US3025167A - Food package - Google Patents

Description

J. P. BUTLER FOOD PACKAGE March 13, 1962 Filed Sept. 19, 1960 N HA A 4 \.V

.l-ersey Filed Sept. 19, 1960. Ser. No. 57,005 10 Claims. (Cl. 99-171) This invention relates to the packaging of various articles, particularly including loaves of bread, wherein the product is wrapped and sealed in a flexible, protective sheet material and the end folds of the resulting package secured by a supplementary sheet material seal or label bearing a thermoplastic composition sealed thereto by heat and pressure. In a particular aspect, the invention relates to a break package bearing end labels coated with a thermoplastic wax composition coating capable of forming strong adhesive bonds to all of the sheet materials commonly utilized in the packaging of articles such as bread.

Heat-scalable labels of the type forming a material component of the package of the present invention are known in the packaging art. Packages utilizing such labels have not been entirely satisfactory in all of their aspects, however, primarily because the heat-scalable compositions coated on such labels have proven deficient in one or more of the several properties all of which are highly desirable for universal applicability in connection with the variety of protective packaging sheet materials which have found use in the packaging field. No single coated sheet material has hitherto been developed which combines all of these desirable properties to a satisfactorily high degree.

To display the optimum utility and adaptability in the packaging of articles such as bread, a thermoplastic coated label should exhibit all of the following properties: The coating should be non-blocking at all ordinary temperatures encountered in storage, preferably having a roll blocking point of 120 F. or higher, without the necessity of applying a special antiblocking coating of any type to the coated surface. The coating should become activated at a relatively low temperature, preferably at about 200-225 F. on label applying machinery, and should not visibly stain the backing sheet by coating strikethrough in the molten state. The coating composition should have excellent stability while maintained in the molten condition during the original coating operation, during storage of the coated sheet material and when being utilized in its ultimate packaging capacity. The coated label must operate on all automatic, thermoplastic label-applying equipment standard in the packaging industry without appreciable coating build-up on any portion of the machinery which would necessitate frequent attention or shut-down for clean-up purposes. The coating should display at least a moderate amount of tackiness or grab in the molten state to prevent slipping or dislocation of the label from the desired position on a package prior to the solidification of the coating, and must form a firm bond to all of the various flexible packaging materials commonly in use in the packaging of various articles such as bread, for example. A strong bond or seal must be maintained even though the finished package be exposed to temperatures as low as F. in order to prevent release of the label under freezer stor age or winter delivery conditions. The strength of the 3,025,167 Patented Mar. 13, 1962 bond must also not deteriorate on aging, and, in the interests of economy, the coating composition should be inexpensive and should contribute high seal strength to the coated sheet material with the application of a minimum of coating weight. It is also desirable that the coating have viscosity characteristics enabling application by hot melt gravure method as well as by reverse roll coaters.

In accordance with the present invention, a package incorporating a coated sheet material label exhibiting a combination of all of the above desired properties to a hitherto unprecedented degree has been developed. The label is produced by coating on a flexible base sheet such as paper a thermoplastic composition comprising, as essential components thereof, between 30% and of a petroleum wax having a melting point between 130 F. and about 170 F. and between 50% and 30% of a high molecular weight polymeric material produced by the co-polymerization of ethylene and vinyl acetate. To a blend of these essential components may be added in an amount necessary to achieve a total of various modifying or tackifying resins which are compatible therewith and which have softening points ranging from F. to about 300 F., preferably between 130 and 230 F. The preferred compositions would include from 2 to 20% of such modifying resins.

The preferred waxes for use in the present invention are petroleum waxes of the microcrystalline type which consist of mixtures of isoparaffins, naphthenes and small amounts of aromatic and straight chain hydrocarbons. These waxes are separated by solvent recrystallization methods from the non-distillable pot or still residue obtained as a result of the fractional distillation of petroleum. They have higher molecular weights and boiling points than paraffin wax, which is obtained from the overead wax distillate fraction of petroleum, and they are generally more ductile and exhibit higher viscosities and refractive indices than paraffin. The preferred microcrystalline waxes have melting points from about l70 F.

Paraifin wax and the intermediate or semi-micro waxes having melting points from 130-l70 F., both of which types of Waxes are obtained from the overhead wax distillate fractions of petroleum, may also be utilized in the coating compositions for use in my invention, although the microcrystalline waxes are preferred by virture of the somewhat higher seal strengths of their compositions, particularly at low temperatures. Blends of petroleum waxes of the several types above are also generally satisfactory.

The essential polymeric component of the thermoplastic coating composition is a co-polymer of ethylene and vinyl acetate having an ethylene to vinyl acetate Weight ratio of between 4:1 and 2: 1, or, in other words, a polymerized vinyl acetate content of between 20% and about 35% by weight, the preferred material having about a 30% polymerized vinyl acetate content. (Io-polymers of ethylene and vinyl acetate may be prepared by an oxygen or peroxide catalyzed polymerization of a suitable blend of the monomers at a moderately elevated temperature under pressures ranging upwards of 10,000 lbs. per square inch. Varying conditions of temperature, pressure and reactant concentrations as well as type and amount of catalyst will give co-polymers of varying molecular Weight, polymerized vinyl acetate content and melt index.

Co-polymers having a melt index of from to 500 have proven useful in the compositions of the present invention, a melt index between about 8 and 12 being preferred, as determined by the method described in the British Plastics 94 (March 1945) article by Hunter and Oakes.

The resinous components which may be added as modifiers to the coating composition may be any of a number of types of materials which are wax-compatible and which serve to intensify or modify some of the properties of the composition, particularly tackiness, viscosity and activation temperature. For this purpose terpene resins, hydrogenated rosin and rosin esters, cyclicized rubber and the like may be used. These may be added to the composition in amounts up to about 20%, preferably from 2 to 20%, to assist in achieving the desired balance of properties in the finished label.

In recent years, bread has been packaged in a variety of heat-scalable, protective sheet materials, namely waxed paper, regenerated cellulose film bearing a nitrocellulose heat-sealing coating, regenerated cellulose film bearing a modified polyvinylidine chloride (saran) coating, polyethylene film, polyethylene terephthalate film, rubber hydrochloride film, cellulose acetate film and polypropylene film, the above list including all of the sheet materials commonly used for this purpose. In the packaging of this commodity, either by hand or by automatic wrapping machinery, a sheet of the packaging material is first wrapped around the lateral surfaces of the bread and the opposite edges of the sheet lap-sealed together usually on the bottom of the loaf so that the wrapper forms an open tube enclosing the product. The wrapper is then folded down to cover the ends of the load in a series of overlapping end folds which are generally sealed in this position by heat and pressure. In general, these overlapping seals are relatively weak and have a tendency to pop open, exposing the product, and are also quite irregular in formation so that they detract from the overall appearance of the package. For these reasons, it has been the standard practice in the industry to seal these end folds more securely by applying over the end folds a supplementary sheet as an end-seal or label coated with a thermoplastic composition which, by the application of heat and pressure, becomes firmly bonded to the wrapping material, thereby strengthening the end closure and adding to the attractiveness of the finished package.

In the accompanying drawings,

FIGURE 1 is a perspective view of a loaf of bread or the like wrapped in a protective packaging sheet material,

FIGURE 2 is an assembly view of a similar packaged bread product, partially cut away to show the contents of the package and illustrating the positioning of a label over the wrapper end folds,

FIGURE 3 is a perspective view of a completely wrapped and sealed loaf of bread,

FIGURE 4 is an enlarged perspective view of a label for covering the end folds of a packaged product,

FIGURES 5 and 6 are sectional perspective views taken along x--x and yy of FIGURE 4, and

FIGURE 7 is a perspective view of an overwrapped carton bearing a label applied over the end folds.

As shown in the drawings, the individual portions of the supplementary coated sheet material comprising labels or seals indicated generally by the numeral 5 (FIGURES 4-6) for covering the end folds of the packaged article include a flexible base sheet 10 generally of paper, regenerated cellulose, paper laminated to metal foil or like material bearing on one side thereof a coating 11 of the thermoplastic adhesive composition which is solid and non-tacky at room temperature, but which softens and becomes adhesive by heating to a temperature of 200- 225 F. The coating may be applied as a thin, even film to the base sheet as shown in FIGURE 5 or may be applied as a series of tiny, discrete islands or mounds of coating as shown in FIGURE 6 by use of an engraved or knurled applicator roll. The coating is generally applied to the base label stock in an amount between about 8 lbs. and 20 lbs. per ream (3000 square feet). In common commercial practice, the labels are supplied to the wrapping or packaging machine in the form of rolls of interconnected labels, the machine being designed to sever the individual labels from the supply roll and apply them singly to the individual packages.

FIGURE 3 illustrates a loaf of bread wrapped in a flexible sheet material wrapper 12, the overlapped end folds 14 of the wrapper having a label superimposed and adhered thereto in sealing relationship. The label may, of course, bear suitable printed matter, if desired. In FIGURE 2, the wrapper 12 is shown partially torn away to reveal the packaged sliced bread 16, and the same figure indicates the act of placing label 5 in covering relationship to the wrapper end folds 14.

Articles may also be packaged in a carton, suitably of paperboard which may be overwrapped with a flexible sheet material wrapper and the end folds of the wrapper secured by a label coated with the thermoplastic coating previously described, as illustrated in FIGURE 7. Although the label is primarily intended for use in covering and securing the end folds on the packaged article, such as bread, for example, it may also be adhered by heat or pressure to any portion of the wrapper surface for the purposes of product identification, price indication or the like.

The various sheet materials which are currently used in the packaging of commodities such as bread have widely differing chemical constitutions and therefore exhibit correspondingly different surface properties. For this reason, it has been found extremely difiicult to formulate a label coating composition which will form strong adhesive bonds to all of the packaging materials, some compositions forming strong bonds to one or several of the packaging materials and poor bonds to others, while another label coating composition may respond conversely with respect to adhesion to the same group of packaging materials. Although a label which would bond satisfactorily to all of the normally utilized breadwrapper materials would have obvious advantages by obviating the necessity of producing, warehousing, distributing and stocking a plurality of types of labels applicable to particular bread packaging needs, no label having the desired universality of adhesion to various surfaces, combined with the other essential characteristics previously mentioned, has hitherto been available.

The label coating composition of the present invention, however, is unique in that the coated labels adhere strongly to every one of the protective sheet materials normally utilized in the packaging of bread and a variety of other food products, forming tightly sealed protective packages, the seals of which do not deteriorate even under the extreme conditions of temperature and humidity which are encountered in the storage of packaged bread in either refrigerator or freezer.

While not wishing to be limited by theory, it is believed that the uniquely universal adhesiveness of the coating utilized in the present invention is related to the fact that the coating component consisting of a co-polymer of ethylene and vinyl acetate contains both polar and non-polar groupings within the high molecular weight polymeric molecule and that the non-polar portions of the co-polymer molecule exhibit a high afiinity for the non-polar surfaces of sheet material wrappers such as polyethylene and polypropylene while the polar groupings in the polymer molecule exhibit an aflinity for the more highly polar materials such as paper, regenerated cellulose and the coatings normally utilized thereon, polyethylene terephthalate and the like. This affinity of the co-polymer molecule for both polar and nonpolar surfaces is apparently responsible, at least in part, for the adhesiveness of the present label coating to a 55 variety of sheet material surfaces of widely divergent surface characteristics.

The ethylene-vinyl acetate co-polymer also has other characteristics which make it particularly suitable for inclusion in label coating compositions. The co-polymer is miscible in the molten state with petroleum wax within the desired composition range and, on cooling to coalescence, the co-polymer solidifies in the same temperature range as the wax components of the blend. This is in sharp contrast to wax-polyethylene blends, in which the polyethylene component solidifies as separate, individual crystals in the molten wax at a temperature above the wax crystallization range, so that the blend has a cloud point very appreciably above the wax crystallization temperature. The cloud point phenomenon is not apparent in the blends of ethylenevinyl acetate co-polymer and wax which are utilized in the present invention because both major components crystallize in the same temperature range.

As previously indicated, the percentage of ethylenevinyl acetate co-polymer and microcrystalline wax pres ent in an end label coating composition may be varied within certain limits, labels with excellent adhesion characteristics to a variety of food packaging sheet materials being obtained when a sheet material such as paper, paper laminated to metallic foil, regenerated cellulose or other flexible sheet material suitable for use as label stock is coated with compositions containing between about 30% and 50% of the co-polymer and from about 70% to about 50% microcrystalline wax. The following Table I summarizes the eifect on label performance of varying percentages of these two composition components in a coating composition applied as a hot melt to the extent of 14-18 lbs. of coating per ream (3000 square feet) on 38 lb. bleached white sulfite paper by means of coating techniques utilizing a two-roll nip coater. The coated sheets were then heat sealed to the surface of the particular sheet materials indicated using a sealing pressure of 1 ounce per square inch applied for 2 to 3 seconds at the temperature indicated in each case. The ethylene-vinyl acetate co-polymer used contained 28% polymerized vinyl acetate.

1y removed the label from the film material after sealing and cooling to room temperature. To be considered satisfactory with respect to adhesiveness, a label should form a fiber tearing bond to the packaging film so that on removal of the label fiber tearing occurs over at least 25% of the sealed area. Labels exhibiting exceptionally good adhesion may exhibit fiber tearing over nearly 100% of the sealed area and attempts to remove the label result in complete rupture of one of the two sheet materials.

From the data in Table I it is evident that labels coated with compositions containing from about 30-50% of ethylene-vinyl acetate co-polymer (hereinafter designated as E-VA co-polymer or simply, E-VA for convenience and simplicity) exhibit excellent adhesion to a variety of packaging film materials. Lower percentages of E- VA co-polymer in the coating composition yield labels having relatively weak adhesion to a number of the commonly utilized packaging films and are therefore not completely satisfactory for the present use. Compositions containing somewhat more than of EVA co-poly mer give excellent sealing characteristics, but are less suitable for economic reasons and are more diificult to handle in coating operations.

Blends of E-VA co-polymer with commercially available rnicrocrystalline waxes having melting points ranging from about 140 to about 170 F., as obtained from a variety of petroleum refiners and wax suppliers, have proven satisfactory in the present invention and provide labels having an adhesion markedly superior in some applications to those in which paraflin wax or semi-microcrystalline wax constitutes all or a major portion of the wax component of the coating composition. Compositions containing paraffin or semi-inicrocrystalline wax as the wax component are satisfactory for use on labels to be applied to certain base sheets, but the versatility of such labels is somewhat limited. Labels coated with a composition based on microcrystalline wax are satisfactory for use on a greater variety of films although a composition in which the wax component comprises a minor amount of paraffin or semi-microcrystalline Wax together with a major amount of microcrystalline wax may be TABLE I Coating Composition by Weight Label Performance on Packaging Films Co-Polymer, Microcrystal- Polyethyl- Waxed Paper Saran Coated gg g f g fi i bercent line Wax, ene 200 F. 300 F. Seal Cellophane phane 0 percent; heal 300 F. Seal 0 R seal 80 Marginal" Marginal Marginal. Marginal.

70 Superior" Superior Sa-tlsfactor Superior. 60 Superior Satisfactory... Superior" Exceptional. Superi0r Superior Superior. Exceptional. 50 Superior Satisfactory Exceptional--. Exceptional.

500 and Shell 8794.

The evaluation of the label performance includes a test of its adhesion characteristics as Well as a consideration of the other qualities previously enumerated as being necessary or particularly desirable attributes of a satisfactory lebel for commercial utilization. The labels were rated as marginal if the combination of properties was such that the labels would be of dubious commercial utility due to relatively low adhesive strength or a less satisfactory combination of operating properties than would be desired. Labels having a very satisfactory combination of properties for commercial utilization were rated as satisfactory, and labels having excellent operating characteristics together with superior or exceptionally desirable adhesive properties were rated as superior or exceptional, respectively.

The adhesive properties of the coated labels as applied to a variety of films were tested by attempting to manualutilized without serious degradation of the adhesive qualities of the label for application to most films.

The data in the following Table II indicate that although the labels coated with compositions utilizing paraffin or semi-microcrystalline wax exhibit very good adhesion to a number of sheet materials at room tempera ture, the adhesive properties deteriorate greatly on films such as polyethylene at low temperatures such as would be encountered in winter season deliveries or in freezer storage of packaged foods. It is evident from the data that although label coatings utilizing parafiin or semimicrocrystalline wax show excellent utility for certain applications, those incorporating microcrystalline wax are somewhat more versatile.

In obtaining the data for Table II, the labels were prepared and the adhesion tests conducted in the manner previously described, except that the adhesiveness was tested both at 73 F. and at 0 F., as indicated.

TABLE 11 in the Coating Composition Label Coating Composition Label Adhesion at 73 F.

E-VA Saran Coated Nitrocellulose Co-Polymer, Wax Component 1 Polyethylene Cellophane Coated Cello- Waxed Paper percent 200 F. Seal 300 F. Seal phane 300 F. 300 F. Seal Seal 40 6tli7 -l licrocrystal- Superior Superior Exceptional Superior.

me. 40 60%-Parafl-ln ..d Marginal do Do. 50 50%Semi-Micro Mar inal Exceptional do Marginal.

crystalline.

Label Adhesion at 0 F.

001%-Mierocrystal- Superior Satisfactory Superior Superior.

1116. 60%-Paraflln Unsatisfactory do do Do. 00%-Semi-Miero do do do Do.

crystalline.

1 The microcrystalline wax used was Shellmax 500 sold by Shell Petroleum Company. The parafiin wax used was a fully refined 135-137 Ml. wax sold by Standard Oil Company of Indiana. The semi-microerystalline wax used was Chevron 1551 having a Ml. of 150 F., sold by Standard Oil Company of California.

E-VA co-polymcrs varying in composition from an ethylene-vinyl acetate ratio of about 4:1 to about 2:1 (Le. a polymerized vinyl acetate content between about and and in melt index from about 5 to about 500 have proven of value in the present invention. The following Table III contains data illustrating the adhesion of labels bearing coatings made with E-VA co-polymcrs of varying melt indices. Labels were prepared and tests conducted as previously described. The wax used was Shellmax 500.

0 co-polymer coatings to enable the production of label coatings which exhibit excellent adhesion to those packaging film materials which have hitherto presented the greatest challenge in the thermoplastic label applying art. It has been hitherto very difficult, if not impossible, to

35 secure excellent adhesion of thermoplastic coated labels TABLE III Efiect of Melt Index of E-VA on Label Adhesion Label Coating Composition, percent Label Adhesion To Viscosity of Molten E-VA Co-Polymer of Melt Coating at Nitrocellu- Viscosity Shown 290 F. in Polyethylene Saran Coated lose Coated Wax Paper Wax cps. 200 F. Seal Cellophane Cellophane 300 F. Seal 300 F. Seal 300 F. Seal 5 l3 19 28 36 500 Superior ExceptionaL Satisfactory. do .do Superior.

-do... Satisfactory. Superior do Superior. Exceptionaldo Satisfactory. Satisfactory Superior Exceptional.

It is evident from the above that E-VA co-polymcrs of melt indiccs between 5 and 500 may be utilized in this invention and that the viscosity of the coating composition may also be varicd considerably. In general, coating composition viscosity at 290 F. may vary from 2000 to 15,000 centipoises, 6000 to 12,000 being preferred. The data also indicate that, in order to maintain a desired level of viscosity of the molten coating for optimum label performance it is desirable to increase the percentage of EVA co-polymer in the coating somewhat as the melt index of the co-polymor is raised. Melt index is, of course, an inverse function of viscosity, the molten copolymers of high melt index being more fluid than those of low melt index.

The adhesion characteristics of the wax-E-VA co-polymer compositions may be further greatly enhanced by the addition of up to about 2% of a modifying wax-compatible resinous component having a melting point between about 130 F. and 300 F. The following materials are representative of the components which may be added to improve the adhesion of the labels of this invention and to extend the number of film materials to which excellent adhesion of such labels may be obtained: terpenc type resins, hydrogenated rosin, polymerized rosin,

to film materials such as for example, polypropylene, polyethylene terephthalate and Saran-coated cellophane, all of which are very hydrophobic in surface characteristics. In particular, it has hitherto been impossible to produce label coating compositions which exhibit excellent adhesion to these film materials and which at the same time meet all of the other qualifications which are necessary or desirable in the heat-scalable label field, these qualifications including non-blocking characteristics under normal or adverse roll storage conditions, low activation temperature, excellent stability of the coating, excellent labeling machine operability, a high degree of grab when the coating is molten, excellent adhesion to all of the commonly used packaging sheet materials and stability of the seal on aging and under extremes of tempcrature variation.

As illustrated by the data in the following Table IV, labels coated with compositions comprising a blend of microcrystalline wax, E-VA co-polymer and from 2% up to about 20% of a modifier such as those hereinbeforc mentioned exhibit excellent adhesion to each of the following sheet materials (each sheet matcrial being identified in the table by the letter designation appended thereto in the following list: Surface modified polypropylene (A), polyethylene (B), waxed paper (C), saran-coated cellophane (D) and nitrocellulose lacquer coated cellophane (E).

TABLE IV packages resulting therefrom display very superior re- The sistance to damage caused by label adhesion failure. labels have proven highly satisfactory as to machine Adhesion of Modified Wax E-VA Co-Polymer Coated Labels to Various Sheet Materials Label Coating Composition Adhesion of Coated Label to Film Designated Percent Co-Poly- Micro- EVA, crystalpercent line Wax Modifier Percent A B O D E 40 40 35 Glyceryl 2O ester of Hydrogenated Rosin.

Hydrogenated Rosin.

Terpene 10 Resin.

Cyelicized 2 Rubber.

Polymer- 20 ized Rosin.

Glyceryl 20 Ester of Polymerized Rosin.

Exceptional- MarginaL.--

Superior- Exceptional- ExceptionaL do. do do i.

. do do ..do

Superlor do Exceptionaldo .do

Superior Exceptional- Exceptional.

Superior:

ExceptionaL Exceptional.

Superior- In addition to the above tabulated results, it was also found that the labels bearing coating compositions containing hydrogenated rosin or glyceryl ester of hydrogenated rosin displayed exceptional adhesive qualities to untreated polypropylene film, polyethylene terephthalate film, polystyrene and cellulose acetate.

It will be evident from the above data that the addition of from about 2% to about 20% of a modifying wax compatible resin, particularly hydrogenated rosin or a glyceryl ester thereof, to a blend of 30 to EVA co-polymer and 40 to microcrystalline wax results in a label coating composition displaying remarkably good adhesion to an unusually wide range of packaging film materials including films such as untreated polypropylene, on which no hitherto known thermoplastic coated end label had proven completely satisfactory.

In the compositions of Table IV, EVA co-polymers varying in melt index from about 5 to 500 and in polymerized vinyl acetate content from about 20 to 35% could be substituted with the achievement of substantially equivalent results, the preferred EVA co-polymer having a polymerized vinyl acetate content of about 30% and a melt index of about 8-12. It should be emphasized that a blend of polyethylene and polyvinyl acetate, each separately polymerized by conventional means and the resulting polymers subsequently blended in the proportions mentioned above, will have vastly Clifierent properties than the EVA co-polymer presently under consideration. Such a blend of polyethylene and polyvinyl acetate would be valueless in the compounding of the coating compositions herein described.

Any of a number of microcrystalline waxes ranging in melting point from 140-170 F. may be substituted in the compositions of the preceding Table IV and wax blends containing minor amounts of paraffin or semimicrocrystalline waxes may also be utilized, although large percentages of these latter type waxes are somewhat less desirable due to their tendency to lower the adhesive qualities of the resulting coating composition to certain films, particularly polypropylene, and due to their tendency to lower the adhesiveness of the label at low temperatures.

Packaging operations wherein a product is machine wrapped in sheet material packaging film and the end folds sealed with labels as hereinbefore described have been carried out with a high degree of success and the operability, coating stability, low activation temperature, resistance to blocking and strike-through, non-slip properties when the label is heated and high seal stability upon aging or at reduced temperatures when applied to a wide variety of packaging films.

I claim:

1. A food package comprising, in combination, a flexible packaging sheet material secured around the lateral surfaces of an article of food, overlapped end folds at the ends of the article, a supplementary sheet on the end folds of the packaging sheet material and secured thereto by a thermoplastic coating composition on the supplementary sheet, said coating composition comprising between about 50% and 70% of a petroleum wax having a melting point between F. and F. and between about 50% and 30% of a high molecular weight thermoplastic co-polymer of ethylene and vinyl acetate, said thermoplastic co-polymer having a melt index between 5 and 500 and a weight content of polymerized vinyl acetate of between 20% and 35%.

2. A food package comprising, in combination, a flexible packaging sheet material secured around the lateral surfaces of an article of food, overlapped end folds at the ends of the article, a supplementary paper sheet on the end folds of the packaging sheet material and secured thereto by a thermoplastic coating composition on the supplementary sheet, said coating composition comprising about 60% of a microcrystalline petroleum wax having a melting point between 130 F. and 170 F. and about 40% of a high molecular weight thermoplastic co-polymer of ethylene and vinyl acetate, said thermoplastic co-polymer having a melt index between about 8 and 12 and a weight content of polymerized vinyl ace tate of between 20% and 35%.

3. A food package comprising, in combination, a flexible packaging sheet material wrapper secured around the lateral surfaces of an article of food, overlapped end folds at the ends of the article, a flexible sheet material label applied over the end folds of the wrapper and secured thereto by a thermoplastic coating composition on the label, said coating composition comprising between about 30% and 70% of a petroleum wax having a melting point between 130 F. and 170 R, up to 20% of a wax compatible modifying resin having a softening point between 130 F. and 300 F., and between about 50% and 30% of a high molecular weight thermoplastic co-polymer of ethylene and vinyl acetate, said thermoplastic co-polymer having a melt index between and 500 and a weight content of polymerized vinyl acetate of between 20% and 35%.

4. A heat-scalable flexible sheet material having on one surface thereof a thermoplastic wax composition coating having a melt viscosity of between 2000 and 15,000 centipoises measured at 290 F., said wax composition comprising between about 50% and 70% of a petroleum wax having a melting point between about 130 F. and 170 F., and between about 50% and 30% of a co-polymer of ethylene and vinyl acetate, said copolymer being the co-polymerization product of ethylene and vinyl acetate in ratio between about 2 to 1 and 4 to 1.

5. An article of food having a flexible sheet wrapper extending laterally about the same and provided with overlapping folds covering the end portions thereof, and a flexible coated sheet material label adhered by heat and pressure in sealing relationship to said overlapping folds, the coating on said coated sheet material comprising a thermoplastic composition of about 60% microcrystalline petroleum wax having a melting point of 130l70 F. and about 40% of a high molecular weight co-polymer of ethylene and vinyl acetate, said co-polymer having a melt index between about 8 and 12 and a polymerized vinyl acetate content of about 30%.

6. A flexible heat-scalable sheet material having on one surface a thehrmoplastic coating in amount between 8 lbs. and 20 lbs. per ream of said sheet, said coating comprising between 30% and 70% of a microcrystalline petroleum wax melting between about 130 F. and 170 F., between 50% and 30% of a co-polymer of vinyl acetate and ethylene polymerized in the ratio of 1 part of vinyl acetate to between 2 and 4 parts of ethylene, and up to 20% of a wax compatible modifying resin, said resin being selected from the group consisting of terpene resins, hydrogenated rosin, hydrogenated rosin esters, polymerized rosin, polymerized rosin esters and cyclicized rubber.

7. A label for heat-sealing to a flexible packaging material comprising a paper base sheet having on one surface a thermoplastic coating in amount between 8 lbs. and 20 lbs. per ream of said sheet, said coating comprising about 40% of a microcrystalline petroleum wax having a melting point between 130 F. and 170 F., about 40% of a high molecular weight thermoplastic co-polymer of ethylene and vinyl acetate and having a melt index between about 8 and 12 and a polymerized vinyl acetate content of about 30%, and about 20% of a wax-compatible resin selected from the group consisting of terpene resins, hydrogenated rosin, hydrogenated rosin esters, polymerized rosin, polymerized rosin esters and cyclicized rubber.

8. A label for heat-sealing to a flexible packaging material comprising a'paper base sheet having on one surface a thermoplastic coating in an amount between 8 lbs. and 20 lbs. per ream of said sheet, said coating comprising about 40% of a microcrystalline petroleum wax having a melting point between F. and F., about 20% of hydrogenated rosin and about 40% of a high molecular weight thermoplastic co-polymer of ethylene and vinyl acetate and having a melt index between about 8 and 12 and a polymerized vinyl acetate content of about 30%.

9. A label for heat-sealing to a flexible packaging material comprising a paper base sheet having on one surface a thermoplastic coating in an amount between 8 lbs. and 20 lbs. per ream of said sheet, said coating comprising about 40% of a microcrystalline wax having a a melting point between 130 F. and 170 F., about 20% of a glyceryl ester of hydrogenated rosin and about 40% of a high molecular weight thermoplastic co-polymer of ethylene and vinyl acetate and having a melt index between about 8 and 12 and a polymerized vinyl acetate content of about 30%.

10. Flexible paper sheet material having on a surface thereof in an amount between about 8 lbs. and 20 lbs. per ream of said sheet material a coating adapted to form fiber tearing bonds to polyethylene, waxed paper, polypropylene, nitrocellulose coated regenerated cellulose, modified polyvinylidene chloride, coated regenerated cellulose and other flexible packaging materials, said coating comprising about 4 0% microcrystalline petroleum wax having a melting point of 130170 F., about 20% of a wax-compatible modifying resin having a softening point of 130200 F., and about 40% of a co-polymer of ethylene and vinyl acetate, said co-polymer having a polymerized vinyl acetate content of 2035% by weight.

References Cited in the file of this patent UNITED STATES PATENTS 2,228,785 Smith et al. Jan. 14, 1941 2,391,621 Powell et a1. Dec. 25, 1945 2,692,723 Elsman Oct. 26, 1954 2,956,036 King Oct. 11, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,025,167 March 13, 1962 John P. Butler It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below- Column l line 16, for "break" read bread column 3, line 33, for "load" read loaf column 5, line 16, for "ethylenevinyl" read ethylene-vinyl line 63, for "lebel" read label column 7, line 68, for "2%" read 20% column ll line 28, for "thehrmoplastic" read thermoplastic Signed and sealed this 24th day of July 1962 (SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Atteefing Officer Commissioner of Patents

Claims (1)

1. A FOOD PACKAGE COMPRISING, IN COMBINATION, A FLEXIBLE PACKAGING SHEET MATERIAL SECURED AROUND THE LATERAL SURFACES OF AN ARTICLE OF FOOD, OVERLAPPED END FOLDS AT THE ENDS OF THE ARTICLE, A SUPPLEMENTARY SHEET ON THE END FOLDS OF THE PACKAGING SHEET MATERIAL AND SECURED THERETO B A THERMOPLASTIC COATING COMPOSITION ON THE SUPPLEMENTARY SHEET, SAID COATING COMPOSITION COMPRISING BETWEENT ABOUT 50% AND 70% OF A PETRELEUM WAX HAVING A MELTING POINT BETWEEN 130*F, AND 170*F. AND BETWEEN ABOUT 50% AND 30% OF A HIGH MOLECULAR WEIGHT THERMOPLASTIC CO-POLYMER OF ETHYLENE AND VINYL ACETATE, SAID THERMOPLASTIC CO-POLYMER HAVING A MELT INDEX BETWEEN 5 AND 500 AND A WEIGHT CONTENT OF POLYMRIZED VINYL ACETATE OF BETWEEN 20% AND 35%.

Images