US3783071A

US3783071A - Heat-sealable coated metal package and method of making same

Info

Publication number: US3783071A
Application number: US00216232A
Authority: US
Inventors: F Monks
Original assignee: Aluminum Company of America
Current assignee: Howmet Aerospace Inc
Priority date: 1972-01-07
Filing date: 1972-01-07
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01

Abstract

A method of manufacturing a package which comprises; coating substantially all of one surface of a metal web or foil or sheet thickness with a homogenous coating of a heat sealable thermoplastic material having a lubricant constituent; applying said coating material in uniform thickness to at least one first elongated zone of metal web; simultaneously applying the coating material in a uniform thickness greater that the coating thickness in the first elongated zone disposed adjacent opposed transverse sides of the first zone; applying the coating by means of a gravure roll; providing a coating thickness in the second zone of about 0.75 to 4.0 lb./ream and providing a coating thickness in the first zone of about 0.30 to 2.0 lb./ream; and forming a package employing said coated metal web as a body component by heat sealing at least a portion of said second zone to a portion of said metal web or to another package component. A coated container body comprising a metal web provided with such two level coating; a first elongated zone of uniform coating thickness spaced inwardly for opposed transverse edges of the metal web; a second elongated zone of uniform coating thickness positioned intermediate each transverse edge of the metal web and the first elongated zone; the first zone having a width substantially greater than the second zone; and said metal web having at least one said second zone heat sealed to another portion of said metal web or to a separate package component to form said container body.

Description

Jan. 1, 1974 F. E. MONKS 3,783,071

HEAT SEALABLE COATED METAL PACKAGE AND METHOD OF MAKING SAME Original Filed Oct. 5. 1969 FIG. I.

36 FIG. 3. 36 I Ax fi I l 1 1 as I38 1 -3a-- --3aaa as 40 L-40 l -40 I v i M, u l

INVENTOR.

FRANK E. MON/(S 12 20 MBM Attorney United States Patent Int. Cl. B05c 1/16; B2911 23/10 US. Cl. 156217 17 Claims ABSTRACT OF THE DISCLOSURE A method of manufacturing a package which comprises: coating substantially all of one surface of a metal web of foil or sheet thickness with a homogeneous coating of a heat scalable thermoplastic material having a lubricant constituent; applying said coating material in uniform thickness to at least one first elongated zone of the metal Web; simultaneously applying the coating material in a uniform thickness greater than the coating thickness in the first elongated zone to at least one elongated zone disposed adjacent opposed transverse sides of the first zone; applying the coating by means of a gravure roll; providing a coating thickness in the second zone of about 0.75 to 4.0 lb./ream and providing a coating thickness in the first zone of about 0.30 to 2.0 lb./ ream; and forming a package employing said coated metal web as a body component by heat sealing at least a portion of said second zone to a portion of said metal web or to another package component.

A coated container body comprising a metal web provided with such a two level coating; a first elongated zone of uniform coating thickness spaced inwardly from opposed transverse edges of the metal web; a second elongated zone of uniform coating thickness positioned intermediate each transverse edge of the metal web and the first elongated zone; the first zone having a width substantially greater than the second zone; and said metal web having at least one said second zone heat sealed to another portion of said metal web or to a separate package component to form said container body.

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation of application Ser. No. 863,431, filed Oct. 3, 1969, now abandoned.

BACKGROUND OF THE INVENTION (a) Field of the invention This invention relates to a package or container comprising a metal web provided with a heat scalable thermoplastic, lubricating coating of two distinct thicknesses and a method of manufacturing the same.

(b) Description of the prior art stock are generally either heat sealed to each other in a lap seam joint, fin seam joint or folded-over fin seamed. In the lap seam joint the inner surface adjacent one edge is adhesively secured to the outer surface adjacent the other edge. In the fin seam joints, inner surfaces adjacent each edge are adhesively secured to each other. Adjacent 3,783,071 Patented Jan. 1, 1974 edges may also be heat sealed to another portion of the container structure as in the taped butt seam joint systems. See US. Pats. 2,982,457, 3,183,802 and 3,274,905.

In such systems, it has been conventional to provide a coating of uniform thickness over the entire metal web. As greater coating thickness is required for heat sealing than lubrication, this uniform thickness has been generally established on the basis of the need to equal or exceed the minimum thickness effective for heat sealing purposes.

This uniformity of coating thickness while advantageous in terms of simplicity of coating procedure and effective functioning of the coated metal web when introduced into its final environment, be it a wound container or other structure, does not provide for economically advantageous use of coating materials. With economic considerations in packaging materials becoming of increasing consequence, these factors have become more meaningful.

SUMMARY OF THE INVENTION This invention provides a way of obtaining the desired heat sealing and lubricating properties in a coated metal web, while obtaining meaningful economic benefits. In essence, the invention contemplates providing a homogeneous coating material which is continuously coated on a metal web. The coating thickness is varied in accordance with the properties needed in a given zone of the metal.

The method of this invention contemplates applying the coating in a uniform thickness to at least one first elongated zone of the metal web, which will generally be of sheet or foil thickness. Simultaneously, the coating is applied in uniform thickness greater than that of the first zone to at least two second zones. The coating material may be applied by a gravure roll which provides the desired quantities of material to the respective zones. When the metal web is to be employed as liner stock for a spirally or convolutely wound container body, the first zone is positioned between a pair of second zones which are disposed adjacent the transverse edges of the metal web. The coating thickness within the first zone is about 0.30 to 2.0 lb./ream and preferably about 0.30 to 0.60 lb./ ream. In the second zone the coating thickness is about 0.75 to 4.0 lb./ream and preferably about 0.75 to 1.5 lb./ ream.

The coated metal web of this invention is provided with a homogeneous coating of a heat scalable thermoplastic material having a lubricant constituent. The coating substantially continuously covers one surface of the metal Web. A first elongated zone of uniform coating thickness is spaced inwardly from the transverse edges of the metal web. A second elongated zone of uniform coating thickness greater than the first zone coating is disposed intermediate each transverse edge of the metal and the first elongated zone. The first and second zones are parallel to each other and are longitudinally substantially coextensive with the metal web. The first zone has a width substantially greater than each second zone.

It is an object of this invention to provide a method of economically coating a metal web with a homogeneous coating material to provide predetermined variations in coating thickness in order to eliminate superfluous material from certain predetermined areas.

It is another object of this invention to provide a meth- 0d of coating an elongated web of metal foil or sheet with a homogeneous coating material having both heat sealing and lubricating properties with the portions of the metal web intended to be heat sealed having a greater coating thickness than other portions of the metal web.

It is another object of this invention to provide a method of manufacturing foil liner stock for use in the manufacture of spirally or convolutely wound container bodies wherein adequate lubricant is provided over the entire surface of the web and sufficient heat sealing material is provided at the regions to be heat sealed.

It is yet another object of this invention to provide a coated elongated metal web which has been preferentially coated in at least two Zones having different coating thicknesses but uniformly coated within any given zone.

These and other objects of the invention will be more fully understood from the following description of the invention on reference to the illustrations appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic elevational view illustrating a method of coating a metal web in accordance with this invention.

FIG. 2 is a transverse sectional elevation showing a web coated in accordance with this invention oriented with the coated side up.

FIG. 3 shows a fragmentary plan view of a multiple width web coated in accordance with this invention oriented with the coated side up.

FIG. 4 is a fragmentary sectional view showing a portion of a gravure roll overlying a metal web.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more specifically to the drawings, in FIG. 1 there is shown one arrangement of apparatus suitable for use in the method of this invention. An elongated metal web 2 is being unwound from reel 4 and passes through the bite of

rolls

6, 8. Roll 8 is a gravure roll which has a plurality of small cells communicating with the cylindrical surface thereof. As the roll 8 is rotated in the direction indicated, it enters coating material reservoir 10 and coating material is received in the cells of roll 8. Continued rotation of the roll causes the roll surface 12 to progressively pass doctor blade 14 which removes excess coating material and causes the excess, under the influence of gravity, to return to the coating material reservoir 10. Back-up roll 6 maintains effective contact between roll surface 12 and web surface 16 in order to insure uniform coating of the web as it progresses through the coating operation. The coated web may then be conveniently wound on a rewind roll for storage or may be transported directly to fabricating station.

In numerous uses, such as foil packaging, it is desired to establish structural integrity of the final product by means of a heat seal obtained by means of the coating material. In addition, in numerous uses such as in winding container bodies it is necessary to provide a lubricated surface which will minimize frictional resistance and readily pass over the forming mandrel or other equipment. The coating material employed in this invention is a homogeneous heat scalable thermoplastic material having a lubricant constituent. A vinyl or epoxy material provided with a slip coat additive may be employed with suitable results.

I have determined that the coating thickness required for effective lubrication is substantially less than the minimum coating thickness required for effective heat seal bonding. Under conventional practice, a uniform coating having a thickness not less than the minimum thickness required for heat seal bonding would be provided over the entire metal web. The method of this invention produces a coated metal web which provides zones of distinct coating thicknesses which correspond directly to the functional needs of the particular metal web zone. Thus, referring to FIG. 2, it is seen that the metal web 20 is provided with a first coating zone 22 having a first coating thickness suitable for providing the desired lubricating properties. This coating thickness is uniform throughout the longitudinal extent of first zone 22. On each opposed side of the first coating zone 22 is a second coating zone 24 provided with a second coating thickness which is substantially thicker than the coating thickness in first zone 22. Second zone 24 has a coating thickness which is at least as great as the minimum required for effecting heat sealing of the material. While not illustrated, it will be appreciated that additional zones of different coating thickness than

zones

22, 24 could be provided if desired.

The web shown in FIG. 2 would be suitable for use as liner stock in a spirally or convolutely wound container body. The full transverse width of the web 20 is provided with an effective slip coating to permit ready passage over a mandrel. Also, second zone 24 provides sufiicient material to permit heat sealing joinder either by way of lap seam or fin seam to adjacent wraps of liner material or to a different member by means of a butt seam. All of this is accomplished while eliminating the quantity of coating material which would be present in void A were the web 20 to have been coated throughout with a single coating of uniform thickness.

Referring now to FIG. 4, with more specific reference to the gravure roll 8, the structure employed to coat an article in the fashion illustrated in FIG. 2 is there shown. It is seen that the roll surface 12 is provided with two series of cells or

openings

30, 32 which are radially oriented within the roll 8 and communicate with surface 12. These cells are substantially uniformly positioned circumferentially about the roll surface 12. The

cells

30, 32, in the form shown, are generally radially oriented and hav a radially innermost portion which is of paraboloid configurations and an outermost portion has a generally diamond shaped transverse sectional configuration. It will be appreciated that other cell configurations may be effectively employed. The surface portions 12 intermediate adjacent cells are relatively narrow with respect to the width of

cells

30, 32 in order to provide for uniform gap free coating of the web.

It is seen that the cells 30 have substantially greater depth than the cells 32 and, therefore, will pick up a greater quantity of coating material from reservoir 10. As the coating material is released from the

respective cells

30, 32, the portion of the web 20 underlying cells 30 will receive a greater quantity of coating material and establish the coating in second coating zone 24. The lesser quantity of coating material will be provided by cells 32 to first coating zone 22 in order to establish that portion of the coating.

The gravure roll may be a steel roll provided with a chrome finish. While a copper finish might be employed, the chrome finish is more durable and will resist the distortions resulting from roll wear. While in FIG. 4 the

cells

30, 32 have been shown with capacity variations related to cell depth, it will be appreciated that these capacity variations could also be effected through variations in cell width, if desired.

In order to provide for effective performance of the coated metal web, while obtaining the desired economic benefits, the coating thickness within the second zone 24 should be about 1.5 to 3 times that of the coating thickness in the first zone 22. In general, the coating thickness in the first zone is about 0.30 to 2.0 lb./ream and in the second zone is about 0.75 to 4.0 lb./ream. Below these ranges the lubricating and heat sealing properties, respectively, are not sufficient to provide the desired performance. Above these ranges the limited advantages of any increase in desired properties is obtained only at a disproportionately high increase in cost of materials. In one preferred form, the coating thickness within the first zone is about 0.30 to 0.60 lb./ream (a ream is defined generally as 3,000 sq. ft. of surface area to be coated) and the coating within the second zone 24 is about 0.75 to 1.5 lb./ream.

It will be appreciated that coating in accordance with this invention need not be applied to single widths of metal web. Multiple webs might be coated preferentially as provided for herein and ultimately slit into individual widths. Such an arrangement is illustrated generally in FIG. 3, wherein web 34 is provided with a plurality of first coating zones 36 and a plurality of second coating zones 38. The second coating zones intermediate the transverse edges of web 34 are of double width. Severance of the web 34 along cutting lines 40 will produce six individual elongated webs of the type illustrated in FIG. 2.

Referring once more to FIG. 2, it is noted that the heat sealing zone 24, in the form illustrated, is substantially narrower in transverse width than the first coating zone 22, with the latter covering about 70 to 98% of the transverse width of the metal web 20. For example, in liner stock having a first zone 22 with a width of about 4 to 6 inches, each second zone 24 might have a width of about /2 to V2 inch.

It will be appreciated that the metal web for most usages will have a thickness within the sheet or foil classes. In a preferred form, the metal web is made of aluminum foil, having a thickness of about 0.00017 to 0.0059 inch. This foil may or may not have its uncoated surface secured to one or more plies of back-up material. The coating material will cover substantially the entire useful portion of the metal web. The two zones of varying thickness will in the form illustrated be oriented longitudinally with respect to the elongated web and will be parallel to each other as well as being substantially coextensive with the elongated web.

While for purposes of illustration, specific reference has been made herein to the use of the coated metal web of this invention as linear material for wound container bodies, it will be appreciated that the invention in its more general aspects is not so limited. The invention may, for example, be advantageously employed in the manufacture of pouch type packages from foil stock. As the method of fabricating a spirally wound container or pouch, apart from provision and use of the unique coating practices described hereinbefore, forms no part of the invention per se, extended discussion of the same is deemed unnecessary. It will be appreciated, however, that the invention may be employed advantageously in a wide variety of conventional packages and methods of making the same, as well as other desired package structures. In

the use of the metal web established by the practice of this invention, heat sealed joinder of at least a portion of the web to another portion thereof or to another package component will permit the advantageous practice of the invention in fabricating the desired package in an economical fashion.

While for purposes of simplicity of illustration the invention has been described with respect to a web provided with a multiple level coating having elongated zones oriented with the elongated direction of the web, it will be appreciated that such zones may be transversely or angularly oriented with respect to the elongated web. Also, by employing additional coating steps one or more additional coatings may be provided at different orientations from the first multilevel coatings with respect to the web. For example, after applying the coating shown in FIG. 4, portions of web 34 may be provided with additional zones of heat sealing thickness disposed transversely with respect to zones 38. This might be readily accomplished by means of a second gravure roll disposed downstream of the first gravure roll. In this fashion various patterns of heat seal zones may be established, while retaining the economic benefits of this invention in zones which are purely lucricating zones.

It will be appreciated that this invention provides a coated metal web adapted to function effectively with respect to the heat sealing and lubricating properties of its coating, while producing meaningful savings through reduced cost of coating material by means of specific preferential coating thicknesses. All of this may be accomplished with a single pass through the coating apparatus without the need for any subsequent mechanical coating alteration. The coated sheet or foil may then be employed in the same fashion as conventional coated material employing conventional equipment.

Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that numerous variations of the details may be made without departing from the invention as defined in the appended claims.

I claim: 1. A method of manufacturing a package, comprising providing an elongated metal web,

coating substantially all of one surface of said metal web with a continuous homogeneous coating of a heat scalable thermoplastic material having a lubricant constituent, applying said coating in uniform thickness to at least one first elongated zone of said metal web, simultaneously applying said coating in uniform thickness greater than the coating thickness in said first elongated zone to at least one second elongated zone, establishing at least one said second zone immediately adjacent and parallel to said first zone, said first zone being wider than each said second zone, said first and second zones each being of substantially uniform width throughout their longitudinal extent, an forming a package employing said coated metal web as a body component by heat sealing at least a portion of said second zone to a portion of said metal web or to another package component. 2. The method of claim 1 including applying coating material to several of said first zones which are transversely spaced from each other, establishing said second zones on opposed sides of each said first zone, and subsequently longitudinally slitting said metal web generally centrally of the tranverse width of at least one said second zone to provide a number of coated webs each having one said first coated zone. 3. The method of claim 2 including said metal web is aluminum having a thickness of about 0.00017 to 0.0059 inch, and applying said coating material to only one surface of said metal web and substantially completely coating said surface. 4. The method of claim 1 including establishing two said second zones with said second zones disposed adjacent opposed transverse sides of said first zone, applying said coating by means of a gravure roll which has cells of varying depth disposed in adjacent circumferential bands on said roll to provide different quantities of said coating material to said first zone and said second zone, and applying coating material in said second zone in a thickness of about 1.5 to 3 times that of said first zone. 5. The method of claim 4 including establishing each said first zone with a coating thickness of about 0.30 to 0.60 lb./ream, establishing each said second zone with a coating thick ness of about 0.75 to 1.5 lb./ream, and after applying said first and said second zone coatings applying a third zone of coating to establish a coating thickness of about 0.75 to 1.5 lb./ream disposed generally transversely with respect to said first and second coating zones. 6. The method of claim 4 including folding said elongated metal web to superpose two portions thereof with said second zones of one side generally aligned with said second zones of said other side, and establishing a pouch by heat sealing said second zones of one said portion to said second zones of the other said portion. 7. The method of claim 4 including winding said metal web over a mandrel to establish a liner of a composite container by heat sealing one said second zone to an adjacent wrap of said metal web or to an independent package component.

8. The method of claim 4 including establishing at least one third zone having a coating of uniform thickness greater than said first elongated zone,

establishing said third zone generally perpendicular to said second zone, and

establishing a pouch by heat sealing said second zones and said third zone to a superposed package defining web portion which is either a portion of said metal web or a separate metal web.

9. A coated metal container body comprising an elongated metal web having a first surface facing toward the container interior and a second surface facing toward the container exterior,

a homogeneous coating of a heat sealable thermoplastic material having a lubricant constituent substantially continuously covering said first surface of said metal web,

a first elongated zone of uniform coating thickness disposed inwardly from opposed transverse edges of said metal web,

a second elongated zone of uniform coating thickness greater than the thickness of said first elongated zone disposed intermediate each transverse edge of said metal web and said first elongated zone,

said first elongated zone of greater width than each said second zone, and

said metal web having at least one said second zone heat sealed to another portion of said metal web or to a separate package component.

10. The package of claim 9 including said metal web folded to establish a pouch having a first portion of one said second zone heat sealed to an adjacent second portion of the same said second zone and a first portion of another said second zone heat sealed to an adjacent second portion of the said other second zone.

11. The package of claim 9 including said metal web being a liner of a wound container with said second zone heat sealed to an adjacent wrap of said metal web or to a separate package component.

12. The package of claim 9 including said package being a pouch formed by joinder of said first metal web to a second metal web,

said first metal web having at least one third zone having a coating of uniform thickness greater than said first elongated zone,

said third zone disposed generally perpendicular to said second zone, and

said pouch having heat sealed joinder between said second and third zones and said second metal web.

13. The coated metal container body portion of claim 9 including said metal web is aluminum and has a thickness of about 0.00017 to 0.0059 inch,

said coating in said first zone is of substantially uniform tranverse width throughout its length,

said coating in said second zone is substantially uniform in width throughout its length,

said first elongated zone has a coating thickness of about 0.30 to 0.60 lb./ream,

said second elongated zone has a coating thickness of about 0.75 to 1.5 lb./ream, and

said first and second zones are parallel to each other and substantially longitudinally coextensive with said metal web.

14. The coated metal contanier body portion of claim 13 including said metal web is adapted to serve as a liner material for a spirally wound container,

each said second zone having a width of about A; to

/2 inch, and

said first zone having a width of about 4 to 6 inches.

15. The coated metal container body portion of claim 13 including 8 at least one-third zone having a coating thickness of about 0.75 to 1.5 lb./ream, and said third zone positioned generally tranversely with respect to said first and second zones. 16. A method of manufacturing a package, comprising:

providing an elongated metal web;

coating substantially all of one surface of said metal web with a continuous homogeneous coating of a heat sealable thermoplastic material having a lubricant constituent;

applying said coating in uniform thickness to at least one first elongated zone of said metal web comprising from about to 98% of the transverse width of said surface of said web;

simultaneously applying said coating to at least one second elongated zone immediately adjacent and parallel to said first zone in uniform thickness of about 1.5 to 3 times the coating thickness in said first elongated zone, said first and second zones each being of substantially uniform width throughout their longitudinal extent, and

forming a package employing said coated metal web as a body component by heat sealing at least a portion of said second zone to a portion of said metal web or to another package component.

17. A coated metal container body comprising:

an elongated aluminum metal web having a thickness of about 0.00017 to 0.0059 inch, a first surface facing toward the container interior, and a second surface facing toward the container exterior;

a homogeneous coating of a heat sealable thermoplastic material having a lubricant constituent substantially continuously covering said first surface of said metal web;

a first elongated zone of substantially uniform transverse width throughout its length and having a uniform coating thickness of about 0.30 to 0.60 lb./ ream disposed inwardly from opposed tranverse edges of said metal web, and covering about 70 to 98% of the transverse width of said first surface of said metal web;

a second elongated zone of uniform coating thickness of about 0.75 to 1.5 lb./ream and of substantially uniform width throughout its length disposed intermediate each transverse edge of said metal web and said first elongated zone, whereby said coating material provides an effective slip coating over the entire surface of said web and sufiicient material within said second zones to effect a heat seal; and

said metal web having at least one said second zone heat sealed to another portion of said metal web or to a separate package component to form said container body.

References Cited UNITED STATES PATENTS RALPH S. KENDALL, Primary Examiner 0 M. F. ESPOSITO, Assistant Examiner U.S. Cl. X.R.