The Study On Svnergetic Tanning With Nano-SiO₂/THP Salt And Regeneration Of Solid Wastes From Leather Manufacturing

Leather industry,which manufactures various leather product,making use of animal tissue such as pigskin,sheepskin and cattleskin,has long history in our country.China is a strong country in manufacturing leather,and more than 1,7000,0000 cattle and sheep skins are processed every year in China rencently.During the entire process of leather-making,tanning is a key process.Among current conventional tanning agents,including chrome tanning agent,aluminium tanning agent,aldehyde tanning agent,vegetable tannin,oil tannin,syntan and resin tanning agent,chrome tanning agent is considered as one of the best tanning agent.Unfortunately,in conventional chrome tanning method,the chrome agent can not be absorbed completely(generally only 60%-80%absorbed),and large amount of unabsorbed chrome is directly discharged into the waste water,which can do great damage to the environment.Additionally,the treatment of solid wastes produced during leather manufacturing has also been a serious social problem.In China,more than 1,400,000 tons of solid wastesare produced from leather manufacturing.The selection of tanning agent and the corresponding mechanism of tanning and the efficient utilization of solid wastes from leather manufacturing will be investgated systematically,and the main contents is listed as follows:1)the mechanism and technological conditions of in-situ tanning by nano-SiO2 was investgated;2)the leather powders with different diameters was furnished by ultrafine grinding,and then the powder was added to LDPE and HDPE,to prepare leather powder/PE composite materials through melt blending;3)in order to improve the compatibility between leather powder and PE,reactive compatibilization was introduced into the procedure,and PE-g-MAH and EAA were employed as compatibilizer respectively,and the collagen was used instead of leather powder to investgate the mechanism of reactive compatibilization,and corresponding composite material collagen/PE was prepared.In Chapter 2,the mechanism and technological conditions of in-situ tanning by nano-SiO2 was investgated systematically,in which TEOS was employed as precursor and modified oil employed as dispersion carrier.With the diffusion and permeation of self-made auxiliaries,the TEOS entered into the skin fiber.Through adjusting pH value,nano-SiO2 was generated in-situ and achieved the tanning of leather.The optimized process condition is listed as follows:pickled sheepskin(100%),deionized water(300%),NaCl(10%),SiO2(5%,the diameters of SiO2 particles were 100-150 nm),modified oil(5%),self-made auxiliaries(6%,auxiliary I,II and III was 2%respectively),tanning temperature was ?,the pH value of basifying was 6 and the duration of tanning was 5 h after basifying.The Ts value and tensile strength of finished leather reached 90.3? and 18.5 N·mm-2,respectively.Auxiliary ?,? and ?was 4-(pyridin-2-yl)-1,3-dithiol-2-one,2-methylsulfanyl-5,6-dihydro-2H-,3-dithiolo[4,5-b][1,4]dioxin-2-iumtetra-fluoroborate and ethyl 4-methyl-2-[4-(trifluoromethyl)phenyl]-1,3-thiazole-5-carboxylate,respectively.The in-situ synergetic tanning by nano-SiO2 and THPC was also investgated in Chapter 2 and technological conditions is listed as follows:pickled sheepskin(100%),deionized water(300%),NaCl(10%),SiO2(5%),modified oil(5%).The self-made auxiliary I(2%)was added to the mixture of modified oil and TEOS aqueous solution,and the mixture oscillated at 25? and then the pH value was adjusted to 3,THPC(6%)was added after 1 h,and auxiliary ?(2%)and auxiliary ?(2%)were added before the pH value was adjusted to 6 after another 1 h,constant temperature shaked 5 h.The Ts value and tensile strength of finished leather reached 98.8? and 25.7 N·mm-2,respectively.In Chapter 3,collagen/PE based composite was prepared from collagen and PE,and PE-g-MAH and EAA were employed as compatibilizer,and the mechanism of reactive compatibilization was also investgated.The optimized process condition is listed as follows:the polyethylene/collagen composites reached the optimal mechanical properties when the PE-g-MAH was used as compatibilizer and the weight ratio of PE/collagen/PE-g-MAH was 100:15:15,the elongation,tensile strength and impact strength were 88.6%,12.5 MPa and 26.7 kJ/m2 respectively,and the decomposition initial temperature was 462.50?;the composites reached the optimal mechanical properties when the EAA was used as compatibilizer and the weight ratio of PE/collagen/EAA was 100:15:20,the elongation,tensile strength and impact strength were 90.5%,11.8MPa and 21.5kJ/m2 respectively,and the decomposition initial temperature was 452.17?.In Chapter 4,leather powder(LP)/PE based composites,including LP/LDPE,LP/recycled LDPE,LP/HDPE,LP/recycled HDPE,were prepared from leather powder and PE,and PE-g-MAH and EAA were employed as compatibilizer.The optimized process condition of LP/LDPE is listed as follows:LDPE(100 PHR),leather powder(12 PHR,20 mesh),DCP(0.2 PHR),PE-g-MAH(10 PHR),reaction temperature was 180?,reaction time was 30 min,and the DSC peak value,elongation,tensile strength of the composite was 126.0?,102.9%and 15.1 MPa respectivelyIn order to prepare leather powder/HDPE based composites,the denaturation temperature of leather powder was increased via in-situ solid-tanning method.After the modification of leather powder by silane coupling agent,the tanning reagent was evenly sprayed onto the surface of leather powder to complete in-situ solid-tanning The Td value of leather powder was improved to 218.5? after treated with Blancotan BC-THPC at pH=3.0;The Td value of leather powder was improved to 235.1?after treated with catechin-black wattle extract at pH=7.5;The Td value of leather powder was improved to 228.3? after treated with THPC-Cerous chloride heptahydrate at pH=7.5.The Td value of leather powder was greatly increased after in-situ solid-tanning and meet the requirements of the technology process.In this dissertation,the in-situ tanning by nano-SiO2 was investgated,and the properties of finished leather such as Ts value resemble closely the effect of chrome tanning.The result provided a novel approach for the replacement of chrome tanning agent.Moreover,leather powder/PE based composites were prepared after the ultrafine grinding of leather solid wastes via reactive compatibilization.The result provided a novel approach for the comprehensive pollution-free utilization of solid wastes from leather manufacturing efficiently.