HK1027313B - In-can and dry coating antimicrobial - Google Patents

Description

Antimicrobial in-can coatings and dry coatings

The present invention relates generally to coating compositions and, more particularly, to pyrithione-containing coating compositions that exhibit a combination of in-can preservation against microbial attack and antimicrobial efficacy of a dry film formed upon application of the coating composition to a substrate.

Heretofore, coating compositions such as latex paints containing pyrithione (typically in the form of zinc pyrithione) to protect the "dry film" paint formed after application against microorganisms, and antimicrobial adjuvants such as hydrazine derivatives are often present in the coating compositions to provide "in-can" preservation and to protect the paint prior to application against microbial (especially bacterial) attack during in-can storage. Unfortunately, these hydrazine derivative in-can preservatives are formaldehyde-releasing agents that are environmentally hazardous, healthy, and toxic. New solutions to this problem must be sought, especially in view of the pressing need for the air quality standards required by the clearair Act of 1990.

Accordingly, there has recently been an urgent need in the industry to meet the long felt need for antimicrobial additives that have an effective in-can preservative effect and protect the dry film coating from microbial release of formaldehyde. The present invention provides a solution to this long-felt need.

In one aspect, the present invention relates to a water-based coating composition comprising:

(a) the amount of water is controlled by the amount of water,

(b) a base medium (such as a polymer latex),

(c) a zinc compound selected from the group consisting of: zinc oxide, zinc hydroxide, zinc salt, combinations thereof, and

(d) pyrithione salts other than zinc pyrithione, preferably sodium pyrithione, alone or in combination with zinc pyrithione,

the zinc compound and the pyrithione salt are present in the composition in a total amount sufficient to provide the composition with in-can and dry film antimicrobial effects.

In another aspect, the present invention relates to a method of imparting antimicrobial growth to a water-based coating composition in-can preservation and imparting antimicrobial effect to a dry film, comprising the steps of:

(a) contacting the composition with a pyrithione salt other than zinc pyrithione, preferably sodium pyrithione, wherein the pyrithione salt is present in an amount sufficient to provide the composition with in-can preservative action against microbial attack, and

(b) contacting the composition with a zinc compound selected from the group consisting of zinc oxide, zinc hydroxide, zinc salts, and combinations thereof, and reacting at least a portion of the zinc compound with at least a portion of the sodium pyrithione, thereby converting the sodium pyrithione to zinc pyrithione in an amount sufficient to provide the coating composition with a dry film antimicrobial effect.

A method for imparting an antimicrobial effect to in-can and dry films of water-based coating compositions comprising the steps of:

(a) incorporating into the coating composition a pot-in antimicrobially effective amount of said soluble pyrithione salt having a solubility in said coating composition of at least 4,000ppm at 20 ℃,

(b) incorporating a metal ion-containing compound (e.g., a metal salt) into said coating composition such that at least a portion of said metal ion-containing compound is transchelated with at least a portion of said soluble pyrithione salt, thereby forming a metal pyrithione-containing coating composition having a solubility in said coating composition of less than 100ppm,

(c) contacting the metal pyrithione-containing coating composition with a substrate to form a metal pyrithione-containing coating on the substrate, and

(d) drying the coating comprising the metal pyrithione on said substrate to form a dry film on said substrate, said dry film comprising a leaching-resistant, antimicrobially effective amount of said metal pyrithione.

These and other aspects will be apparent upon reading the following detailed description of the invention.

The present inventors have now surprisingly found that excellent "in-can" and "dry film" antimicrobial protection can be imparted to waterborne coating compositions by the back-chelation of a more soluble pyrithione salt (e.g., sodium pyrithione) with a metal ion-containing compound to form a more insoluble pyrithione salt (e.g., zinc pyrithione). Thus, for example, the inclusion of sodium pyrithione in a zinc compound (e.g., zinc oxide) in a water-based coating composition (e.g., latex paint) imparts excellent in-can preservation of the coating composition against microbial growth, particularly bacterial growth, during in-can storage of the sodium pyrithione-containing coating composition. In addition, when a substrate is coated with the coating composition, the composition provides excellent "dry film" antimicrobial effects due to the back-chelation of at least a portion of the sodium ions with zinc ions in aqueous solution to form a more insoluble, leach-resistant zinc pyrithione.

Without wishing to be bound by any particular theory, it is believed that the combination of in-can preservation and dry film antimicrobial effects associated with the compositions of the present invention may be attributed to (e.g., for coating compositions containing sodium pyrithione and zinc oxide): during in-can storage of the coating composition in an aqueous medium, the more soluble pyrithione salt (e.g., sodium pyrithione) is more slowly converted to the less soluble pyrithione salt (e.g., zinc pyrithione) by back-chelation. In this example, the pyrithione moiety is primarily responsible for antimicrobial efficacy, while the particular metal counter ion (e.g., sodium) selected for use in combination with pyrithione determines the solubility of the pyrithione moiety in the coating composition, and thus the amount of active antimicrobial agent available to provide "in-can" antimicrobial protection. In turn, the specific metal (e.g., zinc) ion used for the pyrithione salt during coating application affects the rate at which the pyrithione moieties are discharged from the dry film to the outdoor environment. Thus, sodium pyrithione (due to its higher solubility in the coating composition) provides in-can protection to the coating composition prior to conversion by ion exchange; after conversion, the resulting zinc pyrithione (a less soluble compound) provides dry film protection to the coating on the substrate because the zinc pyrithione (or other less soluble pyrithione such as copper pyrithione or titanium pyrithione) does not exude from the dried coating as quickly as the more water soluble pyrithione, thus ensuring long-term antimicrobial protection of the dried coating.

The metal ion-containing compound used for anti-chelation with the pyrithione salt in the water-based coating composition preferably comprises: a zinc compound such as a zinc salt of an organic or inorganic acid, for example zinc borate or chloride, zinc hydroxide or oxide, or mixtures thereof, in an amount sufficient to provide a molar ratio of pyrithione salt to metal ion-containing compound of between about 1: 10 and 10: 1. Metals for which it is useful include copper, for example in the form of copper oxide or copper sulphate; and titanium, suitably titanium dioxide and the like. The amount of metal ion-containing compound in the water-based coating composition can vary widely, for example from 0.001% or less to 10% or more, preferably from 0.005% to 1%, by weight of the coating composition. If a zinc compound is used as the metal ion-containing compound, the amount of zinc compound preferably should be sufficient to allow the total conversion of the pyrithione salt in the coating composition to zinc pyrithione by back chelation during storage.

In preparing the coating compositions of the present invention which are antimicrobially effective, suitable hydroxypyridinethione salts for use as starting materials include: sodium pyrithione, t-butylamine pyrithione, aluminum pyrithione, calcium pyrithione, potassium pyrithione, copper magnesium pyrithione, copper barium pyrithione, and the like. Sodium pyrithione is a preferred pyrithione salt; while zinc oxide is a preferred metal ion-containing compound suitable for use in the present invention for transchelation. The amount of sodium pyrithione applied is preferably from 0.1% to 2% (more preferably from 0.2% to 1%, most preferably from 0.25% to 0.8%) by weight based on the weight of the coating composition, and the amount of zinc oxide applied is preferably from about 1% to 10% by weight. The total amount of sodium pyrithione plus zinc oxide is preferably from about 1% to about 20% based on the total weight of the coating composition.

Sodium pyrithione suitable for use in the present invention is a well known commercial product generally made by reacting 2-chloropyridine-N-oxide with NaSH and NaOH as set forth in the disclosure of U.S. Pat. No.3,159,640. Sodium pyrithione is employed in the coating compositions of the present invention in an antimicrobially effective amount, i.e., in an amount sufficient to provide the desired "in can" and "dry film" antimicrobial protection. While the amount of pyrithione may vary over a wide range depending upon the particular intended application, the amount of pyrithione present in the coating composition is preferably from about 100ppm to about 5,000ppm, which corresponds to a weight percent of pyrithione of from about 0.01% to about 0.5%, based on the weight of the coating composition.

The aqueous coating compositions of the present invention are useful in a wide range of applications, such as soaps, shampoos, skin wellness medicaments, paints, or incorporated into or applied to plastic or woven or non-woven fibers, which are then blended to contain the desired components in addition to the antimicrobial component.

The antimicrobial compositions of the present invention are particularly useful in the form of paints, including indoor and outdoor household paints, industrial and commercial paints, and particularly latex paints. The antimicrobial component of the water-based composition is also suitable for use as an "in-can" preservative during paint storage and prior to application.

Typical paint compositions contain, in addition to the antimicrobial component, a resin, a pigment, and various optional additives such as thickeners, humectants, and the like as are well known in the art. Wherein the resin is preferably selected from the group consisting of vinyl, epoxy, acrylic, polyurethane and polyester resins, and combinations thereof. The amount of resin used is preferably from about 20% to about 80% by weight based on the paint or paint base.

In addition, the lacquer compositions according to the invention optionally also contain optional additives which advantageously influence the viscosity, wetting ability and dispersibility, as well as the freeze and electrolyte stability and the foaming properties. The total amount of optional additives is preferably no greater than 20 wt%, more preferably from about 1 wt% to about 5 wt%, based on the total weight of the paint composition.

Thickeners include, for example: cellulose 30 derivatives such as methyl, hydroxyethyl, hydroxypropyl and carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, salts of polyacrylic acid salts and acrylic acid/acrylamide copolymers.

Suitable wetting and dispersing agents include: sodium polyphosphate, low molecular weight polyacrylates, polyethylene sulfonates, polyvinyl phosphonates, polymaleates and copolymer salts of maleic acid with ethylene, alkenes of 3 to 18 carbon atoms and/or styrene.

To improve the stability to freezing and electrolytes, various 1, 2-diol monomers such as ethylene glycol, 1, 2-propylene glycol and 1, 2-butylene glycol or polymers thereof, or ethoxylated compounds may be added to the lacquer composition. Such as reaction products of ethylene oxide with long chain alkanols, amines, alkyd phenols, polypropylene glycols, or polybutylene glycols, or combinations thereof, and the like.

The minimum temperature at which the lacquer composition forms a film (white point) can be lowered by adding solvents such as glycol ethers, ester alcohols or alkylated aromatics. Suitable defoamers are, for example, polypropylene glycol and polysiloxanes. Other optional antimicrobial agents may additionally be incorporated into the paint formulations of the present invention.

The paint composition of the present invention can be used as a paint for natural materials or synthetic materials such as wood, paper, metal, fabrics and plastics. It is particularly suitable for use as indoor and outdoor latex paints.

Another interesting application of the water-based composition of the invention is as a latex tile adhesive, which typically contains, for example: in addition to the antimicrobial component, a latex emulsion, optionally a rosin emulsion, optionally a plasticizer, optionally an antioxidant and optionally a pigment or filler (e.g. calcium carbonate). Yet another interesting application of the water-based composition of the present invention is as a latex caulk or sealant, which in addition to containing the antimicrobial component, typically contains an acrylic latex, a nonionic surfactant, a dispersant, any plasticizer, and any pigment or filler (e.g., calcium carbonate).

The water-based antimicrobial compositions of the present invention are suitable for use in any of the various applications described herein as disinfectants and preservatives, in liquid or coatable solid form, alone or in combination with inert carriers such as water, liquid hydrocarbons, ethanol, isopropanol, and the like. They can be applied by conventional means to inhibit bacteria and fungi in a variety of substrates and can be applied in an antimicrobial amount to the bacterial or fungal organism or substrate thereof by conventional means such as spraying, dipping, soaking, and the like.

The invention is further illustrated by the following examples. Unless otherwise indicated, "parts" and "%" mean "parts by weight" and "percent by weight", respectively.

While the invention has been described above with reference to specific embodiments thereof, it is evident that many changes, modifications and variations can be made without departing from the inventive concept disclosed herein. Accordingly, it is intended to embrace all such changes, modifications and variations that fall within the spirit and broad scope of the appended claims.

The following examples are intended to illustrate and in no way limit the scope of the invention.

Example 1

Method for preparing acrylic latex paint

Preparing latex by using a grinding material, a pigment color paste and a paint mixing material:

all ingredients were added to the mill with 300RPM (slow) agitation using a disperser blade. The ingredients were added slowly and after addition they were allowed to mix for 5 minutes. Then adding pigment color paste. Titanium dioxide (rutile) and zinc oxide were added slowly. Once the titanium dioxide and zinc oxide are added, the mixing is enhancedThe speed was then increased to about 1000RPM and allowed to grind for 5 minutes. The mixing speed was again reduced to 300, followed by slow addition of magnesium aluminum silicate. After the addition, the mixing speed was again increased to 1000RPM, and the material on the sides of the container was scraped off continuously throughout the operation. The mixing speed was then increased to 5000RPM and milled for 5 minutes. The mixing speed was again reduced to 500RPM and increased to 5000 after addition of attapulgite clay. The resulting mixture was blended at this rate for 10-15 minutes, and the Hergeman readings were recorded periodically until a 4-6 reading was obtained. This step included grinding for about 10 minutes. Water is then added to start the paint mixing step to aid cooling. The mixing rate was slowed to 250-300RPM, during which the latex was slowly added. The mixture was checked to ensure that the pigment did not bottom out during the run and the mixture was blended for 10 minutes at 250-300 RPMs. The Colloid 643 dispersant was then added by syringe at a mixing speed of 250-; and mixing was continued for 5 minutes. Then, Texanol was added via syringe at a mixing speed of 250-300RPM^Surfactant and the resulting mixture was mixed for an additional 5 minutes. The final step involves the addition of hydroxyethyl cellulose and/or water to achieve the appropriate viscosity. In this case, the desired viscosity range is 95 to 105 KU. The pH of the final mixture was 8.5. The amounts of the various additives used to prepare the mixture are listed in the following table:

TABLE 1 paint Components		Amount of paint component expressed in grams
			Grinding materials:
water (W)		240.0
			Hydroxyethyl cellulose		6.0
Tamol8501/		14.2
			Ethylene glycol		50.0
Colloid 6432/		2.0
			TritonCF-103/		5.0
Sodium pyrithione 40% Activity		8.0
			Potassium tripolyphosphate		3.0
Pigment color paste:
			titanium dioxide (rutile)		424.0
Magnesium aluminum silicate		228.0
			Silicon magnesia		3.0
Zinc oxide		50.0
			Aluminium silicate		100.0
Propylene glycol		68.0
			Paint mixing:
water (W)		84.0
			Acrylic latex emulsion	58.0% solids	700.0
Colloid 643		6.0
			Texanol4/		18.6
Hydroxyethyl cellulose	2.5% in water	236.4
			Total mass in grams		2248.2

Physical Properties of the paint of example 1

Viscosity 95.0K.U.

pH＝8.5

Density of 11.50 lb/gal

¹Anionic dispersants, products of Rohm and Haas Company

²Antifoam, Rhone-Poulenc Corp

³Nonionic surfactant, product of Union Carbide Corp

⁴Coalescing Agents, products of Eastman Kodak Company

The paints of example 1 containing sodium pyrithione and zinc oxide were monitored over time using HPLC liquid chromatography, and the results of the conversion of sodium pyrithione to zinc pyrithione over time were recorded as follows:

TABLE 2 HPLC CONVERSION DATA
			Days after birth	% sodium pyrithione	% zinc pyrithione
1	85	15
			30	75	25
90	70	30
			150	62	38

Example 2

Efficacy of sodium pyrithione as an "in-can" preservative

Acrylic latex paints were tested for protection against attack by Pseudomonas aeruginosa (Pseudomonas aeruginosa) for up to 6 weeks with 1800ppm sodium pyrithione with or without 12.5 to 25 pounds zinc oxide per 100 gallons.

Method of producing a composite material

The inventors were unable to demonstrate the growth of pseudomonas in latex paint samples according to ASTM D2574. Thus, they used "Modified spring Method" (J.coatings Techniol.63: 33-38,1991) in which paints were diluted with water to simulate the conditions of bacterial adaptation in paint manufacturers. According to this method, undiluted paint represents in-can product, 1: 2 dilution (i.e. paint to water volume ratio) simulates condensation dilution, and 1: 10 dilution simulates rinse water. Each sample was eroded with approximately 1% of the contaminated paint from the previous experiment and the amount of survival in the first week was monitored. The samples were then eroded with 1% of 10% paint-adapted culture (paint-adapted culture) after the first and third weeks and monitored during the last three weeks of the experiment.

Results

The eroding bacteria did not survive in both the undiluted and 1: 2 samples except for the first week. However, in the 1: 10 sample control, the eroding bacteria survived the entire six weeks, while none survived in the sample containing sodium pyrithione. The added zinc oxide did not affect the corrosion results. Considering the dilution factor, this response indicates that the paint of the present invention provides a high degree of in-can antimicrobial protection.

Case of viable invasion of bacteria (10% diluted paint)
								Sample (I)*	Day 1	Week 1	Week 2	Week 3	Week 4	Week 5	Week 6
Blank space	+	+	+	+	+	+	+
								Sample 1	+	+	+	+	+	+	+
Sample 2	-	-	-	-	-	-	-
								Sample 3	-	+	+	+	+	+	+
Sample No. 4	-	-	-	-	-	-	-

Note for sample number:

sample 1 contained 1.25 wt% zinc oxide; sample 2, 1.25 wt% zinc oxide +1800ppm sodium pyrithione; sample 3, 2.5 wt% zinc oxide; sample 4, 2.5 wt% zinc oxide +1800ppm sodium pyrithione.

In the table, "+" indicates "growth" and "-" indicates "no growth".

Exposure test in south florida:

paints containing 3, 4, 6 and 25 pounds of sodium pyrithione and zinc oxide per 100 gallons, respectively, received a complete 10-grade test (no mildew) after exposure to 45 ° and north-bound environments in the 45 ° and north-south environment of milamia florida for 6 months.

Claims (8)

1. A water-based coating composition characterized by:

(a) the amount of water is controlled by the amount of water,

(b) the basic medium is a mixture of a basic medium,

(c) a zinc compound selected from the group consisting of: zinc oxide, zinc hydroxide, zinc salts, combinations thereof, and

(d) a pyrithione salt other than zinc pyrithione, alone or in combination with zinc pyrithione, wherein the pyrithione salt is selected from the group consisting of: sodium pyrithione, t-butylamine pyrithione, aluminum pyrithione, calcium pyrithione, potassium pyrithione, magnesium pyrithione, barium pyrithione, and combinations thereof,

wherein said zinc compound is present in said composition in an amount of from 0.001% to 10% by weight of the composition and wherein said pyrithione salt is present in said composition in a molar ratio of pyrithione salt to said zinc compound of from about 1: 10 to about 10: 1.

2. The coating composition of claim 1, characterized in that the base medium is a polymer latex.

3. A method of imparting an antimicrobial effect to the water-based coating composition of claim 1, the method characterized by the steps of:

(a) contacting the composition with sodium pyrithione, wherein the amount of sodium pyrithione is from 0.1 wt% to 2 wt%, based on the weight of the coating composition, and

(b) contacting said composition with zinc oxide in an amount of from 1 wt% to 10 wt% based on the weight of the coating composition, and then reacting at least a portion of the zinc oxide with at least a portion of said sodium pyrithione, thereby converting the sodium pyrithione to zinc pyrithione.

4. A method of coating a substrate with the water-based coating composition of claim 1 to provide a coating having an antimicrobial effect on the substrate, characterized by the steps of:

(a) incorporating into the coating composition from about 0.01 wt% to about 0.5 wt%, based on the weight of the coating composition, of a soluble hydroxypyridinethione salt that has a solubility in the coating composition of at least 4,000ppm at 20 ℃,

(b) incorporating 0.001 wt% to 10 wt%, based on the weight of the coating composition, of a metal ion-containing compound into the coating composition such that at least a portion of the metal ion-containing compound is back-chelated with at least a portion of the soluble pyrithione salt, thereby forming a metal pyrithione-containing coating composition having a solubility in the coating composition of less than 100ppm,

(c) contacting a substrate with said metal pyrithione-containing coating composition to form a metal pyrithione-containing coating on said substrate, and

(d) drying the coating comprising the metal pyrithione on said substrate to form a dry film on said substrate, said dry film comprising a leaching-resistant, antimicrobially effective amount of said metal pyrithione.

5. The method of claim 4, characterized in that the metal ion-containing compound is selected from the group consisting of metal salts, metal oxides, metal hydroxides, and combinations thereof.

6. The method of claim 4, characterized in that the metal ion-containing compound comprises a metal ion selected from the group consisting of zinc, copper, titanium, and combinations thereof.

7. The method of claim 4, characterized in that the soluble pyrithione salt is selected from the group consisting of: sodium pyrithione, t-butylamine pyrithione, aluminum pyrithione, calcium pyrithione, potassium pyrithione, magnesium pyrithione, barium pyrithione, and combinations thereof.

8. The process of claim 4, characterized in that the molar ratio of said soluble hydroxypyridiniusothione salt to said metal ion containing compound is from about 1: 10 to about 10: 1.