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
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/10—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of paper or cardboard
• • 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
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
• • 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
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
• • 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
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • 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
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2250/00—Layers arrangement
  • B32B2250/24—All layers being polymeric
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/584—Scratch resistance
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2317/00—Animal or vegetable based
  • B32B2317/12—Paper, e.g. cardboard
• • 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
  • B32B2323/00—Polyalkenes
  • B32B2323/10—Polypropylene
• • 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
  • B32B2377/00—Polyamides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2439/00—Containers; Receptacles
  • B32B2439/02—Open containers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2439/00—Containers; Receptacles
  • B32B2439/70—Food packaging

Definitions

• This invention relates to laminates useful in the manufacture of containers for products, e.g., food, which are ovenable while the product is in the container.
• ovenable food containers be manufactured from a laminate comprising a paperboard substrate, a gre'ase resistant layer applied to the substrate, and a polymethylpentene (PMP) outer food contact layer, which is bonded to the grease resistant layer by a tie layer.
• PMP polymethylpentene
• Such laminates are both difficult to produce and costly, in part due to the relative high cost of PMP.
• One major difficulty in producing this prior art laminate is the difficulty in obtaining good adherence of the PMP layer to the underlying grease resistant layer. Resolution of this bonding limitation has been attempted by using a modified graft copolymer of methylpentene as a distinct tie layer interposed between a layer of PMP and the grease resistant layer.
• a laminate useful in the manufacture of ovenable grease resistant food containers which have the added advantage of good release from the food products, particularly those containing high levels of starch and sugar.
• the laminate of the present invention includes a substrate, preferably of a paperboard, a layer of grease resistant material, such as polyamide, polyester, polyvinyl chloride,polytetrafluoroethylene, or polyvinyl alcohol, etc., a tie layer of low density polyethylene or linear low density polyethylene modified with maleic anhydride, and a food contact layer comprising a blend of polypropylene and polymethylpentene.
• the grease resistant layer, the tie layer and the food contact layer are coextruded onto a paperboard substrate.
• the food contact release layer of the present invention is both less costly versus a 100% PMP layer at the time of its purchase and, importantly, has been found to exhibit higher softening and melting points than non-blends of polymeric materials which have heretofore been employed as the product release layer in ovenable containers. This latter property of the present laminate provides a dramatic increase in the range of the applicable end-use temperatures.
• the laminate of the present invention is most useful for manufacturing trays, bowls or plates.
• Figure 1 is a schematic representation of one embodiment of a laminate of the present invention.
• Figure 2 is a schematic representation of the laminate of Figure 1 and including a grease resistant layer and a tie layer;
• Figure 3 is a schematic representation of the laminate of
• Figure 2 and including a second tie layer.
• one embodiment of a laminate 10 embodying various of the features of the present invention includes a paper board substrate 12 and a food contact release layer 14.
• Figure 2 there is depicted a further embodiment of the laminate depicted in Figure 1 and including a tie layer 16 and a grease resistant layer 18 interposed between the food contact release layer 14 and the paperboard 12.
• Figure 3 depicts the laminate of Figure 2 and including a further tie layer 20 interposed between the first tie layer and the grease resistant layer 18.
• the paperboard substrate is bleached board having a basis weight of between about 18 and about 320 lbs/ 3000ft 2 .
• the choice of basis weight for the paperboard substrate is primarily a function of the strength and/ or rigidity needed or desired in the end product container. Unbleached kraft having a basis weight in the same range can also be used for applications where a white board is not needed or desired.
• substrates of other materials such as polymeric webs or sheets may be employed.
• the grease resistant layer of the present invention may include polyamides such as nylon 6, nylon 6,6, etc., polyesters such as polyethylene terephthalate (PET); halogenated polymers such as polytetrafluoroethylene; polyvinyl alcohol; or other like polymeric materials.
• PET polyethylene terephthalate
• halogenated polymers such as polytetrafluoroethylene
• polyvinyl alcohol or other like polymeric materials.
• Nylon 6 is preferred for many applications by reason of its relatively high impermeability to grease and oils, which may emanate for a food product contained with a container formed from a laminate embodying the present invention. It has been found that a grease resistant layer thickness of 3-10 lbs/ 3000ft 2 will provide an adequate barrier to grease penetration and adhesion to the paperboard.
• a suitable tie layer for a laminate of the present invention may include low density polyethylene (LDPE) or linear low density polyethylene (LLDPE), either being modified by maleic anhydride as is well known in the art.
• Other suitable tie layers may include polyolefins modified with comonomers such as vinyl acetate, acrylic acid or methacrylic acid, depending upon whether the nylon is replaced by another material such as foil and improved inter-layer bonding is required.
• One suitable tie layer material is a maleic anhydride modified LDPE sold by Equistar Chemical under the tradename Plexar.
• the coat weight of the tie layer may range between about 1 and 25 lbs/ 3000ft 2 . The coat weight of this tie layer is adjusted depending upon whether or not adequate inter-layer adhesion has been achieved. As well, an increase in the tie material coat weight supplies both increased mass and heat that will improve the adhesion of the co-extruded structure to the paperboard.
• the product contact layer of the present laminate comprises a blend of polypropylene (PP) and polymethylpentene (PMP).
• PP polypropylene
• PMP polymethylpentene
• PP polypropylene copolymers
• the average market price of PP is $0.38-0.40/lb.
• the approximate price of PMP is $2.50/lb. Therefore, a blend comprised of 50% PP, by weight, would cost up to 43% less than a 100% PMP layer.
• Other polyolefins such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ethylene-propylene copolymers could be used in such blends.
• LDPE low-density polyethylene
• LLDPE linear low-density polyethylene
• ethylene-propylene copolymers could be used in such blends.
• the blend exhibits enhanced bonding of the blend to the tie layer. It appears that this enhanced bonding is a function of the attraction of the PP in the PP/PMP blend to the polyolefin in the tie layer.
• the polypropylene is actually a random copolymer of propylene with a small amount of ethylene. The presence of the propylene, and to a greater degree, the ethylene helps to improve the level of adhesion between the tie material and the PMP containing layer.
• PTFE is known to have the lowest surface tension of any solid material at 17 dynes/ cm.
• PMP and PP have been measured at 24 and 29 dynes/ cm, respectively.
• water has a surface tension of 76 dynes/ cm. That is why water tends to bead on the surface of polyolefins like PP and will not wet and penetrate the surface.
• the surface tension of starch is 39 dynes/ cm, it should not adhere to PMP or PP.
• it will probably "stick” to PET as it has a lower surface tension than PET. This is important in the present invention since starch and materials with "starch-like" chemistries (i.e. sugars) are ingredients in cookies, breads, rolls, etc. PET is also often used as a dual-ovenable coating for paperboard packaging. As illustrated here, a PMP/PP blend will offer a more favorable "non-stick" surface for baking.
• the PP may comprise the majority of the composition of the blend, but preferably ranges between about 25% and 75%, by weight, of the blend, and most preferably about 50%, by weight, of the blend. Adequate release properties can be achieved for blend compositions with greater than 65% PP, by weight. However, for high temperature applications (>300 °F), higher weight percentages of PMP are necessary as the melting temperature (T m ) of PMP is approximately 460 °F versus approximately 280-300 °F for PP.
• T m melting temperature
• the low surface energy laminate of the present invention can also be used in applications where scuff resistance is desired.
• the laminate could be used as a protective layer for glass and glass-like materials, where scratching may be an issue.
• the PMP/PP blend of the present invention may be extrusion coated directly to the paperboard without other layers.

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Applications Claiming Priority (2)

Publications (1)

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Cited By (4)

Citations (3)

• 2003
  • 2003-12-05 AU AU2003302633A patent/AU2003302633A1/en not_active Abandoned
  • 2003-12-05 WO PCT/IB2003/005679 patent/WO2004050357A1/en not_active Application Discontinuation

Patent Citations (3)

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