Waterborne polyurethane is a new type of polyurethane system which uses water instead of organic solvent as dispersion medium. Waterborne polyurethane takes water as solvent, no pollution, safe and reliable, good mechanical properties, good compatibility, easy to modify and so on.
II. Classification of waterborne polyurethane
1. According to particle size and appearance, it can be divided into polyurethane water solution (particle size < 0.001 micron, transparent appearance), polyurethane moisture dispersion (particle size: 0.001-0.1 micron, translucent appearance), and polyurethane emulsion (particle size > 0.1 micron, white appearance);
2. According to the charge properties of hydrophilic groups, waterborne polyurethane can be divided into anionic waterborne polyurethane, cationic waterborne polyurethane and non-ionic waterborne polyurethane. Among them, the anion type is the most important, which can be divided into carboxylic acid type and sulfonic acid type.
3. According to different synthetic monomers, waterborne polyurethane can be divided into polyether type, polyester type and polyether and polyester mixture type. According to the different diisocyanates selected, waterborne polyurethane can be divided into aromatic and aliphatic groups, or specific into TDI, HDI and so on.
4. Waterborne polyurethane can be divided into single-component waterborne polyurethane and two-component waterborne polyurethane according to the product packaging form.
The whole synthetic process of waterborne polyurethane can be divided into two stages. The first stage is preprogressive polymerization, that is, the copolymerization of diol, chain extender, water-based monomer and diisocyanate into a water-based polyurethane prepolymer with a relative molecular weight of l000. The second stage is the dispersion of prepolymer in water after neutralization.
Waterborne PU with its environmental protection, although the history is not long, but very fast development. Waterborne polyurethane consists of polyurethane aqueous solution, aqueous dispersion and water emulsion. It is a binary colloidal system. Polyurethane (PU) particles are dispersed in a continuous aqueous phase.
III. Waterborne polyurethane complete set
1. Production line system: storage and addition of monomer and initiator, prepolymer polymerization, dispersion phase transformation of waterborne polyurethane and desorption of curing process.
2. Main equipment
Different equipment is selected according to different reaction conditions, mainly including: reaction kettle, raw material storage tank, phase inversion kettle, curing desolubilization kettle, etc.
Difficulty: provide different phase inversion kettle equipment according to different requirements.