US 2987483 A
Description (OCR text may contain errors)
United States Patent 2,987,483 CLEANING COL [POSITION Charles Edward Brooker, Drexel Hill, Pa., assignor to Pennsalt Chemicals Corporation, a corporation of Pennsylvania No Drawing. Filed July 2, 1956, Ser. No. 595,127 5 Claims. (Cl. 252-138) This invention relates to alkaline cleaning composi- .tions .and more particularly .to strongly caustic compositions which are packaged in solidform and dissolved in water for use as heavy duty cleaners. .Such compositions are useful as bottle-washing compounds, for cleaning .industrial equipment and in other applications wherein strong lye is an essential component of the cleaner.
In the preparation of blended alkaline detergent products containing dissimilar additives such as synthetic detergents, sequestrants, bleaches and so forth, it is often difiicult to manufacture a product that is homogeneous. In particular, caustic soda is an extremelydiflicult component-to bring into effective and homogeneous admixture with other cleaningcomponents, since firstly, caustic soda is a severely hygroscopic solid which does not lend itself to fine grinding for powdered blends, and secondly, its extreme causticity tends to cause decomposition :and inactivation of the other components, particularly where it is blended with these materials at the greatly elevated temperatures, on the order of 550 F., at which it is molten. Thus, a product containing caustic soda, a polyphosphate sequestrant and a synthetic detergent would be non-uniform both in appearanceand in performance if blended in the solidstate, and if blended :in the molten state, both the detergent and the phosphate would be destroyed by the high temperature combined with the severe alkalinity of the blend.
it has nowbeen'found-that'a wholly uniform blend of caustic soda with'a syntheticdetergent and sodiumtripolyphosphate, wherein "the latter 'two components are substantially-fully active and undecomposed, can be made by combining the detergent and the phosphate with the monohydrate of caustic soda at a temperature of at least 148 F. but not exceeding about 200'F.,. and then solidifying the resulting blend by cooling to below 148 F. The composition thus produced has a high effective caustic content with the added benefits provided by the detergent and phosphate. it is capable of being produced in convenient flake or granular form that does not segregate or separate, but gives consistently uniform performance and is more readily soluble than a blend prepared by mechanical mixing alone.
It has been found that the solid blended cleaner of this invention depends for its excellent qualities on the utilization of the caustic soda monohydrate (NaOH'H O), which in the molten state serves as a medium for attainment of complete dispersion of the other components, at a temperature sufliciently low to prevent their decomposition, and on cooling forms the essential solid crystalline matrix which can be suitably comminuted and packaged. Therefore, in the compositions of this invention the ratio of sodium hydroxide to water on a molar basis should closely approach 1:1. On a weight basis, this is equivalent to 69 parts NaOH to 31 parts H O, or, disregarding the other components, 69% by weight NaOH. This may be varied slightly, but should remain within the limits of 64% NaOH to 75% NaOH if the solid compositions of the present invention are to be obtained. The caustic soda monohydrate should comprise at least 60% by weight of the total composition including the other components. It may be as high as about 90% and is preferably between about 80 and 85%.
With respect to the synthetic detergent additive, this should be one or more of the type known as alkyl aryl greatly :reduced sequestering action. phate should be present .in an'amount of from 10 to 40% Patented June 6, 196.1
sulfonates. Specific examples of various kinds of alkyl aryl sulfonates include the keryl benzene sulfonates having either about 14 carbon atoms in the alkyl group (Nacconol NR), or about 10 carbon atoms in the alkyl group (Santomerse D), monobutylphenyl phenol sodium sulfonate (Areskap), dipropyl naphthalene sulfonate (-Alkanol B or Aerosol OS) or the low-degree polymeric condensation products of formaldehyde and naphthalenesulfonic acid (Daxad II, Lomar PW or Tamol N). A particularly applicable alkyl aryl sulfonate is Kreelon 4G (Wyandotte Chemical Corp.), a keryl benzene sulfonate in which the alkyl portion is predominantly C12. The commercial product, Kreelon 4G, comprises about 40% active material, the remainder being sodium sulfate. The alkyl aryl sulfonate detergent should be present in an amount not exceeding about 5% by weight of the total composition, since at higher concentrations the detergent tends to bleed from the composition. A concentration of about 1% by weight of the detergent is preferred,
With respect to the sodium tripolyphosphate, it is remarkable that this compound, which is an excellent sequestrant, can be incorporated into the severely alkaline compositions of this invention with substantially no reversion to the ortho or pyro form, in which forms it has The tripolyphosby weight of the total composition, This phosphate is known toform'crystalline hydrates, and it is conceivable that it is present as such as in the crystalline product herein described; however, its contribution to the solidity of the product is very small, the principal solid, crystalline phase of the composition being the monohydrate of caustic soda.
Minor amounts of other detergent additives can be incorporated in the formulations, provided they do not interfere with the crystallization of the monohydrate or the attainment of complete homogeneity while the composition is molten. '-Such additives include bleaches, dyes or builders such as sodium carbonate, tri-sodium phosphateor a so'dium silicate. It should be kept in mind, however that thecleaning compositions herein described are essentially strongly caustic cleaners, and these additives should not be present in amounts that would significantly alter the detergent action of the lye.
A particularly desirable formulation is composed of 84% by weight of sodium hydroxide monohydrate, 15% by weight of sodium tripolyphosphate and about 1% by weight of an alkyl aryl sulfonate.
In accordance with the present invention, homogeneous detergent mixtures are produced by mixing together sodium hydroxide containing 36 to 25% water, sodium tripolyphosphate and an alkyl aryl sulfonate at a temperature above 148 F. In this way plastic or fluid conditions are attained and uniformity of mixing of the ingredients is assured.
In a preferred method of forming the compositions of the invention, the sodium hydroxide is generally heated to a temperature within the range of F. to 200 F., with an average mixing temperature of 180 F. producing excellent results. Commercial powdered sodium tripolyphosphate and the alkyl aryl sulfonate in flake or liquid form are then added to the heated sodium hydroxide while agitating the mixture. The uniformly mixed blend may then be circulated through the pan of a conventional flaker wheel assembly.
The size and temperature of the flaker wheel can be proportioned to any rate of production, but for any given area of flaker wheel surface the temperature of the cooling medium in the wheel and the speed of the wheel should be regulated so that complete removal of heat of crystallization of the sodium hydroxide monohydrate is obtained. This involves cooling the mixture to a temperature below 148 F., the crystallization temperature of sodium hydroxide monohydrate. .The solid mixture is preferably cooledto a temperature of about 120 F., in order to assure that the heat of crystallization is completely removed from the entire thickness of the solid product.
The product can be produced in varying thicknesses. However, for most flaking equipment the cooling capacity is such that a flake of approximately /32 inch in thickness is the optimum for this type of product.
The invention will be further illustrated by reference to the following specific example:
Example I To 8375 pounds of a 72% by weight sodium hydroxide solution, heated to a temperature of 180 F., was added, while agitating, 1500 pounds of commercial powdered sodium tripolyphosphate and 125 pounds of Kreelon 4G, identified hereinabove. The sodium tripolyphosphate and Kreelon 46 were maintained in suspension in the sodium hydroxide by continuous agitation, and the uniformly mixed batch was circulated through the pan of a fiaker wheel, the latter being 4 feet in diameter and feet long, internally cooled by water at a temperature of 80 F. and rotating at about 4 revolutions per minute. The flaked mixture deposited on the wheel was cooled to a temperature of 120 F. in order to assure that the heat of crystallization of the sodium hydroxide monohydrate formed was removed. The doctor knife on the flaker wheel removed a flake having a thickness of inch.
The flaked product was permitted to cool to room temperature and was then ground, screened to /2 inch and packaged under dry atmospheric conditions.
When using the blended cleaner of this invention in a cleaning solution, the solution may, for example, contain from about 0.25% to about 10% by weight or more of the cleaner, and the solution is generally used at a temperature of about 90 F. to about 160 F. or higher if desired. The actual cleaning practice will, of course, vary depending on the particular soil conditions encountered, the equipment to be used and so forth.
In addition to the fact that the composition of the invention is homogeneous and is of uniform specific gravity and particle size, it also appears to have an enhanced sol- 4 ubility rate and better detergent properties than comparable mechanical blends.
It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.
This application is a continuation-in-part of my copending application Ser. No. 388,660 filed October 27, 1953, now abandoned.
1. The method of preparing an alkaline cleaning composition which comprises heating to parts by weight of sodium hydroxide which contains 36 to 25% by weight water to a temperature above 148 F. but not exceeding 200 F. to form a molten solution, uniformly dispersing throughout said solution 40 to 10 parts by weight of sodium tripolyphosphate and up to 5 parts by weight of an alkyl aryl sulfonate detergent, and then solidifying the resulting dispersion by cooling to a temperature below 148 F.
2. The method of claim 1 wherein said cooling is done by contacting said dispersion with a cooled surface.
3. The method of claim 1 wherein the dispersion is solidified by spreading the same in a layer having a thickness of about /321'ld of an inch, and cooling said layer to a temperature of about F.
4. The alkaline cleaning composition prepared according to the method of claim 1.
5. The alkaline cleaning composition prepared according to the method of claim 1, and containing about 84% by weight sodium hydroxide monohydrate, 15% by weight sodium tripolyphosphate and about 1% by weight of an alkyl aryl sulfonate detergent.
References Cited in the file of this patent UNITED STATES PATENTS 2,332,497 Burkard Jan. 6, 1941 2,333,443 Robinson Nov. 2, 1943 2,351,559 Treflier June 13, 1944 2,357,723 Beecher Sept. 5, 1944 2,788,328 Merget Apr. 9, 1957 2,804,432 Bonewitz Aug. 27, 1957 OTHER REFERENCES Mellor: Inorganic and Theoretical Chem., vol. 2, p. 502 (1922).