DESC:LINER LESS SELF ADHESIVE MATERIAL WITH NANO THIN AND FASTER DISSOLVING WATER SOLUBLE FILM AND A PROCESS FOR ITS PREPARATION THEREOF.

TECHNICAL FIELD

The present disclosure relates generally to self-adhesive materials and more particularly relates to liner less self-adhesive material (NEWSAM®) with nano thin and faster dissolving water soluble film, that acts as a protective liner over the adhesive layer, process of preparing nano thin and faster dissolving water soluble film formulation and process of coating the same thereof.

BACKGROUND

Generally, a liner is used to cover the pressure sensitive adhesive in self-adhesive materials. Self-adhesive materials consist of a substrate to be print coated with an adhesive on one side and a release liner on the adhesive side, which is removed while applying the same or a pre-printed, precut label on a particular object. Self-adhesive material is known as PSA (pressure sensitive adhesive) material as the adhesive when exposed to open environment, after removal of the backing liner, shall be applied simply by using specified pressure onto the front of the printed substrate and the object to which it is expected to adhere.

All PSA coated materials, also known as self-adhesive materials must have a release liner or a release coating. Usually it is a type of Silicon coating that assists easy release. Release liners are silicon coated papers, films, foils or fabrics. Silicon coating is done by application of solvent based/water based silicones. Most of these liners are not biodegradable and so are not environmental friendly. Silicones coated with aid of solvents also add up polluting the environment.

The water soluble film (WSF) can be used for many purposes viz, liner for self-adhesive materials, packaging chemical products, water soluble laminate film etc. While using the self-adhesive material, the web of self-adhesive material is passed through a water bath in order to dissolve the water-soluble protective layer. It has been noticed that the dissolution of water soluble film takes a longer period of time, resulting in delay in exposure of the adhesive part of the face material.

Generally, uniform coating of water soluble film is difficult to obtain, hence it is utmost important to provide a method or a process of forming a uniform water soluble film, which is not only easy to dissolve but also has the thinnest possible micron along with faster dissolving characteristic, so as to expose the adhesive part of the new improved self-adhesive material in seconds.

DEFINITION’S PERTAINING TO THE INVENTION

Water Soluble Protective Layer: This shall mean water-soluble protective layer(s), however placed in position.
Face Material: This shall mean the substrate to which the pressure sensitive adhesive is applied.
Pressure Sensitive Adhesive (PSA): This shall mean any type of adhesive that adheres firmly to the desired object on application of any kind of pressure. Such adhesives may be water-based, solvent-based, hot melt, although these types are by no means limiting.
Self-Adhesive Material (SAM): This shall mean self-adhesive material wherein the pressure sensitive adhesive is protected with a water-soluble protective layer.
New Self-Adhesive Material (NEWSAM®): This shall mean self-adhesive material wherein the pressure sensitive adhesive is protected with a nano thin water-soluble protective layer.
Nano Water Soluble Film (NWSF): A water soluble film of less than 1 micron.
Batch Mix: The formulation of water soluble film is referred as batch mix.

SUMMARY OF THE INVENTION

One embodiment of the present invention discloses an improved liner less self-adhesive material (NEWSAM®) comprising a face material coated with pressure sensitive adhesive on obverse side, wherein the adhesive side is protected by a water-soluble protective layer of nano thickness of less than 1 micron obtained by air-knife coating process; wherein the Water soluble film is incorporated with plasticizer and surfactants; water soluble film is lined over the pressure sensitive adhesive by a non-contact coating process, so as to minimize the usage of water soluble film and increase the production; and to obtain a faster dissolution of the water soluble protective layer when using the self-adhesive material.

Another embodiment of the present invention discloses a formulation and method of preparing the water soluble formulation, such that it exhibit nano thin quality and faster dissolving characteristic so as to expose the adhesive part of the new improved self-adhesive material in seconds.

Another embodiment of the present invention discloses a method for coating faster dissolving water soluble film on a liner for further use. Another embodiment of the present invention discloses direct and indirect coating method to obtain ready to use Self-Adhesive Material.

OBJECT OF THE INVENTION

It is the primary object of the present disclosure to provide a self-adhesive material with a water soluble film, used as protective liner for adhesive materials.
Another object of the present disclosure is to provide a liner less self-adhesive material with nano thin and faster dissolving water soluble film, that acts as a protective liner over the adhesive layer.
Yet another object of the present invention is to provide nano thin water soluble film, that exhibit faster dissolving characteristics.
Yet another object of the present disclosure is to provide a uniform and pinhole free water soluble film.
Yet another object of the present disclosure is to provide a water soluble film formulation with lower viscosity.
Yet another object of the present disclosure is to provide a water soluble film formulation which exhibit lower surface tension.
Yet another object of the present disclosure is to provide a coating process wherein water soluble film is coated on the pressure sensitive adhesive layer by a non-contact coating process.
Yet another object of the present disclosure is to provide the thinnest coating possible of the water soluble film on the pressure sensitive adhesive layer by non-contact coating processes.
Yet another object of the present disclosure is to avoid contamination, by using the non-contact coating process.
Yet another object of the present disclosure to provide a water soluble film by air knife coating process.
Yet another object of the present disclosure is to minimize wastage of water soluble film and to increase the production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Illustrates a self-adhesive material with nano thin and faster dissolving water-soluble film in accordance with an exemplary embodiment of the present disclosure.
FIG. 2 Illustrates a method for coating faster dissolving nano thin water soluble film on a liner using air-knife coating technique.
FIG.3 Illustrates an indirect lamination coating method to obtain ready to use Self-Adhesive Material using air-knife coating technique.
FIG. 4 Illustrates a direct coating method to obtain ready to use Self-Adhesive Material using air-knife coating technique.

DETAIED DESCRIPTION

The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the present disclosure, and describes several embodiments, adaptations, variations, alternatives, and uses of the present disclosure, including what is presently believed to be the best mode of carrying out the present disclosure

The present invention discloses a liner less self-adhesive material (NEWSAM®) with a water soluble film and a process for preparing the same, wherein said liner less self-adhesive material (NEWSAM®) comprises a face material that is optionally coated with hydrophobic/water repellent lacquer on its obverse surface, whereas the obverse surface comprises of an pressure sensitive adhesive layer, said pressure sensitive adhesive layer is coated with a thin layer of water soluble film as a protective coating, wherein the adhesive layer is coated with a Nano soluble film protective layer which dissolves in water in less than 45 seconds, whereby exposing the adhesive layer for adhesion to desired object.

The present disclosure provides a solution to overcome this problem by providing water soluble film coating that is uniform and possible providing a water soluble film that is nano thin and exhibit faster dissolving characteristics that is less than 1 micron.

The water soluble film (WSF) is coated on the adhesive side, used as a protective liner on the adhesive side of the self-adhesive material. The water soluble film used as a coating layer, wherein said coating layer is a thin layer such that it exhibit nano thin quality and faster dissolving characteristic so as to expose the adhesive part of the new improved self-adhesive material in seconds.

PROBLEM ADDRESSED BY THE PRESENT INVENTION

One embodiment of the present invention discloses a liner less self-adhesive material (NEWSAM®) with a water soluble film in accordance with an exemplary embodiment of the present disclosure.

Referring to figure 1, there is illustrated a liner less self-adhesive material with a water soluble film in accordance with an exemplary embodiment of the present disclosure. The liner less self-adhesive material (NEWSAM®) (4) comprises a face material (3) coated with a pressure sensitive adhesive (PSA) (2) on obverse side, a nano thin water soluble film (1) coated over the pressure adhesive layer (2). The nano water soluble film (1) acts as a protective liner on the adhesive side of the NEWSAM® (4).

The face material may be selected from, but not limited to, uncoated or coated paper, film, metal foils, fabric, ink receptive coated materials, polymeric materials or a combination of any of these materials, and can be selected from, but not limited to, heat sensitive materials such as PVC (poly-vinyl chloride), HIPS (high impact polystyrene), LLOPE (linear low density polyethylene), heat shrinkable linear low density polyethylene, PP (polypropylene), APET (Anhydrous polyester), PETG (polyester glycol), HOPE (high density polyethylene) etc. The above examples of face materials are by no means limiting. Heat sensitive materials may be used at temperatures ranging from 10ºC to 90ºC. Heat resistant face materials such as paper, polyester film, or kapton film may be used, although these examples are by no means limiting. Heat resistant materials may be used at temperatures ranging from 30ºC to 250ºC. The selection of face material to be used also depends upon the properties of pressure sensitive adhesive to be coated upon it. The type of face material will also influence the process of manufacture when practicing this disclosure.

The pre-printing or post-printing coating can be performed on-line or off-line. The coating material can be applied on coating machines during the process of producing the self-adhesive material. Printing on the face material may be done by any Suitable printing methods such as, but not limited to, gravure, flexography, dry or wet offset, inkjet printing, thermal printing, Screen printing, Subliminal ink printing, holographic embossing, or hot foil stamping.

The pressure sensitive adhesive in this disclosure may include adhesives made from resins, polymers or co-polymers of acrylics, rubber, hot melt polymers, ethylene-vinyl acetate copolymers (EVA), starch, UV Curable, and polyurethanes, either dissolved in organic or inorganic/hydrocarbon or water based solvents or crosslinking PSA, or Solvent being Ketone based, Toluene based OR hot melt PSA. Emulsified water based pressure sensitive adhesives are also covered within this definition. However, these examples are by no means limiting. The pressure sensitive adhesives may contain one or more of plasticizer(s), flowing agent(s), tackifier(s) and pigment(s). Pressure can be applied manually or by means of pneumatic or hydraulic cylinders or any type of mechanical device.

The water-soluble film can be made of non-edible or edible grade film-forming polymeric materials. Non edible materials may be selected from, but not limited to, polyvinyl alcohol copolymer ionomers, polyvinyl alcohol homopolymer, non-ionomeric poly vinyl alcohol polymer, polymethacrylate, Poly Vinyl Alcohol, polyacrylamide, Functional Poly Vinyl Alcohol, low molecular weight Poly Vinyl Alcohol, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyurethane. Edible materials may be selected from, but not limited to, polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch, gum arabic, pullulan or dextrin or water-soluble cellulose derivatives such as methyl cellulose, hydroxyl propyl cellulose, hydroxyl propyl methyl cellulose, hydroxyl propyl ethyl cellulose, hydroxy ethyl cellulose or carboxyl methyl cellulose or combination thereof.

The water-soluble protective layer can be cold water soluble, warm water soluble or hot water soluble depending upon the end application. The temperature of dissolution of the water-soluble protective layer will depend upon its composition, the molecular weight of each of the polymers contained therein, and other factors. The water-soluble protective layer can be transparent, pigmented or colored as per requirement. The thickness of the water soluble film ranges from range from 1 to 5 micron, preferably 2 micron and more preferably less than 1 micron.

Further, the said WSF layer may also be incorporated with or without surfactants to remove air bubbles from the self-adhesive material. Surfactants may be selected from anionic based surfactants, cationic based surfactants such as cetyl pyridinium chloride; ampholytic surfactants like dodecyl betaine, dodecyl dimethylamine oxide; nonionic surfactants like alkyl polyethylene oxide, alkyl polyglucosides or a combination thereof.

The said protective layer formed of WSF may further be incorporated with plasticizers selected from but not limited to glycerol, PEG (Poly ethylene glycol), PPG (Poly propylene glycol), maltose and optionally may comprise of stabilizer/ selected from calcium carbonate, titanium dioxide, zinc oxide and the like. The said protective layer formed of WSF may further be incorporated with flowing agent(s), tackifier(s) and pigment(s) or catalyst.

Another embodiment of the present invention discloses, a formulation and method of preparing the water soluble formulation, such that it exhibit nano thin quality and faster dissolving characteristic so as to expose the adhesive part of the new improved liner less self-adhesive material (NEWSAM®) in seconds.

The present invention discloses a water soluble formulation comprising of:
- Film forming agent, said film forming agents are selected from but not limited to, polyvinyl alcohol copolymer ionomers, polyvinyl alcohol homopolymer, non-ionomeric poly vinyl alcohol polymer, polymethacrylate, Poly Vinyl Alcohol, low molecular weight Poly Vinyl Alcohol, Functional Poly Vinyl Alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyurethane. Edible materials may be selected from, but not limited to, polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch, gum arabic, pullulan or dextrin or water-soluble cellulose derivatives such as methyl cellulose, hydroxyl propyl cellulose, hydroxyl propyl methyl cellulose, hydroxyl propyl ethyl cellulose, hydroxy ethyl cellulose or carboxyl methyl cellulose or combination thereof.
- Surfactants selected from anionic based surfactants, cationic based surfactants such as cetyl pyridinium chloride; ampholytic surfactants like dodecyl betaine, dodecyl dimethylamine oxide; nonionic surfactants like alkyl polyethylene oxide, alkyl polyglucosides or a combination thereof,
- Plasticizers selected from but not limited to glycerol, PEG (Poly ethylene glycol), PPG (Poly propylene glycol), maltose, and
- Optionally may comprise of stabilizer selected from calcium carbonate, titanium dioxide, zinc oxide and the like.

Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. Further surfactants are used to reduce the formation of pin holes/air-bubbles, when coated over the adhesive pressure sensitive surface. Surfactants are surface active agents that have the tendency to adsorb at the interfaces in the form of monolayers and to lower the free energy of the phase boundary, also these are used for emulsifying and solubilizing the immiscible substances. Plasticizer are substance (typically a solvent) added to a synthetic resin to produce or promote plasticity and flexibility and to reduce brittleness.

Wherein interaction between polymer, surfactant and plasticizer plays a significant role. The interaction between these influences solution and interfacial property and are controlled by the state of their occurrence in aqueous solution. The ability of surfactants to aggregate and form micelles adds the particular dimensions to their interaction with water soluble polymer, whereas the ability of plasticizer is to promote flexibility to the polymer.

Polymers are usually employed to control the rheology of solutions and suspensions, and when present together with the surfactant and plasticizer, synergistic interaction between polymer surfactants and plasticizer occur. Addition of surfactants and plasticizer to polymer solution changes the properties of polymer and provide surface tension control and increased tensile strength.

The interaction of the surfactants and plasticizer with water soluble polymer has been studied using batch mix cast solution techniques, for preparing the formulation of water soluble film are as follows:

Experiment 1:

Film forming agent such as low molecular weight poly vinyl alcohol is added at a range of 70-90%, preferably at a range of 75-85%, more preferably at a range of 85-90%. Plasticizer is added at a range of 1 -10%, preferably at a range of 2-5%, more preferably at a range of 2-3%. Surfactant is added at a range of 0.5-3%, preferably at a range of 1-2.5%, more preferably at a range of 0.5 -2%. Stabilizer is added at a range of 0.1 to 0.5%.

Step (a) Taking composition (solid content) of film forming agents along with surfactants, plasticizer and stabilizer;
Wherein film forming agent such as low molecular weight poly vinyl alcohol is added at a range of 70-90%;
Plasticizer is added at a range of 1-10%;
Surfactant is added at a range of 0.5 to 3%;
Optionally adding stabilizer at a range of 0.1 to 0.5%;
Step (b) Adding the % solid content of the composition obtained in step (a) at a range of 1 to 10% in water (solvent);
Step (c) Stirring the said solute obtained in step (a) in the solvent (step b) for 2 to 3 hours at a temperature of less than 50-70°C, until a clear solution is obtained.
Step (d) Repeating the process by making different batches of the solution at various ratios.

Experiment 2:

Film forming agent such as Polyvinyl pyrrolidone is added at a range of 80-95%, preferably at a range of 75-85%, more preferably at a range of 85-90%. Plasticizer is added at a range of 1 -5%, preferably at a range of 2-4.5%, more preferably at a range of 3-4%. Surfactant is added at a range of 0.5-3%, preferably at a range of 1-2.5%, more preferably at a range of 0.5 -2%. Stabilizer is added at a range of 0.1 to 0.5%.

Step (a) Taking composition (solid content) of film forming agents along with surfactants, plasticizer and stabilizer;
Wherein film forming agent such as polyvinyl pyrrolidone is added at a range of 80-95%;
Plasticizer is added at a range of 1-5%;
Surfactant is added at a range of 0.5 to 3%;
Optionally adding stabilizer at a range of 0.1 to 0.5%;
Step (b) Adding the % solid content of the composition obtained in step (a) at a range of 1 to 10% in water (solvent);
Step (c) Stirring the said solute obtained in step (a) in the solvent (step b) for 2 to 3 hours at a temperature of less than 50-70°C, until a clear solution is obtained.
Step (d) Repeating the process by making different batches of the solution at various ratios.

Experiment 3:

Film forming agent such as Hydroxyl propyl methyl cellulose is added at a range of 65-85%, preferably at a range of 60-80%, more preferably at a range of 55-75%. Plasticizer is added at a range of 1 -15%, preferably at a range of 2-12%, more preferably at a range of 4-10%. Surfactant is added at a range of 0.5-3%, preferably at a range of 1-2.5%, more preferably at a range of 0.5 -2%. Stabilizer is added at a range of 0.1 to 0.5%

Step (a) Taking composition (solid content) of film forming agents along with surfactants, plasticizer and stabilizer;
Wherein film forming agent such as Hydroxyl propyl methyl cellulose is added at a range of 65-85%;
Plasticizer is added at a range of 1-15%;
Surfactant is added at a range of 0.5 to 3%;
Optionally adding stabilizer at a range of 0.1 to 0.5%;
Step (b) Adding the % solid content of the composition obtained in step (a) at a range of 1 to 10% in water (solvent);
Step (c) Stirring the said solute obtained in step (a) in the solvent (step b) for 2 to 3 hours at a temperature of less than 50-70°C, until a clear solution is obtained.
Step (d) Repeating the process by making different batches of the solution at various ratios.

Wherein, experimental analysis 1 to 3 is carried out to obtain the optimum result, such that a water soluble film batch is obtained having a thickness of less than 1 micron.

Further, adding surfactant, plasticizer and stabilizer to the film forming agent not only provides a clearer formulation, but also stabilizes the film and retain the self life of the film, when coated on the adhesive layer.

Conduct batch study (tabular format) with several Experimental formulations 1 to 3, to obtain the optimum formulation with respect to their thickness and uniformity.

Formulations Ingredients Solid content( %) Viscosity( in Seconds)

1 Low molecular weight poly vinyl alcohol ( 70 to 90%)+ plasticizer ( 1 to 10%)+ surfactant ( 0.5 to 3%) + stabilizer ( 0.1 to 0.5%) Upto 10% 55
9 – 8% 40
5 – 7% 30
5 – 7% 30

2 Polyvinyl pyrrolidone( 80 to 95%)+ plasticizer ( 1 to 5%)+ surfactant ( 0.5 to 3%) + stabilizer ( 0.1 to 0.5%) Upto 10% 55
9 – 8% 40
5 – 7% 30
5 – 7% 30

3 Hydroxyl propyl methyl cellulose ( 65 to 85%)+ plasticizer ( 1 to 15%)+ surfactant ( 0.5 to 3%) + stabilizer ( 0.1 to 0.5%) Upto 10% 95
6 – 8% 85
4 – 6% 65

The formulation of water soluble film prepared by the aforementioned method herein is referred as batch mix.

In conclusion, batch study carried in Experimental formulations 1 and 2, shows a better viscosity in seconds in comparison to viscosity obtained in experimental formulation 3.

Further, in order to achieve the nano thin water soluble film, several variations in thickness of the above experiment may further be obtained by changing the speed and pressure of the air-knife coater, during the coating process.

Yet another embodiment of the present invention discloses various coating process wherein the batch mix are coated over the pressure sensitive adhesive layer by non-contact coating process.

A series of non-contact coating processes can be performed to coat the WSF on the PSA side. The series of non-contact coating processes comprise (i) a direct coating process and (ii) an indirect laminating coating process (iii) coating the WSF over the liner for further use. The pressure sensitive adhesive (PSA) may also be coated on heat resistance face or indirect heat sensitive face by a non-contact coating process.

The present disclosure preferably uses the air knife coating for the series of non-contact coating processes. The air knife coating creates a plurality of patterns on the face material, that is used to remove air bubbles and to form nano thin coating of the water soluble film over the pressure sensitive adhesive layer, such that when the nano thin layer of water soluble film is exposed to water, it quickly dissolves in water, so as to expose the adhesive part of the new improved liner less self adhesive material (NEWSAM®) within seconds.

Fig 2, illustrates a coating process to obtain a nano water soluble film on a detachable liner using air-knife coating technique, comprising the steps of:
Unwinding the liner from unwinder (1) of machine,
Passing the liner over plurality of roller (2, 2a, 2b),
Subsequently, passing the liner over the roller (3), wherein the aqueous batch mix kept in the coating tray (8) is coated on to the liner,
Passing the liner coated with batch mix over the roller (4);
subjecting the liner coated with batch mix to air pressure of the air knife coater (10), wherein the air knife is positioned at a specific angle at a specific distance, at specific air pressure exerted by the air knife coater, wherein the final wet coating is formed as per desired coat weight;
Collecting the residual aqueous batch mix, after the air knife process on to a collector (9) positioned between the aqueous batch mix coating tray (8) and air knife coater (10), and recycling the batch mix.
Drying the liner coated with batch mix by passing through the dryer (7) to form a nano thin layer of water soluble film on a detachable liner;
Passing the liner coated with batch mix over the roller (5) after drying, and
Rewinding the same on to roller (6)

Fig 3, illustrates an indirect lamination coating method to obtain Self-Adhesive Material using air-knife coating technique, comprising the steps of:
Unwinding the detachable liner from unwinder (1) of machine;
Passing the liner over plurality of roller (2, 2a, 2b),
Passing the liner over the roller (3), wherein the aqueous batch mix kept in the coating tray (8) is coated on to the liner;
Passing the liner coated with batch mix over the roller (4);
subjecting the liner coated with batch mix to air pressure of the air knife coater (10), wherein the air knife is positioned at a r specific angle at a specific distance, at specific air pressure exerted by the air knife coater, wherein the final wet coating is formed as per desired coat weight;
Collecting the residual aqueous batch mix, after the air knife process on to a collector (9) positioned between the aqueous batch mix coating tray (8) and air knife coater (10) , and recycling the batch mix.
Drying the liner coated with batch mix by passing through the dryer (7) to form a nano thin layer of water soluble film on a the detachable liner;
Passing the liner coated with batch mix over the roller (5) after drying;
Unwinding the face material from unwinder (11) of machine;
Coating the face material with liquid adhesive (12) positioned at a specific angel;
Drying the face material coated with liquid adhesive and passing through a dryer (13)
Laminating the nano thin layer of water soluble film coated over the liner to the adhesive layer coated over the face material by passing over the nip roller (not shown) ;
Detaching the detachable liner (not shown); and
Rewinding the liner less self adhesive material (NSAM) on to the roller (6).

Optionally, Fig 3, illustrates an indirect lamination coating method to obtain Self-Adhesive Material using air-knife coating technique, comprising the steps of:
Unwinding the detachable liner from unwinder (1) of machine;
Passing the liner over plurality of roller (2, 2a, 2b),
Passing the liner over the roller (3), wherein the aqueous batch mix kept in the coating tray (8) is casted on to the liner;
Passing the liner coated with batch mix over the roller (4);
subjecting the liner coated with batch mix to air pressure of the air knife coater (10), wherein the air knife is positioned at a specific angle at a specific distance,at specific air pressure exerted by the air knife coater, wherein the final wet coating is formed as per desired coat weight;
Collecting the residual aqueous batch mix, after the air knife process on to a collector (9) positioned between the aqueous batch mix coating tray (8) and air knife coater (10) , and recycling the batch mix.
Drying the liner coated with batch mix by passing through the dryer (7) to form a nano thin layer of water soluble film on a the detachable liner;
Passing the liner coated with batch mix over the roller (5) after drying;
Unwinding the face material from unwinder (11) of machine;
Coating the face material with hot melt adhesive (12) positioned at a specific angel;
Drying the face material coated with hot melt adhesive and passing through chilling cylinder (11a, 11b);
Laminating the nano thin layer of water soluble film coated over the liner to the adhesive layer coated over the face material by passing over the nip roller (not shown) ;
Detaching the detachable liner (not shown); and
Rewinding the liner less self adhesive material (NSAM) on to the roller (6).

Fig 4, illustrates a direct coating method to obtain ready to use Self-Adhesive Material using air-knife coating technique, comprising the steps of:
Unwinding the face material from unwinder (1) of machine,
Coating the face material with liquid adhesive (12) positioned at a specific angel;
Drying the face material coated with liquid adhesive and passing the same over a dryer (13);
Passing the face material coated with adhesive over plurality of non stick roller (2, 2a, 2b, 2c, 2d);
Subsequently, passing the face material coated with adhesive over the roller (3), wherein the aqueous batch mix kept in the coating tray (8) is coated on to the adhesive coated side of face material,
Passing the face material coated with batch mix over the roller (4);
subjecting the liner coated with batch mix to air pressure of the air knife coater (10), wherein the air knife is positioned at a specific angle at a specific distance, at specific air pressure exerted by the air knife coater, wherein the final wet coating is formed as per desired coat weight;
Collecting the residual aqueous batch mix, after the air knife process on to a collector (9) positioned between the aqueous batch mix coating tray (8) and air knife coater (10), and recycling the batch mix.
Drying the face material coated with batch mix by passing through the dryer (7);
Passing the liner less self adhesive material (NSAM) formed over the roller (5); and
Rewinding the same on to roller (6).

Optionally Fig 4, illustrates a direct coating method to obtain ready to use Self-Adhesive Material using air-knife coating technique, comprising the steps of:
Unwinding the face material from unwinder (1) of machine,
Coating the face material with hot melt adhesive (12) positioned at a specific angel;
Drying the face material coated with hot melt adhesive and passing the same over a plurality of chilling cylinder (11a, 11b);
Passing the face material coated with adhesive over plurality of non stick roller (2, 2a, 2b,2c,2d);
Subsequently, passing the face material coated with adhesive over the roller (3), wherein the aqueous batch mix kept in the coating tray (8) is coated on to the adhesive coated side of face material,
Passing the face material coated with batch mix over the roller (4);
subjecting the liner coated with batch mix to air pressure of the air knife coater (10), wherein the air knife is positioned at a perpendicular specific angle at a specific distance, such that due to the at specific air pressure exerted by the air knife coater, wherein at a perpendicular angle, it regulates the final wet coating is formed as per desired coat weight;
Collecting the residual aqueous batch mix, after the air knife process on to a collector (9) positioned between the aqueous batch mix coating tray (8) and air knife coater (10), and recycling the batch mix.
Drying the face material coated with batch mix by passing through the dryer (7);
Passing the liner less self adhesive material (NSAM) formed over the roller (5); and
Rewinding the same on to roller (6),

The excess batch mix is collected in an overflow pan/collecting tray and is either recirculated and re-used or scrapped. The coating weight is determined by the coating line speed, the coating solution viscosity, solid content of the batch mix and the air knife characteristics.

The drying step generally includes the use of forced air using a drying oven, drying tunnel, chilling cylinder and the like.

The air knife characteristics are defined by the volume, velocity and air jet geometry impinging on the coated layer, including the air knife angle of incidence relative to the substrate. Increasing fluid viscosity and line speed increase the thickness and increased air knife pressure reduces the thickness. The pressure of the air knife coating is maintained at 700 (± 100 mwc).

Air knife coating as disclosed in the present invention relates to obtaining nano thin coating of the water soluble film, wherein the air knife operates at much higher pressures and coating speeds and effectively blows off the majority of the coating. This process is useful for coating aqueous water soluble film on the PSA layer. It has been found that air knife coating method, effectively functions as a leveling device, and in obtaining the thinnest layer. The present invention discloses that by using the air knife method combined with the water soluble formulation as prepared by the above disclosure, it is possible to obtain water soluble film having a thickness of less than 1 micron or nano thin water soluble film.

Experimental details indicating the characteristic of water soluble film obtained when subjected to air knife coating are as follows:

Table 1 indicates batches 1 to 4, wherein low molecular weight poly vinyl alcohol ( 70 to 90%), plasticizer ( 1 to 10%), surfactant ( 0.5 to 3%) and stabilizer ( 0.1 to 0.5%) are used to prepare a formulation so as to identify the characteristic of water soluble film obtained when subjected to air knife coating.

Batches Viscosity
(in second Water soluble film thickness line speed of air knife
(m/min) Air pressure Solid content (%) coverage uniformity
1 55 3 - 4 µ 20 700 (± 100 mwc) Upto 10% Average
2 40 2 - 3 µ 20 700 (± 100 mwc) 9 – 8% Average
3 30 1 - 2 µ 20 700 (± 100 mwc) 5 – 7% Good
4 30 < - 1 µ 25 700 (± 100 mwc) 5 – 7% Excellent

Table 2 indicates batches 1 to 4, wherein Polyvinyl pyrrolidone ( 80 to 95%)+ plasticizer ( 1 to 5%)+ surfactant ( 0.5 to 3%) + stabilizer ( 0.1 to 0.5%) are used to prepare a formulation so as to identify the characteristic of water soluble film obtained when subjected to air knife coating.

Batches Viscosity
(in second Water soluble film thickness line speed of air knife
(m/min) Air pressure Solid content (%) coverage uniformity
1 55 3 - 4 µ 20 700 (± 100 mwc) Upto 10% Average
2 40 2 - 3 µ 20 700 (± 100 mwc) 9 – 8% Average
3 30 1 - 2 µ 20 700 (± 100 mwc) 5 – 7% Good
4 30 < - 1 µ 25 700 (± 100 mwc) 5 – 7% Excellent

Table 3 indicates batches 1 to 4, wherein Hydroxyl propyl methyl cellulose ( 65 to 85%)+ plasticizer ( 1 to 15%)+ surfactant ( 0.5 to 3%) + stabilizer ( 0.1 to 0.5%) are used to prepare a formulation so as to identify the characteristic of water soluble film obtained when subjected to air knife coating.

Batches Viscosity
(in second Water soluble film thickness line speed of air knife
(m/min) Air pressure Solid content (%) coverage uniformity
1 95 3 - 4 µ 20 700 (± 100 mwc) Upto 10% Average
2 85 2 - 3 µ 20 700 (± 100 mwc) 6 – 8% Average
3 65 1 - 2 µ 20 700 (± 100 mwc) 4 – 6% Average

Experimental analysis:

Table 1 and Table 2: Batch 1 on experimental analysis shows viscosity of the batch mix to be 55 sec flow time, water soluble film thickness 0f 3-4 µ, wherein the line speed of the air knife is maintained to 20 m/min, and has average coverage uniformity when coated using air-knife coating process. Further Batch 2 on experimental analysis shows viscosity of the batch mix to be 40 sec flow time, water soluble film thickness 0f 2-3 µ, wherein the line speed of the air knife is maintained to 20 m/min, and has average coverage uniformity when coated using air-knife coating process. Furthermore Batch 3 on experimental analysis shows viscosity of the batch mix to be 30 sec flow time, water soluble film thickness 0f 1-2 µ, wherein the line speed of the air knife is maintained to 20 m/min, and has good coverage uniformity when coated using air-knife coating process. Furthermore Batch 4 on experimental analysis shows viscosity of the batch mix to be 30 sec flow time, water soluble film thickness 0f < - 1µ, wherein the line speed of the air knife is maintained to 25 m/min, and has excellent coverage uniformity when coated using air-knife coating process. The above experimental analysis proves that the result as shown in batch 3 and batch 4 provides an optimum result. Thus this experimental analysis shows that when aqueous novel formulation as disclosed in the batch 3 and batch 4 used as batch mix is coated over PSA using air knife technique, it exhibit nano thin quality and faster dissolving characteristic so as to expose the adhesive part of the new improved self adhesive material in mili seconds.

Table 3: Batch 1 on experimental analysis shows viscosity of the batch mix to be 95 sec flow time, water soluble film thickness 0f 3-4 µ, wherein the line speed of the air knife is maintained to 20 m/min, and has average coverage uniformity when coated using air-knife coating process. Further Batch 2 on experimental analysis shows viscosity of the batch mix to be 85 sec flow time, water soluble film thickness 0f 2-3 µ, wherein the line speed of the air knife is maintained to 20 m/min, and has average coverage uniformity when coated using air-knife coating process. Furthermore Batch 3 on experimental analysis shows viscosity of the batch mix to be 65 sec flow time, water soluble film thickness 0f 1-2 µ, wherein the line speed of the air knife is maintained to 20 m/min, and has average coverage uniformity when coated using air-knife coating process. The above experimental analysis proves that the result as shown in batch 1 to 3 provides an average result.

The air knife coating being a “non-contact” method does not “contaminate” the quality of the water soluble film, this process enable nano-layer of batch mix of WSF to be coated on adhesive coated substrates without any obstructions. The excess layer of liquid batch mix collected during the air knife coating process, can be collected separately and recycled after appropriate treatment externally or during the process.

In conclusion, the present invention discloses the formation of nano thin water soluble film or water soluble film having a thickness of less than 1 micron, that is achievable by the formulation as disclosed in the present invention and by subjecting the coated batch mix to air knife coating process that not only provides the thinnest possible water soluble film but also ensures no contamination of adhesive and/or batch mix WSF takes place, when compared to the contact coating methods such as gravure or mayer rod coatings or other types of “contact coating” methods.

,CLAIMS:WE CLAIM:

1. A linerless self adhesive material (NEWSAM®) with nano thin and faster dissolving water soluble film comprising of:
- face material;
- pressure sensitive adhesive layer coated on the obverse surface of the face material;
- a nano thin layer of water soluble film coated over the adhesive layer as a protective coating;
Wherein the adhesive layer is coated with a nano water-soluble film protective layer which dissolves in water in less than 45 seconds, whereby exposing the adhesive layer for adhesion to desired object.

2. The linerless self adhesive material (NEWSAM®) as claimed in claim 1, wherein the water soluble film coating is a non contact coating process.

3. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1 and 2, wherein the non contact coating is an air knife coating process.

4. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1, wherein the face material is selected from but not limited to, uncoated or coated paper, film, metal foils, fabric, ink receptive coated materials, polymeric materials or a combination of any of these materials.

5. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1 and 4, wherein the face material is selected from, but not limited to, heat sensitive materials such as PVC (poly-vinyl chloride), HIPS (high impact polystyrene), LLDPE (linear low density polyethylene), heat shrinkable linear low density polyethylene, PP (polypropylene), APET (Anhydrous polyester), PETG (polyester glycol), HDPE (high density polyethylene).

6. The linerless self adhesive material (NEWSAM® ) as claimed in claims 1 to 5, wherein the face material is selected from, but not limited to, heat resistant face materials such as paper, polyester film, or kapton film.

7. The linerless self adhesive material (NEWSAM® ) as claimed in claims 1 to 6, wherein the face material is pre-printed or post-printed.

8. The linerless self adhesive material (NEWSAM® ) as claimed in claims 1 to 7, wherein printing on the face material may be done using suitable printing method such as gravure, flexography, dry or wet offset, inkjet printing, thermal printing, Screen printing, Subliminal ink printing, holographic embossing, or hot foil stamping.

9. The linerless self adhesive material (NEWSAM® ) as claimed in claims 1 to 8, wherein the face material is optionally coated with hydrophobic/water repellent lacquer on its obverse surface.

10. The linerless self adhesive material (NEWSAM® ) as claimed in claims 1 to 9, wherein the PSA (Pressure Sensitive Adhesive)selected are made from resins, polymers or co-polymers of acrylics, rubber, hot melt polymers, ethylene-vinyl acetate copolymers (EVA), starch, UV Curable, and polyurethanes, either dissolved in organic or inorganic/hydrocarbon or are water based solvents or crosslinking PSA or hot melt PSA.

11. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1 and 10, wherein the pressure sensitive adhesives may contain one or more of plasticizer(s), flowing agent(s), tackifier(s) and pigment(s) or catalyst.

12. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1, wherein the water soluble film is selected from but not limited to, polyvinyl alcohol copolymer ionomers, polyvinyl alcohol homopolymer, non-ionomeric poly vinyl alcohol polymer, polymethacrylate, Poly Vinyl Alcohol, low molecular weight Poly Vinyl Alcohol, functional Poly Vinyl Alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyurethane. Edible materials may be selected from, but not limited to, polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch, gum arabic, pullulan or dextrin or water-soluble cellulose derivatives such as methyl cellulose, hydroxyl propyl cellulose, hydroxyl propyl methyl cellulose, hydroxyl propyl ethyl cellulose, hydroxy ethyl cellulose or carboxyl methyl cellulose or combination thereof.

13. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1 and 12, wherein the water soluble film may be made of non-edible or edible grade film-forming polymeric materials.

14. The linerless self adhesive material (NEWSAM® ) as claimed in claims 1 to 13, wherein the water soluble film may be cold water soluble, warm water soluble or hot water soluble.

15. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1, wherein the water soluble layer is incorporated with or without surfactant.

16. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1, wherein the water soluble layer is optionally incorporated with plasticizer.

17. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1 and 16, wherein the water soluble layer is incorporated with surfactant is selected from anionic based surfactants, cationic based surfactants such as cetyl pyridinium chloride; ampholytic surfactants like dodecyl betaine, dodecyl dimethylamine oxide; nonionic surfactants like alkyl polyethylene oxide, alkyl polyglucosides or a combination thereof.

18. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1 and 17, wherein the plasticizer is selected from but not limited to glycerol, PEG (Poly ethylene glycol), PPG (Poly propylene glycol), maltose or a combination thereof.

19. The linerless self adhesive material (NEWSAM® ) as claimed in claim 1, wherein the water soluble layer is optionally incorporated with stabilizer selected from calcium carbonate, titanium dioxide, zinc oxide and the like.

20. A process of preparing water soluble formulation comprises of:
- Film forming agent, said film forming agents are selected from but not limited to, polyvinyl alcohol copolymer ionomers, polyvinyl alcohol homopolymer, non-ionomeric poly vinyl alcohol polymer, polymethacrylate, Poly Vinyl Alcohol, low molecular weight Poly Vinyl Alcohol, functional Poly Vinyl Alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyurethane. Edible materials may be selected from, but not limited to, polyethyleneglycol, polyvinylpyrrolidone, proteinaceous binders such as gelatin, modified gelatins such as phthaloyl gelatin, polysaccharides such as starch, gum arabic, pullulan or dextrin or water-soluble cellulose derivatives such as methyl cellulose, hydroxyl propyl cellulose, hydroxyl propyl methyl cellulose, hydroxyl propyl ethyl cellulose, hydroxy ethyl cellulose or carboxyl methyl cellulose or combination thereof.
- Surfactants selected from anionic based surfactants, cationic based surfactants such as cetyl pyridinium chloride; ampholytic surfactants like dodecyl betaine, dodecyl dimethylamine oxide; nonionic surfactants like alkyl polyethylene oxide, alkyl polyglucosides or a combination thereof, and
- Plasticizer selected from but not limited to glycerol, PEG (Poly ethylene glycol), PPG (Poly propylene glycol), maltose, and
- Optionally may comprise adding of Stabilizing selected from calcium carbonate, titanium dioxide, zinc oxide and the like.

21. The process of preparing water soluble formulation as claimed in claim 20, wherein the water soluble layer has a thickness in the range of less than 5 micron, preferably 2 micron and more preferably less than 1 micron.

22. The process of preparing water soluble formulation as claimed in claim 20 and 21, wherein the pressure sensitive adhesive (PSA) is coated on heat resistance face or indirect heat sensitive face by a non-contact coating process.

23. A coating process to obtain a nano water soluble film on a detachable liner using air-knife coating technique, comprising the steps of:
Unwinding the liner from unwinder (1) of machine,
Passing the liner over plurality of roller (2, 2a, 2b),
Subsequently, passing the liner over the roller (3), wherein the aqueous batch mix kept in the coating tray (8) is coated on to the liner,
Passing the liner coated with batch mix over the roller (4);
subjecting the liner coated with batch mix to air pressure of the air knife coater (10), wherein the air knife is positioned at a specific angle at a specific distance, at specific air pressure exerted by the air knife coater, wherein the final wet coating is formed as per desired coat weight;
Collecting the residual aqueous batch mix, after the air knife process on to a collector (9) positioned between the aqueous batch mix coating tray (8) and air knife coater (10), and recycling the batch mix.
Drying the liner coated with batch mix by passing through the dryer (7) to form a nano thin layer of water soluble film on a detachable liner;
Passing the liner coated with batch mix over the roller (5) after drying, and
Rewinding the same on to roller (6).

24. An indirect lamination coating method to obtain Self-Adhesive Material using air-knife coating technique, comprising the steps of:
Unwinding the detachable liner from unwinder (1) of machine;
Passing the liner over plurality of roller (2, 2a, 2b),
Passing the liner over the roller (3), wherein the aqueous batch mix kept in the coating tray (8) is coated on to the liner;
Passing the liner coated with batch mix over the roller (4);
subjecting the liner coated with batch mix to air pressure of the air knife coater (10), wherein the air knife is positioned at a specific angle at a specific distance, at specific air pressure exerted by the air knife coater, wherein the final wet coating is formed as per desired coat weight;
Collecting the residual aqueous batch mix, after the air knife process on to a collector (9) positioned between the aqueous batch mix coating tray (8) and air knife coater (10) , and recycling the batch mix.
Drying the liner coated with batch mix by passing through the dryer (7) to form a nano thin layer of water soluble film on a the detachable liner;
Passing the liner coated with batch mix over the roller (5) after drying;
Unwinding the face material from unwinder (11) of machine;
Coating the face material with liquid adhesive (12) positioned at a specific angel;
Drying the face material coated with liquid adhesive and passing through a dryer (13)
Laminating the nano thin layer of water soluble film coated over the liner to the adhesive layer coated over the face material by passing over the nip roller (not shown) ;
Detaching the detachable liner (not shown); and
Rewinding the liner less self adhesive material (NSAM) on to the roller (6).

25. The coating process as claimed in claim 24, optionally consists of chilling cylinder (11a,11b) wherein the same may be used for drying the face material coated with hot melt adhesive.

26. A direct coating method to obtain ready to use Self-Adhesive Material using air-knife coating technique,
comprising the steps of:
Unwinding the face material from unwinder (1) of machine,
Coating the face material with liquid adhesive (12) positioned at a specific angel;
Drying the face material coated with liquid adhesive and passing the same over a dryer (13);
Passing the face material coated with adhesive over plurality of non stick roller (2, 2a, 2b,2c,2d);
Subsequently, passing the face material coated with adhesive over the roller (3), wherein the aqueous batch mix kept in the coating tray (8) is coated on to the adhesive coated side of face material,
Passing the face material coated with batch mix over the roller (4);
subjecting the liner coated with batch mix to air pressure of the air knife coater (10), wherein the air knife is positioned at a specific angle at a specific distance, at specific air pressure exerted by the air knife coater, wherein the final wet coating is formed as per desired coat weight;
Collecting the residual aqueous batch mix, after the air knife process on to a collector (9) positioned between the aqueous batch mix coating tray (8) and air knife coater (10), and recycling the batch mix;
Drying the face material coated with batch mix by passing through the dryer (7);
Passing the liner less self adhesive material (NSAM) formed over the roller (5); and
Rewinding the same on to roller (6).

27. The coating process as claimed in claim 26, optionally consists of chilling cylinder (11a,11b) wherein the same may be used for drying the face material coated with batch mix.

28. The process as claimed in claims 1- 27, wherein the pressure of the air knife coating is maintained at 700 (± 100 mwc).

29. The process as claimed in claims 1-28, wherein the water soluble film coated over the PSA has a faster dissolution rate.