The Preparation And Application Of Modified Soy-based Protein Adhesives

Adhesives play an important role in the wood-based panel production and new product development. Aldehyde resin which widely used have brought the issue of formaldehyde emission from plywood and their bonding products, in indoor air pollution, it's a major source of formaldehyde pollution which threat to human settlement and environmental security severely. In order to solve the problem of formaldehyde contamination, the soy protein adhesives due to its rich source of raw materials, environmental protection have become an important research and direction of development. However, high viscosity, poor mobility and low bonding strength of soy-based protein adhesive limit its application and development.Tradition soy-based protein adhesives were modified by sodium hydroxide (NaOH), sodium dodecylsulfonate (SDS) and guanidine hydrochloride (GuHC1), the phenol-formaldehyde (PF) and modified soy-based protein were mixed, urea and condensate were also added in the NaOH-modified soy-based protein (SMN) adhesives. By testing the viscosity, pH value, structure, plywood bonding strength, plywood formaldehyde emission of adhesives, the effects of NaOH,SDS,GuHCl,PF,U and condensate on structure, properties, and plywood physical mechanical properties of soy-based protein adhesives were researched.The result indicates:(1) NaOH, SDS and GuHCl all boosted the bonding strength of tradition soy-based protein adhesives;(2) Soy-based protein resins which contain 40% PF resins performed well for producing plywood compared to SMN adhesives, the bonding strength was increased, and the viscosity decreased;(3) Urea cut down the formaldehyde emission, but decreased the water resistance strength;(4) With the rising of hot-press temperature and hot-press time, the water resistant strength boosting, nevertheless the hot-press pressure and adhesive content didn't affect water resistant strength remarkably; (5) Sodium carbonate (Na2CO3) as a kind of condensate could advance adhesive system curing behavior. It could decrease the hot-press temperature and reduce hot-press time;(6) The plywood made by SPFU-N adhesive with 32% solid content and 2400cP (9r/min) could achieve best bonding strength after boiling resistance test (namely 1.10MPa), and the formaldehyde emission was 0.084mg/L, when hot-press temperature was 145℃, hot-press time was 4.5 min, hot-press pressure was 1.2 MPa, and adhesive content was 310 g/m2.