Recent Progress In Antibacterial Finishing Of Textiles

People have long recognized that

1 textiles

1.1 metal and metal salt antibacterial agents

Many metals in free form or compound form are toxic to microorganisms at very low concentrations.

They kill microorganisms by inactivating proteins in the cell.

Copper, zinc and cobalt are effective antibacterial agents for textiles. Silver has been widely used in ordinary textiles and bandages. The minimum inhibitory concentration (MIC) of silver to E.Coli bacteria is 0.05~0.1mg/L.

But some researchers have pointed out that some strains are resistant to silver.

For synthetic fibers, silver particles can be added to the polymer before extrusion or by electrospinning to form nanofibers.

When used, silver diffuses to the surface of the fiber and forms silver ions in the presence of moisture.

The release rate of silver is influenced by the chemical and physical properties of fibers and the amount of silver in fibers, which gradually release the activity time of biocide.

In addition to direct addition, silver nanoparticles are also used in the form of colloidal solutions for rolling and finishing on fabrics.

Silver particles can also be directly absorbed by SeacellActive algal cellulose fibers.

Metal processing for natural fibers can only be done at the finishing stage, and various methods have been devised to improve intake and durability.

For example, cotton is pretreated with succinic anhydride. It acts as a metal ion ligand to enhance the subsequent adsorption of metal ions to achieve a very effective antibacterial activity. In wool and other protein fibers, the free carboxyl group of aspartyl and glutamyl residues is considered to be the most suitable binding site for metal ions. It can further improve the binding capacity by using tannic acid which can increase the number of binding sites or EDTA two anhydride with chelating ability to metal ions, but these methods have not been applied in industrial production due to technical and environmental problems.

The production of metal antibacterial textiles, especially silver antibacterial textile technology, has been breakthroughs in recent years, and has overcome the difficulties of cost and environment. At present, it has been widely used in the production of commercial antibacterial synthetic fibers and yarns.

For example, Ultra\|Fresh and Silpure products made by Thomsen research group. Silver is added in the form of ultra-fine metal particles in the finishing stage, first used for polyester fabrics.

Miliking has developed a silver based antibacterial agent, AlphaSan, which is a silver phosphate zirconium based ceramic ion exchange resin added in the extrusion process of synthetic fibers.

At present, AlphaSan is used by many companies to produce antibacterial textiles, such as OMara's antibacterial polyester Micro-Fresh and nylon yarn Sole-Fresh; Sinterama's polyester yarn Guard\|Yarn.

AgION technology is based on ion exchange mechanism to produce silver based antibacterial textiles.

In this production process, silver ions are made into polyhedral zeolite carriers and then added to polymers or coatings.

In the condition that bacteria can grow, silver ions in zeolites are exchanged with sodium ions existing in environmental water to inhibit the growth of bacteria.

In addition, the bioactive PET fiber Bioactive produced by Trevira also adds silver to the fibers.

Recently, Nanohorigon has used the dyeing equipment of fabric and clothing to make antibacterial finishing on the scale of wool with the silver nanoparticles (SmartSilver). The original properties of the wool, including handle and dyeing properties, have not changed.

1.2 quaternary ammonium compounds

Quaternary ammonium compounds, especially those quaternary ammonium compounds containing 12~18 long chain of carbon atoms, have been widely used as disinfectants.

In solution, these compounds, N, have positive charges on the atoms and produce many functions with microorganisms, including damaging cell membranes, modifying proteins and destroying cell structures.

When the bacteria cells are inactivated, the quaternary ammonium group remains intact and maintains its antibacterial properties as long as the compound is retained on the fabric.

Quaternary ammonium compounds can be attached to fabrics, mainly due to ionic interactions between cationic quaternary ammonium compounds and anionic surfaces.

Therefore, acrylic acid and sulfonic acid based acrylic and cationic dyeable polyester fabrics can directly adsorb quaternary ammonium compounds near boiling conditions.

Similarly, glutamic acid and aspartic acid residues in wool have carboxyl groups. Quaternary ammonium compounds, especially sixteen alkylpyridinium chloride, have 5%owf adsorption on untreated wool, and wash resistance is 10 times.

Cotton fabric is treated with 4- amino benzene sulfonic acid - chloro three - azine addition compound to increase the anion position on the surface of the fabric, which is conducive to the adsorption of quaternary ammonium compounds.

In these studies, the adsorption of quaternary ammonium compounds was affected by pH, quaternary ammonium compounds concentration, temperature and adsorption time.

Sun et al. Imagine that the fabric is dyed with acid dyes before the treatment of quaternary ammonium compounds under alkaline conditions. The ionic interaction between dye molecules and quaternary ammonium compounds is sufficient to achieve semi durable antibacterial finishing effect.

A new quaternary ammonium compound N - twelve alkyl - amino betaine -2- Mercaptoethylamine hydrochloride (DABM) was synthesized by Dig et al.

DABM can react with wool with its sulfur hydroxyl, that is, sulfur hydroxyl or reaction with cysteine S sulfonic acid residue (bentite salt) prepared from Sodium Bisulfite pretreated wool or two sulfur bond reaction with wool cystine to form an asymmetric two sulfur bond.

The covalent attachment of the quaternary ammonium surfactants has antibacterial activity on wool.

BIOGUARD, a commercial antibacterial textile made from quaternary ammonium compounds, is produced by AEGISEnvironments company. The active agent is 3- trimethoxy silyl propyl two methyl eighteen alkane and its ammonium chloride (AEM5700, formerly known as Dow Corning 5700 antibacterial agent) MIC 10~100mg/L for gram positive bacteria and gram negative bacteria.

AEM5700 is made of water solution and is prepared by rolling, spraying or foam finishing.

During drying, nonvolatile silane forms covalent bonds with fabrics, resulting in excellent washability.

At present, this kind of chemicals has been applied in cotton, polyester and nylon fabrics.

This particular quaternary ammonium compound does not contain much information about bacteria.

1.3 polyhexyl guanidine

Polyhexyl hexagidine (PHMB) is a hetero disperse mixture with an average molecular weight of 2500 and trade name Vantocil.

Because of its low toxicity, high efficiency and broad-spectrum antibacterial properties (MIC= (0.5~10) x 10-6), it has been successfully used as food industry bactericide and swimming pool disinfectant, and is being explored as gargle, bandage bactericide and so on.

PHMB destroys the cell membrane of bacteria, and its activity increases with the increase of polymerization degree.

So far, few PHMB resistant bacteria have been found.

Because of its cationic nature, PHMB is linked to cotton fabrics by ion and hydrogen bonds.

The production of carboxyl and the introduction of sulfonic groups with reactive dyes can increase the uptake of PHMB in cotton fabrics. However, strong ionic bonds may reduce the release of free PHMB and thus reduce the antibacterial efficacy.

For durable finishing, PHMB requires 2%~4% (OWF) and 0.25%~0.1% (OWF) for disposable products.

PHMB can be impregnated directly on cotton at room temperature and neutral pH (8, 9) or by rolling, baking and baking process.

In order to improve durability and overcome the yellowing of fabrics, Payne said in its patent that cellulose fibers were treated with a strong organic acid after PHMB treatment.

They also use a self crosslinking resin and catalyst to shift PHMB to synthetic fiber treatment.

Arch chemical has developed a special PHMBReputex20 for fabric processing. Reputex has a higher molecular weight than Vantocil. The average polymer contains 16 units of guanidine units. This longer polymer length not only produces higher bactericidal activity, but also forms more cations on each molecule, which can be combined as strongly as possible on the fabric surface.

Reputex was originally used for cotton and its blended fabrics by impregnation or rolling - roasting - roasting process, and recently expanded with Purista name for polyester and nylon fabrics.

1.4 three chlorophenoxy chlorophenol

Three chlorophenoxy chlorophenol 2,4,4 '- three chloro -2' - hydroxy two phenyl ether (Triclosan) is a broad-spectrum antibacterial agent, which is less than 10 * 10-6 for many common bacterial species MIC.

Three chlorophenoxy chlorophenol is not ionized in solution.

In 1960s, it has been widely used in special products and consumer goods, including hand washing soap, hand washing liquid, pre operation disinfectant, deodorant, mouthwash and toothpaste. Its antibacterial mechanism is to block the synthesis of microbial lipids and thus inhibit its growth.

Because three chlorophenoxy chlorophenol molecules are small, before the dyeing of polyester and nylon fibers, with dyeing or bath dyeing, the amount of 5%owf is treated by immersion process.

When the fabric is applied, the agent will migrate to the fabric surface at low speed to provide antibacterial effect.

The patent of Payne introduces cotton and its blended fabric treated with three oxygen phenoxy chlorophenol mixed with polyurethane resin and plasticizer.

In order to achieve more durable finishing, three chlorophenoxy chlorophenol was put into the hydrophobic cavity of beta cyclodextrin to form a inclusion complex, then embedded in polymer film or fiber, or encapsulated in the microsphere, and then adhered to the fiber.

Three chlorophenoxy phenol can also be added directly to the synthetic polymer by melt mixing or suspension polymerization.

Many companies manufacture and sell three chlorophenoxophenol fibers, yarns and fabrics, such as nylon and polyester products TinosanAM100 and CEL of Ciba chemical company, Silfresh cellulose acetate yarn of Novaceta company and Microban textile products of Microban international company, all contain three chlorophenoxy chlorophenol.

However, it has been proved that some bacteria are resistant to three chlorophenoxy chlorophenol, and three chlorophenoxy phenol can be decomposed into 2,8- two chloro two benzo P two oxy chloride under sunlight. Its chemical properties are similar to toxic two polychlorinated compounds.

Because of these problems, European governments and major distributors have been concerned about or banned the use of three chlorophenoxy chlorophenol in textiles and other products.

1.5 N chitosan

Chitosan is a deacetylated derivative of chitin, and chitin is a byproduct of the seafood industry.

The study found that chitosan could inhibit the growth of microorganisms, and the activity of chitosan was affected by molecular weight and degree of deacetylation. But for many common bacterial species, its MIC was 0.05%~0.1%w/v.

The antibacterial mechanism of chitosan is not very clear. It is generally believed that the positive charge supplied by primary amine is responsible for the negative charge residues on the surface of microorganisms, resulting in a variety of changes in cell surface and cell permeability, leading to the exudation of substances in cells.

The antibacterial properties of chitosan, its non-toxic, biodegradability and biocompatibility have promoted its application in food science, agriculture, medicine, pharmaceuticals and textiles.

Chitosan is used as an antibacterial agent primarily for cotton. It is pointed out that antibacterial action is effective for many bacteria, but it does not wash well after finishing.

In order to improve the washability, the deacetylation of chitosan was crosslinked on cotton with chemical agents such as Dihydroxymethyl two hydroxyethylurea (DMDHEU), citric acid, 1,2,3,4- butane four carboxylic acid (BTCA) or glutaraldehyde.

Some of these chemicals have been used in durable press finishing of cotton, which are crosslinked by hydroxyl to cotton.

The antibacterial and washability of cotton fabrics after crosslinking can reach 50 times.

Ye and other nano n / shell particles were prepared by using poly n butyl acrylate as core and chitosan as shell. The antibacterial activity of cotton core fabric was increased by more than 90% after 50 washing.

Chitosan as a shrink proof polymer has been used for wool finishing. Due to the hydrophobicity of wool surface, pretreatment with chitosan is required to make polymer adhere to the fiber surface.

Pretreatment includes peroxide oxidation, protease digestion and plasma treatment.

Hsieh reported that wool was oxidized by Potassium Permanganate and crosslinked by chitosan citric acid through drying - baking process.

After treatment, chitosan has enduring durable antibacterial and shrink proof properties, but it has adverse effects on fabric handle and other physical properties.

In addition to natural chitosan, many chitosan derivatives have been synthesized as antibacterial agents for textiles. These derivatives include chitosan oligosaccharides, N - (2 hydroxypropyl) - propyl - 3 - three methylamine chitosan chloride, N-P- (N- methyl pyridine) methylation chitosan chloride and N-4-[3 (trimethylamine) propyl] acetylated chitosan chloride and so on.

Most of these derivatives contain quaternary ammonium genes to increase their antibacterial activity.

Another derivative is O - acrylamide methyl - N - [(2 - hydroxyl - 3 - trimethylamine) propyl] chitosan chloride, acrylamide methyl has fiber reactivity, and can form a covalent bond with cellulose in cotton, thereby having excellent washability.

Kenawy et al. Also connected several compounds to the active amino groups of chitosan, which are highly active for microorganisms, especially mold species.

There are many researches on chitosan for antibacterial treatment of cotton and polyester fabrics. However, the use of chitosan is limited because of poor handle.

Swiss Swicofil has recently made a composite fiber Crabyon of chitosan and viscose. It is said that this fiber has durable antibacterial effect and is suitable for many textiles.

Early studies have shown that although chitosan can be spun into fibers, their applications seem to be limited to medical gauze, sutures and bandages.

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1.6 renewable N - halogen amine and peroxy acid

Another durable antibacterial finish can be obtained by reusing N halogen amine compounds containing chlorine.

N halogen amine compound is a broad-spectrum disinfectant and has been used in water treatment.

Their antibacterial capacity is due to the oxidation property of halogen amine bond (N-Cl).

When the microorganism is inactivated, the N halogen amine bond is reacted to N-H, but the reaction is reversible, and the passivated substance can be regenerated in the washing liquid when the treated fabric is washed.

This regeneration method was first proposed in 1998 by Sun et al. Since then, various heterocyclic N- halogen amines have been studied and covalently linked to nylon, polyester, cotton and keratin fibers, or to be grafted on cellulose and synthetic fabrics.

However, in addition to covalently attached N- halogenamines, a large number of adsorbed chlorine (or other halogens) can be retained on the surface of the fabric when N- halogen amine is treated.

These adsorbed residual halogens cause an unpleasant odour and discolouration of fabrics, resulting in the problem of a promising antibacterial system in the textile industry.

For this reason, sodium sulfite has been suggested as a reduction measure for removing unbonded residual chlorine or other halogens.

Peroxy acid, such as peracetic acid, can be used as another renewable antibacterial finishing agent.

Peracetic acid is known to be a powerful disinfectant commonly used in hospitals.

Peroxic acid is converted to carboxylic acid in the process of inactivation of bacteria, but it can be regenerated by reaction with oxidants such as hydrogen peroxide.

The study of Huang and Sun confirmed that it is similar to the durable press finishing of cotton, and BTCA or citric acid can be grafted on cotton fabric by rolling drying baking process, and the possibility of further antibacterial finishing is further realized.

Graft polycarboxylic acids provide necessary carboxylic groups for cotton fabrics, which are then converted into peroxy acids in oxygen bath or with strong oxidant sodium perborate.

In addition to cotton fabric, this finishing can also be used in polyester fabrics.

After finishing, the peroxy acid in the fabric is stable during the whole storage period, but the antibacterial activity may be weakened after several washing and regeneration cycles.

1.7 dyes

Some synthetic dyes used in textile industry, such as metallic dyes, show antibacterial activity. Therefore, by choosing some specific dyes, they can achieve both purposes of dyeing and antibacterial finishing.

Certain synthetic dyes with specific antibacterial activity, such as a new type of azo disperse dye containing sulfonyl amino part, which are prepared by reaction of sulfadiazine derivative with 1,3 two - ketone, can produce excellent dyeing and antibacterial properties for wool and nylon.

Another way to achieve the effect of dyeing and antibacterial finishing is to bind the antibacterial agent covalently on the dye through the crosslinking agent, for example, cross the quaternary ammonium group on the amino anthraquinone chromophore to synthesize the new cationic dye.

These dyes show various antibacterial activities according to their structure, but when applied to acrylic fabrics, their antibacterial durability is poor, generally not exceeding 5 times.

Some natural dyes, such as turmeric, a common dyestuff used in fabrics and food coloring, a yellow dye and coloring agent berberine separated from oak bark, contain quaternary ammonium groups. When connected to textiles, they can show durable antibacterial efficacy.

1.8 analysis and comparison, the above antibacterial agents are summarized in Table 1. Silver, PHMB, quaternary ammonium compounds and three chlorophenoxy phenol are currently being applied in many kinds of natural and synthetic textiles antibacterial textiles, while chitosan and many renewable antimicrobial agents are still in development stage.

These antibacterial agents can be applied in accordance with specific fibers as finishing agents, and can also be added when synthetic fibers are extruded.

2 Conclusion

Customers' desire for comfort, hygiene and maintaining a good living condition has stimulated the sales of antibacterial textiles to grow rapidly and rapidly.

In the textile industry, a large number of manufacturers have produced their brands of antibacterial products to cater for this need.

These products use broad-spectrum biocide such as silver, Polyhexylene, guanidine, quaternary ammonium compounds and three chlorophenoxy chlorophenol as active agents.

Some treatment is carried out in the finishing stage of fabrics, while some antibacterial agents can be added into the fibers when extruding the synthetic fibers. Generally speaking, commercial antibacterial textiles comprise most of the major fiber types in the textile industry.

On the other hand, several other antibacterial agents, such as chitosan and its derivatives, renewable active N- halogen amine and peroxic acid, and some special antibacterial dyes are still in development stage.

The antibacterial efficacy and durability of antibacterial textile products vary from fiber type, biocide type and finishing method. In some cases, the durability of antibacterial effect is poor.

Although antibacterial textiles have the advantages of preventing textiles from being attached to bacteria, they have the advantages of health and odour. However, the resistance of bacteria to antimicrobials and the possible decomposition products of antibacterial agents themselves have attracted much attention.

Most of the biocide used in textiles can induce bacterial resistance to these substances, which will increase the resistance to some antibiotics used in clinical practice.

Bacterial resistance needs special attention because in order to achieve sufficient activity and durability, large doses of antimicrobials must be applied.

This concern led to the ban of three chlorophenoxy phenol in textiles in Europe.

Therefore, the long-term benefits and potential problems of antibacterial textiles should be considered and monitored strictly.