US3337114A

US3337114A - Moisture resistant packaging

Info

Publication number: US3337114A
Application number: US516861A
Authority: US
Inventors: Norman F Lockwood
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1965-12-28
Filing date: 1965-12-28
Publication date: 1967-08-22
Anticipated expiration: 1984-08-22

Description

1967 N; F. LOCKWOOD 3,337,114

MOI STURE RES ISTANT PACKAGING Filed Dec. 28, 1965 INVENTOR. Y NORMAN F. LOCKWDOD avfl 1 F111,

ATTORNEY United States Patent York Filed Dec. 28, 1965, Ser. No. 516,861 5 Claims. (Cl. 229-37) This invention relates to moisture resistant packaging particularly moisture resistant cellulosic packaging.

The most widely used packaging at present is cellulosic packaging. Particularly, corrugated boxes and paperboard cartons, because of their good strength and protectiveness and their comparatively low cost enjoy great popularity as packaging. A disadvantage of cellulosic packaging is its deterioration upon contact with moist environments. An example is the disintegration of produce shipping boxes after being wetted to insure moist produce upon arrival at the retailer.

This difficulty has been sought to be circumvented by the use of various moisture proof coatings on the exteriors and/or interiors of the cellulosic package. But coating raises problems of its own. The most economical coating techniques, such as roller coating, cover only the top and/or bottom surface and leave the edges thereof unprotected. Moisture attacks the unprotected area and, by a wicking action, the moisture permeates the entire carton resulting in unsightly, badly weakened packaging.

It has also been proposed to provide moisture-proof packaging by inserting a blank of cellulosic stock between two sheets of heat shrinkable thermoplastic film, heat sealing the sheets together around the perimeter of the blank and applying heat to draw the film close to the blank. Generally, the blank is a flat form of the ultimate container, having a body scored for folding and appended flaps spaced one from another by slots and scored for folding at the juncture thereof with the body. As indicated above, the sheets have been heat sealed around the perimeter of the blank including within the slots between the flaps to completely enclose the blank and protect it from the deteriorating effects of moisture. The seal in each slot is then divided by cutting therein to provide two seals, one for each of the adjacent flaps to permit freedom of movement and folding thereof.

It has been found, however, that accomplishing a film seal around the perimeter of a packaging blank including all the slot edges therein is a cumbersome and tedious operation requiring the alignment of heat-ing blades and platens with each slot on both sides of the blank as well as the step, outlined above, of dividing the seal in each slot once it is formed. Moreover, it has frequently been diflicult to obtain an effective seal in these slots, which are often as narrow as inch or less, due to the tendency of the films to shrink during the heat-sealing step causing seal-weakening stresses. The resulting narrow seal in each slot must then, as indicated above, be cut or divided down the middle which results in two even narrower seals at adjacent flap edges; seals which are proportionately weaker than before and tend to pull apart.

Accordingly, it is an object of the present invention to provide improved moisture-proof cellulosic packaging.

It is an other object of the invention to provide cellulosic packaging securely sealed within an envelope of heatshrinkable thermoplastic film.

These and other objects are accomplished in the present invention which provides moisture proof cellulosic packaging material comprising relatively rigid cellulosic packaging stock having a body scored for folding and a plurality of flaps spaced one from another by cleavages and scored for folding at the body, said stock being enclosed within a peripherally sealed heat shrinkable thermoplastic ice film, said cleavages being of ample width to provide adjacent flaps th-us enclosed with sufiicient film slack to permit the facile and independent folding thereof requisite to package formation.

The invention will become more apparent from the following detailed specification and drawings in which:

FIGURE 1 is a plan view of the packaging embodying the invention, showing foldable packaging stock enclosed within a peripherally sealed, heat shrunk, thermoplastic film.

FIGURE 2 is a sectional elevation of the packaging stock as shown in FIGURE 1, taken along line 2-2.

FIGURE 3 is an isometric view of an assembled container embodying the invention.

FIGURE 4 is an enlarged fragmentary perspective of the packaging of FIGURE 1 showing portions of adjacent flaps and the cleavage therebetween.

Referring now to the drawings, the packaging material 10 includes packaging stock 16', shown in FIGURE 2, having a body 12, score lines 13 and flaps 14, enclosed within a heat shrunk, thermoplastic film 17 as shown in FIGURES 1 and 4. Film 17 consists of, for example, sheets 18 and 20 as shown in FIGURES 2. and 4. The film 17 is sealed at the periphery, indicated in FIGURE 1 by straight sides 19 and 21, of packaging material 10, so that it extends across the cleavage 15 which separates each pair of adjacent flaps 14, as shown in FIGURES 1 and 4.

The packaging material 10- is folded into a container 11 and can be secured at the meeting edges of the body 12 by any conventional means, for example, by adhering strip 22 as illustrated in FIGURE 3.

Thus the packaging material of the present invention can be provided, for example, by inserting relatively rigid, foldable cellulosic stock between a pair of sheets of heat shrinkable film, sealing said sheets together only at their peripheries, thus ignoring the contour of any cleavages, including slots, present in the stock and thereafter drawing or shrinking the thermoplastic film close to the stock by application of heat to the film.

The heat shrinking of the film about the packaging stock can take place at any desired time after the above indicated film heat-sealing step. Thus the heat shrinking step can occur before the sealed packaging material is folded, i.e. while still in blank form or such step can be applied after the sealed packaging material is folded and fastened to form a container- Alternatively, the heat sealing step can be postponed until the container is formed, contents placed therein and the container closed, in which event heat shrinking would be applied predominantly to the film situated on the outside thereof. The heat sealing step moreover can take place in one step or in several as where partial heat shrinking is applied to the film before the packaging material is folded with further heat sealing being applied at subsequent stages of container formation.

Any foldable cellulosic packaging stock or blank including linerboard or paperboard is suitable for the present invention. The blank can have one or more flaps, any number of score lines and take any shape appropriate to the desired application.

The cleavage, defined by adjacent edges of adjacent flaps of a blank, can be any suitable shape and size as long as each cleavage is wide enough to permit adjacent flaps to be properly folded, i.e., with sufiicient film-slack therebetween, in the formation of a package from such blank when it is peripherally sealed within heat-shrunk thermoplastic film. Preferably each cleavage tapers inwardly from the outer edges of adjacent flaps but, as indicated, such cleavage can take other shapes suitable to the requirements of the ultimate container.

Thermoplastic film or sheet which can be used in the present invention is sheet, including film, which comprises one or more synthetic, organic thermoplastic polymers. Generally useful polymers are homopolymers of alpha olefins, compounds having the formula R-CI-IiH wherein R is hydrogen, or an aliphatic hydrocarbon group such as an alkyl group, particularly an alkyl group having from 1 to 8 carbon atoms, and copolymers thereof with one or more other compounds copolymerizable therewith which contain polymer producing unsaturation such as is present for example in carbon monoxide and in organic compounds containing the ethylene linkage C=C e.g., ethylene, propylene, styrene, vinyl stearate, butene, vinyl acetate, vinyl formate, methyl methacrylate, monobutyl maleate, 2-ethyl hexyl acrylate, N-methyl-N-vinyl acetamide, methacrylic acid, ethyl acrylate, acrylic acid, isoprene, butadiene acrylamide, vinyl triethoxysilane, bicycloheptene, bicycloheptadiene, divinyl phosphonate and the like.

The term heat shrinkable as used herein refers to a property of a film by which it contracts in length and/ or width upon exposure to sufficient heat. Shrinking is generally attributable to a reorientation of molecules, which were previously oriented by stretching the film either uniaxially longitudinally, transversely, or biaxially. The amount of shrinkability in the film is not critical, the only requirement being that the film fit closely to the cellulosic stock after shrinking. Obviously the greater the shrinkability of the film the less taut the thermoplastic film must be pulled over the stock and the farther from the edges of the stock the seals can be. The absence of criticality in these operations effects great cost savings.

The method of achieving the peripheral seal is not critical. Heat sealing is most convenient and is preferred. However, solvent sealing and adhesive sealing are illustrative of other suitable sealing techniques known in the art. Still others can be used.

The packaging of the invention is highly moisture resistant. It has been found, for example, that a box formed from this packaging can be immersed in Waterfor three days and longer without adverse effechts.

The present invention is useful in providing protection against dirt, moisture and other harmful environmental factors to all relatively rigid cellulosic packaging material. Thus, corrugated stock comprising linerboard and fluted interlayer used in forming boxes for shipping and the like as Well as the less rigid paperboard used in forming 4 cartons for smaller products and the like can be protected.

An important advantage of the present invention is that it is not required that there be any sealing of the thermoplastic film to the cellulosic stock. A peripheral film-to-film seal is sufficient. This eliminates the need for special treatment of the cellulosic stock or thermoplastic film surfaces. Ready removability of the protective covering is another feature of the present invention. With presently known protective covering techniques, such as coatings, the protected cellulosic stock is often not reprocessable and is worthless as scrap. This invention, however, enables easy separation of cellulosic and protective materials. Of course, the film can be sealed to the cellulosic stock if desired.

What is claimed is:

1. Moisture proof cellulosic packaging material comprising relatively rigid cellulosic packaging stock having a body scored for folding and a plurality of flaps spaced one from another by cleavages and scored for folding at the body, said stock being enclosed within a peripheral sealed heat shrinkable thermoplastic film, said cleavages being of ample width to provide adjacent flaps thus enclosed with suflicient film slack therebetween to permit the facile and independent folding thereof requisite to package formation.

2. The packaging material of claim 1 wherein each of said cleavages tapers inwardly from the outer edges of adjacent flaps.

3. The packaging material of claim 1 wherein said body and said flaps are folded along the respective scores thereof and fastened to define a box.

4. The packaging material of claim 1 wherein said film is heat shrunk about said stock.

5. The packaging material of claim 4 wherein said body and said flaps are folded along the respective scores thereof and fastened to define a box.

References Cited UNITED STATES PATENTS 2,545,243 3/1951 Rumsey. 3,026,656 3/ 1962 Rumsey. 3,172,593 3/1965 Potter 2293.5

JOSEPH .R. LECLAIR, Primary Examiner.

R. PESHOCK, Assistant Examiner.

Claims

1. MOISTURE PROOF CELLULOSIC PACKAGING MATERIAL COMPRISING RELATIVELY RIGID CELLULOSIC PACKAGING STOCK HAVING A BODY SCORED FOR FOLDING AND A PLURALITY OF FLAPS SPACED ONE FROM ANOTHER BY CLEAVAGES AND SCORED FOR FOLDING AT THE BODY, SAID STOCK BEING ENCLOSED WITHIN A PERIPHERAL SEALED HEAT SHRINKABLE THERMOSPLASTIC FILM, SAID CLEAVAGES BEING OF AMPLE WIDTH TO PROVIDE ADJACENT FLAPS THUS ENCLOSED WITH SUFFICIENT FILM SLACK THEREBETWEEN TO PERMIT THE FACILE AND INDEPENDENT FOLDING THEREOF REQUISITE TO PACKAGE FORMATION.