US 3231506 A
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United States Patent 3,2315% PROCESS FGF. MAKENG BETERGENT TABLET Albert Lyle Schulerud, Nntley, Ni, assignor to Colgatellalrnolive Company, New York, N.Y., a corporation of Delaware N Drawing. Filed Apr. 3, 1961, Ser. No. 166,033 Claims. (Cl. 25Z--138) The present invention relates to a detergent tablet which is resistant to abrasion and accidental breakage when dry and is also adequately disintegrable in water in normal laundering operations. The invention includes a process for making such a tablet by coating solid detergent particles with soluble and insoluble silicate compounds, lightly compacting the coated particles to a form-retaining tablet and applying to the surface of the tablet a coating of readily water soluble film-forming organic synthetic polymer.
It has been found that the production of detergent tablets from particulate detergent compositions comprising nonionic detergents can be facilitated and the products can be improved by following the processes herein described. In accordance with the invention, a process for making a briquetted detergent tablet begins with mixing together water soluble nonionic organic detergent with a normally solid water soluble inorganic salt and producing therefrom a particulate detergent containing up to 21% moisture. To the particles an aqueous solution of soluble silicate is applied, preferably by spraying. The silicate coating is 3 to of the product and the moisture content of the detergent is raised to about 16 to by the silicate solution. Next, to the coated detergent particles 0.5 to 5% of finely divided water insoluble inorganic siliceous material, such as a silicate, is applied to form another coating, held to the particles by the water soluble silicate. The detergent particles are subsequently pressed into a solid form-retaining briquetted table at a pressure low enough to form a tablet which is very readily disintegrable in water, after which about .25 to 5% of a readily water soluble synthetic organic film-forming polymer is applied to the tablet to form on the surface thereof a water soluble film which is of strength sufficient to help make the detergent tablet resistant to abrasion and accidental breakage, when dry, and of solubility such that the detergent tablet is readily disintegrable in water.
In following the invented process, it is preferred to mix together the major constituents of a heavy duty synthetic organic detergent composition, including nono u F 101110 detergent and inorganic builder salts, in an aqueous solution or dispersion, usually containing 20-70% solids. The uniform slurry is atomized and sprayed into a heated drying gas to form a spray dried detergent in particulate form, preferably of the low-sudsing type formula. instead of spray drying, other production techniques may be employed to produce such detergent powders.
The dry or partially dried detergent is agitated, as by tumbling in a rotating inclined drum and while being so moved is sprayed with a solution of water soluble silicate. The silicate is spread over the surfaces of the particles 'by the tumbling action and causes the finer particles present to adhere to others to form particles of larger size. This agglomeration is often accompanied by a decrease in density. In addition to altering product density, the silicate conditions the particles so that they will adhere together better in subsequent briquetting operations.
coated with soluble silicate. The tale coating tends to arrest agglomeration and improves the ease of pressing into briquettes. The talc is preferably applied in the same mixing drum or vessel as the silicate, preferably as a fluidized powder blown into the mixer by air pressure. After about 5 to 15 minutes mixing the treated detergent particles are withdrawn, oversized agglomerates screened out and the product, preferably agglomerates of particle size within the range of 6 to 60 mesh is removed. The coating process described above may be either of the batch type or continuous, the latter being preferred for high speed commercial procedures.
The coated detergent may be immediately pressed into briquetted tablet form or may be temporarily stored for several hours before compacting. The free flowing particles are fed to mold cavities and are lightly compacted to desired shape, at a pressure of about 10 to 100 pounds per square inch, preferably about to 90 pounds per square inch. The pressure employed is that at which the tablets made are resist-ant to abrasion and accidental breakage, when dry, and are still readily disintegrable in Water. Thus, in a simulated Washing machine test, freshly made tablets, also coated with organic polymer as discussed below, should disintegrate in agitated water at room temperature in less than 90 seconds, preferably less than seconds. When aged, the hardened tablets may take as long as 4 minutes to break up completely. Although it is desirable to have the most rapid solubility characteristics possibie, even the aged tablets stilldissolve fast enough in usual laundry usage to wash satisfactorily.
The lightly compacted tablets are next sprayed with a protective coating of an organic film-forming polymer, preferably polyvinyl alcohol, usually as an aqueous solution applied in spray form. The entire briquette surface is covered and a strong bond between polyvinyl alcohol and the previous coating of soluble silicate and talc is 0 tained. To speed production and make a hard protective coating on the detergent tablet, the polyvinyl alcohol coating is dried by infra-red heating lamps. The finished briquettes are then packed in plastic bags or sleeves, boxed, cased and shipped.
The products made according to this invention are strong and can withstand rigid shipping and handling tests without objectionable breakage occurring. Yet, the tablets disintegrate readily in water.
The materials of the present compositions and the processing operations will now be described in greater detail to enable one of skill in this art better to appreciate the significance of the invention.
The water soluble nonionic detergent is preferably an alkyl phenoxy poly lower alkoxy lower alkanol and nonyl phenoxy polyoxyethylene ethanol of about 9 to 10 ethoxy groups is a specific example of this group found to be excellent. In the preferred class of compounds mentioned the alkyl group is usually of 6 to 14 carbon atoms and the alkoxy chain is of 4 to 12 units long, each unit comprising from 2 to 4 carbon atoms. Commercial products of this type are usually mixtures and mixtures of this and other types of water soluble nonionic detergents may be employed. Thus in appropriate formulas other nonionics, such as the block copolymers of ethylene oxide and propylene oxide (Pluronics) reaction products of higher fatty alcohols and lower alkylene oxide (Emulphogene), polyoxyethylated higher fatty acids (Emulphor), polyetho-xy and poly lower alkoxy esters and others of sugar alcohols, especially of sorbitol and mannitol (Span, Tween), may be used in addition to the alkyl phenoxy polyoxyalkylene alk-anol and in some cases in replacement thereof. In the present detergent compositions the proportion of nonionic detergent, on a final product weight basis, as are all other 3 proportions given, is usually 4 to 14%, preferably 7 to 12%.
In addition to nonionic detergent an anionic organic detergent may also be present, usually primarily to produce some foam and to contribute its cleaning power to the composition. A preferred detergent is sodium tridecyl benzene sulfonate, a mixture of detergents, the alkyl groups of which are derived from a mixture of propylene tetramer and pentamer. The alkyl groups maybe of other structures of 10 to 18 carbon atoms and these compounds may be used as their other Water soluble metal salts of similar properties. In place of some or all of the alkyl benzene sulfonate, one may employ other anionic sulfated or sulfonated organic detergent compounds containing fatty alkyl or acyl groups of 10-18 carbon atoms, such as sodium lauryl sulfate, sodium coconut oil fatty acids monoglyceride sulfate and a sodium salt of a higher fatty acid amide of N-methyl taurine. The proportion of anionic detergent should normally be from about 1 to 5%.
A foam stabilizer, such as a long chain fatty compound having an alkyl group of 12 to 18 carbon atoms, preferably a mixture of cetyl and stearyl alcohols, may also be included to thicken the foam of the anionic detergent. Ordinarily 0.5 to 5% and preferably 0.5 to 3% of this material is sufiicient.
The inorganic water soluble normally solid salt is preferably a builder salt of the polyphosphate type, such as sodium tripolyphosphate. Other useful builders and fillers include alkali metal sulfates, sodium and potassium carbonates, tetrasodium pyrophosphate and sodium silicates of various Na O/SiO ratio. These give the present tablets a useful and functional base for the organic materials. From 30 to 75% of the product may be soluble inorganic salt and preferably 30 to 50% sodium tripolyphosphate is used in mixture with smaller proportions of sodium silicate (N-a O/SiO of 122.35) and sodium sulfate.
Following the spray drying method mentioned earlier a slurry of the above materials in an aqueous medium is dried to a moisture content of 7 to 14%. By this and other methods, moistures of up to 21%, usually 2 to 18%, are obtainable and particles of such moistures can be made into satisfactory tablets by the present methods. If the spray dried particles are high in fines or coarse pieces, they should be screened or classified to substantially all (90% or more) be held by a 100 mesh sieve (U.S. Stand ard Series) with none on 6 or 8 mesh.
The silicate solution sprayed on the detergent beads while they are being tumbled or otherwise agitated is a water soluble metal silicate. the best is sodium silicate of an Na O/SiO ratio from 1:2 to 1:3, most preferably 1:2.35. This silicate is made into an aqueous solution which may be of 25 to 46% solids content. Generally the silicate solution will be of 35 to 43.5% solids content, preferably about 35 to 37%. concentrations can be satisfactorily stored and sprayed. The proportion of water solution of sodium silicate sprayed onto the moving detergent bead surfaces is usually to 30%, preferably about silicate solution. Thus, 15 to 30 parts of solution are sprayed onto about 85 to 70 parts of detergent beads, neglecting to make a minor correction of these figures for the small amounts of polyvinyl alcohol or other coating applied later. The 3 to 15% silicate coating added, preferably 6.5 to 8.5% helps agglornerate the beads to a 6 to 60 mesh range (about 0.25 to 4 millimeter diameters) and helps in creating a strong briquette. It also raises moisture content to 16 to preferably 17.5 to 20.5% which is often best for briquetting.
After coating with silicate and continuing mixing and agglomerating, the tumbling beads are next coated with a very finely divided talc. Other magnesium silicates or other finely divided water insoluble inorganic silicates of equivalent properties may be used with or in place of talc. 0.5 to 5% of tale is sufficient to hinder further ag- Of the alkali metal silicates These glorneration and improves the speed and ease of briquetting. After the particles are coated with talc they are removed from the tumbling zone and are immediately ready for pressing into tablets.
In pressing, the detergent particles are flowed into molds or pockets in high speed shaping equipment. Opposed dies compact the particles in a cylinder and form it into a fiat circular tablet, beveled and with a diametric score line to facilitate breaking in half, if desired. The dies are set with stops to make tablets of a constant thickness so the same volumes of detergent are charged to keep compacting pressures within the correct range of 10 to 100 pounds per square inch.
The pressed tablets, due to their silicate coatings, can be handled Without fear of objectionable breakage. However, such tablets would not be permanently satisfactory unless subsequently coated with a water soluble polymeric film forming polymer, such as polyvinyl alcohol.
The poly-vinyl alcohols of commerce usually contain minor proportions of a lower fatty acid ester, polyvinyl acetate, This may be present in polyvinyl alcohols employed in this invention to the extent of about 10 to The useful polyvinyl alcohols are also of a Weight degree of polymerization between about 30 and 300. A good polyvinyl alcohol for use in accordance with this invention has a Weight average degree of polymerization of about to 250 (viscosity of about 2 to 6 centipoises) and a polyvinyl acetate content of 15 to 25% and a most pre ferred material has a Weight average degree of polymerization of about (viscosity of 3.5 centipoises) and polyvinyl acetate content of 20%.
The polyvinyl alcohol should contain relatively little insoluble matter, should be colorless, odor-free and of neutral pH. Deviations from the above requirements may be made where warranted but, in general, the polyvinyl alcohol of the recited specifications would be most acceptable for household detergent products. Instead of the described polyvinyl alcohol, other readily water soluble synthetic organic film-forming polymers of similar properties can be used, but usually such other compounds will not be as effective. However, polyvinyl pyrrolidone, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose and similar polymeric substances can produce water soluble films for briquette surfaces. When used, it is preferred to mix them with polyvinyl alcohol so that the special advantages attending the presence of that material may be retained.
Coating of the detergent tablet is preferably done by spraying onto the surfaces a liquid comprising the polyvinyl alcohol dissolved in water. The aqueous solution should be sprayed or atomized in fine droplet form as evenly as practicable onto the surface of the briquette. The spray solution may contain glycerol or other low polyols to serve as plasticizers to help to keep the polyvinyl alcohol fiexible and resilient, detergents or wetting agents to improve wetting of the briquette and neutralizing agents, e.g., sodium bicarbonate, to improve the odor of the polyvinyl alcohol by reacting with free acid present. Among other plasticizers that may find use are glycols, e.g., ethylene glycol and sugar alcohols, such as sorbitol.
The amount of polyvinyl alcohol sprayed onto the briquette surface should be from 0.25 to 5% of the briquette weight, preferably 0.3 to 1%. The polyvinyl alcohol is preferably applied as a 10 to 25% solution, such as a 17% solution in water, the proportion of such solutions used being from 3 to 10%, preferably about 6% of the briquette weight. When sprayed onto the detergent briquette surface, the polyvinyl alcohol and its solvent fill the voids between particles and also cover the surfaces of the particles. Because the briquette before coating is not perfectly smooth, it is evident that the coating will be thicker in some spots than in others but it may be said that the average thickness is from 0.01 to 0.8 millimeter, preferably .02 to 0.1 millimeter.
After coating with polyvinyl alcohol solution, the briquette may he surface dried by forced air, heated air, infra-red rays or other suitable drying means to remove essentially all the moisture accompanying the polyvinyl alcohol in the coating spray. Thus, the final product will be of about the same moisture content as that obtained in the particles before pressing. After drying, the briquette may be packed immediately in cartons ready for shipment and use. It is usually preferred that such cartons contain moisture barriers to assist in maintaining the correct moisture content in the briquette. Briquettes made in accordance with this invention may be shipped in commerce without breaking and even though stored for months before use will still disintegrate and dissolve rapidly enough when added to the tub of any of the conventional washing machines. They will also pass the rather severe strength and solubility requirements set for such products, withstanding a drop of at least 1 foot onto a hard surface, e.g., a metal plate, without breaking and also disintegrating in agitated water at 100 Fahrenheit in a washing machine within a period of no greater than 4 minutes, usually within one minute. The washing machine referred to is a commercial top-loading machine with a, center post agitator of average operating and .design characteristics. 7
The following'examples illustrate the invention. All percentages and proportions in the examples, this specification'and the appended claims are by weight unless otherwise indicated.
Example I Nonyl phenol ethoxylate (9.5 ethylene oxides) 13 Sodium tridecyl benzene sulfonate 5 Technical cetyl alcohol 1 Sodium tripolyphosphate 43 Sodium sulfate 25 Sodium silicate (Na O/SiO ratio of 112.35).... 4 Moisture 8.5 Adjuvants (anti-redeposition age n t fluorescent brightener, perfume, anti-oxidant) 0.5
The above formula was made by spray drying an aqueous crutcher mix slurry of all materials except perfume which was added after spraying. In a tumbling drum there were added 100X parts of spray dried particles of such formula of size from 8 to 100 mesh by spraying the following amounts and concentrations of a water solution of sodium silicate of Na O/SiO ratio of 1:2.35. Moisture contents of briquetted tablets made therefrom are also given.
(X) Parts Percentage Final silicate solids moisture solution After about minutes tumbling, talc powder, substantially all less than 200 mesh, was air-blown onto the tumbling particles. The amount of talc used was 2% and the beads were agitated for another ten minutes, after 'whi'ch they had been agglomerated to 6 to 60 mesh and were ready for immediate pressing. Within two hours, they were pressed to flat cylinder shape at a pressure within the 40 to 90 pounds per square inch range and spray coated with about 0.8% polyvinyl alcohol in a 17% aqueous solution at about 150 F. The polyvinyl alcohol was of weightaverage degree of polymerization about 100 and contained 15-25% polyvinyl acetate. Af-
ter coating of the tablet the polyvinyl alcohol was dried under infra-red lamps. The coating made was of irregular thickness, between about 0.01 and 0.8 millimeter.
The tablets resulting pressed very easily in the automatic machinery employed (having Teflon dies and sleeves) and satisfactorily passed drop tests, shipping tests and disintegration tests (in water), They are attractive in appearance, dust free and easy to use. The polyvinyl alcohol of the coating even increases the antiredeposition properties of the detergent. In' storage the tablets did not swell or crumble, but retained their original shapes and surface appearances. They could be shipped, even in cold Weather, and when packed properly, exhibit a surprisingly good resistance to breakage.
Example II Nonyl phenoxy polyoxyethylene ethanol, having This formula was made by the spray drying method, a's in Example I. The beads were coated with 20 parts of a 43.5% solids water solution of sodium silicate' of Na O/SiO ratio of 1:235, which raised the moisture content of the beads (and tablet) to 17.7%. The agglomerated beads resulting from tumbling were coated with 2% talc, then pressed and coated with polyvinyl alcohol, as described in Example I. The talc-coated beads pressed easily and the products resulting were good hard detergent tablets which still are lighter in weight than is usual for pressed powders and can be readily dissolved because of their rapid disintegration in water. They pass the earlier described strength and disintegration tests and are good detergents in a've'ry useful premeasiir'ed form.
When the amount of talc used was cut to 1% adecr'e'ase in pressing ease resulted but still the tablets could be made more readily than without any talc. Instead of talc other siliceous insoluble materials may also be used, e.g., feldspars, micas, even silica flour, preferably as only a partial replacement therefor.
The present invention has been illustrated by decription of the invented products made and manufacturing methods employed. These examples are illustrative only and are not to be considered as limiting the allowed claims.
What is claimed is:
1. A process for making a briquetted detergent tablet soluble alkali metal silicate to cause agglomeration into larger particles and to increase the moisture content thereof to about 16 to 25%, applying to the coated detergent particles 0.5 to 5% of finely divided water insoluble 1 inorganic silicate to form a c'oati'ng'on the particles,h'eid to them by the water soluble silicate, and to arrest agglorneration of the detergent particles and produce agglomerates within the range of 6 to 60 mesh, pressing the detergent particles into a solid form-retaining briquetted tablet at a pressure of about 10 to 100 pounds per square inch to form a tablet which is readily disintegrable in water and applying to the tablet about .25 to of a readily water soluble synthetic organic film-forming polymer selected from the group consisting of polyvinyl alcohol, polyvinylpyrrolidone, sodium carboxymethyl cellulose and hydroxypropyl methyl cellulose to form on the briquette surface a water soluble film which is of strength suificient to help make the detergent tablet resistant to abrasion and accidental breakage, when dry, and of solubility such that the detergent tablet is readily disintegra-ble in water.
2. A process for making a briquetted detergent tablet which is resistant to abrasion and accidental breakage, when dry, and readily disintegrable in water, comprising mixing together 4 to 14% of a water soluble nonionic synthetic organic detergent which is an alkyl phenoxy polyoxyethylene ethanol having 6 to 14 carbon atoms in the alkyl group and 4 to 12 ethylene oxide units, 1 to 5% of a water soluble metal salt of higher alkyl benzene sulfonic acid in which the alkyl group is of to 18 carbon atoms, 0.5 to 5% of a foam stabilizer which is a long chain fatty alcohol having an alkyl group of 12 to 18 carbon atoms, and 30 to 75% of a water soluble inorganic alkali metal builder salt, producing therefrom a particulate detergent containing 2 to 18% moisture, applying to 30% of an aqueous solution of to 46% solids content'sodium silicate of Na O/SiO ratio of 1:2 to 1:3 to the particulate detergent to coat the particles with 3 to 15% sodium silicate, to cause agglomeration into larger particles and to increase the moisture content thereof to about 17 to 24%, applying to the coated detergent particles 1 to 3% of finely divided talc to form a coating on the particles, held to them by the sodium silicate, and to arrest agglomeration of the detergent particles and produce agglomerates within the range of 6 to 60 mesh, pressing the detergent particles into a solid form-retaining briquetted tablet at a pressure of 10 to 100 pounds per square inch, low enough to form a tablet which is readily disintegrable in water, and applying to the tablet about .25 to 5% of a readily water soluble polyvinyl alcohol.
3. A process for making a briquetted detergent tablet which is resistant to abrasion and accidental breakage, when dry, and readily disintegrable in water, comprising mixing together an aqueous slurry of 7 to 12% of a water soluble nonionic synthetic organic detergent which is nonyl phenoxy polyoxyethylene ethanol of about 9 to 10 ethoxy groups, 1.5 to 5% of sodium alkyl benzene sulfonate in which the alkyl group is of 12 to 15 carbons atoms, 0.5 to 3% of fatty alcohol foam stabilizer having a fatty alkyl group of 12to 18 carbon atoms and to of sodium tripolyphosphate builder salt, spray drying the slurry to form particles of moisture content of 7 to 14% and of particle size substantially all between 6 and 100 mesh, tumbling the partially dried particles and while tumbling, spraying onto the particles 15 to 30% of an aqueous solution of 35 to 43.5% solids content sodium silicate of Na O/SiO ratio of about 112.35 to coat the particles with 6.5 to 8.5% sodium silicate, to increase the moisture content thereof to 17.5 to 20.5% and to cause agglomeration into larger particles, after about one to five minutes, applying to the coated detergent particles 1.5 to 2.5% of finely divided talc to form a coating on the particles, held to them by the sodium silicate, and to arrest agglomeration of the detergent particles and produce agglomerates within the range of 6 to mesh, pressing the detergent particles into a solid form-retaining tablet at a pressure of 40 to pounds per square inch, low enough to form a tablet which is readily disintegrable in water, spraying the tablet with 0.3 to 1.0% readily water soluble polyvinyl alcohol, in aqueous solution, the polyvinyl alcohol being of a weight average degree of polymerization of about 30 to 300 and a polyvinyl acetate content of about 10 to 30% thereof, and drying the polyvinyl alcohol solution to form a water soluble protective film coating.
4. A water soluble detergent briquette which is resistant to abrasion and accidental breakage, when dry, and disintegrates readily in water, comprising a multiplicity of solid particles composed of a homogeneous mixture of about 4 to 14% of a Water soluble nonionic organic polyethoxy detergent selected from the group consisting of ethoxylated alkyl phenol, ethoxylated higher fatty alcohol, ethoxylated higher fatty acid and ethoxylated propylene oxide polymers and about 30 to 75% of a Water soluble inorganic alkali metal builder salt, and 16 to 25% moisture content, in the form of adhering particles initially of moisture content up to 21%, consecutively coated with 3 to 20% water soluble alkali metal silicate and 0.5 to 5% of finely divided water insoluble silicate, the coated particles substantially all within the size range of 6 to 60 mesh being lightly compacted at a pressure of about 10 to pounds per square inch to form a shaped briquette, which is coated with an adhering and binding film of 0.25 to 5% of a readily water soluble polyvinyl alcohol of a weight average degree of polymerization of about 30 to 300 and a polyvinyl acetate content of about 10 to 30% which forms on the surface of the detergent briquette a water soluble coating of an average thickness from about 0.01 to 0.8 millimeter.
5. A water soluble detergent-briquette which is resist ant to abrasion and accidental breakage, when dry, and disintegrates and dissolves readily in water, comprising a multiplicity of agglomerated spray dried solid particles of diameters substantially within the range of 0.25 millimeter to 4 millimeters, composed of homogeneous particles comprising a mixture of 7 to 12% of nonyl phenoxy poly oxyethylene ethanol of about 9 to 15 ethoxy groups, 1.5 to 5% of sodium alkyl benzene sulfonate detergent in which the alkyl group is of 12 to 15 carbon atoms, 0.5 to 3% of fatty alcohol of 12 to 18 carbon atoms and 30 to 50% of sodium tripolyphosphate coated with 6.5 to 8.5% of sodium silicate of Na O to SiO ratio of about 122.35 and, over the silicate coating a coating of 1.5 to 2.5% talc, the coated particles being in the form of adhering particles of moisture content of 17.5 to 20.5%, lightly compacted at a pressure of about 10 to 100 pounds per square inch, the compacted tablet being coated with an adhering and strengthening binding film of 0.3 to 1.0% of a readily soluble polyvinyl alcohol of a weight average degree of polymerization of about 100 and a polyvinyl acetate content of 15 to 25% which forms on the surface of substantially the whole detergent briquette a water soluble coating of thickness averaging about 0.02 to 0.1 millimeter.
References Cited by the Examiner UNITED STATES PATENTS 2,382,165 8/1945 MacMahon 252 XR 2,636,008 4/1953 Jurgensen et al. 252-93 2,855,367 10/1958 Buck 252138 2,875,155 2/1959 Miles 252-138 FOREIGN PATENTS 141,503 6/1951 Australia.
OTHER REFERENCES Pont de JULIUS GREENWALD, Primary Examiner. v