Three-dimensional biodegradable containers with improved sensory properties - Patents.com

Abstract

The present invention relates to: 1. a three-dimensional hollow container for containing an edible product, said container having a body formed from a first polymer layer formed from polyhydroxyalkanoate (PHA) having a thickness comprised between 50 μm and 1.5 mm; (i) the container body comprises a second layer deposited on an inner surface of the first layer and comprising a metalloid, a carbon thin film, or a combination thereof, the second layer having a thickness of less than 100 nm; and (ii) The container body further comprises an intermediate polymer layer disposed between the first layer and the second layer, the intermediate layer having a root mean square ("RMS") roughness of less than 20 nm, and the intermediate layer having a thickness comprised between 1 and 100 μm.

Description

[Technical field]

[0001] The present invention relates to a three-dimensional container made from polyhydroxyalkanoates (PHAs) and further comprising a metalloid barrier layer for improving the organoleptic properties of products contained therein. [Background technology]

[0002] Containers made from polyhydroxyalkanoates (PHAs), particularly those designed for containing and dispensing edible products, have the advantage of offering a biodegradable solution to consumers and therefore being environmentally friendly.

[0003] Polyhydroxyalkanoates (PHAs) are a class of polymers (polyesters) that are relatively easy to convert from resins (generally in the form of pellets) into three-dimensional containers (or packaging materials) by known manufacturing processes such as injection molding, compression molding, or extrusion blow molding. Furthermore, PHAs are produced from renewable resources, since they are metabolic by-products of bacteria, and require correspondingly complex conversion steps to be refined into processable polymer resins.

[0004] By "container" it is meant not only the container itself but also the parts necessary to form a complete package, such as a three-dimensional lid or closure.

[0005] Despite many technical and environmental advantages, polyhydroxyalkanoates have a major drawback in that they produce crotonic acid when subjected to heat and / or shear stress during the conversion process, particularly when the pellets are heated to form a molten resin that can be processed into a three-dimensional article such as a container. In this case, when using the packaging formation method as discussed above, the molten PHA resin is heated and then passed through a molding device, such as an extruder, and sometimes also through the injection section of an injection molding machine, whereby high shear stress and temperature are applied to the PHA molecules.

[0006] Due to heat and shear stress, the molecules of PHA undergo a chemical reaction that degrades the material, more specifically a hydrolysis process, during which the so-called crotonic acid is formed as a by-product.

[0007] Containers made from PHA via conventional manufacturing processes, such as those discussed above, have been found to contain large amounts of crotonic acid, which exhibits a strong odor that has a very negative effect on the sensory properties of the packaged product. This odor is, of course, very undesirable for quality reasons, and is particularly undesirable in edible products with a low sensory profile, or even in edible products with a neutral sensory profile, such as mineral water (either non-carbonated or carbonated). In the case of mineral water, consumer tests have shown that the taste of crotonic acid is very strongly perceived by consumers when drinking the water, and is unacceptable.

[0008] Furthermore, beyond the sensory issues specific to the presence of crotonic acid, PHAs can also have additional sensory issues due to bacterial residues following fermentation of the residual feedstock, which can also affect the sensory properties of products contained in packaging made from PHAs.

[0009] To solve this problem, attempts have been made to coat the inner surface of the PHA container (i.e., the surface that comes into contact with the product) with certain compounds known to have barrier properties. For example, metalloids such as silicon oxide (SiOx) have been tested, which are known to have very good barrier properties when applied in very thin layers that are compatible with the biodegradability of the container. Unfortunately, these attempts were unsuccessful because they did not provide a sufficient barrier against the migration of crotonic acid from the container wall to the packaged product, and therefore no substantial and effective sensory improvement was observed.

[0010] In view of the above, there is a need for a PHA container that can be manufactured using known molding techniques of the type that involve the application of heat and / or shear stress to the PHA resin, that does not affect the sensory profile of the container contents, particularly when the container contents are edible products for human or animal consumption, and that is biodegradable. Summary of the Invention

[0011] The above stated object is achieved by a three-dimensional hollow container (or otherwise referred to in the present specification as "packaging material", which is considered to be an equivalent term) for containing an edible product, said container having a body formed from a first polymer layer, said first layer being formed from a polyhydroxyalkanoate (PHA) having a thickness comprised between 50 μm and 1.5 mm, more preferably comprised between 100 and 500 μm, (i) the container body comprises a second layer deposited on an inner surface of the first layer, the second layer comprising a metalloid, a carbon thin film, or a combination thereof, the second layer having a thickness of less than 100 nm, preferably less than 80 nm; and (ii) The container body further comprises an intermediate polymer layer disposed between the first layer and the second layer, the intermediate layer having a roughness mean square value ("RMS") of less than 20 nm, preferably less than 10 nm, and the intermediate layer having a thickness comprised between 1 and 100 μm, preferably between 20 and 80 μm.

[0012] The three-dimensional container thus obtained is preferably rigid, but may also be semi-rigid, or even have some of its components flexible.

[0013] "Polyhydroxyalkanoate (PHA)" refers to the entire class of microbially derived polyester resins, including, but not limited to, poly-3-hydroxybutyrate (PHB), poly-3-hydroxybutyrate-co-4-hydroxybutyrate (P(3-HB-co-4-HB)), poly-3-hydroxybutyrate-co-valerate (PHBV), polyhydroxybutyrate-co-hexanoate (PHBH), and different grades thereof.

[0014] In a preferred embodiment of the invention, the metalloid used in the second layer is silicon oxide (SiOx), boron trioxide (B2O3), germanium dioxide (GeO2) or a combination thereof, and the carbon film is diamond-like carbon (DLC). When SiOx is used, x is preferably comprised between 1.5 and 1.8.

[0015] Advantageously, the intermediate layer comprises a polymer selected from the list: polyethylene terephthalate (PET), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polyglycolic acid (PGA), starch (TPS), polycaprolactone (PCL), or a combination thereof.

[0016] The container according to the invention is preferably a three-dimensional article selected within the following list: food tray, bottle, can, closure, capsule, pod, lid.

[0017] The inventors have surprisingly discovered that by forming an extremely thin intermediate layer between the first layer of PHA and the second layer of metalloid, the surface of the PHA is provided with a microscopically smooth surface, and thus the layer of metalloid (e.g. SiOx) is very homogenous and well distributed over the entire surface of the material, thereby significantly improving its barrier effect against the migration of crotonic acid, thus solving the sensory problems of such PHA containers.

[0018] Such smoothness cannot be achieved with PHA alone, because are inherently biodegradable or biodegradable by structure; and be sufficiently smooth as to allow subsequent metalloid layers to act as an efficient barrier to crotonic acid migration; It has been found that the solution is provided by an additional intermediate "spare" layer of material that is both

[0019] Surface roughness is characterized in the present invention by a "root mean square" value ("RMS") which must be less than 20 nm, preferably less than 10 nm.

[0020] The RMS value is determined by the following method.

[0021] An atomic force microscope (AFM) scans a sample surface laterally with a cantilever. The cantilever has a sharp tip that is in permanent contact with the surface. A laser beam is directed at the cantilever tip and the reflected light is incident on a photodiode. During the scanning process, the cantilever bends in response to the surface roughness, which results in a change in the amount of laser light incident on the photodiode. The height of the cantilever is subsequently adjusted to recover a response signal, resulting in the measured cantilever height.

[0022] Several polymers are believed to be good technical choices for providing sufficient smoothness to the PHA layer in accordance with the principles of the present invention, in particular the following polymers:

[0023] Polyethylene terephthalate (PET) when deposited as an ultrathin layer by dispersion spray coating (the structure makes it biodegradable); Polylactic acid (PLA), which is biobased but biodegradable only by including a thermal step to induce an autohydrolysis step to initiate the degradation process in the presence of microorganisms. Therefore, PLA also needs to be applied as a very thin layer by dispersion spray coating to provide biodegradability by structure; Polybutylene succinate adipate (PBSA), which is considered biobased and inherently biodegradable; Polybutylene adipate terephthalate (PBAT), which is fossil-based but inherently biodegradable; Polyglycolic acid (PGA), which is considered biobased and inherently biodegradable; Other bio-based and / or biodegradable polymers such as thermoplastic starch (TPS) / polycaprolactone (PCL).

[0024] These polymers are applied as intermediate layers in accordance with the principles of the present invention in preparation for deposition of the metalloid barrier layer as an extremely thin layer, said extremely thin intermediate layer being preferably applied to represent less than 0.3% by weight of the total packaging material weight.

[0025] The appropriate deposition technique used to apply the intermediate layer is selected from a list including coating processes such as spray coating, aqueous dispersion coating, dip coating, plasma coating, thermal spraying, powder coating, etc. As mentioned above, some of the mentioned deposition techniques are more suitable for the deposition of certain types of polymers.

[0026] In another embodiment of the invention, the intermediate layer is directly coextruded with the PHA layer by a conventional extrusion blow molding process (EBM) to form the walls of the three-dimensional container.

[0027] Alternatively, a co-extrusion blow molding process may be applied in which the bottle is produced in a single step using a multi-screw co-extruder.

[0028] In this process, a PHA tube with a thin inner layer of additional biomaterial, such as PBSA, is extruded and then blown into a mold to create a thin inner layer of biodegradable material. The weight of the inner layer can also be reduced to less than 1% of the total PHA container weight. This process is suitable for materials that are compatible with PHA. Compatibility depends mainly on the melting temperature (Tm) and thermal stability above Tm, respectively. Polymers such as PBAT, PBSA, and PGA are very suitable for such a process. Commercially available PHA materials (such as PHBH or PHBV with a certain mole % copolymer portion) can be melted at 130°C. <tm>Since low melting point polymers (Tm<100°C) with poor thermal stability above Tm are not suitable for use with PHA, since they have a Tm of 180°C, PCL and thermoplastic starch are more likely candidates that should be used with the coating techniques mentioned above.

[0029] As used herein, "dispersion coating" refers to a coating technique in which an aqueous dispersion of fine polymer particles or a polymer solution is applied neat to the surface of paper or paperboard to form a solid, non-porous film after drying. Dispersion coating can be performed by gravure, flexo-gravure, rod, blade, slot die, curtain air knife, or any other known paper coating method. Because the polymer is mixed into an aqueous solution, dispersion coating can produce a much thinner layer than extrusion. This provides advantages in terms of polymer usage, its barrier performance, and the recyclability of the resulting paper structure. The goal of dispersion coating is to provide a barrier layer against water, water vapor, grease, oil, gas, etc., through an environmentally friendly coating.

[0030] The present invention further provides a packaged product comprising: (i) at least one edible product for human or animal consumption in liquid, semi-liquid form, powder, gel, kibble, or paste form; (ii) at least one container according to any one of claims 1 to 6 in which the edible product is packaged; The present invention relates to a packaged product, including

[0031] Preferably, said edible product is selected within the following list: mineral water based drinks, dairy products, sauces, dressings, soups, coffee or cocoa based products, plant-based meat or fish substitutes, smoothies, nutritional products for babies or adults, confectionery products, sports nutritional supplements, pet food.

[0032] Additional features and advantages of the present invention are described in, or will be apparent from, the following description of the presently preferred embodiments which take place in conjunction with the drawings. [Brief description of the drawings]

[0033] [Figure 1] 2 is a schematic diagram of the multi-layer structure of the container wall according to the present invention at a microscopic level. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Figure 1 illustrates a preferred embodiment of the invention, showing an enlarged view of the wall of a bottle produced by extrusion blow molding of a PHA parison, which after blow molding has been coated on its inner surface with an additional layer according to the invention.

[0035] This results in a blow-molded bottle with a multi-layer structure 1 having a number of layers as follows: starting from the outer layer (i.e., the layer that will come into contact with the external atmosphere when the structure is molded into a packaging material) to the inner layer (i.e., the layer that will ultimately come into contact with the packaged product).

[0036] In the particular example shown in Figure 1, the first outermost layer 2 is a polyhydroxyalkanoate (PHA) layer that constitutes the wall of a hollow bottle produced by extrusion blow molding (EBM) of a PHA resin via a conventional EBM process. The bottle thus obtained is a 1 liter bottle with a thread adapted for a screw cap. The cap is made from polyolefin by injection molding according to standard manufacturing methods.

[0037] The thickness of the PHA layer is not completely uniform over the entire surface of the bottle wall, as shown in FIG. 1, and said thickness is comprised between 0.25 and 1.3 mm.

[0038] In order to smooth the surface of the PHA layer, a second layer is produced, which is the intermediate layer 3 shown in Figure 1. The intermediate layer 3 is a co-extruded layer of polybutylene succinate-co-butylene adipate (PBSA) polymer, coated such that the thickness of said intermediate layer is comprised between 10 and 30 μm. As shown in Figure 1, the innermost surface of the intermediate layer 3 is substantially free of irregularities so that the next layer can be applied subsequently.

[0039] The final layer 4 is a silicon oxide (SiOx) layer, deposited by a direct plasma coating deposition process. The resulting thin layer of SiOx has a thickness of 40 nm.

[0040] The bottles thus obtained were filled with non-carbonated mineral water and closed in the usual manner. They were then stored at ambient temperature for 4 weeks. During the examination of the bottle contents, the water showed no noticeable organoleptic deterioration, indicating good barrier properties of the SiOx coating against the migration of crotonic acid.

[0041] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the present invention and without diminishing its attendant advantages. Accordingly, such changes and modifications are intended to be covered by the appended claims.< / tm>

Claims

1. A three-dimensional hollow container for containing an edible product, said container having a body formed from a first polymer layer, said first layer being formed from polyhydroxyalkanoate (PHA) having a thickness comprised between 50 μm and 1.5 mm, more preferably comprised between 100 and 500 μm, (i) the container body comprises a second layer deposited on an inner surface of the first layer, the second layer comprising a metalloid, a carbon thin film, or a combination thereof, the second layer having a thickness of less than 100 nm, preferably less than 80 nm; and (ii) the container body further comprises an intermediate polymer layer disposed between the first layer and the second layer, the intermediate layer having a root mean square ("RMS") roughness of less than 20 nm, preferably less than 10 nm, and the intermediate layer having a thickness comprised between 1 and 100 μm, preferably between 20 and 80 μm; Three-dimensional hollow container.

2. The metalloid is silicon oxide (SiOx), boron trioxide (B ２ O ３ ), germanium dioxide (GeO ２ 2. The container of claim 1, wherein the carbon film is diamond-like carbon (DLC).

3. 3. The container of claim 1 or 2, wherein the intermediate layer comprises a polymer selected from the list of polyethylene terephthalate (PET), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polyglycolic acid (PGA), starch (TPS), polycaprolactone (PCL), or combinations thereof.

4. Container according to claim 1 or 2, wherein said intermediate layer is a co-extruded layer of polybutylene succinate-co-butylene adipate (PBSA) having a thickness comprised between 10 and 30 μm.

5. 3. A container according to claim 1 or 2, which is a three-dimensional article selected from the list of food trays, bottles, cans, closures, capsules, pods, lids.

6. A packaged product comprising: (i) at least one edible product for human or animal consumption in liquid, semi-liquid form, powder, gel, kibble, or paste form; (ii) at least one container according to claim 1 or 2 in which the edible product is packaged; Packaged products, including

7. 7. The packaged product of claim 6, wherein the edible product is selected from the list of mineral water-based drinks, dairy products, sauces, dressings, soups, coffee-based or cocoa-based products, plant-based meat or fish substitutes, smoothies, nutritional products for infants or adults, confectionery products, sports nutritional supplements, pet food.

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