US 3821119 A
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nited States Patent [191 Temple v 11] 3,821,119 June 28, 1974 1 SILICATED SODA ASH  Inventor: Ralph E. Temple, Chardon, Ohio  Assignee: Diamond Shamrock Corporation,
Cleveland, Ohio  Filed: May 3, 1972  Appl. No.: 250,031
 US. Cl. 252/135, 252/385  InLCI. Cl1d3/08,C11d 3/10  Field of Search 252/135, 385, 99
[5 6] References Cited UNITED STATES PATENTS 2,099,743 11/1937 Kroeger 252/175 X 2,333,443 11/1943 Robinson. 252/135 2,351,559 6/1944 Treffler. 252/135 2,365,215 12/1944 Rhodes 252/135 X 2,515,880 8/1950 MacMahon 252/1-35 2,909,490 10/1959 Metziger 252/135 3,247,1 18 4/1966 Matthaei 252/99 3,285,859 11/1966 .lelen 252/385 3,620,979 11/1971 Corlissetal. ..252/385 3,630,928 12/1971 Fuchs 252/135 FOREIGN PATENTS OR APPLICATIONS 4,1 1 l 4/1912 Great Britain 494,628 10/1938 Great Britain 525,514 8/1940 Great Britain Primary Examiner-Leon D. Rosdol Assistant Examiner-P. E. Willis Attorney, Agent, or Firm-Wi1liarn A. Skinner; Timothy Tinkler  ABSTRACT A method of preparing a particulate detergent builder includes admixing liquid sodium silicate with anhy- 3 Claims, No Drawings SILICATED SODA ASH It is known to be desirable to incorporate alkali metal silicates into various detergent compositions both for their inherent detergency and for their ability to protect ceramic and reactive metal surfaces from corrosive attack. Various problems have presented themselves in attempting to effect this incorporation. The most readily available source of dry, granular soluble SiO is the crystalline sodium metasilicates which, however, are too alkaline for many uses and in any event tend to segregate from the compositions into which they are incorporated. Other particulate sodium silicates having a higher ratio of silica to sodium oxides are not readily available, thus being too expensive for incorporation into most detergent compositions. Furthermore, where used, the tendency of these particulate materials is again tosegregate and/or contribute substantially to dusting. Various techniques have been suggested for blending liquid silicates into a detergent composition followed by drying to achieve the desired particulate state. However these methods, such as spray drying or agglomeration, generally require expensive equipment and hence large scale production to justify the necessary investment.
STATEMENT OF THE INVENTION Therefore it is an object of the present invention to provide a method for incorporating liquid silicates into a detergent formulation.
It is a further object of the present invention to provide a particulate silicated soda ash and-a method of preparing same. i
There has now been found a method of preparing a free-flowing particulate detergent builder, which method consists essentially of:
a. preparing an aqueous solution of sodium silicate having a Na O:SiO weight ratio of from 1:1.6 to 3.3 and a solids content of from 38 to 50 percent by weight;
b. admixing said solution with a substantially anhydrous sodium carbonate having a particle size of less than about 200 microns, said carbonate constituting from 45 to 70 percent by weight of the mixture;
c. maintaining the temperature during admixture bed. after thorough admixing, passing the resultant material through at least an eight mesh screen;
e. rapidly heating the wetted, screened material to a temperature within the range of 105 to 250C.
f. recovering as the product a substantially dry particulate detergent builder having a bulk density of from 25 to 50 pounds per cubic feet and a uniform SiO content of from to 30 percent by weight.
In such a detergent builder the silicate is distributed uniformly on the soda ash particles and a sufficient amount of said silicate may be incorporated to provide the desired and advantageous properties. Further it has been found that the resultant particles are highly absorbent, being capable of taking up, for example, up to percent of their weight of a liquid surfactant. It will be appreciated that the equipment requirements of one desiring to produce such a detergent builder are quite modest. Hence, most any desired size production operation may be achieved.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The sodium silicate employed will generally be one of those commercially available which have an Na O:SiO weight ratio within the stated range of from about l:l.6 to 3.3 and a solids content within the range of from 38-50 percent by weight, the balance being water. Of course it is possible to adjust the ratio of the solution to a desired point by the addition of sodium hydroxide. The amount of such a silicate employed will be within the range of from 30-55 percent of the combined aqueous silicate/soda ash, corresponding to a uniform SiO content in the final product within the range of l0 to 30, preferably 18-22, percent by weight.
The sodium carbonate must be substantially anhydrous since those materials having water bound thereto will not accept the desired quantities of silicate. That the soda ash has a particle size of less than about 200 microns, for example passing through an eighty mesh screen, has been found important to the process since otherwise a sticky mass, essentially impossible to mix while retaining a particulate form, will be obtained on addition of the silicate solution. The amount of sodium carbonate employed falls within the range of 45 to percent by weight of the mixture.
It has been noted that during the admixture of the silicate and soda ash it is essential that the temperature be maintained within the range of 2 1 to 51C. At lower temperatures the mixture becomes quite heterogeneous consisting of quantities of silicate coated with soda ash and free soda ash. On the other hand, at temperatures in excess of about 51C. a taffy-like mass is formed which is unsuitable for the subsequent operations.
The result of the foregoing is a wet granular material which is then passed through at least an eight mesh screen in order to obtain a particle size suitable for subsequent operations. By the phrase at least an eight mesh screen it is intended to refer to an eight mesh screen (Tyler or US. Standard) or one the openings of which are smaller, e.g., a 10 mesh screen.
The thus-screened material is then passed to a heating step wherein the temperature is rapidly raised to within the range of to 250C. For example, the
material being screened may be allowed to fall directly onto the surface of a hot plate having the appropriate temperature. The purpose of the heating step is to cause the formation of water vapor within the silicate and the subsequent release thereof, thereby resulting in the formation of a silicate foam. Temperatures of less than 105C. do not yield any substantial foaming, thus dictating a product having a bulk density higher than is generally desired for use as a detergent builder. While temperatures in excess of 250C. may be used, no significant additional advantage is obtained, an optimum low bulk density being achieved at the stated temperature. Obviously then, control of the temperature within this range is one method of regulating the bulk density of the product within the stated range of 25 to 50, preferably 35 to 50, pounds per cu. ft.
Itwill be apparent from the foregoing that, with the appropriate choice of equipment, the process may be operated either batch-wise, for small amounts with specific formulations, or, preferably, in a continuous manner.
A surprising result of this process, and characteristic of the product, is that the pH of the silicated soda ash is lower than that of either ingredient alone. For example, the pH (measured as a 1 percent aqueous solution) of a product made from sodium silicate having a ratio of l:2.4 and containing 20 percent Si is measured at 1 L0. A solution of soda ash alone reads 1 L4 and the silicate has a pH of l 1.3.
In order that those skilled in the art may more readily understand the present invention and certain preferred embodiments by which it may be carried into effect, the following specific examples are afforded.
EXAMPLE 1 ln the following Table the samples are prepared by adding the silicate to the soda ash over a period of minutes while mixing at low speed in a Hobart mixer at a temperature of about 43C. The soda ash employed is an anhydrous sodium carbonate, 98 percent of the particles of which pass through an 80 mesh Tyler sieve, indicating a particle size of less than 174 microns. Mix- EXAMPIIE 3" scope of the appended claims.
I. A method of preparing a free-flowing particulate silicated sodium carbonate detergent builder which method consists essentially of:
a. prearing an aqueous solution of sodium silicate having an Na O:SiO weight ratio of from 121.6 to 3.3 and a solids content of from 38-50 percent by weight;
b. admixing said solution with substantially anhydrous sodium carbonate having a particle size of less than about 200 microns, said carbonate constiture increase has essentially no further effect on the ultimate bulk density. Sample 8 was determined to be capable of absorbing up to 15 percent of a liquid polyethoxy ether nonionic surfactant while still remaining freeflowing.
By way of comparison, Sample 3 is repeated, substituting a commercially available anhydrous sodium carthssame esul s,
Upon grinding the first of the aforesaid commercial 5 soda ashes until it passes through an eighty mesh screen, a satisfactory product similar to Sample 3 is obtained.
ing is continued for 10 minutes after addition is com- 25 tuting from 45 to percent of the mixture; pleted, following which the wet granular material is c. maintaining the temperature during admixture bescreened through a l0 mesh Tyler sieve onto a hotplate tween 21 and 51C.; having asurface temperature as indicated. n d. after thorough admixing, passing the resultant ma- TABLE Na CO; Aqueous Na O:SiO, Silicate Drying Product Bulk Silicate Solids Tempera- SiO Density Sample (gms.) (gms.) (wt.ratio) (7r) ture (C.) (7:) (lbs/ft) By comparing Samples 1, 2 and 4 of the Table, the terial through at least an eight mesh screen; effect of temperature in the drying step on the bulk e. rapidly heating the screened material to a temperadensity of the product can be seen. Further, Sample 3 ture within the range of 105 to 250C. and, indicates that an additional and substantial temperae er ng as he productasubstantially dry particulate detergent builder having a bulk density of from 25 to 50 pounds per cu. ft. and a uniform SiO content from 10 to 30 percentby weight.
2. The particulate free-flowing silicated sodium carbonate detergent builder produced by the method of claim 1 which is a substantially anhydrous coherent mixture of sodium carbonate and a sodium silicate having a Na O:SiO ratio of 1:1.6 to 3.3, the amount of SiO being within the range of 10 to 30 percent, said builder having a bulk density within the range of 25 to 50 lbs./ft. being capable of absorbing up to 15 percent of its weight of a liquid nonionic surfactant and having a pH lower than that of either the sodium silicate or sodium carbonate from which it is fonned.
3. The particulate free-flowing silicated sodium carbonate detergent builder produced by the process of claim 1 containing from 18 to 22 percent by weight SiO as sodium silicate having a Na O:SiO weight ratio l:2.4, said builder having a bulk density within the range of 35 to 50 lbs/ft, being capable of absorbing about 15 percent of its weight of a liquid nonionic surfactant and having a pH, measured as a 1 percent aqueous solution, of about l 1.0.