Multilayer bottle with separable inner layer and method for forming same

A multilayer plastic container for use with either a positive or negative pressure dispensing system, the container having an integral body with an inner layer which readily separates from an outer layer and collapses to dispense a product from the container. The container is formed by blow-molding a multilayer preform, and a bottom aperture is formed in the container for injecting air to separate the inner layer from the outer layer. Preferably, the inner layer is predelaminated during manufacture to facilitate its later separation during use. In the case of vacuum dispening, air inlet vent holes are preferably formed at the points of maximum deformation to prevent collapse of the outer layer.

This invention relates in general to new and useful improvements in 
dispensing containers, and more specifically to a multi-layer plastic 
container having an inner layer which is readily separable from an outer 
layer for independent collapse under positive or negative pressure to 
dispense a product packaged within the container. 
BACKGROUND OF THE INVENTION 
The known liquid dispensing systems for beverages and concentrated beverage 
syrups include a pressurized stainless steel dispenser and a more recently 
developed "bag in a box." The stainless steel dispenser has the advantage 
of being reusable, however, it is very expensive to manufacture and 
somewhat heavy and difficult to handle. The "bag in a box," consisting of 
a separately formed plastic liner in a corrugated paper box, is lighter in 
weight and less expensive to manufacture, but it is not reusable or 
recyclable and is susceptible to leakage if dropped. Although it has been 
suggested to provide a plastic container with a separately formed liner 
which is inserted in the container, this container has proven to be both 
too difficult and expensive to manufacture and as such is not commercially 
feasible. Thus, there exists the need for a dispensing system which will 
overcome the aforementioned problems. 
SUMMARY OF THE INVENTION 
In accordance with this invention, a multi-layer container for a dispensing 
system is provided having an inner layer which readily separates from an 
outer layer when positive or negative pressure is applied, in order to 
dispense a product from the container. The "inner layer" and "outer layer" 
may each be a single layer, or a plurality of layers. The container is 
economical to manufacture, light in weight, easy to handle, can be made of 
recyclable materials, and is "product efficient" in that substantially all 
of the product can be dispensed from the container during use. 
The multi-layer container is blow molded from a multi-layer polymeric 
preform having at least two layers, wherein the inner layer is made of a 
material having substantially no tendency to form primary chemical bonds 
with the outer layer. The polymer of the inner layer is thus not 
substantially melt soluble in the polymer of the outer layer. The only 
bonding which exists between the non-soluble polymer layers is secondary 
hydrogen (i.e., non-chemical) bonding. As such, the disimilar layers may 
be separated through the application of force. 
For pressure dispensing applications, a positive pressure of 20 psi is 
sufficient to initiate and propogate delamination of the inner layer as 
required to dispense a product. 
In a vacuum dispensing application, the negative pressure levels generated 
are generally insufficient to delaminate the internal layers. As such, it 
is necessary to predelaminate the inner layer via pressure, followed by 
reinflation and product filling prior to vacuum dispensing. 
In a preferred three-layer container, a thin boundary layer of a non-melt 
soluble second polymer is provided between innermost and outermost layers 
of a first polymer. Either the innermost layer alone, or the innermost and 
boundary layers together, may collapse to dispense the product. In a 
preferred five-layer construction, a pair of boundary layers are provided 
between innermost, core and outermost layers. Preferably, only the 
innermost layer, or the innermost and adjacent inner boundary layers 
collapse to dispense the product, although it may be desirable in certain 
applications to collapse both the innermost, boundary and core layers. 
Various other combinations of layers are also contemplated. 
In a first embodiment, an aperture is provided in the bottom of the 
container extending through the outer layer and terminating at least at 
the inner layer, so that a continuous inner layer is preserved. Thus, 
positive pressure may be applied externally through the bottom aperture 
against the inner layer for delaminating and collapsing the same. The 
bottom aperture may be formed in the preform or in the container. 
In a second preferred embodiment, a "predelamination step" is provided 
during manufacture of the container wherein the inner layer is separated 
from and collapsed toward the open end of the container, and the inner 
layer is then reexpanded to its original position adjacent the outer 
layer. This facilitates later collapse of the inner layer via vacuum after 
the container has been filled with a product and is ready for use. 
In yet another embodiment, vent holes are formed in the outer layer during 
the predelamination step, to form a container particularly adapted for 
vacuum dispensing. Thus, when a negative pressure is applied to the mouth 
of the container to dispense a product, the vent holes, located in the 
outer layer at the points of maximum deformation, prevent collapse of the 
outer layer along with the inner layer. 
The container of this invention, consisting of a relatively rigid outer 
layer and a separable liner, is useful for dispensing liquid products, 
such as a beverage or concentrated beverage syrup, as well as liquid/solid 
mixtures or slurries. For use with relatively thick (viscous) materials, 
e.g., ketchup, ice cream, etc., a positive pressure dispensing apparatus 
is particularly preferred wherein positive pressure is applied through a 
bottom opening in the outer layer to delaminate and collapse the inner 
layer and dispense the product. For less viscous liquids, e.g., syrup 
concentrate or carbonated soft drinks, a container with vent holes is 
preferred for use in a high-flow-rate vacuum dispensing system. 
"High-flow" is defined as a product removal rate which exceeds the rate at 
which ambient air enters the region of the container between the external 
and collapsing internal layers via the bottom opening. Thus, whereas a 
high-flow-rate vacuum applied at the mouth of the container may tend to 
cause the outer layer to collapse along with the inner layer, resulting in 
container distortion and standing instability, the vent holes prevent such 
collapse of the outer layer. The air inlet vent holes are located at the 
point(s) of maximum deformation and their number depends on the number of 
such equal potential points. 
In a preferred method of manufacture, the container is prepared according 
to the following steps: 
(1) injection mold a multilayer preform with an innermost layer of a first 
thermoplastic resin (e.g., polyethylene terephthalate) and a next 
innermost layer of a boundary material which is substantially non-melt 
soluble in the first resin (e.g., ethylene vinyl alcohol); 
(2) form a hole in the bottom of the preform to a depth not to break 
through the innermost layer; 
(3) reheat the preform and stretch blow mold a container. 
If the preferred vacuum dispensing container is desired, additional steps 
(4)-(6) are provided: 
(4) predelaminate at least the innermost layer by applying mechanical or 
fluid pressure through the bottom hole, whereby the next innermost 
boundary layer may or may not collapse with the innermost layer; 
(5) form air inlet vent holes in the body of the container through the 
non-collapsed outer layer(s); and 
(6) reinflate the collapsed inner layer(s) and inspect for leaks. 
It is further preferred to form the bottom hole in the preform during 
injection molding of the preform, by an injection nozzle gate pin. 
Alternatively, the bottom hole may be formed (after injection molding) by 
drilling or milling. As a still further alternative, the hole may be 
formed in the bottom of the blown container, as opposed to the preform. 
These and other features of the invention will be more particularly 
described by the following detailed description and drawings of certain 
preferred embodiments.

DETAILED DESCRIPTION 
Referring now to the drawings, FIG. 1 illustrates a positive pressure 
liquid dispensing system 10 which utilizes a container 50 of this 
invention. The system includes a base 14 on which the container 50 is 
seated in sealed relation. The base 14 carries a standard 18 which is 
provided at the upper end thereof with an adjustable clamp member 17. The 
clamp member 17 engages a shoulder portion 56 of the container around and 
below a neck portion or thread finish 51, which includes external screw 
threads 53 and a neck flange 54. The thread finish 51 carries a cap 16 
which is provided with a dispensing hose 11. The dispensing hose 11 
terminates in a valved dispenser 12 which, when actuated, permits the 
product from within the container 50 to flow out through a nozzle 13 
thereof. In typical usage, the product within the container 50 will be a 
liquid and the liquid will be dispensed into a glass or other container 
(not shown). 
The base 14 carries an air line 15 through which air or other gas under 
pressure is directed into a bottom opening 57 in a base portion 52 of the 
container. The positive pressure air pushes a separable inner layer 58 of 
the container upwardly towards the mouth 60 of the container to dispense 
the product, while a substantially rigid outer layer 59 of the container 
remains substantially undeformed. The outer layer 59 remains relatively 
rigid due to the internal pressure for dispensing the product, but would 
be applied relatively flexible without such pressure. 
FIG. 2 shows an alternative dispensing system 510 of this invention, 
wherein the product is dispensed under negative pressure (i.e., vacuum). 
In this system, a container 550 is provided which is substantially similar 
to the container 50 of the first embodiment, but which is "predelaminated" 
and includes a plurality of air inlet vent holes 558 in the rigid outer 
layer 557 at the points of maximum deformation, so that a vacuum applied 
to the mouth 560 of the container to dispense the product collapses the 
inner layer 556, but not the outer layer 557. As shown in FIG. 2, 
atmospheric air enters the vent holes 558 to fill the space between the 
inner layer 556 and the outer layer 557, to prevent collapse of the outer 
layer 557. A cap 516 is provided at the mouth 560 of the container, 
connected to a dispensing hose 511, to which a vacuum pump 509 is attached 
for drawing a vacuum at the mouth of the container. 
FIG. 3 illustrates a multilayer preform 20 for forming a container in 
accordance with this invention. The preform 20 includes an elongated 
cylindrical body 22 having a generally hemispherical closed bottom end 24 
and an open top end 25 with a thread finish 26 and neck flange 23. The 
preform 20 has multiple layers, which as shown in FIGS. 3-4, include an 
innermost layer 36, an inner boundary layer 37, a core layer 38, an outer 
boundary layer 39, and an outermost layer 40, in serial relation from the 
inner to the outer surfaces of the preform. In this preferred five-layer 
structure, the innermost and outermost layers 36 and 40 are of 
substantially equal thickness and are formed of the same thermoplastic 
material, preferably polyethylene terephthalate (PET). The central core 
layer 38 is substantially twice the thickness of the innermost and 
outermost layers and is also formed of PET. The inner and outer boundary 
layers 37 and 39 are substantially thinner and are made of a different 
material having little if any primary affinity for (i.e., tendency to 
chemically bond or adhere to) the adjacent layers 36, 38 and 40. A 
preferred boundary material is ethylene vinyl alcohol (EVOH). Other 
suitable materials include polyethylene, polypropylene, nylon (MXD-6), 
etc. 
The preform may be injected molded substantially as described in U.S. Pat. 
No. 4,609,516 entitled Method of Forming Laminated Preforms, issued Sep. 
2, 1986 on an application by Krishnakumar et al., which is hereby 
incorporated by reference in its entirety. The innermost layer 36 and 
outermost layer 40 are injected into an injection mold 61 (see FIG. 4) at 
the same time and are normally formed of the same material and have the 
same thickness. The molten polymer is injected through a nozzle 64 into a 
space between an outer mold member 62 and core 63. A separate material for 
forming the boundary layers 37 and 39 is next injected into the mold. 
Finally, the core layer 38 is injected into the mold, and preferably is of 
the same material as the layers 36 and 40, so as to complete the 
construction of the preform 20. Other core materials such as post-consumer 
(recycled) PET may be utilized as well. 
The five layer preform thus formed includes innermost and outermost layers 
36 and 40, boundary layers 37 and 39, and core layer 38. As described in 
U.S. Pat. No. 4,609,516, the outermost layer 40 may be discontinued at a 
part of the closed end and the core layer 38 may extend externally through 
the outermost layer. Also, the innermost and outermost layers 36 and 40 
may form a common end wall 3 at the upper neck finish end of the preform, 
as shown in FIG. 23. 
In a preferred embodiment, an aperture 21 is formed in the bottom of the 
preform during the injection molding process. As shown in FIGS. 4 and 5, 
this is preferably accomplished by providing the gate pin 65 of the 
injection nozzle 64 with an extension 66, wherein the aperture 21 may be 
automatically formed. At the time the gate pin 65 is moved to the nozzle 
closing position, the last injected plastic material which forms the core 
layer 38 is still molten with the result that the gate pin extension 66 
will enter into the molten plastic material of the outer layers 40, 39, 38 
and 37, terminating at least at the innermost layer 36, to form the 
opening 21. 
In an alternative embodiment shown in FIG. 6, the aperture 21 in the bottom 
outer layers of the preform 20 is formed after the injection molding 
process, by externally machining an opening through the outer layers 40, 
39, 38 and 37 with a flat end drill or mill 68. 
The preform 20 is now ready for blow molding as shown in FIG. 7. The blow 
mold includes a lower mold body 70 whose inner surfaces define the 
expanded body of the container, while a retaining member 73 engages the 
thread finish 26 of the preform above the neck flange 23. A pressurized 
fluid such as air (shown by arrow 72) enters the open mouth 25 of the 
preform to expand the same and form the container 50. 
The container body 50 is a unitary structure having a plurality of layers 
with a closed bottom end 52 and an open top end or mouth 60 (see FIGS. 1, 
7 and 8). The expanded body includes a graduated shoulder portion 56, a 
cylindrical panel portion 55, and a hemispherical base 52, all of which 
have been expanded within the blow mold 70 from portions of the preform 
20. The neck or thread finish 51 (which is in fact the thread finish 26 of 
the preform 20) includes exterior threads 53 and a neck flange 54. Other 
embodiments may include the freestanding containers of the champagne or 
footed Petalite type as shown in U.S. Design Pat. No. 315,869, and U.S. 
Pat. Nos. 3,598,270, 4,785,949 and 5,066,528. 
There is substantially no primary (chemical) bonding between the expanded 
layers of the container, i.e., between the innermost layer 36 of PET and 
the inner boundary layer 37 of EVOH. At most, secondary (hydrogen) bonding 
exists between these layers. As a result, when fluid under pressure is 
directed through a plug 71 into bottom opening 57, as shown in FIG. 8, the 
fluid will cause separation of innermost layer 36 from inner boundary 
layer 37 and collapse of the innermost layer 36 within the container. As 
shown in FIG. 9, innermost layer 36 collapses upwardly towards the open 
mouth 60 of the container, until reaching the substantially thick and 
rigid thread finish portion 51 or upper shoulder where there has been no 
substantial stretching of the plastic materials of the preform 20, and 
wherein the five layers 36-40 remain connected together. Thus, a 
substantially full collapsing of the innermost layer 36 is possible while 
the extreme upper part of the innermost layer 36 remains tightly joined to 
the outer layers 35. 
For pressure dispensing, the initial delamination and collapse of the inner 
layer may occur while the product is in use. However, for either pressure 
or vacuum dispensing where the pressure may not be sufficient to 
delaminate the layers, a predelamination step is performed. Thus, in the 
same manner as shown in FIG. 8, positive pressure is injected through the 
bottom aperture 57 to delaminate and collapse innermost layer 36. For a 
pressure dispensing system, the innermost layer 36 may then be simply 
returned to its starting position by applying pressure through the open 
mouth of the container (see FIG. 11); alternatively a vacuum may be drawn 
through the bottom aperture 57. However, if the container is to be used in 
a vacuum dispensing system with a high rate of flow which may cause 
deformation of the outer layer, a plurality of vent apertures 41 are 
formed during predelamination in the panel section of the outer layers 35, 
where maximum deformation would occur. The vent holes 41 are formed by a 
drill or flat end mill 80, or by touching with a hot point to melt the 
outer layers, while the innermost layer 36 remains collapsed just below 
the neck of the container. Then, as shown in FIG. 11, the innermost layer 
36 is reinflated by injecting positive pressure air through the mouth 60 
of the container, and the container is automatically pressure tested for 
leaks. 
As shown in FIG. 12, the container 50 is then filled with a liquid product 
8 and is ready for dispensing. If desired, for example with a 
hemispherical base portion 52, the container may further include a 
separate base cup 82 into which the base 52 of the body is inserted for 
stabilizing the container. For use in a pressure dispensing system, a 
pressurized air line would be connected to the bottom aperture 57 (see air 
line 15 in FIG. 1). In a vacuum dispensing system, aperture 57 may remain 
open. 
The container may be made from a variety of materials, limited only by the 
requirement that the inner layer (which may include more than one layer) 
be readily separable from the next inner layer. Thus, the innermost, core 
and outermost layers 36, 38 and 40 may be made of any first thermoplastic 
resin, such as the polymers typically used in the packaging industry, 
i.e., polyethylene teraphthalate (PET), polypropylene, polyethylene, 
polyvinyl chloride, polycarbonate and mixtures thereof. The boundary 
layers 37 and 39 are made of a material which is not substantially melt 
soluble in and thus has substantially no tendency to chemically bond or 
adhere to the material of the other layers 36, 38 and 40. The boundary 
layers may be made of any second polymer resin such as ethylene vinyl 
alcohol (EVOH), polyethylene vinyl alcohol (PVOH), nylon (e.g., MXD-6 sold 
by Mitsubishi Corporation, New York, N.Y.), and mixtures thereof. A 
particularly preferred container has innermost, core and outermost layers 
of PET and thin boundary layers of EVOH. 
It is further contemplated that more than one layer may be collapsed as the 
separable liner. Thus, in the five-layer structure previously described, 
the inner boundary layer 37 may collapse along with the innermost layer 
36. Still further, the core layer 38, inner boundary layer 37 and 
innermost layer 36 may collapse as a unit. Still further, outer boundary 
layer 39, core layer 38, inner boundary layer 37 and innermost layer 36 
may collapse as a unit. All that is required is that the remaining outer 
layer or layers be sufficiently rigid, and the collapsible layers 
sufficiently pliable, to permit ready separation between the inner and 
outer layers and noncollapse of the outer layers. 
As a still further embodiment, FIG. 13 shows a five-layer construction 
wherein all of the layers are of substantially equal thickness. The 
structure includes innermost layer 90, inner boundary layer 89, core layer 
88, outer boundary layer 87, and outermost layer 86. In the illustrated 
case, innermost layer 90 separates from inner boundary layer 89 to form 
the collapsible liner. 
In a further embodiment shown in FIG. 14, a seven-layer structure is 
provided wherein innermost layer 98, inner boundary layer 97 and first 
core layer 96 separate as a unit to form the collapsible liner, and the 
central boundary layer 95, second core layer 94, outer boundary layer 93, 
and outermost layer 92 form the rigid outer layers of the container which 
do not collapse. Numerous other alternatives are possible. 
In the case of a container with air inlet vent holes for vacuum dispensing, 
the holes must be properly located to insure that the internal negative 
dispensing pressure will not pull the entire panel wall inwardly during 
vacuum dispensing. The location and number of vent holes depends on the 
deformation characteristics of the container when it is subjected to 
internal negative pressure. The deformation characteristics are a function 
of the container's shape, size, and wall thickness distribution. For 
proper functionality, the vent holes must be located at the point(s) of 
maximum deformation and their number depends on the number of such equal 
potential points. FIGS. 15-22 illustrate the proper placement of the vent 
holes for a number of different container configurations. 
FIG. 15 shows a schematic side elevational view and FIG. 16 a schematic 
cross-sectional view, of a container 100 having a circular panel cross 
section. The container 100 includes a thread flange 102, shoulder section 
104, panel section 106, and base 108. The panel section 106 is the area of 
maximum deformation under negative pressure. For a panel height L and a 
panel diameter D, where L/D&gt;1, three vent holes 110A, B, C are required at 
equally spaced points around the circumference, i.e., 120.degree. apart. 
An inner layer or liner 114 will then separate from an outer sidewall 
layer 116 as shown by dashed lines. As shown in FIGS. 17-18, a container 
200 is provided similar to that shown in FIGS. 15-16, but having a 
circular cross-section with three vertical vacuum panel ribs 201. For a 
panel height L and a panel diameter D, where L/D&gt;1, three vent holes 
210A-C are required at the midpoints between the ribs 201 (again 
120.degree. apart). An inner layer 214 will then separate from an outer 
layer 216 as shown by dashed lines. 
As shown in FIGS. 19-20, a container 300 is provided similar to that shown 
in FIGS. 15-16, but having a square panel cross section. For the case of a 
vertical panel height L, and a vertical panel width a, where L/a&gt;1, four 
vent holes 310A-D are placed at the horizontal and vertical centers of the 
panel sidewalls 312A-D. An inner layer 314 will then separate from an 
outer layer 316 as shown by dashed lines. 
As shown in FIGS. 21-22, a container 400 is provided similar to the 
container of FIGS. 15-16, but having a rectangular panel cross section. 
For a panel height L and panel widths a and b ("a" defining long sidewalls 
412A and B, and "b" defining short sidewalls 413A and B), where L/b&gt;1 and 
b&gt;a, two vent holes 410A, B are required in the longer sidewalls 412A and 
412B. 
It is readily apparent that the minimum number of vent holes can thus be 
determined for a container of any given size or shape. 
Although several preferred embodiments of the invention have been 
specifically illustrated and described herein, it is to be understood that 
variations may be made in the preform construction, materials, the 
container construction and the method of forming the container without 
departing from the spirit and scope of the invention as defined by the 
appended claims.