IE41682B1 - Heat shrinkable composite structure and container with heat shrunk cellular sleeve - Google Patents

Abstract

1526944 Portable containers OWENSILLINOIS Inc 9 Sept 1975 [9 Sept 1974 6 March 1975] 36937/75 Heading B8D [Also in Division B5] A bottle 10 having a rim 14 defining a mouth opening, a bottom 18 and a wall 20 therebetween characterized by having a heat shrunk polymeric sleeve disposed outwardly of the wall and in snug engagement therewith which comprises a first closed cell layer of an olefine polymer and a second non-cellular layer of an olefine polymer in adhering contact with the first layer, either layer of the sleeve being in contact with the bottle.

Description

The present invention relates to heat shrinkable composite structures and to container packages, like bottles and jars, for example glass containers, wherein a wall portion of the container is externally provided with a heat shrunk, thermoplastic cellular sleeve. 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 cellular thermoplastic material in circumferential snug engagement therewith. This member, which is generally in the form of a sleeve, provides excellent characteristics to the package and especially to a package wherein the container is a glass container. 2q Such packages are, for example, described in U.S. Patent No.3,760,968. Typically these packages are produced by first forming a 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 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 sheet and the depth of the skin at one face is at least about 1.2 times greater than the depth at the other face; these surfaces are smooth, i.e. not roughed up to become fibrillated. This sheet can then be appropriately provided with a decorative image and the sheet then Blit along the machine direction of extrusion to provide rectilinear sheets which are then employed in forming the package. These rectilinear sheets 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. - 4 41682 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. Patent No.3,767,496 and reference may also be had to U.S.Patent No.3,802,942 which discloses suitable apparatus for forming such packages.

Of course, the container in addition to having the heat shrunk sleeve positioned therearound, may be pro15 vided with thermoplastic coating materials at various and numerous locations on the container. This concept of employing the heat shrunk sleeve in combination with various types, and locations, of polymeric coatings is described in United States Patent Specification No.3,912,100.

The materials which are taught to be employed to form the rectilinear sheet, which is then formed into the sleeve and heat shrunk, include polyvinyl chloride, polyethylene, polystyrene, copolymers of ethylenically unsaturated carboxylic aoid monomers with ethylene (sold under the trade name 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 cell general purpose polystyrene material. Unfortunately, however, this cellular polystyrene material is possessed of certain deficiencies not the least of which are brittleness, easy tearing, relatively easy fracture, poor glass retention - 5 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 O.S. Patent No.3,802,942 Prom 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 characteristics when the ultimate package includes a glass container which is accidentally broken, 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 and the problem in the prior art is solved. That is, the present invention satisfies a need in the art for providing a sleeve which has the needed balance of properties.

The present invention provides improved packages and methods of forming same, of the type wherein a container, for example a glass container, like a bottle or jar, is provided externally thereof with a heat shrunk, cellular thermoplastic member, and snugly engaging a side wall portion of the container; the improvement resides in employing as the thermoplastic member a composite structure of a closed cell polymeric layer in which the polymer is a polymer of predominantly olefin moieties and, in adhered relationship to the closed cell layer, a non-cellular polymeric layer in which the polymer is a polymer of predominantly olefin moieties.

According to the present invention there is provided a heat shrinkable composite structure in the form of a laminate, which comprises a first closed cell layer comprising a polymer of an olefin in an amount constituting at least 50% by weight of said first layer and a second non-cellular layer comprising a polymer of an olefin in an amount constituting at least 50% by weight of said second layer, said second layer being in adhering contact with said first layer.

The heat shrinkable composite may be in the form of a sleeve either with the closed cell layer disposed outwardly of the non-cellular layer or with the non-cellular layer disposed outwardly of the closed cell layer.

The heat shrinkable composite structure according to the present invention may have a density of 10 to 40 pounds per cubic foot and a thickness of 10¾ to 34 mils. Further, the closed cell layer may have a cell count of 100,000 to 5,000,000 cells per cubic centimeter. - 7 According to the present invention there is further provided an article of manufacture comprising a container having a rim defining a mouth opening at one end thereof, a lower end providing the bottom thereof, and a wall joining the rim and the bottom and which further includes a heat shrunk, polymeric sleeve disposed outwardly of said wall, at least along an axial portion thereof and in snug engagement therewith, and wherein the polymeric sleeve is a composite structure comprising a first closed cell layer predominantly of a polymer of an oldfin and a second non-cellular layer predominantly of a polymer of an olefin in adhering contact with the closed cell layer.

Preferably, the rim is. an annular rim, the wall is an annular wall and the polymeric sleeve is disposed circumferentially outwardly of the wall.

According to the present invention there is still further provided a method for producing articles of manufacture wherein a heat shrinkable polymeric sheet is formed into a sleeve having a major orientation (as hereinafter defined) circumferentially of the sleeve and telescopically located about the sidewall of a container and heat shrunk into snug engagement with the sidewall, and wherein the polymeric sheet is a composite structure comprising a first closed cell layer predominantly of a polymer of an olefin and a second non-cellular layer predominantly of a polymer of an olefin in adhering contact with the first closed cell layer.

As used herein, the term major orientation is intended to refer to the direction in which the greater amount of shrinkage takes place. For example, in the above method the sleeve has a shrinkage in the circumferential direction which is greater than the shrinkage in the axial direction.

In one embodiment the closed cell layer is in 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 surface. That is, the closed cell layer is disposed intermediate the sidewall and said non-cellular layer.

In a further embodiment, the non-cellular layer is in engagement with the wall of the container and the closed cell layer is disposed outwardly of the non-cellular material and has a smooth, glossy non-fibrillated externally disposed surface. That is, the non-cellular layer is disposed intermediate the sidewall and said closed cell layer.

The present invention will now be further described by reference to the accompanying drawing which is a vertical sectional elevation view of an improved package of this invention:According to one embodiment the package is comprised of a container 10 and a heat shrink 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 18 providing a bottom and an annular sidewall 20 joining rim 14 and lower end 18. The container, of course, can be of any configuration and of any material, but as set forth in the drawing, it is exemplified as a glass container. The ultimate package, - 9 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 cell polymeric material in contact with wall 20 and the second layer 24, whioh is of a non-cellular polymeric material, is disposed outwardly of cellular layer 22 and in adhering engagement therewith. The drawing also shows the lower end 18 of container 10 as being 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, olosed cell layer 22 is a closed cell polyethylene and non -cellular layer 24 is also polyethylene.

The polymeric materials respectively and independently contemplated for closed cell layer 22 and noncellular 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 a mixture thereof, e.g. the predominant moiety will be a polymer of ethene, propene, butene, e.g. butene-1, or a mixture thereof, more commonly referred to as a polymer of ethylene, propylene or butylene. This includes homopolymer, copolymers of these olefins with other copolymerizable monoethylenically unsaturated monomers, wherein the olefin in the copolymerization reactants is such that the moiety thereof in the final copolymer, that is the ethylene, propylene or butylene moiety, is at least 60% by weight, and polymeric blends, or admixtures, wherein the resulting polymeric blend is at least 60% by weight of a polymerized olefin moiety, e.g., at least 60% of an ethylene moiety in the blend. The minor amounts, i.e. less than 40% of the other moiety of material employed, are such as to supplement and complement the basic properties 416 8 2 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 formable, 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 5%, e.g. 0.5-5% by weight, of another polymeric moiety. Accordingly the terms polyethylene, polypropylene and polybutylene are respectively defined herein as including copolymers of ethene, propene and butene respectively which contain at least 95% by weight of ethene, propene and butene moieties respectively. 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 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 theresulting copolymer is not more than 15% by weight, preferably less than 10%, for example 2 to 8 weight percent, of the vinyl ester and the remainder, e.g. at least 85% and preferably at least 90% , substantially being polymerized ethylene moieties or other polymerized olefin moieties. Exemplary of the co-monomerio 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 comonomer being such that the resulting copolymer is desirably not more than 35 weight percent, preferably less than 20% and most suitably 10 to 15 weight percent of moieties from those acids and. the remainder, desirably at least 65% preferably at least 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 comonomer will be suoh that the alkyl ester of alpha-beta monoethylenically unsaturated acid moiety of the copolymer will be not more than 25% by weight, desirably less than 20% by weight and quite suitably 12 to 18% by weight with the balance being moieties of a pdlymerized olefin, e.g. at least 75% ethylene, desirably at least 80%. Suitable blends or admixtures which may be employed are blends of one of the aforementioned olefin homopolymers with a copolymer of any of these olefins and such materials as a vinyl ester of an saturated carboxylic acid, an alpha-beta monoethylenically unsaturated carboxylic acid, or an alkyl ester of an alpha-beta monoethylenically unsaturated carboxylic acid. The copolymer used in blending may include a wide range of the amount of co-monomer polymerized with the olefin but generally when this copolymer is 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 will generally be at least 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 carboxylid acid, e.g. an ethylene-vinyl acetate copolymer, the moiety of the blend will be at least 85 weight percent, preferably at least 90%, e.g. 92 to 98%, of an olefin and not more than 15%, preferably less than 10%, e.g. 2 to 8% of a vinyl ester of a saturated carboxylic acid.Similarly the moiety of the olefin will be at least 65 weight percent, preferably at least 80%, e.g. 85 to 90%, and 'the moiety of an alpha-beta monoethylenically unsaturated carboxylic acid will be not more than 35 weight percent, preferably less than 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 moiety of at least 75 weight percent, preferably at least 80%, e.g. 82% to 88%, and not more than 25%, preferably less than 20%, of an alkyl ester of ah alpha-beta monoethylenically unsaturated carboxylic acid moiety, the preferred moieties are ethyl acrylate and ethylene (supplied via the homopolymer and the copolymer) . 416 8 2 The foregoing generally describes the composition of the polymeric portion of the closed cell 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 and/or stabilizers. Generally, excellent results will be obtained by selecting a polymeric composition for closed cell layer 22 which has a melt index of less than 5, for example from 0.1 to 5 and most desirably 0.2 to 1 and the polymeric material selected for the non-cellular layer 24 will have a melt index of less than 10. The preferred material for both the closed ceil layer and the noncellular layer is polyethylene, which includes low density polyethylene, for example polyethylene having a density of less than .925 grams/cc, generally in the range of .910 to .925, high density polyethylene, for example, that having a density greater then .941, typically .941 to .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 is first prepared which is appropriately cut and slit and formed into rectilinear sheets which are then formed into a heat shrinkable sleeve which is then telescopically located about the container to produce the ultimate package. While a sheet 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 den41682 sity 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, November 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 closed cell 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-dellular 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 of substantially uniform width, this sheet 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 of the composite structure must possess heat shrinkable characteristics appropriate heat shrinking in the machine - 15 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., closed cell 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, a physical foaming agent or a chemical foaming agent, more commonly referred to as a chemical blowing agent. Exemplary of the physical foaming agents are the alkenes, such as, for example, pentane, hexane, and heptane, and halogenated materials such as methyl chloride, methylene chloride, trichloroethylene, dichloroethane, dichlorotetrafluoroethane, trichlorofluoromethane, trichlorotrifluoroethane and dichlorodifluoromethane. If desired a conventional nucleator 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 agent employed will be a chemical foaming agent. Generally, in forming the closed cell layer highly desirable results will be obtained following the teachings of U.S. Patent No.3,502,754, i.e. using both a chemical foaming agent and a nucleating agent. Particularly fine results will be obtained by employing 0.3 to 0.4% by weight of azodicarbonamide as the nucleating agent and about ! - 16 1% of N,N' dimethyl-N,Ν'-dinitrosoterephthalamide as the foaming agent, when considering these two materials along with the polymer, charged to the extruder, as constituting a 100% extruder charge. Another suitable system is to use about 0.6% of azodioarbonamide and about 0.3% of ρ,ρ'-oxybis (benzene-sulfonyl 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 foaming agents include, azodicarbonamide (l,l'-azobisformamide), azobis (isobutyronitrile), diazoaminobenzene, N ,N1-dimethyl-N,N'-dinitrosoterephahalamide, N ,N'-dinitrosopentamethylene-tetramine, benzene sulfonyl hydrazide, p-toluene sulfonyl hydrazide, diphenylsulfon-3,3'-disulfonyl hydrazide, and ρ,ρ'-oxybis benzenesulfonyl hydrazide which are well known and commercially available, all of which are used in effective foaming amounts, but generally less than 2% by weight. For example, satisfactory results can be obtained by using 0.5% to 1% by weight of azodicarbonamide .

The rolled stock of the heat shrinkable composite structure of closed cell layer 22 and non-cellular layer 24 which is in adhering engagement with layer 22 is then used in the manner taught in U.S. Patents No.3,767, 496, No.3,802,942, and No,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 cylindrical shapes such as sleeves for ultimate utilization herein. These sleeves are so formed such that the major - 17 41682 heat 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 of the order of at least 50% and the cross direction, or transverse direction, heat shrinkage will be of the order of 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 2:1, and preferably at least 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 ofthe die) of 2:1 or less. The respective flow rates will be routinely adjusted to produce a noncellular layer 24 having a thickness preferably of the order of 1/2 to 4 mils and a cellular layer having a thickness of the order of 10 to 30 mils with the process similarly being adjusted so that the density of the closed cell layer 22 is in the range of 10 to 35 pounds per cubic foot, and preferably less than 30. The sleeve is formed from the sheet - 18 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 above embodiment described in conjunction with the drawing, the sleeve is formed such that the closed cell layer is disposed inwardly of the sleeve and the non-cellular layer is disposed outwardly. The sleeve will be characterized by having a smooth nonfibrillated generally glossy external surface on noncellular layer 24 and the closed cell layer will be characterized by being of a closed cell structure generally having uniform and small voids therein. The sleeve is then telescopically located about the sidewall 20 of a container 10 with closed cell layer 22 being adjacent the wall surface of the container and the non-cellular layer 24 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 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 tie 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 4168 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 of the order of .015-.050 inch g larger than the diameter of the container involved.

While the foregoing sets forth certain embodiments of the present invention it will be apparent that modification is possible which does not depart from the scope of this invention. For example, in a further embodiment of this invention composite sleeve 12 is a two-layer struc ture, the first layer 22 being a non-cellular polymeric material in contact with wall 20 and interposed wall 20 and the second layer 24; layer 24 being of a closed cell structure and being disposed outwardly of non-cellular layer 22 and in adhering engagement therewith.

In a further embodiment, when forming the composite structure by the co-extrusion technique, the extruder supplying the foamable material, intended to form closed cell layer 24, will still preferably feed the die so that this material forms the internal portion of the tubular extrusion and the extruder feeding the material intended to form non-cellular layer 22 will still preferably be fed to the die so as to form the external portion of the tubular shape.

Also , in the further embodiment, the rolled stock of the heat shrinkable composite structure of closed cell layer 24 and non-cellular layer 22, which is in adhering engagement with layer 24, Is preferably first decorated, with the decoration being applied onto closed cell layer 24 and the resulting rolled stock then slit along the machine direction to form strips of the composite structure.

In the further embodiment non-cellular layer 22 is preferably a non-cellular polyethylene and closed cell layer 24 is preferably a polyethylene.

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 two general examples which should even yet more clearly enable those skilled in the art to make and use the present invention.

EXAMPLE 1 A sheet of composite structure was first manufactured using a blown bubble co-extrusion technique. The closed cell and non-cellular layers of the composite structure were each formed of low density polyethylene. The extruder feeding the polymeric material intended to form the closed cell 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 28O°F to 310°F, on the extruder supplying the closed cell forming composition and 245°F to 300°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 from 50 to 70%; the foregoing blow up ratio resulted in a cross, or transverse direction heat shrinkage of the order of 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 noncellular 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 cell layer was of the order of one hundred thousand to 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. - 22 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 traverse, 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.

Patents Nos. 3,767,496 and 3,802,942. The sleeve was then, from beneath a glass container of the type illustrated in the drawing, 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 24O°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 of the order of about .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 55O°F. for a period of about 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 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.

EXAMPLE 2 A sheet of composite structure is first manufactured using a blown bubble co-extrusion technique. The closed cell and non-cellular layers of the composite structure are each formed of low density polyethylene. The extruder feeding the polymeric material intended to form the closed cell layer is fed into the extrusion die so as to form the inner layer of the resulting tubular member; this extruder is 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 includes about 0.3% by weight of azodicarbonamide and about 1% by weight of N,N'-dimethyl-N,N' dinitrosoterephthalamide as the foaming agents. The extruder intended to supply the material to form the noncellular layer is fed to the co-extrusion die so as to form the external surface of the resulting extruded tubular member; the extruder is charged with the same polyethylene and the charge to this extruder also includes 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 28O°F. to 310°F, on the extruder supplying the closed cell forming composition and 245°F to 300°F on the extruder supplying the noncellular forming composition. The extrudate issues from the co-extrusion die as a tubular member which is 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 is also blown onto the external surface of the bubble. This bubble is 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 from 50 to 70%, the foregoing blow up ratio results in a cross, or transverse direction heat shrinkage of the order of 10 to 20%.

The flattened tube is then cut along its edges, and in the machine direction, to produce two superposed composite structures, which structures are then independently wound onto independent winding wheels. This rolled stock is then again slit in the machine direction to provide strips of a heat shrinkable composite structure in which the closed cell layer is adheringly engaged to the non-cellular layer with a smooth, glossy, nonfibrillated surface. The total thickness of this composite structure is about 14.5 mils, the density was about 35 or 36 pounds per cubic foot and the cell count of the closed cell layer is of the order of one hundred thousand to five million cells per cubic centimeter. Generally, satisfactory results will be obtained using a composite structure having a density of the order of 10 to 40 pounds per cubic foot and a thickness of the order of 10% to 34 mils. The foregoing strips are 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 is done in such fashion that the closed cell layer is disposed outwardly, the non-cellular layer is disposed inwardly and the major direction of shrinkage (formerly the machine direction) is in a circumferential, or radial direction of the sleeve and the minor direction of shrinkage (formerly the cross, or transverse , direction of the sheet) is 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. Patents Nos.3,767,496 and 3,802,942. The sleeve is then,from beneath a glass container of the type illustrated in the drawing, 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 is preheated to a temperature of about 24O°F, and, with the telescopic location of the sleeve about the container, an initial heat shrinking takes place with the sleeve taking on an egg shaped configuration which holds it in place on the container. The inside diameter of the sleeve is sized to be of the order of about .031 inch larger than the diameter of the container. The container with the now egg shaped sleeve on it is then put in a heating tunnel maintained at about 55O°F. for a period of about 15 seconds whereby final shrinking results in which the sleeve is brought into a circumferentially enveloping, snug engagement with the wall surface of the container and the lower portion of the sleeve shrinks so as to extend inwardly into the recessed bottom of the container. The resulting article with the composite structure thereon is possessed of a highly aesthetically pleasing appearance and the adhesion of the two layers is excellent. Difficulties with splitting and tearing are significantly alleviated and the sleeve will exhibit excellent resistance to denting and scarring and excellent glass retention characteristics upon bottle breakage. - 26 41682 In the structure of the invention the respective closed cell and non-cellular layers can include suitable adjuvants in addition to polymeric material.

Claims (40)

1. A heat shrinkable composite structure in the form of a laminate, which comprises a first closed cell layer comprising a polymer of an olefin in an amount constituting at least 50% by weight of said first layer and a second non-cellular layer comprising a polymer of an olefin in an amount constituting at least 50% by weight of said second layer, said second layer being in adhering contact with said first layer.

2. A composite structure as claimed in claim 1 having an average density of 10 to 40 pounds per cubic foot and a substantially uniform thickness of 10¾ to 34 mils.

3. A composite structure as claimed in claim 1 or claim 2 wherein said first layer is a closed cell layer predominantly of a polymer of an olefin having 2 to 4 carbon atoms.

4. A composite structure as claimed in any one of claims 1 to 3, wherein said second layer is a non-cellular layer predominantly of a polymer of an olefin having 2 to 4 carbon atoms.

5. A composite structure as claimed in claim 3, wherein said closed cell layer comprises polyethylene (as hereinbefore defined).

6. A composite structure as claimed in claim 4 or claim 5, wherein said non-cellular layer comprises polyethylene (as hereinbefore defined).

7. A composite structure as claimed in any one of claims 1 to 4, wherein at least one of said layers comprises polypropylene (as hereinbefore defined).

8. A composite structure as claimed in any one of claims 1 to 4, wherein at least one of said layers comprises polybutylene.

9. A composite structure as claimed in any one of claims 1 to 6, wherein said non-cellular layer and said closed cell layer respectively comprise a polymeric material 5 of at least 60% by weight of polymerized ethylene moiety.

10. A composite structure as claimed in any one of claims 1 to 4, wherein at least one of said layers is a copolymer having at least 85 weight per cent ethylene moieties and not more than 15 weight percent of moieties of a vinyl 1q ester of a saturated carboxylic acid, both based on the weight of the copolymer.

11. A composite structure as claimed in olaim 10, wherein the said vinyl ester is vinyl acetate.

12. A composite structure as claimed in claim 11, 15 wherein the vinyl acetate is present in an amount of less than 10 weight percent, based on the weight of the copolymer.

13. A composite structure as claimed in any one of claims 1 to 4, wherein at least one of said layers is a copolymer having at least 65 weight percent ethylene moieties 2q and not more than 35 weight percent of alpha-beta monoethylen ically unsaturated carboxylic acid moieties, both based on the weight of the copolymer.

14. A composite structure as claimed in any one of claims 1 to 4, wherein at least one of said layers is a co25 polymer having at least 75 weight percent ethylene moieties and not more than 25 weight percent of moieties of an alkyl ester of an alpha-beta monoethylenically unsaturated carboxylic acid, both based on the weight of the copolymer.

15. A composite structure as claimed in any one of claims 1 to 4, wherein said closed cell polymeric layer comprises an ethylene homopolymer and a copolymer of ethylene with a vinyl ester of a saturated carboxylic 5 acid, and wherein the ethylene moiety of said closed cell polymeric layer is at least 85 weight percent and the vinyl ester of a saturated carboxylic acid moiety of said closed cell polymeric layer, is not more than 15 weight percent, both based on the weight of the ethylene 10 homopolymer and copolymer.

16. A composite structure as claimed in claim 15, wherein said vinyl ester is vinyl acetate.

17. A composite structure as claimed in claim 16, wherein the vinyl acetate is present in an amount of less than 15 10 weight percent, based on the weight of the ethylene homopolymer and copolymer.

18. A composite structure as claimed in any one of claims 15 to 17, wherein said non-cellular layer comprises polyethylene as hereinbefore defined.

19. 20 19. A composite structure as claimed in any one of claims 1 to 4, wherein said closed cell polymeric layer comprises an ethylene homopolymer and a copolymer of ethylene and an alpha-beta monoethylenically unsaturated carboxylic acid, and wherein the ethylene moiety of 25 said closed cell polymeric layer is at least 65 weight percent and the alpha-beta monoethylenically unsaturated carboxylic acid moiety of said closed cell polymeric layer is not more than 35 weight percent, both based on the weight of the ethylene homopolymer and copolymer. 30 20. A composite structure as claimed in any one of claims 1 to 4, wherein said closed cell polymeric layer comprises an ethylene homopolymer and a copolymer of ethylene and an alkyl ester of an alpha-beta monoethylenically unsaturated carboxylic acid, and wherein the ethylene moiety of said closed cell polymeric layer is at least 75 weight perceht and the alkyl ester of an alpha-beta monoethylenically unsaturated carboxylic acid moiety of said closed cell polymeric layer is not more than 25 weight percent, both based on the weight of the ethylene homopolymer and copolymer.

20. 21. A composite structure as claimed in any one of claims 1 to 20, wherein said structure is formed by coextrusion and has a machine direction heat shrinkage of at least 50% and a cross direction heat shrinkage of 20% Or less.

21. 22. A composite structure as claimed in any one of claims 1 to 21, viierein said closed cell layer has a substantially uniform cell count of 100,000 to 5,000,000 cells per cubic centimeter .

22. 23. A composite structure as claimed in any one of claims 1 to 21 which is in the form of a sleeve having a heat shrinkage of at least 50% in the circumferential direction of said sleeve and 20% or less in the axial direction of said sleeve, and wherein said closed cell layer is disposed internally of said non-cellular layer.

23. 24. A composite structure as claimed in any one of claims 1 to 21 which is in the form of a sleeve having a heat shrinkage of at least 50% in the circumferential direction of said sleeve and 20% or less in the axial direction of said sleeve , and wherein said non-cellular layer is disposed internally of said closed cell layer.

24. 25. A composite structure as claimed in claim 22 which is in the form of a sleeve having a heat shrinkage of at least 50% in the circumferential direction of said sleeve and 20% or less in the axial direction of said sleeve and wherein said closed cell layer is disposed internally of said non-cellular layer.

25. 26. A composite structure as claimed in claim 22 which is in the form of a sleeve having a heat shrinkage of at least 50% in the circumferential direction of said sleeve and 20% or less in the axial direction of said sleeve, and wherein said non-cellular layer is disposed internally of said closed cell layer.

26. 27. An article of manufacture comprising a container having a rim defining a mouth opening at one end thereof, a lower end providing a bottom thereof, and a wall joining said rim and said bottom, and further including a heat shrunk, polymeric sleeve disposed outwardly of said wall and in snug engagement therewith, said polymeric sleeve being a composite structure as claimed in any one of claims 1 to 21 and the non-cellular layer being disposed outwardly of the closed cell layer and in adhering contact therewith.

27. 28. An article of manufacture as claimed in claim 27, wherein said rim is an annular rim, said wall is an annular wall, and said polymeric sleeve is disposed circumferentially outwardly of said wall.

28. 29. An article of manufacture comprising a container having a rim defining a mouth opening at one end thereof, a lower end providing a bottom thereof, and a wall joining said rim and said bottom, and further including a heat shrunk, polymeric sleeve disposed outwardly of said wall and in snug engagement therewith, said polymeric sleeve being a composite structure as claimed in any one of claims 1 to 21 and the non-cellular layer being disposed intermediate said closed cell layer and said wall.

29. 30. An article of manufacture as claimed in claim 29, wherein said rim is an annular rim, said wall is an annular wall, and said polymeric sleeve is disposed circumferentially outwardly of said wall.

30. 31. A method wherein a heat shrinkable polymeric sheet is formed into a sleeve having a major orientation (as hereinbefore defined) circumferentially of said sleeve and telescopically located about the sidewall of a container and heat shrunk into snug engagement with said sidewall, arid wherein said polymeric sheet is a composite structure as claimed in any One of claims 1 to 21 with said noncellular layer being disposed outwardly of said closed cell layer.

31. 32. A method wherein a heat shrinkable polymeric sheet is formed into a sleeve having a major orientation (as hereinbefore defined) circumferentially of said sleeve and telescopically located about the sidewall of a container and heat shrunk into snug engagement with said sidewall, and wherein said polymeric sheet is a composite structure as claimed in any one of claims 1 to 21 with said closed cell layer being disposed outwardly of said non-cellular layer.

32. 33. A composite structure as claimed in claim 1 and substantially as hereinbefore described with reference to Example 1.

33. 34. A composite structure as claimed in claim 1 and substantially as hereinbefore described with reference to Example 2.

34. 35. An article of manufacture as claimed in claim 27 and 5 substantially as hereinbefore described with reference to Example 1.

35. 36. An article of manufacture as claimed in claim 29 and substantially as hereinbefore described with reference to Example 2. 10

36. 37. An article of manufacture as claimed in claim 27 and substantially as hereinbefore described with reference to the accompanying drawing.

37. 38. An article of manufacture as claimed in claim 29 and substantially as hereinbefore described with reference 15 to the accompanying drawing.

38. 39. A method as claimed in claim 31 and substantially as hereinbefore desoribed with reference to Example 1.

39.

40. A method as claimed in claim 32 and substantially as hereinbefore described with reference to Example 2.