CROSS-REFERENCE TO RELATED APPLICATION

The present application gains priority from U.S. Provisional Application No. 63/149,407 filed 15 February, 2021 which is incorporated by reference as if fully set-forth herein.

FIELD OF THE INVENTION

The present invention, in at least some embodiments, is directed to biodegradable sheets, and in particular to multilayered biodegradable sheets wherein at least one layer comprises at least 90% (w/w) polyglycolic acid (PGA).

BACKGROUND OF THE INVENTION

The use of biodegradable materials had increased over the past years due to the environmentally beneficial properties of such materials. Such materials are now commonly used in the manufacture of a wide range of products, including various types of plastic bags and other forms of packaging. In response to the demand for more environmentally friendly packaging materials, a number of new biopolymers have been developed that have been shown to biodegrade when discarded into the environment.

Examples of such polymers include biopolymers based on polylactic acid (PLA), polyhydroxyalkanoates (PHA), which include polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV) and polyhydroxybutyrate-hydroxyvalerate copolymer (PHBV), and poly (epsilon-caprolactone) (PCL).

Each of the foregoing biopolymers has unique properties, benefits and weaknesses. For example, PHB and PLA tend to be strong but are also quite rigid or even brittle. This makes them poor candidates when flexible sheets are desired, such as for use in making wraps, bags and other packaging materials requiring good bend and folding capability.

On the other hand, biopolymers, such as polybutylene adipate terephthalate (PBAT), are many times more flexible than the biopolymers discussed above and have relatively low melting points, so that they tend to be self-adhering and unstable when newly processed and/or exposed to heat. Further, due to the limited number of biodegradable polymers, it is often difficult, or even impossible, to identify a single polymer or copolymer that meets all, or even most, of the desired performance criteria for a given application. For these and other reasons, biodegradable polymers are not as widely used in the area of food packaging materials, particularly in the field of liquid receptacles, as desired for ecological reasons.

In addition, the biodegradable sheets known today are mostly opaque, having low light transmittance and high haze. Further, the known biodegradable sheets either do not include barrier layers or include amounts and types of barrier layers that cause the sheets to be generally highly permeable to gases, having both a high oxygen transmission rate and a high water vapor transmission rate, and thus they cannot serve as long term food or drink receptacles. Additionally, the physical strength of known biodegradable sheets, measured by parameters, such as stress at maximum load, strain at break, and Young’s Modulus, is lacking and, therefore, is deficient when used as packaging, particularly when it is desirable to package liquids. Background art includes PCT Publication Nos. WO 2011/158240, WO 2013/088443, WO 2013/186778, WO 2015/059709, WO 2016/067285, WO 2016/174665 and WO 2016/207888 to the present applicant.

There remains a need for biodegradable sheets for packaging, which are devoid of at least some of the disadvantages of the prior art.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention, there is provided a biodegradable sheet comprising a first outer polymer layer, a second outer polymer layer and at least a first inner polymer layer between said first and said second outer polymer layers, wherein at least one of said first outer layer, said second outer polymer layer and said first inner polymer layer comprises at least about 90% (w/w) polyglycolic acid (PGA), such as about 90%, about 92%, about 95%, about 95%, about 98% or about 100% (w/w) PGA.

According to an embodiment, the layer comprising at least about 90% (w/w) polyglycolic acid (PGA) further comprises up to about 10% (w/w) of a biodegradable polymer optionally selected from the group consisting of polybutylene adipate terephthalate (PBAT) and polycaprolactone (PCL) or combinations thereof, and optionally comprises additional excipients.

According to an embodiment, the first outer polymer layer and the second outer polymer layer are substantially identical. According to an embodiment, the first outer polymer layer is different from the second outer polymer layer.

According to an embodiment, the polymer layer comprising PGA is a first outer polymer layer, wherein at least one of the second outer polymer layer and the first inner polymer layer comprises a polymer selected from the group consisting of polycaprolactone (PCL), polylactic acid (PLA), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT) and combinations thereof. According to some such embodiments, the second outer layer comprises a polymer selected from the group consisting of PBSA, PLA and combinations thereof.

According to an embodiment, the polymer layer comprising PGA is a second outer polymer layer, wherein at least one of the first outer polymer layer and the first inner polymer layer comprises a polymer selected from the group consisting of polycaprolactone (PCL), polylactic acid (PLA), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT) and combinations thereof. According to some such embodiments, the first outer layer comprises a polymer selected from the group consisting of PBSA, PLA and combinations thereof.

According to an embodiment, the polymer layer comprising PGA is a first inner polymer layer, wherein at least one of the first outer polymer layer and the second outer polymer layer comprises a polymer selected from the group consisting of polycaprolactone (PCL), polylactic acid (PLA), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT) and combinations thereof. According to some such embodiments, the second outer layer comprises a polymer selected from the group consisting of PBSA, PLA and combinations thereof.

According to an embodiment, the first outer polymer layer and the second outer polymer layer are substantially identical. According to an embodiment, the first outer polymer layer is different from the second outer polymer layer.

According to an embodiment, the biodegradable sheet further comprises at least one additional polymer layer, such as one additional polymer layer, two additional polymer layers, or more than two additional polymer layers, such that the biodegradable sheet comprises at least four, at least five, or more than five layers. According to some embodiments, the at least one additional polymer layer is an outer layer. According to some such embodiments, the at least one additional layer comprises a polymer selected from the group consisting of polycaprolactone (PCL), polylactic acid (PLA), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT) and combinations thereof.

According to an embodiment, the sheet has a total thickness of about 40m.

According to an embodiment, at least one of said first outer layer, said second outer polymer layer and said first inner polymer layer comprising at least about 90% (w/w) polyglycolic acid (PGA) has a thickness in the range of from about 2 m to about 16 m, or from about 2 m to about 12 m, such as about 2 m, about 4 m, about 6 m, about 8 m, about 10 m, about 12 m, about 14 m, or about 16 m.

According to an embodiment, wherein PGA is present in a first inner layer, a thickness ratio of said first outer layer : said first inner layer : said second inner layer is about 20% : 60% : 20%. According to some embodiments, a thickness of said first outer layer and said second outer layer is substantially the same. According to some embodiments, a thickness of said first outer layer is different from that of said second outer layer.

According to an embodiment, wherein PGA is present in a first outer layer, a thickness ratio of said first outer layer : said first inner layer : said second inner layer is about 60% : 20% : 20%.

According to an embodiment, at least one of said first outer polymer layer and said second outer polymer layer comprises at least 90% (w/w) PGA.

According to an embodiment, said first outer polymer layer comprises at least 90% (w/w) PGA.

According to one such embodiment, said second outer polymer layer comprises at least 90% (w/w) PGA. According to an embodiment, each of said first outer polymer layer and second outer polymer layer comprises at least 90% (w/w) PGA.

According to an embodiment, said first inner polymer layer comprises from about 70 to about 80% (w/w) PLA and from about 20 to about 30% (w/w) PCL. According to some such embodiments, said first inner polymer layer comprises about 70%, about 75% or about 80% (w/w) PLA and about 20%, about 25% or about 30% (w/w) PCL. According to an embodiment, said first inner polymer layer comprises about 70% (w/w) PLA and about 30% (w/w) PCL.

According to an embodiment, said first inner polymer layer comprises about 75% (w/w) PLA and about 25% (w/w) PCL.

According to an embodiment, said first inner polymer layer comprises about 80% (w/w) PLA and about 20% (w/w) PCL.

According to an embodiment, said first inner polymer layer comprises about 85% (w/w) PLA and about 15% (w/w) PCL.

According to an embodiment, said second outer polymer layer comprises PBSA. According to some such embodiments, said first outer polymer layer comprises at least 90% (w/w) PGA; said first inner polymer layer comprises PLA and PCL (such as 70- 90% PLA and 10-30% PCL); and said second outer polymer layer comprises PBSA.

According to an embodiment, said second outer layer comprises 100% (w/w) PBAT. According to some such embodiments, said first outer layer is devoid of PBAT.

According to an embodiment, said first inner layer comprises at least 90% (w/w) PGA.

According to an embodiment, said first inner layer comprises 100% (w/w) PBAT.

According to an aspect of some embodiments of the present invention, there is provided a biodegradable sheet comprising a first outer polymer layer, a second outer polymer layer and at least a first inner polymer layer between said first and second outer polymer layers, wherein each of said first outer polymer layer and second outer polymer layer comprises at least 90% (w/w) polyglycolic acid (PGA), and wherein said first inner polymer layer comprises about 80% (w/w) PLA and about 20% (w/w) PCL.

According to an aspect of some embodiments of the present invention, there is provided biodegradable sheet comprising a first outer polymer layer, a second outer polymer layer and at least a first inner polymer layer between said first and second outer polymer layers, wherein each of said first outer polymer layer and second outer polymer layer comprises at least 90% (w/w) polyglycolic acid (PGA), and wherein said first inner polymer layer comprises about 70% (w/w) PLA and about 30% (w/w) PCL.

According to an embodiment, said first inner polymer comprises at least 90% (w/w) PGA. According to a further aspect of some embodiments of the present invention, there is provided a biodegradable sheet comprising a first outer polymer layer, a second outer polymer layer and at least three inner polymer layers between said first and second outer polymer layers, wherein at least one of said first outer polymer layer, said second outer polymer layer or at least one of said at least three inner polymer layers comprises at least 90% (w/w) polyglycolic acid (PGA).

According to an embodiment, a first inner layer is a core layer; a second inner polymer layer is located between said first outer layer and said first inner layer; a third inner layer is located between said first inner layer and said second outer layer; and at least one of said second inner polymer layer and said third inner polymer layer comprises at least 90% (w/w) PGA.

According to an embodiment, said first inner polymer layer comprises 100% (w/w) PBAT.

According to an embodiment, each of said second inner polymer layer and said third inner polymer layer comprises at least 90% (w/w) PGA.

According to an embodiment, said second inner polymer layer comprises at least 90% (w/w) PGA and said third inner polymer layer comprises 100% (w/w) PBAT.

According to an embodiment, each of said first inner polymer layer and said second inner polymer layer comprises at least 90% (w/w) PGA and wherein said third inner polymer layer comprises 100% (w/w) PBAT.

According to an embodiment, a first inner layer is a core layer; a second inner polymer layer is located between said first outer layer and said first inner layer; a third inner layer is located between said first inner layer and said second outer layer; and said first inner layer comprises at least 90% (w/w) PGA.

According to an embodiment, at least one of said first outer polymer layer and said second outer polymer layer, such as said first outer polymer layer, said second outer polymer layer, or each of said first outer polymer layer and said second outer polymer layer, comprises PBS or PBSA. According to one such embodiment, at least one of said first outer polymer layer and said second outer polymer layer, such as said first outer polymer layer, said second outer polymer layer, or each of said first outer polymer layer and said second outer polymer layer, further comprises PLA. According to an embodiment, at least one of said first outer polymer layer and said second outer polymer layer comprises from about 10% to about 30% (w/w) PLA and from about 70% to about 90% (w/w) PBSA. According to some such embodiments, at least one of said first outer polymer layer and said second outer polymer layer, such as said first outer polymer layer, said second outer polymer layer or each of said first outer polymer layer and second outer polymer layer, comprises about 10%, about 15%, about 20%, about 25% or about 30% (w/w) PLA and about 70%, about 75%, about 80%, about 85% or about 90% (w/w) PBSA.

According to an embodiment, at least one of said first outer polymer layer and said second outer polymer layer comprises about 10% (w/w) PLA and about 90% (w/w) PBSA.

According to an embodiment, at least one of said first outer polymer layer and said second outer polymer layer comprises about 15% (w/w) PLA and about 85% (w/w) PBSA.

According to an embodiment, at least one of said first outer polymer layer and said second outer polymer layer comprises about 20% (w/w) PLA and about 80% (w/w) PBSA.

According to an embodiment, at least one of said first outer polymer layer and said second outer polymer layer comprises about 25% (w/w) PLA and about 75% (w/w) PBSA.

According to an embodiment, at least one of said first outer polymer layer and said second outer polymer layer comprises about 30% (w/w) PLA and about 70% (w/w) PBSA.

According to an embodiment, each of said first outer polymer layer and said second outer polymer layer comprises about 15% (w/w) PLA and about 85% (w/w) PBSA.

According to an aspect of some embodiments of the present invention, there is provided a biodegradable sheet comprising a first outer polymer layer, a second outer polymer layer, and at least three inner polymer layers located between said first and said second outer polymer layers, wherein each of said first outer polymer layer and second outer polymer layer comprises about 85% (w/w) PBSA and about 15% (w/w) PLA, wherein a first inner polymer layer is a core layer comprising 100% (w/w) PBAT, wherein a second inner polymer layer is located between said first outer layer and said first inner layer; wherein a third inner layer is located between said first inner layer and said second outer layer; and wherein each of said second inner polymer layer and said third inner polymer layer comprises at least 90% (w/w) PGA.

According to an aspect of some embodiments of the present invention there is provided a biodegradable sheet comprising a first outer polymer layer, a second outer polymer layer, and at least three inner polymer layers located between said first and said second outer polymer layers, wherein each of said first outer polymer layer and second outer polymer layer comprises about 85% (w/w) PBSA and about 15% (w/w) PLA, wherein a first inner polymer layer is a core layer comprising 100% (w/w) PGA, wherein a second inner polymer layer is located between said first outer layer and said first inner layer; wherein a third inner layer is located between said first inner layer and said second outer layer; and wherein each of said second inner polymer layer and said third inner polymer layer comprises 100% (w/w) PBAT.

BRIEF DESCRIPTION OF THE FIGURES

Some embodiments of the invention are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments of the invention may be practiced. The figures are for the purpose of illustrative discussion and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention. For the sake of clarity, some objects depicted in the figures are not to scale. In the Figures:

Fig. 1 is a schematic representation of a three-layered sheet in accordance with the principles of the present invention; Fig. 2 is a schematic representation of a five-layered sheet in accordance with the principles of the present invention;

Fig. 3 presents bar graphs comparing mechanical properties (modulus and strain at break) of sheets #2 and #3 according to the principles of the present invention having a core layer comprising at least 90% (w/w) PGA with those of reference sheet #1;

Fig. 4 presents bar graphs comparing optical properties (haze and light transmittance) of the sheets of Fig. 3;

Fig. 5 presents a line graph comparing barrier properties (WVTR and OTR) of sheets #2, #3 and #4 according to the principles of the present invention having a core layer comprising at least 90% (w/w) PGA with those of reference sheet #1;

Fig. 6 is a bar graph comparing sealing strength of sheets #2, #3 and #4 according to the principles of the present invention having a core layer comprising at least 90% (w/w) PGA with that of reference sheet #1;

Fig. 7 presents bar graphs comparing stress at yield (MD and TD) of sheet #5 according to the principles of the present invention having a core layer comprising at least 90% (w/w) PGA with that of reference sheet #1;

Fig. 8 is a bar graph comparing WVTR of sheet #6 according to the principles of the present invention having two inner layers comprising at least 90% (w/w) PGA with that of reference sheet #1;

Fig. 9 is a bar graph comparing mechanical properties (modulus and strain at break) of sheet #7 according to the principles of the present invention having an outer layer comprising at least 90% (w/w) PGA with those of reference sheet #1;

Fig. 10 is a bar graph comparing sealing strength of the sheets of Fig. 9;

Fig. 11 is a photograph comparing the sealing line at 115°C seen for the sheets of Fig. 9;

Fig. 12 is a bar graph comparing WVTR of the sheets of Fig. 9; and

Fig. 13 is a bar graph comparing optical properties (haze and light transmittance) of the sheets of Fig. 9. DETAILED DESCRIPTION OF THE INVENTION

Definitions

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. In case of conflict, the specification, including definitions, takes precedence.

The term “biodegradable” as used herein is to be understood to include a polymer, polymer mixture, or polymer-containing sheet that degrades through the action of living organisms in air, water or any combinations thereof within 1 year. Biodegradable polyester degradation is initially by hydrolysis, to eventually break the polymer into short oligomers, and later by microbial degradation, or microbial digestion. Biodegradable material may break down under a variety of conditions, for example under aerobic or anaerobic conditions, in compost, in soil or in water (such as sea, rivers or other waterways).

Material which may be degraded in compost is referred to as compostable. Hence, as used herein, the term “compostable” refers to a polymer, polymer mixture, or polymer- containing sheet which is degraded by biological processes under aerobic conditions to yield carbon dioxide, water, inorganic compounds and biomass and leaves no visible, distinguishable or toxic residues. Composting of such materials may require a commercial composting facility or the material may be home compostable.

As used herein, the term “home compostable” refers to a polymer, polymer mixture, or polymer-containing sheet which is compostable in a home composting container, i.e. at significantly lower temperatures and in the absence of set conditions as compared to those provided in a commercial composting facility, Home composting is usually carried out in significantly smaller volumes than those used for commercial composting, and do not include an industrial shredding process.

The term “sheet” as used herein is to be understood as having its customary meanings as used in the thermoplastic and packaging arts and includes the term “film”. Such sheets may have any suitable thickness, may be of a single polymer layer or of multiple polymer layers. Such sheets may be manufactured using any suitable method including blown film extrusion and cast film extrusion. As used herein, the term “core layer” of a biodegradable sheet having an odd number of layers refers to the innermost layer of the sheet, such that an equal number of layers (an outer layer and at least one inner layer) is positioned on each said of the core layer.

As used herein, the terms “first outer polymer layer” and “second outer polymer layer” refer to layers provided on a first side and a second side, respectively, of the core layer. The sheet may be provided with additional layers on an outer surface of one or more of the first outer polymer layer and the second polymer layer and/or with an additional layer, such as a tie layer, between the core layer and the first outer polymer layer and the second outer polymer layer. In some embodiments, the first outer layer is as a contact layer, having direct contact with the contents of the biodegradable package. In some embodiments, the second outer layer is as a contact layer, having direct contact with the contents of the biodegradable package.

As used herein, reference to a specified percentage (w/w) of a polymer layer is intended to refer to the percentage of the specified polymer in a polymer mixture from which the polymer layer is formed. The layer may further comprise a minor amount (no greater than about 5% (w/w) of the total composition of the layer) additives such as slip, anti block, anti-oxidant and the like.

It is to be noted that, as used herein, the singular forms “a”, “an” and “the” include plural forms unless the content clearly dictates otherwise. Where aspects or embodiments are described in terms of Markush groups or other grouping of alternatives, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the group.

As used herein, when a numerical value is preceded by the term "about", the term "about" is intended to indicate +/- 10%.

As used herein, the terms “comprising”, “including”, "having" and grammatical variants thereof are to be taken as specifying the stated features, integers, steps or components but do not preclude the addition of one or more additional features, integers, steps, components or groups thereof. These terms encompass the terms "consisting of" and "consisting essentially of".

In some embodiments, the biodegradable sheet as disclosed herein is used to prepare a biodegradable package, such as a bag or pouch, for example for containing therein an ingestible substance such as a food, drink or medicine, which may be a solid, semi-solid or liquid substance. For example, in some embodiments, the biodegradable package is prepared by heat sealing of two or more parts of the same sheet or two or more separate sheets. In some such embodiments, the layer referred to herein as a first outer polymer layer serves as a contact layer, having direct contact with the contents of the biodegradable package. In some embodiments, the first outer polymer layer is a contact layer. In some embodiments, the second outer polymer layer is a contact layer.

As known to a person having ordinary skill in the art, some of the polymers discussed herein have one or more names or spelling thereof. For example, poly(epsilon- caprolactone), poly(caprolactone) and polycaprolactone are synonymous and the three terms are used interchangeably. Similarly, polylactic acid and poly(lactic acid) are synonymous.

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

Many modifications and variations are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention can be practiced otherwise than as specifically described.

The specific embodiments listed below exemplify aspects of the teachings herein and are not to be construed as limiting.

Throughout this application, various publications, including United States Patents, are referenced by author and year and patents by number. The disclosures of these publications and patents and patent applications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.

Citation of any document herein is not intended as an admission that such document is pertinent prior art or considered material to the patentability of any claim of the present disclosure. Any statement as to content or a date of any document is based on the information available to applicant at the time of filing and does not constitute an admission as to the correctness of such a statement. Referring now to Fig. 1, there is shown a schematic representation of three-layered sheet 10, comprising a first outer layer 12, a second outer layer 14 and an inner (core layer) 16, wherein core layer 16 is positioned between first outer layer 12 and second outer layer

14. Fig. 2 shows a schematic representation of a five-layered 20 comprising a first outer layer 12; a second outer layer 14, a core layer 16 positioned between first outer layer 12 and second outer layer 14; a first inner polymer layer 22 positioned between first outer layer 12 and core layer 16; and a second inner polymer layer 24 positioned between second outer layer 14 and core layer 16.

EXAMPLES

In the experimental section below, all percentages are weight percentages.

Materials and Methods

All the embodiments of polymer sheets according to the teachings herein were made using commercially-available raw materials and devices, using one or more standard methods including: polymer resin drying, resin mixing, cast film extrusion, cast film co- extrusion, blown film extrusion and coextmsion and adhesive lamination.

Materials

The following polymer resins trials were acquired from commercial sources: PGA polyglycolic acid

PLA poly(lactic acid)

PBSA poly(butylene succinate adipate)

PBAT poly(butylene adipate terephthalate)

The resins were used as supplied, without further drying. Optionally, before use, resins were further dried, such as by drying overnight in an air flow Shini SCD-160U-120H desiccant dryer heated to about 80 °C.

The polymer sheets according to the teachings herein included layers comprising a polymer mixture. Such layers were made by coextmsion of a polymer mixture resin. To make the required polymer mixture resins, the appropriate amounts of the dried constituent resins were dry-blended and then introduced into the feed zone of the extruders and co-extruded as a film.

Cast film coextrusion of sheets Some embodiments of sheets according to the teachings herein were made by coextrusion of three or more layers to make a desired sheet by multilayer cast film co extrusion.

Some embodiments of sheets according to the teachings herein were made by lamination of single and multilayer cast film extruded films. Films and sheets were made using a cast film coextruder Dr. Collin (Collin Lab and Pilot Solutions) using standard settings, typically the mixture was fed into the extruder with the temperature zone settings 230- 245 °C; Adaptor at 245°C; feedblock at 245 °C; Die at 245-250°C. The screw speed was set to provide an extruded layer having the desired thickness in the usual way. For multilayer films, a die having three ports, each fed by a dedicated extruder was used. Methods

In order to define the physical properties of the biodegradable sheets disclosed herein, the following test methods were used: a. Stress at yield and at maximum load, Young’s Modulus and the strain at break were measured using the ASTM D882 Standard Test Method for Tensile Properties of Thin Plastic Sheeting in machine direction and transverse direction. b. Heat sealing was measured using the ASTM F2029/F88 Standard Test Method for Seal Strength of Flexible Barrier Materials in machine direction. c. Impact was measured using the ASTM D1709 Standard Test Method for Impact Resistance of Plastic Film by the Free-Falling Dart Method. d. Haze and light transmittance were measured using the ASTM D1003 Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics. e. Water vapor transmission rate (WVTR) was measured using the ASTM F1249 Standard Test Method for Water Vapor Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infrared Sensor at 38°C, 90%RH. f. Oxygen transmission rate (OTR) was measured using the ASTM D3985 Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor at 25°C, 0%RH. Example 1: Specific embodiments of sheets according to the teachings disclosed herein

Reference sheet #1 and exemplary sheets #2-6, representing specific embodiments according to the teachings disclosed herein were prepared, according to Table 1. The total thickness of each sheet was 40 pm.

Table 1

The sheets were prepared as follows, wherein symmetrical layers (such as first and second outer polymer layers or second and third inner polymer layers) were each extruded from a single extruder which was split symmetrically at the feed block. Alternatively, each layer may be extruded from a dedicated extruder, such that, for example, three extruders are used for preparing a three-layered sheet, five extruders for a five-layered sheet etc.

Sheet #1 made by cast film coextrusion of

85% PBSA:15% PLA 100% PBAT 85% PBSA:15% PLA Sheet #2 made by cast film coextrusion of 85% PBSA:15% PLA 100% PBAT 4 mih 100% PGA 100% PBAT 85% PBSA:15% PLA

Sheet #3 made by cast film coextrusion of 85% PBSA:15% PLA 100% PBAT

8 mih 100% PGA 100% PBAT 85% PBSA:15% PLA Sheet #4 made by cast film coextrusion of 85% PBSA:15% PLA

100% PBAT 12 mih 100% PGA 100% PBAT 85% PBSA:15% PLA

Sheet #5 made by cast film coextrusion of 85% PBSA:15% PLA 100% PBAT 10 mih 100% PGA

100% PBAT 85% PBSA:15% PLA

Sheet #6 made by cast film coextrusion of 85% PBSA:15% PLA 4 mih 100% PGA 100% PBAT 4 mih 100% PGA 85% PBSA:15% PLA Sheet #7 made by cast film coextrusion of 8 pm 100% PGA 100% PBAT 85% PBSA:15% PLA

Example 2: Mechanical properties of sheets of the present invention having PGA as a core layer

Young’s modulus and strain at break were determined for sheets #2 and #3, as well as for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 3, which shows the following: i. Young’s modulus in machine direction (MD) was 196 MPa for reference sheet #1; 415 MPa for sheet #2 comprising 4pm PGA as the core layer; and 1027 MPa for sheet #3 comprising 8pm PGA as the core layer. Sheet #2 therefore showed a 112% increase and sheet #3 showed a 420% increase in Young’s modulus as compared to reference sheet #1. It was therefore concluded that Young’s modulus is significantly higher in sheets having a PGA core layer as compared to a reference sheet devoid of a PGA layer. ii. Young’s modulus in transvers direction (TD) was 139 MPa for reference sheet #1; 360 MPa for sheet #2; and 1088 MPa for sheet #3. Sheet #2 therefore showed a

160% increase and sheet #3 showed a 680% increase in Young’s modulus as compared to reference sheet #1. This further supports the conclusion that Young’s modulus is significantly higher in sheets having a PGA core layer as compared to a reference sheet devoid of a PGA layer. iii. Strain at break in MD direction was 224% for reference sheet #1; 229% for sheet #2; and 312% for sheet #3. It was therefore concluded that despite the increase in Young’s modulus obtained for the sheets comprising a PGA core layer and in view of the standard deviation shown, elongation in MD was not significantly affected. iv. Strain at break in TD direction was 566% for reference sheet #1 ; 400% for sheet #2; and 378% for sheet #3. It was therefore concluded that despite the increase in

Young’s modulus obtained for the sheets comprising a PGA core layer and in view of the standard deviation shown, elongation in TD remained high. v. Strain at break in both directions remained relatively high.

Example 3: Optical properties of sheets of the present invention having PGA as a core layer Haze and light transmittance were determined for sheets #2 and #3, as well as for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 4, which shows that haze and light transmittance values were preserved and even slightly improved in sheets #2 and 3 having a PGA core layer as compared to reference sheet #1 devoid of a PGA layer.

Example 4: Barrier properties of sheets of the present invention having PGA as a core layer

WVTR and OTR were determined for sheets #2, #3 and #4, as well as for reference sheet #1, according to the methods defined above. Results are presented in Fig. 5, which shows the following: i. WVTR decreased significantly from 500 g/m ² /day for reference sheet #1 to 111 g/m ² /day for sheet #2 comprising 4pm PGA as the core layer; 58 g/m ² /day for sheet #3 comprising 8pm PGA as the core layer; and 38 g/m ² /day for sheet #4 comprising 12pm PGA as the core layer. It was therefore concluded that WVTR was improved significantly in sheets having a PGA core layer as compared to a reference sheet devoid of a PGA layer. ii. OTR decreased significantly from 1063 cc/(m ² -day-atm) for reference sheet #1 to 7.5 cc/(m ² -day-atm) for sheet #2 comprising 4pm PGA as the core layer; 4 cc/(m ² -day-atm) for sheet #3 comprising 8pm PGA as the core layer; and 1 cc/(m ² -day-atm) for sheet #4 comprising 12pm PGA as the core layer. It was therefore concluded that OTR was improved significantly in sheets having a PGA core layer as compared to a reference sheet devoid of a PGA layer.

Example 5: Sealing properties of sheets of the present invention having PGA as a core layer Heat sealing properties were determined for sheet #2 and for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 6, which shows the following: i. The sealing window expanded by 30°C i.e. from (80-120)°C for reference sheet #1 to (80-150)°C for sheet #2. ii. Sealing strength was maintained at a relatively high level (about 15-21 N.

It was therefore concluded that sealing properties were significantly improved in sheets having a PGA core layer as compared to a reference sheet devoid of a PGA layer. Example 6: Stress properties of sheets of the present invention having PGA as a core layer

Stress at yield in MD and TD was determined for sheets #3 and #5, and for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 7, which shows that stress at upper yield (MD and TD) for sheets #3 and #% increased by 110% and 180%, respectively. It was therefore concluded that stress at yield properties were significantly improved in sheets having a PGA core layer as compared to a reference sheet devoid of a PGA layer. This resulted in improved processing of the sheets in follow-on processes, such as converting (easier cutting), printing, coating, metallization, and more.

Example 7: Barrier properties of sheets of the present invention having two inner layers comprising PGA

WVTR was determined for sheet #6 which is a five-layered sheet having a second and third inner layer comprising PGA, and for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 8, which shows that WVTR of sheet #6 was 41 g/m ² /day as compared to 500 g/m ² /day for reference sheet #1. It was therefore concluded that WVTR is significantly reduced for sheets comprising PGA inner layers as compared to a reference sheet devoid of a PGA layer. Example 8: Mechanical properties of sheets of the present invention having an outer layer comprising PGA

Young’s modulus and strain at break were determined for sheet #7 having an outer layer comprising PGA, as well as for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 9, which shows the following: i. Young’s modulus in machine direction (MD) was 196 MPa for reference sheet #1 and 810 MPa for sheet #7, representing a 310% increase in Young’s modulus for a sheet having an outer layer comprising PGA as compared to a reference sheet devoid of a PGA outer layer. ii. Young’s modulus in transverse direction (TD) was 139 MPa for reference sheet #1 and 803 MPa for sheet #7, representing a 480% increase in Young’s modulus for a sheet having an outer layer comprising PGA as compared to a reference sheet devoid of a PGA outer layer. iii. Strain at break in MD direction was 224% for reference sheet #1 and 227% for sheet #7. It was therefore concluded that despite the increase in Young’s modulus obtained for the sheets having an outer layer comprising PGA and in view of the standard deviation shown, elongation in MD was not significantly affected. iv. Strain at break in TD direction was 566% for reference sheet #1 and 317% for sheet #7. It was therefore concluded that despite the increase in Young’s modulus obtained for the sheet having an outer layer comprising PGA and in view of the standard deviation shown, elongation in TD remained high. v. Strain at break in both directions remained relatively high. Example 9: Sealing properties of sheets of the present invention having PGA as an outer layer

Heat sealing properties were determined for sheet #7 and for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 10, which shows the following: iii. The sealing window expanded by 30°C i.e. from (80-120)°C for reference sheet #1 to (80-150)°C for sheet #6. iv. Sealing strength was maintained at a relatively high level (about 15-20 N).

It was therefore concluded that sealing properties were significantly improved in sheets having a PGA outer layer as compared to a reference sheet devoid of a PGA layer.

The present inventors further found that (as shown in Fig. 11) the sealing line at 115°C was smoother and less distorted or shrunk in sheet #7 as compared to reference sheet #1. In addition, sheet #7 was released more easily from the heat sealing machine as compared to reference sheet #1. It was therefore considered that PGA in an outer layer constitutes a thermal protective layer and provides a less sticky sheet as compared to a reference sheet devoid of a PGA outer layer.

Example 10: Barrier properties of sheets of the present invention having an outer layer comprising PGA

WVTR was determined for sheet #7 and for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 12, which shows that WVTR of sheet #7 was 62 g/m ² /day as compared to 500 g/m ² /day for reference sheet #1. It was therefore concluded that WVTR is significantly reduced for sheets having an outer layer comprising PGA as compared to a reference sheet devoid of a PGA layer.

Example 11: Optical properties of sheets of the present invention having PGA as an outer layer

Haze and light transmittance were determined for sheet #7 and for reference sheet #1, according to the methods defined above.

Results are presented in Fig. 13, which shows that haze and light transmittance values were preserved and even slightly improved in sheet #7 having a PGA outer layer as compared to reference sheet #1 devoid of a PGA outer layer.

Conclusions As shown above and in the accompanying figures, sheets having at least one layer comprising PGA have been found to be surprisingly advantageous as compared to comparable sheets which are devoid of a PGA layer.

The advantages include:

Improved barrier properties, i.e. decreased WVTR, and OTR.

Increase in Young’s modulus, improved stress at yield point and wider range of sealing temperatures, each of which can aid processing of the sheets in follow-on processes such as converting ( e.g . improving ease of cutting, providing a thermal protective layer - release layer such that the sheet will not stick to itself), printing, coating, metallization, and more.

Increased clarity and decreased haze.

The inventions illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise indicated.

Although the above examples have illustrated particular ways of carrying out embodiments of the invention, in practice persons skilled in the art will appreciate alternative ways of carrying out embodiments of the invention, which are not shown explicitly herein. It should be understood that the present disclosure is to be considered as an exemplification of the principles of this invention and is not intended to limit the invention to the embodiments illustrated.

Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, equivalents of the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.