With the development of modern nonwoven technology, nonwoven materials are increasingly used in medical supplies, health care products, daily use items, upholstery fabrics, automobile interiors, and various public places. However, nonwoven materials are easily contaminated with bacteria. Shortcomings have always been a “worry” in the industry, especially clothing and surgical gowns that come into contact with the human body. Metabolites such as sweat and sebum produced by the human body may be attached to them, which are more suitable for the growth of bacteria. Therefore, nonwoven materials used in related fields must be inspected. Antibacterial processing is urgent. Among them, antibacterial agents, which have always been in a weak position in development, have become the primary task to improve the antibacterial function of nonwoven materials.
Researchers from the University of London in the United Kingdom recently published a paper in the journal “Chemical Science” stating that they have developed a new non-woven photocatalytic antibacterial agent-nano titanium dioxide (TiO2). This material has a fatal effect on bacteria under light conditions and has a good antibacterial effect in a dark environment. If modern hospitals widely use this antibacterial material, it can effectively reduce nosocomial infections.
Three crystal structures jointly achieve antibacterial effect
Compared with ordinary antibacterial properties, nano-TiO2 photocatalytic materials have high temperature resistance (>600℃) and are also better in terms of safety, drug resistance, weather resistance and heat-resistant processing type. They can be widely used in antibacterial fabrics and Nonwovens and other fields. At the same time, TiO2 photocatalytic materials can also decompose harmful gases and organic matter such as formaldehyde, ammonia, benzene, xylene, sulfur dioxide, and nitrogen oxides to achieve antibacterial and air and water purification effects. The antibacterial mechanism and regeneration principle of non-woven fabrics treated with low-light catalytic antibacterial agents will produce antibacterial substances in a circular manner under light conditions, ensuring long-term antibacterial effectiveness.
Professor Jackson of the University of London pointed out that photocatalytic inorganic antibacterial agents are new antibacterial agents that utilize the photocatalytic properties of semiconductor materials to achieve antibacterial effects. The energy band structure of semiconductor materials is generally composed of low-energy entrainment and high-energy conduction bands. There is a forbidden band between the valence band and the conduction band. The bandgap width of semiconductors is generally less than 3.0eV. When it can receive irradiation with energy greater than or equal to the energy gap, the semiconductor material absorbs light and can produce electron (e-)-hole (h+) pairs. Due to the lack of a continuous area between the energy bands of semiconductor materials, photogenerated electron-hole pairs generally have a picosecond lifetime, which is sufficient for photogenerated electrons and photogenerated hole pairs to transfer charges to species adsorbed on the semiconductor surface from the solution or gas phase via the forbidden band. . TiO2 has three crystal structures: rutile, brookite and anatase. The three crystal structures can jointly achieve antibacterial effects. Among them, the bandgap width of anatase TiO2 is 3.2eV, which is equivalent to the photon energy with a wavelength of 387.5nm. At the same time, the size of TiO2 particles also has a certain impact on its antibacterial effect. The smaller the TiO2 particles, the better the effect of killing bacteria. Currently, the particles of commonly used TiO2 antibacterial agents are mostly ultra-fine TiO2, and TiO2 in the nanometer level has more effective of antibacterial properties.
The development of nano-TiO2 antibacterial agents has four trends
There are many semiconductor materials with photocatalytic properties, including TiO2, WO3, ZrO, V2O3, ZnO, CdS, SeO2, GaP, SiC, SnO2, Fe2O3, etc. However, other materials except TiO2 have poor stability and are easy to oxidize and have a long lifespan. It has shortcomings such as shortness, so it does not receive as much attention as TiO2 in research and application.
Based on the characteristics of TiO2 photocatalytic antibacterial performance and its application prospects, Zhang Jian, a researcher at the Northwest Nonferrous Metals Research Institute, believes that future research and development of TiO2 photocatalytic inorganic antibacterial materials may be reflected in four aspects. First, the TiO2 photocatalytic bactericidal reaction is a reaction excited by ultraviolet light. The photocatalytic active oxygen species exist for a very short time, and less ultraviolet light can be utilized in the living space. If the range of its photoexcitation wavelength is further increased, its effect on bacteria will also be improved. The adsorption property and the contact between large reactive oxygen species and bacteria allow more photoactive oxygen species to be produced. Then nano-titanium dioxide antibacterial agents will be able to participate more in photocatalytic reactions and greatly improve the overall function of non-woven materials; The second is to improve its applicability. Photocatalytic antibacterial coatings with low cost, high activity, weather resistance and easy implementation will be an important direction for future development. The third is that the TiO2 photocatalytic coating on the surface of glazed tiles, glass, etc. needs to be sintered again. , therefore, it is necessary to study online coating technology in their surface production process, so as to avoid the cleaning process of the substrate in the coating process, and complete the sintering process required for substrate production and coating process in one step; fourth, because not all Bacteria are harmful to the human body, but the photocatalytic bactericidal effect of TiO2 is targeted at all bacteria. Therefore, how to improve its selective killing of bacteria must be considered by researchers.
The selection of auxiliaries must follow the basic requirements for antibacterial finishing agents for nonwoven fabrics
As an important additive for nonwoven antibacterial materials, there are currently many types of antibacterial agents that can be used for nonwoven finishing. Depending on the final use of nonwoven fiber raw materials and antibacterial nonwovens, the requirements for the antibacterial finishing agents used are not only the same. But in general, antibacterial agents used for antibacterial finishing of nonwovens should meet the following requirements.
1. High antibacterial efficiency. And antibacterial agents have good antibacterial properties at low concentrations. PassableIt is measured by the minimum inhibitory concentration (the minimum concentration of antibacterial agent required to inhibit the development and reproduction of bacteria) and the minimum bactericidal concentration (the low concentration of antibacterial agent MBC). The smaller the MIC or MBC, the higher the antibacterial efficiency of the antibacterial agent.
The evaluation of the antibacterial efficacy of nonwoven fabrics treated with antibacterial agents not only depends on the nature of the antibacterial agent and the content of the antibacterial finishing agent, but is also related to factors such as the fiber properties of the nonwoven fabric and the types and quantities of microorganisms exposed to the environment.
2. Broad antibacterial spectrum. That is, it has an inhibitory or killing effect on a variety of microorganisms and different strains of the same microorganism. There are many types of microorganisms, and antibacterial agents generally can only show antibacterial activity against some undetermined types of microorganisms, but do not show antibacterial properties against other microorganisms. Antibacterial agents that can show antibacterial activity against many microorganisms at the same time are called broad-spectrum antibacterial agents; antibacterial agents that show antibacterial activity against only one or a small number of microorganisms are called specific antibacterial agents. The microorganism species that can show antibacterial activity of an antibacterial agent are collected into the antibacterial spectrum of the antibacterial agent. During the use of non-woven fabrics, especially non-disposable fabrics, they will be exposed to a variety of microorganisms, so the antibacterial finishing agent needs to have broad-spectrum antibacterial properties. However, in practical applications, it is unrealistic to require antibacterial agents to be effective or consistent against all microorganisms. Different requirements can be put forward for the antibacterial spectrum of antibacterial agents according to the use occasions of nonwoven fabrics, such as those related to the hospital environment. The main pathogenic bacteria include Staphylococcus aureus, Klebsiella spp., Serratia spp., etc. Therefore, antibacterial finishing agents for medical nonwovens need to have an inhibitory effect on the activity of the above-mentioned comedies.
3. Good stability. The stability of the antibacterial finishing agent refers to the physical and chemical ability of the antibacterial agent itself to remain stable over time or in the environment, including the antibacterial effect, appearance, color, physical properties, etc. of the antibacterial agent. It requires that the antibacterial agent be processed, used, stored and It is not affected by ultraviolet, visible light, heat, water and other environments during other processing processes. It is inert in reacting with common textile auxiliaries such as fuel and does not affect the physical properties and appearance of nonwoven fabrics.
4. Safe and good. Safety is an important requirement for antimicrobial finishes. Most antibacterial finishing agents are artificially synthesized organic or inorganic compounds with complex chemical compositions and certain body toxicity, which may cause certain harm to the human body during their production and use. For example, some heavy metal compound antibacterial agents used in the early days were banned due to their toxicity to the body.
In order to use antibacterial agents safely, toxicological evaluation of antibacterial agents is generally required. In addition to necessary analytical tests, toxicological evaluation usually obtains data through animal toxicity tests. The important standards for workers now include: acute toxicity test; subacute toxicity test; chronic toxicity test. Carcinogenicity test; mutagenicity test; skin irritation test; eye irritation test; skin allergy test. Among them, the acute toxicity index is important, which refers to the poisoning effect caused by the body’s one-time exposure to foreign compounds. Acute toxicity can initially estimate the danger of the compound to human poisoning. It is usually based on the half-lethal dose, that is, in the group of derivatives, it can cause half of the The degree of toxicity is expressed by the measurement of biological death. The smaller the 50% lethal dose, the greater the toxicity. The toxicity of compounds can be divided into several categories based on the 50% lethal dose: highly toxic, highly toxic, moderately toxic, and lowly toxic.
In addition to the chemical structure and physical and chemical properties of the substance itself, the toxicity of antibacterial agents is also related to conditions such as concentration, action time, contact route and location, interaction of substances, and collective functional status.
5. Good compatibility and suitable for finishing and processing. Antibacterial agents need to be combined with non-woven fabrics to support the use of corresponding products, so the selected antibacterial agents must have good compatibility with the corresponding non-woven fabric fibers and be able to adapt to the requirements of the finishing process. Good compatibility and strong binding force between antibacterial agents and non-woven fibers are also requirements to ensure that antibacterial agents will not cause excessive loss during use and to improve antibacterial durability.
6. The price is appropriate. Price is also a factor to consider when choosing an antibacterial agent. The production cost of nonwoven products treated with antibacterial agents will increase to a certain extent. This increase in cost should be matched with the improvement in economic efficiency brought to the product by the increase in antibacterial phosphonium, and should not cause the product to suffer from cost bring about a shrinking of the market.
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