CA1159759A

CA1159759A - Composite material for container packaging

Info

Publication number: CA1159759A
Application number: CA000340245A
Authority: CA
Inventors: Albert D. Peer, Jr.
Original assignee: Coors Container Co
Current assignee: Coors Container Co
Priority date: 1978-11-20
Filing date: 1979-11-20
Publication date: 1984-01-03
Also published as: ZA796090B; EP0011274A1; DE2967487D1; AU5280679A; US4254173A; AU531635B2; EP0011274B1; JPH0414207Y2; ATE14403T1; JPS5590354A; JPS6397540U

Abstract

ABSTRACT OF THE DISCLOSURE
A container packaging material for use in six pack can wraps, six pack bottle carriers, twelve pack carriers, etc, comprising a composite of a paper material laminated to a plastic film. The plastic film provides tear resistance to the composite, so that paper material may be used which has a tear resistance less than that of other packaging paper materials. The reduced tear resistance allows the use of paper having a lower caliper, basis weight, and, therefore, cost than conventional container packaging material. Natural kraft paper and recycled paper of 12-16 point caliper are preferred for use with the present composite. The plastic film may be .25-2 milk thick and is preferably formed of polyethylene terphthalate, polyethylene, polyvinylchloride, poly-propylene, or cellophane. The preferred films are transparent and permit reverse printing on their inner surface to provide abrasion resistant decoration visible through the film. Adhesives are used to bond the film to the paper and are selected to be compatible with the film used. The film may be metallized to produce a foil effect or may be strengthened by radiation treatment.

Description

~ ~15S~75~

COMPOSITE MATERIAL FOR CONTAINER PACKAGING
The present invention relates to container packaging and more particularly to sheet material for secondary container packaging.
The term "secondary container packaging" as generally understood in the industry and as used herein refers to packaging used in conjunction with primary containers, such as cans or bottles, which contain the ultimate product, such as beer or other beverages.
Secondary container packaging includes container wraps which surround and support the containers, basket bottle caXriers having bottom and side supports for the containers and an upwardly extending handle, 12-pack rectangular carriers completely enclosing the containers, and labels - 15 for application to the containers. Most secondary container packaging is made of paper, or paperboard, typically so-called carton or carrier board. Carrier board is specifically manufactured to be used for secondary container packaging. High strength is desired, ~so the board is usually produced from virgin, strong fiber and contains chemical additives to resist moisture. A smooth white surface is then coated on the carrier board with a white clay-titanium dioxide-latex mixture. The white surface is added to permit decoration 25- of the naturally brown, rough surface of the carrier board.
In some cases, as in the secondary container package described in U.S~ Patent No. 3,603,501, a white outer surface is provided through the lamination of an , :::
~ Ca~e~ ;CCC 78-11 ~ 59759 outer thin layer of high-quality label paper to a thicker backing material. Plastic is also used in some secondary container applications, such as in a bottle carrier formed from p~stic sheet described in U.S. Patent No. 3,815,947, and in webs of plastic rings fitted around the necks of beverage cans as described, for example, in U.S. Patent No. 3,086,651.
The main objectives of secondary container packing are shipping and handling strength and attractive consumer appearance. The two key aspects of packaging strength are tensile load strength, relating to the resistance of the material to diametrically opposed forces and tear strength, relating to the internal resi~tance of the material to tearing. Since the consumer purchages the packaging only incidentally to the container contents, these objectives must be met within the overriding criterion of cost.
According to the present invention there is provided a container packaging material including a paper material having an internal tearing resistance less than that required for said container packaging material, and a plastic film laminated to said paper material and having a tensile load less than that required for ~aid container packaging material, wherein the paper material provides at least 85% of said tensile load and the plastic film provides at least 28% of the tearing resistance.

5,``1, .'1 .4 .
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llS9759 According to a further aspect of the invention there is provided a container packaging label material including a paper material having an internal tearing resistance less than that required for said container packaging material, and a plastic film laminated to said paper material and having a tensile load less than that required for said container packaging material, said paper material providing at least 85%
of said tensile load and the plastic film providing at least 28~ of the tearing resistance.
According to a still further aspect of the invention there is provided a method of manufacturing packaging material for a container package comprising providing a web of a paper material and a web of plastic film, said paper material providing at least 85~ of the tensile load of the container package and said plastic film providing at least 28~ of the tearing resistance : of said container package, printing on a first surface of said plastic film then applying an adhesive to said first surface of said plastic film, pressing said first surface of said plastic film into intimate contact : with a first surface of said paper material to form a web of composite material, and forming said web of composite material into said container package.
The present invention provides a secondary container.packaging material having an improved strength ` and appearance at a lower cost than conventional ~, .

' ' ` , `" ' '.

~15975~

-2b-packaging material. This is done by laminating a paper material, such as kraft paper or recycled board, having an internal tearing resistance less than that required for the secondary container packaging material to a transparent film material having a tensile load less than that required for the secondary packaging material. The internal tearing resistance of the plastic film combines with the tensile load of the paper to create a composite material with strength properties exceeding those cost-comparable grades of either material alone. Furthermore, by reverse printing on a plastic film, an attractive, glossy appearance can be created. The film also protects the printed material from abrasion damage during handling. The film may be strengthened by radiation treatment.
The selection of specific paper materials and plastic films for the present composite will depend on . ' ; . .' :
- ~ ~

1~59759 cost and end use. In general, the preferred paper material i~ unbleached kraft paper or recycled paper of 12 to 16 point thickness. The preferred plastic film is extruded polypropylene or polyethylene. The preferred adhesive i8 extruded polyethylene. In the preferred embodiment, the present secondary container packaging material i8 formed into a 6-pack can wrap for 12 oz.
beverage cansO Alternative embodiments include a 6-pack can wrap for 16 02o beverage can~; a basket carrier for 12 oz. bottles; a 12-pack carrier for cans or bottles or an 8-pack carrier for cans or bottles; and a bottle label for various bottle 8ize~. The present procQss includes providing a web of paper material having an internal tearing resistance le~s than that required for a particular ~econdary container packaging application;
providing a web of plastic film having a tensile load less than that required for the secondary container pa¢kaging application; printing on a first surface of the plaetic film; applying an adhesive to the first surface of the pla~tic film; pressing the fir~t surface of the film into intimate contact with the web of paper material to form a web of composite material; and forming the composite material into a ~econdary container package.
Fig, 1 i~ a diagrammatic representation of the process of forming the composite material of the present invention;
Fig. 2 is an enlarged side view of the composite material of the present invention; and FigO 3 is a per~pective view of a secondary container packaging application of the composite material of the present invention.
Referring now to Figs. l and 2, the composits 10 i8 formed in a continuous web from a web of paper material 12 and a web of plastic film 14 which are joined in a laminating apparatus 16. From the laminating apparatus 16, the compo~ite is formed into a secondary container package in apparatus 18 for scoring, cutting, ,..~

. ~ .

ll~g~59 and folding the material.
Prior to entering the laminating apparatus 16, the plastic film 14 is pretreated in a radiation apparatus 24, decorated with a printed layer 20 in a conventional printing press 26, and coated with adhesive 22 to secure the film to the paper.
The radia~ion pretreatment unit 24 strengthens the plastic film by crosslinking polymer chains in the film to permit the use of thinner films in the composite material. Although the plastic film may ~e treated at any stage of the present process, initial radiation pretreatment improves the material handling properties of the plastic film during subsequent printing and laminating steps. The preferred pretreatment unit is of the type described in Cleland et al. U.S. Patent No.
4,079,328. The radiation pretreatment unit, as described therein, is an electron accelerator having a number of cathodes arranged in parallel lines above a series of elongate~ electron windows. The material to be treated is moved in a continuous web transverse to the electron windows and receives a uniform exposure to a preselected dose of ionizing radiation. Radiation pretreatment is preferred in the present process for use with polyethylene films. Radiation pretreatment is not to be used with certain films such as those formed of polymers with tw~
hydrogen atoms substituted on the same carbon atom, which are known to deteriorate when irradiated.
After pretreatment, the plastic film is collected in a roll 30 for further handling. From the roll 30, the web of plastic film is fed to a printing pxess 26 for applying decoration to a first surface 32 Qf the film. The printing may be carried out on a con~entional printing press of the type used in printing paper, such as a rotogravure press. The printing may be carried out in one Qr more successive steps and may '~

.
.. , .

` 1~597S9 be either continuous or discontinuous, although a continuous layer o~ printing i~ pr~f~rred in that it ~erves to maQk the na~ural brown color of the underlying paper material 12. Although conventional inks and dyes are generally considerea unsa~isfactory for printing 3mooth plastic surfaces due to the ease with which such inks could be lifted or rubbed off, such co~siderations are not critical to the present process, in that the printed layer i8 printed in reverse on the surface of the plastic film facing the paper material and i8 protected from abrasion by the paper and the pla~tic fiim. In general, conventional inks are sQlected which are compatible with ~he film used. The preferred printing process employs polyamide inks on a polyethylene film. Specialized inks and printing techniques involving solvent- or heat-softening of the film could also be use~
in the printing step.
After printing, the fir~t surface 32 of the plastic film may be metalllzed. A metalliz0r, as i~ known in the art, comprises a high vacuum ¢ham~er through which a moving web of plastic film is pa~sed. In the vacuum chamber, a thin, uniform layer of a coating metal iB
aeposited on one or both surface~ of tho moving web.
The motal typically used is aluminum, although copper, silver, and gold can also be used in the proces~. Tho metal i8 vaporized in the high vacuum chamber and the metal ~ap~r is caused to condense on the moving we~ of pla3tic film. The metal may be heated in a resistanoe-heated "boat" containing a small amount of the molten metal, or in an induction-heated crucible, or the vapor may be produced by electron beam evaporation or cathode sputtering. The metal is typically depo~ited on the we~
in a thin, uniform layer approximately 30nm thick. The metallizing process is generally carried out as a semi-continuous process wherein an entire roll of plastic filmi8 contained in the vacuum chamber, is unrollqd to the vapor source, and rewound inside the vacuum cham~er. Due - 1~597S9 to its low outgassing characteristic~, polyester film is preferred for use in the metallizing process. Metallized 50 gauge (.5 mil) polyester film, as well as 90 gauge polyvinylidene chloride (PVdC) coated cellophane ilm,

2 mil low density polyethylene ~L3PE), 75 gauge oriented polypropylene (OPP), and 90 gauge PVdC coated OPP are available commercially.
The web of plastic film 14 i8 taken up on a roller 34 after printing of its first surface 32 and/or any metallizing treatment. From this roller 34, the film is passed to an adhesive applicator 28 and thence to the laminating apparatus 16. The adhesive applicator 28 applies the adhesive in a continuous or discontinuous layer by spraying, brushcoating, or rolling. The adhesive i6 applied to the first surface 32 ofthe film, over the printed layer 20. An offset gravure 6ystem can be used to apply a uniform pattern of adhesive dots to the film. Alternatively, the adhesive may be first applied to the paper material, the adhe~ive may be applied at a high tempersture. The preferred adhesive for use with polyethylene film iB a molten composition consisting essentially of polyethylene resin. Pigments and other additives may be added to the composition if de~ired, but the preferred adhesive composition has been found, surprisingly, to yield a high strength bond without the use of a solvent. The molten resin adhesive can be extruded acro6s the width of the paper and film as they enter the nip between the laminating rollers, with one of the rollers being chilled to prevent excessive softening of the plastic film.
The adhesive composition is primarily cho~en to be compatible with the plastic film 14. ~he adhesive compositions used may, apart from the polyethylene adhesive, generally be in solution or emulsion fo~m and may be either water or organic sol~ent based.
In the l aminating apparatus 16, the adhesive - coated film 14 is fed to the nip of a first pair of J

.~ .

~ ~ ~.59759 opposed laminating rollers 36, 38 together with the web of paper material 12 from a paper supply roll 40. After the web of paper material 12 and the web of plastic film 14 are pressed together by the opposed rollers 36, 38 they pass to a second pair of opposed rollere 41, 42 ~which further press the two webs together to form the composite material 10. Heat i~ introduced to the laminating apparatus 16 to facilitate curing of the adhesive sandwiched between the plastic film and the paper material. The heating of the composite is controlled to prevent stretching or distortion of the printing on the film and is generally insufficient tc heat seal the film. The heat may be provided by a heated first roller 36, by an infrared source between the two pairs of rollers, or by other means. The laminating proce~s bonds the first surface 32 of the plastia film 14, which bears the continuous or discontinuous printed layer, through a continuous or discontinuous adhesive layer to ths ~urface of the paper 12 which is intendea to be outwardly fa~ing ln the secondary container packaging application.
From the laminating apparatus 16, the composite material 10 i8 collected on a roll 45 and then fed from this roll into a package forming apparatus 18 where the material is scored, cut, and folded into the particular secondary container packaging application contemplated.
The preferred package forming apparatus 18 forms a wob of composite material into a plurality of 6-pack 12 oz.
can wraps as shown in Fig. 3. The wrapper of Fig. 3 is formed from a single blank of paper die cut from the composite webO Prior to cutting, strands 48, 50 are glued to the paper side of the compo~ite along the machine direction of the compo~ite web. The web of paper is then fed into a die cutting apparatus having a plurality of cutting edges. The arrangement of the ; cutting steps may be varied, but may suitably be carried out in one step as follow~: as a web advances from left . .

to right, a die cut is made which se~ers the web to form the edges of the blank and simultaneously CUt8 thin lines for the wrap~ These lines include twelve ]pairs of intersecting pependicular line6 54, 56 for receiving the rims of the cans contained in the wrap;
arcuate slits 60 in an intermediate portion of the blank for forming can separation tabs 62; semi-elliptically opposed lines 64, 66 for forming package carrying holes; and machine finger slits 68, 70. Thin, broken, or scored, lines are also cut, including lines 72 across the arcuate slits 60 and a line 74 extending the width of the blank near its leading edge 52. The leading edge 52 of the blank is folded along the adjacent scored line 74 to form a center keel tab 84. The blank is then wrapped tightly about the containers through machine fingers extending through apertures formed by lines 68, 70 in the material. The carton is folded into a top surface 76 and a bottom surface 78, with side surface6 80, 82 extend ing therebetween, and the trailing edge portion 86 i~ glued to the leading edge portion to complete the can wrap package.
As used herein, the term "paper material"
refers to a web of cellulosio fibers in sheet form, ranging from .0015-.030 in. ~.03-.08mm) in thicknes~
and having a den~ity of 5129 lbs. per 1,000 ~quare feet (oO2~~63 kg/sq. in.). This includes paper, which i~ generally .0015-.008 in.(~o3-~omm)~ thick, and paperboard, which is generally .008-.030 in.
(.20-0.8mm) thick.
As stated previously, the selection of a particular paper material will depend to a large extent on the secondary container end use intended.
For example, for a 6-pack 12 oz. can wrap, the preferred paper material i~ 12-14 point natural kraft paper carrier board. The term "point" a~ generally under~tood in the industry and as used herein means a thickness of one ~ n~th Of an inch for each point. Thus, 12 point ..~

11597~9 paper is .012 in. (30.48 microns~ thic~. "Natural kraft paper" refers to kraft paper which has not baen bleached to a white color or dyed. Kraft paper is paper produced by a chemical cooking proces6 using sodium hydroxide and sodium sulfide. There are many different types of kraft paper manufactured with various additives and treatments for various applications, including the carrier board discussed above.
Another type of paper suitable for use with the present invention is recycled paper. Recycled paper may be defined as paper material which has been made using fibers which have previously been used in a paper product. There are a number of different types of recycled paper, including ~lled- cartonboard, fclding cartonboard, and chipboard. Chipboard i3 paperboaxd made from recycled materials that were not repulped into individual fibers but only broken down to fiber bundle~ and then manufactured into board. Recycled paper is generally not used in ~econdary container packaging becau~e it ha~ l~w tear re~istance due to the short fiber~ which it contain~. Recycled paper may be u~ed in the present invention, however, because of the tear re~itance contributed by the plastic film.
The main factors in the selection of a paper material for use in the present invention are its tensile load and its internal tearing resistance. All types of paper are generally high in ten~ile load. Tensile load refers to the amount of force which a ~heet of paper can withstand without ripping or bursting. It can be accurately measured by the Tensile Strength te~t, ASTM
D 828-60. Tensile load i~ similar to ten~ile strength except that tensile load will vary with the thickne~s of the sheet being tested.
The tensile load of the paper uaed in the present composite should be 40 lb~. MD ~Machine Direction)/30 1~8 . CD (Cross Direction) miniumum ~177.92 N MD/133.44 N CD) for 6 packs, 12 oz. can~;

11~'375g 45 lbs. MD/35 lbs~ CD minimum ~200.16 N MD/155. 68 N CD) for 6 packs, 16 ozO cans; 45 lbs. MD/35 lb&. CD ~200:.16 lN MD/155. 68 N CD) for 6 packs, 12 oz. bottle wraps; 45 lbs. MD/35 lbs. CD minimum ~200.16 N MD/155. 68 N CD) for 6 packs, 12 oz. basket bottle carriers and 40 lbs.
~D/30 lbs. CD minimum (177.92 N MD/133. 44 N CD) for 12 pack carriersO In other words, the combined tensile load, MD ~ CD, should be at least 70, generally 70-90 lbs. Since the plastic film used in the present composite is relatively elastic, the tensile load of the paper will contribute at lea~t 85% of the tensile load of the composite. Intqrnal tearing resistance refers to the average force in grams rsquired to tear a single sheet of paper after the tear has baen started.
Internal tearing resistance is determined as described in TAPPI Standard T 414 t~ - 65 and Elmendorf, "Strength Test for Paper", Paper 26 ~April 21, 1930).
The internal tearing re~istance, or tear ~trength, varies in a given paper ~heet with the direction in which it iB measured, being lower in the machine direction and higher in the ¢ross machine direction. This is generally a result of the orientation of the paper fibers relative to the paper making machine from which the paper sheet is~ues. In ~ome types of paper, such as that made by the Fourdrinier proces~, the tear resistance in the cross direction is generally 10-15% higher than that in the machine direction. In paper made with a cylinder machine, the tear resietance in the cros~ direction can be two time~ that of the machine direction. In secondary container packaging, tear strength in both direction~ i5 important.
Accordingly~ the internal tearing resistance herein considered i8 the com~ined tear strength obtained by adding the tear strength in both directions. It i8 generally con6idered that the minimum required combined tear strength for paper used in 6 pack 12 oz. can wrap~
is 500 gm; in 6 pack 16 oz. can wraps, 650 gm; in 6 ~ , 1$59759 pack 12 ozO bottle carriers, 650 gm; in 6 pack 12 oz.
bottle wraps, 650 gm; and in labels, 40 gm.
Although not entirely so, the density, or basis weight and the thickness, or caliper of a paper material are indicative of the material's strength.
For example, 12 point carrier board having a basis weight of 42 lbs/1000 ft2 ~hereinafter 42#) will generally have a combined internal tearing resistance of 250 to 400 gms. making it suitable for composites for 6 pack 12 oz. can wraps~ Composite material using 12 point 42# carrier board and 0.75 ml polyethylene film was found to have a tensile strength of 50 lbs.
MD and 30 lbs. CD and a combined tear resistance of 700 gms making it suitable for 6 pack 12 oz. can wraps wherein 1~ pt., 700 gm tear resistance, 72# carrier board had previously been used. A composite package of 16 pt. 58#/42# carrier board and 0.75 ml polyethylene film has an approximate tensile strength of 55 lbe.
MD/35 lbs. CD and combined tear resistance of 900 gms making it suitable for use on a 12 pack, 12 oz. can and bottle or a 6 pack 12 oz. bottle wrap, or a 6 pack 12 oz.
basket bottle carrier wherein 2~-23 point 79-91#
claycoated carrier board having a tensile strength of 80-90 lb~. and a combined tear resistance of 900--1100 gms had previously been used.
It has generally been found that the film of - the composite provides at least a 40%, and often an 8Q-90~, increase in tear strength over the tear strongth of the paper material used. In other words, assuming that the tear strength of the composite is the sum of the tear strengths of the two materials, the plastic may be said to provide at lea~t about 28% of the composite tear strength~ The reduction in tear strength made possible by the present composite represents a con~iderable economic advantage, since tear strength, like stiffness, is closely related to th~ amount of fiber in the board, and hence its cost.

-` ~1597S9 While the principal ~ac~ors in the selection of the paper material according to tha present invention are tensile load and internal tearing resistance, these factors must be considered, as stated previously, within the criterion of cost. Accordingly, other paper propertie~, as are known in the art, are also considered ln the choice of the pre3ent paper material. An important consideration in this regard is the moisture content of the paper material. As is known, the moisture content affects the price, shrinkage, warpage, and physical strength of the paper. The paper material for use in the present compo~ite should have a moisture content in the range of 4.0-8.5%.
The selection of a paper material for secondary packaging labels, such as bottle labels, is somewhat different than that of paper material for other package application. Conventional labels are made from high-grade bleached kraft paper coated for printability.
Abrasion resi~tance and ~tiffne~s are the important 20 qualities in label paper, ~inoe ten~ile strength and tear resist~nce are only important to the paper handling ~rlng the label manufaoturing proces~. In the present compo~ite, abrasion resi~tance is provided by the film;
stiffness is provided by a combination of the paper and the adhe~ive used to bond the paper to the film.
It iB ~till significant, however, that the present compo~ite permit~ the u~e of paper having a tear strength less than that of conventional label paper, in that tear strength provided by the pla~tic film i~
sufficiont for web handling during the manufacturing proaess. The present composite is also advantageous for use in labels in that no lacquer over¢oat is required to impart a high gloss effect to the label.
Th~ plastic film in the present compo~ite provides a means for imparting additional tear strength and wet ~trength to the ~econdary container packaging material and a means for protecting printed decoration ...,~

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~1~9~S9 underneath. Surprisingly, it has been found that the specific polymer used is not critical to the functions of the plastic film. Thus films of polyethylene ~ph~u~ate, polyethylene, polyvinyl chloride, polypropylene, and cellophane have been evaluated and found structurally satisfactory. Polyvinyl chloride and polypropylene are less favored, however, as requiring more closely controlled manufacturing to produce films of sufficient clarity. It has also surprisingly been found that the thicknes~ of the film is not critical to the functions of the film. Thicknesses from 0.25-2.0 mils can be employed in the present composite.
Generally, however, films in the range of 0.75 mils thickness are preferred.
The most important physical property con-tributed by the plastic film is its tear re3istance.
The tear resistance of plastic film i8 variable with direction in the film depending on whether or not and in which direction the film is oriented. In oriented film~, the polymer chains tend to be aligned along the direction o orientation and the tear strength will be proportional to the degree of orientation achieved.
The orientation direction and magnitude of a film is a function of the method by which the film was produced.
Unoriented film may be fabricated by sy~tems inclu~ing calen~ering, ~olution or monomer ca~ting, and extrusion.
Oriented film may be made by extrusion processes including tubular die blown, cast, and slit die processes.
It has been found, or purposes of the present composite, that both oriented and unoriented films will fulfill the structural functions of the plastic film.
Therefore, the preferred films for the presont invention have been selected on an economic basis. The presently preferred plastic film~ are tubular die blown polyethylene and polypropylene. Polyethylene is also preferred as imparting a high gloss to the composite material and 1~597~

being amenable to radiation-induced crosslinking.
The selection of a type of polymer film produced to a certain thickness by a particular process will, apart from economic considerationæ, primarily be determined by the tear resi~tance of the film. The following films provide the necea~ary tear resistance and have been found structurally satisfactory in the present composite:
Material Load, lb ~N) Tear Resistance MC/CD, ASTM D882 MD/CD
~ AS~M D1922 POLYETHYLENE, Consolidated Thermoplastic 1.16/0.80 238/120 Co., LGFll, .75 mil, ~5.15/3.55)N
15 1.0 mil. 1.44/0.86 282/254 (6.40/3.82)N
POLYPROPYLENE, Hercules Chem. Corp. 5.01/4.69 8/6 B503 .5 mil ~22.28/20.86)N
20 .25 mil 14.81/11.63 10/13 ~65.87/51.73)N
PO~YETHYLENE
~ERPHTHALATE, Celene~e Corp., ~5 .48 mil 4.66/5.~8 8/10 ~20.72/22.59)N
.92 mil - - - 16/16 CELLOPHANE, Dupont, 75 L9T, 30 .75 mil 6O48/8~60 13/20 ~28.82/38.25)N
VINYL, Goodyear, LPC-60 .60 mil 1.23/0.79 693/376 (5 . 47!3 . 51) N
35 ALC - 75, .75 mil 1.47/1.13 734/446 ~6.53/5.02)N
It will be noted from the abo~e table that the tensile loads of the plastics there listed are far below that required for seaondary container packaging applications, the tensile load in the composite being supplied mainly by the paper. It may al~o be noted that the tear resistances of a number of plastic films are . ~

liS9759 them~elves relatively low. It has been found that the tear strength of the composite is in excess of that expected from an addition of the tear strengths of the plaqtic film and the paper. While not completely understood, it is thought that the inter f ace between the paper material adhesive, and film provides the un-expected increase in tear resistance.
Thus there has been provided a composite secondary packaging sheet material which 18 lower in cost but higher in strength than conventional secondary paper packaging materials. Furthermore, the composite material provides a glossy, more attractive appearance and permits a variety in printing or decoration, such as foil appearance, and i~ highly abras$on re~istant and high in wet ~trength. The manufacturing of the present composite can utilize polyethylene film with radiation treatment and molten polyethylene adhesive for further co~t savings.
While the inventive concept~ have been di6-¢losed herein with reference to an illustrative andpre~ently preferred embodiment thereof, it is intended that the appened claim~ be construed a~ including alternative embodiments, except insofar as limited by the prior art.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A container packaging material including a paper material having an internal tearing resistance less than that required for said container packaging material, and a plastic film laminated to said paper material and having a tensile load less than that required for said container packaging material, wherein the paper material provides at least 85% of said tensile load and the plastic film provides at least 28% of the tearing resistance.

2. A container packaging material according to claim 1, wherein the tear resistance is between 500 gms and 600 gms and the tensile load is between 70 lbs and 90 lbs.

3. A container packaging material according to claim 1, wherein the paper material is natural kraft paper.

4. A container packaging material according to claim 1, wherein the paper material is from .012 to .016 ins thick.

5. A container packaging material according to claim 1, wherein the plastic film is transparent and a layer of printing on the plastic film is visible in reverse through said plastic film.

6. A container packaging material according to claim 1, wherein the plastic film is from 0.25 to 2 mils thick.

7. A container packaging material according to claim 6, wherein the plastic film is silected from the group consisting of polyethylene terphthalate, polyethylene, polyvinylchloride, polypropylene and cellophane.

8. A container packaging material according to claim 1, wherein the plastic film is laminated to the paper material through an adhesive.

9. A container packaging material according to claim 8, wherein the plastic film is polyethylene and said adhesive consists essentially of molten polyethylene.

10. A container packaging material according to claim 1, further comprising a thin layer of metal deposited on said plastic film.

11. A container packaging material according to claim 1, wherein the plastic film is treated with radiation.

12. A container packaging label material including a paper material having an internal tearing resistance less than that required for said container packaging material, and a plastic film laminated to said paper material and having a tensile load less than that required for said container packaging material, said paper material providing at least 85% of said tensile load and the plastic film providing at least 28% of the tearing resistance.

13. A method of manufacturing packaging material for a container package comprising providing a web of a paper material and a web of plastic film, said paper material providing at least 85% of the tensile load of the container package and said plastic film providing at least 28% of the tearing resistance of said container package, printing on a first surface of said plastic film then applying an adhesive to said first surface of said plastic film, pressing said first surface of said plastic film into intimate contact with a first surface of said paper material to form a web of composite material, and forming said web of composite material into said container package.

14. The method of claim 13, further comprising radiating said film to crosslink said film prior to said pressing of the film to the paper material.

15. The method of claim 13, wherein said applying an adhesive comprises extruding a molten polymer adhesive.

16. The method of claim 13, further comprising the step of metallizing said plastic film.