Synergistic Mixtures of O-Phenylphenol and Dazomet

Abstract

Ortho phenylphenol acts synergistically with various other antimicrobial compounds commonly used in industrial applications.

Description

RELATED APPLICATION

[0001] This application is a continuation of U.S. application Ser. No. 10/345,798, filed Jan. 16, 2003, which claims the benefit of U.S. Provisional Application No. 60/349,636 filed Jan. 17, 2002. Application Ser. Nos. 10/345,798 and 60/349,636 are incorporated by reference.

TECHNICAL FIELD

[0002] This invention relates to synergistic mixtures of o-phenylphenol and/or its sodium salt with tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione commonly used in cement admixtures and slurries.

BACKGROUND OF THE INVENTION

[0003] O-phenylphenol and Sodium orthophenylphenate (separately or collectively sometimes herein known as "OPP", orthophenylphenol or o-phenylphenol) are used extensively as antimicrobial agents in various industrial applications such as preservation of various materials including paints, adhesives etc. as well as to control unwanted microorganisms found in various process waters such as cooling water, paper mills and petroleum production.

[0004] Microbiological growth can cause contamination of products that requires the use of preservatives, as well as process waters, where Antimicrobials are required to prevent contamination. Preservatives are required for a broad range of products including but not limited to adhesives, cosmetics and toiletries, disinfectants and sanitizers, leather, metalworking fluids, paints and coatings, plastics and resins, latex polymers, textiles and wood. Failure to preserve these products adequately will result in spoilage and loss of the materials to be preserved and will result in an economic loss. Similarly, microbiological growths can have dire consequences if process waters are not adequately treated. Process waters include but are not limited to: industrial recirculating water, paper products and paper, petroleum production and leather tanning. Process waters are of concern because when fouled with biofilms that develop from the indigenous microbes present, biofilms may develop into thick gelatinous like masses. Slime is produced by a wide range of bacteria, fungi, and yeast. Slime will interfere with the process resulting in a loss of heat transfer, corrosion and fouling. Slime also detracts from systems cleanliness.

SUMMARY OF THE INVENTION

[0005] This invention includes synergistic ratios of aqueous suspensions of orthophenylphenol or Sodium orthophenylphenate with the following chemical antimicrobials: [0006] bis (Trichloromethyl) sulfone [0007] 1-Bromo-3-chloro-5,5-dimethylhydantion [0008] 1,2-Benzisothiazolin-3-one [0009] bromonitrostyrene [0010] 2,2-dibromo-3-nitrilopropionamide [0011] 4,5-dicloro-1,2-dithiol-3-one [0012] 5-chloro-2-methyl-4-isothiazoline-3-one/ [0013] 2-methyl-4-isothiazoline-3-one [0014] Diiodomethyl-p-tolylsulfone [0015] sodium hypochlorite [0016] tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione

[0017] Generally, any ratio of OPP to the other antimicrobial within the range of 1%-99% to 99%-1% by weight may demonstrate a synergistic effect to some degree, but we prefer to use the most efficient combinations, which may include a wide range of ratios, as will be seen below.

DETAILED DESCRIPTION OF THE INVENTION:

[0018] Orthophenylphenol was found to produce synergistic blends with other antimicrobials. The synergistic blends were determined using a dose protocol. The actives were evaluated in synthetic white water with pH values of 5.5 and 8.0. The materials were tested against an artificial bacterial consortium containing approximately equal numbers of six bacterial strains. Although the test strains are representative of organisms present in paper mill systems, the effect is not limited to these bacteria. Two of the strains were Kiebsiella pneumoia (ATCC 13883) and Pseudomonas aeruginosa (ATCC 15442). The other four strains were isolated from papermill systems and have been identified as Curtobacterium flaccumfaciens, Burkhlderia cepacia, Bacillus maroccanus, and Pseudomonas glethei. Each strain was inoculated at 37.degree. C. overnight, then suspended in sterile saline. Equal volumes of each strain were then combined to prepare the consortium. The bacterial consortium was distributed into the wells of a microtiter plate in the presence or absence of various concentrations of the active materials. The microtiter plates were incubated at 37.degree. C. Optical density (O.D.) readings at 650 nm were taken initially (t.sub.0) and after time 4 hours (t.sub.4) of incubation.

[0019] The raw data was converted to "bacterial growth inhibition percentages" according to the following formula: % Inhibition=[(a-b)/a]100

[0020] where:

[0021] a=(O.D. of control at t.sub.n)-(O.D. of control at t.sub.0)

[0022] b=(O.D. of treatment at t.sub.n)-(O.D. of treatment at t.sub.0)

[0023] The inhibition values can be plotted versus dosage for each active and the particular blend. This results in a dose response curve from which the dosage to yield 50% inhibition (1.sub.50) can be calculated. In the examples (tables) below, the 1.sub.50 values are expressed as parts per million (ppm) of active material. The synergism index (SI) was calculated by the equations described by F. C. Kull, P. C. Eisman, H. D. Sylwestrowicz, and R. L. Mayer (1961), Applied Microbiology 9, 538-541. The values are based on the amount needed to achieve a specified end point. The end point selected for these studies was 50% inhibition of bacterial growth. Synergy Index (SI)=(QA/Qa)+(QB/Qb)

[0024] where:

[0025] QA=quantity of compound A in mixture, producing the end point

[0026] Qa=quantity of compound A.sub.1 acting alone, producing the end point

[0027] QB=quantity of compound B in mixture, producing the end point

[0028] Qb=quantity of compound B.sub.1 acting alone, producing the end point

[0029] If SI is less than 1, synergism exists; if SI is greater than 1, antagonism exists, if SI is equal to 1, an additive effect exists.

[0030] Example 1 deals with a blend of bis (Trichloromethyl) sulfone and o-phenylphenol.

EXAMPLE 1

[0031] This example shows the synergistic activity between o-phenylphenol and bis (Trichloromethyl) sulfone under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00001 Sulfone* & NaOPP @ pH 5.5 ppm ppm Synergy Sulfone NaOPP Ratio Sulfone:NaOPP Index 1.154 0.00 100:0 1.00 0.504 3.91 1.0:7.8 0.67 0.236 7.81 1.0:33.0 0.39 0.170 15.63 1.0:92.0 0.53 0.156 31.25 1.0:200.8 0.73 0.000 56.78 0:100 1.00

[0032] TABLE-US-00002 Sulfone* & NaOPP @ pH 8.0 Ppm ppm Synergy Sulfone NaOPP Ratio Sulfone:NaOPP Index 1.34 0.00 100:0 1.00 0.77 3.91 1.0:5.0 0.67 0.54 7.81 1.0:14.4 0.56 0.45 15.63 1.0:34.5 0.61 0.35 31.25 1.0:89.4 0.76 0.05 62.50 1.0:1230.4 0.97 0.00 67.8 0:100 1.00 *Sulfone - Bis(trichlormethyl)sulfone

EXAMPLE 2

[0033] This example shows the synergistic activity between o-phenylphenol and 1-Bromo-3-chloro-5,5-dimethylhydantion under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00003 BCDMH* & NaOPP @ pH 5.5 ppm ppm Synergy BCDMH NaOPP Ratio BCDMH:NaOPP Index 14.60 0.00 100:0 1.00 9.10 3.91 1.0:0.4 0.67 9.88 7.81 1.0:0.8 0.78 10.98 15.63 1.0:1.4 0.95 10.86 31.25 1.0:2.9 1.14 6.25 67.52 1.0:10.8 1.29 5.62 62.50 1.0:11.1 1.18 3.13 82.87 1.0:26.5 1.27 1.56 83.18 1.0:53.2 1.17 0.78 80.42 1.0:102.9 1.08 0.39 81.38 1.0:208.3 1.07 0.20 76.21 1.0:390.2 0.99 0.10 76.13 1.0:779.6 0.98 0.00 78.40 0:100 1.00

[0034] TABLE-US-00004 BCDMH* & NaOPP @ pH 8.0 ppm ppm Synergy BCDMH NaOPP Ratio BCDMH:NaOPP Index 34.37 0.00 100:0 1.00 11.51 3.91 1.0:0.3 0.37 13.22 7.81 1.0:0.6 0.45 15.92 15.63 1.0:1.0 0.58 20.74 31.25 1.0:1.5 0.85 20.94 62.50 1.0:3.0 1.09 12.50 90.71 1.0:7.3 1.07 6.25 116.26 1.0:18.6 1.08 3.13 127.26 1.0:40.7 1.08 1.56 136.91 1.0:87.6 1.10 0.78 144.84 1.0:185.4 1.14 0.39 137.29 1.0:351.5 1.07 0.20 136.00 1.0:696.3 1.06 0.10 131.07 1.0:1342.2 1.02 3.13 127.26 0:100 1.00 *BCDMH--1-Bromo-3-chloro-5,5-dimethylhydantoin

EXAMPLE 3

[0035] This example shows the synergistic activity between o-phenylphenol and 1,2-Benzisothiazolin-3-one under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00005 BIT* & NaOPP @ pH 5.5 ppm ppm Synergy BIT NaOPP Ratio BIT:NaOPP Index 1.46 0.00 100:0 1.00 1.14 3.91 1.0:3.4 0.83 1.15 7.81 1.0:6.8 0.88 1.15 15.63 1.0:13.6 0.97 1.00 31.25 1.0:31.2 1.05 0.63 53.37 1.0:85.4 1.06 0.49 62.50 1.0:128.5 1.07 0.31 73.11 1.0:233.9 1.07 0.16 75.81 1.0:485.2 1.00 0.08 78.91 1.0:1010.1 0.98 0.04 75.98 1.0:1945.1 0.92 0.02 81.73 1.0:4184.8 0.96 0.01 82.29 1.0:8426.5 0.96 0.00 84.96 0:100 1.00

[0036] TABLE-US-00006 BIT* & NaOPP @ pH 8.0 ppm ppm Synergy BIT NaOPP Ratio BIT:NaOPP Index 2.86 0.00 100:0 1.00 2.77 3.91 1.0:1.4 1.01 2.87 7.81 1.1:2.7 1.07 2.88 15.63 1.0:5.4 1.14 2.40 31.25 1.0:13.0 1.11 2.28 62.50 1.0:27.4 1.34 0.63 118.64 1.0:189.8 1.24 0.31 117.62 1.0:376.4 1.12 0.16 124.59 1.0:797.4 1.13 0.08 121.17 1.0:1551.0 1.07 0.04 118.13 1.0:3024.0 1.03 0.02 120.98 1.0:6194.3 1.05 0.01 117.97 1.0:12080.4 1.02 0.00 116.41 0:100 1.00 *BIT--1,2-Benzisothiazolin-3-one

EXAMPLE 4

[0037] This example shows the synergistic activity between o-phenylphenol and bromonitrostyrene under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00007 BNS* & NaOPP @ pH 5.5 ppm ppm Synergy BNS NaOPP Ratio BNS:NaOPP Index 1.19 0.00 100:0 1.00 1.14 3.91 1.0:3.4 1.01 1.20 7.81 1.0:6.5 1.10 1.04 15.63 1.0:15.0 1.05 0.85 31.25 1.0:36.6 1.07 0.63 45.57 1.0:72.9 1.03 0.45 62.50 1.0:140.4 1.07 0.31 73.45 1.0:235.0 1.08 0.16 84.59 1.0:541.4 1.07 0.08 89.51 1.0:1145.7 1.06 0.04 91.28 1.0:2336.7 1.04 0.02 92.98 1.0:4760.7 1.04 0.00 90.47 0:100 1.00

[0038] TABLE-US-00008 BNS* & NaOPP @ pH 8.0 ppm ppm Synergy BNS NaOPP Ratio BNS:NaOPP Index 3.08 0.00 100:0 1.00 3.19 3.91 1.0:1.2 1.07 2.83 7.81 1.0:2.8 0.98 2.90 15.63 1.0:5.4 1.07 2.96 31.25 1.0:10.6 1.21 2.50 39.46 1.0:15.8 1.13 2.00 62.50 1.0:31.2 1.16 1.25 86.33 1.0:69.1 1.11 0.63 107.36 1.0:171.8 1.07 0.31 124.73 1.0:399.1 1.11 0.16 128.83 1.0:824.5 1.10 0.08 131.28 1.0:1680.4 1.09 0.04 120.73 1.0:3090.6 0.99 0.02 115.35 1.0:5905.9 0.94 0.00 123.16 0:100 1.00 *BNS--Bromonitrostyrene

EXAMPLE 5

[0039] This example shows the synergistic activity between o-phenylphenol and 2,2-dibromo-3-nitrilopropionamide under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00009 DBNPA & NaOPP @ pH 5.5 ppm ppm Synergy DBNPA NaOPP Ratio DBNPA:NaOPP Index 1.69 0.00 100:0 1.00 1.71 0.49 1.0:0.3 1.02 1.68 0.98 1.0:0.6 1.00 1.72 1.95 1.0:1.1 1.04 1.71 3.91 1.0:2.3 1.06 1.58 7.81 1.0:4.9 1.02 1.54 15.63 1.0:10.1 1.09 1.44 31.25 1.0:21.7 1.20 1.25 62.03 1.0:49.6 1.44 1.21 62.50 1.0:51.6 1.42 0.63 84.50 1.0:135.2 1.33 0.31 88.90 1.0:284.5 1.19 0.16 95.11 1.0:608.7 1.17 0.08 97.67 1.0:1250.1 1.15 0.00 88.38 0:100 1.00

[0040] TABLE-US-00010 DBNPA & NaOPP @ pH 8.0 ppm ppm Synergy DBNPA NaOPP Ratio DBNPA:NaOPP Index 3.01 0.00 100:0 1.00 2.88 0.49 1.0:0.2 0.96 2.73 0.98 1.0:0.4 0.91 2.82 1.95 1.0:0.7 0.95 2.94 3.91 1.0:1.3 1.00 2.80 7.81 1.0:2.8 0.99 2.81 15.63 1.0:5.6 1.05 2.72 31.25 1.0:11.5 1.13 2.50 55.48 1.0:22.2 1.23 2.54 62.50 1.0:24.6 1.30 1.25 121.24 1.0:97.0 1.30 0.63 126.72 1.0:202.7 1.13 0.31 121.38 1.0:388.4 0.99 0.16 140.84 1.0:901.4 1.08 0.08 109.38 1.0:1400.1 0.82 0.00 137.13 0:100 1.00 *DBNPA--2,2-Dibromo-3-nitrilopropionamide

EXAMPLE 6

[0041] This example shows the synergistic activity between o-phenylphenol and 4,5-dicloro-1,2-dithiol-3-one under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00011 Dithiol & NaOPP @ pH 5.5 ppm ppm Ratio Synergy Dithiol NaOPP Dithiol:NaOPP Index 0.073 0.00 100:0 1.00 0.070 0.49 1.0:6.9 0.97 0.074 0.98 1.0:13.2 1.03 0.091 1.95 1.0:21.5 1.26 0.079 3.91 1.0:49.2 1.12 0.073 7.81 1.0:107.5 1.06 0.069 15.63 1.0:227.1 1.08 0.061 31.25 1.0:514.7 1.10 0.058 62.50 1.0:1080.9 1.32 0.039 75.14 1.0:1923.7 1.17 0.000 0.07 0:100 1.00

[0042] TABLE-US-00012 Dithiol & NaOPP @ pH 8.0 ppm ppm Synergy Dithiol NaOPP Ratio Dithiol:NaOPP Index 0.16 0.00 100:0 1.00 0.16 0.49 1.0:3.0 1.00 0.16 0.98 1.0:6.0 1.01 0.17 1.95 1.0:11.6 1.05 0.17 3.91 1.0:22.6 1.09 0.17 7.81 1.0:46.3 1.10 0.16 15.63 1.0:95.5 1.13 0.17 31.25 1.0:183.6 1.28 0.20 62.50 1.0:320.3 1.67 0.08 138.33 1.0:1770.6 1.52 0.04 137.46 1.0:3519.0 1.28 0.00 132.71 0:100 1.00 * Dithiol - 4,5-Dichloro-1,2-dithiol-3-one

EXAMPLE 7

[0043] This example shows the synergistic activity between o-phenylphenol and 5-chloro-2-methyl-4-isothiazoline-3-one/2-methyl-4-isothiazoline-3-on- e under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00013 Iso* & NaOPP @ pH 5.5 ppm ppm % Synergy Iso NaOPP Ratio Iso:NaOPP Inhibition Index 0.09 0.00 100:0 50 1.00 0.09 3.91 1.0:41.4 50 1.10 0.08 7.81 1.0:93.1 50 1.03 0.07 15.63 1.0:219.8 50 0.98 0.06 29.35 1.0:469.5 50 1.05 0.06 31.25 1.0:549.3 50 1.01 0.03 51.17 1.0:1637.4 50 0.97 0.02 62.50 1.0:2649.1 50 1.02 0.02 71.02 1.0:4545.4 50 1.03 0.01 72.33 1.0:9258.8 50 0.96 0.00 71.54 1.0:18313.3 50 0.91 0.00 76.93 1.0:39390.6 50 0.95 0.00 82.73 0:100 50 1.00

[0044] TABLE-US-00014 Iso* & NaOPP @ pH 8.0 ppm ppm % Synergy Iso NaOPP Ratio Iso:NaOPP Inhibition Index 0.09 0.00 100:0 50 1.00 0.09 3.91 1.0:41.4 50 1.13 0.09 7.81 1.1:86.4 50 1.12 0.08 15.63 1.0:191.7 50 1.09 0.08 31.25 1.0:381.2 50 1.23 0.06 53.65 1.0:858.4 50 1.20 0.07 62.50 1.0:955.8 50 1.31 0.03 93.37 1.0:2987.9 50 1.21 0.02 116.98 1.0:7486.9 50 1.09 0.01 114.13 1.0:14609.0 50 1.09 0.00 119.07 1.0:30481.2 50 1.09 0.00 114.29 1.0:58514.5 50 1.02 0.00 114.14 0:100 50 1.00 *Iso - Mixture of 5-Chloro-2-methyl-4-isothiazolin-3-one and 2-Methyl-4-isothiazolin-3-one

EXAMPLE 8

[0045] This example shows the synergistic activity between o-phenylphenol and Diiodomethyl-p-tolylsulfone under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00015 DIMTS* & NaOPP @ pH 5.5 ppm ppm Synergy DIMTS NaOPP Ratio DIMTS:NaOPP Index 31.65 0.00 100:0 1.00 25.82 3.91 1.0:0.15 0.86 46.44 7.81 1.0:0.17 1.56 36.85 15.63 1.0:0.4 1.35 34.20 31.25 1.0:0.9 1.45 25.00 35.97 1.0:1.4 1.22 12.50 58.85 1.0:4.7 1.10 6.33 62.50 1.0:9.9 0.94 6.25 64.52 1.0:10.3 0.97 3.13 77.03 1.0:24.6 1.02 1.56 87.63 1.0:56.1 1.09 0.78 90.32 1.0:115.6 1.10 0.39 80.40 1.0:205.8 0.97 0.20 77.72 1.0:397.9 0.93 0.10 82.24 1.0:842.2 0.98 0.00 84.10 0:100 1.00

[0046] TABLE-US-00016 DIMTS* & NaOPP @ pH 8.0 ppm ppm Synergy DIMTS NaOPP Ratio DIMTS:NaOPP Index** 22.84 0.00 100:0 1.00 33.78 3.91 1.0:0.1 1.52 31.04 7.81 1.0:0.3 1.44 28.66 15.63 1.0:0.5 1.42 25.20 31.25 1.0:1.2 142 14.75 62.50 1.0:4.2 1.29 6.25 63.44 1.0:10.2 0.92 3.13 71.82 1.0:23.0 0.87 1.56 93.40 1.0:59.8 1.02 0.78 96.85 1.0:124.0 1.02 0.39 104.09 1.0:266.5 1.08 0.20 94.29 1.0:482.8 0.97 0.10 99.53 1.0:1019.2 1.02 0.00 97.74 0:100 1.00 *DIMTS - Diiodomethyl-p-tolylsulfone **synergy Index Values Calculated Using 40% Inhibition of Bacterial Growth

EXAMPLE 9

[0047] This example shows the synergistic activity between o-phenylphenol and sodium hypochlorite under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00017 NaOCl* & NaOPP @ pH 5.5 ppm ppm Synergy NaOCl NaOPP Ratio NaOCl:NaOPP Index** 55.27 0.00 100:0 1.00 22.93 3.91 1.0:0.17 0.49 31.92 7.81 1.0:0.24 0.72 31.73 15.63 1.0:0.49 0.86 35.57 31.25 1.0:0.88 1.21 25.00 43.82 1.0:1.8 1.25 12.50 56.87 1.0:4.5 1.26 6.25 57.65 1.0:9.2 1.16 3.13 65.39 1.0:20.9 1.25 1.56 61.92 1.0:39.6 1.16 0.78 61.29 1.0:78.5 1.13 0.39 53.86 1.0:137.9 0.99 0.20 48.05 1.0:246.0 0.88 0.10 47.55 1.0:486.9 087 0.00 54.92 0:100 1.00 *NaOCl - Sodium Hypochlorite **Synergy Index Values Calculated Using 30% Inhibition of Bacterial Growth

EXAMPLE 10

[0048] This example shows the synergistic activity between o-phenylphenol and tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione under a concurrent feed strategy, against article bacterial consortium in synthetic white water at pH 5.5 and 8.0. TABLE-US-00018 Dazomet* & NaOPP @ pH 5.5 ppm ppm Ratio Synergy Dazomet NaOPP Dazomet:NaOPP Index 6.176 0.00 100:0 1.00 3.848 3.91 1.0:1.0 0.66 1.089 7.81 1.0:7.2 0.25 1.119 15.63 1.0:14.0 0.33 0.366 31.25 1.0:85.4 0.36 0.368 62.50 1.0:170.0 0.66 0.000 56.78 0:100 1.00

[0049] TABLE-US-00019 Dazomet* & NaOPP @ pH 8.0 Ppm ppm Ratio Synergy Dazomet NaOPP Dazomet:NaOPP Index 5.34 0.00 100:0 1.00 5.66 3.91 1.0:0.7 1.09 4.97 7.81 1.0:1.6 0.98 4.70 15.63 1.0:3.3 0.98 4.59 31.25 1.0:6.8 1.06 4.51 62.50 1.0:13.9 1.24 2.43 125.0 1.0:51.5 1.24 0.00 158.32 0:100 1.00 *Dazomet - tetrahydo-3,5-dimethyl-2H-1-3-5-thiadiazine-2-thione

[0050] An additional example of the synergism of Dazomet and NaOPP can be seen as follows.

[0051] EQUIPMENT used for the experiment are as follows: [0052] 1. Incubator capable of maintaining a variable temperature range (25-45 C.); [0053] 2. Samples of each biocide or test compound to be examined; [0054] 3. Microtiter plates--96 well with lid, sterile; [0055] 4. 8-12 channel micropipetting device capable of pipetting 0-250 ul volumes; [0056] 5. Micropipette tips capable of holding up to 250 ul volumes; [0057] 6. Sterile microbiological culture broth. Trypticase Soy Broth (TSB) or Nutrient Broth (NB) is recommended for bacteria and Sabouraud Maltose Broth (SMB) or Sabouraud Dextrose Broth (SDB) is recommended for yeasts and molds. In the case of this particular study the microbiological culture medium was Nutrient Broth at pH 7.0, 8.0 and 9.0; [0058] 7. Pure cultures of microorganisms of choice grown on appropriate agar medium; [0059] 8. Sterile distilled water; [0060] 9. 100 mL volumetric flasks (one for each biocide to be tested); [0061] 10. Sterile 10 mL tubes of Phosphate buffer (Butterfield's buffer pH 7.2+/-0.2). Contains purified water, monobasic potassium phosphate and sodium hydroxide for pH adjustment; [0062] 11. Sterile cotton swabs; [0063] 12. 0.5 MacFarland Turbidity Standard;

[0064] Preparation of Bacterial Inocula

[0065] The day before testing, perform a streak plate of each organism to be tested on an appropriate agar medium (Trypticase Soy Agar). Organisms tested in this study were.

[0066] Wild strain bacteria isolated from previously contaminated industrial systems and which were identified as: Pseudomonas sp., Escherchia coli, Enterobacter sp., Alcaligenes sp. and Alcaligenes faecalis. On the day of the test, use a sterile cotton swab to harvest some of the growth. Place swab into a tube containing 10 mL sterile phosphate buffer. Compare and adjust the turbidity of the organisms in the tube to 1.times.10.sup.8 cfu/mL using a 0.5 MacFarland Turbidity Standard. Dilute the 10 mL tube into 90 mL of sterile 2.times. nutrient broth at pH 7.0, 8.0 and 9.0.

[0067] The following procedure was used: [0068] 1. Design the layout of the microtiter plates based on the number of organisms to test and the number of biocides and desired concentrations to test. A separate microtiter plate is required for testing each biocide alone, in addition to the combination microtiter plate. [0069] 2. Prepare a working stock solution of each biocide to be tested. For the combination microtiter plate, the working stock solution of Biocide A will be 8.times. the concentration desired in the first well of the combination microtiter plate. The working stock solution of Biocide B will be 4.times. the concentration desired in the first well of the combination microtiter plate. For the alone microtiter plates, the working stock solutions of Biocide A and Biocide B will both be 4.times. the concentration desired in the first well of the single biocide microtiter plates.

[0070] Biocide A

[0071] Tetrahydro-3-5-dimethyl-2H-1,3-5-thiadiazine-2-thione (Dazomet): (For combination plates) A solution of this product, which is 99% active, was made as follows: 8.times.8000=8000 ppm active=8000/0.99=8080 ppm, 0.8 g into 100 mL MeOH and sterile diH.sub.2O.

[0072] Levels to test are:

[0073] 1000 ppm, 500 ppm, 250 ppm, 125 ppm, 62.5 ppm, 31.2 ppm, 15.6 ppm, 7.8 ppm, 3.9 ppm, 1.95 ppm

[0074] (For alone plates) A solution was made as follows: 4.times.4000=16000 ppm active=16000/0.99=16161 pm, 1.6 g into 100 mL MeOH and sterile diH.sub.2O. Levels to test are: 4000 ppm, 2000 ppm, 1000 ppm, 500 ppm, 250 ppm, 125 ppm, 62.5 ppm, 31.2 ppm, 15.6 ppm, 7.8 ppm, 3.9 ppm, 1.95 ppm.

[0075] Biocide B

[0076] o-Phenylphenol (OPP): (For combination plates) Make a solution of this product which is 99% active, 4.times.125=500 ppm active=500/0.99=505 ppm, 0.05 g into 100 mL MeOH and sterile diH.sub.2O. Level to test is 125 ppm.

[0077] (For alone plates) A solution was made as follows: 4.times.4000=16000 ppm active=16000/0.99=16161 ppm, 1.6 into 100 mL MeOH and sterile diH.sub.2O. Levels to test are: 4000 ppm, 2000 ppm, 1000 ppm, 500 ppm, 250 ppm, 125 ppm, 62.5 ppm, 31.2 ppm, 15.6 ppm, 7.8 ppm, 3.9 ppm, 1.95 ppm [0078] 3. Place 50 ul of sterile distilled water in all of the rows in columns 1 through 10, and 100 ul of sterile distilled water in all of the rows in columns 11 and 12 of the 96 well combination microtiter plate. Place 100 ul of sterile distilled water in each well of the 96 well alone microtiter plates. [0079] 4. For the combination microtiter plate, place 50 ul of the Biocide A stock solution into all of the rows in column 1 of the combination microtiter plate. [0080] 5. Serially dilute Biocide A twofold across the microtiter plate through column 10. Mix each well by pipetting up and down as you are performing the dilution scheme. [0081] 6. Place 50 ul of the Biocide B stock solution into all the rows in columns I through 10 of the combination microtiter plate. [0082] 7. For the single biocide microtiter plates, place 100 ul of Biocide A (4.times. working stock solution) into all rows in the column. Serially dilute Biocide A two fold across the microtiter plate through column 10. Mix each well by pipetting up and down as you are performing the dilution 5 scheme. [0083] 8. Repeat Step 7 for the Biocide B microtiter plate. [0084] 9. The 11.sup.th column in all plates serves as a broth control. Add 100 ul of 2.times. nutrient broth at either pH 7.0, 8.0 or 9.0 into each well in this column. [0085] 10. The 11.sup.th column serves as an organism control. [0086] 11. Add 100 ul of the inoculum to the appropriate rows of the microtiter plate in columns 1 through 10 and 12 as listed below.

[0087] Bacterial Plates

[0088] Row A through H: Mixed Inoculum at a strength of 1X10E6 cfu/ml

[0089] Incubate the microtiter plate at the desired temperature for the desired amount of time. This plate represents the biostatic activity of the test compound(s). Bacterial plates are usually incubated at 35-37 C. for 24 hours.

[0090] Quality Control

[0091] The organism control (12.sup.th column) and the nutrient broth control (11.sup.th column) wells serve as controls for this experiment. If no growth appears in the organism control or if growth appears in the broth control, the test is invalid and must be repeated. TABLE-US-00020 Layout of Combination Biocide Plate each level was replicated 8 times Biocide A (8X) Dazomet Biocide B (4X) OPP Well# Stock Sol 8000 ppm Stock Sol. 500 ppm Ratio A:B 1 1000 125 8:1 2 500 125 4:1 3 250 125 2:1 4 125 125 1:1 5 62.5 125 1:2 6 31.25 125 1:4 7 15.6 125 1:8 8 7.8 125 1:16 9 3.9 125 1:30 10 1.95 125 1:65 11 nutrient broth nutrient broth 12 organism control organism control

[0092] TABLE-US-00021 Layout of Alone Biocide Plate the levels were replicated 8 times: Biocide A (4X) Dazomet Well # Stock Sol. (4000 ppm) 1 1000 2 500 3 250 4 125 5 62.5 6 31.25 7 15.6 8 7.8 9 3.9 10 1.95 11 nutrient broth 12 organism control

[0093] TABLE-US-00022 Layout of Alone Biocide Plate #2 the levels were replicated 8 times: Well # Biocide A (4X) Dazomet Stock Sol. (16000 ppm) 1 4000 2 2000 3 1000 4 nutrient broth 5 organism control Biocide B (4X) OPP Stock Sol. (4000 ppm) 1 1000 2 500 3 250 4 125 5 62.5 6 31.25 7 15.6 8 7.8 9 3.9 10 1.95 11 nutrient broth 12 organism control

[0094] TABLE-US-00023 Layout of Alone Biocide Plate #2 the levels were replicated 8 times: Biocide A (4X) OPP Well # Stock Sol. (16000 ppm) 1 4000 2 2000 3 1000 4 nutrient broth 5 organism control

[0095] Interpretation

[0096] Minimum Inhibitory Concentration (MIC)--the lowest concentration of test compound that results in no evidence of growth at the end of the incubation period.

[0097] Determine the K value for each combination biocide the MIC level: K = concentration .times. .times. of .times. .times. Biocide .times. .times. A .times. .times. in .times. .times. comb Concentration .times. .times. of .times. .times. Biocide .times. .times. A .times. .times. alone + concentration .times. .times. of .times. .times. Biocide .times. .times. B .times. .times. in .times. .times. comb concentration .times. .times. of .times. .times. Biocide .times. .times. B .times. .times. alone ##EQU1##

[0098] If K<1, the biocides are considered to be synergistic.

[0099] If K=1, the biocides are considered to be additive

[0100] If K>1, the biocides are considered to be antagonistic.

[0101] Results of Bacterial Testing TABLE-US-00024 MIC RESULTS against mixed inoculum of bacteria Biocide pH PPM Dazomet 7.0 2000 Dazomet 8.0 2000 Dazomet 9.0 4000 OPP 7.0 2000 OPP 8.0 1000 OPP 9.0 500

[0102] TABLE-US-00025 Dazomet* & NaOPP @ pH 7.0 ppm ppm Ratio Synergy Dazomet NaOPP Dazomet:NaOPP Index 1000 125 8:1 0.5625 500 125 4:1 0.3125 250 125 2:1 0.1875 125 125 1:1 0.1250 62.5 125 1:2 0.0938 31.25 125 1:4 0.0781 15.6 125 1:8 0.0700

[0103] TABLE-US-00026 Dazomet* & NaOPP @ pH 8.0 ppm ppm Ratio Synergy Dazomet NaOPP Dazomet:NaOPP Index 1000 125 8:1 0.6250 500 125 4:1 0.3750 250 125 2:1 0.2500 125 125 1:1 0.1875 62.5 125 1:2 0.1562

[0104] TABLE-US-00027 Dazomet* & NaOPP @ pH 9.0 ppm ppm Ratio Synergy Dazomet NaOPP Dazomet:NaOPP Index 1000 125 8:1 0.5 500 125 4:1 0.375 *Dazomet - tetrahydo-3,5-dimethyl-2H-1-3-5-thiadiazine-2-thione

[0105] In the claims below, where we use the term o-phenylphenol we mean for it to include the sodium salt and/or mixtures of OPP with its sodium salt.

[0106] Cement admixtures includes but is not limited to lignosulfinates, sugars, organic polymers, and slurries such as calcium carbonate, kaolin, titanium dioxide.

[0107] from 8:1 to 1:8 includes any ratio within in that range such as 1:2, 1:3, 1:4, 1:5, 2:3, 2:4, 2:8, 7:1, 7:2, 5.2:1, or 1:5.2.

[0108] Antimicrobial includes any antimicrobial agents, biocides and preservatives. It can be any chemical that inhibit the growth of microorganisms. They are used depending on the products functions and the nature of the end use in the industrial sector. Antimicrobials will inhibit the growth of and or kill microorganisms in their applications, leading to sterile conditions. Antimicrobial agents consist of commodity chemicals as well as specialty chemicals and can be classified as oxidizing types and nonoxidizing types. In these categories, the performance of the antimicrobial is described as sterilant (kills all types of life forms completely), sproicidal (kills spores), disinfectant (kills all infectious bacteria), cidal (kills all organisms) and sanitizers (reduces the number of microorganisms to a safe level), antiseptic (prevents infections) and static (prevents growth of the microorganisms).

[0109] From 1:1 to 1:170 include any ratio that range for example 1:70 or 1:2.5.

Claims

1. An antimicrobial synergistic mixture of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione and o-phenylphenol wherein the mixture is determined to be antimicrobial synergistic by having a synergistic index of less than 1.

2. An antimicrobial synergistic mixture as recited in claim 1 wherein the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is from 8:1 to 1:8.

3. An antimicrobial synergistic mixture as recited in claim 1 wherein at around a pH of 5.5 the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is from 1:1 to 1:170.

4. An antimicrobial synergistic mixture as recited in claim 1 wherein at around a pH of 7.0 the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is from 8:1 to 1:8.

5. An antimicrobial synergistic mixture as recited in claim 1 wherein at around a pH of 8.0 the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is from 8:1 to 1:2.

6. An antimicrobial synergistic mixture as recited in claim 1 wherein at around a pH of 8.0 the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is around 4:1.

7. A method of controlling antimicrobials in cement admixtures and slurries comprising: a. providing a cement admixture; and b. adding an antimicrobial synergistic mixture of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione and o-phenylphenol wherein the mixture is determined to be antimicrobial synergistic by having a synergistic index of less than 1

8. A method as recited in claim 7 wherein the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is from 8:1 to 1:8.

9. A method as recited in claim 7 wherein at around a pH of 5.5 the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is from 1:1 to 1:170.

10. A method as recited in claim 7 wherein at around a pH of 7.0 the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is from 8:1 to 1:8.

11. A method as recited as recited in claim 7 wherein at around a pH of 8.0 the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is from 8:1 to 1:2.

12. A method as recited in claim 7 wherein at around a pH of 8.0 the ratio of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione to o-phenylphenol is around 4:1.