CA2026659A1 - Absorbent bubble laminates - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A moisture absorbent bubble laminate includes a perforated, thermoplastic film and a thermoformable, thermoplastic film adhered at spaced intervals to the perfo-rated film, and formed into a plurality of bubbles. Mois-ture-absorbent material is disposed within the bubbles. A
plurality of the bubbles is in communication with the perfo-rations of the perforated film to permit moisture from a source of moisture to enter the bubbles and be absorbed by the moisture absorbent material. This laminate is particular-ly useful in applications such as purge traps for tray overwrapped moist products, disposable pads and the like.

Description

- ` 2~2~9 ABSORBENT BUBBLE LAMINATES

BACKGROUND OF THE INVENTION

It is well known that "bubble" films, laminates, and packaging, i.e. film or film combinations where air or another gas is trapped at regular intervals between two or more sheets of film, are useful in certain packaging applica-tions. These bubble constructions are sometimes referred to as air-cushioning materials. These constructions are particu-larly~useful where shock absorbance, softness, or physical or thermal insulation is required.

Many patents have issued in this general technolo-~ gY-:' ~ :
An article "Terra-Sorb" discloses a super absorbent copolymer.~; -U~. S~ Patent No. ~4,576,669 (Caputo) discloses an apparatus and method for producing air-cushioning material in which~ a first film is heated and thermoformed on a cooled roll with cavities formed therein, and a second film is heat-ed on a heated roll and heat-sealed to the first film.
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U. S. Patent No. 4,579,516 (Caputo) discloses a forming roller useful as the cooled roller for thermoforming a first film as described in U. S. Patent No. 4,576,669.

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U. S. Patent No. 4,018,946 (Klein) discloses a method of producing expandable styrene-polymers by impregnat-ing discrete styrene polymer bit-pieces, such as pellets or beads, with an aliphatic liquid.

U. S. Patent No. 4,192,699 (Lewicki et al) disclos-es a method of making inflatable cellular assemblies of plas-tic material which incudes the use of multiple sheets of material.

U. S. Patent No. 4,415,398 (Ottaviano) discloses air cell cushioning dunnage formed from two sheets of flexi-ble plastic material, one of the sheets having been embossed to define cells with entrapped air.

U. S. Patent No. 3,508,992 (Chavannes) discloses a method for making cellular material using multiply laminates with at least one of the laminates embossed prior to sealing the laminates together.

U. S. Patent No. 3,142,599 (Chavannes) discloses a method for making laminated cushioning material, and sealed elements in hemispherical form.

U. S. Patent No. 3,208,898 (Chavannes et al) dis-closes an embossed, laminated article having an embossed or molded plastic layer, a sealing layer, a plurality of cells, and a second sealing layer sealed to the top of the cells.

U. S. Patent No. 3,285,793 (Chavannes) discloses an embossed cushioning material made by joining two films of plastic together, one of the films being embossed in a hemi-spherical shape.

U. S. Patent No. 3,586,565 (Fielding) discloses a first sheet sealed to a second embossed sheet to form a plu-rality of hermetically sealed cells.

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,, U. S. Patent No. 3,616,155 (Chavannes) discloses a cellular product formed of multiply laminates wherein at least one of the laminates is embossed and the other laminate seals the embossment. Each laminate has a plastic base and a gas-impervious coating.

U. S. Patent No. 2,020,639 (Grayson et al) disclos-es an insulation board having a skeleton structure constitut-ing a system of cells filled with fibrous insulation sub-stance.

Canadian Patent No. 1,191,437 (Ottaviano) discloses a cushioning dunnage material of a first single stratum film, embossed to form air cells therein, and a second film adhered to the first film.

Canadian Patent No. 1 186 204 (Ottaviano) discloses a cushioning dunnage material of a first multilayer film, embossed to form air cells therein, and a second film adhered to the first film.

Great Britain Patent No. 908,579 discloses a lami-nated multi-cellular sheet packaging material made by emboss-ing a first web on an embossing drum, and adhering a second web to the first web.

U. S. Patent No. 4,181,548 (Weingarten) discloses a three-layer laminated plastic cushioning material having a flat central la~er with sealed air pockets on both sides of the central layer.

The present invention relates generally to absor-bent laminates for use as absorbent pads, and more particular-ly to absorbent pads for use in articles such as purge traps for food trays, disposable diapers, bed pans and the like.

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It is an object of the present invention to provide an absorbent bubble laminate for use in making absorbent pads and the like which has even more absorbency than that offered by previous absorbent bubble laminates.

SUMMARY OF THE INVENTION

A moisture absorbent bubble laminate comprises a perforated, thermoplastic film; a thermoformable, thermoplastic film adhered at spaced intervals to the perfo-rated film, and formed into a plurality of bubbles; and a moisture-absorbent material disposed within a plurality of the bubbles.

A method of making a moisture absorbent bubble ~ -laminate comprises heating a thermoformable, thermoplastic film; advancing the heated, thermoformable, thermoplastic film to an embossing roll;, vacuumizing the heated film to form a plurality of bubbles in the film; placing a moisture absorbent material in a plurality of the bubbles; and adher-ing a perforated, thermoplastic film to the thermoformable film so that the moisture absorbent material in the bubbles of the film is trapped between the first and second films. ~-~

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BRIEF DESCRIPTION OF THE DRAWINGS
' .., The invention may be further understood by refer-ence to the drawing figures, in which:
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Fig. 1 is a cross-sectional view of a prior art bubble laminate;

Fig. 2 is a cross-section of a moisture absorbent bubble laminate in accordance with the present invention; and 4/900818.6/TXTVW/08 30,90/02:17:20 PM

2~26~.~9 Fig 3 is a cross-section of an alternative embodi-ment of the moisture absorbent bubble laminate of Figure 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figure 1, a prior art bubble laminate is depicted in which a first film 22 is adhered to a second film 24. Bubbles 28 having cavities 30 therein are formed from the thermoformable film 24. Portions of film 24 between adjacent bubbles 28 are adhered to first film 22 at segments 26 of the laminate.

The present invention can be understood by refer-ence to Figure 2, wherein a perforated film 22 having perfora-tions 32 at intervals therein is adhered to a thermoformable film 24 at segments 26 of the adjoining films. A plurality of bubbles 28 are formed in film 24 at spaced intervals there-in. As used herein, the term "formed in" with respect to the bubbles 28 of film 24 does nat refer to the occurrence of bub-bles within film 24, but rather to bubbles 28 having cavi-ties 30 therein formed when film 24 is placed on an embossing roll having cavities therein of the shape corresponding to the final desired bubble.

The bubbles may be of various shapes, preferably hemispheric in shape. Other configurations may also be used, and can be obtained by the use of a suitable embossing roll having the desired shape.

Perforated film 22 is preferably a thermoplastic film, and more preferably comprises a non-oriented polymeric material. Various thermoplastic polymeric materials may be used either in monolayer or multilayer constructions for film 22. The term "film" is therefore used broadly to denote monolayer and multilayer thermoplastic structures including laminated as well as coextruded or extrusion coated struc-4/900818.6/TXTVW/08 30,90/02:17:20 PM

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tures. An important characteristic of perforated film 22, or at the least the innermost layer of perforated film 22 which faces thermoformable film 24, is the degree to which film 22 can be sealed or adhered to thermoformable film 24.
Therefore, the perforated film 22, or at least the innermost layer of a multilayer film 22 comprises a polymeric material which will seal to thermoformable film 24 in accordance with the process of this invention. Those skilled in the art will select polymeric materials well known for their sealability, particularly heat sealability. Olefinic polymers and copolymers are generally preferred.

Formable film 24 is preferably made up of an olefin-ic polymer or copolymer. Ethylene polymers and copolymers such as ethylene vinyl acetate copolymer are preferred in monolayer or multilayer constructions which may also include other materials such as oxygen barrier layers (e.g. ethylene vinyl alcohol copolymer, vinylidene chloride copolymer or nylon 6) and linear ethylene alpha-olefin copolymers such as linear low density polyethylene. Like film 22, the term "film" is used for film 24 in a broad sense to include all of these possible variations in both monolayer and multilayer constructions which may be conventionally laminated coextruded or extrusion coated.

The plurality of bubbles depicted in Figure 2 have cavities 30 containing a moisture absorbent material 31.
This moisture absorbent material is preferably a gelatinized, starch-hydrolyzed polyacrylonitrile graft copolymer or an acrylamide potassium acrylate copolymer. Such materials are available under the trademark Terra-Sorb~. Alternative mate-rials suitable for this invention include polyethyloxazoline, starch, calcium chloride, and water absorbent polyetheramide block copolymer.

The moisture absorbent bubble laminate of the present invention can be made by the process generally de-scribed for example in U. S. Patent No. 4,576,669. This 4/900818.6/TXTVW/08 30,90/02:17:20 PM

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process generally involves heating the thermvformable, thermoplastic film, advancing the heated film to an embossing roll with cavities therein, and vacuumizing the heated film to form a plurality of bubbles in the film. The perforated film is fed from a second roller as a discrete film to the first thermoformed film. Before the films are adhered togeth-er, a moisture absorbent material of the type described above is placed manually or mechanically into the bubbles of the thermoformed film. Thereafter the films are adhered together for example by preheating one or both of the films and/or drawing the films between a nip roll and the embossing roll to produce the final moisture absorbent bubble laminate.

The number and placement of the perforations 32 of perforated film 22 can be varied according to the processing restrictions in the production of perforated film 22, and according to the desired density, shape and size of perfora-tions for the purpose of allowing the ingress of moisture from the moisture producing source to the moisture absorbing material 31 of bubbles 28. The distribution of the perfora-tions may be such that one or more perforations 32 will be aligned in communication with each of the plurality of bub-bles 28 of the bubble laminate. This is depicted in Figure 2. Alternatively, the distribution of perforations 32 in perforated film Z2 may be such that some but not all of the perforations are aligned with corresponding bubbles in the bubble laminate. This latter embodiment is depicted in Fig-ure 3 where perforation 32 is in communication with a cavity 30 of bubble 28, and perforation 36 is not in communication with any of the plurality of bubbles 28 and thermoformable film 24. It is therefore not necessary to have strict corre-spondence between the placement of perforations 32 and perfo-rated film 22, and bubbles 28 in thermoformable film 24. Put differently, not every bubble in the matrix of bubbles in film 24 requires communication with a corresponding perfora-tion or perforations, as long as the overall moisture absor-bency of the laminate is sufficient for the desired end use application. It is likewise not critical that a moisture 4/900818.6/TXTVW/08 30,90/02:17:20 PM

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-absorbent material 31 be present in all of the plurality of bubbles of the laminate, although it is preferable that the moisture absorbent material be present in as many of the plurality of bubbles as possible to maximize the moisture absorbency of the laminate. Likewise, the amount of material present in each bubble may be varied. The configurations of the perforations 32 in perforated film 22 can take several shapes and are preferably circular. Slits, elongated or elliptical openings, and other shapes may be used for the perforations 31.

The grain size or powder size of the particular moisture absorbent material 31 used in this invention can be varied depending on the size of the perforations 31 and the ease with which certain moisture absorbent materials may be placed in bubbles 28 during the production of the laminate.

Referring to Figure 3, an additional film 34, which may be monolayer or multilayer in construction, may be sealed to the tops of the bubbles 28 as shown if it is desired to produce a moisture absorbent bubble laminate in which both outer surfaces are substantially planar. The composition of film 34 can be the same as that of films 22 or 24, or can have a composition or construction different from either of these films. Film 34 is preferably a polymeric, thermoplastic or cross-linked thermoplastic monolayer or multilayer film or laminate, and may include e.g. olefinic polymers or copolymers, polyamides, or other suitable materi-als.

Those skilled in the art will understand that modi-fications may be made in the particular configuration of the moisture absorbent bubble laminate of the present invention without departing from the scope of the claims as defined below.

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Claims (4)

1. A moisture absorbent bubble laminate comprising:
a) a perforated, thermoplastic film;

b) a thermoformable, thermoplastic film ad-hered at spaced intervals to the perforat-ed film, and formed into a plurality of bubbles; and c) a moisture-absorbent material disposed within a plurality of the bubbles.

2. The moisture absorbent bubble laminate of claim 1 wherein the thermoformable, thermoplastic film comprises an olefinic polymer or copolymer.

3. The moisture absorbent bubble laminate of claim 1 wherein the moisture absorbent material comprises a materi-al selected from the group consisting of:

a) gelatinized, starch-hydrolized polyacrylonitrile graft copolymer;
b) acrylamide potassium acrylate copolymer;
c) polyethyloxazoline;
d) starch;
e) calcium chloride; and f) water absorbing polyetheramide block copolymer.

4. A method of making a moisture absorbent bubble laminate comprising:

a) heating a thermoformable thermoplastic film;

b) advancing the heated thermoformable thermoplastic film to an embossing roll;

c) vacuumizing the heated film to form a plurality of bubbles in the film;

d) placing a moisture absorbent material in a plurality of the bubbles; and e) adhering a perforated thermoplastic film to the thermoformable film so that the moisture absorbent material in the bubbles of the film is trapped between the first and second films.