Causes and solutions of the deformation of pesticide plastic packaging bottles
At the beginning of 1990s, China's pesticide industry has been on the rise of plastic. In a short span of ten years, plastic bottles with its irreplaceable advantages, to occupy the dominant position of pesticide packaging. It can be said that, in addition to a number of low-grade pesticide products or small businesses are still in use of glass bottles, people have little use it to the packaging of pesticides.
However, in addition to light quality plastic bottles, beautiful, easy to process, not easy to damage, comprehensive cost competitive advantage, but also there is a lack of easy deformation of such a headache. This paper intends to cause this issue and how to solve them for an in-depth study, play a valuable role, benefit by mutual discussion.
The deformation occurs in the packaging of plastic bottles of pesticide emulsifiable concentrate, its deformation can be divided into three categories according to their causes:
One, due to the hot filling caused by deformation
In the pesticide sales season or in some special circumstances, the temperature of the pesticide injected into the plastic bottle will be much higher than the ambient temperature. And general pesticide will immediately seal the sealing cover immediately after filling. In order to avoid pesticide filling spilled or overflow bottle, bottle of the product than the general content required to fill liquid volume of at least 10% more. That is, more than 10% of the temperature of the remaining air in the bottle after hot filling is the same as that of the pesticide. When after a period of time, pesticide and internal air temperature dropped, the bottle will be negative pressure due to thermal expansion and contraction of the liquid liquefied and saic. When the negative pressure exceeds the strength of the bottle wall, the wall of the plastic bottle can be trapped and deformed. Two, due to mutual dissolution, weight loss caused by deformation.
This deformation is derived from the polarity of the chemical substances. Polar organic solvent emulsion pesticide Their natures are much the same. when the polarity of plastic bottles and packaging materials of each other, there will be mutual solubility. With the passage of time, the mutual dissolution will develop into a penetration. The organic solvent will penetrate from the molecular packaging bottle body material clearance to escape. A bottle of 100 ml of pesticides in a certain period of time will become 90 mL, 80 ml, or even less. At this time the pesticide bottle lid is sealed, the leakage caused by the loss of weight is bound to produce negative pressure, and ultimately make the bottle deformation.
In general, when the high density polyethylene (PE) bottles used for packaging or aliphatic esters and ketones, or aromatic solvent; when the polyester bottle packing (PET) two methyl formamide (DMF); when the bottle inner layer of multi-layer co extruded polyvinyl alcohol (EVOH) packaging aromatic or ester and ketone solvents, all this would happen such a phenomenon.
Three, due to the oxidation of negative pressure caused by deformation.
The pesticide composition is very complicated, the ingredients contained in some special solvents or emulsifiers, or unknown impurities in the raw material is often stored in the bottle and the oxygen in the air oxidation reaction occurs, resulting in negative pressure and deformation.
In this phenomenon, we have done a number of rapid aging test to be confirmed. As we will test 1.8% abamectin pesticides into the plastic bottle lid tightly and open a small hole on the cover and put a U - some water pipes are connected. Then, we put this bottle of pesticides and their connected U shaped tube into 50 degrees Celsius 2 degrees Celsius in the oven heat storage for 5 days, while the daily record of U shaped tube of the liquid level changes.
At the beginning of heating up and after a period of time, due to the pesticide bottle of liquid and air heat expansion, the pressure inside the bottle. The liquid level of the U shaped tube and the liquid level in the bottle is lower than that of the outer atmosphere. However, with the passage of time, the liquid level height becomes smaller, 30 hour flush. After that, the liquid level of the atmosphere is lower than that of the liquid level which is communicated with the bottle, which shows the negative pressure in the bottle. When the full five days to remove the test pesticides and return to room temperature, the measured surface difference is converted into a negative pressure value of 20%~21% -12.9 (Kpa), the time, the oxygen content of the bottle is also reduced by about 5%~7%. In view of the plastic bottle deformation is a common phenomenon, plastic bottle manufacturers need to work with the pesticide manufacturers to work together to explore and solve this problem.
A method to overcome the deformation caused by hot filling.
Very simple and very direct, as far as possible at room temperature filling. In order to achieve this goal, the pesticide manufacturers should take or extend the circulation pipeline or increase the cooling device to overcome the temperature of the reactor. If these methods can not be achieved, it should be in the pesticide filling into the plastic bottle, until it is cooled to room temperature and then sealed with a seal.
Two, due to mutual dissolution, weight loss caused by the deformation of the solution. The main method is according to the different solvents on pesticides, choose different plastic bottles for the material of barrier effect, and in the selection of prior to the compatibility test to confirm.
Generally speaking, the liquid pesticide water agent, suspension of the situation is less, the ordinary material plastic bottle has been fully qualified.
Because of the pesticides containing solvent more aggressive, so in the new China promulgated in March 1, 2001 and has since the implementation of the "packaging" in specific pesticide EC should be used glass bottles, HDPE bottles and other equivalent fluoride materials such as packaging bottle (bag).
Should say, polyester bottle (PET) also has a good barrier effect of some pesticides use solvents, but PET because of its easy to absorb moisture in the environment, resulting in water, and even exceed the standard of pesticide decomposition failure of this in the world is congenitally deficient, the restriction of the use of.
On the barrier effect of bottle, glass bottle, aluminum bottle, bottle coextrusion (inner nylon or polyvinyl fluoride bottles) and have good performance. But relatively speaking, the glass bottle because of its
