TECHNICAL FIELD

The present invention generally relates to cellulose products and articles, and in particular to such cellulose products and articles comprising hydrophobation and grease proofing barriers and methods for manufacturing formed cellulose products and articles comprising hydrophobation and grease proofing barriers.

BACKGROUND

Cellulose substrates, such as in the form of pulp sheets and air-laid blanks, are employed to manufacture formed cellulose products by means of, for instance, cutting, pressing, folding, thermoforming and/or dry molding the cellulose substrate. Some illustrative examples of such formed cellulose products include cutlery, plates, bowls, lids and caps, which can be employed as environmentally friendly products for use, for example, with beverages or food. Further examples include packaging products used to protect goods and articles against impact or shock, and/or providing thermal insulation for temperature sensitive goods and articles.

Surfaces of the formed cellulose products generally need to be protected by barriers, often referred to as hydrophobation and grease proofing barriers or surface sizing, to make the formed cellulose products more resistant against absorption of grease and liquids from goods, articles, foodstuff and beverage that will be in contact with the surfaces of the formed cellulose products during use.

Traditionally, barrier agents, such as hydrophobation and grease proofing agents, are in the form of aqueous solutions or emulsions of, for instance, starches. The barrier agents are applied to the cellulose substrates prior to forming. The barrier agents cannot be applied to the formed cellulose products after forming since the formed cellulose products will absorb water from the aqueous solutions or emulsions causing undesired swelling and deformation of the formed cellulose products.

However, the manufacture of the formed cellulose products generally includes one or more cutting operations to get the desired shape of the formed cellulose products. The cutting operations lead to cut edges of the formed cellulose products that are not protected by any barrier agent since the barrier agent had been applied to the surfaces of the cellulose substrates prior to forming and cutting. These exposed edges are thereby not protected by any hydrophobation and grease proofing barrier and may, thus, absorb liquid and grease when the formed cellulose products are in contact with goods, articles, beverages or food.

There is, thus, a need for formed cellulose products comprising hydrophobation and grease proofing barriers for restriction of absorption of liquid and grease during use of the formed cellulose product. There is also a need for a formed cellulose product that eliminates or alleviates at least some of the disadvantages associated with prior art products.

WO 2021/006854 discloses a method for producing disposable tableware from a biopolymer composite material comprising a polymer matrix reinforced with cellulose fiber. The method comprises preliminary molding of a reinforcing cellulose structure. The structure is then compression molded and dried using a hot press with interchangeable dies shaped in accordance with the disposable tableware. The disposable tableware is infiltrated with a polymer matrix, followed by polymerization and air-conditioning of the finished disposable tableware to remove residual odors therefrom.

SUMMARY

It is a general objective to provide cellulose products and articles comprising a hydrophobation and grease proofing barrier.

This and other objectives are met by embodiments of the present invention.

The present invention is defined in the independent claims. Further embodiments of the invention are defined in the dependent claims.

An aspect of the invention relates to a method for manufacturing a formed cellulose product. The method comprises forming a cellulose substrate comprising cellulose and/or lignocellulose fibers into a formed cellulose product. The cellulose substrate is selected from the group consisting of an air-laid substrate and a fluff pulp sheet. The method also comprises applying at least one polymerizable fatty acid or an oil or oil mixture comprising at least one polymerizable fatty acid to the cellulose substrate prior to and/or during forming the cellulose substrate into the formed cellulose product. The method further comprises polymerizing the at least one polymerizable fatty acid to form a hydrophobation and grease proofing barrier of the formed cellulose product. Another aspect of the invention relates to a cellulose article comprising an air-laid material or a fluff pulp material comprising cellulose and/or lignocellulose fibers and a hydrophobation and grease proofing barrier on at least one surface of the cellulose article. The hydrophobation and grease proofing barrier comprises at least one polymerized fatty acid or an oil or oil mixture comprising at least one polymerized fatty acid.

The present invention forms hydrophobation and grease proofing barriers on cellulose products and articles that effectively protect the cellulose products or articles from liquids and grease when in contact with, for instance, beverages or food and food stuff or other goods and articles.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which:

Figs. 1A and 1 B schematically illustrate hot pressing of a cellulose substrate into a formed cellulose product according to an embodiment;

Fig. 2 schematically illustrates molding of a cellulose substrate into a formed cellulose product according to an embodiment;

Fig. 3 schematically illustrates a cellulose substrate (top) and a corresponding formed cellulose product (bottom) according to an embodiment;

Fig. 4 illustrates an example of a formed cellulose product according to an embodiment; and

Fig. 5 is a flow chart of a method for manufacturing a formed cellulose product according to an embodiment.

DETAILED DESCRIPTION

The present invention generally relates to cellulose products and articles, and in particular to such cellulose products and articles comprising hydrophobation and grease proofing barriers and methods for manufacturing formed cellulose products and articles comprising hydrophobation and grease proofing barriers. Cellulose products have become more and more popular as environmentally friendly replacements of disposable plastic products for usage as containers or tools in connection with beverages and food. For instance, disposable cups, plates, bowls, lids, caps and cutlery have traditionally been manufactured in plastics, such as polystyrene and other plastic materials, but alternatives to plastics are needed from environmental and sustainability point of view and due to possible health hazards associated with plastic materials with chemicals leaching into the beverage or food. Cellulose products are also employed as environmentally more friendly replacements to packaging products made of or from foamed polymers, for instance expanded polystyrene (EPS).

Cellulose substrates, such as air-laid substrates or fluff pulp sheets, can be formed by means of, for instance, cutting, pressing, folding, thermoforming and/or dry molding, into formed cellulose products for usage with, for instance, beverage and food, such as disposable cups, plates, bowls, lids, caps and cutlery. However, such cellulose products may readily absorb liquids and grease from the beverage or food unless surfaces of the cellulose products that come into contact with the beverage or food are treated to prevent or at least restrict absorption of liquids and grease.

A similar problem with absorbing liquid and grease is also present for cellulose-based packaging products employed to protect goods and articles during storage and/or transport. For instance, liquids and/or grease may leak from the goods and articles packaged in the cellulose-based packaging products and be absorbed therein. In addition, moisture or other liquids may come in contact with outer surfaces of the packaging products during use.

The present invention uses polymerizable fatty acids and/or oils or oil mixtures comprising such polymerizable fatty acids to form so called hydrophobation and grease proofing barrier of cellulose products and articles. This type of hydrophobation and grease barrier agent, also referred to as hydrophobation and grease proofing agent, has significant advantages over the traditional hydrophobation and grease barrier agents in the form of aqueous solutions or emulsions of, for instance, starches. The prior art aqueous hydrophobation and grease barrier agents need to be applied to the cellulose substrate prior to forming since the cellulose material will absorb water from the aqueous hydrophobation and grease barrier agent causing undesired swelling and deformation of the cellulose material. This swelling and deformation can be compensated for during the forming process, for instance, by pressing, thermoforming or molding the swelled and deformed cellulose substrate. However, such a swelling and deformation cannot be compensated for if it occurs in the formed cellulose product. Hence, the prior art aqueous hydrophobation and grease barrier agents need to be applied to the cellulose substrate prior to forming. The polymerizable fatty acids or oils as hydrophobation and grease barrier agents of the invention do not cause the same degree of swelling and deformation of the cellulose material as the aqueous solutions or emulsions and may therefore be applied to the cellulose substrate prior to or during the forming process.

Another shortcoming of the usage of aqueous hydrophobation and grease barrier agents is that a significant quantity of water will be absorbed by the cellulose material. The absorbed water must then be removed in one or more drying operations. The absorption and removal of water may, in some instances, not be desired as it may negatively affect characteristics of the cellulose substrate. For instance, dry cellulose substrates in the form of air-laid substrates are characterized by being porous, have the character of an open cell foam and are produced in a so-called dry forming method, i.e., generally without addition of water. Addition of water to such an air-laid substrate may compact the air-laid substrate, which thereby loses it porous and open cell foam like structure.

WO 2021/006854 discloses production of disposable tableware from wet cellulose pulp. The formed disposable tableware are then impregnated with 5 to 50 % by weight of a vegetable oil, followed by polymerization at a temperature of 110 to 200°C to form disposable tableware resistant to liquids. The impregnation and absorption of vegetable oils by the disposable tableware may cause a swelling and deformation of the disposable tableware. Hence, the protection of the disposable tableware against liquid by the polymerized vegetable oil comes at the cost of potential deformation of the disposable tableware due to the absorption of 5 to 50 % by weight of vegetable oil. The vegetable oil used to impregnate the disposable tableware must be applied to the disposable tableware first once it has been formed. The reason being that the vegetable oil may otherwise restrict the water or moisture in the cellulose pulp from escaping therefrom during the production of the disposable tableware. This would then mean that the disposable tableware would contain an undesired amount of moisture that cannot escape due to the presence of a hydrophobation and grease proofing barrier formed when polymerizing the vegetable oil.

The hydrophobation and grease proofing effect can be achieved according to the invention without the need for absorption and subsequent removal of water. This means that the invention can also achieve such hydrophobation and grease proofing effect on composite products formed from air-laid substrates.

The present invention can also achieve hydrophobation and grease proofing barriers also for cut edges in the formed cellulose product even if the hydrophobation and grease barrier agent is applied prior to or during the forming process. The polymerizable fatty acids or oils of the invention may penetrate into the bulk of the cellulose substrate to proof or impregnate the whole cellulose substrate or at least a thick portion thereof with the polymerizable fatty acids or oils. Hence, also edges exposed when cutting the formed cellulose product will thereby present hydrophobation and grease proofing barriers and restrict absorption of liquids and grease.

Hydrophobation and grease proofing barrier as used herein is thereby not only limited to such barriers present on the surface of the formed cellulose product. The hydrophobation and grease proofing barrier may in fact extend into at least a portion of the thickness of the formed cellulose product or indeed extend through the whole thickness and bulk of the formed cellulose product.

Fig. 5 is a flow chart illustrating a method for manufacturing a formed cellulose product according to the invention. Reference is also made to Fig. 3 illustrating a cellulose substrate 10 (top) and a corresponding formed cellulose product 20 (bottom) and Fig. 4 illustrating an example of a formed cellulose product 20 according to an embodiment.

The method comprises forming, in step S1 , a cellulose substrate 10 comprising cellulose and/or lignocellulose fibers into a formed cellulose product 20. The cellulose substrate 10 is selected from the group consisting of an air-laid substrate and a fluff pulp sheet. The method also comprises applying, in step S2, at least one polymerizable fatty acid or an oil or oil mixture comprising at least one polymerizable fatty acid to the cellulose substrate 10 prior to and/or during forming the cellulose substrate 10 in step S1 into the formed cellulose product 20. The method further comprises polymerizing, in step S3, the at least one polymerizable fatty acid to form a hydrophobation and grease proofing barrier 25 of the formed cellulose product 20.

The present invention thereby applies at least one polymerizable fatty acid or an oil or oil mixture comprising at least one polymerizable fatty acid as hydrophobation and grease barrier agent by applying the least one polymerizable fatty acid or the oil or oil mixture to the cellulose substrate 10 and then polymerize the at least one polymerizable fatty acid or the oil or oil mixture to obtain the hydrophobation and grease proofing barrier 25 of the formed cellulose product 20. Polymerization of the at least one polymerizable fatty acid causes formation of at least one polymerized fatty acid or an oil or oil mixture comprising at least one such polymerized fatty acid. The at least one polymerized fatty acid is solid on or on and in the cellulose substrate 10 and/or the formed cellulose product 20. This means that the at least one polymerized fatty acid forms a solid hydrophobation and grease proofing barrier at least onto a surface, or a portion thereof, of the cellulose substrate 10 and/or the formed cellulose product 20. The at least one polymerizable fatty acid may also penetrate into the cellulose substrate 10 and when polymerized therein, the at least one polymerized fatty acid forms a hydrophobation and grease proofing barrier also within the bulk of the cellulose substrate 10 and/or the formed cellulose product 20.

The at least one polymerizable fatty acid or the oil or oil mixture is applied in step S2 to at least one surface, or at least a portion of at least one surface, of the cellulose substrate 10 prior to and/or during forming the cellulose substrate 10 into the formed cellulose product 20, which is further described herein.

The formed cellulose product 20 as manufactured in accordance with Fig. 5 is suitable for being in contact with beverages and/or food or foodstuff. The hydrophobation and grease proofing barrier 25 of the formed cellulose product 20 obtained in step S3 of Fig. 5 thereby protects the formed cellulose product 20 and prevents or at least restricts absorption of liquid and/or grease from the beverages and/or food or foodstuff. The formed cellulose product 20 as manufactured in accordance with Fig. 5 is also suitable for usage as a packaging product for protecting goods and particles against impact and shock. The formed cellulose product 20 could also be used to thermally protect temperature sensitive goods and articles, such as foodstuff, packaged and possibly enclosed in the packaging product. The hydrophobation and grease proofing barrier 25 of the formed cellulose product 20 obtained in step S3 of Fig. 5 then protects the formed cellulose product 20 and prevents or at least restricts absorption of liquid and/or grease from the protected goods and articles, and also from the surroundings, such as moisture or liquids falling onto the formed cellulose product 20 during usage.

As is schematically illustrated by the lines L1 and L2 in Fig. 5, the at least one polymerizable fatty acid or the oil or oil mixture could be applied to the cellulose substrate 10 prior to forming the cellulose substrate 10 into the formed cellulose product 20 as indicated by line L1. Alternatively, the at least one polymerizable fatty acid or the oil or oil mixture could be applied to the cellulose substrate 10 during forming the cellulose substrate 10 into the formed cellulose product 20 as indicated by line L2. It is also possible to combine these alternatives. Hence, in an embodiment, the at least one polymerizable fatty acid or the oil or oil mixture is applied in step S2 to the cellulose substrate 10 prior to and during forming the cellulose substrate 10 into the formed cellulose product 20. It is also possible to combine application of the at least one polymerizable fatty acid or the oil or oil mixture prior to and/or during forming the cellulose substrate 10 into the formed cellulose product 20 with application of the at least one polymerizable fatty acid or the oil or oil mixture to the formed cellulose product 20 as indicated by the hatched line L3. Hence, in an embodiment, the at least one polymerizable fatty acid or the oil or oil mixture is applied in step S2 to the cellulose substrate 10 prior to forming the cellulose substrate 10 into the formed cellulose product 20 and to the formed cellulose product 20. In a further embodiment, the at least one polymerizable fatty acid or the oil or oil mixture is applied in step S2 to the cellulose substrate 10 during forming the cellulose substrate 10 into the formed cellulose product 20 and to the formed cellulose product 20. In yet another embodiment, the at least one polymerizable fatty acid or the oil or oil mixture is applied in step S2 to the cellulose substrate 10 prior to and during forming the cellulose substrate 10 into the formed cellulose product 20 and in addition to the formed cellulose product 20.

In some applications it may be advantageous to apply the at least one polymerizable fatty acid or the oil or oil mixture in step S2 at least prior to forming the cellulose substrate 10 into a formed cellulose product 20 in step S1. In these applications, the forming operation in step S1 may comprise heating the cellulose substrate 10, such as in thermoforming operations, which will be described further herein. In such a case, the heating of the cellulose substrate 10 accelerates the polymerization of the at least one polymerizable fatty acid in step S3 so that the polymerization operation in step S3 may be performed simultaneously with or at least partly overlapping with the forming operation in step S1 . In such a case, the polymerization operation in step S3 is part of the forming operation in step S1. Alternatively, an initial polymerization of the at least one polymerizable fatty acid or the oil or oil mixture is performed in the forming operation in step S1 and then a final or remaining polymerization is performed in step S3. This means that any separate polymerization operation can be omitted or at least shortened since polymerization of the at least one polymerizable fatty acid is either completed or at least initiated during the forming operation in step S1.

The heating applied in step S1 preferably heats the cellulose substrate 10 at a sufficient temperature to accelerate the polymerization but not at too high temperature to degrade the cellulose substrate 10. As an illustrative, but non-limiting, example, the cellulose substrate 10 could be heated to a temperature up to but not exceeding 210°C, preferably up to but not exceeding 190°C.

In the case of separate thermoforming and heat-treating operations in steps S1 and S3, i.e., when performing a separate heat treatment of the cellulose substrate 10 in step S3 to accelerate or indeed finish the polymerization of the at least one polymerizable fatty acid or the oil or oil mixture in addition to thermoforming the cellulose substrate 10 in step S1 , then the temperature at the thermoforming operation and the temperature at the heat-treating operation may be the same or different. However, in either case, the temperature or temperatures, to which the cellulose substrate 10 is heated is or are preferably not exceeding 210°C, and more preferably up to but not exceeding 190°C. In an embodiment, step S2 in Fig. 5 comprises spraying the at least one polymerizable fatty acid or the oil or oil mixture onto at least one surface 11 -14 of the cellulose substrate 10. The at least one polymerizable fatty acid or the oil or oil mixture will thereby form a surface coating on the at least one surface 11-14 of the cellulose substrate 10 but preferably also penetrate into at least a portion of the thickness of the cellulose substrate 10 from the at least one surface 11 -14.

In another embodiment, step S2 in Fig. 5 comprises coating at least one surface 11 -14 of the cellulose substrate 10 with the at least one polymerizable fatty acid or the oil or oil mixture. Various coating techniques could be used to apply the at least one polymerizable fatty acid or the oil or oil mixture. Illustrative, but non-limiting, examples include curtain coating and roller coating. The at least one polymerizable fatty acid or the oil or oil mixture will thereby form a surface coating on the at least one surface 11-14 of the cellulose substrate 10 but preferably also penetrate into at least a portion of the thickness of the cellulose substrate 10 from the at least one surface 11 -14.

In a further embodiment, step S2 in Fig. 5 comprises immersing at least a portion of the cellulose substrate 10 into the least one polymerizable fatty acid or the oil or oil mixture. Hence, in this embodiment, the cellulose substrate 10, or at least a portion thereof, is immersed in a bath of the at least one polymerizable fatty acid or the oil or oil mixture to soak the cellulose substrate 10, or at least a portion thereof, with the at least one polymerizable fatty acid or the oil or oil mixture. In this embodiment, the complete cellulose substrate 10 could be immersed in the at least one polymerizable fatty acid or the oil or oil mixture or merely a portion thereof is immersed in the at least one polymerizable fatty acid or the oil or oil mixture. The at least one polymerizable fatty acid or the oil or oil mixture will thereby form a surface coating on the at least one surface 11 -14of the cellulose substrate 10 but preferably also penetrate into at least a portion of the thickness of the cellulose substrate 10 from the at least one surface 11-14.

If the at least one polymerizable fatty acid or the oil or oil mixture is also to be applied to the cellulose product 20 as indicated by the line L3 in Fig. 5, then any of the above-mentioned embodiments of applying the at least one polymerizable fatty acid or the oil or oil mixture could be used for the formed cellulose product 20.

It is also possible to combine two or more of the above-described embodiments of applying the at least one polymerizable fatty acid or the oil or oil mixture, for instance, combining spraying and coating, combining spraying and immersing, combining coating and immersing and combining spraying, coating and immersing. As an example, one of the applying embodiments could be used to apply the at least one polymerizable fatty acid or the oil or oil mixture to the cellulose substrate 10, whereas another applying embodiment could be used for applying the at least one polymerizable fatty acid or the oil or oil mixture to the formed cellulose product 20.

In an embodiment, step S2 in Fig. 5 comprises applying the at least one polymerizable fatty acid or the oil or oil mixture to at least one surface 11 -14 of the cellulose substrate 10 and into at least a portion of a thickness of the cellulose substrate 10 extending from the at least one surface 11 -14. Hence, in this embodiment, the at least one polymerizable fatty acid or the oil or oil mixture is not only present at a surface 11-14 of the cellulose substrate 10 but also penetrates into at least a portion of the thickness of the cellulose substrate 10 from the at least one surface 11 -14. Hence, the at least one polymerizable fatty acid or the oil or oil mixture is present in at least a portion of the bulk of the cellulose substrate 10, where this at least a portion of the bulk faces the at least one surface 11 -14.

In a particular embodiment, the at least one polymerizable fatty acid or the oil or oil mixture penetrates into the complete thickness of the cellulose substrate 10. In such a particular embodiment, preferably all surfaces 11-14 and the bulk of the cellulose substrate 10 comprise the at least one polymerizable fatty acid or the oil or oil mixture. This particular embodiment can, for instance, be achieved by immersing the complete cellulose substrate 10 into the at least one polymerizable fatty acid or the oil or oil mixture.

The at least one polymerizable fatty acid or the oil or oil mixture is applied in a sufficient quantity in step S2 to the cellulose substrate 10 to form a hydrophobation and grease proofing barrier 25 of the formed cellulose product 20 following step S3. This means that the at least one polymerizable fatty acid or the oil or oil mixture is applied onto at least one surface 11 -14 of the cellulose substrate 10 to form the hydrophobation and grease proofing barrier 25 onto at least one surface 21 -24 of the formed cellulose product 20 and optionally also within the bulk, or a portion thereof, of the formed cellulose product 20. The hydrophobation and grease proofing barrier 25 thereby prevents or at least restricts moisture, liquid and/or grease to penetrate into the formed cellulose product 20 through this at least one surface 21 -24.

The amount of polymerizable fatty acid or oil or oil mixture applied in step S2 depends, among others, on the size or volume of the formed cellulose product 20 to be protected by the hydrophobation and grease proofing barrier 25, the type of polymerizable fatty acid or oil or oil mixture, the type of material of the cellulose substrate 10, whether any processing has been applied to the polymerizable fatty acid or oil or oil mixture prior to application in step S2 and whether any forming operations have been applied to the cellulose substrate 10 prior to application in step S2.

In a particular embodiment, step S2 comprises saturating the cellulose substrate 10 with the at least one polymerizable fatty acid or the oil or oil mixture. The at least one polymerizable fatty acid or the oil or oil mixture is then present throughout the whole cellulose substrate 10 including on its surfaces 11 -14 and within the interior of the cellulose substrate 10.

The at least one polymerizable fatty acid is polymerized in step S3 of Fig. 5. Polymerization of the at least one polymerizable fatty acid may, in an embodiment, take place in an oxygen containing atmosphere. The at least one polymerizable fatty acid can thereby be polymerized in ambient air without any particular treatment. However, such a polymerization generally takes quite a long time and would be most suited if the polymerization is allowed to proceed while the formed cellulose product 20 is stored, i.e., during its shelf life, or transport of the formed cellulose product 20. It is, however, generally preferred to accelerate the polymerization of the at least one polymerizable fatty acid in step S3 by treating the cellulose substrate 10 and/or the formed cellulose product 20. Illustrative, but non-limiting examples, of such polymerization accelerating treatments include heat treatment, ultraviolet (UV) light treatment, oxygen treatment (partial pressure of oxygen above 0.21 bar) and using polymerization catalysts. These various polymerization accelerating treatments may also be combined.

In an embodiment, step S3 in Fig. 5 comprises exposing at least a portion of the cellulose substrate 10 and/or the formed cellulose product 20 to heat and/or UV light in the presence of oxygen to form the hydrophobation and grease proofing barrier 25 of the formed cellulose product 20. In such an embodiment, the heat and/or UV light treatment could be a separate treatment operation or may be part of the forming operation in step S1 . The application of heat and/or UV light could be performed in ambient air or in an oxygen enriched (>21 %) atmosphere.

The heat treatment applied to the cellulose substrate 10 and/or the formed cellulose product 20 preferably involves heating the cellulose substrate 10 and/or the formed cellulose product 20 at a sufficient temperature to accelerate the polymerization but not at too high temperature to degrade the cellulose substrate 10 and/or the formed cellulose product 20. As an illustrative, but non-limiting example, the cellulose substrate 10 could be heated to a temperature up to but not exceeding 210°C, preferably up to but not exceeding 190°C. The heat treatment could be applied mainly to polymerize the at least one polymerizable fatty acid or the oil or oil mixture. In such a case, step S3 in Fig. 5 is a heat-based polymerization operation separate from formation of the formed cellulose product 20 from the cellulose substrate 10. Alternatively, the formation of the formed cellulose product 20 from the cellulose substrate 10 may involve a heating operation, such as in the form of a thermoforming operation. In such a case, this thermoforming operation may, in addition to thermoforming the cellulose substrate 10, also promote polymerization of the at least one fatty acid or the oil or oil mixture. In such a case, the polymerization in step S3 could be a combined polymerization and thermoforming step. It is also possible to combine a thermoforming step to accelerate polymerization with a separate polymerization step S3, such as an additional heat treating step. In such a case, the separate polymerization step may further proceed the polymerization of the at least one polymerizable fatty acid or the oil or oil mixture.

In another embodiment, step S2 in Fig. 5 comprises applying the at least one polymerizable fatty acid or the oil or oil mixture and a polymerization catalyst to the cellulose substrate 10 prior to and/or during forming the cellulose substrate 10 into the formed cellulose product 20. In this embodiment, step S3 comprises exposing at least a portion of the cellulose substrate 10 to oxygen to form the hydrophobation and grease proofing barrier 25 of the formed cellulose product 20. The exposure of the at least a portion of the cellulose substrate 10 to oxygen could be simply exposing the at least a portion of the cellulose substrate 10 to ambient air or, to accelerate the polymerization reaction, an oxygen enriched atmosphere.

Illustrative, but non-limiting, examples of polymerization catalysts that could be used according to the invention include cobalt(ll) 2-ethyl hexanoate and oil drying agents, also referred to as siccatives.

The polymerization of the at least one polymerizable fatty acid or the oil or oil mixture in step S3 does not necessarily have to be in the form of a so-called oxypolymerization but could instead be in the form of condensation polymerization or radical polymerization of the at least one polymerizable fatty acid or the oil or oil mixture.

The cellulose substrate 10 used as starting material in the method of Fig. 5 can be any air-laid substrate 10 or fluff pulp sheet or substrate 10 that can be formed into formed cellulose products 20, and in particular into such formed cellulose products 20 to be in contact with beverages and/or food, such as disposable containers for beverages and/or food, disposable lids or caps, or disposable cutlery, and formed cellulose products 20 to be used as packaging products, such as inserts. An air-laid substrate or material, such as in the form of an air-laid blank, sometimes also referred to as, dry-laid blank, air-laid mat, dry-laid mat, air-laid web or dry-laid web, is formed by a process known as air-laying, in which cellulose and/or lignocellulose fibers, and optionally a binder, such as a polymer binder, are mixed with air to form a porous fiber mixture deposited onto a support and consolidated or bonded by heating or thermoforming. This air-laid substrate or material is characterized by being porous, having the character of an open cell foam and being produced in a so-called dry forming method, i.e., generally without addition of water. The air-laying process was initially described in U.S. patent no. 3,575,749. The air-laid substrate may be in the form as produced in the air-laying process.

An example of an air-laid substrate or material that can be used according to the invention is such substrates made from a fluff pulp material in an air-laying process.

In an embodiment, the cellulose substrate 10 is an air-laid substrate.

The air-laid substrate 10 may be in the form of a single-layer air-laid substrate 10 or may be in the form of a multi-layer air-laid substrate 10 comprising multiple, i.e., at least two, layers of air-laid materials, such as multiple air-laid sheets stacked, bonded or pressed together to form a thicker air-laid substrate 10.

According to the invention, the air-laid substrate 10 comprises cellulose and/or lignocellulose fibers. Hence, in an embodiment, the air-laid substrate 10 comprises cellulose, such as in the form of cellulose and/or lignocellulose, i.e., a mixture of cellulose and lignin. The fibers may contain lignin, such as in the form of lignocellulose. The fibers may additionally contain hemicellulose. In a particular embodiment, the cellulose and/or lignocellulose fibers are cellulose and/or lignocellulose pulp fibers produced by chemical, mechanical and/or chemi-mechanical pulping of softwood and/or hardwood. For instance, the cellulose and/or lignocellulose pulp fibers are in a form selected from the group consisting of sulfate pulp, sulfite pulp, dissolving pulp, thermomechanical pulp (TMP), high temperature thermomechanical pulp (HTMP), mechanical fiber intended for medium density fiberboard (MDF-fiber), chemi-thermomechanical pulp (CTMP), high temperature chemi-thermomechanical pulp (HTCTMP), and a combination thereof.

The cellulose and/or lignocellulose fibers can also be produced by other pulping methods and/or from other cellulosic or lignocellulosic raw materials, such as flax, jute, hemp, kenaf, bagasse, cotton, bamboo, straw or rice husk. It is also possible to use cellulose and/or lignocellulose fibers that are a mixture of fibers from different raw materials, such as a mixture of wood and any of the materials mentioned above. In an embodiment, the air-laid substrate 10 comprises, prior to addition of the at least one polymerizable fatty acid or the oil or oil mixture, the cellulose and/or lignocellulose fibers in a concentration of at least 70 % by weight of the air-laid substrate 10. In a preferred embodiment, the air-laid substrate 10 comprises the cellulose and/or lignocellulose fibers in a concentration of at least 72.5 %, more preferably at least 75 %, such as at least 77.5 %, at least 80 %, at least 82.5 %, at least 85 % by weight of the air-laid substrate 10. In some applications, even higher concentrations of the cellulose and/or lignocellulose fibers may be used, such as at least 87.5 %, or at least 90 %, at least 92.5 %, at least 95 %, at least 97.5 %, at least 98 %, at least 98.5 %, at least 99 % or at least 99.5 % by weight of the air-laid substrate 10.

The air-laid substrate 10 may also include a binder, in particular for air-laid substrates 10 in the form of air-laid blanks 10. Such a binder may then be included to bind the cellulose substrate together and preserve its form and structure during use, handling and storage. In an embodiment, the binder may also assist in building up the foam-like structure of the air-laid substrate 10. The binder is, in such an embodiment, intermingled with the cellulose and/or lignocellulose fibers during an air-lying process forming a fiber mixture. The binder may be added in the form of a powder, but is more often added in the form of fibers that are intermingled with the cellulose and/or lignocellulose fibers in the air-laying process. Alternatively, or in addition, the binder may be added as solution, emulsion or dispersion into and onto the air-laid substrate 10.

The binder is preferably a polymer binder and could be a natural or synthetic polymer binder, or a mixture of natural polymer binders, a mixture of synthetic polymer binders, or a mixture of natural and synthetic polymer binders, but is preferably a thermoplastic polymer binder.

In an embodiment, the polymer binder is made from i) a material selected from the group consisting of polyethylene (PE), ethylene acrylic acid copolymer (EAA), ethylene-vinyl acetate (EVA), polypropylene (PP), polystyrene (PS), such as styrene-butadiene rubber (SBR) or styrene acrylate copolymer, polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polylactic acid (PLA), polyethylene terephthalate (PET), polycaprolactone (PCL), polyvinyl alcohol (PVA), polyethylene glycol (PEG), poly(2-ethyl-2-oxazoline) (PEOX), polyvinyl ether (PVE), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), polymethacrylic acid (PMAA), polyvinyl acetate (PVAc), polyurethane (PU) and copolymers thereof and/or mixtures thereof, and ii) optionally one or more additives. In an embodiment, the polymer binder is a thermoplastic polymer binder and preferably selected from the group consisting of a thermoplastic polymer powder, thermoplastic polymer fibers and a combination thereof.

In an embodiment, the air-laid substrate 10 comprises, prior to addition of the at least one polymerizable fatty acid or the oil or oil mixture, the at least one binder at a concentration selected within an interval of from 0.5 up to 30 % by weight of the air-laid substrate 10. Preferably, the air-laid substrate 10 comprises the at least one binder at a concentration selected within an interval of from 0.5 up to 25 % by weight, preferably within an interval of from 0.5 up to 20 % by weight, and more preferably within an interval of from 0.5 up to 15 % by weight of the air-laid substrate 10. In a particular embodiment, the air-laid substrate 10 comprises the at least one binder at a concentration selected within an interval of from 1.0 up to 10 % by weight, preferably within an interval of from 1 .5 up to 7.5 % by weight, and more preferably within an interval of from 2.0 up to 7.5 % of the air-laid substrate 10.

In another embodiment, the cellulose substrate 10 is a fluff pulp sheet, also referred to as fluff pulp substrate.

According to the invention, the fluff pulp sheet 10 comprises cellulose and/or lignocellulose fibers. Hence, in an embodiment, the fluff pulp sheet 10 comprises cellulose, such as in the form of cellulose and/or lignocellulose, i.e., a mixture of cellulose and lignin. The fibers may contain lignin, such as in the form of lignocellulose. The fibers may additionally contain hemicellulose. In a particular embodiment, the cellulose and/or lignocellulose fibers are cellulose and/or lignocellulose pulp fibers produced by chemical pulping of softwood or softwood and hardwood. For instance, the cellulose and/or lignocellulose pulp fibers are in a form selected from the group consisting of sulfate pulp, sulfite pulp, and a combination thereof.

Common raw materials for softwood pulp when producing fluff pulp may be various softwood species, such as Scandinavian pine, spruce, Southern pine, Loblolly pine, slash pine, Radiata pine, Douglas fir, Hemlock Cedar, White spruce, Lodgepole pine, Alpine fir or mixtures thereof.

The cellulose and/or lignocellulose fibers can also be produced by other pulping methods and/or from other cellulosic or lignocellulosic raw materials, such as flax, jute, hemp, kenaf, bagasse, cotton, bamboo, straw or rice husk. It is also possible to use cellulose and/or lignocellulose fibers that are a mixture of fibers from different raw materials, such as a mixture of wood and any of the materials mentioned above. In an embodiment, the fluff pulp sheet 10 comprises, prior to addition of the at least one polymerizable fatty acid or the oil or oil mixture, the cellulose and/or lignocellulose fibers in a concentration of at least 70 % by weight of the fluff pulp sheet 10. In a preferred embodiment, the air-laid substrate 10 comprises the cellulose and/or lignocellulose fibers in a concentration of at least 72.5 %, more preferably at least 75 %, such as at least 77.5 %, at least 80 %, at least 82.5 %, at least 85 % by weight of the fluff pulp sheet 10. In some applications, even higher concentrations of the cellulose and/or lignocellulose fibers may be used, such as at least 87.5 %, or at least 90 %, at least 92.5 %, at least 95 %, at least 97.5 %, at least 98 %, at least 98.5 %, at least 99 %, at least 99.5 % or at least 100 % by weight of the fluff pulp sheet 10.

The cellulose substrate 10, i.e., the air-laid substrate or the fluff pulp sheet, is preferably a so-called dry cellulose substrate. Such a dry cellulose sheet generally has a moisture content less than 20 % by weight, preferably less than 15 % by weight, such as equal to or less than 10 % by weight of the cellulose substrate 10. Moisture content as used herein is measured using standard methods to measure moisture content in cellulose substrates 10, in particular the oven dry method. This oven dry method comprises taking a sample of the cellulose substrate 10, measuring its weight, drying the sample in an oven at a temperature of 105 to 110°C for 24 hours, then weighing the sample and determining the moisture loss by subtracting the oven-dry weight from the moist weight. Moisture content is expressed as a percentage of the oven-dry weight of the sample, i.e., w = 100 x W _w / W _s , wherein W _w is the weight of the water (moist weight - oven-dry weight) and W _s is the oven-dry weight.

The forming step S1 can be performed according to various embodiments comprising one or multiple different forming operations. In an embodiment, step S1 of Fig. 5 comprises at least one of cutting the cellulose substrate 10, dry molding the cellulose substrate 10, thermoforming the cellulose substrate 10, folding the cellulose substrate 10 and pressing the cellulose substrate 10.

The cellulose substrate 10 may be cut in step S1. This cutting operation could include any process of separating the cellulose substrate 10 or the formed cellulose product 20 from any remaining cellulose material and/or from debris cellulose material. The cutting operation may include various cutting operations including, but not limited to, sawing, punching, or cutting the cellulose substrate 10 or indeed the formed cellulose product 20. Dry molding the cellulose substrate 10 involves molding the cellulose substrate 10 in a pair of tools or molds, typically between a male tool or mold and a female tool or mold. Fig. 2 schematically illustrates such a process, in which the cellulose substrate 10 is pressed between a male tool 30 and a female tool 50. Generally, the cellulose substrate 10 is pressed into the female tool 50 by the male tool 30. The male tool 30 may optionally comprise one or more protruding structures that are configured to be depressed into the cellulose substrate 10. In such a case, the three dimensional (3D) shape of the resulting formed product 20, see Fig. 3, is defined by the form of the female tool 50 and the male tool 30, including any protruding structures of the male tool 30. Dry molding implies that the cellulose substrate 10 is in a dry form or substantially dry form. This is in clear contrast to wet molding, in which a wet pulp is drawn by vacuum onto a wire mesh mold.

Thermoforming of the cellulose substrate 10 includes any forming processing involving heating the cellulose substrate 10, such as by using heating tools employed in the forming process. Compression molding and pressing could be thermoforming operations if any of the tools used in the compression molding or pressing operation is heated. Figs. 1A and 1 B illustrate an example of a thermoforming operation by compacting or pressing a heated male tool 30 into a cellulose substrate 10 positioned on a base platen 40. The male tool 30 may then comprise heating elements 34 that are preferably controllable heating elements 34 to heat the male tool 30 to a desired temperature for hot pressing of the cellulose substrate 10. Fig. 1 B illustrates the heated male tool 30 pressed into the cellulose substrate 10. In this illustrative example, the male tool 30 comprises protruding structures 32 that will be pressed into the cellulose substrate 10 to impart a 3D shape into the surface 11 of the cellulose substrate 10 facing the male tool 30.

Thermoforming cellulose substrate 10 may, also or alternatively, involve thermoforming the cellulose substrate 10 in a pair of heated tools or molds, typically between a male tool or mold 30 and a female tool or mold 50, see Fig. 2. In such a case, the cellulose substrate 10 is pressed between a male tool 30 and a female tool 50, of which one or both of the male and female tools 30, 50 are heated. Generally, the cellulose substrate 10 is pressed into the female tool 50 by the male tool 30. The male tool 30 may optionally comprise one or more protruding structures that are configured to be depressed into the cellulose substrate 10. In such a case, the 3D shape of the resulting formed cellulose product 20 is defined by the form of the female tool 50 and the male tool 30, including any protruding structures of the male tool 30. Pressing of the cellulose substrate 10 may also be performed without any heating of the cellulose substrate, such as performing pressing at ambient temperature.

The forming step S1 may also comprise folding the cellulose substrate 10. This folding may be preceded by forming a crease or folding line in the cellulose substrate 10, such as by pressing a die into the cellulose substrate 10 to form a folding line, along which the cellulose substrate 10 may be folded to obtain a formed cellulose product 20.

In a particular embodiment, the forming step S1 comprises at least thermoforming the cellulose substrate 10. In such a case, this thermoforming step is preferably performed after application of the at least one polymerizable fatty acid or the oil or oil mixture in step S2. As mentioned in the foregoing, in such a case, the thermoforming step S1 may also function as a polymerization step S3 thereby omitting the need for a separate polymerization step, or alternatively the thermoforming step S1 may initiate the polymerization of the at least one polymerizable fatty acid or the oil or oil mixture with the remaining polymerization taking place in step S3.

Hence, in an embodiment, the forming step S1 comprises thermoforming the cellulose substrate 10. In a particular embodiment, the applying step S2 then preferably comprises applying the at least one polymerizable fatty acid or the oil or oil mixture to the cellulose substrate 10 prior to thermoforming the cellulose substrate 10.

Any cutting operation in step S1 may be performed following application of the at least one polymerizable fatty acid or the oil or oil mixture in step S2. In such a case, the at least one polymerizable fatty acid or the oil or oil mixture is preferably applied in step S2 to extend into at least a portion of a thickness of the cellulose substrate 10. This means that the surface that is exposed when cutting the cellulose substrate 10 will be treated with the at least one polymerizable fatty acid or the oil or oil mixture. Hence, a hydrophobation and grease proofing barrier will be present on the corresponding cut edge or side in the formed cellulose product 20.

It is also possible to first cut the cellulose substrate 10 prior to application of the at least one polymerizable fatty acid or the oil or oil mixture to get a desired overall shape of the cellulose substrate 10 prior to the subsequent forming operation, such as thermoforming the cut cellulose substrate 10. In such a case, a cut edge or side will comprise a hydrophobation and grease proofing barrier in the formed cellulose product 20 if the at least one polymerizable fatty acid or the oil or oil mixture is applied to the cut edge or side in the cellulose substrate 10 prior to and/or during the subsequent forming operation.

As mentioned in the foregoing, the forming step S1 in Fig. 5 may comprise a combination of the above exemplified forming operations. For instance, dry molding, thermoforming or pressing is usually combined with cutting the dry molded, thermoformed or pressed cellulose product to obtain a separate formed cellulose product 20. Furthermore, a thermoformed cellulose product may also be folded to obtain a final formed cellulose product 20 having a desired 3D shape.

In an embodiment, step S2 comprises applying a single polymerizable fatty acid to the cellulose substrate 10. In another embodiment, a mixture of multiple different polymerizable fatty acids could be applied to the cellulose substrate 10. Illustrative, but non-limiting, examples of such polymerizable fatty acids that can be used in step S2 include unsaturated fatty acids including monounsaturated fatty acids, such as oleic acid, elaidic acid and palmitoleic acid, and/or polyunsaturated fatty acids, such as linoleic acid and linolenic acid, including mixtures thereof. In a preferred embodiment, the polymerizable fatty acids are polyunsaturated fatty acids, a mixture of different polyunsaturated fatty acids or a mixture of at least one polyunsaturated fatty acid and at least one monounsaturated fatty acid.

In another embodiment, step S2 comprises applying the oil to the cellulose substrate 10 prior to and/or during forming the cellulose substrate 10 into the formed cellulose product 20. Hence, in this embodiment, an oil comprising at least one polymerizable fatty acid, including a mixture of different polymerizable fatty acids, is applied to the cellulose substrate 10.

In an embodiment, the oil is a vegetable oil. In a particular embodiment, the vegetable oil is selected from the group consisting of flaxseed oil, avocado oil, sesame oil, safflower oil, sunflower oil, grapeseed oil, rapeseed oil, linseed oil and rosehip seed oil. In a preferred embodiment, the vegetable oil is selected from the group consisting of rapeseed oil, sunflower oil and linseed oil, preferably selected from the group consisting of sunflower oil and linseed oil. A particular illustrative example of a vegetable oil that could be used according to the invention is linseed oil. Another particular example of a vegetable oil that could be used according to the invention is sunflower oil.

The oil, such as vegetable oil, could be a processed oil. For instance, the oil could be a fractionated oil. In such a case, the processing, such as fractionation, of the oil could be done to remove fractions that may otherwise become rancid. In such a case, a fraction of the oil is applied in step S2. This fraction preferably comprises polymerizable fatty acids whereas constituents of the oil that provide an odor or taste are preferably removed during the fractionation.

In an embodiment, a mixture of oils comprising at least one polymerizable fatty acid is used. In such a case, the multiple oils can be selected among the above-mentioned examples.

The result of the polymerization in step S3 is fatty acid based polymers, including fatty acid dimers, fatty acid trimers and/or longer fatty acid based polymers. If multiple different polymerizable fatty acids are applied in step S2, such as in the form of a mixture of polymerizable fatty acids or an oil, the resulting fatty acid based polymers may be in the form of co-polymers of different fatty acid monomers. The at least one polymerizable fatty acid or the oil or oil mixture becomes hardened during the polymerization and forms a solid hydrophobation and grease proofing barrier 25 either only on the surface of the formed cellulose product 20 or on the surface and within at least a portion of the thickness of the formed cellulose product 20.

Another aspect of the invention relates to a cellulose article 10, 20 comprising an air-laid material or fluff pulp material comprising cellulose and/or lignocellulose fibers. The cellulose article 10, 20 also comprises a hydrophobation and grease proofing barrier 25 on at least one surface 11-14, 21-24 of the cellulose article 10, 20. The hydrophobation and grease proofing barrier 25 comprises at least one polymerized fatty acid or an oil or oil mixture comprising at least one polymerized fatty acid.

The cellulose article 10, 20 could the in the form of the above described formed cellulose product 20 or the cellulose substrate 10.

Hence, an embodiment relates to a formed cellulose product 20 comprising a hydrophobation and grease proofing barrier 25 on at least one surface 21 -24 of the formed cellulose product 20. The hydrophobation and grease proofing barrier 25 comprises at least one polymerized fatty acid or an oil or oil mixture comprising at least one polymerized fatty acid.

The formed cellulose product 20 is preferably in the form of a formed cellulose product 20 intended to be in contact with beverages and/or food and food stuff. The formed cellulose product 20 is preferably a disposable formed cellulose product 20, such as disposable cups, plates, bowls, lids, caps and cutlery. In another embodiment, the formed cellulose product 20 is intended to be used as a packaging product designed to protect articles and goods packed in the packaging product from, among others, impacts and shock during transport and storage. The packaging product could also be used to enclose temperature sensitive or tempered articles, such as food or beverages, which should be kept within defined temperature ranges.

Another embodiment relates to a cellulose substrate 10 comprising a hydrophobation and grease proofing barrier on at least one surface 11 -14 of the cellulose substrate 10. The hydrophobation and grease proofing barrier comprises at least one polymerized fatty acid or an oil or oil mixture comprising at least one polymerized fatty acid. The cellulose substrate 10 is selected from the group consisting of an air-laid substrate and a fluff pulp sheet or substrate.

In an embodiment, the polymerized fatty acid or the oil or oil mixture is present from the at least one surface 11 -14, 21 -24 of the cellulose article 10, 20 into at least a portion of a thickness of the cellulose article 10, 20 extending from the at least one surface 11-14, 21-24.

In an embodiment, the cellulose article 10, 20 comprises the hydrophobation and grease proofing barrier 25 on all surfaces 11 -14, 21 -24 of the cellulose article 10, 20.

In an embodiment, the cellulose article 10, 20 is saturated with the polymerized fatty acid or the oil or oil mixture.

According to the invention, the cellulose article 10, 20 comprises cellulose and/or lignocellulose fibers.

In a particular embodiment, the cellulose article 10, 20 is an air-laid material comprising cellulose and/or lignocellulose pulp fibers produced by chemical, mechanical and/or chemi-mechanical pulping of softwood and/or hardwood.

For instance, the cellulose and/or lignocellulose fibers are cellulose and/or lignocellulose pulp fibers in a form selected from the group consisting of sulfate pulp, sulfite pulp, dissolving pulp, TMP, HTMP, MDF- fiber, CTMP, HTCTMP, and a combination thereof.

In another particular embodiment, the cellulose article 10, 20 comprises a fluff pulp material comprising cellulose and/or lignocellulose pulp fibers produced by chemical pulping of softwood or softwood and hardwood. For instance, the cellulose and/or lignocellulose fibers are cellulose and/or lignocellulose pulp fibers in a form selected from the group consisting of sulfate pulp, sulfite pulp, and a combination thereof.

In an embodiment, the hydrophobation and grease proofing barrier 25 comprises the oil or oil mixture. In this embodiment, the oil is a vegetable oil, preferably selected from the group consisting of flaxseed oil, avocado oil, sesame oil, safflower oil, sunflower oil, grapeseed oil, rapeseed oil, linseed oil and rosehip seed oil. Correspondingly, the oil mixture is a mixture of vegetable oils, preferably selected from the above-mentioned group.

The cellulose article 10, 20 may optionally comprise one or more additives traditionally employed when manufacturing cellulose substrates 10 and formed cellulose products 20. These additives should then be compatible with the at least one polymerizable fatty acid or the oil or oil mixture and should preferably not significantly interfere with polymerization of the at least one polymerizable fatty acid.

In an embodiment, the cellulose article 10, 20 is a formed cellulose product 20 formed by cutting, dry molding, thermoforming, folding and/or pressing a cellulose substrate 10.

In another embodiment, the cellulose article 10, 20 is a cellulose substrate 10 configured to be formed into a formed cellulose product 20 by cutting, dry molding, thermoforming, folding and/or pressing the cellulose substrate 10.

The embodiments described above are to be understood as a few illustrative examples of the present invention. It will be understood by those skilled in the art that various modifications, combinations and changes may be made to the embodiments without departing from the scope of the present invention. In particular, different part solutions in the different embodiments can be combined in other configurations, where technically possible.