阅读说明：本技术 一种辛酸淀粉酯的制备方法及其在农药微胶囊上的应用 (Preparation method of starch caprylate and application of starch caprylate in pesticide microcapsule ) 是由 胡华宇 孙宁钊 黄爱民 黄祖强 张燕娟 梁景 陈钰莹 毛鑫 覃宇奔 陈丛瑾 于 2020-04-26 设计创作，主要内容包括：本发明公开了一种辛酸淀粉酯的制备方法及其在农药微胶囊上的应用,属于天然高分子材料制备及应用技术领域,是以淀粉为原料,加入助剂和辛酸酯化剂,并采用机械活化固相技术作用下制备得到辛酸淀粉酯,所述辛酸淀粉酯的取代度超过0.25。将得到的辛酸淀粉酯作为壁材,应用于在农药微胶囊领域上,得到所述农药微胶囊的包埋率超过88.6％。本发明采用机械活化固相技术制备辛酸淀粉酯,方法简单,得到的材料具有成膜性好、粘度低的特点,能克服传统淀粉粘度大流动性差固含量低的缺点、在农药微胶囊领域上应用,绿色环保,并起到缓控释作用,从而提高农药利用率。(The invention discloses a preparation method of starch caprylate and application thereof in pesticide microcapsules, belonging to the technical field of preparation and application of natural high polymer materials, wherein starch is used as a raw material, an auxiliary agent and an octanoic acid esterifying agent are added, and the octanoic acid starch ester is prepared under the action of a mechanical activation solid phase technology, wherein the substitution degree of the octanoic acid starch ester is more than 0.25. The obtained starch caprylate is used as a wall material and applied to the field of pesticide microcapsules, and the embedding rate of the obtained pesticide microcapsules exceeds 88.6 percent. The method for preparing the starch caprylate by adopting the mechanical activation solid phase technology is simple, the obtained material has the characteristics of good film forming property and low viscosity, can overcome the defects of large viscosity, poor fluidity and low solid content of the traditional starch, is applied to the field of pesticide microcapsules, is green and environment-friendly, and plays a role in sustained and controlled release, thereby improving the utilization rate of pesticides.)

1. The starch caprylate is characterized in that starch is used as a raw material, an auxiliary agent and a caprylic esterifying agent are added, and the starch caprylate is prepared under the action of a mechanical activation solid phase technology, wherein the substitution degree of the starch caprylate is over 0.25.

2. The starch caprylate according to claim 1, wherein the auxiliary agent is any one of sodium carbonate, sodium bicarbonate and potassium carbonate.

3. The preparation method of the starch caprylate according to claim 1 or 2, characterized in that the starch, the caprylate esterifying agent and the auxiliary agent are uniformly mixed according to a certain proportion, and the mechanical activation solid phase reaction is carried out to obtain the starch caprylate.

4. The method for preparing starch caprylate according to claim 3, wherein the mechanical activation solid phase reaction is carried out in a ball mill at a rotation speed of 100-.

5. The method for preparing starch caprylate according to claim 3, wherein the caprylic acid accounts for 10-40% of the dry basis of the starch by mass, and the auxiliary agent accounts for 0.5-10% of the dry basis of the starch by mass.

6. The application of the starch caprylate in the pesticide microcapsule as claimed in claim 1 or 2, characterized in that the starch caprylate is used as a wall material, the pesticide is used as a core material, and the ratio of the core to the wall is 1: 1-5 to obtain the pesticide microcapsule.

7. The application of the starch caprylate in the pesticide microcapsule according to claim 6, wherein the wall material and the core material are mixed in water to prepare an emulsion with a solid content of 8-10%, and then the emulsion is subjected to spray drying to obtain the pesticide microcapsule.

8. The use of starch octanoate in pesticide microcapsules according to claim 7, wherein the inlet temperature of the spray drying is 150-200 ℃.

9. The use of the starch caprylate in pesticide microcapsules according to claim 6, wherein the embedding rate of the pesticide microcapsules is more than 88.6%.

Technical Field

The invention belongs to the technical field of preparation and application of natural high polymer materials, and particularly relates to a preparation method of caprylic starch ester and application of the caprylic starch ester in pesticide microcapsules.

Background

A large amount of chemical fertilizer is directly lost, soil pollution and nutrient imbalance are caused, and even the immunity of plant diseases and insect pests is improved due to excessive use of medicines. The reason for this is mainly that the release speed of the active ingredients of the pesticide is fast, and the duration of the pesticide is short, so that the microencapsulation of the pesticide is an inevitable way for the efficient utilization of the pesticide.

The microcapsule is a technology which takes natural or artificial synthetic polymer material as an encapsulating material and coats a capsule core (solid, liquid or gas) substance to form a semipermeable or sealed capsule membrane, and has the characteristics of protecting active substances, reducing external adverse effects, controlling release, prolonging the lasting period and the like. The pesticide microencapsulation can effectively solve the problems of fast release speed, short duration and the like of the active ingredients of the pesticide, has the functions of reducing photolysis and low toxicity, and has strong market competitiveness. Wherein, the wall material is an important component of the microcapsule, and the composition and the selection of the wall material play a decisive role in the functions and the properties of the microcapsule product.

Although the types of pesticides are various, most of the pesticides belong to fat-soluble pesticides, such as organic chlorine pesticides hexachloro cyclohexane, dichlorodiphenyl trichloroethane, abamectin, emamectin benzoate and the like, because the permeability of the fat-soluble pesticides is greater than that of water-soluble pesticides, the prevention and treatment effect of the fat-soluble pesticides is better, but the loss of the fat-soluble pesticides is greater, the residue in organisms and soil is also greater than that of the water-soluble pesticides, and the harm to environment organisms is greater. The microencapsulation of the fat-soluble pesticide can improve the utilization rate of the pesticide and reduce the dosage, thereby reducing the harm to organisms and soil and having important significance. For fat-soluble pesticides, the microencapsulated wall material is required to have certain hydrophilicity while ensuring lipophilic ability, and because only the material with amphiphilicity can form an interface film at an oil-water interface, most researchers consider developing biomacromolecules with good emulsifying property and film-forming property as the wall material.

The starch as natural high molecular polysaccharide has the characteristics of reproducibility, wide source, low price and the like. However, starch has the defects of easy aging, low stability, poor film forming property, poor dissolution and dispersibility and the like, so that the starch is difficult to be directly used as a microcapsule wall material, and is mainly added as an auxiliary material in a small amount in general application, but cannot be directly used as the wall material. The fatty acid starch ester leads the starch to have oleophylic and hydrophilic properties due to the introduction of the fatty acid group, and compared with natural starch, the film forming property and the emulsibility are both improved to a certain extent, so the fatty acid starch ester is particularly suitable for embedding of fat-soluble pesticides. However, the fatty acid starch ester prepared by the traditional method has low degree of substitution, and particularly, the lipophilic property is weakened along with the growth of a fatty acid carbon chain; in addition, the starch has longer chain molecules and large molecular weight, the esterified product has high viscosity, and is not easy to prepare emulsion, and the concentration of the prepared emulsion is low, so that the embedding rate is low.

Therefore, the research on the application of the esterified starch in pesticide microencapsulation can effectively control the pesticide dosage, reduce the loss, improve the pesticide utilization rate and obtain the new field application of natural and friendly high molecular starch, and has important significance.

Disclosure of Invention

In order to solve the problems, the invention provides a preparation method of starch caprylate and application of the starch caprylate in pesticide microcapsules, and the obtained starch caprylate has the characteristics of low viscosity, good emulsifying and film-forming properties and the like. The prepared caprylic acid starch ester is used as a wall material, the defect that the traditional starch-based material cannot be independently applied to the field of wall materials is overcome, and the obtained pesticide microcapsule has high embedding rate and good slow release effect.

In order to achieve the purpose, the scheme provided by the invention is as follows:

starch is used as a raw material, an auxiliary agent and an octanoic acid esterifying agent are added, and the octanoic acid starch ester is prepared under the action of a mechanical activation solid phase technology, wherein the degree of substitution of the octanoic acid starch ester is over 0.25.

Further, the auxiliary agent is any one of sodium carbonate, sodium bicarbonate and potassium carbonate.

Further, the starch is any one of tapioca starch, corn starch and potato starch.

The invention provides a preparation method of caprylic starch ester, which is to uniformly mix starch, caprylic esterifying agent and auxiliary agent according to a certain proportion and carry out mechanical activation solid phase reaction to obtain the caprylic starch ester.

Furthermore, the mechanical activation solid phase reaction is adopted, which is to react for 10 to 90 minutes in a ball mill at the rotating speed of 100-.

Furthermore, the mass of the octanoic acid accounts for 10-40% of the dry base of the starch, and the mass of the auxiliary agent accounts for 0.5-10% of the dry base of the starch.

The invention provides an application of starch caprylate in pesticide microcapsules, which takes the starch caprylate as a wall material and a pesticide as a core material, wherein the ratio of the wall to the core material is 1: 1-5 to obtain the pesticide microcapsule.

Further, mixing the wall material and the core material, then preparing the mixture into emulsion with the solid content of 8-10% in water, and then carrying out spray drying on the emulsion to obtain the pesticide microcapsule.

Further, the inlet temperature of the spray drying was 150-.

Further, the embedding rate of the pesticide microcapsule exceeds 88.6%.

The raw materials used in the invention are as follows: cassava starch, corn starch, potato starch, caprylic acid, sodium carbonate, sodium bicarbonate, potassium carbonate and the like are purchased from chemical raw material companies at home and abroad, and are directly used without being continuously purified.

The prepared caprylic acid starch ester is used for the pesticide microcapsule technology. The application principle is as follows: the starch caprylate obtained by the invention can improve the esterification degree and lipophilic ability of the fatty acid starch ester, and simultaneously overcomes the defects of high viscosity of the esterified starch and low dispersion concentration in emulsion, and the mechanically activated starch caprylate has low viscosity, good emulsifying and film-forming properties and amphiphilicity, so that the starch caprylate can be directly used as a microcapsule wall material to realize the coating with fat-soluble pesticide, water-soluble pesticide and the like, thereby preparing the microencapsulated pesticide, effectively controlling the pesticide dosage, reducing the loss and improving the pesticide utilization rate.

In the application process, the core material is dispersed in the aqueous solution of the wall material to form emulsion, the emulsion is conveyed to an atomizer of a spray dryer by a pump, the emulsion is atomized into small droplets through spray drying, the solvent contained in the droplets is rapidly evaporated in hot airflow, and the dried wall material coats the core material and forms the solidified microcapsule. The wall material has good thermoplasticity, emulsibility and film-forming property, so that the wall material can be prevented from being burst by steam due to high temperature, short time and rapid evaporation of water in the spray drying process, and the microencapsulation effect is further influenced, and the embedding rate of the medicine microcapsule prepared by using the wall material can exceed 88.6%.

The invention has the following beneficial effects:

1. the octanoic acid starch ester obtained by mechanical activation has the substitution degree of more than 0.25, has low viscosity, good emulsifying and film-forming properties and amphipathy, can overcome the defects of large viscosity, poor fluidity and low solid content of the traditional starch, can be directly used as a microcapsule wall material to realize the coating with a fat-soluble pesticide, thereby preparing the pesticide microcapsule.

2. The invention solves the problems of high loss rate, low utilization rate and high residue of the currently applied fat-soluble pesticide, can improve the utilization rate of the pesticide through microencapsulation, effectively control the release and reduce the volatility, meanwhile, starch molecules are decomposed in the control release process, cannot cause harm to soil, can be slowly controlled and controlled together with the pesticide, and are finally decomposed into CO₂And H₂O, has effects of reducing photolysis and reducing toxicity.

3. The starch esterification process of the invention is a solid phase reaction, and the microencapsulation adopts a spray drying technology, so the production process has no pollution and high efficiency. And the wall material is used for wrapping pesticides such as abamectin, emamectin benzoate, ammonium potassium sulfate, urea and the like, so that the embedding rate of the prepared drug microcapsule can exceed 88.6 percent.

Drawings

FIG. 1 is a graph of the shear stress and shear rate change of starch esters of the present invention.

FIG. 2 is a graph of starch ester loss factor versus angular frequency according to the present invention.

In the upper diagram: OAS-starch caprylate, AS-starch acetate, starch-native starch emulsion, LAS-starch laurate, BAS-starch butyrate.

Detailed Description

The invention is further described with reference to the following examples:

the preparation method of the caprylic starch ester of the invention comprises the following steps: