Note: Descriptions are shown in the official language in which they were submitted.
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WO 9~1~t~.39~f PCTIEP95104242
A Process for the Production of Detergent Tablets by Microwave and
Hot Air Treatment
Field of the lnventian
This invention relates to a process for the production of detergent
tablets by microwave and hot air treatment.
Background of the Invention
The disadvantage of conventional detergenfi tablets which are
normally produced by compression molding ar fusion is that they do pat
dissolve sufficiently quickly on account of their carnpactness so that the
active substances are released too slowly. In addition, the rate at whic;.h
such tablets disintegrate is taa law.
International application publication No. W094/25563 describes
in detail the production of washing- and cleaning-active tablets using
microwaves which have an ~xtreme(y high dissolving ar disintegrating rate
coupled with high breaking strength. A crucial requirement for the
production of tablets from powder-form or granular raw materials using
microwaves is that the starting materials should be at least partly present
in hydrated form, "hydrated" meaning "hydrated under certain conditions in
regard to temperature, pressure ar relative atmospheric humidity to which
the raw material is exposed or with which the raw material is in equiEibrium".
4 The term "hydrated" is also defined in WOg4/25563. In genera(,
hydrated starting materials are thane which captain bound water of
crystallization or which are capable of binding externally added water at
least partly as water of crystallization or even those substances which da
pat form defined hydrates, but which are capable of binding water, far
2b example alkali metal hydroxides.
The expression "'microwaves" in the context of the present invention
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is understood to cover the entire frequency range from 3 to 300,000 MHz,
i.e. the frequency range which, in addition to the actual microwave range
above 300 MHz, also encompasses the radio wave range from 3 to 300
MHz. This technique can be used to produce so-called macrosolids which,
besides tablets, also include blocks for example. To this end, the com-
pounds are joined together at their points of contact with one another by
local microwave-induced melting/sintering. The voids present between the
individual components of the compounds before exposure to microwaves
provide the tablets formed with high porosity and thus contribute towards
improving the dissolving properties of the tablets.
To facilitate local sintering of the various components of the
compounds, at least some of the components must be capable of sintering
at their surface. To this end, the components of the compounds themselves
or their surfaces must contain sufficient water so that the components of the
compounds melt at their points of contact when the water is heated.
According to the teaching of International application publication No.
W094/25563, the mixture to be exposed to microwaves must be at
least partly present in hydrated form.
In the context of the present invention, therefore, the term "tablets"
is not confined to any particular three-dimensional form. In principle, the
tablets may assume any three-dimensional form, depending on the shape
which the powder-form or granular compounds are made to~assume.
The chemical composition of the generally powder-form or granular
compounds - and hence the tablets - can be varied over a very broad
range, cf. the disclosure of W094/25563.
It has now been found that tablets produced by the microwave
treatment of powder-form or granular compounds on the one hand lack the
breaking strength required for storage and transport if the microwave
treatment is too short and, on the other hand, undergo core carbonization
if the microwave treatment is too long. Hitherto, it has now always been
possible to solve this problem because, in many cases, adequate breaking
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strength inevitably involved carbonization within fhe tablet and the
avoidance of carbonization resulted in inadequate breaking strength.
Summary of the Invention
Accordingly, the problem addressed by the present invention was to
find a process in which the disadvantages mentioned above would not arise,
i.e. which would give tablets combining a high breaking strength with the
absence of any carbonization.
More particularly a perferred embodiment the invention relates to a
process of producing detergent tablets comprising exposing a detergent
composition to microwave radiation in the frequency range from 3 to
300,000 MHz while treating said detergent composition with hot air having
a temperature of 50°C to 300° C.
Detailed Description of the Invention
According to the present invention, the solution to this problem is
characterized in that, during its exposure to microwaves, the compound is
treated with hot air at a temperature of 50°C to 300°C,
preferably 100°C to
250°C and, more preferably, 150°C to 220°C.
In the context of the invention, the expression "compound" applies to
the powder-form andlor granular mixture of detergent ingredients. Suitable
detergent ingredients are, in principle, any of the substances which are
normally used for the production of solid cleaning formulations for textiles
and hard surfaces, cf. in particular the substances disclosed in
W094/25563.
Suitable builders are, for example, amorphous silicates, such as
metasilicates or waterglasses, phosphates, alkali metal carbonates, alkali
metal sulfates, zeolites and also organic components, such as water-
containing citrates, for example sodium citrate dihydrate, or water-containing
acetates, for example sodium acetate trihydrate. Suitable substitutes or
partial substitutes for phosphates and zeolites are crystalline layer-form
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sodium silicates with the general formula' NaMSiX02X+,~yHzO, where M is
sodium or hydrogen, x is a number of 1.9 to 4 and y is a number of 0 to 20,
preferred values for x being 2, 3 or 4. Corresponding crystalline layer
silicates are described, for example, in European patent application EP-A-0
164 514. Preferred crystalline layer silicates are those in which M is sodium
and x assumes the value 2 or 3. Both a- and y sodium disilicates
Na2Si205~yHz0 are particularly preferred.
Useful , organic builders are, for example, the polycarboxylic acids
preferably used in the form of their sodium salts, such as citric acid, adipic
acid, succinic acid, glutaric acid, tartaric acid, sugar acids,
aminocarboxylic
acids, nitrilotriacetic acid (NTA), providing its use is not objectionable on
ecological grounds, and mixtures thereof. Preferred salts are the salts of
the polycarboxylic acids, such as citric acid, adipic acid, succinic acid,
glutaric acid, tartaric acid, sugar acids and mixtures thereof.
Suitable polymeric polycarboxylates are, for example, the sodium
salts of polyacrylic acid or polymethacrylic acid,_for example those having
a relative molecular weight of 800 to 150,000 (based on acid). Suitable
copolymeric polycarboxylates are, in particular, those of acrylic acid with
methacrylic acid and those of acrylic acid or methacrylic acid with malefic
acid. Copolymers of acrylic acid with malefic acid containing 50 to 90% by
weight of acrylic acid and 50 to 10% by weight of malefic acid have proved
to be particularly suitable. ~Their relative molecular weight, based on free
acids, is generally in the range from 5,000 to 200,000, preferably in the
range from 10,000 to 120,000 and more preferably in the range from 50,000
to 100,000. Biodegradable terpolymers are also particularly preferred, for
example those, containing salts of acrylic acid and malefic acid and also
vinyl
alcohol or vinyl alcohol derivatives as monomers (DE 4300772) or those
containing salts of acrylic acid and 2-alkyl allyl sulfonic acid and also
sugar
derivatives as monomers (DE 42 21 381 ).
Ofher suitable builder systems are oxidation products of carboxy-
functional polyglucosans and/or water-soluble salts thereof which are
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described, for example, in International patent application WO-A-93108251
or of which the production is described, for example, in International patent
application WO-A-93116110.
Other preferred builders are the known polyaspartic acids and salts
and derivatives thereof.
Other suitable builders are polyacetals which may be obtained by
reaction of dialdehydes with polyolcarboxylic acids containing 5 to 7 carbon
atoms and at least three hydroxyl groups, for example as described in
European patent application EP-A-0 280 223. Preferred polyacetals are
obtained from dialdehydes, such as glyoxal, glutaraldehyde, terephthalalde-
hyde and mixtures thereof, and from polyolcarboxylic acids, such as
gluconic acid andlor glucoheptonic acid.
The inorganic and/or organic builders are used in the tablets in
quantities of preferably about 10 to 60% by weight and, more preferably, 15
to 50% by weight.
Solid acids, for example amidosulfonic acid or phosphonic acids, are
used for the production of acidic detergent tablets.
In addition, the tablets generally contain anionic, cationic, amphoteric
or zwitterionic surfactants, but above all the nonionic surfactants disclosed
in W094/25563. Nonionic surfactants, such as fatty alcohol ethoxylates
for example, are preferred. In addition, the tablets may optionally contain
oxygen- or chlorine-based bleaching agents, disinfectants, for example
quaternary ammonium compounds, foam inhibitors, enzymes, fillers, etc.
The microwave. treatment normally lasts 15 seconds to 90 minutes,
preferably 1 minute to 30 minutes and, more preferably, 1 minute to 5
minutes.
In another embodiment of the invention, the tablets are treated with
hot air after the microwave treatment. In principle, there are no limits to
the
time interval between the microwave treatment and the hot air treatment
although the intervening period is normally at most 24 hours, preferably at
most 60 minutes and, more preferably, at most 2 minutes. In principle, the
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hot air treatment may last for as long as the tablet is capable of withstand-
ing the treatment without damage. For economic reasons, the duration of
the hot air treatment is up to 30 minutes, preferably up to 10 minutes and,
more preferably, up to 3 minutes,.
In a particularly preferred embodiment of the process according to
the invention, the treatment with hot air is carried out both during and after
the microwave treatment. In this case, too, the time interval between the
microwave treatment and the following hot air treatment is normally at most
24 hours, preferably at most 60 minutes and, more preferably, at most 2
minutes. The duration of the hot air treatment is also normally in the range
mentioned above.
The hot air is generally produced by a conventional hot air blower
with a controllable air temperature. .
The microwave treatment may be carried out, for example, in the
microwave oven described in ' W094/25563. The products thus
microwaved may then be subjected fo a hot air treatment. The microwave
treatment and the hot air treatment may also be carried out simultaneously
in the oven. Accordingly, the microwave treatment and/or hot air treatment
may be carried out in batches in a single unit, for example an oven, as
described above.
The microwave treatment (accompanied or followed by the hot air
treatment or accompanied and followed by the hot air treatment) may be
carried out continuously. To this end, the compounds to be microwaved are
transported on a conveyor belt through a microwave radiation zone. In
addition, hot air is blown either directly into the radiation zone or into a
zone .
immediately adjoining the radiation zone or both into the radiation zone and
into the adjoining zone.
Examples
s0 60 g of powder-form compounds (corresponding to formulations 1
and 2 below). were brought into the required shape by manual
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precompaction or by precompaction in a pneumatic press under a pressure
of 1 to 400 N/cm2 and were then optionally removed from the container.
"Manual precompaction" means that the compound introduced into a
container open on top is manually compressed from above with a stamp.
The pressure applied for manual precompression is of the order of 1 to 20
N/cmz. Where a pneumatic press is used, the pressure applied is of the
order of 200 to 400 N/cm2. [The manually precompressed compounds were
generally more soluble after microwaving and hot air treatment in accord-
ance with the invention.] The precompactates were then placed on a
conveyor belt and transported through a microwave radiation zone in which
they were not subjected to any treatment with hot air.
Working conditions:
Conveyor speed : 47 cm per minute
Length of the microwave
radiation zone : 210 cm
Microwave source : 18 microwave emitters each with an output of
1200 watts, wavelength 2450 - 2470 MHZ
Distance of microwave
source from conveyor belt : 9 emitters at 11 cm
9 emitters at 4 cm
These conditions are defined as "standard conditions".
Formulation 1: amidosulfonic acid 96% by weight
octane phosphonic acid 1 % by weight
C,Z_,8 fatty alcohol ethoxylate 1 % by weight
Na2S04 1 % by weight
HZO 1 % by weight
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Formulation 2: pentasodium triphosphate 40% by weight
sodium metasilicate 40% by weight
sodium metasilicate pentahydrate 10% by weight
sodium carbonate decahydrate 5% by weight
dimethyl dioctyl ammonium chloride 3% by weight
C,2_,8 fatty alcohol ethoxylate 2% by weight
To increase the output of the assembly line, both the speed of the
conveyor belt and the microwave power were doubled in relation to the
standard conditions. Unfortunately, the tablets thus obtained had unsatis-
factory breaking strength. However, a reduction in the conveyor speed
resulted in carbonization within the tablets.
When the non-breakage-resistant tablets produced at twice the
conveyor speed and twice the microwave power were treated with hot air
(200°C) for 2 minutes 45 seconds after microwaving, breakage-resistant
tablets with no sign of carbonization were obtained.
When the conveyor speed and the microwave power were again
doubled, the duration of the hot air treatment had to be increased to 7
minutes 20 seconds to obtain breakage-resistant tablets.
