Driven by environmental pressure and market demand, water-based technology has become an important technological innovation and market expansion direction in the polyurethane industry. Recently, at the 4th Waterborne Polyurethane Research and Technology Exchange Conference hosted by the China Polyurethane Industry Association Waterborne Materials Committee, Experts attending the conference believe that the water-based transformation of the polyurethane industry is the trend of the times, but it still faces many difficulties, and technological innovation is urgently needed.
Waterborne replacement is the direction
Waterborne polyurethane mainly includes waterborne polyurethane coatings, waterborne polyurethane adhesives, waterborne polyurethane leathers, etc. It is widely used in coatings, adhesives, automobiles and other industries, and these industries are also the key areas for the reduction of VOCs in China.
'The better way to reduce VOCs emissions is to start from the source, and the most effective source control method is the replacement of raw materials for waterborne materials.' Shasha, an expert in the Environmental Engineering Assessment Center of the Ministry of Ecology and Environment.
The Ministry of Industry and Information Technology and the Ministry of Finance issued the “Action Plan for Volatile Organic Compound Reduction in Key Industries”, which proposes that the coatings industry should focus on promoting green coating products such as water-based coatings; the adhesive industry will accelerate the promotion of water-based and other green products; the synthetic leather industry will focus on promoting water-based and non-ferrous materials. Solvent polyurethane, substitute for organic solvent resin to prepare artificial leather, synthetic leather, microfiber leather; automotive industry coating process to promote water-based coatings and other processes. These processes and product replacement are inseparable from the development of water-based polyurethane.
'Polyurized water-based products use water instead of organic solvents to reduce chemical pollution from the source. With the tightening of environmental protection policies and the improvement of people's quality of life, the entire product chain is water-based for coatings, adhesives, leather and other polyurethane products. The market demand is very strong. 'The Secretary General of China Polyurethane Industry Association Lu told the reporter.
Technical gap
However, Lv Congress also pointed out that at present, China's key additives and water-based technology are still far behind the advanced level of foreign countries.
According to Dr. Cui Yanjun, Assistant Dean of Shanghai Huafeng Materials Science and Technology Research Institute, the production process of waterborne polyurethane resin mainly includes acetone method, prepolymer method and mechanical dispersion method. Among them, acetone method is a homogeneous system chain extension, which can obtain larger molecular weight. The cross-linking structure is easy to control; the particle size of the emulsion is controllable from tens of nanometers to 100 micrometers, but the solvent is difficult to refine and cannot be continuously produced. The prepolymer method can avoid the use of a large amount of organic solvents and can achieve high content. The production of emulsion can be continuous production, and the production process is simple; however, because it is extended in a heterogeneous system, the process control is difficult, and the viscosity of organic components is limited. The use of organic solvent in the whole process of mechanical dispersion is not used. , continuous production can be achieved; but it is difficult to achieve dispersion of high molecular weight polymers.
'In the synthesis, it is necessary to improve the stability of the water dispersion system and increase the solid content. In the application, it is necessary to improve the overall performance of the water-based product and accelerate the evaporation rate of water. These are the key points and difficulties in the development of water-based products. 'China Polyurethane Industry Association Director of the Waterborne Materials Committee, Zhang Haoming, Chairman of Oscar Materials Technology Co., Ltd. said.
According to Professor Zhang Junying of Beijing University of Chemical Technology, compared with solvent-based products, the main problems of water-based adhesive products are slow curing speed, poor initial adhesion, poor water resistance, and easy storage and transportation in winter. The use of film-forming auxiliaries causes an increase in VOCs; in addition, there are problems such as swelling of the moisture-sensitive substrate and corrosion of the metal substrate, resulting in limited development.
Cui Yanjun said that in the synthetic leather industry, waterborne polyurethane products mainly include surface finishing agents, water-containing impregnated resins for microfiber synthetic leather, and non-microfiber synthetic leather products. Due to technical and cost issues, the current proportion of waterborne polyurethane applications is still very low. , not mature enough in the production process.
'Cost is another important factor. The production cost of waterborne polyurethane products is significantly higher than that of solvent-based products. Under the pressure of environmental protection, many synthetic leather enterprises in the eastern coastal provinces have intentionally turned to producing water-based products, but some western enterprises have relatively higher environmental pressures. Small, still using solvent-based products. Water-based products lack market competitiveness, so the overall progress of the industry is slower. ' Cui Yanjun said.
Leading companies have achieved results
'The concept of water-based polyurethane is very hot in these years. At the same time, we must also see that the requirements for water-based production equipment and production technology have been improved. We must connect the upstream and downstream to promote the close cooperation of the entire industry chain, continuously optimize the production process, and jointly promote the industry. The water-based process has achieved a green environmental transformation. 'Han Baole, deputy secretary general of China Polyurethane Industry Association.
The reporter learned that Huafeng, Wanhua, Covestro and other leading polyurethane companies have achieved outstanding results in water-based technology innovation and product development.
Cui Yanjun said that at present, Huafeng Synthetic Leather has no longer expanded its solvent-based products, focusing on environmentally-friendly products. Last March, Huafeng Waterborne Polyurethane Production Project started in Wenzhou and is scheduled to be put into operation in the second half of this year. The production capacity is expected to replace 30% of the original solvent-based capacity, including 50,000 tons/year of polyurethane water-based resin for synthetic leather, 50,000 tons/year of closed solvent-free resin, and 60,000 tons/year of open solvent-free resin.
According to Zhang Huichen, head of adhesive technology service of Wanhua Chemical Group Co., Ltd., Wanhua waterborne polyurethane products are widely used in adhesives, textile coatings, industrial paints, architectural coatings, personal care and so on.
'Wanhua's water-based products can provide excellent bonding strength, and have good compatibility in shoe materials, clothing, and automotive interiors. They can be used in transportation, footwear, sports, sports, construction. And other fields provide a good solution. ' Zhang Huichen said.
Experts said that the development of polyurethane to water-based, it also requires the relevant companies to work hard on technology, overcome technical difficulties, develop products that meet environmental needs, have excellent performance, and are competitively priced.