US 3819526 A
This invention involves a process for making an improved detergent composition. In practice it consists in spraying a slurry of some ingredients of the composition on to other ingredients which have been pre-dried. Specifically, a hydrous alkali metal silicate or hydrous blend of silicate and other alkaline component is coated with a solution or slurry of other ingredients and then the composite is dried to give a free-flowing detergent. The resulting composition is very stable, containing a very low concentration of insoluble material. It also resists formation of insoluble material on storage.
Description (OCR text may contain errors)
United States Patent 1191 Pierce et al.
1 1 COATED DETERGENT COMPOSITIONS  Inventors: Richard H. Pierce, Broomall; Eric W. Vessey, Springfield, both of Pa.
 Assignee: Philadelphia Quartz Company,
Independence Square, Philadelphia, Pa.
22 Filed: Dec. 23, 1970 211 App]. No.: 101,163
 US. Cl ..252/135,117/100 B, 117/100 S, 252/527, 252/539  Int. Cl...... Clld 3/08, C1 1d 3/30, Cl 1d 17/06  Field of Search 117/1001; 23/313; 264/117; 252/99, 135
 References Cited UNITED STATES PATENTS 2,308,992 l/1943 Mertens 252/97 3,083,099 3/1963 Swanson et a1. 159/4 X 3,112,274 11/1963 Morgenthaler 252/99 3,208,822 9/1965 Baker et al. 252/135 X 3,216,946 11/1965 Curtin 252/156 3,324,038 6/1967 Chaffee et al. 252/546 June 25, 1974 Primary Examiner-Herbert B. Guynn Assistant ExaminerDennis L. Albrecht Attorney, Agent, or FirmFred C. Philpitt; Ernest G. Posner [5 7 ABSTRACT This invention involves a process for making an improved detergent composition. In practice it consists in spraying a slurry of some ingredients of the composition on to other ingredients which have been predried. Specifically, a hydrous alkali metal silicate or hydrous blend of silicate and other alkaline component is coated with a solution or slurry of other ingredients and then the composite is dried to give a freeflowing detergent. The resulting composition is very stable, containing a very low concentration of insoluble material. It also resists formation of insoluble material on storage.
5 Claims, No Drawings COATED DETERGENT COMPOSITIONS INTRODUCTION Many detergents are made by spray drying a slurry of 5 a blend of the detergent ingredients. Sometimes an ingredient is post blended, such as perfume which is not stable to the high temperature of the spray tower. However, the other ingredients of the detergent are mixed with water, often in a crutcher, and then pumped through a nozzle into a dryer. Most of the water is removed giving a free-flowing powder. These products often contain objectionable insoluble material which increases on storage.
It is generally known that the insolubles formed during drying and on storage consist mainly of silica.'The source of silica is the alkali metal silicate used in many detergents as builders and corrosion inhibitors. These are essential components of detergents. We have found that by changing the manufacturing process, dry detergents can be made containing alkali metal silicates which have greatly reduced insolubles. These products also resist formation of insolubles on storage. Still another advantage of the process modification is that it permits greatly increased production rate and thus reduces the processing costs.
This invention involves introducing the alkali metal silicate into the drying tower as a readily soluble, hydrous powder. The slurry from the crutcher, minus the silicate, is sprayed into the tower, so that the powdered silicate becomes coated with the remainder of the detergent composition. Thus, after drying, the product is either a complete detergent formula or granules of material ready for blending with dye, perfume, etc. to give a complete detergent formula.
Also, according to this invention, a blend of alkali metal silicate and other ingredient (s) of the composition can be introduced into the drying tower as a soluble, hydrous powder. These particles are then coated with a slurry of the remaining composition ingredients and are dried to free-flowing detergent granules.
The ingredients which can be blended with the alkali metal silicate are limited to those which are compatible with the silicate solution, i.e., will not cause a precipitate to form. An example of such a material is SNTA.
The improvement in production rate, from practice of this invention is a result of the higher amount of solids introduced in the spray tower, in relation to the amount of water in the slurry and the final product. It is generally recognized that the production rate of the drying operation is limited by the amount of water which must be removed. Feeding a hydrous, powdered silicate, rather than liquid silicate to the drying tower reduces this amount of water appreciably. Even greater production rate is achieved when other ingredients are added with the silicate as a hydrous powder.
THE INVENTION Detergent compositions according to this invention are produced in the following manner. A slurry of approximately 60 percent solids in water is made by blending all of the major ingredients of the formula ex cept the alkali metal silicate. A crutcher is a suitable blender for these materials. A typical slurry would consist of to 50 percent anionic surfactant, such as sodium tridecylbenzene sodium sulfonate, 10 to 50 percent sequestering agent, such as trisodium nitrilotriacetate (SNTA) or sodium tripolyphosphate, 0 to 30 percent sodium sulfate, 0 to 5 percent CMC, 0 to 2 percent optical brightener. Other ingredients, such as soda ash, borax, etc., can also be included. This slurry is sprayed through a nozzle into the top of a drying tower.
The drying tower is also equipped with a dust nozzle below the slurry nozzle. A fine spray of hydrous alkali metal silicate powder is introduced through the dust nozzle and coated with the slurry. The coated particles are then dried to give a free-flowing detergent composition.
The solid hydrous material added to the spray tower can be hydrous alkali metal silicate particles made by any method, such as thin film drying, spray drying or fluid bed drying of alkali metal silicate solutions, or a hydrous composite of an alkali metal silicate with compatible' detergent ingredients such as sequestering agents, CMC and others. The alkali metal silicate particles are generally sodium or potassium silicate butcan be a mixed sodium and potassium silicate. The SiO M 0 ratio on a mole basis can be 1.6 to 5 where M stands for an alkali metal or combination of alkali metals. The particles contain 10 to 30 percent moisture and have abulk density of 5 to 60 lbs/cu.ft. The alkali metal silicates can constitute 5 to 30 percent of the detergent composition.
Using the same setup, fine sprays of hydrous blends of alkali metal silicate and other detergent, ingredients are introduced through the dust nozzle and coated with a water slurry of the detergent composition minus the alkali metal silicate and the ingredient introduced with the silicate.
It is important that the alkali metal silicate and the other ingredients be in the proper proportion and also that they are compatible. Thus, no acidic materials, which would precipitate SiO should be introduced with the silicate. It is also important that the powdered spray be coated with just the proper amount of slurry so that the final product, after drying, has the correct composition.
EXAMPLES A further understanding of the invention can be obtained from the following illustrative examples which should not be considered restrictive or limiting.
EXAMPLE l A slurry of the following composition was made in a crutcher and heated to 200F: 33 parts of anhydrous STPP, 25 parts of linear tridecyl benzene sodium sulfonate, 1.5 parts of CMC, 0.5 parts of optical brightener and 40 parts of water. This slurry was pumped to the head of the drying tower and through a spray nozzle.
A fine spray of hydrous sodium silicate (SiO /Na O 2.4, H 0 20%), was pumped into the dryer, below the slurry spray, so that the falling slurry coated the silicate particles. The pumping rates were adjusted so that the coated particles, after drying to give free-flowing granules, had the proper composition and particle size. Thus, the pumping rate of the slurry was 15 times that of the powdered sodium silicate. The dried product contained 7 percent water. The product was then sprayed with perfume before packaging. The detergent was effective for home laundry use and had an insoluble content of less than 0.2 percent, after aging for 2 months in the package the insoluble content was only 0.25 percent. This very slow development of insolubles in the detergent indicates that the silicate is protected from reaction with other ingredients in the detergent to form insolubles.
EXAMPLE 2 EXAMPLE 3' The same setup as in example 1 was used. A slurry of the following composition was prepared in the crutcher: 30 parts linear tridecyl benzene sodium sulfonate, parts sodium sulfate, 2 parts CMC, 1 part optical brightener and 30 parts water. It is heated to 200F. and pumped through the spray nozzle at the head of the drying tower.
A composite consisting of 40 parts alkali metal silicate (SiO /Na O 2.9), 40 parts SNTA, parts of water was pumped through the dusting nozzle. It was thus coated with the slurry and dried to a final moisture level of l0 percent. It was a free-flowing, granular product with excellent detersive properties and very low insoluble content.
More or less detailed claims will be presented hereinafter and even though such claims are rather specific in nature those skilled in the art to which this invention pertains will recognize that there are obvious equivalents for the specific materials recited therein. Some of these obvious equivalents are disclosed herein, other obvious equivalents will immediately occur to one skilled in the art, and still other obvious equivalents could be readily ascertained upon rather simple, routine, noninventive experimentation. Certainly no invention would be involved in substituting one or more of such obvious equivalents for the materials specifically recited in the claims. It is intended that all such obvious equivalents be encompassed within the scope of this invention and patent grant in accordance with the well-known doctrine of equivalents, as well as changed proportions of the ingredients which do not render the composition unsuitable for the disclosed purposes. Therefore, this application for Letters Patent is intended to cover all such modifications, changes and substitutions as would reasonably fall within the scope of the appended claims.
What we claim is:
l. A detergent particle consisting of a core and a coating thereon: said core consisting of hydrous alkali metal silicate, said silicate selected from the group consisting of sodium silicate, potassium silicate and sodium-potassium disilicates; said coating consisting essentially of 10 to 50 parts by weight anionic surfactant, 10 to 50 parts by weight sequestering agent, 0 to 30 parts by weight sodium sulfate, 0 to 5 parts by weight CMC and 0 to 2 parts by weight optical brightener; wherein said silicate in said core constitutes 5 to 30 percent of said detergent particle and said particle has a moisture content of 5 to 15 percent and is characterized by a low insolubilities content even upon aging.
2. The particle of claim 1 in which the alkali metal silicates have:
a. a moisture content of 10 to 30%; and
b. a bulk density of 15 to lbs/cu.ft.
3. The particles of claim 1 in which the alkali metal silicate has a mole ratio of SiO /M O of 1.6 to 2.9.
4. The particle of claim 3 wherein the mole ratio of SiO /M O is 2.0 to 2.4/1.0.
5. The particle of claim 4 wherein the alkali metal silicate is sodium silicate.