Preparation Of Polyester-polyether Based Waterborne Polyurethane Adhesive And Application In Caleium-plastic Corrugated Cardboard

With the improvement of people’s environment awareness, polyurethane(PU)adhesives have transfered from the solvent-borne type to the solvent-free type gradually.However, the bad thermal stability, surface tension and nitial bonding strength limit theirapplication as adhesive. A series of waterborne polycarbonate polyurethane adhesiveswere prepared by the acetone process, polyethylene glyeol(MW=2000) and polycarbonatediol(MW=1000，2000) were used as the soft segment, isophorone diisoeyanate and1,4-butanediol were used as the hard segment. Enhanced significantly the adhesivestrength by surface treatment of the calcium carbonate-plastic sheet and adjusting theDMPA content, the initial adhesive strength by adding the polyether diol PEG; Fouriertransform infrared spectroscopy(FT-IR)was used to characterize the chemical structure ofthe PU, the degree of micro-phase separation were studied by computer peak fitting. Atthe same time, some properties of the WPU adhesive were also studied, includingviscosity, particle size, surface tension, thermal stability, mechanical property, hydrolysisresistance and adhesive strength.1. The particle size of WPU emulsion decreased with increasing DMPA content whiledispersion viscosity showed an opposite trend; Particle size distribution of WPU emulsionbecame narrow gradually and tended to stable finally. Elongation at break of the film fromWPU emulsion decreased and the tensile strength increased with an increasing of DMPAcontent. The adhesive strength between the calcium carbonate-plastic corrugatingmedium and liner board was enhanced significantly after surface treatment of the calciumcarbonate-plastic sheet and presented parabolic trend with increasing DMPA content; Theadhesive strength reached a maximum when DMPA content was about4%.2. Polycarbonate diol with different molecular weight (1000,2000) was used toprepare WPU. The increasing of the soft segment would lead to bigger particle, smallerviscosity; lower degree of hydrogen bonding, while better freezing resistance; a increasein elongation at break and adhesive strength while poor tensile strength and initialadhesive strength.3. The experiment results indicated that the incorporation of PEG into the soft segments of the polyurethane backbone increased the viscosity, degree of phaseseparation, elongation at break and initial bonding strength as well as a reduction insurface tension. However, bigger particle size, polydispersity, lower tensile strength andhydrolysis resistance were also observed at the same time. Incorporation of smallamounts of PEG (5mol%) into PU films can slightly enhance adhesive strength to thenovel calcium carbonate-plastic corrugated cardboard, while the higher (>20mol%) willresult in a decrease.