WO2024049930A1 - Film composite biodégradable à orientation biaxiale - Google Patents

Film composite biodégradable à orientation biaxiale Download PDF

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Publication number
WO2024049930A1
WO2024049930A1 PCT/US2023/031579 US2023031579W WO2024049930A1 WO 2024049930 A1 WO2024049930 A1 WO 2024049930A1 US 2023031579 W US2023031579 W US 2023031579W WO 2024049930 A1 WO2024049930 A1 WO 2024049930A1
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WO
WIPO (PCT)
Prior art keywords
film
layer
pla
heat
resin
Prior art date
Application number
PCT/US2023/031579
Other languages
English (en)
Inventor
Shichen Dou
Joshua R. Cloutier
Original Assignee
Toray Plastics (America), Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US18/090,732 external-priority patent/US20240066847A1/en
Application filed by Toray Plastics (America), Inc. filed Critical Toray Plastics (America), Inc.
Publication of WO2024049930A1 publication Critical patent/WO2024049930A1/fr

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    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/022—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the choice of material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
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    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
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    • B29C48/08—Flat, e.g. panels flexible, e.g. films
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    • B32B23/04—Layered products comprising a layer of cellulosic plastic substances, i.e. substances obtained by chemical modification of cellulose, e.g. cellulose ethers, cellulose esters, viscose comprising such cellulosic plastic substance as the main or only constituent of a layer, which is next to another layer of the same or of a different material
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    • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
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Definitions

  • This invention relates to a multi-layer biaxially oriented compostable composite film with a formulation to improve the processability, mechanical, heat seal initiation and hermeticity while maintaining good optical clarity and improving flexibility.
  • This invention also provides a method to improve the heat sealing performance of a biaxially oriented composite film using bioplastics modifiers certified by TUV Austria for home composting application, resulted in the improvements of the inventive film in biodegradability and compostability.
  • Bioplastics or biopolymers are considered either amorphous or semicrystalline.
  • a semi- crystalline biopolymer exhibits organized and tightly packed molecular chains, which can vary in shape and size with amorphous areas existing between the crystalline areas.
  • a semi-crystalline biopolymer has a defined melting temperature point (Tm) for its unique highly organized molecular structure and a glass transition temperature for its amorphous phase located between crystal areas, while an amorphous biopolymer only exhibits a glass transition temperature.
  • Tm melting temperature point
  • semi-crystalline biopolymers are also simplified as “crystalline” biopolymers for the purpose of easy comparison with amorphous biopolymers.
  • Biaxially oriented polypropylene (BOPP) films are typically used for packaging, decorative, and label applications and often perform multiple functions. In a laminate, they provide printability, transparent or matte appearance, or slip properties. The films sometimes provide a surface suitable for receiving organic or inorganic coatings for gas and moisture barrier properties. The films sometimes provide a heat sealable layer for bag forming and sealing, or a layer that is suitable for receiving an adhesive either by coating or by laminating. Bioplastic films (BOPP film counterpart) must exhibit about the same features of a BOPP film to meet the requirements a packaging film.
  • Bio-based plastics are believed to help reduce reliance on petroleum, reduce production of greenhouse gases, and eliminate plastic pollution, and can be biodegradable or compostable as well.
  • bio-based plastics such as polylactic acid (PLA) and polyhydroxyalkanoates (PHA) derived from a renewable resource are the most popular and commercially available for packaging film applications.
  • PBS polybutylene succinate
  • PBSA Polybutylene succinate-co-adipate
  • BOPLA Biaxially oriented polylactic acid
  • One example could be a two-layer coextruded film structure in which a base or core layer including a crystalline PLA and a thinner “skin” layer including amorphous PLA is coextruded upon one side of the core layer and then biaxially oriented into a film.
  • the amorphous PLA layer is often used to provide heat sealability to the film as it is non-crystalline; it has a glass transition temperature of 56 to 60 °C (Tg, transition temperature of solidifying or softening) much lower than the melting temperature of the crystalline PLA resins in the core layer.
  • Tg transition temperature of solidifying or softening
  • PLA is the most inexpensive biodegradable polymer obtained from renewable source.
  • BOPLA packaging due to its very high modulus results in extremely loud noise at about 95 decibels, which is harmfully loud and potentially damages ear hearing, compared to the noise level about 79 decibels for a conventional BOPP film packaging.
  • BOPLA packaging is only industrial compostable under a controlled temperature environment of 58 ⁇ 2 °C (ASTM D 5338-15), this approach has a drawback due to the constraints in public available industrial composting facilities.
  • ASTM D 5338-15 ASTM D 5338-15
  • TUV Austria Group offers a test method called HOME COMPOSTING (AS 5810-2010 or “OK COMPOST HOME – CERTIFICATION, 2019 VERSION”) was developed to evaluate the biodegradability and compostability of new bioplastics compostable films.
  • the method is based on the test procedures of ASTM D5338-15 (industrial composting), but that the composting temperature is set at 25 ⁇ 5°C, the test temperature is kept below 30°C for the duration of the test.
  • Home composting can be conducted in the backyard which is available for most of consumers in North America.
  • Heat resistance is one of the most important properties of food packaging film.
  • the heat resistance of a BOPLA film is lower (thermal dimensional shrinkage higher) than a BOPP film does due to the difference of crystallinity (Xc) and melting temperature (Tm).
  • An oriented bioplastics composite film has a heat resistance even lower than a BOPLA film does, due to characteristics of lower glass transition temperatures (Tg), Tm, and Xc as well as modifiers used in making the composite film.
  • Tg glass transition temperatures
  • Tm melting temperatures
  • Xc crystallinity
  • heat sealing temperature is needed to overcome poor performance such as film blocking and wrinkling (due to high thermal shrinkage) as well as heat distortion (due to poor heat resistance) around the heat-sealed areas, namely the end seals of the bag and the back seal of the bag. All those defects in quality are unacceptable to food packaging companies.
  • heat seal strength can also significantly impact the heat sealing performance.
  • High plateau seal strength is the key to improve the overall heat sealing performance in terms of the hermeticity of a sealed package. Hermeticity means that there are no voids and tunnels formed inside the sealed area and no leaks due to the failure resulted from weak heat seal strength.
  • PHAs Polyhydroxyalkanoates
  • renewable biodegradable polyesters that are synthesized by mainly microorganisms from renewable sources including sugars obtained from lignocellulosic biomasses, agricultural wastes, starches, and vegetable oils; PHAs are completely biodegradable and converted into CO2 and H2O in soil and oceans. PHAs are certified compostable bioplastics that could be used for making compostable food packaging films.
  • a few disadvantages including their poor mechanical properties, poor thermal stability, long crystallization time, high production cost as well as incompatibility with conventional thermal processing techniques have limited their competition with traditional synthetic plastics or their application as ideal bioplastics.
  • a PHA-rich composite is defined as that the content of PHAs is higher than 50 wt % of the total weight of the composite. Therefore, a PHA-rich composite film has a core layer comprising PHA resins not less than 50 wt % of the total weight of the core layer.
  • Narancic et al. published their studies on the biodegradation of individual biopolymers and their blends as well (Article: Environ. Sci. Technol.2018, 52, 10441-10452).
  • thermoplastic starch (TPS) and polyhydroxybutyrate (PHB) resins are the only two individual bioplastics passed the biodegradation test across all seven test environments based on the requirements of international biodegradation standards.
  • crystalline polylactic acid (NatureWorks IngeoTM PLA4043D) is not home compostable, a blend of PLA/PCL at the ratio of 80/20 passed home composting test.
  • Polycaprolactone (PCL) CAPA6500D functioned as a promoter of biodegradation for PLA at test temperature 28 ⁇ 2°C.
  • No.9,238,324 describes a multi-layer biaxially oriented PLA composite film (PLA- rich composition) that is a heat sealable film with a significantly reduced noise level, which is related to a reduction in film modulus.
  • the modulus level of the oriented film was reduced by incorporating low Tg modifiers which are a biodegradable polymer A and an elastomer E into the core layer of the oriented structure as sound dampening materials.
  • the biodegradable polymer A includes low Tg flexible polymers such as polyhydroxyalkanoates (PHA), polyhydroxybutyratevalerate (PHBV), polycaprolactone (PCL), polybutylene-adipate-co- terephthalate (PBAT), polybutylene-succinate (PBS), polybutylene-succinate-adipate (PBSA) or mixtures thereof.
  • the glass transition temperature of polymer A is ⁇ 0°C
  • Elastomer E is modified polyolefin rubbery polymers such SEBS KratonTM FG 1924 and BIOMAX SG 120.
  • the content of the elastomer E is 1 % ⁇ wt % (E) ⁇ 10 %.
  • the invented film was only designed for industrial composting application, and the heat initiation temperature (as high as 210 °F) of the soft oriented film was not reduced to a lower level as the heat resistance of the core layer is reduced.
  • Such a soft film with high SIT (210 °F) can have heat distortion issue in bag forming process.
  • No.9,150,004 describes a method of reducing the seal initiation temperature (SIT) of a biaxially oriented PLA film by modifying the amorphous PLA sealant layer with low Tg biodegradable bioplastics.
  • SIT seal initiation temperature
  • the SIT of the inventive BOPLA film was reduced from 195°F for PLA control film to as low as 170°F for the invented film.
  • the plateau seal strength of the inventive film was not improved at about a range of 290 to 370 g/in, indicating there is no function of hermeticity.
  • No.9,074,042 describes a single-layer biaxially oriented film made from modified lactide copolymer (polyethylene glycol (PEG), PEG-modified-PLA), the oriented film is very flexible and has high elongation rate and low modulus compared to that of PLA control film.
  • the disclosed oriented film is flexible but not designed for either home compostable or heat sealing application.
  • JP2013147580A describes a method of producing a polylactic acid based oriented film with excellent gas barrier and a low noise level by adding modified flexible resins to improve the flexibility of PLA based film.
  • the flexible resins include PLA-PEG-PLA block copolymer, BASF EcoflexTM FBX 7011 resin, and PHBV resins.
  • WO2021185339A1 describes a biodegradable resin composition produced by the method of TORAY NANOALLOYTM TECHNOLOGY comprising at least 70 wt % polylactic acid resin; and 5 to 29.9 wt % biodegradable polymers selected from the biopolymers of PCL, PBS, PBAT, PHA, poly(propylene carbonate) (PPC) and poly(glycolic acid) (PGA) or mixture thereof; and 0.1 to 10 wt % aliphatic carboxylic acids as well as an amount of 50 to 500 ppm metal elements.
  • U.S. Pat. No. 9,120,911 describes a resin composition resin (PLA-rich composition) comprising at least 70 wt % polylactic acid, and 1 to 30 wt % plasticizer which is preferably 1,4:3,6- dianhydrohexitol alkyl ester (IDE) with excellent compatibility to PLA.
  • the resin composition after pelletizing was made into sheet samples by Carver hot press.
  • IDE-modified PLA sheet samples showed a significant reduction in modulus and tensile strength, and a huge increase in elongation at break.
  • the glass transition temperature of the IDE-modified PLA was reduced from 58°C (the Tg of PLA) to 32°C, the Young’s modulus was reduced from 3602 MPa to 1240 MPa, resulting in a film with a much lower level of noise.
  • the invention does not disclose how to make a packaging film from the IDE-modified PLA composition. Plasticizers could potentially impact the biodegradation, physical properties, heat resistance, additive migration, heat sealing performance as well as processability of the packaging film. [020] USPTO Pub.
  • PLA-rich composition comprising PLA resins, plasticizers, compatibilizers, and enzymes.
  • Lactic acid oligomers (LAO) and compatibilizers significantly increase the tear resistance and elongation at break of bioplastic films.
  • Enzymes well dispersed into PLA resins can improve PLA-biodegrading activity.
  • All inventive PLA-based film articles show high toughness and high depolymerization rate. Higher degradation rate could indicate that enzymes in the presence promote the biodegradation of PLA resin.
  • the invention does not teach how to make a heat sealable film for food packaging which is home compostable. [021] USPTO Pub.
  • No.:US2022/0033649A1 describes a biodegradable polymeric composition
  • a biodegradable polymeric composition comprising 5 wt % to 95 wt % PHA resin and about 5 wt % to 95 wt % at least one biodegradable polymer selected from PBS, PBSA, PLA, PBAT, PCL, thermoplastic starch (TPS), cellulose esters, and mixtures thereof; and 0.1 to 5 wt % nucleating agent.
  • An amount of 5 to 15 wt % plasticizer can further be incorporated into the biodegradable polymeric composition.
  • the biodegradable composition is both industrial and home compostable, and suitable for the application of making packaging articles.
  • One solution could be to improve the thermal stability of bioplastics composite films, however, which is limited by the basic thermal properties of selected bioplastics; another solution could be to improve the heat seal temperature range of bioplastics composite films by lowering the seal initiation temperature of the sealant layer such that high bag-making speeds can be maintained with lower setpoint temperatures and a broader heat sealing window on the sealing bars.
  • An embodiment of the invention relates to preparation of a biaxially oriented PHA-rich composite film for snack food packaging with desirable processability, mechanical properties, improved heat sealability, and home compostability by using cost-effective PLA resins as a main modifier, wherein PLA degradation in the PHA-rich environment can be achievable through PHA enzymatic degradation under ambient temperature after modification.
  • PHAs are modified in the core layer of a biaxially oriented composite film by using other biodegradable polymers including PLA, PLA copolymers, PCL, PBAT, PBS, PBSA, chemically modified starch, cellulose derivatives, and different PHA-type blends and mixtures thereof.
  • An embodiment relates to a film comprising a core layer and a heat sealant layer; wherein the core layer comprises PLA resin and a non-PLA modifier X, wherein the core layer has an amount of PLA resin more than 60 wt % of a total weight of the core layer; wherein the non-PLA modifier X has a glass transition temperature of Tg ⁇ 10 °C and a melting temperature of 56 °C ⁇ Tm ⁇ 180 °C; wherein an amount of the modifier X is less than 40 wt % of the total weight of the core layer; wherein the heat sealant layer comprises an amorphous PLA and a modifier Y having a glass transition temperature of Tg ⁇ 0 °C and a peak melting temperature of 56 °C ⁇ Tm ⁇ 90 °C; wherein the film is biaxially oriented compostable composite film having a seal initiation temperature less than 176 °F, a plateau seal strength higher than 800 g/in, and a heat sealing temperature window of
  • PHAs are modified in the core layer of a biaxially oriented composite film by using other biodegradable polymers including PLA, PLA copolymers, PCL, PBAT, PBS, PBSA, chemically modified starch, cellulose derivatives, and different PHA-type blends and mixtures thereof.
  • the core layer comprises PHA resin at an amount of more than 50 wt % of a total weight of the core layer.
  • the PHA resin includes semi-crystalline PHA resins and amorphous PHA resins such as PHB, PHBV, PHB-co-3HV, PHB-co-3HHx, PHB-co-3HO, and PHB-co-4HHx or mixtures thereof.
  • the core layer comprises PLA resin at an amount of more than 50 wt % of a total weight of the core layer.
  • the core layer further comprises a processing aid, a chain extender, a nucleating agent, a biodegradable promoter, a plasticizer, a filler, inorganic particles and/or slip additives or mixtures thereof.
  • the inorganic particles comprise nanoclay, talc, CaCO3 or TiO2 or mixtures thereof.
  • the biodegradable promoter comprises an enzyme or hydrolytic promoter and wherein the filler comprises inorganic particles and/or a slip additive.
  • the heat sealant layer comprises a PLA resin in an amount of about 5 wt % to 80 wt % of the total weight of the heat sealant layer.
  • the PLA resin in the heat sealant layer comprises semi-crystalline PLA resin, amorphous PLA resin and PLA copolymers or mixtures thereof.
  • the heat sealant layer comprises the amorphous PLA in an amount of at least 20 wt % of the total weight of the heat sealant layer.
  • the heat sealant layer comprises the amorphous PLA in the amount of about 20 wt % to about 60 wt % of the total weight of the heat sealant layer.
  • the modifier Y comprises polybutylene succinate-co-adipate (PBSA) or polycaprolactone (PCL) or other biodegradable polymers with a glass transition temperature of Tg ⁇ 0 °C and a melting peak temperature of 56 to 90 °C or mixture thereof.
  • the modifier X comprises PLA, PLA copolymers, PBS, PBSA, PCL, PBAT, and other biodegradable polymers or mixtures thereof with a glass transition temperature of Tg ⁇ 60 °C.
  • the modifier X includes PLA resin at an amount of less than 50 wt % of a total weight of the core layer.
  • the PLA resin in the core layer comprises semi-crystalline PLA resin, amorphous PLA resin and PLA copolymer resin or mixtures thereof.
  • the modifier X further comprises an amount of less than 5 wt % petroleum-based polymeric modifier with a glass transition temperature of Tg ⁇ 10 °C.
  • the amount of the PCL is about 0 wt % to about 35 wt % of the total weight of the heat sealant layer.
  • the amount of the PBSA is about 20 wt % to about 95 wt % of the total weight of the heat sealant layer.
  • the weight of the sealant layer polymer is an amount of 5 wt % to 25 wt % of the total weight of the core layer.
  • an amount of the PCL is at least 5 wt % of a total weight of the heat sealant layer.
  • the amount of the PCL is about 5 wt % to about 35 wt % of the total weight of the heat sealant layer.
  • an amount of the PBSA is at least 20 wt % of a total weight of the heat sealant layer.
  • the amount of the PBSA is about 20 wt % to about 70 wt % of the total weight of the heat sealant layer.
  • the sealant layer polymer is an amount of 5 wt % to 25 wt % of the total weight of the core layer.
  • the core layer comprises PLA resin at least an amount of 60 wt % of a total weight of the core layer, wherein the core layer comprises semi-crytalline PLA resin at least an amount of 35 wt % of a total weight of the core layer.
  • the modifier X comprises PBS, PBSA, PCL, PHBV, PHA or other biodegradable polymers or mixture thereof with a glass transition temperature of Tg ⁇ 10 °C and a melting point of 56 to 180 °C.
  • PHBV is a PHA resin but with a high Tm.
  • the modifier X further comprises a PBAT resin.
  • the polymer further comprises an amorphous polymer with a glass transition temperature of Tg ⁇ 10 °C.
  • An embodiment relates to a multi-layer composite film comprising a PHA-rich core layer (B), a heat sealant layer (C) and a second outer skin layer (A); wherein the PHA-rich core layer comprises PHA resin and non-PHA modifier X, wherein the core layer has an amount of PHA resin more than 50 wt % of the total weight of the core layer; wherein the non-PHA modifier X has a glass transition temperature of Tg ⁇ 60 °C; wherein an amount of the modifier X is less than 50 wt % of the total weight of the core layer; wherein the heat sealant layer comprises a PLA resin and a modifier Y; the modifier Y has a glass transition temperature of Tg ⁇ 0 °C and a peak melting temperature of 56 °C ⁇ Tm ⁇ 90 °C; wherein the film is sequential
  • An embodiment relates to a multi-layer composite film comprising a core layer (B), a heat sealant layer (C) and a second outer skin layer (A).
  • the film comprises a core layer, a heat sealable layer, and a non-heat sealable layer.
  • the film comprises a core layer and two outer layers which are heat sealable.
  • the film optionally comprises either one or two tie-layers which is located between the core layer and the two outer skin layers.
  • the outer skin layer is either a layer of receiving print ink, metal deposition or barrier coating.
  • the film further comprises a skin layer having the core layer at one side and opposite to the heat sealant layer.
  • the skin layer is either is a printing ink receiving layer, a metal receiving layer or a coating receiving layer.
  • the skin layer has a composition same as the core layer.
  • the core layer has a composition different than the core layer.
  • the heat sealant layer comprises an amount of antiblock particles with a spherical size of 2 to 6 ⁇ m.
  • a loading of the antiblock particles is in the range of 100 to 5000PPM of a total weight of the heat sealant layer.
  • the heat sealant layer comprises a migratory slip additive.
  • a loading of the migratory slip additive is in the range of 500 to 5000 ppm of a total weight of the heat sealant layer.
  • the skin layer comprises an antiblock particles with a spherical size of about 2 ⁇ m to 3 ⁇ m.
  • the antiblock particles in the skin layer are in amount of 100 to 5000 ppm of a total weight of the skin layer.
  • the film is configured to be a print film has the core layer comprising migratory particles in an amount of 500 to 1000 ppm.
  • the film is configured for metallization has the core layer devoid of migratory particles.
  • a thickness of the film is about 10 ⁇ m to about 50 ⁇ m.
  • the thickness of the film is about 15 ⁇ m to about 25 ⁇ m.
  • the heat sealant layer has a thickness of about 1 ⁇ m to about 5 ⁇ m.
  • the heat sealant layer has the thickness of about 2 ⁇ m to about 4 ⁇ m.
  • the skin layer has a thickness of about 1 ⁇ m to about 3 ⁇ m.
  • the skin layer has a thickness of about 1 ⁇ m to about 2 ⁇ m.
  • the film has a haze in the range of 8 to 14%.
  • the film has a modulus of 2400 to 3000 MPa in machine direction and a modulus of 2400 to 3400 MPa in transverse direction.
  • the present invention provides a method to make a compostable composite film using the polymer blends to improve the heat sealing properties or characteristics of the biodegradable composite film.
  • the method of making heat sealable film suitable for snack food packaging in particular, heat sealing properties are required for the packaging.
  • the invention provides a method for a heat sealable film for food packaging which has improved compostability
  • the invention provides a packaging film from the IDE-modified PLA composition.
  • the film is not only designed for industrial composting application. In an embodiment, there is no heat distortion issue in bag forming process.
  • the oriented film is flexible and designed for either home compostable or heat sealing application.
  • Fig. 1 shows the heat seal curves of the coextruded films of examples 1-10 of PLA film formulation.
  • Fig. 2 shows the hot tack curves of the coextruded films of examples 1-10 of PLA film formulation.
  • Fig.3 shows the heat seal curves of the coextruded films of PHA film formulation.
  • Fig.4 shows the hot tack curves of the coextruded films of PHA film formulation.
  • the articles “a” and “an” are intended to include items, and may be used interchangeably with “one or more.”
  • the term “set” is intended to include items (e.g., related items, unrelated items, a combination of related items, and unrelated items, etc.), and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used.
  • the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.
  • two or more elements are “integral” if they are comprised of the same piece of material. As defined herein, two or more elements are “non-integral” if each is comprised of a different piece of material.
  • the present invention may be embodied in other specific forms without departing from its spirit or characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
  • “approximately” or “about” can, in some embodiments, mean within plus or minus ten percent of the stated value. In other embodiments, “approximately” can mean within plus or minus five percent of the stated value. In further embodiments, “approximately” can mean within plus or minus three percent of the stated value. In yet other embodiments, “approximately” can mean within plus or minus one percent of the stated value. [0101] Unless defined, all numeric values mentioned should be construed with approximate variations as understood by a person skilled in the art.
  • Polymer is a macromolecule compound prepared by polymerizing monomers of the same or different type. Polymer includes homopolymers, copolymers, terpolymers, tetrapolymer, interpolymers, and so on. The term ‘homopolymer’ when the monomer/repeating unit is same in the polymer chain.
  • copolymer is a polymer derived from more than one species of monomers or comonomers.
  • terpolymer is a polymer made by polymerizing three different monomers.
  • Terpolymers are produced, for example, by grafting a third monomer onto a dimer of two different monomers (graft copolymerization), bulk polymerization or also random copolymerization of three monomers.
  • An example of terpolymer is acrylonitrile-butadiene-styrene copolymer (ABS). Tetrapolymer (which usually refers to polymers prepared from four different types of monomers or comonomers), and the like.
  • ABS acrylonitrile-butadiene-styrene copolymer
  • Tetrapolymer which usually refers to polymers prepared from four different types of monomers or comonomers, and the like.
  • the term “interpolymer” means a polymer prepared by the polymerization of at least two types of monomers or comonomers. [0106] In an embodiment, polymers could include additional additives. The polymer is interchangeable used as “resin”.
  • Biaxially oriented film is a film that is stretched in both machine and transverse directions, producing molecular chain orientation sequentially or simultaneously in two directions.
  • a biaxially oriented film has much higher tearing strength in machine direction in comparison with a blown film which is mainly oriented in machine direction.
  • a blown film can also have high heat shrinkage in machine direction.
  • the biaxially oriented film could be a single layer or multi-layer composite film.
  • “Amorphous resin” has a randomly ordered molecular structure which does not have a sharp melting point. Such resin soften gradually as the temperature rises.
  • Glass transition temperature, Tg is a thermal property associated with the segmental mobility of polymer chains, characterized as softening or solidifying; which in turn governs the toughness and other physical properties of the material.
  • Amorphous resin has a randomly ordered molecular structure which does not have a sharp melting temperature point. Such a resin often softens or solidifies as its temperature is changed to above Tg or below Tg.
  • Glass transition temperature, Tg is a thermal property associated with the long-range segmental mobility of polymer chains. As the temperature increases above Tg, a resin starts softening; as the temperature drops below Tg, the resin starts solidifying.
  • Tg governs the rigidity, toughness and flexibility of a polymer or polymer composite in a specific temperature range. Under ambient temperature condition, a polymer film with a Tg higher than ambient temperature, it is rigid, otherwise it is flexible as it has a Tg below ambient temperature. Either DSC or DMA (dynamic mechanical analysis) can be used to determine the Tg of polymers, polymer blends, composites, and multilayer plastic films.
  • “Low Tg flexible biopolymers” in the invention refer to those biopolymers have a Tg less than 10 °C, including PBSA, PBS and PCL, PBAT, and PHA resins, but PHB and PHBV are excluded.
  • Biodegradable Bioplastics or “Biodegradable Film” or “Compostable Composite Film” or similar refer to polymeric materials that are ‘capable of undergoing decomposition into carbon dioxide, methane, water, inorganic compounds, or biomass in which the predominant mechanism is the enzymatic action of microorganisms, that can be measured by standardized tests, in a specified period of time, reflecting available disposal condition. In an embodiment, more than 50%, 60%, 70%, 80%, 90% of the film could be degraded by the microbial action.
  • the film could be fully degraded by the microbial action.
  • the biodegradable film has a home compositing property as per AS 5810—2010 standard.
  • “Crystallinity” refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, stiffness, density, transparency, and diffusion. In an embodiment, the resin has a crystallinity more than 30%, 40%, 50%, 60%, 70%, 80%.
  • “Semi-crystalline” or “semicrystalline” refers to a polymer that exhibits organized and tightly packed molecular chains.
  • the areas of crystallinity are called spherulites and can vary in shape and size with amorphous areas existing between the crystalline areas. As a result, this highly organized molecular structure results in a defined melting point. These polymers are anisotropic in flow.
  • the semi-crystalline resin has a crystallinity more than 30%, 40%, 50%, 60%, 70%, 80%.
  • Total crystallinity refers to the crystallinity of a polymer blend or composite containing more than one component. The degree of the crystallinity of each component can be measured by using differential scanning calorimetry (DSC). The degree of the crystallinity of a polymer blend or composite can also be determined by using DSC experiment.
  • a composite consists of 50 wt % PHBV, 20 wt % PHB-co-3HHx and 30 wt % amorphous PLA resins, wherein the crystallinity of the PHBV is about 78 wt % and the crystallinity of the PHB-co-3HHx is about 40 wt %, the total crystallinity of the composite is about 47 wt % which can be obtained from calculation.
  • Modifier refers to materials that are added into the resin to improve the properties of a biaxially oriented composite film such as but not limited to improving heat-sealability, mechanical strength (flexibility, modulus, tensile strength, elongation, etc.), biodegradability, compostability, optical properties, and surface properties so on.
  • modifier could be added in the resin during an appropriate step of polymerization, melt compounding and dry blending processes at a desirable amount.
  • Modifier X is a non-PLA based modifier.
  • Modifier X is a non-PHA based modifier used to modify the core layer.
  • Modifier X comprises biopolymers having a glass transition temperature of Tg ⁇ 60 °C. It includes for example but not limited to PBS, PBSA, PCL, PBAT, PLA, and PLA copolymers such as PLA-co-GA, PLA-co-3HP, and PLA-co- ⁇ -CL copolymers. [0121] Modifier X refers to low Tg flexible polymers and additives. The modifier X comprises biopolymers having a glass transition temperature of Tg ⁇ 10 °C and a melting temperature of in the range of 56 to 180 °C.
  • Modifier Y is flexible biopolymers used to modify the heat sealable layer. The biopolymers have a glass transition temperature of Tg ⁇ 0 °C and a melting point between 56 to 90 °C.
  • Modifier Y includes but not limited to polybutylene succinate-co-adipate (PBSA) or polycaprolactone (PCL) or other biodegradable polymers or mixtures thereof.
  • PBSA polybutylene succinate-co-adipate
  • PCL polycaprolactone
  • Transesterification refers to the conversion of one ester to another. Transesterification on polyesters (such as a blend of PLA and PHA resins or a blend of PLA and PCL resins) is a reaction to exchange the group OR’’ of a polyester with the group OR’ of another polyester (OR’ and OR’’ are polyester chain segments or polyester chains).
  • the reaction occurs in the molten state at the ester bond of one polyester with or without the presence of added acid or base catalysts or metal salt catalysts and in situ produce firstly block copolymers and finally random copolymers.
  • the reaction is a useful method for blending noncompatible polyesters and is also responsible for modification effects to improve the compatibility, mechanical properties (such as toughness and modulus), biodegradability, and compostability of a biopolymer composite.
  • the home compostability of a random PLA-co-PHB or PLA-co- ⁇ -CL copolymer can be greatly improved in comparison with that of PLA homopolymers.
  • “PHA-rich” is defined when the content of PHAs is more than 50 wt % in the total weight of the layer.
  • a PHA-rich composite film has a core layer comprising PHA resins not less than 50 wt % of the total weight of the core layer.
  • PHA resin is polymerized from a racemic mixture of L- and D-lactides with the level of (L) and (D) monomers being variable. The crystallinity of PLA resins (including L-dominated PLLA and D-dominated PDLA) can be controlled by the ratio of L and D monomers in PLA chain structure.
  • Peak melting temperature refers to the average melting temperature (Tm) of the crystallites of a semi-crystalline polymer.
  • the Tm of a semi-crystalline polymer is obtained by measuring a polymer sample well annealed at its crystallization temperature using DSC at a heating rate of 10° C./min.
  • Heat seal temperature refers to the heat sealing jaw temperatures at which a specific level of seal strength is obtained for a specific plastic film. The range of heat sealing temperature can be determined by plotting the seal strength versus seal jaw temperature.
  • Heat sealing hermeticity refers to the airtight seal of a plastic package which is created by a heat sealing process using a heat sealer armed with two jaws. Airtight means that no defects such as wrinkles, tunnels and voids are created inside the seals or at the corners of a package bag.
  • shrink film refers to a plastic film which shrinks tightly over whatever it is covering due to high heat shrinkage rate when heat is applied to it. Shrink film can be used for either packaging film or shrinkable label film. Usually, a shrink film has a percentage of the amount of shrink measured in both the machine direction (MD) and the transverse direction (TD) above 20 %.
  • Non-shrink film usually refers to a plastic film which is stretchy and requires no heat application. Stretching tension and cling of a plastic film provide tightness required for packaging.
  • Heat resistant film refers to a plastic film which has heat shrinkage rate less than 10% in both machine direction and transverse direction when processing heat such as metallizing, printing, coating, laminating or heat sealing is applied to it. The characteristics of heat resistance is required for dried snack food packaging.
  • Compatibility and biodegradation of PLA/PHB blends were reviewed by Arrieta et al., The review article was published in Materials (Basel), 2017, Sep, 10(9)1008 (Article: on the Use of PLA-PHB Blends for Sustainable Food Packaging Applications).
  • PLA/PHB blends prepared by solvent casting over the range of compositions of 0 to 100% by weight for each component are immiscible, while the miscibility of PLA and PHA blend made by extrusion are improved through increasing the melt processing temperature up to 200 °C.
  • the improved miscibility was attributed to the transesterification which occurred between PLA and PHB chains and in situ produced PLA- block-PHB copolymers, compatibilizing immiscible PLA and PHB components.
  • PLA/PHB blend at the proportion of 75/25, small PHB spherulites were well dispersed in amorphous PLA phase; while at the proportion of 50/50 and 25/75, crystalline PHB forms a continuous phase, PLA component forms separated sea-island phase depending on the ratio of PLA/PHA components.
  • PHB degradation is mainly enzymatically degraded by various enzymes which are secreted by microorganisms in contact with PHB, those enzymes (including proteinase K, serine protease, lipase, esterase, and alcalase) can accelerate PLA degradation at room temperature due to the faster disintegration of PHA/PLA structure.
  • those enzymes including proteinase K, serine protease, lipase, esterase, and alcalase
  • PLA degradation is considered to undergo a non-enzymatic but hydrolytic degradation since microorganisms associating PLA in nature cannot secret enzymes to break PLA long chains into PLA oligomers which can then be enzymatically degraded into CO2 and H2O.
  • PLA/PHB blend with a higher PHB fraction associates more microorganisms and secretes more enzymes, which speeds up PLA enzymatic biodegradation under lower temperatures.
  • PHA resins Both the mole ratio (3HB/mHZ) and the structure of mHZ dominate the basic properties of PHA resins, especially, the crystallinity and melting temperature of the PHA resins.
  • n 1, the PHA resin is a PHB homopolymer.
  • PHB homopolymer has a Tg of 9 °C and a melting temperature of 175 to 178°C. It is a very rigid biopolymer due to its high crystallinity.
  • PHA resins have a Tg in the range of -44°C ⁇ Tg ⁇ 9 °C and a Tm of in the range of about 120 to 178 °C (Appl. Sci.2017, 7, 242, herein reference is listed for convenience).
  • Amorphous PHA resins comprise a high mole ratio of mHZ monomer so that the PHA copolymers have a Tg less than ⁇ -10 °C, they are very rubbery biopolymers.
  • Common engineering PHA biopolymers include PHB, PHBV, PHB-co- 3HHx, PHB-co-4HHx, PHB-co-3HO, and PHB-co-3HD.
  • An example of PHBV resins include TianAn EnmatTM Y1000P, poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHB-co-3HV or PHBV).
  • 3HV 3hydroxyvaleric acid comonomer
  • the short side chain (ethyl group CH2CH3) of 3HV can incorporate into PHB crystals, leading to a high melting point of 175 °C and a high crystallinity (78%) according to the data obtained from differential scanning calorimetry (DSC) experiment.
  • Y1000P has a glass transition temperature of about 2 °C and a melt flow index 8 to 15 g/10min., and a density of 1.25 g/cm3.
  • Y1000P is a very rigid biopolymer due to its high crystallinity.
  • a reversed extrusion temperature profile is preferably needed for extruding the PHBV resin for the sake of preventing from significant thermal degradation, preferably, an amount of low Tm flexible biopolymers, amorphous biopolymers, and plasticizers or mixtures thereof could be blended into the PHBV resin in the core layer in extrusion to facilitate PHBV melting and eliminate its thermo-mechanically induced degradation.
  • PHA resins with a side chain longer than three carbons are reported in the article published by Noda et. al.
  • the melting temperature of homopolypropylene is in the range of 160 to 170 °C, which is much higher than that of flexible PHA resins (125 to 145 °C) with longer side chain.
  • Both the lower crystallinity and low melting temperature of flexible PHA resins (Tg is about in the same as that of homopolypropylene, about -5 to 5°C) with longer side chain result in lower heat resistance and higher heat shrinkage.
  • optimal tensile strength and Young’s modulus are required for snack food packaging.
  • the tensile strength and stiffness/flexibility of the composite film can be controlled by balancing the ratio of rigid/flexible components in the core layer.
  • PLA resin is considered as a rigid biopolymer which is available at large commercial scale with a relative low cost.
  • These resins have a melt flow rate of about 3.9-4.1 g/10min. at 190 °C/2.16Kg test condition, a melting temperature of about 145-170 °C, a glass transition temperature of about 55-60 °C, a density of about 1.25 g/cm3.
  • Molecular weight Mw is typically about 200,000 g/mole; Mn typically about 100,000 g/mole; polydispersity about 2.0.
  • PLA4032D and LX575 has a melting point of about 165-173 °C, which are more preferred crystalline PLA resins for thermal resistance application.
  • IngeoTM PLA4043D and Luminy ⁇ LX175 has a melting point of about 145-152 °C, lower Tm melting temperature of those PLA resins have the advantages of the capability of melting at lower extrusion temperatures as blended with biopolymers with poor thermal stability such as PHA resins.
  • PLA resins with a Tm of about 150 °C such as LX175 and PLA4043D melt earlier compared to those PLA resins with a Tm of about 165 °C such as LX575 and PLA40432D before PHA resin melts during extrusion.
  • Molten PLA resins can lubricate extrusion and facilitate the melting of PHB or PHBV resin having a Tm in the range of from 170 to 178 °C, as a result, the extent of PHBV thermal degradation can be eliminated.
  • the crystallinity of commercial semi-crystalline PLA resins with a Tm in the range of 145 to 168 °C is in the range of about 35 wt % to 45 wt % resulted from controlling the ratio of L and D enantiomers that are used in polymerization.
  • amorphous PLA resins include NatureWorks IngeoTM 4060D and TotalEnergies Corbion Luminy ⁇ LX975.
  • Those resins have a melt flow index of about 3 to 6 g/10min. measured at the condition of 2.16Kg/190 °C, and a glass transition temperature Tg of about 52-60 °C (softening temperature), heat seal initiation temperature of about 93 °C, a density of about 1.24 g/cm3. Molecular weight Mw is about 180,000 g/mole.
  • Tg glass transition temperature
  • Tg glass transition temperature
  • Molecular weight Mw is about 180,000 g/mole.
  • PLA copolymers include but not limited to lactide-rich copolymers such as poly(lactide-co-glycolide) (PLA-co-GA), poly(lactide-co-3hydroxypropionate) (PLA-co-3HP), and poly(lactide-co- ⁇ -caprolactone) (PLA-co- ⁇ -CL) copolymers.
  • lactide-rich copolymers such as poly(lactide-co-glycolide) (PLA-co-GA), poly(lactide-co-3hydroxypropionate) (PLA-co-3HP), and poly(lactide-co- ⁇ -caprolactone) (PLA-co- ⁇ -CL) copolymers.
  • the comonomers such as glycolide, 3hydroxypropionate, and ⁇ -caprolactone copolymerized with L and D enantiomers so that those comonomers can be inserted into PLA backbone to improve the flexibility and compostability of PLA copoly
  • the PLA copolymers can be either semi-crystalline or amorphous, depending on the ratio of the D, L enantiomers as well as non-lactide monomers.
  • low Tg flexible home compostable biopolymers include polybutylene succinate-co-adipate (PBSA) resins and polycaprolactone (PCL) resins.
  • PBSA resins could be but not limited to PTT MCC BioPBSTM FD92PM, which has a glass transition temperature (Tg) -47 °C and a melting temperature (Tm) 87 °C, and a melt flow index 4 g/10min. at 2.16Kg/190 °C standard condition.
  • suitable example of PCL resins could be but not limited to Ingevity CAPA ⁇ 6500D or CAPA ⁇ 6800D, which has a glass transition temperature (Tg) about -60 °C and a melting temperature (Tm) about 58 °C.
  • the melt flow index is 18 g/10min. for CAPA6500D and 2.4 g/10min. for CAPA6800D, tested with 2.16 kg load and 1” PVC die at 160 °C.
  • Those biodegradable polymers are certified for both industrial composting and home composting by TUV Austria Group.
  • Poly(butylene adipate-co-butylene-terephthalate) (PBAT) resin is also a low Tg flexible biopolymer.
  • PBAT resins is BASF ecoflex ⁇ C1200, which has a density of about 1.25 g/cm3, a glass transition temperature of about ⁇ 30 °C, a melt flow index of 2.7 to 409 g/10min. at the condition of 2.16Kg/190 °C.
  • the PBAT melts between 50 °C and 150 °C with a flat peak at about 120 °C and has a very low crystallinity of only around 15%.
  • multi-functional epoxidized or maleic anhydride grafted polymeric resins can chemically react with the chain end groups (-COOH) of polyesters. Suitable examples of multi-functional reactive polymeric resins with the functional groups include amorphous maleic anhydride modified SEBS KratonTM FG 1924 polymer and Dow Biomax® SG 120 resin.
  • KratonTM FG 1924 polymer is an amorphous elastomer having a glass transition temperature of -90 °C for its polybutadiene blocks and a Tg of 100 °C for its polystyrene blocks, the weight percentage of polystyrene blocks is only about 17 wt %. Therefore, FG 1924 is a very rubbery material with excellent flexibility for modification at a low loading amount to achieve good noise dampening effect.
  • Biomax SG 120 is a type of epoxidized ethylene-acrylate copolymers or terpolymers (non-biodegradable polyolefin elastomers) with contemplated structures of ethylene-n-butyl acrylate-glycidyl methacrylate, ethylene-methyl acrylate-glycidyl methacrylate, ethylene-glycidyl methacrylate, or blends thereof.
  • This additive has a density of about 0.94 g/cm3, a melt flow rate of about 12 g/10min. at 190 °C/2.16 kg test condition, a melting point of about 72 °C, and a glass transition temperature of about ⁇ 55 °C.
  • spherical antiblocks are necessary for film making.
  • the spherical antiblocks includes crosslinked silicone polymer such as Tospearl® grades of polymethlysilsesquioxane of nominal 2.0 and 3.0 ⁇ m sizes and sodium aluminum calcium silicates of nominal 3 ⁇ m or 5 ⁇ m in diameter (such as Mistui Silton® JC-30 and JC-50).
  • PLA10A is an antiblock masterbatch comprising 5 wt % Silton® JC-30 particles and 95 wt % amorphous PLA carrier resin Luminy®LX975, it was made through toll compounding.
  • migratory slip additives may also be contemplated to control COF properties such as fatty amides (e.g. erucamide, stearamide, oleamide, etc.) or silicone oils ranging from low molecular weight oils to ultrahigh molecular weight polysiloxane gums.
  • fatty amides e.g. erucamide, stearamide, oleamide, etc.
  • silicone oils ranging from low molecular weight oils to ultrahigh molecular weight polysiloxane gums.
  • PLA FILM FORMULATION An embodiment relates to a solution that lowers the heat seal initiation temperature (SIT), enhance the plateau heat seal strength, and broadens the heat seal range of typical amorphous PLA (Polylactic acid) heat seal resins.
  • the oriented biodegradable composite films include a heat sealable layer comprising 20 to 60 wt % amorphous polylactic acid resins; 20 to 70 wt % polybutylene succinate co-adipate (PBSA) resins; 5 to 35 wt % PCL resins; and 0.05 to 3 wt % slip and antiblocking agents for slip and blocking control.
  • PBSA polybutylene succinate co-adipate
  • a second layer (B) which is the core layer including a modified PLA- rich (PLA content by weight is ⁇ 60%) biodegradable composite on one side of the sealable layer.
  • This second biodegradable composite layer (B) could be considered as the base layer to provide the bulk strength of the coextruded laminate film.
  • the core layer (B) comprise a modified PLA-rich (PLA wt % ⁇ 60%) biodegradable composite comprising PLA resins, preferably, crystalline PLA resins, certified home compostable polymeric resins with a glass transition temperature of Tg ⁇ 10°C such as PBSA and PCL, PBAT, and PHA resins, and optionally an amount of enzymes, aliphatic acids, and plasticizers or mixture thereof that act as processing aids or hydrolytic promoter or the combination thereof to enable PLA resins in the core layer compostable at lower composting temperature.
  • PLA resins preferably, crystalline PLA resins, certified home compostable polymeric resins with a glass transition temperature of Tg ⁇ 10°C such as PBSA and PCL, PBAT, and PHA resins
  • an amount of enzymes, aliphatic acids, and plasticizers or mixture thereof that act as processing aids or hydrolytic promoter or the combination thereof to enable PLA resins in the core layer compostable at lower composting temperature.
  • the core layer (B) may include flexible biodegradable polymers with a glass transition temperature of Tg ⁇ 10 °C and a melting temperature of 56°C ⁇ Tm ⁇ 180 °C such as PCL, PBSA, and PHA polymers working together with those flexible biodegradable polymers in the heat seal layer (C) to improve the hermeticity and increasing the plateau heat seal strength reducing the SIT.
  • a total amount of the indicated flexible biodegradable polymers added in the core layer is in the range of 5 to 30 wt % of the total weight of the core layer (B) for improved hermeticity.
  • the core layer (B) can also include inorganic antiblock particles, fillers and slip additives selected from amorphous silicas, aluminosilicates, sodium calcium aluminum silicates, calcium carbonate, crosslinked silicone polymers, and/or polymethylmethacrylates to act as antiblocks for film handling or machinability. Suitable amounts range from 0.03 wt. % to 0.5 wt. % of the core layer and typical particle sizes of 2.0-6.0 ⁇ m in diameter. If so desired, cavitating agents may be added to the core layer (B) such that upon biaxial orientation, voids are formed within this layer, thus rendering the film a matte or opaque and often, pearlescent white appearance.
  • inorganic antiblock particles, fillers and slip additives selected from amorphous silicas, aluminosilicates, sodium calcium aluminum silicates, calcium carbonate, crosslinked silicone polymers, and/or polymethylmethacrylates to act as antiblocks for film handling or machinability. Suitable amounts range from 0.03
  • cavitating agents may in inorganic particles such as calcium carbonate, talc, or other minerals; or polymeric cavitating agents such as polystyrene, cyclic olefin copolymer, or other polymers. Titanium oxides may also be incorporated with the cavitating agent to provide a brighter white appearance.
  • semi- crystalline polycaprolactone (PCL) and polybutylene succinate-co-adipate (PBSA) are selected to be dry-blended or melt-blended with the amorphous PLA resin.
  • the heat seal resin composition comprises 20 to 60 wt % amorphous polylactic acid resins; 20 to 70 wt % polybutylene succinate co-adipate (PBSA) resins; 5 to 35 wt % PCL resins; and 0.05 to 3 wt % slip and antiblocking agents for slip and blocking control.
  • the modifier resins PCL and PBSA in the loading range in the invention have been found not only to sufficiently lower the seal initiation temperature, broaden the heat sealing temperature window, and enhance the plateau seal strength, but also maintain the processability during film-making as well as to help keep the sealant layer home compostable.
  • Both PCL and PBSA can crystallize much faster than semi-crystalline PHA resins or PBAT resins, and they have a sharp crystallization peak, indicating less defect in the crystals of PCL and PBSA, as they cool in sealing process compared to PHA resins.
  • Quick solidifying and crystallization provide a huge advantage to heat sealing performance and lowering heat sealing cycle time.
  • both polymers also have the advantage of being fully biodegradable and home compostable and promoting the home compostability of amorphous PLA resins. This is important to maintain the overall biodegradability and / or compostability of the whole multi-layer film structure.
  • the semi-crystalline biopolymeric resins PCL and PBSA have a melting temperature in the range of 56 °C ⁇ Tm ⁇ 90 °C and a glass transition temperature lower than 0 °C (Tg ⁇ 0°C). Therefore, the sealant layer can have a function of preventing from easy blocking in the hot weather conditions such as a summer season and improved SIT by at least 30 °F.
  • the SIT is reduced from 193 °F (a SIT of amorphous PLA sealant layer in the PLA control film) to 152 °F and in the meantime home compostability of the heat sealant layer per AS 5810-2010 standard is maintained in less than 12 months.
  • the laminate could further include a third layer (A) on the core layer (B), opposite the heat sealable layer (C) for use as a printing layer (i.e. printing ink receiving layer) or metal receiving layer or coating receiving layer.
  • This third layer (A) of this laminate can comprise a modified PLA-rich composite which are either the same as the composite in the core layer or a different blend or a mixture thereof.
  • This third layer (A) could also incorporate various additives such as antiblock particles for film-handling purposes.
  • this third layer (A) could also include the same or similar composition as the inventive sealable layer (C), thus rendering the overall multi-layer film a two-side sealable film.
  • the heat sealable layer (C) can include an antiblock component selected from the group consisting of amorphous silicas, aluminosilicates, sodium calcium aluminum silicates, crosslinked silicone polymers, and polymethylmethacrylates to aid in machinability and winding and to lower coefficient of friction (COF) properties. Suitable amounts range from 0.03 to 2 wt % of the heat sealable layer and typical particle sizes of 2.0-6.0 ⁇ m in diameter, depending on the final thickness of this layer. Migratory slip additives may also be contemplated to control COF properties such as fatty amides (e.g.
  • the third PLA-based layer (A) can include similar amounts of antiblock and slip additives as the respective core and heat sealable layers, although the amounts are likely to be optimized for performance.
  • the core layer (B) it is not necessary for the core layer (B) to include antiblock particles (although migratory additives may still be included in the core layer as a reservoir from which such additives may migrate to the outer surface layers as desired).
  • migratory slip additives not to be used as these types of materials may adversely affect the metal adhesion or metallized gas barrier properties of the metallized BOPLA film. It is thought that as the hot metal vapor condenses on the film substrate, such fatty amides or silicone oils on the surface of the film could vaporize and cause pin-holing of the metal-deposited layer, thus compromising gas barrier properties. Thus, only non-migratory antiblock materials should be used to control COF and web-handling.
  • the discharge- treated surface has a corona discharge-treated surface formed in an atmosphere of CO 2 and N 2 to the exclusion of O2.
  • the laminate film embodiments could further include a vacuum- deposited metal layer on the discharge-treated layer's surface.
  • the metal layer has a thickness of about 5 to 100 nm, has an optical density of about 1.5 to 5.0, and includes aluminum, although other metals can be contemplated such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gold, or palladium, or alloys or blends thereof.
  • multi-layer biodegradable composite film was made using a process of coextrusion and sequential orientation.
  • the laminate was coextruded at temperatures of about 160 °C to 210 °C through a 12-inch wide die, cast at a casting speed of about 6 meter per minute (mpm) on a chill drum with temperatures controlled between 15 °C and 30 °C using an electrostatic pinner, and then oriented in the machine direction 2 to 3.5 times through a series of heated and differentially sped rolls controlled at about 50 °C to 65 °C, followed by transverse direction stretching about 3 to 5.0 times in a tenter oven with temperatures controlled at about 75 °C to 90 °C and then annealed at about 90 °C to 140 °C to reduce internal stresses to minimize shrinkage and give a relatively thermally stable biaxially oriented sheet.
  • this invention provides a method to allow the production of improving the heat sealing performance of a biaxially oriented compostable composite film using biodegradable and compostable modifiers. Such a film method and composition can result in faster packaging speeds with less issues in distortion and heat sealing failure while maintaining attractive appearance, and compostability.
  • this invention relates to a multi-layer biaxially oriented compostable composite film with a formulation to improve the heat seal initiation and hermeticity of heat sealing while maintaining good optical clarity of the film's appearance, compostability, as well as reduction in modulus level for sound dampening in the composite film.
  • the invention involves the use of certified home compostable polymeric resins with low a glass transition temperature of Tg ⁇ 10 °C and a melting temperature of 56 °C ⁇ Tm ⁇ 180 °C formulated with PLA resin in the core layer to improve the compostability and sealability of the composite film for packaging applications, providing a film with good hermeticity, good optical clarity, and lower modulus level for noise reduction.
  • the laminate film includes a two-layer biaxially oriented coextruded film of a core layer (B) including a modified PLA-rich biodegradable composite and a heat sealable layer (C) including amorphous polylactic acid (PLA), poly(butylene succinate-co-adipate (PBSA), and polycaprolactone (PCL).
  • the side of the core layer (B) opposite the heat sealable layer (C) can be discharge-treated.
  • the film includes a second outer skin layer (A) disposed on the side of the core layer (B) opposite the heat sealable layer (C).
  • This second outer skin layer (A) can comprise the same biodegradable composite as in the core layer or a blend of different biodegradable polymers and a small amount of slip or antiblocking additives. Generally, it is desirable to discharge-treat the exposed surface of this outer skin layer in order to provide further functionality as a surface to receive metallization, printing, coating, or laminating adhesives.
  • Core layer (B) [0177]
  • the core layer (B) comprises a modified PLA-rich (PLA wt % ⁇ 60) biodegradable composite comprising PLA resins, preferably, crystalline PLA resins.
  • the core layer has PLA resin in an amount about 60 wt %, 65 wt %, 70 wt %, 75 wt %, 80 wt %, 85 wt %, 90 wt %, 95 wt % or more of the total weight of the core layer.
  • the core layer comprises low Tg flexible polymeric resins such as PBAT, PBS, PBSA, PCL, PBHV (which is a PHA resin but with a Tm of 175 to 180 °C), semi- crystalline PHA (-5°C ⁇ Tg ⁇ 10 °C), amorphous PHA (Tg ⁇ -10 °C), a small amount of rubbery petroleum-based elastomer such as KratonTM FG polymer and BIOMAX SG 120, and a small amount of enzymes, aliphatic acids and plasticizers or mixture thereof that act as a hydrolytic promoter to enable PLA resins in the core layer compostable under lower temperatures.
  • low Tg flexible polymeric resins such as PBAT, PBS, PBSA, PCL, PBHV (which is a PHA resin but with a Tm of 175 to 180 °C), semi- crystalline PHA (-5°C ⁇ Tg ⁇ 10 °C), amorphous PHA (Tg ⁇
  • the flexible biodegradable semi-crystalline polymers have a glass transition temperature of Tg ⁇ 10 °C and a melting temperature Tm in the range of from 56 °C to 180 °C, resulting in hermetic sealing performance together with the modifier resins in the heat sealable layer.
  • the amount of the low Tg flexible biodegradable polymer is in the range of 5 wt % to 30 wt % the total weight of the core layer, with minimum value selected from 5 wt %, 7 wt %, 10 wt %, 12 wt %, 15 wt %, 20 wt % and the maximum value selected from 30 wt %, 25 wt %, 20 wt %, 10 wt % of the total weight of the core layer.
  • the core layer has crystalline PHA resin, amorphous PHA resin, certified home compostable polymeric resins with glass transition temperature Tg ⁇ 0 °C such as PBSA and PCL, and an amount of crystalline PLA resins (20% ⁇ PLA wt % ⁇ 40%) to enhance the bulk strength of the coextruded laminate film.
  • an amount of 5 to 30 wt % flexible biodegradable polymers PCL or PBSA is added into the core layer to improve hermeticity, with minimum value selected from 5 wt %, 7 wt %, 10 wt %, 12 wt %, 15 wt %, 20 wt % and the maximum value selected from 30 wt %, 25 wt %, 20 wt %, 10 wt % of the total weight of the core layer.
  • the Tm of semi-crystalline PLA resins used in PLA-rich core layer is preferably in the range of 145 to 155°C since PHA resins are not thermally stable at extrusion temperature higher that 165°C.
  • the melting temperature of PHA resins is lower than 180 °C, 155 °C, 150 °C, 145 °C, 140 °C, 135 °C, 130 °C or lower.
  • suitable examples of crystalline PLA for this invention include NatureWorks® IngeoTM PLA4032D and PLA4043D or PLA2003D or Total Energys Corbion Luminy ⁇ LX575 and LX175. These resins have a melt flow rate of about 3.9-4.19/10min. at 190 °C/2.16Kg test condition, a crystallization temperature of about 145-170 °C, a glass transition temperature of about 55-62 °C, a density of about 1.25 g/cm3. Molecular weight Mw is typically about 200,000; Mn typically about 100,000; polydispersity about 2.0.
  • PLA4032D and LX575 has a melting point of about 165-173 °C, which are more preferred crystalline PLA resins for thermal resistance application.
  • IngeoTM PLA4043D and Luminy ⁇ LX175 has a melting point of about 145- 152 °C, lower Tm melting temperature of those PLA resins have the advantages of the capability of being extruded at lower extrusion temperatures as blended with biopolymers with poor thermal stability such as PHA resins.
  • suitable amorphous PLA resins for this invention include NatureWorks® IngeoTM 4060D and TotalEnergies Corbion Luminy ⁇ LX975.
  • Those resins have a relative viscosity of about 3.25-3.75, a glass transition temperature of Tg about 52-60 °C (softening temperature), heat seal initiation temperature of about 93 °C, a density of about 1.24 g/cm3. Molecular weight Mw is about 180,000 g/mole.
  • Tg glass transition temperature
  • Tg glass transition temperature
  • Molecular weight Mw is about 180,000 g/mole.
  • examples of low Tg flexible home compostable biopolymers include polybutylene succinate-co-adipate (PBSA) resins and polycaprolactone (PCL) resins.
  • PBSA resins could be PTT MCC BioPBSTM FD92PM, which has a glass transition temperature (Tg) -47 °C and a melting temperature (Tm) 87 °C, and a melt flow index 4 grams/10min. at 190 °C/2.16Kg standard condition.
  • PCL resins could be Ingevity CAPA ⁇ 6500D or CAPA ⁇ 6800D, which has a glass transition temperature (Tg) about -60 °C and a melting temperature (Tm) about 58 °C and melt flow index of 18 g/10min. and 2.4 g/10min. for CAPA6800D tested with 2.16 kg load and 1” PVC die at 160 °C.
  • Tg glass transition temperature
  • Tm melting temperature
  • melt flow index 18 g/10min. and 2.4 g/10min.
  • CAPA6800D tested with 2.16 kg load and 1” PVC die at 160 °C.
  • Those biodegradable polymers are certified for both industrial composting and home composting by TUV Austria Group.
  • examples of certified industrial compostable low Tg biopolymers include poly(butylene adipate-co-butylene-terephthalate) (PBAT) resins.
  • PBAT resins could be BASF ecoflex ⁇ C1200, which has a density of about 1.25 g/cm3, a glass transition temperature of about ⁇ 30 °C.
  • the PBAT melts between 50 °C and 150 °C with a flat peak at about 120 °C and has a very low crystallinity of only around 15%. a Vicat softness of about 91°C, it is a very rubbery and soft biopolymer.
  • Ecoflex ⁇ C1200 can provide good effects on modulus reduction and sound dampening. Unfortunately, PBAT is not certified for home compostable application.
  • TianAn EnmatTM Y1000P, poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV) has only about 1.5 mol % 3-hydroxyvalerate (3HV) in the copolymer chain.
  • Short chain segment 3HV can incorporate into PHB crystals, leading to a high melting point of 175 to 180 °C and a high crystallinity (78%) based on DSC test result.
  • PHBV has a glass transition temperature of about 2 °C similar to that of other semi-crystalline PHA resins, and a melt flow index 8 to 15 g/10min., and a density of 1.25 g/cm3.
  • a reversed extrusion temperature profile is preferably needed to extrude the PHBV resin for preventing from significant thermal degradation, preferably, an amount of low Tm flexible biopolymers, amorphous biopolymers, and plasticizers or mixture thereof is being blended into the PHBV resin in the core layer as processing aids or lubricants in extrusion to facilitate PHBV melting in extrusion so the thermomechanically induced degradation of PHBV can be eliminated to a minimum level.
  • PHA resins with a side chain longer than three carbons Poly(3HB-co- 3HZ) are reported in the article published by Noda et. al.
  • the melting temperature of homopolypropylene is in the range of 160 to 170 °C, which is much higher than that of PHA resins (125 to 145 °C) with longer side chain. Both the lower crystallinity and low melting temperature of PHA resins (Tg is about the same as that of homopolypropylene) with longer side chain result in lower heat resistance and higher heat shrinkage.
  • the core layer (B) further comprises a minority amount of multi- functional epoxidized reactive polymeric or maleic anhydride grafted elastomer materials as chain extender or processing aids or compatibilizer or combination thereof.
  • the epoxy groups on the chain of polymeric materials added in the core layer can chemically react with the chain end groups (-COOH) of polyesters.
  • the maleic anhydride group on the elastomers such as Kraton SEBS polymer can chemically react with the end groups (-OH) of polyester.
  • a polymeric chain extender can help increase or maintain the melt strength during the extrusion of making a film.
  • suitable examples of chain extenders include BASF Joncryl ADR 4468, which has a high number of epoxy group per chain.
  • Suitable amounts of polymeric chain extenders to be blended in the core layer is from 0.1 to 1.5 wt % of the core layer, preferably 0.3 to 1.2 wt %, more preferably, 03 to 0.5 wt %.
  • suitable examples of multi-functional reactive polymeric resins include amorphous maleic anhydride modified SEBS KratonTM FG 1924 polymer and Dow Biomax® SG 120.
  • KratonTM FG 1924 polymer is an amorphous elastomer having a glass transition temperature of -90 °C for its polybutadiene blocks and a Tg of 100 °C for its polystyrene blocks, the weight percentage of polystyrene blocks is only about 17 wt %. Therefore, FG 1924 is a very rubbery material with excellent flexibility for modification at a low loading amount.
  • Biomax SG 120 is a type of epoxidized ethylene-acrylate copolymers or terpolymers (non-biodegradable polyolefin elastomers) with contemplated structures of ethylene-n-butyl acrylate-glycidyl methacrylate, ethylene-methyl acrylate-glycidyl methacrylate, ethylene-glycidyl methacrylate, or blends thereof.
  • This additive has a density of about 0.94 g/cm3, a melt flow rate of about 12 g/10min. at 190 °C/2.16 kg test condition, a melting point of about 72 °C, and a glass transition temperature of about ⁇ 55 °C.
  • Suitable amounts of low Tg petroleum-based elastomer copolymers to be blended in the core layer is from 1 to 8 wt % of the core layer, preferably, 2 to 4 wt % because of the characteristics of non-biodegradability, more preferably, 0.5 to 2 wt % as the modifier is a compatibilizer.
  • the acceptable concentrations of chain extender or epoxidized ethylene-acrylate copolymers added into the core layer of biaxially oriented composite film are determined by the aspects of processability, clarity, and home compostability.
  • an option component of the core layer (B) could be a minority mount of enzymes, aliphatic acids, and plasticizers, metal salts, or mixture thereof that act as processing aids or hydrolytic promoters or the combination thereof to enable PLA resins in the core layer home compostable.
  • hermeticity of the heat sealing of a biodegradable composite film can be improved by adding either amorphous PLA resins or low Tg flexible biopolymers as modifiers into the core layer of a biodegradable composite film, more preferably, semi-crytalline biopolymers.
  • modifiers amorphous PLA and low Tg polymeric modifiers and low molecular weight additives
  • a thermally, dimensionally stable film is important if the substrate is to be used as a metallizing, printing, coating, or laminating substrate due to the heating elements or factors in downstream processes.
  • the oriented biodegradable composite film is desired as a heat shrinkable film, this composition and appropriate processing conditions might be suitable.
  • the core resin layer can be surface treated on the side opposite the skin layer by those well-known skills in the art. This treated core layer is then well suited for subsequent purposes of metallizing, printing, coating, or laminating, the preferably embodiment being for printing.
  • the core resin layer (B) is typically 8 ⁇ m to 100 ⁇ m in thickness after biaxial orientation, preferably between 10 ⁇ m and 50 ⁇ m, and more preferably between about 15 ⁇ m and 25 ⁇ m in thickness.
  • a preferred embodiment is to use the higher crystalline, higher L- lactide content PLA such as Ingeo ⁇ 4032D and Luminy ⁇ LX575 to achieve lower heat shrinkage and better thermal stability if home compostability could be achieved by adding biodegradable promoters such as low Tg flexible PCL, PBSA, PHA and other PLA-biodegrading additives.
  • biodegradable promoters such as low Tg flexible PCL, PBSA, PHA and other PLA-biodegrading additives.
  • Heat sealable layer (C), a first outer layer [0197]
  • suitable biopolymers to formulate the heat sealable layer together with amorphous PLA reins could be those certified home compostable biopolymeric resins having a melting temperature Tm in the range of 56 °C ⁇ Tm ⁇ 90 °C and a glass transition temperature Tg lower than 0 °C (Tg ⁇ 0 °C). Aside from low SIT, broader heat sealing window, and high plateau heat seal strength, the sealant layer is needed to have a function of preventing from blocking as well as a function of noise dampening.
  • the blend of components in the heat seal layer improves the seal initiation temperature by at least 20 to 25 °F, preferably, 40 °F.
  • the SIT is reduced from 193 °F (89 °C, SIT of amorphous PLA sealant layer) to 152 °F (67 °C) using certified home compostable biodegradable polymers.
  • suitable resins to formulate the sealant layer (C) for improvement of heat seal initiation and plateau heat seal strength is polybutylene succinate co- adipate (PBSA) resin.
  • PBSA is a random co-polyester synthetized by the reaction of 1,4-butanediol with aliphatic dicarboxylic acids such as succinic and adipic acids.
  • Example of PBSA resins could be PTTMCC BioPBSATM FD92PM, which is commercially available from Mitsui Plastics. FD92PM has 36 wt % renewable source content derived from renewable succinic acid.
  • PBSA typically has a melting temperature point of about 87 °C, a density of about 1.24 g/cm3, a glass transition temperature of about ⁇ 47 °C, a crystallinity of about 30%, a melt flow index of 4 g/10min. at 190°C/2.16Kg test condition.
  • FD92PM has been certified for both industrial and home composting application.
  • another suitable resin to improve further the heat sealing properties of amorphous PLA is poly ⁇ -caprolactone.
  • PCL is a polyester produced by the ring-opening of ⁇ - caprolactone in the presence of aluminum isopropoxide and is currently made from petroleum- based monomers. PCL has been certified for both industrial and home composting application by TUV Austria Group.
  • PCL resins could be Ingevity CAPA®6500D or CAPA®6800D, which has a melting temperature of about 58°C, a glass transition temperature of about ⁇ 60 °C, a density of about 1.15 g/cm3, a crystallinity of about 48%, and a melt flow index of 18 g/10min. and 2.4 g/10min. for CAPA6800D respectively tested with 2.16 kg load and 1” PVC die at 160 °C.
  • PBAT poly(butylene adipate-co-butylene- terephthalate)
  • PBAT resins could be BASF ecoflex® C1200, which has a Tg of about ⁇ 30 °C and low crystallinity of around 15%, giving a broad melting peat between 50 °C and 150 °C with a peak value at about 120 °C. It is a very rubbery and soft biopolymer and can provide good effects on modulus reduction and sound dampening. PBAT is only certified for industrial composting application. [0202] In an embodiment, PHA resins having a very slow crystallization rate unfortunately are often undesirable for use in heat sealant layer of a biodegradable composite film. Amorphous PHA resin is not suitable for use in the heat seal layer since it does not solidify at ambient or sealing temperatures due to its low glass transition temperature.
  • a first heat sealable layer (C) (that is the first outer skin layer) comprises certified home compostable semi-crystalline polycaprolactone (PCL), polybutylene succinate-co- adipate (PBSA) and amorphous PLA resin.
  • Suitable composition for improving the heat seal properties comprises 20 to 60 wt % amorphous polylactic acid resins; 20 to 70 wt % PBSA resins; 5 to 35 wt % PCL resins; and 0.05 to 3 wt % slip and antiblocking agents for slip and blocking control. Quantity of the modifying resin in the range have been found to sufficiently lower the seal initiation temperature yet maintain the processability during film-making as well as to help keep the sealant layer home compostable.
  • Both PBSA and PCL can crystallize much faster than semi- crystalline PHA resins and have a sharp crystallization peak, indicating less defect in the crystals of PBSA and PCL, as they cool in sealing process compared to PHA resins.
  • Quick solidifying and crystallization have a huge advantage to heat sealing performance and lowering heat sealing cycle time.
  • Those two resins also have the advantage of being fully biodegradable and home compostable, they could also promote the home compostability of amorphous PLA resins in the heat seal layer. This is very important to maintain the overall biodegradability and/or compostability of the whole multi-layer coextruded film.
  • this first heat sealable layer (C) can include an antiblock component selected spherical crosslinked silicone polymer such as Tospearl® grades of polymethlysilsesquioxane of nominal 2.0 and 3.0 ⁇ m sizes and sodium aluminum calcium silicates of nominal 3 ⁇ m or 5 ⁇ m in diameter (such as Mistui Silton® JC-30 and JC-50), but other suitable spherical inorganic antiblocks can also be used including polymethylmethacrylate, silicas, and silicates, and ranging in size from 2 ⁇ m to 6 ⁇ m.
  • an antiblock component selected spherical crosslinked silicone polymer such as Tospearl® grades of polymethlysilsesquioxane of nominal 2.0 and 3.0 ⁇ m sizes and sodium aluminum calcium silicates of nominal 3 ⁇ m or 5 ⁇ m in diameter (such as Mistui Silton® JC-30 and JC-50)
  • suitable spherical inorganic antiblocks can also be used including polymethylme
  • Migratory slip agents such as fatty amides or silicone oils can also be optionally added to the heat seal resin layer of types and quantities mentioned previously if lower COF is desired.
  • the films of this invention are desired to be used for metallizing or high definition process printing, it is recommended that the use of migratory slip additives be avoided or minimized in order to maintain metallized barrier properties and metal adhesion or to maintain high printing quality in terms of ink adhesion and reduced ink dot gain.
  • Suitable amounts of slip additives to use can range from 300 ppm to 10,000 ppm of the layer.
  • the thickness of the heat sealable layer is in the range of 1 to 4 ⁇ m, more preferably, 2 to 3 ⁇ m.
  • Second outer skin layer (A), a third layer [0205]
  • a second outer skin layer (A) on the core layer (B) opposite the heat sealable layer (C) (with a coextruded laminate structure of A/B/C) could be included into the coextruded laminate film for use as a printing layer (i.e. printing ink receiving layer) or metal receiving layer or coating receiving layer.
  • This second outer skin layer (A) of this laminate could include biodegradable composite comprising the same compositions as the composite in the core layer or a different blend thereof.
  • the second outer skin layer could comprise a majority of crystalline PLA, PBSA and PCL composition for improving heat resistance.
  • This second outer skin layer (A) could also incorporate various additives such as antiblock particles for film-handling purposes. If desired, this third layer (A) could also include the same or similar composition as the inventive sealable layer (C), thus rendering the overall multi-layer film a two-side sealable film.
  • the second outer skin layer (A) can include similar amounts of antiblock and slip additives as the respective core and heat sealable layers, although the amounts are likely to be optimized for performance. In this embodiment, it is not necessary for the core layer (B) to include antiblock particles (although migratory additives may still be included in the core layer as a reservoir from which such additives may migrate to the outer surface layers as desired).
  • migratory slip additives not be used as these types of materials may adversely affect the metal adhesion or metallized gas barrier properties of the metallized BOPLA film. It is thought that as the hot metal vapor condenses on the film substrate, such fatty amides or silicone oils on the surface of the film could vaporize and cause pin- holing of the metal-deposited layer, thus compromising gas barrier properties. Thus, only non- migratory antiblock materials should be used to control COF and web-handling.
  • antiblocks include crosslinked silicone polymer (polymethlysilsesquioxane) such as Tospearl® grades 120 and 130 of about 2.0 and 3.0 ⁇ m sizes, and sodium aluminum calcium silicates of about 3 ⁇ m and 5 ⁇ m in diameter such as Mitsui Silton® JC-30 and JC-50.
  • polymethlysilsesquioxane polymethlysilsesquioxane
  • sodium aluminum calcium silicates of about 3 ⁇ m and 5 ⁇ m in diameter
  • Mitsui Silton® JC-30 and JC-50 Suitable spherical inorganic antiblocks can be used including polymethylmethacrylate, silicas, and silicates, and ranging in size from 2 to 3 ⁇ m.
  • an amount of migratory slip agents in the art could be included to lower COF if desired.
  • Suitable amounts of slip additives to use can range from 300 ppm to 10,000 ppm of the layer.
  • the thickness of the second outer skin layer is in the range of 0.5 to 2 ⁇ m, more preferably, 1 to 1.5 ⁇ m.
  • the second outer skin layer (A) should not include those additives.
  • the second outer skin layer (A) can function as a cap layer to eliminate additive migration from the core layer to the surface of the second outer skin layer (A).
  • This second outer skin layer is often formulated with materials that are conducive to receiving printing inks, metallizing, adhesives, or coatings.
  • the skills of discharge-treatment in the above embodiments are well known in the art.
  • the embodiments of the coextruded laminate film could further include a primer layer on the discharge-treated layer's surface and a barrier coating layer over the primer layer by offline coating process.
  • a vacuum-deposited metal layer could be coated on the barrier layer to further improve barrier properties.
  • the metal layer has a thickness of about 5 to 100 nm, has an optical density of about 1.5 to 3.0, and includes aluminum, although other metals can be contemplated such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gold, or palladium, or alloys or blends thereof.
  • PHA FILM FORMULATION [0214]
  • the multilayer film is a three-layer film comprising a PHA-rich core layer sandwiched by two outer skin layers, the core layer is considered as the base layer to provide the bulk strength and mechanical properties of the oriented composite film.
  • the core layer (B) comprises PHA resin at an amount of more than 50 wt % of the total weight of the core layer and non-PHA based modifier X at an amount of less than 50 % of the total weight of the core layer.
  • the PHA resins in the core layer include semi-crystalline PHA resins with a glass transition temperature of Tg ⁇ 10 °C such as PHB, PHBV, PHB-co-3HHx, and PHB- co-3HO, and PHB-co-3HD resins, and optionally a small amount of amorphous PHA resins.
  • the modifier X in the core layer comprises biopolymers including PBA, PBSA, PCL, PLA as well as PLA copolymers such as PLA-co-3HP, PLA-co- ⁇ -CL and PLA-co- GA resins having a glass transition temperature of Tg ⁇ 60 °C and a melting temperature Tm in the range of from 56 °C ⁇ Tm ⁇ 165 °C, preferably, the Tm is in the range of from 56 to 155°C.
  • the core layer (B) comprises a desirable amount of low Tg flexible biopolymers working together with the resins in the heat seal layer (C) to improve the SIT, hermeticity, and plateau heat seal strength.
  • a total amount of the adequate low Tg flexible biodegradable polymers added in the core layer is in the range of 5 wt % to 25 wt % of the total weight of the core layer.
  • the low Tg flexible biopolymers including amorphous PHAs, PBSA, PCL and PBAT can enhance the plateau heat seal strength and broadens the heat seal range typically provided by amorphous PLA heat seal resins. They can also reduce the modulus and so that they can dampen the noise of a composite film if desired.
  • rigid biopolymers such as but not limited to PHB, PHBV, and PLA resins in the core layer do not improve the heat seal properties regarding SIT and plateau seal strength.
  • the core layer (B) can include processing aids, antioxidants, plasticizers, nucleating agents, inorganic particles, fillers, lubricants and slip additives.
  • cavitating agents could be added to the core layer (B) such that upon biaxial orientation, voids are formed within this layer, thus rendering the film a matte or opaque and often, pearlescent white appearance.
  • cavitating agents may in inorganic particles such as calcium carbonate, talc, or other minerals; or polymeric cavitating agents such as polystyrene, cyclic olefin copolymer, or other polymers. Titanium oxides may also be incorporated with the cavitating agent to provide a brighter white appearance.
  • the heat sealable layer comprises PLA resin at an amount of 5 to 80 wt % and modifier Y at an amount of 20 to 95 wt % of the total weight of the heat seal layer.
  • the modifier Y in the heat seal layer comprises PBSA at an amount of 20 to 95 wt % and PCL at an amount of 0 to 30 wt % of the total weight of the heat seal layer, and a desirable amount of antiblocks and slip additive for slip and blocking control.
  • the modifier resins PBSA and PCL in the desirable loading range have been found not only to sufficiently lower the seal initiation temperature, broaden the heat sealing temperature window, and enhance the plateau seal strength, but also maintain the processability during film-making as well as to help keep the sealant layer home compostable since amorphous PLA resin is not home compostable.
  • Both PBSA and PCL can crystallize much faster than semi- crystalline PHA resins or PBAT resins, and they have a sharp crystallization peak, indicating less defect in the crystals of PCL and PBSA, as they cool in sealing process compared to PHA resins.
  • Quick solidifying and crystallization provide a huge advantage to heat sealing performance and lowering heat sealing cycle time.
  • both polymers also have the advantage of being fully biodegradable and home compostable and promoting the home compostability of amorphous PLA resins. This is important to maintain the overall biodegradability and / or compostability of the whole multi-layer film structure.
  • the semi-crystalline biopolymeric resins PCL and PBSA have a melting temperature in the range of 56 °C ⁇ Tm ⁇ 90 °C and a glass transition temperature lower than 0 °C (Tg ⁇ 0°C). Therefore, the sealant layer can have a function of preventing from easy blocking in the hot weather conditions such as a summer season and improved SIT by at least 30 °F.
  • the SIT is reduced from 193 °F (a SIT of amorphous PLA sealant layer in the PLA control film) to 160 °F, the composting time of the heat sealant layer per AS 5810-2010 standard could be controlled to less than 12 months.
  • the composite film comprises a second outer skin layer (A) on the top of the core layer (B), opposite the heat sealable layer (C) for use as a printing layer (i.e. print ink receiving layer) or metal receiving layer or coating receiving layer.
  • This second outer layer can comprise either the same composite as in the core layer or a home compostable blend different from that in the core layer.
  • the second outer skin layer (A) could also incorporate various additives such as antiblock particles for film-handling purposes.
  • the heat sealable layer (C) can include an antiblock component selected from the group consisting of amorphous silicas, aluminosilicates, sodium calcium aluminum silicates, crosslinked silicone polymers, and polymethylmethacrylates to aid in machinability and winding and to lower coefficient of friction (COF) properties.
  • Suitable amounts range from 0.03 to 2 wt % of the heat sealable layer and typical particle sizes of 2.0-6.0 ⁇ m in diameter, depending on the final thickness of this layer.
  • a suitable amounts of slip additives can also be included at a amount in the range from 300 ppm to 10,000 ppm of the layer.
  • the layer (A) could also include the same or similar composition as the heat sealable layer (C), thus rendering the overall multi-layer film a two-side sealable film.
  • the outer skin layer (C) could also include the same or similar composition as that in the non-heat sealable layer (A), thus rendering the overall multi-layer film a three-layer non- heat sealable film.
  • all three layers of the film could comprise the same materials, thus rendering the overall multi-layer film a monolayer composite film.
  • the third layer (A) can include similar amounts of antiblock and slip additives as the respective core and heat sealable layers, although the amounts are likely to be optimized for performance.
  • the core layer (B) it is not necessary for the core layer (B) to include antiblock particles (although migratory additives may still be included in the core layer as a reservoir from which such additives may migrate to the outer surface layers as desired).
  • migratory slip additives may adversely affect the metal adhesion or metallized gas barrier properties of the metallized BOPLA film.
  • the second outer skin layer (A) is preferable to discharge-treated for lamination, metallizing, printing, or coating.
  • Discharge-treatment in the above embodiments can be accomplished by several means, including but not limited to corona, flame, plasma, or corona in a controlled atmosphere of selected gases.
  • the discharge-treated surface has a corona discharge-treated surface formed in an atmosphere of CO2 and N2 to the exclusion of O2.
  • the laminate film embodiments could further include a vacuum- deposited metal layer on the discharge-treated layer's surface.
  • the metal layer has a thickness of about 5 to 100 nm, has an optical density of about 1.5 to 5.0, and includes aluminum, although other metals can be contemplated such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gold, or palladium, or alloys or blends thereof.
  • multi-layer biodegradable composite film was made using a process of coextrusion and sequential orientation.
  • the coextrusion was conducted at temperatures of about 160 °C to 210 °C by pushing materials through a 12-inch wide die, cast at a casting speed of about 6 meter per minute (mpm) on a chill drum with temperatures controlled between 15 °C and 30 °C using an electrostatic pinner, and then oriented in the machine direction 2 to 3.5 times through a series of heated and differentially sped rolls controlled at about 50 °C to 65 °C, followed by transverse direction stretching about 3 to 5.0 times in a tenter oven with temperatures controlled at about 75 °C to 90 °C and then annealed at about 90 °C to 140 °C to reduce internal stresses to minimize shrinkage and give a relatively thermally stable biaxially oriented sheet.
  • this invention provides a method to allow the production of improving the heat seal performance of a biaxially oriented PHA-rich composite film using biodegradable and compostable modifiers. Such a film method and composition can result in faster packaging speeds with less issues in distortion and heat-sealing failure while compostability.
  • this invention relates to a multi-layer biaxially oriented PHA-rich composite film with a formulation to improve the processability, heat seal properties, mechanical properties, and compostability.
  • the heat sealable resin layer (C) could be coextruded on one side of the core layer (B), the heat sealable layer has a thickness after biaxial orientation of between 0.5 and 5 ⁇ m, preferably between 2.0 and 3.0 ⁇ m.
  • the core layer thickness can be of any desired thickness after biaxial orientation, but preferred and useful thicknesses are in the range of 10 to 100 ⁇ m, preferably 14 to 25 ⁇ m, and even more preferably 15 to 20 ⁇ m.
  • the coextrusion process includes a multi-layered compositing die, such as a two- or three-layer die. In the case of a two-layer coextruded film, a two-layer compositing die can be used.
  • the core layer can be sandwiched between the heat sealable resin layer and a second outer skin layer using a three-layer compositing die.
  • the laminate film is produced via coextrusion of the heat sealable layer and the core layer and other layers if desired, through a compositing die whereupon the molten multilayer film structure is quenched upon a chilled casting roll system or casting roll and water bath system and subsequently oriented in the machine direction (MD) and/or transverse direction (TD) into an oriented multi-layer film.
  • MD machine direction
  • TD transverse direction
  • MDO machine direction orientation
  • TDO transverse direction orientation
  • a relaxation rate of 5 to 15% after TDO can be applied to the oriented film in TD for reducing heat shrinkage.
  • Heat setting conditions in the TDO oven is also critical to minimize thermal shrinkage effects.
  • Those are well-known processes and skills in the art.
  • examples were practiced on a film making line armed with a three-layer 12-inch-wide flat die for molding and capability of orientation in machine direction (MD) and then in transverse direction (TD).
  • the main composition in the core layer is a PLA-rich biodegradable composite described earlier.
  • the multi-layer laminate sheet was coextruded at extrusion temperatures designed for each layer, cast and pinned—using electrostatic pinning—onto a cooling drum whose surface temperature was controlled between 15 °C and 30 °C to solidify the non-oriented laminate sheet at a casting speed of about 7 to 11 mpm (meter per minute).
  • the non-oriented laminate sheet was stretched first in the machine direction at about 50 °C to 65 °C at a stretching ratio of about 2 to about 3.5 times the original length, using differentially heated and sped rollers and the resulting stretched sheet is heat-set at about 40-50 °C on annealing rollers and cooled at about 30-40 °C on cooling rollers to obtain a uniaxially oriented laminate sheet.
  • the uniaxially oriented laminate sheet is then introduced into a tenter oven at a line speed of about 25 to 38 mpm and preliminarily heated between 60 °C and 75°C, and stretched in the transverse direction at a temperature of about 75-95 °C at a stretching ratio of about 3 to 5 times the original width and then heat-set or annealed at about 90-140 °C, and preferably 125-140 °C, to reduce internal stresses due to the orientation and minimize shrinkage and give a relatively thermally stable biaxially oriented sheet.
  • TD orientation rates were adjusted by moving the transverse direction rails in or out per specified increments based on the TD infeed rail width settings and width of the incoming machine-direction oriented film.
  • the biaxially oriented film has a total thickness between 10 and 100 ⁇ m, preferably between 15 and 30 ⁇ m, and most preferably between 17.5 and 20 ⁇ m.
  • the film may optionally be passed through an on-line discharge-treatment system, such as corona, flame, plasma, or corona treatment in a controlled atmosphere as described previously to whatever desired surface energy. Typically, useful surface energy can be 36-50 dyne/cm.
  • the film is then wound into a roll form through film winding equipment.
  • One embodiment is to offline coat a primer coating on the second outer layer (A) to improve the adhesion of barrier coating to the bulk film, and the surface smoothness.
  • primer coatings include polyurethane (PU) coating, polyacrylate coating, and polyethylenimine (PEI) coating.
  • PU polyurethane
  • PEI polyethylenimine
  • One embodiment is to coat a barrier coating on the top of primer layer.
  • the barrier coating could be a waterborne barrier coating solution derivative from any polymers of PVOH, EVOH, PEI, PU, and mixture thereof.
  • the coextruded laminate is a heat sealable film printable on the surface layer opposite the heat sealable layer.
  • the coextruded laminate is two-side heat sealable.
  • the coextruded film is a heat sealable film with a second outer layer to receive a primer, or coating or vacuum-deposited metal layer or the combination thereof.
  • One embodiment is to directly metallize the discharge-treated surface opposite the heat sealable layer.
  • One embodiment is to metallize the coated barrier layer surface opposite the heat sealable layer.
  • One embodiment is to metallize the surface layer with barrier coating added onto the primer coating opposite the heat sealable layer.
  • a protecting coating layer could be coated over the metal layer to prevent from potential metal cracking and further improve barrier properties.
  • the unmetallized laminate sheet or coated primed sheet is first wound in a roll. The roll is placed in a vacuum metallizing chamber, preferably, the sheet is in-chamber pre-treated at a desirable energy level before the metal is vapor-deposited onto the discharge- treated metal receiving layer surface.
  • the metal film may include titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, gold, or palladium, the preferred being aluminum.
  • Metal oxides can also be contemplated, the preferred being aluminum oxide.
  • the metal layer can have a thickness between 5 and 100 nm, preferably between 20 and 80 nm, more preferably between 30 and 60 nm; and an optical density between 1.5 and 5.0, preferably between 2.0 and 3.0.
  • the metallized film is then tested for oxygen and moisture gas permeability, optical density, metal adhesion, metal appearance and gloss, heat seal performance, tensile properties, thermal dimensional stability, and can be made into a laminate structure.
  • Example 1 A three-layer coextruded biaxially oriented PLA film was made as control using sequential orientation on a 12-inch-wide flat die line as described previously, including a core layer (B) formulation of about 85 wt % of the core layer of crystalline Luminy® LX575 with about 15 wt % of the core layer of amorphous Luminy® LX975.
  • the non-sealable layer (A) included about 84.7 wt % crystalline LX575, 15 wt % Luminy® LX975, and 0.3 wt % PLA10A.
  • the coextruded heat sealable skin layer (C) is composed substantially of LX975 at about 94 wt % of the sealant layer, and 6 wt % PLA10A, such that the concentration of antiblock in the layer (C) is about 3000 ppm (0.3 wt %).
  • the overall effective amount of amorphous PLA resin in the layer (C) was about 99.7 wt % due to the LX975 initially added plus the LX975 used as the carrier resin in the antiblock masterbatch.
  • the total thickness of this film substrate after biaxial orientation was about 80 gauges (G) or 0.8 mil or 20 ⁇ m.
  • the thickness of the respective heat sealable resin layer (C) after biaxial orientation was about 8 G (2.0 ⁇ m).
  • the thickness of the core layer (B) after biaxial orientation was about 68 G (17.0 ⁇ m).
  • the thickness of the non-sealable skin layer (A) was about 4 G (1.0 ⁇ m).
  • the outer skin layers and the core layer were melt coextruded at 204 °C together through a twelve-inch flat die to be cast on a chill drum using an electrostatic pinner.
  • the formed cast sheet was passed through a machine-direction orienter to stretch 2.8 times stretch ratio in the machine direction (MD). This was followed by transverse direction (TD) stretching at about 4.5 times stretch ratio in the tenter oven.
  • MD machine direction
  • TD transverse direction
  • the resultant biaxially oriented film was subsequently heat-set and discharge-treated on the surface of the second outer skin layer (A) opposite the heat sealable skin layer (C) via corona treatment. The film was then wound up in roll form.
  • Example 2 [0256] Example 1 was repeated except that the core layer (B) formulation as well as the second outer skin layer (A) was changed to a PLA-rich biodegradable composite (PLA nanoalloy) modified with 20 wt % CAPA® 6500D and biodegradation promoters (the invention in detail was disclosed in the prior art WO2021185339A1).
  • PLA nanoalloy PLA-rich biodegradable composite
  • PLA nanoalloy developed from NANOALLOYTM TECHNOLOGY is a melt blended biodegradable composite comprising 38.3 wt % Luminy® LX575, 38.3 wt % Luminy® LX975, 20.0 wt % Ingevity CAPA®6500D, 2.0 wt % Oleris® sebacic acid provided by Arkema, 1.2 wt % Joncryl ADR4468, and 0.2 wt % Zinc Stearate (BaerlocherTM RSN131HS).
  • PCL is well dispersed into nano to semi-micron scale in PLA phase according to TEM images.
  • the PLA10A in the second outer skin layer (A) was increased to 0.6 wt %.
  • Example 2 was repeated with the same core layer recipe. However, the second outer layer (A) formulation was changed to about 94 wt % LX975 and 6 wt % PLA10A; the heat sealable layer (C) formulation was changed to 64 wt % LX975, 20 wt % FD92PM, 10 wt % CAPA ⁇ 6500D and 6 wt % PLA10A. The overall effective amount of amorphous PLA resin LX975 in the heat sealable layer was reduced from 99.7 to 69.7 wt %.
  • Example 4 [0258] Example 2 was repeated except that the sealant layer (C) formulation was changed to about 54 wt % LX975, 30 wt % FD92PM, 10 wt % CAPA ⁇ 6500D and 6 wt % PLA10A. The extrusion temperature of the heat sealable layer (C) was reduced from 193 °C to 171 °C.
  • Example 5 [0259] Example 4 was repeated except that the sealant layer (C) formulation was changed to about 44 wt % LX975, 40 wt % FD92PM, 10 wt% CAPA®6500D, and 6 wt % PLA10A. The overall effective amount of amorphous PLA resin LX975 was about 49.7 wt %.
  • Example 6 [0260] Example 4 was repeated except that the sealant layer (C) formulation was changed to about 64 wt % LX975, 30 wt % CAPA ⁇ 6500D, and 6 wt % PLA10A. The overall effective amount of the amorphous PLA resin LX975 was about 69.7 wt %.
  • Example 7 [0261] Example 5 was repeated except that the sealant layer (C) formulation was changed to about 24 wt % LX975, 50 wt % FD92PM, 20 wt% CAPA ⁇ 6500D, and 6 wt % PLA10A. The total content of certified home compostable biodegradable polymers with Tg ⁇ 0 °C was increased from 50 wt % to 70 wt %. The effective amount of amorphous PLA resin LX975 was reduced to about 29.7 wt %.
  • Example 8 [0262] Example 7 was repeated except that the second outer skin layer (A) formulation was changed to about the same as that in the heat sealant layer (C).
  • the effective amount of the amorphous PLA LX975 was about 29.7 wt %.
  • the extrusion temperature of the second outer skin layer was changed from 190 °C to 171 °C.
  • Example 9 [0263] Example 2 was repeated except that the sealant layer (C) formulation was changed to 64wt % PLA nanoalloy, 20 wt % FD92PM, 10 wt % CAPA ⁇ 6500D, and 6 wt % PLA10A.
  • the overall effective amount of amorphous PLA resin LX975 was about 30.2 wt %; and the effective amount of crystalline PLA resin LX575 is about 24.5 wt %; and the effective amount of CAPA ⁇ 6500D is about 22.8%.
  • Example 10 The total content of processing aids such as chain extender is 2.2 wt %.
  • Example 10 [0264] Example 2 was repeated except that the sealant layer (C) formulation was changed to about 100 wt % Ecovio ⁇ F2341, and the second outer skin layer (A) was also changed to Ecovio ⁇ F2341. F2341 is certified for home compostable application by TUV Austria Group.
  • RESULTS [0265] Film properties [0266] The biaxially oriented biodegradable composite films were then tested for heat seal properties, optical properties, COF, and mechanical properties. The formulations of the heat sealable layer (C) of the coextruded films made in the Examples (“Ex.”) are shown in Table 1.
  • Table 1 Formulations of the heat sealable layer (C) of the coextruded films made in the Examples ("Ex.”) Sealant layer (C) composition, wt % PLA Example LX975 PLA10A FD92PM CAPA6500D Nanoalloy F2341 Ex.1 94 6 Ex.2 94 6 Ex.3 64 6 20 10 Ex.4 54 6 30 10 Ex.5 44 6 40 10 Ex.6 64 6 30 Ex.7 24 6 50 20 Ex.8 24 6 50 20 Ex.9 0 6 20 10 64 Ex.10 100 [0267] The heat seal curves and hot tack curves of the coextruded films were shown in Figs.1 and 2, respectively. The heat seal properties including hot tack properties are shown in Table 2.
  • Table 2 Heat seal properties and hot tack properties of the coextruded films made in the Examples ("Ex.”) Heat seal properties Hot tack properties Sealing Plateau Plateau Sealing Plateau S IT ( °F ) temp. seal temp. temp. seal Plateau temp.
  • window strength range SIT ( °F ) window strength range ( °F )** Example ( °F )* (g/in) ( °F )** ( °F )* (g/in) Ex.1 193 77 452 60 194 76 524 60 Ex.2 176 64 500 40 174 66 510 50 Ex.3 165 75 1138 40 165 75 498 60 E x.4 163 77 1029 50 165 75 507 60 Ex.5 167 73 1131 50 160 80 446 70 Ex.6 162 78 1105 40 172 68 382 50 Ex.7 152 88 1122 70 160 80 443 70 Ex.8 152 88 1086 60 152 88 434 70 E x.9 160 80 816 40 175 65 250 50 Ex.10 177 63 779 40 207 33 219 30 *Oriented PLA control film wrinkles at about 270°F, and home compostable composite film wrinkles at about 240°F, heat sealing temperature window (°F) maximum sealing
  • Table 4 Mechanical properties of the coextruded films made in the Examples ("Ex.”) Tensile stress (MPa) Elongation at break (%) Modulus (MPa) Examples MD TD MD TD MD TD Ex.1 121 182 133 64 3530 5813 Ex.2 92 154 183 91 3144 3993 Ex.3 76 98 153 110 2821 3387 Ex.4 92 108 180 113 2940 3112 Ex.5 94 92 167 106 2897 2787 Ex.6 89 97 177 130 2948 3240 Ex.7 92 87 153 101 2951 2476 E x. 8 81 99 163 110 2466 2750 E x. 9 93 111 147 133 3012 3286 E x.
  • Example 1 (Ex.1), as Table 1 shows, is the first control film using a biaxially oriented PLA film with almost 100 wt % PLA resins in all three layers.
  • the sealant layer (C) comprised 97.7 wt % amorphous PLA resin LX975, it showed the highest SIT at 193 °F (which is the temperature to obtain 200 g/in (grams per inch) seal strength) among the samples.
  • the control film started wrinkling at 270 °F, so the effective sealing temperature window is in the heat seal range of from 193 °F to 270 °F, which is roughly about 77 °F in terms of how wide the sealing temperature range is.
  • Example 2 is a second control sample comprising a core layer of PLA-rich biodegradable composite resin PLA nanoalloy.
  • the PLA nanoalloy comprised about 20 wt % polycaprolactone CAPA®6500D, 38.9 wt % LX575, 38.9 wt % LX575, 2 wt % sebacic acid, 1.2 wt % Joncryl ADR 4468 and 0.2 wt % Zn St.
  • PCL CAPA®6500D is low-Tg (-60 °C) certified home compostable flexible biopolymer. Sebacic acid, ADR 4468, and Zn St are lubricants and processing aids.
  • PCL is a flexible biodegradable polymer of improving biodegradation and reducing stiffness (modulus and noise) of an oriented film as discussed earlier.
  • the sealant layer (C) achieved a SIT at 176 °F lower than that of the first control sample (Ex.1) even if the sealant layer formulation between two film samples is unchanged.
  • the film sample started wrinkling at about 240°F during heat sealing test due to the low-Tg flexible PCL biodegradable polymer in the core layer, the heat resistance of the composite film is not as good as that of the first control film (BOPLA film).
  • the plateau seal strength is comparable to that of the first control sample, however, the temperature span of both sealing temperature window and plateau temperature range are reduced to 64 °F and 40 °F, respectively.
  • the PCL resin in the core layer tended to give lower SIT results but not a broader heat seal range. Hot tack performance was similar to the heat sealing performance.
  • Examples 3, 4 and 5 comprised about 6% wt % PLA10A, 10 wt % CAPA®6500D, gradually reduced LX975 and increased FD92PM resins as shown in Table 1.
  • Certified home compostable FD92PM was increased from 20 wt % to 40 wt %, in the meantime, LX975 was reduced 64 wt %, 54 wt % and 44 wt % to match the 100% loading in the formulation.
  • the SITs of the film samples were reduced to 165, 163, 167 °F, respectively. All three samples showed comparable sealing temperature window, plateau seal strength, and plateau temperature range as shown in Fig.1 and Table 2.
  • Example 6 was made to compare Example 3, 30 wt % CAPA®6500 was used to substitute the combination of 20 wt % FD92PM and 10 wt % CAPA®6500D in the sealant layer formation.
  • Example 8 the second outer skin layer (A) has the same formulation as the heat sealable layer (C).
  • This coextruded film is two side heat sealable.
  • the SITs of the film samples were reduced to 152 °F which is the lowest among all film samples.
  • the two film samples also showed the broadest sealing temperature window, their plateau seal strengths are comparable to that of Examples 4 to 6.
  • Examples 9 and 10 (Ex. 9 and Ex. 10) were made to include non-conventional heat seal resins for comparison.
  • the sealant layer of the Ex.9 comprised an amount of 24.5 wt % crystalline PLA resin LX575, which impacts the sealing performance of the sample in low temperature. Therefore, Ex.
  • the materials in the sealant layer comprise crystalline PLA resins such as PLA4043D and PBAT resins such as Ecoflex® C1200 and inorganic filler CaCO3, those materials do not support a good hot tack performance.
  • Optical properties of the coextruded film samples are shown in Table 3.
  • the first control sample (Ex.1) showed the lowest haze at about 2%, and highest gloss for both A side (cast side or drum side) and B side (sealant side or air side).
  • the core layer and the second outer skin layer in Example 2 were changed to a PLA-rich biodegradable composite resin (Ex. 2), the haze was increased from to 8%, and the glosses for A side and B side were reduced to 104 and 81, respectively.
  • Example 3 The haze of the Example 3 was only increased slightly from that of Example 2 (8%) to 10% as the heat sealant layer was modified with 20 wt % FD92PM and 10 wt % CAPA®6500D.
  • the haze of Examples 3, 4, 5, 7 were maintained at the same level of 10 to 12 as the content of FD92PM was increased from 20 wt % to 50 wt % in the sealant layer, the low haze variation observed in those film samples suggests that the good combability was achieved among three polymers of amorphous PLA, PBSA and PCL having a similar refractive index.
  • PCL content was increased to 30% as shown in Ex.6, the haze was increased to 14% from the haze (8%) of the second control sample (Ex.2).
  • the increase in haze is probably due to the formation of large PCL crystals in the sealant layer.
  • the film sample in Ex. 8 is a two-side heat sealable film, both outer skin layers showed contribution to higher haze (23%).
  • the outer skin layers of the film sample in Ex. 10 showed the highest haze (59%) and the lowest gloss for both sides due to the high loading CaCO3 in Ecovio® F2341 resin.
  • the glosses of the outer skin layers are related to surface roughness, all composite film samples in the invention showed much lower glosses due to their higher surface roughness resulted from modification of a few different biopolymers with varied Tg and Tm even if they have shown good compatibility.
  • the COFs of the cast side (A side) and sealant side (C side) of the coextruded film samples were shown in Table 3.
  • the “COF, A/A” is the COF of the cast side to cast side (A to A);
  • the “COF, A/C” is the COF of cast side to sealant side (A to C);
  • the “COF, C/C” is the COF of sealant side to sealant side (C to C).
  • the cast side of the film sample in Example 1 showed the highest COF due to its low content in antiblock (JC-30 particle loading is only 150 ppm).
  • the sealant layer of Example 7 showed COF slightly higher than that of other coextruded film samples is because the total content of low Tg flexible biodegradable polymers in the sealant layer is higher than that of other film samples. All film samples showed acceptable COF for down stream processing.
  • one of the methods is to increase the loading of antiblocks or increase the size of the antiblocks or include slip additives such as erucamide additive into the sealant layer (C) or the second outer skin layer (A).
  • slip additives such as erucamide additive into the sealant layer (C) or the second outer skin layer (A).
  • the inventive film showed tensile strength in both MD and TD direction only slightly lower than that of the control sample Ex. 2, however, the MD modulus in MD was reduced about 6% on average and 27% on average in TD, compared to the moduli of Example 2.
  • Ex. 10 showed the lowest modulus in TD due to its high content of rubbery Ecoflex® C1200 in the outer skin layers. The bulk mechanical strength of the inventive film was maintained at acceptable level, and film modulus was reduced significantly through the modifier heat sealant layer, leading to a reduction in noise level of the film.
  • the outer skin layers have a thickness after biaxial orientation of between 0.5 and 5 ⁇ m, preferably between 1.0 and 3.0 ⁇ m.
  • the core layer thickness after biaxial orientation can be in the range of 10 to 100 ⁇ m, preferably 14 to 25 ⁇ m, and even more preferably 15 to 20 ⁇ m.
  • the coextrusion process includes a multi-layered compositing die, such as three-layer die or even four-layer or five- layer die if tie layer structure is required for film design. In the case of a two-layer coextruded film, a two-layer compositing die can be used.
  • the laminate film is produced via coextrusion of the heat sealable layer and the core layer and other layers if desired, through a compositing die whereupon the molten multilayer film structure is quenched upon a chilled casting roll system or casting roll and water bath system and subsequently oriented in the machine direction (MD) and/or transverse direction (TD) into an oriented multi-layer film.
  • Machine direction orientation (MDO) rate is typically 2.0 to 3.5 times and transverse direction orientation (TDO) is typically 3.0 to 5.0 times in a polyester film line.
  • a relaxation rate of 5 to 15% after TDO can be applied to the oriented film in TD for reducing heat shrinkage. Heat setting conditions in the TDO oven is extremely critical to minimize thermal shrinkage effects.
  • examples were practiced on a film making line armed with a three-layer 12-inch-wide flat die for molding and capability of orientation in MD and then in TD.
  • the main composition in the core layer is a PHA-rich biodegradable composite described earlier except those examples for comparison.
  • the multi-layer laminate sheet was coextruded at extrusion temperatures designed for each layer, cast and pinned—using electrostatic pinning—onto a cooling drum whose surface temperature was controlled between 15 °C and 35 °C to solidify the non-oriented laminate sheet at a casting speed of about 7 to 11 mpm (meter per minute).
  • the non-oriented laminate sheet was stretched first in the machine direction at about 40 to 65 °C at a stretching ratio of about 2 to about 3.5 times the original length, using differentially heated and sped rollers and the resulting stretched sheet is heat-set at about 40 to 50 °C on annealing rollers and cooled at about 30 to 40 °C on cooling rollers to obtain a uniaxially oriented laminate sheet.
  • the uniaxially oriented laminate sheet is then introduced into a tenter oven at a line speed of about 25 to 38 mpm and preliminarily heated between 60 °C and 75°C, and stretched in the transverse direction at a temperature of about 75 to 95 °C at a stretching ratio of about 3 to 5 times the original width and then heat-set or annealed at about 90 to 140 °C, preferably about 110 to140 °C, and more preferably about 120 to 140 °C for making a film with good heat resistance to reduce internal stresses due to the orientation and minimize shrinkage and give a relatively thermally stable biaxially oriented sheet.
  • the TD orientation rates were adjusted by moving the transverse direction rails in or out per specified increments based on the TD infeed rail width settings and width of the incoming machine-direction oriented film.
  • the biaxially oriented film has a total thickness between 10 and 100 ⁇ m, preferably between 15 and 30 ⁇ m, and most preferably between 17.5 and 25 ⁇ m.
  • the film may optionally be passed through an on-line discharge-treatment system, such as corona, flame, plasma, or corona treatment in a controlled atmosphere as described previously to whatever desired surface energy. Typically, useful surface energy can be 36 to 50 dyne/cm.
  • the film is then wound into a roll form through film winding equipment.
  • One embodiment is to offline coat a primer coating on the second outer layer (A) to improve the adhesion of barrier coating to the bulk film, and the surface smoothness.
  • primer coatings include polyurethane (PU) coating, polyacrylate coating, and polyethylenimine (PEI) coating.
  • PU polyurethane
  • PEI polyethylenimine
  • One embodiment is to coat a barrier coating on the top of primer layer.
  • the barrier coating could be a waterborne barrier coating solution derivative from any polymers of PVOH, EVOH, PEI, PU, and mixtures thereof.
  • the coextruded laminate is a heat sealable film printable on the surface layer opposite the heat sealable layer.
  • the coextruded laminate is two-side heat sealable.
  • the coextruded film is a heat sealable film with a second outer layer to receive a primer, or coating or vacuum-deposited metal layer or the combination thereof. Another embodiment is to directly metallize the discharge-treated surface opposite the heat sealable layer. Another embodiment is to metallize the coated barrier layer surface opposite the heat sealable layer. Another embodiment is to metallize the surface layer with barrier coating added onto the primer coating opposite the heat sealable layer. [0289] In another embodiment, a protecting coating layer could be coated over the metal layer to prevent from potential metal cracking and further improve barrier properties. [0290] In an embodiment, the unmetallized laminate sheet or coated primed sheet is first wound in a roll.
  • the roll is placed in a vacuum metallizing chamber, preferably, the sheet is in-chamber pre-treated at a desirable energy level before the metal is vapor-deposited onto the discharge- treated metal receiving layer surface.
  • the metal film may include titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, gold, or palladium, the preferred being aluminum.
  • Metal oxides can also be contemplated, the preferred being aluminum oxide.
  • the metal layer can have a thickness between 5 and 100 nm, preferably between 20 and 80 nm, more preferably between 30 and 60 nm; and an optical density between 1.5 and 5.0, preferably between 2.0 and 3.0.
  • Example 1a The compositions of each layer of the coextruded composite films made in Examples are shown in Table 1a.
  • the temperature profile of extrusion system (extruder, pipe and die) for Examples 1a and 2a are shown in Table 2a; Examples 3a to 19a have the same temperature profile as that in Example 2a.
  • the process condition data includes the orientation ratio in machine direction (MDX) and in transverse direction (TDX), heat set temperature, and TD relaxation for all examples was shown in Table 3a.
  • Table 2a The temperatures used in making the coextruded composite films in Examples (“Ex.”), extruder B has five zones: Z 1 to 5; extruders A and C have three zones: Z1 to 3. Pipe was separated into two zones: Z 1 and Z 2.
  • Examples 3a to 19a have a temperature profile for extrusion like that in Example 2.
  • Table 3a The process data of orientation ratio (MDX and TDX), heat set temperature and TD relaxation used to make the coextruded composite films in Examples (“Ex.”), a typical condition of BOPP film is also listed here for reference.
  • a three-layer coextruded biaxially oriented PLA film was made as control using sequential orientation on a 12-inch-wide flat die line as described previously, including non-heat sealable layer (A), a core layer (B), a heat sealable layer (C).
  • the core layer was sandwiched between two outer skin layers.
  • the PLA10A with 5 wt % JC-30 particles in 95 wt % LX975 carrier resin was added into outer skin layers for the purpose of COF control and anti-blocking.
  • the content of JC-30 particles in the non-heat sealable outer layer (A) is about 150 ppm and the content of JC-30 antiblock in the heat seal layer (C) is about 3000 ppm.
  • the dry blended resins of the core layer and the outer skin layers were melt coextruded individually in extruders A (second outer layer, cast side layer), B (core layer) and C (first outer layer, heat sealant layer) at temperatures of about 204 °C.
  • the molten resins flowed through a set of screen pats and individual melt pipes set at temperature of 204 °C and then met inside the die body of a twelve-inch flat die set at temperature of 204 °C, resulting in a curtain of molten resin.
  • the temperatures of extruders (A, B, C) and die body were shown in Table 2a.
  • the resin curtain was then cast on a chilled drum (set at temperature about 30 °C) using an electrostatic pinner.
  • the formed cast sheet was stretched 2.6 times in the machine direction (MD) through rolls set at temperatures between 40 °C to 65 °C and then stretched 6.0 times in transverse direction (TD) in a tenter oven set temperatures 65 to 82 °C.
  • MD machine direction
  • TD transverse direction
  • the resultant biaxially oriented film was subsequently annealed at 121 °C and then relaxed at 5 % in TD, followed by discharge-treated on the surface of the non-heat sealable skin layer (A) opposite the heat sealable skin layer (C) via corona treatment.
  • the film was then wound up in roll form.
  • the conditions of MDX, TDX, heat set temperatures and TD relaxation were shown in Table 3a.
  • the total thickness of this film substrate after biaxial orientation was about 80 gauges (G) or 0.8 mil or 20 ⁇ m.
  • the thickness of the respective heat sealable resin layer (C) after biaxial orientation was about 8 G (2.0 ⁇ m).
  • the thickness of the core layer (B) after biaxial orientation was about 68 G (17.0 ⁇ m).
  • the thickness of the non-sealable skin layer (A) was about 4 G (1.0 ⁇ m).
  • Example 2a [0297] Example 1a was repeated while the process conditions and formulations were changed.
  • the core layer was changed to a PHA-rich core layer comprising 60 wt % of PHBV Y1000P resin, 37 wt % of PLA4043D PLA resin and 3 wt % of Biomax SG 120 (shown in Table 1).
  • An optimum extrusion temperature profile (shown in Table 2a) was used in extrusion.
  • the design of the extrusion temperatures was attempted to facilitate the chemical reactions (in case Biomax SG 120 is used) and transesterification reactions between PHBV and PLA resins and in the meantime to eliminate PHA thermal degradation during extrusion.
  • the polymer melt temperature of the extruder B was controlled at not higher than 165 °C, at which thermal degradation observed for PHA resins starts.
  • extrusion temperatures of extruder A and C were higher than that of extruder B.
  • the temperature of the die body was set at about 177 °C.
  • the residence time of polymer melt between the entrance of the extruder B and the exit of the die body was estimated at about 5 to 10 minutes, varying with the rpm of extruder B and film thickness.
  • Biomax SG 120 was added into the core layer for modifying film flexibility, toughness as well as the compatibility between PHA and PLA resin.
  • the molten polymer melt was cast on a chilled set 30 °C to form a cast sheet with a width about 9.5 inches. The sheet was oriented in machine direction for 3 times and then in transverse direction for 4.5 times.
  • Example 2a was repeated with the same skin layer recipes. However, the content of PHBV Y1000P resin in the core layer (B) was increased to about 70 wt % and the content of PLA4043D resin was reduced to 27 wt %. MDX was slightly reduced from 3.0 to 2.8.
  • Example 4a Example 2a was repeated by changing the recipes in the two outer layers, and the content of Biomax SG120 in the core layer was increased to 4 wt %.
  • the PLA resins in both skin layers and core layer was changed to TotalEnergies Corbion LX175.
  • the heat set temperature was set at 82 °C, and the MDX and TDX were 2.3 and 3.5, respectively.
  • TD relaxation was reduced from 10% to 5%.
  • Examples 5a to 7a [0300]
  • Example 4a was repeated except that the TDX was increased from 3.5 to 4.8.
  • the heat set temperature was increased from 82 °C to 93 °C, 116 °C, and 127°C, respectively.
  • Example 8a [0301] Example 3a was repeated except that the content of Biomax SG 120 in the core layer was increased from 3 wt % to 5 wt %, and the content of PLA4043D was reduced from 27 wt % to 25 wt %, and the heat set temperature was reduced from 104 °C to 88 °C.
  • Example 9a [0302] Example 8a was repeated except that the heat set temperature was increased from 88 °C to 104 °C.
  • Example 10a [0303] Example 4a was repeated with a few variations. The core layer was changed to comprise 50 wt % Y1000P PHBV resin and 50 wt % LX175 PLA resin. The two outer skin layers have the same non-heat sealable recipe.
  • Example 10a was repeated except that the outer skin layer (C) was changed to a sealant layer formulation with an amount of 74 wt % LX975, and 20 wt % CAPA6500D and 6 wt % PLA10A.
  • the core layer was changed to comprise 60 wt % Y1000P resin and 40 wt % LX175 resin. MDX was reduced from 2.8 to 2.5 and TDX was reduced from 4.5 to 4.0.
  • Example 12a [0305] Example 10a was repeated except that the core layer formulation was changed to comprise 70 wt % Y1000P resin and 30 wt % LX175 resin. The heat set temperature was reduced from 127 °C to 104 °C.
  • Example 13a [0306] Example 12a was repeated except that the two outer layers were changed to a heat sealable formulation comprising 24 wt % LX975, 60 wt % FD92PM, and 10 wt % CAPA6500D, and 6 wt % PLA10A.
  • the PHA-rich composite film is a two-side heat sealable film.
  • Example 14a [0307] Example 13a was repeated except that the second outer layer on the cast drum side was changed to a formulation comprising 24 wt % LX175, 70 wt % FD92PM, and 6 wt % PLA10A. The sealability of the second outer skin layer (cast side) of the PHA-rich composite film was slightly reduced due to the addition of semi-crystalline LX175 resin. MDX was reduced from 2.8 to 2.5.
  • Example 15a [0308] Example 14a was repeated except that the core layer formulation was changed to comprise 30 wt % Y1000P PHBV resin and 70 wt % LX175 PLA resin. In addition, the heat set temperature was increased from 104 °C to 127 °C.
  • Two out skin layers comprises 70 wt % of TUV-certified home compostable flexible resins, while the core layer comprises PHBV resin less than 50 wt %.
  • Example 16a to 17a [0309]
  • Example 15a was repeated except that the heat set temperature was increased from 127 °C to 138 °C and to 146 °C, respectively.
  • Example 18a [0310]
  • Example 13a was repeated except that the core layer formulation was changed to comprise 50 wt % Y1000P PHBV resin and 50 wt % LX175 PLA resin.
  • the heat set temperature was increased from 104 °C to 127 °C.
  • the composite film is a two-side heat sealable film with low Tg flexible biopolymers in the outer skin layers.
  • Example 19a [0311] Example 18a was repeated except that the core layer formulation was changed to comprise 60 wt % Y1000P PHBV resin and 40 wt % LX175 PLA resin; the formulation of the second outer skin layer (cast side) was changed to comprise 70 wt % FD92PM, 24 wt % LX975 and 6 wt % PLA10A. In addition, the heat set temperature was increased from 127 °C to 138°C. The composite film is still a two-side heat sealable film with flexible biopolymers in the two outer skin layers, the loading of 10 wt % CAPA6500D in the cast side was replaced by using 10 wt % FD92PM for better heat resistance.
  • the cast side skin layer should have better heat sealability compared to the cast side skin layer of the composite fin in Examples 14a to 17a.
  • Film Properties [0312] The biaxially oriented coextruded PHA-rich composite films were tested for the properties of mechanical strength, tear resistance, heat shrinkage (heat resistance), heat sealing, optics and COF which are basic film properties required for snack food packaging films. Table 4a: Mechanical properties of the coextruded films made in Examples (“Ex.”) as well as the mechanical properties of BOPP film.
  • the coextruded films were measured for mechanical strength and tear resistance and the results were shown in Table 4a.
  • a typical BOPP film was included for comparison, which were obtained from a commercial clear BOPP film (Torayfan ⁇ YOR4/70G with a thickness of 17.5 ⁇ m made in standard BOPP production line). As expected, BOPP film showed much better mechanical properties outperforming that of biofilm samples.
  • the PLA control sample (Ex. 1a) showed the highest modulus in both MD and TD, which is the root cause of generating high noise observed for conventional BOPLA film.
  • Examples 4a to 7a, Example 11a, and Examples 14a to 18a showed lower MD tensile strength due to their lower MDX (2.3 to 2.5), while Examples 16a, 17a and 19a showed lower MD tensile strength more likely due to their higher heat set temperature.
  • the composite film in Example 17a has low tensile strength, extremely low elongation at break and low tear strength. The film is very brittle due to high heat set temperature, and it is not suitable for downstream processing.
  • the composite films showed high modulus as that observed for Examples 4a to 7a, Example 10a, and Example 12a due to the high Tg of PLA resin in the outer skin layer.
  • Low Tg flexible biopolymers such as PBSA and PCL resins added into the outer skin layers can further reduce the moduli of the composite films.
  • the moduli of the composite films can be further reduced if it is necessary by adding an amount of low Tg flexible biopolymers into the core layer
  • suitable biopolymers include such as PBSA, PCL and PBAT, low Tm PHA resins, and amorphous PHA resins.
  • Table 5a Heat shrinkage of the biaxially oriented coextruded PHA-rich composite films made in Examples (“Ex.”) [0319] Thermal stability of the biaxially oriented coextruded composite films was determined by measuring the heat shrinkage of the composite films made in Examples 1a to 19a at three temperatures 80°C, 100 °C and 120 °C for a duration time of 15 minutes as shown in Table 5a (The heat shrinkage of a BOPP film (YOR4/70G) was used herein for comparison).
  • BOPP film sample showed no heat shrinkage under the same test conditions due to polypropylene’s high crystallinity (about 60 wt %), high melting temperature 160 to 165 °C, and high heat set temperature (about 160 °C).
  • the BOPP film (YOR4/70G) has a MD shrinkage of 4 to 8% and a TD shrinkage of 2 to 5%.
  • BOPLA control film also showed better thermal stability although it was stretched at 6 times in TD and heat set at 121 °C (which was relatively low heat set temperature for BOPLA).
  • the heat set temperature has the greatest influence on thermal stability for the same film formulation.
  • the higher heat set temperature is applied to the composite film the lower heat shrinkage (or higher heat resistance) can be achieved.
  • the heat set temperature is over the up limit of optimal heat set temperature, the film will become very brittle, leading to film breaks in film making or downstream processes.
  • the heat set temperature was increased from 82 °C to 127 °C in Examples 4a to 7a, the heat shrinkage in MD at 120 °C was reduced from 42% to 3%, and TD heat shrinkage was reduced from 33% to 8%.
  • Example 7a The heat shrinkage of the composite film in Example 7a which was annealed 127 °C is comparable to that of Example 1a (BOPLA control film).
  • High heat shrinkage at 120 °C that was observed for Examples 2a to 5a, Examples 8a to 10a and Examples 12a to 14a are mainly resulted from their low heat set temperatures (in the range of 88 °C to 104 °C).
  • the heat set temperature of making the composite film was increased to the range of from 127 to 138°C as that applied to Examples 7a, 11a, 15a, 16a, 18a and 19a, the heat shrinkage of the composite films in both MD and TD at 120 °C is much lower, suggesting a much better heat resistance.
  • the heat set temperature of making the PHA-rich composite films is in the range of from 125 °C to 140 °C. If the heat set temperature is too high, the composite film will become brittle so that the composite film cold be difficult to process in film making or downstream processes. If the heat set temperature of making the PHA-rich composite films is too low, the film will have high heat shrinkage which are not suitable for the application with the processes of printing, coating, metallizing, and lamination. [0322] However, a function of shrink film with high heat shrinkage rate is required for film application, lower heat set temperature in the range of from 80 °C to 110 °C is preferred in film making.
  • Table 6a Heat sealing and oxygen barrier properties of the coextruded PHA-rich composite films made in Examples ("Ex.”) [0323]
  • the heat seal and hot tack curves of the first outer layer (C) of the composite films in Examples 1a, 2a, 3a, 11a, 14a, 15a, 18a, and 19a were drawn in Fig.3 and 4, respectively.
  • the SIT and plateau strength of the curves of those composite films were presented in Table 6a.
  • the second outer layer (A) of some composite films in Examples are also heat sealable, but those were not discussed herein in details.
  • Example 1a (Ex.1a), as shown Table 1a, BOPLA film with amorphous PLA resin LX975 in the sealant layer showed a SIT of 193 °F obtained from its heat seal curve and a SIT of 195 °F obtained from its hot tack curve.
  • SIT is defined as the seal temperature at which gives 200 g/in (grams per inch) seal strength or hot tack strength. The plateau strength on average was at about at 438 g/in for heat sealing and 505 g/in for hot tack.
  • the heat sealant layer of the composite films in Examples 14a,15a and 18a comprised about 6% wt % PLA10A, 10 wt % CAPA®6500D, 24 wt % LX975 and 60 wt % FD92PM resins as shown in Table 1.
  • the composite films in Examples 13a, 14a, 18a and 19a were made to comprise high percentage of TUV certified home compostable biopolymers for improving home compostability.
  • CAPA®6500D and FD92PM are low Tg flexible semi-crystalline biopolymers, both can have excellent effects on noise dampening as they are added into the core layer and out skin layers.
  • FD92PM has a higher melting peak more suitable for the outer skin layers required for better heat resistance.
  • Low Tg flexible biopolymers including PBSA, PCL and amorphous PHA resins can be added into the core layer at an amount of about 5 wt % to 25 wt % of the total weight of the core layer to further improve the hermeticity (high plateau seal strength) of the composite films.
  • the heat seal and hot tack can be significantly improved to achieve SIT as low as 160 °F, plateau strength as high as 600 g/in, and a broadened heat seal temperature range of from 160 to 240 °F.
  • the oxygen barrier of the composite films listed in Table 6a was measured and normalized to the barrier data of one mil thickness film (25 microns) for comparison. It is noted that the biaxially oriented composite film samples showed much better oxygen barrier (31 to 43 cc ⁇ mil/100in2/day) compared to that (77 cc ⁇ mil/100in2/day) of BOPLA control film (Ex.1a).
  • the barrier data among the composite films with Y1000P PHBV resin in the core layer showed no significant difference in terms of barrier data range, the variations observed are more likely due to the changes in processing conditions but not the change in formulation.
  • Table 7a Optical properties and coefficient of friction of the coextruded composite films made in Examples (“Ex.”) [0331] Optical properties of the coextruded film samples are shown in Table 7a.
  • the BOPLA control sample (Ex. 1a) showed the lowest haze at about 2%, and highest gloss for both A side (cast side or drum side) and C side (sealant side or air side).
  • the core layer and the second outer skin layer in Example 2a were changed to a PHA-rich biodegradable composite resin (Ex.2a)
  • the haze was increased sharply from 2% to 22%, and the glosses for A side and B side were also reduced to a lower level.
  • PHBV resin (Y1000P) is immiscible with PLA resin in the core layer, forming two different separate phases, and a boundary is formed between two phases with different refractive index. Large PHBV crystals can form in the core layer, and they can be one of the factors of high haze. As a result, high haze was observed the PHA-rich composite films as Y1000P is the PHA resin.
  • Examples 4a to 9a having Biomax SG 120 as compatibilizer in the core layer showed similar optical properties to that of Example 3a.
  • the optical properties of the composite films in Examples 5a to 7a were not measured since those have the same formulation as that in Example 4a, however, the haze value was observed to decrease with increasing heat set temperature, the size of polymer crystals became smaller with increasing heat set temperature (refer to the haze data in Examples 15a to 17a).
  • the “COF, A/A” is the COF of the cast side to cast side (A to A); the “COF, A/C” is the COF of cast side to air side (A to C); the “COF, C/C” is the COF of air side to air side (C to C).
  • the cast side of the film sample in Example 1a showed the highest COF due to its low content in JC-30 antiblock (150 ppm).
  • the sealant layer (air side) of the composite film in Example 1a comprises 3000 ppm of JC-30 antiblobk and showed static and dynamic COF of 0.56 and 0.53, respectively.
  • the suitable amount of antiblocks or slip additives used in the outer layers varies with the crystallinity and Tg of the biopolymers in the outer layers as well as the final application of the composite films. For a soft, tacky, and flexible skin layer, it needs a higher loading of antiblock and slip additives to meet the requirements for processing and applications.
  • the inventive composite films in Examples showed static and dynamic COFs suitable for downstream processing and packaging film handling. Test Methods [0335] The various properties in the above examples were measured by the following methods: [0336] Transparency of the film was measured by measuring the haze of a single sheet of film using a haze meter model like a BYK Gardner “Haze-Gard Plus®” substantially in accordance with ASTM D1003.
  • Gloss of the film was measured by measuring the desired side of a single sheet of a film by a surface reflectivity gloss meter (BYK Gardner Micro-Gloss) substantially in accordance with ASTM D2457. The A-side or non-sealable layer side was measured at a 60° angle; the sealant layer side was measured at a 20° angle.
  • Heat seal strength was measured using a LAKOTM Heat Sealer (model SL10) at 30 PSI, 0.5 second dwell time, and 15 second delay time before automatically testing the seal strength.
  • the automated LAKOTM Heat Sealer is capable of forming a film seal, determining the seal strength, and generating a seal profile from a test film sample.
  • Hot tack strength was measured by using a LAKOTM Tool hot tack/sealer model SL10 at 30 PSI, 0.5 second dwell time, with heated flat Teflon coated lower seal jaw, and unheated upper seal jaw and with a delay time set to 0 seconds for hot tack testing.
  • Heat seal and hot tack seal initiation temperature SIT: Measured by using the above methods (A) and (B) using the LAKO Heat Sealer or LAKOTM Tool SL10 hot tack sealer. Heat seal initiation temperature is the lowest temperature at which minimum 200 g/in seal strength is achieved. Hot tack initiation temperature is the lowest temperature at which minimum 200 g/in hot tack is achieved.
  • COF of the outer skin layers of the coextruded biodegradable composite films made in Examples was tested under ambient temperature condition to determine the static and dynamic COF ( ⁇ s and ⁇ d) using the method of ASTM D1894.
  • Mechanical properties of the coextruded biodegradable composite films were tested under ambient temperature condition using the method of ASTM D882.
  • Tear resistance of the coextruded composite film was measured substantially accordance with ASTM D1922-09. Three samples each are cut from the plastic film samples in the machine direction (MD) and in the transverse direction (TD) for testing and data collection.
  • Heat shrinkage of the coextruded composite films was measured substantially in accordance with ASTM D1204 except that the measurement condition was at three temperature levels of 80 °C, 100 °C and 120 °C, respectively, for a process duration time of 15 minutes.
  • Oxygen transmission rate (O2TR) of the composite films was directly measured by using a Mocon Oxtran 2/20 unit substantially in accordance with ASTM D3985.
  • Home compostability of the coextruded biodegradable composite film is being evaluated in the home compost under the conditions specified in ASTMD5338-15 except the composting temperatures are controlled in the range 25 ⁇ 5 °C (AS 5810-2010 or “OK COMPOST HOME – CERTIFICATION, 2019 VERSION”).

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Laminated Bodies (AREA)

Abstract

L'invention concerne un film composite compostable multicouche à orientation biaxiale comportant une formulation de couche d'étanchéité présentant une température d'initiation de thermoscellage améliorée, une résistance de scellage stable améliorée et une plage de température de thermoscellage élargie, et un module de film (bruit) réduit. Dans un mode de réalisation, le film comprend une couche centrale comprenant une résine composite biodégradable riche en PLA ou un composite biodégradable riche en PHA et une couche d'agent de thermoscellage comprenant une résine PLA et des biopolymères compostables de manière domestique ayant une température de transition vitreuse Tg < 0 °C et une température de fusion située dans la plage allant de 56 °C < Tm < 90 °C. Le film composite compostable de l'invention présente l'attrait de posséder des propriétés mécaniques, une performance d'agent de thermoscellage et une compostabilité domestique améliorées.
PCT/US2023/031579 2022-08-31 2023-08-31 Film composite biodégradable à orientation biaxiale WO2024049930A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US202263402574P 2022-08-31 2022-08-31
US63/402,574 2022-08-31
US18/090,732 US20240066847A1 (en) 2022-08-31 2022-12-29 Biaxially oriented compostable composite film
US18/090,732 2022-12-29
US18/174,857 2023-02-27
US18/174,857 US20240066848A1 (en) 2022-08-31 2023-02-27 Biaxially oriented pha-rich composite film

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