Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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