The Techniques Of Bleaching And Dyeing Of Cork

Cork is one new decorative material which is one kind of special bark products derived from cork oak bark. In order to develop new techniques for cork bleaching and dyeing to employ the decorative cork products production, this thesis has been mainly developed the bleaching and dyeing process of cork including the selection of optimum decolourant (bleacher) and dyestuff and looking for the optimum conditions of bleaching and dyeing through orthogonal experiments, discussed the influence factors for cork bleaching and dyeing, and determined the lightfastness of the bleached and dyed cork based on cork granule, cork veneer and cork paper (pad).The research results showed that:1.The oxidative decolourants could be employed in cork bleaching and the reduction decolourants had not effect from six bleaching formulations test based on cork granule, cork veneer and cork paper (pad). And hydrogen peroxide (H₂O₂) less than 6% was chosen the optimum decolourant from the oxidative bleacher based on the multitarget thinking such as bleaching effects by measuring the color characteristics between untreated and treated cork paper with three oxidative bleachers, environment concerns to the low toxic and price of the chemicals. 2.The optimum conditions for cork bleaching through orthogonal experiment design were: the concentration of H₂O₂ 5ï¼…, pH value 9 or 10, time 90-120 minutes, the concentration of stabilizer 1.2ï¼…, temperature 70(C. And the importance of influencing factors was: temperature > time > the concentration of stabilizer > the concentration of H₂O₂ .3.The basic dyestuff was the best one for cork dyeing and others direct dyestuff, acid dyestuff and reactive dyestuff had no effect to cork dyeing based on the observation of dyeing tests of cork granule, cork veneer and cork paper (pad). 4.The optimum conditions for cork paper dyeing through orthogonal experiment design with three basic dyestuffs were conducted and results showed that different dyestuff had different optimum dyeing process, also the importance of influencing factors were different. The order of the influencing factors is: To Basic green: the concentration of dyestuff 1.5%, time 1 hour,the concentration of Na2SO4 1.0%, temperature 60(C, bath ratio 1:15; To Basic flavine O: the concentration of dyestuff1.5%, time 1 hour, the concentration of Na2SO4 1.0%,temperature 60(C, bath ratio 1:20; To Basic pink: the concentration of dyestuff 0.5%, time 3 hours, the concentration of Na2SO4 0.5%, temperature 100(C, bath ratio1:20.And the importance of influencing factors was: To Basic green: the concentration of dyestuff > time > bath ratio > the concentration of Na2SO4 > temperature; To Basic flavine O: the concentration of dyestuff > temperature > time > the concentration of Na2SO4 > bath ratio; To Basic pink: temperature > the concentration of dyestuff > bath ratio > time > the concentration of Na2SO4.5.Only basic dyestuff could be employed to cork dyeing by pretreatment with alkali and benzene-ethanol mixtures, and the dyeing effects of untreated and pretreated cork had not remarkably different. This indicated that cork do not need to pretreat with alkali and benzene-ethanol mixtures or need to find new pretreatment ways in cork dyeing. 6.Lightfastness of cork and treated cork was evaluated by UV light irradiation for 144 hours. The lightfastness of bleached cork paper with different concentration hydrogen peroxide (H₂O₂) was decreased when the concentration of bleacher increased. But to the different decolourant, the lightfastness were different. The lightfastness of NaClO₂ was better than that of H₂O₂ in same concentration. 7.The lightfastness of dyed cork paper with different concentration Basic pink was not close relation with the concentration of dyestuff. The lightfastness of dyed cork with the different dyestuff. Basic pink was best, Basic green better and Basic flavine O good. But lightfastness of treated (bleached or dyed) cork was lower than that of untreated cork.