Study On The Preparation Of Polyurethane Coating From Liquefied Benzylated Wood

The polyurethane coating is prepared from renewable resource-liquefied wood and isocyanate in this paper. The potential of this project seems to be great in the view of either the efficient use of energy and raw material or the environmental protect.The wood resource is composed of cellulose, hemicellulose and lignin. It is evident that many potential hydroxyls exist in its structure; they can easily react with isocyanate to produce polyurethane. But recent studies mainly concentrate on the polyols and phenol as liquefied reagents. This paper use DBE as solvents for the liquefaction of modified wood and the preparation of polyurethane. It is obvious that these solvents have no hydroxyl in its structure. Undoubtedly the use of DBE as solvent can eliminate the pollution, which exists prevalently in current coating industry. Furthermore, the polyurethane coating and films have good properties. The all results as following:Considering the liquefaction, we select DBE and other solvent as liquefied reagent. By measuring the hydroxyl number and stability of the solution, the optimal liquefaction condition is obtained, that is, wood with weight gain of 80%:DBE:n-butyl:hydrochloric acid being 1g:2.5g:0.5g:0.1ml; reaction temperature 75～80℃; reaction time is 2.5～3h. Under this condition, the hydroxyl number reaches to 217mg KOH/g wood power, viscosity is 210 mPa*s, stability is 20 days.Considering the properties of polyurethane coating, the optimal technological condition of preparation of polyurethane coating is obtained by measuring the properties of film, that is, the amount of wood solution is 32g; the amount of plastizer with molecule weight-400 is 4g; the amount of catalyst is 0.84ml; the amount of red pigment is 14g, the amount of solvents (ditoluene:n-butyl hydrochloric is 1:1) is 2.8g, the amount of Bayer.N75 is 11.2g. Under this condition, solid content is 65±2％; exterior dry is less than 2h; ultimate dry is less than 24h; impact intensity is more than 50kg.cm; adhension force is less than 1; causticity is very good and other properties are reached national stander of polyurethane coating.We study the effects of the solidify reagent content,solidifying temperature and heat dealing on the properties of polyurethane resin by FT-IR,DSC,XRD,SEM and DTA. With increasing of solidifying reagent content and weakening of solidifying temperature, the degree of microsphase separation is increased and thermal property of polyurethane is improved. With different heat dealing, the degree of microsphase separation is increased in turn of quenching,annealing and no dealing, the initialization decompose temperature of hard segment is increased, the initialization decompose temperature of soft segment is weakened.