Waterborne polyurethane synthetic leather

Generally speaking, waterborne polyurethane for synthetic leather needs to have the following properties:
(1) Waterborne polyurethane dispersion for synthetic leather must have good compatibility and compatibility with various additives and color pastes, and be easy to use; The prepared slurry shall not have layering or demulsification during the storage period and must have a long storage period. This requires that waterborne polyurethane must be highly stable.
(2) The anti-adhesion and anti-adhesion of waterborne polyurethane for synthetic leather must be excellent to prevent the quality from being affected by the difficulty of film forming and peeling and local adhesion of products during stacking. The specific requirement for the resin is to put the prepared adhesive film in an oven at 50 ℃ and press 50g weight, without adhesion within 24 hours.
(3) The leveling and spreading properties of waterborne polyurethane for synthetic leather must be good, otherwise the slurry will have stripes or perforations and other undesirable phenomena after being scraped on the release paper, resulting in cracks, shrinkage holes, pinholes and other defects on the dried adhesive film that affect the beauty of the product.
(4) Waterborne polyurethane for synthetic leather must have excellent water resistance, which requires that the polyurethane film will not deform and whiten when immersed in water. For synthetic leather, especially those used to make shoes, clothing, gloves and other products that are easily exposed to water-based substances (rain, tap water, etc.), if the water-based polyurethane film used is deformed, whitened and even the mechanical properties are reduced when it meets water, then the product will not meet the actual consumption standard and will lose its practical application significance. In addition, most of the synthetic leather, such as clothing leather and bag leather, will undergo the water rubbing operation during the production process. If the water resistance of the polyurethane film coated is not good, the light or the pattern is not full, and the appearance is not ideal, which will affect the simulation effect, and serious problems such as skin breakage will be caused.
(5) Water-based polyurethane for synthetic leather needs to meet the requirements of large-scale mechanized production. The production of synthetic leather is a continuous assembly line operation, which requires that the resin used not only has good viscosity and relatively durable adhesive performance, but also is easy to dry, so as to ensure that the adhesive between resin and substrate does not affect production efficiency and is easy to process control. Drying speed control is a major difficulty in the production of waterborne polyurethane synthetic leather, because the evaporation rate of water is slower than that of most organic solvents, and the drying temperature cannot be too high in production, otherwise the surface smoothness of the film will be affected. This puts forward higher requirements for material selection, process matching and production equipment of waterborne polyurethane for synthetic leather.