A coated controlled-release fertilizer containing a thermosensitive block copolymer switch and a preparation method thereof

Abstract

The present invention discloses a coated controlled-release fertilizer containing a thermosensitive block copolymer switch and a preparation method thereof. The thermosensitive block copolymer is copolymerized by modified three blocks A, B, and C, block A is synthesized by chitosan and trimethylene carbonate, block B is dimethylaminoethyl methacrylate, and block C is synthesized by the reaction of epoxybutene and diethanolamine. The prepared thermosensitive block copolymer is combined with a basic membrane material to obtain a coated controlled-release fertilizer that is sensitive to ambient temperature, thereby realizing intelligent controlled release of fertilizer. The present invention provides a coated controlled-release fertilizer containing a thermosensitive block copolymer switch and a preparation method thereof, so that the controlled-release fertilizer can respond to ambient temperature, thereby controlling the release of nutrients.

Description

Technical Field

[0001] The invention relates to the technical field of slow-release fertilizer production, and in particular to a temperature-sensitive block copolymer switch and application thereof in the field of coated controlled-release fertilizers. Background Art

[0002] Fertilizers can provide the most basic elements necessary for crops and contribute greatly to increasing agricultural production. Traditional fertilizer nutrients are easily lost, resulting in a large waste of resources and environmental pollution. Therefore, the research on slow-release fertilizers has been a hot topic in recent decades. Controlled-release fertilizers refer to granular fertilizers with one or more layers of polymers coated on the surface to control the release of fertilizer nutrients and slow down the rate of nutrient release. There are many types of film materials for controlled-release fertilizers, such as petroleum-based and its derivatives (CN101348395A), sulfur (CN1948227A), polymers (CN102942415A, CN106458780A), polyurethane (CN101648837A, CN114014735B), etc. These controlled-release fertilizers can inhibit nutrient release to a certain extent, making the nutrient release cycle longer, thereby trying to achieve the purpose of synchronizing the release of fertilizer nutrients with the demand law of crops.

[0003] Compared with traditional fertilizers, controlled-release fertilizers can significantly reduce fertilizer waste, effectively improve nutrient utilization, and increase crop yields. However, these controlled-release fertilizers only focus on extending the nutrient controlled-release period, but ignore environmental differences. The absorption of nutrients by crops is not static, and the demand for nutrients is not the same under different conditions. For ambient temperature, crops have a comfort zone for nutrient absorption. The comfort zone of most crops is 15-25℃. When the temperature is too low, crops basically do not absorb nutrients. At this time, if a large amount of nutrients are released from the fertilizer, it will not only cause seedling burn problems, but also cause environmental pollution.

[0004] The biggest factor restricting the controlled release effect of traditional controlled release fertilizers is the micropores in the membrane structure. The larger the volume and the greater the number of micropores, the faster the water enters the fertilizer core, the easier it is for nutrients to enter and exit, and the worse the controlled release effect, which makes the nutrient utilization efficiency low and restricts the green development of agriculture and fertilizers to a certain extent. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention designs a coated controlled-release fertilizer containing a thermosensitive block copolymer switch and a preparation method thereof. The thermosensitive block copolymer switch is copolymerized by modified A, B, and C blocks. The prepared thermosensitive block copolymer switch is combined with a basic membrane material to obtain a coated controlled-release fertilizer that is sensitive to ambient temperature, thereby realizing the intelligent controlled release of fertilizer. Its working principle is as follows: on the one hand, the thermosensitive block copolymer switch is embedded in the network structure of the membrane material to block the micropores on the membrane material, reduce the channels for nutrient outflow, and improve the controlled release performance of the fertilizer; on the other hand, the conformation of the thermosensitive block copolymer switch is different at different temperatures. When it is <15°C, the thermosensitive block copolymer switch shrinks, the molecular chains are arranged tightly, and the pore size is small; when the temperature is >15°C, the thermosensitive block copolymer switch expands, the pore size increases, and nutrients flow out of the pores.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a temperature-sensitive block copolymer switch, wherein the temperature-sensitive block copolymer switch is copolymerized by block A, block B and block C;

[0008] The block A is obtained by reacting chitosan and trimethylene carbonate in a mass ratio of 3:(1-3);

[0009] The block B is obtained by diluting dimethylaminoethyl methacrylate with dichloromethane;

[0010] The block C is obtained by reacting epoxybutene and diethanolamine in a mass ratio of (1-3): (1-3).

[0011] The block A is prepared by the following method:

[0012] Chitosan is added to a sodium hydroxide solution, and trimethylene carbonate is added after 4-6 hours. Triethylamine is used as a catalyst, and the reaction is stirred for 2-3 hours. Hexane is added to precipitate the product, and the precipitate is filtered, washed and dried to obtain block A.

[0013] The block B is prepared by the following method:

[0014] Dimethylaminoethyl methacrylate is added to dichloromethane, and the mass ratio of dimethylaminoethyl methacrylate to dichloromethane is (1-5):10; and block B is obtained by dilution.

[0015] The block C is prepared by the following method:

[0016] Using 1,4-dioxane as solvent, adding ethylene glycol dimethacrylate as a crosslinking toughening agent, stirring evenly, controlling the temperature at 40-55°C, adding epoxybutene and diethanolamine, stirring continuously for 2-3 hours to obtain block C;

[0017] In a second aspect, the present invention provides a method for preparing the above-mentioned temperature-sensitive block copolymer switch, comprising the following steps:

[0018] Block C is diluted with anhydrous ethanol, heated to 50-60°C, and blocks A, B, initiator, and crosslinker are added. The polymerization reaction is carried out under the protection of inert gas for 17-19 hours. The system after polymerization is dialyzed in a buffer solution for 11-13 hours, freeze-dried, and ground to obtain a thermosensitive block copolymer switch;

[0019] The inert gas is nitrogen;

[0020] The buffer is phosphate buffered saline;

[0021] The initiator is azobisisobutyronitrile;

[0022] The crosslinking agent is one or more of N,N-methylenebisacrylamide, vinyltrimethoxysilane and triethylenediamine.

[0023] The mass ratio of the added amounts of block A, block B, block C, initiator and crosslinking agent is (2-4): (2-4): (2-4): (0.3-0.6): (0.3-0.6).

[0024] In a third aspect, the present invention provides the use of the above-mentioned temperature-sensitive block copolymer switch in the following (1) or (2):

[0025] (1) Preparation of coating materials that respond intelligently to temperature changes;

[0026] (2) Prepare controlled-release fertilizers that respond to temperature to regulate nutrient release.

[0027] In a fourth aspect, the present invention provides a coating material containing a temperature-sensitive block copolymer switch, wherein the coating material is made by mixing a base film material and a temperature-sensitive block copolymer switch;

[0028] The added amount of the temperature-sensitive block copolymer switch is 1-10% of the mass of the coating material.

[0029] In a fifth aspect, the present invention provides a coated controlled-release fertilizer containing a thermosensitive block copolymer switch, wherein the coated controlled-release fertilizer is prepared by the following method:

[0030] The coating material containing the temperature-sensitive block copolymer switch is coated on the surface of the fertilizer particles and solidified into a film to obtain a coated controlled-release fertilizer containing the temperature-sensitive block copolymer switch.

[0031] Preferably, the coating material accounts for 3-7% of the total weight of the fertilizer particles.

[0032] The beneficial effects of the present invention are:

[0033] (1) The present invention designs a novel thermosensitive block copolymer switch that can sense temperature changes. When the temperature is less than 15°C, the macromolecular chains of the thermosensitive block copolymer switch aggregate and shrink, the molecular chains are arranged tightly, and the pore size is small; when the temperature is greater than 15°C, the hydrogen bonding forces within and between the molecules of the thermosensitive block copolymer switch decrease, the macromolecular chains are dispersed and expanded, and the pore size increases. The thermosensitive block copolymer is used to block the micropores of the membrane material of the controlled-release fertilizer to improve the controlled-release performance.

[0034] (2) The thermosensitive block copolymer prepared by the present invention can be applied to any coated controlled-release fertilizer to improve its performance and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 : Schematic diagram of the synthesis reaction of the temperature-sensitive block copolymer switch of the present invention.

[0036] Figure 2 : Schematic diagram of the working principle of the coated controlled-release fertilizer containing a thermosensitive block copolymer switch prepared by the present invention at different temperatures; the conformation of the thermosensitive block copolymer switch is different at different temperatures. When the temperature is <15°C, the thermosensitive block copolymer switch shrinks, the molecular chains are tightly arranged, and the pore size is small; when the temperature is >15°C, the thermosensitive block copolymer switch expands, the pore size increases, and nutrients flow out of the pores; wherein A: schematic diagram of the conformation of the thermosensitive block copolymer switch at <15°C, B: schematic diagram of the conformation of the thermosensitive block copolymer switch at >15°C.

[0037] Figure 3 : The nutrient static water release rates of the 5% coated controlled-release fertilizer without a thermosensitive block copolymer switch prepared in Comparative Example 1 of the present invention and the 5% coated controlled-release fertilizer with a thermosensitive block copolymer switch prepared in Example 3 of the present invention at 10°C and 25°C respectively.

[0038] Figure 4 : Comparison chart of the cumulative nutrient release of the coated controlled-release fertilizer containing a thermosensitive block copolymer switch prepared in Example 3 of the present invention, the cumulative nutrient release of wheat at different stages, and the total cumulative nutrient release of wheat. DETAILED DESCRIPTION

[0039] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0040] As mentioned earlier, the comfort zone of most crops is 15-25℃. When the temperature is too low, the crops basically do not absorb nutrients. If a large amount of nutrients are released from the fertilizer at this time, it will not only cause seedling burn, but also cause environmental pollution. Traditional controlled-release fertilizers cannot sense temperature changes and adjust the release of nutrients.

[0041] There are also some reports on temperature-sensitive controlled-release fertilizers in the prior art, but the design ideas for regulating nutrient release based on temperature changes are different, and there is currently no unified design guiding principle.

[0042] The inventor of this patent has been working in the field of intelligent fertilizer for many years. In order to solve the problem of mismatch between nutrient release of controlled-release fertilizer and crop absorption when the ambient temperature is low, the inventor has developed and designed a thermosensitive block copolymer switch, which is copolymerized by block A, block B, and block C. The synthesis diagram is shown in the figure below. Figure 1 The thermosensitive block copolymer switch of the present invention can sense temperature changes through the synergistic effect of block A, block B and block C. When the temperature is less than 15°C, the macromolecular chains of the thermosensitive block copolymer switch aggregate and shrink, the molecular chains are tightly arranged, and the pore size is small; when the temperature is greater than 15°C, the hydrogen bonding forces within and between the molecules of the thermosensitive block copolymer switch decrease, the macromolecular chains are dispersed and expanded, and the pore size increases ( Figure 2 ).

[0043] The thermosensitive block copolymer switch designed based on the present invention can be mixed with a basic membrane material to produce a coating material that can respond to temperature changes. The thermosensitive block copolymer switch is embedded in the network structure of the membrane material to block the micropores on the membrane material. This can not only make the membrane structure denser and reduce the volume of the micropores, but also intelligently sense the temperature changes in the environment, thereby controlling the release of fertilizer nutrients at different temperatures, reducing the problem of nutrient loss and waste, and improving nutrient utilization efficiency.

[0044] Below in conjunction with embodiment, the specific embodiment of the present invention is described in further detail.The following detailed description is all illustrative, is intended to provide further description to the application, but is not intended to limit the scope of the present invention.Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the application belongs.

[0045] Example 1: Preparation of coated controlled-release fertilizer containing a thermosensitive block copolymer switch

[0046] 1. Preparation of Thermosensitive Block Copolymer Switches

[0047] (1) 3 g of chitosan (McLean, Product No. C804726) was added to 50 g of a 30% sodium hydroxide solution for alkalization. After 5 h, 1 g of trimethylene carbonate and 0.15 g of a catalyst (triethylamine) were added. The mixture was stirred continuously under a magnetic stirrer. After reacting for 2 h, 100 ml of hexane was added to precipitate the mixture. The precipitated product was filtered out, washed with deionized water for purification, and dried in a vacuum drying oven to obtain block A.

[0048] (2) 3 g of dimethylaminoethyl methacrylate was poured into 10 g of dichloromethane to dilute to obtain block B.

[0049] (3) Add 2 g of ethylene glycol dimethacrylate to 20 ml of 1,4-dioxane, stir evenly, control the temperature at 50° C., add 4 g of epoxybutene and 4 g of diethanolamine, and react for 2 h under continuous stirring to obtain block C.

[0050] (4) In a three-necked round-bottom flask containing 50 g of anhydrous ethanol, 3 g of block C was added, and a stirrer and a condensing reflux device were connected. The flask was placed in an oil bath at 55°C, and 3 g of block A, 3 g of block B, 0.45 g of azobisisobutyronitrile, and 0.45 g of N,N-methylenebisacrylamide crosslinker were added and mixed evenly. The mixture was polymerized under nitrogen protection for 18 h, and then the solution was dialyzed in phosphate buffered saline for 12 h. The solution was freeze-dried and ground to obtain a thermosensitive block copolymer switch.

[0051] 2. Preparation of Encapsulation Materials Containing Thermosensitive Block Copolymer Switches

[0052] Castor oil and isocyanate are mixed in a weight ratio of 6.47:3.23 to form a base membrane material; the temperature-sensitive block copolymer switch prepared in this embodiment is added to the base membrane material and mixed evenly to prepare a coating material containing the temperature-sensitive block copolymer switch; the amount of the temperature-sensitive block copolymer switch added is 3% of the weight of the coating material.

[0053] 3. Preparation of coated controlled-release fertilizer containing thermosensitive block copolymer switch

[0054] The coating material was heated at 65°C to form a coating liquid, 10g of the coating liquid and 1000g of urea were poured into a drum coating machine, the temperature was adjusted to 65°C, the speed was adjusted to 50r / min, the coating liquid was evenly covered on the outer surface of the fertilizer particles, and after the coating liquid was completely solidified into a film, a controlled-release fertilizer with a coating amount of 1% was obtained. The above-mentioned sample addition process was repeated 5 times to obtain a 5% coated controlled-release fertilizer containing a thermosensitive block copolymer switch.

[0055] Example 2: Preparation of coated controlled-release fertilizer containing a thermosensitive block copolymer switch

[0056] 1. Preparation of Thermosensitive Block Copolymer Switches

[0057] (1) 3 g of chitosan was added to 80 g of a 30% sodium hydroxide solution for alkalization. After 5 h, 2 g of trimethylene carbonate and 0.2 g of a catalyst (triethylamine) were added. The mixture was stirred continuously under a magnetic stirrer. After reacting for 2 h, 100 ml of hexane was added to precipitate the mixture. The precipitated product was filtered out, washed with deionized water for purification, and dried in a vacuum drying oven to obtain block A.

[0058] (2) Pour 2 g of dimethylaminoethyl methacrylate into 10 g of dichloromethane to dilute and obtain block B.

[0059] (3) Add 1 g of ethylene glycol dimethacrylate to 20 ml of 1,4-dioxane, stir evenly, control the temperature at 50° C., add 1 g of epoxybutene and 1 g of diethanolamine, and react for 2 h under continuous stirring to obtain block C.

[0060] (4) In a three-necked round-bottom flask containing 80 g of anhydrous ethanol, 1 g of block C was added, and a stirrer and a condensing reflux device were connected. The flask was placed in an oil bath at 55°C, and 1 g of block A, 1 g of block B, 0.1 g of azobisisobutyronitrile, and 0.1 g of N,N-methylenebisacrylamide crosslinker were added and mixed evenly. The mixture was polymerized under nitrogen protection for 18 h, and then the solution was dialyzed in phosphate buffered saline for 12 h. The solution was freeze-dried and ground to obtain a thermosensitive block copolymer switch.

[0061] 2. Preparation of Encapsulation Materials Containing Thermosensitive Block Copolymer Switches

[0062] Castor oil and isocyanate are mixed in a weight ratio of 6.27:3.13 to form a base membrane material; the temperature-sensitive block copolymer switch prepared in this embodiment is added to the base membrane material and mixed evenly to prepare a coating material containing the temperature-sensitive block copolymer switch; the amount of the temperature-sensitive block copolymer switch added is 6% of the weight of the coating material.

[0063] 3. Preparation of coated controlled-release fertilizer containing thermosensitive block copolymer switch

[0064] The coating material was heated at 65°C to form a coating liquid, 10g of the coating liquid and 1000g of urea were poured into a drum coating machine, the temperature was adjusted to 65°C, the speed was adjusted to 50r / min, the coating liquid was evenly covered on the outer surface of the fertilizer particles, and after the coating liquid was completely solidified into a film, a controlled-release fertilizer with a coating amount of 1% was obtained. The above-mentioned sample addition process was repeated 5 times to obtain a 5% coated controlled-release fertilizer containing a thermosensitive block copolymer switch.

[0065] Example 3: Preparation of coated controlled-release fertilizer containing a thermosensitive block copolymer switch

[0066] 1. Preparation of Thermosensitive Block Copolymer Switches

[0067] (1) 3 g of chitosan was added to 100 g of a 30% sodium hydroxide solution for alkalization. After 5 h, 3 g of trimethylene carbonate and 0.5 g of a catalyst (triethylamine) were added. The mixture was stirred continuously under a magnetic stirrer. After reacting for 2 h, 100 ml of hexane was added to precipitate the mixture. The precipitated product was filtered out, washed with deionized water for purification, and dried in a vacuum drying oven to obtain block A.

[0068] (2) 5 g of dimethylaminoethyl methacrylate was poured into 10 g of dichloromethane to dilute to obtain block B.

[0069] (3) Add 2 g of ethylene glycol dimethacrylate to 40 ml of 1,4-dioxane, stir evenly, control the temperature at 50° C., add 3 g of epoxybutene and 3 g of diethanolamine, and react for 2 h under continuous stirring to obtain block C.

[0070] (4) In a three-necked round-bottom flask containing 100 g of anhydrous ethanol, 5 g of block C was added, and a stirrer and a condensing reflux device were connected. The flask was placed in an oil bath at 55°C, and 5 g of block A, 5 g of block B, 2 g of azobisisobutyronitrile, and 2 g of N,N-methylenebisacrylamide crosslinker were added and mixed evenly. The mixture was polymerized under nitrogen protection for 18 h, and then the solution was dialyzed in phosphate buffered saline for 12 h. The solution was freeze-dried and ground to obtain a thermosensitive block copolymer switch.

[0071] 2. Preparation of Encapsulation Materials Containing Thermosensitive Block Copolymer Switches

[0072] Castor oil and isocyanate are mixed in a weight ratio of 6:3 to form a base membrane material; the temperature-sensitive block copolymer switch prepared in this embodiment is added to the base membrane material and mixed evenly to prepare a coating material containing the temperature-sensitive block copolymer switch; the amount of the temperature-sensitive block copolymer switch added is 10% of the weight of the coating material.

[0073] 3. Preparation of coated controlled-release fertilizer containing thermosensitive block copolymer switch

[0074] The coating material was heated at 65°C to form a coating liquid, 10g of the coating liquid and 1000g of urea were poured into a drum coating machine, the temperature was adjusted to 65°C, the speed was adjusted to 50r / min, the coating liquid was evenly covered on the outer surface of the fertilizer particles, and after the coating liquid was completely solidified into a film, a controlled-release fertilizer with a coating amount of 1% was obtained. The above-mentioned sample addition process was repeated 5 times to obtain a 5% coated controlled-release fertilizer containing a thermosensitive block copolymer switch.

[0075] Comparative Example 1: Preparation of ordinary coated controlled-release fertilizer without adding thermosensitive block copolymer switch

[0076] Castor oil and isocyanate were mixed in a weight ratio of 6:3 to form the base membrane material.

[0077] The base film material was heated at 65°C to form a coating liquid, 10g of the coating liquid and 1000g of urea were poured into a drum coating machine, the temperature was adjusted to 65°C, the speed was adjusted to 50r / min, and the coating liquid was evenly covered on the outer surface of the fertilizer particles. After the coating liquid was completely solidified into a film, a controlled-release fertilizer with a coating amount of 1% was obtained. Repeat the above-mentioned sample addition process 5 times to obtain a 5% ordinary coated controlled-release fertilizer without adding a thermosensitive block copolymer switch.

[0078] Comparative Example 2: Preparation of coated controlled-release fertilizer with only block A added

[0079] The preparation method of block A is the same as that of Example 3. A three-necked round-bottom flask containing 100 g of anhydrous ethanol was connected with a stirrer and a condensing reflux device, and the flask was placed in a 55°C oil bath, 5 g of block A, 2 g of azobisisobutyronitrile, and 2 g of N,N-methylenebisacrylamide crosslinker were added and mixed evenly, polymerized under nitrogen protection for 18 h, and then the solution was dialyzed in phosphate buffered saline for 12 h, freeze-dried, and ground to obtain polymer A.

[0080] Castor oil and isocyanate are mixed in a weight ratio of 6:3 to form a basic membrane material; polymer A is added to the basic membrane material and mixed evenly to prepare a coating material; the amount of polymer A added is 10% of the weight of the coating material.

[0081] The coating material was heated at 65°C to form a coating liquid, 10g of the coating liquid and 1000g of urea were poured into a drum coating machine, the temperature was adjusted to 65°C, the speed was adjusted to 50r / min, the coating liquid was evenly covered on the outer surface of the fertilizer particles, and after the coating liquid was completely solidified into a film, a controlled-release fertilizer with a coating amount of 1% was obtained. The above-mentioned sample addition process was repeated 5 times to obtain a 5% coated controlled-release fertilizer with only block A added.

[0082] Comparative Example 3: Preparation of coated controlled-release fertilizer with only block B added

[0083] The preparation method of block B is the same as that of Example 3. A three-necked round-bottom flask containing 100 g of anhydrous ethanol was connected with a stirrer and a condensing reflux device, and the flask was placed in a 55°C oil bath, 5 g of block B, 2 g of azobisisobutyronitrile, and 2 g of N,N-methylenebisacrylamide crosslinker were added and mixed evenly, polymerized under nitrogen protection for 18 h, and then the solution was dialyzed in phosphate buffered saline for 12 h, freeze-dried, and ground to obtain polymer B.

[0084] Castor oil and isocyanate are mixed in a weight ratio of 6:3 to form a basic membrane material; polymer B is added to the basic membrane material and mixed evenly to prepare a coating material; the amount of polymer B added is 10% of the weight of the coating material.

[0085] The coating material was heated at 65°C to form a coating liquid, 10g of the coating liquid and 1000g of urea were poured into a drum coating machine, the temperature was adjusted to 65°C, the speed was adjusted to 50r / min, the coating liquid was evenly covered on the outer surface of the fertilizer particles, and after the coating liquid was completely solidified into a film, a controlled-release fertilizer with a coating amount of 1% was obtained. The above-mentioned sample addition process was repeated 5 times to obtain a 5% coated controlled-release fertilizer with only block B added.

[0086] Comparative Example 4: Preparation of coated controlled-release fertilizer with only block C added

[0087] The preparation method of block C is the same as that of Example 3. A three-necked round-bottom flask containing 100 g of anhydrous ethanol was connected with a stirrer and a condensing reflux device, and the flask was placed in a 55°C oil bath, 5 g of block C, 2 g of azobisisobutyronitrile, and 2 g of N,N-methylenebisacrylamide crosslinker were added and mixed evenly, polymerized under nitrogen protection for 18 h, and then the solution was dialyzed in phosphate buffered saline for 12 h, freeze-dried, and ground to obtain polymer C.

[0088] Castor oil and isocyanate are mixed in a weight ratio of 6:3 to form a basic membrane material; polymer C is added to the basic membrane material and mixed evenly to prepare a coating material; the amount of polymer C added is 10% of the weight of the coating material.

[0089] The coating material was heated at 65°C to form a coating liquid, 10g of the coating liquid and 1000g of urea were poured into a drum coating machine, the temperature was adjusted to 65°C, the speed was adjusted to 50r / min, the coating liquid was evenly covered on the outer surface of the fertilizer particles, and after the coating liquid was completely solidified into a film, a controlled-release fertilizer with a coating amount of 1% was obtained. The above-mentioned sample addition process was repeated 5 times to obtain a 5% coated controlled-release fertilizer with only block C added.

[0090] Test Example 1: Determination of nutrient release rate under different temperature conditions

[0091] The coated controlled-release fertilizers prepared in Example 3 and Comparative Example 1 were cultured in static water at 10° C. and 25° C., respectively, and samples were taken at regular intervals to determine the nutrient release rates.

[0092] The results are as follows Figure 3As shown in the figure, it can be seen that at 10°C and 25°C, the controlled-release period of the coated controlled-release fertilizer prepared in Example 3 is much longer than that of the coated controlled-release fertilizer prepared in Comparative Example 1, indicating that the addition of the thermosensitive block copolymer switch can extend the controlled-release period of the controlled-release fertilizer; the coated controlled-release fertilizer prepared in Comparative Example 1 has a release rate of 49.03% in 60 days at 10°C and a release rate of 77.58% in 60 days at 25°C, while the nutrient release rate of the coated controlled-release fertilizer prepared in Example 3 is only 8.43% in 60 days at 10°C and reaches 59.76% in 60 days at 25°C, indicating that the addition of the thermosensitive block copolymer switch can achieve different controlled-release effects at different temperatures; at the same time, under the condition of 25°C, the nutrient release rate of the coated controlled-release fertilizer prepared in Example 3 is slower than that of the coated controlled-release fertilizer prepared in Comparative Example 1, which allows the crop to release nutrients while extending the nutrient release period, so that the crop has a continuous nutrient supply within a specific period, and will not cause nutrient loss caused by concentrated nutrient release.

[0093] Test Example 2: Investigation of nutrient controlled release time under low temperature conditions

[0094] The coated controlled-release fertilizers prepared in Example 3 and Comparative Examples 1-4 were cultured in static water at 10° C. Samples were taken at regular intervals to determine the nutrient release rate. The time required for the cumulative nutrient release rate to reach 80% was recorded as the controlled-release period.

[0095] The results show that the controlled-release period of the coated controlled-release fertilizer prepared in Example 3 at 10°C is 126 days, the controlled-release period of the coated controlled-release fertilizer prepared in Comparative Example 1 at 10°C is 96 days, the controlled-release period of the coated controlled-release fertilizer prepared in Comparative Example 2 at 10°C is 110 days, the controlled-release period of the coated controlled-release fertilizer prepared in Comparative Example 3 at 10°C is 100 days, and the controlled-release period of the coated controlled-release fertilizer prepared in Comparative Example 4 at 10°C is 105 days.

[0096] The above results show that the coated controlled-release fertilizer prepared by adding the thermosensitive block copolymer switch of the present invention can slow down the nutrient release under low temperature conditions, prolong the nutrient controlled-release time, and avoid the problems of seedling burning and nutrient waste caused by the small nutrient demand of crops under low temperature conditions and the large nutrient release of fertilizers; and compared with the coated controlled-release fertilizer to which block A, block B and block C are added separately, the addition of the thermosensitive block copolymer switch of the present invention has a synergistic effect in prolonging the nutrient controlled-release time under low temperature conditions.

[0097] Test Example 3: Investigation on the consistency between nutrient release of coated controlled-release fertilizer and crop requirements

[0098] The nutrient release curve of the coated controlled-release fertilizer prepared in Example 3 was compared with the nutrient requirements of wheat at different stages (overwintering, greening, jointing, booting, flowering and maturity) and the total nutrient requirements. The results are as follows: Figure 4As shown, the results show that the nutrient release trend of the coated controlled-release fertilizer prepared by the present invention is relatively synchronized with the nutrient absorption trend of wheat.

[0099] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A temperature sensitive switch, characterized in that: The method for preparing the temperature sensitive switch comprises the following steps: Block C was diluted with anhydrous ethanol, heated to 55°C, and blocks A, B, initiator, and crosslinker were added. The polymerization reaction was carried out under the protection of inert gas for 18 hours. The system after polymerization was dialyzed in a buffer solution for 12 hours, freeze-dried, and ground to obtain a temperature-sensitive switch. The buffer is phosphate buffered saline; The initiator is azobisisobutyronitrile; The cross-linking agent is N,N-methylenebisacrylamide; The mass ratio of the added amounts of block A, block B, block C, initiator, and crosslinking agent is 5:5:5:2:2; Wherein, block A is obtained by reacting chitosan and trimethylene carbonate in a mass ratio of 1:1, and the block A is prepared by the following method: Chitosan was added to a sodium hydroxide solution, and trimethylene carbonate was added after 5 hours, and triethylamine was used as a catalyst. After continuous stirring for 2 hours, hexane was added to precipitate it, and the precipitated product was filtered out, washed and dried to obtain block A; Block B is prepared by the following method: Add dimethylaminoethyl methacrylate to dichloromethane, the mass ratio of dimethylaminoethyl methacrylate to dichloromethane is 1:2; dilute to obtain block B; The block C is prepared by the following method: 1,4-dioxane is used as a solvent, ethylene glycol dimethacrylate is added as a cross-linking toughening agent, and after stirring evenly, the temperature is controlled at 50°C, epoxybutene and diethanolamine are added, and the reaction is stirred continuously for 2 hours to obtain block C; wherein, 1,4-dioxane is added in volume form, and the unit of addition is mL, and ethylene glycol dimethacrylate, epoxybutene and diethanolamine are added in mass form, and the unit of addition is g; the volume-to-mass ratio of 1,4-dioxane, ethylene glycol dimethacrylate, epoxybutene and diethanolamine added is 40:2:3:

3.

2. Application of the temperature sensitive switch according to claim 1 in the following (1) or (2): (1) Preparation of coating materials that respond intelligently to temperature changes; (2) Prepare controlled-release fertilizers that respond to temperature to regulate nutrient release.

3. A coating material, characterized in that: include: A basic film material and a temperature-sensitive switch as claimed in claim 1.

4. The coating material according to claim 3, characterized in that: The added amount of the temperature sensitive switch is 1-10% of the mass of the coating material.

5. A coated controlled-release fertilizer containing a temperature-sensitive switch, characterized in that: The coated controlled-release fertilizer is prepared by the following method: Coating the coating material according to claim 3 or 4 on the surface of the fertilizer particles and solidifying them into a film to obtain a coated controlled-release fertilizer containing a temperature-sensitive switch; The coating material accounts for 3-7% of the total weight of the fertilizer particles.

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