Special metaldehyde snail-killing synergistic aid, preparation method and application of special metaldehyde snail-killing synergistic aid

Abstract

The invention belongs to the field of pesticides, and particularly relates to a metaldehyde molluscicide special-purpose synergistic auxiliary agent, a preparation method and an application thereof, the special synergistic auxiliary agent comprises a chitosan-styrene-acrylic acid copolymer and a surfactant; after being mixed with a metaldehyde suspending agent for use, the special-effect auxiliary agent can form a gel network structure with soil and is firmly adsorbed in soil capillaries, rainwater leaching can be reduced, moisture can be preserved for a long time, depolymerization and sublimation of metaldehyde can be reduced, and the lasting period of pesticide can be effectively prolonged.

Description

Technical Field

[0001] The invention belongs to the field of pesticides, and particularly relates to a special synergistic auxiliary agent for metaldehyde snail killing, a preparation method and application thereof. Background Art

[0002] Oncomelania snails are the only intermediate host of Schistosoma japonicum. Killing Oncomelania snails is an effective way to control the spread of Schistosoma japonicum. Niclosamide is a highly effective molluscicide, which was first developed and produced by Bayer AG in Germany. Currently, niclosamide is the only chemical snailicide designated by the WHO and has been widely promoted and applied. However, the habitats of Oncomelania snails are mostly tidal flats, close to water sources. Dead fish and shrimps frequently occur during the application of the product, causing great negative impact on the ecological environment. The cause of this phenomenon is that niclosamide is highly toxic to aquatic animals such as fish, and this problem has not been solved.

[0003] At present, the registered snail control products with metaldehyde as the active ingredient are mainly suspension concentrates, with only one water-dispersible granule. In the past, metaldehyde was difficult to promote due to its poor control effect. Both metaldehyde and niclosamide are neurotoxins, and their action sites are both acetylcholine receptors. After thousands of tests, our company found that once metaldehyde is diluted, it will depolymerize into trimeraldehyde and acetaldehyde when the temperature rises, and it will sublimate quickly, which is more obvious in open areas in the field. The reason is that the outdoor temperature is high and there is a certain wind speed, which accelerates the sublimation of metaldehyde, resulting in poor efficacy or even no efficacy.

[0004] In response to the above-mentioned defects, our company's R&D team focused on the application scenarios of snail control, deeply understood the living habits of snails, combined with the performance characteristics of metaldehyde, and proposed the use of auxiliary additives to reduce the volatilization of metaldehyde by utilizing the chelation and adsorption between additives and metaldehyde as well as between additives and soil, so as to achieve the goal of extending the effective period of metaldehyde. The aim is to develop a special additive for snail control using metaldehyde, which is low-toxic to fish and shrimp and can significantly improve the prevention effect of metaldehyde. Summary of the invention

[0005] The purpose of the present invention is to provide a special synergistic auxiliary agent for killing snails with metaldehyde, a preparation method and application thereof. The specific technical scheme is as follows:

[0006] A special synergistic auxiliary agent for metaldehyde snail killing comprises a chitosan-styrene-acrylic acid copolymer and a surfactant.

[0007] The preparation method of chitosan-styrene-acrylic acid copolymer comprises the following steps: 2.5% acetic acid solution is placed in a flask, nitrogen is passed through it, chitosan is added, and chitosan is completely dissolved under magnetic stirring, initiator ammonium persulfate is added to initiate for a certain time, acrylic acid and styrene are added, and graft copolymerization reaction is carried out at 65°C, after the reaction is completed, the pH value is adjusted to 7 with 10% sodium hydroxide solution, and ethanol is used for precipitation, the precipitate is washed with water for multiple times, and then vacuum dried, extracted with acetone in a Soxhlet extractor, and vacuum dried.

[0008] Preferably: the mass ratio of chitosan, acrylic acid and styrene monomer is 1:(10-15):5;

[0009] The initiator is 2-4% of the total weight of the monomer;

[0010] The initiation time is 15-30min.

[0011] The surfactant described in the present invention is one or more of an emulsifier, a dispersant or a wetting agent.

[0012] The special synergistic auxiliary agent of the present invention is used for prolonging the efficacy of the metaldehyde suspension.

[0013] Compared with the prior art, the present invention achieves the following beneficial technical effects:

[0014] Chitosan is a deacetylated chitin product widely found in nature, and its chemical name is polyglucosamine. Chitosan molecules contain a large amount of -NH 2 and -OH, have high chemical reactivity, can form a large number of hydrogen bonds and salt bonds with the target substance, have strong adsorption properties, and can also chelate with metal ions or form a network structure, and can be used as an adsorption material, moisturizer, etc.

[0015] The special additive for snail killing with metaldehyde is made of chitosan as raw material. Chitosan derivatives are prepared by chemical modification method. The chitosan derivatives are used as the skeleton. The reaction monomers are connected to the molecular structure of the chitosan derivatives by grafting copolymerization to prepare chitosan-styrene-acrylic acid copolymer, and the special special-effect additive is prepared with the aid of surfactant. The product has good stability and mixing performance.

[0016] When the special-effect adjuvant is mixed with the metaldehyde suspension concentrate, it can form a gel network structure with the soil and be firmly adsorbed in the soil capillaries, which can reduce rainwater leaching, retain moisture for a long time, reduce the depolymerization and sublimation of metaldehyde, and effectively extend the effective period of the pesticide. DETAILED DESCRIPTION

[0017] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0018] The present invention is further explained below in conjunction with specific implementation modes.

[0019] Example 1: Preparation of chitosan-styrene-acrylic acid copolymer

[0020] Materials and Methods

[0021] Experimental raw materials: chitosan CTS, acrylic acid AA, styrene ST, ammonium persulfate, acetic acid; all were purchased from the market.

[0022] Preparation method:

[0023] A certain volume of 2.5% acetic acid solution was placed in a flask, nitrogen was introduced for 30 minutes, then a certain amount of chitosan was added and completely dissolved under magnetic stirring, a certain amount of initiator ammonium persulfate was added to initiate for a certain period of time, and then acrylic acid and styrene were added, and the graft copolymerization reaction was controlled at 65°C. After the reaction, the pH value was adjusted to 7 with 10% sodium hydroxide solution, and then ethanol was used for precipitation. The precipitate was washed with water for several times and then vacuum dried, extracted with acetone in a Soxhlet extractor, and vacuum dried.

[0024] Reaction condition setting

[0025] Table 1: Preparation process parameters

[0026]

[0027] Note: Initiator dosage %: the percentage of initiator in monomer mass.

[0028] Determination of water absorption properties of chitosan-styrene-acrylic acid copolymer

[0029] After the highly water-absorbent copolymers were immersed in sufficient amount of distilled water for 24 hours, the water absorption rate of the copolymers was calculated.

[0030] Table 2: Water absorption performance determination

[0031] serial number Water absorption g / g GAS1 242 GAS2 587 GAS 3 605 GAS 4 251 GAS 5 308 GAS 6 590 GAS 7 595 GAS 8 262 GAS 9 195 GAS10 328 GAS11 574 GAS12 385

[0032] Results and Analysis

[0033] According to the comparison of GAS6 and GAS10-GAS12, when the amount of ST remains unchanged, the water absorption and moisture retention performance of the copolymer can increase with the increase of the AA:CTS ratio. With the increase of the amount of acrylic acid, there is enough acrylic acid in the system to react with the free radicals on the chitosan molecular chain, and the graft copolymerization reaction is more sufficient, which is conducive to the formation of the three-dimensional network structure of the copolymer, thereby improving the water absorption and moisture retention performance; however, the water absorption and moisture retention performance of the copolymer decreases when the AA:CTS ratio continues to increase. It is speculated that the more acrylic acid is used, the larger the molecular weight of the copolymer after polymerization, the greater the viscosity of the system, which hinders the movement of the polymer molecules, and the polymer molecular chains are too long and easy to entangle with each other, which increases the cross-linking degree, thereby reducing the water absorption and moisture retention performance.

[0034] According to the comparison of numbers GAS1-GAS 4, under the same pre-initiation time conditions, when the initiator dosage is low, insufficient pre-initiation leads to fewer grafting points on the chitosan main chain that react with acrylic acid, and the reaction speed is relatively slow, which affects the polymerization and cross-linking reactions. With the increase of the initiator dosage, the number of activated active groups on the chitosan molecular chain increases, the grafting rate increases, and the formation of the three-dimensional network structure of the copolymer is promoted, and the water absorption and moisture retention performance is enhanced. However, if the initiator dosage is too large, the number and types of activated free groups on the chitosan molecular chain increase rapidly, which easily leads to mutual reactions between active groups to form other by-products, resulting in reduced water absorption and moisture retention performance of the copolymer.

[0035] According to the comparison of numbers GAS 5-GAS 8, it can be seen that under the same initiator dosage, within the appropriate pre-initiation time range, as the pre-initiation time increases, the number of activated groups initiated on the chitosan molecular chain increases, the grafting rate increases, and the water absorption and moisture retention properties are enhanced.

[0036] Example 2: Test of the efficacy of metaldehyde suspension

[0037] Test object: Oncomelania tidal flats

[0038] Test agent:

[0039] Drug 1: 40% tetraacetaldehyde suspension 1 + 3% special synergistic additive (chitosan-styrene-acrylic acid copolymer GAS2 and sodium dodecylbenzene sulfonate mass ratio 5:1)

[0040] Agent 2: Same as Agent 1, except that it uses chitosan-styrene-acrylic acid copolymer GAS 3

[0041] Agent 3: Same as Agent 1, except that chitosan-styrene-acrylic acid copolymer GAS 6 is used.

[0042] Agent 4: Same as Agent 1, except that chitosan-styrene-acrylic acid copolymer GAS 7 is used.

[0043] Agent 5: Same as Agent 1, except that chitosan-styrene-acrylic acid copolymer GAS11 is used.

[0044] Control drug: 40% metaldehyde suspension

[0045] Note: 40% metaldehyde suspension concentrate source: Jiangsu Aijin Crop Science and Technology Group Co., Ltd., PD20142015.

[0046] Test method: Select snail-breeding tidal flats with a snail density greater than 10 snails / frame, divide them into several plots, remove weeds taller than 5 cm in the plots and remove them from the test area. Spray the pesticide according to the test dose, with a liquid dosage of 2L / m 2 , the blank group was sprayed with an equal amount of dechlorinated water. At 7, 14, and 28 days after the application of the pesticide, snails were surveyed using the chessboard sampling method. Ten frames were drawn in each test area and control area, and all snails in the frame were captured. The frames were packed in paper bags, and the numbers and the number of snails captured were recorded. The snails were identified as dead or alive using the water culture method and the knocking method when they were returned to the room, and the total number of snails and the number of dead snails in each treatment were recorded. If the snail mortality rate in the blank control group was greater than 10%, the experiment should be repeated.

[0047] Results and analysis:

[0048] Compared with the control agent, the control agent 1-5 has a control effect of 80.6% 7 days after application. Since the half-life of metaldehyde in the soil is short and it is easy to decompose under outdoor conditions, the control effect is significantly reduced 14 days and 28 days after application, especially the control effect of only 20.4% 28 days after application. The special synergistic additives used in agents 1-5 are mixed with the metaldehyde suspension, which can form a gel network structure with the soil and firmly adsorb in the soil capillaries, which can reduce rainwater leaching and keep moisture for a long time, while reducing the depolymerization and sublimation of metaldehyde, effectively extending the effective period of the pesticide.

[0049] Table 3: Test on the efficacy of metaldehyde suspension

[0050]

[0051]

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit it.

Claims

1. A special synergistic aid for metaldehyde snail control, characterized in that: Contains chitosan-styrene-acrylic acid copolymer and a surfactant.

2. The synergistic aid for molluscicidal use of metaldehyde according to claim 1, characterized in that: The preparation method of chitosan-styrene-acrylic acid copolymer comprises the following steps: 2.5% acetic acid solution is placed in a flask, nitrogen is passed through it, chitosan is added, and chitosan is completely dissolved under magnetic stirring, initiator ammonium persulfate is added to initiate for a certain time, acrylic acid and styrene are added, and graft copolymerization reaction is carried out at 65°C, after the reaction is completed, the pH value is adjusted to 7 with 10% sodium hydroxide solution, and ethanol is used for precipitation, the precipitate is washed with water for multiple times, and then vacuum dried, extracted with acetone in a Soxhlet extractor, and vacuum dried.

3. The synergistic aid for molluscicidal use of metaldehyde according to claim 2, characterized in that: The mass ratio of chitosan, acrylic acid and styrene monomers is 1:(10-15):5; The initiator is 2-4% of the total weight of the monomer; The initiation time is 15-30min.

4. The synergistic aid for molluscicidal use of metaldehyde according to claim 1, characterized in that: The surfactant is one or more of an emulsifier, a dispersant or a wetting agent.

5. The use of the special synergistic aid according to any one of claims 1 to 4 for prolonging the efficacy of the metaldehyde suspension concentrate.

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