Patent Application
20210378184
The present application relates to and claims the benefit and priority to European Application No. EP20382493.3, filed Jun. 8, 2020.
The present disclosure relates to agricultural mulch films, and more in particular to agricultural mulch films including one or more degradable layers.
Mulch films are widely used in agricultural applications. Agricultural mulch films may be extended over a cultivation area. Some weight may be placed on the film, e.g. by burying the sides of the film or by placing soil or mass in bags incorporated in the film, to keep the film in place. Agricultural mulch films protect crops and soil from weathering, and help to avoid or at least reduce loss of water and fertilizers in the soil. They are also used to decrease the presence of weeds and regulate the interaction of sunlight with the crop and the soil. The sunlight and heat received by the crop and the soil has a direct influence on crop yield, e.g. the amount of crop that may be harvested, and on the moment when it can be harvested (precocity) and its quality.
Different types of agricultural mulch films are currently available, and a type of mulch film may be selected depending on a desired outcome. For instance, a transparent film maximizes the sunlight that reaches the soil, increasing soil temperature and boosting plant growth. An opaque or semi-opaque film, e.g. a black mulch film, hampers weeds growth and keeps the soil warm. A photoselective mulch film lets specific radiation pass through the film. For example, only photosynthetically active radiation (PAR) may pass through the photoselective film. Agricultural mulch films may also be configured as bicolor films. A bicolor film has its two faces of different colors. For instance, a bicolor film may have a black face and a white, silver, green, brown or grey face. In general, any combination of colors is possible. If one face is white or silver, placing this face upwards, i.e. facing the sky and/or the sunlight, helps to reflect the sunlight that would irradiate the crop and/or decrease the temperature below the film. An additional lower black film may render the film opaque.
The needs of the crop, e.g. in terms of solar radiation, may vary during the crop growth and can depend on climate conditions. In order to regulate the sunlight and temperature received by the crop and the soil, one may think about extending a first agricultural mulch film, and then replacing it with a different film when the needs of the crop have changed. Another option may be placing a bicolor mulch film, e.g. with a black face facing upwards, and later turning the film around, e.g. such that a white face faces upwards instead. However, none of these options are very efficient in terms of the use of resources, e.g. number of mulch films (in the first option), workforce and time needed for replacement. Also, depending on the crop, e.g. if the crop grows above and/or over the mulch film, it may not even be possible to turn around the mulch film without damaging the crop.
The present disclosure aims to provide improvements in agricultural mulch films.
In a first aspect, an agricultural mulch film is provided, which comprises a first layer having a first capacity of light absorption, and a second layer, having a second capacity of light absorption different from the first capacity of light absorption, and wherein the first layer is configured to be removed from the second layer after a period of time.
In accordance with this aspect, a film is provided that instead of having to e.g. flip a mulch film to expose another face of the film, or to substitute a film for another as the needs of the crop change over time, the film may be tailored or engineered to have the suitable varying characteristics over time. The first layer may be configured to degrade, and specifically to degrade more quickly than the second layer and/or the first layer may be configured to be removable from the second layer.
Throughout this disclosure, a capacity of light absorption may be understood as a capacity of a layer of a mulch film to absorb a certain amount of incident electromagnetic energy (e.g. sunlight) in a certain way. A change in capacity of light absorption may be understood as a change in the light (e.g. wavelength and/or amplitude) that is reflected, absorbed, and/or transmitted by a layer. Thus, a change in capacity of light absorption may include a change in at least one of transparency, opacity, translucency, photoselectivity, color and the like of a layer.
Herein, a change in capacity of light absorption may be related to a layer, and in particular to its composition. It may not be related to a variation of incident light, e.g. due to weather changes or sun movement (sunrise, sunset), over time, e.g. during a day. Thus, different layers with same dimensions (e.g. length, width) and shape may have different capacities of light absorption if their capacities of light absorption are distinct when exposed to a same light in the same conditions, e.g. sunlight.
In an example, two different layers of a mulch film have different capacities of absorption due to the fact that they are at least of different colors, e.g. one may be green, and the other may be black. In another example, two different layers of a mulch film have different capacities of absorption as they have at least different opacities (e.g. opacities that differ in at least 5%). Still in another example, two different layers of a mulch film have different capacities of absorption due to the fact that at least their translucency is different (e.g. translucency differs in at least a 5% between layers).
In some examples, electromagnetic energy may be visible light, i.e. the portion of the electromagnetic spectrum that is visible to the human eye. Light and electromagnetic energy may be used interchangeably herein.
For each layer or a sublayer of an agricultural mulch film a capacity of light absorption may be defined. A difference between the capacities of light absorption between layers may be significantly higher than an inevitable variation of the capacity of light absorption within the same layer due to the manufacturing process.
In some examples, the first layer has a first degradation time and the second layer has a second degradation time, the second degradation time being different from the first degradation time. In this or other examples, the first layer may have a first rate of degradation and the second layer may have a second rate of degradation, which is different from the first rate of degradation.
Thus, a layer of a mulch film having a shorter degradation time may degrade faster and the optical and/or thermal properties of the mulch film may change accordingly. Advantageously, light and heat received by a crop may be modified in a controlled and efficient way. The speed of degradation of the first and the second layers may be adapted to the crop being grown, e.g. a certain type of vegetable, and/or to climate conditions, e.g. a crop growing towards the winter or a crop growing towards the summer. The latitude where a crop may be growing may be also considered. The terms degradation rate, degradation speed and speed of degradation may be used interchangeably herein.
A rate of degradation may be defined as quantity of material that degrades per unit of time. A unit of time may be e.g. a month, a few months or a year. Different layers may have different degradation rates if the degradation rate of a layer differs from the degradation rate of another layer by at least 20%, i.e. 20% more or less material is degraded in the same unit of time.
A degradation time may mean a period of time in which substantially at least 90% of a layer has degraded, eroded, decomposed or disappeared. Different layers having different degradation times may be understood to mean that in use, the different layers have times of degradation that differ at least 10%, and more specifically at least 20%. As an example, a degradation time of one layer may be 150 days. Another layer having a different degradation time means that it has a degradation time of either 135 days or less, or 165 days or more; and more specifically 120 days or less, or 180 days or more.
The first layer of the agricultural mulch film may be a top layer of the film, and the second layer may be a bottom layer of the film. In this example, the top layer may have a shorter degradation time than the bottom layer, and specifically the top layer may have a higher rate of degradation than the bottom layer. Accordingly, the top layer of the film may degrade faster and may leave a lower layer, or the bottom layer if the mulch film includes two layers only, with a different capacity of light absorption uncovered. The top layer is the one that absorbs and/or reflects incoming light to a certain extent. The top layer is also the layer that is most visible and most easily inspected. If the top layer degrades faster, it is easy to know how the properties of the mulch film are changing/have changed by visual inspection. In some other examples, the bottom layer has a speed of degradation higher than a speed of degradation of an upper layer. The interaction of a bottom side of the film with crop and soil may thus be changed over time.
Also, some crops may grow above and over the mulch film. In this case, regulation of light and temperature conditions may be performed easily and without damaging or stressing the crop, e.g. in comparison with a situation where people replace or turn around a mulch film.
Degradation times of the mulch film layers together with capacity of light absorption of the upper and lower layers, e.g. a top and a bottom layer, of the mulch film may be varied in order to tailor a mulch film to the needs of a specific crop.
A degradation time of a layer may be a function of a thickness of a layer of film as well as the material of the layer of the film having a certain degradation rate or degradation speed. Additives such as e.g. UV stabilizers may also play a role in the degradation rate. These three aspects, namely thickness, material and additives, may be chosen and adapted (e.g. which materials/additives and in which proportion, and which layer thickness are to be used) to tailor a degradation time or a degradation rate.
A “layer” as used throughout the present disclosure may be regarded as a portion or section of a film which is arranged on top or below one or more further layers. A layer generally extends over the entire length and width of the film. A layer may include a plurality of sublayers. For example, an agricultural mulch film may include e.g. 5, or 7 or 9 or more sublayers. Purely by way of example, when the film comprises 9 sublayers in total, e.g. the first 5 of these sublayers may constitute the first layer, and the other sublayers may constitute a second and/or a third layer. In another example, if the film comprises 9 sublayers, the first 3 sublayers may be regarded as constituting the first layer, and the remaining 6 sublayers may constitute the second layer.
Degradable as used throughout the present disclosure may be understood as that the material or layer is configured to degrade, i.e. break-down, deteriorate or fragment during its normal use. In examples, degradable may mean that the layer or material will degrade within 1 year when exposed to a foreseen environment and weather conditions, and more specifically will degrade within 9 months or less. These times may enable the top layer to degrade according to the light and/or temperature needs of specific crops, and also to the season towards which the crop will be growing. Eroding, degrading, and breaking down are used herein to mean the same process and are herein used interchangeably.
Biodegradable or compostable as used throughout the present disclosure may be understood as any material that is configured to erode, decompose or degrade by microorganisms, such as bacteria and fungi.
Accordingly, the biodegradable layers may decompose in soil, and collecting them or a portion of them may not be necessary. In addition, a compostable layer may help to fertilize the soil. In an example, all the layers are biodegradable.
One or more layers of the film may substantially be non-(bio)degradable or may barely be (bio)degradable. In some of these examples, the top layer of the mulch film is (bio)degradable, and the bottom layer of the mulch film is based on polyolefinic materials. The service life of the bottom layer may thus be longer.
In some examples, the top layer is configured to be removable from the film. This helps to regulate sunlight and temperature by removing the top layer of the film, no matter the degradation of the top layer. I.e., removing the top layer may be an alternative to waiting for the top layer to degrade for changing the properties of the mulch film. In addition, a removable top layer may be used as a security feature in combination with degradability of a layer. For instance, if a top layer is black, a bottom layer is white and temperature has started to increase before expected, the black top layer may be removed, e.g. mechanically or manually, in order to adapt the mulch film to the increase of temperature without needing to wait for the top layer to degrade.
In some examples, the first layer is of a first color and the second layer is of a second color different from the first color. In some of these examples, the bottom layer is black, and the top layer may be white, silver, green, brown, grey, transparent or translucent, or of any color different from black. Likewise, in some other examples, the top layer is black, and the bottom layer may be of any color which is not black. In this way, the advantages offered by the color of the top layer may be used first, and once the top layer is not present, the benefits offered by the color of the bottom layer may be enjoyed.
In a specific example, the upper layer may be white or silver, and the lower layer is black. If the upper layer degrades faster than the lower layer, the white or silver layer may help to reduce soil temperature in the initial stages of crop growth and, once the white or silver layer is no longer present, the black layer may help to increase the soil temperature. Such a mulch film may be useful when over time, the need for absorbance of heat and light increases, e.g. for crops growing towards the winter.
In another specific example, the upper layer may be black, and the lower layer may be white or silver. If the upper layer degrades faster than the lower layer, the black layer may increase the temperature of the soil and, when the black layer is no longer present, the white or silver layer may help to decrease soil temperature. Such a mulch film may be useful when going towards the summer.
The agricultural mulch film disclosed herein may have any number of layers. In some examples, in addition to the first and second layers, the mulch film comprises a third layer. Such a mulch film may have different structures.
In some examples, the mulch film has an A/B/B structure. In this case, in terms of degradability, a top layer A may degrade faster than the other two lower layers B. In some of these examples, layer A is biodegradable and layers B are based on polyolefinic materials. In some other examples, layers A and B are biodegradable, and in particular layer A may degrade faster than layers B. In any of these examples, layer A may be removable from the film, e.g. manually.
A thickness of the mulch film may be between 10-200 microns, and specifically between 30 and 100 microns. A mulch film with a thickness in this range may be sufficiently strong and resistant to protect a crop at the same time that one or more of its layers may degrade at a required time or speed for an optimized crop growth.
In some examples, one or more layers include polyolefins. Introducing polyolefinic materials into one or more layers enables to prolong the service time of such layers.
The proportion of biodegradable, compostable and/or polyolefinic materials included in each layer may be adjusted to the desired duration of that layer of the mulch film.
In any of these examples, a mulch film may include one or more pockets along one or more edges of the mulch film. Introducing some material into the one or more pockets, e.g. soil, sand and/or hygroscopic materials, may provide sufficient weight in order to fix the mulch film to the cultivation soil.
Non-limiting examples of the present disclosure will be described in the following, with reference to the appended figures, in which:
The figures refer to example implementations and are only be used as an aid for understanding the claimed subject matter, not for limiting it in any sense.
The fact that the top 110 and bottom 120 layers of the mulch film 100 may degrade at different speeds means that the optical and/or thermal properties of the film 100 can change over time due to the difference in capacity of light absorption of each layer.
For instance, in some examples, the time and/or speed of degradation of the top layer 110 may be higher than the time and/or speed of degradation of the bottom layer 120. Therefore, the top layer 110 may degrade, as schematically illustrated in
In some examples, the top layer 110 may degrade due to its composition, e.g. due to being made of biodegradable materials. Some biodegradable materials may further be compostable. In these or other examples, the top layer 110 may degrade due to the action of ultraviolet (UV) radiation. In some examples, the bottom layer 120 may be made of, or based on, polyolefinic plastic materials.
In another example, shown in
In an example, a mulch film 100 such as the mulch film 100 of the examples of
The opposite may be implemented for crops growing towards the summer, i.e., the top layer 110 may be black and the bottom layer 120 may be white or silver, so that at the appropriate time, the appropriate reflectivity and light absorbance are used.
In general, the top 110 and bottom 120 layers may be of any color, they do not need to be white, silver or black. Any suitable color pigment may be added to the different layers.
For instance, in some examples the bottom layer is black, and the top layer may be green, brown, grey, transparent, or of any color different from black. Likewise, in some other examples, the top layer is black, and the bottom layer may be of any color which is not black.
In the example of
In some examples, the speed of degradation decreases from the top layer 110 to the bottom layer 130. In this way, each of the three layers 110, 120, 130 may be exposed to sunlight with time and the properties of the mulch film 100 may be varied accordingly. In an example, the first 110 and second 120 layers are made of biodegradable materials and the third layer 130 is made mostly or exclusively of polyolefinic materials.
In some other examples, the third layer 130 has a speed and/or time of degradation substantially equal to the speed and/or time of degradation of the second layer 120. Such a mulch film 100 may then have an A/B/B structure. In an example, the first (top) layer 110 may be black, the second (middle) 120 layer may be white or silver, the third (bottom) 130 layer may be black, and the top layer 110 may degrade faster than the layers 120 and 130. Accordingly, the upper layer 110 may be configured to absorb irradiant (sun)light to increase the temperature below the film 100 first, and a bicolor film may remain when the top layer 110 is no longer present. The middle layer 120 may then reduce the temperature below the film 100 and reflect light towards the crop, and the bottom layer 130 may hamper weeds growth. Therefore, this mulch film 100 may be advantageous for crops growing towards the summer.
A mulch film 100 such as the one described in the paragraph above may provide additional advantages. This may be seen in
In yet a further example, the bottom layer 130 has a speed of degradation substantially equal to the speed of degradation of the top layer 110, and the middle layer is substantially not degradable. Such a mulch film 100 may have an A/B/A structure. In an example, the top 110 and bottom 130 sections are silver or white, and the middle section 120 is black.
In summary, each of the layers may have specific characteristics and may be provided with a specific objective in mind. Thanks to being able to engineer the degradation rate and/or time of the separate layers, a mulch film may be provided that can vary its characteristics over time.
In any of the examples of
A non-biodegradable layer or less biodegradable layer may have a degradation time that is longer than a degradation time of a degradable layer, e.g. more than 1 year.
Concerning (bio)degradability, a biodegradable layer, e.g. the upper layer 110, may include one or more of the following materials: polylactic acid (PLA), poly(butylene adipate-co-tereftalate) (PBAT), polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), polyhydroxyvaleriate (PHV), polyhydroxyhexanoate (PHH), butyrate-co-valerate (PHBV or P(3HB-co-3HV)), butyrate-co-hexanoate (PHBH or P(3HB-co-3HH)), starch and/or starch blends, poly (butylene succinate) (PBS), poly (butylene succinate-co-adipate) (PBSA) and polymers derived from proteins, e.g. milk proteins.
A non-(bio)degradable or less (bio)degradable layer of the mulch film 100 may include one or more of the following materials: polyethylene (PE), PE copolymers, polypropylene (PP), PP copolymers, ethylene vinyl acetate (EVA), ethylene butyl acrylate (EBA), polyamide (PA), ethylene vinyl alcohol (EVOH), polyvinyl alcohol (PVOH), polyethylene terephthalate (PET).
In an example, amounts of PBAT, PLA and/or starch are used to adjust the biodegradability of a layer, e.g. a top layer 110. The proportions of these materials may affect a degradation time and/or degradation speed of a layer. For instance, by varying the proportions of these materials, a degradation time between one and three months may be obtained.
Any of the layers of the mulch films 100 according to the present disclosure, may comprise one or more of the materials mentioned in the above paragraphs. In addition, one or more adhesive polymers may be added to the mulch film 100 to guarantee adherence between layers. In an example, maleic anhydride is included with one or more of the above polyolefinic plastic materials.
Also, the first, second and third layers 110, 120, 130 (and further layers) may be monolayer or multilayer, i.e. the layers may include sublayers. The first, second, and third layers may have a same or a different number of sublayers. The thickness of the layers included in the mulch film 100 may be different or the same. In the examples of
The number of layers, the materials used for each layer and the thickness of each layer may be selected according to desired properties of each layer, e.g. in terms of biodegradability. Additives may also be included to obtain the desired properties of a layer. A mulch film 100 may have more than three layers.
In an example, the total thickness of the mulch film 100 may be between 10 and 200 microns. In such an example, the mulch film 100 may have the following mechanical properties.
In such an example, a biodegradable layer comprised in the mulch film 100 may have a thickness between 2 and 100 microns. For instance, in
In an example, the top layer may be black (or another color with low reflectance and relatively high absorbance of light), the middle layer may be white, and the bottom layer may be black. After degradation of the top layer, the remaining layer may have a top white layer, and a bottom black layer.
A mulch film 100 according to any of the examples disclosed herein may be manufactured in several ways. In an example, the mulch film 100 may be manufactured by coextruding two or more layers or sublayers including any of the materials mentioned above. For example, one or more types of polymer pellets may be melted and shaped into a layer or sublayer. Additives, such as coloring agents, may be melted with the pellets. Two or more layers or sublayers may be then coextruded to manufacture the mulch film 100. Such a coextrusion process may include blowing and/or calendaring, as well as orientation of the film. The film may be oriented in a longitudinal direction (machine direction) and/or a transversal direction. In another example, two or more layers or sublayers including any of the materials mentioned above may be stacked together by lamination, e.g. adhesive lamination or hot-roll lamination. Other manufacturing processes may be possible.
In a preferred example, the pockets may be integrally formed with the film.
Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20382493.3 | Jun 2020 | EP | regional |
