Preparation And Properties Of Modified Zanthoxylum Bungeanum Seed Oil/Layered Double Hydroxide Nanocomposite Fatliquoring Agent

The use of fatliquor increases the flammability and fogging value of the leather and adversely affects the safety of the leather.Therefore,it is imperative to develop a new leather fatliquor with flame retardancy and low fogging value.In this study,modified Zanthoxylum bungeanum seed oil/layered double hydroxide nanocomposite fatliquor is prepared by discarded Zanthoxylum bungeanum seed oil and layered double hydroxides as main raw materials.Then the nanocomposite fatliquor is used in leather fatliquoring process and explored the effects of LDH content on flame retardancy and fogging value of fatliquored leather.The main work is as follows:(1)Taking Zanthoxylum bungeanum seed oil as raw material,firstly,it is subjected to acid reduction treatment,and then succinate sulfonation modification is performed.Then the prepared fatliquor is applied to the fatliquoring process of leather.The results show that the optimal acid reduction process conditions for Zanthoxylum bungeanum seed oil are: the molar ratio of glycerol to Zanthoxylum bungeanum seed oil is 1:1,the amount of catalyst is 2%,the reaction temperature is 130 ?,and the reaction time is 3 h.The molar ratio of methanol to Zanthoxylum bungeanum seed oil is 1:1,the reaction temperature is 70 ?,and the reaction time is 3 h;the optimum succinate sulfonation process conditions are:: the molar ratio of Zanthoxylum bungeanum seed oil to maleic anhydride is 1:1.14,the reaction temperature is 110 ?,and the reaction time is 3 h;the molar ratio of maleic anhydride to sodium pyrosulfite is 1:0.55,the reaction temperature is 80 ? and the reaction time is 2 h.The modified Zanthoxylum bungeanum seed oil(MZBMSO)fatliquor has good stability and dilution stability,good resistance to demulsification to acid and alkali,and particle size of 248 nm.The application results showed that the mechanical properties of MZBMSO fatliquored leather are reach the standards of China's garment leather.;however,the length of the charring of MZBMSO fatliquored leather is 81 mm,the mass loss rate is over 60%,and the fogging value is 24.7 mg.These results indicated that the flame retardancy and fogging performance of MZBMSO fatliquored leather are poor and need to be improved.(2)The MgAl-LDH is modified by sodium stearate,and the stearic acid-LDH(s-LDH)is introduced into MZBMSO by in-situ method to prepare MZBMSO/sLDH nanocomposite fatliquor and apply it to the leather fatliquoring process.The application results showed that when the introduction amount of s-LDH is 4%,the flame retardancy of MZBMSO/s-LDH fatliquored leather is the best,compared with the MZBMSO fatliquored leather,the length of the charring is reduced by 49.4%,the smoke density is reduced by 76%,and the LOI is reached 28.0%;when the introduction amount of s-LDH is 1%,the fogging value of MZBMSO/s-LDH fatliquored leather is the lowest,and the drop rate is 19.3% compared with MZBMSO fatliquored leather.Based on the test results of the flame retardancy of the MZBMSO/s-LDH fatliquored leather.The gas phase and solid phase flame retardant mechanism of the leather are explored,indicating that s-LDH can penetrate into the collagen fiber,improve the fire resistance of the collagen fiber,and inhibit the release of flammable gas during combustion.(3)The MgAl-LDH is modified by sodium alginate(OSA),and then the OSA-LDH is introduced into the MZBMSO by solution blending and apply it in the leather fatliquoring process.The results showed that LDH mainly existed as a monolayer in the nanocomposite fatliquor.When m(OSA): m(LDH)is 1:0.4,LDH partially recovered into a layered structure in the composite fatliquor,and the MZBMSO/OSA-LDH fatliquored leather has the best flame retardancy.Compared with MZBMSO fatliquored leather,the length of the charring of MZBMSO/OSA-LDH fatliquored leather is reduced by 36.1%,the smoke density is reduced by 37.5%,and the LOI is 26.3%;when m(OSA): m(LDH)is 1:0.2,the anti-fogging performance of the leather is optimal,and the fogging value is reduced by 45% compared with the MZBMSO fatliquoring crust leather.Based on the detection result of the fogging value of MZBMSO/OSA-LDH fatliquored leather.The mechanism of action of OSA-LDH and collagen fibers is explored.OSA-LDH can be cross-linked to collagen fibers and evenly dispersed inside the crust,inhibiting the fogging of the leather by steric hindrance and adsorption effect.(4)The MgAl-LDH is treated with aqueous miscible organic solvent,and acetone-treated LDH(AMO-LDH)is introduced into MZBMSO by in-situ method to obtain exfoliated MZBMSO/AMO-LDH nanocomposite fatliquor and apply it to the leather fatliquoring process.When the AMO-LDH introduction amount is 10%,the fatliquored leather has the best flame retardancy.Compared with the MZBMSO fatliquored leather,the length of the charring is reduced by 73.3%,the smoke density is reduced by 69%,and the LOI is 28.3%;When the introduction amount of AMO-LDH is 6%,the fogging value of the MZBMSO/AMO-LDH fatliquored leather is the lowest,and the reduction rate is 84%.The flame retardancy and fogging value of MZBMSO/s-LDH,MZBMSO/OSA-LDH and MZBMSO/AMO-LDH fatliquored leather are compared comprehensively.The order of flame retardancy is as follows: MZBMSO/AMO-LDH fatliquored leather > MZBMSO/s-LDH fatliquored leather > MZBMSO/OSA-LDH fatliquored leather;the decreasing range of fogging value is as follows: MZBMSO/AMO-LDH fatliquored leather >MZBMSO/OSA-LDH fatliquored leather>MZBMSO/s-LDH fatliquored leather.