U.S. patent application number 10/678199 was filed with the patent office on 2004-04-08 for peroxy acid treatment to control pathogenic organisms on growing plants.
This patent application is currently assigned to Ecolab Inc.. Invention is credited to Hei, Robert D. P., Herdt, Brandon Leon, Hilgren, John Dennis, Salverda, Joy Ann.
Application Number | 20040068008 10/678199 |
Document ID | / |
Family ID | 25406879 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040068008 |
Kind Code |
A1 |
Hei, Robert D. P. ; et
al. |
April 8, 2004 |
Peroxy acid treatment to control pathogenic organisms on growing
plants
Abstract
A method of using peracid/acid compositions, where the mole
ratio of acid to peracid is less than about 3:1, to treat field or
greenhouse grown plant tissue, seeds, fruits, and growing media and
containers is described. The peracid/acid system can lower the
natural, plant pathogen and human pathogenic microbial load
resulting in less waste to molding, spoilage, and destruction
because of pathogenic poisons.
Inventors: |
Hei, Robert D. P.; (Baldwin,
WI) ; Hilgren, John Dennis; (Shoreview, MN) ;
Salverda, Joy Ann; (Woodbury, MN) ; Herdt, Brandon
Leon; (Hastings, MN) |
Correspondence
Address: |
Ronald A. Daignault
MERCHANT & GOULD P.C.
P.O. Box 2903
Minneapolis
MN
55402-0903
US
|
Assignee: |
Ecolab Inc.
St. Paul
MN
|
Family ID: |
25406879 |
Appl. No.: |
10/678199 |
Filed: |
October 2, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10678199 |
Oct 2, 2003 |
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09896807 |
Jun 29, 2001 |
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6635286 |
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Current U.S.
Class: |
514/557 ;
504/100 |
Current CPC
Class: |
A01N 37/16 20130101;
A01N 37/16 20130101; A01N 37/04 20130101; A01N 2300/00 20130101;
A01N 37/16 20130101; A01N 37/36 20130101; A01N 37/02 20130101 |
Class at
Publication: |
514/557 ;
504/100 |
International
Class: |
A01N 025/26; A01N
037/00 |
Claims
We claim:
1. A method of controlling microbial pathogens on living plant
tissue comprising treating said plant tissue with a dilute aqueous
solution comprising an effective amount of one or more aliphatic
C.sub.2-C.sub.12 peroxycarboxylic acids, and an aliphatic
C.sub.3-C.sub.12 carboxylic acid, wherein the mole ratio of
aliphatic carboxylic acid to peroxycarboxylic acid is less than
about 3:1.
2. The method of claim 1 wherein the plant tissue comprises a
seed.
3. The method of claim 1 wherein the plant tissue comprises a
tuber.
4. The method of claim 1 wherein the plant tissue comprises a
growing plant.
5. The method of claim 1 wherein the plant tissue comprises a
cutting.
6. The method of claim 1 wherein the plant tissue comprises rooting
stock.
7. The method of claim 1, wherein the aqueous solution comprises:
(a) at least about 5 parts per million (ppm) of one or more
aliphatic C.sub.2-C.sub.12 peroxycarboxylic acids; and (b) at least
about 0.1 parts per million (ppm) of an aliphatic C.sub.3-C.sub.12
carboxylic acid.
8. The method of claim 7, wherein the peroxycarboxylic acid is
peroxyacetic acid, peroxyoctanoic acid, perglycolic acid,
permalonic acid, perlactic acid, peroctanoic acid,
perhydroxycaproic acid, perhydroxycaprylic acid, mono-methyl
peradipate, monomethyl persuccinate, mono-methyl perglutarate,
mono-ethyl peradipate, mono-ethyl persuccinate, mono-ethyl
perglutarate, mono-isobutyl peradipate, mono-isobutyl persuccinate,
mono-isobutyl perglutarate, or a mixture thereof.
9. The method of claim 7, wherein the aliphatic carboxylic acid is
propionic acid, hexanoic acid, heptanoic acid, octanoic acid,
decanoic acid, dodecanoic acid or a mixture thereof.
10. The method of claim 1, wherein the aqueous solution comprises:
(a) at least about 4 parts per million (ppm) of a C.sub.2-C.sub.7
peroxycarboxylic acid; (b) at least about 1 part per million (ppm)
of an aliphatic C.sub.8-C.sub.12 peroxycarboxylic acid; and (c) at
least 0.1 parts per million (ppm) of an aliphatic C.sub.3-C.sub.12
carboxylic acid.
11. The method of claim 10, wherein said C.sub.2-C.sub.7
peroxycarboxylic acid is peroxyacetic acid, mono-methyl
persuccinate, mono-methyl perglutarate, mono-methyl peradipate,
mono-ethyl persuccinate, mono-ethyl perglutarate, or a mixture
thereof.
12. The method of claim 10 wherein said C.sub.8-C.sub.12 aliphatic
peroxycarboxylic acid is peroxyoctanoic acid, mono-ethyl
peradipate, mono-isobutyl peradipate, mono-isobutyl persuccinate,
mono-isobutyl perglutarate, or a mixture thereof.
13. A method for controlling microbial pathogens on living plant
tissue comprising: (a) diluting in an aqueous liquid a concentrate
comprising: (i) about 0.1 to 25 wt-% of one or more aliphatic
C.sub.2-C.sub.12 peroxycarboxylic acids; and (ii) about 0.01 to 30
wt-% of an aliphatic C.sub.3-C.sub.12 carboxylic acid to form a
solution; and (b) contacting said plant tissue with said solution,
wherein the mole ratio of aliphatic carboxylic acid to
peroxycarboxylic acid is less than about 3:1.
14. The process of claim 13, wherein the C.sub.2-C.sub.12
peroxycarboxylic acid is peroxyacetic acid, peroxyoctanoic acid,
mono-methyl persuccinate, mono-methyl perglutarate, mono-methyl
peradipate, mono-ethyl persuccinate, mono-ethyl perglutarate,
mono-ethyl peradipate, mono-isobutyl peradipate, mono-isobutyl
persuccinate, mono-isobutyl perglutarate, or a mixture thereof.
15. The process of claim 13, wherein the aliphatic carboxylic acid
is propionic acid, hexanoic acid, heptanoic acid, octanoic acid,
decanoic acid, dodecanoic acid or a mixture thereof.
16. The process of claim 13, wherein the concentrate further
comprises about 1 to 15 wt-% of a hydrotrope.
17. The process of claim 16, wherein the hydrotrope is
n-octanesulfonate, a xylene sulfonate, an alkylbenzene sulfonate,
an alkyl naphthalene sulfonate, an amine oxide, an alcohol
ethoxylate, or a mixture thereof.
18. The process of claim 13, wherein the concentrate further
comprises a chelating agent.
19. The process of claim 18, wherein the chelating agent is
1-hydroxyethylidene-1,1-diphosphonic acid.
20. The method of claim 13, wherein the concentrate comprises: (a)
about 0.1 to 25 wt-% of a C.sub.2-C.sub.7 peroxycarboxylic acid;
(b) about 0.1 to 20 wt-% of a C.sub.8-C.sub.12 aliphatic
peroxycarboxylic acid; and (c) about 0.01 to 30 wt-% of an
aliphatic C.sub.3-C.sub.12 carboxylic acid.
21. The method of claim 20, wherein the C.sub.2-C.sub.7
peroxycarboxylic acid is peroxyacetic acid, mono-methyl
persuccinate, mono-methyl perglutarate, mono-methyl peradipate,
mono-ethyl persuccinate, mono-ethyl perglutarate, or a mixture
thereof.
22. The method of claim 20, wherein the C.sub.8-C.sub.12
peroxycarboxylic acid is peroxyoctanoic acid, mono-ethyl
peradipate, mono-isobutyl peradipate, mono-isobutyl persuccinate,
mono-isobutyl perglutarate, or a mixture thereof.
23. A method for controlling microbial pathogens on living plant
tissue comprising: (a) diluting in an aqueous liquid a concentrate
comprising: (i) about 1 to 20 wt-% of a C.sub.2-C.sub.7
peroxycarboxylic acid; and (ii) about 0.1 to 20 wt-% of an
aliphatic C.sub.8-C.sub.12 peroxycarboxylic acid; (iii) about 5 to
40 wt-% of a C.sub.2-C.sub.7 carboxylic acid; (iv) about 1 to 20
wt-% of an aliphatic C8-C.sub.1-2 carboxylic acid; (v) about 1 to
30 wt-% of hydrogen peroxide; and (vi) about 0.01 to 30 wt-% of
another C.sub.3-C.sub.12 aliphatic carboxylic acid to form a
solution, wherein the mole ratio of aliphatic carboxylic acid to
peroxycarboxylic acid is less than about 3:1; and (b) contacting
said plant tissue with said solution.
24. The process of claim 23, wherein the C.sub.2-C.sub.7
peroxycarboxylic acid is peroxyacetic acid, mono-methyl
persuccinate, mono-methyl perglutarate, mono-methyl peradipate,
mono-ethyl persuccinate, mono-ethyl perglutarate, or a mixture
thereof.
25. The process of claim 23, wherein the C.sub.8-C.sub.12 aliphatic
peroxycarboxylic acid is peroxyoctanoic acid, mono-ethyl
peradipate, mono-isobutyl peradipate, mono-isobutyl persuccinate,
mono-isobutyl perglutarate, or a mixture thereof.
26. The process of claim 23, wherein the C.sub.3-C.sub.12 aliphatic
carboxylic acid is propionic acid, hexanoic acid, heptanoic acid,
octanoic acid, decanoic acid, dodecanoic acid or a mixture
thereof.
27. The process of claim 23, wherein the concentrate further
comprises about 1 to 15 wt-% of a hydrotrope.
28. The process of claim 27, wherein the hydrotrope is
n-octanesulfonate, a xylene sulfonate, an alkyl benzene sulfonate,
an alkyl naphthalene sulfonate, an amine oxide, an alcohol
ethoxylate, or a mixture thereof.
29. The process of claim 23, wherein the concentrate further
comprises a chelating agent.
30. The process of claim 29, wherein the chelating agent is
1-hydroxyethylidene-1,1-diphosphonic acid.
31. A method of growing at least one plant on a hydroponic
substrate in a hydroponic liquid supply medium to produce usable
fruit or vegetable products with reduced microbial contamination,
the method comprising: (a) establishing growing and living plant
tissue in the hydroponic substrate; (b) contacting the living plant
tissue, the hydroponic substrate and the hydroponic liquid with a
dilute aqueous solution comprising an effective amount of one or
more C.sub.2-C.sub.12 percarboxylic acids and an aliphatic
C.sub.3-C.sub.12 carboxylic acid, wherein the mole ratio of
aliphatic carboxylic acid to peroxycarboxylic acid is less than
about 3:1; and (c) harvesting an improved product.
32. The method of claim 31 wherein the percarboxylic acid is
peracetic acid.
33. The method of claim 31 wherein the aliphatic carboxylic acid
comprises heptanoic acid, octanoic acid, decanoic acid, dodecanoic
acid or a mixture thereof.
34. The method of claim 31 wherein the percarboxylic acid comprises
a mixture of a C.sub.2-C.sub.7 and a C.sub.8-C.sub.12 aliphatic
percarboxylic acid.
35. The method of claim 31 wherein the aqueous solution comprises
about 4 to 100 parts per million of a C.sub.2-C.sub.7 percarboxylic
acid and about 1 to about 100 parts per million of an aliphatic
C.sub.8-C.sub.12 percarboxylic acid.
36. The method of claim 31 wherein the percarboxylic acid comprises
a mixture of peroxyacetic acid and peroxyoctanoic acid.
37. The method of claim 31 wherein the aqueous solution comprises
about 5 to 1000 parts per million of an aliphatic C.sub.3-C.sub.12
carboxylic acid.
38. The process of claim 31 wherein the living tissue comprises a
germinating seed.
39. The method of claim 31 wherein the living tissue comprises a
growing tuber.
40. The method of claim 31 wherein the plant tissue comprises a
growing dicotyledon.
41. The method of claim 31 wherein the plant tissue comprises a
growing monocotyledonis plant.
42. The method of claim 31 wherein the living tissue comprises a
plant cutting.
43. The method of claim 31 wherein the plant tissue comprises
rooting stock and a graft.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a process of using peracid
compositions mixed with another short-chain fatty acid to treat
field, hydroponic or greenhouse growing plant tissue, seeds,
fruits, growing media, storage facilities and equipment, and
containers. The peracid can lower the natural, plant pathogen and
human pathogenic microbial load resulting in less waste to molding,
spoilage, and destruction because of pathogenic poisons.
BACKGROUND OF THE INVENTION
[0002] In the production of fruits and vegetables, plants can be
grown in the field, in greenhouses, and hydroponically. Each
location has its own growing medium, environment and growing
conditions. Agricultural personnel work to maximize production by
maximizing growing conditions while minimizing attack on seeds,
seedlings, plants and fruit by living pests. Such pests include
insects, rodents, bacteria, fungi, etc.
[0003] Substantial attention has been given to antimicrobial
compounds that attack bacteria and fingi on seeds, seedlings,
growing plants and fruit in the production cycle on growing plants.
The use of fungicides in agriculture is necessitated by the great
losses caused by a wide variety of plant-pathogenic microorganisms.
To be economic, the costs of controlling plant diseases by the
application of bactericides and fungicides must be offset by
potential gains of several fold. Large tonages of fungicides are
required in the agriculture of apples, pears, bananas, cereals,
cocoa, coffee, cotton, potatoes, tobacco, grapes, sprouts and other
common fruits and vegetables including celery, leeks, onions,
lettuce, spinach, brussel sprouts, potatoes, truffles, garlic,
shallots, peppers, beans, tomatoes, almonds, pears, apples, peanuts
and others. Fungicides are typically applied in water suspension
with hydraulic sprayers or in the form of dust, granules or
fumigants. Early fungicides included sulfur and polysulfides, heavy
metals and others. Such harsh fungicides have been replaced by
newer but still toxic materials such as quinones, organosulfur
compounds, imidazolines and guanidines,
trichloromethylthiocarboximides, chlorinated and nitrated benzenes,
oxithines, benzimidazoles, pyrimidines, and others. These broad
spectrum protectant materials effect enzyme and membrane systems of
the target microorganism. Typically, the mode of action includes
inhibition of fungal or bacterial energy production, interference
with biosynthesis or disruption of cell membrane structure.
[0004] The above fungicides have had some success; however, they
are viewed as toxic materials and a substantial quantity of plant
produce is wasted due to their deleterious effect.
[0005] Further, human and plant pathogenic bacteria and fungi can
be a contamination problem in growing plants. We have found coli
form, salmonella, and other bacteria common in the agricultural and
greenhouse environment can contaminate growing plants and pose a
threat to human health in consumption of fresh vegetables, fruit
and produce.
[0006] Peroxy acids are strong oxidizers and have the simple
general structure given as formula (1), where R can be essentially
any hydrocarbon group: 1
[0007] Peroxy-containing compositions have been described for use
in the production of microbicidal agents. However, very few peroxy
systems have addressed protection of growing plants from bacterial
contamination. Accordingly, a substantial need exists to develop
antimicrobial materials that can be used directly to protect
growing plants including seeds, cuttings, seedlings, plant parts,
fruit, and other agricultural produce.
SUMMARY OF THE INVENTION
[0008] We have found that a mixed peracid/acid treatment
composition can be used to protect growing plant tissue from the
undesirable effects of microbial attack. The peracid/acid
composition used in this invention can be applied to growing plant
tissues and can provide residual antimicrobial effects after the
plant has completed its growth cycle, fruit or vegetable material
have been harvested and sent to market. The composition of the
invention has been found to have excellent antimicrobial effects
but poses little toxic effects to agricultural workers or the
ultimate consumer.
[0009] We have found that peroxy acid/acid compositions can be an
effective treatment of living or growing plant tissues including
seeds, roots, tubers, seedlings, cuttings, rooting stock, growing
plants, produce, fruits and vegetables, etc. Under certain
circumstances, a single peroxy acid/acid composition can be
effective; however, in other circumstances, a mixed peroxy
acid/acid composition has substantially improved and surprising
properties.
[0010] The invention involves a peroxy acid antimicrobial
concentrate and diluted end use composition including an effective
microbicidal amount of one or more aliphatic C.sub.2-C.sub.12
peroxycarboxylic acids and an aliphatic C.sub.3-C.sub.12 carboxylic
acid wherein the mole ratio of aliphatic carboxylic acid to
peroxycarboxylic acid is less than about 3:1. The concentrate
composition can be diluted with a major proportion of water to form
an antimicrobial sanitizing use solution having a pH in the range
of about 2 to 8, with a peroxycarboxylic acid concentration of at
least about 5 ppm, preferably about 30 to 5000 ppm, and most
preferably about 200 to 1000 ppm. Other components may be added
such as a hydrotrope coupling agent for solubilizing the
peroxyfatty acid in the concentrate form and when the concentrate
composition is diluted with water.
[0011] The invention involves a method of controlling microbial
pathogens on living plant tissue by treating said plant tissue with
a dilute aqueous solution containing an effective amount of one or
more aliphatic C.sub.2-C.sub.12 peroxycarboxylic acids and an
aliphatic C.sub.3-C.sub.12 carboxylic acid, wherein the mole ratio
of aliphatic carboxylic acid to percarboxylic acid is less than
about 3:1.
[0012] The invention further involves a method for controlling
microbial pathogens on living plant tissue by diluting in an
aqueous liquid a concentrate containing: about 0.1 to 25 wt-% of
one or more aliphatic C.sub.2-C.sub.12 peroxycarboxylic acids and
about 0.01 to 30 wt-% of an aliphatic C.sub.3-C.sub.12 carboxylic
acid, wherein the mole ratio of aliphatic carboxylic acid to
percarboxylic acid is less than about 3:1, to form a solution; and
contacting said plant tissue with said solution.
[0013] The invention further involves a method for controlling
microbial pathogens on living plant tissue by diluting in an
aqueous liquid a concentrate containing: about 0.1 to 25 wt-% of
one or more C.sub.1-C.sub.7 aliphatic peroxycarboxylic acids; about
0.01 to 20 wt-% of one or more C.sub.8-C.sub.12 aliphatic
peroxycarboxylic acids; about 0.01 to 30 wt-% of one or more
C.sub.3-C.sub.12 aliphatic carboxylic acid; and about 1 to 30 wt-%
of hydrogen peroxide to form a solution, wherein the mole ratio of
aliphatic carboxylic acid to percarboxylic acid is less than about
3:1; and contacting said growing plants with said solution.
[0014] As the term is used herein, a C.sub.2-C.sub.12 peroxyacid
may be interchangeably used with a C.sub.2-C.sub.12 aliphatic
peroxycarboxylic acid or C.sub.2-C.sub.12 peracid. These terms are
intended to mean the product of the oxidation of a C.sub.2-C.sub.12
acid such as: a fatty acid, a dicarboxylic acid, a mono- or
di-ester dicarboxylic acid, a hydroxy acid, a lactone, a
tricarboxylic acid, or a mixture of these acids, to form a
peroxyacid or mixture of peroxyacids having from about 2 to 12
carbon atoms per molecule. The C.sub.2-C.sub.12 peroxyacids are
straight or branched aliphatic. The C.sub.2-C.sub.12 peroxyacids
can be equilibrium derived, i.e. from a mixture of peracid, its
corresponding carboxylic acid and hydrogen peroxide, such as is
common for peracetic acid, perglycolic acid, permalonic acid,
perlactic acid, peroctanoic acid, perhydroxycaproic acid,
perhydroxycaprylic acid, mono-methyl peradipate, mono-methyl
persuccinate, mono-methyl perglutarate, mono-ethyl peradipate,
mono-ethyl persuccinate, mono-ethyl perglutarate, mono-isobutyl
peradipate, mono-isobutyl persuccinate, mono-isobutyl perglutarate,
and the like. The C.sub.2-C.sub.12 peroxyacids can also be isolated
peracids such as perheptanoic acid, peroctanoic acid, and
perdecanoic acid.
[0015] In a preferred embodiment, the claimed invention includes a
method of controlling microbial pathogens on living plant tissue.
This treatment utilizes a combination of two different peroxy acids
and another carboxylic acid. This mixture comprises at least 4
parts per million (ppm) of a smaller C.sub.2-C.sub.7 peroxy
carboxylic acid, at least 1 ppm of a larger C.sub.8-C.sub.12 peroxy
carboxylic acid, and at least 0.1 ppm of a C.sub.3-C.sub.12
aliphatic carboxylic acid. The more preferred mixture comprises at
least 20 ppm of a smaller C.sub.2-C.sub.7 peroxy acid and at least
2 ppm of an aliphatic C.sub.8-C.sub.12 peroxy acid, and at least 5
ppm of an aliphatic C.sub.3-C.sub.12 carboxylic acid.
[0016] An especially preferred embodiment of the composition
includes a mixture of peroxyacetic acid, formula (2), and
peroctanoic acid, formula (3), with a C.sub.3-C.sub.12 aliphatic
carboxylic acid, such as propionic, hexanoic, heptanoic, octanoic,
nonanoic, decanoic or a mixture thereof. 2
[0017] Another especially preferred embodiment of the composition
includes individual component, or mixtures, of the mono-methyl
esters of peroxyadipic acid, peroxysuccinic acid, and
peroxyglutaric acid, formula (4), and generically described as
monoester peracids derived from diacids or diesters, e.g., such as
adipic, succinic, glutaric, or malonic acid and mixtures
thereof.
R--O--COR'CO.sub.3H (4)
[0018] where R and R' are linear or branched aliphatic
C.sub.1-C.sub.6 hydrocarbons.
[0019] The composition also may contain a hydrotrope or surfactant
for the purpose of increasing the aqueous solubility of various
slightly soluble organic compounds. The preferred embodiment of the
invention utilizes a hydrotrope chosen from the group of
n-octanesulfonate, dodecylbenzene sulfonate, a xylene sulfonate,
cumene sulfonate, an alkyl naphthalene sulfonate, 2-ethylhexyl
sulfate, lauryl sulfate, lauryl ether sulfate, an amine oxide, a
nonionic surfactant, or a mixture thereof.
[0020] The composition may also contain a chelating agent for the
purpose of removing ions from solution. The preferred embodiment of
the invention uses 1-hydroxyethylidene-1,1-diphosphonic acid.
[0021] Further, the invention also provides a method of growing at
least one plant on a hydroponic substrate in a hydroponic liquid
supply medium to produce usable fruit or vegetable products with
reduced microbial contamination, the method including the steps of:
(a) establishing growing and living plant tissue in the hydroponic
substrate; (b) contacting the living plant tissue, the hydroponic
substrate and the hydroponic liquid with a dilute aqueous solution
containing an effective amount of one or more C.sub.2-C.sub.12
percarboxylic acids and an aliphatic C.sub.3-C.sub.12 carboxylic
acid, wherein the mole ratio of aliphatic carboxylic acid to
peroxycarboxylic acid is less than about 3:1; and (c) harvesting an
improved product.
DETAILED DESCRIPTION OF THE INVENTION
Peracids
[0022] We have found surprisingly that peroxy acid compounds mixed
with another C.sub.3-C.sub.12 fatty acid can be contacted directly
with living plant tissue in the form of a seed, a cutting, a root
stock, graft, tuber juvenile or adult plant and reduce microbial
populations without substantially affecting the health of the
living tissue.
[0023] Moreover we have found that when a C8-C.sub.12 peroxyacid is
combined with a C.sub.2-C.sub.7 peroxycarboxylic acid and another
aliphatic C.sub.3-C.sub.12 carboxylic acid, a synergistic effect is
produced and greatly enhanced antimicrobial activity is exhibited
when compared to the C8-C.sub.12 peroxyacid or the C.sub.2-C.sub.7
peroxycarboxylic acid alone. For example, a blend of a
C.sub.8-C.sub.12 peroxyacid, a C.sub.2-C.sub.7 peroxycarboxylic
acid and a C.sub.3-C.sub.12 aliphatic carboxylic acid can
effectively kill microorganisms (e.g., a 5 log10 reduction in 30
seconds) from a concentration level below 100 ppm and as low as 20
ppm of the peracid blend.
[0024] A variety of C.sub.2-C.sub.12 aliphatic peroxyacids may be
employed in the composition of the invention such as peroxyfatty
acids and monoester-monoperoxy-dicarboxylates and monoperoxy- or
diperoxy-dicarboxylic acids. The C.sub.2-C.sub.12 peroxyacids
employed in the present invention may be structurally represented
as: R.sub.1--CO.sub.3H, wherein R.sub.1 is a hydrocarbon moiety
having from about 1 to 11 carbon atoms. R.sub.1 may have
substituents in or at the end of the chain, e.g., --OH,
--CO.sub.2R.sub.1 (e.g., as in monoester dicarboxylates), or
heteroatoms (e.g., --O-as in alkylether carboxylic acids), as long
as the antimicrobial properties of the overall composition are not
significantly affected. It should be recognized that "R.sub.1"
substituents or heteroatoms may change the overall acidity (i.e.,
pKa) of the carboxylic acids herein described. Such modification is
within the contemplation of the present invention provided the
advantageous antimicrobial performance is maintained. Furthermore,
R.sub.1 may be linear or branched. Preferred hydrocarbon moieties
(i.e. preferred R.sub.1's) include linear, saturated, hydrocarbon
aliphatic moieties having from 1 to 3 and 7 to 11 carbon atoms (or
2 to 4 and 8 to 12 carbon atoms per molecule), and hydrocarbon
aliphatic carboxylic ester moieties having 1 to 4 carbon atoms in
the hydrocarbon ester function (e.g., methyl propionate or methyl
ethanoate or methyl butanoate substituents).
[0025] The C.sub.2-C.sub.7 peroxycarboxylic acids can be derived
from a C.sub.2-C.sub.7 carboxylic acid or dicarboxylic acid by
reacting the acid, or the corresponding anhydride or acid chloride,
or C.sub.1-C.sub.6 ester, or lactone with hydrogen peroxide.
Examples of suitable C.sub.2-C.sub.7 carboxylic acids include
acetic acid, propionic acid, glycolic acid, and
alpha-hydroxyheptanoic acid, or their corresponding anhydrides or
acid chlorides or C.sub.1-C.sub.6 esters or lactones. Preferable
C.sub.2-C.sub.7 peroxycarboxylic acids for use in the composition
of the invention include peroxyacetic acid, peroxypropionic acid,
peroxyglycolic acid, or mixtures thereof.
[0026] Specific examples of suitable C.sub.8-C.sub.12 carboxylic
fatty acids which can be reacted with hydrogen peroxide to form
peroxyfatty acids include such saturated fatty acids as caprylic
(octanoic) (C.sub.8), pelargonic (nonanoic) (C.sub.9), capric
(decanoic) (C.sub.10), undecyclic (undecanoic) (C.sub.11), lauric
(dodecanoic) (C.sub.12), or alpha-hydroxyoctanoic (C.sub.8). These
acids can be derived from both natural and synthetic sources.
Natural sources include animal and vegetable fats or oils which
should be fully hydrogenated. Synthetic acids can be produced by
the oxidation of petroleum wax. Particularly preferred peroxyfatty
acids for use in the composition of the invention are linear
monoperoxy aliphatic fatty acids such as peroxyoctanoic acid,
peroxydecanoic acid, or mixtures thereof.
[0027] Other suitable peroxyacids are derived from the oxidation of
dicarboxylic acids, C.sub.1-C.sub.6 esters, and anhydrides.
Suitable dicarboxylic acids, C.sub.1-C.sub.6 esters, and anhydrides
include those of malonic, adipic, glutaric, succinic, sebacic acid
(C.sub.10). These acids, C.sub.1-C.sub.6 esters, and anhydrides can
be reacted with hydrogen peroxide to form the peracid form suitable
for use in the composition of the invention. Preferred peracids in
this group include monoester-monoperoxy- or
monocarboxylate-monoperoxy- or diperoxyadipic acid,
monoester-monoperoxy- or monocarboxylate-monoperoxy- or
diperoxysuccinic acid, monoester-monoperoxy- or
monocarboxylate-monoperox- y- or diperoxyglutaric acid, and
monocarboxylate-monoperoxy- or monoester-monoperoxy- or
diperoxysebacic acid, or mixtures thereof.
[0028] The above peroxyacids provide antibacterial activity against
a wide variety of microorganisms, such as gram positive (e.g.,
Staphylococcus aureus) and gram negative (e.g., Escherichia coli,
salmonella, etc.) microorganisms, yeast, molds, bacterial spores,
etc. When the above C.sub.8-C.sub.12 peroxyacids are combined with
a C.sub.2-C.sub.7 peroxycarboxylic acid, greatly enhanced activity
is shown compared to the C.sub.2-C.sub.7 peroxycarboxylic acid
alone or the C.sub.8-C.sub.12 peroxycarboxylic acid alone.
[0029] The antimicrobial concentrate of the present invention can
contain about 0.1 to 25 wt. %, preferably about 0.5 to 20 wt. %,
and most preferably about 0.4 to 15 wt. % of a C.sub.2-C.sub.12
peroxyacid, and about 0.01 to 30 wt. %, preferably about 0.1 to 10
wt. % and most preferably 0.4-5 wt. % of an aliphatic
C.sub.3-C.sub.12 carboxylic acid. The concentrate composition
preferably has a molar ratio of C.sub.3-C.sub.12 carboxylic acid to
C.sub.2-C.sub.12 peroxycarboxylic acid of about 0.01:1 to 3:1. The
concentrate contains sufficient acid so that the end use solution
has a pH of about 2 to 8, preferably about 3 to 7. Some acidity may
come from an inert acidulant which may be optionally added (e.g.,
sulfuric or phosphoric acid).
[0030] In another embodiment of the present invention, the
antimicrobial concentrate can contain about 0.1 to 20 wt. %,
preferably about 0.1 to 5 wt. %, and most preferably about 0.5 to 2
wt. % of a C.sub.8-C.sub.12 peroxyacid, and about 0.1 to 25 wt. %,
preferably about 1 to 20 wt. %, and most preferably 4-15 wt. % of a
C.sub.2-C.sub.7 peroxycarboxylic acid, and about 0.01 to 30 wt. %,
preferably about 0.1-10 wt. %, and most preferably 0.5-5 wt. % of
an aliphatic C.sub.3-C.sub.12 carboxylic acid. The concentrate
composition preferably has a molar ratio of C.sub.3-C.sub.12
carboxylic acid to C.sub.2-C.sub.12 peroxycarboxylic acid of about
0.01:1 to 3:1. The concentrate composition preferably has a weight
ratio of C.sub.2-C.sub.4 peroxycarboxylic acid to C.sub.8-C.sub.12
peroxylic acid of about 15:1 to 1:1. The concentrate contains
sufficient acid so that the end use solution has a pH of about 1 to
8, preferably about 1 to 5. Some acidity may come from an inert
acidulant which may be optionally added (e.g., sulfuric or
phosphoric acid).
[0031] The peracid components used in the composition of the
invention can be produced in a simple manner by mixing a hydrogen
peroxide (H.sub.2O.sub.2) solution, or by utilizing powdered
peroxide generators such as percarbonates, persulfates, magnesium
peroxide, calcium peroxide, or perborates, with the desired amount
of acid. With the higher molecular weight fatty acids, a hydrotrope
coupler may be required to help solubilize the fatty acid. The
H.sub.2O.sub.2 solution also can be added to previously made
peracids such as peracetic acid or various perfatty acids to
produce the peracid composition of the invention. The concentrate
can contain about 1 to 40 wt. %, preferably about 5 to 25 wt. % of
hydrogen peroxide.
[0032] The concentrate composition can further include a
C.sub.3-C.sub.12 aliphatic carboxylic acid, a free C.sub.8-C.sub.12
carboxylic acid, a free C.sub.2-C.sub.7 carboxylic acid, or
mixtures thereof. The free acids will correspond to the starting
materials used in the preparation of the peroxyacid components and
can be present as a result of an equilibrium reaction with the
hydrogen peroxide to form the peroxyacids. The composition of the
present invention includes, however, at least one other
C.sub.3-C.sub.12 aliphatic carboxylic acid. Preferred
C.sub.3-C.sub.12 aliphatic carboxylic acids include propionic,
hexanoic, heptanoic, octanoic, nonanoic, decanoic, or mixtures
thereof in amounts defined above.
Other Components
[0033] Various optional materials may be added to the composition
of the invention to help solubilize the fatty acids, restrict or
enhance the formation of foam, to control hard water, to stabilize
the composition, or to further enhance the antimicrobial activity
of the composition.
[0034] The composition of the invention can contain a surfactant
hydrotrope coupling agent or solubilizer that permits blending
short chain perfatty acids in aqueous liquids. Functionally
speaking, the suitable couplers which can be employed are non-toxic
and retain the fatty acid and the perfatty acid in aqueous solution
throughout the temperature range and concentration to which a
concentrate or any use solution is exposed.
[0035] Any hydrotrope coupler may be used provided it does not
react with the other components of the composition or negatively
affect the antimicrobial properties of the composition.
Representative classes of hydrotropic coupling agents or
solubilizers which can be employed include anionic surfactants such
as alkyl sulfates and alkane sulfonates, linear alkyl benzene or
naphthalene sulfonates, secondary alkane sulfonates, alkyl ether
sulfates or sulfonates, alkyl phosphates or phosphonates, dialkyl
sulfosuccinic acid esters, sugar esters (e.g., sorbitan esters),
amine oxides (mono-, di-, or tri-alkyl) and C.sub.8-C.sub.10 alkyl
glucosides. Preferred coupling agents for use in the present
invention include n-octanesulfonate, available as NAS 8D from
Ecolab, n-octyl dimethylamine oxide, and the commonly available
aromatic sulfonates such as the alkyl benzene sulfonates (e.g.
xylene sulfonates) or naphthalene sulfonates. Preferred anionic
surfactants include C.sub.6-C.sub.24 alkylbenzene sulfonates;
C.sub.6-C.sub.24 olefin sulfonates; C.sub.6-C.sub.24 paraffin
sulfonates; cumene sulfonate; xylene sulfonate; C.sub.6-C.sub.24
alkyl naphthalene sulfonates; C.sub.6-C.sub.24 alkyl or dialkyl
diphenyl ether sulfonates or disulfonates, C.sub.4-C.sub.24 mono or
dialkyl sulfosuccinates; sulfonated or sulfated fatty acids;
C.sub.6-C.sub.24 alcohol sulfates (preferably C.sub.6-C.sub.12
alcohol sulfates); C.sub.6-C.sub.24 alcohol ether sulfates having 1
to about 20 ethylene oxide groups; and C.sub.4-C.sub.24 alkyl, aryl
or alkaryl phosphate esters or their alkoxylated analogues having 1
to about 40 ethylene, propylene or butylene oxide units or mixtures
thereof.
[0036] Other preferred hydrotropes include nonionic surfactants of
C.sub.6-C.sub.24 alcohol ethoxylates (preferably C.sub.6-C.sub.14
alcohol ethoxylates) having 1 to about 20 ethylene oxide groups
(preferably about 9 to about 20 ethylene oxide groups);
C.sub.6-C.sub.24 alkylphenol ethoxylates (preferably C8-C.sub.1-0
alkylphenol ethoxylates) having 1 to about 100 ethylene oxide
groups (preferably about 12 to about 20 ethylene oxide groups);
C.sub.6-C.sub.24 alkylpolyglycosides (preferably C.sub.6-C.sub.20
alkylpolyglycosides) having 1 to about 20 glycoside groups
(preferably about 9 to about 20 glycoside groups); C.sub.6-C.sub.24
fatty acid ester ethoxylates, propoxylates or glycerides; and
C.sub.4-C.sub.24 mono or dialkanolamides. A particularly useful
nonionic surfactant for use as a defoamer is nonylphenol having an
average of 12 moles of ethylene oxide condensed thereon, it being
encapped with a hydrophobic portion comprising an average of 30
moles of propylene oxide.
[0037] Some of the above hydrotropic coupling agents independently
exhibit antimicrobial activity at low pH. This adds to the efficacy
of the present invention, but is not the primary criterion used in
selecting an appropriate coupling agent. Since it is the presence
of perfatty acid in the protonated neutral state which provides
biocidal activity, the coupling agent should be selected not for
its independent antimicrobial activity but for its ability to
provide effective interaction between the substantially insoluble
perfatty acids described herein and the microorganisms which the
present compositions control.
[0038] The hydrotrope coupling agent can comprise about 0 to 30 wt.
%, preferably about 1 to 15 wt. %, and most preferably about 2 to
15 wt. % of the concentrate composition.
[0039] Compounds such as mono, di and trialkyl phosphate esters may
be added to the composition to suppress foam. Such phosphate esters
would generally be produced from aliphatic linear alcohols, there
being from 8 to 12 carbon atoms in the aliphatic portions of the
alkyl phosphate esters. Alkyl phosphate esters possess some
antimicrobial activity in their own right under the conditions of
the present invention. This antimicrobial activity also tends to
add to the overall antimicrobial activity of the present
compositions even though the phosphate esters may be added for
other reasons. Furthermore, the addition of nonionic surfactants
would tend to reduce foam formation herein. Such materials tend to
enhance performance of the other components of the composition.
Chelating agents can be added to the composition of the invention
to enhance biological activity, cleaning performance and stability
of the peroxyacids. For example, 1-hydroxyethylidene-1,
1-diphosphonic acid commercially available from the Monsanto
Company under the designation "DEQUEST" has been found to be
effective. Chelating agents can be added to the present composition
to control or sequester hardness ions such as calcium and
magnesium. In this manner both detergency and sanitization
capability can be enhanced. These stabilizers and chelating agents
can desirably be employed to improve the storage stability of
solutions according to the invention and are especially desirable
where the proposed application involves the likely chance that the
peracid will be contacted with compounds known to cause
decomposition, for example transition metal ions. Preferred
chelating agents are often aminopolycarboxylic acids or salts
thereof such as EDTA, HEDTA, or DTPA, and/or carboxylic acid
substituted N-containing heterocyclics, such as picolinic or
dipicolinic acid, 8-hydroxyquinoline, and organopolyphosphonates,
including 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), and
alkyleneaminomethylene phosphonic acids such as ethylene diamino
tetra-methylene phosphonic acid, cyclohexane-1,2-diaminotetrameth-
ylene phosphonic acid and diethylenetriaminepenta methylene
phosphonic acid. A combination of an organophosphonate and EDTA is
particularly suitable. The amount of chelant in the solution is at
the discretion of the formulator, but is preferably greater than
0.05% and often not greater than about 5.5%, calculated as active
material therein.
[0040] Other materials which are sufficiently stable at the low pH
contemplated by the present composition may be added to the
composition to impart desirable qualities depending upon the
intended ultimate use. For example, phosphoric acid
(H.sub.3PO.sub.4), or sulfuric acid (H.sub.2SO.sub.4), can be added
to the composition of the invention. Additional compounds can be
added to the concentrate (and thus ultimately to the use solution)
to change its color or odor, to adjust its viscosity, to enhance
its thermal (i.e., freeze-thaw) stability or to provide other
qualities which tend to make it more marketable.
[0041] The composition of the invention can be made, for example,
by simply mixing an effective amount of a C.sub.8-C.sub.12
peroxyacid such as a peroxyfatty acid, e.g. peroxyoctanoic acid,
with some source of a C.sub.2-C.sub.7 peroxycarboxylic acid, such
as peroxyacetic acid, and an aliphatic C.sub.3-C.sub.12 carboxylic
acid. This composition would be formulated with preformed
peroxyoctanoic acid and preformed peroxyacetic acid. A preferred
composition of the invention can be made by mixing a
C.sub.2-C.sub.7 carboxylic acid, a C.sub.8-C.sub.12 carboxylic
acid, a coupler and a stabilizer and reacting this mixture with
hydrogen peroxide. A stable equilibrium mixture is produced
containing a C.sub.2-C.sub.7 peroxycarboxylic acid and a
C.sub.8-C.sub.12 peroxyacid by allowing the mixture to stand for
from one to seven days at 15.degree. C. to 25.degree. C. As with
any aqueous reaction of hydrogen peroxide with a free carboxylic
acid, this gives a true equilibrium mixture. In this case, the
equilibrium mixture will contain hydrogen peroxide, a
C.sub.2-C.sub.7 carboxylic acid, a C.sub.8-C.sub.12 carboxylic
acid, a C.sub.2-C.sub.7 peroxycarboxylic acid, a C.sub.8-C.sub.12
peroxycarboxylic acid, water, and various couplers and stabilizers.
Once equilibrium is reached, another carboxylic acid is added to
the mixture. This is an aliphatic C.sub.3-C.sub.12 carboxylic
acid.
Method of Treatment
[0042] The present invention contemplates a concentrate composition
which is diluted to a use solution prior to its utilization as a
microbicide. Primarily for reasons of economics, the concentrate
would normally be marketed and the end user would dilute the
concentrate with water to a use solution. A preferred antimicrobial
concentrate composition comprises about 0.1 to 5 wt. % of a
C.sub.8-C.sub.12 peroxyfatty acid, about 1 to 20 wt. % of a
C.sub.2-C.sub.7 peroxycarboxylic acid, about 0.4 to 5 wt-% of a
C.sub.3-C.sub.12 aliphatic carboxylic acid, about 0 to 15 wt. % of
a hydrotrope coupling agent, and about 1 to 30 wt. % of hydrogen
peroxide. Other acidulants may optionally be employed in the
composition such as phosphoric acid or sulfuric acid.
[0043] The level of active components in the concentrate
composition is dependent upon the intended dilution factor and
desired acidity in the use solution. The C.sub.8-C.sub.12
peroxyacid component is generally obtained by reacting a
C.sub.8-C.sub.12 carboxylic acid with hydrogen peroxide in the
presence of a C.sub.2-C.sub.7 carboxylic acid. Another
C.sub.3-C.sub.12 aliphatic carboxylic acid is then added to the
mixture. The resulting concentrate is diluted with water to provide
the use solution. Generally, a dilution of 1 fluid oz. to 1-16
gallons (i.e. dilution of .about.1 to .about.2,000 by volume) of
water can be obtained with 2% to 20% total peracids in the
concentrate.
[0044] The compositions of the invention can be applied to growing
plant tissue in a variety of techniques. The aqueous solution can
be sprayed, painted, daubed, fogged, flooded onto or into the
plant, the plant hydroponic substrate, the agricultural earth. The
material can be reapplied periodically as needed.
EXAMPLES
Example 1
[0045] A rice-related mold, Chaetomium funicola (C. funicola), was
treated using the following solutions. The compositions and
controls were evaluated for antimicrobial activity using the
procedure set out in Germicidal and Detergent Sanitizing Action of
Disinfectants, Official Methods of Analysis of the Association of
Official Analytical Chemists, paragraph 960.09 and applicable
sections, 15th Edition, 1990 (EPA Guideline 91-2), using a 10
second contact time at 60.degree. C.
[0046] The data shows that the limited effectiveness of individual
antimicrobial materials such as solvents (Run #'s 1-2), carboxylic
acids (Run #'s 3-4), peroxycarboxylic acids (Run # 5), or binary
mixtures without added carboxylic acids (Run #'s 6-8) yield
substantially less microbial reduction of the mold than the
C.sub.3-C.sub.12 carboxylic acid enhanced formulas (Run #'s
9-10).
1TABLE 1 Peracid Improvements Using Fatty Acids 4 1 Microbial
Peroxy 2 Reduction Run Acid Carboxylic Acid 3 (C. # (ppm) (ppm)
Solvent (%) funicola) 1 0 ppm none 0 ppm benzyl alcohol (2.0%) 0.1
2 0 ppm none 0 ppm DBE-3 (2.0%) 0.2 3 0 ppm glycolic 100,000 ppm
none (0.0%) 0.2 4 0 ppm octanoic 800 ppm none (0.0%) 0.2 5 3000
ppm.sup.1 none 0 ppm none (0.0%) 0.2 6 1500 ppm.sup.2 none 0 ppm
benzyl alcohol (2.0%) 1.4 7 1000 ppm.sup.2 none 0 ppm DBE-3 (1.5%)
0.3 8 1500 ppm.sup.2 none 0 ppm DBE-3 (2.0%) 4.8 9 1500 ppm.sup.2
octanoic 800 ppm DBE-3 (1.5%) >6.5 10 1500 ppm.sup.2 octanoic
800 ppm benzyl alcohol (2.0%) >5.0 .sup.1The active peracetic
level from Oxonia Active; a commercial product from Ecolab Inc.,
St. Paul, MN .sup.2Active peracetic acid concentration.
Example 2
[0047] Various screening organisms were treated using the following
solutions. The compositions and controls were evaluated for
antimicrobial activity using a 10 minute contact time at 25.degree.
C. The data shows the benefit of adding a C.sub.3-C.sub.12
carboxylic acid (octanoic acid) (Run #'s 6-8, 11-12) to a
monoester-monoperoxy-dicarboxylate peracid blend, versus formulas
without; especially with consideration to lowering the amount of
active peroxycarboxylic acid required to achieve a passing
result.
2TABLE 2 Peracid Improvements Using Fatty Acids 1 Monoester 2 3 4
Run Peroxy Acid.sup.1 Octanoic LAS Screening Microbial # (ppm) Acid
(ppm) (ppm) Microbial Result 1 180 ppm 0 ppm 0 ppm S. aureus passed
2 180 ppm 0 ppm 60 ppm S. aureus passed 3 120 ppm 0 ppm 0 ppm S.
aureus passed 4 120 ppm 0 ppm 70 ppm S. aureus passed 5 90 ppm 0
ppm 0 ppm S. aureus failed 6 90 ppm 0 ppm 40 ppm S. aureus failed 6
63 ppm.sup.2 40 ppm 0 ppm S. aureus passed 7 42 ppm.sup.2 40 ppm 80
ppm S. aureus passed 8 42 ppm.sup.2 40 ppm 40 ppm S. aureus passed
9 6636 ppm 0 ppm 0 ppm M. bovis failed 10 531 ppm 0 ppm 500 ppm M.
bovis failed 11 531 ppm 500 ppm 0 ppm M. bovis passed 12 531 ppm
500 ppm 500 ppm M. bovis passed .sup.1The active peracetic level
from Perestane; SOLVAY S.A., 33 rue du Prince Albert, B-1050
Brussels, Belgium .sup.2Buffered with 200 ppm citric acid
* * * * *