WO2002006579A2

WO2002006579A2 - Biocidal polyamides and methods

Info

Publication number: WO2002006579A2
Application number: PCT/US2001/019219
Authority: WO
Inventors: Jian Lin; Shelby D. Worley; Royall M. Broughton
Original assignee: Auburn University
Current assignee: Auburn University
Priority date: 2000-07-13
Filing date: 2001-06-15
Publication date: 2002-01-24
Anticipated expiration: 2003-01-13
Also published as: WO2002006579A3; AU2001266939A1

Abstract

Biocidal polyamide materials such as deodorant and/or biocidal Nylon® polyamide fibers, fabrics and surfaces and biocidal Aramid (such as Kevlar® and Nomex®) fibers, fabrics and surfaces, and methods of preparation. Heterocyclic N-halamine precursor moieties are covalently linked to the polyamide material. The fabrics and/or fibers thereafter obtain antimicrobial activity after washing with a halogenated solution to convert the heterocyclic precursor moieties into heterocyclic N-halamines. The antimicrobial activity against pathogenic microorganism can be repeatedly regenerated by washings with a halogenated solution.

Description

BIOCIDAL POLYAMIDES AND METHODS

Field of the Invention This invention is in the field of antimicrobial textiles and materials; more particularly it relates to biocidal and/or deodorant polyamide and aramid fibers, fabrics and surfaces.

Background of the Invention

Bacteria, fungi, viruses, algae and other microorganisms are always present in our environment. Some microorganisms are highly undesirable as a cause of odors, skin irritation, and illness. Most of the odor on clothing comes from bacteria and fungi which are growing on the perspiration and the skin cells that are in clothing.

Bacteria and fungi are deposited on carpets through the normal traffic of people and animals, food and beverages spilled on the carpet, and animal and infant waste. The unhealthy accumulation of bacterial or fungal growth can create a foul odor. Further, frequent, long-lasting local infections may be brought about by Nylon® polyamide surgical sutures incorporated into tissues and soaked with liquids being potential culture media for bacteria (J. Buchenska, J. Appl. Polym. Sci., 61, 567 (1996)).

There is a need for polyamide materials with antimicrobial activity, including by way of example: antimicrobial surgical sutures, clothing that exhibits a deodorizing action and that inhibits the transmission of pathogenic bacteria; carpets that control the growth of a wide variety of unwanted microorganisms; and aramid materials that possess surface antimicrobial activity.

There are two conventional methods for realizing antimicrobial function in textile fibers. One is to mix in particles of an antimicrobial additive with the yarn itself at the spinning stage, and the other, termed the "after-treatment" method, is to impregnate or coat a fabric with a urethane or other resin in which particles of the antimicrobial additive have been added (T. Kawata, et al, Chem. Fibers Int., 48, 38 (1998)). In the former method of mixing particles into the fibers, particles in the size range of microns are required for normal textile fibers. Even if addition is possible, the particles may lose their function due to the spinning conditions (particularly heat), or because they are buried within the fiber, and thus inaccessible to the microorganisms. The strength of the yarn may deteriorate, or the spinning efficiency may decline.

For these and other reasons, it has been more convenient to impart the antimicrobial function by resin treatment and other after-treatment coating methods. In such after-treatment methods, however, there is the disadvantage that the resin constrains the fibers, and therefore the feel of the fibrous substrate can be remarkably impaired. Also, there is the problem that the resin itself may become detached during use or washing, and the antimicrobial function is then lost. Further, the antimicrobial additives currently employed such as biguanide derivatives, organosilicon-based quaternary ammonium salts, and organic metals (Ag, Cu, Zn) supported on zeolite are not always safe to the human body, and in some cases, they can cause contact dermatitis to humans, especially those having delicate skin, such as newborn babies. Thus, current surface treatments sometimes entail safety problems (T. Kawata, et al., Chem. Fibers Int., 48, 38 (1998)).

Recently, in response to the demand for a safer antimicrobial and deodorizing treatment, methods have been proposed for treating surfaces with antimicrobial halamines that are not toxic, such as N-halohydantoins. Such compounds are disclosed in S.D. Worley, et al. US Patent Nos. 5,057,612; 5,126,057; 5,490,983; 5,670,646; 5,889,130; 5,902,818 and G. Sun, et al. US Patent No. 5,882,357, the disclosures of which are hereby incorporated by reference. While such compounds have been disclosed and are believed to overcome disadvantages of resin treatments noted above, methods for treating polyamide and aramide materials, including fibers and fabrics, with N-halamine materials have not been known previously. Summary of the Invention

The present invention provides antimicrobial polyamide materials, including Nylon® fibers, fabrics and other surfaces and materials, and aramid fibers, fabrics and other surfaces and materials. These materials exhibit deodorant and biocidal properties. The biocidal polyamides are prepared in accordance with the present invention by covalently linking heterocyclic N-halamine precursor compounds to them. The polyamides thereafter obtain antimicrobial activity through washing or other exposure to a halogenated solution including a free halogen, to convert the heterocyclic precursor compounds into heterocyclic N-halamines. Moreover, the antimicrobial activity against pathogenic microorganisms can be repeatedly regenerated by washings or other exposure to a halogenated solution.

In one embodiment, the present invention provides a process for preparing biocidal precursor polyamide fibers, fabrics (or other surfaces and materials). The process entails the steps of: (a) pretreating polyamide fibers or fabrics with a dilute formaldehyde solution under basic or acidic conditions; (b) immersing the pretreated fibers or fabrics in an aqueous finishing bath which contains a heterocyclic N-halamine precursor compound, a wetting agent, and a catalyst; (c) curing the treated fibers or fabrics; and (d) washing and drying the cured fibers or fabrics to yield precursor polyamide fibers or fabrics.

In another embodiment, the present invention provides a process for rendering the precursor polyamide fibers or fabrics antimicrobial, and for regenerating spent polyamide fibers and fabrics that have previously been treated in accordance with the present invention but that have lost a significant degree of biocidal activity. The precursor polyamide fibers or fabrics, or spent fibers or fabrics, are washed, immersed or otherwise exposed to a halogenated solution. In a preferred process, the halogenated solution is a chlorine solution or, alternatively, may suitably be a bromine solution. In a most preferred embodiment, the halogenated solution is a hypochlorite solution (e.g., a chlorine bleach solution such as Clorox®).

In a third embodiment, the present invention provides a process for rendering products containing the polyamide Aramids, such as Kevlar® or Nomex®, antimicrobial active.

Other features, objects, and advantages of the invention and its preferred embodiments will become apparent from the following detailed description. Detailed Description of the Preferred Embodiment "Nylon® fabrics or fibers", as used herein, refers to fabrics, fibers or other surfaces and materials that are primarily produced from polyamides, such as Nylon®-6, Nylon®-66, Nylon®-l l, Nylon®- 12, generic equivalents of such polyamides, and aramids. "Aramid fabrics or fibers", as used herein, refers to fabrics, fibers or other surfaces and materials that are primarily produced from such as Kevlar® and Nomex® aromatic polyamides.

"Antimicrobial", as used herein, refers to the ability to kill or to substantially inhibit the growth of certain predetermined types of microorganisms. The fabrics and fibers prepared in accordance with the present invention preferably have antimicrobial activity against a broad spectrum of pathogenic microorganisms. For example, the materials have antibacterial activity against representative Gram-positive bacteria (such as Staphylococcus aureus) and Gram-negative bacteria (such as Escherichia coli).

"Regenerable" refers to antimicrobial fabrics and fibers treated in accordance with the present invention, that have obtained a reduced level of antimicrobial activity due to exposure to microorganisms or contamination, and which are susceptible to being restored to approximately the initial level of antimicrobial activity.

"Heterocyclic N-halamine precursor compound", as used herein, refers to a 4- to 7-member cyclic compound, wherein at least 3 members of the ring are carbon atoms, 1 to 3 members of the ring are nitrogen atoms, and 0 to 1 member of the ring is oxygen atom. The compound comprises at least one imide, amide or amine group, and preferably 2 to 3 of these groups included in a ring. No hydrogen atom is attached to the carbon atoms that are directly connected to the nitrogen atoms in the ring. The compound preferably contains 0 to 2 carbonyl groups.

"Nylon® precursor fabric or fiber" refers to a Nylon® fabric or fiber to which heterocyclic N-halamine precursor compound moieties have been covalently bonded. "Heterocyclic N-halamine," as used herein, refers to a compound with one or more nitrogen-halogen covalent bonds, which are halogenated derivatives of the above heterocyclic N-halamine precursor compounds.

Examples of heterocyclic N-halamine precursor compounds suitable for use in accordance with the present invention are: 4-hydroxymethyl-4-ethyl- 2-oxazolidinone, 3-hydroxymethyl-2,2,5,5-tetramethyl-l,3-imidazolidin-4-one,

1 -hydroxymethyl-5 , 5 -dimethylhydantoin, 3 -hydroxymethyl-5 ,5 -dimethylhy dantoin, and hydroxymethyl derivatives of 6,6-dimethyl-l,3,5-triazine-2,4-dione, 4,4,5, 5-tetramethyl-l,3-imidazolidin-2-one, and cyanuric acid.

Preferred N-halamine precursors are 4-hydroxymethyl-4-ethyl- 2-oxazolidinone, 3-hydroxymethyl-2,2,5,5-tetramethyl-l,3-imidazolidin-4-one, l-hydroxymethyl-5,5-dimethylhydantoin, and 3-hydroxymethyl-

5 , 5 -dimethylhydantoin.

Most of the heterocyclic N-halamine precursor compounds used in the present invention are commercially available from a number of different sources. For instance, l-hydroxymethyl-5,5-dimethylhydantoin and 3-hydroxymethyl- 5, 5 -dimethylhydantoin are commercially available under the trade name DANTOIN® from LONZA, INC. (Fair Lawn, NJ). Moreover, cyanuric acid is commercially available from ALDRICH, Inc. (Milwaukee, WI). In addition, those of skill in the art will appreciate that the heterocyclic N-halamine precursor compounds used in the present invention can be prepared by a variety of conventional synthetic techniques. It should be noted that many of these types of compounds are widely used in cosmetic products, and their halogenated derivatives are major disinfectants for uses in, for example, swimming pools. As such, these compounds are believed not to generate toxic effects for humans or for the environment either in terms of the treated materials or during the treating process.

"Catalyst", as used herein, refers to a substance which augments the rate of a chemical reaction by a predetermined degree without itself being consumed. Examples of suitable catalysts for use in the present invention are: magnesium salts, zinc salts, and ammonium salts. In preferred embodiments, the employed catalysts are one of the following: MgCl₂, Mg(NO₃)₂, and NH NO₃.

"Wetting agent", as used herein, refers to a substance that increases the rate at which a liquid spreads across a surface, i.e., it renders a surface non-repellent to a liquid. Examples of suitable wetting agents are: Triton® X-100 (Sigma Chemical Co., St. Louis, MO), SEQUAWET® (Sequal Chemical Inc., Chester, SC), and AMWET® (American Emulsions Co., Dalton, GA).

In one embodiment, the present invention provides a process for preparing antimicrobial Nylon® precursor fibers or fabrics. The process includes the steps of:

(a) pretreating Nylon® fibers or fabrics with a dilute formaldehyde solution; and then

(b) immersing the pretreated fibers or fabrics in an aqueous treating bath which contains a heterocyclic N-halamine precursor compound. Preferably, the treating bath also includes a wetting agent and a catalyst. The process preferably further includes the steps of: (c) curing the treated fibers or fabrics; and (d) washing and drying the cured fibers or fabrics.

In step (a), the dilute formaldehyde solution refers to the concentration of formaldehyde solution ranging from 1% to 15%), preferably from 5% to 10%. Preferably the formaldehyde pretreatment takes place under either acidic or basic conditions, to improve results. The pH of the solution should be either at an acidic level of from 0 to 5 (suitably adjusted with H₂SO₄), or at a basic level of 12 to 14 (suitably adjusted with NaOH). Still most preferably, pretreatment is done at an acidic level of less than or equal to 1, or a basic level of greater than or equal to 13. While either acidic or basic conditions are suitable for most polyamides, acidic conditions are necessary for the Aramids. The temperature of pretreatment ranges from room temperature to 100°C, preferably 75°C to 85°C. The period of pretreatment time ranges from 30 minutes to 240 minutes, preferably 120 minutes to 180 minutes. After pretreatment, the pretreated material is preferably neutralized using a water rinse.

In step (b), the aqueous treating bath comprises a heterocyclic N-halamine precursor compound, and preferably also a wetting agent and a catalyst. The concentration of the various components of the aqueous treating bath can be widely varied depending on the particular employed components and the desired results. Typically, the heterocyclic N-halamine precursor compound is present at a concentration ranging from 0.5%> to 20%>, preferably at a concentration of 5% to 10%). The wetting agent is typically present at a concentration ranging from 0.1%) to 3%, preferably at a concentration of 0.1% to 1%>. The concentration of the catalyst depends on the concentration of the heterocyclic N-halamine precursor compound employed. Typically, the ratio of heterocyclic N-halamine precursor compound to catalyst ranges from 25:1 to 5:1. Those of skill in the art will appreciate that other additives can be incorporated into the aqueous treating bath to impart favorable characteristics to the Nylon® fabrics. Such additives include softeners and waterproofing agents. Examples of softeners that can be added to the aqueous treating bath include MYKON® and SEQUASOFT®, both of which are commercially available from Sequal Chemical Inc. (Chester, SC). Examples of waterproofing agents are SEQUAPEL® (Sequal Chemical Inc., Chester, SC) and SCOTCHGARD® (3M, St. Paul, MN). The pH of the aqueous treating bath typically ranges from 2 to 6, preferably, from 2.5 to 4.5. The temperature of the treating process typically ranges from room temperature to 100°C, preferably from 70°C to 85°C. The time of treatment typically ranges from 30 minutes to 120 minutes, preferably from 30 to 60 minutes.

In step (c), the material treated as above is dried, and is then cured at a temperature ranging from 120°C to 180°C, preferably, from 120°C to 140°C, for a period of time ranging from 10 to 60 minutes, preferably 10 to 30 minutes. The curing is carried out in an oven, preferably one having a forced draft of air directed at the surface of the materials and exhausting through a vent to remove fumes.

In step (d), the cured materials are washed or rinsed with either hot or cold water to remove excess unreacted compounds. The formed covalent bonds are stable, insoluble, and durable to mechanical agitation, spraying, and rubbing that occurs in commercial washing machines or in large scale continuous or batch-wise washing equipment.

In a further aspect of the preferred embodiment, the present invention provides a process for rendering the Nylon® precursor fabric or fibers with antimicrobial active. The biocidal precursor fabric or fiber is washed with a halogenated solution and dried. The halogenated solution may suitably be a chlorine solution or a bromine solution. In a preferred embodiment, the halogenated solution is a chlorine solution (e.g., a chlorine bleach solution such as Clorox®). The concentration of active chlorine in the bleach solution ranges from about 0.25%> to about 2.5%), preferably about 0.75%o. The washing with halogenated solution not only renders the fabric or fibers antimicrobial active, but also sterilizes the fabric or fibers. Moreover, the antimicrobial activity which could be weakened after killing microorganisms can be regenerated and enhanced by periodically washing with a halogenated solution.

After use or contamination resulting in degradation of antimicrobial activity, a depleted antimicrobial fabric, fiber or other material produced in accordance with the present invention can be regenerated or restored, multiple times, by repeating the step of washing in a halogenated dilution as described above. In yet another embodiment, polyamide Aramids, such as Kevlar® and

Nomex®, can be rendered biocidal by procedures analogous to those described above for other polyamides. However, for aramids, the formaldehyde pretreatment is carried out under acidic conditions, i.e., pH of 0 to 5, preferably a pH of less than or equal to 1. The methods of the present invention are suitably used to treat: Nylon® polyamide and aramide fibers, which treated fibers can be used to manufacture textile fabrics, carpets, etc.; and woven and nonwoven textile fabrics, which can then be used to manufacture clothing, undergarmets, sheets, medical and dental drapes, stockings, etc. Additionally, the methods of the present invention can be used to treat the finished articles themselves, e.g., clothing, undergarmets, stockings, sheets, medical and dental drapes, etc. While the methods of the present invention are well suited for treating fibers, fabrics, and articles produced therefrom, the methods of the present invention are also useful in treating other polyamide and aramid surfaces and materials, such as polyamide surgical staples and medical devices, toys, countertops, cutting boards, utensils and the like.

The invention will now be further described in more detail by way of specific examples. The following examples are offered for illustrative purposes, and not for limiting the invention.

Example 1 This example illustrates the treatment of Nylon® 66 fabrics with

4-hydroxymethyl-4-ethyl-2-oxazolidinone.

2.0 Grams of Nylon® 66 fabric were dipped in 200 milliliters of 10% concentration of formaldehyde solution under basic conditions (0.5 N NaOH) at 80°C for 2 hours. While basic conditions were utilized, it is noted that acidic conditions (pH < 1 using H₂SO ) can also be used in this treatment. The fabric was squeezed to remove solution and washed with distilled water until neutral. A treating bath was prepared which contained 10 grams of 4-hydroxymethyl-4-ethyl-2-oxazolidinone, 0.5 gram of magnesium chloride as a catalyst, 0.2 gram of Triton X-100 as a wetting agent, and 200 milliliters of distilled water. The pH of the bath was adjusted to 3.5 with 1%) concentration of sulfuric acid solution. Then the pretreated fabric was immersed in the bath at 80°C for 30 minutes. After squeezing and drying, the fabric was cured at 130°C for 15 minutes. Finally, the finished fabrics were washed with a detergent solution 124 at a temperature of about 50°C for 30 minutes.

Thereafter, the treated fabrics were washed with a diluted Clorox® solution containing about 0.75%> active chlorine for a period of 3 hours. Antimicrobial properties of the fabrics were tested against representative Gram-positive bacteria (such as Staphylococcus aureus (ATCC 5368)) using the protocol set forth in Example 5.

Example 2 This example illustrates the treatment of Nylon® 66 fabric with

3-hydroxymethyl-2,2,5,5-tetramethylimidazolidin-4-one.

10.0 Grams of Nylon® fabric were dipped in 200 milliliters of 10% concentration of formaldehyde solution under basic conditions (0.5 N NaOH) at 85°C for 2 hours. Again, it is noted that acidic conditions (pH < 1 using H₂SO₄) could alternatively be used in this treatment. The fabric was squeezed to remove solution and washed with distilled water until neutral. 2,2,5,5-teframethylimidazolidin-4-one was reacted with formaldehyde catalyzed by potassium carbonate to give 3-hydroxymethyl-2,2,5,5-tetramethylimidazolidin-4-one. A treating bath was prepared which contained 10 grams of 3-hydroxymethyl- 2,2,5, 5-tetramethylimidazolidin-4-one, 1.0 gram of magnesium chloride as a catalyst, 0.2 gram of Triton X-100 as a wetting agent, and 200 milliliters of distilled water. The pH of the bath was adjusted to 3.0 with 1% concentration of sulfuric acid solution. Then the fabric was immersed in the bath at 50°C for 30 minutes. After squeezing and drying, the fabric was cured at 130°C for 15 minutes. Finally, the finished fabrics were washed with a detergent solution at a temperature of about 50°C for 30 minutes.

Thereafter, the treated fabric was washed with a diluted Clorox® solution containing about 0.75%> active chlorine for a period of 3 hours. Antimicrobial properties of the fabrics were tested against representative Gram-positive bacteria (such as Staphylococcus aureus (ATCC 5368)) using the protocol set forth in Example 5.

Example 3 This example illustrates the treatment of Nylon® 66 fabrics with a mixture of 3-hydroxymetnyl-5,5-dimethylhydantoin and 1-hydroxymethyl- 5,5-dimethylhydantoin.

8.0 Grams of Nylon® 66 fabric were dipped in 200 milliliters of 10% concentration of formaldehyde solution under basic conditions (0.5 N NaOH) at 80°C for 2 hours. However, acidic conditions (pH < 1 using H₂SO₄) can alternatively be used in this treatment. The fabric was squeezed to remove solution and washed with distilled water until neutral. A treating bath was prepared which contained 10 grams of a mixture of 3-hydroxymethyl-5,5-dimethylhydantoin and 1-hydroxymethyl- 5, 5 -dimethylhydantoin, 1.2 grams of magnesium chloride as a catalyst, 0.4 gram of Triton X-100 as a wetting agent, and 200 milliliters of distilled water. The pH of the bath was adjusted to 2.5 with 1%> concentration of sulfuric acid solution. Then the fabric was immersed in the bath at 80°C for 30 minutes. After squeezing and drying, the fabric was cured at 130°C for 15 minutes. Finally, the finished fabric was washed with a detergent solution at a temperature of about 50°C for 30 minutes.

Thereafter, the treated fabrics were washed with a Clorox® solution containing either 0.75%> or 2.5%> active chlorine for a period of 3 hours. Antimicrobial properties of the fabrics were tested against representative Gram-positive bacteria (such as Staphylococcus aureus (ATCC 5368)) and Gram-negative bacteria ( such as Escherichia coli (ATCC 2666)) using the protocol set forth in Example 5.

Example 4 This example illustrates an antibacterial study of the biocidal Nylon® fibers.

The test and control fiber samples can be tested quantitatively for antibacterial activity using a column bacteria test.

Fiber samples were treated in a manner similar to that set forth in Example 3. The final microbiocidal activity was imparted onto the treated fibers by washing them with a Clorox® solution containing 2.5% chlorine for a period of 3 hours. Antibacterial tests were conducted using a column bacteria test.

In the column bacteria test, the antibacterial sample was placed in a sterile glass buret or pipet, i.e. the column. The empty bed volume of the sample was measured in order to calculate the contact time of the inoculum with the sample. This was done by measuring the volume of water which exactly filled the region of the column containing the fibers. The sample was tested to insure no free chlorine was present. This was achieved by repeatedly washing the sample with chlorine demand free water and testing the resultant wash water with chlorine indicator strips.

A known volume of inoculum containing about 9.2 x 10⁷ CFU/mL of S. aureus in pH 7 buffer, typically 1.0 mL, was passed through the column and collected during which time the flow rate was recorded. A 25.0 μL aliquot of the collected solution was quenched with an equal volume of 0.02 N sodium thiosulphate, and then a 25.0 μL sample of this mixture was plated onto a Nutrient agar plate. The bulk bacterial solution was then passed through the column once again, and again sampled and plated onto agar. This procedure was repeated typically for a total of six passes of the 1.0 mL inoculum.

The resultant aliquots were then incubated for a period of 48 hours. The bacteria colonies were counted at 24 hours and 48 hours providing information with regard to the contact time required to produce an efficient antibacterial activity. Table I sets forth the qualitative antimicrobial evaluations of the treated fibers. The processed fibers exhibited effective antibacterial properties.

The reduction was 8 logs.

Example 5

This example illustrates the antibacterial study of Nylon® 66 fabric treated in accordance with the present invention. Swatches of test and control fabrics can be tested quantitatively for antibacterial activity using AATCC Method 100. The following method is a modified version of the aforementioned method and is applicable for fabric swatches.

The fabrics were treated in a manner similar to that set forth in Example 3. The final antimicrobial activity was imparted to the treated fabrics by washing them with a Clorox® solution containing 2.5% chlorine for a period of 3 hours. The swatches were washed with chlorine-demand-free water until less than 0.1 milligram per liter free chlorine could be detected in the wash water.

Antibacterial tests were conducted using AATCC Method 100. In the method, sized and shaped treated swatches were placed on sterile petri dishes. A known volume of inoculum containing bacteria (about 10⁷ or 10⁸ CFU/mL (Staphylococcus aureus 1.1 x 10⁷ - 5.0 x 10⁸ and Escherichia coli 2.0 x 10⁷)) in pH 7 buffer solution was used. Complete absorption of the bacterial solution was required with no free liquid being available. Swatches of identical fabrics, but containing no biocidal finish, acted as controls. Sterilization of the samples was dependent on the type of fabrics and finish.

After inoculation, each swatch was transferred into a sterile wide mouthed glass vessel containing 0.02 N sodium thiosulfate to quench disinfectant action. The vessel and contents were shaken, and an aliquot of the resulting mixture was removed, and a set of serial dilutions were performed using pH 7 buffer. Typically dilutions of 10° through 10⁶ were sufficient. A 0.025 mL aliquot of each dilution was then plated on Nutrient agar and incubated for a period of 48 hours. Bacterial counting was performed after 24 hours and 48 hours of incubation. Table II sets forth the antimicrobial evaluations of the treated fabrics against S. aureus and E. coli. Table III gives the antimicrobial results for the fabrics treated by the three different N-halamines as in examples 1-3 against S. aureus. The processed fabrics exhibited effective antibacterial properties.

Treated according to example 3 except for the chlorination procedure mentioned above.

Control samples produced only about a 1-Log reduction.

Table III. Swatch Bacterial Test (AATCC Method 100-1999)

The time of chlorination was 3 hours.

Example 6 This example illustrates the regenerable antimicrobial property of the antibacterial Nylon® fabric treated in accordance with the present invention. Fabric samples were treated in a manner similar to that set forth in Example 3. The test and control fabric samples were tested quantitatively for antibacterial activity against S. aureus (1.23 x 10 CFU) using the Swatch Bacteria Test. The two samples were then exposed to 100 milliliters of 0.02 N sodium thiosulfate for one minute. Then a second chlorination was performed on the previously chlorinated sample as outlined in previous examples, and the swatch test was performed a second time for both the chlorinated and unchlorinated samples. The Results are shown in Table IV. It is clear that antibacterial activity was restored to the previously chlorinated sample by a second chlorination.

7.7 logs were recovered from the first control and 3.6 logs from the second control which were exposed to sodium thiosulfate.

Example 7 This example illustrates the biocidal treatment of the polyamide Aramid Kevlar®. 5.0 grams of Kevlar® fiber was soaked in 100 mL of 5% concentration of paraformaldehyde solution at a pH < 1 (adjusted with H₂SO solution) at 85°C for 3 hours. The fiber was then squeezed to remove solution and washed with distilled water until neutral. A treatment bath was prepared which contained 5 grams of a mixture of 3-hydroxymethyl-5,5-dimethylhydantoin and 1-hydroxymethyl- 5, 5 -dimethylhydantoin, 0.2 grams of magnesium chloride as a catalyst, 0.05 grams of Triton® X-100 as a wetting agent, and 100 mL of distilled water. The pH of the bath was adjusted to 2.5 with 1%> concentration of H₂SO₄ solution. Then the fibers were soaked in the bath at 80°C for 30 minutes. After squeezing and drying, the fibers were cured at 130°C for 30 minutes. Finally, the treated fibers were washed with a detergent solution at a temperature of about 50°C for 30 minutes. The antimicrobial activity was then imparted to the fibers by soaking them in a sodium hypochlorite solution containing about 2.5%> active chlorine at ambient temperature for 3 hours. Then the fibers were washed with chlorine-demand-free water until less than 0.1 milligram per liter of free chlorine could be detected in the wash water.

The fibers were then tested against the Gram-positive bacterium S. aureus (ATCC 5368) at a concentration of 1.5 x 10⁷ CFU/mL using a column test with the protocol described in example 4. The column of treated Kevlar^® fibers provided a 3.2 log inactivation of the bacteria within a contact time of 72 seconds and a 5.1 log inactivation within a contact time of 209 seconds. Swatches of Kevlar were also treated in a manner analogous to that described for the fibers above. One of the swatches was exposed to 1.25%> active chlorine for 3 hours; a second swatch was exposed to 508 mg/L of active chlorine for

9 hours before bactericidal testing. After washing with chlorine-demand-free water, a swatch test was conducted using the protocol described in example 5. The o o swatches were exposed to 1.3 x 10 and 2.1 x 10 CFU, respectively, of S. aureus

(ATCC 5368) for a contact time of 60 minutes. Both swatches exhibited about a

2 log inactivation of the bacteria in this test.

Thus, it can be concluded that Kevlar^® modified by attaching hydroxymethyl dimethyl hydantoin moieties which are subsequently chlorinated can be rendered biocidal.

While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for preparing a regenerable biocidal precursor polyamide material, comprising:

(a) pretreating the polyamide material in a pretreatment solution including formaldehyde, to produce a pretreated polyamide material; and

(b) exposing the pretreated polyamide material to a treatment solution including a heterocyclic N-halamine precursor compound to produce a precursor treated polyamide with covalently linked precursor moieties.

2. The method of Claim 1, wherein the formaldehyde pretreatment takes place under either acidic conditions at a pH of 0 to 5 or under basic conditions at a pH of 12 to 14.

3. The method of Claim 2, wherein the polyamide material comprises an aramid and pretreatment takes place under acidic conditions.

4. The method of Claim 1, wherein the formaldehyde solution is an aqueous formaldehyde solution including formaldehyde at a level of 1 to 15 weight percent.

5. The method of Claim 1, wherein the treatment solution is an aqueous solution including the heterocyclic N-halamine precursor compound at a level of 5 to 20 weight percent.

6. The method of Claim 1, wherein the heterocyclic N-halamine precursor compound is selected from the group consisting of 4-hydroxymethyl- 4-ethyl-2-oxazolidinone, 3 -hydroxymethyl-2,2, 5, 5 -tetramethylimidazolidin-4-one, 3-hydroxymethyl-5,5-dimethylhydantoin, l-hydroxymethyl-5,5-dimethyl hydantoin; and hydroxymethyl derivatives of 6,6-dimethyl-l,3,5-triazine-2,4-dione, 4,4,5,5-tetramethyl-l,3-imidazolindin-2-one, and cyanuric acid.

7. The method of Claim 6, wherein the heterocyclic N-halamine precursor is selected from the group consisting of 4-hydroxymethyl- 4-ethyl-2-oxazolidinone, 3-hydroxymethyl-2,2,5,5-imidazolidin-4-one, 3-hydroxymethyl-5,5-dimethylhydantoin, and 1-hydroxymethyl-

5 ,5 -dimethylhydantoin.

8. The method of Claim 1, wherein the treatment solution further comprises a wetting agent.

9. The method of Claim 8, wherein the wetting agent is selected from the group consisting of TRITON® X-100, SEQUAWET®, and AMWET®.

10. The method of Claim 1, wherein the treatment solution further comprises a catalyst.

11. The method of Claim 10, wherein the catalyst is selected from the group consisting of magnesium salts, zinc salts and ammonium salts.

12. The method of Claim 11, wherein the catalyst is selected from the group consisting of MgCl , Mg(NO₃)₂, Zn(NO₃)₂, andNH₄NO₃.

13. The method of Claim 1, wherein the polyamide material that is treated comprises a Nylon®-66 or Nylon®-6 material.

14. The method of Claim 1, wherein the polyamide material comprises a Kevlar® or Nomex® aramid.

15. The method of Claim 1, wherein the polyamide material comprises a fiber or a fabric material.

16. The method of Claim 1, further comprising the steps of curing the precursor treated polyamide material.

17. The method of Claim 16, further comprising washing the cured precursor treated polyamide material.

18. The method of Claim 1, further comprising the step of exposing the precursor treated polyamide to an aqueous solution including a free halogen to produce an active biocidal polyamide material.

19. The method of Claim 18, wherein the free halogen comprises chlorine or bromine.

20. The method of Claim 19, wherein the free halogen comprises chlorine at a concentration of from 500 mg per liter to 2.5 weight percent.

21. The precursor treated polyamide material produced by the method of Claim 1.

22. A method for preparing a regenerable biocidal polyamide material, comprising:

(a) pretreating the polyamide material in a pretreatment solution including formaldehyde under acidic conditions of pH 0 to 5 or basic conditions of pH 12 to 14, to produce a pretreated polyamide material;

(b) exposing the pretreated polyamide material to a treatment solution including a heterocyclic N-halamine precursor compound, a wetting agent and a catalyst; and

(c) exposing the precursor treated polyamide material to an aqueous solution including free halogen to produce a regenerable biocidal polyamide.

23. The method of Claim 22, further comprising the step of curing the precursor treated polyamide material prior to exposing to the free halogen.

24. The method of Claim 23, further comprising the step of washing the cured precursor treated polyamide material prior to exposing the material to the free halogen.

25. A method for regenerating a biocidal polyamide material, comprising:

(a) obtaining a polyamide material to which is covalently bonded a heterocyclic N-halamine precursor compound including nitrogen atoms to which sufficient free halogen was previously bound to exhibit a predetermined initial level of antimicrobial effect, that has been lowered to a reduced level of antimicrobial effect due to loss of free halogen; and

(b) exposing the polyamide material to an aqueous solution including a free halogen to restore the predetermined initial level of antimicrobial effect.

26. An antimicrobial polyamide material, comprising: (a) a polyamide substrate; (b) heterocyclic N-halamine precursor moieties covalently linked to the polyamide material; and

(c) a free halogen bonded to nitrogen atoms of the N-halamine precursor moieties to produce a biocidal surface on the polyamide material.

27. The material of Claim 26 wherein said heterocyclic N-halamine precursor is selected from the group consisting of 4-hydroxymethyl-4-ethyl- 2-oxazolidinone, 3-hydroxymethyl-2,2,5,5-tetramethylimidazolidin-4-one, 3 -hydroxymethyl-5 , 5 -dimethylhydantoin, 1 -hydroxymethyl-5 , 5 -dimethyl hydantoin; and hydroxymethyl derivatives of 6,6-dimethyl-l,3,5-triazine-2,4-dione, 4,4,5, 5-tetramethyl-l,3-imidazolindin-2-one, and cyanuric acid.

28. The material of Claim 27 wherein said heterocyclic N-halamine precursor is selected from the group consisting of 4-hydroxymethyl- 4-ethyl-2-oxazolidinone, 3-hydroxymethyl-2,2,5,5-imidazolidin-4-one, 3-hydroxymethyl-5,5-dimethylhydantoin, and 1-hydroxymethyl- 5 , 5 -dimethylhydantoin.

29. The material of Claim 26, wherein the polyamide comprises Nylon® 66 or Nylon® 6 material.

30. The material of Claim 26, wherein the polyamide material comprises a Kevlar® of Nomex® aramid material.