Molded pulp product

Abstract

The invention relates to a method for producing a molded pulp product (1), the method comprising: a) shaping pulp (2); b) applying to the pulp a composite phase (3) comprising particles (4) of a polymer and a metal, metalloid or an oxide thereof; and c) converting the composite phase (3) into a coating (5) comprising a polymer and a continuous barrier (6) at least partially embedded within the polymer, the continuous barrier (6) comprising a metal, a metalloid or an oxide thereof; and to a molded pulp article.

Description

Technical Field

[0001] This invention relates to molded pulp articles with improved barrier properties and methods for producing the same. Background Technology

[0002] Molded pulp is a material that is increasingly used in packaging, particularly food packaging. A key benefit of these materials is their ease of recycling and biodegradability, often making them compostable at home. Existing technologies for molded pulp allow for the production of rigid containers, such as paper cans, bottles, or capsules for beverages. Made from cellulose fibers, molded pulp typically requires coating or lamination to increase its sealing and barrier properties (e.g., to prevent oxygen from entering).

[0003] Providing molded pulp with effective water vapor barrier remains a challenge and requires significant additional processing to achieve suitable barrier properties. Specifically, it requires providing effective barriers that do not interfere with the recyclability and biodegradability of the molded pulp.

[0004] The purpose of this invention is to solve one or more of the aforementioned problems. Summary of the Invention

[0005] A first aspect of the present invention relates to a method for producing molded pulp articles (1), the method comprising:

[0006] a) To shape the pulp (2);

[0007] b) Applying a composite phase (3) comprising particles (4) of polymer and metal, metalloid, or their oxides to the pulp; and

[0008] c) The composite phase (3) is converted into a coating (5) comprising a polymer and a continuous barrier (6) at least partially embedded in the polymer, the continuous barrier (6) comprising a metal, a metalloid, or an oxide thereof.

[0009] Applying the composite phase (3) may include applying a film of particles (4) comprising a polymer and a metal, a metalloid, or oxides thereof to the surface of the pulp (2), the particles (4) being dispersed throughout the polymer. Alternatively, applying the composite phase (3) may include applying an aqueous dispersion of the polymer and particles (4) comprising a metal, a metalloid, or oxides thereof to the surface of the pulp (2).

[0010] In the implementation scheme, steps a), b), and c) occur sequentially. Alternatively, step b) may occur before step a), and step a) may occur before step c). Further alternatively, steps a) and c) may occur simultaneously.

[0011] Converting the composite phase (3) into a coating (5) may optionally include fusing particles (4) of a metal, a quasi-metal, or their oxides by heating the composite phase (3). Heating the composite phase may include exposing the composite phase to microwave radiation.

[0012] The composite phase (3) may further include a binder. The binder may be a tetraalkyl orthosilicate, optionally selected from tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), and combinations thereof.

[0013] Transforming the composite phase (3) into a coating (5) may optionally involve bonding particles (4) of metals, metalloids or their oxides together with a binder by adding or activating a catalyst.

[0014] A second aspect of the invention relates to a molded pulp article (1) comprising: shaped pulp (2); and a coating (5) comprising a continuous barrier (6) and a polymer, the continuous barrier (6) comprising a metal, a metalloid, or an oxide thereof, wherein the continuous barrier (6) is at least partially embedded within the polymer.

[0015] The polymer can be selected from polylactic acid (PLA), polyvinyl alcohol (PVOH), polyhydroxyalkanoate (PHA), polyglycolic acid (PGA), butene glycol vinyl alcohol (BVOH), poly(butylene succinate-co-butylene adipate) PBSA, polybutylene terephthalate adipate (PBAT), and combinations thereof.

[0016] The metal, metalloid, or their oxides may be selected from aluminum, AlOx, SiOx, and combinations thereof.

[0017] The coating (5) may contain between 0.5% by weight and 15% by weight of a metal, a metalloid, or an oxide thereof. The coating (5) may have a thickness of 1 μm to 150 μm.

[0018] The third aspect of the invention relates to the use of a molded pulp article (1) according to the second aspect of the invention for packaging edible products for human or animal consumption.

[0019] The fourth aspect of the invention relates to a packaged edible product comprising a molded pulp article (1) according to the second aspect of the invention, the molded pulp article being at least partially filled with an edible product intended for human or animal consumption.

[0020] As used in this specification, the words “including,” “contains,” and similar terms should not be construed as having an exclusive or exhaustive meaning. In other words, they are intended to mean “including, but not limited to.” Attached Figure Description

[0021] Further features and advantages of the invention are described below in the description of the presently preferred embodiments given with reference to the accompanying drawings, and these features and advantages will be apparent from the description, wherein:

[0022] Figure 1 A schematic cross-section of a molded pulp article (1) according to the invention is shown. The molded pulp article (1) includes pulp (2) and a coating (5), the coating (5) including a continuous barrier layer (6) at least partially embedded in a polymer;

[0023] Figure 2 A schematic cross-section of a precursor of a molded pulp article (1) according to the invention is shown. The precursor of the molded pulp article (1) comprises pulp (2) and a composite phase (3) containing particles (4) of metal, quasi-metal, or oxides thereof that are at least partially embedded in a polymer. Detailed Implementation

[0024] "Dispersion coating" refers to a coating technique that applies an aqueous dispersion of fine polymer particles or polymer solutions to the surface of paper or paperboard to form a solid, non-porous film after drying. Dispersion coating can be performed using gravure printing, letterpress printing, rod, blade, die, curtain air knife, roll coating, or any other known paper coating method. Dispersion coating can produce much thinner layers than extrusion lamination and / or adhesive lamination because the polymers are mixed in an aqueous solution. This offers advantages in terms of polymer dosage, barrier properties, and the recyclability of the resulting paper structure. The goal of dispersion coating is to obtain a barrier layer against water, water vapor, grease, oil, gases, etc., through environmentally friendly coating. Another goal is to prepare the surface of paper materials for vacuum deposition processes.

[0025] "Fiber" refers to cellulose fibers that are usually extracted from plants, seeds, or trees; such fibers contain not only cellulose molecules, but also hemicellulose and lignin.

[0026] Molded pulp products, also known as molded fiber products, refer to products formed by molding fiber materials. These fiber materials can be obtained from recycled fiber sources such as paper or paperboard, or directly from natural fiber sources such as bagasse, bamboo, and straw. Molded pulp products are commonly used in packaging and are widely considered sustainable.

[0027] "Continuous barrier" means that the material forming the continuous barrier (e.g., aluminum, AlOx, SiOx, and combinations thereof) is essentially free of pores. Continuous barriers are not limited to a flat plane or layer following the surface of the molded pulp below, but can have complex morphologies due to the random distribution of the particles forming the continuous barrier.

[0028] Methods for molding pulp products

[0029] A first aspect of the present invention relates to a method for producing molded pulp articles, the method comprising:

[0030] a) To shape the pulp;

[0031] b) Applying a composite phase comprising polymer and particles of metal, metalloid, or oxides thereof to the pulp; and

[0032] c) Transforming the composite phase into a coating comprising a polymer and a continuous barrier material at least partially embedded within the polymer, the continuous barrier material comprising a metal, a metalloid, or an oxide thereof.

[0033] In the implementation, forming the pulp includes pressing the pulp into a mold.

[0034] In one embodiment, applying the composite phase includes applying a film comprising particles of polymer and metal, metalloid, or oxides thereof, dispersed throughout the polymer, to the surface of the pulp. Applying the film may include placing the film in contact with the surface of the pulp and laminating it. Such lamination may be performed simultaneously with the conversion of the composite phase to a coating.

[0035] In this implementation, the particles have a non-uniform distribution across the entire thickness of the film, with the highest concentration oriented towards the center. This higher concentration at the center reduces the total amount of particles required to form a continuous barrier. Such a distribution can be achieved by using co-extrusion to form the film, with one or more central layers having a higher particle concentration than the outer layers. It should be understood that any suitable method, such as low-temperature SEM or EDX, can be used to determine this distribution.

[0036] In this embodiment, the film has a thickness of 1 μm to 130 μm. Preferably, the film has a thickness of 10 μm to 100 μm, more preferably 40 μm to 90 μm, and most preferably 60 μm to 80 μm.

[0037] In an embodiment, applying the composite phase comprises applying an aqueous dispersion of a polymer and particles of a metal, metalloid, or oxide thereof to the surface of the pulp. The aqueous dispersion may be in liquid or paste form. The aqueous dispersion may have a solids content of 10% w / w to 50% w / w, preferably 20% w / w to 40% w / w, or more preferably 25% w / w to 35% w / w. The solids content is the content of the aqueous dispersion consisting of the polymer and particles. The particles may comprise 0.1% w / w to 5% w / w of the aqueous dispersion, preferably 0.2% w / w to 4% w / w, or more preferably 0.25% w / w to 3.5% w / w. The polymer may comprise 5% w / w to 50% w / w of the aqueous dispersion, preferably 10% w / w to 40% w / w, or more preferably 20% w / w to 30% w / w. The particles may be present in an amount of 0.5% w / w to 15% w / w, preferably 1% w / w to 10% w / w, or more preferably 3% w / w to 7% w / w of the polymer. The aqueous dispersion may be dried prior to conversion into a coating. Alternatively, the aqueous dispersion may be dried during the conversion into a coating.

[0038] In this embodiment, the aqueous dispersion is applied with a thickness of 1 μm to 40 μm. Preferably, the aqueous dispersion is applied with a thickness of 5 μm to 35 μm, more preferably 20 μm to 30 μm. In this embodiment, the aqueous dispersion is applied multiple times to increase the total amount of material applied to the pulp. For example, the aqueous dispersion may be applied up to 2 times, up to 4 times, or up to 6 times.

[0039] Steps a), b), and c) can occur sequentially. In other words, the pulp is shaped, a composite phase is applied to the shaped pulp, and then the composite phase is converted into a coating to provide a molded pulp article.

[0040] In one implementation, step b) occurs before step a), and step a) occurs before step c). In other words, the pulp can be provided unformed (e.g., as a sheet) and a composite phase is applied. The pulp with the composite phase is then formed into the shape of a molded pulp article, and the composite phase of the formed pulp is then converted into a coating.

[0041] Steps a) and c) can occur simultaneously after step b). In other words, the pulp can be provided unformed (e.g., as a sheet) and a composite phase is applied. The pulp is then shaped into a molded pulp article when the composite phase is converted into a coating.

[0042] Transforming a composite phase into a coating can include fusing particles of metals, metalloids, or their oxides into a coherent mass (i.e., a continuous barrier). This can be achieved by subjecting the particles to heating. In one embodiment, microwave radiation is used to heat the particles. Advantageously, heating using microwave radiation primarily and rapidly heats the particles at the contact points, thereby limiting the exposure of the polymer or pulp to heat and minimizing the degradation of these materials.

[0043] When using microwave radiation to transform a composite phase into a coating, the microwave radiation can reach 600 W / cm². 2 Up to 1200W / cm 2 Preferably 700W / cm 2 Up to 1100W / cm 2 , More preferably 800W / cm 2 Up to 1000W / cm 2 The power. Microwave radiation can be applied for a period of 0.5 to 10 seconds, preferably 1 to 5 seconds. Any suitable method or device can be used to apply microwave radiation to the composite phase.

[0044] In the implementation scheme, the composite phase further comprises organic acids, such as carboxylic acids (e.g., acetic acid, citric acid, malic acid, and tartaric acid) or sulfonic acids (e.g., methanesulfonic acid and p-toluenesulfonic acid). It is not desirable to be bound by theory, but it is believed that organic acids induce partial dissolution and softening of the particles, further enhancing their fusion.

[0045] When used, the organic acid can be used in an amount of 0.1% w / w to 5% w / w relative to the particles, preferably 0.5% w / w to 3% w / w relative to the particles, and more preferably 1% w / w to 2% w / w relative to the particles.

[0046] In this embodiment, the composite phase further comprises a binder. The binder is operable to be covalently bonded to itself and the surface of the particles. The binder may be a tetraalkyl orthosilicate, such as tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), or a combination thereof. These binders are additionally covalently bonded to the surface of the pulp fibers.

[0047] When used, the adhesive is present in an amount of 0.1% w / w to 10% w / w relative to the particles, preferably 0.5% w / w to 7% w / w relative to the particles, and more preferably 1% w / w to 5% w / w relative to the particles.

[0048] When using a binder, converting a composite phase into a coating involves bonding particles of a metal, metalloid, or their oxides together with the binder to form a continuous barrier. For tetraalkyl orthosilicate binders, this involves the hydrolysis of hydroxyl groups to leave a silica network to which the particles bind. Converting a composite phase containing a binder into a coating may include heating the composite phase and / or adding a catalyst. Examples of catalysts include acids, such as hydrochloric acid or acetic acid.

[0049] In an embodiment, the transformation of the composite phase includes, for example, fusing the particles by heating as described above and bonding the particles together with a binder.

[0050] Molded pulp products

[0051] A second aspect of the invention relates to a molded pulp article comprising: shaped pulp; and a coating comprising a continuous barrier and a polymer, the continuous barrier comprising a metal, a metalloid, or an oxide thereof, wherein the continuous barrier is at least partially embedded within the polymer.

[0052] Continuous barriers can be formed by fusing particles of metal or metal oxide into a coherent mass. Alternatively or otherwise, continuous barriers can be formed by bonding particles of metal or metal oxide together.

[0053] The coating may further include a binder. The binder may be a tetraalkyl orthosilicate, such as tetramethyl orthosilicate, tetraethyl orthosilicate, or a combination thereof.

[0054] The coating can have a thickness of 1 μm to 150 μm. In embodiments, the coating has a thickness of 15 μm to 130 μm, preferably 20 μm to 100 μm, more preferably 30 μm to 80 μm, or most preferably 40 μm to 60 μm. In alternative embodiments, the coating has a thickness of 5 μm to 35 μm, more preferably 8 μm to 20 μm, and most preferably 10 μm to 15 μm.

[0055] Molded pulp products can be cans, cups, plates, bottles or capsules.

[0056] Molded pulp products can be produced by the method of the first aspect of the present invention.

[0057] Particles of metals, metalloids, or their oxides

[0058] The particles of metals, metalloids, or their oxides may be selected from aluminum, AlOx, SiOx, or combinations thereof.

[0059] In the embodiments, the particles account for 0.5% to 15% by weight of the coating. The particles are required to be present in an amount sufficient to form a continuous network when the composite phase transforms into the coating. Preferably, the particles account for between 1% and 10% by weight of the coating, more preferably between 1.5% and 8% by weight, and most preferably between 2% and 5% by weight.

[0060] The particles may have an average particle size between 10 nm and 1 μm, preferably between 50 nm and 750 nm, and more preferably between 100 nm and 500 nm. Any suitable technique can be applied to measure the particle size, such as scanning electron microscopy (SEM) as described in ISO 19749:2021 or transmission electron microscopy (TEM) as described in ISO 21363:2020.

[0061] polymer

[0062] In this embodiment, the polymer is water-dispersible. This water dispersibility allows for the use of aqueous dispersions in the production of molded articles, which is more environmentally friendly and cost-effective. In this embodiment, the polymer is biodegradable. This biodegradability allows the molded pulp articles to be biodegradable. Preferably, the polymer is selected from polylactic acid (PLA), polyvinyl alcohol (PVOH), polyhydroxyalkanoate (PHA), polyglycolic acid (PGA), butene glycol vinyl alcohol (BVOH), poly(butylene succinate-co-butylene adipate) PBSA, polybutylene terephthalate (PBAT), and combinations thereof.

[0063] Uses of molded pulp products

[0064] The molded pulp articles described herein are used for packaging edible products intended for human or animal consumption. Preferably, the molded pulp articles are in the form of partially open containers, through which the edible products are inserted. Once the molded pulp articles are filled, the openings are sealed, preferably with a polymer film, a removable cap (e.g., a screw cap), or foil.

[0065] A packaged edible product comprising molded pulp articles as described herein, at least partially filled with edible products intended for human or animal consumption.

[0066] Preferably, the edible product is a powder, gel, or coarsely ground food, and is selected from the list of: soluble coffee, nutritional compositions for infants, adults, or the elderly, soups, sweets or confectionery, chocolate products, dried animal products, and dairy products.

Claims

1. A method of producing a molded pulp article (1), the method comprising: a) shaping the pulp (2); b) applying a composite phase (3) comprising a polymer and particles (4) of a metal, a metalloid, or an oxide thereof to the pulp; and c) converting the composite phase (3) into a coating (5) comprising the polymer and a continuous barrier (6) at least partially embedded within the polymer, the continuous barrier (6) comprising a metal, a metalloid, or an oxide thereof.

2. The method of claim 1, wherein applying the composite phase (3) comprises applying a thin film comprising the polymer and particles (4) of a metal, a metalloid, or an oxide thereof to a surface of the pulp (2), the particles (4) being dispersed in the polymer.

3. The method of claim 1, wherein applying the composite phase (3) comprises applying an aqueous dispersion of a polymer and particles (4) of a metal, a metalloid, or an oxide thereof to a surface of the pulp (2).

4. The method of any one of claims 1 to 3, wherein: i. step a), step b), and step c) occur in order; or ii. step b) occurs before step a), and step a) occurs before step c); or iii. wherein step a) and step c) occur simultaneously.

5. The method of any one of the preceding claims, wherein converting the composite phase (3) into a coating (5) comprises fusing the particles (4) of a metal, a metalloid, or an oxide thereof, optionally by heating the composite phase (3).

6. The method of claim 5, wherein heating comprises exposure to microwave radiation.

7. The method of any one of the preceding claims, wherein the composite phase (3) further comprises a binder.

8. The method of claim 7, wherein the binder is a tetraalkyl orthosilicate, optionally wherein the tetraalkyl orthosilicate is selected from the group consisting of tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), and combinations thereof.

9. The method of claim 7 or claim 8, wherein converting the composite phase (3) into the coating (5) comprises binding the particles (4) of a metal, a metalloid, or an oxide thereof to one another with the binder, optionally by adding or activating a catalyst.

10. A molded pulp article (1), the molded pulp article comprising: a shaped pulp (2); and a coating (5) comprising a continuous barrier (6) and a polymer, the continuous barrier (6) comprising a metal, a metalloid, or an oxide thereof, wherein the continuous barrier (6) is at least partially embedded within the polymer. ​ 11. The molded pulp article (1) according to claim 10, wherein the polymer is selected from the group consisting of polylactic acid (PLA), polyvinyl alcohol (PVOH), polyhydroxyalkanoate (PHA), polyglycolic acid (PGA), butylene vinyl alcohol (BVOH), poly(butylene succinate-co-butylene adipate) PBSA, poly(butylene adipate-co-terephthalate) (PBAT), and combinations thereof.

12. The molded pulp article (1) according to claim 10 or claim 11, wherein the particles (4) of metal, metalloid, or oxide thereof are selected from the group consisting of aluminum, AIOx, SiOx, and combinations thereof.

13. The molded pulp article (1) according to any one of claims 10 to 12, wherein the coating (5) comprises between 0.5% w / w and 15% w / w of metal, metalloid, or oxide thereof.

14. The molded pulp article (1) according to any one of claims 10 to 13, wherein the coating (5) has a thickness of 1 pm to 150 pm.

15. Use of the molded pulp article (1) according to any one of claims 10 to 14 for packaging an edible product for human consumption or animal consumption.

16. A packaged edible product comprising the molded pulp article (1) according to any one of claims 10 to 14, the molded pulp article being at least partially filled with an edible product for human consumption or animal consumption.

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