Study On Preparation Of The Papermaking Sizing Agent With Leather Wastes And Its Performance

With the continuous development of papermaking industry in ourcountry, the consumption of the sizing agentsis yearly on the increase.Biomass sizing agent has chronically taken up the larger market share inthe papermaking industry, owing to its extensive sources for rawmaterial, cheap cost, easily biodegradable and renewable. Therefore, itis very important to develop the novel biomass sizing agent product orexpand the modified products of the original biomass sizing agents.This paper aims to prepare two novel and environmental friendly papersizing agents with the collagen extracted from the reclaimed leatherwaste. Their structure and performance were studied systematically. Inaddition, their sizing effect was also studied by coating their on thecorrugated paper. It will expand a new way to largely recycling use ofleather waste for the leather industry, as well as provide a theoreticalbasis and support to develop new biomass for the paper industry. Mainstudied contents are as follows：The first, the relative molecular mass distribution, type and contentof amino acids of collagen from the Debang chemical Co. Ltd. inHaining are determined by the Sodium dodecyl sulphate-polyacrylamidegel electrophoresis (SDS electrophoresis), Gel permeationchromatograph(GPC) and Amino acid analyzer. The determined resultsshow that the relative molecular mass distribution of collagen is at600~80000and mainly concentrates in the low relative molecular massrange. Its number average molecular weight is1123Da and the heavymolecular weight is3609Da. It contains16types of amino acids. And the most content contains proline (Pro) and glycine (Gly), and theircontents are respectively17.84%and17.15%. The total content ofamino acids is65.73%and the purity of collagen is low. Being used asthe biomass material, the molecular chain of collagen still has the basicpropertiesof the natural collagen and its structure is in line with therequirements for the modification.The second, the grafting modified collagen(GMC) sizing agentwith excellent comprehensive sizing performance is prepared by freeradical polymerization, with collagen as the grafted main chain, Butylacrylate(BA) and Styrene(St) as the flexible and rigid side chains,potassium persulphate/sodium bisulfite as redox initiator system. Thegrafting modified collagen(GMC) with the excellent sizing performanceis prepared by the free radical polymerization method. With the graftingrate and precipitation rateof GMC product as the reference index, theprepared conditions are optimized by single factor experiment. Asfollows, m(collagen): m(monomers) is1:1, m(BA): m(St) is1:1.5, thedosage of initiator is3%of the total monomers, the reaction time is4h.The GMC product appears the white emulsion with blue light. Its solidcontent is14.3%and the viscosity is30mPa·s. The performance ofelectrolyte, acid and alkaliresistance and the storage stability are allexcellent. After purifying to GMC in the optimal prepared condition, itsstructure is characterized by Fourier transform infraredspectroscopy(FT-IR). Result explains the amideⅠ, Ⅱ, Ⅲ of collagenare slightly shifted to higher wavenumber and the characteristicabsorption peaks of C=O and C-C(C=O)-O from the saturated aliphaticand5H from the benzene ring are present, after grafting modification. Itproves that the synthesis reaction carry out in accordance with theexpected design route and the expected product is obtained.The morphology, particle size anddistribution of the collagen andGMC are determined by Scanning electron microscopy(SEM),Transmission electron microscopy(TEM) and Laser particle sizeanalyzer. Results show that the structure regularity of the collagengranule is destroyed by the grafting modification and its surface changes into roughness. These white parts belongs to the polymer ofvinyl monomers. The morphology of GMC emulsion is sphericalstructure with size uniformity and its mean particle size is117nm.The crystalline degree, element content and thermostability of thecollagen and GMC are characterized by X-raydiffractionanalyzer(XRD),Energy-dispersive spectrum analyzer(EDS) and Differential scanningcalorimeter(DSC). Results suggest crystalline degree declines andthermostability increases, after grafting modification. There is traces ofchromium in the GMC product，because the removal of chromium of thecollagen extracted from leather shavings was incomplete. But theamount of chromium in the product is less than limited that in the EUdirectives and meet the requirements of environmental safety.With corrugated base paper as the sizing object, GMC emulsion iscoated on its surface. Result of sizing experimental shows the ring crushstrength, the tensile strength and the water-resistance performance ofpaper sized by the GMC are improved significantly, which is nearly thesame as the factory sized papers. The ring crush index and tensile indexare respectively7.11N·m/g and2.38KN/m, being2.6and1.8timesmore than that of base paper. The water resistance performanceenhances greatly. The morphology of fibers in cross-section and surfaceof paper sized before and after is observed by SEM. Results indicatethat fibers of the sized paper are tight,orderly and smooth. It proves thatthe GMC sizing agent emulsion interacts with paper fiber and producesthe sizing effect.The synergistic sizing effect between GMC sizing agent and thecommercial synthetic sizing agents such as alkyl ketene dimers(AKD)and styrene-acrylate copolymer(SAE) is studied. The experimentalresults suggest that the synergy between GMC and SAE is prominent.The ring crush strength and tensile strength of sized paper by the mixedsizing liquid are much better than that of others. The ring crush indexand tensile index are respectively3.3and2.7times more than that ofbase paper. The water resistance performance of the different sized papers is determined by the water contact angle meter. Results showthat the water resistance performance of sized paper by the mixture ofGMC and SAE is strongest and the static water contact angle gets to137.6°. It is consistent with the determined results of value of waterabsorbing for60s.The third, cross-linking modified by the epichlorohydrin(ECH) asthe cross-linked agent and grafting modified by BA as the hydrophobicchain and potassium persulphate/sodium bisulfite as the initiator, thecross-linking/grafting modified collagen(CL-GMC) sizing agent isprepared. The separated and purified product is characterized by thesemodern instrumental analysis methods. With the value of waterabsorbing of sized paper by the cross-linking modified collagen(CLMC)liquid as the reference index, the cross-linking reaction conditions areoptimized by single factor experiment. As follows, the cross-linkingtemperature is50℃, pH is10, the reaction time is3h, the massconcentration of collagen is20%, the dosage of ECH is6%of that ofcollagen. With the grafting rate of CL-GMC as the reference index, thegrafting reaction conditions are optimized by single factor experiment.As follows, m(BA):m(collagen) is1:2, the dosage of initiator is4.5%ofthat of BA, the reaction temperature is80℃, the reaction time is3h.The CL-GMC sizing agent also appears a white emulsion with blue light.The solid content is22.3%and the viscosity is45mPa· s. Theperformance of electrolyte, acid and alkaliresistance and the storagestability are also excellent.The structure of collagen and CL-GMC product is characterized byFT-IR and Raman spectrometer. Results imply that cross-linked/graftedmodified to collagen by the ECH and BA successfully carry outaccording to the expected route, combining characteristic absorptionpeak of FT-IR and Raman. And the expected modified product is gotten.The particle size anddistribution of the CL-GMC emulsion isdetermined by the Laser particle size analyzer. Results show that theparticle size of CL-GMC emulsion is uniform and the mean particle sizeis164.2nm. The crystalline degree, morphology, element content andthermostability of collagen modified before and after are characterizedand analyzed by XRD, SEM/EDS, TG and DSC. Results suggest that thecrystalline trend of the CL-GMC product declines obviously and thestructure regularity of the collagen granule is destroyed by thecross-linking/grafting modification. Although there is traces ofchromium in the CL-GMC product, it would not affect their application.The thermal decomposition temperature of GMC is240℃. It increasesto380℃by the cross-linking/grafting modification. It suggests that theimprovement of thermostability for CL-GMC is more significant thanthat ofthe GMC.Coating CL-GMC emulsion on surface of the corrugated basepaper, the performance of paper sized before and after is characterizedby SEM, TG and DSC. The result shows that the paper fiber is tight,orderly and smooth, and thermal stability of the sized paper alsoimproves. With the ring crush index, the tensile index and the value ofwater absorbing as the review indicators, the sizing performance of thedifferent sized papers is studied. Results states that the ring crush indexand the tensile index of the paper sized by CL-GMC are superior to thatof paper sized by GMC and the mixture of SAE and GMC. Mixed theCL-GMC with SAE as the sizing agent, the sizing effect is better. Thering crush index and the tensile index respectively get to10.82N·m/gand6.14KN/m, and are1.52and2.58times more than that of the sizedpaper by the GMC. But the water resistance performance of the sizedpaper by CL-GMC is inferior to that of the sized paper by GMC. Thevalue of water absorbing improves drastically and surpasses to the othersized papers, mixing CL-GMC with SAE as the sizing agent.The water resistance performance of the different sized papers isanalyzed by the water contact angle meter. Result is consistent with thatof the value of water absorbing. The static water contact angle of thesized paper by CL-GMC is111.1°. Its water resistance performance isinferior to that of the sized paper by the GMC(123.7°) and the mixtureof SAE and GMC(137.6°). The static water contact angle of the sized paper by the mixture of CL-GMC and SAE gets to155.7°. Thecomprehensive sizing performance of the sized papers is good, withCL-GMC or the mixture of CL-GMC and other synthetic sizing agentsas surface sizing agent. It has a certain feasibility for industrialization.In this paper, it not only provides the important theory basis andguidance for developing the novel paper sizing agent, board bindingagent or other coating material, but also opens up the reliable way forrecyclinguse of the chromewaste collagen in the leather industry.