US2351559A

US2351559A - Process for the preparation of

Info

Publication number: US2351559A
Authority: US
Publication date: 1944-06-13
Anticipated expiration: 1961-06-13

Description

increase the sudsing of soaps.

Patented June 13, 1944 PROCESS FOR THE PREPARATION OF DETERGENT MIXTURES Andrew Treiiier, Paterson, N. J assignor to Solvay Sales Corporation, New York, N. Y., a corporation oi New York No Drawing. Application January 13, 1941, Serial No. 374,302

' 4 Claims.

This invention relates to a process for the preparation of detergent mixtures containing an alkali metal carbonate and an alkali metal phosphate with or without other materials.

Tetrasodium pyrophosphate has heretofore been proposed for use as a detergent and watersoi'tening material. It has been widely used to soften water, to suppress the formation of insoluble soap precipitates with hard water, and to It is also known that it is desirable for some purposes to use both a pyrophosphate and another detergent, and various methods have heretofore been proposed for making detergent mixtures containing the pyrophosphate. For example, it has been proposed to grind together dry pyrophosphate, calcined soda and sodium perborate to form a powder. It has also been proposed to spray with water a mixture or flaked pyrophosphate and sodium carbonate or to spray flaked py'rophosphate with a solution of sodium carbonate.

When a finely divided anhydrous alkali metal phosphate, such as tetrasodium pyrophosphate which is commonly used as a detergent, is added to water it cakes into hard lumps which require a long time to dissolve unless the phosphate is very slowly dusted into hot water. The slow dissolving characteristic of the phosphate is apparent even'in mixtures of the phosphate with other salts so that these mixtures may segregate when added to water, the phosphate going into solution only with diiliculty. Furthermore, when soda ash, with or without other materials such as other alkalies which it is frequently desirous to incorporate in detergents, are mixed with phosphate, the particles of the several materials have such divergent physical characteristics ranging, for example, from very fine powders to coarse crystals, it is difilcult to make uniform mixtures. The constituents of such mixtures readily segregate during handling and shipping due to the diflerences in particle size and shape.

It is an object of this invention to provide a process for the production of mixtures of alkali metal phosphate and an alkali metal carbonate. with or without other materials, which are suitably uniform in distribution of the several ingredients throughout the mixture and inwhich mixtures the components will not readily se regate during handling and storage. It is a further object of this invention to provide such mixtures containing the alkali metal phosphate and an alkali metal carbonate which, when added to water, will readily and completely dissolve therein.

I have discovered these and other advantages may be obtained by preparing the mixture or alkali metal phosphate and alkali metal carbonate. with or without other materials, using water in certain proportions and incorporating the materials with each other in a certain order.

In carrying out the process of this invention anhydrous alkali metal phosphate, preferably tetrasodium or tetrapotassium pyrophosphate, in the form of small particles is mixed with a mass of small particles of alkali metal carbonate and water which may contain other ingredients as solids or dissolved in the water. This massv of material, prior to the addition thereto or the phosphate, contains the water disseminated in the solid material in sufiicient amount to form a perceptibly moist or damp mass containing the alkali metal carbonate and to form, after the addition of the phosphate, a moist or damp mass which spontaneously sets into an apparently dry, friable mass. By allowing the mixture containing the phosphate to set into this dry, friable mass and then comminuting the mass, a freeflowing, dry, readily-soluble detergent mixture is obtained.

The actual amount of total water present in the materials mixed with the phosphate may vary widely, depending upon the particular alkali metal carbonate used, the presence of other materials in the mass of alkali metal carbonate, whether. the materials bind a part of the water as water of crystallization and the amount of water which the constituents of the mixture can thus take up to form an apparently dry product after the phosphate has been incorporated with the moist mass, the temperature at which the materials are mixed, etc. In all cases, however, the water present in the material to which the phosphate is added should be sufficient to form a perceptibly moist mass with which the phosphate is mixed to give a moist mixture, but should be further limited, as pointed out above, to an amount which causes the mixture to set spontaneously into an apparently dry, friable mass. At no time in mixing the ingredients should the water present form a paste or sticky mass with the solid materials containing the phosphate.

The water used in carrying out my process may be added to dry alkali metal carbonate or mixture of alkali metal carbonate and other dry solid material to form the desired moist mass to which the phosphate is then added. The water may contain dissolved in it other ingredients such as caustic soda or sodium silicate which it may be desirable to incorporate in the detergent. In-

stead of adding the water to the material containing alkali metal carbonate, the material may contain crystal soda. (NazCOalOHaO) and be warmed to a temperature of about 34 C. or higher at which sumcient of the water of crystallization is liberated from the crystal soda to form the required moist mass to which the phosphate is then added.

The spontaneous setting of the material con- I must be carefully controlled to prevent liquefaction of hydrated salts to form a pasty or sticky mass at any stage of the process. Hydrate formation also appears to be responsible for the nonsegregating, readilyand uniformly-soluble characteristics of the detergent mixtures produced by the proces of this invention. It appears that the anhydrous phosphate takes up water disseminated in the moist mass or material containing the alkali metal carbonate to hydrate at least in part the phosphate, without at the same time the materials being formed into large aggregates or nodules. When the mixture is permitted to stand for a short period of time, it sets to a readily friable mass as a result of this hydration of materials present in the moist mixture which are capable of taking up water 01' crystallization, such as alkali metal carbonates, silicates, caustic soda, metaor orthoor pyrophosphates, etc. When the mixture is prepared in accordance with the process of this invention, however, the set mass may be readily broken down by screening to give a uniform product of free-flowing consistency. To a partial or complete hydration of the alkali metal phosphate I ascribe the fact that when the product of my process is added to water, it readily and completely goes into solu tion instead of the phosphate but slowly and difficultly dissolving in the water.

The alkali metal carbonate and anhydrous alkali metal phosphate used in preparing detergent mixtures by the process of this invention may be any of the materials available on the market in the form of small particles. For example, tetrasodium' pyrophosphate may be employed either in the form of the ground or unground anhydrous material, the former consisting of a powdery material and the latter of a mixture of flake a d powdery material. A tetrasodium pyrophosphate of which 98% passed through a 50 mesh screen and more than 90% passed a 100 mesh screen is particularly suitable. The ordinary finely divided soda ash is well suited for use in my process.

When the mixtures of my invention are to include other materials than the alkali metal carbonate and phosphate, these may be incorporated with the carbonate and water before the phosphate is added. As pointed out above, the water may be used to dissolve one or more of these additional ingredients before they are added to the alkali metal carbonate. When highly hygroscopic materials such as caustic soda or sodium silicates are to be incorporated in the mixture prepared in accordance with the process of my invention, it is preferred to first make the mixture of alkali metal carbonate, water and phosphate in the manner described above and. allow this mixture to stand-until it has set into the apparently dry, friable mass. Finely divided solid caustic soda or silicate is then mixed with the apparently dry mixture of alkali metal carbonate and phosphate. The caustic soda and silicate absorb from the apparently dry mixture suflicient water to cause the particles of material to adhere and the caustic soda and silicate particles to become coated with the liner particles of the alkali metal carbonate and phosphate mixture. By rollowing this procedure, the product has a relatively small tendency to absorb moisture from the air and become damp during storage. The caustic soda or silicate or both may be added to the moist alkali metal carbonate and phosphate mixture in the form of solutions. When water is thus added to the moist mixture containing the phosphate, it must be limited to an amount insuflicient to form a pasty or sticky mass. Such a mass should not be produced at any stage in the process of forming the detergent mixture in accordance with this invention.

When it is desired to make a colored product, the desired dyestuil' may be dissolved in the water or solution used for wetting the alkali metal carbonate. When the other ingredients of the ,mixture are subsequently incorporated with the wetted carbonate, a very evenly-colored product is obtained.

As alkali metal carbonates suitable for use in preparing detergent mixtures in accordance with this invention, sodium or potassium carbonate or bicarbonate may be used or mixtures of two or more of these materials. Soda ash (a finely divided anhydrous sodium carbonate) and tetra-' sodium pyrophosphate are the materials generally employed in making up commercial detergents by the process of my invention. Accordingly, the invention will be more particularly described in connection with the production of detergent mixtures from soda ash and anhydrous tetrasodium pyrophosphate, with or without other materials.

The soda ash is first charged into a mixing device. Water is added and mixed with the soda ash to form a damp mass. The water is added in amount suflicient to form the moist mass but one which is not pasty or sticky and does not become pasty or sticky during the subsequent incorporation of anhydrous tetrasodium pyrophosphate. About 20 to 50 parts by weight of water for every parts of the soda ash are suitable to form the moist mass to which finely divided anhydrous tetrasodium pyrophosphate is added and incorporated therewith by mixing until a relatively uniform, slightly damp to moist, warm mixture is obtained. This mixture to which, as pointed out above, other materials may be added or which may contain other materials incorporated with the soda ash prior to addition thereto of the pyrophosphate, when allowed to stand for a short time, e. g. overnight, cools and sets into an apparently dry, [friable mass which may be readily broken down and screened to give the desired detergent mixture.

If it is desired to introduce into the mixture a higher ratio of water to the other materials than will give a suitably moist mixture with the soda ash or other alkali metal carbonate for incorporation therewith oi the pyrophosphate, this larger amount of water may be incorporated by carrying out the process of my invention in two or more stages. For example, in order to obtain a product containing equal parts of water, soda ash and tetrasodium pyrophosphate, 50 parts oi water may be mixed with 100 parts of soda ask to give a damp mass with which 50 parts of anhydrous sodium tetra pyrophosphate are incorporated. This mixture is allowed to set into a dry, friable mass which is comminuted. To the comminuted material 50 parts of water are added, followed by the addition of 50 parts anhydrous sodium tetra pyrophosphate. The resulting mixture is allowed to set into an apparently dry, friable mass which may then be comminuted to obtain the desired product. In order to prevent the temperature rising too high in incorporating the second 50 parts each of water and anhydrous sodium' tetra pyrophosphate with the previously prepared mixture, it generally would be necessary to cool the material with which the second portions of water and anhydrous tetra sodium pyrophosphate are incorporated. Without adequate cooling of these materials the temperature would tend to rise to a point at which a pasty or sticky mass would form. This would prevent the'desirable friable material being formed when the final mixture is allowed to set. This two-stage procedure for mixing anhydrous pyrophosphate with soda ash or other alkali metal carbonate and water is particularly advantageous where it is desired to hydrate the pyrophosphate to a relatively high degree, and thus increase to a maximum its solubility in water, without at the same time incorporating in the mixture enough alkali metal carbonate to carry the desired amount of water in a single stage of mixing the anhydrous Pyrophosphate with the moist mass containing alkali metal carbonate. =1

The process of this invention will be further illustrated by the following examples:

Example 1.--200 pounds soda ash and 80 pounds water are charged into a mixer and stirred for six minutes to thoroughly incorporate the water with the soda ash. A mass of about the consistency of wet snow is formed having a temperature of about 22 C. to 34 C. due to the heat evolved by hydration of the soda ash by a part of the water added thereto. 200 pounds of anhydrous tetrasodium pyrophosphate in the form of finely divided material as purchased on the market (either the ground or unground product) are then shoveled into the mixer and the materials further stirred for another three minutes. The temperature of the mixture rises to about 50 C. heating of the mass is due to the reaction of a part of the water with the soda ash and pyrophosphate to form hydrated salts. The hydrate formed with the soda ash would appear to be NaaCOsJI-IzO, since this is the sodium carbonate hydrate stable at a temperature of 34 C. or higher to which the mass is heated. The slightly damp mixture which results is discharged and allowed to stand overnight in a pile on the floor. The material lightly sets and is screened through a 20 mesh screen. A dry, granular product suitable for marketing is obtained.

In screening material prepared by the process of this example, only 5% of it remained on the 20 mesh screen. These oversized particles ranged from rice to bean size and were easily crushed. By again screening the crushed material and adding it to the material originally passed through the screen, all of the material was recovered as product.

For comparison with the process of this invention, 200 pounds each of the same soda ash and tetrasodium pyrophosphate as used in this example were first mixed as dry materials in the mixer for six minutes. Then 80 pounds of water were added and mixed with the solid materials for three minutes. The mixture was allowed to set overnight and then screened on a 20 mesh screen. It was found 31% of the material did not pass through the screen. By changing this procedure to first mix the water with the tetrasodium pyrophosphate and then incorporate the soda ash in the mixture, when the product was screenedon a 20 mesh screen 54% of it did not pass through the screen. In both of these cases the oversized material varied from bean to egg size. These large aggregates were very hard as compared'wlth the small amount of readily crushed oversized material obtained when the procedure of the above example, employing the process of my invention, was followed.

Example 2.--52 pounds of soda ash are placed in a mixer and to it are added a mixture of 11.5 pounds of 50 36. caustic soda solution and 22 pounds of 40 B. commercial silicate of soda solution. After these materials are stirred for six minutes 14.5 pounds of tetrasodium pyrophosphate are added. The mixing of the mass warmed by hydration of the solid salts present is continued for another three minutes. After allowing the product to set, which it does in the course of a short time, and screening the set mass, a

stable, readily-soluble product is obtained.

The procedure of this example is particularly advantageous since it permits of producing in a simple, economical manner a dry, stable product using the solutions of caustic soda and of sodium silicate which are readily available on the market without having to use these materials in their more costly tom of solid caustic soda or sodium silicate.

Example 3.35 parts by weight of soda ash and 25 parts of sodium bicarbonate are charged into a mixer and mixed therein. 15 parts Nacconol (NRNO), the proprietary name for an alkyl aryl sulfonate detergent, are mixed with 15 parts water to make a thin, watery paste. This paste is added to the soda ash-bicarbonate mixture and the materials stirred for six minutes to thoroughly mix them. To the mixture 10 pounds of anhydrous tetrasodium pyrophosphate is added. After stirring the warm materials for another three minutes, the mixture is discharged and allowed to stand until it sets. The set mixture is screened to give a dry, uniform, soluble product.

The procedure of this example may be varied,

' if it is desired to make a product of higher pH,

by substituting for a part of the water a solution of caustic soda. In this case the caustic soda solution is mixed with the-soda ash before the bicarbonate is mixed therewith. The remainder of the procedure conforms to that described above.

Soda-red oil soap and other surface active materials may be substituted for the Nacconol (NRNO) used in making up the mixture of this example. An advantage of including in the detergent mixtures such a surface active material is that it appears to slow down the rate of crystallization of salts in the mixture. After curing mixtures containing these surface active materials, the material appears to be especially uniform and, in comminuting through a screen, even less oversized particles are left than the small 'gent mixture which amount which otherwise may be formed in carrying out my process.

Example 4.-80 pounds soda ash are charged into a mixer and 82 pounds water incorporated therewith. 48 pounds of finely divided anhydrous tetrasodium pyrophosphate are then added and the mixing continued to damp, uniform mixture. The materials are removed from the mixer and allowed to stand until they set into an apparently dry, friable mass. This mass is comminuted and reintroduced into the mixer. Then 72 pounds of finely divided anhydrous sodium metasilicate and 160 pounds of ground solid caustic soda are added and incorporated with the apparently dry mixture pre viously formed. After uniformly mixing these materials the mixture isagain allowed to set and the dry, set mass is screened to obtain a product ready for marketing.

By following the procedure of this example, the particles oi sodium silicate and caustic soda, which are highly hygroscopic materials, are given an adherent coating of the less hygroscopic soda ash and tetrasodium pyrophosphate. As a resuit, the product of this example has a much less tendency to absorb moisture from the atmosphere and become damp and unsatisfactory than products containing solid, uncoated caustic or sodium silicate.

The process of this example may be changed by substituting for the anhydrous metasilicate and ground caustic soda a desired proportion of solid crystalline metasilicate, sesquisilicate or orthosilicate. Products suitable for laundry purposes and in dish-washing machines may thusbe made containing hygroscopic materials coated with soda ash and tetrasodium pyrophospate. The tendency of the products to absorb moisture from the air is thus reduced.

If it is desired to color the products obtained in carrying out the processes of any of the above examples, this may be done by dissolving a dyestufi' in the water or solution used in wetting the soda ash.

While the above examples are representative of procedures for making mixtures containing soda' ash and tetrasodium pyrophosphate in accordance with this invention, the invention is not limited to these particular procedures or to the proportions of materials used in making the products of the examples. In can'ying out the processes of my invention anhydrous sodium tetra phosphate (NacPron) may be used in place of the tetrasodium pyrophosphate to obtain a friable mass which may be readily comminuted to give a product suitable for marketing.

I claim:

1. The process for the production of a detercomprises incorporating with a mass of finely divided solid particles comproduce a warm,

water with soda ash in 'minuting the prising sodium carbonate an amount of water sufiicient only to form a moist, non-pasty mass with the water disseminated therein and thereafter mixing with said moist, non-pasty mass a finely divided anhydrous phosphate from the group consisting of tetrasodium pyrophosphate and sodium tetra phosphate in an amount such that the phosphate and the moist mass form a detergent mixture which sets to a friable materoal which is readily broken up into fine particles that are free-flowing and readily soluble in water.

2. The process for the production of a detergent mixture which comprises incorporating with a mass of finely divided solid particles comprising sodium carbonate an amount of water sufiicient only to form a moist, non-pasty mass with the water disseminated therein and thereafter mixing with said. moist, non-pasty mass finely divided anhydrous tetrasodium pyrophosphate in an amount such that the phosphate and the moist mass form a detergent mixture which sets to a friable material which is readily broken up into fine particles that are free-flowing and readily soluble in water, and comminuting the set mixture to a uniformly fine particle size.

3. The process for the production of a detergent mixture which comprises incorporating amount sufficient only to form a moist, non-pasty mass with the water disseminated therein and thereafter mixing with soid moist, non-pasty mass finely divided anhydrous tetrasodium pyrophosphate in the ratio of substantially 0.6 part by weight of said tetrasodium pyrophosphate for every 1 part by weight of said soda ash, thereby forming a detergent mixture which sets to a friable material which is readily broken up into fine particles that are free-flowing and readily soluble in water.

4. The process for the production of a detergent mixture which comprises mixing water with finely divided anhydrous sodium carbonate in amount sufilcient only to form a moist, nonpasty mass containing disseminated therein about 20 to 50 parts by weight of water available for crystallization with every 100 parts sorium carbonate, mixing with said moist, non

pasty mass finely divided anhydrous tetrasodium pyrophosphate at a temperature above 34 C. at which the materials do not form a pasty or sticky mass, said tetrasodium pyphosphate being in amount such that the phosphate and the moist mass form a detergent mixture which sets to a friable material which is readily broken up into fine particles that are free-flowing and readily soluble in water, allowing the mixture to set spontaneously to said friable material, and comset material to a uniformly fine ANDREW TREFFLER.

particle size.