U.S. patent number RE30,805 [Application Number 06/094,992] was granted by the patent office on 1981-11-24 for container with improved heat shrunk cellular sleeve.
This patent grant is currently assigned to Owens-Illinois, Inc.. Invention is credited to Roger R. Rhoads.
United States Patent |
RE30,805 |
Rhoads |
November 24, 1981 |
Container with improved heat shrunk cellular sleeve
Abstract
There is disclosed herein improved packages, and methods of
forming same, of the type wherein a container, such as for example
a glass container, like a bottle or jar, is provided externally
thereof with a heat shrunk, cellular thermoplastic member,
circumferentially and snugly engaging a sidewall portion of the
container; the improvement resides in employing as the
thermoplastic member a composite structure, or laminate, of a
closed cellular polymeric layer in which the polymer is a polymer
of predominantly olefin moieties and, in adhered relationship to
the closed cellular layer, a non-cellular polymeric layer in which
the polymer is a polymer of predominantly olefin moieties with the
cellular layer being in snug, heat shrunk engagement with the
sidewall portion of the container and the non-cellular layer being
disposed outwardly of the cellular layer.
Inventors: |
Rhoads; Roger R. (Toledo,
OH) |
Assignee: |
Owens-Illinois, Inc. (Toledo,
OH)
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Family
ID: |
25626154 |
Appl.
No.: |
06/094,992 |
Filed: |
November 16, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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504111 |
Sep 9, 1974 |
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Reissue of: |
618988 |
Oct 2, 1975 |
04034131 |
Jul 5, 1977 |
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Current U.S.
Class: |
215/12.2; 156/85;
156/244.11; 215/DIG.6; 264/46.1; 264/230; 264/564; 428/34.9;
428/314.8; 428/318.6; 428/515 |
Current CPC
Class: |
B32B
27/32 (20130101); B65D 23/0878 (20130101); B32B
27/08 (20130101); Y10T 428/249977 (20150401); Y10T
428/1328 (20150115); B32B 2325/00 (20130101); Y10T
428/31909 (20150401); B32B 2327/06 (20130101); B32B
2377/00 (20130101); B32B 2323/04 (20130101); Y10T
428/249988 (20150401); B32B 2375/00 (20130101) |
Current International
Class: |
B65D
23/00 (20060101); B65D 23/08 (20060101); B32B
27/32 (20060101); B65D 001/02 () |
Field of
Search: |
;428/35,304,313,315,320,515 ;156/78,84,85,86,244.11 ;264/46.1,230
;215/DIG.6,12R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Bell; James J.
Attorney, Agent or Firm: Holler; E. J. Click; M. E. Wilson;
D. H.
Parent Case Text
This is a division of application Ser. No. 504,111 filed Sept. 9,
1974.
Claims
I claim:
1. In an article of manufacture comprising a container having a
sidewall and further including a heat shrunk, polymeric seamed
sleeve disposed circumferentially outwardly of said sidewall and in
snug engagement therewith, the improvement wherein said polymeric
sleeve is a composite structure of a closed cellular polyethylene
layer and a non-cellular polyethylene layer in adhering contact
with said cellular layer, .Iadd.said composite structure having
been formed by blown bubble co-extrusion with a blow-up ratio of
about 2:1 or less and having a machine direction heat-shrinkage of
at least 50% and a cross-diameter heat-shrinkage of 20% or less,
.Iaddend.said cellular layer being in engagement with said sidewall
and said non-cellular layer being disposed outwardly of said
cellular layer.
2. The improvement of claim 1 wherein said sleeve consists
essentially of said two layers, has a density of about 10 to about
40 pounds per cubic foot and a thickness of about 101/2 to 34 mils
and wherein said polyethylene of said cellular and said
non-cellular layer being independently selected from the group
consisting of high density, low density, medium density
polyethylene and blends thereof.
3. In an article of manufacture comprising a container having a
sidewall and further including a heat shrunk, polymeric sleeve
disposed circumferentially outwardly of said wall and in snug
engagement therewith, the improvement wherein said polymeric sleeve
is a composite structure consisting essentially of two layers, one
of said layers being a closed cellular polymeric layer, said
polymeric layer being at least 60% by weight of polymerized
moieties of an olefin, selected from the group consisting of
ethylene, propylene, butene-1 or mixtures thereof and the other of
said layers being a non-cellular polymeric layer, said latter
polymeric layer being at least 60% by weight of polymerized
moieties of an olefin selected from the group consisting of
ethylene, propylene, butene-1 or mixtures thereof, .Iadd.said
composite structure having been formed by blown bubble co-extrusion
with a blow-up ratio of about 2:1 or less and having a machine
direction heat-shrinkage of at least 50% and a cross-direction
heat-shrinkage of 20% or less, the heat-shrinkage of said sleeve in
the circumferential direction corresponding to the machine
direction heat shrinkage and the heat shrinkage of said sleeve in
the axial direction corresponding to the cross-direction heat
shrinkage, .Iaddend.and wherein said cellular layer is in
engagement with said sidewall and said non-cellular layer being
disposed outwardly of said cellular layer and in adhering contact
therewith.
4. The improvement of claim 3 wherein one of said layers consists
essentially of polymerized ethylene moieties and polymerized
moieties of a vinyl ester of a saturated carboxylic acid and
wherein said vinyl ester moiety is less than about 15 weight
percent and the ethylene moiety is in excess of about 85 weight
percent.
5. The improvement of claim 4 wherein said vinyl ester is vinyl
acetate.
6. The improvement of claim 5 wherein the moiety of said vinyl
acetate is less than about 10% by weight.
7. The improvement of claim 6 wherein the other of said layers
consists essentially of polyethylene.
8. The improvement of claim 3 wherein one of said layers consists
essentially of polymerized ethylene moieties and polymerized
moieties of an alpha-beta monoethylenically unsaturated carboxylic
acid, wherein the ethylene moiety is at least about 65 weight
percent and wherein the alpha-beta monoethylenically unsaturated
carboxylic acid moiety is less than about 35 weight percent and
wherein said other layer consists essentially of polyethylene.
9. The improvement of claim 3 wherein one of said layers consists
essentially of polymerized ethylene moieties and polymerized
moieties of an alkyl ester of an alpha-beta monoethylenically
unsaturated carboxylic acid, wherein the ethylene moiety is at
least about 75 weight percent and wherein the moiety of the alkyl
ester of an alpha-beta monoethylenically unsaturated carboxylic
acid is less than about 25 weight percent and wherein said other
layer consists essentially of polyethylene.
10. The improvement of claim 3 wherein at least one of said layers
consists essentially of polypropylene.
11. In a method wherein a heat shrinkable, polymeric sheet is
formed into a sleeve having a heat sealed overlapped seam and
having a major heat shrinkage circumferentially of said sleeve and
said sleeve is telescopically located about the sidewall of a
container, and heat shrunk into snug engagement with said sidewall,
the improvement wherein said polymeric sheet is a coextruded
composite structure consisting essentially of two layers, one of
said layers being a closed cellular polyethylene layer and the
other being a non-cellular polyethylene layer in adhering contact
with said cellular polyethylene layer, .Iadd.said composite
structure having been formed by blown bubble co-extrusion with a
blow-up ratio of about 2:1 or less and having a machine direction
heat shrinkage of at least 50% and a cross-direction heat shrinkage
of 20% or less, .Iaddend.said cellular layer being brought into
engagement with said wall and said non-cellular layer being
disposed outwardly of said cellular layer and wherein the
circumferential direction of said sleeve corresponds to the machine
direction of coextrusion.
12. In a method wherein a heat shrinkable polymeric sheet is formed
into a sleeve having a major heat shrinkage circumferentially of
said sleeve and said sleeve is telescopically located about the
sidewall of a container and heat shrunk into snug engagement with
said sidewall, the improvement wherein said polymeric sheet is a
composite structure consisting essentially of two layers, one of
said layers being a closed cellular polymeric layer, said polymeric
layer being at least 60% by weight of polymerized moieties of an
olefin, selected from the group consisting of ethylene, propylene,
butene-1 or mixtures thereof and the other of said layers being a
non-cellular polymeric layer, said latter polymeric layer being in
adhering contact with said cellular layer, said non-cellular
polymeric layer being at least 60% by weight of polymerized
moieties of an olefin selected from the group consisting of
ethylene, propylene, butene-1 or mixtures thereof, .Iadd.said
composite structure having been formed by blown bubble co-extrusion
with a blow-up ratio of about 2:1 or less and having a machine
direction heat shrinkage of at least 50% and a cross-direction heat
shrinkage of 20% or less, the heat shrinkage of said sleeve in the
circumferential direction corresponding to the machine direction
heat shrinkage and the heat shrinkage of said sleeve in the axial
direction corresponding to the cross-direction heat shrinkage,
.Iaddend.and wherein said cellular layer is brought into snug heat
shrunk engagement with said sidewall and said non-cellular layer
being disposed outwardly of said cellular layer.
13. The improvement of claim 12 wherein one of said layers consists
essentially of polymerized ethylene moieties and polymerized
moieties of a vinyl ester of a saturated carboxylic acid and
wherein said vinyl ester moiety is less than about 15 weight
percent and the ethylene moiety is in excess of about 85 weight
percent.
14. The improvement of claim 13 wherein said vinyl ester is vinyl
acetate.
15. The improvement of claim 14 wherein the moiety of said vinyl
acetate is less than about 10%.
16. The improvement of claim 15 wherein the other of said layers
consists essentially of polyethylene.
17. The improvement of claim 12 wherein one of said layers consists
essentially of polymerized ethylene moieties and polymerized
moieties of an alpha-beta monoethylenically unsaturated carboxylic
acid wherein the ethylene moiety is at least about 65 weight
percent and wherein the alpha-beta monoethylenically unsaturated
carboxylic acid moiety is less than about 35 weight percent and
wherein said other layer consists essentially of polyethylene.
18. The improvement of claim 13 wherein one of said layers consists
essentially of polymerized ethylene moieties and polymerized
moieties of an alkyl ester of an alpha-beta monoethylenically
unsaturated carboxylic acid, wherein the ethylene moiety is at
least about 75 weight percent and wherein the moiety of the alkyl
ester of an alpha-beta monoethylenically unsaturated carboxylic
acid is less than about 25 weight percent and wherein said other
layer consists essentially of polyethylene.
19. The improvement of claim 12 wherein at least one of said layers
consists essentially of polypropylene.
20. The improvement of claim 11 wherein said sheet has a density of
about 10 to about 40 pounds per cubic foot and a thickness of about
101/2 to about 34 mils and wherein said polyethylene of said
cellular and said non-cellular layer is independently selected from
the group consisting of high density, low density, medium density
polyethylene and blends thereof.
21. The article of claim 1 wherein said container is a glass
container.
22. The method of claim 12 wherein said container is a glass
container.
Description
The present invention relates to container packages, like bottles
and jars, for example, glass containers and, more particularly,
relates to an improvement in packages of the type wherein a wall
portion of a container is externally and circumferentially,
provided with a heat shrunk thermoplastic cellular member. The
present invention is also directed to an improved method for
forming such packages.
Recently the packaging industry has successfully developed a
package wherein a container, such as, for example, a bottle or jar,
which has an upper rim portion defining a mouth opening thereof and
a lower portion defining the bottom thereof and including an
annular wall joining the rim portion to the bottom portion, is
provided, at least along an axial portion of the wall with a heat
shrunk member of a foamed or cellular thermoplastic material in
circumferential snug engagement therewith. This member, which is
generally in the form of a sleeve, or tubular shape, provides
excellent characteristics to the package and especially to a
package wherein the container is a glass container. Such packages
are, for example, described in U.S. Pat. No. 3,760,968. Typically
these packages are produced by first forming a web, film, or sheet,
of a heat shrinkable, cellular thermoplastic material, by
conventional processing, for example by an extrusion process like a
blown bubble extrusion process. The process is carried out to
provide a heat shrinking characteristic in the sheet, by a
conventional stretching operation, in which the major shrinking, or
orientation or stretching, occurs along the machine direction and
only a minor shrinking occurs along the transverse, or cross,
direction. The sheet, or web, is also provided, by air cooling,
with a skin at each opposed surface of higher density than the
central, or core, portion of the cellular web and the depth of the
skin on one side is at least about 1.2 times greater than the depth
on the other side; these surfaces are smooth, i.e. not roughed up
to become fibrillated. This sheet, or web, can then be
appropriately provided with a decorative image and the sheet then
slit along the machine direction of extrusion to provide
rectilinear films or sheets which are then employed in forming the
package. These rectilinear sheets, or films, are again cut and then
formed into a generally, right cylindrical sleeve with the machine
direction of prior forming being the circumferential, or radial,
direction of the sleeve and the axial dimension of the sleeve being
the previous cross, or transverse, dimension. The reason for this
is to provide a more significant circumferential or radial
shrinkage about the container than an axial shrinkage.
Additionally, the sleeve is formed so that the greater skin depth
side is the interior surface. Typically, the rectilinear sheet is
formed into a sleeve by being brought into contact with a mandrel
and the opposed ends of the rectilinear sheet then sealed to each
other, such as, for example, in an overlapping relationship by the
use of appropriate means, for example a compressing heat mechanism.
The sleeve is then brought into telescopic relation with the
container and positioned or located around a wall portion and heat
shrunk to bring it into an annular snug, compressing, engagement
with the wall portion of a container. After heat shrinking,
therefore, the sleeve is disposed circumferentially outwardly of
the annular sidewall of the container and is in a heat shrunk
condition generally disposed at least along a portion of the axial
dimension of the sidewalls. Typically, when containers are employed
that have a recessed bottom, such as a concave bottom, the heat
shrunk sleeve includes a lower annular portion extending partially
inwardly into the recessed area of the bottom. For further details
as to the method of forming such plastic covered containers
reference may be had to U.S. Pat. No. 3,767,496 and reference may
also be had to U.S. Pat. No. 3,802,942 which discloses suitable
apparatus for forming such packages. The three above-noted patents
are hereby incorporated by reference.
Of course, the container, in addition to having the heat shrunk
member position therearound, may be provided with thermoplastic
coating materials at various and numerous locations on the
container. This concept of employing the heat shrunk member in
combination with various types, and locations, of polymeric
coatings is described in co-pending application, U.S. Ser. No.
372,156, filed June 21, 1973.
The materials which are taught to be employed to form the
rectilinear sheet or film, which is then formed into the sleeve and
heat shrunk, include polyvinyl chloride, polyethylene, polystyrene,
"copolymers of carboxylic acid monomers with ethylene (sold under
the tradename SURLYN)", cellulose esters, for example, cellulose
propionate, butyrate, and acetate, polyamides, and polyurethanes.
From a commercial point of view the material which has been found
to be most suitable to date has been a closed cellular, general
purpose polystyrene material. Unfortunately, however, this cellular
polystyrene material is possessed of certain deficiencies not the
least of which include brittleness, easy tearing, relatively easy
fracture, poor glass retention when a glass container breaks and
susceptibility to denting, scarring and splitting. When one
considers the total process which includes slitting or cutting of
the material this latter problem and the tearing tendency is indeed
quite significant. These deficiencies, of course, are reflected in
consumer acceptance and also in economies for providing the above
packages. The other materials are also possessed of deficiencies.
For example, when a non-cellular polyethylene is employed, because
of its limpness, it will be found that difficulty is encountered in
economically using this material on the equipment disclosed in
incorporated patent U.S. Pat. No. 3,802,942. From a practical point
of view production speeds are seriously handicapped by employing
such a non-cellular polyethylene. Additionally, the use of a
non-cellular polyethylene requires the material to be heavily
pigmented in order to get the desired degree of opacity, which
degree of pigmentation obviously carries with it severe economic
penalties. Similarly, if a cellular polyethylene material is
employed difficulties are likewise encountered; for example, it is
difficult to provide a smooth printable surface on the cellular
polyethylene. Additionally, a cellular polyethylene does not have
the desired glass retention characteristics when the ultimate
package which includes a glass container is broken.
Thus, it will be seen that a problem exists in the above referred
to art and a need exists for providing a sleeve member which has
excellent properties including for example ease of printability,
good flexibility, a lack of undesirable brittleness, good
resistance to fracture, good glass retention, good resistance to
denting, scarring, tearing, and splitting, good melt strength, good
handling characteristics and which does not need to be heavily
pigmented to produce the needed opacity. In accordance with this
invention an improvement is provided with respect to the sleeve
member and the problem in the prior art is solved. That is, the
present invention satisfies a need in the art for providing a
sleeve member which has the needed balance of properties.
Thus, in accordance with one feature of this invention there is
provided an improvement in articles of manufacture comprised of a
container having an annular rim defining a mouth opening at one end
thereof, a lower end providing the bottom thereof, and an annular
wall interposed between the rim and the lower end and which further
includes a heat shrunk, polymeric sleeve disposed circumferentially
outwardly of said wall and in snug engagement therewith.
In accordance with another feature of this invention, there is
provided an improvement in methods for producing articles of
manufacture wherein a heat shrinkable polymeric sheet is formed
into a sleeve having a major orientation or heat shrink
characteristic circumferentially of the sleeve, and wherein the
sleeve is telescopically located about the sidewall of the
container and heat shrunk into engagement with the sidewall.
The improvement in the above-noted method and article essentially
resides in employing a heat shrinkable polymeric sheet, and sleeve,
which is of a composite structure having a layer of a closed
cellular predominantly olefin polymer adhered to a layer of a
non-cellular predominantly olefin polymer wherein the cellular
layer is in, and intended for, engagement with the wall of the
container and the non-cellular layer is disposed outwardly of the
cellular material and has a smooth, glossy non-fibrillated
externally disposed, or exposed, surface.
An improved package of this invention is exemplified in FIG. 1
which is a vertical sectional elevation view.
The package is comprised of a container 10 and a heat shrunk sleeve
of composite structure, generally designated 12. Container 10
includes an upper rim 14 defining a mouth opening 16 of the
container and further includes a lower end, or bottom, 18 and an
annular sidewall 20 interposed rim 14 and lower end 18. The
container, of course, can be of any configuration and of any
materal, but as set forth in the drawings it is exemplified as a
glass container. The ultimate package, of course, will include
closure means (not shown) closing mouth opening 16. Composite
polymeric sleeve 12 is disposed circumferentially outwardly of wall
20 in heat shrunk, snug engagement therewith. Composite sleeve 12,
as indicated, is a two-layer structure, the first layer 22 being a
closed cellular structured polymeric material in contact with wall
20 and the second layer 24, which is of a nonfoamed or non-cellular
polymeric material, is disposed outwardly of cellular layer 22 and
in adhering engagement therewith. FIG. 1 also exemplified a package
in which the lower end 18 of container 10 is recessed, i.e.,
possessed of a lower concave bottom, with sleeve 12 including a
lower annular portion extending partially inwardly into the
recessed area of the bottom. Preferably, cellular layer 22 is a
closed cellular polyethylene and non-cellular layer 24 is also
polyethylene.
The polymeric materials respectively and independently contemplated
for cellular layer 22 and non-cellular layer 24 are predominantly
olefin polymers; that is, each of these polymeric layers will have
as the predominant polymeric moiety a polymer of an olefin,
preferably an olefin having 2-4 carbons, or mixtures thereof, e.g.,
the predominant moiety will be a polymer of ethene, propene,
butene, like butene-1, or mixtures thereof, more commonly referred
to as a polymer of ethylene, propylene or butylene. This includes
homopolymers, copolymers of these olefins with other
copolymerizable monoethylenically unsaturated monomers, wherein the
olefin in the copolymerization is such that the moiety thereof in
the final copolymer, that is the ethylene, propylene or butylene
moiety, is at least about 60% by weight, and polymeric blends, or
admixtures, wherein the resulting polymeric blend is at least about
60% by weight of a polymerized olefin moiety, e.g. at least about
60% of an ethylene moiety in the blend. The minor amounts, i.e.
less than about 40% of the other moiety of material employed, are
such as to supplement and compliment the basic properties of the
olefin polymer and this applies whether other moieties are
introduced by way of a polymer blend, or admixture, or by way of a
copolymerized monomer. These other moieties, whether supplied by
blending another polymer with a homopolymerized olefin, e.g.
homopolymerized ethene, (ethylene homopolymer), or by
copolymerization therewith, should not be such as to significantly
interfere with the foamable, heat sealable, heat shrinkable,
extrudable characteristics of the base olefin polymer and should be
compatible, i.e. miscible with it. Exemplary olefin homopolymers
are ethylene, propylene and butylene homopolymers, with the former
being especially preferred, and blends of these homopolymers. In
passing, when the terminology polyethylene, polypropylene and
polybutylene are used, this contemplates not only strict
homopolymers but also those materials recognized and sold
commercially under those names, even though those materials,
strictly and technically, may be viewed by some to be a blend, or
copolymer, since the materials may include small amounts, typically
less than about 5%, e.g. 0.5-3% by weight, of another polymeric
moiety. For example, polyethylene is sold and recognized by that
name when in fact it may be produced by copolymerization with 1-2
percent by weight of hexene, or butadiene, or may, by analysis,
show several percent, e.g. 3-5% of vinyl acetate moiety; for
practical purposes however these materials consist essentially of
polyethylene. Given the foregoing guidelines those skilled in the
art will routinely select the appropriate copolymerizable
monoethylenically unsaturated monomer, or monomers, which will be
copolymerized with the above olefins for use herein. Thus,
exemplary comonomers, especially with regard to copolymerization
with ethene to form an ethylene copolymer, include vinyl esters of
saturated carboxylic acids, alpha-beta monoethylenically
unsaturated carboxylic acids and alkyl esters of alpha-beta
monoethylenically unsaturated carboxylic acids. Exemplary of highly
preferred vinyl esters of saturated carboxylic acids are those
wherein the carboxylic acid moiety contains from 2 to 4 carbon
atoms, with vinyl acetate being especially highly preferred; when
using these co-monomers it will be desirable to employ them in such
amount that the moiety of the resulting copolymer is less than
about 15% by weight, preferably less than about 10%, for example
about 2 to about 8 weight percent, of the vinyl ester and the
remainder, e.g. at least about 85% and preferably at least 90%,
substantially being polymerized ethylene moieties or polymerized
olefin moieties. Exemplary of the co-monomeric alpha-beta
monoethylenically unsaturated carboxylic acids are those acids
having 3 to 5 carbon atoms, for example acrylic acid, methacrylic
acid, and ethacrylic acid with the amount of this co-monomer being
such that the resulting copolymer is desirably less than about 35
weight percent, preferably less than about 20% and most suitably
about 10 to about 15 weight percent of moieties from those acids
and the remainder, desirably at least about 65%, preferably at
least about 80% being moieties of an olefin, e.g. ethylene
moieties. Exemplary of the alkyl esters of alpha-beta
monoethylenically unsaturated carboxylic acids are those wherein
the acid moiety includes 3 to 5 carbon atoms such as, for example
acrylic, methacrylic, and ethacrylic acid moieties, and wherein the
alkyl moiety contains 1 to 3 carbon atoms, for example methyl,
ethyl, and propyl with an ethylene-ethyl acrylate copolymer being
especially preferred; preferably the amount of this co-monomer will
be such that the alkyl ester of alpha-beta monoethylenically
unsaturated acid moiety of the copolymer will be less than about
25% by weight, desirably less than about 20% by weight and quite
suitably about 12 to about 18% by weight with the balance being
moieties of a polymerized olefin, e.g. at least about 75% ethylene,
desirably at least about 80%. Suitable blends or admixtures which
may be employed are blends of the aforementioned olefin
homopolymers with copolymers of any of these olefins and such
materials as vinyl esters of unsaturated carboxylic acids,
alpha-beta monoethylenically unsaturated carboxylic acids, and
alkyl esters of alpha-beta monoethylenically unsaturated carboxylic
acids. These copolymers used in blending may include a wide range
of the amount of co-monomer polymerized with the olefin but
generally when these copolymers are blended with the olefin
homopolymer, the moiety of polymerized olefin (including moieties
supplied by the homopolymer and moieties supplied in the copolymer)
in the polymer blend, or admixture, will generally be at least
about 60% by weight and, most desirably, the blends ultimately will
have the amounts indicated immediately hereinabove with regard to
the discussion of the use of a copolymer per se. That is, if an
olefin homopolymer, e.g. ethylene homopolymer, is blended with a
copolymer of an olefin and a vinyl ester of a saturated carboxylic
acid, e.g. an ethylene-vinyl acetate copolymer, the moiety of the
blend will be at least about 85 weight percent, preferably at least
about 90%, e.g. about 92 to about 98%, of an olefin polymer and
less than about 15%, preferably less than about 10%, e.g. about 2
to about 8% of a vinyl ester of a saturated carboxylic acid.
Similarly the moiety of an olefin polymer will be at least about 65
weight percent, preferably at least about 80%, e.g. about 85 to
about 90%, and the moiety of an alpha-beta monoethylenically
unsaturated carboxylic acid will be less than about 35 weight
percent, preferably less than about 20%, e.g. 10-15%, in a blend of
an olefin homopolymer with a copolymer of an olefin and such acid.
A blend of an olefin homopolymer with a copolymer of an olefin and
an alkyl ester of an alpha-beta monoethylenically unsaturated
carboxylic acid desirably will show an olefin polymer moiety of at
least about 75 weight percent, preferably at least about 80%, e.g.
about 82% to about 88%, and less than about 25%, preferably less
than about 20%, of an alkyl ester of an alpha-beta
monoethylenically unsaturated carboxylic acid moiety; the preferred
moieties will be ethyl acrylate and ethylene (supplied via the
homopolymer and the copolymer).
The foregoing generally describes the composition of the polymeric
portion of the cellular layer 22 and non-cellular layer 24, it
being understood that the layers need not be of the same polymeric
composition. It will, of course, be apparent that suitable
adjuvants may be present in these layers if desired. Thus, for
example in addition to the polymeric material, the respective
layers can include pigments, stabilizers, and the like. Generally,
excellent results will be obtained by selecting a polymeric
composition for cellular layer 22 which has a melt index or melt
flow of less than 5, for example between about 0.1 to 5 and most
desirably about 0.2 to 1 and the polymeric material selected for
the non-cellular layer 24 will have a melt index or melt flow of
less than about 10. The preferred material for both the cellular
layer and the non-cellular layer is polyethylene, which includes
low density polyethylene, for example polyethylene having a density
of less than 0.925 grams/cc, generally in the range of about 0.910
to about 0.925, high density polyethylene, for example that having
a density greater than about 0.941, typically about 0.941 to about
0.965, medium density polyethylene, and blends thereof.
As previously indicated the present invention is directed to an
improvement in the hereinbefore-described packages wherein, in
producing these packages, a heat shrinkable sheet or film is first
prepared which is appropriately cut and slit and formed into
rectilinear sheets which are then formed into a heat shrinkable
sleeve or tubular member which is then telescopically located about
the container to produce the ultimate package. While a sheet or
film of stock material of the composite structure for use herein
may be formed by various techniques it is generally preferred to
employ extrusion technology. This extrusion technology may take
either of two conventional forms, one of which is extrusion coating
and the other of which is the use of co-extrusion technology. The
latter technique, however, is particularly highly preferred because
of the apparent ability to form lower density composite structures.
In the co-extrusion technique, while a slit die may be employed,
the preferred practice is to employ an extrusion die which is
possessed of an annular, circular opening and the composite
structure is initially formed as a tubular shape by what is
referred to in the art as a "blown bubble" technique. These types
of co-extrusion dies are widely available commercially and an
exemplary die is set forth in SPE Journal, Nov. 1969, Vol. 25, page
20, entitled, "Co-Extrusion of Blown Film Laminates". In this known
co-extrusion technique the circular opening is fed from two
independent extruders and, in this particular instance, the
extruder supplying the foamable material, intended to form cellular
layer 22, preferably will feed the die so that this material forms
the internal portion of the tubular extrusion; the extruder feeding
the material intended to form non-cellular layer 24 will preferably
be fed to the die so as to form the external portion of the tubular
shape. The tubular member issuing from the extruder is blown into a
bubble by conventional "bubble" forming techniques, including air
cooling of the external surface thereof, and is then drawn through
the nip of two juxtaposed rollers wherein the tubular member is
compressed to form a flattened tube. As is well known foaming
occurs, and the cellular structure results, just as the extrudate
leaves the die. This flattened tube is then contacted with cutting
knives which slit the flattened tubular member along its edges
(machine direction) so as to form a sheet or film of substantially
uniform width; this sheet or film, which is at this point actually
a sheet of two superimposed composite structures, for use herein,
is separated into two independent sheets and wound onto independent
winding wheels, which provides the stock of the heat shrinkable
composite structure for use herein. Inasmuch as the sheet or film
of the composite structure must possess heat shrinkable
characteristics the appropriate heat shrinking in the machine
direction of extrusion, which preferably is a major amount and is
greater than the cross direction heat shrinkage, is primarily
provided by the impetus of the rate of drawing of the flattened
tube through the nip of the rolls, and using cooling air on the
exterior of the bubble, and the cross direction shrinkage, which is
less than the machine direction shrinkage, is primarily provided by
the internal air employed in forming the bubble and external
cooling air. This of course is known for forming heat shrinkable
films.
Of course the material fed, or charged, to the extruder intended to
supply the foamable material, i.e., cellular forming composition,
will include effective foaming amounts of suitable foaming or
blowing agents, either with or without nucleators. The foaming
agent may be either of the conventionally recognized classes of
foaming agents to wit, physical foaming agents or chemical foaming
agents, more commonly referred to as chemical blowing agents.
Exemplary of the physical foaming, or blowing agents are the
alkanes, such as, for example, pentane, hexane, and heptane, and
halogenated materals such as methyl chloride, methylene chloride,
trichloroethylene, dichloroethane, dichlorotetrafluoroethane,
trichlorofluoromethane, trichlorotrifluoroethane,
dichlorodifluoromethane and the like. If desired conventional
nucleators such as, for example, a mixture of sodium bicarbonate
and citric acid may be employed along with the physical foaming
agent. Preferably, however, the foaming or blowing agent employed
will be a chemical blowing agent. Generally, in forming the foamed
or closed cellular layer highly desirable results will be obtained
following the teachings of U.S. Pat. No. 3,502,754, i.e., using two
chemical blowing agents, one of which is a foaming agent and the
other of which is a nucleating agent. Particularly fine results
will be obtained by employing about 0.3 to 0.4% by weight of
azodicarbonamide as the nucleating agent and about 1% of
N,N'dimethyl-N,N'dinitrosoterephthalamide as the foaming agent,
when considering these two materials along with the resin, or
polymer, charged to the extruder, as constituting a 100% extruder
charge. Another suitable system is to use about 0.6% of
azodicarbonamide and about 0.3% of p,p'-oxybis (benzenesulfonyl
hydrazide).It will, of course, be apparent that other chemical
foaming agents can similarly be employed. Exemplary of these other
materials are the azo compounds, N-nitroso compounds, and the
sulfonyl hydrazides. Thus, exemplary, suitable chemical blowing
agents include; azodicarbonamide (1,1'-azobisformamide), azobis
(isobutyronitrile), diazoaminobenzene, N,N'-dimethyl-N,
N'-dinitrosoterephthalamide, N,N'-dinitrosopentamethylenetetramine,
benzene sulfonyl hydrazide, p-toluene sulfonyl hydrazide,
diphenylsulfon-3,3'-disulfonyl hydrazide, and p,p'-oxybis
benzenesulfonyl hydrazide which are well known and commercially
available, all of which are used in effective foaming amounts, but
generally less than about 2% by weight. For example satisfactory
results can be obtained by using about 0.5% to about 1% by weight
of azodicarbonamide.
The rolled stock of the heat shrinkable composite structure of
closed cellular layer 22 and non-cellular layer 24 which is in
adhering engagement with layer 22 is then used in the manner taught
in incorporated patents U.S. Pat. Nos. 3,767,496, 3,802,942, and
3,760,968. That is, the rolled stock is preferably first decorated,
with the decoration being applied onto non-cellular layer 24 by
conventional techniques, and the resulting rolled stock then slit
along the machine direction to form strips of the composite
structure. These strips are then in turn again cut, or slit, along
the cross direction and formed into generally cylindrically shapes
such as sleeves or tubular members for ultimate utilization herein.
These sleeves are so formed such that the major shrinkage will be
in the circumferential or radial direction of the sleeve and the
minor heat shrinkage will be in the axial direction of the sleeve.
That is, the sleeve will be so formed such that the machine
direction of extrusion will now become the circumferential, or
radial, direction of the sleeve and the cross direction of
extrusion will now become the axial direction of the sleeve. In
order to provide extremely desirable results the machine direction
heat shrinkage will be on the order of at least about 50% and the
cross direction, or transverse direction, heat shrinkage will be on
the order of about 20% or less. The machine direction shrinkage is
primarily provided and controlled by the drawing rate at the nip of
the two juxtaposed rolls and cooling air applied to the bubble
exterior. The appropriate machine direction heat shrinkage can be
simply provided by providing a machine direction linear velocity at
the nip of the rolls in a ratio of at least about 2:1, and
preferably at least about 3:1, relative to the linear velocity of
the extrudate just as it issues from the die. As is well known the
cross direction shrinkage in a "blown bubble" technique is
primarily provided by the internal air employed to blow the bubble
and external cooling air. To provide the desired cross direction
heat shrinkage characteristic it will be preferred to use a blow up
ratio (diameter of the bubble divided by the diameter of the die of
about 2:1 or less). The respective flow rates will be routinely
adjusted to produce a non-cellular layer 24 having a thickness
preferably on the order of about 1/2 to about 4 mils and a cellular
layer having a thickness on the order of about 10 to about 30 mils
with the process similarly being adjusted so that the density of
the cellular layer 22 is in the range of about 10 to about 35
pounds per cubic foot, and preferably less than 30. The sleeve or
tubular member is formed from the sheet or film of composite
material in a conventional manner but it is preferred to bring the
longitudinal extremities of the sheet into engagement, such as, for
example, by winding around a mandrel, and then to seal these
extremities to each other in the axial direction. Preferably these
longitudinal extremities are brought into an overlapped
relationship and then heat sealed by contact with an electrically,
or other appropriately heated, bar or wire. Of course as indicated
in the drawings the sleeve will be formed such that the cellular
layer will be disposed inwardly of the sleeve and the non-cellular
layer will be disposed outwardly. The sleeve member will be
characterized by having a smooth, non-fibrillated generally glossy
external surface on non-cellular layer 24 and the cellular layer
will be characterized by being of a closed cellular structure
generally having uniform and small voids therein. The sleeve member
is then telescopically located about the sidewall 20 of a container
10 with closed cellular layer being adjacent the wall surface of
the container and the non-cellular layer being disposed outwardly
thereof. Subsequently conventional heating techniques are employed,
for example sufficient heating in an oven for a time and at a
temperature, to allow the heat shrinkable sleeve member to shrink
and contract into snug engagement with the container wall surface.
If the container is of the type generally set forth in the drawing,
i.e., it is possessed of a recessed bottom, upon bringing the
sleeve into telescopic location with the sidewall, the lower
portion of the sleeve will be disposed beneath the lowest extremity
of the container; upon heat shrinking the sleeve will be brought
not only into snug engagement with the wall surface but the lower
portion of the sleeve will shrink so as to extend inwardly into the
recessed bottom of the container. The size of the sleeve which is
employed of course will vary with the specific application but in
general it may be stated that the sleeve will be so formed that its
diameter in its heat shrinkable state will be on the order of about
0.015-0.050 inch larger than the diameter of the container
involved.
While the foregoing describes the present invention with sufficient
particularity to enable those skilled in the art to make and use
same and includes the best modes contemplated in practicing this
invention there, nonetheless, follows a general example which
should even yet more clearly enable those skilled in the art to
make and use the present invention.
A sheet of the composite structure contemplated for use herein was
first manufactured using a "blown bubble" co-extrusion technique.
The cellular and non-cellular layers of the composite structure
were low density polyethylene. The extruder feeding the polymeric
material intended to form the cellular layer was fed into the
extrusion die so as to form the inner layer of the resulting
tubular member; this extruder was charged with low density
polyethylene such as that manufactured by U.S. Industrial Company
(U.S.I.) under their designation NA-289 and the charge likewise
included about 0.75% by weight of azodicarbonamide as the foaming
agent. The extruder intended to supply the material to form the
non-cellular layer was fed to the co-extrusion die so as to form
the external surface of the resulting extruded tubular member; the
extruder was charged with the same polyethylene and the charge to
this extruder also included as an adjuvant about 2% of white
pigment. While various temperatures may be employed in the
respective extruders good results will be obtained by employing
temperatures in the range of 280.degree. to about 310.degree. F. on
the extruder supplying the cellular forming composition and about
245.degree. to about 300.degree. F. on the extruder supplying the
non-cellular forming composition. The extrudate issued from the
co-extrusion die as a tubular member which was then blown into a
bubble using a blow up ratio (diameter of the bubble to the
diameter of the circular die) of about 1.5:1. Cooling air was also
blown onto the external surface of the bubble. This bubble was then
compressed into a flattened tube by passage through the nip of two
juxtaposed rolls with the rolls being run at a sufficient speed
relative to the speed of the material issuing from the extruder so
as to provide a heat shrinkage in the machine direction of
extrusion between about 50 to about 70%; the foregoing blow up
ratio resulted in a cross, or transverse, direction heat shrinkage
on the order of about 10 to 20%. The flattened tube was then cut
along its edges, and in the machine direction, to produce two
superposed composite structures, which structures were then
independently wound onto independent winding wheels. This rolled
stock was then, in turn decorated by conventional techniques, with
the decoration being applied to the non-cellular layer, and the
decorated material, in turn, again slit in the machine direction to
provide strips of a heat shrinkable composite structure in which
the cellular layer was of a closed cell structure and adheringly
engaged to this cellular layer, was the non-cellular layer with a
smooth, glossy, non-fibrillated surface. The total thickness of
this composite structure was about 14.5 mils, the density was about
35 or 36 pounds per cubic foot and the cell count of the closed
cellular layer was on the order of about one hundred thousand to
about five million cells per cubic centimeter. The foregoing
produced strips were then again slit, this time along the cross
direction of formation, and wound around a cylindrically shaped
mandrel with the longitudinal extremities of the material being
brought into overlapping contact with each other and then heat
sealed in overlapped relationship by contact with an electrically
heated bar. The formation of this sleeve was done in such fashion
that the cellular layer is disposed inwardly of the sleeve, the
non-cellular layer is disposed outwardly and the major direction of
shrinkage (formerly the machine direction) was in a
circumferential, or radial, direction of the sleeve and the minor
direction of shrinkage (formerly the cross, or transverse,
direction of the sheet) was the axial direction of the sleeve. The
formation of the sleeve and the formation of the package can
generally be done following the disclosures of U.S. Pat. Nos.
3,767,496 and 3,802,942. The sleeve member was then, from beneath a
glass container of the type illustrated in the drawings,
telescopically located about the sidewall of the container with a
portion, i.e. about the lower 1/2 inch of the sleeve being disposed
beneath the lowest extremity of the container. The container had
been preheated to a temperature of about 240.degree. F. and, with
the telescopic location of the sleeve about the container, an
initial heat shrinking took place with the sleeve taking on an egg
shaped configuration which held it in place on the container. The
inside diameter of the sleeve was sized to be on the order of about
0.031 inch larger than the diameter of the container. The container
with the now egg shaped sleeve on it was then put in a heating
tunnel maintained at about 550.degree. F. for a period of about 15
seconds whereby final shrinking resulted in which the sleeve was
brought into snug engagement with the wall surface of the container
and the lower portion of the sleeve shrunk so as to extend inwardly
into the recessed bottom of the container. The resulting article
with the composite structure thereon was possessed of a highly
aesthetically pleasing, glossy, smooth external surface and the
adhesion of the two layers was excellent. It was observed that
difficulties with splitting and tearing were significantly
alleviated and the sleeve member exhibited excellent resistance to
denting and scarring, showed excellent glass retention
characteristics upon bottle breakage, was highly opaque, was quite
flexible and demonstrated the possession of all needed
properties.
While the foregoing sets forth the present invention it will be
apparent that modification is possible which does not depart from
the spirit and scope of this invention. In the claims which follow
reference to the composition of the respective cellular and
non-cellular layers is made to the polymeric material only. It, of
course, being understood that the respective layers can include
suitable adjuvants.
* * * * *