Study On Removal And Detection Of DMF From The Polyurethane Leather

Removing the trace amount of DMF residues from PU synthetic leather is focused onmore and more attention and becomes a new hotspot. The paper reports the results obtainedfor extraction of DMF based on the extraction and drying method and established a detectionmethodology of certain trace amounts of DMF in PU synthetic leather which had thebenefits of fast speed, high bioavailability and convenience. Using methanol as extractantwhile ultrasonic used in this study can be a great aid to extract the DMF from polyurethanesynthetic leather, meantime, the content of the DMF was gained using gas chromatographydetection,duringwhichn-butanol servedas internalstandard.Comparedwith theconventional methodsofextractingDMF. Ethanoland waterwerechosenas theextractionto removetraceDMF.When theethanolwasoflowconcentrationandtheliquid-solidratio was100.TheresidualDMFcontentdropped60mg/kgandremovalratewas96.8%.asto thismethod, itwasup to thesecondgradeofnationalstandard.Butitwas limited anddeficient becauseofhighenergy andtimeconsumption.Thusultrasonicwaschosento extractthe DMFfrompolyurethane syntheticleather.The working conditions of static extraction method were optimized as follows: ultrasonicfrequency of28kHz, ultrasonic power of200W,liquid-solid ratio of100mL g-1, leachingtemperature of60℃, and leaching time of30minutes. Extraction times of1time, residualDMFcontentwasupto135mg/kg and removalratewas92.9%The work also took the dynamic extraction into consideration, the results showed that wecan gained the a minimal amount of DMF residues, which can be up to105mg/kg and theremoval rate was94.5%. When leaching temperature was60℃, and leaching time was40minutes, liquid-solid ratio was200and the flow rate of extraction was180mL/min. Whiletheadded ultrasonicfield hadnoeffect on theamount ofDMFresidues.The practical application of industrial production was considered. Based on the dynamicextraction, PU synthetic leather was dried by far infrared with a temperature of110℃for40min. Under the conditions, PU synthetic leather in DMF minimal residual minimum canreach53mg/kg and theremovalratewas97.2%, Meetthenationalsecondary standards.The operating conditions of process PU synthetic leather were optimized by the method ofmicrowave and infrared drying combined extraction and microwave-assisted extraction-vacuum drying method. Under the condition of infrared drying with temperature of100℃for30min, the DMF residual content can reach as low as23mg/kg with removal rate of98.8% tomeetthenational standards.