EP0249163B1 - Detergents containing granular, agglomerated sodium metasilicate, process for their preparation and their use - Google Patents

Description

Sodium metasilicate is an essential component of so-called machine cleaning agents which are used in machine-based cleaning processes _ for example in the known dishwashers used in the household _. In an anhydrous form, this normally contains dust that attacks the airways because of its high alkalinity. Sifting the dust particles can only solve this problem temporarily, as dust particles form again during storage due to weathering. In addition, the flushing behavior of the cleaning agent is negatively influenced by fine fractions of the metasilicate.

The mechanical cleaning agents commonly used in practice today contain the sodium metasilicate in intimate admixture with other components that have a reinforcing effect, with pentasodium triphosphate (STP) still being of significant importance to this day. Both components are currently agglomerated together with soda, water glass and water in the manufacture of commercially available products to form an essentially dust-free, sufficiently heavy cleaner. A sufficient density _ determined as bulk density _ of the material arises as a necessity because of the size of the cleaning devices built-in dosing box.

In the context of water protection, the partial or complete replacement of STP with other builders is urgently desired and in the field of textile detergents, in particular through the use of synthetic, fine-crystalline sodium aluminosilicate of the zeolite NaA type. Despite numerous attempts, however, a corresponding exchange in machine cleaning agents of the type concerned here has not yet been successful. The different requirements for the manufacture and use of mechanical cleaning agents compared to textile detergents make it impossible to simply transfer the knowledge gained from the field of textile detergents to the problem area concerned.

The object of the invention is to overcome the difficulties presented. The aim is to provide strongly alkaline, granular, agglomerated cleaning agents based on intimate mixtures of sodium metasilicate in admixture with reinforcing builders, whereby the partial or complete elimination of STP as a mixture component is now possible.

The solution to this problem according to the invention is based on the finding that, by observing the measures described below, it is possible to produce suitable granular agglomerated, flowable cleaning agents which are essential components Contain sodium metasilicate in an intimate mixture with synthetic fine crystalline sodium aluminosilicate of the type of zeolite NaA. Accordingly, the invention relates to a first embodiment of the method for producing such machine cleaning agents in agglomerate form. In further embodiments, the invention relates to the new flowable granular agglomerated cleaning agents or corresponding STP-free components which can also be used as an additive to known cleaning agents of the type concerned here, and to their use in machine cleaning, for example in the context of dishwashing agents .

In the first embodiment described, the invention relates to a production process of the type described, which is characterized in that finely divided sodium metasilicate is moistened with a flowable, finely crystalline zeolite-NaA aqueous suspension and the mixture is agglomerated with intensive mixing, whereupon, if desired, the agglomerate is dried at least to remove the surface moisture.

It is therefore crucial for the production process according to the invention that at least a portion of the zeolite NaA is introduced in the form of an aqueous suspension which is used to moisten the anhydrous or essentially anhydrous sodium metasilicate. In this embodiment of the method, the humidification of the dry material presented is _ and thus its conditioning for the subsequent agglomeration associated with the mixing in of at least a portion of the zeolite NaA. It has been shown that in this way the production of granular agglomerates of the structure desired here is really possible for the first time. Depending on the overall desired content of zeolite NaA in the mixture of substances, the fine-crystalline zeolitic material can only be introduced in this form, but additional measures can be associated with this, which in particular enable a substantial increase in the proportion of zeolite in the mixture product. The following applies here:

In a first variation, a mixture of sodium metasilicate and flowable, finely divided zeolite NaA is already in the dry state as the dry material to be agglomerated, and this mixture is then moistened with the aqueous suspension of the zeolite NaA to the extent required for the subsequent agglomeration. In addition to or instead of this measure, the following step can be used to increase the zeolite content in the mixture product:

The granular products that occur primarily in the agglomeration may require a subsequent treatment, at least to lower the surface moisture, in order to avoid undesired clumping and thus to maintain the flowability of the product. One possibility for drying the grain surface is the subsequent application of dry zeolite NaA powder, for example, in such a way that in the mixing system the agglomerate formation, an additional portion of zeolite NaA is added in dry powder form and briefly mixed.

In practice, however, it is generally more important, in addition to or instead of such a drying treatment, to lower at least the surface moisture of the initially formed agglomerate by treating the material in an air stream, e.g. in the fluidized bed.

The aqueous zeolite-NaA suspension used in the process according to the invention for moistening the dry material is preferably a corresponding filter cake from the production of the synthetic zeolite, which has about 30 to 60 percent by weight and preferably about 40 to 55 percent by weight solids content. It is known that filter cakes of this type have thixotropic properties, i.e. appear solid in the rest position, but at the same time are flowable or pumpable. The method according to the invention also makes use of this.

Filter cakes of the type described here are usually mixed with small amounts of surfactants to stabilize the suspension. Use can be made of this for the process according to the invention, but it is preferred to exclude an overall foaming mixture which is possible due to this surfactant content. Correspondingly, in the case of surfactant-stabilized filter cakes, the corresponding components are used, which are characterized by only slight foaming. Numerous such components are known to those skilled in the art of surfactants. Instead, material that is not directly attributable to the surfactants can also be used to stabilize the filter cake. In particular, swellable sheet silicates come into consideration here, in particular from the group of smectite clays such as montmorillonite, Hectorite and / or saponite, water glass, polymer substances based on polycarboxylic acids - for example the commercial product "Carbopol" ® or polysaccharides - the commercial product "Kelzan" ®. These stabilizers for the zeolite filter cake are usually only used in limited quantities. The use of salts, for example Na₂SO₄, can also have a stabilizing effect.

Within the scope of the method according to the invention, three modifications can be distinguished in particular, the elements of which can also be connected to one another:

Submitted dry sodium metasilicate _ here in particular unscreened, finely divided crude product from the production, for example by synthesis in the sintering process or by hydrothermal process, is considered _ is moistened with a zeolite filter cake of the stated solids concentration in such amounts that the subsequent working up of the mixed material is possible to an agglomerate . The amount of moisture used depends on the feed material and can be determined by the expert in a few preliminary tests. If the amount of moisture is too low, the mix does not agglomerate or only to a limited extent becomes a dusty product in the mixing stage; if the amount of moisture is too large, the product immediately turns into a very sticky and possibly sticky mixture during subsequent mixing. even pasty condition over. The moisture range between these product states is _ in a manner known per se _ suitable for agglomeration. In this embodiment, the zeolite NaA can generally be introduced into the mixture in amounts of up to about 10 percent by weight.

Frequently or even predominantly, however, a higher content of zeolite NaA in the mix is desired. Bid here then look at the following two ways, which can also be connected:

The sodium metasilicate is initially introduced together with dry zeolite NaA, preferably mixed with one another in the dry state and then moistened with the zeolite filter cake. So-called dry zeolite NaA is known to still contain a considerable amount of moisture, which, however, is bound inside the crystal and accordingly makes the material appear dry. Spray-dried material, which usually has a solids content of approximately 80%, can in particular be used as the zeolite-NaA dry material.

In addition to or instead of this measure for enriching the zeolite content in the mixed product, the process measure already mentioned can be used, after the agglomeration, to apply dry zeolite powder to the still moist agglomerate surface and to attach it there. The combination of this last-mentioned measure with the method described first of moistening sodium metasilicate with the zeolite filter cake creates the possibility of increasing the zeolite content in the mixed product to about 20 percent by weight. If additional zeolite contents are required in the mixed product, then the use of a dry mixture of sodium metasilicate and dry zeolite NaA is recommended, if necessary in conjunction with the subsequent powdering of the wet agglomerates using dry zeolite powder.

These multiple possibilities of variation of the method according to the invention make it possible to set broad mixing ranges in the ratio of zeolite NaA to sodium metasilicate. Granular agglomerates with corresponding mixing ratios in the range from 0.1: 10 to 8: 1 (zeolite / sodium metasilicate) can thus be obtained. Mixing ratios in the range from 1:10 to 4: 1 and in particular those in the range from about 1: 3 to 2: 1 are preferred. A material in which about 1 part by weight of the zeolite NaA to about 1.3 parts by weight of sodium metasilicate. In all of these figures, the parts by weight relate to the anhydrous materials, as can be determined, for example, by determining the loss on ignition.

The agglomeration process is carried out in mixers, which are preferably equipped with moving tools and in particular enable a high energy input. It can be carried out batchwise or continuously in suitable devices. For example, the known Lödige ploughshare mixers or other comparable devices are suitable.

The amount of the liquid phase used in each case can easily be determined by the person skilled in the art by simple preliminary tests, as has already been stated. The following information can also be used as a guide: A preferred water content in agglomerating is approximately in the range of 20 to 30 percent by weight, in particular approximately 22 to 26 percent by weight for the case of the preparation of mixtures of substances, the zeolite-NaA and sodium metasilicate the weight ratio from about 1 to 1.3 included. The numerical values for the water content relate to the total water and thus include the water content bound in the zeolite NaA.

To produce storage-stable, free-flowing agglomerates, particularly in the case of the products with high zeolite contents, it is generally necessary to re-dry the primary product, whereby in the case shown here numerically, for example, the setting of a residual water content (total water) of about 15 to 18% by weight .-%, but generally from 10 to 20 wt.% May be appropriate. The two most important methods for reducing the proportion of residual moisture are the treatment already described in a dry air stream, for example in a fluidized bed, and / or the subsequent powdering of the primary agglomerate particles with dry zeolite NaA powder.

Another process measure can influence the tendency of the agglomerate to clump and ultimately the free-flowing properties of the finished product. It is important to choose the temperature of the agglomeration process. According to the invention, the agglomeration is carried out in particular in the temperature range from approximately 30 to 75 ° C. and preferably in the range from approximately 45 to 75 ° C. A particularly suitable temperature range for this agglomeration treatment is about 50 to about 65 ° C. The tendency to form lumps becomes more apparent the lower the mixing temperature is selected within this range. Such a tendency to form lumps may be desirable _ if a particular one is desired _ on the other hand, working in the particularly preferred temperature range of about 50_65 ° C. can facilitate the handling of the goods in the industrial process.
The subsequent drying, for example in a fluidized bed and / or the powdering of the agglomerate which has primarily occurred, favors often also the bulk density of the process product. These measures promote the formation of the agglomerate in the form of individual grains. This pushes the bulk weight of the goods upwards. In less preferred cases of the process according to the invention, the formation of grape-like caking of the agglomerate grains can be determined, which generally leads to a material with a lower bulk density. Preferred bulk weights are in the range from about 750 to 1200 g / l and in particular in the range from about 950 to 1200 g / l.

The mixing time required for agglomerate formation is in the range of a few minutes, usually in the range of about 1 to 4 minutes. Increasing the viscosity of the zeolite filter cake used for moistening generally leads to an increase in the mixing time. Another measure that falls within the scope of the action according to the invention can also require an increase in this post-mixing time. In addition to moistening the material with filter cake _ expediently in a subsequent process step _ an additional amount of water is added to the mixed material without the simultaneous addition of suspended zeolite NaA.

The formation of the agglomerate is very easy to determine. When the agglomerate state is reached, the power consumption of the mixing device increases. In this way, the course of the agglomeration process can be followed on the basis of the power consumption of the mixer motors and the mixing process can thus be terminated at the right time.

The invention further relates to the granular, agglomerated, flowable, alkaline cleaning agents of the type described here, which contain sodium metasilicate and zeolite NaA as essential mixture components. Zeolite NaA is especially detergent grade material. Mixtures of the type according to the invention usually contain about 30 to 85 percent by weight sodium metasilicate and 5 to 50 percent by weight zeolite NaA. The rest of the mixture of substances consists of moisture and optionally additives, the substances described in connection with the manufacturing process being useful additives. The cleaning agents according to the invention preferably contain about 40-50 percent by weight sodium metasilicate to about 30-40 percent by weight zeolite NaA.

These mixtures of substances can be used directly as a cleaner or as a component for cleaning agents. If they are produced in its preferred embodiments by the process according to the invention, the agglomerates are stable on storage and do not clump together. The product is largely dust-free. No weathering occurs during storage and therefore no formation of fine particles. With regard to its dissolving and induction properties, the product meets the application requirements. The liter weights are between about 750 and 1200 g.

The flushing properties of the agglomerates are particularly dependent on the particle size distribution. In the preferred embodiment, the material is essentially free of portions <0.4 mm, the grain size distribution extending in particular in the range from about 0.4 to 2 mm. Agglomerates with a medium viscosity have good wash-in properties Particle diameter of about 0.9 to 1.3 mm (DIN 66 145) and a narrow grain spectrum (slope of the RRSB straight line n = 1 to 2.5 according to DIN 66 145). To the extent that certain proportions of coarse grains are obtained during the production of the agglomerates, these are separated off, crushed and mixed into the product. The dust-like or fine-grained fractions, which are also separated, are returned to the granulation process.

The mixed agglomerates according to the invention can be used as cleaners in machine cleaning with complete replacement of the previously used STP. Mixed agglomerates according to the invention are, however, also suitable in any ratio to the partial replacement of the tripolyphosphate with zeolite NaA. The following options are particularly suitable for such a partial replacement:

Mixing a mixed agglomerate according to the invention in any desired ratio with conventional STP-containing alkaline cleaning agent for machine cleaning or mixing mixed agglomerates according to the invention in any desired ratio with agglomerated STP / prehydrate. For example, STP / prehydrates with a water content of about 5 to 22% by weight are preferred, preferably those with a water content of 6 to 8% or 15 to 20% by weight.

It is possible, for example, to mix with conventional cleaners in the form of granules, which contain about 35% by weight of STP, about 45% by weight of anhydrous metasilicate, small amounts of soda, halogen carriers, optionally further minor mixture components and the rest water. The conventional cleaner components can make up, for example, up to 90% by weight, in particular up to 60% by weight, of the total mixture, but can also be present in only minor amounts.

However, the mixing of the mixing agglomerates described here with other, in particular granular cleaning components, as are known and / or desired in cleaning agent mixtures of the type concerned here, also falls within the scope of the invention.

Examples example 1

100 kg of water-free metasilicate and 50 kg of about 20% water-containing, spray-dried zeolite NaA were placed in a Lödige ploughshare mixer of the type FKM 600 D preheated with hot water and mixed until a mixture temperature of 51 ° C. was reached. Now, with the mixing tools running (ploughshare and chopper), 82 kg of a 45% zeolite NaA filter cake which had previously been stabilized with 0.1% Carbopol® and was stabilized with 0.1% Carbopol® were added within 45 seconds. After a further mixing time of 1.5 minutes, an agglomerate of the desired particle size was formed, whereupon the batch was discharged from the mixer. The moist product at 60 ° C. was aftertreated in a fluidized bed with air at 60 ° C. The agglomerate still had a residual water content of 16%. It weighed 980 g / l and was easy to store. It was washable in a Miele G 503 S household dishwasher (HGSM) within 30 minutes.

Example 2

In an unheated Lödige ploughshare mixer, type FM 130 D, 4.8 kg of a 45% zeolite-NaA filter cake stabilized with 0.1% Carbopol® were added in 30 seconds to 18 kg of water-free metasilicate while the mixing tools (ploughshare and chopper) were running. Agglomerate formation occurred after a post-mixing time of 1.25 minutes. The 37 ° C agglomerate was discharged from the mixer. It was easy to pour without further treatment. The liter weight was 1125 g, the wash-in time in a Miele HGSM type G 503 5 was 10 minutes.

Example 3

In an unheated Lödige ploughshare mixer of the type FM 130 D, 10 kg of a 45% zeolite-NaA filter cake stabilized with 0.1% Carbonol® were added in 30 seconds to 20 kg of anhydrous metasilicate silicate while the mixing tools (ploughshare and chopper) were running. After another 30 seconds of mixing, a coarse agglomerate was formed. First, 3 kg of spray-dried Sasil was mixed with this with an additional running chopper. This was followed by a further admixture of 0.5 kg of spray-dried zeolite NaA alone with the ploughshare of the mixer. A very compact, storage-stable agglomerate with a liter weight of 1090 g was obtained. The product was rinsed into a Miele HGSM type G 503 S in about 10 minutes.

Claims (17)

1. A process for the production of granular agglomerated and free-flowing alkaline detergents based on sodium silicate in intimate admixture with reinforcing builders, characterized in that finely divided sodium metasilicate is moistened with a free-flowing aqueous phase containing finely crystalline zeolite NaA in suspended form and the mixture is agglomerated with intensive mixing, after which the agglomerate is optionally subjected to drying in order at least to eliminate the surface moisture.

2. A process as claimed in claim 1, characterized in that the drying treatment carried out after agglomeration is carried out in a stream of air, for example in a fluidized bed, and/or by application of dry powder-form zeolite NaA.

3. A process as claimed in claims 1 and 2, characterized in that substantially anhydrous sodium metasilicate is processed together with a zeolite NaA suspension effectively stabilized against sedimentation of the solid particles.

4. A process as claimed in claims 1 to 3, characterized in that an unsieved finely divided sodium metasilicate crude product from production by the sintering process or from hydrothermal production and preferably a zeolite NaA of detergent quality are used.

5. A process as claimed in claims 1 to 4, characterized in that dry free-flowing zeolite NaA powder is additionally introduced first together with sodium metasilicate in the dry mixture and/or is used to powder the granular agglomerate after agglomeration.

6. A process as claimed in claims 1 to 5, characterized in that the mixing ratio of zeolite NaA to sodium metasilicate _ in parts by weight _ is in the range from 0.1: 10 to 8: 1, preferably in the range from 1: 3 to 2: 1 and more preferably of the order of 1: 1.3.

7. A process as claimed in claims 1 to 6, characterized in that a water-containing zeolite NaA filter cake having solids contents of 30 to 60% by weight and, more particularly, 40 to 55% by weight is used to moisten the material to be agglomerated.

8. A process as claimed in claims 1 to 7, characterized in that a filter cake which is either free from added surfactants or is stabilized with non-overly foaming components is used.

9. A process as claimed in claims 1 to 8, characterized in that agglomeration is carried out at temperatures of from about 30 to 75°C and preferably at temperatures of from about 45 to about 65°C.

10. A process as claimed in claims 1 to 9, characterized in that agglomeration is carried out in mixers comprising moving tools which, in particular, enable large amounts of energy to be introduced into the material to be agglomerated.

11. A process as claimed in claims 1 to 10, characterized in that agglomerates having apparent densitites of from about 750 to 1200 g/l and preferably from about 950 to 1200 g/l are produced.

12. A process as claimed in claims 1 to 11, characterized in that additional mixture components which have a stabilizing effect and/or promote the granular product structure are included in the agglomeration step.

13. Granular agglomerated and free-flowing alkaline detergents based on sodium metasilicate in intimate admixture with reinforcing builders, characterized in that they contain 30 to 85% by weight sodium metasilicate together with 5 to 50% by weight finely crystalline zeolite NaA of detergent quality and, for the rest, moisture and, optionally, additives which enhance the cleaning effect.

14. Detergents as claimed in claim 13, characterized in that they contain 40 to 50% by weight sodium metasilicate together with 30 to 40% by weight zeolite NaA.

15. Detergents as claimed in claims 13 and 14, characterized in that they are substantially dust-free (fines < 0.4 mm) and, in particular, have an average particle diameter of 0.9 to 1.3 mm (DIN 66 145) for a narrow particle size distribution (gradient of the RRSB line n  =  2 to 2.5 according to DIN 66 145).

16. Detergents as claimed in claims 13 to 15, characterized in that they have been produced by the process claimed in claims 1 to 12.

17. The use of the granular agglomerates claimed in claims 13 to 16 in machine detergents, more particularly dishwashing detergents, optionally in admixture with conventional detergents or detergent components.