CN114195590A

CN114195590A - Urea-based biodegradable high-molecular high-adhesion foliar fertilizer with nutrient sustained and controlled release and water absorption and retention functions

Info

Publication number: CN114195590A
Application number: CN202111465241.XA
Authority: CN
Inventors: 刘亚青; 汪调霞; 陈泰安; 向阳; 赵贵哲
Original assignee: North University of China; Shanxi Zhongbei New Material Technology Co Ltd
Current assignee: North University of China; Shanxi Zhongbei New Material Technology Co Ltd
Priority date: 2021-12-03
Filing date: 2021-12-03
Publication date: 2022-03-18
Anticipated expiration: 2041-12-03
Also published as: CN114195590B

Abstract

The invention relates to a urea aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with nutrient sustained and controlled release and water absorption and retention functions, wherein the foliar fertilizer enables a linear macromolecular chain of a urea aldehyde biodegradable high-molecular material capable of slowly controlling and releasing nutrient elements or a derivative containing multiple nutrient elements to be inserted into a network structure of an acrylic acid graft copolymer of a biodegradable high-molecular material, and the two form a high-molecular composite material with a semi-interpenetrating network structure. The invention provides a new idea for designing a foliar fertilizer, and introduces a semi-interpenetrating network polymer into the field of the foliar fertilizer, so that the foliar fertilizer integrates easy spraying, slow release, moisture retention and adhesiveness, and has multiple effects at one stroke. In addition, the polymer network can absorb water vapor in the atmosphere, provides a wetting environment for crop leaves, and is more favorable for the growth of plants in a drought environment. Therefore, the method has very important significance for improving the utilization efficiency of the foliar fertilizer, reducing resource waste and reducing secondary pollution to the environment.

Description

Urea-based biodegradable high-molecular high-adhesion foliar fertilizer with nutrient sustained and controlled release and water absorption and retention functions

Technical Field

The invention relates to the field of foliar fertilizers, in particular to a urea-aldehyde-based biodegradable high-polymer high-adhesion foliar fertilizer with functions of nutrient sustained and controlled release and water absorption and retention and a preparation and use method thereof.

Background

With the development of fertilization technology, the foliar fertilizer is rapidly popularized and applied in agriculture. Foliar fertilization has the following advantages: (1) the nutrient absorption is fast: it is reported that the leaf suction is about 1 times faster than the root suction. (2) Strong action and good fertilizer efficiency: the foliar fertilizer can powerfully promote various physiological processes in crops, remarkably improve the intensity of photosynthesis, improve the activity of enzyme, promote the synthesis, transformation and transportation of organic matters, facilitate the accumulation of dry matters, and improve the yield and quality of crops. (3) The dosage is less: in general, satisfactory results can be achieved with foliar fertilisers in amounts of a fraction or a tenth of the soil fertilisation. (4) High nutrient utilization efficiency, strong pertinence, convenient spraying, economy and environmental protection. However, there are problems in the following respects: (1) the adhesion is poor. On one hand, more than 50% of leaf fertilizer can drip from the surface of the leaf during spraying, on the other hand, the sprayed nutrients are easy to be leached by rainwater, so that the utilization rate is low, and the leached and volatilized nutrients enter the environment and possibly pollute water, soil and air. (2) No slow release performance. On one hand, the loss is easily caused due to the too fast release of nutrients, and on the other hand, the expected effect can be achieved by spraying for many times, which is time-consuming and labor-consuming. (3) No moisture retention property. On one hand, the spray liquid is quickly dried on the leaf surface, which influences the absorption; on the other hand, strong direct sunlight in summer easily causes burn of crop leaves, and further influences yield. (4) The quantity of nutrients provided by the foliar fertilization is limited, which is not enough to meet all the needs of crops, especially nitrogen, phosphorus and potassium major elements.

At present, the development trend of the world fertilizer industry is sustained and controlled release, high-efficiency precision and environmental friendliness. The biodegradable polymer slow-release fertilizer represented by urea aldehyde abandons the use of coating materials, can realize slow release of nutrients by depending on the degradable property of macromolecular chains of the fertilizer, and effectively solves various problems of the coated slow-release fertilizer. However, the urea aldehyde slow-release fertilizer developed at home and abroad basically has the defects of single nutrient, overlong slow-release period and the like, and the application range of the urea aldehyde fertilizer is limited, so that the urea aldehyde fertilizer can only be applied to perennial plants such as forest soil, lawn and the like, but is difficult to be applied to short-period crops such as corn, rice, wheat, vegetables and the like which are planted in a large scale. The foliar fertilizer based on urea aldehyde and having the sustained and controlled release function and the biodegradability is not reported at present.

At present, the semi-interpenetrating network technology has played a great role in the field of high polymer materials. The effective combination of various excellent performances of the high polymer material can be realized by utilizing the semi-interpenetrating network structure technology, and the high polymer material has important practical value, but the high polymer material still has fresh relation in the agricultural field. And the interaction of multiple components on the molecular level is realized by utilizing the semi-interpenetrating network technology, and the fertilizer is applied to the field of agricultural controlled-release fertilizers, so that the nutrient release performance of the controlled-release fertilizers is expected to be improved and other performances are endowed.

Disclosure of Invention

Against the background, the invention aims to provide the urea-aldehyde-based biodegradable high-polymer high-adhesion foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention. The foliar fertilizer consists of an acrylic acid graft copolymer of a biodegradable high polymer material with water absorption and retention functions and a urea aldehyde biodegradable high polymer material capable of slowly and slowly controlling release of nutrient elements or a derivative containing a plurality of nutrient elements, wherein the acrylic acid graft copolymer of the biodegradable high polymer material with water absorption and retention functions forms a cross-linked network structure, linear macromolecular chains of the urea aldehyde biodegradable high polymer material capable of slowly and slowly controlling release of the nutrient elements or the derivative containing the plurality of nutrient elements are inserted into the water absorption and retention cross-linked network, and the two form a high polymer composite material with a semi-interpenetrating network structure.

The invention is realized by the following technical scheme: the urea aldehyde biodegradable high-molecular high-adhesion foliar fertilizer has the functions of nutrient sustained and controlled release and water absorption and retention, and the foliar fertilizer enables the linear macromolecular chains of the urea aldehyde biodegradable high-molecular material capable of slowly controlling the release of nutrient elements or derivatives thereof containing various nutrient elements to be inserted into the network structure of the acrylic acid graft copolymer of the biodegradable high-molecular material, so that the two form the high-molecular composite material with a semi-interpenetrating network structure.

As a further improvement of the technical scheme of the foliar fertilizer, the biodegradable high polymer material is any one or combination of more of polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, chitosan and starch.

The invention further provides a preparation method of the urea aldehyde based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention, which comprises the following steps:

(1) dissolving a biodegradable high polymer material in water, adding an acrylic acid solution with a certain neutralization degree into an aqueous solution of the biodegradable high polymer material, uniformly mixing, adding an initiator, and reacting at a certain temperature for a certain time to obtain an aqueous solution of an acrylic acid graft copolymer of the biodegradable high polymer material, namely a component B;

(2) mixing formaldehyde and urea, adjusting pH, reacting at a certain temperature for a certain time, freezing, filtering, drying and crushing reaction liquid to obtain hydroxymethyl urea powder; uniformly mixing a cross-linking agent and hydroxymethyl urea powder to obtain a component A;

(3) and respectively adding the component A and the component B into deionized water, uniformly mixing, and reacting at a certain temperature to generate the urea-aldehyde biodegradable high-polymer high-adhesion foliar fertilizer.

As a further improvement of the technical scheme of the preparation method, in the step (2), the crosslinking agent and the methylol urea powder are uniform, and meanwhile, an inorganic fertilizer containing various nutrient elements is added.

The invention further provides a preparation mechanism of the biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention, which takes the biodegradable high-molecular material as polyvinyl alcohol and the inorganic fertilizer as monopotassium phosphate as examples:

in the above reaction mechanism, PVA represents polyvinyl alcohol, AA represents acrylic acid, APS represents ammonium persulfate, MBA represents crosslinking agent N-N' methylene bisacrylamide, PAA represents polyacrylic acid, and PVA-g-PAA represents polyvinyl alcohol acrylic acid graft copolymer. First, APS decomposes to produce sulfate anion free radicals (SO)₄ ^{● -}) These radicals abstract hydrogen atoms in-OH on the PVA macromolecular backbone, causing the PVA macromolecular backbone to contain a large number of active alkoxy groups, which initiate polymerization of acrylic monomers on the PVA backbone to form the graft copolymer PVA-g-PAA. Urea and formaldehyde react under certain conditions to produce mono-and dimethylol ureas. When the component A of the nitrogenous phosphorus-potassium biodegradable high-molecular foliar fertilizer consisting of hydroxymethyl urea powder, inorganic fertilizer and cross-linking agent and the component B of the nitrogenous phosphorus-potassium biodegradable high-molecular foliar fertilizer consisting of acrylic acid graft copolymer are added into a certain amount of deionized water in proportion, mixed uniformly and sprayed on the surface of the blade, PVA-g-PAA generates a water-absorbing and water-retaining 3D network under the action of the cross-linking agent, and the network becomes gel after absorbing water and swelling, so that the water-absorbing and water-retaining 3D network can be endowedThe leaf fertilizer has excellent adhesion performance and moisture retention performance; polymerizing hydroxymethyl urea under an acidic condition to generate urea aldehyde, wherein macromolecular chains of the urea aldehyde are inserted into a water absorption and retention network to form a semi-interpenetrating network structure; potassium dihydrogen phosphate which is easy to dissolve in water is separated out and embedded in the urea aldehyde and the biodegradable high polymer material, and the urea aldehyde and the biodegradable high polymer material have excellent nutrient sustained and controlled release performance due to the constraint and the barrier effect of macromolecular chains. The semi-interpenetrating network structure integrates multiple functions of adhesion, slow release and moisture retention, has multiple effects, and can solve the problems of poor adhesion of the foliar fertilizer, no nutrient slow release performance and no moisture retention performance.

As a further improvement of the technical scheme of the preparation method, the initiator is any one of hydrogen peroxide, sodium persulfate, ammonium persulfate, cerous nitrate, persulfate and sodium sulfite, and the cross-linking agent is any one of N, N '-amylene bisacrylamide, N' -methylene bisacrylamide, ethylene glycol di (meth) acrylate, N '-methylene bisacrylamide and N, N' -diallyl tartaric acid diamide.

As a further improvement of the technical scheme of the preparation method, in the step (1), the reaction temperature is 40-100 ℃, and the reaction time is 2-6 h; in the step (2), the reaction temperature of formaldehyde and urea is 20-60 ℃, and the reaction time is 1-4 h.

As a further improvement of the technical scheme of the preparation method, in the step (3), the mass ratio of the component A to the component B is 1-5: 1-10.

As a further improvement of the technical scheme of the preparation method, in the step (2), the mass ratio of the methylol urea powder, the inorganic fertilizer and the cross-linking agent is 100-200: 10-50: 1-10.

As a further improvement of the technical scheme of the preparation method, in the step (3), after the aqueous solution of the component A and the aqueous solution of the component B are uniformly mixed, the reaction temperature is 25-40 DEG C

The invention further provides a use method of the urea-formaldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention, which comprises the following steps: and respectively adding the component A and the component B into deionized water, uniformly mixing, and spraying the mixture to the surface of the blade.

Compared with the prior art, the invention has the following excellent performances:

(1) according to the invention, by graft copolymerization of the biodegradable high polymer material and the acrylic acid, the water absorption and retention performance of the polyacrylic acid can be improved, the environment-friendly characteristic can be given, and the problems of toxic action on a human body and low water absorption rate in the preparation process of the common acrylamide water-absorbent resin can be solved.

(2) The urea-formaldehyde biodegradable high-polymer high-adhesion foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention is a water-soluble substance before being sprayed, is convenient to spray, and the fertilizer droplets are uniformly distributed on the surface of the leaves, so that the fertilizer efficiency is improved, and the problem of poor fertilizer efficiency caused by low dissolution degree of the fertilizer on the surface of the leaves after the suspended foliar fertilizer is sprayed can be solved; after spraying, PVA-g-PAA reacts with the cross-linking agent to form a water-absorbing and water-retaining 3D network on the surface of the leaf, and the network becomes gel after water absorption and swelling. The invention can conveniently regulate and control the temperature and the rate of the crosslinking reaction by controlling the type and the content of the crosslinking agent, thereby conveniently realizing the conversion of the foliar fertilizer from a liquid state to a gel state, and integrating various performances of easy spraying, excellent slow release, moisture retention, adhesiveness and the like.

(3) The invention provides a new idea for designing a foliar fertilizer, and introduces a semi-interpenetrating network polymer into the field of the foliar fertilizer, so that the foliar fertilizer integrates easy spraying, slow release, moisture retention and adhesiveness, and has multiple effects at one stroke. In addition, the polymer network can absorb water vapor in the atmosphere, provides a wetting environment for crop leaves, and is more favorable for the growth of plants in a drought environment.

Therefore, the method has very important significance for improving the utilization efficiency of the foliar fertilizer, reducing resource waste and reducing secondary pollution to the environment.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is an FTIR spectrum of PAA, PVA + PAA, and PVA-g-PAA.

FIG. 2 is a TG and DTG spectrum of PAA, PVA + PAA and PVA-g-PAA. Wherein, the graph (a) is a TG spectrum and the graph (b) is a DTG spectrum.

FIG. 3 shows PVA + PAA and PVA-g-PAA¹³C NMR spectrum.

FIG. 4 is a DSC spectrogram of a urea aldehyde group biodegradable high-molecular high-adhesion foliar fertilizer with functions of nitrogen, phosphorus and potassium nutrient sustained and controlled release and water absorption and retention.

FIG. 5 is a photograph of the water absorption swelling of the urea-based biodegradable high molecular weight high-adhesion foliar fertilizer with controlled release of nutrients of nitrogen, phosphorus and potassium and water absorption and retention functions prepared in example 1.

FIG. 6 shows the contact angle of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with controlled release of nutrients of nitrogen, phosphorus and potassium and water absorption and retention functions prepared in example 1.

FIG. 7 shows the N adhesion performance of the urea-aldehyde-based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained and controlled release of nitrogen, phosphorus and potassium nutrients, water absorption and retention prepared in example 1.

Fig. 8 shows the P adhesion property of the urea-aldehyde-based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained and controlled release of nitrogen, phosphorus and potassium nutrients and water absorption and retention prepared in example 1.

Fig. 9 shows the moisture absorption rate of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained and controlled release of nitrogen, phosphorus and potassium nutrients and water absorption and retention prepared in example 1.

Fig. 10 shows the N release rate of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with both nitrogen, phosphorus and potassium nutrient sustained and controlled release and water absorption and retention functions prepared in example 1.

Fig. 11 shows the P release rate of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with both nitrogen, phosphorus and potassium nutrient sustained and controlled release and water absorption and retention functions prepared in example 1.

As can be seen from FIG. 1, 1452 cm is found in the infrared spectrum of PAA^-1And 1550 cm^-1The peaks of (A) are respectively attributed to the symmetric stretching vibration and the antisymmetric stretching vibration of C = O in potassium carboxylate, 1694 cm^-1The peak of (a) is attributed to C = O stretching vibration in PAA. In the infrared spectrum of PVA, 3280 cm^-1The broad and strong absorption peak can be assigned to the characteristic absorption peak of PVA in association form between or in molecules, 1084 cm^-1The peak of (2) can be attributed to C-O stretching vibration in PVA. In the infrared spectrum of PVA-g-PAA, 1700 cm^-1The peak of (A) is attributed to C = O stretching vibration in PAA, 1550 cm^-1The peak of (a) is attributed to the antisymmetric stretching vibration of C = O in potassium carboxylate. 1250 cm in the IR spectrum of PVA-g-PAA compared to the IR spectrum of a simple physical mixture of PVA and PAA, PVA + PAA^-1A characteristic peak of-O-appeared, indicating that PAA was successfully grafted onto the PVA backbone.

As can be seen from FIG. 2 (a), the thermal stability of PAA is higher than that of PVA, and the addition of PAA improves the thermal stability of PVA + PVA, which is a simple physical mixed system, because the-OH of PVA and the-COOH of PAA form hydrogen bond interaction. The thermal decomposition temperature of PVA-g-PAA shifts to a high temperature region compared to PVA + PAA because the chemical bonding force is stronger than the hydrogen bond formed by physical mixing. In FIG. 2 (b), the DTG curve of PVA + PAA, the heat absorption peak around 294 ℃ is caused by the decomposition of PVA main chain, PAA main chain and side groups, while in the DTG curve of PVA-g-PAA, the endothermic peak caused by the decomposition of PVA main chain, PAA main chain and side groups is shifted to a high temperature region, and the heat decomposition temperature is 343 ℃ which is caused by the chemical bonding force generated by the graft polymerization of PVA and PAA. In the later stage of decomposition, the thermal decomposition temperature of the PAA is 447 ℃, while the thermal decomposition temperature of the PVA-g-PAA moves to a low temperature region, mainly because more active free radicals are introduced after the PVA is added, the number of free radicals in unit volume is large, and the molecular chain is shortened after polymerization under the condition that the number of monomers is as large. After graft polymerization, the PAA side chain on the PVA-g-PAA molecular chain is shortened, which causes the thermal decomposition temperature of the PVA-g-PAA to be reduced. The molecular chain of the physically mixed PVA + PAA is longer, and the thermal decomposition temperature at the later stage of decomposition is consistent with that of the PAA. From FIGS. (a) and (b), it can be concluded that PAA was successfully grafted onto the PVA backbone.

FIG. 3 (a) In δ =20.5, 43.7 and 178.7 ppm peaks ascribed to methylene carbon (-CH) on PAA main chain, respectively₂-CH-), methine carbon (-CH-) and carboxyl carbon (-CH-COOH); peaks at δ =30.2 and 66.13 ppm were assigned to methylene carbon (-CH) on the PVA backbone, respectively₂-CH-) and methine carbon (-CH-). In FIG. 2 (b), peaks at δ =30.2, 65.9 and 178.7 ppm are assigned to methylene carbon (-CH) on the PVA-g-PAA main chain, respectively₂-CH-), methine carbon (-CH-) and carboxyl carbon (-COOH); peaks at δ =43.8 and 178.7 ppm were assigned to methine carbon (-CH-) and carboxyl carbon (-COOH) on the side chain of PVA-g-PAA, respectively. Of PVA-g-PAA, in contrast to the simple physical mixed system PVA + PAA¹³The peak at δ =60.8 ppm in C NMR is assigned to the methine carbon (-O-CH) on the PVA-g-PAA backbone₂-) thereby indicating successful grafting of PAA onto PVA.

As can be seen from FIG. 4, the glass transition temperature Tg of PVA-g-PAA is 143 ℃, and after the hydroxymethyl urea solution is added, the foliar fertilizer has an obvious endothermic peak in a low-temperature region, because the hydroxymethyl urea oligomer and urea play a plasticizing role on the PVA-g-PAA water absorption network, so that the decomposition temperature is reduced. Therefore, a part of urea aldehyde molecular chains in the foliar fertilizer penetrate into the PVA-g-PAA water absorption network to form a semi-interpenetrating polymer network structure.

As can be seen from fig. 5, the urea-aldehyde-based biodegradable high-molecular high-adhesion foliar fertilizer with controlled release of nitrogen, phosphorus and potassium nutrients and functions of water absorption and retention, prepared in example 1, has good water absorption performance, the water absorption rate in tap water is 65.8 g/g, and the water absorption rate in deionized water is 110.5 g/g.

As can be seen from fig. 6, the contact angles of the monopotassium phosphate and the urea solution on the leaf surface of the cabbage are 103.1 degrees and 101.2 degrees respectively, and the contact angle of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained release of the nitrogen, phosphorus and potassium nutrients and water absorption and retention prepared in example 1 is 61 degrees, which indicates that the foliar fertilizer is hydrophilic on the surface of the super-hydrophobic cabbage plant. The good wetting state can ensure the good spreading of the foliar fertilizer on the leaf surface, improve the contact area of the foliar fertilizer and the leaf surface, and reduce the possibility of the liquid drops sliding off from the leaf surface, thereby improving the adhesion performance of the foliar fertilizer on the leaf surface. The PVA-g-PAA has certain viscosity, is adhered to the surface of a hydrophobic plant to form a plano-convex lens shape, is adhered and wetted, and is favorable for plant nutrient absorption in a good wetting state, so that the utilization rate of the fertilizer is improved.

As can be seen from fig. 7, the nitrogen retention rate of the urea solution on the leaf surface of the cabbage is 12.47%, while the nitrogen retention rate of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained release of nitrogen, phosphorus and potassium nutrients, water absorption and water retention, prepared in example 1, is optimally up to 89.98%. Therefore, the urea-formaldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained release of nitrogen, phosphorus and potassium nutrients and water absorption and retention, which is prepared in example 1, has good adhesion performance on the leaf surfaces of the super-hydrophobic cabbage.

As can be seen from fig. 8, the phosphorus retention rate of the potassium dihydrogen phosphate solution on the leaf surface of the cabbage is 14.48%, whereas the phosphorus retention rate of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer prepared in example 1 and having the functions of sustained release of nitrogen, phosphorus and potassium nutrients, water absorption and water retention is 47.46% most preferably. Therefore, the urea-formaldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained release of nitrogen, phosphorus and potassium nutrients and water absorption and retention, which is prepared in example 1, has excellent adhesion performance on the leaf surfaces of the super-hydrophobic cabbage. As can be seen from fig. 7 to 8, the urea-based biodegradable polymer high-adhesion foliar fertilizer nitrogen prepared in example 1, which has both the controlled release of the nitrogen, phosphorus and potassium nutrients, and the water absorption and retention functions, has better adhesion performance than phosphorus. The PVA-g-PAA forms a water-absorbing and water-retaining polymer network to be adhered to the surface of the leaf, and the long-chain macromolecular urea aldehyde can be wound with the super water-absorbing resin network to form a semi-interpenetrating network, so that the binding capacity of the urea aldehyde and the leaf surface is enhanced, and the retention rate of nitrogen on the leaf surface is greatly improved. Whereas the phosphorus is embedded in the semi-interpenetrating network only as small phosphate molecules, the water absorbing component and the phosphate are separate two phases. In aqueous solution, small molecule potassium dihydrogen phosphate dissolves in water to form HPO₄ ^2-And is easily washed away by water, resulting in an improvement in the adhesion properties of phosphorus to nitrogen to a lesser extent.

As can be seen from fig. 9, when the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with controlled release of nutrients of nitrogen, phosphorus and potassium and water absorption and retention functions prepared in example 1 is exposed to an environment with a Relative Humidity (RH) of 90% and a temperature of 20 ℃, the saturated water absorption amount of 1 g/g can be achieved. The leaf fertilizer has certain hydrophilicity, and the dry leaf fertilizer can collect moisture from air and store the moisture in a water absorption network in a cool and humid environment. In a warm and dry environment, sunlight can provide power for the gel to release water, the temperature rises, and the temperature difference between the inside and the outside of the water absorption network provides power for the water release, so that the water release is realized. The water evaporation takes away a large amount of heat, so that the leaf environment can be kept in a low-temperature humid state, and the growth of plants in a drought environment is facilitated.

Fig. 10 shows that the nitrogen nutrient release spectrum of the urea-formaldehyde biodegradable high-molecular high-adhesion foliar fertilizer with controlled release of nitrogen, phosphorus and potassium nutrients and water absorption and retention functions prepared in example 1 shows a rapid increase in the early stage and a gradual and gradual trend in the later stage, and the cumulative release rate of nitrogen reaches 85% on day 10.

Fig. 11 shows that the phosphorus nutrient release spectrum of the urea-formaldehyde biodegradable high-molecular high-adhesion foliar fertilizer with both the nitrogen, phosphorus and potassium nutrient sustained-release and water absorption and retention functions prepared in example 1 shows a rapid increase in the early stage and a gradual and gradual trend in the later stage, and the cumulative release rate of phosphorus reaches 92% on day 7. As can be seen from fig. 10 and 11, the nitrogen, phosphorus and potassium element-containing foliar fertilizers prepared in comparative example 1 and comparative example 2 achieve balance of release of nitrogen and phosphorus nutrients within 1 day, while the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with functions of controlled release of nitrogen, phosphorus and potassium nutrients and water absorption and retention prepared in example 1 achieves balance of nutrient release within 7-10 days, has good slow release performance, solves the problems that the nutrient of the foliar fertilizer is easy to lose and needs to be sprayed for many times, can save manpower, and improves the nutrient utilization rate.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with nutrient sustained and controlled release and water absorption and retention functions, which specifically comprises the following components in part by weight: the urea-formaldehyde biodegradable high molecular material of sustained and controlled release nutrient elements or the linear macromolecular chain of the derivative containing a plurality of nutrient elements thereof are inserted into the network structure of the acrylic acid graft copolymer of the biodegradable high molecular material, and the two form the high molecular composite material with a semi-interpenetrating network structure.

In a specific embodiment of the foliar fertilizer provided by the present invention, the biodegradable polymer material is any one or a combination of more of polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, chitosan, and starch.

The invention also provides a preparation method of the urea aldehyde-based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention, which comprises the following steps:

In one embodiment of the preparation method of the present invention, it is preferable that the biodegradable polymer material contains a large amount of polar water-absorbing functional groups on the main chain and is soluble in water.

In another embodiment of the preparation method of the present invention, in the step (2), the crosslinking agent is added with the inorganic fertilizer containing various nutrient elements while being uniform with the methylol urea powder. Preferably, the inorganic fertilizer adopts easily soluble raw materials. Specifically, the fertilizer can be any one or combination of more of nitrogenous fertilizer, phosphate fertilizer, potash fertilizer, trace element fertilizer, calcium, magnesium, zinc, sulfur, silicon fertilizer and rare earth agricultural products.

In still another embodiment of the preparation method of the present invention, the initiator is any one of hydrogen peroxide, sodium persulfate, ammonium persulfate, ceric nitrate, persulfate and sodium sulfite, and the crosslinking agent is any one of N, N 'amylene bisacrylamide, N' methylene bisacrylamide, ethylene glycol di (meth) acrylate, N 'methylene bisacrylamide and N, N' -diallyl tartaric acid diamide.

As a preferred embodiment of the invention, in the step (1), the reaction temperature is 40-100 ℃, and the reaction time is 2-6 h; in the step (2), the reaction temperature of formaldehyde and urea is 20-60 ℃, and the reaction time is 1-4 h.

Preferably, in step (1), the reaction system after the initiator is added is reacted in an inert atmosphere.

In addition, in the step (1), the mass ratio of the biodegradable polymer material to the acrylic acid is 1: 1-10.

Preferably, the concentration of the biodegradable polymer material in the aqueous solution of the biodegradable polymer material is 1-20 wt%. The initiator is 0.1-1% of the total mass of the biodegradable high polymer material and the acrylic acid.

Further, in the step (1), the neutralization degree of the acrylic acid solution is 20 to 90 wt%.

In one embodiment of the invention, in the step (2), the mass ratio of the methylol urea powder, the inorganic fertilizer and the cross-linking agent is 100-200: 10-50: 1-10.

In another embodiment provided by the invention, the molar ratio of the formaldehyde to the urea is 1: 1-2.

Specifically, in the step (3), after the aqueous solution of the component A and the aqueous solution of the component B are uniformly mixed, the reaction temperature is 30-40 ℃.

Preferably, in the step (3), the mass ratio of the component A to the component B is 1-5: 1-10. In addition, the mass of the cross-linking agent is 0-1% of the total mass of the biodegradable polymer material and the acrylic acid, and is not 0.

The invention also provides a use method of the urea-formaldehyde-based biodegradable high-polymer high-adhesion foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention.

In the invention, the component A and the component B sprayed on the surface of the leaf can react under the outdoor temperature condition to form the urea-formaldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention.

The measurement standards of the experiments in the present invention are as follows:

testing the water absorption performance: and (3) adding the component B prepared in the step (1) and the component A prepared in the step (3) into a certain amount of deionized water according to a certain proportion, uniformly mixing, spraying the mixture on a polytetrafluoroethylene plate, and drying in a drying oven at 35 ℃ to obtain the urea-formaldehyde biodegradable high-adhesion high-molecular foliar fertilizer with the functions of nutrient sustained and controlled release and water absorption and retention. Placing 1 g of the dried sample in 500 mL of tap water at room temperature until the swelling is balanced; then taking out the foliar fertilizer which absorbs water and swells and is saturated, wiping the surface of the foliar fertilizer with absorbent cotton, weighing the foliar fertilizer and obtaining the water absorption multiplying power Q_eq(g/g) is calculated according to the formula (1):

Q_eq

formula (1)

Wherein M and M₀The mass of the sample after and before water absorption is indicated, respectively.

Adhesion performance test: selecting flat parts of cabbage, cutting into 5cm × 5cm squares, washing with deionized water, and drying water on the surface of the leaves. And (3) adding the component B prepared in the step (1) and the component A prepared in the step (3) into a certain amount of deionized water according to a proportion, uniformly mixing, spraying onto plant leaves, and recording the spraying amount. The leaves sprayed with the foliar fertilizer are placed in a 35 ℃ (simulating summer outdoor temperature) incubator for drying, then 10 mL of deionized water is uniformly sprayed on the leaves to simulate rain water, and the washed liquid is collected for digestion to determine the concentration of NP in the solution. The retention rate of nitrogen and phosphorus of the foliar fertilizer on the foliar surface is calculated according to the formula (2) to obtain:

leaf fertilizer N/P retention rate

X 100% formula (2)

Moisture absorption performance test: and (3) adding the component B prepared in the step (1) and the component A prepared in the step (3) into a certain amount of deionized water according to a certain proportion, uniformly mixing and spraying the mixture on a polytetrafluoroethylene plate, drying the mixture in a drying oven at 35 ℃ (simulating summer outdoor temperature) until the weight is constant, weighing 1 g of dried sample, and placing the dried sample in a sealed plastic box, wherein a humidifier is arranged in the plastic box and can provide an environment with constant humidity. And taking out samples every 1 h, wiping the surface water drops to be dry, weighing the mass of the samples, and calculating the moisture absorption amount.

Testing the slow release performance: and (3) adding the component B prepared in the step (1) and the component A prepared in the step (3) into a certain amount of deionized water according to a certain proportion, uniformly mixing, spraying on a polytetrafluoroethylene plate, and drying in a drying oven at 35 ℃. Weighing 0.4 g of dried sample, putting the dried sample into a nylon mesh bag with the particle size of 150 mu m (100 meshes), sealing the nylon mesh bag, putting the nylon mesh bag into a plastic bottle with the particle size of 250 mL, adding 80 mL of deionized water, covering and sealing the plastic bottle, and putting the plastic bottle into a biochemical constant temperature incubator with the temperature of 25 ℃ for sampling for 24 hours, 3 days, 5 days, 7 days, 10 days and 14 days. In sampling, the bottle was turned upside down 3 times to make the concentration of the liquid in the bottle uniform, and the bottle was transferred to a 100 mL volumetric flask, and 20 mL of the liquid was digested and boiled to determine the NP-releasing amount. Then 80 mL of deionized water is added into the nylon mesh bag filled with the fertilizer, and the nylon mesh bag is covered and sealed and then placed into a biochemical constant temperature incubator for continuous culture.

The technical solution of the present invention will be described in detail by the following specific examples.

Example 1

(1) 5 g of PVA powder were dissolved in 25 g of deionised water in a first reaction vesselStirring the mixture in water at 85 ℃ for 2 hours by magnetic force until the mixture is completely dissolved to obtain a polyvinyl alcohol aqueous solution. 31.15 g of a 30% by mass potassium hydroxide solution was added to 10 g of AA, and the neutralization degree of AA was adjusted to 80%. Adding the neutralized acrylic acid into PVA solution under ice bath condition, stirring the mixed solution uniformly, pouring the mixed solution into a single-neck bottle with a nitrogen guide pipe, introducing nitrogen, stirring and mixing uniformly, adding 30 mg APS, magnetically stirring for 10min, heating to 55 ℃, and reacting for 4 h under nitrogen atmosphere to obtain m_(PVA)/m_(AA)PVA-g-PAA at a ratio of 1: 2. The component B is a urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nitrogen nutrient sustained and controlled release and water absorption and retention;

(2) adding 37% by mass of formaldehyde aqueous solution into a second reaction vessel, adjusting the pH of the system to 8 by using 5% by mass of potassium hydroxide solution, then adding urea with the molar ratio of 1:1.2 to the formaldehyde, mechanically stirring until the mixture is clear and transparent, reacting for 2 hours at 40 ℃, freezing, filtering, drying and crushing the reaction solution to obtain hydroxymethyl urea powder;

uniformly mixing 35.4 g of monopotassium phosphate, 1.06 g N, N' -methylene bisacrylamide and 150 g of hydroxymethyl urea powder prepared in the step (2) by using a high-speed mixer to obtain the powdered urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer A component with the functions of nitrogen nutrient sustained and controlled release and water absorption and retention.

(3) Adding 1.86 g of the component A and 10.08 g of the component B into 92.8 g of deionized water, uniformly mixing, and spraying the mixture on the surface of a leaf of cabbage growing in an environment of 35 ℃ to obtain the urea-formaldehyde biodegradable high-polymer high-adhesion foliar fertilizer with the functions of sustained and controlled release of nitrogen, phosphorus and potassium nutrients and water absorption and retention.

The urea aldehyde biodegradable high-polymer high-adhesion foliar fertilizer with the functions of nitrogen, phosphorus and potassium nutrient sustained and controlled release and water absorption and retention prepared by the steps has the nitrogen content of 0.467%, the phosphorus content of 0.068% and the potassium content of 0.086%. The tap water absorption rate is 65.8 g/g, the deionized water absorption rate is 120.5 g/g, the nitrogen retention rate on the leaf surfaces of the cabbage is 89.98%, and the phosphorus retention rate is 47.46%.

Example 2

(1) In a first reaction vessel, 5 g of PVA powder was dissolvedIn 25 g of deionized water, the mixture is magnetically stirred for 2 hours at 85 ℃ until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol aqueous solution. 31.15 g of a 30% by mass potassium hydroxide solution was added to 15 g of AA, and the neutralization degree of AA was adjusted to 80%. Adding the neutralized acrylic acid into PVA solution under ice bath condition, stirring the mixed solution uniformly, pouring the mixed solution into a single-neck bottle with a nitrogen guide pipe, introducing nitrogen, stirring and mixing uniformly, adding 30 mg APS, magnetically stirring for 10min, heating to 55 ℃, and reacting for 4 h under nitrogen atmosphere to obtain m_(PVA)/m_(AA)PVA-g-PAA at a ratio of 1: 2. The component B is a urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nitrogen nutrient sustained and controlled release and water absorption and retention;

(2) adding a formaldehyde aqueous solution with the mass fraction of 37% into a second reaction vessel, adjusting the pH of the system to 8 by using a potassium hydroxide solution with a certain mass fraction, then adding urea with the molar ratio of 1:1.2 to the formaldehyde, mechanically stirring until the mixture is clear and transparent, reacting for 2 hours at 40 ℃, freezing, filtering, drying and crushing the reaction solution to obtain hydroxymethyl urea powder; and (3) uniformly mixing 35.4 g of monopotassium phosphate, 1.06 g of N, N' -methylene bisacrylamide and 150 g of hydroxymethyl urea powder prepared in the step (2) by using a high-speed mixer to obtain the powdery urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer A component with the functions of nitrogen nutrient sustained and controlled release and water absorption and retention.

(3) Adding the 1.86 g A component and the 2.52 g B component into 100.3 g of deionized water, uniformly mixing, and spraying the mixture on the surface of cabbage leaves growing in an environment of 35 ℃ to obtain the urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained and controlled release of nitrogen, phosphorus and potassium nutrients and water absorption and retention.

The urea aldehyde biodegradable polymer high-adhesion foliar fertilizer prepared by the steps has the functions of nitrogen, phosphorus and potassium nutrient sustained and controlled release and water absorption and retention, and has the nitrogen content of 0.467%, the phosphorus content of 0.068% and the potassium content of 0.086%. The tap water absorption rate is 27.0 g/g, the deionized water absorption rate is 58.4 g/g, the nitrogen retention rate on the leaf surfaces of the cabbage is 74.21%, and the phosphorus retention rate is 42.27%.

Example 3

(1) In a first reaction vessel 5 g of PVA powder was dissolved in a quantity of deionized water,and magnetically stirring for 2 h at 85 ℃ until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol aqueous solution. 31.15 g of a 30% by mass potassium hydroxide solution was added to 10 g of AA, and the neutralization degree of AA was adjusted to 80%. Adding the neutralized AA into PVA solution under ice bath condition, stirring the mixed solution uniformly, pouring the mixed solution into a single-neck bottle with a nitrogen guide pipe, introducing nitrogen, stirring and mixing uniformly, adding 30 mg of APS, magnetically stirring for 10min, heating to 55 ℃, and reacting for 4 h under nitrogen atmosphere to obtain m_(PVA)/m_(AA)PVA-g-PAA at a ratio of 1: 2. The component B is a urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nitrogen nutrient sustained and controlled release and water absorption and retention;

(2) adding a formaldehyde solution with the mass fraction of 37% into a second reaction vessel, adjusting the pH of the system to 8 by using a potassium hydroxide solution with a certain mass fraction, then adding urea with the molar ratio of 1:1.2 to the formaldehyde solution, mechanically stirring until the mixture is clear and transparent, reacting for 2 hours at 40 ℃, freezing, filtering, drying and crushing the reaction solution to obtain hydroxymethyl urea powder; and (3) uniformly mixing 35.4 g of monopotassium phosphate, 1.06 g of N, N' -methylene bisacrylamide and 150 g of hydroxymethyl urea powder prepared in the step (2) by using a high-speed mixer to obtain the powdery urea-based biodegradable high-molecular high-adhesion foliar fertilizer A component with the functions of nitrogen nutrient sustained and controlled release and water absorption and retention.

(3) Adding the 1.86 g A component and the 1.26 g B component into 101.6 g of deionized water, uniformly mixing, and spraying the mixture on the surface of cabbage leaves growing in an environment of 35 ℃ to obtain the urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained and controlled release of nitrogen, phosphorus and potassium nutrients and water absorption and retention.

The urea aldehyde biodegradable polymer high-adhesion foliar fertilizer prepared by the steps has the functions of nitrogen, phosphorus and potassium nutrient sustained and controlled release and water absorption and retention, and has the nitrogen content of 0.467%, the phosphorus content of 0.068% and the potassium content of 0.086%. The tap water absorption rate is 7.9 g/g, and the deionized water absorption rate is 33.8 g/g. The nitrogen retention rate of the leaf surfaces of the cabbage is 74.21 percent, and the phosphorus retention rate is 40.04 percent.

Example 4

(1) Dissolving 5 g of PVA powder in a certain amount of deionized water in a first reaction vessel, and magnetically stirring for 2 h at 85 ℃ until the mixture is completely stirredDissolving to obtain the polyvinyl alcohol aqueous solution. 31.15 g of a 30% by mass potassium hydroxide solution was added to 10 g of AA, and the neutralization degree of AA was adjusted to 80%. Adding the neutralized AA into PVA solution under ice bath condition, stirring the mixed solution uniformly, pouring the mixed solution into a single-neck bottle with a nitrogen guide pipe, introducing nitrogen, stirring and mixing uniformly, adding 30 mg of APS, magnetically stirring for 10min, heating to 55 ℃, and reacting for 4 h under nitrogen atmosphere to obtain m_(PVA)/m_(AA)PVA-g-PAA at a ratio of 1: 2. The component B is a urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of nitrogen nutrient sustained and controlled release and water absorption and retention;

(2) adding a formaldehyde solution with the mass fraction of 37% into a second reaction vessel, adjusting the pH of the system to 8 by using a potassium hydroxide solution with a certain mass fraction, then adding urea with the molar ratio of 1:1.2 to the formaldehyde solution, mechanically stirring until the mixture is clear and transparent, reacting for 2 hours at 40 ℃, freezing, filtering, drying and crushing the reaction solution to obtain hydroxymethyl urea powder;

and (3) uniformly mixing 35.4 g of monopotassium phosphate, 1.06 g of N, N' -methylene bisacrylamide and 150 g of hydroxymethyl urea powder prepared in the step (2) by using a high-speed mixer to obtain the powdery urea-based biodegradable high-molecular high-adhesion foliar fertilizer A component with the functions of nitrogen nutrient sustained and controlled release and water absorption and retention.

(3) Adding the 1.86 g A component and the 0.84 g B component into 102 g of deionized water, uniformly mixing, and spraying the mixture on the surface of cabbage leaves growing in an environment of 35 ℃ to obtain the urea-aldehyde biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained release of nitrogen, phosphorus and potassium nutrients and water absorption and retention.

The urea aldehyde biodegradable polymer high-adhesion foliar fertilizer prepared by the steps has the functions of nitrogen, phosphorus and potassium nutrient sustained and controlled release and water absorption and retention, and has the nitrogen content of 0.467%, the phosphorus content of 0.068% and the potassium content of 0.086%. The tap water absorption rate is 8.53 g/g, and the deionized water absorption rate is 34.49 g/g. The nitrogen retention rate of the leaf surfaces of the cabbage is 67.55%, and the phosphorus retention rate is 32.43%.

Comparative example 1

Adding 0.4 g of urea into a certain amount of deionized water, and dissolving to obtain a urea solution. The nitrogen content is 0.467%, and the nitrogen retention rate on the leaf surfaces of the cabbage is 13.22% after the nitrogen content is sprayed on the leaf surfaces of the cabbage.

Comparative example 2

0.2 g of monopotassium phosphate is added into a certain amount of deionized water and dissolved to obtain a potassium dihydrogen phosphate solution. The phosphorus content is 0.068%, the potassium content is 0.086%, and after the fertilizer is sprayed on the leaf surfaces of the cabbage, the phosphorus retention rate on the leaf surfaces of the cabbage is 14.48%.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The urea aldehyde biodegradable high-molecular high-adhesion foliar fertilizer is characterized in that the foliar fertilizer enables linear macromolecular chains of urea aldehyde biodegradable high-molecular materials capable of slowly controlling and releasing nutrient elements or derivatives containing multiple nutrient elements to be inserted into a network structure of acrylic acid graft copolymers of the biodegradable high-molecular materials, and the two form a high-molecular composite material with a semi-interpenetrating network structure.

2. The urea aldehyde based biodegradable high-molecular high-adhesion foliar fertilizer with both sustained and controlled release of nutrients and water absorption and retention functions as claimed in claim 1, wherein the biodegradable high-molecular material is any one or a combination of polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, chitosan and starch.

3. The preparation method of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with sustained and controlled release of nutrients and functions of water absorption and retention as claimed in claim 1 or 2, which is characterized by comprising the following steps:

4. The preparation method of the urea-formaldehyde based biodegradable high-molecular high-adhesion foliar fertilizer with sustained and controlled release of nutrients and functions of water absorption and retention as claimed in claim 3, wherein in the step (2), the inorganic fertilizer containing various nutrient elements is added while the cross-linking agent and the methylol urea powder are uniform.

5. The preparation method of the urea-based biodegradable high-molecular high-adhesion foliar fertilizer with sustained and controlled release of nutrients and water absorption and retention functions as claimed in claim 3, wherein the initiator is any one of hydrogen peroxide, sodium persulfate, ammonium persulfate, cerous nitrate, persulfate and sodium sulfite, and the cross-linking agent is any one of N, N '-amylene bisacrylamide, N' -methylene bisacrylamide, ethylene glycol di (meth) acrylate, N '-methylene bisacrylamide and N, N' -diallyl tartaric acid diamide.

6. The preparation method of the urea aldehyde based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained and controlled release of nutrients and water absorption and retention as claimed in claim 3, wherein in the step (1), the reaction temperature is 40-100 ℃, and the reaction time is 2-6 h; in the step (2), the reaction temperature of formaldehyde and urea is 20-60 ℃, and the reaction time is 1-4 h.

7. The preparation method of the urea aldehyde based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained and controlled release of nutrients and water absorption and retention as claimed in claim 3, wherein in the step (3), the mass ratio of the component A to the component B is 1-5: 1-10.

8. The preparation method of the urea-formaldehyde-based biodegradable high-polymer high-adhesion foliar fertilizer with the functions of sustained and controlled release of nutrients and water absorption and retention as claimed in claim 4, wherein in the step (2), the mass ratio of the methylol urea powder, the inorganic fertilizer and the cross-linking agent is 100-200: 10-50: 1-10.

9. The preparation method of the urea aldehyde based biodegradable high-molecular high-adhesion foliar fertilizer with the functions of sustained and controlled release of nutrients and water absorption and retention as claimed in claim 3, wherein in the step (3), the reaction temperature is 25-40 ℃ after the aqueous solution of the component A and the aqueous solution of the component B are uniformly mixed.

10. The use method of the urea-formaldehyde based biodegradable high-molecular high-adhesion foliar fertilizer with sustained and controlled release of nutrients and functions of water absorption and retention as claimed in claim 3, wherein the component A and the component B are respectively added into deionized water, mixed uniformly and then sprayed onto the surface of the leaves.