Study On Preparation Technology Of Waterborne Polyurethane In Synthetic Leather

At present, solvent polyurethane has been still focused on in the syntheticleather industry. The solid content of polyurethane resin used in synthetic leatheris30%in general,70%in mass of which is organic solvent. Most endanger wascaused to worker and serious pollution was caused to environment. With theincreasing of people’s awareness of safety as well as the constantly improvedenvironmental protection policies of all countries, using of organic solvent hasbecome a technical bottleneck, thus seriously restricted the development ofsynthetic leather industry.Some problems such as residual of DMF and pollution of volatile organicsolvent (VOC) caused by organic solvent can be resolved when water-bornepolyurethane is used instead of organic solvent-polyurethane. In addition,water-borne polyurethane synthetic leather harbors some other specialadvantages, such as breathability, moisture-penetrability, the tactile like leatherand preferable water vapor permeability because of a large number ofhydrophilic groups and porous structure of its film. So water-borne polyurethanesynthetic leather is a green and environment-friendly product, the water-bornepolyurethane synthetic leather base has been developed in some foreigncountries, but this technology was lagging behind in our country. The appliedtechnology of water-borne polyurethane used in synthetic leather was probed inthis paper, aiming at providing references for the industrial production.1The exploration of preparation condition of water-borne polyurethanesynthetic leather baseWaterborne polyurethane synthetic leather base was prepared by scrapingthe foaming pulp to non-woven fabrics. The type, amount of foaming agent, typeof padding, mechanical foaming time, coating thickness and other factors wereinvestigated, by taking the mechanical properties, water vapor permeability,thickness variation and cellular microcosmic structure of waterbornepolyurethane synthetic leather base as indexes. An optimal preparation conditionof water-based polyurethane bass was obtained. The relationship between cellular microcosmic structure and performance of base was analyzed. And somebasic data was provided for further theory research and material development.An optimized processing conditions of making water-borne polyurethanesynthetic leather base was following: the water-borne polyurethane DG-6061was used as the main components, adding5%(calculating by the quality ofwaterborne polyurethane DG-6061) fixed foaming agent ST and SR［m（ST）∶m （SR）=2∶3］, the coating thickness was0.6mm, the time of mechanicalfoaming was40min,drying temperature was60℃～100℃. And the water vaporpermeability of synthetic leather base prepared by water-borne polyurethane wassuperior to that of solvent-synthetic leather base, and the mechanical property ofwater-borne polyurethane synthetic leather base was not very difference fromthat of solvent-synthetic leather.2The exploration of processing condition of surface coating of water-bornepolyurethane synthetic leatherThe water-borne polyurethane synthetic leather was prepared by onecomponent aromatic waterborne polyurethane used as surface film-formingmaterials which was scraped on base prepared in last step. The influences of thefilm-forming conditions, such as the amount of thickener, operating temperatureand coating thickness on the properties of film were investigated in detail. Anoptimal processing condition used to deal with the surface of water-bornepolyurethane synthetic leather was optimized through single factor experiments.The results showed the optimal processing conditions include the dosage ofthickener was0.2%(calculating by the quality of waterborne polyurethaneDG-6913), the coating thickness was0.3mm and the initial operatingtemperature was60℃. Under the above processing conditions, the performanceof as-prepared water-borne polyurethane film was better.3Under this preparation condition for the water-borne polyurethanesynthetic leather, the water vapor permeability of synthetic leather was superiorto that of solvent-synthetic leather. Meanwhile, the mechanical property ofwater-borne polyurethane synthetic leather was close to that of solvent-syntheticleather.