Patent Application
20100251602
The invention relates to cold temperature stable and synergistic biocidal compositions suitable for use in various aqueous and non aqueous matrices, such as liquid fuels.
N-(2-nitroalkyl) morpholine compounds are a class of biocides that are useful for controlling microorganism growth in a variety of environments, such as industrial cooling water systems, recycle process water systems, oil and gas recovery operations, and in fuels. FUELSAVER™, which is based on a mixture of N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane, is an example of a commercially available N-(2-nitroalkyl) morpholine biocide that is used for preserving fuels.
While N-(2-nitroalkyl) morpholines are effective biocides, many crystallize at temperatures above 0° C. Such biocides, therefore, are generally unsuitable for cold temperature applications, storage, or transport.
It would be an advance in the art to provide formulations of N-(2-nitroalkyl) morpholines that are cold stable, particularly those that are stable (i.e., do not freeze) at temperatures as low as −20° C. It would also be an advance to provide formulations that exhibit enhanced activity against a broad spectrum of microorganisms.
In one aspect, the invention provides a biocidal composition that is stable at low temperature and exhibits synergistic behavior. The composition comprises an N-(2-nitroalkyl) morpholine compound of formula I:
where R, x, and y are as defined herein, together with an aromatic alcohol.
In another aspect, the invention provides a fuel blend. The fuel blend comprises a liquid fuel and the cold temperature stable biocidal composition described herein.
In a further aspect, the invention provides a method for imparting microorganism resistance to a matrix in need of such resistance. The method comprises including in the matrix an effective amount of the biocidal composition described herein.
As noted above, the invention provides cold temperature stable biocidal compositions. In particular, compositions according to the invention have been found to be freeze stable (i.e., do not freeze) to temperatures as low as −20° C. This occurs even though the individual components of the composition are not themselves freeze stable at the same temperatures.
In addition to cold temperature stability, compositions according to the invention also exhibit improved control of microorganism growth when compared to other non-inventive cold temperature stable formulations.
For the purposes of this specification, the meaning of “microorganism” includes, but is not limited to, bacteria, fungi, algae, and viruses. The words “control” and “controlling” should be broadly construed to include within their meaning, and without being limited thereto, inhibiting the growth or propagation of microorganisms, killing microorganisms, disinfection, and/or preservation against re-growth of microorganisms.
The composition of the invention comprises: a biocidal N-(2-nitroalkyl) morpholine compound of the formula I:
where R is hydrogen, methyl or ethyl; x is 1 or 2; y is 0 or 1, and the sum of x and y is 2; and an aromatic alcohol.
Preferred biocidal compounds of formula I are those in which R is ethyl.
Also preferred are compounds in which y is 1.
Additionally preferred are compounds wherein y is 0.
Specific examples of preferred compounds of formula I include: N-(2-nitroethyl)morpholine, N-(2-nitropropyl)morpholine, N-(2-nitrobutyl)morpholine, 2-nitro-1,3-dimorpholinopropane, 2-methyl-2-nitro-1,3-dimorpholinopropane, 2-ethyl-2-nitro-1,3-dimorpholinopropane, or mixtures of two or more thereof.
More preferred are N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane.
Particularly preferred is a mixture of N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane. In this embodiment, it is further preferred that the weight ratio of N-(2-nitrobutyl)morpholine to 2-ethyl-2-nitro-1,3-dimorpholinopropane is between about 20:1 and about 10:1, more preferably between about 18:1 and about 14:1.
The aromatic alcohol used in the compositions of the invention functions as a freeze stabilizer and also as an enhancer of biocidal efficacy. Suitable aromatic alcohols include phenoxyethanol, benzyl alcohol, and aromatic glycol ethers. Preferred is phenoxyethanol.
The composition of the invention preferably comprises between about 5 and 95 weight percent, more preferably between about 15 and 75 weight percent, even more preferably between about 30 and 55 weight percent, and further preferably between about 38 and 44 weight percent of the N-(2-nitroalkyl) morpholine compound based on the total weight of the biocide and the aromatic alcohol in the composition.
An especially preferred composition according to the invention comprises from about 38 to 44 weight percent of a mixture of N-(2-nitrobutyl)morpholine and 2-ethyl-2-nitro-1,3-dimorpholinopropane and about 62 to 56 weight percent of phenoxyethanol, based on the total weight of the mixture of N-(2-nitrobutyl)morpholine/2-ethyl-2-nitro-1,3-dimorpholinopropane and the phenoxyethanol present in the composition.
The composition may contain other additives including, but not limited to, other aromatic or non-aromatic solvents, glycolic type solvents, and non-aromatic glycol ethers, as well as various inert or byproduct material that may result from the synthesis of the biocide and that are not removed during workup. In general, it is preferred that the total amount of biocide compound and aromatic alcohol comprise at least about 70 weight percent, more preferably at least about 80 weight percent of the composition, based on the compositions total weight.
As noted, more than one N-(2-nitroalkyl) morpholine compound can be combined for use in the invention; in such cases, ratios and concentrations are calculated using the total weight of all N-(2-nitroalkyl) morpholine compounds present.
N-(2-nitroalkyl) morpholine compounds for use in the invention are commercially available or can be readily prepared by those skilled in the art using well known techniques (see e.g., U.S. Pat. No. 3,054,749 and Canadian patent 982475, both incorporated by reference). Aromatic alcohols are also commercially available or can be readily prepared.
The compositions of the invention are useful at controlling microorganism growth in a variety of aqueous and non-aqueous matrices and in matrices that are mixtures of aqueous and non-aqueous components. Examples include, but are not limited to, metalworking fluids, die cast lubricants, mold release agents, paints, paint spray booth wash water, coatings, adhesives, caulks, sealants, mineral slurries, inks, petroleum (crude oil), or liquid fuels such as gasoline, diesel, biodiesel, water-fuel emulsions, ethanol-based fuels, ether-based fuels, diesel oil, fuel oil, or kerosene based fuels. Because of their cold temperature stability, the compositions of the invention are particularly suitable for controlling microorganisms in liquid fuels.
A person of ordinary skill in the art can readily determine, without undue experimentation, the effective amount of the composition that should be used in any particular matrix to provide microorganisms control. By way of illustration, a suitable effective amount (total for the N-(2-nitroalkyl) morpholine compound(s) and the aromatic alcohol) is at least about 25 ppm or at least about 500 ppm, by weight. Typically, the amount is less than about 20,000 ppm or less than about 2500 ppm, by weight.
The components of the composition of the invention can be added to the matrix separately or they can be preblended prior to addition. A person of ordinary skill in the art can readily determine the appropriate method of addition. Preblending is preferred.
The following examples are illustrative of the invention but are not intended to limit its scope. Unless otherwise indicated, ratios, percentages, parts, and the like used herein are by weight.
In the Examples below, the following compositions are tested:
Sample C: a comparative composition that is freeze stable and that contains a mixture of about 55 weight percent tripropylene glycol methyl ether as a freeze stabilizer and about 45 weight percent of Sample A. The composition does not contain phenoxyethanol.
Sample A (comparative composition), Sample B (inventive), and phenoxyethanol (comparative) are placed in a −20° C. freezer for 24 hours, removed and observed for freezing. Samples are thawed completely and then replaced in the freezer for another 24 hour period. This procedure is carried out for five cycles in which the samples are placed in the freezer for five 24 hour periods. Sample size is 5 ml in a clear glass container with a Bakelite screw top. Results are summarized in Table 1.
As can be seen from the data in Table 1, the inventive composition (Sample B) does not freeze even though the individual ingredients, the biocide mixture (Sample A) and the phenoxyethanol, both freeze under the same temperature conditions.
This example compares the efficacy of compositions of the invention to non-inventive compositions, in diesel fuel, against various microorganisms.
Procedure
Bacteria: Pseudomonas aeruginosa (ATCC# 33988), Yeast: Yarrowia tropicalis (ATCC# 48138), and Mold: Hormoconis resinae ATCC# 20495, are sub-cultured in Bushnell-Haas broth, and used for the inoculum of this example. Bushnell-Haas broth is used as the aqueous phase below the diesel fuel. Testing is carried out for 4 weeks. Microbial survival is measured using the plate count method. Tryptic soy agar is used for Pseudomonas aeruginosa, and Sabouraud dextrose agar with 0.5 ug/ml gentamycin for Yarrowia tropicalis, and bacteriological grade agar 1.5%, with 0.01% potassium tellurite for Hormoconis resinae. Bacteria are incubated at 37° C. for 48 hours, and fungi at 25° C. for 5-7 days.
Testing is carried out in glass bottles with bakelite screw tops. Volumes: 130 ml diesel fuel over 25 ml synthetic water bottom (Bushnell-Haas Broth). Tests are mixed weekly by turning the bottle upside down 5 times.
The diesel fuel is obtained from Halternann Products (Channelview, Tex.) Diesel fuel, with the following specifications: 2007 Certification Diesel, GMPT-5-0,9-; Product Number: HF 582b; Product Code: 20582b.
Table 2 shows results for “Sample B”, a composition according to the invention. Table 3 shows results for “Sample C,” a comparative composition that is freeze stable. Table 4 shows results for phenoxyethanol which is a component in Sample B, but is not freeze stable by itself. Table 5 is a summary of the lowest dosage required to reduce the concentration of viable microorganisms to a <10 CFU/mL level for Samples B, C, and phenoxyethanol.
As can be seen from the data, the inventive composition (Sample B) provides significantly improved microbial control relative to the other low temperature stable formulation (Sample C), as well as relative to phenoxyethanol which is not freeze stable nor very effective as a microbial control agent.
Sample A and Sample C were re-tested at the same biocidal active concentrations using the test method described in Example 2, except the test was carried out for 7 days and the microbial survival was measured at 24 hour and at 7 days. The results are summarized in Table 6.
As shown in Table 6, at equivalent active concentrations, Sample A had generally lower efficacy than Sample C.
Because Sample A is generally less effective than Sample C at the same active concentrations, the data results from Table 5 are used to determine the concentrations of NMB/ENDM in Sample C that are required to achieve a <10 CFU/mL level, to estimate the synergy index between NMB/ENDM and phenoxyethanol. Based on the Synergy Index (SI) calculation equation below, the estimated synergy indices for NMB/ENDM and phenoxyethanol are provided in Table 7.
Ca: Concentration of NMB/ENDM in Sample B required to reduce the concentration of viable microorganism to <10 CFU/ml level
CA: Concentration of NMB/ENDM required to reduce the concentration of viable microorganism to <10 CFU/ml level when used alone
Cb: Concentration of PHE in Sample B required to reduce the concentration of viable microorganism to <10 CFU/ml level
CB: Concentration of PHE required to reduce the concentration of viable microorganism to <10 CFU/ml level when used alone
Synergy Index=1: additivity
The results in Table 7 illustrate that there is a synergistic effect between NMB/ENDM and phenoxyethanol.
While the invention has been described above according to its preferred embodiments, it can be modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using the general principles disclosed herein. Further, the application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the following claims.
This application claims benefit of priority from U.S. Provisional Patent Application No. 61/166,934, filed Apr. 6, 2009, which application is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61166934 | Apr 2009 | US |
