| Cotton fabric has become one of the most widely used textile materials because of its comfortable wearing,hygroscopicity,breathability and softness.Unfortunately,cotton fabrics are prone to wrinkles due to friction between fibers during wearing and washing,and the uneven appearance of the fabrics causes great inconvenience to user.With the increasing demand for natural fibers,anti-wrinkle finishing has become an important post-finishing process of cotton fabric.Anti-wrinkle finishing agents for cotton fabrics can be divided into two categories:formaldehyde finishing agents and formaldehyde-free finishing agents.Formaldehyde finishing agents are mainly N-methylol resin compounds,such as dimethylol dihydroxy ethylene urea(DMDHEU,2D Resin),this type of compound has high reactivity and excellent cross-linking effect,but the formed ether bond is easy to hydrolyze and break and release free formaldehyde,which is harmful to human health.As an alternative finishing agent of 2D resin products,formaldehyde-free finishing agents mainly include dialdehydes,epoxy resins,polyurethanes,silicones,polycarboxylic acids,ion crosslinking,etc.Among them,there are many studies on dialdehydes and polycarboxylic acids.The cotton fabrics they finish have excellent wrinkle resistance,but there are problems such as strong damage and yellowing of the fabric.At the same time,the study also found that cotton fabrics generally have poor hydrophilicity and difficult to dye after anti-wrinkle finishing.This is because the cross-linking of anti-wrinkle finishing agent and cellulose is a complex covalent cross-linking process,which consumes a large amount of cellulose.Hydrophilic groups such as hydroxyl,at the same time,form complex network crosslinks inside the cellulose,which greatly reduces the micropores and internal specific surface area of the cellulose,and the hydrophilicity and dyeability of cotton fabrics are also greatly reduced.At present,the development and research of formaldehyde-free anti-wrinkle finishing of cotton fabrics has entered a bottleneck period,and it mainly focuses on the crosslinking mechanism,the finishing process,the influence of additives,and the compound application of polycarboxylic acids finishing agents.Few researchers start with the type,number,and reactivity of the crosslinking agent's reactive groups,and the new type of non-iron finishing agent designed and prepared has been reported.Studies have found that cotton fabrics are generally poorly hydrophilic and difficult to dye after chemical cross-linking.This is because the cross-linking of non-iron finishing agent and cellulose is a complex covalent cross-linking process,which consumes many hydrophilic groups of cellulose,such as the hydroxyl groups.In addition,cotton fabrics have high crystallinity and complex supramolecular structure,the chemical cross-linking reaction mainly occurs in the amorphous area of cellulose,forming complex network cross-links inside the cellulose,making a greatly reduced of the cellulose micropores and internal specific surface area,resulting in a significantly decrease of the hydrophilicity and dyeability of cotton fabrics.Therefore,this topic mainly focuses on non-reducing sucrose,trehalose,and raffinose as the main research objects,using periodate and 2,2,6,6-tetramethylpiperidine oxide(TEMPO)system to selectively oxidize.A series of formaldehyde-free hydrophilic anti-wrinkle finishing agents of glycosyl polyaldehyde and glycosyl polyuronic acid have been designed and successfully prepared.There are highly reactive aldehyde groups and hydrophilic hydroxyl groups in the molecular structure of the sugar-based polyaldehyde anti-wrinkle finishing agent,which not only ensures the full cross-linking of the anti-wrinkle finishing agent and cellulose,but also preserves the affinity of the cotton fabric to the utmost extent,and achieved a significant improvement in the anti-wrinkle,hydrophilic and dyeability properties of cotton fabrics.Glycopolyuronic acid anti-wrinkle finishing agent introduces carboxyl reactive groups on the basis of sugar-based polyaldehyde anti-wrinkle finishing agent.The carboxyl groups not only reduces the self-polymerization between aldehyde groups and hydroxyl groups in the finishing agent,but also can interact with cellulose through the esterification which can further improve the anti-wrinkle performance of the finished fabric.Through computational chemistry and molecular simulation methods,the differences of the cross-linking properties of sugar-based anti-wrinkle finishing agents with different sugar units,different molecular structures and different chain lengths were clarified,and their relationship with the anti-wrinkle properties of cotton fabrics.The main research contents are as follows:The preparation process of sucrose polyaldehyde(OSu)through selective oxidation of sodium periodate with sucrose was studied,analyzed the influence of oxidation conditions on the aldehyde content of OSu,and characterized the structure of OSu;optimized the anti-wrinkle finishing process of OSu finished cotton fabrics,analyzed its influence on the anti-wrinkle,hydrophilic and dyeing properties of cotton fabrics,and revealed the possible cross-linking mechanism of OSu and cellulose.Used NaClO/NaBr/TEMPO system and periodate system to prepare sucrose polyaldehyde acid finishing agent(openSu),which containing carboxyl and aldehyde group,analyzed the influence of TEMPO system on the carboxylation of sucrose,measured the carboxyl content and aldehyde content of openSu and characterized the molecular structure of openSu,the reaction mechanism of TEMPO system for selective oxidation of sucrose was also studied.The effects of catalysts and curing conditions on the anti-wrinkle properties of openSu were analysized,and the possible cross-linking mechanism of openSu and cellulose was proposed.The results showed that:OSu and openSu were successfully prepared,and their aldehyde contents were 18.42 mmol/g and 50.11 mmol/g,respectively.The introduction of carboxyl groups significantly reduced the polymerization between the aldehyde group and the hydroxyl group of the oxidation products;the cotton fabric after OSu and openSu finishing shown good anti-wrinkle performance,hydrophilic performance and dyeability;under the appropriate catalyst and curing conditions,the aldehyde group of OSu and the hydroxyl groups of cellulose were dehydrated to form ether bonds,and the aldehyde and carboxyl groups of openSu formed ether and ester bonds with the hydroxyl groups of cotton cellulose to realize the covalent cross-linking of the finishing agent and cellulose.The sodium periodate selective system was used to prepare trehalose polyaldehyde finishing agent(OTr),and the relationship between the aldehyde content of OTr and the oxidation conditions was analyzed,and the molecular structure of OTr was characterized,and its effect on the anti-wrinkle performance,hydrophilic performance and dyeing performance of cotton fabrics was studied,and verify the possible cross-linking mechanism of OTr and cellulose.Used TEMPO-laccase system and periodate system to prepare trehalose polyaldehyde acid finishing agent(openTr),analyzed the influence of oxidation conditions on the carboxylation of trehalose,and characterized the molecular structure of openTr,reveal the oxidation reaction mechanism of openTr;studied the effect of catalyst and curing conditions on the anti-wrinkle performance of openTr,and analyzed the possible cross-linking mechanism of carboxyl and aldehyde groups with cellulose.The results showed that:OTr was successfully prepared by the direct oxidation of NaIO4 system,and openTr could also be successfully prepared through the two-step method of TEMPO-laccase and sodium periodate,the aldehyde group content of OTr and openTr was 20.14mmol/g and 54.48mmol/g respectively.After OTr finishing,the maximum wrinkle recovery angle of the cotton fabric could have reached 227°,the stiffness was 5.96cm,the whiteness index was 72.5,and the strength retention rate was 68.5%,the wetting time was less than 2 seconds;after the openTr finishing,the anti-wrinkle,hydrophilic and mechanical properties of the fabric have also been greatly improved.The possible cross-linking mechanism of openTr and cellulose was similar to that of openSu,and it was also a covalent cross-linking reaction between aldehyde groups and hydroxyl groups were dehydrated to form ether bonds,and carboxyl groups and hydroxyl groups formed ester bonds.The selective oxidation system of sodium periodate was extended to prepare the raffinose polyaldehyde finishing agent(ORa),and the relationship between the aldehyde group content of ORa and the oxidation conditions was analyzed.The molecular structure,oxidation reaction mechanism,and cross-linking process of ORa and cellulose were analyzed;the response surface method was used to analyze its influence on the anti-wrinkle,hydrophilic and dyeing properties of cotton fabrics.Compared and analyzed the difference of TEMPO-laccase and TEMPO/NaClO/NaBr system on the carboxylation and oxidation of raffinose,determined the carboxyl group content and aldehyde group content of raffinose polyaldehyde acid finishing agent(open Ra);reveal the raffinose through its molecular structure characterization The oxidation reaction mechanism of open Ra;analyzed of the effect of finishing agent dosage,finishing solution pH and curing conditions on the anti-wrinkle performance of open Ra.The results show that the sodium periodate system can also be used for the selective oxidation of raffinose,and the ORa was successfully prepared,with an aldehyde content of 18.0 mmol/g;comparative analysis the difference between the TEMPO-laccase and TEMPO/NaClO/NaBr system in the preparation of carboxylated raffinose(oxyRa),which proved that the chemical method has the advantages of rapid reaction and high product purity;after anti-wrinkle and then dyeing and dyeing and anti-wrinkle finishing,it proved the defects of the anti-wrinkle finishing process after dyeing and the possibility of designing the finishing process of anti-wrinkle before dyeing by using glycosyl polyaldehyde anti-wrinkle finishing agent;after open Ra finishing,the anti-wrinkle performance of cotton fabric has been greatly improved,the wrinkle recovery angle can reach261.5°,WI was 61.5,and TS was more than 65%,and the finished fabric has excellent hydrophilicity and dyeability.Used monosaccharides(glucose and fructose),disaccharides(sucrose and trehalose),trisaccharides(raffinose)and tetrasaccharides(stachyose)as the research objects,the corresponding sugar-based formaldehyde-free anti-wrinkle finishing agents were prepared,evaluated the difference in anti-wrinkle performance,hydrophilic performance and dyeability;used Chem3D 19.0 software to calculate the molecular radius of the finishing agent and evaluated its diffusion rate in the fiber;calculated the number of reaction groups of the finishing agent,the number of reaction sites and the number of rotatable bonds were used to analyze the structural characteristics of different finishing agents;molecular dynamics simulation was carried out through Gromacs software to calculate the number of possible conformations of the finishing agent in a single cross-linking state,measured the distance between different cross-linking points,reveal the relationship between the effective cross-linking range of different finishing agents and the cross-linking property.The results show that:OTr,ORa,openTr,and open Ra exhibited excellent anti-wrinkle performance;the smaller the molecular radius,the easier the finishing agent will diffuse into the cellulose;the cross-linking radius distribution was calculated,and the most suitable crosslinking radius range was 3.5-6.0(?). |
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