Biodegradable reinforced paper packaging mater

Abstract

A paper packaging material having a paper layer with a polyethylene coating on one surface, a biodegradable resin grid on the opposite surface to enhance its strength while maintaining reduced weight and a thermo-sealing resin, which eliminates the use of glues in the packaging process. The vegetal resin is made out of vegetable wax, acrylic styrene copolymer, demineralized water, water based silicone and natural fungicide.

Claims

1. A packaging material, comprising: A) a paper web having between 70 and 85 gsm having first and second surfaces; B) a layer of a biodegradable vegetal resin covering said first surface, said layer having a thickness between 3 and 4 gsm and further having at least one grid design applied on said layer first surface partially penetrating said paper web; C) a polyethylene film covering said second surface, said film having a density between 8 and 10 gsm; and D) an effective amount of a thermo-sealing varnish applied on selected areas over the polyethylene film, said effective amount being equal or greater than 3 grams per square meter.

2. The packaging material set forth in claim 1 wherein said biodegradable vegetal resin consists essentially of a vegetal wax, acrylic styrene copolymer, demineralized water, water based silicone and a natural fungicide.

3. The packaging material set forth in claim 1 wherein said biodegradable vegetal resin consists essentially of: acrylic styrene copolymer between 23% and 33% of the weight of said resin, vegetable wax between 45% and 55% of the weight of said resin, demineralized water between 15% and 22% of the weight of said resin, and water-based silicone between 0.8% and 1.2% of the weight of said biodegradable vegetal resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an isometric representation of a portion of the dried paper web with graphics printed on one face and the vegetal resin applied on the other face. The vegetal resin is shown to penetrate inside the paper layer in the areas of the applied reinforcing alveolar designs.

(2) FIG. 1A is cross-section representation of a portion of the dried paper web showing the alveolar design 25 applied thereon illustrating its penetration.

(3) FIG. 1B through 1E represent different possible shapes for the alveolar designs 25.

(4) FIG. 2 is a representation of the paper core layer passing through an engraving cylinder and a rubber cylinder used to apply the vegetal resin.

(5) FIG. 3 is a representation of an application for the packaging material to protect reams of paper.

(6) FIG. 4 is a detail enlarged isometric representation of a portion of the paper web.

(7) FIG. 5 is a detail enlarged isometric representation of the paper web 20 shown in the previous figure after the rotogravure operation has applied the vegetable resin and the alveolar design 25 was applied.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

(8) The present invention relates to a paper packaging material 10 using a biodegradable vegetal based resin 30 to create a strong chemical pulp fiber bonding that penetrates inside the layer of a paper web or core layer 20, vegetal based resin 30 creates a better barrier against moisture (only applied on the selected areas to ensure closure function). The packaging material 10 includes a controlled thermo-sealing area on the side 22 of the paper web 20 where it has been previously covered with a layer of polyethylene. The resulting packaging material 10 is biodegradable and a compostable additive is added to turn it sustainable.

(9) The first step of the method for manufacturing package material 10 is printing the graphics for publicity and/or the advertising. These can be applied preferably by flexographic, rotogravure, offset and/or digital printing technologies on surface or face 22.

(10) The second step of the method is drying paper web 20 that will be used by unwinding it in a proper machine suitable for this purpose and known in the paper industry. The drying process should remove between 30% and 60% of thin paper original moisture by either using heated calendars or blown hot air with temperatures in the range between 60° C. and 120° C. during enough time and speed to achieve the mentioned parameters.

(11) The third step is the application of a waterproof liquid vegetal resin composition to the paper. The printing or application of vegetal resin 30 is performed using, in one of the preferred embodiments, namely, rotogravure techniques. Rotogravures techniques include the use of an electrostatic field to achieve resin penetration inside paper web 20. The electrostatic process is referred to as ESA. See eltex.com.

(12) Vegetal resin is applied on the other surface 24 of paper web 20 either by rotogravure or indirect flexography technologies, utilizing engraved cylinders with alveolar shaped designs. By alveolar shaped designs it is to be understood any patterns or designs 25 that are closed such as squares, diamonds, rhomboids, honeycomb like, etc. These designs are similar to those used in construction for reinforcement grids inserted in concrete slabs. This third step has the following characteristics: a) The vegetal liquid resins 30 used have a viscosity between 17 seconds and 55 seconds under Zahn 2 method. See es-france.com. b) The cylinder for the vegetal resin 30 application applies the latter with two or more transfer depths in the alveolar shaped designs. In addition, surface 24 of the paper (opposite to where the advertising is printed) will be covered 100% by vegetal resin 30 with at least 3 grains per square meter. This application of the vegetal resin 30 covers 100% of surface 24 and increases paper impermeability. The application with the vegetal resin 30, will reach deep 21 in paper web 20, as shown in FIGS. 1A and 5. The application of resin 30 will occur in selected areas that can be done by repeating closed patterns 25 (alveolar designs) which, in combination, define the reinforcement areas. c) The vegetal resin 30 application using rotogravure technology is more efficient using ESA (electrostatic assist) liquid transfer technology optimized by electrostatic charges that improve resin penetration in paper fissures and micro cavities, as illustrated in FIG. 1A. d) Vegetal resin 30 has biodegradable and compostable characteristics, offering a sustainable condition to paper as for well as the resulting package that can be re-pulpable.

(13) The fourth step is the application of polyethylene 40 by extrusion coating on the same surface 22 of the paper where publicity or advertising printing is applied as follows: a) The polyethylene 40 application is done with flat die, where the liquid polyethylene film is deposited on the paper forming a uniform polyethylene film with controlled thickness. This step is known in the industry. b) The application of a predetermined amount of polyethylene 40 can vary between 6 and 20 grains per square meter of film of paper. Better impermeability is achieved with a thicker polyethylene film. c) The polyethylene extrusion coating must receive corona treatment to allow graphic printing by using thermo-sealing varnish, which defines the areas for sealing the package. See vetaphone.com. d) The polyethylene has biodegradable and compostable characteristics, offering a sustainable condition to paper as well as the resulting package that can be re-pulpable.

(14) The fifth step is the application of a thermo-sealing varnish 50 by using the rotogravure process on pre-defined areas that will be set for closing the package with the following characteristics: a) The thermo-sealing resin or varnish 50 will be applied with a volume equal or greater than 3 grains per square meter on preselected areas. These areas are selected to ensure the closure function for the package. b) The thermo-sealing resin has a fusion temperature equal or greater than 70° C. and its fusion is compatible with the polyethylene 40 layer coating fusion combining both sealing strengths. c) The application of such thermo-sealing resin 50 replaces and eliminates the use of liquid or viscous glues.

(15) The above five described steps complete the production of the film of paper with alveolar shape design 25 providing reinforcement and thermo-sealing features. The film of paper in rolls (that can be cut in sheets) is now ready to be used in the packaging process generating savings by reducing the packaging material weight in addition to eliminating of glue cost.

(16) This new chemical strengthening technique and thermo-sealing control affinity can be used with monolayer papers or laminated papers with other substrates such as polypropylene with one or more layers and can also be used with bi-axially oriented polypropylene (BOPP) with one or more layers. The thickness for above-mentioned films may vary from 10 microns (0.4 mil) to 300 microns (12 mil).

(17) The biodegradable and compostable resin chemical formula is disclosed below.

(18) TABLE-US-00001 PRODUCT OPTIMAL MINIMUM MAXIMUM Vegetal wax 50%  45%  55% Acrylic Styrene Copolymer 30%  23%  33% Demineralized water 18%  15%  22% Water based silicone  1% 0.8% 1.2% Biocidal/Natural Fungicide  1% 0.9% 1.1%

(19) TABLE-US-00002 TECHNICAL SPECS PROPERTIES MINIMUM MAXIMUM Solid content (%) 30 35 Viscosity Brookfield at 25° C. (cps) 200 300 pH at 25° C. 7.5 8.5 Stability Separation Free Aspect Milky White Liquid Diluent while still humid Water
Comparative Resistance Tests

(20) Hereafter a comparison between Product 1 (traditional package) and Product 2 (Invention's package):

(21) TABLE-US-00003 Product 1 Product 2   81 gsm paper   78 gsm paper   11 gsm polyethylene resin   10 gsm polyethylene resin  1.5 gsm inks  3.5 gsm vegetal resin  0.5 gsm thermo-sealing resin (overall)  1.5 gsm inks 93.5 gsm total weight 93.5 gsm total weight

(22) The total weight of the abovementioned products (Product 1 and Product 2) refers to their overall weight. The “gsm total weight” includes the weight of each application of the vegetal and thermo-sealing resin in the entire area of the package material. The vegetal resin is applied throughout the entire surface 24 and therefore its overall thickness (3-4 gsm) is maintained. The thermo-sealing resin also has a thickness or density of 3-4 gsm but it is only applied in preselected areas for closure purposes. When computing the total weight of the product, the contribution to the total weight of the package material by the thermo sealing resin drops to 0.5 gsm since there are areas that do not include the thermo-sealing resin. For example, if the total surface area where thermo-sealing resin 50 is going to be selectively covered has 1 square m. and thermo-sealing resin 50 with a density of 4 gsm is selectively applied in one eighth of the total area, then the overall amount of thermo resin 50 is:
1 sq m×⅛×4 g/sq m=0.5 g

(23) Then, the overall weight contribution of the thermo-sealing resin having 4 gsm on surface 22 of 1 m is 0.5 gsm. The products comparison was held constant as to the total weight and the relative strength of the resulting package then compared. The unexpected increase in the strength of the material is extraordinary. Those skilled in the art are preoccupied with keeping the weight down of the packaging material while enhancing its strength.

(24) TABLE-US-00004 COMPAR- CONVEN- ATIVE UNIT OF TIONAL INVENTION'S RESULT DATA MEASURE PACKAGE PACKAGE % Basis weight grams/m.sup.2 92 92    0% Thickness Micron 109 110    +1% COBB Test % 53% 30%   −15% (humidity) Burst KPa 288 313  +8.68% Longitudinal KN/m 4.9 5.6 +14.28% Tension Cross Tension KNm 3.0 3.4 +13.33% Longitudinal m/N 630 708 +12.38% Tear Cross Tear m/N 619 680  +9.85% Longitudinal Grain- 1.5 2.3 +53.33% Stiffness force/cm Cross Stiffness Gram- 0.9 1.1 +22.22% force/cm

(25) By analyzing laboratory tests made on the new product in comparison to the conventional packing material, we can observe a mechanical resistance increase by 12.38%, plus a humidity resistance increase by 15% by reducing the water absorption by 15%. Both parameters lead to the conclusion that the present invention results in better product allowing the possibility to reduce the paper basis weight as well as the polyethylene resin volume application by approximately 12% while maintaining the same protection level. This results in substantial packaging cost savings. The greater tear resistance provides greater physical strength of the packaging and reducing moisture absorption, keeping these mechanical strength characteristics more stable and durable. For example, if the mechanical strength increases by 12% we can say that it is possible to reduce the thickness of the paper proportionally, thus reducing its cost per package and follow having an equal resistance of the package. If the moisture in the paper falls by 15%, will have greater strength of the paper in the package not break when exposed to moisture.

(26) The foregoing description conveys the best understanding of the objectives and advantages of the present invention. It is to be understood that all matter disclosed herein is to be interpreted merely as illustrative, and not in a limiting sense.