CN114766481A - High-encapsulation-rate pesticide microcapsule and preparation method and application thereof - Google Patents
High-encapsulation-rate pesticide microcapsule and preparation method and application thereof Download PDFInfo
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
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- A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
- A01N25/26—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests in coated particulate form
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
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- A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
- A01N25/08—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests containing solids as carriers or diluents
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- A01N43/00—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds
- A01N43/48—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with two nitrogen atoms as the only ring hetero atoms
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Abstract
The invention discloses a high-encapsulation-rate pesticide microcapsule and a preparation method and application thereof, wherein cellulose nanocrystalline formed after acidolysis of cotton is used as a stabilizer to prepare O/W type emulsion with good homogeneous emulsification effect, and then hexamethylene diisocyanate and ethylenediamine are polymerized at the emulsion interface to form polyurea polymer which is used as a wall material of the microcapsule and coats encapsulated pesticide components, so that the problems of short action period and high pesticide toxicity of the existing pesticide are solved, and the pesticide microcapsule with good slow release effect is obtained, thereby prolonging the pesticide action duration, reducing the pesticide application amount and reducing the harm of the pesticide to the environment to a certain extent.
Description
Technical Field
The invention relates to the technical field of pesticide preparations, in particular to a high-encapsulation-rate pesticide microcapsule and a preparation method and application thereof.
Background
China is the first world country where agricultural pesticides are produced and used, and more than 100 agricultural pests occur throughout the year at present, so that the pesticides become one of important material bases for agricultural safety production, and are exemplified by imidacloprid.
Imidacloprid is a nitro methylene systemic insecticide, belongs to chloronicotinyl insecticides, is also called neonicotinyl insecticides, and has stomach toxicity and contact poisoning effects. The pure product is a crystalline solid with a molecular formula of C9H10ClN5O2The chemical name is 1- (6-chloro-3-picolyl) -N-nitro-2-imidazoline imine, and the chemical structural formula is shown as follows:
the imidacloprid can selectively act on a nicotinic acetylcholine receptor in an insect nervous system so as to destroy the normal conduction of central nervous system signals of the insect, and has the characteristics of high insecticidal activity, broad spectrum, high efficiency, safety and low toxicity. However, abuse of imidacloprid can have adverse environmental effects such as soil contamination, surface/ground water contamination, damaged ecological environment and harm to human health.
Therefore, how to prolong the action period of the pesticide, reduce the toxicity of the pesticide and have extremely important significance for the application of the pesticide in crops.
Disclosure of Invention
In order to solve the problems of short action period and great toxicity of the existing pesticide, one of the purposes of the invention is to provide a preparation method of a pesticide microcapsule with high encapsulation rate.
The technical scheme for solving the technical problems is as follows: a preparation method of a high-encapsulation-rate pesticide microcapsule comprises the following steps:
Homogenizing and emulsifying an aqueous phase and an oil phase to form an O/W type emulsion, wherein the aqueous phase comprises a cellulose nanocrystal suspension and an inorganic salt electrolyte for shielding the charge of the cellulose nanocrystal, and the oil phase comprises corn oil;
Adding hexamethylene diisocyanate and the encapsulated pesticide component to the oil phase in the step 1, thereby obtaining an O/W type emulsion containing the encapsulated pesticide component;
and slowly dripping an ethylenediamine solution into the O/W type emulsion containing the encapsulated pesticide component, reacting at room temperature, and filtering, washing and drying in sequence after the reaction to obtain the pesticide microcapsule.
The beneficial effects of the invention are as follows: the preparation method of the high-encapsulation-rate pesticide microcapsule has the characteristics of simple process and mild conditions, is easy for industrial production, and has good slow release effect, so that the pesticide microcapsule prepared in the invention has the characteristics of prolonging the lasting period of pesticide action, improving the utilization rate of pesticide, reducing the application amount of high-toxicity pesticide and reducing the application times, and effectively solves the problem of high toxicity of the traditional pesticide preparation. In addition, the inorganic salt electrolyte is added into the cellulose nanocrystalline suspension to shield the repulsion effect of negative charges among cellulose nanocrystalline particles, so that an interface film with certain strength is favorably formed by adsorption on an oil-water interface, and the stability of the emulsion is improved.
On the basis of the technical scheme, the invention can be further improved as follows:
further, the mass fraction of the cellulose nanocrystals in the cellulose nanocrystal suspension in step 1 is 0.6 wt%, wherein 1mg to 20mg of the inorganic salt electrolyte is added to each milliliter of the cellulose nanocrystal suspension.
The beneficial effect of adopting the further technical scheme is as follows: the inorganic salt electrolyte for shielding the charge of the cellulose nanocrystal in the mass range ensures that the prepared pesticide microcapsule has better dispersibility and proper particle size, avoids the interaction of the cellulose nanocrystal phases on the surfaces between the liquid drops of the O/W type emulsion caused by excessive inorganic salt electrolyte, further causes floccules and conglobate aggregates to appear between the microcapsules when the microcapsules are prepared, causes poor dispersibility of the microcapsules and overlarge particle size of the microcapsules, and is further not beneficial to the formation of the microcapsules in the later period.
Furthermore, the mass ratio of the encapsulated pesticide component to hexamethylene diisocyanate and ethylenediamine is (0.035-0.050): (0.5-2.0): 0.2-0.71.
The beneficial effects of adopting the further technical scheme are as follows: the O/W type emulsion prepared by the mass ratio is still stable, and the emulsification efficiency of the emulsion is not changed.
Further, the volume ratio of the oil phase to the water phase in the homogenization and emulsification in the step 1 is 1:4, and the reaction time in the step 2 is 2 h.
Further, the inorganic salt electrolyte includes NaCl, Na2SO4And KCl, the encapsulated pesticide component comprising imidacloprid.
Further, the cellulose nanocrystals in the cellulose nanocrystal suspension in step 1 are prepared by the following method:
placing the biomass material rich in cellulose in an acid water solution for acidolysis reaction, then adding distilled water to terminate the acidolysis reaction, finally collecting the precipitate obtained by the acidolysis reaction, and washing and dialyzing the precipitate in sequence to finally obtain cellulose nanocrystal;
wherein the acid water solution is a sulfuric acid water solution with the mass fraction of 63 wt% -65 wt%, the mass ratio of the sulfuric acid water solution to the cellulose-rich biomass material is 10:1, and the volume ratio of the distilled water to the sulfuric acid water solution is 10: 1.
Further, the acidolysis reaction time is 2h, and the acidolysis reaction temperature is 49-51 ℃.
The beneficial effects of adopting the further technical scheme are as follows: the cellulose nanocrystalline obtained by acidolysis under the condition has a proper length-diameter ratio, so that the problem that the length-diameter ratio of the obtained cellulose nanocrystalline is reduced and the stability of the emulsion is reduced due to overlong acidolysis reaction time or overhigh acidolysis reaction temperature, and finally the oil-water separation of the emulsion is caused, and the microcapsule cannot be prepared; and simultaneously, the problem that the cellulose nanocrystalline cannot be obtained due to too short acidolysis reaction time or too low acidolysis reaction temperature is avoided.
Further, the cellulose-rich biomass material comprises cotton.
The beneficial effects of adopting the further technical scheme are as follows: the invention takes cotton cellulose as raw material, which is cheap and easy to obtain, and the cellulose nanocrystalline material obtained after acidolysis is in a rod-like structure, has the advantages of high length-diameter ratio, high crystallinity, high Young modulus, high strength, high transparency, excellent amphipathy and the like, and is beneficial to forming an O/W type emulsion system by a water phase and an oil phase.
The second purpose of the invention is to prepare a pesticide microcapsule by utilizing the first purpose of the invention.
The third purpose of the invention is to use the pesticide microcapsule in the second purpose of the invention for controlling pests.
The invention has the following beneficial effects:
the preparation method of the pesticide microcapsule has the characteristics of simple process and mild conditions, and the pesticide microcapsule prepared by the method has a good slow release effect, prolongs the lasting period of pesticide action to a certain extent, reduces the application amount of pesticide, effectively solves the problems of high toxicity, low pesticide utilization rate, easy environmental loss and the like of the traditional pesticide preparation, and provides a new idea for taking cellulose as a pesticide carrier.
Drawings
FIG. 1 is an ultraviolet (UV-vis) spectrum of cellulose nanocrystal suspensions prepared in examples 1 to 8 of the present invention;
FIG. 2 is a UV spectrum at 500nm of cellulose nanocrystal suspensions prepared in examples 1 to 8 of the present invention;
FIG. 3 is a view of a polarizing microscope (POM) of O/W type Pickering emulsions prepared in examples 1 to 8 of the present invention;
FIG. 4 is an SEM photograph of imidacloprid polyurea microcapsules prepared in example 9 of the invention;
FIG. 5 is an SEM photograph of imidacloprid polyurea microcapsules prepared in example 10 according to the invention;
FIG. 6 is an SEM photograph of imidacloprid polyurea microcapsules prepared in example 11 of the invention;
FIG. 7 is a graph of the encapsulation efficiency of imidacloprid polyurea microcapsules prepared in examples 9 to 11 of this invention;
FIG. 8 is a graph of the cumulative release rate of imidacloprid polyurea microcapsules prepared in example 10 of this invention.
Detailed Description
The high encapsulation efficiency pesticide microcapsule and its preparation method and application in this application will be described with reference to the following examples. This application may, however, be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein, but rather these embodiments are provided so that this application will be thorough and complete and will fully convey the scope of this application to those skilled in the art.
In order to reduce the toxicity of the encapsulated pesticide components and enable the encapsulated pesticide components to be released continuously, thereby achieving the purposes of prolonging the action period of the pesticide and effectively avoiding the loss of imidacloprid, the microencapsulated pesticide is mainly realized by adopting a microencapsulation technology at present.
A microcapsule is a micro particle of a nano or micro scale formed by coating a core material with a film. The preparation technology of the microcapsule mainly comprises the following steps: chemical methods, physical methods and physicochemical methods, and the emulsion template method in the chemical methods is one of the most effective ways to prepare the microcapsules; in addition, emulsions are classified into conventional emulsions and Pickering emulsions.
Based on the above, the inventor utilizes Cellulose Nanocrystals (CNCs) obtained after charges are shielded by inorganic salt electrolyte as an emulsifier of O/W type emulsion (i.e. O/W type Pickering emulsion), and prepares a pesticide microcapsule with high encapsulation efficiency by using the emulsion as a template.
One of the purposes of the invention is to provide a preparation method of a high-encapsulation-rate pesticide microcapsule, which comprises the following steps:
Homogenizing and emulsifying an aqueous phase and an oil phase to form an O/W type emulsion, wherein the aqueous phase comprises a cellulose nanocrystal suspension and an inorganic salt electrolyte for shielding the charge of the cellulose nanocrystal, and the oil phase comprises corn oil; in this example, the cellulose nanocrystal suspension after shielding the charge with an inorganic salt electrolyte was the aqueous phase.
Adding hexamethylene diisocyanate and the encapsulated pesticide component to the oil phase in the step 1, thereby obtaining an O/W type emulsion containing the encapsulated pesticide component; slowly dripping an ethylenediamine solution into O/W type emulsion containing encapsulated pesticide components, reacting at room temperature, and filtering, washing and drying in sequence after the reaction to obtain pesticide microcapsules; wherein the mass ratio of the encapsulated pesticide to hexamethylene diisocyanate and ethylenediamine is (0.035-0.050): 0.5-2.0: 0.2-0.71.
Wherein, the cellulose nanocrystals in the cellulose nanocrystal suspension in step 1 are prepared as follows:
placing the biomass material rich in cellulose in an acid water solution for acidolysis reaction, adding distilled water to terminate the acidolysis reaction, collecting the precipitate obtained by the acidolysis reaction, and sequentially washing and dialyzing the precipitate to finally obtain Cellulose Nanocrystals (CNCs); in the present example, the acid aqueous solution is an aqueous sulfuric acid solution having a mass fraction of 63 wt% to 65 wt%, and the cellulose nanocrystals obtained by acidolysis with the aqueous sulfuric acid solution are well dispersed in the aqueous solution due to the presence of sulfate bonds on the surface thereof.
In this example, the mass ratio of the aqueous sulfuric acid solution to the cellulose-rich biomass material was 10:1, and the mass ratio of distilled water to sulfuric acid was 7: 13; preferably, the mass fraction of the sulfuric acid aqueous solution in this embodiment is also 64%, and the cellulose-rich biomass in this embodiment includes cotton, preferably 45-2 cotton of Xinluohao Shihuozi, Xinjiang Shihuozi, though other cellulose-rich substances may be used in practice. In addition, the cotton in this embodiment needs to be pretreated before the acidolysis reaction with the acid aqueous solution, and the pretreatment mainly includes cleaning the cotton, cutting the cotton into pieces, and beating the cotton pieces into cotton pulp, which is beneficial to the full acidolysis of the cotton; in addition, the sulfuric acid in the present example is preferably 98% by mass.
In the embodiment, firstly, the cotton rich in cellulose is placed in a sulfuric acid aqueous solution for acidolysis, so as to finally obtain a cellulose nanocrystal suspension with sulfate ester bond negative charges, and then the charges of the cellulose nanocrystals are shielded by an inorganic salt electrolyte; in this embodiment, a large amount of negative charges are introduced to the surface of the cellulose nanocrystals prepared by sulfuric acid hydrolysis, and a large amount of apparent charges can cause repulsion between the cellulose nanocrystals, so that an interface film with a certain strength is difficult to form in an oil-water interface by adsorption, thereby affecting the stability of the emulsion; for this reason, in this example, the repulsion of negative charges between cellulose nanocrystal particles was suppressed by adding an inorganic salt electrolyte; in this example, the addition of the inorganic salt electrolyte can shield the surface charge of the CNCs, and avoid the emulsion from being unstable; however, when the inorganic salt electrolyte is added too much, the CNCs will interact with CNCs on the surface of other emulsion droplets and entangle together to form a network structure, resulting in a decrease in the emulsification efficiency of the O/W type Pickering emulsion.
In some embodiments, the mass fraction of the cellulose nanocrystals in the cellulose nanocrystal suspension in step 1 is 0.6 wt%, wherein 1mg to 20mg of the inorganic salt electrolyte is added to each milliliter of the cellulose nanocrystal suspension to shield the charge of the cellulose nanocrystals, and the inorganic salt electrolyte for shielding the charge of the cellulose nanocrystals comprises NaCl, Na2SO4And KCl, however, the inorganic salt electrolyte in the present embodiment may be other inorganic salt electrolytes, and the present embodiment will not be illustrated in detail. In addition, in this example, the O/W Pickering emulsion formed by using the cellulose nanocrystal suspension with the mass fraction of cellulose nanocrystals of 0.6 wt% has the best emulsification efficiency, which is beneficial to the later preparation of the microcapsule.
In this example, a stable O/W type Pickering emulsion was formed from the cellulose nanocrystal, and the microcapsule was formed by polymerizing hexamethylene diisocyanate and ethylenediamine at the O/W type emulsion interface formed from the cellulose nanocrystal. Specifically, firstly, when the water phase and the oil phase are homogenized and emulsified, the cellulose nanocrystals in the water phase are used as a stabilizer, the oil phase and the water phase are homogenized and emulsified into a stable O/W type emulsion, and the cellulose nanocrystals firstly form a microcapsule framework at a water-oil interface; then adding ethylenediamine into the O/W type emulsion system, with the addition of the ethylenediamine, polymerizing hexamethylene diisocyanate in an oil phase and the ethylenediamine in a water phase at an emulsion interface with stable cellulose nanocrystals to form polyurea macromolecules serving as a wall material of the microcapsule, and embedding the cellulose nanocrystals into the polyurea so as to coat the encapsulated pesticide component; and finally, obtaining the pesticide microcapsule with high encapsulation efficiency by filtering or precipitating.
The preparation method of the pesticide microcapsule with high encapsulation efficiency in the embodiment has the characteristics of simple process and mild conditions, is easy for industrial production, and has high encapsulation efficiency and good slow release effect; therefore, the pesticide microcapsule prepared in the embodiment has the characteristics of prolonging the lasting period of pesticide action, improving the utilization rate of pesticide, reducing the application amount of high-toxicity pesticide and reducing the application times, effectively solves the problems of high toxicity, low utilization rate of pesticide, easy environmental loss and the like of the traditional pesticide preparation, provides a new idea for taking cellulose as a pesticide carrier, and has very important significance for the health of an applicator and environmental protection. In addition, in the embodiment, nontoxic and pollution-free corn oil is selected as the oil phase, so that the influence of the pesticide microcapsule on the environment is further reduced.
In addition, in the embodiment, cotton is used as a raw material for preparing the cellulose nanocrystals, which is cheap and easily available, and the cellulose nanocrystals obtained after acid hydrolysis have a rod-like structure, have the advantages of high length-diameter ratio, high crystallinity, high young modulus, high strength, high transparency, excellent amphipathy and the like, are solid particles with good stable emulsion, and are beneficial to forming an O/W type Pickering emulsion system by using a water phase and an oil phase.
In addition, in the present example, the ethylenediamine is added to the O/W type emulsion by slow dropping, and the dropping conditions may be: 0.2g to 0.71g of ethylenediamine is dripped into the O/W type emulsion for 30 min; of course, when the ethylenediamine is added dropwise, the O/W type emulsion must be stirred at a speed of 200 r/min.
In addition, in some examples, the volume ratio of the oil phase to the water phase at the time of homogeneous emulsification in step 1 is 1:4, and the rotation speed at the time of homogeneous emulsification is 10000rpm/min, which ensure formation of an O/W type emulsion; in practice, the time for homogeneous emulsification at 10000rpm/min for 10mL of the aqueous phase and 40mL of the oil phase is 8 min.
Additionally, in some embodiments, the mass ratio of the encapsulated pesticide component to hexamethylene diisocyanate and ethylenediamine is: (0.035-0.050): (0.5-2.0): 0.2-0.71); in this example, the encapsulated pesticide component includes imidacloprid. The mass relation ratio among the hexamethylene diisocyanate, the ethylenediamine and the imidacloprid within the range can ensure that the formed pesticide microcapsule has high encapsulation efficiency and simultaneously has better slow release effect; the O/W type emulsion prepared by the mass ratio is still stable, and the emulsifying efficiency of the O/W type Pickering emulsion is not changed; in this embodiment, when the mass ratio of hexamethylene diisocyanate to ethylenediamine is less than 0.5:0.2, the polyurea wall material formed is too thin, the pesticide microcapsule is easily broken, which results in a decrease in encapsulation efficiency, and the encapsulated pesticide component is also decomposed with the addition of ethylenediamine; when the mass ratio of the methylene diisocyanate to the ethylenediamine is greater than 2.0:0.71, the formed polyurea wall material is too thick, and a lot of residual wall materials remain on the surface of the microcapsule, so that the encapsulated pesticide components are bonded together, and the encapsulated pesticide components cannot be well attached to the surface of the microcapsule. In addition, the preparation method in this embodiment can also be used to prepare pesticide microcapsules containing different encapsulated pesticide components, such as deltamethrin and the like.
In addition, in some embodiments, the O/W type emulsion of the ethylene diamine dropped in the step 2 reacts for 2 hours at room temperature; after the reaction is finished, an organic filter membrane with the aperture of 0.45um is selected to carry out suction filtration on a sand core funnel to obtain the imidacloprid polyurea composite microcapsule, the pressure during suction filtration is 0.08MPa, a methanol aqueous solution (the volume ratio of methanol to water is 4: 6) is selected to wash the imidacloprid polyurea composite microcapsule after suction filtration, and finally the obtained imidacloprid polyurea composite microcapsule is placed in an oven with the temperature of 50 ℃ for drying for 24 hours.
In addition, in some embodiments, the time of the acidolysis reaction in the preparation of the cellulose nanocrystal in step 1 is 2 hours, the temperature of the acidolysis reaction is 49 to 51 ℃, and the stirring speed during the acidolysis reaction is 800 rpm/min. In addition, in this example, after the acid hydrolysis reaction was completed, the solution after acid hydrolysis was left to stand for 24 hours to remove the supernatant, and then a precipitate containing Cellulose Nanocrystals (CNCs) was obtained, and then the collected precipitate was subjected to centrifugal washing, and then the precipitate was stirred and dispersed for dialysis to a pH of 6 to 7. In this example, the centrifugation step needs to be repeated until no Cellulose Nanocrystals (CNCs) precipitate out, the centrifugation speed being typically 10000 rpm. In the embodiment, the cellulose nanocrystal obtained by acidolysis under the condition has a proper length-diameter ratio, so that the particle size of the obtained cellulose nanocrystal is prevented from being reduced due to overlong acidolysis reaction time or overhigh acidolysis reaction temperature, the stability of the O/W-type Pickering emulsion is reduced, and finally the O/W-type Pickering emulsion is subjected to oil-water separation, so that a microcapsule cannot be obtained; and simultaneously, the problem that the cellulose nanocrystalline cannot be obtained due to too short acidolysis reaction time or too low acidolysis reaction temperature is avoided.
The embodiment of the second aspect of the present invention is to utilize the pesticide microcapsule of the embodiment of the first aspect, and the pesticide microcapsule of the present embodiment has a high encapsulation efficiency and a good slow release effect through tests. The action period of the pesticide microcapsule is prolonged to a certain extent, and the toxicity of the pesticide to the environment is reduced.
The third aspect of the invention is implemented by using the pesticide microcapsule in the second aspect for controlling pests on plants.
Examples
Example 1
The preparation of O/W type emulsion includes the following steps:
step S1, carrying out acidolysis on cotton by using a sulfuric acid aqueous solution to prepare Cellulose Nanocrystals (CNCs), and specifically, adding 10g of cotton into 200mL of a sulfuric acid aqueous solution (which is prepared from 98% by weight of sulfuric acid and distilled water) with the mass fraction of 64 wt% to carry out acidolysis reaction for 2 hours; then adding distilled water to terminate acidolysis reaction so as to obtain cellulose nanocrystalline suspension, wherein the mass ratio of the distilled water to sulfuric acid (namely sulfuric acid with the mass fraction of 98%) is 7: 13; and finally, standing the solution after the acidolysis reaction for 24 hours, removing supernatant, collecting precipitate containing the cellulose nanocrystals, centrifugally washing until no Cellulose Nanocrystals (CNCs) precipitate, wherein the centrifugal time is 8min, the centrifugal speed is 10000rpm, magnetically stirring to disperse the Cellulose Nanocrystals (CNCs), dialyzing the cellulose nanocrystals until the pH value is 6-7, and finally obtaining the cellulose nanocrystals.
And S2, preparing the Cellulose Nanocrystals (CNCs) obtained in the step S1 into a cellulose nanocrystal suspension with the cellulose nanocrystal content of 0.6 wt%, and then adding sodium chloride into the cellulose nanocrystal suspension to shield the charges of the cellulose nanocrystals, wherein 1mg/mL of sodium chloride is added into each milliliter of the cellulose nanocrystal suspension, and the mixture is used as a water phase.
Step S3, taking corn oil as an oil phase, and mixing the oil phase and the water phase obtained in the step S2 according to the volume ratio of 2:8, homogenizing and emulsifying to form O/W Pickering emulsion (namely O/W emulsion), wherein the homogenizing and emulsifying time is 8min, and the rotation speed during homogenizing and emulsifying is 10000 rpm/min.
Example 2:
the preparation of the O/W type emulsion in this example is the same as the preparation method in example 1 except that 2mg/mL of sodium chloride is added to the cellulose nanocrystal suspension in step S2.
Example 3:
the preparation of the O/W type emulsion in this example was the same as the preparation method in example 1 except that 4mg/mL of sodium chloride was added to the cellulose nanocrystal suspension in step S2.
Example 4:
the preparation of the O/W type emulsion in this example was the same as the preparation method in example 1 except that 6mg/mL of sodium chloride was added to the cellulose nanocrystal suspension in step S2.
Example 5:
the preparation of the O/W type emulsion in this example was the same as the preparation method in example 1 except that 8mg/mL of sodium chloride was added to the cellulose nanocrystal suspension in step S2.
Example 6:
the preparation of the O/W type emulsion in this example was the same as the preparation method in example 1 except that 10mg/mL of sodium chloride was added to the cellulose nanocrystal suspension in step S2.
Example 7:
the preparation of the O/W type emulsion in this example is the same as the preparation method in example 1 except that 12mg/mL of sodium chloride is added to the cellulose nanocrystal suspension in step S2.
Example 8:
the preparation of the O/W type emulsion in this example was the same as the preparation method in example 1 except that 20mg/mL of sodium chloride was added to the cellulose nanocrystal suspension in step S2.
Example 9:
the preparation method of the imidacloprid polyurea composite microcapsule comprises the following steps:
step C1, carrying out acidolysis on cotton by using a sulfuric acid aqueous solution to prepare Cellulose Nanocrystals (CNCs), specifically, adding 10g of cotton into 200mL of sulfuric acid aqueous solution with the mass fraction of 64 wt% to carry out acidolysis reaction for 2 hours; then adding distilled water to terminate the acidolysis reaction to obtain a cellulose nanocrystal suspension, wherein the mass ratio of the distilled water to sulfuric acid (namely the sulfuric acid with the mass fraction of 98%) is 7: 13; and finally, standing the solution after the acidolysis reaction for 24 hours, removing supernatant, collecting precipitate containing the cellulose nanocrystals, centrifugally washing until no Cellulose Nanocrystals (CNCs) precipitate, wherein the centrifugal time is 8min, the centrifugal speed is 10000rpm, magnetically stirring to disperse the Cellulose Nanocrystals (CNCs), dialyzing the cellulose nanocrystals until the pH value is 6-7, and finally obtaining the cellulose nanocrystals.
And step C2, preparing the Cellulose Nanocrystals (CNCs) obtained in the step C1 into a cellulose nanocrystal suspension with the cellulose nanocrystal content of 0.6 wt%, then adding sodium chloride into the cellulose nanocrystal suspension to shield the charges of the cellulose nanocrystals, and adding 10mg/mL of sodium chloride into each milliliter of the cellulose nanocrystal suspension to obtain a water phase.
And step C3, using the corn oil as an oil phase, adding 0.5g of hexamethylene diisocyanate and 50mg of imidacloprid into the corn oil, and then homogenizing and emulsifying the mixture and the water phase in the step C2 according to the volume ratio of 2:8 to form O/W type emulsion containing the encapsulated pesticide component, wherein the homogenizing time is 8min, and the rotating speed is 10000 rpm/min.
C4, slowly dripping 0.2g of ethylenediamine into the O/W type emulsion which is obtained in the C3 and contains the encapsulated pesticide component to obtain a reaction solution, wherein the stirring speed of the O/W type emulsion during dripping is 200 r/min; wherein 0.2g of ethylenediamine was added in 30 min.
In addition, after the ethylene diamine is dripped, the reaction solution needs to be stirred and reacted for 2 hours at room temperature, wherein the stirring speed is 200 rpm/min.
And C5, sequentially filtering, washing and drying the reaction solution after the reaction in the step C4 is finished to obtain the imidacloprid polyurea composite microcapsule, wherein the drying temperature is 50 ℃, and the drying time is 24 hours.
Example 10:
the preparation method of the imidacloprid polyurea composite microcapsule in this embodiment is the same as that in embodiment 9, except that 0.36g of ethylenediamine is added dropwise to the O/W type emulsion containing the encapsulated pesticide component in step C4.
Example 11:
the preparation method of the imidacloprid polyurea composite microcapsule in this embodiment is the same as that in embodiment 9, except that 0.71g of ethylenediamine is added dropwise to the O/W type emulsion containing the encapsulated pesticide component in step C4.
Comparative example 1
The preparation method of the imidacloprid polyurea composite microcapsule in the present embodiment is the same as the preparation method in embodiment 9, except that no sodium chloride is added in step C2. In this example, no pesticide microcapsules could be prepared.
And (3) testing and analyzing:
test analysis 1: the cellulose nanocrystal suspensions obtained in examples 1 to 8 of the present invention were examined by ultraviolet (UV-vis) light, and the O/W type Pickering emulsions obtained in examples 1 to 8 of the present invention were examined by a polarization microscope (POM).
And (3) test results: fig. 1-2 are ultraviolet spectrograms of cellulose nanocrystal suspensions obtained in examples 1 to 8 of the present invention, and it can be seen from fig. 1 to 2 that the cellulose nanocrystal suspensions prepared in examples 1 to 8 all have higher light transmittance in a high wavelength region, which proves that they form a nanosuspension with better dispersibility after being homogenized by ultrasound. FIG. 3 is a POM graph of the O/W type Pickering emulsions obtained in examples 1 to 8 of the present invention, and it can be seen from FIG. 3 that the droplet size of the O/W type Pickering emulsion of the present invention decreases with the increase of the salt concentration in the O/W type Pickering emulsion (i.e., the droplet size of the O/W type Pickering emulsion decreases with the increase of NaCl added), but the stability of the O/W type Pickering emulsion is consistent with the Stokes' law.
Test analysis 2: the imidacloprid polyurea composite microcapsules obtained in examples 9 to 11 of the invention were detected by Scanning Electron Microscope (SEM) and ultraviolet (UV-vis) respectively.
And (3) test results: fig. 4 to 6 are SEM images of the imidacloprid polyurea composite microcapsules prepared in examples 9 to 11 of the present invention, respectively, and as can be seen from fig. 4 to 6, the imidacloprid polyurea composite microcapsules prepared in the present invention are spherical in structure, which proves that the pesticide microcapsules prepared in the present invention have a good encapsulation effect. In addition, the encapsulation efficiency of the imidacloprid polyurea composite microcapsules obtained in examples 9 to 11 of the invention is measured by ultraviolet, and as can be seen from fig. 7, the encapsulation efficiency of the microcapsules prepared in example 9 is 77.15%, the encapsulation efficiency of the microcapsules prepared in example 10 is 96.81%, and the encapsulation efficiency of the microcapsules prepared in example 11 is 77.55%, further proving that the imidacloprid polyurea composite microcapsules prepared by the invention have higher encapsulation efficiency.
Test analysis 3: the slow release capability of the imidacloprid polyurea composite microcapsule obtained in the embodiment 10 of the invention is determined, and the test method comprises the following steps:
firstly, respectively dispersing 1.0g of imidacloprid polyurea composite microcapsule suspension (the mass fraction of the imidacloprid polyurea composite microcapsules in the suspension is 13.38%) into a magnesium chloride solution, a potassium sulfate solution and a sodium bicarbonate solution, wherein the molar concentrations of the magnesium chloride solution, the potassium sulfate solution and the sodium bicarbonate solution are all 0.1mol/L, the volumes of the magnesium chloride solution, the potassium sulfate solution and the sodium bicarbonate solution are all 1mL, and respectively filling into dialysis bags; then the dialysis bags were respectively put into brown sample bottles containing salt solutions (wherein the salt solutions were sodium bicarbonate, magnesium chloride, and potassium sulfate, respectively) and the bottles were kept at room temperature (25 ℃) with magnetic stirring at 200 rpm. And then 1mL of suspension (the suspension is liquid in a brown sample bottle) is taken out at 1h, 3h, 6h, 9h, 12h, 24h, 36h, 48h, 60h, 72h and 84h respectively, the imidacloprid concentration is detected by adopting UV-2600, 1mL of salt solution is supplemented into the brown sample bottle at the same time, and finally the slow release capacity of the imidacloprid polyurea microcapsule is calculated by a cumulative release rate formula, wherein the cumulative release rate formula is as follows:
and (3) test results: FIG. 8 shows the slow release result of the imidacloprid polyurea microcapsules obtained in example 10 of the invention under the laboratory simulation condition. As can be seen from fig. 8, when the imidacloprid polyurea microcapsule obtained in example 10 of the present invention is slowly released for 84 hours under the laboratory simulation condition, the cumulative release percentages are 93.96% (imidacloprid polyurea composite microcapsule suspension is dispersed in magnesium chloride solution), 100% (imidacloprid polyurea composite microcapsule suspension is dispersed in potassium sulfate solution), and 99.87% (imidacloprid polyurea composite microcapsule suspension is dispersed in sodium bicarbonate solution), respectively, and the data can prove that the microcapsule prepared by the present invention realizes the slow release of imidacloprid and prolongs the lasting period of imidacloprid; therefore, the pesticide microcapsule prepared by the invention has good slow release capability, and is beneficial to the application of the pesticide microcapsule as a pesticide controlled release preparation in the field of agricultural diseases and insect pests.
In conclusion, the O/W type emulsion with good homogeneous emulsification effect is prepared by using the cellulose nanocrystals formed after acidolysis of cotton as the stabilizer, and then the polyurea polymer formed by polymerization of hexamethylene diisocyanate and ethylenediamine at the interface of the emulsion is used as the wall material of the microcapsule to coat the encapsulated pesticide component, so that the problems of short action period and great pesticide toxicity of the existing pesticide are solved, and the pesticide microcapsule with good slow-release effect is obtained, thereby prolonging the duration of pesticide action, reducing the application amount of the pesticide and reducing the harm of the pesticide to the environment to a certain extent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A preparation method of a high-encapsulation-rate pesticide microcapsule is characterized by comprising the following steps:
step 1, preparation of O/W type emulsion
Homogenizing and emulsifying an aqueous phase and an oil phase to form an O/W type emulsion, wherein the aqueous phase comprises a cellulose nanocrystal suspension and an inorganic salt electrolyte for shielding the charge of the cellulose nanocrystal, and the oil phase comprises corn oil;
step 2, preparation of pesticide microcapsule
Adding hexamethylene diisocyanate and an encapsulated pesticide component to the oil phase in the step 1, thereby obtaining an O/W type emulsion containing the encapsulated pesticide component;
and slowly dripping an ethylenediamine solution into the O/W type emulsion containing the encapsulated pesticide component, reacting at room temperature, and filtering, washing and drying in sequence after the reaction to obtain the pesticide microcapsule.
2. The method according to claim 1, wherein the mass fraction of the cellulose nanocrystals in the cellulose nanocrystal suspension in step 1 is 0.6 wt%, and wherein 1mg to 20mg of the inorganic salt electrolyte is added per ml of the cellulose nanocrystal suspension.
3. The method for preparing a pesticide composition according to claim 2, wherein the mass ratio of the encapsulated pesticide to hexamethylene diisocyanate and ethylenediamine is (0.035-0.050): 0.5-2.0: 0.2-0.71.
4. The method according to claim 2, wherein the volume ratio of the oil phase to the water phase in the step 1 of homogeneous emulsification is 1:4, and the reaction time in the step 2 is 2 hours.
5. The production method according to claim 3, wherein the inorganic salt electrolyte includes NaCl, Na2SO4And KCl, the encapsulated pesticide component comprising imidacloprid.
6. The production method according to claim 1, wherein the cellulose nanocrystals in the cellulose nanocrystal suspension in step 1 are produced by:
placing the biomass material rich in cellulose in an acid water solution for acidolysis reaction, adding distilled water to terminate the acidolysis reaction, collecting the precipitate obtained by the acidolysis reaction, and sequentially washing and dialyzing the precipitate to finally obtain cellulose nanocrystals;
the acid water solution is a sulfuric acid water solution with the mass fraction of 63 wt% -65 wt%, the mass ratio of the sulfuric acid water solution to the biomass material rich in cellulose is 10:1, and the mass ratio of the distilled water to the sulfuric acid is 7: 13.
7. The method as claimed in claim 6, wherein the acidolysis reaction is carried out for 2 hours at a temperature of 49-51 ℃.
8. The method of claim 6, wherein the cellulose-rich biomass material comprises cotton.
9. The pesticide prepared by the process of any one of claims 1 to 8 is in the form of a capsule.
10. Use of the pesticidal microcapsule of claim 9 for controlling pests.
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| CN116019098A (en) * | 2022-12-08 | 2023-04-28 | 上海师范大学 | Nanocellulose-based uvioresistant pesticide microcapsule and preparation method thereof |
| CN117378605A (en) * | 2023-12-12 | 2024-01-12 | 中国农业科学院农业环境与可持续发展研究所 | Pyrethroid pesticide microcapsule suspending agent and preparation method thereof |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116019098A (en) * | 2022-12-08 | 2023-04-28 | 上海师范大学 | Nanocellulose-based uvioresistant pesticide microcapsule and preparation method thereof |
| CN116019098B (en) * | 2022-12-08 | 2024-04-02 | 上海师范大学 | Nanocellulose-based uvioresistant pesticide microcapsule and preparation method thereof |
| CN117378605A (en) * | 2023-12-12 | 2024-01-12 | 中国农业科学院农业环境与可持续发展研究所 | Pyrethroid pesticide microcapsule suspending agent and preparation method thereof |
| CN117378605B (en) * | 2023-12-12 | 2024-03-15 | 中国农业科学院农业环境与可持续发展研究所 | Pyrethroid pesticide microcapsule suspending agent and preparation method thereof |
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