When waterborne polyurethane is used as adhesive, it must be mixed generally. Based on waterborne polyurethane, crosslinking agent, thickening agent, filler, plasticizer, pigment and other additives can be added. Other types of waterborne resin and water can be added.In order to obtain higher resistance to water Heat resistance and bonding strength, at present a lot of waterborne polyurethane systems have been popular use of crosslinking agent, a two-component system, and this single component solvent (volatile) polyurethane adhesive system is similar to the sizing methods of waterborne polyurethane adhesive and solvent adhesive basic same, such as manual brush mechanical roller coating, etc.When spraying, the particle size and viscosity of emulsion should not be too large.

Adhesive is the key factor affecting the quality and performance of composite film, adhesive composite packaging film using the base material has plastic aluminum foil, and plastic is divided into many types, to these different surface characteristics of the film together, adhesive must have the ability to bond two different film materials at the same time.The main reason for the popularity of plastic-based composites is their lightness and flexibility.This in addition to its own to be flexible and foldable, the adhesive itself should also have this property if the hard film is brittle and not foldable, it loses the meaning of packaging.

Heat resistance Many food packages are subjected to high temperatures (180~220) during manufacturing operations ), for example, heat sealing bag, packaged food by high temperature sterilization and cooking food, which not only requires a variety of substrate film to withstand the test of high temperature, the adhesive used can also withstand the test of high temperature, otherwise, after high temperature treatment of the film layered peel, is not a composite packaging film.This must be carefully considered in the selection of adhesive cold resistance many food packaging to low temperature refrigeration or cryopreservation, which requires the packaging film itself can withstand low temperature.If the adhesive becomes hard and brittle under low temperature, it does not meet the requirements of the phenomenon of delamination and degumming, dielectric resistance food itself is a very complex substance, containing oil salt wine, spicy spices, and even acetic acid citric acid lactic acid sugar sulfide oxide.In the face of these complex ingredients, packaging and then to the high and low temperature test of processing and long-term storage, to maintain the packing film is perfect, in addition to the base material good medium erosion resistance of the film itself, the stability of the adhesive is very important also, need to be able to resist a variety of media, otherwise it will cause composite film layer stripping, lost package.The safety and health of food packaging compound film is to protect the packaging of the thing is direct entry, in order to be responsible for the health and safety of the consumer body, not only the substrate film to odorless, the adhesive used should also have the same performance, safety and health is a big problem.

Due to the hydrophilic groups in the molecular structure, its water resistance and solvent resistance are poor. There are many research measures to improve its water resistance and solvent resistance, among which the more effective measures are cross-linking and cross-linking methods, including internal cross-linking and diplomatic linking.Internal crosslinking refers to the bridging and crosslinking behaviors that have been completed in the preparation process. Internal crosslinking method often leads to the failure of the prepolymer to disperse in water due to excessive careless crosslinking. If the prepolymer is dispersed at the same time, it is easy to precipitate and stratify.Even without the above phenomenon, mesh structure of waterborne polyurethane are often poor wettability and film at room temperature Foreign league is pointing in the direction of waterborne polyurethane and crosslinking agent, the equivalent of two-component system and component before use added crosslinking agent on the principal agent, waterborne polyurethane in suitable for dry film forming conditions, produce chemical reaction, form the crosslinked film.Compared with the internal crosslinking method, the emulsion performance is good, and can be adjusted according to different types and dosage of crosslinking agent, diplomatic linking method is one of the most widely used in industry, usually crosslinking can improve the solvent resistance of waterborne polyurethane film, heat resistant creep and adhesive properties According to the reaction of functional groups, the suitable crosslinking system are as follows: containing carboxyl group (-cooh) group, a group of melamine/formaldehyde of polyfunctional aziridine carbonation two imine epoxy zinc sexual intercourse or zirconium salt ion agent: containing hydroxyl (OH) groups in melamine formaldehyde epoxy resin/blocked isocyanate crosslinking agent: a (NH) containing amine groups/melamine formaldehyde Epoxy resin blocked isocyanate crosslinking agent water dispersion isocyanate aziridine crosslinking agent water polyurethane adhesive of low initial viscosity is one of the factors hindering the research on the it is widely used Besides adding tackifier improve drainage polyurethane made of epoxy resin, show good initial adhesion, and its resistance to water solvent thermal creep resistant, indiscrete performance have been improved significantly.

Sinograce chemical produces water-based glue, water-based polyurethane, water-based acrylic glue and other raw materials, welcome to consult, contact email is sales@sinogracechem.com