CA1199566A - Laminated wrapper - Google Patents

Abstract

ABSTRACT

A padded packaging wrapper for guarding against rust and corrosion of tinplate, for example incorporates a coating ofvolatile corrosion inhibitor (VCI) on a pliable layer of sealed-cell microcellular foam supported on a strong sheet. The VCI can be incorporated in a cohesive non-adhesive coating on the microcellular layer or directly on the microcellular layer in the absence of such cohesive coating. The effectiveness of the VCI can be further enhanced by incorporating in the wrapper a vapor barrier such as for example, aluminum foil or a film of hydrophobic polymer such as a silicone or a poly-ester such as Mylar (polyethylene terephthalate). A water-repellant layer can also be added. The wrapper can be made anti-static and/or opaque, and strengthened with fibers that make it almost impossible to tear.

Description

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Uni-ted States Patent 4,086,384 describes a highly use-ful sheet packaging material in which a layer of a sealed cell microcellular foam polymer, such as Microfoam*, is adhered to a layer of kraft paper, which may be reinforced by fiberglass strands. Such material forms highly effective packages, bu-t does not sufficiently protect moisture-sensitive objects, such as tin plate, which are subject to corrosion under ordinary atmospheric conditions. An object of this invention is to provide laminated sheet material for packaging a moisture-sensitive material and protecting it from being damaged by moisture over extended per-iods of storage. Another object is to provide such a laminated sheet material which is suitable for packaging sheets of tin-plated steel or other metals and preventing them from rusting or corroding over extended periods of storage.
Thus, this invention provides a laminated wrapper for wrapping around corrodible material, the wrapper having a layer of not over 1/8 inch thick of pliable sealed-cell microcellular foam, adhesive material securely bonding the microcellular foam to a strong supporting sheet, and a layer of volatile corrosion inhibitor on the surface of the foam remote from the supporting sheet, to inhibit corrosion of the material wrapped against the foam.
This invention also provides cushioned packaging of moisture-sensitive material, in which the moisture-sensitive ma-terial is wrapped against the foam of the laminated wrapper of the invention.

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In another aspect the inventlon provides a laminated wrapper for wrapping around corrodible material, the wrapper having a layer no-t over about 1/8 inch thick of resilient and pliable sealed-cell microcellular foam, a strong foldable sup-porting sheet, adhesive material securely bonding the microcel-lular foam to the supporting sheet and an aluminum foil not over 0.0008 inch thick, all laminated together with the foam layer as a surface layer, an adhesive coating being on the outer face of the foam layer.
In yet another aspect the invention provides a lami-nated wrapper for wrapping around corrodible material, the wrap-per havinga layernot overabout l/8inchthick ofresilientand pliable sealed-cell microcellular foam, a strong foldable support-ing sheet, adhesive material securely bonding the microcellular foam to the supporting sheet and an aluminum foil not over 0.0008 inch thick, all laminated together with the foam layer as a sur-face layer, a protective coating being on the outer face of the foam layer.
In one embodiment of the invention, a padded sheet material for packaging a moisture-sensitive material has a layer of paper which is adhered on one side to a layer of a sealed cell microcellular foam polymer, such as Microfoam*. It i3 coated on the other side with a layer of polymer, which excludes the passage of drops of water but transmi-ts moisture vapor through it whereby any condensate within the package evaporates out through the material. The paper may be reinforced with strands of fiberglass or other suitable reinforcing fibers to - la -35~

strengthen it.
Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following description in conjunction with the accompanying drawings wherein similar reference char-ac-ters refer to similar parts and in which:
Figure 1 is a cross-sectional view in elevatjon of a laminated sheet material which is one embodiment of this invention;
Figure 2 is another cross-sectional view in elevation of another laminated sheet material which is another embodiment of this invention; and Figure 3 is a further cross~section view in elevation of a further laminated sheet material which is a further emhodiment of this invention.
In Figure 1 is shown a laminated sheet material 10 for packaging or wrapping moisture-sensitive material, such as tin-plated s-teel ~ew shown).
Till plateis aspecialty grade of steel sold to canners. Because of the end use application, the tin plate must be completely free from corrosion. Because of this, the steel mill must exert extra care in the packaging o tin plate and will guarantee the product for thirty da~s. If corrosion occurs prior to the thirty day period, the steel companies will take back cmy shipment where corro-sion has formed.
Sheet 10 includes a layer of paper material 12 which has two plies of kraft paper 14 rein:Eorced by strands of fiberglass 16. Kraft paper plies 14 are each, -for example, fifty pound kraft paper. ~ther useful types of kraft p~per are, for example, thirty pound, sixty pound or ninety pound, or even forty-two pound liner board. Fiberglass strands 16 arranged, for example, in a diamond pattern, are interspersed between paper plies 14. Plies 14 are adhered to each other and to the interspersed fiberglass in a diamond pattern and longitudinal fiber arrangement and sealed overall by adhesive 17 which is for example, of the hot melt type, such as amorphous polypropylene. The ~9~;6 ultilllately laminated sheet 10 has remarkable strength to weight ratio and is extremely useful for wrapping and packaging where substantial tear s~rength and protection against moisture are required, such as in packaging sheets of tin-plated steel. Reinforcement may also be accomplished by adheri.ng other types of mesh to the laminate, such as polypropylene.
The bottom layer 18 is a sealed cell microcellular polymer. It may be, for example, from about 1/16 inch to l/8 inch thick. A highly effective sealed cell microcellular foam polymer is, for example, a l/16 inch or 3/32 inch thick layer of microfoam, which is, for example, P~licrofoam*, available from E.I. DuPont de Nemours ~ Co. of l~ilmington, Delaware. It is made from polypropylene resin, and constitutes a high-bulk material with approx-imately fifty thousand closed air cushioned cells per cubic inch. ~oam poly-mer layer 18 is adhered to the paper by the same hot melt adhesive used in conjunction with the original two-ply kraft paper.
A layer 20 of a hydrophobic polymer, such as polyethylene, is disposed over top of two-ply kraft paper layer 12 to complete the laminated sheet. It is, for example, adhered to the kraft side by coating or extrusion.
Polymer coating 20 may be colored to distinguish it and to control the passage of light through it. It also may be made of other suitable water vapor trans-

2~ missive hydrophobic polymers, such as polypropylene, polycarbonate and the like. A '5 micron thick layer 20 is adequate.
Laminate lO may be used for wrapping loads of tin plate and othermetals preventing corrosion prior to use. Corrosion and rust prevention for over thirty days have been thus accomplished. The product has excellent ver-satility and performance for ~he special problems of tin plate packaging. In addition to lts ability to protect the tin plate from external moisture damage, the construction permits the wrap to "breathe". This means that as condensate *Trade mar~

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is formed because of temperature variation in shipment, such function permits evaporation of the condensate rather than its retention within -the package which would cause corrosion. Laminate 10 has excellent properties helpcd by the contact of the microporous foam with the tin plate (not shown). Such mi-crOcellu]ar foam material made of polypropylene complies with F.D.A. regulations, which permit it to be safely used as an article or a component of an article intended for use in contact with food. It is unaffected by exposure to grease, water and most acids, bases and solvents. It stays flexible within a wide temperature range, has a neutral pH, is non-toxic, non-corrosive, lint-free, has excellent abrasion resistance and will not support the growth of mildew or fungus. It has an excellent, clean-white appearance which is highly desir-able for the packaging of tin plate.
Figure 2 shows another laminate lOA of this invention in which a layer 22A of cohesive material is applied to the outer surface Of microcellular foam layer 18A. Cohesive layer 22A is~ for example, a latex material 'naving a property of sticking to itself but not adhering to other materials. This co-hesiveness facilitates securing sheet lOA about an object wrapped within it.
Although it is nonadherent to objects other than itself, it does have extremely high frictional resistance and is somewhat rubbery to the touch. It, therefore, does not slide off an object and makes it easy to wrap and advantageously stays in place to further facilitate the enfolding and sealing process. ~aminated sheet lOA is otherwise the same as sheet 10.
Figure 3 shows a further laminated sheet lOB which is the same as sheet lO in Figure 1, except that a single ply 14B of kraft paper of, for example, sixty pound weight is utilized instead of reinforced two-ply kraft paper layer 12 of Figure 1. Sheet lOB can be used when the extremely great tear strength of sheet 10 is not required. Microcellular foam layer l&B could 5~t~

have cohesive layer applied as shown in Figure 2.
Instead of or in addition to the latex in coating 22A, a volatile corrosion inhibitor (VCI) such as those described in United States Patents 2,829,080 and 3,080,211 can be incorporated in that coating. Because of the ready deformability of the foam layer, that layer brings a VCI coating in much better contact with metal objects packed against such a modified packaging sheet, particularly where the metal objects do not have perfectly flat sur-faces. A packing sheet that does not have a foam surface provides much poorer contact, and does not protect metals as well against corrosion. 'I'in plate, steel, copper ~7 aluminum alloys are examples of corrodible metals better protected by the VCI-coated packaging slleets of the present invelltion, and the water repellellt coatings 20, 20A and 20B are helpful in this connection.
A VCI coating weight of only about 0.00~ grams per square foot of foam surface is generally all that is needed, but weights of 0.01 or even 0.02 grams per square foot can be used if desired. Water-soluble VCI's are preferably deposited from water solution, and water-insoluble VCI's from solution in a solvent like methyl chloroform. Wllcn a water-soluble VCI is mixed with a rubber latex, care should be taken to keep the latex emulsion from breaking into two laycrs before the mixture is applied to the foam surface.
S01ne water-sensitive metals are deliberately coated with a film of water-repellent oil to help prevent corrosion. ~hen packaging such coated metals it is helpful to use a packaging laminate in which the plies are bonded together with an oil-resistant laminant or bonding adhesive such as rubber latex or polyvinyl acetate or highly polymeri~ed polyvinyl chloride. Amorphous polypropylene melt polymer can be dissolved by some coating oils ~o the extent that delamination and great loss of strength can occur.
The VCI's are generally more vola~ile than they need to be, and S6t;

can be mixed with other chemicals such as fatty alcohol phosp}lates, which are less volatile or non-vola-tile. Su,ch mixtures will also protect metals against ~;?/C'0~/
corrosion. In fact, fatty ~G~4~ phosphates also have a corrosion-inhibiting effect on iron and other metals. The Zelec NE* and Zelec Nll* fatty alcohol phosphate anti-static agents sold by E. I. duPont de Nemours ~ Co., as well as di-[2-ethyl-hexyl]-hydrogen phosphate and the morpholine salt of di-[9-octa-decenyl]-hydrogen phosphate make good corrosion inhibitors and are also very effective anti-static agents whether or not mixed with a VCI. I~here the VCI is not sufficiently soluble in water, the addition of a fatty alcohol phosphate anti-static agent will help dispcrse the VCI in waterJ inasmucll as the anti-static agent also has surfactant properties. Anionic surEactants sucll as those phosphates should not be mixed with a cationic latex, nor shoulcl a cationic surfactc~lt be used with an aniollic latex, unless the proportion of surfactant is too small or too large to break the latex emulsion, or a stabilizer is added.
Polyacrylic acid having a molecular weight of about 3000 to about 20,000 makes a good stabilizer, as does gelatine and surfactants.
A very useful packaging sheet is thus obtained with the laminated construction of Figure 1, by applying as the layer 22A a 5~ dispersion of morpholine caprylate in water, and thell permitting the solvent to evaporate. A
single application is generally enougll to provide the desired amount of VCI, and the closed-cell character of the foam layer 1~, keeps the VCI on the outer face of the foam, even when that foam layer is only 1/16 inch thick or less.
Such a thin foam layer, with reinforced or un-reinforced paper plies each of 50-pound kraft paper, makes a good corrosion-resistant sheet for wrapping or interleaving with steel sheets.
A layer of natural rubber latex can then be applied over the VCI
layer, or if desired the rubber latex is mixed with the VCI dispersion before *Trade Mark 5~i that dispersion is applied. rhe alllo~mt of rubber remainillg Oll thC? outer Eace of the foam shoulcl be enough -to provide the cohesive non-adheiive character, generally at least about 0.05 gram per square foot.
Alternatively the VCI coating can be the only coating on the exposed surface of the foam, with the latex coating applied to the paper sur-face on the opposite face of the laminated assembly.
~ efore anything is applied to the foam surface it can first be coated with about 0.01 gram per square foot of anti-static layer such as the morpholille salt of di-[9-octadecenyl]-hydrogen phosphate or one of the above-noted Zelec products, although such a coating can be applied aEter the VCI
coating, or after the cohesive non-adhesive coating. An anti-static agent that is not oily is desired wllen used with the cohesive non-adllesive coating, inasmuc}l as oily Eilms detract Erom the cohesion otherwise obtainable.
Ordinary kraft paper when used in weigllts as high as 90 pouncls or even higher, is not perfectly opaque. For use in packaging light-sensitive material such as une~posed microfilm, a single opaque paper ply laminated to the microporous closed-cell foam can be usecl, as for example whell the paper is a fifty-pound sheet beater-dyed with Basic Viole-t No. 3 or Pigmen-t ~lack No. 7, to a dye content of about 1/2% by weight. IYhere two paper plies are present in the lamillated assembly, either one, or both can be dyecl> and when both are dyecl their dye content can be lower and as little as 1/4% by weight. l-lowever lighter sheets should contain proportionately more dye. Carbon black can also be incorporated in the papers instead of or together with one or more dyes.
Aluminum foil that is extremely thin, e.g. 0.5 to 0.8 mil, is also opaque and can be laminated in the assembly of Figure 2, but such thin foil usually contains pin-holes that admit light. It is accordingly best not to rely on such thin foils for all but the least sensitive of articles. Carbon black ~9~9S6~

can likewise be incorporated in the Eoam, as by Eormillg carbon-loadecl rcsin, and will impart anti-static properties in addition to opaqueness.
For wrapping light-sensitive material, the opaque wrapping sheet preferab]y carries the cohesive non-adhesive coating, but does not need the VCI unless the light-sensitive material is packaged with corrodible metal.
The cohesive non-adhesive coating, or the foam surface under it, can also con-tain the anti-static agent inasmuch as the pulling apart of a cohesively secured wrapper can otherwise generate sufficient static elec-tricity to cause luminous discharges that fog very sensitive photographic emulsions.
The wrapping sheets of the present invention can be used :Eor any wrapping or interleavillg application. The cohesive non-adhesive layer makes these sheets particularly desirable inasmuch as such sheets are readily securecl to each otller without the need for holcl-dowlls such as baling straps or twille.
Ihus the trunk of a tree is readily protected by wrapping using a sheet that is longer than the tree circumference. The sheet is wrapped com-pletely around the trunk to leave a proje~ing end a-t each end of the sheet, and these projecting ends then pressed together to bring their respective cohesive non-adhesive layers in contact with each other. This causes those ends to become adhered to each other and thus secllrely retains the sheet in place. ~ne sheet can have a width as large as the trullk heigll-t desired to be wrappecl, or two or more sheets wrapped besicle each other to cover the desired height.
The foanl surfaces of the wrapping sheet are sufficiently yieldable to permit the sheets to be drawn up tightly against the trunk by the wrapping, without causing any trunk irregularity to puncture the wrap.
It appears that a wrap of the above type will not only protect the trunk from abrasion and the like, as for example when a package of trees s~

is shipped by truck, but it also keeps h~mgry anlmals from eating the barlc.
The cohesive non-adhesive paper-foam laminated sheets also make very good bases on which to place objects -that are to be held in posit:ion. Thus a carton of labelled bottles can be packed without the usual separator grid when the bottles are placed on the cohesive non-adhesive coated foam surface of a packaging sheet. Such packing keeps the bottles from rubbing or vibrating against each other when subjected to the usual shipping conditions, and the labels on the bottles will not become damaged or blurred.
For this purpose the sheet can have a single paper ply of as little as 20 pounds weight, and the foam thickness need be no greater than l/16 inch. Reducing that foam thickness or eliminating the foam altogethcr and having the cohesive non-adhesive layer only on a sheet of paper, gives poorer results.
The cohesive non-aclhesive coatings also permit the sheets to be sandwiched together around any object to be wrapped, by having the sheets project in at least two directions beyond the object. Thus L text book is very simply sandwiched to make a complete book-mailing package that only needs an address label, with the sheets projecting only abou-t 1 1/2 to 3 inclles beyond the book at each edge.
Even liquids can be similarly packaged, as by folding a sheet in two to bring the cohesive noll-adllesive faces of the folds toward each other and pressing the facing side margins together to make a pocket. The liquid to be packed is poured into the pocket after which the top of the pocket is sealed pressing the folds together in that location. The closed-cell nature of the foam will not permit leakage of the liquid.
While paper sheets are quite suitable for the plies 14, 14 or 14A, 14A, or 14B, these plies can be made of woven or knitted textile fibers, or of s~

air-:Eelted textile fibers, or even of plastic film. ~ strong plastic such as polye-thylene terephthalate is preferred for such film or Eor the fibers. Instead of the usual type of plastic fibers, narrow widths of plastic film can be woven to make one or both of the plies. I~hen a ply is made of strong material such as the polyethylene terephthalate, i-t makes a very effective reinforcement for a paper ply whether such reinforcement be an outer layer of the packaging sheet or a layer between the foam layer 18 and the adjacent ply 14. }laving a relatively smooth surface on one face of the packaging sheet is desirable be-cause such a surface can be printed with advertising or the like.
The use of even two paper plies without any reinforcemellt is not as desirable as having one ply of paper together witll a high-strellgt}l reinforce-ment. Glass fibers or nylon or qi~la Eibers are very effective and glass is particularly desirable by reason of its low cost. ~\n un-reinforced paper-foam packing sheet is only suitable for very light duty use, w}lereas a well-reinforced packing sheet is almost impossible to tear. This is of major impor-tance when packaging or padding metals.
Obviously many modifications and variations of the present inven-tion are possible in the light of the abovc teachings. It is, therefore, to be wlderstood -that Wit}lill the scope of the appended claims the inventioll may bc practiced otherwise than as speciEically described.

Claims (22)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A laminated wrapper for wrapping around corrodible material, the wrapper having a layer not over about 1/8 inch thick of pliable sealed-cell microcellular foam, adhesive material securely-bonding the microcellular foam to a strong supporting sheet, and a layer of volatile corrosion inhibitor on the surface of the foam remote from the supporting sheet, to inhibit corrosion of the material wrapped against the foam.

2. A laminated wrapper as set forth in claim 1, in which the supporting sheet is paper.

3. A laminated wrapper as set forth in claim 2, and further containing a water-repellant stratum.

4. A laminated wrapper as set forth in claim 1, and further containing a vapor barrier stratum.

5. A laminated wrapper as set forth in claim 1, wherein the paper has reinforcing fibers attached thereto.

6. A laminated wrapper as set forth in claim 5, wherein the reinforcing fibers are fiberglass strands.

7. A laminated wrapper as set forth in claim 6, wherein the fiberglass fibers are sandwiched between two plies of paper.

8. A laminated wrapper as set forth in claim 1, wherein the volatile corrosion inhibitor layer is in a cohesive non-adhesive coating that will adhere to itself but not to other parts of the wrapper.

9. A laminated wrapper as set forth in claim 1, wherein the foam is a polypropylene foam.

10. A laminated wrapper as set forth in claim 2, wherein the paper has two plies of fifty pound kraft paper each.

11. A laminated wrapper as set forth in claim 4, wherein the vapor barrier is a film of polyethylene terephthalate.

12. A laminated wrapper as set forth in claim 1, wherein the adhesive is a hot melt adhesive.

13. A laminated wrapper as set forth in claim 4, wherein the vapor barrier is an aluminum foil.

14. A laminated wrapper as set forth in claim 1 in which the adhesive is an oil-resistant bonding agent.

15. A cushioned packaging of moisture-sensitive material, in which the moisture-sensitive material is wrapped against the foam of the laminated wrapper of claim 1.

16. The cushioned packaging as set forth in claim 15, in which the moisture-sensitive material is tin plate.

17. A laminated wrapper for wrapping around corrodible material, the wrapper having a layer not over about 1/8 inch thick of resilient and pliable sealed-cell microcellular foam, a strong foldable supporting sheet, adhesive material securely bonding the microcellular foam to the supporting sheet and an aluminum foil not over 0.0008 inch thick, all laminated together with the foam layer as a surface layer, an adhesive coating being on the outer face of the foam layer.

18. A laminated wrapper for wrapping around corrodible material, the wrapper having a layer not over about 1/8 inch thick of resilient and pliable sealed-cell microcellular foam, a strong foldable supporting sheet, adhesive material securely bonding the microcellular foam to the supporting sheet and an aluminum foil not over 0.0008 inch thick, all laminated together with the foam layer as a surface layer, a protective coating being on the outer face of the foam layer.

19. A laminated wrapper as set forth in claim 18 wherein the protective layer is a layer of volatile corrosion inhibitor.

20. A laminated wrapper as set forth in claim 18 wherein the protective layer is a layer of anti-static agent.

21. A package having a sensitive material wrapped in the laminated wrapper of claim 17, 18 or 19.

22. A package having a sensitive material wrapped in the laminated wrapper of claim 20.