Study Of Modified Dyeing And Air Finishing Technology For Denim

Denim products are popular and in great demand because of their unique style.The sizing and dyeing of denim warp and finishing of denim are two very important processes in the production of denim.In the 1980 s and 1990 s,denim sizing and dyeing joint production technology has been mature,but the existence of Coulomb repulsion between indigo cryptochromes and cotton fibers and low affinity leading to low dyeing rate has been a problem of indigo sizing and dyeing.Denim finishing let it get a unique style,conventional finishing need to be washed and penetrated,in order to get soft effect,often using formaldehyde,not easy to degrade the soft and smooth finishing agent for finishing,does not meet the green development trend.This project uses cationic modifiers and their compounding in denim dyeing process to improve the affinity between indigo dye and cotton fiber,improve the dyeing rate and evenness,reduce the number of dyeing dip and improve the dyeing efficiency;in denim finishing process using short flow air finishing instead of conventional finishing to improve finishing efficiency,save water resources and obtain soft handfeel at the same time.In this project,3-chloro-2-hydroxypropyltrimethylammonium chloride(CHPTAC)small molecule cationic modifier and poly(epichlorohydrin dimethylamine)large molecule cationic modifier were used to modify cotton fiber yarn,and the modification effect was visually characterized by the K/S value of dyeing depth and unevenness rate.In order to make the large and small molecule cationic modifiers complement each other,the two modifiers were compounded and the optimized process was obtained by orthogonal test and quadratic regression model using Minitab as follows: compounding ratio 1:3.38,concentration of sodium hydroxide 2.15.The concentration of sodium hydroxide was 2.15 g/L and the concentration of penetrant ZD was 3.55 g/L.The physical properties and dyeing effect of cotton yarn before and after modification were further analyzed,and the results showed that: the modification process does not cause damage to the physical properties of the yarn,and the color light of the modified cotton yarn is basically unchanged when compared with the unmodified cotton yarn dyed under the same conditions;the color fastness to rubbing and soaping is unchanged with CHPTAC modification only,and the color fastness to rubbing is decreased by 0.5 level with the modification containing poly(epichlorohydrin)dimethylamine,and the dyeing depth K/S value is increased by 8.41.The dyeing principle and the parameters of the dyeing process(half dyeing time,dyeing rate constant,equilibrium dye adsorption)of the modified cotton yarns were analyzed by using the dyeing kinetics.The parameters of the dyeing process were basically the same between the poly(ethylene chlorhydrin)dimethylamine modified and the compound modified yarns,and the dye content at adsorption equilibrium was increased by nearly 50% compared with the conventional dyeing and CHPTAC modified dyeing,and the dyeing rate constant was also higher than that of the conventional dyeing and CHPTAC modified dyeing.The compound modified cotton yarn can achieve the effect of traditional 8-tank dip-dyeing by 6-tank dipdyeing,which is equivalent to reducing 2 dyeing tanks in the dyeing stage of denim warp yarn,saving about 14 tons of water and 53.33 kw of electricity in total,effectively reducing water and energy consumption.This project developed PTT/spandex double core core yarn,PTT/PET double core core yarn,T400/spandex double core core yarn,spandex core yarn as weft yarn,and compounded modified top-dyed cotton yarn as warp yarn to weave denim with different elasticity.The results showed that the air finishing improved the fabric hand feel,elastic recovery rate,tear strength and elastic recovery angle,and the color light and rubbing fastness(wet and dry)were consistent with those of conventional finishing.The results show that the air finishing effect of different stretch denim is better and air finishing can be applied to different elastic fabrics;and under the air finishing process,the more elastic the weft yarn,the greater the thickness,the greater the weft slope,the better the weft wrinkle resistance and the more obvious the increase in weft tear strength.