| Straw pulp is the main raw materials for paper-making in China. The main problems of paper and paperboard were their low intensity, especially the ring crush strength, bursting strength and tensile strength, so it needs resolving urgently. Thus, in recent years, the study on preparation and application of amphoteric acrylic resin has become a hot topic of the acrylic polymeric sizing agents. Through emulsifier-free emulsion polymerization, the multivariate copolymer emulsion with amphiphilic structure was prepared. Its latex had bond properties, the molecular contained many active groups which can be combined with fiber, and the ratio of hydrophobic and hydrophilic in molecule can be regulated according to the requirements of the use. So it has specific features and a wide range of applications.Self-cross linking amphoteric Polyacrylate resin-b-Poly (Glycidyl Methacrylate) Copolymer for paper strengthening agent was prepared by the emulsifier-free copolymerization with acrylic acid(AA)/acryl amide(AM)/vinyl cyanide (AN) / methacryloxyethyl trimethylammonium chloride(DMC) as the main materials, using glycidyl methacrylate (GMA) as cross linking agent,polyvinyl alcohol (PVA) as dispersing agent. Their structure, morphology and performance were characterized by various modern analysis methods. Effects of w(PVA) ,w(DMC) ,w(GMA) ,w(KPS)and w(AN) on the strength of papers were studied, and the effects of various pH on the dry strength of papers were studied.The Polyacrylate resin -b-Poly (Glycidyl Methacrylate) self-cross linking amphoteric copolymer can be used in surface and internal sizing; No organic solvents or emulsifier was added in the preparation process, and polyvinyl alcohol film itself is good,so it can give the necessary surface sizing of paper strength and the basic physical and chemical properties.Meanwhile, because of the introduction of glycidyl methacrylate (GMA) as a crosslinking monomer, the active groups such as ,epoxy groups, double bond, carboxyl or hydroxyl, etc.were introduced into the molecular chains, in which the epoxy group has a very high reactivity,easily with alcohols, amines, acid reacts,so it has given a particularly attention in the synthesis of acrylate copolymer. Moreover, GMA can be polyvinyl alcohol and acrylic ester copolymers to form cross-linked network structure slightly, therefore, it can significantly improve the dry strength of paper. The sizing progress and the function mechanism are discussed at last.The main results are shown as follow:(1)The optimum reaction conditions were described as below: seed polymerization, polymerization temperature 80℃～85℃, reaction time 5h,w(PVA)=3%～4%,w(DMC)=2% ~2.5%, w(GMA)= 0.7%, w(AN)=1.5%,4% monomers were firstly added into the flask, 1/2 initiators were added when the temperature was 75℃, After 1 hour,the left monomers and initiators were added into the flask by drop-wise addition process in 1 hour, heat for 3 hours, the reaction end.(2)FT-IR indicates the structure of the copolymer, and the self-cross linking reaction is successfully preceded because of GMA. The TEM indicates that the latex particles are regular sphericity, latex particles has bonded with each other obviously, GMA and the polyacrylate has generated a mild cross-linking.(3)Copolymer emulsion particle size analysis indicates that the average particle size in the dispersed state is about 20nm, particle size distribution in the 10 ~ 30 nm, belongs to the micro-emulsion, so it has good storage stability.XRD spectrum displays a dispersion-shaped peak, indicating a small amount of crystal formation, while the polymer presents a amorphous structure of diffraction curve, indicating that this polymer are amorphous polymers. DSC diagram shows that the glass transition temperature of the polymer is 62.8℃, indicates the copolymer is in a glassy state at room temperature, and it has certain rigidity. Thermogravimetry (TG) analysis shows that the original decomposition temperature is about 198.3℃, meeting the temperature requirements in general paper-making process.(4)The self-cross linking amphoteric Polyacrylate resin -b-Poly (Glycidyl Methacrylate) Copolymer can be used in paper-making as surface and internal sizing agents. The strength properties of paper can be greatly improved. The surface sizing application results shows that when using mixed emulsions, the paper's ring crush index, tensile index, bursting strength, folding strength were respectively increased by 38.3%,88%,34.3%,30% relative to oxidized starch ;the internal sizing application results shows that under the condition of w(resin)is 0.4% in wide pH value, the paper's ring crush index, tensile index bursting strength, can be respectively raised by 23.5%,18.3%,21% relative to blank paper.(5) SEM shows that the unsizing paper's fibers are relatively loose, small fibers easily; but after surface sizing, tiny fibers bonded with each other into pieces and run through with the coarser fibers, so that fibers interweaved more tightly.(6)Sizing value become higher with the increase of PVA'S polymerization degree and hydrolysis degree. However, 1799 was commonly adopted by factory due to their viscosity.
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