The Release Formaldehyde In Steaming Moist Cross-Linked Fabrics

The release formaldehyde in the low or ultra-low formaldehyde easy care finishing was concerned.In this research,the cotton fabrics were treated with ultra-low formaldehyde finishing agent of SDP1 to improve easy care performances by the conventional pad-dry-cure process and steaming moist process.The high release formaldehyde from the finished fabrics in steaming moist cross-linked process is studied.Compared with the conventional pad-dry-cure process,the steaming process can impart the treated fabrics better easy-care properties,higher tensile and tear strength retention,good abrasion resistance and whiteness,and a pleasing handle,which can also be derived from the result of Ding's paper.The only disadvantage is the higher formaldehyde release from the finished fabrics.In order to analysis the reasons(hydrolysis of covalent bond between fiber and cross-linking agent,uncross-linked agent or single-end products of-NCH₂OH )for the higher formaldehyde releases from finished fabrics in the steaming moist process, three groups of experiments were designed:â‘ The multiple release formaldehyde and the corresponding WRA of the two treated fabrics without washing were studied. With the similar WRA,the release formaldehyde in steaming moist process (206mg/kg) was higher than that of in pad-dry-cure process.WRA decreased gradually from 274°to 234°with an increase in the release formaldehyde in steaming moist process while WRA were stable relatively in 270～275°in pad-dry-cure process.The remaining catalyst may make the covalent bond between fiber and cross-linking agent hydrolysis,resulting in a decline in WRA and a crease in release formaldehyde.â‘¡The multiple release formaldehyde and the corresponding WRA of the two treated fabrics with one time washing were studied.With the similar WRA, after one time washing,the release formaldehyde in steaming moist process (233mg/kg) is higher than that of the pad-dry-cure process(54mg/kg).The former fell to 53mg/kg and the latter fell to 24mg/kg in the second formaldehyde release.After one time washing,the formaldehyde released multiply has no effect on WRA in steaming moist process and pad-dry-cure process.WRA in pad-dry-cure process is 260～264°and 247～250°in steaming moist process.It may be surmised that, cross-linking agent may crosslink with each other and then link with fiber when the fibers were in the swelling state.The oligomer is useful for WRA but non-washable. Therefore the WRA decreased 16°after one time washing.The hydrolysis of oligomer may produce single-end products of-NCH₂OH and make formaldehyde release higherâ‘¢The release formaldehyde and the corresponding WRA of the two treated fabrics with repeated washing were studied.After repeated washing(washing times＞5),the release formaldehyde were in 110～130mg/kg in steaming moist process and 20～30mg/kg in pad-dry-cure process,WRA were about 250°and 260°,the SA was similar in 3.6.The finished fabrics in steaming moist process have a better washable stability.The high release formaldehyde was from the rupture of covalent.It may not affect WRA and SA with so small amount.The detailed cross-linking of fabrics was conducted by means of EA.The results showed that:Due to the mild reaction conditions in the steaming moist process,the fiber cross-linked with finishing agent insufficiently and there existed uncross-linked agent,Cross-linked dimmer and single-end products of-N-CH₂OH.The covalent bonds of fiber with agent and the ether bonds in multimer were ruptured,resulting in Fiber and cross-linking between the covalent bond and the multimer of the ether bond hydrolysis rupture,which could generate many of-N-CH₂OH and lower WRA.The whole -N-CH₂OH released more formaldehyde.At the same time,experiments proved that the uncross-linked agent were not the main reasons for higher formaldehyde. As regards to the higher formaldehyde releases in steaming moist process,the finishing time,temperature,humidity and catalysts for steaming moist process were respectively studied.The results showed that:the release formaldehyde from fabrics can be reduced by increasing temperature or decreasing steaming humidity,and extending finish time is not obvious.Chosen MgCl₂·6H₂O/GA as catalyst can further improve properties of finished fabrics,although not reduce the formaldehyde release from steamed fabric.In addition,strengthening washing and adding appropriate formaldehyde scavengers can also reduce the release formaldehyde.The effects of washing temperature and washing with urea were also studied.Finally,several formaldehyde scavengers such as urea,diglycol,polyethylene glycol and ethylene glycol were used to reduce the formaldehyde release.Selected warm-warm wash stalls,the release formaldehyde can be reduced to 74 mg / kg; Adding 20 g / L of urea or 50 g / L diglycol,the release formaldehyde can be reduced to about 80mg/kg;Using polyethylene glycol and ethylene glycol could not reduce the release formaldehyde effectively in steam moist process.