Note: Descriptions are shown in the official language in which they were submitted.
5~ 7
Background of the Invention
Field of the Invention
The invention is concerned with powder peroxide bleach
compositions and their formation. More particularly the
invention is concerned with powder percarbonate bieach
compositions which exhibit relatively long term stability
,, ~
and which retain integrity of composi-tion from the top to
the bottom of a box filled therewith.
Prior Art
.~_
Powder bleach compositions are of course very well
known to the prior artO In these compositions attempts have
been made to utilize commercial grades of percarbonate
having about lO~ to 15~ available oxygen to provide at least
a portion of the available oxygen therein. However, because
of the relatively low stability of the percarbonate
compounds of the prior art it has generally been necessary
to use another peroxide compound, for example sodium
perborate or the like in the powder bleach composition to
assure that it maintains at least adequate available oxygen
level after long term storage. The use of sodium perborate
in a bleach composition along with sufficient soda ash to
provide a desired alkalinity thereto has lead to a problem
in tha-t the sodium perborate dissolves relatively slowly in
both warm and cold water as compared to sodium percarbonate.
~lso, such perborate based bleach compositions have a
tendency to cake on standing so that they do not retain a
free flowing character for a sufficiently long period of
time. Fur-ther, such compositions have a tendency to
separate on handling and storage whereby a dry bleach
composition which originally might have sodium perborate and
soda ash uni-Eormly distributed therethroughout can
eventually have a concentration of one of these products
towards the bottom of a box thereof with a concentration of
another of the ingredients towards the top thereoEa Such
separation occurs because of differences in density,
differences in particle size, diEferences in particle shape
and the like. Such separation can also occur in a bleach
composition which comprises sodium percarbonate and soda
ash if the composition is made by mixlng together the two
individual components. Further still, a composition of
sodium percarbonate and soda ash made by mixing the two
components together, as mentioned previously has a rela-
tively low storage stability and exhibits a reduction in
available oxygen content with time of storage which is
undesirably high.
Accordingly, it is an object of the present invention
to provide a powder bleach composition having the active
oxygen content thereof supplied by sodium percarbonate.
Summary of the Invention
According to one aspect of the invention there is
provided a pro~ess for making a separation resistarlt dry
bleach composition, comprising: contacting particulate
soda ash with sufficient of a spray of an aqueous solution
of hydrogen peroxide, said contacting being at a tempera-
ture which falls within a range from about 35C to about
ZO 7~C to provide a dry bleach composition having sufficient
sodium percarbonate to provide available oxygen in an
amount of from about 1 to about 6 weight percent of said
composition and a remainder which comprises soda ash; and
recovering said dry bleach composition from said contact
ing step.
According to another apsect of the invention there is
provided a composition of matter, comprising: a plurality
of dry bleach particles, substantially each oE said parti-
cles comprising soda ash and sufficient sodium percarbona-te
to provide about 1 to about 6 weight percent avallable
oxygen.
It is an advantage of the present invention, at least
in preferred forms, that it can provide a powder bleach
composition which is resistant to separation.
It is another advan-tage of the present invention, at
least in preferred forms, that it can provide a powder
bleach composition having sodium percarbona-te therein to
supply the available oxygen content thereof, which com-
position exhibits improved storage stability.
Yet another advantage of the present invention, at
least in preferred forms, is that it can provide a powcler
bleach composition wherein substantially each particle
thereof comprises both soda ash and sodium percarbonate
so that separation of the composition does not occur on
handling or storage.
A still further advantage of the present inVentiQn, at
least in preferred forms, is that it can provide a sodium
percarbonate powder bleach composition wherein the avail-
able oxygen content is more quickly available in solution
than in prior art compositions.
Another advantage of the present invention, at least
in preferred forms, is that it can provide a process for
making a separation resistant dry bleach composition
having the advantages stated in the above objects.
These and other advantages of the present invention,
as will become apparent from reading the followiny speci-
fication, are accomplished as set out herein.
Brief Description of the Drawing
The invention will be better understood by reference
to the figures of the drawing wherein:
Figure 1 comprises a schematic flow diagram oE a
process in accordance with the present invention,
~`7
Figure 2 illustrates a plurality of dry bleach
particles in accordance with the composition of matter
of the present invention;
- 4a
. . ~
Figure 3 illustrates an alternate schematic flow
diagram of a process in accordance with the present
invention; and
Figure 4 illustrates an important detail of the
process embodiment of Figure 3.
Detailed_Descrlp _on of the Preferred Embodiment
Adverting now to Figure 1 of the drawing -there is
illustrated therein a process in accordance with the present
invention wherein a plurality of powder bleach particles 10,
as seen in Figure 2, each of the particles comprising soda
ash monohydrate 12 and sodium percarbonate 14, are produced.
Generally at least some anhydrous .soda ash 15 will also form
a part of each particle 10, al-though as illus-trated, some
par-ticles 10 may contain only the monohydrate 12 along with
the percarbonate 14.
Soda ash, either in the form of anhydrous sodium
carbonate or sodium carbonate monohydrate and preferably in
the form of anhydrous sodium carbonate is loaded via a
hopper 16 wherefrom it passes as represented by an arrow 18
to a continuous feeder 20 from whence it is delivered as
represented by an arrow 22 to a fluid bed reactor 24. The
soda ash is fluidized within the reactor 24 by air delivered
to the fl.uid bed reactor 24 from a fan 26 as represented by
an arrow 28, The air after leaving the fan 26 can also pass
throuyh a heat exchanger 30 to adjust its temperature and
through a flow meter 32 to assure that the flow rate is
correct. A f.irst temperature sensor 34 checks the
temperature of the air from the Ean 26 while a second
temperature sensor 36 is used to control the heat exchanger
30 so as to maintain the temperature of the air exiting the
heat exchanger 30 at a desired value, -for example 80C. The
temperature of the air entering the fluid bed reactor 24
will generally all within a range Erom about 60C to abou-t
140C and more preferably within a range from abou-t 80~C to
about 120C.
By proper control of air temperature~ air velocity
and solid and liquid reactant addition and withdrawal rates
the contacting (reaction mass) temperature is maintained
generally within a range from about 35C to about 70C and
preferably within a range from about 38C to about 50C.
In the embodiment of Figure 1 hydrogen peroxide is
introduced into the fluid bed reactor 24 as represented by a
line 38. The hydrogen peroxide is introduced into the fluid
bed reactor 24 via a conventional spray system represented
schematically by an arrowhead 40. The entering hydrogen
peroxide comprises a solution of hydrogen peroxide in water
and generally comprises Erom about 20 to about 70 weight
percent hydrogen peroxide in water. Preferablyr the
concentration of hydrogen peroxide will fall with.in a range
from about 20 to about 50 weight percent. 5till more
preferably, the concentration of hydrogen peroxide i.n the
hydrogen peroxide solution will fall within a range from
about 25 to about 35 weight percent, While the hydrogen
perox.ide solution can be supplied in any manner, in the
2S particular embodiment illustrated in Figure 1 commercial
high grade hydrogen peroxide is pumped via a p~mp 42 to a
tank 44 wherein additional water is added as represented by
an arrow 46. The hydrogen peroxide solution from the tank
44 then passes as represented by a line 48 and under the
impetus o-E a pump 50 to a surge tank S2 from whence the
solution is pumped by a pump 54 and proceeds as represented
by a line 56 through a flow meter controller 58 to the
aforementioned line 38 and thence to the sprayer 40.
While any of a number oE fluid bed reactors may be
utilized the particular type of fluid bed reactor 24 as is
illustrated in Figure 1 is one preferred embodiment. This
reactor includes an air plenum 60 adjacent a bottom 61
thereof, the air plenum 60 being covered by a perforate
plate 62 (generally about 2 to 7% perforation wi-th holes
generally 0~1 to 0.5 mm in diameter). The air will exit the
fluid bed reactor 24 as represented by a line 64 and then
pass via a damper 66 to a dust collector 68 wherein any
particles contained therein will be separated and removed
downwardly as represented by an arrow 70~ The air within
the dust collector 68 will proceed as represented by a line
72 and under the impetus of a fan 74 to be evacuated to the
atmosphere. It should be noted that a majority of -the
water, originally introduced along with the hydrogen
peroxide, will be evaporated in this manner and will leave
the fluid bed reactor 24 along with the air introduced
thereinto.
The velocity of the air usecl to fluidize the
particles within the ~luid bed reactor 24 is also of extreme
importance~ If too low of an air velocity is provided highly
undesirable caking can occur leading to an inferior or even
unusable product. Thus, the air velocity must be at least
about lm/sec through the perforate plate 62~ On the other
hand, too high of an air velocity can be detrimental by
causing high dust formation and particle erosion with
concurrent grinding off oE the percarbonate 14~ Thus air
velocities above about 2.5m/sec should be avoided.
Preferably the air velocity should fall within a range from
about 1.2m/sec to about 1.7m/sec and most preferably within
a range from about 1.4m/sec to about 1.6m/sec. With respect
to an alternate embo~iment of the process of the present
invention as discussed below, it is not necessary that the
minimum air velocity of at leas-t about lm/sec be maintained
over the entire extent of the perforate plate 62 although
such rate must be maintained over at least a portion o the
perforate plate 620
The residence time of the reactants within the
reactor 24 should be as short as is reasonably possible to
obtain proper formation o~ product. Surprisin~ly it has
been found that a residence time of as little as about 1
minute is sufficient to attain an available oxygen content
of about 1% to 2% with about 95% efficient utilization o~
the added hydrogen peroxide. Generally the residence time
should, however, be at least about 2.5 minutes and more
preferably at least about 3.5 minutes to attain available
oxygen contents in the 2% -to 6% range. The reactants and
the resultant product can be kept in the reactor 24 as long
as desired but this will both lower the yield and needlessly
waste energyO A preferable residence time ranye is 3.5 to
20 minutes with times of 4 to 10 minutes having been
repeatedly used successfully and with high yields.
The hydrogen peroxide is added at a su~ficient
rate to ass~lre a desired oxygen content based upon reactor
capacity and the particular reactant~product residence time
chosen.
Q
~5~ 7
The bleach product produced within the fluid bed
reactor 24 will proceed therefrom as represented by an arrow
76 to a continuous tumbling mixer 78 and thence as
represented by an arrow 80 to a screening apparatus 82 from
S whence it will proceed as represented by an arrow 84 to a
storage silo 86 and thence as represented by a line 88 to
packaging machinery or the like~ Any lumps or overly small
material removed by the screening apparatus 82 will be
removed therefrom as represented by a line 90 ~nd led off to
a barrel 92 or the like.
~ Addi-tional materials may be added to the dry
;:: bleach composition to improve its properties or to make it
more acceptable to the ultimate user. For example perfume
may be added from a perfume tank 94 as represented by an
arrow 96 and surfactant may be added from a container 98 as
represented by a line 100. If desired the perfume and
surfactant can be premixed in a mixer 102 from whence the
mixture will proceed via a pump 104, past a flow meter 106
and, as represented by an arrow 108, to the continuous
tumble mixer 78. Color, whitening agent, water softening
agent and the like may be added as represented by lines 110,
112 and 114 and common arrow 116 to the continuous tumble
mixer 78. It is noted that while a number of ingredients
may be added to the product from the fluid bed reactor 24 it
is desirable that these products not be added prior to the
entry of the sodium carbonate into the fluid bed reactor 24
since they would have a tendency to interfere with the
reaction taking place in the fluid bed reactor 24. Other
additives as are common in the art maybe added to the
continuous tumble mixer 78 in a like manner. For example,
sodium tripolyphosphate may be added as a sequestering
agent. Still further, the continuous turnble mixer 78 may
have other additives added thereto to increase the stability
of or otherwise modify the product. For example, sodium
silicate can be added if desired to add ~o the stability oE
the product.
There are certain features which are important and
indeed essential to the satisfactory practice of the process
of the present invention. If these features are ignored
then the resulting product will not be nearly as
satisfactory for bleaching use as is the powder bleach
composition of the present invention. First, it is
important that the temperature be maintained within the
aforesetout ranges. If lower temperatures are used there
will be a tendency for sodium carbonate heptahydrate and/or
decahydrate to form. This can cause caking to occur if the
product is later exposed to temperatures above the
temperatures at which these higher hydrates are stable. If
higher temperatures are used some of the hydrogen peroxide
may be decomposed before it has time to enter into the
desired reaction. Further, the air velocity used to
fluidize the soda ash must fall within the aforesetout range
or caking and an unusable product will result from overly
low air velocities or excessive abrasion and product loss
from overly high air velocities.
In addition to the abovementioned features which
are essential to the practice of the present invention~ it
is important to the practice of the present invention that
the sodium carbonate which is added to the Eluid bed reactor
24 as represented by the line 22, be first properly sized in
accordance with the size of the desired end product. Thus
~'~1
it is important that a relatively small range of particle
sizes be present in the sodium carbonate added to the fluid
bed reactor 24. This assures that the particles 10 when
they exit the fluid bed reactor 24 will all be of a
relatively small range of particle sizes and in accordance
with the size of the desired end product. The final product
must be made up of particles within a relatively small size
ranye so as to assure that when someone is measuring out the
particles by dry measure, each volume measure will contain
essentially an equal weight of the dry bleach composition.
Generally the mesh size of the entering sodium carbonate as
well as the mesh size of the final product particles 10 will
fall within a range from about 10 mesh to about 200 mesh and
more preferably within a range from about 20 mesh to about
100 mesh.
It is also important to the presen~ invention that
the ratio of hydrogen peroxide to sodium carbonate added to
the fluid reactor 24 is appropriately chosen to provide a
final dry bleach composition which has sufficient sodium
percarbonate to provide the desired available oxygen
content, preferably from about 1 to about 6 weight percent.
It is preferred that each of the particles 10 have from
about 1 to about 5 weight percent available oxygen and more
preferably about 2 to about 4 weight percent o~ available
oxygen. If the available oxygen content is made too high,
i.e~, is made significantly above about 6%, then it will be
found that the reaction mixture within the fluid bed reactor
24 will tend to cake up. Also, if the available oxygen
content is above about 6 weight percent the bleach
composition will have an unduly high ratio of sodium
,;j~; / , 1 1 _
percarbonate to soda ash for the intended end usage whereby
it will become necessary to add additional soda ash thereto.
If this is done then problems of separation between the pure
soda ash particles and the particles 10 in accordance with
the present invention will result. It is preferred that the
range of available oxygen content as a function o particle
size falls generally within - 1 weight percent and
preferably within - 0.5 weight percent of the nominal
available oxygen content of the composition ~o eliminate
settling and separation effects.
Alternate Embodiment
Adverting to Figures 3 and 4, there is illustrated
therein an alternate embodiment of the process of the
present invention which utili~es a commercial mixer-
fluidized drying bed apparatus the mixer portion of ~hich is
available from Shugi and known by the trademark "Flexomix".
Those portions o~ the diagram of Figure 1 which are not
reproduced in Figure 3 are operatively identical. Also,
the various temperatures, fluidizing velocities, etc.,
discussed with respect to the embodiment of Figure 1 are the
same in the embodiment of Figures 3 and 4O Further, the
product obtained by using the embodiment of Figures 3 and 4
has the same advantageous properties as that of the
embodiment of Figure 1, and, indeed~ the available oxygen
distribution is even more uniform.
Briefly, the embodiment oE Figures 3 and 4 differs
from that of Figure 1 in that the soda ash is delivered by
the line 22 to a premix chamber 118 (The Flexomix~ and -the
hydrogen peroxide is also delivered via a spray system 40'
to the premix chamber 118. The premix chamber 118 is
1 ~ _
normally at ambient temperature and residence time of the
soda ash-hydrogen peroxide premix formed therein is of the
order o~ less than 5 seconds and usually less than about 1
second. The soda ash from the line 22 enters -the premix
chamber 118 via peripheral entrances 120 and -the entire
mixture is agitated by rotary mixing blades 122. The blades
- 122 force the premix outwardly against an elastomeric sleeve
124 and a plurality of rollers 126 roll up and down in
contact with the outside of the sleeve 124 to -force the
premix down into a reactor 24' wherein the premix is
converted to the powder bleach particles 13 under the
previously discussed conditions of temperature, flow~ etc.
In an apparatus as just discussed, it has been
found that the reactor 24' can be advantageously modified as
illustrated in Figure 3. In particular, the air delivery
system can be modified to provide air flow to different
portions 60A and 60B of the air plenum 60. The air delivery
system to the plenum portion 60A is via heat exchanger 30A
as represented by an arrow 28A, etc., and a parallel air
delivery system is used to the plenum portion 60B. This
allows a higher temperature and a higher fluidizlng velocity
to be used in the leftmost portion of the reactor 24' where
the premix enters and a lower te~mperature and a lower
-~luidizing velocity to be used in the rightmost (product
exit) portion of the reactor 24'. Particularly good results
have been ob-tained with a temperature of about 96C and a
fluidizing velocity of about 1.3m/sec through the perforate
plate 62 above the plenum portion 60A and a temperature of
about 81C and a Eluidizing velocity of about 0.84 above the
plenum portion 60B. Thus, an addi-tional step of fluidizing
,,~
h~
~S~
is provided at a reduced gas velocity which falls within a
range from about 0.5 to about 1.5m/sec and at a tempera-ture
from about G0C to about 120C. :[t will be noted that after
fluidizing at an air velocity of at least about lm/sec
(1.3m/sec) above the plenum portion 60Ar milder temperatures
and lower flow rates can be utilized for the additional
fluidizing above the plenum portion 60B thus reducing dust
formation and particle erosion.
The invention will be better understood by
reference to the following examples.
Example 1:
This example demonstrates the production of a
powder bleach in accordance with the Figure 1 embodiment of
the present invention.
Anhydrous soda ash was Eed into a fluidized bed
reactor at the rate of 266 kg/hr. Heated air (93 C) was
used at an air velocity of 1.17m/sec across the bed to
fluidize the reaction mass and to keep the reaction mass at
42-7 C. 35% H202 was sprayed on the fluidized bed of soda
ash at the rate of 84.5 kg/hr. The residence time within
the reactor was about 10 minutes. The product was collected
at the rate of 318 kg/hr. The production run continued for
80 minutes. The final product had 3.81~ oE available
oxygen.
xample 2:
This example illustrates the formation via the
Figure 1 process of the present invention of additional
product in accordance with the present invention using
conditions as follows:
~ - 14 -
L5~
Soda ash feed rate 629 kg/hr.
35% ~ydrogen peroxide 192 kg/hr~
Air velocity 1~5m/sec.
Residence time 4.6 minutes
Air temperature 88~7C
Reaction mass
temperature 47~8C
Production rate 775 kg/hr,
Available oxygen 3.95%
Production run 3 hours
Example 3:
~ product was produced in accordance with the
Figure l embodiment of the present invention and tested for
storage stability. A prior art product was produced by
blending together commercial ~15% available oxygen) sodium
percarbonate with anhydrous soda ash. An identical storage
test was performed or comparison on the prior art
composition. The original available oxygen contents were
substantially the same. The two different products were
stored side-by-side ~or two months under three different
temperature/relative humidity conditions. The first of such
conditions was an uncontrolled temperature/relative humidity
twice daily monitored storage; the second and third
conditions were controlled, constant temperature/relative
humidity storages. Following are the results of these side-
by-side stability tests.
'~
o Initial Available Oxygen
After Two Months
56-90~F/36-92~ R~Ho ~ 120F/20~ R.H.
Dry Blend
Product 74.l68.5 55.8
New Process
Product 80.778.3 57.1
a. Sodium percarbonate produced by Food
Machlnery Corporation, V~S.A.,
initial available oxygen con~ent oE
mixture = 3,9
b. Product of the present invention,
initial available oxygen content of
mixture = 4-29
Example 4:
A series oE experiments were performed to
determine the relative rates of availability of oxygen in
solution of a product produced in accordance wi-th Figure 1
of the present invention and a mixture of commercial sodium
percarbonate (13.5% to 14% available oxygen) and sodium
carbonate. The experiments were run as follows: All
components were sieved -to form a 30 to 40 mesh fraction and
thereby standardize the particle gross surface area. While
90 ml of deionized water at 25C was stirred at a moderate
pace, l0 grams of the appropriate sample was rapidly addedO
After 0.5, l, 5 and 12 minutes, 5.0 ml a:Liquots were removed
and immediately added to 20 ml of 5~ sulfuric acid. The
resulting solutions were each titrated with a standardized
permanganate solution. The oxygen contents in the aliquots
were then calculated relative to the total amount present
applying proper correction factors to compensate for
concentration chan~es during the course of the experiment.
LS9~ ~
The results are summarized as follows:
Sampling Relative Available _xyyen %
Ali~uot No. Time, Minutes Commercial (a) Present (b)
Mixture Product
1 0.5 53 100
2 1.0 88 101*
3 5.0 98 99
4 12.0 92 94
* Equal ~o 100 within experimental error.
a. Peroxid Chemi GMBH, Werkl Honningen,
West Germany, available oxygen content
of mixture = 3.19%
b. Product of the present invention,
available oxygen content - 3.37%
This example demonstrates quicker availability of
oxygen in solution with a product in accordance with the
present invention thus potentially increasing efective
bleaching time during a wash cycle.
~ Example 5:
A series of experiments were performed to
determine the distribution of available oxygen as a -function
of particle si~e for a product produced in accordance with
Figure 1 of the present invention, a product produced in
accordance with Figures 3 and 4 of the preCent invention and
a mixture oE commercial (13.5% to 14% available oxygen)
sodium percarbonate and sodium carbonate. The samples were
sieved and an available oxygen analysis was performed for
each separate Eraction. The results are summarized as
follows:
~ __ 1 7 .. _
37
_.
u
,
d~
a
u~ Q a)o~ In o a~ o o~
5 rl X ~ ~ r~
~) (IS O
.,, ~
~ ~,~o
~o
V ~
S ,~~ ~ ~ o~o
~:1 ~) O ~1 U~ O ~ O
O .~ .. . . , . .. ~ -
~ ~ ooIn ~ o o
~ ~ o
,_
Q a)
,1
~ a~ ot~
a~ ~ ~ o
~ ,1 ~,I / . . o
3 ~ X ~ ~ <~ ~ o
tll (~ O
.,., ~
~ oQ
C: I`~ U~ ~ ~ CO o~o
tl~ OU~ O cn~o~r ~ o o
O ,~ . -
~ ~ O~1 ~ ~ O ~ ~ ~ O
~4 ~ 1 o
~ a
_ ~1 ~
r~ x ~ `3 o o o o o
r~
.~ ~
d
~ dP
u
SJ ~
o ~ r~ d~
a~ I o ~ O
~ .r~ .
o a) O In ~ ~1 In ~o o o
c~ 3~ r~
~ s
a~ o o o o o o o o~c
~n ~ ~ ~ ~r In t_ o~ c~ ~
~ ~ ~ ~ ~ o
p E~
a. Peroxid GMBH, Werk r Honningen, West
Germany, available oxygen content of
mixture = 3.23%
b. Product of Figure 1 oE the present
invention available oxygen
content = 3.69%
c. Product of Figures 3 and 4 of the
present invention, available
oxygen content = 3.58%
This example demonstrates the extremely good
uniformity of available oxygen (sodium percarbonate~ over a
wide particle size range for a product in accordance with
the present invention whether made by the process
illustrated in Figure 1 or in Figures 3 and 4. The example
also illustrates relatively poor uniformity of available
oxygen with particle size of a simple sodium percarbonate-
sodium carbonate mixture. It should be noted that about 50~
of the commercial product demonstrated overly high available
oxygen contents (30-50 mesh) which could lead to
overbleaching while the other about 50% thereof ~the through
50 mesh portion) demonstrated very low available oxygen
content which would be ineffective or at best only partially
efective in providing bleaching action. Separation of
particles by size during shipment and storage could thus
lead to large (overbleaching) particles predominating in
measures removed from a freshly opened box and small
(ineffective) particles predominating in measures removed
from the bottom of the box.
Example 6:
A series of experiments were performed to determine
pour characteristicsr lumping and caking formation after
storage for both a product in accordance with Figure 1 of the
present in~ention and a mixture of commercial (15~ available
ox~gen) sodium percarbonate with anhydrous soda ash. The
three different storage conditions were as in example 3;
storage was for 2 mon-ths. The below indicated values
represent -the average of a pour grade, a lump grade and a
caking grade.
Pour, lump and caking grades were evaluated on a
scale of 1-10 with higher numbers indicating more desirable
properties (easier pouring, less lumping, less caking). ~ny
ranking of 7 or above is considered acceptable for consumer
use.
For the pour test, a scale value of 10 represents
even, continuous flow; a scale value oE 8 represents partial
blockage of carton opening with continuous Elow~
For the lump test, a scale value of 10 represents
no lumps visible in the poured product; a scale value of 8
represents visible lumps after shaking which cannot be
picked up with the fingers. Each pour was made at a 45
angle 4 inches over a 2 foot section of cardboard.
For the caking test, a scale value of 10
represents no lumps, free 1Owing product oE which 100% will
pass freely through a 1/2" screen; a scale value of 8
represents compacted, but easily dispensible o~ which 100%
will pass freely through a 1/2" screen. The caking test
consisted of pouring an aliquot of the -test material onto a
1/2" screen.
~5~S7
Pour/Lum~/Ca g/Grade Average
Temp/R.H. conditions 1 2 3
Dry Blend Product (a~ 10 10 10
New Process Product (b) 8.3 9.9 10
Commercial Perborate
Product (c) 7.8 9.0
a. Food Machinery Corporation/ U.S.A.,
initial available oxygen con~ent
o mixture = 3.94
b. Product of Figure 1 of the present
invention, initial available oxygen
content of mixture = 4.29
c. Blend of nominally 36% sodium
perborate tetrahydrate, 63.5~
sodium carbonate (anhydrous) plus
minor amounts of brighteners, bluing,
fragrance, deduster; initial available
oxygen content of mixture = 3.88
This example demonstrates the excellent pour
characteristics and low degree of lump and caking Eormation
for a product of the invention subjected to relatively
severe storage conditions. Although the otherwise
unacceptable dry blend product shows a slight advant:age in
this area, the product of the present invention is
significantly better than the normal commercial (perborate~
product which is itself Eully commercially acceptable.
While the invention has been described in
connection with specific embodiments thereof, it will be
understood that it is capable of Eurther modification, and
this application is intended to cover any variations, uses
or adaptations of the invention following1 in general, the
principles of the invention and including such departures
from the present disclosure as come withill known or
customary practice in the art to which the invention
~5~i~7
pertains and as may be applied to the essential features
hereinbefore set forth, and as fall within the scope of the
invention and the limits of the appended claims~
. --. ~,~.
