WO2007010553A2

WO2007010553A2 - Combined multi-layered water soluble film and process for producing the same

Info

Publication number: WO2007010553A2
Application number: PCT/IN2006/000105
Authority: WO
Inventors: Shilpan Pravinchandra Patel
Original assignee: Arrow Coated Products Ltd
Priority date: 2005-03-24
Filing date: 2006-03-24
Publication date: 2007-01-25
Also published as: WO2007010553B1; ZA200709177B; EP1863635A2; WO2007010553A3

Abstract

This invention relates to a combined water soluble film wherein at least one layer is a solution cast water soluble film on a liner and at least one layer is a preformed water soluble film, preferably a thermally extruded water soluble film. The said water soluble films may be edible or non edible. The said water-soluble film on a liner is coated with a tie-coat to enable coating of a water-based binder used for combining the water soluble films without dissolving/damaging WSF on liner. The water based binder used for combining the said water soluble films may be incorporated with active ingredients like flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine. The said combined water soluble film so achieved will be a substantially pinhole free multi-layered water soluble film of desired mechanical strength at low cost. The invention farther relates to the methods/processes used for producing a cast-extruded or cast-cast combined WSF.

Description

Combined multi-layered water soluble film and process for producing the same

FIELD OF INVENTION

This invention relates . to combined multi-layer water soluble film and process for producing the same.

BACKGROUND OF INVENTION

Water soluble films (WSFs) are commercially well known in the market. These films are usually used for packaging purpose such as liquid detergents, agrochemicals, toilet blocks, laundry bags, fish baits, pigments and dyestuffs, liquid chemicals and for embroidery purpose such as for making lace or can be used as a backing or a topping for embroidery. However, these applications are by no means limiting. These films may be biodegradable.

These known films are commonly produced by a solution cast method or by an extrusion method. Solution cast films are cast from a slot, which controls thickness and weight, onto a steel belt or steel drum or a suitable liner etc. Extruded films can be blown (bubble type) or slit-die cast (Extrusion curtain type).

In blown film extrusion, the molten polymer from the extruder enters the die and is forced around a mandrel and emerges from a ring shaped die. The extruded film tube is then expanded to a specific diameter by air pressure from the center of the mandrel. As the bubble expands, the film thickness decreases.

In slit die extrusion or flat film extrusion, the WSF is produced by extruding molten polymer through a slit-die and then cooling it on chilled rollers or in a water bath. In flat film extrusion, it is important to cool the material within a short distance of the die head so that a clear film is produced and necking (reduction in width) does not occur. These films can be co-extruded in multiple layers or can be fed through multiple hoppers and/or screws. Manufacturing process and the blend will determine the quality of the film.

Extrusion processes are economical but suffer from the disadvantage that all types of extrusion methods are thermally reactive and create pinholes in the resultant films. These pinholes are due to various reasons including improper thermal reactions, changes in polymer's molecular weight, improper gauge variation, uneven relative humidity acceptance, improper polymer melts, etc. Pinholes are detrimental to the final quality of the product being packed and are not acceptable to the industry. The films so formed have less "shrink back" property. Another problem of this method is control of moisture equilibrium within the WSF. This equilibrium is vital to get the right mechanical properties of WSF.

Solution cast manufacturing process is a well accepted process to produce water soluble film with considerably less pinholes. In this process the polymers and additives are all dissolved completely in solvents, like, but not limited to, water of varying qualities and varying temperatures, while mixing in a batch mixing reactor. This leaves less possibility of pinholes as the polymers melts/dissolves in near totality. The additives mix properly and completely and thus the resultant film is of better quality. Moisture equilibrium, thickness and solubility can be finely controlled in this process.

The solution cast process is expensive, as the solution has to be cast on metal belt or a conveyor or a detachable liner and cured after the solvents dry out. So there has been a need for an economical and substantially pinhole free water soluble film, with optimal mechanical properties.

Combining two water soluble films also gives rise to problems. One cannot blow a film on top of a solution cast film, as blown films are in a bubble form and solution cast films are in web forms individually wound. One cannot do T Die extrusion of a water soluble film on a solution cast film web as the film shall not come out unstuck from the chilling cylinder, which is inherent part of the T die extrusion process. Similar problems shall be faced during any of the combination of thermally activated extruded film with cast film.

Similarly, one cannot cast a wet mix solution on a web of blown/extruded film as this will dissolve partially or completely the web prior to the combined web reaching the dryers making it commercially unviable.

Also, while dispersing active ingredient into the water soluble film, it has been noticed that some active ingredients like perfumes which are mixed in the batch used for forming the water soluble film layer diminishes after some time during storage, thereby affecting the quality.

Indian patent 443/MUM/2001, relates to a water soluble film embedded/entrapped with active ingredients for precise delivery of active ingredients. The patent is restricted to embedding active ingredients within WSF and does not describe a process of combining two water soluble films.

Indian patent 1158/MUM/2001 relates to a pinhole free multi-layered film by barrier coating on a water soluble film along with a liner. However, the patent does not describe a process of combining two water soluble films.

Hence, an object of the present invention is to provide a cast-extruded or a cast-cast combined water soluble film and a process for combining layers of water soluble films to achieve a substantially pinhole free multi-layered water soluble film of desired mechanical strength at low cost.

Another preferred object of this invention is to provide a combined water soluble film in which active ingredients like flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine are added and the properties of the active ingredient such as perfume are retained for a longer period.

Yet another preferred object of this invention is to provide a combined water soluble film, wherein active ingredients like flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine are added to the binder and/or the tie- coat for different applications .

SUMMARY

Thus according to one aspect of this invention, there is provided a multi-layer WSF as defined in claim 1.

More particularly, the multi-layer WSF comprisies at least one layer of solution cast WSF with a detachable liner preferably provided with a tie coat, a binder coating provided on the said solution cast WSF with liner and at least one layer of preformed WSF provided over the said binder coat and forming a substantially pin hole free combined multi- layered WSF.

In one embodiment, the combined water soluble film comprises at least one layer of solution cast water soluble film on a liner and at least one layer of a preformed water soluble film, either a solution cast or a thermally extruded water soluble film. The combined water soluble films so produced provide a substantially pinhole free multi- layered water soluble film of desired mechanical strength at low cost.

The said water soluble films may be edible or non edible. The solution cast water-soluble film on a liner is preferably coated with a tie-coat to enable application of a water-based binder coating for combining the water soluble films without dissolving/damaging the solution cast WSF on liner. The water based binder used for combining the water soluble films may be incorporated with active ingredients like flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine.

The preformed WSF may be a thermally extruded WSF, such as blown (bubble type) or slit die-cast (extrusion curtain type), forming a cast-extruded combined WSF.

Alternatively the preformed WSF may be a solution cast WSF forming a cast-cast combined WSF.

The binder coating may be applied directly on the solution cast WSF. Alternatively, a tie coat may be provided on the solution cast WSF prior to application of the binder coating. The tie coat may be selected from acrylic acid polymers, acrylic ester polymers, soluble acrylic acid copolymers, soluble acrylic ester copolymers, soluble copolymers of acrylic acids and esters, cross linked polyvinyl alcohols, cross linked cellulose derivatives, ethyl cellulose, nitrocellulose, cellulose butyrate, cellulose acetate butyrate, ethylene vinyl polyalcohol, ethylene vinyl acetate, PVDC (polyvinyldene chloride), acrylic emulsion, PVC (polyvinyl chloride) emulsion, PVDC emulsion, PVB (polyvinyl butyral), natural arid synthetic waxes, polyurethanes and modified polyvinyl alcohols.

The binder may be selected from any low viscosity, low solid content binder like different types of adhesives such as pressure sensitive adhesives, cast water soluble film solution, polyurethane dispersion or even a liquid flavour.

The solution cast WSF with liner forming one layer and the preformed WSF forming another layer may be formed of non-edible materials selected from Polyvinyl alcohol copolymer ionomers, Polyvinyl alcohol homopolymer, non - ionomeric poly vinyl alcohol polymer, Polymethacrylate., polyvinyl alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, biodegradable polyesters such as ecoflex; polylactic acid (PLA), polyhydroxyalkanoic acid (PHA) and polyurethane.

Alternatively, the solution cast WSF with liner forming one layer and the preformed WSF forming another layer may be formed of edible materials selected from polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch and its derivatives, sorbitol, sucrose derivatives, gum Arabic, pullulan and dextrin and water- soluble cellulose derivatives or combination thereof. The cellulose derivatives used are methyl cellulose, hydroxy propyl cellulose, hydroxy propyl methyl cellulose, hydroxy propyl ethyl cellulose, hydroxy ethyl cellulose and carboxy methyl cellulose.

In some embodiments, the tie coat and/or the binder coat may incorporate a desired amount of one or more of the same or different types of active ingredients, as per the requirement for a given application.As the active ingredient is added to the binder coat and/or the tie-coat, it remains blocked between the outer layers of the water soluble film thereby improving the retention and quality of the active ingredient, for example a perfume..

Preferably, the one or more active agents are selected from flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine.

The detachable liner of the solution cast WSF may be made of paper, film, foil or fabric, treated or untreated, coated or uncoated, preferably the said liner is made of film, more preferably polyester film. The films can thickness ranging from 3 microns to 500 microns, preferably from 10 microns to 300 microns, more preferably from 25 microns to 100 microns. The film liner may be plain, metallised, embossed, gloss, matt, extrusion coated, laminated or release coated depending on the desired characteristics of the end product. Paper liners are also used for production of WSF. Paper liners that accept temperatures needed for the production of WSF and have thickness ranging from 7 GSM (grams per sq meter - the standard for measuring weight of paper) to 500 GSM, preferably from 20 GSM to 300 GSM, more preferably from 60 GSM to 180 GSM can be used. The paper liner may be plain, embossed, gloss, matt, extrusion coated laminated or release coated depending on the desired characteristics of the end product. Fabrics made of cotton or synthetic yarns, solution coated, plain, embossed, gloss, matt, extrusion coated or laminated. The preformed WSF may be provided with a detachable liner made of materials similar to those used for the solution cast WSF. The solution cast WSF and preformed WSF may have liners of the same or different materials according to the requirements of a particular application.

In some embodiments of the combined WSF, the WSF may be cold water soluble, or warm water soluble, or hot water soluble, and may be edible or non edible, depending upon the raw materials used according to the requirement of a particular application.

Accordingly to another aspect of this invention there is provided a process for producing a multi-layer combined WSF comprising of the following steps: a. providing a first preformed WSF with detachable liner, b. providing a second preformed WSF with or without a detachable liner c. applying a tie-coat on one side of the WSF with the liner; d. drying and curing the WSF coated with tie coat; e. applying a binder coat over the said tie coat of the WSF with liner; , f. semi-drying the binder coat, g. combining the second preformed WSF with the first WSF of the step (f) by passing through a nip roll and forming a laminated double layered combined WSF, h. passing the double layered combined WSF through heated rolls for dissipating the entrapped moisture; i. storing the combined WSF laminate for internal ageing, and j. detaching the liner and slitting/cutting the combined WSF laminate, as per requirement.

The second preformed WSF may be a cast WSF or an extruded WSF whereby the invention provides a process for producing a cast-extruded or cast-cast combined WSF.

The binder coat may be applied directly to the cast WSF with detachable liner.

Accordingly, in one embodiment, the process comprises the following steps: a. casting WSF on a liner using edible or non-edible formulations of WSF in a batch reactor b. drying the cast WSF of step (a) at a primary drying section to form one/first layer of a combined WSF, c. applying a tie-coat on one side of the WSF with the liner d. drying and curing the WSF coated with tie coat; e. applying a binder coat over the said tie coat of the WSF with liner; f. semi-drying the binder coat, g. combining the first WSF of the step (f) with a second preformed WSF by passing through a nip roll and forming a laminated double layered combined WSF₅ k. passing the double layered combined WSF through heated rolls for dissipating the

^' entrapped moisture; h. storing the double layered combined WSF for internal ageing, and i. detaching the liner and slitting/cutting the combined WSF laminate, as per requirement.

Alternatively, the binder coat may be applied directly to the cast WSF with detachable liner according to one of the processes mentioned in the invention.

The said tie-coat is preferably applied by using a gravure cylinder of varying cell sizes and depths; or by using flexo plates of varying cell sizes and depths, or by combination of flexo plates with gravure cylinder, for transferring net solid contents of the tie-coat from the cells of the cylinder and that maximum water/solvent is scrapped before hand by cam shaft moving doctoring blade.

The said tie coat is preferably selected from acrylic acid polymers, acrylic ester polymers, soluble acrylic acid copolymers, soluble acrylic ester copolymers, soluble copolymers of acrylic acids and esters, cross linked polyvinyl alcohols, cross linked cellulose derivatives, ethyl cellulose, nitrocellulose, cellulose butyrate, cellulose acetate butyrate, ethylene vinyl polyalcohol, ethylene vinyl acetate, PVDC (polyvinyldene chloride), acrylic emulsion, PVC (polyvinyl chloride) emulsion, PVDC emulsion, PVB (polyvinyl butyral), natural arid synthetic waxes, polyurethanes and modified polyvinyl alcohols.

The said binder coat is preferably applied by using a wire bound mayer bar.

Preferably, the said liner is made of paper, film, foil or fabric, treated or untreated, coated or uncoated, preferably the said liner is made of film, more preferably polyester film. The films can thickness ranging from 3 microns to 500 microns, preferably from 10 microns to 300 microns, more preferably from 25 microns to 100 microns. The film liner may be plain, metallised, embossed, gloss, matt, extrusion coated, laminated or release coated depending on the desired characteristics of the end product. Paper liners are also used for production of WSF. Paper liners that accept temperatures needed for the production of WSF and have thickness ranging from 7 GSM (grams per sq meter - the standard for measuring weight of paper) to 500 GSM, preferably from 20 GSM to 300 GSM, more preferably from 60 GSM to 180 GSM can be used. The paper liner may be plain, embossed, gloss, matt, extrusion coated laminated or release coated depending on the desired characteristics of the end product. Fabrics made of cotton or synthetic yarns, solution coated, plain, embossed, gloss, matt, extrusion coated or laminated.

The said binder is preferably selected from any low viscosity, low solid content binder like different types of adhesives such as pressure sensitive adhesives, cast water soluble film solution, polyurethane dispersion or even a liquid flavour. The WSF formulation may be formed of edible materials selected from polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch and its derivatives, sorbitol, sucrose derivatives, gum Arabic, pullulan and dextrin and water- soluble cellulose derivatives or combination thereof. The cellulose derivatives used are methyl cellulose, hydroxy propyl cellulose, hydroxy propyl methyl cellulose, hydroxy propyl ethyl cellulose, hydroxy ethyl cellulose and carboxy methyl cellulose.

Alternatively, the WSF formulation may be formed of non-edible materials selected from Polyvinyl alcohol copolymer ionomers, polyvinyl alcohol homopolymer, non - ionomeric poly vinyl alcohol polymer, polymethacrylate., polyvinyl alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid biodegradable polyesters such as ecoflex; polylactic acid (PLA), polyhydroxyalkanoic acid (PHA) and polyurethane.

In some embodiments, one or more of same or different types of active ingredients may be incorporated in the said binder coat and/or the said tie coat where provided.

The said active ingredients may be selected from flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio- pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine.

The raw materials of the WSF, the binder coat and/or the tie-coat where provided may be selected such that the combined WSF is soluble in cold water, or warm water or hot water, as per requirement. Preferably, the WSF with liner is moved at high speed, preferably from 15 to 100 meter/min., more preferably from 25 to 70 meter/min. for preventing the WSF from dissolving when the binder coat is applied directly to the WSF without the tie-coat.

Preferably, the WSF with liner and binder coat is subjected to a temperature ranging from 20⁰C to 100⁰C, preferably from 30⁰C to 70⁰C, more preferably from 50⁰C to 60⁰C for instantly (rapidly?) semi-drying the said binder coated applied directly to the WSF without the tie-coat, for preventing the WSF from dissolving.

In another embodiment the present invention provides a process for producing cast- extruded combined WSF, comprising the following steps: a. providing a preformed WSF with a detachable liner, b. extruding a desired thickness of WSF directly onto the said preformed cast WSF with liner, c. cooling the combined WSF laminate of step (b) d. storing the combined WSF laminate of step (c) for an internal ageing period, e. detaching the liner and slitting/cutting the combined WSF laminate as per requirement.

Preferably the combined WSF laminate is cooled by passing through one or more chilling cylinders keeping the said liner in contact with the chilling cylinder.

Preferably, the said liner is a hydrophobic, thermally active detachable liner.

Preferably, the said combined WSF laminate is stored for an internal ageing period ranging from 1 hour to 720 hours, preferably from 10 hours to 360 hours and more preferably from 24 hours to 100 hours.

The said double layered cast-cast or cast-extruded combined double layered WSF with liner may be combined with a third layer of WSF to form a three layered combined WSF by any of the processes previously described. For example the combined double layered WSF may be applied with binder coat with or without a tie-coat inbetween, semi drying the binder coat and combining with a third layer of WSF with or without detachable liner by passing through a nip roll and forming three layered combined WSF.

The third layer of WSF may be a preformed WSF with or without a liner or it may be extruded. The said process may be repeated to form a combined multi-layer WSF having any desired number of layers of WSF.

Preferably, one or more of the same or different types of active ingredients are incorporated in the binder and/or the tie-coat and/or in the flat die extruder while extruding the desired thickness of WSF directly on the preformed WSF with liner.

The invention will now be described with reference to accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.l shows a schematic line diagram illustrating an offline process of combining two layers of water soluble films using a tie-coat and a binder according to an embodiment of this invention.

Fig. 2 shows a schematic line diagram illustrating an online process of combining two layers of water soluble films using a tie-coat and a binder, according to another embodiment of this invention.

Fig. 3 shows a schematic line diagram illustrating a process of combining two layers of water soluble films, using a binder according to a further embodiment of the invention.

Fig. 4 shows a schematic line diagram illustrating a process of combining two layers of water soluble films by flat-die extruding of a water soluble film onto a water soluble film along with a detachable liner. /

Fig. 5 shows a diagram illustrating a three layered combined water soluble film produced according to an embodiment of this invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring to fig.l, illustrating the offline process of producing a cast-blown or a cast-cast combined water soluble film comprising the following steps:

I. Placing a web of preformed WSF (1) with detachable liner, forming one layer of the combined WSF, on an unwinder (2) of a coating machine, wherein the said WSF (1) is a solution cast film.

II. Placing a web of preformed WSF (3) with or without detachable liner, forming another layer of the combined WSF, on another unwinder (4) of the coating machine, wherein the said WSF (3) is a solution cast film or a thermally extruded film. III. Unwinding the preformed WSF (1) along with detachable liner at unwinder (2).

IV. Applying a tie-coat on the preformed WSF (1) by passing the WSF along with the liner through the coating head (5) of the coating machine.

The tie-coat is preferably applied preferably, by using a gravure cylinder of varying cell sizes and depths; or by using flexo plates of varying cell sizes and depths, or by combination of flexo plates with gravure cylinder, for transferring net solid contents of the tie-coat from the cells of the cylinder and that maximum water/solvent is scrapped before hand by cam shaft moving doctoring blade. These processes reduce the possibility of the pre-formed water soluble film from dissolving when the binder or subsequent WSF casting is done for the end purpose of affixing another water soluble film.

The tie-coat being selected from acrylic acid polymers, acrylic ester polymers, soluble acrylic acid copolymers, soluble acrylic ester copolymers, soluble copolymers of acrylic acids and esters, cross linked polyvinyl alcohols, cross linked cellulose derivatives, ethyl cellulose, nitrocellulose, cellulose butyrate, cellulose acetate butyrate, ethylene vinyl polyalcohol, ethylene vinyl acetate,

PVDC (polyvinyldene chloride), acrylic emulsion, PVC (polyvinyl chloride) emulsion, PVDC emulsion, PVB (polyvinyl butyral), natural arid synthetic waxes, polyurethanes and modified polyvinyl alcohols. However, these tie- coats are by no means limiting.

These tie-coats will not allow the WSF to dissolve and will act as a barrier between the WSF and the binder to be applied at a later stage.

Optionally, the tie-coat is incorporated with one or more active ingredients such as flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine. However, these active ingredients are by no means limiting.

V. Drying and curing of WSF (1) coated with tie-coat, at the drying section (6). The temperature in the dryers ranges from 50⁰C to 200⁰C, preferably from 60⁰C to 175⁰C, more preferably from 75⁰C to 150⁰C.

VI. Passing the WSF (1) coated with tie-coat through another coating section (7) for applying/coating a binder on the tie-coat coated side of WSF. The binder is coated using a wire wound mayer bar.

The said binder being selected from any low viscosity, low solid content binder like different types of adhesives such as pressure sensitive adhesives, cast water soluble film, solution, polyurethane dispersion or even a liquid flavour. However, these binders are by no means limiting. Optionally, the binder is incorporated with one or more of the active ingredients as per requirement. VII. Passing through an air blower section (8) of the coating machine with or without applying heat, for semi-drying the binder. The temperature in the blower section ranges from 10⁰C to 100⁰C, preferably from 30⁰C to 70⁰C, more preferably from 30⁰C to 50⁰C.

VIII. Unwinding the pre-formed WSF (3) from the unwinder (4) and guiding it through the guide rolls (9) to combine with the WSF (1) from step VII by passing through the nip roll (10). IX. Passing the laminate through heated rolls (11 and 12) for dissipating the moisture entrapped between the two films while laminating. The temperature in the heated rolls ranges from 40⁰C to 200⁰C₃ preferably from 50⁰C to 120⁰C, more preferably from 60⁰C to 90⁰C. X. Rewinding the laminate of combined WSF on a rewinder (13) and store for internal ageing period ranging from 1 hour to 720 hours, preferably 10 hours to 360 hours, more preferably from 24 hours to 100 hours. XI. Detaching the liner and slitting/cutting the combined WSF as per requirement.

Now, referring to fig.2, illustrating the online process of producing a cast-blown or a cast-cast combined water soluble film comprising the following steps:

I. Placing a liner (14), for casting of WSF, on an unwinder (15) of a casting-cum- coating machine. The liner (14) is optionally treated or untreated and coated or uncoated. The liner can be of paper, film, foil or fabric, preferably of film, more preferably of polyester film. The film thickness ranges from 3 microns to 500 microns, preferably from 10 microns to 300 microns, more preferably from 25 microns to 100 microns. The film liner may be plain, metallised, embossed, gloss, matt, extrusion coated, laminated or release coated depending on the desired characteristics of the end product. Paper liner is also used for production of WSF.

Paper liner that accept temperatures needed for the production of WSF and have thickness ranging from 7 GSM (grams per sq meter - the standard for measuring weight of paper) to 500 GSM, preferably from 20 GSM to 300 GSM, more preferably from 60 GSM to 180 GSM can be used. The paper liner may be plain, embossed, gloss, matt, extrusion coated laminated or release coated depending on the desired characteristics of the end product. Fabrics made of cotton or synthetic yarns, solution coated, plain, embossed, gloss, matt, extrusion coated or laminated may be used as liner based on the desired end product properties. However, these liners are by no means limiting. II. Placing the preformed WSF (3) with or without a detachable liner, forming another layer of the combined WSF, on another unwinder (4) of the coating machine, wherein the said WSF (3) is a solution cast film or a thermally extruded film.

III. Unwinding of the liner (14) at unwinder (15) for the formation of WSF. IV. Casting of WSF by using known formulation of WSF in a batch reactor (16), on the liner (14), at the primary casting head (17). The temperature of the batch solution ranges from 10⁰C to 95⁰C, preferably from 20⁰C to 85⁰C₅ more preferably from 25⁰C to 70⁰C. The non-edible raw materials used for making the WSF are selected from Polyvinyl alcohol copolymer ionomers, Polyvinyl alcohol homopolymer, non - ionomeric poly vinyl alcohol polymer, Polymethacrylate., polyvinyl alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyurethane and edible raw materials are selected from polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch, gum Arabic, pullulan and dextrin and water-soluble cellulose derivatives or combination thereof. The cellulose derivatives used are methyl cellulose, hydroxy propyl cellulose, hydroxy propyl methyl cellulose, hydroxy propyl ethyl cellulose, hydroxy ethyl cellulose, carboxy methyl cellulose. However, these are by no means limiting. V. Metering of the cast WSF at the primary casting head (17).

VI. Drying of the WSF of the above step V at primary drying section (18) to form the first layer of WSF (1) with the liner. The temperature in the dryers ranges form 50⁰C to 200⁰C, preferably from 60⁰C to 175⁰C, more preferably from 75⁰C to 150⁰C.

VII. Applying/Coating a tie-coat on the formed WSF (1) by passing the WSF along with the liner through a coating head (5).

The tie-coat is preferably applied preferably, by using a gravure cylinder of varying cell sizes and depths; or by using flexo plates of varying cell sizes and depths, or by combination of flexo plates with gravure cylinder, for transferring net solid contents of the tie-coat from the cells of the cylinder and that maximum water/solvent is scrapped before hand by cam shaft moving doctoring blade. These processes reduce the possibility of the pre-formed water soluble film from dissolving when the binder or subsequent WSF casting is done for the end purpose of affixing another water soluble film. The tie-coat is preferably applied by using a gravure cylinder of varying cell sizes and depths, by transferring the net solid contents of the active polymers of the tie coat from the cells of the cylinder, and the water/solvent liquid is scraped before hand by the cam shaft moving doctoring blade. This process reduces the possibility of the pre-formed water soluble film from dissolving when the tie coat or subsequent WSF casting is done for the end purpose of lamination to another water soluble film. The tie-coat being selected from acrylic acid polymers, acrylic ester polymers, soluble acrylic acid copolymers, soluble acrylic ester copolymers, soluble copolymers of acrylic acids and esters, cross linked polyvinyl alcohols, cross linked cellulose derivatives, ethyl cellulose, nitrocellulose, cellulose butyrate, cellulose acetate butyrate, ethylene vinyl polyalcohol, ethylene vinyl acetate, PVDC (polyvinyldene chloride), acrylic emulsion, PVC (polyvinyl chloride)emulsion, PVDC emulsion, PVB (polyvinyl butyral), natural arid synthetic waxes, polyurethanes and modified polyvinyl alcohols. However, these tie-coats are by no means limiting.

These tie-coats will not allow the WSF to dissolve and will act as a barrier between the WSF and the binder to be applied at a later stage. Optionally, the tie-coat is incorporated with one or more active ingredients such as flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine. However, these active ingredients are by no means limiting.

VIII.Drying and curing of WSF (1) coated with tie-coat at the drying section (6). The temperature in the dryers ranges from 50⁰C to 200⁰C, preferably from 60⁰C to 175⁰C, more preferably from 75⁰C to 150⁰C. IX. Passing the WSF (1) coated with tie-coat through another coating section (7) for applying/coating of the binder on the tie-coat coated side of WSF. The binder is coated using a wire wound mayer bar.

The said binder being selected from any low viscosity, low solid content binder like different types of adhesives such as pressure sensitive adhesives, cast water soluble film solution, polyurethane dispersion or even a liquid flavour. However, these binders are by no means limiting. Optionally, the binder is incorporated with one or more of the active ingredients as described earlier. X. Passing through an air blower section (8) with or without applying heat, for semi- drying the binder. The temperature in the blower section ranges from 10⁰C to 100⁰C, preferably from 30⁰C to 70⁰C, more preferably from 30⁰C to 50⁰C.

XI. Unwinding the pre-formed WSF (3) from the unwinder (4) and guiding it through the guide rolls (9) to combine with the WSF (1) from the step X by passing through ^' the nip roll (10).

XII. Passing the laminate through heated rolls (11 and 12) for dissipating the moisture entrapped between the two films while laminating. The temperature in the heated rolls ranges from 40⁰C to 200⁰C, preferably from 50⁰C to 120⁰C, more preferably from 60⁰C to 90⁰C. XIII.Rewinding the laminate of combined WSF on a rewinder (13) and store for internal ageing period ranging from 1 hour to 720 hours, preferably 10 hours to 360 hours, more preferably from 24 hours to 100 hours. XIV. Detaching the liner and slitting/cutting as per requirement.

Referring to fig 3, illustrating the process of producing a cast-blown or a cast-cast combined water soluble film using only the binder directly on the water soluble film along with a liner without applying any tie-coat comprising the following steps:

I. Placing the preformed WSF (1) with a detachable liner, forming one layer of the combined WSF, on an unwinder (2) of a coating machine, wherein the said WSF (1) is a solution cast film. II. Placing the preformed WSF (3) with or without a detachable liner, forming another layer of the combined WSF, on another unwinder (4) of the coating machine, wherein the said WSF (3) is a solution cast film or a thermally extruded film.

III. Unwinding the preformed WSF (1) along with a detachable liner at unwinder (2). IV. Passing the WSF (1) through the coating section (7) for coating of the binder on the WSF.

The said binder being selected from any low viscosity, low solid content binder like different types of adhesives such as pressure sensitive adhesives, cast water soluble film solution, polyurethane dispersion or even a liquid flavour. However, these binders are by no means limiting. Optionally, the binder is incorporated with one or more of the active ingredients as described earlier.

V. Passing through an air blower section (8) with or without applying heat, for semi- drying the binder. The temperature in the blower section ranges from 20⁰C to 100⁰C₅ preferably from 40⁰C to 80⁰C, more preferably from 50⁰C to 60⁰C.

VI. Unwinding the pre-formed WSF (3) from the unwinder (4) and guiding it through the guide rolls (9) to combine with the WSF (1) from step V by passing through the nip roll (10).

XII. Passing the laminate through heated rolls (11 and 12) for dissipating the moisture entrapped between the two films while laminating. The temperature in the heated rolls ranges from 40⁰C to 200⁰C, preferably from 50⁰C to 120⁰C, more preferably from 60⁰C to 90⁰C.

VII. Rewinding the laminate of combined WSF on a rewinder (13) and storing for internal ageing period ranging from 1 hour to 720 hours, preferably 10 hours to 360 hours, more preferably from 24 hours to 100 hours.

VIII.Detaching the liner and slitting/cutting as per requirement.

As this process has a detachable liner as a pre-requisite, speed of WSF (1) is kept high, preferably from 15 to 100 metres/min, more preferably from 25 to 70 metres/min, the binder will not be able to dissolve the WSF and will enable combining two films even without using a tie-coat. The property of a specified binder of thixotropic nature shall determine this process of speed, which shall not be treated as a limiting factor for this invention.

Further, the liner provided with the WSF (1) gives the desired strength for withstanding the binder coating for the required time enabling the combining of two layers of WSF without a tie-coat.

Further, the temperature of the air blower section being kept at 20⁰C to 100⁰C₅ preferably from 40⁰C to 80⁰C, more preferably from 50⁰C to 60⁰C (higher then the temperature used for the process using tie-coat), the binder will dry instantly and will not dissolve the WSF and will enable combining two films even without using a tie-coat.

Fig. 3 of the accompanying drawing though illustrates an offline process, is equally applicable in an online process.

Referring to fig 4, illustrating the process of producing a cast-blown combined water soluble film by directly extruding a water soluble film through a flat die extruder onto a water soluble film along with a liner comprising the following steps:

I. Load a roll of preformed WSF (1) along with a detachable liner on a flat die extruder.

II. Extruding the desired thickness of WSF directly through the extruder (19) onto the preformed cast WSF.

III. Passing the construction from step II through chilling cylinder(s) (20), keeping the hydrophobic, but thermally active detachable liner in contact with the chilling cylinder.

IV. Rewinding the laminate at rewinder (22) by passing through the guide roll (21) and store for interna! ageing period ranging from 1 hour to 720 hours, preferably 10 hours to 360 hours, more preferably from 24 hours to 100 hours. V. Detaching the liner and slitting/cutting as per requirement. To make a three layered combined WSF, the double layered combined WSF on liner, produced as per any of the above processes, is again unwound along with the liner and passed through a tie-coat coating head and dried. The tie-coat coated double layered WSF is then coated with a binder and semi-dried by passing through the air blowing section. A third layer of preformed WSF is passed through the affixing nip roll and laminated with the double layered WSF forming thee layered combined WSF. Fig. 5 represents a three layered combined WSF, wherein a WSF with liner (23) is coated with a tie-coat (24) and further coated with a binder (25) to laminate another WSF (26). This will form a double layered WSF. The WSF (26) of the double layered WSF is again coated with a tie coat (27) and further coated with a binder (28) to laminate the third layer of WSF (29) to form a three layered film. The tie-coats (24) and (27) and the binders (25) and (28) coated on the respective water soluble films can be of same type or different type. In the same way, by repeating the above process, any number of layers can be laminated to form a combined multi-layered WSF.

While making a multi-layered WSF, different or same kind of active ingredients in desired amount can be incorporated in the binder and/or tie-coat so as to have a multi- layered WSF to carry several or same types of active ingredients, for diverse uses.

The water soluble films mentioned in the above processes may be cold water soluble, hot water soluble, warm water soluble, edible or non edible depending upon the end application.

From one aspect, the invention provides a process for combining two or more water soluble films to form a substantially pin hole free multi-layer WSF by providing a binder coat and optionally a tie coat between two layers of WSF so as to prevent the WSF dissolving and forming pin holes. The binder coat is semi-dried to promote adhesion between the layers of WSF. Where provided the tie coat is made of a material that acts as a time delay barrier layer to prevent the WSF dissolving when the binder coat is applied. Alternatively or additionally, the binder coated WSF may be rapidly dried to prevent the WSF dissolving. For example, the line speed of the binder coated WSF may be increased.

From another aspect, the invention provides a process for incorporating one or more active ingredients in a multi-layer WSF for improving the retention and/or other properties of the active ingredient by adding them or each active ingredient to a binder coat and/or a tie coat employed to secure two layers of WSF to each other. In this way, each active ingredient is trapped between the two layers of WSF thereby preventing or restricting escape of the active ingredient(s).

From another aspect, the invention provides multi-layered WSF made by the above processes separately or in combination.

Claims

We Claim:

1. A combined WSF comprising of at least one layer of solution cast WSF with a detachable liner, preferably provided with a tie coat, a binder coating provided on the said solution cast WSF with liner, with or without the said tie coat and at least one layer of preformed WSF forming a substantially pin hole free combined multi- layered WSF.

2. The combined WSF according to claim 1, wherein the said preformed WSF is a thermally extruded WSF₅ such as blown (bubble type) or slit die-cast (extrusion curtain type), forming a cast-extruded combined WSF.

3. The combined WSF according to claim 1, wherein said preformed WSF is a solution cast WSF.

4. The combined WSF according to claim 1, wherein said tie coat provided on the solution cast WSF with liner is selected from acrylic acid polymers, acrylic ester polymers, soluble acrylic acid copolymers, soluble acrylic ester copolymers, soluble copolymers of acrylic acids and esters, cross linked polyvinyl alcohols, cross linked cellulose derivatives, ethyl cellulose, nitrocellulose, cellulose butyrate, cellulose acetate butyrate, ethylene vinyl polyalcohol, ethylene vinyl acetate, PVDC (polyvinyldene chloride), acrylic emulsion, PVC (polyvinyl chloride) emulsion, PVDC emulsion, PVB (polyvinyl butyral), natural arid synthetic waxes, polyurethanes and modified polyvinyl alcohols.

5. The combined WSF according to claim 1, wherein the said binder coating is selected from any low viscosity, low solid content binder like different types of adhesives such as pressure sensitive adhesives, cast water soluble film solution, polyurethane . dispersion or even a liquid flavour.

6. The combined WSF according to claim 1, wherein the said solution cast WSF with liner forming one layer and the said preformed WSF forming another layer, are formed of non-edible materials.

7. The combined WSF according to claim 6 wherein said non-edible materials are selected from Polyvinyl alcohol copolymer ionomers, Polyvinyl alcohol homopolymer, non — ionomeric poly vinyl alcohol polymer, Polymethacrylate., polyvinyl alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, biodegradable polyesters such as ecoflex; polylactic acid (PLA), polyhydroxyalkanoic acid (PHA) and polyurethane.

8. The combined WSF according to claim 1, wherein the said solution cast WSF with liner forming one layer and the said preformed WSF forming another layer, are formed of edible materials.

9. The combined WSF according to claim 8 wherein said edible materials are selected from polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch and its derivatives, sorbitol, sucrose derivatives, gum Arabic, pullulan and dextrin and water-soluble cellulose derivatives or combination thereof. The cellulose derivatives used are methyl cellulose, hydroxy propyl cellulose, hydroxy propyl methyl cellulose, hydroxy propyl ethyl cellulose, hydroxy ethyl cellulose and carboxy methyl cellulose.

10. The combined WSF according to any of claims 1 to 3, wherein the said tie coat and/or the said binder coating is incorporated with a desired amount of one or more, same or different types of active ingredients, as per the requirement.

11. The combined WSF according to claim 10, wherein the said one or more active ingredients are selected from flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine.

12. The combined WSF according to claim 1, wherein the said preformed WSF is provided with a detachable liner.

13. The combined WSF according to claim 1 or claim 12 wherein the detachable liner of the said solution cast WSF and, where provided with the said preformed WSF, is made of paper, film, foil or fabric, treated or untreated, coated or uncoated.

14. The combined WSF according to claim 13 wherein the detachable liner is made of film, more preferably polyester film.

15. The combined WSF according to claim 14 wherein the films thickness ranges from 3 microns to 500 microns, preferably from 10 microns to 300 microns, more preferably from 25 microns to 100 microns.

16. The combined WSF according to claim 14 or claim 15 wherein the film is plain, metallised, embossed, gloss, matt, extrusion coated, laminated or release coated depending on the desired characteristics of the end product.

17. The combined WSF according to claim 13 wherein the liner is a paper liner that accepts temperatures needed for the production of WSF and has a thickness ranging from 7 GSM (grams per sq meter - the standard for measuring weight of paper) to 500 GSM, preferably from 20 GSM to 300 GSM, more preferably from 60 GSM to

180 GSM.

18. The combined WSF according to claim 17 wherein the paper liner is plain, embossed, gloss, matt, extrusion coated laminated or release coated depending on the desired characteristics of the end product.

19. The combined WSF according to claim 13 wherein the liner is a fabric made of cotton or synthetic yarns.

20. The combined WSF according to claim 19 wherein the liner is solution coated, plain, embossed, gloss, matt, extrusion coated or laminated depending on the desired characteristics of the end product.

21. The combined WSF according to claim 1, wherein the said WSF is cold water soluble, warm water soluble, hot water soluble, edible or non edible, depending upon the raw materials used.

22. A process for producing a combined WSF according to any of the claims 1 to 21, comprising of the following steps: a. providing a first WSF with detachable liner forming one layer of the multi-layer

WSF, b. providing a second preformed WSF with or without a detachable liner forming another layer of the multi-layer WSF, _. c. applying a tie-coat on one side of the WSF with the liner, d. drying and curing the WSF coated with tie coat, e. applying a binder coat over the said tie coat of the WSF with liner, f. semi-drying the binder coat of the first WSF with liner, g. passing the second preformed WSF with the first preformed WSF from step (f) through a nip roll of the coating machine to form a laminated double layered WSF, h. passing the double layered combined WSF through heated rolls for dissipating the entrapped moisture, i. storing the double layered WSF from step (e) for internal ageing, and j. detaching the liner and slitting/cutting the double layered WSF as per requirement.

23. The process according to claim 22 wherein the first WSF is a preformed WSF.

24. The process according to claim 23 wherein the first WSF is formed in situ by: a. providing a liner and casting the first WSF on it using WSF in a batch reactor and metering the cast WSF at a primary casting head, the temperature of the batch solution in the reactor ranging from 10⁰C to 95⁰C, preferably from 13⁰C to 90⁰C and more preferably from 15⁰C to 85⁰C, b. drying the cast WSF of step (a) to form said first WSF with liner, the temperature in the drying section ranging form 50⁰C to 200⁰C, preferably from 60⁰C to 175⁰C and more preferably from 75⁰C to 150⁰C,

25. The process according to claim 22, wherein the said tie-coat is applied by using a gravure cylinder of varying cell sizes and depths; or by using flexo plates of varying cell sizes and depths, or by combination of flexo plates with gravure cylinder, for transferring net solid contents of the tie-coat from the cells of the cylinder.

26. The process according to claim 22 or 25, wherein the said tie coat is selected from acrylic acid polymers, acrylic ester polymers, soluble acrylic acid copolymers, soluble acrylic ester copolymers, soluble copolymers of acrylic acids and esters, cross linked polyvinyl alcohols, cross linked cellulose derivatives, ethyl cellulose, nitrocellulose, cellulose butyrate, cellulose acetate butyrate, ethylene vinyl polyalcohol, ethylene vinyl acetate, PVDC (polyvinyldene chloride), acrylic emulsion, PVC (polyvinyl chloride) emulsion, PVDC emulsion, PVB (polyvinyl butyral), natural arid synthetic waxes, polyurethanes and modified polyvinyl alcohols.

27. The process according to claim 22, 25 or 27 wherein the tie coat is dried at a temperature ranging from 5O⁰C to 200⁰C, preferably from 6O⁰C to 175⁰C, more preferably from 75⁰C to 15O⁰C.

28. The process according to any of claims 22, wherein the said binder coat is applied by using a wire bound mayer bar.

29. The process according to any of claims 22 or 28, wherein the said binder is a low viscosity, low solid content binder.

30. The process according to any of claims 29. wherein the binder is selected from adhesives such as pressure sensitive adhesives, cast water soluble film solution, polyurethane dispersion or even a liquid flavour

31. The process according to any of claims 22, 28, 29 or 30 wherein the binder coat is semi-dried at a temperature ranging from 1O⁰C to 100⁰C, preferably from 3O⁰C to 7O⁰C, more preferably from 30⁰C to 5O⁰C.

32. The process according to any of claims 22 to 31, wherein the said liner is made of paper, film, foil or fabric, treated or untreated, coated or uncoated.

33. The process according to claim 32 wherein the said liner is made of film, preferably polyester film.

34. The process according to claim 33 wherein the film thickness ranges from 3 microns to 500 microns, preferably from 10 microns to 300 microns, more preferably from 25 microns to 100 microns.

35. The process according to claim 33 or claim 34 wherein the film liner is plain, metallised, embossed, gloss, matt, extrusion coated, laminated or release coated depending on the desired characteristics of the end product.

36. The process according to claim 32 wherein the said liner is made of paper that accepts temperatures needed for the production of WSF.

37. The process according to claim 36 wherein the paper liner has a thickness ranging from 7 GSM (grams per sq meter - the standard for measuring weight of paper) to 500 GSM, preferably from 20 GSM to 300 GSM, more preferably from 60 GSM to 180 GSM.

38. The process according to claim 36 or claim 37 wherein the paper liner is plain, embossed, gloss, matt, extrusion coated laminated or release coated depending on the desired characteristics of the end product.

39. The process according to claim 32 wherein the said liner is a fabric made of cotton or synthetic yarns.

40. The process according to claim 39 wherein the fabric is solution coated, plain, embossed, gloss, matt, extrusion coated or laminated depending on the desired characteristics of the end product.

41. The process according to claim 22 wherein the temperature in the heated rolls ranges from 40⁰C to 200⁰C, preferably from 50⁰C to 120⁰C, more preferably from 60⁰C to

90⁰C.

42. The process according to any of claims 22 to 41, wherein the said first and/or second WSF is formed of edible materials selected from polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch and its derivatives, sorbitol, sucrose derivatives, gum Arabic, pullulan and dextrin and water-soluble cellulose derivatives or combination thereof. The cellulose derivatives used are methyl cellulose, hydroxy propyl cellulose, hydroxy propyl methyl cellulose, hydroxy propyl ethyl cellulose, hydroxy ethyl cellulose and carboxy methyl cellulose.

43. The process according to any of claims 22 to 41, wherein the said first and/or second WSF is formed of non-edible materials selected from polyvinyl alcohol copolymer ionomers, polyvinyl alcohol homopolymer, non - ionomeric poly vinyl alcohol polymer, polymethacrylate., polyvinyl alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid biodegradable polyesters such as ecoflex; polylactic acid (PLA), polyhydroxyalkanoic acid (PHA) and polyurethane.

44. The process according to any of claims 22 to 41, wherein one or more of same or different types of active ingredients are incorporated in the said binder and/or where provided said tie-coat.

45. The process according to claim 44, wherein the said active ingredients are selected from flavours, perfumes, detergents, enzymes, softeners, active agents for cleaning laundry, dishes, floorings, walls, furniture; various agrochemicals like pesticides, insecticides, weedicides, fungicides, bio-pesticides; agro nutrients like urea, fertilizers; dyes, pigments, fluff, pulp, super absorbents and active pharma ingredients like vitamins, drugs, medicine.

46. The process according to any of claims 22 to 45, wherein the raw materials of the WSF, the binder and/or where provided tie-coat are selected such that the combined WSF is soluble in cold water, or warm water or hot water, as per requirement.

47. The process according to claim 22, wherein the said first WSF with liner is moved at high speed, preferably from 15 to 100 meter/min., more preferably from 25 to 70 meter/min. for preventing the WSF from dissolving when the binder is applied on it directly, without the tie-coat.

48. The process according to claim 22, wherein the binder coat applied directly to the first WSF is instantly semi-dried for preventing the WSF from dissolving.

49. A method/process of producing cast-cast or cast-extruded combined WSF, comprising of the following steps: a. extruding a desired thickness of WSF directly onto a preformed cast WSF with liner through an extruder, b. passing the combined WSF laminate of step (a) through chilling cylinders, keeping the said liner in contact with the chilling cylinder, c. storing the combined WSF for an internal ageing period, d. detaching the liner and slitting/cutting the combined WSF laminate as per requirement.

50. The process according to claim 49, wherein the said preformed WSF with detachable liner is a cast/solution cast WSF.

51. The process according to claim 49, wherein the said liner is a hydrophobic, thermally active detachable liner.

52. The process according to claim 22 or claim 49, wherein the said combined WSF laminate is stored for an internal ageing period ranging from 1 hour to 720 hours, preferably from 10 hours to 360 hours and more preferably from 24 hours to 100 hours.

53. The process according to claim 22 or 49, further including the step of providing the said double layered combined WSF with liner with a tie coat and then a binder coat and combined with a third layer of WSF by passing through a nip roll to form a three layered combined WSF.

54. The process according to claim 53, wherein the said double layered combined WSF with liner is provided with a binder coat directly, without a tie-coat, in a coating section.

55. The process according to claim 49, wherein the said double layered combined WSF with liner is passed through an extruder for extruding a desired thickness of WSF directly on it to form a three layered combined WSF.

56. The process according to claim 53 or claim 55, wherein the said process is repeated to form a multi-layered combined WSF having any desired number of layers of WSF.

57. The method/process according to any of claims 53 to 56, wherein one or more of the same or different types of active ingredients are incorporated in the binder and/or where provided the tie-coat and/or in the extruder while extruding the desired thickness of WSF directly on the preformed WSF with liner.

58. The process according to any of claims 53 to 57, wherein the said combined WSF laminate is stored for an internal ageing period ranging from 1 hour to 720 hours, preferably from 10 hours to 360 hours and more preferably from 24 hours to 100 hours.

59. A process for producing cast-extruded or cast-cast combined WSF substantially as herein described and illustrated in figs. 1 to 5 of the accompanying drawings.