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CN-122010623-A - Straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer and preparation method thereof

CN122010623ACN 122010623 ACN122010623 ACN 122010623ACN-122010623-A

Abstract

The invention discloses a straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer and a preparation method thereof, and belongs to the technical field of agricultural fertilizers. The coating layer is formed by solidifying a coating material containing a bio-based composite coating material, a solvent-free solidifying system and a nano reinforcing agent, wherein the bio-based composite coating material contains steam explosion straw-based polyol, a temperature-sensitive-moisture-sensitive copolymer, a moisture-sensitive monomer and a self-repairing agent. The invention also discloses a preparation method of the slow and controlled release fertilizer. According to the invention, the straws are used as a main film forming matrix, and the problems of low biological base content, mismatching with field actual conditions, easy damage of a coating layer, failure of controlled release and the like of the traditional slow-release and controlled-release fertilizer are solved through the cooperative design of temperature and humidity dual response and self-repair function and the gradient distribution of double-layer coating, so that the resource utilization value of the straws is improved, the controlled release accuracy and environmental adaptability of the fertilizer are enhanced, and the service life of the product is prolonged.

Inventors

  • CAI QIULIANG
  • ZHU ZHENGJIE
  • HUANG TUAN

Assignees

  • 百色学院

Dates

Publication Date
20260512
Application Date
20260213

Claims (10)

  1. 1. The straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer is characterized by comprising a fertilizer core and a coating layer coated outside the fertilizer core, wherein the fertilizer core is a compound fertilizer core, the content of the compound fertilizer core is 85-92 parts by mass based on the total mass of the sustained and controlled release fertilizer, the proportion of N-P-K elements of the compound fertilizer core is 15-10-15, the particle size is 2-5mm, and the compressive strength is more than or equal to 120N; the coating layer is formed by solidifying a coating material containing the following components in percentage by mass: 8-15 parts by mass of a bio-based composite coating material, wherein the bio-based composite coating material comprises steam explosion straw-based polyol, a temperature-sensitive-moisture-sensitive copolymer, a moisture-sensitive monomer and a self-repairing agent, the hydroxyl value of the steam explosion straw-based polyol is 45-60 mgKOH/g, the liquefaction rate is more than or equal to 82%, the temperature-sensitive-moisture-sensitive copolymer and the moisture-sensitive monomer cooperate to realize temperature and humidity dual response, and the self-repairing agent cooperates with a hydrogen bond to self-repair a coating layer through dynamic disulfide bonds; 1-3 parts by mass of a solvent-free curing system, wherein the solvent-free curing system is a mixture of liquefied MDI and hexamethylene diisocyanate, and the mass ratio of the liquefied MDI to the hexamethylene diisocyanate is 1:1-1:3; 0.1 to 0.5 part by mass of nano reinforcing agent is nano silicon dioxide with the particle size of 50 to 100nm and the surface subjected to hydroxylation treatment.
  2. 2. The straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer according to claim 1, wherein the steam explosion straw-based polyol is prepared by the following method: Cutting the straw into sections, soaking the sections in alkali liquor to remove impurities, adjusting the water content, and then maintaining the sections for 5 minutes under the pressure of 1.9MPa under the condition of saturated steam to carry out steam explosion treatment; And adding a Ni/Al 2 O 3 supported catalyst with the mass accounting for 5% of the total mass of the liquefied product into the liquefied product for quality improvement, wherein the Ni loading amount in the catalyst is 10%, and finally, the steam explosion straw-based polyol with the hydroxyl value of 45-60 mgKOH/g and the liquefaction rate of more than or equal to 82% is prepared.
  3. 3. The straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer is characterized in that the low critical dissolution temperature of a temperature-sensitive-humidity-sensitive copolymer is 28-32 ℃, the temperature-sensitive-humidity-sensitive copolymer is formed by copolymerizing N-isopropyl acrylamide and polycaprolactone diol with the molecular weight of 2000 according to the mass ratio of 1:1-1:1.5, and methacrylic acid-beta-hydroxyethyl accounting for 5% of the total mass of a comonomer is introduced in the copolymerization process as a humidity-sensitive functional monomer.
  4. 4. The straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer is characterized in that the self-repairing agent is formed by compounding dithiothreitol and polyamide-amine dendrimer according to a mass ratio of 1:3, and the self-repairing agent enables a coating layer to obtain a self-repairing function through the synergistic effect of dynamic disulfide bonds and hydrogen bonds in a molecular structure of the self-repairing agent, wherein the fracture and recombination of the dynamic disulfide bonds are reversible, and the hydrogen bonds provide auxiliary physical adsorption and bonding effects.
  5. 5. The straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer is characterized in that in the bio-based composite coating material, the proportions of each component in the total mass of the bio-based composite coating material are as follows: 40-60% of steam explosion straw-based polyol, 15-25% of temperature-sensitive-moisture-sensitive copolymer, 5-10% of moisture-sensitive monomer and 1-3% of self-repairing agent.
  6. 6. The straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer is characterized in that the coating layer is of a double-layer composite structure and is formed by sequentially coating an inner layer and an outer layer on the surface of the compound fertilizer core; the inner layer is formed by curing a first coating composition, and comprises, based on the total mass of the first coating composition: 55-75% of steam explosion straw-based polyol, 5-15% of temperature-sensitive-moisture-sensitive copolymer, 2-8% of moisture-sensitive monomer, 0.5-2% of self-repairing agent, 0.2-0.6% of nano reinforcing agent and the balance of solvent-free curing system; The outer layer is formed by curing a second coating composition comprising, based on the total mass of the second coating composition: 30% -50% of steam explosion straw-based polyol, 25% -35% of temperature-sensitive-moisture-sensitive copolymer, 8% -15% of moisture-sensitive monomer, 2% -4% of self-repairing agent, 0.1% -0.3% of nano reinforcing agent and the balance of solvent-free curing system; The total mass ratio of the temperature-sensitive-moisture-sensitive copolymer to the self-repairing agent in the outer layer is higher than that of the temperature-sensitive-moisture-sensitive copolymer to the self-repairing agent in the inner layer, the thickness ratio of the inner layer to the outer layer is 1:1.5-1:2.5, and the total thickness of the coating layer is 15-20 mu m.
  7. 7. The straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer according to claim 1, wherein the temperature-sensitive-humidity-sensitive copolymer is a block copolymer and comprises a temperature-sensitive block and a degradable block; The temperature-sensitive block is poly (N-isopropyl acrylamide) and is used for providing temperature response characteristics; The degradable block is polycaprolactone, the number average molecular weight of the degradable block is 1000-3000, ester bonds contained in the main chain of the polycaprolactone can be hydrolyzed by esterase in soil or in weak acid soil environment, the mass of the degradable block accounts for 5-20% of the total mass of the block copolymer, and the low critical solution temperature of the block copolymer containing the degradable block is kept in the range of 28-32 ℃.
  8. 8. The straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer is characterized in that a block copolymer comprising a poly (N-isopropyl acrylamide) block and a polycaprolactone block is prepared by the following method: synthesizing a hydroxyl-terminated functionalized polycaprolactone macromolecular initiator through ring-opening polymerization of epsilon-caprolactone, wherein the number average molecular weight of the initiator is controlled to be 1000-3000; b, initiating N-isopropyl acrylamide to carry out atom transfer radical polymerization by using the macromolecular initiator obtained in the step a to obtain an amphiphilic block copolymer; c, adding methacrylic acid-beta-hydroxyethyl ester accounting for 5 percent of the total mass of the monomers into the copolymerization system in the step b for copolymerization reaction so as to introduce a humidity-sensitive side chain; and d, obtaining the temperature-sensitive-moisture-sensitive copolymer with the low critical solution temperature of 28-32 ℃ and the mass ratio of the polycaprolactone block of 5-20% through precipitation, washing and drying.
  9. 9. A method for preparing the straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer according to any one of claims 1 to 8, which is characterized by adopting a rotary drum fluidized bed layered spraying process and comprising the following steps of: S1, fertilizer core pretreatment, namely adding the compound fertilizer core into a rotary drum fluidized bed, preheating at 65 ℃ and maintaining the rotary drum to rotate at the rotating speed of 30r/min, and simultaneously introducing hot air at 50 ℃ for drying until the water content of the compound fertilizer core is less than or equal to 0.5%; S2, preparing a coating liquid, namely mixing the steam explosion straw-based polyol, the temperature-sensitive-moisture-sensitive copolymer, the self-repairing agent and the nano reinforcing agent, stirring for 40 minutes at 60 ℃ to form a uniform mixture, and then adding the solvent-free curing system to continuously stir for 10 minutes to prepare the coating liquid with the viscosity of 800-1000 mPa.s; S3, layered spraying, namely synchronously spraying the coating liquid in the rotary drum fluidized bed by adopting a double-nozzle side spraying system, spraying the curing agent at the speed of 2g/min by adopting an inner nozzle and spraying the curing agent at the speed of 0.5g/min by adopting an outer nozzle, wherein the spraying operation is carried out in an environment with the temperature of 60 ℃ and the relative humidity of less than or equal to 30%, and the intermittent spraying mode is adopted, wherein the spraying is suspended for 2 minutes after each 5 minutes of continuous spraying, the spraying period is repeated for 3 times, and finally, a wet coating layer with the thickness of 15-20 mu m is formed on the surface of the compound fertilizer core; And S4, gradient curing, namely firstly curing the wet coating layer for 10 minutes by using hot air at 70 ℃, then reducing the temperature to 45 ℃ and continuously curing for 20 minutes, and finally naturally cooling to room temperature to obtain the double-response self-repairing bio-based slow-release fertilizer finished product with the complete coating layer.
  10. 10. The method according to claim 9, wherein the coating layer is a double-layer composite structure, and is formed by sequentially coating an inner layer and an outer layer on the surface of the compound fertilizer core, the inner layer is formed by curing a first coating composition, the outer layer is formed by curing a second coating composition, the thickness ratio of the inner layer to the outer layer is 1:1.5-1:2.5, the total thickness of the coating layer is 15-20 μm, and the layered spraying in step S3 specifically comprises: a first spraying stage of spraying the first coating composition to form the inner layer; An intermediate curing stage, namely carrying out hot air treatment for 5-8 minutes at 60-65 ℃ to primarily cure the inner layer; And a second spraying stage, namely spraying the second coating composition on the surface of the inner layer to form the outer layer.

Description

Straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer and preparation method thereof Technical Field The invention relates to the technical field of agricultural fertilizers, in particular to a straw-based temperature and humidity dual-response self-repairing sustained and controlled release fertilizer and a preparation method thereof. Background In agricultural production, a huge amount of crop straw is produced each year. How to efficiently and highly utilize the agricultural wastes, reduce the pressure on the environment and convert the environmental pressure into beneficial resources is one of the important subjects of the current green development of agriculture. Meanwhile, in conventional agricultural production, chemical fertilizers are applied in large quantities in order to improve crop yield, which results in a series of environmental and ecological problems such as low nutrient utilization rate of nitrogen, phosphorus and the like, serious nutrient loss, soil hardening and water eutrophication caused by the low nutrient utilization rate. The slow-release fertilizer technology is one of effective ways for improving the utilization rate of the fertilizer and reducing environmental pollution, and is characterized in that the release rate of nutrients in the fertilizer in soil is delayed or controlled by physical or chemical means, so that the release rate is more synchronous with the absorption requirements of crops. In various technical routes of the slow-release fertilizer, the coated slow-release fertilizer is widely applied due to the relatively stable controlled-release effect and mature process. The coating material is critical in determining its properties. The ideal coating material has the characteristics of good film forming property, proper mechanical strength, controllable permeability, environmental friendliness and the like. The biomass resources, especially the straws, are utilized to develop the bio-based coating material to become a research hot spot, so that the resource utilization of wastes can be realized, the dependence on petroleum-based raw materials can be reduced, and the sustainable development concept is met. However, some existing straw-based coated sustained-release fertilizer technologies still face some challenges. For example, chinese patent document CN116375531a discloses a temperature-sensitive sustained-release fertilizer, whose coating layer can respond to temperature changes. However, the technology generally has only a single temperature response function, is difficult to adapt to complex environments of field temperature and humidity coupling changes, and still has room for improvement in the matching degree of nutrient release, actual climate conditions and water and fertilizer requirement rules of crops. In addition, the coating layer in the prior art lacks effective self-repairing capability after microcracks are generated under mechanical damage or environmental stress, and once damaged, the controlled release function is invalid, so that the long-acting property of the controlled release function is influenced. In addition, the high-efficiency conversion and utilization degree of the straws is to be improved, the liquefaction rate of the straws in the prior art is low, so that the actual bio-based active ingredients in the final coating material occupy a relatively low proportion, and a large amount of petrochemical-based auxiliary agents are often required to be added to ensure the film forming performance, so that the environmental protection advantage of the novel coating material is weakened, and the cost is possibly increased. Secondly, nutrient release of most traditional coated slow-release fertilizers mainly depends on diffusion of moisture through a film layer, a release curve is relatively fixed, and active response capability to complex environmental changes in the field is lacking. Crops have different demands for nutrients in different growth stages, and field temperature and humidity (such as rainfall and irrigation) are in dynamic change. For example, during the critical fertilizer-requiring period of some crops, the environmental temperature may be in a specific higher range, and the response temperature threshold of some existing temperature-sensitive coating materials may not be matched with the environmental temperature, so that the release function of the existing temperature-sensitive coating materials cannot be effectively triggered when required, and the accuracy of controlled release is reduced. Furthermore, the mechanical durability of the encapsulation layer is a common problem. During the processing, transportation, storage and mechanized fertilization of the fertilizer, friction and collision between particles and equipment are unavoidable, and microcracks and even breakage of the coating layer can be caused. In addition, the dry and wet cycle of the field soil can also st