Development history of dye processing technology
There are many varieties of dyes, but in terms of the physical form of their products, they can Divided into solid, liquid and slurry. It can be further divided into:
Solid dyes – powder, granular, dust-free powder, block, flake, short columnar;
Liquid dye——Water-soluble liquid and dispersion;
Slurry dye—— —Solid/liquid mixture.
Dyes are organic compounds that often complete chemical reactions in the presence of liquid. For this reason, the world’s first synthetic dye was first sold in liquid form. , Of course, the quality of the original dye was far different from today’s, and it can only be considered the original form of today’s liquid dye. At that time, about 20% of the products were in liquid form, and these liquid dyes were mainly vat dyes and mordant dyes.
By 1923, the British first added selected additives to the original dyes and crushed them to form a dispersion of insoluble disperse dye aqueous solution. By 1910, most dyes were processed into a certain size of fine powder after removing the moisture.
According to literature in 1924, about 80% of dyes were processed into fine powder at that time, and vat dyes had been produced with a wide particle size distribution, ranging from extremely fine to Powdered dye products up to 50um. However, the original powder dye had the disadvantages of serious dust flying and poor wetting performance.
After 1930, dyes in dispersion form have been further developed, but they still have the disadvantages of easy precipitation of dyes and poor storage stability.
The current liquid dyes have been optimized This performance has been significantly improved, and the storage time can reach more than half a year without deterioration. Liquid dyes have been continuously developed due to their low processing costs and easy use.
Since 1950, the emergence of sand mills has promoted the development of post-processing technology. Using sand mills for wet grinding can obtain finer particle size and distribution. narrowerparticles. The processing formula has been improved to make the basic particles of the dye reach about 1um. The quality of products produced using new processes and new equipment has been significantly improved, and the processing of non-water-soluble dyes has made great progress.
With the advancement of chemical machinery and equipment, granular dyes began to appear. The apparent particle size of granular dyes is 100~300um. There are hollow particles and solid particles. Its fluidity, wettability and dispersion are better than those of powdered dyes. At the same time, it overcomes the shortcomings of powdered dyes flying dust. This As soon as this dosage form appeared, it was immediately welcomed by the production and application departments. Now many dyes are processed into granular products.
Dye processing
The research content of dye processing technology mainly includes the determination of raw dyes and Treatment, research on the performance of processing aids, design and selection of processing equipment and research on processing technology.
If post-processing technology is complex, it is mainly because it is not very regular, has many individualities and few commonalities, and it is difficult to summarize quantitative rules. So people say that dye processing technology is a combination of science, technology and experience.
1. Dye processing has the following characteristics
① There are many varieties of processing, because dyes are Fine chemical products generally have a small production tonnage, many varieties, and certain differences in processing methods, so the processes and equipment are quite complex;
②Dye factories need to adjust dosage forms or change varieties according to market conditions, which requires processing equipment to have certain adaptability, production equipment to be multi-functional and highly mobile;
③The technical content is high. Post-processing includes many aspects and involves many professional knowledge. There are both physical changes and chemical changes during the processing, and many factors are both interconnected and mutually restrictive;
④ Product quality requirements are high. Commercial dyes have a number of economic and technical indicators, and some have formulated national standards. Production conditions are harsh and require stable operation. Operators should have high quality and Strong sense of responsibility.
2. Dye processing involves several aspects
2.1 Raw dyes Analysis
The raw dye analysis mentioned here refers to testing and analyzing the physical and chemical properties of raw dyes for the needs of dye processing. After years of research, it has been discovered that post-processing is by no means a simple physical process. Before dye processing, it is necessary to first analyze the intensity, color, hydrophilicity, crystal form, energy level, impurity content and many other indicators of the original dye. In order to determine Provide basic data for developing reasonable processing technology.
After the dye is synthesized, the raw dye filter cake is provided to the post-processing workshop through liquid-solid separation. After receiving the filter cake, the post-processing workshop first tests the raw dye.
Different dye varieties, different synthesis processes, even the same variety from different manufacturers, the same manufacturer from different production batches, the product quality may have some differences. Each batch of dyes must be thoroughly tested so that a correct processing method can be developed.
2.2 Processing aids
The so-called dye processing aids are added during the post-processing process of dyes to help improve the performance of specific dye commercial dosage forms (such as dispersion, thermal stability, dustproofness, anti-aggregation, solubilization, etc.) or Substances that are beneficial to improving given properties (such as leveling, dyeing promotion, deepening, etc.) and the properties of dyeing on fibers (such as color fixation, softness, etc.), enhancing heat resistance, maintaining or improving dispersion stability, and preventing dyes A substance that condenses and helps improve dyeing levelness.
Commercial processing is inseparable from additives. Without understanding the performance of processing aids, it is impossible to optimize the processing formula. Correct use of additives can improve dye quality, reduce production costs, and increase the added value of dyes.
In recent years, the auxiliaries used in dye processing have developed to hundreds of types of dispersants, which are used in large quantities and play an important role in the processing results. It is increasing year by year, and the physical and chemical indicators and economic indicators are also different. For example, lignin dispersants can already produce multiple series of varieties with different molecular weights and different degrees of sulfonation, and the appropriate variety can be selected according to needs.
For the processing of non-water-soluble (disperse, vat) dyes, a large number of additives need to be added to adjust the strength and other properties. There are many types of additives, and they are used. The properties shown in different dyes are also different, and the additive performance and physical and chemical indicators determine its scope of use. Only by understanding the performance can we use it correctly. Studying the compatibility of additives so that they can play the best role in the formula is one of the contents of post-processing technology research..
2.3 Processing equipment
Processing equipment (post-processing equipment) is the post-processing equipment As an important means of operation, reasonable design and selection of processing equipment are the primary conditions for the successful completion of post-processing operations. It can be said that the development of post-processing technology is inseparable from the advancement of equipment.
In other words, the development of equipment is also driving the continuous development of post-processing technology. In dye processing, the use of ultrafiltration and reverse osmosis membranes plays an important role in desalting water-soluble dyes and improving purity. The development and application of ultra-fine grinding equipment can reduce the dye particle size to about 1μm. Drying technology and equipment are also widely used. Currently, there are many professional drying equipment manufacturers conducting research and development on dye drying equipment, and an independent industrial sector has been formed. Domestic drying equipment can basically meet the needs of dye drying.
Some literature often divides processing equipment into the category of chemical equipment and regards it as a general equipment of chemical equipment. From the dye professional point of view, it should also be regarded as special equipment. In dye processing and post-processing, due to the characteristics of dye production and commercialization, these factors are very closely related. General equipment has no special effects when used, and product quality is highly dependent on equipment to some extent. Only Only targeted design can unleash the maximum potential of equipment.
2.4 Processing technology
Processing technology is a comprehensive application of the above three parts method. Practice has proved that the same raw dyes, auxiliaries and equipment can produce completely different results using different processing techniques, which shows the importance of process conditions. It is not difficult to see from the above introduction that these four aspects mark the technical level of post-processing.
Many large foreign companies have their own professionals engaged in research work in this area, and some even have more personnel engaged in post-processing technology development than synthesis personnel. If the post-processing process is reasonable, the purpose of reducing production costs, protecting the production environment, and improving product quality can be achieved.
These four factors are interrelated and restrict each other, and each one is indispensable. It can be considered that the comprehensive application effect of the above four factors is a concrete reflection of the level of post-processing technology.
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