Correct application and selection of high permeability auxiliaries

Definition and characteristics of 1. high permeability additives

Generally speaking, the definition of high permeability synergist is an additive with surface activity such as penetration, wetting and expansion. It is also called "high permeability synergist", "extended penetration agent", "pesticide synergist", "wetting and spreading agent", "penetrating agent", "skin penetration agent", "penetrating agent", "high permeability agent", "penetration agent" and other agricultural additives in agrochemical industry, that is to say, the auxiliaries that can help pesticides, fungicides, herbicides, regulators and foliar fertilizers to improve their effects are collectively referred to as "agricultural hypertonic auxiliaries" and "hypertonic" for short ". Hypertonic additives into non-ionic, anionic and anionic and non-ionic mixed three types are more commonly used, they all belong to the category of surfactants. No matter any type of hyperosmotic agent is used, its common application characteristics are: it has good wettability, spreading, adhesion and strong penetration ability. In the correct application, it can achieve fast knock-down speed and resistance to rainwater erosion, obviously improve drug effect, reduce pesticide dosage, reduce preparation cost, reduce environmental pollution and reduce the resistance of agricultural chemical products to harmful organisms, and it can improve the absorption and conduction of drugs to plants. Another common feature of hypertonic agents is that they all have different degrees of reducing the surface tension of aqueous solutions (the surface tension of standard water is 72mN/m). Generally speaking, the surface tension of hypertonic agents is mostly below 40mN/m, while the surface tension of silicone additives is as low as 20.5mN /m. The lower the surface tension value, the faster the expansion speed of the product, but the quality of the high permeability agent cannot be defined by the expansion speed of the auxiliary agent. The expansion speed does not represent the speed of the auxiliary agent's penetration force. The quality and reasonable selection of the high permeability agent depend on the speed value of "wetting speed" and "penetration force" of the high permeability agent species. Therefore, the faster the wetting speed and the penetration force of the hypertonic agent, the better the effect of the hypertonic agent and the better the quality. Although the quality of some high permeability agent is excellent, but the price is expensive, the amount of addition is large and too high to increase the cost of the preparation, or because its PH value is easy to decompose and unstable under acid-base conditions, it will also be kept away by the user. Therefore, the basis for selecting high-efficiency, low-cost, stable and good hyperosmotic agents is to scientifically determine the time values of "wetting speed" and "osmotic force" of different concentrations of hyperosmotic agents and their corresponding step experiments and stability experiments. Only in this way can the true quality of the hypertonic agent be identified and the variety of the corresponding hypertonic agent be selected.

Effect of 2. hyperosmotic agents on the quality of agrochemical products

Agrochemical products refer to chemical, biological and plant-derived fungicides, insecticides, herbicides, plant growth regulators, foliar fertilizers, and other agrochemical preparation products used to control plant diseases, insects, weeds and regulate plant growth. If these products are not added or mixed with hyperosmotic agents, their wettability, spreading and penetration will be poor. If the liquid medicine is sprayed on harmful organisms, especially on waxy body surfaces, the adhesion will be worse, and most of them will be lost to the field, while the liquid medicine attached to harmful organisms cannot quickly penetrate into the body to exert its efficacy. Especially in the high temperature, the sun is easy to volatile decomposition, at the same time easy to be rain, dew wash and decomposition effect (because dew is alkaline, and most of the agricultural products are acidic, will be neutralized by acid and alkali failure). Therefore, the effect of agrochemical products without high osmotic agent is obviously poor. Why is there a big difference between the effects of agricultural products imported from developed countries and domestic products of the same variety and content? It is because the auxiliaries used in the products of developed countries are all high-end hyperosmotic agents. These agrochemical products are highlighted as follows: good wetting performance, very strong adhesion and penetration, and obviously excellent killing effect on harmful organisms. Therefore, the Chinese still worship the quality of imported preparations, even at higher prices. This is the quality impact that hypertonic agents play in agrochemical products.

3. hyperosmolar agents are affected by pH

The influence of PH value on hypertonic agent is very important. Generally, hypertonic agent is very stable under neutral (PH value 6-7) conditions. The so-called stability means that when the preparation is processed, the hypertonic agent and the original drug will not produce chemical reaction, and will not be turbid or stratified. More importantly, after the hypertonic agent is added, it is affected by the PH value, so that the hypertonic agent decomposes and fails, reduces or disappears the penetration, wetting adhesion and expansion ability in a short time, and cannot normally exert the efficacy of the hypertonic agent. Such as now widely used in the barrel mixed with silicone additives, its performance indicators are very good, in the pH value of 6-7.5 in the neutral medium, very stable (and unstable in water easy hydrolysis), can maintain its surface activity for a long time. When the narrow pH value is lower than 6 or higher than 7.5, its surface activity (I. e. surface tension, expansion force and penetration force) will be significantly reduced in a relatively short period of time (in the case of pH 5-6 or 8-9 drug solution stored overnight, the surface tension, spreading ability and penetration force will be significantly reduced). Therefore, the silicone additives in acidic (pH less than 5) or alkaline (pH greater than 9) under the condition of preparation into the liquid must be applied immediately, otherwise it will quickly lose its surface activity. Therefore, silicone additives cannot be used in formulations with a pH value lower than 6 or a pH value higher than 8. Another example is the commonly used azone additives in the agricultural chemical industry, whose penetration was recognized by the agricultural chemical industry in the 1960 s. At that time, it was a relatively good hyperosmotic agent and the price was moderate. Therefore, in the production of pesticides, azone is still in large demand at present. However, azone has different degrees of surface activity under the conditions of strong acid and alkali, and its penetration and expansion speed are different from those of organic silicon additives, the use of pesticides in recent years has been slightly reduced. Recently, according to the technical department of the agrochemical industry, silicone additives have attracted much attention in the industry due to their excellent performance in wetting speed, permeability and extensibility. However, silicone additives have not been fully promoted due to the shortcomings of too narrow pH range and relatively expensive price. At present, the technical department in the industry urgently needs to introduce as soon as possible high-efficiency penetration additives that can not only have a wide range of PH value, but also have particularly excellent penetration ability and good wetting expansibility, and have relatively moderate price and dosage. This is bound to be a major wish of the agrochemical industry and a major measure to upgrade agrochemical products.

Application effect of 4. hyperosmotic agent in agrochemical products

Hypertonic agents can be recognized in agrochemical products, is very related to its characteristics:

1. Strong wetting and adhesion ability

Whether the hypertonic agent is added with the preparation or mixed with the tank, it can improve its wetting and adhesion ability to harmful organisms in the liquid medicine, resist rain erosion, reduce the loss of the liquid medicine, and improve the effect (when the liquid medicine is sprayed on the leaves of plants or the surface of harmful organisms, it will easily adhere to the body surface of plants and harmful organisms, such as adding a hypertonic agent with appropriate adhesion, that is, the liquid medicine will not be washed away when it is washed by rain in a very short period of time after spraying). The faster the wetting speed of the hyperosmotic agent, the better its adhesion. The effect of adding high osmotic agent with strong wetting adhesion is much higher than that of the product without high osmotic agent.

2, with strong penetration

The penetration force of hypertonic additives is very important, the speed of the penetration force is proportional to its penetration effect, and the speed of the penetration force is an important basis for identifying the quality of hypertonic additives. As far as the production of hypertonic pesticides is concerned, it is generally stipulated that when declaring hypertonic pesticides, the time index of their penetration force shall not be higher than 240 seconds under the premise of 500 times the concentration. Within the speed of less than 240 seconds, the less the penetration force time, the better the product quality. If some products do not add human hypertonic varieties, the penetration time actually has more than 600 seconds of varieties, and some products with excellent hypertonic, the penetration time can reach the speed of less than 20 seconds, so the penetration speed of products, its synergistic effect is very good, and even can improve the efficacy of more than twice. Therefore, the development trend of high permeability agrochemical products has been paid more and more attention by manufacturers, and some excellent enterprises pursuing product quality are very cautious about the scientific selection and application of high permeability agents and are willing to invest in scientific research.

3, with good expansion function

The expansion (also called extension or spreading) speed of high permeability additives is related to the surface tension. The lower the surface tension, the faster the expansion speed. Generally speaking, the surface tension of high permeability additives, such as those higher than 40mN/m, cannot be used as penetrant. The extended function of hypertonic agent is also very important to the quality effect of the product. If hypertonic agent has a good extended function, when the liquid medicine is sprayed, it can extend the liquid medicine to the unsprayed part through the extended function to reduce the decent contact angle of the spray droplet, to achieve the liquid medicine can be evenly spread on the entire body surface and improve the efficacy (expansion function and wetting adhesion and osmotic force combined to play the real effect of hypertonic agent), on the contrary, if the hypertonic agent does not have a good expansion function, it can not achieve the same corresponding effect.

4, increase the rate of pest killing and improve the absorption of plant leaves

Due to its strong permeability, the liquid sprayed on plant diseases, insects and weeds can quickly penetrate into the foliar tissues of plants and the body of harmful organisms to play a role, combined with its wetting, adhesion and expansion ability to improve the knock-down and killing speed of agrochemical products, and can effectively improve the internal absorption and conduction function of drugs, especially the killing effect of herbicides is more prominent. Generally, the killing speed of products added with hypertonic agent will be increased by 2-10 times compared with products without hypertonic agent (added according to the quality of hypertonic agent and scientific ratio).

5, the release of pesticide preparations to pest resistance.

The resistance of agrochemical products mainly exists in pesticide products, and the reasons for the resistance of pesticide products to pests are more complex. What is more prominent is that after spraying a pesticide for many times, the wax or cuticle of the pest epidermis will be thickened, because the wax can resist the liquid medicine from adhering to the surface of harmful organisms, while the thickened cuticle can make the liquid medicine adhering to the epidermis not easy to penetrate into the harmful organisms to exert its force, which is a biological physical function. The other is because after repeated application of a pesticide, when the liquid medicine penetrates into the pest body, a protease will be secreted to decompose the active ingredients in the liquid medicine, which can make the concentration of the liquid medicine in the pest body not reach the concentration., So that the medicine loses the effect of pest control, which is a biochemical effect. These two effects occur simultaneously or separately on the same harmful organism, and these two phenomena are relatively common. Because the agent added with hypertonic agent has strong penetration ability and good wetting and developing function, it can effectively adhere the liquid medicine to wax and penetrate into harmful organisms, and can also rapidly expand and penetrate into harmful organisms through air channels and pores in harmful organisms, so that harmful organisms can reach their death and be killed when they have no time to secrete the drug effect of resistant protease. This is the scientific truth that hypertonic additives can relieve resistance.

6, enhance efficacy, reduce costs, optimize the environment.

No matter whether the hypertonic agent is used for formula addition or tank mixing, as long as the quality of the hypertonic agent added is excellent, the drug effect can be improved by about 20%-50% after the hypertonic agent is added to the product without reducing the active ingredient, and at the same time, the active ingredient can be reduced by about 20%-50% on the premise of adding high-quality hypertonic agent, the effect is comparable to the effect of the formulation without reducing the content without adding the hypertonic agent, and even becomes better. As a result, its production costs will be reduced accordingly, and profits will increase at the same time, especially for expensive pesticide varieties. If the effective content of agricultural products is reduced, the corresponding pollution of farmland and air environment is also reduced, which is very beneficial to the environment.

The 5. use and identification of hyperosmolar agents should go out of the misunderstanding of their surface phenomena.

The use of high permeability agent can not only look at the surface phenomenon without paying attention to the substantive effect, take the current prevalence of silicone additives as an example to prove. In recent years, due to the excellent performance of silicone additives in agriculture, the production and sales of silicone additives in the agrochemical market have swarmed, and the price varies. Crude oil ranges from imported 120000 yuan/ton to domestic 6-80000 yuan/ton, and even lower prices. The preparation of silicone products is a wide variety of high and low price gap. Whether it is a pesticide manufacturer or a pesticide distributor, they are willing to buy products with good quality and low price, but each supplier will say that their products are good. At present, whether pesticide manufacturers or pesticide distributors are using a simple and inaccurate test method to determine the expansion rate to identify the quality of silicone additives. The method is: dip a "toothpick" with silicone additives and point the water droplets on the coated paper. For example, the water droplets can quickly expand to the surrounding area after point. The faster the speed, the better the quality, and vice versa. We have also done related experiments on this method: using our own production of silicone extended penetrant crude oil and content of 50%, 20% silicone additives, tested in the same way, the results of their performance of the expansion rate is basically the same. The "canvas sedimentation method" was used to determine the wetting rate and permeability of different concentrations.

The index of transmission force, the numerical result of the determination is increased with the increase of the dilution factor, and the value of each concentration has changed significantly. Therefore, the true quality of silicone additives cannot be measured by this method. If the manufacturer uses silicone with a content of less than 50% as 98% silicone crude oil, if the above simple method is used for determination, the true quality cannot be identified at all. Therefore, this identification method is only a phenomenon on the surface. If you want to determine the true quality of hypertonic agents, the use of scientific detection methods to get out of the surface phenomenon to identify hypertonic errors. The detailed results can be seen in the "Comparison Table of Determination Results" attached to this article for silicone additives, SS-2 high-efficiency spreading agents and azone.

How can 6. identify and select excellent hypertonic auxiliaries?

The effect of adding hyperosmotic agent to agrochemical products is difficult to define without correct measurement methods. Only through scientific experimental comparison by farmers can the products be known roughly. Therefore, most manufacturers and distributors add hyperosmotic agent based on psychological feeling. They feel that the quality of adding hyperosmotic agent is better than that of not adding hyperosmotic agent. There is no data on how much the quality is improved, even with the addition of some very poor hypertonic agents, it cannot be measured. Therefore, input costs often occur without corresponding effects and cannot be measured. In response to this problem, our institute according to the relevant pesticide chemical analysis and penetration determination method after years of experience improvement, high permeability additives, high permeability pesticides and other agrochemical products in the determination of the product of the "wetting speed" and "penetration" index, to determine the wetting speed and penetration time to the length of the wetting speed and penetration force. The determination method is simple and easy to operate, anyone can operate, and the determination is accurate, in order to enable the producers and distributors of the agrochemical industry to correctly identify and apply the real quality and effect of high permeability, and jointly contribute to the development of China's agrochemical industry. It is hereby made public to colleagues in the industry as follows:

Method for determination of wetting speed and penetration

(Canvas settlement method)

1. Use of instruments and materials:

Use a 250ml beaker, a stopwatch (or a stopwatch in a mobile phone tool), a cotton canvas disc (made of 21 3 strands × 21 4 strands of coarse canvas with a diameter of 30mm), a magnetic stirrer (with a magnetic stirrer) or a glass rod, and a measuring cylinder.

2. Operation steps:

A. Remove the original weight from the balance with a beaker, weigh one gram of the sample (1mL can also be measured with a syringe or measuring cup), and then accurately measure the standard hard (or tap water) and dilute it 200 times with a measuring cylinder. After the measurement is completed, put the magnetic stirrer and then put the beaker on the magnetic stirrer for stirring (glass rod can also be used to replace the stirrer for stirring, until the sample is fully dissolved in water). After about 1-3 minutes, the stirring can be stopped, and the foam in the aqueous solution disappears. You can also use a device (such as business card paper) to slowly scrape the foam out.

B. Take out 3 or 5 canvas pieces, place them horizontally into the sample solution successively, and record the placing time of each piece respectively.

3. Calculation of wetting speed

When all the canvases are soaked, record the soaking time of each piece of canvas, and the average time consumed from the time each piece of canvas is put in to the time when it is soaked is the soaking speed of the sample.

4. Calculation of penetration force

When the canvas pieces start to sink respectively, record the time for each piece of canvas to sink to the bottom of the beaker, and then the average value of the whole time from the time when each piece of canvas is put into the beaker to the time when the canvas pieces sink to the bottom of the beaker is the penetration force of the sample (penetration force = soaking time and sinking time).

In the test process of this method, the accuracy of the test is slightly different from the proficiency of the operation and the indoor temperature. Generally, it is appropriate to keep the room temperature at 25 ℃, but the measured value controlled at the same temperature is more accurate.

7. Accessories

Determination of different concentrations of silicone extended penetrant, SS-2 high-efficiency penetrant, azone crude oil using the "Determination Method of Wetting Speed and Penetration Force".

value for reference.

Conclusion

From the above table, it can be seen that the time values of silicone extended penetration agent, SS-2 high-efficiency penetration agent, wetting speed and penetration force of azone all increase with the increase of dilution multiple. From 200 times to 6400 times the measured values, the wetting speed of silicone additives and SS-2 high-efficiency spreading agents is almost the same as the penetration value, and the performance is excellent. However, the penetration time of SS-2 high-efficiency spreading agent is faster than that of silicone additive in each dilution ratio, especially at 1600 times, the penetration time of SS-2 high-efficiency spreading agent and the penetration time of silicone are more than twice as fast. The wetting speed of SS-2 high-efficiency spreading agent is 200 times and 6400 times faster than that of silicone, and other numerical silicone additives are faster than SS-2 high-efficiency spreading agent. Overall, the penetration of SS-2 efficient spreading agent is better than that of silicone additives. The penetration time of these two penetrants is still around 30 seconds at 6400 times the concentration, while the penetration time of azone is 131.9 seconds at 3200 times the concentration. From the determination of the value of azone, its values are significantly slower than the value of silicone additives and SS-2 high-efficiency spreading agent. At the same time, it can be seen that the measured values of each variety in each concentration have obvious changes. Therefore, using the above method to determine the quality of hypertonic agent is a more scientific detection method, and it is a reliable basis for identifying the quality of hypertonic agent.