WO2016174665A1

WO2016174665A1 - Biodegradable sheets

Info

Publication number: WO2016174665A1
Application number: PCT/IL2016/050426
Authority: WO
Inventors: Tal Neuman; Nili KONIECZNY; Shai GARTY; Steve ARNAUTOFF
Original assignee: Tipa Corp Ltd
Current assignee: Tipa Corp Ltd
Priority date: 2015-04-29
Filing date: 2016-04-21
Publication date: 2016-11-03
Anticipated expiration: 2017-10-29
Also published as: GB201507332D0; GB2537879A

Abstract

The present invention is directed to biodegradable sheets and films, and in particular to biodegradable sheets including an inner polymer layer comprising about 35-45% PCL and about 55-65% PLA, PBS, PBSA or a mixture thereof.

Description

BIODEGRADABLE SHEETS

FIELD OF THE INVENTION

The present invention, in at least some embodiments, is directed to biodegradable sheets, and in particular to biodegradable sheets including an inner polymer layer comprising about 35-45% poly(epsilon-caprolactone) (PCL) and about 55-65% poly(lactic acid) (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), or a mixture thereof.

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 polyesteramide (PEA), modified polyethylene terephthalate (PET), 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, modified PET, PEA, 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 PHBV and polybutylene adipate terphtalate (PBAT) are many times more flexible than the biopolymers discussed above, but 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.

International Patent Application No. WO 2011/158240 to the assignee of the present application discloses biodegradable sheets and an array of separable pouches for liquids.

International Patent Publication No. WO 2013/088443 to the assignee of the present application discloses a biodegradable sheet comprising a gas barrier material, which is a nanoclay and/or polyvinyl alcohol.

International Patent Application No. WO 2013/186778 to the assignee of the present application discloses a biodegradable sheet comprising at least one layer which comprises a biodegradable polymer and surface treated nanoclay particles and/or polyvinyl alcohol (PVOH) grafted with a crosslinker and polybutylene succinate (PBS) or polybutylene succinate adipate (PBSA).

There remains a need for flexible and biodegradable packaging with improved impermeability to water vapor and/or oxygen.

SUMMARY OF THE INVENTION

The present invention, in at least some embodiments, is directed to biodegradable sheets, and in particular to biodegradable sheets including an inner polymer layer comprising about 35-45% poly(epsilon-caprolactone) (PCL) and about 55-65% poly(lactic acid) (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), or a mixture thereof. In some embodiments, the second biodegradable polymer comprises PLA.

In some embodiments, the second biodegradable polymer comprises a mixture of PLA and PBS or a mixture of PLA and PBSA.

In some embodiments, the first inner polymer layer, said first outer polymer layer and said second outer polymer layer are co-extruded.

In some embodiments, the first outer polymer layer comprises PBS, and optionally further comprises PHA.

In some embodiments, the first outer polymer layer comprises PBAT or PBSA, and optionally further comprises PLA.

In some embodiments, the second outer polymer layer comprises PBSA, and optionally further comprises PCL.

In some embodiments, the second outer polymer layer comprises PBAT, and optionally further comprises PLA.

In some embodiments, the second outer polymer layer comprises PBS.

In some embodiments, the second outer polymer layer comprises a mixture of PLA and PBSA.

In some embodiments, the biodegradable sheet further comprises a second inner polymer layer.

In some embodiments, the second inner polymer layer, first inner polymer layer, first outer polymer layer and second outer polymer layer are co-extruded.

In some embodiments, the second inner polymer layer comprises PVOH and optionally further comprises PLA or PCL.

In some embodiments, the biodegradable sheet further comprises a third inner polymer layer.

In some embodiments, the third inner polymer layer, second inner polymer layer, first inner polymer layer, first outer polymer layer and second outer polymer layer are co- extruded.

In some embodiments, the third inner polymer layer comprises a polymer selected from the group consisting of PBAT, a mixture of PLA and PBSA and a mixture of PCL and PLA.

In some embodiments, the first inner polymer layer is optionally metalized on one or both sides and optionally further comprises a coating on one or both sides, further comprising a second inner polymer layer comprising PBS or PBSA, located between said first inner polymer layer and second outer polymer layer. In some embodiments, the second inner polymer layer is co-extruded with the first inner layer.

In some embodiments, the first outer polymer layer comprises PBS.

In some embodiments, the biodegradable sheet further comprises at least two additional inner polymer layers located between said first outer polymer layer and said first inner polymer layer.

In some embodiments, a first of the two additional inner polymer layers comprises PBSA or PLA.

In some embodiments, a second of the two additional inner polymer layers comprises PBAT or PBS.

In some embodiments, the second of two additional inner polymer layers is located between the first of the two additional polymer layers and the first outer layer.

In some embodiments, the first outer polymer layer and the two additional inner polymer layers are co-extruded.

In some embodiments, the second outer layer comprises PBSA or cellulose.

In some embodiments, the second outer layer includes a composition comprising PBAT and PLA.

In some embodiments, the inner polymer layer serves as a barrier layer, providing reduced water vapor transmission rate (WVTR) and reduced oxygen transmission rate (OTR).

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.

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.

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".

The biodegradable compositions according to the invention can be used to manufacture a wide variety of articles of manufacture, including articles useful for packaging solid, semi-solid or liquid substances, including ingestible substances such as food substances, drinks and medicines.

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, air, water or any combinations thereof within 180 days in a controlled-condition industrial compost facility with high ventilation and controlled humidity. Biodegradable polyester degradation is initially by hydrolysis, to eventually break the polymer into short oligomers, and later by microbial degradation, or microbial digestion.

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.

In some embodiments, the total thickness of the sheet is less than about 100 μπι. The biodegradable compositions according to the invention can be used to manufacture a wide variety of articles of manufacture, including articles useful to package solid and liquid substances, including food substances. Thus, the sheets according to this invention include sheets having a wide variety of thicknesses (both measured and calculated) and layers, for example 1 , 2, 3, 4, 5, 7 or more layers. A sheet may be generated by methods known in the art, for example, co-extrusion casting, and blown molding.

As known in the art, multilayer sheets are produced by co-extrusion, lamination or combination thereof. In lamination, at least two previously-made sheets are mutually adhered, for example by heat, pressure and/or adhesive.

A "tie layer" refers to a polymer layer that bonds to both polar and non-polar polymers that are typically used to produce a sheet having at least three coextruded layers: a layer of polar polymer, a layer of non-polar polymer and the tie layer therebetween. Tie layer resins are commercially available and typically include anhydride-modified polymers resins, such as, for example, 1 ,4-benzenedicarbonyl thiourea resin, BTR-8002P (Nippon Gohsei).

As known in 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.

The present invention, in at least some embodiments, is directed to biodegradable sheets and films, and in particular to biodegradable sheets including an inner polymer layer comprising about 35-45% PCL and about 55-65% PLA, PBS, PBSA, or a mixture thereof.

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 the first and second outer polymer layers, wherein the first inner polymer layer comprises:

a first biodegradable polymer comprising PCL at a concentration of from about

35% to about 45% (w/w) of the first inner polymer layer; and a second biodegradable polymer selected from the group consisting of PLA, PBS, PBSA and mixtures thereof, at a concentration of from about 55 to about 65% (w/w) of the first inner polymer layer.

In some embodiments, the second biodegradable polymer comprises PLA. In some such embodiments, the first inner polymer layer comprises about 40% (w/w) PCL and about 60% (w/w) PLA. In some such embodiments, the first inner polymer layer comprises about 45% (w/w) PCL and about 55% (w/w) PLA.

In some embodiments, the second biodegradable polymer comprises a mixture of PLA and PBS. In some such embodiments, the first inner polymer layer comprises about 35 to about 40% (w/w) PCL and about 60 to 65 % (w/w) of a mixture of PLA and PBS.

In some embodiments, the first inner polymer layer comprises about 36% (w/w) PCL and about 64% (w/w) of a mixture of PLA and PBS. In some such embodiments, the mixture of PLA and PBS comprises about 54% (w/w) PLA and about 10% (w/w) PBS.

In some embodiments, the mixture of PLA and PBS comprises about 50 to about 55% (w/w) PLA and about 5 to about 15% (w/w) PBS.

In some embodiments, the first inner polymer layer comprises about 40% (w/w) PCL and about 60% (w/w) of a mixture of PLA and PBS. In some such embodiments, the mixture of PLA and PBS comprises about 50 to about 55% (w/w) PLA and about 5 to about 15% (w/w) PBS, such as, for example, about 50% (w/w) PLA and about 10% (w/w) PBS, or about 55% (w/w) PLA and about 5% (w/w) PBS.

According to an exemplary embodiment of the biodegradable sheet disclosed herein, the first inner polymer layer comprises about 36% (w/w) PCL, about 54% (w/w) PLA and about 10% (w/s) PBS.

In some embodiments, the second biodegradable polymer comprises a mixture of PLA and PBSA. In some such embodiments, the first inner polymer layer comprises about 35 to about 40% (w/w) PCL and about 60 to 65% (w/w) of a mixture of PLA and PBSA. In some such embodiments, the first inner polymer layer comprises about 36% (w/w) PCL and about 64% (w/w) of a mixture of PLA and PBSA. In some such embodiments, the first inner polymer layer comprises about 50 to about 55% (w/w) PLA and about 5 to about 15% (w/w) PBSA, such as, for example, about 36% (w/w) PCL, about 54% (w/w) PLA and about 10% (w/s) PBSA. In some embodiments, the first inner polymer layer, the first outer polymer layer and the second outer polymer layer are co-extruded. In some embodiments, two layers of the first inner polymer layer, the first outer polymer layer and the second outer polymer layer are co-extruded as a first film, the third layer is separately extruded as a second film, and the first and second film are subsequently laminated to form the sheet. In some embodiments, the three layers are separately extruded as films, and subsequently laminated to form the sheet.

In some embodiments of the biodegradable sheet disclosed herein, the first outer polymer layer comprises PBS.

In some embodiments, the first outer polymer layer comprises a mixture of PLA and PBSA. In some such embodiments, the first outer polymer layer comprises from about 10 to about 30% (w/w) PLA and about 70% to about 90% (w/w) PBSA, such as, for example, about 15% (w/w) PLA and about 85% (w/w) PBSA or about 25% (w/w) PLA and about 75% (w/w) PBSA.

In some embodiments, the first outer polymer layer further comprises a PHA, such as, for example, a PHA selected from the group consisting of polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), or polyhydroxybutyrate-hydroxyvalerate copolymer (PHBV); or a mixture thereof.

In some embodiments, the first outer polymer layer comprises a PHA at a concentration of from about 5 to about 45% (w/w) of the first outer polymer layer and PBS at a concentration of from about 55 to about 95% (w/w) of the first outer polymer layer, such as, for example, about 5% (w/w) PHA and about 95% (w/w) PBS, about 10% (w/w) PHA and about 90% (w/w) PBS, about 15% (w/w) PHA and about 85% (w/w) PBS, about 20% (w/w) PHA and about 80% (w/w) PBS, or about 25% (w/w) PHA and about 75% (w/w) PBS.

In some embodiments, the first outer polymer layer comprises a mixture of PLA and PBSA. In some such embodiments, the first outer polymer layer comprises from about 10 to about 30% (w/w) PLA and from about 70% to about 90% (w/w) PBSA, such as, for example, about 15% (w/w) PLA and about 85% (w/w) PBSA.

In some embodiments, the first outer polymer layer comprises polybutylene adipate terphtalate (PBAT). In some such embodiments, the first outer polymer layer further comprises PLA. In some such embodiments, the first outer layer comprises from about 85% to about 95% (w/w) PBAT and about 5% to about 15% (w/w) PLA, such as, for example, about 90% (w/w) PBAT and about 10% (w/w) PLA.

In some embodiments of the biodegradable sheet disclosed herein, the second outer polymer layer comprises PBSA. In some such embodiments, the second outer polymer layer comprises about 90 to about 99% (w/w) PBSA and from about 1 to about 10% (w/w) PCL, such as, for example, about 95% (w/w) PBSA and about 5% (w/w) PCL.

In some embodiments of the biodegradable sheet disclosed herein, the second outer polymer layer comprises PBAT. In some such embodiments, the second outer polymer layer further comprises PLA. In some such embodiments, the second outer polymer layer comprises from about 85% to about 95% (w/w) PBAT and from about 5% to about 15% (w/w) PLA, such as, for example, about 90% (w/w) PBAT and about 10% (w/w) PLA.

In some embodiments of the biodegradable sheet disclosed herein, the second outer polymer layer comprises PBS.

In some embodiments of the biodegradable sheet disclosed herein, the second outer polymer layer comprises a mixture of PLA and PBSA. In some such embodiments, the second outer polymer layer comprises from about 10 to about 30% (w/w) PLA and from about 70% to about 90% (w/w) PBSA, such as, for examples, about 15% (w/w) PLA and about 85% (w/w) PBSA, about 20% (w/w) PLA and about 80% (w/w) PBSA or about 25% (w/w) PBSA and about 75% (w/w) PLA. .

In some embodiments, the first inner layer has a thickness of from about 20 to about 45 μπι, such as, for example, about 20 μπι, about 25 μπι, about 30 μπι, about 35 μπι, about 40 μπι or about 45 μπι.

In some embodiments, the first outer layer has a thickness of from about 5 to about 15 μπι, such as, for example, about 5 μπι, about 10 μπι, about 15 μιη.

In some embodiments, the second outer layer has a thickness of from about 5 to about 20 μπι, such as, for example, about 5 μπι, about 10 μπι, about 15 μπι, about 20 μπι.

In some embodiments, the biodegradable sheet disclosed herein further comprises a second inner polymer layer between the first inner polymer layer and the second outer polymer layer. In some embodiments, the second inner polymer layer, the first inner polymer layer, the first outer polymer layer and the second outer polymer layer are co-extruded. In some embodiments, the sheet is made by producing at least two films by extrusion or coextrusion, each such film comprising one or more of the layers, and subsequently the films are laminated to form the sheet.

In some embodiments, the second inner polymer layer comprises polyvinyl alcohol (PVOH). In some such embodiments, the PVOH inner polymer layer has a thickness of from about 5 μπι to about 10 μπι, such as, for example, about 5 μπι, about 6 μπι, about 7 μπι, about 8 μπι, about 9 μπι or about 10 μιη.

In some embodiments the second inner polymer layer comprises PVOH and further comprises PLA. In some such embodiments, the second inner polymer layer comprises from about 60 to about 90% (w/w) PVOH and about 10 to about 40% (w/w) PLA, such as, for example, about 80% (w/w) PVOH and about 20% (w/w) PLA, or about 70% (w/w) PVOH and about 30% (w/w) PLA, or about 60% (w/w) PVOH and about 40% (w/w) PLA.

In some embodiments the second inner polymer layer comprises PVOH and further comprises PCL. In some such embodiments, the second inner polymer layer comprises from about 60 to about 90% (w/w) PVOH and about 10 to about 40% (w/w) PCL, such as, for example, about 80% (w/w) PVOH and about 20% (w/w) PCL, or about 70% (w/w) PVOH and about 30% (w/w) PCL, or about 60% (w/w) PVOH and about 40% (w/w) PCL.

In some embodiments, the second inner layer has a thickness of from about 5 μπι to about 10 μπι, such as, for example, about 5 μπι, about 6 μπι, about 7 μπι, about 8 μπι, about 9 μπι about 10 μπι.

In some embodiments, the biodegradable sheet further comprises a first tie layer between the first inner polymer layer and the second inner polymer layer. In some embodiments, the first tie layer comprises a commercially available adhesive resinil

In some embodiments, the first tie layer has a thickness of from about 1 μπι to about 5 μπι, such as, for example, about 1 μπι, about 2 μπι, about 3 μπι, about 4 μπι, about 5 μπι.

In some embodiments, the biodegradable sheet further comprises a third inner polymer layer between the second inner polymer layer and the second outer polymer layer. In some such embodiments, the third inner polymer layer, the second inner polymer layer, the first inner polymer layer, the first outer polymer layer and the second outer polymer layer are co-extruded.

According to an aspect of some embodiments disclosed herein, there is provided a biodegradable sheet comprising a first outer polymer layer, a second outer polymer layer, a first inner polymer layer between the first and second outer polymer layers, and a second inner polymer layer comprising PVOH between the first inner polymer layer and the third inner polymer layer. The first and third inner polymer layer comprises a first biodegradable polymer comprising PCL at a concentration of from about 35% to about 45% (w/w) of the first inner polymer layer; and a second biodegradable polymer selected from the group consisting of PLA, PBS, PBSA and mixtures thereof, at a concentration of from about 55 to about 65% (w/w) of the first and third inner polymer layer.

In some embodiments, the composition of the third inner polymer layer is the same as that of the first inner polymer layer.

In some embodiments, the biodegradable sheet further comprises a second tie layer between the second inner polymer layer and the third inner polymer layer. In some embodiments, the first tie layer comprises a commercially available adhesive resin.

In some embodiments, the third inner polymer layer comprises a mixture of PCL and PLA. In some such embodiments, the third inner polymer layer comprises about 35% to about 45% (w/w) PCL, and about 55 to about 65% (w/w) PLA, such as, for example, about 40% (w/w) PCL and about 60% (w/w) PLA or about 45% (w/w) PCL and about 55% (w/w) PLA. In some such embodiments, the third inner polymer layer further comprises PBS. In some embodiments, the third inner polymer layer comprises about 36% (w/w) PCL and about 64% (w/w) of a mixture of PLA and PBS. In some such embodiments, the mixture of PLA and PBS comprises about 54% (w/w) PLA and about 10% (w/w) PBS. In some embodiments, the third inner polymer layer comprises about 40% (w/w) PCL and about 60% (w/w) of a mixture of PLA and PBS. In some such embodiments, the mixture of PLA and PBS comprises about 55% (w/w) PLA and about 5% (w/w) PBS.

In some embodiments, the third inner polymer layer has a thickness of from about 10 to about 25 μπι, such as, for example, about 10 μπι, about 15 μπι, about 20 μπι, about 25 μπι.

In some embodiments, the biodegradable sheet disclosed herein comprises a plurality of co-extruded layers, such as, for example, three co-extruded layers, four co-extruded layers, five co-extruded layers, six co-extruded layers, seven co-extruded layers.

In some embodiments, the biodegradable sheet disclosed herein comprises a laminated structure i.e., the sheet is made by producing at least two films by extrusion or coextrusion, each such film comprising one or more of the layers, and subsequently the films are laminated to form the sheet.

In some embodiments, the first inner polymer layer is metallized on one side. In some embodiments, the first inner polymer layer is metallized on both sides. In some embodiments, the first inner polymer layer is devoid of metallization. In some such embodiments, the first inner polymer layer is metalized with aluminum dioxide, either by direct metallization or by use of a laminated layer.

In some embodiments, the first inner polymer layer further comprises a coating on one side. In some embodiments, the first inner polymer layer further comprises a coating on both sides. In some embodiments, the first inner polymer layer is devoid of a coating. In some embodiments wherein the first inner polymer layer further comprises a coating on the surface of one or both sides, the coating is selected from the group consisting of a shellac-based coating, a cellulose-based coating (such as a nitrocellulose coating), a plasma-deposited siloxane-based coating, or mixtures thereof. In some embodiments, such coatings further improve the impermeability of the layer to, for example, oxygen and water. In some embodiments, the coating comprises shellac.

In some embodiments, the first inner layer is adhered to the second outer layer by a biodegradable adhesive, such as, for example, a polyester-polyurethane adhesive such as Epotal® PI 00 Eco (BASF).

In some embodiments, the biodegradable sheet further comprises a second inner polymer layer located between the first inner polymer layer and the second outer polymer layer. In some embodiments, the second inner polymer layer comprises PBS. In some embodiments, the second inner polymer layer comprises PBSA.

In some embodiments, the second inner layer is adhered to the second outer layer by a biodegradable adhesive, such as, for example, a polyester-polyurethane adhesive such as Epotal® PI 00 Eco (BASF).

In some embodiments, the second inner polymer layer is co-extruded with the first inner layer.

In some embodiments, the first outer polymer layer comprises PBS.

In some embodiments, the first outer polymer layer comprises PLA.

In some embodiments, the first outer polymer layer comprises PLA and PBSA. In some such embodiments, the first outer polymer layer comprises about 25 % (w/w) PLA and about 75% (w/w) PBSA. In some such embodiments, the first outer polymer layer comprises about 15% (w/w) PLA and about 85% (w/w) PBSA

In some embodiments, the first outer polymer layer comprises about 36% (w/w) PCL and about 64% (w/w) of a mixture of PLA and PBSA. In some such embodiments, the first outer polymer layer comprises about 50 to about 55% (w/w) PLA and about 5 to about 15% (w/w) PBSA, such as, for example, about 36% (w/w) PCL, about 54% (w/w) PLA and about 10% (w/s) PBSA.

In some embodiments, the biodegradable sheet disclosed herein further comprises an additional inner polymer layer located between the first outer polymer layer and the first inner polymer layer.

In some embodiments, the biodegradable sheet disclosed herein further comprises at least two additional inner polymer layers located between the first outer polymer layer and the first inner polymer layer. In some such embodiments, a second of the two additional inner polymer layers is located between a first of the two additional polymer layers and the first outer layer. In some such embodiments, the first outer polymer layer and the two additional inner polymer layers are co-extruded. In some such embodiments, the co-extruded first outer polymer layer and two additional inner polymer layers are adhered to the first inner polymer layer by a biodegradable adhesive, such as, for example, a polyester-polyurethane adhesive such as Epotal® PI 00 Eco (BASF). In some embodiments, a first of the two additional inner polymer layers comprises PBS.

In some embodiments, a first of the two additional inner polymer layers comprises PBSA.

In some embodiments, a second of the two additional inner polymer layers comprises PBAT.

In some embodiments, a first of the two additional inner polymer layers comprises PLA. In some embodiments, a second of the two additional inner polymer layers comprises PBS.

In some embodiments, the second outer layer comprises PBSA.

In some embodiments, the second outer layer comprises cellulose.

In some embodiments, the second outer layer is metalized on one side. In some embodiments, the second outer layer is metalized on both sides. In some embodiments, the second outer layer is devoid of metallization.

In some embodiments, the second outer layer includes a composition comprising PBAT and PLA. In some such embodiments, the second outer layer comprises from about 80 to about 95% (w/w) PBAT and from about 5 to about 20% (w/w) PLA, such as, for example, about 90% (w/w) PBAT and about 10% (w/w) PLA.

In some embodiments, the biodegradable sheet disclosed herein further comprises an additional inner polymer layer located between the first inner polymer layer and the second outer polymer layer.

In some embodiments, the biodegradable sheet disclosed herein further comprises at least two additional inner polymer layers located between the first inner polymer layer and the second polymer layer. In some such embodiments, a second of the two additional inner polymer layers is located between a first of the two additional polymer layers and the second outer layer. In some such embodiments, the second outer polymer layer and the two additional inner polymer layers are co-extruded. In some such embodiments, the co-extruded first outer polymer layer and two additional inner polymer layers are adhered to the first inner polymer layer by a biodegradable adhesive, such as, for example, a polyester-polyurethane adhesive such as Epotal® PI 00 Eco (BASF). In some embodiments, the first additional polymer layer comprises PBS. In some embodiments, the second additional polymer layer comprises PBAT.

In some embodiments, the first additional inner polymer layer comprises a mixture of PLA and PBSA. In some such embodiments, the first additional inner polymer layer comprises from about 10 to about 30% (w/w) PLA and about 70% to about 90% (w/w) PBSA, such as, for example, about 15% (w/w) PLA and about 85% (w/w) PBSA or about 25% (w/w) PLA and about 75% (w/w) PBSA.

According to an aspect of some embodiments disclosed herein, there is also provided a method of preparing a biodegradable sheet comprising a first outer polymer layer, a second outer polymer layer and at least a first inner polymer layer between the first and second outer polymer layers, wherein the first inner polymer layer comprises a first biodegradable polymer comprising poly(epsilon-caprolactone) (PCL) at a concentration of from about 35% to about 45% (w/w) of the first inner polymer layer; and a second biodegradable polymer selected from the group consisting of poly(lactic acid) (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA) and mixtures thereof, at a concentration of from about 55 to about 65% (w/w) of the first inner polymer layer. The method comprises melt-extruding the polymers or polymer mixtures to form the first and second outer layers and the at least one first inner layer, optionally metallizing at least one of the first outer layer, second outer layer and/or at least one first inner layer, optionally applying a coating on one or more of the metalized or non-metallized layers and laminating the first outer layer, second outer layer and at least one inner layer to form a biodegradable sheet.

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, semisolid 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 layer serves as a contact layer, having direct contact with the contents of the biodegradable package. In some embodiments, the biodegradable sheet according has a degradation time in the range of 4 to 24 months. In some embodiments, the biodegradable sheet according has a shelf life of up to 12 months or up to 18 months.

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.

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, metallization and thermal lamination.

Materials

The following polymer resins and raw materials were acquired from commercial sources: PCL poly(epsilon-caprolactone)

PLA poly(lactic acid)

PBS poly(butylene succinate)

PBSA poly(butylene succinate adipate)

PBAT poly(butylene adipate te htalate)

PHA poly(hydroxyalkanoate)

PVOH poly( vinyl alcohol)

Tie later: poly( vinyl acetate)

Adhesive: water-based polyester-polyureth;

Cellulose

Resin drying

Before use, resins were dried overnight in an air flow Shini SCD-160U-120H dryer desiccator heated to 50 °C.

Resin mixtures

As seen from Tables 1 and 2, some embodiments of the polymer sheets according to the teachings herein included layers comprising a polymer mixture. Such layers were made by extrusion / coextrusion of a polymer mixture resin.

To make the required polymer mixture resins, the appropriate amounts of the dried constituent resins were dry-blended, introduced into the feed of a twin screw compounder and then melt extruded to form a polymer mixture resin. During melt extrusion in the compounder, the temperature zone settings were 170-175-180-185-190 °C Die at 190 °C, a screw speed of 350 rpm and pressure 15-25 bar.

The compounded polymer resin was ground into 1-5 mm diameter pellets using strand pelletizer.

Cast film coextrusion of films and 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 feed into the extruder with the temperature zone settings 170-180-200 °C; Adaptor at 200°C; feedblock at 200 °C; Die at 200 °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.

Metallization

Metallization was performed using a physical vapor deposition process with aluminum vapor under vacuum.

Heat Set Lamination

Heat set lamination to make a sheet according to the teachings herein was performed by feeding the constituent films from spools into a lamination machine. In some cases two films were directly laminated. In some embodiments, two films were laminated with the help of an applied water-based adhesive at 2 g/m as a 2 micrometer thick tie layer between the two films.

Coating

A thin film coating of shellac or nitrocellulose was applied on the different sheets at a 3 g/m² concentration. In metallized films, the coating was applied on the metallized side. The film was dried overnight at ambient temperature.

Alternatively, the sheets were coated with siloxane mixture using plasma surface treatment. Specifically, a sheet to be treated was placed in a vacuum chamber. An RF generator was used to generate plasma to treat the surface of the sheet in two steps: a first cleaning step including a short plasma treatment cycle, and a second siloxane- mixture deposition step. This step was done by a RF generator who creates a plasma flow of energetic radicals which bombarding the surface of an object.

The object is placed at a low vacuum environment in a vacuum chamber for the entire process.

The process include a short plasma treatment cycle for cleaning purposes and another plasma treatment cycle of plasma deposition of siloxane mixture (two different chemistry where tested) that attached to the surface. Section I: Specific embodiments of sheets according to the teachings TABLE 1

Table 1, sheet #1 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer PBSA (extruder III)

Table 1, sheet #2 made by cast film coextrusion of

10 micrometer 25% PHA: 75% PBS (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer PBSA (extruder III)

Table 1, sheet #3 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II), 15 micrometer PBSA (extruder III)

Table 1, sheet #4 made by cast film coextrusion of 10 micrometer 25% PHA: 75% PBS (extruder I),

40 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

15 micrometer PBSA (extruder III)

Table 1, sheet #5 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #6 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #7 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer PBAT (extruder III)

Table 1, sheet #7b made by sheet cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer commercially available 90% PBAT: 10% PLA (extruder III) Table I, sheet #8a made by cast film coextrusion of

10 micrometer 25% PHA: 75% PBS (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer PBAT (extruder III)

Table I, sheet #8b made by cast film coextrusion of

10 micrometer 25% PHA: 75% PBS (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer commercially available 90%PBAT: 10%PLA (extruder III) Table I, sheet #9a made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

15 micrometer PBAT (extruder III)

Table I, sheet #9b made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II), 15 micrometer commercially available 90%PBAT: 10%PLA (extruder III) Table 1, sheet #10a made by cast film coextrusion of

10 micrometer 25% PHA: 75% PBS (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer PBAT (extruder III)

Table 1, sheet #10b made by cast film coextrusion of

10 micrometer 25% PHA: 75%PBS (extruder I),

40 micrometer 54% PLA: 36%PCL: 10%PBS (extruder II),

15 micrometer commercially available 90% PBAT: 10%PLA (extruder III) Table 1, sheet #1 la made by film coextrusion of

10 micrometer PBAT (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #1 lb made by cast film coextrusion of

10 micrometer commercially available 90% PBAT: 10% PLA (extruder I),

40 micrometer 60% PLA: 40% PCL (extruder II),

15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #12a made by cast film coextrusion of

10 micrometer PBAT (extruder I),

40 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #sl2b made by cast film coextrusion of

10 micrometer commercially available 90% PBAT: 10% PLA (extruder I)

40 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #15 made by cast film coextrusion of

5 micrometer 5% PHA: 95% PBS (extruder I)

20 micrometer 60% PLA: 40% PCL (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 60% PLA: 40% PCL (extruder II),

10 micrometer PBSA (extruder V)

Table 1, sheet #16 made by cast film coextrusion of 5 micrometer PBS (extruder I)

20 micrometer 60% PLA: 40% PCL (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 60% PLA: 40% PCL (extruder II),

10 micrometer PBSA (extruder V)

Table 1, sheet #17 made by cast film coextrusion of

5 micrometer PBS (extruder I)

20 micrometer 60% PLA: 40% PCL (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 60% PLA: 40% PCL (extruder II),

10 micrometer 95% PBSA: 5% PCL (extruder V)

Table 1, sheet #18 made by cast film coextrusion of

5 micrometer 5% PHA: 95% PBS (extruder I)

20 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

10 micrometer PBSA (extruder V)

Table 1, sheet #19 made by cast film coextrusion of

5 micrometer PBS (extruder I)

20 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

10 micrometer PBSA (extruder V)

Table 1, sheet #20 made by cast film coextrusion of

5 micrometer PBS (extruder I)

20 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II), 2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 54% PLA: 36% PCL: 10% PBS (extruder II),

10 micrometer 95% PBSA: 5% PCL (extruder V)

Table 1, sheet #21 made by cast film coextrusion of

5 micrometer PBS (extruder I)

20 micrometer 60% PLA: 40% PCL (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 60% PLA: 40% PCL (extruder II),

10 micrometer PBS (extruder I)

Table 1, sheet #22 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 55% PLA: 45% PCL (extruder II),

15 micrometer PBSA (extruder III)

Table 1, sheet #23 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 50% PLA: 40% PCL: 10% PBS (extruder II),

15 micrometer PBSA (extruder III)

Table 1, sheet #24 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 55% PLA: 45% PCL (extruder II),

15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #25 made by cast film coextrusion of

10 micrometer PBS (extruder I)

40 micrometer 50% PLA: 40% PCL: 10% PBS (extruder II),

15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #26a made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 55% PLA: 45% PCL (extruder II),

15 micrometer PBAT (extruder III)

Table 1, sheet #26b made by cast film coextrusion of 10 micrometer PBS (extruder I),

40 micrometer 55% PLA: 45% PCL (extruder II),

15 micrometer commercially available 90% PBSA: 10% PLA (extruder III) Table 1, sheet #27 a made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 50% PLA: 40% PCL: 10% PBS (extruder II),

15 micrometer PBAT (extruder III)

Table 1, sheet #27b made by cast film coextrusion of

10 micrometer PBS (extruder I)

40 micrometer 50% PLA: 40% PCL: 10% PBS (extruder II),

15 micrometer commercially available 90% PBSA: 10% PLA (extruder III) Table 1, sheet #28 made by cast film coextrusion of

5 micrometer PBS (extruder I),

20 micrometer 55% PLA: 45% PCL (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 55% PLA: 45% PCL (extruder II),

10 micrometer PBSA (extruder V)

Table 1, sheet #29 made by cast film coextrusion of

5 micrometer PBS (extruder I),

20 micrometer 50% PLA: 40% PCL: 10% PBS (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 50% PLA: 40% PCL: 10% PBS (extruder II),

10 micrometer PBSA (extruder V)

Table 1, sheet #30 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 55% PLA: 40% PCL: 5% PBS (extruder II),

15 micrometer PBSA (extruder III)

Table 1, sheet #31 made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 55% PLA: 40% PCL: 5% PBS (extruder II), 15 micrometer 95% PBSA: 5% PCL (extruder III)

Table 1, sheet #32a made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 55% PLA: 40% PCL: 5% PBS (extruder II),

15 micrometer PBAT (extruder III)

Table 1, sheet #32b made by cast film coextrusion of

10 micrometer PBS (extruder I),

40 micrometer 55% PLA: 40% PCL: 5% PBS (extruder II),

15 micrometer commercially available 90% PBSA: 10% PLA (extruder III) Table 1, sheet #33 made by cast film coextrusion of

5 micrometer PBS (extruder I),

20 micrometer 55% PLA: 40% PCL: 5% PBS (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 55% PLA: 40% PCL: 5% PBS (extruder II),

10 micrometer PBSA (extruder V)

Table 1, sheet #34 made by cast film coextrusion of

5 micrometer 75% PBSA: 25% PLA (extruder I),

20 micrometer 60% PLA: 40% PCL (extruder III),

8 micrometer 80% PVOH: 20% PLA (extruder II),

20 micrometer 60% PLA: 40% PCL (extruder III),

5 micrometer 75% PBSA: 25% PLA (extruder I)

Table I, sheet #35 made by cast film coextrusion of

5 micrometer 75% PBSA: 25% PLA (extruder I),

20 micrometer 60% PLA: 40% PCL (extruder III),

8 micrometer 70% PVOH: 30% PLA (extruder II),

20 micrometer 60% PLA: 40% PCL (extruder III),

5 micrometer 75% PBSA: 25% PLA (extruder I)

Table I, sheet #36 made by cast film coextrusion of

5 micrometer 75% PBSA: 25% PLA (extruder I),

20 micrometer 60% PLA: 40% PCL (extruder III),

8 micrometer 60% PVOH: 40% PLA (extruder II),

20 micrometer 60% PLA: 40% PCL (extruder III), 5 micrometer 75% PBSA: 25% PLA (extruder I)

Table 1, sheet #37 made by cast film coextrusion of

5 micrometer 75% PBSA: 25% PLA (extruder I),

20 micrometer 60% PLA: 40% PCL (extruder III),

8 micrometer 80% PVOH: 20% PCL (extruder II),

20 micrometer 60% PLA: 40% PCL (extruder III),

5 micrometer 75% PBSA: 25% PLA (extruder I)

Table 1, sheet #38 made by cast film coextrusion of

5 micrometer 75% PBSA: 25% PLA (extruder I),

20 micrometer 60% PLA: 40% PCL (extruder III),

8 micrometer 70% PVOH: 30% PCL (extruder II),

20 micrometer 60% PLA: 40% PCL (extruder III),

5 micrometer 75% PBSA: 25% PLA (extruder I)

Table 1, sheet #39 made by cast film coextrusion of

5 micrometer 75 % PBSA: 25 % PLA (extruder I),

20 micrometer 60% PLA: 40% PCL (extruder III),

8 micrometer 60% PVOH: 40% PCL (extruder II),

20 micrometer 60% PLA: 40% PCL (extruder III),

5 micrometer 75% PBSA: 25% PLA (extruder I)

Table 1, sheet #40 ( reference sheet) made by cast film coextrusion of

25 micrometer 75% PBSA: 25% PLA (extruder I),

2 micrometer tie layer (extruder II),

8 micrometer 60% PVOH: 40% PCL (extruder III),

2 micrometer tie layer (extruder II),

25 micrometer 75% PBSA: 25% PLA (extruder I)

Table 1, sheet #41 (reference sheet) made by cast film coextrusion of

15 micrometer 75% PBSA: 25% PLA (extruder I),

10 micrometer PBAT (extruder II),

8 micrometer 60% PVOH: 40% PCL (extruder III),

10 micrometer PBAT (extruder II),

15 micrometer 75% PBSA: 25% PLA (extruder I)

Table 1, sheet #42 (reference sheet) made by cast film coextrusion of

15 micrometer 75% PBSA: 25% PLA (extruder I),

10 micrometer commercially available 90% PBSA: 10% PLA (extruder II), 8 micrometer 60% PVOH: 40% PCL (extruder III),

10 micrometer commercially available 90% PBSA: 10% PLA (extruder II),

15 micrometer 75% PBSA: 25% PLA (extruder I)

Table 1, sheet #43 made by cast film coextrusion of

5 micrometer 5% PHA: 95% PBS (extruder I)

20 micrometer 60% PLA: 40% PCL (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 85% PBSA: 15% PLA (extruder V),

10 micrometer PBSA (extruder VI)

Table 1, sheet #44 made by cast film coextrusion of

5 micrometer PBS (extruder I)

20 micrometer 60% PLA: 40% PCL (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 85% PBSA: 15% PLA (extruder V),

10 micrometer PBSA (extruder VI)

Table I, sheet #45 made by cast film coextrusion of

5 micrometer PBS (extruder I)

20 micrometer 60% PLA: 40% PCL (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 85% PBSA: 15% PLA (extruder V),

10 micrometer 95% PBSA: 5% PCL (extruder VI)

Table I, sheet #46 made by cast film coextrusion of

5 micrometer 5% PHA: 95% PBS (extruder I)

20 micrometer 54% PLA: 36% PCL:10%PBS (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 85% PBSA: 15% PLA (extruder V), 10 micrometer PBSA (extruder VI)

Table 1, sheet #47 cast film coextrusion of

5 micrometer PBS (extruder I)

20 micrometer 54% PLA: 36% PCL:10%PBS (extruder II), 2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 85% PBSA: 15% PLA (extruder V), 10 micrometer PBSA (extruder VI)

Table 1, sheet #48 made by cast film coextrusion of

5 micrometer PBS (extruder I)

20 micrometer 54% PLA: 36% PCL:10%PBS (extruder II),

2 micrometer of tie later (extruder III),

8 micrometer of PVOH (extruder IV),

2 micrometer of tie later (extruder III),

20 micrometer 85% PBSA: 15% PLA (extruder V),

10 micrometer 95% PBSA: 5% PCL (extruder VI).

TABLE2

Examples in Table 2 are produced with or without metallization and with or without coating. The following examples are presented with metallization and shellac coating.

Table 2, sheet #1 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75 PBSA: 25 PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 60% PLA:40% PCL laminated to the second film with an adhesion layer, a third film of 35 micrometer PBSA

Table 2, sheet #2 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75% PBSA:25% PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 60%PLA:40%PCL

laminated to the second film with an adhesion layer to the metallized face, a third film of 25 micrometer metallized cellulose

Table 2, sheet #3 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%P BSA:25% PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

laminated to the second film with an adhesion layer, a third film of 25 micrometer cellulose

Table 2, sheet #4 made by laminating three films:

First film of 25 micrometer metalized cellulose high barrier film,

laminated with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized

60%PLA:40%PCL,

laminated to the second film with an adhesion layer, a third film of 25 micrometer to a coextruded film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75% PBSA: 25% PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III), Table 2, sheet #5 made by laminating three films:

First film of 25 micrometer cellulose high barrier film,

laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 60 PLA:40 PCL,

10 micrometer 75% PBSA: 25% PLA (extruder I),

10 micrometer PB AT (extruder II),

10 micrometer PBSA (extruder III),

Table 2, sheet #6 made by laminating three films:

First film of 25 micrometer metalized cellulose high barrier film,

laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 60% PLA:40% PCL,

laminated to the second film with an adhesion layer, a third film of 25 micrometer to a coextruded film 20 micrometers thick made by cast film coextrusion of:

10 micrometer 85% PBSA: 15% PLA (extruder I),

10 micrometer PBSA (extruder II),

Table 2, sheet #7 made by laminating three films:

First film of 25 micrometer cellulose high barrier film,

10 micrometer 85% PBSA: 15% PLA (extruder I),

10 micrometer PBSA (extruder II),

Table 2, sheet #8 made by laminating three films:

First film of 25 micrometer metalized cellulose high barrier film, laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 60% PLA:40% PCL,

10 micrometer PBS A (extruder I),

10 micrometer 85% PBSA: 15% PLA (extruder II),

10 micrometer PBSA (extruder III),

Table 2, sheet #9 made by laminating three films:

First film of 25 micrometer cellulose high barrier film,

10 micrometer PBSA (extruder I),

10 micrometer 85% PBSA: 15% PLA (extruder II),

10 micrometer PBSA (extruder III),

Table 2, sheet #10 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 60%PLA:40%PCL,

laminated to the second film with an adhesion layer, a third film of 35 micrometer PBSA

Table 2, sheet #11 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II), 10 micrometer PBS A (extruder III),

Table 2, sheet #12 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PB AT (extruder II),

10 micrometer PBS A (extruder III),

laminated to the second film with an adhesion layer, a third film of 25 micrometer cellulose.

Table 2, sheet #13 made by laminating three films:

First film of 25 micrometer metalized cellulose high barrier film,

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

Table 2, sheet #14 made by laminating three films:

First film of 25 micrometer cellulose high barrier film,

laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 60% PLA:40% PCL, laminated to the second film with an adhesion layer, a third film of 25 micrometer to a coextruded film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

Table 2, sheet #15 made by laminating three films:

First film of coextruded 24 micrometers thick made by cast film coextrusion of:

15 micrometer PL A (extruder I),

9 micrometer PBS (extruder II),

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

Table 2, sheet #16 made by laminating three films:

First film of coextruded 20 micrometers thick made by cast film coextrusion of:

10 micrometer 54% PLA: 36% PCL and 10% PBS (extruder I), 10 micrometer PBS (extruder II),

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

Table 2, sheet #17 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of: 10 micrometer 75%PBSA:25%PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 54%PLA:36%PCL:10%PBS,

Table 2, sheet #18 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%PBSA:25%PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

laminated to the second film with an adhesion layer, the metallized face, a third film of 25 micrometer metallized cellulose.

Table 2, sheet #19 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%PBSA:25%PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

Table 2, sheet #20 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III), laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film of 25 micrometer metallized 54%PLA:36%PCL:10%PBS,

laminated to the second film with an adhesion layer, a third film of 35 micrometer PBSA.

Table 2, sheet #21 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

laminated to the second film with an adhesion layer to the metallized face, a third film of 25 micrometer metallized cellulose.

Table 2, sheet #22 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

Table 2, sheet #23 sheet made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%PBSA:25%PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film made by cast film coextrusion of:

25 micrometer metallized 60%PLA:40%PCL; (extruder I) 10 micrometer PBS (extruder II)

laminated to the second film with an adhesion layer, a third film of 35 micrometer commercially available 90%PBAT:10%PLA.

Table 2, sheet #24 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

25 micrometer metallized 60%PLA:40%PCL (extruder I) 10 micrometer PBS (extruder II)

laminated to the second film with an adhesion layer, a third film of 35 micrometer commercially available 90%PBAT: 10%PLA

Table 2, sheet #25 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%PBSA:25%PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III),

25 micrometer metallized 60%PLA:40%PCL (extruder I) 10 micrometer PBSA (extruder II)

Table 2, sheet #26 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%PBSA:25 %PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBSA (extruder III), laminated to the first film with an adhesion layer through an intervening shellac layer applied to the metallized face of a second film made by cast film coextrusion of:

Table 2, sheet #27 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

25 micrometer metallized 60%PLA:40%PCL (extruder I) 10 micrometer PBS A (extruder II)

Table 2, sheet #28 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

Table 2, sheet #29 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%PBSA:25%PLA (extruder I), 10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

25 micrometer metallized 54%PLA:36%PCL:10%PBS (extruder I)

10 micrometer PBS (extruder II)

laminated to the second film with an adhesion layer, a third film of 35 micrometer commercially available 90%PBAT:10%PLA

Table 2, sheet #30 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

25 micrometer metallized 54%PLA:36%PCL:10%PBS (extruder I)

10 micrometer PBS (extruder II)

Table 2, sheet #31 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%PBSA:25%PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

25 micrometer metallized 54%PLA:36%PCL:10%PBS (extruder I) 10 micrometer PBS A (extruder II)

Table 2, sheet #32 made by laminating three films:

41 a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer 75%PBSA:25%PLA (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

25 micrometer metallized 54%PLA:36%PCL:10%PBS (extruder I) 10 micrometer PBS

Table 2, sheet #33 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

25 micrometer metallized 54%PLA:36%PCL:10%PBS (extruder I)

10 micrometer PBS A (extruder II)

Table 2, sheet #34 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBAT (extruder II),

10 micrometer PBS A (extruder III),

25 micrometer metallized 54%PLA:36%PCL:10%PBS (extruder I) 10 micrometer PBS (extruder II) laminated to the second film with an adhesion layer, a third film of 25 micrometer cellulose.

Table 2, sheet #35 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #36 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #37 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

laminated to the second film with an adhesion layer, a third film of 35 micrometer commercially available 90%PBAT:10%PLA. Table 2, sheet #38 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #39 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #40 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #41 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of: 10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #42 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #43 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #44 made by laminating three films:

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

Table 2, sheet #45 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

25 micrometer metallized 60%PLA:40%PCL (extruder I)

10 micrometer PBS A (extruder II)

Table 2, sheet #46 made by laminating three films:

a first film 30 micrometers thick made by cast film coextrusion of:

10 micrometer PBS (extruder I),

10 micrometer PBS (extruder II),

10 micrometer PL A (extruder III),

25 micrometer metallized 54%PLA:36%PCL:10%PBS (extruder I)

10 micrometer PBS A (extruder II)

laminated to the second film with an adhesion layer, a third film of 25 micrometer cellulose. Section II: Measurement of physical properties of selected sheets

In order to define the physical properties of selected biodegradable sheets disclosed herein, sheets #35-38 and 40-42 of Table 1, as defined in Section I above and in the Table were used.

Reference sheets were prepared as follows

Sheet #1: A single layer biodegradable sheet consisting of about 25.0% w/w PLA and about 75.0% w/w PBSA was prepared as follows:

A. Melt extrusion compounding stage:

1. 250gr PLA and 750gr PBSA were dried overnight at a temperature of 50°C in a SHIM SCD-160U-120H desiccant dryer;

2. The dried polymers were dry blended and placed in a two screw Collin compounder;

3. The polymers were melt-extruded in the compounder set to the following profile:

4. Temperature profile: 175-180-185-185-190°C (the Die is set to 190°C);

5. Screw speed: 200rpm; and

6. Pressure: 15-25 bar.

B. Cast extrusion stage:

1. The melt extruded compounds were dried overnight at a temperature of 40°C in a desiccant dryer;

2. The material was placed into a Randcastle Extruder set to the following profile: 3. 170-180-185°C - 185 °C- Adaptor; 185°C -feedblock; Die-185°C;

4. Screw speed: 80rpm; and

5. Head pressure 450bar.

Sheet #11: A single layer biodegradable sheet consisting of about 20.0% w/w PLA, 60.0% w/w PBS and 20.0% w/w PCL was prepared according to a method similar to that described above for sheet #1, but with the following differences:

200gr PLA, 600gr PBS and 200gr PCL were used for the melt extrusion compounding stage; the temperature profile for the melt extrusion compounding stage was: 160-175- 180-185-190°C (the Die is set to 190°C); and the temperature profile for the cast extrusion stage was 160-180-185°C - 185 °C- Adaptor; 185°C -feedblock; Die-185°C.

Sheet #111: A single layered biodegradable sheet consisting of about 17.5% w/w PLA and 52.5% w/w PBS and 30.0% w/w PCL was prepared with the amounts of the polymers used were 175gr PLA, 525gr PBS and 300gr PCL, as described above for Sheet # II.

Sheet #IV: A single layered biodegradable sheet consisting of about 15.0% w/w PLA and 45.0% w/w PBS, 40.0% w/w PCL was prepared with the amounts of the polymers used were 150gr PLA, 450gr PBS and 400gr PCL, as described above for Sheet # II. Sheet #V: A single layered biodegradable sheet consisting of 100% PCL was prepared using the same procedure described above for Sheet # II, wherein the amounts of the polymers used were lOOOgr PCL.

Barrier properties

Water vapor transmittance rate (WVTR) [g/(m2^»d)] was tested according to ASTM E96 and correlated according to the measured thickness of the film [g^»mil/(m2^»d)]. Results are presented in Tables 3 and 4.

As seen in the Tables, the WVTR was shown to be lower by 10-100 fold in sheets comprising inner layers of 60% PLA:40% PCL (sheets #35-38) as compared to multilayered or single layered reference sheets which did not include an inner layer of PLA with PCL (sheets #40-42 and #I-V). .

Table 3. WVTR data

Film properties

The films were next tested for their mechanical properties (ASTM D882; machine direction or MD and trans-machine direction or TD) and heat seal (ASTM F2029). Results are presented in Tables 5 and 6 (mechanical properties data) and Table 7 (heat seal data).

The mechanical data show that the Young's modulus is higher in sheets comprising an inner layer of 40% PCL: 60% PLA as compared to reference sheets, which do not include such a layer. The heat seal data suggest comparable heating seal for all films, which is above the heating seal for the reference polyester film I (75 -85 °C). In addition, the average seal strength of > 30 was shown for the films containing PVOH with 30-40% PLA. Polyesters with PVOH (with or without tie layer) or PVOH with 20- 30% PCL had average seal strength of 23, which is comparable to the reference polyester film I.

Table 5 mechanical properties data

Table 6. Mechanical properties of reference sheets

Table 7 heat seal data

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.

Claims

1. 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 said first inner polymer layer comprises:

a first biodegradable polymer comprising PCL at a concentration of from about 35% to about 45% (w/w) of said first inner polymer layer; and

a second biodegradable polymer selected from the group consisting of PLA, PBS, PBSA and mixtures thereof, at a concentration of from about 55 to about 65% (w/w) of said first inner polymer layer.

2. The biodegradable sheet according to claim 1 , wherein said second biodegradable polymer comprises PLA.

3. The biodegradable sheet according to any one of claims 1 and 2, wherein said second biodegradable polymer comprises a mixture of PLA and PBS or a mixture of PLA and PBSA.

4. The biodegradable sheet according to any one of claims 1 to 3, wherein said first inner polymer layer, said first outer polymer layer and said second outer polymer layer are co-extruded.

5. The biodegradable sheet according to any one of claims 1 to 4, wherein said first outer polymer layer comprises PBS, and optionally further comprises PHA.

6. The biodegradable sheet according to any one of claims 1 to 4, wherein said first outer polymer layer comprises PBAT or PBSA, and optionally further comprises PLA.

7. The biodegradable sheet according to any one of claims 1 to 6, wherein said second outer polymer layer comprises PBSA, and optionally further comprises PCL.

8. The biodegradable sheet according to any one of claims 1 to 6, wherein said second outer polymer layer comprises PBAT, and optionally further comprises PLA.

9. The biodegradable sheet according to any one of claims 1 to 6, wherein said second outer polymer layer comprises PBS.

10. The biodegradable sheet according to any one of claims 1 to 6, wherein said second outer polymer layer comprises a mixture of PLA and PBSA.

11. The biodegradable sheet according to any one of claims 1 to 10, further comprising a second inner polymer layer.

12. The biodegradable sheet according to claim 11, wherein said second inner polymer layer, said first inner polymer layer, said first outer polymer layer and said second outer polymer layer are co-extruded.

13. The biodegradable sheet according to any one of claims 11 and 12, wherein said second inner polymer layer comprises PVOH and optionally further comprises PLA or PCL.

14. The biodegradable sheet according to any one of claims 11 to 13, further comprising a third inner polymer layer.

15. The biodegradable sheet according to claim 14, wherein said third inner polymer layer, said second inner polymer layer, said first inner polymer layer, said first outer polymer layer and said second outer polymer layer are co-extruded.

16. The biodegradable sheet according to any one of claims 14 to 15, wherein said third inner polymer layer comprises a polymer selected from the group consisting of PBAT, a mixture of PLA and PBSA and a mixture of PCL and PLA.

17. The biodegradable sheet according to any one of claims 1 to 3, wherein said first inner polymer layer is optionally metalized on one or both sides and optionally further comprises a coating on one or both sides, further comprising a second inner polymer layer comprising PBS or PBSA, located between said first inner polymer layer and second outer polymer layer.

18 The biodegradable sheet according to claim 17, wherein said second inner polymer layer is co-extruded with said first inner layer.

19. The biodegradable sheet according to any one of claims 17 and 18, wherein said first outer polymer layer comprises PBS.

20. The biodegradable sheet according to any one of claims 17 to 19, further comprising at least two additional inner polymer layers located between said first outer polymer layer and said first inner polymer layer.

21. The biodegradable sheet according to claim 20, wherein a first of said two additional inner polymer layers comprises PBSA or PLA.

22. The biodegradable sheet according to any one of claims 20 and 21, wherein a second of said two additional inner polymer layers comprises PBAT or PBS.

23. The biodegradable sheet according to any one of claims 20 to 22, wherein said second of two additional inner polymer layers is located between said first of said two additional polymer layers and said first outer layer.

24. The biodegradable sheet according to any one of claims 20 to 23, wherein said first outer polymer layer and said two additional inner polymer layers are co-extruded.

25. The biodegradable sheet according to any one of claims 20 to 24, wherein said second outer layer comprises PBSA or cellulose.

26. The biodegradable sheet according to any one of claims 20 to 24, wherein said second outer layer includes a composition comprising PBAT and PLA.