| With the rapid development of leather industry, significant ecnomic benefit was created, but plenty of pollutants also were produced. Therefore, the recycling of leather wastes not only can reduce the pollution to the environment, and also can produce market value. In this study, the industrial collagen extracted from leather wastes was as raw material, two kinds of surface sizing agents for papers were synthesized by using vinyl monomer to modify collagen and via collagen to modify polyurethane. The structures and properties of the sizing agents were studied. The specific studies as follows.Firstly, the structure of collagen extracted from leather wastes were analyzed. The relative molecular mass, composition and content of amino acid of collagen were tested by GPC and automatic amino acid analyzer. The results showed that the weight-molecular mass of collagen was 1830, the collagen contained 17 kinds of amino acids and the total content of amino acids was 80.81%. This showed that the collagen had the basic properties of natural collagen.Secondly, the collagen, as the grafted main chain, firstly reacted with maleic anhydride (MAH), and then reacted with ethyl acrylate and styrene monomer, as a result, vinyl grafted collagen (VGC) sizing agent for papers was prepared in aqueous phase. The best prepared conditions were optimized through single-factor experiment and orthogonal experiment. Results showed that the dosage of MAH was 15% basing on the weight of collagen, m(modified collagen):m(monomers) was 4:6, m(EA):m(St) was 1:1, the dosage of initiator was 3% calculated according to the total weight of monomers and the reaction time was 2.5 h. The structure, morphology, crystallization properties and thermal stability were characterized by FT-IR,1H-NMR, TEM, XRD, TG and DSC. Results showed that the collagen reacted with vinyl monomers. The particle size distribution of VGC emulsion was relatively narrow and its average particle size was approximately 350nm to 400 nm. The crystallizing tendency and the thermal stability of collagen increased after modification.The VGC emulsion was applied in the surface sizing of the corrugated paper. The results showed that the optimal sizing amount of VGC was 8g/m2, the tensile index, ring crush index and water resistance of sized papers increased respectively for 12.46%,36.82% and 53.61% than that of base paper. Then the compound proportions of VGC with gelatinized starch and VGC with styrene-acrylic emulsion were studied, respectively. The results showed that the optimal proportion of VGC with gelatinized starch and VGC with SAE was 4:6 and 2:8. Lastly, the pilot study of VGC sizing agent was carried out in the factory. The pilot studies results of VGC sizing agent showed that the sizing effect used on high-strength corrugated paper and white board paper was good.The biodegradability of VGC sizing agent was evaluated based on BOD5/CODCr, OECD-301B, ATP test method, OECD-310B and comprehensive assessment method. The results showed that the BOD5/CODCr value, the IB index and the ATP evaluation index of VGC was respectively 0.36,138.82% and 106.25. The biodegradation rate of VGC before 14d was faster and the biodegradation rate was 64% and the IW index of VGC was 94.95. In a word, VGC was biodegradable material.Lastly, IPDI, PTMG,1,4-butanediol and DMPA were used as raw materials, the collagen was introduced during the preparation of polyurethane and the polyurethane sizing agent modified by collagen (CWPU) was synthesized. The best prepared conditions were optimized through single-factor experiment. The n(-NCO):n(-OH) was 4, the dosage of DMPA was 3.5% basing on the total weight of monomers, and the dosage of collagen was 10% according to the total weight of monomers. The structure and properties of CWPU were characterized by FT-IR, XRD and TG. Results showed that the collagen had reacted with polyurethane, the crystallizing tendency and the thermal stability of product increased after modification.The CWPU emulsion was applied in the surface sizing of the corrugated paper. Result showed that the optimal sizing amount of CWPU was 6g/m2, and the tensile index, ring crush index and water resistance of sized papers increased respectively for 25.22%,14.89% and 23.89% than that of base paper. The compound proportion of CWPU and gelatinized starch was studied. Result showed that the optimal proportion of CWPU with gelatinized starch was 4:96, and the tensile index and ring crush index of sized papers increased respectively for 26.85% and 38.71% than that of base paper.The biodegradability of CWPU sizing agent was evaluated by BOD5/CODCr method and the effect of the dosage of collagen on the biodegradability of CWPU was studied. The results showed that the BOD5/CODCr value of CWPU prepared under optimal condition was 0.32, so it was biodegradable material. With the increase of dosage of collagen, the BOD5/CODCr value of CWPU sizing agent increased, the biodegradability became better. |
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