US 2895916 A
Description (OCR text may contain errors)
July 2l, 1959 J. A. MlLENKr-:vlcH l-:T AL 2,895,916
` METHOD FOR PREPARING DETERGENT coMPosITroNs Filed May 15, 1956 wwwa,
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ATroRNEYs METHOD FOR PRfEPARlNG 'DETERGENT COMPOSITIONS Joseph A. Milenkevich and James Henium, Cincinnati, 1Ohio, assignors to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of `Ohio Application May 15, 1956, Serial No. 585,017
8 Claims. (Cl. 252 99) This invention relates toA a method for preparing deter-gent compositions.
More expressly, this invention relates to a method for preparing detergent compositions which are particularly useful in automatic dishwashing machines.
Detergent compositions comprising in combination an alkaline detergent salt (eg. sodium metasilicate), an alkaline condensed phosphate (e.g. sodium tripolyphosphate), and chlorinated trisodium phosphate have been suggested as having particular utility for dishwashing applications (U.S. Letters Patent 2,689,225). The formulation of such compositions, which are made up of agglomerates of the various ingredients, has heretofore been accomplished through the addition of aqueous silicate to a mechanical mixture of alkaline condensed phosphate and chlorinated trisodium phosphate.
It has now been observed that a composition prepared in this manner and packed in cardboard cartons is characterized by a tendency to cake during normal storage and to form a gum or gel in use. This latter characteristic isparticularly evident when such a composition is used in a dishwashing machine which has two wash cycles, i.e., two distinct intervals of operating time with a detergent present in the water. Machines of this type normally contain. two cups for holding a detergent composition, each of which automatically releases the detergent into the machine near the beginning of the successive wash cycles. With detergent compositions preparedaspointed out above, the detergent present in the cup adjusted to releasenear the beginning of the second wash` cycle usually becomes gummy and does not completely dischargefrom the detergent cupa condition which is objectionable for several apparent reasons.-
4It is an object of this invention to Vprovide a means `for preparing `detergent compositions suitable for dishwashing applications whichV are essentially free of the aforementioned undesirable characteristics. Other objects and advantages will be apparent from the following detailed description and accompanying drawing, which -is a comparison of the rate of hydration of'sodium t-ripolyphosphate in a particular detergent composition. when that composition is prepared in accordance with the process of the present invention and when the composition is prepared by prior methods;
Althoughwe do not wish to be bound by any theoreti- `V`cal considerations, vit is our belief that the undesirable United sans Paf-em o w 2,895,916 Patented July 21, 1959 ice thus gives rise to the above mentioned defects in the product.
We have now found a method whereby detergent compositions may be prepared which exhibit none of the `aforementioned undesirable characteristics although such compositions comprise the constituents set forth hereinphates of the calcium and magnesium ion sequestering characteristics ofthe aforementioned compositions preinhibits rapidhydration of the condensed phosphateand type whose Na2O/P2O5 ratios range from lvl to 1.67:1`. The term alkali metal silicate indicates those silicates having an average Si02/ alkali metal oxide ratio of about 2.0 to 3.4 and includes mixtures of silicates having dissimilar SiO2/ alkali metal `oxide ratios. The term chlorinated trisodium phosphate is used to designate a composition consisting of trisodium phosphate and sodium hypochlorite in intimate association in a crystalline form. The chlorinated trisodium phosphate may contain from 1% to 5% available chlorine and may be prepared by the methods of U.S. Letters Patent 1,555,474 or 1,965,- 304, or modifications thereof.
rPhe essence of our invention lies in the particular rsequence in which the various constituents of the detergent compositions are admixed. We have found that in order to obtain a composition comprising the aforementioned constituents which is characterized by resistance to caking on storage and formation of dicultly soluble gels in use, the particular sequence of steps herein described must be closely adhered to.
By way of illustration, a dishwashing composition comprising, by weight, 45 parts sodium tripolyphosphate, 32 parts of a 41% aqueous solution of sodium silicate having an average SiO2/Na20 ratio of about 2.9, and 20 parts chlorinated trisodium phosphate was prepared in accordance with the process of our invention in the following manner:
The sodium tripolyphosphate, in a substantially anhydrous condition, and at room temperature, was placed Iin a ribbon mixer wherein the sodium silicate in the form of a 41% aqueous solution, heated to a temperature of about 1GO-120 F. to control viscosity, was sprayed onto the phosphate while it was being agitated. The addition of the aqueous silicate caused hydration of the `tripolyphosphate to `take place with the evolution of heat. Consequently, in `order to maintain the phosphate-silicate mixture in a non-liquid condition, precautions were taken to prevent the temperature of the mix from rising above about F. (Above thistemperature, this mixture losses its discrete particle characteristicrand becomes pasty.) Following the addition of the entire amount `of silicate solution, the chlorinated trisodium phosphate was added and the entire mixture was then cooled to room temperature with continuous agitation. The resultant mixture was then allowed to age for about four hours. During this aging period, while hydration of the tripolyphosphate was proceeding to substantial completion, the mixture was intermittently stirred to prevent solidiication into a hard mass. After completion of the aging period, the agglomerates resulting from the foregoing process were reduced to the desired sizerfor subsequent packaging.
In connection with the theoretical considerations hereinbefore expressed, a comparison was made of the rate of hydration of the alkaline condensedphosphate in detertionand the second was prepared by rst mechanicallyV mixing the 4sodium tripolyphosphate and the chlorinated ytrisodium phosphate and then. spraying the aqueous sili, cate solution onto this mixture.
The rate'of hydration of the sodium tripolyphosphate in each Vof these mixtures,
as j depicted bythe curves ofthe drawing, was based upon the amount of the hexahydrate' of this phosphate present in the composition after certain periods of time as 'deter-V rnined by X-ray diffraction measurements.`
Itis apparent vfrom the drawing that the sodium tripoly# r phosphate in the detergent composition prepared in ac-v cordance with thefpres'ent' process hydrates at a much more'rapid rate Ythan'it does in the detergent'compo'sition 'prepared according' to prior methods.
Although our process has been described herein as a batch operation, it is to bev appreciated that it can also beV readily carried out as a semi-continuous or continuous operation. Moreover, phosphates other than tripolyphosphate, for example, tretrasodium pyrophosphate and Ythe higher phosphates, can berused to advantage. It is also to be appreciated that other silicates can be used, the average SiO2/ alkali metal oxide ratio of such silicates as we have found suitable being in the range from about 2.0 to about 3.4 and more preferably in the range from about 2.7 to about 2.9.V y I These silicates can be added inlour process in a number of diiferentways. They can be in drypowder form- ',this would call for the independent addition of water to hydrate the alkaline condensed phosphate-or they can be in aqueous solution-serving as the carrier for at least a portion of the water required for the desired hydration the phosphate. Alternatively, a portion of the silicate, normally in the form of an aqueous solution, can be added to the alkaline condensed phosphate prior to addition of the chlorinated phosphate with the remaining amount of silicate being added after the chlorinated phosphate addition. We have found that when observingV the precautions relative to moisture additionj as pointed out hereinafter, at least about 50% of the water which is to be added, whether such water is added independently or,
in combination in an aqueous silicate solution, should be added prior to addition of the chlorinated trisodium lphosphate if the benelits 'of our inventionV are to Vbe realized. In any fevent, the addition of the alkali-metal silicate prior to the chlorinated trisodium phosphate addition appears to promote the desired agglomeration of -the product constituents. i Y Y 'Regardless of whether the water is added `independently, as whenV the silicate is in the form of a dry powder,
Yor in combinaiton -iri an aqueous silicate solution, the addition of amounts of Water from about 12% to about 25% by weight of the nished product (exclusive of that water introduced with the chlorinated trisodium phosphate) find ready application in ourV process. However, the amount of water must be at least adequate in all cases to wet the condensed phosphate sufficiently to in- Iduce agglomeration of the constituents. VNormally, the total amountof water which We prefer to add, either independently or in combinaton in an aqueous silicate solution, is sufficient to theoretically completely hydrate'the condensed phosphate. The total amount ofwater added, however, shouldv not be in excess of that amount which will allow the condensed phosphate-silicate mixture to -maintain'its discrete particle characteristic.
l.; If desired, a non-ionic detergent, such as the Pluronics -(condensates.of.ethy1ene oxidewith afhydrophobic base i of a non-ionic detergent agent( Also, we have found that some additional benefits Yin formed by condensing propylene oxide with propylene glycol-marketed by Wyandotte Chemicals Corp.) or the Hyonics (e.g. fatty alkylolamides-'marketed by Nopco Chemical Co.) can be used in conjunction with the aforementioned constituents in a detergent composition. A1- though in our process the YpointY of addition of such nonionic detergent, normally in the form of an aqueous solution,"is`,`not critical, 'we have found 'indications that it aids in promoting agglomerationof the constituents and promotes, in general, further. improvements in the caking and gummiug "or`ge1ling characteristics of theproduct.
Detergent compositions which can be advantageously prepared our process comprise in combination from about% to about 60% alkaline condensed phosphate, from about 8% to about 20% alkali metal silicate as silicate solids, and from about 15% Vto about 30% of chlorinated trisodium phosphate with or without the addition product caking and gumming .orA gelling characteristics can'be'obtained by adding other ingredients to the deter,-V
gent composition prepared in accordance with our process. Additiveswhich we have found to be particularly advantageous Vfor these purposes Vinclude such endothermic,
rapidly dissolving salts as urea and potassium nitrate, hyi drated salts such'as hydrated ortho, pyro, and tripolyphosphate, and inertdiluents such assilica andtalc.
-In the, following examples,which are merely illustrative, Your invention being limited only by the scope of the appended claims; all p arts are byv weight.
Example I f; poured, atroom temperature, over the phosphates, while they were being agitated, during aperiod of about 3 minutes." During .this silicate addition, agglomerates ranging Vfrom the size ofY grains of sand to marbles formed, while the temperature of the mixture rose from 82 to 95 F.
These `agglomeratesrwere then aged in the mixer for about 15V minutes with periodicv agitation every two to three minutes. The temperature of the agglomerates rose to 113 l1:",during this aging period.
' The agglomerates were granulated in la low-speed hammer mill to pass a 10-mesh Tyler screen, and this product was immediately packed into cardboard cartons. "After two hours, the pouring characteristics of the product were noted. The product was then repacked in cardboard cartons, allowed to stand at room temperature for 24 hours, and 4the'po'uring characteristics were again -noted." n n A second detergent composition was prepared in ac- Vcordance' with the above procedure except that the sil- Yicate solution was Yadded'prior to theaddition of the chlorinated trisodium phosphate. During the silicate addition, the temperature in the mixer rose from 84 to 114"` F. and then dropped to 108 F. after a 15-minute aging period. 'Ihe pouring characteristics of the product were observed in the Ysame manner as above described.
It was observed from these pouring tests that the addition of' the silicate solution p rior to the addition of chlorinated trisodium phosphate resulted in a product having markedly/superior characteristics, especially with regard to resistance to caking'. 7
It has been pointed out hereinbefore that detergent compositions comprising an Valkaline condensed phosphate, anY alkali-metal silicate, and chlorinated trisodium phosphate, when prepared by adding aqueous silicate `to a mechanical mixture ofthe the phosphates, tend to -form a gum or gel in use and that Vthis characteristic is particularly evident when'such composition is used in a dishwashing machine having two -wash cycles.V vIn the followingexamples, a comparison is made of the gumming and/ or gelling tendencies of detergent compositions prepared by the above method and by the method of our invention. Since this characteristic can ybe appropriately evaluated through practical use in an automatic dishwasher utilizing twowarsh cycles, the data appearing in the subsequent examples were obtained through this medium.
The particular dishwashing machine used for the evaluations had two separate detergent cups, each having aV capacity of. about 20 cc., which were filled with the productto be tested. The machine cycle was as follows: First wash, second wash; first rinse; second rinse. During the first wash cycle, the detergent in one of the cups was washed out by the water action in the machine and was utilized in this Wash cycle. During this time, the detergent in the second cup was protected against Washing out but did come into contact with steam and sprayA during the first wash cycle. At the beginning of the second wash cycle, `the detergent in the second cup was made available to the water action in the machine and was washed out of the cup and utilized in this second Wash. Thedegree of gumming and/ or gelling Was determined by observing the proportionate amount of detergent retained by lthe second cup after each of the second wash, rst rinse, and second rinse cycles.
Example 2 The detergent compositions prepared in accordance with -the processes outlined in Example 1 after aging for two hours were used in a dishwasher of the type described above; The figuresk appearing in the table below Krepresent the proportionate amount of detergent retained in the second detergent cup after completion of It may be readily seen from the above data that the process of our invention results in a detergent product which has remarkably superior resistance to gumming or gelling.
Example 3 A number of detergent compositions, each comprising 45 parts by weight sodium tripolyphosphate, 32 parts by weight of a 41% aqueous solution of sodium silicate having an average SiO2/Na20 ratio of 2.9, and 20 parts by weight of chlorinated trisodium phosphate, were prepared according to the following general processes. In all cases, subsequent to the addition of the last product constituent, the products were aged for about 15 minutes during which time they were intermittently agitated, and the resultant agglomerates were reduced in size to pass a -mesh Tyler screen.
Sample A.-The sodium silicate, in the form of a 41% aqueous solution, was added to a mechanical mixture of the sodium tripolyphosphate and chlorinated trisodium phosphate.
Sample B.-The sodium silicate, in the form of a 41% aqueous solution, was added to the sodium tripolyphosphate prior to the addition thereto of the chlorinated trisodium phosphate.
Sample C.-90% of the total aqueous sodium silicate solution to be used was added to the tripolyphosphate prior to the addition thereto of the chlorinated trisodium phosphate. The remaining 10% of the silicate solution was added subsequent to the chlorinated trisodium phosphate addition. r
Sample D.-70% of the total aqueous sodium silicate solution was added prior to the chlorinated trisodium phosphate addition and the remaining 30% Was added subsequent to the chlorinated trisodium phosphate addition.
Each of the samples Vwas evaluated for gumming and gelling characteristics by means of the double cup dish- Washer test` described above, with the results indicated in the table below. All figures shown represent the 300 parts of substantially anhydrous sodium tripolyphosphate and 114 parts of sodium silicate having an average SiOz/NazO ratio of about 2.6 were placed in a paddle-type mixer and thoroughly mixed. 88 parts of water were then added to the phosphate-silicate mixture. To the resultant mixture, 133 parts of chlorinated trisodium phosphate and 20 parts of Pluronic L62 (a con.- qdensate of ethylene oxide with a hydrophobic base formed by condensing propylene oxide with propylene glycol, the composition having a molecular weight of 2500) were added and thoroughly mixed. The resultant mixture was allowed to age with intermittent agitation. The agglomerates formed during the foregoing process were reduced to the desired size` 'The product was evaluated for gumrning and gelling characteristics by means of the double cup dishwasher test described hereinbefore with the results indicated below:
These values, representing the proportionate amount of detergent contained in the second detergent cup, may be compared with the values obtained in the previous examples wherein the chlorinated trisodium phosphate was added before the silicate addition.
Having thus described our invention, We claim:
l. A process for preparing detergent compositions comprising a water-soluble alkaline condensed phosphate, a water-soluble alkali metal silicate, and chlorinated trisodium phosphate which comprises adding to a substantially anhydrous alkaline condensed phosphate an alkalimetal silicate having a SiOz/alka'li metal oxide ratio in the range from about 2.0 -to about 3.4, and `water in an amount at least adequate to wet the said condensed phosphate suiiiciently to induce agglomeration and insuicient to destroy the discrete particle characteristic of the condensed phosphate-silicate mixture, agitating the mixture while keeping the temperature from using above about F., then adding chlorinated trisodium phosphate to the said mixture, agitating the resultant mixture, aging the said resultant mixture to substantially complete hydration while intermittently agitating it and reducing the agglomerates formed to the desired size, the total amount of water added, exclusive of water introduced with the chlorinated trisodium phosphate, being from about 12% to about 25% by weight of the final detergent composition, whereby a composition characterized by resistance to caking on storage and formation of difficultly soluble gels during use is produced.
2. The process of claim 1, wherein the water and silicate are added in the form of an aqueous silicate solution.
3. 'Ihe process of claim 2, wherein the water-soluble ,.7 Y alkali'metal silicate is sodium ,silicatehayingjan average SiO2'/Na20 ratio of from about 2'.7-to about 2.19 1 j, i g 4I V@The process` ofY claim 2, wherein a' Vn on-ion-v1c TvsyntheticV detergent irs'radded to the anhydrous;alkaline',con
Y densed phosphate simultaneously with the aqueoussilicate Solution.' "l "1V ""Y'; 1*, 'ff f`ljr` The process of claim ,1, .Whereiu-the alkaline condensed phosphate issodium tripolyphosphate.,-Vfh Y. The process of claim 1 whereinvthre total amount of water to be added lis applied directly/to the `substantially anhydrous alkaline condensed phosphate. d 7. A process VforY preparing detergent jcompositions comprising a Waterfsoluble alkaline condensed phosphate, ,a Water-soluble alkali Ynietal silicate, and chlorinated trisodium phosphate which comprises adding to a substantially anhydrous alkaline condensed phosphate an aqueous solution Vof an alkali metal silicatehaving an average SiOz/alkali metalv oxide ratio inthe range from about 2.0 to about 3.4, the amount of said'silicate solution lcomprising at least 50%N of the total amount of silicate solution to'be added, the vtotal amount of moisture in said aqueous silicate solution being at least adequate to wet the fsaid condensed phosphate suiciently. to` induce agglomeration and insufficient todestroy the discrete particle characteristic of the resultant condensed phosphatesilicate mixture, agitating the mixture-While keeping'the temperature thereof from rising above about 130 F., then adding thereto chlorinated trisodium phosphate, agi'- -tating the mixture, then adding the balance of the 'said aqueous silicate solution While 4agitating'tltie mixture, the total amount of Water incorporated inthe said mixture by -the addition of aqueous silicate solution being from about 12% to about 25% by weight ofthe final deter- '.gent composition, aging the resultant mixture to substantially complete hydration while* intermittently agitating it, and thereafter reducing the'agglomeratesiformedlto the desired size, whereby a composition' characterized by resistance to caking on storage,andrtoformation.of
ous solutionof an valkali-metal Vsilicatehaving Va'nayera'ge SiOz/alkali-metal oxide ratioof from aboutl2.0fto about 3.4, .the rtotalamount'of moisture in said aqueous silicate solution being atleast-adequate to Wet the said condensed phosphatelsuciently Vto induce agglomeration and insurcient `to destroythe discrete particlefcharactc'ristic of the resultant condensed phosphate-silicatemxture, agitatng the mixture While keeping the,'temperaturey thereof :below about 120 F., the total Yamount offwater added `Abeing from about 12%,lto` about 25% byiweight of' the final detergentrcomposition', thereafter adding chlorinated trisodium phosphate,la`gitating the rmixture whilefcooling to room temperature, aging the "resultant` mixture. toV substantially completerhydration'while intermittently agitating it, and thereafterY reducingV thevagglomerates 4formed to the desired ,size whereb`y a composition characterized by resistance to Ycaking on storage and to formationV of difticultly soluble gels during' useis produced.
y' YRei'erences Cited in the file this patent vUNITED STATES PATENTS 2,034,361 Sutton Mar. 17, 1936 r2,324,302 Hull July 13, 1943 2,473,822 g kRobinson -g -..v June 2 1, 1949 2,524,394 Madorsky f... Oct.13, 1950 2,689,225 Anderson etal. Sept. 14, 1954 Mills et al. July 5, 1955