Note: Descriptions are shown in the official language in which they were submitted.
3~745~
Title
Aqueous Fungicidal Formulations and Th~ir Preparation
Back~oun~ of the~ Invention
This invention relates to the preparation of
~table formulations of manganese(II) ethylenebis~
(dithiocarbamate) (maneb) and, more particularly,
to the preparation of aqueous formulations of maneb
having unexpectealy low concentrations of ethylene-
thiourea (ETU).
Maneb is a known important fungicide, but
the compound is unstable and tends to decompose.
Decomposition products, such as ethylenethiourea
(ETU), appear in freshly made maneb and
increase in concentration during periods of
lS storage.
Although much work has been done which
relates to improving the stability of maneb, there
are no known references which teach the present
invention,
L. Donev IKhimiyai industriya (Sofia) 41,
lO0-lOl (1969), No, 3], for example, teaches a method
of preparing maneb of increased dithiocarbamate
content in which aqueous formaldehyde is added to a
manganese(II) sulfate solution. Then a solution of
ammonium ethylenebis(dithiocarbamate) (amobam) is
added to precipitate the maneb,~ ETU concentration is
not discussed.
U~S. Patent 3,856,836 discloses a maneb
derived ~rom a ormaldehyde-treated reaction mixture.
~he maneb is precipitated in aqueous medium rom a
'~
9~
water-soluble s~lt o~ ethylenebis~dithiocarbamic acid)
and a water-~oluble manganese(II) salt. Formaldehyde
is a~ded to th~ reaction mixture after preclpitation.
The reference does not ~iscuss ETU concentration.
~ S. Patent 2,974,156 teaches that hexa-
~ethylenetetram~ne ~HMTA~ can be added to maneb ~o
improve stability.
U.S. Patent 3,173,832 teaches that para-
formaldehy~e can be addea to maneb to improve stability
and that a soluble zinc salt can reduce phytotoxicity.
Althoug~ the prior art discloses various
methods o~ formulating maneb to improve strength
and/or stability of the product, no known references
discuss the preparation of maneb having a low ETU
concentration, eit~er as 2 dry or an aqueous product.
Summary of the Inventlon
The present invention is a process for
preparing a unique aqueous composition of maneb
having an unexpectedly low concentration of
ethylenethiourea consisting essentially of
maneb, 0.05 to 5.0% by weight of a soluble zinc
salt ~on Zn basis) and 0.05 to 5.0% by weight
formaldehyde.
The combination of zinc (soluble Zn2~) and
formaldehyde in aqueous medium with maneb unexpectedly
retards the buildup of ETU in maneb.
Detailed Description of the Invention
The maneb used in pxeparing the co~positions
of this invention can be dihydrate, anhydrous or
partially dehydrated~ The dihydrate form of maneb is
preferred because o~ it~ hi~her overall stability with
-
respect to decomposition to ETU and because it can be
formulated in a~ueous mixtures dtrectly without
having to dry it first.
~745~4
Maneb, which has been prepared according to
the process disclosed in Canadian patent application
Serial No. 334 102 filed 1979 August 20, is preferred
because of its resistance to decomposition. According
to that process, maneb can be prepared by reacting a
soluble manganese ~II) salt with the disodium ~nabam)
or dipotassium salt of ethylenebis(dithiocarbamic acid)
which has been treated with formaldehyde. As used herein,
the term "nabam" is intended to include the potassium
analog of disodium ethylenebis(dithiocarbamate). Alter-
natively maneb can be precipitated by reacting ammonium
ethylenebis(dithiocarbamate) (amobam) or plain nabam
with an aqueous solution of a manganese (II) salt.
Nabam is the preferred salt because it yields maneb of
lower initial ETU content.
It has been noted that nabam treated with
formaldehyde produces maneb of a relatively large
particle size. Thus, it is preferable to precipitate
the maneb in the presence of a dispersant which will
cause the maneb to form and remain as small particles
and reduce or eliminate the need for grinding, etc.,
prior to formulation.
Suitable dispersantsinclude some of the
ligninsulfonate type, such as Polyfon* H (a sodium
lignosulfonate produced by Westvaco Chemical Division,
N. Charleston, South Carolina). The amount of dispersant
will ordinarily depend on the nature of the dispersant.
Economic considerations suggest using no more dispersant
than necessary for obtaining the desired maneb particle
size. Using too much dispersant could slow filtration
o~ the maneb reaation mixture, which may neaessitate
other means ~e.g., aentrifugation) for satisfactory
maneb recovery. Generally, the amount of disper$ant
can range from about 0.1 to 10% of the reaction mixture.
* denotes trade mark
4S9~
Surprisingly, when nabam is used without formaldehyde,
the presence of a dispersant, even though satisfactory
when used with formaldehyde, may cause formation of
maneb particles which are larger than if no dispersant
S is used at all.
~ e maneb concentration in the compositions
of this inYention can vary ~epending on the strength
desire2. For example, maneb strength can vary from
about 10 to 50~ by weight, with 25 to 40% by weight
la being the preferred concentration for economic reasons.
The use of formaldehyde with a soluble zinc
salt achieves an unexpectedly low concentration of ETU
when maneb is form~lated as an aqueous composition.
Although either formaldehyde or soluble zinc salts
15 might contri~ute toward producing low ETU concentrations
in fresh aqueous mane~ compositions, storage studies
show that a zinc salt, in the absence of formaldehyde,
can actually increase ETU concentration. Even though
formal~ehyae alone operates to minimize ETU levels,
20 the use of both a soluble zinc salt and formaldehyde in
the composition can produce surprisingly low ETV levels
in aqueous maneb.
The compositions of this invention will
ordinarily contain about 0.05 - 5,0~ by weight of zinc
25 salt (based on Zn) and about 0.05 - 5.0~ by weight of
formaldehyde. Prefera~ly, the compositions will contain
about 0.1 to 2.5% by weight each ~f zinc salt and
formaldehyde. Too much formaldehyde can create odor
or phyto~oxicity problems and too much soluble zinc
30 salt in the composition can affect maneb stability.
~his invention is illustrated in a preferred embodiment in
Table A and the exampl~s which ~ollow. The table and
examples are not to be considered as limiting, but
merely exemplary. ~he significant feature i8 the co~bined
35 action of formaldehyde and a soluble zinc salt in
reducing ETU concentrations in aqueous maneb composi-
tions.
~74~9~
Additional formulation ingre~ients, s.uch as
dispersants, anticorrosion agents, etc., as well
as other fungicides, such as methyl 2-benzimidazole-
carbamate (car~endazim), and 2 cyano-N-~(et~ylamino)-
S carbonyl]-2--~methoximino)acetamide (Curzate*), can be
present as long as they do not cause ETU ~uildup in
the formulation or react substantially with formaldehyde
to the detriment of thP formulation.
As used he~e.in, the te~m '!mancQzebt' is
intended to ~ean a complex of maneb and zinc
resulting from reaction of maneb with.a soluble
zinc salt under wet conditions. IFor a description
o~ maneb and mancozeb~ see Pesticide Manual,
;th Edition, edited by H. Martin and C. R. Worthing,
issued by the British Crop Protection Council,
pages 328 and 32g.]
The term ~Imaneb~ is intended to include
', mancozeb when the maneb has been treated under wet
conditions with a soluble salt of zinc.
* denotes: trade mark
3S
~7~5~4
Table A
¦~ormaldehyde (CH2O)/Nabam + MnS04¦
Dispersant
~ /
Maneb Fi Lter Cake~
1. Wash with water
2. Wash with
zn2f (.soluble) I ~ (a)*
3. Add into agueous
CH20
~ f
¦ Maneb + Zn2+ + CH2O¦ = stabilized aque-
ous composition
The preparation of the co~position may be accomplished
several ways:
(a) As shown abo~e, marked with the asterisk.
20 (b) Add the filter cake directly into aqueous
CH2O + Zn2~ ~soluble~;
(c) Wash the filter cake with aqueous ~CH2O + Zn2+
(soluble)~ and then add to water;
(d) Wash with aqueous CH2O and add to aqueous Zn2+
(soluble);
(e) Wash with aqueous Zn2~ (soluble) and add to
aqueous CH2O.
Any other suitable variation o:E ~he above procedures,
e.g., wash with aqueous Zn2~ (soluble) and add to water
30 simultaneously wlth ~H2O, can be used.
~ urther reduction in maneb particle size can
be accomplished, if desired, by wet-milling. If
desired, the conversion o~ maneb to zinebl during
tOe ~illin5 pro:e~s can be avoided by adding
35 1 zineb - zinc ethylenebis(dithiocarbamate)
:~7~594
zn2~ (solu~le) after the milling process.
Wet-milling is further described in U.S. Patent
3,157,486 A
5Exa~Dle 1
Ta~le s
Formal~ehy~e/Nabam:
Dispersant Duri~g ~recipitation:
10Maneb Aqueous
¦ CH20/Nabam I MnS04~
Dispersant
1~ ~
~Water-washed M, Lneb Filter Cakel
-- --
ZnC12 Wash;
~dd into water with
~0: ~2% CH2O
¦Mancozeb Aqueous Suspension with CH~O
-- ~ .
P~M Agln~
ETU 1-2 1 day, r~om t~mperature (R.T.)
2 0 days, R . T .
In~o a flask containing a stirred ~2-blanketed
solution o~ 15.2 g. of Polyfon ~ in 1160 ml. of water
at 2Sn was simultaneously added during a 50-minute peri-
od an aqueous solution o~ 723.2 g. of 23~ MnSO4 and
~ormaldehyde/nabam ~1115 g. of 23~ nabam and 40.6 g.
o~ 37% CH20 mixed and let stand at ambient temperature
~or 30 minutes beore beginning to use in reaction with
MnSO4]. After 10 minutes, the maneb was ~iltered o~f,
L5~
washed with water and with 1 kg. of 7% ZnC12. The
filter cake was s~spended in aqueous formal~ehyde such
that the ~aneb concentration (expressed as anhy~rous)
was a~out ~5% and the formaldehyde concentration was
2.2~. The zinc assay was 1.1% total and 0.9% soluble.
The ETU assays are noted above.
The method of adding reactants simultaneously
to a common body of water as in this exarnple is usually
~eferred to as a "heel pr~cess".
~_
Example 2
Table C
Fonmaldehyde/Nabam;
Dispersant During Precipitation;
Maneb Aqueous
¦ CH2o/Nabam ~ Mn ~
¦Dispersant
___
IWater-washed Maneb Filter Ca
ZnC12 Wash;
Put into water with
~ ~ 0.1% CH2O
. _ ,
Mancozeb Aqueous Suspension with CH20
PPr5 Aging
ETU 4 2 days, R.T,
2 22 days, R.T.
The same general procedure was used as in
Example 1. The final maneb mixture contained about
28~ maneb (expressed as anhydrous), about 0.1% CH2O,
and the zinc assay was 1,3%, total, and 1.0% soluble.
The ETU assays are noted above.
9~
Exam~le 3
Table D
¦ C~20/Nabam + MnS04 ¦
. .
Beel Pr~cess ! 25
with Polyfon H, ~5%
~ ,
~Water-washe2 Maneb ~ilter 3
.
No Wash ~ nC12 Wash
1/
rManebFilter Cake¦¦~ancozeb Filter Cake~
1 1
Add ~ Add H2O ~ Add ~ Add H2O +
H20~ \ CH20 ~ \~CH20
~Maneb ~ Maneb ~ancozeb¦
aqueousI aqueous ~gE~ aqueous
l wit~ CH2O I
A' B, Cl D
I
ETU51 12 3 1 ~ 1 day.,
ppm . .
121 34 728 <33~ ~ 51 w~-
*This figure is unusually high ~ecause of interference
peaks encountered in the liquid chromatographi.c
method used ~or ETU assay. The true ETU level could
possibly b~ as low as zero 7 i~ all the inter~erence
plus ETU is reported as ETU, the ETU level is
~till less than 33 pp~. Similar comments apply to
other examples herein where a "~No." is reported ~or
ETU eoncentration.
~7~59~
The same general proce~ure was followed as
in Example l! except the filter caXes were split at
various stages as indicated to show effects of the
CH2O and ZnC12 as to their absence, separate use, and
combined use. Initially, CH2O and ZnC12 separately,
and especially CH2O and ZnC12 combined, help reduce
ETU, whereas after 1 wee~ at 45, the combination of
CH2O and ZnC12 is more favorable. The CH2O concentra-
tion in samples B and D was a~out 2%,
1 0 ~
Example 4
Table_E
r
~lain Nabam + MnSO4¦
' - - -
~eel Pr~cess! 25
No Dispersant
\ ,
IWater-washea Mane~ Filter Cakel
.. . _ .. . . .
No Wash ~ ZnC12 Wash
¦Maneb Filter Cake~ ¦Mancoæeb Filter Cakel
Add 1 Add H2O ~ Add 1 Add H2O +
H20 / \ CH20 H2Y \ CH20
~ J ~
Maneb ¦Man~ozeb¦
aqueous ~ laqueous
I with CH~O I¦with CH7O¦
3 0
A 1 B, C l D
t
-
ETU57 12 31 ~ 1 day.,
pp~ R.T~
518 40 ~45
174~9~
The sam~les were ~repared generally as
describe~ in Example 3, except that plain nabam
(no CH20) was used to prepare the initial maneb
precipitate in the absence of a dispersant. Again,
the sample (D) wit~ ~oth CH20 and Zn2~ is more
~atisfactory.
. Example 5
Ta~le ~
~Plain Nabam + MnS04¦
Heel Process~ 25n
with Polyfon~9 H, Q, 5%
1 5 \ ~ .
Water-washed Maneb Filter Cake¦
N~ Wa~nC12 Wash
¦Maneb Filter Cake1 ¦Mancozeb Filter Cake¦
Add ~ Add H20 + Add 1 Add H20 +
H20l~/ ~ CH~0 ~ \~CH20
¦Maneb ¦ I Maneb ¦Mancozeb1l Mancozeb
laqueous J aqueous laqueous I aqueous
ll with C~20 II with CH20
A~ B, Cl D,
ETU 112 4 113 ~ 2 day.,
297 66 ~450
__
. .
e.
~:~7~L~ii9~
12
The. samples were ~ade generally as described
in Example 4, except that dispersant was present
during precipitation of maneb, A~ain ~ the sample (D)
with both CH2O and Zn2~ is more satisfactory,
S
Example 6
Table G
I CH20/Nabc m ~ MnSO~
~eel Proces 5 ~ 2 5
\ No Dispersant
¦ Water-washea Mc neb Filter Cak3
No Wa ~ nC12 Wash
¦Maneb F~ rCak~ ~Mancozeb ~Filter cakeJ
Add f ~ Add H2O ~ Add 1 Add H2O +
H20~ \ CH20 ~ \CH20
1 Maneb lManco zeb ¦ ¦ Ma=
aqueo ~ aqueous ~aqueous ¦¦aqueous
~ I with C~2O ~ Iwith CH~O
25 A~ B, Cl Dl
ETU 27 5 2 1 r 2 day.,
ppm S_ R .'T,
1~2 24 ~4 ~16 ~ wk~
~ he ~ame general procedure was followed
a~s in Example 3, eXcept that no dispersant was present
durlng precipitation. The particle size of the maneb
obtained in this example was ~ar greater than that
obtained in Example 3. It is perhaps for this reason
1~7~Sg~
13
that in this example alone, t~e presence of Zn2+
(in absence of CH20, sample C) has helped hold
down ETU concentration during the l-week, 4S
storage of the aqueous ~aneb as compared to sample A,
-
~L~7459~
14
Example 7
Table H
Mane~ Dihydrate YS. Maneb Anhydrous
For Mane~ ~ueous Suspensi~ns
¦Plain Nabam + MnS04 ¦
10 ¦ ~eer-W~sh~d I Dry to ¦Anhydrous 1
Maneb Filter Cake = 0% H 0 Maneb
, Maneb Dihydrate + Water 2 (38p~ m ETU)~
L/
~1 H20 -+1 C~2 + I
~ ZnC12¦ 2
20 A B C D
ETU 101 10 18 2 ~3 da.,
ppEn
306 9 324 2 ~ 510 wk.,
1- 1H2~+
¦;~ rH2 ~1 CH20 +
~ ¦ZnCl~¦ ZnC12
__ E F G H
ETU 215 22 137 3 ~R.T.
pp~
400 25 1561 ~120 ~ 5o
~ 7~59~
In this example, ~aneb dihydrate was compared
to anhydrous maneb in aquecus composition. In each
case, the presence or absence of ZnCl2 and CH2O and
their combination were examined, Pr~ssure built up
~uring the accelerated storage o~ samples F, G, a~d H,
~hough ETU levels were held down with CH2O and with
CH2O/ZnCl2. Overa~l, stability is good for the
samples made from maneb dihydrate.
.. . . . .. ..
Example 8
Table I
Maneb Aqueous From Amobam
¦Amobam + MnS04¦
_
Heel Process
\ /
_ . __ _ _
Water-Washed Mane~ Filter Cake
ZnCl2 Wash
/
. . .
Mancozeb Filter Cake
~ Add H2O + CH2O
¦ Mancozeb Aqueous + CH2O~
~ e~L33Y~ 2n, ~otal
16 as-made ~,l9
25 a~ter l wk. at 45
~mobam, as previously exemplified with nabam,
can also provide low-ETU aqueous maneb when used in
conjunction Wit}l Zn2' ~soluble) + CH2O. The levels of
~il745~
16
ETU obtained appear to be somewhat higher than those
obtained when the maneb is deri~ed from nabam or
CH20/nabam .
_
