GB2106483A - Non-gelling inorganic salt crutcher slurrie - Google Patents

Abstract

Gelation and setting of desirably miscible and pumpable crutcher slurries comprising sodium carbonate, sodium bicarbonate and sodium silicate in an aqueous medium are retarded and often prevented by the addition to such medium of a citric material, such as citric acid and/or water soluble citrate, and magnesium sulphate.

Description

SPECIFICATION Non-gelling inorganic salt crutcher slurries The present invention relates to non-gelling aqueous slurries of inorganic salt mixtures and to methods for their manufacture. More particularly, it relates to the utilization of certain materials, which, in combination, exert an exceptionally good and improved anti-gelling action, preventing gelation, excess thickening and setting up of bicarbonate-carbonate-silicate slurries, from which particulate heavy duty synthetic organic detergent compositions may be made, as by spray drying and post-spraying.

Aqueous crutcher mixes containing substantial proportions of bicarbonate, carbonate and silicate tend to gel or set prematurely, sometimes before they can be thoroughly mixed and pumped out of a crutcher to spray towers. Consequently, extensive experimentation has been undertaken to find ways to diminish the tendencies of such systems tó solidify or gel in the crutcher. Small quantities of citric acid or water soluble citrate incorporate in the crutcher mix delay or prevent gelation and setting of bicarbonatecarbonate-silicate mixes and allow commercial spray drying thereof, following normal procedures for pumping out the crutcher contents to the spray nozzles. However, while the use of citric acid or citrate was successful, it has been supplanted by the present process, which represents a significant improvement over it.In addition to improving the anti-gelling activity and increasing the length of time in which a crutcher mix will be workable without the need for significantly larger proportions of anti-gelling agent being incorporated, the present invention allows the use of a lesser proportion of organic material, thereby decreasing the likelihood of the spray dried composition deteriorating in the heat of the dryer and improving the absorbency and flowability of the product. Also, whereas the citric acid component, if used in larger quantity, might interfere with the absorption of liquid nonionic detergent sprayed onto the spray dried base beads, magnesium sulphate appears to be desirably absorbent, thereby helping to make the product free flowing.

In the aqueous crutcher mix the various dissolved compounds can ionize and therefore it may be considered that in the crutcher mix there are present magnesium, citrate and sulphate ions.

Accordingly, crutcher mixes having charged thereto mixtures of compounds that result in the same ionic composition are also useful for retarding and preventing gelations of inorganic crutcher mixes. Thus, magnesium citrate or magnesium acid citrate can be employed in the present invention, preferably with sodium sulphate, but also without the sulphate being present. Citric acid and the various water-soluble citrates may be referred to herein as "citric material".

In accordance with the present invention, a miscible and pumpable crutcher slurry which does not prematurely set and which is capable of being mixed and pumped for a period of at least one or two hours after making, comprises from 40 to 70% of solids and 60 to 30% of water, of which solids content, on a 100% solids basis, about 55 to 85% is sodium bicarbonate, about 5 to 25% is sodium carbonate and about 5 to 25% is sodium silicate of Na20: 8iO2 ratio within the range of 1:1.4 to 1:3, with the ratio of sodium bicarbonate :sodium carbonate being within the range of about 2:1 to 8 :1, the ratio of the sodium carbonate :sodium silicate being within the range of about 1:3 to 3:1, and the ratio of sodium bicarbonate: sodium silicate being within the range of about 3:1 to 10:1, and a gelation retarding proportion of a combination of 0.1 to 2% of a citric material comprising citric acid, one or more water soluble citrates or mixtures thereof, and from 0.1 to 1.4% of magnesium sulphate, with the total of such citric material and magnesium sulphate, in combination, being gelation retarding and at least 0.4% of the slurry.

The invention also relates to a method for retarding or preventing the gelation of a miscible and pumpable crutcher slurry of the general bicarbonate-ca rbonate-silicate type described, by addition thereto of a citric material and magnesium sulphate, in the described small quantities. The invention is also of similar products and methods wherein magnesium citrate is present in an anti-gelling material.

Although the anti-gelling features of the present invention may also be obtained with other inorganic builder base compositions than those which are primarily of bicarbonate, carbonate, silicate and water, the most significant anti-gelling effects are noted when crutcher mixes based substantially (preferably essentially) on such materials and water are treated by the method of this invention, i.e., addition of citric material and magnesium sulphate (or magnesium citrate). The compositions so treated in accordance with the present invention preferably comprise 40 to 70% of solids and are 60 to 30% of water. The solids contents, on a 100% solids basis, are preferably 55 to 85% of sodium bicarbonate, 5 to 25% of sodium carbonate and 5 to 25% of sodium silicate, preferably of Na2O :SiO2 ratio within the range of 1:1.4 to 1:3.In such compositions the ratio of sodium bicarbonate:sodium carbonate is preferably within the range of 2:1 to 8:1, the ratio of sodium carbonate:sodium silicate is preferably within the range of 1:3 to 3 :1, and the ratio of sodium bicarbonate:sodium silicate is preferably within the range of 2 :1 to 10:1. The proportion of citric material, namely citric acid, water soluble citrate, mixtures of such citrates or mixtures of citric acid and such citrate or citrates is preferably from 0.1 to 2% and the percentage of magnesium sulphate is preferably from 0.1 to 1.4%. The total of citric material and magnesium sulphate is preferably at least 0.4% and will usually not exceed 2.5 or 3%, with the percentages mentioned being on a total crutcher mix or slurry basis, including the mentioned salts, water and any adjuvants which may be present.A preferred range of such total is 0.5 to 3%, more preferably 0.6 to 2% and most preferably, usually, 0.7 to 1.2%. Although the employment of a combination of citric material, such as citric acid, and magnesium sulphate is preferable, there may be used in substitution for it from 0.3 to 3% of magnesium acid citrate (MgHCssHsO7 5H2O) or equivalent proportion of equivalent magnesium citrate.

Preferably, the crutcher slurry contains from 50 to 65% of solids, with the balance being water, and of the solids content, 55 to 80% is sodium bicarbonate, 10 to 25% is sodium carbonate and 10 to 25% is sodium silicate, with the ratio of sodium bicarbonate :sodium carbonate being in the range of 3 :1 to 5 :1, the ratio of sodium carbonate sodium silicate being within the range of 2 :5 to 5:2 and the ratio of sodium bicarbonate sodium silicate being within the range of 4:1 to 8:1. More preferably, the crutcher slurry contains from 58 to 64% of solids and 42 to 36% of water, of which solids content 70 to 75% is sodium bicarbonate, 13 to 19% is sodium carbonate and 8 to 15% is sodium silicate.In such more preferred compositions the ratio of sodium bicarbonate :sodium carbonate is within the range of 4 to 5:l,the ratio of sodium carbonate :sodium silicate is within the range of 1:1 to 3:2 and the ratio of sodium bicarbonate:sodium silicate is within the range of 5:1 to 7 :1. The materials described herein, except for water, are all normally solid and the percentages and ratios are on an anhydrous basis, although the various materials may be added to the crutcher as hydrates or dissolved or dispersed in water. Normally, however, the sodium bicarbonate is anhydrous and the sodium carbonate is soda ash. However the carbonate monohydrate may also be employed.The silicate is usually added to the crutcher slurry as an aqueous solution, normally of 40 to 50% solids content, e.g., 47.5%, and is preferably added near the end of the mixing process and after previous additions and dispersions and dissolutions of the citric material and magnesium sulphate (or magnesium citrate). The silicate employed will preferably be of Na2O : Si02 ratio within the range of 1:1.5 to 1:2.6, more preferably 1:1.6 to 1:2.4 and most preferably 1:2.0 to 1:2.4.

Although it is highly preferred to make the crutcher slurry and the base bead product of this invention (from which a heavy duty built nonionic synthetic organic detergent composition can be produced) of essentially inorganic salts, in such manner that they will be of bead properties that promote absorption through the bead surfaces of nonionic detergent sprayed thereon in liquid form, and although often the adjuvants, such as perfumes, colourants, enzymes, bleaches and flow promoting agents, may be sprayed onto the beads with the nonionic detergent or may be post-added, for stable and normally solid adjuvants, mixing in with the inorganic salt slurry in the crutcher may be feasible. Thus, it is contemplated that from 0 to as much as 20% of the crutcher slurry may be of suitable adjuvants or diluents (diluents include inorganic salts, such as sodium sulphate and sodium chloride).However, if such adjuvants are present, normally the proportion thereof will be from 0.1 to 10% and often their content will be limited to 5%, and sometimes to 1 to 2%.

Normally the organic material content of the crutcher slurry will be limited to about 5% maximum, preferably 3% maximum and most preferably 1 to 1.5% maximum, so as to avoid any problems of tackiness of the base beads after spray drying and to avoid any adverse effects on absorption of synthetic nonionic organic detergent by the beads.

The preferred combination of gelation preventing materials employed, which have been found to be startingly successful in preventing gelation, thickening, setting and freezing up of the crutcher slurry before it can be emptied from the crutcher and spray dried, using normal crutching, pumping and spray drying equipment, are citric material and magnesium sulphate. Because the crutcher slurry, including both dissolved and dispersed inorganic salts, is normally alkaline, usually being of a pH in the range of 9 to 12, preferably 10 to 11, when the citric material employed is citric acid it is considered to be ionized and converted to the corresponding citrate or brought into equilibrium with citrate ions.Thus, other soluble citrates may be employed instead of citric acid, including sodium citrate, potassium citrate and magnesium citrate, although for many applications the acid is considered to be superior.

Instead of adding citrate, a mixture of the acid and a neutralizing agent, e.g., NaOH, KOH, Mg(OH)2, may be used, and instead of the acid form, a citrate plus an acid can be substituted, if desired (although this latter course of action will rarely be followed). The proportion of citric material, in combination with magnesium sulphate will normally be only sufficient to accomplish the gelation preventing task in the particular crutcher slurry to be treated. However, for safety's sake an excess, e.g., 5 to 20% more than the sufficient quantities of citric material and magnesium sulphate, may be employed. While it is possible to use as much as 3.4% of the combination of citric material and magnesium sulphate, on a crutcher contents weight basis, to retard or prevent gelation, usually from 0.4 to 1.5% will suffice, preferably from 0.5 to 1.2%. When employing a citrate, such as an alkali metal citrate, one may wish to increase the percentage of the additive slightly to compensate for the presence of the heavier cation but for simplicity's sake the range of proportions of additives given will apply to both the acid and salt forms. With respect to the magnesium compound, the sulphate is highly preferred but this may be replaced by other source of magnesium as by the magnesium ion in magnesium citrate, when that compound is used, preferably in proportion from 0.4 to 1.2% or 0.5 to 0.8%.

The order of addition of the various components to the crutcher is not considered to be critical, except that it is highly desirable to added the silicate solution last, and if not last, at least after the addition of the gel preventive combination gel retarding materials. Also, minor variations in orders of addition may be made under certain circumstances, as when objectionable foaming accompanies the following of a specific order. However, such problems have not been found to be serious. In some instances it is possible to premix the magnesium sulphate and citric material and to add the mixture thereof to the crutcher. In other cases the citric material is added first, followed by the magnesium sulphate, or vice versa. If desired, one or both of the citric material and magnesium sulphate may be premixed with another material or with other materials.In such instances it will be preferred for the anti-gelling additive components to be mixed in with other crutcher mix materials before addition of the silicate to the crutcher. However, in some instances one can add the anti-gelling materials after adding of the silicate, but preferably very promptly thereafter.

Usually, during the manufacture of the crutcher mix some water will be added to the crutcher initially, followed by some inorganic salt, either carbonate or bicarbonate, more water and more salt, and then, gel preventive materials and silicate, but dispersion-solutions of the individual components may be made beforehand, if feasible.

The water employed may be city water of ordinary hardness. In theory, it is preferable to utilize deionized water or distilled water, if available, because some metallic impurities in the water may have a triggering action on gel formation, but that is not considered to be necessary.

The temperature of the aqueous medium in the crutcher will usually be elevated, normally to the 40 to 700C range and preferably will be from 50 to 600 C. Heating the crutcher medium promotes solution of the water soluble salts of the mix and thereby increases mix mobility. However, temperatures higher than 700C will usually be avoided because of the possibility of decomposition of one or more crutcher mix components, e.g., sodium bicarbonate. Heating of the crutcher mix, which may be effected by utilizing hot aqueous medium charged or by heating the crutcher contents by means of a heating jacket or heating coils or both, also helps to increase drying tower throughput because less energy has to be transferred to the sprayed droplets of crutcher mix in the tower. Using higher solids mixes also increases production.

Crutcher mixing times to obtain good slurries can vary widely, from as little as ten minutes for small crutchers and for slurries of higher moisture contents, to as much as four hours, in some cases.

The mixing times needed to bring all the crutcher mix components together in one medium may be as little as five minutes but in some cases, can take up to an hour, although 30 minutes is a preferable upper limit. Counting any such initial admixing times, normal crutching periods will be from 20 minutes to two hours, e.g., 30 minutes to one hour, but the crutcher mix will be such as to be mobile, not gelled or set, for at least one hour, preferably for two hours and more preferably for four hours or so after completion of the making of the mix, e.g., 10 to 30 hours.

The crutched slurry, with the various salts, dissolved or in particulate form, uniformly distributed therein, in part due to the desirable anti-gelling effects of the citric compound and the magnesium sulphate, is transferred in usual manner to a spray drying tower, which is located near the crutcher. The slurry is normally dropped from the bottom of the crutcher to a positive displacement pump, which forces it at high pressure through spray nozzles at the top of a conventional spray tower (countercurrent or concurrent), wherein the droplets of the slurry fall through a hot drying gas, which is usually composed of fuel oil or natural gas combustion products, in which the droplets are dried to desired absorptive bead form.During the drying, part of the bicarbonate is converted to carbonate, with the release of carbon dioxide, which appears to improve the physical characteristics of the beads made so that they become more absorptive of liquids, such as liquid nonionic detergent, which may be post sprayed onto them subsequently.

After drying, the product is screened to desired size, e.g., 10 to 100 mesh, U.S. Standard Sieve Series (10 mesh has sieve openings of 2.00 mm, 100 mesh has openings of 149 microns), and is ready for application of nonionic detergent spray thereto, with the beads being either in warm or cooled (to room temperature condition). However, the nonionic detergent will usually be at an elevated temperature to assure that it will be liquid; yet, upon cooling to room temperature, desirably it will be a solid, often resembling a waxy solid. The nonionic detergent, is preferably applied to the beads whilst they are tumbling, e.g. in known manner, as a spray or as droplets.The nonionic detergent is preferably a condensation product of ethylene oxide and higher fatty alcohol, with the higher fatty alcohol being of 10 to 20 carbon atoms, preferably of 1 2 to 1 6 carbon atoms, and more preferably averaging 12 to 1 3 carbon atoms, and with the nonionic detergent containing from 3 to 20 ethylene oxide groups per mole, preferably from 5 to 12, more preferably 6 to 8. The proportion of nonionic detergent in the final product will usually be from 10 to 25%, such as from 20 to 25%. Whereas when using citric acid alone as the anti-gelling agent, without the magnesium sulphate, the absorbency of the base beads would be good, with some base bead compositions and nonionic detergents it would be difficult to have more than 20% of the nonionic detergents satisfactorily absorbed by the base beads.It has been found that the present antigelling treatment, utilizing a mixture of citric material and magnesium sulphate, e.g., citric acid and magnesium sulphate, can result in beads of significantly greater absorbency, allowing absorption of 22% of nonionic detergent, with the production of a free flowing product and sometimes allowing absorption of as much as 25% of the nonionic detergent. In comparative tests against beads made using citric material alone (citric acid) as the anti-gelling agent in the base bead crutcher mix, the compositions of the present invention, made by the method thereof, are more absorptive, as a general rule.

A preferred finish formulation made from base beads of this invention contains from 1 5 to 25%, preferably 20 to 25% of the nonionic detergent, e.g., Neodol (Registered Trade Mark) 23-6.5, made by Shell Chemical Company, 30 to 40% of sodium bicarbonate, 20 to 30% of sodium carbonate, 5 to 15% of sodium silicate of Na20 : SiO2 ratio of 1:2.4, 1 to 3% of fluorescent brightener, 0.5 to 2% of proteolytic enzyme, sufficient bluing to colour the product and whiten the wash, as desired, 0.5 to 3% of moisture, 0.5 to 1.2% of citric material, preferably sodium citrate and 0.8 to 2% of magnesium sulphate. Instead of the mixture of citric material and magnesium sulphate there may be present from 0.3 to 3% of magnesium citrate, preferably 0.4 to 1.2%.

Optionally, sodium sulphate may be present, as a diluent, but the amounts thereof will normally be restricted to 20% preferably to 10% and most preferably to less than 5%, if it is present at all.

The base beads made, devoid of nonionic detergent and adjuvants, will preferably comprise from 35 or 40 to 60% of sodium bicarbonate, 15, 20 or 25 to 45% of sodium carbonate, 10 to 20% of sodium silicate, 0.1 to 3% of sodium citrate plus 0.1 to 2% of magnesium sulphate (or 0.5 to 5% of magnesium citrate), 0 to 10% of one or more adjuvants or diluents or mixtures thereof and 1 to 10% of moisture. In such products the proportion of sodium bicarbonate in the sprayed beads will normally be within the range of 1.2 to 4 times that of sodium carbonate, e.g., 1.5 to 3 times.

The highly beneficial result of incorporating the mentioned small percentages of citric compound and magnesium sulphate or magnesium citrate in the crutcher slurry in accordance with this invention is two-fold. Gelation and setting of the crutcher mix in the vessel before complete discharge thereof is prevented and additionally, higher solids content crutcher slurries may be made. Thus, down times and cleanouts are reduced and energy savings are achieved due to less water having to be evaporated from the crutcher droplets in the spray dryer.

Although many bicarbonate-carbonate-silicate mixtures desirably employed in crutcher mixes for making base beads for built particulate nonionic detergent compositions would normally gel and set up in the crutcher, with the present invention, at little expense and without any detrimental effects on the product, the desired proportions of such builder salts can be employed and variations in such proportions can be made, as desired, with much reduced fear of freeze-ups of the crutcher.

Tests of the final product show no adverse effects due to the presence of the citric material and magnesium sulphate therein. In fact, some positive results, due to metal ion sequestration and improved absorption of nonionic detergent, may result. The presence of the citric material is though to promote maintenance of the stability of perfumes and colours present and it may help to prevent development of malodors from deteriorations of other organic additives, such as proteolytic enzymes and proteinaceous materials.

The presence of the citric materials and the magnesium sulphate in the base beads also has the desirable effect of having the gelation preventing material present in any base beads or detergent beads being reworked, so that such material, if off-specification (as for being undersize or for being tower wall builup), may be mixed with water and made into a more concentrated rework mix for subsequent blending back with the regular crutcher mix. Such mixing with water is easier than would be the case were the anti-gelling composition not present in the base beads to prevent or retard gelation or excessive thickening.

The invention may be put into practice in various ways and a number of specific embodiments will be described to illustrate the invention with reference to the accompanying examples. Unless otherwise indicated all temperatures are in OC and all parts are by weight in the examples and throughout the specification.

EXAMPLES 1A, 1BAND 1C Base beads were made by adding to the crutcher 308 parts of water, 1 5 parts of fluorescent brightener, 1.5 parts of blue pigment, 4.5 parts of anhydrous citric acid, 10 parts of magnesium sulphate (Epsom salt), 403 parts of sodium bicarbonate (anhydrous), 87.5 parts of soda ash, and 1 70 parts of a 47.5% solids content aqueous sodium silicate solution, the sodium silicate of which is of Na20 : Si02 ratio of 1:2.4.

During the mixing of this base builder composition the temperature in the crutcher was maintained at about 380C. It took about 20 minutes for the various materials to be mixed together in the order given (except that the brightener, pigment and citric acid were added in two parts, with the second halves being added after the soda ash), and after completion of addition of the last component the mixing was continued for about another 20 minutes to produce crutcher mix (A), after which spray drying of the product was begun. Some of the crutcher mix (B) was not sent to the spray dryer so that the time for gelation thereof could be measured. It was found that the crutcher mix (B) remained miscible and pumpable, ungelled and uncongealed for 30 hours.

EXAMPLE 1 B The crutcher mix (A) of Example 1 A which was pumped to the spray tower, using a Triplex positive displacement pump generating a pressure of about 30 kg/sq cm, was dried in drying air, which was the combustion products of an oil burner, at a temperature ranging from a high of 400 to 6000C to a low of about 100 to 200OC and the drying was to a moisture content of about 1.9%. The base beads resulting were screened so as to be within the 10 to 100 mesh U.S. Sieve Series range and were free flowing, non-tacky and of a bulk density of about 0.7 g/ml. They were porous, yet firm on the surfaces thereof and were capable of readily absorbing significant proportions of liquid nonionic detergent without becoming objectionably tacky.

EXAMPLE 1C Finai Product Component Percent Nonionic Detergent 18.6 (Neodol 23-6.5) Proteolytic enzyme 1.4 Moisture 1.5 NaHC93 46.0 Na2CO3 19.0 Sodium silicate 10.9 (Na2O :SiO2 = 1:2.4) Sodium citrate 0.9 Magnesium sulphate 0.8 (as Epsom salt) Adjuvants 0.9 (fluorescent brightener, bluing, perfume) 100.0 A product of the above formula was made by spray drying crutcher mix (A) comprising sodium bicarbonate, sodium carbonate, sodium silicate, citric acid, magnesium sulphate, fluorescent brightener and water in a spray tower. This produced essentially inorganic base beads, as described in Example 1 B, which then had sprayed onto their surfaces a nonionic detergent in liquid state, solidifiable at room temperature.The beads and detergent were cooled and proteolytic enzyme powder and perfume were applied to them. The product made, of the formula given above, was of a bulk density of 0.8 g/ml and an initial adhesion of 40% and exhibited a fines characteristic (through U.S. Standard Sieve No. 50 (mesh 50 has openings of 297 microns)) of 1 5%.

The detergent products made, including absorbed nonionic detergent, were excellent heavy duty laundry detergents, useful in washing household laundry in automatic washing machines and in cleaning textile materials by other methods, too.

EXAMPLES 2A TO 2H In a variation of Example 1A, using the same proportions of all components except for water, citric acid and magnesium sulphate, when the amounts of such components are changed to 322, 3.5 and 10, respectively (Example 2A), the gelation time at 37.80C was found to be ten hours; when changed to 313, 4.5 and 5, respectively (Example 2B), it was eight hours; when changed to 307, 4.5 and 11.3, respectively (Example 2C) it was 7.5 hours; when changed to 314,3.5 and 5, respectively (Example 2D), it was five hours; and when changed to 311,2.5 and 10 respectively (Example 2E), it was four hours.Such crutcher mix compositions are of excellent stability and are very useful in commercial production of the present detergent base beads because they allow extra time before gelation, so that any "normal" problems associated with crutching and spray drying may usually be overcome before gelation or setting up in the crutcher could become a problem. When the mentioned proportions are 309, 2.5 and 11.3 (Example 2F) or 317, 4.5 and 1 (Example 2G) respectively, the crutching time, at 37.80C, before gelation will be 3.5 hours and when the proportions are 316,1.5 and 5 (Example 2H) it will be 1.5 hours. Such formulations are also acceptable, especially the first two (2F and 2G), because usually the contents of the crutcher can be completely sprayed out within 1.5 hours and almost always within 3.5 hours.However, it will usually be desirable to utilize more citric acid or magnesium sulphate or equivalent materials than the 1.5 and 5 parts mentioned, just to provide extra time against untoward incidents.

EXAMPLE 3A When the proportions of citric acid and/or magnesium sulphate and/or the sum thereof are outside the ranges given herein, premature gelation occurs or a satisfactory dispersion may not be made. Thus in mix (A), when 302 parts of water, 2.5 parts of citric acid and 19 parts of magnesium sulphate (Example 3A) are employed the product gels immediately, which also occurs when 304 parts of water, 0.5 parts of citric acid and 1 9 parts of magnesium sulphate (Example 3B) are utilized, or when such proportions are 304, 3.5 and 1 5 (Example 3C) or 306, 1.5 and 1 5 (Example 3D). Gelation occurs within about 25 minutes when the proportions are 321,0.5 and 1 (Example 3E) and within about 20 minutes when they are 313, 0.5 and 10 (Example 3F).Thus, it can be seen that the compositions of the present invention, made by the described methods, are especially useful in the preparation of spray dried base builder beads for heavy duty laundry detergents, without the danger of premature gelation of the crutcher mix.

EXAMPLE 4 When sodium citrate is substituted for citric acid in the formula given above, with the magnesium sulphate being either anhydrous form or as Epsom salt, similar results are obtained to Example 1A.

EXAMPLE 5 Also, when equivalent proportions of magnesium citrate are employed, whether Mg2 (citrate)3 or MgHC8H5O7. 5H2O, e.g. at 1.5%, good anti-gelling effects are obtained, although they are not as good as those for the combination of citric acid (or sodium citrate) and magnesium sulphate.

The crutcher mixes of this invention may be of greater solids contents than those for similar compositions in which a sufficient quantity of citric acid is employed (without the magnesium sulphate) to obtain the same (or somewhat inferior) anti-gelling effects. Thus, the presence of the magnesium sulphate with the citric acid appears to improve the anti-gelling effects so that even higher contents of solids may be present in the crutcher slurries without gelation. In the past we have found that solids content and gelation tendencies were directly proportional and this is also the case when combinations of citric acid and magnesium sulphate are employed. Still. one can utilize higher solids content crutcher mixes without objectionable gelling, whereas similar mixes, when treated with citric acid alone, could gel prematurely.Also, when the citric acidmagnesium sulphate mixtures is employed the content of organic material in the product may be minimized, while still maintaining the crutcher slurry miscible for sufficiently long periods of time to avoid crutcher set-ups or line blockages.

EXAMPLES 6ATO 6J AND 6K A crutcher mix formulation was made essentially like that of the crutcher mix given in Example 1 A which resulted in a base bead for making a detergent composition of the formula given in Example 1 C, but with the solids content of the crutcher mix being kept at 56.5%. The mix was made in the same manner to produce a crutcher mix (C) and the crutching times up to objectionable gelation were measured when various materials were added with the citric acid as anti-gelling agents, in replacement of the magnesium sulphate.Using 0.25% of citric acid and 1% of each of such other anti-gelling "salt" additives, on an anhydrous basis, the slurry fluidity was maintained for only about 20 minutes when either sodium chloride (Example 6A) or calcium chlorida (Example 6B) was the salt employed, which was about the same time for which fluidity was maintained when citric acid (Example 6C) was used alone. With sodium sulphate (Example 6D) as the salt added the slurry life was extended to 1.5 hours and calcium sulphate (Example 6E) allowed mixing for up to five hours. Magnesium silicate (Example 6F) resulted in an initially thin slurry, which solidified in about five hours. Calcium oxide (Example 6G) and magnesium oxide (Example 6H) made very highly viscous slurries which solidified in a few hours.Magnesium chloride (Example 6J) extended the slurry life to ten hours and magnesium sulphate (Example 6K) extended it to more than 32 hours. However, when various heat stable adjuvants were present in the crutcher mix, such as bluing, fluorescent brightener and other normal detergent adjuvants for crutcher mixes, it was found that gelation was accelerated, sometimes occurring in one-tenth to one-half the time normally taken. Thus, since it is desirable that at least an hour be provided before gelation and preferably, that more time should be available, none of the anti-gelling salts except the magnesium chloride (Example 6J) and magnesium sulphate (Example 6K) are considered to be useful and of these two the magnesium sulphate is clearly superior.On the basis of above experiments it is within the invention to utilize magnesium chloride with citric acid or to employ a mixture of magnesium chloride and magnesium sulphate with citric acid.

EXAMPLE 7A AND 7B A crutcher mix formulation was made essentially like that given in Example 1 A but with the solids content of the crutcher mix being kept at 56.5%, and the order of addition of the detergent builder salt components to the crutcher being altered so that the bicarbonate, carbonate and silicate were mixed together in the aqueous medium before addition thereto of the magnesium sulphate and citric acid. In such case, after a few minutes the mix became objectionably thick and solidified in an irreversible manner.

EXAMPLE 7B However if as it was noted that the mix of Example 7A was thickening, the magnesium sulphate component or the magnesium sulphatecitric acid anti-gelling composition was quickly added at that time, before solidification, it thinned the mix to a workable state. This is another advantage of the present invention because, in addition to extending the crutching time, it allows control of the fluidity of the crutcher mix in response to indications of gelation, as they appear.

Thus, the crutcher operator has improved processing control during the period in which the mix is held in the crutcher before spay drying.

Should there be some interruption of spray tower operation, necessitating holding the mix longer in the crutcher than planned, he can extend the period of miscibility of the crutcher mix by further addition of magnesium sulphate and citric acid or equivalent anti-gelling agent(s) of this invention or magnesium sulphate alone, in many instances. For example, it has been found that often as little as 0.3% of MgSO4 or 0.6% of Epsom salt will reverse gelation, providing that the mix is still fluid enough to permit mixing in of the magnesium salts.

Normally, from 0.3 to 1% of MgSO4 will be added.

This feature of the invention allows minimizing of the magnesium sulphate and citric acid contents of the product, so that product characteristics will not be changed noticeably, and yet assures the operator that he will not have to dig solidified crutcher mix out of the crutcher, with the waste of material and loss of production time that would be involved. This improvement in the manufacturing process is important because if the crutcher mix solidifies, spray tower operation can be halted, essentially shutting down the detergent manufacturing operation. When operations are restarted even when that is done reasonably promptly after gelling first occurs, the spray tower will have to be brought to equilibrium, and during the first part of such resumed manufacturing some unacceptable product can result.Sometimes gelation in the crutcher is not so extensive as to solidify the mass of mix but still the production of some gel can block spray nozzles and cause interruption of production. Such adverse effects are avoided or reduced by use of the present process, as herein described.

EXAMPLE 8 An attempt was made to make a crutcher mix of the type described in Example 1 A but with the solids content of the crutcher mix being kept at 56.5%, utilizing 0.25% of citric acid and 1% of magnesium sulphate (anhydrous), with the order of addition of the various components being changed so that the water, silicate, magnesium sulphate and citric acid were first mixed together, after which the bicarbonate and carbonate were added, plus the fluorescent dye and pigment.

However, such crutcher mixes gel prematurely and for that reason the mentioned order of addition is unsatisfactory. The experiment was repeated several times but in all cases the crutcher mix froze so that it could not be stirred, pumped and spray dried.

EXAMPLE 9 Attempts were made to manufacture in laboratory equipment crutcher mixes containing high solids contents. Thus using the basic formulas previously given, with 0.25% of citric acid and 1% of magnesium sulphate, and adding the components in the operative order described in Examples 1 and 2, the builder salt composition was 70% of sodium bicarbonate, 20% of soda ash and 10% of sodium silicate in one instance (Example 9A), 77%, 13% and 10% in the second (Example 9B) and 67%, 23% and 10% in the third (Example 9C), so that the bicarbonate; carbonate ratios were 3.5:1, 6:1 and 3 :1, respectively.Such products could not be made in laboratory equipment but were makable, especially with additional magnesium sulphate and citric acid, up to twice as much as being employed initially, when heavy duty plant equipment was utilized.

In a similar manner three other formulations were made, lower in solids content, comprising 56%, 19% and 25% in the one case (Example 9D), 60%, 15% and 25% in the second case (Example 9E) and 60%, 20% and 20% in the third case (Example 9F), of sodium bicarbonate, soda ash and sodium silicate, so that the bicarbonate: carbonate ratios are 3 :1, 4:1 and 3:1, respectively. Such products were very easily manufactured, even in laboratory equipment, but because of the need to evaporate more water during the spray drying process they are not as economically feasible as higher solids content crutcher mixes. In the described experiments the silicate used was that of Example 1A.

From the above experiments it is seen that the present invention is an important one. The antigelling materials being employed allow the use of higher solids content crutcher mixes and thereby conserve energy (less drying air being needed) and increase throughputs. The invention also ensures that incidence of crutcher mix freeze-ups is much reduced, thus lowering or eliminating the loss of time and materials that result from such problems.

Operations at higher crutcher temperatures are permissible despite the fact that increasing such temperatures would otherwise increase the probability of gelation of the crutcher mix. The magnesium salt anti-gelling agents improve product characteristics to a significant extent and although one will usually attempt to minimize the citric acid or other citric material content, the presence of such materials have good effects, too.

It appears from the experimental results that the solids content of the crutcher mix may be as high as 70% in some circumstances and good mixing and sufficiently delayed gelation are obtainable by means of the present invention, despite such high solids contents. Also, the crutcher mix temperature may go as high as 70 C. Of course, at such higher solids contents and temperatures stronger mixing would usually be used and often more anti-gelling agent will be present.

Claims (38)

1. A method of retarding or preventing gelation of a miscible and pumpable crutcher slurry comprising sodium bicarbonate, sodium carbonate, and sodium silicate, which comprises preparing a crutcher slurry of the said material containing a gelation retarding proportion of a gelation retarding material comprising citrate ions and magnesium ions, and mixing such composition in a crutcher during preparation thereof.

2. A method as claimed in Claim 1 in which the miscible and pumpable crutcher slurry contains from 40 to 70 ,0 of solids and 60 to 30% of water, of which solids content, on a 1 00% solids basis, 55 to 85% is sodium bicarbonate, 5 to 25% is sodium carbonate, and 5 to 25% is sodium silicate of Na2O : SiO2 ratio within the range of 1:1.4 to 1:3, with the ratio of sodium bicarbonate :sodium carbonate being within the range of 2 :1 to 8 :1, the ratio of sodium carbonate :sodium silicate being within the range of about 1 .3 to 3 :1, and the ratio of sodium bicarbonate : sodium silicate being within the range of 2 :1 to 10:1.

3. A method as claimed in Claim 1 or Claim 2 in which the gelation retarding material comprises at least 0.4% of the slurry.

4. A method as claimed in Claim 1,2 or 3 in which the gelation retarding material comprises 0.1 to 2% of citric material and 0.1 to 1.4% of magnesium sulphate.

5. A method of retarding or preventing gelation of a miscible and pumpable crutcher slurry containing from 40 to 70% of solids and 60 to 30% of water, of which solids content, on a 100% solids basis, 55 to 85% is sodium bicarbonate, 5 to 25% is sodium carbonate, and 5 to 25% is sodium silicate of Na2O :SiO2 ratio within the range of 1:1.4 to 1:3, with the ratio of sodium bicarbonate:sodium carbonate being with the range of 2:1 to 8:1, the ratio of sodium carbonate sodium silicate being within the range of 1:3 to 3 :1,the ratio of sodium bicarbonate sodium silicate being within the range of 2:1 to 10:1, which comprises preparing a crutcher slurry of the described composition containing a gelation retarding proportion of a gelation retarding material comprising, on a slurry basis, from 0.1 to 2% of a citric material, and from 0.1 to 1.4% of magnesium sulphate, the gelation retarding material comprising at least 0.4% of the slurry, and mixing such composition in a crutcher during preparation thereof.

6. A method as claimed in any one of Claims 1 to 5 in which the crutcher slurry contains from 50 to 65% of solids and 50 to 35% of water, of which solids content 55 to 80% is sodium bicarbonate, 10 to 25% is sodium carbonate, 5 to 25% is sodium silicate of Na2O : SiO2 ratio within the range of 1:1.6 to 1:2.6, the ratio of sodium bicarbonate:sodium carbonate is within the range of 3 :1 to 6 :1, the ratio of sodium carbonate :sodium silicate is within the range of 2 5 to 5:2 and the ratio of sodium bicarbonate :sodium silicate is within the range of 4:1 to 8:1.

7. A method as claimed in Claim 5 in which the percentages of citric material and magnesium sulphate are in the ranges of 0.1 to 0.8 and 0.1 to

1.2, respectively.

8. A method as claimed in Claim 5 in which the crutcher slurry contains from 50 to 65% of solids and 50 to 35% of water, of which solids content 55 to 80% is sodium bicarbonate, 10 to 25% is sodium carbonate, 5 to 25% is sodium silicate of Na2O : SiO2 ratio within the range of 1:1.6 to 1 :2.6, the ratio of sodium bicarbonate :sodium carbonate is within the range of 3:1 to 6:1, the ratio of sodium carbonate:sodium silicate is within the range of 2 :5 to 5 :2, the ratio of sodium bicarbonate :sodium silicate is within the range of 4:1 to 8:1, and wherein the percentages of citric material and magnesium sulphate are in the ranges of 0.1 to 0.8 and 0.1 to 1.2, respectively.

9. A method as claimed in Claim 6, in which the crutcher slurry contains from 58 to 64% of solids and 42 to 36% of water, of which solids content 70 to 75% is sodium bicarbonate, 13 to 19% is sodium carbonate, 8 to 15% is sodium silicate of Na2O : SiO2 ratio of 1:1.6 to 1:2.4, the ratio of sodium bicarbonate :sodium carbonate is within the range of 4:1 to 5:1, the ratio of sodium carbonate :sodium silicate is within the range of 1:1 to 3 :2, and the ratio of sodium bicarbonate :sodium silicate is within the range of 5:1 to 7:1.

10. A method as claimed in Claim 5 in which the percentages of citric material and magnesium sulphate are in the ranges of 0.25 to 0.6 and 0.4 to 1.0, respectively.

11. A method as claimed in Claim 5 in which the crutcher slurry contains from 58 to 64% of solids and 42 to 36% of water, of which solids content 70 to 75% is sodium bicarbonate, 13 to 19% is sodium carbonate, 8 to 15% is sodium silicate of Na2O :SiO2 ratio of 1:1.6 to 1:2.4, the ratio of sodium bicarbonate :sodium carbonate is within the range of 4:1 to 5:1, the ratio of sodium carbonate sodium silicate is within the range of 1:1 to 3:2, the ratio of sodium bicarbonate:sodium silicate is within the range of 5:1 to 7:1, and wherein the percentages of citric material and magnesium sulphate are in the ranges of 0.25 to 0.6 and 0.4 to 1.0, respectively.

12. A method as claimed in Claim 1 or Claim 2 in which the gelation retarding material comprises a magnesium citrate salt.

13. A method as claimed in Claim 12 in which the magnesium citrate salt is magnesium citrate or magnesium acid citrate.

1 4. A method of retarding or preventing the gelation of a miscible and pumpable crutcher slurry containing from 40 to 70% of solids and 60 to 30% of water, of which solids content, on a 100% solids basis, 55 to 85% is sodium bicarbonate, 5 to 25% is sodium carbonate, 5 to 25% is sodium silicate of Na2O :SiO2 ratio within the range of 1:1.4 to 1:3, with the ratio of sodium bicarbonate:sodium carbonate being within the range of 2:1 to 8:1, the ratio of sodium carbonate sodium silicate being within the range of 1:3 to 3:1, and the ratio of sodium bicarbonate sodium silicate being within the range of 2 :1 to 10 ::1, which comprises preparing a crutcher slurry of the described composition in which there is admixed from 0.3 to 3% of magnesium citrate or magnesium acid citrate, on a slurry basis, and mixing such composition in a crutcher during preparation thereof.

1 5. A method as claimed in any one of Claims 1 to 14 in which the crutcher slurry is at a temperature in the range of 20 to 700C, at atmospheric pressure, and the gel retarding material is incorporated into the slurry before addition thereto of at least some of the sodium silicate.

16. A method as claimed in any one of Claims 1 to 15 in which the mixing is at a temperature in the range of 40 to 700C, the gel retarding material is incorporated into the slurry before the sodium silicate, and mixing is continued for at least one hour after completion of the making of the crutcher slurry.

17. A method as claimed in any one of Claims 1 to 1 6 in which the crutcher slurry temperature is from 40 to 600 C, mixing is effected for at least two hours after completion of the making of the crutcher slurry, and at least a part of the crutcher mix is pumped out of the crutcher to a spray drying tower and is spray dried therein after the said mixing after the said two hours.

1 8. A method as claimed in any one of Claims 1 to 1 7 in which the citric material is citric acid or sodium citrate.

1 9. A method as claimed in any one of Claims 1 to 1 8 in which magnesium sulphate is added to the slurry as epsom salts.

20. A method as claimed in any one of Claims 1 to 19 in which from 0.1 to 10% of the crutcher slurry comprises one or more adjuvants or diluents or mixtures thereof.

21. A method as claimed in Claim 2 substantially as specifically described herein with reference to Examples 1 A, 2A to 2G, 4, 6J or 6K or7B.

22. A miscible and pumpable crutcher slurry comprising sodium bicarbonate, sodium carbonate, and sodium silicate and containing a gelation retarding proportion of a gelation retarding material comprising citrate ions and magnesium ions.

23. A miscible and pumpable crutcher slurry as claimed in Claim 22 comprising from 40 to 70% of solids and 60 to 30% of water, of which solids content, on a 100% solids basis, 55 to 85% is sodium bicarbonate, 5 to 25% is sodium carbonate, 5 to 25% is sodium silicate of Na2O : SiO2 ratio within the range of 1:1.4 to 1:3, with the ratio of sodium bicarbonate :sodium carbonate being within the range of 2:1 to 8:1, the ratio of sodium carbonate :sodium silicate being within the range of 1:3 to 3 :1, and the ratio of sodium bicarbonate :sodium silicate being within the range of2:1 to 10:1.

24. A slurry as claimed in Claim 22 or Claim 23 in which the gelation retarding material comprises at least 0.4% of the slurry.

25. A slurry as claimed in Claim 22, 23 or 24 in which the gelation retarding material comprises 0.1 to 2% of citric material and 0.1 to 1.4% of magnesium sulphate.

26. A miscible and pumpable crutcher slurry comprising from 40 to 70% of solids and 60 to 30% of water, of which solids content, on a 1 00% solids basis, 55 to 85% is sodium bicarbonate, 5 to 25% is sodium carbonate, and 5 to 25% is sodium silicate of Na2O : SiO2 ratio within the range of 1:1.4 to 1 :3, with the ratio of sodium bicarbonate :sodium carbonate being within the range of 2 :1 to 8:1, the ratio of sodium carbonate :sodium silicate being within the range of 1:3 to 3:1, and the ratio of sodium bicarbonate :sodium silicate being within the range of 2:1 to 10::1, and which solids content includes, on a slurry basis, a gelation retarding proportion of a gelation retarding material comprising 0.1 to 2% of a citric material, and from 0.1 to 1.4% of magnesium sulphate, with the total of such citric material and magnesium sulphate being at least 0.4% of the slurry.

27. A slurry as claimed in Claim 22 or Claim 23 in which the gelation retarding material comprises a magnesium citrate salt.

28. A slurry as claimed in Claim 27 in which the magnesium citrate salt is magnesium citrate or magnesium acid citrate.

29. A miscible and pumpable crutcher slurry comprising from 40 to 70% of solids and 60 to 30% of water, of which solids content, on a 100% solids basis, 55 to 85% is sodium bicarbonate, 5 to 25% is sodium carbonate, and 5 to 25% is sodium silicate of Na2O : SiO2 ratio within the range of 1:1.4 to 1:3, with the ratio of sodium bicarbonate :sodium carbonate being within the range of 2:1 to 8 :1, the ratio of sodium carbonate sodium silicate being within the range of 1:3 to 3:1, and the ratio of sodium bicarbonate :sodium silicate being within the range of 2 :1 to 10:1, and which solids content includes on a slurry basis, a gelation retarding proportion of magnesium citrate or magnesium acid citrate, in an amount of 0.3 to 3% of the slurry.

30. A miscible and pumpable slurry as claimed in Claim 22 substantially as specifically described herein with reference to Example 1 A, 2A to 2G, 4, 6J or 6K or 7B.

31. A method of making a particulate base material in bead form, suitable for absorbing detergent e.g. non-ionic detergent to make a built heavy duty synthetic organic detergent compositions, which comprises making a miscible and pumpable slurry in a crutcher by a method as claimed in any one of Claims 1 to 21, pumping the slurry out of the crutcher in ungelled and readily pumpable state and spray drying the slurry to particulate bead form.

32. A method as claimed in Claim 31 substantially as specifically described herein with reference to Example 1 B.

33. A particulate base material in bead form, suitable for absorbing detergent to make a built heavy duty synthetic organic detergent composition whenever made by a method as claimed in Claim 31 or Claim 32.

34. A method of making a built heavy duty synthetic organic detergent composition, which comprises causing a detergent to be absorbed into base bead as claimed in Claim 33.

35. A method as claimed in Claim 34 substantially as specifically described herein with reference to Example 1 C.

36. A built heavy duty synthetic organic detergent composition whenever made by a method as claimed in Claim 34 or Claim 35.

37. A particulate base material in bead form, suitable for absorbing detergent to make a built heavy duty synthetic organic detergent composition comprising 35 to 60% of sodium bicarbonate, 1 5 to 45% of sodium carbonate,10 to 20% of sodium silicate, and 0.5 to 5% of magnesium citrate or magnesium acid citrate or 0.1 to 3.0% of citric material and 0.1 to 2% of magnesium sulphate, 0 to 10% of one or more adjuvants or diluents or both and 1 to 10% of moisture, and optionally not more than 20% of sodium sulphate as a diluent.

38. A built heavy duty synthetic detergent composition comprising 1 5 to 25% non-ionic detergent, 30 to 40% of sodium bicarbonate, 20 to 30% of sodium carbonate, 5 to 15% of sodium silicate, optionally 1 to 3% of fluorescent brightener, optionally 0.5 to 2% of proteolytic enzyme, optionally sufficient bluing to colour the product and whiten the wash, 0.5 to 3% moisture, and 0.3 to 3% of magnesium citrate or magnesium acid citrate or 0.5% to 1 .2% of citric material and 0.8 to 2% of magnesium sulphate, and optionally not more than 20% of sodium sulphate as a diluent.