Towards solvent-free polyurethane adhesives

      Solvent-free compounding processes, equipment and solvent-free polyurethane adhesives were developed in the 1970s and have been highly respected in the last decade or so. The solvent-free adhesives used today are also basically composed of two-component polyurethane adhesives. Their main agents and curing agents have high viscosity at room temperature and are solid or semi-solid substances, and some still have fluidity. When compounding, the main agent and curing agent are first heated to 50 -value="60" unitname="°C"> 60 °C, and some must reach value="80" unitname="°C"> 80 °C for viscosity Reduced to 1Pa · s or lower, and then delivered to the mixer in proportion with a metering pump. After thorough mixing, it is then transferred to the sizing roller and coated on the substrate. After being glued, it is not necessary to heat and dry it through a drying tunnel, because it does not have any solvent itself and can be directly compounded with another substrate. The compound is rolled up and aged at a certain temperature for a certain period of time.

    The use of solvent-free adhesives does not have the problem of exhaust emissions, there is no problem of residual solvents, there is no need for large and complex heating blasts, exhaust air or exhaust gas treatment devices, equipment is simple, and the cost is low, only the dry composite machine 50% to 60% , low investment, high speed operation, value="400" unitname="meter"> 400 meters per minute, less glue, raw materials, energy consumption, low maintenance costs, increased labor productivity , so the benefits are very significant. According to reports, most of the middle and low-end bulk composite packaging materials in Europe and the United States are compounded with solvent-free adhesives, and even high-grade composite packaging materials that are resistant to value="121" unitname="°C"> 121 °C are available. This adhesive is made.

    Since 1995 , China has introduced nearly 40 sets of solvent-free composite equipment, basically mastering a solvent-free composite process, and domestic flexible packaging equipment manufacturers are also developing solvent-free laminators. The most suitable solvent-free adhesives are still imported, but in the 1990s , there was a UK8150 solvent-free adhesive available. After entering the 21st century, LY-100N solvent-free adhesives Formally introduced to the market. According to industry surveys, the quality of solvent-free compounding processes and products has not been universally recognized so far. The main problems are the low initial adhesive strength of the adhesive, the low interlaminar peel force of the final product, and the waste during the production process. High rates, low yields, and some equipment failures cannot be solved. In recent years, research and development of solvent-free adhesives that are dedicated to improving initial tack and final peel strength are believed to be successful in the near future.