Reversible photochromic pigment, reversible photochromic agricultural functional film and preparation method of reversible photochromic agricultural functional film

Abstract

The invention provides a reversible photochromic pigment, a reversible photochromic agricultural functional film and a preparation method of the reversible photochromic agricultural functional film, and belongs to the technical field of agricultural films. The preparation method comprises the following steps: preparing a reversible photochromic pigment precursor from a polyacrylic acid solution, a tungstate solution, glycerol, a coloring pigment and a dispersant, then preparing a reversible photochromic pigment from the reversible photochromic pigment precursor, an initiator and a diluent, and finally preparing the reversible photochromic agricultural functional film. Comprising an anti-aging layer, a reversible color changing layer and a liquid drop preventing layer which are sequentially stacked, and the reversible color-changing layer is prepared by coating the anti-aging layer with a reversible light-changing pigment. The agricultural functional film provided by the invention is gradually changed from original white to different degrees of black under the irradiation of ultraviolet rays with different intensities, so that the light transmittance is reduced, the damage of strong sun illumination to seedlings under the film can be prevented, the light transmittance of the agricultural functional film is gradually increased along with the weakening of the ultraviolet rays, and the agricultural functional film has relatively strong photochromic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural films, and in particular to a reversible light-changing pigment and a reversible light-changing agricultural functional film and a preparation method thereof. Background Art

[0002] Agricultural films are a hallmark of modern agriculture, playing a significant role in improving low-temperature performance, retaining moisture, transforming soil nutrients, suppressing weeds, and optimizing soil microbial communities. Early inventions, such as black and white double-sided films, enhanced light reflection, lowered ground temperature, retained water, and eliminated weeds, primarily used for heat-resistant cultivation of vegetables and melons in summer and autumn. Advances in material technology and the high-quality development of modern agriculture have also placed new demands on the functionality of agricultural films. Consequently, functional films such as green, blue, red, purple, silver-gray, black, and light-converting films have emerged. The widespread use of agricultural films has expanded the cultivation period for many crops, particularly tobacco and vegetables, contributing significantly to the "off-season" effect and bringing significant economic benefits to farmers.

[0003] In order to deal with the problem of low temperature during the transplanting period, a technology of transplanting under film has been invented in agricultural production. That is, the plant seedlings are first transplanted in the ridge with holes, and then covered with agricultural film. The seedlings are allowed to grow under the film for a period of time. After the low temperature weather in the early stage of transplanting, the seedlings are taken out from under the film and grown on the film. Although this transplanting method can ensure that the plant seedlings are transplanted in advance and optimize the light, temperature and water resource allocation during the field period, when encountering continuous sunny and strong light weather, it will cause the temperature under the film to rise sharply in a short period of time, causing large-scale scalding or even death of seedlings. In production, to deal with this problem, agricultural producers often solve it by punching holes in the film to dissipate heat, but at night or in continuous low temperature and low light weather, it will cause plant seedlings to be frostbitten or seedling growth to stagnate. Regardless of the occurrence of any weather conditions, it has brought huge losses to agricultural production, and existing types of agricultural films have failed to effectively solve the above problems. Therefore, it is of great significance to study a reversible light-changing pigment and a reversible light-changing agricultural functional film and preparation method. Summary of the Invention

[0004] The purpose of the present invention is to provide a reversible light-changing pigment and a reversible light-changing agricultural functional film and a preparation method, so as to solve the problem of seedling scalding caused by strong light weather in agricultural films in the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a reversible light-changing pigment, which comprises the following raw materials in parts by weight: 2 to 40 parts of a reversible light-changing pigment precursor, 2 to 20 parts of an initiator, and 2 to 40 parts of a diluent;

[0007] The reversible light-variable pigment precursor is prepared from a polyacrylic acid solution, a tungstate solution, glycerol, a coloring pigment and a dispersant.

[0008] Preferably, the mass ratio of the polyacrylic acid solution, tungstate solution, glycerol, coloring pigment and dispersant is 100:15-25:12-25:1-5:1-5; the mass concentration of the polyacrylic acid solution is 0.5-1.5%; and the molar concentration of the tungstate solution is 0.5-1.5 mol / L.

[0009] The present invention also provides a reversible light-changing agricultural functional film, comprising an anti-aging layer, a reversible color-changing layer and a droplet-proof layer stacked in sequence; the reversible color-changing layer is made by coating a reversible light-changing pigment on the anti-aging layer.

[0010] Preferably, the raw materials of the anti-aging layer include base resin, inorganic filler and anti-aging agent.

[0011] Preferably, the raw materials of the anti-drip layer include base resin, inorganic filler and anti-fogging agent.

[0012] Preferably, the thickness of the anti-aging layer and the anti-drip layer are independently 10 to 50 μm; the thickness of the reversible color change layer is 5 to 25 μm.

[0013] The present invention also provides a method for preparing the above-mentioned reversible light-changing agricultural functional film, comprising the following steps:

[0014] (1) preparing an anti-aging layer and an anti-drip layer respectively by reacting, granulating and blowing films according to the above raw materials;

[0015] (2) laser etching the anti-aging layer, then coating it with a reversible light-changing pigment and drying it to obtain a reversible color-changing layer;

[0016] (3) The anti-aging layer, the reversible color-changing layer and the anti-drip layer are compounded by a three-layer co-extrusion method to obtain a reversible light-changing agricultural functional film.

[0017] Preferably, in step (2), the power of the laser etching is 1 to 2 W, and the scanning rate is 300 to 600 mm·s -1 .

[0018] Preferably, in step (2), the coating method is screen printing, and the process parameters are: the screen printing mesh is 150-300 mesh, the temperature is 20-30°C, the pressure is 1-10kgf / cm, the speed is 200-300m / min, the printing angle is 30°-50°, and the number of overprinting is 3-10 times.

[0019] Preferably, in step (3), the compounding temperature is 100-200°C.

[0020] Beneficial effects of the present invention:

[0021] The reversible light-changing pigment of the present invention can be used as a color-changing ink and is suitable for printing on various materials, including fabrics, paper, leather, synthetic films, toys, glass, ceramics, plastics, etc. Drying methods include air drying, baking drying, and UV curing.

[0022] The reversible light-changing pigment of the present invention can be used in coatings and is suitable for various surface coating products, including PMMA spray paint, ABS spray paint, PVC, PE, PP, PS, PVCPE, EVA, PET, spray paint and water-based spray paint.

[0023] The agricultural functional film prepared by the present invention gradually changes from its original white to different degrees of black under the irradiation of ultraviolet rays of different intensities, thereby reducing the light transmittance and preventing strong sunlight from causing damage to the seedlings under the film. As the ultraviolet rays weaken, the light transmittance of the agricultural functional film gradually increases, and it has strong photochromic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the reversible light-changing agricultural functional film of the present invention;

[0025] Figure 2 A physical picture of the reversible light-changing agricultural functional film prepared by the present invention;

[0026] Figure 3 This is a diagram showing the color change effect of the reversible light-changing agricultural functional film of the present invention under ultraviolet irradiation;

[0027] Figure 4 This is a comparison diagram of the reversible light-changing agricultural functional film of the present invention before and after color change;

[0028] Figure 5 Schematic diagram of the laser etching process. DETAILED DESCRIPTION

[0029] The present invention provides a reversible light-changing pigment, which comprises the following raw materials in parts by weight: 2 to 40 parts of a reversible light-changing pigment precursor, 2 to 20 parts of an initiator, and 2 to 40 parts of a diluent;

[0030] The reversible light-variable pigment precursor is prepared from a polyacrylic acid solution, a tungstate solution, glycerol, a coloring pigment and a dispersant.

[0031] In the present invention, the initiator includes one or more of benzophenone, epoxy acrylate, rose bengal and benzoyl peroxide.

[0032] In the present invention, the diluent includes one or more of ethanol, isopropanol, acetone, methyl ethyl ketone, dimethyl ether and butyl acetate.

[0033] In the present invention, the reversible light-changing pigment is preferably prepared according to a specific ratio of the reversible light-changing pigment precursor and the diluent. The ratio of the reversible light-changing pigment precursor and the diluent is preferably 1:1, 2:1, 4:1, 10:1, or 20:1.

[0034] In the present invention, the mass ratio of the polyacrylic acid solution, tungstate solution, glycerol, coloring pigment and dispersant is 100:15-25:12-25:1-5:1-5, preferably 100:18-22:14-22:2-4:2-4, and more preferably 100:20:16-18:3:3; the mass concentration of the polyacrylic acid solution is 0.5-1.5%, preferably 1%; and the molar concentration of the tungstate solution is 0.5-1.5 mol / L, preferably 1.0 mol / L.

[0035] In the present invention, the coloring pigment is preferably spiropyran; and the dispersant is preferably polyvinyl alcohol.

[0036] The present invention adds spiropyran as an active ingredient, which produces a synergistic effect with tungsten oxide in the reversible light-changing pigment precursor, thereby enhancing the photochromic effect of the system and improving the contrast and sensitivity during color change.

[0037] The present invention also provides a reversible light-changing agricultural functional film, comprising an anti-aging layer, a reversible color-changing layer and a droplet-proof layer stacked in sequence; the reversible color-changing layer is made by coating a reversible light-changing pigment on the anti-aging layer.

[0038] In the present invention, the anti-aging layer is the outer layer, the reversible color-changing layer is the middle layer, and the anti-drip layer is the inner layer.

[0039] In the present invention, the raw materials of the anti-aging layer include base resin, inorganic filler and anti-aging agent.

[0040] In the present invention, the raw materials of the anti-drip layer include base resin, inorganic filler and anti-fogging agent.

[0041] In the present invention, the matrix resin includes one or more of polyphenylene ether, polyethylene, polyvinylidene fluoride, polyvinyl chloride, poly-1-butene, polypropylene, poly-4-methyl-1-pentene, polyisobutylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer and ethylene-vinyl acetate copolymer.

[0042] In the present invention, the inorganic filler includes one or more of calcium carbonate, magnesium sulfate, talc, potassium sulfate, and mica powder.

[0043] The present invention has no particular limitation on the type of anti-aging agent, as long as it satisfies the anti-aging effect of the present invention. The anti-aging agent can be selected from hindered amine light stabilizers, phosphite antioxidants, and hindered phenol antioxidants.

[0044] The present invention has no particular limitation on the type of anti-fogging agent, as long as it meets the requirements of the present invention. The anti-fogging agent can be selected from fatty acid polyol esters, polyoxyethylene surfactants, and organic amine surfactants.

[0045] In the present invention, the mass ratio of the inorganic filler to the matrix resin is 1:15 to 30, preferably 1:20.

[0046] In the present invention, the mass ratio of the anti-aging agent to the base resin is 0.5-1.5:15-30, preferably 1:20.

[0047] In the present invention, the raw materials of the anti-aging layer may further include additives, and the additives include one or more of anti-ultraviolet agents, antioxidants, plasticizers, antistatic agents, colorants, lubricants and dispersants.

[0048] In the present invention, the thickness of the anti-aging layer and the anti-drip layer are independently 10 to 50 μm; the thickness of the reversible color change layer is 5 to 25 μm.

[0049] In the present invention, the width of the reversibly light-changing agricultural functional film is 800 to 1500 mm.

[0050] The present invention also provides a method for preparing the above-mentioned reversible light-changing agricultural functional film, comprising the following steps:

[0051] (1) preparing an anti-aging layer and an anti-drip layer respectively by reacting, granulating and blowing films according to the above raw materials;

[0052] (2) laser etching the anti-aging layer, then coating it with a reversible light-changing pigment and drying it to obtain a reversible color-changing layer;

[0053] (3) The anti-aging layer, the reversible color-changing layer and the anti-drip layer are compounded by a three-layer co-extrusion method to obtain a reversible light-changing agricultural functional film.

[0054] In the present invention, in step (1), the specific process of the reaction is: under the protection of inert gas, the base resin and the inorganic filler are mixed, the reaction pressure is controlled to be 100-500 Pa, and the reaction is carried out at 200-300° C. for 1-3 hours, then the temperature is increased to 250-350° C., the pressure is reduced to 40-80 Pa, and a condensation reaction is carried out for 1-3 hours, and then an anti-aging agent or an anti-fogging agent is added and mixed evenly.

[0055] In the present invention, the temperatures of the granulation and film blowing are independently 150-200°C.

[0056] In the present invention, two anti-aging layers of equal size and thickness are prepared, one of which is used to prepare the reversible color-changing layer.

[0057] In the present invention, in step (2), the power of the laser etching is 1 to 2 W, and the scanning rate is 300 to 600 mm·s -1 .

[0058] In the present invention, in step (2), the coating method is screen printing, and the process parameters are: the screen printing mesh is 150-300 mesh, the temperature is 20-30°C, the pressure is 1-10kgf / cm, the speed is 200-300m / min, the printing angle is 30°-50°, and the number of overprinting is 3-10 times.

[0059] In the present invention, in step (3), during the compounding, the side of the reversible color-changing layer coated with the reversible light-changing pigment faces the anti-aging layer.

[0060] In the present invention, the reversible color-changing layer is placed in the middle because the surface of the reversible light-changing pigment is not protected after being coated on the anti-aging layer after etching. Adding an anti-aging layer not only protects the reversible color-changing layer, but also prolongs the service life of the film.

[0061] In the present invention, in step (3), the compounding temperature is 100-200°C.

[0062] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0063] Example 1

[0064] The inorganic filler (calcium carbonate, talc powder, mica powder mixed according to 2:2:1) and the matrix resin (polyethylene resin and polypropylene resin mixed according to 3:2) were mixed evenly, wherein the mass ratio of the inorganic filler to the matrix resin was 1:20. Under the protection of inert gas, the pressure was controlled at 200Pa, the temperature was raised to 250℃, and the reaction was carried out for 2h. Then the temperature was raised to 300℃, the pressure was controlled at 60Pa, and the condensation reaction was carried out for 2h. Then, an anti-aging agent (anti-aging agent is UV-P, brand name Lianlong, in which the mass ratio of the anti-aging agent to the base resin is 1:20, is mixed evenly and then melted through a twin-screw extruder, extruded into granules at 180°C, and then sent to a film blowing machine for film blowing at 180°C. The above method is used to prepare two equal-sized anti-aging layers for use. The thickness of the anti-aging layer is 10 μm.

[0065] The above-mentioned anti-aging agent was replaced with an anti-fogging agent (the anti-fogging agent was Polyquart 149A, a brand of BASF), and an anti-drip layer was prepared in the same manner for standby use. The thickness of the anti-drip layer was 10 μm.

[0066] Polyacrylic acid was dissolved in deionized water to prepare a polyacrylic acid solution (mass concentration of 1%), and sodium tungstate solution (concentration of 1 mol / L), glycerol, spiropyran and polyvinyl alcohol were added under high-speed stirring conditions, wherein the mass ratio of the polyacrylic acid solution, sodium tungstate solution, glycerol, spiropyran and polyvinyl alcohol was 100:20:18:3:3, and the mixture was evenly mixed to obtain a reversible photochromic pigment precursor.

[0067] Take a piece of anti-aging layer and use laser etching to etch one side of the film surface. During laser etching, the laser etches the film surface through the mask. The process parameters are: etching power of 2W, scanning rate of 400mm·s -1 The etching depth is 1 μm and it will be used for future use after etching is completed.

[0068] 40 parts of a reversible photovariable pigment precursor, 20 parts of benzoyl peroxide and 40 parts of isopropyl alcohol were evenly mixed, and the mass ratio of the reversible photovariable pigment precursor to the isopropyl alcohol was 1:1 to obtain a reversible photovariable pigment. The reversible photovariable pigment was then coated on the film surface of the etched anti-aging layer by screen printing. The process parameters were: mesh size 200 mesh, temperature 25°C, printing pressure 5 kgf / cm, speed 250 m / min, angle 40°, overprinting times 5 times, and finally dried in a ventilated environment for 2 hours to obtain a reversible color-changing layer.

[0069] Take another unetched anti-aging layer, reversible color-changing layer and anti-drip layer, and use a three-layer co-extrusion blow molding machine to compound them at 150°C. During the compounding, the anti-aging layer is the outer layer, the reversible color-changing layer is the middle layer, and the anti-drip layer is the inner layer. The side of the reversible color-changing layer coated with the reversible photochromic pigment faces the anti-aging layer to obtain a reversible photochromic agricultural functional film.

[0070] Example 2

[0071] The difference from Example 1 is that the weight parts of isopropyl alcohol are 20 parts, the mass ratio of the reversible photovariable pigment precursor to isopropyl alcohol is 2:1, and other conditions are the same.

[0072] Example 3

[0073] The difference from Example 1 is that the weight parts of isopropyl alcohol are 10 parts, the mass ratio of the reversible photovariable pigment precursor to isopropyl alcohol is 4:1, and other conditions are the same.

[0074] Example 4

[0075] The difference from Example 1 is that the weight parts of isopropyl alcohol are 4 parts, the mass ratio of the reversible photovariable pigment precursor to isopropyl alcohol is 10:1, and other conditions are the same.

[0076] Example 5

[0077] The difference from Example 1 is that the weight parts of isopropyl alcohol are 2 parts, the mass ratio of the reversible photovariable pigment precursor to isopropyl alcohol is 20:1, and other conditions are the same.

[0078] Test method:

[0079] The agricultural functional films of Examples 1 to 5 and ordinary mulch films were used for light transmittance test. The ordinary mulch films of the control group were purchased from Shandong Changhao Plastic Industry Co., Ltd., and the base resin was polyethylene.

[0080] Before ultraviolet light irradiation, the corresponding transmittance was recorded using an ocean spectrometer. -2 After irradiation with 365nm ultraviolet light for 1 minute, the relevant transmittance data were recorded using an ocean spectrometer. 350nm was taken as the reference wavelength point to compare the transmittance data. The test results are shown in Table 1.

[0081] Table 1 Transmittance test results

[0082]

[0083]

[0084] The performance tests of the agricultural functional films and ordinary ground films prepared in Examples 1 to 5 were carried out, wherein the film thickness and tensile performance tests were carried out in accordance with GB13735-2017 "Polyethylene Blown Agricultural Ground Covering Film". The test results are shown in Table 2:

[0085] Table 2 Tensile properties test results

[0086]

[0087] The anti-ultraviolet performance of Examples 1 to 5 was tested using an ultraviolet light blocking tester, i.e., a solar film tester, which emits light containing the ultraviolet spectrum. After passing through the film to be tested, the instrument detects the intensity of the ultraviolet light after passing through and automatically calculates the blocking rate.

[0088] Table 3 Anti-ultraviolet performance test results

[0089]

[0090] It can be seen that the agricultural functional films prepared in Examples 1 to 5 have good color-changing effects and their light transmittance is significantly reduced, while the ordinary mulch films have no color-changing effects and their light transmittance remains unchanged.

[0091] It can be seen from Table 2 that as the proportion of the reversible photovariable pigment precursor gradually increases, the tensile properties of the film also gradually increase, indicating that the tensile strength of the agricultural functional film gradually increases, so that it has better tensile resistance during use and is less likely to be broken or damaged by external forces.

[0092] As can be seen from Table 3, as the content of the UV reversible photochromic pigment precursor increases, the UV resistance of the agricultural functional film significantly improves, as evidenced by a gradual decrease in transmittance and an increase in UV rejection. This demonstrates the effectiveness of the UV reversible photochromic pigment, which not only improves the UV rejection capability of the agricultural functional film but also imparts color-changing properties.

[0093] The agricultural functional film was prepared according to the method of Example 4, and then different etching depths were controlled to obtain agricultural functional films with different etching depths. The anti-ultraviolet performance of the films was tested, and the results are shown in Table 4.

[0094] Table 4 Anti-ultraviolet performance of agricultural functional films at different etching depths

[0095]

[0096] It can be seen from Table 4 that as the etching depth increases, the transmittance of the agricultural functional film decreases.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A reversible light-changing pigment, characterized in that: The reversible light-changing pigment comprises the following raw materials in parts by weight: 2 to 40 parts of a reversible light-changing pigment precursor, 2 to 20 parts of an initiator, and 2 to 40 parts of a diluent; The reversible light-variable pigment precursor is prepared from a polyacrylic acid solution, a tungstate solution, glycerol, a coloring pigment and a dispersant.

2. The reversible light-changing pigment according to claim 1, characterized in that: The mass ratio of the polyacrylic acid solution, tungstate solution, glycerol, coloring pigment and dispersant is 100:15-25:12-25:1-5:1-5; the mass concentration of the polyacrylic acid solution is 0.5-1.5%; and the molar concentration of the tungstate solution is 0.5-1.5 mol / L.

3. A reversible light-changing agricultural functional film, characterized in that: The invention comprises an anti-aging layer, a reversible color-changing layer and an anti-drip layer which are stacked in sequence; the reversible color-changing layer is made by coating the reversible light-changing pigment according to claim 1 or 2 on the anti-aging layer.

4. The reversible light-changing agricultural functional film according to claim 3, characterized in that: The raw materials of the anti-aging layer include base resin, inorganic filler and anti-aging agent.

5. The reversible light-changing agricultural functional film according to claim 3 or 4, characterized in that: The raw materials of the anti-drip layer include base resin, inorganic filler and anti-fogging agent.

6. The reversible light-changing agricultural functional film according to claim 5, characterized in that: The thickness of the anti-aging layer and the anti-drip layer is independently 10 to 50 μm; the thickness of the reversible color change layer is 5 to 25 μm.

7. The method for preparing the reversibly light-changing agricultural functional film according to any one of claims 3 to 6, characterized in that: The steps include: (1) preparing an anti-aging layer and an anti-drip layer respectively by reacting, granulating and blowing films according to the above raw materials; (2) laser etching the anti-aging layer, then coating it with a reversible light-changing pigment and drying it to obtain a reversible color-changing layer; (3) The anti-aging layer, the reversible color-changing layer and the anti-drip layer are compounded by a three-layer co-extrusion method to obtain a reversible light-changing agricultural functional film.

8. The method for preparing a reversibly light-changing agricultural functional film according to claim 7, characterized in that: In step (2), the power of the laser etching is 1-2W, and the scanning rate is 300-600mm·s -1 .

9. The method for preparing a reversibly light-changing agricultural functional film according to claim 7 or 8, characterized in that: In step (2), the coating method is screen printing, and the process parameters are: the screen printing mesh is 150-300 mesh, the temperature is 20-30°C, the pressure is 1-10kgf / cm, the speed is 200-300m / min, the printing angle is 30°-50°, and the number of overprinting is 3-10 times.

10. The method for preparing a reversibly light-changing agricultural functional film according to claim 9, characterized in that: In step (3), the compounding temperature is 100-200°C.

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