Process for manufacturing sodium carbonate perhydrate particles and coating them with sodium borosilicate

A process to manufacture and coat a sodium carbonate perhydrate containing 10.5% to 14% active oxygen which is stable in a non-phosphate detergent composition and which has a bulk density of from 900 to 1,050 kg/m.sup.3. Anhydrous sodium carbonate with a pore volume of at least 0.29 ml/g is contacted with 50% to 75% by weight hydrogen peroxide in the presence of 1-hydroxyethylidene-1,1-diphosphonic acid and water is evaporated at a rate to maintain a dry reaction mixture. The product is coated by sparging sodium borosilicate at a rate to avoid moistening the particles.

This invention is a process to manufacture a stable, sodium carbonate 
perhydrate composition that is stable in laundry detergent formulations 
and which readily releases its active oxygen in use. 
BACKGROUND OF THE INVENTION 
Sodium carbonate perhydrate has been recognized to be a desirable component 
for a detergent composition because it is readily soluble in water, 
because it has a high active oxygen content, and because it also provides 
an inexpensive source of nonpolluting alkalinity. Pure sodium carbonate 
perhydrate conforms to the chemical formula 2Na.sub.2 CO.sub.3.3H.sub.2 
O.sub.2 which contains 15.28% active oxygen (AO). However, sodium 
carbonate perhydrate generally requires a coating to protect it from 
decomposition when formulated into a detergent and stored in an open 
container in a laundry room. 
Numerous processes have been proposed for manufacturing sodium carbonate 
perhydrate (SCP). One of the primary methods is a crystallization process 
in which aqueous solutions of hydrogen peroxide and sodium carbonate are 
mixed in a reactor and the SCP formed is filtered off. The product is 
usually salted out by the addition of sodium chloride or other suitable 
reagents. Such processes are disclosed in U.S. Pat. Nos. 2,380,620 and 
2,541,733. While the crystallization process can produce a product with a 
bulk density of 900 kg/m.sup.3 or more and offers advantages such as good 
mixing and heat transfer, it has the disadvantage that there typically is 
a substantial loss of active oxygen in the mother liquor, so that low 
peroxygen efficiencies are obtained. That is, conversion of hydrogen 
peroxide utilized to active oxygen in the finished product is low. 
In another method, taught by U.S. Pat. No. 3,555,696, SCP is made by a 
spray-drying process in which hydrogen peroxide solution is added 
immediately before atomization of a spray charge of sodium carbonate in a 
spray tower. Thereafter the product SCP is dried, yielding a very dusty 
product with a very low bulk density. 
It is apparent from the prior art that large volumes of mother liquor are 
to be avoided. A process yielding high peroxygen efficiencies usually uses 
only a sufficiently large amount of water to act as a reaction medium and 
to provide a heat sink for the heat of reaction. 
The desire to minimize the amount of water in the reaction system has led 
to exploration of the so-called "dry" method. However, when the reaction 
is carried out in the absence of a sufficient amount of water, the 
reaction is not efficient and decomposition losses are quite high. In the 
dry method, hydrogen peroxide is sprinkled directly onto sodium carbonate 
powder to form a moist mass, the mass is then dried. The procedure may be 
repeated to build up the oxygen content of the perhydrate. Attempts to 
operate such a process have produced only unsatisfactory perhydrate 
products with a low bulk density and thus the process is not in commercial 
use insofar as is known. Typical dry processes are taught in U.S. Pat. No. 
3,864,454, in which it is necessary to dry the product in carbon dioxide 
and in European Patent Application 0070711, in which the reaction mixture 
is maintained in a vacuum before drying. In accordance with East German 
patent 212,947, the product is so fine that a separate recycling 
granulation step is required. On the other hand, U.S. Pat. No. 4,171,280 
avoids the heat sink problem by restricting the amount of hydrogen 
peroxide to provide a maximum active oxygen content of the product to 6%, 
thereby avoiding decomposition and caking of wet reaction mixtures. 
The dry process for the formation of SCP has a basic deficiency, namely, 
the difficulty of proper heat transfer of the exotherms that are generated 
as a result of the reaction. Reaction between aqueous hydrogen peroxide 
and solid soda ash generates an exotherm in two ways: the heat of 
hydration of sodium carbonate with the water present in hydrogen peroxide, 
and the heat of perhydration, that is, the reaction of sodium carbonate 
with hydrogen peroxide to produce sodium carbonate perhydrate. Both these 
heats tend to increase the reaction temperature quite markedly, 
particularly in the absence of efficient mixing and/or cooling. 
Dusting is another problem associated with the dry process. When finely 
divided soda ash is sprinkled with hydrogen peroxide solution and mixed 
very efficiently to dissipate the heat, a large amount of dust is formed. 
This results in low peroxygen efficiency and/or a product having low 
active oxygen values. On the other hand, if granular, dense soda ash is 
used, the dusting effects are less but the reaction becomes relatively 
inefficient. In either case, the product tends to agglomerate to form a 
product with a low bulk density. 
A hybrid process combining the dry process and the wet process is taught by 
U.S. Pat. No. 3,860,694 in which anhydrous or hydrated sodium carbonate 
having a particle size distribution between U.S. Standard Sieve No. 14 and 
325 is contacted with from 35% to 90% hydrogen peroxide, a magnesium 
stabilizer, and sufficient water to maintain the reaction mass moist. The 
moist reaction mass is reacted from 5 minutes to 3 hours. Subsequently the 
moist reaction is dried. 
U.S. Pat. No. 4,970,058, teaches a sodium carbonate perhydrate process in 
which hydrogen peroxide, anhydrous sodium carbonate, and a diphosphonic 
acid are reacted to make a composition in which sufficient anhydrous 
sodium carbonate is present to react with any water either already present 
in the composition, or any water which may be formed from the hydrogen 
peroxide. The diphosphonic acid appears to permit any water present during 
the manufacture from being retained as sodium carbonate monohydrate. The 
process provides high peroxygen efficiency, low dusting and the product is 
very stable on storage. Its only apparent disadvantage is the maximum 
active oxygen concentration is about 11.2%. It is desirable to have a 
product with an active oxygen content higher than 11.2%. 
U.S. Pat. No. 5,045,296 teaches a process for SCP by uniformly distributing 
aqueous 50% to 75% hydrogen peroxide and 11/2% to 13% by weight of a 
diphosphonic acid onto a dry, particulate reaction mixture of anhydrous 
sodium carbonate with a particle size distribution between 300 and 74 
micrometers. The process concurrently balances the heats of hydration and 
of perhydration of sodium carbonate and the heat of evaporation of water 
to maintain the reaction mixture between 50.degree. C. and 80.degree. C. 
to evaporate substantially all of the water from the resulting reaction 
mixture and cooling the resulting reaction mixture to provide said product 
as a free-flowing, stable, granular material with a particle size 
distribution substantially the same as the anhydrous sodium carbonate, and 
containing between 13% and 141/2% active oxygen. 
Coating SCP to minimize decomposition when formulated into a detergent not 
only has the obvious disadvantage of diluting the overall active oxygen 
content, but also has added disadvantages. These disadvantages include 
reducing the bulk density because of agglomerating the particles and 
retarding the rate of release of active oxygen into the solution. 
It has been suggested that particles of peroxygen compounds be coated by 
compounds, such as trona (U.S. Pat. No. 4,105,827); sodium silicate (U.S. 
Pat. No. 3,951,838); sodium perborate plus sodium silicate (U.S. Pat. No. 
4,194,025); boric acid (U.S. Pat. No. 4,321,301); wax (U.S. Pat. No. 
4,421,669); a polymer latex (U.S. Pat. No. 4,759,956); sodium silicate 
plus a chelate (U.S. Pat. No. 4,117,087); and wax plus a fatty acid (U.S. 
Pat. No. 4,126,717). Many of these treatments show some improvement in 
short term storage stability in a humid environment. Those few coated SCP 
products that were stable when formulated into a dry household laundry 
detergent were found to release their active oxygen when added to water 
too slowly to be of value in a laundry detergent formulation. 
U.S. patent application Ser. No. 5,194,176 filed Apr. 2, 1991 teaches a 
storage-stable compound of 45% to 75% sodium carbonate perhydrate, 0.1% to 
3% diphosphonic acid or salt and anhydrous sodium carbonate coated with 
sodium borosilicate. 
The composition is storage-stable, but has the disadvantage of a low assay. 
SUMMARY OF THE INVENTION 
The present invention overcomes the disadvantages of the prior art by 
providing a process for preparing a coated sodium carbonate perhydrate 
stable in detergent formulations consisting essentially of 
(a) preparing sodium carbonate perhydrate by the steps of: 
(i) uniformly distributing an aqueous hydrogen peroxide solution containing 
about 50% to about 75% by weight hydrogen peroxide, and an effective 
amount of 1-hydroxyethylidene-1,1-diphosphonic acid onto a substantially 
dry particulate reaction mixture, the reaction mixture initially 
consisting essentially of anhydrous sodium carbonate with a pore volume of 
at least 0.29 ml/g, 
(ii) concurrently balancing the heat of hydration and heat of perhydration 
of the sodium carbonate in the reaction mixture with the heat of 
evaporation of water and adding sufficient sensible heat to maintain the 
reaction mixture between 50.degree. C. and 80.degree. C. and to maintain 
the reaction mixture substantially dry by evaporating water added as the 
aqueous hydrogen peroxide solution, and 
(iii) withdrawing at least a portion of the reaction mixture as a 
particulate sodium carbonate perhydrate containing about 12% to about 14% 
active oxygen, and about 0.5% to 10% 1-hydroxyethylidene-1,1-diphosphonic 
acid, and 
(b) coating sodium carbonate perhydrate particles withdrawn in step (a) 
(iii) by the steps of: 
(i) suspending the particles of sodium carbonate perhydrate in a gas stream 
thereby substantially eliminating solid-solid contact between the 
particles, 
(ii) contacting the suspended particles with a plurality of fine drops of 
an aqueous sodium borosilicate solution, the sodium borosilicate 
consisting essentially of a mixture of 25 to 75 parts by weight sodium 
silicate and from 75 to 25 parts by weight sodium metaborate to provide a 
SiO.sub.2 :B.sub.2 O.sub.3 weight ratio of from 1:1 to 2:1, and 
(iii) concomitantly evaporating substantially all the water added with the 
aqueous borosilicate solution at a sufficient rate to avoid moistening or 
hydrating the suspended particles, to provide thereby a coated sodium 
carbonate perhydrate stable in detergent formulations, containing from 
about 3% to about 10% coating by weight, the coated particles having a 
bulk density of from 800 to 1050 kg/m.sup.3 and containing from 10.5% to 
about 14% by weight active oxygen, the coated particles releasing 
substantially all of the active oxygen into water within two minutes. 
DETAILED DESCRIPTION OF THE INVENTION 
Preferably the temperature should be maintained between 60.degree. C. and 
70.degree. C. during and for a short time after addition of the aqueous 
peroxide/phosphonate solution, and the rate of addition should be 
controlled to maintain a substantially dry reaction mixture. 
The temperature of the reaction mixture can be maintained easily. For 
example, by a heat exchanger means providing sensible heat transfer 
between the reaction mixture and the reactor shell or by a gas stream 
contacting the reaction mixture providing sensible heat transfer for the 
reaction mixture. 
Any suitable solids mixing reactor may be employed such as a fluid bed 
reactor or a solids mixing device such as a cone mixer, a ribbon mixer, or 
the like, provided the solids mixing reactor does not function as a size 
reduction device. Means should be provided in the reactor to conduct water 
vapor from the surface of the reaction mixture, such as, by directing a 
gas stream, preferably air, through the reactor. It is not necessary for a 
gas stream to be directed into the reaction mixture to provide part the 
agitation of the reaction mixture. The velocity of a gas stream should be 
sufficiently low to avoid carrying off fines from the reactor. 
However, it is contemplated that stabilizers such as magnesium compounds, 
silicates and chelating agents or mixtures thereof may be added if desired 
to the soda ash, to the reaction mixture or to the hydrogen peroxide. 
Other chelating agents may include citrates, phosphates, phosphonic acids 
and salts, N-carboxylic acids (NTA, EDTA, DTPA) and the like. In addition, 
it is contemplated that the SCP product may be subsequently coated or 
formulated into a product. 
Any aqueous hydrogen peroxide solution can be used for the process. 
Desirably, the hydrogen peroxide will be about 65% to 85% by weight, 
thereby providing a concentration of about 50% to 75% after addition of 
the diphosphonic acid (usually supplied as a 60% solution). Preferably 
about 70% hydrogen peroxide will be employed thereby minimizing the 
sensible heat needed to be added or deducted from the system. The hydrogen 
peroxide-diphosphonic acid solution must be added at a controlled rate to 
provide that the reaction mixture remains substantially dry. Water must be 
permitted to escape from the reaction mixture as vapor, and hydrogen 
peroxide must be permitted time to form SCP and not accumulate as a 
liquid. 
The presence of an effective amount of hydroxyalkylidene diphosphonic acid 
in the hydrogen peroxide is critical to obtain a dry product. The 
diphosphonic acid appears to be effective during the reaction to permit 
water to be released from the reaction mixture rather than be retained as 
free or hydrate water. It is particularly effective to add all the 
diphosphonic acid at the beginning of the reaction (with the first 20-50% 
of the H.sub.2 O.sub.2). The amount of diphosphonic acid required is not 
related to chelation of polyvalent cations. The diphosphonic acid appears 
to promote the release of water from the reaction mixture in a similar 
manner to that described in U.S. Pat. Nos. 4,966,762, 4,970,058 and 
5,045,296. However, an entirely different product is formed than by the 
process of the above patent applications. The product made by the present 
process generally has a higher active oxygen content. 
A particularly desirable diphosphonic acid is commercially available as a 
60% solution of 1-hydroxyethylidene-1,1-diphosphonic acid under the 
tradename DEQUEST 2010 by Monsanto Corporation. The diphosphonic acid 
solution is usually employed in sufficient quantity to reduce the 
concentration of 65% to 85% hydrogen peroxide to about 50% to 75%. 
Preferably sufficient diphosphonic acid should be employed to provide 
about 0.5% to 10%, preferably 0.5% to 3.5% diphosphonic acid in the 
product. 
The anhydrous sodium carbonate must have a pore volume of at least 0.29 
ml/g to produce a stable high assay product without agglomeration. 
Unexpectedly it is a much better indicator than absorbancy as employed by 
the detergent industry. In the latter procedure, a liquid non-ionic 
wetting agent, such as, for example, TRITON X-100, is added to a known 
weight of sodium carbonate until the mixture becomes tacky and loses its 
free-flowing properties. The absorbancy is reported as: 
##EQU1## 
Pore volume is measured by the well-known process disclosed in U.S. Pat. 
No. 4,588,569, which is incorporated herein by reference. The procedure 
utilizes a mercury porosimeter, such as described in ASTM Standard C699-72 
(Section 106-114). A suitable anhydrous sodium carbonate is available 
commercially from FMC Corporation under the designation Grade 90. 
The amount of sensible heat necessary can be determined easily by one 
skilled in the art without undue experimentation. Sensible heat can be 
added to the reaction mixture when more dilute hydrogen peroxide is 
employed or in the event that insufficient water is being evaporated to 
maintain the desired temperature or sensible heat can be withdrawn when 
more highly concentrated hydrogen peroxide is employed. Heat transfer can 
be accomplished by means well known to the art such as heating or cooling 
the reactor walls, or by heating or cooling with air or gas contacting the 
reaction mixture. 
The product may then be cooled by any known means, for example, by passing 
ambient air through the reactor, cooling the reactor walls, preferably to 
a temperature in the range of 15.degree. C. to 50.degree. C. to provide a 
free-flowing, stable, granular sodium carbonate perhydrate product. 
The granular sodium carbonate perhydrate particles can be coated in a fluid 
bed by suspending the dry particles in fluidizing gas and applying a 
solution of sodium borosilicate as a coating by a spray. For the purpose 
of this invention "suspending . . . to eliminate solid-solid contact" 
would include permitting particles to be separately lifted by a stream of 
air or to fall separately as in a tower. Alternately, the invention can be 
carried out in a tower and applying the coating in a countercurrent, 
cocurrent or radial spray. Other alternative processes will be apparent to 
one skilled in the art, such as a spray dryer with both liquid and solids 
injection, or the like. 
It is critical for the present invention that the drops of aqueous solution 
of sodium borosilicate be much smaller in diameter than the solid SCP 
particles to avoid agglomerating the particles by wetting the surface, or 
to avoid forming either a hydrate of SCP, or a sodium carbonate hydrate. 
It is well known that once formed, sodium carbonate monohydrate is very 
difficult to dehydrate without concomitantly decomposing any active oxygen 
compound associated with it. 
Unexpectedly a synergism appears to occur when an aqueous solution of 25% 
to 75% sodium silicate (with a SiO.sub.2 :Na.sub.2 O ratio of about 3.22) 
and 75% to 25% sodium metaborate is applied as a solution of sodium 
borosilicate to the sodium carbonate perhydrate according to the present 
process, desirably the solution contains 40% to 60% sodium silicate and 
60% to 40% sodium metaborate to provide a SiO.sub.2 to B.sub.2 O.sub.3 
ratio of about 1:1 to about 2:1. This effect is particularly evident when 
the coating solution is prepared with about 50% sodium silicate and about 
50% sodium metaborate, and the combined solids content is about 25% by 
weight when applied to the sodium carbonate perhydrate. The invention is 
described and exemplified in terms of forming a sodium borosilicate 
solution by combining a sodium silicate solution with a 3.22 weight ratio 
of SiO.sub.2 to Na.sub.2 O and sodium metaborate. Other sodium silicates 
with SiO.sub.2 :Na.sub.2 O weight ratios ranging from 2.0 to 4.0 and other 
boron sources, such as borax or boric acid can easily be substituted to 
provide an equivalent solution. This synergy is observed both by the 
percent active oxygen retained on coating and the stability of the coated 
product. 
It is essential to avoid substantial agglomeration of particles during 
coating. Agglomeration is easily measured by a decrease in bulk density. 
The SCP product should have a bulk density after coating of at least 800 
kg/m.sup.3 (50 lb/cu.ft.), preferably from 900 kg/m.sup.3 to 1,050 
kg/m.sup.3 when coated with from 3% to 14% sodium borosilicate by weight. 
The particles are coated with 3-10% of their weight of sodium borosilicate 
coating compound. The single coating material may be applied either as a 
single coat or as multiple coats. The efficacy of the coating is 
determined by how well the coated particles maintain active oxygen 
(hydrogen peroxide content). 
Solutions of the coating compound can vary in concentration over a large 
range. Preferably the solutions should contain about 12% to 25% solids. 
Higher concentrations than 25% can be used but usually must be preheated 
to prevent crystallization or solids formation and to permit atomization 
into fine droplets. More dilute solutions require a greater heat input to 
evaporate the water sufficiently to prevent wetting the particles being 
coated. With care solutions can range from about 15% solids to about 35% 
solids. 
Typical 25% solids solution preparation is illustrated as follows: 
Sodium metaborate: Add 261.8 g sodium metaborate tetrahydrate to 238.2 g 
water. 
Sodium silicate: Add 334.4 g of a 37.4% solution of sodium silicate 
(SiO.sub.2 :Na.sub.2 O weight ratio=3.22) to 165.8 g water. 
Sodium borosilicate: A blend of above solutions, or their equivalents will 
contain about 1.4 parts by weight SiO.sub.2 per part by weight B.sub.2 
O.sub.3, a solution containing from about 40 to 60 parts by weight sodium 
silicate and from about 60 to 40 parts by weight sodium metaborate will 
have a SiO.sub.2 to B.sub.2 O.sub.3 ratio ranging from 1:1 to about 2:1. 
The following examples are provided to further illustrate features of the 
process to one skilled in the art and are not intended to limit the 
claimed invention in any way.

EXAMPLES 
Coating Solution Preparation 
The following laboratory procedure outlines the preparation of 25% sodium 
borosilicate solution (50:50 by weight blend of sodium silicate to sodium 
borate): 
(1) Add 404 g deionized water to 1,000 ml beaker. 
(2) Start agitation. 
(3) Heat contents to 63.degree. C. (145.degree. F.). 
(4) Add 261.8 g of granular, technical grade sodium metaborate 8 mol 
(Na.sub.2 B.sub.2 O.sub.4.8H.sub.2 O while maintaining temperature at 
63.degree. C. (145.degree. F.). 
(5) When solution clears add 334.2 g of sodium silicate solution 
(41.degree. Be; SiO.sub.2 :Na.sub.2 O of 3.2 by weight) while maintaining 
temperature at 63.degree. C. (145.degree. F.). 
(6) Maintain temperature at 63.degree. C. (145.degree. F.) during coating 
application. 
The resulting solution when maintained at 63.degree. C. (145.degree. F.) 
was clear. Solutions with the other proportions were made in a similar 
manner. 
Stability Tests 
Quick: The Quick Test is a method for determining the relative thermal 
stability (decomposition) of samples in only eight hours. Sufficient 
sample is added to a closed container connected to a manometer to provide 
a constant volume to sample weight ratio. The temperature is maintained at 
50.degree. C. and the oxygen evolved (the increase in pressure is measured 
hourly by the slope of the line and is reported as ml/hr). The test can be 
employed for samples formulated in a detergent base or for unformulated 
samples of a peroxygen compound ("neat stability"). 
The Relative Decomposition which is calculated by dividing the Quick 
Stability by percent AO is useful when comparing samples of widely 
different assay. The units are ml/hr/% AO. 
80/80: The 80/80 Open Box Test simulates the storage of an open box of a 
detergent formulation. Unless otherwise specified sufficient peroxygen 
compound to be evaluated is blended in a commercial detergent formulation 
to provide 0.7% active oxygen by weight. The box containing 0.45 kilograms 
of formulation is stored with an open lid at 26.7.degree. C. (80.degree. 
F.) and 80% relative humidity for six weeks. At two week intervals samples 
are selected by riffling the contents of the box. Active oxygen retained 
is determined in triplicate. 
Coating Process 
The apparatus used for coating the dry particles was the STREA-1 Laboratory 
Fluid-Bed Coater, manufactured by Aeromatic, a division of Niro 
Industries. 
The unit consists of a coating feed container, a tubing pump to dispense 
the coating solution and the fluid bed coater. The fluid bed coater 
consists of a clear outer shell for easy viewing, a grid plate to 
introduce the fluidizing air, and a center draft tube containing an air 
atomizing spray nozzle. The product introduced into the container is 
fluidized by a stream of preheated air from below the grid plate. The 
particles to be coated are recycled through the draft tube until the 
desired amount of coating is applied. 
Coating Procedure 
1. Adjust the space between the grid plate and the bottom of the center 
tube to the specified setting. 
2. Adjust the nozzle atomizing air to the desired setting by adjusting the 
nozzle spray cap. 
3. Preheat the fluid bed apparatus to coating temperature. 
4. Load the required amount of peroxygen compound into the bed coater. 
5. Heat the contents using preheated air which is used to fluidize the 
contents at mild fluidizing velocity. 
6. After the bed temperature of 38.degree.-71.degree. C. 
(100.degree.-160.degree. F.), preferably 48.degree.-60.degree. C. 
(120.degree.-140.degree. F.) is attained, increase the air atomizing rate 
and fluid bed velocity and start the coating application preferably at the 
predetermined rate. 
7. During the coating application, maintain the bed temperature by 
adjusting the inlet air rate and temperature. Also maintain coating 
application rate. 
8. After the required amount of coating is applied, reverse the coating 
pump to empty the lines of coating material back to the the feed 
container, deactivate the air preheater, stop the fluid air to the fluid 
bed and empty the contents of the container. 
9. Weigh the coated material. 
EXAMPLE 1 
Preparation of SCP Base 
The effect of bulk density absorbancy and pore volume of anhydrous sodium 
carbonate for preparing SCP base were compared by determining the maximum 
active oxygen content attainable and the Relative Decomposition (reported 
as ml oxygen per hour per percent of AO). Results are presented as Table 
I. 
Although the bulk density and absorbancy of sample Nos. 1 and 4 were almost 
the same, sample No. 1 was clearly superior, the maximum active oxygen 
(AO) attainable being 14.7% vs. 12.7% and the relative decomposition (RD) 
being one-third. 
EXAMPLE 2 
A laboratory test was used to evaluate potential SCP coating agents. 
Samples of SCP were coated and the product was formulated into a 6% 
phosphate-based laundry detergent containing 0.71% active oxygen. The 
residual active oxygen was determined after 6 weeks at room temperature. 
Results are presented as Table II. 
In an otherwise identical second series of screening tests the stability 
was determined only after 4 weeks. Results are presented as Table III. 
Unless otherwise specified the SCP contained only 8%-9% active oxygen, the 
balance being anhydrous sodium carbonate. In some runs 2% sodium silicate 
or other additives, such as sodium perborosilicate (U.S. Pat. No. 
2,955,086). Although the test is not as severe a test as subsequent ones 
with a zeolite non-phosphate detergent, it was useful to eliminate many 
coating compounds disclosed as "useful" in the prior art. 
EXAMPLE 3 
The rate of release of active oxygen (AO) from coated SPC was determined in 
a series of experiments. Sufficient coated SPC was added to water at 
15.degree. C. to provide about 0.2% active oxygen. The solution was 
stirred at 200 RPM and the concentration of hydrogen peroxide was measured 
as a function of time. The data are presented in Table IV as time required 
for 25%, 50%, 75% and 100% release of AO. Uncoated sodium perborate 
monohydrate and sodium perborate tetrahydrate are included as controls for 
comparison. 
It is evident from Table IV that sodium borosilicate coatings allowed a 
much more rapid release of active oxygen than sodium silicate alone. 
Replication of a 4% sodium silicate example showed some coating 
variability, but in both cases indicated a very poor rate of solubility 
when a sodium silicate coating is employed. 
EXAMPLE 4 
Two samples of sodium carbonate perhydrate base prepared according to 
Example 1 were coated to 6% level with solutions containing the following 
sodium metaborate to sodium silicate ratios 0:100, 25:75, 50:50, 75:25 and 
100:0 (0:1, 1:3, 1:1, 3:1 and 1:0). Quick stabilities and 80/80 long term 
detergent box stabilities at 26.degree. C. (80.degree. F.) and 80% 
relative humidity were determined. 
Table V shows the synergy when a sodium borosilicate is used to coat base 
sodium carbonate peroxide with varying sodium metaborate to sodium 
silicate ratios compared with the sodium silicate and sodium borate alone. 
Due to the sticky nature of sodium metaborate solutions, it was difficult 
to coat base SCP with solution at the 100:0 (1:0) sodium metaborate to 
sodium silicate ratio. The resulting coated product retained water and was 
highly agglomerated. This problem was also evident with the coating 
solution ratio of 75:25 (3:1) sodium metaborate to sodium silicate. The 
resulting coated product quick stability was 0.34 cm/hr as compared to a 
range between 0.06 to 0.12 cm/hr. 
Table V shows the coated product characteristics. Based on 6-week detergent 
box storage stabilities at 80.degree. F. and 80% RH, products made from 
coating solutions with a 50:50 (1:1) sodium metaborate to sodium silicate 
ratio produced the most stable product. The products coated with 1:3 and 
3:1 while not as good were still very stable. This indicates the preferred 
range is about 1:1 (40:60 to 60:40). 
EXAMPLE 5 
SCP was produced and coated with 50:50 (1:1) borate:silicate as in Examples 
1 and 2 using plantscale equipment and stored in plastic lined drums (and 
one in an unlined supersack) for varying lengths of time under warehouse 
conditions. 
Table VI shows that all of these samples had excellent stability over the 
periods of time stored. 
EXAMPLE 6 
The effect of varying the concentration 
1-hydroxyethylidene-1,1-diphosphonic acid while making the base SCP and 
substitution of other chelating agents and additives was evaluated. The 
other additives were a commercial chelant, mixture of 15-40% 
pentasodiumdiethylenetriamine acetate and 10-30% trisodium 
ethylenediaminetetraacetic acid and polyethylene glycol 600. Table VII 
indicates the maximum AO obtainable and the H.sub.2 O.sub.2 efficiency of 
SCP produced. 
The results show that other chelating agents and additives have 
substantially no adverse effect on producing base SCP. It also shows that 
a minimum about 0.5% (1% of a 60% solution) 
1-hydroxyethylidene-1,1-diphosphonic acid is necessary for the production 
of base SCP. Increasing the percentage from 1.5% to 4.2% (3% to 7% 
solution) has little increase in effect. 
EXAMPLE 7 
The two preferable grades of sodium carbonate (Samples 1 and 4) to make SCP 
base as indicated in Example No. 1 and 4 were evaluated further. The 
results in Table VIII indicate sample 1, having a typical pore volume of 
0.30 was consistently better than sample 4 with a typical pore volume of 
0.24 to 0.28. 
Other work demonstrated that pore volume decreases with aging of the sodium 
carbonate. This probably explains some of the variations in the examples. 
The example also demonstrates that about 0.5% or more 
1-hydroxyethylidene-1,1-diphosphonic acid is required to make base SCP. 
EXAMPLE 8 
A series of runs were made to study the effect of varying the addition of 
the diphosphonic acid (1-hydroxyethylidene-1,1-diphosphonic acid) on the 
base SCP. Approximately 200 parts by weight anhydrous sodium carbonate 
(bulk density 750 kg/m.sup.3) was charged to a ribbon blender. 
Approximately 84.5 parts H.sub.2 O.sub.2 100% containing varying amounts 
of diphosphonic was sprayed onto the sodium carbonate as a 65%-70% 
solution. The reaction mixture was swept with sufficient air at 80.degree. 
C. to maintain the reaction mixture dry and at 70.degree. C. 
The specific conditions are presented as Table IX. Several facts are 
apparent from the Table. The H.sub.2 O.sub.2 efficiency, the % active 
oxygen (AO) retained, is a function of the diphosphonic acid employed. The 
control (no diphosphonic acid) had only a 74% efficiency which increased 
to 86% with 0.6% and 88%-90% with 1.8% and above. In particular, it shows 
the advantage of adding all the diphosphonic acid with the first 20% to 
50%, preferably the first 25% to 45% of the H.sub.2 O.sub.2 (runs 4 and 8; 
5 and 9). Also obvious is that the bulk density of the reaction mixture 
generally increases from the initial 750 kg/m.sup.3 to 960 and higher 
(with the single exception of run 9). The example confirms that at least 
0.5% diphosphonic acid is desirable with 1% to 3% preferable. 
EXAMPLE 9 
U.S. Pat. No. 5,045,296 teaches that it is critical for the particle size 
of the sodium carbonate feed to be less than 70 mesh (213 .mu.m in order 
to produce a SCP product with a high active oxygen (AO) assay. Example 1 
of that patent shows that the assay of 40 and 20 mesh product respectively 
was 9.4% and 6.8% AO using screened FMC Grade 120 sodium carbonate. 
Samples of unscreened FMC Grade 90 and sufficient hydrogen peroxide to 
produce 13.5% AO SCP product but with varying proportions of diphosphonic 
were prepared. The products were screened and the fractions assayed. The 
conditions and results are presented as Table X. It is remarkable that 
even in the absence of diphosphonic acid there was only a slight decrease 
in assay with an increase in particle size, and in the presence of even 
low amounts of diphosphonic acid the differences of AO assays were not 
significant. Clearly, sodium carbonate with a pore volume of more than 
0.29 ml/g unexpectedly has no such critical sizing limitation. 
In the tables it is important to note that the bulk density of the sodium 
carbonate feed generally increases substantially as it is converted to 
sodium carbonate perhydrate (provided there is no dusting and 
agglomeration). Generally there is some decrease of bulk density during 
coating owing to agglomeration. 
TABLE I 
______________________________________ 
EFFECT OF SODIUM CARBONATE ON SCP 
PROPERTIES 
Sodium Carbonate Feed 
SCP Base (Uncoated) 
Absorb- Bulk Dens. 
Pore Vol. 
Max. Rel. Decomp. 
No. ancy % kg/m.sup.3 
Vol. ml/g 
AO % ml/hr/% AO 
______________________________________ 
1 20.6 720 0.30 14.7 0.022 
2 4.0 1,010 0.12 9.8 0.053 
3 11.7 915 0.21 11.7 0.206* 
0.048* 
4 19.7 762 0.24* 12.7 0.064 
0.28* 
______________________________________ 
*indicates two separate determinations were made 
TABLE II 
______________________________________ 
6 WEEK SCREENING TEST FOR COATED 
SODIUM CARBONATE PERHYDRATE 
RT Stability in a 6% PO.sub.4 
Base 
Detergent Formulation SCP + % AO 
% Coating Compound SCP 2% Na.sub.2 SiO.sub.3 
Retained 
______________________________________ 
2 Na.sub.2 SiO.sub.3 (3.22) 
X 84 
2 Na.sub.2 SiO.sub.3 (3.22) 
X 90 
4 Na.sub.2 SiO.sub.3 (3.22) 
X 97 
6 Na.sub.2 SiO.sub.3 (3.22) 
X 96 
8 Na.sub.2 SiO.sub.3 (3.22) 
X 99 
1 NaBO.sub.2 X 89 
2 NaBO.sub.2 X 90 
4 NaBO.sub.2 X 96 
6 NaBO.sub.2 X 96 
2 NaBO.sub.2 X 84 
4 NaBO.sub.2 X 99 
2 Sod. Perborate X 93 
2 K.sub.2 SiO.sub.3 (2.10) 
X 59 
2 K.sub.2 SiO.sub.3 (2.50) 
X 55 
2 Na.sub.2 SiO.sub.3 (2.40) 
X 38 
1 polypropylene glycol X 83 
(MW 4000) 
2 polypropylene glycol 
X 82 
(MW 4000) 
1 polyacrylic acid + MgO X 90 
(pH 9.8) 
1 polyacrylic acid + NaOH 
X 83 
(pH 8) 
2 polyacrylic acid + NaOH 
X 97 
(pH 8) 
2 polyacrylic acid + MgO 
X 82 
(pH 9.8) 
2 polyacrylic acid (pH 6) 
X 89 
1 polyacrylic acid (pH 6) X 94 
2 sodium perborosilicate X 66 
2 sodium borosilicate X 100 
2 sodium borosilicate 
X 89 
2 sodium perborosilicate X 91 
2 sodium perborosilicate 
X 77 
1 Na.sub.2 SiO.sub.3 (3.22) 
X 92* 
2 Na.sub.2 SiO.sub.3 (3.22) 
X 73* 
1 parafin/linoleic acid X 76 
1 dimethylpolysiloxane X 62 
2 Na.sub.2 SiO.sub.3 (3.22) 
X 63 
2 dimethylpolysiloxane 
X 87 
______________________________________ 
*base also contained 2% sodium perborosilicate as well as 2% Na.sub.2 
SiO.sub.3. 
TABLE III 
______________________________________ 
4 WEEK SCREENING TEST FOR COATED 
SODIUM CARBONATE PERHYDRATE 
RT STABILITY IN A 6% DETERGENT FORMULATION 
SCP Base 
+2% % AO 
% Coating Compound % AO Na.sub.2 SiO.sub.3 
Retained 
______________________________________ 
1 C16-18 fatty acid 8 X 56 
2 Octadecane 8 96 
2 K.sub.2 P.sub.4 O.sub.7 
8 82 
2 Na.sub.2 SiO.sub.3 (3.22) 
4 85 
4 Na.sub.2 SiO.sub.3 (3.22) 
4 72 
2 Na.sub.2 SiO.sub.3 (3.22) 
8 93 
4 Na.sub.2 SiO.sub.3 (3.22) 
8 98 
1 Polyvinylpyrrolidone 
8 X 73 
1 Polyvinylpyrrolidone 
8 X 71 
1 GANTREZ Methylvinyl 
8 X 48 
Ether Resin AN119 
1 GANTREZ Methylvinyl 
8 X 97 
Ether Resin AN119 
1 Dimethylpolysiloxane 
8 X 59 
2 Polyacrylic + MgO 8 86 
1 Polyacrylic + MgO 8 X 90 
1 DEQUEST 2000 Na salt 
8 X 82 
1 SCP + 2% Na.sub.2 SiO.sub.3 
8 X 79 
1 DEQUEST 2060 Mg salt 
8 X 76* 
1 Polyacrylic Na salt 
8 99* 
2 MgSO.sub.4 8 99* 
1 MgSO.sub.4 8 X 97* 
2 MgSO.sub.4 8 97* 
1 MgSO.sub.4 8 X 73* 
2 Na.sub.2 S.sub.2 O.sub.8 
8 0.69* 
1 Na.sub.2 S.sub.2 O.sub.8 
8 X 0.70* 
2 Na.sub.2 S.sub.2 O.sub.8 
8 0.70 
1 Na.sub.2 S.sub.2 O.sub.8 
______________________________________ 
*2 weeks 
**GANTREZ AN119-methyl vinyl ethermaleic anhydride resin 
TABLE IV 
______________________________________ 
ACTIVE OXYGEN RELEASE RATE FROM COATED 
SODIUM CARBONATE PERHYDRATE SCP AT 15.degree. C. 
Seconds for 
% Release of AO at 15.degree. C. 
SPC Sample Coating 
Coating 25% 50% 75% 100% 
______________________________________ 
Uncoated SCP* 
0 2 6 11 28 
Sodium Perborate. 
0 .about.1 
3 4 8 
1H.sub.2 O* 
Sodium Perborate. 
0 39 120 -- -- 
4H.sub.2 O* 
Sodium Silicate 
4 15 40 100 -- 
Polyacrylate 2 2 3 11 25 
Sodium Silicate 
2 30 73 145 475 
Sodium Silicate 
4 60 153 300 -- 
Sodium Silicate 
6 200 440 -- -- 
Sodium Borosilicate 
2 6 14 24 59 
Sodium Borosilicate 
4 10 17 27 59 
Sodium Borosilicate 
6 14 25 39 92 
Sodium Borosilicate 
8 14 25 39 92 
Sodium Borosilicate 
10 15 27 42 92 
Sodium hexameta- 
10 8 17 29 62 
phosphate 
Sodium metaborate** 
2 
Sodium silicate 
2 30 57 97 -- 
______________________________________ 
*Controls no coating 
**SCP coated first with 2% sodium metaborate then with 2% sodium silicate 
TABLE V 
______________________________________ 
EFFECT OF VARYING RATIOS OF SODIUM 
METABORATE AND SODIUM SILICATE ON 
6% BOROSILICATE COATED SCP 
6% Coated Product 
Bulk Density 
Quick 80/80 Box 
Base Ratio % AO kg/m.sup.3 
ml/hr % AO Ret. 
______________________________________ 
A 1:3 9.6 1,062 0.07 33 
A 1:1 9.5 1,025 0.06 58 
A 3:1 8.6 988 0.34 42 
B 1:3 8.2 1,009 0.08 24 
B 1:1 8.1 964 0.11 40 
B 1:1 8.0 953 0.12 45 
B 0:1 7.8 1,004 0.07 6 
______________________________________ 
Base A: AO 10.8%; Quick Stab. 0.05 ml/hr. 
Base B: AO 9.1%; Quick Stab. 0.13 ml/hr. 
Ratio Wt. Sodium Metaboratee: Sodium Silicate 
TABLE VI 
______________________________________ 
STABILITY OF COATED SCP IN DRUMS 
Coating % 
Borosilicate % AO Months % AO 
Sample 
1:1 Initial Final Stored Retained 
______________________________________ 
1 0 10.8 10.3 20 95 
2 4 8.7 8.5 9 98 
3 6 8.7 8.2 3 94 
4 10 8.0 7.8 10 98 
5 10 7.9 7.8 9 99 
6* 10 7.7 7.7 10 100 
______________________________________ 
*Stored in an unlined supersack 
TABLE VII 
______________________________________ 
EFFECT OF ADDITIVES ON PREATION 
OF SCP BASE 
SCP 
Run % % 
No. 1-hydrox PEG 600 Chelant 
MAX % AO H.sub.2 O.sub.2 Eff. 
______________________________________ 
1 7 0 0 12.0 93 
2 3 0 0 13.3 93 
3 1 6 0 10.8 82 
4 0 0 7 9.2 75 
5 0.5 0 0 10.6 74 
6 0.5 0 6.5 10.1 74 
7 3 0 4 11.7 88 
______________________________________ 
Notes: 
1hydroxy 60% 1hydroxyethylidene-1,1-diphosphonic acid 
PEG600 polyethylene glycol 600 
chelant mixture of 15-40% pentasodium diethylenetriamine acetate and 
10-30% trisodium ethylenediamine tetraacetic acid 
TABLE VIII 
______________________________________ 
COMISON OF SODIUM CARBONATE (SODA ASH) 
FEEDS ON SCP 
Parts by Weight H.sub.2 O.sub.2 Added 
80 
SA #4 SA #1 120 
Parts H.sub.2 O.sub.2 
H.sub.2 O.sub.2 
SA #1 
Chelant* 
% AO Eff. % AO Eff. % AO H.sub.2 O.sub.2 
______________________________________ 
Eff. 
7 9.3 94 9.8 94 13.2 90 
5 9.2 90 9.4 93 13.2 85 
3 9.1 90 9.4 91 13.0 86 
1 9.1 87 9.3 94 12.8 85 
0 8.0 76 8.9 85 11.4 74 
______________________________________ 
*Parts by weight of a 60% solution of 1hydroxyethylidene-1,1-diphosphonic 
acid 
SA #1 = sodium carbonate sample No. 1 from Example 1 (pore vol. = 0.30 
mg/g) 
SA #2 = sodium carbonate sample No. 4 from Example 1 (pore vol. = 
0.24-0.28) 
TABLE IX 
______________________________________ 
EFFECTS OF DIPHOSPHONIC ACID ON SCP 
H2O2 Bulk Density 
Stability 
Run Eff. % AO % kg/m.sup.3 
ml/hr. 
______________________________________ 
0.0% Diphosphonic Acid in H.sub.2 O.sub.2 
Control 73.9 11.4 956 0.18 
0.6% Diphosphonic Acid in H.sub.2 O.sub.2 
1 86.0 13.2 971 0.16 
2 82.7 12.7 964 0.13 
3 86.9 12.7 972 0.11 
4* 86.4 12.5 1,001 0.11 
5** 86.1 12.5 1,052 0.14 
1.8% Diphosphonic Acid in H.sub.2 O.sub.2 
6 87.9 13.2 1,006 0.17 
7 90.8 13.2 972 0.07 
8* 92.9 13.2 987 0.16 
9** 94.0 13.5 945 0.13 
3.0% Diphosphonic Acid in H.sub.2 O.sub.2 
10 88.0 13.2 1,011 0.47 
4.2% Diphosphonic Acid in H.sub.2 O.sub.2 
11 93.3 13.2 1,009 0.31 
12 89.7 12.9 993 0.29 
______________________________________ 
*All the diphosphonic acid added with the first 45% of H.sub.2 
**All the diphosphonic acid added with the first 25% of H.sub.2 O.sub.2 
TABLE X 
______________________________________ 
SCP ASSAY BY TICLE SIZE AND 
DIPHOSPHONIC ACID (DPA) 
ASSAY - % AO 
% Compo- Size Retained on U.S. Sieve # 
DPA site 20 40 50 100 140 200 Pan 
______________________________________ 
0.0 11.4 9.8 11.4 10.8 11.3 11.7 12.3 13.3 
0.6 13.2 12.8 12.6 12.9 12.9 13.0 13.0 13.0 
1.8 13.2 12.9 12.7 12.8 12.8 12.9 14.0 14.0 
3.0 13.2 13.6 12.8 12.7 13.1 13.1 13.6 13.8 
4.2 13.2 12.8 12.5 12.8 12.9 13.0 13.4 13.4 
______________________________________ 
DPA = 1hydroxyethylidene-1,1-diphosphonic acid in product