WO1993020950A1 - Absorbent structure for incorporation into packages - Google Patents

Absorbent structure for incorporation into packages Download PDF

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Publication number
WO1993020950A1
WO1993020950A1 PCT/US1993/003475 US9303475W WO9320950A1 WO 1993020950 A1 WO1993020950 A1 WO 1993020950A1 US 9303475 W US9303475 W US 9303475W WO 9320950 A1 WO9320950 A1 WO 9320950A1
Authority
WO
WIPO (PCT)
Prior art keywords
sheet
powder
absorbent structure
roller
longitudinally extending
Prior art date
Application number
PCT/US1993/003475
Other languages
French (fr)
Inventor
Thomas J. Belina
Drayton G. Miller
Original Assignee
Prototype Machinery Specialists, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Prototype Machinery Specialists, Inc. filed Critical Prototype Machinery Specialists, Inc.
Publication of WO1993020950A1 publication Critical patent/WO1993020950A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B32B5/30—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being formed of particles, e.g. chips, granules, powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/24—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer not being coherent before laminating, e.g. made up from granular material sprinkled onto a substrate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/022—Non-woven fabric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/16—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer formed of particles, e.g. chips, powder or granules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B32B5/24—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
    • B32B5/245—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer another layer next to it being a foam layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D81/00—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
    • B65D81/24—Adaptations for preventing deterioration or decay of contents; Applications to the container or packaging material of food preservatives, fungicides, pesticides or animal repellants
    • B65D81/26—Adaptations for preventing deterioration or decay of contents; Applications to the container or packaging material of food preservatives, fungicides, pesticides or animal repellants with provision for draining away, or absorbing, or removing by ventilation, fluids, e.g. exuded by contents; Applications of corrosion inhibitors or desiccators
    • B65D81/264—Adaptations for preventing deterioration or decay of contents; Applications to the container or packaging material of food preservatives, fungicides, pesticides or animal repellants with provision for draining away, or absorbing, or removing by ventilation, fluids, e.g. exuded by contents; Applications of corrosion inhibitors or desiccators for absorbing liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/31—Heat sealable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/726—Permeability to liquids, absorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2317/00—Animal or vegetable based
    • B32B2317/18—Cellulose, modified cellulose or cellulose derivatives, e.g. viscose
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/70—Food packaging

Definitions

  • the present invention relates to a new and improved structure for absorbing fluids encountered in the packaging industry, particularly liquids in food product trays.
  • the structure is designed to work in conjunction with the tray and to be incorporated into the tray during production of the tray.
  • This absorbent structure may be incorporated into many other forms of packaging as well.
  • the food product tray provides a means to secure food products such as poultry and meat individually for purposes of inventory control and aesthetic presentation to the consumer.
  • the tray is often used in conjunction with a transparent plastic film.
  • the plastic film wraps around the food product and the tray.
  • the tray and plastic wrap prevent contact with other food products and unclean surfaces but cannot prevent leakage of exudates, such as water and blood, encountered in the packaging of poultry and meat.
  • the amount of water and blood normally found in these trays overwhelms the capacity of the tray, and leaks through the plastic wrap. It is common to place absorbent material in the tray to absorb these excess fluids.
  • This absorbent material is generally placed into the tray after the tray is manufactured. It is placed between the produce and the top surface of the tray during packaging and market display and must be peeled off afterward by the consumer.
  • the inventive absorbent strip takes advantage of the structural support of the tray and the manufacturing process for the tray.
  • the inventive absorbent strip may be paid out from rolled form into the production line of the tray manufacturer.
  • the absorbent structure of the present invention was designed with this application in mind and is free of cellulose fluff, which is common in absorbent structures. This fluff, when not contained properly, will float in the air in the manufacturing facility. This is a fire hazard. It contributes to maintenance and cleanliness problems.
  • the fluff was needed in the past to act as an absorbent as well as to enhance the performance of any superabsorbent powder.
  • the fluff enhances the performance of the superabsorbent by dispersing it.
  • Superabsorbent powders tend to gel-lock when wetted, forming gummy masses where the outer surface of the mass is in solution or has absorbed moisture and no more moisture can penetrate through the outer surface. The powder trapped, or gel- locked within, is wasted.
  • the present invention relates to a new structure for absorbing fluids encountered in the packaging industry, particularly fluids exuded into food product trays from food products such as chicken and meat.
  • the present invention also relates to a new structure for absorbing fluids encountered in the packaging industry, particularly fluids exuded into food product trays from food products such as chicken and meat.
  • the present invention also relates to a new structure for absorbing fluids encountered in the packaging industry, particularly fluids exuded into food product trays from food products such as chicken and meat.
  • the present invention also
  • SUBSTITUTESHEET relates to a new method of incorporating an absorbent structure into a finished package. This new method is dependent upon the basic configuration of the absorbent structure of the present invention.
  • the absorbent structure of the present invention is comprised of a top sheet and a bottom sheet with a superabsorbent powder trapped therebetween through use of seals joining the top and bottom sheets on two opposing sides, with the superabsorbent powder being adhered to one or both sheets.
  • the top and bottom sheets are preferably fluid permeable, but one or the other can be fluid impermeable if called for in a particular package. Both sheets are preferably heat-sealable.
  • Elasticity and strength of the sheets are also factors with regard, respectively, to trimming methods and durability requirements.
  • the adhesion of the superabsorbent powder can be accomplished by an adhesive coated onto the sheet(s) or can be formed through the interaction and subsequent evaporation of water, with certain superabsorbents.
  • This second form of adhesive is accomplished by applying a light coating of water onto the sheet followed by a layer of superabsorbent powder.
  • a superabsorbent powder such as carboxymethylcellulose or crosscarmellose will adhere to the sheet after absorbing a small amount of water from the sheet, and then allowing the evaporation of the water.
  • the adhesion of the superabsorbent powder to one or both sheets in this absorbent structure acts to evenly disperse the
  • SUBSTITUTESHEET superabsorbent powder until the end use of the product as an absorbent structure.
  • the adhesion also allows indiscriminate slitting and chopping of the absorbent structure prior to its end use. Such slitting and chopping would occur during the incorporation of the inventive absorbent structure into individual packages such as rigid foam food product trays.
  • a packaging product including the inventive absorbent structure.
  • the present invention provides an absorbent structure which does not suffer from the disadvantages of prior structures, particularly those related to the use of cellulose fluf and to the difficulties of incorporating an absorbent structure into a packaging product after production of the packaging product has been completed.
  • the present invention also relates to a method and apparatus for manufacturing a continuous composite sheet comprising upper and lower layers of semi-permeable material with a center layer of powder which is adhered to at least one of the layers of material.
  • the adhesion of the powder is accomplished through a coating of adhesive applied to either the upper or lower layer.
  • the adhered powder will remain in position if the composite sheet is shaken or otherwise disturbed. If the composite sheet is cut open, the powder will still remain in position.
  • This composite sheet can be used in many industries for packaging or filtration. End use depends on the properties of the powder sandwiched between the upper and lower layers.
  • the upper and lower layers are a material chosen partially for their permeability. Different applications require different degrees of permeability.
  • the composite sheet has longitudinal seals which allow the sheet to be slit into narrower strips down the center of the seal, leaving a strip with two effective side seals which hold the upper and lower layers of material in place.
  • the material chosen for the upper and lower layers allows a thermoplastic fusion through application of heat and pressure to form the seals.
  • the fusion is accomplished by passing the sheet through a nip formed by two rollers, one of which is heated. The other roller rides atop the heated roller and provides pressure due to its weight.
  • the heated roller has collars set along its length, fitted to the outer diameter of the roller and raised sufficiently to seal only along intended paths of the composite sheet. The width of each strip is determined by the spacing of the collars along the heated roller.
  • the surface of at least one of the upper and lower layers is coated with an adhesive. Powder is then sprinkled or otherwise applied to the lower layer.
  • the powder meets the adhesive directly upon application to the lower layer.
  • the adhesive is on the upper layer, the powder rides on the lower layer after application to the lower layer, and meets the adhesive as the upper and lower layers meet.
  • the layers are roller-pressed together before entering the nip, securing the powder in position before the longitudinal seals are formed. Hot blown air serves to dry the adhesive either before or after the nip.
  • the composite sheet passes through a slitting stage which cuts down the center of each longitudinal seal, effecting narrower strips.
  • the material is then wound onto a torque-controlled center winding take-up roller.
  • Fig. 1 is a perspective view of a first embodiment of an absorbent structure of the present invention
  • Fig. 2 is a perspective view of a second embodiment of an absorbent structure of the present invention.
  • Fig. 3 is a graph showing the absorbency of the superabsorbent crosscarmellose
  • Fig. 4 is a perspective view showing the incorporation of an absorbent structure of the present invention in a food package product
  • Fig. 5 is a cross-sectional view showing the incorporation of an absorbent structure of the present invention in a food package product during manufacturing of the food package product;
  • S U B S TITUTESHEET Fig. 6 is a schematic view showing the composite sheet manufacturing apparatus of the present invention in which the bottom sheet is coated with adhesive or water;
  • Fig. 7 is a schematic view showing the composite sheet manufacturing apparatus of the present invention in which the top sheet i3 coated with adhesive or water;
  • Fig. 8 is a schematic view of a powder doctor blade and hopper arrangement according to the invention.
  • Fig. 9 is a side view showing the adhesive coating roller of the manufacturing apparatus.
  • Fig. 10 is an elevational view of the heated roller and collar configuration of the manufacturing apparatus
  • Fig. 11 is a perspective view of a powder sprinkling technique according to the invention
  • Fig. 12 is a perspective view of an element used in the powder sprinkling technique of Fig. 11;
  • Fig. 13 is a perspective view of an alternative powder sprinkling technique according to the invention.
  • Fig. 14 is a perspective view of an element used in the alternative powder sprinkling technique of Fig. 13;
  • Fig. 15 is a view in side elevation of a hanger bearing assembly for positioning a pressure roller in the manufacturing apparatus according to the present invention.
  • Fig. 1 shows an absorbent structure 6 according to the present invention which may be placed in a tray for collecting and retaining exudates of poultry and meat.
  • the structure 6 has a outer top sheet 1 of fluid permeable material such as nonwoven fabric and an outer bottom sheet 3 of fluid permeable material such as nonwoven fabric.
  • a superabsorbent powder 2 Positioned between the top and bottom sheets and adhered to the bottom sheet is a superabsorbent powder 2 ("top" and ⁇ • bottom” refer only to the drawing, and the structure described is equally effective when inverted) .
  • Adhesion of the superabsorbent particles 2 to the bottom sheet 3 is necessary to prevent the particles from flowing freely between the top and bottom sheets 1,3. Free flowing powder would tend to collect in one area of the structure and diminish the overall absorption performance of the structure.
  • the superabsorbent powder chosen for food contact usage must be made from materials cleared by the USFDA.
  • One such superabsorbent is carboxymethylcellulose -(CMC) , which is manufactured in a highly purified cross-linked form by Akzo Dreeland, Inc., and is sold as Akucell SW 3009-X21 (also in SZ-270 and SZ-271 variants) .
  • This cross-linked form of CMC is also known as sodium crosscarmellose.
  • Akucell SW is a natural polysaccharide which in chemical structure is closely related to seaweed and other natural products, and is biodegradable. Due to its absorbent capacity (see absorbency graph in Fig. 3) and low environmental
  • Fluid absorption capacity of the absorbent structure 6 may be altered by altering the amount of superabsorbent particles 2 per square inch adhered to the bottom sheet 3.
  • the poultry industry requires a minimum absorption capacity of 2.3 grams of water per square inch surface area.
  • Experience with the Akucell SW 3009 SZ-270 superabsorbent powder (see absorbency graph in Fig. 3) demonstrates that a powder concentration of 0.03 grams of powder per square inch of surface area of the sheet will provide adequate absorption per square inch of surface area of the absorbent structure for the poultry industries' produce tray packaging needs.
  • SUBSTITUTESHEET water (film) coverage should be no more than 0.04 grams/inch 2 , and should be evaporated immediately after the powder contacts and begins absorbing this water coating.
  • the water coating thickness can be easily found empirically by a variable thickness coating system, such as the system described below. After proper evaporation, there is no moisture in the finished absorbent structure 6.
  • a preferred form of absorbent structure 6 is seen as structure 7 in Fig. 2.
  • the addition of longitudinal edge seals 4 secure the top and bottom sheets 1,3 together and provide means to trap the gel formed during the structure's end use.
  • the sheets 1,3 are both heat-sealable nonwoven material. These seals are formed by applying heat and pressure to the heat-sealable nonwoven material.
  • structure 7 may be sandwiched between two layers of rigid foam 8,9 as shown in Fig. 4, where the top layer 8 allows passage of fluid through an array of holes 10 formed in the foam of top layer 8.
  • a two-part rigid foam tray, such as structure 11, is produced by the Lin-Pac Plastics Group in Wilson, NC.
  • fluids released by food products contained on the tray 11 flow through the holes 10 in the upper foam layer 8 and are absorbed by structure 7.
  • the tray's unique characteristics prevent structure 7 from contact with the food product and presents a very attractive package to the Consumer.
  • the gel formed during the absorption by the particles 2 of the released fluid is trapped in
  • SUBSTITUTESHEET a reservoir formed by edge seals 4 and as seen in Fig. 5, by the crimped edge 12 of the tray 11.
  • Fig. 1 shows the structure 6 with an outer top sheet 1 of fluid permeable material such as nonwoven fabric and an outer bottom sheet 3 of fluid permeable material such as nonwoven fabric or plastic film. Positioned between the top and bottom sheets 1,3 and adhered to the bottom sheet 3 is a superabsorbent powder 2 ("top" and "bottom” refer only to the drawing, and the structure described is equally effective when inverted) .
  • the nonwoven fabric should be comprised primarily of cellulose fibers.
  • An example of the nonwoven fabric is found in heat-sealable tea-bag material. This material is not elastic, is easily ripped, and lends itself to stamp-cutting processes as found in the paper industry.
  • Bollore Technologies supplies a line of this fabric marketed as HUDS. Some end uses require a stronger, more elastic absorbent strip. Addition of synthetic fiber components such as polyester to a nonwoven web allows such strength and elasticity. Such a web is available in food grade lots from Lydall Manning Nonwovens and is marketed as
  • SUBSTITUTESHEET maximal strength is the Reemay 2200-series of spunbonded polyester nonwovens, sold by Reemay, Inc.
  • a plastic film such as polyethylene can also be used as substrate material. All of the aforementioned material options have been tested to comply with USFDA regulations, and are heat-sealable.
  • structure 7 The preferred form of structure 6 is seen as structure 7 in Fig. 2.
  • longitudinal edge seals 4 secure the top and bottom sheets 1,3 together and provide means to trap the gel formed during the structure's end use. These seals are formed by applying heat and pressure to the heat-sealable nonwoven material. There is no powder applied to the sheets where the seals are formed.
  • This strip 7 is very easy to handle and can be produced in any length.
  • Adhesion of the superabsorbent particles 2 to the bottom sheet 3 is necessary to prevent the particles from flowing freely between the top and bottom sheets.
  • the powder adhered in this fashion will not fall out from between the sheets if the strip is cut crosswise from seam 4 to the opposing seam 4. Also, free flowing powder would tend to collect in one area of the structure and diminish the overall absorption performance of the structure.
  • a packaging manufacturer would purchase this material as rolled goods to be paid out into the production line.
  • the strip may be sliced at any point along its length without loss of powder and can, therefore, be processed into the finished package, then cut to length at any point. Registration for this automatic collation is not needed.
  • SUBSTITUTESHEET Fig. 4 shows a food product tray 11 manufactured in Wilson, NC by Lin-Pac Plastics Group.
  • the absorbent strip 7 is paid out as shown in Fig. 5 in between two layers 8,9 of rigid foam.
  • the absorbent strip 7 becomes an integral part of the tray 11.
  • the strip 7 is cut to the needed length as the tray is cut to its final dimensions.
  • the stamping process crimps the edges of the tray 11 and seals the cut ends of the strip 7. With the ends crimped as shown in Fig. 5, a permanent reservoir is formed between the crimped ends 12 and the edge seals 4.
  • fluids released by food products flow through the holes 10 of the upper foam layer 8 and are absorbed by structure 7.
  • the tray's unique characteristics prevent structure 7 from contact with the food product and presents a very attractive package to the consumer.
  • the gel formed during the absorption of the released fluid by particles 2 is trapped in the permanent reservoir described above, which is formed by edge seals 4 and by the crimped edges 12 of the tray 11 (Fig. 5) .
  • Fig. 6 is a side view of the preferred embodiment of the apparatus 100 of the present invention.
  • Rolls of material 104 and 105 are mounted on shafts which ride in slotted guides 104a and 105a.
  • the rolls of material which generally are sold wound on rigid paperboard cores, could be mounted on standard side
  • the lower layer of heat sealable material in the form of a web 115 is fed from roll 105 and passes through a switch-back coating system which allows a coating of adhesive from lick tray 111c to be applied to one side 115a of the web 115.
  • the sheet or web of material 115 passes over guide roller 107, arriving inverted underneath guide roller 108a and guide roller 108b. These rollers are adjusted vertically to create adequate wrap around a meyer rod 111b.
  • a meyer rod is a wire-wound rod used primarily in the coating industry as a precise doctoring device.
  • a meyer rod consists of a steel shaft with a specific gauge steel wire wound tightly around it. The depth of the valleys created between each additional contacting wire wrap determines the thickness of the liquid coating. The valley depth depends on the gauge of the wire.
  • RD Specialties Inc. specializes in meyer rods and their rods #40 and #60 provide adequate versatility for the adhesive coating roller or coating system shown in Fig. 9. In the present invention, it is used as a precise applicator roller. This arrangement is necessary due to the permeable nature of the material which constitutes web 115. A normal applicator roller and doctor blade would apply too much adhesive, then force the adhesive through the permeable fabric while doctoring it. With the present arrangement as seen in Figs. 6 and 9, the meyer rod 111b picks up a precise amount of adhesive from pick-up roller ilia, which turns in trough 111c. Trough 111c is filled with water or a known
  • the adhesive in tray 111c should be carried in water as its solvent.
  • the solvent can be evaporated with no harmful side effects to workers, and therefore no costly safety measures.
  • the solvent being water, it can be evaporated with hot air blower 125, shown in Fig. 6.
  • the pick-up roller Ilia should be chosen to be as small in diameter as is practical since liquid adhesives tend to sheer, causing a separation of components in the trough 111c. A smaller diameter roller has less of an impelling effect on the liquid adhesive, reducing the chances of sheer.
  • the rod 111b and roller Ilia must be mechanically driven. As shown in Fig. 9, the meyer rod 111b and pick-up roller Ilia are turning in opposite directions. The rod 111b is turning opposite
  • SUBSTITUTESHEET angularly to the moving web 115.
  • This arrangement of counter rotating rod 111b and roller 111c allows a precise continuous pick up of adhesive to be transferred to rod 111b, which then, in a hybrid doctoring and lifting step, transfers the adhesive to web 115.
  • the opposed movement of web 115 and rod 111b enables application of a continuous precise coating of adhesive on the presenting lower surface, i.e., surface 115a, of web 115.
  • This system will insure an even coating of adhesive or any liquid material as long as the speeds remain linearly equal relative to one another, and within a window of operational speeds necessitated by the thickness of the liquid to be coated. This can be easily visually determined.
  • the relative speeds of rod Ilia and roller 111b can be altered in relation to web 115 and to each other through a variable speed transmission or by controlling independent motor speeds. These speed alterations allow a wide range of coating thicknesses. With the number of variables at hand, a useful operational technique is trial and error and visual observation for feedback. This empirical method will quickly determine the proper speed settings for a practical coating thickness.
  • roller 103 After receiving a coating of adhesive from rod 111b, the web 115 passes past guide roller 108b and around switch-back roller 106. Inside hopper 102 is the powder material to be sprinkled onto web 115. Roller 103 has threads cut into its surface or may be a knurled roller to allow it to pick up powder from hopper 102 as it rotates beneath hopper 102. The threads or knurled surface are
  • the volume of material removed from the surface of roller 103 is proportional to 0.03 grams of powder per square inch surface area of roller 103.
  • the powder carries a slight electrical charge and will cling to a steel roller. Once some powder clings, this clinging fine powder layer will effectively serve as an anti-static coating and prevent additional powder from clinging.
  • Increasing the cut ⁇ away volume per area by adding an opposing cross-thread back across the cut-away section, the same thread setting slightly more than doubles the 16 thread one-way cut. This is required to overcome the volume loss due to the static-adhered powder coating.
  • SUBSTITUTESHEET sheaths 103a and 103b guide the powder and control its flow onto web 115.
  • the roller speed is not required to be synchronized with the web, therefore the mass flow rate of the powder is controlled (adjustable) by the angular speed of the applicator roller 103.
  • roller 103 are seen in Fig. 11.
  • the threaded or knurled surface 103c of roller 103 picks up powder from the open bottom of hopper 102. Some of the powder begins to fall away from the roller's surface almost immediately and slides along the inside of sheath 103a. The powder is mostly free from the surface of roller 103 as it rotates through 180 * , and sheath 103b, seen in Fig. 8 controls the fall of any reluctant particles which cling beyond 180 * .
  • An operational consideration is the application of mildly charged particles to web 115 which tend to cling to the steel roller 103.
  • the roller is coated with a thin layer of dust from the powder which repels any additional powder.
  • Speed of the roller can easily be adjusted for mass flow rate lost due to volumetric loss from the resulting ' coating.
  • the coating becomes steady and speed is then adjusted to insure an even powder flow onto web 115 passing beneath the roller and sheath arrangement. Relative speeds of roller 103 and web 115 determine area density of powder 117 in finished strip 121.
  • SUBSTITUTESHEET 103a and 103b The advantage to this configuration is that the powder application is automatically timed to the speed of web 115. If the web stops, the powder flow immediately stops.
  • the need for contact with roller 103 and web 115 eliminates the possibility of coating web 115 with an adhesive or water. Any such coating would contact the applicator roller after passing over guide roller 118 and affect the surface of roller 103 to disturb the powder application process.
  • Fig. 7 shows a method for coating the top sheet with adhesive or water and therefore, allows usage of the powder application apparatus of Fig. 13. In this situation, the inner surface 116a of web 116 would be coated with adhesive in the manner described for web 115.
  • the end product of this process is a strip form of the composite sheet described above.
  • the formation of said strips requires seaming the web 115 with top web 116 along longitudinal paths where powder 117 has been masked out. With the powder sprinkler shown in Fig. 11, powder-free paths are created by
  • doctor blades 102a are present in both powder sprinkling apparatuses, and can be best seen in Fig. 8.
  • the doctor blades 102a are made of thin flexible steel or copper and are held in place by bolts 102b which clamp the blades 102a between the bottom edges of hopper 102 and steel supports 102c. They can be unbolted and replaced as needed.
  • the weight of the hopper 102 holds the blades firmly against roller 103 and the blades 102a wipe the roller clean except where a thread has been cut. Either system results in narrow strips of powder 117, as seen in Figs. 12 and 13, with empty or powder-free strips 117a in between them.
  • upper sheet 116 is brought in contact and roller-pressed against lower sheet 115 between soft rubber-coated rollers 123. These rollers 123 press the sheets firmly together and increase the adhesion of the super- absorbent particles to the adhesive coated sheet.
  • Roller 112b of Fig. 6 is driven by conventional means with either a belt and pulley system, or sprocket and chain.
  • Roller 122 rides atop the collars 112a.
  • Shown in Fig. 15 is a hanger bearing arrangement which positions the roller 122 securely in its horizontal position.
  • Hanger bearing 123a is set into shaft 123b which slides freely through frame segment 123c. This insures proper pressure resulting freely from the weight of the roller 122.
  • the collars 112a span the length of roller 112b in spaced fashion, see Fig. 10, and are fitted snugly to the outer diameter of roller 112b.
  • Fig. 10 shows roller 112b with two collars 112a of the plurality which extend in equally spaced relation across the axial length of roller 112b.
  • Roller 112b is a hollow aluminum roller. It houses an electrical heating element at its center which has swivel fittings at either end to allow free rotation of roller 112b. This heating element is controlled to heat the surface of aluminum collars 112a.
  • Aluminum is the preferred material for the heated roller 112b and collars 112a due to its high thermal conductivity qualities. Aluminum also has a very low thermal emissivity ( ⁇ 0.03); it will resist radiating heat and concentrate the heat through the contact heat-sealing surfaces of collars 112a.
  • the heating element is controlled through a thermocouple and logical relay feedback loop to heat the surface of collars 112a to such a degree as to partially melt webs 115 and 116 together along the powder-free paths 117a (see Figs. 11 and 12) . Pressure from roller 122 finishes the sealing action along the powder-free paths.
  • element 125 is a hot air blower which finishes the evaporation of the adhesive solvent (water) .
  • Blade 120 slits the composite material 124 down the center of each seal, creating individual composite strips 121 from the composite sheet.
  • Roller 113 feeds the composite strips 121 to roller 114 which is a web take-up mechanism which is driven through a sprocket, chain, and a torque-controlled DC motor.
  • DC motors have a characteristic of being easily torque-controlled. This is due to the nature of the wiring and the electric and magnetic fields which drive the motor.
  • a constant electrical load means a constant physical torque on the shaft of the motor.

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Abstract

An absorbent structure (6) formed in a continuous strip for collecting and retaining exuded fluids in conjunction with structurally supportive packages such as food product trays. The structure has a fluid permeable material either as the top sheet (1), bottom sheet (3), or both. The inner face of one or both sheets is coated with superabsorbent powder particles (2) which are adhered to the sheet to insure an even distribution and the absorption quality of the particles. Superabsorbents such as cross-linked carboxymethylcellulose may serve as this superabsorbent powder. The internally-adhered superabsorbent powder configuration allows the strip to be sliced crosswise at any point with minimal or no loss of powder. This feature allows the absorbent structure to be used in high speed production with inherent collation during the manufacture of packages such as semi-rigid foam product trays without any need for discrete registration.

Description

"ABSORBENT STRUCTURE FOR INCORPORATION INTO PACKAGES"
Background of the Invention
The present invention relates to a new and improved structure for absorbing fluids encountered in the packaging industry, particularly liquids in food product trays. The structure is designed to work in conjunction with the tray and to be incorporated into the tray during production of the tray. This absorbent structure may be incorporated into many other forms of packaging as well.
In the past, food product trays and absorbent pads were combined in time consuming post production processes. In the marketplace, the food product tray provides a means to secure food products such as poultry and meat individually for purposes of inventory control and aesthetic presentation to the consumer. The tray is often used in conjunction with a transparent plastic film. The plastic film wraps around the food product and the tray. The tray and plastic wrap prevent contact with other food products and unclean surfaces but cannot prevent leakage of exudates, such as water and blood, encountered in the packaging of poultry and meat. The amount of water and blood normally found in these trays overwhelms the capacity of the tray, and leaks through the plastic wrap. It is common to place absorbent material in the tray to absorb these excess fluids.
This absorbent material is generally placed into the tray after the tray is manufactured. It is placed between the produce and the top surface of the tray during packaging and market display and must be peeled off afterward by the consumer.
The inventive absorbent strip takes advantage of the structural support of the tray and the manufacturing process for the tray. The inventive absorbent strip may be paid out from rolled form into the production line of the tray manufacturer.
The absorbent structure of the present invention was designed with this application in mind and is free of cellulose fluff, which is common in absorbent structures. This fluff, when not contained properly, will float in the air in the manufacturing facility. This is a fire hazard. It contributes to maintenance and cleanliness problems.
The fluff was needed in the past to act as an absorbent as well as to enhance the performance of any superabsorbent powder. The fluff enhances the performance of the superabsorbent by dispersing it. Superabsorbent powders tend to gel-lock when wetted, forming gummy masses where the outer surface of the mass is in solution or has absorbed moisture and no more moisture can penetrate through the outer surface. The powder trapped, or gel- locked within, is wasted.
Summary of the Invention
The present invention relates to a new structure for absorbing fluids encountered in the packaging industry, particularly fluids exuded into food product trays from food products such as chicken and meat. The present invention also
SUBSTITUTESHEET relates to a new method of incorporating an absorbent structure into a finished package. This new method is dependent upon the basic configuration of the absorbent structure of the present invention. The absorbent structure of the present invention is comprised of a top sheet and a bottom sheet with a superabsorbent powder trapped therebetween through use of seals joining the top and bottom sheets on two opposing sides, with the superabsorbent powder being adhered to one or both sheets. The top and bottom sheets are preferably fluid permeable, but one or the other can be fluid impermeable if called for in a particular package. Both sheets are preferably heat-sealable.
Elasticity and strength of the sheets are also factors with regard, respectively, to trimming methods and durability requirements. The adhesion of the superabsorbent powder can be accomplished by an adhesive coated onto the sheet(s) or can be formed through the interaction and subsequent evaporation of water, with certain superabsorbents.
This second form of adhesive is accomplished by applying a light coating of water onto the sheet followed by a layer of superabsorbent powder. A superabsorbent powder such as carboxymethylcellulose or crosscarmellose will adhere to the sheet after absorbing a small amount of water from the sheet, and then allowing the evaporation of the water. The adhesion of the superabsorbent powder to one or both sheets in this absorbent structure acts to evenly disperse the
SUBSTITUTESHEET superabsorbent powder until the end use of the product as an absorbent structure. The adhesion also allows indiscriminate slitting and chopping of the absorbent structure prior to its end use. Such slitting and chopping would occur during the incorporation of the inventive absorbent structure into individual packages such as rigid foam food product trays. According to another aspect of the invention, there is provided a packaging product including the inventive absorbent structure.
The present invention provides an absorbent structure which does not suffer from the disadvantages of prior structures, particularly those related to the use of cellulose fluf and to the difficulties of incorporating an absorbent structure into a packaging product after production of the packaging product has been completed. The present invention also relates to a method and apparatus for manufacturing a continuous composite sheet comprising upper and lower layers of semi-permeable material with a center layer of powder which is adhered to at least one of the layers of material. The adhesion of the powder is accomplished through a coating of adhesive applied to either the upper or lower layer. The adhered powder will remain in position if the composite sheet is shaken or otherwise disturbed. If the composite sheet is cut open, the powder will still remain in position.
This composite sheet can be used in many industries for packaging or filtration. End use depends on the properties of the powder sandwiched between the upper and lower layers. The upper and lower layers are a material chosen partially for their permeability. Different applications require different degrees of permeability.
The composite sheet has longitudinal seals which allow the sheet to be slit into narrower strips down the center of the seal, leaving a strip with two effective side seals which hold the upper and lower layers of material in place. The material chosen for the upper and lower layers allows a thermoplastic fusion through application of heat and pressure to form the seals. The fusion is accomplished by passing the sheet through a nip formed by two rollers, one of which is heated. The other roller rides atop the heated roller and provides pressure due to its weight. The heated roller has collars set along its length, fitted to the outer diameter of the roller and raised sufficiently to seal only along intended paths of the composite sheet. The width of each strip is determined by the spacing of the collars along the heated roller.
Prior to the nip, the surface of at least one of the upper and lower layers is coated with an adhesive. Powder is then sprinkled or otherwise applied to the lower layer. When the lower layer is the adhesive-coated layer, the powder meets the adhesive directly upon application to the lower layer. When the adhesive is on the upper layer, the powder rides on the lower layer after application to the lower layer, and meets the adhesive as the upper and lower layers meet. The layers are roller-pressed together before entering the nip, securing the powder in position before the longitudinal seals are formed. Hot blown air serves to dry the adhesive either before or after the nip.
Once the longitudinal seals are formed in the nip, the composite sheet passes through a slitting stage which cuts down the center of each longitudinal seal, effecting narrower strips. The material is then wound onto a torque-controlled center winding take-up roller.
The above and other objects, features and advantages of this invention will become more readily apparent and be further understood by reference to the following detailed description and drawings, wherein:
Brief Description of the Drawings
Fig. 1 is a perspective view of a first embodiment of an absorbent structure of the present invention;
Fig. 2 is a perspective view of a second embodiment of an absorbent structure of the present invention;
Fig. 3 is a graph showing the absorbency of the superabsorbent crosscarmellose; Fig. 4 is a perspective view showing the incorporation of an absorbent structure of the present invention in a food package product;
Fig. 5 is a cross-sectional view showing the incorporation of an absorbent structure of the present invention in a food package product during manufacturing of the food package product;
SUBSTITUTESHEET Fig. 6 is a schematic view showing the composite sheet manufacturing apparatus of the present invention in which the bottom sheet is coated with adhesive or water;
Fig. 7 is a schematic view showing the composite sheet manufacturing apparatus of the present invention in which the top sheet i3 coated with adhesive or water;
Fig. 8 is a schematic view of a powder doctor blade and hopper arrangement according to the invention;
Fig. 9 is a side view showing the adhesive coating roller of the manufacturing apparatus;
Fig. 10 is an elevational view of the heated roller and collar configuration of the manufacturing apparatus;
Fig. 11 is a perspective view of a powder sprinkling technique according to the invention; Fig. 12 is a perspective view of an element used in the powder sprinkling technique of Fig. 11;
Fig. 13 is a perspective view of an alternative powder sprinkling technique according to the invention;
Fig. 14 is a perspective view of an element used in the alternative powder sprinkling technique of Fig. 13; and
Fig. 15 is a view in side elevation of a hanger bearing assembly for positioning a pressure roller in the manufacturing apparatus according to the present invention. Detailed Description of the Invention
Fig. 1 shows an absorbent structure 6 according to the present invention which may be placed in a tray for collecting and retaining exudates of poultry and meat. The structure 6 has a outer top sheet 1 of fluid permeable material such as nonwoven fabric and an outer bottom sheet 3 of fluid permeable material such as nonwoven fabric. Positioned between the top and bottom sheets and adhered to the bottom sheet is a superabsorbent powder 2 ("top" and ■•bottom" refer only to the drawing, and the structure described is equally effective when inverted) .
Adhesion of the superabsorbent particles 2 to the bottom sheet 3 is necessary to prevent the particles from flowing freely between the top and bottom sheets 1,3. Free flowing powder would tend to collect in one area of the structure and diminish the overall absorption performance of the structure.
The superabsorbent powder chosen for food contact usage must be made from materials cleared by the USFDA. One such superabsorbent is carboxymethylcellulose -(CMC) , which is manufactured in a highly purified cross-linked form by Akzo Dreeland, Inc., and is sold as Akucell SW 3009-X21 (also in SZ-270 and SZ-271 variants) . This cross-linked form of CMC is also known as sodium crosscarmellose. Akucell SW is a natural polysaccharide which in chemical structure is closely related to seaweed and other natural products, and is biodegradable. Due to its absorbent capacity (see absorbency graph in Fig. 3) and low environmental
SUBSTITUTESHEET impact, it is an ideal choice for extensive use in the packaging industry.
Fluid absorption capacity of the absorbent structure 6 may be altered by altering the amount of superabsorbent particles 2 per square inch adhered to the bottom sheet 3. The poultry industry requires a minimum absorption capacity of 2.3 grams of water per square inch surface area. Experience with the Akucell SW 3009 SZ-270 superabsorbent powder (see absorbency graph in Fig. 3) demonstrates that a powder concentration of 0.03 grams of powder per square inch of surface area of the sheet will provide adequate absorption per square inch of surface area of the absorbent structure for the poultry industries' produce tray packaging needs.
The preferred method for adhering the CMC-based particles
2 to the bottom sheet 3 is achieved by coating the bottom sheet 3 with ordinary water before sprinkling the powder onto the sheet. Once the particles 2 absorb a small amount of the water, they slightly gel at the point of contact with the sheet 3. This gel will stick to the sheet. A hot air blower easily drys the gel and leaves the particles 2 adhered to the sheet 3. The thickness of the water coating is dependent upon the absorbency desired to be obtained and, therefore, the amount of powder per square inch needed. The amount of water (thickness of the water film) should be sufficient to cause the contact portion of the particle to swell slightly with absorbed water molecules, but leaving the majority of the particle free from the moisture. For the powder coverage described above at 0.03 grams/inch2 of composite sheet, initial
SUBSTITUTESHEET water (film) coverage should be no more than 0.04 grams/inch2, and should be evaporated immediately after the powder contacts and begins absorbing this water coating. The water coating thickness can be easily found empirically by a variable thickness coating system, such as the system described below. After proper evaporation, there is no moisture in the finished absorbent structure 6.
A preferred form of absorbent structure 6 is seen as structure 7 in Fig. 2. The addition of longitudinal edge seals 4 secure the top and bottom sheets 1,3 together and provide means to trap the gel formed during the structure's end use. In this embodiment, the sheets 1,3 are both heat-sealable nonwoven material. These seals are formed by applying heat and pressure to the heat-sealable nonwoven material. For use in the produce tray market, structure 7 may be sandwiched between two layers of rigid foam 8,9 as shown in Fig. 4, where the top layer 8 allows passage of fluid through an array of holes 10 formed in the foam of top layer 8. A two-part rigid foam tray, such as structure 11, is produced by the Lin-Pac Plastics Group in Wilson, NC. According to the teachings of the present invention, fluids released by food products contained on the tray 11 flow through the holes 10 in the upper foam layer 8 and are absorbed by structure 7. The tray's unique characteristics prevent structure 7 from contact with the food product and presents a very attractive package to the Consumer. The gel formed during the absorption by the particles 2 of the released fluid is trapped in
10
SUBSTITUTESHEET a reservoir formed by edge seals 4 and as seen in Fig. 5, by the crimped edge 12 of the tray 11.
The absorbent strip shown in Fig. 2 may be incorporated into a packaging system such as the tray 11 pictured in Fig. 4. This incorporation takes place during the manufacturing process of the package. Fig. 1 shows the structure 6 with an outer top sheet 1 of fluid permeable material such as nonwoven fabric and an outer bottom sheet 3 of fluid permeable material such as nonwoven fabric or plastic film. Positioned between the top and bottom sheets 1,3 and adhered to the bottom sheet 3 is a superabsorbent powder 2 ("top" and "bottom" refer only to the drawing, and the structure described is equally effective when inverted) .
This inventive structure's intended versatility requires knowledge of the intended packaging process to follow. If a straight stamp-cutting or chopping process is to be performed on the absorbent strip, the nonwoven fabric should be comprised primarily of cellulose fibers. An example of the nonwoven fabric is found in heat-sealable tea-bag material. This material is not elastic, is easily ripped, and lends itself to stamp-cutting processes as found in the paper industry. Bollore Technologies supplies a line of this fabric marketed as HUDS. Some end uses require a stronger, more elastic absorbent strip. Addition of synthetic fiber components such as polyester to a nonwoven web allows such strength and elasticity. Such a web is available in food grade lots from Lydall Manning Nonwovens and is marketed as
Manniweb. A nonwoven material comprised of 100% polyester for
11
SUBSTITUTESHEET maximal strength is the Reemay 2200-series of spunbonded polyester nonwovens, sold by Reemay, Inc. A plastic film such as polyethylene can also be used as substrate material. All of the aforementioned material options have been tested to comply with USFDA regulations, and are heat-sealable.
The preferred form of structure 6 is seen as structure 7 in Fig. 2. The addition of longitudinal edge seals 4 secure the top and bottom sheets 1,3 together and provide means to trap the gel formed during the structure's end use. These seals are formed by applying heat and pressure to the heat-sealable nonwoven material. There is no powder applied to the sheets where the seals are formed. This strip 7 is very easy to handle and can be produced in any length.
Adhesion of the superabsorbent particles 2 to the bottom sheet 3 is necessary to prevent the particles from flowing freely between the top and bottom sheets. The powder adhered in this fashion will not fall out from between the sheets if the strip is cut crosswise from seam 4 to the opposing seam 4. Also, free flowing powder would tend to collect in one area of the structure and diminish the overall absorption performance of the structure.
A packaging manufacturer would purchase this material as rolled goods to be paid out into the production line. The strip may be sliced at any point along its length without loss of powder and can, therefore, be processed into the finished package, then cut to length at any point. Registration for this automatic collation is not needed.
12
SUBSTITUTESHEET Fig. 4 shows a food product tray 11 manufactured in Wilson, NC by Lin-Pac Plastics Group. The absorbent strip 7 is paid out as shown in Fig. 5 in between two layers 8,9 of rigid foam. When the tray is formed and stamped from the rigid foam, the absorbent strip 7 becomes an integral part of the tray 11. The strip 7 is cut to the needed length as the tray is cut to its final dimensions. The stamping process crimps the edges of the tray 11 and seals the cut ends of the strip 7. With the ends crimped as shown in Fig. 5, a permanent reservoir is formed between the crimped ends 12 and the edge seals 4. Referring to Fig. 4, fluids released by food products flow through the holes 10 of the upper foam layer 8 and are absorbed by structure 7. The tray's unique characteristics prevent structure 7 from contact with the food product and presents a very attractive package to the consumer. The gel formed during the absorption of the released fluid by particles 2 is trapped in the permanent reservoir described above, which is formed by edge seals 4 and by the crimped edges 12 of the tray 11 (Fig. 5) .
Referring now to Figs. 6 and 8-12, there is shown one embodiment of a composite sheet manufacturing apparatus according to the present invention. Fig. 6 is a side view of the preferred embodiment of the apparatus 100 of the present invention. Rolls of material 104 and 105, at least one of which is semi-permeable, are mounted on shafts which ride in slotted guides 104a and 105a. Alternatively, the rolls of material, which generally are sold wound on rigid paperboard cores, could be mounted on standard side
13
SUBSTITUTESHEE" chucks which are widely available in the paper and plastics converting industry. The materials must be heat sealable.
The lower layer of heat sealable material in the form of a web 115 is fed from roll 105 and passes through a switch-back coating system which allows a coating of adhesive from lick tray 111c to be applied to one side 115a of the web 115. The sheet or web of material 115 passes over guide roller 107, arriving inverted underneath guide roller 108a and guide roller 108b. These rollers are adjusted vertically to create adequate wrap around a meyer rod 111b. A meyer rod is a wire-wound rod used primarily in the coating industry as a precise doctoring device.
A meyer rod consists of a steel shaft with a specific gauge steel wire wound tightly around it. The depth of the valleys created between each additional contacting wire wrap determines the thickness of the liquid coating. The valley depth depends on the gauge of the wire. RD Specialties Inc. specializes in meyer rods and their rods #40 and #60 provide adequate versatility for the adhesive coating roller or coating system shown in Fig. 9. In the present invention, it is used as a precise applicator roller. This arrangement is necessary due to the permeable nature of the material which constitutes web 115. A normal applicator roller and doctor blade would apply too much adhesive, then force the adhesive through the permeable fabric while doctoring it. With the present arrangement as seen in Figs. 6 and 9, the meyer rod 111b picks up a precise amount of adhesive from pick-up roller ilia, which turns in trough 111c. Trough 111c is filled with water or a known
14
SUBSTITUTESHEET adhesive and solvent (water) mixture required to effect a desirable coating thickness.
Southern Chemical Formulators of Mobile, Alabama, has developed a pressure-sensitive adhesive bearing their experimental label, EX-180, which works well in this application. The Adhesives, Coatings and Sealers Division of 3M sells an industrial pressure sensitive adhesive 4213 which also works well. Both of these adhesives are water-based with a consistency of thin syrup (approximately 1500-3000 cps) . Ordinary water may also be used in place of an adhesive with some absorbent powders as described hereinafter. When this is the case, water takes the place of the adhesive in the adhesive application system described below.
When water does not supplant the liquid adhesive function in this system, the adhesive in tray 111c should be carried in water as its solvent. With such choice of material, the solvent can be evaporated with no harmful side effects to workers, and therefore no costly safety measures. The solvent being water, it can be evaporated with hot air blower 125, shown in Fig. 6. Additionally, the pick-up roller Ilia should be chosen to be as small in diameter as is practical since liquid adhesives tend to sheer, causing a separation of components in the trough 111c. A smaller diameter roller has less of an impelling effect on the liquid adhesive, reducing the chances of sheer.
The rod 111b and roller Ilia must be mechanically driven. As shown in Fig. 9, the meyer rod 111b and pick-up roller Ilia are turning in opposite directions. The rod 111b is turning opposite
15
SUBSTITUTESHEET angularly to the moving web 115. This arrangement of counter rotating rod 111b and roller 111c allows a precise continuous pick up of adhesive to be transferred to rod 111b, which then, in a hybrid doctoring and lifting step, transfers the adhesive to web 115. The opposed movement of web 115 and rod 111b enables application of a continuous precise coating of adhesive on the presenting lower surface, i.e., surface 115a, of web 115. This system will insure an even coating of adhesive or any liquid material as long as the speeds remain linearly equal relative to one another, and within a window of operational speeds necessitated by the thickness of the liquid to be coated. This can be easily visually determined.
The relative speeds of rod Ilia and roller 111b can be altered in relation to web 115 and to each other through a variable speed transmission or by controlling independent motor speeds. These speed alterations allow a wide range of coating thicknesses. With the number of variables at hand, a useful operational technique is trial and error and visual observation for feedback. This empirical method will quickly determine the proper speed settings for a practical coating thickness.
After receiving a coating of adhesive from rod 111b, the web 115 passes past guide roller 108b and around switch-back roller 106. Inside hopper 102 is the powder material to be sprinkled onto web 115. Roller 103 has threads cut into its surface or may be a knurled roller to allow it to pick up powder from hopper 102 as it rotates beneath hopper 102. The threads or knurled surface are
16 machined with the density, viscosity, and minimum and maximum particle size of the powder in mind, as well as the amount of powder to be applied to the web 115. For most applications, the volume of material removed from the surface of roller 103 is proportional to 0.03 grams of powder per square inch surface area of roller 103. The Akzo Akucell SW 270 grade has the following properties: density = 8.2 g/in3 maximum retained on a 19 mesh screen < 2%. Assuming the roller is timed at the linear speed of the web, the above information suggests a preferred thread configuration of 1/32 in. wide, 1/64 in. deep, and 32 threads per inch. This removes a volume of about 0.00012 in3 per inch of linear thread, so 16 threads per inch, cut in two directions over the same area, ideally will meet the minimum powder required considering the above powder properties, i.e., powder/per square inch deposited = 0.000.12 in3/groove * inch x 32 grooves/in x 8.2 g/in3 = 0.031 grams/in2. -
The powder carries a slight electrical charge and will cling to a steel roller. Once some powder clings, this clinging fine powder layer will effectively serve as an anti-static coating and prevent additional powder from clinging. Increasing the cut¬ away volume per area by adding an opposing cross-thread back across the cut-away section, the same thread setting slightly more than doubles the 16 thread one-way cut. This is required to overcome the volume loss due to the static-adhered powder coating. Roller
17
SUBSTITUTESHEET sheaths 103a and 103b guide the powder and control its flow onto web 115. " The roller speed is not required to be synchronized with the web, therefore the mass flow rate of the powder is controlled (adjustable) by the angular speed of the applicator roller 103. A detailed cut-away perspective of hopper 102 and roller
103 are seen in Fig. 11. The threaded or knurled surface 103c of roller 103 picks up powder from the open bottom of hopper 102. Some of the powder begins to fall away from the roller's surface almost immediately and slides along the inside of sheath 103a. The powder is mostly free from the surface of roller 103 as it rotates through 180*, and sheath 103b, seen in Fig. 8 controls the fall of any reluctant particles which cling beyond 180*.
An operational consideration is the application of mildly charged particles to web 115 which tend to cling to the steel roller 103. Generally, after the initial turns of roller 103, the roller is coated with a thin layer of dust from the powder which repels any additional powder. Speed of the roller can easily be adjusted for mass flow rate lost due to volumetric loss from the resulting' coating. As roller 103 begins operation, the coating becomes steady and speed is then adjusted to insure an even powder flow onto web 115 passing beneath the roller and sheath arrangement. Relative speeds of roller 103 and web 115 determine area density of powder 117 in finished strip 121.
An alternative powder sprinkler is seen in Fig. 13. In this version, web 115 directly wraps around roller 103 via guide roller 118; This direct wrapping precludes the need for sheaths
18
SUBSTITUTESHEET 103a and 103b. The advantage to this configuration is that the powder application is automatically timed to the speed of web 115. If the web stops, the powder flow immediately stops. The need for contact with roller 103 and web 115 eliminates the possibility of coating web 115 with an adhesive or water. Any such coating would contact the applicator roller after passing over guide roller 118 and affect the surface of roller 103 to disturb the powder application process. Fig. 7 shows a method for coating the top sheet with adhesive or water and therefore, allows usage of the powder application apparatus of Fig. 13. In this situation, the inner surface 116a of web 116 would be coated with adhesive in the manner described for web 115.
As a comparison between the two powder sprinklers, there will be a minuscule length of non-powder-coated web 115 with the arrangement in Fig. 11 due to the partially free-fall nature of the powder flow. This inconsistency is minimized by reducing the diameter of roller 103 and shortening the distance from the bottom of roller 103 to the upper surface 115a of web 115. The version in Fig. 13 is more precise but necessitates that only the top sheet 116 be coated with adhesive or water and is, therefore, less versatile.
The end product of this process is a strip form of the composite sheet described above. The formation of said strips requires seaming the web 115 with top web 116 along longitudinal paths where powder 117 has been masked out. With the powder sprinkler shown in Fig. 11, powder-free paths are created by
19 placing narrow strips of sheet metal 119b (as shown in Fig. 12) spanning from the bottom of sheath 103a, across opening 119a, to sheath 103b. Alternatively, the masking of powder from the powder sprinkler in Fig. 13 is shown as strips of non-threaded or non- knurled surface steel 128b on the surface of roller 103 as seen in Fig. 14. Powder is picked up by strips of threaded or knurled surface steel 128a provided on the roller 103. Absence of the powder pick-up threads along strips 128b in conjunction with the doctor blades 102a as shown in Fig. 8 results in a clean roller along these paths and, therefore, no powder is applied to web 115. These doctor blades 102a are present in both powder sprinkling apparatuses, and can be best seen in Fig. 8. The doctor blades 102a are made of thin flexible steel or copper and are held in place by bolts 102b which clamp the blades 102a between the bottom edges of hopper 102 and steel supports 102c. They can be unbolted and replaced as needed. The weight of the hopper 102 holds the blades firmly against roller 103 and the blades 102a wipe the roller clean except where a thread has been cut. Either system results in narrow strips of powder 117, as seen in Figs. 12 and 13, with empty or powder-free strips 117a in between them.
As shown in both Figs. 6 and 7, upper sheet 116 is brought in contact and roller-pressed against lower sheet 115 between soft rubber-coated rollers 123. These rollers 123 press the sheets firmly together and increase the adhesion of the super- absorbent particles to the adhesive coated sheet.
20 Roller 112b of Fig. 6 is driven by conventional means with either a belt and pulley system, or sprocket and chain. Roller 122 rides atop the collars 112a. Shown in Fig. 15 is a hanger bearing arrangement which positions the roller 122 securely in its horizontal position. Hanger bearing 123a is set into shaft 123b which slides freely through frame segment 123c. This insures proper pressure resulting freely from the weight of the roller 122. The collars 112a span the length of roller 112b in spaced fashion, see Fig. 10, and are fitted snugly to the outer diameter of roller 112b. Fig. 10 shows roller 112b with two collars 112a of the plurality which extend in equally spaced relation across the axial length of roller 112b.
Roller 112b is a hollow aluminum roller. It houses an electrical heating element at its center which has swivel fittings at either end to allow free rotation of roller 112b. This heating element is controlled to heat the surface of aluminum collars 112a. Aluminum is the preferred material for the heated roller 112b and collars 112a due to its high thermal conductivity qualities. Aluminum also has a very low thermal emissivity (< 0.03); it will resist radiating heat and concentrate the heat through the contact heat-sealing surfaces of collars 112a. The heating element is controlled through a thermocouple and logical relay feedback loop to heat the surface of collars 112a to such a degree as to partially melt webs 115 and 116 together along the powder-free paths 117a (see Figs. 11 and 12) . Pressure from roller 122 finishes the sealing action along the powder-free paths.
21
SUBSTITUTESHEET In Figs. 6 and 7, element 125 is a hot air blower which finishes the evaporation of the adhesive solvent (water) . Blade 120 slits the composite material 124 down the center of each seal, creating individual composite strips 121 from the composite sheet. Roller 113 feeds the composite strips 121 to roller 114 which is a web take-up mechanism which is driven through a sprocket, chain, and a torque-controlled DC motor. DC motors have a characteristic of being easily torque-controlled. This is due to the nature of the wiring and the electric and magnetic fields which drive the motor. A constant electrical load means a constant physical torque on the shaft of the motor. Since there is a direct relationship between the torque on the shaft, and the product of the distance from the shaft center to the outer diameter of the roller with the tension (force) of the web, a constant take-up speed is achieved through means of a constant torque setting, controlled electrically and governing the field of the motor through electronic feedback.
The finished goods are then slit crosswise, unloaded, and a new take-up core installed. Although the invention has been described with reference to preferred embodiments and examples thereof, it is not intended that the present invention be limited to only those described embodiments. The description of the preferred embodiments contained herein is intended in no way to limit the scope of the invention. As will be apparent to a person skilled in the art, modifications and adaptations of the above-described invention can
22 be made without departing from the spirit and scope of the invention, the scope of which is defined and circumscribed by the appended claims.
23

Claims

What is claimed is:
1. An absorbent structure comprising a first sheet material and a second sheet material, at least one of said first and second sheet materials being fluid permeable, and a superabsorbent powder sandwiched between said first and second sheet materials and adhesively secured to at least one of said first and second sheet materials, said superabsorbent powder being a particulate carboxymethylcellulose.
2. An absorbent structure according to claim 1, wherein said superabsorbent powder is sodium crosscarmellose.
3. An absorbent structure according to claim 1, wherein said first and second sheet materials are heat sealable, nonwoven fabrics. '
4. An absorbent structure according to claim 3, wherein said first and second sheet materials are in the form of longitudinal strips and said first and second sheet materials are heat sealed together along opposed longitudinal edges thereof with said superabsorbent powder between said heat sealed longitudinal edges.
5. A food product package comprising a lower tray, an upper tray, said upper tray having a plurality of holes formed therein, and the absorbent structure according to claim 1 sandwiched between said upper tray and said lower tray.
24
6. A method of making an absorbent structure comprising the steps of: providing a first sheet material and a second sheet material, at least one of said first and second sheet materials being fluid permeable; applying a coating of water to a surface of one of said first and second sheet materials to produce a wetted sheet material surface; applying a layer of particulate superabsorbent powder to said wetted sheet material surface, said superabsorbent powder being carboxymethylcellulose; drying said wetted sheet material surface to produce a sheet material surface having said superabsorbent powder adhered thereto; and then joining said first sheet material to said second sheet material such that said superabsorbent powder adhered to said sheet material surface is sandwiched between said first and second sheet materials to form an absorbent structure.
7. A method of making a food product tray, comprising the steps of: feeding an absorbent structure according to claim 1 between an upper layer of rigid foam material and a lower layer of rigid foam material, said upper layer of rigid foam material having a plurality of holes therethrough;
25 simultaneously cutting said upper and lower layers of rigid foam material and said absorbent structure into complementary shapes; and securing said upper layer of rigid foam material to said lower layer of rigid foam material with said absorbent structure therebetween to produce a food product tray.
8. A method of making a composite material comprising the steps of: providing a first sheet of material; applying a coating of adhesive to a first surface of said first sheet; depositing a layer of powder on the adhesive coated first surface of said first sheet to form a powder covered first surface having at least two longitudinally extending powder-free zones and at least one longitudinally extending powder covered zone therebetween; feeding a second sheet of material over the powder covered first surface of said first sheet; heat sealing said sheet of material to said first sheet of material along said longitudinally extending powder-free zones on the powder covered first surface of said first sheet; and drying said adhesive to produce a composite material; wherein at least one of said first and second sheets of material is semi-permeable, and wherein said first and second sheets of material are heat sealable.
26
9. A method of making a composite material according to claim 8,' wherein said powder is deposited on the adhesive coated first surface of said first sheet such that the powder covered first surface of said first sheet has at least three longitudinally extending powder-free zones with at least two longitudinally extending powder covered zones, each of said longitudinally extending powder covered zones being located between two of said longitudinally extending powder-free zones, said method further comprising the step of cutting said composite material along at least one of said longitudinal heat seals to produce at least two separate composite strip materials.
10. An apparatus for producing a composite material, said apparatus comprising: means for feeding a first sheet of material in a longitudinal direction; means for longitudinally applying a coating of adhesive to a first surface of said first sheet material; means for depositing a layer of powder on the adhesive coated first surface of said first sheet material to form a powder covered first surface of said first sheet having at least two longitudinally extending powder-free zones and at least one longitudinally extending powder covered zone located therebetween; means for feeding a second sheet of material in a longitudinal direction over the powder covered first surface of said first sheet of material;
27 means for heating sealing said second sheet of material to said first sheet of material along said longitudinally extending powder-free zones; and means for drying said adhesive.
11. Apparatus according to claim 10, further comprising means for longitudinally cutting the composite material along at least one longitudinally extending heat sealed portion thereof.
12. Apparatus according to claim 10, wherein said means for depositing a layer of powder on the adhesive coated first surface of said first sheet includes a roller and a roller surrounding sheath, said sheath being coaxial with said roller.
13. Apparatus according to claim 10, wherein the means for depositing a layer of powder on the adhesive coated first surface of the first sheet includes a roller having a plurality of powder-receiving passages formed in the surface thereof.
28
PCT/US1993/003475 1992-04-14 1993-04-14 Absorbent structure for incorporation into packages WO1993020950A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US86840592A 1992-04-14 1992-04-14
US07/868,405 1992-04-14

Publications (1)

Publication Number Publication Date
WO1993020950A1 true WO1993020950A1 (en) 1993-10-28

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1993/003475 WO1993020950A1 (en) 1992-04-14 1993-04-14 Absorbent structure for incorporation into packages

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AU (1) AU4048993A (en)
WO (1) WO1993020950A1 (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4418319A1 (en) * 1994-05-26 1995-11-30 Stockhausen Chem Fab Gmbh Laminate for absorption of water and aq. liq. with good retention
US6171695B1 (en) 1994-09-21 2001-01-09 Kimberly-Clark Worldwide, Inc. Thin absorbent pads for food products
GB2355228A (en) * 1999-07-03 2001-04-18 Dyecor Ltd Absorbent
US6449035B1 (en) * 1999-05-12 2002-09-10 John Samuel Batchelder Method and apparatus for surface particle detection
DE10205828A1 (en) * 2002-02-13 2003-08-21 Corovin Gmbh Composite with an absorbent layer
US8414997B2 (en) * 2005-07-12 2013-04-09 Mcairlaid's Vliesstoffe Gmbh & Co. Kg Absorbent insert for foodstuff packaging
CN112874114A (en) * 2020-12-22 2021-06-01 重庆新士腾包装制品有限公司 Heat seal separator is used in cotton processing of pearl

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US4297410A (en) * 1978-10-12 1981-10-27 Kao Soap Co., Ltd. Absorbent material
US4929480A (en) * 1987-07-20 1990-05-29 Kimberly-Clark Corporation Absorbent structure for absorbing food product liquids
US4994053A (en) * 1985-06-26 1991-02-19 Kimberly-Clark Corporation Composite article having discrete particulate areas formed therein
US5091234A (en) * 1989-06-30 1992-02-25 Mcgroarty Bryan M Composite water barrier sheet

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4297410A (en) * 1978-10-12 1981-10-27 Kao Soap Co., Ltd. Absorbent material
US4994053A (en) * 1985-06-26 1991-02-19 Kimberly-Clark Corporation Composite article having discrete particulate areas formed therein
US4929480A (en) * 1987-07-20 1990-05-29 Kimberly-Clark Corporation Absorbent structure for absorbing food product liquids
US5091234A (en) * 1989-06-30 1992-02-25 Mcgroarty Bryan M Composite water barrier sheet

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4418319A1 (en) * 1994-05-26 1995-11-30 Stockhausen Chem Fab Gmbh Laminate for absorption of water and aq. liq. with good retention
DE4418319C3 (en) * 1994-05-26 2001-08-09 Stockhausen Chem Fab Gmbh Layered body for the absorption of liquids and its manufacture and use
US6171695B1 (en) 1994-09-21 2001-01-09 Kimberly-Clark Worldwide, Inc. Thin absorbent pads for food products
US6449035B1 (en) * 1999-05-12 2002-09-10 John Samuel Batchelder Method and apparatus for surface particle detection
GB2355228A (en) * 1999-07-03 2001-04-18 Dyecor Ltd Absorbent
DE10205828A1 (en) * 2002-02-13 2003-08-21 Corovin Gmbh Composite with an absorbent layer
US7271113B2 (en) 2002-02-13 2007-09-18 Fiberweb Corovin Gmbh Composite with an absorbent layer
US8414997B2 (en) * 2005-07-12 2013-04-09 Mcairlaid's Vliesstoffe Gmbh & Co. Kg Absorbent insert for foodstuff packaging
CN112874114A (en) * 2020-12-22 2021-06-01 重庆新士腾包装制品有限公司 Heat seal separator is used in cotton processing of pearl
CN112874114B (en) * 2020-12-22 2024-05-14 重庆新士腾包装制品有限公司 Heat seal separation device for processing pearl wool

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