RED GREENHOUSE FILM THAT SIMULATES PHOTOSYNTHETIC RADIATION INSIDE THE GREENHOUSE

Abstract

The present invention aims to provide a novel composition for manufacturing greenhouse covers using the blown film extrusion process. This composition gives the film a reddish hue, while its components allow the radiant energy within the greenhouse to resemble that which optimizes photosynthetically active radiation. The composition of the present invention is intended for the plastics processing industry, specifically for the extrusion of greenhouse films.

Description

From the beginning of the use of plastics for agricultural crops, it was observed that there is a relationship between the assimilation of solar energy by plants for the production of leaves, stems, flowers, and fruits through the production of chlorophyll, which, together with a wide series of phenomena that occur in the plant due to nutrients, the environment in which they are found, and the water supplied; there is an influence in the use of plastics that can interfere with or modify the amount and type of radiation received inside greenhouses. In the prior art, particularly that carried out by the team to which the authors of the present invention belong, formulations of additives have been reported that achieve a synergistic effect for protecting against the degradation of the polyethylenes used to manufacture the films that will be used as greenhouse covers (Angulo Sánchez JL Patent MX300450), as well as the use of fillers that promote light diffusion within the greenhouse, and the control of the interior temperature (González de los Santos, EA Patent MX311701). Therefore, the present invention represents an effort to further the application of the technique and improve previously developed technologies. Regarding the use of films as greenhouse covers, there are reported precedents of the use of various materials for specific purposes of managing radiation ranges, which are mentioned below. The use of red polymethyl methacrylate films in conjunction with metal oxide nanoparticles (El-Bashir. Renewable Energy 2016, 85, 928-938), such as silicon oxide, zinc oxide, and titanium dioxide, has been reported, with the aim of making the film function as a solar luminescent concentrator. The focus of films with this composition is to achieve high efficiency in the infrared range; they are even proposed for use as covers for solar dryers and evaporators for desalination. Regarding modifications to plastic materials for solar concentrators, progress has been reported with several alternatives (Lamnatou, Chr. Renewable & Sustainable Energy Reviews 2013, 27, 175-190), primarily by modifying the ratios in the red-to-far-red, red-to-blue, and blue-to-far-red radiation ranges. These films are used as covers for various applications, such as solar concentrator covers, desalination plants, and covers to increase light diffusion. The same article notes that for their use as greenhouse covers, certain characteristics and critical light factors must be considered to ensure that the film and the resulting radiation are optimally utilized by the plants. Regarding the effect of using red films as greenhouse coverings on crops, it has been reported that in aromatic herb crops, plant dehydration is reduced by manipulating the spectrum obtained with the use of colored films (Huckstadt, AB European Journal of Horticultural Science 2013, 78 5, 303-208), especially concerning the ratio of the red to the far-red range. However, this manipulation reduces photosynthetically active radiation, which can lead to decreased crop development and yield. Ambient sunlight has been reported to contain information for the regulation of photomorphogenetic processes carried out by plants (Kotzabasis, K. Zeitschrift für Naturforschung, C: Journal of Biosciences 2008, 63 113-123), therefore a high transmission of photosynthetically active radiation is required, combined with increases in the energy ratio factors in the red to far-red, blue to near-ultraviolet and blue to far-red ranges, energies that are known to have an effect on plant responses to biochemical, physiological and morphological processes In the case of the composition of the formulation with which the red greenhouse film is obtained that resembles the photosynthetically active radiation inside the greenhouse, the present invention is considered to be novel since a spectrum is obtained that adjusts to the spectrum that optimizes the photosynthetically active radiation in most of the range, achieving an increase in radiation in the range of the blue and red colors simultaneously. BRIEF DESCRIPTION OF THE FIGURES Figure 1. Optimal photosynthetically active radiation. Shown is the curve describing energy utilization according to wavelength (1) Taken from: Fondriest Environmental, Inc. “Solar Radiation and Photosynthetically Active Radiation.” Fundamentals of Environmental Measurements. 21 Mar. 2014. Web. <https: / / www.fondr¡est.com / env¡ronmentalmeasurements / parameters / weather / solarradiation / >. b IO / RI Π7 / E / YILI > ω Ν C .J <£ C £ > > £ Figure 2. Measurement of radiation transmission through the films. Shown are: the characteristic spectrum of the lamp simulating solar radiation (1); the spectrum obtained with the white film from Example 1 between the lamp and the sensor (2); and the spectrum obtained with the red film from Example 2 between the lamp and the sensor (3). Figure 3. Measurement of the color spectrum of the films. Shown are: the color spectrum obtained with the white film from Example 1 (1); the color spectrum obtained with the red film from Example 2 (2); the color spectrum obtained with the red film from Example 3 (3); and the color spectrum obtained with the red film from Example 4 (4). DETAILED DESCRIPTION OF THE INVENTION The greenhouse film is obtained by using the blown film extrusion process, using a composition of polyethylene mixtures that may include ethylene vinyl acetate (EVA) copolymers, additive concentrates, filler concentrates, and red pigment concentrates. Polyethylene blends consist of: low-density polyethylene in proportions of between 10 and 40% by weight, preferably between 20 and 30% by weight; linear low-density polyethylene in proportions of between 45 and 65% by weight, preferably between 55 and 60% by weight; and EVA in proportions of between 0 and 20%, preferably between 5 and 10%. The concentrates used consist of: ultraviolet light protection additives at concentrations of 10 to 17% by weight, preferably between 12 and 14% by weight; antioxidant additives at concentrations of 1 to 3% by weight, preferably between 1.5 and 2% by weight; inorganic fillers to promote light scattering into the greenhouse at concentrations of 20 to 25% by weight, preferably 22 to 24% by weight; red pigments at concentrations of 30 to 40% by weight, preferably 34 to 36% by weight; and blue pigments at concentrations of 30 to 40% by weight, preferably 34 to 36% by weight. The film is manufactured using the film extrusion process, preferably a single-layer blown film extrusion line or equipment, although it can also be co-extruded to give functionality to one of the layers of the film structure. Polyethylene formulations are prepared, EVA if present, filler concentrates, additive concentrates, and pigment concentrates. The extruder temperature profile is established in an ascending manner according to the following series: Zone 1 at 160 - 170SC; Zone 2 at 170 - 180eC; Zone 3 at 190 - 200SC; Zone 4 at 200 - 205QC; Adapter at 200 - 205QC; Die at 200 - 205eC. The formulation is fed into the extruder feed hopper, the extruder is started and the film bubble is lifted, then stabilized at a suitable blowing ratio to the die size and a drawing speed that allows cooling and bubble stability. The speed is then adjusted to obtain the required film thickness in the thickness range from 50 to 208 microns, preferably in the thickness range of 150 to 208 microns. The film is cut from one or both edges, as required, and optionally identified with a seal or label bearing the name, grade, and trademark. Finally, it is wound onto a reel so that, once the desired reel size is reached, it can be removed from the reel for sale and application as greenhouse coverings. EXAMPLE 1 In this example, a white film was obtained that would be the reference for the performance of a greenhouse film without red color, through the blown film extrusion process whose temperature profile of the one-inch diameter laboratory extruder was established according to the following sign: Zone 1 at 160eC; Zone 2 at 180eC; Zone 3 at 200SC; Adapter at 205QC; Die at 205QC. For the preparation of the white film formulation, Dowlex 2045 linear low-density polyethylene, sold by Dow, and LDPE 1321 low-density polyethylene, also sold by Dow, were used. A concentrate of ultraviolet light-protective additives with a content of 14% by weight, antioxidants with a content of 1% by weight, and inorganic light-scattering fillers with a content of 14% by weight were used, in accordance with the state of the art (Angle fe? 7b I n / RI Π7 / E / YILI). Sánchez JL Patent MX300450 and González de los Santos, EA Patent MX311701). The formulation components were mixed in a weight ratio of: 60% linear low-density polyethylene, 28% low-density polyethylene, 5% additive concentrate, and 7% mineral filler concentrate with dispersant function. The formulation was fed into the extruder and processed to obtain a film 180 microns thick. The film was characterized in terms of the light transmission of a xenon lamp and the spectrum was obtained using a radiometer. The comparison of the white film with respect to the light emitted by the lamp without film is shown in Figure 2 (2). According to this spectrum and by similarity with the shape of the spectrum shown in Figure 1, it can be inferred that the energy that the white film manages to promote is not similar across the entire spectrum to that which optimizes photosynthetically active radiation for use by crops grown under a greenhouse cover made with white film with these characteristics. EXAMPLE 2 For the preparation of the red film formulation in this example, Dowlex 2045 linear low-density polyethylene (LDPE) and Dow LDPE 1321 were used. A concentrate of ultraviolet light-protective additives with a content of 14% by weight, antioxidants (toJ IO / AI n7 / E / YIAI) with a content of 1% by weight, and inorganic light-scattering fillers with a content of 14% by weight were used, as reported in the prior art (Angulo Sánchez JL Patent MX300450 and González de los Santos Patent MX311701). A mineral filler concentrate with a dispersing function, trade name Iriodin 235, sold by Merck, was used at a content of 25% by weight. A red pigment concentrate, trade name Glo Prill Rocket Red GPL-13, sold by Tecma Comercializadora, SA de CV, was also used. The formulation components were mixed in a weight ratio of: 60% linear low-density polyethylene, 29% low-density polyethylene, 5% additive concentrate, 5% mineral filler concentrate with dispersant function, and 1% red pigment concentrate. The formulation was fed into the extruder and processed to obtain a film 180 microns thick. The film was characterized in terms of light transmission from a xenon lamp and the spectrum was obtained using a radiometer. The comparison of the white film from Example 1 and the red film from this Example with respect to the light emitted by the lamp without film is shown in Figure 2. According to this spectrum and by similarity with the shape of the spectrum shown in Figure 1, it can be inferred that the energy promoted by the red film is similar to that which optimizes photosynthetically active radiation for use by crops grown under a greenhouse cover made with red film with these characteristics. b IO / RI Ο7 / Ε / ΥΙΛΙ > ω ίο Ν C .J <£ C £ > > £ EXAMPLE 3 For the preparation of the red film formulation in this example, Dowlex 2045 linear low-density polyethylene (LDPE) and Dow LDPE 1321 were used. A concentrate of ultraviolet light-protective additives with a content of 14% by weight, antioxidants with a content of 1% by weight, and inorganic light-scattering fillers with a content of 14% by weight were used, in accordance with the prior art (Angulo Sánchez JL Patent MX300450 and González de los Santos Patent MX311701). A mineral filler concentrate with a dispersing function, trade name Iriodin 212, sold by Merk, was used at a content of 25% by weight. A red pigment concentrate, trade name Glo Prill Rocket Red GPL-13, sold by Tecma Comercializadora, SA de CV, was also used. The formulation components were mixed in a weight ratio of: 60% linear low-density polyethylene, 29% low-density polyethylene, 5% additive concentrate, 5% mineral filler concentrate with dispersant function which has the particularity that pearlescence is seen in the red range of the spectrum, and 1% red pigment concentrate. The formulation was fed into the extruder and processed to obtain a film 180 microns thick. The film was characterized in terms of color measurement with a spectrophotometer. The comparison of the white film of Example 1 Figure 2(2) and the red film of this Example in Figure 2(3) shows that there is a similarity in the shape of the spectra and in the radiation values; it can be inferred that the energy that the red film manages to promote is similar between both. EXAMPLE 4 For the preparation of the red film formulation in this example, Dowlex 2045 linear low-density polyethylene (LDPE) and Dow LDPE 1321 were used. A concentrate of ultraviolet light-protective additives with a content of 14% by weight, antioxidants with a content of 1% by weight, and inorganic light-scattering fillers with a content of 14% by weight were used, in accordance with the prior art (Angulo Sánchez JL Patent MX300450 and González de los Santos Patent MX311701). A mineral filler concentrate with a dispersing function, trade name Iriodin 7215, sold by Merk, was used at a content of 25% by weight. A red pigment concentrate, trade name Glo Prill Rocket Red GPL-13, sold by Tecma Comercializadora, SA de CV, was also used. The formulation components were mixed in a weight ratio of: 60% linear low-density polyethylene, 29% low-density polyethylene, 5% additive concentrate, 5% mineral filler concentrate with dispersant function which has the particularity that pearlescence is observed, and 1% red pigment concentrate. The formulation was fed into the extruder and processed to obtain a film 180 microns thick. et 7b I n / RI Π7 / E / YILI Ln / A ίΠΖ / Ε / YΙΛΙ The film was characterized in terms of color measurement with a spectrophotometer. The comparison of the white film of Example 1 Figure 2(2) and the red film of this Example in Figure 2(4) shows that there is a similarity in the shape of the spectra and in the radiation values; it can be inferred that the energy that the red film manages to promote is similar between both.

Claims

1. The manufacture of a red greenhouse cover, according to the film extrusion process, whose composition is characterized in that it comprises: a) mixtures of polyethylenes that may include ethylene vinyl acetate (EVA) copolymers, additive concentrates, filler concentrates and red pigment concentrates in proportions that allow a red color to be observed with the naked eye, while promoting the passage of solar radiation in such a way that inside the greenhouse there is a spectrum that resembles the optimization of photosynthetically active radiation by observing the speed of photosynthesis with respect to the wavelength; b) a uniform thickness in the thickness range from 50 to 208 microns, preferably in the thickness range from 150 to 208 microns.

2. A composition characterized in that the red pigment concentrate is made of fluorescent red pigment, in order to have the claimed performance in accordance with claim 1. fe? 7b I n / RI Π7 / E / YILI 3. A composition characterized in that the filler concentrate is made up of a pigment that generates pearlescence in the red color range, in order to have the claimed performance in accordance with claim 1.

4. A composition characterized in that the red pigment concentrate is made up of a mixture of red pigment with a small portion of blue pigment, preferably in a ratio of nine parts red pigment to one part blue pigment, in order to have the claimed performance in accordance with claim 1.

5. A composition characterized in that the filler concentrate is made up of a pigment that generates pearlescence, in order to have the claimed performance in accordance with claim 1.

6. A composition characterized in that the polyethylene mixtures used according to claim 1 are made up of: low-density polyethylene in proportions of between 10 and 40% by weight, preferably between 20 and 30% by weight; linear low-density polyethylene in proportions of between 45 and 65% by weight, preferably between 55 and 60% by weight; and EVA in proportions of between 0 and 20%, preferably between 5 and 10%.

7. A composition characterized in that the ultraviolet light protective additive concentrates used according to claim 1 are constituted of: ultraviolet light protective additives in concentrations of 10 to 17% by weight, preferably between 12 and 14% by weight.

8. A composition characterized in that the antioxidant additive concentrates used in accordance with claim 1 are constituted by ultraviolet light additives in concentrations of 1 to 3% by weight, preferably between 1.5 and 2% by weight.

9. A composition characterized in that the concentrates of inorganic fillers for promoting light scattering into the greenhouse used according to claim 1 are constituted by inorganic fillers in concentrations of 20 to 25% by weight, preferably 22 to 24% by weight.

10. A composition characterized in that the red pigment concentrates are present in concentrations of 30 to 40% by weight, preferably 34 to 36% by weight, and the blue pigments are present in concentrations of 30 to 40% by weight, preferably 34 to 36% by weight.

11. The comparison of the spectrum obtained by the greenhouse cover with the spectrum of the optimization of photosynthetically active radiation by the rate of photosynthesis with respect to wavelength, in accordance with claim 1, can be carried out by field measurements with radiometers inside and outside the greenhouse and their comparison, preferably carrying out the measurements with a standard xenon lamp that simulates solar radiation in the laboratory and the comparison with the spectrum obtained by the red film, as shown in Figure 2.