What are the advantages and disadvantages of water-based adhesives?

The water-based adhesive is an environment-friendly adhesive prepared by using natural or synthetic polymers as a viscous material and water as a solvent or dispersant to replace toxic organic solvents that pollute the environment. Existing water-based adhesives are not 100% solvent-free, and may contain limited volatile organic compounds as additives for their aqueous media to control viscosity or fluidity. The main advantages are non-toxic, non-polluting, non-combustible, safe to use, and easy to achieve clean production processes. The disadvantages include slow drying speed, poor water resistance, and poor antifreeze.

The water-based adhesive is an environment-friendly adhesive prepared by using natural or synthetic polymers as a viscous material and water as a solvent or dispersant to replace toxic organic solvents that pollute the environment. Existing water-based adhesives are not 100% solvent-free, and may contain limited volatile organic compounds as additives for their aqueous media to control viscosity or fluidity.

Classification of water-based adhesives

⒈ Classified by material:

Polyvinyl alcohol-based water-based adhesives, ethylene acetate-based water-based adhesives, acrylic-based water-based adhesives, polyurethane-based water-based adhesives, epoxy water-based adhesives, phenolic water-based adhesives, silicone-based water-based adhesives Adhesives, rubber-based water-based adhesives.

⒉Classified by application:

Water-based adhesives for construction, water-based adhesives for packaging, water-based adhesives for automobiles, water-based adhesives for shoemaking, and water-based adhesives for daily use

⒊According to the classification of solvents, there are two characteristics and modifications of water-soluble and emulsion adhesives

1. Aqueous polyurethane (APU) adhesive APU is a new type of polyurethane system in which water replaces organic solvents as the dispersion medium. It is also called water-dispersed polyurethane, water-based polyurethane or water-based polyurethane. Waterborne polyurethane uses water as solvent, is pollution-free, safe and reliable, has excellent mechanical properties, good compatibility, and is easy to modify.

APU adhesive is non-toxic and non-polluting. Its high molecular weight enables it to form an adhesive film with excellent performance. It has the advantages of low temperature resistance, flexibility, good bonding performance, and a wide range of adjustable film properties; its molecular structure has flexible molecules Chain, showing excellent impact resistance, fatigue resistance, low temperature resistance, and performance designability, the adhesive layer can be adjusted from flexible to rigid, which can meet the bonding requirements between different materials; currently, water-based polyurethane adhesives The synthesis method of is relatively mature, and there are mainly the following methods:

(1) Introduce some hydrophilic groups into the polyurethane resin structure to make it self-emulsify.

(2) Acetone method: firstly prepare a high-viscosity prepolymer, then add acetone to reduce the viscosity, and then extend the chain with a hydrophilic monomer, add it to water under high-speed stirring, and disperse it in the water through strong shearing, and reduce it after emulsification. The solvent is recovered by pressure distillation to obtain the PU water dispersion system.

(3) Blocked isocyanate method: select a suitable blocking agent to protect the terminal -NCO group of the water-sensitive isocyanate to make it inactive, and then add a chain extender and a crosslinking agent to co-emulsify to make an emulsion for use , Demasking through a certain temperature and special catalyst, and then generate -NCO end group, extend the chain to prepare waterborne polyurethane

Precautions

1. Water-based glue must be protected from light and stored in a ventilated indoor environment at 5-40°C.

2. The water-based glue is tasteless, non-flammable, and has a yellowing resistance of 4.5 or higher, suitable for light-colored materials and high requirements for yellowing resistance. The glue brush can be cleaned with warm water.

3. Except PE and PP materials, water-based glue is suitable for bonding between all materials currently used in footwear.

4. Water-based glue can be mixed with no more than 5% of water, but it must be stirred well, otherwise the glue layer will affect the glueing effect. The glue after mixing with water must be used up on the same day.

5. Water-based glue should be packed in plastic containers, not iron containers, otherwise it will affect the yellowing resistance coefficient of the glue.

6. Because the water-based glue evaporates slowly, 5% water-based curing agent must be added, and it must be stirred for 5-8 minutes to make it fully mixed. The glue with curing agent must be used up within 4 hours, not the next day use.

7. The drying temperature of the water-based glue is between 50-60℃, and the drying time is about 3-5 minutes.

8. Do not add oil-based curing agent to water-based glue, otherwise it will easily cause dead glue or glue agglomeration and cannot be used.

9. When the water-based glue is applied, it should be thin and even, not too thick. After drying, you can clearly see the bottom layer of the material. If you see a white layer, it means that the glue brush is too thick.

10. If there is a wire drawing phenomenon in the glue after drying, it means that the glue has not dried completely, it may be because the temperature is not enough, the drying time is too short, and the curing agent is added too little or the mixing is not even enough.

11. Generally, water-based glue only needs to be applied with one glue. If it is a loose porous structure material, two layers of glue can be applied thinly. Each glue must be dried thoroughly before applying the second glue, otherwise the primer will not dry out and affect the adhesion performance. , On the contrary, it is easy to cause the glue to open.

12. It is better to use special glue glue for the opened shoes. Small area glue can dry at room temperature for 5 minutes and can be pressed by hand. Large area needs to go through an oven and press by a press.

13. Use water-based adhesives to be equipped with the following tools:

a. Pneumatic or electric mixer b. Plastic mixing container c. Plastic plastic container.