CN115279970A

CN115279970A - Heat sealable paperboard structure and method

Info

Publication number: CN115279970A
Application number: CN202180023385.1A
Authority: CN
Inventors: 逄杰斌
Original assignee: WestRock MWV LLC
Current assignee: WestRock MWV LLC
Priority date: 2020-01-22
Filing date: 2021-01-13
Publication date: 2022-11-01
Also published as: US20210222370A1; BR112022014447A2; WO2021150404A1; EP4093913A1; CA3165612A1; JP2023511176A

Abstract

A heat sealable paperboard structure comprising: a paperboard substrate having a first major face and a second major face opposite the first major face; a heat sealable barrier coating on the first major face of the paperboard substrate; and a top coat positioned over the heat sealable barrier coating, wherein the top coat forms a discontinuous layer over the heat sealable barrier coating.

Description

Heat sealable paperboard structure and method

Priority

This application claims priority to U.S. serial No. 62/964,198, filed on 22/1/2020.

Technical Field

The present application relates to paperboard structures and, more particularly, to heat sealable paperboard structures that have no or minimal tendency to block.

Background

Paperboard is used in various packaging applications. For example, coated unbleached paperboard is used for packaging beverage containers, frozen foods, cereals, and a wide variety of other food and non-food consumer products. Other forms of bleached and unbleached coated paperboard are used in various packaging options for food service and consumer products.

Sustainability is one of the key drivers to develop new packaging for food and non-food consumer goods. Paperboard structures coated with waterborne coatings are generally considered to be repulpable and recyclable, and thus more sustainable than paperboard coated with extruded Low Density Polyethylene Extrudates (LDPE). However, most polymers in waterborne coatings are amorphous and do not have a melting point like LDPE. Thus, during the production, storage, transport or processing of waterborne coated paperboard, the binder or polymer in the waterborne coating often gradually softens or becomes tacky at elevated temperatures (even at, for example, 120-130F.) and/or pressures, causing blocking problems in the coated paperboard, which in practice does not typically occur with polyethylene coated paperboard.

Furthermore, due to the high binder level and thus due to the hot tack, aqueous heat sealable barrier coatings cannot withstand the calendering temperatures typically used to smooth the coating surface. Blocking at high temperature and pressure (tendency of layers to stick to each other in a paperboard roll) is also a major technical challenge during the production and processing of aqueous heat sealable barrier coated paperboard. This blocking problem becomes more critical with waterborne heat-sealable barrier coated paperboard, which requires high barrier properties and also needs to be able to be heat sealed in a process package such as a cup.

Accordingly, those skilled in the art continue to research and develop in the field of heat sealable barrier paperboard structures that use waterborne coatings.

Disclosure of Invention

Heat sealable paperboard structures having no or minimal tendency to block are disclosed.

In one example, the disclosed heat sealable paperboard structure includes a paperboard substrate including a first major face and a second major face opposite the first major face, a heat sealable barrier coating on the first major face of the paperboard substrate, and a top coating positioned on the heat sealable barrier coating, wherein the top coating forms a discontinuous layer on the heat sealable barrier coating.

Also disclosed is a method for making a heat sealable paperboard structure having no or minimal tendency to block.

In one example, the disclosed method for manufacturing a heat sealable paperboard structure includes the steps of: the method includes (1) preparing a heat sealable barrier coating formulation comprising an adhesive and a pigment, (2) applying the heat sealable barrier coating formulation to the first major face of the paperboard substrate, (3) preparing a top coat formulation comprising an adhesive and a pigment, and (4) applying the top coat formulation to the heat sealable barrier coating to form a discontinuous layer of top coat over the heat sealable barrier coating.

Other examples of the disclosed heat sealable paperboard structures and methods will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

Drawings

FIG. 1 is a cross-sectional elevation view of one example of a container (e.g., a cup) that can be manufactured using the disclosed heat sealable paperboard structure;

FIG. 2 is a top plan view of the container of FIG. 1;

FIG. 3 is a plan view of a die cut blank that may be wrapped around a mandrel to form the side walls of the container of FIG. 1;

FIG. 4 is a schematic cross-sectional view of one example of the disclosed heat sealable paperboard structure;

FIG. 5 is a schematic cross-sectional view of another example of the disclosed heat sealable paperboard structure;

FIG. 6 is a top view of an exemplary heat-sealable paperboard structure taken using a scanning electron microscope at 200x magnification;

FIG. 7 is a cross-sectional view of an exemplary heat sealable paperboard structure taken using a scanning electron microscope at 1000x magnification; and

fig. 8 is a schematic of an apparatus for testing coated paperboard samples for blocking.

Detailed Description

It has now been found that a heat sealable paperboard-based structure having a first major surface with high water blocking properties and minimal tendency to tack free can be achieved by positioning a heat sealable barrier coating on a first major face of a bottom paperboard substrate that conventionally forms the first major surface of the structure, beneath a low adhesive, calenderable top coating applied as a discontinuous layer on (e.g., directly onto) the barrier coating, such that the heat sealable barrier coating is positioned between the paperboard substrate and the top coating. Heat sealability is provided by the heat sealable barrier coating. Such a structure may be particularly suitable for preserving cold beverages (e.g., iced soft drinks), cold foods (e.g., ice cream), hot beverages (e.g., coffee), and hot foods (e.g., soup).

Referring to fig. 1 and 2, one example of the disclosed paperboard-based container, generally designated 10, may include a sidewall 12 having an upper end 14 and a lower end 16, and a bottom wall 18 connected (e.g., heat sealed) to the lower end 16 of the sidewall 12, thereby defining an interior volume 20 within the container 10. The upper end 14 of the sidewall 12 may define an opening 22 to the interior volume 20. Optionally, the upper end 14 of the sidewall 12 may additionally include a lip 24 (e.g., a curled lip), such as for securing a lid (not shown) or the like to the container 10.

While the container 10 is shown in fig. 1 as a tall cup with a frustoconical sidewall 12 (e.g., a 12 ounce, 16 ounce, 21 ounce, or 24 ounce disposable take-out cup), those skilled in the art will appreciate that the disclosed container 10 may be formed in a variety of shapes, sizes, and configurations, and may be formed with fewer or more walls than the above-described sidewall and

bottom walls

12, 18 without departing from the scope of the present disclosure.

As shown in fig. 2, the side walls 12 of the container 10 may be assembled from a blank 30 (fig. 3), which blank 30 has been cut to the desired profile and then wrapped around a mandrel (not shown). When the blank 30 is wrapped around the mandrel, the first end 32 of the blank 30 overlaps the second end 34 of the blank 30, and the

overlapping ends

32, 34 may be joined (e.g., by heat sealing) to define a seam 36 extending from the upper end 14 to the lower end 16 of the sidewall 12. Once the side walls 12 have been assembled, the bottom wall 18 may be attached (e.g., heat sealed) to the lower end 16 of the side walls 12, thereby creating the container 10.

Referring to fig. 4, the side wall 12 of the container 10 may be formed from a paperboard structure 40 having a first major surface 42 and a second major surface 44. The first major surface 42 of the paperboard structure 40 may correspond to the interior surface 28 of the container 10. The second major surface 44 of the paperboard structure 40 may correspond to the outer surface 26 of the container 10.

The paperboard structure 40 may be a layered structure comprising a paperboard substrate 46 having a first major face 48 and a second major face 50. The heat sealable barrier coating 52 and the top coat 54 can be applied to the first major face 48 of the paperboard substrate 46 such that the top coat 54 forms a discontinuous layer 56 on (e.g., immediately adjacent to) the heat sealable barrier coating 52. The heat sealable barrier coating 52 may be positioned between the top coating 54 and the paperboard substrate 46. The discontinuous layer 56 of the top coat 54 may at least partially define the first major surface 42 of the paperboard structure 40, and thus the interior surface 28 of the container 10.

In this regard, those skilled in the art will appreciate that various additional layers, barrier layers or non-barrier layers may be incorporated into the paperboard structure 40 between the paperboard substrate 46 and the discontinuous layer 56, or on top of the second major face 50, without departing from the scope of the present disclosure. In one variant, as shown in fig. 5, the paperboard structure 40 'may comprise a base coating 45' between the paperboard substrate 46 'and the heat-sealable barrier coating 52'. In another variation, as shown in fig. 5, the heat-sealable paperboard structure 40 may include a primer layer 47 on a second major face 50 of the paperboard substrate 46 ". In yet another variant, as shown in fig. 5, the paperboard structure 40 may include a first primer layer 45 between the paperboard substrate 46 'and the heat-sealable barrier coating 52' and a second primer layer 47 on the second major face 50 of the paperboard substrate 46.

Referring back to fig. 4, the paperboard substrate 46 of the paperboard structure 40 may be (or may include) any cellulosic material that can be coated with a heat sealable barrier coating 52 and a top coating 54. One skilled in the art will appreciate that the paperboard substrate 46 may be bleached or unbleached. Examples of suitable paperboard substrates include corrugated medium, linerboard, solid Bleached Sulfate (SBS), and unbleached kraft.

The paperboard substrate 46 may have at least about 50 pounds per 3000 ft²Uncoated basis weight of (a). In one expression, the paperboard substrate 46 may have a range of from about 60 pounds per 3000 ft²To about 400 pounds per 3000 ft²Uncoated basis weight of (a). In another expression, the paperboard substrate 46 may have a range of from about 80 pounds per 3000 ft²To about 300 pounds per 3000 ft²Uncoated basis weight of (a). In another expression, the paperboard substrate 46 may have a range of from about 90 pounds per 3000 ft²To about 250 pounds per 3000 ft²Uncoated basis weight of (a). In yet another expression, the paperboard substrate 46 may have a range of from about 100 pounds per 3000 ft²To about 200 pounds per 3000 ft²Uncoated basis weight of (a).

Further, the paperboard substrate 46 may have a caliper (caliper) ranging, for example, from about 4 points to about 30 points (0.004 inches to 0.030 inches). In one expression, the caliper ranges from about 8 points to about 24 points. In another expression, the caliper ranges from about 12 points to about 20 points.

One particular non-limiting example of a suitable paperboard substrate 46 is a 13-point SBS cup blank (SBS cupstock) manufactured by WestRock corporation of atlanta, georgia. Another specific, non-limiting example of a suitable paperboard substrate 46 is a 16.5-point SBS cup blank manufactured by WestRock, inc. Another specific, non-limiting example of a suitable paperboard substrate 46 is an 18-point SBS cup blank manufactured by WestRock, inc.

The heat sealable barrier coating 52 may be applied to the first major face 48 of the paperboard substrate 46 using any suitable method, such as one or more coaters, either on a paper machine or as an off-machine coater. When heated, the heat seal coating provides adhesion to other areas of the product with which it is in contact.

The heat sealable barrier coating 52 can beApplied to the paperboard substrate 46 at various coating weights. In one expression, the heat-sealable barrier coating 52 can be at about 4 to about 20 pounds per 3000 ft²(dry weight) coat weight application. In another expression, the heat-sealable barrier coating 52 can be at about 6 to about 16 pounds per 3000 ft²(dry weight) coat weight application. In another expression, the heat-sealable barrier coating 52 can be at about 8 to about 12 pounds per 3000 ft²Coating weight application (dry weight).

The heat sealable barrier coating 52 can include a binder and a pigment. In one expression, the ratio of pigment to binder can be up to 1 part by weight pigment per 1 part by weight binder. In another expression, the weight ratio of pigment to binder can be from about 1: 1 to about 1: 9. In yet another expression, the weight ratio of pigment to binder can be from about 1: 2 to about 1: 6. In yet another expression, the weight ratio of pigment to binder can be from about 1: 3 to about 1: 4.

In a particular embodiment, the adhesive of the heat-sealable barrier coating 52 can be an aqueous adhesive. As a general non-limiting example, the binder may be latex. As another general non-limiting example, the binder may be a water-based acrylic emulsion polymer. Specific non-limiting examples of suitable binders are given in table 2. Other aqueous binders are also contemplated, such as styrene-butadiene rubber (SBR), ethylene Acrylic Acid (EAA), polyvinyl acetate (PVAC), polyethylene acrylic acid, polyester dispersions, and combinations thereof.

The color component of the heat sealable barrier coating 52 can be (or can include) a variety of materials. Several non-limiting examples of suitable inorganic pigments are given in table 1. Other pigments, such as plastic pigments, titanium dioxide pigments, talc pigments, and the like, may be used without departing from the scope of the invention.

In one variation, the pigment component of the heat sealable barrier coating 52 may be a clay pigment. As one example, the clay pigment may be a platy clay, such as a high aspect ratio platy clay (e.g., an average aspect ratio of at least 40: 1, such as an average aspect ratio of at least 60: 1).

In another variation, the pigment component of the heat sealable barrier coating 52 may be calcium carbonate (CaCO)₃) A pigment. As an example, caCO₃The pigment may be coarse ground CaCO₃And has a particle size distribution wherein about 60% of the particles are less than 2 microns. As another example, caCO₃The pigment may be finely ground CaCO₃And has a particle size distribution wherein about 90% of the particles are less than 2 microns.

In yet another variation, the pigment component of the heat sealable barrier coating 52 may be a pigment mixture including both calcium carbonate pigment and clay pigment.

The top coat 54 is applied to the heat sealable barrier coating 52 to form a discontinuous layer 56 on (e.g., directly adjacent to) the heat sealable barrier coating 52. Various techniques may be used to form the discontinuous layer 56 of the top coat 54 on the heat sealable barrier coating 52, such as one or more coaters on a paper machine or as an off-machine coater.

The top coat 54 may be applied to the heat sealable barrier coating 52 at various coating weights to achieve a discontinuous layer 56 of the top coat 54. In one expression, the topcoat layer 54 may be applied at about 0.1 to 4.0 pounds per 3000 ft²Coating weight application (dry weight). In another expression, the topcoat layer 54 may be applied at about 0.5 to 3.0 pounds per 3000 ft²Coating weight application (dry weight). In another expression, the topcoat layer 54 may be applied at about 0.5 to 2.5 pounds per 3000 ft²(dry weight) coat weight application. In yet another expression, the topcoat layer 54 may be applied at about 0.5 to 2.0 pounds per 3000 ft²Coating weight (dry weight) of (c).

Referring to fig. 6, a sem is used to show a top view of the discontinuous layer 56 of the top coat 54 deposited onto the heat sealable barrier coating 52. The area with the heat sealable barrier coating 52 is darker and the area with both the heat sealable barrier coating 52 and the top coating 54 is lighter.

Referring to fig. 7, sem is used to show a cross-sectional view of the discontinuous layer 56 of the top coat 54 deposited onto the heat sealable barrier coating 52.

The top coat 54 may include a binder and a pigment. Pigments and adhesives that may be used in the heat seal barrier coating 52 may also be used in the top coat 54. However, the pigment to binder ratio of the top coat 54 may be significantly different from the pigment to binder ratio of the heat sealable barrier coating 52. In one expression, the ratio of pigment to binder in the top coat layer 54 can be at least about 1 part by weight pigment per 1 part by weight binder. In another expression, the weight ratio of pigment to binder in the top coat layer 54 can be from about 1: 1 to about 10: 1. In another expression, the weight ratio of pigment to binder in the top coat layer 54 can be from about 1: 1 to about 5: 1. In yet another expression, the weight ratio of pigment to binder in the top coat layer 54 can be from about 2: 1 to about 4: 1.

In a particular embodiment, the binder of the top coat 54 may be an aqueous binder. As a general non-limiting example, the binder may be latex. As another general non-limiting example, the binder may be a water-based acrylic emulsion polymer. One specific non-limiting example of a suitable adhesive is given in table 2. Other aqueous binders are also contemplated, such as styrene-butadiene rubber (SBR), ethylene Acrylic Acid (EAA), polyvinyl acetate (PVAC), polyethylene acrylic acid, polyester dispersions, and combinations thereof.

The pigment component of topcoat 54 may be (or may include) a variety of materials. Several non-limiting examples of suitable inorganic pigments are given in table 1. Other pigments, such as plastic pigments, titanium dioxide pigments, talc pigments, and the like, may be used without departing from the scope of the present invention.

In one variation, the pigment component of the top coat 54 may be a clay pigment. As one example, the clay pigment may be a platy clay, such as a high aspect ratio platy clay (e.g., an aspect ratio of at least 40: 1).

In another variation, the pigment component of the top coat 54 may be calcium carbonate (CaCO)₃) A pigment. As an example, caCO₃The pigment may be coarse ground CaCO₃Having a particle size distribution of about 6 therein0% of the particles are smaller than 2 microns. As another example, caCO₃The pigment may be finely ground CaCO₃And has a particle size distribution wherein about 90% of the particles are less than 2 microns.

Referring back to fig. 1, the bottom wall 18 of the container 10 may be formed of a paperboard structure, such as the heat sealable paperboard structure 40 shown in fig. 4 or the heat sealable paperboard structure 40 shown in fig. 5. However, various other paperboard structures may be used to form bottom wall 18, such as when printability of bottom wall 18 is less important or not important.

Examples of the invention

Experiments were conducted to evaluate the use of a discontinuous layer of top coat on a heat sealable barrier coating in relation to paperboard structures. A heat sealable barrier coating formulation (BC 1) and a top coat formulation (TC 1) were prepared and used in the experiments. The pigments used in the formulations are given in table 1. The binders used in the formulations are given in table 2. The heat sealable barrier coating formulation (BC 1) is given in table 3. Table 4 shows the top coat formulation (TC 1).

TABLE 1

Name(s)	Pigment(s)	Description of the preferred embodiment
			CL-1	BARRISURF ™ XP (Georgia IMERYS kaolin)	Platy clays with high aspect ratio
CC-1	HYDROCARB^®60 (Omya AG of Ovetelin, switzerland)	Coarse grinding CaCO₃(particle size 60%<2 micron)
			CC-2	HYDROCARB^® 90 （Omya AG）	Finely ground CaCO₃(particle size 90%<2 micron)

TABLE 2

Name (R)	Adhesive agent	Description of the invention
			SA-1	CARTASEAL^®SCR (Archroma, reinach, switzerland)	Water-based acrylic emulsion polymers having a Tg of 30 deg.C

TABLE 3

	Barrier coating formula (parts)
			BC-1
CaCO₃（CC-1）	65
		CaCO₃（CC-2）
Clay (CL-1)	35
		Adhesive (SA-1)	400

TABLE 4

	Top coat formula (parts)
			TC-1
CaCO₃（CC-1）
		CaCO₃（CC-2）	100
Clay (CL-1)
		Adhesive (SA-1)	50

The formulations were applied at different coat weights to 16.5 point solid bleached sulfate cup blanks having a basis weight of 175 pounds per 3000 square feet. The heat sealable barrier coating formulation was applied to the felt side of the paperboard substrate using a knife coater. The top coat formulation was again applied to the heat sealable barrier coating using a knife coater, resulting in a two layer coating on the felt side of the paperboard substrate. Examples and experimental results (Parker printed surface smoothness; water can, coffee can, blocking grade; and heat sealability) are shown in table 5.

TABLE 5

。

Thus, the use of a discontinuous layer of top coat over the heat sealable barrier coating of the paperboard structure provides a smooth surface as shown by the Parker printed surface (PPS-10S) smoothness results measured according to TAPPI standard T555. All examples of the disclosed heat sealable paperboard structures exhibit a PPS smoothness of 3 microns or less.

In addition to high smoothness, these examples surprisingly also exhibit excellent barrier properties as evidenced by the 30 minute water-bobby results measured according to TAPPI standard T441 om-04. For most purposes, the additional discontinuous layer of the top coat improves or at least maintains the water-blocking properties of the underlying heat-sealable barrier coating 52. All exemplary 30 minute Water Calibre grades are less than 10 g/m²Many are less than 4 g/m²。

The hot coffee variant, which can be Bob tested, was also used to evaluate the water resistance of the examples shown in Table 5. The test passed by replacing 23 ℃ water with 90 ℃ coffee, but otherwise metTAPPI Standard T441 om-04. The coffee used was obtained by brewing 36g of starbucks moderately homemade mixed ground coffee with 1100 mL of distilled water in a 12 cup mr. Coffee machine. All examples shown in Table 5 have less than 15 g/m after 30 minutes²Of coffee of 90 ℃ of the same grade, most after 30 minutes less than 10 g/m²。

The heat sealability of the coated samples of table 5 was evaluated on a PMC (paper machine company) cup machine, model PMC-1250, by using each of these samples as the sidewall of the cup and a control bottom blank for all cups. All cups were successfully formed and fiber tear was estimated as a percentage of the seam area when the heat sealed sidewall seam was torn. A high percentage of fiber tear means better heat sealability. Both samples 1 and 2 exhibited 100% fiber tear, similar to the control sample without the discontinuous layer of the top coat, and

samples

3 and 4 also exhibited 95% excellent fiber tear.

Finally, the blocking rating (50 ℃/60 psi/24 hours) was less than 3.0 for all samples, actually less than 2.1, and less than 1.0 for one sample. Table 6 defines the adhesion test rating system.

TABLE 6

Grade	Description of the invention
		0	The sample broke without any applied force
1	The samples were slightly tacky, but separated without fiber tear
		2	The samples had high tack, but separated without fiber tear
3	The samples were tacky and up to 25% fiber tear or coating failure (area basis)
		4	The samples had more than 25% fiber tear or coating damage (area basis)

The samples were tested for blocking behavior by evaluating the adhesion between the barrier coated side and the other uncoated side. Fig. 8 shows a simplified illustration of the blocking test. The board was cut into 2 inch by 2 inch square samples. Several copies were tested for each condition, with each copy being evaluated for blocking between a pair of

samples

252, 254. (for example, if four copies were tested, four pairs (eight pieces) would be used). Each pair is positioned so that the "barrier coated" side of one 252 contacts the uncoated side of the other 254. The pairs are placed in a stack 250 with a spacer 256 between adjacent pairs, which is a foil, a release paper or even a copy paper. The entire sample stack is placed into the testing device 200 shown in fig. 8.

The test device 200 includes a frame 210. The adjustment knob 212 is attached to a screw 214 threaded through a frame top 216. The lower end of the screw 214 is attached to a plate 218, the plate 218 being carried on a heavy coil spring 220. The lower end of the spring 220 is carried on a plate 222, the lower surface 224 of the plate 222 having an area of 1 square inch. The scale 226 enables the user to read the applied force (which is equal to the pressure applied to the sample stack by the one square inch lower surface 224).

The sample stack 250 is placed between the lower surface 224 and the frame bottom 228. The knob 212 is tightened until the scale 226 reads the required force of 100 pounds force (100 psi applied to the sample) or 60 pounds force (60 psi applied to the sample). High pressures, such as 1000 psi, are achieved by reducing the lower surface area 224 contacting the sample stack 250 to 0.11 square inches with a force applied of 110 pounds. The entire device 200 including the sample is then placed in an oven at 50 ℃ for 24 hours or 2 hours. The device 200 is then removed from the test environment and cooled to room temperature. The pressure was then released and the sample was removed from the device.

The samples were evaluated for tackiness and blocking by separating each pair of cardboard sheets. Blocking damage is visible as fiber tearing, which typically occurs when the fibers are pulled from the non-barrier surface of sample 254, if present. If the non-barrier surface is coated with a printed coating, damage to the printed coating may also show blocking.

For example, as symbolically depicted in fig. 8, the samples 252 (0)/254 (0) may represent a "0" scale (no adhesion). The circular shape in the sample indicates an approximate area under pressure, e.g., about one square inch of the entire sample. Samples 252 (3)/254 (3) may represent a "3" blocking rating with up to 25% fiber tear in the compressed area, particularly on the uncoated surface of sample 254 (3). Samples 252 (4)/254 (4) may represent a "4" blocking rating with more than 25% fiber tear, particularly in the uncoated surface of sample 254 (4). The depiction in fig. 8 is meant only to approximately imply the percent damage to such test samples, rather than to show the true appearance of the samples.

While various examples of the disclosed heat sealable paperboard structures and methods have been shown and described, modifications may occur to those skilled in the art upon reading the specification. This application includes such modifications and is limited only by the scope of the claims.

Claims

1. A heat sealable paperboard structure comprising:

a paperboard substrate comprising a first major face and a second major face opposite the first major face;

a heat sealable barrier coating on the first major face of the paperboard substrate; and

a top coat layer positioned over the heat sealable barrier coating, wherein the top coat layer forms a discontinuous layer over the heat sealable barrier coating.

2. A heat sealable paperboard structure according to claim 1 wherein said top coat comprises a binder and a pigment.

3. A heat sealable paperboard structure according to claim 2 wherein the weight ratio of pigment to binder in said top coat is at least about 1: 1.

4. The heat sealable paperboard structure of claim 2 wherein the weight ratio of pigment to binder in said top coat is from about 1: 1 to about 10: 1.

5. A heat sealable paperboard structure according to claim 2 wherein the weight ratio of pigment to binder in said top coat is from about 1: 1 to about 5: 1.

6. A heat sealable paperboard structure according to claim 2 wherein the weight ratio of pigment to binder in said top coat is from about 2: 1 to about 4: 1.

7. A heat sealable paperboard structure according to any of claims 2-6 wherein said binder comprises latex.

8. A heat sealable paperboard structure according to any of claims 2-7 wherein said binder comprises a water based acrylic emulsion polymer having a glass transition temperature of about 30 ℃.

9. A heat sealable paperboard structure according to any of claims 2-8 wherein said pigment comprises calcium carbonate.

10. A heat sealable paperboard structure according to any of claims 2-9 wherein said pigment comprises ground calcium carbonate and wherein at most about 90% of the ground calcium carbonate has a particle size of less than 2 microns.

11. A heat sealable paperboard structure according to any preceding claim wherein said discontinuous layer has a range of from about 0.1 lb/3000 ft²To about 4.0 lb/3000 ft²Coating weight of (c).

12. A heat sealable paperboard structure according to any preceding claim wherein said discontinuous layer has from about 0.5 lb/3000 ft²To about 3.0 lb/3000 ft²Coating weight of (c).

13. A heat sealable paperboard structure according to any preceding claim wherein said discontinuous layer has from about 0.5 lb/3000 ft²To about 2.5 lb/3000 ft²Coating weight of (c).

14. A heat sealable paperboard structure according to any preceding claim wherein said discontinuous layer has from about 0.5 lb/3000 ft²To about 2.0 lb/3000 ft²Coating weight of (c).

15. A heat sealable paperboard structure according to any preceding claim wherein said heat sealable barrier coating comprises a binder and a pigment.

16. A heat sealable paperboard structure according to claim 15 wherein said pigment to binder weight ratio in said heat sealable barrier coating is at most 1: 1.

17. A heat sealable paperboard structure according to claim 15 wherein said pigment to binder weight ratio in said heat sealable barrier coating is from about 1: 1 to about 1: 9.

18. A heat sealable paperboard structure according to claim 15 wherein the weight ratio of pigment to binder in said heat sealable barrier coating is from about 1: 2 to about 1: 6.

19. A heat sealable paperboard structure according to claim 15 wherein the weight ratio of pigment to binder in said heat sealable barrier coating is from about 1: 3 to about 1: 4.

20. A heat sealable paperboard structure according to any of claims 15-19 wherein said binder comprises latex.

21. A heat sealable paperboard structure according to any of claims 15-20 wherein said adhesive comprises a water based acrylic emulsion polymer having a glass transition temperature of 30 ℃.

22. A heat sealable paperboard structure according to any of claims 15-21 wherein said pigments comprise a first pigment and a second pigment.

23. A heat sealable paperboard structure according to any of claims 15-22 wherein said pigment comprises at least one of clay and calcium carbonate.

24. The heat sealable paperboard structure of any one of claims 15-23 wherein the pigment comprises ground calcium carbonate, and wherein up to about 60% of the ground calcium carbonate has a particle size of less than 2 microns.

25. A heat sealable paperboard structure according to any of claims 15 to 24 wherein said pigment comprises a platy clay.

26. The heat sealable paperboard structure of claim 25 wherein said platy clay has an average aspect ratio of at least about 40: 1.

27. A heat sealable paperboard structure according to any preceding claim wherein said heat sealable barrier coating has a coat weight ranging from about 4 lb/3000 ft²To about20 lb/3000 ft²。

28. A heat sealable paperboard structure according to any preceding claim wherein said heat sealable barrier coating has a coat weight ranging from about 6 lb/3000 ft²To about 16 lb/3000 ft²。

29. The heat sealable paperboard structure of any preceding claim, wherein the heat sealable barrier coating has a coat weight ranging from about 8 lb/3000 ft²To about 12 lb/3000 ft²。

30. A heat sealable paperboard structure according to any preceding claim wherein the paperboard substrate comprises a solid bleached sulphate salt.

31. A heat sealable paperboard structure according to any preceding claim wherein said paperboard substrate has a basis weight ranging from about 80 lb/3000 ft²To about 300 lb/3000 ft²。

32. The heat sealable paperboard structure of any preceding claim, wherein the caliper of said paperboard substrate ranges from about 4 points to about 30 points.

33. A heat sealable paperboard structure according to any preceding claim wherein said paperboard substrate has a thickness ranging from about 8 to about 24 points.

34. The heat sealable paperboard structure of any preceding claim wherein said paperboard substrate has a thickness ranging from about 12 to about 20 points.

35. A heat sealable paperboard structure according to any preceding claim further comprising one or more coatings positioned between said paperboard substrate and said heat sealable barrier coating.

36. A heat sealable paperboard structure according to any preceding claim further comprising one or more coatings on said second major face.

37. A heat sealable paperboard structure according to any preceding claim having a parker printing surface (PPS-10S) smoothness of at most about 3.1 μm.

38. A heat sealable paperboard structure according to any preceding claim having a parker printing surface (PPS-10S) smoothness of at most about 2.5 μm.

39. A heat sealable paperboard structure according to any preceding claim having a parker printing surface (PPS-10S) smoothness of at most about 2 μm.

40. The heat sealable paperboard structure of any preceding claim having up to about 10 g/m²Water can be graded for 30 minutes.

41. The heat sealable paperboard structure of any preceding claim having up to about 5 g/m²Water can be graded for 30 minutes.

42. A heat sealable paperboard structure according to any preceding claim having up to about 3 g/m²Water can be graded for 30 minutes.

43. A heat sealable paperboard structure according to any preceding claim having up to about 15 g/m²For 30 minutes, a coffee may be of a brix grade.

44. The heat sealable paperboard structure of any preceding claim having up to about 12 g/m²The 30 minute coffee may be of a brix grade.

45. A heat sealable paperboard structure according to any preceding claim,it has a viscosity of at most about 9 g/m²The 30 minute coffee may be of a brix grade.

46. A heat sealable paperboard structure according to any of the preceding claims having a blocking rating of less than 2 at 50 ℃ and 60 psi over a 24 hour period.

47. A heat sealable paperboard structure according to any of the preceding claims having a blocking rating of less than 1.7 over a 24 hour period at 50 ℃ and 60 psi.

48. A heat sealable paperboard structure according to any of the preceding claims having a blocking rating of less than 1.4 over a 24 hour period at 50 ℃ and 60 psi.

49. A heat sealable paperboard structure according to any preceding claim which has a heat sealability (% fiber tear) of at least about 95%.

50. A container comprising the heat sealable paperboard structure of any preceding claim.

51. A method for manufacturing a heat sealable paperboard structure comprising:

preparing a heat sealable barrier coating formulation comprising a binder and a pigment;

applying the heat sealable barrier coating formulation to a first major face of a paperboard substrate to form a heat sealable barrier coating;

preparing a top coat formulation comprising a binder and a pigment; and

applying the top coat formulation over the heat sealable barrier coating to form a discontinuous layer of top coat over the heat sealable barrier coating.

52. The method of claim 51, wherein the heat sealable barrier coating formulation is applied to the first major face of the paperboard substrate using a knife coater.

53. The method of claim 51 or 52, wherein the topcoat formulation is applied directly to the heat sealable barrier coating formulation using a knife coater.

54. The method of any one of claims 51-53, further comprising drying the heat sealable barrier coating formulation.

55. The method of any one of claims 51-54, further comprising drying the topcoat formulation.