Claims:We Claim
1. An aqueous coating formulation for reducing OTR of a polyester film comprising an interpreting network (IPN) of a crosslinked network of PVOH copolymers in the range of at least 2-15 wt% crosslinked with self-linked network of silica precursors in the range of at least 0.5-5 wt%, and exfoliated nanoclay in the range of at least 0.1-5 wt%.
2. The coating formulation of claim 1, wherein the coating is applied in-line or offline on the polyester film.
3. The coating formulation of claim 1, wherein the formulation also comprising at least one or more of a hydrolysis catalyst in the range of at least 0.1-2 wt%; crosslinker or a mixture thereof in the range of at least 0.01-1 wt%; lower alcohols in the range of at least 5-25 wt%; remaining deionized water; and combinations thereof.
4. The coating formulation of claim 1, wherein the PVOH copolymers further comprising polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 0.2-20 wt% of Polyvinyl acetate (PVAc).
5. The coating formulation of claim 1, wherein the PVOH copolymers further comprising polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 0.8-8 wt% of Polyvinyl amine.
6. The coating formulation of claim 1, wherein the PVOH copolymers further comprising polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 5-35 wt% of Ethylene vinyl alcohol.
7. The coating formulation of claim 1, wherein the silica precursors are selected from at least one of the group of precursors further comprising teraethyloxysilane (TEOS), methyl triethyloxy silane (MTES), bis(triethyloxysilyl)ethane (BTES), organo functional (amino/mercapto/hydroxy) silanes or bis-silanes, and combinations thereof.
8. The coating formulation of claim1, wherein the nanoclay is selected from at least one of the group further comprising Na-MMT, LDH, Montmorillonite (MMT), kaolinite, cloisite, CNC, vermiculites, saponite, bentonite, halloysite and combinations thereof.
9. A transparent polyester film structure (300A) with reduced OTR comprising a biaxially-oriented PET film (302) coated inline or offline with a coating formulation (304) further comprising a crosslinked network of PVOH copolymers in the range of at least 2-15 wt% crosslinked with nanoclay in the range of at least 0.1-5 wt%, further crosslinked with self-linked network of silica precursors in the range of at least 0.5-5 wt%.
10. A method for reducing OTR by providing a biaxially-oriented film coated with a composition comprising an aqueous coating formulation for reducing OTR of a polyester film comprising an interpreting network (IPN) of a crosslinked network of PVOH copolymers in the range of at least 2-15 wt% crosslinked with self-linked network of silica precursors in the range of at least 0.5-5 wt%, and exfoliated nanoclay in the range of at least 0.1-5 wt%, the method comprising:
adding the silica precursors to the crosslinked network of PVOH copolymers, forming a hybrid interpreting network (IPN) network;
adding the nanoclay to the IPN network;
adding hydrolysis catalyst in the range of at least 0.1-2 wt%; crosslinker or a mixture thereof in the range of at least 0.01-1 wt%; lower alcohols in the range of at least 5-25 wt%; and remaining water to the IPN network, preparing the coating formulation;
applying the coating formulation on the film; and
drying the coating formulation.

Description:
FIELD OF INVENTION
The present disclosure generally relates to the field of flexible packaging. More specifically, the present disclosure relates to a transparent, high barrier biaxially oriented PET film having enhanced barrier to oxygen and other gases even at high moisture environment.

BACKGROUND OF THE INVENTION
One of the major concerns of food packaging industry these days is to provide protection to the food product from decay within desired shelf life. Air, water vapour, and other gases like oxygen; carbon dioxide can intrude the food products from outside and can affect quality thereof. In addition, aroma can also be lost from inside to outside. The protection therefor can be achieved by providing proper barrier packaging films having impermeability from a number of factors, for example gas (oxygen, carbon dioxide, and so on), light (visible, ultra-violet), moisture, chemicals (aroma, flavour). For example, biscuits can be degraded by humidity uptake, leading to loss of crispiness and can be affected by oxidation and rancidity of fatty substances in the presence of oxygen. Dehydrated foods and beverages like coffee, tea, etc. require a very high barrier to oxygen, water, and aroma, retaining long shelf life thereof. Wet pet foods again need to be highly impermeable to oxygen even in presence of high moisture conditions. In a nutshell, dry fruits, fruits, sea-foods, pet foods, solid dairy products, milk creamers, confectionaries, crispy snacks, cereals, beverages, tea, coffee, protein drink powders, etc. require a good oxygen barrier to retain their shelf life. Without oxygen barrier, there can be change in color, odour, taste, and overall quality of the food products.
Different materials like BOPP, BOPET, nylon, etc. available for flexible packaging have varying oxygen barrier characteristics. Such characteristics can be defined by oxygen transmission rate (OTR) calculated by measuring amount of oxygen passing through the material over 24 hours. Out of many such materials available, BOPET is considered as one of the best film having good oxygen barrier properties. However, impermeability to oxygen and other gases in BOPET films is still unsatisfactory and need improvements. There are many conventional arts and formulations which pertain to provide the BOPET films with improved barrier to oxygen.
One of the most conventional methods is to coat metals such as aluminium to a non-metallic substrate through metal evaporation. Such a technique is known as vacuum metallization or physical vapour deposition (PVD). The most common metal employed is aluminium due to its low cost, and good barrier properties. Such a technique enhances barrier properties of the film substrate in addition to providing a unique, eye-catchy appearance thereto. However, such a technique provides non-transparent films with poor flex crack resistance impacting the barrier property.
Another conventional technique is to coat the BOPET film substrate with polyvinylidene chloride (PVDC). Such coatings may provide a good gas barrier and resistance to oils and fats. Such type of coatings can either be water-based or solvent-based. Due to presence of chlorine therein, PVDC can pose serious threats to human health and the environment. Also, solvent recovery is quite expensive and in-efficient, if not recovered, cause threat to the environment.
EVOH and PVOH provide safer alternatives over PVDC coatings. However, both have poor water resistance, and EVOH has not very good OTR values. Such coatings can have their lamination strength and OTR affected in presence of high humidity/moisture conditions.
Some researchers have also tried providing PVOH based coating formulations involving nanoclays. However, such formulations do not provide stable film structures and have lower water resistance. As the OTR increases rapidly with moisture, the existing formulations based on PVOH are not stable as required. Another technology for providing barrier properties to the BOPET film is sol-gel process. The sol-gel process involves formation of an inorganic colloidal suspension (sol) and gelation thereof in a continuous liquid phase (gel) to form a three-dimensional network structure. Such a method allows deposition of inorganic coatings on a variety of different surfaces. However, such technology when applied alone on BOPET films tends to provide shrinkage in large volume; such coatings are not stretchable and may crack during drying and machine processing.
Another prevalent technology of producing high barrier film is metal oxide deposition on plastic films. The most common material is Aluminum oxide –ALOx in such a technique. This film is formed by vapor deposition of Aluminum oxide layer on a base film (PET), which exhibits a good oxygen and moisture barrier properties. At present, AlOx film has been used in many fields such as food packaging, daily chemical packaging, medical packaging, electronic component packaging, etc. However, ALOx layer is a hard inorganic layer, and is prone to generate cracks during further processing, and such cracks adversely affect the barrier properties significantly.
Hence, all of the conventional techniques or coating formulations have one or more draw backs. Therefore, in light of the foregoing discussion, there exists a need for developing a low-cost, simple, and efficient coating formulation which can further improve barrier of the BOPET film to gases and aroma over the existing formulations or techniques, which can overcome all the drawbacks of prevailing techniques.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a coating formulation for polyester film substrate which is configured to enhance oxygen barrier of the BOPET substrate. The coating formulation involves an interpenetrating network of silica in the crosslinked PVOH copolymer network forming the polyester substrate free of voids, stable and compact structure.
Another object of the present invention is to provide a transparent high-barrier biaxially-oriented PET film which is coated with a coating formulation involving a dense network of self-crosslinked silica within the PVOH co-polymer network. Such coating formulation is configured to provide the film stability, stretchability and compactness. Therefore, the film provides extremely low OTR even at high moisture conditions.
Another objective of the present invention is to provide a transparent high barrier biaxially-oriented PET film which is coated with a coating configured to provide good water resistance, Gelbo flex crack resistance, barrier sustenance at higher humidity, and rid of the chlorine gas on storage, post processing and incineration.
Another object of the present invention is to provide a transparent high-barrier BOPET film in which the coated layer thickness is in the range of 0.2 – 0.8 gsm.
Another object of the present invention is that, the coated layer has excellent printability and excellent adhesion to inks and adhesives.
Yet another object of the present invention is to provide a laminate structure including the aforementioned film along with Cast Polypropylene (CPP) sustains the retort conditions up to 130DegC for 40 minutes.
SUMMARY OF THE INVENTION
In one aspect of the present invention, an aqueous coating formulation for reducing OTR of a polyester film is disclosed. The formulation includes an interpreting network (IPN) of a crosslinked network of PVOH copolymers in the range of at least 2-15 wt% crosslinked with self-linked network of silica precursors in the range of at least 0.5-5 wt%. The formulation also includes exfoliated nanoclay in the range of at least 0.1-5 wt%. The coating is applied in-line or offline on the polyester film. The formulation also includes at least one or more of a hydrolysis catalyst in the range of at least 0.1-2 wt%; crosslinker or a mixture thereof in the range of at least 0.01-1 wt%; lower alcohols in the range of at least 5-25 wt%; and remaining deionized water; and/or combinations thereof. The PVOH copolymers further includes polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 0.2-20 wt% of Polyvinyl acetate (PVAc). In some embodiments, the PVOH copolymers further includes polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 0.8-8 wt% of Polyvinyl amine. However, in some other embodiments, the PVOH copolymers further includes polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 5-35 wt% of Ethylene vinyl alcohol.
Another aspect of the present invention discloses a transparent polyester film structure (300Aor 300B) with reduced OTR. The film structure (300A or 300B) includes a biaxially-oriented PET film (302) coated inline or offline with a coating formulation (304). The formulation (304) includes a crosslinked network of PVOH copolymers in the range of at least 2-15 wt% which further is crosslinked with self-linked network of silica precursors in the range of at least 0.5-5 wt%.
In yet another aspect of the present invention, a method for reducing OTR by providing a biaxially-oriented film coated with a composition is disclosed. The composition provides an aqueous coating formulation for reducing OTR of a polyester film. The coating includes an interpreting network (IPN) of a crosslinked network of PVOH copolymers in the range of at least 2-15 wt% crosslinked with self-linked network of silica precursors in the range of at least 0.5-5 wt%, and exfoliated nanoclay in the range of at least 0.1-5 wt%. The method includes adding the silica precursors to the crosslinked network of PVOH copolymers, forming a hybrid interpreting network (IPN) network, followed by adding the nanoclay to the IPN network. The method further includes adding hydrolysis catalyst in the range of at least 0.1-2 wt%; crosslinker or a mixture thereof in the range of at least 0.01-1 wt%; lower alcohols in the range of at least 5-25 wt%; and remaining water to the IPN network, forming the coating formulation. Thereafter, the coating formulation is applied on the film. Finally, the coating formulation is dried in a hot dry oven at 150oC for 10-20 seconds.
In this respect, before explaining at least one embodiment of the present invention in detail, it is to be understood that the invention is not limited to in its application to the details of processing and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practised and carried out in various ways. Also, it is to be understood that the phraseology terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
STATEMENT OF THE PRESENT INVENTION
The present invention provides a coating for BOPET films which gives enhanced oxygen and aroma barrier, transparency, high flex crack and moisture-resistance and boiling water resistance for food and medical packaging applications.

BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features, and advantages of the embodiment will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:
Referring to Figures 1A-1C, Figure 1A illustrates a crosslinked PVOH network; Figure 1B illustrates an interpreting network (IPN) of self-linked silica crosslinked with the crosslinked PVOH network crosslinked PVOH network and nanoclay; and Figure 1C illustrates the IPN network and the nanoclay, in accordance with an illustrated embodiment of a present invention;
Referring to Figure 2, illustrates crosslinking between the self-linked silica network and the crosslinked PVOH network, in accordance with the illustrated embodiment of the present invention;
Referring to Figures 3A and 3B, illustrates a polyester substrate film coated with a coating formulation enhancing oxygen barrier thereof, the coating applied in-line and offline in Figures 3A and 3B respectively, in accordance with the illustrated embodiment of the present invention; and
Referring to Figure 4, illustrates a comparison of OTR values between different PVOH based coating compositions: A- crosslinked PVOH; B- crosslinked PVOH and nanoclay; and C- IPN network of crosslinked PVOH + nanoclay + silica sol IPN, in accordance with the illustrated embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as hereinbefore described with reference to the accompanying drawings.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
As used herein, the singular forms “a”, “an”, “the” include plural referents unless the context clearly dictates otherwise. Further, the terms “like”, “as such”, “for example”, “including” are meant to introduce examples which further clarify more general subject matter, and should be contemplated for the persons skilled in the art to understand the subject matter.
The reference in this specification to any prior art publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgement or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
The term “Flexible packaging” herein relates to any packaging or a part thereof whose shape can be changed readily. For example, bags, pouches, tubes, and so on.
The term “Polyethylene terephthalate (PET)” herein defines a form of polyester, which can be extruded, casted, and stretched bidirectional to form a thin film for packaging for the purposes of packaging foods, beverages, pharmaceutical products like tablets, and so on.
The term “Biaxially-oriented polyethylene terephthalate (BOPET)” herein defines a polyester film which is obtained by stretching the PET film in two perpendicular directions thereof, achieving the BOPET film. The film is well preferred for flexible packaging due to its special properties such as high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties(low gas permeability), and electrical insulation (good insulation performance), good deflection, , good optical property, and so on.
For packaging purposes, the packaging film must bear properties of good heat resistance, low thermal shrinkage, good machinability, good printability, good transparency, good barrier to oxygen and water vapour, good impact resistance; good puncture resistance. The BOPET film is considered as the most preferred flexible film for packaging food and non-food products.
In case of inline coatings, the BOPET film can be treated with inline corona. In case of offline coatings, an in-line primer can be applied on the BOPET film with water dispersible co-polyester or polyurethane dispersions or acrylics for high surface energy.
The term “Coating” herein relates to a thin layer of a covering applied on a substrate.
The term “OTR” defines a steady state rate at which oxygen can gas can permeate through a film. OTR is expressed as a volume of oxygen that penetrates a given area in a one-day period in cc/m2/24h or cc/100in2/24hr, measured at a standard temperature of 73°F (23°C), and 0% relative humidity (RH).
The term “WVTR” or “MVTR” defines moisture vapour transfer rate which indicates transmission of moisture permeating through a packaging film.
The term “flex crack resistance” defines resistance of the polyester film against repetitive strain and is also called flex durability. Such resistance can be checked by a standard test Gelbo flex test. Aim of conducting such test is to measure performance of a material through assessment of cracks therein. If there are no cracks, the cycle count may be too low.
The term “Co-extruded” is a well known term used in the industry of polymers and flexible packaging. The “co-extruded” or “co-extrusion” defines a process of forming a single film from more than one type of thermoplastic resin layers.
The present embodiment discloses a coating formulation for polyester substrate. In the embodiment, the polyester substrate is biaxially oriented PET (BOPET) film. The formulation includes polyvinyl alcohol (PVOH) copolymers; nanoclay; silica or inorganic precursors; hydrolysis catalyst; crosslinker; lower alcohols; and water. The PVOH copolymers are in the range of at least 2-15 wt%. In some embodiments, the PVOH copolymers can be in any form including such but not limited to a granular, powder, liquid, and so on. The PVOH copolymers may further include PVOH copolymers which can be amine, or amide or ethylene based, and/or combinations thereof. Such copolymers may have tendency to provide better flexibility, barrier and adhesion to substrates. The PVOH crosslinked network (102) is shown in Figure 1A.
In the embodiment, the PVOH copolymers further include polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 0.2-20 wt% of Polyvinyl acetate (PVAc). In another embodiment, the PVOH copolymers may further include polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 0.8-8 wt% of Polyvinyl amine. In yet another embodiment, the PVOH copolymers may further include polyvinyl alcohol (PVOH) in the range of at least 70-98 wt%; and 5-35 wt% of Ethylene vinyl alcohol.
The silica precursors are in the range of at least 0.5-5 wt%. Examples of the silica precursors may include such as but are not limited to at least one of the group of precursors further comprising teraethyloxysilane (TEOS), methyl triethyloxy silane (MTES), bis(triethyloxysilyl)ethane (BTES), organo functional (amino/mercapto/hydroxy) silanes or bis-silanes, and/or combinations thereof. The silica precursors are configured to form a dense network of the constituents of the formulation contributing to stability of the film substrate. Such a network involves crosslinking between a self-linking network of oxides of silica and the PVOH copolymer network forming organic-inorganic hybrid interpenetrating network (hybrid-IPN). In some embodiments, the self-linking network can occur between oxides of aluminium or titanium and the PVOH copolymer network forming the hybrid-IPN. As shown in Figure 1B, the self-linking silica precursors (104) form the IPN when crosslinked with the crosslinked PVOH co-polymers network. Chemical reactions involving bonding within the IPN is illustrated in Figure 2. The IPN is further configured to provide stability and compactness to the polyester film substrate.
The nanoclay is in the range of at least 0.1-5%. In the embodiment, the nanoclay is in exfoliated form. The exfoliated form involves increased distance among nanoclay platelets, and the polymer chains entered the space between the platelets. Examples of the nanoclay may include such as but are not limited to Na-MMT, LDH, Montmorillonite (MMT), kaolinite, cloisite, CNC, vermiculites, saponite, bentonite, halloysite and/or the combinations. The preferred nanoclays are but not limited to Na-MMT, and LDH. The nanoclays are configured to enhance the barrier properties of the film substrate by filling voids within the polyester substrate, and creating a tortuous path for migrating gases or moisture therefrom. The nanoclay further reduces the water sensitivity of PVOH copolymers.
The hydrolysis catalyst is in the range of at least 0.1-2% in liquid form. The crosslinker is in the range of at least 0.01-1.0%. The crosslinker may be in the liquid form. Examples of such crosslinkers may include such as including but are not limited to glutaraldehyde, glyoxal, melamine, epichlorohydrin, a multifunctional isocyanate-functional material, a melamine formaldehyde, N-methylol acrylamide, N-methylolmethacrylamide and their corresponding ethers; epoxide materials such as glycidyl acrylate, glycidyl methacrylate and allylglycidyl ether; carboxyl containing monomers such as crotonic acid, itaconic acid or acrylic acid; anhydrides such as maleic anhydride or itaconic anhydride; hydroxy containing monomers such as allyl alcohol and hydroxy ethyl or propyl acrylate or methacrylate; amides such as acrylamide, methacrylamide or maleamide; and isocyanates such as vinylisocyanate or allylisocyanate, and so on. The lower alcohols are in the range of at least 5-25%; and water is in the range of at least 65-95%. Examples of lower alcohols include such as but are not limited to methanol, ethanol, ispropanol, n-propanaol, and so on.
In another aspect of the present invention, a transparent, high-barrier biaxially-oriented PET film structure (300A) is disclosed as shown in Figure 3A. The film structure (300A) includes a biaxially-oriented PET film substrate (302); and aforementioned formulation of the coating (304). It is contemplated that usage of the coating (304) or coating formulation (304) or the formulation (304) may be considered as aforementioned. The coating (304) is configured to be applied on at least one side surface of the substrate (300A). In some embodiments, the coating (304) can be applied in-line with the side surface of the substrate (300A) as shown in Figure 3A. In case of inline coatings, the BOPET film substrate (300A) can be treated with corona or plasma. However, in some embodiments, the coating (304)can be applied offline on at least one of the side surfaces of the BOPET film substrate (302) as shown in Figure 3B, forming the film structure 300B. In such an embodiment, a primer (306) can be applied on the film substrate (302), followed by the coating formulation (304). In case of such type of coatings, the in-line primer can be applied on the BOPET film with water dispersible co-polyester or polyurethane dispersions or Polyethylene imine (PEI) high surface energy. After applying the coating on the film, the film along with the coating is administered to drying through the devices and methods already known in the art. One of such devices is a hot dry oven. In exemplary embodiment, the film and the coating may undergo drying in the hot dry oven at 150oC for 10-20 seconds. Such a drying escapes water from the coating formulation.
In yet another aspect of the present invention, a method for forming a transparent, and oxygen-barrier biaxially-oriented film substrate is disclosed. The method includes a number of steps; sequence thereof may be contemplated to be as exemplary for the skilled persons to understand the invention. The method includes adding the silica precursors to the crosslinked network of PVOH copolymers, forming a hybrid interpreting network (IPN) network, followed by adding the nanoclay to the IPN network. The method further includes adding hydrolysis catalyst in the range of at least 0.1-2 wt%; crosslinker or a mixture thereof in the range of at least 0.01-1 wt%; lower alcohols in the range of at least 5-25 wt%; and remaining water to the IPN network, forming the coating formulation. In some embodiments, the water may be distilled water, double distilled water, etc. Thereafter, the coating formulation is applied on the film. Finally, the coating formulation is dried in a hot dry oven at 150oC for 10-20 seconds.
The present invention discloses the coating formulation which can provide enhanced oxygen barrier properties. The OTR value at 0% RH is found to be 0.1cc/m2/day; at 80% RH is found to be 0.3cc/m2/day; and after Gelbo-flex test, is found to be unchanged. Other resultant values of the film structure having the coating formulation applied inline are shown in the table below.
Oxygen Barrier film (Present embodiment: ULP-1)
Parameter Test standard ULP-1
Laminate structure 12µ PET/ULP/adh./60µ LDPE
Appearance Visual Transparent laminate
Laminate thickness (µ) 76 -77
OTR at 0%RH (cc/m2/day) 0.10
OTR at 80%RH (cc/m2/day) 0.30
OTR after Gelbo-flex test (cc/m2/day) – 0%RH 0.12
WVTR (g/m2/d) <5
Water resistance -
(100oC/30min & 70oC/24Hrs) no delamination Pass

A comparison of OTR values of PVOH based coatings at different humidity conditions is shown in Figure 4. The composition ‘A’ relates to Crosslinked PVOH network; composition ‘B’ relates to a composition including crosslinked PVOH and nanoclay; and ‘C’ relates to the IPN formed by addition of silica or inorganic precursors to the crosslinked PVOH network and nanoclay. As elucidated from the graph in Figure 4 (each value shown in following table), the OTR values for the composition ‘C’ significantly decreases despite of high humidity.
Coating Compositions OTR at 23oC/0% Rh
(cc/m2/d) OTR at 39oC/0% Rh
(cc/m2/d)
A 0.8 5
B 0.3 1.8
C 0.1 0.3

The above barrier values are obtained at ~ 0.4 gsm of coating thickness. Hence, the present invention provides a polyester film with lower OTR values even at low coat weights and hence with reduced cost. Further, from the table below, it shows that the OTR decreases with the increase in coating thickness, but beyond 0.8 gsm the reduction in OTR is not linear.
Thickness of coating
(Dry gsm) - approx OTR (Cc/m2/day))
0% humidity OTR (cc/m2/day)
80% humidity
0.2 0.21, 0.23, 0.34 0.24, 0.29, 0.34
0.4 0.13, 0.12, 0.10 0.21, 0.24, 0.19
0.6 0.12, 0.08, 0.15, 0.06 0.19, 0.13, 0.20
0.8 0.08, 0.11, 0.05,0.08 0.21, 0.19, 0.11
The coating is water based, with all non-hazardous ingredients. The film also has excellent printability and adhesion to inks and adhesives. The PVOH based polymer backbone in the copolymer network thereof provides higher surface energy i.e.>56 dynes/cm2. Consequently, the PVOH copolymer network facilitates the wetting & adhesion of inks & adhesives, ultimately improving printability & lamination strength. The packaging film coated with aforementioned coating formulation can be applicable for packaging dry and semi solid food including such as but are not limited to Cereals, Coffee, tea, crispy snacks, confectionaries, solid dairy products, meat & sea-foods, pet-foods, fruits & dry-fruits, and so on. Such films can also be used for other barrier packaging such as vacuum packaging, packing electronic components, air-filled balloons & protective packaging, and so on.
Such a transparent high barrier packaging film is economically advantageous, and can be employed for various packaging applications, industrial applications and food packaging applications for aroma retention and improving shelf life of the packed materials.
The foregoing descriptions of exemplary embodiments of the present disclosure have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to best explain the principles of the disclosure and its practical application, to thereby enable others skilled in the art to best utilize the disclosure and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions, substitutions of equivalents are contemplated as circumstance may suggest or render expedient but is intended to cover the application or implementation without departing from the spirit or scope of the claims of the present disclosure.