| In view of the environmental pollution caused by chrome tanning in the current tanning process,the development of chrome-free ecological leather manufacturing technology has become one of the most important directions in the leather industry in recent years.However,the positive charges of collagen fiber will be reduced after chrome-free ecological organic tanning,which lead to the decrease of binding sites of most anionic dyeing and finishing materials in traditional chrome tanning system(especially the fatliquoring agent which gives leather softness and other hand feeling properties),resulting in a significant decrease in the absorption and chemical bonding rate of dyeing and finishing materials,causing in color fading and poor handle of finished leather.Therefore,developing of amphoteric polymer fatliquoring agent which can match the organic chrome-free tanning system has become a hot spot.Based on the above reasons,imidazole ionic liquid,dimethylaminoethyl methacrylate,1,3-propane sultone,acrylic acid were used as raw materials to synthesize the amphoteric polymer with anions and cations via free radical polymerization and quaternization in this work.Then the synthesized amphoteric polymer was used in the chrome-free non-metal tanned leather fatliquoring process.In order to improve the adaptability of the subsequent anionic wet finishing materials and endow the leather with antibacterial function,taking advantages of imidazole ionic liquid,such as environmental protection,designability of molecular structure and antibacterial property,amphoteric polymer with anion and cation group based on imidazole ionic liquid was used to control the surface charge of the leather.The main research works are listed as follows:(1)Amphiphilic polymers were prepared by radical polymerization of 1-hexyl-3-vinylimidazole bromide([HVIM]Br),1-octyl-3-vinylimidazole bromide([OVIM]Br),1-decyl-3-vinylimidazole bromide([DVIM]Br)and 1-dodecyl-3-vinylimidazole([DDVIM]Br)with dimethylaminoethyl methacrylate(DMAE).The effects of the ratio of monomers,reaction time and initiator dosage on the synthesis conditions were investigated.The structure and properties of polymers were characterized by FI-IR,1H-NMR,X-ray diffractometer(XRD),surface tension tester and nano particle size analyzer(DLS).The results showed that the target product was successfully prepared,and the prepared copolymer had certain surface activity.The particle size of emulsion was mainly distributed among 67?400 nm.After that,the polymer and castor oil were compounded and used in the fatliquoring process of sheepskin white wet leather.The properties of fatliquored leather were measured by scanning electron microscope(SEM),ultra-depth of field microscope,thermogravimetric analyzer(TG)and softness instrument.The results showed that the softness,physical and mechanical properties of leather treated with the synthetic fatliquoring agent were improved compared with the unfatliquored leather.However,compared with the crust leather treated with commercially fatliquoring agent,the polymer fatliquoring agents prepared in this work still need to be improved in terms of softness,physical and mechanical properties.(2)In order to enhance the softness of crust leather and the binding ability of polymer and collagen fiber,four amphoteric polymers were synthesized by quaternization of copolymer p(DMAE-co-[HVIM]Br),p(DMAE-co-[OVIM]Br),p(DMAE-co-[DVIM]Br),p(DMAE-co-[DDVIM]Br)with 1,3-propane sultone.The expected structure of amphoteric polymers were proved by FT-IR,'H-NMR,gel permeation chromatography(GPC)and XRD.The number average molecular weight of the four amphoteric polymers measured by GPC is 6212 g/mol,4492 g/mol,4382 g/mol and 4027 g/mol separately.The antibacterial experiment showed that all of the four amphoteric polymers had good antibacterial effects.After that,the amphoteric polymer and castor oil were compounded for the fatliquoring of F-90 organic chrome-free tanned leather.The results showed that the absorption rate of dye was up to 99.01%after treated with amphoteric p(DMAE-co-[DDVIM]Br)PS fatliquoring agent.The dye bath was transparent and clear,and the K/S value(12.80)of the crust leather surface was higher than the K/S value(4.47)of the crust leather surface treated with the commercially fatliquoring agent.At the same time,the softness and physical and mechanical properties of crust leather treated with amphoteric polymer fatliquoring agents were better than those of the commercially available fatliquoring agent.(3)Based on improving the solubility of the amphoteric polymer p(DMAE-co-[DDVIM]Br)PS and solving the color fading problem of acrylic resin.An amphoteric polymer(pADD)was copolymerized with acrylic acid(AA),DMAE and[DDVIM]Br as monomers.The amphoteric polymer was characterized by FT-IR,1H-NMR,GPC,Zeta and surface tension meter.The results showed that the amphoteric polymer had the expected structure and the number average molecular weight of the polymer is 7414 g/mol.The surface tension was 22.9 nm,and the average particle size was 642.5 nm.The detection of ionic characteristics and isoelectric point(8.91)showed that the synthesized target products had obvious amphoteric property.The amphoteric polymer fatliquoring agent pADD-1 was prepared by compounding the amphoteric polymer pADD and castor oil,which was applied to F-90 tanned sheep wet white leather for fatliquoring experiments.The results showed that the absorption rate of amphoteric polymer fatliquoring agent was 95.3%,which was 19.8%higher than the commercial fatliquoring agent absorption rate.The crust leather had a bright color and no color fading problem after dyeing.Meanwhile,the amphoteric polymer fatliquoring agent had good antibacterial function.The size of antibacterial zone was 52.1 mm,and as a control the size of antibacterial zone without antibacterial material was 20 mm.A "monomolecular membrane"model was proposed in which amphoteric polymers and leather collagen were combined with fatliquoring sites under the organic chrome-free tanned leather system by adjusting the charge.The amphoteric polymer forms a molecular film on the surface of the collagen fibers,thereby achieve the isolation and lubrication of the collagen fibers.The penetration and dispersion mechanism of amphoteric polymer fatliquor in crust leather and the mechanism of action with collagen fibers were also studied.It was preliminarily confirmed that carboxyl group and quaternary ammonium group of the amphoteric polymer fatliquoring agent could combine with amino group,amide group and hydroxyl group in collagen molecule by ionic bonds and hydrogen bonds.(4)For the purpose of improving the comprehensive properties of crust leather such as softness,smoothness and fullness,the amphoteric polymer compound fatliquoring agent pADD-2 was prepared by using amphoteric polymer pADD,cow shoe oil,lecithin,lanolin and castor oil as raw materials.The optimized conditions to prepare pADD-2 were obtained as follows:the ratio of castor oil,lanolin,lecithin,and amphoteric polymer pADD was 2:4:3:2,the reaction time was 30 min,the reaction temperature was 60?,and the stirring speed was 600 r/min,the pH value of the reaction system was 6.5.The optimized pADD-2 was applied to F-90 organic chrome-free tanned sheepskin garment leather and the chrome-tanned leather fatliquoring process.Compared with the commercially fatliquoring agent,the results showed that the softness,tensile strength,and tear strength of F-90 organic chrome-free tanned leather after fatliquoring were increased by 90.20%,3.43%,and 2.12%,separately.The softness,tensile strength and tear strength of chrome-tanned leather were increased by 5.79%,8.93%and 75.93%,separately.The absorption rate of pADD-2 fatliquoring agent in F-90 tanned organic chrome-free tanning was 98.98%and the absorption rate of chrome tanned leather was 92.47%,which were 23.48%and 3.14%higher than those of commercial fatliquoring agent.The dye absorption rate of F-90 tanned leather dyeing was 98.65%and the dye absorption rate in chrome tanned leather dyeing was 89.94%,which were 9.31%and 5.69%higher than those of commercial contrast dyes respectively.The mechanism of amphoteric polymer fatliquoring agent on subsequent anionic materials in the ecological chrome-free tanning nonmetal system and sheep blue wet leather system were investigated.The results showed that the amphoteric polymer fatliquoring agent pADD-2 and F-90 organic chrome-free tanned white wet leather collagen fibers were mainly bonded by ionic bond and hydrogen bond.The main binding mechanism between amphoteric polymer fatliquoring agent pADD-2 and blue wet chrome collagen fiber were ionic bonds,hydrogen bonds and coordination bonds.The results showed that the amphoteric polymer fatliquoring agent will have a good application prospect for the ecological chrome-free tanning non-metallic system. |
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