Note: Descriptions are shown in the official language in which they were submitted.
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CASTING METHOD
The present invention relates to a method of
casting a material, such as soap, non-soap detergent or
mixture thereof, in a liquid or semi-liquid state into a
pack.
US 31491~8 describes a method of casting soap into
a pre-formed mould which is designed to serve as a package
or container for the ready-to-use cake and subjecting the
liquid mass in the mould to cooling whereby the mass
solidifies into a cake having the contour of the mould. The
mould is airtightly sealed after casting. The moulds are
preferably rigid or semi-rigid bodies whose shape determines
the shape oE the cake of soap. The mould can be plastic and
can have flexible wall portions whose depression will
facilitate the removal of the ready-to-use cake from the
mould. The method is applicable to transparent soap and
thus obviates the traditional open cast method of casting
transparent soap into blocks and cutting the blocks into
bars and overcomes the ~hrinkage, loss of perfume and
surface deterioration problems associated with open cast
bars.
Rather similarly, FR 910256 describes a method of
casting liquid soap into a pre-formed mould which is
retained as an envelope around the soap and thus delivered
to the consumer. The mould should be sufficiently rigid to
retain its shape when empty.
- According to the present invention there is
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provided a method of casting a material comprising soap, non-
soap detergent or a mixture thereof, the method comprising
melting the material, filling the material in a liquid or
semi-liquid state into a pack made at least substantially of
a flexible, heat-shrinkable and/or heat extendable film, such
that the material occupies the whole internal volume of the
pack, airtightly sealing the pack while the material is in a
liquid or semi-liquid state, and allowing the material to set
to a substantially solid state while contacting the exterior
of the pack to control the shape of the pack during the
setting of the material.
The present invention thus provides a method of
casting and simultaneously packing a material such as soap.
Use of flexible film can be economical with regard to the
lS initial cost of the pack material. The method can be
carried out on a continuous basis. Moreover, a supply of
empty packs can be stored in a flat or rolled form, or a
supply of flexible film for making packs can be stored and
converted into packs only immediately prior to use. If
desired forced cooling can be employed whilst the material
is being allowed to set.
The present method can be carried out on a high
speed packa~ing machine analogous to a conventional machine
for forming and filling sachets. The method can thus not
only be performed at high speeds, but also obviates the need
to form and store rigid three-dimensional packs prior to
use. Moreover, the invention enables a molten mixture to be
made directly into a bar or the like having rounded corners
and edges and of a pleasing shape. Thus unlike conventional
casting of soap mixture into large slabs followed by cutting
into blocks with prominent edges which require time
consuming die stamping, the present method can readily and
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speedily produce suitably shaped bars or the like.
The present method can allow the shape of the pack
to be controlled by contact with the exterior of the pack
during the setting of the material. Thus for example a
filled and sealed pack made substantially from flexible film
could, for example, be lightly moulded in a die and/or have
a motif impressed on it. A filled and sealed pack could be
pressed between two surfaces in order to produce a bar or
tablet-like shape. The surfaces could be fla-t or one or
both of them could be, for example, concave so as to produce
a substantially "cushion" shaped bar. The con-trol need only
_ be exerted for as long as necessary for the ma-terial to
assume a permanent shape. Pressures in the range 0.1 to
0.3kgf/cm2 are preferred, the actual pressure selected
depending on the properties of the pack in each case.
In order to give an attriactive appearance, it is
very desirable that the pack should be a skin-tight wrinkle-
free fit over the cast material within. To accomplish this,
it can be beneficial to shape the ~pack by distending it with
internal pressure, which can be done in various ways.
Pressing the exterior of a filled and sealed pack
between two surfaces to control its shape will tend to
reduce the volume to surface ratio and so pressurize the
incompressible material within the pack. The internal
pressure then distends and tensions the film material.
The pack may be of a heat-extendible material,
i.e. a material which can stretch permanently when
sufficiently hot. If stretching occurs at the temperature
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of the material filled into the pack, the pack will stretch
and adjust its shape under the hydrostatic pressure of the
hot material in the pack and/or pressure in that material
arising from pressure on the pack exterior. Stretching of
flat film to adjust its shape to that of the filling of the
pack will of course mean that the film is no longer flat.
Another possibility is to use a heat-shrinkable
flexible film. As this shrinks onto the material in the
pack it will pressurize this material which will accordingly
stretch the shrinking film taut.
Yet another possibility is that the pack could be
at least partially shaped prior to filling. This could be
carried out by blowing, e.g. into a mould, which is a
further instance of shaping the pack by distending it with
internal pressure, and again stretching the film. The film
will remain flexible, but the shaping of it will influence
the shape which the pack takes when filled.
~ n order to achieve a skin-tight fit the material
preferably occupies substantially the whole internal volume
of the pack on being airtightly sealed. Contact between the
material and air can thus be excluded which could be of
importance in achieving a long shelf life. such an
arrangement can also ensure that when the material is
unpacked immediately prior to use, due to the close contact
between the material and the pack, the material is presented
to the consumer having an unblemished and even surface
appearance.
The flexible film is preferably made of
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thermoplastic material. The pack suitably comprises two
layers of its constituent film in the form of a bag or
sachet having an open end into which to fill the material.
In its unused for the pack material either preformed into
sachets or as separate sheets of film can therefore be
stored flat or for example in rolls as supplied from the
manufacturers.
The two layers of film can, for example, be formed
into a bag or sachet by sealing them together along one or
more seams so as to define the flat (unfilled) shape of the
pack while leaving an unsealed portion as the filling
opening. The seal could extend around the total periphery
of th0 pack or alternativaly the pack could be derived from
a tube of flexible film material having a transverse seal at
one end and being open at the other end so as to allow the
pack to be filled. For a thermoplastic material the seal
can conveniently be performed by heat welding. Any "skirt"
of the film material projecting ou-twardly from the seamts)
_ can be trimmed away from the set product. Alternatively a
"s}cirt" of film may be avoided by employing knife-edge
welding methods.
It is preferred that a film material is employed
which allows the pack when filled to be airtightly sealed by
heat welding through a slight excess of soap or the like at
the opening to the pack. This can ensure that the material
occupies the whole internal volume of the pack, and ensures
exclusion of any air from the pack.
Preferably the pack is formed immediately prior to
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filling with both operations carried out on the same
machine. Where the pack is formed from two layers of its
constituent film, the pack can be filled with the material
and airtightly sealed, with the sealing step conveniently
forming at the same time at least a portion of the seam of
the next pack to be filled. The present process can thus
readily lend itself to operation on a continuous basis. For
example a four side sealed sachet/vertical fill process
could be employed.
The flexible film can rsadily be removed from the
bar or the like immediately prior to use by a peeling
action. If desired a tear strip(s) or the like can be
included integral with the flexible film or attached for
example glued to the flexible film in order to help initiatc
removal of the film from the bar. Alternatively the film
can be made of a water-soluble material which dissolves
during the first use of the bar or the like.
The actual film selected in any one case will
depend on the circumstances of each case. Conveniently the
film will be selected such that it can be heat-sealed. A
variety of heat-sealing methods are available and genPrally
involve melting the film layers in contact. The available
methods include radio frequency or dielectric, bar, band,
impulse, hot wire or knife and ultrasonic welding. As
mentioned above, the film may have properties such that it
can extend and/or shrink around the material being packed so
as to provide a skin-tight and wrinkle-free fit at the
temperatures encountered on contact with the liquids or
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semi-liquid material and/or during the time that the
material is setting.
Suitable flexible film materials are commercially
~ available. Examples include polyvinylchloride,
polyvinylalcohol, polyethylene, Nylon ~trade name for
polyamide), Surlyn (trade name for ethylene methacrylate
copolymer) and polyethyleneterephthalate mixtures thereof.
The thickness of the film selected may depend inter alia on
the degree of adjustment, if any, required in -the film in
order to provide a skin-tight and wrinkle-frse fit. For
polyvinylchloride film for example the pre~erred thickness
range is from 20 to 60,um, with a more preferred thickness
being from 30 to 50~m.
I~ desired laminated, co-extruded or other
multilayer films can be employed. For example a multilayer
film could be employed which is designed to combine the good
heat-sealing characteristics of one polymer with the
barrier/high melting point or other useful characteristics
for example ease of printing of another. The ~ilm could for
instance be printed with a motif, the product's name or
advertising. In some applications it may be preferable to
employ transparent film so that the cast soap bar or the
like can be readily viewed.
The present method can be applicable to any
castable soap, non-soap detergent or mixture thereof. The
_ soap and/or non-soap detergent being packed can of course
include any additional materials conventionally found in
toilet or laundry bars. In particular, however, the mathod
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obviates the problems encountered in traditional pressing
techniques as well as those itemised in US 3149188 having
regard to transparent bars. The method can thus be
especially applicable to transparent, translucent and low
fatty matter soap bars.
It is to be understood that the present invention
extends to bars, tablets, cakes, blocks or the like of soap,
non-soap detergent or mixtures thereof airtightly sealed in
a pack according to the present method.
Embodiments of the present invention will now be
described by way of example only and with reference to the
accompanying drawings in which:
Fig. 1 shows a pack formed by heat-sealing two
sheets of fle~cible film;
Figs. 2a, 2b, 2c and 2d are side views of the pack
seen in the direction of arrow II of Fig. 1 showing
progressive stages from filling to finished product;
Fig. 3 diagrammatically illustrates the forming
and filling of packs on a vertica]L forming and filling
machine, and is a view on arrow III of Fig. 4;
Fig. 4 is a diagrammatic view of film being formed
and filled on the machine, seen in the direction of arrow IV ,
of Fig. 3.
Referring first to Fig. 1 of the drawings, a
preformed pack 10 was prepared by overlaying two layers of
flat polyvinylchloride film, each layer having a thickness
of 130 micron, and radio frequency welding the two layers
together along a seam 12 which is generally in the shape of
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a U narrowing at the top with a curvature substantially
symmetrical to the closed bottom end of the U. Seam 12
defines a bag with a filling neck 14 at the top of the bag.
Molten soap at a temperature of about 80C was
poured down the neck 14 into this bag, so as to fill the bag
to capacity and provide an excess extending up the neck 14
to the line indicated at 16. The pack was held upright and
closed across its top opening by heat-sealing through the
soap composition along the line 18.
The polyvinylchloride material of the bag
stretched at the temperature of the soap poured into it so
that as the bag was filled it distended and stretched to the
_ shape shown by Fig. 2a. This shape is little changed by
sealing as shown by Fig. 2b.
A~ter sealing the filled pack was shaped so that
its side view became as shown in Fig. 2d. One possibility
for doing this was to place the pack in a mould completely
surrounding it and allow cooling in the mould until the soap
had set. Such a mould needed to be slightly larger than the
filled pack so as to avoid destroying the pack by attempting
to confine it in a space which was too small.
The alternative to this, which was preferred, was
to press the pack between two plates 20 arranged
substantially parallel to each other and to a plane
containing the welded seam of the pack as shown in Fig. 2c.
To do this, these plates and the filled pack were
placed in a horizontal position. The upper plate carried a
weight 22 so as to apply a pressure on the pack of about
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0.2kgf/cm~. The pressure so applied was maintained until
the soap in the pack had cooled and set. This pressure
applied to the pack served to maintain a pressure within the
pack and thus to distend the film of the pack.
The resulting product had an attractive
appearance, the cast bar being substantially "cushion"
shaped and the polyvinylchloride film being a skin-tight and
wrinkle-free fit, any creases which originally formed around
the seam disappearing due to the film stretching and
accommodating itself in order to conform to the contours of
the pressed bar. The neck 14 was cut away, and a "skirt" of
film projecting around the seam 12 was also readily cut away
in order to improve the overall appearance of the product
yet further.
Figs. 3 and 4 illustrate diagrammatically the
continuous forming and filling of packs. The packs are
formed from flexible film laminate comprising a supporting
material and a heat-sealable material at one face of the ~,
laminate. Two webs of the film laminate are drawn off from
a pair of supply reels 30 so that the heat-sealable faces of
the film laminates contact each other and become the inside
surfaces of packs. At a first station 32, the two layers of
film are sealed together along a pair of side seams 34 which
extend generally vertically and have curved upper and lower
end portions, as shown in Fig. 4. Fig. 3 shows station 32
just before the seams 34 are formed at this station;
accordingly they are shown in chain dotted lines in Fig. 4.
After a pair of such seams 34 has been formed, the film is
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drawn downwardly to bring the seams 34 to the positions
indicated 34'. A filling nozzle 36 projects downwardly
between these seams. Horizontal sealing is carried out at a
second station 42. Sealing at this s-ta-tion occurs across
the line 44 shown chain dotted in Fig. 4. It closes one
pack and simultaneously forms the bottom of the next pack in
succession.
As shown by Fig. 4 the pack 46 which is currently
immediately below the station 42 has its bottom closed by
seam 44' formed in a previous cycle of operation. Before
sealing takes place at the station 42 this pack 46 is filled
with molten soap from the nozzle 36. Filling continues
until an excess of soap partially fills the pack 48 above,
e.g. up to the level 50. Sealinq at the station 42 seals
! 15 through the soap along the line 44 so forming an airtight
seal to close the pack 46. Simultaneously it forms the
bottom seam for the pack 48 next in succession. The filled
packs are separated by shears 52 cutting horizontally
through a previously formed seam 44".
Machinery for carrying out the process illustrated
by Figs. 3 and 4 can be derived from conventional machinery
for forming and filling four sided sealed sachets. Figs. 3
and 4 illustrate a process carried out down a single
vertical column but it is feasible to have a number of such
columns arranged side by side.
For carrying out a process as illustrated by Figs.
,`~ 3 and 4 a suitable film material is 5~ micron Nylon
(polyamide) laminated with a 40 micron layer of Surlyn which
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is a heat-sealable cross-linked ethylene methacrylate
copolymer. The Nylon does not stretch at the temperature
(80C) of the molten soap.
In a development of this process a further station
is included at which the heat-sealable laminate is heated
and stretched to a desired shape (while remaining flexible)
by introducing air pressure between the two layers of film
before a pack is filled with soap.
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