CN113831178B

CN113831178B - Slow-release coated fertilizer and preparation method thereof

Info

Publication number: CN113831178B
Application number: CN202111043261.8A
Authority: CN
Inventors: 王�华; 周传健; 梁艳; 卢海峰; 张晨
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2021-09-07
Filing date: 2021-09-07
Publication date: 2023-05-30
Anticipated expiration: 2041-09-07
Also published as: WO2023035193A1; CN113831178A

Abstract

The application discloses a slow-release coated fertilizer and a preparation method thereof, belonging to the field of composite materials. The slow-release coated fertilizer comprises fertilizer particles and a film coated outside the fertilizer particles, wherein the film is prepared from an organosilicon polymer material; the organic silicon polymer material is prepared by Diels-Alder reaction of modified polysiloxane A and modified polysiloxane B, wherein the organic polysiloxane A has at least one conjugated diene bond which is not aromatic hydrocarbon in 1 molecule, and the organic polysiloxane B has at least one substituted olefin bond which has Diels-Alder reaction with the diene bond which is not aromatic hydrocarbon in 1 molecule. The slow-release coated fertilizer has high uniformity of coating, is beneficial to slow release of the fertilizer and has good slow release effect; the film of the slow-release coated fertilizer has good hydrophobic property, permeability, film forming property and reusability, so the slow-release coated fertilizer has remarkable advantage of low coating material amount and has positive effect on environmental protection.

Description

Slow-release coated fertilizer and preparation method thereof

Technical Field

The application relates to a slow-release coated fertilizer and a preparation method thereof, and belongs to the field of fertilizer preparation.

Background

With the rapid growth of world population and the gradual improvement of the living standard of people, the demands for the yield and quality of grains are increased year by year, and the application of the fertilizer becomes the most effective method for improving the quality and yield of grains at present. With the rapid development of agriculture, the phenomenon of overapplication of fertilizer in agricultural production is frequent, and the reason is that most of nutrients are lost before being absorbed by crops due to the influence of external factors such as rain wash, light decomposition and the like after the fertilizer is applied, so that the utilization rate of the fertilizer is greatly reduced, and the phenomenon of overapplication of the fertilizer is caused. And excessive application of the fertilizer can inhibit the growth of crops, reduce the quality of agricultural products, cause the damage of soil structures, cause non-point source pollution and the like. Therefore, how to improve the fertilizer utilization rate on the premise of ensuring high and stable yield of grains, further reduce the agricultural production cost, lighten the non-point source pollution caused by the development of the agricultural acceleration, realize the green ecological sustainable development of the agriculture and become the key problem of the agricultural development research in China and even the world at present.

The organic silicon polymer material is used as a special polymer material, and the special Si-O chain segment of the organic silicon polymer material has special advantages in the aspects of thermal performance, flexibility, film forming property, hydrophobicity and the like. The early research results show that the organosilicon polymer can form a compact protective film on the surface of the matrix, can still prevent the organosilicon polymer from corroding the matrix under the action of strong acid and strong alkali, has excellent hydrophobicity, and can be used as a hydrophobic coating for slow release of fertilizer. However, pt catalyst is needed in the preparation process of the organic silicon polymer, so that the cost is relatively high, and the application of the organic silicon polymer in the agricultural field is hindered. On the other hand, the existing slow-release fertilizer has the problems of resource waste and abusive application of the fertilizer caused by poor slow-release effect due to poor performance of the coating material.

Disclosure of Invention

In order to solve the problems, the application provides a slow-release coated fertilizer and a preparation method thereof, wherein the slow-release coated fertilizer has high uniformity of coating, is favorable for slow release of the fertilizer and has good slow release effect; the coating material of the outer layer of the slow-release coated fertilizer has good hydrophobic property, permeability, film forming property and reusability, so the slow-release coated fertilizer has remarkable advantage of low amount of the coating material, and has positive effect on environmental protection; the processing cost of the slow-release coated fertilizer is low.

According to one aspect of the present application, there is provided a slow release coated fertilizer comprising fertilizer particles and a film coated over the fertilizer particles, the film being made of a silicone polymeric material;

the organic silicon polymer material is prepared by Diels-Alder reaction of modified polysiloxane A and modified polysiloxane B, wherein the organic polysiloxane A has at least one substituted olefin bond group in 1 molecule, and the organic polysiloxane B has at least one conjugated diene bond group containing non-aromatic hydrocarbon and having Diels-Alder reaction with the substituted olefin bond group in 1 molecule.

The Si-O chain segment in the organopolysiloxane has special advantages in thermal performance, flexibility, film forming property, hydrophobicity and the like, the organopolysiloxane forms a compact protective film on the surface of the fertilizer, the organopolysiloxane can still prevent the organopolysiloxane from corroding the fertilizer under the action of strong acid and strong alkali, and the organopolysiloxane has excellent hydrophobicity and excellent characteristics as a fertilizer coating; in addition, the organic polysiloxane is directly prepared through Diels-Alder reaction, so that the coating cost of the fertilizer is reduced, the porosity of the prepared organic polysiloxane is controlled, the release of the fertilizer can be ensured, the release rate is relatively slow, the plant can fully absorb fertilizer nutrients, and the utilization rate of the fertilizer is improved; and the organopolysiloxane can undergo Diels-Alder reaction so that repeated coating can be realized to provide uniformity of the formed film, so as to avoid the problem of uneven release of fertilizer caused by uneven coating.

Optionally, the mass ratio of the organosilicon polymeric material to the fertilizer granule is 0.3% -5%. Alternatively, the upper and lower limits of the mass ratio of the silicone polymeric material to the fertilizer granule are independently selected from 0.5%, 1%, 2%, 3% or 4%, respectively. Selected from 0.5% -5%. Preferably, the mass ratio of the silicone polymeric material to the fertilizer particles is 0.3% -3%, more preferably 1% -3%. The control of the mass ratio can ensure the integrity of the fertilizer coating, reduce the use amount of the coating material, and is beneficial to controlling the optimal release rate of the fertilizer.

Optionally, the fertilizer particles have a particle size of 10-40 mesh. Preferably, the fertilizer particles have a particle size of 20 to 30 mesh. The mesh number of the fertilizer particles can enable the fertilizer to be fully released in a proper time, and excessive fertilizer particles can cause incomplete release of nutrients in a limited time, so that the utilization rate of the fertilizer is reduced; too small can result in complete release of the fertilizer when the fertilizer does not reach 28 days, and the slow release fertilizer standard is not met.

Optionally, the fertilizer particles are at least one selected from urea, nitrogen-phosphorus-potassium compound fertilizer, diammonium phosphate, medium element fertilizer, biological fertilizer and organic fertilizer.

Alternatively, the substituted olefinic bond-containing group in the modified polysiloxane a may be a maleimide group, and the non-aromatic hydrocarbon-containing diene bond group in the organopolysiloxane B is a furoacetyl group; alternatively, the substituted olefinic bond-containing group in the modified polysiloxane a may be a maleimide derivative, and the non-aromatic hydrocarbon-containing diene bond group in the organopolysiloxane B is a furoacetyl derivative.

Optionally, the substituted olefin bond-containing group in the modified polysiloxane a is a maleimide group, and the non-aromatic hydrocarbon-containing diene bond group in the organopolysiloxane B is a furoacetyl group;

the modified polysiloxane A and the modified polysiloxane B are subjected to crosslinking polymerization to form at least one reversible substituted cyclohexenyl to prepare the organosilicon polymeric material, and the structure of the reversible substituted cyclohexenyl is shown as a formula I:

optionally, the modified polysiloxane A and the modified polysiloxane B are reversibly crosslinked and polymerized through a plurality of maleimide groups and furoacetyl groups, so that the prepared organosilicon polymer material is a porous material and can be used as a slow-release coating material.

Optionally, the grafting ratio of the maleimide group in the modified polysiloxane A is X, the grafting ratio of the furan acetyl group in the modified polysiloxane B is Y, and the ratio of the grafting ratio X to the grafting ratio Y is 1:1.2-1.5.

Preferably, the ratio of the grafting ratio X to the grafting ratio Y is 1:1.2-1.5; more preferably, the ratio of the grafting ratio X to the grafting ratio Y is 1:1.5, so that the grafted maleimide group and the furan acetyl group can be fully reacted, and the utilization rate of the grafting raw material is improved.

Specifically, the grafting rate X is 8% -20%, and the grafting rate Y is 5% -25%; preferably, the grafting ratio X is 10% -20% and the grafting ratio Y is 12% -24%. The values of the grafting ratio X and the grafting ratio Y can ensure the slow release effect of the prepared organosilicon polymeric material, in particular to the slow release effect of the fertilizer coating.

The calculation of X, Y graft ratio was performed as follows: about 1.5g of the modified polysiloxane was accurately weighed in a conical flask with an analytical balance, about 20mL of tetrahydrofuran and toluene were added for dissolution, then 0.1mol/L hydrochloric acid solution was added, after shaking for 5min, phenolphthalein indicator was added, and excess acid was measured with a calibrated sodium hydroxide standard solution until the solution was discolored. In addition, a blank was made on the hydrochloric acid solution. The amino concentration and the graft ratio of X, Y were calculated according to the following formula:

amino concentration= (V ₀ -V)C _NaOH /m；

Grafting ratio = (concentration of amino before reaction-concentration of amino after reaction)/concentration of amino before reaction × 100%

Wherein: v (V) ₀ -titration of sodium hydroxide volume (mL) consumed by the blank;

v-titration of sodium hydroxide volume consumed (mL) by the sample;

C _NaOH standard sodium hydroxide concentration (mol/L);

m-sample mass (g).

Alternatively, the polysiloxane a and the polysiloxane B are each independently selected from poly (diorganosiloxanes).

Optionally, the structural formula of the polysiloxane A is shown as a formula II:

wherein R1, R2, R3 and R4 are each independently selected from one of hydrocarbyl, substituted hydrocarbyl, heteroaryl, substituted heteroaryl and non-hydrocarbon substituents; m1 and n1 are respectively taken from integers more than 0, the weight average molecular weight of the amino polysiloxane A in the formula II is 2000-20000, and the grafting rate of amino groups in the amino polysiloxane A is 3% -30%; the R is ₁ 、R ₂ 、R ₃ And R is ₄ Is linked to a maleimide group of a reversibly substituted cyclohexenyl group of formula I.

Optionally, the structural formula of the polysiloxane B is shown as a formula III respectively:

wherein R5, R6, R7 and R8 are each independently selected from one of hydrocarbyl, substituted hydrocarbyl, heteroaryl, substituted heteroaryl and non-hydrocarbon substituents; m2 and n2 are respectively taken from integers more than 0, the weight average molecular weight of the amino polysiloxane B in the formula III is 2000-20000, and the grafting rate of amino groups in the amino polysiloxane B is 3% -30%; the imino groups contained in R5, R6, R7 and R8 are connected with the furylacetyl group of the reversibly substituted cyclohexenyl of the formula I.

Preferably, each of R1, R2, R3 and R4 is independently selected from alkyl; one of R1, R2, R3 and R4 is connected with a nitrogen atom of the reversibly substituted cyclohexenyl of the formula I; preferably, each of R5, R6, R7 and R8 is independently selected from imino-substituted alkyl; the imino group of one of R5, R6, R7 and R8 is linked to the furoacetyl group of the reversibly substituted cyclohexenyl group of formula I.

More preferably, the carbon chain parts in R1, R2, R3, R4 and R5, R6, R7 and R8 are respectively and independently selected from one of C1-C5 alkyl.

Most preferably, R2 and R6 are each propyl and imino substituted propyl or of formula VI, and R3, R4, R5, R7 and R8 are each methyl;

wherein m3 and n3 are each selected from integers not less than 1, specifically, if m3 is 2 and n3 is 3.

Specifically, the preparation of the aminated polysiloxane is prepared based on hydrolysis and end capping of an amino dialkoxysilane coupling agent, dimethyl dialkoxysilane and hexamethyldisiloxane, and the calculation of the amino grafting rate is carried out according to a nuclear magnetic method by calculating the ratio of the amino peak area to the Si-CH3 peak area:

grafting = 3 x amino peak area/2 x Si-CH3 peak area x 100%.

Preferably, the ratio between the m1 value and the m2 value is 1:1.5, so as to ensure that the Diels-Alder reaction can be completely carried out.

Optionally, the modified polysiloxane A and the modified polysiloxane B are respectively linear polysiloxanes, so that the flexibility and the film forming property of the prepared organosilicon polymer material are improved.

According to another aspect of the present application, there is provided a method of preparing a self-healing silicone polymeric material comprising the steps of:

providing a modified polysiloxane a, which is a polysiloxane a having at least one maleimide group substitution in 1 molecule;

providing a modified polysiloxane B, wherein the modified polysiloxane B is polysiloxane B with at least one furan acetyl group substitution in 1 molecule;

and (3) dissolving the modified polysiloxane A and the modified polysiloxane B, and heating to enable Diels-Alder reaction to occur, so as to generate at least one reversible substituted cyclohexene crosslinked organosilicon polymer material.

Optionally, the preparation method of the modified polysiloxane A comprises the following steps:

providing an aminated polysiloxane a;

after the aminated polysiloxane A and the maleic anhydride are dissolved in the organic solvent I, heating and refluxing are carried out for at least 3 hours, thus obtaining the modified polysiloxane A.

Optionally, the molecular weight of the aminated polysiloxane A is 2000-20000; and the grafting rate of the amino groups in the amino polysiloxane A is 3-30%, and the molar ratio of the amino polysiloxane A to the maleic anhydride is 1:1-3 based on the amino groups. The weight average molecular weight range of the aminated polysiloxane A is 2000-20000, and the molecular weight range can promote the free stretching of a molecular chain in a benign solvent due to lower amino grafting rate, so that the reaction between maleic anhydride and amino in a side chain is facilitated, and the problem of incomplete reaction caused by incapability of free stretching of the molecular chain due to overlarge molecular weight is avoided. The grafting ratio of the amino groups in the aminated polysiloxane A is favorable for grafting maleimide functional groups with larger space volume, and incomplete reaction caused by steric hindrance among the maleimide groups is avoided. The molar ratio of the amino group to the maleic anhydride is favorable for the full reaction between the maleic anhydride and the amino group, and the incomplete reaction problem is avoided.

In particular, the upper and lower limits of the range of weight average molecular weights of the aminated polysiloxane a may be selected from 3000, 5000, 8000, 11000, 14000, 17000 or 19000, respectively, and the weight average molecular weight of a particular aminated polysiloxane a may be 3000, 5000, 8000, 10000 or 15000.

Preferably, the amino groups in the aminated polysiloxane A have a grafting ratio of 3% to 30%. Still further, the amino groups in the aminated polysiloxane A have a grafting ratio of 10% to 15%.

Preferably, the molar ratio of the aminated polysiloxane A to the maleic anhydride is 1:1.5-2.5 on amino basis.

Preferably, the organic solvent I is glacial acetic acid.

Optionally, after the aminated polysiloxane A and the maleic anhydride are dissolved in the organic solvent I, heating and reacting at 140-180 ℃ for 4-8 hours, and obtaining the modified polysiloxane A.

Optionally, the preparation method of the modified polysiloxane B comprises the following steps:

providing an aminated polysiloxane B;

in an inactive atmosphere, mixing the amination polysiloxane B dissolved in the organic solvent II with an acid binding agent, adding the furan acetyl chloride dissolved in the organic solvent II, and carrying out heating reflux reaction for at least 0.5h to obtain the modified polysiloxane B.

Preferably, the molecular weight of the aminated polysiloxane B is 2000-20000;

the grafting rate of the amino groups in the aminated polysiloxane B is 3-30%, and the molar ratio of the amino groups to the furan acetyl chloride is 1:1-5; the mass ratio of the acid binding agent to the amino polysiloxane B is 3-7wt%. The weight average molecular weight range of the aminated polysiloxane B is favorable for the reaction of furan acetyl chloride and amino side chains in the aminated polysiloxane, and the incomplete reaction phenomenon is avoided. The grafting rate of the amino groups in the aminated polysiloxane B is favorable for the dispersion and distribution of the amino side chains on the polysiloxane main chain, and the problem of incomplete reaction caused by too concentrated dispersion is avoided. The molar ratio of the amino group to the furan acetyl chloride is favorable for the completeness of the reaction between the furan acetyl chloride and the side chain amino group, and incomplete reaction is avoided. The mass ratio of the acid binding agent to the aminated polysiloxane B is favorable for timely adsorbing hydrogen chloride generated by the reaction of acyl chloride and amino, and the breakage of polysiloxane chain units caused by over high acidity is avoided.

In particular, the upper and lower limits of the range of weight average molecular weights of the aminated polysiloxane B may be selected from 3000, 5000, 8000, 11000, 14000, 17000 or 19000, respectively, and the weight average molecular weight of the specific aminated polysiloxane B may be 3000, 5000, 8000, 10000 or 15000.

Preferably, the amino groups in the aminated polysiloxane B have a grafting ratio of 3% to 30%. Still further, the amino groups in the aminated polysiloxane B have a grafting ratio of 10% to 15%.

Preferably, the molar ratio of the aminated polysiloxane B to the furan acetyl chloride is 1:1-1.5 on amino basis.

Preferably, the mass ratio of the acid-binding agent to the aminated polysiloxane B is 4wt% to 6wt%.

Preferably, the acid-binding agent is selected from at least one of pyridine, triethylamine, 4-dimethylaminopyridine, potassium carbonate, sodium carbonate and cesium carbonate. More preferably, the acid binding agent is a pyridine.

Preferably, the organic solvent II is at least one selected from the group consisting of dehydrated ether, tetrahydrofuran and dichloromethane.

Optionally, mixing the aminated polysiloxane B dissolved in the organic solvent II with an acid binding agent in a nitrogen atmosphere, adding the furan acetyl chloride dissolved in the organic solvent II, and carrying out heating reflux reaction for 1-3h to obtain the modified polysiloxane B.

Optionally, the modified polysiloxane A and the modified polysiloxane B are reacted at a temperature of 150-200 ℃ for at least 15 hours, preferably 24-48 hours after being dissolved in the organic solvent III, so as to ensure that the reaction yield can reach more than 95%.

The molar ratio of the modified polysiloxane A based on maleimide groups to the modified polysiloxane B based on furoacetyl groups is 1:1-4. Preferably, the molar ratio of modified polysiloxane A based on maleimide groups to modified polysiloxane B based on furoacetyl groups is 1:2-3.

Preferably, the organic solvent III is selected from one of dimethyl ether, xylene, benzyl alcohol, a dicarboxylic acid ester and ethyl benzoate.

According to another aspect of the present application, there is provided a method for preparing a slow release coated fertilizer according to any one of the above, comprising the steps of:

providing said fertilizer granules having a target number;

providing the silicone polymeric material;

adding the fertilizer particles into a rotary drum coating machine, adjusting the coating machine to rotate at an angle of 35-45 degrees, and preheating to control the micro-melting of the surfaces of the fertilizer particles;

spraying the organosilicon polymeric material dissolved in the organic solvent VI on the surface of the fertilizer particles to obtain the slow-release coated fertilizer.

In the application, the angle of the coating machine is controlled to further control the fertilizer particles in the coating machine to form a continuous material curtain, so that the organosilicon polymeric material can be directly sprayed on the surface of the suspended fertilizer particles and fall onto the inner cavity wall of the coating machine after film formation, and the uniformity of film formation of the coating is more facilitated. In addition, the temperature is controlled so that micro-melting of the surface of the fertilizer is beneficial to better adhesion and combination of the surface of the fertilizer and the organosilicon polymer material.

Optionally, the speed of rotation of the coating machine is 40-80r/m. Preferably, the speed of rotation of the coating machine is 50-70r/m. The control of the rotation speed can prevent the coated fertilizers from being stuck to each other.

Optionally, the mass ratio of the organosilicon polymeric material to the fertilizer granule is 1% -8%.

Optionally, the temperature of the preheated fertilizer particles is 80-140 ℃. Preferably, the temperature of the preheated fertilizer particles is between 90 and 110 ℃. The fertilizer which is preferably suitable for the preheating temperature is urea.

Benefits of the present application include, but are not limited to:

1. according to the slow-release coated fertilizer, the coated organosilicon polymeric material used for coating in the slow-release coated fertilizer can realize the breaking and crosslinking of crosslinking bonds at a specific temperature, and the slow-release coated fertilizer has the characteristics of temperature reversibility and bonding and dissociation of chemical bonds through temperature control by using Diels-Alder reaction when the coating is uneven, can repeatedly carry out coating treatment for multiple times, reduces the defective rate, improves the coating yield, and avoids the problem of poor slow-release effect of the fertilizer caused by uneven coating.

2. According to the slow-release coated fertilizer, the Si-O chain segment of the coated organic silicon material in the slow-release coated fertilizer has extremely strong hydrophobic property, but the reversible crosslinking of the maleimide group and the furan acetylation group provides holes for the inside of the composite material, so that the slow-release effect of the coated fertilizer is ensured.

3. According to the slow-release coated fertilizer, industrialization of the slow-release coated fertilizer can be realized, and the slow-release coated fertilizer has great economic value and industrial influence; the method is environment-friendly, can realize the recycling of the polymer material, and has great development potential.

4. According to the preparation method of the slow-release coated fertilizer, the film formed by coating is uniform, the combination of fertilizer particles and the film is good, and the film can be repeatedly processed to repair the generated problem of nonuniform coating, so that the problem of waste generated due to nonuniform coating is avoided.

5. According to the preparation method of the slow-release coated fertilizer, the coated organic silicon polymeric material used in the slow-release coated fertilizer is constructed by utilizing a catalyst-free Diels-Alder reaction between maleimide functionalization and furan acetylated polysiloxane, so that the problems of catalyst removal and residue do not exist, and the post-treatment step is simple and convenient.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:

FIGS. 1 (A) and (B) are respectively the infrared spectra of maleimido polysiloxane A1# and furan-acetylated polysiloxane B1# according to example 1 of the present application;

FIGS. 2 (A) and (B) are GPC spectra of maleimido polysiloxane A1# and furan-acetylated polysiloxane B1# of example 1, respectively;

FIG. 3 (A) is a thermogravimetric analysis of a silicone polymeric material 1# under nitrogen and air; (B) is a DSC spectrum of organosilicon polymeric material 1#;

FIG. 4 is a schematic view showing the microstructure of the silicone polymer material 1# obtained in example 1;

FIG. 5 is an optical property spectrum of the silicone polymer material 1# obtained in example 1, (A) being an ultraviolet spectrum and (B) being a fluorescence spectrum;

FIG. 6 (A) is a diagram of the urea precursor particles used in example 2; (B) A photograph of coated fertilizer 1# after coating urea particles with organosilicon polymer material 1 #;

FIG. 7 is a graph showing the slow release characteristics of coated fertilizer 1# -3# prepared in examples 2, 4, and 6, respectively, within 60 days;

FIG. 8 is a self-repairing graph of the silicone composite fertilizer obtained in example 2, (A) a silicone polymeric material 1# shell after urea release; (B) And the organic silicon polymer material 2# shell is repaired by Diels-Alder reverse reaction.

Fig. 9 is a schematic view of a process and a structure for preparing a silicone polymer material in the embodiment.

Detailed Description

The present application is described in detail below with reference to examples, but the present application is not limited to these examples.

"hydrocarbyl" is inclusive of alkyl, alkenyl, alkynyl, and aryl.

"alkyl" refers to a monovalent aliphatic hydrocarbon group. The alkyl groups may have any number of carbon atoms. Many alkyl groups are C1 to C30. Some alkyl groups may be C1 or greater, such as C2 or greater, C4 or greater, C6 or greater, or C8 or greater. Some alkyl groups may be C22 or less, C16 or less, C12 or less, C8 or less, or C4 or less. Unless otherwise indicated, any alkyl group may independently be linear, branched, cyclic, or a combination thereof (e.g., cyclic alkyl groups may also have linear or branched components.) exemplary alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, sec-butyl, isobutyl, 2-ethylhexyl, isooctyl, dodecyl, hexadecyl, docosyl, and the like.

"aryl" refers to a monovalent aromatic radical. Aryl groups may include only carbon and hydrogen, or may also include one or more heteroatoms such as one or more of oxygen, nitrogen, and sulfur. Aryl groups may have aromatic rings with three or more atoms, four or more atoms, or five or more atoms. Aryl groups may have a ring with ten or fewer atoms, eight or fewer atoms, seven or fewer atoms, or six or fewer atoms. Exemplary aryl groups include phenyl, furyl, naphthyl, anthracyl, and the like. Phenyl is a common aryl substituent.

"amino" refers to a group having the formula-Nc (H) p (R ') q, wherein each R' is independently alkyl, alkenyl, alkynyl, aryl or alkylaryl, any of which may be optionally substituted, p+q is 2 or 3, and c represents the charge on the nitrogen atom, which is 0 or 1+. Typically, each R' is an alkyl group. When p+q is 2, c is 0; when p+q is 3, c is 1+. The amino group may be primary, secondary, tertiary or quaternary depending on the value of q. Amino groups having q values of 0, 1, 2 and 3 are primary, secondary, tertiary and quaternary, respectively.

"polydiorganosiloxane" means having repeating units-Si (G) ₂ O-, wherein each occurrence of G is independently an organic moiety. Each occurrence of G is typically independently an alkyl, aryl, alkenyl, or alkynyl group. Alkyl and aryl groups are the most common, and alkyl groups are more common than aryl groups. When G is aryl, it may be any aryl group, for example any group referred to herein by the definition of "aryl". Classical bookAryl groups of this type include phenyl. Typical alkyl groups include those discussed with reference to the definition of alkyl herein, and also include C1 to C22 alkyl, C1 to C16 alkyl, C1 to C12 alkyl, C1 to C8 alkyl, or C1 to C4 alkyl, such as methyl, ethyl, propyl, butyl (such as tert-butyl, isobutyl, n-butyl, and sec-butyl), and C8 alkyl, such as 2-ethylhexyl and isooctyl. When unspecified, the end groups of the polydiorganosiloxane may be changed; typical end groups include triorganosilyl groups and hydroxyl groups, as well as capping groups, quenching groups, and chain transfer groups.

Raw materials, reagents and fertilizers in the examples of the present application were purchased commercially, unless otherwise specified. The amino polysiloxane is prepared by hydrolyzing aminopropyl methyl diethoxy silane or 3- (2-aminoethyl) -aminopropyl methyl diethoxy silane and dimethyl diethoxy silane to prepare side amino polysiloxane, and hydrolyzing aminopropyl dimethyl ethoxy silane or 3- (2-aminoethyl) -aminopropyl dimethyl ethoxy silane.

The analytical method in the examples of the present application is as follows:

infrared analysis and test are carried out by using an infrared instrument of model Nicolet710 of Nigao company of America;

gel Permeation Chromatography (GPC) analysis tests were performed using a model II gel permeation chromatography instrument from DAWN HELEOS, usa Huai Yate;

thermal analysis testing was performed using a TGA2 thermal analysis instrument from mertrel-toli company;

by SUPRA from Chuiss, germany ^TM Performing microstructure analysis test by a 55-model scanning electron microscope;

ultraviolet spectrum testing is carried out by using an Agilent company Cary 5000 model instrument;

performing fluorescence spectrum analysis and test by using an FLS-1000 type instrument of Edinburgh company;

analyzing and testing the release rate of nitrogen in water by using a total nitrogen content measurement-post-distillation titration method in the compound fertilizer in GB/T23148-2009; the test method is a method of soaking in water, and the film-coated controlled-release fertilizer is leached by water or saline solution with a certain concentration so as to calculate the leaching amount of nutrients in a certain time. 4g of fertilizer to be tested is added into a beaker containing 80mL of deionized water, covered on the beaker, placed in a constant temperature box at 30 ℃ for culture, sampled 1 time every 6 hours, taken 2.5mL each time, and the nitrogen content in the leaching solution is measured.

Referring to FIG. 9, there is illustrated a schematic diagram of the process of reversible reaction and thermal self-repair, and a schematic diagram of the structure of the resulting organosilicon composite, wherein 1 is a Si-O-Si segment in polysiloxane, 2 is a maleimido group, 3 is a furoacetyl group, 4 is

The process of reaction and the method of preparing a self-healing silicone polymeric material according to one embodiment of the present application, comprises the steps of:

step one, preparation of modified polysiloxane A (maleimido polysiloxane A): placing end amino polysiloxane A or side amino polysiloxane A with different molecular weights and different amino contents dispersed in 30mL glacial acetic acid and maleic anhydride in a 100mL round bottom flask equipped with an air duct, a constant pressure low liquid funnel and a spherical condensation tube, heating to 140-180 ℃ under electromagnetic stirring and refluxing for 4-8 hours, removing glacial acetic acid under reduced pressure, dissolving residues with chloroform, purifying and washing for several times with saturated sodium chloride aqueous solution, and separating organic phases; adding anhydrous magnesium sulfate into the organic phase, drying overnight, and removing the organic solvent under reduced pressure to obtain brown transparent oily liquid, thus obtaining modified polysiloxane A;

wherein the weight average molecular weight of the aminated polysiloxane A comprises, but is not limited to 3000, 5000, 10000 and 15000, the amino grafting rate of the aminated polysiloxane A comprises, but is not limited to 3% -30%, and the molar ratio of amino to maleic anhydride is 1:1-1:3;

Step two, preparing modified polysiloxane B (furan acetylated polysiloxane B): introducing nitrogen into a 50mL round bottom flask for protection after three-suction and three-discharge, dissolving end group amino modified polysiloxane B or side group amino modified polysiloxane B with different weight average molecular weights and different amino contents into 20mL of organic solvent II, and introducing an acid-binding agent, wherein the addition amount of the acid-binding agent is 3% -7% of the mass of the amino modified polysiloxane B; after electromagnetic stirring for 15-30min, slowly dripping furan acetyl chloride dissolved in an organic solvent II into a round-bottom flask, wherein the molar ratio of amino to furan acetyl chloride is 1:1-1:1.5, and reacting for 1-3 h in a reflux state; vacuum distillation and purification are carried out after the generated salt is removed by suction filtration, and light yellow oily liquid is obtained, thus obtaining modified polysiloxane B;

wherein the weight average molecular weight of the amino modified polysiloxane B comprises, but is not limited to, 3000, 5000, 10000 and 15000, the amino grafting rate of the amino modified polysiloxane B comprises, but is not limited to, 3% -30%, and the organic solvent II comprises, but is not limited to, anhydrous diethyl ether, tetrahydrofuran and dichloromethane; acid binding agents include, but are not limited to, pyridine, triethylamine, 4-dimethylaminopyridine, potassium carbonate, sodium carbonate, cesium carbonate, and the like; volume of furylacetylchloride in organic solvent II: the volume (v: v) ratio is 1:5-1:10;

Preparing an organosilicon polymer material: dissolving modified polysiloxane A (maleimido polysiloxane A) and modified polysiloxane B (furan acetylated polysiloxane B) in an organic solvent III, transferring into a round bottom flask, heating to 150-200 ℃ under electromagnetic stirring, and reacting for 24-48 h; pouring the mixture into an anhydrous methanol solution after the reaction is finished to obtain a light red precipitate, filtering to remove an organic solvent III, repeatedly washing the solution with the anhydrous methanol for several times, and drying the solution in vacuum overnight to obtain the organosilicon polymeric material;

wherein the molar ratio of maleimide groups to furoacetyl groups is 1:1-1:4, and the organic solvent III comprises but is not limited to dimethyl ether, dimethylbenzene, benzyl alcohol, diformate, ethyl benzoate and the like.

According to another embodiment of the present application, the use of a self-healing silicone polymeric material as a fertilizer coating comprises the steps of:

the organic silicon polymer material is used as a fertilizer coating process: sieving the fertilizer with sieves with different meshes (10-40 meshes), and subpackaging with 50g as one part;

taking a part of fertilizer in a rotary drum coating machine, adjusting the angle of the coating machine to 35-45 degrees, and controlling the rotating speed to 40-80r/m so that the fertilizer can form a continuous material curtain in the coating machine; preheating after 15min, controlling the temperature at about 90-110 ℃ to enable the surfaces of fertilizer particles to be in a micro-melting state, spraying organic silicon polymer materials dissolved in methylene dichloride solution, wherein the sprayed organic silicon polymer materials account for 0.5-5% of the mass of the fertilizer, so that uniform films are formed on the surfaces of the fertilizer particles. The uniformity of the encapsulation of the organosilicon polymeric material on the surface of the fertilizer particles can be observed under an ultraviolet lamp. Further, the mutual adhesion is prevented by adjusting the rotating speed in the coating process.

Example 1 preparation of organosilicon polymeric Material 1#

The reaction equations of the modified polysiloxane A1# and the modified polysiloxane B1# of this example are shown below, respectively

The preparation method of the self-repairing organosilicon polymer material 1# comprises the following steps:

(1) Modified polysiloxane a1# (maleinized polysiloxane a1#) preparation: the terminal aminopropyl-modified polysiloxane having a weight average molecular weight of 5000 and maleic anhydride dispersed in 30mL of glacial acetic acid were placed in a 100mL round bottom flask equipped with an air duct, a constant pressure low liquid funnel and a spherical condenser in an amount of 1:1 molar ratio of amino groups to maleic anhydride, heated to 140 ℃ under electromagnetic stirring and reacted under reflux for 4 hours, the glacial acetic acid was removed under reduced pressure and the residue was dissolved with chloroform, and the organic phase was separated after purified and washed several times with saturated aqueous sodium chloride solution. Adding anhydrous magnesium sulfate into the organic phase, drying overnight, and removing the organic solvent under reduced pressure to obtain brown transparent oily liquid to obtain modified polysiloxane A1# (maleimido polysiloxane A1#), wherein the infrared test result is shown in FIG. 1 (A), and the GPC test GPC chart is shown in FIG. 2 (A);

(2) Modified polysiloxane b1# (furan acetylated polysiloxane b1#): and (3) carrying out three-pumping and three-discharging on a 50mL round-bottom flask, and then introducing nitrogen for protection, so as to ensure that the Diels-Alder reaction between the modified polysiloxane A and the modified polysiloxane B is more complete, the obtained film has better performance, and the selected aminopropyl polysiloxane is the same as that selected from A1#. Dissolving the aminopropyl-terminated modified polysiloxane with the weight-average molecular weight of 5000 in 20mL of anhydrous diethyl ether, and adding an acid-binding agent pyridine, wherein the addition amount of the pyridine is 3% of the mass of the aminopropyl-terminated modified polysiloxane; slowly dripping furan acetyl chloride dissolved in anhydrous diethyl ether serving as an organic solvent into a round-bottom flask at a volume-to-mass ratio (mL: g) of 10:1 after electromagnetic stirring for 15min, reacting for 1h in a reflux state, filtering to remove generated salt, and performing reduced pressure distillation and purification to obtain light yellow oily liquid, thereby obtaining modified polysiloxane B1#, wherein the infrared test result is shown in FIG. 1 (B), and the GPC chart is shown in FIG. 2 (B);

(3) Preparation of organosilicon polymeric material 1 #: and respectively dissolving maleimide polysiloxane A1# and furan acetylated polysiloxane B1# in an organic solvent dimethyl ether with the molar ratio of maleimide groups to furan acetyl groups of 1:2, wherein the volume mass ratio (mL: g) between the solvent and the raw materials is 20:1, transferring the mixture into a round-bottomed flask, heating to 150 ℃ under electromagnetic stirring, reacting for 24 hours, pouring the mixture into an anhydrous methanol solution, obtaining a pale red precipitate, filtering to remove the solvent, repeatedly washing the solution with the anhydrous methanol for a plurality of times, and drying the solution in vacuum overnight to obtain the organosilicon polymeric material 1#.

Thermogravimetric analysis of the organosilicon polymeric material 1# under nitrogen and air is shown in fig. 3 (a), a dsc diagram of the organosilicon polymeric material 1# is shown in fig. 3 (B), and a microstructure schematic diagram of the organosilicon polymeric material 1# is shown in fig. 4. The ultraviolet spectrum of the organic silicon composite material 1# is shown in fig. 5 (A) and the fluorescence spectrum is shown in fig. 5 (B).

Example 2 preparation of coated fertilizer 1#

The silicone polymeric material 1# of example 1# was used as a fertilizer coating process: sieving urea with a 10-mesh sieve, and packaging with 50g serving as one part; taking a part of urea in a rotary drum coating machine, adjusting the angle of the coating machine to 35 degrees, and controlling the rotating speed to 40r/m so that the urea can form a continuous material curtain in the coating machine; preheating after 15min, controlling the temperature at about 90 ℃ to enable the surfaces of urea particles to be in a micro-melting state, spraying an organosilicon polymeric material 1# dissolved in a dichloromethane solution, wherein the adding amount of the organosilicon polymeric material 1# is 1% of the mass of the fertilizer, and adjusting the rotating speed to prevent the mutual adhesion in the coating process so that the organosilicon polymeric material 1# forms a uniform film on the surfaces of the urea particles to prepare the coated fertilizer 1#.

The uniformity of the coating of the organosilicon polymeric material on the surface of the urea particles is observed by an ultraviolet lamp. FIG. 6 (A) is a photograph of raw urea particles; FIG. 6 (B) is a photograph of coated fertilizer 1 #.

Example 3 preparation of organosilicon polymeric Material 2#

The preparation method of the self-repairing organosilicon polymer material No. 2 comprises the following steps:

(1) Modified polysiloxane a2# (maleinized polysiloxane a2#) preparation: the pendant aminopropyl-modified polysiloxane having a weight average molecular weight of 5000 and maleic anhydride, which were dispersed in 30mL of glacial acetic acid, were placed in a 100mL round bottom flask equipped with an air duct, an amino grafting ratio of 15%, a constant pressure low liquid funnel and a spherical condenser in an amount of 1:3 in terms of molar ratio of amino groups to maleic anhydride, and after heating to 160 ℃ under electromagnetic stirring and reflux reaction for 6 hours, glacial acetic acid was removed under reduced pressure and the residue was dissolved with chloroform, and the organic phase was separated after washing with saturated aqueous sodium chloride solution purified several times. Adding anhydrous magnesium sulfate into the organic phase, drying overnight, and removing the organic solvent under reduced pressure to obtain brown transparent oily liquid, thus obtaining modified polysiloxane A2# (maleimido polysiloxane A2#);

(2) Modified polysiloxane b2# (furan acetylated polysiloxane b2#): introducing nitrogen into a 50mL round bottom flask for protection after three-suction and three-discharge, dissolving the lateral aminopropyl modified polysiloxane with the weight-average molecular weight of 5000 in 20mL anhydrous diethyl ether, adding an acid-binding agent triethylamine with the amino grafting rate of 15% and the addition amount of the triethylamine being 5% of the weight of the lateral aminopropyl modified polysiloxane; after electromagnetic stirring for 20min, slowly dripping furan acetyl chloride which is dissolved in organic solvent tetrahydrofuran with the volume-mass ratio (mL: g) of 15:1 into a round-bottom flask, wherein the molar ratio of amino to furan acetyl chloride is 1:3, reacting for 2h in a reflux state, filtering out generated salt, and performing reduced pressure distillation and purification to obtain light yellow oily liquid, namely the modified polysiloxane B2#;

(3) Preparation of organosilicon polymeric material 2 #: and respectively dissolving maleimide polysiloxane A2# and furan acetylated polysiloxane B2# in an organic solvent xylene according to the molar ratio of maleimide groups to furan acetyl groups of 1:2.5, wherein the volume mass ratio (mL: g) between the solvent and the raw materials is 25:1, transferring the mixture into a round-bottomed flask, heating to 180 ℃ under electromagnetic stirring, reacting for 36 hours, pouring the mixture into an anhydrous methanol solution, obtaining a pale red precipitate, filtering the solution, repeatedly washing the solution with the anhydrous methanol for several times, and drying the solution in vacuum overnight to obtain the organosilicon polymeric material 2#.

Example 4 preparation of coated fertilizer 2#

The silicone polymeric material 2# of example 3# was used as a fertilizer coating process: sieving urea with 39 mesh sieve, and packaging with 50g as one part; taking a part of urea in a rotary drum coating machine, adjusting the angle of the coating machine to 40 degrees, and controlling the rotating speed to 60r/m so that the urea can form a continuous material curtain in the coating machine; preheating after 15min, controlling the temperature at about 100 ℃ to enable the surfaces of urea particles to be in a micro-melting state, spraying organic silicon polymer material No. 2 dissolved in dichloromethane solution, wherein the addition amount of the organic silicon polymer material No. 2 is 1.5% of the mass of the fertilizer, and preventing the organic silicon polymer material No. 1 from forming a uniform film on the surfaces of the urea particles by adjusting the rotating speed in the coating process.

The uniformity of the coating of the organosilicon polymeric material on the surface of the urea particles is observed by an ultraviolet lamp.

Example 5 preparation of self-healing Silicone polymeric Material 3#

The preparation method of the self-repairing organosilicon polymer material 3# comprises the following steps:

(1) Modified polysiloxane a3# (maleinized polysiloxane a3#) preparation: the pendant aminopropyl-modified polysiloxane having a weight average molecular weight of 15000 and maleic anhydride, which were dispersed in 30mL of glacial acetic acid, were placed in a 100mL round bottom flask equipped with an air duct, an amino grafting ratio of 30%, a constant pressure low liquid funnel and a spherical condenser in an amount of 1:2.5 in terms of molar ratio of amino groups to maleic anhydride, and after heating to 160 ℃ under electromagnetic stirring and reflux reaction for 8 hours, glacial acetic acid was removed under reduced pressure and the residue was dissolved with chloroform, and after washing with saturated aqueous sodium chloride solution for several times, the organic phase was separated. Adding anhydrous magnesium sulfate into the organic phase, drying overnight, and removing the organic solvent under reduced pressure to obtain brown transparent oily liquid, thus obtaining modified polysiloxane A3# (maleimido polysiloxane A3#);

(2) Modified polysiloxane b3# (furan acetylated polysiloxane b3#): introducing nitrogen into a 50mL round bottom flask for protection after three-suction and three-discharge, dissolving the lateral aminopropyl modified polysiloxane with the weight-average molecular weight of 15000 in 20mL anhydrous diethyl ether, wherein the amino grafting rate is 30%, and adding an acid-binding agent 4-dimethylaminopyridine, wherein the addition amount of the 4-dimethylaminopyridine is 5% of the mass of the lateral aminopropyl modified polysiloxane B3#; after electromagnetic stirring for 30min, slowly dripping furan acetyl chloride which is dissolved in organic solvent dichloromethane with the volume-mass ratio (mL: g) of 30:1 into a round-bottom flask, wherein the molar ratio of amino to furan acetyl chloride is 1:5, reacting for 3h in a reflux state, filtering out generated salt, and performing reduced pressure distillation and purification to obtain light yellow oily liquid, namely the modified polysiloxane B3#;

(3) Preparation of organosilicon polymeric material 3 #: and respectively dissolving maleimide polysiloxane A < 3 > and furan acetylated polysiloxane B < 3 > in benzyl alcohol which is an organic solvent in a molar ratio of 1:3 based on maleimide groups and furan acetyl groups, wherein the volume mass ratio (mL: g) between the solvent and the raw materials is 30:1, transferring the mixture into a round-bottomed flask, heating to 200 ℃ under electromagnetic stirring, reacting for 48 hours, pouring the mixture into an anhydrous methanol solution, obtaining a pale red precipitate, filtering the solution, repeatedly washing the solution with the anhydrous methanol for a plurality of times, and drying the solution in vacuum overnight to obtain the organosilicon polymeric material 3#.

Example 6 preparation of coated fertilizer 3#

The silicone polymeric material 3# of example 5# was used as a fertilizer coating process: sieving urea with a 40-mesh sieve, and respectively split charging with 50g as one part; taking a part of urea in a rotary drum coating machine, adjusting the angle of the coating machine to 45 degrees, and controlling the rotating speed to 80r/m so that the urea can form a continuous material curtain in the coating machine; preheating after 15min, controlling the temperature at about 110 ℃ to enable the surfaces of urea particles to be in a micro-melting state, spraying organic silicon polymer material 3# dissolved in methylene dichloride solution, wherein the adding amount of the organic silicon polymer material 3# is 2% of the mass of the fertilizer, and preventing the organic silicon polymer material 3# from forming a uniform film on the surfaces of the urea particles by adjusting the rotating speed in the coating process.

Example 7 test of sustained Release Property of coated fertilizers 1-3#

The coated fertilizers 1-3# prepared in examples 2, 4 and 6 were tested for their slow release properties by the water immersion method. The test results are shown in fig. 7, and it can be seen from fig. 7 that example 3 has a better slow release effect than 1,2, and the cumulative release rate within 28 days is not more than 80%, so that the slow release fertilizer requirement is met.

The coated fertilizers 1 to 3# prepared in examples 2, 4 and 6 were tested for nutrient release period (d), cumulative nitrogen release rate for 28 days and repairable times of the coated materials with the commercial products, respectively, and are shown in Table 1.

TABLE 1

As can be seen from Table 1, the coated fertilizer prepared by the method has a slow release speed, can keep nutrients fully absorbed by crops, has a low fertilizer loss rate, and greatly improves the fertilizer utilization rate, so that excessive application of the fertilizer can be avoided. The release rate of the prepared coated fertilizer No. 1, no. 2 and No. 3 is not more than 80% on 28 days, and the requirements of GB/T23148-2009 are met, wherein the release rate of the coated fertilizer No. 3 on 28 days is lower than that of No. 1, no. 2 and commercial products, which shows that the coated fertilizer No. 3 has better slow release effect.

Fig. 8 (a) shows that the surface of the shell of the organosilicon composite material after release of the nutrients of the coated fertilizer 1# is prepared, and fig. 8 (a) shows that the organosilicon composite material can form a shell with holes on the surface of the fertilizer, but the surface can collapse and generate scraps around the surface after release of the nutrients. Fig. 8 (B) shows that the organosilicon composite material 2# shell after Diels-Alder reverse reaction repair occurs after the coated fertilizer 3# material is subjected to the condition treatment, and fig. 8 (B) shows that the organosilicon composite material still can form a compact protection layer on the surface of the fertilizer after self-repair, but the holes on the surface become more after repair, and the pore diameter becomes larger, which means that the organosilicon composite material designed in the application has a certain number of self-repair times.

Example 8

Coated fertilizers 4# -10# and comparative coating materials D1# -D2# were prepared according to different conditions from those in Table 2 as in examples 1 and 2, and the cumulative nitrogen release rate and the repairable times of the coating materials were tested for 28 days by using the test method of example 7, respectively, and the results are shown in Table 2.

TABLE 2

As shown in Table 2, when the weight average molecular weight of the comparative coated fertilizer D1# exceeds the protection range of the application, the release rate of nitrogen is not greatly different from that of the coated fertilizers 4# and 5#, but the repairable times of the coated fertilizer are obviously reduced due to the lower proportion of the reversible substituted cyclohexene structure; compared with the coated fertilizer D2# grafting rate exceeding the protection range of the application, the proportion of the reversible substituted cyclohexene structure is improved, the crosslinking density of maleimide groups and furoacetyl groups is increased, the void density in the coated material is increased, the accumulated nitrogen release rate in 28 days is overhigh, and the slow release effect is poor. In the comprehensive view, the molecular weight and the grafting rate can be ensured to have good slow release effect and more repairable times only when the molecular weight and the grafting rate are within the protection range.

Example 9

The coated fertilizer 11 and the comparative coated material D2 were prepared according to different conditions from those in table 3 according to the methods of example 1 and example 2, and the cumulative nitrogen release rate and the repairable times of the coated material were tested for 28 days by using the test method of example 7, respectively, and the results are shown in table 2.

TABLE 3 Table 3

As can be seen from Table 3, in the comparative coated fertilizer D3#, the coating machine angle is too high or too low to negatively influence the nitrogen release rate, when the coating angle of the coating machine is low, the fertilizer moves in an arc manner in the coating machine, when the angle is too small, the fertilizer is too fast due to insufficient centrifugal force, uneven distribution of the coating material caused by friction fit is easy to occur due to too high dropping speed, the slow release effect is poor, but when the angle is high, the centrifugal force is large, but the coating effect is not greatly different from that of the coated fertilizer 1#, but the cost is increased due to high energy consumption; compared with the coated fertilizer D4#, the rotating speed can also have negative influence on the slow release effect, when the rotating speed is higher, the rotating speed rate of the material curtain in the coating machine is higher, the curing time of the coated material on the surface of the fertilizer is shorter, when the coated material collides with other fertilizer particles, the coated material is easy to fall off from the surface of the fertilizer or gaps are generated, the slow release effect is poor, but when the rotating speed is lower, the coated material has enough curing time on the surface of the fertilizer, but the coating efficiency is lower due to the too slow speed; in contrast to coated fertilizer D5#, with the improvement of the mass ratio of the organosilicon polymeric material to the fertilizer particles, on one hand, the viscosity of the coating liquid can be improved, so that the adhesive force of the coating liquid on the surface of the fertilizer is increased, and on the other hand, the concentration of the coating liquid can be increased, so that the thickness of the film layer of the coating material on the surface of the fertilizer is increased, which is beneficial to reducing the accumulated nitrogen release rate in 28 days, but the European Commission of standards indicates that in the relevant regulations of slow release fertilizer: in the specified time, the nutrient release rate of the slow release fertilizer should not be lower than 75%, and although the 28-day accumulated nitrogen release rate of the coated fertilizer D5# is lower than that of the embodiment, the release rate is too low, so that the fertilizer cannot provide sufficient nutrients for crops in the specified time and does not meet the slow release fertilizer standard, and cannot be put into the slow release fertilizer market.

The foregoing is merely exemplary of the present application, and the scope of the present application is not limited to the specific embodiments, but is defined by the claims of the present application. Various modifications and changes may be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. The slow release coated fertilizer is characterized by comprising fertilizer particles and a film coated outside the fertilizer particles, wherein the film is made of an organosilicon polymer material;

the organic silicon polymer material is prepared by Diels-Alder reaction of modified polysiloxane A and modified polysiloxane B;

the modified polysiloxane a has at least one group comprising a substituted olefinic bond in 1 molecule;

the modified polysiloxane B has at least one conjugated diene bond group containing non-aromatic hydrocarbon which has Diels-Alder reaction with the substituted olefin bond group in 1 molecule;

the modified polysiloxane A and the modified polysiloxane B are subjected to cross-linking polymerization to form at least one reversible substituted cyclohexenyl to prepare the organosilicon polymer material;

The substituted olefin bond group in the modified polysiloxane A is maleimide group, and the non-aromatic hydrocarbon-containing diene bond group in the modified polysiloxane B is furacetyl;

the modified polysiloxane A is maleimido polysiloxane A obtained by reacting side amino polysiloxane A with maleic anhydride, the modified polysiloxane B is furan acetylated polysiloxane B obtained by reacting side amino polysiloxane B with furan acetyl chloride, and the structure of the reversible substituted cyclohexenyl is shown as formula I:

a formula I;

wherein, the structural formula of the polysiloxane A is shown as a formula II:

a formula II;

wherein R is ₁ 、R ₂ 、R ₃ And R is ₄ Each independently selected from one of C1-C5 alkyl groups; m1 and n1 are respectively taken from integers more than 0; the weight average molecular weight of the side amino polysiloxane A of the polysiloxane A ranges from 15000 to 20000, and the grafting rate of amino groups in the side amino polysiloxane A ranges from 3% to 30%; the R is ₁ 、R ₂ 、R ₃ And R is ₄ Is linked to a maleimide group of a reversibly substituted cyclohexenyl group of formula I;

the structural formula of the polysiloxane B is shown as a formula III:

a formula III;

wherein R5, R6, R7 and R8 are respectively and independently selected from one of C1-C5 alkyl; m2 and n2 are respectively taken from integers more than 0; the weight average molecular weight of the side amino polysiloxane B of the polysiloxane B is 15000-20000, and the grafting rate of amino groups in the side amino polysiloxane B is 3% -30%; at least one of R5, R6, R7 and R8 is linked to a furan acetyl group of a reversibly substituted cyclohexenyl group of formula I.

2. The slow release coated fertilizer of claim 1, wherein the mass ratio of the silicone polymeric material to the fertilizer particles is 0.3% -5%.

3. The slow release coated fertilizer of claim 2, wherein the mass ratio of the silicone polymeric material to the fertilizer particles is 1% -3%.

4. The slow release coated fertilizer of claim 1, wherein the fertilizer particles have a particle size of 10-40 mesh.

5. The slow release coated fertilizer of claim 4, wherein the fertilizer particles have a particle size of 20-30 mesh.

6. The slow release coated fertilizer of claim 1, wherein the fertilizer particles are selected from at least one of urea, nitrogen-phosphorus-potassium compound fertilizer, diammonium phosphate, a medium element fertilizer, a biological fertilizer, and an organic fertilizer.

7. The slow release coated fertilizer according to claim 1, wherein the ratio between the grafting ratio X of maleimide groups in the modified polysiloxane a and the grafting ratio Y of furoacetyl groups in the modified polysiloxane B is 1:1.2-1.5;

the polysiloxane A and the polysiloxane B are respectively and independently selected from polydiorganosiloxane.

8. A method for preparing the slow release coated fertilizer according to any one of claims 1 to 7, comprising the steps of:

Providing said fertilizer granules having a target number;

providing the silicone polymeric material;

spraying the organic silicon polymer material dissolved in the organic solvent on the surface of the fertilizer particles to obtain the slow-release coated fertilizer.

9. The method for preparing a slow-release coated fertilizer according to claim 8, wherein the speed of rotation of the coating machine is 40-80r/m;

the mass ratio of the organosilicon polymeric material to the fertilizer particles is 0.3% -5%.

10. The method for producing a slow release coated fertilizer according to claim 8, wherein the temperature of the preheated fertilizer particles is 80-140 ℃.

11. The method for producing a slow release coated fertilizer according to claim 10, wherein the temperature of the preheated fertilizer particles is 90-110 ℃.