A fruit anti-sunburn protective agent, and a preparation method and application thereof

Abstract

The application discloses a fruit anti-sunburn protective agent, which is prepared from the following raw materials in parts by mass: 1-20 parts of monodisperse calcium carbonate filter cake, 0.01-0.9 parts of ethoxylated polysiloxane, 0.01-0.8 parts of polyvinyl acetate emulsion, 0.01-0.8 parts of glycerol, 0.01-0.8 parts of enzyme and 10-180 parts of water. The raw materials are mixed in two steps in a certain order, and a new type of fruit anti-sunburn protective agent is obtained after stirring and dispersing. The fruit anti-sunburn protective agent can be used for fruit anti-sunburn planting after being diluted with water to a solid content of calcium carbonate of 2-6%. The fruit anti-sunburn protective agent is safe and non-toxic, and can be sprayed on the surface of fruits or the leaves of fruit trees when used, so that the risk of sunburn of fruits and fruit trees caused by strong sunlight can be obviously avoided, the disease resistance and adversity resistance of the fruit trees are improved, and the probability of sunburn spots, sun fruits and diseased fruits is reduced. The fruit anti-sunburn protective agent has little influence on the transmission of visible light, does not affect the normal photosynthesis of the fruit trees, and can obviously improve the yield and quality of fruits in fruit planting compared with other shading modes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of plant growth protectants, and particularly relates to a fruit anti-sunburn protectant and a preparation method and application thereof. BACKGROUND

[0002] Fruit sunburn is a physiological disease caused by solar radiation heat. In most regions of China, during the late summer and early autumn, the weather is sunny, the air temperature is relatively high, the solar radiation intensity and radiation time are in the longest period of the year, and long-term high-intensity sunlight radiation can make the field air temperature reach above 40 DEG C, and the temperature of the fruit surface and leaf surface directly exposed to sunlight can be as high as 55-60 DEG C, resulting in high-temperature dehydration of leaves and fruits and destruction of the antioxidant defense system, causing sunburn, which is irreversible.

[0003] Sunburn mainly harms fruits in the expansion period and large leaves directly exposed to the sun. After the occurrence of sunburn, a yellow halo appears on the fruit, which is usually circular, and then gradually expands, the oil cell of the fruit skin cell ruptures, and finally turns brown and black and dies. Sunburn is relatively common, and even if there is no obvious disease on the fruit skin, the fruit pulp will also be lignified due to high-temperature dehydration, losing its edible value. In addition, sunburn can form yellowish green spots on the leaf surface, which are easily infected with anthracnose after rain, so sunburn not only directly damages the fruit trees, but also significantly reduces the stress resistance of the fruit trees.

[0004] At present, measures such as bagging, covering sunshade nets, and applying lime milk are often used to prevent sunburn during fruit tree planting. These measures can achieve certain effects, but have problems such as high cost, large demand for labor, and poor comprehensive effect. Some protective measures also have their own negative effects that cannot be overcome, for example, both bagging and covering sunshade nets will inhibit the normal photosynthesis of fruit trees, and the application of lime milk will bring huge labor costs. Therefore, it is urgent to develop a safe and low-cost protective agent that can effectively protect fruits from sunburn damage. SUMMARY

[0005] The main purpose of the present application is to provide a fruit anti-sunburn protective agent, which can be directly sprayed onto the surface of the fruit or the leaves of the fruit tree, can significantly avoid the risk of sunburn of the fruit and the fruit tree, can improve the disease resistance and stress resistance of the fruit tree, and can reduce the probability of sunburn spots, sun fruits, and diseased fruits.

[0006] The technical scheme adopted by the present application to achieve the above purpose is as follows:

[0007] A fruit anti-sunburn protective agent, which comprises, by mass fraction, 1-20 parts of monodisperse calcium carbonate filter cake, 0.01-0.9 parts of ethoxylated polytrisiloxane, 0.01-0.8 parts of polyvinyl acetate emulsion, 0.01-0.8 parts of glycerol, 0.01-0.8 parts of enzyme, and 10-180 parts of water.

[0008] Further preferably, the fruit anti-sunburn protective agent, whose raw material composition comprises, in terms of mass fraction: 1-20 parts of monodispersed calcium carbonate filter cake, 0.01-0.5 parts of ethoxylated polysiloxane, 0.02-0.8 parts of polyvinyl acetate emulsion, 0.01-0.5 parts of glycerol, 0.01-0.8 parts of enzyme, and 30-166 parts of water.

[0009] Further, the mass of the monodispersed calcium carbonate filter cake is 20-150 times, preferably 20-90 times, of the mass of the ethoxylated polysiloxane.

[0010] Further, the mass of the water is 1.9-30 times, preferably 9-15 times, of the mass of the monodispersed calcium carbonate filter cake.

[0011] Further, the mass of the monodispersed calcium carbonate filter cake is 25-60 times of the mass of the polyvinyl acetate emulsion.

[0012] Further, the mass of the monodispersed calcium carbonate filter cake is 36-300 times, preferably 36-100 times, of the mass of the glycerol.

[0013] Further, the mass of the monodispersed calcium carbonate filter cake is 25-300 times, preferably 25-100 times, of the mass of the enzyme.

[0014] According to the above scheme, the monodispersed calcium carbonate filter cake has the following characteristics: the filter cake has a water content of 35%-40%, the calcium carbonate particles have a cubic or near-spherical shape, the average particle size is between 200 nm and 400 nm, and the number of particles with a particle size greater than 400 nm is less than 5%; the particle surface is clean and in a monodispersed state, has a small surface energy, and has a specific surface area of less than 17 m 2 / g, preferably 13-15 m 2 / g; the content of harmful metal elements such as cadmium in the calcium carbonate is less than 200 ppm; the monodispersed calcium carbonate filter cake can be stirred and dispersed in an aqueous solution without adding any chemical dispersant and can be stably suspended. Specifically, the monodispersed calcium carbonate filter cake is dispersed in water to obtain a suspension; when the solid content of the suspension is 2%-5%, the suspension can be stably suspended for more than 2 hours.

[0015] According to the above scheme, the method for preparing the monodispersed calcium carbonate filter cake comprises the following steps:

[0016] S1. Adopting calcination, digestion, carbonization and other processes to prepare calcium carbonate slurry. Among them, the calcination process is: selecting limestone with uniform grain size, harmful heavy metal content of cadmium, lead, chromium and other harmful heavy metals less than 400ppm as raw material, adopting calcination temperature matching with grain size, obtaining ideal activity of quicklime, the activity of quicklime is between 250-300mL(4mol / L HCl, 40±1℃, 10min), uniformity and consistency are good; the digestion process is: digesting the quicklime obtained by the above calcination in hot water at 50-90℃ to obtain lime milk; the storage and impurity removal process is: storing the lime milk slurry obtained by digestion for 24-48h, and removing impurities after filtration to obtain refined slurry; the carbonization process is: adjusting the solid content of refined slurry to 8%-12% by adding water, then carbonizing, the initial carbonization temperature is 20-30℃, CO2 content is 30%-40%, carbonizing until the slurry pH reaches 7.5-8.5, ending carbonization, obtaining calcium carbonate slurry;

[0017] The calcium carbonate particles in the calcium carbonate slurry are near-spherical or chain-shaped, the average particle size of the near-spherical particles is 100-150nm, and the average width(transverse dimension) of the chain-shaped particles is 100-150nm;

[0018] S2. Adding inorganic salt grain surface restructuring agent and organic grain surface restructuring agent to the calcium carbonate slurry obtained in S1, then heat treating at 160-200℃ for 2.0-6.0h to obtain calcium carbonate suspension; wherein the inorganic grain surface restructuring agent is one or more of sodium silicate, sodium chloride, aluminum chloride, zinc sulfate and other inorganic salts, the amount is 0.5%-3% of the dry mass of calcium carbonate; the organic grain surface restructuring agent is one or more of ethanol, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, sodium dodecyl sulfate, ethylenediaminetetraacetic acid disodium salt and other organic substances, the amount is 1%-5% of the dry mass of calcium carbonate;

[0019] S3. Filtering and dewatering the calcium carbonate suspension obtained in S2 to obtain calcium carbonate filter cake, the water content of the filter cake is controlled between 35%-40%, that is, monodisperse calcium carbonate filter cake. At this time, it meets the characteristics of "calcium carbonate particle morphology is cubic or near-spherical, average particle size is between 200-400nm, particles with a particle size greater than 400nm are less than 10%; the particle surface is clean, in a monodisperse state, with small surface energy, the specific surface area is less than 17m 2 / g; the content of harmful metal elements such as cadmium in calcium carbonate is less than 200ppm; it can be dispersed in aqueous solution without adding any chemical dispersant after stirring and keep stable suspension".

[0020] According to the above scheme, the enzyme is a commercially available agricultural enzyme, and the enzyme contains agricultural biological agents, polysaccharides, amino acids and other components, and is used in cooperation with calcium carbonate, so that the level of micro-nano calcium carbonate absorbed from plants can be improved.

[0021] The preparation method of the fruit sunburn protection agent comprises the following steps:

[0022] (1) According to the mass fraction of each raw material of the sunburn protection agent according to the present application, 1-20 parts of monodisperse calcium carbonate filter cake, 0.01-0.9 parts of ethoxylated polytrisiloxane, 0.01-0.8 parts of polyvinyl acetate emulsion, 0.01-0.8 parts of glycerol, 0.01-0.8 parts of enzyme, and 10-180 parts of water are prepared;

[0023] (2) The monodisperse calcium carbonate filter cake is placed in a small amount of water (here, the weight of the "small amount of water" is 1-2 times the weight of the monodisperse calcium carbonate filter cake in the formula) at a temperature of 5-30°C, and is dispersed in a high-speed dispersing machine at a linear speed of 80-120 m / min at room temperature for 15-40 min;

[0024] (3) After the stirring in step (2) is completed, the remaining other raw materials and the remaining amount of water are added, and the dispersion is continued in the high-speed dispersing machine at a linear speed of 80-120 m / min for 15-30 min, and the fruit sunburn protection agent according to the present application is obtained.

[0025] When the fruit sunburn protection agent according to the present application is used, it is diluted with water to a solid content of calcium carbonate of 2%-6% for spraying.

[0026] According to the above scheme, the fruits to which the sunburn prevention agent according to the present application can be applied include citrus, apples, pears, grapes, dragon fruits, kiwis, and pomelos.

[0027] The application method of the fruit sunburn protection agent according to the present application is as follows: in dry and rainless weather, the fruit sunburn protection agent according to the present application is diluted and sprayed on the surface of the fruit (generally diluted to a solid content of calcium carbonate of 2%-6% before spraying), without the need to specially avoid branches and leaves, and according to the different types of fruits, 1-4 times of spraying are required during the ripening process of the fruits; when it rains for more than 5 days within 24 hours after spraying, and the total rainfall reaches 250 mm or more, it is necessary to spray again after the rain.

[0028] The present application selects limestone with uniform grain size and harmful heavy metal content less than 400 ppm, such as cadmium, lead and chromium, as raw material for preparing monodisperse calcium carbonate filter cake, and then adopts calcination temperature matching the grain size to obtain lime with moderate and uniform activity, which is carbonized after slaking to obtain calcium carbonate slurry. The limestone with uniform grain size adjusts the activity of lime through limestone calcination process, avoiding partial under-burning and partial over-burning caused by spotted grain. The lime with good uniformity and moderate activity is conducive to the control of slaking reaction, obtaining uniform lime milk with controllable properties, and then realizing the control of the later carbonization process, thereby obtaining calcium carbonate slurry with expected particle size and grain morphology. The harmful heavy metal content in limestone, such as cadmium, lead and chromium, is less than 400 ppm, which can ensure that the harmful heavy metal content in the prepared monodisperse calcium carbonate filter cake is less than 200 ppm.

[0029] After the carbonization is completed, there is a process step of grain surface reconstruction, which is to add inorganic surface reconstruction agent and organic surface reconstruction agent and keep at a certain temperature to promote the grain surface reconstruction, so that the crystal is more complete and the particle surface is smoother, thereby reducing the surface energy and being conducive to dispersion. The inorganic surface reconstruction agent promotes the crystal growth and repairs defects, so that the crystal is more complete; the organic surface reconstruction agent adjusts the surface potential of the particle and controls the mutual repulsion of the grains in water, avoiding the adhesion during the crystal repair process. The present application controls the average particle size of calcium carbonate particles to be 200-400 nm and in high monodisperse state by controlling the grain surface reconstruction temperature and time. The calcium carbonate particles in this form can ensure the diffraction of visible light in the wavelength range of 400-800 nm to be transmitted, so as to not affect the photosynthesis of fruits and the surface coloring, and can effectively absorb the ultraviolet light harmful to plants (for example, the anti-sunscald protective agent described in the present application is diluted to 2% solid content of calcium carbonate, sprayed to form a film, and the absorption of ultraviolet light can be more than 90%, and the absorption of visible light is less than 40%). The present application utilizes the wide absorption band of calcium carbonate near 1425 wave number to realize the absorption of infrared in the solar spectrum and the atmospheric emission, thereby significantly reducing the fruit surface temperature. The monodisperse calcium carbonate slurry obtained by grain surface reconstruction is then subjected to pressure filtration or centrifugation to obtain monodisperse calcium carbonate filter cake with the required particle size. The pressure filtration and centrifugation can remove excess water to form monodisperse calcium carbonate filter cake, which is conducive to the processing and transportation of calcium carbonate, and also rapidly reduces other soluble ions existing in the solution in the production process, thereby not affecting and interfering with the use and performance of the fruit anti-sunscald protective agent of the present application.

[0030] On the basis of the above, the fruit anti-sunburn protective agent is obtained by dispersing the monodisperse calcium carbonate filter cake and other raw materials in clean water. The monodisperse calcium carbonate filter cake maintains 35-40% moisture, maintains water film and double-layer structure between calcium carbonate solid particles, can maximize the surface state of calcium carbonate particles and repulsion, and does not produce agglomeration, so that the calcium carbonate particles can be quickly dispersed in the aqueous solution again under the assistance of a dispersing machine and can be stably suspended.

[0031] The fruit anti-sunburn protective agent is sprayed on the surface of the fruit, and a light white protective film can be quickly formed. Due to the special particle size and dispersibility design of calcium carbonate, the protective film does not affect the transmission of visible light, and therefore does not affect the photosynthesis of the fruit. In addition, the fruit anti-sunburn protective agent can effectively reduce the sunburn of the fruit surface caused by ultraviolet rays and reduce the temperature of the fruit by utilizing the ultraviolet light absorption and infrared radiation characteristics of calcium carbonate and combining the particle size design of the fruit anti-sunburn protective agent.

[0032] Compared with the prior art, the fruit anti-sunburn protective agent has the following beneficial effects:

[0033] 1. The fruit anti-sunburn protective agent is directly sprayed on the surface of the fruit, without the need to specially avoid branches and leaves, can significantly avoid the risk of sunburn of the fruit and the fruit tree, can effectively absorb ultraviolet rays and radiate infrared rays, and can reduce the temperature of the fruit surface, thereby reducing the probability of sunburn spots, sun fruits and diseased fruits.

[0034] 2. The fruit anti-sunburn protective agent is safe and non-toxic, is directly sprayed on the surface of the fruit and the leaf surface of the fruit tree, has good physical protection effect, significantly improves the disease resistance and stress resistance of the fruit, and can significantly improve the yield and quality of the fruit compared with other shading methods.

[0035] 3. The fruit anti-sunburn protective agent is sprayed on the surface of the fruit and the leaf surface of the fruit tree, does not affect the transmission of visible light, does not interfere with the normal photosynthesis of the fruit, increases the fullness of the fruit, and significantly improves the taste and quality of the fruit. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The scanning electron microscope photograph of the calcium carbonate particles in the calcium carbonate slurry prepared in Example 1 is shown in the figure.

[0037] Figure 2 The scanning electron microscope photograph of the monodisperse calcium carbonate prepared in Example 1 is shown in the figure.

[0038] Figure 3 The use effect of the anti-sunburn protective agent prepared in Example 1 on citrus is shown in the figure.

[0039] Figure 4Comparison of the surface temperature of the citrus fruit sprayed with the anti-sunburn protective agent prepared in Example 1 (left) and the surface temperature of the citrus fruit sprayed with water (right);

[0040] Figure 5 Comparison of the flesh of the mature fruit of the citrus fruit sprayed with the anti-sunburn protective agent prepared in Example 1 and the fruit sprayed with water;

[0041] Figure 6 Scanning electron microscope photograph of the calcium carbonate particles in the calcium carbonate slurry prepared in Example 2;

[0042] Figure 7 Scanning electron microscope photograph of the monodisperse calcium carbonate prepared in Example 2;

[0043] Figure 8 Effect diagram of the use of the anti-sunburn protective agent prepared in Example 2 on the apple;

[0044] Figure 9 Scanning electron microscope photograph of the calcium carbonate particles in the calcium carbonate slurry prepared in Example 3;

[0045] Figure 10 Scanning electron microscope photograph of the monodisperse calcium carbonate prepared in Example 3;

[0046] Figure 11 Effect diagram of the use of the anti-sunburn protective agent prepared in Example 3 on the pear;

[0047] Figure 12 Scanning electron microscope photograph of the calcium carbonate particles in the calcium carbonate slurry prepared in Example 4;

[0048] Figure 13 Scanning electron microscope photograph of the monodisperse calcium carbonate prepared in Example 4;

[0049] Figure 14 Scanning electron microscope photograph of the calcium carbonate prepared in Comparative Example 1;

[0050] Figure 15 Effect diagram of the use of the anti-sunburn protective agent prepared in Example 4 on the pitaya;

[0051] Figure 16 Comparison diagram of the effect of dispersing the calcium carbonate prepared in the examples and comparative examples in water;

[0052] Figure 17 Effect diagram of the use of the anti-sunburn protective agent prepared from the calcium carbonate of Comparative Examples 1 and 2 on the citrus fruit;

[0053] Figure 18 Scanning electron microscope photograph of the calcium carbonate prepared in Comparative Example 2;

[0054] Figure 19The use effect diagram of the anti-sunburn protective agent for apples prepared by using the calcium carbonate of Comparative Example 3;

[0055] Figure 20 The use effect diagram of the anti-sunburn protective agent for pears prepared by using the calcium carbonate of Comparative Example 4. Specific implementation method

[0056] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0057] In the following examples, the ethoxy-modified polysiloxane is a commercially available product, which is purchased from GE Silicone USA Company, and the model number is Silwet, and the effective ingredient is greater than 98%.

[0058] In the following examples, the polyvinyl acetate emulsion is a commercially available reagent, also known as polyvinyl acetate, and the CAS number is 9003-20-7.

[0059] In the following examples, the glycerol is a commercially available product, and the product index meets the requirements of the national standard GB / T 13206-2022.

[0060] In the following examples, the enzyme is a commercially available agricultural enzyme, and the main component is an agricultural biological agent, and it also contains components such as polysaccharides and amino acids, which is purchased from Jining Alida Biological Engineering Co., Ltd., and the model number is MLQ-plant enzyme.

[0061] Example 1

[0062] The present example provides a fruit anti-sunburn protective agent prepared from the following raw materials in mass parts: monodisperse calcium carbonate filter cake 20 parts, ethoxy-modified polysiloxane 0.5 parts, polyvinyl acetate emulsion 0.8 parts, glycerol 0.1 parts, enzyme 0.8 parts, and water 38 parts.

[0063] The preparation method of the fruit anti-sunburn protective agent described in the present example is as follows: according to the above raw materials and mass parts, 20 parts of monodisperse calcium carbonate filter cake is placed in 28 parts of water, and stirred at a stirring speed of 100 m / min for 40 min by using a high-speed dispersing machine, then 0.5 parts of ethoxy-modified polysiloxane, 0.8 parts of polyvinyl acetate emulsion, 0.1 parts of glycerol, 0.8 parts of enzyme and the remaining 10 parts of water are added according to the above formula, and the stirring is continued at a stirring speed of 120 m / min for 15 min, thereby obtaining the anti-sunburn protective agent described in the present example, and the solid content of calcium carbonate is about 20%.

[0064] In the present example, the monodisperse calcium carbonate filter cake used has the following preparation steps:

[0065] S1. Adopting calcination, digestion, carbonization and other processes to prepare calcium carbonate slurry. Among them, the calcination process is: selecting limestone with grain size of 0.2-0.5mm and harmful heavy metal content of cadmium, lead, chromium and other harmful heavy metals less than 400ppm as raw material, adopting calcination temperature of 900℃, calcining for 2h to obtain ideal activity of quicklime; the digestion process is: digesting the quicklime obtained by the above calcination with water at 90℃ to obtain lime milk, and storing for 24h to remove impurities to obtain refined raw slurry; the carbonization process is: adjusting the solid content of the refined raw slurry obtained by digestion to 10% by adding water, then carbonizing, the initial carbonization temperature is 20℃, the CO2 content is 33%, carbonizing until the slurry pH reaches 7.5-8.5, ending the carbonization to obtain calcium carbonate slurry;

[0066] From the scanning electron microscope photos (see Figure 1 ), it can be observed that the calcium carbonate particles in the obtained slurry are chain-shaped, and the average width of the particles is about 110nm;

[0067] S2. Adding 0.5% aluminum chloride, 1.0% sodium silicate, 2.0% ethanol and 0.5% disodium ethylenediaminetetraacetate to the calcium carbonate slurry obtained in S1 based on the mass of calcium carbonate dry basis, and keeping at 160℃ for 4.0h to obtain a calcium carbonate suspension;

[0068] S3. Filtering and dewatering the calcium carbonate suspension obtained in S2 to obtain a calcium carbonate filter cake, and controlling the moisture content of the filter cake to be between 35%-40%, i.e. monodisperse calcium carbonate, at this time, taking an appropriate amount of filter cake, drying it at 105℃, and then testing and analyzing its composition, specific surface area, micro-morphology and particle size according to the "Calcium Carbonate Analysis Method" (GB / T 19281-2014) standard and the "Nanometer Calcium Carbonate" (GB / T 19590-2023) standard. The harmful impurities content of cadmium, lead, barium, mercury, arsenic and other harmful impurities in the obtained monodisperse calcium carbonate is less than 0.0002%, and the total content of harmful impurities is less than 200ppm; the specific surface area is about 16.86m 2 / g; from the scanning electron microscope photos (see Figure 2 ), it can be clearly seen that the average particle size of the obtained monodisperse calcium carbonate is about 200nm, and the particles are cubic with smooth and clean surface. Dispersing the monodisperse calcium carbonate filter cake in clean water to obtain a suspension with a solid content of 2%, and then observing the suspension effect after standing for 2h (see Figure 16 ).

[0069] Application test: the fruit anti-sunburn protective agent prepared in this embodiment is used for citrus anti-sunburn planting, and the specific process is as follows: before the fruit enlargement period or the middle period, at the end of June to the beginning of July every year, before the high temperature above 30℃ and strong sunlight environment, the anti-sunburn protective agent is diluted 4 times (the solid content of calcium carbonate after dilution is about 5%) and sprayed on the surface of citrus fruits and the parts of branches and leaves that are easy to be exposed to sunlight, and then the growth of the whole citrus tree is recorded by taking pictures. After that, the observation is carried out once a month. If it rains for more than 5 days within 24 hours after spraying, and the total rainfall reaches 250 mm or more, the spraying needs to be supplemented after the rain. The spraying needs to be supplemented once again in the late fruit enlargement period, and the anti-sunburn protective agent is diluted 6 times (the solid content of calcium carbonate after dilution is about 3%) and sprayed on the surface of citrus fruits and the parts of branches and leaves that are easy to be exposed to sunlight.

[0070] As shown in Figure 3 , the fruit anti-sunburn protective agent is uniformly attached to the surface of citrus fruits and leaves, forming a thin and uniform protective film; as shown in Figure 4 , the temperature of the surface of the citrus fruits sprayed with water is 49.9℃, while the temperature of the surface of the citrus fruits sprayed with the fruit anti-sunburn protective agent prepared in this embodiment is 39.7℃, and the fruit surface temperature is effectively reduced by about 26%.

[0071] After the citrus fruits sprayed with the fruit anti-sunburn protective agent of this embodiment and the citrus fruits sprayed with water are matured, the state of the pulp is observed (see Figure 5 ), the pulp of the citrus fruits sprayed with water appears dry, while the pulp of the citrus fruits sprayed with the fruit anti-sunburn protective agent of this embodiment is sweet and juicy. Compared with the spraying of water, the spraying of the fruit anti-sunburn protective agent of this embodiment can effectively prevent the occurrence of citrus sunburn disease, and the incidence of sunburn disease is reduced by 100%.

[0072] The price of the fruit anti-sunburn protective agent of this embodiment is calculated in detail, and the cost per year per mu is only about 780 yuan. The specific calculation of the cost is as follows: one mu is about 100 fruit trees, the annual fruit yield is about 3600 jin, the anti-sunburn protective agent is used at a dosage of 35 kg per mu, the unit price is about 10 yuan per kg, the unmanned aerial vehicle is used for spraying, and the machine rental fee (including labor cost) is about 40 yuan per mu per time. The cost of spraying twice a year in one mu is (2*35*10+2*40) yuan, that is, 780 yuan per mu. The economic loss of not spraying the anti-sunburn protective agent is calculated as follows: the bad fruit rate is 20%, the selling price of citrus is 1.5 yuan per jin, and the selling price of the fruit with poor appearance is 0.2 yuan per jin. The economic loss is estimated to be 1656 yuan per mu (3600*1.5-3600*0.8*1.3). The fruit anti-sunburn protective agent can save 876 yuan per mu of economic loss, improve the economic benefit, and has a broad market prospect.

[0073] Example 2

[0074] The present embodiment provides a monodisperse calcium carbonate fruit anti-sunburn protective agent prepared from the following raw materials in parts by mass: monodisperse calcium carbonate filter cake 1 part, ethoxylated modified polysiloxane 0.05 part, polyvinyl acetate emulsion 0.02 part, glycerol 0.01 part, enzyme 0.01 part, and water 30 parts.

[0075] The preparation method of the monodisperse calcium carbonate fruit anti-sunburn protective agent described in the present embodiment is as follows: according to the above raw materials and mass parts, 1 part of monodisperse calcium carbonate filter cake is placed in 2 parts of water, and stirred at a stirring line speed of 80 m / min for 40 min using a high-speed disperser. Then, 0.05 parts of ethoxylated modified polysiloxane, 0.02 parts of polyvinyl acetate emulsion, 0.01 parts of glycerol, 0.01 parts of enzyme, and the remaining 28 parts of water are added according to the above formulation, and stirring is continued at a stirring line speed of 80 m / min for 20 min. The anti-sunburn protective agent described in the present embodiment is obtained, and the solid content of calcium carbonate is about 2%.

[0076] In the preparation steps of the monodisperse calcium carbonate filter cake, the difference from Example 1 is that the digestion temperature of step S1 is 50°C, the aging time is 48 h, the refined raw slurry solid content during carbonation is 12%, the CO2 content is 40%, the carbonation is ended when the pH reaches 7.5-8.0, and the calcium carbonate particles in the obtained mature slurry are characterized for microscopic morphology after the carbonation is ended. It can be observed that the calcium carbonate particles are in the form of near-spherical and short rod-like, and the average particle size is about 149 nm (see Figure 6 ); 1.0% zinc sulfate, 0.5% aluminum chloride, and 2.0% polyvinyl alcohol based on the mass of the calcium carbonate dry base are added during the crystal grain surface reconstruction process, and the temperature is kept at 180°C for 3.0 h.

[0077] The same test method as in Example 1 is used to test and analyze the composition, specific surface area, microscopic morphology, and particle size of the monodisperse calcium carbonate filter cake obtained in the present embodiment. The harmful impurities such as cadmium, lead, barium, mercury, and arsenic in the obtained monodisperse calcium carbonate are less than 0.0002%, and the total content of harmful impurities is less than 200 ppm; the specific surface area is about 14.27 m 2 / g; from the SEM photo (see Figure 7 ), it can be clearly seen that the average particle size of the obtained monodisperse calcium carbonate is about 260 nm, and the particles are in the form of cubes with smooth and clean surfaces. The monodisperse calcium carbonate filter cake is dispersed in clean water to obtain a suspension with a solid content of 2%, and then the suspension effect is observed after standing for 2 h. It can be stably suspended (see Figure 16 ).

[0078] For apple spraying: before the apple fruit swelling period, the anti-sunburn protective agent prepared in this example is directly sprayed on the surface of the apple fruit, and the spraying process does not need to be particularly avoided from the leaves and branches of the apple tree. After spraying, the growth status of the apple tree is recorded by taking pictures, and then it is observed regularly every week. During the maturation process of the apple, it needs to be sprayed 2-3 times, and if it encounters 5 days or more of continuous rainfall, and the total rainfall reaches 250 mm or more, it needs to be sprayed once after the rain.

[0079] The use effect diagram of the anti-sunburn protective agent for apples in this example is shown in Figure 8 After spraying, compared with bagging, the anti-sunburn protective agent of this example can effectively prevent the occurrence of apple sunburn disease, and the incidence of sunburn disease is reduced by 100%.

[0080] The price of the product of this example is calculated in detail, and the cost per year per mu is only about 580 yuan. The specific cost calculation is as follows: one mu of land is about 100 fruit trees, and the annual fruit yield is about 2500 kg. The anti-sunburn protective agent dosage is 250 kg / mu, the unit price of the anti-sunburn protective agent is about 1 yuan / kg, and the spraying operation is carried out by using a plant protection machine. The machine rental fee (including labor cost) is about 40 yuan / mu·time. The cost of spraying twice a year in one mu of land is (2*250*1+2*40) yuan, that is, 580 yuan / mu. The bagging cost calculation is as follows: one mu of land needs to be bagged about 10000 bags / mu, and the labor cost of bagging is about 0.24 yuan / bag. Therefore, the labor cost of bagging is 2400 yuan / mu (10000*0.24). Spraying the anti-sunburn protective agent of this example can save 1820 yuan per mu compared with manual bagging, greatly improving the economic benefit and having a broad market prospect.

[0081] Example 3

[0082] The present example provides a monodisperse calcium carbonate fruit anti-sunburn protective agent, which is prepared by using the following mass ratio: 5 parts of monodisperse calcium carbonate filter cake, 0.2 parts of ethoxylated polytrisiloxane, 0.1 parts of polyvinyl acetate emulsion, 0.05 parts of glycerol, 0.05 parts of enzyme, and 55 parts of water.

[0083] The preparation method of the monodisperse calcium carbonate fruit anti-sunburn protective agent described in this example is as follows: according to the above raw materials and mass fraction, 5 parts of monodisperse calcium carbonate filter cake is placed in 10 parts of water, and stirred at a stirring line speed of 120 m / min for 15 min by using a high-speed disperser. Then, 0.2 parts of ethoxylated polytrisiloxane, 0.1 parts of polyvinyl acetate emulsion, 0.05 parts of glycerol, 0.05 parts of enzyme, and the remaining 45 parts of water are added according to the above formula, and continue to stir at a stirring line speed of 90 m / min for 30 min. Thus, the anti-sunburn protective agent described in this example is obtained, and the solid content of calcium carbonate is about 5%.

[0084] The preparation steps of the monodisperse calcium carbonate filter cake are different from those of Example 1 in that the digestion temperature of step S1 is 80°C, the aging time is 30 h, the refined slurry solid content during carbonation is 8%, the carbonation starting temperature is 30°C, the CO2 content is 30%, the carbonation is ended when the pH reaches 8.0-8.5, and the calcium carbonate particles in the obtained slurry are characterized by microscopic morphology after the carbonation is ended. It can be observed that the calcium carbonate particles are nearly spherical, and the average particle size is about 120 nm (see Figure 9 ); 1.5% sodium chloride, 1.0% aluminum chloride, 0.5% sodium silicate, 0.5% sodium dodecylbenzenesulfonate, and 0.5% sodium dodecyl sulfate based on the mass of the dry calcium carbonate are added during the crystal grain surface reconstruction process of step S2, and the temperature is kept at 180°C for 4 h.

[0085] The monodisperse calcium carbonate filter cake obtained in this example is tested and analyzed for composition, specific surface area, microscopic morphology, and particle size using the same test methods as in Example 1. The harmful impurities such as cadmium, lead, barium, mercury, and arsenic in the obtained monodisperse calcium carbonate are all less than 0.0002%, and the total content of harmful impurities is less than 200 ppm; the specific surface area is about 13.02 m 2 / g; it can be clearly seen from the SEM photos (see Figure 10 ) that the average particle size of the obtained monodisperse calcium carbonate particles is about 285 nm, and the particles are cubic with smooth and clean surfaces. The obtained monodisperse calcium carbonate filter cake is dispersed in clean water to obtain a suspension with a solid content of 2%, and then the suspension effect is observed after standing for 2 h (see Figure 16 ).

[0086] For pear spraying: before the fruit expansion stage of the pear, the monodisperse calcium carbonate fruit anti-sunburn protective agent is diluted 2 times (the solid content of the calcium carbonate is about 2.5%) and sprayed on the fruit surface of the pear. After spraying, the growth status of the whole pear tree is recorded by taking photos, and then observed regularly every week. The pear needs to be sprayed 1-2 times during the ripening process. If it encounters continuous rainfall of 5 days or more, and the total rainfall reaches 250 mm or more, it needs to be supplemented after the rain, and it is ensured that there will be no rainfall for 24 h before the supplement.

[0087] The use effect diagram of the anti-sunburn protective agent prepared in this example on pears is shown in Figure 11 . The protective agent can quickly spread on the fruit surface and adhere uniformly. After spraying, compared with bagging, the use of the anti-sunburn protective agent of this example can effectively prevent the occurrence of sunburn disease of pears, and the incidence of sunburn disease is reduced by 100%.

[0088] The cost of the product of the embodiment is calculated in detail, and the cost of each mu of land per year is only about 780 yuan. The specific calculation of the cost is as follows: about 110 fruit trees per mu of land, annual fruit yield of about 2500 kg, the dosage of the anti-sun scald protective agent is 140 kg / mu once, the unit price of the anti-sun scald protective agent is about 2.5 yuan / kg, and the spraying operation is carried out by using a plant protection machine. The machine rental fee (including labor cost) is about 40 yuan / mu·time. The cost of spraying twice a year per mu of land is 780 yuan / mu (2*140*2.5+2*40); the cost of bagging is calculated as follows: the bagging cost is about 1.4 yuan / kg, and the manual bagging cost is 3500 yuan / mu (2500*1.4). Spraying the anti-sun scald protective agent of the embodiment can save 2720 yuan per mu compared with manual bagging, greatly improving the economic benefit and having a broad market prospect.

[0089] Embodiment 4

[0090] The embodiment provides an anti-sun scald protective agent for fruits, which is prepared from the following raw materials in parts by mass: monodisperse calcium carbonate filter cake 15 parts, ethoxylated polysiloxane 0.2 parts, polyvinyl acetate emulsion 0.5 parts, glycerol 0.2 parts, enzyme 0.5 parts, and water 45 parts.

[0091] The preparation method of the anti-sun scald protective agent for fruits is as follows: 15 parts of monodisperse calcium carbonate filter cake is placed in 20 parts of water, and stirred at a stirring speed of 90 m / min for 30 min by using a high-speed dispersing machine. Then, 0.2 parts of ethoxylated polysiloxane, 0.5 parts of polyvinyl acetate emulsion, 0.2 parts of glycerol, 0.5 parts of enzyme, and the remaining 25 parts of water are added according to the above formula, and stirring is continued at a stirring speed of 110 m / min for 25 min. Thus, the anti-sun scald protective agent is obtained, and the solid content of calcium carbonate is about 15%. In the preparation process of the monodisperse calcium carbonate filter cake, the difference from the embodiment 1 is that the digestion temperature of step S1 is 70°C, the aging time is 40 h, the refined slurry solid content during carbonization is 11%, the carbonization starting temperature is 25°C, the CO2 content is 35%, the carbonization is ended when the pH reaches 7.5-8.0, and the calcium carbonate particles in the obtained slurry are characterized by microscopic morphology. It can be observed that the calcium carbonate particles are chain-shaped, and the average width is about 130 nm (see FIG. 1). Figure 12 During the surface reconstruction process of the crystal grains in step S2, 0.5% of zinc sulfate, 1.4% of polyethylene glycol, 0.6% of ethanol, 0.5% of cetyltrimethylammonium bromide, and 2.5% of polyvinylpyrrolidone are added to the dry base of calcium carbonate, and the mixture is kept at 200°C for 2 h.

[0092] The monodisperse calcium carbonate filter cake obtained in the example was subjected to component, specific surface area, micro-morphology and particle size test analysis using the same test method as in Example 1. The harmful impurities such as cadmium, lead, barium, mercury and arsenic in the obtained monodisperse calcium carbonate were less than 0.0002%, and the total content of harmful impurities was less than 200 ppm; the specific surface area was about 15.73 m2 / g; and the average particle size of the obtained monodisperse calcium carbonate particles was about 230 nm, as can be clearly seen from the SEM photos (see 2 ). Figure 13 The obtained monodisperse calcium carbonate filter cake was dispersed in clean water to obtain a suspension with a solid content of 2%, and then the suspension effect was observed after standing for 2 h (see Figure 16 ).

[0093] For the sunscald prevention planting of pitaya: during the fruit swelling period of pitaya, the sunscald prevention agent was diluted 5 times (the solid content of calcium carbonate was about 3%) using a conventional sprayer and sprayed on the surface of pitaya fruits on dry and rainless days, without the need to specially avoid the branches of the fruit trees. The growth status of the whole pitaya tree was recorded by taking photos after spraying, and then observed regularly once a week. If it rained for more than 5 days, and the total rainfall reached 250 mm or more, the sunscald prevention agent needed to be sprayed again after the rain. If there was no rain before harvesting, no additional spraying was needed.

[0094] The use effect of the sunscald prevention agent prepared in the example on pitaya is shown in Figure 15 . The sunscald prevention agent was evenly attached to the surface of the pitaya fruits, forming a thin and uniform protective film. After spraying, compared with bagging, the sunscald prevention agent prepared in the example could effectively prevent the occurrence of sunscald disease of pitaya, and the incidence of sunscald disease was reduced by 100%.

[0095] The price of the product of the example was calculated in detail. The cost per year per mu was only about 350 yuan. The specific cost calculation was as follows: one mu was about 450 fruit trees, the annual fruit yield was about 2500 kg, the sunscald prevention agent dosage was 10 kg / mu once, the unit price of the sunscald prevention agent was about 7.5 yuan / kg, and the labor cost was about 100 yuan / mu·time for manual spraying. The cost of spraying twice a year per mu was 350 yuan / mu (2*10*7.5+2*100). The bagging cost was calculated as follows: the bagging cost was about 0.3 yuan / kg, and the labor cost for manual bagging was 750 yuan / mu (0.3*2500). Spraying the sunscald prevention agent prepared in the example could save 400 yuan per mu compared with manual bagging, improving the economic benefit and having a broad market prospect.

[0096] Example 5

[0097] The present embodiment provides a kind of monodisperse calcium carbonate fruit sunburn protection agent, which is prepared from the following raw materials in parts by mass: monodisperse calcium carbonate filter cake 18 parts, ethoxy modified polysiloxane 0.2 parts, polyvinyl acetate emulsion 0.6 parts, glycerol 0.5 parts, enzyme 0.6 parts, and water 166 parts.

[0098] The preparation method of the monodisperse calcium carbonate fruit sunburn protection agent described in the present embodiment is as follows: according to the above-mentioned raw materials and mass parts, 18 parts of monodisperse calcium carbonate filter cake is placed in 26 parts of water, and stirred for 35 minutes at a stirring speed of 85 m / min using a high-speed dispersing machine. Then, 0.2 parts of ethoxy modified polysiloxane, 0.6 parts of polyvinyl acetate emulsion, 0.5 parts of glycerol, 0.6 parts of enzyme, and the remaining 140 parts of water are added according to the above-mentioned formula, and stirring is continued for 25 minutes at a stirring speed of 90 m / min. Thus, the sunburn protection agent described in the present embodiment is obtained, and the solid content of calcium carbonate is about 6%. The preparation method of the monodisperse micro-nano calcium carbonate filter cake is the same as that of Example 3.

[0099] For kiwi fruit sunburn prevention planting: about 30 days after flowering, choose dry and rainless days, dilute the sunburn protection agent 3 times (the solid content of calcium carbonate is about 2%) with a conventional sprayer, and spray it on the surface of kiwi fruit. There is no need to avoid the leaves and branches of the fruit trees. After spraying, take photos to record the growth status of the whole kiwi fruit tree. Then, observe it regularly every week. If it rains for more than 5 days, and the total rainfall reaches 250 mm or more, it needs to be sprayed again after the rain. If there is no rain before picking, it does not need to be sprayed again.

[0100] The kiwi fruit sprayed with the sunburn protection agent prepared in the present embodiment has little sunburn damage. The natural fruit without treatment has brownish fruit surface towards the sunlight, and the fruit is shriveled. The sunburn prevention effect of the kiwi fruit sprayed with the sunburn protection agent prepared in the present embodiment is much higher than that of the untreated fruit, and is the same as that of the bagged fruit.

[0101] The cost of the product of the present embodiment is calculated as follows: one mu of land is about 55 fruit trees, and the annual fruit yield is about 2000 kg. The sunburn protection agent is used at a dosage of 40 kg per mu, and the unit price of the sunburn protection agent is about 3 yuan / kg. Manual spraying is used, and the labor cost is about 100 yuan per mu per time. The cost of spraying twice a year is 440 yuan per mu (2*40*3+2*100). The cost of bagging is calculated as follows: the cost of bagging is about 0.06 yuan per bag, and the weight of a single fruit is 120 g. Therefore, the cost of manual bagging is 1000 yuan per mu (0.06*2000 / 0.12). Compared with manual bagging, spraying the sunburn protection agent prepared in the present embodiment can save 560 yuan per mu, improve the economic benefits, and has a broad market prospect.

[0102] Example 6

[0103] The present embodiment provides a monodisperse calcium carbonate fruit sunburn protection agent prepared from the following raw materials in parts by mass: monodisperse calcium carbonate filter cake 3 parts, ethoxylated modified polysiloxane 0.02 parts, polyvinyl acetate emulsion 0.05 parts, glycerol 0.01 parts, enzyme 0.01 parts, and water 43 parts.

[0104] The present embodiment provides a monodisperse calcium carbonate fruit sunburn protection agent prepared from the following raw materials in parts by mass: monodisperse calcium carbonate filter cake 3 parts, ethoxylated modified polysiloxane 0.02 parts, polyvinyl acetate emulsion 0.05 parts, glycerol 0.01 parts, enzyme 0.01 parts, and water 43 parts.

[0105] For honey pomelo planting: when the fruit diameter reaches 3-5 cm, choose dry and rainless days, dilute the sunburn protection agent 2 times (the solid content of calcium carbonate is about 2%) with a conventional sprayer, and spray it on the surface of the honey pomelo fruit. There is no need to avoid the leaves and branches of the fruit tree. After spraying, take photos to record the growth status of the whole pomelo tree. Then observe it regularly every week. If it rains for more than 5 days and the total rainfall reaches 250 mm or more, it needs to be sprayed again after the rain. If there is no rain before picking, it does not need to be sprayed again.

[0106] The honey pomelo sprayed with the sunburn protection agent prepared in the present embodiment has little sunburn damage, and the natural fruit sprayed with clean water has more dry and waterless pulp near the fruit stem. The sunburn protection effect of the honey pomelo sprayed with the sunburn protection agent of the present embodiment is much higher than that of the clean water control, and is on par with that of bagging.

[0107] The cost of the product of the present embodiment is calculated as follows: one mu of land is about 50 fruit trees, the annual fruit yield is about 3000 kg, the sunburn protection agent dosage is 60 kg / mu, the sunburn protection agent unit price is about 2 yuan / kg, the manual spraying cost is about 100 yuan / mu·time, and the cost of spraying twice a year in one mu of land is 440 yuan / mu (2*60*2+2*100). The bagging cost is calculated as follows: the bagging cost is about 0.4 yuan per bag, and the manual bagging cost is 1200 yuan / mu (0.4*3000 / 1). Compared with manual bagging, spraying the sunburn protection agent of the present embodiment can save 760 yuan per mu, improve economic benefits, and has broad market prospects.

[0108] Comparative Example 1

[0109] Comparative Example 1 is the same as Example 1 except that no inorganic grain surface modifier is added in the preparation of calcium carbonate. The micro-morphology of the product is shown in Figure 14 .

[0110] Comparative Example 1 has rough calcium carbonate grain surface and relatively poor dispersibility between particles because no inorganic grain surface modifier is added. The particles are connected to each other, resulting in reduced dispersion stability in water, as shown in Figure 16 . Furthermore, the film formed on the surface of citrus fruits after spraying is uneven (see Figure 17 ), and better visible light transmission cannot be achieved, resulting in lower fruit maturity, sour taste, and uneven fruit surface color.

[0111] Comparative Example 2

[0112] Comparative Example 2 is the same as Example 1 except that no organic grain surface modifier is added in the preparation of calcium carbonate. The micro-morphology of the product is shown in Figure 18 .

[0113] Comparative Example 2 has clean calcium carbonate grain surface, but the dispersibility between particles is still relatively poor because no organic grain surface modifier is added. The particles are connected to each other, resulting in reduced dispersion stability in water, as shown in Figure 16 . Furthermore, the film formed on the surface of citrus fruits after spraying is uneven (see Figure 17 ), and better visible light transmission cannot be achieved, resulting in lower fruit maturity, sour taste, and uneven fruit surface color.

[0114] Comparative Example 3

[0115] Comparative Example 3 is the same as Example 2 except that the special-shaped monodisperse calcium carbonate filter cake is not obtained by pressure filtration, but the slurry obtained after grain surface modification is directly used for compounding according to the compounding ratio described in Example 1.

[0116] Comparative Example 3 has harmful ions affecting the surface of apples because no soluble ions in the slurry are removed by pressure filtration. After maturation, there are many spots and cracks on the surface of the fruits, as shown in Figure 19 .

[0117] Comparative Example 4

[0118] Comparative Example 4 has the same formulation as Example 3, except that the preparation method of the anti-sunburn protective agent does not follow the two-step dispersion procedure, but 5 parts of monodisperse calcium carbonate filter cake is directly added to 55 parts of clean water, stirred for 15 minutes with a high-speed dispersion machine at a stirring line speed of 120 m / min, after uniform stirring, 0.2 parts of ethoxylated modified polysiloxane, 0.1 parts of polyvinyl acetate emulsion, 0.05 parts of glycerol and 0.05 parts of enzyme are added according to the proportion, and stirring is continued for 15 minutes at a stirring line speed of 100 m / min.

[0119] Comparative Example 5 has poor dispersion effect of calcium carbonate due to the absence of high-concentration stirring step, and when sprayed on the surface of pear fruit, the slurry cannot form a film on the fruit surface (see Figure 20 ), there are local differences in concentration and unevenness, and more accumulation in the fruit stem part, resulting in more spots on the fruit surface after ripening, and a higher fruit drop rate.

[0120] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the inventive concept, several improvements and changes can be made, which are all within the scope of protection of the present application.

Claims

1. A fruit sunburn protectant, characterized in that, The raw material composition, by mass parts, includes: 1-20 parts of monodisperse calcium carbonate filter cake, 0.01-0.9 parts of ethoxylated modified polytrisiloxane, 0.01-0.8 parts of polyvinyl acetate emulsion, 0.01-0.8 parts of glycerol, 0.01-0.8 parts of enzyme, and 10-180 parts of water; The monodisperse calcium carbonate filter cake has a moisture content of 35%–40%, and the calcium carbonate particles are cubic or nearly spherical in shape, with an average particle size between 200 and 400 nm. Particles larger than 400 nm account for less than 5%, and the specific surface area is less than 17 m². 2 / g; and the monodisperse calcium carbonate filter cake is stirred and dispersed in aqueous solution without the addition of any chemical dispersant, and remains stably suspended; The preparation method of the fruit sunburn protectant is as follows: at a temperature of 5~30℃, monodisperse calcium carbonate filter cake is placed in a portion of water and dispersed in a high-speed disperser at a linear velocity of 80~120 m / min for 15~40 min. Then, other raw materials and the remaining water are added, and the mixture is dispersed in a high-speed disperser at a linear velocity of 80~120 m / min for 15~30 min to obtain the fruit sunburn protectant.

2. The fruit sunburn protectant according to claim 1, characterized in that, The raw material composition, by mass parts, includes: 1-20 parts of monodisperse calcium carbonate filter cake, 0.01-0.5 parts of ethoxylated modified polytrisiloxane, 0.02-0.8 parts of polyvinyl acetate emulsion, 0.01-0.5 parts of glycerol, 0.01-0.8 parts of enzyme, and 30-166 parts of water.

3. The fruit sunburn protectant according to claim 1, characterized in that, The method for preparing the monodisperse calcium carbonate filter cake includes the following steps: S1. Calcium carbonate slurry is prepared using a process including calcination, digestion, and carbonation. S2. Add inorganic salt grain surface remodeling agent and organic grain surface remodeling agent to the calcium carbonate slurry obtained in S1, and then keep it at 160~200℃ for 2.0~6.0 h to obtain calcium carbonate suspension; S3. The calcium carbonate suspension obtained in S2 is dehydrated by hydraulic filtration to obtain a calcium carbonate filter cake. The moisture content of the filter cake is controlled between 35% and 40%, which is a monodisperse calcium carbonate filter cake.

4. The fruit sunburn protectant according to claim 3, characterized in that, The calcination process is as follows: limestone with uniform grain size and a harmful heavy metal content of less than 400 ppm is selected as raw material and calcined to obtain quicklime. The activity of quicklime is in the range of 250-300 mL. The digestion process is as follows: the quicklime obtained from the above calcination is digested in hot water at 50-90℃ to obtain lime milk, then aged for 24-48 hours, and filtered to remove impurities to obtain refined raw pulp; The carbonation process is as follows: water is added to the refined raw pulp to adjust the solid content to 8% to 12%, and then carbonation is carried out. The initial carbonation temperature is 20 to 30°C, the CO2 content is 30% to 40%, and carbonation is carried out until the pH of the pulp reaches 7.5 to 8.

5. The carbonation is then stopped to obtain calcium carbonate cooked pulp.

5. The fruit sunburn protectant according to claim 3, characterized in that, The inorganic salt grain surface reconstructing agent is one or more of sodium silicate, sodium chloride, aluminum chloride, and zinc sulfate, and the amount used is 0.5-3% of the dry weight of calcium carbonate; the organic grain surface reconstructing agent is one or more of ethanol, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, and disodium ethylenediaminetetraacetate, and the amount used is 1%-5% of the dry weight of calcium carbonate; the monodisperse calcium carbonate filter cake is stirred and dispersed in an aqueous solution without the addition of any chemical dispersant to obtain a suspension, and when the solid content of the suspension is 2%-5%, it is stably suspended for more than 2 hours.

6. The fruit sunburn protectant according to claim 1, characterized in that, The enzyme in question is a commercially available agricultural enzyme.

7. A method for preparing the fruit sunburn protectant according to any one of claims 1 or 3 to 6, characterized in that, Includes the following steps: (1) According to the raw materials and their mass fractions, prepare 1-20 parts of monodisperse calcium carbonate filter cake, 0.01-0.9 parts of ethoxylated modified polytrisiloxane, 0.01-0.8 parts of polyvinyl acetate emulsion, 0.01-0.8 parts of glycerol, 0.01-0.8 parts of enzyme, and 10-180 parts of water; (2) Place the monodisperse calcium carbonate filter cake in a portion of water at a temperature of 5~30℃ and disperse it in a high-speed disperser at a linear velocity of 80~120 m / min for 15~40 min. (3) After stirring in step (2), add other raw materials and the remaining water, and continue to disperse in a high-speed disperser at a linear speed of 80~120 m / min for 15~30 min to obtain the fruit sunburn protectant.

8. The method for preparing the fruit sunburn protectant according to claim 7, characterized in that, In step (2), the amount of water used to disperse the monodisperse calcium carbonate filter cake is 1 to 2 times the weight of the monodisperse calcium carbonate filter cake.

9. The method of applying the fruit sunburn protectant according to any one of claims 1 to 6, characterized in that: When used for sunburn protection in fruit cultivation, the fruit sunburn protectant is diluted with water until the calcium carbonate solid content is 2%~6% before spraying.

10. The method of applying the fruit sunburn protectant according to claim 9, characterized in that, In dry, rainless weather, dilute the fruit sunburn protectant and spray it onto the fruit surface. There is no need to avoid branches and leaves. Spray 1 to 4 times during the fruit ripening process. If there is more than 5 days of rainfall within 24 hours after spraying, and the total rainfall reaches 250 mm or more, it is necessary to spray again after the rain.

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