An anti-caking urotropine and a method for its production, and an anti-caking additive used therefor

Abstract

The application belongs to the field of fine chemical processing, and particularly relates to an anti-caking urotropine and a preparation method thereof, and an anti-caking additive used in the application. The method comprises the following steps: placing urotropine particles in a fluidized bed for fluidization, using an anti-caking additive as a spraying agent to perform fluidized bed top spraying treatment on the urotropine particles, drying and solidifying the urotropine particles after the anti-caking additive uniformly covers the surface of the urotropine particles, and obtaining the anti-caking urotropine. The application constructs a ternary composite anti-caking system through a multi-level interface regulation strategy. After nano-silicon dioxide and zinc stearate, polyethylene glycol are mixed, the surface of the urotropine particles is uniformly covered, a composite isolation layer is formed, and the risk of urotropine hygroscopic caking is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fine chemical processing, and particularly relates to an anti-caking urotropine and a preparation method thereof, and an anti-caking additive used in the preparation method. BACKGROUND

[0002] Urotropine, also known as hexamethylenetetramine, is a white crystalline powder. Due to its strong hygroscopicity, urotropine is easily absorbed and caked in the air, which further affects its quality and use performance. The anti-caking agent is one or more substances, and its function is to ensure the flowability of urotropine in the storage and handling process. The mechanism of action of the anti-caking agent includes: participating in the crystal formation process, adjusting the crystal growth rate, and thus changing the crystal morphology; forming a hydrophobic layer on the surface of the particles to hinder the exchange of water and the outside world; forming a protective film on the surface of the particles to achieve mechanical isolation between particles; reducing the surface tension of the solution on the surface of the particles, changing the solid-liquid contact angle, and thus reducing the capillary adsorption force, etc.

[0003] CN117510510A patent discloses a preparation method of non-caking sand-like urotropine, which belongs to the technical field of organic synthesis, and focuses on the preparation process of urotropine. The specific preparation steps are as follows: first, the urotropine with a particle size of 80-100 mesh is fully mixed with a nano inorganic particle nucleating agent according to a mass ratio of 100:(0.02-0.08), and is uniformly stirred, thereby obtaining a nucleated urotropine; then, a saturated urotropine solution is prepared; then, the saturated urotropine solution is mixed with an anti-caking agent according to a volume-mass ratio of 20 mL:(0.2-0.8) g, and an anti-caking agent solution is prepared; then, under the condition of continuous stirring, the saturated urotropine solution is added to the nucleated urotropine, and a paste-like urotropine is formed by stirring; then, the paste-like urotropine is filtered through a 60 mesh sieve, the filtrate is returned to the saturated urotropine solution for reuse, and the urotropine with a particle size greater than 60 mesh is collected; finally, the anti-caking agent solution in mist form is sprayed in the dehydration process, and the target product is obtained. However, through in-depth analysis of the preparation method, it can be found that there are some problems to be improved. First, the saturation urotropine solution ratio of 50 g:100 mL mentioned is not accurate, which may have an adverse effect on the subsequent preparation process. Second, the method is only suitable for producing urotropine products with a particle size greater than 60 mesh, and the application range is relatively narrow. Third, in the whole preparation process, it is stipulated that 80-100 mesh urotropine must be used to prepare nucleated urotropine, prepare a saturated urotropine solution, and prepare a paste-like urotropine. This means that the urotropine that has completed the crystallization production needs to be mixed with water and then crystallized again, which not only repeats the process, but also makes the operation process more complicated, increasing the production cost and time cost. Fourth, the product is obtained only by spraying the anti-caking agent solution in mist form in the dehydration stage, which is difficult to effectively control the water content in the product. In actual situations, water content is the most critical factor causing product caking, and improper control of water content will directly affect the quality and storage stability of the product. SUMMARY

[0004] The technical scheme of the present application is aimed at the problems of easy caking in the production process of urotropine, such as airflow drying, silo, warehouse storage, and sea transportation, and provides a kind of anti-caking additive.

[0005] The main purpose of the present application is:

[0006] I. A kind of urotropine with good anti-caking performance can be prepared;

[0007] II. The preparation process of the anti-caking additive is optimized;

[0008] III. The preparation process of the anti-caking additive is improved.

[0009] To achieve the above object, the present application adopts the following technical solutions.

[0010] A preparation method of anti-caking urotropine,

[0011] The method comprises the following steps:

[0012] The urotropine particles are placed in a fluidized bed for fluidization, an anti-caking additive is used as a spraying agent, and the urotropine particles are subjected to fluidized bed top spraying treatment, so that the anti-caking additive is uniformly covered on the surface of the urotropine particles, and then the urotropine particles are dried and solidified to obtain anti-caking urotropine.

[0013] Preferably,

[0014] The fluidization process controls the fluidization gas flow rate to be 0.8-1.2 m / s;

[0015] The anti-caking additive is used in an amount of 0.5-1.0 wt% of the urotropine;

[0016] The spraying pressure in the spraying treatment process is 0.5-0.7 MPa.

[0017] Preferably,

[0018] The drying and solidification adopts gradient temperature rising and holding treatment;

[0019] The gradient temperature rising and holding treatment is sequentially performed at 28-32 ℃ for 25-35 min, at 42-47 ℃ for 25-35 min, and at 55-65 ℃ for 55-65 min.

[0020] An anti-caking additive,

[0021] The anti-caking additive is prepared by the following method:

[0022] (1) mixing a polypeptide and an acyclic carboxylic acid uniformly in proportion to form a mixture, and performing heat preservation and copolymerization to prepare an organic copolymer;

[0023] (2) mixing a non-metallic oxide, an organic zinc, and a fatty alcohol derivative uniformly in proportion, and performing ultrasonic treatment to prepare a modified inorganic material;

[0024] (3) mixing the organic copolymer, the modified inorganic material, and a polymer uniformly in proportion to prepare the anti-caking additive.

[0025] Preferably,

[0026] In step (1), the polypeptide is polyaspartic acid;

[0027] In step (1), the acyclic carboxylic acid is palmitic acid;

[0028] The polypeptide and acyclic carboxylic acid in step (1) are mixed uniformly at a mass ratio of (2.4-2.8):1.

[0029] As preferred,

[0030] The heat preservation copolymerization in step (1) is carried out under the conditions of inert atmosphere and temperature of 55-65 ℃, 1,2-dichloroethane is used as catalyst at a mass of 1.5-2.5 wt% of the mixture, and the reaction is carried out for 4-6 h.

[0031] As preferred,

[0032] The non-metallic oxide in step (2) is nano-silicon dioxide;

[0033] The organic zinc in step (2) is zinc stearate;

[0034] The fatty alcohol derivative in step (2) is ethanol;

[0035] The non-metallic oxide, organic zinc and fatty alcohol derivative in step (2) are mixed uniformly at a mass ratio of 1:(0.03-0.07):30.

[0036] As preferred,

[0037] The ultrasonic treatment in step (2) is controlled at an ultrasonic power of 50-80 W and an ultrasonic time of 0.5-1 h.

[0038] As preferred,

[0039] The organic copolymer, modified inorganic material and polymer in step (3) are mixed uniformly at a mass ratio of (1.5-2.5):1:(3.9-4.1).

[0040] An anti-caking urotropine.

[0041] Urotropin, chemically named as hexamethylene tetramine, appears as white crystalline powder. Due to its strong hygroscopicity, it is easy to absorb water vapor in the air and form lumps when exposed to air. This change not only affects the chemical quality of urotropin itself, but also significantly reduces its performance in practical application scenarios. To effectively solve the problem of urotropin lumping, adding a specific type of anti-caking agent to the urotropin system has become one of the common strategies widely used in existing technical solutions. Among them, benzoic acid and some specific surfactants, such as sodium dodecyl benzene sulfonate, OP-10, etc., have been proven to have excellent anti-caking performance. From the mechanism of action, these anti-caking agents can reduce the surface energy of urotropin particles, thereby reducing their tendency to adsorb moisture from the surrounding environment. More importantly, during the drying process, these anti-caking agents can play a unique role, promoting the mutual adhesion between urotropin particles, and ultimately forming a sand-like particle structure. This carefully constructed special microstructure further reduces the contact area between urotropin and external moisture, thereby significantly improving the overall anti-caking ability of urotropin, ensuring its stability and reliability during storage and use.

[0042] The present application provides a kind of urotropin surface modification with anti-caking additive and its application process, i.e.

[0043] In the technical scheme of the present application, the core is to form a hydrogen bond network on the surface of urotropine by using organic acid, to form a barrier layer through the dual action of physical adsorption and chemical bond coordination, to change the charge distribution on the surface of urotropine crystal, and to reduce the caking rate. The present method relies on the free radical graft copolymerization reaction between polyaspartic acid and palmitic acid, and successfully synthesizes an organic copolymer with an amphiphilic block structure. In the organic copolymer, the palmitic acid segment plays a key role, which can provide a hydrophobic surface, and by reducing the hydrophilicity of urotropine particles, an effective hydrophobic barrier is constructed around the particles. It greatly reduces the opportunity for water to contact urotropine particles, thereby reducing the risk of moisture absorption. At the same time, the carboxylic acid groups carried by polyaspartic acid exhibit unique functional properties. These carboxylic acid groups have strong adsorption capacity and can specifically adsorb trace metal ions on the surface of urotropine particles. Since crystal bridge growth is often triggered by ion migration, the adsorption of polyaspartic acid to metal ions effectively inhibits the ion migration process, thereby inhibiting the growth of crystal bridges from the root and preventing urotropine particles from caking due to crystal bridge connection. When the organic copolymer is treated by a spraying process, it will be tightly adsorbed on the surface of urotropine particles by means of hydrogen bonds and van der Waals forces and other intermolecular forces. In this process, the organic copolymer will self-assemble on the surface of the particles to form a dense hydrophobic film, isolating the urotropine particles from the outside humid environment and completing the coating of the crystal surface. In addition, the negatively charged carboxylic acid groups carried by polyaspartic acid have another important function. These negatively charged groups enhance the electrostatic repulsion between urotropine particles, causing the particles to move away from each other, thereby significantly reducing the occurrence of particle agglomeration. Furthermore, polyaspartic acid itself has a certain moisture absorption, which can locally regulate the humidity of the microenvironment around the urotropine particles. When the environmental humidity is high, polyaspartic acid will absorb part of the water, reducing the water vapor concentration around the particles; while in a low humidity environment, it will slowly release water, maintaining the relative stability of the microenvironment humidity. That is, the moisture absorption behavior of polyaspartic acid conforms to the moisture absorption-desorption isotherm characteristics. This dynamic humidity regulation mechanism effectively delays the moisture absorption process of urotropine, ensuring its good physical stability for a long time, and can effectively realize the local humidity reduction on the surface of the particles, further inhibiting the moisture absorption process.

[0044] In the technical scheme of the present application, another core is to select and modify nano-silicon dioxide to enable the organic copolymer to strengthen the anti-caking effect of urotropine particles. As a high-performance inorganic nano material, nano-silicon dioxide has excellent surface effect, small size effect, macro quantum tunnel effect and unique physical and chemical properties. These characteristics enable nano-silicon dioxide to exhibit great application potential in strengthening material strength, improving material toughness, improving material processing performance and endowing materials with special functions. Based on the multi-level interface regulation strategy, the present application constructs a nano-silicon dioxide-zinc stearate-polyethylene glycol ternary composite anti-caking system. The present application realizes the anchoring of zinc stearate molecules on the surface of silicon dioxide by carboxylate coordination bond through mechanical chemical action. In the present application, nano-silicon dioxide, as a special non-metallic oxide, is precisely mixed with zinc stearate and ethanol in a specific ratio and subjected to ultrasonic treatment process, thereby preparing modified inorganic materials. The modification process aims to endow nano-silicon dioxide with more complex and diversified surface chemical properties and significantly improve its dispersion performance in the system. The modified nano-silicon dioxide can uniformly cover the surface of urotropine particles in actual application scenarios. In this way, the effect of van der Waals force and capillary force between particles is effectively weakened, thereby forming a physical isolation layer between urotropine particles. At the same time, after the participation of zinc stearate in modification, the surface energy of urotropine particles is reduced, effectively inhibiting the formation of crystal bridges due to water adsorption, constructing a hydrophobic barrier and greatly reducing the possibility of urotropine moisture caking. In addition, polyethylene glycol, as a stabilizer of the additive, can ensure the chemical stability and physical stability of the entire additive system and ensure the continuous and stable play of the synergistic effect between components. On the other hand, as a trace moisture regulator, polyethylene glycol preferentially adsorbs moisture in the surrounding environment, forming a local low-humidity microenvironment around urotropine particles, further delaying the moisture absorption process of urotropine and improving its anti-caking performance.

[0045] The present application has the following advantages: the hydrogen bond network formed by the organic acid changes the surface charge distribution of urotropine through physical adsorption and chemical bond coordination, thereby reducing the caking rate; the amphiphilic block structure organic copolymer is synthesized through the free radical graft copolymerization of polyaspartic acid and palmitic acid, the palmitic acid segment provides a hydrophobic surface, and the carboxylate groups of polyaspartic acid adsorb metal ions to inhibit crystal bridge growth, thereby preventing particle caking; the modified nano-silicon dioxide enhances the anti-caking effect of the organic copolymer, a ternary composite anti-caking system is constructed through a multi-level interface regulation strategy, and after mixing nano-silicon dioxide with zinc stearate and polyethylene glycol, the nano-silicon dioxide uniformly covers the surface of urotropine particles to form a composite isolation layer, thereby reducing the risk of moisture caking. DETAILED DESCRIPTION

[0046] The present application will be further described in greater detail by way of specific embodiments. Those skilled in the art will be able to implement the present application based on the description. In addition, the embodiments of the present application described in the following description are merely exemplary embodiments of the present application and are not intended to be complete or exhaustive. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort should be within the scope of the present application.

[0047] Unless otherwise specified, the raw materials used in the embodiments of the present application are commercially available or available to those skilled in the art. Unless otherwise specified, the methods used in the embodiments of the present application are methods mastered by those skilled in the art.

[0048] Example 1: An anti-caking additive,

[0049] The method comprises:

[0050] (1) uniformly mixing polyaspartic acid and palmitic acid in a mass ratio of 2.4:1 to obtain a mixture, and under the environmental conditions of a nitrogen atmosphere and a temperature of 55°C, using 1,2-dichloroethane with a mass of 2 wt% of the mixture as a catalyst, incubating and reacting for 6h to prepare an organic copolymer;

[0051] (2) uniformly mixing nano-silicon dioxide, zinc stearate and ethanol in a mass ratio of 1:0.03:30, treating with ultrasonic waves at 50 W for 1h, filtering and drying to obtain a modified inorganic material;

[0052] (3) uniformly mixing the organic copolymer, the modified inorganic material and 0.5% polyethylene glycol aqueous solution in a mass ratio of 1.5:1:3.9 to prepare an anti-caking additive.

[0053] Example 2: An anti-caking additive,

[0054] The method comprises:

[0055] (1) uniformly mixing polyaspartic acid and palmitic acid in a mass ratio of 2.6:1 to obtain a mixture, and under the environmental conditions of a nitrogen atmosphere and a temperature of 60°C, using 1,2-dichloroethane with a mass of 2 wt% of the mixture as a catalyst, incubating and reacting for 5h to prepare an organic copolymer;

[0056] (2) uniformly mixing nano-silicon dioxide, zinc stearate and ethanol in a mass ratio of 1:0.05:30, treating with ultrasonic waves at 60 W for 0.75h, filtering and drying to obtain a modified inorganic material;

[0057] (3) uniformly mixing the organic copolymer, the modified inorganic material and 0.5% polyethylene glycol aqueous solution in a mass ratio of 2:1:4 to prepare an anti-caking additive.

[0058] Example 3: An anti-caking additive,

[0059] The method comprises:

[0060] (1) mixing polyaspartic acid and palmitic acid uniformly at a mass ratio of 2.8:1 to obtain a mixture, and preparing an organic copolymer under the conditions of a nitrogen atmosphere and a temperature of 65°C, using 1,2-dichloroethane with a mass fraction of 2% of the mixture as a catalyst, and incubating for 4h;

[0061] (2) mixing nano-silicon dioxide, zinc stearate and ethanol uniformly at a mass ratio of 1:0.07:30, treating with ultrasonic waves at 50W for 1h, filtering and drying to obtain a modified inorganic material;

[0062] (3) mixing the organic copolymer, the modified inorganic material and 0.5% polyethylene glycol aqueous solution uniformly at a mass ratio of 2.5:1:4.1 to prepare an anti-caking additive.

[0063] Application Example 1: A preparation method of an anti-caking urotropine, and the specific operation steps are as follows.

[0064] The 120-mesh urotropine particles were placed in a fluidized bed for fluidization, and the anti-caking additive prepared in Examples 1-3 was used as a spraying agent, and the addition amount was 1.0 wt% of the mass of the urotropine. The fluidized bed spraying was carried out under the conditions of a fluidization gas velocity of 1 m / s and a spraying pressure of 0.5 MPa. After spraying, the temperature was raised in three steps of 30°C, 45°C and 60°C, and then incubated. The incubation time of each gradient was controlled for 30 min, 30 min and 45 min, respectively, to realize drying and coating curing. Finally, an anti-caking urotropine product with low surface energy and stable lattice structure was obtained, which was used as a detection sample. Another group of blank samples was set, and no additive was used. Only the 120-mesh urotropine particle product was used as a detection sample for surface energy, caking rate, fluidity detection and biodegradation rate detection. The specific characterization results are as follows.

[0065]

[0066] Caking rate: The detection samples were weighed and the weighing results were recorded. Each group of detection samples was divided into two parts and placed in two groups of simulation boxes with a temperature of 40°C and a relative humidity of 75%, and a temperature of 40°C and a relative humidity of 90%, respectively, for 30 days. Finally, the detection samples were dried in a constant temperature environment at a temperature of 60°C for 45 min to remove surface moisture. After the detection samples were completely dried, they were quickly sieved and separated through a filter screen with a pore size of 100 meshes. The caked part that failed to pass through the sieve was weighed and recorded, and the caking rate was calculated according to the following formula:

[0067] In the formula: — the mass of the caked part, g;

[0068] — the mass of the test sample, g.

[0069]

[0070] Flowability test: the performance of Examples 1-3 and the blank group was tested according to the test standard in ISO 4324 "Surface active agents - Determination of angle of repose of powders and granules", and the characterization results are as follows.

[0071]

[0072] Biodegradability test: according to the construction of microbial flora in ISO-14855-1-2012 "Determination of the ultimate aerobic biodegradability of materials under controlled composting conditions - Method using the measurement of carbon dioxide evolution", the test sample in the application example was placed in the microbial environment, and the degradation rate was tested on the 30th day and the 60th day, and the characterization results are as follows.

[0073]

[0074] The above standard sample is the anti-caking additive prepared in Example 2.

[0075] Compared with the blank control group, the surface energy of the methenamine particles is significantly reduced, the caking rate is greatly reduced, the flowability is obviously optimized, and good biodegradation performance is exhibited after the anti-caking additive provided by the application is applied. According to the analysis of the characterization data, the surface energy of the methenamine particles of examples 1-3 is reduced to 27 mN / m, 26 mN / m and 28 mN / m respectively, and the surface energy of the blank control group is as high as 72 mN / m. After the additive of the application is used, the surface energy of the methenamine particles is significantly reduced. The caking rate of the methenamine of examples 1-3 is much lower than that of the blank group under different environmental conditions, i.e. the temperature is set to 40 ℃, and the relative humidity of the environment is 75% and 90% respectively. According to the comparison of the characterization results of the flowability detection such as the angle of repose, the Hausner ratio and the compressive strength, the angle of repose of the methenamine particles is significantly reduced, the Hausner ratio is significantly reduced, and the compressive strength is weakened after the anti-caking additive of the application is used, so that the flowability of the methenamine particles is significantly improved. In addition, through in-depth analysis of the characterization data of the control standard sample and the blank group, it is found that the data measured by the blank group reflects the degradation rate of methenamine in the microbial environment. In the microbial environment, the degradation degree of methenamine is extremely limited, and it is almost impossible to observe obvious degradation phenomenon. Methenamine will release formaldehyde in the hydrolysis process, and almost all bacteria and fungi show high sensitivity to formaldehyde produced after methenamine hydrolysis. The non-specific antibacterial properties of formaldehyde can significantly interfere with the physiological metabolism of microorganisms, thereby inhibiting the growth and reproduction of bacteria and fungi, making it difficult for microorganisms to effectively degrade methenamine. However, the additive prepared by the application exhibits excellent biodegradation performance through reasonable utilization of the synergistic effect of polyaspartic acid and other components. Further analysis of the characterization data of examples 1-3 shows that in the technical system of the application, the anti-caking additive can significantly reduce the surface energy of the methenamine particles, and fundamentally inhibit the crystal bridge formation phenomenon caused by water adsorption. The additive can build a dense hydrophobic barrier on the surface of the methenamine particles, effectively preventing the intrusion of external water, thereby preventing the hydrolysis reaction of methenamine. Due to its unique molecular structure and biodegradation properties, polyaspartic acid has a significant synergistic regulation effect in the microbial-mediated degradation system. The amide bond (peptide bond) in the main chain can be enzymatically hydrolyzed by proteinase (including peptidase and deaminase) secreted by microorganisms or fungi, and finally mineralized into environmentally friendly products such as ammonia, carbon dioxide and water. This degradation process not only realizes the biological elimination of polyaspartic acid itself, but also the mineralization products can be used as a nitrogen source, and carbon dioxide can participate in the tricarboxylic acid cycle of microorganisms to provide additional energy and synthesis precursors for microbial metabolism, thereby significantly enhancing the respiratory intensity and metabolic activity of microorganisms, forming a positive feedback regulation mechanism for the degradation bacteria.In addition, the polyaspartic acid main chain is rich in carboxylic acid groups and amino groups, which can be used as a high-quality carbon and nitrogen composite nutrient source for microbial growth. By activating the expression of genes related to the proliferation of bacterial flora, the microbial biomass increases exponentially. With the gradual degradation of the polyaspartic acid segment in the copolymer, the physical coating or spatial shielding effect of the copolymer on urotropine gradually weakens, resulting in the dynamic release of urotropine molecules from the composite system. In this process, the high-density microbial community induced by the degradation products of polyaspartic acid has formed a dominant population, and its extracellular enzyme secretion capacity and substrate affinity have been significantly improved. At this time, the simultaneous enhancement of the efficient exposure of urotropine and the metabolic activity of the bacterial flora forms a spatiotemporal synergistic effect: on the one hand, the probability of interface contact between microorganisms and urotropine increases in a geometric progression with the increase in the density of the bacterial flora; on the other hand, the bacterial flora accelerates the oxidative ring-opening of the six-membered ring structure of urotropine and the cleavage of the C-N bond by up-regulating the expression of degradation-related functional proteins (monooxygenase, dehydrogenase), ultimately achieving overall improvement in the degradation kinetics. In the technical solution of the present application, the polar groups of the organic acid interact with the active sites on the surface of urotropine, causing a redistribution of charges, thereby reducing the attraction between particles and ultimately significantly reducing the caking rate. At the same time, this process involves intermolecular force balance, and the formation of a hydrogen bond network acts as a bridge to tightly connect the organic acid and urotropine molecules. The organic copolymer synthesized by radical graft copolymerization of polyaspartic acid and palmitic acid forms an amphiphilic block structure. In this structure, the palmitic acid segment gives the copolymer a hydrophobic surface property. According to the crystal growth inhibition principle, the carboxylic acid groups of polyaspartic acid can specifically adsorb metal ions in the system. In the caking process of urotropine, metal ions promote the growth of crystal bridges, while the adsorption of polyaspartic acid on metal ions effectively inhibits this process, thereby preventing particle caking. In addition, in the ternary composite anti-caking system constructed based on the multi-level interface regulation strategy, after mixing nano-silica with zinc stearate and polyethylene glycol, a composite system is formed. From a microscopic perspective, this composite system can uniformly cover the surface of urotropine particles, forming a physical isolation layer that effectively prevents the intrusion of external moisture and direct contact between particles, thereby significantly reducing the risk of moisture-induced caking.

[0076] Comparative Example 1: An anti-caking additive, only citric acid was added as an anti-caking additive, and part of the performance detection was carried out by referring to Application Example 1, and the specific characterization results are as follows.

[0077]

[0078] Analyzing the above characterization results, the core role played by the organic acid in the system of the present application is to build a hydrogen bond network. Through in-depth analysis of this mechanism of action, it is found that it has an important influence on the performance of the system. Based on the analysis of the detailed characterization results of Comparative Example 1, it can be seen that the hydrogen bond network built by the organic acid does indeed reduce the surface polarity of the system to some extent. However, it is worth noting that this system relies solely on the role of the hydrogen bond network, but lacks an effective hydrophobic barrier. This limitation is intuitively reflected in the actual caking rate data comparison. Compared with the blank group in the application example, the caking rate of Comparative Example 1 is only reduced by 26%. This shows that relying solely on a single mechanism of action - building a hydrogen bond network, while it can have some effect on reducing the caking rate, the overall effect is limited and it is difficult to meet the requirements of high-efficiency anti-caking performance.

[0079] Comparative Example 2: An anti-caking additive, the specific preparation method is the same as Example 2, this example only uses the organic copolymer prepared in step (1) of Example 2 as an anti-caking additive, and refers to Application Example 1 for partial performance testing, the specific characterization results are as follows.

[0080]

[0081] Analyzing the above characterization results, in the system constructed by the present application, the hydrophobic segment of the organic copolymer plays a crucial role, which can significantly inhibit the growth of crystal bridges. Thanks to this key role, the caking rate of the system is successfully reduced to 24.3%. However, through in-depth analysis of the detailed characterization results of Comparative Example 2, it is found that in the system of Comparative Example 2, although the carboxylic acid group can effectively adsorb metal ions, which helps to alleviate the caking problem to some extent, but this system has a obvious deficiency, that is, it fails to form a physical isolation layer. This deficiency results in the compressive strength of the system remaining at a relatively high level of 4.8 kPa. This result fully shows that relying solely on the single mechanism of action of the carboxylic acid group adsorbing metal ions cannot comprehensively and effectively solve the caking problem and reduce the compressive strength of the system, further demonstrating the importance and unique advantages of the synergistic action of multiple mechanisms of action in the system of the present application to achieve excellent anti-caking performance.

[0082] Comparative Example 3: An anti-caking additive, the specific preparation method is the same as Example 2, this example only uses the modified nanosilica prepared in step (2) of Example 2 as an anti-caking additive, and refers to Application Example 1 for partial performance testing, the specific characterization results are as follows.

[0083]

[0084] Based on the unique size effect and surface characteristics of nanomaterials, the modified nanosilica can be highly dispersed in the system and form a continuous and uniform physical isolation layer at the micro level. This physical isolation layer significantly reduces the contact probability between particles in the system by virtue of its steric hindrance effect, effectively inhibiting the caking trend of particles caused by their close proximity and aggregation from the physical level. However, analyzing the characterization data of Comparative Example 3, although the physical isolation layer plays an important role in reducing particle contact, the system still has obvious deficiencies, which are mainly manifested in that the surface energy has not been effectively regulated. As a key parameter reflecting the physical and chemical properties of the particle surface, the unregulated surface energy makes the particle surface in a high energy state. This high energy state enhances the activity of the particle surface, making it more likely to interact with substances in the surrounding environment, such as adsorbing water vapor, impurities, etc., and then forming an unfavorable force between particles for dispersion. Even though the physical isolation layer has reduced the possibility of direct contact between particles, the particles will still overcome the steric hindrance and approach each other due to the driving of surface energy, ultimately leading to a caking rate of 31.2% in the system.

[0085] Comparative Example 4: A commercially available anti-caking additive whose main active ingredient is calcium stearate. Partial performance testing was carried out with reference to Application Example 1, and the specific characterization results are as follows.

[0086]

[0087] By analyzing the above characterization results, compared with the current market calcium stearate anti-caking additive, the additive developed in the anti-caking additive system constructed in the application shows more excellent and comprehensive comprehensive performance. Although the commercially available calcium stearate additive has certain effect in the field of anti-caking, it can inhibit the occurrence of urotropine caking phenomenon to a certain extent, however, from the quantitative index, its anti-caking effect has obvious limitations, and the caking rate of urotropine is still as high as 29.8%. Moreover, through the determination of the key parameters such as the angle of repose and the compressive strength, it is found that the angle of repose and the compressive strength of urotropine under the action of the additive are high. As an important indicator of urotropine fluidity, the larger value means that the internal friction between urotropine particles is larger, and the fluidity is poor; and the higher compressive strength indicates that the compactness of urotropine after caking is higher, which further reflects the deficiency of the anti-caking effect and the adverse effect on the fluidity of urotropine. In addition, the biodegradation rate of calcium stearate additive is less than 10% in the 60-day biodegradation test period, which shows that it is difficult to be decomposed and utilized by microorganisms in the natural environment, and there is a risk of environmental pollution. The anti-caking additive of the application has remarkable effect in reducing the caking rate, and can control the caking rate to be much lower than that of the market similar products; in improving the fluidity of urotropine, by optimizing the formula and the action mechanism, the angle of repose of urotropine is effectively reduced, and the flow performance of urotropine is significantly improved, which is convenient for the transportation and storage of urotropine; at the same time, it shows good biodegradability.

Claims

1.A method for preparing anti-caking urotropin, characterized in that, the method comprises: placing urotropin particles in a fluidized bed for fluidization, and performing fluidized bed top spraying treatment on the urotropin particles with an anti-caking additive as a spraying agent, so that the anti-caking additive uniformly covers the surface of the urotropin particles, and then drying and solidifying the urotropin particles to obtain anti-caking urotropin; the anti-caking additive is prepared by the following method: (1) uniformly mixing polypeptide and acyclic carboxylic acid in a certain proportion to form a mixture, and performing heat preservation copolymerization to prepare an organic copolymer; (2) uniformly mixing non-metallic oxide, organic zinc and fatty alcohol derivative in a certain proportion, and performing ultrasonic treatment to prepare modified inorganic material; (3) uniformly mixing the organic copolymer, modified inorganic material and polymer in a certain proportion to prepare the anti-caking additive; in step (1), the polypeptide is polyaspartic acid; in step (1), the acyclic carboxylic acid is palmitic acid; in step (1), the polypeptide and the acyclic carboxylic acid are uniformly mixed in a mass ratio of (2.4-2.8):1; in step (2), the non-metallic oxide is nano silicon dioxide; in step (2), the organic zinc is zinc stearate; in step (2), the fatty alcohol derivative is ethanol; in step (2), the non-metallic oxide, organic zinc and fatty alcohol derivative are uniformly mixed in a mass ratio of 1:(0.03-0.07):30; in step (3), the organic copolymer, modified inorganic material and polymer are uniformly mixed in a mass ratio of (1.5-2.5):1:(3.9-4.1), and the polymer is polyethylene glycol. 2.The method for preparing anti-caking urotropin according to claim 1, characterized in that, the fluidization process controls the fluidized gas flow rate to be 0.8-1.2 m / s; the amount of the anti-caking additive is 0.5-1.0 wt% of the urotropin; the spraying pressure in the spraying process is 0.5-0.7 MPa. 3.The method for preparing anti-caking urotropin according to claim 1, characterized in that, the drying and solidification adopts gradient temperature rising and heat preservation treatment; the gradient temperature rising and heat preservation treatment is performed in turn at 28-32 ℃ for 25-35 min, at 42-47 ℃ for 25-35 min and at 55-65 ℃ for 55-65 min. 4.The method for preparing anti-caking urotropin according to claim 1, characterized in that, in step (1), the heat preservation copolymerization is performed in an inert atmosphere at an environmental condition of a temperature of 55-65 ℃, with 1,2-dichloroethane as a catalyst at a mass of 1.5-2.5 wt% of the mixture, and heat preservation reaction is performed for 4-6 h. 5.The method for preparing anti-caking urotropin according to claim 1, characterized in that, in step (2), the ultrasonic treatment controls the ultrasonic power to be 50-80 W, and the ultrasonic time is 0.5-1 h. 6.Anti-caking urotropin prepared by any one of the methods according to claims 1 to 3.

Images