EP0283885A2 - Process for the production of free flowing alkaline cleaning agents by compactible granulation - Google Patents

Abstract

For the production of granular, free-flowing cleaning agents made from sodium metasilicate, pentasodium triphosphate or zeolite NaA or a triphosphate-zeolite mixture, at least 2 of the components are first agglomerated and mixed as granular pre-agglomerate with the other components present in powder form and compacted by means of rollers, using the limit pressure at which no further compression occurs, does not significantly exceed. The compact is then crushed to the desired grain size.

Description

An essential component of commercially available cleaners for use in machine cleaning processes - for example in the known dishwashers used in the home - are to date generally sodium metasilicate in a mixture with sodium tripolyphosphate (also called pentasodium triphosphate and hereinafter referred to as STP). In particular, soda and water glass as well as further components for strengthening the granulating and / or cleaning effect are used as further components. The mixtures of substances exist as free-flowing agglomerates, whereby a number of requirements are placed on the product properties.

The substance mixtures are generally strongly alkaline and therefore irritating to the respiratory tract. Accordingly, the occurrence of dust in the product, as would be expected when using powdered raw materials, must be avoided. Furthermore, products of this type with high fines in the dishwasher's washing-in box tend to clump when water enters, so that a sufficiently short washing-in time is no longer guaranteed.

In addition to being washable and free of dust, other important evaluation criteria are the bulk density and the storage stability of the cleaners. The bulk density should be above 900 g / l to enable the product quantity required for the cleaning cycle to be filled into the dispenser box without problems. Since the free-flowing agglomerates contain water, it must be ensured when processing the recipe that the water remains largely crystalline in order to prevent caking of the granules during storage.

Today's commercial cleaners are manufactured according to two process variants, namely either by mixing granulation or by mixing granular dust-free raw materials.

Mixed granulation in the presence of water presents a number of complications that require careful control of the process. In the case of water-wet granulation, various components of the mixture of substances (in particular STP, anhydrous metasilicate and soda) compete for the binding of the free water present. The thermodynamically most stable composition may only be achieved when the raw material properties are not constant or the process conditions are not exactly adhered to when the products are stored. The migration of the water required for this is generally accompanied by a clumping of the product.

The formulation flexibility of the mixed granulation process is also relatively low, and in particular in a very specific direction: The replacement of larger proportions of the STP with the finely crystalline zeolite NaA, which is desirable for reasons of environmental protection, causes difficulties. In particular, products that are too light with unsatisfactory ones are often found here Get induction properties. When mixing granulation in appropriate devices with high energy input, for example in the known Lödige mixer, sticking to the mixer walls occurs, which necessitates regular cleaning of the mixer. The use of soda and water glass as a granulation aid is necessary without these components making a significant contribution to the effectiveness of the cleaning formulation.

The production of mixed products according to the information in the prior art partially avoids the disadvantages of mixed granulation mentioned above, but it is still necessary to use pre-granulated and thus very expensive raw materials in order to ultimately produce dust-free mixed products.

The invention is based on the task of using granular detergent formulation with good flowability, good washability and good storage stability using inexpensive raw materials while reducing the disadvantages of water-moist mixed granulation. In addition to the processability of previously customary formulations for agents of the type specified here, the invention also intends to use finely crystalline zeolite NaA in addition to or instead of STP and to use other components, for. B. of cleaning boosters - enable.

The earlier application DE 36 24 336 (D 7298) relates to a process for the production of granular, free-flowing alkaline cleaning agents based on sodium metasilicate in intimate admixture with pentasodium triphosphate and / or finely crystalline zeolite NaA as reinforcing builders and, if desired, further auxiliaries for an improved Granulating or cleaning action by means of a mixing process, the process of this main patent being characterized in that the starting components of the mixture of substances in Powder mixed together, this mixture of substances compacted in the nip under increased pressure and the resulting compactate crushed to the desired grain size. In this case, the limit pressures in the roll nip are preferably not significantly exceeded, from which point further compression no longer occurs. In particular, the mixture to be granulated is converted under compression pressure in the nip of a pair of rollers of two rollers running in opposite directions at approximately the same circumferential speed to form a plate-shaped compact which is subsequently comminuted to the desired particle shape. With this process, it is possible to easily produce strongly alkaline substance mixtures of the type concerned in the form of free-flowing products which are free of dust and which, when used, are distinguished by their high specific density and good washing-up behavior in conventional dishwashers. At the same time, the free-flowing products obtained are stable in storage and, in particular, do not tend to cake even after prolonged storage.

The further development of this teaching in the context of the present invention relates to a further simplification of the process in those cases in which, in particular, fine-powder mixture components are to be used for the production of the overall compact, whose homogeneous incorporation into the mixture of substances and subsequent processing in the nip to form the compact can be difficult.

It has been shown that, for example, the zeolite NaA used as the phosphate substitute can cause undesirable process engineering difficulties if it is to be used in the form of a spray-dried fine powder, as is currently available on the market for the production of detergents containing zeolite NaA. The use of a Such generally spray-dried zeolite material can be problematic because of its poor pouring properties and the very fine powder structure, especially in large-scale plants, for example because metering problems, the clogging of powder paths or the extraction of fine particles via the system dedusting can result as sources of error. In addition, very poorly flowing powders, which tend to form adhesions, can cause difficulties. They are occasionally insufficiently drawn in by the rollers, so that the rollers are forced to be fed via a screw or a similar unit. However, the compulsory loading can be undesirable, particularly in the case of formulations which contain, for example, water-containing metasilicates or other components which can be melted or plasticized at relatively low temperatures, since there is then a risk of partial plasticization of the material to be compacted due to the temperature increase in the compression area of the stuffing screw which can generally be determined , which can lead to sticking in the area of the screw and on the rollers. This is often associated with a further increase in temperature due to increased friction, which can, for example, damage organic components or lead to undesired release of water of crystallization.

Such procedural disadvantages can be significantly reduced in the sense of the task according to the invention by introducing higher proportions of already granular, free-flowing components into the raw material mixture.

The invention relates to a process for the production of granular, free-flowing alkaline cleaning agents based on sodium metasilicate in intimate admixture with pentasodium triphosphate (STP) and / or finely crystalline zeolite NaA as reinforcing builders and If desired, further auxiliaries for an improved granulating and / or cleaning effect by means of a mixing process in which the starting components of the substance mixture are mixed with one another, this substance mixture is compacted in the roller gap under increased pressures and the resulting compactate is comminuted to the desired particle size, characterized in that at least two of the mixture components to be compacted are agglomerated with one another in an upstream process stage and entered as granular pre-agglomerate in the compacting of the mixture of substances in the roll nip.

In such a production of granular pre-agglomerates, according to the invention, in particular the fine-powdered mixture constituents are included, which, if appropriate, are also worked up here with the use of water with further mixture components to form the granular pre-agglomerate. As a rule, the pre-agglomerates have lower solids densities than the end products of the compacting process after compaction in the nip. It is a particular advantage of the process according to the invention that the setting of certain solid densities need not be taken into account in the production of the pre-agglomerates, but that the desired setting of high solid densities has to be preferably above 1.8 g / cm 3 in the subsequent stage of compacting in the roll nip he follows.

Any suitable simple agglomeration process is suitable for the production of such pre-agglomerates from finely divided mixture components. In practice, the most favorable process types for the respective application will be chosen. A particularly simple method can be seen in individual cases in a spray drying process in which the pre-agglomerate is a free-flowing tower powder made from very fine powders Mixing with solutions and / or suspensions of other mixture components in water is obtained.

For example, as a mixture component for compacting in accordance with the teaching of the main patent, free-flowing tower precursors that already have a grain structure can be produced, which, in addition to zeolite NaA, can contain further finely divided components, for example STP and / or soda. Of course, STP and / or soda alone can also be subjected to pre-agglomeration in such a form. It is advisable, particularly for cost reasons, to incorporate additional auxiliaries, for example cleaning-enhancing components, such as nitrilotriacetic acid (NTA) and / or polymeric carboxylic acids or their sodium salts (for example the copolymer of acrylic acid and maleic acid known as the commercial product "Sokalan CP 5") via the tower , because in this way these auxiliaries can be used instead of powdered goods in the form of the much cheaper corresponding solutions and at the same time in this form still give rise to the described process advantages for the overall process. It has also been found that such auxiliary components can in turn contribute significantly to grain formation in spray drying.

With the method according to the invention, difficulties are particularly easy to avoid if completely phosphate-free formulations are to be produced as a high-density compact that require the use of relatively large amounts of finely powdered zeolite. It has been shown that by selecting and adapting the components in the pre-agglomeration step, the compacting granulation in the sense of the teaching of the main patent leads in all cases to products which are acceptable in grain size and in application properties.

The teaching of the invention includes a procedure in which all components of the mixed product form one or more pre-agglomerates processed, then mixed as necessary and compacted in the nip. For this purpose, the material to be granulated is passed under pressure through the gap of a pair of two rollers running in opposite directions with approximately the same circumferential speed and thereby compressed into a plate-shaped material to be pressed.

The roller compression can take place without or with a pre-compression of the premixed powdery material. The pair of rollers can be arranged in any spatial direction, in particular thus vertically or horizontally to one another. The pulverulent material is then fed to the roller gap either by gravity filling or by means of a suitable device, for example by means of a stuffing screw.

The pressing pressure in the nip and the dwell time of the material in the area of the pressing pressure are to be set so high that a well-formed, hard, high-density band is produced. The high degree of compaction is to be striven for in order to set the desired bulk densities of the free-flowing material ultimately obtained, which should be above 900 g / l. The abrasion resistance of the granules is also influenced by the degree of compaction. High degrees of compaction lead to abrasion-stable granules, which in turn are desirable. Here However, it must be noted that excessive pressures impair the process reliability, since when they are used the material is plasticized on the rollers and leads to sticking. This undesirable effect occurs when an increase in the pressing pressure no longer causes further compression of the material and the additional force that is now added predominantly causes the heating and plasticization of the material - for example by partial melting of water-containing constituents, in particular water-containing metasilicate.

The optimum pressing force to be used depends on the recipe. Usually, according to the invention, a specific pressing force in the range of about 10 to 30 kN per cm of roller length is used in the nip, the range of about 15 to 25 kN per cm of roller length being particularly preferred.

The fat density in the compactate is preferably at least about 1.7 g / cm³. Corresponding solid densities of at least about 1.8 to over 2 g / cm 3 are particularly suitable. Here, too, the optimal density value to be set depends to a certain extent on the recipe.

Contrary to expectations, the ability of the granules to be flushed in - determined as the flushing time of a predetermined amount of material in a test apparatus - is favored by higher compression pressures and thus by higher solids densities, and not deteriorated. Apparently, fillings made of harder particles tend to clump less and also form fewer fines during the flushing-in process, so that an unimpeded flow of water through the fill is promoted here.

In addition to the setting of optimal baling pressures in the roll gap, the setting of the thickness of the plate-like or band-shaped compact is important for achieving the desired high bulk densities of the finally granulated free-flowing cleaning agents. If the selected bowl thickness is significantly smaller than the desired upper grain limit of the granulated product to be produced, platelet-shaped particles are obtained during the comminution of the initially obtained plate-shaped compactate, which lead to fillings with a high void volume and therefore comparatively low bulk density. At higher compactate thicknesses, however, particles are obtained in the subsequent comminution, the dimensions of which can approximate the desired ratio of 1: 1: 1. Such a grain shape leads to denser fillings, the void volume of which is a maximum of about 50%. Although this value is still relatively high in comparison to fillings made from spherical particles - the usual corresponding values are around 35 to 45% - a somewhat higher void volume can also bring advantages in the sense of the inventive action. This obviously favors the flushing process in the sense of an unimpeded flow of water through the fill.

Accordingly, the press pressure in the nip and the dwell time of the material in the area of the press pressure are set so high that a well-formed, hard, high-density band is produced. Bulk weights of the free-flowing material ultimately obtained are aimed at, which are above 900 g / l. The optimum pressing force to be used depends on the recipe.

Depending on the recipe, the value of the pressing force to be set is additionally limited by the maximum temperature permitted in the slugs, above which e.g. Water of crystallization is released, organic components are damaged or the properties and structure of the zeolite used is changed by interaction with the surrounding recipe components. For e.g. Sodium silicate hydrate (Na₂H₂SiO₄. 4 H₂O, K5) and / or recipe types containing zeolite, such a temperature limit is about 45 to 50 ° C. Temperatures below 40 ° C. are preferred.

The plate-like or band-shaped material to be pressed is then subjected to a comminution process and granular material of the desired particle size and particle size distribution is obtained in the process. The comminution of the plate-like or band-shaped material can take place in a mill. The comminuted material is then expediently fed to a screening process. Material which is too coarse is separated off and returned to the comminution device, while material which is too fine is added to the batch of the mixture to be compacted and is again fed to the compacting in the roll gap.

The desired upper grain limit in the free-flowing agglomerate is in the range from about 1.6 to 2 mm, while on the other hand fine fractions below about 0.2 mm are undesirable. The preferred free-flowing agglomerates accordingly show a broad grain size range in the range from about 0.2 to 2 mm. It is preferred to have plate-like or band-shaped compactates with a layer thickness of at least about 1.5 mm after the nip. The layer thickness here is preferably at least about 2 mm. Layer thicknesses of the compact in the range from about 4 to over 10 mm can be particularly preferred.

The basic formulations for the components of the finished compacted products essentially correspond to the information in the older application DE 36 24 336, although there is even greater scope here due to the teaching according to the invention of incorporating pre-agglomerates produced separately. The proportion of metasilicate is generally in amounts of about 20 to 75 percent by weight and preferably in amounts of about 35 to 65 percent by weight of the total mixture. The metasilicate can be used as an anhydrous product and / or in the form of hydrated phases with certain predetermined and / or varying amounts of hydrated water content. Suitable metasilicate phases containing water of hydration are known to be corresponding products with 5 or 9 water of crystallization, with particular importance being attached to the corresponding metasilicate with 5 water of crystallization. The combination of anhydrous sodium metasilicate (KO) and sodium metasilicate containing water of crystallization, in particular corresponding product with 5 water of crystallization (K5), can preferably be used.

In addition to the main components with a cleaning effect, other auxiliaries can also be used, for example solubility-improving substances, foam inhibitors (e.g. paraffins), surfactants, in particular low-foam nonionic surfactants, chlorine carriers (e.g. trichloroisocyanuric acid), cleaning enhancers, dyes and the like.

Compactates with good cleaning action contain the individual active ingredients or groups of active ingredients in the following areas, for example: 20 to 75 percent by weight Na metasilicate, 20 to 50 percent by weight STP and / or zeolite NaA, not more than 20 percent by weight soda, not more than 10 percent by weight Na water glass, no more than 15 percent by weight of other additives with about 8 to 25 percent by weight of total water.

In a further embodiment, the invention changes the teaching of the main patent and the teaching of the present additional application to the effect that the use of STP and zeolite NaA is completely dispensed with in the production of the free-flowing alkaline cleaning agents by compacting granulation. Corresponding formulations then contain, as cleaning agents, essentially metasilicates which, when mixed with cleaning-enhancing auxiliaries and, if desired - as described in the main patent - can also be present together with soda and / or water glass and other additives of the type described in the main patent. Suitable cleaning-enhancing additives are the sodium salts of polymeric carboxylic acids customary in today's laundry detergents, for example of homopolymeric acrylic acid (abbreviation AA-Na salt) with a molecular weight (MW) of 2,000 to 1,500,000 or of copolymers of acrylic acid and maleic acid in a ratio of 4: 1 to 1: 1 with a MW of 30,000 to 150,000, for example the commercial product "Sokalan CP 5", and / or the sodium salt of nitrilotriacetic acid (NTA). This class of cleaning adjuvants, which can be used in addition to and / or instead of STP and / or zeolite NaA in the detergent mixtures of the invention, belong to the so-called cobuilders from textile detergent compositions. Among other things, it excels through the ability to bind water hardness complex.

• (a) Sasil      20 - 75 %
• (b) STP      0 - 40 %
• (c) AA/MA-Na-Salz      0 - 30 %
• (d) Soda      0 - 30 %
• (e) NTA      0 - 15 %
• (f) H₂O      10 - 23 %

In the case of phosphate-free or low-phosphate agents, the composition of the pregranules which can be produced by means of a tower spraying process can be as follows (at least one of the substances (b) to (e) should be wholly or partly present):

• (a) Sasil 20 - 75%
• (b) STP 0 - 40%
• (c) AA / MA Na salt 0-30%
• (d) soda 0 - 30%
• (e) NTA 0 - 15%
• (f) H₂O 10-23%

In addition, small proportions of suspension stabilizers can be present, which are used in the production of aqueous, stable zeolite suspensions (masterbatch), e.g. B. small proportions of fatty alcohol ethoxylates and neutral salts such as sodium sulfate. These accompanying substances are called "micro components".

Examples example 1

A zeolite-containing NaA tower intermediate with the following composition was produced via a spray tower:
STP 37%
Zeolite NaA 43.55%
Water 19.45%
The roller pair of a compactor (Bepex, type MS 150) were 1 t / h of a mixture consisting of
Na₂SiO₃ anhydrous (K0) 17%
Na₂SiO₃ + 5H₂O (K5) 40%
STP 2.5%
Tower intermediate 40.5%
fed via a stuffing screw. The pressing force of the rolls was adjusted in the range from 25 to 50 kN / cm so that the temperature of the emerging, approximately 4 to 8 mm thick slugs was between 30 and 35 ° C. The slugs were crushed with a hammer basket mill. The resulting product was sieved. Coarse grain was fed back into the mill. The fine fractions were returned to the compaction with the fresh raw materials. The good grain content was easy to wash in with a washing-up time of 20 to 25 minutes in a standard household dishwasher (Miele G 503 S).

Example 2

At the spray tower, a concentrate consisting of
Zeolite NaA 71%
AA / MA Na salt 8%
Water 20%
(Rest of small components)
produced.

24 parts of the preliminary product were mixed with 27.3 parts KO, 27.3 parts K5, 16.3 parts STP and 1 part paraffin. The mixture was then pressed at 16 kN / cm specific pressing force and then crushed and sieved. The product with a grain spectrum of 0.2 to 1.6 mm showed good application properties. The commercial product "Sokalan CP5" (molecular weight 70,000) was used as AA / MA.

Example 3

31.8 parts of a spray-dried intermediate of the composition
Zeolite NaA 65.5%
AA / MA-Na 15.4%
H₂O 18.5%
(Rest of small components)
were mixed with 16.2 parts of KO and 50 parts of K5 and then pressed with a specific pressing force of 16 kN / cm into slugs. Subsequent comminution and sieving to 0.2 to 1.6 mm and preparation of 98% of the roller granules with 1% paraffin oil and 1% trichloroisocyanuric acid (abbreviation TICA) gave a product with good application properties.

Example 4

A premix consisting of 43.6 parts K5, 20.5 parts KO, 15.0 parts STP, 10.0 parts soda calc. 10.9 parts of AA / MA Na powder (92%) was compacted using a roller press at a specific pressing force of 16 kN / cm and then comminuted. After screening with 1% TICA (chlorine carrier), the screened portion of good grain (0.2 - 1.6 mm) showed a bulk density of 967 g / l. The material was acceptable in terms of induction time and residue behavior.

Example 5

A premix consisting of 53 parts of K5, 15 parts of KO, 9.5 parts of soda ash, 21.5 parts of AA / MA Na powder (92%) is processed as described in Example 1. The finished product with a bulk density of 904 g / l shows good washability and favorable residue behavior.

Examples 6 to 10

The compositions of further cleaning agents produced according to the invention are given in the following summary table. The composition of the detergents as a whole is described in Table 1, with one component of the mixture being referred to as a "preliminary product".

The composition of these "preliminary products" is broken down in Table 2 below. These preliminary products have been produced by processing over the tower in the sense of the teaching according to the invention. FA-EO-PO is a C8₁₂₋₁₈ fatty alcohol reacted with 10 moles of ethylene oxide and 4 moles of propylene oxide. Blue Speckle is a 1: 1 mixture of STP and KO, stained with a blue dye (Ultramarine). The AA Na salt had a MW of 1,250,000.

The cleaning performance of the roller compacts produced according to the invention according to Examples 6 to 10 is determined on test soils according to Th. Altenschöpfer, soaps, oils, fats, waxes, booklets 23 and 24 (1972), pages 3 to 12.

The cleaning performance, determined in a household dishwasher (Miele GS 540), with a universal program at 55 ° C and a water hardness of 16 ° d (160 mg CaO / liter) are summarized in Table 3 below.

Claims (10)

1. Process for the production of granular, free-flowing alkaline cleaning agents based on sodium metasilicate in intimate admixture with pentasodium triphosphate and / or finely crystalline zeolite NaA as reinforcing builders and, if desired, further auxiliaries by means of a mixing process in which the starting components of the mixture of substances are mixed with one another, this mixture of substances compacted in the roll gap under increased pressures and the resulting compactate comminuted to the desired grain size, characterized in that at least two of the mixture components to be compacted agglomerate with one another in an upstream process stage and are introduced as granular pre-agglomerate into the compacting of the mixture of substances in the roll gap. 2. The method according to claim 1, characterized in that the pre-agglomerates are produced with lower solid densities than those of the finished compact and are entered into the compacting. 3. Process according to claims 1 and 2, characterized in that fine-powdered mixture constituents are included in the pre-agglomeration and are optionally worked up here with the use of water with further mixture components to form the granular agglomerate. 4. Process according to Claims 1 to 3, characterized in that free-flowing pre-agglomerates are produced by means of spray drying and are then added to the compacting. 5. Process according to Claims 1 to 4, characterized in that zeolite NaA, STP and / or soda are subjected to the pre-agglomeration if desired together with auxiliaries which have a cleaning-enhancing effect as fine powder mixture components. 6. The method according to claims 1 to 5, characterized in that one works in the compacting in the nip with a specific pressing force in the range of about 10 to 30 kN / cm roller length - preferably in the range of about 15 to 25 kN / cm roller length. 7. The method according to claim 6, characterized in that the material to be granulated under pressure under pressure in the nip of a pair of rollers two rollers running at approximately the same peripheral speed in opposite directions to a plate-shaped material to be pressed, which is then reduced to the desired grain shape. 8. The method according to claims 6 to 7, characterized in that the premixed material is compacted to layer thicknesses of at least about 1.5 mm after the roll gap, preferably layer thicknesses of the compact of at least 2 mm and in particular those in the range from about 4 to 8 mm can be set. 9. The method according to claims 6 to 8, characterized in that the starting mixture is compacted in the nip to form compactates with solid densities of at least about 1.7 g / cm³, preferably in the range of about 1.8 to over 2 g / cm³. 10. The method according to claims 1 to 7, characterized in that a grain spectrum of about 0.2 to 2 mm is set in the finished product.