Study On The Structure And Removal Technique Of Oligomers In The Recycled Polyester Trademark Fabric

Common polyester fibers and recycled polyester fibers are both facing the same problemthat oligomers percipitated from the fabric. When the recycled polyester fibers are used toproduce superior quality trademark cloth, many gray powders (it includes linear oligomers,cyclic oligomers and polymer additives residues, etc.) precipitated in the calendering process.The presence of gray powder has seriously impact on the quality of trademark fabrics; theeffect of printing, even can reduces productivity.therefore,This article based on the study andcharacterization of the major components of the gray powder,Preferably oligomer inhibitorauxiliary,The impact of oligomer inhibitor auxiliary and pre-treatment conditions on thecontent of surface oligomers of the fabric were explored, and the pre-treatment process wasimproved and optimized,So the the content of surface oligomers of the fabric were reducedduring the calendering process,and the quality of the trademark cloth and printing effect wereimproved.Firstly,the solubility property of gray powder was analyzed,Then,thecomposition,chemical structure and properties of the main component of gray powders werestudied by the testing means of infrared spectrum (FT-IR), ultraviolet spectrum(UV), gelpermeation chromatography(GPC),differential scanning calorimetry (DSC) and nuclearmagnetic resonance spectroscopy (1HNMR).The results of experiment were given.The graypowder had a good solubility in chloroform,the dissolved mass fraction of the gray powderreached above75%,and the main component of gray powder was poly (ethylene terephthalate)three membered cyclic oligomer.Which was stable and crystallize,its maximum absorptionwavelength ultraviolet near248nm and melting temperature at about314℃.The structure and optical absorption properties of surface oligomers were studied throughinfrared spectrum,thin-layer chromatogram, ultraviolet spectrum.And on this basis, Selectingappropriate oligomer inhibitor auxiliary used in pre-treatment process.The results confirmedthat the surface oligomers of the chloroform extraction and the oligomers of gray powder havethe same chemical structure.Which was poly (ethylene terephthalate) three membered cyclic oligomer. Its the biggest ultraviolet absorption wavelength at about251nm;The study foundthat the mass fraction of oligomers of recycled polyester fibres was higher than the commonpolyester fibers, and the mass fraction of oligomers were1.98%and1.52%respectively, Butthe content of surface oligomers had a little difference,and the mass fraction of surfaceoligomers were around0.35%;The single non-ionic surfactant T-80, anionic surfactant SDBS,the mixed surfactant (T-80+SDBS)and oligomer inhibitor auxiliary DM for the surfaceoligomers removal of recycled polyester fabric all have certain effect,When the treatmenttemperature was120℃,The surface oligomers decrease rate can reach45.521%,27.239%,68.190%and45.521%respectively, So the oligomer inhibitor auxiliary DM has batterremoval effect of surface oligomers than the mixed surfactant (T-80+SDBS), Therefore, thisarticle choose oligomer inhibitor auxiliary DM,Which used in polyester fabric pre-treatmentprocess.The pre-treatment process of effective removal surface oligomers of recycled polyesterfabric was studied,The best removal process of surface oligomers,Which is the first viaultrasonic/alkali coordinated pre-treatment, again after desizing and scouring one bathpre-treatment.The optimal pre-treatment process conditions for the surface oligomers removalof recycled polyester fabric were as follows:ultrasonic frequency40kHz,ultrasonic power80W,ultrasonic/alkali treatment time15min, the processing temperature70℃， NaOHconcentration9g/L,bath ratio1:50; The optimal desizing and scouring one bath pre-treatmentprocess conditions for the surface oligomers removal of recycled polyester fabric were asfollows:desizing agent TF-127K6g/L, TF-1016g/L,high-efficiency scouring agent TF-1886g/L,hydrogen peroxide H2O22g/L,sodium hydroxide NaOH9g/L,oligomer inhibitorauxiliary DM4g/L,,bath ratio1:50,treatment time15min,treatment temperature98℃.According to the above process to deal with polyester fabric,Compared with theconventional pre-treatment process, Using high temperature heat treatment method to judgethe optimal process whether to effectively reduce the content of surface oligomers of thepolyester fabric,The results of experiment were given,The mass fraction of surface oligomerscan be decreased from0.713%to0.546%,and the surface oligomers decrease rate was23.422%,During the heat treatment temperature of190℃, the processing time for5min.Therefore, Compared with the conventional pre-treatment process, The ultrasonic/alkali system pre-treatment, then after desizing, scouring one bath pre-treatment can effectivelyreduce the surface oligomers agglomeration problem during heat treatment.The crystalline morphology,thermal property, mechanical properties of recycledpolyester fabric after ultrasonic/alkali coordinated pre-treatment were analyzed by the testingmeans of x-ray diffraction(XRD),thermo gravimetric analyzer(TGA),universal material testingmachine. The results showed that the thermal decomposition temperature, breaking strengthand crystallinityof the fabric were decreased slightly after ultrasonic/alkali collaborativetreatment,and the radial strength loss was13.4%, the latitudinal strength loss was8.3%, Thephysical properties of recycled polyester fiber had less influence after the optimalpre-treatment process,and the trademark cloth also can be used.Theoretical basis and specific process guidance were provided for the production throughthe structure and removal technique of oligomers in the recycled polyester fabric were studied,Its solve the problem of oligomers precipitation,improve the quality and printing effect oftrademark cloth.