Antimicrobial compositions comprising iodopropargyl butylcarbamate and 2-mercaptopyridine n-oxide and method of controlling microbes

A synergistic antimicrobial composition comprising 2-mercaptopyridine N-oxide, and salts thereof, and iodopropargyl butylcarbamate in a ratio to each other which exhibits synergism is disclosed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to antimicrobial compositions and methods of 
controlling microbes. 
2. Description of the Prior Art 
The presence of microbes in various aqueous systems such as latices, 
paints, coatings, cooling water systems, decorative ponds and the like, 
can cause deterioration or disfigurement of these systems. For example, 
painted surfaces may be disfigured by the unsightly buildup of microbes, 
thus detracting from the overall aesthetics of the painted article; 
cooling towers may lose efficiency due to the buildup of microbes on 
surfaces, thus reducing the heat transfer capabilities of the tower. It is 
conventional to practice methods which inhibit the microbial deterioration 
of such systems by incorporating a variety of additives or combination of 
additives that are characterized by having antimicrobial activity. 
A wide variety of materials have been used to control microbes in different 
environments, some of which are: chlorine/bromine compounds, 
glutaraldehyde, isothiazolones, organotin formulations, copper salts, 
quaternary ammonium compounds (SD Strauss and PR Puckorius in J. Power, 
S1, June 1984), and triazines. Each has deficiencies related to toxicity, 
pH and temperature sensitivity, limited effectiveness, chemical stability, 
and/or compatibility. 
Based on the aforementioned performance deficiencies of conventional 
antimicrobial compounds there is a need for more effective antimicrobial 
agents that can be used at lower dosage rates, thus being more cost 
effective for the end user, reducing the pollution load on the affected 
environmental systems, and reducing the side effects to nearby non-target 
organisms, such as fish, useful crops, etc. 
Among the many antimicrobial compounds which have been proposed, only a 
relatively small number have become useful in practice among which are 
iodopropargyl butylcarbamate and 2-mercaptopyridine n-oxide. However, as 
far as we know, no one has ever proposed using these two antimicrobials 
together. 
SUMMARY OF THE INVENTION 
It is the object of this invention to provide a method of controlling 
microbes at very low levels of active ingredient. It is a further object 
to use compositions which are compatible with a variety of systems 
susceptible to deterioration by microbes. Another object is to provide a 
method of controlling microbes in cooling towers, paints, marine 
antifoulant coatings, spray washes, swimming pools, coatings, decorative 
ponds, fabric, leather, paper, wood, metal working fluids, cosmetic 
formulations, fuel systems, therapeutic pharmaceutical formulations, and 
the like, without objectionable by-product odors, discoloration, or 
otherwise detrimental effects on the treated (and controlled) systems. 
These objects, and others which will become apparent from the following 
disclosure, are achieved by the present invention which, in one aspect 
comprises a composition useful for controlling microbes comprising 
(A) a compound (metal salt of 2-mercaptopyridine N-oxide) of the formula 
##STR1## 
wherein M is a metal cation selected from the group consisting of sodium, 
potassium, calcium, magnesium and zinc; and where X=1 when M is sodium or 
potassium and X=2 when M is magnesium, calcium or zinc; 
and (B) a compound (iodopropargyl butylcarbamate) of the formula 
##STR2## 
in a ratio to each other which exhibits synergism. 
In another aspect, the invention comprises a method for inhibiting the 
growth of a member selected from the group consisting of bacteria, fungi, 
algae and mixtures thereof in a locus subject to contamination by said 
member, which comprises incorporating onto or into the locus, in an amount 
which is effective to adversely affect the growth of said member, the 
aforementioned composition. 
Another aspect of the invention is a method of controlling microbes in 
cooling tower water comprising maintaining a concentration of the 
aforementioned composition in the water. 
The invention also comprises microbe-resistant coating or impregnant 
compositions and marine antifoulant compositions comprising the 
antimicrobial composition. 
In a preferred aspect of the invention the antimicrobial composition is 
incorporated into therapeutic pharmaceutical formulations, e.g., topical 
antifungal treatments such as shampoos, creams and ointments. 
DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS 
We have discovered an especially effective composition useful for 
controlling microbes comprising 
(A) a compound (metal salt of 2-mercaptopyridine N-oxide) of the formula 
##STR3## 
wherein M is a metal cation selected from the group consisting of sodium, 
potassium, calcium, magnesium and zinc; and where X=1 when M is sodium or 
potassium and X=2 when M is magnesium, calcium or zinc; 
and (B) a compound (iodopropargyl butylcarbamate) of the formula 
##STR4## 
in a ratio to each other which exhibits synergism. 
In accordance with the invention a method of controlling microbes comprises 
using an effective amount of the aforementioned composition. 
Another important utility is in imparting microbial resistance to a coating 
or an impregnant composition comprising incorporation of the composition 
of the invention in the coating or impregnant, preferably at a 
concentration of about 0.1 ppm to about 2 percent, more preferably at a 
concentration of about 1 ppm to 1 percent, and most preferably at a 
concentration of about 10 to 4000 ppm. 
In a marine antifoulant composition, on the other hand, the antimicrobial 
composition of the invention comprises about 1 to 10 percent of the 
antifoulant composition. 
In a therapeutic pharmaceutical formulation, e.g., lotion, cream, ointment 
or topical treatment; in the treatment of metal working fluids; and in the 
protection of fabric, leather, paper or wood materials, the microbicidal 
composition is added at a concentration of from about 0.1 ppm to about 2 
percent by weight. In aqueous media, the microbicidal composition 
comprises from about 0.1 ppm to about 1 percent of the aqueous system 
depending on the specific end use; for example, in cooling water tower 
applications and with pulp or paper manufacturing processes, the 
microbicidal composition is added at a concentration from about 0.1 to 
about 1000 ppm by weight. In cosmetic formulations, e.g., face or hand 
creams, toiletries, etc.; and in the treatment of fuel systems, e.g., jet 
fuel, gasoline, heating oil, etc., the microbicidal composition is added 
at a concentration of from about 0.1 ppm to about 1 percent by weight. 
The microbial resistant compositions can also be used in construction 
products such as stucco, roof mastics, wall mastics, and masonry coatings 
for algae protection; in clear finishes and coatings to protect underlying 
substrates from algae; for algae control in aquaculture, including 
aquaria, fish hatcheries, shrimp ponds, finfish ponds, mollusc and 
crustacean cultivation; for algae control in recreational and decorative 
bodies of water such as swimming pools, lakes, fountains and decorative 
ponds; for algae control in bodies of water for industrial or munidpal 
use, such as settling or separation ponds, waste treatment ponds, and 
water reservoirs; for algae control in hydroponic farming; for algae 
control in processing and manufacture of pulp and paper products; for 
inclusion in plastics or in coatings for plastics to protect against 
algae; and in plastics or coatings for plastics for swimming pool liners., 
We prefer compositions wherein the weight ratio of (A) to (B) is about 
0.1:100 to about 100:0.1. A particularly preferred ratio range is about 
200:1 to about 1:99 by weight.