| Starch is a renewable and macromolecular compound of greenenvironmental protection. Graft modification of starch is a common andimportant modification method. The traditional method was use of vinylmonomer to preparartion modified starch with cerium ammonium nitrate andammonium persulfate as initiator. Its advantage is graft modified reaction easilyand its disadvantage is the structure of modified profucts regulation difficultly.Recently, enzyme catalysis graft polymerization has attaracted wide attentionboth at home and abroad due to the characteristics of high efficiency, strongselectivity, mild reaction conditions, structure-controllable, green environmentaland so on. Products, which are difficult to synthesize by means of traditionalchemical method, can be obtained by enzyme catalysis. In this paper, the graftcopolymerization of starch and phenols and the polymerization of sulfonylureamethylation phenol were carried out using horseradish peroxidase (HRP) ascatalyst. The products were used as leather tanning agent, and the applicationeffect was studied.Firstly, it was explored that the graft copolymerization of phloroglucinol(PG)、Hydroxyl benzene sulfonic acid sodium(HBS) and degraded starch, whichwas catalyzed by hrseradish peroxidase (HRP)/H2O2, and starch-phenols graftcopolymer was synthesized. It was investigated the effects of degradation degreeof starch, monomer ratio of phenols and polymerization temperature, system pH,the dosage of HRP on structure，reaction time and applied properties ofmodification starch. The results indicated that the suitable degradation starch wasprepared by15g starch with0.3g a-amylase. The optimum reaction conditionsare12:20mass ratio of PG to HBS, polymerization at30°C, pH7.0,10mL ofHRP and3h of reaction time. The surface tension of aqueous modificationstarch solution was26.6mN/m. The modification starch has excellent tanningeffects due to its short branch chain of conjugated structure. The conjugated structures and starch have synergistic effect on leather fibers. The results showedthat the activity of functional groups and bonding power with leather fibers wasenhanced. The chemical structure of the graft modified starch was characterizedby FTIR，1H-NMR，GPC and UV-Vis. The modified starch was used as tannageand retannage respectively in applied experiment. The shrinkage temperature (Ts)of tanned leather reached78.3°C and the rates of thickness of retanned leatheraverage reached26.6%.The relationship of monomer structure and properties of the graftcopolymers was studied according to applying experiment and GPC detectionmethod. The graftcopolymer of phloroglucinol/Hydroxyl benzene sulfonic acidsodium and starch has the best properties with the catalytic system of HRP/H2O2.While the graftcopolymer modified by phenol has the worst properties.Meanwhile the relationship of monomer structure and performance ofgraftcopolymers was explored. Result verified the theory that monomerstructures have influence on monomer activity.The sulfomethylate reaction of phenol was carried out using sodiumsulphite/sodium hydrogensulfite/formaldehyde as modifing reagent. Then thepolymer of sulfomethylated phloroglucinol was prepared by HRP/H202asinitiator. Effects of main influencing factors on sulfomethylate reaction andpolymerization were discussed respectively. The structure and properties of thecopolymer were characterized by Fourier Transform Infrared spectroscopy(FTIR) and ultraviolet spectroscopy (UV-Vis). Molecular weight (MW) wasdetermined by gel permeation chromate graphy (GPC). The result showed thatthe maximum Mnof the copolymer is about3.4×104. The copolymer was used astanning and retanning agent, applied results showed that the shrinkagetemperature (Ts) of tanned leather may increase from46℃to76℃. It hasexcellent retanning properties when the dosage of the tannage was7％of theleather quality. The thickening rate of retanned leather was18.3%. Morphologyof fibers was observed by SEM, the products have good dispersion effect tofibers. The testing results showed that the expeted product was abtained.The innovation in this study was that the graft copolymer of starch andphenols was synthesized by HRP catalytic polymerization, and at the same timethe polymer of sulfonylurea methylation phenol was carried out using sulfomethylation and enzyme catalyzed copolymerization. |
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