Multilayer plastic film for perrenial agricultural use with self-adjusting shading attribute

Abstract

A multilayer plastic film for perennial agricultural use (1) either in greenhouses or under low tunnels (2) that, self-adjusts the shading provided in the covered space (4). The shading effect can be present in the whole surface of the film, or it could be partial at specific surfaces (3) where shading would be most needed. The shading is achieved by incorporating a photochromic compound or a combination of photochromic compounds in a layer of multiple layers in a multilayer film (1). The layer or layers that incorporate the photochromic compound or compounds are protected from oxidation by bilateral layers that incorporate materials that exhibit low permeability to gases and in particular to oxygen. The advantage of the film is that the grower would not need to apply any shading material on the surface of the film and/or any mechanism to facilitate opening and closing of the shading material.

Claims

1. A multilayer plastic film for perennial agricultural uses, the film having a self-adjusting shading attribute, width (W.sub.1), a thickness (t.sub.1), and an ability to self-adjust the shading of the space it covers according to existing ambient light conditions, comprising: a photochromic compound that is incorporated into a matrix, the multilayered plastic film of said film and encapsulating layers, the encapsulating layers being formed of an oxygen barrier material that has oxygen barrier properties and that encapsulate and protect the photochromic compound from exposure to atmospheric oxygen, wherein the film is a coextruded seven-layer film which, in cross section and in sequence, is formed of the following layers: Layer A: a polyolefin from the group consisting of LDPE (low density polyethylene), LLDPE (Linear Low Density Polyethylene), EVA (ethylene vinyl acetate) and a blend thereof, Layer B: a tie material compatible with both polyolefins and the oxygen barrier material, Layer C: a low oxygen permeability (barrier) material, Layer D: the core layer that incorporates the photochromic compound and has as a matrix a material that exhibits thermal properties, Layer E: a low oxygen permeability (barrier) material, Layer F: a tie material compatible with both polyolefins and the oxygen barrier material, and Layer G: a polyolefin from the group consisting of LDPE, LLDPE, EVA and a blend thereof.

2. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 1, wherein the photochromic compound is of width (W.sub.1) and thickness (t.sub.1) and is superimposed and continuously welded on a multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.2) where W.sub.1<W.sub.2.

3. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 1, further comprising two films which incorporate the photochromic compound and are of a first of the two films has width (W.sub.1) and a thickness (t.sub.1) and a second of the two films has a width (W.sub.3) and a thickness (t.sub.3), respectively and the two films being superimposed and welded with continuous welds on at least one surface of a multilayer greenhouse or low tunnel film (W.sub.2) and thickness (t.sub.2) where W.sub.1<W.sub.2 and W.sub.3<W.sub.2.

4. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 1, wherein one or several of the plastic photochromic films is in the form of strips that are welded along the length of the film on at least one surface of a photochromic multilayered greenhouse or low tunnel film.

5. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 1, wherein the produced shading is of any coloration of the visible electromagnetic spectrum or the non-visible electromagnetic spectrum.

6. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 1, wherein at least one of said layers has at least one of antioxidants and UV radiation stabilizers-absorbers.

7. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 1, wherein two films incorporate the photochromic compound, and a first of the two films having a width (W.sub.1) and a thickness (t.sub.1) and a second of the two films having a width (W.sub.3) and thickness (t.sub.1) respectively and are superimposed and welded with discontinuous welds on at least one surface of a multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.1) where W.sub.1<W.sub.2 and W.sub.3<W.sub.2 and t.sub.2>t.sub.1 and t.sub.2>t.sub.3.

8. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 1, wherein said matrix is formed of a core layer of the multilayer plastic film.

9. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 1, wherein said matrix is formed of multiple layers of the multilayer plastic film.

10. A multilayer plastic film for perennial agricultural uses, the film having a self-adjusting shading attribute, a width (W.sub.1), a thickness (t.sub.1), and having an ability to self-adjust shading of a space covered thereby according to existing ambient light conditions, comprising: a photochromic compound that is incorporated into a matrix, the matrix being comprised of at least a core layer and encapsulating layers, the encapsulating layers being formed of layers of a material having oxygen barrier properties and that encapsulates and protects the photochromic compound so that the photochromic compound is protected from exposure to atmospheric oxygen, wherein the film is a coextruded nine-layer film which, in cross section and in sequence, is formed of the following layers: Layer A: a polyolefin from the group consisting of LDPE (low density polyethylene), LLDPE (Linear Low Density Polyethylene), EVA (ethylene vinyl acetate) and a blend thereof, Layer B: a tie material compatible with both polyolefins and the oxygen barrier material, Layer C: a low oxygen permeability (barrier) material, Layer D: a tie material compatible with both polyolefins and the oxygen barrier material, Layer E: the core layer that incorporates the photochromic material and has a matrix material that exhibits thermal properties, Layer F: a tie material compatible with both polyolefins and the oxygen barrier material, Layer G: a low oxygen permeability (barrier) material, Layer H: a tie material compatible with both polyolefins and the oxygen barrier material, and Layer J: a polyolefin from the group consisting of LDPE, LLDPE, EVA and a blend thereof.

11. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 10, wherein the photochromic compound has a width (W.sub.1), a thickness (t.sub.1) and is superimposed and continuously welded on a multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.2), where W.sub.1<W.sub.2.

12. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 10, further comprising two films which incorporate the photochromic compound, wherein a first of the two films has a width (W.sub.1) and a thickness (t.sub.1) and a second of the two films has a width (W.sub.3) and a thickness (t.sub.3), the two films being superimposed and welded with continuous welds on both surfaces of a conventional multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.2) where W.sub.1<W.sub.2 and W.sub.3<W.sub.2, and t.sub.2>t.sub.1 and t.sub.2>t.sub.3.

13. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 10, wherein the plastic photochromic film is in the form of strips welded along the length of the film on at least one surface of a photochromic multilayered greenhouse or low tunnel film.

14. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 10, wherein the produced shading is of any coloration of the visible electromagnetic spectrum or the non-visible electromagnetic spectrum.

15. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 10, wherein at least one of said layers has at least one of antioxidants and UV radiation stabilizers-absorbers.

16. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 10, wherein two films incorporate the photochromic compound, and a first of the two films having a width (W.sub.1) and a thickness (t.sub.1) and a second of the two films having a width (W.sub.3) and thickness (t.sub.1) respectively and are superimposed and welded with discontinuous welds on at least one surface of a multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.1) where W.sub.1<W.sub.2 and W.sub.3<W.sub.2 and t.sub.2>t.sub.1 and t.sub.2>t.sub.3.

17. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 10, wherein said matrix is formed of a core layer of the multilayer plastic film.

18. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 10, wherein said matrix is formed of multiple layers of the multilayer plastic film.

19. A multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute, the film having a width (W.sub.1), and of a thickness (t.sub.1), and a self-adjust shading attribute having an ability to self-adjust shading of a space covered thereby according to existing ambient light conditions, comprising: a photochromic compound that is incorporated into a matrix of the multilayered plastic film and which is encapsulated by layers, the encapsulating layers being formed of an oxygen barrier material having oxygen barrier properties and that encapsulates and protects the photochromic compound the photochromic compound so that the photochromic compound is protected from exposure to atmospheric oxygen, wherein the film is a coextruded nine-layer film which, in cross section and in sequence, is formed of the following layers: Layer A: a polyolefin from the group consisting of LDPE (low density polyethylene), LLDPE (Linear Low Density Polyethylene), EVA (ethylene vinyl acetate) and a blend thereof, Layer B: a tie material compatible with both polyolefins and the oxygen barrier material, Layer C: a low oxygen permeability (barrier) material, Layer D: a layer that incorporates the photochromic material and has as a matrix a material that exhibits thermal properties, Layer E: the core layer and a matrix a material that exhibits thermal properties, Layer F: a layer that incorporates the photochromic material and has as a matrix a material that exhibits thermal properties Layer G: a low oxygen permeability (barrier) material, Layer H: a tie material compatible with both polyolefins and the oxygen barrier material, and Layer J: a polyolefin from the group consisting of LDPE, LLDPE, EVA and a blend thereof.

20. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 19, the photochromic compound is of a width (W.sub.1) and a thickness (t.sub.1) and is superimposed and welded on a multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.2) where W.sub.1<W.sub.2, and t.sub.2>t.sub.1.

21. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 19, further comprising two films which incorporate the photochromic compound, wherein a first of the two films has width (W.sub.1) and a thickness (t.sub.1) and a second of the two films has a width (W.sub.3) and a thickness (t.sub.3), the two films being superimposed and welded with continuous welds on both surfaces of a multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.2) where W.sub.1<W.sub.2 and W.sub.3<W.sub.2, and t.sub.2>t.sub.1 and t.sub.2>t.sub.3.

22. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 19, wherein one or several of the plastic photochromic films in the form of strips welded along the length of the film on at least one surface of a or photochromic multilayered greenhouse or low tunnel film.

23. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 19, wherein the produced shading is of any coloration of the visible electromagnetic spectrum or the non-visible electromagnetic spectrum.

24. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 19, wherein at least one of said layers has at least one of antioxidants and UV radiation stabilizers-absorbers.

25. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 19, the photochromic compound is of width (W.sub.1) and thickness (t.sub.1) and is superimposed and welded with discontinuous welds on a multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.2) where W.sub.1<W.sub.2 and t.sub.2>t.sub.1.

26. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 19, wherein two films incorporate the photochromic compound and are of width (W.sub.1) and thickness (t.sub.1) and (W.sub.3) and thickness (t.sub.3) respectively and are superimposed and welded with discontinuous welds on both surfaces of a monolayer or multilayer greenhouse or low tunnel film of width (W.sub.2) and thickness (t.sub.2) where W.sub.1<W.sub.2 and W.sub.3<W.sub.2, and t.sub.2>t.sub.1 and t.sub.2>t.sub.3.

27. The multilayer plastic film for perennial agricultural uses with the self-adjusting shading attribute according to claim 19, wherein said matrix is formed of a core layer of the multilayer plastic film.

28. The multilayer plastic film for perennial agricultural uses with self-adjusting the shading attribute according to claim 19, wherein said matrix is formed of multiple layers of the multilayer plastic film.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A: shows a photochromic plastic film in a greenhouse or low tunnel that is permeable to sunlight due to low light intensity and an enlarged detail showing the functionality of the film.

(2) FIG. 1B: shows a photochromic plastic film in a greenhouse or low tunnel that exhibits drastically reduced permeable to sunlight and the shading functionality of the covered space and an enlarged detail of it.

(3) FIG. 2: shows a core layer that incorporates a photochromic compound in its matrix (spiro-oxazine in this case) and an enlarged detail of the core layer.

(4) FIG. 3: shows a seven-layer film structure (in cross section) incorporating a photochromic compound in the core layer, encapsulated by barrier layers (PVDC preferably), two Tie Layers that interface the structure to the skin layers and that incorporate Polyolefins.

(5) FIG. 4: shows a structure (in cross section) of a plastic film for greenhouses or low tunnel film that comprises a welded or laminated photochromic multilayer film on top of a conventional three-layer film.

(6) FIG. 5: shows a structure (in cross section) of a plastic film for greenhouses or low tunnel film that comprises two welded or laminated photochromic multilayer film on top of both skin layers of a conventional three-layer film.

(7) FIGS. 6 & 7: show a photochromic multilayer film welded on top of a conventional greenhouse film with continuous welds and a detail thereof.

(8) FIGS. 8 & 9: show a photochromic multilayer film welded on top of a conventional greenhouse film with discontinuous welds and a detail thereof.

(9) FIGS. 10A & 10B: show strips of a photochromic multilayer film welded on a conventional plastic greenhouse film with continuous or discontinuous welds.

DETAILED DESCRIPTION OF THE INVENTION

(10) Several embodiments of the invention are described below:

(11) The plastic film produced by the method of co-extrusion from a circular or flat die or mold having width (W.sub.1) and thickness (t.sub.1) and preferably having a seven-layer structure (FIG. 3). The photochromic compound is inserted into the extruder either as a master batch or in liquid form using an accurate dosi-metric unit and preferably in the core layer (D). The main material of the core layer (D) could be any polyolefin or a blend thereof that exhibits thermal properties such as EVA. The layers (C&E) encapsulate the layer (D) that incorporates the photochromic compound would exhibit low oxygen permeability and would preferably be PVDC. To interface the layers (C&E) with the skin layers (A&G) that comprise polyolefins, such as LDPE, LLDPE, EVA or a blend thereof, tie layers (B&F) are placed in between. Hence a multilayer structure of the plastic film is formed comprising:

(12) Layer A: Polyolefin such as LDPE, LLDPE, EVA or a blend thereof

(13) Layer B: Tie material compatible with both polyolefins and the barrier material

(14) Layer C: Low oxygen permeability (barrier) material (preferably PVDC)

(15) Layer D: Core Layer that incorporates the photochromic material and has as a matrix a material that exhibits thermal properties such as EVA, preferably with high VA content so that it can be readily interfaced with the barrier layer (preferably PVDC)

(16) Layer E: Low oxygen permeability (barrier) material (preferably PVDC)

(17) Layer F: Tie material compatible with both polyolefins and the barrier material

(18) Layer G: Polyolefin such as LDPE, LLDPE, EVA or a blend thereof

(19) An alternative to this structure would be to use as a matrix for the core layer EBA or EVA of low VA content, so that two more tie layers will be needed between the EBA or the low VA content EVA and the respective PVDC layers so that the structure (in cross section) would consist of nine layers.

(20) A nine-layer structure of the plastic film could also arise in case of having two layers incorporating the photochromic compounds bilaterally of the core layer that would consist of EVA of any VA content or EBA.

(21) Layer A: Polyolefin such as LDPE, LLDPE, EVA or a blend thereof

(22) Layer B: Tie material compatible with both polyolefins and the barrier material

(23) Layer C: Low oxygen permeability (barrier) material (preferably PVDC)

(24) Layer D: Layer that incorporates the photochromic material and has as a matrix a material that exhibits thermal properties such as EVA, preferably with high VA content so that it can be readily interfaced with the barrier layer (preferably PVDC)

(25) Layer E: Core layer that has as a matrix a material that exhibits preferably thermal properties such as EVA with high VA content or preferably EBA or EVA with low VA content

(26) Layer F: Layer that incorporates the photochromic material and has as a matrix a material that exhibits thermal properties such as EVA, preferably with high VA content so that it can be readily interfaced with the barrier layer (preferably PVDC)

(27) Layer G: Low oxygen permeability (barrier) material (preferably PVDC)

(28) Layer H: Tie material compatible with both polyolefins and the barrier material

(29) Layer J: Polyolefin such as LDPE, LLDPE, EVA or a blend thereof

(30) An alternative to this structure would be to use as a matrix for the core layer EBA or EVA of low VA content, so that two more tie layers will be needed between the EBA or the low VA content EVA and the bilaterally respective PVDC layers so that the structure (in cross section) would consist of eleven layers.

(31) It is apparent that in this reasoning there could be a multitude of combinations of layers and multilayered films that could incorporate, in one or several layers, photochromic materials protected by layers than incorporate low oxygen permeation materials and tie layers, preferable of which is the aforementioned seven-layer structure.

(32) A second embodiment of the invention is by welding a superimposed photochromic film (1) of width (W.sub.1) and thickness (t.sub.1), on a conventional greenhouse or low tunnel film (2) of width (W.sub.2) and thickness (t.sub.2) (FIG. 4), where W.sub.1<W.sub.2. The welds can be at the whole width of the films (1 & 9) or at some distinct sections, continuous (11) (FIGS. 6 & 7), or discontinuous (12) (FIGS. 8 & 9), in such a manner that the superimposed photochromic film (1) that incorporates the photochromic materials, is fixed on the conventional plastic film (9). A further step would be to weld a second photochromic plastic film (10) of the same or of different composition, having thickness (t.sub.3=t.sub.2 or t.sub.3t.sub.2) on the other side of the conventional greenhouse plastic film (9) or low tunnel (FIG. 5) so that a combination of photochromic result is achieved (for example in the visible and infrared spectra).

(33) In case that partial shading is needed, a photochromic plastic film of thickness (t.sub.2) could be welded in repetitive stripes (3) along the length of the film (FIGS. 10A & 10B). It is of paramount importance to note that the photochromic compound could also have a colored effect that could be employed to provide a shade of a specific coloration in the tunnel.

(34) For the end user the plastic film with self-adjusting shading attribute leads to the next generation of greenhouse films that ensure optimization of the light conditions in the greenhouse or low tunnel and most importantly the self-adjusting of the light conditions according to the ambient light conditions in order to maximize both yield and quality of the crop.