Corrugated cardboard sheet and method for producing same
AssigneeMitsubishi Petrochemical Co., Ltd.
InventorsTakao Yazaki, Kazuhide Hattori
Life of this patent
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Abstract
An improved corrugated carboard sheet and a method for producing corrugated cardboard sheets of the type which utilize paper at least for either of the core sheet or the liner sheets, including feeding and shaping the core sheet into the desired corrugated configuration by using corrugating rolls, applying as the adhesive a film of a molten thermoplastic polymer to a face of the corrugated sheet, and pressing a liner sheet against the face of the core sheet covered with adhesive.
Claims23
A method for producing corrugated cardboard sheets comprising a corrugated core sheet and a liner sheet wherein at least either of the core sheet or the liner sheet is constructed from paper, said method comprising
- feeding and shaping a core sheet into the desired corrugated configuration,
- extruding a continuous film of a molten thermoplastic polymer,
- feeding the extruded continuous film of molten thermoplastic polymer through free space at a rate which is substantially equal to the production rate of the shaped core sheet,
- applying as the adhesive said film of extruded continuous molten thermoplastic polymer to at least one side of the shaped core sheet as said shaped core sheet is fed, and
- substantially simultaneously pressing in a bonding zone a liner sheet to said adhesive applied side of the shaped core sheet as said shaped core sheet is fed to bond said liner sheet and said core sheet by the interposition of said film of the molten thermoplastic polymer to form a corrugated sheet assembly.
A method for bonding a second liner sheet using a film of a molten thermoplastic polymer to a single faced corrugated sheet assembly comprising a corrugated core sheet and a liner sheet bonded to a side of said core sheet, comprising applying as an adhesive a film of a molten thermoplastic polymer to the side of the corrugated core sheet opposite the liner sheet bonded thereto and simultaneously pressing a second liner sheet to said adhesive applied side of said corrugated core sheet to bond said second liner sheet to said corrugated core sheet between a pair of pressure rolls in which the pressure roll contacting said single faced corrugated sheet assembly is maintained at a surface temperature of about 100.degree. to 180.degree. C and the pressure roll contacting the second liner sheet is maintained at a surface temperature of about 40.degree. to 120.degree. C and is always maintained at a surface temperature of about 20.degree. to 140.degree. C lower than the surface temperature of said pressure roll contacting said single faced corrugated sheet assembly.
A method for producing corrugated cardboard sheets comprising a corrugated core sheet and liner sheets on the opposite sides of a core sheet wherein both the core sheet and the liner sheets are paper, said method comprising
- pre-heating a core sheet to a temperature of about 140.degree. to 180.degree. C,
- feeding said pre-heated core sheet to corrugating rolls and controlling the feeding rate using tension control rolls at a ratio to the peripheral speed of the corrugating rolls corresponding to the corrugation ratio as defined by the length of the core sheet prior to shaping divided by length of the core sheet after shaping,
- shaping said core sheet using said corrugating rolls,
- feeding said shaped core sheet to a bonding zone while retaining said shaped core sheet on the surface of one of said corrugating rolls using a vacuum acting from the inside of said corrugating roll,
- bonding a first liner sheet to said shaped core sheet by the interposition of a film of a molten thermoplastic polymer under a pressure provided by a first pressure roll maintained at a temperature of 90.degree. to 140.degree. C, said thermoplastic polymer comprising a thermoplastic polymer selected from the group consisting of polyethylene, polypropylene, an ethylene-propylene copolymer, an ethylene-vinyl acetate copolymer and a mixture thereof and said film being of such a size and in such a position that the edge portions of said film extend beyond the opposite edges of the single faced sheet assembly comprising said shaped core sheet and said first liner sheet and contact coatings of silicone oil on the corresponding edge portions of said corrugating rolls and the edge portions of said pressure roll,
- again pressing and cooling the sheet assembly using a second pressure roll maintained at a temperature of 5.degree. to 30.degree. C, and
- bonding a second liner sheet to the opposite side of the shaped core sheet to the first liner sheet with a second film of a molten thermoplastic polymer by passing said second liner sheet and said single faced sheet assembly between a pair of pressure rolls in which the pressure roll contacting said second liner sheet is maintained at a temperature of 40.degree. to 100.degree. C below the temperature of the pressure roll contacting said single faced sheet assembly.
An apparatus for producing corrugated cardboard sheets comprising a core sheet and liner sheets on each surface of the core sheet wherein both the core sheet and the liner sheets are made of paper, comprising
- means for pre-heating and feeding a core sheet,
- means including corrugating rolls for shaping said core sheet,
- means for finely controlling the rate of feeding said core sheet to said corrugating rolls,
- means for retaining said shaped core sheet on the surface of at least one of said corrugating rolls,
- means for extruding and feeding through free space a first continuous film of a motlen thermoplastic polymer for bonding said shaped core sheet to a first liner sheet,
- means for pre-heating said first liner sheet and feeding said liner sheet into a position for press-bonding with said shaped core sheet,
- means for press-bonding said pre-heated first liner sheet against said shaped core sheet to form a single faced corrugated sheet assembly by the interposition of said first continuous film of molten thermoplastic polymer,
- means for again pressing the single faced corrugated sheet assembly of said shape core sheet and said first liner sheet,
- means for cooling said single faced corrugated sheet assembly,
- means for pre-heating said single faced sheet assembly,
- means for extruding and feeding through free space a second continuous film of a molten thermoplastic polymer between said pre-heated single faced corrugated sheet assembly and a second liner sheet,
- means for feeding said second liner sheet into a position for press-bonding with the side of said shaped core sheet of said single faced corrugated sheet assembly opposite said first liner sheet, and
- means for press-bonding said single faced corrugated sheet assembly against said second liner sheet to form a double faced corrugated sheet assembly by the interposition of said second continuous film of molten thermoplastic polymer.
Dependencies are inferred from the claim text.