Abstract: This paper pass through Mancozeb 80% water dispersible granule formulation research, experiment and discuss the various additives on the water dispersible granule properties.
Key words: water dispersible granule formulation of mancozeb
WG (water dispersible granules, WDG or WG), is a rapidly after the collapse of water and dispersed into the high dispersion of the particulate suspension formulations in the United States early as dry flow agent or dry SC (dry flowable, referred to as DF), also known as grain WP (granule type wettable powder) [1]. WG 80 in the early 20th century from the WP and the suspension developed on the basis of new pesticide formulations, as of the advanced water-based formulations. WP and SC both have strengths and overcome its shortcomings: no dust, no organic solvents, environmentally friendly, good liquidity; easy to measure, easy packaging, storage and transportation safety and convenience; preparations by high dispersion and good suspension in water considered high, stable, easy to use. The 21st century is considered one of the most viable dosage form, the green one of the development of pesticide formulations.
Mancozeb is a good protective fungicides, because of its wide range of sterilization, not easy to produce drug resistance, it has been in the international large-tonnage products. The original drug to pale yellow powder melting point (136 ° C) the following decomposition of the flash point temperature of 137.8 ° C (open). Does not melt in water and most organic solvents. Case of high temperature, moisture and acids break down. Currently, the domestic market, mainly for agricultural sterilization drug Mancozeb WP and SC two formulations. Mancozeb WP is a traditional solid dosage forms, because of its fine grain size, production and use of flying dust will appear with the phenomenon of Pharmacy, not only directly harm human and animal health, and environmental pollution. To avoid this phenomenon, the formation of a mancozeb improved suspension. That will then be processed into solid dosage forms of liquid water dispersible formulations, the average size of only a few? M floating rate, good efficacy, quickly accepted by users. However, the process in the promotion of certain problems have also emerged, Mancozeb suspension concentrate formulation and process technology than Mancozeb WP complex, many factors affecting the quality. Stored for a long time, there will be stratification, precipitation and agglomeration, and packaging materials difficult to handle. Coupled with packaging capacity, to the storage, transportation, without inconveniences. Mancozeb agricultural products, the problem facing the further improvement. Now the market has slowly emerged a small amount of Mancozeb WG, such as the U.S. imports 75% of the fierce killing (mancozeb dry SC); of Mancozeb WG also saw the development of reports, such as the 2003 double Xinji City, Hebei Chemical Co., Ltd. Xu Ji on application for cooking water dispersible granules of mancozeb and its manufacturing method patent [2]. But has yet to appear very mature manufacturing process, the market appears Mancozeb WDG products are very little. Mancozeb WG actually save some time by the rate of decline after the suspension has been the failure to resolve the world problems, this paper focuses on this as mancozeb 80% water dispersible granule preparation process. Taking into account its rate of decline in suspension after storage may be related to condensation on the particles during storage, so the selection of other additives in the same time, against the coagulant type and dosage were studied.
1 Experimental
1.1 Raw materials and specifications
Mancozeb original powder (90%); emulsifier: anhydrous calcium dodecyl benzene sulfonate (500 #), phenylethyl phenol polyoxyethylene polyoxypropylene ether, polyoxyethylene polyoxypropylene block copolymer complex; dispersing agent: SOPA, dispersant LS, dispersant FM, dispersing agent NNO, N-methyl - a fatty acyl taurine salt, peregal, lignin sodium, D-425, 207, NV-1203; wetting agent: TXC, SXC, K12 powder, dibutyl naphthalene sulfonate, EFW; disintegrating agents: D-450, sodium sulfate, RXB, ZJ105, ZJ109, ZJ101; vector: diatomaceous earth, attapulgite, bentonite. kaolin, silica, calcium carbonate, talc; anti-coagulant: ZJ15, potassium ferrocyanide, LXC, calcium stearate, WG3.
1.2 The main instruments and equipment
JY2002-type electronic balance (Shanghai Scientific Instrument Co., Ltd. japonica), LK100 small high-speed grinder (Wuhan Science Optoelectronics Technology Co., Ltd.), DHG-9035A-type oven (Shanghai Science and Technology Co., Ltd. a constant), SHZ-D (Ⅲ)-type circulating water vacuum pump (China Gongyi City British margin to the Instrument), a stopwatch, a 30 mesh sieve, with stopper cylinders.
1.3 Process [1]
Water dispersible granules have a lot of processing methods, in general two types of customers: one is the "wet", one is "dry." Wet is the pesticides, additives, auxiliary agents, water as medium, small study in the grinding machine, made of suspension, and then granulation, the granulation method is spray drying granulation, fluid bed drying granulation and freeze-drying granulation; dry is to pesticides, additives, auxiliary agents used in conjunction with jet mill or fine grinding, into WP, and then granulation, rotary granulation the granulation method, extrusion granulation, high-speed mixing granulation, fluid bed granulation and compression granulation. Manufacturing process generally includes the following steps: mixing, crushing, or grinding, granulation, drying, screening. Wet process, although you can make from raw materials to finished the whole process no dust, environmental pollution, but the high energy consumption, and which suspension system between the stability of the water and affected by many factors, not conducive to the formulation Technology stereotypes. In this experiment dry manufacturing process, the following steps: (1) of each component according to formula feeding, even after the mechanical mixing crushed. (2) the powder for ultra-fine powder. (3) to collect after the powder by ultra-fine powder, by powder: water ratio of 5:1 made of soft material. (4) granulation, drying, sieving (20-60 mesh). (5) determination of product performance.
1.4 Determination of the performance agents [3]
1.4.1 Determination of dispersion: determined by CIPAC MT 174.
1.4.2 Determination of Run:
Determined by CIPAC MT 53.3.
1.4.3 Determination of disintegration:
Disintegration-I: in 250ml graduated cylinder add 100 ml of water, then pour 0.5 g sample was detected by visual particles sink to the bottom of the cylinder; by the following indicators to assess A. Almost all particles have been collapsing. B. About half of particles has been collapsing. C. small particles collapse. Disintegration-II: particle 1 min to reach the bottom cylinder, it will be reversed in both directions up and down the mixture, each about 2 s, and record the complete collapse of the reversal of particle number.
1.4.4 Determination of suspension rate:
Determined by CIPAC MT 168.
1.4.5 Thermal storage stability test:
Determined by CIPAC MT 46.3.
2 Experimental results and analysis
2.1 Screening of additives to determine the amount of
Emphasis on the experimental preparation performance impact on dispersant additives, wetting agents, disintegrating agents and anti-coagulant dosage types of screening and selection. Can first be elected by a preliminary screening test in addition to the four additives other than additives: Mancozeb 80% of total active ingredients, emulsifiers, fillers. Because the active ingredient preparations, so it is not to join the carrier as the basis for individually dispersant, wetting agents and disintegrants were screened, in the amount of wetting agent and the selection, the formula first without dispersant , Similarly, the amount of dispersant and its selection, the formula without wetting agent; final preparations by examining the 54 ℃ heat storage properties before and after the change to filter the anti-coagulant type and dosage.
2.1.1 Selection of dispersant
WG dispersant mainly to help provide particles dispersed into the water and prevent them from re-aggregation, to ensure that in suspension. The role of dispersant by certain basic characteristics with the processing technology to promote insoluble or hardly soluble in water, the original drug in small solid particles dispersed in water to form a stable water dispersion with a certain solution or suspension, the dispersant performance of screening agents that affect one of the main factors [4]. Unchanged in other additive to add different dispersants and dispersion of products, and suspension rates, the results in Table 1:
Table 1 Screening results of dispersant
Dispersant (%)
Dispersion
Suspension Performance
SL (7%)
+ +
+
MF (7%)
+ + +
+ +
207 (7%)
-
-
NV-1203 (5%)
-
-
Peregal (5%)
+ +
+
D-425 (5%)
+ + + +
+ +
LS + NNO (4% +2%)
+ + + +
+ + +
207 + D-425 (4% +3%)
+ + + +
+ + +
NV-1203 + D-425 (4% +3%)
+ + + +
+ + +
MF + LS + NNO (4% +2% +1%)
+ + + +
+ + + +
Note: "-" indicates poor; "+" indicates the general; "+ +" that is better; "+ + +" indicates good; "+ + + +" means excellent. The same below.
Can be drawn from Table 1, the use of a single dispersion effect of dispersants is not very satisfactory, with the use of several dispersants can get a better dispersion performance, special is the non-ionic or anionic surfactant molecular weight when used in combination better, the fastest lignosulfonate dissolved in water, but also conducive to the early collapse of the particle dispersion, but it's scattered persistent poor performance. Naphthalene sulfonate formaldehyde condensate with strong dispersion, but the products when exposed to moisture during storage, dispersion will be reduced. Use both in the formulation dispersing agent, can play a synergistic role of complement each other. It is also consistent with most literature reports.
2.1.2 Screening of wetting agent
The addition of wetting agent particles into the water main in order to increase the wetting speed and improve water infiltration into the WG. Wetting agent is a water dispersible granule properties of the key factors. Many crops are often a layer of leaf stem surface highly hydrophobic wax layer, the water is difficult to wet, and most chemical pesticides itself insoluble or insoluble in water, so the processing is necessary to use pesticides surfactant as wetting agent , thereby reducing the object to be processed and the interfacial tension between liquid and strengthen the role of pesticide droplets wetting penetration in order to better hair efficacy. This experiment with different wetting agent, addition of 2%, combined with better selected above dispersant, wetting of products, and suspension, better compatibility of selected combinations. The results shown in Table 2:
Table 2 Screening results of wetting agent
Powder
Wetting agent (2%)
Wettability
Suspension Performance
207 + D-425
K12 powder
+ +
+ +
EFW
+ +
+ +
SXC
+ + +
+ + +
TXC
+ + +
+ + +
NV-1203 + D-425
K12 powder
+ +
+ +
EFW
+ +
+ +
SXC
+ + +
+ + +
TXC
+ + +
+ + +
MF + LS + NNO
K12 Powder
+ +
+ +
EFW
+ + +
+ + +
SXC
+ + + +
+ + + +
TXC
+ + +
+ + + +
It was found that the product particles are better wettability, wetting time is less than 30 seconds, and the compatibility of different dispersants, the product is different from the suspension performance, through experiments selected combination of better compatibility.
2.1.3 Screening of disintegrants
Disintegrating agent is to accelerate the speed of particles in the water add the material disintegration, and it can be completely dispersed into the original particle size. The role of its mechanism is mechanical, not chemical in nature. It absorbs water molecules into larger size expansion, or expansion into a curved shape and straight, until the WG particles are dispersed into smaller fragments. In this experiment the D-450, sodium sulfate, RXB, ZJ105, ZJ109, ZJ101 objects such as screening, determination of disintegration time of the product to filter out the better disintegrating. Results see table 3 below:
Table 3 Screening results of disintegrating
No.
Disintegrating agents (2%)
Disintegration time / s
Suspension Performance
1
Sodium
55
+ +
2
RXB
50
+ + +
3
ZJ105
30
+ + + + +
4
ZJ109
40
+ + + +
5
D-450
45
+ + + +
6
ZJ101
65
+ +
Note: + denotes the suspension performance is good or bad, that the better the more +
Screening by disintegrating agents was found, plus the amount of disintegration of poor performance when there are fewer, and some particles in the sinking process does not smear, basic does not collapse after the disintegration of Canada amounted to 2% of the performance are good, mostly less than 60 seconds. Obtained with the better performance of the final collapse of suspension agent.
2.1.4 Screening of anti-coagulant
WG in the storage process, its internal cohesion particles will slowly leaving in a product suspension rate has dropped, the addition of anti-coagulant can effectively improve the changes of the product to save some time after the suspension rate. The proceeds to better the previous formula, based on anti-coagulant with different water dispersible particles made of 1.5%, by measuring the 54 ℃ heat storage rate changes before and after the suspension to filter out the effect of anti coagulant. Results following table 4:
Table 4 Screening results of anti-coagulant
No.
Anti-coagulant (1.5%)
Storage before the suspension rate
After the suspension rate of storage
1
Potassium ferrocyanide
55%
30%
2
YUS-LXC
58%
45%
3
Calcium stearate
50%
28%
4
WG3
60%
50%
5
ZJ15
70%
65%
WG during storage due to the agglomeration of particles inside, will make the suspension stability of the product spread down the addition of anti-coagulant to prevent this can have an effective role in maintaining the storage of products before and after the suspension rate.
2.1.5 80% water dispersible granule formulation of mancozeb
Through the above experiment, selected the final 80% Mancozeb better water dispersible granule formulation is as follows: 80% of the active ingredient mancozeb, dispersant MF + LS + NNO (4% +2% +1%), wetting agent SXC (2%), disintegrating agents ZJ105 (2%), anti-coagulant ZJ15 (1.5%). Samples prepared by the selected recipe with good physical and chemical stability, accelerated storage tests showed that the product can meet the requirements of the technical indicators: wetting time 4 ~ 5 s, the suspension rate of 70% or more, disintegration time within 60 s in the heat storage ((54 ± 2 ℃ 2 weeks) after the suspension rate has dropped 5%.
3 Summary and Outlook
Water dispersible granules, as a new water-based formulation of green pesticides, formulations can not be compared with the advantages of traditional, special for those in the water and organic solvents of low solubility of pesticides, processed into WG is the most suitable dose form. But WG is in the development stage, not truly put into actual production use, and thus feel it is not true with respect to the advantages of the traditional dosage forms. Generally the reasons that hinder its development are: ① the development and production costs of large infrastructure investments; ② processing technology is quite complex (with a variety of process technology), require skilled operators and experienced management personnel; ③ WG formulation specific and strong , more sensitive to the raw materials; ④ more stringent manufacturing conditions, the development cycle is long; ⑤ Development of various additives failed to keep pace, not much choice of agent types, and higher prices; ⑥ because the processing costs higher research and development of its product range is generally a number of pesticide products with high added value, not widely available. The WG formulation is in the domestic research and development stage, the variety of small, far behind the developed countries must strengthen future research and development.
Prospects for future work: Mancozeb WG's suspension rate is still not very satisfactory, needs to be further improved; try different types of products processed into water dispersible granules, the WP, the suspension to be some theoretical changes applied to the WG to the study, and gradually formed a number of water dispersible granules processing method of processing theory.
No comments:
Post a Comment