A review At present, some packaging color printing companies in the production of ordinary bag packaging, due to the relatively large production volume, while the smaller curing room, can not meet the production needs. Therefore, the curing time of the adhesive is required to be shorter, that is, the time for storing the product in the curing chamber is shortened, and the delivery time of the product is shortened (especially for products with tight production delivery). Thus, a fast curing polyurethane adhesive comes into being, and The application volume is also increasing. The reaction mechanism of two fast curing adhesives The two-component polyurethane adhesive is composed of a main agent and a curing agent. The main agent is a hydroxyl (-OH) terminated macropolyester polyol or polyester prepolymer; the curing agent is an isocyanate (-NC0) terminated trihydroxy prepolymer. When the two are mixed in a certain proportion, a chemical reaction takes place under certain conditions to form a macromolecular polymer having a network-like crosslinked structure, which has good cohesive strength and peel strength. The mechanism is as follows: First, when -NCO reacts with -OH, the precondition is that the molecule with -OH end capped is collided with the molecule with NCO capping, and -OH is caused to collide with -NC0; followed by the collision The molecules and radicals must have a certain amount of reaction energy, and chemical reactions can proceed, so that the old chemical bonds break and new chemical bonds are formed. The minimum energy that a molecule or group needs to absorb in a reaction is the activation energy of that chemical reaction. Any chemical reaction can take place and must absorb a certain amount of activation energy under certain conditions. Only such chemical reactions can continue to continue. The difference in activation energy of chemical reaction between different substances and different groups accounts for the fact that the reaction principle of fast-curing polyurethane adhesives is how to reduce the activation energy of chemical reactions and increase the effective collisional maneuverability. At present, there are two main types of fast-curing two-component polyurethane adhesives used on composite packaging in China: 1. The purpose of increasing the amount of catalyst is to reduce the activation energy of the chemical reaction, thereby shortening the time for the main agent and the curing agent to crosslink, and achieve the purpose of rapid curing. The disadvantage is that the catalyst is more toxic, and it is used in food packaging, and it is easy to cause pollution to food. In addition, the catalyst shortens the time for the crosslinking of the main agent and the curing agent, and also shortens the time for the reaction of the curing agent with moisture and alcohols, and thus has a high requirement for the quality of the solvent. It can easily cause viscosity increase or whitening during production. 2. The purpose of reducing the molecular weight of the curing agent and increasing the proportion of the curing agent is to increase the concentration of the reactants so as to increase the chance of effective collision, thereby increasing the reactivity of the main agent and the curing agent. However, the curing agent produced by this method contains more free TDI monomer, which reduces the hygienic properties of the produced packaging bag and makes the odor heavy. In view of the above situation, the PU-1975F fast-cure polyurethane adhesive developed by Zhejiang Huangyan Huaguang Resin Co., Ltd. uses a change in the structure of the main agent chain to introduce an amine-based molecule to the main agent chain to increase the rigidity of the molecular chain. Due to the rigidity of the main adhesive agent, the technical problem of poor coating performance has been solved. At the same time, due to the introduction of amine-based molecules, the reaction activity between the main agent and the curing agent is increased, the reaction time between the main agent and the curing agent is shortened, and the reaction time between the water and the alcohol and the curing agent is not changed. When used in PE film composite products, the friction coefficient is small and the opening is good. See Table 1 -. Through application trials and mass market launches, users are recognized. The PU-1975F adhesive shortens the curing time of the product from a certain extent to 24 hours from the original curing time to 12 hours, shortens the delivery time of the product, speeds up the production turnaround time, and saves energy.
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Three PU-1975F fast curing polyurethane adhesive
Four basic properties 
Five sticking performance
See Table 2.
Six PU-1975F glue diluted viscosity curve table
Seven conclusions
Author/Wang Tailin Xiao Haiyi
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