Environmental Protection, Sizing, Dyeing And Finishing, Energy Saving And Emission Reduction

In recent years, with the increasing production of grey cloth and printing and dyeing cloth and the increasing demand for environmental protection, the standard of sewage discharge in textile industry is getting higher and higher.

According to experts, the COD value of pretreatment wastewater in printing and dyeing industry is about 40%~60% of the total amount of COD emissions in the printing and dyeing industry, and the main reason for the high COD value of the pretreatment wastewater is the PVA and other slurry which is difficult to degrade.

Therefore, solving the environmental problems of textile sizing and reducing the COD value of desizing waste liquor are the common goals pursued by the cotton textile industry and printing and dyeing industry.

　　環保上漿是發展需要

Textile sizing is a key link in the entire weaving process. The quality of sizing plays a decisive role in weaving efficiency.

To ensure smooth weaving, yarn sizing must be done to enhance yarn strength, wear resistance and hairiness.

However, when the warp and weft yarns are interwoven on the loom, the slurry adhered to the yarn will accomplish the mission and become an obstacle to the dyeing and finishing of the rear track.

Because before desizing and finishing, desizing is necessary and must be removed.

According to the national standards for wastewater discharge, desizing waste liquid should be degradable and recyclable. Therefore, ensuring the environmental protection of textile sizing is very important for energy saving and emission reduction in dyeing and finishing.

　　PVA漿料不能滿足環保要求

Polyvinyl alcohol (PVA) is a kind of polymer with good film forming property. It is one of the best film forming properties in commonly used slurry.

Before the 70s of the last century, because PVA had very low BOD (biochemical oxygen demand), its harm to the environment has not attracted much attention, so the market of PVA used for textile sizing has been expanding.

However, with the increasing demand for environmental protection, PVA was first introduced to the ranks of pollutants in the United States in 1978, because it is stable to acids, alkalis and microbes, and is not easily decomposed.

　　推行環保上漿對環境負責

Although PVA has excellent sizing performance, its biodegradability is poor, and it can not meet the environmental requirements. It is an indisputable consensus to use environmental slurry to replace PVA sizing.

China's cotton textile industry has also been actively promoting propaganda and promotion of environmental protection sizing technology in textile sizing.

In 2008, the cotton textile association and the printing and dyeing Association jointly launched promotional activities without PVA sizing, and evaluated the environmental evaluation of the desizing waste liquid of grey fabrics.

Through comprehensive evaluation of such indexes as net yield, CODcr, BOD5, biodegradability (BOD/COD), ammonia nitrogen content and phosphorus content, the Cotton Spinning Association and the printing and dyeing Association recommended 10 excellent products without PVA sizing. 9 excellent products without PVA sizing were recommended, and 10 products without PVA sizing were recommended.

This year, the cotton textile association and the printing and dyeing Association will continue to carry out the activities of recommending "no PVA sizing products".

These activities in recent years have effectively promoted the process of replacing PVA sizing, and have also been actively supported and supported by the vast number of textile enterprises and pulp manufacturers and experts and scholars.

Over the past few years, from the effect of promoting the sizing of PVA instead of PVA sizing on pure cotton medium and fine products, the amount of PVA used in polyester cotton products and high cotton, high density, high density products has been gradually reduced.

Printing and dyeing enterprises are also actively using gray cloth without PVA sizing to boost PVA sizing.

From the development of more than ten years, it is not easy to replace PVA with environment-friendly slurry. Various market factors, technical factors, social responsibility and benefit factors, policies and laws and regulations are affecting the process of applying environmental protection slurry.

More and more high, whether the pulp contains phosphorus or content, and is easy to biodegradate and so on; three is the demand for cleaning and energy saving in the process of slurry production, sizing production, weaving production, dyeing and finishing, and so on; four, the capability of slurry research and development is weak, and it can be comparable to PVA sizing performance, good performance price ratio, stable performance and less mature products; five, the pursuit of corporate social responsibility and enterprise efficiency is different, so it is easy to be affected by the price drop of PVA, and giving up no PVA sizing; six, the driving force of the market is insufficient, and the downstream printing and dyeing enterprises have little demand for no PVA sizing cloth, and no PVA sizing is still in a passive situation with less demand. Specifically, the first is the improvement of yarn and fabric product grades, the requirements of sizing and technical difficulties, and the two is environmental protection requirements.

All these factors make the process of replacing PVA completely slow, but it has achieved obvious results in less PVA.

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　　上下游應聯手促進無PVA上漿

Now, when studying the textile sizing process, the engineers of textile sizing have changed the concept that they only looked at the requirements of dyeing and finishing without the requirement of dyeing and finishing. The environmental protection and energy saving of dyeing and finishing have been selected as one of the important factors for sizing and formulation.

Sizing can meet the requirements of weaving.

The quality of sizing is the key factor to ensure the weaving quality. The purpose of sizing is to evenly adhere the pulp to the inside and outside the yarn, making the yarn wear-resistant, smooth and flexible, so as to adapt to the tension change and strength requirement of high-speed weaving.

It is easy to degrade pulp with little environmental pollution.

The main size must meet the environmental requirements, and the environmental protection of other auxiliary slurry must be considered to ensure the environmental requirements of the whole slurry formula.

The main sizing agent of BOD5/CODcr or more should be selected, and the biological treatment of wastewater is better. For example, high performance modified starch, degradable polyacrylic acid slurry, etc., the main size without phosphorus or low phosphorus content is 0.3.

The grey cloth without PVA sizing provides the necessary guarantee for improving the dyeing and finishing quality.

At present, people's requirements for quality, color, handle and functionality of the products are getting higher and higher. To achieve these requirements, the quality of pretreatment before dyeing and finishing is the key link. Then the problem of PVA desizing is also highlighted. If PVA's grey cloth is not pure, it will appear dyed shade and depth difference.

Sizing without PVA is also a prerequisite for using biochemical dyeing and finishing technology.

Biochemical dyeing and finishing process can not only effectively reduce processing procedures, shorten processing time, reduce energy consumption and water consumption, but also greatly reduce processing costs.

The application of biotechnology can bring hope to the printing and dyeing industry to achieve cleaner production.

But the premise of application is that it can not contain PVA.

Therefore, sizing without PVA has become an urgent problem to improve the quality of dyeing and finishing and the application of biotechnology.

Some experts have suggested that the environmental pollution problem caused by PVA slurry can be taken by the textile industry at present. The countermeasures are to develop commercial PVA degrading enzymes and their desizing processes, or to carry out the oxidative desizing process instead of the existing alkali desizing process.

The measures that do not need PVA are: developing degradable environment-friendly slurry, such as high performance deep modified starch, developing natural polymer slurry, high performance and easily degradable polyacrylic acid slurry, low viscosity modified PVA, optimizing slurry formula, studying less component and multifunctional environmental protection agent, using advanced spinning process, improving yarn quality, applying advanced sizing process technology, reducing sizing capacity, and application of PVA recycling and recycling technology, at present can not completely abandon PVA sizing, reduce PVA's environmental pollution, and recycling PVA is an effective measure.

The implementation of PVA free sizing, especially the development and application of key technologies for textile sizing, needs the encouragement and support of national policies.

The cotton textile industry and printing and dyeing industry will also work together to achieve the green pulp each rice cloth and reduce the COD value of each ton of desizing waste liquid.