Note: Descriptions are shown in the official language in which they were submitted.
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A HAND HOLDABLE MANUALLY DISPENSING
MASTIC CONTAINER AND MATERIAL THEREFOR
The present invention relates to a hand holdable manually
dispensing mastic container and a method of dispensing mastic,
and more particularly to a material therefor.
Mastic is a substance which is used in the construction
and repair industry, more particularly it is used for filling
dents and scratches etc in the automobile industry.
Mastic is a soft putty like substance having a high
viscosity and stickiness. Using the Haake viscometer, for a
shear rate (speed of rotation) of 7.22 s-1, typical viscosity
values are between 3,500 poise and 1,500 poise at 10 °C and
1,500 poise and 650 poise at 30 °C. The mastic is typically
dispensed onto a planar surface where it is mixed by a spatula
with a relatively smaller proportion of hardener in a
prescribed proportion to start a chemical reaction which
causes the mixture to eventually set or harden within a
predetermined hardening time.
The unset mixture should be easily spreadable for
application to an automobile, for example, but should not flow
once applied to a repair except where a self levelling mixture
is used in a self levelling application. The set mixture
should provide a smooth hard finish. The hardening time is
carefully selected to provide a balance between a usefully
long working time and an undesirably long hardening time. To
obtain the aforementioned criteria, considerable expertise and
care is employed when selecting the chemical components for
the mastic. As a result, mastic generally has a high viscosity
and contains strong chemical fumes arising from the solvents
employed therein. For these reasons, storing and dispensing
of the mastic is not an easy matter particularly since such
mastics have styrene therein which is very difficult to
contain.
Traditionally, for commercial use, mastic is stored in
dispensing containers comprising metal tubes filled from one
end and with a convergent dispensing nozzle at the other end.
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An end cap is then forced to slide into the tube by means of
a special apparatus or gun so that the mastic is pushed out
through the dispensing nozzle. A similar arrangement is also ,
used to dispense the hardener from a small tube.
Traditionally, for non-commercial use in which smaller ,
amounts of mastic are used, metal tubes are not used because
their cost is quite high in comparison to the cost of the
mastic itself. It should be noted that this cost derives
partly from the cost of the metal tube itself and partly from
the storage and transport costs associated with empty tubes
prior to filling with mastic. Therefore, small cylindrical
tins with a lever lid are used instead. The mastic is
dispensed by dipping a knife into the mastic and then mixing
it with hardener from a tube after removal. However, this is
not really satisfactory because the mastic in the tin tends
to dry out, the user is more exposed to chemical fumes, and
contamination of the filler paste can occur. Furthermore,
during filling of the tin, air can be taken up by the mastic
resulting in bubbles in the final mixture which detracts from
the finish of the set mixture, and the cost of the tin and the
filling thereof is quite high. There is also a likelihood of
contamination from dust etc in the area.
The aforementioned cylindrical tins, which are of a
relatively larger size, are also employed for commercial use.
Such metal tins of the tin plate variety have been used
because they seal in the fumes from the from the solvents in
the mastic, in particular the styrene. Such tins also provide
a container which will maintain its integrity, that is to say,
they are not subject to leakage over time, and which will not
fracture if dropped, a not unusual occurrence in a busy
workshop. The latter aspect is an important consideration
considering the hazardous nature of the strong chemical fumes '
and the difficulty of clearing up spilt mastic. Moreover, the
interior surface of such tins is not quickly degraded by the '
chemicals in the mastic so that a reasonably long guaranteed
shelf life can be specified.
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It has been proposed to use a container made from
plastics material. The use of a container made from plastics
material should offer a much more cost effective way to
deliver the mastic to the end user. In addition, the cost of
~
the container itself
should be considerably less than a metal
tin, and the container should be able to be produced,
transported and filled much more cost effectively than
hitherto containers.
US-A-4 795 062 describes a large bag like container in
the form of two generally square two ply sheets of material
which are fused together around the four edges to form four
connected linear sealing flanges. A nozzle arrangement is then
adhered to one sheet with that sheet surface closing the
nozzle arrangement until use. Such a container is simpler than
the aforementioned metal tubes. However, it is difficult to
open the container. Furthermore, the nozzle arrangement can
become very messy in use because of the high viscosity and
stickiness of the mastic and the nozzle arrangement can also
sometimes come away from the sheet surface. In addition, once
again, a special dispensing apparatus must be used and hence
purchased in order to use the container. This makes such a
container particularly unsuitable for the non-commercial
usages.
Further problems have been found with mastic containers
made from plastic materials. In particular, it has been found
that the plastics material selected can not provide a suitable
barrier to adequately confine the strong corrosive chemical
fumes of the mastic. It has also been found that the seals
made of the plastics material do not adequately prevent
leakage and can weaken over time making this problem worse'.
Furthermore, if such a container made from plastics material
is dropped, catastrophic failure cf the seams can occur. The
risk of these problems occurring tends to increase over time
making it difficult to specify a reasonably long shelf life,
for example 2 years . It has been found that the latter problem
derives either from the fact that the plastics material is
dissolved by the solvents used in mastic, leading to
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contamination of the mastic, softening of the container producing distortion
of the shape, as
well as weakening ofthe seals and walls, or from the fact that the solvents
cause hardening
of the container seals and walls leading to leakage and brittleness of the
container. Finally,
the use of plastics material offers the opportunity of using a clear material
providing sight of
the mastic. However, it has been found that the plastics material becomes
cloudy.
The present invention seeks to eliminate, or at least mitigate, the
disadvantages of the
prior art, or at least provide an alternative.
According to the present invention, there is provided a hand held mastic
container
comprising: mastic; a flexible sheet material having facing surfaces joined
together to define
a generally elongate bag-like container shaped in the form of two trapezoidal
portions which
are joined together at their longer bases, said elongate bag-like container
holding said mastic
therein and including a dispensing edge having an exit aperture, wherein said
dispensing edge
. is formed in an edge, parallel to said longer base, of one trapezoidal
portion, and wherein the
exit aperture in said dispensing edge is formed to provide dispensing of the
mastic in the
container by application of a hand pressure to the facing surfaces of said
flexible sheet
material.
Prior art mastic containers made from a flexible sheet material are of a form
which
requires a special apparatus for dispensing. With the present inventior~ the
mastic container
has a size such that it is hand holdable and allows comfortable manual
dispensing. The ability
to hold the container and manually dispense therefrom derives from the
container having the
defined shape. With this shape, the container sits firmly and snugly in one
hand in a manner
that enables smooth and well controlled dispensing ofthe contents by simple
pressure applied
thereto. Thus, the other hand is left free to control the spatula or mixing
board thereby
enabling efficient production of the mastic and hardener mixture. Since the
mixture is ready
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where the mixing step take a long time. Moreover, due to the
widest dimension, the pressure from the contents can be
focused on the dispensing edge to give good dispensing control
even when the container is partially empty. In addition, the
filled container is balanced during dispensing so that it does
not easily fall from the hand.
In one embodiment, the container volume between the
opposing end and the widest dimension is greater than the
container volume between the dispensing edge and the widest
dimension.
Thus, the higher weight volume is disposed towards the
body reducing the leverage effect resulting from the weight
of the mastic in the container. In addition, the dispensing
control is maintained even when a significant proportion of
the container contents have been dispensed.
In another embodiment, the container volume between the
opposing end and the widest dimension is smaller than the
container volume between the dispensing edge and the widest
dimension.
Thus, as the mastic is squeezed out, the centre of
gravity remains in the region of the palm of the hand thus
allowing continued easy manipulation during dispensing.
In still another embodiment, the container volume between
the opposing end and the widest dimension is substantially the
same as the container volume between the dispensing edge and
the widest dimension.
In a preferred embodiment, the length of the container
is between 200 mm and 300 mm.
If the length is less than 200 mm, the volume of the
container reduces to a point where it limits its application
and if the length is greater than 300 mm, the container is
unwieldy rendering it effectively no longer easily hand
holdable.
. Conveniently, the length of the container is between 250
mm and 280 mm.
This has been found to be an ideal length for dispensing
control from an average sized hand.
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In another preferred embodiment, said widest dimension
is between 100 mm and 200 mm.
If the widest dimension is less than 100 mm, the volume
of the container reduces to a point where it limits its
application and if the widest dimension is greater than 200
mm, it exceeds the normal span of the hands which makes the
container unwieldy rendering it effectively no longer easily
hand holdable.
Conveniently, said widest dimension is between 130 mm and
150 mm.
This has been found to be an ideal dimension for
dispensing control from an average sized hand.
Preferably, the container has an average width which
exceeds 60 mm.
In a particularly convenient embodiment, the container
volume between the opposing end anal the widest dimension and
the container volume between the dispensing edge and the
widest dimension are both generally trapezoidal with their
parallel sides parallel to the dispensing edge.
By using a trapezoidal volume, it has been found that the
container is simple and hence cost effective to make, with
little waste of the sheet material, whilst giving a good feel
and balance to the container when manually held. Furthermore,
this shape allows pressure to be applied evenly on the
trapezoidal volume remote from the dispensing edge which molds
to the shape of the hand holding the container.
Preferably, the ratio of the widest dimension to the
length of, the container is in the region of 0.46 to 0.80.
In one case, said widest dimension is located
substantially 2/5's of the container length from said
dispensing edge.
This results in a container which has a good feel and
balance when manually held.
In one case, said dispensing edge defines an exit .
aperture, the exit aperture being formed by cutting along the
dispensing edge.
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Consequently, the container can be simply opened by
cutting along the dispensing edge with the dispensing edge
forming the exit aperture. Accordingly, no preformed nozzle
is required.
It is preferred that a plurality of cutting guides are
provided in the region of said dispensing edge to provide a
variety of exit aperture sizes.
In this way, the container exit aperture can be tailored
according to the users need or can give a renewed clean edge
for future use.
Preferably, the guides comprise notches in flaps disposed
adjacent said dispensing edge.
Thus, a simple form of indicating the exit aperture sizes
is provided which can be integrated into the container forming
thereby avoiding the need for printing or the like.
In one embodiment, the container has opposing walls of
said material with side seams joining said wall at least in
the region of said dispensing edge.
Conveniently, said seams in the region of the dispensing
edge are enlarged to define a pair of flaps for stiffening
said exit aperture.
Thus, dispensing control is improved.'
In another case, a separate closable nozzle attachment
is sealed into the dispensing edge for dispensing relatively
less viscous mastic.
As a result, a closure can be attached to the nozzle
attachment to prevent the mastic from flowing out.
Conveniently, said nozzle attachment is disposed
centrally.in the dispensing edge and extends only partially
along that edge.
It is preferred that said opposing edge comprises an edge
for filling the container.
Thus, simple and quick filling and closure of the
. container can be obtained without the ingress of air or other
gases.
It is preferred that said material is a clear
thermoplastic material.
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Thus, the user can easily identify the'contents of the
container.
The present invention encompasses a container as
hereinabove described filled with mastic.
According to another aspect of the present invention
there is provided a method of dispensing mastic from a
container comprising:-
filling mastic into a container formed of a flexible
sheet material and having a generally elongate shape which
diverges from a dispensing edge to a widest dimension and
converges to an opposing end;
opening an exit aperture in said dispensing edge; and
holding the container in a hand and applying pressure to
the container to dispense the mastic from said exit aperture.
Thus, a simple, convenient and clean method of manually
dispensing mastic is provided compared with the prior art
which does not require a special apparatus. With the present
method, the mastic can be manually dispensed in a well
controlled manner.
According to still another aspect of the present
invention there is provided a mastic container formed of a
laminated sheet of plastics material, the sheet comprising:-
a layer selected to provide a barrier to chemical
components of the mastic and to enable bonding or sealing to
another such layer, and an outer covering layer;
wherein the outer covering layer individually or in
combination with said first mentioned layer provide structural
strength for the container.
In this way, a suitable mastics container can be made
from plastics material.
Preferably, said first mentioned layer comprises an inner
layer selected to enable bonding or sealing to another such
inner layer and an intermediate layer selected to provide a
barrier to chemical components of the mastic, said
intermediate layer being located between said inner and outer
layers.
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As a result, an improved seal can be provided enhancing
the integrity of the container and reducing the likelihood of
leakage.
In one embodiment, said laminated sheet is flexible and
said container comprises a non-rigid flexible container.
As a result, it is possible to make a flexible container
making it resistant to leakage through breaking.
In a particular embodiment, it is preferred that said
inner layer is selected from a polyalkylene, for example
polypropylene or polyethylene.
These materials are not dissolved by the mastic or
degraded thereby and hence do not react with the mastic so
that the container can have a long shelf life. In addition,
these materials provide a good seal or bond together during
sealing so that leakage at seams or the like is reduced:
In another particular embodiment, said outer layer is a
heat resistant material.
By using a heat resistant material, heat can be applied
to the sheet will be reach to the inner layer without causing
degradation or weakening of the outer layer and the subsequent
risk of leakage.
Conveniently, said outer layer is selected from a
polyalkylene, for example polypropylene or polyethylene, or
a nylon.
These materials provide good structural strength for the
container and since the chemical fumes from the mastic are
sealed in by the layer providing a barrier, the structural
strength of the container is not degraded over time or
rendered soft or brittle.
Conveniently, said layer selected to provide a barrier
to chemical components of the mastic comprises an alkylene
vinyl alcohol co-polymer, for example, ethylene vinyl alcohol
co-polymer.
It has been found that ethylene vinyl alcohol co-polymer
provides a good barrier to the mastic to confine the strong
chemical fumes without being degraded thereby over a
significant time scale.
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In another particular embodiment, the container is vacuum
formed from said laminated sheet whereby said container
comprises a rigid flexible container.
As a result, a rapid production of containers can be
achieved.
Preferably, the container comprises a single piece open
topped container.
It has been found that the hitherto used tin can be
replaced by a mastic container vacuum formed from the
l0 aforementioned material. The container can be made as a single
piece with a wide neck enabling a user to access the mastic
therein. The structural strength of the container means that
even with dropping, the integrity of the container is not
compromised by fracturing which is remarkable considering the
mass of the mastic, typically in excess of 1 Kg. Furthermore,
the container is remains substantially unaffected by the
aforementioned solvents so that the container does not become
softer or more brittle over normal time limits, which could
affect its integrity, and the container shape does not distort
over normal time limits so that a suitable shelf life can be
specified.
Preferably, the wall thickness of the container is
between 650 microns and 900 microns.
It has been found that when the container wall has a
thickness within this range, the various~advantages mentioned
above are optimised.
Conveniently, the container has a substantially flat base
with upstanding walls.
Accordingly, i.t is possible to scrape all the mastic off
the base thereby reducing waste.
It is preferred that the container is tub or barrel
shaped.
This shape enables good stacking of the full container,
good nesting of empty containers, provides optimum use of
stacking space, enables a good surface area for labelling etc,
and gives a good open access to the mastic for the user.
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In a particular embodiment, the area of said base is
similar to the area of said open top.
With this embodiment, all the above mentioned advantages
are optimised.
Preferably, said single piece container has a lip around
the edge thereof and a closure closing the container.
Conveniently, said closure comprises a sealing member
sealed to said lip.
By using a closure made from the laminated sheet above,
a good seal of the container can be made.
Preferably, said inner layer is selected from a
polyalkylene, for example polypropylene or polyethylene.
These materials are not dissolved by the mastic or
degraded thereby and hence do not react with the mastic so
that the container can have a long shelf life. In addition,
these materials provide a good seal or bond together during
sealing so that leakage at seams or the like is reduced.
Conveniently, said outer layer is selected from a
polyalkylene, for example polypropylene or polyethylene.
These materials provide good structural strength for the
container and since the chemical fumes from the mastic are
sealed in by the 7_ayer providing a barrier, the structural
strength of the container is not degraded over time or
rendered soft or brittle. Thus, in a rigid container,
panelling or bowing of the walls thereof does not occur on
a
significant time scale.
Conveniently, said layer selected to provide a barrier
to chemical components of the mastic comprises an alkylene
vinyl alcohol co-polymer for example, ethylene vinyl alcohol
co-polymer.
It has been found that ethylene vinyl alcohol co-polymer
provides a good barrier to the mastic to confine the strong
chemical fumes without being degraded thereby over a
significant time scale.
According to yet another aspect of the present invention
there is provided a method of forming a mastic container from
plastics material, the method comprising the steps of:-
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(a) forming a laminated sheet comprising a layer selected
to provide a barrier to chemical components of the mastic and
to enable bonding or sealing to another such layer, and an
outer layer selected to individually, or in combination with
said first mentioned layer, provide structural strength for ,
the container; and
(b) forming said laminated sheet into a container.
As a result, a mastics container can be formed which does
not have the above mentioned drawbacks associated therewith.
Preferably, step (a) comprises forming said first
mentioned layer as an inner layer selected to enable bonding
or sealing to another such inner layer and an intermediate
layer selected to provide a barrier to chemical components of
the mastic, said intermediate layer being located between said
inner and outer layers.
As a result, an improved seal can be provided enhancing
the integrity of the container and reducing the likelihood of
leakage.
In one case, step (b) comprises vacuum forming a rigid
said container.
Consequently, a rigid container can be formed which
enables stacking in a nested format thereby reducing the cost
of transportation of the empty container prior to use.
In another case, step (b) comprises forming a flexible
bag like said container.
By having such a flexible bag like container, it is
possible to obtain the advantages of the above mentioned hand
held container without the above mentioned drawbacks
associated with hitherto containers made of flexible plastics
materials.
Examples of the present invention will now be described
with reference to the accompanying drawings, in which:-
Figure 1 shows in plan view an unfilled hand holdable
manually dispensing mastic container of a first embodiment of
the present invention;
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Figure 2 shows a transverse section along line A-A of
Figure 1 for a filled container; and
Figure 3 shows in plan view of an unfilled hand holdable
manually dispensing mastic container of a second embodiment
of the present invention.
Referring to figures 1 and 2, a hand holdable manually
dispensing mastic container 1 is made from two sheets of
transparent plastics material which are welded together at
a
seam 7 around the periphery thereof. The container is formed
to have a dispensing edge 4 and a filling end 3 which are
parallel to one another. The container has a generally
elongate shape which diverges from the dispensing edge to
a
widest dimension, indicated by numeral 6 and parallel to the
dispensing edge, and then converges to the filling end. The
widened dimension 6 is located substantially 2/5's of the
distance along the axis of the elongate shape from the
dispensing edge 4 and substantially 3/5's of the distance
along the axis of the elongate shape from the filling end
3.
Thus, two trapezoidal portions are formed generally
identified by numerals 11 and 12 respectively. The volume
of
portion 11 closest to the dispensing edge is smaller than
the
volume of portion 12 closest to the filling end.
Close to the dispensing edge, the seams 7 are extended
sideways as illustrated to form triangular shaped flaps 2.
Each flap 2 is provided with three notches 5. The purpose
of
these will become apparent hereinafter.
The container is made by cutting two sheets of plastics
material to have the required shape and then welding them
at
seams along all edges except along the filling end 3. Then,
the container is filled with mastic and the filling end sealed.
to make a closed container. It will be appreciated that the
unfilled container can be made in one location and transported
to another location for filling.
To use the container of this embodiment, the seam 7 along
the dispensing edge 3 is cut off to expose the mastic. This
makes an exit aperture of a predetermined width. The three
notches 5 are positioned to provide guides for different
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widths of exit aperture which in turn enables control of the
rate of dispensing of mastic. The flaps 2 also provide an
element of stiffness at the dispensing edge leading to
improved stability of the exit aperture.
To dispense mastic, the container is held in the hand ,
with the widest dimension 6 fitting into the palm of the hand.
Then, pressure is applied to the volume 12 to squeeze out
mastic. Due to the shape of the container, the exit aperture
can be easily manipulated thereby enabling neat, simple and
clean dispensing. In addition, special dispensing apparatus
or a special knife are not required. Moreover, the weight of
the volume 12 is greater than the weight of volume 11 so
overall the weight of the filled container is disposed more
towards the body improving control of the exit aperture at the
dispensing edge 4.
In the present case, for an average hand length, the
length of the container is made to be 260 mm, but can be
between 200 mm and 300 mm.
In the present case, for an average hand span, the widest
dimension 6 is made to be 140 mm, but can be between 100 mm
and 200 mm.
The filling end 3 has a dimension of 30 mm and the
dispensing edge 4 and flaps 2 give a combined dimension of 60
mm.
A hand holdable manually dispensing mastic container of
a second embodiment of the present invention is shown in
figure 3. A container 31 is formed of a plastics sheet
material which in a preferred form is transparent or
translucent. The container is shaped in the form of two
trapezoids, one relatively larger, which are joined together
at their longer bases to define an intermediate point 36
between a filling end 33 and a dispensing edge 34 of the
container. Thus, the intermediate point 36 along the axial
length of the container is relatively wider than the filling
end 33 and the discharge end 34. The intermediate point 36 is
located 2/s's of the axial length from the discharge end 34
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and 3/5's of the axial length from the filling end 33. The
narrowest part of the shape defines the discharge end 34.
Facing surfaces of the container defining the relatively
larger trapezoidal shape are sealed together along side seams
37 and 37A. Facing surfaces of the container defining the
relatively smaller trapezoidal shape are sealed together along
side seams 38 and 38A.
Facing surfaces at the filling end are sealed together
along filling end seam 39 after filling. Facing surfaces at
the discharge end 34 are sealed together along end seam 40.
A nozzle attachment 41 is provided at the discharge end and
has a generally inverted T shape defined by a base 42 and
an
upright 43. The base 42 of the attachment 41 is sealed into
the end seam 40. A central discharge channel 46 is formed
in
the base 42 to extend from the interior of the container 31
through and along the axis of the upright 43 to a discharge
exit nozzle 44. The exterior surface of the upright 43 has
a
thread thereon for receiving a cap 45. A tamper evident or
restraining band can be connected to the cap 45 to hold it
in
place. The exterior surface of the base 42 includes bands
for
assisting in bonding to the seam 40. The base is disposed
centrally along the seam 40, but extends only partially along
that seam.
. With the second embodiment, all the discharge advantages
of the first embodiment are obtained, but instead the
container can be sealed with a cap. Thus, the second
embodiment can be employed with fluent material that is not
sufficiently viscous to stay within the container, but instead
has a tendency to flow out, although the use of the nozzle
attachment does enable easy closure of the container so that
it can still be used with more viscous mastics but a wider
- exit nozzle and discharge channel are required in this case.
By providing the nozzle attachment 41, the container can be
closed rather than relying on the inherent viscosity of the
material in the container to hold the material therein.
The container of the present invention is simple and
cheap to manufacture thus providing convenient and cost
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effective manufacture in comparison with hitherto known mastic
containers. The shape of the container allows comfortable and
controlled manually dispensing of the mastic within whilst
being held in the hand. As the mastic is squeezed out, the
centre of gravity remains in the region of the widest part of s
the container thus maintaining the seating of the container
in the palm of the hand thereby continuing to enable it to be
easily manipulated during dispensing. The shape of the
container enables pressure to be applied evenly on the larger
trapezoidal section which molds to the shape of the hand
holding the container. Gentle pressure at this point allows
the mastic to be squeezed out.
Moreover, because the container is completely sealed, the
mastic therein can remain relatively air free so that the
final hardened product after application can have a good
finish. Furthermore, because the shape of the container allows
more control when the mastic is being squeezed out, the mastic
can be squeezed out smoothly and evenly, thus preventing air
bubbles from forming. This reduces the likelihood of pin
holing in the final hardened product after application. Thus,
an improved finish is obtained. In addition, by simple changes
to the tooling producing the container, considerable
flexibility of size of container can be achieved. In
particular, the container can be made to an appropriate size
to contain an exact amount of mastic needed for a single
application. In this case, the container is disposable after
single use thus preventing wastage of material through
prolonged storage.
Moreover, whilst a clear thermoplastics sheet material
has been described, other forms of sheet material can be used.
It should be noted that a clear material may preferably not
be used since otherwise the mastic could be subject to
degradation due to exposure to ultraviolet light. In addition,
the sheet material can take the form of single, two ply or '
three ply material. It will be appreciated that the flaps 2
and the guides 5 may be omitted as in figure 3.
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In another aspect of the present invention, the container
shown in the accompanying figures can also be formed from a
laminated sheet of plastics material. The laminated sheet has
a layer selected to provide a barrier to chemical components
of the mastic and to enable bonding or sealing to another such
layer, and an outer covering layer which either individually
or in combination with said first mentioned layer provide
structural strength for the container.
In one example, the laminated sheet is an easily flexed
sheet which is made as an inner layer of polyethylene, an
outer layer of polyethylene with an intermediate layer of
ethylene vinyl alcohol co-polymer sandwiched therebetween. The
three ply layer is produced in sheets.
A roll of the sheet of the three ply material is folded
as it passes to a machine such that the inner layers are
facing. The machine cuts the sheet to the form shown in figure
1 for example and then applies heat around the position of the
seams 7. In the present case, the heat causes the inner layers
of polyethylene to bond together which together with the fold
line along dispensing edge 4 forms a mastic container. The
container is then filled through filling end 3 before heat is
applied along this edge to cause the -inner layers of
polyethylene to bond together at this edge sealing the
container. Such a machine is well known in the art and does
not form part of the present invention. It will be appreciated
that microwaves or some other manner of effecting the
seal/bond can be employed.
Polyethylene is selected for the inner layer because it
is not dissolved by the solvents present in the mastic, for
example styrene. Thus, there is no softening or hardening of
this layer. Indeed, polypropylene is relatively inert to those
solvents so that there is no chemical interaction with the
mastic which could cause chemical deterioration. Furthermore,
polyethylene provides a very good seal and bond to
polyethylene thereby providing leak tight seals 7. However,
polyethylene is porous to the solvents and fumes present in
the mastic so it can not be used for the container itself.
CA 02231146 1998-03-04
WO 97/11895 PCT/GB96/02384
- 18 -
After considerable testing, ethylene vinyl alcohol co-polymer
is used as the intermediate layer because it has been found
to act as a barrier to the chemical fumes present in the ,
mastic thereby ensuring that the container is sealed and does
not react to those fumes. Polyethylene is selected as the
outer layer because it exhibits very good structural strength
so that the integrity of the container is assured. Moreover,
neither the polyethylene nor the ethylene vinyl alcohol co-
polymer are caused to go cloudy over a significant time so
that shelf life is prolonged and the purchaser of the mastic
filled container can see the product and check that there has
been no deterioration. It should be noted though that it may
be preferably to use already opaque materials to prevent
deterioration of the mastic due to exposure to ultraviolet
light.
It has been found that when the aforementioned flexible
sheet is used to make the container of figure 3 a problem can
arise with heat sealing in the nozzle attachment 41. The
problem arise because substantial heat is required to produce
bonding between the nozzle attachment and the inner layer. As
a result, there is damage to the outer layer resulting in
weakening in the vicinity of the attachment leading to
bursting if the container is dropped. Thus, in this case it
is preferred that a heat resistant material is used for the
outer layer. It has been found that an outer layer of nylon
is particularly suitable and overcomes the aforementioned
weakening problem.
In another example, the laminated sheet is a more rigid
sheet which is made as an inner layer of polypropylene, an
outer layer of polypropylene with an intermediate layer of
ethylene vinyl alcohol co-polymer sandwiched therebetween. The
three ply layer is produced in sheets.
A sheet of the material having a thickness of 850 microns
is vacuum forming using a standard vacuum forming machine into '
a mold so as to produce a container which~has a generally
rectangular base with upstanding walls to define a generally
rectangular open top such that a tub shape is formed. The
CA 02231146 1998-03-04
WO 97/11895 PCT/GB96/02384
- 19 -
upper edge of the walls have a lip which extends around the
periphery of the open top. The container is then filled with
mastic and a closure made, from the same material as the walls
is heat bonded or the like to the lip. This closure is then
torn off to open the container. A replaceable lid also of the
same material can be provided.
This container has been found to resist leakage of the
solvents in the mastic through the base, walls, or closure.
In addition, it has been found that the base and walls are
resistant to panelling or bowing thereof due to the action of
the solvents in the mastic. Moreover, the mastic remains
substantially unaffected by contact with the base and walls.
Thus, overall, a long shelf life for the mastic can be
obtained. Additionally, the material provides significant
structural strength which does not significantly alter over
time so that even with dropping, the integrity of the
container is not compromised by fracturing, and the container
shape does not distort over time.
It will be appreciated that whilst the shape of the
container described is basically tub shaped, other broad
opening container shapes may be selected. The use of vacuum
forming is convenient since it is a rapid production process
and enables a variety of shapes to be produced.
In tests, it has been found that containers made using
the aforementioned plastics materials and which are several
years old have retained their integrity in terms of mastic
leakage (tested by weight loss) and retain a good visual
appearance.
It will be appreciated that whilst an inner layer of
polyethylene has been described, this layer can be omitted.
Whilst polyethylene has been described for use as the inner
and outer layer, the inner and/or outer layer can be
polypropylene.
It will be appreciated that the embodiment illustrated
shows an application of the invention in one form only for the
purpose of illustration. In practice, the invention may be.
applied to may different configurations, the detailed
CA 02231146 2004-05-21
embodiments being straightforward for those skilled in the art to implement.
In particular, whilst the shape of the container described is basically that
of a reversed
double trapezoid conjoined along its longer edges at the widest dimension,
other
configurations both asymmetric and symmetric may be selected.
5 With regard to the &rst embodiment, it will also be appreciated that if use
of the
container is terminated before the container is empty, the dispensing edge may
be freed from
mastic, folded back on itself, and retained by adhesive tape or such like so
as to exclude air
6-om the container on a temporary basis.
The laminated sheet material described can be made flexible so that it can be
applied
10 to different forms and shapes of mastic container. Thus, the material can
be used for bag like
containers of differing shapes, not limited to those shown in the accompanying
drawings.
Alternatively; by using a thicker outer layer, the container can be vacuum
formed to be rigid
with a sufficiently broad opening to enable access of a knife or spatula. The
use of vacuum
forming is convenient since it is a rapid production process and enables a
variety of shapes
15 to be produced. In addition, due to the selection of the intermediate layer
compound, the
mastic does not cause the walls of the container to degrade such that
panelling or bowing
occurs. Furthermore, due to the selection of the compounds for the container,
it is possible
to heat seal or the like a suitable closure to the container, for example foil
or the like, which
can be easily removed yet provides a leak free seal.
20 Advantageously, embodiments of the present invernion may provide a mastic
container which is cheap and easy to produce, which is a hand held container
and which
enables manual dispensing.
Moreover, embodiments ofthe present invention may provide a method of
dispensing
mastic from a container which is simple, convenient and cheap.
Also, embodiments of the present invention may provide a mastic container made
of
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