Development trends of polyurethane adhesives

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This post was last edited by PU3618988 on 2016-3-9 at 16:36. As an independent industry with a complete production chain, and also as a special auxiliary sector within the packaging industry, adhesives play an indispensable role in driving the production processes of the entire packaging industry. They have a significant impact on technological advancements in packaging and related industries, as well as on the development and updating of products. Therefore, the research and development and production of new types of adhesives with greater quality assurance and superior performance have naturally become areas of increasing focus in research activities within the packaging industry. This has also contributed significantly to the development and growth of the adhesive industry. At present, polyurethane adhesives are mainly of the solvent-type variety. The vast majority of adhesives used in the domestic food packaging composite film industry are of this type, which leads to environmental pollution and safety issues, as well as high energy consumption. It is estimated that the food packaging industry alone releases over 400,000 tons of organic solvents into the atmosphere each year. Organic solvents are flammable and explosive, volatile, have strong odors, cause air pollution when used, and are more or less toxic. The solvents emitted during the production of solvent-based adhesives not only contaminate the air and pose a direct threat to the health of workers, but a small amount of these solvents remains unremoved and ends up in food packaging, thereby harming consumers’ health. This is more terrifying than the safety hazards inherent in the food itself. Currently, the functions and applications of adhesives have received widespread attention, whereas their environmental impact is often overlooked. Whether it is environmentally friendly has become a bottleneck for the further development of adhesives, and addressing their environmental pollution issues has become an urgent task. Hot melt adhesives, which have seen the fastest demand growth in our country in recent years, offer excellent prospects for development due to their use of no organic solvents, rapid application speed, and good bonding properties. In addition to traditional EVA hot melts, the market should also actively develop new types of polyester and polyamide hot melts. Currently, foreign companies are producing urea-formaldehyde adhesives with low formaldehyde emissions in China, while also establishing large-scale wood processing plants. Currently, solvent-free adhesives that are truly environmentally friendly are widely used abroad. Solvent-free means that the adhesive contains no solvents; since there are no solvents to evaporate into the atmosphere, it does not cause pollution or harm. Solvent-free polyurethane adhesives are suitable for various types of plastic composite packaging; they also provide good adhesion to aluminum foil. Their resistance to the properties of the contents and their tolerance to high-temperature steaming are comparable to those of ester-soluble polyurethane adhesives, in addition to offering high peel strength. Water-based adhesives are highly favored for their non-flammability, non-toxicity, environmental friendliness, and strong adaptability to various products. However, the disadvantages of water-based adhesives include slow drying speed, poor water resistance, weak freeze resistance, high costs, and high energy consumption; therefore, they cannot fully replace ester-soluble polyurethane adhesives in the next 10 years. Therefore, in future production and research efforts, it is necessary to increase the solid content of water-based adhesives, accelerate their drying speed, and employ cross-linking methods to enhance both the drying speed and water resistance, thereby expanding their range of applications and market share. With the growing environmental awareness among humans and increasingly stringent relevant laws and regulations, it is an inevitable trend to promote the use of environmentally friendly adhesives. Due to issues with the application process and adhesion properties, reactive polyurethane hot-melt adhesives are not very suitable for the low-cost, high-efficiency production methods used in China’s industry. Water-based polyurethane adhesives have similar processing conditions and adhesion characteristics to solvent-based ones, and they represent the future direction of development. However, due to their current high cost, insufficiently mature application processes, and lower adhesive quality compared to solvent-based adhesives, it is unlikely that water-based polyurethane adhesives will replace solvent-based ones on a large scale within the next 2–3 years. During this period, the market will still be dominated by adhesives containing low levels of triphenyl solvents. In the coming years, our country will make significant efforts to research, develop, and produce new adhesive products with high technological content, high added value, and excellent performance. These include water-based polyurethane adhesives, water-based neoprene adhesives, high-performance and high-quality pressure-sensitive adhesives and their derivatives, VAE (vinyl acetate-ethylene) emulsions, EVA (ethylene-vinyl acetate) resins, SIS (styrene-isoprene-styrene) resins, etc. At the same time, greater emphasis will be placed on the development of environmentally friendly and energy-saving adhesives, in order to comply with the laws of market development and the principles necessary for human survival. Source: HuiCong Surface Treatment Network