaction layer performs the supporting function, the
former is as a rule thinner than the latter. The cover layer
can be very thin, since it has been found that due to product-
ion by extrusion, even a layer thickness of 1 to 5 ,um, more
particularly 2 to 3 ~m, is fully adequate to achieve the
required density. ~s a rule, therefore, the thickness of
the cover layer is less than 10 ~m. The thickness of the
reaction layer depends upon how many further layers the
composite foil contains, and what mechanical loadings they
are required to withstand. Their layer thickness is at least
10 to 50 ~m, and can have the thickness of paper, cardboard
or pasteboard. The thickness of the reaction layer or layers
can be up to 0.5 mm or even 1 mm, in this case there are no
limits. Reinforcements can also be inserted into the layers
or between the layers, preferably taking care that the re-
inforcements themselves readily d~compose during the dis-
solution process, as is the case, for example, with individualfibres. The reaction layer can also be porous and even have
the structure of corrugated pasteboard, more particularly a
~g~
structure of corrugated pastehoard with a fine corrugation
(~-corrugation) and/or a double corrugation. The composite
foil can have thicknesses up to 5 mm and above. If the
mechanical loadability of the cover layer is important,
however, it can be as thick as or thicker than the reaction
layer, if the cover layer is required to withstand some
detrition or scratching without endangering its resistance
to water. In that case the cover :Layer can be constructed
self-supporting ~o rigid, so that essentially the only
purpose of the polymer of the reaction layer is to act as
a carrier or binder for the dissolving intermediary.
At least if the thickness of the cover layer is
of the order of magnitude of the thickness of the reaction
layer, or the cover layer is even thicker than the latter,
the reaction layer is preferably so structured and formulated
that it dissolves relatively slowly after having previously,
however, stored as much moisture as possible. As a result
the dissolving intermediary in the reaction layer can start
to be dissolved, and its dissolution can cause the dissolu-
tion of the cover layer before the reaction layer is dissolvedaway, so that there is a risk that the dissolving intermediary
will be washed away before the cover layer is dissolved. For
this purpose binders suitable for the reaction layer are
swellable substances which become gelatinous under the action
of water, but decompose only when the cover layer also de-
composes. The polymer of the reaction layer can also be so
adjusted that it is soluble in a substantially neutral pH or
in the case of a weakly acid or weakly basic pH, but not in
strongly acid or strongly alkaline pH. However, if due to
water absorption by the dissolving intermediary the pH becomes
relatively strong:ly acid or strongly basic, at first only the
cover layer disso:Lves. When this has been dissolved away and
-- 5
the dissolv:ing interrnediary has been partly leached out, the
reaction layer can also dissolve.
The material of the cover layer is preferably
resiliently formulated, so that the foil or sheet or a
punched or pre-embossed blank for a packing can be bent or
kinked without the cover layer brea~ing or tearing.
Suitable materials for the cover layer are extrudable
plastics which are insoluble in water and the usual, mainly
neutral aqueous solutions, but can be rendered soluble by
suitable dissolving intermediaries, more particularly acids
or bases. In contrast, the reaction layer can consist of or
contain a water-soluble or retardedly soluble plastics such
as polyvinyl alcohol or hydroxy-propyl cellulose (Klucel J
of Hercules Powder), for example, as a binder for fibres and/or
for the dissol~ing intermediary.
Preferred materials for a flexible cover or reaction
layer are copolymers or terpolymers of unsaturated organic
acids, such as acrylic acid, methacrylic acid, maleic acid
anhydride and crotonic acid as the component reac~ing with
the dissolving intermediary, and with vinyl ethers or acrylates
as the flexibilizing component. The reactive components and
the flexibilizing components can each be used on its own or
as a mixture. Examples of flexible rnaterials are given in
the Table, more particularly Nos. 39 and 68.
Preferred materials for a rigid cover and reaction
layer are copolymers and terpolymers of unsaturated organic
acids, such as acrylic acid, methacrylic acid, maleic acid
anhydride or crotonic acid as the component reacting with
the dissolving intermediary, with styrene or vinyl acetate
or methyl methacrylate as the stiffening components and
vinyl ethers and acrylates as the viscosity-mediating com-
ponents. The reactive components and the flexibilizing or
viscosity-mediating components can be used on their own or as
a mixture.
For instance, in one embodiment at least the cover
layer consists of a thermoplastic, water-soluble homopolymeric
or copolymeric acid which is, however, dissolvable in a basic
medium, more particularly such an acid which has been obtained
by the use of acrylic acid, methacrylic acid, crotonic acid
and/or maleic acid anhydride with styrene and vinyl ether in
the molar ratio 1:1~0~3.
Suitable extrudable plastics are also solid copolymers
of vinyl acetate and a small proportion of crotonic acid,
which are present in the form of a low-viscosity polymer and
are soluble in alkali. Such a polymer is marketed, for in-
stance, under the trade mark Vinnapas C 305 by Wacker-Chemie
GmbH, Munich.
The individual layers of the composite foil can also
consist of mixtures of plastics.
The dissolving intermediaries which can be used for
dissolving the cover layer are acid polymers, more particular-
ly water-soluble carbonates, secondary and tertiary phosphates,
silicates, borates, amines and basic amides. The co-use of
so-called detonators, which swell considerably or generate
gases on contact with water, can also be advantageous. Such
a detonator is, for instance, sodium carboxy-methyl cellulose
(~ymcel ZSB 10 of Nyma). Preferably attention is paid to
all the materials for the composite foil which are environ-
mentally harmless, as is substantially the case with the
aforementioned products.
To make the composite foil individual, preferably
all layers of the foil are formed by the extrusion of thermo-
plastic substances with suitable properties and interconnected.
The individual layers can be extruded as separate foils and
C3~ l4
then interconnected. Interconnection is preferably performed
merely by laying the foils on one another while they are
still hot and sticky.
~ Iowever, as already mentioned, the surfaces can
also be made sticky subsequently. The foils arriving from
the extruder and if necessary stretched can either be further
processed immediately or rolled UE) for intermediate storage,
either individually or preferably in the form of a cornposite
foil.
The individual layers can be extruded through a co-
extrusion noæzle, while at the same time being interconnected.
The result is a particularly intimate connection. ~owever,
care should be taken that the components of both layers are
so adapted to one another that any waste can be re-used in
one or other of the extruders, without having a disadvantageous
influence on the composition of the material of the layers.
Thus, wastes which contain dissolving intermediary can be
re-used for making a reaction layer or intermediate layer
which contains the dissolving intermediary.
As a rule the individual foils come out of the
extruder thicker than their required thickness in the com-
posite foil. In that case the foils are stretched to the
required thickness, this can be done individually or com-
positely. There are numerous possible uses for the foil
according to the invention, mainly in the packaging sector.
Nowadays it is a considerable problem to dispose of no longer
usable packaging materials. This can be done by the foil
according to the invention, since after use it can be dis-
solved in water or aqueous solutions, and its material can be
of such a cornposition that the substances dissolving are
harmless and comE)atib]e with the environment. After hydrolysis,
maleic acid anhydride and acrylic acid copo]ymers give similar
products to the polymers of an acrylic acid basis used on a
large scale as auxiliary flocculation agents in the treatment
of clarified sludge. They are therefore useful products in
sewage.
According to the Manufacturers' statements, in
the toxicological aspect, the cellulose derivative Klucel~M
has the same effect as purified celiulose.
q~he carbonates, phosphates, silicates and borates
which can be used as dissolving intermediaries are components
of detergents, and so is the detonator NymcelTM, which can
also be used as an auxiliary flocculation agent.
Since the composite foil according to the invention
is at least partly made of thermoplastic materials, the
packages made from the foil can be tightly closed by welding
or sealing.
All the packaging forms have the property that when
thrown away after use, within an adjustable time they dissolve
in an aqueous medium, or with the approach of moisture, for
instance, in the open air.
In a preferred embodiment of the invention, the
foil takes the form of a carton, box, container or the like.
In each case the wall can be so constructed as to have a
cover layer on both its inner and outer sides. This can be
achieved by each wall being formed by two composite sheets
being so laid on one another that their water-soluble sides
adjoin one another and the cover layers point outwards. This
prevents the boxes or the like from being sensitive to moisture.
If, on the other hand, they are mechanically torn open during
or after use, water can get between the water-soluble layers
of the foil so that the foils and therefore the boxes or the
like can dissolve. ~Iowever, it is also possible so as to
construct the composite foil that a water-soluble reaction
0~3~
layer is provided on both sides with a cover layer~ After
mechanical des-truction this foil is also completely dis-
solvahle, since the water can penetrate between the cover
layers into the foil and dissolve the reaction layer and
then the cover layer. In this embodiment it is also possible
to construc-t the reaction layer porous in the inside or to
give it a suctional insert, so that the penetration of water
into the reaction layer is boostecl, and therefore the dis-
solution process accelerated. Similar considerations apply
to packages made of a rigid composite foil which, as already
mentioned, can have a corrugated structure in the supporting
layer.
The physlcal and also chemical properties of the
individual layers of the composite foil can be varied by
using for such layers plastics formulations whose composition
is correspondingly varied. The speed of dissolution of the
individual layers can be determined by the ratio between the
acid or basic component of the copolymer or-terpolymer and
the proportion of comonomers and termonomers, and additionally
by the nature and content of the dissolving intermediary in
the reaction layer. Furthermore, the dissolution speed of
the composite foil can be further reduced by incorporating
less soluble or hardly soluble substances in the disperse
phase or in dissolved form in the materials of the individual
layers. If desired, stickiness-increasing additives can also
be incorporated in one and/or the other layer.
According to a further embodiment of the invention,
the dissolving intermediary for the water-insoluble cover
layer can also be incorporated in the reaction layer by the
use of water-soluble hollow fibres or porous hollow fibres
which are filled or impregnated with the dissolving inter-
mediary. This can facilitate the mixing and binding in of a
dissolving intermediary which is no-t readily miscible with
the material of the reaction layer. It is also possible
to provide the dissolving lntermediary in encapsulated
form in the reaction layer or the edge layer for sealing.
m us, the dissolving intermediary can advantageously be
enclosed in so-called rnicrocapsules, whose skin or envelope
consists of water-soluble material which does not melt at
the production temperature.
Further features of the invention can be gathered
from the following description of preferred embodiments, in
combination with the drawings and claims.
In the drawings which illustrate the invention:
Figure 1 is a cross-section through an embodiment
of the invention in the form of a packaging for dry materials
Figure 2 shows diagrammatically the embodiment
illustrated in Figure 1 after emptying and the entry of
water' and
Figure 3 is a cross-section through a variant in the
form of a packaging for water-containing materials,
In the embodiment of the invention as illustrated
in Figures 1 and 2, to make the drawings clearer the wall
thicknesses of the individual layers of the packaging are
shown exaggerated in size. The wall 1 of the packaging has
a self-supporting reaction layer 2 which is provided with a
thinner cover layer 3 on its outside. The ratio between the
wall thicknesses of the reaction layer and the cover layer is
about 3:1. Both the reaction layer 2 and the cover layer 3
are made of a thermoplastic copolymer which has free carboxy
groups or forms such groups under the action of water and
which is soluble :in a basic medium, but not in acid or in
substantially neutral solutions. The reaction layer 2 also
contains very fine particles 4 of a basic substance which is
~o~
incorporated as a dissolving intermediary. The quantity of
dissolvlng intermediary 4 is such or present in an adequate
excess to make both the reaction and cover layers soluble.
~ he packaging illustrated in Figure 1 has a closed
form in cross-section and can be produced, for example, by
the co-extrusion of the two layers directly as a rectangular
section through a correspondingly shaped rectangular nozzle.
Suitable pieces can be cut to length from the resulting endless
section and, after filling, closed at the ends by welding. ~le
packaging is used for materia]s in the form of lumps or powder
for, e.g., small domestic goods such as nails, screws or the
like, but it can also be used for cigarettes, foodstuffs, etc.
The water-tight cover layer makes the packaging
resistant to the entry of water from outside As shown
diagrammatically in Figure 2, when the pack has been opened
and emptied, water can penetrate into the pack and gradually
dissolve the reaction layer, due to the dissolving intermediary
uniformly distributed therein. The moisture penetrates
through the softened reactlon layer as far as the cover
layer and can dissolve the latter, due to the dissolved
alkaline dissolving intermediary and the high pH value thereby
obtained. In this way the pack is completely dissolved, and
the time within which the pack is supposed to fall apart on
the entry of water can be adjusted by a suitable formulation
of the layers.
It is also possible to make the pack by folding from
a foil or sheet and then interconnecting the edges by welding
or glueing. With an adequate overlap of the edges, without
disadvantage the reaction layer can be left unprotected at
the cut edges, since as a rule the packs do not come into
immediate contact with water before their contents are removed,
but are merely meant to protect their contents against the
~g~3~
entry of molsture.
It is also possible to deform the foil according
to the invention by deep drawing or the like, so as to produce
a pack which consists of a carton on which the article to be
packed lies, and then to cover the latter with a hood-shaped
transparent plastics part of the foil according to the
invention, which is rigidly connected by its edges to the
carton and therefore encloses the article to be pac}ced. The
carton also advantageously has the structure of the foil or
sheet according to the invention.
In the embodiment of the invention illustrated in
Figure 3, in addition to the outer cover layex 3 the pack
has an inner cover layer 5 so that the pack can also be
filled internally with a liquid without the pack being
dissolved. The reaction layer 2 is also double in con-
struction' an outer part 6 of the reaction layer 2 being
separated from an inner part 7 by a corrugated structure 8
acting as a spacer. The two reaction layers can also merely
bear loosely against one another. The purpose of the
corrugated structure ~ is to enable water to get freely
in between the two parts 6 and 7 of the reaction layer 2
when the pack has been torn open, so that after the pack has
been used dissolution can take place rapidly. The corrugated
structure can consist of a fibrous material which also falls
to pieces after or during the dissolution of the packing. It
is also possible to make from such a double composite foil
with cover layers on both sides, boxes and flasks, for in-
stance, by the deep-drawing or blowing p.ocesses.
Examples
A number of examples will now be given for the
production of acid copolymers and termonomers for the cover
layer, when such polymers are mixed with basic substances,
3()~
they can also be used as material for the reaction layer.
The preferred monomer producing solubility in bases i8
rnaleic acid anhydrideO The comonomers used in the case of
copolymers are preferably styrene or methacrylate, in the
case of terpolymers, ethyl-vinyl ether or methyl acrylate
and butyl acrylate also being used.
Polymerization is pexformed in conventional manner,
using radical formers, for instance, peroxides, as catalysts
at temperatures between roorn temperature and 200C. The
polymerization processes can be the known ones, including
substance polymerization, they are preferably performed in
the reaction extruder. The following Table gives a number of
properties of the copolymers and terpolymers obtained~ To
form the reaction layer, the polymers can be mixed with up
to 50% by weight of basic substance.
In the Table the abbreviations s-tand for the
following:
SOL = Solvent
MAA = Maleic acid anhydride
WAT = Water
PHOS ~ Triammonium phosphate
EVE = Ethyl-vinyl ether
MAC = Methyl acrylate
BAC = n-Butyl acrylate
SUB = Substance (solvent-free)
ACE = Acetone
BEN = Benzene
LAP = Lauroyl peroxide
CHC = Bis (4-tertiary butyl-cyclohexyl) peroxibi-
carbonate ("Perkadox"rM 16)
- 14 -
3~0~L~
a) ~ a) a) a
r-l r-¦ r-¦ r~i r-lr-¦
~ R R ~ R ~ ~ R ,Q
U~ r~ rl rl ~1) rY rl a ) r~ r~ ri
E~ X X X ,~ u X ,~ u X X
,~ ~ a) a) ~ -~1 ~ ~ ~1 a) a)
rl r-i r--¦ r~ r~r-i r-i
i4~H ~1 ~1-1 ~i lq ~1~1 ~ ~1-1 ~H
U ~
rl a) o o o o o
~_~
~ U C~
S~ r_i
~ i ~ r~i
Q ~ t~) ~ ~ R
O ,i ~ ~ O
r~ R o ~ ~ d~ ~ ~ ~ ,:>~
ra ~) ~ d~l r) r~
~ ~ l ~ ~J
R~ 11
~ ri r-i ~ 1 d~
Ui U~ ~ r-i r-i r~ r~i r-i r-i .
u ~ R
~ O ~ W~O t~ ~D t~ t~ O
~H h r-l
~ _~ r-l
o ~ ,~ o o o o o o tn
~i , a) po~ ~ O ~ I` 00 0~ W D
m~
E~ ri ~ H d~ 10
U h O O O r-¦ ttl
~-1 tl) ~) 1~ rl O ~H
tn ~ H r-i r-l ~i r-i O U 3 1n
~0 ~1. R, 11 >,
r tfl r i ~ (I) t~l ~
~ O ~ X r i r-i r-l r lr l r-l~ ~
o ,, tn ~ 11
,~ ~ ~ z m ~ z; m m o
,~ o
h :> u~ m u~ ~ m tn t" ~i ~n
R ~ h tn rl
~- 1-) ta ~ 1 r-l
O O O ri r-l r-l
rd rCI
~ P~ ~' O
O ~ o ~ F a~
m m E~ rc~
~0 ~ r-l ~n O
o ~ ~
c~ ~ t~ , i t~
n ~ ~ ~i ,4 U
-- 15 --
Examples of rigid Copolymers
Vinyl acetate/maleic acid anhydride copolymerization:
13 g (0.5 mole) of vinyl acetate, 49 g (0.5 molel
of maleic acid anhydride and 0.1 g of lauroyl peroxide were
dissolved in 400 cc of benzene and heated for five hours
at 70C. The copolymer was precipitated from the viscous
solution with petroleum ether (80 to 100C). ~he copolymer
dissolved well. in diluted caustic soda.
Styrene/maleic acid anhydride copo~ymerization:
52 g (0.5 mole) of styrene and 49 g (0.5 mole~ of
maleic acid anhydride were heated with 0.1% lauroyl peroxide
for six hours at 80C. A polymer was obtained whic-h dissolved
very well in diluted caustic soda.
- 16 -
