WO2019197805A1

WO2019197805A1 - Polymeric film

Info

Publication number: WO2019197805A1
Application number: PCT/GB2019/050997
Authority: WO
Inventors: Kenneth Gargan
Original assignee: British Polythene Ltd
Current assignee: British Polythene Ltd
Priority date: 2018-04-12
Filing date: 2019-04-05
Publication date: 2019-10-17
Anticipated expiration: 2020-10-12
Also published as: GB2572865B; GB201904809D0; GB2572865A

Abstract

A film is provided and is capable of at least partly blocking the region of the solar spectrum around and/or up to a wavelength in the range 400-490nm.

Description

POLYMERIC FILM

The present invention relates generally to a polymer film for modifying solar light and particularly, although not exclusively, to greenhouse and greenhouse-like structures which includes covering materials that protect plants from external climate conditions and diseases, create optimal growth microenvironments, and offer a flexible solution for sustainable and efficient year-round cultivation.

Glass and polycarbonate were traditionally utilised for such materials, but with advances in technology many types of flexible plastic materials, including copolymers such as polyethylene and polyvinyl acetate, have become popular.

Produced with co-extrusion technology, flexible plastic films can be tailored specifically to the unique light and temperature requirements of many field-grown plants including fruits and vegetables. At the same time, plastic films can help to reduce water consumption by reducing evaporation.

Most greenhouse polyethylene plastic films contain ultraviolet (UV) light-protection components added to prolong the life of the material and maintain high levels of transmission of photosynthetically active radiation (PAR). The commonly used UV protection chemicals include UV absorber or blocker and light stabiliser. When absorbers are used standard greenhouse films generally block the majority of UV light transmission at wavelengths below 360nm. Some absorbers block a greater proportion of the UV light spectrum by blocking transmission below 380nm.

Insects are known to“see” in certain wavelength range. For example, films containing UV absorbers have been marketed as insect control films in the past. Studies have previously reported a reduction in insect populations grown under <380nm conditions compared to <360nm. The presumed method of action is alteration of normal solar wavelength patterns, especially the violet-blue light range (400- 490nm), used by insects during orientation and flight using engineered flexible greenhouse films.

The present invention provides a polymer film for modifying solar light, the film being capable of at least partially blocking the solar spectrum up to and/or within a wavelength and/or wavelength band in the 400-490nm violet-blue range.

The present invention also provides a plastic film capable of at least partially blocking the electromagnetic spectrum up to and/or within a wavelength and/or wavelength band in the 400-490nm range.

The present invention also provides a greenhouse film that is capable of at least partially blocking the solar spectrum up to a wavelength in the 400-490nm violet-blue range.

I The present invention also provides a greenhouse film that is capable of at least partly blocking the region of the solar spectrum around and/or up to a wavelength in the range 400-490nm.

The present invention also provides a polyethylene-based multilayer greenhouse film that is capable of blocking the 400-440nm violet region of the solar spectrum.

The present invention also provides a polyethylene-based multilayer greenhouse film that is capable of blocking the 450-490nm blue region of the solar spectrum.

The present invention also provides a violet light-blocking insect control film which absorbs violet light around and/or up to approximately: 400nm, 41 Onm 420nm, 430nm or 440nm.

The present invention also provides a blue light-blocking insect control film which absorbs blue light around and/or up to approximately: 450nm, 460nm 470nm, 480nm or 490nm.

The present invention also provides a greenhouse film having a yellow colour that is capable of at least partly blocking the region of the solar spectrum around and/or up to a wavelength in the range 400- 490nm.

The present invention also provides a greenhouse film having a yellow colour that is capable of at least partially blocking the solar spectrum up to a wavelength in the range 400-490nm.

The present invention also provides a polyethylene-based multilayer greenhouse film having a yellow colour that is capable of blocking the 400-490nm region of the solar spectrum.

The present invention also provides a violet light-blocking film which absorbs the violet light in the solar radiation around and/or up to approximately: 400nm, 41 Onm 420nm, 430nm, or 440nm.

The present invention also provides a blue light-blocking film which absorbs the blue light in the solar radiation around and/or up to approximately: 450nm, 460nm, 470nm, 480nm, or 490nm.

In some aspects and embodiments the film blocks all violet light wavelengths up to and including 400nm, 41 Onm 420nm, 430nm, or 440nm.

In some aspects and embodiments the film blocks all blue light wavelengths up to and including 450nm, 460nm 470nm, 480nm, or 490nm.

The present invention may provide a multilayer polymer film for modifying solar violet-blue light. In some embodiments the present invention provides a disease and insect control film which can contribute efficiently in integrated pest management systems and help to reduce the usage of pesticides. Reduction of the population of insects in greenhouses also reduces the viruses which are vectored by these insects.

In some embodiments the film blocks all violet-blue wavelengths up to and including 400nm, 4 I Onm 420nm, 430nm,440nm, 450nm, 460nm, 470nm, 480nm, or 490nm. In other embodiments a specific band of violet-blue wavelengths is blocked.

In some embodiments the film blocks violet light wavelengths up to around the 400-440nm range, for example 420-430nm.

In some embodiments additives are provided so that the film is configured to absorb the blue light (450- 490nm) of the spectrum.

Some embodiments provide a speciality greenhouse film which will perform as a regular greenhouse film, but in addition provides insect control properties.

The present invention also provides a polyethylene based multilayer greenhouse film that is capable of blocking the 400-490nm region of the solar spectrum.

In some aspects and embodiments the present invention provides a polyethylene based multilayer greenhouse film that is capable of blocking at least the 400-490nm region of the solar spectrum by 40- 100%.

In some aspects and embodiments the present invention provides a polyethylene based multilayer greenhouse film that is capable of blocking at least the 420-430nm region of the solar spectrum by 50- 100%.

In some aspects and embodiments the present invention provides or relates to a yellow greenhouse film (UV-blue blocking) which has high PAR transmittance.

In some aspects and embodiments the film may comprises a UV absorber.

The film may comprise UV blocker to block 350 nm-400 nm.

The film may be capable of increasing fruit yield.

The film may be capable of increasing fruit size and fruit number. The film may be capable of reducing un-marketable and waste fruit number.

The film may be capable of reducing time required for fruit or flower to achieve mature stage.

The film may be a monolayer or a multi-layer.

In some embodiments the film has a multilayer structure. The light modifier or blocker will be added to at least one layer.

The film may contain at least one layer of polyethylene.

The film may have UV protection for the, some or all layers.

Other embodiments use alternative types of UV absorber and pigment that result in blocking transmission in a wavelength region of interest.

In some embodiments a 7-layer film is composed of different types of polymer including LDPE and/or LLDPE.

The film thickness may be approximately 150 microns but could be thinner or thicker and maintain the same effect by adjusting the additive concentration.

Conventional UV absorbers such as BASF Tinuvin 326 block up to around 380nm.

Another commonly used UV absorber is Chimassorb 81 which is a benzophenone type but only blocks up to approximately 350nm.

In some embodiments Tinuvin 326 is used to block transmission up to 380nm, combined with a yellow pigment that has a peak absorbance at 400nm. The yellow pigment has a broad absorption band, so reduced transmission up to 500nm.

The film is still a functional greenhouse film. Adding a violet-blue light modifier will reduce the PAR light transmittance (which is a critical property for greenhouse film). In some embodiments the film has an overall light transmittance larger than 70%.

In some embodiments the film has an overall 550-750nm yellow-red light transmittance larger than 85%.

In some embodiments the film is formed using blow extrusion technology. The polymers used could be any polyethylene types that are suitable for blown film production but could also contain non- polyethylene polymers such as ethylene vinyl acetate, polypropylene, polyamide, ethylene vinyl alcohol (EVOH), etc.

In some embodiments the film is formed using cast extrusion technology. The polymers used could be any polyethylene types that are suitable for blown film production but could also contain nonpolyethylene polymers such as ethylene vinyl acetate, polypropylene, polyamide, ethylene vinyl alcohol (EVOH), etc.

In some embodiments the film will also pass certain physical standards as a greenhouse film, including tear resistance, puncture resistance, elongation, etc.

Components of layer/s of the film may comprise, consist of or include at least one of: LDPE; mLL; LLDPE; UV absorber; pigmented masterbatch; UV stabiliser; process aid; EVA.

LDPE, for example a grade with very good toughness and biaxial shrink properties. Available, for example, from Sabic, Versalis or Carmel.

Metallocene ethylene-hexene (mLL) copolymer providing, for example outstanding tensile, impact strength and puncture. Available, for example, from Exxon, Chevron or Ineos.

Linear low density polyethylene (LLDPE) copolymer, for example containing hexene- 1 as the comonomer. It may, for example offer some/all of the following properties: excellent impact strength and puncture resistance; high tear strength; good optical properties; good bubble stability; excellent sealability and hot-tack strength. Available, for example, from Ineos, Dow or Exxon.

A UV absorber which slows down the degradation process by absorbing UV radiation and dissipating it as thermal energy. Available, for example, from Ampacet, Schulman or Tosaf.

Yellow masterbatch, with yellow pigment as a light modifier. Available, for example, from Gabriel Chemie. Pigments available, for example, from BASF.

A UV stabiliser used to prevent a chemical process referred to as "photo degradation" which occurs when ultraviolet radiation coming from an artificial light source or the sun collapses chemical bonds within a polymer. Available, for example, from Schulman, Tosaf or Ampacet.

Polymer processing aids are commonly used during the extrusion process to improve melt processability, improve handling of high molecular weight polymers, burning or anisotropy. They are first and foremost used to reduce the friction between melting mass and metal machine parts, enabling the smooth flow of the molten material. Available, for example, from Tosaf, Schulman or Ampacet. Ethylene vinyl acetate copolymer (EVA), for example 14% EVA for blown film extrusion may be used as an alternative resin. Available, for example, from Versalis or Exxon.

In some embodiments the film is aimed specifically at controlling Spotted Wing Drosophila (SWD), which is a type of fruit fly that lays its eggs into unripe fruit and has the potential to be very damaging to soft fruit crops in the UK and elsewhere.

Based on the wavelengths that SWD respond to, blocking up to 430nm may be provided. That takes the requirements for such embodiments of present invention out of the range that conventional UV absorbers can block (290 - 385nm) and into the violet-blue region of the visible spectrum where a yellow pigment is needed.

In some aspects and embodiments UV absorbers are provided and in addition one or more pigments are provided.

A further aspect provides multi-layer greenhouse film, in which one or more of the layers include yellow pigment. Yellow is the colour between orange and green on the spectrum of visible light. It is evoked by light with a dominant wavelength of roughly 570-590 nm.

Aspects and embodiments may include a masterbatch component. The masterbatch may be a solid product in which pigments or additives are optimally dispersed at high concentration in a carrier material. The carrier material is compatible with the main plastic/s in which it will be blended during moulding, whereby the final plastic product obtains the colour and/or properties from the masterbatch.

Examples of yellow pigments that may be used in aspects and embodiments of the present invention, for example forming part of a masterbatch, include: BASF Pigment Yellow 1 38; BASF Pigment Yellow 155; BASF Pigment Yellow 180.

Some aspects and embodiments may additionally or alternatively include one or more of the following:

- films containing more than one (minimum two) light modifiers with an overall modification result as described herein; for example, one does 390-420 the other does 400-450, etc.

- described previously, with light modifiers separated in each layer; for example, a layer of yellow pigment, another layer of more yellow pigment, etc.

- described previously, with light modifiers mixed together.

- films containing pigments that are weathering grade.

- films containing pigments that are non-weathering grade;

- colour fading can be used as an indicator of losing“insect control” or“yield enhance” properties.

- films combating both weathering and non-weathering grade pigments so the film“changes” its light modification capability during usage. A further aspect provides a greenhouse film comprising one or more pigments, in which the or at least one of the pigments is of a non-weathering grade, such that its colour fades over time.

Different aspects and embodiments can be used together or separately.

The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings.

Example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described.

It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

The terminology used herein to describe embodiments is not intended to limit the scope. The articles “a,”“an,” and“the” are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise.

It will be further understood that the terms“comprises,”“comprising,”“includes,” and/or“including,” when used herein, specify the presence of stated features, items, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art.

It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealized or overly formal sense unless expressly so defined herein.

The scope of the invention is indicated by the appended claims. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Figure I shows an example of a control vs violet-blue blocking film; the modification occurs from 400- 490 (violet-blue range).

Examples Example I

Typical 7-layer violet-blue light modifying film structure:

Example 2

Typical 7-layer violet-blue light modifying film structure:

Example 3

Typical 5-layer violet-blue light modifying film structure:

Example 4

Typical 5-layer violet-blue light modifying film structure:

Example 5

A 1 50pm thick 7-layer polyethylene-based greenhouse covering film having two layers containing violet- blue lighter modifier. The overall PAR light transmission of the film is 81 .4%. The overall 400-440nm light transmission is 25%. The overall 400-490nm light transmission of the film is 45.6%. The overall yellow-red light transmission of the film is 95%.

Example 6

A 1 50pm thick 5-layer polyethylene-based greenhouse covering film having one layer containing violet- blue lighter modifier. The overall PAR light transmission of the film is 78.4%. The overall 400-440nm light transmission is 22%. The overall 400-490 nm light transmission of the film is 55%. The overall yellow-red light transmission of the film is 95.5%.

Figure 2 shows a cross-section of a typical 7-layer violet-blue light modifying greenhouse film with the following layers:

I , 4, 6, and 7 strength-providing layers of the film, typically containing LLDPE-rich blend

2 light modifying layer of the film, typically containing LDPE and light modifier

3 2nd light modifying layer of the film, typically containing LDPE and light modifier 5 LDPE rich layer

Example 7

A 1 50pm thick 7-layer polyethylene-based greenhouse covering film comprising violet-blue lighter modifier is used to grow strawberry plants. The peak absorption in the violet-blue range of solar spectrum using this yellow colour film is at -430 nm. 1 5-26% increase in marketable yield is achieved. 15% increase in marketable berry number is achieved comparing to control film. 5- 10% berry weight increase is achieved. Further, a significant reduction in un-marketable and waste berry number is achieved comparing to control film.

Example 8

A 200pm thick 5-layer polyethylene-based greenhouse covering film comprising violet-blue lighter modifier is used to grow strawberry plants. The peak absorption in the violet-blue range of solar spectrum using this yellow colour film is at -400 nm. 1 5-26% increase in marketable yield is achieved. 15% increase in marketable berry number is achieved comparing to control film. 5- 10% berry weight increase is achieved. Further, a significant reduction in un-marketable and waste berry number is achieved comparing to control film.

Example 9

A 200pm thick 5-layer polyethylene-based greenhouse covering film comprising violet-blue lighter modifier is used to reduce western flower thrip (WFT) activities. The peak absorption in the violet-blue range of solar spectrum using this yellow colour film is at 430 nm / 400 nm. Said film is bumblebee- friendly. 50% reduction in WFT population is achieved comparing to a control greenhouse film.

Example 10

A 200pm thick 7-layer polyethylene-based greenhouse covering film comprising violet-blue lighter modifier is used to reduce SWD activities. The peak absorption in the violet-blue range of solar spectrum using this yellow colour film is at 430 nm / 400 nm. Said film is bumblebee-friendly. Up to 80% reduction in SWD population is achieved comparing to a control greenhouse film.

Example I I

A I 50pm thick 7-layer polyethylene-based greenhouse covering film comprising violet-blue lighter modifier is used to reduce whitefly and spider mite activities. The peak absorption in the violet-blue range of solar spectrum using this yellow colour film is at 430 nm / 400 nm. Said film is bumblebee- friendly. 60% reduction in whitefly and spider mite population is achieved comparing to a control greenhouse film.

Example 12

An approximately I 50pm thick 7-layer polyethylene-based greenhouse covering film with a yellow tint. Peak absorption is around 430nm.

Layer I

UV Stabiliser

LDPE

Processing Aid

LLDPE

Layer 2

mLLDPE

UV Stabiliser

LDPE UV Absorber

Yellow Masterbatch

Layer 3

mLLDPE

UV Stabiliser

LDPE

Layer 4

mLLDPE

UV Stabiliser

LDPE

Layer 5

mLLDPE

UV Stabiliser

LDPE

Layer 6

mLLDPE

UV Stabiliser

LDPE

UV Absorber

Yellow Masterbatch

Layer 7

UV Stabiliser

LDPE

Processing Aid

LLDPE

Example 1 3

A I 50pm thick 7-layer polyethylene-based greenhouse covering film with a yellow tint to provide a violet-blue light modifier. Peak absorption is around 430nm.

Layer I (thickness: 20%)

UV Stabiliser 3%

LDPE (0.923 density) 66%

Processing Aid 1 % LLDPE 30%

Layer 2 (thickness: 20%)

mLLDPE (0.918 density) 54.5%

UV Stabiliser 3%

LDPE (0.923 density) 20%

UV Absorber 12.5%

Yellow Masterbatch 10% Layer 3 (thickness: 8%)

mLLDPE (0.918 density)

UV Stabiliser 3%

LDPE (0.923 density) 20% Layer 4 (thickness: 4%)

mLLDPE (0.918 density)

UV Stabiliser 3%

LDPE (0.923 density) 20% Layer 5 (thickness: 8%)

mLLDPE (0.918 density)

UV Stabiliser 3%

LDPE (0.923 density) 20% Layer 6 (thickness: 20%)

mLLDPE (0.918 density) 54.5%

UV Stabiliser 3%

LDPE (0.923 density) 20%

UV Absorber 12.5%

Yellow Masterbatch 10%

Layer 7 (thickness: 20%)

UV Stabiliser 3%

LDPE (0.923 density) 66%

Process Aid 1 %

LLDPE 30%

Figure 3 details some results relating to test performed using films formed in accordance with the present invention. The present inventions can be embodied in other specific apparatus and/or methods. The described embodiments are to be considered in all respects as illustrative and not restrictive. In particular, the scope of the invention is indicated by the appended claims rather than by the description and figures herein. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Further aspects and embodiments of the present invention are listed below in the following numbered paragraphs.

1 . A greenhouse film that is capable of at least partly blocking the region of the solar spectrum around and/or up to a wavelength in the range 400-490nm.

2. A greenhouse film that is capable of at least partially blocking the solar spectrum up to a wavelength in the range 400-490nm.

3. A polyethylene-based multilayer greenhouse film that is capable of blocking the 400-490nm region of the solar spectrum.

4. A violet light-blocking film which absorbs the violet light in the solar radiation around and/or up to approximately: 400nm, 41 Onm 420nm, 430nm, or 440nm.

5. A blue light-blocking film which absorbs the blue light in the solar radiation around and/or up to approximately: 450nm, 460nm, 470nm, 480nm, or 490nm.

6. A film as listed in any preceding paragraph, in which the film blocks all violet light wavelengths up to and including 400nm, 41 Onm 420nm, 430nm, or 440nm.

7. A film as listed in any preceding paragraph, in which the film blocks all blue light wavelengths up to and including 450nm, 460nm 470nm, 480nm, or 490nm.

8. A film as listed in any preceding paragraph and capable of blocking the 400-440nm region of the solar spectrum.

9. A film as listed in any preceding paragraph and capable of blocking the 450-490nm region of the solar spectrum.

10. A film as listed in any preceding paragraph and capable of blocking the 420-430nm region of the solar spectrum. I I . A film as listed in any preceding paragraph, in which wavelength transmission is blocked by 40-

100%.

12. A film as listed in any preceding paragraph, in which the film is a monolayer.

1 3. A film as listed in any of paragraph I to I I , in which the film has multilayer structure.

1 . A film as listed in paragraph I 3, in which the film has at least one layer of polyethylene.

15. A film as listed in paragraph 1 3 or paragraph 14, in which the film has seven layers.

16. A film as listed in any of paragraph I 3 to 1 5, in which the film is composed of three different types of polymer.

17. A film as listed in paragraph 1 6, in which the film is composed of LDPE and/or LLDPE including metallocene.

18. A film as listed in any preceding paragraph, in which a light modifier or blocker is added to the or at least one layer.

19. A film as listed in any preceding paragraph, in which the film has UV protection for the or all of the layers.

20. A film as listed in any preceding paragraph, in which the film is a diffused film with high PAR scattering rate ranging from 50- 100%.

21 . A film as listed in any preceding paragraph, in which the film has a thickness of approximately 150 microns. 22. A film as listed in any preceding paragraph, in which the film has an overall PAR light transmittance larger than 70%.

23. A film as listed in any preceding paragraph, in which the film has an overall 550nm-750nm light transmittance larger than 85%.

24. A film as listed in any preceding paragraph, in which the film is formed using blow extrusion technology.

25. A film as listed in any preceding paragraph, in which the film is formed using cast extrusion technology. 26. A film as listed in any preceding paragraph, in which the or at least one of the layers of the film comprises: polyethylene, poly ethylene-vinyl acetate, polypropylene, polyamide, or ethylene vinyl alcohol (EVOH).

27. A film as listed in any preceding paragraph, comprising one or more UV absorber additives and one or more pigment additives.

28. A film as listed in any preceding paragraph, comprising a yellow pigment that has a peak absorbance at approximately 400nm.

29. A film as listed in any preceding paragraph, comprising one or more UV absorber additives and one or more pigment additives.

30. A film as listed in any preceding paragraph, further comprising an anti-fogging agent.

31 . A film as listed in any preceding paragraph, further comprising an infrared blocker.

32. A film as listed in any preceding paragraph, in which the film provides for selective blocking of spectral bands.

33. A film as listed in any preceding paragraph, in which the film comprises an additive for modifying the transmitted light spectrum.

34. A film as listed in any preceding paragraph, in which the film comprises an additive for blocking the transmitted light spectrum.

35. A greenhouse film having a yellow colour that is capable of at least partly blocking the region of the solar spectrum around and/or up to a wavelength in the range 400-490nm.

36. A greenhouse film having a yellow colour that is capable of at least partially blocking the solar spectrum up to a wavelength in the range 400-490nm.

37. A polyethylene-based multilayer greenhouse film having a yellow colour that is capable of blocking the 400-490nm region of the solar spectrum.

38. A polymer film for modifying solar light, the film being capable of at least partially blocking the solar spectrum up to and/or within a wavelength and/or wavelength band in the 400-490nm violet-blue range. 39. A Spotted Wing Drosophila (SWD) control film, comprising a film as claimed in any preceding claim.

40. A greenhouse comprising, including, having or being fitted with film as listed in any preceding paragraph.

41. An insect control film comprising a film as listed in any of paragraphs I to 39.

Claims

1. A film that is capable of at least partly blocking the region of the solar spectrum around and/or up to a wavelength in the range 400-490nm.

2. A film as claimed in claim I , which absorbs the violet light in the solar radiation around and/or up to approximately: 400nm, 41 Onm 420nm, 430nm, or 440nm.

3. A film as claimed in claim I or clam 2, which absorbs the blue light in the solar radiation around and/or up to approximately: 450nm, 460nm, 470nm, 480nm, or 490nm.

4. A film as claimed in any preceding claim and capable of blocking in the 400-440nm and/or 450- 490nm and/or 420-430nm region of the solar spectrum.

5. A film as claimed in any preceding claim, in which wavelength transmission is blocked by 40-

100%.

6. A film as claimed in any preceding claim, in which the film is a monolayer.

7. A film as claimed in any of claims I to 5, in which the film has multilayer structure.

8. A film as claimed in claim 7, in which the film has at least one layer of polyethylene.

9. A film as claimed in claim 7 or claim 8, in which the film has seven layers.

10. A film as claimed in any preceding claim, in which the or at least one layer of the film is composed of LDPE and/or LLDPE including metallocene.

I I . A film as claimed in any preceding claim, in which a light modifier or blocker is added to the or at least one layer.

12. A film as claimed in any preceding claim, in which the film has UV protection for the, some or all of the layers.

13. A film as claimed in any preceding claim, in which the film is a diffused film with high PAR scattering rate ranging from 50- 100%.

14. A film as claimed in any preceding claim, in which the film has a thickness of approximately 150 microns.

15. A film as claimed in any preceding claim, in which the film has an overall PAR light transmittance larger than 70%.

16. A film as claimed in any preceding claim, in which the film has an overall 550nm-750nm light transmittance larger than 85%.

17. A film as claimed in any preceding claim, in which the or at least one of the layers of the film comprises: polyethylene, poly ethylene-vinyl acetate, polypropylene, polyamide, or ethylene vinyl alcohol (EVOH).

18. A film as claimed in any preceding claim, comprising one or more UV absorber additives and one or more pigment additives.

19. A film as claimed in any preceding claim, comprising a yellow pigment that has a peak absorbance at approximately 400nm.

20. A film as claimed in any preceding claim, comprising one or more pigment additives.

21. A film as claimed in any preceding claim and having a generally yellow colour.

22. A Spotted Wing Drosophila (SWD) control film, comprising a film as claimed in any preceding claim.

23. A greenhouse film comprising a film as claimed in any preceding claim.

24. A greenhouse comprising film as claimed in any preceding claim.