Hybrid moulded pulp object

Abstract

The present invention relates to a moulded pulp article, the moulded pulp article comprising: a shaped pulp comprising cellulose fibres; and a polymer reinforcement. The polymer reinforcement may be in the form of polymer dispersed throughout the shaped pulp and / or in the form of a polymer interlayer disposed between the shaped pulp and a tactile layer.

Description

[0001] HYBRID MOULDED PULP OBJECT

[0002] Field of the invention

[0003] The present invention relates to moulded pulp articles with improved robustness and / or barrier properties and methods for their production.

[0004] Background of the invention

[0005] Moulded pulp is a material that is used with increasing frequency for packaging, particularly of foodstuffs. A key benefit of these materials is that they are easily recycled and biodegrade, often being home compostable. Existing technologies of moulded pulp allow the production of rigid containers such as paper cans, paper bottles or capsules for beverages through wet or drying processing of cellulose fibres. However, moulded pulp articles often lack mechanical robustness, which is exacerbated by exposure to excessive humidity or liquid water. This is especially true of moulded pulp articles formed by dry processes, which rapidly swell and delaminate on exposure to water.

[0006] Internal coatings or liners are often applied to enhance the barrier properties of moulded pulp articles (e.g. to oxygen, water, and grease). However, these do not protect the external surfaces of the articles from environmental conditions. External coatings or liners may be used, but these detract from the paper-feel of the moulded article. In addition, these coatings or liners often fail to improve the mechanical properties of the moulded pulp article and can compromise the biodegradable nature of the moulded pulp article.

[0007] It is an object of the present invention to solve one or more of the foregoing problems. Summary of the invention

[0008] A first aspect of the present invention relates to a moulded pulp article, the moulded pulp article comprising: a shaped pulp comprising cellulose fibres; and a polymer reinforcement.

[0009] The polymer reinforcement may comprise polymer dispersed throughout the shaped pulp. The polymer may comprise up to 50 wt% of the total mass of the shaped pulp and the polymer reinforcement, optionally between 1 and 50 wt%, optionally between 10 and 40 wt%, optionally between 20 and 30 wt%, optionally about 30 wt%.

[0010] In embodiments, the moulded pulp article further comprises a tactile layer and the polymer reinforcement comprises a polymer layer located between the shaped pulp and the tactile layer. The polymer layer may be a net or a film, optionally with a thickness of from 1 to 200 pm, optionally of from 10 to 150 pm, more preferably from 20 to 120 pm, further preferably from 30 to 80 pm, yet further preferably from 40 to 60 pm, most preferably about 50 pm. The tactile layer may have a paper feel, optionally the tactile layer is selected from a thin pulp layer, a paperboard, and a paper layer. The tactile layer may have a weight of from 5 to 150 gsm, optionally from 10 to 100 gsm, optionally from 15 to 50 gsm, optionally about 20 gsm.

[0011] The polymer may be a biodegradable polymer, optionally the biodegradable polymer is selected from polylactic acid (PLA), polyvinyl alcohol (PVOH), polyhydroxyalkanoates (PHA), polycaprolactone (PCL), polyglycolic acid (PGA), butenediol vinyl alcohol (BVOH), ethylene vinyl alcohol (EVOH), poly(butylene succinate-co-butylene adipate) (PBSA), polybutylene adipate terephthalate (PBAT), lignin, polyhydroxylated polysaccharides (such as starch, cellulose, carboxymethyl cellulose, hydroxypropylmethyl cellulose), proteins (such as casein, zein, soy protein, silk) and combinations thereof.

[0012] A second aspect of the present invention relates to a method of producing a moulded pulp article, the method comprising: a) providing a mass of cellulose fibres; b) providing a polymer; c) shaping the mass of cellulose fibres into a shaped pulp; d) heating the shaped pulp to effect at least partial melting of the polymer; and e) cooling the shaped pulp to solidify the polymer.

[0013] The mass of cellulose fibres and the polymer may be provided as a mixture, wherein the polymer is dispersed throughout the mass of cellulose fibres. The polymer may be provided in the form of a powder and / or pellets and the polymer is dispersed throughout the mass of cellulose fibres by mixing the cellulose fibres with the powder and / or pellets. The polymer may be dispersed throughout the mass of cellulose fibres by mixing the cellulose fibres with an aqueous dispersion of polymer, optionally in the presence of a surfactant.

[0014] The method may further comprise the step of providing a tactile layer and wherein the polymer is provided as a polymer layer located between the mass of cellulose fibres and the tactile layer.

[0015] Step c) may precede step d). Alternatively, steps c) and d) may occur simultaneously.

[0016] Step c) may comprise thermoforming.

[0017] Step d) may comprise heating the shaped pulp to a temperature below 250 °C, preferably between 50 and 200 °C, more preferably between 100 and 150 °C, most preferably about 120 °C.

[0018] A third aspect of the present invention relates to the use of a moulded pulp article according to the first aspect of the present invention, for packing an edible product for human or animal consumption.

[0019] A fourth aspect of the present invention relates to a packaged edible product, comprising a moulded pulp article according to the first aspect of the present invention, at least partially filled with an edible product for human or animal consumption.

[0020] As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”. Brief description of the drawings

[0021] Additional features and advantages of the present invention are described in, and will be apparent from, the description of the presently preferred embodiments which are set out below with reference to the drawings in which:

[0022] Figure 1 shows a schematic cross section of a moulded pulp article (1) according to the present invention. The moulded pulp article (1) includes a pulp (2) with a polymer reinforcement. As is shown in the inset, the polymer reinforcement is in the form of polymer (4) dispersed throughout the fibres (3) of the pulp;

[0023] Figure 2 shows a schematic cross section of a moulded pulp article (1) according to the present invention. The moulded pulp article (1) includes a pulp (5), a polymer reinforcement in the form of a polymer layer (6) and a tactile layer (7).

[0024] Figure 3 shows the effects of adding a water droplet to a conventional moulded pulp article without a polymer reinforcement (Figure 3A - rapid swelling and loss of shape) and to a moulded pulp article according to the present invention comprising a polymer reinforcement (Figure 3B - reduced water uptake, retention of structure).

[0025] Figure 4 shows the results of tensile strength testing for a conventional moulded pulp article without a polymer reinforcement and moulded pulp article according to the present invention comprising a polymer reinforcement. Figure 4A shows that the moulded pulp article comprising a polymer reinforcement has improved tensile strength. Figure 4B shows that the moulded pulp article comprising a polymer reinforcement has increased Tensile Energy Absorption. Figure 4C shows that the moulded pulp article comprising a polymer reinforcement has increased maximum force. Figure 4D shows that the moulded pulp article comprising a polymer reinforcement has greater elongation at break.

[0026] Detailed description of the invention

[0027] By “fibre”, it is meant a cellulosic fibre, which is generally extracted from plants, seeds or trees; such fibres contain not only cellulose molecules, but also hemi-cellulose as well as lignin. By “moulded pulp articles”, also known as “moulded fibre articles”, it is meant articles that are formed by the moulding of fibrous materials. The fibrous materials may be obtained by recycling processed fibre sources, such as paper or cardboard, or obtained directly from natural fibre sources, such as sugarcane bagasse, bamboo, and straw. Moulded pulp articles are commonly used for packaging and are widely considered to be sustainable.

[0028] Moulded Pulp Article

[0029] A first aspect of the present invention relates to a moulded pulp article. The moulded pulp article comprises a shaped pulp comprising cellulose fibres and a polymer reinforcement. The polymer reinforcement adds mechanical strength to the moulded pulp and enhances its resistance to water. In addition, the polymer may also improve the barrier properties of the moulded pulp article to oxygen and / or moisture.

[0030] In a first embodiment, the polymer reinforcement comprises polymer dispersed throughout the shaped pulp. Without wishing to be bound by theory, it is believed that the polymer and cellulose fibres of the pulp form a bonded network, immobilising the cellulose fibres and enhancing the rigidity and strength of the moulded pulp article. The polymer may comprise up to 50 wt% of the total mass of the shaped pulp, optionally between 1 and 50 wt%, optionally between 10 and 40 wt%, optionally between 20 and 30 wt%, optionally about 30 wt%. These loadings are sufficient to improve the mechanical properties of the moulded pulp article without causing detriment to its tactile qualities (i.e. its paper-like texture).

[0031] In a second embodiment, the polymer reinforcement comprises a polymer layer, the polymer layer disposed between the outer surface of the shaped pulp and the inner surface of a tactile layer. The polymer layer reinforces the moulded pulp and acts as an adhesive to affix the tactile layer to the moulded pulp. The tactile layer maintains the paper feel of the moulded pulp article and may be selected from a thin pulp layer, a paperboard, and a paper layer. The tactile layer may have a weight of from 5 to 150 gsm, optionally from 10 to 100 gsm, optionally from 15 to 50 gsm, optionally about 20 gsm.

[0032] The polymer layer may be in the form of a net or a film. The net has openings such that it partially covers the surface of the shaped pulp, this reduces the quantity of polymer required while still fulfilling the reinforcing and adhering functions. The film provides a substantially continuous covering to the surface of the shaped pulp, thereby providing an additional function as a barrier layer, inhibiting the movement of gasses and water through the moulded pulp article. The polymer layer may have a thickness of from 1 to 200 pm, preferably of from 10 to 150 pm, more preferably from 20 to 120 pm, further preferably from 30 to 80 pm, yet further preferably from 40 to 60 pm, most preferably about 50 pm. In embodiments, the thickness of the polymer layer is about 100 pm.

[0033] It will be understood that the foregoing embodiments may be combined (i.e. a moulded pulp article may comprise polymer reinforcement in the form of polymer dispersed throughout the shaped pulp and in the form of a polymer layer). It will be further understood that the moulded pulp article may comprise multiple layers of polymer reinforcement and / or shaped pulp, for example, the moulded pulp article may comprise one or more additional polymer layers and one or more additional layers of shaped pulp, the one or more additional polymer layers disposed between layers of shaped pulp.

[0034] In any of the foregoing embodiments, the polymer may be a biodegradable polymer. The use of a biodegradable polymer ensures that the biodegradable nature of the moulded pulp article, and consequent environmental benefits, are maintained. The biodegradable polymer may be selected from polylactic acid (PLA), polyvinyl alcohol (PVOH), polyhydroxyalkanoates (PHA), polycaprolactone (PCL) polyglycolic acid (PGA), butenediol vinyl alcohol (BVOH), ethylene vinyl alcohol (EVOH), poly(butylene succinate-co-butylene adipate) (PBSA), polybutylene adipate terephthalate (PBAT), lignin, polyhydroxylated polysaccharides (such as starch, cellulose, carboxymethyl cellulose, hydroxypropylmethyl cellulose), proteins (such as casein, zein, soy protein, silk) and combinations thereof. In embodiments, the polymer has a melting point of below 200 °C, such as from 100 to 200 °C, from 100 to 150 °C, or from 100 to 120 °C.

[0035] The skilled person will understand that the moulded pulp article may include further layers depending on the intended contents of the moulded pulp article. For example, the moulded pulp article may further comprise any of an inorganic barrier layer, an organic barrier layer, an ink layer, an overprint varnish, a contact layer, and so on.

[0036] Method for Producing a Moulded Pulp Article A second aspect of the present invention relates to a method of producing a moulded pulp article, the method comprising the steps of: a) providing a mass of cellulose fibres; b) providing a polymer; c) shaping the mass of cellulose fibres into a shaped pulp; d) heating the shaped pulp to effect melting of the polymer; and e) cooling the shaped pulp to solidify the polymer

[0037] In a first embodiment, the mass of cellulose fibres and the polymer are provided as a mixture, wherein the polymer is dispersed throughout the mass of cellulose fibres. Preferably, the polymer is dispersed substantially homogenously throughout the mass of cellulose fibres.

[0038] The polymer may be provided as a solid, such as in the form of a powder and / or pellets. The polymer powder or pellets may have a particle size of below 500 pm, below 250 pm, or below 100 pm, such as from 0.1 to 500 pm, from 0.5 to 250 pm, from 1 to 100 pm, from 5 to 50 pm, or from 10 to 20 pm. The solid polymer is mixed with the cellulose fibres until it is evenly dispersed throughout. Any suitable mixing method may be employed, such as a ball mill. The mass of cellulose fibres (and the solid polymer mixed therewith) is then shaped to form a shaped pulp. The shaped pulp is then heated to effect at least partial melting of the polymer and then cooled to solidify the polymer. While at least partially liquid, the polymer comes into intimate contact with the cellulose fibres and remains in this close contact when subsequently solidified, thereby binding adjacent cellulose fibres, and / or agglomerates with adjacent polymer, forming a polymer network.

[0039] Alternatively, or additionally, the polymer may be provided as an aqueous dispersion or solution of the polymer in the form of a liquid or a paste. The aqueous dispersion may have a solids content of from 10 to 50% w / w, preferably from 20 to 40% w / w, or more preferably from 25 to 35% w / w. The solids content is the content of the aqueous dispersion comprised of the polymer. The aqueous dispersion or solution is mixed with the cellulose fibres (optionally in the presence of a surfactant). The mass of cellulose fibres (and the polymer mixed therewith) is then shaped to form a shaped pulp. The shaped pulp is then heated to effect at least partial melting of the polymer and then cooled to solidify the polymer. Optionally, the mass of cellulose fibres is dried prior to shaping or dries during the heating step. While at least partially liquid, the polymer comes into intimate contact with the cellulose fibres and remains in this close contact when subsequently solidified, thereby binding adjacent cellulose fibres, and / or agglomerates with adjacent polymer, forming a polymer network. The cellulose fibres may be wet or dry (i.e. a moist pulp or a dry moulding pulp fluff), with the heating step removing the water from the wet cellulose fibres, should they be used.

[0040] In a second embodiment, the method further comprises providing a tactile layer and the polymer is provided as a polymer layer located between the mass of cellulose fibres and the tactile layer. The polymer layer and tactile layer may be as described herein. Shaping the mass of cellulose also comprises shaping the polymer layer and tactile layer to provide a layered structure. Heating and at least partially melting the polymer layer has the effect of laminating the tactile layer to the shaped pulp. The polymer layer may be in the form of a net or film. The cellulose fibres may be wet or dry (i.e. a moist pulp or a dry moulding pulp fluff), with the heating step removing the water from the wet cellulose fibres, should they be used. Preferably, should the polymer layer be a film, the cellulose fibres are dry.

[0041] In further embodiments, the first and second embodiments of the method disclosed herein may be combined. For example, the polymer (preferably in the form of a powder or pellets) is dispersed throughout the mass of cellulose fibres, a tactile layer is provided, and a polymer layer is located between the mass of cellulose fibres and the tactile layer. The ensemble is then shaped and heated as described herein to form a moulded pulp article comprising both polymer dispersed throughout the shaped pulp and the polymer layer located between the shaped pulp and the tactile layer.

[0042] In any of the foregoing methods, the heating step effects at least partial melting of the polymer (whether in the form of powder, pellets, an aqueous dispersion, or a layer) without damaging the shaped pulp. Substantially any heating technique and temperature may be used that achieves at least partial melting of the polymer without damaging the pulp. The shaped pulp and polymer may be heated to a temperature below 250 °C, such as from 50 to 200 °C, from 100 to 150 °C, or from about 120 °C.

[0043] In any of the foregoing methods, the step of shaping the mass of cellulose fibres into a shaped pulp may occur prior to the step of heating the shaped pulp to effect at least partial melting of the polymer. Alternatively, the shaping and heating steps may occur simultaneously (e.g. by thermoforming), which provides a benefit of compressing the cellulose fibres while the polymer (whether in the form of polymer dispersed throughout the pulp, a polymer layer, or a combination thereof) is at least partially liquid, thereby enhancing their contact area and the robustness of the resulting moulded pulp article.

[0044] Uses of the Moulded Pulp Article

[0045] Use of a moulded pulp article as described herein, for packing an edible product for human or animal consumption. Preferably, the moulded pulp article is in the form of a partially open vessel and the edible product is inserted via the opening. Once the moulded pulp article is filled, the opening is sealed, preferably with a polymeric film, a removable cap (e.g. a screw-cap), or a foil (which may be a tightly-bonded foil or a peelable foil intended for later removal).

[0046] A packaged edible product, comprising a moulded pulp article as described herein, at least partially filled with an edible product for human or animal consumption.

[0047] Preferably, said edible product is a powder, a gel, or kibbles and is selected within the list of: ground coffee, soluble coffee, nutrition compositions for infant, adult, or elderly consumption, soup, confectionery or candies, chocolate-based products, dry animal food, dairy products.

[0048] Examples

[0049] Example 1 - Polymer Reinforcement in the Form of a Polymer Layer

[0050] The following materials were arranged in a series of layers:

[0051] - dry moulding pulp fluff,

[0052] - a PHA film with a thickness of 100 pm, and

[0053] - a paper with a weight of 20 gsm.

[0054] The layered arrangement was subjected to a pressure of 500 MPa and a temperature of 125 °C for 5 minutes in order to effect lamination of the pulp fluff to the paper. The resulting construction is suitable for further shaping into a moulded pulp article and was found to be impermeable to water both on wetting and following immersion. Example 2 - Polymer Reinforcement in the Form of a Polymer Dispersed Throughout the Pulp

[0055] Dry moulding pulp fluff (from 50 to 90 wt%) and PHA polymer powder (from 10 to 50 wt%) are mixed. The mixture is placed into a mould where it is pressed and heated to effect intimate contact between the cellulose fibres and polymer and the formation of a moulded pulp article.

[0056] Example 3 - Physical Characterisation of the Moulded Pulp Articles

[0057] A moulded pulp article of the present invention comprising a polymer reinforcement was compared to a non-reinforced moulded pulp article.

[0058] In a first test, water was applied to the surface of each article. The non-reinforced moulded pulp article (Fig. 3A) rapidly absorbed the water and swelled, losing its coherence. In contrast, the water droplet remained on the surface of the moulded pulp article of the present invention comprising a polymer reinforcement (Fig. 3B) and did not distort. This test shows that moulded pulp articles according to the present invention have improved water resistance compared to conventional moulded pulp articles.

[0059] In a second test, moulded pulp articles with and without polymer reinforcement were each subjected to tensile strength testing, with the results shown in Fig. 4. This test shows that moulded pulp articles according to the present invention have improved tensile strength compared to conventional moulded pulp articles.

Claims

CLAIMS:

1. A moulded pulp article, the moulded pulp article comprising: a shaped pulp comprising cellulose fibres; and a polymer reinforcement.

2. The moulded pulp article of claim 1 , wherein the polymer reinforcement comprises polymer dispersed throughout the shaped pulp.

3. The moulded pulp article of claim 2, wherein the polymer comprises up to 50 wt% of the total mass of the shaped pulp and the polymer reinforcement, optionally between 1 and 50 wt%, optionally between 10 and 40 wt%, optionally between 20 and 30 wt%, optionally about 30 wt%.

4. The moulded pulp article of any one of the preceding claims, wherein the moulded pulp article further comprises a tactile layer and the polymer reinforcement comprises a polymer layer located between the shaped pulp and the tactile layer.

5. The moulded pulp article of claim 4, herein the polymer layer is a net or a film, optionally with a thickness of from 1 to 200 pm, optionally of from 10 to 150 pm, more preferably from 20 to 120 pm, further preferably from 30 to 80 pm, yet further preferably from 40 to 60 pm, most preferably about 50 pm.

6. The moulded pulp article of claim 4 or claim 5, wherein the tactile layer has a paper feel, optionally the tactile layer is selected from a thin pulp layer, a paperboard, and a paper layer.

7. The moulded pulp article of any one of claims 4 to 6, wherein the tactile layer has a weight of from 5 to 150 gsm, optionally from 10 to 100 gsm, optionally from 15 to 50 gsm, optionally about 20 gsm.

8. The moulded pulp article of any one of claims 1 to 7, wherein the polymer is a biodegradable polymer, optionally the biodegradable polymer is selected from polylactic acid (PLA), polyvinyl alcohol (PVOH), polyhydroxyalkanoates (PHA),polycaprolactone (PCL), polyglycolic acid (PGA), butenediol vinyl alcohol (BVOH), ethylene vinyl alcohol (EVOH), poly(butylene succinate-co-butylene adipate) (PBSA), polybutylene adipate terephthalate (PBAT), lignin, polyhydroxylated polysaccharides (such as starch, cellulose, carboxymethyl cellulose, hydroxypropylmethyl cellulose), proteins (such as casein, zein, soy protein, silk) and combinations thereof.

9. A method of producing a moulded pulp article, the method comprising: a) providing a mass of cellulose fibres; b) providing a polymer; c) shaping the mass of cellulose fibres into a shaped pulp; d) heating the shaped pulp to effect at least partial melting of the polymer; and e) cooling the shaped pulp to solidify the polymer.

10. The method of claim 9, wherein the mass of cellulose fibres and the polymer are provided as a mixture, wherein the polymer is dispersed throughout the mass of cellulose fibres.11 . The method of claim 10, wherein the polymer is provided in the form of a powder and / or pellets and the polymer is dispersed throughout the mass of cellulose fibres by mixing the cellulose fibres with the powder and / or pellets.

12. The method of claim 10, wherein the polymer is dispersed throughout the mass of cellulose fibres by mixing the cellulose fibres with an aqueous dispersion of polymer, optionally in the presence of a surfactant.

13. The method of any one of claims 9 to 12, wherein the method further comprises the step of providing a tactile layer and wherein the polymer is provided as a polymer layer located between the mass of cellulose fibres and the tactile layer.

14. The method of any one of claims 9 to 13, wherein step c) precedes step d) or wherein steps c) and d) occur simultaneously.

15. The method of any one of claims 9 to 14, wherein step c) comprises thermoforming.

16. The method of any one of claims 9 to 15, wherein step d) comprises heating the shaped pulp to a temperature below 250 °C, preferably between 50 and 200 °C, more preferably between 100 and 150 °C, most preferably about 120 °C.

17. Use of a moulded pulp article according to any one of claims 1 to 8, for packing an edible product for human or animal consumption.

18. A packaged edible product, comprising a moulded pulp article according to any one of claims 1 to 8, at least partially filled with an edible product for human or animal consumption.

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