TECHNICAL FIELD

The present invention generally relates to composite products and substrates, and in particular to such composite products resistant against absorption of moisture, liquids and grease.

BACKGROUND

With growing awareness for the environment and humanly induced climate change, the use of plastic items and products has come more and more into question. However, despite this concern the use of these items and products has grown vastly with new trends in lifestyles and consumer habits of the last decade. There is therefore a need to provide cost-effective composite materials that are derived from renewable feedstock. An example of such environmentally friendly composite material is cellulosic composites comprising cellulose and/or lignocellulose fibers.

A common disadvantage of cellulosic composites is that they may be sensitive to exposure to moisture, liquids and/or grease. In more detail, the cellulosic composite may absorb moisture, liquids and/or grease when in contact with moist or greasy goods or articles, or when exposed to, in particular, moisture or liquids from the surroundings. Such absorption may cause a deformation of the product made from the cellulosic composite and possible even a weakening of the structural integrity of the product.

There is therefore a need for composite substrates comprising cellulose and/or lignocellulose fibers and composite products and articles made therefrom that are resistant against absorption of moisture, liquids and grease.

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 composite substrates comprising cellulose and/or lignocellulose fibers and composite products made therefrom that are resistant against absorption of moisture, liquids and grease.

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 composite product comprising a cellulose and/or lignocellulose fiber matrix in the form of an air-laid material and at least one polymerized fatty acid or an oil or oil mixture comprising at least one polymerized fatty acid. The at least one polymerized fatty acid or the oil or oil mixture is distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix. The at least a portion of the cellulose and/or lignocellulose fiber matrix extends from a first surface of the cellulose and/or lignocellulose fiber matrix to a second, opposite surface of the cellulose and/or lignocellulose fiber matrix.

Another aspect of the invention relates to a composite air-laid substrate comprising a cellulose and/or lignocellulose fiber matrix and at least one polymerizable fatty acid or an oil or oil mixture comprising at least one polymerizable fatty acid. The at least one polymerizable fatty acid or the oil or oil mixture is distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix. The at least a portion of the cellulose and/or lignocellulose fiber matrix extends from a first surface of the cellulose and/or lignocellulose fiber matrix to a second, opposite surface of the cellulose and/or lignocellulose fiber matrix.

The composite products of the present invention are capable to be in contact with moisture, liquid and grease and still significantly restrict absorption of such moisture or liquid into the cellulose and/or lignocellulose material of the composite products.

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: Fig. 1 is a cross-sectional view of a composite product according to an embodiment;

Fig. 2 is a cross-sectional view of a composite product according to another embodiment; and

Fig. 3 is a cross-sectional view of a composite air-laid substrate according to an embodiment.

DETAILED DESCRIPTION

The present invention generally relates to composite products and composite substrates comprising cellulose and/or lignocellulose fibers, and in particular to such composite products resistant against absorption of moisture, liquids and grease.

Products comprising cellulose and/or lignocellulose fibers have become more and more popular as environmentally friendly replacements of plastic products, such as made of polystyrene or other plastic materials. Alternatives to plastics are needed, however, from environmental and sustainability point of view and due to possible health hazards associated with plastic materials with chemicals leakage from the plastic materials.

The present invention uses polymerized fatty acids and/or oils or oil mixtures comprising such polymerized fatty acids to form a composite product that is resistant against environmental conditions, such as moisture, liquid and grease. Hence, the polymerized fatty acids and/or oils or oil mixtures effectively prevent or at least restrict absorption of moisture, liquid and grease from the ambient environment or goods into the composite product.

It is known in the art to use an aqueous solution or emulsion of so-called hydrophobation and grease barrier agents, typically an aqueous solution or emulsion of starches. The prior art aqueous hydrophobation and grease barrier agents need to be applied to a cellulose and/or lignocellulose substrate prior to forming the cellulose and/or lignocellulose substrate into a final product 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 and/or lignocellulose substrate. However, such a swelling and deformation cannot be compensated for if it occurs in the formed final product. Hence, the prior art aqueous hydrophobation and grease barrier agents need to be applied to the cellulose and/or lignocellulose substrate prior to forming. 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 and/or lignocellulose substrate. 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 and/or lignocellulose substrate. For instance, dry cellulose and/or lignocellulose 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 weight percentage (wt%) 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 wt% vegetable oil.

The present invention applies at least one polymerizable fatty acid or an oil or oil mixture comprising at least one polymerizable fatty acid to a cellulose and/or lignocellulose fiber matrix of an air-laid substrate and then polymerizes the at least one polymerizable fatty acid to obtain at least one polymerized fatty acid distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix. The polymerizable fatty acids or the oils or oil mixtures of the invention do not cause the same degree of swelling and deformation of the cellulose and/or lignocellulose material as the aqueous solutions or emulsions. Hence, the need for compensating for any swelling and deformation is generally lower for the present invention as compared to using aqueous hydrophobation and grease barrier agents. Furthermore, 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 airlaid substrates.

The present invention can achieve hydrophobation and grease proofing effect also for cut edges in the composite product. The polymerized fatty acids or the oils or oil mixtures of the invention are distributed within the bulk of the cellulose and/or lignocellulose fiber matrix of the composite product to proof or impregnate the cellulose and/or lignocellulose fiber matrix. Hence, also edges exposed when cutting the composite product will thereby present hydrophobation and grease proofing effect and restrict absorption of moisture, liquids and grease if the at least one polymerized fatty acid or the oil or oil mixture is distributed throughout the complete cellulose and/or lignocellulose fiber matrix or if the cutting of the composite product is performed through the at least a portion of the cellulose and/or lignocellulose fiber matrix comprising the at least one polymerized fatty acid or the oil or oil mixture.

An aspect of the invention therefore relates to a composite product comprising a cellulose and/or lignocellulose fiber matrix in the form of an air-laid material and at least one polymerized fatty acid or an oil or oil mixture comprising at least one polymerized fatty acid. According to the invention, the at least one polymerized fatty acid or the oil or oil mixture is distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix. The at least a portion of the cellulose and/or lignocellulose fiber matrix extends from a first surface of the cellulose and/or lignocellulose fiber matrix to a second, opposite surface of the cellulose and/or lignocellulose fiber matrix.

The composite product of the invention, also referred to as composite article, could be regarded as a composite, and in particular a biocomposite, since it comprises a cellulose and/or lignocellulose fiber matrix in the form of an air-laid material and additionally comprises 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 or the oil or oil mixture is then distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix. This means that at least a portion of the composite product is thereby a composite between a cellulose and/or lignocellulose material and at least one polymerized fatty acid or the oil or oil mixture. The at least one polymerized fatty acid or the oil or oil mixture is preferably in at least partly solid state within the at least a portion of the cellulose and/or lignocellulose fiber matrix. For instance, at least one polymerizable fatty acid or an oil or oil mixture comprising at least one polymerizable fatty acid could be distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix, which is further described herein. The at least one polymerizable fatty acid or the oil or oil mixture comprising the at least one polymerizable fatty acid is then in a liquid form. The at least one polymerizable fatty acid is then polymerized to form the at least one polymerized fatty acid or the oil or oil mixture comprising the at least one polymerized fatty acid distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix. The polymerization of the at least one polymerizable fatty acid causes the at least one polymerizable fatty acid to solidify forming a composite or biocomposite together with the cellulose and/or lignocellulose material of the cellulose and/or lignocellulose fiber matrix. The at least one polymerized fatty acid or the oil or oil mixture distributed within at least a portion of the cellulose and/or lignocellulose matrix protects the composite product or at least a portion thereof from ambient conditions, such as moisture, liquids or grease, which may come into contact with the composite product and its cellulose and/or lignocellulose matrix. Thus, the at least a portion of the cellulose and/or lignocellulose matrix is thereby impregnated with the at least one polymerized fatty acid or the oil or oil mixture to obtain a hydrophobation and grease proofing effect.

The at least one polymerized fatty acid or the oil or oil mixture is distributed within at least a portion 22, 24 of the cellulose and/or lignocellulose fiber matrix 20, see Figs. 1 and 2. This at least a portion 22, 24 extends from a first surface 21 of the cellulose and/or lignocellulose fiber matrix 20 to a second, opposite surface 23 of the cellulose and/or lignocellulose fiber matrix 20.

Fig. 1 schematically illustrates a composite product 10 comprising a cellulose and/or lignocellulose fiber matrix 20 in the form of an air-laid material. In the embodiment illustrated in Fig. 1 , the at least one polymerized fatty acid or the oil or oil mixture is distributed within the cellulose and/or lignocellulose fiber matrix 20 of the composite product 10. Hence, the at least one polymerized fatty acid or the oil or oil mixture is, in the embodiment shown in Fig. 1 , distributed within and throughout the complete cellulose and/or lignocellulose fiber matrix 20 and not merely within a portion thereof.

Fig. 2 illustrates another embodiment of a composite product 10 that has been processed in terms of compressed during manufacture. Hence, the composite product 10 shown in Fig. 2 comprises portions 22 that are pressed, also referred to as pressed portions 22, and portions 24 that are not pressed, also referred to as non-pressed portions 24. In the figure, the hatched lines enclose pressed portions 22 of the composite product 10 and the dotted lines enclose non-pressed portions 24 of the composite product 10. In an embodiment, the at least one polymerized fatty acid or the oil or oil mixture is distributed within the portions 22 of the cellulose and/or lignocellulose fiber matrix 20 and thereby of the composite product 10 that have been pressed. If the composite product 10 comprises multiple pressed portions 22 as shown in Fig. 2, then the at least one polymerized fatty acid or the oil or oil mixture could be distributed within all these pressed portions 22 or merely in a subset of the pressed portions 22.

In another embodiment, the at least one polymerized fatty acid or the oil or oil mixture is distributed within the portions 24 of the cellulose and/or lignocellulose fiber matrix 20 and thereby of the composite product 10 that have not been pressed. If the composite product 10 comprises multiple non-pressed portions 24 as shown in Fig. 2, then the at least one polymerized fatty acid or the oil or oil mixture could be distributed within all these non-pressed portions 24 or merely in a subset of the non-pressed portions 24.

In a further embodiment, the at least one polymerized fatty acid or the oil or oil mixture is distributed within a subset of the portions 24 of the cellulose and/or lignocellulose fiber matrix 20 and thereby of the composite product 10 that have not been pressed and within a subset of the portions 22 of the cellulose and/or lignocellulose fiber matrix 20 and thereby of the composite product 10 that have been pressed.

The portions 22, 24 of the cellulose and/or lignocellulose fiber matrix 20 extend from a first surface 21 of the cellulose and/or lignocellulose fiber matrix 20 to a second, opposite surface 23 of the cellulose and/or lignocellulose fiber matrix 20 as shown in Fig. 2. This means that if merely one portion 22, 24 of the cellulose and/or lignocellulose fiber matrix 20 comprises the at least one polymerized fatty acid or the oil or oil mixture then that portion 22, 24 extends through the whole cellulose and/or lignocellulose fiber matrix 20, i.e., between opposite surfaces 21 , 23 or sides of the cellulose and/or lignocellulose fiber matrix 20. Correspondingly, if multiple portions 22, 24 of the cellulose and/or lignocellulose fiber matrix 20 comprise the at least one polymerized fatty acid or the oil or oil mixture then those portions 22, 24 extend through the whole cellulose and/or lignocellulose fiber matrix 20.

The two opposite surfaces 21 , 23 of the cellulose and/or lignocellulose fiber matrix 20 could be substantially parallel to each other as shown in Figs. 1 and 2 but do not necessary have to be parallel to each other. The cellulose and/or lignocellulose fiber matrix 20 could in turn extend through the complete thickness of the composite product 10. In such a case, the two opposite surfaces 21 , 23 could also be regarded as first and second, opposite surfaces of the composite product 10. However, in some applications, the composite product 10 could comprise additional material besides the cellulose and/or lignocellulose fiber matrix 20, such as a surface layer of some other type of material. In such a case, the at least a portion 22, 24 of the cellulose and/or lignocellulose fiber matrix 20 comprising the at least one polymerized fatty acid or the oil or oil mixture extends between opposite surfaces 21 , 23 of the cellulose and/or lignocellulose fiber matrix 20 but not between opposite surfaces of the cellulose product 10.

In an embodiment, the at least one polymerized fatty acid or the oil or oil mixture is distributed within a complete thickness of the at least a portion 22, 24 of the cellulose and/or lignocellulose fiber matrix 20. This means that the at least one polymerized fatty acid or the oil or oil mixture is distributed throughout the whole of the at least a portion 22, 24 of the cellulose and/or lignocellulose fiber matrix 20 and not merely provided as a surface layer or coating. In clear contrast, the at least one polymerized fatty acid or the oil or oil mixture is provided in and distributed throughout the complete thickness of the at least a portion of the cellulose and/or lignocellulose fiber matrix 20.

With reference to Fig. 1 , the at least one polymerized fatty acid or the oil or oil mixture is distributed within a complete thickness T of the cellulose and/or lignocellulose fiber matrix 20, i.e. , from a first or upper surface 21 of the cellulose and/or lignocellulose fiber matrix 20 and of the composite product 10 to a second or lower surface 23 of the cellulose and/or lignocellulose fiber matrix 20 and of the composite product 10.

In Fig. 2, the pressed portions 22 of the cellulose and/or lignocellulose fiber matrix 20 have thicknesses T1 to T7. Hence, in a preferred embodiment, the at least one polymerized fatty acid or the oil or oil mixture is distributed within a complete thickness T1 to T7 of the pressed portions 22 of the cellulose and/or lignocellulose fiber matrix 20. Correspondingly, the non-pressed portions 24 of the cellulose and/or lignocellulose fiber matrix 20 have a thickness T8 as shown in Fig. 2. Hence, in a preferred embodiment, the at least one polymerized fatty acid or the oil or oil mixture is distributed within a complete thickness T8 of the non-pressed portions 24 of the cellulose and/or lignocellulose fiber matrix 20.

A pressed portion 22 of the cellulose and/or lignocellulose fiber matrix 20 thereby has a smaller thickness T1 to T7 as compared to any non-pressed portions 24 of the cellulose and/or lignocellulose fiber matrix 20. The pressing typically results in a pressed portion 22 having a thickness T1 to T7 that is equal to or less than 90 % of the thickness T8 of the non-pressed portion(s) 24, preferably equal to or less than 80 %, such as equal to or less than 70 %, 60 % or 50 % of the thickness T8 of the nonpressed portion(s) 24. If the cellulose and/or lignocellulose fiber matrix 20 comprises multiple pressed portions 22 as shown in Fig. 2 then these may all have the same thickness or, as shown in the figure, at least some of the pressed portions 22 may have different thicknesses T1 to T7.

In an embodiment, the at least one polymerized fatty acid or the oil or oil mixture is homogenously distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix. Thus, it is generally preferred if the at least one polymerized fatty acid or the oil or oil mixture is at least fairly homogenously distributed throughout the at least a portion of the cellulose and/or lignocellulose fiber matrix so that the concentration of the at least one polymerized fatty acid or the oil or oil mixture is substantially the same throughout the at least a portion of the cellulose and/or lignocellulose fiber matrix.

In an embodiment, the at least a portion of the cellulose and/or lignocellulose fiber matrix is saturated with the at least one polymerized fatty acid or the oil or oil mixture. Thus, the at least a portion of the cellulose and/or lignocellulose fiber matrix preferably comprises a sufficient amount of polymerized fatty acid(s) or oil or oil mixture to be saturated with the at least one polymerized fatty acid or the oil or oil mixture. The at least one polymerized fatty acid or the oil or oil mixture will then provide an efficient hydrophobation or grease proofing effect to the at least a portion of the cellulose and/or lignocellulose fiber matrix.

As mentioned in the foregoing and illustrated in Fig. 1 , in an embodiment, the at least one polymerized fatty acid or the oil or oil mixture is distributed within the cellulose and/or lignocellulose fiber matrix 20. Hence, in this embodiment, not only a single portion or multiple, i.e., at least two, separate portions of the cellulose and/or lignocellulose fiber matrix 20 is or are treated with the at least one polymerized fatty acid or the oil or oil mixture. In clear contrast, the at least one polymerized fatty acid or the oil or oil mixture is preferably distributed within the complete cellulose and/or lignocellulose fiber matrix 20 and thereby preferably throughout the complete composite product 10 or the portion(s) thereof made of or comprising the cellulose and/or lignocellulose fiber matrix 20.

In an embodiment, the composite product comprises cellulose and/or lignocellulose fibers forming the cellulose and/or lignocellulose fiber matrix in the form of an air-laid material. Hence, in an embodiment, the composite product 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 fiber matrix comprises 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 cellulose and/or lignocellulose matrix comprises the cellulose and/or lignocellulose fibers in a concentration of at least 70 % by weight of the cellulose and/or lignocellulose matrix. In a preferred embodiment, the cellulose and/or lignocellulose matrix 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 cellulose and/or lignocellulose matrix. 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 cellulose and/or lignocellulose matrix.

In an embodiment, a single polymerized fatty acid is distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix. In another embodiment, a mixture of multiple different polymerized fatty acids is distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix. Illustrative, but non-limiting, examples of such polymerized fatty acids that can be used 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, which have been polymerized. In a preferred embodiment, the polymerized 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, which have been polymerized.

In another embodiment, an oil comprising at least one polymerized fatty acid, including a mixture of different polymerized fatty acids, is distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix.

In an embodiment, the oil is a vegetable oil or the oil mixture is a mixture of vegetable oils. 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 another embodiment, a mixture of multiple oils comprising at least one polymerized fatty acid is distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix. In this embodiment, the multiple oils can be selected among the above mentioned examples.

In an embodiment, the cellulose and/or lignocellulose fiber matrix also comprises at least one binder, preferably at least one polymer binder and more preferably at least one thermoplastic polymer binder. Such a binder may then be included to bind the cellulose and/or lignocellulose fibers together to form the cellulose and/or lignocellulose fiber matrix. In an embodiment, the binder may also assist in building up the foam-like structure of the cellulose and/or lignocellulose fiber matrix.

The binder, in particular polymer binders, such as thermoplastic polymer binders, may be intermingled with the cellulose and/or lignocellulose fibers during an air-lying process to form the cellulose and/or lignocellulose fiber matrix. 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 cellulose and/or lignocellulose fiber matrix.

The binder 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 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 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 cellulose and/or lignocellulose fiber matrix comprises the at least one binder at a concentration selected within an interval of from 0.5 up to 30 % by weight of the cellulose and/or lignocellulose fiber matrix. Preferably, the cellulose and/or lignocellulose fiber matrix 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 cellulose and/or lignocellulose fiber matrix. In a particular embodiment, the cellulose and/or lignocellulose fiber matrix 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 % by weight of the cellulose and/or lignocellulose fiber matrix.

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

The air-laid substrate may be in the form of a single-layer cellulose and/or lignocellulose substrate or may be in the form of a multi-layer cellulose and/or lignocellulose substrate comprising multiple layers of cellulose and/or lignocellulose materials, such as multiple air-laid substrates or sheets stacked, bonded or pressed together to form a thicker air-laid board.

The composite product of the present invention finds uses in many different applications where there is a need for an environmentally friendly composite that is resistant against absorption of moisture, liquid and/or grease. Illustrative, but non-limiting examples, include various three-dimensional (3D) construction elements, parts used in the automotive industry, such as instrument panels, interior elements in vehicles, door panels, etc., furniture, among others.

Another aspect of the invention relates to a composite air-laid substrate 30 comprising a cellulose and/or lignocellulose fiber matrix 40 and at least one polymerizable fatty acid or an oil or oil mixture comprising at least one polymerizable fatty acid, see Fig. 3. In this aspect, the at least one polymerizable fatty acid or the oil or oil mixture is distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix 40. The at least a portion of the cellulose and/or lignocellulose fiber matrix 40 extends from a first surface 41 of the cellulose and/or lignocellulose fiber matrix 40 to a second, opposite surface 43 of the cellulose and/or lignocellulose fiber matrix 40.

The composite product of the invention can be formed by polymerizing the at least one polymerizable fatty acid or the oil or oil mixture comprising the at least one polymerizable fatty acid distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix of the composite air-laid substrate to obtain the at least one polymerized fatty acid or the oil or oil mixture comprising the at least one polymerized fatty acid distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix of the composite product.

In an embodiment, the composite air-laid substrate may be subject to a forming operation prior to polymerizing the at least one polymerizable fatty acid. Illustrative, but non-limiting, examples of such forming operations include cutting, pressing or compressing, folding, thermoforming, and/or dry molding. In particular, the composite air-laid substrate may be subject to a thermoforming operation. In such a case, the heat applied to the composite air-laid substrate during the thermoforming operation will promote polymerization of the at least one polymerizable fatty acid. Hence, in such a case, the thermoforming operation can be a combined thermoforming and polymerization operation. 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 thermoforming operation. Thermoforming of the air-laid substrate includes any forming processing involving heating the air-laid substrate, 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. As an example, a thermoforming operation could comprise compacting or pressing a heated male tool into an air-laid substrate positioned on a base platen. The male tool may then comprise heating elements that are preferably controllable heating elements to heat the male tool to a desired temperature for hot pressing of the air-laid substrate. The male tool may comprise protruding structures that will be pressed into the air-laid substrate to impart a three-dimensional (3D) shape into the surface of the air-laid substrate facing the male tool.

Thermoforming the air-laid substrate may, also or alternatively, involve thermoforming the air-laid substrate in a pair of heated tools or molds, typically between a male tool or mold and a female tool or mold. In such a case, the air-laid substrate is pressed between a male tool and a female tool, of which one or both of the male and female tools are heated. Generally, the air-laid substrate is pressed into the female tool by the male tool. The male tool may optionally comprise one or more protruding structures that are configured to be depressed into the air-laid substrate. In such a case, the 3D shape of the resulting composite product 20 is defined by the form of the female tool and the male tool, including any protruding structures of the male tool 30.

The composite air-laid substrate according to this aspect comprising at least one polymerizable fatty acid or an oil or oil mixture comprising at least one polymerizable fatty acid distributed within at least a portion of the composite air-laid substrate can be used to produce a composite product according to the present invention by exposing the composite air-laid substrate or at least the portion thereof comprising the at least one polymerizable fatty acid or an oil or oil mixture to polymerizing conditions to form at least one polymerized fatty acid or an oil or oil mixture comprising at least one polymerized fatty acid distributed within at least a portion of the so formed composite product.

In an embodiment, the at least one polymerizable fatty acid or the oil or oil mixture is distributed within a complete thickness T of the at least a portion of the cellulose and/or lignocellulose fiber matrix 40 of the composite air-laid substrate 30, see Fig. 3. In an embodiment, the at least one polymerizable fatty acid or the oil or oil mixture is homogenously distributed within the at least a portion of the cellulose and/or lignocellulose fiber matrix of the composite air-laid substrate.

In an embodiment, the at least a portion of the cellulose and/or lignocellulose fiber matrix of the composite substrate is saturated with the at least one polymerizable fatty acid or the oil or oil mixture.

In an embodiment, the at least one polymerizable fatty acid or the oil or oil mixture is distributed within the complete cellulose and/or lignocellulose fiber matrix of the composite substrate.

In an 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.

In a particular embodiment, 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 an embodiment, the cellulose and/or lignocellulose matrix comprises the cellulose and/or lignocellulose fibers in a concentration of at least 70 % by weight of the cellulose and/or lignocellulose matrix. In a preferred embodiment, the cellulose and/or lignocellulose matrix 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 cellulose and/or lignocellulose matrix. 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 cellulose and/or lignocellulose matrix.

In an embodiment, the oil is a vegetable oil or the oil mixture is a mixture of vegetable oils. In a particular embodiment, the vegetable oil is 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. For instance, the oil is linseed oil or the oil mixture is a mixture of linseed oil and at least one other vegetable oil. In an embodiment, the composite substrate further comprises at least one binder, preferably at least one polymer binder and more preferably at least one thermoplastic polymer binder.

In a particular embodiment, the binder is made from i) a material selected from the group consisting of PE, EAA, EVA, PP, PS, such as SBR or styrene acrylate copolymer, PBAT, PBS, PLA, PET, PCL, PVA, PEG, PEOX, PVE, PVP, PAA, PMAA, PVAc, PU and copolymers thereof and/or mixtures thereof, and ii) optionally one or more additives.

In an embodiment, the cellulose and/or lignocellulose fiber matrix comprises the at least one binder at a concentration selected within an interval of from 0.5 up to 30 % by weight of the cellulose and/or lignocellulose fiber matrix. Preferably, the cellulose and/or lignocellulose fiber matrix 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 cellulose and/or lignocellulose fiber matrix. In a particular embodiment, the cellulose and/or lignocellulose fiber matrix 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 % by weight of the cellulose and/or lignocellulose fiber matrix.

The composite product and the composite air-laid substrate may optionally comprise one or more additives traditionally employed when manufacturing cellulose and/or lignocellulose fiber matrices. 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.

The composite product of the invention can be formed from the composite air-laid substrate by polymerizing the at least one polymerizable fatty acid to form the composite product comprising at least one polymerized fatty acid or an oil or oil mixture comprising at least one polymerized fatty acid distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix of the composite product.

The result of the polymerization 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 distributed within at least a portion of the cellulose and/or lignocellulose fiber matrix of the composite air-laid substrate, such as in the form of a mixture of polymerizable fatty acids or an oil or oil mixture, 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 protection within the at least a portion of the cellulose and/or lignocellulose fiber matrix of the composite product.

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 composite product is stored, i.e. , during its shelf life, or transport of the composite product. It is, however, generally preferred to accelerate the polymerization of the at least one polymerizable fatty acid by treating the composite air-laid substrate or at least a portion thereof. 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.

The heat treatment applied to the composite air-laid substrate or at least a portion thereof preferably involves heating the composite air-laid substrate or at least a portion thereof at a sufficient temperature to accelerate the polymerization but not at too high temperature to degrade the composite air-laid substrate. As an illustrative, but non-limiting example, the composite air-laid substrate or at least a portion thereof could be heated to a temperature up to but not exceeding 210°C, preferably up to but not exceeding 190°C. Such a heating of the composite air-laid substrate or at least a portion thereof could be performed during thermoforming of the air-laid substrate and/or as a separate heating operation.

In the case of separate thermoforming and heat-treating operations, i.e., when performing a separate heat treatment of the composite air-laid substrate or at least a portion thereof 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 composite air-laid substrate, 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 composite air-laid substrate is heated is or are preferably not exceeding 210°C, and more preferably up to but not exceeding 190°C. 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 agent, also referred to as siccatives.

The polymerization of the at least one polymerizable fatty acid or the oil or oil mixture 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 at least one polymerizable fatty acid or the oil or oil mixture comprising at least one polymerizable fatty acid may be applied to the cellulose and/or lignocellulose fiber matrix of the composite air-laid substrate or a portion thereof according to various embodiments.

For instance, the at least one polymerizable fatty acid or the oil or oil mixture could be sprayed onto the cellulose and/or lignocellulose fiber matrix, or a portion thereof. In such a case, a sufficient amount of the at least one polymerizable fatty acid or the oil or oil mixture is preferably sprayed onto the cellulose and/or lignocellulose fiber matrix or the portion thereof to allow the at least one polymerizable fatty acid or the oil or oil mixture to penetrate into the cellulose and/or lignocellulose fiber matrix and thereby become distributed within the cellulose and/or lignocellulose fiber matrix or the portion thereof. In another example, the at least one polymerizable fatty acid or the oil or oil mixture could be poured onto the cellulose and/or lignocellulose fiber matrix or the portion thereof. A further example is to immerse at least a portion of the cellulose and/or lignocellulose fiber matrix into the least one polymerizable fatty acid or the oil or oil mixture. Hence, in this embodiment, the cellulose and/or lignocellulose fiber matrix or the 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 and/or lignocellulose fiber matrix or the portion thereof with the at least one polymerizable fatty acid or the oil or oil mixture. It is also possible to combine two or more of the above-described examples of applying 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 preferably applied in a sufficient quantity to the cellulose and/or lignocellulose fiber matrix to achieve a hydrophobation and grease proofing effect for at least a portion of the cellulose and/or lignocellulose fiber matrix following polymerization. The amount of polymerizable fatty acid or oil or oil mixture applied depends, among others, on the volume of the at least a portion of the cellulose and/or lignocellulose fiber matrix, to which the at least one polymerizable fatty acid or the oil or oil mixture is to be applied, the type of polymerizable fatty acid or oil or oil mixture, the type of material of the cellulose and/or lignocellulose fiber matrix, whether any processing has been applied to the polymerizable fatty acid or oil or oil mixture prior to application and whether any forming operations have been applied to the cellulose and/or lignocellulose fiber matrix prior to application.

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.