Factors affecting whiteness of heat transfer print

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Factors affecting the whiteness of cotton heat transfer printing products

heat transfer printing is a dry printing process without liquid medium, which has the advantages of realistic patterns, fine patterns, clear layers and so on. At present, heat transfer printing has been widely used in synthetic fiber products, and has not yet achieved industrial production on natural fibers. Our research group has developed a bridging agent. After cotton fabric is treated with this bridging agent, disperse dyes can be used for heat transfer printing, and the indicators of the product, such as washing resistance, friction resistance, lead screw wiping resistance, Perspiration resistance, can meet the national standards. However, during the experiment, it was found that the whiteness of cotton fabrics with different sources and the same tissue (refers to yarn count density) after heat transfer printing was quite different, that is, some were yellowing, some were graying, and some had good whiteness

cotton fabric has good heat resistance, and its whiteness difference is mainly determined by the heat resistance of different additives left on the fabric. After conventional pretreatment and bridging treatment before cotton heat transfer, the additives remaining on the cloth are mainly fluorescent whitening agents. Bayer will also launch insqin co manufacturer planner and bridging agent. It is speculated that the above phenomenon may be caused by the joint action of bridging agent and fluorescent brightener at a high temperature of 200 ℃. Because there is only one bridging agent developed by our research group, and there are many kinds of fluorescent brighteners, and the varieties used by different printing and dyeing plants are also different, it is obvious that the phenomenon of different whiteness is mainly caused by fluorescent brighteners

in order to explore the structure of bridging agent and fluorescent brightener and the influence of additives in fluorescent brightener products on whitening effect and heat resistance, 9 kinds of common fluorescent brighteners were selected for experiments, in order to provide some reference basis for the industrialization research of cotton heat transfer technology

1 experiment (omitted)

1.1 drugs and fabrics

fluorescent whitening agent VBL (powder), fluorescent whitening agent CXT (powder), fluorescent whitening agent Vbu (liquid), Hangzhou Huayang Chemical Co., Ltd; Fluorescent brightener N-C (liquid), fluorescent brightener S-C (liquid), fluorescent brightener cp-3d (bulk), fluorescent brightener cp-3l (liquid), Hangzhou Ludian Chemical Co., Ltd; Fluorescent brightener BA (powder), fluorescent brightener NT-3 (powder), Nantong Lisi Chemical Co., Ltd; Our research group made bridging agent; The fabric is pure cotton plain cloth after scouring and bleaching

1.2 process flow

1) fluorescent whitening of cotton cloth by absorption method (dosage, temperature, time, pH value, etc. shall be operated according to the best conditions of each brightener) drying

2) whitening cotton bridging agent treatment has organized resources with rich construction experience to enter the project construction (two dipping and two rolling, with a liquid rate of about 80%) for drying

3) whitened cotton cloth (or cotton cloth treated with bridging agent) is pressed and ironed at 220 ℃ for 30s

2 results and discussion

2.1 the effect of the molecular structure of fluorescent brighteners on the whiteness of heat transfer products of cotton fabrics

five kinds of triazine Aminostilbene fluorescent brighteners with known structures were selected to whiten cotton fabrics

the whitening effect of brighteners varies, and CXT has the best whitening effect. From the whiteness difference, the heat resistance of CXT, NT-3 and Ba is poor. After high temperature press ironing, the whiteness decreases by 21.92, 22.13 and 22.32 respectively, while the whiteness of Vbu and VBL only decreases by 7.74 and 10.17 after press ironing. It may be that the molecules of NT-3 and Ba contain multiple Oh, which is easy to be oxidized under the condition of high temperature and oxygen, thus reducing the whiteness; There are two Oh in CXT molecule, and the hydroxyethyl amino group formed is also prone to oxidation under high temperature aerobic conditions; However, Vbu has no oh in its molecule, and its heat resistance and oxidation resistance are relatively good. Therefore, it can be said that the less oxidizable groups contained in the brightener molecule, the better the heat resistance, and the whiteness of the cotton fabric whitened with it after heat transfer printing is better

2.2 the effect of additives in brightener commodities on the whiteness of cotton heat transfer products

in order to investigate the effect of additives in fluorescent brightener commodities on the whiteness, four commodities containing the same brightener structure and different additives were selected for UV spectrum detection. The absorption of these four brighteners in the UV region is completely consistent, and it is certain that their structures are the same. Different additives are added to make them not only used for whitening cotton, but also used for silk, acrylic, polyester and other fabrics. 3.2 flocking like interior materials; Different additives also give them their own advantages. Some have good light fastness, while others have a wider range of pH applications. So, do these additives have an effect on its whitening performance? Therefore, the cotton cloth is whitened with the above four brighteners, and then the whitened cotton cloth is pressed with a heat transfer machine. The whiteness values (Ganz whiteness 1 and Ganz whiteness 2) before and after pressing are detected respectively, and their whitening effect and heat resistance are analyzed

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