RU2269548C1 - Composition for manufacturing agriculture-destination film - Google Patents

Abstract

FIELD: polymer materials.

SUBSTANCE: invention relates to novel agriculture-destination materials and, specifically, to polymer compositions for manufacturing film materials based on light-transparent thermoplastic polymers and destined for use as greenhouse coatings. Invention discloses composition including thermoplastic polymer, additive, and stabilizer. Additive contains green silicon carbide α-phase with particle size 0.1-10 μm in amounts between 0.1 and 2.0 %. Thermoplastic polymer is selected from group consisting of polyethylene, polyvinylchloride, polypropylene, polystyrene, polymethylmethacrylate, polycarbonate, polyamide, copolymers thereof, and other suitable thermoplastic polymers.

EFFECT: enabled manufacture of film showing elevated heat-retention properties and providing most favorable temperature conditions in greenhouse.

5 cl, 5 dwg, 1 tbl, 8 ex

Description

The invention relates to the field of new agricultural materials, in particular to polymer compositions for the production of film materials based on translucent thermoplastic polymers as coatings for greenhouses.

Polymer film materials based on polyethylene, a copolymer of ethylene with vinyl acetate, polyvinyl chloride and other polymers used for growing plants in protective soil (Polymer film materials. / Ed. By V.E. Gulya. - M .: Chemistry, 1976, p. .103-105, 24-25), must satisfy the following basic requirements:

- have high transmittance in the visible region of the spectrum (0.45-0.75 microns);

- have a high reflective and absorbing ability in the thermal portion of the spectrum (8-15 microns) emitted by the soil (heat-retaining effect);

- have a high absorption capacity of ultraviolet radiation (0.29-0.33 microns).

Known polymer film material for enclosing greenhouses (RF Patent No. 2059999, IPC ⁶ C 08 L 23/02, C 08 K 5/00, 1996), containing a translucent thermoplastic polymer and an optically active additive, which serves as at least one of the inorganic high-temperature oxohalide and chalcogenide compounds of lanthanum, yttrium, europium, and erbium, which provides the conversion of the ultraviolet component of light and the absorption of far-infrared radiation.

The composition for producing this material contains an active additive of 0.05-1.00 wt.% And component 99.00-99.95 wt.%.

The disadvantage is that due to the complex composition, this film material has a rather high cost, in addition, the limited stability of the luminescent properties under solar radiation (300-600 days). Since all rare earth oxo halides in air and, especially in the presence of moisture, are destroyed, and the increase in heat-holding properties is achieved by absorption of far infrared radiation, and in this connection only part of the soil radiation energy is returned to the greenhouse, and the most effective way of heat holding radiation energy due to reflection is absent.

A known composition for producing agricultural films (Aut. St. USSR No. 1106818, IPC ³ C 08 L 23/04, C 08 K 3/22, 1984). This composition includes high-pressure polyethylene or a copolymer of ethylene with vinyl acetate, alumina hydrate and a stabilizer, and to increase the heat-holding properties while reducing the scattering of visible light by the film, it additionally contains a metal oxide selected from the group: zinc oxide, titanium dioxide and antimony trioxide, in the following the ratio of components, wt.%: high-pressure polyethylene or a copolymer of ethylene with vinyl acetate 92.9-98.88; alumina hydrate 1-6; metal oxide 0.02-0.3; stabilizer - the rest.

The presence of OA in the material of benzene reduces its spectral transmittance of UV radiation by 15%, and heat-retaining additives (metal oxides - titanium, zinc, antimony) reduce the spectral transmittance in the far infrared to 15-25%. Due to the complex composition and cost, this material is not widely used in the practice of cultivating vegetables in closed ground. In addition, the incomplete absorption of ultraviolet radiation does not allow to fully use this effect for yield increase, and the reduction in the transmission of radiation in the infrared region is achieved mainly due to its absorption, and there is no most effective way to heat radiation radiation due to scattering.

The closest technical solution is the composition of the film polymer material for coating greenhouses, containing a thermoplastic polymer, a stabilizer and an optical activator based on europium compounds (RF Patent No. 2127511, IPC ⁶ A 01 G 9/22, 1999).

The disadvantage of the composition is the high cost of the material and low heat-saving properties.

The objective of the invention is to provide a composition for producing agricultural film, which allows to obtain a film with improved heat-saving properties, which allows you to create the most favorable temperature conditions in the greenhouse.

The problem is solved using the composition to obtain a film for agricultural purposes, including a thermoplastic polymer, additive and stabilizer. As an additive, the composition contains green silicon carbide in the α phase in an amount of 0.1-0.2 wt.% With a particle size of 0.1-10 microns.

Preferably, the composition has the following ratio of components, wt.%: The specified silicon carbide is 0.1-2.0; stabilizer 5.5-6.0; thermoplastic polymer - the rest.

To obtain a thermoplastic polymer transparent in the visible region of the light, the composition preferably contains the indicated silicon carbide in an amount of 0.1-0.2 wt.% With the following components, wt.%: The specified silicon carbide 0.1-0.2, stabilizer 5, 5-6.0; thermoplastic polymer - the rest.

The composition contains the specified silicon carbide, preferably with a particle size of 1.0-7.0 microns.

As a thermoplastic polymer, the composition preferably contains polyethylene, polyvinyl chloride, polypropylene, polystyrene, polymethyl methacrylate, polycarbonate, polyamide and their copolymers.

As a stabilizer in the proposed composition can be used any known stabilizers, non-dyeing polymers with light stabilizing and thermostabilizing effect and capable of preventing aging of the films. If necessary, antioxidants may be added to the composition.

The table gives examples of compositions.

The proposed heat-retaining material is both a scattering and absorbing system. The processes of attenuation of radiation are composed of the processes of absorption and scattering by silicon carbide particles located in a thermoplastic polymer.

We found that the polymer composition for agricultural films, including silicon carbide, has the greatest heat-holding effect, as it has a minimum transmittance and maximum reflectivity in the radiation spectrum of the protected soil. At a soil temperature of 0-20 ° C, the main radiation energy is concentrated in the wavelength range of 8-15 microns.

) достигает очень больших значений (до 10), а действительная часть (показатель преломления) принимает очень малые значения (n→0), при этом относительный показатель преломления имеет очень большие значения. В связи с этим обстоятельством ослабление падающего излучения светопрозрачным материалом в рассматриваемой области спектра происходит в основном за счет рассеяния с малым поглощением.Consider a translucent heat-retaining material consists of a translucent matrix (thermoplastic polymer) and particles of silicon carbide with a diameter of preferably 1-7 microns. In this spectral region relative refractive index of the matrix n _Matras ≅1,5, and radiation penetrating into the deep layers, affects the particles with longer wavelengths 8-22 microns. In this spectral region, the optical properties of silicon carbide undergo normal and anomalous dispersion. In the vicinity of the absorption band of 10-12 μm (the region of anomalous dispersion), the imaginary part of the complex refractive index (absorption coefficient -

) reaches very large values (up to 10), and the real part (refractive index) takes very small values (n → 0), while the relative refractive index has very large values. In connection with this circumstance, the attenuation of the incident radiation by the translucent material in the considered region of the spectrum occurs mainly due to scattering with low absorption.

In this spectral region, the radiation comes from the soil and has a diffuse nature, which leads to an increase in the effective interaction length with translucent heat-retaining material and, ultimately, to more efficient scattering of the incoming radiation.

For example, the reflection of radiation in the spectral range of 8-15 microns from a 150 mm thick PVC film is 4%, and the reflection of this radiation from a translucent heat-holding material with a concentration of 0.15% silicon carbide particles is already 38%.

In the visible part of the spectrum (0.45-0.75 μm), the process of interaction of radiation with the material occurs with low absorption, since the imaginary parts of the complex refractive indices of the substances of silicon carbide particles and the matrix (thermoplastic polymer) are very small

The presence of the scattering factor of the radiation attenuation (relative refractive index n _portions ./n _{Matras ≅1,5.)} Contributes enlightened heat-retaining layer of translucent material, since the diffraction parameter ρ = πd / λ»1, where d - the average particle diameter, λ - the wavelength of radiation, which means that diffractively scattered light, is mainly concentrated in a narrow beam directed forward along the incident solar radiation.

For example, the transmittance in the visible spectral range of a PVC film with a thickness of 150 μm is 75-78%, and the hemispherical transmittance of the shear material of a similar thickness with a content of 0.15% silicon carbide is 70%.

In the ultraviolet region of the spectrum (0.29-0.33 μm), the absorption index of silicon carbide increases markedly, and the refractive index n _sic ~ n _matr . This circumstance leads to the fact that the attenuation of the incident radiation on the material occurs mainly due to absorption.

For example, the transmittance of a PVC film with a thickness of 150 μm is 15% at a wavelength of 0.32 μm, and the transmittance of a layer of material with a thickness of 150 μm containing 0.15% silicon carbide particles is already ~ 1%.

Thus, the proposed heat-retaining material is characterized by near-zero spectral transmittance of UV radiation (0.29-0.33 μm), high spectral reflection and strong absorption of the far-infrared radiation (8-15 μm), high spectral transmittance in the visible region spectrum (0.45-0.75 μm).

The proposed polymer composition is prepared as follows: additive - dispersed substance (silicon carbide) is thoroughly mixed with a plasticizer in a ratio of 1: 2. PVC is heated to 70 ° C, a stabilizer and a mixture of silicon carbide with a plasticizer are introduced. They are mixed at high speeds at a temperature of 110 ± 5 ° C and processed into products by known methods, for example, by extrusion, injection molding, etc.

The heat-saving properties of experimental coatings were investigated in laboratory conditions. The measurements were performed using the method of a dynamic thermoradiometer (Emelyanov A.A. Instruments and experimental equipment, 2003, No. 4, pp. 149-153). The blackened metal disk was placed in a capsule, the walls of which were made of the studied heat-saving coating, and was exposed for a certain period of time to external influence of radiant energy, the spectral composition of which was close to solar. In the experiment, heating and cooling of the disk was recorded in the presence of external radiation and without it. The results of the experiments indicate that the optical properties of the capsule material have a significant effect on the thermal state of the disk. The inventive composition is selected from experimental data. To produce an experimental batch of heat-saving coatings, the composition composition was chosen that had the capsule wall material in the experiment with the highest temperature, heating rate and cooling time, and showed the best heat-saving properties: 0.15% silicon carbide, 6.0% stabilizer, polyvinyl chloride - the rest .

The samples of the experimental heat-saving coating and polyvinyl chloride film with a thickness of 150 μm were obtained spectral characteristics, which are presented in the following drawings.

From figure 1 it follows that the PVC film in the region of the thermal portion of the solar spectrum has a high transmittance with respect to translucent heat-holding material (STM) with a silicon carbide compound. When using the materials in question as greenhouse coatings under the influence of solar radiation in a greenhouse with a PVC film, its higher transmittance will lead to elevated temperatures in this greenhouse.

From figure 2 and 3 it follows that in the region of the thermal portion of the solar spectrum there is a higher reflectivity of the STM. This circumstance is important from the point of view of reducing the temperature of superheat under intense solar radiation. In the region of the long-wavelength thermal region of the spectrum W> 800 (the spectral region of soil radiation), the appearance of reflectivity in STMs is observed, which is not the case with PVC film. The presence of a higher reflectivity of the STM in this part of the spectrum causes the thermal radiation of the soil to return back to the greenhouse and thereby increase heat saving and slow down cooling in the absence of solar radiation. Therefore, the thermal inertia of the greenhouse with STM increases, and the time of approaching the lowest temperature will increase with decreasing ambient temperature.

Figure 4 presents a graph of changes in ambient temperatures in greenhouses July 29-30, 2003. Thermocouples were located in all cases at a distance of 100 mm from the soil surface. Each thermocouple was protected by an opaque screen from direct sunlight. Heat transfer of greenhouses with the surrounding space due to the movement of air masses from the protected space outside the coating was excluded.

From figure 4 it is seen that at the surface of the soil the temperature in the greenhouses in the maximum value differs by more than 4 ° C. In this case, the maximum temperature outside the greenhouses reaches 21 ° C, and in a greenhouse with STM 37 ° C and with a PVC film 41 ° C. The presence of two humps is explained by a change in the energy of solar radiation due to cloud cover. With a decrease in the intensity of solar radiation, a drop in the temperature of the outside air, and consequently the temperature in the greenhouses, occurs. However, at night, the rate of temperature decrease in the greenhouse with STM becomes slower and already at the coldest time of the day (8.5 ° C) the experimental greenhouse is 0.5 ° C warmer than the base greenhouse. With the advent of the sun, the temperatures of the outside air and in the greenhouses begin to increase. In this case, the heating rate in the experimental greenhouse lags behind and by 12 o’clock in the afternoon the temperature difference in the greenhouses reaches 3 ° C.

Figure 5 presents the temperature changes in greenhouses during a period of severe cooling. Figure 5 shows that with a decrease in the temperature of the outside air after sunrise by 5 ° C, the temperature in the base greenhouse also decreases by 5 ° C, and in the greenhouse with STM, the temperature decreases by 4 ° C during the same time. Further warming for one hour causes the outside air to warm up by 6 ° C, in a greenhouse with PVC film 18 ° C, in a greenhouse with STM 14 ° C. When the outdoor temperature decreases by 6 ° C from 8 am to 11 hours to 1 ° C in greenhouses, a decrease occurs with PVC film by 16 ° C, from STM by 12.5 ° C. A very important point is that the temperature difference in greenhouses under such conditions is 1.5 ° C. From experimental data on the temperature state of greenhouses it follows that the greatest heat-saving effect in a greenhouse in a greenhouse with STM is manifested in the region of lower temperatures. So, for example, at an outdoor temperature (Fig. 4) + 8.5 ° C, the temperature difference between the greenhouses is 0.5 ° C, and when the external temperature (Fig. 5) decreases to + 1 ° C in a greenhouse with STM already 1.5 ° C warmer. This circumstance has the following explanation. When the temperature of the soil decreases, the maximum of its radiation energy shifts to the longer wavelength part of the spectrum according to the Wien law, and in this region the STM reflection coefficient increases noticeably (Fig. 3), which ultimately leads to an increase in the heat-saving effect.

The proposed greenhouse coating has significant advantages. Due to the scattering by the coating of the thermal radiation emitted by the soil, positive temperatures are retained in the greenhouse for a longer time, the value of which is 0.5-1 ° C higher than the temperatures in greenhouses with a conventional film. This circumstance allows us to pass the peak of zero temperatures and ensure the safety of plants. The establishment of higher temperatures in the greenhouse with the proposed coating at night reduces the likelihood of developing diseases such as late blight, powdery mildew.

In the hot time of the day, with the scorching sun in greenhouses with a conventional film coating, there is a danger of overheating of plants. The proposed coating reduces the maximum temperature in the greenhouse and thereby allows you to provide more comfortable living conditions of plants.

Similar properties were obtained when polyethylene was used as a thermoplastic film polymer.

Thus, the use of a greenhouse coating with enhanced heat-saving properties will help to solve important practical problems of plant protection: reduce the harmful effects of low night temperatures and protect plants from sunburn. It can be recommended as a promising greenhouse cover for greenhouses.

No. p / p Thermoplastic polymer Stabilizer Silicon carbide Transmittance at a wavelength of 0.32 microns,% The reflection of radiation in the spectral range of 8-15 microns,% mark % wt. % wt. Particle Size, MKM one. Polyvinyl chloride Phenozan-23 TU 6-22-0205603-3-88 0.05 0.15 1,0 1,0 38 2. High pressure polyethylene Benzone OA *
Phosphite NF ** 0.5
0.5 0.1 0.1 1,5 39 3. Polypropylene Phenozan-23 0.1 2.0 10.0 1,2 37 four. Polyamide Benzon OA
Phosphite NF 1,0
1,0 0.1 7.0 1,1 38 5. Polyvinyl chloride Benzon OA
Sintamide S-5 *** 4.0
2.0 0.15 7.0 1,1 36 6. Polystyrene Benzon OA
Phosphite NF 0.1
0.1 0.2 10.0 1.3 35 7. Polyvinyl chloride Benzon OA
Sintamide S-5 4.0
2.0 - - 15.0 four 8. According to the prototype Phenozan-23 0.1 - - 13.0 8 Benzone OA * - 2-hydroxy-4-alkoxybenzophenone.
Phosphite NF ** - Tris-nonylphenylphosphite.
Syntamide C-5 *** is an ethoxylated monoethanolamide of the acid fraction C ₁₈ -C ₁₆ .

Claims (4)

1. Composition for producing agricultural films, including thermoplastic polymer, additive and stabilizer, characterized in that as an additive it contains green silicon carbide in the α phase in an amount of 0.1-0.2 wt.%. with a particle size of 0.1-10 microns. 2. The composition according to claim 1, characterized in that it has the following content of components, wt.%: Specified Silicon Carbide 0.1-2.0 Stabilizer 5.5-6.0 Thermoplastic polymer Rest 3. The composition according to claim 1, characterized in that to obtain a thermoplastic polymer transparent in the visible region of the light, the composition contains said silicon carbide in an amount of 0.1-0.2 wt.% With the following content of components, wt.%: Specified Silicon Carbide 0.1-0.2 Stabilizer 5.5-6.0 Thermoplastic polymer Rest 4. The composition according to claim 1 or 2, characterized in that it contains the specified silicon carbide with a particle size of 1.0-7.0 microns. 5, The composition according to claim 1, characterized in that as a thermoplastic polymer it contains polyethylene, polyvinyl chloride, polypropylene, polystyrene, polymethyl methacrylate, polycarbonate, polyamide and their copolymers.

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