[0001] This invention relates to a method for the preparation of cleaning compositions in
the form of tablets for example, for use in fabric washing or machine dishwashing.
[0002] Detergent compositions in tablet form have advantages over powdered products in that
they do not require measuring and are thus easier to handle and dispense into the
washload.
[0003] Tablets of a cleaning composition are generally made by compressing or compacting
a quantity of the composition in particulate form.
[0004] Tablets comprising two or more separate regions have also been described. For example
WO 01/42416 describes the production of multi-phase moulded bodies comprising a combination of
core moulded bodies and a particulate premix.
WO 00/61717 describes a detergent tablet which is characterised in that at least part of its
outer surface is smooth.
WO 00/04129 describes a multi-phase detergent tablet comprising a first phase in the form of
a shaped body having at least one mould therein and a second phase in the form of
a particulate solid compressed within said mould.
[0005] It is an object of the present invention to provide a method to produce cleaning
tablets comprising a smooth phase, wherein the tablets can be produced at high speed
at a relatively low cost.
[0006] A further objective of the present invention is to provide a method to produce a
smooth tablet or phase thereof wherein the choice of materials and the manufacturing
method allows the low cost production of tablets of good performance and of good consistency
and texture.
[0007] The present invention relates to a method for the preparation of a cleaning tablet
which has a plurality of discrete regions with differing compositions, characterised
in that at least one first region of the tablet is a smooth region and at least one
second region of the tablet which preferably is a solid region of compacted particulate
material.
[0008] One method of producing smooth phases which can be used in cleaning tablets is first
to produce a large quantity e.g. an extruded strand or a log of the material, followed
by partitioning this quantity into smaller quantities for example by cutting.
[0009] Another method of producing smooth phases may be manufacture pieces of smooth material
for example by shaping or by a so-called casting process, whereby a fluid material
is introduced into a mould, the material hardens or solidifies in said mould followed
by removal of the smooth phases from the mould.
[0010] A problem with the use of seperately prepared smooth phases is that these require
an assembly process to prepare the multi-phase tablet. Such an assembly process often
is complicated and may lead to undesirable cost increases.
[0011] WO 00/52127 (Henkel) describes a method of preparing multi-phase moulded detergent articles by compressing
a particulate premix, applying one or more adhesive agents and then applying further
active substances in solid, high-viscous or plastic form.
[0012] WO 01/60965 (P&G) describes a process of making a multi-phase detergent tablet comprising the contacting
of a first and second phase below the melting temperature of an adhesive present in
the second phase, followed by adhering the two phases by subjecting the mixture to
a temperature above the melting temperature of said adhesive.
[0013] In a first aspect the present invention relates to a method for the preparation of
a multi-phase cleaning tablet comprising a first smooth phase having a weight of from
3 to 10 grammes and comprising a meltable material and a second phase having a weight
of from 15 to 40 grammes, said method comprising the steps of
- A) pre-preparing a smooth phase comprising an extrusion step;
- B) treating the outer surface of said smooth phase such that at least part of the
outer surface thereof melts;
- C) bringing said melted part of said smooth phase into contact with the outer surface
of the second phase such that the melted surface part of the smooth phase is used
as a contact surface; and
- D) pressing the two phases together to ensure adequate adhesion of the smooth phase
to the second phase.
[0014] In the method of the invention, said melted part of the smooth phase is preferably
used as the contact surface.
[0015] Surprisingly it has been found that the (partial) melting of the outer surface of
the smooth phase followed by adhesion of the smooth phase to a second phase of the
tablet, provides a cost effective, convenient method to ensure a good quality assembly
of the multi-phase tablet. Especially the method can be carried out at a high throughput
rate without the need for separate adhesives applied between the two phases and without
the need of fully heating the tablet or the entire smooth phase.
[0016] Preferably, multi-phase tablets used in the invention and each of the separate phases
thereof are of cylindrical shape wherein the two main surfaces (upper side and bottom
side) are substantially flat. Preferably the smooth phases (and other phases of the
multi-phase tablet) are flat slices of cleaning material, for example having a diameter
of from 1 to 10 cm (preferably 2 to 6 cm) and a height of from 0.1 to 5 cm (preferably
0.3 to 1.5 cm).
[0017] A preferred embodiment of the invention relates to a multiphase tablet obtained according
to the above defined process, wherein at least one smooth phase is present and additionally
one or more other phases are present. Suitably, these additional phases can be smooth
or solid. Particularly suitable additional phases are solid phases composed of compacted
particulate solids.
[0018] The regions of a multi-phase tablet are preferably separate layers within a tablet.
However, a discrete region of a tablet could also have other forms for example one
or more core(s) or insert(s). In a preferred embodiment, the first region is a smooth
layer and the second region is a layer of compacted particulate material. In a further
advantageous embodiment, the first region is a core or insert of smooth material embedded
in the second region which is a layer of compacted particulate material.
[0019] The multi-phase tablet used in the invention comprises the smooth phase being present
as a distinctive region having a weight of from 3 to 10 grammes. Preferably, the other
phases of the tablet together have a weight of 15 to 40 grammes.
[0020] For the purpose of this invention the term smooth phase refers to compositions which
are on the one hand solid enough to retain their shape at ambient temperature and
on the other hand smooth in appearance. Smooth textures are generally of low or no
porosity and have -at normal viewing distance- the appearance of a continuous phase
for example as opposed to porous and particulate appearance of a compacted particulate
material.
[0021] Smooth phases for use in an assembly process in accordance to the invention are pre-prepared,
said pre-preparation comprising an extrusion step. For example our non-pre-published
case
EP 0277267 discloses the preparation of compressed shaped smooth phase, our non-pre-published
case
EP0278247 discloses the preparation of smooth phases by extrusion and our non pre-published
case
EP 0279186 discloses suitable methods for the cutting of smooth phases.
[0022] Sometimes it is preferable that the smooth phase is transparent or translucent. Preferably,
this means that the composition has an optical transmissivity of at least 10%, most
preferably 20%, still more preferably 30%, through a path length of 0.5 cm at 25°
C. These measurements may be obtained using a Perkin Elmer UV/VIS Spectrometer Lambda
12 or a Brinkman PC801 Colorimeter at a wavelength of 520nm, using water as the 100%
standard.
[0023] The transparency or translucency of the compositions according to the invention does
not preclude the composition being coloured, e.g. by addition of a dye, provided that
it does not detract substantially from clarity. Examples of suitable smooth phases
are given in our non-prepublished
application EP 0256833.
[0024] In an advantageous embodiment of the invention the smooth phase comprises from 10-90
wt% of non-soap surfactants (based on the total weight of said smooth phase), more
preferred from 25 to 75 wt%, most preferred 30 to 70 wt%. It has been found that the
combination of a separate smooth first region and these high surfactant levels provide
very good dispersing and cleaning properties to the tablet.
[0025] Preferably the non-soap surfactants in the first region comprise a combination of
anionic surfactants and non-ionic surfactants in a weight ratio of from 5 : 1 to 1
: 5, more preferred 3 : 1 to 1 : 3, more preferred 2 : 1 to 1: 2. Further surfactants,
for example cationic surfactants may equally be present for example at a level of
0.1 to 10 wt% based on the weight of the smooth part.
[0026] The smooth region will also comprise a meltable material. Preferably the smooth region
is formulated such that is becomes fluid at elevated temperatures, for example somewhere
between 30 and 100°C, more preferably between 35-90°C most preferably 40-60°C. The
presence of anionic and/or nonionic surfactants as meltable materials in the smooth
phase is especially useful.
[0027] Other suitable meltable materials are for example diluent materials.
[0028] In addition to the non-soap surfactants the smooth region may comprise additional
solid materials such as mineral salts, sugar or structuring soaps for example at a
level of 2 to 90 wt% based on the weight of the smooth part, more preferred from 3
to 70 wt%, most preferred 5 to 40 wt%. Examples of suitable salts are for example
soluble salts such as acetate, citrate, urea. The use of these materials can advantageously
lead to improved structuring and/or improved dissolution properties of the smooth
phase.
[0029] The smooth region of the tablet may also contain diluent materials for example polyethyleneglycol,
dipropyleneglycol, isopropanol or (mono-)propyleneglycol. Preferable the level of
these diluents is from 0 to 40 wt%, more preferred 1 to 20, most preferred from 4
to 15 wt% based on the weight of the smooth phase.
[0030] The smooth phase preferably comprises no or only low levels of water. Preferably
the level of water is less than 20 wt % based on the weight of the smooth phase, more
preferred less than 15 wt%, most preferred from 5 to 12 wt%. Most preferably the smooth
phases are substantially free from water, which means that apart from low levels of
moisture (e.g. for neutralisation or as crystal water) no additional added water is
present.
[0031] Preferably the total weight of surfactants in the smooth phase is from 2 to 20 grammes,
more preferred from 3 to 10 grammes.
[0032] Preferably the smooth phase comprises no or only low levels of ingredients such as
builders, bleach activators and bleach materials. Preferably the level of these ingredients
in the smooth phase is less than 5 wt%.
[0033] In a preferred embodiment of the invention, the tablet may be a multi-phase tablet
wherein the phases other than the smooth phase as described above comprise no or only
low levels of surfactants. Preferably the level of surfactants in the other phases
is less than 10 wt%(based on the total weight of said phases), more preferred from
0 to 9 wt%, most preferred from 1 to 8 wt%.
[0034] In an advantageous embodiment of the invention the cleaning tablets comprise a first
smooth region (as described above) in combination with a second region of the tablet
which is a solid region, for example prepared by compression of a particulate composition.
[0035] Although the second region may comprise surfactant materials, this region preferably
comprises ingredients of the tablet other than surfactants. Examples of these ingredients
are for example builders, bleach system, enzymes etc. Preferably the builders in the
tablet are predominantly present in the second region. Preferably the bleach system
is predominantly present in the second region. Preferably the enzymes are predominantly
present in the second region. For the purpose of this invention, unless stated otherwise,
the term "predominantly present" refers to a situation wherein at least 90 wt% of
an ingredient is present in the second region, more preferred more than 98 wt%, most
preferred substantially 100 wt%.
[0036] The above description of the tablet has been given with reference to a tablet constituted
by two regions. It will however be understood that each of the regions may be composed
of a limited number of discrete regions. For example the first smooth region may be
a single discrete part of the tablet but may also be a limited number (say 1-5) discrete
smooth parts. Preferably each of these smooth parts are at least 1 gramme, also preferably
each of these smooth parts is substantially of the same composition. If reference
is made to the composition or weight of the first region it is understood that this
concerns the total weight and composition of these smooth parts.
[0037] Similarly the second region may be composed of a limited number (say 1-5) of parts
e.g. separate layers in the tablet. Preferably each of these parts has a weight of
at least 10 grammes, also preferably each of the solid parts is substantially of the
same composition. If reference is made to the composition or weight of the second
region it is understood that this concerns the total weight and composition of these
solid parts.
[0038] In addition to the smooth first region and the solid second region the cleaning tablets
of the invention may optionally comprise further regions, for example the tablet may
be partly or wholly coated.
[0039] Cleaning tablets used in the invention are preferably manufactured by firstly preparing
a smooth part. Advantageously the preparation of the smooth phase may include the
heating of the cleaning material followed by cooling. Advantageously the preparation
of the cleaning material may involve extrusion.
[0040] Extrusion processes for washing articles are known, for example
WO 01/02532 describes the extrusion of washing articles with a pressure of less than 10 bar.
[0041] Preferably extrusion processes will involve the forming of an extrudable mass which
is then subsequently extruded from an extrusion device and optionally then partitioned
into parts of the desired size and weight. Optionally the smooth parts may then be
hardened.
[0042] The extrudable mass preferably has before extrusion an initial elevated temperature
for example from 60 to 120 C, more preferred from 70 to 90 C. Preferably the extrudable
mass is during the production of the smooth mass cooled e.g. to a final temperature
of 20 C and then extruded. If extrusion is used this low temperature may for example
be the temperature at the extrusion die for example from 10 to 40, preferably from
15 to 25, most preferred at ambient temperature (20 C).
[0043] In a preferred embodiment of the invention the second phase is pre-compressed at
a force of 0.1 to 20 kN/cm
2 prior to attachment of the (partially melted) first phase thereto. In another preferred
embodiment the particulate composition is flattened prior to attachment of first phase
thereto.
[0044] Optionally the attachment of the first phase to the second phase may involve the
(co-)compression of the combination of the first and the second region(s) for example
at a force of from 0.05 to 20 kN/cm
2. Especially if the second region has been pre-compressed the co-compression in step
(c) can advantageously be at a force of 0.1- 10 kN/cm
2, more preferred 0.5 to 5 kN/cm
2. If the second region has not been pre-compressed, the co-compression preferably
takes place at a force of 1- 100 kN/cm
2, more preferred 2-50 kN/cm
2., most preferred 2-10 kN/cm
2.
[0045] A tablet used in the invention may be intended for use in machine dishwashing. Such
a tablet is likely to contain surfactant in a low concentration such as 0.5 to 2 wt%
based on the whole tablet, although higher concentrations ranging up to 10 wt% may
be used. Such will typically contain salts, such as over 60 wt%, often over 85 wt%
of the tablet.
[0046] Water-soluble salts typically used in machine dishwashing compositions are phosphates
(including condensed phosphates) carbonates and silicates, generally as alkali metal
salts. Water soluble alkali metal salts selected from phosphates, carbonates and silicates
may provide 60 wt% or more of a dishwashing composition.
[0047] Another preferred possibility is that a tablet used in the invention will be intended
for fabric washing. In this event the tablet will be likely to contain at least 2
wt%, probably at least 5 wt%, up to 40 or 50 wt% non-soap surfactant based on the
whole tablet, and from 5 to 80 wt% detergency builder, based on the whole tablet.
[0048] Materials that may be used in tablets used in the invention will now be discussed
in more detail.
Surfactant Compounds
[0049] Compositions which are used in tablets used in the invention will contain one or
more detergent surfactants. In a fabric washing composition, these preferably provide
from 5 to 50% by weight of the overall tablet composition, more preferably from 8
or 9% by weight of the overall composition up to 40% or 50% by weight. Surfactant
may be anionic (soap or non-soap), cationic, zwitterionic, amphoteric, nonionic or
a combination of these.
[0050] Anionic surfactant may be present in an amount from 0.5 to 50% by weight, preferably
from 2% or 4% up to 30% or 40% by weight of the tablet composition.
[0051] Synthetic (i.e. non-soap) anionic surfactants are well known to those skilled in
the art. Examples include alkylbenzene sulphonates, particularly sodium linear alkylbenzene
sulphonates having an alkyl chain length of C
8-C
15; olefin sulphonates; alkane sulphonates; dialkyl sulphosuccinates; and fatty acid
ester sulphonates.
[0052] Primary alkyl sulphate having the formula
ROSO
3- M
+
in which R is an alkyl or alkenyl chain of 8 to 18 carbon atoms especially 10 to 14
carbon atoms and M
+ is a solubilising cation, is commercially significant as an anionic surfactant.
Linear alkyl benzene sulphonate of the formula
where R is linear alkyl of 8 to 15 carbon atoms and M
+ is a solubilising cation, especially sodium, is also a commercially significant anionic
surfactant.
[0053] Frequently, such linear alkyl benzene sulphonate or primary alkyl sulphate of the
formula above, or a mixture thereof will be the desired anionic surfactant and may
provide 75 to 100 wt% of any anionic non-soap surfactant in the composition.
[0054] In some forms of this invention the amount of non-soap anionic surfactant lies in
a range from 5 to 20 wt% of the tablet composition.
[0055] Soaps for use in accordance to the invention are preferably sodium soaps derived
from naturally occurring fatty acids, for example, the fatty acids from beef tallow.
[0056] Suitable nonionic surfactant compounds which may be used include in particular the
reaction products of compounds having a hydrophobic group and a reactive hydrogen
atom, for example, aliphatic alcohols, acids, amides or alkyl phenols with alkylene
oxides, especially ethylene oxide.
[0057] Specific nonionic surfactant compounds are alkyl (C
8-22) phenol-ethylene oxide condensates, the condensation products of linear or branched
aliphatic C
8-20 primary or secondary alcohols with ethylene oxide, and products made by condensation
of ethylene oxide with the reaction products of propylene oxide and ethylene-diamine.
[0058] Especially preferred are the primary and secondary alcohol ethoxylates, especially
the C
9-11 and C
12-15 primary and secondary alcohols ethoxylated with an average of from 5 to 20 moles
of ethylene oxide per mole of alcohol.
[0059] In some fabric washing tablets of this invention, the amount of nonionic surfactant
lies in a range from 4 to 40%, better 4 or 5 to 30% by weight of the whole tablet.
[0060] Many nonionic surfactants are liquids. These may be absorbed onto particles of the
composition.
[0061] In a machine dishwashing tablet the surfactant may be wholly nonionic, in an amount
below 5 wt% of the whole tablet although it is known to include some anionic surfactant
and to use up to 10 wt% surfactant in total.
Detergency Builder
[0062] A composition which is used in tablets used in the invention will usually contain
from 5 to 80%, more usually 15 to 60% by weight of detergency builder. This may be
provided wholly by water soluble materials, or may be provided in large part or even
entirely by water-insoluble material with water-softening properties. Water-insoluble
detergency builder may be present as 5 to 80 wt%, better 5 to 60 wt% of the composition.
[0063] Alkali metal aluminosilicates are strongly favoured as environmentally acceptable
water-insoluble builders for fabric washing. Alkali metal (preferably sodium) aluminosilicates
may be either crystalline or amorphous or mixtures thereof, having the general formula:
0.8 - 1.5 Na
2O. Al
2O
3 . 0.8 - 6 SiO
2. xH
2O
[0064] These materials contain some bound water (indicated as "xH2O") and are required to
have a calcium ion exchange capacity of at least 50 mg CaO/g. The preferred sodium
aluminosilicates contain 1.5-3.5 SiO
2 units (in the formula above). Both the amorphous and the crystalline materials can
be prepared readily by reaction between sodium silicate and sodium aluminate, as amply
described in the literature.
[0065] Suitable crystalline sodium aluminosilicate ion-exchange detergency builders are
described, for example, in
GB 1429143 (Procter & Gamble). The preferred sodium aluminosilicates of this type are the well known commercially
available zeolites A and X, the novel zeolite P described and claimed in
EP 384070 (Unilever) and mixtures thereof.
[0066] Conceivably a water-insoluble detergency builder could be a layered sodium silicate
as described in
US 4664839.
NaSKS-6 is the trademark for a crystalline layered silicate marketed by Hoechst (commonly
abbreviated as "SKS-6"). NaSKS-6 has the delta-Na
2SiO
5 morphology form of layered silicate. It can be prepared by methods such as described
in
DE-A-3,417,649 and
DE-A-3,742,043. Other such layered silicates, such as those having the general formula NaMSi
xO
2x+1·yH
2O wherein M is sodium or hydrogen, x is a number from 1.9 to 4, preferably 2, and
y is a number from 0 to 20, preferably 0 can be used.
[0067] Water-soluble phosphorous-containing inorganic detergency builders, include the alkali-metal
orthophosphates, metaphosphates, pyrophosphates and polyphosphates. Specific examples
of inorganic phosphate builders include sodium and potassium tripolyphosphates, orthophosphates
and hexametaphosphates.
[0068] Non-phosphorous water-soluble builders may be organic or inorganic. Inorganic builders
that may be present include alkali metal (generally sodium) carbonate; while organic
builders include polycarboxylate polymers, such as polyacrylates, acrylic/maleic copolymers,
and acrylic phosphonates, monomeric polycarboxylates such as citrates, gluconates,
oxydisuccinates, glycerol mono- di- and trisuccinates, carboxymethyloxysuccinates,
carboxymethyloxymalonates, dipicolinates and hydroxyethyliminodiacetates.
[0069] At least one region (preferably the second region) of a fabric washing tablet preferably
include polycarboxylate polymers, more especially polyacrylates and acrylic/maleic
copolymers which can function as builders and also inhibit unwanted deposition onto
fabric from the wash liquor.
Bleach System
[0070] Tablets used in to the invention may contain a bleach system in at least one region
of a tablet, preferably in the second region. This preferably comprises one or more
peroxy bleach compounds, for example, inorganic persalts or organic peroxyacids, which
may be employed in conjunction with activators to improve bleaching action at low
wash temperatures. If any peroxygen compound is present, the amount is likely to lie
in a range from 10 to 25% by weight of the composition.
[0071] Preferred inorganic persalts are sodium perborate monohydrate and tetrahydrate, and
sodium percarbonate, advantageously employed together with an activator. Bleach activators,
also referred to as bleach precursors, have been widely disclosed in the art. Preferred
examples include peracetic acid precursors, for example, tetraacetylethylene diamine
(TAED), now in widespread commercial use in conjunction with sodium perborate; and
perbenzoic acid precursors. The quaternary ammonium and phosphonium bleach activators
disclosed in
US 4751015 and
US 4818426 (Lever Brothers Company) are also of interest. Another type of bleach activator which may be used, but which
is not a bleach precursor, is a transition metal catalyst as disclosed in
EP-A-458397,
EP-A-458398 and
EP-A-549272. A bleach system may also include a bleach stabiliser (heavy metal sequestrant) such
as ethylenediamine tetramethylene phosphonate and diethylenetriamine pentamethylene
phosphonate.
[0072] As indicated above, if a bleach is present and is a water-soluble inorganic peroxygen
bleach, the amount may well be from 10% to 25% by weight of the composition.
Other Detergent Ingredients
[0073] The detergent tablets used in the invention may also contain (preferably in the second
region) one of the detergency enzymes well known in the art for their ability to degrade
and aid in the removal of various soils and stains. Suitable enzymes include the various
proteases, cellulases, lipases, amylases, and mixtures thereof, which are designed
to remove a variety of soils and stains from fabrics. Examples of suitable proteases
are Maxatase (Trade Mark), as supplied by Gist-Brocades N.V., Delft, Holland, and
Alcalase (Trade Mark), and Savinase (Trade Mark), as supplied by Novo Industri A/S,
Copenhagen, Denmark. Detergency enzymes are commonly employed in the form of granules
or marumes, optionally with a protective coating, in amount of from about 0.1% to
about 3.0% by weight of the composition; and these granules or marumes present no
problems with respect to compaction to form a tablet.
[0074] The detergent tablets used in the invention may also contain (preferably in the second
region) a fluorescer (optical brightener), for example, Tinopal (Trade Mark) DMS or
Tinopal CBS available from Ciba-Geigy AG, Basel, Switzerland. Tinopal DMS is disodium
4,4'bis-(2-morpholino-4-anilino-s-triazin-6-ylamino) stilbene disulphonate; and Tinopal
CBS is disodium 2,2'-bis-(phenyl-styryl) disulphonate.
[0075] An antifoam material is advantageously included (preferably in the second region),
especially if a detergent tablet is primarily intended for use in front-loading drum-type
automatic washing machines. Suitable antifoam materials are usually in granular form,
such as those described in
EP 266863A (Unilever). Such antifoam granules typically comprise a mixture of silicone oil, petroleum
jelly, hydrophobic silica and alkyl phosphate as antifoam active material, absorbed
onto a porous absorbed water-soluble carbonate-based inorganic carrier material. Antifoam
granules may be present in an amount up to 5% by weight of the composition.
[0076] It may also be desirable that a detergent tablet used in the invention includes an
amount of an alkali metal silicate, particularly sodium ortho-, meta- or disilicate.
The presence of such alkali metal silicates at levels, for example, of 0.1 to 10 wt%,
may be advantageous in providing protection against the corrosion of metal parts in
washing machines, besides providing some measure of building and giving processing
benefits in manufacture of the particulate material which is compacted into tablets.
[0077] A tablet for fabric washing will generally not contain more than 15 wt% silicate.
A tablet for machine dishwashing will often contain more than 20 wt% silicate. Preferably
the silicate is present in the second region of the tablet.
[0078] Further ingredients which can optionally be employed in a region of a fabric washing
detergent of the invention tablet (preferably the second region) include anti-redeposition
agents such as sodium carboxymethylcellulose, straight-chain polyvinyl pyrrolidone
and the cellulose ethers such as methyl cellulose and ethyl hydroxyethyl cellulose,
fabric-softening agents; heavy metal sequestrants such as EDTA; perfumes; and colorants
or coloured speckles.
[0079] Further ingredients which can optionally be used in tablets used in the invention,
preferably in the second region are dispersing aids. Examples of suitable dispersing
aids are water-swellable polymers (e.g. SCMC) highly soluble materials (e.g. sodium
citrate, potassium carbonate or sodium acetate) or sodium tripolyphospate with preferably
at least 40% of the anhydrous phase I form.
Particle Size and Distribution
[0080] The second region of a detergent tablet used in the invention, is a preferably a
matrix of compacted particles.
[0081] Preferably the particulate composition has an average particle size in the range
from 200 to 2000 µm, more preferably from 250 to 1400 µm. Fine particles, smaller
than 180 µm or 200 µm may be eliminated by sieving before tableting, if desired, although
we have observed that this is not always essential.
[0082] While the starting particulate composition may in principle have any bulk density,
the present invention is especially relevant to tablets made by compacting powders
of relatively high bulk density, because of their greater tendency to exhibit disintegration
and dispersion problems. Such tablets have the advantage that, as compared with a
tablet derived from a low bulk density powder, a given dose of composition can be
presented as a smaller tablet.
[0083] Thus the starting particulate composition may suitably have a bulk density of at
least 400 g/litre, preferably at least 500 g/litre, and perhaps at least 600 g/litre.
[0084] Tableting machinery able to carry out the manufacture of tablets of the invention
is known, for example suitable tablet presses are available from Fette and from Korch.
[0085] Tableting may be carried out at ambient temperature or at a temperature above ambient
which may allow adequate strength to be achieved with less applied pressure during
compaction. In order to carry out the tableting at a temperature which is above ambient,
the particulate composition is preferably supplied to the tableting machinery at an
elevated temperature. This will of course supply heat to the tableting machinery,
but the machinery may be heated in some other way also.
[0086] The size of a tablet will suitably range from 10 to 160 grams, preferably from 15
to 60 g, depending on the conditions of intended use, and whether it represents a
dose for an average load in a fabric washing or dishwashing machine or a fractional
part of such a dose. The tablets may be of any shape. However, for ease of packaging
they are preferably blocks of substantially uniform cross-section, such as cylinders
or cuboids. The overall density of a tablet preferably lies in a range from 1040 or
1050gm/litre up to 1600gm/litre.
Example 1
[0087] 1.6 kg of anionic surfactant (Dobanic acid 103 ex Shell) and 1.5 kg of nonionic surfactant
(Lutensol AO7 ex BASF) were mixed and neutralised to a pH of 9 using a 50% NaOH solution.
[0088] 0.9 kg of C16/C18 soap fatty acid was added, 0.5 kg dipropylene glycol (ex Vopak)
a,d 0.6 kg Of Tween 40 (ex Uniqema) was also added to the mixture. The mixture was
further neutralised with a 50% NaOH solution to a pH of 11.
[0089] After neutralisation to pH of 11, the mixture was pumped into a sequence of 2 stainless
steel tubes by a Maag Sinox P7 pump or a piston pump, type SIBa
HK 05016SST4000M000 ex Prominent, Vleuten (NL). Both tubes were double jacketed. The first
tube was 2.5m long and had an inner diameter of 73mm. The second tube was 1.5m long
and had an inner diameter of 45mm. The tubes were connected by a 10cm long pipe.
[0090] The mixture was pumped into the tubes at a temperature of 85°C at a throughput of
4 kg/hr. The first tube was cooled using a water bath at 40°C. The second tube was
cooled using a 50:50 weight mixture of ethylene glycol and water. The coolant temperature
was -15°C. The material coming out of the second tube had a temperature of abour 20
C and was collected and divided into bars of around 0.5m.
[0091] After storage the bars can for example be cut into slices of 4.9 grammes each.
Example II: multi-phase tablets
[0092] A detergent powder was made of the following composition by pregranulating the granule
ingredients, followed by post-dosing the rest of the ingredients
Ingredient |
Parts by weight |
Granules |
|
Na-las |
1.1 |
Nonionic 7EO |
0.5 |
C12 soap |
0.1 |
NaAc.3aq |
0.3 |
Zeolite A24 |
2.4 |
Light soda ash |
0.4 |
Moisture/minors |
0.4 |
Post-dose |
|
EAG (17% silicone) |
0.8 |
Fluorescer (15%) |
0.6 |
STP |
8.4 |
Na-disilicate (80%) |
1.0 |
TAED (83%) |
1.1 |
Percarbonate |
4.4 |
Dequest 2047 |
0.5 |
Minors/ enzymes/colour |
to 23 |
Smooth parts of 4.9 grammes were prepared as in example 1
[0093] The tablets were made as follows:
[0094] 23 grammes of the powder are inserted into a 45 mm die of a tabletting machine, followed
by a compression step at 80 kN. A smooth part as described above was partially melted
by applying heat to the bottom of the slice of smooth material. The heat was applied
such that the bottom of the smooth phase melted, while the rest of the smooth phase
did not melt. The partially melted smooth part was then placed on top of the pre-compressed
phase whereby the melted surface part was used as the contact surface. The two phase
were gently pressed together to ensure adequate adhesion of the smooth phase to the
compressed phase.