MXPA99002540A - Improved plastic film formulation for agricultural use that effectives temperat control - Google Patents

Abstract

The present invention is related to the development of an improved formulation for the production of a plastic film with thermo-controlled characteristics for use as a cover for protected systems (greenhouse, tunnels, microtunnels or soil mulching of employees in agriculture). The formulation of said film is based on mixtures of polyethylene, and / or ethylene-vinyl acetate (EVA) copolymers and / or mixture thereof, with an ultraviolet light absorber and with a pigment or thermocontroller additive. Formulations I, II, III, and IV can contain any of the following materials and additives a) Polyethylenes can be low density, medium density or high density polyethylenes (LDPE, MDPE or HDPE) and / or ethylene with alpha copolymers -olefins (LLDPE). The ethylene-vinyl acetate copolymers can be copolymers with different vinyl acetate contents. b) The ultraviolet light absorber can be of the hindered amines type or organic complexes of nickel or hydroxybenzophenones and / or mixtures thereof. c) The pigment or thermocontroller additive can be photochromic or thermochromatic of organic type such as anilines, hydrazones, fulgida, thioindigo pigments, azo-aromatics, spiro compounds, anthrones, sindrones, naphthalenones, or incorganic metal oxides, mercury compounds, sulfides of zinc, copper compounds. d) Perlents such as guanine and hypoxanthine or inorganic pigments of the basic lead carbonate type, bismuth oxychloride, lead hydrogen arsenate, as well as mica coated with small layers of titanium dioxide c) Fusforecentes of the inorganic type are of two types mixtures of sulfides of zinc and cadmium activated with traces of copper, silver or magnesium, mixtures of zinc sulphides and cadmium activator by copper or calcium sulphides and strontium with bismuth and copper f) Metallizations of the type aluminum, iron, bronze, copper; these or some other metal such as zinc, with particle size between 10 and 85 microns preferably. g) Fluorescents in daylight such as derivatives of amino-phthalimides, phthalocyamines and others. In addition to the formulation of this film can be added antistatic, antioxidants, anti-drip, inorganic charges opaque to infrared, etc. The classes and concentrations of the above additives may be those typically used for polyolefin films for agricultural use.

Description

IMPROVED FORMULATION OF PLASTIC FILM FOR AGRICULTURAL USE THAT EFFECTIVES THE CONTROL OF THE TEMPERATURE DESCRIPTION: Plastics have been a part of our daily life for a long time, and since the mid 70's advances have followed a very great evolution, especially in agricultural applications, mainly in regions with climates not suitable for agriculture. Outdoor cultivation or regions that compete strongly in export markets. With the introduction of plastics in agriculture radically changed the most traditional cultural techniques of the crops, and continue to evolve, for the foregoing a bright future is glimpsed with new techniques based on different compositions of the polymers and additives used in the formulations1 . In addition, with the new systems for the transformation of plastics that companies are progressively introducing in their production, better quality materials will be achieved.

In plastics for agriculture such as protected systems (greenhouse, tunnels, microtuneles, soil mulching, etc.) has been working on aspects such as improvement in thermal, mechanical and optical properties. Recently, greater awareness has been taken of the importance of the optical properties of these materials, given that the quantity and quality of light directly affects the speed and quality of crop growth.

An example of the above is the patent registered on the synthesis of thermochromic and photochromatic additives (Mexican Patent No. 947449) 3 and the patent on the application of these color additives in films for protected systems (Mexican Patent No. 9600095), 4 publications where it is mentioned that the adequate incorporation of photochromic additives to the formulation of polyethylene films used as greenhouse coverings allows optimal use of solar radiation, increasing the photosynthetically active radiation (PAR) which promotes productivity in the vegetables without affecting the mechanical properties of the films, the assimilation activity of C02 in the lettuce plants was also significantly increased, as well as the percentages of yield in the harvest up to 42.74%.

The solar radiation is divided into a series of bands according to their wavelength. The area perceptible to our vision comprises between 360 nm and 780 nm, and includes all the colors of the rainbow, and our vision is more sensitive to some than to others, specifically our eyes are ten times more sensitive to green radiation than to the red or the blue. So then, plants can have their preference and respond more to one wavelength than to another. This concept is based on the research and development of thermo-control plastics, which modify the quantity and type of light that they transmit and reflect, producing a better control of the temperature inside the protected system, for example greenhouse 1 > 2.

The floriculture industry in our country is one of the most important in agricultural production, and requires more the use of advanced technologies such as protected systems (greenhouses, tunnels, microtuneles, soil mulching, etc.) to produce with quality for export. Within the protected systems, most of the greenhouses in Mexico have a flexible polyethylene film cover, with an approximate duration of 18 to 24 months.

A problem faced by producers who use greenhouses are the high temperatures within these in the summer months, so they use the practice of whitewashing films or shade mesh, with the finality of reducing the passage of solar radiation and thus lower the interior temperature of the greenhouse. However, this practice results in a reduction in the useful life of the films since the substances used for liming remove the additives from the film, negatively affecting their properties and accelerating their degradation8. This problem has been detected and depending on this problem an opportunity is displayed to develop a thermocontrol film that has the property of blocking the passage of a certain type of radiation when a temperature higher than 35 ° C is reached. Blocking can be by means of changes in the coloring of the film, thus allowing to reduce the amount of radiation transmitted and consequently the temperature will also be lowered. In this case the film has to return to its original characteristic to be within the established temperature limits, which will allow to always have a transparency that does not affect the normal development of the crop. It can also be through the ability of the film to absorb in one region of the visible spectrum and transmit in another or using additives and / or pigments that reflect or deflect the radiation that hits the film, preventing the passage of radiation from the film. short wavelength Based on the above, and depending on the needs of producers in Mexico and Latin American countries that produce under protected systems, it is important to have materials that respond more to their production expectations and help them improve the conditions of the interior of the enclosure that directly affects the performance and quality.

In particular, the present invention relates to the development of a formulation for the production of a thermo-controlled plastic film, which controls the temperature inside the greenhouse, in order to avoid high internal temperatures which cause severe damage to crops, without affecting the yield of the crops and the quality of it. This film can be used mainly as protected systems (greenhouse, tunnels, microtunnels, soil mulching, etc.), thus providing an alternative to help solve the problem of overheating of crops grown in protected systems.

This film for crops under protected systems is formulated based on mixtures of polyethylene, and / or ethylene-vinyl acetate copolymers (EVA) and / or mixture thereof, with an ultraviolet light absorber and with a pigment or thermocontroller additive, manufactured by the blown extrusion and / or flat extrusion process, as well as by the blown or flat coextrusion process.

The film may be composed of quaternary polyethylene mixtures, an ethylene-vinyl acetate copolymer and ultraviolet light absorbers (I) with a thermocontroller additive concentrate based on polyethylene (II) or ternary polyethylene blends, an ethylene copolymer - vinyl acetate and ultraviolet light absorbers (III) with a concentrate of thermocontroller additive based on polyethylene (II) or binary mixtures of polyethylene and ultraviolet light absorbers (IV) with a thermocontroller additive concentrate based on polyethylene (II) ).

EXAMPLES By way of non-limiting title, the following examples are described to illustrate the use of the patent.

Example No. 1 Comparative study of a commercial film and a thermocontroller film based on a metallized additive, for protected systems (greenhouse).

A general formulation for making a commercial film for protected systems (greenhouse) is prepared with the mixture of the following components: Ingredients Proportion (per *) Resin Low density polyethylene (LDPE) 80 Resin Linear low density polyethylene (LLDPE) 20 Ultraviolet stabilizer 0.5 * pcr = parts per hundred resin A formulation for manufacturing a heat shrink film for cover of protected systems (microtunnel) is prepared with the mixture of the following components: Ingredients Proportion (per) Resin Low density polyethylene (LDPE) 80 Resin Linear low density polyethylene (LLDPE) 20 Ultraviolet stabilizer 0.5 Metallized Pigment 3.0 The film made with the aforementioned metallized additive-based formulation led to a loss of radiation transmission with respect to the commercial film of more than 22% and a decrease in temperature heat inside the protected system (microtunnel) of up to more than 4 ° C. In addition to the commercial film, a total production of 6.7 ton / ha was obtained, while with this thermocontrolled film based on metallized additive, 9.2 ton / ha was obtained, which translates into an increase of more than 37% in productivity.

Example No 2 Comparative study of a commercial film and a thermocontroller film based on a pearlescent pigment additive for protected systems (greenhouse).

A formulation for manufacturing a heat shrink film for cover of protected systems (microtunnel) is prepared with the mixture of the following components: Ingredients Proportion (per) Resin Low density polyethylene (LDPE) 80 Resin Linear low density polyethylene (LLDPE) 20 Ultraviolet stabilizer 0.5 Pigment perlecent 3.0 In this case, the film made from pearlescent pigment, led to a loss of transmission of radiation with respect to the commercial film of more than 30% and a decrease in temperature heat inside the protected system (microtunnel) of up to more of 3 ° C. On the other hand, by comparing the productivity obtained using the film based on pearlescent pigment (6.4 ton / ha) and the commercial film (6.7 ton / ha) it can be seen that the pearlescent additive did not have a significant effect on crop productivity.

Formulations I, II, III and IV may contain any of the following materials and additives a) The polyethylenes may be of low density, medium density or high density or copolymers of l-butene, 1 -hexene or 1-ketene known as ( LLDPE). Ethylene-vinyl acetate copolymers may contain to 80% by weight of vinyl acetate. b) The ultraviolet light absorber can be of the hindered amine type, benzophenones, organic nickel complexes and / or mixture thereof. c) The pigment or thermocontroller additive can be photochromic or thermochromatic9, of the organic type such as indigo, hydrazones, fulgida, thioindigo pigments, azo-aromatic compounds, spiro compounds, anthrones, sindrones, naphthalenones; or inorganic such as metal oxides, mercury compounds, zinc sulphides, copper compounds d) Perlents such as guanine and hypoxanthine or inorganic pigments of the basic lead carbonate type, bismuth oxychloride, hydrogen lead arsenate, as well as mica coated with small layers of titanium dioxide e) Fosforecentes of the inorganic type are of two types mixtures of sulfides of zinc and cadmium activated with traces of copper, silver or magnesium, mixtures of n zinc sulphides and cadmium activator for copper or calcium sulphides and strontium with bismuth and copper f) Metallized pigments of the aluminum, iron, bronze, copper type, mixed of these or some other metal such as zinc, with particle size between 10 and 85 microns preferably g) Fluorescent pigments in daylight such as derivatives of aminonañalimidas, phthalocyamines and others.

The formulation of the film is based on a mixture of 100% by weight of (I) or (III) or (IV) with 0.01 to 30 parts per hundred resin (per) of (II). 1. In these formulations, (I) is composed of a low density polyethylene, a medium density polyethylene, a high density polyethylene and copolymers of ethylene with l-butene, 1-hexene or 1-octene having densities in the range of 0.915 to 0.970 , an index of fluidity in the range of 0.5 to 7.5 g / 10 min. and in a proportion of 30 to 85% by weight; as well as a copolymer of ethylene with vinyl acetate (EVA) with contents of 5 to 80% by weight of vinyl acetate and in a proportion of 5 to 60% by weight, and an ultraviolet absorber of the group of hindered amines , benzophenones or organic nickel complexes, such as nickel dithiocarbamate in a proportion of 0.05 to 10% by weight.

In the case of (II), it is formed by a concentrate based on polyethylene which can be low density polyethylene, high density or copolymer of ethylene with l-butene, 1 -hexene or 1-ketene, and a pigment or additive thermocontroller that can be as previously mentioned photochromic or thermochromatic (c); perlecentes (d); phosphorecent (e); metallic (f) and fluorescent in daylight (g). The thermocontroller compound can be physically mixed with the polyethylene matrix, microencapsulated and then mixed with the matrix or chemically bound to the polyethylene matrix (grafted). The change of coloration in the case of photochromic additives can be colorless to any color (violet, red, green, blue, pink, yellow, etc.) or of any color to colorless, or from one color to another color. In the case of thermochromatic additives, the range of color change temperature of the additive can be at least between -4 ° C and 5 ° C and at most between 44 ° C and 58 ° C. The thermocontroller additive may be contained in the matrix within the range of 0.01 to 50% by weight of the concentrate. 3. While (III) is composed of a low density polyethylene, a high density polyethylene and copolymers of ethylene with l-butene, 1 -hexene or 1-ketene; as well as a copolymer of ethylene with vinyl acetate (EVA) and an ultraviolet light absorber, with the same characteristics as the components of the formulation (I). 4. On the other hand, (IV) is composed of low or high density polyethylene and copolymers of ethylene with l-butene, 1 -hexene or 1-ketene; and an ultraviolet light absorber, with the same characteristics as the components of the formulation (I).

Additionally, plastic film can be formulated with other additives used in films for agricultural use, such as anti-static, antioxidants, anti-drip, inorganic charges opaque to infrared, etc. The classes and concentrations of the above additives may be those typically used for polyolefin films for agricultural use.

The total thickness of the film is in the range of 5 to 200 microns.

Claims (1)

1. CLAIMS: An improved formulation for the production of a thermo-controlled plastic film, which improves the temperature control in the protected systems, thus leading to avoid damage to the plants due to the high temperatures that are generated inside the protected systems, without affecting the yield and quality of the crop or product. This film can be used mainly as greenhouse cover, soil padding for employees in agriculture, tunnels or microtunnels, thus providing an alternative to help solve the problem of overheating of protected systems. This greenhouse cover film is formulated based on polyethylene blends, and / or ethylene-vinyl acetate (EVA) copolymers and / or mixtures thereof, with an ultraviolet light absorber and with a pigment or thermocontroller additive. The formulation of the film is based on a quaternary mixture of polyethylenes and a copolymer of ethylene vinyl acetate (I) 100% by weight, with 0.01 to 30 parts per hundred resin (per) of pigment or thermocontroller additive (II). In this formulation, (I) is composed of a low density polyethylene, a medium density polyethylene, a high density polyethylene and copolymers of ethylene with l-butene, 1-hexene or 1-octene having densities in the range of 0.915 to 0.970 , an index of fluidity in the range of 0.5 to 7.5 g / 10 min. and in a proportion of 30 to 85% by weight; as well as a copolymer of ethylene with vinyl acetate (EVA) with contents of 5 to 80% by weight of vinyl acetate and in a proportion of 5 to 60% by weight, and an ultraviolet light absorber of the group of hindered amines , benzophenones or organic nickel complexes, such as nickel dithiocarbamate in a proportion of 0.05 to 10% by weight. In the case of (II), it is formed by a concentrate based on polyethylene which can be low density polyethylene, high density or copolymer of ethylene with l-butene, 1 -hexene or 1-ketene having a density in the range from 0.915 to 0.970 and a flow index 0.5 to 7.5 g / 10 min. and a pigment or additive c) Thermocontroller can be photochromic or thermochromatic, of the organic type such as iles, hydrazones, fulgida, thioindigo pigments, aromatic azo compounds, spiro compounds, anthrones, sindrones, naphthalenones; or inorganic such as metal oxides, mercury compounds, zinc sulphides, copper compounds d) Perlents such as guanine and hypoxanthine or inorganic pigments of the basic lead carbonate type, bismuth oxychloride, hydrogen lead arsenate, as well as mica coated with small layers of titanium dioxide e) Fosforecentes of the inorganic type are of two types mixtures of zinc sulphides and cadmium activated with traces of copper, silver or magnesium, mixtures of zinc sulphides and activating cadmium by copper or calcium sulphides and strontium with bismuth and copper f) Metallized pigments of the type aluminum, iron, bronze, copper, mixed of these or some other metal such as zinc, with particle size between 10 and 85 microns preferably. g) Fluorescent pigments in daylight such as derivatives of aminonaphthalimides, phthalocyamines and others. The thermocontroller compound can be physically mixed with the polyethylene matrix, microencapsulated and then mixed with the matrix or chemically bound to the polyethylene matrix (grafted). In the case of thermochromatic and photochromatic the color change can be colorless to any color (violet, red, green, blue, pink, yellow, etc.) or from any color to colorless, or from one color to another color. In the case of thermochromatic additives, the color change temperature range of the additive can be at least between -4 ° C and 5 ° C and at most between 44 ° C and 58 ° C and the other pigments or additives. The thermocontroller additive may be contained in the matrix within the range of 0.01 to 50% by weight of the concentrate. Additionally, plastic film can be formulated with other additives used in films for agricultural use, such as anti-static, antioxidants, anti-drip, inorganic charges opaque to infrared, etc. The classes and concentrations of the above additives may be those typically used for polyolefin films for agricultural use. 3. An improved plastic film as defined in claim 1, wherein the improvement consists of using ternary polyethylene blends, and an ethylene vinyl acetate copolymer (EVA) (Til) 100% by weight, with 0.05 to 30 parts by weight. one hundred resin (per) of thermocontroller additive (II). Where the formulation (III) is composed of a low density polyethylene, a high density polyethylene and copolymers of ethylene with l-butene, 1-hexene or 1-ketene having densities in the range of 0.915 to 0.970, an index of fluidity in the range from 0.5 to 7.5 g / 10 min. and in a proportion of 30 to 85% by weight; an ethylene-vinyl acetate (EVA) copolymer with contents of 5 to 80% by weight of vinyl acetate and in a proportion of 5 to 60% by weight, and an ultraviolet light absorber in a proportion of 0.05 to 10% in weight, with the same characteristics as the components of the formulation (I). 4. An improved plastic film as defined in claim 1, wherein the improvement consists in using polyethylene binary mixtures and ultraviolet (IV) light absorbers with a thermocontroller additive concentrate based on polyethylene (II). The formulation of the film is based practically on a mixture of 100% by weight of (IV) with 0.01 to 30 parts per hundred resin (per) of thermocontroller additive (II). On the other hand, (IV) is composed of a mixture of low density polyethylene and copolymers of ethylene with l-butene, 1-hexene or 1-octene having densities in the range of 0.915 to 0.970, a rate of fluidity in the range from 0.5 to 7.5 g / 10 min. and in a proportion of 30 to 85% by weight, with an ultraviolet light absorber in a proportion of 0.05 to 10% by weight, with the same characteristics as the components of the formulation (I). SUMMARY: The present invention is related to the development of an improved formulation for the production of a plastic film with thermo-controlled characteristics for use as a cover for protected systems (greenhouse, tunnels, microtunnels or soil mulch of agricultural employees) . The formulation of said film is based on mixtures of polyethylene, and / or ethylene-vinyl acetate (EVA) copolymers and / or mixture thereof, with an ultraviolet light absorber and with a pigment or thermocontroller additive. Formulations I, II, III and IV can contain any of the following materials and additives: a) Polyethylenes can be low density, medium density or high density polyethylenes (LDPE, MDPE or ELDPE) and / or ethylene copolymers with alpha- olefins (LLDPE). The ethylene-vinyl acetate copolymers can be copolymers with different vinyl acetate contents. b) The ultraviolet light absorber can be of the hindered amines type or organic nickel complexes, or hydroxybenzophenones and / or mixtures thereof. c) The pigment or thermocontroller additive can be photochromic or thermochromatic of organic type such as anilines, hydrazones, fulgida, thioindigo pigments, azo-aromatics, spiro compounds, anthrones, sindrones, naphthalenones; or inorganic such as metal oxides, mercury compounds, zinc sulphides, copper compounds. d) Pericles such as guanine and hypoxanthine or inorganic pigments of the basic lead carbonate type, bismuth oxychloride, hydrogen lead arsenate, as well as mica coated with small layers of titanium dioxide e) Fosforecentes of the inorganic type are of two types mixtures of Zinc and cadmium sulphides activated with traces of copper, silver or magnesium, mixtures of zinc sulphides and copper activating cadmium or calcium sulphides and strontium with bismuth and copper f) Metallizations of the aluminum, iron, bronze, copper type, mixed of these or some other metal such as zinc, with a particle size between 10 and 85 microns preferably. g) Fluorescents in daylight such as derivatives of aminonaphthalimides, phthalocyamines and others. In addition to the formulation of this film, anti-static additives, antioxidants, anti-drip, inorganic opaque infrared charges, etc. can be added. The classes and concentrations of the above additives may be those typically used for polyolefin films for agricultural use. Saltillo, Coah. Mexico February 21, 2000 Dr. Luis F. Ramos de Valle