In recent years, with the improvement of people's awareness of environmental protection and health and the sustainable development of wood processing industry, protein-based adhesives have attracted more and more attention. Soybean protein is rich in resources, low in price and contains a large number of active groups. Soybean protein glue made from soybean meal has great development potential.

Soybean protein glue has been used in plywood production, and China also realized the industrial production of soybean protein glue plywood in 2005. In 2006, Nanjing Forestry University applied for the patent of "Manufacturing Method of Fast-growing Italian Poplar with Formaldehyde-free Soybean Glue for Industrial Production of Type II Plywood". In 2009, Shandong province realized the industrial production of soybean protein glue fiberboard. The results show that urea concentration has a significant effect on the expansion of the tertiary structure of soybean protein, and urea modified soybean protein has better water resistance than alkali modified soybean protein.

Ultrasonic treatment is widely used in all kinds of research, especially ultrasonic can accelerate chemical reaction [8]. At present, soybean-based adhesives are mainly used in wood processing industry, but less used in cardboard bonding.

Ultrasonic treatment is widely used in all kinds of research, especially ultrasonic treatment can accelerate chemical reactions. At present, soybean-based adhesives are mainly used in wood processing industry, and rarely used for cardboard bonding.

In this experiment, soybean protein powder was modified by ultrasonic-assisted urea, and soybean protein adhesive was prepared for bonding cardboard. The effects of protein concentration, urea concentration, treatment time, treatment temperature and ultrasonic treatment time on the bonding strength of soybean protein adhesive were systematically studied. This experiment provides a new idea for the wide application of soybean-based adhesives.

In this experiment, ultrasonic-assisted urea was used to modify soybean protein powder to prepare soybean protein adhesive and bond paperboard. The effects of protein concentration, urea concentration, treatment time, treatment temperature and ultrasonic treatment time on the bonding strength of soybean protein adhesive were systematically studied. This experiment provides a new idea for the wide application of soybean-based adhesives.

Limited ability, for reference only.