Note: Descriptions are shown in the official language in which they were submitted.
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MtIL,TI-LAYERED PLASTIC CONTAINER PROVIDING GOOD PRODiJCT DRAINAGE
TECHNICAL FIELD
The present invention relates to multi-layered plastic containers and methods
of
making such containers. More particularly, the present invention relates to a
multi-
layered plastic container having inside surface properties that results in
enhanced product
drainage from the container and the reduction of product residual levels.
BACKGROUND OF THE INVENTION
Typically, viscous liquid or semi-liquid products are packaged in jars,
bottles,
tubes, or other containers, and frequently these containers provide a pour-
spout or other
form of egress for pouring, pumping, or squeezing the product out of the
container.
Polyethylene (PE) resins have been widely used as favorable material for
making
packages, for example squeeze bottles, which contain viscous fluids due to
their good
thermoplasticity, good moldability, and good squeezability. They are also
economic,
which is an important factor for packaging material, as consumers are usually
not willing
to pay a significant upcharge for packaging which will eventually be
discarded. Certain
viscous products have a tendency to stick to or hang-up on the inside surface
of these
containers, so that a certain portion of the product stays in the container as
residue which
is thrown out with the container. This results in wasted product and decreases
the value
the consumer receives from purchasing the product. Therefore, there exists a
need to
provide a product-contacting inner surface on containers and a particular
bottle shape that
prompts the product to drain more readily from the container to decrease the
residual
level.
High product residual levels have been a problem with polyethylene containers,
especially when the products contained in the containers are viscous, e.g.,
oil-in-water
emulsions, water-in-oil emulsions, polymeric gels, foams, surfactant mixtures,
dispersions, colloidal dispersions, suspensions, polymer solutions, polymer
melts,
CONFIRMATION COPY
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products like catsup, mustard, syrup, etc. Typically, such viscous products
are attracted
to the interior surface of polyethylene containers. This attraction leads to a
residual layer
of product remaining on the interior container walls. As a result, a large
percentage of
the product (from 5% to 25%, or more depending on the ambient temperature and
product rheology) cannot be evacuated from the container, and ends up as
waste,
particularly at cooler ambient temperatures when the products become very
thick, almost
to the point of non-flowing. Therefore, an object of the present invention is
to reduce
product residual levels to a level less than about 5% by weight of product
initially in the
container, which is a reduction of at least 35% by weight as compared~to a PE
container
of similar shape, thereby minimizing the amount of wasted product.
SUMMARY OF THE INVENTION
The present invention provides a mufti-layered plastic container for
containing a
viscous product of at least 10,000 cps which provides enhanced product
drainage from
the container. The container comprises an outer polymer layer providing
relative
flexibility and structural support, connected to an inner polymer layer having
an inner
surface that contacts the product and provides for enhanced product drainage
from the
inner surface. The viscous products suitable for use in accordance with the
present
invention include water-in-oil emulsions, oil-in-water emulsions, polymeric
gels, foams,
surfactant mixtures, dispersions, colloidal dispersions, suspensions, polymer
solutions,
polymer melts, and products like catsup, mustard, syrup, etc.
The inner layer may be formed from polyester, ethylene vinyl acetate,
polymethylmethacrylate, a thermoplastic cellulosic, a poiycarbonate,
polyvinylchloride,
polyvinylidene chloride, or Surlyn. The polyester may be either polyethylene
terephthalate or glycol-modified polyethylene terephthalate. The ethylene
vinyl acetate
preferably has a vinyl acetate content of at least about 7.5%, more preferably
at least
about 12%, and most preferably at least about 18%. The grade of Surlyn; which
is an
ionomer manufactured by DuPont, may be selected from, but not limited to,
1650, 1652,
and 9120. The thermoplastic cellulosic may be cellulose acetate, cellulose
acetate
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propionate, or cellulose acetate butyrate. The plastic container may also
include an
adhesive layer and a regrind layer.
To further enhance product drainage from the container, the inner layer should
have a surface roughness of no more than O.Spm.
The present invention is still further directed to a method of draining a
viscous
content from a package comprising the steps of (a) providing a package as
described
above; and (b) draining the viscous content as described above.
These and other features, aspects, and advantages of the present invention
will
become evident to those skilled in the art from a reading of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing out and
distinctly claiming the subject matter regarded as forming the present
invention, it is
believed that the invention will be better understood from the following
description with
reference to the drawings, in which like reference numerals identify like
elements, and
wherein:
FIG. 1 is a front view of a multi-layered plastic container of the present
invention
with a portion of the container's sidewall cut away to illustrate its multi-
layered
construction;
FIG. 1 A is an enlarged partial view of the multi-layered construction shown
in
FIG. 1;
FIG. 2 is an instantaneous cross-sectional view of a container of the present
invention, depicting substantially reduced product residuals; and
FIG. 3 is an instantaneous cross-sectional view of a prior art container,
depicting
substantial residual product.
DETAILED DESCRIPTION OF THE INVENTION
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In the following detailed description of the present invention, the terms
"container", "package", and "bottle" are used synonymously throughout. FIG. 1
is a
front view of a container generally indicated as 10 having a portion of its
body section 12
cut away to more clearly illustrate its laminate construction. In this
particularly preferred
embodiment, and referring to FIG. 1 A, container 10 includes an outer layer 14
comprised, for example, of a polyolefin material such as polyethylene or
polypropylene,
or a mixture thereof, or polyvinylchloride, or polystyrene; these are
traditional container
materials that provide for strength, flexibility, and aesthetic benefits, all
at a relatively
low cost. Also included is an innermost product-contacting layer 16 which is
selected for
its ability to enhance product drainage from the container due to hydrophilic
properties,
to be described in further detail below. This inner layer 16 is made, for
example, of a
polyester material such as polyethylene terephthalate or glycol-modified
polyethylene
terephthalate (hereinafter referred to as "PET or PETG") or of ethylene vinyl
acetate with
a vinyl acetate content of at least about 7.5%, more preferably at least about
12%, and
most preferably at least about 18%. The innermost layer 16 may also be made of
Surlyn
(grades such as 1650, 1652, 9120), polymethylmethacrylate, a thermoplastic
cellulosic
(cellulose acetate, cellulose acetate propionate, or cellulose acetate
butyrate), a
polycarbonate, or polyvinylchloride, or polyvinylidene chloride. Surlyn is a
commercially available ionomer resin from DuPont, typical of those well-known
in the
art, which may be characterized as a metal-containing ionic copolymer obtained
by the
reaction between ethylene or an alpha-olefin with an ethylenically unsaturated
monocarboxylic acid such as acrylic or methacrylic acid wherein at least 10%
of the
carboxylic acid groups are neutralized by an alkali metal ion. Such ionomer
resins are
disclosed in U.S. Pat. No. 3,496,061.
The inner or draining layer 16 can also be made from materials having free
hydroxy groups, such as ethylene vinyl alcohol copolymer, polyethylene
terephthalate,
glycol-modified polyethylene terephthalate, and mixtures thereof. Commercially
available materials useful herein for the draining layer include ethylene
vinyl alcohol
copolymers available with tradenames in the EVAL~ series available from
Kuraray Co.,
Ltd.
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To improve adhesion between these two layers, as well as to increase the drop
strength of finished container 10 by promoting structurally sound pinch-off
welds at the
container's base, an intermediate adhesive or tie layer 18 may optionally be
included.
The need for a tie layer is determined by the materials selected for the inner
and outer
' layers of the container. For example, a tie layer is not required when an
inner layer of
Dupont EVA 3165 is bonded to an HDPE outer layer. However, a tie layer is
required to
adhere a PETG inner layer to an HDPE outer layer. Tie layer resins are
generally
polyolefin-based, interlaminar bonding agents that are used to adhere
incompatible layers
in laminated polymer structures. Choosing a tie resin for a particular
application depends
on various factors such as the chemical nature of the materials being bonded,
their melt
viscosities, processing temperatures, and the type of laminating process and
equipment
being used. Examples of tie resins include the CXA family available from
DuPont
Chemical. Other examples include the Plexar family available from Northern
Petrochemical Company, which include LDPE, MDPE, HDPE, PP, and EVA
copolymers. Examples of particularly preferred materials suitable for tie
layer 18
between a HDPE outer layer and a PET or PETG inner layer include DuPont CXA
1123,
and DuPont CXA 2100 series anhydride-modified ethylene acrylates. An inner
scrap or
regrind layer may also be included; the regrind layer is comprised of a blend
of the three
other layers recovered from the flash removed from the finished container. The
inner,
smoother, product contacting surface 20 possesses hydrophilic properties,
which account
for the product shedding characteristics of the containers of the present
invention.
It is possible to manufacture a container totally from a hydrophilic material
like
polyester (e.g., polyethylene terephthalate (PET) and glycol-modified
polyethylene
terephthalate (PETG)) which has excellent product shedding characteristics,
but such
containers are inherently clear which is undesirable for many products, are
more
expensive to produce due to material and manufacturing costs, and have less
favorable
' "squeezability" characteristics than HDPE containers. Unfortunately, a
container made
from most grades of PET cannot be extrusion blow-molded, because an extrusion
blow-
moiding process can only be used when the polymer has sufficient viscosity,
cohesion,
and tensile strength in its molten state to support its own weight. Molten PET
simply
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does not possess these properties. Extrusion grade PET {EPET) may be blow
molded,
but it can be more costly and difficult to process due to the.necessity of
high processing
temperatures. Thus the need for the multi-layer construction to deliver the
benefits of the
present invention along with the strength, flexibility, cost, and aesthetic
benefits of a
container made mostly of HDPE.
Container 10 is typically made by using an extrusion blow-molding process, for
example as described in U.S. Patent No. 4,846,359 by Baird et al., hereby
incorporated
by reference herein. In such a process, molten thermoplastic material is
extruded through
an extrusion die head to form a parison. A mold is closed around the parison
such that it
pinches the parison's tail to form the container's bottom wall. The parison is
then
expanded by injecting pressurized air into the parison until it comes into
contact with the
mold's interior surface. After the formed container has cooled and solidified,
the mold is
opened and the finished container removed.
Container 10 may also be made by using an injection molding process, for
example as described in U.S. Patent No. 4,923,723 by Collette et al., U.S.
Patent No.
4,743,479 by Nakamura et al., and U.S. Patent No. 4,525,134 by McHenry et al.,
all
hereby incorporated by reference herein. In such a process, typically a
preform is
injection molded, cooled, then subsequently reheated and blow-molded into the
final
container shape and size.
Normally, one skilled in the art would expect that an emulsion, especially one
that is more than 50% water, would have an affinity for a hydrophilic material
like PET;
PETG, or EVA. However, our work has demonstrated surprisingly that the surface
chemistry of these draining inner layers is such that the emulsion drains more
readily
from these materials than it does from HDPE which is hydrophobic. Figure 2
depicts the
minimal residual Ie~cls of product 22 remaining in a container of the present
invention.
Products to be used with the present invention include water-in-oil emulsions,
oil-in-
water emulsions, polymeric gels, surfactant mixtures, dispersions, colloidal
dispersions,
suspensions, foams, polymer solutions, polymer melts, and products like
catsup, mustard,
syrup, etc.
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In addition to the surface chemistry of the inner draining layer, the surface
roughness of the inner layer also effects product drainage. A viscous liquid,
like an
emulsion, will drain more quickly from a smooth surface than from a rough
surface.
Therefore, the container of the present invention comprises a inner layer with
a surface
roughness of no more than O.Spm, preferably no more than 0.2 pm. The surface
roughness as used herein is measured by a Wyko NT-2000 Optical Profiler. The
surface
of blow-molded PET, PETG, or EVA tends to be smoother than blow-molded HDPE;
this is believed to add to the container's overall enhanced ability to reduce
residual levels
and increase product drainage from the container. Due to the flow properties
and
characteristics inherent in PETG, an almost minor-like finish can be obtained
when
PETG is blow molded. On a microscale, blow molded HDPE has a much higher
surface
roughness, and this adds to product hanging up inside containers. For example,
the
surface roughness of a co-extruded PETG inner lining is 0.3 pm, while the
roughness on
the inner surface of a blow molded HDPE container can be greater than 0.8 pm.
To further aid in the evacuation of the viscous product from the container,
the
package should provide the consumer squeezability. To enhance performance and
squeezeability, the cross-section of the prefeaed embodiment is either oval or
circular. If
the cross-section is oval, the aspect ratio should be no more than about
2.5:1, more
preferably 1.5:1. If the cross-section is circular, the diameter should be
less than about
90 mm, preferably 60 mm. A plastic container, particularly a squeeze bottle,
made to
these specifications is easier for the consumer to hold and squeeze with one
hand. In a
preferred embodiment, the mufti-layered plastic container is resiliently
deformable by
external forces during normal use such that it tends to return to its
original, undeformed
shape following application of squeezing forces by a consumer.
The thickness of the package, as well as the layers which construct the
package,
also affect the squeezability and cost of the final package. Generally, the
average
thickness of the wall of the package is less than 1.5 mm, preferably from
about 0.5 mm
to about 1.5 mm. The average thickness ratio of the outer supporting layer to
the inner
draining layer is at least about 5 times, preferably from about 20 : 1 to
about 5 : 1, more
preferably about 10 : 1. When an adhesive layer is provided in-between the
supporting
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layer and the draining layer, the adhesive layer should have a thickness of
less than about
1/10, preferably less than about 1/20, as that of the supporting layer to
provide good
squeezability.
The angle of the shoulder area of the container will also affect the amount of
the
viscous product that can be evacuated from the package. When the squeeze-to-
dispense
package is stored inverted, a sloped shoulder allows more product to drain
towards the
dispensing orifice of the bottle versus a shoulder without a slope. Therefore,
the present
invention incorporates a shoulder angle of at least 5°, more preferably
10°. This will
help the consumer remove more of the contents from the container. To further
help the
consumer direct the flow of product from the container, the cross-sectional
area of the
opening in the bottle finish is less than about 50% of the cross-sectional
area of the body
portion of the container.
While much of the foregoing discussion has focused upon container designs
where product drainage toward the fitment is desirable, such as for inverted-
bottle
dispensing, the principles of the present invention are believed to be equally
applicable to
other container configurations where low product residual levels are
important. For
example, containers could be designed for use with pump dispensing devices
wherein the
lower portion of the container opposite from the fitment facilitates
collection of product
for evacuation via a diptube, such as a container with a converging and/or
conical base
opposite from the fitment. Many suitable bottle designs may prove suitable for
such an
execution, including those with an outer base element to support a generally
conical
bottle wall design.
The packaged product of the present invention comprises a content in contact
with the draining layer, the content having a viscosity of at least about
10,000 cps. The
viscosity as used herein is measured by the Rheometric Scientific dynamic
stress
rheometer model SR-5000 with a parallel plate configuration at 25°C.
The content can be in any form having the above defined viscosity -including
oil-
in-water emulsions, water-in-oil emulsions, polymeric gels, aqueous
dispersions and
suspensions, colloidal dispersions, foams, liquid crystals, polymer solutions,
polymer
melts and can be any kind of product including; cosmetic or beauty care
products for the
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hair and skin such as shampoo, conditioner, treatment, gel, lotion, oil,
cream; laundry and
cleaning products such as dishwashing detergent, liquid hand soap, liquid
laundry
- detergent, stain remover, fabric softener; food products such as salad
dressing, catsup,
mustard, and syrup; health care products such as tooth paste and liquid
medicine; and
other industrial products.
Our testing has resulted in product residual levels of only about 2% for a
viscous
product contained in a squeeze bottle of the present invention, while normal
residual
levels associated with a similarly-sized and shaped HDPE squeeze container at
normal
temperatures average about 7% to 15%. Figure 3 depicts an instantaneous cross-
sectional view of a conventional package 10' made of a single polyethylene
layer 14'
after drainage of a viscous content, such as a content described above, and
shows
substantial residual content 22'. Fig. 2 is an instantaneous cross-sectional
view of a
preferred embodiment of the packaged product of the present invention having
the same
package form, after drainage, depicting significantly reduced residual levels
22 compared
to Fig. 3. Here in, "significantly reduced residuals levels" refers to a
reduction in product
residuals levels of at least 35% compared to a polyethylene package having the
same
package shape. A 35% reduction in residuals will normally yield a residuals
level of less
than about 5% for a typical squeeze bottle. Therefore, the inner polymer layer
of the
container and the product interact synergistically in accordance with the
present
invention to provide a product containment and delivery system yielding a
product
residual level by weight of less than about 5%, more preferably less than
about 4%, still
more preferably less than about 3%, and most preferably about 2%.
The amount of residual product left in a container was measured using the
following test method:
1. Record weight of each assembled package.
2. Fill each sample with a predetermined fill weight and record weight.
3. Allow the package to sit in an "inverted" position for 24 hours at a given
temperature (normally ambient temperature).
4. Dispense the package to approximately 1/3 full and allow package to rest
inverted for at least one hour.
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5. Repeatedly squeeze package until less than five grams of product is
dispensed
per squeeze.
6. Tap the package five times against hard surface and dispense the product.
Repeat the process until package does not dispense a minimal dosage of five
grams.
7. Allow package to rest in an inverted position for 24 hours and repeat steps
5
and then 6. The test is finished when less than five grams is dispensed on the
first
dispensing cycle after a 24 hour waiting period.
8. Record empty weight and calculate the percent residual.
EXAMPLES
The following examples further describe and demonstrate embodiments within
the scope of the present invention. The examples are given solely for the
purpose of
illustration and are not to be construed as limitations of the present
invention, since many
variations thereof are possible without departing from the spirit and scope of
the
invention. Ingredients are identified by chemical or CTFA name, or otherwise
defined
below.
The ingredients herein are expressed by weight percentage of the total
compositions, unless otherwise specified.
EXAMPLES I and II
These examples show packaged hair conditioning products of the present
invention. Such compositions are described in greater detail in published PCT
patent
applications WO 97/31616 and WO 97/31617. The package for EXAMPLES I and II
are
the cylindrical bottles as shown in Fig. 1. The contents are hair conditioning
compositions including the following components and made with the method
following
thereof.
Component (Wt.%) Ex.I Ex. II
Stearamidopropyldimethylamine*1 2.00 1.60
L-Glutamic Acid*2 0.64 0.51
Cetyl Alcohol*3 2.50 2.00
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Stearyl Alcohol*4 4.50 3.60
Silicones*5 4.20 3.36
Benzyl Alcohol 0.40 0.40
EDTA 0.10 0.10
Kathon CG*6 0.03 0.03
Sodium Chloride -- 0.01
Perfume 0.20 0.20
Water 85.43 88.19 -
Water, stearamidopropyldimethylamine and about 50% of L-glutamic acid are
mixed at a temperature above 70°C. Then the fatty alcohols and benzyl
alcohol are
added with agitation. After cooling down below 60°C, the remaining L-
glutamic acid
and other remaining components are added with agitation, then cooled down to
about
30°C. The cylindrical bottles are filled with the hair conditioning
compositions for sale
to consumers.
The cylindrical bottles for Examples I and II have an interior surface
roughness in
the range of from about 0.085~m to about 0.090~.m. The hair conditioning
compositions
of Example I and II have a viscosity in the range of from about 11,000 cps to
about
29,000 cps, and from about 11,000 cps to about 21,000 cps, respectively.
Examples I and II have many advantages. For example, they can provide good
drainage of the hair conditioning composition, good squeezability upon
dispensing, and
retain the shape of the package quickly after squeezing pressure is released.
Definitions
* 1 Stearamidopmpyldimethylamine: AMIDOAMINE MPS obtained by Nikko
*2 L-glutamic acid: L-GLUTAMIC ACiD (cosmetic grade) obtained by Ajinomoto
*3 Cetyl Alcohol: KONOL series obtained by New Japan Chemical
*4 Stearyl Alcohol: KONOL series obtained by New Japan Chemical
*5 Silicones: 85%/15% (weight base) mixture of DS Cyclomethicone and
dimethicone gum (weight average molecular weight of about 400,000 to about
600,000) obtained by General Electric Co.
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*6 Kathon CG: Mixture of methylchloroisothiazoline and methylisothiazoline
obtained by Rohm & Haas Co.
Example III
The percent residual obtained in a monolayer HDPE package was compared to a
package with a HDPE outer layer and an inner layer of Dupont Elvax 3165 and a
package with a HDPE outer layer and an inner layer of Eastman 7673 PETG. The
product used in the test was Olay Moisturizing Body Wash which contains:
water,
sodium laureth sulfate, soybean oil, sodium lauroamphoacetate, PEG-6
caprylic/capric
glycerides, glycerin, cocamide MEA, palm kernel acid, maleated soybean oiI,
fragrances,
citric acid, magnesium sulfate, sodium citrate, polyquaterium-10, sodium
benzoate;
DMDM hydantoin, and disodium EDTA. All three package types were identical in
shape. Ten samples of each package type were tested.
The results of the test are below.
Monolayer HDPE Bottle
Initial Initial Final
Weight Weight Weight Percent
Sample Bottle Bottle
Bottle + + Residual
(g) Product Product
(g) (g)
1 25.75 255.85 43.54 7.7%
2 26.03 258.96 45.16 8.2%
3 ~ 26.15 256.03 43.59 7.6%
4 25.86 256.08 44.50 8. I
S 26.24 259.61 41.56 6.6%
6 26.29 257.08 44.56 7.9%
7 26.29 257.78 48.92 9.8%
8 25.84 256.40 42.42 7.2%
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9 25.72 257.29 45.92 8.7%
25.89 255.97 43.27 7.6%
Average 7, 9%
HDPE Outer Laver w/ Elvax 3165 Inner Layer Bottle
Initial Initial Final
Weight Weight Weight Percent
Sample Bottle Bottle
Bottle + + Residual
(g) Product Product
(g) (g)
1 27.84 248.72 33.01 2.3%
2 27.91 247.89 33.03 2.3%
3 27.20 247.01 31.64 2.0%
4 27.40 248.40 32.18 2.2%
5 27.90 249.39 32.68 2.2%
6 27.67 246.27 32.68 2.3%
7 26.54 248.22 32.44 2.7%
8 27.70 246.26 35.13 3.4%
9 26.43 247.54 30.80 2.0%
10 27.32 246.76 34.07 3.1%
Average 2.4%
HDPE Outer Layer w/ 6763 PETG Inner Leer Bottle
Initial Initial Final
Weight Weight Weight
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Bottle Bottle Percent
SampleBottle + + Residual
(g) Product Product
(g) (g)
1 26.76 255.08 31.70 2.2%
2 26.85 258.02 31.67 2.1%
3 29.02 260.60 34.70 2.5%
4 28.78 258.01 34.44 2.5%
26.79 258.66 32.68 2.5%
6 26.96 258.82 31.57 2.0%
7 28.67 259.68 33.68 2.2%
8 28.29 258.70 33.54 2.3%
-
9 26.87 256.63 32.32 2.4%
28.58 259.49 34.23 2.4%
Average 2.3%
As the data shows, the PETG inner layer and the Elvax 3165 inner layer
significantly reduced the product residuals in the package as compared to the
monolayer
HDPE package.
While several particularly preferred embodiments of the present invention have
been described and illustrated, it will now be obvious to those skilled in the
art that
various changes and modifications can be made thereto without departing from
the spirit
and scope of the invention. Accordingly, the following claims are intended to
embrace
such changes and modifications.
