US3423321A

US3423321A - Detergent processes

Info

Publication number: US3423321A
Application number: US383479A
Authority: US
Inventors: Kenneth J Shaver
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1964-07-17
Filing date: 1964-07-17
Publication date: 1969-01-21
Anticipated expiration: 1986-01-21
Also published as: NL131792C; LU49100A1; DE1467637A1; BE667032A; NL6509189A

Description

Jan. 21, 1969 K. .1. SHAVER 3,423,321

DETERGENT PROCESSES Filed Jul-y 17, 1964 INVENTOR KENNETH J. SHA

ATTORNEY United States Patent Ofiice 3,423,321 Patented Jan. 21, 1969 3,423,321 DETERGENT PROCESSES Kenneth J. Shaver, St. Louis, Mo., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed July 17, 1964, Ser. No. 383,479 US. Cl. 252-135 Int. Cl. Clld 9/14 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to improved methods for manufacturing detergent compositions that contain hydrated sodium tripolyphosphate. More specifically, this invention relates to improved processes for manufacturing low bulk density detergent compositions that contain sodium tripolyphosphate hexahydrate, which processes do not include a spray-drying step.

In Belgium Patent No. 633,146 granted Dec. 2, 1963 (the disclosure of which is hereby incorporated into the present patent application by reference), processes for manufacturing relatively low \bulk density detergent compositions that contain sodium tripolyphosphate hexahydrate are disclosed. These processes precluded the necessity to manufacture low bulk density products via the well-known spray-drying procedure. The preferred processes of the invention detailed in said copending patent application irivolve, basically, reacting together sodium trimetaphosphate and an appropriate strong inorganic sodium cation-containing base (such as sodium hydroxide, sodium carbonate, or a sodium silicate having an SiO /Na O ratio less than 2, and the like) in a fluid aqueous slurry (containing more than suflicient water to hydrate all of the sodium tripolyphosphate ultimately present in the slurry, but preferably at least about 20 weight percent of water) to form crystalline sodium tripolyphosphate hexahydrate. Thus:

Na P Om 6H2O Na5P O o-6H2O sodium tripolyphosphate sodium tripolyphosphate hexahydrate It was discovered by the inventors of the invention in said copending patent application that a solid, porous product of relatively low bulk density is obtained if a substantial proportion (preferably, at least about one-third) of the sodium trimetaphosphate in the slurry is converted into sodium tripolyphosphate hexahydrate while the slurry is in a highly foamed condition (i.e., by means of a gas such as air, oxygen, nitrogen, carbon dioxide, steam, and the like being interspersed into the slurry either as a result of some of the Water in the slurry being converted into steam due to the heat of the trimetaphosphate conversion reaction or because the gas was injected into the slurry, or a combination of both of these methods). This step of these processes has, for obvious reasons, been termed the foaming-hydration step. In addition, enough free water has to be removed from the continuous aqueous phase of the slurry in these processes while the slurry is in the foamed condition to result in the loss by the slurry of its fluid properties. Thus the slurry is converted into a solid, porous product containing the desired sodium tripolyphosphate hexahydrate crystals and having a relatively low bulk density. In addition to being consumed by the sodium tripolyphosphate in the formation of the hexahydrate (as in step (1) of the above reaction), free water can be removed from the foamed slurry by evaporation due to the large amounts of heat evolved in the desired reaction, or by heating the foamed slurry externally; for example by infra-red lamps or hot tubes or pipes, or in a hot container; or by passing dry and/ or hot gases through the foamed slurry, as well as by many expedients which will be obvious to those skilled in the art in the light of the aforesaid disclosure. Still more of the free water can be removed from the resulting lighter density solid, porous product by subjecting said product to an additional drying step in, for example, a rotary drying oven, a pan drying oven, or a fluidized bed dryer after it no longer demonstrates any fluid (slurry) properties.

While detergent products having relatively low bulk densities and excellent overall properties can be manufactured without being spray-dried in accordance with the above-described preferred processes of the invention disclosed in said copending patent application, products resulting from such processes for some unexplained reason often lack uniformity both in density and in particle size distribution. In addition, the +-mesh particles result ing from such processes are often more frangible (or more subject to breakage during normal handling and shipping) than is usually desired in commercial detergent products. These shortcomings are also of considerably more concern when the detergent active material is largely nonionic in character.

It is a major object of the present invention to provide an improvement in the above-described processes for manufacturing lig-ht density detergent products without the necessity for a spray-drying step, which improvement makes it possible to manufacture products having more uniform bulk density, as well as excellent frangibility qualities and better particle size distribution.

This object, as well as others which will become apparent from the following discussion and claims, can be accomplished by incorporating into the slurry, prior to the so-called foaming-hydration step, an effective amount of crystalline sodium tripolyphosphate hexahydrate. Still further improvement in these properties; particularly when fairly large amounts of nonionic surfactants are present in the slurries; can be achieved by using an effective amount of a lower molecular weight alkali metal aromatic sulfonate compound having the structure VSO M gen and alkyl radicals containing from 1 to 6 carbon atoms, R is selected from the group consisting of hydrogen and alkyl radicals containing from 1 to 2 carbon atoms, and M is an alkali metal cation.

For a more thorough understanding of the overall processes of this invention, reference is now made to the drawing. The drawing illustrates one of the preferred detergent processes of the invention disclosed in said copending United States patent application, of which processes the present invention represents a significant improvement. Into a typical detergent crutcher 1, fitted with an efiicient stirrer 3 and a jacket 5 through which steam or hot or cold water can be circulated by means of lines 7 and 8, are charged (all parts being by weight) 355 parts of water, 782 parts of sodium trimetaphosphate, 14 parts of sodium carboxymethylcellulose, 258 parts of sodium dodecylbenzene sulfonate, and 191 parts of aqueous sodium silicate (47% solids) having an SiO /Na O ratio of 2.40, 30 parts of lauryl monoisopropanolamide. The resulting precursor slurry is stirred for about minutes during which steam is passed through jacket 5 in order to increase the temperature of the precursor slurry to about 85 C. The hot slurry is then pumped through lines 9 and 11 to a conventional vacuum type deaerator 13. Deaerated slurry then passes through

lines

15 and 17, through slurry pump 19, and line 21 to an efficient blender 31 (in this instance line 21 leads to the inlet port of a conventional centrifugal pump). During its passage through line 21 the slurry is monitored by means of a flow meter and a density meter 27. While the precursor slurry is being pumped through line 21, a 50 weight percent aqueous solution of sodium hydroxide is pumped from the caustic storage tank 33 through line 35 and caustic metering pump 37 to heat exchanger 39 where its temperature is increased to about 70 C. From there it is pumped through line 41 into the same entry port of blender 31 as that into which the precursor slurry is being introduced. The speed of caustic metering pump 37 is adjusted (depending upon the data from flow meter 25 and density meter 27) so that for every 100 parts by weight of precursor slurry there are introduced into blender 31, 24.5 parts by weight of NaOH. This is approximately the stoichiometric amount of NaOH required to convert the sodium trimetaphosphate in the precursor slurry into sodium tripolyphosphate. Within less than a second, the NaOH is well blended with the precursor slurry in blender 31 due to the extremely violent agitation of the mixture achieved in the blender. The resulting final slurry is withdrawn from blender 31 through pipe 43 in which the final slurry remains for only a few seconds. From pipe 43, the final slurry 49 is poured onto one end of an endless stainless steel belt 45. At this point the slurry is still fluid, and at a temperature of about 95 C. Within the next several seconds the temperature of the final slurry is observed to increase to about 105 C. (due largely to the reaction of trimetaphosphate with NaOH), at which point the slurry appears to expand internally, forming a light density foam 47. Steam is observed escaping from the surface of the foam as it moves along belt 45. At the same time, the foam becomes gradually solidified into a hot granulated detergent mass 51. The temperature of the foamed material on belt 45 is maintained above about 100 C. for several minutes after the foam has been converted into the solidified detergent composition by means of a cover 53 over the belt as well as by steam-heating the underside of the belt. After about 8 minutes on belt 45, the granulated product 51 is gently wiped by a series of rotating stainless steel wires 55 in order to break up any soft agglomerated lumps, and then transferred via ramp 57 to transfer belt 59. From there it is dropped onto a vibrating screen 61 to break up any remaining agglomerates. At this point the detergent product contains about 12 weight percent of free water and 13 weight percent of combined (hydration) water in the form of sodium tripolyphosphate hexahydrate. This product is then passed through a conventional fluidized bed dryer 63 to remove almost all of the free water, and from there into product storage bin 65.

In accordance with the present invention, the sodium tripolyphosphate hexahydrate crystals that are incorporated into the detergent slurries can be intermixed with the water, sodium trimetaphosphate, and other ingredients that may be utilized in the formulation of the desired detergent composition can apparently be incorporated into the slurry in practically any particular manner desired. Apparently the only significant limitation in this respect is that the hexahydrate crystals be incorporated into the slurry prior to the foaming-hydration step of the preferred detergent process described above (i.e., prior to that point in the process wherein a significant proportion of the sodium trimetaphosphate is converted to sodium tripolyphosphate hexahydrate while the slurry is in the foamed condition). Thus, the hexahydrate crystals can be intermixed with any one of the slurry ingredients (or a combination of any of the slurry ingredients) that are to be blended into the slurry prior to the foaminghydration step. They can be added separately to the slurry, if desired, in a relatively pure form, or even initially in the form of anhydrous Form I or Form II sodium tripolyphosphate (in which case the tripolyphosphate is permitted to hydrate prior to the critical foaming-hydration step). Still another way in which the desired sodium tripolyphosphate hexahydrate crystals can be incorporated into the detergent slurry in accordance with the improved processes of this invention is via the in situ conversion of some of the sodium trimetaphosphate in the slurry prior to the foaming-hydration step; for example, by adding less than the stoichiometric amount of strong base required to react with all of the sodium trimetaphosphate in the slurry sutficiently prior to the foaming-hydration step so that the desired amount of sodium tripolyphosphate crystals are formed in the slurry prior to the foaming-hydration step, or by permitting a certain amount of the trimetaphosphate reaction with strong base to occur before the light density foam is formed. Note that the desired results can be obtained when sodium tripolyphosphate crystals are intermixed into the slurry even when the slurry is in the foamed condition, provided that the trimetaphosphate conversion reaction in the foam has not yet been initiated.

While even very small amounts of sodium tripolyphosphate crystals (for example, as little as 1 weight percent, or even less) can be utilized advantageously in the practice of the present invention, generally, for best results, from about 3 to about 50, and preferably from about 5 to about 15 weight percent, based upon the total amount of sodium trimetaphosphate used in the detergent slurries should be used. While the size of these sodium tripolyphosphate crystals is not critical with respect to the successful practice of the present invention, it is preferred that they be small enough to pass through as mesh US. Standard screen.

The advantages that can result from practicing this aspect of the present invention can perhaps best be illustrated via the following preferred embodiment thereof.

Example I Into a conventional stainless steel mixing vessel which is fitted with a conventional paddle-type stirrer and jacketed so that either hot or cold water or steam can be used in the jacket, are charged 2,200 parts of water, 900 parts of sodium dodecylbenzene sulfonate, 600 parts of sodium lauryl sulfate, 1,000 parts of sodium sulfate, 2,940 parts of sodium trimetaphosphate, parts of powdered 100 mesh) sodium tripolyphosphate hexahydrate, 1,140 parts of sodium silicate (47% solids) having an SiO Na O ratio of 2.40 and 55 parts of detergent grade sodium carboxymethylcellulose. The resulting precursor slurry is stirred for about 10 minutes, during which time the temperature of the slurry is raised to 80 C. by circulating steam through the mixer jacket.

Into the hot precursor slurry which is being moderately agitated is then quickly poured 1,590 parts of a 50% aqueous sodium hydroxide solution. After about 45 seconds of moderate agitation, during which the sodium hydroxide is blended well with the precursor slurry, the temperature of the slurry begins to rise. The agitation is halted just before the temperature of the slurry reaches 100 C. When the slurry temperature reaches about 103 C., the slurry begins to expand in volume, rising in the mixing vessel, so that the volume of the foamed slurry becomes at least about 2-8 times that of the unaerated precursor slurry. Steam begins to escape from the bubbling mass, and it hardens quickly, to a particulated, seemingly wet, softmass. Within a few minutes, no more steam is evolved from the solidified reaction mass, and its volume decreases slightly while it is cooled to room temperature. At this point it contains about 30 weight percent of water (of which about 12.7% is considered free water) and about 92% of the theoretical equivalent (based on the amount of sodium trimetaphopshate charged into the precursor slurry) of sodium tripolyphosphate, which is substantially all present in the form of the hexahydrate. After being air-dried overnight to remove most of the excess free water, the final detergent product is free flowing, noncaking, essentially non-hygroscopic, has a bulk density of about 0.35, and contains about 57 weight percent of sodium tripolyphosphate hexahydrate. Its particle size distribution, and frangibility, are tabulated in Table 1, below. In Table 1 is also tabulated particle size distribution for a product made via a procedure practically identical to that of Example I, above, using similar raw materials, except that no sodium tripolyphosphate hexahydrate crystals were added to the slurry prior to the foaming-hydration step. The material made without the hexahydrate crystals is termed the control in Table 1.

TABLE 1.-PROPERTIES OF AIR-DRIED DETERGENT COMPOSITIONS Detergent Retained on Screen 2 Property Tested Control Example I 1 U.S. Standard screen sizes.

2 In terms of weight percent of the total product.

3 Amount passed through 100 mesh U.S. Standard screen.

Data for the Frangibility test in the present tables is derived as follows:

One hundred grams of the air-dried product of the particular detergent composition being tested are placed on a 100 mesh US. Standard screen, along with three oneinch rubber balls. The sample and rubber balls are then shaken by means of a Ro-Tap sieve shaking machine for 30 minutes. At the end of this time the amount of detergent product that has passed through the 100 mesh screen is weighed. Most of the material which passes through the screen results from the breaking down of the original agglomerated detergent particles due to the pounding of the rubber balls. The weight in grams of material which passes through the 100 mesh screen is given as percent dust in the tables. The detergent pro ducts having relatively higher percent dust in the tables are more frangible (more easily broken down to produce irritating dust on handling, etc.) than are those that have relatively lower percent dust in the frangibility test. Note that the product in Table 1 which demonstrates the greater resistance to friation is that made according to the instant invention.

The data in Table 1 illustrate both the significant improvement in particle size distribution and the frangibility of the detergent products that can result from use of the sodium tripolyphosphate hexahydrate crystals in accordance with this aspect of the present invention. Note that +10 mesh and 100 mesh material is generally considered undesirable for detergent products, with the dusty 100 mesh material being the least desirable. Another unexpected advantage of such use of hexahydrate crystals is that the particle size distribution is more uniform (when the process is repeated, for example, under what are apparently identical conditions) from batch to batch or over an extended continuous run with a given detergent formulation than was heretofore believed possible.

Still another surprising advantage resulting from use of sodium tripolyphosphate hexahydrate crystals in accordance with the processes of this invention relates to the rate of conversion of the sodium trime-taphosphate to sodium tripolyphosphate hexahydrate. Thus, under practically identical process conditions (except when extremely prolonged reaction times are utilized), the proportion of unconverted trimetaphosphate that appears in the final detergent product when hexahydrate crystals are utilized (as in the present processes), as compared to the amount initially charged into the slurry, is significantly lower than when hexahydrate crystals are not used. Thus, only about 2% of unreacted trimetaphosphate remains in the product from Example I, above, while more than 7% unreacted trimetaphosphate is present in the so-called control material.

It has also been discovered that the physical properties described above (particle size distribution, frangibili ty, and production uniformity and reproducibility) of the detergent products that can be made via the light density without spray-drying techniques outlined above can be still further improved by the incorporation into the detergent slurry, prior to the foaming-hydration" step, of a lower molecular weight aromatic sulfonate compound having the structure SO M wherein R is selected from the group consisting of hydrogen and alkyl radicals containing from 1 to 6 carbon atoms, R is selected from the group consisting of hydrogen and alkyl radicals containing from 1 to 2 carbon atoms, and M is either an alkali metal cation or an ammonium cation. R, for example, can be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl, isoamyl, hexyl, isohexyl, 1,1-dimethyl butyl, 1,2-dimethyl butyl, and the like, which R can be hydrogen, methyl, or ethyl. Typical examples of the lower molecular sulfate compounds of structure (I), above, include benzene sulfonates, toluene sulfonates, xylene sulfonates, 3-ethylbenzene sulfonates, cumene sulfonate, Z-t-butylbenzene sulfonates, 3-n-hexylbenzene sulfonates, and the like. M can be ammonium, sodium, potassium, lithium, rubidium or cesium, but is preferably either ammonium, sodium, or potassium. Of these, because of its cost advantage and its general availability, as well as other considerations, sodium is still further preferred. The lower molecular weight aromatic sulfonate compounds that appear to perform most advantageously in the processes of the present invention are sodium benzene sulfonate, sodium toluene sulfonate, and sodium xylene sulfonate. No logical reasons can be offered as to how or why these lower molecular weight aromatic sulfonate compounds have the surprising eifect that they do on the granulated detergent products. These effects are readily observable, however, and will apparently result no matter in what particular manipulative manner the aromatic sulfonate material is introduced into the slurry, so long as it is reasonably well dispersed or dissolved therein prior to the foaminghydration step of the process.

While some advantages will accrue to those who practice the present invention even when very small amounts, for example, about 1 weight percent, of one or more of the above-described aromatic sulfonates is utilized, generally significantly more uniform, less friable products having better granularity will result when at least about 3 weight percent of the lower molecular weight aromatic sulfonate material is used in the process. Optimum results can apparently be achieved when from about 4 to about 12 weight percent, based on the weight of detergent solids (non-volatile at about 105 C.) of one or more aromatic sulfonates is used in the slurry. Although as much as 30 weight percent or more of the aromatic sulfonate material can be used without any apparently detrimental effect on the processes of the present invention, generally no additional advantages can be observed when more than about 15 weight percent is utilized in the present processes, although it is generally better to use higher levels of aromatic sulfonate material when the organic detergent active material in the detergent composition is a nonionic one, as compared to those instances in which the organic detergent active portion of the formulation is mainly anionic in nature.

Although no theoretical explanation can be given for the phenomenon, it is of significant import that while substantial benefits can be obtained (with respect to the properties, described hereinbefore, of the detergent products resulting from the processes of this invention) by using the sodium tripolyphosphate hexahydrate crystals (as detailed above) in the absence of any of the lower molecular Weight aromatic sulfonates, the reverse is apparently not true. That is, the advantages described hereinbefore have not been observed in products made using one of the aromatic sulfonate materials, but in the absence of sodium tripolyphosphate hexahydrate crystals (prior to the foaming-hydration step of the processes).

Example II Example I is repeated, except that, instead of the 125 parts of sodium tripolyphosphate hexahydrate crystals, 250 parts of a mixture containing 50 weight percent of powdered (-100 mesh) sodium toluene sulfonate and 50 weight percent of powdered (100 mesh) sodium tripolyphosphate hexahydrate crystals is used. Data comparing the properties of the resulting product with that of Example I, above, can be found in Table 2, below.

TABLE 2.EFFECT OF AROIVATIC SULFONATE Property Tested Product From Product From Example I Example II Screen Size:

+10 mesh l7. 4 2. 1 -10, +20 1nesh. 25.2 8. 6 20, +40 mesh. 38. 3 66. 7 -40, +100 mesh. 13.0 21. 4 -l mes 5. 8 3. 2

Example III Example I is repeated, except that only 1800 parts of water and only 100 parts of sodium lauryl sulfate are used, and 500 parts of a condensation product of 12 moles of ethylene oxide with one mole of n-dodecylphenol are utilized in place of the sodium dodecylbenzene sulfonate. The resulting particulated product (after being airdried overnight) contains only about 13 weight percent of mesh particles, and only about 2 weight percent of -100 mesh particles.

By comparison, in a practically identical experiment,

8 except that in this instance no sodium tripolyphosphate hexahydrate crystals are utilized, the final, particulated (air-dried) detergent product consists mostly (more than 60' weight percent) of +l0-mesh particles.

Still further imrovement in the overall granularity of largely or totally nonionic-type detergent products can be observed in the presence of one or more of the abovedescribed lower molecular weight aromatic sulfonate compounds (in addition to the remainder of the formulation) in appropriately effective amounts.

What is claimed is:

1. In a process for manufacturing a detergent composition containing sodium tripolyphosphate hexahydrate, which process comprises the steps of (a) interspersing a gas in a fluid aqueous slurry to thereby form a foam; said slurry having a solid dispersed phase comprising sodium trimetaphosphate; (b) simultaneously, maintaining said foam at a temperature below about 135 C. and coverting a substantial proportion of said sodium trimetaphosphate to sodium tripolyphosphate hexahydrate; and removing sufiicient free water from the continuous aqueous phase of said foam to produce a solid porous product containing said sodium tripolyphosphate hexahydrate; the improvement which comprises incorporating into said slurry prior to step (b) at least about 1 percent, based on the weight of said slurry, of crystals of sodium tripolyphosphate hexahydrate.

2. An improved process as in claim 1, wherein the amount of said crystals of sodium tripolyphosphate hexahydrate incorporated into said slurry prior to said step is between about 3 and about 50 weight percent of the weight of said sodium trimetaphosphate in said slurry.

3. An improved process as in claim 2, wherein said crystals of sodium tripolyphosphate hexahydrate are produced by reaction of sodium trimetaphosphate with a strong sodium cation-containing base in the presence of free water.

4. An improved process as in claim 2, wherein said slurry additionally contains from about 1 to about 30 weight percent, on a detergent solids basis, of a lower molecular weight aromatic sulfonate compound having the structure wherein R is selected from the group consisting of hydrogen and alkyl radicals containing from 1 to 6 carbon atoms, R is selected from the group consisting of hydrogen and alkyl radicals containing from 1 to 2 carbon atoms, and. M is an alkali metal cation.

5. In a process for manufacturing a porous, particulated solid detergent composition containing sodium tripolyphosphate hexahydrate without the. necessity for a spray-drying step, which process comprises the steps of (a) intermixing Water and sodium trimetaphosphate to thereby form a fluid aqueous slurry containing at least about 10 weight percent of sodium trimetaphosphate, (b) adjusting the temperature of at least a portion of said slurry to between about 60 C. and about C., (c) intermixing into said portion an aqueous solution containing between about 1.4 and about 6 moles of sodium hydroxide per mole of said sodium trimetaphosphate in said portion to thereby form a blend, (d) allowing the heat of conversion of said sodium trimetaphosphate to sodium tripolyphosphate to convert part of the water in said blend to steam to thereby convert said portion into a light density foam, and (e) removing sufficient water from said portion while said portion is in the foamed condition to thereby convert said portion into said porous, particulated solid detergent composition; the improvement which comprises intermixing into said slurry, prior to the time said blend is formed, from about 3 to about 50 weight percent, based on the weight of said slurry, of

crystalline, particulated sodium tripolyphosphate hexahydrate.

6. An improved process as in claim 5, wherein said slurry additionally contains from about 3 to 15 weight percent, on a detergent solids basis, of a lower molecular weight aromatic sulfonate compound having the structure is sodium benzene sulfonate.

9. An improved process as in claim 6, wherein said lower molecular weight aromatic sulfonate compound is sodium toluene sulfonate.

10. An improved process as in claim 6, wherein said lower molecular weight aromatic sulfonate compound is sodium xylene sulfonate.

11. An improved process as in claim 6, wherein said lower molecular weight aromatic sulfonate compound is sodium cumene sulfonate.

References Cited UNITED STATES PATENTS 2,920,939 1/1960 Edward 23106 2,622,068 12/1952 Hizer 252138 2,365,190 12/1944 Hatch 252 3,232,880 4/1961 Mausner 252135 FOREIGN PATENTS 622,142 3/1963 Belgium. 633,146 12/1963 Belgium.

OTHER REFERENCES Derwent Belgium Patent Report 10/63 Pl (General Inorganic) Mar. 15, 1963, Rochdale House, Theobalds Road, London, W.C.1.

LEON D. ROSDOL, Primary Examiner. B. BETTS, Assistant Examiner.

US. Cl. X.R.