2,343,048‘
Patented Feb. 29, 7194.4.
UNITED STATES PATENT orrica
raoonss or BLEACIIING s'raacu
om n. Eble and Monroe J. Mason, St. Louis, Mo.,
assignors to Anheuser-Busch, Incorporated, St.
Louis, Mo” a corporation of Missouri
No Drawing. Application August 3,1940. '
p
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Serial no. 351,201
7 Claims. (Cl. 127-70)
This invention relates to the manufacture of 'tion of sodium hypochlorite in water containing
starch and particularly to the bleaching thereof. ' about twelve per cen'tiof available chlorine is
In the usual method of manufacturing starch,
- used, which is equivalent to about .04 per cent
‘ it is common ‘practice to use chlorine gas. chlorine
' chlorine on the dry substance starch. _
water or a hypochlorite as a bleaching agent; but
, , In carrying out this operation, the temperature
the starch thus produced’ is. liable to have a gray
or pink or greenish tinge, and the starch is liable
to undergo some modi?cation and a paste made
of the starch liquor is kept in the neighborhood
of 120 to 125 degrees Fahrenheit; and the opera
' tion is continued for say an hour. In a typical
case, the hydrogen ion concentration is approxi- ,
from such starch will have a lower viscosity than
natural starch. The object of the present inven 10 mately between pH 4.5 and pH 5.0. At the end
tion is to produce a clear white starch, that'is
of this operation, the starch is ‘washed, ?ltered
substantially unmodi?ed, and whose viscosity is
and dried in any well known manner.
substantially equal to the viscosity of natural
The starch produced as hereinbefore described
starch and which will be stable throughout long
has a clear white color, is unmodi?ed to any ap
preciable extent, is stable over long periods of
, periods of storage.
The invention consists principallyiin using a .
salt of chlorous acid in connection with chlorine
storage, and alpaste made therefrom has sub
or a hypochlorite as hereinafter described.‘ It
bleaching. Accordingly thestaroh thus produced
also consists in the steps and combinations of
steps hereinafter described and claimed. ‘
\
My invention is particularly adapted for pro-
stantially the same viscosity as the starch before
, is well adapted for such uses as sizing high grade
20 paper and other purposes where a clear vwhitesize
__0r starch is requisite and for food products where
~ducing clear white corn starch and thefollowing
stability and viscosity value are important. is aidescription of my process as applied to they
While I‘ have described a typical example of
manufacture of corn starch.
my process as applied to the bleaching of corn
In the commercial production of starch from 25 starch, it is noted that the process is ‘applicable
com, the crude starch is suspended in‘ water and
to the bleaching of other starches and that it is
filtered. The moist starch is washed by again
not limited to the particular reagents and condi
suspending it in water and ?ltering and this op
tions speci?ed. For instance, calcium chlorite
eration may be repeated several times depending
or any other salt of chlorous acid may be sub
upon the amount of solubles contained in the 80 stituted for sodium chlorite, but, on account of
original crude starch and the‘ degree of re?ne
chlorous acid itself being unstable and dangerous,
ment desired. Following the second or later wash
it is not considered suitable for practical use.
ins‘, the moist starch is suspended in such amount
Likewise, chlorine, chlorine water, calcium hypo
of' water as to obtain a starch liquor preferably
chlor'ite or any other hypochlorlte may be sub
85 stituted for sodium hypochlorite. Allthe mem
- of about 20 degrees Be'aumé.
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,
Solutions of sodium chlorite and of sodium'hyé ' vbers of this last mentioned group are chlorine or
pochlorite are added to the starch liquor in suit
yield chlorine as the active bleaching agent; and
able quantity. For instance, a su?icient quantity
of this. starch liquor is used to represent, say 7500
pounds of dry substance \ starch.
they are all so vigorous in their action that they /
are liable to. overoxidize the starch, cause dis
The sodium 40 coloration and modi?cation thereof and vary the
chlorite and sodium hypochlorite are-dissolved in
viscosity of its paste. On the other hand, the
water, preferably in separate tanks each of which
members of the ?rst group, namely the chlorites
is provided with a valved outlet pipe and these
or salts of chlorous acid, act too weakly when
pipes are connected to form a ‘single feed pipe for
used alone. When, however, members of the
delivering the mixture of the two solutions into 45 two groups are used conjointly, they produce re
markably satisfactory bleaching effects without
the main tank that contains the starch and which
appreciably impairing the desired qualities of the
is provided with a suitable mechanical stirring
device for keeping the starch in suspension and
-In the speci?c example stated, the tempera
for adequately mixing the solutions with the
starch liquor. For 7500 pounds of dry substance 50 ture of the starch liquor is speci?ed as from about
120 to about 125 degrees Fahrenheit. .A higher
starch, about seven and one-half pounds of
temperature is permissible but ordinarily would
sodium chlorite are used, which is equivalent to
not be desirable if it'added to the cost. On the
about .10 per cent of sodium chlorite on the dry
other hand, the operation may be carried out
substance starch. For this same amount of
at a temperature as low as 85 degrees Fahrenheit.
starch, about two and one-half gallons of a solu~
starch.
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7
2,848,048
although such low temperature is undesirable
2; The process or bleaching starch which com
prises subjecting the starch. while in suspension
from the standpointof economy and other prac
tical considerations.
- and at a temperature high enough to bleach the
hour. This time could have been prolonged to as
- chlorous acid, the weight oi’ said salt being about
one tenth of one percent of the weight of the
starch without appreciably modifying it. to the
In the speci?c "example given, the duration of
the bleaching operation is speci?ed as about one 5 action of chlorine in the presence of a salt oi’
much as three or four hours under the conditions
starch dry and the weight of the chlorine being
speci?ed without destructive effect on the starch.
about four-hundredths of one percent of the
The'time might also have been shortened to less
v
than an hour under the conditions speci?ed, al- 10 weight of the starch dry.
3. The process oi’ bleaching starch which com
though, in the average case, it is not desirable
prises subjecting the starch, while in suspension
to shorten the period to less than one-half hour.
and at a temperature high enough to bleach the
starch and low enough to prevent appreciable
as between pH 4.5 and pH 5.0. This range may 15 modi?cation thereof. to the action of sodium hy
pochlorite in the ‘presence of sodium chlorite. the
beextended to from pH 4.0 to pH ‘7.0. If the
weight of said sodium chlorite being about one
operation of the starch manufacturing process
tenth of one percent of the weight of the starch
is such as to yield a starch liquor that is not
dry and the weight of the chlorine derived from
within the desired hydrogen ion concentration
range, it may be brought within said range by 20 sodium hypochlorite being about four-hundredths
adding any suitable acid, such as sulphuric or _ of one percent of the weight of the starch dry.
In the speci?c example given, the hydrogen‘
ion concentration of the starch liquor is speci?ed
4. The process of bleaching corn starch which
hydrochloric acid. or alkaline. material, such as
consists in subjecting it, while in suspension in
sodium carbonate or caustic soda, as conditions
starch. liquor having a hydrogen ion concentra
may require.
If it is desired to produce a ?nished dry starch 25 tion value between pH 4 and pH 7 and a tem
perature between 85 and 125 degrees Fahrenheit.
which would have a pH value of say 5.5, the prop
er amount of a suitable alkaline agent, such as ' to the simultaneous action of a salt of chlorous
sodium carbonate or caustic soda, is added to the
bleaching starch suspension prior to ?ltration of
the bleached starch.
.
' The starch may be bleached in a single batch or
the bleaching operation may \be conducted in
stages. a part of the reagents being added prior
to the ?rst or second washing, and the rest of said
acid and a member or the group consisting of
chlorine. hypochlorite of sodium and hypochlorite
30 of calcium, using the salt of chlorous’acid at the
rate of aboutone tenth of one percent of the
weight of the starch dry and using enough of
said group member to yield chlorine equivalent
to iour-hundredths of one percent of the weight
(
reagents being added prior to thelast washing. :5 of the starch dry.
5. The process of bleaching corn starch which
In such cases, the amount of bleaching agents
consists in subjecting it, while in suspension in
which are applied during the ?rst stage is ap
starch liquor having a hydrogen ion concentra
proximately, or slightly more than, one-half of
tion value between pH 4.5 and pH 5 and a tem
the total amount of reagents required in a single
batch bleaching, and a similar amount is used 40 perature of approximately 120 to 125 degrees
Fahrenheit. to the simultaneous action of a salt
in a subsequent bleaching operation. .Whether
of chlorous acid and a member oi.’ the group con
the bleaching process is conducted as a' single
sisting of chlorine, hypochlorite of sodium and
bleach or in separate stages, it is advantageous
to use the ?ltrate from such bleached starch liq“ hypochlorite of calcium, using the salt of chlorous
uor 'as ?uid for the suspension of crude starch 45 acid at the rate of about one tenth 01' one percent
of the weight of the starch dry and using enough
or other mill house fractions. Thus, all the avail
of said group member to yield chlorine equivalent
able bleaching acting will be utilized at some stage
to four-hundredths of one percent of the weight
in the re?ning process.
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of the starch dry.
The proportion of available chlorine derived
from the chlorite to the chlorine derived from 50 6. The process of bleaching starchwhich com
prises subjecting the starch for a period of from
chlorine or a chlorine-yielding compound may be
‘about one half hour to about four hours, while
varied. While ‘the active chlorine may be 25 to
the starch is in suspension in starch liquor hav
75 per cent of that derived from the chlorite salt,
ing a hydrogen ion concentration value between
it is preferable to‘use an amount of active avail
able chlorine, whether supplied as chlorine or 55 pH 4 and pH 7 and at a temperature between 85
yielded by the hypochlorite salt, which is equal
to 25 to 60 per cent of the chlorine yielded by the
'
chlorite.
degrees Fahrenheit and 125 degrees Fahrenheit.
to the action of chlorine in the presence of a salt
of chlorous acid.
'7. The process of bleaching starch by subject
What we claim is:
1. The process of bleaching starch which com- 60 ing the starch in an aqueous medium to the ac
tion of sodium chlorlte in an amount 01' about
prises subjecting the starch. while in suspension
0.10 per cent of the dry weight of the starch and
in starch liquor having a hydrogen ion concen
a minor proportion of a hypochlorite. of a pH of
about 4 to 6 and at a temperature of about 90
125 degrees Fahrenheit, to theaction of a hypo- 66 120° F.
o'rro H. EBLE.
chlorite salt in the presence of a salt of chlorous
tration value between pH 4 and pH '7 and at a
temperature between 85 degrees Fahrenheit and
acid.
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MONROE .1. MASON.