CA1190014A

CA1190014A - Composite foil

Info

Publication number: CA1190014A
Application number: CA000406873A
Authority: CA
Inventors: Roland K. Belz
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-07-08
Filing date: 1982-07-08
Publication date: 1985-07-09
Also published as: BR8203944A; EP0069296A3; EP0069296B1; EP0193213A2; JPS5824440A; ES284841U; EP0069296A2; AU8571182A; EP0193213A3; DD230831A1; ES284841Y; AU554636B2; ATE33010T1; ZA824816B; JPH0380097B2; DE3278238D1

Abstract

ABSTRACT OF THE DISCLOSURE The invention relates to a composite foil or sheet, in which 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. To achieve complete sealing-tightness, at least the cover layer is constructed free from pores by the extrusion of a foil of a thermoplastic material. As a sheet the foil is constructed self-supporting or rigid. Components can have fertilizing properties and/or properties useful for water purifying. The composite foil is mainly used for packing purposes and can take the form, for instance, of a box.

Description

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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-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 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,

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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) 3~0~L~
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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.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A composite foil consisting of at least 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, characterized in that the composite foil is con-structed in the form of a self-supporting composite sheet.

2. A composite foil according to Claim 1, characterized in that the reaction layer is constructed semi-rigid.

3. A composite foil according to Claim 1, characterized in that the reaction layer is constructed rigid.

4. A composite foil according to Claims 1 or 2, charact-erized in that the reaction layer contains fillers, and/or fibrous material.

5. A composite foil according to Claims 1 or 2, char-acterized in that the reaction layer contains mineral fillers and/or fibrous material.

6. A composite foil according to one of Claims 1 to 3, characterized in that the reaction layer has a paper, card-board, pasteboard or corrugated pasteboard structure, the reaction layer contains a binder and the binder is water-soluble or soluble in the dissolving intermediary contained in the reaction layer.

7. A composite foil according to Claims 1 to 3, char-acterized in that it is shaped.

8. A composite foil according to Claims 1 to 3, char-acterized in that it is folded into the form of a box.

9. A composite foil according to Claims 1 to 3, char-acterized in that the reaction layer and/or the cover layer are printed.

10. A composite foil according to Claims 1 to 3, char-acterized in that the reaction layer and/or the cover layer can be printed on.

11. A composite foil comprising at least 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, the reaction layer containing dissolving intermediaries for the cover layer and at least the cover layer being constructed free from pores by the extrusion of a foil of a thermoplastic material, as set out in Claims 1 to 3, characterized in that when the composite foil is used for packings which are adapted to dissolve in liquids, more par-ticularly sewage, the reaction layer and/or the cover layer are at least partly made of materials which are flocculation agents or produce such when they dissolve.

12. A composite foil comprising at least 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, the reaction layer containing dissolving intermediaries for the cover layer and at least the cover layer being constructed free from pores by the extrusion of a foil of a thermoplastic material, as set out in Claims 1 to 3, characterized in that when the composite foil is used for packings which are adapted to rot by composting or the like, the reaction layer and/or the cover layer consist at least partly of materials which after dissolution have soil-improv-ing properties and/or fertilizer properties.

13. A composite foil according to Claims 1 to 3, char-acterized in that the cover layer and the reaction layer are made of the same thermoplastic material, and the reaction layer contains dissolving intermediary additives for itself and for the cover layer.

14. A composite foil according to Claims 1 to 3, char-acterized in that it has on the cover layer and/or between two layers a substantially light impervious layer.

15. A composite foil according to Claims 1 to 3, char-acterized in that it has on the cover layer and/or between two layers, an aluminium vapor coating.