Solvent-free adhesives are polyurethane-based adhesives. According to the components used, solvent-free adhesives are divided into two categories, two-component and one-component. The curing reaction principle is similar, but the adhesive performance, working mode, applicable to the occasion. Two-component adhesive refers to the two components are mixed in a certain proportion, and then crosslinked by the curing reaction, can be applied to a variety of flexible packaging composite substrates; one-component adhesive refers to the one-component adhesive and the moisture in the air (moisture) reaction to form a cross-linking effect, is mainly applicable to the composite material of the fiber substrate, such as paper/plastic, paper/paper. Among them, two-component adhesives are widely used in the field of flexible packaging composites.
The use of two-component adhesives is inextricably linked to the mixing process. The two components of A and B are uniformly mixed in a certain proportion through a stirrer, so that coating and blending can be carried out smoothly.

Basic requirements for mixing
In the production of solvent-free composites, the basic requirements of double adhesive mixing mainly include the following three aspects.
(1) The mixing ratio is correct. The mixing ratio, i.e., the mixing ratio of the main agent (-NC0 component) and the curing agent (-0H component) is usually a weight ratio, not a volume ratio. It should be noted that the concepts of the main agent and curing agent in a solvent-free blending process are different from those in a dry mixing process. The mixing ratios mentioned here are only applicable to solvent-free mixing methods.
The mixing ratios of different brands of adhesives are usually between 100...50 and 100...100, e.g. the mixing ratio of Coanda 811 8A / B glue is 100...75, the mixing ratio of Boss 830/730 glue and Rohma 698A / C79 glue is 100...50, the mixing ratio of Henkel 6029-2l / 7723-22 glue is 100...90 and so on. ratio is 100..90, etc. In actual production, when using the same brand of adhesive, customers can also adjust the mixing ratio according to the type of composite products.
(2) The two components should be mixed thoroughly.
(3) Mixing time, coating and laminating operation time should be matched with each other to meet the requirement of adhesive opening time. Open time, from the time of mixing solvent-free two-component adhesive to the time when the coating and compounding operation can be carried out normally. According to the glue manufacturers know the requirements of the operation, control time, each glue factory adhesive open time is not the same.