US2046192A - Sodium silicate detergent - Google Patents

Description

Patented June 30, 1936 UNITED STATES PATENT -OFFI CE SODIUM SILIGATE DETERGENT No Drawing.

8 Claims.

This invention relates to sodium silicate detergents and in particular to" detergents containing high alkali ratio sodium silicates.

One object of this invention is to provide a detergent which is entirely water soluble and has improved emulsifying properties.

Another object is to provide a sodium silicate detergent which has water softening properties.

Still another object of this invention is to 10 provide a detergent which when dissolved in water will provide a higher hydroxyl ion concentration and at the same time a lower interfaclal tension than other buffered alkaline salts in like concentration. The term buffered alkaline salts as ordinarily understood refers to those salts which in solution do not deliver their full alkalinity at once. However, as the alkalinity of solutions of such salts is used up, either by neutralization or saponification, these salts have the property of liberating additional alkalinity, thus maintaining a uniform hydroxyl ion concentration.

We have now discovered that alkali silicates can be produced having a higher ratio of alkali to silica than that contained in alkali meta silicate and that such high alkali ratio silicates in solution yield a higher concentration of hydroxyl ions, a lower interfacial tension, and possess greater detergent power than alkali silicates of lower alkali ratio. In fact,-we have found our new detergent to possess greater detergent power than any buffered alkaline salt which we have thus far examined.

Our new detergent may be produced in the following manner:-

Take 670 pounds of sodium metasllicate of the composition represented by the formula NazSiOafiHzO and which has been ground to pass through a mesh screen and mix it with 180 .pounds of caustic soda of 76% NazO content, which has been ground to the same fineness. The metasilicate may vary in its content of water of hydration above and below the hexahydrate above mentioned in which case the amount of caustic added to a given quantity of hydrate is such as 40 C. and being maintained at preferably lessthan C. by means of cold water circulating through the -jacket. As the ingredients become mixed, a chemical reaction takes place, ;forming to give a ratio of NazOzsioz in the final silicate Application April 10, 1931, Serial No. 529,284 I a compound of sodium silicate wherein the proportion of NazO to $102 is that employed in the mix, and the powdery mass becomes plastic. On continued stirring granular particles form in the plastic mass, the particles growing as the stirring continues and becoming gradually more dry and less plastic. At the same time the particles become rounded by the continued rolling and rubbing together, and gradually become larger as the plasticity of the mass decreases and agglomeration proceeds.

The entire mass thus becomes gradually less plastic in character and the charge may be removed from the mixer as a mass of small more or less spherical granules still, however, somewhat plastic. If the product is to be used as such, we have found it desirable to spray the granules with approximately 0.1% of oleic acid to lower the hygroscopic character of the substance. This particular fatty acid or any other suitable saponiiiable fats, such as stearic or palmitic acid, is added by means of a spraying device before the product is discharged from the mixer.

In addition to using the sodium silicate alone, we have found that the addition of soda ash and trisodium phosphate aid in the keeping and free flowing qualities of the product. It has also been observed that the addition of finely divided soda ash and anhydrous trisedium phosphate to the granular mass in the mixer prevents further growth of the particles already formed during subsequent mixing or handling. Accordingly, we prefer to add to the above mentioned quantities while still in the mixer, pounds of fine soda ash and 50 pounds of anhydrous trisodium phosphate. This addition is preferably made after spraying with the oleic acid or other saponifiable oil, which in this case is added to the mass in the manner described above.

After all the ingredients have been added as above described, the product is discharged from the mixer and is allowed to age for a period, say, 24 hours, in covered containers during which time the chemical reactions taking place are given an opportunity of proceeding to completion. After the ageing period has been concluded,which ageing period is desirable for these silicates, whether or not the soda ash and trisodium phosphate has been added to the glom'erated or lightly caked together. These are now broken up by grinding or otherwise, and the product screened and placed in containers.

While, of course, any excess of NazO over that present in metasilicate may be used, we prefer sodium silicate,- -the granules are somewhat agto work with a ratio of NaeO to $102 greater than that of sodium metasilicate in which the ratio is 1 to 1, and have in fact used a ratio up to and including 2 to 1. YA particularly desirable ratio we have found to be 1.666 to 1, or 5 NazO to 3 SlOz.

When working ,with ratios between the limits of 1.600 to 1 and .1750 to 1, expressed as mols of F NazO to S102, we have observed that the agglomeration of the mass with formation of granules of lower plasticityijfollows the more highly plastic stage in a noticeable manner. We believe this phenomena to be due to certain chemical reactions talning place with the formation of new also be employed. In a co-pendiiig application,

Serial No. 463,758, filed June 25, 21930, new Patout No. 1,989,765, we have described and claimed aproduct consisting of sodium irietasilicate, together with a process for making same, in which a low alkali ratio silicate is treated with caustic to bring the molal ratio of NazO to S102 in. the compound to 1 to 1. A compound such as this latter may be employed as one of the starting materials in the present invention if desired. On the other hand, as we ha'ge pointed out above, if a sodium silicate pf the proper ratio is not available, it is possible; to use a lower alkali ratio sili-' cate and by adding an equivalent amount of caustic soda bring the final ratio to that herein specified. 3

As has already been pointed out, the use of hydrateslor other forms of metasilicate other than the hexahydrate is contemplatedby this invention. For example, we may use either the anhydrous salt, or the salt with 4, 5, 6, 9,- or 14 molecules of water or mixtures of these as starting material, altho we prefer to start with either the pentacr hexahydrated meta silicate, as giving a more *desirable product.

7 Another valuable property of our new product that the high hydroxyl ion concentration developed in aqueous solutions of said product increases the detergent power of .soap solutions, because of its eiliect on the interfacial tension and the increase in wetting power of its solutions. By virtue of the buifering effect of thesilica in our product we are enabled to obtain a solution containing the required amount of alkalinity for a washing operation without at any time exceeding the safe hydroxyl ion concentra-' tion. I Solutions prepared from our product are therefore especially valuable for laundering fine cotton fabrics and particularly as a soap builder in industrial laundry operations.

While we have described our invention in but one form, it will obvious to those skilled in the art that it is notgso limited, but is susceptible of various changes :and modifications, without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be j placed thereupon as are imposed by the prior art or as are specifically set'jcrth in the appended Z claims. Q

What iwe olaim'is:

1. A process of producing a detergent which' consists in providing a finely ground sodinm silicate, adding finely ground caustic soda thereto until the ratio of alkali expressed as NazO, to silica expressed as SiO2 is greater than 1 to 1 and not more than 2 to 1, mixing and stirring said finely ground ingredients to bring about a reactioi; therebetween and form a mass of gran ular particles, protectively coating said granular; particles by spraying with approximately 0.1%: of a sp onifiable oil, and cooling with disintegrai tion tol iorm a dry free flowing product. 2. Aprocess of producing a detergent which consists in providing a finely ground sodium silicate, adding finely ground caustic soda; thereto until the ratio of alkali in the mixture expressed as NazO to silica expressed as $102 greater than 1 to 1 and not more than 2 to 1i stirring said finely ground ingredients until ah'nass of granular particles is formed, pr-gtectively coating said particles by spraying with approximately 0.1% of a sapcnifiable oil, adding finely ground soda ash and anhydrous trisir'dium phosphate thereto to approximately 15% of the weight of the mass to aid in the' keeping and free flowing properties thereofiand ageing and cooling with distintegration to form a dry granular free flowing product. i

3. A granular detergent containing more than" 50% of the reaction products of caustic soda and sodium silicate? in which the ratio of alkali ex- -*pressed asNazG to silica expressed as SiOz is approximately 5 to 3. H

4. A granular. detergent containing more than 50% of the reaction products of caustic soda and sodium silicate in which the ratio 01' alkali err pressed as NazO to silica expressed as $102 is approximately 5 tov 3, and a lesser percentage of soda ash and trisodium phosphate intimately mixed with said reaction product. 5. A granular detergent containing more than 50% of the reaction products of causticasoda and sodium siilcatein which the ratio of alkali expressed as NazO to silica expressed as SiOz is approximately 5 to 3, and a lesser percentage of soda ash and trisodium phosphate intimately mixed with said reaction product and-coated with approximately 0.1% of a saponifiable oil.

6. A detergent comprising irregular granular to spherical particles containing as a 'principai ingredient the reaction product of caustic soda and sodium silicate in which the ratio of alkali expressed as NacO to silica expressed as S10: is greater than 1 to 1 and not more than 2 to 1 7. A detergent comprising irregular granular to spherical particles containing as a principal ingrecflent the reaction product of caustic soda and sodium silicate in which the ratio of alkali expressed as NazO to silica expressed as $102 is greater than B to 1 and not more than 2 to 1, said detergent having incorporated therein a minor proportion of soda ash and trisodium phosphate. 7

8. A detergent comprising irregular granular to spherical particles containing as a principal ingredient the'reaction productof caustic soda and sodium silicate in which the ratio of alkaii exprem'ed as NazO to silica expressed as S102 greater than 1 to 1 and not more than 2 to 1, said detergent having incorporated therein a minor proportion of soda ash and trisodium phosphate and coated with approximately 0.1% of a saponiilable oil.

FOSTER DEE SNELL. HENRY V. MOSS.