Biaxially oriented biodegradable film

Abstract

A biaxially oriented industrial or household compostable film web having at least three co-extruded layers selected from the group consisting of a facing film layer, a sealant film layer, and a combination of sealant film layers and facing film layers, wherein the sealant film layer and the surface film layer each comprise from 0 wt% to about 80 wt% of a polyhydroxyalkanoate (PHA) and from about 20 wt% to about 100 wt% of a polylactic acid (PLA), and optionally a small amount of a blend of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers; and a core film layer comprising from about 30 wt% to about 80 wt% of a polyhydroxyalkanoate (PHA), from about 20 wt% to about 40 wt% of a polylactic acid (PLA), and optionally a small amount of a blend of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers.

Description

[0001] Related applications

[0002] This application is a continuation-in-part of provisional application serial number 63 / 369,997 filed on August 1, 2022, which is now pending. Technical Field

[0003] The present disclosure relates to biodegradable films and, more particularly, to methods of improving the dimensional stability of poly(hydroxyalkanoate)-based polymer films. Background Art

[0004] Polymer films are used in a variety of flexible packaging applications, including food packaging. Polymer films are often used in bag making and heat sealing processes that are widely used in flexible packaging. The stability of polymer films is critical to maintaining product quality and preventing food quality from deteriorating during storage. Bag making and heat sealing processes are usually carried out at high temperatures. Semi-crystalline polymer films shrink when cooled at high temperatures. The extent of shrinkage depends largely on the composition of the film material and the processing conditions used to produce the film. Semi-crystalline materials shrink more than amorphous materials. The dimensional instability or shrinkage of the film when cooling from high temperatures plays an important role in the overall quality of the finished product. Significant shrinkage during or after the bag making or heat sealing process can lead to several defects in the finished product, including leaks, risk of pinhole formation, and rupture in the sealed area.

[0005] Conventional polymer films are generally not compostable in industry or at home, and therefore create environmental waste that must be disposed of. Biodegradable poly(hydroxyalkanoate)-based polymer films also shrink when cooled from high temperatures to room temperature. The shrinkage properties of poly(hydroxyalkanoate)-based films create significant problems in the coating, metallization, lamination, printing, bag making and sealing processes that use the films. Poly(hydroxyalkanoate)-based polymer films produced by conventional blown film processes have shrinkages of 45% to 50% measured in the machine direction (MD) at 110°C. The temperature selected for the shrinkage measurement is the temperature used by most film post-processing equipment. Compared to the industry standard of less than 5% for other polymer films, the shrinkage values ​​of poly(hydroxyalkanoate)-based polymer films are significantly higher. Therefore, there is a need for an improved method for making poly(hydroxyalkanoate)-based polymer films that are compostable at home, which provides films with significantly lower shrinkage when used for packaging applications.

[0006] Oriented films are made from plastic pellets by unidirectional or bidirectional stretching and extrusion. The film can be oriented only in the longitudinal direction (MD), only in the transverse direction (TD), oriented in both MD and TD, or oriented in MD and TD in sequence. Sequential orientation (i.e., orientation in MD and then orientation in TD) is the most common method for commercially producing biaxially oriented films. A typical biaxial orientation process may include one or more of the following steps arranged in sequence:

[0007] 1. A relatively thick plastic sheet is cast from a slot die and rapidly cooled on a cooling roller.

[0008] 2. The cast sheet of film is stretched in the machine direction using heated rollers (to raise the temperature of the plastic above its glass transition temperature (Tg)). The rollers consist of a series of nips rotating at increasingly faster speeds.

[0009] 3. Stretching a machine direction oriented (MDO) film sheet in the cross direction by grasping each edge of the film with a clamp rotating on a continuous chain. As the clamp pulls the sheet forward, the tracks carrying the clamps separate to pull the plastic laterally.

[0010] 4. The clamps continue to carry the now relatively thin film (under uniform MD and TD tension) through a warm oven to anneal the plastic film.

[0011] 5. After annealing, the film is subjected to any desired surface treatment. The thick edges of the film, which are held by the clamps gripping its sides, are trimmed off and the film is rewound.

[0012] Due to the changes in the morphology of the film's molecular structure caused by the orientation process, oriented films can obtain a variety of favorable properties. Examples of such favorable properties include optimal physical properties (such as hardness and tear strength), good optical properties (such as transparency or gloss), and enhanced barrier properties. Compared with other packaging materials, oriented films are lightweight and energy-efficient to produce.

[0013] The main materials for biaxially oriented films are polypropylene, polyester and polyamide. Polyethylene and polylactic acid are also biaxially oriented in commercial processing and used in commercial packaging applications. With the exception of polylactic acid, conventional biaxially oriented films are made from non-biodegradable petroleum-based materials. In view of the foregoing, there is a need for an industrial or home compostable biaxially oriented film for use as a printing film and a barrier film that can be converted into a packaging structure that meets the performance requirements and required end-use certifications for a variety of packaging applications. Summary of the invention

[0014] In view of the foregoing, provided are industrially and / or home compostable biaxially oriented composite films that can be produced using the materials and methods described herein.

[0015] In one embodiment of the present disclosure, a biaxially oriented industrial or home compostable film web is provided, comprising at least 3 coextruded layers selected from: a surface film layer, a sealant film layer and a core layer, wherein the sealant film layer and the surface film layer each comprise a blend of 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA), and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers; and the core film layer comprises a blend of about 30 wt % to about 80 wt % polyhydroxyalkanoate (PHA), about 20 wt % to about 40 wt % polylactic acid (PLA), and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers. The core film layer is disposed between a combination of a surface film layer and a sealant film layer, between two sealant film layers, or between two surface film layers, wherein the sealant film layer and the surface film layer each contain the same or different amounts of PHA, PLA and other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers.

[0016] In another embodiment, a method for improving the dimensional stability of a biaxially oriented industrial or home compostable film web comprising at least three coextruded layers is provided. The method comprises extruding a composite poly(hydroxyalkanoate)-based polymer film; and annealing the composite poly(hydroxyalkanoate) polymer film at a temperature range of about 110° C. to about 130° C. during the biaxial orientation process.

[0017] In some embodiments, a biaxially oriented industrial or home compostable film web comprises: at least two sealant film layers, wherein the at least two sealant film layers comprise a blend of about 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA), and optionally other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers, wherein each of the two sealant film layers may have the same amount or different amounts of PHA, PLA, and other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers; and a core film layer comprising a blend of about 30 wt % to about 80 wt % polyhydroxyalkanoate (PHA), about 20 wt % to about 40 wt % polylactic acid (PLA), and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers, wherein the core film layer is disposed between the at least two sealant film layers.

[0018] In some embodiments, a biaxially oriented industrial or home compostable film web comprises: at least two surface film layers and a core film layer, wherein at least the two surface film layers comprise a blend of about 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA), and optionally other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers, wherein each of the two sealant film layers may have the same amount or different amounts of PHA, PLA, and other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers; and the core film layer comprises a blend of about 30 wt % to about 80 wt % polyhydroxyalkanoate (PHA), about 20 wt % to about 40 wt % polylactic acid (PLA), and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers, wherein the core film layer is disposed between the at least two surface film layers.

[0019] In some embodiments, the biaxially oriented industrial or home compostable film web comprises: a surface film layer, a core film layer, and a sealant film layer, the surface film layer comprising about 0 wt % to about 80 wt % of a polyhydroxyalkanoate (PHA) and about 50 wt % to about 70 wt % of a polylactic acid (PLA) and optionally a small amount of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers; the core film layer comprises about 30 wt % to about 80 wt % of a polyhydroxyalkanoate (PHA), about 20 wt % of a polylactic acid (PLA); A blend of about 40 wt % polylactic acid (PLA) and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers; a sealant film layer comprising 0 wt % to about 80 wt % of polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA) and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers, wherein the core film layer is disposed between the surface film layer and the sealant film layer.

[0020] In some embodiments, the PHA of the core film layer includes from about 2 mol % to about 10 mol % 3-hydroxyhexanoate and the balance 3-hydroxybutyrate.

[0021] In some embodiments, the PHA of the sealant film layer includes from about 2 mol % to about 10 mol % 3-hydroxyhexanoate and the balance 3-hydroxybutyrate.

[0022] In some embodiments, the PHA of the surface film layer includes from about 2 mol % to about 10 mol % 3-hydroxyhexanoate and the balance 3-hydroxybutyrate.

[0023] In some embodiments, the biaxially oriented industrial or home compostable film has an oven shrinkage of 0% to less than about 5% in the machine direction (MD) and an oven shrinkage of 0% to less than about 15% in the transverse direction (TD).

[0024] In some embodiments, the biaxially oriented industrial or home compostable film has a needle penetration greater than about 700 grams-force (gf).

[0025] In some embodiments, a biaxially oriented industrial or home compostable printed film web is provided having a core film layer disposed between a combination of a face film layer and a sealant film layer.

[0026] In some embodiments, a biaxially oriented industrial or home compostable barrier film web is provided having a core film layer disposed between a combination of a face film layer and a sealant film layer.

[0027] In some embodiments, the biaxially oriented industrial or home compostable printed film web has an oven shrinkage of 0 to less than about 5.0% in the machine direction (MD) and 0 to less than about 15% in the transverse direction (TD).

[0028] In some embodiments, the biaxially oriented industrial or home compostable printed film has a needle penetration range of greater than about 700 grams-force (gf).

[0029] In some embodiments, the biaxially oriented industrial or home compostable printed film web has a haze value of less than 15%.

[0030] In some embodiments, a biaxially oriented industrial or home compostable barrier film web is provided having a core film layer disposed between two sealant film layers.

[0031] In some embodiments, the biaxially oriented barrier film has an oven shrinkage in the machine direction (MD) of 0% to less than about 5.0% and an oven shrinkage in the transverse direction (TD) of 0% to less than about 15%.

[0032] In some embodiments, the biaxially oriented barrier film has a needle penetration range of greater than about 700 grams-force (gf).

[0033] In some embodiments, a biaxially oriented industrial or home compostable printed film web is provided having a core film layer disposed between two surface film layers.

[0034] In some embodiments, the biaxially oriented industrial or home compostable film web is relaxed from about 5% to about 25% in the transverse direction (TD) from stretching in the transverse direction (TD) prior to or concurrently with the annealing step.

[0035] In some embodiments, the biaxially oriented industrial or home compostable film web is annealed in a temperature range of about 110° C. to about 130° C. during the biaxial orientation process, and the industrial or home compostable film web is relaxed from transverse direction (TD) stretching by about 15% to about 25% prior to or simultaneously with the annealing step.

[0036] In some embodiments, a coated and / or metallized biaxially oriented barrier web is provided.

[0037] As described in more detail below, certain annealing conditions can provide optimal dimensional stability or minimize shrinkage of the poly(hydroxyalkanoate) base film in the MD and TD directions. If properly annealed, the diameter of the poly(hydroxyalkanoate) base film does not change over time or when exposed to high temperatures. Therefore, embodiments of the present disclosure provide conditions that can provide biaxial dimensional stability of the poly(hydroxyalkanoate) base film. The dimensionally stable poly(hydroxyalkanoate) base film manufactured according to the present disclosure can be particularly useful in the food packaging industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a cross-sectional view, not to scale, of a portion of a biaxially oriented web according to a first embodiment of the present disclosure.

[0039] Figure 2 is a cross-sectional view, not to scale, of a portion of a biaxially oriented web according to a second embodiment of the present disclosure.

[0040] Figure 3 is a cross-sectional view, not to scale, of a portion of a biaxially oriented web according to a third embodiment of the present disclosure.

[0041] Figure 4 is a cross-sectional view, not to scale, of a portion of a biaxially oriented web according to a fourth embodiment of the present disclosure.

[0042] Figure 5 is a cross-sectional view, not to scale, of a portion of a biaxially oriented web according to a fifth embodiment of the present disclosure.

[0043] Figure 6 is a not-to-scale cross-sectional view of a portion of a biaxially oriented web according to a sixth embodiment of the present disclosure. DETAILED DESCRIPTION

[0044] In one aspect, the present disclosure provides polymer film compositions that are particularly suitable for use in consumer product packaging, among other uses.

[0045] Preferably, the polymer film composition is biodegradable and / or industrially or home compostable. More particularly, the polymer film composition is both biodegradable and industrially or home compostable.

[0046] As used herein, the term "biodegradable" means that a plastic or polymer material will be biodegraded by living organisms (microorganisms) in anaerobic and aerobic environments (as determined by ASTM D5511), soil environments (as determined by ASTM 5988), freshwater environments (as determined by ASTM D5271 (EN 29408)), or marine environments (as determined by ASTM D6691). The biodegradability of biodegradable plastics can also be determined using ASTM D6868 and European EN 13432.

[0047] The polymer film compositions of the present disclosure are also preferably "compostable," as determined by ASTM D6400 for industrial or home compostability.

[0048] In particular, the biodegradable polymer film composition comprises poly(hydroxyalkanoates) as the biodegradable polymer. The composition is typically composed of about 5% to about 95% by weight of the poly(hydroxyalkanoates). More preferably, the composition is composed of about 20% to about 90% by weight of the poly(hydroxyalkanoates). More preferably, the polymer composition comprises about 30% to about 70% by weight of the poly(hydroxyalkanoates).

[0049] In some cases, the poly(hydroxyalkanoates) for making biodegradable films are preferably composed of a mixture of monomer units. Therefore, the poly(hydroxyalkanoates) can include about 90 mol % to about 99.9 mol % of the monomer residues of 3-hydroxybutyrate and about 0.1 mol % to about 10 mol % of the monomer residues of the second 3-hydroxyalkanoate with 5 to 12 carbon atoms. In one embodiment, the poly(hydroxyalkanoates) comprising about 97 mol % to about 99 mol % of the monomer residues of 3-hydroxybutyrate and about 1 mol % to about 3 mol % of the monomer residues of 3-hydroxyhexanoate can be used to make one or more layers of composite polymer films. Another layer or layers of the composite polymer film can include the poly(hydroxyalkanoates) comprising about 92 mol % to about 96 mol % of the monomer residues of 3-hydroxybutyrate and about 4 mol % to about 10 mol % of the monomer residues of 3-hydroxyhexanoate.

[0050] The polymer composition film may also include a second biodegradable polymer selected from the group consisting of poly(butylene succinate), poly(butylene succinate-co-adipate), polylactic acid, cellulose esters (such as cellulose acetate), thermoplastic starch, and mixtures thereof. The amount of the second biodegradable polymer is generally about 10% to about 90% by weight of the total composition.

[0051] In some embodiments, the second biodegradable polymer may include poly(butylene succinate) in an amount of about 5 wt % to about 50 wt % of the polymer film composition. More preferably, the polymer film composition includes about 10 wt % to about 30 wt % poly(butylene succinate).

[0052] According to some embodiments, the second biodegradable polymer may include poly(butylene succinate)-co-butylene adipate in an amount of about 5 wt % to about 50 wt % of the polymer film composition. More preferably, the polymer film composition includes about 10 wt % to about 30 wt % of poly(butylene succinate)-co-butylene adipate.

[0053] In some cases, the second biodegradable polymer may include polylactic acid in an amount of about 10% to about 70% by weight of the polymer composition. More preferably, the polymer film composition includes about 20% to about 80% by weight of polylactic acid.

[0054] In certain embodiments, the second biodegradable polymer may include cellulose acetate or another cellulose ester in an amount of about 5 wt % to about 50 wt % of the polymer film composition. More preferably, the polymer film composition includes about 10 wt % to about 30 wt % cellulose acetate or another cellulose ester.

[0055] Typically, the poly(hydroxyalkanoate) polymers have a weight average molecular weight (as determined by ASTM D6474-20) of about 50,000 Daltons to about 7.5 million Daltons, more preferably a weight average molecular weight of about 300,000 Daltons to about 3 million Daltons.

[0056] In certain embodiments, the poly(hydroxyalkanoate) and at least one biodegradable polymer are melt blended together in a film extrusion process.

[0057] In some embodiments, the transesterification reaction is performed by reacting the poly(hydroxyalkanoate) and at least one biodegradable polymer with each other in a reactive extrusion process.

[0058] In some embodiments, the nucleating agent may be present in the polymer film composition in an amount of about 0.1 wt % to about 5 wt %. In certain embodiments, the core layer nucleating agent is preferably selected from the group consisting of erythritol, pentaerythritol, dipentaerythritol, artificial sweeteners, stearates, polysaccharides, sorbitol, mannitol, inositol, polyester waxes, nanoclays, behenamide, erucamide, stearamide, oleamide, polyhydroxybutyrate, thymine, cyanuric acid, cytosine, adenine, uracil, guanine, boron nitride, and mixtures thereof.

[0059] The polymer film composition may also include an optional plasticizer material. Suitable materials for plasticizers are generally selected from the group consisting of sebacates, citrates, fatty esters of adipic acid, succinic acid and glucaric acid, lactates, alkyl diesters, citrates, alkyl methyl esters, dibenzoates, propylene carbonate, caprolactone diols having a number average molecular weight of 200-10,000 g / mol as determined by ASTM D6474-20, polyethylene glycols having a number average molecular weight of 400-10,000 g / mol as determined by ASTM D6474-20, vegetable oil esters, long chain alkyl acids, adipates, glycerol, isosorbide derivatives or mixtures thereof, polymeric plasticizers, poly(hydroxyalkanoate) copolymers comprising at least 18 mole % of hydroxyalkanoate monomer residues other than hydroxybutyrate, and mixtures thereof.

[0060] The amount of plasticizer in the polymer film composition may be up to about 15 wt %. More preferably, the polymer composition is composed of about 1 wt % to about 8 wt % of plasticizer.

[0061] Optionally, the polymer film composition may also include filler materials. Suitable materials for fillers are typically selected from the group consisting of calcium carbonate, talc, nanoclays, nanocellulose, hemp fibers, kaolin, carbon black, wollastonite, glass fibers, carbon fibers, graphite fibers, mica, silica, dolomite, barium sulfate, magnetite, halloysite, zinc oxide, titanium dioxide, montmorillonite, feldspar, asbestos, boron, steel, carbon nanotubes, cellulose fibers, flax, cotton, starch, polysaccharides, aluminum hydroxide, magnesium hydroxide, modified starch, chitin and chitosan, alginates, gluten, zein, casein, collagen, gelatin, polysaccharides, guar gum, xanthan gum, succinoglycans, natural rubber, rosinic acid, lignin, natural fibers, jute, kenaf, hemp, ground nut shells, wood flour, and mixtures thereof.

[0062] The amount of filler in the polymer film composition may be up to about 50 wt %. More preferably, the core polymer film composition is composed of about 5 wt % to about 30 wt % filler.

[0063] Additionally, in some cases, the polymer film composition may include up to 50 weight percent of one or more additives selected from the group consisting of poly(vinyl alcohol), poly(vinyl acetate), poly(vinyl laurate), poly(ethylene vinyl acetate), poly(glycolic acid), furan dicarboxylic acid-based polyesters, cellulose, nanocellulose, dextran, and mixtures thereof.

[0064] Typically, the at least one poly(hydroxyalkanoate) polymer has a weight average molecular weight (as determined by ASTM D6474-20) of about 50,000 Daltons to about 7.5 million Daltons, more preferably a weight average molecular weight of about 300,000 Daltons to about 3 million Daltons.

[0065] In another aspect, the present disclosure also provides a product packaging for a consumer product, which utilizes the aforementioned polymer composition. Specifically, the product packaging includes at least one biodegradable packaging portion comprising the aforementioned polymer composition. The product packaging can be used to package clothing, household goods, food, and health and beauty products.

[0066] In certain embodiments, such biodegradable packaging can be formed by a coextrusion process. The packaging can be manufactured by coextruding at least three layers selected from a surface film layer, a sealant film layer, a combination of a sealant film layer and a surface film layer, and a core film layer, wherein the sealant film layer and the surface film layer each include a blend of 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA) and optionally a small amount of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers; the core film layer comprises a blend of about 30 wt % to about 80 wt % polyhydroxyalkanoate (PHA), about 20 wt % to about 40 wt % polylactic acid (PLA) and optionally a small amount of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers. The core film layer is disposed between a combination of a surface film layer and a sealant film layer, between two sealant film layers, or between two surface film layers, wherein the sealant film layer and the surface film layer each contain the same or different amounts of PHA, PLA and other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers.

[0067] For example, refer to Figure 1 , the barrier film 10 may include one or more core layers 12 between two sealant layers 14, wherein each sealant layer 14 may include one or more sealant layers 14. Figure 2 , the printed film 16 may include one or more core layers 12 between two surface layers 18, wherein each surface layer 18 may include one or more surface layers 18. Figure 3 As shown, the printed film or barrier film 20 can also be made of one or more core layers 12, a surface layer 18 including one or more surface layers 18, and a sealant layer 14 including one or more sealant layers 14. Other variations of composite biaxially oriented films such as Figure 4-6 As shown. Figure 4-6In each of the layers 24, one or more layers 24 may be any combination of one or more surface layers, barrier layers, other biodegradable layers, metallized layers, coatings, etc. The core layer 12, sealant layer 14, and surface layer 18 are as described above. Figure 1 and Figure 4 The structure shown may be a heat sealable barrier film structure. Figure 2 and Figure 6 The structure shown can be a printed film structure, and Figure 3 and Figure 5 The structure shown can be a printed film structure or a barrier film structure.

[0068] Crystallinity

[0069] Volume percentage crystallinity (Φ c ) often determines the end-use properties a polymer possesses. For example, highly (greater than 50%) crystalline polyethylene polymers are strong and rigid, making them suitable for products such as plastic milk containers. Low-crystallinity polyethylene, on the other hand, is soft and tough, making it suitable for products such as food packaging and trash bags. Crystallinity can be determined in a variety of ways, including x-ray diffraction, differential scanning calorimetry (DSC), density measurements, and infrared absorption. The most appropriate method will depend on the material being tested.

[0070] Volume percent crystallinity (Φ) of poly(hydroxyalkanoate) copolymers c ) can vary depending on the mole percentage of poly(3-hydroxyhexanoate) in the poly(hydroxyalkanoate) copolymer. The addition of poly(3-hydroxyhexanoate) effectively reduces the volume percent crystallinity, crystallization rate, and melting temperature of the poly(hydroxyalkanoate) copolymer, while increasing the flexibility of the copolymer. As described herein, nucleating agents can be used to accelerate the crystallization process of poly(hydroxyalkanoate) copolymers.

[0071] Typically, the poly(hydroxyalkanoates) used to make the composite film structures described herein preferably have a crystallinity (as measured by x-ray diffraction) of from about 0.1% to about 99%; more preferably from about 2% to about 80%; more preferably from about 20% to about 70%.

[0072] When the poly(hydroxyalkanoate) of the present invention is processed into a molded article or film, the amount of crystallinity (measured by x-ray diffraction) of such poly(hydroxyalkanoate) is more preferably from about 10% to about 80%; more preferably from about 20% to about 70%; more preferably from about 30% to about 60%.

[0073] Melting temperature

[0074] Preferably, the melting temperature (Tm) of the biodegradable poly(hydroxyalkanoate) of the present invention is from about 30°C to about 170°C, more preferably from about 90°C to about 165°C, more preferably from about 130°C to about 160°C.

[0075] Film manufacturing method

[0076] The biaxially oriented industrial or home compostable films disclosed herein have improved biodegradability and / or compostability and can be processed using conventional procedures for producing monolayer or multilayer films on conventional film making equipment. The poly(hydroxyalkanoate) pellets of the present invention can be dry blended and then melt mixed in a film extruder. Alternatively, if insufficient mixing occurs in a film extruder, the pellets can be dry blended and then melt mixed in a premix extruder and then regranulated before film extrusion. Coextrusion of a surface film layer or sealant film layer with a core film layer is a particularly suitable process for making barrier webs and printed webs described herein.

[0077] Poly(hydroxyalkanoates) can be melt processed into films using a cast film extrusion process. In the cast film process, a molten polymer mixture is extruded through a slot die. Typically, the flat web from the slot die is cooled on large moving polished metal rolls. The web cools rapidly and is peeled off the first roll, passed through one or more auxiliary cooling rolls, then through a set of rubber-coated traction or "pull" rolls, and finally to a winder.

[0078] For the production of multilayer films, a coextrusion process is preferably used. This process requires more than one extruder and a coextrusion feed block or a multi-manifold die system or a combination of both to obtain multiple film structures.

[0079] It has been found very surprisingly that the annealing temperature in the TD furnace during the biaxial orientation process of the cast film production process may help or minimize the shrinkage of poly(hydroxyalkanoate)-based polymer films. The improved annealing process of the poly(hydroxyalkanoate)-based polymer film can be accomplished by heating the film to a temperature of about 110°C to about 135°C (preferably about 125°C to about 130°C) during the biaxial orientation process and then relaxing the film in the transverse direction (TD) by about 5% to about 25%. In some embodiments, the film is first relaxed by about 15% to about 25% in the transverse direction (TC) and then annealed in a temperature range of about 110°C to about 120°C during the biaxial orientation step. It is believed that annealing the semi-crystalline film material at a relatively high temperature can improve the quality of the film in terms of micro- and macrostructural features (such as crystalline morphology, density, grain size, etc.). The overall shrinkage improvement of the film depends on the annealing temperature, annealing time, biaxial orientation temperature, and the amount of relaxation of the film after the annealing step.

[0080] The following non-limiting examples illustrate methods of controlling shrinkage of blown films of poly(hydroxyalkanoate)-based polymers.

[0081] Example 1

[0082] The formulated poly(hydroxyalkanoate)-based polymer materials are converted into barrier films and printed films by using a coextrusion process in which three or more layers are extruded simultaneously. Experiments were conducted at different annealing roller temperatures using the same extruder. Film samples were prepared at annealing roller temperatures of 60°C, 80°C, 100°C, 110°C and 120°C. The longitudinal (MD) and transverse (TD) shrinkages were studied using the method described in ASTM D2732. The film annealing temperatures and shrinkage data are shown in Table 2. The shrinkage measurement temperature was selected based on a storage temperature of 45°C for storage and transportation of the finished product and post-processing temperatures such as coating, metallization and sealing temperatures (80°C, 100°C and 110°C).

[0083] Table 1

[0084] Annealing roller temperature (℃) Shrinkage measurement temperature (℃) Oil bath time (seconds) MD shrinkage (%) TD shrinkage (%) 60 45 30 4 0 60 80 30 33 -1.3 60 100 30 43 -1.7 60 110 30 49.3 -2 80 45 30 2 0 80 80 30 26.7 -3.7 80 100 30 37.7 -4.2 80 110 30 44.8 -4.5 100 45 30 1.7 0 100 80 30 14.7 -3 100 100 30 25.7 -4.2 100 110 30 32.7 -5 110 45 30 0.8 0 110 80 30 6.7 -1 110 100 30 13 -2.3 110 110 30 18 -2.7 120 45 30 0 0 120 80 30 1.8 -0.2 120 100 30 4 -1 120 110 30 6 -1

[0085] As shown in the table above, the shrinkage values ​​of poly(hydroxyalkanoate) films with a lower annealing temperature (60°C) are very high compared to the industry standard of less than 5%. When the annealing temperature is above 100°C, the shrinkage values ​​decrease significantly, and when the annealing temperature is 120°C, the shrinkage value reaches the industry standard value of less than 5%.

[0086] The following non-limiting examples illustrate processes for controlling shrinkage of poly(hydroxyalkanoate)-based polymer films prepared by a biaxially oriented film process.

[0087] Example 2

[0088] Sample poly(hydroxyalkanoate) based films were prepared using the same extruder and MDO profile using different transverse orientation (TDO) annealing temperatures. The transverse (TD) annealing temperatures used were 60°C, 93°C, and 129°C. The shrinkage measurement temperatures were selected based on the expected maximum temperatures for finished product storage / transportation (45°C) and post-processing processes such as coating, metallization, and sealing temperatures (80°C, 100°C, and 110°C). The machine direction (MD) and transverse direction (TD) shrinkage were studied by heating the finished film in an oven at 110°C for 10 minutes. The results are shown in the table below.

[0089] Table 2

[0090] Annealing temperature(℃) Oven shrinkage temperature (℃) Oven time (minutes) Longitudinal shrinkage (%) TD shrinkage (%) 60 110 10 14 39 93 110 10 6 22 129 110 10 0 0

[0091] The shrinkage values ​​of poly(hydroxyalkanoate) films at lower annealing temperatures (60°C) are very high compared to the industry standard of less than 5%. The shrinkage values ​​decrease significantly with increasing annealing temperature and reach the industry standard value of less than 5% at an annealing temperature of 129°C.

[0092] Poly(hydroxyalkanoate)-based polymer films are prepared by modifying poly(hydroxyalkanoate) with melt strength enhancers, chain extenders, and other processing aids. Poly(hydroxyalkanoate)-based films made according to the present disclosure may include about 50 wt % to 80 wt % of a poly(hydroxyalkanoate) copolymer and about 20 wt % to about 50 wt % of a polymer modifier. In some embodiments, the poly(hydroxyalkanoate) copolymer is poly-3-hydroxybutyrate-co-3-hydroxyhexanoate.

[0093] According to the present disclosure, exemplary formulations can be used to make coextruded biaxially oriented biodegradable films. The main components of the core film, sealant film, and surface film are listed in Table 3 below.

[0094] Table 3 - Film formulation

[0095]

[0096] In the table below, using the same oven shrink temperature, different biaxial annealing temperatures and relaxation percentages are used to determine shrinkage in the MD and TD directions. Needle penetration force is determined according to ASTM D-4833. Haze values ​​are determined according to ASTM D1003.

[0097] Table 4 - Barrier Film Results

[0098]

[0099] Table 5 - Printed Film Results

[0100]

[0101] Table 6 provides illustrations of printed films made according to the present disclosure having relatively low haze values.

[0102] Table 6

[0103]

[0104] The aforementioned embodiments of the composite biaxially oriented biodegradable film illustrate that, at an annealing temperature of about 110°C to about 130°C, when the TD relaxation rate of stretching in the TD direction is 5% to 25%, a biaxially oriented biodegradable film having a longitudinal shrinkage of about 1% to less than 5% and a transverse shrinkage of about 6% to less than 15% can be produced.

[0105] The foregoing descriptions of preferred embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are selected and described in order to provide the best illustration of the principles of the present invention and its practical application, so that those of ordinary skill in the art can utilize the present invention in various embodiments and make various modifications to suit the intended specific use. All such modifications and variations are within the scope of the present invention as determined by the appended claims when interpreted in accordance with the scope of fair, legal and equitable authorization.

Claims

1. A biaxially oriented industrial or home compostable film web comprising at least 3 coextruded layers selected from the group consisting of: A surface film layer, a sealant film layer, and a combination of a sealant film layer and a surface film layer, wherein the sealant film layer and the surface film layer each comprise a blend of 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA), and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers; and A core film layer, the core film layer comprising a blend of about 30 wt % to about 80 wt % polyhydroxyalkanoate (PHA), about 20 wt % to about 40 wt % polylactic acid (PLA) and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers; wherein the core film layer is disposed between a combination of the surface film layer and the sealant film layer, between two sealant film layers, or between two surface film layers; wherein the sealant film layer and the surface film layer each comprise the same amount or different amounts of PHA, PLA and other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers.

2. The biaxially oriented industrial or home compostable film web according to claim 1, wherein the PHA of the core film layer comprises from about 2 mol% to about 10 mol% 3-hydroxyhexanoate and the balance 3-hydroxybutyrate.

3. The biaxially oriented industrial or home compostable film web of claim 1, wherein the PHA of the sealant film layer comprises from about 2 mol % to about 10 mol % 3-hydroxyhexanoate and the balance 3-hydroxybutyrate.

4. The biaxially oriented industrial or home compostable film web of claim 1, wherein the PHA of the surface film layer comprises from about 2 mol% to about 10 mol% 3-hydroxyhexanoate and the balance 3-hydroxybutyrate.

5. The biaxially oriented industrial or home compostable film web of claim 1, wherein the biaxially oriented industrial or home compostable film has an oven shrinkage in the machine direction (MD) of 0% to less than about 5% and an oven shrinkage in the transverse direction (TD) of 0% to less than about 15%.

6. The biaxially oriented industrial or home compostable film web of claim 1, wherein the biaxially oriented industrial or home compostable film has a needle penetration greater than about 700 grams force (gf).

7. A biaxially oriented industrial or home compostable printed film web comprising a core film layer disposed between the combination of a surface film layer and a sealant film layer of claim 1.

8. A biaxially oriented industrial or domestic compostable barrier film web comprising a core film layer disposed between the combination of a surface film layer and a sealant film layer of claim 1.

9. The biaxially oriented industrial or home compostable printed film web of claim 8, wherein the printed film web has an oven shrinkage in the machine direction (MD) of 0% to less than about 5.0% and an oven shrinkage in the transverse direction (TD) of 0% to less than about 15%.

10. The biaxially oriented industrial or home compostable printed film web of claim 8, wherein the biaxially oriented industrial or home compostable printed film web has a needle penetration range of greater than about 700 grams-force (gf).

11. The biaxially oriented industrial or home compostable printed film web of claim 8, wherein the biaxially oriented industrial or home compostable printed film has a haze value of less than 15%.

12. A biaxially oriented industrial or home compostable barrier film web comprising a core film layer disposed between two sealant film layers of claim 1.

13. The biaxially oriented industrial or home compostable barrier film web according to claim 12, wherein the biaxially oriented barrier film has an oven shrinkage in the machine direction (MD) of 0% to less than about 5.0% and an oven shrinkage in the transverse direction (TD) of 0% to less than about 15%.

14. The biaxially oriented industrial or home compostable barrier film web of claim 12, wherein the biaxially oriented barrier film has a needle penetration range of greater than about 700 grams-force (gf).

15. A biaxially oriented industrial or home compostable printed film web comprising a core film layer disposed between two surface film layers of claim 1.

16. A method for improving the dimensional stability of a biaxially oriented industrial or home compostable film web comprising at least three coextruded layers, the method comprising extruding a composite poly(hydroxyalkanoate)-based polymer film; and annealing the composite poly(hydroxyalkanoate) polymer film at a temperature in the range of about 110°C to about 130°C during the biaxial orientation process.

17. The method according to claim 16, wherein: Prior to or simultaneously with the annealing step, the biaxially oriented industrial or home compostable film web is relaxed in the transverse direction (TD) from about 5% to about 25% from transverse direction (TD) stretching.

18. The method of claim 16, wherein the biaxially oriented industrial or domestic compostable film web is annealed in a temperature range of about 110°C to about 130°C during the biaxial orientation process, and the industrial or domestic compostable film web is relaxed from transverse direction (TD) stretching by about 15% to about 25% prior to or simultaneously with the annealing step.

19. The method of claim 16, wherein the biaxially oriented industrial or home compostable film web comprises: at least two sealant film layers, wherein the at least two sealant film layers comprise a blend of about 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA), and optionally other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers, wherein each of the two sealant film layers may have the same amount or different amounts of PHA, PLA, and other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers; and A core film layer comprising a blend of about 30 wt % to about 80 wt % polyhydroxyalkanoate (PHA), about 20 wt % to about 40 wt % polylactic acid (PLA), and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers, wherein the core film layer is disposed between the at least two sealant film layers.

20. A biaxially oriented barrier web made by the method of claim 19, further comprising coating and / or metallizing the barrier web.

21. The method of claim 16, wherein the biaxially oriented industrial or home compostable film web comprises: at least two surface film layers, wherein the at least two surface film layers comprise a blend of about 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA), and optionally other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers, wherein each of the two sealant film layers may have the same or different amounts of PHA, PLA, and other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers; and A core film layer, the core film layer comprising a blend of about 30 wt % to about 80 wt % of polyhydroxyalkanoate (PHA), about 20 wt % to about 40 wt % of polylactic acid (PLA) and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers, wherein the core film layer is disposed between the at least two surface film layers.

22. A biaxially oriented printing web made by the method of claim 21 further comprising printing on the printing web.

23. The method of claim 16, wherein the biaxially oriented industrial or home compostable film web comprises: A surface film layer comprising a blend of about 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 50 wt % to about 70 wt % polylactic acid (PLA) and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides and fillers; A core film layer comprising a blend of about 30 wt % to about 80 wt % polyhydroxyalkanoate (PHA), about 20 wt % to about 40 wt % polylactic acid (PLA), and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers; and A sealant film layer comprising a blend of 0 wt % to about 80 wt % polyhydroxyalkanoate (PHA) and about 20 wt % to about 100 wt % polylactic acid (PLA), and optionally small amounts of other biopolymers, other polymers, nucleating agents, chain extenders, fatty amides, and fillers, wherein the core film layer is disposed between the surface film layer and the sealant film layer.

24. The method of claim 16, wherein the biaxially oriented industrial or home compostable film web has a haze value of less than about 15%.

25. The method of claim 16, wherein the biaxially oriented industrial or home compostable film web comprising at least 3 coextruded layers has an oven shrinkage at 120°C of 0% to less than about 5% in the machine direction (MD) and 0% to less than about 15% in the transverse direction (TD).

26. The method of claim 16, wherein the biaxially oriented industrial or home compostable film web has a needle penetration range of about 700 grams-force (gf).

27. A biaxially oriented industrial or home compostable film web made by the method of claim 16.

28. A biaxially oriented industrial or home compostable film web comprising at least three coextruded layers made by the method of claim 16.

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