Microwave heating of heat-expandable materials for making packaging substrates and products

Abstract

Packaging containers (e.g., cups) or protective wraps may be made with two layers of sheet material and an expanded thermal insulation between the layers. The thermal insulation may be made from microencapsulated, heat-expandable particles that are expanded with a microwave heater at some point during processing substrate, building, conveying or packaging the containers. The particles may be applied to blanks formed from die cutting, expanded by heating, and then tampered. The blanks may be outer wraps to a double wall cup, formed by placing and adhering an inner cup to the outer wrap. Alternatively, an adhesive containing the particles are applied to inner cups, which may be adhered to outer wraps to complete formation of the double wall cups. The cups may then be heated with a microwave heater at a subsequent workstation as the cups are conveyed, stacked, placed in bags, the bags in cartons and the cartons stacked and palletized.

We claim: 
     
         1 . A method for manufacturing, comprising:
 positioning blanks on a conveyor system;   applying heat-expandable particles in a pattern on the blanks as a belt of the vacuum conveyor system moves the blanks below an applicator;   heating the particles with a microwave heater to expand the particles; and   sending the blanks along the conveyor system to a product-building machine that assembles products from the blanks.   
     
     
         2 . The method of  claim 1 , further comprising:
 tampering the expanded particles to a uniform height by a sizing device before sending the blanks to the product-building machine.   
     
     
         3 . The method of  claim 1 , where applying the particles further includes leaving a gap in the pattern of the applied particles, the gap configured to correspond to a raised strip of a mandrel that vacuum-grips the blanks from a side of the applied particles, to move the blanks within the product-building machine. 
     
     
         4 . The method of  claim 3 , further comprising:
 controlling a speed of the belt of the vacuum conveyor system such as to apply the particles evenly in the pattern on respective blanks.   
     
     
         5 . The method of  claim 1 , where the blanks comprise outer wraps and the products comprise double wall cups. 
     
     
         6 . A blank moving device, comprising:
 a frustoconical mandrel; and   a raised strip formed on a side of the frustoconical mandrel, the raised strip including vacuum holes adapted to grip, with vacuum suction, a side of a blank comprising an applied pattern of expanded microencapsulated particles.   
     
     
         7 . The blank moving device of  claim 6 , where the raised strip is configured to match a gap left in the applied pattern of expanded microencapsulated particles of the side of the blank. 
     
     
         8 . The blank moving device of  claim 6 , where a height of the raised strip above the surface of the frustoconical mandrel comprises at least about a height of the expanded microencapsulated particles. 
     
     
         9 . The blank moving device of  claim 6 , where the raised strip comprises a first strip, further comprising:
 a second strip formed in another location of the side of the frustoconical mandrel for alignment of a seam of outside edges of the blank.   
     
     
         10 . A method for manufacturing double wall cups with heat-expandable material between the inner and outer wall, comprising:
 forming an outer wrap for a double wall cup;   forming an inner cup;   applying an adhesive to an outer surface of the inner layer with an applicator, the adhesive having microencapsulated, heat-expandable particles;   conveying and inserting the inner cup into the outer wrap within the cup-building machine; and   heating the double wall cup with a microwave heater to expand the particles in the adhesive.   
     
     
         11 . The method of  claim 10 , where the adhesive comprises a coating. 
     
     
         12 . The method of  claim 10 , further comprising:
 conveying the double wall cup through a tube passing through the microwave heater to expand the particles and to subsequently be stacked in preparation for bagging.   
     
     
         13 . The method of  claim 12 , where the double wall cup is heated with the microwave heater while stacked with other double wall cups. 
     
     
         14 . The method of  claim 12 , further comprising:
 packaging double wall cups into cartons, where each carton is heated with the microwave heater to activate and expand the heat-expandable adhesive in the double wall cups.   
     
     
         15 . The method of  claim 14 , further comprising:
 stacking the cartons of the double wall cups with the heat expandable adhesive onto a pallet, where the adhesive in the cups is activated and expanded with the microwave heater.   
     
     
         16 . The method of  claim 10 , further comprising:
 spinning the mandrels past the applicator to facilitate applying the adhesive onto the outer surface of the inner layer; and   controlling the speed of the spinning to uniformly apply the adhesive.   
     
     
         17 . The method of  claim 10 , where the microwave heater is selected from a group of different types of industrial microwave heaters consisting of tubular, planar and non-tubular microwave applicators adopted to radiate individual cup flow or a stack of cups. 
     
     
         18 . A method for manufacturing packaging substrate material and containers, comprising:
 passing at least first and second sheet materials into a conveyor-type machine system;   forming a substrate from the first and second sheet materials, and from an adhesive containing microencapsulated, heat-expandable particles positioned between the first and second sheet materials;   forming packaging containers from the substrate;   conveying the packaging containers to be shipped; and   heating the adhesive with a microwave heater at some point during the passing, the forming, and the conveying, to expand the microencapsulated, heat-expandable particles, where the microwave heater is employed at or between one or more workstations selected from the group consisting of: printing, coating or laminating, die cutting, forming, stacking, cartoning and palletizing.   
     
     
         19 . The method of  claim 18 , where the microwave heater comprises a microwave applicator surrounding a space through which the substrate passes or through which the packaging containers pass. 
     
     
         20 . The method of  claim 18 , further comprising processing the substrate including:
 coating or printing on the multilayer substrate with a material including the microencapsulated, heat-expandable particles;   die cutting the multilayer substrate to produce blanks; and   forming the packaging containers from the blanks.   
     
     
         21 . The method of  claim 20 , where the packaging containers are selected from the group consisting of: folding carton containers, hot and cold cups, clamshells, fluted sleeves, bags, and boxes. 
     
     
         22 . The method of  claim 20 , further comprising:
 laminating the multilayer substrate after printing and before die cutting. .