Melt processed SOY protein thermoplastic materials and blends

Abstract

A melt processed soy protein-based thermoplastic material comprising soy protein isolate, a plasticizer, and a crosslinking agent. The material may include glycerol and water as plasticizers and tannic acid as a crosslinking agent. The material may exhibit a tensile strength of more than 10 MPa and a maximal strain of up to 100%. The material may be processable by compression molding, batch mixing followed by compression molding, or compounding followed by cast extrusion. A method of producing the material and a biodegradable blend incorporating the material with a synthetic biodegradable polymer are also provided. The blend may exhibit improved mechanical properties compared to the soy protein material alone. A multi-layer film for food packaging comprising the material is also disclosed.

Description

[0001] MELT PROCESSED SOY PROTEIN THERMOPLASTIC MATERIALS AND BLENDS

[0002] RELATED APPLICATION

[0003] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 729,408 filed on December 8, 2024, the contents of which are incorporated herein by reference in their entirety.

[0004] FIELD OF INVENTION

[0005] The present disclosure relates to biodegradable polymeric materials, and more particularly to melt processed soy protein-based thermoplastic materials and blends with improved mechanical properties for use in packaging and other applications.

[0006] BACKGROUND

[0007] Biodegradable polymeric materials derived from renewable natural resources have gained significant attention in recent years as promising alternatives to petroleum-based non-biodegradable polymers. These materials offer potential solutions to environmental concerns associated with plastic waste accumulation and pollution. Among various natural polymers, soy protein has emerged as an attractive option due to its abundance, low cost, and relatively long storage time compared to other natural polymers.

[0008] Soy protein-based materials have shown potential for various applications, including food packaging, agricultural films, and disposable consumer goods. One of the key advantages of soy protein is its low oxygen permeability, which is approximately 500 times lower than that of polyethylene. This property makes soy protein-based materials particularly suitable for food packaging applications where oxygen barrier properties are crucial for preserving food quality and extending shelf life.

[0009] However, the development of soy protein-based thermoplastic materials faces several challenges. One of the primary difficulties is achieving suitable mechanical properties that can compete with conventional synthetic plastics. Soy protein-based materials often exhibit lower tensile strength, flexibility, and water resistance compared to petroleum-based polymers, limiting their practical applications.

[0010] Another significant challenge in the production of soy protein-based thermoplastic materials is the narrow processing window during melt processing. Soy proteins have high softening temperatures, often above their decomposition temperature, which makes it difficult to process them using conventional thermoplastic processing techniques without causing thermal degradation. This limitation necessitates the use of additives and modifications to improve the processability of soy protein-based materials.

[0011] The hydrophilic nature of soy proteins also poses challenges in terms of moisture sensitivity and dimensional stability of the resulting materials. Soy protein-based products tend to absorb moisture from the environment, leading to changes in their mechanical properties and potentially limiting their use in high-humidity conditions or applications requiring prolonged exposure to moisture.

[0012] Jane, J., & Wang, S. (1996). US5523293A discloses a soy protein-based thermoplastic composition for preparing molded articles. The composition includes soy protein, a reducing agent, a plasticizer, water, and optionally a filler, a cross-linking agent, and other additives. The composition has a high degree of flowability for processing by extrusion or injection molding.

[0013] Verbeek, C. J. R., & van den Berg, L. E. (2010). Extrusion processing and properties of protein-based thermoplastic materials. Macromolecular Materials and Engineering, 295(1), 10-21. This study explores the complexities of processing protein-based thermoplastics using extrusion techniques, focusing on challenges such as high decomposition temperatures and the necessity of using plasticizers and process optimization to mitigate protein degradation.

[0014] Jimenez-Rosado, M., Bouroudian, E., Perez-Puyana, V., Guerrero, A., & Romero, A. (2020). Evaluation of different strengthening methods in the mechanical and functional properties of soy protein-based bioplastics. Journal of Cleaner Production, 262, 121345. This research evaluates various methods to improve the mechanical and functional properties of soy protein-based bioplastics, emphasizing the role of plasticizers and crosslinking agents.

[0015] Draou-Renoux, J., Dani, J., Douchain, C., Prashantha, K., Lacrampe, M. F., & Krawczak, P. (2016). Simultaneous plasticization and blending of isolated soy protein with poly (butylene succinate-co-adipate). Proceedings of the 7th International Conference on Polymers and Moulds Innovations (PMI-2016), Belgium, 21-23. This work investigates blending isolated soy protein with poly(butylene succinate-co-adipate) to address the poor mechanical and barrier properties of proteinbased polymers.

[0016] Tian, H., Guo, G., Fu, X., Yao, Y., Yuan, L., & Xiang, A. (2018). Fabrication, properties, and applications of soy-protein-based materials: A review. International Journal of Biological Macromolecules, 120, 475-490. This comprehensive review outlines methods for fabricating soyprotein-based materials and discusses the benefits of blending soy protein with synthetic biodegradable polymers. SUMMARY This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0017] The present invention relates to the development of biodegradable thermoplastic soy proteinbased materials using melt processing techniques compatible with industrial-scale manufacturing, including compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion. The invention addresses the challenge of melt-processing natural polymers, like soy protein, which typically decompose before softening, by employing plasticizers such as glycerol and double-distilled water to impart flexibility and reduce softening temperature, as well as crosslinking agents like tannic acid and epoxidized soybean oil (ESBO) to enhance tensile strength and ductility, alongside reducing agents such as sodium sulfite to control crosslinking. The invention further includes blends of soy protein with synthetic biodegradable polymers such as polylactic acid (PLA) or polybutylene adipate terephthalate (PBAT) to improve mechanical properties and accelerate biodegradation while maintaining environmental benefits and cost advantages given soy protein’s renewable and inexpensive nature. The films and materials exhibit low oxygen permeability, making them suitable for applications such as food packaging, and provide an improved environmental solution by utilizing melt processing, which is economically and industrially preferable, thereby facilitating seamless integration into existing manufacturing processes and offering significant benefits in terms of enhanced packaging solutions, biodegradability, and reduced plastic waste.

[0018] According to an aspect of some embodiments of the present invention, there is provided a thermoplastic composition including: soy protein; and at least one plasticizer.

[0019] In some embodiments, the thermoplastic composition provided herein includes soy protein in the form of soy protein isolate (SPI) and / or soy protein concentrate (SPC).

[0020] In some embodiments, the soy protein isolate or soy protein concentrate provided herein has a protein content of at least 90% by dry weight.

[0021] In some embodiments, the plasticizer provided herein is selected from the group consisting of glycerol, water, tannic acid, sorbitol, ethylene glycol, diethylene glycol, and combinations thereof.

[0022] In some embodiments, the plasticizer provided herein is present in an amount ranging from 10% to 60% by weight of the total composition.

[0023] In some embodiments, the thermoplastic composition provided herein further includes at least one thermoplastic polymer that is not a soy protein. In some embodiments, the thermoplastic polymer provided herein is selected from polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polycaprolactone (PCL), and any combination thereof.

[0024] In some embodiments, the thermoplastic polymer provided herein is present in the composition an amount ranging from 10% to 80% by weight of the total composition.

[0025] In some embodiments, the thermoplastic composition provided herein further includes an additional synthetic biodegradable polymer, forming a blend of at least three polymeric components.

[0026] In some embodiments, the thermoplastic composition provided herein further includes at least one crosslinking agent.

[0027] In some embodiments, the crosslinking agent provided herein is selected from the group consisting of tannic acid, epoxidized soybean oil, L-cysteine, glyoxal, genipin, alginate, pectin, chitosan, and combinations thereof.

[0028] In some embodiments, the crosslinking agent provided herein comprises tannic acid in an amount ranging from 0.5% to 10% by weight of the soy protein.

[0029] In some embodiments, the thermoplastic composition provided herein further includes at least one compatibilizer.

[0030] In some embodiments, the compatibilizer provided herein is selected from the group consisting of poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid.

[0031] In some embodiments, the thermoplastic composition provided herein further includes at least one reducing agent.

[0032] In some embodiments, the reducing agent provided herein is sodium sulfite, which is present in a concentration ranging from 0.1% to 5% by weight of the soy protein.

[0033] In some embodiments, the thermoplastic composition provided herein is prepared using a method selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion.

[0034] In some embodiments, the method provided herein includes using a twin-screw extruder at a temperature range of 80 °C to 160 °C.

[0035] In some embodiments, the thermoplastic composition provided herein further includes a stabilizer to prevent thermal degradation during processing.

[0036] In some embodiments, the thermoplastic composition provided herein is characterized by a tensile strength of at least 5 MPa.

[0037] In some embodiments, the thermoplastic composition provided herein is characterized by an elongation at break (strain) of at least 5%. In some embodiments, the thermoplastic composition provided herein is characterized by Oxygen Transmission Rate (OTR) below 100 cc / m2 / day.

[0038] In some embodiments, the thermoplastic composition provided herein is characterized by Water Vapor Transmission Rate (WVTR) below 10 g / m2 / day.

[0039] According to an aspect of some embodiments of the present invention, there is provided a method that is effected by: providing a precursor blend of the thermoplastic composition provided herein; melting and homogenizing the precursor blend to thereby obtain a melt-blended intermediate; and processing the melt-blended intermediate using a melt-processing process to thereby obtain a film of the thermoplastic composition, wherein the melt-processing process is effected under conditions that maintain structural integrity of the soy protein.

[0040] In some embodiments, the thermoplastic composition provided herein includes at least one crosslinking agent.

[0041] In some embodiments, the melt-processing process provided herein is selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion.

[0042] In some embodiments, the melting and homogenizing provided herein is effected at a temperature of 100-150 °C and a speed of 30-90 rpm for at least 2-15 minutes.

[0043] In some embodiments, subsequent to the melt-processing process provided herein, there is further included a drying step at a temperature of 20-50 °C for at least 5-20 hours to remove excess moisture.

[0044] In some embodiments, at least one stabilizer is added to the melt-blended intermediate during the melting and homogenizing provided herein.

[0045] In some embodiments, when the melt processing technique provided herein is compression molding, the compression molding is performed at a temperature of 100-150 °C under a pressure of 2-5 metric tons for 3-5 minutes.

[0046] In some embodiments, when the melt processing technique provided herein is compounding, it is followed by cast extrusion, and the cast extrusion is carried out using a single-screw extruder with a screw speed of 30-60 rpm and a temperature gradient of 100-150 °C.

[0047] In some embodiments, the method provided herein further includes chemically modifying the soy protein isolate or soy protein concentrate through acetylation, succinylation, or Maillard reaction with reducing sugars.

[0048] In some embodiments, the method provided herein further includes a post-processing crosslinking step comprising spraying a crosslinker solution on the film followed by a drying step. In some embodiments, the film provided herein is characterized by a tensile strength of at least 5 MPa, and an elongation at break (strain) of at least 5%.

[0049] According to an aspect of some embodiments of the present invention, there is provided a method for preparing a biodegradable film that includes a multilayer structure, the method is effected by: forming a first layer that includes the thermoplastic composition provided herein; forming at least one additional layer that includes a synthetic biodegradable polymer that is not the thermoplastic composition provided herein; and laminating the layers together to form a composite film, wherein the first layer provides a low oxygen permeability barrier suitable for food packaging applications.

[0050] In some embodiments, the first layer provided herein has a thickness ranging from 50 to 500 micrometers.

[0051] In some embodiments, the method further includes a step of treating the first layer with an alkali solution to enhance its barrier properties.

[0052] In some embodiments, the additional layer provided herein includes a polymer selected from the group consisting of polybutylene succinate, polycaprolactone, polylactic acid, and polybutylene adipate terephthalate.

[0053] In some embodiments, the multilayer film provided herein is annealed at 80 °C.

[0054] In some embodiments, the method further includes a lamination process effected using a hot- pressing technique at a temperature ranging 100-150 °C under a pressure of 10-20 bar.

[0055] In some embodiments, the method further includes forming a tie layer between the first layer and the additional layer, wherein the tie layer includes a compatibilized blend of soy protein and the synthetic biodegradable polymer.

[0056] According to an aspect of some embodiments of the present invention, there is provided a biodegradable film article including: a core layer composed of the thermoplastic composition provided herein; and at least one outer layer including a synthetic biodegradable polymer, wherein the core layer has a low oxygen permeability and the outer layer provides mechanical strength and water resistance, and wherein the film is suitable for packaging applications that require both biodegradability and gas barrier properties.

[0057] In some embodiments, the core layer provided herein includes 40% to 60% by weight of the total film structure.

[0058] In some embodiments, the outer layer provided herein has a water vapor transmission rate (WVTR) of less than 100 g / m2 / day at 38°C and 90% relative humidity.

[0059] In some embodiments, the core layer includes an antioxidant additive to enhance the shelflife of the packaged product. In some embodiments, the biodegradable film article further includes a coating of hydrophobic nanoparticles on the outer layer to improve the film's water resistance.

[0060] In some embodiments, the film provided herein is heat-sealable at a temperature below 120 °C.

[0061] In some embodiments, the film further includes a tie layer between the core layer and the outer layer, wherein the tie layer includes a compatibilized blend of soy protein and the synthetic biodegradable polymer.

[0062] In some embodiments, the synthetic biodegradable polymer provided herein is selected from the group consisting of polylactic acid, polybutylene adipate terephthalate, polybutylene succinate, and polycaprolactone.

[0063] In some embodiments, the core layer includes a crosslinking agent selected from the group consisting of tannic acid, epoxidized soybean oil, L-cysteine, glyoxal, genipin, alginate, pectin, and chitosan.

[0064] In some embodiments, the core layer includes a plasticizer selected from the group consisting of glycerol, water, tannic acid, sorbitol, ethylene glycol, and di ethylene glycol.

[0065] In some embodiments, the core layer includes a compatibilizer selected from the group consisting of poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid.

[0066] In some embodiments, the soy protein in the core layer is chemically modified through acetylation, succinyl ati on, or Maillard reaction with reducing sugars.

[0067] In some embodiments, the core layer is crosslinked through a post-processing crosslinking method that includes spraying a crosslinker solution on the layer followed by a drying step.

[0068] In some embodiments, the film includes three polymeric components including the soy protein and two different synthetic biodegradable polymers.

[0069] According to an aspect of some embodiments of the present invention, there is provided a method for improving the mechanical properties of a biodegradable polymer, the method is effected by: blending a precursor blend of the thermoplastic composition provided herein with at least one synthetic biodegradable polymer to form a blend; and processing the blend using a melt processing technique.

[0070] In some embodiments, the synthetic biodegradable polymer provided herein is selected from the group consisting of polylactic acid, polybutylene adipate terephthalate, polybutylene succinate, and polycaprolactone.

[0071] In some embodiments, the method further includes adding a compatibilizer to improve interfacial adhesion between the thermoplastic composition and the synthetic biodegradable polymer. In some embodiments, the compatibilizer provided herein is selected from the group consisting of poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid.

[0072] In some embodiments, the melt processing technique provided herein is selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion.

[0073] Alternatively, according to an aspect of some embodiments of the present invention, there is provided a thermoplastic composition including soy protein isolate (SPI) or soy protein concentrate (SPC), at least one plasticizer, optionally at least one crosslinking agent, and optionally a reducing agent, wherein the composition is capable of being melt-processed under conditions that maintain the structural integrity of the soy protein without thermal decomposition.

[0074] In some embodiments, the thermoplastic composition may include one or more of the following features: the plasticizer is selected from the group consisting of glycerol, water, tannic acid, sorbitol, ethylene glycol, diethylene glycol, and combinations thereof; the crosslinking agent is selected from the group consisting of tannic acid, epoxidized soybean oil, L-cysteine, glyoxal, genipin, alginate, pectin, chitosan, and combinations thereof; the plasticizer is present in an amount ranging from 10% to 60% by weight of the total composition; the soy protein isolate or soy protein concentrate has a protein content of at least 90% by weight on a dry basis; the reducing agent is sodium sulfite present in a concentration ranging from 0.1% to 5% by weight of the soy protein isolate or soy protein concentrate; the composition further includes a compatibilizer selected from the group consisting of poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid; the crosslinking agent includes tannic acid in an amount ranging from 0.5% to 10% by weight of the soy protein isolate or soy protein concentrate; the composition further includes a synthetic biodegradable polymer selected from polylactic acid (PL A), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), or polycaprolactone (PCL); the synthetic biodegradable polymer is present in an amount ranging from 10% to 80% by weight of the total composition; the composition further includes an additional synthetic biodegradable polymer, forming a blend of three polymeric components; the composition is prepared using a method selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion; the method includes using a twin-screw extruder at a temperature range of about 80 °C to about 160 °C; the composition exhibits a tensile strength of at least 6 MPa and an elongation at break of at least 50%; the composition further includes a stabilizer to prevent thermal degradation during processing. According to another aspect of some embodiments of the present invention, there is provided a method for producing a thermoplastic soy protein-based film, the method including mixing soy protein isolate (SPI), or soy protein concentrate with at least one plasticizer and at least one crosslinking agent, melt blending the mixture to form a homogeneous composition, and processing the composition using a melt processing technique, wherein the resulting film exhibits both high tensile strength and ductility.

[0075] In some embodiments, the method may include one or more of the following features: the melt processing technique is selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion; the mixing step includes using a Brabender batch mixer at a temperature of about 120 °C and a speed of 60 rpm for at least 5 minutes; the method further includes a drying step at 40 °C for at least 12 hours to remove excess moisture before film formation; the melt blending step includes the addition of a stabilizer to prevent thermal degradation during processing; when the melt processing technique is compression molding, the compression molding is performed at a temperature of up to 160 °C under a pressure of 3 metric tons for 3 to 5 minutes; when the melt processing technique is compounding followed by cast extrusion, the cast extrusion is carried out using a single-screw extruder with a screw speed of 45 rpm and a temperature gradient from about 100 °C to about 160 °C; the method further includes chemically modifying the soy protein isolate or soy protein concentrate through acetylation, succinylation, or Maillard reaction with reducing sugars; the method further includes a postprocessing crosslinking step including spraying a crosslinker solution on the film followed by a drying step.

[0076] According to another aspect of some embodiments of the present invention, there is provided a method for preparing a biodegradable film including a multilayer structure, the method including forming a first layer including soy protein isolate or soy protein concentrate and at least one plasticizer, forming at least one additional layer including a synthetic biodegradable polymer, and laminating the layers together to form a composite film, wherein the first layer provides a low oxygen permeability barrier suitable for food packaging applications.

[0077] In some embodiments, the method may include one or more of the following features: the first layer has a thickness ranging from 50 to 500 micrometers; the method further includes a step of treating the first layer with an alkali solution to enhance its barrier properties; the additional layer includes a polymer selected from the group consisting of polybutylene succinate, polycaprolactone, polylactic acid, and polybutylene adipate terephthalate; the multilayer film is annealed at 80 °C to improve interlayer adhesion and reduce residual stresses; the lamination process is carried out using a hot pressing technique at a temperature of 100 °C to 150 °C under a pressure of 10 to 20 bar; the method further includes forming a tie layer between the first layer and the additional layer, wherein the tie layer includes a compatibilized blend of soy protein and the synthetic biodegradable polymer.

[0078] According to another aspect of some embodiments of the present invention, there is provided a biodegradable film article including a core layer composed of soy protein isolate or soy protein concentrate and at least one plasticizer, and at least one outer layer including a synthetic biodegradable polymer, wherein the core layer has a low oxygen permeability and the outer layer provides mechanical strength and water resistance, and wherein the film is suitable for packaging applications that require both biodegradability and gas barrier properties.

[0079] In some embodiments, the biodegradable film article may include one or more of the following features: the core layer includes 40% to 60% by weight of the total film structure; the outer layer has a water vapor transmission rate (WVTR) of less than 100 g / m2 / day at 38 °C and 90% relative humidity; the core layer includes an antioxidant additive to enhance the shelf life of the packaged product; the article further includes a coating of hydrophobic nanoparticles on the outer layer to improve the film's water resistance; the film is heat-sealable at a temperature below 120 °C, making it suitable for automated packaging processes; the article further includes a tie layer between the core layer and the outer layer, wherein the tie layer includes a compatibilized blend of soy protein and the synthetic biodegradable polymer; the synthetic biodegradable polymer is selected from the group consisting of polylactic acid, polybutylene adipate terephthalate, polybutylene succinate, and polycaprolactone; the core layer includes a crosslinking agent selected from the group consisting of tannic acid, epoxidized soybean oil, L-cysteine, glyoxal, genipin, alginate, pectin, and chitosan; the core layer includes a plasticizer selected from the group consisting of glycerol, water, tannic acid, sorbitol, ethylene glycol, and diethylene glycol; the core layer includes a compatibilizer selected from the group consisting of poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid; the soy protein in the core layer is chemically modified through acetylation, succinylation, or Maillard reaction with reducing sugars; the core layer is crosslinked through a post-processing crosslinking method including spraying a crosslinker solution on the layer followed by a drying step; the film includes three polymeric components including the soy protein and two different synthetic biodegradable polymers.

[0080] According to another aspect of some embodiments of the present invention, there is provided a method for improving the mechanical properties of a biodegradable polymer, the method including blending a melt processed soy protein based thermoplastic material with at least one synthetic biodegradable polymer to form a blend, and processing the blend using a melt processing technique to form a final product. In some embodiments, the method may include one or more of the following features: the synthetic biodegradable polymer is selected from the group consisting of polylactic acid, polybutylene adipate terephthalate, polybutylene succinate, and polycaprolactone; the method further includes adding a compatibilizer to improve interfacial adhesion between the soy protein and the synthetic biodegradable polymer; the compatibilizer is selected from the group consisting of poly(2- ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid; the melt processing technique is selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion.

[0081] Thus, the present invention advances the field of biodegradable, plant-based thermoplastics by addressing challenges in melt processing of soy protein and achieving improved mechanical properties using industrially relevant techniques. Some aspects of the present invention include the development of melt-processed soy protein films using industrial-scale compounding followed by cast extrusion, the use of tannic acid as a crosslinking agent, and the optimization of formulations with high water content and glycerol as plasticizers. These advancements result in soy protein-based thermoplastic films with enhanced tensile strength, maximal strain, and Young's modulus.

[0082] While the state of the art has explored various methods to improve soy protein-based materials, including the use of crosslinking agents and blending with synthetic polymers, the present invention uniquely combines these approaches in a melt processing context. The invention also introduces novel concepts such as multi-layer films incorporating a soy protein-based layer for enhanced oxygen barrier properties, particularly suited for food packaging applications. These developments represent significant progress in creating biodegradable materials with controlled properties, lower density, and faster degradation rates compared to synthetic biodegradable polymers alone, addressing growing environmental concerns and industry demands.

[0083] The foregoing general description of the illustrative embodiments and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure and are not restrictive.

[0084] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0085] Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying figures. With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the figures makes apparent to those skilled in the art how embodiments of the invention may be practiced. Non-limiting and non-exhaustive examples are described with reference to the following figures.

[0086] FIGs. l(a-d) show raw soy protein material (a), a front view of a processed soy protein film (b), a side view of a flexible soy protein film (c), and a reference page related to soy protein film processing (d).

[0087] FIGs. 2(a-c) illustrates steps of batch mixing and compression molding soy protein films.

[0088] FIGs. 3(a-d) depict three steps of compounding and cast extruding soy protein films.

[0089] FIG. 4 shows tensile stress-strain curves for films of soy protein compositions with various additives, tannic acid (TA), epoxidized soybean oil (ESBO, or SBO) and sodium sulfite (SS).

[0090] FIGs. 5(a-c) illustrates mechanical properties of soy protein films with different additives, tannic acid (TA), epoxidized soybean oil (ESBO, or SBO) and sodium sulfite (SS).

[0091] FIG. 6 depicts tensile stress-strain curves for soy protein films with varying water and additive content of tannic acid (TA) or epoxidized soybean oil (ESBO, or SBO).

[0092] FIGs. 7(a-c) shows mechanical properties of soy protein films with different pH and tannic acid (TA) or epoxidized soybean oil (ESBO, or SBO) additive concentrations.

[0093] FIGs. 8(a-c) compares mechanical properties of soy protein films prepared by different processing methods and different tannic acid (TA) or epoxidized soybean oil (ESBO, or SBO) additive concentrations.

[0094] FIG. 9 illustrates tensile stress-strain curves for soy protein films with various compositions and processing conditions, with tannic acid (TA) as an optional additive.

[0095] FIGs. 10(a-c) depicts mechanical properties of compounded and cast extruded soy protein films with different formulations, with tannic acid (TA) as an optional additive.

[0096] FIG. 11 is an FTIR spectra obtained for each material and for the adhesive blend that consists of 10 % SPI (in red), SPI alone (in green), PCL alone (in blue), and epoxidized soybean oil alone (ESBO in orange).

[0097] FIG. 12 presents SEM analysis for compositions comprising 10%, 20%, and 30% SPI (left to right).

[0098] FIG. 13 presents the effect of SPI concentrations on the mechanical properties of the adhesive films.

[0099] FIG. 14 presents the effect of SPI concentrations on the peel strength (N / cm) on different substrates, PBAT substrate (in red), PLA substrate (in blue) and SIP and glycerol films (in green).

[0100] FIG. 15 presents the peel strength on SPI / PCL substrate compared to SPI / glycerol films.

[0101] FIG. 16 shows the results of an Oxygen Transmission Rate (OTR) comparison assay conducted for various films comprising the composition provided herein. FIG. 17 shows stress strain curves of 75 / 25 PLA / Soy blends, as affected by addition of compatibilizers.

[0102] FIG. 18 shows the WVTR values for the tested 75 / 25 PDLGA / Soy blends.

[0103] DETAILED DESCRIPTION

[0104] The present disclosure relates to biodegradable polymeric materials, and more particularly to melt processed soy protein-based thermoplastic materials and blends with improved mechanical properties for use in packaging and other applications.

[0105] The present invention relates to melt processed soy protein-based thermoplastic materials and blends. These materials may be derived from soy protein isolate (SPI) or soy protein concentrate (SPC) and may be capable of being melt-processed under conditions that maintain the structural integrity of the soy protein without thermal decomposition.

[0106] As discussed above, soy protein-based adhesives have been extensively studied in the context of wood bonding. Numerous modifications have been proposed to overcome their inherent weaknesses, including enzymatic hydrolysis, chemical cross-linking (with triglycidylamine, furfuryl alcohol, phytic acid, or undecylenic acid), blending with synthetic polymers, and plasticization. These approaches have achieved notable improvements in wet shear strength and durability, demonstrating the potential of soy protein as a sustainable adhesive material. However, nearly all published studies focus on porous, hydrophilic substrates such as wood, where penetration and mechanical interlocking aid adhesion.

[0107] A critical gap in the literature remains unaddressed: there is no systematic investigation into the use of soy protein-based adhesives for bonding non-porous polymeric films. This is particularly relevant for packaging, where multilayer systems involve smooth polymer interfaces rather than porous wood surfaces. The absence of research on this interface presents a significant limitation for translating soy protein adhesives into industrial packaging applications.

[0108] The present disclosure addresses this gap by providing and characterizing biodegradable hot- melt adhesives compositions composed of SPI and other components, including PCL, epoxidized soybean oil (ESBO) and more. By systematically studying chemical structure, morphology, mechanical behavior, and adhesion performance on different polymeric substrates, the present invention provides the feasibility of SPLbased adhesives as tie layers in multilayer biodegradable packaging films.

[0109] Studies conducted during the initial stages of conceiving the present intention included the development and characterization of a biodegradable thermoplastic adhesive composition that incorporates soy protein isolate (SPI), polycaprolactone (PCL), and epoxidized soybean oil (ESBO) for use in multilayer film applications. While reducing the present invention to practice, exemplary adhesive formulations that included 10-30 wt.% SPI were prepared through a process of melt blending at 160 °C, followed by compression molding. The adhesive films were analyzed using various methods, including Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), tensile testing, and T-peel adhesion tests, with a focus on polylactic acid (PL A), polybutylene adipate terephthalate (PBAT), and soy protein-based substrates. The FTIR spectra did not show any signs of covalent epoxy-amine reactions, indicating that the adhesion was mainly dependent on hydrogen bonding and physical interactions. The SEM analysis revealed a consistent dispersion of SPI at a concentration of 10 wt.%, while higher SPI loadings resulted in increased phase separation and the formation of aggregates. Mechanical testing revealed that an increase in SPI content led to a reduction in both tensile strength and elongation at break, whereas adhesion performance reached its highest point at 20 wt.% SPI. The findings underscore the promise of SPI- based hot-melt adhesives as sustainable tie-layers in fully biodegradable multilayer packaging, effectively integrating oxygen barrier properties with improved interfacial adhesion

[0110] The melt processed soy protein-based thermoplastic materials and blends provided herein may be used in a wide range of applications. In some cases, these materials may be suitable for packaging, particularly food packaging due to their potential oxygen barrier properties. Other potential applications may include agricultural films, disposable consumer goods, and biomedical products.

[0111] The ability to melt process these soy protein-based materials may allow for the use of conventional plastic processing techniques, such as extrusion, injection molding, and thermoforming. This compatibility with existing manufacturing processes may facilitate the adoption of these materials as alternatives to traditional plastics in various industries.

[0112] Thermoplastic composition

[0113] Thus, according to an aspect of some embodiments of the present invention, there is provided a thermoplastic composition includes at least: soy protein; and at least one plasticizer.

[0114] The composition may optionally include other ingredients and additives, such as additional thermoplastic polymers, compatibilizers, crosslinking agents, and other functional components that can enhance the processability, mechanical properties, or barrier characteristics of the final material.

[0115] As used herein, the phrases “thermoplastic composition”, “soybean-based thermoplastic composition”, “biodegradable thermoplastic adhesive”, “adhesive composition”, “soybean-based adhesive composition”, while replacing “composition” with “formulation”, and the like, are used herein interchangeably and refer to a blend comprising at least one proteinaceous component originating, extracted or otherwise obtained from soybeans, at least one plasticizer, at least one thermoplastic polymer, and optionally at least one reducing agent compatibilizer, or functional additive, wherein the blend is processable under melt conditions to form films or tie layers exhibiting adhesion between similar and / or dissimilar polymer substrates.

[0116] The thermoplastic composition provided herein is characterized as a melt-processed material derived from a precursor blend comprising a mixture of ingredients. This precursor blend includes, in various embodiments, soy protein, at least one plasticizer, and optionally, one or more additional components such as crosslinking agents, reducing agents, compatibilizers, stabilizers, antioxidants, and / or synthetic biodegradable polymers. The precursor blend exists substantially in a solid, powder, or granular form prior to undergoing melt-processing, and is intended to serve as the feed material for thermomechanical processing techniques such as internal batch mixing, extrusion, or compression molding. In some embodiments there may be one or more ingredient in a liquid state, which may contribute to a paste-like or slurry-like form prior to undergoing melt-processing.

[0117] The term "thermoplastic composition," as used in the present disclosure and claims, refers to the product of melt-processing this precursor blend under suitable conditions that promote component dispersion, thermal softening, and in some cases, partial chemical interaction among ingredients, while avoiding structural damage or decomposition of the soy protein phase. The thermoplastic composition thus obtained is a cohesive, processable material capable of being formed into films, molded articles, or multilayer structures, and is characterized by properties such as tensile strength, elongation at break, oxygen and water vapor permeability, and thermal stability.

[0118] It is understood that while the structural and functional attributes of the thermoplastic composition, including its mechanical, barrier, and interfacial properties, are expressed as characteristics of the melt-processed product, the quantitative amounts of the individual ingredients specified in the description and claims refer to the proportions present in the dry precursor blend prior to melt-processing. This approach ensures that component ratios are reported with respect to the initially blended formulation, which governs processability and end-use properties, rather than postprocessing concentrations that may be altered due to thermal expansion, moisture loss, or reactivity during processing. It is assumed that the ratios and concentrations of at least some of the individual ingredients may be detectable in the post-molten composition using the appropriate chemical analysis tools and analytical techniques.

[0119] Accordingly, the precursor blend serves as the composition input, and the thermoplastic composition disclosed and claimed herein is the resulting melt-processed output, wherein the physical form, internal structure, and performance characteristics are determined in large part by the processing history and interaction among the components during the melt-processing stage. Thus, as used herein, the term “precursor blend” refers to the composition comprising soy protein, at least one plasticizer, and optionally one or more additional components including compatibilizers, crosslinking agents, reducing agents, stabilizers, antioxidants, and / or synthetic biodegradable polymers, prior to being subjected to melt-processing. The precursor blend serves as the formulation input to a thermomechanical processing step that yields the thermoplastic composition described and claimed herein.

[0120] The precursor blend may exist in various physical forms depending on the nature and proportions of its ingredients. In some embodiments, the precursor blend is a free-flowing powder or granular mixture. In other embodiments, it may assume a cohesive paste or semi-solid state, particularly when liquid plasticizers or reactive agents are included. In yet other embodiments, the precursor blend may be formulated as a viscous slurry or suspension, for example when hydrating agents or partially solubilized proteins are present. Regardless of its initial physical state, the precursor blend is defined by its compositional content and readiness for melt-processing, and the ingredient quantities referred to in the present disclosure and claims are expressed relative to the precursor blend prior to thermal treatment.

[0121] Soy protein

[0122] As discussed above, a critical component of the compositions provided herein is derived from soy, primarily soybean protein. In some embodiments of the present invention, the thermoplastic compositions comprising soy protein may offer advantages over traditional petroleum-based plastics. The soy protein-based materials may be biodegradable and derived from renewable resources, potentially reducing environmental impact. Additionally, these materials may exhibit desirable mechanical properties and barrier characteristics suitable for various applications.

[0123] In the context of the present invention, the terms “soy” and “soybeans” are used interchangeably, and the composition disclosed herein include soybean protein (i.e., soy protein) in the form of soy protein isolate (SPI) or soy protein concentrate (SPC). Hence, the term “soybean protein” or “soy protein” refers to soy protein isolate (SPI) or soy protein concentrate (SPC).

[0124] As used herein, the term “soy protein isolate” (SPI) refers to a purified proteinaceous fraction derived from soybeans (Glycine max), a leguminous plant species in the Fabaceae family. Glycine max is native to East Asia and is cultivated globally for its high protein content, oil yield, and agricultural versatility. Within the Glycine genus, cultivated soybean (Glycine max) is distinguished from its wild relative (Glycine soja) and encompasses numerous cultivars, including both conventional varieties and genetically modified (GM) strains engineered for traits such as herbicide resistance, pest tolerance, or altered protein expression. Soybeans serve as a major source of plant protein due to their relatively balanced amino acid profile and high yield per hectare. Protein content and composition can vary between cultivars and growing conditions, but soybeans typically contain 35%-40% protein by dry weight. This protein fraction, which is used in the compositions provided herein, includes globulins (such as glycinin and P-conglycinin), which are water-insoluble storage proteins, as well as minor fractions of albumins, enzymes, and structural proteins. These proteins contain a diverse set of reactive functional groups, including primary amines, carboxylates, hydroxyls, and thiols, which enable interaction with other polymers or crosslinking agents in composite formulations.

[0125] The term “isolate” in the context of soy protein refers to a processing grade in which the protein is selectively extracted and purified from defatted soybean meal. The isolate may be obtained in various processes, including aqueous extraction under controlled pH conditions, followed by precipitation and drying, typically resulting in a product with 90 wt.% protein content on a dry material basis. This distinguishes SPI from “soy protein concentrate” (SPC), which is also contemplated as an ingredient in the compositions provided herein, and contains at least 70 wt.% protein with a higher proportion of non-protein components such as dietary fiber, carbohydrates, and residual oil. SPC is typically produced by removing soluble carbohydrates from defatted soy flour via alcohol extraction, acid leaching, or moist heat denaturation.

[0126] Both SPI and SPC are suitable for incorporation into thermoplastic compositions provided herein, as described hereinbelow. SPI is preferred in formulations requiring high purity, structural protein content, or reactive site density. SPC may be used where moderate protein levels are sufficient and added bulk or fiber content is beneficial. In either case, the functional groups present in the soy protein enable physical or chemical interaction with other components of the composition, such as plasticizers, compatibilizers, or biodegradable synthetic polymers. The choice between SPI and SPC may affect properties such as dispersion, melt-processability, adhesion, and final mechanical performance.

[0127] The soy protein content in the compositions provided herein may range from 1 wt.% to 40 wt.%, or from 5 wt.% to 30 wt.%, or from 10 wt.% to 20 wt.%. In certain preferred embodiments, the soy protein is present in an amount of 10 wt.% or 20 wt.%, based on the total weight of the composition, wherein uniform dispersion of soy protein is maintained and mechanical integrity is preserved. In some embodiments, the soy protein content may be present in an amount of at least 1 wt.%, at least 5 wt.%, at least 10 wt.%, at least 15 wt.%, at least 20 wt.%, at least 25 wt.%, at least 30 wt.%, at least 35 wt.%, or at least 40 wt.% of the total composition on dry basis.

[0128] Above a certain soy protein contents, such as 30-40 wt.% and higher, the formation of phase- separated protein aggregates may impair cohesion and film-forming properties unless additional ingredients are added to the composition, as discussed hereinbelow. When additional components are added, such as plasticizers, additional thermoplastic polymers, compatibilizers and the like, the thermoplastic composition may comprise soy protein as a primary component of up to 30 wt.%, 40 wt.%, 50 wt.%, 60 wt.%, 70 wt.%, 80 wt.%, and up to 90 % by weight of the total weight of the composition on dry basis. The high protein content may contribute to the mechanical properties and structural integrity of the final material.

[0129] FIGs. l(a-d) illustrate the transformation of soy protein from raw material to processed film. As shown in FIG. 1(a), a soy protein powder may serve as the starting material for the thermoplastic composition. The soy protein powder may be derived from soybeans through various extraction and purification processes.

[0130] In some cases, the soy protein powder may undergo melt processing to form a flexible film. FIG. 1(b) depicts a processed film front view, which may be obtained after the melt processing step. The processed film front view may appear as a circular, semi-transparent sheet with a slight yellow tint.

[0131] FIG. 1(c) presents a processed film side view. A flexible film may be observed in this view, demonstrating the pliability and thinness of the processed soy protein material. The flexible film may bend easily without breaking, illustrating its flexible nature.

[0132] As can be seen in FIGs. l(a-d) the transformation from soy protein powder to flexible film may involve various processing steps, such as plasticization, blending with additives, and thermal treatment. These steps may be tailored to maintain the structural integrity of the soy protein while achieving the desired thermoplastic properties.

[0133] In some cases, the use of SPI or SPC with high protein content may result in films with improved mechanical strength and barrier properties compared to materials with lower protein content. The protein-rich composition may also contribute to the biodegradability of the final product, as soy proteins are naturally occurring polymers that can be broken down by environmental factors.

[0134] Plasticizer

[0135] The composition provided herein comprises at least one plasticizer to improve processability and flexibility of the soy protein-based material.

[0136] As used herein, the term “plasticizer” refers to a compound that increases the flexibility, ductility, and processability of a polymeric material by reducing the glass transition temperature (Tg) and enhancing chain mobility within a single polymer phase. Plasticizers are generally low- molecular-weight or oligomeric substances that are at least partially miscible with the host polymer. They function by intercalating between polymer chains and weakening secondary intermolecular forces, such as hydrogen bonding or van der Waals interactions, thereby increasing the free volume and molecular mobility of the matrix.

[0137] Non-limiting examples of plasticizers, which are contemplated within the scope of the present invention, include, without limitation, glycerol, sorbitol, water, ethylene glycol, diethylene glycol, triethyl citrate, polyethylene glycol (low molecular weight), epoxidized oils, and citrate esters. The selection of plasticizer depends on the polymer’ s chemical structure, processing conditions, and target mechanical properties. For soy protein-based materials, plasticizers such as glycerol and water are preferrable, as they reduce brittleness and enable thermal processing, while in polyesters such as PLA or PCL, aliphatic esters or epoxides may be used to enhance flexibility and elongation.

[0138] In some preferred embodiments, the plasticizer may be selected from glycerol, water, tannic acid, sorbitol, ethylene glycol, diethylene glycol, and any combinations thereof.

[0139] In some preferred embodiments, glycerol may be used as a primary plasticizer in the soy protein-based thermoplastic composition provided herein. FIG. 4 illustrates the stress-strain curves for various soy protein-based film compositions, including those plasticized with glycerol. The reference sample in FIG. 4 contains soy protein isolate with 40% w / w glycerol. As shown in FIGs. 5(a-c), the glycerol-plasticized reference sample exhibits a tensile strength of approximately 3 MPa and a maximal tensile strain of about 40%.

[0140] Water may also serve as a plasticizer in the soy protein-based compositions. In some cases, water may be used in combination with other plasticizers. FIG. 6 demonstrates the effect of water content on the mechanical properties of soy protein-based films. Compositions with 10% and 40% water content are compared, showing differences in tensile strength and elongation at break.

[0141] Ethylene glycol may be used as an alternative plasticizer to glycerol. In some cases, ethylene glycol may allow for the use of lower plasticizer concentrations while maintaining desirable mechanical properties. FIGs. 7(a-c) present the mechanical properties of soy protein-based films plasticized with ethylene glycol. The tensile strength, maximal tensile strain, and Young's modulus are shown for various ethylene glycol concentrations.

[0142] In some cases, a combination of ethylene glycol and glycerol may be used as plasticizers in the soy protein-based thermoplastic composition. This combination may allow for tailoring of the mechanical properties by adjusting the relative concentrations of the two plasticizers. The total plasticizer content may be maintained within the range of 20% to 60% by weight of the total composition.

[0143] Triethanolamine may also be used as a plasticizer for soy protein films. In some cases, triethanolamine may be incorporated into formulations containing glycerol and water. The addition of triethanolamine may result in increased elongation at break while maintaining reasonable tensile strength.

[0144] Tannic acid, while considered also as a crosslinking agent, may also exhibit plasticizing effects in soy protein-based compositions. As shown in FIGs. 7(a-c), the addition of tannic acid may influence the mechanical properties of the films, potentially contributing to both plasticization and crosslinking effects.

[0145] The choice and concentration of plasticizers may significantly impact the processability and final properties of the soy protein-based thermoplastic materials. By carefully selecting and combining different plasticizers, the mechanical properties and flexibility of the resulting films may be tailored for specific applications.

[0146] The plasticizer may be absent from the composition, or present under a different definition, such as compatibilizer. The plasticizer or any combination of plasticizers, may be present in an amount ranging from 20% to 60% by weight of the total composition, such as from 20% to 35%, or from 25% to 40%, or from 30% to 45%, or from 35% to 50%, or from 40% to 60% by weight. In some embodiments, the plasticizer is present in an amount of at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, or at least 60% by weight of the total composition.

[0147] It is recognized that certain compounds may exhibit both compatibilizing and plasticizing effects in specific formulations. For example, epoxidized soybean oil (ESBO) may serve as a plasticizer for PCL or PLA by softening the matrix, while simultaneously improving compatibility with hydrophilic phases such as soy protein via its epoxy or polar ester groups. However, the roles of compatibilizer and plasticizer remain mechanistically and functionally distinct: the former targets interfacial adhesion between unlike phases, while the latter modulates the mobility within a single phase. Therefore, although certain additives may serve dual functions depending on context, the terms “compatibilizer” and “plasticizer” are not used interchangeably herein and are to be interpreted in accordance with their primary functional attributes unless expressly stated otherwise.

[0148] Thermoplastic polymer

[0149] According to some embodiments of the present invention, the thermoplastic composition includes: soy protein isolate (SPI) or soy protein concentrate (SPC); at least one plasticizer; and at least one thermoplastic polymer that is not a soy protein.

[0150] In other words, in some embodiments of the invention, the composition provided herein comprises at least one additional thermoplastic polymer. To further improve the properties of soy protein-based composition, at least one additional thermoplastic polymer is included in the composition, in the form of various synthetic or natural thermoplastic polymers, thermoplastic biodegradable polymer, and any blend thereof. The blending of soy protein with synthetic biodegradable polymers may result in materials with a range of properties. In some cases, the tensile strength of the blends may range from 10 to 22.5 MPa, with elongation at break values between 1.2% and 1.6%. These properties may vary depending on the specific blend composition and processing conditions.

[0151] In some embodiments, the thermoplastic polymer comprises a biodegradable aliphatic polyester, such as polycaprolactone (PCL), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), or polybutylene succinate (PBS). PCL is preferred in certain adhesive formulations due to its low melting point and mechanical ductility.

[0152] In some embodiments, the thermoplastic composition further comprise an additional thermoplastic polymer in the form of a synthetic biodegradable polymer. As used herein, the term “synthetic biodegradable polymer” refers to a polymer that is chemically synthesized through polymerization reactions involving monomers that may be of natural or synthetic origin, wherein the resulting polymer is capable of undergoing biological degradation by microorganisms, enzymes, or environmental conditions into non-toxic byproducts such as water, carbon dioxide, methane, and biomass. Synthetic biodegradable polymers are distinguished from naturally occurring biodegradable polymers, such as polysaccharides (e.g., starch, cellulose) or proteins (e.g., collagen, gelatin), in that they do not occur in nature in polymerized form and are not directly extracted from biological sources, but are instead manufactured through controlled chemical processes such as ring-opening polymerization, condensation, or radical polymerization.

[0153] A synthetic biodegradable polymer may be selected from polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), or polycaprolactone (PCL). These synthetic biodegradable polymers may be blended with the soy protein-based material to enhance certain properties of the final composition.

[0154] The synthetic biodegradable polymer may be present in an amount ranging from 10% to 50% by weight of the total composition. This range may allow for tailoring of the blend properties to meet specific application requirements. By adjusting the ratio of synthetic biodegradable polymer to soy protein, the mechanical, thermal, and barrier properties of the resulting material may be optimized.

[0155] PLA may be used as a primary synthetic biodegradable polymer in blends with soy protein to arrive at a soy protein-based composition as disclosed herein. In some cases, a specific blend composition may comprise 75% PLA and 25% soy protein, or any relative value therebetween. This blend ratio may provide a balance between the properties of PLA and soy protein, potentially resulting in improved mechanical strength compared to soy protein alone. In certain embodiments, the blend may comprise 75% PLA and 25% soy protein, 65% PLA and 35% soy protein, 55% PLA and 45% soy protein, 45% PLA and 55% soy protein, 35% PLA and 65% soy protein, or 25% PLA and 75% soy protein. These varying ratios allow for tunable properties, where higher PLA content may enhance stiffness and processability, while higher soy protein content may improve biodegradability and gas barrier characteristics.

[0156] Polycaprolactone (PCL) may also be used as a primary synthetic biodegradable polymer in blends with soy protein to arrive at a soy protein-based composition as disclosed herein. In some embodiments, a blend comprising 75% PCL and 25% soy protein, or any relative proportion within that range, may provide enhanced flexibility and melt processability while retaining functional properties from the protein component. Example ratios include 75% PCL and 25% soy protein, 65% PCL and 35% soy protein, 55% PCL and 45% soy protein, 45% PCL and 55% soy protein, 35% PCL and 65% soy protein, and 25% PCL and 75% soy protein. These formulations allow for the tuning of film properties such as elongation, compatibility, and thermal behavior, with increasing soy protein content contributing to higher polarity and potential for interfacial adhesion in multilayer structures.

[0157] In some cases, the thermoplastic composition may comprise three polymeric components, including soy protein and two different synthetic biodegradable polymers. For example, a blend may be formed using soy protein, PLA, and PB AT. The incorporation of multiple synthetic biodegradable polymers may allow for further customization of material properties, potentially combining the advantages of each component.

[0158] Compatibilization methods may be employed to improve the interfacial adhesion between the soy protein and the synthetic biodegradable polymers. In some cases, compatibilizers such as maleic anhydride or poly(2-ethyl-2-oxazoline) (PEOX) may be added to the composition to enhance the dispersion of components and improve overall material properties.

[0159] Compatibilizer

[0160] According to some embodiments of the present invention, the thermoplastic composition includes: soy protein isolate (SPI) or soy protein concentrate (SPC); at least one plasticizer; optionally at least one thermoplastic polymer, and at least one compatibilizer.

[0161] In other words, in some embodiments of the invention, the composition provided herein comprises at least one compatibilizer. As used herein, the term “compatibilizer” refers to an additive that improves interfacial interaction between dissimilar polymeric phases, such as in immiscible polymer blends, polymer- filler systems, or polymer-biopolymer composites. Compatibilizers function by localizing at the interface between incompatible domains, where they mediate adhesion through mechanisms such as physical entanglement, hydrogen bonding, or covalent interaction. Their presence reduces interfacial tension, enhances dispersion, and improves the mechanical integrity of the multiphase system. Compatibilizers are often block copolymers, graft copolymers, or functionalized polymers bearing moieties that are selectively miscible or reactive with each constituent phase.

[0162] Compatibilizers may be added to the thermoplastic composition provided herein to improve the dispersion of components, enhance interfacial adhesion between soy protein and other components, and strengthen mechanical properties. Suitable compatibilizers include, without limitation, poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylic acid, epoxidized soybean oil (ESBO), ethylene-glycidyl methacrylate copolymers, maleic anhydride-grafted polyolefins, oligomeric silanes, and any combination thereof.

[0163] In certain embodiments, the compatibilizer may be reactive under melt-processing conditions, forming in-situ block or graft copolymers at the interface of otherwise incompatible phases. In other embodiments, the compatibilizer may remain physically dispersed yet effective, functioning by reducing interfacial tension or bridging polarity differences without chemical reaction.

[0164] In particular embodiments involving soy protein isolate (SPI) and polycaprolactone (PCL), epoxidized soybean oil (ESBO) serves as a dual-function additive, acting as both a plasticizer and a compatibilizer. Its epoxy and ester functionalities contribute to improved phase mixing and interfacial bonding between the hydrophilic and hydrophobic components of the system.

[0165] The compatibilizer may be absent from the composition, or present under a different definition, such as plasticizer. The compatibilizer or any combination of compatibilizers, may be present in an amount ranging from 1% to 30% by weight of the total composition, such as from 5% to 15%, or from 5% to 25% or from 10% to 20%, or from 15% to 25%, or from 20% to 30% by weight. In some embodiments, the compatibilizer is present in an amount of at least 1%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, or at least 30% by weight of the total composition.

[0166] Crosslinking agent

[0167] According to some embodiments of the present invention, the thermoplastic composition includes: soy protein isolate (SPI) or soy protein concentrate (SPC); at least one plasticizer; optionally at least one thermoplastic polymer, optionally at least one compatibilizer, and at least one crosslinking agent.

[0168] In other words, in some embodiments of the invention, the composition provided herein comprises at least one crosslinking agent, which is added to further control and augment the mechanical properties and stability of the soy protein-based composition. In some cases, the crosslinking agent may be selected from tannic acid, epoxidized soybean oil, L-cysteine, glyoxal, genipin, alginate, pectin, chitosan, and combinations thereof.

[0169] Tannic acid may be used as a primary crosslinking agent in the soy protein-based thermoplastic composition. In some cases, tannic acid may be present in an amount ranging from 0.5% to 10% by weight of the soy protein isolate or soy protein concentrate. FIG. 6 demonstrates the effect of tannic acid and epoxidized soybean oil (ESBO) concentration on the mechanical properties of soy protein-based films. Compositions with 0.5wt.%, 2.5 wt.%, and 5 wt.% tannic acid were compared, showing differences in tensile strength and elongation at break.

[0170] Epoxidized soybean oil (ESBO, or SBO) may also serve as a crosslinking agent in the soy protein-based compositions. FIGs. 7(a-c) present the mechanical properties of soy protein-based films containing ESBO. The tensile strength, maximal tensile strain, and Young's modulus are shown for various ESBO concentrations.

[0171] It is noted that natural polymers such as, for a non-limiting example, alginate, pectin and chitosan, are expected to create a interpenetrating network (IPN) structure, when combined with the soy protein. IPN is known to behave as "physical crosslinking".

[0172] In some embodiments, "post processing crosslinking method" are contemplated to avoid crosslinking during the melt processing step. This method may be used in cases where crosslinking results in too viscous material. This method may be effected by spraying the crosslinker solution on the films, followed by a drying step.

[0173] In some cases, the crosslinking agent may be incorporated into the core layer of a multilayer film structure. The core layer may comprise a crosslinking agent selected from tannic acid, epoxidized soybean oil, L-cysteine, glyoxal, genipin, alginate, pectin, and chitosan. The presence of the crosslinking agent in the core layer may enhance the mechanical strength and barrier properties of the film.

[0174] A post-processing crosslinking method may be employed to avoid crosslinking during the melt processing step. This method may be particularly useful in cases where crosslinking results in a material that is too viscous for efficient processing. In some cases, the post-processing crosslinking method may comprise spraying a crosslinker solution on the film followed by a drying step.

[0175] The post-processing crosslinking method may involve the following steps:

[0176] 1. Formation of the soy protein-based film through melt processing techniques such as extrusion or compression molding.

[0177] 2. Preparation of a crosslinker solution containing one or more of the aforementioned crosslinking agents.

[0178] 3. Spraying the crosslinker solution onto the surface of the formed film.

[0179] 4. Drying the film to allow for crosslinking reactions to occur.

[0180] In some cases, the post-processing crosslinking method may allow for greater control over the degree of crosslinking and may result in improved mechanical properties of the final film. The method may also enable the use of crosslinking agents that are sensitive to high temperatures or shear forces encountered during melt processing.

[0181] The choice and concentration of crosslinking agents may significantly impact the final properties of the soy protein-based thermoplastic materials. By carefully selecting and combining different crosslinking agents and methods, the mechanical strength, barrier properties, and stability of the resulting films may be tailored for specific applications.

[0182] Additional additives

[0183] According to some embodiments of the present invention, the thermoplastic composition includes: soy protein isolate (SPI) or soy protein concentrate (SPC); at least one plasticizer; optionally at least one thermoplastic polymer, optionally at least one compatibilizer, optionally at least one crosslinking agent, and at least one additional additive.

[0184] In other words, in some embodiments of the invention, the composition provided herein comprises at least one additional additives, which is added to improve material properties and processing characteristics. These additives may include reducing agents, stabilizers, pH-setting agents, and other functional components. The incorporation of such optional additives may allow for tailoring of the thermoplastic composition's properties to meet specific application requirements. By carefully selecting and combining different additives, the processability, mechanical properties, and stability of the soy protein-based materials may be optimized for various end-use scenarios. Reducing agents

[0185] Reducing agents may be incorporated into the thermoplastic composition to modify the protein structure and improve processability. In some cases, sodium sulfite may be used as a reducing agent. The sodium sulfite may be present in a concentration ranging from 0.1% to 5% by weight of the soy protein isolate or soy protein concentrate. FIGs. 5(a-c) illustrate the effect of sodium sulfite (SS) on the mechanical properties of soy protein-based films. As shown in FIGs. 5(a-c), the addition of sodium sulfite may influence the tensile strength, maximal tensile strain, and Young's modulus of the films.

[0186] Additional reducing agents suitable for use in the compositions described herein include, without limitation, sodium metabisulfite, dithiothreitol (DTT), P-mercaptoethanol, tris(2- carboxyethyl)phosphine (TCEP), thioglycolic acid, and cysteine. These agents are capable of cleaving disulfide bonds or modifying thiol groups within soy protein structures, thereby reducing intermolecular crosslinking and enhancing chain flexibility. The selection of reducing agent may depend on the processing temperature, desired degree of denaturation, or compatibility with other formulation components.

[0187] In some embodiments, the reducing agent is present in an amount of at least 0.1%, at least 0.5%, at least 1%, at least 2%, or at least 3% by weight of the soy protein component. The concentration may range from 0.1% to 1%, or from 0.5% to 2%, or from 1% to 3%, or from 2% to 5% by weight of the soy protein isolate or concentrate. The optimal concentration may be selected to achieve improved melt-processability or tailored mechanical properties without excessive softening or degradation of the protein structure.

[0188] Stabilizers

[0189] Stabilizers may be incorporated into the thermoplastic composition to prevent thermal degradation during processing. In some cases, the addition of a stabilizer may help to maintain the structural integrity of the soy protein and other components at elevated temperatures encountered during melt processing. The stabilizer may contribute to improved thermal stability and processability of the composition.

[0190] Suitable stabilizers include, without limitation, antioxidants, radical scavengers, and acid scavengers such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tocopherols (vitamin E), citric acid, phosphoric acid esters, calcium stearate, zinc oxide, magnesium carbonate, and hindered phenol-based stabilizers. These compounds may inhibit oxidative chain scission, radical-mediated crosslinking, or acid-catalyzed degradation, particularly in formulations that undergo extrusion or molding above 100°C. In protein-based systems, stabilizers may also mitigate Maillard reactions or thermal unfolding of protein domains by neutralizing reactive intermediates or maintaining pH stability.

[0191] In some embodiments, the stabilizer is present in an amount of at least 0.05%, at least 0.1%, at least 0.25%, at least 0.5%, or at least 1% by weight of the total composition. The concentration may range from 0.05% to 0.5%, or from 0.1% to 1%, or from 0.5% to 2% by weight. The specific concentration and type of stabilizer may be selected based on the thermal profile of the processing method, the oxidative or hydrolytic sensitivity of the other components, and the desired shelf life or performance attributes of the final product.

[0192] Antioxidants

[0193] Antioxidants may be included as an additive to the thermoplastic composition provided herein. The antioxidant may be incorporated into the core layer of a multilayer film structure to enhance the shelflife of packaged products. The antioxidant may help to prevent oxidation of the soy protein and other components, potentially improving the long-term stability of the material.

[0194] Suitable antioxidants include, without limitation, natural and synthetic compounds capable of neutralizing reactive oxygen species or inhibiting radical chain reactions. Examples include tocopherols (e.g., a-tocopherol), ascorbic acid, ascorbyl palmitate, citric acid, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), propyl gallate, and rosemary extract. These agents may protect unsaturated bonds in fatty acid residues, prevent oxidative cleavage of protein side chains, and suppress degradation of polymer additives. In multilayer structures, antioxidants may be embedded in the inner or core layer to minimize migration into contacting media while providing extended oxidative stability.

[0195] In some embodiments, the antioxidant is present in an amount of at least 0.01%, at least 0.05%, at least 0.1%, at least 0.25%, or at least 0.5% by weight of the total composition. The concentration may range from 0.01% to 0.5%, or from 0.05% to 1%, or from 0.1% to 2% by weight. The type and dosage of antioxidant may be tailored based on the composition’s susceptibility to oxidation, the intended shelf life, and regulatory constraints for food-contact applications.

[0196] Functional components

[0197] Functional components such as a coating of hydrophobic nanoparticles may be applied to the outer layer of a multilayer film structure to improve water resistance. In some cases, the hydrophobic nanoparticle coating may enhance the barrier properties of the film, potentially extending its applicability in moisture-sensitive packaging applications.

[0198] Suitable hydrophobic nanoparticles include, without limitation, surface-modified silica, titanium dioxide, aluminum oxide, zinc oxide, graphene oxide, and cellulose nanocrystals treated with hydrophobic agents such as alkylsilanes, fluorosilanes, or fatty acid derivatives. These particles may form a nanostructured surface that reduces wettability and capillary penetration of water, thereby enhancing the water vapor barrier and surface hydrophobicity. The nanoparticle coating may be applied by spray coating, dip coating, roll-to-roll deposition, or plasma-enhanced vapor deposition, followed by curing or drying. The coating may additionally contribute to self-cleaning behavior, antifouling properties, or UV resistance, depending on particle composition.

[0199] In some embodiments, the nanoparticle coating is applied at a dry weight concentration of at least 0.1%, at least 0.25%, at least 0.5%, at least 1%, or at least 2% relative to the total weight of the multilayer film. The coating thickness may range from 50 nm to 1 pm, or from 100 nm to 500 nm, depending on the desired balance between barrier enhancement and transparency. The surface water contact angle of the coated layer may exceed 90°, 100°, 110°, 120°, or 130°, with higher angles indicating stronger hydrophobicity.

[0200] Multilayer structure

[0201] As used herein, the term “multilayer film” refers to a structure comprising at least one barrier layer and one structural or protective layer, adhered via an intermediate tie layer or adhesive. In some non-limiting illustrative embodiments, the multilayer film comprises a soy protein-based film as the oxygen barrier layer, a thermoplastic polymer as the outer structural layer, and the SPI / PCLZESBO adhesive composition as the tie layer.

[0202] The multilayer structure may comprise 2, 3, 4, 5 or more layers, where the SPI film is centrally located as the 2nd, 3rd, 4th, or 5thlayer. The SPI film may be present as a single layer in a multilayer film embodiment, or present in more than one layer.

[0203] In some embodiments, a biodegradable film may comprise a multilayer structure. The multilayer structure may include a core layer composed of soy protein isolate or soy protein concentrate and at least one plasticizer. The core layer may provide a low oxygen and / or moisture permeability barrier suitable for food packaging applications. Applications include but are not limited to snack packaging, agricultural film, biodegradable laminates, and pouches.

[0204] The multilayer structure may further comprise at least one additional layer comprising a synthetic biodegradable polymer. In some cases, the additional layer may comprise a polymer selected from polybutylene succinate, polycaprolactone, polylactic acid, and polybutylene adipate terephthalate. The additional layer may provide mechanical strength and water resistance to the multilayer film.

[0205] A method for preparing the biodegradable film comprising a multilayer structure may involve forming a first layer comprising soy protein isolate or soy protein concentrate and at least one plasticizer. In some cases, the first layer may have a thickness ranging from 50 to 500 micrometers. The method may further include forming at least one additional layer comprising a synthetic biodegradable polymer.

[0206] The layers may be laminated together to form a composite film. In some cases, the lamination process may be carried out using a hot-pressing technique at a temperature of 100 °C to 150 °C under a pressure of 10 to 20 bar. This process may help ensure good adhesion between the layers and uniform thickness of the final film.

[0207] To enhance the barrier properties of the first layer, a treatment step may be incorporated into the preparation method. In some cases, the first layer may be treated with an alkali solution. This treatment may modify the protein structure, potentially improving the oxygen barrier properties of the layer.

[0208] A tie layer may be formed between the first layer and the additional layer to improve adhesion and compatibility between the different materials. In some cases, the tie layer may comprise a compatibilized blend of soy protein and the synthetic biodegradable polymer. The tie layer may help prevent delamination and improve the overall mechanical properties of the multilayer film.

[0209] After the lamination process, the multilayer film may be annealed at 80 °C. This annealing step may improve interlayer adhesion and reduce residual stresses in the film. The annealing process may contribute to the overall stability and performance of the multilayer structure.

[0210] The resulting biodegradable film article may combine the advantages of both the soy proteinbased core layer and the synthetic biodegradable polymer outer layer. The core layer may provide excellent oxygen barrier properties, while the outer layer may contribute to water resistance and mechanical strength. This combination of properties may make the multilayer film particularly suitable for food packaging applications where both biodegradability and gas barrier properties are required.

[0211] In some cases, the multilayer structure may allow for tailoring of film properties to meet specific packaging requirements. By adjusting the composition and thickness of each layer, the overall performance of the film may be optimized for different types of food products or storage conditions.

[0212] In some cases, the soy protein in the abovementioned films will form the core layer, protected from the environment (in special from humidity), surrounded by shell layers based on biodegradable polymer blends. This unique 3-layer structure improves the oxygen barrier inherent to the soy protein, which is usually reduced due to the water absorption. The compatibilized blends can be used as tie layers between the SPI and the additional polymer (PLA, PB AT and others). Mechanical properties

[0213] As used herein, “mechanical properties” refer to performance metrics including tensile strength, elongation at break, and peel adhesion of the thermoplastic composition provided herein, as well as any film or other article made therefrom or therewith.

[0214] Strain

[0215] As used herein, the term “strain” refers to the relative deformation of a material under applied stress, typically quantified as the change in length divided by the original length of the test specimen. Strain is a dimensionless quantity and is commonly expressed in percent (%) units, where 100% strain corresponds to a doubling in length (i.e., an elongation equal to the original length). Strain provides a measure of the ductility or flexibility of a material, indicating how much it can elongate or stretch before failure.

[0216] As used herein, the term “strain” refers broadly to the relative deformation experienced by a material under applied stress, encompassing all stages of mechanical response including elastic deformation, yielding, necking, and eventual fracture. In specific contexts such as tensile testing, the term “elongation at break” denotes the strain measured at the point of failure, representing the material’s total ductility prior to rupture. While “strain” is a general descriptor applicable across the stress-strain curve, “elongation at break” serves as a fixed endpoint metric indicative of ultimate tensile ductility. Unless otherwise indicated, references to “strain” in the context of the present invention are intended to encompass or correspond to elongation at break as determined in standard tensile testing procedures (e.g., ASTM D638), and reflect the material’s capacity to undergo deformation until failure.

[0217] Strain is typically determined using standardized tensile testing methods, such as ASTM D638 for plastic materials or ISO 527. In a typical test, a dog-bone-shaped specimen is clamped in a universal testing machine and stretched at a controlled rate until breakage. The strain is calculated based on the elongation of the gauge length recorded during the test. Elongation at break (also known as “maximal tensile strain”) is commonly reported to characterize the flexibility and toughness of films or molded parts.

[0218] The thermoplastic compositions provided herein, comprising any combination of soy protein isolate (SPI), soy protein concentrate (SPC), plasticizers, compatibilizers, crosslinking agents, reducing agents, and optional synthetic biodegradable polymers, may be characterized by a maximal tensile strain of at least 2%, preferably at least 20%, and up to 500%. In various embodiments, the strain may be at least 2%, at least 4%, at least 6%, at least 8%, at least 10%, at least 12%, at least 14%, at least 16%, at least 18%, or at least 20%. In further embodiments, the strain may be at least 50%, at least 100%, at least 150%, at least 200%, at least 250%, at least 300%, at least 350%, at least 400%, at least 450%, or at least 500%. The actual strain values may depend on the composition, processing method, and presence or absence of reinforcing or plasticizing additives, with lower values typically associated with higher soy protein content and higher values achieved through the use of flexible synthetic polymers and optimized plasticizer systems.

[0219] Tensile strength

[0220] As used herein, the term “tensile strength” refers to the maximum stress that a material can withstand while being stretched or pulled before breaking. It is a measure of the material’s resistance to tensile loading and is typically expressed in units of megapascals (MPa), where 1 MPa equals 1 million pascals or one newton per square millimeter. Tensile strength is a key mechanical property for evaluating the durability, structural performance, and load-bearing capacity of polymeric films, molded parts, or composite materials.

[0221] Tensile strength is commonly measured using standardized testing methods such as ASTM D638 or ISO 527. A specimen is clamped in a universal testing machine and subjected to uniaxial tensile force at a controlled rate until fracture. The maximum force applied before failure, divided by the initial cross-sectional area of the specimen, defines the tensile strength. This value reflects both molecular structure and formulation elements such as fillers, plasticizers, and crosslinking density.

[0222] The thermoplastic compositions provided herein, comprising combinations of soy protein isolate (SPI), soy protein concentrate (SPC), plasticizers, compatibilizers, crosslinking agents, reducing agents, and optional synthetic biodegradable polymers, may be characterized by a tensile strength of at least 5 MPa, preferably at least 10 MPa, and up to 50 MPa. In various embodiments, the tensile strength may be at least 5 MPa, at least 6 MPa, at least 7 MPa, at least 8 MPa, at least 9 MPa, or at least 10 MPa. In further embodiments, the tensile strength may be at least 15 MPa, at least 20 MPa, at least 25 MPa, at least 30 MPa, at least 35 MPa, at least 40 MPa, at least 45 MPa, or at least 50 MPa. The tensile strength achieved depends on multiple factors including the relative proportion of protein and polymer phases, degree of plasticization, compatibilizer efficiency, and processing conditions. Compositions containing optimized levels of crosslinking agents and reinforcing polymers may achieve tensile strength values near the upper end of the range.

[0223] For an illustrative example only in one non-limiting embodiment, a composition comprising 10 wt.% SPI, 90 wt.% PCL, and 20% ESBO exhibits a tensile strength of approximately 9 MPa and an elongation at break (strain) of approximately 10%.

[0224] Increasing SPI content beyond 20 wt.% may result in diminished tensile strength (e.g., below 5 MPa) and reduced elongation (e.g., below 6%), due to phase separation and poor stress transfer. Hence, compositions with 10-20 wt.% SPI represent an optimal balance between strength and adhesion performance. Peel adhesion

[0225] As used herein, the term “peel adhesion” refers to the force required to separate two bonded layers by peeling one layer away from the other at a defined angle and rate. It is an important measure of interfacial bonding strength, particularly in multilayer films, laminates, or coated structures. Peel adhesion quantifies the effectiveness of tie layers, adhesives, or interfacial compatibilization strategies, and is critical in applications where delamination resistance is required during processing, handling, or end use.

[0226] Peel adhesion is typically expressed in units of N / m (newtons per meter) or N / 15 mm (a standard width for test strips), and is measured using standardized methods such as ASTM DI 876 (T-peel test) or ASTM D903 (180° peel test). In these tests, a bonded specimen is subjected to tensile force in a defined geometry and the force required to propagate the interfacial failure is recorded as the peel strength. The method selected and the direction of peeling (e.g., 90°, 180°, T-peel) influence the interpretation and should be consistent with the intended application of the film.

[0227] The thermoplastic compositions and multilayer film structures provided herein, including those comprising soy protein isolate (SPI), soy protein concentrate (SPC), and synthetic biodegradable polymers such as PCL or PLA, optionally with compatibilizers or plasticizers, exhibit peel adhesion values sufficient for use in packaging and barrier film applications. In the Examples section of the present disclosure, multilayer films incorporating SPI / PCL blends with epoxidized soybean oil (ESBO) as a compatibilizer exhibited peel adhesion values ranging from approximately 50 N / m to over 300 N / m, depending on the specific formulation and processing method.

[0228] In some embodiments, the peel adhesion of the composition is at least 50 N / m, at least 75 N / m, at least 100 N / m, at least 125 N / m, at least 150 N / m, at least 175 N / m, at least 200 N / m, at least 225 N / m, at least 250 N / m, at least 275 N / m, or at least 300 N / m. Higher peel adhesion values may be obtained through optimized formulation, such as using 10-20 wt.% SPI with 80-90 wt.% PCL and 15-20 wt.% ESBO, or by employing surface pretreatments (e.g., abrasion or solvent activation) prior to lamination. In further embodiments, the composition may exhibit peel adhesion values up to 400 N / m, 500 N / m, or even higher in systems with synergistic interfacial compatibility and minimal phase separation.

[0229] Such peel strengths are comparable to or exceed those reported for commercial biodegradable tie layers and are suitable for use in laminates requiring moisture resistance, gas barrier performance, and mechanical durability across a range of end-use conditions.

[0230] Peel strength of the adhesive composition may vary depending on the substrate. In one embodiment, a 20 wt.% SPI / PCLZESBO blend demonstrates enhanced adhesion to PBAT films containing a chain extender, reaching peak performance relative to control formulations. Modified SPI / PCL films used as substrates also show improved compatibility and increased adhesion over glycerol-plasticized SPI films.

[0231] In some cases, the mechanical properties of the soy protein-based thermoplastic materials and blends provided herein may vary depending on the composition and processing method used. FIG. 9 illustrates the stress-strain curves for various soy protein-based film compositions prepared using different processing techniques.

[0232] In some embodiments it is contemplated to add more than one thermoplastic polymers to the soy protein ( / .<?.., PLA-PBAT).

[0233] The tensile strength of the soy protein-based materials may range from approximately 4 MPa to 10 MPa, as shown in FIG. 9. In some cases, compositions containing ethylene glycol (EG) as a plasticizer may exhibit higher tensile strengths compared to those containing glycerol. For example, a composition with 20% EG and 10% water may achieve a tensile strength of about 10.5 MPa.

[0234] The maximal strain, or elongation at break, of the soy protein-based materials may vary significantly depending on the formulation. As illustrated in FIG. 9, some compositions may exhibit maximal strains ranging from 50% to over 100%. In some cases, the addition of tannic acid or triethanolamine may increase the maximal strain of the materials.

[0235] FIGs. 10(a-c) present a comparison of the mechanical properties for different soy proteinbased film compositions prepared by compounding followed by cast extrusion. The tensile strength, maximal tensile strain, and Young's modulus are shown for various formulations.

[0236] In some cases, the soy protein-based materials may exhibit a tensile strength of at least 6 MPa and an elongation at break of at least 50%. For example, FIG. 10(a) shows that several compositions achieve tensile strengths above 6 MPa, while FIG. 10(b) demonstrates maximal strains exceeding 50% for multiple formulations.

[0237] The Young's modulus of the soy protein-based materials may range from approximately 50 MPa to 500 MPa, as shown in FIG. 10(c). The modulus may be influenced by factors such as plasticizer type and concentration, pH, and the presence of additives like tannic acid.

[0238] In some cases, blending melt processed soy protein-based thermoplastic material with a synthetic biodegradable polymer may improve the mechanical properties of the resulting material. The blend may be processed using melt processing techniques such as extrusion or compression molding to form a final product.

[0239] To enhance the compatibility between the soy protein and the synthetic biodegradable polymer, a compatibilizer may be added to the blend. In some cases, the compatibilizer may be selected from poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid. The addition of a compatibilizer may improve interfacial adhesion between the soy protein and the synthetic biodegradable polymer, potentially leading to enhanced mechanical properties.

[0240] The resulting film from the blending process may exhibit both high tensile strength and ductility. In some cases, the combination of soy protein-based material with a synthetic biodegradable polymer may allow for tailoring of mechanical properties to meet specific application requirements.

[0241] By carefully selecting the composition, processing method, and additives, the mechanical properties of soy protein-based thermoplastic materials and blends may be optimized for various applications. The ability to achieve a balance between tensile strength and ductility may make these materials suitable for use in packaging, agricultural films, and other products where biodegradability and mechanical performance are desired.

[0242] In some cases, the biodegradability of soy protein-based thermoplastic materials may be evaluated in soil and water environments. The degradation behavior of these materials may provide insights into their environmental impact and potential for sustainable applications.

[0243] Biodegradation testing of soy protein films may be conducted in soil and water environments. In some cases, the soil environment may consist of a mixture of soil and compost in a 2: 1 ratio. The water environment may involve immersion in tap water with the addition of a preservative such as sodium azide.

[0244] The biodegradation process may be monitored through weight loss measurements and visual observations over time. In some cases, samples may be retrieved at specific time intervals, such as 2, 5, 8, 14, 21, and 29 days, to assess the progression of degradation.

[0245] In soil environments, soy protein-based films may exhibit rapid degradation. In some cases, the films may lose cohesive strength within one week of exposure to soil. After two weeks, only remnants of the original film may remain, and by three weeks, the film may be barely visible and difficult to weigh accurately. The weight loss profile in soil may show that only 35-40% of the initial weight remains after two weeks of exposure.

[0246] The degradation behavior in water environments may differ significantly from that observed in soil. In some cases, soy protein-based films may show minimal changes in appearance even after one month of immersion in water. The weight loss profile in water may indicate an initial loss of 15- 20% within the first two days for films containing ethylene glycol with or without water. This initial weight loss may remain relatively stable for up to 30 days. Films containing both ethylene glycol and glycerol may exhibit slightly higher weight loss, ranging from 27-30%.

[0247] The limited weight loss observed in water environments may be attributed to the diffusion of plasticizers from the film into the surrounding water. In some cases, glycerol may have a higher tendency to diffuse out of the film compared to ethylene glycol, which may influence the choice of plasticizer for applications where water resistance is desired.

[0248] The rapid degradation of soy protein-based films in soil environments may suggest their potential for use in applications where quick biodegradation is advantageous, such as agricultural mulch films or short-term packaging materials. Conversely, the stability of these films in water environments may indicate their suitability for applications where prolonged exposure to moisture is expected.

[0249] In some cases, the biodegradation behavior of soy protein-based films may be influenced by factors such as film composition, plasticizer type and concentration, and the presence of additives or crosslinking agents. By tailoring these parameters, the degradation rate and environmental impact of the materials may be optimized for specific applications and end-of-life scenarios.

[0250] In some cases, the various components of the soy protein-based thermoplastic materials may interact synergistically to create a functional material with improved mechanical properties, processability, and biodegradability. The combination of soy protein, plasticizers, crosslinking agents, and optional additives may result in a material that exhibits desirable characteristics for various applications.

[0251] The core layer of a multilayer film structure may comprise soy protein isolate or soy protein concentrate along with a plasticizer. In some cases, the plasticizer may be selected from glycerol, water, tannic acid, sorbitol, ethylene glycol, and di ethylene glycol. The interaction between the soy protein and the plasticizer may contribute to the flexibility and processability of the core layer. The plasticizer may reduce intermolecular interactions between protein chains, allowing for improved mobility and easier processing.

[0252] The core layer may exhibit low oxygen permeability, making it suitable for packaging applications that require gas barrier properties. In some cases, the core layer may comprise 40% to 60% by weight of the total film structure. This composition may provide an optimal balance between barrier properties and overall film performance.

[0253] Chemical modification of the soy protein in the core layer may further enhance its properties. In some cases, the soy protein may be chemically modified through acetylation, succinylation, or Maillard reaction with reducing sugars. These modifications may alter the protein structure, potentially improving its compatibility with other components and enhancing its functional properties.

[0254] The outer layer of the multilayer film structure may comprise a synthetic biodegradable polymer. This layer may provide mechanical strength and water resistance to the overall film structure. In some cases, the outer layer may have a water vapor transmission rate (WVTR) of less than 100 g / m2 / day at 38 °C and 90% relative humidity. The low WVTR may contribute to the film's ability to protect packaged contents from moisture.

[0255] A tie layer may be incorporated between the core layer and the outer layer to improve adhesion and compatibility. In some cases, the tie layer may comprise a compatibilized blend of soy protein and the synthetic biodegradable polymer. The tie layer may help to create a strong interface between the core and outer layers, potentially enhancing the overall mechanical properties of the film.

[0256] The interaction between the core layer, tie layer, and outer layer may result in a film that is suitable for packaging applications requiring both biodegradability and gas barrier properties. The combination of the oxygen barrier properties of the core layer and the water resistance of the outer layer may create a versatile packaging material.

[0257] In some cases, the multilayer film may be heat-sealable at a temperature below 120 °C. This property may make the film suitable for automated packaging processes, potentially expanding its range of applications in the packaging industry.

[0258] The synergistic effects of the various components in the soy protein-based thermoplastic materials may contribute to their overall performance in different applications. For example, the combination of plasticizers and crosslinking agents may allow for tailoring of mechanical properties such as tensile strength and elongation at break. The interaction between the soy protein and synthetic biodegradable polymers in blends or multilayer structures may result in materials with improved processability and enhanced mechanical properties compared to soy protein alone.

[0259] The biodegradability of the soy protein-based materials may be influenced by the interactions between the various components. In some cases, the presence of certain additives or the chemical modification of the soy protein may affect the rate of degradation in different environments. The balance between mechanical properties, barrier characteristics, and biodegradability may be optimized through careful selection and combination of components.

[0260] By leveraging the interactions between different elements of the soy protein-based thermoplastic materials, it may be possible to create functional materials with a range of properties suitable for various applications. The ability to tailor these interactions through composition and processing may allow for the development of sustainable alternatives to traditional petroleum-based plastics in packaging and other industries.

[0261] Chemical film properties:

[0262] Polymeric films, such as a biodegradable film articles, comprising or consisting of the composition provided herein, can be characterized by a wide range of chemical properties that influence its performance in practical applications involving mass transport, environmental exposure, and interfacial interactions. Collectively referred to as “chemical film properties,” these characteristics pertain to how the film interacts with surrounding media, such as gases, liquids, vapors, and solutes, and how it maintains its structural and functional integrity under various chemical, physical, and operational conditions.

[0263] These chemical film properties are particularly relevant in the context of packaging, where films are often required to block or regulate the transmission of specific gases or volatile compounds, maintain stability under humid or chemically aggressive environments, resist migration of internal or external additives, and ensure compatibility with sensitive payloads such as food or pharmaceuticals. The interplay between permeability, sorption, and stability defines the suitability of a film material for a given barrier or protective role.

[0264] Moreover, these properties often have synergistic or competing effects: for instance, improving gas barrier performance may reduce moisture tolerance or increase brittleness, while enhancing solvent resistance may compromise transparency or flexibility. Therefore, when designing or selecting films for advanced applications — such as biodegradable packaging, multilayer barrier assemblies, membrane systems, or functional coatings — an integrated understanding of these chemical film properties is essential.

[0265] In the context of the present invention, the chemical film properties include, without limitation:

[0266] Oxygen transmission rate (OTR);

[0267] Water vapor transmission rate (WVTR);

[0268] Carbon dioxide transmission rate (CO2TR);

[0269] Nitrogen transmission rate (N2 permeation rate);

[0270] Overall gas permeability (generic gas barrier rating);

[0271] Aroma / odor barrier (organic vapor transmission rate);

[0272] Oil and fat resistance (grease barrier);

[0273] Chemical resistance (to acids, bases, solvents); pH stability range (chemical stability window);

[0274] Sorption / uptake of water (water absorption);

[0275] Sorption / uptake of organic solvents (solvent absorption);

[0276] Swelling ratio in specific media (swelling index);

[0277] Extractables and leachables content (migration tendency);

[0278] Specific migration into food simulants (food-contact migration);

[0279] Permeability to plasticizers or additives (additive loss rate);

[0280] Permeability to small organic molecules (flavor scalping tendency);

[0281] UV barrier or UV transmission (UV screening efficiency); Light transmission / haze (optical clarity vs. diffusion);

[0282] Surface energy (wettability / spread of liquids);

[0283] Surface tension / critical surface tension (coating / printing suitability);

[0284] Contact angle with water (hydrophobicity / hydrophilicity);

[0285] Surface charge density (electrostatic behavior);

[0286] Zeta potential in aqueous media (surface electrokinetic property);

[0287] Oxidative stability (resistance to oxidative degradation);

[0288] Hydrolytic stability (resistance to hydrolysis);

[0289] Environmental stress cracking resistance in chemicals (ESCR);

[0290] Flame retardancy / flammability rating (e.g., UL-94 class);

[0291] Gas solubility coefficient (e.g., oxygen solubility);

[0292] Diffusion coefficient for penetrant gases (diffusivity); and

[0293] Partition coefficient between film and contacting phase (sorption selectivity).

[0294] These properties are typically evaluated through standardized test methods and may vary depending on composition, processing conditions, film thickness, and environmental exposure. As such, the compositions described herein may be formulated and optimized to achieve tailored combinations of at least some these properties, depending on the intended end-use application.

[0295] Oxygen transmission rate ( OTR )

[0296] As used herein, the term "oxygen transmission rate" or "OTR" refers to the rate at which molecular oxygen permeates through a polymeric film under a defined set of temperature and humidity conditions. It is typically expressed in units of cc / m2day or cc / 100 in2day. OTR is a critical measure of the film’s gas barrier performance, especially in applications such as food packaging, where oxidative spoilage must be minimized.

[0297] OTR may be determined using methods such as ASTM D3985 (using a coulometric sensor) or ISO 15105-2. The test is typically conducted at 23°C and 0% or 50% relative humidity.

[0298] In some embodiments, the film exhibits an OTR of less than 10 cc / m2day, or less than 5 cc / m2day, or less than 1 cc / m2day. In preferred embodiments, the film exhibits an OTR of less than 0.5 cc / m2day, or even less than 0.1 cc / m2day. In some embodiments, the OTR is less than 0.01 cc / m2day, less than 0.05 cc / m2day, less than 0.1 cc / m2day, less than 0.5 cc / m2day, or less than 1 cc / m2day. In one non-limiting embodiment, a multilayer film exhibits an oxygen transmission rate (OTR) less than 2 cc / (m2day), or less than 1 cc / (m2day), or as low as 0.07 cc / (m2day), depending on the outer polymer. PLA outer films may offer superior oxygen barrier properties relative to PBAT due to lower chain mobility and higher glass transition temperature. Water Vapor Transmission Rate (WVTR)

[0299] As used herein, "water vapor transmission rate" or "WVTR" denotes the amount of water vapor that diffuses through a unit area of film per unit time under defined conditions of temperature and relative humidity. It is typically expressed in units of g / m2day. WVTR is a key determinant of moisture barrier performance.

[0300] Standard test methods include ASTM E96 (gravimetric method) and ASTM F1249 (infrared sensor method), often conducted at 38°C and 90% RH.

[0301] In some embodiments, the film exhibits a WVTR of less than 10 g / m2day, less than 5 g / m2day, or less than 1 g / m2day. In other embodiments, the WVTR is less than 0.1 g / m2day, less than 0.5 g / m2day, less than 1 g / m2day, or less than 5 g / m2day, depending on the target application and film thickness. In some embodiments, a biodegradable multi-layer film article comprising the SPI-containing composition provided herein, includes at least one layer, such as the outer layer, characterized by a water vapor transmission rate (WVTR) of less than 100 g / m2 / day at 38°C and 90% relative humidity.

[0302] Carbon Dioxide Transmission Rate (CChTR)

[0303] The term "carbon dioxide transmission rate" or "CO2TR" refers to the rate at which carbon dioxide permeates through a polymeric film under specified conditions. It is generally expressed in cc / m2day or cc / 100 in2- day. CO2TR is significant in packaging of carbonated beverages, fresh produce, and fermentation-sensitive products.

[0304] CChTR is typically measured by a manometric method (ASTM D1434) or a gas chromatographic method under standard testing conditions (23°C and 0-50% RH).

[0305] In certain embodiments, the CO2TR of a film comprising the composition provided herein, is less than 50 cc / m2day, or less than 25 cc / m2day, or less than 10 cc / m2day. In other embodiments, it is less than 1 cc / m2day, less than 5 cc / m2day, or less than 10 cc / m2day.

[0306] Nitrogen Transmission Rate (N2 Permeation Rate)

[0307] "Nitrogen transmission rate" refers to the rate of nitrogen gas permeation through a film, commonly used as a reference for inert gas barrier testing. The units are generally cc / m2day or cc / 100 in2- day. Nitrogen is often used as a control gas in permeability studies due to its low sorption and inert behavior.

[0308] Evaluation methods include ASTM D1434 or ISO 15105-1 using pressure decay or gas chromatography techniques.

[0309] Exemplary nitrogen permeation rates for high-barrier films comprising the composition provided herein, may be less than 5 cc / m2day. In other embodiments, the N2 transmission rate may be less than 0.1 cc / m2day, less than 1 cc / m2day, or less than 2.5 cc / m2day. Aroma / Odor Barrier (Organic Vapor Transmission Rate)

[0310] As used herein, "aroma barrier" or "organic vapor transmission rate" refers to the film's resistance to the migration or diffusion of volatile organic compounds (VOCs), flavor molecules, or aroma substances. This property is critical in applications involving aroma-sensitive foods, cosmetics, and pharmaceuticals.

[0311] Testing may involve permeation cells with VOC probes (e.g., limonene, ethanol, or hexanal) and quantification by gas chromatography-mass spectrometry (GC-MS). No universal standard exists, but methods are based on migration limits defined by EU or FDA food-contact regulations.

[0312] In preferred embodiments, the film comprising the composition provided herein exhibits an aroma barrier that results in less than 0.5 pg / cm2day of VOC permeation. In some embodiments, the organic vapor permeation rate is less than 0.01 pg / cm2day, less than 0.1 pg / cm2day, or less than 0.25 pg / cm2day.

[0313] Chemical Resistance (to Acids, Bases, Solvents)

[0314] "Chemical resistance" refers to the film’s ability to retain its mechanical and barrier properties when exposed to chemical agents such as acids, alkalis, organic solvents, oxidants, or cleaning agents. Evaluation is typically done by exposing the film to defined concentrations of test chemicals, followed by tensile, swelling, or mass retention tests (e.g., ASTM D543).

[0315] Chemical resistance may be assessed against categories such as 0.1-1 M hydrochloric acid, 0.1-1 M sodium hydroxide, 50% ethanol, or acetone.

[0316] In some embodiments, a film comprising the composition provided herein, retains at least 90%, 95%, or 98% of its tensile strength after 24 hours of chemical exposure. In others, it exhibits no more than 2%-, 5%-, or 10%-dimensional swelling after immersion.

[0317] UV Barrier or UV Transmission (UV Screening Efficiency)

[0318] "UV barrier" or "UV transmission" refers to the extent to which the film absorbs or transmits ultraviolet radiation, typically measured across the UV-A and UV-B spectra (280-400 nm). This is relevant for UV-sensitive contents such as light-degradable foods, pharmaceuticals, and cosmetics.

[0319] Measurement is commonly performed via UV-visible spectrophotometry (e.g., ASTM DI 003 or ISO 9050).

[0320] A UV barrier film comprising the composition provided herein may transmit less than 5%, less than 2%, or less than 1% of UV light at 300 nm. In certain embodiments, UV transmittance is less than 0.1%, less than 0.5%, or less than 1%, depending on the required transparency. Light Transmission / Haze (Optical Clarity vs. Diffusion)

[0321] The terms "light transmission" and "haze" describe the film’s optical properties, specifically, the percentage of visible light that passes through the film (transmittance) and the degree to which the light is scattered (haze). These are important for visual appeal, transparency, and label readability.

[0322] Measurement is typically performed using ASTM D1003 or ISO 14782 with a haze meter or spectrophotometer.

[0323] In some embodiments, the total light transmittance of a film comprising the composition provided herein is greater than 85%, greater than 90%, or greater than 95%. Haze values may be less than 20%, less than 10%, or less than 5%, depending on the application. In alternative embodiments, a film may exhibit less than 1%, less than 5%, or less than 10% haze for applications where diffusion is beneficial (e.g., light-diffusing films).

[0324] Processes

[0325] The thermoplastic soy protein-based compositions described herein may be processed using various melt-processing techniques, beginning with a precursor blend, as defined hereinabove. These compositions typically comprise soy protein isolate (SPI) or soy protein concentrate (SPC), one or more plasticizers, and optionally, compatibilizers, crosslinking agents, reducing agents, stabilizers, or synthetic biodegradable polymers. To form a homogeneous and processable material, the precursor blend is subjected to thermomechanical treatment under controlled conditions that ensure uniform dispersion and activation of functional components while preserving the structural integrity of the soy protein.

[0326] The process typically involves melt blending, which refers to a process of heating and shearing a precursor blend to produce a cohesive, partially or fully molten mixture in which the individual components are uniformly dispersed - this mixture is referred to herein as a melt-blended intermediate. Tools commonly used for this stage include thermomechanical batch mixers (such as a Brabender measuring mixer), single-screw extruders, and twin-screw extruders. A single-screw extruder is defined herein as a continuous melt-processing apparatus employing a single rotating screw to convey and mix thermoplastic materials. A twin-screw extruder refers to a melt-processing device with two intermeshing screws, capable of applying high shear and promoting dispersion and interfacial interaction in heterogeneous or reactive blends.

[0327] Also suitable for this stage are compounding systems, which are defined herein as thermal and mechanical mixing devices used to blend multiple components, such as polymers, fillers, plasticizers, or additives, into a homogeneous material suitable for downstream processing.

[0328] The mixer or extruder is equipped with heating zones and shear-imparting elements, allowing controlled melting, mixing, and partial reactive processing, which refers to the initiation of covalent or non-covalent interactions between components (e.g., compatibilization or crosslinking) without full polymerization or curing. In the case of soy protein-based compositions, it is essential that the processing temperature remains below the thermal denaturation threshold of the protein component, typically not exceeding 160 °C and preferably maintained in the range of 100-150 °C, or less than any intermediate temperature value. Thermal denaturation is defined herein as the irreversible unfolding of the protein’s secondary and tertiary structure due to heat, which can impair mechanical properties or film-forming ability. Film-forming ability refers to the capacity of a composition to form continuous, cohesive films without cracking or defects under standard molding or casting conditions. Excessive temperature or shear can also lead to protein decomposition, defined as the breakdown of peptide bonds or the formation of char and degradation products, or trigger Maillard browning, a non-enzymatic reaction between amino groups and reducing sugars that results in discoloration and potential embrittlement.

[0329] As used herein, the term “melt-blended intermediate” refers to the composition resulting from the thermal and mechanical mixing of a precursor blend comprising soy protein, at least one plasticizer, and optionally additional components such as compatibilizers, crosslinking agents, reducing agents, stabilizers, antioxidants, and / or synthetic biodegradable polymers, wherein the components have been sufficiently heated and sheared to form a cohesive, substantially homogeneous thermoplastic material, but prior to being shaped or solidified into a final article by compression molding, extrusion, casting, or other melt-processing techniques.

[0330] The melt-blended intermediate exists in a softened or molten state and is characterized by uniform dispersion of its constituents, activation of functional additives, and preservation of the structural integrity of the soy protein. It represents a transitional state between the unprocessed precursor blend and the final thermoplastic composition as embodied in a molded or formed article.

[0331] Once a uniform melt-blended intermediate is obtained, the material may be shaped into films, sheets, or molded articles using standard polymer processing techniques. In some embodiments, the dry mixture may be formed into a pre-compacted mass or sheet using powder mixing followed by compression molding, wherein the dry -blended powders are loaded into a mold and subjected to heat and pressure in a batch press. Compression molding is defined herein as a batch process in which a composition is shaped into a dense form by the application of elevated temperature and compressive force in a closed mold. This approach minimizes thermal residence time, meaning the duration that the composition remains under elevated temperature during processing, and is particularly suitable for temperature-sensitive protein-based formulations.

[0332] In another approach, the ingredients are first homogenized in a thermomechanical batch mixer, which is an internal batch mixer with thermal control and high-shear rotors that allows simultaneous heat and shear treatment in discrete, pre-measured cycles. The resulting plastified blend is then transferred to a compression mold for final shaping and consolidation. This batch mixing followed by compression molding method enables enhanced control over dispersion and melt uniformity, particularly when viscous additives or interfacial compatibilizers are used. Interfacial compatibilizers are defined herein as additives that enhance adhesion between chemically dissimilar phases, such as hydrophilic soy protein and hydrophobic synthetic polymers.

[0333] Alternatively, in compounding followed by cast extrusion, the thermoplastic blend is first compounded in a twin-screw extruder and then passed through a flat die onto a chill roll to produce continuous films. Cast extrusion refers to a film-forming process in which a molten polymer is extruded into a flat sheet or film and cooled rapidly to fix its morphology.

[0334] Across all processing modes, care must be taken to maintain conditions that support effective plasticization, dispersion, and interfacial compatibility, which refers to the mechanical and / or chemical affinity between immiscible domains, while avoiding denaturation or degradation of the protein phase. Accordingly, processing protocols are selected and tuned based on the composition, target properties, and intended application of the final soy protein-based thermoplastic article.

[0335] The process for obtaining the thermoplastic composition and any article formed thereof or containing the same is effected under conditions that maintain structural integrity of said soy protein. The phrase “said melt-processing process is effected under conditions that maintain structural integrity of said soy protein without thermal decomposition thereof’ shall be understood to mean that the thermal, mechanical, and chemical parameters employed during melt-processing, such as temperature, residence time, and shear intensity, are selected and controlled so as to avoid degradation of the primary molecular structure of the soy protein component.

[0336] As used herein, “structural integrity” refers to the preservation of the native or functional proteinaceous backbone of the soy protein isolate or concentrate, including its ability to participate in film formation, phase continuity, and interfacial adhesion in the thermoplastic matrix. This term excludes irreversible breakdown of the protein’s primary structure or excessive denaturation that leads to coagulation, browning, or loss of film-forming capability.

[0337] The phrase “without thermal decomposition” refers to the avoidance of thermal conditions that would cause scission of peptide bonds, formation of degradation by-products, or carbonization of the soy protein, such as might occur at elevated temperatures beyond the processing window typically ranging about 80-160 °C, or 100-150 °C. Acceptable processing conditions are those that allow partial unfolding or plasticization of the protein for melt-processability, while preserving its functionality within the resulting thermoplastic article. The initial step generally involves dry blending, defined herein as a low-shear, non-thermal mixing process in which powdered or granulated ingredients are homogenized without the use of external heat or plasticizing solvents. This may be carried out in a V-blender, ribbon blender, or planetary mixer. The dry mixing step ensures macroscopic homogeneity but does not initiate significant molecular-level interaction. It is critical that the materials remain free-flowing and do not prematurely agglomerate or hydrate at this stage.

[0338] FIGs. 8(a-c) illustrate and exemplifies the mechanical properties of soy protein-based films prepared by different melt-processing methods.

[0339] Powder mixing

[0340] Powder mixing with compression molding may involve the following steps:

[0341] 1. Mixing soy protein isolate or soy protein concentrate with at least one plasticizer and at least one crosslinking agent in powder form.

[0342] 2. Melt blending the mixture to form a homogeneous composition.

[0343] 3. Compression molding the composition to form a film.

[0344] In some cases, the compression molding may be performed at a temperature of 140 °C under a pressure of 3 metric tons for 3 to 5 minutes. This process may result in films with specific mechanical properties, as shown in FIGs. 8(a-c).

[0345] Batch mixing

[0346] Batch mixing followed by compression molding may involve the following steps:

[0347] 1. Mixing soy protein isolate or soy protein concentrate with at least one plasticizer and at least one crosslinking agent using a thermomechanical batch mixer or an internal batch mixer with thermal control, such as, e.g., a Brabender batch mixer.

[0348] 2. Operating the batch mixer at a temperature of 120 °C and a speed of 60 rpm for at least 5 minutes to form a homogeneous composition.

[0349] 3. Compression molding the resulting composition to form a film.

[0350] The batch mixing process may allow for better dispersion of components compared to powder mixing, potentially resulting in improved mechanical properties as illustrated in FIGs. 8(a-c).

[0351] Compounding

[0352] Compounding followed by cast extrusion may involve the following steps:

[0353] 1. Compounding the soy protein isolate or soy protein concentrate with plasticizers and crosslinking agents using a twin-screw extruder.

[0354] 2. Operating the twin-screw extruder at a temperature range of 80 °C to 140 °C.

[0355] 3. Using a screw speed of 250 rpm for the compounding process.

[0356] 4. Cast extruding the compounded material to form a film. In some cases, the compounding process may be carried out at a temperature range of 80 °C to 100 °C. The cast extrusion step may be performed using a single-screw extruder with specific processing parameters.

[0357] A drying step may be incorporated into any of these processing methods. In some cases, the drying step may be performed at 40 °C for at least 12 hours to remove excess moisture before film formation. This drying step may help improve the final properties of the thermoplastic material.

[0358] The choice of processing method may influence the mechanical properties of the resulting soy protein-based films. As shown in FIGs. 8(a-c), films prepared by different processing methods may exhibit varying tensile strength, maximal tensile strain, and Young's modulus values. The specific processing conditions and parameters may be adjusted to optimize the properties of the thermoplastic material for different applications.

[0359] According to some embodiments, there are provided three alternative processes to combine the soy, the additional polymer and the compatibilizer:

[0360] • Combining the additional polymer with the compatibilizer, and then adding the soy;

[0361] • Combining the soy with the compatibilizer, and then adding the additional polymer; and

[0362] • Combining the soy with the additional polymer and then adding the compatibilizer.

[0363] An additional method of compatibilization can be achieved through chemical modification of the soy protein, using acetylation or succinylation which can improve the solubility and processability of soy protein.

[0364] Another way is though Maillard reaction with reducing sugars which can create cross-links between protein molecules. This is the way to create also an internal plasticizer to the soy protein in order to reduce the impact of external plasticizers such as glycerol and ethylene glycol on the mechanical properties of the soy protein and possible bleeding / migration to the surface leaving it sticky.

[0365] Melt processing

[0366] A preferred process method for producing the thermoplastic composition provided herein is melt processing. As used herein, “melt processing” refers to thermomechanical processing techniques including batch blending, twin-screw extrusion, or compression molding, wherein the components are mixed above the melting point of the thermoplastic polymer to form a homogeneous composition. In one non-limiting embodiment, SPI, PCL, and ESBO are pre-weighed and blended at 160 °C to form a uniform melt, followed by casting or molding.

[0367] In some embodiments, compression molding is performed at a temperature between 100°C and 130°C, optionally for a time period ranging from 1 to 5 minutes. The temperature may range from 100°C to 110°C, or from 105°C to 115°C, or from 110°C to 120°C, or from 115°C to 125°C, or from 120°C to 130°C. In some embodiments, the temperature is at least 100°C, at least 105°C, at least 110°C, at least 115°C, at least 120°C, or at least 125°C. The time period may range from 1 to 2 minutes, or from 1.5 to 3 minutes, or from 2 to 4 minutes, or from 3 to 5 minutes, or from 4 to 6 minutes. In some embodiments, the compression time is at least 1 minute, at least 2 minutes, at least 3 minutes, at least 4 minutes, or at least 5 minutes.

[0368] The pressing temperature and time may depend on SPI content, with longer times preferred for higher protein concentrations to ensure uniformity.

[0369] Pretreatment of polymeric substrates prior to adhesive application may be performed to enhance adhesion. Suitable pretreatments include surface abrasion, solvent wiping (e.g., acetone), or corona discharge.

[0370] In further embodiments, the adhesive thermoplastic composition is laminated between two polymeric films to form a multilayer assembly, using thermal lamination techniques. In certain examples, the adhesive is hot-pressed between substrate films under light pressure at 120 °C for a duration of 1.5 to 3 minutes.

[0371] General definitions:

[0372] As used herein the term “about” or “approximately,” refers to ±10 %. For example, the term “about 100 units” encompasses the value 100 units, as well as the values 90 units, 91 units, 92 units, 93 units, 94 units, 95 units, 96 units, 97 units, 98 units, 98 units, 99 units, 100 units, 101 units, 102 units, 103 units, 104 units, 105 units, 106 units, 107 units, 108 units, 109 units, and 110 units.

[0373] The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to"; namely, as used herein, these terms are intended to be open- ended and not limiting. They indicate that the presence of the listed elements does not preclude the inclusion of additional, unrecited elements or method steps.

[0374] The term “consisting of’ means “including and limited to”.

[0375] The term "consisting essentially of means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0376] The phrase “one or more” as used herein includes one, two, three, or more of the described elements or components and does not exclude any combinations or sub-combinations thereof.

[0377] The terms “preferred” or “preferably” indicate an example or embodiment that is more suitable or favorable under certain circumstances, but these terms are not intended to limit the scope of the invention or to suggest that other variations are excluded. As used herein, the phrase “selected from the group consisting of’ includes all members of the recited group, each member of the recited group, and all possible combinations. For example, selected from the group consisting of A, B, and C, includes A, only, as well as B, only, as well as C, only, as well as A and B, as well as A and C, as well as B and C, and as well as A, B, and C.

[0378] The term “substantially,” when used in reference to a characteristic or parameter, means that the characteristic or parameter need not be absolute but is close enough to the specified value or condition so as to achieve the intended purpose or effect.

[0379] As used herein, the phrases "substantially devoid of and / or "essentially devoid of in the context of a certain substance, refer to a composition that is totally devoid of this substance or includes less than about 5, 1, 0.5 or 0.1 percent of the substance by total weight or volume of the composition. Alternatively, the phrases "substantially devoid of and / or "essentially devoid of in the context of a process, a method, a property or a characteristic, refer to a process, a composition, a structure or an article that is totally devoid of a certain process / method step, or a certain property or a certain characteristic, or a process / method wherein the certain process / method step is effected at less than about 5, 1, 0.5 or 0.1 percent compared to a given standard process / method, or property or a characteristic characterized by less than about 5, 1, 0.5 or 0.1 percent of the property or characteristic, compared to a given standard. Further alternatively, the terms "substantially" and / or "essentially " in the context of a characterizing property, means that the characterizing property is expressed to at least 99 %, at least 95 %, at least 90 % of its full or complete expression. For example, the phrase “the elements are maintained substantially in a certain configuration” should be read as “at least 99 % of the elements are maintained in the certain configuration.”

[0380] As used herein, the phrases "substantially devoid of and / or "essentially devoid of in the context of a certain substance, refer to a composition that is totally devoid of this substance or includes less than about 5, 1, 0.5 or 0.1 percent of the substance by total weight or volume of the composition. Alternatively, the phrases "substantially devoid of and / or "essentially devoid of in the context of a process, a method, a property or a characteristic, refer to a process, a composition, a structure or an article that is totally devoid of a certain process / method step, or a certain property or a certain characteristic, or a process / method wherein the certain process / method step is effected at less than about 5, 1, 0.5 or 0.1 percent compared to a given standard process / method, or property or a characteristic characterized by less than about 5, 1, 0.5 or 0.1 percent of the property or characteristic, compared to a given standard.

[0381] When applied to an original property, or a desired property, or an afforded property of an object or a composition, the term “substantially maintaining”, as used herein, means that the property has not change by more than 20 %, 10 % or more than 5 % in the processed object or composition. The term “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and / or to exclude the incorporation of features from other embodiments.

[0382] The words “optionally” or “alternatively” are used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the invention may include a plurality of “optional” features unless such features conflict.

[0383] As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

[0384] Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0385] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging / ranges between” a first indicate number and a second indicate number and “ranging / ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

[0386] As used herein the terms “process” and "method" refer to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, material, mechanical, computational and digital arts.

[0387] Terms used in the singular form shall also include the plural, and vice versa, unless context clearly indicates otherwise. Furthermore, words of any gender include all genders and are intended to cover all corresponding terms.

[0388] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0389] Unless expressly defined otherwise hereinabove, chemical and technical terms are to be understood in their ordinary meaning as would be recognized by a person of ordinary skill in the relevant art, in view of the general body of scientific and technical knowledge available at the time of filing.

[0390] For the avoidance of doubt, definitions of specific chemicals, reagents, materials, polymers, functional groups, chemical terms, analytical methods, laboratory techniques, unit operations, and chemical processes and reactions are to be interpreted in accordance with: (i) the common general knowledge of a person of ordinary skill in the art; and (ii) standard reference sources, including without limitation the Periodic Table of the Elements, the CAS Registry and CAS Registry Numbers, and the most recent edition available at the relevant time of the CRC Handbook of Chemistry and Physics (e.g., 106thEd.).

[0391] Unless otherwise indicated, general principles of organic chemistry, including nomenclature, bonding, stereochemistry, reaction mechanisms, functional group transformations, and reactivity patterns, are to be understood in light of conventional organic chemistry textbooks and reference works, such as Sorrell, Organic Chemistry (University Science Books); March’s Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (e.g., 8thEd., Wiley); and Larock, Comprehensive Organic Transformations: A Guide to Functional Group Preparations (VCH Publishers and subsequent expanded editions).

[0392] In case of any inconsistency between such ordinary-meaning interpretations and an explicit definition provided in the document, the explicit definition shall prevail for purposes of that document.

[0393] It is expected that during the life of a patent maturing from this application many relevant thermoplastic composition comprising soy protein isolate (SPI) will be developed and the scope of the phrase "thermoplastic composition" is intended to include all such new technologies a priori.

[0394] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0395] Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

[0396] EXAMPLES

[0397] Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non-limiting fashion.

[0398] Example 1

[0399] Materials

[0400] Soy Protein Isolate (SPI) (Wilpro G100, minimum 90wt.% protein, on a dry basis, Wilmar) was used as the soy protein source. Glycerol (Bio-Lab) and double distilled water (DDW) were used as a plasticizers. Tannic Acid (TA) and Epoxidized soybean oil (ESBO) were used for crosslinking the films. Sodium Sulfite (SS) was used as a reducing agent.

[0401] Film preparation methods

[0402] Films were prepared using three methods:

[0403] 1. Powder mixing + Compression molding

[0404] 2. Batch mixing + compression molding

[0405] 3. Compounding + Cast Extrusion

[0406] First, powder mixing + compression molding was used. At advanced stage of the study the most promising compositions were prepared using batch mixing + compression molding and additional compositions were prepared to fit the batch mixing processing. Compounding + cast extrusion, which is the most similar to industrial processing, was also used and the most suitable processing parameters were fitted.

[0407] Preparation of the soy films using powder mixing + compression molding

[0408] SPI was mixed with glycerol, along with other plasticizers and crosslinkers in various compositions (Table la). Each composition was then blended using an electrical grinder.

[0409] Then compression molded was performed using a Carver laboratory press at 140 °C for 3 minutes under a load of 3 metric tons. The mold was then cooled to 50 °C. A yellow and transparent film was released from the mold. The average thickness of the films was approximately 0.5mm. These films are shown in FIGs. l(a-d). The reference sample contained SPI and 40 %w / w glycerol. Preparation of the soy films using batch mixing + compression molding

[0410] The SPI compositions (presented in Table lb) were melt-blended in a thermomechanical batch mixer or an internal batch mixer with thermal control, such as, e.g., a Brabender batch mixer, set to 60 rpm and 120 °C for 5-10 min to form a homogeneous molten batch ready for compression. Then these batches were compression-molded into films, as described above. These films are shown in FIGs. 2(a-c).

[0411] Preparation of the soy films using compounding + cast extrusion

[0412] Compounded samples (compositions presented in Table 1c) were produced by melt blending in a EUROLAB Digital 16 (PRISM) twin screw co-rotating extruder (D=16 mm, L / D=24), using a temperature range of 80 °C to 100 °C, and screw speed of 250 rpm.

[0413] Then extruded films were produced by MICRO-TRUDER (Randcastle Extrusion Systems, Inc. New lersey, USA) Cast-film single screw extruder (D=13 mm, L / D=20), using a temperature range of 110 °C-140 °C. The machine was operated at a screw speed of 45 rpm. A yellow-brown and transparent sheet was produced from the extrusion. The average thickness of the films was 0.8mm. These films are shown in FIGs. 3(a-d).

[0414] Mechanical properties measurements

[0415] The soy protein films’ tensile mechanical properties were measured at room temperature, under unidirectional tension, at a rate of 15mm / min (according to a standard test method, ASTM D 882), using a 5944 Instron Universal Testing machine. Each film sample was cut into a two- dimensional “dog-bone” shape with a neck length of 17mm and a width of 5mm. The maximal tensile strength was defined as the maximum strength in the stress-strain curve. The maximal strain was defined as the strain at break. Young’s modulus was defined as the slope of the stress-strain curve in the elastic (linear) region. 7-10 samples were tested for each film type.

[0416] Tables la-c present details of the compositions of melt processed soy protein-based samples.

[0417] Table la

[0418] Table 1b

[0419] Table 1c

[0420] Results and discussion

[0421] Powder mixed + compression molded films

[0422] The reference composition contained only SPI and glycerol (40 %w / w) as plasticizer. All other samples contained also DDW as additional plasticizer, at concentration of 10% w / w and pH 7 or 10. Various stress-strain curves were obtained for the powder mixed + compression molded films (FIG. 4 and FIGs. 5(a-c)), indicating that the strength, modulus and maximal strain are affected by the composition parameters.

[0423] All studied formulations exhibited maximal strain in the range of 20-75%, which indicates good ductility and flexibility. This behavior is obtained due to the glycerol and water incorporation. While incorporation of epoxidized soy bean oil (ESBO) has almost no effect on the tensile properties, incorporation of tannic acid strongly increased the tensile strength and the maximal strain. Also, incorporation of sodium sulfite (SS) at relatively low concentration of 0.5% w / w resulted in increased tensile strength and maximal strain (FIG. 4 and FIGs. 5(a-c)). The best formulation contained tannic acid (1.5%w / w) and DDW at pHlO. The former resulted in tensile strength of 6 MPa and maximal strain of 75%, and the latter resulted in tensile strength of 6.5 MPa and maximal strain of 72%. All studied formulations exhibited Young’s modulus of 120-265 MPa, which was less affected by the formulation parameters, compared to the tensile strength and maximal strain.

[0424] Batch mixed + compression molded films

[0425] In order to optimize the mixing of all components together, batch mixer was use prior to film preparation using compression molding. All studied formulations contained 40 % w / w glycerol and at least 10 % w / w DDW as plasticizers. Since part of the water was lost during the mixing step, 40 % w / w DDW (pH7) was incorporated to most formulations. The stress-strain curves obtained for the batch mixed + compression molded films are presented in Fig. 6, and the tensile strength, maximal strain and Young's modulus are presented in FIGs. 7(a-c).

[0426] The results show that the batch mixing resulted in tensile strength of 4.5-9 MPa, maximal strain of 4-34%, and Young's modulus of 180-505 MPa (FIGs. 7(a-c)). The best formulation contained 5%w / w tannic acid and 40 %w / w DDW at pH7, and resulted in tensile strength of 9 MPa and maximal strain of 18%. Addition of epoxidized Soy Bean Oil (ESBO) at relatively low concentration of 0.5% to the formulation containing 40% w / w DDW resulted in relatively high maximal strain (33%), compared to the other batched mixed samples. However, its tensile strength and modulus are relatively low.

[0427] In general, all batch mixed + compression molded films exhibited higher tensile strength and Young's modulus values, compared to powder mixed + compression molded films, due to the more effective mixing process at elevated temperature. However, the batch mixing resulted in significantly lower strain values, probably due to loss of part of the DDW which acts as a plasticizer in our SPI systems, in addition to glycerol. These trends are clearly shown in FIGs. 8(a-c), which presents a comparison between the tensile properties of selected films prepared using the two processing methods. Compounded + cast extruded films

[0428] In order to further optimize the mixing of all components together and perform a process which is the most similar to industrial processes, SPI films were prepared using a Lab twin screw corotating extruder for compounding and followed by cast extrusion, using a cast-film single screw extruder.

[0429] Based on our previous experience with melt blending, all studied formulations contained relatively high DDW concentration of 60% or 90%, in addition to 40 % w / w glycerol. The TA crosslinker was incorporated in part of the formulations.

[0430] The stress-strain curves obtained for the compounded + cast extruded films are presented in Fig. 9, and the tensile strength, maximal strain and Young's modulus are presented in FIGs. 10(a-c). Relatively high tensile strengths (5.4-8.1 MPa) were obtained, combined with high maximal strain values (63-100%), for all studied formulations. However, relatively low Young's modulus values were obtained (Fig. 10c), compared to these of powder mixed + compression molded films (Fig. 5c) and batch mixed + compression molded films (Fig. 7c).

[0431] The best formulation contained 60 %w / w DDW at pH7, and resulted in tensile strength of 8 MPa and maximal strain of 63%. Drying this formulation for overnight at 40°C practically did not change the mechanical properties. Addition of TA to this formulation at concentrations of 0.5% and 5% resulted in a lower tensile strength (6 MPa and 5.5 MPa, respectively), and higher maximal strains (100% and 88%, respectively). Similar effects to these of adding TA were obtained also when using 90% DDW instead of 60%.

[0432] Summary and conclusions

[0433] Soy Protein films were developed using three different melt processing techniques, and studied for the effect of processing method and composition parameters on the tensile properties. Glycerol and DDW were used as plasticizers. Tannic Acid and epoxidized soybean oil were used for crosslinking the films. Sodium Sulfite was used as a reducing agent. In the first stage of research the films were prepared using simple powder mixing followed by compression molding. Then advanced formulations were processed using batch mixing followed by compression molding, and compounding followed by cast extrusion. The latter is the most similar method to industrial processing. The tensile properties, obtained using the three processing methods, are summarized and presented in Table 2 for comparison.

[0434] • While the plasticized effect of the glycerol and water enabled relatively high maximal strains for power mixed + compression molded sample, using batch mixing resulted in much lower strains but enabled to get higher strengths and Modulus values. • The best results were obtained using compounding followed by cast extrusion, i.e., combination of good strength with high maximal strain. Relatively high water concentration (60%) was needed.

[0435] • Addition of tannic acid resulted in higher strength and maximal strain for powder mixed samples, and optimal tensile properties for batch mixed+ compression molded samples. Also, it increased the maximal strain of the cast extruded films.

[0436] Our study shows that various melt processing techniques are feasible for plasticized soy protein formulation, and result in relatively high ductility and flexibility. Incorporation of tannic acid improved the tensile properties of the soy based films, obtained using the three techniques, although in different way for each technique. Additional crosslinkers should be used in order to further increase the tensile strength of the films.

[0437] Table 2 presents the tensile properties of soy protein films prepared using different processing methods.

[0438] Table 2

[0439] Example 2

[0440] Preparation of Soy Protein Films by Powder Mixing and Compression Molding Materials:

[0441] - Soy Protein Isolate (SPI) (Wilpro G100, minimum 90wt.% protein, on a dry basis, Wilmar)

[0442] - Glycerol (Bio-Lab)

[0443] - Double distilled water (DDW)

[0444] - Tannic Acid (TA)

[0445] - Electrical grinder

[0446] - Carver laboratory press

[0447] Methods:

[0448] 1. SPI was mixed with glycerol (40% w / w) and DDW (10% w / w) at pH 7.

[0449] 2. The mixture was blended using an electrical grinder. 3. Compression molding was performed using a Carver laboratory press at 140 °C for 3 minutes under a load of 3 metric tons.

[0450] 4. The mold was cooled to 50 °C and the film was released.

[0451] Results:

[0452] A yellow and transparent film was obtained with an average thickness of approximately 0.5 mm. The film exhibited a tensile strength of 6 MPa and a maximal strain of 75%. The addition of tannic acid (1.5% w / w) and DDW at pH 10 resulted in improved mechanical properties compared to the reference sample. The tannic acid formulation showed a tensile strength of 6 MPa and maximal strain of 75%, while the pH 10 formulation resulted in a tensile strength of 6.5 MPa and maximal strain of 72%.

[0453] Example 3

[0454] Effect of Ethylene Glycol as a Plasticizer on Soy Protein Films

[0455] Materials:

[0456] - Soy Protein Isolate (SPI)

[0457] - Ethylene Glycol (EG)

[0458] - Double distilled water (DDW)

[0459] - Carver laboratory press

[0460] Methods:

[0461] 1. SPI was mixed with EG (20% w / w) and DDW (10% w / w) at pH 7.

[0462] 2. The mixture was processed by compression molding as described in Example 1.

[0463] Results:

[0464] The film plasticized with EG exhibited a tensile strength of 10.5 MPa, a maximal strain of 62%, and a yield stress of 8 MPa. These properties were improved compared to films plasticized with glycerol. The use of EG allowed for lower concentrations of plasticizer and water compared to glycerol-based formulations.

[0465] Example 4

[0466] Effect of Tannic Acid on Ethylene Glycol Plasticized Soy Protein Films

[0467] Materials:

[0468] - Soy Protein Isolate (SPI)

[0469] - Ethylene Glycol (EG)

[0470] - Tannic Acid (TA)

[0471] - Double distilled water (DDW)

[0472] - Carver laboratory press Methods:

[0473] 1. SPI was mixed with EG (20% w / w), TA (0.5% w / w), and DDW (10% w / w) at pH 7.

[0474] 2. The mixture was processed by compression molding as described in Example 1.

[0475] Results:

[0476] The addition of TA (0.5% w / w) increased the maximal strain from 50% to 90% with a slight decrease in strength from 9.5 to 8 MPa. This suggests a softening effect rather than an increase in strength due to crosslinking.

[0477] Example 5

[0478] Soy Protein Films with Combined Ethylene Glycol and Glycerol Plasticizers

[0479] Materials:

[0480] - Soy Protein Isolate (SPI)

[0481] - Ethylene Glycol (EG)

[0482] - Glycerol

[0483] - Carver laboratory press

[0484] Methods:

[0485] 1. SPI was mixed with EG and glycerol in various ratios, keeping the total plasticizer content constant at 40% w / w relative to SPI.

[0486] 2. The mixtures were processed by compression molding as described in Example 1.

[0487] Results:

[0488] All samples achieved relatively high maximum elongations (about 100%). Formulations plasticized with 10% EG + 30% glycerol or 20% EG and 20% glycerol were stronger than those plasticized with 30% EG and 10% glycerol. The combination of EG and glycerol as plasticizers may allow for tailoring of mechanical properties to suit specific applications.

[0489] Example 6

[0490] Biodegradability Evaluation of Soy Protein Films

[0491] Materials:

[0492] - Soy protein films prepared as described in previous examples

[0493] - Tap water

[0494] - Sodium Azide

[0495] - Soil (pH ~6) and compost mixture

[0496] Methods:

[0497] 1. Rectangular samples (2x3 cm) were prepared from three different film formulations. 2. Samples were dried overnight at 40 °C and weighed before testing.

[0498] 3. Water immersion: Samples were placed in 2L of tap water with 750mg of Sodium Azide as a preservative.

[0499] 4. Soil degradation: Samples were maintained in a 2: 1 mixture of soil and compost at room temperature.

[0500] 5. Samples were retrieved at intervals of 2, 5, 8, 14, 21, and 29 days, dried for one hour at 40 °C, and weighed.

[0501] Results:

[0502] The weight loss percentage was calculated according to the equation: Wl% = (Wi - Wf) / Wi 100%, where WI is the weight loss percentage, Wi is the initial weight, and Wf is the weight at the point of interest. In soil, the degradation of all three film types was rapid, with only 35-40% of the initial weight remaining after two weeks. In water, the films showed minimal changes over a month, losing 15-30% of their weight within the first two days, primarily due to plasticizer diffusion into the water.

[0503] Example 7

[0504] Preparation and Characterization of Soy Protein / PLA Blends

[0505] Materials:

[0506] - Soy Protein Isolate (SPI)

[0507] - Polylactic acid (PLA)

[0508] - Glycerol

[0509] - Twin screw extruder

[0510] - Compression molding equipment

[0511] Methods:

[0512] Blends of SPI and PLA were prepared in a fixed ratio of 75 wt.% PLA and 25 wt.% SPI. In selected formulations, SPI was chemically modified with reducing agents prior to blending. The components were melt-processed using a twin-screw extruder at controlled temperatures (150 °C- 160 °C), then formed into films by compression molding under standardized conditions. No plasticizers or compatibilizers were added in this set of experiments. The films were conditioned and tested for tensile properties using standard tensile testing methods (e.g., ASTM D638).

[0513] Results:

[0514] Initial experiments using untreated SPI in 75 / 25 PLA / SPI blends resulted in films with tensile strengths ranging from 10 to 22.5 MPa, but with limited ductility, as elongation at break was restricted to a narrow range of 1.2% to 1.6%. These values indicated poor phase compatibility between PLA and SPI, leading to brittle fracture behavior despite relatively high stiffness and strength.

[0515] To address these limitations, SPI was chemically modified using different reducing agents before blending. The resulting formulations were processed under the same conditions and tested for mechanical performance. The results are shown in Table 3.

[0516] Table 3

[0517] These results demonstrate that chemical reduction of the soy protein phase significantly enhances interfacial compatibility with PLA. All tested reducing agents led to blends with elongation at break above 18% and tensile strengths around 7 MPa, indicating a favorable balance of strength and ductility. This performance is in contrast to the low-strain, brittle behavior observed in blends without reducing agents, confirming the importance of SPI pre-treatment in achieving flexible and resilient thermoplastic materials.

[0518] This example demonstrates that thermoplastic blends of SPI and PLA can be optimized through chemical modification of the protein component. The use of reducing agents such as sodium sulfite, cysteine, or sodium metabisulfite improves compatibility between the hydrophilic and hydrophobic phases, enabling improved mechanical properties without the need for added compatibilizers or plasticizers. The reproducibility of these results across independent datasets confirms the robustness of the formulation strategy. Moreover, biodegradability testing supports the use of these blends in applications requiring rapid degradation in soil and retained stability in aqueous environments.

[0519] Example 8

[0520] Exemplary Soy Protein / PLA Blends

[0521] Materials:

[0522] Exemplary adhesive formulations, or thermoplastic composition as disclosed herein, were prepared using soy protein isolate (SPI, Wilpro G100, Wilmar, China), poly caprolactone (PCL, Capa 6400, Mw = 37,000 g / mol, Perstorp, UK), and epoxidized soybean oil (ESBO, Edenol D81, Emery Oleochemicals, USA). In this system, SPI served as the functional component providing reactive groups such as amine, hydroxyl, carboxyl, and thiol, PCL acted as the thermoplastic matrix responsible for flexibility and film-forming ability, and ESBO functioned as a plasticizer and compatibilizer.

[0523] Preparation of adhesive formulations

[0524] To prepare the adhesive blends, PCL and SPI were weighed to yield formulations containing 10, 20, and 30 wt.% SPI. The components were placed in a beaker immersed in a silicone oil bath maintained at 160 °C and stirred until a uniform melt was obtained. ESBO was then incorporated into the mixture, and blending continued until homogeneity was achieved. The molten blends were cast into silicone molds with round cavities and cooled to room temperature, forming solid discs. These discs were subsequently compression-molded using a CARVER Laboratory Press (Model 2697-5) at 120 °C under low pressure. For the 10 wt.% SPI formulation, the hot-pressing time was 1.5 minutes, while for the 20 wt.% and 30 wt.% SPI formulations the time was extended to 2.5 minutes to ensure complete processing and uniformity.

[0525] Table 4 presents adhesive blends and materials concentrations in the adhesive.

[0526] Table 4

[0527] Characterization methods

[0528] The prepared adhesive films were characterized by several analytical techniques. Fourier- transform infrared spectroscopy (FTIR) was performed in the range of 4000-500 cm1to identify functional groups in the raw materials and to detect possible chemical interactions within the blends. Scanning electron microscopy (SEM, JEOL JSM-IT200, 5.0 kV) was employed to examine the cryofractured surfaces of the adhesive films, allowing evaluation of SPI dispersion and the degree of phase separation within the PCL matrix. Mechanical performance was assessed through tensile testing using an Instron 4481 universal testing machine equipped with a 500 N load cell. The adhesive films were cut into rectangular strips (100 x 10 mm2, thickness <1 mm) and tested at a crosshead speed of 50 mm / min under ambient laboratory conditions. Adhesion performance was evaluated by T-peel tests carried out with the same Instron system equipped with a 100 N load cell, at a speed of 100 mm / min. The substrates used in these tests included PLA films, PBAT films containing an amide chain extender, and soy protein-based films plasticized with glycerol. All substrates were pretreated by mechanical abrasion followed by acetone wiping to remove contaminants. For sample preparation, the adhesive was hot-pressed between two substrates at 120 °C for 1.5 minutes under minimal pressure, yielding bonded specimens with a 100 mm bonded area and a free length of 30 mm for peel testing.

[0529] Results:

[0530] Chemical Structure Analysis ( FTIR )

[0531] FIG. 11 is an FTIR spectra obtained for each material and for the adhesive blend that consists of 10 % SPI (in red).

[0532] FTIR spectroscopy was used to investigate potential chemical interactions between the adhesive components and to verify whether epoxy-amine reactions occurred. The results can be seen in FIG. 11. The spectra of the individual raw materials showed characteristic absorption bands: PCL exhibited a strong carbonyl (C=O) stretching at -1722 cm1and C-O-C stretching near 1159 and 1043 cm while SPI presented bands corresponding to amide I (C=O stretching, -1650 cm ') and amide II (N-H bending, -1540 cm '). ESBO contained characteristic ester peaks in a similar region as PCL, in addition to epoxy vibrations expected at 850-910

[0533] In the adhesive blend containing 10 wt.% SPI, the overall spectrum closely resembled that of pure PCL. The absence of a distinct epoxy peak and the lack of new bands suggested that the epoxy groups of ESBO did not react covalently with the amine or hydroxyl groups of SPI. This result indicates that the system relies primarily on non-covalent interactions such as hydrogen bonding and van der Waals forces, consistent with earlier reports on SPI / PCL blends. The dominance of PCL peaks likely masked SPI and ESBO signals due to their lower concentrations. These findings confirm that although ESBO was added as a compatibilizer, its role was limited to improving miscibility rather than enabling chemical crosslinking.

[0534] Morphological analysis (SEM)

[0535] FIG. 12 presents SEM analysis for 10%, 20%, and 30% SPI (left to right). These SEM images of cryo-fractured surfaces provided insight into the dispersion of SPI within the PCL matrix, as demonstrated in FIG. 12. At 10 wt.% SPI, the fracture surface appeared relatively smooth and homogeneous, with protein particles well distributed throughout the matrix. No significant phase boundaries were observed, indicating acceptable compatibility between the hydrophobic PCL and the hydrophilic SPI at this concentration. At 20 wt.% SPI, the morphology changed: discrete protein aggregates were detected, leading to localized discontinuities within the PCL network. Although partial compatibility remained, the system started to display phase separation. At 30 wt.% SPI, large aggregates of protein were clearly visible, disrupting the matrix continuity and producing voids at the interface between SPI and PCL. These aggregates serve as stress concentrators, which can accelerate crack initiation and propagation under mechanical load. This behavior aligns with previous studies on PCL / SPI hot-melt blends, which reported that low concentrations of SPI can be homogeneously dispersed. Still, higher concentrations tend to destabilize the matrix due to differences in polarity and crystallization kinetics. Thus, SEM analysis confirms that increasing SPI beyond 20 wt.% undermines structural uniformity and compromises the integrity of the adhesive films.15 16

[0536] Mechanical Properties

[0537] FIG. 13 presents the effect of SPI concentrations on the mechanical properties of the adhesive films. The tensile properties of the adhesive films reflected the morphological observations, and can be seen in FIG. 13, with 10 wt.% SPI, the adhesive exhibited tensile strength of 9.35 MPa and elongation at break of 9.73%, values that are reasonably close to neat PCL films. Increasing SPI to 20 wt.% reduced tensile strength to 6.83 MPa and elongation to 8.87%, while 30 wt.% SPI caused a sharp decrease to 3.51 MPa and 5.03%, respectively.

[0538] These results suggest that SPI does not participate in the cohesive network of the PCL matrix but instead disrupts chain entanglements and van der Waals interactions. While PCL provides flexibility and mechanical strength through its semi-crystalline domains, the rigid, hydrophilic SPI particles introduce heterogeneity and reduce the ability of the matrix to transfer stress. The results are consistent with literature reports where increasing protein content in thermoplastic blends weakened the tensile properties due to phase separation. Although ESBO was expected to act as a compatibilizer by reducing interfacial tension between SPI and PCL, FTIR and SEM results indicate that its effect was limited. Without strong covalent bonding, ESBO could only partially improve dispersion. At 30 wt.% SPI, the rigid domains dominated the microstructure, leading to poor load-bearing capacity and brittle fracture behavior.15 17

[0539] Adhesion Performance

[0540] FIG. 14 presents the effect of SPI concentrations on the peel strength (N / cm) on different substrates. As demonstrated in FIG. 14, the adhesion strength of the developed adhesives showed distinct trends depending on the substrate type.

[0541] On soy protein isolate (SPI) films plasticized with glycerol, the increase in peel strength with higher SPI content in the adhesive was minimal. Even at 30 wt.% SPI, adhesion values remained low, reflecting the inherently weak bonding between SPLbased adhesives and native soy protein films. This weakness is primarily due to migration of plasticizers such as glycerol to the film surface, which interferes with the formation of stable interfacial bonds. In contrast, for PLA substrates, the behavior was non-linear. At 0 wt.% SPI (the PCL / ESBO reference adhesive), adhesion was poor, indicating the limited compatibility between hydrophobic PLA and the adhesive matrix. Upon addition of SPI, an initial decrease in adhesion was observed, likely due to the introduction of polar domains that were poorly compatible with PLA. However, at higher SPI content, adhesion improved again, suggesting that the presence of accessible polar groups eventually enhanced interfacial interactions with the ester groups of PLA. For PBAT substrates with an amide chain extender, adhesion performance showed the clearest improvement. The peel strength increased significantly with SPI addition, reaching a maximum at 20 wt.% SPI. This result highlights the beneficial role of the chain extender in enhancing compatibility between the polar SPI domains and the more flexible PBAT matrix. The 20 wt.% SPI formulation provided the optimal balance between interfacial bonding and matrix integrity, as confirmed by SEM observations of relatively uniform morphology at this concentration.

[0542] FIG. 15 presents the peel strength on SPI / PCL substrate compared to SPEglycerol films. As can be seen in FIG. 15, the incorporation of PCL into the soy protein film markedly improved adhesion performance compared to the unmodified SPI films.

[0543] Recognizing the weak adhesion obtained with conventional SPI films, an additional set of experiments was carried out using modified soy protein films containing 10 wt.% PCL. These films were designed to better represent the intended multilayer structure for sustainable packaging applications. The chemical and morphological compatibility between the adhesive (SPI / PCL blend) and the modified SPI / PCL substrate facilitated stronger interfacial bonding, overcoming the limitations of native SPI films.

[0544] The oxygen transmission rate (OTR) values of two five-layer films are presented below. Both multilayer structures include a central SPI-based film plasticized with 30% glycerol, laminated on both sides with the adhesive formulation that gave the best results, composed of PCL, 20% SPI, and ESBO. The only difference between the two samples is the external layer: one multilayer uses PBAT as the outer film, and the other uses PLA.

[0545] FIG. 16 shows an Oxygen Transmission Rate (OTR) Comparison. As can be seen in FIG. 16, the measurements show that the PBAT -based multilayer exhibits an OTR of 1.85 cc / (m2day), while the PLA-based multilayer shows a significantly lower value of 0.07 cc / (m2day). For comparison, the oxygen transmission rates of the individual materials are much higher: PBAT ~ 704 cc / (m2day), PLA ~ 1067 cc / (m2day), and the adhesive ~ 485 cc / (m2day).

[0546] These results clearly indicate that combining these materials into a multilayer structure with an SPI-based film at the core leads to a substantial improvement in oxygen barrier performance. This enhancement aligns with the well-known oxygen-b airier properties of soy protein. SPI films maintain good oxygen-b arri er behavior even when plasticized only with glycerol. This is mainly due to the compact and strongly hydrogen-bonded network formed by the protein chains, which reduces the free volume and restricts molecular mobility within the matrix. As a result, oxygen molecules follow a longer and more tortuous diffusion path through the film, yielding lower permeability. In literature, the typical oxygen transmission value for glycerol-plasticized SPI films is approximately 20 cc / (m2day), which supports the barrier improvement observed in the multilayer structures.

[0547] A clear difference was observed between the two multilayer structures that differed only in their external layer. Although PLA and PBAT are both biodegradable polyesters, their inherent oxygen-b arri er properties are not the same. PLA typically exhibits lower chain mobility and a more rigid and partially ordered structure, which can reduce gas diffusion under certain processing conditions. PBAT, on the other hand, contains flexible aliphatic segments that increase molecular mobility and generally lead to higher gas permeability.

[0548] These intrinsic differences are reflected in the final OTR measurements: the PLA-based multilayer achieved an exceptionally low value of 0.07 cc / (m2day), while the PBAT -based multilayer reached 1.85 cc / (m2day). Even though the individual PLA and PBAT films are themselves highly permeable (-1067 and 704 cc / (m2day), respectively), the multilayer configuration dramatically improved their performance.

[0549] This improvement originates from the contribution of each layer in the structure. The central SPI film plasticized with 30% glycerol provides the dominant oxygen barrier, as soy protein forms a dense, hydrogen-bonded matrix that restricts oxygen diffusion. The adhesive layer (composed of PCL, 20% SPI, and ESBO) also plays an important role by ensuring good interfacial compatibility and limiting defects at the interfaces that could otherwise facilitate gas transmission. Finally, the outer PLA or PBAT layers provide mechanical stability and protect the core barrier layer. Together, these layers function synergistically, demonstrating the advantage of using a multilayer design in which each component contributes a complementary property to achieve an overall high-performance, biodegradable barrier film.

[0550] Conclusions

[0551] For multilayer film applications, this study successfully created a new biodegradable adhesive made of polycaprolactone (PCL) and soy protein isolate (SPI). FTIR research revealed that hydrogen bonding was the primary force driving adhesion. There was no sign of covalent epoxy-amine interactions, even though ESBO and SPI were present. SEM analysis showed that protein particles were well-dispersed at 10 wt% SPI, which indicates compatibility between phases. However, when the SPI concentration was 30 wt%, larger aggregates formed, which made the phases separate and the interfacial zones weak. Mechanical testing showed that there was a trade-off between strength and adhesion. For example, tensile strength went from 9.35 MPa at 10% SPI to 3.51 MPa at 30%, and elongation at break went from 9.73% to 5.03%. Adhesion performance depended on the substrate. For PBAT, the best peel strength was at 20% SPI, which was 196% better than the control. For PLA, the best adhesion was observed at 30% SPI, as the polar contacts were weaker. The 20% SPI formulation had the optimum balance between adhesion and mechanical properties. Moreover, the results demonstrated a substantial improvement in oxygen-b airier performance. The multilayer structure led to a reduction in OTR values, more than 99% compared to the individual PLA and PBAT films, highlighting the significant contribution of the SPI core layer.

[0552] Future work should focus on improving compatibility between PCL and SPI to reduce phase separation. Enhancing adhesion on different substrates via covalent bonding at the interface, using surface treatments or reactive additives, could further improve performance. Additionally, a biodegradability test will be performed to evaluate the degradation rate. Finally, scale-up challenges such as industrial lamination, thermal stability, and process optimization must be addressed to transition this technology toward commercial biodegradable packaging solutions.

[0553] Example 9

[0554] Plasticizer and Compatibilizer Screening

[0555] Additional experiments were conducted to improve compatibilization between soy protein and polylactic acid (PLA) in 75 / 25 PLA / SPI blends by introducing low concentrations of hydrophilic or partially hydrophilic synthetic polymers expected to localize at the PLA-soy interface and enhance interfacial adhesion. Polyethylene glycol (PEG), polyacrylic acid (PAA), and polyvinyl alcohol (PVA) were evaluated as compatibilizers, both in blends without plasticizer and in blends additionally containing glycerol. The stress-strain curves of the resulting films are presented in FIG. 17.

[0556] In blends without glycerol, addition of PEG increased maximal tensile strain to about 10.5% while reducing tensile strength to about 7 MPa, indicating improved ductility accompanied by some loss of strength. In contrast, addition of PAA produced a markedly different response, yielding high tensile strength of about 25 MPa with low maximal strain of about 1.5%, suggesting strong interfacial reinforcement but limited ductility. PVA-containing blends showed intermediate behavior consistent with partial compatibilization, although their performance was more sensitive to plasticization. When glycerol was incorporated into the PEG-, PAA-, or PVA-compatibilized blends, a significant reduction in tensile strength was observed, particularly for PAA- and PVA-containing systems, indicating that glycerol-driven softening can offset the strength gains afforded by hydrophilic interfacial compatibilizers. These results support a novel compatibilization concept for PLA / soy blends in which synthetic hydrophilic polymers are used at low loading to bridge the hydrophilic protein and hydrophobic polyester phases. The distinct mechanical profiles obtained with PEG and PAA suggest different compatibilization mechanisms, with PEG favoring ductility enhancement and PAA favoring strength enhancement, and both approaches warrant further investigation and optimization for targeted biodegradable film applications.

[0557] Example 10

[0558] Influence of Processing Temperature

[0559] A series of experiments was performed to evaluate the influence of melt-processing temperature on the mechanical properties, film quality, and thermal behavior of thermoplastic blends comprising 75 wt.% polylactic acid (PLA) and 25 wt.% soy protein isolate (SPI). The formulations contained no plasticizers or compatibilizers and were processed using a twin-screw extruder at controlled temperatures of 140 °C, 150 °C, and 160 °C. Film samples were produced by compression molding and conditioned prior to mechanical testing. The results are summarized in Table 5.

[0560] Table 5

[0561] The results indicate that increasing the processing temperature improves both tensile strength and elongation at break, likely due to enhanced interdiffusion and partial denaturation of the protein phase, promoting better interfacial adhesion and mechanical integration. However, films processed at 160 °C exhibited slight discoloration, suggesting partial thermal degradation of the protein component or the onset of Maillard-type reactions.

[0562] To further understand the thermal response of the blends, differential scanning calorimetry (DSC) was conducted on representative samples. The thermograms revealed a glass transition temperature (Tg) of PLA at approximately 60 °C and a melting peak in the range of 140-150 °C across all formulations. Notably, the blend containing 20% glycerol (tested in a separate series) exhibited a slightly reduced melting peak around 140 °C, suggesting plasticizer-induced softening and altered crystallinity. In contrast, non-plasticized blends showed melting endotherms closer to 150 °C, consistent with PLA’s typical melting behavior and thermal stability under the tested conditions.

[0563] This example demonstrates that thermal processing conditions, particularly temperature, have a critical impact on the structural, mechanical, and thermal performance of PLA / SPI blends. Optimization of the processing window in light of Tg and Tm behavior can support improved interfacial compatibility, mechanical performance, and prevention of premature thermal degradation. A processing temperature of 150 °C appears optimal for balancing cohesion, morphology, and mechanical integrity in these systems.

[0564] Example 11

[0565] Water Vapor Transmission Rate

[0566] The water vapor transmission rate (WVTR) of thermoplastic compositions comprising 75 wt.% poly(D,L-lactic-co-glycolic acid) (PDLGA) and 25 wt.% soy protein isolate (SPI) was evaluated to assess their suitability for moisture-sensitive applications. Several blend formulations were prepared with and without plasticizers, and WVTR values were measured under controlled conditions (38 °C and 90% RH) according to the gravimetric method.

[0567] FIG. 18 shows the WVTR values for the tested blends, which ranged from 11 to 43 g / m2- day . These values are significantly lower than those measured for soy protein alone, which typically exceeds 1000 g / m2- day, and also lower than the WVTR of neat PLA (reported at approximately 80 g / m2- day). The results indicate that incorporation of soy protein into PDLGA, even at a high loading of 25%, substantially reduces water vapor permeability. The improved barrier effect is attributed to the densification of the blend matrix and the molecular interactions between the protein and polymer phases, which limit moisture diffusion pathways.

[0568] Notably, all tested blends outperformed neat PLA in terms of water vapor barrier performance. This unexpected result underscores the synergistic effect of soy protein inclusion, particularly when modified with selected plasticizers, which further modulate matrix morphology and free volume.

[0569] The WVTR values of 11-43 g / m2day make these 75 / 25 PDLGA / Soy blends suitable for a variety of applications, including biodegradable food packaging, multilayer barrier films, and moisture-sensitive product containment. These findings confirm the potential of soy protein-based thermoplastic systems to provide enhanced water vapor resistance when properly formulated and processed. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. It is the intent of the applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is / are hereby incorporated herein by reference in its / their entirety.

Claims

IQWHAT IS CLAIMED IS:

1. A thermoplastic composition comprising: soy protein; and at least one plasticizer.

2. The thermoplastic composition of claim 1, wherein said soy protein is in the form of soy protein isolate (SPI) and / or soy protein concentrate (SPC).

3. The thermoplastic composition of claim 2, wherein said soy protein isolate or soy protein concentrate has a protein content of at least 90 % by dry weight.

4. The thermoplastic composition of any one of claims 1-3, wherein the plasticizer is selected from the group consisting of glycerol, water, tannic acid, sorbitol, ethylene glycol, diethylene glycol, and combinations thereof.

5. The thermoplastic composition of claim 4, wherein said plasticizer is present in an amount ranging from 10% to 60% by weight of the total composition.

6. The thermoplastic composition of any one of claims 1-4, further comprising at least one thermoplastic polymer that is not a soy protein.

7. The thermoplastic composition of claim 6, wherein said thermoplastic polymer is selected from polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polycaprolactone (PCL), and any combination thereof.

8. The thermoplastic composition of any one of claims 6-7, wherein said thermoplastic polymer is present in the composition an amount ranging from 10% to 80% by weight of the total composition.

9. The thermoplastic composition of any one of claims 1-8, further comprising an additional synthetic biodegradable polymer, forming a blend of at least three polymeric components.

10. The thermoplastic composition of any one of claims 1-9, further comprising at least one crosslinking agent.

11. The thermoplastic composition of claim 10, wherein said crosslinking agent is selected from the group consisting of tannic acid, epoxidized soybean oil, L-cysteine, glyoxal, genipin, alginate, pectin, chitosan, and combinations thereof.

12. The thermoplastic composition of any one of claims 10-11, wherein the crosslinking agent comprises tannic acid in an amount ranging from 0.5% to 10% by weight of said soy protein.

13. The thermoplastic composition of any one of claims 1-11, further comprising at least one compatibilizer.

14. The thermoplastic composition of claim 13, wherein said compatibilizer is selected from the group consisting of poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid.

15. The thermoplastic composition of any one of claims 1-14, further comprising at least one reducing agent.

16. The thermoplastic composition of claim 15, wherein said reducing agent is sodium sulfite, which is present in a concentration ranging from 0.1% to 5% by weight of said soy protein.

17. The thermoplastic composition of any one of claims 1-16, wherein the composition is prepared using a method selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion.

18. The thermoplastic composition of claim 17, wherein the method comprises using a twin-screw extruder at a temperature range of 80 °C to 160 °C.

19. The thermoplastic composition of any one of claims 1-18, further comprising a stabilizer to prevent thermal degradation during processing.

20. The thermoplastic composition of any one of claims 1-19, characterized by a tensile strength of at least 5 MPa.

21. The thermoplastic composition of any one of claims 1-20, characterized by an elongation at break (strain) of at least 5%.

22. The thermoplastic composition of any one of claims 1-21, characterized by Oxygen Transmission Rate (OTR) less than 100 cc / m2 / day.

23. The thermoplastic composition of any one of claims 1-22, characterized by Water Vapor Transmission Rate (WVTR) less than 10 g / m2 / day.

24. A method for producing a thermoplastic soy protein-based film, the method comprising: providing a precursor blend of the thermoplastic composition of any one of claims 1- 23; melting and homogenizing said precursor blend to thereby obtain a melt-blended intermediate; and processing said melt-blended intermediate using a melt-processing process to thereby obtain a film of the thermoplastic composition, wherein said melt-processing process is effected under conditions that maintain structural integrity of said soy protein.

25. The method of claim 24, wherein in the thermoplastic composition comprises at least one crosslinking agent.

26. The method of any one of claims 24-25, wherein said melt-processing process is selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion.

27. The method of any one of claims 24-26, wherein said melting and homogenizing is effected at a temperature of 100-150 °C and a speed of 30-90 rpm for at least 2-15 minutes.

28. The method of any one of claims 24-27, further comprising, subsequent to said melt-processing process, a drying step at a temperature of 20-50 °C for at least 5-20 hours to remove excess moisture.

29. The method of any one of claims 24-28, wherein at least one stabilizer is added to said melt-blended intermediate during said melting and homogenizing.

30. The method of any one of claims 24-29, wherein when the melt processing technique is compression molding, the compression molding is performed at a temperature of 100-150 °C under a pressure of 2-5 metric tons for 3-5 minutes.

31. The method of any one of claims 24-29, wherein when the melt processing technique is compounding, it is followed by cast extrusion, and said cast extrusion is carried out using a single-screw extruder with a screw speed of 30-60 rpm and a temperature gradient of 100-150 °C.

32. The method of any one of claims 24-31, further comprising chemically modifying the soy protein isolate or soy protein concentrate through acetylation, succinylation, or Maillard reaction with reducing sugars.

33. The method of any one of claims 24-32, further comprising a post-processing crosslinking step comprising spraying a crosslinker solution on the film followed by a drying step.

34. The method of any one of claims 24-33, wherein the film is characterized by a tensile strength of at least 5 MPa, and an elongation at break (strain) of at least 5%.

35. A method for preparing a biodegradable film comprising a multilayer structure, the method comprising:forming a first layer comprising the thermoplastic composition of any one of claims 1- 23; forming at least one additional layer comprising a synthetic biodegradable polymer that is not said thermoplastic composition; and laminating the layers together to form a composite film, wherein the first layer provides a low oxygen permeability barrier suitable for food packaging applications.

36. The method of claim 35, wherein the first layer has a thickness ranging from 50 to 500 micrometers.

37. The method of any one of claims 35-36, further comprising a step of treating the first layer with an alkali solution to enhance its barrier properties.

38. The method of any one of claims 35-37, wherein said additional layer comprises a polymer selected from the group consisting of polybutylene succinate, polycaprolactone, polylactic acid, and polybutylene adipate terephthalate.

39. The method of any one of claims 35-38, wherein the multilayer film is annealed at 80 °C.

40. The method of any one of claims 35-39, further comprising a lamination process effected using a hot-pressing technique at a temperature ranging 100-150 °C under a pressure of 10-20 bar.

41. The method of any one of claims 35-40, further comprising forming a tie layer between the first layer and the additional layer, wherein the tie layer comprises a compatibilized blend of soy protein and the synthetic biodegradable polymer.

42. A biodegradable film article comprising: a core layer composed of the thermoplastic composition of any one of claims 1-23; and at least one outer layer comprising a synthetic biodegradable polymer, wherein the core layer has a low oxygen permeability and the outer layer provides mechanical strength and water resistance, andwherein the film is suitable for packaging applications that require both biodegradability and gas barrier properties.

43. The biodegradable film article of claim 42, wherein the core layer comprises 40% to 60% by weight of the total film structure.

44. The biodegradable film article of any one of claims 42-43, wherein the outer layer has a water vapor transmission rate (WVTR) of less than 100 g / m2 / day at 38°C and 90% relative humidity.

45. The biodegradable film article of any one of claims 42-44, wherein the core layer includes an antioxidant additive to enhance the shelf life of the packaged product.

46. The biodegradable film article of any one of claims 42-45, further comprising a coating of hydrophobic nanoparticles on the outer layer to improve the film's water resistance.

47. The biodegradable film article of any one of claims 42-46, wherein the film is heat-sealable at a temperature below 120 °C.

48. The biodegradable film article of any one of claims 42-47, further comprising a tie layer between the core layer and the outer layer, wherein the tie layer comprises a compatibilized blend of soy protein and the synthetic biodegradable polymer.

49. The biodegradable film article of any one of claims 42-48, wherein the synthetic biodegradable polymer is selected from the group consisting of polylactic acid, polybutylene adipate terephthalate, polybutylene succinate, and polycaprolactone.

50. The biodegradable film article of any one of claims 42-49, wherein the core layer comprises a crosslinking agent selected from the group consisting of tannic acid, epoxidized soybean oil, L-cysteine, glyoxal, genipin, alginate, pectin, and chitosan.

51. The biodegradable film article of any one of claims 42-50, wherein the core layer comprises a plasticizer selected from the group consisting of glycerol, water, tannic acid, sorbitol, ethylene glycol, and di ethylene glycol.

52. The biodegradable film article of any one of claims 42-51, wherein the core layer comprises a compatibilizer selected from the group consisting of poly(2-ethyl-2- oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid.

53. The biodegradable film article of any one of claims 42-52, wherein the soy protein in the core layer is chemically modified through acetylation, succinylation, or Maillard reaction with reducing sugars.

54. The biodegradable film article of any one of claims 42-53, wherein the core layer is crosslinked through a post-processing crosslinking method comprising spraying a crosslinker solution on the layer followed by a drying step.

55. The biodegradable film article of any one of claims 42-54, wherein the film comprises three polymeric components including the soy protein and two different synthetic biodegradable polymers.

56. A method for improving the mechanical properties of a biodegradable polymer, the method comprising: blending a precursor blend of the thermoplastic composition of any one of claims 1-23 with at least one synthetic biodegradable polymer to form a blend; and processing the blend using a melt processing technique.

57. The method of claim 56, wherein the synthetic biodegradable polymer is selected from the group consisting of polylactic acid, polybutylene adipate terephthalate, polybutylene succinate, and polycaprolactone.

58. The method of any one of claims 56-57, further comprising adding a compatibilizer to improve interfacial adhesion between the thermoplastic composition and the synthetic biodegradable polymer.

59. The method of claim 58, wherein the compatibilizer is selected from the group consisting of poly(2-ethyl-2-oxazoline), maleic anhydride, adipic anhydride, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid.

60. The method of any one of claims 56-59, wherein the melt processing technique is selected from the group consisting of compression molding, batch mixing followed by compression molding, and compounding followed by cast extrusion.

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