The preparation of N-halamine antibacterial materials based on cyanuric chloride

Abstract

The invention discloses a method to prepare N-halamine antibacterial materials based on cyanuric chloride. Firstly, cyanuric chloride is dissolved in alkaline solution to produce finishing solution. Then the materials are dipped in the finishing solution to absorb liquid. The wetted materials are taken out, cured under 90˜120° C. for 10˜40 min, chlorinated by bleach solution, washed and dried to get antibacterial materials. The processing method in this invention is simple, cheap, and energy-saving. In addition, it only caused very small loss of physical strength. The resulted materials have strong antibacterial efficacy, are safe for application.

Description

FIELD OF THE INVENTION

The invention belongs to the technical field of antibacterial materials. It presents a method to produce N-halamine antibacterial materials based on cyanuric chloride.

BACKGROUND OF THE INVENTION

Infections caused by microorganisms are among the greatest threats to human being, and materials including plastics and textiles are ideal carriers and media for microorganisms. Extensive researches on producing antimicrobial materials have focused on biocidal agents, such as quaternary ammonium salts, metal ions, light-activated coatings, phosphonium salts, and N-halamines.

N-Halamines are the most promising candidates for use in preparing antimicrobial materials because of their broad-spectrum antibacterial activity, nontoxicity, and low environmental impacts. In addition, their antibacterial properties are durable and rechargeable. They have long shelf life once covalently attached to materials, and their chlorine can be regenerated simply by exposure to household bleach in the washing process.

However, there are inherent disadvantages in coating these compounds onto fabrics. Because of their poor solubility in water, or organic solvents are needed during the preparation of coating solutions used for some of N-halamine precursors.

In this patent, a novel method is used to form N-halamine precursors through controlled hydrolysis of cyanuric chloride, and attach them onto cellulose by covalent bonds. The reactions progressed under a facile condition and employed water as a solvent. They are easy to scale-up in practical applications.

SUMMARY OF THE INVENTION

The invention discloses a method to prepare N-halamine antibacterial materials based on cyanuric chloride. The processing method in this invention is simple, cheap, and energy-saving. This method only caused very small loss of physical strength. The resulted materials have strong antibacterial efficacy.

The aim of invention can be realized by the following technical scheme. Firstly, cyanuric chloride is dissolved in alkaline solution to produce finishing solution. Then the materials are dipped in the finishing solution to absorb liquid. The wetted materials are taken out, cured under 90-120° C. for 10-40 min, chlorinated by bleach solution, washed and dried to get antibacterial materials.

More detailed technical scheme is present as follow.

The cyanuric chloride concentration is from 0.5-30% and optimized as 1-5%. Concentration of alkalines including NaOH, KOH, Na₂CO₃, K₂CO₃ mentioned above in finishing solution ranges from 1-30% and optimized as 2-5%.

The bleaching solution mentioned above includes but not limited to, NaClO, NaBrO, and Ca(ClO)₂. The concentration of the active halogen is from 0.01-5% and optimized as 0.01-0.05%. The pH value of the bleaching solution is from 4-12.

The treated materials mentioned in claim 1 include but not limited to natural fiber or synthetic fiber textiles, plastics, sponge, natural rubber, synthetic rubber, wood, paper, paint, chitosan and chitin.

The curing process can be chosen from baking oven, hot pressing, roller handle, and hot air treatment. When the treated material is textile, a traditional two-dip-two-rolling process can be used. The wet pick-up is 100%.

Compared with the preparation process of existing N-halamine antibacterial materials, this invention has the following advantages.

Preparation process and finished product are formaldehyde-free and non-toxic.

The processing method in this invention is simple, cheap, and energy-saving. This method only caused very small loss of physical strength. For example, the treated fabric loses less than 20% breaking strength. The resulted materials have strong antibacterial efficacy. For example, the treated cotton fabrics inactivated 99.999% S. aureus (ATCC 6538) and E. coli 0157:H7 (ATCC43895) within 1 min of contact time. The treated fabrics provide a total inactivation of S. aureus (ATCC 6538) and E. coli 0157:H7 (ATCC43895) with 7-logs within the contact time of 10 and 5 min, respectively, according to AATCC 100 standard testing method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. The schematic diagram of the antibacterial finishing method.

FIG. 2. The schematic diagram of antibacterial material's inactivation and bactericidal activity regeneration.

FIG. 3. FTIR spectra of (A) untreated cotton, (B) cotton treated with 4% triazine, and (C) cotton treated with 4% triazine after chlorination.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS OF THE INVENTION

In this patent, a novel method was used to form N-halamine precursors through controlled hydrolysis of cyanuric chloride, and attach them onto cellulose by covalent bonds. When compared to ordinary alkyl halides, the C—Cl groups in cyanuric chloride are quite active because of triazine ring's strong electron withdrawing effect. The first chlorine atom of cyanuric chloride can be replaced by a hydroxyl group in an alkali aqueous solution forming water soluble compounds in the form of sodium salts, as shown in FIG. 1. The amide and imide of triazine rings immobilized on cotton fibers were transformed to amide and imide N-halamines after bleach treatment, which have efficient and renewable antibacterial property as shown in FIG. 2.

FTIR spectrum of cotton treated with triazine in FIG. 3 shows characteristic absorption bands at 1713 cm⁻¹ and at 1610 cm⁻¹, which indicated that triazine was successfully attached to cellulose through covalent bonds because unreacted water-soluble triazine could be easily washed off from the surface of cotton fabric.

Example 1

1 g cyanuric chloride and 2 g sodium hydroxide were added to 97 g distilled water and stirred for 10 min to obtain a clear solution. Then, cotton swatches were soaked in baths for 15 min and padded with a wet pick-up of 100%. The fabrics were dipped and padded twice, then dried at 80° C. for 5 min, followed by curing at 120° C. for 10 min. The treated cotton swatches were soaked in 0.5% detergent solution for 15 min, washed with distilled water, and dried in air. The treated cotton fabric swatches were soaked in a 0.01% commercial aqueous Ca(ClO)₂ solution at pH 7 at room temperature for 1 h to produce biocidal materials. The chlorinated cotton samples were washed thoroughly with distilled water and dried at 45° C. for 2 h to remove all unbonded chlorine from the surface of the fabric. The concentration of loaded chlorine on the samples was 0.68%, determined by the iodometric/thiosulfate titration method.

Example 2

8 g cyanuric chloride and 7 g potassium hydroxide were added to 87 g distilled water and stirred for 10 min to obtain a clear solution. Then, cotton swatches were soaked in baths for 15 min and padded with a wet pick-up of 100%. The fabrics were dipped and padded twice, then dried at 80° C. for 5 min, followed by curing at 90° C. for 40 min. The treated cotton swatches were soaked in 0.5% detergent solution for 15 min, washed with distilled water, and dried in air. The treated cotton fabric swatches were soaked in a 0.5% commercial aqueous sodium hypochlorite solution at pH 12 at room temperature for 1 h to produce biocidal materials. The chlorinated cotton samples were washed thoroughly with distilled water and dried at 45° C. for 2 h to remove all unbonded chlorine from the surface of the fabric. The concentration of loaded chlorine on the samples was 0.86%, determined by the iodometric/thiosulfate titration method.

Example 3

5 g cyanuric chloride and 11 g sodium hydroxide were added to 84 g distilled water and stirred for 10 min to obtain a clear solution. Then, cotton swatches were soaked in baths for 15 min and padded with a wet pick-up of 100%. The fabrics were dipped and padded twice, then dried at then dried at 80° C. for 5 min, followed by curing at 100° C. for 20 min. The treated cotton swatches were soaked in 0.1% detergent solution for 15 min, washed with distilled water, and dried in air. The treated cotton fabric swatches were soaked in a 0.1% commercial aqueous sodium hypochlorite solution at pH 7 at room temperature for 1 h to produce biocidal materials. The chlorinated cotton samples were washed thoroughly with distilled water and dried at 45° C. for 2 h to remove all unbonded chlorine from the surface of the fabric. The concentration of loaded chlorine on the samples was 0.99%, determined by the iodometric/thiosulfate titration method.

When compared to the control samples, all of the treated cotton fabrics with triazine showed a small degree of tensile strength loss, and over 84% of the original breaking strength could be maintained after chlorination both in warp and weft directions. This result means this method has a very small effect on physical properties.

Antimicrobial Testing

Both unchlorinated and chlorinated cotton treated with triazine from the example 2 were challenged with S. aureus (ATCC 6538) and E. coli 0157:H7 (ATCC43895) at concentrations of about 107 CFUs (colony-forming units). The antimicrobial test results of the triazine treated cotton samples before and after chlorination are shown in Table III. The unchlorinated cotton samples treated with triazine was used as a control, and showed only 0.98 and 0.12 log reductions of S. aureus (ATCC 6538) and E. coli 0157:H7 (ATCC43895) within 10 min of contact time, respectively, mainly due to adhesion of bacteria to the samples. The chlorinated modified cotton fabrics inactivated 99.999% S. aureus (ATCC 6538) and E. coli 0157:H7 (ATCC43895) within 1 min of contact time. The chlorinated modified fabrics provide a total inactivation of S. aureus (ATCC 6538) and E. coli 0157:H7 (ATCC43895) with 7-logs within the contact time of 10 and 5 min, respectively. The biocidal efficacy is comparable to amide N-halamine modified fabrics, but better than those amine N-halamines reported previously.

TABLE 1
Biocidal efcacy testing.
		S. aureus b	E. coli 0.157:H7c
	Contact	Bacterial reduction	Bacterial reduction
Sample	Time	%	Log	%	Log
Unchlorinated	10 min	89.58	0.98	27.23	0.14
Chlorinateda	1 min	99.999	4.82	99.999	5.00
	5 min	99.999	5.13	100	7.43
	10 min	100	7.26	100	7.43
a0.23% oxidative chlorine content
bTotal bacteria: 1.80 × 107 (cfu/sample)
cTotal bacteria: 2.67 × 107 (cfu/sample)

The present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments and examples be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A method for preparing N-halamine antibacterial materials based on cyanuric chloride, characterized in that: cyanuric chloride is completely dissolved alkaline solution, and the material was immersed in the prepared solution until thoroughly wetted. The wet material was dried and cured for 10˜40 min at 90˜120° C. The antimicrobial material was obtained after halogenation, washing, and drying.

2. The method according to claim 1, wherein the alkalis are sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate solution, with mass percent of 1˜30%.

3. The method according to claim 1, wherein the mass percent of cyanuric chloride in the solution is 0.5˜30%.

4. The method according to claim 1, wherein the halogenation process means the activation of material through soaking the mentioned material in a solution containing the active halogens.

5. The method according to claim 1, wherein the treated materials include natural fiber or synthetic fiber textiles, plastics, sponge, natural rubber, synthetic rubber, wood, paper, paint, chitosan and chitin.

6. The method according to claim 1, wherein the treatment method includes two dipping-padding processes for the treatment of natural fiber or synthetic fiber textiles.

7. The method according to claim 2, wherein the alkaline concentration in solution is 2˜5%.

8. The method according to claim 3, wherein the mass percent of cyanuric chloride is 1˜5%.

9. The method according to claim 4, wherein the halogenation solution contains the active halogen including sodium hypochlorite, sodium bromate or calcium hypochlorite solution, and the mass percent is from 0.01 to 5%.