US3630928A - Particles containing mixtures of polyphosphates and silicates - Google Patents

Abstract

STRONG, STABLE PARTICLES CONTAINING A MIXTURE OF A SODIUM TRIPOLYPHOSPHATE AND A SILCATE, WHREIN THE SIO2 TO TRIPOLYPHOSPHATE MOLE RATIO IS AT LEAST 1:1, WERE PRODUCED BY ADMIXING SODIUM TRIPOLYPHOSPHATE AND AN AQUEOUS SOLUTION OF AN ALKALI METAL SILICATE TO OBTAIN A STICKY MIXTURE WHICH AGGLOMERATES INTO SOFT, DEFORMABLE GRANULES, DRYING THE GRANULES AT FROM 60 TO 80*C. AND RECOVERING THE RESULTING, DRIED, GRANULAR PARTICLES.

Description

AU 165 EX VII-lbw ubwuvu 3,630,928 Patented Dec. 28, 1971 U.S. Cl. 252135 Claims ABSTRACT OF THE DISCLOSURE Strong, s'table particles containing a mixture of a sodium tripolyphosphate and a silicate, wherein the SiO, to tripolyphosphate mole ratio is at least 1:1, were produced by admixing sodium tripolyphosphate and an aqueous solution of an alkali metal silicate to obtain a sticky mixture which agglomerates into soft, deformable granules, drying the granules at from 60 to 80 C. and recovering the resulting, dried, granular particles.

BACKGROUND OF THE INVENTION (A) Field of the invention The invention relates to producing strong, stable particles that contain a mixture of a polyphosphate and a silicate.

(B) Description of the prior art In the process of manufacturing a dry-mixed, built, detergent formulation for use in dishwashers or cleansing, it is common to use sodium tripolyphosphate as the builder, along with other common ingredients; these may include anionic or nonionic, synthetic surfactants, antiredeposition agents, such as sodium carboxymethylcellulose, extenders, perfumes, bleaching agents, e.g., chlorinated cyanurates, alkaline cleansers, e.g., soda ash, caustic soda, and'the like. The aboyg polyphosphate-built, a1- kaline detergent, when us In conventional dishwashers insisting equipment, is known to be corrosive to both the metal "and enamelware it contacts. To inhibit such cori qsign, an alkali metal silicate normallyuodiumnsih- Eate, is iriEbTfi'dr'at'edTiitb Thedetergentjprmulatign... ""Regrettablyflhe "niixturebf sodium tripolyphosphate and a silicate in a dry-mixed, detergent formulation results in serious problems. These ingredients cake together into hard agglomerates that are difficult to pour and handle and which :cause undesired segregation of some components of the formulation. One solution to the caking problem is set {orth in U.S. Patent 2,909,490 issued to Max Metziger on Oct. 20, 1959, wherein the patenteede'scribesthe manufacture of duplex compositions of sodium tripolyphosphate and sodium silicate by contacting these ingredients at helow 1591;, so that anhydrous sodium tripolyphosphate dehydrates the aqueous liquid forms of sodium silicate to yield a dry mixture.

This patented duplex mixture has certain drawbacks. Initially, it can only be formed with the less alkaline silicates, i.e., SiO /Na; weight ratios of 3.22:1 to 2.40: 1. Further, when high silica to polyphdsphate mole ratios, e.g., at least 1:1, are desired in the mixture for optimum corrosion inhibition, only the less alkaline (Slog/N830 of 3.22:1) silicate can be employed to obtain the patentees duplex product. This is a disadvantage because highly alkaline ingredients are desired in the makeup of these detergent formulations, preferably those yielding a pH of at least 10.5 (when made up in an aqueous 1% solution thereof), to obtain better detergency and to avoid precipitates in the dissolved detergent solution.

OBJECTS OF THE INVENTION It is an object of the present invention to produce strong, stable particles that contain a mixture of a silicate and sodium tripolyphosphate in which the silicate to polyphosphate mole rat o is at least 1:1, and the particles yield a pH of at least 10.5 in an aqueous 1% solution.

It is a further object of the present invention to produce strong, stable particles that contain a mixture of a silicate and sodium tripolyphosphate in which the silicate has an SiO /-Na=O weight ratio of below about 2.40:1.

These and other objects will be apparent from the following description of the invention.

SUMMARY OF THE INVENTION I have now found that strong, stable particles containing a mixture of a silicate and sodium tripolyphosphate in the mole proportion of at least 1:1 can be produced by adding an aqueous solution of a sodium silicate having an SiO /Na O mole ratio of below 2.40:1 (preferably 2.0: 1) to a bed of powdered sodium tripolyphosphate until the SiO: to tripolyphosphate mole ratio is at least 1:1 and a sticky mixture results from said addition, stirring said sticky mixture to form deformable, plastic granules, heating said plastic granules in a heating zone maintained at a temperature of from about 60 to about 80 C. until said granules are dried, and recovering dried, granular particles which yield a pH of at least 10.5 in an aqueous 1% solution.

DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS In carrying out the present invention, powdered sodium tripolyphosphate is used as one of the feed reactant. If the sodium tripolyphosphate is not in powdered form, it should be ground by conventional means so that substantially all of the polyphosphate passes through a 40 mesh screen with at least about being --80 mesh. The sodium tripolyphosphate is then placed in an agitated reaction chamber such as a ribbon blender or rotating drum and maintained in a state of constant agitation.

To this agitated bed of polyphosphate material is then added a sodium silicate solution. The silicate solution should have an SiO;/Na,O weight ratio of below 2.40:1 and preferably 2.0:1. An especially useful sodium silicate solution is the Philadelphia. Quartz Company product D -brand silicate which contains 14.7% N330; 29.4% SiO,; and 55.9% H 0.- The silicate solution is dispersed into the bed of sodium tripolyphosphate, preferably through spray nozzles or other distributing means. In many cases it is preferred to added up to about 10% by weight of water to the D -brand silicate solution as received in order to decrease its viscosity and permit more easy distribution of the sodium silicate solution on the bed of polyphosphate. For convenience sake, ambient temperatures are preferred during this mixing process although higher temperatures can be employed, provided material amounts of water in the silicate solution are not evaporated off.

The silica 'ol hosphate the mole ratio of SiO, to tripolyphosp insist 1:1. The mixture becomes sticky and agglomerates of the granules is then increased in a heated chamber so that the granules reach a temperature of from to C. during which they lose moisture. The granules are maintained at this temperature until they are dry appearing. Thereafter, they are ground, if necessary, so that they are chiefly in the 8 to +50 mesh size and recovered as product. Any powdered product less than $0 mesh can be recycled to the reaction chamber by mixing it with additional, powdered polyphosphate before the addition of more silicate solution. i

In many cases it is desirable to add a small amount of a wetting agent, i.e., a surfactant, to the sodium silicate 3 ture with less mixing. Suitable wetting agents include lower alkyl ethers of polyoxyethylated octyl phenols, such as those sold under the Triton CF trade name, for example Triton CF-54 which is the butylether of polyoxyethylated octyl phenol; and Triton X-100 which is the isooctyl phenyl polyethoxyethanol.

A sodium silicate solution such as D -brand silicate which contains about 55% water can be used as received from the manufacturer and added directly to the sodium tripolyphosphate. However, in many cases it is desired to add water to the silicate solution until the H content of the solution reaches about 60% by weight. The added water lowers the viscosity of the silicate solution and permits it to be more readily dispersed throughout the polyphosphate. It should be added, however, that the addition of larger amounts of water is undesirable because the resulting mixture of sodium tripolyphosphate and aqueous silicate does not yield the proper degree of tackiness necessary to obtain the desired soft, plastic, deformable granules. The production of these plastic, deformhable granules is necessary in the practice of the present invention to obtain, after drying, strong granules which have a desirably low density, e.g., about 0.7 to about 0.8 g./cc. which do not crumble on being dry mixed with other'ingredients in a blender.

In the manufacture of the present product, it is desired to maintain the SiO, to sodium tripolyphosphate mole ratio at least at 1:1 in order to provide good corrosion inhibition. This ratio of silicate to sodium tripolyphosphate is sufficient to materially reduce or eliminate undue corrosion of metal equipment by the final detergent product. Lower ratios of silicates are not as effective. The sodium silicate solutions which have been found effective in the present invention are listed below:

Weight percent Welglht Product name NmO B10; B10 SlOflNmO D 14.7 29.4 55.9 2.00:1 C 18.0 86.0 46.0 2.00:1 B-W 19. 81. 2 49. 3 1. 81:1

The above products are registered trademarks of Philadelphia Quartz 00., Philadelphia, Pennsylvania.

The following examples are given to illustrate the present invention and are not deemed to be limiting thereof.

EXAMPLE 1 Twenty-five pounds of powdered sodium tripolyphosphate having a screen size distribution as follows:

and having a bulk density of 0.93 g./cc. was placed in a rotary mixer. The mixer was 18 inches in diameter by 18 inches long and contained seven 2-inch high flights to lift and tumble the product therein. The mixer was then activated and permitted to rotate at a speed of 15 r.p.m. While the mixer was rotating, a mixture of 17.2 pounds of D -brand silicate solution (Philadelphia Quartz Co. product containing 14.7% Na O, 29.4% SiO,, and 55.9% 11,0) and 0.51 pounds of water (equivalent to 3% by weight water to reduce the viscosity of the silicate solution) was fed by gravity through a lei-inch pipe into the mixer. The base of the pipew hich extended into the mixer contained eight small holes about 2 inches apart through which the silicate solution could be finely distributed onto the tumbling bed of sodium tripolyphosphate. The entire silicate solution was added over a period of twenty minute's. The batch became sticky, and all of the powdered material agglomerated into irregular lumps whichwere tacky and plastic. These plastic lumps were dried at 65 C. until they were hard and were then crushed and screened. About 80% of the crushed particles were recovered as a 8 +50 mesh granular product having a bulk density of 0.85 g./cc., with about 20% being separated as 50 mesh fines. A sample of the granular product was used to make up an aqueous 1% solution and found to be completely free of insolubles, and further was found to have a pH of 10.7. The granular product contained 19.5% total moisture (on ignition) and had a mole ratio of SiO, to sodium tripolyphosphate of 1.23:1. To determine the strength of the granular product a' sample was thoroguhly blended with other conventional detergent ingredients in a mechanical mixer and the granular product did not break down, nor did the bulk density increase.

EXAMPLE 2 The procedure of Example 1 was repeated except that only 20 pounds of powdered sodium tripolyphosphate was added to the mixer along with 5 pounds of the -50 mesh granular product of Example 1. Further, the amount of silicate solution added was reduced by 20%. The silicate solution was added at a slower rate and required 36 minutes to add the entire silicate solution. The resulting tacky lumps were again dried at 65 C. until hard, crushed and screened. About of the total batch was recovered as 8 +50 mesh granular product having a bulk density of 0.76 g./cc. A sample of the resulting product was used to make up an aqueous 1% solution and was found to contain no insolubles and to give a pH of 10.7. The product was found to contain 20.5% total moisture (on ignition) and to have a mole ratio of SiO, to sodium tripolyphosphate of 1.23:1. The resulting product was formed of hard particles that did not break down upon being mechanically blended with other detergent ingredients.

EXAMPLE 3 The procedure of Example 1 was repeated except that 30 pounds of powdered sodium tripolyphosphate was used having a screen size distribution as follows:

0.9%: -50 +60 mesh 2.1%: 60 +70 mesh 8.8%: 70 mesh 88.2%: -100 mesh and having a bulk density of 0.91 g./cc. A mixture of 19.0 pounds of D -brand sodium silicate and 0.78 pound of Triton X-100 (Rohm and Haas Co. wetting agent, isooctyl phenyl polyethoxy ethanol), was added to the agitated bed of sodium tripolyphosphate over a period of one hour. No water was added to the sodium silicate solution. The resulting tacky and plastic lumps were then dried at 65 C. and were crushed and screened. About 80% of the resulting batch was recovered as a -8 +50 mesh granular product. It had a bulk density of 0.68 g./cc., a mole ratio of SiO; to sodium tripolyphosphate of 1.22:1 and a total moisture (on ignition) of 19.9%. A sample of the granular product when made up into an aqueous 1% solution gave a pH of 10.6 and was clear and free of insolubles. In the above example the slow addition of silicate and the use of a'wetting agent appear to contribute to lowering the bulk density of the resulting product.

EXAMPLE 4 Twenty pounds of powdered sodium tripolyphosphate having a particle size as set forth in Example 3 at a temperature of 75 C. was added to the rotary mixture described in Example 1, and 5 pounds of --50 mesh fines from the product of Example 3 were added. A mixture of 12.6 pounds of D -brand silicate solution, 0.39 pounds of water, and 0.52 pounds of Tergitol Min-Foam (Union Carbide Co. wetting agent, modified linear alcohol ethoxylate) were added to the tumbling bed of sodium tripolyphosphate over a period of 27 minutes. The resulting mixture was almost entirely in the form of a 4 +8 mesh plastic, sticky agglomerate. The product was dried at 65 C. until hard and then was crushed and screened. The greater portion of the product was separated as a 8 +50 mesh granular product which had a bulk density of 0.79

g./cc., a total moisture content of 16.6% (on ignition) and a mole ratio of SiO; to sodium tripolyphosphate of 1.10:1. A sample of the resulting product when made up into an aqueous 1% solution gave a pH of 10.6. The dried product was found to be hard granules which did not break or crumble upon being blended with other detergent ingredients in a mechanical blender.

Pursuant to the requirements of the patent statutes, the principle of this invention has been explained and exemplified in a manner so that it can be readily practiced by those skilled in the art, such exemplification including what is considered to represent the best embodiment of the invention. However, it should be clearly understood that, within the scope of the appended claims, the invention may be practiced by those skilled in the art, and having the benefit of this disclosure otherwise than as specifically described and exemplified herein.

What is claimed is:

1. Process for producing strong, stable particles containing a mixture of a silicate and sodium tripolyphosphate in the mole proportion of at least 1:1 which comprises adding an aqueous solution of a sodium silicate having an SiO /Na O weight ratio of about 2.0:1 or less to a bed of powdered, sodium tripolyphosphate until the Si to sodium tripolyphosphate mole ratio is at least 1:1 and a sticky mixture results from said addition, agitating References Cited UNITED STATES PATENTS 2,895,916 7/1959 Milenkevich et al 252-99 2,909,490 10/1959 Metziger 252- 3,154,496 10/1964 Roald 252-99 3,231,505 1/1966 Farrar et al 252-138 3,255,117 6/1966 Knapp et al 252-99 3,248,330 4/1966 Feierstein et a1 252-99 LEON D. ROSDOL, Primary Examiner D. L. ALBRECHT, Assistant Examiner US. Cl. 'X. R. 252-99