A hydrophobic fertilizer anti-caking agent and a method for preparing the same

Abstract

The application discloses a kind of hydrophobic fertilizer anti-caking agent and preparation method thereof, it is related to fertilizer adjuvant and granular fertilizer surface treatment technical field, its technical points the hydrophobic fertilizer anti-caking agent is prepared by the following mass parts of raw materials: porous mineral carrier 100 parts, long-chain fatty acid 8-25 parts, divalent metal source 2-10 parts, waxy hydrophobic agent 10-35 parts, liquid hydrophobic oil 3-15 parts, organic silicon hydrophobic agent 2-10 parts, alkyl silane coupling agent 0.5-4 parts, emulsifier 1-6 parts, dispersing agent 0.2-2 parts, anti-adhesion adjusting micro powder 1-8 parts, pH regulator 0.2-2 parts and water 80-260 parts;By in-situ generation fatty acid metal soap anchor layer on the surface of porous mineral carrier, originally hydrophilic mineral carrier is changed into hydrophobic anchor carrier, improve the combination stability between hydrophobic component and powder carrier.The application constructs wax-silicon composite hydrophobic layer outside fatty acid metal soap anchor layer, so that anti-caking agent has waxy moisture-proof, organic silicon low surface energy, liquid hydrophobic oil spreading and alkyl silane coupling enhancement effect simultaneously.

Description

Technical Field

[0001] This invention relates to the field of fertilizer additives and granular fertilizer surface treatment technology, specifically to a hydrophobic fertilizer anti-caking agent and its preparation method. Background Technology

[0002] Granular fertilizers are prone to caking during production, cooling, screening, conveying, packaging, storage, and transportation due to factors such as moisture, temperature, pressure, salt bridges on the granule surface, crystal dissolution-recrystallization, and fine powder adhesion. Clumping not only affects product appearance and flowability but also leads to uneven fertilization, packaging damage, storage difficulties, and a decreased user experience. The caking problem is particularly pronounced for highly hygroscopic fertilizers such as urea, ammonium sulfate, ammonium chloride, ammonium phosphate, and high-nitrogen compound fertilizers.

[0003] Existing fertilizer anti-caking technologies mainly include oil coating, powder coating, surfactant treatment, wax coating, and inorganic powder isolation. Among these, while using mineral powder alone can reduce the direct contact area between particles, its strong hydrophilicity makes it prone to absorbing moisture under high humidity conditions, limiting its long-term anti-caking effect. Using oil or wax alone can improve hydrophobicity, but problems such as uneven spraying, localized stickiness, low-temperature wax precipitation, high-temperature softening, and insufficient powdering can easily occur. When using fatty acid salt anti-caking agents alone, although they have certain hydrophobicity and lubricity, their adhesion stability and resistance to water vapor migration on the fertilizer particle surface are still insufficient.

[0004] Furthermore, many anti-caking agents are simply physical mixtures of mineral powder, wax, oil, and surfactants, lacking a structural design to stably anchor the hydrophobic components to the pores and surface of the mineral carrier. During fertilizer storage, anti-caking agents easily migrate or agglomerate from the granule surface, resulting in good early effects but decreased long-term anti-caking performance. For compound fertilizer granules containing a large amount of fine powder or with rough surfaces, ordinary anti-caking agents are also prone to problems such as poor powder adhesion, discontinuous hydrophobic films, and insufficient improvement in the water contact angle of the granule surface. Summary of the Invention

[0005] The purpose of this invention is to address the problems of existing fertilizer anti-caking agents, such as the easy migration of hydrophilic and hydrophobic components in mineral powders, uneven wax and oil coating, discontinuous hydrophobic layers on particle surfaces, and high agglomeration rates under high humidity storage conditions, by providing a hydrophobic fertilizer anti-caking agent and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a hydrophobic fertilizer anti-caking agent and its preparation method, wherein the hydrophobic fertilizer anti-caking agent is prepared from the following raw materials in parts by weight: The composition includes 100 parts porous mineral carrier, 8-25 parts long-chain fatty acid, 2-10 parts divalent metal source, 10-35 parts waxy hydrophobic agent, 3-15 parts liquid hydrophobic oil, 2-10 parts organosilicon hydrophobic agent, 0.5-4 parts alkylsilane coupling agent, 1-6 parts emulsifier, 0.2-2 parts dispersant, 1-8 parts anti-blocking regulating micro powder, 0.2-2 parts pH adjuster, and 80-260 parts water.

[0007] The long-chain fatty acid and the divalent metal source form a fatty acid metal soap anchoring layer on the surface of the porous mineral carrier, and the wax hydrophobic agent, liquid hydrophobic oil, organosilicon hydrophobic agent and alkylsilane coupling agent form a wax-silicon composite hydrophobic layer on the outside of the fatty acid metal soap anchoring layer.

[0008] By adopting the above technical solution, the present invention does not simply mix mineral powder, wax and oil, but first uses the pores, hydroxyl surface and rough structure of the porous mineral carrier to fix the fatty acid metal soap anchoring layer, and then uses the anchoring layer to carry the wax hydrophobic agent, liquid hydrophobic oil, organosilicon hydrophobic agent and alkylsilane coupling agent, so that the anti-caking agent particles have the functions of inorganic powder isolation, long-chain alkyl hydrophobicity, wax film moisture barrier, organosilicon low surface energy and interparticle lubrication.

[0009] Preferably, the porous mineral carrier is composed of the following components in parts by weight: 30-60 parts calcined kaolin, 15-40 parts diatomaceous earth, 10-30 parts attapulgite, 5-20 parts precipitated silica, and 5-20 parts talc.

[0010] By adopting the above technical solutions, calcined kaolin provides better thermal stability and powder skeleton; diatomaceous earth has high porosity and oil absorption capacity, which can adsorb and fix hydrophobic components; attapulgite has fibrous or rod-shaped structure, which is beneficial to improve the adhesion of anti-caking agents on the surface of fertilizer particles; precipitated silica is used to increase specific surface area and anti-adhesion ability; talc has a flake structure and lubricity, which can reduce inter-particle friction and adhesion.

[0011] Preferably, the porous mineral carrier has a D50 particle size of 5-35 μm, an oil absorption value of 35-95 g / 100 g, and a moisture content of no more than 1.5%.

[0012] By adopting the above technical solutions, it is found that when the porous mineral carrier particle size is too large, it is not conducive to uniform adhesion to the surface of fertilizer particles; when the particle size is too small, it is easy to generate dust and increase the risk of agglomeration. When the oil absorption value is too low, it is difficult to effectively carry the hydrophobic components of wax oil; when the oil absorption value is too high, it may adsorb excessive oil and wax, resulting in a decrease in powder flowability.

[0013] Preferably, the long-chain fatty acid is one or a combination of two or more of stearic acid, palmitic acid, oleic acid, behenic acid, and dodecyl hydroxystearic acid.

[0014] Preferably, the divalent metal source is one or a combination of two or more of calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, zinc oxide, calcium acetate, and magnesium acetate.

[0015] Preferably, the long-chain fatty acid and the divalent metal source are in a molar ratio of 1.6-2.4:1, representing the metal ions required to form a metal soap.

[0016] By employing the above technical solution, long-chain fatty acids react in situ with divalent metal sources on the mineral surface to form calcium soap, magnesium soap, or zinc soap structures, which can reduce the surface polarity of the mineral carrier and improve the adhesion stability of hydrophobic components. If the long-chain fatty acids are insufficient, the surface hydrophobic anchoring will be inadequate; if the long-chain fatty acids are excessive, the free fatty acids may cause the anti-caking agent surface to become sticky. Excessive metal sources may result in excessively high alkalinity of the powder, which is not conducive to fertilizer compatibility.

[0017] Preferably, the waxy hydrophobic agent is one or a combination of two or more of carnauba wax, rice bran wax, beeswax, Fischer-Tropsch wax, polyethylene wax, and oxidized polyethylene wax.

[0018] Preferably, the liquid hydrophobic oil is one or a combination of two or more of the following: white oil, epoxidized soybean oil, fatty acid methyl ester, rapeseed oil methyl ester, and dimethyl silicone oil.

[0019] Preferably, the mass ratio of the waxy hydrophobic agent to the liquid hydrophobic oil is 1.5-6.0:1.

[0020] By adopting the above technical solution, the waxy hydrophobic agent can form a hydrophobic barrier film resistant to water vapor migration on the surface of fertilizer granules. The liquid hydrophobic oil can improve the spreadability and flexibility of the waxy material, avoiding the formation of a brittle film or low-temperature cracking of the pure waxy material. When the proportion of wax oil is too low, the anti-caking agent is prone to stickiness; when the proportion of wax oil is too high, the spreadability decreases and the film continuity is insufficient.

[0021] Preferably, the organosilicon hydrophobic agent is one or a combination of two or more of hydroxyl silicone oil, hydrogen-containing silicone oil, polyether-modified silicone oil, and amino-modified silicone oil.

[0022] Preferably, the alkylsilane coupling agent is one or a combination of two or more of octyltriethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0023] By adopting the above technical solutions, organosilicon hydrophobic agents can reduce the surface energy of anti-caking agents and increase the water contact angle of fertilizer granules; alkylsilane coupling agents can condense with hydroxyl groups on the surface of mineral carriers or form strong interfacial interactions, and further enhance hydrophobicity through long alkyl chains.

[0024] This invention also provides a method for preparing a hydrophobic fertilizer anti-caking agent, comprising the following steps: S1. The porous mineral carrier is dried and then added to a high-speed mixing device, and stirred and preheated at 70-105℃ to obtain a preheated mineral carrier. S2. The long-chain fatty acid is melted and added to the preheated mineral carrier, so that the long-chain fatty acid wets the pores and surface of the porous mineral carrier; then the divalent metal source and some water are added, and the reaction is carried out at 75-105℃ for 20-90 minutes, so that a fatty acid metal soap anchoring layer is formed in situ on the surface of the porous mineral carrier, and a metal soap anchoring carrier is obtained. S3. Mix the waxy hydrophobic agent, liquid hydrophobic oil, organosilicon hydrophobic agent, alkylsilane coupling agent, emulsifier, dispersant, pH adjuster and remaining water, and emulsify at high speed at 70-95℃ to obtain a wax-silicone composite hydrophobic emulsion. S4. Spray the wax-silicone composite hydrophobic emulsion into the metal soap anchoring carrier, and add the anti-adhesion regulating micro powder. Continue mixing at 75-105℃ to spread and fix the wax-silicone composite hydrophobic emulsion on the outside of the fatty acid metal soap anchoring layer. S5. The material obtained in S4 is dried, cooled, depolymerized, and sieved to obtain the hydrophobic fertilizer anti-caking agent.

[0025] By adopting the above technical solution, the present invention employs a process sequence of "carrier drying and preheating - fatty acid wetting - in-situ soaping from metal source - wax-silicone emulsion spreading and fixing - drying and depolymerization", which allows the hydrophobic components to be anchored first and then coated by the composite hydrophobic layer, reducing the proportion of free oil and wax, and improving the powder flowability and surface adhesion stability of fertilizer particles.

[0026] Compared with existing technologies, this invention provides a hydrophobic fertilizer anti-caking agent and its preparation method, which has the following beneficial effects: By generating a fatty acid metal soap anchoring layer in situ on the surface of a porous mineral carrier, the originally hydrophilic mineral carrier is transformed into a hydrophobic anchoring carrier, improving the bonding stability between the hydrophobic component and the powder carrier. This invention constructs a wax-silicon composite hydrophobic layer on the outside of the fatty acid metal soap anchoring layer, enabling the anti-caking agent to simultaneously possess the moisture-blocking properties of wax, the low surface energy of organosilicon, the spreading effect of liquid hydrophobic oil, and the coupling enhancement effect of alkylsilanes.

[0027] The anti-caking agent obtained by this invention is a powder system, which is convenient to mix with fertilizer granules or to apply as a powder coating. At the same time, it can reduce the problems of uneven spraying of oil-based anti-caking agents and stickiness on the surface of granules.

[0028] The hydrophobic fertilizer anti-caking agent obtained in this invention, when used for surface treatment of fertilizer granules, can increase the water contact angle of the fertilizer granule surface, reduce the moisture absorption weight gain rate and caking rate, and improve the looseness and flowability of the fertilizer after storage. Attached Figure Description

[0029] Figure 1 Here is a SEM image of the hydrophobic fertilizer anti-caking agent obtained in Example 1; Figure 2 The FTIR spectrum of the hydrophobic fertilizer anti-caking agent obtained in Example 1 is shown below. Figure 3 This is a comparison of SEM images of the fertilizer granule surface before treatment in Example 1; Figure 4 The images show SEM comparisons of the fertilizer granule surfaces after treatment in Example 1. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Please see Figures 1-4 This invention provides a technical solution for a hydrophobic fertilizer anti-caking agent and its preparation method: In the following embodiments, unless otherwise specified, all parts are parts by weight.

[0032] Preparation Example 1: Preparation of porous mineral supports: Raw material composition: 45 parts of calcined kaolin, 25 parts of diatomaceous earth, 15 parts of attapulgite, 8 parts of precipitated silica, and 7 parts of talc.

[0033] Preparation method: Calcined kaolin, diatomaceous earth, attapulgite, precipitated silica, and talc were added to a high-speed mixer and mixed at 800 r / min for 30 min. The mixture was then subjected to air jet pulverization and classification to obtain a porous mineral carrier.

[0034] The obtained porous mineral carrier has a D50 particle size of 18.6 μm, an oil absorption value of 68 g / 100 g, and a moisture content of 0.62%.

[0035] Preparation Example 2: Preparation of wax-silicone composite hydrophobic emulsion: Raw material composition: 12 parts carnauba wax, 8 parts Fischer-Tropsch wax, 5 parts epoxidized soybean oil, 3 parts white oil, 4 parts hydroxyl silicone oil, 1.2 parts octyltriethoxysilane, 2 parts sorbitan monostearate, 1.5 parts polyoxyethylene sorbitan monostearate, 0.6 parts sodium polyacrylate, 0.5 parts citric acid, and 80 parts water.

[0036] Preparation method: Carnauba wax, Fischer-Tropsch wax, epoxidized soybean oil, white oil, hydroxyl silicone oil, octyltriethoxysilane, and sorbitan monostearate were added to an emulsifying tank, melted at 85°C, and stirred evenly to obtain an oil-wax phase.

[0037] Polyoxyethylene sorbitan monostearate, sodium polyacrylate, citric acid and water were mixed and heated to 85°C to obtain an aqueous phase.

[0038] The aqueous phase was slowly added to the oil-wax phase, and emulsification was carried out at a high speed of 6000 r / min for 25 min to obtain a wax-silicone composite hydrophobic emulsion. The average droplet size of the obtained emulsion was 2.1 μm.

[0039] Example 1: Preparation of a hydrophobic fertilizer anti-caking agent: Raw material composition: 100 parts of porous mineral carrier obtained in Preparation Example 1, 12 parts of stearic acid, 4 parts of palmitic acid, 3.5 parts of calcium hydroxide, 1.5 parts of magnesium oxide, 28 parts of wax-silicon composite hydrophobic emulsion obtained in Preparation Example 2 (based on solids), 3 parts of hydrophobic modified silica, and 40 parts of water.

[0040] Stearic acid and palmitic acid together are long-chain fatty acids, while calcium hydroxide and magnesium oxide are divalent metal sources.

[0041] Preparation method: S1. The porous mineral carrier obtained in Preparation Example 1 is added to a high-speed mixer and dried at 120°C for 2 hours to reduce the moisture content of the carrier to 0.45%. Then, the temperature is lowered to 90°C and stirred to obtain a preheated mineral carrier.

[0042] S2. Stearic acid and palmitic acid are heated to 85°C and melted, then sprayed into the preheated mineral carrier. They are mixed at 1000 r / min for 20 min to allow the long-chain fatty acids to wet the pores and surface of the porous mineral carrier. Then, calcium hydroxide, magnesium oxide and water are added, and the reaction is carried out at 90°C for 50 min. The final pH of the reaction is 8.6, and a metal soap anchoring carrier is obtained.

[0043] S3. Prepare a wax-silicone composite hydrophobic emulsion according to Preparation Example 2.

[0044] S4. Spray the wax-silicone composite hydrophobic emulsion into the metal soap anchoring carrier, continue mixing at 90°C for 35 min, then add hydrophobic modified silica and continue mixing for 15 min, so that the wax-silicone composite hydrophobic emulsion spreads and fixes on the outside of the fatty acid metal soap anchoring layer.

[0045] S5. The material obtained in S4 is dried at 90°C to a moisture content of 0.58%, cooled to room temperature and depolymerized, and then passed through a 200-mesh sieve to obtain a hydrophobic fertilizer anti-caking agent.

[0046] The resulting hydrophobic fertilizer anti-caking agent has a D50 particle size of 22.4 μm and a water contact angle of 137°.

[0047] Example 2 was carried out with reference to Example 1, except that: 100 parts of porous mineral carrier, 10 parts of stearic acid, 3 parts of behenic acid, 3 parts of calcium hydroxide, 22 parts of the wax-silicon composite hydrophobic emulsion obtained in Example 2 (based on the solid content), and 2 parts of hydrophobic modified silica.

[0048] All other conditions remain the same as in Example 1.

[0049] The resulting hydrophobic fertilizer anti-caking agent has a D50 particle size of 20.8 μm and a water contact angle of 130°.

[0050] Example 3 was carried out with reference to Example 1, except that: 100 parts of porous mineral carrier, 15 parts of stearic acid, 5 parts of dodecyl hydroxystearic acid, 4 parts of calcium hydroxide, 2 parts of zinc oxide, 34 parts of the wax-silicon composite hydrophobic emulsion obtained in Example 2 (based on the solid content), and 5 parts of hydrophobic modified silica.

[0051] All other conditions remain the same as in Example 1.

[0052] The resulting hydrophobic fertilizer anti-caking agent has a D50 particle size of 25.6 μm and a water contact angle of 142°.

[0053] Comparative Example 1 was carried out in accordance with Example 1, except that: no long-chain fatty acids and divalent metal sources were added, that is, no fatty acid metal soap anchoring layer was formed, and the wax-silicon composite hydrophobic emulsion was directly sprayed onto the surface of the porous mineral carrier.

[0054] Comparative Example 2 was carried out in accordance with Example 1, except that no waxy hydrophobic agent, liquid hydrophobic oil, organosilicon hydrophobic agent and alkylsilane coupling agent were added, and a fatty acid metal soap anchoring layer was formed only on the surface of the porous mineral carrier.

[0055] Comparative Example 3 was carried out in accordance with Example 1, except that: no organosilicon hydrophobic agent and alkylsilane coupling agent were added, and the mixture was made up with an equal mass of wax hydrophobic agent and liquid hydrophobic oil.

[0056] Comparative Example 4 was carried out with reference to Example 1, except that the porous mineral carrier obtained in Example 1 was replaced with an equal mass of ordinary talc powder, the ordinary talc powder having a D50 particle size of 18.0 μm and an oil absorption value of 28 g / 100 g.

[0057] Comparative Example 5 was carried out in accordance with Example 1, except that the in-situ reaction process between the long-chain fatty acid and the divalent metal source in S2 was cancelled, and the porous mineral carrier, stearic acid, palmitic acid, calcium hydroxide, magnesium oxide and wax-silicon composite hydrophobic emulsion were added to the high-speed mixer at one time for mixing, while other conditions remained unchanged.

[0058] Comparative Example 6 was carried out in accordance with Example 1, except that the mass ratio of waxy hydrophobic agent to liquid hydrophobic oil was adjusted to 0.8:1.

[0059] Comparative Example 7 was carried out in accordance with Example 1, except that the mass ratio of waxy hydrophobic agent to liquid hydrophobic oil was adjusted to 8.0:1.

[0060] Comparative Example 8 was carried out in accordance with Example 1, except that anti-blocking regulating powder was not added, while other conditions remained unchanged.

[0061] Performance testing 1. Particle size distribution test The particle size distribution of the anti-caking agent was tested according to GB / T 19077-2024 "Particle Size Analysis - Laser Diffraction Method". An appropriate amount of sample was taken, dry-dispersed, and the D10, D50, and D90 particle sizes were measured. Each sample was tested in triplicate, and the average value was taken. GB / T 19077-2024 has replaced GB / T 19077-2016 and is applicable to laser diffraction particle size analysis.

[0062] 2. Oil absorption value test The oil absorption value of porous mineral carriers was tested according to GB / T 5211.15-2014 "General Test Methods for Pigments and Extenders - Part 15: Determination of Oil Absorption", using refined linseed oil as the test medium. The results are expressed in g / 100g. This standard is the current standard used for determining the oil absorption of pigments and extenders.

[0063] 3. Moisture content test The moisture content of the anti-caking agent shall be tested in accordance with the moisture-related testing requirements in HG / T 5520-2019 "Anti-caking Agents for Fertilizers"; HG / T 5520-2019 is the current industry standard and is applicable to powdered, paste-like or liquid anti-caking agents for fertilizers used in the fertilizer production process.

[0064] The free water content of the treated compound fertilizer samples was tested according to GB / T 8577-2010 "Determination of Free Water Content in Compound Fertilizers - Karl Fischer Method"; for samples that are not suitable for the Karl Fischer method, the test can be performed according to GB / T 8576-2010 "Determination of Free Water Content in Compound Fertilizers - Vacuum Oven Method". Both of the above standards are current standards.

[0065] 4. Water contact angle test The water contact angle test for anti-caking agents was conducted according to the static drop method principle of GB / T 30693-2014 "Measurement of Water Contact Angle of Plastic Films". The anti-caking agent was pressed into a flat sheet sample under 10 MPa pressure, and 3 μL of deionized water was added. The contact angle was read after 5 seconds. For fertilizer granules, the water contact angle was measured by static drop measurement on either a pressed sheet of fertilizer granules treated with the anti-caking agent or on a flat granule surface. Five locations were tested for each sample, and the average value was taken. GB / T 30693-2014 is the current standard and specifies the method for measuring the water contact angle.

[0066] 5. Anti-caking treatment methods Potassium sulfate compound fertilizer granules with a particle size of 2-4 mm were selected as the test fertilizer, and the initial free water content of the fertilizer was 0.42%. An anti-caking agent was added to the fertilizer granules at 0.20% of the fertilizer mass, and the mixture was stirred in a drum mixer for 8 minutes to ensure that the anti-caking agent was evenly adhered to the surface of the fertilizer granules, thus obtaining the anti-caking treated fertilizer.

[0067] 6. Moisture Absorption Weight Gain Rate Test Weigh 100.0g of anti-caking fertilizer, spread it evenly in a petri dish, and place it in a constant temperature and humidity chamber at 30℃ and 75% relative humidity. Weigh the sample at 24h, 48h, 72h, and 168h, and calculate the moisture absorption weight gain rate using the following formula: Moisture absorption weight gain rate = (mass of sample after moisture absorption - initial sample mass) / initial sample mass × 100%.

[0068] 7. Agglomeration rate test The caking rate test was conducted according to the evaluation method for anti-caking performance in HG / T 5520-2019 "Fertilizer Anti-caking Agents". 500g of anti-caking treated fertilizer was weighed and placed in a simulated packaging container, and placed for 7 days at a temperature of 40℃, relative humidity of 75%, and pressure of 20kPa. After the test, the sample was removed, lightly sieved using a 5mm sieve for 30 seconds, and the mass of caking material on the sieve was weighed. The caking rate was calculated using the following formula: Agglomeration rate = mass of agglomerated material on the sieve / initial mass of sample × 100%.

[0069] 8. Powder flowability test Take 100g of anti-caking agent sample and allow it to flow naturally through a specified funnel, recording the outflow time; simultaneously observe whether bridging, adhesion to the wall, or agglomeration occurs. For treated fertilizer granules, evaluate their flowability using the angle of repose.

[0070] Table 1

[0071] Table 2

[0072] Table 3

[0073] As shown in Tables 1 to 3, Example 1 exhibits superior overall performance. Its anti-caking agent achieves a water contact angle of 137°, and the treated fertilizer granules achieve a water contact angle of 108°. The 168-hour moisture absorption weight gain rate is 1.92%, and the 7-day agglomeration rate is 6.8%, significantly better than the untreated fertilizer and the comparative examples. Examples 2 and 3, even with variations in the amounts of long-chain fatty acids, divalent metal sources, and wax-silicone composite hydrophobic emulsion, still maintain low moisture absorption weight gain rates and low agglomeration rates, indicating that the anti-caking agent within the scope of this invention has good process adaptability.

[0074] Comparative Example 1 did not form a fatty acid metal soap anchoring layer. Although a wax-silicone composite hydrophobic emulsion was added, the hydrophobic component's bonding stability with the mineral carrier was insufficient. The water contact angle and anti-caking effect on the fertilizer surface were lower than those in Example 1, indicating that the metal soap anchoring layer plays a key role in stabilizing the hydrophobic component.

[0075] Comparative Example 2 only formed a fatty acid metal soap anchoring layer without forming a wax-silicon composite hydrophobic layer. The water contact angle of the anti-caking agent and the water contact angle of the fertilizer surface were both low, and the agglomeration rate increased, indicating that a single metal soap layer is difficult to provide sufficient moisture barrier and low surface energy effect.

[0076] Comparative Example 3, which did not contain any organosilicon hydrophobic agent or alkylsilane coupling agent, had inferior anti-caking performance compared to Example 1, indicating that the low surface energy components of organosilicon and the alkylsilane coupling agent help improve the hydrophobicity and water vapor barrier capacity of the fertilizer particle surface.

[0077] Comparative Example 4 used ordinary talc powder to replace the porous mineral carrier, which significantly reduced the oil absorption value, resulting in insufficient hydrophobic component carrying capacity, uneven powder adhesion, and increased agglomeration rate after fertilizer treatment. This indicates that the porous mineral carrier plays an important role in adsorbing, dispersing, and immobilizing hydrophobic components.

[0078] Comparative Example 5 eliminated the in-situ reaction sequence and mixed all components at once. The surface hydrophobicity of the anti-caking agent and the anti-caking effect of the fertilizer both decreased, indicating that the preparation sequence of "first impregnating into soap, then spreading and fixing with emulsion" is conducive to the formation of a stable anchoring layer and an outer hydrophobic layer.

[0079] In Comparative Example 6, the proportion of liquid hydrophobic oil was too high, resulting in prolonged powder outflow time and a slightly sticky fertilizer surface after storage. This indicates that a low ratio of waxy hydrophobic agent to liquid hydrophobic oil weakens the powder's looseness. In Comparative Example 7, the proportion of waxy hydrophobic agent was too high. Although the hydrophobicity was acceptable, the hydrophobic film's spreadability was insufficient, and the anti-caking effect was still lower than in the examples. In Comparative Example 8, no anti-caking regulating microparticles were added, resulting in increased powder outflow time and the presence of agglomeration points after storage. This indicates that the anti-caking regulating microparticles help improve the looseness of the anti-caking agent powder and the uniformity of fertilizer surface distribution.

[0080] In summary, this invention, through the overall structural design of a porous mineral carrier, a fatty acid metal soap anchoring layer, and a wax-silica composite hydrophobic layer, enables the anti-caking agent to possess powder isolation, hydrophobic moisture barrier, low surface energy, and adhesion stability. The technical contribution of this solution lies not in the use of mineral powder, wax, or oil alone, but in the synergistic construction of a stable hydrophobic powder through in-situ metal soap anchoring and the wax-silica composite hydrophobic layer, thereby significantly reducing the moisture absorption weight gain rate and agglomeration rate of fertilizers under high temperature, high humidity, and pressurized storage conditions.

Claims

1. A hydrophobic fertilizer anti-caking agent, characterized in that: The hydrophobic fertilizer anti-caking agent is prepared from the following raw materials in parts by weight: The composition includes 100 parts porous mineral carrier, 8-25 parts long-chain fatty acid, 2-10 parts divalent metal source, 10-35 parts waxy hydrophobic agent, 3-15 parts liquid hydrophobic oil, 2-10 parts organosilicon hydrophobic agent, 0.5-4 parts alkylsilane coupling agent, 1-6 parts emulsifier, 0.2-2 parts dispersant, 1-8 parts anti-blocking regulating micro powder, 0.2-2 parts pH adjuster, and 80-260 parts water. The long-chain fatty acid and the divalent metal source form a fatty acid metal soap anchoring layer on the surface of the porous mineral carrier, and the wax hydrophobic agent, liquid hydrophobic oil, organosilicon hydrophobic agent and alkylsilane coupling agent form a wax-silicon composite hydrophobic layer on the outside of the fatty acid metal soap anchoring layer.

2. The hydrophobic fertilizer anti-caking agent according to claim 1, characterized in that: The porous mineral carrier is composed of the following components in parts by weight: Calcined kaolin 30-60 parts, diatomaceous earth 15-40 parts, attapulgite 10-30 parts, precipitated silica 5-20 parts, and talc 5-20 parts; The porous mineral carrier has a D50 particle size of 5-35μm, an oil absorption value of 35-95g / 100g, and a moisture content of no more than 1.5%.

3. The hydrophobic fertilizer anti-caking agent according to claim 1, characterized in that: The long-chain fatty acid is one or a combination of two or more of stearic acid, palmitic acid, oleic acid, behenic acid, and dodecyl hydroxystearic acid; The divalent metal source is one or a combination of two or more of the following: calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, zinc oxide, calcium acetate, and magnesium acetate. The long-chain fatty acid and the divalent metal source are in a molar ratio of 1.6-2.4:1, which is required for the formation of a metal soap.

4. The hydrophobic fertilizer anti-caking agent according to claim 1, characterized in that: The waxy hydrophobic agent is one or a combination of two or more of carnauba wax, rice bran wax, beeswax, Fischer-Tropsch wax, polyethylene wax, and oxidized polyethylene wax. The melting point of the waxy hydrophobic agent is 55-105℃; The liquid hydrophobic oil is one or a combination of two or more of the following: white oil, epoxidized soybean oil, fatty acid methyl ester, rapeseed oil methyl ester, and dimethyl silicone oil. The mass ratio of the waxy hydrophobic agent to the liquid hydrophobic oil is 1.5-6.0:

1.

5. The hydrophobic fertilizer anti-caking agent according to claim 1, characterized in that: The organosilicon hydrophobic agent is one or a combination of two or more of hydroxyl silicone oil, hydrogen-containing silicone oil, polyether-modified silicone oil, and amino-modified silicone oil. The alkylsilane coupling agent is one or a combination of two or more of octyltriethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, and hexadecyltrimethoxysilane. The mass ratio of the organosilicon hydrophobic agent to the alkylsilane coupling agent is 2-12:

1.

6. The hydrophobic fertilizer anti-caking agent according to claim 1, characterized in that: The emulsifier is one or a combination of two or more of the following: sorbitan monostearate, polyoxyethylene sorbitan monostearate, fatty alcohol polyoxyethylene ether, and polyglycerol fatty acid ester. The dispersant is one or a combination of two or more of sodium polyacrylate, sodium lignosulfonate, and polyvinylpyrrolidone. The anti-adhesion regulating micro powder is one or a combination of two or more of the following: hydrophobically modified silica, talc, light calcium carbonate, and calcined kaolin. The hydrophobic fertilizer anti-caking agent has a D50 particle size of 8-45μm, a water contact angle of not less than 120°, and a moisture content of not more than 1.0%.

7. A method for preparing a hydrophobic fertilizer anti-caking agent as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. The porous mineral carrier is dried and then added to a high-speed mixing device, and stirred and preheated at 70-105℃ to obtain a preheated mineral carrier. S2. The long-chain fatty acid is melted and added to the preheated mineral carrier, so that the long-chain fatty acid wets the pores and surface of the porous mineral carrier; then the divalent metal source and some water are added, and the reaction is carried out at 75-105℃ for 20-90 minutes, so that a fatty acid metal soap anchoring layer is formed in situ on the surface of the porous mineral carrier, and a metal soap anchoring carrier is obtained. S3. Mix the waxy hydrophobic agent, liquid hydrophobic oil, organosilicon hydrophobic agent, alkylsilane coupling agent, emulsifier, dispersant, pH adjuster and remaining water, and emulsify at high speed at 70-95℃ to obtain a wax-silicone composite hydrophobic emulsion. S4. Spray the wax-silicone composite hydrophobic emulsion into the metal soap anchoring carrier, and add the anti-adhesion regulating micro powder. Continue mixing at 75-105℃ to spread and fix the wax-silicone composite hydrophobic emulsion on the outside of the fatty acid metal soap anchoring layer. S5. The material obtained in S4 is dried, cooled, depolymerized, and sieved to obtain the hydrophobic fertilizer anti-caking agent.

8. The method for preparing a hydrophobic fertilizer anti-caking agent according to claim 7, characterized in that, In S1, the drying temperature of the porous mineral carrier is 105-140℃, and the drying time is 1-4h. In S2, the long-chain fatty acid is added at a temperature of 75-95°C, the divalent metal source is added in the form of powder or an aqueous dispersion with a mass fraction of 10-35%, and the final pH of the reaction is 7.5-9.

5. In step S3, the high-speed emulsification rotation speed is 3000-9000 r / min, the emulsification time is 10-40 min, and the average droplet size of the resulting wax-silicone composite hydrophobic emulsion is 0.5-5 μm. In step S5, the drying temperature is 70-110℃, the material is dried until the moisture content is not higher than 1.0%, and the sieve mesh size is 100-400 mesh.

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