1. Antibacterial agents for metals and metal salts
Many metals in the free state or in the form of compounds are toxic to microorganisms at very low concentrations. They kill microorganisms by binding proteins inside cells to inactivate microorganisms. Metal copper, zinc and cobalt are effective antibacterial agents for textiles. Silver has been most widely used in ordinary textiles and bandages. The minimum inhibitory concentration (MIC value) of silver against E. coli bacteria is 0.05 ~ 0.1mg / L. But some researchers have pointed out that certain strains are resistant to silver.
For synthetic fibers, silver particles can be added to the polymer before extrusion or electrospinning to form nanofibers. In use, silver will diffuse to the fiber surface and form silver ions in the presence of moisture. The release rate of silver is affected by the chemical and physical properties of the fiber and the amount of silver in the fiber. The gradual release can extend the active time of the biocide. In addition to being directly mixed in, the silver nanoparticles are also paddled on the fabric in the form of colloidal solution to achieve durable finishing. Silver particles can also be directly absorbed by Seacell Active algae cellulose fibers.
The treatment of natural fibers with metals can only be carried out during the finishing stage, and various methods have been devised to improve intake and durability. For example, cotton is pretreated with succinic anhydride, which acts as a ligand for metal ions to increase the amount of metal ions that are subsequently adsorbed, achieving very effective antibacterial activity; in protein fibers such as wool, aspartyl and glutamyl residue The free carboxyl group of the group is considered to be the most suitable binding site for metal ions. Pretreatment with tannic acid that can increase the number of binding sites or EDTA dianhydride with chelating ability for metal ions can further increase this binding capacity. But these treatment methods have not been applied in industrial production due to technical and environmental problems.
The technology of producing metal antibacterial textiles, especially silver antibacterial textiles on an industrial scale, has recently made breakthroughs, overcoming the difficulties of cost and environment, and has been widely used in the production of commercial antibacterial synthetic fibers and yarns. For example, Ultra \ | Fresh and Silpure products manufactured by Thomson Research Group, silver is added in the form of ultra-fine metal particles in the finishing stage and is first used in polyester fabrics. Milkin has developed a silver-based antibacterial agent Alpha San, which is a silver-containing zirconium phosphate-based ceramic ion exchange resin, which is added during the extrusion of synthetic fibers. Alpha San is currently used by many companies to produce antibacterial textiles, such as O Mara's antibacterial polyester Micro-Fresh and nylon yarn Sole-Fresh; Sinterama's polyester yarn Guard \ | Yarn. AgION technology is the production of silver-based antibacterial textiles using ion exchange mechanism. In this production process, silver ions are made into multi-faceted zeolite supports, which are then added to the polymer or coating. Under the conditions that bacteria can grow, the silver ions in the zeolite exchange with sodium ions present in the environmental moisture to inhibit the growth of bacteria. In addition, the bioactive polyester fiber Bioactive produced by Trevira also adds silver to the fiber. Recently, Nanohorigon has used silver nanoparticles (Smart Silver) in fabric and clothing dyeing equipment to antibacterially finish the wool on an industrial scale. After treatment, the original properties of the wool, including feel and dyeing performance, have not changed.
2. Polyhexamethylene biguanide
Polyhexamethylene biguanide (PHMB) is a heterodisperse mixture with an average molecular weight of 2,500 and trade name Vantocil. Due to its low toxicity, high efficiency and broad-spectrum antibacterial properties (MIC = (0.5 ~ 10) × 10-6), it has been successfully used as a food industry fungicide and swimming pool disinfectant, and is being explored as a mouthwash and bandage Use fungicides, etc. PHMB destroys the bacterial cell membrane, and its activity increases with the degree of polymerization. So far, few PHMB-resistant bacteria have been found. Because PHMB is cationic, it is connected to cotton fabrics by ionic and hydrogen bonding. Chemical finishing of cotton fabrics to produce carboxyl groups and dyeing with reactive dyes to introduce sulfonic acid groups can increase PHMB uptake, but strong ionic bonds may reduce the release of free PHMB, thereby reducing antibacterial efficacy. For durable finishing, PHMB requires 2% ~ 4% (owf), while for disposable applications, the dosage is 0.25% ~ 0.1% (owf). PHMB can be directly immersed on cotton at room temperature and neutral pH (8, 9), or implemented in a roll-bake-bake process.
In order to improve the durability and overcome the yellowing of the fabric, Payne [6] stated in his patent that after the PHMB treatment, the cellulose fiber is treated with a strong organic acid. They also used a self-crosslinking resin and catalyst to transfer PHMB to synthetic fiber processing.
Arch Chemicals has developed a special grade PHMBReputex 20 for fabric treatment. Reputex has a higher molecular weight than Vantocil, and the polymer contains an average of 16 biguanide units.This longer polymer length not only produces higher bactericidal activity And, more cation positions are formed on each molecule, which can be bound to the fabric surface as strong as possible. Reputex's impregnation or rolling-baking-baking process was originally used for cotton and its blended fabrics, and it has recently been expanded to polyester and nylon fabrics under the Purista trade name.
3. Quaternary ammonium compounds
Quaternary ammonium compounds, especially those with a long chain of 12 to 18 carbon atoms, have been widely used as disinfectants. Such compounds have a positive charge on the N atom of the compound, and have a variety of effects with microorganisms, including damage to cell membranes, modification of proteins and destruction of cell structure. When the bacterial cells are inactivated, as long as the compound remains on the fabric, the quaternary ammonium group remains intact and maintains its antibacterial properties. The quaternary ammonium compound can be attached to the fabric, mainly due to the ionic interaction between the cationic quaternary ammonium compound and the anionic fiber surface. Therefore, for acrylic and cationic dyeable polyester fabrics containing carboxyl and sulfonic acid groups, they can directly adsorb quaternary ammonium compounds under conditions close to boiling. Similarly, the glutamyl and aspartyl residues in wool have carboxyl groups, and quaternary ammonium compounds, especially cetylpyridinium chloride, adsorb about 5% owf on untreated wool, and the washability reaches 10 times. Cotton fabrics are treated with 4-aminobenzenesulfonic acid-chloro-triazine addition compound to increase the anion position on the surface of the fabric, thus facilitating the adsorption of quaternary ammonium compounds. In these studies, the adsorption of quaternary ammonium compounds is affected by pH, quaternary ammonium compound concentration, temperature and adsorption time.
Sun et al. [4] assumed that fabrics were first dyed with acid dyes before being treated with quaternary ammonium compounds under alkaline conditions. The ionic interaction between the dye molecules and the quaternary ammonium compounds was sufficient to achieve semi-durable antibacterial finishing effects.
Dig et al. [5] synthesized a new quaternary ammonium compound N-dodecyl-amino-betaine-2-mercaptoethylamine hydrochloride (DABM). DABM can use its thiol group to react with wool, that is, the thiol group can react with the cysteine-S-sulfonic acid residue (bent salt) of the pretreatment wool of sodium bisulfite or with cysteine The disulfide bond reacts to form an asymmetric disulfide bond. The covalent linkage of this quaternary ammonium surfactant gives the wool antibacterial activity.
A commercial antibacterial textile made with quaternary ammonium compounds as an active agent, BIOGUARD, is produced by AEGIS Environments, this active agent is 3-trimethoxysilanepropyl dimethyl octadecane and its ammonium chloride (AEM5700, Formerly known as Dow Corning 5700 antibacterial agent) The MIC for Gram-positive and Gram-negative bacteria is 10-100 mg / L. AEM5700 is made into an aqueous solution, and it is finished by padding, spraying or foam finishing methods. During drying, the non-volatile silane forms a covalent bond with the fabric, resulting in excellent wash resistance. At present, this chemical has been applied to cotton, polyester and nylon fabrics. There is not much information about bacteria resistant to this particular quaternary ammonium compound.
