Preparation Of High Length Diameter Ratio Micronano Cellulose Filaments And Its Application In Paper Enhancement And Filling

Cellulose is the most abundant natural macromolecular carbohydrate in the world.Micronano cellulose filaments can be prepared by chemical,mechanical or a combination of chemical methods.It has the characteristics of large specific surface area,high strength,high lengthdiameter ratio and low thermal expansion coefficient,etc.It is widely used in the fields of food,cosmetics,tobacco,coating and paper making.In this paper,micro-nano cellulose filaments with high aspect ratio was prepared by carboxymethylation pretreatment combined with ultrasonic method,and it was applied in reinforcing and filling.The preparation,performance and preparation mechanism of high length-diameter ratio micro-nano cellulose filaments were studied.The composite of high length-diameter ratio micro-nano cellulose filaments and nanometer calcium carbonate was applied to paper filling.The relationship between the amount of addition and the degree of beating or the composition of softwood fibers was studied in detail.The main conclusions are as follows:1.A method of carboxymethyl pretreatment combined with ultrasonic preparation of high aspect ratio micro-nano cellulose filaments was proposed.Using the carboxyl content and the ratio of length to diameter of the fiber as evaluation indexes,the best preparation process was obtained: the mass ratio of cellulose to sodium hydroxide and sodium chloroacetate was1:0.30:1.05-1.20,the reaction temperature was 70-75?,the reaction time was 50-60 min,and the ultrasonic time was 60-120 min.Through fiber analysis,scanning electron microscope(SEM)observation,mechanical and optical index detection and other related experiments,it is concluded that the carboxyl content of the fiber is closely related to the swelling shape,length and width distribution,strength and light transmittance of the fiber.The results of X-ray diffraction(XRD)showed that the crystallinity of the fibers decreased slightly after carboxymethyl pretreatment and ultrasonic treatment,but the crystallinity still remained at about 69%.By analyzing the thermogravimetric(TG)curves,it was found that the initial thermal degradation temperature and the maximum weight loss rate temperature of the micronano cellulose decreased,but the residual content increased to about 39% at 700?.2.Analysis of the preparation mechanism of micro-nano cellulose: FT-IR results show that carboxymethyl pretreatment successfully introduces carboxymethyl into the fiber,which will increase the electronegativity,enhance the electrostatic repulsion between the fibers,weaken the hydrogen bonding force,and lead to the swelling of the fiber.By observing the microstructure of fiber before and after the preparation,we found that different carboxyl content of different fiber swelling degree,at the same time,the high frequency ultrasound in ultrasonic processing of acoustic cavitation bubble collapse violently in the dispersion of the modified carboxymethyl cellulose cause micro fluidic and shock wave on the surface,role in the region of the fiber swelling,further weakening the interaction of cellulose.The fiber is stripped from the axial direction to obtain micro-nano cellulose filaments.3.The optimal preparation process of micro/nano cellulose and nano calcium carbonate composite filler is as follows: the concentration of micro/nano cellulose is 2.0%,the dosage of CPAM is 0.8%,the speed of agitator is 800 rpm,and the optimal adsorption rate of composite filler is 81.06%.Compared with nano calcium carbonate,the total retention rate of composite fillers reached the highest of 92.3%.When the addition amount was 20%,the whiteness and opacity of finished paper increased by 7.0% and 5.9%,respectively.The tensile index of the paper increases first and then decreases with a certain amount of addition(0-20%),but the strength of the paper is still higher than that of the paper without filling at 20%.4.By adding 1-3% micro/nano cellulose filaments into 32°SR pulp,the strength index of the finished paper was improved to different degrees.With the increase of the addition amount,the overall strength index of the paper presents an upward trend.When the addition amount was3%,the tensile index of the finished paper was close to the pattern of 78°SR,while the bursting index,tearing index and folding strength were better than the highest values in the control group.2% micro/nano cellulose filaments were added to hardwood pulp,respectively.The results showed that the strength index of the paper was almost the same as that of the paper with the addition of 40% micro-nano cellulose filaments at 2%.When the volume of addition was 5%,the four strength properties of the paper were better than that of the paper with 40% softwood pulp.