Pesticide-soft compound bagged features and adhesive process

Polyester polyurethanes are synthesized from polyester prepolymers, and polyester prepolymers are made from polyols and polybasic acids. As long as appropriate raw materials are selected from polyols or polyols, the molecules of polyester polyurethanes can be made The structure contains epoxy groups and carboxyl groups.

Due to the particularity of the umbrella structure, the molecular weight of this adhesive is small, and the viscosity of the glue is also low, but due to its large polarity, high crystallinity, and large cohesion between molecules, the initial adhesive force is large. Unlike other high-solid-low-viscosity adhesives, due to the low molecular weight, the initial tack is low, and wrinkles and tunnels and other quality accidents occur in the composite.

The first step in the reaction is the esterification reaction of a polyol and a polybasic acid. Under the action of a catalyst, under the protection of an inert gas, the esterification reaction produces an ester with incidental water. .

The second step is a condensation polymerization reaction. The esterified hydroxyl-terminated ester undergoes a condensation reaction at a high temperature and then under a high vacuum. The molecular weight is extremely low to become a polyester polyol having a medium molecular weight, accompanied by a polyol additive. product.

The third step is the addition of salty polymerization: Polyester isolating with a polyisocyanate: this process can be carried out by solution polymerization or by mass polymerization: The final product of the modification is a solution containing a certain amount of solids. The solvent may be ethyl acetate, acetone, butanone, butyl acetate, toluene, or some mixture thereof: The modification reaction in this step must control its molecular weight to prevent cross-linking during the reaction. At the same time, it is also necessary to control the viscosity of its glue, too large or too small to be suitable.

The curing agent synthesis is the same as other types of curing agents.

Main agent: Hardener=100:40 (weight ratio). The ratio of the operating solution is the main agent:
Curing agent: Diluent=100:40:20 (by weight), the glue concentration is 30% at this time, and the viscosity of the glue is about 14-18 seconds (3#NAHN CUP).

Fourth, the process conditions

The cleanliness and surface tension of various substrate surfaces should be the same as those for food and pharmaceutical composite packaging materials. Those who fail must not use them. The amount of glue should be in the range of 4.2-5.0 g/m2 (dry basis) and the residual solvent should be less than 10 mg/m2. In the case of multi-layered compounding, it can be carried out one time at a time without any interruption, and it is not necessary to perform deburring of the compound before compounding the third or fourth layer. After being compounded, it should be fully cured at 50-55 degrees C for more than 48 hours.

V. Composite properties

1, composite fastness: plastic / plastic ship peeling force 4N/15mm. Can not be stripped. Aluminum/plastic peel force

2. Drug resistance: Within the composite bag of PET (OPA)/AL/PE (CPP) structure,
A mixture of toluene, xylene, toluene, and dimethylformamide, a mixture of toluene and xylene, ethyl acetate, 99.5% of ethanol, dimethoate, cypermethrin, and Shi Tianbu, etc. °C tested for 60 days and stored at room temperature. When tested at a high temperature of 60°C, from the appearance point of view, speckles and delaminations occurred in the packaging of dimethoate and DMF, and the rest was intact. From the standpoint of peeling force, apart from the problems of separation, pitting, and vesicles in packaging bags containing dimethoate and DMF-containing mixtures, toluene, xylene, a mixture of toluene and xylene, 99.5% of ethanol, and chrysanthemum were added. In the ester bag, the peeling force was 4N/15mm or more, and the height was as high as 8N/15mm, and the Shi Tiantian bag was tested for ten months and the peel force was about 1.5N/15mm. However, when the contents of Shi Tian's patch were poured for several hours and then examined, the peeling force was increased to 4 N/15 mm or more. This indicates that the adhesive layer swelled after being eroded by the solvent, and the strength decreased, and when the adhesive layer was eroded After the solvent escaped the film dried, the strength increased, indicating that the adhesive was not damaged in nature. Stored at room temperature, with the exception of dimethoate, there are no problems.

Six, a few instructions

1. At present, there is no adhesive that fully satisfies all pesticide packaging requirements. It is understood that with the imported UK3640/UK6800 this type of adhesive can handle the packaging of most pesticides, but it cannot yet completely eliminate pesticides containing DMF mixed solvents. % clearance,
Therefore, when using adhesives, be sure to provide customers with care when it comes to packaging bags. Ask what the pesticides are, what solvents they have, and how long the shelf life is. Then, we must: After the physical package is packed, carry out practical tests. If both parties believe that there are no problems and they are all recognized, they must be sealed and kept for examination.

2. As far as I know, the names of the same pesticides and products of different manufacturers have different performances. The degree of erosion of the packaging bags is also different. Do not think that the same medicine name is exactly the same. The products of different manufacturers can only be determined after the actual filling test.

3. If the actual test can be concluded after two or three years, then it is unrealistic and business opportunities will be lost. In order to reach a conclusion as soon as possible, the actual filling test can be performed using the rapid method. It is said that after the pesticide is sealed and stored at 60°C for two months, if the packaging bag is not damaged or delaminated, the apparent quality does not change significantly (such as pitting, wrinkles, separation, tunnels, bubbles, etc.) , it can be considered that it has a shelf life of two years under normal atmospheric temperature conditions.

4. The structure of the compound, that is, what substrate to use and how many layers to use, must be determined based on the specific pesticide. Some can be used two layers of plastic, some to add a layer of aluminum foil, some available general plastic, and some use high barrier materials, and some also four, five, in order to increase its overall strength. All of these must be agreed with the pesticide plant and reached consensus before they can be manufactured as formal products. Otherwise there will be great risks.