WO2024112982A1

WO2024112982A1 - Mulching film

Info

Publication number: WO2024112982A1
Application number: PCT/AT2022/060426
Authority: WO
Inventors: Lars Göran Berglund; Anna ERNISA; Paulus GOESS
Original assignee: Mondi Ag
Filing date: 2022-12-02
Publication date: 2024-06-06

Abstract

The invention relates to a mulching film, in particular for a mulching period of at least three months, the mulching film (2) comprising or consisting of a base material (1), wherein the base material (1) is made of mechanically and/or chemically processed cellulose fibers derived from wood, rags, grasses or other vegetable sources, wherein the mulching film (2) has a tensile energy absorption between 250 J/m² and 400 J/m². The invention further relates to a use, an arrangement and a method in relation to mulching films.

Description

Mulching film

The present invention relates to a mulching film, as well as to a use, an arrangement, and a method in relation to said mulching film.

In the prior art is has been known to cover soil areas designated for specific purposes, such as agriculture, horticulture, and forestry, with mulching films made of plastics. The intention behind using such mulching films is that growth of pest plants on the covered soil areas can be prevented, whereas the crop plants are allowed to penetrate the mulching film through specifically provided openings, which enables their substantially unimpaired growth. A further advantage provided by mulching films is that the covered soil areas are kept moist, as evaporation of water from the soil surface is hindered by the presence of the film.

A particular prerequisite for mulching films is that the materials exhibit sufficient strength in both dry and wet state so that the films can withstand the forces exerted on them during their lifetime, including the application and any fixation of the film to the ground. Different plastics materials have been the materials of choice in the past due to their beneficial properties for the desired purpose, such as tear resistance, water resistance, and durability.

However, in recent years, many concerns have come up with respect to the use of plastics materials. In particular, the widespread use of non-renewable sources and the limited I slow degradability of these materials have raised considerable concerns. Additionally, governmental regulations and elevated environmental awareness have brought up the need for substitute materials.

Specifically in the case of mulching films, the high durability of plastics materials leads to the problem that the films have to be removed after the growth season, which imposes additional workload for the users of such films. Additionally, UV-initiated degradation may lead to embrittlement of the plastics material, posing the risk of microplastics input into the soil. Said microplastics may be subsequently incorporated by the crops, which may constitute a health hazard for animals and humans.

In order to reduce the amount of plastics and other of the above-mentioned drawbacks, alternative mulching films have been proposed in the past. Notable example are twolayered films made of a paper layer and a plastics layer, or films with polymeric coatings. As the paper layer provides the necessary support, the plastics layer, which particularly imparts durability and water resistance, may have decreased thickness as compared to conventional mulching films. However, as these films are still not completely plastics-free, further improvements are required to overcome the aboveillustrated drawbacks of the prior art. This similarly applies to films with polymeric coatings.

The prior art therefore faces the problem that the use of plastics materials is connected with a number of concerns, but at least a certain amount of plastics has been thought to be necessary in order to obtain mulching films that can provide the required properties.

An object of the present invention can therefore be seen in overcoming this conflict of interests. A particular object of the present invention can be seen in providing a mulching film, which allows for reduced workload and/or environmental impact. A further object of the invention can be seen in providing a use, an arrangement and/or a method that can at least partially solve one or more of the above problems.

The present inventors have now surprisingly found that materials made of mechanically and/or chemically processed cellulose fibers can also be used as mulching films under certain circumstances. This is completely contrary to common belief as such materials usually exhibit limited durability, especially when exposed to wet conditions.

The present invention therefore relates to a mulching film, which comprises or consists of a base material made of mechanically and/or chemically processed cellulose fibers. These fibers may be derived from wood, rags, grasses or other vegetable and/or renewable sources. A particular example of the base material may be paper.

It has particularly been found in the course of making the present invention that the above-mentioned materials can be used as mulching films if films produced therefrom have a specific combination of extensibility and tensile strength, which may provide them with sufficient strength in both dry and wet state.

Preferably, the mulching film of the present invention therefore has a tensile energy absorption (TEA) in machine direction (MD) of between 250 J/m² and 400 J/m² The tensile energy absorption of the mulching film may particularly be determined in accordance with ISO 1924-3:2005. The tensile energy absorption (TEA) in cross direction (CD) of the mulching film may range between 250 J/m² and 350 J/m².

Providing the film with said tensile energy absorption may allow omitting the use of plastics in the mulching film of the invention.

The mulching film of the invention may therefore be plastics-free. The term “plastics- free” particularly describes the fact that the mulching film does not contain synthetic or semi-synthetic polymers. Materials that contain traces of plastics are covered by the term “plastics-free”.

As the mulching film according to the invention may be plastics-free, there is no specific need for removing it from the soil surface after the growth season.

The mulching film may be uncoated and/or composed of only one layer. “One layer” particularly means that the film has a substantially uniform composition at least in the thickness direction of the film. The term “thickness direction” may refer to an orientation that runs transverse to the main plane of extension of the film. The mulching film of the invention may be an uncoated, single-layer film.

The mulching film of the invention may be suitable for a mulching period of at least three months. This particularly means that the film can withstand environmental conditions like rain and wind for a period of at least three months without undergoing excessive degradation.

The tensile strength of the mulching film in the machine direction may range between 6.5 and 9.0 kN/m and/or the tensile strength of the mulching film in the transverse direction may range between 4.5 and 7.0 kN/m. The tensile strength may particularly be determined in accordance with ISO 1924-3:2005.

The stretch at break of the film in the machine direction may range between 6.0 and 11 % and/or the stretch at break of the film in the transverse direction may range between 6.0 to 12 %. The stretch at break may particularly be determined in accordance with ISO 1924-3:2005.

The wet tensile strength of the film in the machine direction may range between 1 .6 and 2.7 kN/m. The wet tensile strength may particularly be determined in accordance with ISO 3781 :2011.

The tear strength of the film in both machine and transverse direction may range between 800 and 1700 mN. The tear strength may particularly be determined in accordance with ISO 1974:2012.

The properties if the mulching film according to the invention may further be enhanced by the application of certain additives. It is noted that all weight percentages are given relative to the total weight of dry material, except indicated otherwise. The additives may be added to the fiber suspension during production of the film.

The mulching film may contain a wet strength agent in the range of between 1 .5 and 6.5 kg/t paper atro. The wet strength agent may particularly be or comprise polyamidoamine-epichlorohydrine (PAAE). Moreover, it can be envisaged that the mulching film comprises between 2.0 and 4.0 kg/t paper atro of starch and/or a starch derivative, preferably cationic starch.

The mulching film of the invention may contain a sizing agent in a content of between 0.5 and 2.0 kg/t paper atro.

These additives, alone or in combination, may provide a film that is more resilient and shows a lesser tendency to crack in both dry and wet state, thereby further improving the properties required for use as mulching film.

Further beneficial properties may be imparted to the mulching film of the invention by selecting specific production steps and/or production parameters.

The fibers contained in the base material of the film may be mechanically treated to further increase the tensile strength of the film. This may particularly be achieved by means of low consistency refining of the fibers. Low consistency refining may be particularly performed at between 2 and 5% pulp consistency. The treatment may be performed in one or more low consistency refiners. Such treatment can be carried out at a specific refining energy of about 20 to 100 kWh/ton of dry pulp, as for example 80 kWh/ton.

Stretchability of the film may be improved by refining at higher pulp consistency, which may particularly be performed in a range of between 25 and 40% pulp consistency. Such treatment can be carried out at a specific refining energy of about 250 to 310 kWh/ton of dry pulp, as for example 280 kWh/ton. This treatment may result in better deformability or flexibility of the mulching film and as such has a favorable impact on the film properties.

The mulching film of the invention may also be microcrepped and/or subjected to a microcrepping treatment. This may also result in an improvement in the film’s stretchability. Microcrepping may be performed via a Clupak device, which usually forms a unit being integrated in a paper machine. Another method for microcrepping treatment is the use of an Expanda unit, which also may be integrated in paper machine.

As raw material for the fibers contained in the base material of the mulching film of the invention, it is preferred to use softwood such as any species of spruce or pine or mixtures thereof. Liberation of the cellulose fibers may be achieved by chemical pulping, preferably using the so-called Kraft process. The base material may therefore comprise or consist of Kraft paper.

The mechanically treated pulp optionally containing certain amounts of additives may in a further production step be diluted to a consistency of approx, between 0.02 and 0.06 wt% relative to the total amount of suspension. The diluted suspension may thereafter be applied onto the wire of a wire section by means of a material outlet, thereby forming a paper web. The wire may move at a speed that is between 0.8% and 1.6%, higher or lower than the application rate of the suspension onto the wire.

The wet web formed thereby may then be dewatered by pressing the web in a press section.

Finally, the web may be dried in a drying section. Microcrepping may be performed in the drying section using either a Clupak device or an Expanda unit. Consequently, the drying section may be divided into a pre-dryer section preceding the microcreping treatment and an after-dryer section following the microcreping unit.

Afterwards, the formed material may be cut or confectioned to the desired size and/or shape. The mulching film may be rolled for easier transport, storage, and use.

The mulching film of the invention may have a length of at least 5 m, but the length may also be at least 100 m, or at least 500 m.

The mulching film may have a basis weight of between 50 and 150 g/m² in accordance with ISO 536:2019. The mulching film may have a tensile energy absorption index in machine direction of between 3.0 and 5.0 J/g. The mulching film may have a tensile energy absorption index in transverse direction of between 3.0 and 5.0 J/g. The tensile energy absorption index may be determined in accordance with ISO 1924-3:2005.

The mulching film may have a tensile energy absorption ratio MD/CD of between 1.0 and 2.0.

The mulching film may have a tensile index in machine direction of between 70 and 120 kNm/kg. The mulching film may have a tensile index in transverse direction of between 40 and 90 kNm/kg. The tensile index may be determined in accordance with ISO 1924- 3:2005.

The mulching film may have a stretch at break in machine direction of between 6.0 and 11 .0 %. The mulching film may have a stretch at break in transverse direction of between 6.0 and 12.0 %. The stretch at break may be determined in accordance with ISO 1924-3:2005.

The mulching film may have a tear index in machine direction of between 8.0 and 12.0 Nm²/kg. The mulching film may have a tear index in transverse direction of between 12.0 and 18.0 Nm²/kg. The tear index may be determined in accordance with ISO 1974:2012.

The mulching film may have a Gurley value of between 20 and 50 s. The Gurley value may be determined in accordance with ISO 5636-5:2013.

The mulching film may have a Cobb 60s value on the wire side of between 15 and 35 g/m² The mulching film may have a Cobb 60s value on the upper side of between 15 and 35 g/m². The mulching film may have an average Cobb 60s value of between 15 and 35 g/m².

The mulching film may have a Cobb 60s value of at most 35 g/m². The mulching film may have a Cobb 1800s value of at most 70 g/m² The mulching film may have a Cobb 1800s value of between 20 g/m² and 70 g/m². The mulching film may have an average Cobb 1800s value of between 20 g/m² and 70 g/m².

Cobb 1800s values of at most 70 g/m² are preferable as this may provide the mulching film with high durability.

The Cobb value may be determined in accordance with ISO 535:2014.

The mulching film may have a formation of between 60 and 90.

The mulching film may have a wet tensile index in machine direction of between 15 and 35 kNm/kg. The wet tensile index may be determined in accordance with ISO 3781 :2011.

The mulching film may have a burst index on the wire side of between 6.0 and 9.0 mN/kg. The mulching film may have a burst index on the upper side of between 6.0 and 9.0 mN/kg. The mulching film may have an average burst index of between 6.0 and 9.0 mN/kg. The burst index may be determined in accordance with ISO 2758:2014.

The mulching film may have a thickness of between 100 and 150 pm. The thickness may be determined in accordance with ISO 534:2011 .

The mulching film may have a bending stiffness in machine direction of between 60 and 100 mN. The mulching film may have a bending stiffness in transverse direction of between 50 and 90 mN. The bending stiffness may be determined in accordance with ISO 2493-1 :2010. The bending stiffness may be determined at a bending length of 10 mm and at a bending angle of 15°.

The mulching film may have a Bendtsen roughness on the wire side of between 700 and 1200 ml/min. The mulching film may have a Bendtsen roughness on the upper side of between 1200 and 1700 ml/min. The Bendtsen roughness may be determined in accordance with ISO 8791-2:2013. The mulching film may have a static friction coefficient on the wire side of between 0.3 and 0.7. The mulching film may have a static friction coefficient on the upper side of between 0.3 and 0.7. The static friction coefficient may be determined in accordance with ISO 15359:1999.

The mulching film may have a density of between 500 and 1000 kg/m³

The mulching film may have a dynamic friction coefficient on the wire side of between 0.3 and 0.7. The mulching film may have a dynamic friction coefficient on the upper side of between 0.3 and 0.7. The dynamic friction coefficient may be determined in accordance with ISO 15359:1999.

Apart from the mulching film as such, the present invention also relates to a use of the film for covering a soil surface.

The invention also relates to an arrangement of an inventive mulching film on a soil surface. The mulching film is preferably attached to the soil surface, in order to be kept in place in particular under strong wind conditions.

For attaching the mulching film, fastening means may be provided, which fastening means may be embodied as sticks, in particular wooden sticks.

The fastening means may penetrate the mulching film and they may be partially inserted into the soil. In the inventive arrangement, the fastening means may be provided at a regular distance in the region of the edges of the mulching film.

A multiplicity of fastening means may be provided, such to form a row of fastening means. A multiplicity of fastening means may particularly mean that more than five, preferably more than ten, fastening means are provided. A row of fastening means may particularly run substantially parallel to an edge of the mulching film. In the arrangement of the invention, at least two rows of fastening means may be provided.

The fastening means, in particular the sticks, may be inserted into the soil at a certain angle relative to horizontal. This may improve the attachment properties especially in relation to wind resistance.

The fastening means may have a tapered portion, which is inserted or insertable into the soil.

The edges of the mulching paper may be loose; in particular, they may not be covered by soil. This is preferable, as long-time exposition to moist conditions may weaken the durability of the mulching film. If the sticks or other similar fastening means are used for attaching the mulching film to the soil surface, this problem can be circumvented.

In the arrangement, the mulching film may be provided with plant openings. The plant opening may have any suitable size and/or shape, such that the desired crop or plant can penetrate the mulching film. A plant may be arranged in the area of the plant opening and/or a plant may penetrate the mulching film in the area of the plant opening.

The mulching film may comprise a multiplicity of plant openings, such that a plantopening row is formed. Neighboring plant openings in one row may be arranged at distances that are suitable for the specific plants or crops.

The invention may further relate to a method for covering a soil surface or a part of a soil surface with a mulching film. In the method, a mulching film according to the invention may be placed on the area of interest and then attached to the soil surface by fastening means. Using said method, an arrangement of the invention may be formed. In the method, plant openings may be formed in the mulching film. This step may be performed before, during, and/or after the film has been placed on or attached to the soil surface. The invention particularly relates to a mulching film, optionally for a mulching period of at least three months, the mulching film comprising or consisting of a base material, wherein the base material is made of mechanically and/or chemically processed cellulose fibers derived from wood, rags, grasses or other vegetable sources,

Preferably, it is provided that the mulching film has a tensile energy absorption in machine direction of between 250 J/m² and 400 J/m².

Optionally, it may be provided that the base material is uncoated.

Optionally, it may be provided that the mulching film has a Cobb 60s value of at most 35 g/m²

Optionally, it may be provided that the mulching film has a Cobb 1800s value of at most 70 g/m²

Optionally, it may be provided that the base material contains a wet strength agent in a content of between 1 .5 and 6.5 kg/t paper atro, wherein the wet strength agent preferably is polyamidoamine-epichlorohydrin (PAE).

Optionally, it may be provided that the base material contains a sizing agent in a content of between 0.5 and 2.0 kg/t paper atro and/or characterized in that the base material contains starch, in particular cationic starch, in a content of between 2.0 and 4.0 kg/t paper atro.

Optionally, it may be provided that the pulp of the base material is mechanically treated by low consistency refining, in particular at between 2% and 5% pulp consistency and/or at a specific refining energy of between 20 kWh/to and 100 kWh/to.

Optionally, it may be provided that the pulp of the base material is mechanically treated by high consistency refining, in particular at between 25% and 40% pulp consistency and/or at a specific refining energy of between 250 kWh/to and 310 kWh/to. Optionally, it may be provided that the base material is microcrepped.

Optionally, it may be provided that the base material is paper, in particular Kraft paper.

Optionally, it may be provided that it has a wet tensile strength in machine direction (MD) of between 1 .6 kN/m and 2.7 kN/m.

The invention may further relate to a use of a mulching film according the invention for covering a soil surface, in particular in an area of interest for agriculture, horticulture, and/or forestry.

The invention may also relate to an arrangement of a mulching film according to the invention on a soil surface, wherein the mulching film is attached to the soil surface.

Optionally, it may be provided that the mulching film is attached to the soil surface via fastening means, which fastening means penetrate the mulching film and are partially inserted into the soil.

Optionally, it may be provided that the fastening means are sticks, in particular wooden sticks.

Optionally, it may be provided that the fastening means, in particular the sticks, are partially inserted into the soil at an angle between 45° and 80° relative to horizontal.

Optionally, it may be provided that the upper side of the mulching film is not covered by soil material.

Optionally, it may be provided that the mulching film has plant openings.

The invention may further relate to a method of covering a soil surface, in particular in an area of interest for agriculture, horticulture, and/or forestry, the method comprising the following steps: - placing a mulching film according to the invention on the soil surface to be covered, and

- attaching the mulching film to the soil surface.

Further features of the present invention are given in the appended claims. The invention will now be described in detail by referring to exemplary embodiments of the invention. The exemplary embodiments are not intended to restrict the scope of protection of the independent patent claims.

In the drawings:

Fig. 1 shows a schematic sectioned view of an arrangement according to an exemplary embodiment of the invention; and

Fig. 2 shows a schematic section of a mulching film according to an exemplary embodiment of the invention.

Except indicated otherwise, the following elements are shown in the drawings: Base material 1 , mulching film 2, soil surface 3, fastening means 4, upper side 5, plant opening 6, soil 7.

Fig. 1 shows a schematic sectioned view of an arrangement according to an exemplary embodiment of the invention. The mulching film 2 is attached to an area of soil 7 via fastening means 4.

In this embodiment, the fastening means 4 are wooden sticks, which are arranged in rows running parallel to two opposite edges of the mulching film 2. The distance between the edges of the mulching film 2 and the rows of fastening means 4 is approx.

5 cm. The fastening means 4 penetrate the mulching film 2 and they are partially inserted into the soil 7. The fastening means 4 are arranged at an angle of approx. 70°C relative to horizontal. The distance between two neighboring fastening means 7 is approx. 25 cm.

The mulching film 2 is further equipped with plant openings 6, which are arranged in one row running along the central part of the mulching film 2. The distance between neighboring plant openings 6 is approx. 35 cm.

Fig. 2 shows a schematic section of the mulching film 2 used in the arrangement depicted in Fig. 1. It can be seen in Fig. 2 that the mulching film 2 has a substantially homogeneous composition in its thickness direction; in particular, the mulching film 2 is a one-layered film.

The base material 1 of the mulching film 2 is Kraft paper made of softwood fibers. Selected parameters of the mulching film 2 according to this exemplary embodiment are shown in Table 1 .

A mulching film 2 according to an exemplary embodiment of the present invention may be obtained by following the below protocol:

An unbleached pulp consisting of 100% primary pulp of softwood (mixture of spruce and pine) with a kappa number of 51 was first subjected to high consistency refining at a specific refining energy of 270 to 280 kWh/t, a refining degree of the pulp after high consistency refining being 18°SR.

Subsequently, this pulp was subjected to low-consistency refining with a specific refining energy of 70 to 80 kWh/t. In the approach flow system of the paper machine, the following additives were added. The pH value was adjusted to a pH value of 5.4-5.6 with sulfuric acid and aluminum sulphate. Cationic starch with a cationisation degree, DS, of 0.045 was added in a quantity of 3 kg/t paper atro, alkenyl succinic anhydrides were used as sizing agents in a quantity of 1.3 kg/t paper atro and 4.5 kg/t PAAE as wet strength agent. Furthermore, no fillers were added. The consistency of the pulp at the headbox was 0.19 %. Dewatering was carried out on a foudrinier wire section and with a press section equipped with three conventional press roll nips. Before the still moist paper was fed to the Clupak unit, it was subjected to contact drying in the pre-drying section. The first drying groups in the pre dryer are equipped with slalom drying fabric whereas the rest of the drying groups are equipped with a two tier drying fabric configuration. After the pre-dryer, the still moist web is treated in a Clupak unit with a differential speed of -6.8% and finally dried in the after dryer to a final residual moisture content of 7.5%.

The Kraft paper can be used as such as a mulching film according to the present invention and the paper properties described in the table below were measured in this Kraft paper.

Table 1: Parameters of the exemplary mulching film

Claims

1. A mulching film, in particular for a mulching period of at least three months, the mulching film (2) comprising or consisting of a base material (1 ), wherein the base material (1 ) is made of mechanically and/or chemically processed cellulose fibers derived from wood, rags, grasses or other vegetable sources, characterized in that the mulching film (2) has a tensile energy absorption in machine direction of between 250 J/m² and 400 J/m².

2. Mulching film according to claim 1 , characterized in that the base material (1 ) is uncoated.

3. Mulching film according to claim 1 or 2, characterized in that the mulching film (2) has a Cobb 60s value of at most 35 g/m²

4. Mulching film according to claim 1 or 2, characterized in that the mulching film (2) has a Cobb 1800s value of at most 70 g/m²

5. Mulching film according to any of claims 1 to 4, characterized in that the base material (1 ) contains a wet strength agent in a content of between 1 .5 and 6.5 kg/t paper atro, wherein the wet strength agent preferably is polyamidoamineepichlorohydrin (PAE).

6. Mulching film according to any of claims 1 to 5, characterized in that the base material (1 ) contains a sizing agent in a content of between 0.5 and 2.0 kg/t paper atro and/or characterized in that the base material (1 ) contains starch, in particular cationic starch, in a content of between 2.0 and 4.0 kg/t paper atro.

7. Mulching film according to any of claims 1 to 6, characterized in that the pulp of the base material (1 ) is mechanically treated by low consistency refining, in particular at between 2% and 5% pulp consistency and/or at a specific refining energy of between 20 kWh/to and 100 kWh/to. Mulching film according to any of claims 1 to 7, characterized in that the pulp of the base material (1 ) is mechanically treated by high consistency refining, in particular at between 25% and 40% pulp consistency and/or at a specific refining energy of between 250 kWh/to and 310 kWh/to. Mulching film according to any of claims 1 to 8, characterized in that the base material (1 ) is microcrepped. Mulching film according to any of claims 1 to 9, characterized in that the base material (1 ) is paper, in particular Kraft paper. Mulching film according to any of claims 1 to 10, characterized in that it has a wet tensile strength in machine direction (MD) of between 1.6 kN/m and 2.7 kN/m. A use of a mulching film (2) according to any of claims 1 to 11 for covering a soil surface (3), in particular in an area of interest for agriculture, horticulture, and/or forestry. An arrangement of a mulching film (2) according to any of claims 1 to 11 on a soil surface (3), wherein the mulching film (2) is attached to the soil surface (3). Arrangement according to claim 13, characterized in that the mulching film (2) is attached to the soil surface (3) via fastening means (4), which fastening means (4) penetrate the mulching film (2) and are partially inserted into the soil (7). Arrangement according to claim 14, characterized in that the fastening means (4) are sticks, in particular wooden sticks. Arrangement according to claim 14 or 15, characterized in that the fastening means (4), in particular the sticks, are partially inserted into the soil (7) at an angle between 45° and 80° relative to horizontal. Arrangement according to any of claims 13 to 16, characterized in that the upper side (5) of the mulching film (2) is not covered by soil material. Arrangement according to any of claims 13 to 17, characterized in that the mulching film (2) has plant openings (6). A method of covering a soil surface (3), in particular in an area of interest for agriculture, horticulture, and/or forestry, the method comprising the following steps:

- placing a mulching film (2) according to any of claims 1 to 11 on the soil surface (3) to be covered, and

- attaching the mulching film (2) to the soil surface (3). Method according to claim 19, characterized in that the mulching film (2) is attached to the soil surface (3) via fastening means (4), which fastening means (4) penetrate the mulching film (2) and are partially inserted into the soil (7).