Self-disinfecting surfaces

Abstract

The invention relates to an aqueous coating composition comprising a compound having reactive groups A, and a quaternary ammonium compound according to Formula I, II or III ##STR00001##
wherein R.sup.1 is an alkyl, alkenyl, alkylaryl or arylalkyl group having from 5 to 50 carbon atoms; R.sup.2 is a C.sub.1-C.sub.100 hydrocarbyl group, optionally containing heteroatoms; R.sup.3 and R.sup.4 are alkylene groups having from 1 to 4 carbon atoms; R.sup.5 and R.sup.6 are H or C.sub.1-C.sub.100 hydrocarbyl group, optionally containing heteroatoms; R.sup.7 is a C.sub.1-C.sub.100 hydrocarbyl group, optionally containing heteroatoms; R.sup.8 is a C.sub.1-C.sub.100 hydrocarbyl group, optionally containing heteroatoms; R.sup.9 is H or a methyl group; Z is a substituent containing at least one reactive group B which is capable of reacting with the reactive group A; X.sup.− is an anion; y is 0 or 1; a is 0 or 1; and the sum of y and a is 1 or 2 and m is an integer from 1 to 30, preferably between 1 and 10, or between 2 and 6 n is an integer from 0-30, preferably between 1 and 10, or 2 and 6 T is a monomer unit; U is a monomer unit; V is a C.sub.1-C.sub.100 hydrocarbyl group, optionally containing hetero atoms; d is an integer between 1 and 5, preferably 1; e is an integer between 1 and 1000, preferably between 5 and 100; g is an integer between 1 and 100, preferably between 2 and 10; h is an integer between 1 and 5, preferably 2 or 3.

Claims

1. A process for forming a coating having antimicrobial properties on a substrate comprising the steps of: a. applying a coating composition comprising a quaternary ammonium compound having an alkoxylated substituent having a reactive hydroxyl group according to formula (Ia), (II), or (III) to a substrate, and b. curing the coating composition to obtain a cured coating, wherein the reactive hydroxyl group of the alkoxylated substituent has reacted within the cured coating, ##STR00011## wherein: R.sup.1 is an alkyl, alkenyl, alkylaryl or arylalkyl group having from 5 to 50 carbon atoms; R.sup.2 is a C.sub.1-C.sub.100 hydrocarbyl group, optionally containing heteroatoms; R.sup.3 is a C.sub.1-C.sub.4 alkylene group; R.sup.4 is a C.sub.1-C.sub.4 alkylene group; R.sup.5 and R.sup.6 are H or C.sub.1-C.sub.100 hydrocarbyl group, optionally containing heteroatoms; R.sup.7 is a C.sub.1-C.sub.100 hydrocarbyl group, optionally containing heteroatoms; R.sup.9 is H or methyl; Z is OH; X.sup.− is an anion; m is an integer from 1 to 30; n is an integer from 1 to 30; and T is a monomer unit; U is a monomer unit; V is a C.sub.1-C.sub.100 hydrocarbyl group, optionally containing hetero atoms; d is an integer between 1 and 5; e is an integer between 1 and 1000; g is an integer between 1 and 100; h is an integer between 1 and 5.

2. The process according to claim 1, wherein R.sup.9 is H.

3. The process according to claim 1, wherein R.sup.1 is a linear alkyl group having from 10 to 15 carbon atoms.

4. The process according to claim 1, wherein the coating composition has a low anti-microbial activity, wherein the low anti-microbial activity is defined as less than 20% inhibition of bacterial growth of pseudomonas aeruginosa, according to ISO/FDIS 20776-1 (2006).

5. The process according to claim 1, wherein the cured coating has a surface charge above 1×10.sup.15 /cm.sup.2.

Description

EXAMPLES

Example 1

Formation of a Quaternary Ammonium Compound According to Formula (I) and a Polymer According to Formula (II)

(1) An amount of 50.00 grams of cocoalkylmethyl[polyoxyethylene (13)]ammonium chloride according to formula (V)

(2) ##STR00006##
wherein m+n=13 and a cocoalkyl group is a blend of mainly C.sub.12 to C.sub.14 linear alkyl chains, was mixed with 5.54 grams of succinic anhydride (molar ratio 1:2), dissolved in 20.0 grams acetone and heated up to 50° C. for 8 hour in a reaction vessel equipped with a condenser, thermometer and dropping funnel. The progress of the reaction is monitored using acid value titration. The reaction was completed when the acid value no longer decreased. A complex according to formula (VI) has been formed (which is a specific example of a compound according to formula (I)).

(3) ##STR00007##

(4) The mixture was cooled to 40° C. and glycidyl methacrylate (8.59 grams) and butyl methacrylate (4.30 grams) are slowly added. The ratio of glycidyl methacrylate to ethoxylated cocoalkyl ammonium is 1.1 to 1 moles. The reaction proceeded for 2 hours at 40° C., giving a structure according to formula (VII) (which is a specific compound to formula (I)). Subsequently, triethylamine (5.5 grams) and water (110.00 grams) were added.

(5) ##STR00008##

(6) The mixture was diluted to 25% solid content using demi water and heated to 60° C. A nitrogen inlet was added to the reaction vessel. A redox polymerization reaction was carried out using sodium formaldehyde sulfoxylate (0.38 grams) and tertiair butyl hydroxyl peroxide (0.42 grams) as redox couple under a progressive flow of nitrogen. After one hour at 60° C. the mixture was cooled to room temperature. The obtained polymer has a structure according to formula (VIII). Acetone was removed from the emulsion by using a rotary evaporator.

(7) ##STR00009##
random blockcopolymer, a specific example of a compound according to formula (II).

Example 2

Preparation of Coating Compositions

(8) The emulsion according to Example 1 was diluted with demineralized water up to a solid content of 20 wt %. Afterwards, the emulsion was neutralized using an amine neutralizing agent, preferably triethylamine, to a pH of 8.5±0.1. After neutralization, the emulsion was added dropwise to a polyurethane (PU) dispersion; SYNTEGRA® YA 500 available from Dow Chemical.

(9) Different coating compositions have been prepared by mixing the neutralized emulsions with the PU-dispersion and with 7.5% (m/m) carbodiimide crosslinking agent in ratios as described in table 2.

(10) Formation of the Coating

(11) The different coating compositions (see table 2 for the ratio of the components) have been applied on a glass substrate in a thickness of 120 μm using a laboratory test applicator (TQC VF 2146 baker applicator). After the application of the coating composition, the coating composition was cured at 70° C. for 30 minutes to prepare the coating.

Example 3

Test Procedure for Determination of Antimicrobial Properties of the Coating Composition

(12) The anti-microbial properties of the coating composition were tested according ISO/FDIS 20776-1 (2006). This method is described hereafter.

(13) The antimicrobial activity of the compound was determined in the so-called ‘minimal inhibitory concentration’ (MIC-) assay.

(14) With this test the AM compound can be evaluated for use as an in-can preservative for paints etc.

(15) The anti-microbial activity of the polymers was quantitatively determined in accordance with the principle of the absorption method, as recorded in the standard method of ISO 20776-1: ““Clinical laboratory testing and in vitro diagnostic test systems—Susceptibility testing of infectious agents and evaluation of performance of antimicrobial susceptibility test devices—Part 1: Reference method for testing the in vitro activity of antimicrobial agents against rapidly growing aerobic bacteria involved in infectious diseases”. The test was carried out with the gram negative bacteria Pseudomonas aeruginosa (BM 179).

(16) After 24 hours of contact at 37° C., the number of surviving organisms was determined and the anti-microbial activity of the polymer samples could be calculated.

(17) The starting concentration of the liquid coating of Example 2 in water was 3%. After dilution (1:1) in Brain Heart Infusion (BHI) medium, 200 μl was applied in the first column of a 96-well plate (Corning 3596) subsequently 100 μl 1:1 diluted liquid coating was three times diluted. The end concentration of the liquid coating in the wells was resp. 1.5, 0.75, 0.375 and 0.188%.

(18) Columns 6 and 12 were used as blank; columns 5 and 11 for 100% growth.

(19) The 96-well plates were closed and sealed with autoclave tape and subsequently packed in aluminum foil. After incubation at 37° C. (timed at T24), the number of the bacteria in the wells was determined with a Tecan Reader by measurement of the OD600.

(20) The density of the used test organism was determined by titration and plating on Tryptic Soy Agar (TSA) base. These TSA sheets were incubated overnight at 35° C., where upon the number of multiplied colonies was counted.

(21) TABLE-US-00001 % growth inhibition concentration of coating in water P. aeruginosa (24 hours)  1.5% 15  0.75% 20 0.375% 6 0.188% 9

(22) In all experiments bacterial growth was clearly visible. From table above it can be concluded that the coating of example 2 showed no antimicrobial activity against the Gram-negative bacteria Pseudomonas aeruginosa (BM179).

Example 4

Test Procedure for Determination of Antimicrobial Properties

(23) For determination of the antimicrobial properties of the coatings a test was applied according the Japanese standard JIS L 1902 (2002). In brief, one of the coating formulations described in example 2 was applied to a microscopy glass substrate and cured for 24 hrs at 70° C. Meanwhile, suspensions of P. aeruginosa, E. Coli and S. Aureus were grown in BHI medium for 24 hrs at 37° C., resulting in suspensions of at least 10.sup.5-10.sup.6 bacteria/ml. Afterwards, the cured coating plates were contaminated with bacteria via dropping 100 μL of the suspension on the coating. The droplet was covered by a microscopy glass-slide and incubated at 37° C. for 24 hrs. After incubation, the glass slide was removed and the suspension droplet was diluted with another 100 μL of fresh BHI medium. In the case of E. Coli and P. aeruginosa, the droplet was plated out on a freshly prepared agar plate containing tryptic soy agar which was able to stain colonies of E. Coli and P. aeruginosa specifically. In the case of S. Aureus the droplet was poured in an empty petri-dish and mixed with freshly sterilized tryptic soy agar, which was able to stain S. Aureus colonies specifically. The plates were incubated at 37° C. for 24 hrs, after which the colonies were counted to determine the antimicrobial effectivity of the coating. The tests were carried out in duplo. The results are shown in Table 2. The given weight percentages are based on total weight of the solids present in the coating formulation. The percentage inhibition is the amount of inhibition of bacteria growth on the coating relative to a coating wherein no quaternary ammonium component was present.

(24) TABLE-US-00002 TABLE 2 Formulation quaternary ammonium carbodiimide Syntegra ® YA compound crosslinker Inhibition % Inhibition % Inhibition % Exp 500 (wt %) (wt %) (wt %) of E. Coli. of P. aeruginosa. of MRSA. C4.1 0 0 0 <1% <1% <1% C4.2 80 0 20 20% 20% 35% C4.3 80 10 10 35% 35% 55% 4.4 75 15 10 60% 60% 75% 4.5 70 20 10 >98% >98% >99% 4.6 65 25 10 >99% >99% >99% 4.7 60 30 10 >99% >99% >99% 4.8 55 35 10 >99% >99% >99% 4.9 50 40 10 >99% >99% >99%

(25) The results in Table 2 clearly show that an effective antimicrobial coating is obtained when the amount of quaternary ammonium compound in the coating formulation is 15 or preferably 20% weight % or higher relative to the weight of the total amount of solids in the coating formulation.

Example 5

Test Procedure for Determination of the Surface Charge Density

(26) The density of quaternary ammonium groups on surfaces was measured as the amount of fluorescein bound on the surface of the coatings. The coating compositions from Example 2 were applied on glass slides (test surface 1×1 cm.sup.2) and placed in a tube containing 10 mL of a 1% (wt) solution of sodium salt fluorescein in distilled water for 10 minutes. The samples were removed from the fluorescein solution and were extensively rinsed with distilled water and placed in 3 mL of 0.1% solution of cetyltrimethylammonium chloride in a fresh tube. Subsequently, the samples were shaken for 20 minutes at 300 rpm on an orbital shaker to desorb the dye. The absorbance of the resultant aqueous solution was measured at 501 nm after adding 1 ml of 100 mM PBS (phosphate buffered saline) (pH 8).

(27) The amount of fluorescein bound to quaternary ammonium groups on the surface of the coating was calculated using a value of 77 mM−1/cm as the extinction coefficient. The number of quaternary ammonium units on the coating surface was determined by using a 1:1 fluorescein to accessible quaternary ammonium ratio. Table 3 shows the results as previously presented in table 2 complemented with the measured mole cationic groups accessible at the coating surface. The surface charge per cm.sup.2 was calculated by multiplying the surface charge with the Avogadro constant (6.022*10.sup.23 mol.sup.−1).

(28) TABLE-US-00003 TABLE 3 Inhibition % Inhibition % Accessible cationic Surface of E. Coli. of MRSA groups [mol N.sup.+/cm.sup.2] charge/cm.sup.2 C4.1 <1% <1% — — C4.2 20% 35% — — C4.3 35% 55% 1.3 × 10.sup.−06 0.8 × 10.sup.15 4.4 60% 75% 2.4 × 10.sup.−06 1.4 × 10.sup.15 4.5 >98% >99% 3.7 × 10.sup.−06 2.2 × 10.sup.15 4.6 >99% >99% 5.3 × 10.sup.−06 3.2 × 10.sup.15 4.7 >99% >99% 7.2 × 10.sup.−06 4.3 × 10.sup.15 4.8 >99% >99% 9.3 × 10.sup.−06 5.6 × 10.sup.15 4.9 >99% >99% 1.2 × 10.sup.−05 7.0 × 10.sup.15

(29) The results in Table 3 show clearly that an effective antimicrobial coating can be obtained when the surface charge on the coatings is above of 1×10.sup.15/cm.sup.2, better results when surface charge is at least 2×10.sup.15/cm.sup.2, best results are obtained when the surface charge is the material specific threshold of at least 3×10.sup.15/cm.sup.2.

Example 6

Assessment of Leaching of Antimicrobial Substances from Coatings of Example 2

(30) The coating of Example 2 was applied on glass in a coating thickeness of 120 μm using a laboratory test applicator (TQC VF 2146 baker applicator). After drying the coating was removed from the glass and cut into little pieces. About 0.6 to 0.7 grams of coating pieces were extracted in a soxhlet with 150 ml ultra-pure water (Milli-Q) for 16 hours. Samples of the extracts were diluted 10 times with eluent and injected with flow injection in a Q-TOF™ hybrid instrument Flow injection electrospray Mass Spectrometer with standard Z-spray™ interface and an Alliance liquid chromatograph type 2690 (eluent: H.sub.2O:CH.sub.3CN 1:1 with 0.2% formic acid; flow 20 μl/min.). From the analyses it was concluded that no quaternary ammonium compounds were extracted from the samples. The detection limit of quaternary ammonium compounds is <1 ppm, so the extractable amount of quaternary ammonium compounds from the coatings is lower than 0.2%.

Example 7

Formation of a Quaternary Ammonium Compound Carrying Free Acrylic Groups According to Formula (III)

(31) An amount of 59.6 grams of ethoxylated cocoalkyl methyl ammonium chloride (m+n=13 moles) was mixed with 10.0 grams of Desmolux D 100, an isocyanate bearing urethane acrylate (equivalent ratio 2:1) and 0.01 grams of DBTL (dibutyltin dilaurat) and heated up to 65° C. for 2 hours in a reaction vessel equipped with a condenser and thermometer. The progress of the reaction was monitored by determining the NCO-number. The reaction was stopped when the NCO number was below 0.1%. The reaction resulted in the structure according to formula (VIII). Finally, distilled water was added to obtain a solid matter content of 50%.

(32) ##STR00010##

Example 8

Formation of a PUR-coating of the QAC from Example 7

(33) To 50 grams of OH functional acrylate dispersion AC 27401 (Alberdingk Boley) was mixed thoroughly with 20 grams of the 50% solid QAC solution comprising the compound of Example 7 and 41 grams of hydrophilic aliphatic polyisocyanate Bayhydur XP 2547 (Bayer). A coating was applied on a glass substrate using a laboratory test applicator (TQC VF 2146 baker applicator). After the application, the coating was cured at 50° C. for 30 minutes. The resulting coating layer was a clear transparent, flexible and shiny coherent layer.

Example 9

Formation of a Waterborne UV-coating of the QAC from Example 7

(34) To 50 grams of UV-Curable Polyurethane/Acrylic Copolymer Dispersions LUX 560 VP (Alberdigk), 1.25 grams of photo-initiator Irgacure 500 (BASF) and 15 grams of the 50% QAC solution (example 7) were added under stirring.

(35) The coating was applied on a glass substrate using a laboratory test applicator (TQC VF 2146 baker applicator). After the application the coating dried for 10 minutes at 40° C. in a stove and subsequently cured in 2 passes of 5 seconds each with a Decorad handheld lamp type D03.

(36) The cured coating layer was a transparent, uniform, leathery tough and shiny coherent layer.