Material for making packaging comprising a polyhydroxyalkanoate resin mixed with a very high content of cellulose

Abstract

The present invention is primarily directed to a hollow container made of a polymer compound, said polymer compound comprising: (i) a polyhydroxyalkanoate (PHA) resin; (ii) hardwood cellulose fibers having a length falling within the range of 15 μm to 150 μm, preferably within the range of 20 μm to 120 μm, and having a density of at least 1.0 g / cm3, preferably at least 1.5 g / cm3, said fibers being present in an amount of more than 50% by weight of the total compound weight.

Description

[Technical field]

[0001] The present invention relates to a material for making packaging that includes a polyhydroxyalkanoate resin mixed with a very high content of cellulose for high biodegradability and enhanced mechanical properties. [Background technology]

[0002] Plastic packaging is often used in economic activities and people's daily lives. It has several advantages, such as flexibility and light weight. Light weight contributes, for example, to fuel savings and CO2 reduction during transportation. The barrier properties of plastic packaging help to reduce food waste, as they have a positive effect on extending shelf life. The barrier properties also help to ensure food safety.

[0003] However, according to the European Strategy for Plastics in a Circular Economy recently published by the European Commission, around 25.8 million tonnes of plastic waste is generated in Europe every year, less than 30% of this waste is recovered for recycling, and as much as 150,000-500,000 tonnes of plastic waste enters the oceans every year.

[0004] There are great efforts in industry and commerce to ensure the reduction of plastic waste. For example, supermarkets and shops tend to replace plastic bags with paper bags. However, replacing plastic with paper in food packaging is not an easy task due to the fact that paper is a material sensitive to moisture, grease, and many other ingredients present in edible products. Also, the lack of barrier properties of paper against oxygen, moisture or liquids does not meet the requirements for shelf life extension for most food or beverage products. Furthermore, any change in packaging material must not compromise the safety of consumers. The packaging must not only serve to protect the food, but also be robust enough to be handled by machines during the production process and such that the food product can be effectively presented.

[0005] New polymers have been found that can be derived from renewable resources to replace non-renewable plastics and offer similar properties to classical polymers such as polyolefins.

[0006] Polyhydroxyalkanoates (PHAs) are a type of biopolymer naturally produced by bacteria that offer interesting features for food packaging. In the following description, by convention and for the sake of simplicity of description and interpretation, polyhydroxyalkanoates are collectively referred to as "PHAs", although various types of polyhydroxyalkanoates include types other than PHAs.

[0007] Furthermore, PHA is somehow biodegradable material, making it an environmentally friendly material for packaging food products.

[0008] However, its degradation is limited and it may not be possible to meet the requirements for biodegradability within a given time frame to meet international biodegradability standards.

[0009] In addition, the crystallization rate of PHAs is slow, which requires long cycle times when they are processed into packaging by injection molding processes, which affects the entire production chain.

[0010] Furthermore, when injection molded by conventional injection molding techniques, PHAs have a relatively large shrinkage upon cooling compared to synthetic polyolefins, which makes the design and manufacture of injection molds difficult, since there is no guarantee that the injection molded part will not shrink in an unexpected manner after cooling that adversely affects its function or use, and the final dimensions of the injection molded part must be highly predictable.

[0011] To address these shortcomings of PHA, some solutions have been developed, such as the use of inert fillers (e.g., CaCOH) to promote nucleation or reduce the cost of PHA-based composites. However, the above additives do not improve the degradability of PHA materials.

[0012] To solve the above problems with inert fillers, in PCT Publication WO 2021 / 64422 (A1) by Moving Beans Ltd., the inventors propose injection molding of beverage capsules from PHA resin, where a filler made of bamboo and rice husk cellulose fibers is added to the PHA resin during injection. The cellulose filler is introduced into the injection machine through a hopper separate from the resin hopper and mixed into the resin by use of a filling screw in the injection press. In this PCT publication, it is argued that cellulose fibers are a good alternative to inorganic fillers, since they are biodegradable.

[0013] Additionally, the cellulose fibers create preferential initiation sites for bacteria to initiate and advance biodegradation within manufactured articles made from the fiber-plastic resin blend: the more fiber there is, the more efficient the biodegradation process.

[0014] Also, EP 1693416 discloses the use of kenaf fibres to make blends with biodegradable polymers for use in injection moulding of articles or in the manufacture of films. The kenaf fibres used in connection with the invention are long fibres having a length of up to 20 mm.

[0015] However, the present inventors have recognized that the above prior art documents contain several important shortcomings.

[0016] First, adding the cellulosic material through a feed hopper of the injector that is separate from the hopper through which the PHA resin is fed to the injector creates a fire hazard due to the heat generated by the injector itself.

[0017] Secondly, and importantly, the inventors have discovered that very high shear stresses occur within the matrix of the material composed of PHA resin and cellulosic fibers, so that the total amount of cellulosic fibers cannot exceed a certain limit. Essentially, the more fibers there are in the packaging material, the more viscous the material will be, and the higher the viscosity, the more difficult it will be to process into the final package. To make the material processable, it is necessary to increase the temperature of the injection machine, but also the involvement of a screw that forces the raw material of the molten material into the mold cavity. However, increasing the temperature of the injection machine causes a decrease in viscosity, which is of course undesirable since it causes damage to the fibers and polymer. Furthermore, an increased involvement of the screw increases the shear stress applied to the material, which results in more heat generation and mechanical and thermal degradation of the fibers. And last but not least, the more fibers there are in the material, the more non-Newtonian (shear thinning) it becomes. This means that the applied shear stress is localized at the very edge of the product, and the center of the product does not experience shear stress. Thus, the localization of high shear stresses near the walls of the manufactured packages can result in localized high temperature increases during processing, thus causing localized damage to the material, while other areas of the same product remain substantially undamaged, resulting in a substantial reduction in the overall quality and mechanical resistance of the manufactured packaging, which is of course undesirable.

[0018] Third, due to the fact that injection molded articles made from unstabilized resins or compounds undergo shrinkage during cooling (after the injection molded article is removed from the injection press), injection molded articles made according to the invention disclosed in WO '422 will undergo shrinkage after cooling, which is undesirable as it affects the dimensions of the final packaging article.

[0019] In view of the above, there is a need for a packaging construction material that is suitable for manufacturing techniques to create highly biodegradable packages of various volumes, and that overcomes the main drawbacks of the solutions already available in the prior art as described above.

[0020] [Summary of the invention] The above object is achieved by a hollow vessel as described in the appended claims, in particular a hollow vessel made of a polymer compound, said polymer compound having (i) a polyhydroxyalkanoate (PHA) resin; (ii) hardwood cellulose fibers having a length comprised within the range of 15 μm to 150 μm, preferably within the range of 20 μm to 120 μm, and a density of at least 1.0 g / cm3, preferably at least 1.5 g / cm3, said fibers being present in an amount of more than 50% by weight of the total compound weight; This is achieved by a hollow vessel comprising:

[0021] The inventors have found that the length of the fibers used in connection with the present invention is important to ensure that the compound formed therewith is processable in the manufacturing techniques applicable to the present invention, particularly extrusion blow molding or compression molding. If the fibers are too long (i.e., greater than 150 μm), the compound will not be processable because the long fibers will block the flow path of the compound in the manufacturing equipment.

[0022] The present invention further relates to a polymeric compound for extrusion blow molding or compression molding of hollow containers, said polymeric compound comprising: (i) a polyhydroxyalkanoate (PHA) resin; (ii) hardwood cellulose fibers having a length comprised within the range of 15 μm to 150 μm, preferably within the range of 20 μm to 120 μm, and a density of at least 1.0 g / cm3, preferably at least 1.5 g / cm3, said fibers being present in an amount of more than 50% by weight of the total compound weight; The present invention relates to a polymer compound comprising:

[0023] In another aspect, the present invention provides a method for forming a bottle for edible liquids by extrusion blow molding of a polymeric compound as described above, comprising the steps of: (i) extruding a parison from a molten compound according to the present invention; (ii) placing the parison adjacent a blow mold, the mold being in an open position; (iii) closing the blow mold around the parison and blowing a fluid into the parison so that the parison expands to conform to an inner cavity surface; (iv) opening the mold to remove the stretched parison formed into a bottle; The present invention relates to a method comprising the steps of:

[0024] In yet another aspect, the present invention provides a method for forming a beverage capsule by compression molding, the method comprising the steps of: (i) forming liquid or semi-liquid droplets of a molten compound according to the present invention; (ii) placing the droplet of molten compound into a mold having at least two cavities movable relative to one another, the mold being in an open position; (iii) closing the mold and applying pressure to the molten compound to form a capsule; (iv) opening the mould to remove the formed capsule; The present invention relates to a method comprising the steps of:

[0025] It should be noted that PHAs modified by chemical reaction with maleic anhydride are known from the prior art and have been previously found to improve the grafting performance between PHA and cellulose fibers, therefore, although not absolutely necessary, PHAs modified with maleic anhydride are advantageously a preferred option within the scope of the present invention.

[0026] Last but not least, the present invention relates to the use of the compounds described herein for the manufacture by an extrusion blow moulding process of bottles suitable for containing edible liquids or for the manufacture by a compression moulding process of capsules suitable for use in beverage preparation machines. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The present invention mainly relates to a hollow vessel as described in the appended claims, in particular a hollow vessel made of a polymer compound, said polymer compound having (i) a polyhydroxyalkanoate (PHA) resin; (ii) hardwood cellulose fibers having a length comprised within the range of 15 μm to 150 μm, preferably within the range of 20 μm to 120 μm, and a density of at least 1.0 g / cm3, preferably at least 1.5 g / cm3, said fibers being present in an amount of more than 50% by weight of the total compound weight; The present invention relates to a hollow container comprising:

[0028] By "hollow container" is meant any article having a three-dimensional shape and used to package an edible product for human or animal consumption. This includes not only the container receptacle within which the product is packaged, but also any three-dimensional container element useful for completing the receptacle, such as, for example, a receptacle closure.

[0029] By "hardwood cellulose fibers" is meant fibers obtained from deciduous trees ("hardwoods") and having a length of less than 1.5 millimeters, preferably less than 0.5 mm. Hardwood cellulose fibers suitable for use in connection with the present invention are sourced from the following trees (Latin names given in parentheses): ash (Genus Fraxinus), beech (Genus Fagus), linden (Genus Tilia), birch (Genus Betula), black cherry (Genus Prunus), black walnut / butternut (Genus Juglans), cottonwood (Genus Populus), elm (Genus Ulmus), hackberry (Genus Celtis), hickory (Genus Carya), holly (Genus Ilex), black locust (Genus Robinia); Genus Gleditsia), magnolia (Genus Magnolia), maple (Genus Acer), oak (Genus Quercus), poplar (Genus Poplar), red alder (Genus Alnus), paulownia (Genus Paulownia), sassafras (Genus Sassafras), maple tree (Genus Liquidambar), plane tree (Genus Platanus), chupelo (Genus Nyssa), willow (Genus Salix), tulip tree (Genus Liriodendron), eucalyptus, or combinations thereof.

[0030] The fibers are not compatibilized, i.e., they have not been chemically treated to enhance compatibility with other raw materials.

[0031] According to the principles of the present invention, it is now possible to obtain hollow containers of various volumes, especially large volume containers, which are made from a single-layer compound of polyhydroxyalkanoate and cellulose fibers, and have low shrinkage and improved biodegradation properties. Such containers are made possible by using a compound of PHA and cellulose fibers in a compression molding or extrusion blow molding process, which allows the compound to contain a higher amount of cellulose fibers than the articles produced by mixing PHA and cellulose fibers in a conventional injection molding process, since the process causes less shear and degradation of the fibers. Furthermore, the presence of fibers with high density in the compound formulation makes it possible to produce packages that do not shrink when cooled and therefore have uniform and reproducible dimensional stability.

[0032] Moreover, the PHA and fiber compound according to the present invention is made to produce ready-to-use granules or pellets, which can be processed directly into machines for the production of hollow containers by extrusion blow molding or compression molding. The use of such ready-to-use compound in the form of pellets or granules eliminates the need to add powdered fibers separately from the PHA resin in an open hopper. Generally, powders have a high specific surface area, i.e., they have high reactivity, and when such powders are mixed with other raw materials and put into a screw mixer, they are prone to explosion or fire when subjected to heat or friction. In the present invention, since there is no cellulose powder (cellulose is mixed with resin beforehand during the production of the container), the container production process is fully compatible with safety aspects.

[0033] Furthermore, in the present invention, the density of the fibers constituting the compound is such that the product does not shrink upon cooling, and such fibers are also food safe, so that the packaging is suitable for containing edible products.

[0034] Preferably, the polymeric compounds according to the invention and the packaging made from them are home compostable, which means that the compounds and the packaging must achieve at least 90% biodegradation over 12 months at ambient temperature (25±5°C) and 90% disintegration after 6 months at ambient temperature (25±5°C) according to the standards for home composting performance: EN 13432, AS 5810, NF T 51800, prEN17427.

[0035] The ecotoxicological and chemical analysis levels set out in the standards above must also be met.

[0036] Thus, in a highly preferred embodiment of the present invention, the polyhydroxyalkanoate fraction of the compound and resulting packaging is poly 3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH).

[0037] PHBH is a polyester similar to polyethylene (PE) and polypropylene (PP) and has excellent biodegradability in a variety of different conditions. For example, PHBH is compostable at ambient temperature (home compostable) and also biodegradable in soil and seawater. As an alternative resin to polyolefins such as polyethylene (PE) or polypropylene (PP), PHBH can be used in a variety of applications. The most suitable applications are agricultural mulch films, food packaging, garbage bags, fishing nets, etc., which are difficult to recollect and sort after use. Furthermore, since PHBH decomposes into carbon dioxide and water over time when exposed to microorganisms, PHBH may play a role in solving the problem of plastic waste in developing countries.

[0038] PHBH is produced by microbial fermentation using vegetable oil as a carbon source. PHBH can be processed into various plastic products using commonly used equipment. After use, PHBH biodegrades into carbon dioxide and water in the presence of microorganisms. In other words, PHBH produces a carbon-neutral system. Furthermore, the biodegradability of PHBH in seawater provides an important solution to the problem of marine microplastic pollution, which is a major global issue.

[0039] PHBH has excellent biodegradability under aerobic, anaerobic, aquatic and composting conditions, proving to be an environmentally friendly plastic.

[0040] Under aerobic conditions, PHBH exhibits a higher level of biodegradability than cellulose when tested according to the ISO 14855 standard. Through biodegradation, PHBH is converted into reusable resources such as compost and methane gas.

[0041] PHBH is available in two grades, soft type 151C and hard type X131A, and can be used for a variety of applications. PHBH has better gas barrier properties and moisture barrier properties than other biodegradable polymers.

[0042] The hollow container according to the present invention is preferably a bottle for containing an edible liquid, said bottle being produced by blow moulding an extruded parison, said parison being stretched in at least one of the longitudinal or lateral directions.

[0043] Alternatively, the hollow container may be a capsule (or pod or pad) for containing beverage precursor ingredients for preparing a beverage in a beverage preparation machine, the capsule being formed by compression moulding.

[0044] The present invention further relates to a polymeric compound for extrusion blow molding or compression molding of hollow containers, said polymeric compound comprising: (i) a polyhydroxyalkanoate (PHA) resin; (ii) hardwood cellulose fibers having a length comprised within the range of 15 μm to 150 μm, preferably within the range of 20 μm to 120 μm, and a density of at least 1.0 g / cm3, preferably at least 1.5 g / cm3, said fibers being present in an amount of more than 50% by weight of the total compound weight; The present invention relates to a polymer compound comprising:

[0045] In the context of the present invention, the polyhydroxyalkanoate (PHA) resins that can be used to prepare the compounds used to manufacture the hollow containers are selected from the list of poly 3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), poly-3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV) or poly-3-hydroxyhexanoate (PHHx), and derivatives thereof, or combinations thereof.

[0046] In one possible embodiment of the invention, the PHA resin selected from the list above may be completed by a quantity of at least a second polymer selected from the list: polybutylene adipate terephthalate (PBAT), polypropylene glycol (PG), polyvinyl alcohol (PVA), starch, or a combination thereof.

[0047] The compound also preferably contains at least one plasticizer. Any plasticizer commonly used in polyhydroxyalkanoate processing can be used, but examples thereof include lecithin, mannitol, polyesters, sebacates, citrates, fatty acids, fatty alcohols, fatty acid esters of adipic acid, succinic acid, or glucaric acid, lactates, alkyl diesters, citrates, alkyl methyl esters, dibenzoates, propylene carbonate, caprolactone diols having a number average molecular weight of 200 to 10,000 g / mol, polyethylene glycols having a number average molecular weight of 400 to 10,000 g / mol, and the like. Preferred are those which can be selected from the list of esters of oils such as oleic acid, esters of vegetable oils such as soybean oil, long chain alkyl acids, adipates, glycerol, isosorbide derivatives, surfactants, terpenes D-limonene (LIM), tri(ethylene glycol) bis(2-ethylhexanoate) (TEGB), tributyrin, triethanolamine (TEA), triethyl citrate (TEC), trilaurin, urea, water, waxes, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, sebacic acid or adipic acid, or mixtures thereof.

[0048] Furthermore, the compound used to manufacture the container according to the invention may advantageously contain at least one nucleating agent. Any nucleating agent conventionally used in the processing of PHAs may be used, but preferably the nucleating agent selected is selected from the group consisting of sulfur, polyvinylpyrrolidone (PVP), erythritol, pentaerythritol, dipentaerythritol, artificial sweeteners such as saccharin, orotic acid, stearates, sorbitol, mannitol, polyester waxes, chitin, cyclodextrin complexes, cyclohexylphosphonic acid / zinc stearate, dibasic acids, inorganic metal salts, organic metal salts, organic phosphonic acid-based systems, starch, compounds with a 2:1 / 2:1 crystalline chemical structure, and mixtures thereof.

[0049] Compounds suitable for use in connection with the present invention may also further comprise a chain extender preferably selected within the list of anhydrides, carbodiimides, carboxylates, epoxides, isocyanates, at least one inorganic filler, at least one mineral oil, peroxides, or combinations thereof. EXAMPLES

[0050] Example 1: [Table 1]

[0051] The compound is prepared according to the above list of raw materials and then processed into a bottle for containing mineral water. The bottle is generally made according to state-of-the-art extrusion processes by blow molding an extruded parison, which is stretched both longitudinally and transversely. The bottle thus obtained is suitable for containing 1 liter of mineral water.

[0052] Example 2: [Table 2]

[0053] The compound is prepared according to the above list of raw materials and then processed into a closure for capping / closing the bottle. The closure is manufactured by compression molding according to known techniques (the manufacturing environment can be adapted to the properties of the compound within the framework of the practice).

[0054] 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 spirit and 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.

Claims

1. A hollow container made of a polymer compound, wherein the polymer compound is (i) a polyhydroxyalkanoate (PHA) resin, and (ii) hardwood cellulose fibers having a length within the range of 15 μm to 150 μm, preferably within the range of 20 μm to 120 μm, and having a density of at least 1.0 g / cm3, preferably at least 1.5 g / cm3, and wherein the hardwood cellulose fibers are present in an amount of more than 50% by weight of the total compound weight, A hollow container characterized by comprising.

2. The hollow container according to claim 1, which is extrusion blow-molded or compression-molded.

3. The hollow container according to claim 1, wherein the polyhydroxyalkanoate resin is selected from the list of poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), poly-3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV), or poly-3-hydroxyhexanoate (PHHx), and derivatives thereof, or combinations thereof.

4. A bottle for containing an edible liquid, the bottle being produced by blow-molding an extruded parison, the parison being stretched in at least one of the longitudinal direction or the transverse direction, the hollow container according to claim 1.

5. A capsule for containing a beverage precursor raw material for preparing a beverage in a beverage preparation machine, the capsule being formed by compression molding, the hollow container according to claim 1.

6. The hollow container according to any one of claims 1 to 5, wherein the hardwood cellulose fiber is supplied from a tree of Paulownia (Genus Paulownia), beech (Genus Fagus), linden (Genus Tilia), birch (Genus Betula), black cherry (Genus Prunus), walnut (Genus Juglans), poplar (Genus Populus), elm (Genus Ulmus), hackberry (Genus Celtis), hickory (Genus Carya), holly (Genus Ilex), locust (Genus Robinia; Genus Gleditsia), magnolia (Genus Magnolia), maple (Genus Acer), oak (Genus Quercus), poplar (Genus Populus), red alder (Genus Alnus), paulownia (Genus Paulownia), sassafras (Genus Sassafras), sweetgum (Genus Liquidambar), sycamore (Genus Platanus), tupelo (Genus Nyssa), willow (Genus Salix), tulip tree (Genus Liriodendron), eucalyptus, or a combination thereof.

7. A polymer compound for the extrusion blow molding or compression molding of a hollow container, wherein the polymer compound comprises (i) a polyhydroxyalkanoate (PHA) resin, and (ii) hardwood cellulose fibers having a length in the range of 15 µm to 150 µm, preferably in the range of 20 µm to 120 µm, and a density of at least 1.0 g / cm3, preferably at least 1.5 g / cm3, wherein the hardwood cellulose fibers are present in an amount of more than 50% by weight of the total compound weight. A polymer compound, characterized by comprising the above.

8. The polymer compound according to claim 7, wherein the polyhydroxyalkanoate resin is selected from the list of poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), poly-3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV), or poly-3-hydroxyhexanoate (PHHx), and derivatives thereof, or combinations thereof.

9. The polymer compound according to claim 7, wherein the hardwood cellulose fiber is supplied from a tree of or a combination of Torneria (Torneria), beech (Fagus), cinnamon (Cinnamomum), oak (Quercus), black cherry (Prunus), walnut (Juglans), box elder (Acer), willow (Salix), elm (Ulmus), hickory (Carya), holly (Ilex), arrowhead (Sagittaria), magnolia (Magnolia), maple (Acer), poplar (Populus), red alder (Alnus), paulownia (Paulownia), sassafras (Sassafras), Euonymus, Platanus, tupelo (Nyssa), willow (Salix), elm (Ulmus), eucalyptus.

10. In order, (i) extruding a parison from a molten compound of the polymer compound according to any one of claims 7 to 9; (ii) placing the parison in the vicinity of a blow mold, the blow mold being in an open position; (iii) closing the blow mold around the parison and blowing a fluid into the parison so that the parison expands and conforms to the inner surface of the cavity; (iv) opening the blow mold and taking out the stretched parison formed in a bottle shape; A method for forming a bottle for an edible liquid by extrusion blow molding of the polymer compound according to any one of claims 7 to 9, comprising the steps.

11. In order, (i) forming liquid or semi-liquid droplets of a molten compound of the polymer compound according to any one of claims 7 to 9; (ii)a step of disposing droplets of the molten compound in a mold having at least two cavities movable relative to each other, the mold being in an open position; (iii)a step of closing the mold and applying pressure to the molten compound to form a capsule; (iv)a step of opening the mold and removing the formed capsule; A method for forming a beverage capsule by compression molding, comprising:

12. Use of a polymer compound according to any one of claims 7 to 9 for production by an extrusion blow molding method of a bottle suitable for containing an edible liquid.

13. Use of a polymer compound according to any one of claims 7 to 9 for production by a compression molding process of a capsule suitable for use in a beverage preparation machine.