Study On Testing And Evaluation Method For The Related Quality And Control Parameters Of Typical Wet-End Chemicals

In the process of approach and sheet forming,the addition of non-fibrous chemicals in the wet-end of papermaking is helpful to improve the paper quality,increase the wet-end forming efficiency and ensure the continuity and stability of the paper machine,etc.However,improper control of the chemical synthesis process will cause some problems such as inaccurate effective content or degree of substitution of chemicals,excessive levels of toxic by-products in the product,and eventually the chemicals fail to meet the product quality,stability,and safety standards.Therefore,in order to achieve a small amount of efficient use of chemicals while giving consideration to environmental protection,strict quality control requirements must be imposed on the quality of wet-end chemicals,which plays an important role in reducing production costs,maintaining the balance of wet end and the whole papermaking process.However,domestic paper mills lack the necessary monitoring and control methods in the use of chemical additives,and some traditional and backward determining concepts and methods are difficult to meet the testing requirements of key parameters of various new additives?such as effective content,degree of substitution,chlorine-containing harmful by-products,stability during storage and use,etc.?,which is not conducive to accurate and timely evaluation of the quality wet end chemicals.Therefore,in order to evaluate the quality performance,safety performance,and process stability of wet-end chemicals more objectively,some fast,accurate,scientific and reasonable new methods for determining key parameters are developed based on headspace analysis technology and UV-visible spectroscopy technology.Aiming at the problems existing in the testing concept and method of chemicals'solid or moisture content,the new concept of effective solid content is introduced,and some accurate and rapid quantitative methods are established based on instrumental analysis technology,including:a new method for determining the effective solid content of polyamide-polyamine epichlorohydrin?PAE?resin solution based on dual wavelength UV-Vis spectroscopy;A new method for rapid determination of the effective content of alky ketone dimer emulsion?AKD?based on ion-liquid-assisted headspace chromatography;A new method for rapid determination of the concentration of carboxymethyl cellulose aqueous solution based on tracer spectral attenuation technique;A new method for the determination of water content of polyacrylamide?PAM?based on multiple extraction headspace gas chromatography.The establishment of these methodologies is from the perspective of the actual effective component of a sample,and the test results are objective and accurate,which provides a more scientific guidance for the effective identification of the product quality and its application in the wet-end.In addition,the ionic liquid assisted headspace analysis is used for the first time in the method of AKD's effective content determination,which has certain enlightening significance for the development of other detection methods.Some new methods for determining the degree of deacetylation or substitution of key biomass-based chemicals in the wet-end of papermaking are established.Firstly,a new headspace analysis based titrimetric technique is developed to determine deacetylation degree chitosan molecule after acidification and using sodium bicarbonate as the base titrant instead of the traditional sodium hydroxide solution.According to the relationship between the CO₂signal released and the volume of the Na HCO₃ titrant,the deacetylation degree of the final product can be obtained.Based on this and combined with dialysis pretreatment,a phase reaction headspace gas chromatographic method for simultaneous determination of the degree of carboxymethyl chitosan deacetylation and substitution is developed.Secondly,a new multi-wavelength spectroscopic method is developed to determine the carboxyl content of nanocellulose.This method uses methylene blue as a tracer.Based on the ion exchange reaction and multi-wavelength spectral analysis,a formula for calculating the carboxyl group of nanocellulose is finally obtained.This method overcomes the problem of highly overlapping spectra of methylene blue and its associated products in mixed solutions.Finally,a new ion-exchange based spectroscopic method is proposed to determine the degree of substitution of cationic starch.This method uses the combined chlorine content on the structure of cationic starch to describe the degree of substitution.These methods are simple,practical,and highly automated.They are more effective than existing chemical titration methods in analyzing batch samples.Some new methods are developed for the determination of harmful chlorine components in PAE resin solution,such as residual monomer epichlorohydrin?ECH?and its hydrolytic or acidolysis products 1,3-dichloro-2-propanol?DCP?and 3,chloro-1,2-propanediol?MCPD?.This method can be used to quantify the single component of chlorine-containing substances separately and requires no pretreatment and external standard calibration operations,which is high selectivity and efficiency.Secondly,a new reaction based headspace gas chromatographic method for the determination of MCPD in PAE resin solution is described.The indirect quantification of MCPD is achieved based on GC-FID analysis of methanol by using periodate to selectively oxidize o-diols on MCPD to formaldehyde and then being reduced to methanol by sodium borohydride.Compared with the reference method,this method has high accuracy and is very suitable for quantification of MCPD in PAE resin solution.The analysis method of process parameters,process control and the and the method of and application model evaluation of related wet-end chemicals are proposed.Firstly,a new automatic temperature-programmed multi-extraction headspace gas chromatographic method for the determination of AKD's melting point is described,which is simple,accurate and highly automated.Secondly,a kinetic model for describing hydrolysis reaction of AKD emulsion during storage and papermaking process is obtained by mathematical fitting on the data of process parameters?temperature,time and system p H?effect on the hydrolysis behavior of AKD emulsion.This provides an important theoretical basis for the practical application and process control of AKD emulsion in the wet-end process of papermaking.Finally,the UV-Vis technique is used to monitor and control the real-time viscosity and epoxidation degree during the PAE resin synthesis process,which provides an effective control method for its synthesis process.