WO2010123689A1

WO2010123689A1 - A method of making multilayer paper-based packaging materials having enhanced barrier performance

Info

Publication number: WO2010123689A1
Application number: PCT/US2010/030327
Authority: WO
Inventors: David E. Knox; Julie A. Willoughby; James C. Ewing; Timothy C. Mclaughlin; Charles G. Ruffner, Jr.; Stephanie Al Crette; George R. Brown
Original assignee: Meadwestvaco Corp
Current assignee: WestRock MWV LLC
Priority date: 2009-04-21
Filing date: 2010-04-08
Publication date: 2010-10-28
Anticipated expiration: 2011-10-21

Abstract

A method of making multilayer paper-based packaging materials with enhanced barrier performance is disclosed that is economical on a per-package cost basis. The disclosed method comprises steps of coating a water-based barrier composition on-line during papermaking process onto at least one surface of the paper-based substrate, and then applying a polymeric film onto the surface of the resulting coated paper-based structure. When desired, the disclosed method may include a step of applying a layer of base coat between the paper-based substrate and the barrier layer to enhance the surface smoothness and reduce the porosity of the paper-based substrate.

Description

A METHOD OF MAKING MULTILAYER PAPER-BASED PACKAGING MATERIALS HAVING ENHANCED BARRIER PERFORMANCE

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional application relies on the filing date of provisional U.S. Application Serial No. 61 /171142 filed on April 21 , 2009, having been filed within twelve (12) months thereof, which is incorporated herein by reference, and priority thereto is claimed under 35 USC § 1.19(e).

BACKGROUND OF THE DISCLOSURE

[0001 ] Barrier properties are typical performance requirements of packaging materials to prevent the premature deterioration of the packaged goods. It is highly desirable that packages for perishable liquid or dry foods be moisture-, oxygen- and aroma-proof for improving the durability of the product. One known method for rendering paperboard packaging substrate impermeable to liquid and gas is to provide the board with a metal foil. This method, however, has several drawbacks, including high manufacturing costs, non-biodegradability of the foil layer, problems of regeneration of the packaging material, and the unsuitability of the packaging for heating in a microwave oven.

[0002] To address the aforementioned drawbacks of aluminum foil, the industry has shifted to the use polymeric films as an oxygen and aroma barrier in packaging applications. Examples of polymers known for their barrier properties are ethyl-vinyl alcohol copolymer (EVOH), polyamide, polyethylene terephthalate (PET), polyacrylonitrile, polyvinylidene chloride, and polyvinyl chloride. U.S. Patent No. 6,110,548 discloses a container structure having low oxygen permeability, excellent bulge resistance and durability. The structure consists of paperboards; a first heat- sealable polymer layer coated on one side of the paperboards; a polyamide layer laminated on the other side of the paperboard to impart mechanical strength, thermal resistance, and improved durability; a layer of EVOH copolymer laminated on the surface of the polyamide layer to provide oxygen barrier performance; a second heat-sealable polymer layer applied over the EVOH layer; and a tie layer between the EVOH layer and the second heat-sealable polymer layer. U.S. Patent No. 6, 193,827 teaches a non-foil composite laminate having improved oxygen and flavor barrier that i is suitable as a packaging material for products such as fruit and citrus juices, beverages and the like, and non-liquid dry products. The non-foil laminate is produced by applying a layer of heat-sealable olefin polymer on one side of the paperboard to provide one outer surface of the laminate; coextruding over the other surface of the paperboard substrate a sandwich layer comprising a first adhesive tie layer, an amorphous nylon layer and a second adhesive tie layer; and extruding a layer of heat-sealable olefin polymer over the sandwich layer to provide the other outer surface of the laminate. Unfortunately, these multilayer structures with enhanced barrier performance require successive incorporation of barrier layers and tie layers onto the paperboard substrate after the papermaking process. The functional layers are applied, off-line from the papermaking process, onto the board using lamination or extrusion techniques. Accordingly, the production of these multilayer boards is rather complicated and costly.

[0003] Current commercial paperboard materials for barrier packaging applications comprise multiple layers, wherein each layer performs different functions. Oxygen barrier films, such as EVOH and nylon, are laminated off-line from the papermaking process. The paperboard from papermaking process must be transported to a lamination site, unwound prior to lamination, and processed to give the final structure. The commercial materials require several layers of costly barrier components to achieve the barrier level that is typically demanded for packaged goods sensitive to oxygen and water vapor.

[0004] There have been reports of alternative methods for producing a multilayer packaging board with enhanced barrier performance that simplifies the production process and lowers the production cost. It is known that the polymer barrier properties can be improved by addition of layered particles capable of being at least partially intercalated or exfoliated, or particles having particle size in nanometer range, creating a polymer-particle matrix. When the continuous film of the polymer-particle matrix is on the surface of treated substrate, the particles in the polymeric matrix create a tortuous path that lowers the rate of the molecular diffusion through the polymeric structure, resulting in a significant reduction in the composite permeability. Examples of the patents disclosing this alternative method including U.S. Patent Numbers 7,119,138; 7,208,039; and 7,474,729. [0005] In order to achieve high barrier performance, the aforementioned coating compositions must form a continuous film on the substrate upon drying without pinholes, since the pinhole areas allow oxygen to diffuse through the coated substrate without going to the tortuous path of the layered particles or nanoparticles. Unfortunately, paper-based substrates have high porosity and poor surface smoothness that impedes the formation of continuous barrier film on its surface, and the oxygen performance achieved is typically insufficient for packaging applications. Since the formation for continuous barrier film on the surface of paper-based substrate is critical in achieving high oxygen barrier performance required for packaging applications, several approaches have been reported to address the continuous film forming problem. PCT Patent Publication No. WO 00/76862 teaches a laminated structure for packaging applications comprising a paper substrate and at least one polymer/nanoclay composite layer. Nanoclay particles are dispersed in a molten polymer matrix, and consequently the molten polymer/nanoclay composite is applied onto the paper substrate off-line from papermaking process, either through extrusion coating or extrusion lamination.

[0006] Accordingly, there is still a need for a method of producing multilayer structure from a paper-based substrate that has barrier performance suitable for packaging applications, yet may be achieved by applying the barrier coating composition on-line during the papermaking process to minimize the process complexity and production cost.

[0007] Additionally, it is desirable that such a production process is compatible with the existing papermaking process and converting process, so that the produced paperboard packaging material is economical on a per- package cost basis and may be formed, filled and sealed at economically high speeds using conventional packaging machine temperatures, pressures and dwell times.

SUMMARY OF THE DISCLOSURE

[0008] A method of making multilayer paper-based packaging materials with enhanced barrier performance is disclosed that is economical on a per- package cost basis. The disclosed method comprises steps of coating a water-based barrier composition on-line during papermaking process onto at least one surface of the paper-based substrate, and then applying a polymeric film onto the surface of the resulting coated paper-based structure. When desired, the disclosed method may include a step of applying a layer of base coat between the paper-based substrate and the barrier layer to enhance the surface smoothness and reduce the porosity of the paper-based substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 shows one embodiment of the disclosed multilayer packaging material, comprising a paper-based substrate, a barrier layer derived from water- based barrier coating composition on one surface of the substrate, and a polymeric film layer applied over the barrier coating layer;

[0010] FIG. 2 shows one embodiment of the disclosed multilayer packaging material, comprising a paper- based substrate, a layer of base coat applied on one surface of the substrate, a barrier layer derived from water-based barrier coating composition applied over the base coat, and a polymeric film layer applied over the barrier coating layer; and

[0011 ] FIG. 3 shows one embodiment of the disclosed multilayer packaging material, comprising a paper-based substrate, a barrier layer derived from water- based barrier coating composition on one surface of the substrate, a first polymeric film layer applied over the barrier coating layer; and a second polymeric film layer positioned on the other side of the substrate.

DESCRIPTION OF THE DISCLOSURE

[0012] While the disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof.

[0013] The present method of producing multilayer paper-based packaging materials includes steps of:

(i) applying a layer of water-based barrier coating composition, on-line during papermaking process, onto at least one surface of a paper-based substrate; and (ii) applying a layer of polymeric film onto the barrier coating layer.

[0014] Various known water-based barrier coating compositions may be used in the present method. The water-based barrier coating compositions may be applied onto the paper-based substrate by any known application methods. These include, but are not limited to, size press application, brushing, spraying, roll coating, rod- coatings, dipping, spreading, printing methods, air knife coating, and curtain coating. To reduce both production cost and complexity, the water-based barrier coating composition may be applied onto the paper-based substrate on-line during the papermaking process.

[0015] FIGURE 1 shows one embodiment of the multilayer paper-based packaging material produced from the presently disclosed method. The multilayer packaging material 100 comprises a paper-based substrate 10, a layer of barrier coating 11 derived from a water-based coating composition, and a layer of polymeric film 12 on the outer surface of the barrier coating layer 11. The polymeric film may be applied onto the barrier-coated structure by many known application techniques. These include, but are not limited to, lamination and extruded coating. Examples of polymeric films suitable for use in the present disclosure include, but are not limited to, polyolefins such as polyethylene and biaxially oriented polypropylene; polyesters such as polyethylene terephthalate (PET) and biaxially oriented polyester film; polyamides such as nylon and metallocene catalyzed nylon; poly(ethylene- vinyl alcohol); polyvinylidene chloride; polyvinyl alcohol; lactic acid-based polymer such as polylactic acid (PLA); polyvinyl chloride; polyacrylonitrile; and combinations thereof. [0016] A variety of paper-based substrate may be used in the present disclosure. These include, but are not limited to, paperboard, bleached kraft paper, unbleached kraft paper, fiberboard, and combinations thereof. The paper-based substrates may be either a single ply or multi-ply.

[0017] In one embodiment, the disclosed method further comprises a step of applying a layer of base coat formulation onto the substrate prior to the application of the barrier coating layer. Any standard base coat formulation may be used in the present disclosure. FIGURE 2 shows such embodiment, wherein the multilayer packaging material 200 comprises a paper-based substrate 10; a layer of the basecoat 13 applied on one surface of the substrate; a layer of barrier coating 11 applied over the basecoat 13; and a layer of polymeric film 12 positioned over the barrier layer 11.

[0018] In one embodiment, the disclosed method of producing multilayer paper-based packaging materials includes steps of:

(i) applying a layer of water-based barrier coating composition, on-line during papermaking process, onto one surface of a paper-based substrate; (ii) applying a first polymeric film onto an opposite surface of the substrate; and (iii) applying a second polymeric film onto the barrier coating layer.

[0019] FIGURE 3 shows the multilayer packaging material 300 comprises a paper-based substrate 10; a layer of barrier coating 11 positioned on one surface of the substrate, a first polymeric film layer 14 positioned on the other surface of the substrate; and a second layer of polymeric film 12 positioned over the barrier layer 11. When desired, the first polymeric film may have the same composition as the second polymeric film.

[0020] FIGURES 1 -3 are only to demonstrate some structural examples for the multilayer packaging material of the present disclosure. It is to be understood that one skill in the art may tailor the structure of multilayer product to provide the desired performance for the selected end use applications, without departing from the concept of present disclosure. [0021 ] Oxygen transmission rate (OTR) is the measurement of the amount of oxygen gas that passes through a substrate over a given period. In the present disclosure, the OTR was measured at 23⁰C and 0% RH using Mocon OXTRAN 35 2/20 or 2/60 modules. Each tested sample was loaded onto the modules and conditioned for 2 hours prior to the OTR measurement. Two controls were used for the study of the enhanced barrier performance of the presently disclosed multilayer paper- based packaging structure. The first control (CONTROL I) was the uncoated paper-based substrate. The second control (CONTROL II) was the paper-based substrate coated with a barrier layer derived from the same water- based barrier coating composition as that used for the multilayer structure of FIGURES 1 and 2.

TABLE 1

[0022] The disclosed multilayer packaging materials have an excellent oxygen barrier performance that is suitable for packaging applications. When desired, the disclosed multilayer packaging material may be designed such that its OTR is less than 100 cc/m².day.atm as determined at 23⁰C and 0% RH using Mocon OXTRAN 35 2/20 or 2/60 modules. In one embodiment, the disclosed multilayer packaging material has an OTR value of less than 10 cc/m².day.atm.

[0023] While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. It is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.

Claims

CLAIMSWe Claim:

1. A method of making a multilayer packaging material, including steps of:

(i) applying a layer of water-based barrier coating composition onto at least one surface of a paper-based substrate; and (ii) applying a layer of polymeric film onto the barrier coating layer.

2. The method of Claim 1 , wherein the polymeric film includes a polymer selected from the group consisting of polyolefin, polyester, polyamide, nylon, polyvinyl alcohol, poly(ethylene-vinyl alcohol), polyvinylidene chloride, polyvinyl chloride, polyacrylonitrile, polyvinylidene chloride, polyvinyl alcohol, lactic acid-based polymer, polyvinyl chloride, polyacrylonitrile, and combinations thereof.

3. The method of Claim 1 , further comprising a step of applying a layer of base coat onto the surface of paper-based substrate prior to an application of the barrier coating layer.

4. A method of making a multilayer packaging material, including steps of:

(i) applying a layer of water-based barrier coating composition onto one surface of a paper-based substrate; (ii) applying a first polymeric film layer onto an opposite surface of the substrate; and (iii) applying a second polymeric film layer onto the barrier coating layer.

5. The method of Claim 4, wherein the first polymeric film includes a polymer selected from the group consisting of polyolefin, polyester, polyamide, nylon, polyvinyl alcohol, poly(ethylene-vinyl alcohol), polyvinylidene chloride, polyvinyl chloride, polyacrylonitrile, polyvinylidene chloride, polyvinyl alcohol, lactic acid- based polymer, polyvinyl chloride, polyacrylonitrile, and combinations thereof.

6. The method of Claim 4, wherein the second polymeric film includes a polymer selected from the group consisting of polyolefin, polyester, polyamide, nylon, polyvinyl alcohol, poly(ethylene-vinyl alcohol), polyvinylidene chloride, polyvinyl chloride, polyacrylonitrile, polyvinylidene chloride, polyvinyl alcohol, lactic acid- based polymer, polyvinyl chloride, polyacrylonitrile, and combinations thereof.

7. The method of Claim 4, further comprising a step of applying a layer of base coat onto the surface of paper-based substrate prior to an application of the barrier coating layer.

8. A multilayer packaging material produced by the method of Claim 1.

9. A multilayer packaging material produced by the method of Claim 3.

10. A multilayer packaging material produced by the method of Claim 4.

11.A multilayer packaging material produced by the method of Claim 7.