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
  • B32B5/18—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 of foamed material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/20—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length
  • B29C44/22—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length consisting of at least two parts of chemically or physically different materials, e.g. having different densities
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
  • B29C48/10—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels flexible, e.g. blown foils
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
  • B29C48/885—External treatment, e.g. by using air rings for cooling tubular films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
  • B29C48/89—Internal treatment, e.g. by applying an internal cooling fluid stream
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
  • B29C48/911—Cooling
  • B29C48/9115—Cooling of hollow articles
  • B29C48/912—Cooling of hollow articles of tubular films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/001—Combinations of extrusion moulding with other shaping operations
  • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
  • B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/355—Conveyors for extruded articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
  • B29K2995/0037—Other properties
  • B29K2995/0049—Heat shrinkable
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
  • B29K2995/0037—Other properties
  • B29K2995/0072—Roughness, e.g. anti-slip
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
  • B29K2995/0037—Other properties
  • B29K2995/0072—Roughness, e.g. anti-slip
  • B29K2995/0073—Roughness, e.g. anti-slip smooth
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2007/00—Flat articles, e.g. films or sheets
  • B29L2007/008—Wide strips, e.g. films, webs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2009/00—Layered products
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2023/00—Tubular articles
  • B29L2023/001—Tubular films, sleeves
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1328—Shrinkable or shrunk [e.g., due to heat, solvent, volatile agent, restraint removal, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
  • Y10T428/1376—Foam or porous material containing
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24355—Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
  • Y10T428/249978—Voids specified as micro
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
  • Y10T428/249978—Voids specified as micro
  • Y10T428/249979—Specified thickness of void-containing component [absolute or relative] or numerical cell dimension
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
  • Y10T428/249987—With nonvoid component of specified composition
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
  • Y10T428/249987—With nonvoid component of specified composition
  • Y10T428/249988—Of about the same composition as, and adjacent to, the void-containing component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
  • Y10T428/249987—With nonvoid component of specified composition
  • Y10T428/249988—Of about the same composition as, and adjacent to, the void-containing component
  • Y10T428/249989—Integrally formed skin

Definitions

• the present invention relates to a heat shrinkable foamed sheet.
• Some preferred embodiments relate to a heat shrinkable foamed sheet excellent in . glossiness and surface smoothness and also excellent in printing performance.
• a resin foamed sheet having a heat shrinkable nature such as, e.g., a foamed polystyrene resin foamed sheet
• various products such as, e.g., cups, plates, food containers, packaging materials, or packaging labels
• decoration printing is performed on a surface of the label applied to a glass/plastic container to provide its content's information.
• This kind of heat shrinkable resin foamed sheet can be manufactured by a method disclosed in, for example, U.S. Patent No. 5,925,450 (JP, H07(1995)-64005, B), U.S. Patent No. 3,979,000 (JP, S61(1986)-21826, B), U.S. Patent No. 5,342,560 (JP, H05(1993)-505774, A), and JP, H07(1995)-32525, A.
• a general-purpose polystyrene resin as a raw material of a foamed sheet, a nucleus forming agent for forming foamed cells, a spreading agent, and white mineral oil or polybutene acting as a viscosity controlling agent are introduced into a first extruder to be melted therein while adding polymeric ester such as ditridecyl adipate (DTDA) as a plasticizer.
• DTDA ditridecyl adipate
• Nitrogen or carbon dioxide acting as a foaming agent is added under high pressure to the molten polystyrene and kneaded, and then the resulting melt is transferred to a cooling extruder provided at a rear part of the first extruder to be cooled therein.
• the transferred melt is cooled to a temperature appropriate to the extrusion, and then sent to an annular die portion provided at the front end of the cooling extruder.
• non-foamed polystyrene resin is introduced into a second extruder and melted therein, and then transferred to the die portion provided at the front end of the cooling first extruder in a state in which no foam is contained in the molten resin.
• the extrusion material from the first extruder and the extrusion material from the second extruder are joined together and co-extruded as a cylindrical two-layered sheet in which a non-foamed resin layer is coated on a foamed resin layer.
• the inner and outer surfaces of the cylindrical sheet co-extruded from the extrusion die are cooled with air and/or a cooling mandrel.
• the sheet is stretched by blowing between the extrusion die and the mandrel ring having a large diameter at a temperature range higher than a softening point of the resin, and then cooled to a temperature which is the softening point or below thereof on a cylindrical mandrel provided at the downstream side of the mandrel ring.
• tension is applied using nip rolls to be stretched in a longitudinal direction of the sheet, and the stretched sheet is cut in halves with a cutter.
• the resulting sheet having two layers, i.e., a foamed layer and a non-foamed layer, will be wound.
• the printing characteristic is also one of important characteristics to provide decoration for giving a visual product image on the surface of the sheet.
• the inventors performed various experiments and studies to provide a heat shrinkable foamed sheet excellent in surface glossiness, surface smoothness and printing nature. As a result, they found the fact that in a multi-layer foamed sheet having at least a non-foamed layer as a skin layer small in thickness and a foamed layer as a core layer larger in thickness than the non-foamed layer, various dimensions, such as, e.g., surface smoothness of the non-foamed layer and sizes of foam cells formed in the foamed layer, exert a strong influence on a printing performance of the non-foamed layer constituting the surface skin layer. The inventors further continued experiments and studies and finally made the present invention.
• the preferred embodiments of the present invention have been developed in view of the above-mentioned and/or other problems in the related art.
• the preferred embodiments of the present invention can significantly improve upon existing methods and/or apparatuses.
• some embodiments can provide a heat shrinkable foamed sheet excellent in surface glossiness and surface smoothness preferably used as a packaging heat shrinkable label capable of performing high-grade clear printing while preventing breakage of a container by its cushioning properties and giving thermal insulating properties when the sheet is applied to a container.
• some embodiments can provide a heat shrinkable foamed sheet excellent in printing characteristics comprising at least two layers consisting of a non-foamed layer and a foamed layer, i.e., a non-foamed polystyrene layer excellent in surface glossiness and surface smoothness and a foamed polystyrene layer.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the non-foamed layer is less than about 1.55 ⁇ m in maximum surface smoothness measured in accordance with ISO8791-4.
• the maximum surface smoothness is about 1.49 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed layer is less than about 20.4 ⁇ m in average equivalent diameter of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer and less than about 20.0 ⁇ m in average equivalent diameter of foamed cells formed in the foamed layer in a cross-section taken along a direction perpendicular to the extrusion direction.
• the average equivalent diameter of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 18.8 ⁇ m or less and the average equivalent diameter of the foamed cells in the cross-section taken along the direction perpendicular to the extrusion direction is about 19.2 ⁇ m or less. More preferably, the average equivalent diameter of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 17.1 ⁇ m or less and the average equivalent diameter of the foamed cells in the cross-section taken along the direction perpendicular to the extrusion direction is about 18.4 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed layer is less than about 231.5 ⁇ m in average length of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer.
• the average length of the foamed cells of the foamed layer in the cross-section taken along the extrusion direction of the formed layer is about 199.3 ⁇ m or less. More preferably, the average length of the foamed cells of the foamed layer in the cross-section taken along the extrusion direction of the formed layer is about 167.0 ⁇ m or less and the average length of the foamed cells of the foamed layer in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 66.2 ⁇ m or less.
• the maximum surface smoothness of the non-foamed layer is less than about 1.55 ⁇ m. More preferably, the maximum surface smoothness of the non-foamed layer is about 1.49 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed layer is less than about 15.0 ⁇ m in average height of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer and the foamed layer is less than about 15.2 ⁇ m in average height of the foamed cells formed in the foamed layer in a cross-section taken along a direction perpendicular to the extrusion direction of the formed layer.
• the average height of the foamed cells formed in the foamed layer in the cross-section taken along the extrusion direction of the formed layer is about 13.5 ⁇ m or less and the average height of the foamed cells formed in the foamed layer in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 13.4 ⁇ m or less.
• the average height of the foamed cells formed in the foamed layer in the cross-section taken along the extrusion direction of the formed layer is about 12.0 ⁇ m or less and the average height of the foamed cells formed in the foamed layer in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is less than about 11.6 ⁇ m.
• the maximum surface smoothness of the non-foamed layer is less than about 1.55 ⁇ m. More preferably, the maximum surface smoothness of the non-foamed layer is about 1.49 ⁇ m or less.
• a heat shrinkable foamed * sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed layer is less than about 2,511.6 ⁇ m 2 /cell in average area of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer and the foamed layer is less than about 970.7 ⁇ m 2 /cell in average area of foamed cells formed in the foamed layer in a cross-section taken along a direction perpendicular to the extrusion direction of the formed layer.
• the average area of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 1,986.8 ⁇ m 2 /cell or less and the average area of the foamed cells in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 759.9 ⁇ m 2 /cell or less.
• the average area of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 1,462.0 ⁇ m 2 /cell or less and the average area of the foamed cells in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 549.1 ⁇ m 2 /cell or less.
• the maximum surface smoothness of the non-foamed layer is less than about 1.55 ⁇ m. More preferably, the maximum surface smoothness of the non-foamed layer is about 1.49 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed sheet is less than about 468.7 ⁇ m in average circumferential length of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer.
• the average circumferential length of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 405.4 ⁇ m or less.
• the average circumferential length of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 342.1 ⁇ m or less and the average circumferential length of the foamed cells in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 138.0 ⁇ m or less.
• the maximum surface smoothness of the non-foamed layer is less than about 1.55 ⁇ m. More preferably, the maximum surface smoothness of the non-foamed layer is about 1.49 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed layer exceeds about 195.5 cells/mm 2 in average number of foamed cells formed in the foamed layer per unit area in a cross-section taken along an extrusion direction of the formed layer.
• the average number of foamed cells formed in the foamed layer per unit area in the cross-section taken along the extrusion direction is about 272.5 cells/mm 2 or more. More preferably, the average number of foamed cells formed in the foamed layer per unit area in the cross-section taken along the extrusion direction of the formed layer is about 349.5 cells/mm 2 or more and the average number of the foamed cells formed in the foamed layer per unit area in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer exceeds about 647.9 cells/mm 2 .
• the maximum surface smoothness of the non-foamed layer is less than about 1.55 ⁇ m. More preferably, the maximum surface smoothness of the non-foamed layer is about 1.49 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed layer is about 167.0 ⁇ m or less in average length of foamed cells of the foamed layer in a cross-section taken along an extrusion direction of the formed layer, about 342.1 ⁇ m or less in average circumferential length of foamed cells of the foamed layer in the cross-section taken along the extrusion direction of the formed layer, and about 349.5 cells/mm 2 or more in average number of foamed cells formed in the foamed layer per unit area in the cross-section taken along the extrusion direction of the formed layer.
• the maximum surface smoothness of the non-foamed layer is less than about 1.55 ⁇ m. More preferably, the maximum surface smoothness of the non-foamed layer is about 1.49 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed layer is about 66.2 ⁇ m or less in average length of foamed cells of the foamed layer in a cross-section taken along a direction perpendicular to an extrusion direction of the formed layer, about 138.0 ⁇ m or less in average circumferential length of foamed cells of the foamed layer in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer, and exceeds about 647.9 cells/mm 2 in average number of foamed cells formed in the foamed layer per unit area in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer.
• the maximum surface smoothness of the non-foamed layer is less than about 1.55 ⁇ m. More preferably, the maximum surface smoothness of the non-foamed layer is about 1.49 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the foamed layer is about 17.1 ⁇ m or less in average equivalent diameter of foamed cells in a cross-section taken along an extrusion direction of the formed layer and about 18.4 ⁇ m or less in average equivalent diameter of the foamed cells in a cross-section taken along a direction perpendicular to the extrusion direction, wherein the foamed layer is about 167.0 ⁇ m or less in average length of the foamed cells formed in the foamed layer in the cross-section taken along the extrusion direction of the formed layer and about 66.2 ⁇ m or less in average length of the foamed cells of the foamed layer in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer, wherein the foamed layer
• the maximum surface smoothness of the non-foamed layer is less than about 1.55 ⁇ m. More preferably, the maximum surface smoothness of the non-foamed layer is about 1.49 ⁇ m or less.
• a heat shrinkable foamed sheet comprising: a foamed layer constituting a core layer; and a non-foamed layer constituting a surface skin layer integrally formed on the formed layer, wherein the non-foamed layer exceeds about 51.54 % in glossiness measured in accordance with ISO2813-1944 in an extrusion direction of the non-foamed layer and exceeds about 25.18 % in glossiness measured in accordance with ISO2813-1944 in a direction perpendicular to the extrusion direction of the non-foamed layer.
• the non-foamed layer is about 68.68% or more in glossiness measured in accordance with ISO2813-1944 in an extrusion direction of the non-foamed layer and is about 30.70% or more in glossiness measured in accordance with ISO2813-1944 in a direction perpendicular to the extrusion direction of the non-foamed layer.
• the foamed layer is formed by extruding a melt from a co-extrusion two-layer annular extrusion die of one of extruders, the melt containing a nucleus forming agent and at least one of polybutene, ditridecyl adipate, diisodecyl adipate, and trioctyl trimellitate blended to a polystyrene resin acting as a main component and further containing at least one of nitrogen, carbon dioxide, and a mixture thereof in a supercritical state, and the non-foamed layer is formed by extruding a resin from the co-extrusion two-layer annular extrusion die of the other of the extruders, the resin being obtained by blending polyolefin, and a compatibilizer of polystyrene and polyolefin with polystyrene as a main component, and melting them in a state in which the non-fo
• the non-foamed layer has a print layer on a surface thereof.
• a heat shrinkable foamed sheet according to the present invention can be a sheet which satisfies any combination of the aforementioned conditions as recited in the first to twelfth aspects of the present invention and the preferable conditions.
• a container comprising: a container main body; and one of the aforementioned heat shrinkable sheets, wherein the heat shrinkable sheet is closely adhered to a peripheral surface of the container main body in a heat shrank manner.
• the foamed sheet in which the sizes of the foam cells in the foamed layer fall within the aforementioned ranges is excellent in surface smoothness and therefore it is excellent in printing characteristics. For example, at the time of performing electrostatic printing which is one of precise printing, a smooth surface appropriate to high-grade printing can be obtained. As a result, a heat shrinkable foamed sheet, which can be used as a foamed polystyrene label, capable of giving a high-grade nature to a packaging can be obtained.
• the smoothness and glossiness of the surface of the non-foamed polystyrene layer corresponding to the printing surface can be improved.
• original fabrics of printing heat shrinkable labels can be produced.
• the foamed sheet can be used as a heat shrinkable label for containers or cups including beverage containers.
• Rg. 1 is a schematic view showing a production apparatus including extruders used to produce a heat shrinkable foamed sheet according to an embodiment of the present invention
• Rg. 2 is a schematic cross-sectional view showing a cooling device located at a front end of the extruder
• Rg. 3 is a cross-sectional view taken along the line 3-3 in Rg. 2;
• Rg. 4 is a partial cross-sectional view showing a partial cross-section of the heat shrinkable foamed sheet according to the present invention.
• the heat shrinkable resin foamed sheet 1 can be used as follows.
• the sheet 1 is formed into, e.g., a cylindrical shape and then disposed on an external periphery of a packaging container such as a bottle or a cup. Then, heat is applied to the sheet 1 to shrink it, so that the sheet is secured to the container in a closely adhered manner.
• the heat shrinkable foamed sheet according to this embodiment has a two-layered structure having a foamed layer 2 constituting a core layer having foamed cells C therein and a non-foamed layer 3 constituting a skin layer integrally formed on the foamed layer 2, the non-foamed layer being smaller in thickness than the foamed layer 2.
• This heat shrinkable foamed sheet is formed by co-extrusion.
• Fig. 1 shows an extruder for use in the production method.
• This extruder includes a first extruder 11, a cooling extruder 12 (melt cooling portion of the first extruder), and a second extruder 13.
• polystyrene resin as a raw material is introduced in the first extruder 11 as a primary extruder.
• a nucleus forming agent such as, e.g., sodium bicarbonate or citric acid
• a plasticizer such as, e.g., nonvolatile polymer ester exemplified by asditridecyl adipate (DTDA)
• DTDA asditridecyl adipate
• wetting agent acting as a spreading agent of the nucleus forming agent such as polybute ⁇ e and having a resin viscosity controlling function.
• polystyrene resin melt in which the nitrogen or carbon dioxide is solved in a supercritical state.
• the polystyrene resin melt is mixed and kneaded with a screw in a kneading part of the first extruder 11, transported to the cooling extruder 12 (a melt cooling part of the rear part of the first extruder), and cooled to a temperature appropriate to the extrusion.
• the resulting resin is integrally coated on an upper surface of a non-foamed layer transported in advance from the second extruder 13 within a co-extrusion annular die 20 provided at the front end of the first extruder 12.
• the non-foamed layer 3 (surface skin layer) constituting a liner of the two-layered sheet consisting of the foamed polystyrene layer 2 and the non-foamed polystyrene layer 3 is produced as follows. At the same time of the preparation of the foamed layer 2 (core layer) in the first extruder 11, a mixture of polystyrene and polyolefin (ratio: about 80 % of polystyrene, about 5 % of polypropylene, and about 15 % of additive agent) as the material of the non-foamed polystyrene layer 3 (skin layer) is melted in a barrel of the second extruder 13.
• the molten mixture is transported to the annular die 20 provided at the front end of the cooling extruder 12 of the first extruder 11 to be joined to the foamed polystyrene layer 2 (core layer) from the first extruder 11, and extruded from the annular die 20 with the two layers with two layers integrated together.
• the non-foamed layer resin is not limited to polystyrene resin, but can be any thermosetting resin including, e.g., a butadiene series or acrylic series copolymer resin copolymerized with polystyrene or its mixed resin, or a polyolefin series resin including, e.g., polyethylene, polypropylene, or copolymer thereof.
• the foamed resin layer can be any thermosetting resin including, e.g., polystyrene series resin, block polymer thereof, copolymer resin or mixed resin copolymerized with butadiene series resin, or polyolefin resin.
• the foaming agent can be carbon dioxide, nitrogen, a mixture of carbon . dioxide and nitrogen, or nonvolatile gas which cannot be dissolved in a resin in a standard state of the atmosphere.
• the foaming agent is melted in the molten resin in a supercritical state in the extruder.
• the nucleus forming agent can be inorganic and organic foaming nucleus forming agents, such as, e.g., sodium bicarbonates, citric acids, and amide azodicarboxylates, or a mixture thereof.
• the wetting agent can be white mineral oil, polybutene, or low-molecular-weight polyethylene wax.
• the wetting agent is used as a dispersing agent for dispersing the nucleus forming agent into the molten resin.
• the plasticizer for providing a heat shrinkage property to the foamed layer 2 and controlling resin viscosity to improve physical properties of the foamed sheet 1, for example, resin properties such as toughness or shear properties of the sheet 1, and extrudability can be a high-molecular-weight ester, such as, e.g., ditridecyl adipate (DTDA), diisodecyl adipate (DIDA), and trioctyl trimellitate (TOTM). About 1% of the plasticizer is added in the resin.
• DTDA ditridecyl adipate
• DIDA diisodecyl adipate
• TOTM trioctyl trimellitate
• the surface adjustment of the non-foamed sheet 3 is important since the surface is served as a printing surface of a label.
• White pigment is added to control the color tone of the surface to thereby keep the opacity of the sheet surface.
• 5 to 10 % of titanium oxides are added with respect to the non-foamed layer portion.
• an about 5 to 10% of ethylene-butadiene block copolymer is added as a compatibilizer.
• the extruded cylindrical two-layered sheet 21 is forcibly cooled by blowing cooling air against the outside foamed polystyrene layer from the annular air ring 22 disposed adjacent to the extrusion die 20.
• An inner ring 26 is provided at the inner surface side of the extruded cylindrical sheet 21, so that the cylindrical sheet 21 is cooled from its inside by air from the inner ring 26.
• the cooling rate using air can be adjusted by controlling air pressure of air applied to the inner and outer surfaces of the cylinder.
• the extruded cylindrical sheet 21 is transported in a state in which the sheet is in contact with the mandrel 24 and cooled.
• the cylindrical sheet 21 is stretched in the circumference direction thereof toward the mandrel 24 having a diameter larger than the diameter of the extrusion die 20 before the temperature of the sheet 21 drops below the glass transition point.
• the blowup ratio which is a ratio of the diameter of the die 20 to that of the mandrel 24, is set to 1.75, which is a typical ratio of a heat shrinkable label.
• the cylindrical sheet 21 is cooled using the mandrel 24 to cool the temperature to the glass transition temperature or below.
• the cooling is performed by both the mandrel 24 and the mandrel ring 23 provided at the upstream side of the mandrel 24.
• the extruded cylindrical sheet 21 is stretched in the longitudinal direction by applying tension with the nip rolls for winding the sheet 21.
• the tension can be controlled in accordance with the degree of the required heat shrinkage of the heat shrinkable label.
• the cylindrical sheet 21 After being stretched in the longitudinal direction by the tension using the nip rolls, the cylindrical sheet 21 is cut into halves and each will be wound on a reel as a two-layered sheet consisting of a foamed layer and a non-foamed layer.
• the obtained heat shrinkable foamed sheet has a non-foamed layer 3 as a surface skin layer excellent in glossiness, hign in grade and excellent in surface smoothness, thereby enabling a clear printing thereon.
• GPPS having a weight average molecular weight of 280,000 and a meltflow value of about 3.5-4.0 (ASTM standard 12378-70: condition G) and a 1:1 mixture of sodium bicarbonate and citric acid as nucleus forming agent were added to polystyrene resin in a body portion of the first extruder 11 so that the mixture was contained by 1 wt% of the resin, and mixed and melted.
• high-molecular-weight ester ditridecyl adipate and polybutene each serving as a blending agent were added to the melt with a pump (not illustrated) provided on the extrusion line so that each blending agent was contained by 0.5 wt% of the resin.
• the kneaded resin melt was transferred from the first extruder 11 to the cooling extruder 12, and cooled to the temperature appropriate to the extrusion.
• the cooled resin melt was transferred to a co-extrusion two-layer annular die 20 provided at the front end of the extruder 12.
• the extrusion temperature was about 340 0 F.
• the melt containing nitrogen gas as foaming agent in the first extruder 11 was also transferred to the annular die 20, and co-extruded from an orifice of the annular die 20 (co-extrusion two-layer annular die) with the melt adhered to the upper layer of the non-foamed polystyrene sheet from the second extruder 13.
• the target thickness of the co-extruded sheet was set to about 170 ⁇ m ⁇ 25 ⁇ m and the target thickness of the non-foamed layer was set to about 13 ⁇ m ⁇ 2 ⁇ m at the time of the winding.
• an inner cooling ring 26 was provided between the extrusion die 20 and the cooling mandrel 24 to cool the inner surface of the cylindrical sheet 21 by the cooling air injected from the inner cooling ring 26.
• the annular air ring 22 was provided adjacent to the output portion of the extrusion die 20 so that cooling air was supplied from the air ring 22 against the outer surface of the sheet 21 at an acute angle to prevent the deterioration of the cooling effect due to air turbulent flow.
• the air pressure against the outer surface of the sheet 21 by the air ring 22 and the air pressure against the inner surface of the sheet 21 by the inner cooling ring 26 were set to the same as those employed in producing a conventional heat shrinkable sheet for labels.
• the polystyrene sheet 21 cooled by air from the inside and outside thereof was further forcibly cooled to the glass transition temperature or below with a water-cooling type mandrel 24 and a water cooling type mandrel ring 23 disposed before the mandrel 24.
• the temperature of the mandrel 24 and that of the mandrel ring 23 were set to the same conditions as in a conventional method by water cooling.
• the cooled sheet 21 was cut into halves with a cutter 31, and wounded on a winding reel 33, 34 via nip rolls, respectively.
• the present inventors also found the fact that this is not sufficient to obtain a high-grade printing surface due to the foamed cells formed in the foamed layer 2 and that it is necessary to minimize the influence of the foamed layer 2 on the surface smoothness of the printing surface of the non-foamed layer 3 by controlling the size of the foamed cells in the foamed layer as small as possible.
• the present inventors considered that since the thickness of the non-foamed layer 3 to be printed is as small as about 13 ⁇ m, the surface state of the foamed cells of the foamed polystyrene layer 2 disposed under the non-foamed layer 3 affects the surface state of the non-foamed layer 3.
• the non-foamed layer 3 of the co-extruded sheet 21 consisting of the non-foamed layer 3 and the foamed layer 2 was brought into direct contact with the mandrel ring 23 to perform the cooling, and then cooled by the mandrel 24 to improve the surface smoothness of the non-foamed layer 3. Furthermore, the sheet 21 was quickly and forcibly cooled by applying cooling air from the outside so that the size of the foamed cells in the foamed layer 2 becomes as small as possible.
• Example 2 to 9 the cooling conditions of the external side of the foamed sheet 21 using air immediately after the extrusion of the foamed sheet, the cooling conditions of the internal side of the foamed sheet 21 by air, the cooling conditions of the internal side of the foamed sheet 21 by the mandrel ring 23, and the cooling conditions of the internal side of the foamed sheet 21 by the mandrel 24, were changed.
• a formed sheet was obtained under the same conditions as in Example 1 except that the outer air pressure was increased by 34 % to cool the outside of the foamed sheet using air.
• a formed sheet was obtained under the same conditions as in Example 1 except that the outer air pressure was decreased by 50 % to cool the outside of the foamed sheet using air.
• EXAMPLE 4 A formed sheet was obtained under the same conditions as in Example 1 except that the inner air pressure was increased by 6 % to cool the inner side of the foamed sheet using air.
• a formed sheet was obtained under the same conditions as in Example 1 except that the inner air pressure was decreased by 50% to cool the inner side of the foamed sheet using air.
• a formed sheet was obtained under the same conditions as in Example 1 except that the mandrel ring temperature was decreased by 20 % to cool the inner side of the foamed sheet with the mandrel ring.
• a formed sheet was obtained under the same conditions as in Example 1 except that the mandrel ring temperature was increased by 30 % to cool the inner side of the foamed sheet with the mandrel ring.
• a formed sheet was obtained under the same conditions as in Example 1 except that the mandrel temperature was decreased by 20 % to cool the inner side of the foamed sheet with the mandrel.
• a formed sheet was obtained under the same conditions as in Example 1 except that the mandrel temperature was increased by 10 % to cool the inner side of the foamed sheet with the mandrel.
• a foamed sheet was obtained under the same conditions including the raw material, the composition and the cooling conditions as in Example 1 only except that polymer for a foamed layer was transferred in advance to the annular extrusion die and formed into a cylinder shape within the die before the extrusion, and then a non-foamed layer was coated on the external surface of the cylindrical structure to extrude the two-layered structure from the extrusion die.
• the polystyrene resin and propylene resin for the foamed layer and the non-foamed layer as raw materials, nucleus forming agent, polybutene, and high-molecular weight ester were the same as those of [Example 1, and the amounts thereof were the same as in [Example 1.
• nitrogen was used as the foaming agent in the same manner as in Example 1, and the pressure and the amount thereof were the same as those in Example 1.
• the extruder, the extrusion conditions, the stretching conditions, and the cooling conditions were the same as those in Example 1.
• the only difference between Comparative Example 1 and Example 1 was as follows.
• Molten resin for the foamed layer was introduced in advance into the die portion provided at the front end of the cooling extruder of the first extruder and formed into a cylinder shape within the die, and then a molten resin for the non-foamed layer was applied onto the upper surface of the cylindrical structure to extrude the cylindrical sheet consisting of an upper non-foamed polystyrene layer and a lower foamed polystyrene layer through the extrusion die.
• the cooling was performed using air from the inside and the outside.
• the inner surface of the sheet came into contact with the mandrel ring 23 and the surface of the mandrel 24 to be cooled.
• the non-foamed layer was cooled only by air from the outside through the annular air ring 22 at the exit of the extruder.
• the extrusion and the cooling were performed in such a state in which the inner surface and the outer surface of the non-foamed layer/foamed layer sheet were opposite to those in Example 1.
• Example 1 except that the mixture of nitrogen and air (94 % nitrogen) was used as foaming agent.
• Comparative example 2 was different from Example 1 in that the foamed layer was disposed at the outside of the cylindrical sheet and the mixture of nitrogen and air was used as foaming agent.
• the non-foamed layer surface was subjected to a printing test, and surface glossiness and surface smoothness of the non-foamed layer were evaluated. Furthermore, the dimensions of the foamed cells formed in the foamed layer were measured. The surface glossiness and the surface smoothness were measured according to the standard of the ISO respectively.
• a cross-section in the extrusion direction (hereinafter referred to as "Machine Direction (MD)") of the foamed sheet and a cross-section perpendicular to the extrusion direction (hereinafter referred to as "Transverse Direction (TD)”) of the foamed sheet were observed using a scanning electron microscope to analyze the foamed cells.
• MD Machine Direction
• TD Transverse Direction
• the dimensions of the foamed cells appeared in the cross-section of the resin the number, the length, the width, the area, the circumferential length, the aspect ratio, the equivalent diameter, and the density (the total area of the foamed cells per unit area) of the foamed cells) were measured using an image analysis device.
• the length L and the width W of the foamed cell in the sheet cross-section in the MD were defined as the longest cell length and the longest width of the foamed cell formed in a shape of a leaf extending almost in parallel to the non-foamed surface.
• the length L and the width W were optically measured and the average length and the average width were obtained.
• the width W and the height H of the foamed cell in the TD were defined as the longest width and the highest height of the foamed cell extending almost in parallel to the non-foamed surface, respectively, and measured in the same manner as mentioned above. Then, the average width and the average height were obtained.
• the binarized number of foamed cells was counted and converted into the number of foamed cells per unit area (mm 2 ).
• the area of the foamed cell and the circumferential length of the foamed cell were measured using the image processing software and the average values thereof were obtained in the same manner as in the measurement of the length of the cell.
• each equivalent diameter was obtained based on measured results by calculation (i.e., 4 x the surface area of the foamed cell / the circumferential length of the foamed cell). The average value was calculated from the total area and the total circumferential length of the entire foamed cells using the calculation.
• the total cell area of the foamed cells per unit area it was obtained by adding each area of the measured foamed cells and converting it into a unit area per area (mm 2 ).
• Each of the aforementioned value is an average of values at two observation points in the cross-section of the foamed sheet.
• the measurement in the case of a portion in which the interface between the cell and the resin was dim due to burrs, the measurement was performed using the straight lines extending from both sides of the above-mentioned portion. Furthermore, with respect to the image processing of the foamed cell which was not entirely displayed within ends of the field of vision, the field of vision was considered 1/2 of the size of the foamed cell.
• the surface smoothness of the surface of the non-foamed layer (solid layer) of the co-extruded polystyrene sheet was measured at 10 points using Parker Print Surf Flex Tester, manufactured by Lorentzen & Wetter Co., at an air pressure of 300 kPa to obtain the average PPS smoothness and the maximum PPS smoothness.
• Reflectance of the surface of the non-foamed layer (solid layer) of the co-extruded polystyrene sheet was measured at five points using UGV-5DV, a digital variable angle glossiness meter manufactured by Suga Test Instruments Co., Ltd. in the MD and TD at an incident angle of 60° and light receiving angle of 60°, and the average value was calculated.
• the non-foamed layer is about 1.49 ⁇ m or less in maximum surface smoothness measured in accordance with ISO8791-4, and/or
• the average equivalent diameter of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 17.1 ⁇ m or less and the average equivalent diameter of the foamed cells in the cross-section taken along the direction perpendicular to the extrusion direction is about 18.4 ⁇ m or less, and/or
• the average length of the foamed cells of the foamed layer in the cross-section taken along the extrusion direction of the formed layer is about 167.0 ⁇ m or less and the average length of the foamed cells of the foamed layer in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 66.2 ⁇ m or less, and/or
• the average height of the foamed cells formed in the foamed layer in the cross-section taken along the extrusion direction of the formed layer is about 12.0 ⁇ m or less and the average height of the foamed cells formed in the foamed layer in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 11.6 ⁇ m or less, and/or
• the average area of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 1,462.0 ⁇ m 2 /cell or less and the average area of the foamed cells in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 549.1 ⁇ m 2 /cell or less, and/or
• the average circumferential length of the foamed cells in the cross-section taken along the extrusion direction of the formed layer is about 342.1 ⁇ m or less, and/or and the average circumferential length of the foamed cells of the foamed layer in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 138.0 ⁇ m or less, (7) the average number of foamed cells formed in the foamed layer per unit area in the cross-section taken along the extrusion direction of the formed layer is about 349.5 cells/mm 2 or more and exceeds the average number of the foamed cells formed in the foamed layer per unit area in the cross-section taken along the direction perpendicular to the extrusion direction of the formed layer is about 647.9 cells/mm 2 .
• the non-foamed layer is less than about 1.55 ⁇ m in maximum surface smoothness measured in accordance with ISO8791-4, and/or
• the foamed layer is less than about 20.4 ⁇ m in average equivalent diameter of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer and less than about 20.0 ⁇ m in average equivalent diameter of foamed cells formed in the foamed layer in a cross-section taken along a direction perpendicular to the extrusion direction, and/or (10) the foamed layer is less than about 231.5 ⁇ m in average length of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer, and/or (11) the foamed layer is less than about 15.0 ⁇ m in average height of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer and the foamed layer is less than about 15.2 ⁇ m in average height of the foamed cells formed in the foamed layer in a cross-section taken along a direction perpendicular to the extrusion direction of the formed layer
• the foamed layer is less than about 2,511.6 ⁇ m 2 /c ⁇ ll in average area of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer and the foamed layer is less than about 970.7 ⁇ m 2 /cell in average area of foamed cells formed in the foamed layer in a cross-section taken along a direction perpendicular to the extrusion direction of the formed layer, and/or
• the foamed sheet is less than about 468.7 ⁇ m in average circumferential length of foamed cells formed in the foamed layer in a cross-section taken along an extrusion direction of the formed layer, and/or
• the foamed layer exceeds about 195.5 cells/mm 2 in average number of foamed cells formed in the foamed layer per unit area in a cross-section taken along an extrusion direction of the formed layer.
• the heat shrinkable foamed sheets consisting of a foamed polystyrene layer and a non-foamed polystyrene layer sheet formed by co-extrusion was exemplified. It should be understood, however, that the present invention is not limited to the above.
• a heat shrinkable foamed sheet excellent in surface quality can be produced by separately producing a foamed sheet and a non-foamed sheet and then laminating them.
• a foamed sheet formed by two layers i.e., a foamed layer and a non-foamed layer
• the present invention is not limited to this.
• the present invention can also be applied to a multi-layered foamed sheet having three or more layers.
• the method for cooling the extruded foamed sheet was revised as opposed to a conventional method. That is, a conventional, method for cooling a non-foamed layer (surface skin layer) is applied to the cooling of a foamed layer and a conventional method for cooling a foamed layer (core layer) is applied to the cooling of a non-formed layer. Accordingly, it is considered that the cooling speed of the foamed layer is enhanced, causing an improved surface smoothness of the foamed layer, which in turn results in excellent surface smoothness of the non-foamed layer.
• the foamed sheet was subjected to a required extension treatment between the extrusion die and the cooling mandrel.
• the cylindrical sheet extruded from the annular die of the extruder is stretched in the circumferential direction thereof by blowing before being cooled to the glass transient point or below and also stretched in the longitudinal direction thereof by a tensile force applied by nip rolls.
• the foamed cell was formed not into a circular shape but into a flattened shape extended both in the circumferential direction and in the longitudinal direction and very small in size.
• the small dimensions resulted in small surface roughness of the foamed layer surface at the boundary of the foamed layer/non-foamed layer, which made a positive impact on the non-foamed layer as a surface skin layer to thereby improve the surface smoothness and the glossiness.
• the term "preferably” is non-exclusive and means “preferably, but not limited to.”
• means-plus-function or step-plus-function limitations will only be employed where for a specific claim limitation all of the following conditions are present in that limitation: a) "means for” or “step for” is expressly recited; b) a corresponding function is expressly recited; and c) structure, material or acts that support that structure are not recited.
• the terminology "present invention” or “invention” may be used as a reference to one or more aspect within the present disclosure.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Laminated Bodies (AREA)
• Wrappers (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

Family

ID=39681983

Family Applications (1)

Country Status (9)

Cited By (1)

Families Citing this family (28)

Citations (8)

Family Cites Families (8)

• 2007
  • 2007-05-14 CA CA002600559A patent/CA2600559A1/en not_active Abandoned
  • 2007-05-14 WO PCT/US2007/011505 patent/WO2008097240A1/en not_active Ceased
  • 2007-05-14 EP EP07794826A patent/EP2109534B1/en not_active Not-in-force
  • 2007-05-14 AU AU2007219325A patent/AU2007219325A1/en not_active Abandoned
  • 2007-05-14 US US11/909,124 patent/US8043695B2/en not_active Expired - Fee Related
  • 2007-05-14 BR BRPI0706060-2A patent/BRPI0706060A2/pt not_active IP Right Cessation
  • 2007-05-14 MX MX2007014259A patent/MX2007014259A/es active IP Right Grant
  • 2007-05-14 JP JP2009548212A patent/JP2010517813A/ja active Pending
• 2008
  • 2008-01-23 CL CL2008000183A patent/CL2008000183A1/es unknown

Patent Citations (8)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events