US3329615A - Tableted detergent and detergentbleach compositions comprising alkyl orthophosphate salts - Google Patents

Description

United States Patent 3,329,615 TABLETED DETERGENT AND DETERGENT- BLEACH COMPOSITIONS COMPRISING AL- KYL ORTHOPHOSPHATE SALTS Robert S. Cooper, Park Forest, and Allen D. Urfer, De-

catur, Ill., assignors to Staufier Chemical Company,

New York, N.Y., a corporation of Delaware No Drawing. Filed July 23, 1964, Ser. No. 384,794

. 1 Claim. (Cl. 252-99) This invention relates to tableted cleaning compositions comprising water soluble alkyl orthophosphate salts and a method of producing the same.

Today, tableted cleaning compositions are familiar articles in the marketplace; among their advantages are obviation of the need for measuring cups and elimination of the usual spillage problems encountered with granular cleaning compositions. In the manufacture of tableted cleaning compositions by compression of dry particulate compositions two principal methods have evolved: the first, and by far the more frequently used, comprises tableting at high pressure a cleaning composition comprising at least one hydratable compound (usually an inorganic salt of a phosphorous acid) and thereafter hydrating this hydratable compound to increase surface strength and abrasion resistance of the tablets. The second method involves adding certain binding agents, e.g., talc and starch, and water to the cleaning composition before tableting to improve cohesion in the final tablet. Although these methods have been successful in the past, they have inherent disadvantages and limitations which will be explained more fully hereinafter.

Most cleaning compositions, and in particular heavy duty detergent compositions comprising alkyl aryl sulfonates, show a tendency to stick to die surfaces when the same are used to compress the composition into tablet form. Where significant amounts of water are added to, or present in, the compositions before tableting, sticking becomes even more pronounced. In some instances it is necessary to include water in the cleaning composition before tableting to insure that the tablets will have adequate strength. Sticking, of course, causes breakage of tablets when the dies are separated, as well as mottling of tablet surfaces. On the other hand, the addition of water to finished tablets to increase the strength thereof tends to decrease the rate at which the tablets will disintegrate in water. Also, the addition of water or a surface active agent to a cleaning composition comprising a bleaching agent either before or after tableting, can severely diminish the activity of the bleach. It is therefore selfevident that many tableted cleaning compositions should contain as little water as possible commensurate with high strength and rapid distintegration properties. Binding agents, such as talc and starch, which are presently used in some hard surface cleaners, tend to diminish sticking and reduce the amount of water necessary to obtain tablets with acceptable physical properties. Unfortunately, the binders used heretofore generally do not contribute to the detergent or building properties of the cleaning compositions and/or are not totally water soluble. Tablets containing such binders produce turbid solutions which are unsuitable for the laundering of clothes and the like. In laundering operations insolubles are obviously difficult to rinse out of clothing.

It is an object of this invention to provide a process for producing detergent and detergent-bleach composi- ICC tions which may be tableted to yield tablets of high quality and strength and having a rapid rate of disintegration in water.

It is another object of this invention to furnish tableted compositions comprising inorganic bleaching agents togetlliler with surface active materials compatible therewit It is still another object of this invention to furnish a process for producing tableted detergent and detergent bleach compositions comprising novel binding agents which are totally water soluble.

It is still a further object of this invention to furnish tableted detergent and detergent bleach compositions containing surface active compounds which provide binding action for said compositions.

It is yet another object of this invention to furnish home and commercial cleaning com-positions comprising bleaching agents together with compatible surface active compounds.

Other objects will become apparent as the disclosure proceeds.

We have now discovered that certain monoand dialkyl orthophosphate salts may be included in tableted cleaning compositions to yield tablets having high strength and good disintegration properties and which do not stick to dies during formation. A number of important advantages follow from using the alkyl orthophosphate salts: for example, their use will substantially reduce or obviate entirely the need for'water or other binders in producing firm, non-flaking tablets. Unlike most of the well-known prior art synthetic detergents, such as sodium lauryl sulfate and sodium dodecyl benzene sulfonate, the monoand diakyl orthophosphates of the invention (some of which are excellent detergents) are highly compatible with chlorine bleaching agents. Some further advantages of using the alkyl orthophosphate salts include a more rapid rate of disintegration of tablets and high degree of pourability of the cleaning composition prior to tableting. Regarding the latter, cleaning compositions comprising the alkyl aryl sulfonates of the prior art often will not flow freely through feed hoppers and the like prior to tableting.

The alkyl orthophosphates suitable for use according to the present invention are the water soluble salts of monoand dialkyl orthophosphates in which the organic portion of the molecule comprises a total of between 6 and 26 carbon atoms per molecule. It is common in the art to speak of detergent compounds in terms of their salts and it is well known that salts of various detergents may be prepared by reacting the corresponding acid material with sodium, lithium, or potassium hydroxide or carbonate. Although the alkali metal salts of the orthophosphates of the invention are preferred, ammonium and amine salts are also useful. All of the aforementioned compounds are waxy, water soluble solids which impart a high degree of binding action when added to dry particulate composition. A group of alkyl orthophosphates which are preferred for use in the present invention are those in which the alkyl group contains a total of between 18 apd 22 carbon atoms, for example, sodium 2-ethylhexyl decyl orthophosphate, sodium dinonyl orthophosphate, potassium di(n-decyl)orthophosphate, sodium didecyl orthophosphate, sodium methyl eicosyl orthophosphate. These preferred compounds all have excellent detergent properties and thus serve the dual purpose of binding the tableted composition and enhancing its detergent action.

The cleaning compositions of the present invention may be divided into two principal categories: (a) those which contain no chlorine bleaching agents and (b) those which do contain chlorine bleaches. Where used herein the expression detergent tablets refers generally to bleach-free tablets such as those used for laundry detergents, suds boosters, and hard surface cleaners. In its broadest sense, the term may include tablets which contain little or no detergent (surfactant). Likewise, the expression detergent-bleach tablets refers to those cleaning compositions which contain chlorine bleaching agents, and in a broad sense will include tablets which contain little or no surfactant. The alkyl orthophosphates of the invention are suitable for use in both detergent and detergent-bleach tablets.

The alkyl orthophosphate salts disclosed herein are useful in the preparation of tableted compositions containing any of the standard cleaning ingredients known heretofore in this art. Principal among the necessary detergent tablet ingredients are the surfactant and builder. The popular known builders are the alkali metal metaphosphates, pyrophosphates, and triphosphates, all of which will be referred to herein generically as condensed phosphates. Typical examples of widely used condensed phosphate builders are sodium tripolyphosphate, tetrasodium pyrophosphate, and tetrapotassium pyrophosphate. The surfactant may be any of the known synthetic anionic detergents such as the alkyl aryl sulfonates or the nonionic detergents such as those containing a water solubilizing polyoxyethylene group in chemical combination with an organic hydrophobic compound such as polyoxypropylene, alkylphenol, etc. A third important component of a detergent composition may be referred to as auxiliary material. The auxiliary material may be inorganic and/or organic. Among the conventional inorganic auxiliary material ingredients are the various bleaches, binders, alkayl metal silicates, carbonates, orthophosphates and sulfates. Among the organic auxiliary materials are anti-redeposition agents sodium carboxymethyl cellulose) suds builders,%g tarnish inhibitors, foam stabilizers, binders, oaming agents, whiteners, preservatives, perfumes, bacteriostatic agents, coloring matter, and the like.

Regarding the proportions of the foregoing ingredients, tableted laundry detergents will normally contain more surfactant and builder and less auxiliary material than hard surface cleaners. Tableted laundry detergents will normally comprise between 25% and 90% by weight, preferably between 35% and 70% builder. Also the tableted laundry detergent will necessarily comprise between 3% and 25%, preferably between 5% and by weight of a surfactant. Tableted suds boosters on the other hand will comprise predominantly a builder such as sodium tripolyphosphate and possibly a minor amount of surfactant and auxiliary material. Most straight bleach tablets (those formulated specifically for bleaching purposes only) contain in addition to the bleaching agent a predominant proportion of either a filler, i.e., sodium sulfate, sodium corbonate, sodium silicate, or trisodium phosphate, or an inorganic alkayl metal condensed phosphate, i.e., sodium tripolyphosphate, potassium tripolyphosphate, tetrapotassium pyrophosphate, or tetrasodium pyrophosphate. When the tablet contains a large proportion of condensed phosphate it is more correctly referred to as a bleach-builder or bleach-suds booster tablet since the condensed phosphate will furnish building action. The straight bleach tablet may also contain a minor proportion of surfactant, optical brightener, sodium carboxymethyl cellulose, binder, or the like. In accordance with the invention a typical bleach tablet for home laundry or commercial bleaching operations will comprise between 50 and 90 parts by weight of condensed phosphate or filler, 10 to 50 parts bleach compound, e.g.,

potassium dichloroisocyanurate, and l to 20 parts, preferably 2 to 10 parts, of one or more of the alkyl orthophosphate salts. Detergent-bleach tablets will comprise the same proportions of builder, surfactant, filler and auxiliary materials described hereinabove for ordinary detergent tablets, except that from about 1% to 25% of the builder and/or filler is replaced by a bleach compound.

The granular cleaning compositions to be tableted in accordance with the process of this invention may comprise a uniform physical mixture of the individual components or a homogeneous mixture such as that obtained by spray drying or roll drying a slurry of the ingredients. In a preferred embodiment of the process (applicable only to tableted bleach-free detergents) the orthophosphate salts are added in the last step of the process prior to tableting. The same procedure is preferred when preparing bleach-containing tablets, except that the bleach must be added after any water is added. In such manner any water added prior to the addition of the bleach may be absorbed by the other ingredients of the granular mixture, thereby reducing its availability to react with the bleach. The alkyl orthophosphate salt may be added directly to the other ingredients or, preferably, mixed with water to form a 40% to 70% slurry which may then be sprayed upon a bed of the agitated material. Significantly, the alkyl orthophosphate salt tends to disperse more uniformly on or among the granular particles when applied from an aqueous slurry than when admixed as a dry component.

The granular mixture may be compressed at a pressure between 3 pounds per square inch and about 1000 pounds per square inch, depending upon the tableting characteristics of its particular ingredients. Tablets have been prepared under even higher pressure, but these generally have prohibitive hardness and disintegrate only slowly in warm water. As a rule tablets designed for hard surface cleaning and bleach uses are formed at relatively high pressures, preferably between about and 500 pounds per square inch, while detergent tablets and detergentbleach tablets require less pressure, preferably 25 to 200 pounds per square inch. Further, the greater the amount of alkyl orthophosphate salt present in the composition to be tableted, the lower the pressure requirements. Any of the known methods for curing the tableted products may be employed by the present invention. Except for those which contain bleach, the tablets may be subjected to a water spray or steam treatment after compression to harden the tablet surface. Alternately, the tablets may be heated for a time after compression to improve strength. Both heat treatments and water treatments are generally undesirable with bleach-containing tablets since such tend to degrade the bleach.

The proportion of alkyl orthophosphate salt required in any of the aforesaid cleaning compositions will depend upon the particular compound selected. While all of the alkyl orthophosphate salts will furnish some binding action and some detergent action there are large differences between individual compounds and these differences correlate directly with differences in the number of carbon atoms contained in the alkyl radicals. There is a gradual increase in binding action as the number of carbon atoms increase from 6 to 26 while a more pronounced and sudden change in detergent performance is observed when the total number of carbon atoms exceeds 17. Detergency decreases after 22 carbons although binding action continues to increase with the higher molecular weights.

As a means of expressing the performance of various surfactants in built detergent mixtures, we prefer to use a mathematical expression of these various characteristics to provide what may be termed a Performance Index (P.I.). This index is defined as follows:

Max. Detergency-Builder Detergency wherein P1. is the Performance Index and is calculated by taking the maximum detergency obtained using a given surfactant formulation, minus the detergency of the builder used, and then dividing this value by the minimum use level of the surfactant which will produce the indicated maximum detergency value for the mixture in question. The following are Performance Indexes for some of the alkyl orthophosphate salts of the invention.

invention for the sole pur- When used by the present the tableted cleaning pose of providing binding action to composition, invention will comprise between about 0.1% and by weight of the composition, and preferably between 2% and 5% by weight. When used to provide both detergent and binding action the compounds having between 18 and 22 carbon atoms may be included in higher proportions usually between 0.1 and 25% by weight of the cleaning compositions, preferably between 2 and 15%.

The alkyl orthophosphate salts may also be used in combinations with the known anionic and nonionic surfactants of the prior art since in all proportions the former are compatible with such surfactants. This is particularly the alkyl orthophosphate salts of the present important in certain laundry detergent tablets where inclusion of a sufficient quantity of alkyl orthophosphate salt to provide good detergent action would yield a somewhat hard, slowly water soluble tablet. A1; detergent tablet comprising 1% to 10% oghgphosphate (as a combination surfactant and bin er) plus 5 0 togL5% isodium lauiyl sulfateit common surfactant) is especially suitable for laundering purposes.

It should be especially noted that the principal prior art surfactants and chlorine bleaches are mutually incompatible, that is, the chlorine reacts with the surfactant resulting in a loss of detergent properties as well as bleaching potential.

Although it is one object of this invention to reduce the amount of water needed to furnish satisfactory binding power in tableted cleaning compositions, a small amount of water may be added to the ingredients before tableting or thereafter to harden the surface thereof. Where a significant amount of alkyl orthophosphate salt is used, usually 3-5% by weight of the tablet, or more, little or no water is needed to produce a strong tablet. Some water, however, may be helpful where it is desirable to use less of the phosphate binder or where it is preferred to add the phosphate binder in a water slurry or solution which is sprayed upon the other granular materials.

3 About 3 to 5% by weight of water may be added to the ingredients of a straight bleach composition without markedly degrading the added chlorine bleaching agent.

Slightly higher amounts of water may be added when formulating laundry detergent-bleach tablets. Any water added to the ingredients before the bleach will be adsorbed on the dry granular particles and hence will not readily react with the bleach. On the other hand, it is generally undesirable to add water to the surface of sodium didecyl the tablets (containing the bleaching agent) since the added water may react with and degrade the bleach.

The following specific examples will further illustrate the above-mentioned principles of the invention and in particular the specific results which may be obtained by using the alkyl orthophosphate salts of the present invention in specific detergent formulations. These examples are intended to be illustrative only and no limitations should be implied therefrom,

Example 1 To determine the stability of the alkyl orthophosphate salts in the presence of organic chlorine bleaching compounds an alkaline solution containing a popular chlorine bleaching compound and a small amount of alkaline material was prepared. To this solution was added various prior art surfactants as well as an alkyl orthophosphate salt of the invention (sodium didecyl phosphate). The stability of each surfactant was determined by measuring the surface tension of its solution periodically.

(Note: as the surfactant is inactivated by the bleach the surface tension increases.)

ALKALINE SOLUTION Percent Soda ash 5.0 Potassium dichlorisocyanurate 5.0 Water 90.0

TABLE I,SI'RFACTA.\T STABILITY IN THE PRESENCE OF ORGANIC CllLORlNE BLEACUING COUPOI'NDS Surface tension in Conccntradyncs/cm. Surfactant added to solution tion of surfactant.

p.p.iu. Initiilly After 20 days Sodium didecyl phosphate... 50 26.0 20.0 Sodium lauryl sulfate H 50 28. 9 55. 8 Sodium dojecyl benzene sulfonate 50 27. 0 55. 0 lsooctyl phenyl polyethoxyethanol 50 31. 3 6G. 0 Dioctyl ester of sodium sulfosuccinie acid 50 25. 5 41.4 Fatty acid alkanolamide 5U 27. S 6%. 6 Polycthenoxy tallitem. 37. 6 (32. 2 Sodium Q-ethylhexyl sulfate 47. 8 72. 0 Polyoxyetliylene ester of fatty acld 100 as. 9 60. 9 Alkyl polyoxyethylenc ethers. 50 3t. 6 63. 2 Polyoxyethylene lauryl ether. 50 28. 1 50. 5

Example 2 Granular detergent-bleach compositions were prepared by mixing the following ingredients in a Hobart mixer:

Percent by weight Sodium tripolyphosphate 48.0

Sodium sulfate 24.0

Water 4.5 Surfactant (specified in Table II, infra) 7.5

Potassium dichloroisocyanurate 16.0

The sodium tripolyphosphate, sodium sulfate, surfactant and water were first thoroughly intermixed after which the potassium dichloroisocyanurate (bleach) was added, with mixing. The mixture was then fed to a Stokes Single Punch R-4 Model tableting machine where it was compressed in the form of tablets at a pressure between )0 00 ounds per square i bsequent to compression the ta e s were a owed to stand at room tempera- 7 ture (about 75 F.) and 70% relative humidity for forty days. At ten and forty days the tablets were analyzed to determine the percentage of original chlorine still available. The results of these tests are presented in Table II.

the surfactant, immediately prior to tableting. The tablets were neither treated nor cured in any manner after tableting, but rather, were stored at room temperature and 75% relative humidity for thirty-five days to determine TABLE III.LI1\1ITS OF ALKALINITY IN TABLETED CHLORINE BLEACIIES [Formulations (Percent by weight)] Ingredients 1 2 3 4 5 6 l 7 i 8 9 10 ll 12 NQ;SO 72.5 30.0 20.0 11.0 29.0 1 I S'Illtgranularl 3515 43. s l 30. 5 as. 5 as. 5

Sodium dldEC} p 7.5 7. 7.5 7.5 7.5 7.5 7.5 7. 5

Potassium dichloroisocyanurate 40. 0 20. O 20. 0 20. 0 20.0 20. 0 20.0 20. 0 Percent of ori inal active Cl after days at RT. and 75% RH 98 98 93 90 95 98 87 83 97 48 70 Percent of Original active Cl after 35 days at R.T. and 75% RH 90 97 93 91 S1 86 9G 97 85 78 60 3 N.A.

Condition of tablets after 35 days Good Flaky Good Good Fair Good Hard Good Good Soft Poor Disintegrated l STPP-sodium tripolyphosphate. 1 TSlP-tetrasodium pyrophosphate. I Tablet disintegrated completely-no chlorine analysts.

TABLE II.CIILORINE BLEACH STABILITY IN TIIE PRES- ENCE OI VARIOUS SI'RFACTANTS 'A P7 )s-tlecyl alcohol reaction mixture containing both inonodeeyl and didecyl esters.

the loss in chlorine during such time. At ten days and thirty-five days the percentage of available chlorine, compared to the originally available chlorine, was determined. The formulations used and the results of the storage tests are summarized in Table III.

Example 4 Employing the procedure described in Examples 2 and 3 above, a series of detergent-bleach tablets containing a high proportion of bleach were prepared. Two anionic surfactants, i.e., sodium dodecyl benzene sulfonate and sodium lauryl sulfate and one nonionic surfactant, i.e., isooctyl phenyl polyethoxyethanol were compared to sodium didecyl orthophosphate in these tests. The didecyl phosphate salt was added to the other ingredients as an aqueous slurry while the sodium dodecyl benzene sul- TABLE I\'.CIILORINE STABILITY 1N DETERGENT-BLEACH TABLETS CONTAINING VARIOUS SURFACTANTS [Formulations (ingredients in percent by weight)] Ingredients NaDlJBS 3 (dry) NaDDBS i aqueous slurry) Isooclyl phenyl polyethoxvethanol i Sodium lauryl sulfate (drv). l

Optical brightener Water.

Potassium Percent chlorine (active) remaining after 15 days at R.T. and 70; R.ll Percent chlorine (active) remaining I after today's at R.T.and 757 .11..

3 ounce 59 s9 s0 62 7s 72 7o 70 i s Example 3 To ascertain the effect of alkalinity on the chlorine stability of tablets containing the alkyl orthophosphate salts, tablets were prepared containing some of the more common commercial ingredients. The alkaline ingredients chosen were sodium tripolyphosphate (pH=9.7), tetrasodium pyrophosphate (pH=10.2), soda ash (pH=11.4), and sodium silicate (pH=l2.3). Sodium sulfate, which is nearly neutral in a 1% solution, was also used as an ingredient. The granular ingredients were intermixed and tableted in essentially the same manner as the tablets described in Example 2 with the exception that the orthophosphate surfactant-binder was added as a 65% aqueous slurry and was sprayed upon the pre-mixed dry ingredients. The potassium dichloroisocyanurate was added after fonate was added both dry and as a 60% aqueous slurry. The nonionic surfactant and sodium lauryl sulfate were both added dry to the other dry ingredients. In a first series of tests the tablets, after compression, were held for fifteen days at room temperature and 70% relative humidity. A second series of tests involved holding the tablets at room temperature and 75% relative humidity for forty days. At the end of each storage period the tablets were inspected for physical condition and were analyzed to determine the amount of active chlorine remaining. The results of these tests are set forth in Table IV.

Example 5 The binding action of the alkyl orthophosphate salts in tableted suds booster formulations and hard surface cleaner formulations was determined. The phosphate salts tested contained alkyl radicals ranging from 8 to carbon atoms and included the mono-esters, di-esters, and mixed mono-di esters. Tablets were prepared in accordance with the procedure described in Examples 2 and 3 and were allowed to stand from one to two hours after compression before testing. The suds booster and hard surface cleaner formulations used were as follows:

Tablets prepared from the ingredients shown in each of the above formulations were tested for impact strength (drop test) and compression strength (crushing test). The drop test consists of dropping the tablets three feet to a concrete floor: results are evaluated by visual observations of the tablet after being dropped; in general, a tablet which does not crumble after being dropped is considered satisfactory while a tablet which crumbles or disintegrates into a powder does not have the physical characteristics acceptable for a commercial product. Crushing strength is a measure of the weight required to crush a tablet standing on its edge. In this test a tablet (1.75 inches in diameter and 0.72 inch thick) is rested vertically on a horizontal fixed support and a varying weight load is applied tangentially (through the vertical axis) to the top edge of the tablet. A crushing strength of over about 2000 grams, and preferably between about 2500 grams and 4000 grams, is considered satisfactory for tableted products. Tablets having a crushing strength below about 2000 grams readily disintegrate or flake during handling while tablets above about 4000 grams tend to disintegrate too slowly when placed in water. The impact strength and compression strength of various tableted suds boosters (A) and hard-surface cleaners (B) are presented in the following table.

TABLE V.-PHYSICAL CHARACTE RISTICS OF TABLETED Although not shown in the above table, all of the tablets containing the alkyl orthophosphate salts disintegrated rapidly in a large volume of warm water (120 F.). Further, no difference was observed in the rate of disintegration between tablets containing a small amount of water as a binder and those containing the alkyl orthophosphate salts.

The cleaning compositions described and tested in accordance with Examples 2 through 5 were evaluated by standard laboratory cleaning procedures to determine their suitability for each disclosed use. To illustrate, standard laundering tests were accomplished to evaluate the efficiencies of those compositions formulated for laundering operations, while the straight bleach formulations were evaluated for bleaching capacity. These tests indicated that all of the compositions comprising the alkyl phosphate salts of the invention were equivalent or superior in overall cleaning power to similar compositions (where such exist) presently manufactured and marketed for the same uses. Some of the compositions included for comparison purposes, e.g., those seriously degraded by the action of the surfactant on the bleach and vice versa, were, of course, somewhat inferior and/or unsuitable for the intended use.

Another feature of tableted cleaning compositions containing the alkyl orthophosphate salts, especially those which have high surfactant properties, is that the alkyl orthophosphate salt is readily biodegradable. Considerably public concern has been expressed in recent years regarding the amount of detergent present in surface water and sub-surface waters. Of particular concern is the fact that many of the widely used alkyl benzene sulfonate and sulfate materials are not readily biodegradable.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations are to be derived therefrom, as modifications will be obvious to those skilled in the art.

We claim:

A bleach composition in the form of a water soluble tablet having high impact and crushing strength and rapid disintegrability in warm water comprising the following ingredients in the indicated proportions:

Parts by weight Sodium sulfate, sodium tripolyphosphate, tetrasodium pyrophosphate, sodium carbonate -90 Sodium didecyl phosphate 2-10 Potassium dichloroisocyanurate 10-50 (References on following page) SUDS BOOSTERS AND HARD SURFACE CLEANERS CONTAINING ALKYL PHOSPHATE BINDE RS Drop Test 1 Crushing Test, gms. Binder used 1 (Number of C atoms) A B A B Water 5 3 1, 800 1, 900 Sodium dibutyl phosphate (8).... 5 5 1, 500 2,200 Sodium monooctyl phosphate (8) 4 2 3, 000 3,200 Sodium mono dioctyl phosphate (average 12) 3 2 3, 300 2, 700 Sodium dioctyl phosphate (16)... 2-3 2 3,800 3,800 Sodium didecyl phosphate (20) 2 1 3. 800 3, 900 Sodium mono dllauryl phosphate (average 18).. 2 1 3, 700 4, 200 Sodium mono di tridecyl phosphate (average 20). 2 1 4, 3, 500 Sodium mono stearyl phosphate (18) 3 2 4, 000 4, 200

into several pieces; 5=tablet crumbles into powder.

Water used at 5% by weight-a1kyl phosphates in 50% aqueous slurry (phosphate=2.5%

of total tablet ingredients).

1 1 12 References Cited 3,120,378 2/1964 Lee et a1. 252-95 1 3,172,859 3/1965 Percival et a1. 252-138 XR UNITED STATES PATENTS LEON D. ROSDOL, Primary Examiner.

2,005,619 6/1935 Graves 260-4613 2,656,372 10/1953 Ernst 6:61. 260-461 5 JULIUS GREENWALD Exammer- 3,081,267 3/1963 Laskey 252-135 J. T. FEDIGAN, Assistant Examiner.