The Synthesis And Application Technology Of Modified Soy Bean Protein Adhesive

China as a big country of wood products manufacture, process and trade, the output of wood base panels and floors had taken first place in the world. At present, formaldehyde-based adhesives such as phenol–formaldehyde (PF) and urea–formaldehyde (UF) resins are used predominantly for production of wood composites. With recent increases in formaldehyde emission concerns, countries have organized and formulated series of national standards to regulate indoor air quality and create health conditions.Reductionof formaldehyde emission in wood base panels and research on low formaldehyde or non-formaldehyde adhesive is becoming more popular topics a in the world, facing the rise in the price of raw materials for petrochemical industry,the wood industry is currently under pressure to look for environmentally friendly adhesives derived from renewable resources.In this paper, soy flours were chosen as basic materials, and then under modification, stabilization and crosslinking treatment to formulated modified soybean protein adhesive.Then the applied technology of that adhesive in panel manufacture were to do. The modified and crosslinked technology and effect were mainly discussed. Physical and chemical properties, rheological property, curing properties, aicd treatment effect and bonding strength of modified soybean protein adhesive were investigated. the effect of hot-pressing technology on physical and mehanical properties of plywood, particleboard and fiberboard were discussed. On the base, the laboratory, pilot-scale and industrial tests of modified soybean protein adhesive, plywood and high density fiberboard were made. So it will offer some effective technologies for the extension and application of modified soybean protein adhesive.The main results are summarized as follows:(1) The results showed that pH 12.0 and 90℃reaction conditions were the best modified effect. Under these conditions,the viscosity of modified soybean protein dispersion was 640mPa.s, the solid content was 34.48%,the result indicated that the modified technology has solved the solid content low and viscosity high problem of tranditional soybean adhesive efficiently.the content of free amino acid was 0.37g/100g. The hydrolysis of soybean proteins were in minute amounts, the secondary, tertiary and quaternary structure of soybean proteins is also changed. Mw, Mn and mean gyration radius of chains of higher molecular weigh region got the minimum, the molecular distribution got the maxima.(2) The modified soybean protein were crosslinking treatment with formaldehyde and phenol to formulated modified soybean protein adhesive. The optimal dosage of formaldehyde stabilizing agent was approximately 0.4 mol of formaldehyde per 100g of soy flour, the optimal dosage of phenol crosslinking agent as follow: phenol : formaldehyde : alkali =1:2.08:0.2. The Mw and Mn of soybean protein under modification, stabilizing and crosslinking treatment increased continuously, the molecular distribution of protein in lower molecular weight region got tapered off, the mean gyration radius of chains in higher molecular weight region were growing larger. the water residual extract accounts of modified soybean protein adhesive was 74.32%, the result indicated that the crosslinking technology has solved the water resistance poor problem of tranditional soybean adhesive efficiently.(3) The physical and chemical properties of adhesives shows: appearance was reddish-brown not transparent liquids, specific gravity 1.15, solid content about 36%～38% , pH 10.3～10.5, free phenol content<0.41%, free formaldehyde content<0.35% and storage life>30day.The apparent viscosity decreased with shear rate increased, the viscosity of adhesive at 20rpm was 1 404mPa.s. The adhesive were curved at 90℃～120℃.(4)With the pH value of modified soybean protein adhesive decrease, the appearance change from reddish-brown to creamy, the color of adhesive get ligter.Viscosity appeared to have a decline trend after an initial ascent, bonding strength were lowered at first and rised later, the peak of curve were moved from low temperature towards high temperature at first then moved on the contrary.The pH 6.25 of adhesive was the turning point of viscosity, bonding strength and peak of curve.(5) The optimize hot-pressing technique of modified soy-based protein adhesive in the Poplar plywood manufacture as follow: the hot-pressing pressure was 1.4MPa,temperature was 165℃,time was1.4 mim/mmand glue spread was about 220g/m2 . Industrial tests of modified soybean protein adhesive plywood satisfy the requirement of GB/T 9846 -2004 of typeⅠplywood. Formaldehyde emission was 0.1mg/L,which met with the requirment of E0 grade plywood.(6) The suitable techniques of manufacture Poplar particleboard with modified soy-based protein adhesive as follow: hot-pressing temperature was 170℃,time was 1.2mim/mm, glue content was about 10% and water-proofing agent was 1.4%. Under the suitable conditions, the performance of board met the requirements for load-bearing boards for use in dry conditions at GB/T 4897-2003.(7) When hot-pressing temperature was 180℃, glue content was 10%, time was 40s/mm and water-proofing agent was 1.0%, the mechanical and physical properties of modified soy-based protein adhesive high density fiberboard met the requirement of LY/T 1611-2003 . The Formaldehyde emission was 0.5mg/100g that met the E1 grade.According to the ASTM D 6007-02 standard the formaldehyde concentration was 0.04ppm ,emission speed was 0.090mg/(m2h).