|| SYNTHESIS OF MODIFIED CATIONIC ACRYLIC RESIN AND INFUENCES OF ITS STRUCTURE AND PROPERTIES ON PAPER SIZING|
|| cationic acrylic resin, soap-emulsion, surface sizing agent，neutral sizing agent|
(1)较佳的无皂乳液聚合工艺：半连续种子聚合法，w (DMC)=10%，w(PVA)=8%，w (catalyst)=0.2%，w (MAA)=5%，n (BA)：n (St)=1.1：1，w(ODA)=0.8%，w(乙二醛)=3.5%，w(异丙醇)=0.5%；聚合反应温度为80℃，在反应初期加入1/4的单体及1/3的引发剂，反应1h，然后在1h内缓慢滴加完剩余单体及引发剂，继续反应3h。然后与乙二醛在85℃下，反应2h即得产品。
(3)流变性测试表明，改性阳离子丙烯酸树脂乳液为非牛顿流体，有一定的假塑性和触变性，表观粘度随切变速率的变化规律呈现一定的切力变稀特征，流动指数范围n为0.982~0.675之间，随w (PVA)、w (DMC)、w (乙二醛)、w (异丙醇)的不同而异。乳液的表观粘度随w (PVA)和w (乙二醛)的增加而增加；随w (DMC)的增加而降低；助溶剂的加入改善了乳液的流动性。
With the action of catalyst and cosolvent, using polyvinyl alcohol (PVA) as dispersing agent and glyoxal as crosslinker modified cationic acrylic resin were prepared by emulsifier-free copolymerization with styrene(St), butylacrylate(BA), methacryloxyethyl trimethylammonium chloride(DMC), methacrylic acid(MAA) and octadecyl acrylate(ODA) as main monomers. Their structure, morphology and performance were characterized by various modern analysis methods. Effects of w(PVA), n(BA)/n(St), w(DMC)，w(MAA) and w(glyoxal) on the particle size and size distribution of resin emulsions and the sizing value and galling speed of papers were studied. And effects of w(PVA), n(BA)/n(St), w(crosslinker) and w(solvent) on the emulsion’s rheological properties were analyzed. Finally, the factors that affect the mechanical properties and water resistant performance of the membranes were discussed.
The modified cationic acrylic resin can be used in surface and internal sizing, the sizing progress and the function mechanism are discussed at last.
The main results are shown as follow:
1.The optimum reaction condition was described as below: seed semi-batch polymerization. w(DMC)=10%，w(PVA)=8%，w (catalyst)=0.2%，w (MAA)=5%，n(BA)：n(St)=1.1：1，w (ODA)=0.8%, w (glyoxal)=3.5%, w (isopropanol)=0.5%. Polymerization temperature: 80℃.1/4 monomers and 1/3 initiators was firstly added into flask. After 1 hour, the rest of monomers and initiators were added into the flask by drop-wise addition process in 1 hour followed by an additional 3 hour of reaction. Then it reacted with glyoxal in 2 hours at the temperature of 85℃.
2.The result of film-forming test shows that the mechanical properties and water resistant performance of the membranes are better under the condition of w(PVA)=8.0%、w(glyoxal)=3.5%、w(isopropanol)=0.5%, that is, the tensile strength(σ) and the elongation at break are 8.520 MPa and more than 40% respectively, and water contact angle can receive 92.5°.
3.The result of rheology test shows that the modified cationic acrylic resin emulsion is non-Newtonian fluid, exhibits endowed with pseudoplasticity and thixotropy. It is noticed that the apparent viscosity decreases with increasing the shear rate, that is, the emulsions show a characteristic of shear thinning, and their flow-behavior index (n) ranges from 0.982 to 0.675, changing with w(PVA)、w(DMC)、w(glyoxal)、w(isopropanol). The emulsions’ apparent viscosity are increased by the increase of the w(PVA) and w(isopropanol), decreased by the increase of w(DMC), and the emulsions’ rheological properties are approved by the addition of the cosolvent.
4.The Fourier transform infared spectrometer (FT-IR) indicates the exist of the structure of monomers of the resin, the modified cationic acrylic resin is successfully prepared. The transmission electron microscope (TEM) indicates that the latex particles are regular sphericity, the surface of the particles is clean. The dynamic laser light scattering (DLLS) indicates that the average diameter of the particles is 165.7nm. The wide-angle X-ray diffraction (WAXD) diagram indicates that the modified cationic acrylic resin is amorphous polymer. The differential scanning calorimeter (DSC) diagram shows that the glass transition temperature of the polymer is 50.3℃. The thermogravimetry (TG) indicates that the original decomposition temperature of the resin is near 150℃, this temperature is fit for general technics of paper making. The atomic force microscopy (AFM) indicates that the surface of the membrane of the resin is relatively leveling, smoothing, and even.
5.The modified cationic acrylic resin is used in paper-making as surface and internal sizing agents. The two methods both can endow the paper with good water repellency performance, at the same time the paper’s strength properties are raised. The surface sizing application result shows that the paper’s tensile strength, fracture-resist degree, smoothness degree and whiteness were respectively increased by 22.32%、38.2%、20.25%、1.71%, and the effects are close to or higher than single polymer emulsion when the oxidized starch and polymer emulsion are used as a complex system in different proportions. The surface sizing application result shows that, paper performace is better when the dosage of resin is about 1.5% in wide pH range. The scanning electron microscope (SEM) spectrums of the papers indicate the function of the emulsion.
Learned from the results, the preparation technology of the stable modified cationic acrylic resin emulsion by soap-emulsion copolymerization is possible and successful. Emulsion is non-Newtonian fluid, exhibits endowed with pseudoplasticity and thixotropy; and its rheological properties is good, so it is good to paper sizing. The mechanical properties and water resistant performance of the membranes are better. The application of this resin is good as surface sizing agent and internal sizing agent in paper-making.