| Internal sizing has been widely used since 1807,although the amount has been reduced to certain extent,it has not yet been completely replaced by the surface Sizing.The main reason is that there still exist some major technical problems in the application of polymer surface sizing agent.For example,individual surface sizing still can not guarantee equivalent sizing performance with internal sizing; furthermore,the shortcoming in water resistance and surface strength are still serious.The innovation of this research lies in following four points:(1) Internal sizing procedure can be cancelled through the use of the product,which can reduce the variability of wet-end chemistry and the burden of papermaking whitewater to achieve nonpolluting production. (2) The products are endowed with the structure of organic/inorganic interpenetrating three-dimensional Network,not only possess the flexibility of polymeric material but also rigidity and wear resistance, which can greatly improve the comprehensive properties of paper.(3) strengthening crosslinking structure can be formed in paper surface by the introduction of silica sol.The bonding strength among fibers can be enhanced due to the interaction between active group and fiber, resulting in the improvement of solvent resistance,ink absorption and washing durability.(4) Organic solvent and small molecular emulsifier were not used in the preparation process,which is beneficial to environment protection.In this research,with the action of maleic half-ester polymeri sable emulsifier(MT),series of core-shell emulsions with "soft co re and hard shell" were prepared with butyl acrylate(BA) as core monomer,and BA,styrene(St) andγ-methacryloxypropyltrimetho xysilane(KH-570) as shell monomers,at the same time,functional monomer methacrylic acid(MAA) was introduced.Factors influen cing the stability,micromorphology and rheological properties of t he emulsion were studied,as well as factors influencing mechanic al properties,medium resistance,crystallinity and dynamic mechan ical properties.Furthermore,the products were applied in paper su rface sizing,and its substitute effect for internal sizing was invest igated.The detailed conclusions were described as following:(1) Structure and properties of core-shell emulsion with action of MTFT-IR spectra indicated that a characteristic peak correspondin g to polymerisable group- double bond was found in the chain str ucture of MT,but this peak disappeared in the core-shell copolym er,indicating that most of polymerisable emulsifier has been bond ed to the molecular chain of copolymer.Transmission electron microscope(TEM) indicated that core-shell emulsions displayed sphere morphology,and a remarkable core-shell structure was detected.Atomic force microscope(AFM) indicated that the surface of the membrane with 0.0%KH-570 was relative smoother, but it became coarse with the increase of KH-570 dosage.It was also found that the stability of the emulsion was optimum under the following conditions:w(MT)＞1.5%,w(ODA)=0.5%,the pH value ranges from 7 to 9,the solid content lower than 40%,w(dodecyl mercaptan)＞1%,w(KH-570)＜2.5%,w(silica sol)＜8%.Light scattering experiment indicates that the particle size of emulsion increases with the increase of KH-570 dosage.While with the increase of w(ODA),particle size decreases and then increases,and a smaller particle size was found when w(ODA) equals to 0.5%.Rheological investigation was also performed on the system.The viscosity of the emulsion decreased with KH-570 addition,but increased when KH-570 dosage was greater than 1.5%,which can be ascribed to enhanced interaction among particles.However,when the shear rate was higher than 1s-1,viscosity almost kept invariable with shear rate,but increased with KH-570 and silica sol dosage.It was also found that the emulsion presented pseudoplastic behavior,and an enhanced pseudoplastic was detected with the increase of silica sol dosage.Mechanical test indicates that tensile strength increased gradually with KH-570 and silica sol addition,while the breaking elongation was opposite.However,tensile strength decreased when KH-570 dosage was greater than 2.5%and silica sol dosage greater than 6%.Dynamic mechanical Analysis(DMA) indicated storage modulus increased gradually with KH-570 and silica sol addition.However,it decreased when KH-570 dosage was greater than 2.5%and silica sol dosage greater than 6%.Wide X-ray diffraction(WXRD) indicated that crystallinity increased from 3.04%to 5.12%when KH-570 dosage increased from 0.5%to 2%,however,it decreased from 5.12%to 4.52%when KH-570 dosage greater than 3%.The heat-resistance and solvent resistance can be improved with the increase of crystallinity.Furthermore,the crystallinity increased from 5.12%to 10.98%with 4%silica sol addition,resulting in the improvement of mechanical properties and medium resistance.Thermal Gravimetry(TG-DTG) indicated that the initial decomposition temperature increased with KH-570 and silica sol addition,but thermal stability was weakened when KH-570 dosage higher than 1.5%and silica sol dosage reach 10%.(2)Application experimentThe paper properties reached optimum under following conditions: w(MT)=2%,w(KH-570)=2%,w(silica)=6%,w(dodecyl mercaptan)=2%.Scanning Electron microscope(SEM) indicated that compacted knitted fibers were found after surface sizing.The sizing degree of paper sized with modified starch nearly close to zero,with 27 N tensile strength,140 times folding strength,4.2 KN.m/g ring crush strength.And the sizing degree increased with the increase of polymer emulsion(BS-1),while surface strength was opposite,with little decrease amplitude.The tensile strength of the paper sized with individual BS-1 reached 35N,folding strength reached 241 times,and ring crush strength reached 6.8KN.m/g.Furthermore,the folding strength reached 276 times and ring crush strength reached 7.6 KN.m/g when m(starch)/m(BS-1)=2:1.When BS-1/PVA blend was applied in paper surface sizing,better papers' properties were detected while hydrolysis degree of PVA with the same polymerization degree was higher.But PVA with moderate polymerization degree was usually adopted owing to higher viscosity of PVA solution.Besides,the application performance of PVA was better than modified starch.The sizing value of paper sized with PVA is about 5s,the surface strength was 4.5m/s,while the sizing degree of paper sized with starch close to 0s,and surface strength was only about 2.8m/s.Furthermore,the folding strength reached 326 times and ring crush strength reached 8.5 KN.m/g when m(starch)/m(BS-1)=2:1.The test of surface sizing substituting for internal sizing showed that the Cobb value of paper sized with 2.0 kg/t BS-1 and 0g AKD reached 24%,surface strength reached 3.9 m/s,which was better than that of the paper sized with 18 Kg/t internal sizing AKD and 3Kg/t surface sizing AKD.The test in factory also indicated the paper can reach physical performance index with individual BS-1 instead of internal sizing agents.The properties of paper sized with 1.5 Kg/t BS-1 was nearly equal to that of paper sized with 1.5 Kg/t Germany K-532 and 3Kg aluminum sulfate per ton of 5%starch suspensions. |
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