PVC membranes and coatings

Abstract

Disclosed herein is a protective coating that selectively transmits beneficial UV-wavelengths through a membrane to preserve greenhouse glazing and support plant growth. Anti-drip coatings also described herein can prevent condensation within the inside surface of the membrane. Further, a polymer textile-supported membrane with high transmission in the visible wavelengths is described, which can be coated with one or both of a UV-selective coating and a coating with anti-drip and hydrophilic properties.

Description

PVC MEMBRANES AND COATINGSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and any benefit of U.S. Provisional Application No. 63 / 513,893, filed July 16, 2023, the content of which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates generally to a membrane, and particularly a polymer membrane, with selective ultra-violet (UV)-transmissibility and anti-drip properties. The present disclosure further relates to UV-selective coatings and anti-drip coatings. These coatings and membranes may be applied to a number of systems, including greenhouse systems for growing agricultural products.BACKGROUND

[0003] Flexible greenhouse glazing materials, such as those found in hoop-and-tunnel greenhouses, need to have high levels of visible light transmission. Use of clear sheet and film polymers as greenhouse glazing is generally known. These materials allow for the transmission of light to the plants growing within a greenhouse, while regulating the temperature and exposure to the plants growing therein. The gamut of glazing material properties ranges from expensive, rigid, and durable to low-cost, flexible, and short-lived. Current greenhouse designs must often resort to lower-cost, flexible glazings with simple installations, that require frequent replacement, because rigid, long-lasting sheets are often cost prohibitive and incur higher upfront installation costs and complexity. Current low-cost greenhouse glazing solutions are often quickly degraded by weather and sunlight and thus require frequent replacement. Furthermore, condensation that develops on the inside surface of the glazing can often provide an unwanted and excessive sourceof moisture to the plants growing therein. Flexible greenhouse glazing materials, such as those found in hoop-and-tunnel greenhouses, need to have high levels of visible light transmission. Photosynthetically active radiation (PAR) in the 400-700 nm range of the electromagnetic spectrum, in particular, must be transmitted because it is essential for the development of all plants. Contributions from the UV band (250-400 nm) may also be beneficial for plant development and for pollinator vision. That said, only a select amount of UV radiation is beneficial to plants. More UV transmission than this can actually be harmful and may degrade the membrane’s glazing material.SUMMARY

[0004] Disclosed herein are protective coatings that selectively transmit beneficial UV- wavelengths through a membrane to preserve greenhouse glazing while still supporting plant growth. Anti-drip coatings also described herein can prevent condensation within the inside surface of a membrane. Further, a polymer textile- supported membrane with high transmission in the visible wavelengths is described, which can be coated with one or both of a UV-selective coating and a coating with anti-drip and hydrophilic properties. This polymer membrane can provide a flexible, highly transmissive sheet, that can be used as a greenhouse glazing, with a lower up-front cost, simple install using conventional hoop-and-tunnel designs and has a service life of up to 10 years.BRIEF DESCRIPTION OF DRAWINGS

[0005] FIG. 1 depicts a schematic of an exemplary polyvinyl chloride (PVC) membrane system 100 comprising a base membrane 120 with top-surface 120a and a bottom-surface 120b.

[0006] FIG. 2A includes images showing the degradation of the underlying clear PVC membrane after a 1600-hour exposure to a wet environment compared to unprotected films.

[0007] FIG. 2B compares images of Formulas #1-8 after exposure to the treatment described in the context of FIG. 2A.

[0008] FIG. 3 shows measured transmission through each of Formulas #1-8 whose compositions are represented in Tables 1-8.

[0009] FIG. 4 provides experimental results showing absorbance vs. wavelength for triazine and tetracyanoacrylate UV absorbers.

[0010] FIG. 5 illustrates the case of an exemplary PVC membrane comprising an anti-drip back- finish on the bottom surface of said PVC membrane.

[0011] FIG. 6 shows the molecular structure of two exemplary polyhydritic units and their long- chain fatty acid monoester structures that may be used to create back finish 510.

[0012] FIG. 7 compares a photograph of treated film 710 and untreated clear PVC film 720.DETAILED DESCRIPTION

[0013] Aspects and implementations of the present disclosure will be understood more fully from the detailed description given below and from the accompanying drawings. The disclosure and drawings are meant to provide explanation and facilitate understanding only. The disclosure should not be considered limited to the specific aspects or implementations presented here.

[0014] A flexible polymer membrane is described herein. The flexible polymer membrane, such as a polyvinyl chloride (PVC) membrane, has a top surface and a bottom surface and comprises a coating on at least one of the top surface and bottom surfaces. In exemplary embodiments, the top surface of the PVC membrane is coated with a UV-selective coating, or top-finish, according to any one of the embodiments described below. In exemplary embodiments, the bottom surface is coated with an anti-drip coating, or bottom-finish. However, it is to be understood that embodiments may include one or both of these coatings.

[0015] The highly transmissive and flexible PVC membrane allows transmission of UV wavelengths between 360-400 nm and the PAR region of the electromagnetic spectrum (between 400-700 nm) of greater than 70%, and preferably greater than 80%. PVC has a strong and broad UV absorption at < 280 nm and a lesser but critical absorption centered at 346 nm. Plants and pollinators have UV light needs at wavelengths as low as 340 nm, but they can still benefit from UV availability from 360-400 nm. A UV-selective, oxidatively stable, and weatherable acrylic top-finish can be applied to maintain the high UV transmission of a PVC membrane in the 360- 400 nm range while still protecting the PVC from the energetic and destructive radiation at lower wavelengths.

[0016] Top-Finish

[0017] Embodiments include a UV-selective coating for a membrane, such as a flexible PVC membrane. The term “UV-selective” is intended to mean the coating allows for the transmission of a certain range of UV wavelengths beneficial to plant growth while blocking UV wavelengths outside of the preferred range. In exemplary embodiments, the UV-selective coating blocks high- energy UV radiation with wavelengths shorter than -350 nm, and preferably shorter than -400 nm. PVC is vulnerable to UV radiation centered around 345 nm and < 280 nm. Therefore, this most energetic band of the UV spectrum should be substantially blocked to decrease degradation of the PVC substrate.

[0018] FIG. 1 depicts a schematic of an exemplary PVC membrane system 100 comprising a base membrane 120 with top-surface 120a and a bottom-surface 120b. The top-surface 120a is coated with a UV-selective coating, or top-finish 110. In exemplary embodiments, the UV-selective coating 110 comprises an acrylic resin, a solvent system, a silicone fluid, a light stabilizer, and at a UV absorber.

[0019] Acrylic Resin

[0020] In exemplary embodiments, the UV-selective top-finish 110 comprises 50-95 wt. % of an acrylic resin, preferably 70-90 wt. %, and more preferably between 85-90 wt. %, and most preferably between 86-88 wt. %. In exemplary embodiments, the acrylic top-finish 110 has inherent interfacial adhesion to the PVC membrane and a designed elongation of -25% to complement and adhere to the flexible PVC membrane during its undulations and movement out in the field. In exemplary embodiments, the acrylic resin comprises plexiglas. For example, the acrylic resin may comprise 50 wt. % Plexiglas V052i (Plexiglas V052i being an impact-modified thermoplastic acrylic resin designed for injection molding) and 50 wt. % Solarcote A200 (an acrylic capstock resin, a type of thermoplastic polymer known for its superior UV protection and weatherability). It is to be understood that other formulations of these components are within the scope of the present disclosure.

[0021] Solvent System

[0022] The UV-selective coating of top-finish 110 further comprises a solvent system. Any suitable solvent can be used, including but not limited to ketones, alcohols, ethers, aromatics, and / or polar aprotic organics, and suitable combinations thereof. In exemplary embodiments, the UV-selective coating comprises 1-20 wt. % of a solvent system, preferably 5-15 wt. %, and more preferably 9-10 wt. %. The solvent selection is mostly dependent on the total amount of acrylic polymers and the choice of UV absorbers. Triazine UV absorbers may require aromatic solvents such as toluene, xylenes, anisole, or chlorinated benzenes. The acrylic resin described above is dissolved in an organic solvent. Methyl ethyl ketone (MEK), tetrahydrofuran (THF) are the preferred solvents. Other solvents can be used as well, exclusively or as blends. In exemplary embodiments, the acrylic resin is dissolved in a solvent system comprising MEK and THF in a 1 : 1 ratio at 20% solids. In some embodiments, the solvent system may comprise additional solvents, including but not limited to, dimethyl acetamide (DMAC), toluene, or a combination thereof. The additional solvent may comprise 5-30 wt. % of the solvent system. It is to be understood that other suitable solvent combinations are within the scope of this disclosure.

[0023] Silicone Fluid

[0024] The UV-selective coating of top finish 110 further may comprise a silicone fluid. In exemplary embodiments, the UV-selective coating comprises 0.1-1 wt. % of the silicone fluid, and preferably about 0.2%. This can be any suitable silicone fluid that has surface active properties. Examples include, but are not limited to, BYK 330 (a solution of polyether-modified dimethylpoly siloxane) or BYK 303 (another silicone-based additive designed for solvent-free, solvent-borne, and aqueous coating systems). With these and similar formulations described herein, surface active properties allow for the silicone polymer to rise to the surface, decrease antiblock, and provide slip properties to the UV-selective coating. When the addition level is relatively low, this will not interfere with weldability needed to laminate the membrane into larger more complex structures.

[0025] Light Stabilizer

[0026] The UV-selective coating of top finish 110 may further comprise a light stabilizer. For example, adding hindered amine light stabilizer (HALS) can provide oxidative resistance to theacrylic matrix of the UV-selective coating as well as the UV absorbers. In exemplary embodiments, the UV-selective coating comprises 0.1-2 wt. % of a light stabilizer, preferably 0.3 - 1 wt. %, and more preferably 0.4-0.6 wt. %. The HALS molecule, through the Denisov Cycle, is able to confer a level of photooxidative protection to the UV absorber. The light stabilizer may be any suitable composition, including but not limited to Tinuvin 770 DF.

[0027] UV Absorber

[0028] The UV-selective coating of top finish 110 further comprises a UV absorber in an amount of 0.1 -10 wt. %, preferably 1 -5 wt. %, and more preferably 2-3 wt. %. Any suitable UV absorber, or blends, will provide initial protection, but their photopermanence may be dependent on their molecular structure, the matrix they are in, and the other additives in the matrix. In exemplary embodiments, the UV absorber system provides long-lasting photopermanence and protection from the most deleterious regions of the UV spectral region. It can also allow transmission of parts of the UV spectrum that can benefit fruiting plants and pollinators’ vision. Preferred UV absorbers include members of the triazine or cyanoacrylate classes or blends thereof. In exemplary embodiments, the UV-selective coating comprises a 1 :2- 1:6 ratio (by weight) of a light stabilizer to a UV Absorber, and preferably a 1 :4 ratio.

[0029] The UV-selective coating of top finish 110 may further comprise additional inorganic additives, such as quantum dots or metal oxides. These materials have optical properties that can be used to alter the transmission through a formulated coating or membrane.

[0030] The UV-selective coating of top finish 110 may comprise a blend of weatherable acrylic polymers and stabilizers dissolved in a suitable solvent system. In exemplary embodiments, it may be gravure printed and cured onto a laminated fabric. The laminated fabric may be a flexible PVC on a textile reinforcement.

[0031] After accelerated aging in a Xenon weatherometer (ASTM G155), which represents one year of environmental aging, the change (D) of the transmission in the ultraviolet and visible range of the spectrum is less than the D of a clear PVC membrane protected with a polyvinyl fluoride (PVF) fdm. PVF fdms can confer decades of environmental protection.

[0032] Tables 1-8 (below) describe Formulas 1-8 of exemplary UV-selective top finishes 1 10 compared against comparative PVC acrylic polymer coatings. FIG. 2A includes images showing the degradation of the underlying clear PVC membrane after 1600 hours in a QUVB chamber (a device used to simulate the effects of sunlight, rain, and dew on materials to predict their durability and longevity in outdoor conditions) compared to an unprotected PVC film, a PVC film proected by PVF, and a reduced UVA loaded coating. As shown in FIG. 2A, the unprotected PVC is heavily browned and cracking. The PVF protected film shows no visible changes and almost no measurable changes in its visible wavelength % transmission. A formulation similar to Formula #1 but with a standard benzotriazole UV absorber shows lower initial % transmission in the UV range, -32%, and has noticeable yellowing after 1600 hours in a QUVB chamber and ablation of the acrylic coating at its low points.Table 1: Exemplary Formula # 1.Table 2: Exemplary Formula # 2.Table 3: Exemplary Formula # 3.Table 4: Exemplary Formula # 4.Table 5: Exemplary Formula # 5.Table 6: Exemplary Formula # 6.Table 7: Exemplary Formula # 7.Table 8: Exemplary Formula # 8.

[0033] FIG. 2B compares images of Formulas #1-8 after exposure to the treatment described in the context of FIG. 2A. Formulas #1 and #2 of Tables 1 and 2 represent acrylic polymers that are commercially available for capstock or top finishes. These coatings do not contain additives in the embodiments described above. Their images in FIG. 2B show substantial browning of the clear PVC substrate. Formulas #3 and #4 have the same acrylic coatings but with the desired dose ofthe Triazine UV absorber. Formulas #5 and #6 are protected with a tetracyanoacrylate UV absorber. Formulas #7 and #8 are a reduced blend of both UV absorbers but provide a more complete level of protection over the more deleterious region of the UV spectral range.

[0034] Changes in the UV and visible % transmission can be monitored with a spectrophotometer, and these values show various changes depending on the amount of the acrylic coating matrix and the choice of the UV absorber. FIG. 3 shows measured transmission through each of the Formulas #1-8 whose compositions are represented in Tables 1-8.

[0035] The synergistic benefits of the UV-selective coating are that the UV absorber and HALS components do not need to be added directly to the PVC formulation, which has a variety of positive outcomes, such as:• Simplification of the PVC compound formulation.• Concentration of the stabilizers in the acrylic top finish, where they can be most impactful, maximizing their protective features while reducing use levels and cost,• Addition to the PVC formulation, particularly clear formulations, leads to immediate and measurable changes in the color and % transmission of the PVC compound and subsequent films.• Broader choice of UV absorbers due to compatibility, solubility, and HC1 by-products associated with the PVC matrix• Broader choice of low-cost Basic-HALS molecules. The same HC1 by-products readily deactivate low cost basic HALS molecules when they are added directly to the PVC formula. In a traditional system the formulator must use higher cost NOR-HALS molecules.

[0036] FIG. 4 shows how these absorbers can additively combine to protect the PVC substrate from high energy UV radiation at and below 346 nm while still transmitting a high level of UV radiation in the region above 346 nm which is beneficial to plant development and pollinator vision.

[0037] Anti-Drip Back-Finish

[0038] Exemplary anti -drip coatings are further described herein. The anti-drip coating may be applied to a bottom surface of a polymer membrane 100, such as a flexible PVC membrane 120, for use as a greenhouse glazing. Greenhouse glazing material, and any subsequent layers or coatings it is comprised of, should increase or maximize, or at least not block, PAR transmission. Changes or fouling of the glazing material out in the field will likely affect its transmission. Of particular concern to the interior face of the glazing material is the build-up of water condensation in this self-contained microclimate. The build-up of water droplets on the glazing will alter the amount and focus of incoming radiation. Furthermore, these drops can rain down inconsistently over the greenhouse crops leading to overwatering, fungal growth and disease, and unintentional and potentially detrimental redistribution of fertilizers and chemicals.

[0039] Exemplary embodiments of the anti-drip coating can comprise a back-finish 510 to a PVC membrane 120, as shown in FIG. 5. This back-finish may be gravure printed and cured onto a PVC laminated fabric, preferably a transparent PVC laminated fabric. In exemplary embodiments, the back-finish is a solution of hydrophobic polymers with amphiphilic surface-active small molecules. In exemplary embodiments, the components are dissolved in a suitable solvent system. The amphiphilic surface-active molecules can migrate to the surface of the back-finish and can raise the surface tension from ~36 dynes / cm to ~70 dynes / cm to form a hydrophilic surface. At this high surface tension, approaching 72 dynes / cm of water, water condensation can spread as a thin clear sheet vis-a-vis the beading up behavior normally observed on a hydrophobic finish. In exemplary embodiments, a clear PVC laminated fabric coated with the anti-drip back-finish can be used as glazing material for a greenhouse. In the high humidity internal environment of a greenhouse, a glazing material with this hydrophilic back-finish will exhibit a lower condensation of water droplets. With this inventive back-finish the water will form a thin invisible sheet of water. This thin sheet can travel along the inner glazing face in a convective cycle instead of inconsistently raining down on the plants. It can also maintain consistent transmission of the clear laminated fabric instead of inconsistently scattering and refocusing incoming radiation.

[0040] In exemplary embodiments, the anti-drip back-finish 510 comprises an acrylic polymer base or a polyamide polymer base and an anti-drip agent. In exemplary embodiments, the antidrip back finish exhibits interfacial adhesion to the PVC substrate and a designed elongation of-25% to complement and adhere to flexible PVC membrane. Other polymer bases, including all- suitable vinyl or vinyl-acrylic based polymers may also be used.

[0041] In exemplary embodiments, the polymer base solutions are formulated to a solids level of 5-40%, and preferably 10-30%, and more preferably 20% with a suitable solvent system. In exemplary embodiments, the acrylic polymer base can be dissolved in a solvent system comprising ketones, ethers, aromatics, or polar aprotic solvents. In exemplary embodiments, the solvent system comprises a 1 : 1 blend of MEK:THF solution. In exemplary embodiments, the polyamide polymer base can be dissolved in a solvent system comprising alcohols, ethers, polar aprotic solvents, or any of these with a minority blend of an aromatic solvent. The solvent system may comprise a 3:1 blend of isopropanol (IPA):toluene.

[0042] Long-chain greasy apolar segments esterified to polyhydritic units are one class in a broad field of surfactants suitable for use with the anti-drip coating. In exemplary embodiments, the surfactants exhibit reverse alignment with the polar polyhydritic end at the air-water interface, which raises the surface tension from the 30-40 dynes / cm range to ~70 dynes / cm, and the long- chain apolar end is embedded in the hydrophobic polymer base to resist extraction.

[0043] In exemplary embodiments, the surfactant comprises long-chain fatty acid monoesters of glycerol or sorbitan. Also preferable are glycerol monostearate (GMS) or sorbitan monostearate (Span-60). GMS is a viscous liquid used in anti-fog applications in food packaging and Span-60 is a waxy solid used as an emulsifier in many aqueous systems. GMS has two hydroxyls it can contribute to a hydrophilic network at the surface of a back-finish. Span-60 has three hydroxyls it can contribute to a hydrophilic network at the surface of a back-finish. At stoichiometric balanced levels the three hydroxyls of Span-60 are expected to be more productive than the two hydroxyls of GMS in a back-finish. The liquid nature of GMS can make it easier to solubilize and include in a wide variety of formulations. However, the solid nature of Span-60 may give it better extraction resistance over the life of the back-finish during its service life.

[0044] FIG. 6 shows the molecular structure of two exemplary polyhydritic units and their long- chain fatty acid monoester structures that may be used to create back finish 510.

[0045] An exemplary anti-drip formulation comprises 1-20 wt. % of an anti-drip agent, preferably 2-10 wt%, and most preferably the concentration of the anti-drip agent is 5 wt% and the polymer base is 20 wt%. In exemplary embodiments, the total solids content is 10-50 %, preferably 20-40 % and most preferably 25%. In exemplary embodiments, the dried and fully cured back-finish has a preferred thickness of 0.2 mil (12.5m) and the anti-drip formulation comprises 20% of the total mass.

[0046] In exemplary embodiments, the anti-drip back finish 510 comprises a blend of two antidrip agents together at a 1 : 1 ratio 2.5 wt% of each and 5 wt% in total. This system has less hydroxyls at the surface than a pure Span-60 system but leads to a less-ordered network with a higher surface tension at the back-finish surface. In exemplary embodiments, the anti-drip back- finish 150 comprises 80-99 wt. % of a polymeric base and 1-20 wt. % of the anti-drip agent, and more preferably 90-97 wt. % of the polymeric base and 3-10 wt, % of the anti-drip agent, and most preferably about 95 wt. % of the polymeric base and 5 wt. % of the anti-drip agent. Exemplary Formulations #9 and #10 are shown in Tables 9 and 10 below.Table 9: Exemplary Formulation 9.Table 10: Exemplary Formulation 10.

[0047] Hydrophilic water insoluble materials were readily soluble in the polyamide resin solution.Once coated onto the clear PVC film surface, this coating had excellent and long-lasting anti-dripperformance. Lower amounts of anti-drip agent provides a more optically transparent coating. The polar polyamide resin provides adhesion to the PVC fdm, anti-blocking properties and a matrix for the anti-drip agent to reside. The anti-drip agent at these lower doses acts as a small molecule compatibilizer for the polar but dissimilar resins, which improves optical transmission and enhances the anti-drip performance.

[0048] Certain anti-fog tests used in the food packaging industry such as the “Coldfog” and “Hotfog” tests are known. There is also a European standard that tests an anti -fog component and how it affects optical transmission: EN 168:2001 - Personal eye-protection - Non-optical test methods. This work used a larger scale version of the “Hotfog” test. A tabletop sized clear vinyl greenhouse was used as the closed test environment. This was staged in a room with a climate controlled temperature at 70 °F. In the test greenhouse there was a 1” deep oven sized pan filled with distilled water. Also in the test greenhouse was a lamp fitted with a red sauna bulb in close proximity to and pointed directly at the pan of water. Test strips of anti-drip back-finished materials could be mounted on the inner vertical surfaces of the greenhouse. The environment reached 100% humidity and temperatures of -100 °F in 2hrs. A +30 °F temperature differential was monitored with two digital thermometers, one outside the greenhouse and the other inside the greenhouse.

[0049] Anti-drip treated samples in the test greenhouse remain free of water drops while untreated samples develop large water beads that fall and drip to the greenhouse floor. FIG. 7 compares a photograph of treated 710 and untreated 720 clear PVC film. More specifically, treated film 710 is an anti-drip back-finished clear PVC sample according to the embodiments described herein. Untreated film 720 is an untreated clear PVC sample. Drips of moisture are clearly visible on untreated film 720. Far fewer drips are visible on treated film 710. This performance differential was maintained throughout the days long test as the greenhouse lamp was turned on and off to represent the day-night sun cycle.

[0050] Polymer Membrane

[0001] In exemplary embodiments, either one or both of the anti-drip back -finish and UV-selective top finish described above is applied to a flexible polymer membrane, such as an exemplary flexible PVC membrane as described further herein. A greenhouse film or membrane glazing couldbenefit from selectively transmitting beneficial UV wavelengths through itself while blocking those wavelengths most harmful to the integrity and performance of the greenhouse glazing, which could shorten the service life of the glazing material.

[0052] In exemplary embodiments, the membrane is a clear PVC laminated to a dense scrim woven from transparent monofilament. Any suitable monofilament can be used, including but not limited to a polyester monofilament. In exemplary embodiments, the PVC laminated membrane exhibits greater than 70% optical transmission, preferably greater than 85% optical transmission, and more preferably greater than 90% optical transmission. The monofilament could be any suitable monofilament. In exemplary embodiments, the optical transmission of the polyester monofilament is greater than 95%, and when laminated into a clear PVC the total reduction in % transmission is only about 1-2%.

[0053] While various inventive aspects, concepts and features of the inventions may be described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects, concepts and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present inventions. Still further, while various alternative embodiments as to the various aspects, concepts and features of the inventions— such as alternative materials, structures, configurations, methods, circuits, devices and components, software, hardware, control logic, alternatives as to form, fit and function, and so on— may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts or features into additional embodiments and uses within the scope of the present inventions even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Still further, exemplary or representative values and ranges maybe included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Parameters identified as “approximate” or “about” a specified value are intended to include both the specified value and values within 10% of the specified value, unless expressly stated otherwise. Further, it is to be understood that the drawings accompanying the present application may, but need not, be to scale, and therefore may be understood as teaching various ratios and proportions evident in the drawings. Moreover, while various aspects, features and concepts may be expressly identified herein as being inventive or forming part of an invention, such identification is not intended to be exclusive, but rather there may be inventive aspects, concepts and features that are fully described herein without being expressly identified as such or as part of a specific invention, the inventions instead being set forth in the appended claims. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as being required in all cases, nor is the order that the steps are presented to be construed as required or necessary unless expressly so stated.

Claims

We claim:

1. A flexible polymer membrane comprising: at least one of: a top surface having a UV-selective coating; and a bottom surface having an anti-drip coating; and wherein the membrane demonstrates greater than 70 % optical transmission.

2. The membrane of claim 1, wherein the membrane demonstrates greater than 85% optical transmission.

3. The membrane of claim 2, wherein the membrane demonstrates greater than 90% optical transmission.

4. The membrane of claim 1, wherein the membrane comprises polyvinyl chloride (PVC).

5. The membrane of claim 4, wherein the PVC is laminated.

6. The membrane of claim 5, wherein the laminated PVC forms a scrim.

7. The membrane of claim 1, wherein the UV-selective coating transmits 70 % or greater of light having wavelengths between 360-400 nm.

8. The membrane of claim 1, wherein the UV-selective coating transmits 80 % or greater of light having wavelengths between 360-400 nm.

9. The membrane of claim 1, wherein the UV-selective coating comprises an acrylic resin.

10. The membrane of claim 9, wherein the UV-selective coating comprises the acrylic resin at 50-95 wt. %.

11. The membrane of claim 10, wherein the UV-selective coating comprises the acrylic resin at 70-90 wt. %.

12. The membrane of claim 11, wherein the UV-selective coating comprises the acrylic resin at 86-88 wt. %.

13. The membrane of claim 1, wherein the UV-selective coating exhibits inherent adhesion to PVC.

14. The membrane of claim 1, wherein the UV-selective coating has a designed elongation of 20% or more.

15. The membrane of claim 1, wherein the UV-selective coating has a designed elongation of 25% or more.

16. The membrane of claim 9, wherein the acrylic resin comprises plexiglas.

17. The membrane of claim 16, wherein the acrylic resin comprises Plexiglas V052i and Solarcote A200.

18. The membrane of claim 17, wherein the acrylic resin comprises 50 wt. % Plexiglas V052i and 50 wt. % Solarcote A200.

19. The membrane of claim 1, wherein the UV-selective coating comprises triazine.

20. The membrane of claim 1, wherein the UV-selective coating comprises a silicone fluid.

21. The membrane of claim 20 wherein the UV-selective coating comprises 0.1-1.1 wt. % silicone fluid.

22. The membrane of claim 20, wherein the silicone fluid comprises at least one of BYK 330 and BYK 303.

23. The membrane of claim 1, wherein the UV-selective coating comprises a light stabilizer.

24. The membrane of claim 23, wherein the UV-selective coating comprises the light stabilizer at 0.1-2 wt. %.

25. The membrane of claim 24, wherein the UV-selective coating comprises the light stabilizer at 0.3-1 wt. %.

26. The membrane of claim 25, wherein the UV-selective coating comprises the light stabilizer at 0.4-0.6 wt. %.

27. The membrane of claim 23, wherein the light stabilizer comprises at least one of hindered amine light stabilizer (HALS) and Tinuvin 770 DF.

28. The membrane of claim 1, wherein the UV-selective coating comprises a UV absorber.

29. The membrane of claim 28, wherein the UV absorber comprises a member of a triazine class and a cyanoacrylate class.

30. The membrane of claim 1, wherein the UV-selective coating comprises a 1:2- 1 :6 ratio (by weight) of a light stabilizer to a UV Absorber.

31. The membrane of claim 30, wherein the UV-selective coating comprises a 1 :4 ratio (by weight) of the light stabilizer to the UV Absorber.

32. The membrane of claim 1, wherein the anti-drip coating is formed from a solution of hydrophobic polymers with amphiphilic surface-active small molecules.

33. The membrane of claim 1, wherein the anti-drip coating comprises at least one of an acrylic polymer base and a polyamide polymer base.

34. The membrane of claim 1, wherein the anti-drip coating comprises an anti-drip agent.

35. The membrane of claim 1, wherein the anti-drip coating raises a surface tension of the membrane to form a hydrophilic surface.

36. The membrane of claim 35, wherein the surface tension is greater than 35 dynes / cm.

37. The membrane of claim 36, wherein the surface tension is less than 70 dynes / cm.

38. A greenhouse including the membrane of claim 1.

39. A method of creating a flexible polymer membrane comprising: providing a polyvinyl chloride (PVC) layer with a top surface and a bottom surface; coating the top surface with a UV-selective coating; and coating the bottom surface with an anti -drip coating, wherein the coated membrane demonstrates greater than 70 % optical transmission.

40. The method of claim 39, wherein the UV-selective coating transmits 80 % or greater of light having wavelengths between 360-400 nm.

41. The method of claim 39, wherein the UV-selective coating comprises at least one of an acrylic resin, a silicone fluid, a light stabilizer, and a UV absorber.

42. The method of claim 39, wherein the anti -drip coating comprises at least one of an acrylic polymer base and a polyamide polymer base.

43. The method of claim 39, wherein the anti -drip coating raises a surface tension of the membrane to form a hydrophilic surface.

44. The method of claim 43, wherein the surface tension is greater than 35 dynes / cm.

45. The method of claim 44, wherein the surface tension is less than 70 dynes / cm.

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