KR20200028900A - How to use cardboard, cardboard containers, and cardboard items - Google Patents

Abstract

A method of using a cardboard article includes heating the cardboard article by microwave irradiation. The cardboard article includes a cardboard substrate having a first major surface and a second major surface, and at least one high density polyethylene layer on at least one of the first major surface and the second major surface of the cardboard substrate.

Description

How to use cardboard, cardboard containers, and cardboard items

The present application relates to polymer coated cardboard and, in particular, polymer coated cardboard which can be converted into a container suitable for food heating or cooking by microwave irradiation.

Extrusion coating of low density polyethylene was used to coat butcher wrappers in the 1950s, and low density polyethylene is widely used as a barrier coating for cold and hot beverage cups and in a variety of other applications.

Polypropylene resins are used in fully-plastic containers for microwave heating of food products. The polypropylene-coated cardboard can be converted into a container or cup suitable for heating or cooking food through microwave radiation. However, the extrusion coating of polypropylene into cardboard and the conversion of polypropylene coated cardboard into containers and cups has created problems for the cardboard industry. In order to solve the problems associated with extrusion coating of polypropylene and conversion of polypropylene coated cardboard onto cardboard, a mixture of 20% low density polyethylene and polypropylene is coated on cardboard, into a container suitable for food heating or cooking by microwave irradiation. A polymer coated cardboard that can be converted is prepared.

The skilled person continues his research and development efforts in the field of polymer coated cardboard.

The present invention provides an improved method of using cardboard, cardboard containers and cardboard articles.

In one aspect, the disclosed method of using cardboard includes heating the cardboard article by microwave irradiation. The cardboard article includes a cardboard substrate having a first major surface and a second major surface, and at least one high density polyethylene layer over at least one of the first major surface and the second major surface of the cardboard substrate.

In another aspect, the disclosed cardboard container comprises a cardboard substrate having a first major surface facing the interior of the cardboard container and a second major surface facing the exterior of the cardboard container, and one immediately above the first major surface of the cardboard container The above-mentioned high density polyethylene layer is included.

In another aspect, a cardboard substrate having a first major surface and a second major surface, and at least one high density polyethylene layer over at least one of the first major surface and the second major surface of the cardboard substrate, and optionally, the Disclosed is a paperboard substrate and a clay coating layer between the at least one high density polyethylene layer over at least one of the first major surface and the second major surface of the cardboard substrate.

Other aspects of the disclosed cardboard, cardboard container, and method of using cardboard articles will become apparent from the following description, accompanying drawings, and claims.

1 is a cross-sectional view of a cardboard according to the first embodiment;
2 is a cross-sectional view of a cardboard according to a second embodiment;
3 is a sectional view of a cardboard according to a third embodiment;
4 is a sectional view of a cardboard according to a fourth embodiment;
5 is a sectional view of a cardboard according to a fifth embodiment;
6 is a sectional view of a cardboard according to a sixth embodiment;
7 is a sectional view of a cardboard according to the seventh embodiment;
8 is a sectional view of a cardboard according to an eighth embodiment;
9 is a schematic view of an extrusion coating system for coating a high density polyethylene layer on a cardboard substrate;
10 is a top view of an unprinted sidewall blank;
11 is a top view of a printed sidewall blank with a marking printed on its main surface;
12 is a perspective view of an embodiment of an exemplary cardboard container;
13 is a side sectional view of the cardboard container of FIG. 12;
14 is a perspective view of the lid of the cardboard container of FIG. 12;
15 is a perspective view of another embodiment of an exemplary cardboard container;
16 is a side sectional view of the cardboard container of FIG. 15;
FIG. 17 is a graph of polymer extrusion coating testing showing melt curtain neck-in of cardboard with high density polyethylene coating compared to melt curtain neck-in of cardboard with polypropylene / low density polyethylene coating;
18 is a graph of a polymer extrusion coating test showing the corona treatment level of a cardboard with a high density polyethylene coating compared to the corona treatment level of a cardboard with a polypropylene / low density polyethylene coating;
19 is a graph of a polymer extrusion coating test showing the coefficient of friction (CoF) of a cardboard with a high density polyethylene coating compared to the coefficient of friction (CoF) of a cardboard with polypropylene / low density polyethylene coating;
20 is a graph of a polymer extrusion coating test showing the wear resistance of a cardboard with a high density polyethylene coating compared to the wear resistance of a polypropylene / low density polyethylene coated cardboard;
FIG. 21 is a graph related to a polymer extrusion coating test showing a water vapor transmission rate (WVTR) of a paperboard having a high density polyethylene coating compared to a water transmission rate (WTR) of a paperboard having a polypropylene / low density polyethylene coating as a coating;
FIG. 22 is a graph of a polymer extrusion coating test showing the cup forming heat sealing profile of a cardboard with high density polyethylene compared to the cup forming heat sealing profile of a polypropylene / low density polyethylene coated cardboard.

The cardboard includes a cardboard substrate having a first major surface and a second major surface, and at least one high density polyethylene layer over at least one of the first major surface and the second major surface of the cardboard substrate. The cardboard may further include a clay coating layer between the cardboard substrate and the one or more high density polyethylene layers on one or more of the first and second major sides of the cardboard substrate.

1 is a cross-sectional view of a cardboard 10 according to the first embodiment. The cardboard 10 is a cardboard substrate 11 having a first main surface 12 and a second main surface 13 and a high density polyethylene layer 15 on the first main surface 12 of the cardboard substrate 11 ). The high density polyethylene layer 15 can be disposed directly on the first major surface 12 of the cardboard substrate 11, ie without an intervening layer. The high density polyethylene layer 15 can be disposed on the outermost surface of the cardboard 10 on the first major surface 12. The cardboard substrate 11 may be disposed on the outermost surface of the cardboard 10 on the second main surface 13.

2 is a cross-sectional view of a cardboard 20 according to a second embodiment. The cardboard 20 is a cardboard substrate 21 having a first main surface 22 and a second main surface 23, a clay coating layer 24 on the first main surface 22 of the cardboard substrate 21 , And a high density polyethylene layer 25 over the clay coating layer 24. The clay coating layer 24 can be disposed directly on the first major surface 22 of the cardboard substrate 21, ie without an intervening layer. The high density polyethylene layer 25 can be disposed directly on the clay coating layer 24, ie without an intervening layer. The high-density polyethylene layer 25 may be disposed on the outermost surface of the cardboard substrate 20 at the first major surface 22. The cardboard substrate 21 may be disposed on the outermost surface of the cardboard 20 on the second main surface.

3 is a cross-sectional view of a cardboard 30 according to the third embodiment. The cardboard 30 is a cardboard substrate 31 having a first main surface 32 and a second main surface 33 and a high density polyethylene layer 35 on the first main surface 32 of the cardboard substrate 31 ) And a clay coating layer 36 on the second major surface. The high density polyethylene layer 35 can be disposed directly on the first major surface 32 of the cardboard substrate 31, ie without an intervening layer. The clay coating layer 36 can be disposed directly on the second main surface 33 of the cardboard substrate 31, ie without an intervening layer. The high density polyethylene layer 35 may be disposed on the outermost surface of the cardboard 30 at the first major surface 32. The clay coating layer 36 may be disposed on the outermost surface of the cardboard 30 on the second major surface 33.

4 is a cross-sectional view of a cardboard 40 according to a fourth embodiment. The cardboard 40 is a cardboard substrate 41 having a first main surface 42 and a second main surface 43, a first clay coating layer 44 on the first main surface 42 of the cardboard substrate 41 And a high density polyethylene layer 45 on the first clay coating layer 44, and a second clay coating layer 46 on the second major surface 43 of the cardboard substrate 41. The first clay coating layer 44 can be disposed directly on the first major surface 42 of the cardboard substrate 41, ie without an intervening layer, and the high density polyethylene layer 45 is the first clay coating layer ( 44) can be disposed directly on, ie, without intervening layers. The second clay coating layer 46 can be disposed directly on the second major surface of the cardboard substrate 41, ie without an intervening layer. The high density polyethylene layer 45 can be disposed on the outermost surface of the cardboard 40 at the first major surface 42. The second clay coating layer 46 may be disposed on the outermost surface of the cardboard 40 at the second major surface.

5 is a cross-sectional view of a cardboard 50 according to a fifth embodiment. The cardboard 50 is a cardboard substrate 51 having a first main surface 52 and a second main surface 53, and a first high density polyethylene layer 55 on the first main surface 52 of the cardboard substrate 51 And a second high density polyethylene layer 57 on the second major surface 53 of the cardboard substrate 51. The first high density polyethylene layer 55 can be disposed on the first major surface 52 of the cardboard substrate 51 directly, without an intervening layer. The second high density polyethylene layer 57 can be disposed directly on the second major surface 53 of the cardboard substrate 51, ie without an intervening layer. The first high density polyethylene layer 55 may be disposed on the outermost surface of the cardboard 50 at the first major surface 52. The second high density polyethylene layer 57 can be disposed on the outermost surface of the cardboard 50 at the second major surface 53.

6 is a cross-sectional view of the cardboard 60 according to the sixth embodiment. The cardboard 60 is a cardboard substrate 61 having a first main surface 62 and a second main surface 63, a clay coating layer 64 on the first main surface 62 of the cardboard substrate 61, clay And a first high density polyethylene layer 65 on the coating layer 64 and a second high density polyethylene layer 67 on the second major surface 63 of the cardboard substrate 61. The clay coating layer 64 can be disposed directly on the first major surface 62 of the cardboard substrate 61, ie without an intervening layer. The first high density polyethylene layer 65 can be disposed directly on the clay coating layer 64, ie without an intervening layer. The second high density polyethylene layer 67 can be disposed directly on the second major surface of the cardboard substrate 61, ie without an intervening layer. The first high density polyethylene layer 65 may be disposed on the outermost surface of the cardboard 60 at the first major surface 62. The second high density polyethylene layer 67 can be disposed on the outermost surface of the cardboard 60 on the second major surface 63.

7 is a cross-sectional view of a cardboard 70 according to the seventh embodiment. The cardboard 70 is a cardboard substrate 71 having a first main surface 72 and a second main surface 73, a first high density polyethylene layer 75 on the first main surface 72 of the cardboard substrate 71 , A clay coating layer 76 on the second major surface 73 of the cardboard substrate 71, and a second high density polyethylene layer 77 on the clay coating layer 76. The first high density polyethylene layer 75 can be disposed directly on the first major surface 72 of the cardboard substrate 71, ie without an intervening layer. The clay coating layer 76 can be disposed directly on the second major surface 73 of the cardboard substrate 71, ie without an intervening layer. The second high density polyethylene layer 77 can be disposed directly on the clay coating layer 76, ie without an intervening layer. The first high density polyethylene layer 75 may be disposed on the outermost surface of the cardboard 70 at the first major surface 72. The second high density polyethylene layer 77 may be disposed on the outermost surface of the cardboard 70 at the second major surface 73.

8 is a cross-sectional view of a cardboard 80 according to the eighth embodiment. The cardboard 80 is a cardboard substrate 81 having a first major surface 82 and a second major surface 83, a first clay coating layer 84 on the first major surface 82 of the cardboard substrate 81 , A first high density polyethylene layer 85 on the first clay coating layer 84, a second clay coating layer 86 on the second major surface 83 of the cardboard substrate 81, and a second clay coating layer 86 ) On the second high density polyethylene layer 87. The first clay coating layer 84 can be disposed directly on the first major surface 82 of the cardboard substrate 81, ie without an intervening layer. The first high density polyethylene layer 85 can be disposed directly on the first clay coating layer 84, ie without intervening layers. The second clay coating layer 86 can be disposed directly on the second major surface 83 of the cardboard substrate 81, ie without an intervening layer. The second high density polyethylene layer 87 can be disposed directly on the second clay coating layer 86, ie without intervening layers. The first high density polyethylene layer 85 can be disposed on the outermost surface of the cardboard 80 at the first major surface 82. The second high density polyethylene layer 87 can be disposed on the outermost surface of the cardboard 80 at the second major surface 83.

Although various embodiments of cardboard have been described above with reference to FIGS. 1 to 8, variations may occur to those skilled in the art upon reading this specification. For example, in any one of Figures 1-8, any of the high density polyethylene layers can be replaced with multiple high density polyethylene layers. This application includes such modifications and is limited only by the claims.

The cardboard substrate may include any web of fibrous materials to which a high density polyethylene layer can be applied. The cardboard substrate may or may not be bleached. For example, the cardboard substrate may be coated natural kraft board, solid bleached sulfate board, solid unbleached sulfate board, coated recycle board, coated white stripe chipboard, or folding. It may include a boxboard (boxboard).

The thickness of the cardboard substrate can depend on various factors such as the density of the cardboard substrate. For example, the cardboard substrate can have a caliper thickness ranging from 6 points to 36 points (1 point equals 0.001 inches). As one specific example, the cardboard substrate may have a caliper thickness of 7 to 30 points. As another specific example, the cardboard substrate can have a caliper thickness ranging from 14 points to 20 points. As another specific example, the cardboard substrate can have a caliper thickness ranging from 16 points to 18 points. As used herein, one point is equal to 0.001 inches, which is equal to 25.4 micrometers (μm).

The weight of the cardboard substrate can depend on various factors. For example, the cardboard substrate can have a basis weight ranging from 60 to 350 pounds per 3,000 square feet. As one specific example, the cardboard substrate may have a basis weight of 100 to 150 pounds per 3000 ft ² . As another specific example, the cardboard substrate can have a basis weight of 150 to 180 pounds per 3000 ft ² . As another specific example, the cardboard substrate may have a basis weight of 180 to 220 pounds per 3000 ft ² .

The clay coating layer can be applied to the cardboard substrate to improve the print quality of the cardboard surface. The clay coating layer can include a mixture of inorganic pigments and one or more other materials, such as a binder (eg, emulsion polymer binder) and a dispersant. As a specific example, the clay coating layer may include kaolin clay.

The clay coating layer can be applied in any way that can apply the clay coating layer to a cardboard substrate. In certain examples, the clay coating layer can be coated on a cardboard substrate. Examples of coaters that can be used are air knife coaters, blade coaters, rod coaters, bar coaters, multi-head coaters, roll coaters, rolls / Blade coating machine, cast coating machine, laboratory coating machine, gravure coating machine, kiss coating machine, liquid coating system, reverse roll coating machine, curtain coating machine, spray coating machine and extrusion coating machine Can be employed.

Surprisingly, it has been found that high density polyethylene protects the cardboard substrate from moisture even after the same heating by microwave irradiation.

The density of the high density polyethylene of the one or more high density polyethylene layers may range from 0.93 to 0.97 g / cm ³ . In one example, the density of high density polyethylene ranges from 0.95 to 0.96 g / cm ³ . In one aspect, high density polyethylene can have a melt index greater than 0.3 g / 10 min (190 ° C./2.16 kg). In another aspect, the high density polyethylene can have a melt index greater than 4 g / 10 min (190 ° C./2.16 kg). In another aspect, the high density polyethylene can have a melt index greater than 8 g / 10 min (190 ° C./2.16 kg). In one aspect, the first layer of the one or more high density polyethylene layers has a first density and a first melt index, and the second layer of the one or more high density polyethylene layers has a second density different from the first density and the first application index. And a second melt index.

An exemplary high density polyethylene layer is a single layer of 100% high density polyethylene resin extrusion coated on one or both sides of a cardboard substrate, where the high density polyethylene has a density of 0.950 g / cm ³ per ASTM D792 and the melt index (MI) is 12 g / 10 min per ASTM D1238 test at 2.16 kg load and 190 ° C.

The one or more high density polyethylene layers can be applied to a cardboard substrate using any available technology. Examples of suitable techniques for applying one or more high density polyethylene layers include extrusion coating, extrusion laminate, curtain coating and adhesive lamination. In one example, multiple layers of high density polyethylene can be coextruded onto a cardboard substrate. In another example, a first high density polyethylene layer can be laminated on a cardboard, and then a second high density polyethylene layer can be extruded onto the cardboard. In another example, a first high density polyethylene layer may be extruded onto a cardboard, and then a second high density polyethylene layer may be laminated onto the cardboard.

9 shows an exemplary extrusion coating system 90 for coating a high density polyethylene layer on a cardboard substrate. As shown, the cardboard substrate 91 can be unwound from the unwind roll 92 and passed between a nip roll 93 and a cooling roll 94 to be wound on a rewind roll 95. On the other hand, the resin 96 can be extruded onto the cardboard substrate moving from the slot die 97 at an elevated temperature. The resin-coated cardboard substrate 91 can pass through the nip roll 93 and the cooling roll 94 to cool the resin 96 and impart a desired finish. The coating thickness can be controlled by controlling the ratio of the speed of the moving cardboard substrate 91 and the speed at which the resin 96 is extruded from the slot die 97.

The composition of the at least one high-density polyethylene layer is a pure high-density polyethylene layer, or a mixture of one or more substances and a high-density high-density polyethylene that does not interfere with the function of the high-density high-density polyethylene layer that protects the cardboard substrate from moisture after the same heating by microwave radiation. Can be For example, the one or more high density polyethylene layers include high density polyethylene in an amount of 50% or more, such as 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, 99% or more, or 100% can do. In one example, the first high density polyethylene layer can include a first percentage of high density polyethylene, and the second high density polyethylene layer can include a second percentage of high density polyethylene that is different from the first percentage of high density polyethylene.

The disclosed cardboard can be made of cardboard articles using any available technique. Various operations for manufacturing cardboard articles are described below, but variations may arise to those skilled in the art when reading the specification. This application includes such modifications and is limited only by the scope of the claims.

The disclosed cardboard can be printed with high quality advertising text or graphics (indicia) on one or both of the major sides by a print job. The print job may include any device or system capable of displaying a sign on a cardboard. For example, a print job may include a print press capable of printing high quality text and / or graphics (eg, advertising text and graphics) on cardboard. Specific examples of printing techniques include offset printing, gravure printing, flexographic printing and digital printing.

The disclosed cardboard can be cut into blanks by way of a cutting operation. The cutting operation may include any device or system capable of cutting blanks from cardboard. For example, the cutting operation may include a die cutting machine. The cutting operation can give the blank a desired shape. The shape of the blank can depend on the intended shape and construction of the cardboard article. Also, when cutting after a print job, the cut job can cut the blank so that the printed indicia is located at the desired location.

The blanks can be formed into cardboard articles by molding operations. The forming operation can form and assemble one or more blanks into cardboard articles having a desired shape and configuration. The forming operation can include any device or system capable of forming one or more blanks into a cardboard article having a desired shape and configuration. The molding operation may include, for example, a press mold or a thermoforming mold.

Although the various operations for manufacturing cardboard articles have been described above as independent operations performed in a particular order and by separate machines or systems, one or more operations are performed in a different sequence, one or more operations are combined into a single operation, or one It will be understood that the work sheet of a work piece may be divided into a number of tasks, or that one or more tasks may be performed by a single machine or system.

An embodiment of a method for using a cardboard article includes heating the cardboard article disclosed above by microwave irradiation. For example, a cardboard article comprising a cardboard substrate having a first major surface and a second major surface, and at least one high density polyethylene layer on at least one of the first major surface and the second major surface of the cardboard substrate, eg For example, the cardboard article may be heated by microwave irradiation, such as heating in a microwave oven. Food products (eg, soup, oatmeal, coffee, water, etc.) may be on the surface of the cardboard article during heating of the cardboard article.

In one example, the cardboard article can be a cardboard container (eg, cup, bowl). The cardboard container can have any desired container configuration.

It will be appreciated that the cardboard container can be made from the cardboard disclosed above using any available technique. Various operations for manufacturing cardboard containers are described below, but variations may occur to those skilled in the art upon reading the specification.

Marks can be printed on one or both major sides of a roll of the disclosed cardboard by printing operations such as offset printing, gravure printing, flexographic printing, or digital printing methods. Printed or unprinted cardboard can be cut into container blanks, such as sidewall blanks, bottom blanks or lid blanks, for example by cutting using a die cutting machine. 10 and 11 show exemplary sidewall blanks 100, 110 that can be used in the manufacture of cardboard containers. FIG. 10 shows the unprinted sidewall blank 100, and FIG. 11 shows the printed sidewall blank 110 with the marking 112 printed on its main surface.

The printed or unprinted container blank is then formed into a cardboard container by a forming operation. For example, the sidewall blanks 100, 110 of FIG. 1 or 2 can be shaped by rolling the sidewall blanks 100, 110 around the mandrel to form a truncated-conical sidewall. In one example, the sidewall blank can have a caliper thickness of 16 points. The sidewall can be completed by overlapping and sealing the longitudinal ends of the shaped sidewall blank to form an overlapping and sealed seam. The seams can be sealed using any available technique. In one example, the seam can be sealed by heating and connecting the first high density polyethylene layer and the second high density polyethylene layer in the overlapped portion. In another example, the seam can be sealed by folding the first longitudinal end and heating and connecting the first high density polyethylene layer at the first longitudinal end and the first high density polyethylene layer at the second longitudinal end.

In a non-limiting embodiment, the container can include a bottom. This floor can be made from the disclosed cardboard or from different cardboard or from non-cardboard materials. In one example, the bottom blank may have a caliper thickness of 13 points. The floor can be sealed to the sidewall using any available technique. In one example, the lower end of the sidewall can be shaped to form a circumferential recess. The bottom may be disposed in the circumferential recess and sealed to the sidewall. In a particular example, at least one of the sidewalls and bottom has a high density polyethylene layer, which facilitates good sealing.

In a non-limiting embodiment, the container can include a lid. These lids can be made from the disclosed cardboard or from different cardboard, or from non-cardboard materials such as film materials (eg, metal; metal-polymer combinations), pressurized lids (eg, molded plastic lids). The lid may remain on the sidewalls or as an unsealed lid. The lid can be sealed to the sidewall using any available technique, and, among other possible factors, can depend on the type of lid used. In certain examples, at least one of the sidewalls and lid has a high density polyethylene layer, which facilitates good sealing.

During packaging, foodstuffs (e.g., soup, oatmeal, etc.) can be placed in the internal volume of the cardboard container, and the lid is, for example, a cardboard container with heat-seal, adhesive or interference fit, etc. It can be sealed on the side wall.

In one example, the upper end of the sidewall can be curled to form a flange, and the lid can be sealed to the flange.

In another example, the film material can be sealed on the sidewall by lamination or the like to seal the cardboard container. A second non-sealable lid can be provided to cover the film material.

While various embodiments of cardboard containers are described below, variations may occur to those skilled in the art after reading the specification.

12-14 illustrate embodiments of an exemplary cardboard container 120. The cardboard container 120 formed from the disclosed cardboard may include side walls 122, a floor 124, and a lid 126. The sidewall 122 can be formed by die-cutting the sidewall blank from a sheet of disclosed cardboard into a desired configuration (eg, trapezoidal), such as the sidewall blanks 100 and 110 of FIGS. 10 and 11, for example. . The sidewall blank can include a first longitudinal end and a second longitudinal end. The sidewall 122 is to be formed by overlapping the longitudinal ends to surround the inner cavity of the container, and by forming an overlapping overlapped seam 128 where the first longitudinal end is located inside the second longitudinal end. You can. The seam 128 can be sealed, for example, by connecting a high density polyethylene layer at the first longitudinal end to a high density polyethylene layer at the second longitudinal end.

The bottom 124 can be formed from the disclosed cardboard. Various techniques can be used to seal the bottom 124 to the sidewall 122. As an example, the lower end of the side wall 122 may be shaped to form a columnar recess 130. The bottom 124 can be disposed within the recess 130 and sealed to the sidewall 122. Suitable techniques for sealing the bottom 124 to the side wall 122 include hot air heat sealing and ultrasonic sealing.

The lid 126 may be an unsealed plastic lid 126. The lid 126 may be attached to the sidewall 122 by, for example, interference fit. The upper end of the side wall 122 is dried to form a bead 132. The lid 126 is made to form an interference fit with the bead 132 at the upper end of the side wall 122, so that the lid 126 is repeatedly removed and attached to cover the cardboard container 120.

Another embodiment of an exemplary cardboard container 140 is shown in FIGS. 15 and 16. A cardboard container 140 formed from the disclosed cardboard can include sidewalls 142, a bottom 144, and a lid 146. The sidewall 142 may be formed by die-cutting the sidewall blank from a sheet of disclosed cardboard into a desired configuration (eg, trapezoidal), such as the sidewall blanks 100 and 110 of FIGS. 10 and 11, for example. . The sidewall blank can include a first longitudinal end and a second longitudinal end. Sidewalls 142 are formed by overlapping the longitudinal ends to surround the inner cavity of the container and forming overlapping overlapping seams (not shown) with the first longitudinal end positioned inside the second longitudinal end. Can be. The seam can be sealed, for example, by connecting and heating the high density polyethylene layer at the first longitudinal end to the high density polyethylene layer at the second longitudinal end.

The bottom 144 can be formed from the disclosed cardboard. Various techniques can be used to seal the bottom 144 to the sidewall 142. As an example, the lower end of the side wall 142 may be shaped to form a columnar recess 150. The bottom 144 may be disposed within the recess 150 and sealed to the sidewall 142. Suitable techniques for sealing the bottom 144 to the side wall 142 include hot air heat sealing and ultrasonic sealing.

The lid can be sealed to the sidewall 142. The cardboard lid 146 can be formed from the disclosed cardboard or from other cardboard, or from other materials such as film materials (eg, polymers; metals; metal-polymer combinations). Various techniques can be used to seal the lid 146 to the sidewall 142. As an example, the upper end of the side wall may be curled to form a flange 152 and the lid 146 may be sealed to the flange 152. The lid 146 can be sealed to the flange 152, for example, by connecting and heating the high density polyethylene layer of the cardboard lid 146 to the high density polyethylene layer of the flange 152. As another example, the film lid 146 can be sealed to the flange 152, for example, by heat sealing or adhesive, and a second lid can be provided to cover the film lid 146.

Another embodiment of an exemplary cardboard container may include a food product contained in the interior volume of the cardboard container and a lid sealing the interior volume of the cardboard container. The lid can be sealed using any available technology and can depend on the type of lid used, among other possible factors. The label may include instructions for heating the food product by microwave irradiation. The instructions can be included in the cardboard container in any way, such as printing on the outside of the cardboard container or attaching additional packaging material to the cardboard container. Thus, a cardboard container containing foodstuffs can be purchased by the consumer and the foodstuffs can be heated by microwave irradiation according to the instructions in a state contained in the cardboard container. Additional steps may be included without departing from the scope of the present disclosure.

17-22 show the comparison results of a conventional polypropylene (PP / LDPE) coating with 20% low density polyethylene on a cardboard substrate and a high density polyethylene (HDPE) coating on a cardboard substrate.

17 relates to a polymer extrusion coating test performed on a solid bleached sulfate cardboard substrate. The die width for the polymer extrusion coating test was 19 inches. The width of the polymer coating on the cardboard was measured after the extrusion coating process. The difference between the die width (19 inches) and the width of the polymer coating on the cardboard is called the total neck-in. The reduced neck-in is advantageous for the polymer extrusion process to increase material utilization by reducing trim waste. In this test, the HDPE extrusion coating had significantly less total neck-in (1.5 inches) than PP / LDPE (3.6 inches). HDPE extrusion coating shows better process performance by increasing material utilization than PP / LDPE extrusion coating.

18 relates to a polymer extrusion coating test conducted on a solid bleached sulfate cardboard substrate. After extrusion, a corona treatment was applied to the surface of the polymer coating. The polymer surface energy measured by dyne level was monitored over 28 days (4 weeks). A higher dyne level is advantageous for the polymer coated surface to ensure easy printability on the polymer surface. In this example, the HDPE surface can be initially corona treated at a higher dyne level than the PP / LDPE surface. Also, the dyne level attenuates slower for HDPE surfaces than for PP / LDPE surfaces. HDPE coating shows better printability properties than PP / LDPE coating.

FIG. 19 relates to a polymer extrusion coating test performed on a solid bleached sulfate cardboard substrate. The coefficient of friction (CoF) was measured as the frictional force for sliding two surfaces, the polymer coating and the same type of polymer coating. Lower coefficient of friction (CoF) is advantageous to reduce the force required to facilitate sliding the two polymer surfaces relative to each other. Static CoF is a measure of the initial force required to initiate a sliding movement. Dynamic CoF is a measure of the force required to maintain motion. In this example, HDPE surface shows lower static CoF and lower dynamic CoF than PP / LDPE surface. This means that HDPE surfaces can be more advantageous in the conversion and packaging process.

20 relates to a polymer extrusion coating test performed on a solid bleached sulfate cardboard substrate. The abrasion resistance of the polymer coated surface was tested by carrying out 999 reciprocations of sled sliding and friction of 2-lb weight on the polymer surface. In this test, the high density polyethylene surface had better abrasion resistance because of less frictional material loss than the polypropylene / low density polyethylene surface.

21 relates to a polymer extrusion coating test performed on a solid bleached sulfate cardboard substrate. The moisture vapor transmission rate (MVTR: Moisture Vapor Transmission Rate, WVTR: Water Vapor Transmission Rate) of the polymer coated cardboard was measured at 100 ° F (37.8 ° C) and 90% RH (relative humidity). WVTR is a measure of water vapor transmission through a substrate. In this example, high density polyethylene exhibits a lower WVTR than polypropylene / low density polyethylene. This means that high density polyethylene has better moisture resistance or water vapor barrier properties than polypropylene / low density polyethylene.

22 relates to a polymer extrusion coating test performed on a solid bleached sulfate cardboard substrate. The polymer coated cardboard was then cut into sidewall blanks and bottom blanks suitable for forming a 16 oz beverage cup. The cup conversion test was performed at a speed of 165 cups per minute in the PMC-1250 cup forming machine. The sidewall temperature setting was changed. Fiber tear of the cup side-seam seal was measured as an indicator of side-seam heat seal performance. In this example, the high density polyethylene coated cardboard can be heat-sealed at lower temperatures and exhibits better fiber tearing than the polypropylene / low density polyethylene coated cardboard at the same cup conversion rate.

Tables 1 and 2 relate to polymer extrusion coating tests for kaolin clay coated cardboard on one side for side wall loading and solid bleached sulfate cardboard for floor loading. The sidewall and bottom loading rolls were cut into suitable sizes to form 12-oz and 17-oz cups. In both examples, the high density polyethylene coated cardboard was formed and sealed at a faster conversion rate at lower sidewall temperatures.

Setting / condition PP / LDPE conditions HDPE conditions Cup speed (cup / min)  180  210 Side wall temperature (F) 1075 1025

Table 1: Heat seal conditions for cup formation (12 oz cup)

Setting / condition PP / LDPE conditions HDPE conditions Cup speed (cup / min) 125 135 Side wall temperature (F) 950 900

Table 2: Heat seal conditions for cup formation (17 oz cup)

While various embodiments of the disclosed cardboard, cardboard container, and method of using the same have been described, variations may arise to those skilled in the art who have read the specification. This application includes such modifications and is limited only by the scope of the claims.

Claims (22)

As a method of using cardboard articles,
Heating the cardboard article by microwave irradiation, the cardboard article comprising:
A cardboard substrate having a first major surface and a second major surface; And
At least one high density polyethylene layer over at least one of the first major surface and the second major surface of the cardboard substrate;
How to include. According to claim 1,
The cardboard substrate is coated natural kraft board, solid bleached sulfate board, solid unbleached sulfate board, coated recycle board, coated whiteboard chipboard, and folding boxboard A method comprising one or more of (boxboard). According to claim 1,
Wherein the cardboard substrate has a caliper thickness in the range of 7 to 30 points. According to claim 1,
Wherein the at least one high density polyethylene layer has a density in the range of 0.93 to 0.97 g / cm ³ . According to claim 1,
Wherein the one or more high density polyethylene layers have a melt index greater than 0.3 g / 10 min (190 ° C./2.16 kg). According to claim 1,
A method in which foodstuff is on the surface of the cardboard article while heating the cardboard article. According to claim 1,
Wherein the cardboard article has the configuration of a container. As a cardboard container,
A cardboard substrate having a first major surface facing the inside of the cardboard container and a second major surface facing the outside of the cardboard container; And
At least one high density polyethylene layer disposed directly on the first major side of the cardboard substrate;
Containing, cardboard container. The method of claim 8,
The cardboard container, wherein the cardboard substrate is disposed on the outermost surface of the second main surface of the cardboard. The method of claim 8,
A cardboard container further comprising one or more high density polyethylene layers on the second major side of the cardboard substrate. The method of claim 8,
A cardboard container further comprising a clay coating layer on the second major side of the cardboard substrate. The method of claim 11,
A cardboard container further comprising one or more high density polyethylene layers on the clay coating layer. The method of claim 8,
The cardboard substrate has a caliper thickness in the range of 7 to 30 points. The method of claim 8,
The at least one high density polyethylene layer has a density in the range of 0.93 to 0.97 g / cm ³ , a cardboard container. The method of claim 8,
The at least one high density polyethylene layer has a melt index greater than 0.3 g / 10 min (190 ° C./2.16 kg), a cardboard container. The method of claim 8,
The cardboard container has a configuration of a cup or bowl, a cardboard container. The method of claim 8,
The cardboard container comprises a food container accommodated in an interior volume of the cardboard container and a lid sealing the internal volume of the cardboard container. The method of claim 17,
An indicia on the outside of the cardboard container or an indication on a packaging material attached to the cardboard container includes instructions for heating the food by microwave irradiation. A cardboard substrate having a first major surface and a second major surface; And
At least one high density polyethylene layer over one or both of the first major surface and the second major surface of the cardboard substrate;
Is made of,
Optionally, a cardboard having a clay coating layer between the at least one high density polyethylene layer and the cardboard substrate on one or both of the first major surface and the second major surface of the cardboard substrate. The method of claim 19,
The cardboard substrate has a caliper thickness in the range of 7 to 30 points. The method of claim 19,
The at least one high density polyethylene layer has a density in the range of 0.93 to 0.97 g / cm ³ . The method of claim 19,
The at least one high density polyethylene layer has a melt index greater than 0.3 g / 10 min (190 ° C./2.16 kg).

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