CA1334824C - Biocide protectors - Google Patents

Abstract

A process for achieving sustained biocidal effectiveness of organic biocides detrimentally affected by the presence of iron metal, using one or more biocide protectors selected from the group consisting of molybdates, chromates, zinc salts, copper salts, cadmium salts, dialkylthioureas, alkoxylated rosin amines, certain azoles, certain phosphonates and zinc dust. Biocidal compositions comprising one or more such biocidal protectors are also described.

Description

-1 33482~
FIELD OF THE lNV~I~lION

This invention relates in general to treatment of aqueous fluids to protect the effectiveness of biocides contained therein, and more particularly, to treating an aqueous fluid in contact with iron metal to sustain the biocidal effectiveness of organic biocides contained in the fluid and detrimentally affected in untreated fluid by the presence of the iron metal.
BACKGROUND OF THE l~v~NlION

Biocides have long been used to prevent the proliferation of bacteria and other microorganisms in aqueous solutions. They are often instrumental for the efficient operation of industrial processes. Much work has been directed to developing organic biocides such as various isothiazolones, sulphones, thiocyanates and nitrilopropionamides which are now known to be effective in aqueous solution. Certain 3-isothiazolones have been particularly useful as broad spectrum microbicides. For example, U.S. Patent No. 4,539,071 to Clifford et al. describes their use in certain cooling waters and paper-making process waters with glutaraldehyde to inhibit bacterial growth and slime formation. However, the tendency of 3-isothiazolones to chemically decompose in solution requires the addition of stabilizers for many applications. U.S.
Patent No. 4,031,055 to DuPont et al. describes use of compounds containing zinc, molybdenum, copper, lead, or - 2 - ~

, .

mercury to stabilize formulations for mildew resistant coatings. U.S. Patent No. 3,870,795 to Miller et al.
describes a method of stabilizing various isothiazolone-containing solutions against chemical decomposition by adding nitrates and nitrites of selected metals such as zinc. In any case isothiazolones, as well as other organic biocides, have been developed and adapted for use in aqueous solution.

SUMMARY OF THE INVENTION

It has been found that when exposed to iron metal, solutions containing isothiazolones or certain other organic biocides can rapidly lose their biocidal effectiveness, and that addition of certain protective agents to the solution can inhibit such loss. The biocide protectors of this invention comprise a group consistinq of molybdates, chromates, sulphates, zinc salts, zinc dust, copper salts, cadmium salts, dialkylthioureas, alkoxylated rosin amines, certain azoles, and certain phosphonates and mixtures thereof.
Preferably, the biocide protectors are water soluble.
It is an object of this invention to sustain the biocidal effectiveness of organic biocides contained in aqueous fluids in contact with iron metal. It is a specific object to provide biocide protectors which inhibit the loss of biocidal effectiveness in aqueous solutions in contact with iron metal and containing organic biocides detrimentally affected by the presence of the iron metal. Other objects and advantages of the ~ I 334~32~
invention will be apparent from the following detailed description of the invention.

DETAILED DESCRIPTION OF THE lNV~NlION
The present invention is directed toward protecting the biocidal effectiveness of aqueous solutions of organic biocides in general, and isothiazolones (i.e. isothiazolinones) in particular, which come into contact with iron metal. As used in this specification, isothiazolones are intended to include, in general, those which lose their effectiveness upon exposure to iron metal and have the formula:

C/

o wherein Rl is a hydrogen atom, an alkyl group of 1 to 18 carbon atoms, alkenyl or alkynyl group of 2 to 18 carbon atoms, and preferably 2 to 4 carbon atoms, a cycloalkyl group of 3 to 12 carbon atoms, preferably having a 3 to 8 carbon atom ring, an aralkyl group of up to 10 carbon atoms, or an aryl group of up to 10 carbon atoms; and R2 is a hydrogen atom, a halogen atom, or an alkyl group, preferably having 1 to 4 carbon atoms; and R3 is a hydrogen atom, a halogen atom, or an alkyl group, preferably having 1 to 4 carbon atoms; or R2 and R3, taken together, complete a 1 33~824 benzene ring, optionally substituted with one or more halogen atoms, nitro groups, alkyl groups having 1 to 4 carbon atoms, cyano groups, alkoxy groups having 1 to 4 carbon atoms, or the like.
Examples of these biocides are presented in U.S.
Patent No. 3,870,795 to Miller et al.Cwhich is hereby incorporated in this specification by reference. In a commercial preferenc~, R1 is methyl, R2 is hydrogen, and R3 is either hydrogen or a halogen, most preferably hydrogen or chlorine. However, protection of other isothiazolones as well as other classes of organic biocides which are found to lose effectiveness in the presence of metal iron is also contemplated within the ~ scope of this invention. Indeed, as discussed below, the invention can be practiced with a broad range of other organic biocides which are detrimentally influenced by metal iron.
The effect of iron metal on isothiazolones is illustrated by the non-limiting examples, numbered I
through VI, which follow.

EXAMPLE I

Isothiazolone solutions were prepared using Kathon*
886 marketed by Rohm & Haas Co. of Philadelphia, Pennsylvania and having as active ingredients 8.6 weight percent 5-chloro-2-methyl-4-isothiazolin-3-one, and 2.6 weight percent methyl-4-isothiazolin-3-one; and Dearborn 6102*marketed by Dearborn Chemical Co. of Mississauga, Onatrio and having as active ingredients 0.86 weight percent 5-chloro-2-methyl-4-isothiazolin-* Trademark .~

- --- 1 3 ~

3-one, and 0.26 weight percent methyl-4-isothiazolin-3-one. Dearborn 6012 also contained a plant extract with saponins which was not believed to influence biocidal effectiveness.
A mixed bacterial population was cultivated on a tryptone glucose extract agar plate which had been innoculated with 50 microliters of industrial cooling water. The bacteria was harvested and suspended in tap water which had been dechlorinated by passage through a carbon filter.
The biocidal effectiveness of isothiazolones over time in the presence of mild steel was tested by adding 100 milliliters (mls) of solution containing 100 parts per million (ppm) Kathon 886 to sterile plastic containers, with and without a mild steel corrosion coupon. The containers were then incubated. After the containers containing isothiazolone solution had been incubated for two days, 1.0 ml aliquots of the bacterial suspension were distributed into each container. The containers were further incubated for six days. The comparitive amount of living bacteria in each container was then measured by filtering a one ml sample from each container, and measuring the micro-organisms retained on the filter by extracting and analyzing adenosine triphosphate by the firefly luciferase assay method. As described in Standard Test Method for Adenosine Triphosphate (ATP) Content of Microorganisms in Water, Designation D4012-81 (1981, reapproved 1985), American Society for Testing and Materials (ASTM), the firefly luciferase assay method measures the luminescence produced by luciferase reagent in the presence of adenosine triphosphate, a compound which can be related to viable biomass, or metabolic activity. The degree of luminescence is dependent upon the ATP present and can be measured through the use of a photometer such as the one used in these examples which is an ATP photometer produced by SAI Technology Co. of San Diego, California. It is well-known that when bacteria are killed their ATP
content decreases. Thus, the extent of reduction in ATP in a biocide-treated sample is a measure of the degree of biocide effectiveness. The detection limit of the ATP assay used ranged from about 0.01 nanograms per milliliter (ng/ml) of sample to about .001 ng/ml depending upon the amount of sample filtered, the volume of ATP extract, and the specific activity of the luciferase reagent used in the analysis.
Parallel runs were made using 1000 ppm of Dearborn 6102 instead of the Kathon 886, and a control run was made using no biocide. The results of these runs are presented in Table I below:
TABLE I
ISOTHIAZOLONE PRESENCE OF MILD STEEL ATP AFTER
TREATMENT CORROSION COUPON 6 DAYS (ng/ml) 11.2 ppm (1) No 0.013 11.2 ppm (1) Yes 0.16 11.2 ppm (2) No 0.02 11.2 ppm (2) Yes 0.4 None (control) No 0.28 (1) Added as 100 ppm Kathon 886 (2) Added as 1000 ppm Dearborn 6102 8~
EXAMPLE II

This example used the same general procedures as Example I, modified as follows: 1000 ppm of ferric oxide (Fe2O3) was added as a generally insoluble powder to sterile plastic containers, with and without Kathon 886 (50 ppm). A bacterial suspension was added to each container three days later. After a further three day incubation, the ATP assays were performed.
The results of these runs are presented in Table II
below:

TABLE II
TREATMENT ATP AFTER 3 DAYS (ng/ml) 5.6 ppm Isothiazolones <0.01 + 1000 ppm Fe2O3 1000 ppm Fe2O3 1.1 EXAMPLE III

This example used the same general procedures as Example I, modified as follows: A mild steel corrosion coupon, a stainless steel corrosion coupon, and steel wool were added to separate sterile plastic containers, each with 1000 ppm Dearborn 6102. A mild steel corrosion coupon run was also made without the biocide.
A bacterial suspension was added to each container three days later. After a further three days incubation, the ATP assays were performed. The results of these runs are presented in Table III below:

, ~

`- 1 334824 TABLE III
TEST DOSAGE OF ATP AFTER
METAL ISOTHIAZOLONES 3 DAYS (ng/ml) Mild Steel Corrosion Coupon None 3.3 Mild Steel Corrosion Coupon 11.2 ppm 0.33 Stainless Steel Corrosion Coupon 11.2 ppm 0.057 Steel Wool 11.2 ppm 1.6 *The one-half inch steel wool strips used for these experiments were cut from a pad of #0000 grade steel wool marketed by Thamesville Metal Products Limited of Thamesville, Ontario under the name Bull Dog*Brand.
EXAMPLE IV

This example used the same general procedures as Example I, modified as follows: Aluminum corrosion coupons were added to sterile plastic containers, with and without Dearborn 6102 (1000 ppm). A bacterial suspension was added to each container one day later.
After a further 11 days incubation, the ATP assays were performed. A control run was also made without biocide ~ and without coupons. The results of these runs are presented in Table IV below:

* Trademark , J",,!~

1 33~824 TABLE IV
ISOTHIAZOLONE PRESENCE OF ALUMINUM ATP AFTER
TREATMENT CORROSION COUPONS 11 DAYS (ng/ml) 11.2 ppm No 0.09 11.2 ppm Yes 0.07 None (control) No 1.0 The kinetics of the reduction of biocidal activity was examined in the following example.
EXAMPLE V

100 ml of carbon-filtered tap water were added to a series of six sterile whirl pack plastic bags.
One-half inch strips of steel wool were placed in five of the bags, along with 500 ppm Dearborn 6102. The sixth bag was a control. The steel wool strips were removed from the bags after various exposure time intervals ranging from 10 minutes to 24 hours. When the last strip was removed a bacterial suspension, prepared as in Example I, was added to each of the six bags. After a one-day incubation, the ATP assays were conducted. The results of these runs are presented in Table V below:

1 334~24 TABLE V
DURATION OF EXPOSURE DOSAGE OF ATP AFTER
TO STEEL WOOL ISOTHIAZOLONES ONE DAY (ng/ml) None (control) NONE 1.3 10 minutes 5.6 ppm 0.11 ] hour 5.6 ppm 0.11 3 hours 5.6 ppm 0.13 5 hours 5.6 ppm 1.9 24 hours 5.6 ppm 2.1 The effect of iron surface area upon the reduction of biocidal activity was monitored in the following example.

EXAMPLE VI

Iron dust (minimum assay: 95% iron) was distributed in various amounts ranging from 0.01 grams to 1.0 grams into a series of 250 ml Erylenmeyer flasks. 100 ml of carbon-filtered tap water containing 1000 ppm of Dearborn 6102 were added to each flask, and to a control flask to which no iron had been added.
The flasks were placed overnight on orbit shaker operating at 205 rpm. A bacterial suspension, prepared as in Example I, was then added to each container.
After a further two-day incubation with shaking, the ATP assays were performed. The results of these runs are presented in Table VI below:

-TABLE VI
AMOUNT OF IRON DOSAGE OF ATP AFTER
DUST (gm) ISOTHIAZOLONES TWO DAYS (ng/ml) None 11.2 ppm 0.077 0.01 11.2 ppm 0.088 0.05 11.2 ppm 0.051 0.1 11.2 ppm 0.047 0.5 11.2 ppm 0.81 1.0 11.2 ppm 0.32 In sum, the Examples above demonstrate that the biocidal effectiveness of isothiazolones can be substantially reduced by exposure to iron metal, whether it be in the form of mild steel, steel wool, or iron dust. However, no substantial detrimental affect on biocidal effectiveness was evident by contact with stainless steel. The term "iron metal" is used in this specification to signify the forms thereof which do detrimentally affect organic biocides, and consequently, does not include stainless steel.
The invention described herein provides for protection of biocidal activity of isothiazolones when iron metal is present. The general benefits achieved by using various protectors is illustrated in the non-limiting examples numbered VII through XIII which follow.

EXAMPLE VII

100 ml of carbon-filtered tap water were added along with 1000 ppm Dearborn 6102 to a series of 1 3 3 ~

sterile plastic containers. Sodium molybdate (NaMoO4.2H2O) was added to two containers at dosages of 1000 ppm and 3000 ppm respectively, while the third container contained no molybdate. A fourth container having neither biocide nor molybdate was used as a control. A
mild steel corrosion coupon was added to each container. After two days a bacterial suspension, prepared as in Example I, was added to each container.
After an additional four-day incubation, ATP assays were conducted. The results of these runs are presented in Table VII below:

- TABLE VII
ISOTHIAZOLONE PRESENCE OF MILD NaMoO .2H2O ATP AFTER
TREATMENT STEEL CORROSION COUPON AD~ED 4 DAYS (ng/ml) 11.2 ppm Yes None 0.72*
11.2 ppm Yes 1000 ppm 0.12 11.2 ppm Yes 3000 ppm 0.015 None (control) Yes None 0.90 *Significant corrosion observed. It is noted that corrosion occurred in many samples listed herein. It was also observed, however, that corrosion was not a prerequisite to biocide protection. Consequently, the degree of corrosion observed is not generally reported.
It is evident that in the samples treated with molybdate, the biocide remains effective even in the presence of iron. In another experiment using only 100 ppm sodium molybdate (data not shown), biocide effectiveness was not achieved and corrosion was evident.

- ` 1 334~24 Zinc, which like molybdate is a well-known agent used in water treatment to prevent corrosion, was also tested as a biocide protector.

EXAMPLE VIII

100 ml of carbon-filtered tap water were added along with mild steel corrosion to a series of sterile plastic containers. 200 ppm zinc sulphate (ZnSO4.H2O) were added to the containers, with and without Kathon 886 ~100 ppm). For comparison, 1000 ppm sodium molybdate were added to other containers, again with and without Kathon 886 (100 ppm). A control was run with neither biocide nor protector, but with a mild steel coupon. After three days incubation a bacterial suspension, prepared as in Example I, was added.
After an additional eight-day incubation, the ATP
assays were conducted. The results of these runs are presented in Table VIII below:
TABLE VIII

TREATMENT CORROSION COUPONPROTECTOR DAYS (ng/ml) 11.2 ppm Yes 1000 ppm <0.01 None Yes 1000 ppm 1.0 11.2 ppm Yes 200 ppm (0.01 Z SO4. 2 None Yes 200 ppm 0.1 Zns4 H2 None Yes None 0.58 It is evident from Table VIII that zinc sulphate was effective in protecting the biocidal activity of isothiazolones. However, in contrast to the molybdate treatment, significant corrosion occurred in the zinc-treated samples. This may indicate a different mechanism of isothiazolone protection from that achieved with molybdates.
The effect of zinc sulphate concentration on the isothiazolone biocidal activity in the presence of iron was also monitored.

EXAMPLE IX

100 ml of carbon-filtered tap water were added along with a mild steel corrosion coupon to a series of sterile plastic containers. 50 ppm Kathon 886 was added to all but a control container, and zinc sulphate (ZnSO4.H2O) was added to the containers in varying concentrations ranging from 50 ppm to 200 ppm. Runs with Kathon 886, but without zinc sulphate, were also made. After one day a bacterial suspension, prepared as in Example I, was added to each container. After further incubation ranging from two days to nine days, the ATP assays were performed. The results of these runs are presented in Table IX below:

- ` 1 334824 -TABLE IX
DOSAGE OF PRESENCE OF DOSAGE OF ATP (ng/ml) AFTER
ISOTHIAZOLONES CORROSION COUPON S 1--2 2 days/5 days/9 days 5.6 ppm Yes None 0.064 0.28 0.68 5.6 ppm Yes 50 0.030 0.050 0.27 5.6 ppm Yes 100 0.023 0.024 0.020 5.6 ppm Yes 150 0.023 0.018 0.015 5.6 ppm Yes 200 0.023 0.016 <0.010 None Yes None 2.3 1.9 2.1 It is evident from Table IX that where retention of biocidal activity in the presence of iron is desired for more than one week, more than 50 ppm of zinc sulphate monohydrate should be added.
As shown in Examples X, XI, XII, and XIII below, a wide variety of water treatment chemicals were tested for suitability as biocide protectors.

EXAMPLE X

100 ml of carbon-filtered tap water was added along with a mild steel corrosion coupon to each of a series of sterile plastic containers. Chemicals to be tested for their protective qualities were added to the containers in the amounts shown in Table X, and isothiazolones (as 1000 ppm of Dearborn 6102) was added where shown in the table. Control runs without a coupon were also run with and without biocide. After three days a bacterial suspension, prepared as in Example I, was added to each container. After a ~ 1 334824 further three-day incubation, ATP assays were performed. The results are shown in Table X below:

`' 1 334824 TABLE X
PRESENCE OF
MILD STEEL DOSAGE OF ATP (ng/ml) ISOTHIAZOLONES COUPON PROTECTOR PROTECTOR DAYS
None No None None 3.8 None Yes None None 3.1 11.2 ppm No None None 0.1 11.2 ppm Yes None None 4.9 None Yes 4' 2 200 ppm 2.1 11.2 ppm Yes SO4 2 200 ppm 0.12 None Yes (CH3COO)2Zn.2H2O 280 ppm 2.0 11.2 ppm Yes (CH3COO)2Zn.2H2O 280 ppm 0.24 None Yes Zinc Dust 75 ppm 2.4 11.2 ppm Yes Zinc Dust 75 ppm 0.18 None Yes Na2SiO3.9H2O1000 ppm 1.9 11.2 ppm Yes Na2SiO3.9H2O1000 ppm 1.9 None Yes Al2(SO4)3100 ppm 6.5 11.2 ppm Yes Al2(SO4)3100 ppm 2.5 None Yes NiS04.6 2110 ppm 3.5 11.2 ppm Yes i 4. 2 110 ppm 1.9 None Yes K2CrO4 300 ppm 1.8 11.2 ppm Yes K2CrO4 300 ppm 0.06 None Yes SnCl2 160 ppm 4.1 11.2 ppm Yes SnCl2 160 ppm 3.8 None Yes Co(NO3)2.6H2O100 ppm 2.2 11.2 ppm Yes Co(NO3)2.6H2O100 ppm 3.3 11.2 ppm Yes Na2B4O7.5H2O600 ppm 2.8 None Yes Cd(NO3)2 4H2)150 ppm 1.9 11.2 ppm Yes Cd(NO3)2 4H2O)150 ppm 0.22 None Yes KH2A2O4 50 ppm 2.9 11.2 ppm Yes KH2A2O4 50 ppm 2.3 11.2 ppm Yes MgSO4 500 ppm 3.2 11.2 ppm Yes MnSO4. 2 60 ppm 3.1 EXAMPLE XI

Additional chemicals were tested in another series of runs conducted in accordance with the procedure used in Example X. The results of these runs are shown in Table XI below:

TABLE XI

PRESENCE OF
MILD STEEL TEST DOSAGE OF ATP (ng/ml) ISOTHIAZOLONES COUPON PROTECTOR PROTECTOR DAYS
None No None None 1.2 15 None Yes None None 3.0 11.2 ppm Yes None None 2.0 11.2 ppm No None None 0.09 11.2 ppm Yes 4 2200 ppm 0.14 None Yes ZnSO4 H2O200 ppm 1.9 11.2 ppm Yes Pb(NO3)2 30 ppm 1.8 None Yes Pb(NO3)2 30 ppm 0.9 None Yes CuSO4 50 ppm 0.7 11.2 ppm Yes CuSO4 S0 ppm 0.06 11.2 ppm Yes EDTA (1)100 ppm 2.04 None Yes EDTA (1)100 ppm 4.6 None Yes BaCl2 150 ppm 2.3 11.2 ppm Yes BaC12 150 ppm 1.8 (1) Ethylene diamine tetracetic acid r EXAMPLE XII

Other chemicals were tested in yet another series of runs conducted in accordance with the prodecure used in Example X. The results of these runs are shown in Table XII below:

TABLE XII
PRESENCE OF
MILD STEEL TEST DOSAGE OF ATP (ng/ml) ISOTHIAZOLONES COUPON PROTECTOR PROTECTOR DAYS
None Yes None None 1.0 11.2 ppm No None None 0.02 11.2 ppm Yes None None 0.64 11.2 ppm Yes Canarad 0515 (1) 10 ppm 0.35 None Yes Canarad 0515 (1) 10 ppm 0.84 11.2 ppm Yes Rodine 95 (2)10 ppm 0.23 None Yes Rodine 95 (2)10 ppm 1.2 11.2 ppm Yes Dequest 2010 (3) 100 ppm 0.63 None Yes Dequest 2010 (3) 100 ppm 1.9 11.2 ppm Yes K2CrO4 100 ppm 0.04 None Yes K2CrO4 100 ppm 0.37 11.2 ppm Yes K2CrO4 50 ppm 0.64 None Yes K2CrO4 50 ppm 0.90 11.2 ppm Yes K2CrO4 25 ppm 1.1 (1) Ethoxylated rosin amine, 15%, marketed by Diamond Shamrock, Canada, Ltd. of Hamilton, Ontario.
(2) Proprietary Blended Corrosion Inhibitor, containing detergent and30marketed by Amchem Products, Inc. of Ambler, Pennsylvania.
(3) Hydroxyethylidine diphosphonic acid, 60%, marketed by Monsanto ofSt. Louis, Missouri.

~ 334~24 EXAMPLE XIII
Several more chemicals were tested in still another series of runs conducted in accordance with the procedure used in Example X. The results of these runs are shown in Table XIII below:

~ U~
e~: ~ O a~ .
o o In~ oo o ~~1 ~ ,., . . . . . . . . .
--~ O O O ~ O ~ O
P~
P~
~n o ..
'J
O P~
H--OE~ O ~ e e o o ~ a) a) a) ~ ~ ~ Q ~ ~
~: ~ O O O O O O O O O
C~ ~ Z Z Z ~U~ O O

o ~
`J

a) a) 5~
H - ~ ~; a) ~ a) ~ a) `I a) Cl O a) H 'j -I ~: ~ S
o ~ a ~ ~ a H ~a)G~ a) ~ e ~ e ~ e ~ e , ~ x O O O O~ ~
ir E~ ~;Z Z Z ~ ~ ~ e VJ ~ U 1~ 0 1~ C) ~ ~ ~
a) a)~D
a N
J~ Z
O
H )U~ a UiUl U~
~: oa) a) o a~a) a)a) a) a ~ ~ z ~ ~ ~ ~ ~ ~ ~
~ z i~
oo - ~
~ n c~ c ~
z ~ ~
-~
no c Y' o ~V~ e e e e e Z
C~ ~ ~ Q~ ~ ~ b~

~ c a) ~ ~ ~ a) ~ a) ~ a~
o ~
o ~ ~ ~ o ~ o ~ o ~
~: - Z ., ~ ~ Z ~ Z ~ Z a I ~
~ - ~
v. o o u~
G ~ ~c - -. 1 33~2~

Some of the chemicals tested above as protectors changed the pH of the water. In those cases where the pH was substantially altered from 7.5, sodium hydroxide or hydrochloric acid was added to ad~ust the pH to 7.5.
It is evident from the Examples above that sodium molybdate, zinc sulphate, zinc acetate, zinc dust, zinc dibenzylcarbamate, the zinc-phosphonate formulation of Dearborn 909, potassium chromate, cadmium nitrate, copper sulphate, and diethylthiourea were clearly effective in protecting biocidal activity in the presence of iron metal. The effectiveness of Canarad*
0515, Dequest*2010, and Rodine*95 is also evident but to a somewhat lesser extent.
~ From the foregoing results, it is also concluded that protective activity will be generally demonstrated by other molybdates, chromates, zinc salts, copper salts, cadmium salts, dialkylthioureas, alkoxylated rosin amines, and phosphonates or a mixture of agents which effectively protect biocidal activity.
Preferably, the biocide protectors are water soluble to achieve effective dispersion throughout the aquoues fluid containing the biocide. However, the zinc dust results demonstrate that water solubility is not essential in every case.
As used in this invention, the term "phosphonate biocide protector" means an organophosphonic acid having one of the following formulae, A, B, or C:

* Trademark "~
. ~

HO O R O OH
11 14 1~"~
~P C P
HO 5 m OH
or FORMULA B

R Y O OH

6~
N C- P
R7 Y' OH
or FORMULA C

O O
(H)2=PCH2 OH CH2P=(OH)2 N -(CH2- CH-CH2- N)q~CH2PI=(OH)2 (HO)2=PCH2~ O
o wherein m is an integer from 1 to 10; R4 is hydrogen, or an alkyl group having from 1 to 4 carbons; R5 is hydroxyl, amino, hydrogen or an alkyl group having from 1 to 4 carbons; R6 is a member selected from the group consisting of hydrogen, hydroxyl, hydroxy alkyl groups containing from 1 to 4 carbon atoms, aliphatic groups containing from 1 to 30 carbon atoms, and Y O OH
11 ~
- C P ~
Y OH

R7 is a member selected from the group consisting of hydrogen, aliphatic groups containing from 1 to 30 carbon atoms, Y O OH Y
C P / and C N - Z
y~ OH ~ Y ~ n wherein n is an integer from 1 to 30; Y and Y' are members selected from the group consisting of hydrogen and lower alkyl groups containing from 1 to 4 carbon atoms; Z is a member selected from the group consisting of hydrogen and Y O OH
- C- P
Y OH

and Z' is a member selected from the group consisting of hydrogen, Y O OH Y Y O OH
C p < and - (C)n N C7 U"~
Y' OH Y' Z P y~ OH

wherein p is an integer from 1 to 30; with at least one of the groups represented by R6 and R7 containing at least one Y O OH

- C P~
Y OH

group; q is an integer from 1 to 10; and the water-soluble salts and esters thereof; or mixtures thereof.
The preferred organophosphonic acid compound for use in this invention is an alkylene diphosphonic acid having the foregoing Formula A, such as those disclosed in U.S. Pat. Nos. 3,214,454 and 3,297,578, the entire disclosures of which are incorporated herein by reference. Also suitable is an organophosphonic acid having the foregoing Formula B such as those disclosed in U.S. Pat. No. 3,298,956, the entire disclosure of which is incorporated herein by reference. Suitable acids of this type include methylenediphosphonic acid;
ethylidenediphosphonic acid; isopropylidenediphosphonic acid; 1-hydroxy, ethylidenediphosphonic acid;
hexamethylenediphosphonic acid; trimethylenediphosphonic 2d acid; decamethylenediphosphonic acid; 1-hydroxy, propylidenediphosphonic acid; 1,6-dihydroxy, 1-6-dimethyl, hexamethylenediphosphonic acid;
1,4-dihydroxyl, 1,4-diethyl, tetramethylenediphosphonic acid; 1,3-dihydroxy 1,3-dipropyl, trimethylenediphos-phonic acid; 1,4-dibutyl, tetramethylenediphosphonic acid; dihydroxy, diethyl, ethylenediphosphonic acid;
4-hydroxy, 6-ethyl, hexamethylenediphosphonic acid;
l-hydroxy, butylidenediphosphonic acid; butylidene-diphosphonic acid; 1-aminoethane-1,1-diphosphonic acid;
1-aminopropane-1,1-diphosphonic acid; 1-aminoethane-1,1--` 1 334824 diphosphonic acid monoethyl ester, amino tri(methyl phosphonic acid), amino tri(ethylidene phosphonic acid), amino tri(isopropylidene phosphonic acid), amino tri(butylidene phosphonic acid), amino tri(isopen-tylidene phosphonic acid, ethylene diamine tetra(methyl phosphonic acid), ethylene diamine tri(methyl phosphonic acid), ethylene diamine di(methyl phosphonic acid), hexamethylene diamine tetra(methyl phosphonic acid), diethylene triamine penta(methyl phosphonic acid), N-(2-hydroxy-ethyl) nitrilo N,N-di(methyl phosphonic acid), and 2-hydroxy propylene 1,3-diamine tetra(methvl phosphonic acid). The water-soluble salts of these acids such as the alkali metal, alkaline earth metal, zinc, cobalt, lead, tin, nickel, ammonium, or amine and lower alkanol amine salts can be used. Also, esters of these acids with an aliphatic alcohol having from 1 to 4 carbons, or mixtures of the above acids, salts or esters can be used. Use of mixtures of any of the general types of organophosphonic acid compounds described above is also contemplated within the scope of this invention. Hydroxy ethylidenediphosphonic acid is particularly preferred.
The foregoing results also demonstrate that the amount of each substance which is efficiently added can vary according to the nature and amount of iron metal present in the system. In general, however, the following dosages are preferred. Where molybdates are used as the sole protective agent at least about 150 ppm is used, with the preferred concentration range being from about 150 ppm to about 10,000 ppm; most preferably from about 500 ppm to about 3,000 ppm.

`- 1 334824 Where chromates are used as the sole protective agent at least about 20 ppm is preferably added, with the most preferred range being from about 40 ppm to about 300 ppm. Where zinc salts are used as the sole protective agent at least about 10 ppm is used, with the preferred concentration range being from about 10 ppm to about 2000 ppm; and most preferably from about 30 ppm to about 100 ppm. Where copper salts are used as the sole protective agent at least about 2 ppm is preferably used, with the preferred range being between about 20 ppm and about 100 ppm. When cadmium salts are used as the sole protective agent at least about 5 ppm is preferably added, with the most preferred range being between about 25 ppm and about 250 ppm. Where dialkylthioureas are used as the sole protective agents, at least about 1 ppm is preferably added, with the most preferred range being between about 5 ppm and about 100 ppm. Where alkoxylated rosin amines are used as the sole protective agent, at least about 0.15 ppm is preferably added, with the most preferred range being between about 1 ppm and about 100 ppm. Where phosphonate biocide protectors are used as a sole protective agent at least about 5 ppm is preferably added, with the most preferred range being between about 25 ppm and about 500 ppm. Where zinc dust is used as the sole protective agent at least about 5 ppm is preferably added, with the most preferred range being between about 50 ppm and about 500 ppm.
The addition of these protective agents may be made separately or together with the organic biocide.
Indeed, various compositions containing the biocide in - ` 1 334824 combination with biocide protectors are within the scope of this invention. Weight ratios of total protectors to biocide between about 0.1:1 and about 30,000:1 are generally preferred. Representative compositions exemplified by the above Examples comprise isothiazolones and, alternatively, molybdates;
chromates; zinc salts; dialkylthioureas; alkoxylated rosin amines; phosphonate biocide protectors; and zinc dust. In these compositions the most preferred weight ratio range of molybdate to isothiazolone is from about 50:1 to about 30,000:1; that of chromate to isothiazolone is from about 4:1 to about 3,000:1; that of zinc salts to isothiazolone is from about 1:1 to about 20,000:1; that of dialkylthiourea to isothiazolone is from about 0.5:1 to about 1,000:1;
that of ethoxylated rosin amine to isothiazolone is from about 0.1:1 to about 1,000:1; that of phosphonate biocide protectors to isothiazolone is from about 2.5:1 to about 5,000:1; and that of zinc dust to isothiazolone is from about 5:1 to about 5,000:1.
Mixtures, of course, may contain at least proportionately lower ratios of each protector to biocide. These compositions may be added to the aqueous fluid in dry form such as powder or pellets, where feasible. Such dry compositions preferably contain between 0.1 weight percent and 100 weight percent total active biocide plus protector, with the weight ratio of the components being that identified above.

_ 29 -The compositions may also be added as aqueous solutions. Such aqueous solutions are preferably containing between about 0.1 and 50 weight percent total active biocide plus protector. The biocide concentration after addition is preferably kept within its normal effective range; generally for organic biocides between about 0.1 ppm and about 10,000 ppm.
A mixture of the protective agents discussed above can be used advantageously. Indeed, many of the effective biocide protectors are also corrosion inhibitors; and it is well known that some combinations of corrosion inhibitors, such as zinc and phosphonates, work together synergistically to prevent corrosion.
Synergism in protecting biocide effectiveness in the presence of iron was tested in the following non-limiting example.

EXAMPLE XIV

100 ml of carbon-filtered tap water was added along with a mild steel corrosion coupon to each of a series of sterile plastic containers. As shown in Table XIV below, zinc sulphate (ZnSO4.H2O) was added to some of the containers in various concentrations ranging from 50 ppm to 100 ppm; and Dequest 2010 (containing l-hydroxyethylidene-1,1-diphosphonic acid) was added to some of the containers in various concentrations ranging from 25 ppm to 100 ppm.
Isothiazolones (as 1000 ppm Dearborn 6102) were also added where shown in the Table. Control runs without a coupon, without a protector, and without either biocide or protector were also run as shown. After three days a bacterial solution, prepared as in Example I, was added to each container. After a further three-day incubation, ATP assays were performed on some of the containers. As seen in the Table, it was evident that the biocide was relatively effective in all the samples and synergism would be difficult to observe. Thus, a second dosage of bacterial solution was added on the day following the initial ATP assays. After an additional nine-day incubation, ATP assays were repeated on the samples. In some cases an ATP assay was also conducted 11 days after the second bacterial dosage. The results are shown in Table XIV below:

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a-~ 1 334824 , It is evident from the Table, and the comparative low level of protection of Dequest 2010 evident from Table XII, that synergism in biocide protection does occur between zinc sulphate and phosphonate. Thus, as little as 25 ppm of Dequest 2010 used in combination with as little as 50 ppm zinc sulphate, afforded substantial protection of the biocidal activity of isothiazolones in the presence of mild steel over comparatively long periods of time. Preferably, at least 10 ppm of zinc sulfate is combined with at least 5 ppm 1-hydroxyethylidene-1,1-diphosphonic acid.
Compositions containing zinc sulphate in a weight ratio to isothiazolone of about 0.5:1 to about 1,000:1, and 1-hydroxyethylidene-1,1-diphosphonic acid in a weight ratio to isothiazolone of about 0.25:1 to about 1,000:1 are preferable for use in this synergistic manner.
While the invention herein described may be utilized in many aqueous systems such as cooling towers, pulp and paper mill process water, oil field water treatment, and preservatives for various industrial products, it is believed that the invention is particularly suited for application in aqueous systems with long retention times, such as in metal working systems. Bacteria tend to accumulate in these systems and the obvious presence of iron in some of these applications can threaten the effectiveness of isothiazolone biocide.
To test the protectors in aqueous metal working fluids, a sample of cutting oil fluid containing endogenous bacteria was obtained from a General Motors transmission plant in Windsor, Ontario Canada. The protection afforded metal working fluids by practice of this invention is illustrated by the non-limiting examples numbered XV and XVI which follow.

EXAMPLE XV

100 ml of cutting oil fluid were added to each of a series of sterile plastic containers. As shown in Table XV below, a mild steel corrosion coupon was added to some of these containers; and 200 ppm zinc sulphate (ZnSO4.H2O) was added to some of the containers. As also shown in the Table, isothiazolones were added to some of the containers in various amounts (ranging from 200 ppm to 1000 ppm Dearborn 6102.) After eight days of incubation, ATP assays were performed. The assays showed that the biocide was functioning except where used in low dosages without protector. Another ATP
assay was performed on same samples after 15 days of incubation. The biocide evidently functioned longer in the cutting oil fluid than in tap water. The biocide-treated samples were thus re-innoculated after 16 days with 0.5 ml of an untreated cutting oil fluid which contained 10 ng/ml ATP. Additional ATP assays were then performed on some samples after 22 days, 26 days, and 31 days. The results are shown in Table XV
below:

TABLE XV

ISOTHIAZOLONE PRESENCE OF DOSAGE OF ATP (ng/ml) AFTER:
DOSAGE CORROSION COUPON ZnSOq.H2O8 days15 days 22 days26 days 31 days None No No 4.2 6 0 8 5 * *
None Yes No 3.5 * * * *
None No 200 ppm 13.0 21 20 * *
None Yes 200 ppm 5.0 * * * *
2.24 ppm No No 2.3 * * * *
2.24 ppm Yes No 3.2 * 4 5 * *
2.24 ppm No 200 ppm(0.01 ~0.01 * * *
I 2.24 ppm Yes 200 ppm<0.01 * 16.5 * *
w 5.6 ppm No No <0.01 * * 17,0 *5.6 ppm Yes No ~0.0l. ~0.01 13.0 9.8 *
1 5.6 ppm No 200 ppm<0.01 ~0.01 * 20 *5.6 ppm Yes 200 ppm<0.01 * 4.1 50 *
11.2 ppm No No ~0.01 * 0.45 * 25 : 11.2 ppm Yes No ~0.01 ~0,01 2.4 28 100 11.2 ppm No 200 ppm<0.01 ~0.01 0.01 * 0.43 11.2 ppm Yes 200 ppm~0.01 * O,07 1.0 20 - * Analysis Not Done , r~
, -It is evident from the Table that the presence of iron can reduce the duration of biocidal effectiveness in cutting oil fluids. The presence of 200 ppm zinc sulphate monohydrate increased the length of biocidal effectiveness of every dosage of Dearborn 6102 tested.
The length of effectiveness was increased even when corrosion coupons were not added to the test samples.
However, because particles of iron were present in the cutting fluid sample as it was received, the same mechanism of protection of biocidal activity was evidently occurring in each sample. In any case, the samples containing corrosion coupons appeared to lose biocidal activity more quickly.
A variety of chemicals were tested for use as protectors in metal working fluids using commercial cutting oil stock.

EXAMPLE XVI

A stock cutting oil was diluted to 6% in tap water, and 100 ml of the diluted stock cutting oil fluid was added to each of a series of sterile plastic containers. Chemicals to be tested for their protective qualities were added to the containers in the amounts shown in Table XVI. One-half inch strips of steel wool were placed in each of the containers along with Dearborn 6102 (either 500 ppm or 1000 ppm).
Control runs were also made without biocide, without protector, and without iron. After two days, S ml of a microbiologically contaminated cutting oil sample from the General Motors transmission plant in Windsor was added to each container. ATP assays were performed weekly for four weeks and no growth in any of the biocide-treated samples was observed. After each ATP
assay, an additional dosage of contaminated cutting oil was added. After four weeks, the steel wool strips were removed and replaced by mild steel corrosion coupons, and the dosage of cutting oil containing micro-organisms was repeated. The results of the assay two weeks after the corrosion coupons were introduced are given for Table XVI.

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~ 38 --No growth in any of the biocide treated samples was observed until after the corrosion coupons had been added.
This Example also demonstrates that benzotriazole can be an effective protector of biocide effectiveness.
From these results, it is concluded that other suitable azoles may be selected from a group consisting of triazoles, pyrazoles, imidazoles, isoxazoles, oxazoles, isothiazoles, thiazoles, and mixtures thereof as disclosed in U.S. Pat. Nos. 2,618,608, 2,742,369, and 2,941,953. As used in this invention, the term "azole biocide protector" means an azole having one of the following Formulae D, E, F, G, H, I, or J, including the indicated substituted forms thereof.
The triazoles which can be employed in this invention are water-soluble 1,2,3-triazoles such as 1,2,3-triazole itself or a substitute 1,2,3-triazole where the substitution takes place in either the 4 or 5 position (or both~ of the triazole ring, as shown here by the structural Formula D:

FORMULA D

NH
~\

4 3~

!

` 1 334824 Suitable triazoles include benzotriazole (the preferred triazole); 4-phenyl-1,2,3-triazole; 1,2-naphthotriazole and 4-nitrobenzotriazole; and the like.
The pyrazoles which can be used in this invention include water-soluble pyrazoles such as pyrazole itself or a substituted pyrazole where the substitution takes place in the 3, 4, or S position (or several of these positions) of the pyrazole ring, as shown by the structural Formula E: 0 FORMULA E

NH
/1\

HC4 3~H

Suitable pyrazoles include pyrazole; 3,5-dimethyl pyrazole; 6-nitroindazole; 4-benzyl pyrazole; 4,S-dimethyl pyrazole; and 3-allyl pyrazole; and the like.
Imidazoles which can be used in this invention include water-soluble imidazoles such as imidazole 2S itself or a substituted imidazole where the substitution takes place in the 2, 4, or S position (or several of these positions) of the imidazole ring, as shown here by the structural Formula F:

~ --`

FORMULA F
NH
/1\

Suitable imidazoles which can be employed in this invention include imidazole; adenine; quanine;
benzimidazole; 5-methyl benzimidazole; 2-phenyl imidazole; 2-benzyl imidazole; 4-allyl imidazole;
4-(betahydroxy ethyl)-imidazole; purine;
4-methylimidazole; xanthine; hypoxanthene; 2-methyl imidazole; and the like.
Isoxazoles which can be used in this invention include water-soluble isoxazoles such as isoxazole itself or a substituted isoxazole where the substitution takes place in the 3, 4, or 5 position (or several of these positions) of the isoxazole ring, as shown here by the structural Formula G:

FORMULA G

-Suitable isoxazoles include isoxazole; 3-mercaptoisox-azole; 3-mercaptobenzisoxazole; benzisoxazole; and the like.
The oxazoles which can be used in this invention include water-soluble oxazoles such as oxazole itself or a substituted oxazole where the substitution takes place in the 2, 4, or 5 position (or several of these positions) of the oxazole ring, as shown here by the structural Formula H:

1~ FORMULA H

HC5 2~H

HC4 3~

Suitable oxazoles include oxazole; 2-mercaptoxazole;
2-mercaptobenzoxazole; and the like.
The isothiazoles which can be used in this invention include water-soluble isothiazoles such as isothiazole itself or a substituted isothiazole where the substitution takes place in the 3, 4, or 5 position (or several of these positions) of the isothiazole ring, as shown here by the structural Formula I:

i,_, FORMULA I

HC

HC4 3C~

Suitable isothiazoles include isothiazole; 3-mercapto-isothiazole; 3-mercaptobenzisothiazole; benzisothiazole;
and the like.
The thiazoles which can be used in this invention include water-soluble thiazoles such as thiazole itself or a substituted thiazole where the substitution takes place in the 2, 4, or 5 position (or several of these positions) of the thiazole ring, as shown here by the structural Formula J:

FORMULA J

S

/ 1 \

H~4 3~

Suitable thiazoles include thiazole; 2-mercaptothiazole;
2-mercaptobenzothiazole; benzothiazole; and the like.

In the above azole compounds, the constituents substituted in the azole rings can be alkyl, aryl, aralkyl, alkylol, and alkenyl radicals so long as the substituted azole is water-soluble. Typically, substituted members have from 1 to about 12 carbon atoms. The triazoles are the preferred azoles, with benzotriazole and tolyltriazole particularly preferred.
Azoles in general, and benzotriazole in particular, are preferably used in concentrations of at least 10 ppm with the preferred range being from about 20 ppm to about 1,000 ppm. They may be added together with an isothiazolone in dry or liquid form, as explained above, with the preferred weight ratio of azole to isothiazolone being~from about 2:1 to about 10,000:1.
Example XVI also demonstrates effective use of zinc sulphate in combination with chromate to protect the effectiveness of isothiazolone. Preferably in such a combination, at least 10 ppm of zinc sulfate is combined with at least 10 ppm of chromate; the weight ratio of zinc sulfate to organic biocide is from about 0.5:1 to about 1,000:1; and the weight ratio of chromate to organic biocide is about 0.5:1 to about 1 , 000 : 1 .
A test of the influence of ferrous sulphate on the effectiveness of isothiazolones was also conducted using the contaminated cutting oil.

EXAMPLE XVII

One gram of ferrous sulphate (FeSO4) was dissolved in 10 grams of Dearborn 6102 and allowed to incubate 1 334~24 overnight. Samples of the cutting oil contaminated with micro-organisms were treated in sterile plastic containers with either 500 ppm or 1000 ppm of this solution. As control runs, contaminated cutting oil samples were run with no treatment, and with treatment with Dearborn 6102 alone. ATP assays were performed after a five-hour incubation and after a one-day incubation. The results are shown in Table XVII below:

TABLE XVII
ATP ( ng/ml) TREATMENT INCUBATION INCUBATION
No treatment 10 3.9 -500 ppm Dearborn 6102 + FeSO4 1.1 0.12 1000 ppm Dearborn 6102 + FeSO4 0.40 0.091 500 ppm Dearborn 6102 0.59 0.12 1000 ppm Dearborn 61020.35 0.11 It is evident from the Table that, although there may be a slight interaction between the ferrous ion and the isothiazolones, this interaction is not comparable at the dosages tested with the influence observed with the mild steel corrosion coupons.
Other known non-oxidizing type organic biocides were also studied to determine whether their activity was reduced in the presence of iron. The effect of iron on these biocides is illustrated by the following non-limiting example.

- ` 1 334824 EXAMPLE XVIII

100 ml of carbon-filtered tap water was added to each of a series of sterile plastic containers. The biocides to be tested in the presence of iron were added in the amounts shown in Table XVIII. As shown, one-half inch strips of steel wool were added to some of the containers, and steel wool strips together with 200 ppm zinc sulphate (ZnSO4.H2O) were added to other containers. A control run was made using steel wool without either biocide or protector. After two days bacterial solution, prepared as in Example I, was added to each container. After a further three-day incubation, ATP assays were performed. The results are shown in Table XVIII.

.
TABLE XVI I I
ATP (ng/ml) AFTER 3 DAYS INCUBATION
NO STEEL WOOL STEEL WOOL STEEL WOOL +
BIOCIDE ADDED ADDED200 ppm ZnSO4.H2O
5 None ------- 2.6 --------15 ppm bis- 0.012 2.0 0.04 trichloro-methyl-sulphone plus 4.5 ppm bis-tributyltin-oxide (1) 30 ppm bis- 0.0034 0.038 0.0033 10 trichloro-methyl-sulphone plus 9 ppm bis-tributyltin-oxide (1) 10 ppm methylene 0.017 2.8 0.0089 ~ bis-thiocyanate (21 20 ppm methylene 0.0032 0.00840.0064 bis-thiocyanate (2) 5 ppm 2,2 dibromo- 0.015 1.8 0.071 3-nitrilopropion-amide (3) (1) added as Dearcide*703 marketed by Dearborn Chemical Co.
of Mississauga, Ontario (2) added as Dearcid~ 709 marketed by Dearborn Chemical Co.
of Mississauga, Ontario (3) added as Dearcide*723 marketed by Dearborn Chemical Co.
of Mississauga, Ontario * Trademark ~ ~, L~

It is evident from the Table that other organic biocides can be detrimentally affected by iron and that they can also be protected from the influence of this metal. Indeed, the results indicate that a broad range of organic biocides are succeptible to losing effectiveness in the presence of iron metal. Whether a particular organic biocide is detrimetally affected in untreated fluid by the presence of iron metal can be simply determined by the test procedures used herein (eg. Example I). If a loss of effectiveness is confirmed, the biocide protectors of this invention may be used advantageously to inhibit the affect of the iron metal. Of course, compositions of such biocides with biocide protectors similar to those disclosed above using isothiazolone may be prepared.
No attempt was made to maintain the same source or strength of bacteria throughout the examples. The examples describe particular embodiments of the invention. Other embodiments will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is understood that modifications and variations may be practiced without departing from the spirit and scope of the novel concepts of this invention. It is further understood that the invention is not confined to the particular formulations and examples herein illustrated, but it embraces such modified forms thereof as come within the scope of the following claims.

Claims (42)

1) A process for treating an aqueous fluid in contact with iron metal to sustain the biocidal effectiveness of an organic biocide contained in the fluid and detrimentally affected in untreated fluid by the presence of the iron metal, comprising the step of adding to the fluid at least one biocide protector selected from the group consisting of molybdates, chromates, zinc salts, copper salts, cadmium salts, dialkylthioureas, alkoxylated rosin amines, azole biocide protectors, phosphonate biocide protectors, and zinc dust, or a mixture thereof, in an amount effective to inhibit the loss of biocidal effectiveness and wherein the weight ratio of biocide protector to biocide is in the range of from 0.1:1 to 30,000:1.

2) The process of Claim 1 wherein the weight ratio of biocide protector to biocide is in the range of from 1:1 to 20,000:1.

3) The process of Claim 1 wherein at least two of said biocide protectors are added.

4) The process of Claim 1 wherein the biocide protector is water insoluble.

5) The process of Claim 4 wherein the biocide protector comprises zinc dust.

6) The process of Claim 1 wherein the biocide protector comprises a zinc salt.

7) The process of Claim 6 wherein the zinc salt is zinc dibenzylcarbamate or zinc sulphate.

8) The process of Claim 6 wherein the zinc salt is zinc sulphate and wherein the dosage is between 10 ppm and 2,000 ppm.

9) The process of Claim 1 wherein the biocide protector is a chromate.

10) The process of Claim 9 wherein the chromate is potassium chromate.

11) The process of Claim 9 or Claim 10 wherein at least 20 ppm of the chromate is added.

12) A process according to Claim 1 wherein the biocide protector comprises molybdate.

13) The process of Claim 12 wherein the molybdate is sodium molybdate in a dosage of at least 150 ppm.

14) The process of Claim 1 wherein the copper salt is copper sulfate in a dosage of at least 2 ppm.

15) The process of Claim 1 wherein the cadmium salt is cadmium nitrate in a dosage of at least 5 ppm.

16) The process of Claim 1 wherein the biocide protector is a phosphonate biocide protector having the formula:

wherein m is an integer from 1 to 10; R4 is hydrogen or an alkyl group having from 1 to 4 carbons, and R5 is hydroxy, amino, hydrogen or an alkyl group having from 1 to 4 carbons.

17) The process of Claim 1 wherein the organic biocide comprises bis-trichloromethyl-sulphone, bis-tributyltin-oxide, methylene bis-thiocyanate, 2,2-dibromo-3-nitrilo-propionamide, and/or isothiazolone.

18) The process of Claim 1 wherein the organic biocide comprises an isothiazolone having the general formula:

wherein R1 is a hydrogen atom, an alkyl group of 1 to 18 carbon atoms, alkenyl or alkynyl group of 2 to 18 carbon atoms, and preferably 2 to 4 carbon atoms, a cycloalkyl group of 3 to 12 carbon atoms, preferably having a 3 to 8 carbon atom ring, an aralkyl group of up to 10 carbon atoms, or an aryl group of up to 10 carbon atoms; and R2 is a hydrogen atom, a halogen atom, or an alkyl group, preferably having 1 to 4 carbon atoms; and R3 is a hydrogen atom, a halogen atom, or an alkyl group, preferably having 1 to 4 carbon atoms; or R2 and R3, taken together, complete a benzene ring, optionally substituted with at least one member selected from the group consisting of halogen atoms, nitro groups, alkyl groups having 1 to 4 carbon atoms, cyano groups, and alkoxy groups having 1 to 4 carbon atoms.

19) The process of any one of claims 1 to 10 or 12 to 18 wherein the organic biocide concentration is between 0.1 ppm and 10,000 ppm.

20) The process of Claim 17 wherein the organic biocide comprises 5-chloro-2-methyl-4-isothiazolin-3-one and/or methyl-4-isothiazolin-3-one.

21) A process for treating an aqueous metal working fluid in contact with iron metal to sustain the biocidal effectiveness of an organic biocide contained in the fluid and detrimentally affected by the presence of the iron metal, comprising the step of adding to the fluid at least one biocide protector selected from the group consisting of molybdates, chromates, zinc salts, copper salts, cadmium salts, dialkylthioureas, alkoxylated rosin amines, azole biocide protectors, phosphonate biocide protectors, and zinc dust, or a mixture thereof, in an amount effective to inhibit the loss of biocidal effectiveness and wherein the weight ratio of biocide protector to biocide is in the range of 0.1:1 to 30,000:1.

22) The process of Claim 21 wherein the aqueous metal working fluid is a cutting oil.

23) The process of any one of claims 1 to 10, 12 to 18 or 20 to 22 wherein the aqueous fluid has an alkaline pH.

24) The process of claims 19 wherein the aqueous fluid has an alkaline pH.

25) A biocidal composition for use in treatment of aqueous fluids in contact with iron metal comprising an organic biocide which is detrimentally affected by the presence of iron metal and at least two biocide protectors selected from the group consisting of molybdates, chromates, zinc salts, copper salts, cadmium salts, dialkylthioureas, alkoxylated rosin amines, azole biocide protectors, phosphonate biocide protectors, and zinc dust and wherein the weight ratio of biocide protector to biocide is in the range of from .1:1 to 30,000:1.

26) The composition of Claim 25 wherein at least one of the biocide protectors is a zinc salt.

27) The composition of Claim 25 wherein the organic biocide comprises bis trichloromethyl-sulphone, bis tributyltin-oxide, methylene bis-thiocyanate and/or 2,2 dibromo-3-nitrilo-propionamide.

28) The composition of Claim 27 wherein the organic biocide comprises an isothiazolone having the general formula:

wherein R1 is a hydrogen atom, an alkyl group of 1 to 18 carbon atoms, alkenyl or alkynyl group of 2 to 18 carbon atoms, and preferably 2 to 4 carbon atoms, a cycloalkyl group of 3 to 12 carbon atoms, preferably having a 3 to 8 carbon atom ring, an aralkyl group of up to 10 carbon atoms, or an aryl group of up to 10 carbon atoms; and R2 is a hydrogen atom, a halogen atom, or an alkyl group, preferably having 1 to 4 carbon atoms; and R3 is a hydrogen atom, a halogen atom, or an alkyl group, preferably having 1 to 4 carbon atoms; or R2 and R3, taken together, complete a benzene ring, optionally substituted with at least one member selected from the group consisting of halogen atoms, nitro groups, alkyl groups having 1 to 4 carbon atoms, cyano groups, and alkoxy groups having 1 to 4 carbon atoms.

29) The composition of Claim 25 the two biocide protectors are zinc sulphate and hydroxyethylidene diphosphonic acid; wherein the weight ratio of zinc sulphate to the organic biocide is from 0.5:1 to 1,000:1;
and wherein the weight ratio of hydroxyethylidene diphosphonic acid to the organic biocide is from 0.25:1 to 1,000:1.

30) The composition of Claim 25 comprising zinc sulphate and a chromate; wherein the weight ratio of zinc sulphate to the organic biocide is from 0.5:1 to 1,000:1; and wherein the weight ratio of the chromate to the organic biocide is from 0.5:1 to 1,000:1.

31) The composition of Claim 25 wherein the organic biocide comprises 5-chloro-2-methyl-4-isothiazolin-3-one.

32) The composition of Claim 25 wherein the organic biocide comprises methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one in a weight ratio of approximately 8.6:2.6.

33) A biocidal composition for use in treatment of aqueous fluids in contact with iron metal comprising an organic biocide which is detrimentally affected by the presence of iron metal and at least one biocide protector selected from the group consisting of molybdates, chromates, zinc salts, copper salts, cadmium salts, dialkylthioureas, alkoxylated rosin amines, azole biocide protectors, phosphonate biocide protectors, and zinc dust, or a mixture thereof, in an amount effective to inhibit the loss of biocidal effectiveness and wherein the weight ratio of biocide protector to biocide is in the range of 0.1:1 to 30,000:1.

34) The composition of Claim 33 wherein the organic biocide comprises an isothiazolone and the biocide protector is molybdate in a weight ratio of isothiazolone to molybdate of from 50:1 to 30,000:1.

35) The composition of Claim 33 wherein the organic biocide comprises an isothiazolone and the biocide protector is chromate in a weight ratio to isothiazolone to chromate of from 4:1 to 3,000:1.

36) The composition of Claim 33 wherein the organic biocide is an isothiazolone and the biocide protector is selected from diethylthiourea in a weight ratio to isothiazolone from 0.5:1 to 1,000:1, ethyoxylated rosin amine in a weight ratio to isothiazolone from 0.1:1 to 1,000:1, benzotriazole in a weight ratio of isothiazolone from 2:1 to 10,000:1, and 1-hydroxyethylidene-1,1-diphosphonic acid in a weight ratio to isothiazolone from 2.5:1 to 5,000:1.

37) The composition of Claim 33 wherein the biocide protector is water insoluble.

38) The composition of Claim 37 wherein the biocide protector is zinc dust.

39) The composition of Claim 38 wherein the organic biocide is isothiazolone; the biocide protector is zinc dust; and wherein the weight ratio of zinc dust to isothiazolone is from 5:1 to 5,000:1.

40) The composition of Claim 33 wherein the organic biocide comprises methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one in a weight ratio of approximately 8.6:2.6.

41) The process of claim 11 wherein the organic biocide concentration is between 0.1 ppm and 10,000 ppm.

42) The process of claim 11 wherein the aqueous fluid has an alkaline pH.