| Digital printing technology is a kind of emerging technologies that print designed digital artwork on textiles through a dedicated textile inkjet printer. It is also known as ‘non-forme’ printing, as the name suggests the technique can be achieved without the plate printing. And digital printing has no restriction on the printed pattern. It can print fabric patterns from simple to complex, even color photographs also can be printed. Compared with traditional printing processes, the digital printing workflow is greatly simplified, the work cycle is shortened. And even without the pattern printing paste formulation. It has avoided the waste of dyes and water, also get rid of the drawbacks of traditional printing of high energy consumption, high pollution. In general, it is a clean production process.Unlike traditional printing, When receiving digital printing with reactive dye ink, it is restricted by the digital printing equipment. The basic conditions required for reactive dyes binding cotton fiber can not achieve in the ink and the viscosity of the dye ink itself can not too high, which causes the ink to the fabric surface is easy to spread. So the fabrics must be pre-treated to prevent it. Therefore, this aspect of the pre-processing of digital printing of cotton fabrics were studied.After the preliminary experiments, 6 thickners has been chosen. They are DGT-6, DGT-7, SR-9000, DM-5310, CRD-40 and Ta. To characterize the effect of printing results we use apparent color quantity, edge sharpness, penetration, thickner removal rate and other parameters. The results showed that compared to DGT-6 which has the best overall performance among the other five thickners, Ta has lower dosage, higher thickening ability and good anti-spread characteristics. Its shortcoming is that its apparent color quantity is lower than DGT-6, de- paste performance slightly worse.Due to the weaknesses of Ta we did some chemically modified. After several attempts, we got DM-8812 which has a close performance comparable with DGT-6. Edge sharpness and color performance parameters of digital prints were used to characterize the effect of DM-8812. We have explored the influence of the other components of the pretreatment liquid to the printing results by the orthogonal experiment. And we got the preliminary best ratio of the pretreatment solution. The results showed that the apparent color yield in terms of the main factors are sodium bicarbonate and urea: with the increase amount of sodium bicarbonate the K/S value showed a decreasing trend after the first increases, and as the amount of urea increased the K/S value is decreasing. To edge sharpness the urea and DM-8812 are the main factors affect the degree of bleeding: with the increase of the amount of urea, bleeding is more serious and with DM-8812 dosage increase it is effective suppressed. Sodium bicarbonate, sodium sulfate and resist salt S are led to increased amounts of increased bleeding. Orthogonal experiment finally give us the optimal combination of the pretreatment liquid : 0.9% DM-8812, 2% sodium bicarbonate,6% urea,8% sodium sulfate,0 resist salt S.Finally, we have done the single factor experiments to verify the result of the orthogonal experiments. Experimental verification pretreatment liquid formula is : DM-8812: 0.7%, sodium bicarbonate : 2%, urea : 6 %, sodium sulfate: 6%, resist salt S: 0. The friction fastness of digital prints is level 3-4, and the washing fastness is level 4-5which are in line with the requirements of digital printing. At 20 ℃ the formulated pretreatment solution can be stored for at least 15-20 days and their constant printing results are ensured. |
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