Method for producing antimicrobial yarns and fabrics by nanoparticle impregnation
The invention relates to a method for producing an antimicrobial fabric or yarn, said method comprising the steps of immersing a fabric or yarn in an aqueous solution of a metal salt while simultaneously subjecting said solution to ultrasonic radiation; and removing the fabric or yarn from said solution and subsequently converting the metal salt in situ in the fabric or yarn into metal oxide nanoparticles, preferably via chemical and heat treatment. Fabrics and yarns obtained or obtainable by such method are also provided. In a further aspect the invention provides an apparatus for performing such method.
1. A method for producing an antimicrobial fabric or yarn, said method comprising the steps of:
(i) immersing a fabric or yarn in an aqueous solution of a metal salt whilst simultaneously subjecting said solution to ultrasonic radiation; and
(ii) removing the fabric or yarn from said solution and subsequently converting the metal salt in situ in the fabric or yarn into metal oxide nanoparticles;
wherein step (ii) comprises exposing the fabric or yarn, whilst still damp, to ammonia or a primary amine in gaseous form; and heating the fabric or yarn.
2. A method according to claim 1 , wherein the metal salt is a salt of a metal whose oxide has antimicrobial properties.
3. A method according to claim 1 , wherein the metal salt is a salt of copper, zinc or magnesium.
4. A method according to claim 1 , wherein the metal salt is a halide, nitrate, nitrite, sulphate, acetate, propanoate or butanoate.
5. A method according to claim 1 , wherein the metal salt is selected from the group consisting of copper (II) sulphate, copper (II) acetate, copper (II) chloride, copper (II) fluoride, copper (II) bromide, copper (II) iodide, copper (II) nitrate, copper (II) nitrite, copper (II) propanoate, copper (II) butanoate, zinc sulphate, zinc acetate, zinc chloride, zinc fluoride, zinc bromide, zinc iodide, zinc nitrate, zinc nitrite, zinc propanoate, zinc butanoate, magnesium sulphate, magnesium acetate, magnesium chloride, magnesium fluoride, magnesium bromide, magnesium iodide, magnesium nitrate, magnesium nitrite, magnesium propanoate, magnesium butanoate, and mixtures thereof.
6. A method according to claim 1 , wherein the aqueous solution contains only a single metal salt.
7. A method according to claim 1 , wherein the aqueous solution contains a plurality of metal salts.
8. A method according to claim 1 , wherein the metal salt(s) is/are present in the aqueous solution in an amount of about 0.001 mol/L to about 0.25 mol/L.
9. A method according to claim 1 , wherein the aqueous solution is substantially free of ammonia.
10. A method according to claim 1 , wherein the duration of ultrasonic radiation is about 15 minutes or less.
11. A method according to claim 1 , wherein step (i) is carried out at a temperature of up to about 60° C.
12. A method according to claim 1 , wherein the duration of exposure of the fabric or yarn to ammonia or a primary amine is about 25 minutes or less.
13. A method according to claim 1 , wherein heating is carried out at a temperature of about 100° C. to about 150° C.
14. A method according to claim 1 , wherein heating is carried out by microwave heating or electrical heating.
15. A method according to claim 1 further comprising the following steps:
(iii) washing the fabric or yarn after step (ii) and, optionally,
(vi) drying the fabric or yarn.
16. A method according to claim 1 , wherein the method is performed as a continuous process.
17. A method according to claim 1 , wherein the method is performed as a batch process.
18. A method according to claim 1 , wherein the fabric or yarn comprises naturally-occurring or semi-synthetic fibres.
19. A method according to claim 1 , wherein the fabric or yarn comprises cotton, hemp, or silk.
20. An apparatus for performing a method as described in claim 1 , said apparatus comprising: a first vessel for immersing a fabric in a metal salt solution, said vessel being adapted to provide ultrasound radiation to said solution; a second vessel arranged to receive the fabric or yarn from said first vessel, said second vessel being adapted for the exposure of the fabric or yarn to gaseous ammonia; a source of ammonia gas connected to said second vessel; and heating means for heating the fabric or yarn.
21. An apparatus according to claim 20 further comprising a recirculation circuit adapted to allow a metal salt solution to be continuously circulated through the first vessel whereby to maintain a substantially constant metal salt concentration in the metal salt solution located in the first vessel.