US3236373A

US3236373A - Cigarette package

Info

Publication number: US3236373A
Application number: US322161A
Authority: US
Inventors: John H Lux
Original assignee: Haveg Industries Inc
Current assignee: Haveg Industries Inc
Priority date: 1963-11-07
Filing date: 1963-11-07
Publication date: 1966-02-22
Anticipated expiration: 1983-02-22
Also published as: GB1051377A

Description

Feb. 22, 1966 J, ux 3,236,373

G IGARETTE PACKAGE Filed Nov. '7, 1965 2 Sheets-Sheet 2 l/pizw ATTORNEYS United States Patent 3,236,373 CEGARETTE PAK'JKAGE John H. Lux, Charlestown, Md., assignor to Haveg Industries, Inc., New Castle, Del., a wholly-owned subsidiary of Hercules Powder Company, a corporation of Delaware Filed Nov. 7, 1963, Ser. No. 322,161 14 Claims. (Cl. 206-41) The present application is a continuation-in-part of application Serial No. 296,558, filed July 22, 1963.

This invention relates to the packaging of articles, especially cigarettes.

It is customary to employ a cellophane wrap around cigarette packages to insure freshness of the cigarettes. The use of cellophane, however, entails loss of time and an extra cost in the overall packaging operation.

It recently has been proposed to employ plastic cigarette packages. These packages, however, sutier from the disadvantage that they have a relatively high cost compared with the conventional paper-metal foil combination. Furthermore, the need for the additional metal foil vapor barrier even with the plastic package is a disadvantage.

It is an object of the present invention to reduce the moisture vapor transmission of foamed packages.

Another object is to reduce the cost of plastic cigarette packages without sacrificing rigidity or strength.

An additional object is to thermoform relatively shallow packages.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications Within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

It has now been found that these objects can be attained in several fashions.

Thus, a thermoplastic composition containing a leafingtype pigment can be extruded in the form of a sheet or tube and the leafing oriented in the plane of the sheet or, in the case of a tube, is oriented around the axis of the tube. The tube can be subsequently cut to form a sheet or it can be used as a parison to form a blow molded package.

The leafing should have a thickness which is less than 4 and preferably less than A the smaller of its width or length. The thickness can be or V1090 the smaller of the width or length. Thus, the thickness can be 0.1 to 2 microns. The leafing itself preferably is such as to pass a sieve of 50 mesh or smaller, e.g., 100 mesh, 200 mesh or 325 mesh, of the United States sieve series.

The leafing pigment can be a metal such as aluminum, gold, iron, silver, tin, copper, lead, alloys, e.g., bronze, brass, pewter and steel, or it can be mica or an organic pigment, e.g., a phthalocyanine such as co per phthalocyanine, copper octachlorophthalocyanine, copper hexadecachlorophthalocyanine or aluminum phthalocyanine. The pigment should be well dispersed in the plastic so that the full surface of the platelets is uncovered and that substantially all of the platelets are oriented parallel to the surface of the plastic sheet. This can be achieved, for example, by repeated shearing along planes parallel to the direction of the finished sheets. The leafing can be any flake material which melts above the extrusion temperature (usually 250 to 350 P.) which is a moisture impermeable solid.

The leafing pigment is encouraged to orient itself in the plane of the plastic material and to migrate as much 3,236,373 Patented Feb. 22, 1966 as possible toward the surface thereof. This is accomplished by first thoroughly dispersing the leafing pigment in the form of platelets in the plastic by conventional means such as mixing in a Banbury mixer, roll mill or other conventional equipment. The mass is then sheeted by extrusion through a slot die and calendering or casting, each of which operations serves to efiect some orientation of the platelets in the desired fashion. The orientation in the plane of the sheet is heightened by repeated rolling or calendering of the sheet so as to cause a further stretching of the sheet. The stretching orients the leafing in the direction of the surface. The plastic containing the leafing can be extruded as a tube and blown in the form of a bubble. In such case, the product is biaxially oriented and the platelets become oriented.

The leafing can be 1 or 2% up to 10% of the Weight of the composition. While the leafing is throughout the plastic sheet or tube, it is much more concentrated on the exterior surfaces. As a result of this concentration and orientation of the leafing the moisture vapor transmission of the film is reduced.

The sheet material composition is a foamable plastic mixture such that at extrusion temperature and upon release to atmospheric pressure it tends to foam to about twice or more times its original volume.

In order to make the sheet tougher and more resistant to crushing an impervious tough skin is formed on one or both surfaces. This can be accomplished by chilling one or both surfaces while permitting the core of the sheet to expand. The core comprises 50 to 96% of the total thickness of the skins and core. The skins each normally range from 3 to 25% of the total thickness.

The density of the foam can be from 1.5 to 75% of the density of the unfoamed polymer. Preferably, the density of the foam is from 10 to 50% the density of the unfoarned polymer. Thus, with polystyrene and polymers of similar density the foam has a density between 1 and lbs./ cu. ft. Normally, the density is at least 5 lbs/cu. ft. and preferably between 12 and 35 lbs/cu. ft. If an impervious skin is present, it has a density nearly that of the polymer itself, e.g., the skin will have a density of 60 to 66 lbs./ cu. ft. in the case of polystyrene. The density of the skin will be even greater than that of the polymer in the event that the higher amounts of the more dense leafing agents are employed.

Among the preferred polymers are high impact polystyrene, high density polyethylene (e.g., density 0.96),

polypropylene, ethylene propylene copolymer e .g., :50), ethylene-butene1 copolymer (e.g., 90 10), acrylonitrile-butadiene-styrene copolymer e.g., 25

butadiene, 15% acrylonitrile and styrene) vinylidene chloride copolymers (saran) containing a major amount of vinylidene chloride, e.g., vinylidine chloridevinyl chloride (:15) and vinylidene chloride-acrylonitrile (80:20), polyvinyl chloride, vinyl chloride-vinyl acetate copolymer (e.g., 87:13), vinyl chloride-acrylonitrile copolymer (e.g., 80:20) polyvinyl acetals, e.g., polyvinyl formal and polyvinyl butyral.

When employing polystyrene there can be employed normal crystal grade polystyrene or high impact polystyrene or a mixture containing 5 to normal crystal grade polystyrene and the balance high impact polystyrene. When employing a thermoplastic styrene polymer it normally contains greater than 50% by Weight of styrene and preferably at least 70% by weight of styrene in its structure. Preferably, the polystyrene is at least 10% high impact polystyrene. High impact polystyrenes are frequently prepared by polymerizing monomeric styrene in the presence of 2 to 15% by weight of a rubbery diene polymer or by polymerizing styrene in the presence of such amounts of a difunctional material.

Examples of high impact styrene include .a terpolymer of 5% *acrylonitrile, 5% butadiene and 90% styrene; a copolymer of 5% b-utadiene and 95% styrene; the product made by polymerizing 95 of styrene in the presence of 5% of polybutadiene; a copolymer of 5% chlorosulfonated polyethylene and 95% styrene; a blend of 97.5% polystyrene and 2.5% polybutadiene; a blend of 95% polystyrene and 5% hydrogenated polybutadiene containing 35.4% residual unsaturation; polystyrene formed in the presence of 5% hydrogenated polybutadiene containing 4.5% of residual unsaturation, a blend of 95 polystyrene and 5% polyiso-prene, a blend of 98% polystyrene with 2% rubbery butadiene-styrene copolymer, a blend of 85% polystyrene with rubbery butadienestyrene copolymer, and a copolymer of 99.5% styrene and 0.5% divinyl benzene.

Unless otherwise indicated, all parts and percentages are by weight.

The foamable thermoplastic resins which can be extruded according to the invention include cellulose ethers and esters, e.g., ethyl cellulose, cellulose acetate, cellulose acetate-butyrate, homopolymers and interpolymers of monomeric compounds containing the CH C grouping, such as olefins, e.g., ethylene, propylene, isobutylene, butene-l, vinyl halides, e.g., vinyl chloride; vinylidene chloride; vinyl esters of carboxylic acids, e.g., vinyl acetate, vinyl stearate, vinyl benzoate, vinyl ethers, e.g., vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; chlorotrifluoroethylene, tetrafiuoroethylene, hexafluoropropylene, unsaturated carboxylic acids and derivatives thereof, e.g., acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, acrylarnide, acrylonitrile, methacrylonitrile, and interpolymers of the above-mentioned vinylidene monomers with alpha, betaunsaturated polycarboxylic acids and derivatives thereof, e.g., maleic anhydride, diethyl maleate, dibutyl fumarate, diallyl maleate, dipropyl maleate, etc. A preferred class of materials with which optimum results are obtained are rigid, relatively non-elastic, thermoplastic resins, such as homopolymers and interpolymers of vinyl chloride, e.g., polyvinyl chloride, vinyl chloride-vinyl acetate copolymer (87:13), vinyl chloride-acrylonitrile copolymer (80:20); homopolymers of vinylidene aromatic hydrocarbons and ring halogenated derivatives thereof, e.g., styrene, o-chlorostyrene, p-chlorostyrene, 2,5-dichlorostyrene, 2,4-dichlorostyrene, p-methylstyrene, p-ethylstyrene, alpha-methylstyrene, vinyl naphthalene and interpolymers of such vinylidene monomers with each other and with other vinylidene monomers in which the interpolymer contains at least 70% of the vinylidene aromatic hydrocarbon compound, e.g., a copolymer of 70% styrene and 30% acrylonitrile. As previously indicated, for many uses the most preferred resins are thermoplastic styrene polymers containing at least 70% by weight styrene in the structure.

Other suitable thermoplastic resins include polycarbonates, e.g., the polymer from bisphenol A and diphenyl carbonate; polyoxymethylene (Delrin) oxymethylenealkylene oxide copolymers, e.g., oxymethylene-ethylene oxide (95:5), polyurethanes, e.g., from toluene diisocyanate and polypropylene glycol molecular weight 2025; Dacron (polyethylene terephthalate), nylon (e.g., polymeric hexamethylene adipamide). ABS terpolymers can be used, e.g., the terpolymer of 25% b-utadiene, 15% acrylonitrile and 60% styrene (a rigid ABS terpolymer) as well as other terpolymers containing 25 to 60% butadiene, 10 to acrylonitrile and 20 to 60% styrene.

To insure the formation of a uniform foamed plastic core a nucleating agent should be used in forming the foamed sheet.

When a nucleating agent is employed, it is used in an amount of from 0.02 to 10% of the total polystyrene by weight. Prefrably, 0.4 to 2% of the nucleating agent is used.

Conventionally, the nucleating agents are made up of two materials which react to form carbon dioxide and water. The tw materials are normally used in approximately equivalent amounts. As the carbon dioxide liberating materials there can be used ammonium, alkali and alkaline earth carbonates or bicarbonates, e.g., ammonium bicarbonate, sodium bicarbonate, sodium carbonate, potassium bicarbonate, calcium carbonate. The other material is an acid or acid-reacting salt, preferably solid, which is sufiiciently strong to liberate the carbon dioxide from the carbonate or bicarbonate. Generally, the acid has at least 3.0 milliequivalents of acidic hydrogen, and preferably at least 10.0 milliequivalents, per gram. The acid can be organic or inorganic. Suitable acidic materials include boric acid, sodium dihydrogen phosphate, fumaric acid, malonic acid, oxalic acid, citric acid, tartaric acid, potassium acid tartrate, chloroacetic acid, maleic acid, succinic acid and phthalic acid. In place of the anhydrous acids or salts there can be used the solid hydrates, e.g., oxalic-acid dihydrate and citric acid monohydrate.

While not essential, there can also be added a wetting agent such as Bayol 35 (a petroleum aliphatic hydrocarbon white oil), kerosene having an average of at least 8 carbon atoms in the molecule, alkylphenol-alkylene oxide adducts, e.g., Triton Xl00 (t-octylphenol-ethylene oxide 'adduct having 10 ethylene oxide units in the molecule), sodium lauryl sulfate and sodium dodecylbenzene sulfonate. The wetting agent can be nonionic or anionic.

The preferred mode of incorporating the foaming agent into the polymer is by premixing the pelletized, solid, thermoplastic polymer, e.g., high impact styrene polymer, with a minor amount of an absorbent having absorbed thereon a volatile liquid (i.e., the foaming agent), which is non-reactive with and which has not more than a slight solvent action on the polymer. The volatile liquid should volatilize 'below the softening point of the polymer.

As the absorbent there can be employed any conventional absorbent in finely divided form, such as diatomaceous earth (Celite), fullers earth, silica gel, e.g., Cab- O-Sil and Hi-Sil, activated alumina, molecular sieves, attapulgus clay and activated carbon. The absorbent is usually used in an amount of 0.1 to 15%, preferably 0.5 to 10% by weight of the polymer, although up to 25 or 30% of absorbent can be employed. The absorbent is an inert filler of large surface area but small particle size, e.g., 200 mesh or below.

As the volatile liquid there can be used aliphatic hydrocarbons boiling between 10 and C. and preferably between 30 and 90 C., e.g., petroleum ether (containing primarily pentane or hexane or a mixture of these hydrocarbons), pentane, hexane, isopentane, heptane, cyclohexane, cyclopentane, pentadiene and neopentane. Other volatile liquids include methanol, ethanol, methyl acetate, ethyl formate, dichloroethylene, perchloroethylene, dichlorotetrafiuoroethane, isopropyl chloride, propionaldehyde, diisopropyl ether, dichlorodifluoromethane, a mixture of pentane with 5 to 30% of methylene chloride or other volatile lower halogenated hydrocarbon.

The amount of volatile liquid absorbed on the absorbent can vary from 5 to or more based on the weight of the absorbent. The amount of liquid absorbed will depend upon the capacity of the absorbent for the particular liquid. Normally, the absorbent containing the volatile liquid will appear to be a dry powder. The volatile liquid employed should be one which is non-reactive with the particular polymer employed. Usually, the amount of volatile liquid will be 0.1 to 15% by weight of the polymer, e.g., polystyrene, to be expanded. The amount of volatile liquid will depend upon the extent of foaming desired. In general, the greater the amount of absorbed volatile liquid in the polymer-absorbent mixture the more the expansion. It has been found that good expansion can be obtained using very small amounts of the volatile liquid.

The free-flowing powder consisting of the low boiling solvent or semi-solvent adsorbed on the inert filler of large .5 surface area is added to the extrusion grade plastic pellets, preferably along with the nucleating agent, and tumbled in a mixer. The powder containing the volatile blowing agent will then disperse uniformly throughout the mixture While adhering to the plastic pellets. The mixture is then fed into the hopper of an extruder.

Alternatively, foaming can be accomplished by adding a blowing agent to the plastic composition containing the leafing agent. The blowing agent selected is one which does not release a gas at the extrusion temperature but which will release gas at a higher temperature, e.g., upon heating the sheet after calendering to orient the leafing pigment. The foaming agent can be used in an amount of 0.5 to 25%, preferably 1 to 10% based on the total plastic composition by weight. The surfaces of the sheet can be chilled in the manner previously indicated after foaming has started.

Typical examples of foaming agents which will not cause foaming at extruding temperatures but which will decompose to form gases and thus cause foaming at higher temperatures are given in the following table:

Table I Foaming agent: Gas release temperature, C. Azobisisobutyronitrile 115 N,N-dimethyl-N,N-dinitrosoterephthalamide 105 p,p'-Oxybis(benzenesulfonyl hydrazide) 150 Dinitrosopentamethylenetetramine 185 Azodicarbonamide 200 Sodium bicarbonate-citric acid (4:3) 140 Urea-biuret (33:67) 135 Diazoaminobenzene 100* 1,6-di-n-decyl azobisformamide 145 1,6-di-phenyl azobisformamide 176 Diphenyl 4,4'-di(sulfonyl azide) 145 p,p-Oxy-bis(N-nitroso-N-me'thyl benzenesulfonarnide) 130 Tetramethylene dinitrosodimethyl urethane 125 p,p-Oxybis(benzenesulfonyl semicarbazide) 210 Benzene sulfonic acid hydrazide 104 B-naphthalene sulfonic acid hydrazide 138 Diphenyl sulfone-3,3'-disulfonyl hydrazide 150 Benzene 1,3-disulfonic acid dihydrazide 145 Benzene sulfonic acid N-phenyl hydrazide 146 95% sodium bicarbonate and 5% melamine 140 When a skin or skins are formed these can be obtained by quenching, i.e., rapidly chilling the skin or skins of the foaming sheet or tube. The chilling can be accomplished by the use of an inert fluid, e.g., with an air blast, an air-water mist, a water spray, argon, helium. The cooling fluid is considerably below the temperature of the foaming mixture (mixture temperature is usually 250 to 400 F.). Thus, temperatures of 0 to 100 F. are employed for chilling. When air or other gas is the cooling fluid it can be employed as a blast at a flow rate of 40 to 100 ft./sec., for example.

Instead of employing a metal leafing in the foamable composition, moisture vapor transmission through a a foamed hydrocarbon polymer having a skin, e.g., polystyrene, polyethylene or polypropylene, can be retarded by applying an integral protective coating of Saran. In the case of polyethylene, polypropylene or copolymers of ethylene with propylene or butylene to improve the adherence of the Saran to the skin surface the skin is treated with an oxidizing agent, e.g., oxidizing gas flame, corona discharge, ozone, chromic acid or the like prior to application of the Saran. The Saran layer need not be thick, e.g., it can be 0.1 to 2 mils.

The metal leafing also can be eliminated by forming the cigarette case of a foamed vinylidine chloride polymer having at least one skin and preferably two non-porous, impervious skins, integrally united to the foamed portion. Such cases can be blow molded or thermoformed. A

6 typical suitable foamed vinylidine chloride polymer is vinylidine chloride-vinyl chloride (:20).

Thus, a blow molded cigarette package can be made in two portions from a thermoplastic resin foam consisting of a foam resin portion and at least one non-porous, impervious tough resin skin integral therewith, the foam portion being between 50 and 94% of the total thickness of the package. Preferably, the foam portion is a foam resin core integrally united to inner and outer skins. The two halves of the package are blow molded from a foamed tubular parison which has at least one nonporous, impervious skin and preferably has both inner and outer non-porous, impervious tough skins. The skins are formed by internal and external quench chilling of the parison formed from a foamable composition as it emerges from a hot extruder having an annular orifice. The blow molded foamed package can be made as indicated from a vinylidine chloride resin, e.g., vinylidine chloride-vinyl chloride 15). Blowing is accomplished in a conventional blow mold while the parison is still hot using air, for example, as the blowing fluid. One half of the skinned foamed package is blow molded with a crinkle in it and is then cut so that the crinkle slides under the larger diameter of the other half. After filling with the cigarettes the upper half, for example, with the crinkle is slid into place and the package heat sealed to insure that the cigarettes remain fresh and that no air can leak in. A tear strip can be included in the sealing area to aid in subsequent opening.

An alternative procedure for making an airtight closure on the skinned foamed package is to vacuum form or injection mold the skinned foamed plastic container in two halves with a ridge on one half and a groove on the other so that it will snap in place and lock around the groove. To insure against air leakage the area of jointure can be heat sealed.

The cigarette packages of the present invention function as a low cost humidor and crush-proof container. The use of the foamed plastic allows the construction of a rigid crush-proof box from smaller amounts of more inexpensive polymers than if this property had to be obtained by use of a non-foamed composition. Retardation of moisture vapor penetration is enhanced by the presence of the closed cell bubbles in the wall structure and are further reinforced by the leafing pigment when such is employed. As indicated previously, the leafing pigment tends to be oriented parallel to the surface of the package in both sheeting and forming operations, thus further enhancing moisture vapor scaling properties.

The package can be formed by thermoforming, e.g., pressure or vacuum forming, blow molding or even by injection molding. The package can :be only 5 to 10 mils thick after foaming and 10 to 20% of the thickness is in skin. However, thicker packages can be prepared, e.g., up to 50 mils or more.

Thermoforming is a particularly desirable way for making novel cigarette packages and other packages from the foamed thermoplastic materials having one or more skins.

In a specific application of the thermoforming technique two adjacent halves of the package are contiguously thermoformed and cut out as a unit from a sheet of material and folded together with a continuous hinge folded in between the two halves. This procedure is a very economical method of thermoforming, e.g., vacuum forming a flat plastic cigarette package. Previous methods for vacuum forming cigarette packages require deep drawing and the use of two separate portions to form the container. Also, the previous procedures did not employ foamed plastics.

The shallow drawing is accomplished by making the draw only the depth required to place 1 or 2 layers of cigarettes in the package (i.e., a depth equal to the diameter of 1 or 2 cigarettes) whereas the deep draw procedures require drawing to an extent equal to about the full length of the cigarettes. Thus, in prior art techniques at least one portion of the cigarette case must be drawn 80 mm. or more for king size cigarettes (or 70 mils for regular size cigarettes) while, with the instant procedure, the draw for the deepest half of the package can be as little as 6 mm. for a single layer of cigarettes or 12 mm. for a double layer. Slightly deeper draws, e.g., up to 20 mm. can be used. The draw for the shallow portion of the package can be even less, e.g., 3 or 4 mm.

This method of shallow drawing is most advantageously used with a material such as polypropylene which has inherently good hinging properties.

Preferably, the package is made of the skinned foamed thermoplastic materials of the types previously set forth. However, the novel unitary shallow drawn containers can be formed from unfoamed sheets and can be used to package other materials, e.g., wrist watches, rings, playing cards, paper clips, staples, paper, etc. This phase of the invention, particularly when a skinned foamed plastic material is employed, makes possible the low cost use of stronger and self-supporting plastic packages.

The invention will be understood best in connection with the drawings wherein:

FIGURE 1 is a schematic view illustrating a procedure for forming a skinned foamed plastic sheet for use in the invention;

FIGURE 2 is a view along the line 2-2 of FIGURE 1',

FIGURE 3 is a schematic view illustrating an alternative procedure for making a sheet for use according to the invention;

FIGURE 4 is a view taken along the line 44 of FIG- URE 3;

FIGURE 5 is a view, partially broken away in section, of a cigarette package vacuum formed from the sheet of FIGURE 1;

FIGURE 6 is a View of a cigarette package blow molded from a skinned foamed vinylidene chloride resin;

FIGURE 7 is a view of a shallow drawn package according to the invention; and

FIGURE 8 is a view showing the apparatus for making the package of FIGURE 7. 7

Referring more specifically to FIGURE 1 of the drawings there was provided a mixture of 50 parts of high impact polystyrene (Foster Grants Tuflex 216, polystyrene modified with 5% polybutadiene) and 50 parts of regular crystal polystyrene (Koppers D'ylene 8). This mixture is called hereinafter Composition A.

100 parts of Composition A were tumbled with 2 parts of Celite (diatomaceous earth) containing absorbed pentane (the Celite-pentane material was made up of 1 part Celite and 1 part pentane). There were then added 0.5 part of Bayol 35, 0.3 part of powdered anhydrous citric acid, 0.4 part of powdered sodium bicarbonate and 4 parts of leafed aluminum pigment having an average leaf size of 2 microns maximum dimension and an average thickness of the lesser of the length or width.

This mixture was placed in the hopper 2 of extruder 4. The mixture was heated in the barrel portion 6 of the extruder where it was softened and kneaded with the aid of a screw (not shown). The plastic mixture was extruded at a temperature of 150 C. as a sheet 8 through slot opening 10in the die portion 12 of the extruder. The sheet foamed as it was formed. The top surface 14 of the sheet was rapidly chilled with an air blast at C. and 80 ft./sec. from nozzle 18 and the bottom surface 16 of the sheet was rapidly chilled with an air blast at 20 C. and 60 ft./sec. from nozzle 20 to form a sheet composed of an upper, impervious, unfoamed tough skin 22, a lower, impervious, unfoamed tough skin 24 and integrally united to the skins a foamed core 26 (FIGURE 2). The sheet was passed through calendering rolls 28 and 30 to aid in orienting the aluminum leafing. The platelets of the aluminum leafing were preferentially oriented in the plane of the sheet and were most heavily concentrated in the skin portions of the sheet. The skinned foamed sheet then went to vacuum former 32 where the skinned foam sheet was formed into a cigarette package 34 (FIGURE 5) using conventional vacuum forming techniques. The package 34 was vacuum formed in two separate portions. The main portion was slightly higher than the height of the cigarettes 36 which were placed therein. The main portion 34 was formed with grooves 38 near the open end 40 thereof. After positioning the cigarettes 36 in the main or base portion 35 the cover portion 42 was slid onto the main portion. The cover 42 was formed with ridges 44 which mated with the grooves vacuum molded into the base. As the cover was slid onto the base the ridges 44 near the open end of the cover engaged the grooves near the open end of the base. Sufficient tension was provided so that the ridge snapped into the groove and maintained a tight seal. The ridge had an elevation of 10 mils with respect to the surrounding surface. The use of ridges elevated only 5 mils also can be employed.

The overall dimensions of the package were an overall thickness of 25 mils, an inner, unfoamed, non-porous, impervious skin 46 of 4 mils, an outer, unfoamed, nonporous, impervious skin 48 of 7 mils, a foamed core 50 of 14 mils and an overall density of 35 lbs./ cu. ft.

The vacuum former 32, as stated, was of the conventional type. The top and

bottom portions

42 and 35 of the package were separately formed from the hot sheet using a vacuum of 10 mm. Hg and a male assist plug.

Referring to FIGURE 3, there was mixed with 100 polyethylene (Alathon A14 molecular weight 20,000, density 0.915) and 4 parts of diazoaminobenzene. This mixture was placed in extruder where it was heated to 110 C., softened and kneaded with the aid of a screw. It was extruded as a sheet 62 through slot opening 64 in the die portion 66 of the extruder. The sheet commenced to foam as it formed from the extruder. The top surface 68 of the sheet was rapidly chilled with an air blast at 15 C. and 70 ft./sec. from nozzle 72 and the bottom surface 70 of the sheet was rapidly chilled with an air blast at 15 C., and 70 ft./sec. from nozzle 74 to form a sheet composed of an upper impervious, unfoamed tough skin 76, a lower, impervious, tough skin 78 and integrally united to the skins a foamed core 80 (FIGURE 4). The sheet was passed through rolls 82 and 84 and then was subjected to corona discharge (15,000 volts at /s inch distance) from corona discharge device 86. Next the upper surface of the foamed sheet having unfoamed top and bottom skins received a coating of saran 88. The coating was applied from a 7% solution of Saran F-12O (vinylidene chloride-acrylonitrile copolymer, 80:20 by weight) in methyl ethyl ketone by means of applicator which was dipped in the saran solution held in reservoir 92. The sheet 62 having upper and lower skins and an upper coating of saran, integral with the upper skin 76, then went into drying oven 94 to remove the solvent. The sheet was then converted into a cigarette package similar to that shown in FIGURE 5, except that it has an external coating of saran, by use of a vacuum mold such as vacuum former 32 of FIGURE 1.

FIGURE 6 illustrates a blow molded cigarette case. Both the top half and the bottom half 102 of the cigarette case were made from parisons of vinylidene chloride-vinyl chloride copolymer (85: 15). Each parison comprised a foam core 15 mils thick integrally united to inner and outer skins 3 mils thick. The halves of the cigarette package were then blow molded using conventional techniques while the parisons were still hot using a blowing pressure of 35 psi. The wall of both the upper and lower halves of the package was made of a foamed vinylidene-chloride-vinyl chloride copolymer core 104 integrally united to a non-porous, unfoamed, tough inner skin 106 of vinylidene chloride-vinyl chloride copolymer and a non-porous, unfoamed, tough outer skin 108 of vinylidene chloride-vinyl chloride copolymer. After positioning cigarettes 110 in the lower half, the upper half 100 was slid over the crinkle 112 in the lower half 102. The two halves were then heat sealed together, e.g., with a split rectangularly shaped heating element. The sealing was done along the juncture of the lower edge 114 of the top half of the package and the area 116 just below the crinkle. In this manner a perfect air seal was prepared. To aid in opening the pack a tear strip 118 can be provided.

Referring to FIGURES 7 and 8 there was provided a sheet of foamed polypropylene having an upper non-porous, unfoamed, tough skin, a lower non-porous, unfoamed, tough skin and a foamed core. Each skin was 3 mils thick and the core was 30 mils. There was also provided a vacuum mold 132. The left hand portion 134 of the mold was designed to form the bottom section 136 of the cigarette package 137 and the right hand portion 138 of the mold was designed to form the shallower top section 140 of the cigarette package. As can be seen from FIGURE 8, only a very shallow draw is required. The mold is provided with a stamping ring 142 for forming the edges of the package bottom 136. There is also provided a stamping tool 144 for thinning the polyethylene sheet or web 130 in the hinge area 146 joining the halves of the package. The hinge area has a thickness of one-third that of the bottom of the package. There is also provided a stamping ring 148 for forming the edges of the package top 140. Additionally a cutting edge 150 is provided on the stamping ring 142 to cut the package bottom out of the sheet and a cutting edge 152 is provided on the stamping ring 148 to cut the package top out of the sheet. There are provided lip forming rings 154 and 156 and on the stamping rings 142 and 148. The package is formed by passing the sheet 130 of thermoplastic skinned foam polypropylene preheated to forming temperature over mold 132. At this point, vacuum, e.g. 10 mm., is applied and stamping

rings

142 and 148 and stamping tool 144 are lowered into contact with the sheet. Simultaneously male plugs 158 and 160 are lowered into the bottom and top forming portions of the mold to assist in the vacuum forming of the shallow rigid box. The thin web 146 formed between the package halves by the stamping tool 144 can be readily folded to serve as a hinge as shown in FIGURE 7. The package bottom is molded so that the sidewalls such as 164, 166 and 167 are vertical in their lower portion. Near the middle of the sidewalls, the vertical portion merges into a short, inwardly sloping portion 162 which terminates in a vertical upper portion such as 168, 170 and 172. The inward slope 162 insures that the top will fit tightly and smoothly over the bottom. Cigarettes 174 are placed in the bottom portion of the package and the portion 145 between the two halves folded to form a hinged joint. The shallower or cover portion 140 is then fitted over the larger or base portion. As indicated, the cover portion fits over the base portion substantially to the bottom of the inwardly sloping portion 162 of the bottom sidewalls. The cigarette package can then be heat sealed to insure freshness of the cigarettes. If desired, a saran (e.g. vinylidene chloride acrylonitrile copolymer 80:20) coating can be applied from methyl ethyl ketone solution to the outside of the package to further retard infiltration of air. If the saran coat is employed preferably the polypropylene is treated first with an oxidizing agent, e.g., a gas flame or corona discharge in the manner set forth previously.

The process of preparing the flat cigarette package in FIGURES 7 and 8 results in the formation of a lightweight rigid box. If desired, the package can be encased in cellophane, biaxially oriented rubber hydrochloride film or biaxially oriented irradiated saran coated polyethylene film (12 megarads of irradiation) although this is not necessary.

The process illustrated in FIGURE 7 thus provides a shallower cover portion and a deeper base portion contiguously thermoformed from a single sheet of thermoplastic material. While the example uses polypropylene sheeting which has a foamed core integrally united to upper and lower non-porous skins it is possible to operate with only a single skin-either upper or lower. In fact in this form of the invention, thermoplastic materials, e.g. 20 mil polypropylene, can be employed without any foaming. However, it is preferred to form a foamed package having unfoamed skins in order to form a stronger and self supporting package using a minimum of material.

Containers for other materials can be formed by the procedure shown in FIGURE 7. Thus there can be formed an egg carton from a polypropylene foamed sheet having at least one external, unfoamed skin and preferably two external unfoamed skins using such procedure.

In forming the skinned foamed cigarette package as described in connection with FIGURE 8, there can be dispersed oriented metal leafing, e.g. 4% of aluminum leafing, throughout the sheet used to form the package. Also, the foamed package with or without the leafing can have a thin layer of saran, e.g. Saran F-120, applied to one or both exposed surfaces. The saran coating can be applied either before or after forming the package.

I claim:

1. Cigarettes packaged in a container, said container being impermeable to air and water vapor, said container comprising a foamed plastic layer integral with at least one unfoamed, non-porous skin of said plastic and oriented leafing pigment dispersed throughout said plastic, said pigment being more concentrated on the exterior surfaces of the container.

2. Cigarettes packaged according to claim 1 wherein the leafing pigment is a metal.

3. Cigarettes packaged in a container, the walls of said container comprising 1) a foamed thermoplastic polymer core, (2) a substantially unfoamed, outer skin integral with said core, and (3) a substantially unfoamed inner skin integral with said core, said core comprising 50 to 94% of the total thickness of the skins and core and oriented metal leafing pigment dispersed throughout said walls whereby said container is impervious to air and water vapor, said metal leafing having a thickness less than the smaller of its width or length, said pigment being more concentrated on the exterior surfaces of the container.

4. Cigarettes packaged according to claim 3 wherein the plastic is selected from the group consisting of styrene polymers, polymers of an olefin having 23 carbon atoms, vinyl chloride polymers and vinylidene chloride polymers.

5. Cigarettes packaged in a container, the walls of said container comprising 1) a foamed thermoplastic hydrocarbon polymer layer, (2) at least one substantially unfoamed skin of said polymer integral with said layer, and (3) a thin layer of a vinylidene chloride polymer directly coating at least one skin whereby said container is impervious to air and water vapor.

6. Cigarettes packaged according to claim 5 wherein said hydrocarbon polymer is a polymer of an olefin having 23 carbon atoms and the surface of said skin is oxidized and integral with said vinylidene chloride polymer.

7. Cigarettes packaged in a container, the walls of said container comprising 1) a foamed thermoplastic hydrocarbon polymer core, (2) a substantially unfoamed outer skin of said polymer integral with said core, (3) a substantially unfoamed inner skin of said polymer integral with said core, and (4) a thin layer of saran directly coating at least one of said skins whereby said container is impervious to air and water vapor.

8. Cigarettes packaged in a container according to claim 7 wherein said hydrocarbon polymer is a polymer of an olefin having 23 carbon atoms and the surface of the skin coated with the saran is in oxidized condition and integrally united to said saran.

9. A shallow container of a thermoplastic material comprising contiguous thermoformed cover and base portions united by a hinged joint of a foamed thermoplastic polymer layer integral with at least one unfoamed nonporous skin of said polymer and wherein oriented leafing pigment is dispersed throughout said polymer, said pigment being more concentrated on the exterior surfaces of the container.

10. A container according to claim 9 wherein the plastic is polypropylene.

11. A shallow container according to claim 9 containing cigarettes.

12. A thermoplastic rectangular container comprising contiguously thermoformed cover and base portions united by a hinged joint, the lower portion of the walls of said base portion extending vertically upward, said lower portion terminating in an upward and inwardly inclined portion and the top portion of said walls extending vertically downward to join said inclined portion, said cover portion fitting snugly around said top portion, said hinged joint being substantially thinner than said cover and base portions, said container comprising a foamed thermoplastic polymer integral with at least one unfoamed, nonporous skin of said polymer.

13. A thermoplastic container according to claim 12 made of polypropylene wherein said container comprises a foamed thermoplastic polypropylene layer integral with at least one unfoamed, non-porous skin of said polypropylene.

14. A shallow container of a thermoplastic material comprising contiguously thermoformed cover and base portions united by a hinged joint of a foamed thermoplastic polymer layer integral with at least one unfoamed non-porous skin of said polymer, oriented leafing pigment being dispersed throughout said polymer and a coating of saran being on said skin.

References Cited by the Examiner UNITED STATES PATENTS 1,950,740 3/1934 Mueller 2064l 2,387,243 10/1945 Castor.

2,552,641 5/1951 Morrison 2209 2,670,501 3/ 1954 Michiels 264 2,737,503 3/1956 Sprague et al.

2,951,246 8/1960 Halpern et al.

3,063,549 11/ 1962 Weichselbaum 220-31 3,084,086 4/ 1963 Roberts et al. 26490 3,088,166 5/1963 Colombo 264--90 3,123,206 3/ 1964 Gerber 206-41 3,125,213 3/1964 Keating 20641 3,133,661 5/1964 Schurman et al. 220-31 FOREIGN PATENTS 936,113 12/1955 Germany.

THERON E. CONDON, Primary Examiner.

J. M. CASKIE, Assistant Examiner.

Claims

1. CIGARETTES PACKAGED IN A CONTAINER, SAID CONTAINER BEING IMPERMEABLE TO AIR AND WATER VAPOR, SAID CONTAINER COMPRISING A FOAMED PLASTIC LAYER INTEGRAL WITH A LEAST ONE UNFOAMED, NON-POROUS SKIN OF SAID PLASTIC AND