US 3882034 A
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United States Patent [191 Gibbons [451 May 6,1975
 SIMULTANEOUS FORMATION OF EXPANDING BORAX PARTICLES AND SPRAY DRIED DETERGENTS Edward James Gibbons, Fanwood, NJ.
 Assignee: Colgate-Palmolive Company, New
22 Filed: Feb. 11, 1974 211 Appl. No.: 441,302
Related US. Application Data  Division of Ser. No. 885,079, Dec. 15, 1969,
Primary Examiner-Benjamin R. Padgett Assistant Examiner-Christine M. Nucker Attorney, Agent, or Firm-Herbert S. Sylvester; Murray M. Grill; Norman Blumenkopf [5 7] ABSTRACT Hydrated borax, such as Na E,O,-5H 0, is expanded to a product of low density by passing individual particles downwardly through a relatively slow-moving countercurrent hot air stream in which the particles are heated by convection and by radiation from internal walls of a confining structure. The expanded and dehydrated borax particles resulting are of a bulk density about half or less than that of the density of the original particles. In a preferred embodiment of the invention, a detergent composition less borax is sprayed into the top of a countercurrent spray tower and at a point below the spray inlet, where the produced detergent composition particles are virtually dry, borax pentahydrate is fed into the tower and is dehydrated, expanded and intimately mixed with the other spray dried particles to form a built detergent product containing desired low density borax. Since the densities of the products and particle sizes thereof may be controlled, non-stratifying built detergent can be made, in which the detergent and borax particles are of comparable size and density, or the bulk density of the overall product can be varied by controlling the degree of expansion of the borax.
7 Claims, 2 Drawing Figures PATENTEUHAY 61975 FIG. 2
INVENTOR EDWARD J. GIBBONS ATTORNEY SIMULTANEOUS FORMATION OF EXPANDING BORAX PARTICLES AND SPRAY DRIED DETERGENTS This is a divison of application Ser. No. 885,079 filed Dec. l5, 1969, now abandoned.
As usually sold in commerce, borax is a solid hydrated particulate material. For some purposes it is desirable that it be employed in such condition but in other applications, the anhydrous particulate form or particles of lower degrees of hydration are preferred, especially if a rapid solubility is required.
It has been known that calcining or decrepitation of borax hydrates produces an expanded particle, apparently due to the swelling action of escaping water vapor. The property of expansion of the borax seems to depend on the heated crystals, while still containing water, being fluid enough to be enlarged and, at the same time, being strong enough not to collapse upon cooling. Various methods have been suggested for effecting the drying and puffing or decrepitation of borax hydrates, such as the use of kilns, roasting pans and fluidized bed apparatuses, when solid borax crystals are being dehydrated, and spray towers for drying liquid solutions or crutcher mixes of borax.
Borax has examples accepted as a desirable constituent of built synthetic organic detergent compositions. lt exerts a water softening It and appears to improve detergency of compositions containing synthetic organic detersive ingredients. lt retards the growth of fungi and helps make wash aesthetically more pleasing, as well as cleaner, causing it principles smell sweeter. Consequently, borax powders have been sold for addition to washing solutions and borax detergent compositions have been made by blending borax particles with other detergents or by drying fluid mixtures or pastes of borax and other detergents. Despite the need for an improved way of preparing dehydrated borax of these uses, before the present invention it was not known to expand solid particles of borax by dropping them through a relatively slowly upwardly rising heated gas so as to produce a final structurally stable borax product of desired dryness and low density. Nor was it known to decrepitate borax in such manner in an operation undertaken in conjunction with the preparation of other detergent product components.
The advantages of the invented process are many. Compared to prior art processes in which borax particles were entrained in a rapidly moving heated gas, which caused calcination, much less breakage of product results and less heat is needed, thereby raising the efficiency of the process ad decreasing expense. Also, the present process lends itself to use in many standard spray drying towers, thereby not requiring special apparatuses which cannot be made by rather simple modifications of existing equipment. In addition to economic and design advantages and to the obtaining of a product in better physical form, the present method also allows the puffing of the borax to be used as a control of density of the borax or a detergent incorporating borax particles. The gentle dehydration of the borax particles allows one to dispense with the need for complex dust collecting equipment, if the initial feed of borax particles contains no fines. lf fines are present, they may be removed from the borax feed initially, thereby saving the need for dust collecting equipment on the drying apparatus, or they may be charged to the dryer and any fine expanded particles resulting may be removed by dust collectors, which are already parts of conventional spray dryer installations. Of course, much of the fine material charged will be so much expanded by the present process that the particles produced will not be dusty.
Other advantages of the present process include allowing a single spray tower to be used for several types of products, those containing borax or other calcinable materials and those containing none of these. Thus, in a detergent plant, borax may be puffed in the same spray tower in which other detergent ingredients are being spray dried. By varying the feeds of borax to such a tower, the composition of the product can be changed or its density can be desirably controlled. The injection of the borax solid below the point of spraying of other constituents of the detergents increases the ca pacity of the crutchers and the drying tower, because it is not necessary to mix the borax with the other detergent ingredients in the crutcher. Furthermore, the process lends itself to the addition to detergent compositions of materials of stability insufficient to allow them to be blended with other ingredients in a crutcher. As examples of such materials may be mentioned sodium perborate and other oxygen-releasing compounds such as sodium percarbonate, sodium peracetate and potassium persulfate.
By means of this decrepitation process, utilizing equipment already on site in a detergent plant, different forms of borax may readily be made available for incorporation in detergent products of different desired characteristics. For example, where the highly hydrated form is wanted, no calcining will need to be effected but in fomulations where different degrees of hydration are required or where low density products are desirable, the hydrated borax in stock may readily be changed to other, more acceptable, less hydrated forms for these particular uses. Thus, it is only necessary to purchase and stock the borax of the highest degree of hydration desired and convert it to other forms, when needed.
ln accordance with the present invention, a method for expanding a hydrate or borax to produce a low density product comprises passing particles of borax hydrate downwardly through a slow moving countercurrent hot drying gas stream in a walled drying zone, so that the particles are heated by convection from the hot gas and by radiation from a wall of the zone, and are dehydrated, and removing from the zone dehydrated, puffed particles of low density. In a preferred embodiment of the invention, a particulate detergent composition is manufactured by spraying into an upper portion of a countercurrent spray tower or drying zone a liquid mixture of detergent components, and feeding into the spray tower or drying zone, at a point below the spray inlet, and where the sprayed detergent composition is in a virtually dry particulate form, particles of borax hydrate or other calcinable and puffable material to heat, dehydrate, and expand the borax hydrate and intimately to mix it with the other spray dried particles of detergent composition, to form a built detergent prod uct containing low density borax, and removing the built detergent product from the drying zone. In another embodiment of the invention, the rate of feed borax hydrate particles is varied or the location of the point of feed is changed to adjust the proportion of puffed borax and the extent of puffing of such product in the detergent composition, whereby the bulk density of the final detergent product containing borax is controllable to rigid density specifications.
The present invention, and the objects and advantages thereof will be understood by one of skill in the art from reference to the following description and the accompanying schematic drawing, in which:
FIG. 1 is a schematic partial vertical central sectional elevation of an apparatus for calcining hydrated borax; and
FIG. 2 is a schematic partial vertical central sectional elevation of an apparatus employed to practice a pre ferred method of the present invention, wherein the detergent composition containing puffed borax is produced, illustrating how final product density is controlled either by varying the feed of borax hydrate or by changing the extent of hydration of the borax.
In FIG. 1 a drying zone 11 in a tower 13 is heated by heater 15 on the external walls 17 of the tower, thereby conducting heat to the internal walls from which it radiates onto material within the drying zone. Purge air at a comparatively low temperature enters the drying zone at the bottom thereof through conduit 19 and passes through the drying zone and out exit conduit 21. During passage through the drying zone the purge air increases in moisture content and temperature. At the top of the drying zone is an inlet 23 through which borax hydrate 25 is dropped. During passage through the heated portion of and tower, the hydrate is reduced in moisture content and exits through outlet 24 as anhydrous borax or borax monohydrate, which drops into receptacle 29. The feed of borax to the drying zone is from a hopper 31 through a worm feeder 33. The rate of feed of borax is controllable by varying the speed of a drive motor 35 operatively connected with worm feed mechanism 33. The temperature of the drying zone is controllable by increasing or decreasing the amount of heat furnished to heaters 15 and regulating the flow of the purge air. Thus, the desired feed, air anad heating rates may be regulated to produce most economically the dried product wanted. By heating only the upper proportions of heater units 15, the dwell of particles in a heated zone can be diminished so as to decrease dehydration. Such dwell time can also be regulated by varying the speed of the purge air, the temperature of the heaters and the fineness of the borax hydrate feed crystals.
In FIG. 2 a detergent composition less borax, sodium perborate or other hydrated solid material that it is desired to dehydrate, is prepared as an aqueous suspension or paste in a crutcher or other suitable mixer 41 and is pumped via pump 43 and line 45 to spray head 47, from which it is sprayed into the interior of a spray towr 49. tower falling through the tower the spray 51 is dried to solid particles 53 by hot air entering the tower at inlet 57 and exiting through outlet 59. The hot air is usually produced by burning either fuel oil or gas in a burner, not illustrated. Solid hydrated borax or other non-crutchable solid material which can be dehydrated and expanded is fed by feeder means, such as the worm feeder 33, from hopper 61 through pipe 63 past valves 65 and 67 and through valve 69 into the drying zone 71 through inlet pipe 73. Another valve 75 and other inlets 77, 79 and 81 are provided to allow for feeding borax pentahydrate to any of several desired levels in the spray tower. Instead of plurality pluarlity of the valves with a single feeder, a plurality of controllable feeders may be utilized to regulate the rate and height of borax addition to the tower. Thus, the time of dwell of the borax hydrate particles in a heated area can be controlled by controlling the height at which they are fed into the spray tower. This also allows it to be assured that the particles fed to the tower do not contact wet detergent composition being sprayed, in those instances where it is important that the materials do not agglomerate. Of course, the degree of hydration of the borax can also be controlled by changing the temperature of the hot air being fed into the spray tower but lowering this temperature too much will have an adverse affect on the drying of the rest of the detergent composition.
The desired product, a blend of detergent composition and borax or other non-crutchable dehydrated constituent, is removed at 83 and is dropped onto a weighing belt 85, which supports a given volume of material. When the weight on the belt becomes excessive, indicating too high density of product, an electrical contact is made which opens a valve 87, which regulates the amount of feed of borax hydrate, in those instances where the dehydrated borax is lower in density than the detergent composition. Conversely, if the borax is heavier than the detergent composition, the excess weight on the weighing belt 85 will decrease the rate of feed of borax hydrate. Altenatively, when the belt indicates that product made is too light, the weigh belt can actuate valves 65, 67, 69 and 75, so as to feed the borax hydrate into the tower at a lower point to diminish dehydration and puffing and to increase its density. Such a modification has the advantage of making a product with a constant proportion of borax in it, rather than one in which the percentage of this builder salt varies. Of course, controllable feeders may be used instead of valve controls, to regulate borax hydrate additions.
Through exit 59 go cooled and moist drying gas and any dust particles of detergent composition or borax fines. Usually, little borax will go through duct 59, unless the solid material is exceedingly fine. However, due to the particle size distribution obtained by spraying crutcher mixes through fine orifices, which include many fine particles, dust collectors, not shown, will ordinarily be employed in communication with exit 59 to avoid discharging fine detergent powder into the atomsphere.
In carrying out the puffing of borax hydrate particles to convert them to the anhydrous or monohydrate form, as desired, the particle sizes of the borax fed to a decrepitation tower are those suitable for the particlar operation and use. As a general guide, applicable to most commercial detergent products on the retail market, the particle size resulting should be such that the expanded borax will pass through a 6 mesh sieve and over or substantially all will not pass through a 200 mesh sieve. Preferably, the particles will pass through an 8 mesh sieve and be deposited on a 140 mesh sieve. Most preferably, the particles will be within the 20 to mesh sieve range. Because the expanded particles are larger than those of the hydrate charged, the corresponding ranges for the borax hydrate to be expanded are adjusted downwardly, accordingly. Thus, the particles charged will usually be within the range of 20 to 200 mesh, perferably from 40 to 180 mesh and most preferably from 40 to mesh.
The extent of puffing may be adjusted by control of the temperature in the zone where the expansion takes place and by the dwell of the particles in that zone, for particles of given sizes. Also it is evident that faster expansion or greater relative puffing will be obtained with smaller particles than those of larger sizes, if the same temperature and time conditions prevail. Keeping in mind that such adjustments of conditions will be made to obtain the desired results, nevertheless, general ranges of such conditions may be given, which will produce particles of bulk density from about 0.1 to 0.8 times the bulk density of the borax hydrate charged, which will be 0.1 to 0.6 g./cc. The dwell of particles in a heated zone where they are being decrepitated will usually be for a period of time from as little as 0.1 to seconds, on the average, although it is preferred to maintain this time as short as possible, so as to effect a most efficient operation and obtain speediest throughput. The preferred dwell is form 0.2 to 5 seconds and most preferably, from 0.2 to 3 seconds. In such time, the particle will be inserted into the hot drying zone and will have fallen through it to a relatively cool collecting zone. To obtain the monohydrate or more highly hydrated form of the borax charged, one will usually hold the dwell in the heated zone to the lower portions of the ranges given and might begin with a more highly hydrated form of borax, such as the borax decahydrate. Conversely, when an anhydrous product is desired, the decrepitation time will normally be increased to the higher limits of the time ranges given and, if desired, the borax particles charged may be the lower hydrates.
The decrepitation zone will normally be operated under atmospheric pressure or at a very slight vacuum or pressure up to about 1 millimeter of mercury. At such conditions, the temperature of the gas in the decrepitation zone, usually air, sometimes containing products of fuel combustion, will be from about 120 to 600C, preferably from 140 to 300C. and most preferably from about 180 to 240C. At such temperatures, good control of puffing is obtainable and the particles resulting are usually structurally stronger than if other temperatures are employed. Furthermore, good production rates are obtainable. Unless the anhydrous form of the borax is desired, the dwell time of the particles in the decrepitation zone will be short enough so that the temperature of the particles themselves will not greatly exceed 100 of the C., at which temperature all the water of hydration will be removed. Of course, where there are particles of different sizes, it is possible that some of them may be completely dehydrated and others will be only partially dehydrated. It is recognized that although uniformity of hydration is desirable and is substantially obtainable by the method of this invention, mixtures of particles having an average degree of hydration within the range herein described are contemplated.
The internal temperature of the decrepitation or drying zone is obtained by regulation of the heat supplied, zone size, rate of feed of material to be dehydrated, its initial degreee of hydration, and passage of gas through the zone. The heat may be supplied by an external heating device, such as that illustrated in FIG. 1, whereby the zone walls radiate heat onto the particles and allow convection currents to carry heat from the walls to gas adjacent to the drying particles. If such a technique is applied, the zone wall should normally be heated to within the range of to 400C, preferably from 300 to 350C. The diameter of the zone will usually be from as little as 3 inches for laboratory and pilot plant equipment, to as much as 30 feet for production apparatuses. Usually, drying towers will have diameters of from 8 to 20 feet. Of course, the heat supplied to the walls of the drying zone will have to be at a sufficiently high temperature so that the radiation and convection resulting are sufficient to raise the temperatures of the paricles to be decrepitated to the levels indicated previously. To assist in the transfer of heat by convection, and to remove water from the decrepitation zone, it is usually desirable to employ a purge gas, which may be air, products of combustion or other suitable dry gas. Such gas will normally pass through the drying zone in an upward direction at a rate of from 0.05 to 5 feet per second, preferably from 0.1 to 2 feet per second. By regulation of the flow of this gas it is possible to control the dwell time of the borax particles to an extent.
if, instead of a heated wall of the drying zone, a heated drying gas is employed, use of a purging gas is unnecessary, although it may be employed and proportions thereof may be controlled, with respect to the drying gas used, to regulate the temperature of the zone. To an extent, such regulation will also control the speed of free fall of the particles. The temperature of the drying gas or the mixture of drying gas and diluting gas, if such is employed, should be held within the ranges given previously for the interior temperature of the drying zone.
As was mentioned previously, it is desired to maintain the borax particles in the puffing Zone for a comparatively short period of time. By employing high speed gas flow upwardly through the drying zone, the tendency would be for fines to be carried upwardly and out of the tower and for other particles to be held suspended, with the speed of the gas acting to a significant extent to nullify the forces of gravity. In the present invention wherein short dwell time in the decrepitation zone is desired, the upward flow of gas is at a comparatively slow rate, so that the force of gravity is largely determinative of the dwell of particles in the active dehydrating zone. Thus, the speed of the drying gas, which will usually be within the range of 0.05 to 5 feet per second and preferably less than 1 or 2 feet per second, has little effect on the free fall of the borax particles and allows rapid movement thereof through the dehydrating zone.
Tl-le relatively short stay of the borax particles in the dehydrating zone is important in maintaining the integrity of the particles because it limits the number of contacts these relatively fragile materials with other particles in the dehydrating zone. It also prevents much contact with the walls of the zone. Therefore, the product resulting is in effect, merely an enlarged form of that which was charged to the decrepitation zone and includes very little fine material. Even if fines are initially charged, they are enlarged by the decrepitation process and may become substantially unobjectionable. If some fines are produced, either due to initial charging of fines or to drying of other materials in the dehydrating zone, these may be removed in the exit gas by usual means, such as dust collectors, cyclone separators, spray washes or other suitable apparatuses.
THe practice of the invention is trouble-free and subject to simple controls to modify the characteristics of the product desired. Thus, as is illustrated in H6. 2,
which shows a preferred modification of the invention, the feed of the borax hydrate may be varied and the height at which it is fed into the tower or dehydrating zone may be changed, so as to obtain different dehydrating effects. Such changes may be controlled manually or by automatic equipment response to the density or other characteristics of the product made. The decrepitation method is highly efficient, inexpensive, readily controllable and produces an excellent product, which does not have to be further dried or modified to acquire desired preperties. The method lends itself to other modifications which make it useful in conjunction with ordinary spray drying processes. For example, in many detergent products it is desirable to include compounds which are not sufi'lciently heat-stable to permit ordinary spray drying. Such materials, for example, sodium perborate, organic dyes or desired by drates, can be sprayed into the decrepitation zone together with the solid borax particles and the decrepitating borax will furnish supports for the usually smaller quantities of the unstable material. Mixtures of borax and perborate, for example, may then be blended in with other ordinary spray dried detergent components. in such operations, by utilizing different heights of spray nozzles or borax addition points, as illustrated in FIG. 2, the drying process can be modified so as to obtain the most efficient drying and the greatest stability of the perborate or other decomposable material.
In a preferred embodiment of the invention, as is illustrated in FIG. 2, a detergent composition, less borax and less unstable materials, such as sodium perborate, is spray dried in a conventional countercurrent spray tower and below the dried particles the borax hydrate is added so that the decrepitation thereof occurs while the particles are falling, with the spray dried particles, through a slowly rising hot air current. The conditions employed, with respect to the borax particles are the same as those previously described. So are the temperatures and air flow rates in the lower portion of the drying zone, wherein decrepitation of the borax takes place. However, although it is usually desirable to employ similar conditions throughout the entire drying zone, in some instances it will be important to obtian higher temperatures to assist in drying aqueous solution-suspensions of detergent, which usually include larger proportions of water than are found in the borax hydrates, or else are otherwise more difficult to dry. In such instances, additional drying gas may be added to the drying zones above the borax inlets and the temperature of the gas may be higher. In such cases temperatures of the drying gas may be from 300 to 800C, although it is preferred to employ temperatures within the range of 500 to 600C. The spray nozzles employed and the spray pressures used are those known to the art, with the pressures normally being from 400 to 800 pounds per square inch, preferably from 500 to 700 pounds per square inch, and the particle sizes resulting from atomization being such as to produce particles mostly within the range of 12 to 100 mesh, preferably 20 to 100 mesh. Of course, some fines will be produced in spray drying because of the variety of particle sizes in the sprays created. The fines are usually collected form the exit gas by a dust collector or other suitable means, after which they may be fed back into the system. An advantage of the decrepitation of borax below the spray drying zone is in the curing which the release of small proportions of water in the decrepitation zone can exert on the dried detergent particles. The moisture content of such particles may be raised slightly and the subjection of the particles to the moisture at a relatively low temperature can assist in partial hydration thereof and can counteract a tendency of some such particles to develop tackiness upon subsequent exposure to a humid atmosphere. The moisture content of the spray dried detergent containing borax will usually be from about 3 to 10%, with the borax particles themselves containing from about 0 to 10% water of hydration. The proportion of borax in the detergent may be whatever is considered suitable for the intended purpose thereof but usually from 10 to 50%, preferably from 15 to 30% will be employed.
The detergent component of the spray dried material will generally be from 5 to 45%, preferably from 10 to 30% of a synthetic anionic or nonanionic detergent; l5 to preferably from 25 to 45% of a water soluble inorganic builder or filler salt; and the balance of adju vant materials. As examples of the adjuvants may be mentioned coloring agents, pigments, perfumes, colloidal anti-redeposition agents, thickeners, gums, dispersing agents, hydrotropes, wetting agents, corrosion in hibitors, conditioning agents, desiccants, bactericides, fungicides, enzymes, solvents, bleaching agents, oxidizing agents, catalysts, reductants, or other suitable materials to impart specific properties to the product.
The anionic synthetic organic detergents ar usually either sulfated or sulfonated compounds having lipophilic and hydrophilic portions thereon. They are generally used as water soluble salts, such as the alkali metal, alkaline earth metal, ammonoum, alkylamine or alkanolamine salts. The sulfated or sulfonated materi' als are usually either higher alkyl or higher alkyl aryl compounds, such as lauryl sulfate, tridecyl benzene sulfonate, palmityl sulfonate, or analogous phosphates or phosphonates. The alkyl groups are usually of 12 to 18 carbon atoms and the aryl group will ordinarily be benzene, although toluene and xylene coupounds may also be employed. The nonionic detergents are usually fairly long chain materials obtained by polymerization of iower alkylene oxides, such as ethylene oxide or propylene oxide, and termination of the chain with a hydroxyl group. As examples thereof there may be mentioned the block co-polymers of ethylene oxide and propylene oxide or polyoxyethylene ethanol, wherein the polymer is of 5 to 15 ethylene oxide groups. Also employed are those nonionics wherein the polyoxy lower alkylene chain is joined to an aryl or alkyl group, such as nonyl phenol polyoxyethylene ethanol and lauryl polyoxyethylene ethanol. Higher fatty esters and ethers thereof are also useful. Among the inorganic builder and filler salts are pentasodium tripolyphosphate, tetrasodium pyrophosphate, sodium sulphate, sodium carbonate, sodium bicarbonate, potassium tripolyphosphate, potassium orthophosphate, magnesium pyrophosphate and various equivalent acidic salts, hydrates and derivatives thereof.
The following example illustrate preferred embodiments of the present invention, utilizing apparatuses substantially as shown in the accompanying illustrations. IT is understood that the invention is not limited to the illustrated examples or to the drawings. Obviously, equivalents may be substituted and various modifications may be made without departing from the priciples of the invention.
EXAMPLE l One hundred parts of borax pentahydrate, Na B- O .5H O, sold commercially by American Potash Company as V Bor, are fed from a hopper into a heated tower of the design illustrated in FIG. 1, at the rate of 100 parts per minute. The particles being decrepitated in the tower are of sizes within the range of 16 mesh to 200 mesh, with about one-half the weight of particles passing a 60 mesh screen, and with about 2 /2% being finer than 200 mesh. The tower is at substantially atmospheric pressure and the internal temperature of the gas in the tower, heated by the external heaters, is from 130 to 160C. The air flow is an unforced natural venting flow upward at an average speed of 0.5 ft./second, with the air serving as a purge to remove water vapor from the tower and also, to an extent, helping to control the dwell time of the falling borax particles in the tower. No blowers are employed. The tower, whose walls are at a temperature of about 300C, heated by the gaseous products of combustion of fuel oil in air, is of a diameter of about 2 feet and a height of about feet, with the actual decrepitation zone height being about 6 feet. The dwell of the average particle of borax in the decrepitation zone is about 3 seconds.
The borax pentahydrate particles, in falling through the tower or decrepitation zone in an essentially free fall, are dehydrated and expand, so that the particles removed at the base of the tower are in a particle size range from to 100 mesh, mostly beng capable of passing through a 50 mesh screen. They are essentially anhydrous, although by lowering the temperature of the walls of the tower and decreasing dwell time in the tower, particles of monohydrate or other hydrates lower than the pentahydrate may be produced, as may be mixtures thereof. The density of the particles made is about 0.l3 g./cc., compared with the density of the particles charged, of 0.93 g./cc., measured as bulk density. The decrepitated particles are all larger than 200 mesh, and are more uniform in size.
The particles produced are more delicate than ordinary spray dried beads but are sufficiently strong to withstand breakage when processed in accordance with the method of this invention. The particles dissolve readily in water and the product is suitable for blending with other detergent ingredients in dry mixes, or it may be employed alone. The method described is economical and may be practiced in ordinary spray drying or.
crystallizing towers, thereby avoiding the need for the construction of special facilities. Furthermore, the process lends itself to use in factories where it is desired to use both anhydrous and hydrated forms of borax, either alone or in conjunction with the processing of detergent compositions.
EXAMPLE 2 Following essentially the same method as practiced in Example 1, but with the modification that the decrepitation zone is part of a spray drying tower employed to dry detergent mixtures, a combination of sprayed and decrepitated detergents is made. The apparatus employed is that shown in FIG. 2. The tower is heated by the products of fuel oil combustion in air, which raise the interior temperature of the tower to 400"C., hot enough to spray dry the detergent composition charged, which is a crutcher mix of 10% sodium lauryl benzene sulfonate, 18% pentasodium tripolyphosphate, 22% adjuvants, including hydrotrope, wetting agent, colloids, pigments, bactericides, and conditioning agents, and 50% water. One hundred parts per minute of such a crutcher mix are sprayed into the upper portion of the tower at a pressure of 600 lbs/sq. in. and a temperature of 60C. through spray nozzles that form particles mostly within the 12 to 100 mesh size range. Simultaneously with the spraying of the crutcher mix, 8 parts of borax pentahydrate are fed to the decrepitation zone of the tower, below the point where the spray dried beads are essentially dry. The regulation of feed rates results in a product having about 19% organic detergent, 35% tripolyphosphate, 10% anhydrous borax and 3% water, the balance being adjuvants.
Other than the internal temperature and the use of combustion gases as the gas feed to the tower, other conditions mentioned in when l are employed to give the desired decrepitated product. Of course, dwell in the tower is decreased with the gas temperature is high so that the borax will not'be converted to a form that has little physical strength. To accomplish this, the point of addition of the borax may be lowered so that it enters the tower through valve 75, when desired. Actually, the point of inlet of the borax will usually be near the bottom of the drying zone and the four inlets illustrated are all close to the bottom, in actual practice.
EXAMPLE 3 The procedure of Example 2 is followed with the exception that the 8 parts of borax pentahydrate are replaced with 5 parts and 2 parts sodium perborate, an unstable oxidizing agent. Both are admitted as solids, near the bottom of the tower, or the perborate is sprayed in there as an aqueous solution-suspension. Particle sizes approximate those given above and the resulting fortified oxidizing detergent composition is a good bleaching detergent.
Following the processes of either Example 2 or Example 3, when the weigh belt indicates that the density of the product is too high, an electrical impulse actuates valve 87 to increase borax feed (since the borax has a lower density than that of the detergent particles alone), whereby average product density is increased. The opposite procedure is followed when the density becomes too low. Where borax-detergent ratios are to be maintained constant, the electrical impulse from the weigh belt actuates valves 65, 67, 69 and to lower the effective point of addition of the borax and decrease average dwell time in the tower when density is too low and to raise the point of entry of the borax when the density exceeds that desired. This permits adjustment of the water content and the degree of expansion of the borax beads and adjusts the overall density of the detergent particles containing borax particles. Of course, both adjustments of height of addition and amount of addition of borax may be used together and the other conditions of operation of the spray tower and the decrepitation zone may be modified to permit the making of a product of the desired density.
What is claimed is:
1. A method for producing a non-stratifying, boraxcontaining detergent composition wherein the proportion of borax in the which comprises passing particles is from Ill-50% of feed hydrated borax having a particle size within the range of 20 to 200 mesh downwardly through a hot drying gas moving countercurrently at a speed of 0.05 to 5 ft./sec. in a drying zone defined by an enclosing wall, the temperature of said drying gas being from 120 to 600C, the pressure in said drying zone ranging from atmospheric to l m.m. of mercury vacuum, the dwell time of said borax particles in the drying zone being from 0.1 to seconds so that the temperature of the borax particles does not exceed 100C, whereby to produce a product borax particles having a moisture content of l to 10% and a bulk density about 0.1 to 0.8 times the bulk density of the feed borax particles, concurrently spraying into said drying zone a detergent slurry at a point above the point of introduction of the hydrated borax particles blending the spray dried particles of detergent composition with the particles of borax being decrepitated and removing the mixed detergent borax composition from the dehydrating zone.
2. A method according to claim 1 wherein the removed detergent-borax composition is tested for density and the ratio of borax hydrate to detergent mixture charged to the drying zone is changed to control the density of the detergent-borax composition being made.
3. A method according to claim 1 wherein the removed detergent-borax composition is tested for density and the point or points of introduction of the borax hydrate into the drying zone are changed to control the density of the borax particles produced and thereby control the density of the detergent-borax composition.
4. A method according to claim 2 wherein the means for testing density is a weigh belt and the deflection of the belt actuates means for adding borax hydrate particles to the dehydrating zone when the density is higher than desired and diminishes the feed rate of the borax hydrate when the density is lower than desired.
5. A method according to claim 3 wherin the means for testing density is a weigh belt and the deflection of the belt actuates means for adding borax particles to the dehydrating zone at a relatively high level when the density is too high and of adding such particles at a relatively low level when the density is too low.
6. A method to claim 1 wherein a detergent composition constituent that is not stable to spray drying conditions is added to the decrepitation zone with the borax hydrate.
7. A method according to claim 6 wherein the unstable constituent is sodium perborate.