Dalian University of Technology Liaoning Provincial Key Laboratory of Clean Textile Zhang Juan Zheng Huanda
Abstract: As a new type of waterless dyeing technology, supercritical carbon dioxide dyeing has the characteristics of high dye uptake, short process, zero emission and no pollution, and has shown obvious industrialization prospects. Supercritical carbon dioxide dyeing uses high-temperature and high-pressure equipment, which has a special structure different from ordinary chemical equipment. Therefore, the development and innovation of a complete set of supercritical fluid dyeing equipment is the key to the development of this technology and has always been the focus of many research institutions. This article reviews the new research progress of supercritical carbon dioxide dyeing devices at home and abroad in recent years. At the same time, based on the structural diversity characteristics of fiber materials to be dyed, the research and development status of special dyeing kettles for supercritical fluids was summarized. He also proposed several issues that should be addressed during the industrialization of supercritical carbon dioxide dyeing technology, hoping to further promote research on supercritical carbon dioxide dyeing technology and devices through multidisciplinary collaboration.
Keywords: supercritical carbon dioxide dyeing, waterless device, dyeing kettle body
After experiencing industrialization and informatization, the world economic model is gradually moving towards a “low-carbon” process, which means that in the next 40 years from now to 2050, the “low-carbon economy” will become the key to national competitiveness and corporate competitiveness. important manifestation. In recent years, supercritical fluid technology has attracted much attention as a green and environmentally friendly processing technology that meets the requirements of clean production. With the continuous development of science and technology and the gradual solving of scientific problems, supercritical fluid technology has been significantly improved and expanded from basic theoretical research to practical applications, and has penetrated into supercritical dyeing, supercritical extraction, and supercritical chemical reactions. , supercritical cleaning technology and many other aspects are gradually penetrating into high-tech fields such as new materials and biotechnology, and will also play a greater role in the progress of other scientific and technological fields.
In 1988, Schollmeyer et al. proposed the first patent for supercritical fluid dyeing of textiles, thus proposing a new idea for solving the problem of textile dyeing and finishing pollution. Carbon dioxide has become a commonly used supercritical fluid because it is non-toxic, non-flammable, cheap and easy to obtain, and has relatively mild critical temperature and pressure. Supercritical carbon dioxide dyeing technology uses industrial carbon dioxide waste gas to dissolve dyes in a supercritical state, and carries the dyes to the fiber surface. After adsorption and fixation, the fabrics are dyed quickly and evenly; after the dyeing is completed, the temperature and pressure are reduced, and the carbon dioxide vaporizes and The dyes are fully separated, eliminating the need for cleaning and drying processes, and the remaining dyes and carbon dioxide can be recovered and recycled. Reduce greenhouse gas emissions. Supercritical carbon dioxide dyeing technology overcomes the main shortcomings of water medium dyeing technology. The fiber can be dyed without water during the dyeing process, which fully embodies the modern processing concepts of cleanliness, greenness and environmental protection.
The supercritical carbon dioxide dyeing process uses high-temperature and high-pressure equipment. Whether it is small and medium-sized equipment or large-scale industrial equipment, it has a special structure that is different from ordinary chemical equipment. The development of a complete set of supercritical fluid dyeing equipment is the key to the development of supercritical fluid waterless dyeing and finishing technology. Due to the high temperature and high pressure of the dyeing and finishing process and the diverse structural characteristics of fiber materials, taking the lead in achieving breakthroughs and innovations in industrialized equipment is the focus of research. This article summarizes and reviews the new research progress of supercritical carbon dioxide dyeing devices at home and abroad in recent years. At the same time, based on the diverse characteristics of fiber materials to be dyed, the research and development status of special dyeing kettles for supercritical fluids is summarized. In view of the current research and development status of improved technology, several issues that should be addressed during the industrialization of supercritical carbon dioxide dyeing technology were put forward.
▲DyeCoo supercritical CO2 dyeing machine
1 Supercritical fluid properties and dyeing and finishing processes
1.1 Properties of supercritical fluid
The formation process of supercritical fluid refers to the coexistence of liquid and gaseous states under normal temperature and pressure. There is an obvious interface between the two. As the temperature increases and the pressure increases, the interface between the liquid and gaseous states gradually blurs. When When reaching above the critical temperature (TC) and critical pressure (PC), the interface between the liquid and gaseous states completely disappears and exists in a fluid state, which is a supercritical state. Therefore, when the temperature and pressure of a substance are both higher than its critical temperature and critical pressure, it is called a supercritical fluid (Supercritical fluid, referred to as SCF). Commonly used SCFs in industrial technology include carbon dioxide, ammonia, ethylene, propane, propylene, water, etc. Supercritical fluids are different from both gases and liquids. They have many unique physical and chemical properties. Comparing the three basic properties (density, viscosity, and diffusion coefficient) of supercritical fluids with gases and liquids at room temperature, it can be seen that supercritical fluids have many unique physical and chemical properties. Critical fluids have a density close to that of a liquid, a viscosity and a diffusion coefficient close to that of a gas, and therefore have a higher mass transfer rate.
The important property of supercritical fluid is that it has great compressibility, especially near the critical point. Small changes in temperature and pressure can cause large changes in the volume of supercritical fluid. Further research found that the dissolving ability of supercritical fluids mainly depends on density, and its density is very sensitive to changes in temperature and pressure, so it can be controlled by controlling the temperature.�� and pressure change the solubility of a substance.
Table 1 Performance comparison of gases, liquids and supercritical fluids
|
Physical properties |
Gas |
Supercritical fluid |
Liquid |
|
Density/(g/cm3) Viscosity/(Pa·s) Diffusion coefficient (cm2/s) |
1.01325KPa, 15-30℃ (0.6-2)×lO0 (1-3)×10-4 0.1-0.4 |
Tc, Pc 0.2-O． 5 (1-3)×10-4 0.7×10-3 |
15-30℃ 0.6-1.6 (0.2-3)×10-2 (0.2-3)×100-5 |
1.2 Supercritical carbon dioxide fluid dyeing process
As a non-toxic, non-flammable, environmentally harmless and chemically inert gas under most conditions, carbon dioxide is a widely used supercritical fluid with low critical temperature and critical pressure of 31.1°C and 7.37MPa respectively. During the dyeing and finishing process of supercritical carbon dioxide, the dyestuff is first dissolved in carbon dioxide, and the dissolved dye gradually approaches the fiber interface as the dye liquor circulates. Since there is a dynamic boundary layer at the fiber interface that is difficult to flow, the dye enters the dynamic boundary layer and is close to the fiber interface. After reaching a certain distance, it mainly relies on self-diffusion to approach the fiber; when the dye is close to the fiber interface and the molecular force is strong enough, it is quickly adsorbed by the fiber surface and generates a concentration difference or chemical potential difference between the inside and outside of the fiber, thereby diffusing and transferring to the interior of the fiber. . The viscosity of carbon dioxide molecules is low, the intermolecular force with the dye is small, and the diffusion coefficient is extremely high, which can make the dye molecules quickly diffuse into the pores of the fiber and achieve uniform dyeing of the fiber.
2 Research and development of a complete set of supercritical carbon dioxide dyeing equipment
The complete set of Chaolinqiao fluid dyeing equipment mainly includes nine systems, namely dyeing system, refrigeration system, heating system, pressurization system, instrument system, carbon dioxide storage system, separation and recovery system, safety protection system, and auxiliary system. The main equipment in each system includes dyeing kettles, dye kettles, high-pressure pumps, circulation pumps and separators. The entire system is closed-circuit, which can realize the recycling of dyes and carbon dioxide, and zero emission of dyes.
As a pioneer in the development of supercritical carbon dioxide dyeing technology, the German Textile Research Center Northwest (DTNW) has played an important role in the development of a complete set of supercritical carbon dioxide equipment. In 1989, DTNW designed and developed a static supercritical carbon dioxide dyeing device for the first time, which mainly consisted of an autoclave (400ml) and a stirrable warp beam, which could be used for polyester dyeing experiments. In 1991, Jasper cooperated with DTNW to develop a Till dyeing prototype with a dye liquor stirring device. The dyeing kettle has a capacity of 67L and can dye four 2kg packages (see Figure 2). Since then, DTNW has cooperated with Uhde, a high-pressure vessel manufacturer, to develop dyeing equipment with a dyeing kettle capacity of 30L and equipped with a carbon dioxide recovery and circulation system. The centrifugal pump was selected as the circulation pump, which realized the circulation of dye liquor for the first time. The dyeing effect was equivalent to that of water medium dyeing, which attracted widespread attention from the international community.
Accordingly, developed countries such as the United States, France, and Japan have begun research on this technology. North Carolina State University in the United States developed a pilot supercritical carbon dioxide dyeing machine for single cheese yarn in 1996. By changing the flow direction of the dye liquor, forward and reverse cycle dyeing in the dyeing unit can be realized, improving levelness. In 1997, the European Union launched the three-year supercritical fluid dyeing research project SUPERCOLOR with the participation of many countries, and designed and developed the RotaColor supercritical dyeing equipment (7L) to explore the possibility of its industrial application. In 2001, ITEC Co., Ltd. developed a 40L supercritical fluid dyeing equipment for Fukuoka University. Since then, they have jointly developed a production-type supercritical fluid dyeing equipment. In 2004, Fukui University also carried out the development of industrial equipment for supercritical fluid dyeing.
In 2008, the establishment of the Dutch company DyeC00 marked the beginning of the industrial application stage of supercritical carbon dioxide dyeing technology. DyeC00 is a manufacturer specializing in the production of production-type supercritical dyeing equipment for polyester and cotton. Its Dyeox2250 series device has two dyeing kettle bodies, with a design temperature of 10-130°C, a design pressure of 0-30MPa, and a loading capacity of 150-180kg. Reports show that in 2010, the 150-pound production-type supercritical dyeing equipment produced by DyeC00 Company cooperated with Yeh Group Company in Thailand to begin trial production of waterless dyed sportswear. In 2013, DyeC00 Company’s dyeing equipment was put into production at NIKE’s Taiwan factory. Further promote the application process of this technology.
The significant advantages of supercritical carbon dioxide dyeing technology have also attracted the attention of Chinese research institutions and teams. my country’s Donghua University National Dyeing and Finishing IndustryThe Engineering Technology Research Center, Dalian University of Technology, Hong Kong Productivity Promotion Center, Soochow University and other units have also conducted research on supercritical carbon dioxide dyeing technology and developed their own dyeing equipment. In September 2013, the Second International Textile Science Supercritical Fluid Technology Symposium was held in Nagoya, Japan. The conference gathered well-known scholars in the field of supercritical fluid technology from the United States, the Netherlands, and South Korea. Dalian University of Technology, as the only representative from China, was invited to attend the meeting and gave a keynote report, which was well received by the experts attending the meeting. It shows that my country is at the forefront of the world in the research on the industrial application of supercritical carbon dioxide dyeing technology.
Taking Dalian University of Technology as an example, it has been conducting research on supercritical fluid dyeing technology in China since 2001 and is a key research unit for supercritical carbon dioxide dyeing technology in my country. The team successfully designed the supercritical carbon dioxide dyeing and finishing device system and main equipment, simulated the fluid flow process in the dyeing and finishing device, established a software simulation process for the device, and improved the feasibility of the dyeing process. In 2004, my country’s first supercritical carbon dioxide dyeing device suitable for dyeing natural fibers was developed; in 2009, a supercritical fluid engineered dyeing device with independent intellectual property rights was developed; in 2012, a supercritical carbon dioxide industrialized dyeing device was developed. The entire device realizes automatic control of the dyeing process and visual dyeing, and has a large-flow internal circulation system for dyeing, which has good mass transfer effect, effectively reduces the energy consumption in the supercritical fluid dyeing process and shortens the dyeing time. Proposed a unique process that combines internal and external dyeing, dynamic and static dyeing, the dye is easy to diffuse and adsorb; and in order to solve the problem of dye residue in the kettle body and pipelines, a self-cleaning technology for supercritical fluid dyeing equipment was invented, which improved
Dyeing reproducibility. At the same time, the dyeing device includes pressure, temperature, flow, safety interlocking systems, etc., and has functions such as over-pressure audible and visual alarms, automatic parking, pressure reduction to zero lid opening interlock, and pressure increase before closing the door in place interlock, ensuring the operation of the device. safety and reliability.
3Cyclic dyeing system of supercritical carbon dioxide dyeing device
The circulating dyeing system of supercritical carbon dioxide dyeing is the key to the entire device. Its main function is to complete the dyeing of textiles after supercritical carbon dioxide dissolves the dye. The working principle of the supercritical fluid circulation dyeing system is: during the dyeing process, it is pressurized by a high-pressure pump and heated by a heat exchanger to form a supercritical carbon dioxide fluid that dissolves the dye in the dye kettle, and then flows into the dyeing kettle for fabric dyeing. During the dyeing process, the high-pressure pump is turned off and the circulation pump is turned on to complete the cyclic dyeing process. The heat exchanger in the system supplements the energy loss of the dyeing system during the dyeing process. The main equipment of the system is dye kettle, dyeing kettle, circulation pump and heat exchanger. During dyeing, when the circulation pump is turned on, the high-pressure pump is turned off at the same time. The circulation of the circulation pump can drive the fluid flow in the entire device. The specially designed circulation pump realizes the dynamic dyeing of supercritical carbon dioxide fluid reciprocating and automatically circulating under high pressure and high temperature.
3.1 Dyeing kettle of supercritical carbon dioxide dyeing device
The supercritical fluid dyeing kettle is the core equipment of the supercritical fluid dyeing and finishing device. Its advanced nature directly affects the process flow and performance level of the entire device. When dyeing with supercritical carbon dioxide, an inner cylinder with penetration holes evenly distributed on the cylinder wall is usually placed inside the dyeing kettle body to control the reversal of the dye solution to ensure forward and reverse penetration of the material to be dyed, and realize the internal and external dyeing processes of fiber materials. combination. In order to simplify the transportation pipeline, the dye kettle and dyeing kettle can also be integrated into one. The final dyeing of dyes and textiles is realized in the same kettle. At the same time, in order to solve the problem of uneven dyeing, by rationally setting the warp beam mode, fabric roll form and process conditions, the dye can evenly penetrate the fabric, reducing the uneven pressure loss, fluid path changes and fluid circulation problems during fluid flow. Unevenness.
In order to meet the dyeing needs of loose fibers, yarns, wool balls, ready-made garments and other products, a special supercritical fluid dyeing kettle body is designed based on the physical and chemical properties and appearance characteristics of the fiber materials to be dyed to ensure uniform distribution and efficient mass transfer of carbon dioxide fluid. , is an important breakthrough to promote the industrial application of this technology. On the basis of the above research, the research team of Dalian University of Technology has successively invented supercritical carbon dioxide water-free special dyeing kettles suitable for garments, hanks, cheeses, loose fibers, and wool balls, and carried out the fluid flow process in the dyeing equipment. Computer simulation has been used to improve the feasibility, reproducibility, and safety of the dyeing process: a unique process that combines internal and external dyeing, and dynamic and static dyeing has been proposed to make the dye easy to diffuse and adsorb, enabling small batches and multi-variety dyeing production; and In order to solve the problem of dye residue in the kettle and pipelines, the self-cleaning technology of supercritical fluid dyeing equipment was invented to improve the reproducibility of dyeing. The above research has initially completed the docking of key components from the water medium dyeing device to the supercritical fluid dyeing device, thereby meeting the dyeing needs of different textiles.
3.2 Dye kettle of supercritical carbon dioxide dyeing device
The dye kettle is another main piece of equipment in the supercritical carbon dioxide dyeing device. Its main function is to contain dye.When dyeing, the dye is completely dissolved in the supercritical carbon dioxide fluid, so that the fluid carries the dye to dye the fabric. Specially designed dye cylinders are used to store solid dyes, which can effectively prevent dyes from fusing during the dyeing process. The structure of the dye kettle mainly includes a cylinder, a head that can be opened and sealed with the cylinder, an inner cylinder located inside the cylinder, a thermal oil heating jacket outside the cylinder, and carbon dioxide inlet and outlet 13, etc. Dye kettle structure, the inner cylinder in the cylinder contains the dye required for dyeing. During dyeing, supercritical carbon dioxide enters from the gas inlet, flows out from the gas outlet carrying dye, and enters the dyeing kettle to dye the fabric.
At normal pressure and temperature, the dye exists in solid form in the kettle (see Figures a and b). The main reason is that the flow rate of supercritical carbon dioxide is too low, so that the supercritical carbon dioxide fluid cannot fully dissolve the dye; as the system pressure increases Gradually increasing, the density of supercritical carbon dioxide gradually increases, more carbon dioxide is converted from gas to supercritical fluid, and the proportion of supercritical fluid continues to increase. At the same time, the increase in mass transfer driving force causes the diffusion rate to increase, and the solubility of the dye in the fluid increases. larger, the aggregation state increases, the single molecular state decreases, and the dye gradually dissolves in the fluid; when the temperature and pressure continue to increase, reaching and exceeding the supercritical carbon dioxide critical point, a homogeneous supercritical carbon dioxide fluid appears in the system, and the aggregation state of the dye and The single molecular state reaches equilibrium, the dye is basically dissolved, and as time continues to extend, the color of the fluid further deepens.
4 Issues that need attention in the industrialization process of supercritical carbon dioxide dyeing technology
In the “Twelfth Five-Year Plan” Scientific and Technological Progress Outline for the textile industry, my country has clearly proposed the development of high-tech technologies for low-water and waterless printing and dyeing processing. Supercritical carbon dioxide dyeing technology is pollution-free and zero-emission, realizes clean production in the dyeing process, improves the sustainable development capabilities of the printing and dyeing industry, has significant economic and social benefits, and shows obvious industrialization prospects. After years of hard work by scientific and technological workers, my country has made great progress in the research and development of supercritical carbon dioxide dyeing technology and has reached the international leading level. In order to continue to maintain my country’s leading position in the research and application of this technology’s industrialization, in addition to multidisciplinary collaboration to further promote this technology, the following aspects need to be paid attention to:
A: Special dye for supercritical carbon dioxide dyeing. Supercritical carbon dioxide has a low dielectric constant and can dissolve non-polar or low-polarity dyes, while water-soluble dyes are difficult to dissolve. Disperse dyes generally have weak molecular polarity, small molecular weight, and are easily soluble in carbon dioxide fluids. They can better achieve supercritical waterless dyeing of fiber materials. On the basis of the research on dyeing technology, we continue to carry out in-depth research on the polar structure of disperse dyes. At the same time, there are reactive disperse dyes with reactive groups such as s-triazine and 2-bromoacrylic acid, which can achieve supercritical carbon dioxide for natural fiber materials. Dyeing, thus accelerating the industrial application of this technology.
B: Supercritical carbon dioxide dyeing device cleaning technology. The entire set of supercritical carbon dioxide dyeing equipment has a complex structure and the temperature is high during the dyeing process. As a result, the excess dye remaining at the pipe connections and pipe walls in the dyeing system cannot be completely separated from the carbon dioxide fluid after the dyeing is completed, and some residual dye is still retained. In the dyeing device, it is easy to affect the quality of the next batch of dyed products, which restricts dyeing. Color change operations in production. Based on the theoretical basis of the solubility of dyes in supercritical fluids, the supercritical carbon dioxide fluid itself is used as a cleaning agent or the supercritical carbon dioxide fluid with an entraining agent is added as an entraining agent. The dyeing device is fully inspected after dyeing fiber materials and before color change production. Cleaning can effectively ensure the re-dying and color-changing needs of supercritical carbon dioxide dyeing, thereby creating better promotion conditions for the industrial application of this technology.
C: Mass transfer and simulation of supercritical carbon dioxide dyeing device. Due to technical confidentiality and intellectual property protection, there is still little research data on supercritical carbon dioxide fluid dyeing devices in the world. Further expand the application of computer software in supercritical carbon dioxide dyeing devices and conduct physical modeling and simulation of supercritical carbon dioxide dyeing devices. Simulation can provide significant reference guidance for the industrial amplification of the entire device and the optimization simulation of industrial production.
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