Synthesis Of Modified Melamine Formaldehyde Resin And Its Application

Melamine formaldehyde resin is a very important wet strength agent and water repellent in paper-making industry.Its wide sources of raw materials and low manufacturing cost make it play an vital role in the field of paper-making.As one of the thermosetting resins,it possesses properties like being water-resistant,heat resistant,ageing resistant,arc resistant,chemical resistant and at the same time exhibits excellent insulation properties,flame retardant properties,and strong mechanical strength which enable it be widely used in plastics,paper,wood,paint,textile,pharmaceutical and leather industries.In addition,wet strength is an important indicator as it determines the uses of paper.It is an important indicator of tissue paper including facial tissue,paper handkerchiefs,toilet paper,particularlythe fruit-bagged paperwhich is used to protect the fruit.The main purpose of this paper was to have melamine formaldehyde resin cationized.Since pulp fibrescarry negative charge,cationic melamine-formaldehyde resin could be better combined with the pulp fibres improving the wet tensile strength of paper.Wet tensile strength of both fruit-bagged paperand wrapping paper was improved and was able to adapt to the surroundings which is humid,harsh while maintaining sufficient wet strength.Thesis determined the synthesis and application of cationic melamine formaldehyde resin in fruit-bagged paper.Experiments were carried out mainly from two aspects,one was modified melamine resin with small molecule Amines;the other was melamine resinmodified by inorganic radicals.Several major factors affecting the synthesis reaction were discussed to determine the optimum conditions.Infrared spectroscopy and DSC were used to characterise and validate synthetic cationic melamine-formaldehyde resins.Cationic melamine-formaldehyde resin in an aqueous solution was measured by charge density of the slurry after adding the resin as well as UV spectroscopy detection and Zeta potential conductivity.Scanning electron microscopy,wet and dry tensile strength tensile strength,tear strength,bursting strength,physical performance testing air permeability and resistance index of hand sheets with resin were conducted.The results showed that with small molecule Amines added when nmelamine:n formaldehyde:n dimethylamine(1:3.3:0.1)was applied,wet tensile strength of modified melamine formaldehyde resin sheet was improved by 15.2%(compared to unmodified resin).With inorganic free radicals added,when nmelamine:n formaldehyde:n methanoln:n ammonium persulfate(100:330:450:1)was appliedand ammonium persulfate was added,wet tensile strength of modified melamine formaldehyde resin sheet was increased by up to 14.72%(compared to unmodified resin).It was concluded that dimethylamine modified melamine-formaldehyde resin to the unmodified resins are significantly improved in improving the wet tensile strength of paper.With small molecule-modified amines added,as n dimethylamine:n formaldehyde:n dimethylamine was 1:3.3:0.1,the modification can best improve the paper wet tensile strength by 15.2%,improve dry tensile strength by 4.76%;and improve paper bursting strength by 2.59%.