FIELD OF THE INVENTION:
The present invention relates to a water vapour barrier coated packaging laminate of transparent polymeric films, especially involving a biaxially oriented polypropylene (BOPP) film substrate.
BACKGROUND OF THE INVENTION:
It has been observed that laminates tend to suffer substantial reduction in their water vapour barrier properties, as well as mechanical properties. Because of poor water vapour barrier properties of laminates, quality of the contents inside the laminate packaging article gets degraded when the package is exposed to humid environments.
The reduction of mechanical properties has been linked to water vapour absorption from the surroundings. The water vapour absorption further worsens in hotter atmospheric conditions. The combined effects of temperature and humidity result in water vapour intrusion with a resultant increase in water vapour content of the laminate material up to an equilibrium water vapour content for the particular temperature and humidity conditions, over a certain duration typically from 100 to 300 hours. The duration of water vapour content to reach the point of equilibrium generally varies, based on the structure of the laminate, the materials used, relative atmospheric humidity and the surrounding temperature. Irrespective of the duration of exposure of the laminate to such conditions, the slow absorption of water vapour considerably degrades the mechanical and physical properties of the laminate, and also degrades the quality of contents within the laminate packaging article.
US5604042A discloses a polymeric film structure having barrier characteristics, the structure includes a polymeric substrate adapted to receive an oxygen barrier on one side thereof and a moisture barrier on the other side of the oxygen barrier. The oxygen barrier includes polyvinyl alcohol cross-linked with aldehyde containing cross-linking agents in the presence of a catalytic amount of sulfuric acid.
US2017088311A1 discloses a reinforced multilayer material that includes a mesh material covered on at least one side, by a layer of a resinous film material. The mesh material includes filaments that intersect one another, at least some of the

filaments being composite filaments having a carrier portion of a relatively high melting point and a bonding portion of a relatively low melting point, the bonding portion of each composite filament being thermally bonded to other filaments at least some points of intersection.
US10463570B2 discloses a film suitable for medical packaging, where the barrier layer includes a high barrier resin and a branched co-polymer. The high barrier resin has a density of at least 0.963 g/cm3. The barrier layer includes between 25% and 85% high barrier resin. An additional laminate layer may be affixed to the heat resistant layer of the multi-layer film. The final film is between 3.0 and 3.8 mils in thickness, and has a moisture vapour transmission rate of less than 0.08.
EP3497024A1 discloses a gas and moisture vapour barrier coating compositions that comprise an amine modified polyvinyl alcohol and an acetoacetate modified polyvinyl.
US5387449A discloses composites of plastic films and packaging forms made thereof that feature a permeability barrier layer, said forms of packaging being made from a composite featuring, from outside to inside, for example the layers a) a polyester film b) a ceramic layer, and c) a polyolefin film.
KR101472917B1 discloses a moisture blocking film and a method for manufacturing the same. Interlayer delamination does not occur on the moisture blocking film, and the film has excellent moisture blocking properties. The moisture blocking film includes: a substrate; an organic/inorganic hybrid layer which includes a gradient forming interfacial structure formed on the substrate; and an inorganic barrier layer formed on the organic/inorganic hybrid layer. The moisture blocking film may additionally include a buffer layer between the organic/inorganic hybrid layer and the inorganic barrier layer.
OBJECTS OF THE INVENTION:
The principal objective of the present invention is to provide improved water vapour barrier properties to the packaging laminate involving transparent biaxially oriented polypropylene (BOPP) film substrate.

Another objective of the present invention is to provide a water vapour barrier coated laminate that reduces intrusion of water vapour into the water vapour barrier coated laminate through the surface by at least about 80%.
A further objective of the present invention is to provide a water vapour barrier coated laminate with improved display performance.
Yet another objective of the present invention is to provide a water vapour barrier coated laminate that has improved recyclability.
SUMMARY OF THE INVENTION:
A water vapour barrier coated laminate with improved barrier properties is provided, wherein the laminate is made of biaxially oriented polypropylene (BOPP) and another lamination film such as cast polypropylene (CPP) film, polyethylene (PE) film, or a second BOPP film, wherein the BOPP, CPP, and PE films are transparent.
The water vapour barrier coated laminate includes a biaxially oriented polypropylene (BOPP) substrate, on which water vapour barrier coating is applied, and a printing ink layer is applied on the top of the water vapour barrier coating layer; in turn a layer of adhesive is applied on the printing ink layer, and finally a transparent film is laminated to the adhesive applied side of the BOPP substrate. The transparent film is selected from a cast polypropylene (CPP) film, a polyethylene (PE) film, and a second BOPP film.
When the water vapour barrier coated laminate of the present invention is in a humid environment, the water vapour barrier coating reduces the intrusion of water vapour into the water vapour barrier coated laminate through its surface by at least about 80%, and the transparent films provides the articles made from the laminate of the present invention an improved display performance.
When CPP is used as a layer in the water vapour barrier coated laminate, due to the mono-family structure of BOPP and CPP films, the recyclability of the laminates is improved.

BRIEF DESCRIPTION OF THE DRAWINGS:
Fig. 1 illustrates a water vapour barrier coated laminate of a biaxially oriented polypropylene (BOPP) film substrate and a cast polypropylene (CPP) film.
Fig. 2 illustrates a water vapour barrier coated laminate of biaxially oriented polypropylene (BOPP) film substrate and a polyethylene (PE) film.
Fig. 3 illustrates a water vapour barrier coated laminate of a First biaxially oriented polypropylene (First-BOPP) film substrate and a Second biaxially oriented polypropylene (Second-BOPP) film.
DETAILED DESCRIPTION OF THE INVENTION:
The preferred embodiments of the present invention will be described in detail with the following disclosure and examples. The foregoing general description and the following detailed description are provided to illustrate only some embodiments of the present invention and not to limit the scope of the present invention. The invention is capable of other embodiments and can be carried out or practiced in various other ways.
Unless otherwise specified, all the technical and scientific terms used herein have the same meaning as is generally understood by a person skilled in the art pertaining to the present invention. All the patents, published patent applications referred to throughout the entire disclosure herein, unless specified otherwise, are incorporated by reference in their entirety.
A method of forming a water vapour barrier coated laminate with improved barrier properties is provided, wherein the laminate is made of biaxially oriented polypropylene (BOPP) film substrate and another transparent film such as cast polypropylene (CPP) film, polyethylene (PE) film, or a second BOPP film, wherein the BOPP, CPP, and PE films are transparent.
The water vapour barrier coated laminate includes a biaxially oriented polypropylene (BOPP) substrate, on which a coat of water vapour barrier coating is applied, and a printing ink layer is applied on the top of the water vapour barrier coating layer; in turn

a layer of adhesive is applied on the printing ink layer, and finally a transparent film is laminated to the adhesive applied side of the BOPP substrate.
The transparent film laminated on the adhesive layer may be selected from a cast polypropylene (CPP) film, polyethylene (PE) or a second BOPP film.
The water vapour barrier coating used in the laminate is commercially available "Primer PMA010®" manufactured by Yansefu® Inks and Coatings Pvt. Ltd. India.
The adhesive may be solvent base (SB) adhesive or solvent-less (SL) adhesive
The solvent base (SB) adhesive is a polyurethane (PU) based adhesive Loctite® procured from Henkel®.
The solvent-less (SL) adhesive is a polyurethane (PU) based adhesive Loctite® procured from Henkel®.
The printing ink composition may be selected from PU based Sarjo®Lam, or a PU-Vinyl Chloride-Vinyl Acetate-Vinyl Alcohol Terpolymer based Sarjo®Top manufactured by Yansefu® Inks and Coatings Pvt. Ltd. India.
When the coated laminate is in a humid environment, the water vapour barrier-coating reduces intrusion of water vapour into the water vapour barrier coated laminate through its surface by at least about 80%, and the transparent BOPP film provides the articles prepared from the laminate of the present invention an improved display performance. Due to the mono-family structure of BOPP and CPP films used in the laminate, the recyclability of the laminates is improved.
In one embodiment of the present invention, as shown in Figure 1, a water vapour barrier laminate (10) of a transparent biaxially oriented polypropylene (BOPP) substrate and a transparent cast polypropylene (CPP) film is provided, comprising of a transparent BOPP film (101) having a first surface (101a) and a second surface (101b), a layer of water vapour (WV) barrier coating (102) applied on the first surface (101a) of the transparent BOPP film, a printing ink layer (103) applied above the water vapour barrier coating layer (102), a coat of adhesive (104) applied above the printing ink layer; and a transparent CPP film (105) laminated on top of the adhesive

layer. The structure of Fig. 1 may be defined as BOPP/ WV barrier /Ink/ Adhesive / CPP.
In a second embodiment of the present invention, as shown in Figure 2, a water vapour barrier laminate (20) of a transparent biaxially oriented polypropylene (BOPP) substrate and a transparent Polyethylene (PE) film is provided, comprising of a transparent BOPP film (201) having a first surface (201a) and a second surface (201b), a layer of water vapour (WV) barrier coating (202) applied on the first surface (201a) of the transparent BOPP film, a printing ink layer (203) applied above the water vapour barrier coating layer (202), a coat of adhesive (204) applied above the printing ink layer; and a transparent PE film (205) laminated on top of the adhesive layer. The structure of Fig. 2 may be defined as BOPP/ WV barrier /Ink/ Adhesive / PE.
In a third embodiment of the present invention, as shown in Figure 3, a water vapour barrier laminate (30) of a first transparent biaxially oriented polypropylene (BOPP) substrate and a second transparent BOPP film is provided, comprising of a first transparent BOPP film (301) having a first surface (301a) and a second surface (301b), a layer of water vapour (WV) barrier coating (302) applied on the first surface (301a) of the first transparent BOPP film, a printing ink layer (303) applied above the water vapour barrier coating layer (302), a coat of adhesive (304) applied above the printing ink layer; and a second transparent BOPP film (305) laminated on top of the adhesive layer. The structure of Fig. 3 may be defined as BOPP/ WV barrier /Ink/ Adhesive /BOPP.
The water vapour barrier coated packaging laminate of the present invention, wherein the BOPP films have a thickness of about 8.0 - 50.0 u, whereas the CPP and PE films are of a thickness of about 15.0 - 75.0 u, the adhesive layer has an areal density of about 1.5 - 3.0 gsm, the water vapour barrier coating layer has an areal density of about 1.5 - 3.0 gsm.
Examples:
The present disclosure will now be explained in further detail by the following examples. These examples are illustrative of certain embodiments of the invention without being limited to the specific examples given here.

Example 1 to 4
Process parameters for forming the water vapour barrier coated packaging
laminate:
According to four preferred embodiments of the invention, the structures of the water vapour barrier coated laminate according to Figure 1 are given below in Table 1.
Table 1

Laminate Structure
Example 1 BOPP/ WV barrier /PU-Ink/ SB Adhesive / CPP
Example 2 BOPP/ WV-barrier /PU-Vinyl-Terpolymer Ink/ SB Adhesive/CPP
Example 3 BOPP/ WV barrier /PU-Ink/ SL Adhesive / CPP
Example 4 BOPP/WV barrier /PU-Vinyl-Terpolymer Ink/ SL Adhesive/CPP
BOPP = transparent biaxially oriented polypropylene film
WV barrier = water vapour barrier coating layer
PU-Ink = Polyurethane based ink
PU-Vinyl-Terpolymer Ink = PU and Vinyl Chloride-Vinyl Acetate-Vinyl Alcohol-
Terpolymer based Ink
SB Adhesive = Solvent base adhesive
SL Adhesive = Solventless adhesive
CPP = transparent cast polypropylene film
According to another four preferred embodiments of the invention, the structures of the water vapour barrier coated laminate according to Figure 2 are given below in Table 2.
Table 2

Laminate Structure
Example 5 BOPP/ WV barrier /PU-Ink/ SB Adhesive / PE
Example 6 BOPP/ WV-barrier / PU-Vinyl-Terpolymer Ink / SB Adhesive/PE

Example 7 BOPP/ WV barrier /PU-Ink/ SL Adhesive / PE
Example 8 BOPP/ WV barrier / PU-Vinyl-Terpolymer Ink / SL Adhesive / PE
BOPP = transparent biaxially oriented polypropylene film
WV barrier = water vapour barrier coating layer
PU-Ink = Polyurethane based ink
PU-Vinyl-Terpolymer Ink = PU and Vinyl Chloride-Vinyl Acetate-Vinyl Alcohol-
Terpolymer based Ink
SB Adhesive = Solvent base adhesive
SL Adhesive = Solventless adhesive
PE = transparent polyethylene film
According to yet another four preferred embodiments of the invention, the structures of the water vapour barrier coated laminate according to Figure 3 are given below in Table 3.
Table 3

Laminate Structure
Example 9 BOPP/ WV barrier /PU-Ink/ SB Adhesive / BOPP
Example 10 BOPP/WV-barrier/ PU-Vinyl-Terpolymer Ink/ SB Adhesive/BOPP
Example 11 BOPP/ WV barrier /PU-Ink/ SL Adhesive / BOPP
Example 12 BOPP/ WV barrier / PU-Vinyl-Terpolymer Ink / SL Adhesive / BOPP
BOPP = transparent biaxially oriented polypropylene film
WV barrier = water vapour barrier coating layer
PU-Ink = Polyurethane based ink
PU-Vinyl-Terpolymer Ink = PU and Vinyl Chloride-Vinyl Acetate-Vinyl Alcohol-
Terpolymer based Ink
SB Adhesive = Solvent base adhesive
SL Adhesive = Solventless adhesive

Property Evaluation results for Examples 1 to 4
Light transmittance of the laminate was measured using TOBIAS Transmission Densitometer (Model TBX2000).
Water vapour transmission rate (WVTR) of the laminate was measured at 90% relative humidity and at a temperature of 37.8 °C using Mocon Permatran-W.
The evaluation results for the laminates of Examples 1 to 4 have been provided in Table 4.
Table 4

% Light transmittance WVTR (g/m2/24 hours)
Example 1 92.0 2.77
Example 2 92.6 3.18
Example 3 92.8 2.87
Example 4 92.4 2.55
Property Evaluation results for Examples 5 to 8
The evaluation results for the laminates of Examples 5 to 8 have been provided in Table 5.
Table 5

% Light transmittance WVTR (g/m2/24 hours.)
Example 5 91.4 3.75
Example 6 90.8 3.93
Example 7 90.0 4.08
Example 8 90.2 3.54
Property Evaluation results for Examples 9 to 12
The evaluation results for the laminates of Examples 9 to 12 have been provided in Table 6.

Table 6

% Light transmittance WVTR (g/m2/24 hours.)
Example 9 93.2 2.62
Example 10 93.8 2.84
Example 11 94.0 3.05
Example 12 93.6 2.65
Although the present disclosure is described in terms of certain preferred embodiments and examples, other embodiments and examples will be apparent to those of ordinary skill in the art, given the benefit of this disclosure, including embodiments and examples that do not provide all of the benefits and features set forth herein, which are also within the scope of this disclosure. It is to be understood that other embodiments may be utilized, without departing from the true spirit and scope of the present invention being indicated by the following claims.

CLAIMS

We claim

1.A water vapour barrier laminate for a packaging article comprising:
a) a transparent biaxially oriented polypropylene (BOPP) film substrate having a first surface and a second surface,
b) a layer of water vapour (WV) barrier coating applied onto the first surface of the BOPP film,
c) a printing ink image above the water vapour (WV) barrier coating layer,
d) an adhesive coating layer above the printed image; and
e) a transparent polymeric film laminated on top of the adhesive coating layer.
2. The water vapour barrier laminate for a packaging article according to claim 1,
wherein, the BOPP film is of a thickness of about 8.0 - 50.0 u,
the transparent polymeric film is of a thickness of about 15.0 - 75.0 u,
the adhesive layer has an areal density of about 1.5 - 3.0 gsm; and
the water vapour barrier coating layer has an areal density of about 1.5 - 3.0
gsm.
3. The water vapour barrier laminate for a packaging article according to claim 1,
wherein, the adhesive is selected from a solvent base adhesive, or a solvent-less
adhesive.
4. The water vapour barrier laminate for a packaging article according to claim 1, wherein, the printing ink is selected from a polyurethane (PU) based ink, and a PU-Vinyl Chloride-Vinyl Acetate-Vinyl Alcohol Terpolymer (PU-Vinyl-Terpolymer) based ink.
5. The water vapour barrier laminate for a packaging article according to claim 1, wherein the water vapour barrier laminate has a calculated water vapour transmission rate of about 2.5 to 4.0 g/m2/24 hours, and a light transmittance of 90% to 94%.

A method of forming a water vapour barrier laminate for a packaging article comprising:
a) providing a transparent biaxially oriented polypropylene (BOPP) film substrate having a first surface and a second surface,
b) applying a layer of water vapour (WV) barrier coating onto the first surface of the BOPP film,
c) printing an image above the water vapour (WV) barrier coating layer,
d) applying an adhesive coating above the printed image; and
e) laminating a transparent polymeric film on top of the adhesive coating layer.
A water vapour barrier laminate for a packaging article comprising:
a) a transparent biaxially oriented polypropylene (BOPP) film substrate having a first surface and a second surface,
b) a layer of water vapour (WV) barrier coating applied onto the first surface of the BOPP film,
c) a printing ink image above the water vapour (WV) barrier coating layer,
d) an adhesive coating layer above the printed image; and
e) a cast polypropylene (CPP) film laminated on top of the adhesive coating layer.
A water vapour barrier laminate for a packaging article comprising:
a) a transparent biaxially oriented polypropylene (BOPP) film substrate having a first surface and a second surface,
b) a layer of water vapour (WV) barrier coating applied onto the first surface of the BOPP film,
c) a printing ink image above the water vapour (WV) barrier coating layer,
d) an adhesive coating layer above the printed image; and
e) a polyethylene (PE) film laminated on top of the adhesive coating layer.
A water vapour barrier laminate for a packaging article comprising:
a) a first transparent biaxially oriented polypropylene (First-BOPP) film substrate having a first surface and a second surface,
b) a layer of water vapour (WV) barrier coating applied onto the first surface of the BOPP film,
c) a printing ink image above the water vapour (WV) barrier coating layer,

d) an adhesive coating layer above the printed image; and
e) a second transparent biaxially oriented polypropylene (Second-BOPP) film laminated on top of the adhesive coating layer.
10. A method of forming a water vapour barrier laminate for a packaging article comprising:
a) providing a first transparent biaxially oriented polypropylene (First-BOPP) film substrate having a first surface and a second surface,
b) applying a layer of water vapour (WV) barrier coating onto the first surface of the First-BOPP film,
c) printing an image above the water vapour (WV) barrier coating layer,
d) applying an adhesive coating above the printed image; and
e) laminating a transparent polymeric film on top of the adhesive coating layer, wherein,
the transparent polymeric film is selected from a transparent cast
polypropylene (CPP) film, a transparent polyethylene (PE) film, or a second
transparent biaxially oriented polypropylene (Second-BOPP) film,
the First-BOPP, and the Second-BOPP films are of a thickness of about 8.0 -
50.0 u,
the CPP film or the PE film if used is of a thickness of about 15.0 - 75.0 u,
the adhesive layer has an areal density of about 1.5 - 3.0 gsm; and
the water vapour barrier coating layer has an areal density of about 1.5 - 3.0
gsm.