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CN-122003479-A - Laminating adhesive for compostable flexible packaging

CN122003479ACN 122003479 ACN122003479 ACN 122003479ACN-122003479-A

Abstract

A one-component, moisture-curable laminating adhesive that provides surprisingly high bond strength and desirable failure modes when bonding paper films to polymeric films, even at low adhesive coat weights of 1 to 2 pounds per ream. The paper film and polymer film bonded with 1 to 2 lbs/ream of the disclosed adhesive have properties suitable for use as a flexible packaging material for food or medicine, and the flexible packaging material is compostable under ASTM 6400.

Inventors

  • S. Skrinierz
  • G. Kenyon

Assignees

  • 汉高股份有限及两合公司

Dates

Publication Date
20260508
Application Date
20240905
Priority Date
20230908

Claims (14)

  1. 1. A one-part, isocyanate-functional, moisture-curable laminating adhesive comprising the reaction product of a polyisocyanate component, a high functionality polyester polyol component, and a linear polyester polyol component.
  2. 2. The one-part, isocyanate-functional, moisture-curable laminating adhesive of claim 1, wherein the high functionality polyester polyol component has a functionality of about 4 and comprises about 2 primary and two secondary hydroxyl groups per molecule.
  3. 3. The one-part, isocyanate-functional, moisture-curable laminating adhesive of claim 1 or 2, wherein the linear polyester polyol component comprises a polycaprolactone polyol.
  4. 4. The one-part, isocyanate-functional, moisture-curable laminating adhesive of any of claims 1 to 3, wherein the cured reaction product of the adhesive provides >50% fiber tear and >100 grams strength when applied at 1.5 lbs/ream between a C1S paper film and a PET film.
  5. 5. The one-part, isocyanate-functional, moisture-curable laminating adhesive of any of claims 1 to 4, further comprising an additional polyol that is different from the high functionality polyester polyol component and the linear polyester polyol component.
  6. 6. The one-part, isocyanate-functional, moisture-curable laminating adhesive of any of claims 1 to 5, wherein said mixture comprises about 40 to 44 weight percent of said polyisocyanate component, about 27 to 31 weight percent of said high functionality polyester polyol component, and about 27 to 31 weight percent of said linear polyester polyol component.
  7. 7. A flexible packaging laminate comprising a paper substrate bonded to a second substrate by a cured reaction product of a one-component, isocyanate-functional, moisture-curable laminating adhesive comprising the reaction product of a mixture of a polyisocyanate component, a high functionality polyester polyol component and a linear polyester polyol component.
  8. 8. The flexible packaging laminate of claim 7 comprising about 1 to 4 pounds, preferably about 1 to 3 pounds, more preferably about 1 to 1.5 pounds of adhesive per substrate.
  9. 9. The flexible packaging laminate of claim 7 or 8 having a bond strength of greater than 100 grams force and a fiber tear of greater than 50%.
  10. 10. The flexible packaging laminate of any of claims 7 to 9, wherein the flexible packaging material is compostable when tested under ASTM 6400.
  11. 11. The flexible packaging laminate of any one of claims 7 to 9, wherein the first substrate and the second substrate are each independently selected from a paper film, a polymer film, a metallized polymer film, or a metal foil.
  12. 12. A flexible package comprising: A first portion of a flexible laminate having a perimeter and comprising a polymeric film bonded to a paper film by a cured reaction product of a one-component laminating adhesive comprising an aromatic polyisocyanate, a high functionality polyol and a linear polyester diol, and A second portion of the flexible laminate having a perimeter and comprising a polymeric film bonded to a paper film by a cured reaction product of a one-component laminating adhesive comprising an aromatic polyisocyanate, a high functionality polyol, and a linear polyester diol; the first portion is disposed adjacent the second portion and the first portion is sealed to the second portion about at least some of the perimeter to form a pouch having an interior cavity for receiving material; Wherein the flexible package is compostable when tested under ASTM 6400.
  13. 13. The flexible package of claim 12, wherein the polymeric film of the first portion of the flexible laminate is disposed adjacent the polymeric film of the second portion of the flexible laminate and the polymeric film of the first portion of the flexible laminate is heat sealed to the polymeric film of the second portion of the flexible laminate around at least some of the perimeter to form a pouch having an interior cavity for receiving the material.
  14. 14. The flexible package of claim 12, wherein the first portion of the flexible laminate and the second portion of the laminate are opposite ends of a sheet of flexible laminate folded upon itself.

Description

Laminating adhesive for compostable flexible packaging Technical Field The present disclosure relates generally to one-part, moisture-curable polyurethane laminating adhesives for use in the manufacture of flexible packages. More particularly, the present disclosure relates generally to solvent-free, one-component, moisture-curable polyurethane laminating adhesives that can bond paper films to polymeric films to provide compostable flexible packaging. Background This section provides background information that is not necessarily prior art to the inventive concepts associated with the disclosure. Product packaging has changed from sealed metal cans and glass bottles to sealed flexible packages, such as bags. As one example, tuna is now available in conventional metal cans and flexible bags. Flexible packages can be easily altered in shape by manipulation by a user when filled with food or other products and closed or sealed. Flexible packages are typically made of two layers of flexible packaging material that are covered and sealed around most of their periphery to form a cavity therein. Typically, two layers of flexible packaging material are heat sealed by applying heat and pressure to fuse together the polymer layers around a thin portion of the majority of the package perimeter. Food or other products are placed in the cavity through the opening and the opening is closed by heat sealing the open layers together. The sealed package and the closed product may be heated for preservation purposes. In some demanding applications, the sealed package and the closed product may be cooked, i.e. heated to a temperature of 100 ℃ or more. Flexible packaging materials are prepared by laminating two or more films. Each film is selected for a particular property. For example, the flexible packaging material may be a laminate of a paper film and a plastic film. In some embodiments, the plastic film is in contact with a food product and the paper film is an outer surface. In another embodiment, the flexible packaging material may be a three-layer laminate. The inner layer will contact the packaged product. Polypropylene has desirable product contact properties as well as heat sealability and can be used as an inner layer. An optional intermediate layer may be used to provide a barrier to moisture, oxygen, and/or light. The metal film or foil has the desired barrier properties and a metal film such as aluminum foil may be used as an intermediate layer. The outer layer will provide protection for the package and also provide a surface for printing information such as the contents, date of the package, warnings, etc. The polyester film is tough, can receive printing ink and can be used as an outer layer. The flexible packaging material may have a thickness in the range of about 13 to about 75 micrometers (0.0005 inch to 0.003 inch). Each layer of flexible packaging material is bonded to an adjacent layer by an adhesive. The adhesive may be applied to the layer from a solution of a suitable solvent using gravure or smooth roll coating cylinders or from a solvent-free state using special application machinery and laminating the layer to an adjacent layer. The laminated packaging material is dried and accumulated into rolls, if necessary. Although there are many possible types of adhesives, polyurethane-based adhesives are preferred for use in flexible packaging materials because they have many desirable characteristics, including good adhesion to materials in each layer, high peel strength, heat resistance such as from heat sealing or cooking, and resistance to food products. Typically, two-component polyurethane adhesives are used. The first component is the isocyanate portion of the (isocyanate functional) polyurethane prepolymer, which is obtained by reaction of an excess of diisocyanate with polyethers and/or polyesters containing two or more active hydrogen groups per molecule. The second component is typically a polyol. The two components are combined just prior to use to initiate a curing reaction between the components and applied to the film surface to be laminated. In some embodiments, solvents are used as diluents for some polyurethane laminating adhesives because the viscosity of those mixed adhesives is too high to reliably apply them in liquid form during roll-to-roll lamination. Solvent-based or water-based laminating adhesives are limited in the rate at which solvent or water can be effectively removed in an oven. Typical line speeds for solvent-based and water-based laminating adhesives are 300 to 600 feet per minute due to drying limitations. In other embodiments, the laminating adhesive is solvent-free (an adhesive that can be applied at 100% solids and does not contain an organic solvent or water). Solvent-free laminating adhesives have significant advantages in that they can be applied and run at very high line speeds because there is no solvent or water that must be removed from the adhesive during the