Acetate fiber membrane material or "star of tomorrow" in the field of filtration and separation

Although tobacco tows occupy an absolute market share of acetate fiber (CA), their market in high-end apparel fabrics , linings, technical textiles and other fields has opened. Among them, in the field of technical textiles, cellulose acetate film materials have been widely used in the field of filtration and separation, and have achieved great market potential success in the development of high-end products. Here are some of the latest developments.

Hollow fiber membrane

Membrane separation and filtration are the most effective separation and concentration methods and have been successfully used in the filtration of nanoparticles. By changing the preparation conditions of the film, film materials of different porosities can be obtained.

Pore ​​of membrane material

Cellulose acetate has been widely used as reverse osmosis (RO), microfiltration (MF) and gas separation operations. It is an environmentally friendly raw material for membrane material preparation. It is non-toxic and relatively inexpensive. It has been successfully used in brackish water, seawater desalination, ethanol, methanol filtration and urea permeation treatment. For example, the cellulose acetate nanofiltration membrane bioreactor (NF-MBR) used for wastewater treatment is a U-shaped hollow fiber membrane with a single filament number of 85,000 and a single module having a specific surface area of ​​11.7 square meters. Japan Daicel FT50 CA Ultrafiltration Membrane (UF) has been widely used in the removal of turbidity from groundwater and industrial water. Green cellulose acetate hollow fiber ultrafiltration membrane developed by Chemique Laboratories, France, for wastewater treatment, bioactive substances Separation and gas separation. The UF membrane is prepared by using a natural or biodegradable raw material, and the solvent used in the membrane preparation process is a methyl lactate or ethyl lactate green solvent system, and the acute LC50 is 5 g/kg.

Hollow fiber membrane

Among the medical membrane materials, the cellulose acetate membrane of Toyobo Co., Ltd. has been used for artificial kidney, and the modified cellulose triacetate (CTA) membrane has also been used clinically in hemodialyzers.

Bio-based fiber

Researchers at the North American Center for Agricultural Applied Research use agricultural waste such as corn fiber, rice husks and wheat straw as raw materials to prepare cellulose acetate.

The preparation of cellulose acetate for the biomass raw material of corn fiber requires pretreatment. Usually, the corn fiber material is dried at 55 ° C under forced air supply for 4 hours, and is pulverized to control a certain particle size to be stored at room temperature. Before the pretreatment, the oil traces of the material were removed by using hexane. The mass fraction of the material was controlled at 15%, the rice shell was 15%, and the wheat straw material was 8.5%. The pretreatment was carried out in a reaction kettle at a temperature of 121 ° C for 4 h. The pretreated material enters the acetylation process. The conversion rate of acetylation in the current test is around 25%.

In an exploratory study to prepare cellulose acetate using renewable biomass resources, the researchers used unrefined biomass materials, such as powdered palm fruit, to dissolve in ionic liquid (BMIMCI) at 45 ° C, lignocellulose. Selective separation, modified cellulose can be used as a raw material for vinegar.

The acetification reaction is carried out at 55 ° C and the process is very compact. CTA has a degree of esterification of 2.9 and can be used for fiber or film processing. The study also showed that the selection of biomass materials is diversified, and the available biomass includes bagasse, tulip, hybrid poplar, oak, Japanese red pine, rice husk and so on.

French company Roquette uses plant starch to synthesize bio-based cellulose acetate to provide eco-friendly raw materials for Rhodia's tobacco acetate tow, and it also has an advantage in cost. The research is currently in progress.

Nanofibers

Nanofiber preparation dates back to the 1930s, and the first material to be successfully spun polymer nanofibers was cellulose acetate. In recent years, some progress has been made in the technology and application research of submicron-nanoacetate fibers. For example, the Polish Institute of Fibers and Medicinal Plants has successfully obtained a modified cellulose acetate nanofiber web by using an electrospinning method. The diameter of the monofilament is controlled at 200-600 nm, which has an antibacterial function and a very high particle collection efficiency.

A cellulose fiber spinning solution prepared by using an acetone/DMAc/ethanol composite solvent system (component ratio 4/1/1) was prepared by an electrospinning process, and the diameter of the monofilament was in the range of 100 to 500 nm. The test results prove that the nanofiber web has a controlled release function of the liquid medicine.

Nanofiber mesh

Donghua University uses a mixture of cellulose acetate and silk protein to produce a nanofilament with a monofilament diameter of 50-300 nm by electrospinning, showing good mechanical properties, tear strength of 88.9 cN/mm2 and elongation at break of 27.77%. .

The cellulose acetate nanofiber membrane developed by the researchers, used as a particulate separation medium, showed good separation. The fiber was prepared by using dichloromethane, formic acid, and trifluoroacetic acid (TFA) as a solvent, and 8% of the spinning solution was placed at room temperature, and the degree of esterification of the cellulose acetate used was 2.5. The electrospinning method was used, the voltage was 15 kV, and the distance from the collecting device was 10 cm. The nanofiber membrane has a monofilament diameter ranging from 100 to 300 nm, and the membrane material quality is a monofilament diameter (0.19 ± 0.05) μm, a thickness of 406 μm, and a porosity of 87%.