MATHEMATICAL MODELS FOR DETERMINING THE INFLUENCE OF PROCESS PARAMETERS ON THE PHYSICO-CHEMICAL PROPERTIES FOR UREA-FORMALDEHYDE RESINS

V razvojnem laboratoriju podjetja Nafta Petrochem d.o.o. iz Lendave smo pripravljali sečninsko-formaldehidne smole. V laboratoriju smo po standardnih metodah izvedli tudi vse potrebne analize. Določili smo najpomembnejše parametre in njihove vrednosti, ki bi zagotavljali nespremenjeno kvaliteto smole glede na pretečeni čas po sintezi smole in pri različnih dodatkih sečnine. Med raziskavami smo opazovali čas kondenzacije in ugotovili, da dodatki sečnine vplivajo na hitrost reakcije kondenzacije med sečnino in formaldehidom. Če več sečnine sodeluje v kondenzaciji, moramo povišati pH vrednosti reakcijske mešanice in znižati temperaturo kondenzacije, da dosežemo enake čase kondenzacije. Ugotovili smo, da ne glede na način sinteze (mišljeni so različni premiki dodatkov sečnine iz enega dodatka v drugega), trajanja časa reakcije kondenzacije in končne viskoznosti ima stabilizirana smola po enem tednu in ob različnih premikih med tremi dodatki sečnine, takšne vrednosti, ki so znotraj napake metode. Določili smo tudi matematične modele z linearno in nelinearno regresijo za določitev vpliva procesnih parametrov na fizikalno-kemijske lastnosti sečninsko-formaldehidnih smol, ki se zelo ujemajo z realnimi meritvami (saj je determinacijski koeficient, R2, blizu vrednosti 1).Urea-formaldehyde resins were prepared in the development laboratory of Nafta Petrochem d.o.o. company in Lendava. In the laboratory, necessary analyses were performed using standard methods. Main parameters and their values that would ensure stable quality of resin, regarding the passage of time after synthesis and various movements of urea were determined. During the studies, we observed the condensation time and found that the movement of urea influences the rate of condensation reaction between urea and formaldehyde. When higher quantity of urea participates in the condensation, pH of the reaction mixture should be increased and condensing temperature should be lowered to obtain the same time of condensation. We found that irrespective of the mode of synthesis (that means different movements of urea additives from one additive to another), the duration of the condensation reaction time and final viscosity of the resin, values of the resin stabilized after a week and after various shifts between the three additions of urea, are within the error of the method. We have determined the mathematical models using linear and nonlinear regression to determine the influence of process parameters on the physico-chemical properties for urea-formaldehyde resins, which are very consistent with real measurements (the coefficient of determination, R2, is close to 1)