| Reusing waste paper fiber has great significance in relieving the fiber shortage problem in papermaking industry.However,the source of waste paper is very complex,the quality of fiber is uneven and the waste paper contains high quantities of sticky substances,all these shortcomings have bad effects on the quality of paper products and the runnability of paper machine.The study was designed to help a coated white board mill in Fuyang,Zhejiang Province,solve the problems of paper break and stickies deposition in the manufacturing procerss.The purpose was to find the reason from the source,and therefore alleviate the stickies deposition problem to great extent.In the research,the quality of fibers from each 23 kinds of waste papers that had been using in the mill was evaluated,and the chemical compositions of the stickies extracted from the waste papers were analysed.And a fast method which can be used to evaluate the control effect of stickies was provided.In the waste paper fiber quality evaluation section,the composition and morphological feature of fibers were determined.Fiber composition was measured by staining method.The length,width,macrofibrillation index and shives of the fibers dissociated from the waste papers were determined with a fiber quality analyzer.Then,the morphological parameters of fiber were analyzed by principal component analysis(PCA)to evaluate the quality of fibers.The results showed that two principal components can be summarized from six fiber morphological parameters.The first principal component was mainly affected by macrofibrillation index,broken fiber content,and shives content of fiber,and the second principal component was mainly affected by length-width ratio,kinked fiber content and mean fibre curl index.The quality of fiber was ranked by the composite scores and the 5#,8#,9#,16#and 19#waste papers were recommended to be kept for continuous use in the manufacturing process.In the second part,the chemical compositions of stickies were analyzed.At first,the waste papers were extracted with tetrahydrofuran(THF).Then,fourier-transformed infrared spectroscopy(FTIR),gas chromatography coupled with mass spectrometry(GC-MS)and Pyrolysis-GC-MS were used to analyze the composition of the THF extractives.At last,the possible sources of stickies were conjectured from the extractive components.Results indicated that fatty acids existed in all the waste papers,but resin acids only exited in a part of waste papers.Potential stickies in waste papers were found to be styrene-butadiene rubber(SBR),polystyrene(PS),polyvinyl chloride(PVC)which might had been used as coating binders,or adhesives,or composited films.For developing a rapid evaluation method of stickies control,surface tension measurement was used.The main principle is that the surface tension of pulp water is highly related to the content of the surface active substances in the pulp slurry,which is mainly contributed by the dissolved and colloid substances.An interfacial tension tester was used to measure the surface tension of the filtrate separated from the waste paper pulp before and after being treated with different kinds of DCS controlling agents,and the DCS control effect was evaluated.Compared with the traditional methods like turbidity and cationic demand measurements,the results showed a high similarity on the tendency between surface tension and turbidity of the filtrate for the chemical controlling agents.Therefore,it can be concluded that the measurement of surface tension can be a useful tool to evaluate stickies control effect. |
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