Note: Descriptions are shown in the official language in which they were submitted.
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Multiple lair Preform and Method for Producing the Same.
The invention relates to a multiple layer preform according to the preamble of
Claim 1.
Further, the invention relates to a method for the production of a multiple
layer preform
according to the preamble of claim 8.
Multiple layer preforms composed of PET or other thermoplastic mouldable
materials such as
1o PEN, Polyamide, Polycarbonate etc. are generally well known and are used to
produce
containers, especially bottles for beverages. To do this, the preforms are
brought into the
desired shape by stretch blow moulding. One such method is known from the
publication
VllO 99/22926 for example. This well-known method enables the production of
multiple layer
preforms having relatively thin layers, especially a thin outer skin and / or
a thin ba«ier layer.
1s
A thin outer skin is desired in order to allow the proportion of the core or
inner layer, which
is made out of economically priced recycling material, to become as large as
possible.
A thin barrier layer is desirable since the plastics which are used to produce
it, for example
2o PEN, Nylon or EVOH, are relatively expensive. A disadvantage of a preform
produced
according to this method is the fact that the thickness of the inner layer,
especially around
the base region of the preform cannot be varied. During the stretch blow
moulding of the
preform into the final container shape, a beverage bottle for example, the
side walls
experience a pronounced bi-axial stretching, whereas that part of the preform,
which forms
2s the base region of the bottle, experiences a much smaller stretching during
stretch blow
moulding and thus a much smaller reduction of its layer thickness, so that the
individual
layers in the base region remain relatively thick.
A so-called three-five layer preform is known from the publication EP 0 596
872 A2, in which
3o an additional material is introduced into the part which forms the base
region of the
beverage bottle, in such a way that the material forming the barrier layer is
filled with this
additional material in the base region. The disadvantage of this well-known
preform is the
fact that a relatively large amount of inner layer material is still present
in the base region,
which, as has already been mentioned, is comparatively expensive. A reduction
in the
3s consumption of inner or barrier layer material is therefore necessary in
order to reduce costs.
A further disadvantage of this well known preform is the fact that the
production process
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becomes slower, more complicated and more expensive due to the insertion of an
additional
material in the inner or barrier layer.
Moreover, it becomes evident that as a rule no or only insufficient adhesion
exists between
the individual layers. It is in the nature of the plastics used, that they do
not mix or only very
poorly and therefore do not make an intimate bond to each other. This missing
adhesion
between the individual layers can lead to flaws or weak points during stretch
blow moulding,
which in turn can lead to damage or accidents occurring during the normal
everyday use of
the filled plastic bottles.
It is the aim of the present invention to provide a more economically
advantageous preform
and a corresponding method for producing the same.
Furthermore, it is the aim of the present invention to provide a preform in
which the
adhesion between the individual layers is improved, preferably in the base
region.
Particularly, it is the aim of the present invention to provide a method,
which results in an
improved attachment / adhesion between barrier layer and A-component in the
base region.
This aim is accomplished by a multiple layer preform having the
characteristics of claim 1. The
2o subsidiary claims 2-7 relate to further favourably designed preforms. The
aim is further
accomplished by a method for producing a multiple layer preform according to
claim 8.
The aim is accomplished particularly by a multiple layer preform, consisting
of at least two
components, an A-component and a B-component, in which at least one of the
layers in the
2s base region of the preform has a section, along which a part of the layer
is peeled off and in
the transition region a part of the layer is split away, forming a partial
layer. In the casing
region this one layer is not split away.
In a favourable design, the B-component is composed of the inner or barrier
layer material, in
3o which preferably the section of the preform which approximately forms the
base region of
the beverage bottle has a separated or split layer, i.e. exhibits a detached
partial layer. A
preform designed in such a way possesses a very thin inner- or barrier layer
in the base
region. Furthermore, the detached partial layer can be very thin, e.g. having
a thickness
between 50um and 500Nm. According to the invention this partial layer is
irregularly shaped,
35 in particular having a crumpled corrugated shape. This irregular
geometrical shape of the
partial layer results in the creation of a larger contact area between this
thin partial layer and
the neighbouring layers, and thus the adhesive forces between the individual
layers are
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increased. The irregular shape of this partial layer leads additionally to a
mechanical
attachment, i.e. a form-locking connection between the individual layers.
In the design according to the invention the inner layer in the base region is
stripped, so that
only very little barrier material remains in the base region.
In a possible design the A-component is composed of new material - PET,
whereas the B-
component consists of a barrier material like nylon. However, further
components can also
be introduced, for example a C-component composed of reprocessed recycling
material as an
additional layer in the preform.
to
The method according to the invention for producing the multiple layer preform
can be
carried out in such a way that in a prephase, material composed of the A-
component is
injected into the mould cavity bordering the shape of the preform in the
direction of material
flow until it is partially filled; and in a subsequent main phase, limited
amounts of the A-
component and B-component are injected. Thus, the B-component, which is to
form the
barrier layer, is introduced in a parallel process. At the same time the B-
component can be
surrounded on both sides by a layer of the A-component during the injection
process. The B-
component flows together with the A-component in the direction of material
flow forwards
into the mould cavity of the injection mould.
In a concluding phase, a limited amount of the A-component is injected into
the cavity under
such conditions, that part of the B component is stripped from the base region
and is split
off, i.e. separated or peeled away, while forming a separate partial layer in
the transition
region. This is particularly achieved by introducing the A-component before
the B-component
becomes hard. This causes a stripping and a peeling away of the B-component.
The B-
component, e.g. Nylon, is injected within a short period of time. After that,
the A-component
is supplied very quickly so that the B-component is still plastically
deformable during the
subsequent flow of the A-component.
3o Thus in the transition region, a layer consisting of A-component is located
between the split
layers consisting of the B-component. In this way the preform exhibits a five-
layer structure in
this transition region, in what is otherwise a three-layer structure. A
structure having more
than five layers is naturally also possible.
3s It is to be understood that in the concluding phase a third component can
also be
introduced.
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The transition region of the preform having the five layer structure forms a
kind of anchoring
section, in which the split away partial layer of B-component acts like an
anchor during the
stretching of the preform, i.e. it creates an increased adhesion due to its
irregular shape and
forms a form-locking connection.
s
Furthermore, preforms manufactured in such a way have an inner layer, which
has an
increased thickness in the casing region; a fact that in turn has a positive
effect on the
strength of the stretch blow moulded bottle.
to This mutual anchoring effect has the advantage that it is also possible to
form a beverage
bottle having a very thin base, which nevertheless exhibits an uninterrupted
barrier layer of
Nylon.
In the following sections the invention is described in more detail with the
help of several
1s example designs.
Figure 1 shows a longitudinal section through a well know multiple layer
preform, arranged
in the moulding cavity of an injection mould.
2o Figure 2 shows a longitudinal section through a hot channel (runner) nozzle
with needle seal.
Figure 3a shows a partial view of a longitudinal section through the preform
according to the
invention during the injection process.
2s Figure 3b shows a partial view of a longitudinal section of the preform
during the injection
process when a partial layer starts to be stripped.
Figure 3c shows a partial view of a longitudinal section of the completed
preform.
3o Figure 3d shows a partial view of a longitudinal section of a further
completed preform
having an additional C-component.
3s
Figure 5 shows a side view, partly in section, of a beverage bottle produced
by stretch blow
moulding.
Figure 6 shows a side view of a preform, partly in section, and
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Figure 7 is a representation of the five-layer structure of the beverage
bottle according to
figure 5.
Figure 1 shows a longitudinal section of the injection mould 2, disclosed in
the publication EP
0596 872 A2, in which a preform 1 is arranged in the mould cavity 4 formed by
the core 3
s and the outer part 6. The heated thermoplastic material is fed into the
opening 5 by an
injection-moulding device 7. The represented preform 1 is a so-called Three-
Five-Layer
preform, since the preform 1 exhibits three layers near the neck; a layer of a
B-component is
surrounded on both sides by one layer each of an A-component. In contrast, the
preform 1
exhibits five layers in the base region, where the innermost layer consists of
a C-component
to enclosed on both sides by the B-component, which is itself enclosed by the
A-component on
the outside.
Figure 2 shows an injection moulding device 7 with an injection nozzle 16,
where the
injection mould 2 is arranged in succession to the aperture 5. In one
preferable arrangement
15 48 or 96 injection moulds 2 are located next each other, in order to
produce 48 or 96
preforms 1 simultaneously pro operation.
The injection nozzle 16 is arranged such, that an A-component of a
thermoplastic material
from a first container and a B-component of a thermoplastic material from a
second
2o container can be injected into the mould cavity 4 through the aperture 5.
To do this, the injection nozzle 16 possesses a first channel 11 in one nozzle
part 13, into
which the A-component is fed via the supply line 14. The channel 11 surrounds
a further
channel 12 coaxially, into which the B-component is fed via the supply line
15.
Channel 12 has a gate 9 at the front, which is situated in the direction of
flow behind a gate
8 belonging to channel 11. A needle 10, movable in the longitudinal direction,
extends
through the gates 8 and 9 and, in the represented position, seals the aperture
5. The needle
can be controllably retracted to open the aperture 5 as well as the gates 8
and 9.
The A-component, a thermoplastic material, particularly PET, is fed in via the
supply line 14.
The B-component, a thermoplastic material suitable for forming a barrier
layer, is fed in via
the supply line 15. This plastic can be PEN, Nylon, EVOH or a polyamide, for
example. The
materials in the supply lines 14 and 15 can also be interchanged.
The preform 1 is formed by the A-component being injected in a limited amount
through the
channel 11 into the mould cavity 4 in one step of the method. At this time the
needle 10 is in
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a partly retracted position. Then, the mould cavity 4 is filled with the A-
component only in
the sprue region. In a main phase, as shown in figure 3a, a limited amount of
a B-material is
injected into the mould cavity 4. However, this injection can occur in
parallel with the
injection of an additional amount of A-component. In this case, the needle 10
is retracted so
s far, that channel 11 as well as channel 12 are open to the mould cavity 4 at
the same time.
The A-component as well as the B-component force their way into the mould
cavity 4,
flowing in the direction of material flow F. At the same time, layers SA,
composed of the A-
component, and a layer SB, composed of the B-component, are formed.
1o In an intermediate phase, as illustrated in figure 3b, the channel 12 is
closed by the needle
10, and the component-A continues to be injected into the mould cavity 4 via
the supply line
14. This A-component is injected into the mould cavity 4 in such a way, that a
part of the
layer SB is stripped or peeled back, as represented in figure 3b. This
stripping takes place
during the injection of the A-component into the mould cavity 4, so that at
the end, the
~s preform exhibits the structure illustrated in Figure 3c. This preform 1
possesses a section E,
running in the direction of material flow F, along which a part of the
thickness of the layer SB
is split off, accompanying the formation of a partial layer TSB. A layer
consisting of A-
component is situated between the layer SB and the partial layer TSB. In this
region the
preform 1 exhibits a five-layer structure.
Figure 3d shows a further design example of a preform 1, in which a new C-
component is
introduced instead of the A-component in the final phase.
In order to bring about the splitting off of a partial layer TSB, the A- or C-
components must
2s be fed in sufficiently quickly, that the B-component is still plastically
deformable during the
introduction of the A- or C- component. In order to create a split off partial
layer, the whole
injection process has to be carried out in a relatively short time, for
example within a filling
time of 3-4 seconds. Additionally, the timing and duration of the injection,
the rapid closing
of the needle 10, the pressure and temperature of the injected thermoplastic
material are
3o particularly important.
Using the knowledge of the technical procedure disclosed here, a specialist is
in the position
to find other suitable times for opening and closing the needle 10, in order
to achieve the
effect, that part of the layer is separated or peeled away. Additionally, the
specialist is in the
3s position to choose the further injection moulding parameters such as
temperature, flow
speed, pressure etc., according to the requirements. All these parameter
settings, which lead
to achieving the effect mentioned previously, are included in this disclosure.
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Figure 6 shows a side view of the complete preform 1, which is only partially
represented in
figure 3c. The preform 1 is a three-five-layer preform design, and has a layer
SB composed of
the B-component, which is surrounded on both sides by a layer SA, composed of
the A-
component. The partial layers, arranged in the transition region of the
preform 1, are also
shown.
The plastic bottle 30, illustrated in figure 5, includes a bottom 31, a side
wall 32, as well as a
transition region 33 arranged between them. The side wall 32 possesses, as
shown
1o magnified, a three-layer structure consisting of a succession of layers SA,
SB, SA. The partial
layers TSB are preferably arranged in the preform 1 in such a way, that, after
the stretch blow
moulding of the preform, these partial layers TSB are situated in the
transition region 33 of
the plastic bottle 30 and there form a five layer structure, having a
succession of layers SA,
SB, SA, SB, SA, as represented magnified in figure 7. The split off partial
layer TSB is generally
is considerably thinner than the layer SB, from which the partial layer TSB
was split off. This
aspect is not represented in figure 7.
The advantages of the preform according to the invention, are immediately
obvious to the
man skilled in the art, and can be especially seen in the fact, that the
thickness of the barrier
20 layer in the base region can be varied by a suitable setting of the
injection cycle parameters.
A significant advantage lies in the improved contact force between
neighbouring layers,
especially due to an increased adhesion and a form-locking connection.
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