RU2579136C1 - Light-converting composite polymer material for greenhouses - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: invention relates to agriculture, particularly to polymer composite materials for greenhouses. Light-converting composite polymer material contains a polymer matrix with dispersed therein red inorganic broadband luminophor, which has the formula: Li_s(M_(1-x)-Eu_x)₁Mg_mAl_nSi_pN_q, where m = Sr, Ca, BA, taken separately or together, and where values of indices in elements of the compounds are as follows: 0.045 ≤ s ≤ 0.60, 0.005 ≤ x ≤ 0.12, 0 ≤ m ≤ 0.12, 0 ≤ n ≤ 1.0, 1.0 ≤ p ≤ 2.40, 3.015 ≤ q ≤ 4.20, with restriction concerning all compositions 2.0 ≤ p+n ≤ 2.40 and q ≠ 4. Proposed phosphor converts in red-orange phyto-active radiation within the 580-750 nm not only ultraviolet and, partially, blue-green radiation of sunlight.

EFFECT: technical result consists in stimulation of growth and development of green plants.

5 cl, 2 dwg, 2 tbl, 12 ex

Description

The invention relates to agriculture, in particular to polymeric composite materials for greenhouses and greenhouses, including a polymer matrix with a red inorganic broadband phosphor dispersed in it, converting the absorbed ultraviolet and, in part, blue-green radiation of sunlight or replacing artificial light with the conversion of primary light in red-orange radiation. The invention can be used for the production of light-converting covering material and polymer coatings on the surface of greenhouses and greenhouses.

At present, it has been reliably established that not the entire spectrum of visible radiation has a phytoactive effect, but its individual sections corresponding to the bands of photosynthetically active radiation (PAR).

In the case of green plants, the PHA includes bands in the violet-blue region with absorption maxima at 426, 440 nm, covering the region from 410 to 480 nm. Radiation in this area has both substrate and regulatory effects. Radiation in the region of 600–700 nm (bands with peaks at 612, 642, 660, and 700 nm) has a significantly more pronounced substrate and regulatory effect than in the short-wave region of the spectrum. Finally, radiation in the region of 700-750 nm has a pronounced regulatory and weak substrate effect [A. Rakitin The effect of red light in mixed light flow on the production process of plants. Abstract of diss. Ph.D., Tomsk. 2001; Minich I.B. The effect of red fluorescent radiation on the morphogenesis and balance of endogenous plant hormones. Abstract of diss. Ph.D., Tomsk. 2005].

The optimum in the distribution of PARs by wavelength depends on the type of plant, but in the case of green plants, radiation in the red region always plays the dominant role. With regard to the phytoactive effect, the absorption of light in the orange-red region is at least twice as effective as in the blue-violet region, and 4 times higher than in the yellow-green region.

Given this, the main idea of using modern film covering materials in agriculture, just like the principles of designing modern artificial lighting systems, comes down to either correcting solar radiation or creating radiation sources with a spectrum close to the spectrum of phytoactive radiation. In both cases, the ultimate goal is to increase the proportion of biostimulating red radiation, the absorption of which by green plants promotes the processes of photosynthesis.

The conversion of light in composite polymer coating materials is usually carried out as a result of incorporation into a transparent polymer matrix

- or chemical compounds of europium [British Patent N 2158833 A, cl. C08K 5/00, 1985; Swiss patent N 667463 A, cl. C09K 11/06, 1985; Patents of the Russian Federation 2153519, 2248386];

- either organic or inorganic phosphors activated by europium [German Patent No. 2642704, RF Patents 1463737, 2008316, 2059999, 2407770, USPatents 6153665, 7366834, 8057703, USPatent Application 20100307055]

In the first case, the polymer light-converting material is obtained by mixing the starting polymer with a complex organic or inorganic europium compound, followed by extrusion of a thermoplastic polymer or dissolving a complex compound containing europium in a liquid monomer followed by block polymerization.

In the case of the use of powdered inorganic phosphors, they are mixed with the selected granular thermoplastic polymer and a film composite is obtained by extrusion by heating the prepared mixture of polymer with phosphor. At the same time, it was recommended to use various polymers as a component forming the polymer matrix, in particular high and low pressure polyethylene, a copolymer of ethylene with vinyl acetate (EVA), polyvinyl chloride, polyethylene terephthalate, etc.

The complex organic compounds of europium with organic ligands, as well as the Eu salts of organic acids, have low radiation resistance and quickly degrade due to photodestruction, photooxidation or hydrolysis. For this reason, in the manufacture of light-converting covering materials, in recent years, preference has been given to powdered polymer materials with dispersed inorganic phosphors.

Two groups of europium-activated inorganic phosphors are known - narrow-band and broad-band. In the first case, when excited by ultraviolet light, several narrow bands are observed in their luminescence spectrum, associated with electronic transitions between the d and f states in the Eu ^{2+ ion} . Such phosphors include oxide, oxysulfide, aluminate, halophosphate, borate systems. Patents are known, for example, which describe the use of:

- europium activated yttrium oxide in a mixture with strontium halophosphate activated with antimony and manganese and yttrium orthovanadate [German Patent No. 2642704];

- europium activated yttrium oxide in a three-component mixture comprising yttrium orthovanadate activated by europium, as well as strontium halophosphate activated by antimony and manganese [RF patent 2008316];

- europium activated halogen-containing oxosulphide or together with them oxo-selenide compounds of lanthanum of the general formula

[(La _1-x Eu _x ) O] _m (Lig) _n , where Lig is F, Cl, Br, O, S, Se [RF patent No. 205959], as well as yttrium oxysulfide activated by europium Y _2-x Eu _x O ₂ S _{1 ± 0.2} , where x = 0.001-0.1, which was previously used as an effective red phospholumin phosphor [RF patent 2160289 and USPatent No. 6153665].

A significant drawback of the compositions proposed in [RF 2059999, 2160289, US 6153665] is that all oxo-halides, and especially oxo-selenides of rare-earth elements, are destroyed in air in the presence of moisture.

The second drawback is that their luminescence spectrum is formed by a combination of several narrow peaks corresponding to transitions ⁵ D _J → ⁷ F _{J '} . In this case, the peaks with the highest intensity lie in the region of 610-630 nm. The presence of several narrow peaks, in contrast to a wide band, reduces the integral efficiency of the phosphor for the reason that under normal conditions the plant comes into contact with sunlight, the emission spectrum of which is continuous in the visible region. Since the width of the absorption bands in plants is much larger than that of the bands in the luminescence spectrum, the plant utilizes radiation not only of those wavelengths that corresponds to a narrow band in the luminescence spectrum, but a wider set of wavelengths in the absorption band.

The authors of the patent application USPatent Application 20100307055 (12/09/2010), PCT / GB 2008/003584 (10/22/2008) note that the excitation of the phosphor with ultraviolet radiation and subsequent highlighting in the red region can be observed as in the Ce (Mg, Mn) Al compositions claimed by them ₁₁ O ₁₉ : Cr and (Ba, Eu, Mn, Mg) Al ₁₀ O ₁₇ : Cr, as well as in aluminate phosphors with Ce, Mn, Cr, as well as in barium-magnesium aluminates (BAM) with Eu, Mn, Cr and in the general case in the families of aluminates, silicates, aluminosilicates, phosphates, borates and their mixtures in the presence of Fe, Cr, Ni, Mn, or other transition metals together Eu, Ce and other rare earths bubbled elements.

Closest to the proposed invention is the patent US 7536834 (05.26.2009) [PCT / FR 03/03283: 04/04/2003], which describes a light-converting material including barium-magnesium silicate phosphor activated by europium and manganese, composition:

Ba _{3 (1-x)} Eu _3x Mg _(1-y) Mn _y Si ₂ O ₈ , where 0 <x≤0.3 0 <y≤0.3.

The luminescence spectrum of this phosphor when excited by ultraviolet radiation (250-390 nm) included two broad bands in the blue-blue (400-500 nm) and red-orange (550-700 nm) regions. This patent has been selected as a prototype.

Compared with narrow-band phosphors, the composition proposed in the prototype has a higher integrated efficiency, but, as in previous technical solutions, the conversion of light in the film is carried out mainly due to the UV part of sunlight. Another disadvantage is that the proposed silicate phosphors, like oxo sulfides, are easily hydrolyzed.

The objective of the invention is to create a light-converting composite polymer material for greenhouses and greenhouses, which can significantly increase the intensity of phytoactive red radiation as a result of an increase in the proportion of light energy converted into red-orange radiation due to the conversion of primary light not only in ultraviolet, but also in visible parts of solar radiation.

The problem is solved by a light-converting composite polymer material, including a polymer matrix with a red inorganic broadband phosphor dispersed in it, belonging to the class of lithium-aluminum nitride silicates of alkaline earth metals, activated by europium, which converts not only ultraviolet, but also, partially, blue-green radiation from sunlight artificial light replacing it, with the conversion of the primary light flux into red-orange radiation, while the composition is the removed phosphor corresponds to the general formula:

Li _s (M _{(1-x) -} Eu _x ) ₁ Mg _m Al _n Si _p N _q

where M = Sr, Ca, Ba, taken separately or together, and where the values of the indices of the elements that make up the compound are:

0.045≤s≤0.60

0.005≤x≤0.12

0≤m≤0.12

0≤n≤1.0

1,0≤r≤2,40

3.015≤q≤4.20

with the restriction that for all compositions 2.0 ≤ p + n ≤ 2.40 and q ≠ 4.

There are two areas of practical use of the proposed light-converting composite materials based on the developed red phosphor, namely:

1) obtaining a covering film material for greenhouses with natural light.

2) obtaining thin-layer polymerizable paint coatings applied to the surface of glass or transparent polymeric materials and, in particular, polycarbonate.

In the first case, the red inorganic broadband phosphor is dispersed in a polymer matrix, which is used as a thermoplastic polymer from a group of substances including high and low pressure polyethylene, linear low density polyethylene, copolyolefins, copolymer blends, polyvinyl chloride, polycarbonate, methyl methacrylate, polystyrene, PET phthalate, silicone the concentration of the phosphor in the polymer matrix varies in the range of 0.05 to 10 wt. %

In the second case, the red inorganic broadband phosphor is dispersed in a polymer matrix, which is taken as a transparent, colorless, waterproof, curable in air, polymer varnish from the group of alkyd-urethane, alkyd-pentaphthalic, polyurethane, acrylic or silicone-acrylic compounds, while the concentration the phosphor in the polymer matrix varies in the range of 0.5 to 10 wt. %

Practical examples

Example No. 1 provides information on the composition, synthesis conditions, and optical properties of the proposed red phosphor. In examples No. 2-12, a description is made of the conditions for the preparation of light-converting composite materials with the participation of the obtained red phosphor.

Example No. 1

The synthesis of red phosphors was carried out using metal nitrides: Sr ₃ N ₂ , EuN, Mg ₃ N ₂ obtained by direct synthesis from Sr and Mg elements (3N: by Changlong Co. LTD), Eu (metal 4N: by Baotou rare earth element Co . LTD). The remaining nitrides were purchased from various companies, namely: Li ₃ N and Ca ₃ N ₂ (3N: Alfa-Aesa (Shanghai) Co. Ltd.), AlN (3N: by Sigma (Tianjin) Co. LTD), Si ₃ N ₄ (3N: by Japanese Yubu Co..LTD). For the introduction of europium, oxide (Eu ₂ O ₃ -4N: by Yangzhong rare earth Co LTD) or europium nitride obtained from elements was used. In this case, no significant differences in the optical characteristics of the samples were found.

Along with these substances for the synthesis of phosphors used fluvide - metal halides (CaF ₂ , BaF ₂ , BaCl ₂ , SrF ₂ ), introduced in an amount of 1.5-5 wt. % These substances are present at the stage of synthesis in the molten state. They increase the speed of transport of reacting substances and contribute to a homogeneous product.

Mixing and grinding of the starting materials was carried out in dry nitrogen in cabinets with a lock chamber. The resulting mixture of starting materials was loaded into a crucible of boron nitride with a tightly closed lid. After loading into the furnace, the sample was heated in a stream of 3H ₂ + N ₂ for 5 hours to 1700 ° C. The duration of calcination was 5 hours, after which the sample was cooled to 100 ° C for 8 hours. The particle size of the prepared samples (D50) was 8-10 microns according to data on laser light scattering.

Lighting characteristics [color coordinates (x, y): maximum position (λ _peak ), emission bandwidth at a wavelength corresponding to the maximum position (Δλ), and peak luminescence intensity (L)] are given in table No. 1.

The given set of samples gives an idea of a possible variation in the optical properties of phosphors. As can be seen, an increase in the concentration of europium in the phosphor leads to a shift in the maximum in the luminescence spectrum to the red region, but is accompanied by a noticeable decrease in the brightness of the glow. Despite the decrease in brightness, samples with a high concentration of europium are of considerable practical interest for a number of plants that absorb light with wavelengths greater than 650 nm.

In FIG. 1 for sample No. 2, the luminescence excitation spectrum (a line located in the wavelength region of 200-600 nm) and the luminescence spectrum excited by radiation with a wavelength of 455 nm are shown together. The left curve shows the dependence of the intensity of the excited luminescence (ordinate axis - arbitrary units) on the wavelength of the exciting light (abscissa axis). The stronger the absorption of light, the higher the intensity of the excited red luminescence. As can be seen, the sample effectively absorbs radiation not only in the ultraviolet range (200-400 nm), but also in the blue-green region of the spectrum (more than 60% at 500 nm and 15% at 560 nm). To the right of the luminescence excitation spectrum is the luminescence spectrum observed upon excitation by light with a wavelength of 455 nm. The maximum in the luminescence spectrum is located at 625.0 nm, and the width of the spectrum at half height is 88.2 nm.

Example No. 2

The light-converting covering material for greenhouses was obtained using red phosphor No. 2 and granules (≈3 × 3 × 3 mm) of high-pressure polyethylene, while the concentration of the phosphor in the polymer material was changed from 0.1 to 10 wt. % The process included the stage of preparation of the superconcentrate (masterbutch). For this, the granules of the starting polyethylene were first mixed with a powder phosphor. The mass fraction of the phosphor in the mixture was 5%. After that, the resulting mixture was heated to 140 ° C, stirred in the molten state and granulated. The size of the obtained granules of the superconcentrate was close to the size of the granules of the original polyethylene. The use of superconcentrate ensured uniform distribution of the phosphor throughout the volume.

The prepared superconcentrate was thoroughly mixed with granules of polyethylene in a mass ratio (1:49). Antioxidant (Irganox (0.1%), UV-protector (Tinuvin - 1.5%) and polyethylene glycol (PEG-400 - 0.1%) as a binding agent were also added to the mixture.

The concentration of the phosphor in the initial mixture of all components was 0.1 wt. %

The light-converting polymer composite film material was obtained by extrusion at 140 ° C. The thickness of the obtained film was 100 microns, the transparency of the film was 89.2%, and the scattering factor (Haze) on the solid particles of the introduced phosphor was 19.2. In FIG. Figure 2 shows the luminescence spectrum of the obtained film upon excitation of the glow by a blue LED with a wavelength of 455 nm. As can be seen, the absorbed blue radiation is transformed into the most phytosynthetically active radiation corresponding to the region (600-700 nm), and to a small extent into green-blue radiation. One can also observe the appearance of two narrow bands, the appearance of which, along with a wide band in the red region, is connected, as can be expected, with the redistribution of europium between the phases of the polymer matrix and the nitride phosphor.

Examples No. 3-6

According to the method described in example No. 2, samples of a light-converting composite polymer film material were prepared using the same starting materials. The concentration of the introduced red phosphor in the final product was 0.1; 0.3; 1.0; 5 and 10 wt. % Samples No. 3 and No. 4 were obtained using superconcentrate. The initial compositions for the film material in the case of samples No. 5 and No. 6 were prepared bypassing the stage of manufacturing a superconcentrate, i.e. by directly mixing the phosphor powder with polyethylene granules. The thickness of the obtained film in all cases was 100 μm.

Data on the characteristics of the obtained material depending on the content of the red phosphor are given in table. No. 2.

Example No. 7

The light-converting material for polymer coatings was made on the basis of transparent, colorless, waterproof varnishes, while the concentration of the phosphor in the polymer matrix was changed from 1 to 10%. Depending on the material of the surface to be painted, the varnish can belong to one of the following groups of compounds: alkyd-urethane, alkyd-pentaphthalic, polyurethane, acrylic silicone and silicone-acrylic.

In this example, the light-converting polymer material for paint coatings was made on the basis of the marketed JACHTLAK S-1006 alkyd-urethane varnish. Phosphor No. 2, taken in an amount of 1.5 g, was added to 48.5 g of varnish and mixed in a 3D mixer for 20 minutes. The resulting paint material containing 3 wt. % phosphor, luminescent in red when excited by a blue LED (455 nm). The luminescence spectrum did not differ from that shown in FIG. 1. After drying the applied coating at 85 ° C, the decrease in brightness with the invariance of the spectral composition of the glow did not exceed 5-7%.

Thus, the light-converting phosphor introduced into the polymer matrix effectively absorbs not only ultraviolet radiation in the region of 250-400 nm, but also blue and partially blue-green radiation, transforming it into red-orange radiation in the region of the spectrum where light stimulates growth and development green plants.

Example No. 8-12

In the examples below, light-transforming composite polymeric paints and varnishes were made using a colorless varnish based on acrylic polymers. The concentration of the red light-converting phosphor, with a maximum in the luminescence spectrum located at a wavelength of 650 nm, was varied from 1 to 10 wt. %

Table 3 shows the data on the intensity of red luminescence upon excitation by blue light with a wavelength of 455 nm.

As can be seen from the data presented, an increase in the concentration of the phosphor in the paint material over 5% does not increase the brightness of the luminescence, the intensity of which, however, is practically not reduced. This allows the use of more concentrated suspensions in order to reduce the number of applied layers of paint material in the manufacture of coatings.

Claims (5)

1. Light-converting composite polymer material for greenhouses and greenhouses, including a polymer matrix with an inorganic red broadband phosphor dispersed in it, the composition of which corresponds to the general formula:
Li _s (M _{(1-x) -} Eu _x ) ₁ Mg _m Al _n Si _p N _q ,
where M = Sr, Ca, Ba, taken separately or together, and where the values of the indices of the elements that make up the compound are:
0.045≤s≤0.60
0.005≤x≤0.12
0≤m≤0.12
0≤n≤1.0
1,0≤p≤2,40
3.015≤q≤4.20
with the restriction that for all compositions 2.0≤p + n≤2.40 and q ≠ 4. 2. The light-converting composite polymer material for greenhouses and greenhouses according to claim 1, characterized in that the thermoplastic polymer from the group of substances including high and low pressure polyethylene, linear low density polyethylene, copolyolefins, copolymer blends, polyvinyl chloride, polycarbonate is used as a polymer matrix , methyl methacrylate, polystyrene, polyethylene terephthalate, silicone. 3. The light-converting composite polymer material for greenhouses and greenhouses according to claim 1, characterized in that the polymer matrix is a transparent, colorless, waterproof, curable in the air polymer varnish from the group of alkyd-urethane, alkyd-pentaphthalic, polyurethane, acrylic or silicone acrylic compounds. 4. Light-converting composite polymer material for greenhouses and greenhouses according to claim 1 or 2, characterized in that the concentration of the phosphor in the polymer matrix varies in the range of 0.05-10.0 wt.%. 5. Light-converting composite polymer material for greenhouses and greenhouses according to claim 1 or 3, characterized in that the concentration of the phosphor in the polymer matrix varies in the range of 0.5-10.0 wt.%.

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