Method of coating a greenhouse panel

Abstract

A durable diffusive coating for a greenhouse panel is provided that is capable of improving the light properties from incident solar radiation and that is capable of remaining on the greenhouse panel throughout the year, a method of coating a transparent panel is provided comprising the steps of applying a coating composition to the transparent panel and curing the coating composition. The cured coating comprises a crosslinked polymeric binder in an amount of 30-95 wt.%, an adhesion promoter in an amount of 0.05-5 wt.%, and at least one light scattering agent in an amount of 0.2-40 wt.% having a volume to surface mean diameter D 32 0.5-20 µm. The at least one light scattering agent is selected from a volume light scattering producing agent and a surface light scattering producing agent. The volume light scattering producing agent (1) comprises inorganic oxide particles, the surface light scattering producing agent (2) comprises wax particles.

Description

[0001] This invention relates to a method of coating a greenhouse panel. The invention also relates to a coated greenhouse panel, a greenhouse comprising the coated greenhouse panel, and a coating composition.

[0002] background

[0003] Greenhouses provide a controlled climatic environment for the effective growth of plants and crops. Greenhouses consist of essentially transparent greenhouse panels, such as roof panels and side panels, which allow, for example, sunlight to enter the greenhouse.

[0004] Solar radiation reaches greenhouses in both direct and diffuse components. Direct radiation comes directly from the sun and travels in a straight line undisturbed. Diffuse radiation is the result of light scattering and therefore arrives from multiple directions. The natural source of diffuse light is light scattering from atmospheric particles such as dust or water molecules. However, diffuse light can also be generated using scattering materials such as light-diffusing curtains or coatings. These scatter direct light in multiple directions, thus making it "diffuse." In a horticultural context, diffuse light has been shown to have beneficial effects on crop growth compared to direct light by increasing net photosynthetic rate and reducing temperature peaks. In this context, light quality in greenhouses is typically characterized by two parameters: hemispherical transmittance and hortiscatter.

[0005] According to the NEN2675+C1:2018 protocol, hemispherical transmittance is a term that measures the transmittance of garden blinds, developed by Wageningen University and Research. It is defined as follows: The total transmittance of incident light on a hemisphere is defined as the light incident from all directions and uniformly distributed on the surface of the hemisphere. According to this definition, hemispherical transmittance can be expressed as a fraction that assesses how much light is transmitted through a material when it is exposed to light from all directions (hemispherical light) within the photosynthetically active radiation (PAR) range (i.e., light waves with wavelengths between 400 and 700 nm, including direct sunlight and scattered indirect light).

[0006] Horticultural scattering rate is a term defined in the NEN2675+C1:2018 protocol, meaning Light expressed as a percentage "Scattering degree" This is a numerical value commonly used to describe light scattering introduced by greenhouse covering materials. Unlike haze, which considers all scattered light irradiance deviating from the normal (90°) and with a scattering angle greater than 2.5°, horticultural scattering rate is expressed as a percentage in the range of 0 to 100% compared to a perfect Lambertian scatterer. Here, non-scattering materials (such as transparent glass) are defined as having a horticultural scattering rate of 0%, while materials that scatter incident light uniformly in all directions (or are called Lambertian scatterers) have a horticultural scattering rate of 100%.

[0007] Diffuse light has a positive impact on plant growth and development. Incident diffuse light produces a more uniform horizontal and vertical light distribution throughout the growing area, which translates to more efficient utilization of solar radiation. For example, in greenhouse crops, diffuse light can penetrate deeper into the canopy and better activate lower-lying leaves. Compared to direct light, diffuse light leads to increased yields in crops such as bell peppers, cucumbers, and tomatoes, as well as increased dry weight in ornamental plants such as potted chrysanthemums, schefflera, orchids, and kalanchoe. Furthermore, it has been shown that using diffuse light can increase the yield of cut flowers such as roses compared to direct light.

[0008] Diffused light can be artificially generated inside a greenhouse by using specialized materials that promote the diffusion and scattering of incident sunlight. Applying a coating to a transparent greenhouse panel is known as a way to functionalize the panel to diffuse incident sunlight. Various coatings have been developed in this field. For example, EP4119512A1 describes a greenhouse and a glass panel containing a coating film with high diffuse transmittance. This coating comprises first and second fine silica particles, fine titanium dioxide particles, and a binder. The coating has portions protruding from the surface of the glass panel.

[0009] Another option for increasing the light diffuser component within a greenhouse is seasonal coatings, which can be sprayed onto the roof of an existing greenhouse. However, seasonal coatings typically degrade over time, for example, during periods of 2–3 months to 4–6 months. This is also a common target, as many seasonal coatings result in a substantial loss of transmitted light, which is detrimental during the relatively darker periods of the year, such as autumn and winter. Furthermore, greenhouses are exposed to weathering, and cleaning may also be required during the period these seasonal coatings are in place, potentially leading to partial or even complete removal of the coating. The direct consequence of this coating degradation is the release of (micro)plastics into the surrounding environment, but it also necessitates recoating, which is labor-intensive.

[0010] WO2022 / 177432A1 describes a biodegradable seasonal coating composition comprising crosslinked starch and fillers, which can be used as a sunshade. Sunshades provide protection against excessive light and heat during the spring and summer months and are degraded or actively removed to adapt to periods of less light and heat. The coating composition described in WO2022 / 177432A1 can mitigate microplastic release due to coating wear. However, this coating remains seasonal and requires annual reapplication.

[0011] JP2012111142 describes a weather-resistant laminated resin glass whose hue is not significantly different from conventional colored glass and exhibits stable chromaticity under various light sources and intensities. The resin glass comprises a colored substrate layer containing a polycarbonate resin composition. An acrylic resin layer containing a UV absorber and an organosiloxane layer containing fine cerium oxide particles are laminated onto the colored polycarbonate. This resin glass does not diffuse light.

[0012] WO2014197393 and WO2015168439 describe the use of chromophores in wavelength conversion compositions. Chromophores absorb photons of a specific wavelength or wavelength range and re-emit photons at different wavelengths. Wavelength conversion compositions can be used in greenhouse panels to improve the wavelength distribution for plant growth. Wavelength conversion compositions do not cause light scattering.

[0013] Therefore, one objective of the present invention is to provide a durable diffuse coating for greenhouse panels that can improve the light properties from incident solar radiation and can remain on the greenhouse panels year-round. Invention Overview

[0015] This invention relates to a method for coating a transparent panel, comprising the steps of applying a coating composition to the transparent panel and curing the coating composition to form a cured coating. The cured coating comprises:

[0016] - Crosslinking adhesive, in an amount of 30-95 wt.% based on the total weight of the coating, wherein the crosslinking adhesive comprises a polymeric adhesive;

[0017] - Adhesion promoter, calculated based on the total weight of the coating, in an amount of 0.05-5 wt.%, and

[0018] - At least one light scattering agent whose volume is proportional to the average surface diameter D 32 The thickness ranges from 0.5 to 20 µm, and the amount is calculated based on the total weight of the coating, ranging from 0.2 to 40 wt.%.

[0019] The at least one light scattering agent is selected from:

[0020] - A reagent that produces volumetric light scattering, whose refractive index (measured at 589 nm) is at least 0.01 higher than the refractive index of the crosslinking adhesive surrounding the reagent, and

[0021] - Reagents that produce surface light scattering

[0022] The reagent (1) that produces volumetric light scattering contains inorganic oxide particles, and

[0023] The reagent (2) that produces surface light scattering includes wax particles.

[0024] If the at least one light scattering agent is a reagent that generates surface light scattering, then the root mean square surface roughness of the cured coating is 0.1-1 µm.

[0025] It has been found that transparent panels coated in this manner diffuse incident light well with only limited loss of hemispherical transmittance. The coated transparent panels exhibit high hemispherical transmittance of 50-84% and horticultural scattering of 1-75%. In one embodiment, the coated transparent panels exhibit high hemispherical transmittance of 75-84% and horticultural scattering of 20-75%. Due to the minimal light loss, the coating can also be retained on the greenhouse transparent panels during relatively darker periods of the year, such as autumn and winter.

[0026] Furthermore, the coating is durable. "Durable" should be understood as the cured coating being able to withstand abrasion caused by weather conditions and common cleaning processes (such as rain, UV exposure, and scrubbing) without substantial degradation of the coating for at least one year. Preferably, the coating is able to withstand at least two years of abrasion, more preferably at least three years, and most preferably at least five years. Preferably, compared to when the coating is applied to a transparent panel, the hemispherical transmittance of the coated transparent panel decreases by less than 2 percentage points after one year, more preferably after two years, even more preferably after three years, and most preferably after five years, and the horticultural scattering decreases by less than 5 percentage points.

[0027] Due to the coating's durability, less waste is released into the surrounding environment. Furthermore, the coating needs to be applied to the existing greenhouse's transparent panels fewer times, thus reducing the labor intensity of coating greenhouse transparent panels in the long run.

[0028] Furthermore, when wear does eventually lead to coating damage, the coating according to the invention is repairable. Wear caused by sand and brushing is, to some extent, unavoidable over time. The coating according to the invention can be repaired by reapplying the coating composition to the transparent panel (partially). This extends the lifespan of the coating.

[0029] Furthermore, the present invention relates to a coated transparent panel, a structure comprising the coated transparent panel, and a coating composition.

[0030] Other advantages of various embodiments of the method of the present invention will become apparent in the following description.

[0031] Detailed description

[0032] The present invention will now be discussed in more detail.

[0033] Transparent panel

[0034] This invention relates to a method of coating a transparent panel, comprising the step of applying a coating composition to the transparent panel. The term "transparent" means that at least a portion of light falling on one side of the panel can pass through the other side of the panel. Preferably, the hemispherical transmittance of the transparent panel is at least 50%, more preferably at least 60%, more preferably at least 75%, even more preferably at least 85%, for example at least 90%. Most preferably, the hemispherical transmittance of the transparent panel is 100%. The transparent panel can be made of any type of transparent material. Preferably, the transparent panel is a glass panel, a polycarbonate panel, a polyvinylidene fluoride (PVDF) panel, a polyacrylate panel, a polyvinyl chloride (PVC) panel, or a polyethylene panel.

[0035] coating

[0036] Here, “coating composition” means a wet composition applied to a transparent panel and subsequently cured, including any solvents, co-solvents, and other volatile components. “Coating” means a dried, cured coating. Unless otherwise stated, percentages are expressed as a weight percentage calculated based on the cured coating and do not include any other solvents and other volatile components that disappear during curing.

[0037] Crosslinking adhesives and adhesion promoters

[0038] The coating comprises a cross-linked binder. The cross-linked binder constitutes the base structure of the coating. The interaction between the binder and at least one light-scattering agent ensures the stability of the light-scattering agent within the coating. In this way, the coating provides the desired optical properties while resisting physical weathering and erosion, and allows for cleaning of the coating. The binder is an optically transparent binder.

[0039] Based on the weight of the coating, the coating preferably contains at least 40 wt.% crosslinking binder, more preferably at least 50 wt.%, even more preferably at least 55 wt.%, and most preferably at least 60 wt.% crosslinking binder. However, if the coating contains too much crosslinking binder, the stability of at least one light scattering agent may be affected. Therefore, based on the weight of the coating, the coating contains at most 95 wt.% crosslinking binder, preferably at most 90 wt.%, more preferably at most 80 wt.% crosslinking binder.

[0040] Crosslinking adhesives comprise polymeric adhesives. Preferably, the polymeric adhesive is an acrylic polymer, a polyurethane adhesive, a fluoropolymer, an alkyd resin, a silicone-based binder, or a mixture of two or more thereof. Acrylic polymers are, for example, in the form of anionic acrylic suspensions, acrylic copolymers, multiphase acrylic emulsions, self-crosslinking acrylic polymers, or mixtures of two or more thereof. Polyurethane adhesives are, for example, in the form of polyurethane composite dispersions, self-crosslinking polyurethane dispersions, aliphatic polyurethane dispersions, solvent-free polyurethane dispersions, bio-based polyurethane dispersions, or mixtures of two or more thereof.

[0041] The coating preferably also contains a crosslinking agent, especially when the adhesive is not a self-crosslinking adhesive. The crosslinking agent interacts with the other components of the coating to help form a network structure, improving the coating's durability by preventing swelling and enhancing its scrub resistance. The crosslinking agent crosslinks the adhesive and is UV-curable or room-temperature curable. Upon curing, the adhesive and crosslinking agent form a crosslinked adhesive matrix.

[0042] The crosslinking agent is preferably a multifunctional polyaziridine, isocyanate, or polycarbodiimide. Based on the total weight of the coating, the amount of crosslinking agent in the coating is preferably 1-10 wt.%, more preferably 2.5-9 wt.%, and more preferably 4-8.5 wt.%.

[0043] Selecting a suitable crosslinking adhesive within the parameter range given above is within the scope of expertise of those skilled in the art. No further explanation is needed here.

[0044] The coating also contains an adhesion promoter to facilitate adhesion between the coating and the transparent panel. The choice of adhesion promoter depends on the properties of the coating and the transparent panel being coated. For glass and silica-containing panels, adhesion promoters are, for example, silane compounds with amine or epoxy functional groups, such as g-aminopropyltriethoxysilane, g-aminopropyltrimethoxysilane, g-(methylamino)propyltrimethoxysilane, g-aminopropylmethyldiethoxysilane, γ-(2-aminoethyl-3-aminopropyl)triethoxysilane, γ-(2-aminoethyl-3-aminopropyl)methyldimethoxysilane, g-glycidoxypropyltriethoxysilane, g-glycidoxypropyltrimethoxysilane, and polyfunctional glycidoxypropyltrimethoxysilane. However, for plastic panels, chlorinated and non-chlorinated polyolefin agents are preferred.

[0045] Based on the total weight of the coating, the amount of adhesion promoter present in the coating is preferably 0.05-5 wt.%, more preferably 0.5-4 wt.%, and most preferably 1-3 wt.%.

[0046] Adhesion promoters are well known in the field of coating compositions and require no further explanation. Selecting a suitable adhesion promoter is within the scope of those skilled in the art.

[0047] Light scattering agent

[0048] In addition, the coating contains at least one light scattering agent. This light scattering agent exists in the form of particles that act as scattering centers, thereby diffusing the incident light. Compared to the photosynthetically active radiation (PAR) portion of the incident light, the PAR portion of the diffused light has a higher horticultural scattering rate score, which is more beneficial to plant and crop growth.

[0049] While the primary function of the coating is to improve the quality of PAR light falling on a transparent panel by diffusing incident light, there may be additional requirements for the coating, such as aesthetics related to the film's color, opacity, and transparency, as well as its abrasion resistance and weather resistance. Preferably, the at least one light-scattering agent helps to meet at least one of these additional requirements.

[0050] The at least one light scattering agent is selected from reagents that produce volume light scattering and reagents that produce surface light scattering. Both volume scattering and surface scattering are physical phenomena that describe how light (or other waves) interacts with a medium containing, for example, particles.

[0051] Volume scattering occurs when light penetrates a medium containing particles distributed throughout the medium, and the medium and particles have different refractive indices. Therefore, the reagent that produces volume light scattering has a refractive index at least 0.01 higher than that of the crosslinked adhesive surrounding the light scattering agent (measured at 589 nm).

[0052] Preferably, the refractive index of the light scattering agent that produces volumetric light scattering (measured at 589 nm) is at least 0.02 higher than that of the crosslinked adhesive, and even more preferably at least 0.03 higher.

[0053] Preferably, the refractive index of the crosslinking adhesive is 1.35-2.70, 1.38-2.70, more preferably 1.40-2.30, and most preferably 1.42-1.90. The refractive index of the light scattering agent that generates volume light scattering is preferably 1.40-2.70, more preferably 1.41-2.30, and more preferably 1.42-1.90.

[0054] The light scattering agent that produces volume scattering contains inorganic oxide particles. The inorganic oxide particles are preferably selected from SiO2 and Mg3Si4O. 10 (OH)₂, ZnO, ZrO₂, Al₂O₃, TiO₂, SrO, SnO₂, CaO, BaO, CuO, Fe₂O₃, MnO, MgO, NiO, or mixtures thereof. Mg₃Si₄O 10(OH)2 is commonly known as talc.

[0055] In addition to PAR light, which is important for photosynthesis and plant growth, natural sunlight also includes near-infrared radiation (NIR, the portion of light radiation with wavelengths roughly between 750 and 2500 nm). From a greenhouse energy efficiency perspective, controlling the transmission of NIR from natural sunlight is also important, as this is the primary source of radiative heat in greenhouses in hot climates.

[0056] When the coating is intended for use in relatively sunny or hot climates, the light-scattering agent that produces volumetric scattering is preferably selected from SnO2, TiO2, ZnO, SiO2, Fe2O3, and one or more mixtures thereof. These particles also act as NIR reflective particles and help control the temperature inside the greenhouse, especially in hot climates. NIR reflective particles diffusely reflect a portion of visible light and near-infrared radiation. This results in reduced near-infrared transmittance, thereby reducing the heating effect, while still allowing the transmission of long-wave infrared radiation.

[0057] The surface roughness of a coating can be characterized by the root mean square roughness (Rq) as defined in ISO 4287. Rq is the most commonly used parameter representing the root mean square vertical deviation of the profile, and its calculation formula is:

[0058] ,

[0059] Where n is the number of peaks determined on the surface, and Z is the measured peak height.

[0060] If at least one light scattering agent is a volume scattering agent, the root mean square surface roughness (Rq) of the cured coating can be essentially 0 µm.

[0061] On the other hand, surface scattering occurs when light (or other waves) strikes a textured surface (e.g., the interface between air and the top layer of the coating). When the at least one light scattering agent is a surface scattering agent, the Rq of the cured coating is between 0.1 and 1 μm, more preferably 0.15 to 0.8 μm, and even more preferably 0.2 to 0.6 μm. The roughness or texture of the surface is essentially a result of the surface scattering agent. Two mechanisms contribute to at least a portion of the surface scattering agent being localized on the surface of the cured coating. The first mechanism is a floating effect resulting from density differences or incompatibility between the surface scattering agent and the coating composition, for example, a particle density lower than that of the coating composition. The second mechanism is the ball bearing effect, which is caused by the average particle size of the surface scattering agent being larger than the thickness of the crosslinked adhesive, or by the accumulation of light-scattering particles near the coating surface.

[0062] The density of the light scattering agent that produces surface scattering at 20°C is preferably 0.8-1.2 g / cm³. 3 Preferably, it is 0.75-1.15, and more preferably 0.8-1.1 g / cm³. 3 .

[0063] The light scattering agent that produces surface scattering comprises wax particles. The wax particles are preferably selected from natural, synthetic or semi-synthetic wax particles, such as, but not limited to, carnauba wax, rice bran wax, beeswax, paraffin wax, amides, polyethylene, polypropylene polymers or mixtures thereof.

[0064] Besides their function as light scattering agents, wax particles can also have other functions. For example, amides can also act as slip additives to control friction between the coating and the processing equipment or the surface of a transparent panel, which could otherwise cause difficulties in processing the coating composition or the coating itself. Slip additives reduce friction, thereby allowing the formation of a solid lubricating layer. Preferred amides are stearamide, erucamide, and oleamide.

[0065] Preferably, the coating comprises both a light scattering agent that generates volumetric light scattering and a light scattering agent that generates surface light scattering. More preferably, the coating comprises a light scattering agent that generates volumetric light scattering, which comprises an inorganic oxide; and a light scattering agent that generates surface light scattering, which comprises wax particles.

[0066] If the amount of light scattering agent is too low, the agent will not be able to sufficiently scatter the incident light. On the other hand, a higher amount of light scattering agent may over-diffuse the incident light, resulting in excessive diffuse reflection, i.e., a loss of hemispherical transmittance. Therefore, based on the total weight of the coating, the amount of light scattering agent contained in the coating is preferably between 0.2 wt.% and 40 wt.%, more preferably between 2.5 wt.% and 30 wt.%, and most preferably between 5 wt.% and 20 wt.%.

[0067] The size of the light scattering agent also affects the diffusion of incident light. Unlike the terms Dv10, Dv50, and Dv90, which are commonly used to describe the particle size distribution (PSD) of light scattering (especially horticultural scattering), the average volume is related to the average surface diameter D. 3,2 It is used as a single parameter to describe the particle size of polydisperse particle assemblies. D 3,2 It is also represented as D[3,2], or referred to as the Sauter average diameter. D in the PSD of the light scattering agent 3,2 Preferably, it is between 0.5 and 20 µm, more preferably between 1 and 16 µm, even more preferably between 3 and 14 µm, and most preferably between 5 and 10 µm.

[0068] Optional other coating components

[0069] The coating may also contain one or more of the following: light stabilizers, dispersants, wetting agents or leveling agents, defoamers and rheology modifiers.

[0070] Preferably, the coating also contains a light stabilizer. The light stabilizer helps mitigate the damaging effects of long-term exposure to UV radiation (wavelengths approximately between 200 and 400 nm) present in the solar spectrum by reducing the transmission of ultraviolet radiation. Light stabilizers are, for example, hindered oligomeric amine light stabilizers (HALS), HALS-containing triazine UV absorbers, benzotriazole UV absorbers, or combinations thereof. Based on the total weight of the coating, the amount of light stabilizer is preferably 0.1-10 wt.%, more preferably 0.5-9 wt.%, and more preferably 1-8 wt.

[0071] The coating preferably includes a dispersant. The dispersant supports the stability of the light-scattering agent in the coating composition, preventing particle agglomeration and sedimentation, which could otherwise lead to poor performance of the agent in the coating. The dispersant is preferably a polymeric dispersant, such as an ammonium aqueous solution of a styrene-maleic anhydride derivative, an esterified styrene-maleic anhydride ammonium salt, an ammonium or sodium salt of polyacrylic acid, an acrylic copolymer emulsion, a polymeric alkoxylate, or a polyurethane. Based on the total weight of the coating, the amount of dispersant in the coating is preferably 0.1-40 wt.%, more preferably 1-30 wt.%, even more preferably 2-20 wt.%, and most preferably 4-10 wt.%.

[0072] A wetting agent or leveling agent is an additive that promotes the interaction between the dispersant (if present) and the light-scattering agent in the coating composition by reducing the contact angle of the particle surface. It further promotes the interaction at the coating-substrate interface, again reducing the contact angle at that interface. This promotes substrate wetting, leveling of the coating composition during drying, and surface slip. Wetting agents are, for example, ethynylene glycol in ethylene glycol, or organomodified silicone, such as, but not limited to, polyether siloxanes or silicone-polyether block copolymers, mixtures of polyalkylene oxide copolymers and octamethylcyclotetrasiloxane, or polyalkylene oxide modified heptamethyltrisiloxane. The amount of wetting agent present is preferably 0.05-5 wt.%, more preferably 0.1-3.5 wt.%, based on the total weight of the coating.

[0073] The coating preferably contains a defoamer or defoaming agent. The defoamer or defoaming agent minimizes the presence of air bubbles in the coating composition, thereby improving film formation on a transparent panel and resulting in a more uniform coating. The defoaming agent is, for example, a nonionic surfactant, such as silicone or siloxane. The defoaming agent is preferably polydimethylsiloxane or a water-based silicone emulsion. Based on the total weight of the coating, the amount of defoaming agent is preferably 0.05-1 wt.%, more preferably 0.1-0.5 wt.%.

[0074] Rheology modifiers or thickeners are used to adjust the rheological properties of the coating composition. The thickener interacts with the binder to form a network structure, which reduces the flowability of the binder and thus increases the viscosity of the formulation. This also contributes to the formation of a more uniform coating. Thickeners are, for example, polyurethane-based thickeners, layered silicates, cellulose or cellulose derivatives such as hydroxyethyl cellulose (HEC) or microfibrillated cellulose (MFC), anionic hydrophobically modified alkali-swellable emulsions (HASE), hydrophobically modified ethylene oxide polyurethanes (HEUR), or combinations thereof, such as HASE and HEUR. Based on the total weight of the coating, the amount of thickener present is preferably 0.05-3.5 wt.%, more preferably 0.075-2 wt.%, even more preferably 0.1-1 wt.%, and most preferably 0.1-0.6 wt.%.

[0075] For technicians, other suitable coating components will be obvious.

[0076] Apply coating composition

[0077] The coating composition is preferably applied to the transparent panel in the form of a liquid coating composition, but it can also be applied in any other suitable form, such as a paste.

[0078] Methods for applying coating compositions to transparent panels are known in the art. Coating compositions can be applied, for example, by squeegee coating, wireline coating, roller coating, dip coating, or spray coating. Squeegee and wireline coating are generally limited to small samples because the coating formulation is deposited onto the transparent panel by a single, uniform motion of a squeegee or wireline across the substrate. However, for large surface areas, other techniques are preferred. Coating compositions can be applied by dip coating, which involves immersing the transparent panel in a tank filled with the coating composition and then removing it at a constant rate and under controlled conditions. Coating compositions can also be applied by roller coating, where the coating is deposited by a combination of multiple rollers. In the case of large surface areas, the coating composition is preferably applied to the transparent panel by airless spraying, an industrially accepted method that involves atomizing a coating fluid into small droplets that are deposited onto the panel without the use of compressed air, and this method has been used to apply seasonal coatings on existing greenhouses. It is also a rapid method for applying coating compositions and can form a uniform coating surface.

[0079] Technicians know how to adjust the viscosity of the coating composition to suit the selected application method. For example, in airless spraying applications, the coating preferably exhibits shear-thinning rheological behavior. This facilitates the uniform application of the coating composition onto the transparent panel to form a uniform layer. When the coating composition is intended for low-pressure spraying applications with nozzle pressures between 3 and 10 bar, the viscosity of the coating composition is preferably between 1 and 100 mPa. Between 5 and 50 mPa Between 7.5 and 15 mPa, the optimal range is between 7.5 and 15 mPa. The viscosity of the coating composition is preferably between 100 and 150 mPa when the composition is intended for high-pressure spraying applications with nozzle pressures between 10 and 250 bar. Between s.

[0080] A coated transparent panel can be obtained by applying one or more coating compositions. For example, two, three, four, or five coating compositions can be applied to obtain a coated transparent panel. If a single coating composition is applied, all components of the coating are applied to the transparent panel as a single coating composition.

[0081] If a multilayer coating composition is applied, the first layer may be a first coating composition, and the second layer may be a second composition. The first and second coating compositions may be the same or different. If the first and second coating compositions are different, the first coating composition contains a crosslinking binder, an adhesion promoter, and preferably a light scattering agent that produces volumetric light scattering. The second coating composition contains a crosslinking binder and preferably a light scattering agent that produces surface light scattering. In any case, at least one of the first and second compositions contains a light scattering agent. When referring to a coating in this specification, the sum of all layers and all components is implied.

[0082] In a preferred embodiment, the step of applying a coating composition to a transparent panel includes applying a coating composition comprising:

[0083] - A polymeric adhesive, selected from acrylic polymers, polyurethane polymers, or combinations thereof, comprising 70-80 wt.% based on the total weight of the coating.

[0084] - A light-scattering agent that generates surface light scattering, selected from polyethylene polymer wax and / or polypropylene polymer wax, in an amount of 1-15 wt.% based on the total weight of the coating.

[0085] - Crosslinking agent, selected from polyaziridine or polycarbodiimide, in an amount of 5-9 wt.% based on the total weight of the coating.

[0086] - Adhesion promoter, selected from silane compounds having amine or epoxy functional groups, in an amount of 1-3 wt.% based on the total weight of the coating.

[0087] - A wetting agent, selected from siloxane polyalkylene oxides, polyether siloxanes, or mixtures thereof, in an amount of 0.5-3.5 wt.% based on the total weight of the coating.

[0088] - Defoaming agent, selected from polydimethylsiloxane, water-based silicone emulsions, or mixtures thereof, in an amount of 0.1-0.5 wt.% based on the total weight of the coating.

[0089] - A rheology modifier selected from hydrophobically modified ethylene oxide polyurethane (HEUR), anionic hydrophobically modified alkali-swellable emulsion (HASE), or mixtures thereof, in an amount of 0.1-0.6 wt.% based on the total weight of the coating.

[0090] - Light stabilizer, selected from hindered oligomeric amine light stabilizers (HALS), triazine UV absorbers or mixtures thereof, in an amount of 0.1-5 wt., based on the total weight of the coating.

[0091] In another preferred embodiment, the step of applying a coating composition to a transparent panel includes applying a coating composition comprising:

[0092] - A polymeric adhesive, selected from acrylic polymers, polyurethane polymers, or combinations thereof, comprising 60-80 wt.% based on the total weight of the coating.

[0093] - A light scattering agent that produces volumetric light scattering, selected from SiO2, Al2O3, Mg3Si4O 10 (OH)2 or mixtures thereof, in an amount of 5-20 wt.% based on the total weight of the coating.

[0094] - A light-scattering agent that generates surface light scattering, selected from polyethylene polymer wax, polypropylene polymer wax, and mixtures thereof, in an amount of 0.5-5 wt.% based on the total weight of the coating.

[0095] - Crosslinking agent, selected from polyaziridine or polycarbodiimide, in an amount of 5-9 wt.% based on the total weight of the coating.

[0096] - Adhesion promoter, selected from silane compounds having amine or epoxy functional groups, in an amount of 1-3 wt.% based on the total weight of the coating.

[0097] - Dispersant, selected from acrylic polymers, polymeric alkoxylates, or polyurethanes, in an amount of 4-10 wt.% based on the total weight of the coating.

[0098] - A wetting agent, selected from acetylene glycol, siloxane polyalkylene oxide, polyether siloxane, or mixtures thereof, in an amount of 0.5-3.5 wt.% based on the total weight of the coating.

[0099] - Defoaming agent, selected from polydimethylsiloxane, water-based silicone emulsions, or mixtures thereof, in an amount of 0.1-0.5 wt.% based on the total weight of the coating.

[0100] - A rheology modifier selected from hydrophobically modified ethylene oxide polyurethane (HEUR), anionic hydrophobically modified alkali-swellable emulsion (HASE), or mixtures thereof, in an amount of 0.1-0.6 wt.% based on the total weight of the coating, and

[0101] - Light stabilizer, selected from hindered oligomeric amine light stabilizers (HALS), triazine UV absorbers or mixtures thereof, in an amount of 0.1-5 wt. based on the total weight of the coating.

[0102] In another preferred embodiment, the step of applying a coating composition to a transparent panel includes applying a first coating composition and a second coating composition, wherein the first coating composition comprises:

[0103] - A polymeric adhesive, selected from acrylic polymers, polyurethane polymers, or combinations thereof, comprising 70-90 wt.% based on the total weight of the coating.

[0104] - Reagents that produce volumetric light scattering, selected from SiO2, Al2O3, Mg3Si4O 10 (OH)2 or mixtures thereof, in an amount of 5-20 wt.% based on the total weight of the coating.

[0105] - Crosslinking agent, selected from polyaziridine or polycarbodiimide, in an amount of 5-9 wt.% based on the total weight of the coating.

[0106] - Adhesion promoter, selected from silane compounds having amine or epoxy functional groups, in an amount of 1-3 wt.% based on the total weight of the coating.

[0107] - Dispersant, selected from acrylic polymers, polymeric alkoxylates, or polyurethanes, in an amount of 4-10 wt.% based on the total weight of the coating.

[0108] - Wetting agent, selected from acetylene glycol, polyether siloxane, or mixtures thereof, in an amount of 0.1-2 wt.% based on the total weight of the coating.

[0109] - Defoaming agent, selected from polydimethylsiloxane, water-based silicone emulsions, or mixtures thereof, in an amount of 0.1-0.5 wt.% based on the total weight of the coating.

[0110] - Rheology modifier, selected from hydrophobically modified ethylene oxide polyurethane (HEUR), anionic hydrophobically modified alkali swelling emulsion (HASE), or mixtures thereof, in an amount of 0.1-0.6 wt.% based on the total weight of the coating.

[0111] - Light stabilizers, selected from hindered oligomeric amine light stabilizers (HALS), triazine UV absorbers, or mixtures thereof, in an amount of 1-5 wt.% based on the total weight of the coating.

[0112] And the second coating composition comprises:

[0113] - A polymeric adhesive, selected from acrylic polymers, polyurethane polymers, or mixtures thereof, comprising 80-95 wt.% based on the total weight of the coating.

[0114] - The reagent that generates surface light scattering, selected from polyethylene polymer wax, polypropylene polymer wax, and mixtures thereof, is present in an amount of 0.5-2.5 wt.% based on the total weight of the coating.

[0115] - Crosslinking agent, selected from polyaziridine or polycarbodiimide, in an amount of 5-7.5 wt.% based on the total weight of the coating.

[0116] - Adhesion promoter, selected from silane compounds having amine or epoxy functional groups, in an amount of 0.1-3 wt.% based on the total weight of the coating.

[0117] - Wetting agent, selected from polyether siloxanes or siloxane polyalkylene oxides, in an amount of 0.1-2 wt.% based on the total weight of the coating.

[0118] - Defoaming agent, selected from polydimethylsiloxane or water-based silicone emulsions, in an amount of 0.1-0.6 wt.% based on the total weight of the coating.

[0119] - Hydrophobically modified ethylene oxide polyurethane (HEUR) rheology modifier, in an amount of 0.1-0.2 wt.% based on the total weight of the coating, and

[0120] - Light stabilizer, selected from hindered oligomeric amine light stabilizers (HALS), triazine UV absorbers or mixtures thereof, in an amount of 0.1-8 wt. based on the total weight of the coating.

[0121] Over time, the coating on a coated transparent panel may be damaged due to factors such as sand scraping or brushing. In such cases, another coating composition can be applied to the already cured coating on the transparent panel. This extends the lifespan of both the coating and the coated transparent panel.

[0122] Curing the coating composition to obtain a transparent panel with a coating.

[0123] After the coating composition is applied to the transparent panel, the coating composition is cured. Curing can be promoted by heating. Preferably, the coating composition is cured at a temperature of 5-80°C, more preferably 10-60°C, even more preferably 15-45°C, and most preferably 20-40°C.

[0124] If the coating is applied in multiple layers, the first layer is at least partially cured before the second layer is applied. Curing time varies depending on the thickness and curing conditions, and is shorter with heating. Generally, if the coating is left to cure at room temperature, the curing time is 2–16 hours, such as 4 hours, 6 hours, 8 hours, 10 hours, or 12 hours. When heat is applied, the curing time can be shortened to 2–6 hours, such as 3 hours, 4 hours, or 5 hours. Curing can be carried out, for example, in an oven.

[0125] After curing, the thickness of the coating is preferably 10-150 μm, more preferably 20-100 μm, even more preferably 30-80 μm, and most preferably 30-50 μm.

[0126] Preferably, the resulting coated transparent panel has a hemispherical transmittance of at least 75%, more preferably at least 76%, and most preferably at least 77%. Preferably, the coated transparent panel has a horticultural scattering rate of at least 20%, more preferably at least 30%, and most preferably at least 35%. Because excessively high horticultural scattering rates are detrimental to plants, the horticultural scattering rate is preferably at most 70%, more preferably at most 65%, and most preferably at most 55%.

[0127] In a second aspect, the present invention relates to a transparent panel with a coating. The transparent panel may be, for example, a wall panel or a door. Preferably, the transparent panel is a roof panel.

[0128] In a third aspect, the present invention relates to a structure comprising a transparent panel having a coating. Preferably, the structure is a greenhouse.

[0129] In a final aspect, the present invention relates to a coating composition for coating a transparent panel, the coating composition comprising:

[0130] - Adhesive, in an amount of 30-95 wt.% based on the total weight of the coating, wherein the adhesive comprises a polymeric adhesive.

[0131] - Adhesion promoter, calculated based on the total weight of the coating, in an amount of 0.05-5 wt.%, and

[0132] - At least one light scattering agent whose volume is proportional to the average surface diameter D 32 The thickness is 0.5-20 µm, and the amount is 0.2-40 wt.% based on the total weight of the coating.

[0133] The at least one light scattering agent is selected from:

[0134] - A reagent that produces volumetric light scattering has a refractive index (measured at 589 nm) that is at least 0.01 higher than the refractive index of the crosslinking adhesive surrounding the reagent; and

[0135] - Reagents that induce surface light scattering result in a root mean square surface roughness (Rq) of 0.1-1 µm after curing.

[0136] The reagent (1) that produces volumetric light scattering contains inorganic oxide particles, and

[0137] The reagent (2) that produces surface light scattering includes wax particles.

[0138] Preferably, the coating composition comprises one or more selected from the group consisting of solvents, cosolvents, pH adjusters, coalescing agents, and combinations thereof.

[0139] The solvent can be an organic solvent. It can be, for example, alcohols such as ethanol and isopropanol; ketones such as acetone or methyl isobutyl ketone; esters such as propylene glycol monomethyl ether acetate; glycol ethers such as propylene glycol methyl ether and ethylene glycol monobutyl ether; and mixtures thereof. Preferably, the coating composition is an aqueous composition. Most preferably, the solvent is water.

[0140] The coating composition may also contain a co-solvent, which is a chemical substance added in a relatively small amount to the main solvent to increase the solubility of a poorly soluble compound. Examples of suitable co-solvents are ethylene glycol; glycol ethers, such as dipropylene glycol n-butyl ether, propylene glycol phenyl ether, propylene glycol monomethyl ether acetate, diethylene glycol hexyl ether, and dipropylene glycol dimethyl ether, and one or more mixtures thereof.

[0141] The coating composition may also contain a pH adjuster. The pH adjuster is typically an acid or base used to adjust the pH value of the coating composition, such as, but not limited to, ammonia, dimethylglucosamine, dimethylmethoxypropylamine, and other organic amines. Based on the total weight of the coating composition, the amount of the pH adjuster in the coating composition is preferably 0.1-1 wt.%, more preferably 0.1-0.6 wt.%, and even more preferably 0.1-0.5 wt.%. For water-based coatings, the amount of pH adjuster present is preferably such that the pH of the coating is 3-10, more preferably 7.5-9.

[0142] Preferably, the coating composition includes a coalescing agent. The coalescing agent facilitates the formation of a more uniform coating composition layer on the transparent panel, contributing to a more uniform coating. The coalescing agent is, for example, a glycol ether, such as dipropylene glycol n-butyl ether, propylene glycol phenyl ether, diethylene glycol hexyl ether, and dipropylene glycol dimethyl ether, or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 1-isopropyl-2,2-dimethyltrimethylene diisobutyrate, or butyl levulinate, ester alcohols, or combinations thereof. Based on the total weight of the coating composition, the amount of the coalescing agent in the coating composition is preferably 0.1-10 wt.%, more preferably 1-8 wt.%, and more preferably 2-6 wt.%.

[0143] As will be apparent to those skilled in the art, different embodiments of the invention can be used in combination unless they are mutually exclusive. When quantities, concentrations, dimensions, and other parameters are expressed as ranges, preferred ranges, upper limits, lower limits, or preferred upper and lower limits, it should be understood that any range obtainable by combining any upper or preferred value with any lower or preferred value has also been specifically disclosed, regardless of whether the obtained range is explicitly mentioned in the context. The preference for methods of coating transparent panels also applies to coated transparent panels, structures, and coating compositions.

[0144] Furthermore, it should be noted that the title is provided for the reader's convenience and does not limit the invention. Preferences set forth with respect to one aspect of the invention also apply to other aspects. For example, preferences described with respect to coatings also apply to coating compositions, and vice versa.

[0145] The following examples will illustrate the practice of the invention in some preferred embodiments. Other embodiments within the scope of the claims will be apparent to those skilled in the art.

[0146] Explanatory Implementation Plan

[0147] The present invention is illustrated by the following figures, but is not limited thereto or restricted thereto.

[0148] Figure 1A A first embodiment of the present invention is described, wherein a transparent panel is coated with a coating containing a light-scattering agent that produces volumetric light scattering.

[0149] Figure 1B A second embodiment of the invention is described, wherein the transparent panel is coated with a coating containing a light-scattering agent that produces surface scattering.

[0150] Figure 1C A third embodiment of the invention is described, wherein a transparent panel is coated with a coating comprising a light scattering agent that generates volume scattering and a light scattering agent that generates surface scattering, and the light scattering agent that generates volume scattering and the light scattering agent that generates surface scattering are applied as a single layer and as a single coating composition.

[0151] Figure 2 A fourth embodiment of the present invention is described, wherein a transparent panel is coated with a coating comprising a light scattering agent that generates volume scattering and a light scattering agent that generates surface scattering, wherein the light scattering agent that generates volume scattering is applied as a layer of a first coating composition and the light scattering agent that generates surface scattering is applied as a layer of a second coating composition.

[0152] Figure 3The vertical transmittance of coated glass panels, uncoated low-iron float glass, and uncoated ordinary float glass according to the present invention is shown in the near-infrared (1.0 to 5.0 µm) range.

[0153] Figure 1A A schematic cross-sectional view of a first embodiment of a transparent panel 3 with a coating 5 according to the present invention is shown. A coating composition comprising a volumetric light scattering agent 1 is applied to a transparent glass plate 3 and cured at room temperature to obtain a transparent panel 3 with a coating 5. The volumetric light scattering agent 1 is embedded in the crosslinking adhesive 4 of the coating 5, and the coating 5 has a root mean square roughness (Rq) of substantially 0 µm.

[0154] Figure 1B A schematic cross-sectional view of a second embodiment of a transparent panel 3 with a coating 5 according to the present invention is shown. A coating composition comprising a surface light scattering agent 2 is applied to a transparent glass plate 3 and cured at room temperature to obtain a transparent panel 3 with a coating 5. A portion of the surface light scattering agent 2 extends from the surface of the crosslinked adhesive 4. The coating 5 has a root mean square roughness (Rq) of approximately 0.5 µm.

[0155] Figure 1C A schematic cross-sectional view of a third embodiment of a transparent panel 3 with a coating 5 according to the present invention is shown. A coating composition comprising both a volume scattering agent 1 and a surface light scattering agent 2 is applied to a transparent glass plate 3 and cured at room temperature to obtain a transparent panel 3 with coating 5. A portion of the surface scattering agent 2 extends from the surface of the crosslinked adhesive 4. Coating 5 has a root mean square roughness (Rq) of approximately 0.5 µm.

[0156] Figure 2 A schematic cross-sectional view of a fourth embodiment of a transparent panel 3 with a coating 5 according to the present invention is shown. A first coating composition comprising a volumetric light scattering agent 1 is applied as a substrate to the transparent panel 3. The volumetric light scattering agent 1 is embedded in a crosslinking adhesive 4. The first coating composition is cured at room temperature, and then a second coating composition comprising a surface light scattering agent 2 is applied on top of the substrate. After curing the second coating composition at room temperature, a transparent panel 3 with a coating 5 is obtained. A portion of the surface light scattering agent 2 extends from the surface of the crosslinking adhesive 4. The coating 5 has a root mean square roughness (Rq) of approximately 0.5 µm.

[0157] Example

[0158] Techniques and tests used to characterize and compare the properties of different coating compositions.

[0159] Hemispherical transmittance, horticultural scattering and near-infrared transmittance

[0160] Hemispherical transmittance (HT) and horticultural scattering (HS) were measured as described in NEN 2675+C1:2018.

[0161] HT is the total transmittance weighted by the plant response function for multiple incident angles within the PAR range (i.e., light wavelengths between 400 and 700 nm). The error range of HT measurement is + / - 1 point.

[0162] HS is a fractional value that compares the bidirectional transmission distribution function produced by a collimated incident beam at 0° with that of a Lambertian scatterer (the scattering profile of light scattered with constant radiance). The error range of the HS measurement is + / - 5 points.

[0163] Scratch / hardness test

[0164] The hardness and abrasion / scratch resistance of the coating are tested using a DIN 55656 hardness tester equipped with an SP0014 tungsten carbide needle with a diameter of 1.0 mm. The measurement involves moving the tester perpendicular to the surface at a constant speed and constant load, followed by visual inspection of scratch marks. The applied load is increased until the coating's fracture point is reached; this value is used as the test result.

[0165] Soaking in water

[0166] To simulate the effects of prolonged exposure to water, the samples were fully immersed in cold water for 18 hours. Next, their stability was tested by manually applying varying pressures to the sample surface using fingers. Starting with slight pressure, the pressure was gradually increased if the sample withstood the test. Based on the results, the qualitative test was classified into an eight-level system.

[0167]

[0168] Anti-separation

[0169] The coating's resistance to peeling from the substrate is tested according to the cross-cut test of standard ISO 2409. Here, a right-angle lattice pattern is cut through the coating, penetrating to the substrate. According to ISO 2409, the results are expressed using a six-step classification, where 0 corresponds to no peeling and 5 corresponds to high peeling.

[0170] Scrub resistance / scratch resistance test

[0171] The scrub resistance / scratch resistance of the samples was characterized using a system simulating equipment commonly used for cleaning greenhouse roofs. Here, the samples were placed at a 30° angle and scrubbed at 200 rpm. The brush material used was nylon, and an application of 5–7 g / cm² was applied between the brush and the coating. 2 The pressure.

[0172] The scrub / scratch resistance of samples was investigated by performing different cleaning cycles and monitoring the evolution of optical properties as the cycles progressed. A cleaning cycle was considered to be a double pass of the brush, once forward and once backward.

[0173] Accelerated weathering test

[0174] According to ISO 16474-3:2013, the QUV accelerated weathering tester is used to simulate outdoor weathering, thereby simulating damage that may occur to the coating due to prolonged exposure to outdoor conditions caused by sunlight, rain, and dew. The coating is thus exposed to cycles of fluorescent UV light, heat, and water, which allows for the study of the long-term stability of the sample. Although there is no standard equivalence between the number of hours the sample is exposed to this accelerated weathering test and the equivalent time under actual conditions, different companies have developed conversion methods based on the weathering conditions of specific regions. The result used here for reference is that proposed by Asahi Glass Co., where 1000 hours is considered approximately equivalent to 1 year.

[0175] Dry thickness

[0176] The thickness of the dry coating deposited on the transparent panel was measured using a DeFelsko PosiTector 200 ultrasonic coating thickness gauge according to the instrument's instruction manual v2.0. A coupling gel was deposited on the instrument tip. Next, the probe emitted a high-frequency acoustic pulse, which penetrated the coating and reflected from surfaces of varying densities. The thickness was then calculated by considering the time required for the ultrasonic signal to travel from the probe through the coating to the substrate and back.

[0177] roughness

[0178] The roughness of the coating was characterized using a stylus profilometer. This instrument generates a 1D surface profile by moving a 2 µm diamond probe across the sample surface while applying a small force to maintain contact with the surface. As a result of this measurement, a vertical displacement signal that can be interpreted as the surface profile was obtained. The surface roughness was characterized here by Rq (root mean square roughness) as defined in ISO 4287. The standard deviation of the Rq parameter is 0.2 µm.

[0179] Infrared measurement

[0180] Near-infrared (NIR) transmission data were generated using Fourier transform infrared (FT-IR) spectroscopy. A Bruker VERTEX 80V vacuum FT-IR spectrometer equipped with a tungsten-halogen source, a DLaTGS detector, and a KBr beam splitter was used to cover the near-infrared and part of the mid-infrared range of the electromagnetic spectrum. The reductions mentioned were estimated as a relative proportion of the integrated transmission spectrum.

[0181] result

[0182] Examples 1-3: Volumetric light scattering agents and light quality

[0183] Weigh 146.25 g of dispersant (NeoCryl BT-24, anionic acrylic copolymer emulsion) and 146.25 g of purified water into a plastic container. Stir the container using a high-speed laboratory disperser while simultaneously adding 7.5 g of a 25% ammonia solution dropwise to neutralize the solution. This first solution is referred to as the dispersant solution.

[0184] In a plastic container, 29.327 g of the above dispersant solution, 1.222 g of wetting agent (Surfynol 104E, ethynylene glycol in ethylene glycol), 1.222 g of defoamer (FoamStar SI2292, modified polydimethylsiloxane), and 12.228 g of volumetric light scattering particles (ThermoFisher, 10 µm silica particles) were weighed, stirred, and mixed to obtain a so-called paste solution. The solid content of this paste solution was 44%.

[0185] Mix and stir 9.750 g of paste solution and 30.958 g of acrylic adhesive (Neocryl XK-99, anionic acrylic emulsion). Then, add 0.0645 g of HASE thickener (Acrysol TT935, anionic hydrophobic modified alkali-swellable emulsion) and 0.172 g of HEUR thickener (Rheobyk H 3300 VF, a hydrophobic modified ethylene oxide polyurethane solution) to the solution and stir until completely homogenized.

[0186] Next, 0.335 g of adhesion promoter (Silquest A 1781, γ-glycidoxypropyltrimethoxysilane) was added to the solution and stirred. Finally, 1.720 g of multifunctional polymeric aziridine crosslinking agent (NeoAdd PAX-523, multifunctional polymeric aziridine) was added, stirred and mixed to obtain the coating solution.

[0187] The coating liquid was applied to the surface of a low-iron extra-white float glass plate (10 x 10 cm, 4 mm thick) that had been pre-washed with soap and water and then with isopropanol. The sample was then air-dried overnight. This yielded a glass piece with a coated film according to Example 1.

[0188] Following the same procedure used in Example 1, glass plates with coated films according to Examples 2 and 3 were obtained by varying the ratio of silica particles to acrylic binder (as shown in Table 1). The hemispherical transmittance, horticultural scattering, and root mean square roughness (Rq) of the resulting coated panels were measured.

[0189]

[0190] Table 1. Comparison of the effects of different amounts of volumetric light scattering particles. Wt.% is calculated based on the total weight of the coating.

[0191] As shown in Table 1, the horticultural scattering rate of the coated panel increases sharply with increasing silica particle content, while the hemispherical transmittance decreases only slightly. Furthermore, the roughness of the coated panel increases only slightly. Therefore, coated panels with different horticultural scattering rates can be produced by selecting an appropriate amount of volumetric light-scattering particles without significantly affecting the hemispherical transmittance or roughness of the coated panel.

[0192] Examples 4-6: Coating Thickness and Gloss Quality

[0193] Glass plates with coated films according to Examples 4 to 6 were obtained using the same procedure as in Example 1, but the coating solution was diluted with 5% water as a solvent. The diluted coating solutions were applied to the glass plates at different thicknesses, as shown in Table 2.

[0194]

[0195] Table 2. Comparison of the effects of coatings with different thicknesses.

[0196] As shown in Table 2, the horticultural scattering rate of the coated panel increases sharply with increasing coating thickness, while the hemispherical transmittance decreases only slightly. Therefore, coated panels with different horticultural scattering rates can be produced by selecting an appropriate coating thickness without significantly affecting the hemispherical transmittance of the coated panel.

[0197] Examples 7-11: Durability

[0198] In a plastic container, weigh 24.92 g of dispersant (NeoCryl BT-24, anionic acrylic copolymer emulsion) and 0.05 g of HEUR thickener (Rheobyk H 3300 VF, a hydrophobically modified ethylene oxide polyurethane solution) and stir using a high-speed laboratory disperser. Next, add 1.08 g of multifunctional polymeric aziridine crosslinking agent (NeoAdd PAX-523, multifunctional polymeric aziridine) and mix, increasing the mixing speed until a good vortex is obtained. Then, add 0.81 g of defoamer (FoamStar SI2292, modified polydimethylsiloxane) to the solution and continue stirring until homogenized. Finally, add 0.135 g of surface light scattering agent (Ceraflour 927 N, modified HD polyethylene wax) while stirring to obtain a uniform and homogeneous solution. This coating solution is referred to as the overcoat solution.

[0199] The glass plate with a coated film according to Example 7 is the result of applying two different layers to the surface of a float glass plate. The first base layer corresponds to the coating of Example 1, having the same composition and deposition technique. Once the first layer has cured, a second layer corresponding to a topcoat solution is applied by scraping.

[0200] The glass plate with the coating film according to Example 8 was prepared according to the same procedure as in Example 7, but the amount of surface light scattering agent added to the topcoat formulation was increased as shown in Table 3.

[0201] Comparative Example 9 is a commercially available seasonal diffuse coating (from ReduSystems' ReduFuse). A coating solution diluted 1:3 was prepared in a plastic container according to the manufacturer's instructions. The solution was then applied to a glass substrate as described in Example 1 to obtain a glass plate with the coating film.

[0202] For Example 10, 34.136 g of acrylic adhesive (Neocryl XK-99, anionic acrylic emulsion) and 0.531 g of polyethylene wax (BYK CeraFlour 927N) were mixed and stirred in a plastic container. Then, 0.213 g of wetting agent (Surfynol 104E, ethynyl glycol in ethylene glycol) was added to the mixture and mixed until homogeneous. Next, 0.128 g of adhesion promoter (Silquest A 1781, γ-glycidoxypropyltrimethoxysilane) was added to the solution and stirred. 0.213 g of defoamer (Afcona 2590E) was added to the mixture, and upon reaching homogeneity, 0.901 g of multifunctional polyaziridine crosslinking agent (NeoAdd PAX-523, multifunctional polyaziridine) was added and mixed. Finally, 11.595 g of deionized water was added and stirred to obtain a sprayable coating. The resulting coating was sprayed onto a glass plate in a single layer to obtain a coated glass plate as shown in Example 10 of Table 3.

[0203] For Example 11, the paste solution was prepared as described in Example 1. In a separate plastic container, 15.927 g of polyurethane adhesive (NeoRez R-2190) was mixed with 0.950 g of cosolvent (Dowanol DPnB, a mixture of dipropylene glycol monobutyl ether and butoxydipropanol). 2.245 g of water was added to the mixture and mixed until homogeneous. Then, 4.295 g of the previously prepared paste solution was added to the adhesive-cosolvent-aqueous solution. Next, 0.0313 g of HASE thickener (Acrysol TT935, anionic hydrophobic modified alkali-swellable emulsion) and 0.085 g of HEUR thickener (Rheobyk H 3300 VF, a solution of hydrophobic modified ethylene oxide polyurethane) were added to the solution. The resulting solution was stirred until completely homogenized. Next, 0.176 g of adhesion promoter (Silquest A 1781, γ-glycidoxypropyltrimethoxysilane) was added to the solution and stirred. Finally, 1.020 g of multifunctional polymeric aziridine crosslinking agent (NeoAdd PAX-523 multifunctional polymeric aziridine) was added, stirred, and mixed to obtain a coating solution. The obtained coating solution was applied as a monolayer to a glass plate to obtain a coated glass plate as described in Example 11 of Table 3.

[0204]

[0205] Table 3. Durability Comparison. Wt.% is calculated based on the total weight of the coating.

[0206] As shown in Table 3, the coated panel of Comparative Example 9 failed the water immersion test or accelerated weathering test. Furthermore, in the scratch test, at 2 N / mm...2 The coating reached its fracture point and essentially disappeared after five brushing cycles. Therefore, no further brushing cycles were performed. Therefore, the coating according to Comparative Example 9 cannot be considered a durable coating.

[0207] In contrast, the coated panel according to Example 1 (where the coating according to the invention is applied in a single layer) passed the water immersion and accelerated weathering tests. The coating fractured at a later point of 4 N / mm in the scratch test. 2 The coating achieves its desired consistency and can withstand at least 20 brushing cycles. Therefore, the coating on the panel according to Example 1 is a durable coating.

[0208] Compared to Example 1, the coatings of the coated panels according to Examples 7 and 8 include an additional topcoat containing wax as a surface light scattering agent. This additional topcoat increases the horticultural scattering of the coated panel, while the hemispherical transmittance remains unaffected. Furthermore, the hardness of the coated panels according to Examples 7 and 8 is increased, as the coating only fractures at 15 N / mm. The coated panel according to Example 7 can withstand at least 60 brushing cycles, and the coated panel according to Example 8 can withstand at least 90 brushing cycles, without significant changes in the hemispherical transmittance or horticultural scattering of the coated panels. Therefore, the coatings of the coated panels according to Examples 7 and 8 are even more durable than the coating of the coated panel according to Example 1.

[0209] Furthermore, the coating according to Example 10 (which comprises a layer containing wax as a surface light scattering agent but no volumetric light scattering agent) and the coating according to Example 11 (which comprises cross-linked polyurethane as a binder and silica particles as a volumetric light scattering agent) withstood water immersion tests and showed good results in scratch tests. After 90 brushing cycles, the coatings still exhibited very good properties in terms of hemispherical transmittance and horticultural scattering. Therefore, the coatings on the panels according to Examples 10 and 11 are also durable coatings with good transmittance and horticultural scattering properties.

[0210] Specifically, a combination of volumetric agents with polyurethane adhesives, or a combination of surface scattering agents (optionally together with volumetric scattering agents) with acrylic adhesives, provides a coating with an estimated durability of at least 5 years.

[0211] Example 12: Effect of coating on NIR transmittance

[0212] Near-infrared light (NIR; electromagnetic radiation with wavelengths between 0.7 and 3 µm) and mid-infrared light (electromagnetic radiation with wavelengths between 3 and 50 µm) are not consumed by plants for photosynthesis, but are largely responsible for the increase in temperature inside greenhouses.

[0213] like Figure 3As shown, compared to uncoated ordinary float glass (FG) and low-iron FG, the coated panels according to Examples 1 and 8 exhibited a reduction in transmittance over a wavelength range of 1 to 5 µm. This reduction is quantified as the relative proportion of the integrated transmittance spectrum of the coated transparent panel to that of the uncoated ordinary FG or low-iron FG.

[0214] The coated panel according to Example 1 reduced the transmittance by 13% in the wavelength range of 1 to 5 µm compared to low-iron FG, and by 7% compared to ordinary FG.

[0215] The coated panel according to Example 8 reduced the transmittance by 18% in the 1 to 5 µm wavelength range compared to low-iron FG and by 12% compared to ordinary FG.

[0216] Therefore, the coatings on the coated panels according to Examples 1 and 8 are more effective than those on uncoated panels in reducing transmitted NIR and MIR light.

Claims

1. A method for coating a transparent panel (3), comprising the following steps: - Applying a coating composition to a transparent panel, and - Curing the coating composition to form a cured coating. The cured coating comprises: - Crosslinking adhesive (4), in an amount of 30-95 wt.% based on the total weight of the coating, wherein the crosslinking adhesive comprises a polymeric adhesive. - Adhesion promoter, calculated based on the total weight of the coating, in an amount of 0.05-5 wt.%, and - At least one light scattering agent (1, 2) having a volume equal to the average surface diameter D 3,2 The thickness is 0.5-20 µm, and the amount is 0.2-40 wt.% based on the total weight of the coating. The at least one light scattering agent (1, 2) is selected from: - A reagent (1) that produces volumetric light scattering, having a refractive index (measured at 589 nm) at least 0.01 higher than the refractive index of the crosslinking adhesive; and - Reagents that produce surface light scattering (2), The reagent (1) that generates volumetric light scattering comprises inorganic oxide particles, and The reagent (2) that generates surface light scattering comprises wax particles. And if the at least one light scattering agent (1, 2) is a reagent (2) that generates surface light scattering, then the cured coating (5) has a root mean square surface roughness (Rq) of 0.1-1 µm.

2. The method according to claim 1, wherein the inorganic oxide particles are selected from SiO2, Mg3Si4O 10 (OH)2, ZnO, ZrO2, Al2O3, TiO2, SrO, SnO2, CaO, BaO, CuO, Fe2O3, MnO, MgO, NiO, and / or the wax particles are selected from carnauba wax or rice bran wax, beeswax, paraffin wax, amide or polyethylene polymer, polypropylene polymer or mixtures thereof.

3. The method according to claim 2, wherein the inorganic oxide particles are selected from SnO2, TiO2, ZnO, SiO2, Fe2O3 and one or more mixtures thereof.

4. The method according to any one of the preceding claims, wherein the volume of the at least one light scattering agent (1, 2) is related to the average surface diameter D. 3,2 The value is 0.5 to 20 µm, more preferably 1 to 16 µm, even more preferably 3 to 14 µm, and most preferably 5 to 10 µm.

5. The method according to any one of the preceding claims, wherein the adhesive is anionic acrylic suspension, acrylic copolymer, multiphase acrylic emulsion, self-crosslinking acrylic polymer, polyurethane composite dispersion, fluoropolymer, alkyd resin and silicone adhesive or a mixture thereof.

6. The method according to any one of the preceding claims, wherein the crosslinking adhesive (4) comprises a crosslinking agent selected from multifunctional polyaziridine, isocyanate, polycarbodiimide and mixtures thereof.

7. The method according to any one of the preceding claims, wherein the adhesion promoter is selected from g-aminopropyltriethoxysilane, g-aminopropyltrimethoxysilane, g-(methylamino)propyltrimethoxysilane, g-aminopropylmethyldiethoxysilane, γ-(2-aminoethyl-3-aminopropyl)triethoxysilane, γ-(2-aminoethyl-3-aminopropyl)methyldimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropyltrimethoxysilane, and polyfunctional glycidoxypropyltrimethoxysilane, chlorinated polyolefins, non-chlorinated polyolefins, and mixtures thereof.

8. The method according to any one of the preceding claims, wherein the coating (5) comprises one or more selected from the group consisting of: dispersants, wetting agents or leveling agents, defoamers, rheology modifiers and light stabilizers.

9. The method according to any one of the preceding claims, wherein the coating composition is a first coating composition, and the step of applying the coating composition to the transparent panel (3) comprises: - Apply the first coating composition to the transparent panel (3), - Optionally, at least partially cure the first coating composition. - Apply a second coating composition on top of the first coating composition.

10. A transparent panel (3) having a cured coating (5), wherein the cured coating (5) comprises: - Crosslinking adhesive (4), in an amount of 30-95 wt.% based on the total weight of the coating, wherein the crosslinking adhesive comprises a polymeric adhesive. - Adhesion promoter, calculated based on the total weight of the coating, in an amount of 0.05-5 wt.%, and - At least one light scattering agent (1, 2) having a volume equal to the average surface diameter D 32 The thickness is 0.5-20 µm, and the amount is 0.2-40 wt.% based on the total weight of the coating (5). The at least one light scattering agent (1, 2) is selected from: - A reagent (1) that produces volumetric light scattering has a refractive index (measured at 589 nm) that is at least 0.01 higher than the refractive index of the crosslinking adhesive (4) surrounding the reagent (1); and - Reagents that produce surface light scattering (2), The reagent (1) that generates volumetric light scattering comprises inorganic oxide particles, and The reagent (2) that generates surface light scattering comprises wax particles. And if the at least one light scattering agent (1, 2) is a reagent (2) that generates surface light scattering, then the cured coating (5) has a root mean square surface roughness (Rq) of 0.1-1 µm.

11. A structure comprising a transparent panel (3) having a cured coating (5) as claimed in claim 10, wherein the structure is preferably a greenhouse.

12. A coating composition for coating a transparent panel (3), the coating composition comprising: - An adhesive, in an amount of 30-95 wt.% based on the total weight of the coating, wherein the adhesive comprises a polymeric adhesive. - Adhesion promoter, calculated based on the total weight of the coating, in an amount of 0.05-5 wt.%, and - At least one light scattering agent (1, 2) having a volume equal to the average surface diameter D 32 The thickness is 0.5-20 µm, and the amount is 0.2-40 wt.% based on the total weight of the coating. The at least one light scattering agent (1, 2) is selected from: - A reagent (1) that produces volumetric light scattering, having a refractive index (measured at 589 nm) at least 0.01 higher than the refractive index of the adhesive surrounding the cured reagent; and - A reagent (2) that generates surface light scattering, resulting in a root mean square surface roughness (Rq) of 0.1-1 µm after curing. The reagent (1) that generates volumetric light scattering comprises inorganic oxide particles, and The reagent (2) that generates surface light scattering contains wax particles.

13. The coating composition according to claim 12, wherein the coating composition contains 1-10 wt.% of a crosslinking agent based on the total weight of the coating (5).

14. The coating composition of claim 13, wherein the coating composition comprises one or more selected from the group consisting of solvents, cosolvents, pH adjusters, coalescing agents, and combinations thereof.

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