Functional dyes are a type of dyes with special functions or special professionalism. This special function is usually related to optical, electrical, thermal, chemical, biochemical properties related to modern high and new technical fields. This type of dye absorbs very little energy and can produce certain special functions. Therefore, it uses less and has high prices and is of great economic benefit.
At present, functional dyes have been widely used in high-tech fields such as liquid crystal display, thermal pressure sensitive recording, optical disc recording, photochemical catalysis, and photochemical therapy in some countries. Major dye companies in Japan have made the production of functional dyes the focus of their respective developments. In addition to photography, electrostatic copying, copying and other varieties, domestic functional dyes have almost no application in other fields, or are still in the trial production stage and have not received enough attention. In particular, the application of functional dyes in dyeing and finishing has begun to emerge, and their research, manufacturing, application and management levels are still far behind those of advanced countries. It should be said that functional dyes are worthy of dye workers and dyeing and finishing workers. Strive to explore new areas.
1 Classification and development methods of functional dyes
1.1 Classification of functional dyes
Functional dyes are in a stage of rapid development, and the classification of them is not uniform. According to the function, they can be classified into the following categories Classification is as follows.
Color-changing heterogeneous dyes: light-changing, thermal-changing, electrical-changing, wet-changing, pressure-sensitive (pressure-sensitive) color-changing dyes
Energy-converting dyes: for luminescence, solar energy conversion, laser, organic nonlinear optical materials Dyes, etc.
Dyes for functional dye information and display recording: liquid crystal, color filter, optical information recording, electronic copying, inkjet printing (printing), etc.
Biochemical and medical dyes: for biological coloring , medical dyes, etc.
Dyes for chemical reactions: catalysis, chain suspension dyes, etc.
1.2 Development ways of functional dyes
There are two main development ways of functional dyes: one is to screen original dyes , utilizes certain potential properties of traditional dyes and pigments. The second is to change the coloring system of traditional dyes to have new functions.
2 Application of functional dyes in textile dyeing and finishing
At present, photochromic dyes, fluorescent dyes, infrared absorption and camouflage dyes, thermal discoloration dyes, moisture-sensitive (thermal-sensitive) coatings, electrochromic dyes, Special non-colored polymers, metal ions, solvent-discolored dyes, far-infrared insulation coatings and other functional dyes have entered the practical stage in textile dyeing and finishing or have shown their potential application prospects.
2.1 Photochromic dyes and pigments
Compounds with “photochromic (i.e., the color of a substance varies with light)” are called “photochromic dyes (pigments). There are not many light-colored dyes directly used in textiles now. The main reason is that the light fastness of these dyes is not ideal, expensive, has low affinity for fibers, and it is difficult to process through conventional dyeing and printing processes. But it can be predicted that with the development of textile dyeing and finishing processing technology and photochromic dyeing, light-colored textiles will surely mature gradually.
2.2 Fluorescent dyes and pigments
The definition of fluorescent dyes is not uniform. Generally, dyes that can strongly absorb and radiate fluorescence in the visible light range are called fluorescent dyes. The fluorescent pigment is essentially a resin solid solution of fluorescent dye with very fine particles.
Rodamamine and its derivatives are fluorescent dyes used in textiles early. They can dye natural or synthetic fibers such as silk, polyester, nylon, etc., so that they can obtain eye-catching colors and effects. Fluorescent yellow tennis balls are made of fluorescent yellow dyes. Made of dyed tennis surface fiber material.
Fluorescent pigments are mainly used in printing or coating processing on textiles, and are used in clothing or textile products that require bright colors, such as travel supplies, sports clothing and children’s clothing. At present, this type of pigment has become increasingly popular.
2.3 Infrared absorption dyes and infrared camouflage dyes
Infrared absorption dyes refer to dyes that have strong absorption of infrared rays. Like ordinary dyes, these dyes also have specific Л-electron common rail systems, so they are different. ,Their first excitation energy is relatively low, and they absorb not visible light but infrared rays with longer wavelengths. Infrared camouflage dyes (or pigments) refer to some dyes with specific colors whose infrared absorption characteristics are similar to those of the natural environment. The difference from ordinary dyes is that their infrared absorption characteristics are similar to those of the natural environment. They can camouflage the chromatinized objects, making it difficult for objects to be easily. Discovered by infrared observation.
In recent years, near-infrared absorption dyes and textile dyeing have been closely related to solar energy conversion and storage. Plastic films or textile clothing made of this dye (or pigment) have good application prospects in industry, agriculture and clothing.
Infrared camouflage dyes (or pigments) are mainly used for camouflage of military equipment and combat personnel. Since infrared camouflage research is highly confidential in various countries, there are few relevant technologies published. Information obtained from patent documents shows that a few screened reducing dyes not only have good infrared absorption performance, but also have various color safety. The degree can also meet the requirements of military textiles.
2.4 Thermal discoloration dyes and pigments
Dyes (pigments) with “thermal discoloration properties” are called thermal discoloration dyes (pigments). The dyes used for textile color-changing printing are some dyes used for thermal recording. In recent years, thermal color-changing dyes have been increasingly used for textile dyeing and printing.
2.5 Wet and heat-sensitive coatings
Humidity and heat-sensitive coatings are inorganic coatings made of cobalt salts. These two coatings can be used according to the usual coating printing process, but in general, the color change sensitivity and color depth of this type of color change paint have low color change sensitivity and color depth, the water washing fastness is not good enough, and it is more sensitive to acids and alkalis, so further research is needed .
2.6 Electrochromic dyes
When the direction of the dipole moment of the dye is changed by the electric field at the moment, a type of dye whose color also changes with the electric field is called electrochromic dyes, or electrosensitive dyeingmaterial. If textile materials are used as substrates, the required products are made of this electronically controlled discoloration functional dye, such as large color displays, light-shielding materials, etc., which will have some special functions and are worth studying.
2.7 Colored polymers
Colored polymers refer to molecular polymers that have a chromogenic system themselves. In fact, colored polymers can be used to color in stock liquids of plastics or fibers. Similarly, this color should be used for coatings, paint printing and dyeing foam printing. Polymer pigments have the advantages of pigment coloring and solvent-soluble dye coloring. They can even react with the colored polymer and combine them into one through covalent bonding, so they deserve more in-depth research.
2.8 Metal ion and solvent discoloration dyes
Metal ion discoloration dyes refer to a type of dye that can chelate with metal ions to cause color changes. Solvent discoloration dyes refer to a type of dye whose color can vary with the polarity of the solvent. Metal ion coloring dyes make it possible to obtain multi-color dyeing or printing products due to their discoloration properties, and have certain application prospects in the textile and garment industries; solvent coloring dyes can be used to color fabrics and garments, so that these textiles can be encountered in water or other The solvent produces a discoloration effect and the development prospect is optimistic.
2.9 Far infrared insulation coating
Coatings made of inorganic ceramic powders with strong infrared emission characteristics and some magnesium-aluminum silicates are called far infrared insulation coatings. Far infrared insulation coatings are mainly used to process sunlight thermal insulation fabrics. In addition, through coating printing or coating processing, it can also impart infrared radiation to the fabric, making the fabric have good thermal insulation or thermal insulation.
3 Application prospects of functional dyes in the dyeing and finishing industry in other fields
3.1 Functional dyes for electrophotography
Electronic photography, also known as photoelectric imaging, includes photoelectric copying and laser printing, which all involve The interaction between light and electrical energy requires the use of some special dyes. This photography technology has good prospects in textile dyeing and finishing processing.
3.2 Functional dyes for electrostatic, ion and magnetic imaging printing
The electrostatic, ion and magnetic imaging printing methods are three non-contact printing technologies, although they are not as good as electrophotography, inkjet printing and thermal printing The manufacturing technology is popular, but they all have their own characteristics.
Electrostatic imaging can be used in the dyeing and finishing industry, as long as the surface of the textile is insulated, and the electrostatic color toner with affinity for fibers and can be prepared from specific functional dyes is printed, and the dye is fixed to the textile by heat treatment. superior.
Ion deposition printing technology can print images of primary or full colors, and has high application prospects in textile printing. The key is to develop toners suitable for textiles, that is, it is necessary to develop or screen suitable functional dyes. .
The advantage of magnetic imaging printing is that it can be transferred continuously and repeatedly, and the printing speed is very high. The disadvantage is that the resolution is not high and the drum is easy to corrode, so printing is done.It is suitable to make some simple and large images, and unlike ordinary transfer printing and transfer paper, there is no need to clean the textile after transfer, and the process is simple; however, the price of toner and the magnetic materials in it are in color The problems of the impact of textile performance need to be solved.
3.3 Functional dyes for inkjet printing
Inkjet printing uses nozzles to spray ink (or colored liquid) to form text or images on paper. Some new functional dyes can meet their requirements. With the promotion of inkjet printing technology, textiles have gradually adopted this principle for printing, that is, inkjet printing, which has developed rapidly in recent years.
3.4 Functional dyes for thermal diffusion transfer and hot wax transfer
The basic principles of dye thermal diffusion technology (D2T2 for short) imaging are very similar to the transfer printing of textiles, so it is also a promising technology for the production of color printed fabrics. However, functional dyes particularly suitable for thermal diffusion transfer printing in textiles have not been specifically reported, and are now in the research and development stage.
There is little possibility that the hot wax transfer technology is directly used in textiles, but this transfer method is very simple. If you find a film-forming substance with strong adhesion to textiles, such as some low-melting adhesives instead As a pigment dispersion and transfer medium, that is, the pigment transfer technology commonly described, wax is still very promising in application.
3.5 Functional dyes for biochemical and medical purposes
The functional dyes have a long history of use in biological and chemical activities. It is mainly used in cell coloring, bactericidal, enzyme purification analysis and other aspects. The antibacterial and anticorrosive properties of dyes are of great significance to processing textiles with hygienic functions. Textiles dyed with this type of dye can not only meet the requirements of a certain color, but also have antibacterial and anticorrosive functions. Therefore, textiles dyed with some functional dyes have the function of health care, and it is very meaningful to carry out research in this area.
3.6 Functional dyes for laser radiation
Laser is currently mainly used in communications, medical care, spectroscopy, photochemistry, reaction kinetics research, isotope separation, micro analysis, and military industry. It is used in textile dyeing and finishing. Processing applications have also become a new trend, such as laser engraving, fiber laser modification, and functional dye printing for laser radiation.
4 Conclusion
The types and functions of functional dyes are constantly expanding with the research in various fields. This article only introduces some dyes that have been or are being developed and applied. In addition to these, many organic compound dyes with conductive, magnetic, catalytic properties actually fall into the category of functional dyes.
The application of functional dyes will definitely have broader prospects, and are mostly closely linked to high-tech and new product development. The dyeing and finishing industry is an important part of traditional application of dyes. In the past, it mainly utilized the light and color characteristics of dyes. In the future, although it is still inseparable from the fields of light and color, in the process of developing new products, especially industrial fiber products, we will pay attention to the performance of dyes in various aspects. Therefore,The application of energy dyes in the textile dyeing and finishing industry will have great potential.
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