RO123582B1 - Sheets with properties of selecting luminous radiation within the uv and ir range, for plastic greenhouses and low tunnels - Google Patents

Abstract

The invention relates to a polymeric sheet having UV- and IR-range selectivity for luminous radiation, which is meant to be used in agriculture, for obtaining an optimal micro climate for vegetable crops in plastic greenhouses and tunnels. According to the invention, the sheet consists of a single layer of low-density polyethylene with a flow index of 0.29 g/10 min, which includes 1.7...11% UV stabilizer of the sterically hindered amine type, 0.9...11% condensation preventing additive and 0.09...1.2% dyestuff.

Description

The invention relates to a polymeric film with properties of selectivity of the light radiation in the UV and IR field, used for the coverage of solariums and low tunnels, in order to achieve the optimum microclimate for vegetable crops, inside them.

in the conditions of expansion of human action on the environment, by expanding urban areas and industrial buildings, due to the reduction of forested areas, it was necessary to reformulate the practice of agriculture and it was necessary to ensure the biological protection of the plants and increase the productive capacity of the soil.

It is known a polymeric film composed of five layers, based on polyolefins and ethylene vinyl acetate, which has the following structure: layer 1, made of low density polyethylene, which contains 0.1% UV protection agent, of the sterically hindered amine type. ; layer 2 with properties of tear resistance, consisting of linear polyethylene; layer 3 with photoselectivity properties, consisting of low density polyethylene in which dye is incorporated; layer 4 consisting of ethylene vinyl acetate copolymer and layer 5 of low density polyethylene with flow rate 2 g / 10 min [RO 116260 Bj. These films are made by co-extrusion-blowing technology. From the analysis of the figures presented in the patent, it is observed that the transmittance of sunlight in the U V domain, has a rather high value, between 55 and 65%, which allows the penetration into the solar of the rays with high energy value and with harmful effect for plants. In contrast, in the 400 - 700 nm range (photosynthetic active radiation), optimum value is not provided for plants, but only about 78%. Also, the films do not ensure the preservation of the corresponding optical and mechanical characteristics for more than two years, under special working conditions, such as:

- accelerated aging, due to the action of the natural environment through: sunlight, low and high temperatures according to the periodicity of the seasons in which they are used, the weather (humidity, wind),

- degradation under the action of pesticides used in solariums.

It has no antimicrobial and anti-condensation properties.

It is also known a monolayer foil based on polyolefins, which incorporates in a proportion of 0.1 ... 1% a specific color concentrate, depending on the species of vegetables grown in the solar [RO 114262 B], This film has a reduced resistance to the action of the natural environment because it does not contain UV stabilizers. The role of this film is only for selective transmission of sunlight in the UV field, due to coloring additives.

The problem solved by the invention is to obtain a monolayer polymeric foil, which, by incorporating specific additives, has superior optical properties, light transmission in the UV, VIS and IR fields and of aging resistance under the action of environmental factors. It is envisaged to apply a new solution on polymeric films with special properties of photoselectivity, anticondensation, antivirus etc., in order to diversify the offer to agricultural producers, at a convenient quality / price ratio.

The polymeric foil with light radiation selectivity properties in the UV and IR field, for solariums and low tunnels, according to the invention, consists of a single low density polyethylene layer with a flow rate of 0.29 g / 10 min, which includes 1.7 ... 11% UV stabilizer, sterically hindered amine type, 0.9 ... 11% anti-condensation additive and 0.09 ... 1.2% dyes, preferably yellow, red , green.

The photoselective polymeric foil according to the invention has the following advantages:

- ensures a good transmission of photosynthetic active radiation between 400 and 700 nm, between 80 and 90%;

- by incorporating a specific additive, it shields the transmission of sunlight in the UV field, allowing it to pass only between 380 and 400 nm, a vital area for insects that ensure pollination;

RO 123582 Β1

- by incorporating a specific additive, a good transmission of 1 radiant thermal energy (IR close to the range 700 ... 2100 nm) is ensured, achieving good heat retention properties; 3

- achieving the anticondensation effect, by including the respective additives on the lower layer of the multilayer foil;

- it is made on traditional polymer processing equipment without requiring additional investment; 7

- low cost price;

- the possibility of processing at large dimensions, the possibility of thermal welding, reduced mass 9.

By using photoselective polymeric films in the protection of horticultural crops, with 11 predilections, vegetables, the following advantages are obtained:

- ensuring early productions, improving precocity; 13

- increasing productivity;

- obtaining superior quality products; 15

- a more efficient use of irrigation water;

- reducing fertilizer consumption; 17

- use of fertigation technology; reducing the incidence of plant diseases;

- controlling the appearance of weeds, 19

- reducing soil compaction;

- the possibility of obtaining more crops per year.21

Plastic culture represents both the science and technology related to the use of plastics in agriculture. Polyethylene sheets successfully replace the glass in the solariums. 23 They are more resistant to mechanical stress, because of their flexibility, they can selectively transmit solar radiation and allow for more complex forms of solarium. The synthesis of new additives capable of 25 improving light transmission and creating the optimum microclimate for agricultural crops in solariums covered with polymeric foils allowed the extension of the lands on which protected agriculture can be practiced. The role of these additives is to select only certain wavelengths of sunlight, suitable for plant development. The main advantages are 29 improving precocity and productivity, inhibiting certain diseases and implicitly reducing the agrochemicals used. 31

Polymer films can be defined as photoselective, if by incorporating specific pigments, they are able to reduce by absorption the passage of a band determined by 33 radiation or in other words reduce the passage of visible radiation within a specific wavelength band. 35

From sunlight, man only perceives radiation whose wavelength is in the range 400 ... 700 nm. Plants respond to a much larger range, comprising part 37 of UV 290 ... 400 nm and part of far IR, over 800 nm. The term RIP is used to describe the radiation domain responsible for plant growth. Most 39 plants respond to radiation 400 ... 450 nm (blue) and especially 625 ... 675 nm (red). But other wavelengths can trigger the photosynthesis process, and the peak of the emitted solar intensity 41 is found in the region of 525 nm (yellow). Thus, cutting any wavelength in the spectrum will reduce the growth rate of the plants. 43

Some areas of the spectrum may influence the shape, height and other aspects of plant quality. Colored sheets are sometimes proposed for coating greenhouses (usually 45 yellow, green, blue, red).

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Although this is not significant for photosynthesis, UV radiation can be a factor in the development of colors and odors of some plants. Short UV wavelengths (200 ... 310 nm) can be a factor in preventing plant elevation. These wavelengths are usually cut by a UV filtering system. Some infections (especially botrytis) may be influenced by UV radiation, because the production of spores is triggered by UV radiation. Removing UV radiation slows the growth of insects. This has proven to be helpful in Mediterranean territories where there is a high risk of infection of crops and where it is difficult to keep insects out of greenhouses when they have an open structure. Because insects are viruses, reducing them is a way to reduce viral infections.

The sheets for covering the solariums allow and selectively prevent the energy transfers between the interior environment of the solarium and the external environment, leading to the greenhouse effect. In order to retain maximum heat inside the solar, the ideal foil should have the maximum transmission of solar radiation, and especially from the near and medium IR range (760 ... 3000 nm), which allow the air inside the solar to remain warm throughout duration of the day. Heat retention is achieved by choosing specific polymers for the creation of foils and using additives. The thickness of the sheets influences as follows: the thin sheets will maintain a lower temperature than the thicker sheets.

The following are three examples of making the monolayer polymeric foil according to the invention.

Example 1. Monolayer foil with the following composition:

Table 1

compound Amount % LDPE (low density polyethylene) - flow rate 0.29 g / 10 min 80 ... 100 Sterically hindered amine UV stabilizer 2 ...... 10 Yellow dye 0.1 ... 1 A common anti-condensation additive in the art 1 ... 1Ό

Way of working

The raw materials are dosed and inserted into the feed funnel of the extrusion machine - blowing. The dosed raw materials are mixed and homogenized in the melt in the extruder. At the base of the extrusion-blowing process is the process of material flow through a nozzle of form corresponding to the finished product.

The processing parameters in the extruder are:

Table 2

Operating parameters stock Temperature zone I cylinder 185 ° C Temperature zone li cylinder 190 ° C Temperature zone III cylinder 210 ° C Temperature zone IV cylinder 220 ° C

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Table 2 (continued)

Operating parameters stock Temperature zone V cylinder 225 ° C Temperature zone A - Replacement filter 215 ° C Temperature zone C - Extension Page 21 Temperature zone D - Black fixed 205'0 Temperature zone HI - Cap 190 ° C Temperature zone H 2 - Cap 230 ° C Temperature zone H 3 - Nozzle 228 ... 230 ° C Screw speed 65 rpm 65 rpm Productivity 100 kg / h Extrusion speed 40 rpm Shooting speed 7 rpm

The tubular foil obtained has the following characteristics: 15

- width of 4200 mm,

- width deviation according to STAS 8171-84: ± 50 mm, 17

- thickness 0.18 mm.

The monolayer film has tensile strength 100 ... 150 N / mm ² , tear resistance 19

83 .. .98 N / mm, elongation at break 320 .. .390%, properties suitable for use for roofing solariums and low tunnels in agriculture.21

Example 2. Monolayer foil with the following composition:

Table 323

compound Quantity% LDPE - flow rate 0.29 g / 10 min 80 ... 100 Sterically hindered amine UV stabilizer 2.8 ... 11 Red dye 0.1 ... 1.2 An anti-condensation additive known in the art 4 ... 41

The working method is the same as in Example 1. The tubular foil obtained has the following 31 characteristics:

- width of 4200 mm, 33

- width deviation according to STAS 8171-84: ± 50 mm,

- thickness 0.18 mm.35

The monolayer foil has tensile strength 146 ... 160 N / mm ² , tear resistance

95 ... 109 N / mm, elongation at break 300 ... 320%, properties suitable for use for covering 37 solariums and low tunnels in agriculture.

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Example 3. Monolayer foil with the following composition:

Table 4

compound Quantity% LDPE - flow rate 0.29 g / 10 min 80 ... 100 Sterically hindered amine UV stabilizer 1.7 ... 10 Green dye 0.09 ... 0.98 An anti-condensation additive known in the art 0.9 ... 9.7

The working method is the same as in Example 1. The tubular foil obtained has the following characteristics:

- width of 4200 mm,

- width deviation according to STAS 8171-84: ± 50 mm,

- thickness 0.18 mm.

The monolayer foil has tensile strength 142 ... 157 N / mm ² , tear resistance

92 ... 114 N / mm, elongation at break 320 .. .520%, properties suitable for use for roofing solariums and low tunnels in agriculture.

The influence of photoselective films on vegetable crops is as follows:

- The photoselective films used to cover the solariums have determined changes of the microclimate in the protected spaces.

- The differences in the amount of light that the plants benefit from under different types of foils were more evident in the days with high cloudiness.

- The best results were obtained under the pink foil, at which the illumination level increased by 2700 Ix and 2195 Ix respectively compared to the control.

- Inside the solarium, global heat accumulations, higher than the control, were recorded under the pink and green foil (with differences of 17.6 ° C and 7.9 ° C), but decreased to the yellow foil (-32.4 ° C).

- In the soil, the temperature accumulations were favored by the protection with photoselective foils, the biggest differences from the control being obtained on the yellow and green sheets (6 ... 11,5 ° C).

- as a whole, in terms of thermal regime, the pink foil can be considered warm, while the yellow foil is cold.

- The photoselective films generally determined the increase of the relative humidity of the air in the solarium by 1.75 ..., 2% and the decrease of the humidity of the soil by 0.5 ... 10.1% compared to the control.

- The pink leaf was highlighted by reducing by 0.6% the relative humidity of the air and the lowest decrease (0.5%) of the soil humidity over the control, thus favoring the general water regime in the culture space.

- depending on the plant's claims against the climatic factors, it is advisable to cover different types of photoselective foils for the solariums: pink and green ones for the heat-demanding species and which require lower atmospheric humidity, the yellow one for the less heat-sensitive species and which supports higher relative humidity.

- The use of photo-selective leaflets to cover solariums influences the growth of salad plants in early culture.

- The green and pink sheets resulted in an increase of the diameter of the rosettes by 8% and 6% respectively, while the yellow foil reduced its relative to the control. Significant differences were obtained on the green foil.

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- The mass of the rosettes was higher than the control only in the pink foil variant, the other 1 variants caused the mass reduction.

- The characteristics of the root system are not significantly influenced by the protection of the plants with photoselective leaves, although there has been an increase of the root volume in the case of the green leaf, with implications in increasing the absorption capacity of the plants. 5

- For the protected culture of the salad, it is recommended to use when covering solariums the pink and green photoselective leaves, which determines the increase of the diameter, the mass of 7 rosettes and favors the root system of plants.

- Photoselective leaves influence the growth of tomato plants. The height of the 9 plants and the number of inflorescences were favored by the protection with yellow and pink leaves.

- The pink and yellow leaves had a beneficial effect on the percentage of fruiting and as a result of the total number of fruits harvested on the plant, while the green foil inhibited the fruiting.13

- The average mass of the fruit was reduced by 4 ... 15 g / fruit in all the variants of photoselective films compared to the usual foil - control.15

- The yields obtained from the tomatoes grown in the lot increased very significantly compared to the control with 27% increases in the pink and insignificant foil (7% in the yellow foil), while 17 green foil caused very significant decreases.

- The use of photoselective foils to protect tomatoes grown in low tunnels has led to 19 increased production compared to the control in most variants. The pink leaf caused 51% very significant growth, and the yellow and green ones showed significant growth (9 ... 17%).

- depending on the claims of the plants against the climatic factors that have an influence on the growth and the productive potential of the plants, it is recommended, for covering solariums 23 and tunnels, different types of photoselective sheets: pink and yellow for tomatoes and pink for salad. 25

- The research must be continued in order to establish correlations between the modification of the microclimate and the behavior of the plants under the conditions created under different types of photoselective sheets, in order to establish with greater precision their suitability for different vegetable crops. 29

Claims (4)

1 Claim 3 Polymer foil with light radiation selectivity properties in the UV and IR field, for solariums and low tunnels, characterized by its 5 single layer of low density polyethylene with flow rate 0.29 g / 10 min, including 1.7 ... 11% UV stabilizer, sterically hindered amine type, 0.9 ... 11% anti-condensation additive and 7 0.09 ... 1.2% dyes, preferably yellow, red, green.