EP0327963A2 - Process for increasing the density of spray-dried detergents - Google Patents

Abstract

The density of spray-dried detergents is increased without the use of liquid granulating agents by continuously introducing the powder, which has a bulk density of at least 350 g / l, into a cylindrical, horizontally arranged or slightly inclined mixing drum with a smooth inner wall, in which axially a shaft rotates. The shaft is equipped with radially arranged striking tools, the length (calculated from the central axis) of 80% to 98% of the inner radius of the drum. The rotational speed of the shaft is regulated in such a way that the Froude number is between 50 and 1,200 with an average residence time of the powder in the drum of 10 to 60 seconds and a constant powder throughput.

Description

Spray-dried detergents of conventional compositions generally have bulk densities of 250 to 450 g / l (grams per liter) and, depending on the composition and method of operation, and only in exceptional cases of 480 g / l. In recent times, powders with higher bulk densities, for example from 550 to 750 g / l, have been of increasing interest since they require less packaging material and thus enable raw material to be saved and waste to be reduced.

There are also spray-dried detergents with bulk densities between 550 and 900 g / l and methods for their preparation known, for. B. from EP 120 492 (US 45 52 681), but it is special, rich in nonionic surfactants compositions. An addition of anionic surfactants, especially soaps, causes the bulk density to decrease sharply to values below 500 g / l. Granulation of the detergent components with the addition of granulating liquids such as water or nonionic surfactants also favors high bulk densities. However, granulation with water generally requires the presence of larger proportions of salts which bind water of crystallization, mostly of phosphates such as tripolyphosphate or of soda. However, this also means a restriction with regard to the freedom from recipes and makes it more difficult to produce p-free or low-p detergents. Spraying nonionic surfactants on the other hand increases this Bulk weight is only slight, unless larger proportions are used, which in turn requires the production of specially composed basic powder with high absorbency.

DE-A-25 48 639 teaches a process for increasing the bulk density of granulated or spray-dried detergents in a device which is known in the art under the name "Marumerizer" and is normally used to round off extruded particles of irregular shape. This device consists of a vertical cylinder with smooth side walls and a surface roughened turntable that rotates in the lower area of the cylinder. The device is primarily intended for intermittent operation. The largest available systems of this type with a diameter of the turntable of approx. 1m can only take up a batch of a maximum of 45 to 50 kg of tower powder. With a dwell time of approx. 10 minutes of the powder in the device according to Example 3 of DE-A cited, the throughput, based on an average hourly output of an average spray tower of 5 to 25 t (tons), is much too low, or one would be required very large number of "Marumerizers" that are constantly in operation in order to keep up with the tower performance. On the other hand, it is uneconomical to operate the tower including the complex heating system only intermittently and thus to adapt it to the low power of the granulator. It is also not advisable to use the tower only sporadically for the production of the pre-granules, to store them and to use the tower for other purposes in the meantime. DE-A-25 48 639 teaches that the pre-granules or spray powder must be processed in the "Marumerizer" for a short time, ie within a few minutes, in order to achieve a noteworthy powder compaction.

It was therefore the task of avoiding the disadvantages described and of developing a process which worked continuously, allowed higher throughput quantities and shorter residence times, guaranteed the greatest possible flexibility with regard to the quantity, the physical nature and the composition of the spray powders and the time of production, and a lower one Investment and energy expenditure required.

The invention with which these objects are achieved is a process for increasing the density of spray-dried detergents without the use of liquid granulating agents, characterized in that the spray-dried powder, which has a bulk density of at least 400 g / liter, is continuously in a cylindrical, horizontally arranged or introduces cylindrical mixing drum with a smooth inner wall inclined slightly to the horizontal, in which axially rotates a shaft equipped with radially arranged striking tools, the length (calculated from the central axis) of which is 80% to 98% of the inner radius of the drum, and that regulates the rotational speed of the shaft so that the Froude number is between 50 and 1,000 with an average residence time of the powder in the drum of 10 to 60 seconds and constant powder throughput.

The spray-dried powder leaving the drying tower (hereinafter referred to briefly as "tower powder") should have an initial density (liter weight) of at least 350 g / l in the interest of a desired high final density. The density of the tower powder is preferably at least 400 g / l. Specifically light tower powders, for example those containing zeolite, can be compressed more than those that already have a higher one Have initial density, but overall they reach a lower final weight than relatively heavy tower powder.

There are no special requirements with regard to the grain size or the grain spectrum of the tower powder. Rather, the process can be used to process powders with a broad and narrow grain spectrum. It is also not necessary to previously screen out coarse fractions from the tower powder, as is the case with conventional powders. Rather, the process means that coarse parts are crushed, loose, voluminous components are compacted, irregularly shaped parts are rounded off and very fine parts are compacted. Overall, the process reduces the average grain size.

The powders leaving the tower can be processed immediately in the manner according to the invention. The temperature of the powder is not critical per se, especially not when it has dried thoroughly, i. H. if its water content corresponds to or is below the theoretical water-binding capacity. In the case of plastic, in particular water-rich powders, however, it should not exceed 50 ° C., preferably 40 ° C., as is generally the case when the powder is conveyed pneumatically. The powder can also be stored for any length of time, but this generally only plays a role in the event of production interruptions. A continuous flow of material is always advantageous, for which the method according to the invention is particularly suitable due to the continuous procedure.

The powder should be free-flowing and not sticky. However, the processing of slightly adhesive powders is also possible if water-soluble, moisture-absorbing salts or introduces a finely divided adsorption material into the mixer. Suitable salts are e.g. B. sodium sulfate, soda or phosphates or polyphosphates, which can be mixed in proportions up to 20 wt .-%, preferably up to 10 wt .-%. Suitable adsorbents are zeolite and finely divided silica. It is preferred to add finely divided zeolite, that is to say a particle size of at most 10 μm, NaA in proportions of up to 4% by weight, preferably 0.5 to 3% by weight.

The mixing device used to carry out the method consists of an elongated mixing drum of essentially cylindrical shape, which is mounted horizontally or moderately descending against the horizontal and is equipped with at least one filler neck or funnel and a discharge opening. Inside, there is a central, rotatable shaft that carries several radially aligned striking tools. When rotating, these should be at a certain distance from the smooth inner wall of the drum. The length of the striking tools should be 80% to 98%, preferably 85% to 95% of the inner radius of the mixing drum.

The shape of the striking tools can be of any type, ie they can be straight or angled, of uniform cross-section or pointed, rounded or widened at their ends. Their cross-section can be circular or angular with rounded edges. Different shaped tools can also be combined. Those with a drop-shaped or wedge-shaped cross-section have proven successful, with a flat or rounded surface pointing in the direction of rotation, since with such tools the compaction effect outweighs the crushing effect. The tools can be used diametrically in pairs or in order to avoid imbalances be attached to the shaft in a star shape. A spiral arrangement has proven to be advantageous. The number of tools is not critical, but it is advisable to arrange them at a distance of 5 to 25 cm in the interest of high efficiency. Furthermore, it is advantageous to mount them rotatably on the shaft, which gives the possibility of influencing the horizontal conveyance of the mixed material by setting a flat side surface of the tools at an oblique angle in the direction of the material flow. The shape of the tools does not need to be uniform either, rather it is possible to alternately arrange tools with a more compacting and more promoting effect.

The conveying of the mixed material in the mixer can also be accomplished or accelerated by means of additional conveyor blades or. These conveyor blades can be arranged individually or in pairs between the mixing tools. The degree of delivery can be regulated by the angle of attack of the blades.

The inner radius of the mixer is, depending on the desired throughput, advantageously 10 to 60, preferably 15 to 50 cm, its inner length 70 to 400 cm, preferably 80 to 300 cm and the ratio of inner length to inner radius 4: 1 to 15: 1, preferably 5: 1 to 10: 1. With these dimensions, the number of striking tools is usually 10 to 100, usually 20 to 80. The inner wall of the cylinder should be bare in order to avoid undesired sticking of the powder. With smaller dimensions, the rotational speed of the shaft is above 800 rpm, taking into account the Froude number per minute), usually between 1,000 and 3,000 rpm. With larger mixers it can be reduced accordingly.

The residence time of the powder in the mixer depends on the performance of the system and the size of the desired effect. It should not be less than 10 seconds and not more than 60 seconds. It is preferably 20 to 50 seconds. It can be influenced by the inclination of the mixer, by the shape and arrangement of the striking and conveying tools and, to a certain extent, also by the amount of the powder supplied and removed. By reducing the initial cross-section, a certain back pressure and thus an increase in the residence time in the mixer can be achieved. The mixer should be operated so that after the start-up time there is a constant powder throughput, i. H. that the amount of powder fed in and taken out is the same and constant at all times.

gegeben ist (w = Winkelgeschwindigkeit, r = Länge der Werkzeuge ab Mittelachse, g = Erdbeschleunigung). Die Froude-Zahl soll 50 bis 1 200, vorzugsweise 100 bis 1 000 und insbesondere 150 bis 800 betragen.An essential measure of the mixer operation is the Froude number, a dimensionless number that results from the relationship

is given (w = angular velocity, r = length of the tools from the central axis, g = gravitational acceleration). The Froude number should be 50 to 1,200, preferably 100 to 1,000 and in particular 150 to 800.

The powder may heat up slightly as a result of mechanical processing. However, additional cooling is generally unnecessary or is only required if the supplied Powder tends to stick at elevated temperature. However, this problem can advantageously be solved by cooling the tower powder sufficiently beforehand, for example in the case of pneumatic conveying.

If the aforementioned conditions are met, a continuous, trouble-free process execution with high throughputs is possible. A process takes place in the mixer, which can be described as follows.

The powder entered is taken away by the rotating striking tools and hits the inner wall of the mixer without sticking to it. At most, a thin powder coating is formed, which is constantly renewed and the bare inner surface of the mixer can be seen again and again. The powder particles thus describe a spiral movement from the mixer inlet to the mixer outlet. If the powder adheres to the inner wall for a long time, so that a layer of powder forms which has to be scraped off by the rotating tools, the powder is too moist or too sticky, or too warm. This non-stationary condition causes the mix to heat up excessively and the mixer to settle. One can counteract the formation of such deposits by the described addition of adsorbents.

The products obtained have a bulk density increased by 100 to 200 g / l compared to the tower powder used, are extremely free-flowing and do not require any aftertreatment, in particular no post-drying and no sieving of enlarged or lumpy agglomerates. You can therefore immediately after leaving the mixer, if necessary after adding more Powder components such as bleach (e.g. sodium perborate as monohydrate or tetrahydrate), bleach activators (e.g. granulated tetraacetylethylenediamine), enzyme granules, defoamers (e.g. silicone or paraffin defoamers applied to carrier material) are filled directly into the shipping container . Of course, it is also possible to treat two or more separately produced tower powders of different compositions together in the mixer or to compress only one of them and subsequently add a second one.

Examples

A horizontally arranged mixer was used, the cylindrical interior of which had a radius of 15 cm and an inner length of 125 cm. In the inlet area (length 30 cm) several conveyor blades were arranged spirally on the inner shaft. In the subsequent mixing section between inlet and outlet, 5 tapered, angled at their ends and then 25 additional mixing tools were spirally attached to the inner shaft, the latter having a wedge-shaped cross-section with rounded corners. The distance between the tools and the inside wall of the cylinder was 0.5 cm, which resulted in a ratio of tool length from the central axis to the inside wall of the mixer of 96.7% of the inside radius. In order to support the conveying effect, inclined conveying blades (total number 10) were installed in a spiral arrangement between the mixing tools. The size of the outflow opening could be regulated by means of a slide. In the following Examples 1 to 3, this slide was set so that a slight back pressure and thus a uniform filling state formed in the mixer during continuous operation. In Examples 1 to 3, the rotation speed was 1,500 RPM and the average residence time was 20 to 60 seconds on average 30 to 40 seconds. The mixer was charged with spray-dried powder, which was transported via a pneumatic conveyor system after leaving the tower discharge and had a temperature of 30 ° -2 ° C.

The composition of the powder and the throughput in tons per hour (t / h) and the liter weight before and after the treatment can be found in Table I. The components a - m as well as the water and the main part of the sodium sulfate (component n) accounted for the tower spray powder. The remainder of the sodium sulfate and the minor constituents served as a granulation base and as coating substances for the constituents listed under p to r. These were subsequently mixed with the perborate (which had been sprayed with the perfume) into the treated powder. The resulting bulk density of the respective finished mixture A is also given (in each case in g / liter). The abbreviations mean: Na ABS Sodium dodecylbenzenesulfonate (C₁₀₋₁₃) FA + x EO Fatty alcohol + x moles of attached ethylene oxide STP Sodium tripolyphosphate (anhydrous) AA-MA Acrylic acid: maleic acid 3: 1 (MW 70,000) Phosphonate Ethylene diamine tetramethylene phosphonic acid Na₆ salt NTA Nitrilotriacetic acid Na₃ salt TAED Tetracetylethylenediamine

The powders proved to be free-flowing, non-dusting and dissolved by hand when sprinkled into the wash liquor Fast, without lumps and residue-free, even with automatic rinsing in household washing machines.

In a vibrating test that simulated mechanical stress during the transport of the packs, the powder components did not separate.

In a further series of experiments, 2% zeolite was eliminated from the tower powder formulation and instead added as a powder during the mixing process. A finished product B with an even higher bulk density was obtained. composition 1 2nd 3rd a Na - ABS 6 7 7 b C₁₂₋₁₄-FA + 3 EO 1 1.4 1 c C₁₂₋₁₈-FA + 5 EO 4.6 3.4 3.8 d soap 2nd 0.5 1.0 e STP 20th - - f zeolite NaA 10th 25th 20th g AA-MA copolymer 1.0 4th 3rd h phosphonate 0.6 2nd 2nd i Na₂CO₃ 10th 7 10th j Na₂O.3.3 SiO₂ 5 3.5 2.5 k cellulose ether 0.8 1.1 1.1 l opt. Brightener 0.1 0.1 0.1 m Na sulfate, water and minor components rest rest rest n NaBO₃ · 4H₂O 15 - - o NaBO₃ H₂O - 10th 10th p TAED 2.5 3.5 3.5 q enzyme 0.5 0.5 0.5 r silicone 0.2 0.2 0.2 s perfume 0.2 0.1 0.2 Throughput (t / h) 1.6 2.7 1.9 Froude number 365 385 350 Bulk density (g / l) TP before compression 545 524 440 TP after compression 595 639 538 Ready mix A 621 660 573 Ready mix B 656 700 625

Example 4

Starting from a composition according to Example 2, a tower powder with a zeolite content of 17% by weight without the nonionic surfactant component (c) and a copolymer content (component g) reduced to 1% was produced. Granules of 55 parts by weight of zeolite, 9 parts by weight of the copolymer, 19.8 nonionic surfactant according to component (c), 4.2 parts by weight of sodium sulfate and 12 parts by weight of water were used as the second powder component. Both powder components were mixed together in the mixer, the second powder component being used in such an amount that the content of the finished product (as in Example 2) totaled 25% by weight. The mixture tended to stick in the mixer during the processing process. The bulk density after compression was 538 g / l and in the finished product 573 g / l. If a further 2% of the zeolite was eliminated from the tower powder and fed into the mixing process as powder, no sticking occurred and the bulk weights were 570 (compressed) and 650 (finished product).

Example 5

Example 2 was repeated, but the drying in the spray tower was carried out at a slightly elevated temperature, as a result of which the water content in the tower powder was reduced by 1.5%. These powders were removed directly from the tower discharge and processed at a temperature of 80 to 85 ° C in the manner specified. The following bulk weights were determined:
Tower powder 500 g / l, after compression 661 g / l,
Finished product A 685 g / l,
Finished product B 729 g / l.

Claims (9)

1. A process for increasing the density of spray-dried detergents without the use of liquid granulating agents, characterized in that the spray-dried powder having a bulk density of at least 350 g / liter is continuously introduced into a cylindrical, horizontally arranged or slightly inclined mixing drum with a smooth inner wall , in which a shaft rotates axially, which is equipped with radially arranged impact tools, the length (calculated from the central axis) of which is 80% to 98% of the inner radius of the drum, and that the speed of rotation of the shaft is regulated in such a way that with a medium dwell time of the powder in the drum from 10 to 60 seconds and constant powder throughput the Froude number is between 50 and 1 200. 2. The method according to claim 1, characterized in that the length of the rotating tools is 85% to 96% of the inner radius of the drum. 3. The method according to claim 1 and 2, characterized in that the bulk density of the tower powder supplied is 420 to 550 g / l. 4. The method according to claim 1 to 3, that the average residence time of the powder is 20 to 50 sec. 5. The method according to claim 1 to 4, characterized in that the Froude number is 100 to 1,000. 6. The method according to claim 1 to 5, characterized in that the temperature of the powder does not exceed 50 ° C. 7. The method according to claim 1 to 7, characterized in that up to 5 wt .-% of finely divided adsorbents are added to the powder. 8. The method according to claim 7, characterized in that 0.5 to 3 wt .-% of finely divided dry zeolite is added to the powder. 9. The method according to one or more of the preceding claims, characterized in that several powder components are processed simultaneously.