HK1179214B - Process of expediting activation of heat-expandable adhesives/coatings used in making packaging substrates - Google Patents

Description

Accelerated activation process for thermally-intumescent adhesives/coatings for making packaging substrates

Reference to earlier filed application

This application is in accordance with the benefit OF U.S. provisional patent application No. 61/379,030 entitled "accelerated activation PROCESS for thermally-intumescent adhesive/coating for making packaging SUBSTRATES" (processes OF exterior insulation utilization OF HEAT-exterior adhesion/COATINGS USED IN MAKINGPACKAGING SUBSTRATES), filed 2010, 9/1/119 (e), which is incorporated herein by reference in its entirety.

Background

Consumers often purchase ready-made products, such as food and beverages, and other products, packaged in containers made from packaging substrates (packaging substrates). For hot or cold liquids or food products, such as hot coffee, iced tea or pizza, a thermally insulated container may be used. These containers can maintain the temperature of the liquid or food contents by reducing the transfer of heat or cold from the contents to the consumer's hands.

To help thermally or cold insulate the consumer's hand from the contents of a food or beverage container, thermally-intumescent adhesives and coatings have been developed for micro-grooved boards or co-packaging substrates. Such intumescent adhesives and coatings expand after heating to a certain temperature.

Disclosure of Invention

A method is disclosed for using microwave heaters to heat a sheet or roll web ("sheet") for containers and other substrates during the manufacturing process, thereby causing rapid expansion of a thermally-intumescent adhesive or coating applied to the sheet or substrate and accelerated activation of the co-substrate. The thermally intumescent adhesive or coating expands to insulate and stiffen the material, which helps transform the material into a package or container, keeps fluid and solid contents in the container cold or hot, and insulates such contents from human contact during human handling of the container. The process is fully automated and uses rolls and/or other sheet materials, for example, single facer materials and slotted plate materials. The thermally intumescent adhesive or coating may be a composition of some intumescent microspheres per weight of starch or other binder and suitable compositions, such as those discussed below. The material is heated by a microwave heater at different points in the process, but especially after application of the thermally-intumescent adhesive or coating. The multi-layer sheet may be laminated and conveyed for final processing, e.g., to be stamped, die cut, removed from a blank, and/or otherwise assembled into a container. The single layer sheet may also be patterned by a thermally intumescent coating, which may also be processed directly into containers after being heated.

Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.

Drawings

FIG. 1 is a perspective view of a cup fitted with an outer wall.

FIG. 2 is a side cross-sectional view of a double wall cup.

Figure 3 is a cross-sectional view of the sleeve with the cup.

Fig. 4 is a diagram of an exemplary machine system for making packaging material and a substrate for a container.

Fig. 5 is a perspective schematic view of an exemplary industrial microwave heater positioned above a conveyor belt.

Fig. 6 is a top plan schematic view of the microwave applicator shown in fig. 5.

Fig. 7 is a side plan view of the industrial microwave applicator of fig. 5.

Fig. 8 is a front cross-sectional view of the industrial microwave applicator shown in fig. 5.

FIG. 9 is a flow diagram of an exemplary method for making a multiwall sheet in a process that includes microwave heating of the multiwall sheet to accelerate expansion of a thermally-intumescent adhesive or coating.

Detailed Description

The package, container or container sleeve may be made of and/or insulated with an insulating material such as an intumescent adhesive or coating. The insulating material may be secured to the container or may be applied to a removable sleeve before or after the packaging material or substrate is formed into the shape of the container. The insulating material, such as a thermally expansive material, may be coated into the container or within the container material, or may be coated onto the outer wall of the container, or a combination thereof. The insulating material may expand before reaching the end user, for example, when manufacturing the container and/or container sleeve, and/or the insulating material may expand only at the end use and only in response to temperature, etc. The insulating material may be used to enhance the insulating ability of the container and/or container sleeve, and/or to increase the rigidity of the container and/or container sleeve, e.g., to reduce the thickness of the material composition of the container and/or container sleeve.

The sheet material used to make the packages, containers and/or container sleeves may be manufactured on a conveyor-type machine system using an automated assembly line process, which will be discussed in more detail below. The intumescent adhesive or coating may be applied by conventional coating methods such as roll coating, or sprayed or otherwise applied to the sheet material, for example, to the corrugating medium before the liner is laminated thereto. Thus, the intumescent adhesive or coating may be positioned between two layers of a sheet material prior to expansion during the manufacturing process. If the insulating material is a coating, the insulating material may be applied to a single layer (or sheet) or to the outer surface of a multi-layer sheet prior to expansion upon heating. Additionally or alternatively, the intumescent adhesive or coating may be expanded by the application of heat prior to being placed between the two pieces of material. Other embodiments are also possible, as discussed below.

In some embodiments, the thermally intumescent adhesive/coating is heated during the conveyor-type machine assembly process, and therefore expands during the process of manufacturing the container. In conventional machine systems, the heat source is supported by a temperature source, for example, from a heat gun or an Infrared (IR) heater or an infrared lamp. Conventional heating methods, such as, for example, in-line hot blast stoves and/or infrared heaters mounted on a machine system, are not effective to adequately activate thermally expanded microspheres at production speeds typically in the range of 250 feet per minute (fpm) to 600 fpm. This is due in part to space and thermal power limitations, as well as the heating mechanisms of these approaches, which are based primarily on conduction, convection, and radiation. Therefore, when these heat sources are used, the following technical problems arise: the heat energy is limited, the expansion efficiency is low, and the process speed is low. Lower speeds can slow the production of containers by conventional machine systems.

The present invention proposes the use of microwave energy from an industrial microwave applicator adapted to irradiate a sheet passing through the microwave applicator during a process. Thus, the microwaves from the microwave heater energize the intumescent adhesive or insulating coating causing them to heat up more quickly than a hot temperature source or other heat source. This is because the water and other polar molecules in the thermally intumescent adhesive/coating absorb a large amount of heat in a short time. For example, the expanded microspheres mixed in the binder/coating may expand rapidly when the mixture in which the microspheres are placed heats up rapidly due to exposure to stronger microwave energy.

The thermally intumescent adhesive or insulating material may include a starch based glue, may be synthetic based, and may be applied as a laminating adhesive in corrugated board products to allow for greater volume, reduced paper, or both. The corrugated board, in turn, can be converted into many useful food and non-food corrugated packaging products such as, but not limited to, slotted sleeves, micro-slotted clam shells, and E-slotted boxes and bag-in-boxes. These thermally intumescent adhesives/coatings can be applied using a conventional corrugator (corrugator) or laminator and expanded with the aid of industrial microwave heaters for increased efficiency and speed. Other thermally intumescent coatings may be applied to the paper substrate in a full coverage or pattern and subsequently expanded by microwave heaters to form a foam layer or structure with different end use benefits, some of which are explained below.

Fig. 1 shows a container 100, such as a cup, having a common inner wall 102 and outer wall 104, which may be made of sheet material, such as cardboard, manufactured by the machine system previously mentioned and shown in fig. 4. The blank of the outer wall 104 may take the form of: a container sleeve, or a wall or body of the container 100. The container 100 is not limited to a cup, but may be any other container including, but not limited to, a bulk coffee container, a soup tub, a press formed container, a plate, a sleeve (e.g., single faced corrugated cardboard, double faced corrugated cardboard, non-corrugated cardboard, etc.), a folding carton, a tray, a bowl, a clamshell, and other containers with or without a lid or sleeve. The container 100 may be a cylindrical cup or a container having other geometric configurations, including conical, rectangular, etc.

The blank of the outer wall 104 is not limited to a corrugated die cut blank but may be constructed of any type of paperboard, paper, foil, film, fabric, foam, plastic, etc. The outer wall 104 may be made of any nominal stock, including, but not limited to, natural single facer stock, white-edged single facer stock, coated bleached top single facer stock, corrugated stock, fluted corrugated stock, or combinations thereof. The outer wall 104 may be removable from the container 100 or the outer wall 104 may be bonded to the container 100. For example, the outer wall 104 may be bonded by laminating the blank of the outer wall 104 to the container using a hot adhesive, a cold melt, and/or any other adhesive or sealing mechanism. Alternatively or additionally, the blank of the outer wall 104 may be bonded with an insulating material. If the outer wall 104 is attached to the cup during the manufacturing process, efficiency may be improved by eliminating the assembly step of a commercial end user. In addition, this can reduce the amount of storage space required for commercial end users, for example, storing only one item, rather than two.

Figure 1 is not necessarily drawn to scale. For example, the outer wall 104 may cover a greater or lesser portion than the surface of the illustrated container 100. For example, the outer wall 104 may completely cover the body. Increasing the surface area of the outer wall 104 may increase the insulation area and the stamping surface. Although the outer wall 104 is shown on a cup, the outer wall 104 may be added to any other container, such as, but not limited to, bulk beverage containers, press formed containers, and soup basins. Alternatively or additionally, the outer wall 104 may be added to the container sleeve (fig. 3).

Fig. 2 is a side cross-sectional view of a container 100, which may be a double-walled cup. The container 100 may provide an air jacket 200 between the outer wall 104 of the container 100 and the contents 206, such as hot or cold beverages or food products. The air jacket 200 may achieve thermal insulation as measured by the outside surface temperature. The air jacket 200 may partially or completely surround the vessel 100. When the container 100 is grasped, the pressure applied to the outer wall 104 may act to collapse the outer wall 104 at the point of compression, thereby contracting the air jacket 200 and possibly causing contact with the inner wall 102 of the container 100. The air jacket 200 may collapse at the point of compression and may give a less rigid feel, and this contact may create hot spots on the outer wall 104.

The insulating material 216 coated between the inner wall 102 and the outer wall 104 may reduce or eliminate this effect. If a sufficient amount of insulation 216 is used, the insulation 216 may provide rigidity to the outer wall 104 without compromising the thermal insulation of the air jacket 200 so that the outer wall 104 does not collapse partially or completely. The insulating material 216 may increase the mechanical strength of the container 100. Based on the increased mechanical strength provided by the insulating material 216, lighter weight materials may be used to produce the container 100, thereby reducing the source of substrate material from which the container 100 is formed. The insulating material 216 may be applied in spots, such as small dots, or other patterns, to the inner wall 102, the outer wall 104, or both, such that the insulating material 216 defines the air gap 200 and prevents the outer wall 104 from collapsing onto the inner wall 102 under the gripping pressure. The insulating material 216 may also provide a rigid feel to the user while allowing for the reduction of substrate material, e.g., the inner wall 102 or the outer wall 104.

The insulating material 216 may be expanded when activated or may be pre-expanded, for example, by the addition of air or an inert gas, in-situ bubbles, microspheres, expanded microspheres, or other foaming agent. For example, the insulating material 216 may be activated by temperature or other methods. In one example, the insulating material 216 may be thermally activated by high temperatures. The insulating material 216 may be an intumescent insulating material or an adhesive. Additionally or alternatively, the insulating material 216 may include, but is not limited to, binders, expanded microspheres or other microencapsulated particles, pigments and other additives, adhesives, inert gas foamed hot melt adhesives, aqueous coatings containing thermally expanded microspheres, starch-based adhesives, natural polymer adhesives, PVC, foam coatings, biodegradable glues, or any combination of the above or other materials. The insulating material 216 may include in-situ bubbles, microspheres, particulates, fibers, expanded fibers, dissolved particles, and the like. In one example, the insulation 216 with microspheres may include a starch composition, with some, e.g., 1% to 5%, of the microspheres mixed into the insulation 216. The insulating material 216 may be biodegradable, compostable, and/or recyclable.

The insulating material 216 may expand when wet or dry. The insulating material 216 may include any synthetic or natural material, including water-based, solvent-based, high solids, or 100% solids materials. The amount of solids content is typically 30% to 80%, more preferably 40% to 70% of the material. Additional components may be added to the binder and/or insulating material 216 including, but not limited to, pigments or dyes, fillers/extenders, surfactants for dispersion, thickeners or solvents to control viscosity for optimal application, foaming agents, waxes or slip agents, and the like. Alternatively, the binder and/or insulating material 216 may be an adhesive. The insulating material 216 may have a variety of properties, including, but not limited to, thermal insulation to keep the contents of the container hot or cold, absorbency for droplets and/or liquids, and/or the insulating material may expand upon contact with a hot material (e.g., above 150 ° F), and preferably remains in an inactive state until a certain designed activation temperature is reached. For example, the insulating material 216 will remain inactive at about room temperature. The insulating material 216 may be repulpable, recyclable, and/or biodegradable.

In yet another example, an inert gas, such as nitrogen, may be injected into the insulating material 216. For example, an inert gas such as nitrogen may be injected into the hot melt adhesive, starch-based adhesive, or a natural polymer adhesive may be used. Gas may be applied to the outer surface of the inner wall 102 prior to placement of the outer wall 104 in order to give these materials a foam structure, thereby enhancing the mechanical and thermal insulating properties of the double-walled container. For example, the gas may be injected into the insulating material 216 before the gas is applied to the outer wall 104, or during application to the outer wall 104.

Fig. 3 shows a cross-sectional view of an outer wall 104 (fig. 2) of a sleeve or the like fitted with the container 100. This diagram is intended to be illustrative, not limiting. The cup may be replaced by any container, for example a press-formed tray, a soup bowl or a bulk beverage container. The outer wall 104 may have an inner surface 306 and an outer surface 304. The insulating material 216 may be applied to the inner surface 306, the outer surface 304, and/or to the surface 302 between the inner surface 306 and the outer surface 304, for example, to an inner wall of the sleeve. The space 302 is not necessarily contained between the inner surface 306 and the outer surface 304.

An insulating material 216, such as a thermally intumescent material, may be applied to the inner surface 306 of the outer wall 104 in an activated or unactivated form. The insulating material 216 may be coated as a thin film that does not substantially change the thickness of the outer wall 104. Applying the insulating material 216 to the interior of the outer wall 104 may also maintain the printability of the outer surface of the outer wall 104. The slim profile of the cup can be maintained if the insulating material 216 on the outer wall 104 is assembled with a standard paper cup or the like. In the alternative, the thermally intumescent material may be activated by microwaves to accelerate expansion during manufacture prior to assembly into a sleeve. This ensures that the intumescent adhesive/coating expands during manufacture and provides additional rigidity and strength after manufacture and before use.

Fig. 4 is a diagram of an exemplary machine system 400 for manufacturing packaging material or substrates for making containers such as the container 100 described above. For example, machine system 400 may be a conveyor-type machine system having multiple stages, such as an ehrlichia @ laminator manufactured by Asitrade AG of Grenchen, Switzerland, glansylvania, cited merely as an example. Fig. 4 shows three parallel views of the process: view a of the machine, view B of the way the sheet may pass through the machine, and cross-sectional view C of the final finished product. The machine system 400 may extend longitudinally for a substantial length and may include a number of workstations along a common length. The sheet of material assembled into the packaging material or substrate travels from right to left along the machine shown in fig. 4.

The machine system 400 may use a first sheet 402 that is provided in bulk in the form of a roll or web. The first sheet 402 may be fed into the machine system 400 by a wheel, belt, or other transport system and subjected to various steps of the process. Figure 4 illustrates the use of a wheeled system. Alternatively or additionally, the machine system 100 may use a sheet material that may be pre-stamped and may have been die cut with a pattern or blank of a particular package, such as, for example, a blank of, inter alia, a cup, container, tray, clamshell, tray, bag, or beverage container stand.

The first sheet 402 may be composed of a generally flat material that is somewhat rigid and capable of being bent or scored to facilitate bending along a defined line. For example, the sheet 402 may be a single-sided linered paper, such as, but not limited to, kraft paper, clay-coated newsprint board, white-edged liner, containerboard, Solid Bleached Sulfate (SBS) board, or other material. The material may be treated, for example, to provide higher water or fluid resistance, and selected portions of the material may have printing thereon. Alternatively or additionally, the sheet 402 may be composed of corrugated board, chip board, plywood, metalized paper, plastic, polymers, fibers, composites, blends, combinations thereof, or the like. The first sheet 402 may be made of recyclable materials, or the first sheet may be compostable, biodegradable, or may be a combination of the above.

The first sheet 402 may be conveyed by a roller 408 to a first station 420. The first work station 420 may be a corrugating station. The first work station 420 may also include corrugating rollers. The corrugating rollers may form the first sheet 402 or a medium paper (medium paper) into a series of corrugations or flutes. In the alternative, a single layer or sheet of substrate may enter directly without corrugating as with first sheet 402 or paper media.

The first station 420 may also include an applicator that may apply the securing material to one side of the first sheet 402, i.e., to the top of the grooves, or to one side of another core paper. For example, the applicator may be a channel containing a securing material such as an adhesive. The grooves may be located adjacent the corrugating rollers so that the adhesive is applied to the tips of the corrugations or flutes formed by the corrugating rollers. Additionally or alternatively, the securing material may be applied by spraying, brushing, or other means. For example, the applicator may apply the securing material by spraying the securing material onto one side of the first sheet 402 (or other core paper). The spray from the applicator may be continuous or intermittent and may form the securing material into a dotted line, stripe, dot or oval. The design and pattern can be applied by moving the applicator or moving the first sheet 402 relative to the sprayer.

For example, the securing material may be an adhesive, a thermally insulating material 216, or a co-material or coating, such as those having securing properties. Various intumescent insulating materials 216 have been previously discussed in detail. Further, the securing material may be a hot or non-hot melt adhesive or a cold melt adhesive, such as, for example, a hot melt adhesive, a starch-based adhesive, a natural polymer adhesive, a cellulose-based adhesive, glue, hot melt, polymeric binder, composite, foam, and the like.

The securing material may be delivered to the applicator from line 422, which may originate from conditioning and preparation station 432. The microspheres or other intumescent insulating material may be pre-mixed with the starch, binder or other adhesive material in the conditioning and preparation station 432 before being delivered to the applicator of the first station 420.

In some embodiments, the applicator may apply a pattern of the thermally intumescent coating to a first sheet or other paper media (referred to herein as a single layer sheet) which is subsequently heated by a microwave heater in order to expand the thermally intumescent coating. This single-ply sheet with the coating and pattern can then be conveyed for processing into a final product with a patterned coating.

In other embodiments, first sheet 402 may also be combined with second sheet 404, e.g., by pressing second sheet 404 against first sheet 402. The second sheet 404 may be secured to the first sheet 402 by a securing material to form a double-layer sheet 426, for example, a single-sided slotted sheet as shown in fig. 4, C.

Any temperature in the corrugating station or first station 420 that exceeds the predetermined temperature may have the negative side effect of over-drying the thermally-intumescent adhesive or coating, which may result in premature partial expansion of the microspheres in the adhesive or coating. If too dry, the thermally intumescent adhesive or coating will not have sufficient moisture to absorb the microwave energy and thus will not heat up quickly. Thus, the temperature applied to the composite corrugated board, e.g., single face board, at the corrugating station is preferably maintained at about 200 degrees fahrenheit or less.

The two-ply sheet 426 may then pass through an industrial microwave applicator 427, which may be disposed about the conveyor belt after the first station 420, to apply microwaves to the two-ply sheet. A certain humidity is preferably maintained in the thermally intumescent insulating material 216 from the time the mixture is prepared in conditioning and preparation station 432. This humidity is susceptible to absorption of microwave energy emitted by microwave heaters 427 and thus heats up rapidly, causing expansion of the adhesive/coating insulation 216 applied by the applicator.

The microwave heaters 427 are preferably planar heaters operating at 915MHz or 2.45GHz or some other acceptable frequency. Microwave heater 427 may also be a tube or other type of heater. These types of industrial microwave heaters are commonly used to dry aqueous mixtures or products that contain polar molecules that absorb electromagnetic energy in a microwave field, thereby heating and drying the water and sometimes cooking the product. In the case of planar heaters, the microwave heaters 427 may include a relatively narrow open slot between two panels of a microwave waveguide or channel through which the web or other substrate passes, as shown in FIGS. 5-8. The microwave heaters 427 may not only dry the web or substrate, but may also activate and expand intumescent materials previously coated between layers of paper or on the paper.

A two-layer sheet 426, such as a single-sided slotted sheet, may exit the machine system 400 and proceed to further processing, e.g., die cutting, embossing, conditioning, folding, etc., to form the final product. Alternatively, the bi-layer sheet 426 may be further processed by the machine system 400, as described below. Note that microwave heater 427 may alternatively be positioned along a further processing station below machine system 400. For example, the intumescent adhesive or coating may be applied at a later stage of the process, at some point thereafter, microwave heaters 427 may be placed to expand the adhesive/coating, as discussed below. Thus, the location of the microwave heater 427 is not critical, but some locations may be better for ease of attachment to portions of the machine system 400.

The two-ply sheet 426 may be conveyed to a second workstation 430. The second station 430 may include an applicator that may apply a securing material to one side of the two-layer sheet 426. For example, the applicator may apply a securing material to the second sheet 404 side of the bi-layer sheet 426, which may be the backing side of the bi-layer sheet 426. Alternatively or additionally, an applicator may apply a securing material to the first sheet 402 side of the two-layer sheet 426. The fixing material may be or include an intumescent adhesive or an insulating coating. For example, the securing material may be an adhesive, such as a hot melt adhesive, a starch-based adhesive, a natural polymer adhesive, a cellulose-based adhesive, a glue, a hot melt adhesive, a cold set adhesive, an adhesive, a composite, a polymeric adhesive, a foam, and the like.

The fixing material may be applied by spraying, brushing or other means. For example, the applicator may be a channel containing a securing material. The grooves may be located adjacent to a roller for feeding paper to the second station 430 so that the fixing material is applied to the tips of the corrugations or grooves produced by the corrugating rollers. As a second example, the applicator may apply the securing material by spraying the securing material onto one side of the first sheet 402, the second sheet 404, or both. The spray from the applicator may be continuous or intermittent and may form the securing material into a dotted line, stripe, dot or oval. The design and pattern can be applied by moving the applicator or moving the first sheet 402 relative to the sprayer.

The two-ply sheet 426 may be combined with a third sheet 410, which may be a second liner, for example, by pressing the third sheet 410 against the two-ply sheet 426 to form a three-ply sheet 434.

The three-layer sheet 410 may be composed of a generally flat material that is somewhat rigid and capable of being bent or scored to facilitate bending along a defined line. For example, the three-ply sheet material 410 may be single-sided linered paper, such as, but not limited to, kraft paper. The material may be treated, for example, to provide higher water or fluid resistance, and selected portions of the material may have printing thereon. Alternatively or additionally, the third sheet 410 may be composed of corrugated cardboard, chip board, SBS, metalized paper, plastic, polymer, fiber, composite, blends, combinations thereof, or the like. The third sheet 410 may be made of recyclable materials, or the third sheet may be compostable, biodegradable, or may be a combination of the above.

The second workstation 430 may be a laminator. Each layer of the multi-layer laminate, such as the three-layer sheet 434, can improve the structural integrity and appearance of the resulting packaging material. Alternatively, microwave heaters 427 may be located at or near the second station 430 to radiate microwave energy through the multilayer web of the second station 430, for example, during lamination. The microwave heater 427 can then rapidly heat and thus co-expand the adhesive or coating applied to the multilayer sheet as a fixing material, which contains a thermally-intumescent component, e.g., microspheres. The multi-ply sheets exiting the second station 430 may be further conditioned, cut or stamped, and stacked for shipping. Subsequently, the multiwall sheet can be formed into a container 100.

Several laboratory feasibility tests have been performed using common office microwave ovens and experimental planar industrial microwave heaters. Both E-grooved single-face corrugated board and F-grooved single-wall corrugated board were used as substrates in these tests. The results of these tests include confirmation that the thermally-intumescent adhesive and coating sandwiched between the media and the liner can activate and expand. Tests have also shown an enhancement in drying and reduction of steam energy consumption. Tests have also shown that angled waveguides, such as 45 degree oriented micro-waveguide configurations, can be used in-line on the machine system 400 to increase the speed of the process comparable to that when no thermally-intumescent adhesive or coating is used.

Fig. 5-8 include various schematic views of a micro-waveguide that may be used with microwave heater 427. microwave heater 427 may be mounted about one or more conveyor belts 503, conveyor belts 503 being used to convey cardboard, sheet, or other substrates through machine system 400. Microwave heater 427 is shown as a planar heater having a narrow slot 505 through which the sheet material may pass. Fig. 7 shows a cross-machine side view, while fig. 8 shows a front or machine direction view of microwave applicator 427. Microwave applicator 427 may include a plurality of micro-waveguide channels that are connected to increase the surface area for radiating the sheet. The dimensions of microwave applicator 427 shown in fig. 5-8 are exemplary only and not intended to be limiting.

FIG. 9 is a flow diagram of an exemplary method for making a multiwall sheet in a process that includes microwave heating of the multiwall sheet to accelerate expansion of a thermally-intumescent adhesive or coating. The dashed lines in fig. 9 include optional routes that may bypass one or more steps of the method. At block 900, a first sheet may be loaded into the machine system 400 and may be corrugated. At block 910, a securing material may be applied to one side of the first sheet. The fixing material may be a thermally intumescent adhesive or coating, which may comprise starch and microspheres or some other composition. At block 920, the second sheet may be attached to the first sheet. If this two-layer sheet has a securing material that includes a thermally intumescent coating, the two-layer sheet may be heated with microwave energy at block 930 to expand the thermally intumescent adhesive/coating. At block 940, the two-ply sheet may be conveyed for processing into a final product by stamping, die cutting, removal from a blank, and/or assembly, etc.

At block 950, a second securing material may be applied to one side of the bi-layer sheet. The second fixing material may be a thermally intumescent adhesive or coating, which may include starch and microspheres and/or some other suitable composition. After this step, the multilayer sheet may be passed forward through certain steps and heated and/or laminated without first applying a third sheet. Otherwise, at block 960, the third sheet may be adhered to the exposed side of the first or second sheet. At block 970, if the second securing material is a thermally-intumescent adhesive or coating, the multilayer sheet may be heated with microwave energy to expand the thermally-intumescent adhesive or coating. At block 980, the multi-layer sheet may be laminated. That is, if the first, second, and third sheets have been adhered together, they may be laminated together at block 980. At block 940, the multi-layer sheet or substrate may then be processed into a final product, which may include stamping, die cutting, removal from a blank, and/or assembly.

For example, the resulting multilayer sheet may be further processed, e.g., coated, followed by removal of the packaging blank from the sheet and assembly of the blank into a final product (block 940). The end product of the process (which may be, for example, a cup, container holder, container sleeve, clamshell, tray, or the like) may be made from one or more layers of one or more of the foregoing materials. Where multiple layers of material are used, the multiple layers of material may be joined, for example, but not limited to, fastened together by lamination, gluing, or other means to increase strength.

As discussed above, the use of the insulating material 216 may help reduce the thickness of the substrate required for the manufacture of containers, sleeves, and the like, while maintaining a rigid feel to the consumer. The insulating material 216 may also enhance the insulating properties of the container and help keep the beverage or food hot or cold for an extended period of time depending on the particular application. The substrate may be made of natural fibers, synthetic or both, for example, SBS (solid bleached sulfate) cardboard or boxboard. The jacket material, e.g., liner and media, may be made of 10LB/1000ft²To 100LB/1000ft²Of (2) aMade, preferably 15LB/1000ft²To 40LB/1000ft²The material of (1).

While the invention has been described in terms of various embodiments, those of ordinary skill in the art will readily appreciate that many other embodiments and implementations are possible that are within the scope of the invention. For example, unless explicitly stated otherwise, the steps of a method as shown in the figures or reflected in the appended claims must be performed in the particular order presented. The disclosed steps are exemplary and, thus, additional or different steps may be performed, or the steps may be performed in a different order.

Claims (8)

1. A method of making a multilayer substrate for packaging, the method comprising:

transferring a flat first sheet into a conveyor type machine system, the first sheet having at least two sides;

corrugating the first sheet to create a series of flutes;

applying a first fixing material to the top of the corrugated flute on one side of the first sheet, the first fixing material comprising a first thermally intumescent adhesive consisting of a binder mixed with 1-5 wt% thermally intumescent microspheres;

applying a flat second sheet to the one side of the first sheet to form a series of air gaps defined by the first sheet's corrugated flutes, the first securing material, and the second sheet; and

heating the first sheet and the second sheet with an industrial microwave heater to cause the thermally intumescent adhesive to expand and form the multilayer substrate.

2. The method of claim 1, wherein the first sheet comprises paper.

3. The method of claim 1, wherein the second sheet comprises paper.

4. The method of claim 1, wherein the one side of the first sheet comprises a first side, further comprising:

applying a second securing material to a second side of the first sheet or to the second sheet;

applying a flat third sheet to the second side of the first sheet or the second sheet;

laminating the first, second, and third sheets to form a second multi-layer substrate.

5. The method of claim 4, wherein the second fixation material comprises a second thermally-intumescent adhesive, the method further comprising:

heating the multi-layer substrate with the second securing material after the first thermally-intumescent adhesive of the first securing material has expanded to expand the second thermally-intumescent adhesive.

6. The method of claim 5, wherein the second thermally intumescent adhesive comprises starch or other bonding material and thermally intumescent microspheres.

7. The method of claim 2 or 5, wherein the microwave heater comprises a planar microwave heater having a plurality of microwave waveguides surrounding a space through which the sheet passes, the microwave heater operating at 915MHz or 2.45 GHz.

8. The method of claim 1, wherein the binder is starch.