In recent years, with the production of grey cloth and dyeing cloth increasing year by year and the increasing environmental requirements, the textile wastewater discharge standards are also higher and higher. According to experts, the COD value of pretreatment wastewater accounts for about 40% ~ 60% of the total COD discharge of the printing and dyeing industry. Therefore, to solve the environmental protection of sizing and reduce the COD value of desizing waste liquid is the common goal of Cotton Textile Industry and printing and dyeing industry.
Environmental Sizing is the need of development.
Sizing is an indispensable key link in the whole weaving process. Sizing effect plays a decisive role in weaving efficiency. In order to ensure the weaving process smoothly, the yarn must be sized, so that the yarn strength increased, abrasion resistance increased, hairiness reduced. However, when the warp and weft yarns are interwoven on the loom to form the fabric, the size attached to the yarns completes the task and becomes an obstacle to the dyeing and finishing process. Because before dyeing and finishing process must desizing, and must be removed clean. According to the national standard of wastewater discharge, desizing wastewater should be degradable and recyclable, so it is very important to ensure the environmental protection of textile sizing and to save energy and reduce discharge in dyeing and finishing process.
PVA SIZE can not meet the requirements of environmental protection
PVA Is a kind of macromolecule with excellent film-forming property, which is the best one among common size polyvinyl alcohol. Before the 1970s, because PVA had very low BOD (biochemical oxygen demand) , its harm to the environment did not attract people's attention, so the market of PVA for textile sizing was expanding. However, in 1978, Pva was first listed as a pollutant in the United States due to its stability to acids, alkalis and general microorganisms.
The implementation of environmentally friendly sizing is responsible for the environment.
Although PVA has excellent sizing performance, but its poor biodegradability, can not meet the requirements of environmental protection, must use environmental protection slurry instead of PVA sizing, this has been an indisputable consensus. China's cotton textile industry in the textile sizing, also has been actively doing a good job in environmental sizing technology publicity and promotion. In 2008, Cotton Spinning Association and Dyeing Association jointly launched a PVA-free sizing publicity campaign, and gray cloth desizing waste water environmental assessment. The Cotton Spinning Association and the Printing and Dyeing Association jointly recommended 10 PVA-free sizing products based on the comprehensive evaluation of detergency rate, CODCR, BOD5, biodegradability (BOD/COD) , ammonia nitrogen content and phosphorus content, nine PVA-free sizing products and 10 PVA-free sizing applications are recommended. This year, the Cotton Textile Association and Dyeing Association will continue to carry out the“Recommended PVA sizing products” activities. In recent years, these activities have effectively promoted the process of replacing PVA sizing, and also received positive response and strong support from textile enterprises, sizing enterprises and experts and scholars.
In recent years, from the effect of promoting PVA sizing substitution, PVA sizing can be completely eliminated in pure cotton medium and fine count ordinary products, and PVA dosage is gradually reduced for polyester cotton and pure cotton high count, high density and high compactness products, it has also been effective in reducing use. Printing and dyeing enterprises are also actively using non-PVA sizing gray cloth, to promote non-PVA sizing.
From the development of more than ten years, it is not easy to replace PVA with environment-friendly pulp. Various factors such as market, technology, social responsibility and benefit, policy and law influence the process of using environment-friendly pulp. The first is that the quality of yarn and fabric is improved, and the sizing requirement and technical difficulty are increased. The second is that the environmental protection requirement is higher and higher, and the requirement is very high on whether the size contains phosphorus or the content of phosphorus, and whether it is easy to be biodegraded Third, the demand for cleaning and energy-saving in the processes of size production, sizing production, weaving production and dyeing and finishing production is becoming higher and higher, there are few substitute products that can be compared with PVA sizing with good performance-price ratio, stable performance and mature performance. 5. Enterprises have different pursuit of social responsibility and enterprise benefit, so they are easy to be affected by PVA price drop and give up PVA sizing without Pva Sixth, the market's driving force is insufficient, downstream dyeing and printing enterprises to seek non-PVA sizing gray fabric demand is not much, non-PVA sizing is also in the demand for less passive situation.