Research On The Modification Of Oxidized Starch And Its Application In Wood Adhesives

With the development of social economy, the environmental problems involved in wood processing industry has been a hot issue of concern. The selection of wood adhesive is one of the most important parts in the wood processing industry, which has a significant impact on the performance of wood products. At present, China's market mainly use formaldehyde wood adhesive glue (mainly urea-formaldehyde resin adhesive, phenolic resin adhesive and modified melamine resin adhesive) and white latex (PVAc). We know that formaldehyde series glue will release formaldehyde gas is bad for our health. The release of formaldehyde has been strictly regulated in the world, So it is urgent to development of a new non-toxic environmentally friendly cheap wood adhesive.In this paper, the modification of natural high molecular adhesive material, the development of a composite modified starch based wood adhesive for wood-based panel production. Starch is a natural polymer adhesive is widely used, it has excellent adhesive properties, cheap, easy to get raw materials. The main problems of Starch based wood adhesive are water resistance and adhesive strength. Aiming at the improvement of its water resistance, it is mainly to reduce the number of hydrophilic group hydroxyl groups or cross-linking modification to form large molecular network structure.First we prepared the poly(vinylalcohol furfural) resin, the resin synthesis by 10% polyvinyl alcohol solution and furfural with under acidic conditions. With the polyvinyl alcohol (PVA) and furfural molar ratio, reaction temperature, reaction time and pH value as the experimental factors, with the degree of acetalization as evaluation indicators, using L9(34) orthogonal test to choose the best way of experimental scheme, the study found that when the polyvinyl alcohol (PVA) and furfural molar ratio of 3:1, 95 degrees Celsius temperature, pH value was 1.5, reaction time 1h, the synthesis of resin acetal degree was 41%. Through range analysis we can know the influence of various factors:the amount of epichlorohydrin content> temperature>pH> time. Poly(vinylalcohol furfural) has the best physical and chemical properties.Epichlorohydrin crosslinked modified blend of oxidized starch. A certain amount of oxidized starch was fully mixed with distilled water, add a certain amount of NaOH to gelatinizing oxidized starch. In the end, the oxidized starch was modified by using 20%wt poly(vinylalcohol furfural) resin. With the epichlorohydrin amount, pH value, reaction time, reaction temperature as the experimental factors, with the bonding strength of the adhesive as evaluation indicators, using L9(34) orthogonal test to choose the best way of experimental scheme, the study found that when the 1g epichlorohydrin into the 120g of blending of oxidized glue, the temperature of 60 degrees Celsius temperature, pH value was 11, reaction time 2.5h. Bonding strength can reach 0.69Mpa, through the range analysis shows that the influence of various factors: epichlorohydrin content> temperature>pH value> time.Before the sizing, to add 3.0wt% hydrophilic modified polyisocyanates to the starch-based wood adhesive, in order to make sure the resulting starch-based wood adhesive can reach accord II plywood standards.In this paper, through a variety of scientific instruments and scientific method to characterize the oxidation of starch. The performance of starch based wood adhesive by composite modification can reached the standards of production, such as water resistance and bonding strength and storage stability.