Patent Publication Number: US-2005115007-A1

Title: Anti-microbial fabric treatment

Description:
The invention relates to a method of modifying polymers so as to impart an antimicrobial finish to fabrics or other polymeric materials and to the modified polymers produced thereby.  
      It is known to coat fibres with various bactericides. However the coatings lack durability and are generally lost on washing. For example products based on a polydiguanide, as described in WO99/12021, are available commercially.  
      An alternative approach is to modify the polymer of the fibre with a reactive compound, which is capable of introducing a bactericidal site into the polymer molecule. The main commercial product embodying this principle is a quaternised alkylamino silane, of the type described in U.S. Pat. No. 4,504,541. This product is unstable in water and has to be supplied as a solution in methanol, giving rise to serious health, safety and environmental concerns. Moreover, the product tends to make the fabric hydrophobic, which is undesirable for many applications.  
      We have now discovered that quaternary alkylamino-2-hydroxy-3-chloropropanes, which may be obtained from the acid catalysed reaction of epichlorhydrin with tertiary amines, form stable aqueous solutions under acidic or neutral conditions, which are capable of reacting with the free amino or carboxy groups of protein or polyamide fibres at elevated temperatures. Moreover, they are converted at alkaline pH to epoxides, which react with polymers having epoxy-reactive groups, e.g. hydroxyl-containing polymers. We have discovered that polymers modified by the above reactions exhibit strong and lasting anti-microbial properties:  
                 
 
      According to its most general embodiment the invention provides a polymer modified, by the incorporation into the molecule thereof of quaternary amino-2-hydroxypropyl-3 groups.  
      According to one specific embodiment, our invention provides a method of modifying a polymer having epoxy-reactive groups, which comprises contacting it with an aqueous solution of a quaternary amino-2,3-epoxypropane.  
      According to a second specific embodiment the invention provides a method of modifying a polymer having free carboxy and/or amino groups, which comprises contacting it with an aqueous solution of a quaternary amino-2-hydroxy-3-chloropropane.  
      In the following discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.  
      The quaternary amino groups preferably have the formula:  
                 
 
 (where R, R′ and R″ are organic groups, which may be the same or different). 
 
      Preferably R is an aliphatic group and more preferably a linear or branched chain group, or mixture of groups, having from 6 to 30 carbon atoms, preferably at least 10, more preferably at least 12, most preferably at least 14, but preferably less than 25, more preferably less than 22, most preferably less than 20 carbon atoms. R is preferably an alkyl group, but may, optionally be, for example, an alkenyl, polypropoxy, alkylpolyethoxy, alkenylpolyethoxy, polypropoxypolyethoxy or alkylamidopropyl group.  
      R′ and R″ can be the same or different. Either, but preferably not both, could, for example be the same as R, or a benzyl group. However, they are each preferably alkyl or hydroxyalkyl groups with less than five carbon atoms, especially methyl groups, or optionally ethyl or hydroxyethyl groups.  
      The polymer is preferably a natural or synthetic fibre, or woven or unwoven fabric manufactured therefrom, especially a cellulosic fibre such as cotton, linen, cellulose acetate or viscose. Such hydroxy-containing polymers normally require a pH high enough to form the aminopropylene oxide in order to react to a commercially acceptable extent.  
      The fibre may alternatively be a protein, such as wool, silk or casein, or a polyamide. Other polymeric materials, which may be treated, include collagen. The polymer may, for example, comprise the collagenous and/or keratinous integuments of animals, e.g. skins, including the skins of mammals, reptiles, fishes or birds, fleeces, woolskins, plumage or leather obtained by tanning any of the foregoing.  
      Protein polymers may be damaged by the high pH needed to form the epoxide, but react readily when heated with its amino-2-hydroxy-3-chloropropane precursor.  
      The aminopropylene oxide is unstable to storage, being slowly hydrolysed to the corresponding aminopropylene glycol. The reagent is therefore preferably formed in situ or immediately prior to use by basification of the amino-2-hydroxy-3-chloro propane. The latter may be prepared by reacting epichlorhydrin with tertiary amine in acid solution. The solution is preferably maintained at a pH below 7, e.g. 4 to 6. The counter ion of the cationic quaternary amino group is not critical. It will normally be chloride, but could be any other anion, preferably of a strong mineral acid, that does not adversely affect the product.  
      The reagent may be applied to a polymer as the acid solution and then basified, if necessary. Alternatively the solution may be basified immediately prior to contacting with the substrate to be treated. Preferably for cellulosic fibre, the pH is raised above 7.5, more preferably above 8, most preferably above 9, especially above 10, typically above 11, e.g. 12 to 13.5. For protein substrates, the pH is preferably raised close to, but preferably not above, neutral, e.g. 6 to 7. Basification is preferably effected by adding alkali such as sodium hydroxide, or any obvious equivalent, such as potassium or ammonium hydroxide.  
      The concentration of active ingredient in the solution is preferably greater than 5% by weight, more preferably greater than 10%, even more preferably greater than 15%, more preferably still, greater than 20%, most preferably greater than 25%, e.g. greater than 30%, and up to saturation. The reagent is preferably applied at a loading of at least 0.5%, more preferably at least 1%, even more preferably a least 1.5%, most preferably at least 2%, but preferably less than 10%, more preferably less than 5% even more preferably less than 3%, most preferably less than 2.5% by weight based on dry weight of polymer. According to a particularly preferred embodiment, the reagent is applied to cloth at the mercerising stage, thereby avoiding the introduction of an additional step in the manufacturing process.  
      The cloth is preferably treated for from 1 to 20, e.g. 2 to 10, especially 3 to 7 minutes at elevated temperatures, preferably above 50° C., more preferably above 60° C., most preferably above 70° C., e.g. above 80° C. It is especially preferred, particularly when treating proteins, to heat to temperatures above 100° C., e.g. 110 to 160° C.  
      The reagent may be used in conjunction with compatible surfactants, such as amine oxides, e.g. in conventional concentrations.  
      The invention is of particular value in the production of textiles for medical use, such as hospital uniforms, surgical masks, gowns and drapes, sutures bandages and dressings, carpeting and upholstery, bed linen, underwear, socks and air filters. It is also of value for wet wipes for domestic and personal care applications.  
      A particular advantage of the invention is that the treated fibres or fabric exhibit improved uptake of certain dyes, especially anionic dyes, from dyebaths. A further aspect of the invention therefore provides a method of dyeing in which the substrate comprises a polymer having epoxy-reactive groups, which is contacted with a quaternary amino-2,3-epoxypropane, and subsequently with an anionic dyebath.  
      The invention is of value in the treatment of leather. We prefer that the reagent is applied as, or as part of, the tannage, e.g. in conjunction with syntans, vegetable tannages or mineral tannages such as chrometan.  
      The invention is illustrated by the following examples in which percentages are by weight, unless stated to the contrary. 
    
    
     EXAMPLE 1  
      A 35% active aqueous solution of a fatty alkyl dimethylamino-2-hydroxy-3-chloropropane, wherein the fatty alkyl feedstock comprised a mixture of alkyl groups with 12 to 18 carbon atoms, was adjusted from its pH of 5 to a pH of 13 with 0.6% of solid sodium hydroxide. Cotton fabric was impregnated with the alkaline solution at an application rate of 2.3% active matter, based on the dry weight of cloth. The fabric was passed through a pad mangle to give 60% uptake and heated to 140° C. over a period of five minutes. After treatment the cloth was boiled in 5 g/l aqueous Cl 12-18  alkyl dimethyl amine oxide and rinsed. The treated cloth exhibited excellent antimicrobial activity, which was retained after washing in boiling water.  
      Three samples of the cloth were washed in domestic washing powder at 60° C. for five wash cycles. The washed samples gave 97.3%, 98.8% and 98.1% reduction, respectively, in a standard antimicrobial performance test. (Pass result is 85% reduction)  
     EXAMPLE 2  
      10 gram of scoured and bleached woolen plain fabric was boiled for 60 minutes in 200 ml of a liquor containing 1% N-C 18  alkyl N,N-dimethyl N-(3-chloro-2-hydroxy propyl)-ammonium chloride (“Quabb”® 426, supplied by Degussa A G) adjusted to an initial pH of 6 by adding 47% NaOH to the liquor. Upon the completion of this treatment, the fabric was removed from the liquor and rinsed thoroughly in tap water, and then treated in a hot water bath at the boil for 30 minutes followed by a second thorough rinsing under the tap water. The fabric was left to dry under room temperature. The treated cloth exhibited excellent antimicrobial activity, giving 98.5% reduction in the antimicrobial performance test.  
     EXAMPLE 3  
      Example 2 was repeated except that the pH of the liquor was maintained throughout the treatment by adding 47% NaOH to the liquor as required. The treated cloth exhibited excellent antimicrobial activity, giving 99.9% reduction in the antimicrobial performance test.  
     EXAMPLE 4  
      Example 2 was repeated except that the liquor also contained 1% C 12 -C 18 alkyl dimethyl amine oxide. The treated cloth exhibited excellent antimicrobial activity, giving 95.5% reduction in the antimicrobial performance test.  
      The antimicrobial performance test used in the foregoing examples measured the percentage reduction in optical density of a suspension of approximately one million counts of  Klebsiella pneumoniae  after one hour&#39;s contact.