Alginate-starch film

Abstract

The present invention relates to the field of heat sealable, highly biodegradable films comprising a polymer of fully natural plant origin comprising a salt of alginic acid and a carbohydrate. The films of the invention are useful for packaging products, such as powder and liquid products, in bags using current heat sealing equipment and with commercially viable productivity. In particular, the films of the present invention can be used in vertical form-fill-seal (VFFS) packaging equipment without the need for equipment retrofit. The membranes of the present invention use natural materials that are readily available, inexpensive, and do not require large or expensive chemical modifications. The films do not contain synthetic polymers and can be quickly and completely biodegraded. The membrane may be soluble or insoluble.

Description

Field of the Invention

[0001] The present invention relates to the field of heat sealable, highly biodegradable films comprising completely natural plant-derived polymers comprising salts of alginic acid and carbohydrates. The films of the present invention can be used to package products (e.g., powders and liquid products) in bags using current heat sealing equipment and at commercially viable production rates. In particular, the films of the present invention can be used in vertical form-fill-seal (VFFS) packaging equipment without the need for equipment modification. The films of the present invention use natural materials that are easily available, inexpensive, and do not require large amounts or expensive chemical modifications. The films do not contain synthetic polymers and are rapidly and completely biodegradable. The films can be soluble or insoluble.

[0002] background

[0003] As environmental pressures force people to move away from oil-based raw materials, packaging materials made from renewable materials are increasingly gaining attention and importance. Such packaging materials include films that are particularly suitable for wrapping and / or encapsulating products. Examples of products that use films for packaging include pouches and bags. It is highly preferred if the packaging material is not only derived from renewable materials, but also highly biodegradable in order to minimize waste disposal problems. Typically, products made from renewable natural raw materials are highly biodegradable, provided that they are not chemically modified. Chemical modification can significantly reduce the biodegradability characteristics.

[0004] Some packaging films combine natural and synthetic materials. Such products generally have improved environmental characteristics compared to equivalent products using only synthetic materials. In addition, they can provide an optimal balance of physical properties such as strength and barrier resistance. However, the use of synthetic, usually non-biodegradable materials inherently means that the biodegradability characteristics are not as good as materials using completely natural raw materials.

[0005] Water-soluble films made from polyvinyl alcohol are widely available and widely used—for example, in packaging for detergents. Often, they are promoted as environmentally friendly. Examples include Monosol M-8630 from Monosol (now Kuraray). Normally, such films are soluble, but in reality have poor biodegradability in marine biodegradation tests and can accumulate in the environment.

[0006] Some products and packaging applications require that the packaging material itself be edible. In this context, "edible" refers to all materials classified as safe for consumption, regardless of whether they are digestible by humans or can provide human nutrition.

[0007] Many biopolymers or materials of natural origin can be used to make packaging films. Examples of widely used biopolymer films include films based on starch and cellulose. Starch is particularly widely used due to its low cost and easy availability. Typically, starch is chemically modified to improve its processability and functionality. An example of a modified starch is hydroxypropylated amylose. Other substituents can be hydroxyethyl or hydroxybutyl to form hydroxy ether substitutions, or anhydrides such as maleic anhydride phthalic anhydride or octenyl succinic anhydride can be used to prepare starch ester derivatives. Starch films typically have high tensile strength at moderate humidity (e.g., 30% to 50% humidity at 20°C), but typically become much weaker at higher humidity unless they have been highly chemically modified. In particular, many starch films are very susceptible during low temperature storage because starch is prone to retrogradation.

[0008] Many starch-based products (e.g., compostable bags) include significant levels of polybutylene terephthalate-adipate or PBAT to improve their processability and physical properties. PBAT is a biodegradable synthetic polymer. However, it is apparently obtained from non-renewable raw materials. Examples of starch-based films are those sold by Plantic Technologies Ltd (now part of Kuraray). Plantic films contain modified starch and are available as monolayer and multilayer films.

[0009] Cellulose-based polymers and materials can also form films and are also widely used. Typically, cellulose films are made from so-called "regenerated" cellulose, in which cellulose fibers are dissolved in carbon disulfide under alkaline conditions to form a viscose. The viscose is then contacted with an acidic solution to "regenerate" the cellulose. Such processes are resource and energy intensive, and the resulting cellulose films are not water-soluble or water-dispersible at all, and they are also unable to achieve heat sealing. Regenerated cellulose is used in NatureFlex films, which are cellulose-based compostable packaging films sold by Futamura. Other cellulose materials include hydroxypropyl methylcellulose (HPMC) and carboxymethyl cellulose (CMC). HPMC films have long been used as coatings for tablets in the medical field. However, the synthesis of HPMC itself requires a lot of effort and is therefore relatively expensive. Due to the level of synthetic modification, it is not completely biodegradable.

[0010] Other biopolymers that can be used to make films include proteins from animal and plant sources. Examples of animal proteins that can be used to form films include gelatin, collagen and casein. Gelatin is widely used as a material for tablets and capsules. Casein (a milk protein collected from whey) has long been used to make plastic materials, and can form soluble and thermoformable particles or sheets. This type of material does have very good biodegradability characteristics, but it is animal-derived. Therefore, some people have moral and ethical issues when using such products. In addition, with regard to effective resource use, it is usually better to be able to use plant materials directly rather than indirectly using plant materials by feeding plants to animals on the environment.

[0011] The use of biopolymers to make films and coatings is becoming more widespread, and much effort continues to be invested in using naturally derived renewable materials as substitutes for non-renewable feedstocks such as petroleum. The art is large and extensive, and the examples given below are for illustrative purposes.

[0012] Many biopolymers are being used, including plant-based and animal-based materials. Examples of animal-based materials for making films and coatings include collagen, gelatin, chitosan, shellac and casein. Examples of plant-based materials used include starch, cellulose, protein (including peas, soybeans, corn and potatoes), alginates, carrageenan and other gums, pullulan, pectin, etc. The scope of the reasons for using biopolymers in these applications ranges from wanting to use renewable raw materials to having more biodegradable materials, to using more biocompatible materials for medical applications, and even providing edible packaging. Films and other packaging materials made of biopolymers can be soluble or insoluble. For ethical reasons and resource efficiency, it is necessary to use biopolymers of plant origin rather than biopolymers of animal origin. Alginate is an attractive biopolymer because they are usually derived from seaweed, and can be made into a stable film. However, alginate films are not easy to heat seal.

[0013] Biopolymers are complex materials and are generally more difficult to process and handle than synthetic polymers. Generally, they are susceptible to moisture and lose strength in high humidity environments. This susceptibility to moisture of biopolymers is generally an inherent feature due to their natural origin and is a major limitation to their wider use. Other problems include poor thermoplastic properties, including the heat sealing of biopolymer films. Rapid and effective heat sealing without thermal damage is crucial for the industrial production of bags and many packaging forms. Problems associated with many biopolymers, and especially their poor water resistance, mean that they are generally chemically modified to improve their properties, blended with synthetic polymers or laminated with other materials (including other biopolymers) to obtain films with improved properties.

[0014] Polyhydroxyalkanoates (PHA) are increasingly used due to their good thermoplastic properties. PHA is a natural biopolymer derived from microbial fermentation, but it biodegrades slowly and is insoluble.

[0015] The example of animal-based biopolymer is casein. EP3728477A1 describes thermoplastic casein compositions and packaging films made of thermoplastic casein. US9662400B2 describes chitosan films that can be used for medical applications. US6448378B2 describes soluble collagen films for delivering drug treatments. The large-scale application of many edible films (including films based on collagen, alginate and protein, among others) is for sausage casings. Sausage casings do not require heat sealing. US3408916 describes collagen films for sausage casings. US6730340B1 describes plant-based biopolymer blends for sausage casings based on a mixture of carrageenan and gellan gum.

[0016] US10092925B2 and JP6010068B2 describe production methods for preparing alginate films. Heat sealing is not mentioned. JPH0530891A describes the use of blends of alginate and other polysaccharides (mainly pullulan). It points out that pure alginate films are not heat-sealable. Blending high levels of pullulan with alginate produces a sealable and insoluble film. Pullulan is expensive to use on a large scale as the main component of the film.

[0017] Chemical modification of natural polymers or blending of natural and synthetic polymers can improve the physical and processing properties of films made from these materials but often reduces overall biodegradability, is complex, and does require the use of non-renewable materials.

[0018] Starch is cheap and its properties can be improved by chemical modification. US5498662 describes a gas barrier film comprising a blend of poly(meth)acrylic acid and starch. Thermoplastic starch is available under the trade name MATER-BI provided by Novamont. US20040242732A1, EP2496644B1 and WO2011080623A2 describe biodegradable polymer compositions based on chemically modified starch plus synthetic polymers. These materials can be used to form films.

[0019] Cellulose derivatives, and especially cellulose ethers, such as hydroxypropyl methylcellulose, are used to prepare films, often for medical applications. EP1045000B1 describes an ingestible HPMC film. Although such materials are generally safe to ingest, they require a high level of synthetic modification. HPMC is commonly used in drug coatings due to its selective pH solubility.

[0020] It is known to use laminated films to overcome some of the limitations of single biopolymers. These laminates may comprise two or more layers. One of the layers may be a synthetic polymer. The synthetic polymer may be partially or fully biodegradable. Due to the use of non-renewable materials, the use of synthetic polymers is not preferred over the use of biopolymers, but the use of a combination of natural and synthetic materials may still be preferred over fully synthetic materials. Synthetic polymer layers or highly modified biopolymer layers typically provide enhanced barrier properties or enhanced heat sealing properties. The layers may preferably be different biopolymers.

[0021] A common type of biopolymer-based laminate is a modified starch laminated with a synthetic polymer. An example of this is EP1581388B1, which describes a coextrusion process for preparing a modified starch film laminated with a biodegradable polyester. US8715816 describes a multilayer film comprising a thermoplastic starch layer and a thermoplastic polyester layer. Other examples of composite laminated films are where a synthetic polymer is used to provide a heat seal layer.

[0022] EP2013290B1 describes a silk protein laminate film, in which the silk protein is laminated with another layer, which may be a different protein such as collagen, or a synthetic polymer. Heat sealing is not mentioned, and the use of animal products is not preferred.

[0023] JP2009061108A discloses an edible laminated film comprising alginate and starch layers (and a variety of other layers) that can be used to form packaging. The starch layers can be sealed together. No details about the film or material characteristics are given, nor are any details about the production of articles comprising the laminated film.

[0024] JP2016034841A discloses an edible laminated film comprising a layer of shellac and another layer of starch, gelatin or pullulan. The packaging may be made of the laminated film with the shellac layer on the inside. Shellac is an animal product and no production details are given.

[0025] JP2010136685A describes a laminated film comprising a cationic biopolymer (usually chitosan) and an anionic biopolymer (usually gelatin). One biopolymer is cast and then the second biopolymer is cast on top. The resulting film is insoluble. The film can be heat sealed, but no details are given and the use of animal products is undesirable.

[0026] US5089307A describes an edible, heat-sealable laminated film. The film comprises a carrageenan layer and a sealing layer selected from casein, soy protein or gelatin. Alginate is not disclosed.

[0027] JP4063481B2 describes a multilayer packaging film in which one layer comprises regenerated cellulose. The other layers include acrylic and other synthetic resins.

[0028] EP3721721A1 describes an edible multilayer film comprising three layers of different "hydrocolloid substances", wherein the first layer may be alginate, the second layer may contain starch, and the third layer may contain agar. The film may be heat-sealed, but no production details are given.

[0029] Therefore, there is a need to develop alginate-based films with tunable solubility that have mechanical properties robust enough to be used as packaging films, including handling during manufacturing and able to withstand transportation and storage at low temperatures. A preferred feature for food packaging is that it is edible, in order to further minimize waste and increase consumer convenience. SUMMARY OF THE INVENTION

[0031] Viewed from a first aspect, the invention provides a membrane comprising:

[0032] A first layer, based on the total weight of the first layer, the first layer comprises:

[0033] at least 20 wt.-% of one or more monovalent salts of alginic acid, and

[0034] at least 5 wt.-% of one or more organic plasticizers;

[0035] A second layer, based on the total weight of the second layer, the second layer comprises:

[0036] one or more carbohydrates other than alginic acid and any salts thereof,

[0037] at least 5 wt.-% of one or more organic plasticizers, and

[0038] Less than 20 wt.-% alginate;

[0039] wherein a surface of the second layer is sealed to a surface of the first layer.

[0040] Preferably, the film of the first aspect of the invention has a thickness of from 20 μm to 120 μm.

[0041] Preferably, in the film of the first aspect of the present invention, the first layer further comprises one or more divalent alginates selected from calcium alginate and magnesium alginate.

[0042] Preferably, in the film of the first aspect of the present invention, the second layer has an onset melting temperature in the range of 55°C to 85°C as measured by the method described in Example 3 of the specification.

[0043] Preferably, in the film of the first aspect of the present invention, the second layer comprises starch and / or pullulan.

[0044] Preferably, the membrane of the first aspect of the invention comprises 3-90 wt.-%, preferably 15-85 wt.-%, more preferably 25-80 wt.-%, most preferably 35-70 wt.-% of one or more alginates based on the total weight of the membrane, as determined according to the HPLC method in Journal of Chromatographic Science 2013; 51:208-214.

[0045] Preferably, the film of the first aspect of the invention has a heat seal strength of at least 40 N / m, preferably at least 60 N / m, more preferably at least 80 N / m, even more preferably at least 100 N / m, most preferably at least 120 N / m as measured by ASTM F88 / F88M-15 at 55% relative humidity and 20°C, after conditioning the film at 55% relative humidity and 20°C for at least one hour and then sealing at a temperature of 120°C and an applied pressure of 3 bar for a period of 1 second.

[0046] From a second aspect, the present invention provides a method for preparing a membrane as described above, comprising the following steps:

[0047] (i) providing a first layer, the first layer comprising, based on the total weight of the first layer:

[0048] at least 20 wt.-% of one or more monovalent salts of alginic acid, and

[0049] at least 5 wt.-% of one or more organic plasticizers;

[0050] (ii) providing a second layer, the second layer comprising, based on the total weight of the second layer:

[0051] one or more carbohydrates other than alginic acid and any salts thereof,

[0052] at least 5 wt.-% of one or more organic plasticizers, and

[0053] less than 20 wt.-% alginate; and

[0054] (iii) sealing a surface of the second layer to a surface of the first layer.

[0055] Viewed from a third aspect, the invention provides a product packaged by a film as hereinbefore described.

[0056] Preferably, in the product of the third aspect of the invention, the film is greater than 75%, preferably greater than 80%, more preferably greater than 85%, even more preferably greater than 90%, most preferably greater than 95% biodegradable according to ASTM D6691.

[0057] From a fourth aspect, the present invention provides a method for packaging a product, comprising the following steps:

[0058] (i) wrapping a product in a film as claimed in any one of claims 1 to 7 such that the first layer is the outer layer; and

[0059] (ii) Heat sealing the film around the product to form a bag.

[0060] Preferably, in the method of the fourth aspect of the invention, the duration of step (ii) is less than 2 seconds, more preferably less than 1 second, more preferably less than 0.5 seconds, and wherein step (ii) is carried out at a temperature below 160°C, preferably below 140°C, preferably below 120°C.

[0061] Viewed from a fifth aspect, the invention provides the use of a film as hereinbefore described for packaging a product and / or making a bag.

[0062] Viewed from a sixth aspect, the invention provides a bag prepared by a method as hereinbefore described.

[0063] Viewed from a seventh aspect, the invention provides a method of releasing a product encapsulated in a film as described above, comprising the steps of:

[0064] (i) placing the packaged product in water; and

[0065] (ii) causing the film to disperse, thereby releasing the product. DETAILED DESCRIPTION OF THE INVENTION

[0067] When looking for raw material sources for the packaging film of the present invention, it is preferred if biopolymers from non-traditional sources can be used as much as possible. Such non-traditional raw materials can be combined with traditional raw materials. "Traditional" refers to biopolymers commonly used as human feed, such as starch. Particularly preferred biopolymers for the film of the present invention are polymers and salts based on alginic acid. Alginates are generally derived from seaweed, which does not directly compete with food crops and does not require valuable farmland.

[0068] Alginic acid is a polysaccharide generally obtained from the cell walls of brown algae. Alginic acid is a biocopolymer of β-D-mannuronic acid and α-L-guluronic acid that can be obtained with a range of molecular weights and monomer ratios depending on the source. This produces alginic acid solutions with a range of viscosities. Alginates are widely used in many applications, including the manufacture of membranes. Membranes can be water-soluble or water-insoluble, depending on whether the alginate has been cross-linked or not (generally cross-linked by divalent metal ions). Membranes based on sodium alginate are generally water-soluble, while membranes containing calcium alginate are mostly water-insoluble.

[0069] The suitability of the films of the present invention for commercial use depends not only on their positive environmental characteristics. The films must be processable. They must remain robust in the multiple environments they are subjected to, including manufacturing, storage, and end use. They must meet a variety of different requirements, such as permeability, elongation, and tensile strength. They must also be heat sealable.

[0070] The inventors have found that many films with high (>20%) alginate content are generally difficult to heat seal. This lack of heat sealability severely limits the wider use of alginate-based films due to the large existing manufacturing base using heat seal packaging lines and many types of different packaging equipment using heat sealing.

[0071] In heat sealing, two films are pressed together and heated for a specified time. The application of heat causes the polymer chains at the interface to diffuse and migrate between the films, forming a bond as the seal cools. Not all polymer materials will heat seal, as the mechanism depends on the behavior of the polymer chains at the interface. If these chains do not move or migrate easily, then the films will not seal. The ease of heat sealing is a complex interaction of polymer type, level of crystallinity, plasticization, temperature and time.

[0072] Without wishing to be bound by theory, it is believed that the poor heat sealing behavior of typical alginate films is caused by the denser structure that the alginate material appears to form when subjected to heating. This effect has been reported in the art and is used in some alginate film preparation processes, where heat treatment is used to prepare denser and less permeable films. The production of alginate films generally involves the application of heat to remove water. By definition, heat sealing requires the application of heat. Therefore, alginates appear to be inherently unsuitable for heat sealing applications. If high levels of selected other materials are added to the film composition, it may be possible to heat seal the alginate film, but this sacrifices many of the benefits of using alginate in the first place.

[0073] One established way to seal alginate films is to glue the films together using an adhesive. This can be combined with the application of heat and pressure to ensure a good seal. This approach is feasible with certain types of equipment, such as the Hydroforma bag making machine from Cloud Packaging Inc. (now part of Mespack), because the design of the drum allows the adhesive layer to be applied to one or both films. Nonetheless, adhesives have their own disadvantages, such as contamination of the packaging material or the risk of the adhesive being contaminated by the packaged product, especially when liquids or powders reduce the robustness of the seal. However, many packaging companies use vertical form fill seal (VFFS) technology to make bags.

[0074] In the VFFS process, the film is pulled through the packaging equipment and folded together and sealed to form a bag. Typically, the film strip is folded around the filling head and sealed to form a cylinder or tube, which is then sealed at the bottom, filled with contents through the filling head, and then sealed at the top. This method can be used for both powders and liquids. The need to "pull" the film through the equipment means that the film needs to have a minimum strength. The film cannot stretch too much, otherwise it will be difficult to control the correct positioning and alignment of the film. The film cannot be sticky to the touch, otherwise the friction on the film will be too great as it is pulled through the equipment. This means that it is impractical to spray or apply a coating to a surface as the film strip is pulled through the packaging line.

[0075] The film is also suitable for horizontal form-fill-seal packaging equipment. In a typical HFFS machine, such as in a Hydroforma bag making machine, a film sheet is pulled down into a mold by applying a vacuum to form a cavity, the material is placed in the cavity and a second film sheet is used to seal the cavity. Sealing can be done by heat sealing or by solvent / adhesive sealing or a combination thereof.

[0076] Typically, the films of the present invention are suitable for producing a variety of packaging formats including flexible bags, blister packs, pods, pouches, flowraps, envelopes, sticks and doypacks.

[0077] The inventors have found that, based on the selection of the material and thickness of the layer, a multilayer film comprising a layer rich in alginate and a layer rich in carbohydrates can overcome the various challenges emphasized above. This film of the present invention has good physical properties, such as strength, under wide conditions. They can be made of plant-based materials, do not require chemical modification, and are low in cost and easily available. They can have controlled solubility and have very high biodegradability. Careful selection of material properties and the thickness of the layer means that they can be heat-sealed under industrially relevant conditions without damaging the bag. The film of the present invention generally needs to be sealed together by the layer rich in carbohydrates to obtain a good seal, whether it is heat-sealed or solvent-sealed (when used in HFFS equipment). Attempting to seal the alginate layer together or to seal the carbohydrate layer to the alginate layer will not provide a stable seal.

[0078] In order to make any production industrially feasible, any film needs to be heat-sealable in a short time. The design of the VFFS packaging line means that the productivity is directly related to the time required to perform the heat seal. If it takes 5 seconds to perform the heat sealing operation, a single production line can only make 12 bags per minute. This rate is too low, so that it is not economically feasible. In order to make any production process economically feasible for most products, the sealing time needs to be less than 1 second, and preferably less than 0.5 seconds. Therefore, the actual definition of heat sealability needs to include the ability to form a stable seal and this needs to be achievable in less than 1 second and preferably less than 0.5 seconds.

[0079] Heat sealing depends on a temperature at the interface of the two films being sealed that is high enough to begin melting the materials at the interface so that they begin to migrate and interpenetrate. The temperature at the interface of the two films depends on the following variables.

[0080] (i) The temperature of the sealing plate to which the heat is applied. The higher the temperature, the faster the interface heats.

[0081] (ii) The time the heating plate is in contact with the membrane. The longer the time, the longer it takes for heat to be transferred through the membrane layer to the interface.

[0082] (iii) The thickness of the film through which the heat is conducted. The thicker the film, the longer it takes for the interface in between to reach a sufficient temperature.

[0083] (iv) Thermal conductivity of the layers forming the film. The rate at which heat is transferred between each layer in the film depends on the thermal conductivity of the film. The higher the thermal conductivity, the faster the heat is transferred to the interface.

[0084] As mentioned above, the time that the heating plate is in contact with the film needs to be as short as possible. One way to minimize the time required for the interface temperature to rise sufficiently to cause sealing is to use a high sealing temperature. This is effective, but if the temperature is too high (e.g. >160°C), it will cause thermal damage to the alginate layer of the film in contact with the sealing plate, resulting in visual defects around the seal and other defects.

[0085] Therefore, the thermal stability of the alginate-rich layer and the limited time available for heat sealing are crucial. According to the present invention, it is preferred to select a carbohydrate layer composition with a heat start temperature below 85°C, and the total thickness of the two layers that form the film together is 20 μm to 120 μm. The heat start temperature is the temperature at which the composition begins to soften and partially melt. In order for heat sealing to occur, the material at the interface must be at or above the heat start temperature. Controlling the thickness of the film allows sufficient heat to be transferred to the interface within the available time, while giving the film sufficient thickness and stability for practical use.

[0086] Therefore, a film comprising two layers, one rich in alginate and the other rich in carbohydrates, wherein the thickness of the two layers are controlled within specified limits and wherein the carbohydrate-rich layer has an onset temperature below 85°C, provides a preferred plant biopolymer-based film that is robust and processable with current heat sealing equipment.

[0087] Accordingly, the present invention provides a membrane comprising:

[0088] A first layer, based on the total weight of the first layer, the first layer comprises:

[0089] at least 20 wt.-% of one or more monovalent salts of alginic acid, and

[0090] at least 5 wt.-% of one or more organic plasticizers;

[0091] A second layer, based on the total weight of the second layer, the second layer comprises:

[0092] one or more carbohydrates other than alginic acid and any salts thereof,

[0093] at least 5 wt.-% of one or more organic plasticizers, and

[0094] Less than 20 wt.-% alginate;

[0095] wherein a surface of the second layer is sealed to a surface of the first layer.

[0096] In the membrane of the present invention, the first layer comprises at least one monovalent alginate. In the preferred membrane of the present invention, the first layer comprises at least one alkali metal salt of alginic acid. More preferably, the first layer comprises lithium alginate, sodium alginate, potassium alginate, ammonium alginate or a mixture thereof, wherein sodium alginate is most preferred.

[0097] In an optional preferred film of the present invention, the first layer further comprises one or more divalent alginates selected from calcium alginate and magnesium alginate, wherein calcium alginate is most preferred.

[0098] In preferred films of the invention, the first layer has a thickness of 15 μm to 115 μm. In optional preferred films of the invention, the second layer has a thickness of 5 μm to 80 μm. Preferred films of the invention have a thickness of 20 μm to 120 μm.

[0099] In preferred films of the present invention, the second layer has an onset melting temperature below 85°C, preferably below 80°C, as determined as described in Example 3 of the specification.

[0100] In an alternative preferred film of the present invention, the second layer has an onset melting temperature of at least 55°C as determined as described in Example 3 of the specification.

[0101] Most preferably, the second layer has an onset melting temperature in the range of 55 to 85°C, as determined as described in Example 3 of the specification.

[0102] In preferred films of the present invention, the one or more carbohydrates in the second layer other than alginic acid and any salt thereof are selected from monosaccharides, disaccharides, oligosaccharides, polysaccharides and mixtures thereof. More preferably, the second layer comprises at least one carbohydrate which is a polysaccharide. Most preferably, the polysaccharide is starch.

[0103] Starch is a carbohydrate polymer. Starch is essentially composed of amylose and / or amylopectin, and the natural form is usually in the form of semi-crystalline granules. The sources of starch include, but are not limited to, fruits, seeds, and rhizomes or tubers of plants.

[0104] Some starches are classified as waxy starches. Waxy starches consist essentially of amylopectin and lack appreciable amounts of amylose. Typical waxy starches include waxy corn starch, waxy rice starch, waxy potato starch, and waxy wheat starch.

[0105] Alternatively, some starches are classified as high amylose starches.

[0106] Modified starch is prepared by physically, enzymatically or chemically treating natural starch to change its properties. Starch can be modified, for example, by enzymes, by heat treatment, oxidation or reaction with various chemicals.

[0107] In the film of the present invention, the starch may be natural starch or modified starch, or a mixture thereof.

[0108] In preferred films of the present invention, the starch is selected from wheat starch, potato starch, pea starch, waxy potato starch, corn starch, waxy corn starch, high amylose corn starch, tapioca starch, cassava starch, rye starch, sorghum starch, chickpea starch, soy starch or mixtures thereof, preferably potato starch.

[0109] In the optional preferred film of the present invention, the starch is a modified starch selected from acid-treated starch, dextrin, alkali-modified starch, bleached starch, oxidized starch, enzyme-treated starch, maltodextrin, cyclodextrin monostarch phosphate, distarch phosphate, acetylated starch, hydroxypropylated starch, hydroxyethyl starch, sodium starch octenyl succinate, aluminum starch octenyl succinate or cationic starch or a mixture thereof, preferably acid-treated starch.

[0110] Optionally, the polysaccharide is pullulan.

[0111] In preferred films of the invention, the second layer comprises starch and / or pullulan.

[0112] In preferred films of the present invention, the second layer comprises 40-95 wt%, preferably 50-80 wt%, more preferably 55-75 wt% carbohydrate based on the total weight of the second layer.

[0113] An optional preferred membrane of the present invention comprises 1-80 wt%, preferably 7-70 wt%, more preferably 15-50 wt% of one or more carbohydrates based on the total weight of the membrane.

[0114] Preferred membranes of the present invention comprise 3-90 wt.-%, preferably 15-85 wt.-%, more preferably 25-80 wt.-%, most preferably 35-70 wt.-% of one or more monovalent alginic acid salts, based on the total weight of the membrane, as determined by the HPLC method in Journal of Chromatographic Science 2013; 51:208-214.

[0115] Preferred films of the present invention comprise 10-50 wt%, preferably 15-45 wt%, more preferably 20-40 wt% of one or more organic plasticizers based on the total weight of the film.

[0116] Preferably, the one or more organic plasticizers in the first layer are independently selected from the group consisting of:

[0117] a) a polyol formed from 1 to 20 repeating hydroxylated units, each unit comprising 2 to 6 carbon atoms, provided that when the polyol is formed from only one repeating unit, it has at least 4 carbon atoms, excluding sorbitol,

[0118] b) ethers, thioethers, inorganic and organic esters, acetals and amino derivatives of polyols formed from 1 to 20 repeating hydroxylated units, each unit comprising 2 to 6 carbon atoms, excluding triacetin, triethyl citrate and tributyl citrate,

[0119] c) the reaction product of a polyol having 1 to 20 repeating hydroxylated units, each unit containing 2 to 6 carbon atoms, and a chain extender,

[0120] d) Oxidation products of polyols having from 1 to 20 repeating hydroxylated units, each unit comprising from 2 to 6 carbon atoms, comprising at least one aldehyde or carboxyl functional group or mixtures thereof.

[0121] More preferably, the one or more organic plasticizers in the first layer are independently selected from glycerol, polyethylene glycol, propylene glycol, sorbitol, mannitol, xylitol, triethyl citrate, fatty acids (e.g. oleic acid), glucose, mannose, fructose, sucrose, urea, lecithin, waxes, amino acids and organic acids (e.g. lactic acid, citric acid, glycolic acid, malic acid or tartaric acid) or mixtures thereof, wherein a mixture of glycerol, sorbitol and oleic acid is most preferred. Preferably, the plasticizer is of plant origin.

[0122] In preferred films of the invention, the one or more organic plasticizers are present in the first layer in an amount of 10-50% wt%, more preferably 20 to 40% wt%, based on the total weight of the first layer at 55% relative humidity and 20°C.

[0123] In an alternative preferred film of the present invention, the weight ratio of alginate to organic plasticizer in the first layer is in the range of 4:1 to 1:1.

[0124] Preferably, the one or more organic plasticizers in the second layer are independently selected from the group consisting of:

[0125] a) a polyol formed from 1 to 20 repeating hydroxylated units, each unit comprising 2 to 6 carbon atoms, provided that when the polyol is formed from only one repeating unit, it has at least 4 carbon atoms, excluding sorbitol,

[0126] b) ethers, thioethers, inorganic and organic esters, acetals and amino derivatives of polyols formed from 1 to 20 repeating hydroxylated units, each unit comprising 2 to 6 carbon atoms, excluding triacetin, triethyl citrate and tributyl citrate,

[0127] c) the reaction product of a polyol having 1 to 20 repeating hydroxylated units, each unit containing 2 to 6 carbon atoms, and a chain extender,

[0128] d) Oxidation products of polyols having from 1 to 20 repeating hydroxylated units, each unit comprising from 2 to 6 carbon atoms, comprising at least one aldehyde or carboxyl functional group or mixtures thereof.

[0129] More preferably, the one or more organic plasticizers in the second layer are independently selected from glycerol, diglycerol, triethylene glycol, polyethylene glycol such as PEG400 and other polyethylene glycols, propylene glycol, dipropylene glycol, polypropylene glycol, sorbitol, mannitol, xylitol, compounds produced by the addition of ethylene oxide to glycerol, pentaerythritol, sorbitol and other polyols, triethyl citrate, fatty acids (e.g. oleic acid), glucose, mannose, fructose, sucrose, urea, lecithin, waxes, amino acids and organic acids (e.g. lactic acid, citric acid, glycolic acid, malic acid or tartaric acid), sugar surfactants or mixtures thereof, wherein a mixture of glycerol and sorbitol is most preferred. Preferably, the plasticizer is of plant origin.

[0130] The term sugar surfactant means that the surfactant comprises at least one sugar moiety. Sugar surfactants preferably comprise at least one, preferably more than two, monosaccharide units linked by glycosidic bonds, and may comprise the term "sugar" moiety (2 monosaccharide units) or be derived from 3 monosaccharides.

[0131] The monosaccharides of the carbohydrate moiety may be of the same type (homopolysaccharides) or of different types (heteropolysaccharides).

[0132] Preferably, the sugar surfactant is ionic, more preferably it is anionic, cationic or amphoteric. More preferably it is anionic. The sugar surfactant is preferably selected from functionalized alkyl polyglycosides, fatty acid glucosamides, glycinates, glycolipid biosurfactants such as rhamnose-based surfactants (e.g. rhamnolipids) or sophorolipids; or any combination thereof.

[0133] In preferred films of the present invention, the one or more organic plasticizers are present in the second layer in an amount of 10-50 wt%, more preferably 20 to 40 wt%, based on the total weight of the second layer at 55% relative humidity and 20°C.

[0134] In preferred films of the present invention, the weight ratio of the one or more carbohydrates to the one or more organic plasticizers in the second layer is in the range of 4:1 to 1:1.

[0135] As will be appreciated by those skilled in the art, the one or more organic plasticizers in the first and second layers may be the same, or the one or more organic plasticizers in the first and second layers may be different.

[0136] When the film is intended for packaging food, the plasticizer must be suitable for human ingestion.

[0137] At 55% relative humidity and 20° C., preferred films of the present invention comprise 7.5-35 wt.-%, more preferably 10-30 wt.-%, most preferably 15-25 wt.-% water, based on the total weight of the film.

[0138] In preferred films of the present invention, the first layer further comprises at least one carbohydrate, more preferably a polysaccharide, most preferably starch.

[0139] In an optional preferred film of the present invention, the second layer further comprises a divalent metal salt. Preferably, the divalent metal salt is an alkaline earth metal salt or a transition metal salt, more preferably the alkaline earth metal salt is a magnesium salt or a calcium salt, wherein the calcium salt is most preferred.

[0140] Preferred transition metal salts are zinc salts.

[0141] Preferably, the calcium salt is selected from calcium chloride, calcium acetate, calcium citrate, calcium gluconate, wherein calcium chloride is most preferred.

[0142] In preferred films of the invention the divalent metal salt is present in the second layer in an amount of 0.1-5 wt.-%, more preferably 0.2-4 wt.-%, most preferably 0.5-3 wt.-%, based on the total weight of the second layer at 55% relative humidity and 20°C.

[0143] Preferred films of the invention also comprise one or more additives, for example gums, oils, flavors, dyes, pigments, opacifiers, bittering agents, antimicrobial agents such as thymol, antiblocking agents or structural enhancers such as cellulose nanofibers, cellulose nanocrystals and cellulose fibers.

[0144] The preferred membrane of the present invention also comprises a layered silicate. Preferably, the layered silicate is a serpentine mineral, a clay mineral, a chlorite mineral or a mica mineral, or a mixture thereof. Preferably, the clay mineral is selected from bentonite, kaolinite, pyrophyllite, vermiculite and smectite (e.g. montmorillonite, cloisite, laponite, hectorite, etc.) or a mixture thereof.

[0145] As the skilled person will appreciate, the layered silicate may be present in the first layer and / or the second layer.

[0146] Preferred films of the invention have a heat seal strength of at least 40 N / m, more preferably at least 60 N / m, even more preferably at least 80 N / m, even more preferably at least 100 N / m, most preferably at least 120 N / m as measured by ASTM F88 / F88M-15 at 55% relative humidity and 20°C after conditioning the film at 55% relative humidity at 20°C for at least one hour and then sealing at an applied temperature of 120°C under a pressure of 3 bar for a period of 1 second.

[0147] Preferred optional films of the present invention have a heat seal strength of at least 40 N / m, more preferably at least 60 N / m, as measured by ASTM F88 / F88M-15 at 55% relative humidity and 20°C, after conditioning the film at 55% relative humidity at 20°C for at least one hour and then sealing at an applied temperature of 120°C under a pressure of 3 bar for a period of 1 second.

[0148] The present invention also provides a method for preparing the membrane as described above, comprising the following steps:

[0149] (i) providing a first layer, the first layer comprising, based on the total weight of the first layer:

[0150] at least 20 wt.-% of one or more alginates, and

[0151] at least 5 wt.-% of one or more organic plasticizers;

[0152] (ii) providing a second layer, the second layer comprising, based on the total weight of the second layer:

[0153] one or more carbohydrates other than alginic acid and any salts thereof,

[0154] at least 5 wt.-% of one or more organic plasticizers, and

[0155] less than 20 wt.-% alginate; and

[0156] (iii) sealing a surface of the second layer to a surface of the first layer.

[0157] In a preferred method of the invention, step (i) comprises using a preformed first layer.

[0158] In an alternative preferred method of the invention, step (ii) comprises using a preformed second layer.

[0159] In a preferred method of the present invention, step (i) comprises forming the first layer. Preferably, the first layer is formed by casting, lamination or extrusion.

[0160] In a preferred method of the present invention, step (ii) comprises forming the second layer. Preferably, the second layer is formed by casting, lamination or extrusion.

[0161] The preferred method of the present invention comprises the following steps:

[0162] (a) mixing at least one alginate and at least one organic plasticizer in water, optionally with sonication, to form a mixture (a);

[0163] (b) forming the mixture (a) into the first layer on the surface;

[0164] (c) mixing at least one carbohydrate and at least one organic plasticizer in water, optionally with sonication, to form mixture (b); and

[0165] (d) forming the mixture (b) into the second layer on the first layer.

[0166] Preferably, step (a) comprises additionally mixing at least one carbohydrate to form said mixture (a).

[0167] Preferably, in step (b), mixture (a) is at a temperature in the range of 40 to 85°C, more preferably 50 to 60°C (eg 55°C). Most preferably, in step (b), mixture (a) is at ambient temperature.

[0168] Preferably, step (c) comprises additionally mixing a divalent metal salt to form said mixture (b).

[0169] Preferably, step (c) is carried out at a temperature in the range of 10 to 90°C,

[0170] Preferably, in step (d), mixture (b) is at a temperature in the range of 40 to 85°C, more preferably 50 to 60°C (eg 55°C). Most preferably, in step (d), mixture (b) is at ambient temperature.

[0171] Preferably, prior to step (d), mixture (b) is degassed.

[0172] The preferred method of the present invention comprises the following steps:

[0173] (a) mixing at least one carbohydrate and at least one organic plasticizer in water, optionally with sonication, to form a mixture (c);

[0174] (b) forming the mixture (c) into the second layer on the surface;

[0175] (c) mixing at least one alginate and at least one organic plasticizer in water, optionally with sonication, to form a mixture (d);

[0176] (d) forming the mixture (d) into the first layer on the second layer.

[0177] Preferably, step (a) comprises additionally mixing a divalent metal salt to form said mixture (c).

[0178] Preferably, step (c) comprises additionally mixing at least one carbohydrate to form said mixture (d).

[0179] Preferably, step (a) is carried out at a temperature in the range of 10 to 90°C,

[0180] Preferably, in step (b), mixture (c) is at a temperature in the range of 40 to 70°C, more preferably 50 to 60°C (eg 55°C).

[0181] Preferably, prior to step (b), mixture (c) is degassed.

[0182] Preferably, step (c) is carried out at a temperature in the range of 18 to 25°C, more preferably 20 to 23°C.

[0183] Preferably, in step (d), the mixture (d) is at a temperature in the range of 10 to 90°C.

[0184] In a preferred process of the invention, one or more films are independently produced by cast or blown film extrusion, preferably by casting, more preferably by solvent casting.

[0185] Solvent casting can be a 2-step process where a first layer of material is cast onto a substrate such as or corona treated or metal strip. Casting of the mixture can be done at room temperature or under heating. Immediately after coating, the material is dried in an oven and the film is wound onto a core. The roll of the first layer (which may still be The coating is then cast (on the roll) and then rolled through the production line again so that the second layer can be cast on top of the first layer and dried in an oven again. Similarly, the mixture casting can be carried out at room temperature or under heating. The process can be described as a "wet-on-dry process". In order to control the casting thickness, the casting line is equipped with a metal roller system, in which the gap between the rollers controls the wet thickness of the coating. The production line speed and oven temperature are adjusted to obtain the desired dry film thickness and final moisture content. The final dry film is peeled off from the backing substrate and then rolled onto a core and stored until the product needs to be wrapped or packaged and the film is optionally sealed to form a bag.

[0186] Solvent casting can also be a 1-step continuous process where the first layer of material is cast onto a substrate such as Corona treated Or on a metal belt. The mixture casting can be carried out at room temperature or under heating. After coating and drying or partial drying in an oven, the second layer can be cast on top of the first layer and finally dried in a second oven. Similarly, the mixture casting can be carried out at room temperature or under heating. The process can be described as a "wet-on-wet process" or a "wet-on-semi-dry process". In order to control the casting thickness, the production line is equipped with a metal roller system, in which the gap between the rollers controls the wet thickness of the coating. The production line speed and the oven temperature are adjusted to obtain the desired final dry film thickness and final moisture content. The final dry film is peeled off from the backing substrate and then wound onto a core and stored until the product needs to be wrapped or packaged and the film is optionally sealed to form a bag.

[0187] In both solvent casting processes, it is important that the final film roll can be easily unrolled without damaging the film. This is necessary in the middle of a dry-on-wet process or when the final film is used in a product packaging line. The ease with which the film can be unrolled is evaluated in the peeling method described in this article.

[0188] The present invention also provides a product coated or encapsulated with the film as described above.

[0189] In preferred products of the invention, the membrane is made only from food grade materials.

[0190] In an optional preferred product of the present invention, the film is greater than 75%, more preferably greater than 80%, even more preferably greater than 85%, even more preferably greater than 90%, most preferably greater than 95% biodegradable after 28 days according to ASTM D6691.

[0191] Preferred products of the invention are foods, pharmaceuticals, cleaning products, agricultural products (eg animal feed) or medicines, chemical products or cosmetics.

[0192] Preferably, the product of the present invention is a solid product, a powdered product or a liquid product having a water activity of less than 60%.

[0193] An alternative preferred product of the present invention is a solid product selected from a soup or dressing preparation (eg a stock cube), a personal cleanser (eg a soap bar, a body scrub or a solid shampoo), a laundry detergent tablet or bar or a dishwasher detergent tablet.

[0194] Preferably, the product of the invention is a stock cube or a laundry detergent tablet or a dishwasher detergent tablet.

[0195] An optional preferred product of the present invention is a powdered product selected from the group consisting of powdered food, powdered drink, powdered milk, powdered soup, powdered hot chocolate, powdered coffee, soap flakes, powdered laundry detergent and powdered shampoo.

[0196] Preferably, the product of the present invention is a powdered drink.

[0197] Also preferably, the product of the invention is a liquid product chosen from oils or hair care or body care products having a water activity of less than 60%.

[0198] The present invention also provides a method for packaging a product, comprising the following steps:

[0199] (i) wrapping the product in a film as described above such that the first layer is the outer layer; and

[0200] (ii) Heat sealing the film around the product.

[0201] As will be appreciated by the technician, the heat sealing step needs to contact between the film parts comprising one or more carbohydrates except alginic acid and any salt thereof. For example, the composite film comprising starch and alginate can be sealed with another composite film comprising starch and alginate or with itself. However, if the film is a multilayer film comprising, for example, a starch layer and an alginate layer, it is necessary to seal the starch layer with another film comprising starch or with itself. This is because compared with alginate, starch can be melted (or gelatinized) at a much lower temperature. The residual water present in the starch layer also helps to reduce the melting (or gelatinization) temperature of starch.

[0202] In a preferred process of the invention, the duration of step (ii) is less than 2 seconds, more preferably less than 1 second, most preferably less than 0.5 seconds.

[0203] In an alternative preferred process of the present invention, step (ii) is carried out at a temperature below 160°C, more preferably below 140°C, most preferably below 120°C.

[0204] The invention also provides the use of a film as described above for packaging a product.

[0205] The present invention also provides a bag prepared by the method as described above.

[0206] Preferred bags of the present invention are dispersible in water.

[0207] The films of the present invention have high dispersibility in water. This means that they can be used as packaging materials for products without generating any waste during the final use of the product. For example, the films of the present invention can be used to package detergents so that the films will disperse in water to release the detergents during the washing process. Alternatively, the films of the present invention can be used to package food so that the films will disperse in water to release the food during the cooking process.

[0208] According to the present invention, the water dispersibility of the membrane is evaluated using a 0.75g sample of each final membrane conditioned at 55% relative humidity and 20°C. The sample is mixed in 300ml of 20°C reverse osmosis water and freshly boiled reverse osmosis water (i.e., having a temperature range of 75.1°C to 90.2°C) in a 600ml beaker at room temperature using an overhead stirrer at 300rpm for 3 minutes. Any remaining particles of the final mixture are visually inspected, and their size is used to judge water dispersibility according to the following scale: very low-most particles>30mm; low-most particles~20-30mm; average-most particles~10-20mm; high-most particles~1-10mm; very high-most particles<1mm; maximum-no visible particles. Dispersibility is reported as the average of two different temperature observations, where each observation is assigned an integer value for these purposes. Advantageously, the residue is completely biodegradable, which means that the membrane does not have a negative impact on the environment.

[0209] The invention also provides the use of a film as described above for the preparation of a bag.

[0210] The present invention also provides a method for releasing a product encapsulated in a film as described above, comprising the following steps:

[0211] (i) placing the packaged product in water; and

[0212] (ii) causing the film to disperse, thereby releasing the product.

[0213] In a preferred method of the invention, the product is released in step (ii) during the cooking process.

[0214] In an alternative preferred method of the invention the product is released in step (ii) during the washing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0216] Figure 1a is a photograph of the bag prepared in Example 13.

[0217] Figure 1b is a photograph of the bag prepared in Example 13 just after being placed in a beaker of water.

[0218] Figure 1c-1gA series of photographs of the bag prepared in Example 13 at 2 seconds, 52 seconds, 60 seconds, 72 seconds and 138 seconds after being placed in a beaker of water. Example

[0219] Material

[0220] Alginate sodium salt and calcium chloride dihydrate were purchased from Thermo Fisher Scientific. The viscosity of a 1% solution of alginate sodium salt at 20°C was 350 to 550 mPas.

[0221] FD150 sodium alginate was purchased from JRS, Germany. The viscosity of a 1% solution of sodium alginate at 20°C is 20 to 50 mPas.

[0222] Tapioca starch (Alpha Instant), potato starch (pregelatinized), corn starch, and rice starch were purchased from BakeRite.

[0223] Food grade glycerin (APC pure), propylene glycol, and potato starch (hot soluble) were purchased from APC.

[0224] Defoamer (aqueous silicone emulsion), polysorbate 80, and corn pullulan (starch from corn) were purchased from Sigma-Aldrich Co.

[0225] Waxy maize starch (Ultratex) was purchased from Special Ingredients Ltd.

[0226] Pullulan was purchased from Rongsheng Biotechnology Co. Ltd.

[0227] Maltodextrin was purchased from Sigma-Aldrich Co.

[0228] Oleic acid, sorbitol, and thymol were purchased from Thermo Fisher Scientific.

[0229] In the following examples, all references to "ambient temperature" or "room temperature" refer to a temperature of about 20°C.

[0230] Example 1: Preparation of alginate monolayer

[0231] At ambient temperature, 400 ml of water was mixed with 14 g of alginic acid in a 600 ml beaker using an overhead stirrer to form a homogenous solution. Then 6 g of glycerol and 4 drops of defoamer were added under stirring. The mixture was stirred for 45 minutes. 25 ml of the mixture was poured into a 50 ml Falcon tube. The mixture was removed and poured into a The liquid was evenly spread on the plate using a blade to obtain a 700 micron wet film of the alginate mixture. The glass plate was then dried overnight at ambient temperature to form a dry film.

[0232] Example 2: Preparation of Carbohydrate Monolayers

[0233] 30.0 g of cassava starch (STT) was dispersed in 300 ml of deionized water in a 600 ml flask at ambient temperature with overhead stirring. 12.86 g of glycerol was then added and the suspension was stirred. The suspension was then sonicated using a Bandelin sonicator for 30 minutes at an amplitude of 95% with a cycle of 1 second on and 0.2 seconds off. The solution was then placed in a sonic bath at 80°C for 1 minute to remove any bubbles.

[0234] 20 ml of the solution was poured into a 50 ml Falcon tube. The solution was then further degassed by removing large bubbles with a pipette, then allowed to cool to 55 °C and poured into a 50 ml Falcon tube. The liquid was evenly spread using a blade to obtain a wet film of the starch mixture of approximately 400 microns thick. The plate was then placed in an oven at 80°C for 50 minutes to form a dry film.

[0235] Example 3: Determination of the onset melting temperature and seal strength of a carbohydrate monolayer

[0236] (i) Preparation of Carbohydrate Monolayer

[0237] 10.0 g of carbohydrate was dispersed in 100 ml of deionized water in a 250 ml flask at ambient temperature with overhead stirring. 4.29 g of glycerol was then added and the suspension was stirred. The suspension was then sonicated using a Bandelin sonicator for 10 minutes at an amplitude of 95% with a cycle of 1 second on, 0.2 seconds off. The solution was then placed in a sonic bath at 80°C for 1 minute to remove any bubbles.

[0238] 20 ml of the solution was poured into a 50 ml Falcon tube. The solution was then further degassed by removing large bubbles with a pipette, then allowed to cool to 55 °C and poured into a 50 ml Falcon tube. The liquid was evenly spread using a blade to obtain a wet film of approximately 400 microns thick. The plate was then placed in an oven at 80°C for 50 minutes to dry the film layer.

[0239] (ii) Onset melting temperature measured by differential scanning calorimetry (DSC)

[0240] The film produced in step (i) is conditioned overnight at 55% relative humidity and 20°C. The initial melting temperature varies with the change of the entire film composition (including moisture level). A small test sample (10-20mg) is cut from each film and accurately weighed. Each sample is placed in a 40μL aluminum pan (#51119870, purchased from Mettler Toledo) and heated from 25°C to 160°C at a heating rate of 10°C / min in a nitrogen atmosphere using a DSC822e from Mettler Toledo. Before sealing, a needle with a diameter of 50μm is used to pierce the pan cover. Use an empty pan as a reference. Record normalized heat flow and plot as a function of temperature.

[0241] The onset melting point of the sample is defined as the first inflection point in the DSC curve, which shows that the rate of heat flow to the sample increases as the temperature rises. When the sample begins to melt, the heat flow to the sample increases, resulting in a gradient change and an inflection point in the graph.

[0242] An operator can visually evaluate the normalized heat flow plot to determine the inflection point in the plot. However, this analysis is now typically done using software analysis tools. Such analysis tools are typically included as part of the equipment operating system. Suitable software includes the STARe evaluation software provided by Mettler-Toledo.

[0243] The data from the normalized DSC plots obtained above were analyzed using STARe evaluation software version 16.30 to determine the onset melting temperature. The results are shown in Table 1 below. The thermal properties of starch mixtures are a complex combination of the relative ratio of amylose to amylopectin in the starch, previous heat treatment, and the level and nature of other ingredients.

[0244]

[0245]

[0246] Table 1

[0247] (iii) Determination of seal strength

[0248] Test samples of some of the layers produced in step (i) were prepared and subjected to seal strength measurements. Test samples with a width of 25 mm were cut to the dimensions given in ASTM F88 / F88M-15 and conditioned overnight at 55% RH and 20°C. The test strip samples were then sealed using an RDM heat sealer to produce a fin seal. The sealed specimens were tested in a Tinnius Olsen tensile tester using Technique A (unsupported).

[0249] A sealing temperature of 100°C and a dwell time of 1 second were used. The results are shown in Table 2 below.

[0250]

[0251] Table 2

[0252] As shown above, the onset melting temperature of a material is inversely related to its ability to form a strong seal. For example, an STT-based layer has a low onset temperature and forms a strong seal. A BPS-based layer has a slightly higher onset temperature and also forms a strong seal. However, a CSS-based layer has a much higher onset temperature and therefore forms a seal with a much lower seal strength.

[0253] The lower starting temperature of the carbohydrate-containing layer of the multilayer film of the present invention is advantageous for a number of reasons. Not only has it been shown to achieve a stronger seal strength, but the lower starting temperature means that a lower temperature needs to be applied to the outer alginate-containing layer of the multilayer film of the present invention to result in effective sealing of the inner carbohydrate-containing layer. This means that film degradation (e.g. due to burning) is avoided, and the residence time required to form the seal is shorter, making the sealing process more industrially feasible.

[0254] Example 4: Preparation of alginate-starch multilayer films

[0255] (i) Preparation of alginate mixture

[0256] At ambient temperature, 400 ml of water was mixed with 14 g of alginic acid in a 600 ml beaker using an overhead stirrer to form a homogenous solution. 6 g of glycerol and 4 drops of defoamer were then added under stirring. The mixture was stirred for 45 minutes. The mixture was then further degassed under vacuum using a laboratory speed mixer.

[0257] (ii) Membrane formation - alginate layer

[0258] Pour 25 ml of the mixture produced in step (i) into a 50 ml Falcon tube. Remove the mixture and pour into a The liquid was evenly spread on the plate using a blade to obtain a wet film of 1100 microns of the alginate mixture. The glass plate was then dried overnight at ambient temperature to form a dry film layer.

[0259] (iii) Preparation of starch mixture

[0260] 40.0 g of cassava starch (STT) was dispersed in 400 ml of deionized water in a 600 ml flask at ambient temperature with overhead stirring. 17.14 g of glycerol was then added and the suspension was stirred. The suspension was then sonicated using a Bandelin sonicator for 40 minutes at an amplitude of 95% with a cycle of 1 second on and 0.2 seconds off. The solution was then placed in a sonic bath at 80°C for 1 minute to remove any bubbles.

[0261] (iv) Film formation - starch layer

[0262] 7 ml of the mixture produced in step (iii) is poured into a 50 ml Falcon tube. The mixture is then further degassed by removing large bubbles with a pipette, then cooled to 55 ° C, and then applied to the exposed surface (i.e., the surface not in contact with the glass plate) of the dry film prepared in step (ii) using a blade to obtain a wet film of the starch mixture having a thickness of about 250 microns. The plate is then placed in an oven at 80 ° C for 30 minutes to form a multilayer film.

[0263] Comparative Example 1: Preparation of alginate / starch monolayer

[0264] At ambient temperature, 50 ml of the mixture produced in step (iii) of Example 4 was added to 220 ml of the mixture produced in step (i) of Example 4 in a 400 ml beaker using an overhead stirrer to form a homogenous mixture. The mixture was placed in a sonication bath at 80°C for 5 minutes to remove air bubbles. 30 ml of the mixture was poured into a 50 ml Falcon tube. The mixture was removed and poured into a glass with The alginate-starch blend was coated evenly on a flat glass plate with a surface of 1.30 μm and spread evenly using a blade to obtain a 1350 μm wet film of the alginate-starch blend. The glass plate was then dried overnight at ambient temperature to form a dry film.

[0265] Example 5: Measurement of film tensile strength and elongation

[0266] Rectangular test specimens of 80 mm in length and 10 mm in width (which fall within the specifications described in ASTM D882) were cut and conditioned overnight at 55% RH and 20° C. The test specimens were tested using a Tinnius Olsen tensile tester with flat grip inserts, an initial grip spacing of 50 mm, and a test speed of 50 mm / min (strain rate of 1 mm / mm·min).

[0267] Great care was taken when cutting the samples to prevent nicks and tears that lead to premature failure and to ensure repeatable sample quality.

[0268] The results are shown below in Table 3. The tensile strength is reported in MPa and the elongation at break is reported in %.

[0269] Example Tensile strength(MPa) Elongation at break (%) Example 1 (comparative) 29.5 29.2 Example 2 (Comparative) 1.8 50.4 Example 4 23.9 36.7 Comparative Example 1 20.3 13.9

[0270] Table 3

[0271] The alginate film of embodiment 1 has very good tensile strength, while the starch film of embodiment 2 does not have, because it is too brittle to use. When two materials are combined, the film produced has acceptable tensile strength whether as a blend or as a multilayer. However, the blend (comparative example 1) has almost no elongation, while the multilayer (embodiment 4) has an elongation closer to the elongation of the alginate film of embodiment 1. The results show that the multilayer film of the present invention has good strength and is not easy to crack under elongation strain.

[0272] Example 6: Measurement of seal strength

[0273] Test samples with a width of 25 mm were cut to the dimensions given in ASTM F88 / F88M-15 and conditioned overnight at 55% relative humidity and 20°C. The test strip samples were then sealed using an RDM heat sealer to produce a fin seal. The sealed specimens were tested in a Tinnius Olsen tensile tester using Technique A (unsupported). A sealing temperature of 140°C and a dwell time of 1 second and a pressure of 3 bars were used. The results are shown in Table 4 below. The maximum force encountered when each sample was stressed to failure is reported as Newton / meter (N / m).

[0274]

[0275]

[0276] Table 4

[0277] The results show that the alginate film of Example 1 does not seal at all, while the starch film of Example 2 has good seal strength. When the two materials are combined into a blend (Comparative Example 1), the resulting film has poor seal strength, but if they are combined into multiple layers (Example 4), extremely high seal strength is achieved. The results show that the multilayer film of the present invention has excellent seal strength.

[0278] The alginate / starch multilayer of Example 4 (having a film thickness of 58 μm and conditioned and stored at 55% relative humidity and 20° C.) was subjected to further seal strength testing at different sealing temperatures and dwell times and a pressure of 3 bar. The results are shown in Table 5 below.

[0279]

[0280] Table 5

[0281] The results show that for the multilayer films of the present invention, the longer the residence time, the lower the temperature required to achieve effective seal strength.

[0282] Example 7: With Ca 2+ Preparation of ionic alginate monolayers

[0283] At ambient temperature, 400 ml of water was mixed with 14 g of alginic acid in a 600 ml beaker using an overhead stirrer to form a homogenous solution. Then 6 g of glycerol and 4 drops of defoamer were added under stirring. The mixture was stirred for 45 minutes. 0.26 g of CaCl2 was added to the solution and stirred. 50 ml of the mixture was poured into a 50 ml Falcon tube. The mixture was removed and poured into a The liquid was evenly spread on the plate using a blade to obtain a wet film of 1100 microns of the alginate mixture. The glass plate was then dried overnight at ambient temperature to form a dry film.

[0284] Example 8: With Ca 2+ Preparation of ionic starch monolayers

[0285] 20.0 g of cassava starch (STT) was dispersed in 200 ml of deionized water in a 600 ml flask at ambient temperature with overhead stirring. 8.57 g of glycerol was then added and the suspension was stirred. The suspension was then sonicated using a Bandelin sonicator for 20 minutes with an amplitude of 95% and a cycle of 1 second on and 0.2 seconds off. 0.41 g of CaCl2 was added to the solution and stirred. The solution was then placed in a sonic bath at 80°C for 1 minute to remove any bubbles.

[0286] 20 ml of the mixture was poured into a 50 ml Falcon tube. The mixture was then further degassed by removing large bubbles with a pipette, then allowed to cool to 55 °C and poured into a The liquid was evenly spread using a blade to obtain a wet film of the starch mixture of approximately 400 microns thick. The plate was then placed in an oven at 80°C for 50 minutes to form a dry film.

[0287] Comparative Example 2: With Ca 2+ Preparation of ionic alginate-starch monolayers

[0288] The membrane was prepared according to the method of Comparative Example 1 except that 0.30 g of CaCl2 was added during overhead stirring once a homogenous mixture was formed and before removing air bubbles in a sonication bath.

[0289] Example 9: With Ca 2+ Preparation of ionic alginate-starch multilayer films

[0290] (i) Preparation of alginate mixture

[0291] At ambient temperature, 400 ml of water was mixed with 14 g of alginic acid in a 600 ml beaker using an overhead stirrer to form a homogenous solution. Then 6 g of glycerol and 4 drops of defoamer were added under stirring. The mixture was stirred for 45 minutes.

[0292] (ii) Membrane formation - alginate layer

[0293] Pour 50 ml of the mixture produced in step (i) into a 50 ml Falcon tube. Remove the mixture and pour it into a The liquid was spread evenly on the plate using a blade to obtain a wet film of 1100 microns of the alginate mixture. The glass plate was then dried overnight at ambient temperature to form a dry layer.

[0294] (iii) Preparation of starch and calcium mixture

[0295] 20.0 g of cassava starch (STT) was dispersed in 200 ml of deionized water in a 600 ml flask at ambient temperature with overhead stirring. 8.57 g of glycerol was then added and the suspension was stirred. The suspension was then sonicated using a Bandelin sonicator for 20 minutes with an amplitude of 95% and a cycle of 1 second on and 0.2 seconds off. 0.41 g of CaCl2 was added to the solution and stirred. The solution was then placed in a sonic bath at 80°C for 1 minute to remove any bubbles.

[0296] (iv) Film formation - starch / calcium layer

[0297] 20 ml of the mixture produced in step (iii) was poured into a 50 ml Falcon tube. The mixture was then further degassed by removing large bubbles with a pipette, then cooled to 55 ° C and applied to the exposed surface (i.e., the surface not in contact with the glass plate) of the dry film prepared in step (ii) using a blade to obtain a wet film of the starch mixture having a thickness of about 250 microns. The plate was then placed in an oven at 80 ° C for 30 minutes to form a multilayer film.

[0298] Example 10: Preparation of starch-alginate multilayer films with calcium ions

[0299] (i) Preparation of starch and calcium mixture

[0300] 20.0 g of cassava starch (STT) was dispersed in 200 ml of deionized water in a 600 ml flask at ambient temperature with overhead stirring. 8.57 g of glycerol was then added and the suspension was stirred. The suspension was then sonicated using a Bandelin sonicator for 20 minutes with an amplitude of 95% and a cycle of 1 second on and 0.2 seconds off. 0.41 g of CaCl2 was added to the solution and stirred. The solution was then placed in a sonic bath at 80°C for 1 minute to remove any bubbles.

[0301] (ii) Film formation - starch / calcium layer

[0302] 20 ml of the mixture produced in step (i) was poured into a 50 ml Falcon tube. The mixture was then further degassed by removing large bubbles with a pipette, then allowed to cool to 55°C, and then poured into a 50 ml Falcon tube. The liquid was evenly spread using a blade to obtain a wet film of the starch mixture of about 250 microns thick. The plate was then placed in an oven at 80°C for 30 minutes to form a film.

[0303] (iii) Preparation of alginate mixture

[0304] At ambient temperature, 400 ml of water was mixed with 14 g of alginic acid in a 600 ml beaker using an overhead stirrer to form a homogenous solution. Then 6 g of glycerol and 4 drops of defoamer were added under stirring. The mixture was stirred for 45 minutes.

[0305] (iv) Membrane formation - alginate layer

[0306] 50 ml of the mixture produced in step (iii) was poured into a 50 ml Falcon tube. The mixture was removed and coated onto the exposed surface (i.e., the surface not in contact with the glass plate) of the dry film prepared in step (ii) using a blade to obtain a wet film of the alginate mixture having a thickness of about 1100 microns. The glass plate was then dried overnight at ambient temperature to form a multilayer film.

[0307] Example 11: Measurement of film tensile strength, elongation, seal strength and water dispersibility

[0308] The films of Examples 4 and 7 to 10 and Comparative Example 2 were tested for tensile strength and elongation at break according to the method outlined in Example 5.

[0309] The seal strength of the films of Examples 4 and 7 to 10 and Comparative Example 2 were tested according to the method outlined in Example 6, except that a sealing temperature of 100° C. and a dwell time of 1 second were used.

[0310] The water dispersibility of the films of Examples 4 and 7 to 10 and Comparative Example 2 was evaluated using 0.75 g samples of each final film conditioned at 55% relative humidity and 20°C. The samples were mixed in 300 ml of 20°C reverse osmosis water and freshly boiled reverse osmosis water (i.e., having a temperature range of 75.1°C to 90.2°C) in a 600 ml beaker at room temperature using an overhead stirrer at 300 rpm for 3 minutes. The final mixture was visually inspected for any remaining particles, and their size was used to judge water dispersibility on the following scale: Very low - most particles>30 mm; Low - most particles ~20-30 mm; Average - most particles ~10-20 mm; High - most particles ~1-10 mm; Very high - most particles <1 mm; Maximum - no visible particles. Dispersibility is reported as the average of two different temperature observations, where each observation can be assigned an integer value for these purposes.

[0311] The results of all of these tests are shown in Table 6 below.

[0312]

[0313] Table 6

[0314] The results show that the inclusion of calcium ions in the alginate monolayer (Example 7) leads to low seal strength values. In the case of the starch monolayer (Example 8), the inclusion of calcium ions reduces the seal strength to a lower but still acceptable value compared to the starch monolayer without calcium ions (Example 2).

[0315] At low heat sealing temperature (e.g., 100° C. as used herein), the multilayer film without calcium ions (Example 4) had a seal strength of 194.8 N / m, while the multilayer film containing Ca ions in the starch layer had a seal strength of 194.8 N / m. 2+ The ions increased the seal strength to 516 to 600 N / m (Examples 9 and 10). Without wishing to be bound by theory, this is believed to be due to the presence of alginate ions and Ca at the interface between the two layers. 2+ A small amount of cross-linking occurs between the ions. Interestingly, this effect can be achieved by casting either the alginate layer or the starch layer first. 2+ ions, it is not possible to cast the starch layer first, because the high water content of the alginate mixture to be cast would destroy the first starch layer. 2+ ions, this becomes possible. Again, without wishing to be bound by theory, this is believed to be due to the presence of alginate / Ca at the interface between the two layers. 2+Cross-linking, which provides a barrier to water. In addition, it is found that the multilayer (Example 10) that first forms a starch layer has higher tensile strength and elongation than the multilayer (Example 9) that first forms an alginate layer. Without wishing to be bound by any theory, it is believed that when the alginate layer interacts with calcium ions, it begins to cross-link. In the case of first forming an alginate layer (Example 9), when wet starch begins to dissolve at the interface due to the water it carries, alginate is dry and solid. Therefore, it is also cross-linked at the interface, but because the remaining body of the layer is solid, it remains uncross-linked. In the case of first forming a starch layer (Example 10), the alginate layer is still wet and has strong fluidity, so a higher level of cross-linking can be achieved until it is completely dried.

[0316] Contains Ca 2+ The water dispersibility of the multilayer films depends on the order of layer formation. When the alginate layer is formed first (as in Example 9), the final multilayer film has high dispersibility, similar to that in the absence of Ca. 2+ ions (Example 4). When the starch layer is formed first (as in Example 10), the final multilayer film has very low dispersibility. Without wishing to be bound by any theory, it is believed that in the case of Example 9, crosslinking is only achieved at the interface of the two layers, while in Example 10, crosslinking is achieved in a larger volume. Therefore, the order of layer formation can be used as a means to control the water dispersibility of the film (for example, for different end-use applications) while maintaining good heat sealing properties.

[0317] Example 12: Moisture content of membranes

[0318] The moisture content of the various films prepared in the above examples was measured using an Ohaus MB23 moisture analyzer, wherein the film samples were first conditioned at 55% relative humidity and a temperature of 20° C. The results are shown in Table 7 below.

[0319]

[0320] Table 7

[0321] Example 13: Dispersion of laundry detergent bags

[0322] Using the multilayer film of Example 9, bags were produced by heat sealing along the length and ends of the film using an RS PRO heat sealer at power 2. The sealed bags contained concentrated laundry liquid detergent for use in liquid laundry pods.

[0323] The bag can be easily handled and maintains its integrity. When added to 250 ml of water in a 400 ml beaker at 20°C and stirred with a magnetic stirrer at ~340 rpm, the bag disintegrated and completely released its contents after about 2 minutes and 20 seconds, as Figures 1a-1g shown.

[0324] This example illustrates one of the many uses of the multilayer film of the present invention, namely the preparation of heat-sealed bags to provide a single dose of laundry liquid detergent. The bag can be safely handled by the consumer and will release the detergent when in contact with water in a washing machine.

[0325] Example 14: Preparation of Alginate-Starch Multilayer Films with Mixed Plasticizers

[0326] (i) Preparation of alginate mixture

[0327] In a plastic container, 6.49 g of oleic acid and 3.20 g of polysorbate 80 were added to 200 ml of deionized water. This was sonicated using a Bandelin sonicator for 5 minutes at an amplitude of 50% with a cycle of 1 second on and 0.2 seconds off to form an emulsion.

[0328] In a Klarstein Grand Prix food processor (500W power, 2.5L capacity) equipped with 4 standard stainless steel blades, the following room temperature materials were added while mixing at speed 4: 1800.00 g reverse osmosis water, 56.54 g glycerol, and 56.54 g sorbitol. Next, the sonicated oleic acid emulsion prepared above was added to the mixture, followed by 210.00 g Sodium alginate.

[0329] The food processor was set at a temperature of 85°C and mixed for 60 minutes while scraping material accumulated on the walls back into the mixture every 10 minutes.

[0330] The mixture was then transferred to a Hauschild Speedmixer at 50 mbar and 1500 rpm for 3 minutes and cooled to room temperature.

[0331] (ii) Membrane formation - alginate layer

[0332] At room temperature, 80-100 ml of the mixture produced in step (i) was poured onto a flat glass plate. The liquid was evenly coated on the plate using an RK Print K303S multilayer coater with a doctor blade (set to speed 3) to obtain a 600 micron wet film of the alginate mixture. The glass plate was then dried in an oven at 50° C. for 40 minutes to form a dry film layer.

[0333] (iii) Preparation of starch mixture

[0334] In a Klarstein Grand Prix food processor (500W power, 2.5 liter capacity) equipped with 4 standard stainless steel blades, the following room temperature materials were added while mixing at speed 4: 2000.00 g reverse osmosis water, 45.00 g glycerol, and 45.00 g sorbitol. Next, 210.00 g tapioca starch (STT).

[0335] The food processor was set at a temperature of 85°C and mixed for 60 minutes while scraping material accumulated on the walls back into the mixture every 10 minutes.

[0336] The mixture was then transferred to a Hauschild Speedmixer at 50 mbar and 1500 rpm for 3 minutes and cooled to room temperature.

[0337] (iv) Film formation - starch layer

[0338] 30-45 ml of the mixture produced in step (iii) was poured at room temperature and then coated on the exposed surface (i.e., the surface not in contact with the glass plate) of the dry film prepared in step (ii) using a RKPrint K303S multilayer coater (set to speed 3) with a doctor blade to obtain a wet film of the starch mixture of about 350 microns thick. The plate was then placed in an oven at 50° C. for 15 minutes to form a multilayer film.

[0339] Example 15: Preparation of alginate-starch multilayer films on a solvent casting production line

[0340] (i) Preparation of alginate mixture

[0341] For each film, the alginate layer was prepared by first adding the following room temperature materials to a Klarstein Grand Prix food processor (500W power, 2.5 liter capacity) equipped with 4 standard stainless steel blades while mixing at speed 4:

[0342] a) For membrane 15A: 2000 g reverse osmosis water, 90.00 g glycerol and 210.00 g

[0343] Sodium alginate.

[0344] b) For membrane 15B: 2000 g reverse osmosis water, 90.00 g glycerol and 210.00 g

[0345] Sodium alginate.

[0346] c) For membrane 15C: 2000 g reverse osmosis water, 56.54 g glycerol, 56.54 g sorbitol and 210.00 g Sodium alginate.

[0347] d) For membrane 15D: 2000 g reverse osmosis water, 56.54 g glycerol, 56.54 g sorbitol and 210.00 g Sodium alginate.

[0348] In each case, the food processor was set at a temperature of 85°C and mixed for 60 minutes, while material accumulated on the walls was shoveled back into the mixture every 10 minutes. Each mixture was then transferred to a Hauschild Speedmixer at 50 mbar and 1500 rpm for 3 minutes and cooled to room temperature.

[0349] For membrane 15E, the preparation of the alginate mixture was carried out as in Example 14, part (i).

[0350] (ii) Preparation of starch mixture

[0351] For each film, a starch layer was prepared by first adding the following room temperature materials to a Klarstein Grand Prix food processor (500W power, 2.5 liter capacity) equipped with 4 standard stainless steel blades while mixing at speed 4:

[0352] a) For membrane 15A: 2000 g reverse osmosis water, 75.00 g glycerol and 0.30 g thymol. Then 300.00 g tapioca starch (STT) was gradually added.

[0353] b) For membrane 15B: 2000 g reverse osmosis water, 64.29 g glycerol, 64.29 g sorbitol and 0.30 g thymol. Then 300.00 g tapioca starch (STT) was gradually added.

[0354] c) For membrane 15C: 2000.00 g reverse osmosis water, 75.00 g glycerol and 0.30 g thymol. Then 300.00 g tapioca starch (STT) was gradually added.

[0355] d) For membrane 15D: 2000.00 g reverse osmosis water, 64.29 g glycerol, 64.29 g sorbitol and 0.3 g thymol. Then 300.00 g tapioca starch (STT) was gradually added.

[0356] In each case, the food processor was set at a temperature of 85°C and mixed for 60 minutes, while material accumulated on the walls was shoveled back into the mixture every 10 minutes. Each mixture was then transferred to a Hauschild Speedmixer at 50 mbar and 1500 rpm for 3 minutes and cooled to room temperature.

[0357] For Film 15E, the starch mixture was prepared as in Example 14, part (iii).

[0358] (iii) Solvent casting

[0359] On a production line running at 4m / min through a 10m long oven, On the substrate, the films were prepared by a solvent casting dry-on-wet process by drying the alginate mixture as the first layer and then drying the starch mixture as the second layer. For film 15E, The substrate had been corona treated. The oven conditions were set as in Table 8, and the roll settings and line speeds were varied to achieve the desired dry thickness and moisture content.

[0360]

[0361] Table 8

[0362] Example 16: Properties of alginate-starch multilayer films prepared on a solvent casting line

[0363] The film prepared in Example 15 was then tested for strength and elongation, the ability to peel the film from a roll, seal strength, and dispersibility in water. These are important properties required to be able to handle the film in an industrial packaging line, form a bag around the product, and disperse the package in water to release the contents.

[0364] The films were tested for tensile strength and elongation at break according to the methods outlined in Example 5. The results are provided in Table 9.

[0365]

[0366] Table 9

[0367] All films have good tensile strength and elongation, making them suitable films for use in packaging lines.

[0368] Film peeling was tested according to the "peel test" described herein. Before winding, the sample was balanced at a selected relative humidity for 24 hours. Typically, the test was carried out at a relative humidity of 33%, 44%, 55% and 75%, to cover the humidity range experienced in an industrial environment. A film strip of typically 25 cm long and 4 cm wide was wound onto a small cardboard core of 1 cm in diameter. The rolled film was placed at a selected humidity of 23 ° C for 24 hours. The film was then peeled off from the roll and evaluated according to the scale in Table 10. The results are provided in Table 11.

[0369]

[0370] Table 10

[0371] The seal strength of the films was tested according to the method outlined in Example 6 except that a sealing temperature of 130°C and a dwell time of 1 second and 4 bar were used. The results are provided in Table 11.

[0372] Water dispersibility was tested by the method given in Example 11. The results are provided in Table 11.

[0373]

[0374] Table 11

[0375] In the peel test, films 15A and 15B were difficult to peel from the roll and failed at all relative humidities. This would make it difficult to use a cast line process since the final film cannot be wound, but other casting and drying techniques can be used. Both films had only glycerol as a plasticizer in the first layer.

[0376] Films 15C and 15D both passed the peel test at 33% RH with no resistance and also passed the peel test at 55% RH with some resistance.Both films comprised a first layer having a mixed plasticizer system of glycerol and sorbitol.

[0377] Film 15E also passed the peel test at 33% RH with no resistance, at 55% RH with only slight resistance, and at 75% RH with some resistance.This film comprises a first layer having a mixed plasticizer system of glycerol, sorbitol, and the fatty acid oleic acid.

[0378] Films 15C, 15D and 15E all have good maximum heat seal strength. Films 15A and 15B are also suitable for heat sealing because they have the same second layer as films 15C and 15D. All of these films are also suitable for preparing sealed closed bags and other sealed packages.

[0379] All films had very good dispersibility in water, demonstrating that bags formed from these films would be suitable for releasing their contents into water during use, such as in a dishwasher, washing machine or in a shower, bath or sink.

[0380] Example 17: Properties of Alginate-Starch Multilayer Films with Propylene Glycol

[0381] (i) Preparation of alginate mixture

[0382] In a Klarstein Grand Prix food processor (500W, 2.5L capacity) equipped with 4 standard stainless steel blades, the following room temperature ingredients were added while mixing at speed 4: 2000 g reverse osmosis water, 35 g glycerol, 35 g sorbitol, 70 g propylene glycol, and 210 g Alginate.

[0383] The food processor was set at a temperature of 85°C and mixed for 60 minutes, while scraping material accumulated on the walls back into the mixture every 10 minutes. The mixture was then transferred to a Hauschild Speedmixer at 50 mbar and 1500 rpm for 3 minutes and cooled to room temperature.

[0384] (ii) Membrane formation - alginate layer

[0385] At room temperature, 80-100 ml of the mixture produced in step (i) was poured onto a flat glass plate. The liquid was evenly coated on the plate using an RK Print K303S multilayer coater with a doctor blade (set to speed 3) to obtain a 600 micron wet film of the alginate mixture. The glass plate was then dried in an oven at 50° C. for 40 minutes to form a dry film layer.

[0386] (iii) Preparation of starch mixture

[0387] In a Klarstein Grand Prix food processor (500W power, 2.5 liter capacity) equipped with 4 standard stainless steel blades, the following room temperature ingredients were added while mixing at speed 4: 2000.00 g reverse osmosis water, 90.00 g glycerin. Next, 210.00 g tapioca starch (STT).

[0388] The food processor was set at a temperature of 85°C and mixed for 60 minutes, while scraping material accumulated on the walls back into the mixture every 10 minutes. The mixture was then transferred to a Hauschild Speedmixer at 50 mbar and 1500 rpm for 3 minutes and cooled to room temperature.

[0389] (iv) Film formation - starch layer

[0390] 30-45 ml of the mixture produced in step (iii) was poured at room temperature and then coated on the exposed surface (i.e., the surface not in contact with the glass plate) of the dry film prepared in step (ii) using a RK Print K303S multilayer coater with a doctor blade (set to speed 3) to obtain a wet film of the starch mixture of about 350 microns thick. The plate was then placed in an oven at 50° C. for 15 minutes to form a multilayer film.

[0391] The produced film 17A had good mechanical properties. Peel was tested according to the "Peel Test" described in Example 15. The seal strength of the films was tested according to the method outlined in Example 6 except that a sealing temperature of 130°C and a dwell time of 1 second and 4 bar were used.

[0392] The results are provided in Table 11.

[0393]

[0394] Table 11

[0395] Film 17A contains a mixture of plasticizers glycerol, sorbitol, and propylene glycol in the first layer. Propylene glycol has no detrimental effect on the heat seal, as can be seen by comparison with similar values ​​for film 15C. The peel properties of film 17A are slightly improved compared to 15C.

Claims

1. A film comprising: A first layer, based on the total weight of the first layer, the first layer comprises: at least 20 wt.-% of one or more monovalent salts of alginic acid, and at least 5 wt.-% of one or more organic plasticizers; A second layer, based on the total weight of the second layer, the second layer comprises: one or more carbohydrates other than alginic acid and any salts thereof, at least 5 wt.-% of one or more organic plasticizers, and Less than 20 wt.-% alginate; wherein a surface of the second layer is sealed to a surface of the first layer. 2 . The film according to claim 1 , wherein the film has a thickness of 20 μm to 120 μm.

3. The film according to any one of claims 1 and 2, wherein the first layer further comprises one or more divalent alginates selected from calcium alginate and magnesium alginate.

4. The film according to any one of claims 1 to 3, wherein the second layer has an onset melting temperature in the range of 55°C to 85°C, measured as described in Example 3 of the specification.

5. The film according to any one of claims 1 to 4, wherein the second layer comprises starch and / or pullulan.

6. The membrane according to any one of claims 1 to 5, wherein the membrane comprises 3-90 wt.-%, preferably 15-85 wt.-%, more preferably 25-80 wt.-%, most preferably 35-70 wt.-% of one or more alginates, based on the total weight of the membrane, as determined according to the HPLC method in Journal of Chromatographic Science 2013; 51: 208-214.

7. The film according to any one of claims 1 to 6, wherein the film has a heat seal strength of at least 40 N / m, preferably at least 60 N / m, more preferably at least 80 N / m, even more preferably at least 100 N / m, most preferably at least 120 N / m, measured by ASTM F88 / F88M-15 at 55% relative humidity and 20°C after conditioning the film at 55% relative humidity and 20°C for at least one hour and then sealing at a temperature of 120°C and an applied pressure of 1 to 3 bar for a period of 1 second.

8. The film according to any one of claims 1 to 7, wherein the organic plasticizer in the first layer is selected from glycerol, polyethylene glycol, propylene glycol, sorbitol, mannitol, xylitol, triethyl citrate, oleic acid, glucose, mannose, fructose, sucrose, urea, lecithin, waxes, amino acids, lactic acid, citric acid, glycolic acid, malic acid, tartaric acid and mixtures thereof, preferably a mixture of glycerol, sorbitol and oleic acid.

9. The film according to any one of claims 1 to 8, wherein the organic plasticizer in the second layer is selected from glycerol, polyethylene glycol, sorbitol, mannitol, xylitol, triethyl citrate, glucose, mannose, fructose, sucrose, urea, lecithin, amino acids, lactic acid, citric acid, glycolic acid, malic acid, tartaric acid and mixtures thereof, preferably a mixture of glycerol and sorbitol.

10. A method for preparing a membrane according to any one of claims 1 to 9, comprising the steps of: (i) providing a first layer, the first layer comprising, based on the total weight of the first layer: at least 20 wt.-% of one or more monovalent salts of alginic acid, and at least 5 wt.-% of one or more organic plasticizers; (ii) providing a second layer, the second layer comprising, based on the total weight of the second layer: one or more carbohydrates other than alginic acid and any salts thereof, at least 5 wt.-% of one or more organic plasticizers, and Less than 20 wt.-% alginate; and (iii) sealing a surface of the second layer to a surface of the first layer.

11. A product packaged by the film according to any one of claims 1 to 9.

12. The product according to claim 11, wherein the film is greater than 75%, preferably greater than 80%, more preferably greater than 85%, even more preferably greater than 90%, most preferably greater than 95% biodegradable after 28 days testing according to ASTM D6691.

13. A method for packaging a product, the method comprising the following steps: (i) wrapping the product in a film according to any one of claims 1 to 9 such that the first layer is the outer layer; and (ii) heat sealing the film around the product to form a bag.

14. The method according to claim 13, wherein the duration of step (ii) is less than 2 seconds, more preferably less than 1 second, more preferably less than 0.5 seconds, and wherein step (ii) is performed at a temperature below 160°C, preferably below 140°C, preferably below 120°C.

15. Use of the film according to any one of claims 1 to 9 for packaging products and / or preparing bags.

16. A bag prepared by the method according to any one of claims 13 and 14.

17. A method of releasing a product encapsulated in a film according to any one of claims 1 to 9, the method comprising the steps of: (i) placing the packaged product in water; and (ii) causing the film to disperse, thereby releasing the product.

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